JP2006208839A - Process cartridge and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process cartridge and an image forming apparatus capable of preventing a transfer defect in both a thin transfer medium and a thick transfer medium.
A first guide member 71 and a second guide member 72 made of a flexible film member are provided on the upstream side of a transfer position. The first guide member 71 fixes the position of the first base end 73 on the upstream side of the first tip 74 so that the first tip 74 is close to the photosensitive drum 27 on the upstream side of the transfer position. The second guide member 72 has the second base end portion 75 at the second tip end so that the second tip portion 76 is close to the photosensitive drum 27 between the transfer position and the first tip portion 74 of the first guide member 71. The position is fixed on the upstream side of the portion 76. A plane 77 connecting the first distal end portion 74 and the first proximal end portion 73 of the first guide member 71 and a plane 78 connecting the second distal end portion 76 and the second proximal end portion 75 of the second guide member 72 are It intersects on the upstream side of the one base end portion 73.
[Selection] Figure 2

Description

  The present invention relates to an image forming apparatus such as a laser printer, and a process cartridge provided in the image forming apparatus.

Generally, an image forming apparatus such as a laser printer is detachably mounted with a process unit including a photosensitive drum on which a toner image is carried by developing an electrostatic latent image.
The photosensitive drum is disposed so as to be in contact with the transfer roller, and an image is formed on the sheet by transferring the toner image onto the sheet while the sheet passes between the photosensitive drum and the transfer roller.

However, if there is a gap between the sheet and the photosensitive drum on the upstream side in the sheet conveyance direction with respect to the transfer position, which is a contact portion between the photosensitive drum and the transfer roller, a discharge may occur between them. When such a discharge occurs, a spot-like discharge pattern that penetrates a sheet called “Tsukinuke” appears, particularly in a thin sheet.
For this reason, it has been proposed to provide a guide member for guiding the front end of the sheet so as to approach the surface of the photosensitive drum on the upstream side in the sheet conveyance direction with respect to the transfer position.

  14 and 15 show the state of paper transport in the conventional process cartridge 90 in stages. In the process cartridge 90, a photosensitive drum 91 and a transfer roller 92 disposed so as to be in contact with the photosensitive drum 91 are held by a casing 93. The housing 93 is provided with a guide member 95 for guiding the paper 94 to a transfer position which is a contact portion between the photosensitive drum 91 and the transfer roller 92.

  The guide member 95 is inclined upward from the upstream side in the conveyance direction of the paper 94 toward the downstream side (hereinafter, the downstream or upstream side in the conveyance direction of the paper 94 may be simply referred to as a downstream side or an upstream side). Thus, the base end portion 96 (the end portion on the upstream side in the conveyance direction of the paper 94, the same applies hereinafter) is fixed to the housing 93. A leading end portion 97 of the guide member 95 (an end portion on the downstream side in the conveyance direction of the sheet 94, hereinafter the same) is close to the photosensitive drum 91 on the upstream side with respect to the transfer position.

As shown in FIGS. 14A and 14B, in the process cartridge 90, first, when the paper 94 is conveyed, the front end of the paper 94 is located downstream along the upper surface of the guide member 95. To the front end 97 from the base end portion 96 of the guide member 95 and then guided so as to contact the upstream side of the transfer position on the photosensitive drum 91.
Thereafter, as shown in FIG. 15A, the sheet 94 is in close contact with the photosensitive drum 91 from the front end to the upstream side of the transfer position, and is guided to the transfer position in close contact with the photosensitive drum 91 to the vicinity of the rear end. The For this reason, the paper 94 does not form a gap with the photosensitive drum 91 on the upstream side of the transfer position, and this can suppress the occurrence of discharge between them. As a result, it is possible to prevent spotted discharge patterns from appearing on the paper 94.

However, in the guide member 95, when the rear end of the sheet 94 passes through the leading end 97 of the guide member 95, the rear end of the sheet 94 is guided as shown in FIGS. 15 (b) and 15 (c). The member 95 is dropped from the front end portion 97 of the member 95 and guided to the transfer position. For this reason, the rear end of the sheet 94 flutters, and there is a problem that transfer failure occurs at the rear end.
Therefore, for example, it has been proposed that the first guide member and the second guide member made of polyester films having the same thickness are arranged in parallel to each other on the upstream side in the transfer paper conveyance direction with respect to the image carrier (for example, , See Patent Document 1). According to this proposal, the rear end of the transfer paper that has passed through the first guide member is guided to the image carrier by the second guide member that is disposed closer to the transfer position. As a result, transfer defects at the trailing edge of the transfer paper are reduced.
JP-A-8-36313

  However, thin paper such as plain paper is susceptible to electric discharge, and as described above, it is necessary to prevent such electric discharge by bringing it into close contact with the photosensitive drum on the upstream side of the transfer position. is there. On the other hand, thick paper, such as postcards, is less likely to cause discharge than thin paper, and as described above, if it is brought into close contact with the photosensitive drum, it will be bent, so it will be conveyed as straight as possible. However, it is desirable to transfer it.

  However, in the proposal of Patent Document 1, since the second guide member is arranged in parallel with the first guide member, the transfer paper that has passed through the first guide member is the same as the first guide member. It abuts at a large angle with the second guide member arranged at an inclination angle. Then, the resistance force of the second guide member to the transfer paper is increased, and the transfer paper is strongly pressed toward the image carrier by the second guide member. For this reason, when the transfer paper is the above-described thick paper, the transfer paper is bent by the pressing, resulting in a transfer failure.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a process cartridge and an image forming apparatus that can prevent transfer failure in both a thin transfer medium and a thick transfer medium.

  In order to achieve the above object, according to a first aspect of the present invention, there is provided a process cartridge including: an image carrier that carries a developer image transferred to a transfer medium at a transfer position; and a flexible first guide surface. And the first base end side of the first guide surface is fixed on the upstream side in the transport direction of the transfer medium with respect to the transfer position, and the first tip end portion of the first guide surface is fixed to the transfer position. The transfer medium is extended toward the image carrier located on the upstream side in the transport direction of the transfer medium from the first base end and downstream in the transport direction of the transfer medium. And a second guide surface having flexibility, and a second base end side of the second guide surface is in the transport direction of the transfer medium with respect to the transfer position. While fixed at the upstream side A second front end portion of the second guide surface is located between the transfer position in the transport direction of the transfer medium and the first front end portion of the first guide member from the second base end portion to the transfer medium. A plane that extends toward the image carrier located on the downstream side in the transport direction and connects the second tip portion and the second base end portion is the first tip portion and the first base of the first guide member. A plane connecting the end portions and the first base end portion or the first base end portion are arranged so as to intersect on the upstream side in the transport direction of the transfer medium, and the transfer medium faces the image carrier. And a second guide member for guiding.

  According to such a configuration, the position of the first guide surface is fixed on the first base end side so that the first tip end portion can be bent. Therefore, when guiding a thin transfer medium, the thin guide of the thin transfer medium is weak, so even if the front end of the thin transfer medium comes into contact with the image carrier, the first guide surface does not bend much, As it is, a thin transfer medium can be brought into close contact with the image carrier and guided to the transfer position. Therefore, it is possible to prevent a discharge pattern from being generated due to discharge on a thin transfer medium.

  On the downstream side of the transfer direction of the transfer medium with respect to the first guide member, the second guide surface is fixed at the second base end side so that the second tip end portion can be bent. Accordingly, the trailing edge of the thin transfer medium is guided by the first leading end portion of the first guide surface and then elastically received by the second guiding surface, so that the trailing edge of the thin transfer medium flutters. It is possible to suppress the transfer failure at the rear end.

  In the case of guiding a thick transfer medium, when the front end of the thick transfer medium comes into contact with the image carrier, the first guide surface is strong in the thick transfer medium. The transfer medium is continuously bent by the first guide surface and the second guide surface by being greatly bent correspondingly to the second guide surface. Therefore, flapping of the rear end of the thick transfer medium can be suppressed, and transfer failure at the rear end can be prevented.

  The second guide surface is not parallel to the first guide surface, and the plane connecting the second tip portion and the second base end portion connects the first tip portion and the first base end portion of the first guide member. Since the connecting plane and the first base end portion or the first base end portion are arranged so as to intersect on the upstream side in the transport direction of the transfer medium, the transfer medium moves from the first guide surface to the second guide surface. When guided, it comes into contact with the second guide surface at a small angle. Then, the resistance force of the second guide surface to the transfer medium is reduced, the transfer medium strongly presses the second guide surface, and the second guide surface is greatly bent corresponding to the direction of the thick transfer medium. Can do.

  Therefore, since the thick transfer medium is guided relatively straight to the transfer position, it is possible to prevent the occurrence of transfer failure due to the bending of the thick transfer medium. In addition, since the friction when the transfer medium and the second guide surface abut can be reduced, it is possible to reduce the occurrence of vibration in the transfer medium due to the friction of the second guide surface against the transfer medium. Occurrence can also be prevented.

Therefore, transfer defects can be prevented in both the thin transfer medium and the thick transfer medium.
According to a second aspect of the present invention, in the first aspect of the present invention, at least one of the first guide member and the second guide member is formed of a film member.

According to such a configuration, since at least one of the first guide member and the second guide member is formed by the film member, a simple configuration can be obtained while ensuring flexibility. Therefore, transfer failure can be prevented with a simple configuration in both a thin transfer medium and a thick transfer medium.
According to a third aspect of the present invention, in the first or second aspect of the present invention, the second cross section is oriented in a direction parallel to the longitudinal direction of the image carrier and perpendicular to the widest surface of the first guide member. The second moment I ₁ is larger than the sectional second moment I ₂ in the direction parallel to the longitudinal direction of the image carrier and perpendicular to the widest surface of the second guide member.

According to such a configuration, since the first guide member is stronger than the second guide member, when guiding a thin transfer medium, the front end of the thin transfer medium is imaged by the first guide member having a stronger waist. It is possible to guide to a position as close as possible to the carrier. Therefore, it is possible to further prevent the occurrence of a discharge pattern due to discharge on a thin transfer medium.
Since the second guide member is weaker than the first guide member, the force with which the second guide surface presses the transfer medium toward the image carrier is relatively weak, and the friction of the transfer medium with respect to the second guide surface is relatively low. Can be small. Therefore, since the thick transfer medium is guided more straightly to the transfer position, it is possible to further prevent the occurrence of transfer failure due to the bending of the thick transfer medium. Further, it is possible to further prevent the transfer medium from being vibrated due to the friction of the second guide member against the transfer medium and causing a transfer failure.

According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, a length from the first distal end portion to the first proximal end portion of the first guide surface is the second length. The guide surface is longer than the length from the second tip end portion to the second base end portion.
According to such a configuration, since the second guide surface is disposed at a position closer to the transfer position than the first guide surface, even if the second guide surface is formed shorter than the first guide surface, the second tip portion is imaged. It can be made sufficiently close to the carrier. Therefore, the transfer medium can be smoothly guided to the transfer position.

The invention according to claim 5 is the invention according to any one of claims 1 to 4, wherein the first guide member has a Young's modulus E _{1 in} a direction parallel to a transfer direction of the transfer medium, and the image carrier. The product E ₁ I ₁ with the secondary moment of inertia I _{1 in} a direction parallel to the longitudinal direction of the body and perpendicular to the widest surface of the first guide member is 3.49 × 10 ⁻⁵ ≦ E ₁ I ₂ ≦ 1.18 × 10 ⁻³ , and the second guide member has a Young's modulus E _{2 in} a direction parallel to the transfer direction of the transfer medium, the image carrier The product E ₂ I ₂ with the cross-sectional secondary moment I _{2 in} a direction parallel to the longitudinal direction and perpendicular to the widest surface of the second guide member is 3.49 × 10 ⁻⁵ ≦ E ₂ I ₂ ≦ 1.18 × 10 ⁻³ is formed.

According to such a configuration, the product E ₁ I ₁ of the Young's modulus E ₁ of the first guide member and the secondary moment of inertia I ₁ is 3.49 × 10 ⁻⁵ ≦ E ₁ I ₁ ≦ 1.18 × 10. ^-3 , and the product E ₂ I ₂ of the Young's modulus E ₂ of the second guide member and the secondary moment of inertia I ₂ is 3.49 × 10 ⁻⁵ ≦ E ₂ I ₂ ≦ 1.18 × 10 Since it is in the range of ⁻³ , the first guide member and the second guide member can be flexed satisfactorily according to the thickness of the transfer medium. Therefore, the transfer medium can be smoothly guided to the transfer position.

The invention according to claim 6 is the invention according to any one of claims 1 to 5, wherein the first guide member has a contact angle θ between the image carrier and the transfer medium of θ <90 °. It is characterized by being provided at a position where it can be guided.
When the contact angle between the image carrier and the transfer medium is 90 °, when the transfer medium comes into contact with the image carrier, the front end becomes jammed, and when the contact angle exceeds 90 °, the transfer medium becomes a contact portion. In contrast, it is guided to the opposite side of the transfer position.

However, according to such a configuration, when the transfer medium comes into contact with the image carrier, it is guided by the first guide surface so that the contact angle θ of the image carrier with the transfer medium is θ <90 °. The transfer medium can be smoothly guided to the transfer position.
The invention according to claim 7 is the invention according to any one of claims 1 to 6, wherein the first guide member and the second guide member are formed in a predetermined shape by cutting by press working, In press working, when the surface that contacts the cutting blade first is the front surface and the opposite surface is the back surface, the surface is arranged to be the first guide surface and the second guide surface. It is characterized by that.

