JP5341226B2 - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve an image quality without causing irregularities in an image. <P>SOLUTION: An image forming device is equipped with a first conveyance part, an intermediate transfer belt on which a developer image is transferred in a primary transfer part and a first conveyance member for forming a nip part between the intermediate transfer belt and the first conveyance member and has a second conveyance part for forming a second transfer part for transferring the developer image to a medium and a medium guiding part for guiding the medium toward the second conveyance part. The first conveyance member is arranged facing the surface on which the developer image on the intermediate transfer belt is transferred and the medium guiding part guides the medium toward the first conveyance member on the second conveyance part and firstly abuts the medium on the first conveyance member without abutting the medium on the intermediate transfer belt. Since the medium is firstly abutted on the first conveyance member, the front end of the medium is not oriented in a different direction from the conveyance direction even if a vibration or the like is generated in association with the conveyance of the medium. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to an image forming apparatus.

  2. Description of the Related Art Conventionally, in an image forming apparatus such as a printer, a copier, a facsimile machine, and a multifunction machine using an electrophotographic method, for example, a printer, the surface of a photosensitive drum uniformly charged by a charging roller is exposed by an LED head. Then, an electrostatic latent image is formed, and the electrostatic latent image is developed by a developing device to form a toner image on the photosensitive drum, and then the toner image is transferred to a sheet and fixed.

  As a method for transferring the toner image to the paper, a first method for directly transferring the toner image on the photosensitive drum to the paper, and a toner image on the photosensitive drum are transferred to an intermediate transfer belt at a primary transfer portion, There is a second method in which the toner image transferred to the transfer belt is transferred to a sheet by a secondary transfer unit.

  In order to transfer the toner image by the second method, a pair of rollers is provided in the secondary transfer unit, and the transfer unit is configured such that the intermediate transfer belt is sandwiched between the rollers. . A guide member is disposed on the upstream side of the secondary transfer portion in the paper transport direction, and the paper is guided to the secondary transfer portion by the guide member (see, for example, Patent Document 1).

JP 2006-113275 A

  However, in the conventional printer, for example, when vibration or the like is generated along with the conveyance of the sheet and the front end of the sheet is directed in a direction different from the conveyance direction, the sheet is moved before entering the secondary transfer unit. The front end hits the toner image before fixing on the intermediate transfer belt, and the toner image is disturbed. In that case, the image is disturbed, and the image quality is lowered.

  It is an object of the present invention to provide an image forming apparatus that solves the problems of the conventional printer and can improve image quality without causing image distortion.

  For this purpose, in the image forming apparatus of the present invention, a first transport unit that transports a medium, an intermediate transfer belt to which a developer image is transferred in a primary transfer unit, and a first transport unit in the transport direction of the medium A first conveying member that is disposed further downstream and forms a nip portion with the intermediate transfer belt is provided, conveys the medium supplied from the first conveying unit, and transfers the medium to the intermediate transfer belt. A second transfer unit that forms a secondary transfer unit that transfers the developed developer image to the medium, and a medium transfer path between the first and second transfer units, and the first transfer unit A medium guide unit that guides the supplied medium toward the second transport unit.

The second transport unit is disposed to face the first transport member via the intermediate transfer belt, and the second transport unit sandwiches the intermediate transfer belt between the second transport unit and the first transport member. A member is provided.
The first conveying member is disposed to face a surface to which a developer image is transferred in the primary transfer portion of the intermediate transfer belt.

The medium guide unit includes first and second guide members disposed across the conveyance path, and the medium supplied from the first conveyance unit is transferred to the second conveyance unit. The guide is directed toward the first conveying member, and is first brought into contact with the first conveying member without being brought into contact with the intermediate transfer belt.
In the direction perpendicular to the medium transport direction, the first guide member is disposed closer to the second transport member than the transport path, and the second guide member is disposed closer to the first transport member than the transport path. Established.
The extension line of the downstream end portion of the first guide member in the medium transport direction and the extension line of the downstream end portion of the second guide member in the medium transport direction are parallel to each other. The

  According to the present invention, in the image forming apparatus, the first transport unit that transports the medium, the intermediate transfer belt to which the developer image is transferred in the primary transfer unit, and the first transport unit in the transport direction of the medium. A first conveying member that is disposed further downstream and forms a nip portion with the intermediate transfer belt is provided, conveys the medium supplied from the first conveying unit, and transfers the medium to the intermediate transfer belt. A second transfer unit that forms a secondary transfer unit that transfers the developed developer image to the medium, and a medium transfer path between the first and second transfer units, and the first transfer unit A medium guide unit that guides the supplied medium toward the second transport unit.

The second transport unit is disposed to face the first transport member via the intermediate transfer belt, and the second transport unit sandwiches the intermediate transfer belt between the second transport unit and the first transport member. A member is provided.
The first conveying member is disposed to face a surface to which a developer image is transferred in the primary transfer portion of the intermediate transfer belt.

The medium guide unit includes first and second guide members disposed across the conveyance path, and the medium supplied from the first conveyance unit is transferred to the second conveyance unit. The guide is directed toward the first conveying member, and is first brought into contact with the first conveying member without being brought into contact with the intermediate transfer belt.
In the direction perpendicular to the medium transport direction, the first guide member is disposed closer to the second transport member than the transport path, and the second guide member is disposed closer to the first transport member than the transport path. Established.
The extension line of the downstream end portion of the first guide member in the medium transport direction and the extension line of the downstream end portion of the second guide member in the medium transport direction are parallel to each other. The

  In this case, the medium guide unit first guides the medium supplied from the first transport unit toward the first transport member in the second transport unit, and first makes contact with the intermediate transfer belt. Since it is brought into contact with one transport member, the front end of the medium does not face in a direction different from the transport direction even if vibration or the like is generated as the medium is transported.

  Therefore, since the front end of the medium does not hit the developer image before fixing, it is possible to prevent the developer image from being disturbed and to improve the image quality.

  In addition, the medium can be smoothly conveyed without causing a jam or wrinkles in the image forming apparatus.

It is a figure which shows the conveyance system in the 1st Embodiment of this invention. 1 is a schematic diagram of a color printer according to a first embodiment of the present invention. FIG. 3 is a control block diagram of the color printer in the first embodiment of the present invention. It is a 1st figure for demonstrating operation | movement of the conveyance system in the 1st Embodiment of this invention. It is a 2nd figure for demonstrating operation | movement of the conveyance system in the 1st Embodiment of this invention. It is a 3rd figure for demonstrating operation | movement of the conveyance system in the 1st Embodiment of this invention. It is a 4th figure for demonstrating operation | movement of the conveyance system in the 1st Embodiment of this invention. It is a figure which shows the conveyance system in the 2nd Embodiment of this invention. It is a 1st figure for demonstrating operation | movement of the conveyance system in the 2nd Embodiment of this invention. It is a 2nd figure for demonstrating operation | movement of the conveyance system in the 2nd Embodiment of this invention. It is a 3rd figure for demonstrating operation | movement of the conveyance system in the 2nd Embodiment of this invention. It is a 4th figure for demonstrating operation | movement of the conveyance system in the 2nd Embodiment of this invention. It is a 5th figure for demonstrating operation | movement of the conveyance system in the 2nd Embodiment of this invention. It is a 6th figure for demonstrating operation | movement of the conveyance system in the 2nd Embodiment of this invention. It is a 7th figure for demonstrating operation | movement of the conveyance system in the 2nd Embodiment of this invention. It is a figure which shows the conveyance system in the 3rd Embodiment of this invention. It is a 1st figure for demonstrating operation | movement of the conveyance system in the 3rd Embodiment of this invention. It is a 2nd figure for demonstrating operation | movement of the conveyance system in the 3rd Embodiment of this invention. It is a 3rd figure for demonstrating operation | movement of the conveyance system in the 3rd Embodiment of this invention. It is a 4th figure for demonstrating operation | movement of the conveyance system in the 3rd Embodiment of this invention. It is a 5th figure for demonstrating operation | movement of the conveyance system in the 3rd Embodiment of this invention. It is a figure which shows the conveyance system in the 4th Embodiment of this invention. It is a control block diagram of the color printer in the 4th Embodiment of this invention. It is a 1st figure for demonstrating operation | movement of the conveyance system in the 4th Embodiment of this invention. It is a 2nd figure for demonstrating operation | movement of the conveyance system in the 4th Embodiment of this invention. It is a 3rd figure for demonstrating operation | movement of the conveyance system in the 4th Embodiment of this invention. It is a 4th figure for demonstrating operation | movement of the conveyance system in the 4th Embodiment of this invention. It is a 5th figure for demonstrating operation | movement of the conveyance system in the 4th Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In this case, a color printer as an image forming apparatus, that is, a color printer will be described.

