JP2005037676A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus in which damage to a tip part of transfer medium occurring due to a guide after transferring and wrapping of the transfer medium to a transfer roll are prevented. <P>SOLUTION: In a printer 10, the transfer roll 48 is nipped by biting into a secondary transfer drum 40C and paper P after transferring is moved toward the transfer roll 48 side. Therefore, the guide after transferring 62 is installed to cover the transfer roll 48 and the tip part of the paper P is dipped up. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus.

  In an image forming apparatus such as a printer or a copying machine, a transfer medium such as plain paper is pressed against an image carrier by a transfer roller, and a toner image formed on the image carrier is transferred to the downstream side in the running direction of the transfer roller. Traveled by being guided by a post-transfer guide provided on the side facing the running surface of the transfer medium.

  In the conventional model, the end portion of the post-transfer guide on the upstream side in the running direction of the transfer medium is a wall surface standing substantially vertically with respect to the running direction of the transfer medium. This wall surface is a part of the housing of the transfer roller unit, and played a role of preventing electrical interference between the transfer roller and the static elimination needle adjacent to the transfer roller (see, for example, Patent Documents 1 and 2). ).

  Generally, the relationship between the hardness of the image carrier and the transfer roller is image carrier> transfer roller. In such a case, since the leading end portion of the transfer medium after transfer travels toward the image carrier, there is no problem of conveyance due to the post-transfer guide.

  However, if the relationship between the hardness of the image carrier and the transfer roller is such that the image carrier <transfer roller, the tip of the transfer medium after transfer travels toward the guide side after transfer. Will hit the wall of the guide after transfer. For this reason, the leading end of the transfer medium enters between the transfer roller and the post-transfer guide, causing a transfer trouble such as the transfer medium being caught in the transfer roller or damaging the leading end of the transfer medium. .

  Even if the relationship between the hardness of the image carrier and the transfer roller is image carrier> transfer roller, it is difficult to peel off the transfer medium when the image carrier is thick or when the conveyance speed is increased. The rear guide must be close to the image carrier. For this reason, there is a possibility that a conveyance trouble may occur as in the case where the relationship between the hardness of the image carrier and the transfer roller is image carrier <transfer roller.

Further, in the case of double-sided printing, the transfer medium is curled during the printing of the first side, so that there is a problem that it becomes easy to hit the post-transfer guide during the transfer of the second side.
JP 2002-123102 A JP 2002-278322 A

  The present invention has been made in consideration of the above-described facts, and an object of the present invention is to prevent damage to the leading end portion of the transfer medium caused by the post-transfer guide and winding of the transfer medium around the transfer roller.

  The image forming apparatus according to claim 1, an image carrier on which a toner image is formed, a transfer roller that presses a transfer medium against the image carrier and transfers the toner image to the transfer medium, and the transfer roller The discharge medium is provided on the downstream side of the transfer medium in the running direction so as to face the non-transfer surface of the transfer medium and neutralizes the non-transfer surface, and guides the transfer medium on which the toner image is transferred. A post-transfer guide, wherein the post-transfer guide is a travel surface of the transfer medium on the downstream side of the transfer roller, a curved surface of the transfer roller facing the travel surface, It is located in a region surrounded by a curved surface that is substantially perpendicular to the traveling surface and scoops up the leading end of the transfer medium.

  In the image forming apparatus according to the first aspect, a toner image is formed on the image carrier, and the transfer medium is pressed against the image carrier by the transfer roller to transfer the toner image to the transfer medium. On the downstream side in the running direction of the transfer medium with respect to the transfer roller, a charge eliminating unit is provided facing the non-transfer surface, which is the back surface of the surface onto which the toner image of the transfer medium is transferred. The non-transfer surface is neutralized by the neutralizing means and is guided by the post-transfer guide to travel.

  Here, the transfer medium to which the toner image is transferred tends to run toward the transfer roller when the image carrier is softer than the transfer roller, for example. However, the post-transfer guide includes a travel surface downstream of the transfer roller of the transfer medium, a curved surface of the transfer roller that faces the travel surface, and a surface that is in contact with the curved surface and substantially perpendicular to the travel surface. It is located in the enclosed area and covers the curved surface.