According to such a configuration, since the first guide surface and the second guide surface are the press working surfaces, the transfer medium is smoothly caught without being caught on the edges of the first guide surface and the second guide surface. I can guide you.
The invention according to claim 8 is the invention according to any one of claims 1 to 7, wherein at least one of the first guide member and the second guide member is in a width direction orthogonal to the transfer direction of the transfer medium. 1 is characterized by being divided.

According to such a configuration, the first guide member or the second guide member is divided and formed in the width direction perpendicular to the transfer medium conveyance direction, so that the frictional resistance during transfer medium conveyance can be reduced. And smooth guidance can be achieved.
The invention according to claim 9 is the invention according to any one of claims 1 to 7, wherein at least one of the first guide member and the second guide member is along the transport direction of the transfer medium, A cut extending from the edge of the first distal end or the second distal end to the middle toward the first proximal end or the second proximal end is formed.

According to such a configuration, the first guide member or the second guide member is attached when the first guide member or the second guide member is thin and is elongated in the width direction orthogonal to the transfer medium conveyance direction. Occasional wrinkles can be absorbed by the cuts. Therefore, the first guide member or the second guide member can be attached with high accuracy without causing wrinkles.
Further, the first leading end portion of the first guide member or the second leading end portion of the second guide member is divided into a plurality of portions in the width direction perpendicular to the transfer medium conveyance direction by the cut, so that it is narrow in the width direction. When the transfer medium is transported, the first guide member or the second guide member can be bent only at a portion in contact with the transfer medium, and the entire first guide member or the second guide member can be prevented from being bent. . Therefore, when a narrow transfer medium is continuously conveyed, it is possible to suppress the entire first guide member or the second guide member from becoming hazy, and the durability reliability of the first guide member or the second guide member can be suppressed. Can be improved.

The invention according to claim 10 is the invention according to claim 9, wherein at least one of the first guide member and the second guide member has the first base end side or the second base on the cut. It is characterized in that it is provided with an anti-division part formed at an end on the end side to prevent the division of the first guide member or the second guide member from the cut.
According to such a structure, it can prevent that a 1st guide member or a 2nd guide member tears from the edge part of a cut | interruption.

  According to an eleventh aspect of the present invention, in the invention according to any one of the first to seventh aspects, at least one of the first guide member and the second guide member extends along the transport direction of the transfer medium. A slit-shaped cut portion extending from the edge of the first tip portion or the second tip portion to the middle toward the first base end portion or the second base end portion is formed. .

According to such a configuration, the first guide member or the second guide member is attached when the first guide member or the second guide member is thin and is elongated in the width direction orthogonal to the transfer medium conveyance direction. The wrinkles that sometimes occur can be absorbed by the cuts. Therefore, the first guide member or the second guide member can be attached with high accuracy without causing wrinkles.
Further, if the notch portion has a width, when the first guide member or the second guide member is attached, the opposing portions across the notch portion of the first guide member or the second guide member are prevented from overlapping each other. be able to.

  Further, the first tip portion of the first guide member or the second tip portion of the second guide member is divided into a plurality of portions in the width direction orthogonal to the transfer medium conveyance direction by the notch portion. When the narrow transfer medium is transported, the first guide member or the second guide member can be bent only at a portion in contact with the transfer medium, and the entire first guide member or the second guide member can be prevented from being bent. it can. Therefore, when a narrow transfer medium is continuously conveyed, it is possible to suppress the entire first guide member or the second guide member from becoming hazy, and the durability reliability of the first guide member or the second guide member can be suppressed. Can be improved.

According to a twelfth aspect of the invention, in the invention of the eleventh aspect, the cut portion is formed in a substantially rectangular shape in plan view.
According to such a structure, it can prevent that a 1st guide member or a 2nd guide member tears from the edge part of a notch part.
A thirteenth aspect of the invention is characterized in that, in the invention of the eleventh aspect, the cut portion is formed in a substantially V shape in plan view.

According to such a configuration, since the portions facing each other across the notch portion of the first guide member or the second guide member are separated, the notch portion is sandwiched when attaching the first guide member or the second guide member. It is possible to further prevent the opposing portions from overlapping each other.
The invention according to claim 14 is the invention according to claim 13, wherein at least one of the first guide member and the second guide member is the first base end side of the notch or the second base. A split prevention portion is provided at an end portion on the end portion side, for preventing splitting of the first guide member or the second guide member from the cut portion.

According to such a configuration, when the cut portion is formed in a substantially V shape in plan view, the first guide member or the second guide member can be reliably prevented from tearing from the end portion of the cut portion. .
According to a fifteenth aspect of the invention, in the invention of the eleventh aspect, the cut portion is formed in a substantially U shape in plan view.

According to such a structure, it can prevent that a 1st guide member or a 2nd guide member tears from the edge part of a notch part.
According to a sixteenth aspect of the present invention, in the invention according to any one of the first to seventh aspects, a flexible guide surface is formed, and a base end side of the guide surface is located on the transfer position with respect to the transfer position. The position of the guide surface is fixed on the upstream side in the conveyance direction of the medium, and the leading end of the guide surface is upstream in the conveyance direction of the transfer medium with respect to the transfer position, and the downstream side in the conveyance direction of the transfer medium from the base end portion. The image carrier is stretched toward the image carrier, and is formed along the transfer medium transport direction so as to extend from the edge of the distal end portion to the middle toward the base end portion. A plate-like member having a plurality of tip pieces formed along a direction parallel to the longitudinal direction, wherein the first guide member and the second guide member have a plurality of the tip pieces of the plate-like member, The base end side edge It is characterized in that it is formed by being bent at a different angle around.

According to such a configuration, the first guide member and the second guide member can be easily formed using one plate-like member. Therefore, transfer failure can be prevented with a simple configuration in both a thin transfer medium and a thick transfer medium.
A seventeenth aspect of the invention is characterized in that in the invention according to any one of the first to sixteenth aspects, the image forming apparatus includes a transfer unit that is in contact with the image carrier and that forms the transfer position at the contact position. Yes.

According to such a configuration, since the transfer means is provided in the process cartridge, the relative position between the first guide member and the second guide member and the transfer position can be accurately maintained. Therefore, it is possible to further prevent the occurrence of transfer failure in both the thin transfer medium and the thick transfer medium.
According to an eighteenth aspect of the present invention, in the invention of the seventeenth aspect, an edge of the first leading end portion of the first guide surface is a contact position between the image carrier and the transfer means, and The transfer guided by the first guide member with respect to a line segment that is located upstream of the one guide member in the transport direction of the transfer medium and connects the contact positions of the two registration means that are arranged opposite to each other. The medium is arranged on a side opposite to a direction in which the medium is pressed against the first guide member.

  According to such a configuration, the transfer medium has an edge of the first leading end portion of the first guide surface with respect to a line segment connecting the contact position between the image carrier and the transfer means and the contact position between the two resist means. Is disposed on the side opposite to the direction in which the first guide member is pressed, so that the transfer medium can be guided toward the upstream side of the transfer position in the moving direction of the image carrier. Therefore, the occurrence of a discharge pattern due to the discharge of the thin transfer medium can be reliably prevented.

The invention according to claim 19 is the invention according to any one of claims 1 to 18, wherein the first guide member and the second guide member are formed of an insulating material.
According to such a configuration, since the first guide member and the second guide member are formed of an insulating material, it is possible to prevent conduction from the image carrier through the transfer medium. Therefore, reliable transfer of the developer image can be achieved.

  The invention according to claim 20 is the invention according to any one of claims 1 to 19, further comprising a housing for holding the image carrier, the first guide member, and the second guide member. The guide member is fixed to the housing on the upstream side in the transport direction of the transfer medium with respect to the transfer position, and the second guide member has the second base end portion on the transfer position. The position is fixed to the housing on the upstream side in the transport direction of the transfer medium with respect to the position.

According to such a configuration, the image carrier, the first guide member, and the second guide are fixed by fixing the first base end portion of the first guide member and the second base end portion of the second guide member to the housing. Since the member can be integrally held by the housing, a reliable arrangement of the first guide surface and the second guide surface with respect to the image carrier can be achieved.
According to a twenty-first aspect of the present invention, an image forming apparatus includes the process cartridge according to any one of the first to twentieth aspects.

According to such a configuration, since the image forming apparatus includes the process cartridge that can prevent transfer failure in both the thin transfer medium and the thick transfer medium, stable image formation can be achieved.
According to a twenty-second aspect of the present invention, in the image forming apparatus, an image carrier that carries a developer image transferred to a transfer medium at a transfer position, a developer is carried, and the developer is supplied to the image carrier. Then, the developing means for forming the developer image on the image carrier and the image carrier are brought into contact with each other, the transfer position is formed at the contact position, and the developer image is transferred to the transfer medium. A transfer means, a transfer means for transferring the transfer medium toward the transfer position, and a flexible first guide surface are formed, and a first base end side of the first guide surface is located with respect to the transfer position. In addition, the second distal end portion of the first guide surface is fixed on the upstream side in the transport direction of the transfer medium with respect to the transfer position. Located on the downstream side in the transport direction of the transfer medium from A first guide member that is extended toward the carrier and guides the transfer medium toward the image carrier and a second guide surface having flexibility are formed, and a second guide surface on the second guide surface is formed. The base end side is fixed at the upstream side in the transport direction of the transfer medium with respect to the transfer position, and the second leading end portion of the second guide surface is connected to the transfer position in the transport direction of the transfer medium and the first position. The first guide member is extended from the second base end portion toward the image carrier located on the downstream side in the transport direction of the transfer medium between the first front end portion and the second front end portion and the first front end portion. A plane connecting two base ends is a plane connecting the first tip end and the first base end of the first guide member and the first base end or the first base end with respect to the transfer. The transfer medium is arranged so as to intersect on the upstream side of the medium conveyance direction, It is characterized in that it comprises a second guide member for guiding toward the image bearing member.

  According to such a configuration, the position of the first guide surface is fixed on the first base end side so that the first tip end portion can be bent. Therefore, when guiding a thin transfer medium, the thin guide of the thin transfer medium is weak, so even if the front end of the thin transfer medium comes into contact with the image carrier, the first guide surface does not bend much, As it is, a thin transfer medium can be brought into close contact with the image carrier and guided to the transfer position. Therefore, it is possible to prevent a discharge pattern from being generated due to discharge on a thin transfer medium.

  On the downstream side of the transfer direction of the transfer medium with respect to the first guide member, the second guide surface is fixed at the second base end side so that the second tip end portion can be bent. Accordingly, the trailing edge of the thin transfer medium is guided by the first leading end portion of the first guide surface and then elastically received by the second guiding surface, so that the trailing edge of the thin transfer medium flutters. It is possible to suppress the transfer failure at the rear end.

  In the case of guiding a thick transfer medium, when the front end of the thick transfer medium comes into contact with the image carrier, the first guide surface is strong in the thick transfer medium. The transfer medium is continuously bent by the first guide surface and the second guide surface by being greatly bent correspondingly to the second guide surface. Therefore, flapping of the rear end of the thick transfer medium can be suppressed, and transfer failure at the rear end can be prevented.

  The second guide surface is not parallel to the first guide surface, and the plane connecting the second tip portion and the second base end portion connects the first tip portion and the first base end portion of the first guide member. Since the connecting plane and the first base end portion or the first base end portion are arranged so as to intersect on the upstream side in the transport direction of the transfer medium, the transfer medium moves from the first guide surface to the second guide surface. When guided, it comes into contact with the second guide surface at a small angle. Then, the resistance force of the second guide surface to the transfer medium is reduced, the transfer medium strongly presses the second guide surface, and the second guide surface is greatly bent corresponding to the direction of the thick transfer medium. Can do.

  Therefore, since the thick transfer medium is guided relatively straight to the transfer position, it is possible to prevent the occurrence of transfer failure due to the bending of the thick transfer medium. In addition, since the friction when the transfer medium and the second guide surface abut can be reduced, it is possible to reduce the occurrence of vibration in the transfer medium due to the friction of the second guide surface against the transfer medium. Occurrence can also be prevented.

Therefore, in both the thin transfer medium and the thick transfer medium, it is possible to prevent transfer failure and achieve stable image formation.
According to a twenty-third aspect, in the twenty-second aspect, at least one of the first guide member and the second guide member is formed of a film member.

According to such a configuration, since at least one of the first guide member and the second guide member is formed by the film member, a simple configuration can be obtained while ensuring flexibility. Therefore, transfer failure can be prevented with a simple configuration in both a thin transfer medium and a thick transfer medium.
According to a twenty-fourth aspect of the present invention, in the invention of the twenty-second or twenty-third aspect, the second cross section is oriented in a direction parallel to the longitudinal direction of the image carrier and perpendicular to the widest surface of the first guide member. The second moment I ₁ is larger than the sectional second moment I ₂ in the direction parallel to the longitudinal direction of the image carrier and perpendicular to the widest surface of the second guide member.