  FIG. 2 is a schematic diagram of the color printer according to the first embodiment of the present invention.

  In the figure, reference numeral 11 denotes a paper cassette (paper tray) as a medium accommodating portion for accommodating paper P as a medium. The paper cassette 11 is detachably arranged on the main body of the color printer, that is, the apparatus main body. Established. At the front end of the paper cassette 11, a paper feeding unit 20 that separates and feeds the paper P one by one is disposed. The paper feeding unit 20 is disposed in pressure contact with the uppermost paper P, and a hopping roller (pickup roller) 22 that feeds the paper P with rotation, and one paper P fed by the hopping roller 22. A roller pair composed of a feed roller 23 and a retard roller 24 is provided for separating the rollers one by one. The hopping roller 22 is rotated by driving a paper feed motor (not shown) as a paper feed drive unit. The feeding portion is constituted by the hopping roller 22, and the separating portion is constituted by the feed roller 23 and the retard roller 24.

  In addition, 30 is a sheet conveying unit as a first conveying unit that conveys the sheet P fed from the sheet feeding unit 20, and 40 is a plurality of four images arranged in series in the present embodiment. Forming unit C, M, Y, Bk, and LED head 43 as an exposure device, and each image forming unit C, M, Y, Bk and LED head 43 allows developers of each color of cyan, magenta, yellow, and black An image forming unit 50 for forming a toner image as an image includes an intermediate transfer belt 51 as a belt member, and the toner images of the respective colors are sequentially transferred onto the intermediate transfer belt 51 in a superimposed manner. A transfer unit for forming an image and transferring the color toner image on the intermediate transfer belt 51 onto the paper P conveyed by the paper conveyance unit 30; 6 Is the color toner image transferred to the sheet P, heated and then fixed to the sheet P by pressurizing a fixing device as a fixing device for forming a color image.

  Reference numeral 64 denotes a discharge roller pair for discharging the paper P discharged from the fixing device 60 to the outside of the apparatus main body, and 65 denotes a stacker unit for stacking the paper P discharged from the apparatus main body by the discharge roller pair 64. It is.

  The paper transport unit 30 includes transport roller pairs 32, 34, and 35 as first transport elements disposed from the upstream side to the downstream side in the transport direction of the paper P. The conveyance roller pairs 32, 34, and 35 are rotated by driving a conveyance motor (not shown) as a conveyance drive unit.

  In the image forming unit 40, each of the image forming units C, M, Y, and Bk has a photosensitive drum 41 for carrying the toner image, and the surface of the photosensitive drum 41 has a uniform negative polarity. A developing roller 45 as a developer carrying member that develops an electrostatic latent image as a latent image formed on the surface of the photosensitive drum 41 and forms a toner image. And a toner container 46 as a developer container for storing the toner. The photosensitive drum 41 is rotated by driving a drum motor (not shown) as an image forming drive unit.

  The photosensitive drum 41 constitutes a first image carrier and the intermediate transfer belt 51 constitutes a second image carrier. The electrostatic latent image is formed by irradiating and exposing the surface of the photosensitive drum 41 with the LED head 43.

  The transfer unit 50 includes an intermediate transfer belt 51, a driving roller 52 as a first roller, a tension roller 53 as a second roller for applying tension to the intermediate transfer belt 51, and a backup roller as a third roller. 55, primary transfer as a first transfer member and as a first transfer roller facing the photosensitive drum 41 of each of the image forming units C, M, Y, and Bk through the intermediate transfer belt 51 A second transfer member that is pressed against the backup roller 55 via the roller 54 and the intermediate transfer belt 51 and forms a nip portion between the backup roller 55 and the second transfer roller. The next transfer roller 57 is disposed adjacent to the backup roller 55 inside the intermediate transfer belt 51, Comprising a support roller 56 or the like as a fourth roller for adjusting the contact area of the contact area of the shooting belt 51 and the secondary transfer roller 57. The intermediate transfer belt 51 is stretched by the driving roller 52, the tension roller 53, and the backup roller 55, and is moved in the direction of the arrow. The driving roller 52 is rotated by driving a belt motor (not shown) as a belt driving unit, and causes the intermediate transfer belt 51 to travel. In the running direction of the intermediate transfer belt 51, a tension roller 53 is disposed upstream from the drive roller 52, a backup roller 55 is disposed upstream from the tension roller 53, and a support roller 56 is disposed upstream from the backup roller 55. The The secondary transfer roller 57 constitutes a first conveying member, and the backup roller 55 and the support roller 56 constitute a second conveying member.

  A primary transfer portion T1 as a first transfer portion is formed between each of the photosensitive drums 41 and the primary transfer roller 54. In the primary transfer portion T1, as the intermediate transfer belt 51 travels, the photosensitive member is exposed to light. The toner images of the respective colors on the body drum 41 are sequentially transferred (primary transfer) on the intermediate transfer belt 51 by the Coulomb force to form a color toner image. For this purpose, a voltage is applied to the primary transfer roller 54 by the power supply device, and the toner image of each color is transferred to the intermediate transfer belt 51 by an electric field formed between the primary transfer roller 54 and the photosensitive drum 41. The photosensitive drum 41 and the driving roller 52 are rotated by driving the drum motor and the belt motor in synchronization. Further, a secondary transfer portion T2 as a second transfer portion is formed between the intermediate transfer belt 51 and the backup roller 55 and the secondary transfer roller 57, and the secondary transfer portion T2 is formed on the intermediate transfer belt 51. The color toner image is transferred (secondary transfer) to the paper P by Coulomb force. For this purpose, a voltage is applied to the secondary transfer roller 57 by the power supply device, and the color toner image is transferred to the paper P by an electric field formed between the secondary transfer roller 57 and the backup roller 55 grounded to the ground. Is transcribed.

  Each primary transfer roller 54 drives a primary transfer motor (not shown) as a first transfer drive unit, so that the backup roller 55 is a secondary transfer motor (not shown) as a second transfer drive unit. It is rotated by driving. In the present embodiment, the secondary transfer roller 57 is rotated along with the travel of the intermediate transfer belt 51 and the rotation of the backup roller 55. It can be rotated by driving a transfer motor (not shown) as a connected third transfer drive unit.