  For this reason, the leading end portion of the transfer medium after transfer is scooped up by the post-transfer guide and does not enter between the transfer roller and the post-transfer guide. Therefore, the leading end of the transfer medium after transfer is not caught in the gap between the transfer roller and the guide after transfer, or hits the guide after transfer and is not damaged, and the transfer medium after transfer is wound around the transfer roller. There is nothing.

  The image forming apparatus according to claim 2 is the image forming apparatus according to claim 1, wherein the relationship between the hardness of the image carrier and the transfer roller is image carrier <transfer roller. And

  In the image forming apparatus of the second aspect, the relationship between the hardness of the image carrier and the transfer roller is image carrier <transfer roller. That is, since the toner image is transferred to the transfer medium by causing the hard transfer roller to bite into the soft image carrier, the leading end of the transfer medium after the toner image is transferred runs toward the transfer roller.

  However, since the leading end portion of the transfer medium is scooped up by the post-transfer guide, the transfer medium does not enter between the post-transfer guide and the transfer roller, and no conveyance trouble occurs.

  An image forming apparatus according to a third aspect is the image forming apparatus according to the first or second aspect, wherein the neutralizing unit includes a plurality of neutralizing needles arranged in a direction orthogonal to a traveling direction of the transfer medium. The post-transfer guide is provided between the static elimination needles.

  In the image forming apparatus according to the third aspect, a plurality of static elimination needles are arranged in a direction perpendicular to the traveling direction of the transfer medium, and the post-transfer guide is provided between the static elimination needles. For this reason, the discharge between the transfer medium and the charge eliminating needle is not blocked by the post-transfer guide.

  The image forming apparatus according to claim 4 is the image forming apparatus according to claim 3, wherein the post-transfer guide extends in a direction orthogonal to a traveling direction of the transfer medium, and the support A plurality of ribs standing up from a body at a predetermined interval and in line contact with the transfer medium to scoop up the transfer medium.

  In the image forming apparatus according to the fourth aspect, the post-transfer guide includes a support and a rib. The support extends in a direction orthogonal to the transfer medium conveyance direction, and the ribs stand from the support at a predetermined interval, line-contact with the transfer medium, and scoop up the transfer medium.

  By disposing the rib between the static elimination needles, the discharge between the transfer medium and the static elimination needle is not blocked. In addition, since the rib is in line contact with the transfer medium, and the contact area between the transfer medium and the post-transfer guide is narrow, the triboelectric charge amount of the transfer medium due to the friction with the post-transfer guide can be reduced. Scattering and density unevenness due to electrostatic explosion of unfixed toner on the transfer medium can be reduced.

  Further, since the rib is reinforced by the support, it is possible to prevent the rib from being damaged when the post-conveying guide is assembled or when the post-transfer guide is cut out.

  The image forming apparatus according to claim 5 is the image forming apparatus according to claim 3 or 4, wherein a cross section of the rib has a stepped shape in which a contact portion in contact with the transfer medium is thinned. Features.

  In the image forming apparatus according to the fifth aspect, the cross section of the rib has a stepped shape, and the contact portion in contact with the transfer medium is thin. For this reason, the contact area between the rib and the transfer medium is narrowed, and the triboelectric charge amount between the rib and the transfer medium is reduced. Therefore, electrostatic scattering of unfixed toner on the transfer medium due to frictional charging between the rib and the transfer medium can be reduced, and white spots and density unevenness of the image can be reduced.

  An image forming apparatus according to a sixth aspect is the image forming apparatus according to any one of the first to fifth aspects, wherein the post-transfer guide is detachably attached to a housing that rotatably supports the transfer roller. It is characterized by being.

  In the image forming apparatus according to the sixth aspect, the post-transfer guide is interposed between the traveling surface and the curved surface of the transfer roller facing the traveling surface. That is, the post-transfer guide covers the curved surface of the transfer roller facing the running surface. However, since the post-conveying guide is detachable from the housing that rotatably supports the transfer roller, the transfer roller can be easily attached to and detached from the housing.

  An image forming apparatus according to a seventh aspect is the image forming apparatus according to the sixth aspect, wherein the post-transfer guide is integrated with a neutralizing unit cover that is detachable from the housing and houses the neutralizing unit. It is characterized by that.