According to such a configuration, since the first guide member is stronger than the second guide member, when guiding a thin transfer medium, the front end of the thin transfer medium is moved by the stronger first guide member. It is possible to guide to a position as close as possible to the image carrier. Therefore, it is possible to further prevent the occurrence of a discharge pattern due to discharge on a thin transfer medium.
Since the second guide member is weaker than the first guide member, the force with which the second guide surface presses the transfer medium toward the image carrier is relatively weak, and the friction of the transfer medium with respect to the second guide surface is relatively low. Can be small. Therefore, since the thick transfer medium is guided more straightly to the transfer position, it is possible to further prevent the occurrence of transfer failure due to the bending of the thick transfer medium. Further, it is possible to further prevent the transfer medium from being vibrated due to the friction of the second guide member against the transfer medium and causing a transfer failure.

According to a twenty-fifth aspect of the present invention, in the invention according to any one of the twenty-second to twenty-fourth aspects, a length from the first distal end portion to the first proximal end portion of the first guide surface is the second length. The guide surface is longer than the length from the second tip end portion to the second base end portion.
According to such a configuration, since the second guide surface is disposed at a position closer to the transfer position than the first guide surface, even if the second guide surface is formed shorter than the first guide surface, the second tip portion is imaged. It can be made sufficiently close to the carrier. Therefore, the transfer medium can be smoothly guided to the transfer position.

According to a twenty-sixth aspect of the present invention, in the invention according to any one of the twenty-second to twenty-fifth aspects, the first guide member has a Young's modulus E _{1 in} a direction parallel to a transfer direction of the transfer medium, and the image carrier. The product E ₁ I ₁ with the secondary moment of inertia I _{1 in} a direction parallel to the longitudinal direction of the body and perpendicular to the widest surface of the first guide member is 3.49 × 10 ⁻⁵ ≦ E ₁ I ₂ ≦ 1.18 × 10 ⁻³ , and the second guide member has a Young's modulus E _{2 in} a direction parallel to the transfer direction of the transfer medium, the image carrier The product E ₂ I ₂ with the cross-sectional secondary moment I _{2 in} a direction parallel to the longitudinal direction and perpendicular to the widest surface of the second guide member is 3.49 × 10 ⁻⁵ ≦ E ₂ I ₂ ≦ 1.18 × 10 ⁻³ is formed.

According to such a configuration, the product E ₁ I ₁ of the Young's modulus E ₁ of the first guide member and the secondary moment of inertia I ₁ is 3.49 × 10 ⁻⁵ ≦ E ₁ I ₁ ≦ 1.18 × 10. ^-3 , and the product E ₂ I ₂ of the Young's modulus E ₂ of the second guide member and the secondary moment of inertia I ₂ is 3.49 × 10 ⁻⁵ ≦ E ₂ I ₂ ≦ 1.18 × 10 Since it is in the range of ⁻³ , the first guide member and the second guide member can be flexed satisfactorily according to the thickness of the transfer medium. Therefore, the transfer medium can be smoothly guided to the transfer position.

According to a twenty-seventh aspect of the present invention, in the invention according to any one of the twenty-second to twenty-sixth aspects, the first guide member has a contact angle θ between the image carrier and the transfer medium of θ <90 °. It is characterized by being provided at a position where it can be guided.
When the contact angle between the image carrier and the transfer medium is 90 °, when the transfer medium comes into contact with the image carrier, the front end becomes jammed, and when the contact angle exceeds 90 °, the transfer medium becomes a contact portion. In contrast, it is guided to the opposite side of the transfer position.

However, according to such a configuration, when the transfer medium comes into contact with the image carrier, it is guided by the first guide surface so that the contact angle θ of the image carrier with the transfer medium is θ <90 °. The transfer medium can be smoothly guided to the transfer position.
The invention according to claim 28 is the invention according to any one of claims 22 to 27, wherein the first guide member and the second guide member are formed into a predetermined shape by cutting by press working, In press working, when the surface that contacts the cutting blade first is the front surface and the opposite surface is the back surface, the surface is arranged to be the first guide surface and the second guide surface. It is characterized by that.

According to such a configuration, since the first guide surface and the second guide surface are the press working surfaces, the transfer medium is smoothly caught without being caught on the edges of the first guide surface and the second guide surface. I can guide you.
According to a twenty-ninth aspect of the present invention, in the invention according to any one of the twenty-second to twenty-eighth aspects, at least one of the first guide member and the second guide member is a width direction orthogonal to the transport direction of the transfer medium. 1 is characterized by being divided.

According to such a configuration, the first guide member or the second guide member is divided and formed in the width direction perpendicular to the transfer medium conveyance direction, so that the frictional resistance during transfer medium conveyance can be reduced. And smooth guidance can be achieved.
According to a thirty-third aspect of the invention, in the invention according to any one of the twenty-second to twenty-eighth aspects, at least one of the first guide member and the second guide member extends along the transport direction of the transfer medium. A cut extending from the edge of the first distal end or the second distal end to the middle toward the first proximal end or the second proximal end is formed.

According to such a configuration, the first guide member or the second guide member is attached when the first guide member or the second guide member is thin and is elongated in the width direction orthogonal to the transfer medium conveyance direction. Occasional wrinkles can be absorbed by the cuts. Therefore, the first guide member or the second guide member can be attached with high accuracy without causing wrinkles.
The invention according to claim 31 is the invention according to claim 30, wherein at least one of the first guide member and the second guide member has the first base end side or the second base on the cut. It is characterized in that it is provided with an anti-division part formed at an end on the end side to prevent the division of the first guide member or the second guide member from the cut.

According to such a structure, it can prevent that a 1st guide member or a 2nd guide member tears from the edge part of a cut | interruption.
According to a thirty-second aspect of the invention, in the invention according to any one of the twenty-second to twenty-eighth aspects, at least one of the first guide member and the second guide member extends along the conveyance direction of the transfer medium. A slit-shaped cut portion extending from the edge of the first tip portion or the second tip portion to the middle toward the first base end portion or the second base end portion is formed. .

According to such a configuration, the first guide member or the second guide member is attached when the first guide member or the second guide member is thin and is elongated in the width direction orthogonal to the transfer medium conveyance direction. The wrinkles that sometimes occur can be absorbed by the cuts. Therefore, the first guide member or the second guide member can be attached with high accuracy without causing wrinkles.
Further, if the notch portion has a width, when the first guide member or the second guide member is attached, the opposing portions across the notch portion of the first guide member or the second guide member are prevented from overlapping each other. be able to.

  Further, the first tip portion of the first guide member or the second tip portion of the second guide member is divided into a plurality of portions in the width direction orthogonal to the transfer medium conveyance direction by the notch portion. When the narrow transfer medium is transported, the first guide member or the second guide member can be bent only at a portion in contact with the transfer medium, and the entire first guide member or the second guide member can be prevented from being bent. it can. Therefore, when a narrow transfer medium is continuously conveyed, it is possible to suppress the entire first guide member or the second guide member from becoming hazy, and the durability reliability of the first guide member or the second guide member can be suppressed. Can be improved.

A thirty-third aspect of the invention is characterized in that, in the thirty-second aspect of the invention, the cut portion is formed in a substantially rectangular shape in plan view.
According to such a structure, it can prevent that a 1st guide member or a 2nd guide member tears from the edge part of a notch part.
A thirty-fourth aspect of the invention is characterized in that, in the thirty-second aspect of the invention, the cut portion is formed in a substantially V shape in plan view.

According to such a configuration, since the portions facing each other across the notch portion of the first guide member or the second guide member are separated, the notch portion is sandwiched when attaching the first guide member or the second guide member. It is possible to further prevent the opposing portions from overlapping each other.
According to a thirty-fifth aspect of the present invention, in the thirty-fourth aspect, at least one of the first guide member and the second guide member is the first base end side of the cut portion or the second base. A split prevention portion is provided at an end portion on the end portion side, for preventing splitting of the first guide member or the second guide member from the cut portion.

According to such a configuration, when the cut portion is formed in a substantially V shape in plan view, the first guide member or the second guide member can be reliably prevented from tearing from the end portion of the cut portion. .
A thirty-sixth aspect of the invention is characterized in that, in the thirty-second aspect of the invention, the cut portion is formed in a substantially U shape in a plan view.

According to such a structure, it can prevent that a 1st guide member or a 2nd guide member tears from the edge part of a notch part.
According to a thirty-seventh aspect, in the invention according to any one of the twenty-second to twenty-eighth aspects, a flexible guide surface is formed, and a base end side of the guide surface is located on the transfer position with respect to the transfer position. The position of the guide surface is fixed on the upstream side in the conveyance direction of the medium, and the leading end of the guide surface is upstream in the conveyance direction of the transfer medium with respect to the transfer position, and the downstream side in the conveyance direction of the transfer medium from the base end portion. The image carrier is stretched toward the image carrier located at a position extending along the transfer medium conveyance direction from the end edge of the tip portion toward the base end portion. A plate-like member having a plurality of tip pieces formed along a direction parallel to the longitudinal direction, wherein the first guide member and the second guide member have a plurality of the tip pieces of the plate-like member, The base end side It is characterized in that it is formed by being bent at different angles around the edges.

According to such a configuration, the first guide member and the second guide member can be easily formed using one plate-like member. Therefore, transfer failure can be prevented with a simple configuration in both a thin transfer medium and a thick transfer medium.
According to a thirty-eighth aspect of the invention, in the invention according to any one of the twenty-second to thirty-seventh aspects, an edge of the first leading end portion of the first guide surface is a contact between the image carrier and the transfer means. With respect to the line segment connecting the position and the contact position of the two registration means arranged on the upstream side in the transport direction of the transfer medium with respect to the first guide member and opposed to each other, the first guide member The transfer medium to be guided is arranged on the side opposite to the direction in which the first guide member is pressed.

  According to such a configuration, the transfer medium has an edge of the first leading end portion of the first guide surface with respect to a line segment connecting the contact position between the image carrier and the transfer means and the contact position between the two resist means. Is disposed on the side opposite to the direction in which the first guide member is pressed, so that the transfer medium can be guided toward the upstream side of the transfer position in the moving direction of the image carrier. Therefore, the occurrence of a discharge pattern due to the discharge of the thin transfer medium can be reliably prevented.

According to a thirty-ninth aspect of the present invention, in the invention according to any one of the twenty-second to thirty-eighth aspects, the first guide member and the second guide member are made of an insulating material.
According to such a configuration, since the first guide member and the second guide member are formed of an insulating material, it is possible to prevent conduction from the image carrier through the transfer medium. Therefore, reliable transfer of the developer image can be achieved.

  A forty-second aspect of the invention is the invention according to any one of the twenty-second to thirty-ninth aspects, further comprising a housing that holds the image carrier, the first guide member, and the second guide member. The guide member is fixed to the housing on the upstream side in the transport direction of the transfer medium with respect to the transfer position, and the second guide member has the second base end portion on the transfer position. The position is fixed to the housing on the upstream side in the transport direction of the transfer medium with respect to the position.

  According to such a configuration, the image carrier, the first guide member, and the second guide are fixed by fixing the first base end portion of the first guide member and the second base end portion of the second guide member to the housing. Since the member can be integrally held by the housing, a reliable arrangement of the first guide surface and the second guide surface with respect to the image carrier can be achieved.

According to the first aspect of the present invention, transfer failure can be prevented in both the thin transfer medium and the thick transfer medium.
According to the second aspect of the present invention, it is possible to prevent a transfer failure with a simple configuration in both a thin transfer medium and a thick transfer medium.
According to the third aspect of the present invention, it is possible to further prevent the occurrence of transfer failure in both the thin transfer medium and the thick transfer medium.

According to the fourth aspect of the present invention, the transfer medium can be smoothly guided to the transfer position.
According to the invention described in claim 5, the transfer medium can be smoothly guided to the transfer position.
According to the sixth aspect of the present invention, the transfer medium can be smoothly guided to the transfer position.
According to the seventh aspect of the present invention, the transfer medium can be smoothly guided without being caught on the edges of the first guide surface and the second guide surface.

According to the eighth aspect of the present invention, it is possible to reduce the frictional resistance when the transfer medium is conveyed, and to achieve smooth guidance.
According to the ninth aspect of the present invention, the first guide member or the second guide member can be attached with high accuracy without causing wrinkles. Further, it is possible to improve the durability reliability of the first guide member or the second guide member.

According to invention of Claim 10, it can prevent that a 1st guide member or a 2nd guide member tears from the edge part of a cut | interruption.
According to the eleventh aspect of the present invention, the first guide member or the second guide member can be accurately attached without causing wrinkles. Moreover, it can prevent that the part which opposes on both sides of the notch part of a 1st guide member or a 2nd guide member overlaps. Furthermore, the durability reliability of the first guide member or the second guide member can be improved.

According to invention of Claim 12, it can prevent that a 1st guide member or a 2nd guide member tears from the edge part of a notch part.
According to invention of Claim 13, when attaching a 1st guide member or a 2nd guide member, it can prevent further that the part which opposes on both sides of the notch part mutually overlaps.

According to the fourteenth aspect of the present invention, when the cut portion is formed in a substantially V shape in plan view, the first guide member or the second guide member is reliably prevented from tearing from the end portion of the cut portion. can do.
According to invention of Claim 15, it can prevent that a 1st guide member or a 2nd guide member tears from the edge part of a notch part.

According to the sixteenth aspect of the present invention, it is possible to prevent defective transfer with a simpler structure, both in a thin transfer medium and a thick transfer medium.
According to the seventeenth aspect of the present invention, it is possible to further prevent a transfer failure from occurring in both the thin transfer medium and the thick transfer medium.
According to the invention described in claim 18, the transfer medium can be guided toward the upstream side of the transfer position in the moving direction of the image carrier, and the occurrence of a discharge pattern due to the discharge of the thin transfer medium is ensured. Can be prevented.