  In the secondary transfer unit T2, the intermediate transfer belt 51, the backup roller 55, and the secondary transfer roller 57 receive the paper P supplied from the paper transport unit 30 on the downstream side of the paper transport unit 30 in the transport direction of the paper P. The 2nd conveyance part to convey is comprised. Note that the backup roller 55 and the secondary transfer roller 57 are disposed in the secondary transfer portion T2 so as to face each other in the direction perpendicular to the traveling direction of the intermediate transfer belt 51 and the conveyance direction of the paper P. The

  An upper guide member 36 as a first guide member for guiding the paper P and a lower guide member 37 as a second guide member are arranged between the pair of conveying rollers 35 and the secondary transfer portion T2. Established.

  The fixing device 60 includes an upper roller 61 as a first fixing roller and a lower roller 62 as a second fixing roller. The upper roller 61 and the lower roller 62 are formed of an elastic body on the surface, and have a heat source therein. And a halogen lamp 63 as a heating body.

  In the figure, between a pair of rollers comprising a feed roller 23 and a retard roller 24, between each pair of conveying rollers 32, 34, 35, between an upper guide member 36 and a lower guide member 37, and between a secondary transfer roller 57 and an intermediate. A solid line extending between the transfer belt 51, between the upper roller 61 and the lower roller 62, and between each discharge roller pair 64 represents a conveyance path of the paper P.

  Next, the operation of the color printer having the above configuration will be described.

  First, when the paper feeding motor is driven and the hopping roller 22 is rotated in the paper feeding unit 20, the paper P is fed from the paper cassette 11 and conveyed to the nip position of the feed roller 23 and retard roller 24 roller pair. Separated one by one. Subsequently, the paper P is sent to the paper transport unit 30, transported by the transport roller pairs 32, 34 and 35, and sent to the secondary transfer unit T <b> 2.

  In each of the image forming units C, M, Y, and Bk of the image forming unit 40, when the charging roller 42 uniformly charges the surface of the photosensitive drum 41 to a negative polarity, the LED head 43 is moved to the photosensitive drum 41. The surface of the substrate is irradiated and exposed to form an electrostatic latent image. Subsequently, the toner supplied from the toner container 46 is attached to the photosensitive drum 41 by the developing roller 45 and development is performed, and a toner image is formed on the surface of the photosensitive drum 41. Then, the toner images of the respective colors on the respective photosensitive drums 41 are sequentially transferred onto the intermediate transfer belt 51 by the primary transfer roller 54, thereby forming a color toner image.

  Subsequently, as the intermediate transfer belt 51 travels, the color toner image transferred onto the intermediate transfer belt 51 is sent to the secondary transfer portion T2 and transferred to the paper P at the secondary transfer portion T2.

  Then, the paper P is sent to the fixing device 60, and the color toner image is fixed on the paper P in the fixing device 60 to form a color image. Thereafter, the paper P is discharged to the stacker unit 65 by the discharge roller pair 64.

  Next, a control device for the color printer having the above-described configuration will be described.

  FIG. 3 is a control block diagram of the color printer according to the first embodiment of the present invention.

  As shown in the figure, the control device of the color printer operates a control unit 70 that controls the entire color printer, an interface 76 that transmits / receives information to / from an external device (such as a host computer) not shown, and a color printer. A storage unit 77 for recording setting value information for recording, information received from an external device, and the like, a user interface for displaying color printer setting contents, color printer status, and the like. The first conveyance control that controls the conveyance of the paper P in the paper conveyance unit 30 by driving the operation panel 78 and the conveyance motor 73 that function as the rotation of the conveyance roller pair 32, 34, and 35 (FIG. 2). The medium transfer control unit 72 and the belt motor 75 are driven to rotate the driving roller 52, thereby driving the intermediate transfer belt 51. The medium transfer control unit 74 as a second transfer control unit that controls the transfer of the paper P in the secondary transfer unit T2, and the print control for forming, transferring, and fixing the toner image on the paper P. The unit 71 is provided.

  In this case, the rotation speeds of the conveyance motor 73 and the belt motor 75 are controlled by the medium conveyance control units 72 and 74, and the conveyance speed of the paper P by the paper conveyance unit 30 is higher than the conveyance speed of the paper P by the secondary transfer unit T2. As a result, the sheet P is bent between the sheet conveying unit 30 and the secondary transfer unit T2. Accordingly, it is possible to prevent the conveyance state of the paper P in the paper conveyance unit 30 from becoming a load on the conveyance of the paper P in the secondary transfer unit T2, so that the color toner image is transferred to the paper P in the secondary transfer unit T2. It is possible to prevent the image from being disturbed during the transfer, and to improve the image quality.

  In this embodiment, by controlling the rotational speeds of the transport motor 73 and the belt motor 75, the transport speed of the paper P in the paper transport section 30 is higher than the transport speed of the paper P in the secondary transfer section T2. The number of gear teeth arranged between the conveying motor 73 and the conveying roller pair 32, 34, 35 and the gear arranged between the belt motor 75 and the driving roller 52 are shown. By making the number of teeth different, the conveyance speed of the paper P in the paper conveyance section 30 can be made higher than the conveyance speed of the paper P in the secondary transfer section T2.

  Next, a transport system including the paper transport unit 30 and the secondary transfer unit T2 will be described.

  FIG. 1 is a diagram showing a transport system according to the first embodiment of the present invention.

  In the figure, u1 is a conveyance system, 30 is a sheet conveyance unit, 31 is disposed between the sheet conveyance unit 30 and the secondary transfer unit T2, and the sheet P (from the sheet conveyance unit 30 toward the secondary transfer unit T2) 2 is a sheet guide section as a medium guide section for guiding the sheet, and the sheet guide section 31 includes an upper guide member 36 and a lower guide member 37. Reference numeral 35 denotes a conveying roller pair, 55 denotes a backup roller, 56 denotes a support roller, and 57 denotes a secondary transfer roller.

  The backup roller 55 is made of a metal, in this embodiment, an aluminum roller, and is grounded to a frame ground formed by a housing of the color printer.

Further, the secondary transfer roller 57 is made of a conductive metal, in the present embodiment, made of SUS, and a rubber that covers the shaft, and in this embodiment, urethane rubber. It consists of a rubber part (coating layer) made of metal, and both ends of the shaft part are exposed, and the rubber part is formed in parts other than both ends. Therefore, the diameter of the rubber part is larger than the diameter of the shaft part by the thickness of the urethane rubber. Further, bearings are disposed at both ends of the shaft portion, and the secondary transfer roller 57 is rotatably supported by the bearings. The urethane rubber has electrical conductivity and is formed by adding a conductive material such as carbon or pigment to the rubber material, and the volume resistivity is 10 ² [Ωcm] or more and 10 ⁸ [Ωcm] or less, For example, it is set to 10 ⁶ [Ωcm].

  In addition, a power supply device is connected to the shaft portion, and a voltage of +1 [kV] or more and +5 [kV] or less, for example, +2 [kV] is applied to the secondary transfer roller 57 by the power supply device. A potential difference is formed between the secondary transfer roller 57 and the backup roller 55, and an electric field is formed.

  By the way, as described above, the secondary transfer roller 57 is pressed against the backup roller 55 via the intermediate transfer belt 51, and a nip portion is formed in a contact area between the secondary transfer roller 57 and the backup roller 55. .

  In this case, the backup roller 55 is formed of aluminum and has rigidity, whereas the rubber portion of the secondary transfer roller 57 is formed of urethane rubber and has elasticity. The rubber portion of the secondary transfer roller 57 is crushed, and the surface of the secondary transfer roller 57 has a shape corresponding to the shape of the surface of the backup roller 55, and has a concave surface having a radius of curvature equal to the outer diameter of the backup roller 55. (Concave part) is formed.