  In the image forming apparatus according to the seventh aspect of the present invention, the neutralization unit cover that houses the neutralization unit is provided, and electrical interference from the neutralization unit to the transfer roller or the like is prevented. In addition, the post-transfer guide is integrated with the static elimination means cover, and the number of parts is reduced.

  An image forming apparatus according to an eighth aspect is the image forming apparatus according to any one of the first to seventh aspects, wherein the post-transfer guide is formed of a material that is easily charged with the same polarity as the toner. It is characterized by.

  In the image forming apparatus according to the eighth aspect, the post-transfer guide is formed of a material that is easily charged to the same polarity as the toner. For this reason, the charge applied to the non-transfer surface by the transfer roller does not repel the charge oppositely charged to the post-transfer guide and the toner transferred to the transfer medium is scattered. hard. For this reason, it is possible to prevent a white image from being formed on the transfer medium.

  An image forming apparatus according to a ninth aspect is the image forming apparatus according to the eighth aspect, wherein the material is polypropylene.

  In the image forming apparatus according to the ninth aspect, since the post-transfer guide is formed of polypropylene that is easily charged to the same polarity as the toner, the toner transferred to the transfer medium is hardly scattered.

  Since the present invention is configured as described above, the leading end portion of the transfer medium after transfer is scooped up by the post-transfer guide and does not enter between the transfer roller and the post-transfer guide. Therefore, the leading end of the transfer medium after transfer does not hit the post-transfer guide and is not damaged, and the transfer medium after transfer does not wind around the transfer roller.

  The first embodiment will be described below with reference to the drawings.

  As shown in FIG. 1, a color laser printer (hereinafter referred to as a printer) 10 as an image forming apparatus includes a full color on plain paper, recycled paper, or an OHP sheet (hereinafter referred to as paper P) as a transfer medium. A print head device 12 for forming an image is provided.

  The print head device 12 includes four photosensitive drums 14Y, 14M, 14K, and 14C, and the printer 10 transmits a light beam to the four photosensitive drums 14Y, 14M, 14K, and 14C. An optical scanning device 16 that scans to form a latent image is provided.

  The print head device 12 is provided with four developing devices 18Y, 18M, 18K, and 18C that individually develop the latent images formed on the four photosensitive drums 14Y, 14M, 14K, and 14C. The printer 10 includes four toner boxes 20Y for supplying yellow (Y), magenta (M), black (K), and cyan (C) toners to the developing devices 18Y, 18M, 18K, and 18C, respectively. 20M, 20K, and 20C are provided.

  Further, the printer 10 includes a paper feed cassette 22 that stores the paper P that is conveyed to the transfer unit of the print head device 12, and a manual paper feed tray 24 that supplies the paper P from the outside to the transfer unit of the print head device 12. Is provided.

  Further, the printer 10 includes a fixing device 26 that performs a fixing process on the paper P on which the toner image is transferred by the print head device 12, and the print head device by reversing the front and back of the paper P on which the toner image is fixed. A transport device 28 for double-sided printing that transports again to a transfer unit 12; a controller 30 that includes a control circuit that controls the operation of the printer; an image processing circuit that performs image processing on image signals; and an electric circuit that includes a high-voltage power supply circuit 32 and a discharge tray 34 for stocking the paper P on which an image has been formed and discharged.

  As shown in FIG. 2, the optical scanning device 16 is lit and driven based on image data of each color of Y, M, K, and C, and has four laser beams corresponding to each color of Y, M, K, and C. And a polygon mirror that deflects and scans four laser beams emitted from the semiconductor laser 36 onto the photosensitive drums 14Y, 14M, 14K, and 14C, an f-θ lens, a reflection mirror, and the like. An optical unit 38 is provided.

  In addition, the print head device 12 includes a developing unit 18 including four developing devices 18Y, 18M, 18K, and 18C, a photosensitive unit 14 including four photosensitive drums 14Y, 14M, 14K, and 14C, and a photosensitive unit. 14 includes an intermediate transfer body unit 40 that conveys the toner image formed on the paper 14 to the paper P.