According to the nineteenth aspect of the present invention, reliable transfer of the developer image can be achieved.
According to the twentieth aspect of the present invention, it is possible to achieve a reliable arrangement of the first guide surface and the second guide surface with respect to the image carrier.
According to the twenty-first aspect of the present invention, stable image formation can be achieved.
According to the twenty-second aspect of the present invention, it is possible to prevent a transfer defect and achieve stable image formation in both the thin transfer medium and the thick transfer medium.

According to the twenty-third aspect of the present invention, it is possible to prevent a transfer failure with a simple configuration in both a thin transfer medium and a thick transfer medium.
According to the twenty-fourth aspect of the present invention, it is possible to further prevent the occurrence of transfer failure in both the thin transfer medium and the thick transfer medium.
According to the invention of claim 25, the transfer medium can be smoothly guided to the transfer position.

According to the twenty-sixth aspect, the transfer medium can be smoothly guided to the transfer position.
According to the twenty-seventh aspect, the transfer medium can be smoothly guided to the transfer position.
According to the twenty-eighth aspect, the transfer medium can be smoothly guided without being caught on the edges of the first guide surface and the second guide surface.

According to the twenty-ninth aspect of the present invention, it is possible to reduce the frictional resistance during conveyance of the transfer medium, and to achieve smooth guidance.
According to the invention of claim 30, the first guide member or the second guide member can be attached with high accuracy without causing wrinkles. Further, it is possible to improve the durability reliability of the first guide member or the second guide member.

According to invention of Claim 31, it can prevent that a 1st guide member or a 2nd guide member tears from the edge part of a cut | interruption.
According to the invention of Claim 32, the first guide member or the second guide member can be attached with high accuracy without causing wrinkles. Moreover, it can prevent that the part which opposes on both sides of the notch part of a 1st guide member or a 2nd guide member overlaps. Furthermore, the durability reliability of the first guide member or the second guide member can be improved.

According to the invention of claim 33, it is possible to prevent the first guide member or the second guide member from being torn from the end of the cut portion.
According to the thirty-fourth aspect of the present invention, when the first guide member or the second guide member is attached, it is possible to further prevent the portions facing each other across the cut portion from overlapping each other.

According to the invention of claim 35, when the cut portion is formed in a substantially V shape in plan view, the first guide member or the second guide member is reliably prevented from tearing from the end portion of the cut portion. can do.
According to the thirty-sixth aspect of the present invention, it is possible to prevent the first guide member or the second guide member from tearing from the end portion of the cut portion.

According to the thirty-seventh aspect of the present invention, transfer failure can be prevented with a simpler configuration in both a thin transfer medium and a thick transfer medium.
According to the invention of claim 38, the transfer medium can be guided toward the upstream side of the transfer position in the moving direction of the image carrier, and the occurrence of the discharge pattern due to the discharge of the thin transfer medium is ensured. Can be prevented.

According to the thirty-ninth aspect of the present invention, reliable transfer of the developer image can be achieved.
According to the 40th aspect of the invention, it is possible to achieve a reliable arrangement of the first guide surface and the second guide surface with respect to the image carrier.

<Overall configuration of laser printer>
FIG. 1 is a side sectional view showing an embodiment of a laser printer as an image forming apparatus of the present invention.
In FIG. 1, a laser printer 1 includes a feeder unit 4 for feeding a sheet 3 as a transfer medium in a main body casing 2, an image forming unit 5 for forming an image on the fed sheet 3, and the like. It has.
<Configuration of feeder section>
The feeder unit 4 includes a paper feed tray 6 that is detachably attached to the bottom of the main casing 2, a paper pressing plate 7 provided in the paper feed tray 6, and one end side end of the paper feed tray 6. A paper feed roller 8 and a paper feed pad 9 as transport means provided above, and a downstream side in the transport direction of the paper 3 with respect to the paper feed roller 8 (hereinafter referred to as a downstream or upstream side in the transport direction of the paper 3) Paper dust removing rollers 10 and 11 provided on the downstream side or upstream side), and a registration roller 12 provided on the downstream side with respect to the paper dust removing rollers 10 and 11.

  The sheet pressing plate 7 can stack the sheets 3 in a stacked manner, and is supported at the end farther from the sheet feeding roller 8 so as to be swingable, so that the end closer to the sheet feeding roller 8 is provided. Can be moved in the vertical direction, and is biased upward by a spring (not shown) from the back side. Therefore, the sheet pressing plate 7 is swung downward against the urging force of the spring, with the end far from the sheet feeding roller 8 as a fulcrum as the amount of stacked sheets 3 increases. The paper feed roller 8 and the paper feed pad 9 are disposed to face each other, and the paper feed pad 9 is pressed toward the paper feed roller 8 by a spring 13 disposed on the back side of the paper feed pad 9. .

The uppermost sheet 3 on the sheet pressing plate 7 is pressed toward the sheet feeding roller 8 by a spring (not shown) from the back side of the sheet pressing plate 7, and the sheet feeding roller 8 and the sheet feeding are rotated by the rotation of the sheet feeding roller 8. After being sandwiched between the pads 9, the sheets are fed one by one.
The fed paper 3 is conveyed to the registration roller 12 after the paper dust is removed by the paper dust removing rollers 10 and 11. The registration roller 12 is composed of a pair of rollers facing each other, and sends the paper 3 to the image forming position after registration. Note that the image forming position is a transfer position at which the toner image on the photosensitive drum 27 is transferred to the paper 3, and is a contact position between the photosensitive drum 27 and the transfer roller 30 in this embodiment.

  The feeder unit 4 further includes a multi-purpose tray 14, a multi-purpose side feed roller 15 and a multi-purpose side feed pad 25 for feeding the sheets 3 stacked on the multi-purpose tray 14. I have. The multi-purpose-side paper feed roller 15 and the multi-purpose-side paper feed pad 25 are disposed so as to face each other, and a multi-purpose-side paper feed pad 25 is provided by a spring 26 disposed on the back side of the multi-purpose-side paper feed pad 25. Is pressed toward the multi-purpose side paper feed roller 15.

The sheets 3 stacked on the multi-purpose tray 14 are fed one by one after being sandwiched between the multi-purpose side feed roller 15 and the multi-purpose side feed pad 25 by the rotation of the multi-purpose side feed roller 15. Paper.
<Configuration of image forming unit>
The image forming unit 5 includes a scanner unit 16, a process cartridge 17, a fixing unit 18, and the like.
<Configuration of scanner unit>
The scanner unit 16 is provided at an upper portion in the main body casing 2 and includes a laser light emitting unit (not shown), a polygon mirror 19 that is rotationally driven, lenses 20 and 21, reflecting mirrors 22, 23, and 24. . The laser beam based on the image data emitted from the laser emission unit passes or reflects in the order of the polygon mirror 19, the lens 20, the reflecting mirrors 22 and 23, the lens 21, and the reflecting mirror 24, as indicated by the chain line, and the process cartridge. The surface of the 17 photosensitive drums 27 is irradiated by high-speed scanning.
<Configuration of process cartridge>
The process cartridge 17 is disposed below the scanner unit 16 and is detachably attached to the main casing 2. The process cartridge 17 includes a developing cartridge 28 and a photosensitive drum as an image carrier in the casing 51. 27, a scorotron charger 29, a conductive brush 52, and a transfer roller 30 as transfer means.

The casing 51 includes an upper casing 53 and a lower casing 54 across the passage path of the paper 3. The upper casing 53 accommodates the photosensitive drum 27, the scorotron charger 29, and the conductive brush 52, and the developing cartridge 28 is detachably mounted. Further, the lower casing 54 accommodates the transfer roller 30.
The developing cartridge 28 is detachably attached to the casing 51, and includes a developing roller 31, a layer thickness regulating blade 32, a supply roller 33, and a toner hopper 34 as developing means.

  The toner hopper 34 is partitioned as an internal space on one side of the housing 51. In the toner hopper 34, positively charged non-magnetic one-component toner is accommodated as a developer. Examples of the toner include polymerizable monomers such as styrene monomers such as styrene, and acrylic monomers such as acrylic acid, alkyl (C1 to C4) acrylate, and alkyl (C1 to C4) methacrylate. Polymerized toners obtained by copolymerization by a known polymerization method such as suspension polymerization are used. Such a polymerized toner is substantially spherical and has very good fluidity. Such a toner is blended with a colorant such as carbon black, wax, or the like, and an external additive such as silica is added to improve fluidity. The particle diameter is about 6 to 10 μm.

  The toner in the toner hopper 34 is agitated by an agitator 36 supported by a rotating shaft 35 provided at the center of the toner hopper 34 and discharged from a toner supply port 37 opened on the other side portion of the toner hopper 34. Note that a toner remaining amount detection window 38 is provided on the side wall of the toner hopper 34 and is cleaned by a cleaner 39 supported by the rotating shaft 35.

A supply roller 33 is rotatably disposed at the other side position of the toner supply port 37, and a developing roller 31 is rotatably disposed so as to face the supply roller 33. The supply roller 33 and the developing roller 31 are in contact with each other in a state where they are compressed to some extent.
The supply roller 33 has a metal roller shaft covered with a roller made of a conductive foam material.

  The developing roller 31 has a metal roller shaft covered with a roller made of a conductive rubber material. More specifically, the roller of the developing roller 31 is coated with a coating layer of urethane rubber or silicone rubber containing fluorine on the surface of a roller body made of conductive urethane rubber or silicone rubber containing carbon fine particles. Has been. A developing bias is applied to the developing roller 31 during development.

  In addition, a layer thickness regulating blade 32 is disposed in the vicinity of the developing roller 31. The layer thickness regulating blade 32 includes a pressing portion 40 having a semicircular cross section made of insulating silicone rubber at the tip of a blade body made of a metal leaf spring material. 28, the pressing portion 40 is configured to be pressed against the developing roller 31 by the elastic force of the blade body.

  The toner discharged from the toner supply port 37 is supplied to the developing roller 31 by the rotation of the supplying roller 33 in the arrow direction (counterclockwise direction). At this time, the toner is supplied between the supplying roller 33 and the developing roller 31. Positively triboelectrically charged. The toner supplied onto the developing roller 31 enters between the pressing portion 40 of the layer thickness regulating blade 32 and the developing roller 31 as the developing roller 31 rotates in the arrow direction (counterclockwise). It is carried on the developing roller 31 as a thin layer having a constant thickness.

The photosensitive drum 27 is supported by the upper housing 53 so as to be rotatable in the arrow direction (clockwise) in a state of facing the developing roller 31 at a position on the other side of the developing roller 31. The photosensitive drum 27 is formed of a positively chargeable photosensitive layer made of polycarbonate, while the drum body is grounded.
The scorotron charger 29 is disposed above the photosensitive drum 27 so as not to come into contact with the photosensitive drum 27 at a predetermined interval and is supported by the upper housing 53. The scorotron charger 29 is a positively charged scorotron charger that generates corona discharge from a charging wire such as tungsten, and is configured to uniformly charge the surface of the photosensitive drum 27 to a positive polarity. ing.

Further, the conductive brush 52 is disposed to face the photosensitive drum 27 at the other side position of the photosensitive drum 27 (side position opposite to the developing roller 31). The conductive brush 52 is fixed to the upper housing 53 in a state where the tip of the brush is in contact with the surface of the photosensitive drum 27.
The transfer roller 30 is disposed below the photosensitive drum 27 so as to face and contact the photosensitive drum 27, and is supported by the lower housing 54 so as to be rotatable in the arrow direction (counterclockwise). The transfer roller 30 is an ion conductive type transfer roller, and a metal roller shaft is covered with a roller made of a conductive rubber material. A transfer bias is applied to the transfer roller 30 by constant current control during transfer. A transfer position is formed at the contact position (nip position) between the transfer roller 30 and the photosensitive drum 27.

The surface of the photosensitive drum 27 is uniformly positively charged by the scorotron charger 29 and then exposed by high-speed scanning of the laser beam from the scanner unit 16 to form an electrostatic latent image based on the image data. .
Next, the electrostatic latent image formed on the surface of the photosensitive drum 27 when the toner carried on the developing roller 31 and positively charged comes into contact with the photosensitive drum 27 by rotation of the developing roller 31. That is, the surface of the photosensitive drum 27 that is uniformly positively charged is supplied to an exposed portion that is exposed to a laser beam and the potential is lowered, and is selectively carried to be visualized. Thus, a toner image as a developer image is formed by reversal development.

Thereafter, the photosensitive drum 27 and the transfer roller 30 are rotationally driven so as to sandwich and convey the sheet 3 between them at the transfer position, and the sheet 3 is conveyed between the photosensitive drum 27 and the transfer roller 30. As a result, the toner image carried on the surface of the photosensitive drum 27 is transferred onto the paper 3.
Note that after the transfer, the paper dust adhering to the surface of the photosensitive drum 27 due to contact with the paper 3 faces the brush of the conductive brush 52 as the surface of the photosensitive drum 27 rotates. Sometimes removed by the brush.