  Accordingly, the paper P that has entered the secondary transfer portion T2 is deformed along the concave surface, and as a result, the vicinity of the secondary transfer portion T2 on the paper P is urged toward the backup roller 55 side.

  Next, the paper guide unit 31 will be described.

  The upper guide member 36 is opposed to the printing surface of the paper P, and the lower guide member 37 is opposed to the non-printing surface (the surface opposite to the printing surface) of the paper P, so These are disposed between the secondary transfer portion T2 and both are made of a plastic plate and guide the paper P to the secondary transfer portion T2.

  The lower guide member 37 is disposed so as to be able to support the paper P between the conveying roller pair 35 and the secondary transfer portion T2, and is formed by a surface facing the upper guide member 36. A guide portion 37f as a surface is provided.

  The downstream end 37 a of the lower guide member 37 in the conveyance direction of the paper P is opposed to the secondary transfer roller 57 in the vicinity of the secondary transfer roller 57. An extended surface when the guide portion 37 f is extended toward the secondary transfer roller 57 intersects the surface of the secondary transfer roller 57. Therefore, when the paper P is conveyed with the non-printing surface in contact with the guide portion 37 f, the paper P is guided toward the secondary transfer roller 57, and the front end of the paper P is brought into contact with the secondary transfer roller 57.

  The upper guide member 36 is disposed so as to cover the conveyance path between the conveyance roller pair 35 and the vicinity of the support roller 56, and the downstream end portion of the upper guide member 36 in the conveyance direction of the paper P. 36a is opposed to the secondary transfer roller 57 at a predetermined distance on the upstream side of the end portion 37a. When the center of the support roller 56 is e1, and the contact start point indicating the point where the intermediate transfer belt 51 and the support roller 56 start to contact is p1, the end 36a is the center e1 in the transport direction of the paper P. The upper guide member 36 intersects with an extension of a line connecting the center e1 and the contact start point p1 at a position upstream by a predetermined distance. Thus, the end 36a is opposed to the secondary transfer roller 57 at a predetermined distance, so that the intermediate transfer belt 51 and the paper P are directly connected between the end 36a and the secondary transfer roller 57. Can be opposed.

  Further, a guide portion 36 f as a guide surface is formed by a surface of the upper guide member 36 that faces the lower guide member 37. The extended surface X when the guide portion 36 f is extended toward the secondary transfer roller 57 intersects the surface of the secondary transfer roller 57. That is, the guide portion 36f is positioned below the secondary transfer portion T2 (secondary transfer roller 57 side) in the vertical direction.

  The support roller 56 is made of metal, in the present embodiment, made of SUS, and is grounded to the frame ground, and upstream of the backup roller 55 in the traveling direction of the intermediate transfer belt 51. The intermediate transfer belt 51 is disposed in the vicinity of the backup roller 55 and bends in a “<” shape, and between the backup roller 55 in the intermediate transfer belt 51 (secondary transfer portion in the running direction of the intermediate transfer belt 51). On the upstream side of T, an area Sa that extends substantially parallel to the conveyance path of the paper P and close to the conveyance path and faces the paper P is formed.

  When the support roller 56 is not provided, the end 36a of the upper guide member 36 is positioned outside the region where the backup roller 55 is provided.

  Next, the operation of the transport system u1 will be described.

  FIG. 4 is a first diagram for explaining the operation of the transport system in the first embodiment of the present invention, and FIG. 5 is a first diagram for explaining the operation of the transport system in the first embodiment of the present invention. FIG. 2 and FIG. 6 are a third diagram for explaining the operation of the transport system in the first embodiment of the present invention, and FIG. 7 is a diagram for explaining the operation of the transport system in the first embodiment of the present invention. It is the 4th figure for doing.

  First, the paper P is transported by the transport roller pair 35, guided by the paper guide unit 31, and sent (supplied) to the secondary transfer unit T2. The direction of the front end of the paper P is regulated by the guide portions 36f and 37f formed on the secondary transfer roller 57 side from the region Sa, and is brought into contact with the secondary transfer roller 57 as shown in FIG. .

  At this time, since the secondary transfer roller 57 is rotated, as shown in FIG. 5, the front end of the paper P is kept in contact with the secondary transfer roller 57, and the secondary transfer roller 57 is rotated upward. It is moved toward the transfer portion T2. At this time, since the transport speed of the paper P in the paper transport section 30 is higher than the transport speed of the paper P in the secondary transfer section T2, the paper P bends in the direction in which the printing surface comes into contact with the upper guide member 36. start.

  Subsequently, as shown in FIG. 6, the front end of the sheet P enters the secondary transfer portion T2. At this time, the deflection of the sheet P becomes larger than the state of FIG. 5, and the printing surface of the sheet P is almost the same timing as the front end of the sheet P enters the secondary transfer portion T2 or slightly delayed. It contacts the area Sa of the intermediate transfer belt 51.

  Next, as shown in FIG. 7, when the paper P is further conveyed, the deflection of the paper P becomes larger than the state of FIG. 6, and the area where the printing surface of the paper P contacts the area Sa of the intermediate transfer belt 51. Becomes even larger.

  When the trailing edge of the paper P is separated from the transport roller pair 35, the paper P is not bent due to the speed difference of the transport speed. However, as described above, the paper P is the concave surface in the secondary transfer portion T2. Therefore, the vicinity of the secondary transfer portion T2 on the paper P is urged toward the backup roller 55 side. Therefore, even after the rear end of the paper P is separated from the transport roller pair 35, the paper P can be transported while the printing surface of the paper P and the intermediate transfer belt 51 are in contact with each other.

  As described above, in this embodiment, when the front end of the sheet P conveyed with the non-printing surface in contact with the guide portion 37f contacts the secondary transfer roller 57, a part of the printing surface contacts the region Sa. Be made. Accordingly, the sheet P can be transported while being brought into contact with the printing surface of the sheet P and the intermediate transfer belt 51 and can enter the secondary transfer portion T2. Therefore, even if vibration or the like occurs as the sheet P is transported, The front end of the paper P does not face in a direction different from the transport direction. As a result, since the front end of the paper P does not hit the toner image before fixing on the intermediate transfer belt 51 before the paper P enters the secondary transfer portion T2, it is possible to prevent the toner image from being disturbed. Can do.

  Further, the paper P can be smoothly conveyed without causing a jam in the color printer and without causing wrinkles on the paper P.

  The electric field formed between the secondary transfer roller 57 and the backup roller 55 is so weak that it is away from the secondary transfer portion T2, so that the printing surface of the paper P and the intermediate transfer belt 51 are brought into contact with each other at a portion where the electric field is weak. To be able to. Therefore, a part of the toner of the toner image before fixing on the intermediate transfer belt 51 is not scattered by the electric field, so that the toner image can be prevented from being disturbed.

  Further, when the conveyance of the paper P in the secondary transfer portion T proceeds, as shown in FIG. 7, the area where the printing surface of the paper P contacts the area Sa of the intermediate transfer belt 51 increases. Even after the end is separated from the conveying roller pair 35, the sheet P can be conveyed while the printing surface of the sheet P and the intermediate transfer belt 51 are in contact with each other. Therefore, it is possible to prevent the toner image from being disturbed.

  Since the end 36a is disposed upstream of the contact start point p1 in the conveyance direction of the paper P, the rear end of the paper P is separated from the upper guide member 36 upstream of the contact start point p1. become. Therefore, even if the trailing edge of the sheet P jumps up when leaving the upper guide member 36, the intermediate transfer belt 51 is separated from the conveyance path of the sheet P on the upstream side from the contact start point p1. The end does not collide with the intermediate transfer belt 51. As a result, it is possible to prevent the toner image from being disturbed.