  The intermediate transfer unit 40 contacts the photosensitive drums 14Y and 14M and contacts the first primary intermediate transfer drum 40A on which the toner images of two colors Y and M are transferred and the photosensitive drums 14K and 14C. The second primary intermediate transfer drum 40B, the first primary intermediate transfer drum 40A, the second primary intermediate transfer drum 40B, and the transfer roller 48 to which toner images of two colors K and C are transferred in an overlapping manner are transferred to the transfer roller 48. There is provided a secondary intermediate transfer drum (image carrier) 40C that contacts and transfers the toner images of four colors Y, M, K, and C in a superimposed manner and transfers the toner image superimposed on the paper P to the four colors. Yes.

  The photosensitive drums 14Y, 14M, 14K, and 14C are not transferred to the charging rolls 42Y, 42M, 42K, and 42C for primary charging, the first primary intermediate transfer drum 40A, and the second primary intermediate transfer drum 40B, respectively. Further, cleaning rollers 44Y, 44M, 44K, and 44C that collect and temporarily hold untransferred residual toner remaining on the photosensitive drums 14Y, 14M, 14K, and 14C are in contact with each other. Each charging roll is arranged on the upstream side in the rotation direction of each photosensitive drum from the scanning area of each photosensitive drum, and each cleaning roll is arranged on the upstream side in the rotation direction of each photosensitive drum from each charging roll. Has been.

  Further, the first primary intermediate transfer drum 40A, the second primary intermediate transfer drum 40B, and the secondary intermediate transfer drum 40C are not transferred to the sheet P, but are transferred to the first primary intermediate transfer drum 40A and the second primary intermediate transfer drum 40A. Cleaning rollers 46A, 46B, and 46C that remove untransferred residual toner remaining on the intermediate transfer drum 40B and the secondary intermediate transfer drum 40C are in contact with each other.

  Further, as shown in FIG. 3, the transfer roller unit 50 is provided with a transfer roller for transferring the toner image by pressing the paper P against the secondary intermediate transfer drum 40C. The transfer roller 48 has a roll structure in which an elastic layer 48B made of epichlorohydrin rubber or the like is formed on a metal roll core material 48A, and a drive gear 52 is attached to one end portion in the axial direction of the roll core material 48A. The transfer roller 48 is rotated by the driving force transmitted to the driving gear 52.

  At the time of transfer, the transfer roller 48 is applied with a transfer voltage having a polarity opposite to the charging polarity of the toner image from the transfer power supply device (not shown) to the roll core material 48A under constant voltage control. As a result, as shown in FIG. 4, the sheet P fed into the nip N between the secondary intermediate transfer drum 40C and the transfer roller 48 is formed between the secondary intermediate transfer drum 40C and the transfer roller 48. The toner image formed on the secondary intermediate transfer drum 40C is electrostatically transferred by the transfer electric field.

  Further, as shown in FIG. 3, a bearing 54 and a ball bearing 56 are rotatably fitted to both ends of the roll core metal 48A. The bearing 54 is disposed inside the ball bearing 56 and is attached to the unit housing 58 of the transfer roller unit 50. The transfer roller 48 is accommodated in a U-shaped groove 58E (see FIG. 4) of the unit housing 58. . The ball bearing 56 is urged toward the secondary intermediate transfer drum 40C by an urging means (not shown) provided in the apparatus main body, whereby the transfer roller 48 is pressed against the secondary intermediate transfer drum 40C.

  Here, the unit housing 58 is not fixed to the apparatus main body by fixing means such as screws, but is suspended from the apparatus main body by the transfer roller 48. A rotation stop pin 58B is provided on the side surface 58A of the unit housing 58, and the rotation stop pin 58B is inserted into a rotation stop long hole 61 formed in a side plate of the apparatus main body. Thus, the unit housing 58 is prevented from rotating around the transfer roller 48, and each part of the unit housing 58 is positioned.

  The position of the unit housing 58 includes a pre-transfer guide 60 that guides the leading end of the paper P conveyed to the nip N between the secondary intermediate transfer drum 40C and the transfer roller 48, and after the toner image is transferred. There are a post-transfer guide 62 that guides the leading end of the paper P, a static elimination needle 64 that is discharged from the paper P on which the toner image is transferred, and the like.