In the laser printer 1, the residual toner remaining on the surface of the photosensitive drum 27 after being transferred onto the sheet 3 by the transfer roller 30 is recovered by the developing roller 31 so as to recover the residual image toner by a so-called cleanerless system. I have to. If the toner remaining on the photosensitive drum 27 is collected by such a cleaner-less method, a toner cleaner device and a waste toner storage unit become unnecessary, and the device configuration can be simplified.
<Configuration of fixing unit>
The fixing unit 18 is disposed on the downstream side of the other side of the process cartridge 17, the heating roller 41, the pressing roller 42 that is disposed to face the heating roller 41 and presses the heating roller 41, and the heating roller 41 and the pressing roller A pair of transport rollers 43 provided on the downstream side of 42 are provided.

The heating roller 41 is made of a metal and includes a halogen lamp for heating, and the toner transferred onto the paper 3 in the process cartridge 17 is passed while the paper 3 passes between the heating roller 41 and the pressing roller 42. Then, the sheet 3 is transported to the paper discharge path 44 by the transport roller 43. The paper 3 sent to the paper discharge path 44 is sent to the paper discharge roller 45 and is discharged onto the paper discharge tray 46 by the paper discharge roller 45.
<Description of duplex printing mechanism>
The laser printer 1 is provided with a reverse conveyance unit 47 as a double-sided printing mechanism in order to form images on both sides of the paper 3. The reverse conveyance unit 47 includes a paper discharge roller 45, a reverse conveyance path 48, a flapper 49, and a plurality of reverse conveyance rollers 50.

The paper discharge roller 45 includes a pair of rollers and is configured to be able to switch between forward rotation and reverse rotation. As described above, the paper discharge roller 45 rotates in the forward direction when the paper 3 is discharged onto the paper discharge tray 46, but rotates in the reverse direction when the paper 3 is reversed.
The reverse conveyance path 48 is provided along the vertical direction so that the paper 3 can be conveyed from the paper discharge roller 45 to a plurality of reverse conveyance rollers 50 disposed below the image forming position. The upstream end is disposed near the paper discharge roller 45, and the downstream end is disposed near the reverse conveyance roller 50.

The flapper 49 is provided so as to be able to swing so as to face a branch portion between the paper discharge path 44 and the reverse conveyance path 48, and the paper reversed by the paper discharge roller 45 by excitation or non-excitation of a solenoid (not shown). 3 is configured to be able to be switched from the direction toward the paper discharge path 44 to the direction toward the reverse conveyance path 48.
A plurality of reverse conveyance rollers 50 are provided in a substantially horizontal direction above the paper feed tray 6, and the most upstream reverse conveyance roller 50 is disposed near the rear end of the reverse conveyance path 48, and The most downstream reverse conveying roller 50 is provided so as to be disposed below the registration roller 12.

  When images are formed on both sides of the paper 3, the reverse conveying unit 47 is operated as follows. That is, when the sheet 3 having an image formed on one side is sent from the sheet discharge path 44 to the sheet discharge roller 45 by the transport roller 43, the sheet discharge roller 45 rotates forward with the sheet 3 interposed therebetween. The paper 3 is once transported to the outside (the discharge tray 46 side), and when the majority of the paper 3 is sent to the outside and the rear end of the paper 3 is sandwiched between the paper discharge rollers 45, the paper 3 rotates forward. To stop. Next, the paper discharge roller 45 rotates in the reverse direction, and the flapper 49 switches the transport direction so that the paper 3 is transported to the reverse transport path 48, and the reverse transport path 48 in the reverse direction of the paper 3. To be transported. When the conveyance of the paper 3 is completed, the flapper 49 is switched to the original state, that is, the state where the paper 3 sent from the conveyance roller 43 is sent to the paper discharge roller 45.

Next, the sheet 3 conveyed in the reverse direction to the reverse conveyance path 48 is conveyed to the reverse conveyance roller 50, reversed from the reverse conveyance roller 50 in the upward direction, and sent to the registration roller 12. The paper 3 conveyed to the registration roller 12 is turned upside down and again sent to the image forming position after a predetermined registration, whereby an image is formed on both sides of the paper 3.
<Configuration of main parts of process cartridge>
FIG. 2 is a sectional side view of the main part of the process cartridge 17 of the laser printer 1 shown in FIG.

As shown in FIG. 2, the lower housing 54 of the process cartridge 17 is disposed on the transfer roller receiving portion 55 that receives the transfer roller 30 and on the upstream side of the transfer roller receiving portion 55, and the sheet 3 is placed on the photosensitive drum 27. A sheet guide unit 56 for guiding toward the user is provided continuously and integrally.
The transfer roller receiving portion 55 is formed to have a concave cross section along the width direction (hereinafter simply referred to as the width direction) perpendicular to the conveyance direction of the paper 3, and the transfer roller 30 is configured to receive the transfer roller having the concave shape. It is received by the section 55 and is rotatably supported in the transfer roller receiving section 55 in a state of being opposed to the photosensitive drum 27 in contact with the photosensitive drum 27 below the photosensitive drum 27.

The paper guide 56 is slightly from the rear end (the end on the upstream side in the transport direction of the paper 3; the same applies hereinafter) toward the front end (the end on the downstream side in the transport direction of the paper 3; the same applies hereinafter). The holding portion 57 that holds the first guide member 71 and the second guide member 72 and the introduction portion 59 provided with the rib member 58 are integrated integrally in a continuous manner. In preparation.
The holding portion 57 is fixed to the transfer roller receiving portion 55, and its front end portion is continuous with the rear end portion of the transfer roller receiving portion 55, and its rear end portion is continuous with the front end portion of the introducing portion 59. Is formed. A stepped portion 61 for holding the first guide member 71 is provided at the rear end of the holding portion 57. The step portion 61 is formed as a step having a substantially L-shaped cross section that is recessed downward, and the height of the step is set so that the sheet 3 conveyed from the upstream side is not caught. It is set to be equal to or greater than the thickness of 71.

  As shown in FIG. 2, the introduction portion 59 is formed such that its front end portion is continuous with the rear end portion of the holding portion 57 and its rear end portion extends in the vicinity of the side of the registration roller 12. The introduction portion 59 is provided with a rib member 58. The rib member 58 is formed for the purpose of reinforcing the lower casing 54 and reducing the frictional resistance at the time of paper conveyance. The rib member 58 has a plate shape and is erected along the vertical direction at the introduction portion 59 along the paper conveyance direction. In the upper surface of the introduction portion 59, a plurality of them are formed at predetermined intervals along the width direction of the paper 3. Further, the front end portion of each rib member 58 is provided at a height substantially equal to the rear end portion of the stepped portion 61, that is, the height of the higher surface of the high surface and the low surface forming the step. Yes.

In the process cartridge 17, the first guide member 71 and the second guide member 72 are supported by the holding portion 57.
Each of the first guide member 71 and the second guide member 72 is made of a flexible insulating material, for example, a resin such as polyethylene terephthalate, and is formed as a substantially rectangular film member by pressing.

  The first base member 73 is fixed to the step surface of the step portion 61 of the holding portion 57 so that the first guide member 71 is inclined upward from the upstream side toward the downstream side. Yes. The first guide member 71 extends from the first base end portion 73 toward the photosensitive drum 27, and the upper surface of the first guide member 71 guides the sheet 3 toward the photosensitive drum 27. The surface 71A is configured. A first front end portion 74 that is a front end portion of the first guide member 71 is close to the photosensitive drum 27 above the front end portion of the holding portion 57 on the upstream side of the transfer position. The first guide member 71 is formed to a thickness of about 0.100 to 0.200 mm, more preferably 0.125 mm.

  The second base member 75, which is the rear end of the second guide member 72, is inclined downstream from the first base end 73 of the first guide member 71 so that the second guide member 72 is inclined upward from the upstream side toward the downstream side. On the side, the position is fixed to the upper surface of the front end portion of the holding portion 57. The second guide member 72 extends from the second base end portion 75 toward the photosensitive drum 27, and the upper surface of the second guide member 72 guides the paper 3 toward the photosensitive drum 27. The surface 72A is configured. A second front end portion 76 that is a front end portion of the second guide member 72 is close to the photosensitive drum 27 between the transfer position and the first front end portion 74 of the first guide member 71. The second guide member 72 is formed to a thickness of about 0.075 to 0.125 mm, more preferably 0.100 mm.

  Each of the first guide member 71 and the second guide member 72 has its surface, that is, press processing, when the surface on the side that comes into contact with the cutting blade is the front surface and the opposite surface is the back surface in the press processing. The sloping surface is disposed so as to be an upper surface (first guide surface 71A and second guide surface 72A) in contact with the sheet 3, and the rear surface is disposed so as to be a lower surface facing the upper surface of the holding portion 57. Yes.

The edge of the first tip 74 of the first guide surface 71A and the edge of the second tip 76 of the second guide surface 72A are the contact position (transfer position) between the photosensitive drum 27 and the transfer roller 30, respectively. It is arranged on the upper side with respect to a line segment L connecting the contact positions of the two registration rollers 12 arranged to face each other.
As shown in FIG. 3A, the first guide member 71 and the second guide member 72 are continuous in the width direction orthogonal to the conveyance direction of the sheet 3, that is, in the direction parallel to the axial direction of the photosensitive drum 27. It may be formed. In addition, as shown in FIG. 3B, a plurality of first guide members 71 and second guide members 72 are provided in parallel at a predetermined interval in the width direction orthogonal to the transport direction of the paper 3. It may be divided and formed.

  The first guide member 71 can set the contact position of the front end of the sheet 3 with respect to the photosensitive drum 27 by using the bending of the first tip 74, and the contact angle θ1 between the photosensitive drum 27 and the sheet 3 is , Θ1 <90 ° so that the guide can be provided. Further, the second guide member 72 can set the contact position of the front end of the sheet 3 with respect to the photosensitive drum 27 by utilizing the bending of the second tip 76, and the contact angle between the photosensitive drum 27 and the sheet 3. θ2 is provided at a position where it can be guided so that θ2 <90 °. The inclination angles of the first guide member 71 and the second guide member 72 with respect to the holding portion 57 are set so that θ1 and θ2 satisfy θ1> θ2.

The first guide member 71 has a Young's modulus E _{1 in} a direction parallel to the conveyance direction of the paper 3, a direction parallel to the axial direction of the photosensitive drum 27, and the widest surface (upper surface or lower surface) of the first guide member 71. to the product E ₁ I ₁ the moment of inertia of I ₁ of the vertical orientation, and is formed to be in the range of _{^{3.49 × 10 -5 ≦ E 1 I}} 1 ≦ 1.18 × 10 -3 . The second guide member 72 has a Young's modulus E _{2 in} a direction parallel to the conveyance direction of the paper 3, a direction parallel to the axial direction of the photosensitive drum 27, and the widest surface (upper surface or lower surface) of the second guide member 72. to the product E ₂ I ₂ with the second moment I ₂ of vertical orientation, and is formed to be in the range of _{^{3.49 × 10 -5 ≦ E 2 I}} 2 ≦ 1.18 × 10 -3 .

The length from the first distal end portion 74 to the first base end portion 73 of the first guide surface 71A is longer than the length from the second front end portion 76 to the second base end portion 75 of the second guide surface 72A. Has been. Further, the second leading end portion 76 of the second guide surface 72A is projected from the projection surface of the first guide surface 71A in the direction (downward) in which the sheet 3 guided by the first guide surface 71A presses the first guide member 71. Is also located downstream. As described above, the first guide member 71 is formed to be thicker than the second guide member 72, so that the cross-sectional secondary moment I ₁ of the first guide member 71 is the cross-section of the second guide member 72. It is set larger than the secondary moment I ₂ .

However, the moment of inertia of I ₁ of the first guide member 71, as a way to set larger than the second moment I ₂ of the second guide member 72, as described above, the first guide member 71 The method is not limited to the method in which the second guide member 72 is formed thicker. For example, the width in the width direction of the first guide member 71 is longer than the length in the width direction of the second guide member 72. There may be.

  The inclination angle θ3 (see FIG. 5C) of the first guide member 71 with respect to the holding portion 57 is 30 to 45 °, and preferably about 30 °. The inclination angle θ4 (see FIG. 5C) of the second guide member 72 with respect to the holding portion 57 is 10 to 40 °, and preferably about 20 °. The inclination angle θ4 of the second guide member 72 with respect to the holding portion 57 is set to be smaller than the inclination angle θ3 of the first guide member 71 with respect to the holding portion 57, so that A plane 77 connecting the first base end portion 73 and a plane 78 connecting the second tip end portion 76 and the second base end portion 75 of the second guide member 72 intersect on the upstream side of the first base end portion 73. .

Next, the operation of guiding the thin paper 3 and the thick paper 3 to the transfer position in the process cartridge 17 will be described in detail. In this embodiment, when the weight per square meter of the normal thickness paper 3 (plain paper) is 75 to 105 g / m ² , such plain paper and the weight per square meter are used. A paper having a thickness of 56 to 75 g / m ² (for example, tracing paper) is described as a thin paper, and a paper having a weight per square meter of 105 to 200 g / m ² or more (for example, a postcard) is described as a thick paper. To do.
<Description of operation for guiding thin sheet to transfer position>
4 and 5 show stepwise operations for guiding the thin paper 3 to the transfer position. As shown in FIG. 4A, in the process cartridge 17, when the thin paper 3 is first conveyed, the front end of the paper 3 is downstream along the first guide surface 71 A of the first guide member 71. To the first tip 74 from the first base end 73 of the first guide surface 71A, and then guided so as to contact the upstream side of the transfer position on the photosensitive drum 27.