  As described above, since it is possible to prevent the toner image from being disturbed, it is possible to prevent the image from being disturbed (image fringing) and to improve the image quality.

  When the downstream end of the upper guide member 36 is placed at a position upstream of the end 36a in the present embodiment, the distance that the upper guide member 36 can guide the paper P is shortened, and the upper The function of guiding the paper P by the guide member 36 is lowered.

  By the way, as described above, the deflection of the paper P is generated by making the transport speed of the paper P in the paper transport section 30 higher than the transport speed of the paper P in the secondary transfer section T2. If the speed difference between the transport speed of the paper P in the paper transport section 30 and the transport speed of the paper P in the secondary transfer section T2 is excessively large, before the front end of the paper P enters the secondary transfer section T2, the paper There is a possibility that the bent portion of P will hit the toner image before fixing on the intermediate transfer belt 51.

  Therefore, in the present embodiment, the bent portion of the paper P is on the intermediate transfer belt 51 between the time when the front end of the paper P contacts the secondary transfer roller 57 and the time when the paper P reaches the secondary transfer portion T2. The speed difference is set so as not to hit the toner image before fixing, and is set to 0.3% or more and 1.5% or less of the conveyance speed of the paper P in the secondary transfer portion T2. . Note that the conveyance speed of the paper P varies depending on the characteristics, arrangement, and the like of the paper conveyance unit 30, the intermediate transfer belt 51, the backup roller 55, the secondary transfer roller 57, and the like.

  In the present embodiment, the lower guide member 37 is disposed closer to the secondary transfer roller 57 than the secondary transfer portion T2 so that the front end of the sheet P is brought into contact with the secondary transfer roller 57. For example, even when the entire sheet guide portion 31 is inclined toward the backup roller 55 side, the lower guide member 37 and the upper guide member 36 in the conveyance direction of the sheet P can be used. By bending the vicinity of the downstream end toward the secondary transfer roller 57, the sheet P can be bent and guided, and the front end can be brought into contact with the secondary transfer roller 57.

  Next, a second embodiment of the present invention will be described. In addition, about the thing which has the same structure as 1st Embodiment, the same code | symbol is provided and the effect of the same embodiment is used about the effect of the invention by having the same structure.

  FIG. 8 is a diagram showing a transport system according to the second embodiment of the present invention.

  In this case, a line connecting the center of the secondary transfer roller 57 as the second transfer member and the center of the backup roller 55 as the third roller, and the belt member, In addition, the angle θ formed by the region Sa between the backup roller 55 and the support roller 56 as the fourth roller in the intermediate transfer belt 51 as the second image carrier is an angle smaller than 90 °, that is, The arrangement position of the secondary transfer roller 57 is set on the upstream side in the transport direction of the sheet P as a medium as compared with the first embodiment so as to have an acute angle.

  Accordingly, the intermediate transfer belt 51 covers a portion slightly upstream of the concave surface in the rotation direction of the secondary transfer roller 57, and the contact area between the secondary transfer roller 57 and the intermediate transfer belt 51 is increased.

  In this case, when the paper P enters the secondary transfer portion T2 as the second transfer portion between the intermediate transfer belt 51 and the secondary transfer roller 57, the printing surface faces the intermediate transfer belt 51 due to the rigidity of the paper P. Energized and brought into contact with the intermediate transfer belt 51.

  Next, the paper guide unit 31 as a medium guide unit will be described.

  In this case, the upper guide member 36 as the first guide member includes a guide portion 36f as a guide surface formed by a surface facing the lower guide member 37 as the second guide member. The upper guide member 36 extends toward the side away from the main body 39 that extends in parallel with the lower guide member 37 and the downstream end of the main body 39 in the transport direction of the paper P (that is, the paper A retracting portion 38 is provided that is formed so as to be inclined in the conveying direction of P and in a direction perpendicular to the guide portion 36f (guide surface) from the conveying path toward the backup roller 55. The guide portion 36f includes a main body guide surface 36g as a first guide surface formed in the main body portion 39 and a retracting portion guide surface 36h as a second guide surface formed in the retracting portion 38. Prepare.

  The angle θ2 formed by the retracting portion guide surface 36h and the region Sa of the intermediate transfer belt 51 on the downstream side of the retracting portion 38 in the transport direction of the paper P is an angle greater than 90 °, that is, an obtuse angle. The The angle θ2 is determined based on the distance between the leading end 38a of the retracting portion 38 and the conveyance path of the paper P and the distance between the leading edge 38a and the secondary transfer roller 57 in the conveyance direction of the paper P.

  Further, when the area Sa is extended toward the sheet conveying unit 30 side, an extension surface A (formed by a backup roller 55 and a support roller 56 and forms a plane substantially parallel to the sheet P conveying path). The retracting portion 38 intersects, and the leading end 38a is positioned on the intermediate transfer belt 51 side from the extended surface A. A gap of a predetermined distance t is formed between the leading end 38a and the intermediate transfer belt 51. In this case, the distance t is preferably as short as possible, but the retracting portion 38 and the intermediate transfer belt 51 are not in contact with each other in consideration of the vibration of the intermediate transfer belt 51 caused by vibration when the intermediate transfer belt 51 is run. Set to In this embodiment, since the deflection of the intermediate transfer belt 51 generated by the vibration of the intermediate transfer belt 51 is approximately 1 [mm], the distance t is set to 1 [mm] or more and 2 [mm] or less. The In the present embodiment, the distance t can be accurately set because the front end of the retracting portion 38 has a sharp shape.

  Next, the operation of the transport system u1 will be described.

  FIG. 9 is a first diagram for explaining the operation of the transport system in the second embodiment of the present invention, and FIG. 10 is a first diagram for explaining the operation of the transport system in the second embodiment of the present invention. FIG. 2 is a third diagram for explaining the operation of the transport system in the second embodiment of the present invention, and FIG. 12 is a diagram for explaining the operation of the transport system in the second embodiment of the present invention. FIG. 13 is a fifth diagram for explaining the operation of the transport system in the second embodiment of the present invention, and FIG. 14 is a transport system in the second embodiment of the present invention. FIG. 15 is a sixth diagram for explaining the operation of the transport system in the second embodiment of the present invention.

  First, the sheet P is transported by a pair of transport rollers 35 as a first transport element, guided by the sheet guide unit 31, and sent to the secondary transfer unit T2. The orientation of the front end of the paper P is regulated by the guide portions 36f and 37f and brought into contact with the secondary transfer roller 57 as shown in FIG.

  At this time, since the secondary transfer roller 57 is rotated, the front end of the sheet P is kept in contact with the secondary transfer roller 57 as shown in FIG. As the sheet P is moved toward the transfer portion T2, the sheet P is bent, and a predetermined portion of the sheet P is brought into contact with the front end of the main body guide surface 36g.

  Subsequently, as shown in FIG. 11, the front end of the sheet P enters the secondary transfer portion T2. At this time, the secondary transfer roller 57 is disposed so that the angle θ is an acute angle, and the intermediate transfer belt 51 covers the secondary transfer roller 57 in the vicinity of the secondary transfer portion T2, so that the paper P is the secondary paper. The next transfer roller 57 is curved and conveyed along the outer peripheral surface. Then, since the restoring force is generated in the paper P in the direction of returning the curvature due to the rigidity of the paper P, the upstream portion of the paper P from the secondary transfer portion T2 is urged toward the intermediate transfer belt 51, Causes deflection. Accordingly, the printing surface of the paper P comes into contact with the area Sa of the secondary transfer belt 51.