  As shown in FIG. 4, the static elimination needle 64 is a stainless steel plate that extends in a direction orthogonal to the conveyance direction of the paper P (hereinafter referred to as the width direction), has an end surface facing the paper P, and has a blade shape. Is disposed so that the tip of the blade shape does not contact the paper P substantially parallel to the axial direction of the transfer roller 48. A recess 58D is formed in the unit housing 58 on the downstream side of the partition wall 58C, and a charge removal needle cover 66 is fitted into the unit housing 58 to hold the charge removal needle 64 inserted in the recess 58D.

  A static elimination voltage having a polarity opposite to the charge applied to the back surface of the paper P by the transfer roller 48 is applied to the static elimination needle 64 from a static elimination power supply device (not shown). As a result, the charge is eliminated so that the charge existing on the back surface of the paper P after passing through the nip portion N is reduced. As a result, the electrostatic attraction force between the paper P and the secondary intermediate transfer drum 40C is reduced, so that the paper P after transfer is easily peeled off from the secondary intermediate transfer body 40C.

  In addition, a neutralizing cloth 68 is bonded to the back surface of the surface of the neutralizing needle cover 66 that presses the neutralizing needle 64. The neutralizing cloth 68 protrudes from the transport path of the paper P toward the secondary intermediate transfer body 40C, and contacts the back surface of the transported paper P to remove charges accumulated on the back surface of the paper P.

  Here, the surface layer of the secondary intermediate transfer drum 40C is formed by coating a resin layer on silicon rubber, and the surface layer has a hardness of 45 ° and a thickness of 5 mm. In contrast, the elastic layer 48B of the transfer roller 48 has a hardness of 80 ° and a thickness of 2.2 mm, which is higher than the hardness of the secondary intermediate transfer drum 40C. Therefore, at the nip portion N between the transfer roller 48 and the secondary intermediate transfer drum 40C, the transfer roller 48 bites into the secondary intermediate transfer drum 40C. The amount of biting of the transfer roller 48 into the secondary intermediate transfer drum 40C is 0.5 mm.

  The leading edge of the paper P that has passed through the nip portion N has a habit of traveling toward the roller side having high hardness due to the influence of the nip shape. In the case of the printer 10, the transfer roller 48 is more than the secondary intermediate transfer drum 40C. Since the hardness of the paper P is also high, the leading edge of the paper P travels toward the transfer roller 48 side.

  Therefore, in the printer 10, the post-transfer guide 62 and the running surface S 1 on the downstream side in the running direction from the nip portion N of the paper P so that the leading end of the paper P does not enter between the partition wall 58 C and the transfer roller 48. The transfer roller 48 is covered with the curved surface S2 by interposing a curved surface S2 facing the traveling surface S1 and an area surrounded by the surface S3 which is in contact with the curved surface S2 and is substantially perpendicular to the traveling surface S1. Crawling up to the transfer drum 40C side.

  As a result, the leading edge of the peeled paper P enters between the post-transfer guide 62 and the transfer roller 48, and the conveyance jam that the paper P is wound around the transfer roller 48 is prevented. Further, it is possible to prevent the leading edge of the paper P from hitting the post-transfer guide 62 and damaging the leading edge of the paper P.

  As shown in FIG. 5, the post-transfer guide 62 has a structure in which a plurality of ribs 62A arranged at a predetermined pitch in the width direction of the paper P are connected by a support body 62B extending in the width direction of the paper P. It has become. Further, the post-transfer guide 62 is formed integrally with the charge elimination needle cover 66 and is detachable from the unit housing 58. For this reason, if it is removed together with the pre-transfer guide 60 which is also detachable, the transfer roller 48 can be inserted into the U-shaped groove 58E from directly above, and can be easily detached, so that it can be easily assembled and maintained. The nature is also high.

  Further, as shown in FIG. 4, the rib 62A is formed at an acute angle between a curve L1 along the curved surface S2 and a straight line L2 along the traveling surface S1, and straddles the static elimination needle 64. For this reason, the rib 62A does not block the discharge between the static elimination needle 64 and the paper P.