However, since the thin paper 3 is weak, even if the front end of the thin paper 3 abuts against the photosensitive drum 27 as shown in FIG. 4B, the first tip 74 of the first guide member 71. The sheet 3 is guided to the transfer position in a state of being in close contact with the photosensitive drum 27 without being bent so much.
Thereafter, as shown in FIG. 5A, the thin sheet 3 is in close contact with the photosensitive drum 27 from the front end to the upstream side of the transfer position, and is guided to the transfer position in close contact with the photosensitive drum 27 to the vicinity of the rear end. Is done. Therefore, the thin paper 3 does not form a gap with the photosensitive drum 27 on the upstream side of the transfer position, and it is possible to suppress the occurrence of discharge between them. As a result, it is possible to prevent the thin paper 3 from appearing a spot-like discharge pattern that penetrates the paper 3 called “Tsukinuke”.

While the thin sheet 3 is guided from the front end to the rear end by the first guide member 71, the lower surface of the sheet 3 is slidably contacted with the second guide surface 72A of the second guide member 72 and guided to the transfer position. Alternatively, the second guide member 72 may be guided to the transfer position without sliding on the second guide surface 72A.
The second leading end portion 76 of the second guide surface 72A is downstream of the projection surface of the first guide surface 71A in the direction (downward) in which the paper 3 guided by the first guide surface 71A presses the first guide member 71. Located on the side. Therefore, when the rear end of the thin paper 3 passes through the first leading end portion 74 of the first guide surface 71A, as shown in FIGS. 5B and 5C, the rear end of the thin paper 3 is The first guide surface 71A falls downward from the first tip 74, is elastically received by the second tip 76 of the second guide surface 72A, and is guided to the transfer position. Therefore, flapping of the rear end of the thin paper 3 can be suppressed, and transfer failure at the rear end can be prevented.
<Description of operation for guiding thick paper to transfer position>
6 and 7 show the step-by-step operation for guiding the thick paper 3 to the transfer position. As shown in FIG. 6A, in the process cartridge 17, when the thick sheet 3 is first conveyed, the front end of the sheet 3 is downstream along the first guide surface 71A of the first guide member 71. To the first tip 74 from the first base end 73 of the first guide surface 71A, and then guided so as to contact the upstream side of the transfer position on the photosensitive drum 27.

  However, since the thick paper 3 is stiff, as shown in FIG. 6B, when the front end of the thick paper 3 comes into contact with the photosensitive drum 27, the second guide member 72 is moved to the front end of the paper 3. Is thickly deformed corresponding to the downward direction toward the contact, and the thick sheet 3 has the first guide member 71 and the second guide member 72 in a state where the first guide member 71 and the second guide member 72 are in contact with each other or close to each other. To guide the transfer position.

  As shown in FIG. 2, the second guide member 72 has a plane 78 connecting the second distal end portion 76 and the second proximal end portion 75 so that the first distal end portion 74 and the first proximal portion of the first guide member 71 are connected. Since the plane 77 connecting the end portion 73 and the first base end portion 73 are arranged so as to intersect with each other on the upstream side, when the sheet 3 is guided from the first guide surface 71A to the second guide surface 72A, the first Compared to the case where the two guide members 72 are arranged in parallel to the first guide member 71, the sheet 3 comes into contact with the second guide surface 72A at a small angle. Then, the resistance force of the second guide surface 72A to the paper 3 is reduced, the paper 3 strongly presses the second guide surface 72A, and the second guide surface 72A is increased corresponding to the direction in which the thick paper 3 is directed. Can be bent.

  Therefore, as shown in FIG. 7A, since the thick paper 3 is guided relatively straight to the transfer position, it is possible to prevent the occurrence of transfer failure due to the thick paper 3 being bent. Further, since the friction when the sheet 3 and the second guide surface 72A come into contact with each other can be reduced, it is possible to reduce the occurrence of vibration in the sheet 3 due to the friction of the second guide surface 72A against the sheet 3, and the transfer caused by the vibration. It is also possible to prevent the occurrence of defects.

Since the thick paper 3 is less likely to generate discharge even if there is a gap between the thick paper 3 and the photosensitive drum 27, even when the thick paper 3 is guided relatively straight to the transfer position, It is difficult for a discharge pattern due to discharge to occur.
After the thick sheet 3 is guided to the transfer position to the vicinity of the rear end as shown in FIG. 7A, the first guide member 71 is greatly bent and comes into contact with or close to the second guide member 72. Therefore, it is continuously received from the first tip portion 74 of the first guide surface 71A to the second tip portion 76 of the second guide surface 72A, and is guided to the transfer position as shown in FIG. The Therefore, flapping of the trailing edge of the thick paper 3 can be suppressed, and transfer failure at the trailing edge can be prevented.

  As described above, the process cartridge 17 has a simple configuration using the first guide member 71 and the second guide member 72 formed of a film member that ensures flexibility, so that the thin paper 3 and the thick paper 3 can be used. In either case, transfer defects can be prevented. A stable image formation can be achieved by forming an image on a sheet with the laser printer 1 having such a process cartridge 17.

However, at least one of the first guide member 71 and the second guide member 72 may be formed of a flexible member other than a film member such as a sponge, for example.
Since the sectional secondary moment I ₁ of the first guide member 71 is set larger than the sectional secondary moment I ₂ of the second guide member 72, the first guide member 71 is lower than the second guide member 72. Is strong. Therefore, when guiding the thin paper 3, the front end of the thin paper 3 can be guided to a position as close as possible to the photosensitive drum 27 by the stiff first guide member 71. Therefore, it is possible to further prevent the discharge pattern due to the discharge from occurring on the thin paper 3.

  Since the second guide member 72 is weaker than the first guide member 71, the force with which the second guide surface 72A presses the sheet 3 toward the photosensitive drum 27 is relatively weak, and the sheet 3 against the second guide surface 72A is relatively weak. The friction can be made relatively small. Therefore, since the thick paper 3 is guided more straightly to the transfer position, it is possible to further prevent the occurrence of transfer failure due to the thick paper 3 being bent. Further, it is possible to further prevent the transfer failure due to the vibration of the sheet 3 due to the friction of the second guide member 72 against the sheet 3.

  The length from the first distal end portion 74 to the first base end portion 73 of the first guide surface 71A is longer than the length from the second front end portion 76 to the second base end portion 75 of the second guide surface 72A. However, since the second guide surface 72A is disposed at a position closer to the transfer position than the first guide surface 71A, even if the second guide surface 72A is formed shorter than the first guide surface 71A, the second tip portion 76 thereof. Can be made sufficiently close to the photosensitive drum 27. Therefore, the paper 3 can be smoothly guided to the transfer position.

The product E ₁ I ₁ of the Young's modulus E ₁ of the first guide member 71 and the secondary moment of inertia I ₁ is in the range of 3.49 × 10 ⁻⁵ ≦ E ₁ I ₁ ≦ 1.18 × 10 ⁻³ . The product E ₂ I ₂ of the Young's modulus E ₂ of the second guide member 72 and the secondary moment of inertia I ₂ is 3.49 × 10 ⁻⁵ ≦ E ₂ I ₂ ≦ 1.18 × 10 ⁻³ . Since it is within the range, the first guide member 71 and the second guide member 72 can be flexed satisfactorily according to the thickness of the paper 3. Therefore, the paper 3 can be smoothly guided to the transfer position.

  If the contact angle θ1 between the sheet 3 guided by the first guide member 71 and the photosensitive drum 27 is 90 °, when the sheet 3 comes into contact with the photosensitive drum 27, the front end thereof is jammed, and the contact angle θ1 is If the angle exceeds 90 °, the contact portion is guided to the opposite side of the transfer position. However, the first guide member 71 is provided at a position where the contact angle θ1 between the sheet 3 and the photosensitive drum 27 can be guided such that θ1 <90 °. Therefore, when the sheet 3 comes into contact with the photosensitive drum 27, the contact angle θ1 between the sheet 3 and the photosensitive drum 27 is guided to be less than 90 °, so that the sheet 3 is smoothly guided toward the transfer position. be able to.

In addition, since the first guide surface 71A and the second guide surface 72A are the drafting surfaces, the paper 3 is smoothly guided without being caught on the edges of the first guide surface 71A and the second guide surface 72A. can do.
That is, when the first guide member 71 and the second guide member 72 are formed by press working, as shown in FIG. 8, the end portion 65 of the back surface 64 opposite to the front surface 63 is formed at the time of press molding. It is cut by the shearing force of the cutting blade to form a protrusion (burr). Then, when such a back surface 64 is arranged as an upper surface (first guide surface 71A and second guide surface 72A) in contact with the sheet 3, the sheet 3 is caught on the protruding end 65 (burr), and smooth. Can not be transported.

  However, in the process cartridge 17, as described above, the front surface 63 that is the dip surface of the press working is the upper surface, the rear surface 64 opposite to the upper surface is the lower surface, and the lower surface faces the upper surface of the holding portion 57. In other words, since the back surface 64 is arranged so as not to contact the paper 3, the paper 3 can be smoothly guided without being caught on the edge 65 of the back surface 64.

In addition, since the transfer roller 30 is provided in the process cartridge 17, the relative position between the first guide member 71 and the second guide member 72 and the transfer position can be accurately maintained. Therefore, it is possible to further prevent the transfer failure from occurring in both the thin paper 3 and the thick paper 3.
The edge of the first leading end portion 74 of the first guide surface 71A is arranged on the upper side with respect to the line segment L connecting the contact position between the photosensitive drum 27 and the transfer roller 30 and the contact position between the two registration rollers 12. Therefore, the sheet 3 can be guided toward the upstream side of the transfer position in the rotation direction of the photosensitive drum 27. Therefore, the occurrence of a discharge pattern due to the discharge of the thin paper 3 can be reliably prevented.

Since the first guide member 71 and the second guide member 72 are formed of an insulating material such as a resin film, it is possible to prevent conduction from the photosensitive drum 27 through the paper 3. Therefore, reliable transfer of the toner image can be achieved.
Further, by fixing the position of the first base end portion 73 of the first guide member 71 and the second base end portion 75 of the second guide member 72 to the casing 51, the photosensitive drum 27, the first guide member 71, and the second guide end portion 72 are fixed. Since the guide member 72 can be integrally held by the casing 51, a reliable arrangement of the first guide surface 71A and the second guide surface 72A with respect to the photosensitive drum 27 can be achieved.

As shown in FIG. 3B described above, when the first guide member 71 and the second guide member 72 are formed separately in the width direction, the first guide member 71 and the second guide member 72 Frictional resistance during paper conveyance can be reduced, and smooth guidance can be achieved.
<Modification>
FIG. 9 is a schematic plan view showing another configuration of the first guide member 71 and the second guide member 72. The first guide member 71 and the second guide member 72 shown in FIG. 9 are spaced apart from the first tip portion 74 and the second tip portion 76 at substantially equal intervals in the width direction perpendicular to the transport direction of the sheet 3, respectively. A plurality of cuts 66 are formed in parallel. Each cut 66 extends from the edge of the first tip 74 or the edge of the second tip 76 along the conveyance direction of the sheet 3 to the first base 73 or the second base 75 (see FIG. 2). ) To the middle of the road.

By forming such a plurality of cuts 66, the first guide member 71 and the second guide member 72 are held by the holding portion 57 (FIG. 2) without causing wrinkles in the first guide member 71 and the second guide member 72. Can be attached with high accuracy.
That is, since the first guide member 71 and the second guide member 72 are thin and are formed to be elongated in the width direction, the first guide member 71 and the second guide member 72 with respect to the holding portion 57. If both end portions in the width direction are aligned and attached (attached), the positions of the center portions in the width direction of the first guide member 71 and the second guide member 72 are displaced. Moreover, when the width direction one end part of the 1st guide member 71 and the 2nd guide member 72 is aligned with respect to the holding | maintenance part 57, it attaches in order toward the width direction other end part from the width direction one end part. Although it is possible to avoid the displacement of the central portion in the width direction of the first guide member 71 and the second guide member 72, the first guide member 71 and the second guide member 72 are prone to wrinkles. In the first guide member 71 and the second guide member 72 of this embodiment, since a plurality of cuts 66 are formed, the first guide member 71 and the second guide member 72 are arranged at one end in the width direction with respect to the holding portion 57. The wrinkles that are generated when attaching in order can be absorbed by each cut 66. Therefore, the first guide member 71 and the second guide member 72 can be accurately attached to the holding portion 57 without causing wrinkles in the first guide member 71 and the second guide member 72.

  In addition, since the first tip portion 74 of the first guide member 71 and the second tip portion 76 of the second guide member 72 are divided into a plurality of portions in the width direction by the cuts 66, the width of the sheet 3 narrow in the width direction is reduced. At the time of conveyance, the first guide member 71 and the second guide member 72 can be bent only at a portion in contact with the paper 3. Therefore, when the narrow paper 3 is continuously conveyed, it is possible to prevent the first guide member 71 and the second guide member 72 from becoming hazy due to the bending of the portion in contact with the paper 3. The durability reliability of the first guide member 71 and the second guide member 72 can be improved.