  Then, as shown in FIG. 12, when the trailing edge of the sheet P passes through the conveying roller pair 35, the upstream portion of the sheet P from the secondary transfer portion T2 is urged toward the intermediate transfer belt 51. Therefore, the paper P is conveyed while a predetermined portion is in contact with the front end of the main body guide surface 36g.

  Subsequently, as shown in FIG. 13, when the rear end of the sheet P passes the front end of the main body guide surface 36g, the sheet P is conveyed while the rear end is in contact with the retracting part guide surface 36h of the retracting part 38. The In this state, a certain load is applied to the operation in the vertical direction of the rear end of the paper P due to friction between the rear end and the retracting portion guide surface 36h. The retracting portion guide surface 36h functions as a damper for the operation of the paper P due to the load.

  Next, as shown in FIGS. 14 and 15, when the trailing edge of the paper P reaches before the point where the retracting portion 38 and the extension surface A intersect, it leaves the retracting portion guide surface 36 h. At this time, since a constant load is applied to the operation in the vertical direction of the rear end of the paper P until immediately before, no vibration occurs in the paper P as the rear end moves away from the retracting portion guide surface 36h.

  Thereafter, the sheet P is further conveyed as the secondary transfer roller 57 rotates, and the rear end of the sheet P moves on the extended surface A.

  As described above, in this embodiment, when the front end of the sheet P enters the secondary transfer portion T2, the upstream portion of the sheet P from the secondary transfer portion T2 is biased toward the intermediate transfer belt 51. Therefore, a part of the printing surface can be brought into contact with the region Sa. Accordingly, since the paper P can be conveyed while the printing surface of the paper P and the intermediate transfer belt 51 are in contact with each other, it is possible to prevent the toner image as the developer image from being disturbed.

  Further, since the paper P is conveyed while the printing surface is in contact with the region Sa, the rear end of the paper P is moved while being in contact with the retracting portion guide surface 36h of the retracting portion 38. Accordingly, the sheet P does not vibrate as the rear end moves away from the retracting portion guide surface 36h, and therefore the rear end of the sheet P can be prevented from hitting the toner image before fixing on the intermediate transfer belt 51. . As a result, it is possible to prevent the toner image from being disturbed.

  As described above, since the toner image can be prevented from being disturbed, the image can be prevented from being disturbed, and the image quality can be improved.

  Further, since the trailing edge of the paper P does not jump up, it is possible to prevent the jumping sound from being generated.

  In the present embodiment, as described above, since the intermediate transfer belt 51 covers the secondary transfer roller 57 in the vicinity of the secondary transfer portion T2, the upstream side of the secondary transfer portion T2 of the paper P is upstream. This portion is biased toward the intermediate transfer belt 51. Therefore, as in the first embodiment, even if the conveyance speed of the paper P in the paper conveyance section 30 is not made higher than the conveyance speed of the paper P in the secondary transfer section T2, the paper conveyance section 30 and the secondary The sheet P can be bent with respect to the transfer portion T2, and the printing surface of the sheet P can be brought into contact with the region Sa of the secondary transfer belt 51.

  Therefore, the speed difference between the transport roller pair 35 and the secondary transfer portion T2 can be reduced, and the speed difference can be set to zero (0). However, if the conveyance speed of the paper P in the paper conveyance unit 30 becomes lower than the conveyance speed of the paper P in the secondary transfer unit T2 due to manufacturing errors, assembly errors, etc. of the component parts, the conveyance state of the paper P in the paper conveyance unit 30 However, this is a load for transporting the paper P in the secondary transfer portion T2. Therefore, in the present embodiment, the speed difference is preferably set to 0.1 [%] or more and 0.2 [%] or less of the conveyance speed of the paper P in the secondary transfer portion T2.

  Next, a third embodiment of the present invention will be described. In addition, about the thing which has the same structure as 1st, 2nd embodiment, the same code | symbol is provided and the effect of the embodiment is used about the effect of the invention by having the same structure.

  FIG. 16 is a diagram showing a transport system according to the third embodiment of the present invention.

  In the figure, reference numeral 31 denotes a paper guide portion as a medium guide portion, and the paper guide portion 31 includes an upper guide member 91 as a first guide member and a lower guide member 37 as a second guide member.

  The upper guide member 91 includes a guide portion 91 f as a guide surface formed by a surface facing the lower guide member 37. Further, the upper guide member 91 includes a main body 92, a retracting section 95 that is disposed so as to be swingable in the arrow Y direction at the downstream end of the main body 92 in the transport direction of the sheet P as a medium, A hinge 93 as a support member that supports the retracting portion 95 and a spring 96 as an urging member are provided. The spring 96 is disposed with one end abutting against the retracting portion 95 and the other end abutting against a spring receiving portion (not shown) as a predetermined fixing portion in the color printer. It biases toward the guide member 37 side. The guide portion 91f includes a main body portion guide surface 91g as a first guide surface formed in the main body portion 92 and a retracting portion guide surface 91h as a second guide surface formed in the retracting portion 95. . The secondary transfer roller 57 intersects with the extended surface X on the downstream side of the upper guide member in the transport direction of the paper P.

  The upper guide member 91, the main body 92, and the retracting portion 95 are all made of plastic, and the surface in contact with the paper P is smoothly formed.

  The distal end 95a of the retracting portion 95 serves as the second transfer member from the extended surface A, the secondary transfer roller 57 side as the second transfer roller, and the backup roller 55 side as the third roller. Selectively positioned. That is, when the retracting portion 95 is directed obliquely downward (to the lower guide member 37 side) by the urging force of the spring 96, the tip 95a is positioned below the extended surfaces A and X, and the retracting portion 95 is When the spring 96 is directed obliquely upward (to the intermediate transfer belt 51 side) against the urging force of the spring 96, the tip 95a is positioned above the extended surfaces A and X.

  Next, the operation of the transport system u1 will be described.

  FIG. 17 is a first diagram for explaining the operation of the transport system in the third embodiment of the present invention, and FIG. 18 is a first diagram for explaining the operation of the transport system in the third embodiment of the present invention. FIG. 2 is a diagram for explaining the operation of the transport system in the third embodiment of the present invention, and FIG. 20 is a diagram for explaining the operation of the transport system in the third embodiment of the present invention. FIG. 21 is a fifth diagram for explaining the operation of the transport system in the third embodiment of the present invention.

  First, the paper P is transported by the transport roller pair 35, guided by the paper guide unit 31, and sent to the secondary transfer unit T <b> 2 as the second transfer unit. Here, when the front end of the sheet P passes through the main body 92, the front end of the sheet P is guided by the retracting unit 95. At this time, as shown in FIG. 17, since the retracting portion 95 is directed obliquely downward by the biasing force of the spring 96, the sheet P is directed to the lower guide member 37 by the retracting portion 95 and then the lower side. The paper P is conveyed along the guide member 37 and the front end of the paper P is brought into contact with the secondary transfer roller 57.

  Since the secondary transfer roller 57 is rotated, the front end of the sheet P is moved upward and toward the secondary transfer portion T2 while being in contact with the secondary transfer roller 57. Accordingly, the paper P is bent.