  Further, as shown in FIG. 6, the ribs 62 </ b> A are arranged at one pitch with respect to the three teeth of the static elimination needle 64 in accordance with the valley portion 64 </ b> A of the static elimination needle 64. The distance between the upper end of the rib 62A and the apex 64B of the static elimination needle 64 is 2 mm. Here, if the paper P gets too close to the vertex 64B of the static elimination needle 64, the discharge area by the static elimination needle 64 becomes narrow, but the distance between the paper P and the vertex 64B of the static elimination needle 64 becomes 2 mm or less. Therefore, the entire back surface of the paper P can be neutralized uniformly.

  As shown in FIG. 7, the cross section of the rib 62 </ b> A has a stepped shape with a thin upper end that may contact the paper P. For this reason, the contact area between the paper P and the rib 62A can be reduced, and electrostatic scattering of unfixed toner due to frictional charging between the rib 62A and the paper P can be reduced.

  Furthermore, although negatively charged toner is used in this embodiment, the rib 62A is formed of polypropylene, which is a material that has the same polarity as that of the toner, that is, is easily negatively charged. For this reason, the charge on the back surface of the paper P that is frictionally charged by rubbing against the rib 62A becomes positive, so that it has the same polarity as the positive transfer charge applied to the back surface of the paper P by the transfer roller 48. The toner on P does not repel only the rubbing portion of the rib 62A, and a stable state in which the toner is electrostatically attracted can be maintained as in the portion without the rib 62A. For this reason, the toner on the paper P does not scatter from the portion of the paper P in contact with the rib 62A, and a toner image with white streaks is not formed on the paper P.

  Next, a second embodiment will be described. In addition, the same code | symbol is attached | subjected to the structure same as 1st Embodiment, and description is abbreviate | omitted.

  As shown in FIG. 8A, both ends of the transfer roller 70 are attached to the unit housing 58 by bearings 72. The transfer roller 70 has a smaller outer diameter than the transfer roller 48 of the first embodiment. As described above, since the unit housing 58 is suspended from the transfer roller 48, when the outer diameter of the transfer roller 70 is changed, the positional relationship of each part of the unit housing 58 with respect to the secondary intermediate transfer body 40C. Change.

  When the outer diameter of the transfer roller 70 is reduced and the shape of the bearing 72 and the shape of the unit housing 58 are not changed as in the present embodiment, as shown in FIG. The post-transfer guide 62 approaches the secondary intermediate transfer drum 40C. In particular, the corner portion K facing the nip portion N of the post-transfer guide 62 is located on the secondary intermediate transfer drum 40C side with respect to the progress line L of the paper P after separation illustrated by a chain line. For this reason, the leading end portion of the paper P after peeling enters between the post-transfer guide 62 and the transfer roller 70, and the paper P is wound around the transfer roller 70. Alternatively, the leading edge of the paper P hits the post-transfer guide 62 and the leading edge of the paper P is damaged.

  In order to prevent this, normally, when the outer diameter of the transfer roller 70 is changed, the shape of the unit housing 58 is changed in order to change the mounting position of the bearing 72. For this reason, the mold shape of the unit housing 58 has to be changed, resulting in an increase in cost.

  Therefore, in this embodiment, as shown in FIGS. 8A and 9, the unit housing of the bearing 72 is made eccentric by a predetermined amount Q with respect to the center P1 of the inner diameter of the bearing 72 with respect to the center P2 of the outer diameter. Therefore, it is not necessary to change the position of the unit housing 58 or to change the shape of the post-transfer guide 62, thereby making it unnecessary to change the die shape of the unit housing 58.

  The bearing 72 has an outer diameter, a shape of a rotation stop key 72A that engages with a key groove 58G formed in a bearing mounting portion 58F of the unit housing 58, and a flange 72B that prevents the transfer roller 70 from coming off in the axial direction. The shape and the like are exactly the same as those of the bearing 54 of the first embodiment, and are different from the bearing 54 of the first embodiment in that the thickness of the cylindrical portion 72C fitted to the roll core 70A of the transfer roller 72 is not uniform.