  Note that only one (one) cut line 66 may be formed in the first tip portion 74 of the first guide member 71 or the second tip portion 76 of the second guide member 72. Further, when a plurality of cuts 66 are formed, the intervals between the plurality of cuts 66 do not necessarily have to be formed at substantially equal intervals in the width direction, and may be formed at different intervals. Good. For example, in accordance with various sizes of the paper 3 that can be used in the laser printer 1, the first guide member 71 has a first tip 74 or a second tip 76 of the second guide member 72 on the first guide member 71. Alternatively, the cuts 66 may be formed at positions facing both edges in the width direction of the paper 3 of various sizes conveyed on the second guide member 72. In this case, when the paper 3 is conveyed, the first guide member 71 or the second guide member 72 can be bent more reliably only at the portion in contact with the paper 3.

FIG. 10 is a schematic plan view showing another configuration of the first guide member 71 and the second guide member 72. 10, parts corresponding to the respective parts shown in FIG. 9 are given the same reference numerals as those in FIG. 9, and detailed description thereof will be omitted below.
In the first guide member 71 and the second guide member 72 shown in FIG. 10, the split preventing portion 67 is provided at the end of each cut 66 on the first base end portion 73 side or the second base end portion 75 side (see FIG. 2). Is formed. The split preventing portion 67 is formed as a hole (space) having a substantially circular shape in a plan view at the end of each cut 66, and the first guide member 71 and the second guide member 72 are arranged along the conveyance direction of the sheet 3. It penetrates from the upper surface in contact with the paper 3 to the lower surface on the opposite side.

Thereby, it is possible to prevent the first guide member 71 and the second guide member 72 from tearing from the end portions of the cuts 66.
FIGS. 11A to 11D are schematic plan views showing other configurations of the first guide member 71 and the second guide member 72. In each of the first guide member 71 and the second guide member 72 shown in FIGS. 11A to 11D, a plurality of slit-shaped cut portions 68 are formed in the first tip portion 74 and the second tip portion 76, respectively. In the width direction perpendicular to the conveyance direction of the paper 3, the paper 3 is formed in parallel at substantially equal intervals. Each notch 68 extends from the edge of the first tip 74 or the edge of the second tip 76 along the conveyance direction of the sheet 3 from the first base 73 or the second base 75 (FIG. 2). It extends halfway to (see).

  By forming such a plurality of notches 68, the first guide member 71 and the second guide member 72 are not wrinkled as in the case where the cut 66 is formed. The second guide member 72 can be attached to the holding portion 57 with high accuracy. Further, when the narrow paper 3 is continuously conveyed, it is possible to prevent the first guide member 71 and the second guide member 72 from becoming hazy due to the bending of the portion in contact with the paper 3. The durability reliability of the first guide member 71 and the second guide member 72 can be improved.

In addition, unlike the cut 66, the cut portion 68 has a width in a direction perpendicular to the conveyance direction of the sheet 3, and therefore when the first guide member 71 and the second guide member 72 are attached to the holding portion 57. Further, it is possible to prevent overlapping portions of the first guide member 71 and the second guide member 72 that face each other with the notch 68 therebetween.
Each cut portion 68 may be formed in a substantially rectangular shape in plan view as shown in FIG. 11A, or in a substantially V shape in plan view as shown in FIG. As shown in FIG. 11C, it may be formed in a substantially U shape in plan view.

If each notch 68 is formed in a substantially rectangular shape in plan view or a substantially U-shape in plan view, the first guide member 71 and the second guide member 72 are arranged on the first base end 73 side of each notch 68 or It is possible to prevent tearing from the end portion on the second base end portion 75 side (see FIG. 2).
Further, if each notch 68 is formed in a substantially V shape in plan view, the portion of the first guide member 71 and the second guide member 72 facing each other with the notch 68 sandwiched from the rear end side to the front end side. Therefore, when the first guide member 71 and the second guide member 72 are attached to the holding portion 57, the portions facing each other with the notch 68 between the first guide member 71 and the second guide member 72 overlap each other. Can be further prevented.

  In this case, as shown in FIG. 11 (d), it is more preferable that the split preventing portion 69 is formed at the end portion of the cut portion 68 on the first base end portion 73 side or the second base end portion 75 side. . The split prevention portion 69 is formed as a hole (space) having a substantially circular shape in plan view at the end of each notch portion 68, and the first guide member 71 and the second guide member 72 are arranged along the conveyance direction of the sheet 3. It penetrates from the upper surface in contact with the paper 3 to the lower surface on the opposite side. By forming such a split prevention part 69, it is possible to prevent the first guide member 71 and the second guide member 72 from tearing from the deepest part of each cut part 68.

  Further, only one (one) cut portion 68 may be formed in the first tip portion 74 of the first guide member 71 or the second tip portion 76 of the second guide member 72. Further, when the plurality of cut portions 68 are formed, the intervals between the plurality of cut portions 68 do not necessarily have to be formed at substantially equal intervals in the width direction, and are formed at different intervals. May be. For example, in accordance with various sizes of the paper 3 that can be used in the laser printer 1, the first guide member 71 has a first tip 74 or a second tip 76 of the second guide member 72 on the first guide member 71. Alternatively, the cut portions 68 may be formed at positions facing both ends in the width direction of the paper 3 of various sizes conveyed on the second guide member 72. In this case, when the paper 3 is conveyed, the first guide member 71 or the second guide member 72 can be bent more reliably only at the portion in contact with the paper 3.

FIG. 12 is a perspective view showing another configuration of the first guide member 71 and the second guide member 72.
In FIG. 12, the first guide member 71 and the second guide member 72 are made of an insulating material having flexibility, for example, a resin such as polyethylene terephthalate, and formed as a substantially rectangular film member by pressing. A single plate member 80 is used.
The plate-like member 80 has a lower surface on the base end portion 83 side, which is a rear end portion in the short direction, in the longitudinal direction along the width direction, and the upper surface rear end portion of the holding portion 57 shown in FIG. The position is fixed along. A front end portion 84 which is a front end portion in the short direction of the plate member 80 is disposed so as to be close to the photosensitive drum 27 on the upstream side with respect to the transfer position.

A plurality of cuts 81 extending along the width direction from the edge of the plate member 80 to the middle of the base end portion 83 are formed along the width direction. A plurality of tip pieces 82 are formed.
The plurality of tip pieces 82 are formed such that the lengths from the rear end portion to the front end portion are alternately different along the width direction. The tip piece 82 having a shorter length from the front end portion (first tip portion 74) to the rear end portion (first base end portion 73) constitutes the first guide member 71, and the front end portion (second end). A distal end piece 82 having a longer length from the distal end portion 76) to the rear end portion (second proximal end portion 75) constitutes the second guide member 72. The upper surface of the first guide member 71 constitutes a first guide surface 71A, and the upper surface of the second guide member 72 constitutes a second guide surface 72A. Therefore, the first guide member 71 and the second guide member 72 can be easily formed using one plate-like member 80.

  The first guide member 71 and the second guide member 72 are in the direction (upward) opposite to the direction in which the sheet 3 presses the first guide member 71 and the second guide member 72 around the rear end edge of the cut 81. It is bent at different angles. The inclination angle of the first guide member 71 with respect to the direction in which the base end portion 83 of the plate-like member 80 extends in the short direction, that is, the inclination angle θ3 of the first guide member 71 with respect to the holding portion 57 is 30 to 45 °, more preferably. It is about 30 °. The inclination angle of the second guide member 72 with respect to the direction in which the base end portion 83 of the plate-like member 80 extends in the short direction, that is, the inclination angle θ4 of the second guide member 72 with respect to the holding portion 57 is 10 to 40 °, more preferably. It is about 20 ° and is smaller than the inclination angle θ3 of the first guide member 71 with respect to the holding portion 57.

  As described above, the inclination angle θ4 of the second guide member 72 with respect to the holding portion 57 is set to be smaller than the inclination angle θ3 of the first guide member 71 with respect to the holding portion 57, whereby the first tip of the first guide member 71 is set. The plane connecting the portion 74 and the first base end portion 73 and the plane connecting the second tip end portion 76 and the second base end portion 75 of the second guide member 72 are behind the first base end portion 73, that is, the cut 81. It intersects on a straight line 85 connecting the end side edges. Therefore, transfer failure can be prevented in both the thin paper 3 and the thick paper 3 by the same action as the first guide member 71 and the second guide member 72 according to the above-described embodiment.

FIG. 13 is a side view showing another configuration of the first guide member 71 and the second guide member 72.
In FIG. 13, the first guide member 71 and the second guide member 72 are integrally formed by a flexible member 70 such as a sponge, for example. That is, the flexible member 70 is disposed such that the lower surface thereof faces the upper surface of the holding portion 57 shown in FIG. 2, and the first guide surface 71A and the second guide surface 72A have different inclination angles on the upper surface. It is formed with. A portion of the flexible member 70 that forms the first guide surface 71A constitutes the first guide member 71, and a portion that forms the second guide surface 72A constitutes the second guide member 72.

  A plane 77 connecting the first tip 74 and the first base end 73 of the first guide surface 71A and a plane 78 connecting the second tip 76 and the second base 75 of the second guide surface 72A are It intersects on the upstream side of the one base end portion 73. Therefore, transfer failure can be prevented in both the thin paper 3 and the thick paper 3 by the same action as the first guide member 71 and the second guide member 72 according to the above-described embodiment.

In the embodiment and the modified example, the transfer roller 30, the first guide member 71, and the second guide member 72 are provided in the process cartridge 17. However, the present invention is not limited to this, and the main body casing 2 side is not limited thereto. May be provided.
Also in the above-described modification, the same physical properties (cross-sectional secondary moment, length, product of Young's modulus and cross-sectional secondary moment, material, etc.) and arrangement (paper) within the scope of the claims It is also possible to carry out by combining the contact angle between the photosensitive drum and the photosensitive drum, the direction of the draft surface by pressing, and the like.

1 is a side sectional view showing an embodiment of a laser printer as an image forming apparatus of the present invention. FIG. 2 is a side sectional view of a main part of a process cartridge of the laser printer shown in FIG. 1. It is a schematic plan view of a 1st guide member and a 2nd guide member, Comprising: (a) is the aspect with which the 1st guide member and the 2nd guide member are continuing in the width direction, (b) is the 1st guide member. And the 2nd guide member is the aspect divided | segmented in the width direction. It is a schematic sectional side view which shows the operation | movement which guides a thin paper to a transfer position in steps, (a) is the aspect which the front end of the thin paper reached the 1st front-end | tip part of a 1st guide surface, (b) is The front end portion of the thin paper is in close contact with the photosensitive drum. FIG. 4 is a schematic side cross-sectional view showing an operation for guiding a thin sheet to a transfer position step by step, wherein (a) shows a state in which the rear end portion of the thin sheet is in close contact with the photosensitive drum, and (b) shows a state after the thin sheet. A mode in which the end is elastically received by the second leading end portion of the second guide surface, and (c) is a mode in which the rear end portion of the thin sheet is guided to the transfer position. It is a schematic sectional side view which shows the operation | movement which guides a thick paper to a transfer position in steps, (a) is the aspect which the front end of the thick paper reached the 1st front-end | tip part of a 1st guide surface, (b) is This is a mode in which the front end of a thick sheet is in contact with the photosensitive drum. FIG. 5 is a schematic side cross-sectional view showing an operation for guiding a thick sheet to a transfer position step by step, wherein (a) shows a state in which the rear end of the thick sheet is in contact with the photosensitive drum, and (b) shows a thick sheet. In this mode, the rear end is guided to the transfer position. It is principal part side sectional drawing of the front-end part of a 1st guide member and a 2nd guide member. It is a schematic plan view which shows the other structure (mode in which a cut | interruption is formed) of the 1st guide member and the 2nd guide member. It is a schematic top view which shows the other structure (a mode in which the division | segmentation prevention part is formed in the edge part of a cut) of the 1st guide member and the 2nd guide member. It is a schematic plan view which shows the other structure (aspect in which a notch part is formed) of the 1st guide member and the 2nd guide member, (a) is an aspect in which a notch part is formed in planar view substantially rectangular shape, ( b) is an aspect formed in a substantially V shape in a plan view, (c) is an aspect formed in a substantially U shape in a plan view, and (d) is an end portion of a cut portion that is substantially V-shaped in a plan view. This is a mode in which a division preventing portion is formed. It is a perspective view which shows the other structure (The aspect in which a 1st guide member and a 2nd guide member are integrally comprised from a plate-shaped member) the 1st guide member 71 and the 2nd guide member 72. FIG. It is a side view which shows the other structure (The aspect with which the 1st guide member and the 2nd guide member are integrally comprised from a sponge member) the 1st guide member 71 and the 2nd guide member 72. FIG. FIG. 9 is a schematic side cross-sectional view showing a state of conveyance of a sheet in a conventional process cartridge, in which (a) is a mode in which the front end of the sheet reaches the leading end of the guide member, and (b) is a front end of the sheet. This is a mode in which the portion is in close contact with the photosensitive drum. FIG. 7 is a schematic side cross-sectional view showing a paper conveyance state in a conventional process cartridge in a stepwise manner, where (a) shows a state in which the rear end portion of the paper is in close contact with the photosensitive drum, and (b) shows a rear end of the paper. (C) is a mode in which the rear end portion of the sheet is guided to the transfer position.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser printer 3 Paper 17 Process cartridge 27 Photosensitive drum 30 Transfer roller 66 Break 67 Split prevention part 68 Notch part 69 Split prevention part 71 1st guide member 71A 1st guide surface 72 2nd guide member 72A 2nd guide surface 73 1st Base end portion 74 First tip end portion 75 Second base end portion 76 Second tip end portion 77 Plane plane connecting the first tip end portion and the first base end portion 78 Plane plane connecting the second tip end portion and the second base end portion 80 Plate shape Member 81 Cut 82 Tip piece 83 Base end 84 Tip