  Subsequently, as shown in FIG. 18, the front end of the sheet P enters the secondary transfer portion T2. At this time, the secondary transfer roller 57 is disposed so that the angle θ is an acute angle, and the intermediate transfer belt 51 covers the secondary transfer roller 57 in the vicinity of the secondary transfer portion T2. Is curved along the outer peripheral surface of the secondary transfer roller 57 and conveyed. Then, since the restoring force is generated in the paper P in the direction of returning the curvature due to the rigidity of the paper P, the upstream portion of the paper P from the secondary transfer portion T2 is urged toward the intermediate transfer belt 51, Causes deflection. Accordingly, the printing surface of the paper P comes into contact with the area Sa of the secondary transfer belt 51.

  At this time, since the retracting portion 95 receives an upward force from the paper P, the retracting portion 95 is rotated clockwise in FIG. 18 against the urging force of the spring 96, and the upward force and the urging force are balanced. Stopped at position.

  When the trailing edge of the paper P reaches the retracting portion 95, the restoring force of the paper P is applied to the retracting portion 95, so that the retracting portion 95 is further rotated clockwise in FIG. 18, as shown in FIG. To be directed diagonally upward. As a result, the sheet P is conveyed along the extended surface A of the region Sa while the rear end is in contact with the retracting portion guide surface 91h. Meanwhile, the retracting portion 95 is rotated counterclockwise in FIG. 19 by the biasing force of the spring 96. In this state, a constant load is applied to the operation in the vertical direction of the rear end of the paper P due to friction between the rear end and the retracting portion guide surface 91h. The retracting portion guide surface 91h functions as a damper for the operation of the paper P due to the load.

  In this state, the leading end 95a of the retracting portion 95 is positioned closer to the intermediate transfer belt 51 than the extension surface A.

  Subsequently, when the paper P is further conveyed, the rear end of the paper P reaches the front end 95a of the retracting portion 95 and the rear end of the paper P is placed on the extension surface A as shown in FIG. The tip 95a of the retracting portion 95 is also placed on the extended surface A.

  Then, as shown in FIG. 21, when the rear end of the paper P is separated from the retracting portion 95, the retracting portion 95 is directed obliquely downward by the urging force of the spring 96, and the leading end 95a is placed below the extension surface A. .

  As described above, in the present embodiment, the front end of the paper P is secondary even when curling is likely to occur during double-sided printing in which printing is performed on the front and back surfaces of the paper P, as in the case of printing on the back surface. The sheet P can be conveyed along the lower guide member 37 until it is brought into contact with the transfer roller 57. Accordingly, the occurrence of curling can be suppressed, so that the front end of the paper P does not hit the toner image before fixing on the intermediate transfer belt 51 before the paper P enters the secondary transfer portion T2.

  As a result, the toner image can be prevented from being disturbed, so that the image can be prevented from being disturbed, and the image quality can be improved.

  Next, a fourth embodiment of the present invention will be described. In addition, about the thing which has the same structure as 1st-3rd embodiment, the same code | symbol is provided and the effect of the same embodiment is used about the effect of the invention by having the same structure.

  FIG. 22 is a diagram showing a transport system in the fourth embodiment of the present invention, and FIG. 23 is a control block diagram of a color printer in the fourth embodiment of the present invention.

  In this case, as a medium detection unit that detects the front end of the sheet P downstream of the pair of conveyance rollers 35 as the first conveyance element in the conveyance direction of the sheet P as the medium and upstream of the retracting unit 95, A non-contact (optical) paper sensor 81 is provided, and the paper sensor 81 is connected to the control unit 70. A medium determination processing unit (not shown) of the control unit 70 performs a medium determination process, and determines that the paper P has passed the transport roller pair 35 upon receiving the sensor output of the paper sensor 81. The paper sensor 81 may be a contact type.

  The upper guide member 91 as the first guide member includes a main body 92, a retracting section 95 that is swingably disposed at the downstream end of the main body 92 in the transport direction of the paper P, and the retracting section A hinge 93 serving as a support member that supports 95, a spring 98 serving as an urging member, and a push-type solenoid 80 serving as a drive unit for rotating the retracting unit 95 are provided. The spring 98 is disposed with one end locked to the retracting portion 95 and the other end locked to a spring receiving portion (not shown) as a predetermined fixing portion in the color printer. And a bias toward the intermediate transfer belt 51 as the second image carrier.

  The solenoid 80 is connected to the control unit 70 via the retreat unit control unit 79, and a retreat unit control processing unit (not shown) of the control unit 70 performs retreat unit control processing and receives the sensor output of the paper sensor 81. Then, the solenoid 80 is turned on / off (driven) via the retracting unit control unit 79. The solenoid 80 turns the retracting portion 95 counterclockwise against the urging force of the spring 98 in the ON state so that the retracting portion 95 is directed obliquely downward (to the lower guide member 37 side), and the retracting portion 95. The front end 95a is placed below the extended surface X, and in the off state, the retracting portion 95 is rotated clockwise by the biasing force of the spring 98 so that the retracting portion 95 is directed obliquely upward (to the intermediate transfer belt 51 side). The front end 95a of the retracting portion 95 is placed above the extended surface A.

  Next, the operation of the transport system u1 will be described.

  FIG. 24 is a first diagram for explaining the operation of the transport system in the fourth embodiment of the present invention, and FIG. 25 is a diagram for explaining the operation of the transport system in the fourth embodiment of the present invention. FIG. 2 and FIG. 26 are third diagrams for explaining the operation of the transport system in the fourth embodiment of the present invention. FIG. 27 is a diagram for explaining the operation of the transport system in the fourth embodiment of the present invention. FIG. 28 and FIG. 28 are diagrams for explaining the operation of the transport system in the fourth embodiment of the present invention.

  First, the paper P is transported by the transport roller pair 35 and guided by the paper guide unit 31. As shown in FIG. 24, before the front end of the paper P reaches the paper sensor 81, the solenoid 80 is turned off and the retracting portion 95 is directed obliquely upward.

  When the front end of the paper P reaches the paper sensor 81, the front end of the paper P is detected by the paper sensor 81, and the sensor output of the paper sensor 81 is sent to the control unit 70. When the medium determination processing unit receives the sensor output of the paper sensor 81, the medium determination processing unit determines that the paper P has passed the transport roller pair 35, and the retracting unit control processing unit turns on the solenoid 80 to turn on the retracting unit. Turn 95 diagonally downward. The paper sensor 81 continues to send the sensor output to the control unit 70 until the trailing edge of the paper P passes, and the retracting unit control processing means maintains the solenoid 80 in the on state and directs the retracting unit 95 obliquely downward. to continue.

  Therefore, as shown in FIG. 25, the sheet P is conveyed along the lower guide member 37, and the front end of the sheet P serves as the second transfer member and the second transfer roller as the second transfer roller. It is brought into contact with the roller 57.

  Since the secondary transfer roller 57 is rotated, the front end of the paper P is kept in contact with the secondary transfer roller 57 and is located upward and as a second transfer unit. The sheet P is moved toward T2, and the sheet P is bent accordingly.

  Subsequently, as shown in FIG. 26, the front end of the sheet P enters the secondary transfer portion T2. At this time, the secondary transfer roller 57 is disposed so that the angle θ is an acute angle, and the intermediate transfer belt 51 covers the secondary transfer roller 57. It is curved along the surface and conveyed. Then, since the restoring force is generated in the paper P in the direction of returning the curvature due to the rigidity of the paper P, the upstream portion of the paper P from the secondary transfer portion T2 is urged toward the intermediate transfer belt 51, Causes deflection. Accordingly, the printing surface of the paper P comes into contact with the area Sa of the secondary transfer belt 51.