  The center P1 of the inner diameter of the cylindrical portion 72C of the bearing 72 is eccentric by a predetermined amount Q on the opposite side of the rotation stop key 72A in the radial direction with respect to the center P2 of the outer diameter. Since the rotation stop key 72A is disposed on the opposite side of the secondary intermediate transfer drum 40C with the center P2 of the outer diameter therebetween, the unit housing 58 is secondary by a predetermined amount Q from the state of FIG. Move away from the intermediate transfer drum 40C. Thus, the position of the corner portion K of the post-transfer guide 62 is closer to the transfer roller 70 than the travel line L of the paper P after peeling, so that there is no trouble in transporting the paper P.

  Next, a modified example of the bearing 72 will be described. In addition, the same code | symbol is attached | subjected to the structure same as 1st, 2nd embodiment, and description is abbreviate | omitted.

  As shown in FIG. 10C, on the outer peripheral surface of the cylindrical portion 74C of the bearing 74 in which the center P1 of the inner diameter is eccentric by a predetermined amount Q with respect to the center of the outer diameter, eight rotations are made at intervals of 45 degrees. A stop key 74A is formed.

  Further, five key grooves 76G for locking the rotation stop key 74A are formed in the bearing mounting portion 76F of the unit housing 76 to which the bearing 74 is mounted. For this reason, as shown in FIG. 10A, when the bearing 74 is mounted on the bearing mounting portion 76F with the thickest portion of the cylindrical portion 74C facing the pre-transfer guide 60, the post-transfer guide 62 is moved to the transfer roller 70. To approach. Also, as shown in FIG. 10B, when the bearing 74 is attached to the bearing attachment portion 76F with the thinnest portion of the cylindrical portion 74C facing the pre-transfer guide 60, the post-transfer guide 62 is moved from the transfer roller 70. Leave.

  As described above, the center P1 of the inner diameter of the bearing 74 is decentered by a predetermined amount Q with respect to the center P2 of the outer diameter, and the direction in which the bearing 74 is attached can be selected in a stepwise manner. The position of each part of the unit housing 76 can be adjusted stepwise.

  As a result, when the outer diameter of the transfer roller 70 is changed or when the process speed is changed and the behavior of the conveyance of the paper P is changed, the shape of the unit housing 76, the post-transfer guide 62, etc. is changed. It can be made unnecessary.

  Even if there are some errors between the finished dimensions of the unit housing 76 and the post-transfer guide 62 and the design values, the errors can be canceled depending on the direction in which the bearing 74 is attached. Therefore, there is a margin for slightly reducing the required degree of dimensional accuracy of the unit housing 76, the post-transfer guide 62, and the like, and the yield of the unit housing 76, the post-transfer guide 62, etc. is increased.

  Next, modified examples of the bearings 72 and 74 will be described.

  As shown in FIG. 11, in the bearing 78, five key grooves 78G are formed at predetermined intervals on the outer peripheral surface of the cylindrical body 78C, and the key groove 78G is locked to the bearing mounting portion 80F of the unit housing 80. One rotation stop key 80A is formed. As a result, the mounting direction can be adjusted stepwise as with the bearing 74 described above.

  As shown in FIG. 12, the bearing 82 is provided with a flange 82B at one end of the cylindrical body 82C in the axial direction. The flange 82B has one or a plurality of protrusions protruding from the bearing mounting portion of the unit housing. Eight anti-rotation locking holes 82G into which anti-rotation pins are fitted are formed at intervals of 45 °. Thereby, the mounting direction of the bearing 82 can be adjusted stepwise.

  As shown in FIG. 13, a U-shaped anti-rotation locking hole 84 </ b> G that engages with an anti-rotation protrusion formed on the bearing mounting portion of the unit housing is provided at a flange portion 84 </ b> B of the bearing 84 at an interval of 45 °. 8 and the mounting direction of the bearing 84 can be adjusted stepwise.

  In the first and second embodiments, the outer shape of the bearing serving as the bearing mounting portion mounted on the bearing mounting portion is circular. However, as illustrated in FIG. 14A, the mounting portion 86D of the bearing 86, that is, The outer shape may be rectangular. In this case, the center P2 of the attachment portion 86D is an intersection of the two diagonal lines L.