Claims (40)

An image carrier that carries a developer image transferred to a transfer medium at a transfer position;
A flexible first guide surface is formed, and the first base end side of the first guide surface is fixed on the upstream side of the transfer medium with respect to the transfer position, and the first guide surface is fixed. A first front end of the surface extends toward the image carrier located upstream of the transfer position in the transport direction of the transfer medium and from the first base end downstream of the transfer medium in the transport direction. A first guide member for guiding the transfer medium toward the image carrier;
A flexible second guide surface is formed, and a second base end side of the second guide surface is fixed on the upstream side of the transfer medium with respect to the transfer position, and the second guide surface is fixed. A second front end portion of the surface between the transfer position in the transport direction of the transfer medium and the first front end portion of the first guide member, and a downstream side in the transport direction of the transfer medium from the second base end portion. A plane that extends toward the image carrier located at a position and connects the second distal end portion and the second proximal end portion connects the first distal end portion and the first proximal end portion of the first guide member. A plane is arranged to intersect the first base end portion or the first base end portion on the upstream side in the transport direction of the transfer medium, and for guiding the transfer medium toward the image carrier. A process cart comprising a second guide member Tsu di.   2. The process cartridge according to claim 1, wherein at least one of the first guide member and the second guide member is formed of a film member. A cross-sectional secondary moment I _{1 in} a direction parallel to the longitudinal direction of the image carrier and perpendicular to the widest surface of the first guide member is in a direction parallel to the longitudinal direction of the image carrier; and 3. The process cartridge according to claim 1, wherein the process second moment is greater than a cross-sectional secondary moment I _{2 in} a direction perpendicular to the widest surface of the second guide member.   The length of the first guide surface from the first tip portion to the first base end portion is longer than the length of the second guide surface from the second tip portion to the second base end portion. The process cartridge according to any one of claims 1 to 3, wherein The first guide member has a Young's modulus E _{1 in} a direction parallel to the transfer direction of the transfer medium, a direction parallel to the longitudinal direction of the image carrier, and perpendicular to the widest surface of the first guide member. The product E ₁ I ₁ with the cross-sectional secondary moment I _{1 in the} direction
3.49 × 10 ⁻⁵ ≦ E ₁ I ₁ ≦ 1.18 × 10 ⁻³
The second guide member has a Young's modulus E _{2 in} a direction parallel to the transfer direction of the transfer medium, a direction parallel to the longitudinal direction of the image carrier, and perpendicular to the widest surface of the second guide member. The product E ₂ I ₂ with the _second moment of inertia I ₂
5. The process cartridge according to claim 1, wherein the process cartridge is formed so as to satisfy a range of 3.49 × 10 ⁻⁵ ≦ E ₂ I ₂ ≦ 1.18 × 10 ⁻³ .   6. The first guide member according to claim 1, wherein the first guide member is provided at a position where the first guide member can be guided so that a contact angle θ between the image carrier and the transfer medium is θ <90 °. One of the process cartridges.   The first guide member and the second guide member are formed into a predetermined shape by cutting by pressing, and the surface that contacts the cutting blade in the pressing process is the front surface, and the opposite surface is the back surface. 7. The process cartridge according to claim 1, wherein the process cartridge is arranged so that the surface becomes the first guide surface and the second guide surface.   8. The device according to claim 1, wherein at least one of the first guide member and the second guide member is divided and formed in a width direction orthogonal to a transfer direction of the transfer medium. Process cartridge according to.   At least one of the first guide member and the second guide member extends from the edge of the first tip portion or the second tip portion along the transfer direction of the transfer medium from the first base end portion or The process cartridge according to any one of claims 1 to 7, wherein a cut extending to the middle of the second base end is formed.   At least one of the first guide member and the second guide member is formed on the first base end side or the second base end side end of the cut, and the first guide from the cut The process cartridge according to claim 9, further comprising a split prevention unit for preventing splitting of the member or the second guide member.   At least one of the first guide member and the second guide member extends from the edge of the first tip portion or the second tip portion along the transfer direction of the transfer medium from the first base end portion or The process cartridge according to any one of claims 1 to 7, wherein a slit-like cut-out portion extending partway toward the second base end portion is formed.   The process cartridge according to claim 11, wherein the cut portion is formed in a substantially rectangular shape in plan view.   The process cartridge according to claim 11, wherein the cut portion is formed in a substantially V shape in plan view.   At least one of the first guide member and the second guide member is formed at an end of the cut portion on the first base end side or the second base end portion side, and the first guide member and the second guide member are provided with the first guide member from the cut portion. The process cartridge according to claim 13, further comprising a split prevention unit for preventing splitting of the guide member or the second guide member.   The process cartridge according to claim 11, wherein the cut portion is formed in a substantially U shape in a plan view. A guide surface having flexibility is formed, and a base end side of the guide surface is fixed on the upstream side in the transport direction of the transfer medium with respect to the transfer position, and a front end portion of the guide surface is fixed to the transfer surface. It is extended toward the image carrier located on the upstream side in the conveyance direction of the transfer medium with respect to the position and from the base end portion on the downstream side in the conveyance direction of the transfer medium, and along the conveyance direction of the transfer medium. A plate-like member in which a plurality of tip pieces are formed along a direction parallel to the longitudinal direction of the image carrier by forming a cut extending from the edge of the tip portion to the middle toward the base end portion;
The first guide member and the second guide member are formed by bending the plurality of tip pieces of the plate-like member at different angles around the base end side edge of the cut. The process cartridge according to claim 1, wherein:   17. The process cartridge according to claim 1, further comprising a transfer unit that is brought into contact with the image carrier and that forms the transfer position at the contact position.   An edge of the first leading end portion of the first guide surface is disposed at a contact position between the image carrier and the transfer unit, upstream of the first guide member in the transport direction of the transfer medium, and The transfer medium guided by the first guide member is arranged on the opposite side to the direction in which the first guide member is pressed with respect to a line segment connecting the contact positions of the two resist means arranged opposite to each other. The process cartridge according to claim 17, wherein   The process cartridge according to claim 1, wherein the first guide member and the second guide member are formed of an insulating material. A housing for holding the image carrier, the first guide member, and the second guide member;
The first guide member is fixed to the housing at the first base end portion on the upstream side in the transport direction of the transfer medium with respect to the transfer position,
20. The second guide member, wherein the second base end portion is fixed to the casing on the upstream side in the transport direction of the transfer medium with respect to the transfer position. One of the process cartridges.   An image forming apparatus comprising the process cartridge according to claim 1. An image carrier that carries a developer image transferred to a transfer medium at a transfer position;
A developing unit that carries a developer, supplies the developer to the image carrier, and forms the developer image on the image carrier;
A transfer means that contacts the image carrier, forms the transfer position at the contact position, and transfers the developer image to the transfer medium;
Conveying means for conveying the transfer medium toward the transfer position;
A flexible first guide surface is formed, and the first base end side of the first guide surface is fixed on the upstream side of the transfer medium with respect to the transfer position, and the first guide surface is fixed. A first front end of the surface extends toward the image carrier located upstream of the transfer position in the transport direction of the transfer medium and from the first base end downstream of the transfer medium in the transport direction. A first guide member for guiding the transfer medium toward the image carrier;
A flexible second guide surface is formed, and a second base end side of the second guide surface is fixed on the upstream side of the transfer medium with respect to the transfer position, and the second guide surface is fixed. A second front end portion of the surface between the transfer position in the transport direction of the transfer medium and the first front end portion of the first guide member, and a downstream side in the transport direction of the transfer medium from the second base end portion. A plane that extends toward the image carrier located at a position and connects the second distal end portion and the second proximal end portion connects the first distal end portion and the first proximal end portion of the first guide member. A plane is arranged to intersect the first base end portion or the first base end portion on the upstream side in the transport direction of the transfer medium, and for guiding the transfer medium toward the image carrier. An image forming apparatus comprising: a second guide member.   The image forming apparatus according to claim 22, wherein at least one of the first guide member and the second guide member is formed of a film member. A cross-sectional secondary moment I _{1 in} a direction parallel to the longitudinal direction of the image carrier and perpendicular to the widest surface of the first guide member is in a direction parallel to the longitudinal direction of the image carrier; and than said vertical orientation of the second moment I ₂ to the widest surface of the second guide member, being larger, the image forming apparatus according to claim 22 or 23.   The length of the first guide surface from the first tip portion to the first base end portion is longer than the length of the second guide surface from the second tip portion to the second base end portion. The image forming apparatus according to claim 22, wherein the image forming apparatus is an image forming apparatus. The first guide member has a Young's modulus E _{1 in} a direction parallel to the transfer direction of the transfer medium, a direction parallel to the longitudinal direction of the image carrier, and perpendicular to the widest surface of the first guide member. The product E ₁ I ₁ with the cross-sectional secondary moment I _{1 in the} direction
3.49 × 10 ⁻⁵ ≦ E ₁ I ₁ ≦ 1.18 × 10 ⁻³
The second guide member has a Young's modulus E _{2 in} a direction parallel to the transfer direction of the transfer medium, a direction parallel to the longitudinal direction of the image carrier, and perpendicular to the widest surface of the second guide member. The product E ₂ I ₂ with the _second moment of inertia I ₂
26. The image forming apparatus according to claim 22, wherein the image forming apparatus is formed so as to be in a range of 3.49 × 10 ⁻⁵ ≦ E ₂ I ₂ ≦ 1.18 × 10 ^−3. .   27. The first guide member is provided at a position where the first guide member can be guided so that a contact angle θ between the image carrier and the transfer medium is θ <90 °. The image forming apparatus according to any one of the above.   The first guide member and the second guide member are formed into a predetermined shape by being cut by pressing, and the surface that comes into contact with the cutting blade in the pressing process is the front surface, and the opposite surface is the back surface. 28. The image forming apparatus according to claim 22, wherein the image forming apparatus is arranged so that the surface becomes the first guide surface and the second guide surface.   29. At least one of the first guide member and the second guide member is divided and formed in a width direction perpendicular to the transfer direction of the transfer medium. The image forming apparatus described in 1.   At least one of the first guide member and the second guide member extends from the edge of the first tip portion or the second tip portion along the transfer direction of the transfer medium from the first base end portion or The image forming apparatus according to any one of claims 22 to 28, wherein a slit extending partway toward the second base end is formed.   At least one of the first guide member and the second guide member is formed on the first base end side or the second base end side end of the cut, and the first guide from the cut 31. The image forming apparatus according to claim 30, further comprising a split prevention unit for preventing splitting of the member or the second guide member.   At least one of the first guide member and the second guide member extends from the edge of the first tip portion or the second tip portion along the transfer direction of the transfer medium from the first base end portion or The image forming apparatus according to any one of claims 22 to 28, wherein a slit-shaped cut portion extending partway toward the second base end portion is formed.   The image forming apparatus according to claim 32, wherein the cut portion is formed in a substantially rectangular shape in plan view.   The image forming apparatus according to claim 32, wherein the cut portion is formed in a substantially V shape in plan view.   At least one of the first guide member and the second guide member is formed on the first base end side or the second base end side end of the cut portion, and the first guide member and the second guide member side 35. The image forming apparatus according to claim 34, further comprising a split prevention unit for preventing splitting of the guide member or the second guide member.   The image forming apparatus according to claim 32, wherein the cut portion is formed in a substantially U shape in a plan view. A guide surface having flexibility is formed, and a base end side of the guide surface is fixed on the upstream side in the transport direction of the transfer medium with respect to the transfer position, and a front end portion of the guide surface is fixed to the transfer surface. It is extended toward the image carrier located on the upstream side in the conveyance direction of the transfer medium with respect to the position and from the base end portion on the downstream side in the conveyance direction of the transfer medium, and along the conveyance direction of the transfer medium. A plate-like member in which a plurality of tip pieces are formed along a direction parallel to the longitudinal direction of the image carrier by forming a cut extending from the edge of the tip portion to the middle toward the base end portion;
The first guide member and the second guide member are formed by bending the plurality of tip pieces of the plate-like member at different angles around the base end side edge of the cut. The image forming apparatus according to any one of claims 22 to 28, wherein:   An edge of the first leading end portion of the first guide surface is disposed at a contact position between the image carrier and the transfer unit, upstream of the first guide member in the transport direction of the transfer medium, and The transfer medium guided by the first guide member is arranged on the opposite side to the direction in which the first guide member is pressed with respect to a line segment connecting the contact positions of the two resist means arranged opposite to each other. The image forming apparatus according to claim 22, wherein the image forming apparatus is an image forming apparatus.   The image forming apparatus according to any one of claims 22 to 38, wherein the first guide member and the second guide member are made of an insulating material. A housing for holding the image carrier, the first guide member, and the second guide member;
The first guide member is fixed to the housing at the first base end portion on the upstream side of the transfer position in the transport direction of the transfer medium,
40. The second guide member, wherein the second base end portion is fixed to the casing on the upstream side in the transport direction of the transfer medium with respect to the transfer position. The image forming apparatus according to any one of the above.

Images