  Then, as shown in FIG. 27, when the trailing edge of the paper P passes through the paper sensor 81, the retracting part control processing means turns off the solenoid 80 and directs the retracting part 95 obliquely upward. Subsequently, as shown in FIG. 28, when the rear end of the paper P reaches the retracting portion 95, the paper P brings the rear end into contact with a retracting portion guide surface 91 h as a second guide surface of the retracting portion 95. It is conveyed in the state. In this state, a constant load is applied to the operation in the vertical direction of the rear end of the paper P due to friction between the rear end and the retracting portion guide surface 91h. The retracting portion guide surface 91h functions as a damper for the operation of the paper P due to the load.

  Subsequently, when the rear end of the paper P reaches before the point where the retracting portion 95 and the extension surface A intersect, the paper P leaves the retracting portion guide surface 91h. At this time, since a certain load is applied to the operation in the vertical direction of the rear end of the paper P until immediately before, no vibration occurs in the paper P as the rear end moves away from the retracting portion guide surface 91h.

  Thereafter, the sheet P is further conveyed as the secondary transfer roller 57 rotates, and the rear end of the sheet P moves on the extended surface A.

  As described above, in the present embodiment, by turning the solenoid 80 on and off, the retracting portion 95 is directed obliquely downward, so that the front end of the sheet P is brought into contact with the secondary transfer roller 57 and the secondary transfer portion. Can be led to T2. Accordingly, it is possible to urge the upstream portion of the sheet P from the secondary transfer portion T <b> 2 toward the intermediate transfer belt 51 so that the printing surface of the sheet P is brought into contact with the region Sa of the secondary transfer belt 51. Then, the paper P can be smoothly conveyed without causing a jam in the color printer or causing the paper P to be wrinkled.

  Further, by directing the retracting portion 95 obliquely upward, the rear end of the paper P can be moved while being in contact with the retracting portion guide surface 91h of the retracting portion 95. Accordingly, the sheet P does not vibrate as the rear end moves away from the retracting portion guide surface 91h, and therefore the rear end of the sheet P can be prevented from hitting the toner image before fixing on the intermediate transfer belt 51. . As a result, the toner image can be prevented from being disturbed, so that the image can be prevented from being disturbed, and the image quality can be improved.

  Further, by driving the solenoid 80, the retracting portion 95 can be directed obliquely downward or obliquely upward, so that a thick paper, a highly rigid paper P, a paper P that is easily curled, or the like is used. However, the movement of the front edge and the rear edge of the paper P can be controlled.

  Accordingly, it is possible to prevent the front end and the rear end of the paper P from hitting the toner image before fixing on the intermediate transfer belt 51, and thus it is possible to prevent the toner image from being disturbed. As a result, the image can be prevented from being disturbed, and the image quality can be improved.

  In each of the above embodiments, an electrophotographic color printer has been described. However, the present invention can be applied to an image forming apparatus such as a copying machine, a facsimile machine, and a multifunction machine.

  In each of the above embodiments, the case where the paper P is transported in the substantially horizontal direction in the secondary transfer unit T2 has been described. However, the transport direction of the paper P can be changed as appropriate, and the transport of the paper P Corresponding to the direction, the direction of the guide member, the retracting portion, etc. can be changed.

  The present invention is not limited to the above embodiments, and various modifications can be made based on the gist of the present invention, and they are not excluded from the scope of the present invention.

30 Paper transport section 31 Paper guide section 51 Intermediate transfer belt 55 Backup roller 57 Secondary transfer roller P Paper T1 Primary transfer section T2 Secondary transfer section

Claims (9)

(A) a first transport unit for transporting the medium;
(B) an intermediate transfer belt onto which the developer image is transferred in the primary transfer portion;
(C) a first conveyance member that is disposed downstream of the first conveyance unit in the conveyance direction of the medium and forms a nip portion with the intermediate transfer belt; A second transport unit that forms a secondary transfer unit that transports the supplied medium and transfers the developer image transferred to the intermediate transfer belt to the medium;
(D) a medium guide unit disposed in a medium conveyance path between the first and second conveyance units and guiding the medium supplied from the first conveyance unit toward the second conveyance unit; With
(E) The second transport unit is disposed to face the first transport member with the intermediate transfer belt interposed therebetween, and the second transport unit sandwiches the intermediate transfer belt with the first transport member. A conveying member,
(F) The first conveying member is disposed to face a surface to which a developer image is transferred in the primary transfer portion of the intermediate transfer belt,
(G) The medium guide unit includes first and second guide members arranged with the conveyance path interposed therebetween, and the medium supplied from the first conveyance unit is transferred to the second conveyance unit. Guiding to the first conveying member, and first contacting the first conveying member without contacting the intermediate transfer belt ,
(H) In a direction perpendicular to the medium transport direction, the first guide member is closer to the second transport member than the transport path, and the second guide member is closer to the first transport member than the transport path. Arranged,
(I) An extension line of the downstream end portion of the first guide member in the medium transport direction and an extension line of the downstream end portion of the second guide member in the medium transport direction are parallel to each other. an image forming apparatus characterized in that it is. (A) a first transport unit for transporting the medium;
(B) an intermediate transfer belt onto which the developer image is transferred in the primary transfer portion;
(C) a first conveyance member that is disposed downstream of the first conveyance unit in the conveyance direction of the medium and forms a nip portion with the intermediate transfer belt; A second transport unit that forms a secondary transfer unit that transports the supplied medium and transfers the developer image transferred to the intermediate transfer belt to the medium;
(D) a medium guide unit disposed in a medium conveyance path between the first and second conveyance units and guiding the medium supplied from the first conveyance unit toward the second conveyance unit; With
(E) The second transport unit is disposed to face the first transport member with the intermediate transfer belt interposed therebetween, and the second transport unit sandwiches the intermediate transfer belt with the first transport member. A conveying member,
(F) The first conveying member is disposed to face a surface to which a developer image is transferred in the primary transfer portion of the intermediate transfer belt,
(G) The medium guide unit includes first and second guide members arranged with the conveyance path interposed therebetween, and the medium supplied from the first conveyance unit is transferred to the second conveyance unit. Guiding to the first conveying member, and first contacting the first conveying member without contacting the intermediate transfer belt,
(H) In a direction perpendicular to the medium transport direction, the first guide member is closer to the second transport member than the transport path, and the second guide member is closer to the first transport member than the transport path. Arranged,
(I) A guide surface formed by a surface of the first guide member facing the second guide member is perpendicular to the medium conveyance direction and is closer to the first conveyance member than the nip portion. An image forming apparatus that is positioned. The downstream end of the first guide member in the conveying direction of the medium body, an image forming apparatus according to claim 1 or 2 is directed to the second guide member side. The downstream end of the first guide member in the conveying direction of the medium, the image forming apparatus according to claim 1 or 2 is disposed upstream from the downstream end of the second guide member. A guide surface formed by a surface of the first guide member facing the second guide member is positioned closer to the first transport member than the nip portion in a direction perpendicular to the medium transport direction. The image forming apparatus according to claim 1 . The extension line of the downstream end portion of the first guide member in the medium transport direction and the extension line of the downstream end portion of the second guide member in the medium transport direction are parallel to each other. Item 3. The image forming apparatus according to Item 2 . The conveying speed of the first conveying section by medium, the image forming apparatus according to any one of claims 1 to 6, which is higher than the conveying speed of the medium by the second transport unit. The image forming apparatus according to any one of claims 1 to 7 having a control panel that serves as an operation unit and a display unit. The image forming apparatus according to any one of the image forming apparatus according to claim 1-8 is the MFP.

Images