  As shown in FIG. 14B, the mounting portion 88D of the bearing 88, that is, the outer shape may be a polygon such as a hexagon. In this case, the center P2 of the attachment portion 88D is an intersection of the three diagonal lines L.

1 is a diagram illustrating an outline of a printer according to a first embodiment. 1 is a diagram schematically illustrating a print head device of a printer according to a first embodiment. It is a perspective view which shows the transfer roller unit of the printer of 1st Embodiment. It is sectional drawing which shows the transfer roller unit of the printer of 1st Embodiment. It is a perspective view which shows the static elimination needle cover of the printer of 1st Embodiment. It is sectional drawing which shows the static elimination needle and post-transfer guide of the printer of 1st Embodiment. It is sectional drawing of the after-transfer guide of the printer of 1st Embodiment. (A) It is sectional drawing which shows the transfer roller unit of the printer of 2nd Embodiment. (B) It is sectional drawing which shows the transfer roller unit of the printer of 2nd Embodiment. It is a perspective view which shows the bearing of the printer of 2nd Embodiment. (A) It is a figure which shows the modification of the bearing of the printer of 1st, 2nd embodiment. (B) It is a figure which shows the modification of the bearing of the printer of 1st, 2nd embodiment. (C) It is a figure which shows the modification of the bearing of the printer of 1st, 2nd embodiment. It is a figure which shows the modification of the bearing of the printer of 1st, 2nd embodiment. It is a figure which shows the modification of the bearing of the printer of 1st, 2nd embodiment. It is a figure which shows the modification of the bearing of the printer of 1st, 2nd embodiment. (A) It is a figure which shows the modification of the bearing of the printer of 1st, 2nd embodiment. (B) It is a figure which shows the modification of the bearing of the printer of 1st, 2nd embodiment.

Explanation of symbols

10 Printer (image forming device)
40C secondary intermediate transfer drum (image carrier)
48 Transfer roller 58 Unit housing (housing)
62 Post-transfer guide 62A Rib 62B Support 64 Static elimination needle (static elimination means)
66 Static elimination needle cover 70 Transfer roller S1 Traveling surface S2 Curved surface S3 Surface P Paper (transfer medium)

Claims (9)

An image carrier on which a toner image is formed;
A transfer roller for pressing the transfer medium against the image carrier and transferring the toner image to the transfer medium;
A neutralizing means provided on the downstream side of the transfer roller in the running direction of the transfer medium so as to face the non-transfer surface of the transfer medium, and neutralizing the non-transfer surface;
A post-transfer guide for guiding the transfer medium on which the toner image has been transferred;
An image forming apparatus comprising:
The post-transfer guide includes a travel surface downstream of the transfer roller of the transfer medium, a curved surface of the transfer roller facing the travel surface, and a surface that is in contact with the curved surface and substantially perpendicular to the travel surface. An image forming apparatus, wherein the image forming apparatus is located in a region surrounded by a front end of the transfer medium.   The image forming apparatus according to claim 1, wherein the relationship between the hardness of the image carrier and the transfer roller is image carrier <transfer roller. The static elimination means includes a plurality of static elimination needles arranged in a direction orthogonal to the traveling direction of the transfer medium,
The image forming apparatus according to claim 1, wherein the post-transfer guide is provided between the static elimination needles. The post-transfer guide is
A support extending in a direction perpendicular to the running direction of the transfer medium;
A plurality of ribs standing from the support at a predetermined interval and line-contacting the transfer medium to scoop up the transfer medium;
The image forming apparatus according to claim 3, comprising:   The image forming apparatus according to claim 3, wherein a cross section of the rib has a stepped shape in which a contact portion that contacts the transfer medium is thinned.   The image forming apparatus according to claim 1, wherein the post-transfer guide is detachably attached to a housing that rotatably supports the transfer roller.   The image forming apparatus according to claim 6, wherein the post-transfer guide is integrated with a neutralizing unit cover that is detachable from the housing and accommodates the neutralizing unit.   8. The image forming apparatus according to claim 1, wherein the post-transfer guide is formed of a material that is easily charged with the same polarity as the toner.   The image forming apparatus according to claim 8, wherein the material is polypropylene.

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