JP5251607B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a printer.

  In an image forming apparatus, a final image is formed on a sheet by directly or indirectly transferring an image formed on a photoconductor to a sheet (transfer material).

  For example, as a tandem type electrophotographic printer, there is an apparatus that superimposes and transfers an image of each color component on a plurality of photoconductors to an intermediate transfer belt, and transfers the image (full color image) on the intermediate transfer belt to a sheet. Exists (see Patent Document 1).

  In such an image forming apparatus, when a sheet passes through a nip portion which is a facing portion between a transfer roller (secondary transfer roller) and a driving roller of an intermediate transfer belt, intermediate transfer is performed by applying a voltage to the secondary transfer roller. The image on the belt is transferred to the paper.

JP 2006-317627 A

  However, when the sheet passes through such a nip portion, when the sheet enters the nip portion (or when the sheet reaches the vicinity of the driving roller of the intermediate transfer belt immediately before entering the nip portion). The paper collides with the intermediate transfer belt or the like. Here, when the sheet collides with the intermediate transfer belt or the like, a large impact force may be generated. In particular, when the paper is relatively thick, a relatively large impact force is generated. Such an impact force may cause image disturbance and adversely affect image formation. Note that with the technique of Patent Document 1, the impact force is not sufficiently reduced.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus capable of satisfactorily reducing the impact force generated during image transfer.

In order to solve the above-described problems, the invention of claim 1 is an image forming apparatus, wherein an image carrier that carries a toner image, a transfer roller that faces the image carrier, and substantially parallel to the transfer roller. A roller member provided on the belt, a belt member wound around the transfer roller and the roller member, and a conveying unit that conveys a transfer material to which the toner image is to be transferred toward a flexible portion of the belt member. wherein the belt member is to have a configured elastic layer of a conductive elastic material, the elastic layer is characterized by made of expandable conductive rubber.

The invention of claim 2 is an image forming apparatus, an image carrier that carries a toner image, a transfer roller that faces the image carrier, a roller member that is provided substantially parallel to the transfer roller, A belt member wound around the transfer roller and the roller member; and a conveying unit that conveys a transfer material to which the toner image is to be transferred toward a flexible portion of the belt member. The roller member and the transfer roller have an elastic layer made of a conductive elastic material, and the roller member and the transfer roller can move relative to each other in a direction in which the distance between the roller member and the transfer roller expands or contracts. Tension is applied to the belt member wound around the transfer roller and the roller member. The image forming apparatus further comprising a regulating means for adjusting the tension in accordance with the thickness of the transfer material.

According to a third aspect of the present invention, there is provided an image forming apparatus comprising: an image carrier that carries a toner image; a transfer roller that faces the image carrier; and a roller member that is provided substantially parallel to the transfer roller; A belt member wound around the transfer roller and the roller member; a conveying unit that conveys a transfer material to which the toner image is to be transferred toward a flexible portion of the belt member; and the transfer material by the conveying unit And changing means for changing a collision angle when the leading end portion of the transfer material collides with the belt member, and the belt member includes an elastic layer made of a conductive elastic material. And the changing means changes the collision angle according to the thickness of the transfer material.

According to a fourth aspect of the present invention, in the image forming apparatus according to the second or third aspect of the present invention, the image forming apparatus further comprises a detecting means for detecting the thickness of the transfer material.

According to a fifth aspect of the invention, in the image forming apparatus according to the second or third aspect of the invention, the thickness of the transfer material is acquired based on a print setting content included in a print instruction. .

According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, the belt member is rotatable while being wound around the transfer roller and the roller member. After the front end of the transfer material collides with the belt member, the front end portion of the transfer material is in contact with the belt member at a speed that is substantially the same as the speed of the belt member. It is characterized by proceeding toward.

According to the first to sixth aspects of the present invention, when the transfer material collides with the belt member, the impact force of the transfer material collision is reduced by the bending of the belt member accompanied by the deformation of the elastic layer of the belt member. . That is, it is possible to satisfactorily reduce the impact force generated during image transfer.

In particular, according to the first aspect of the present invention, since the elastic layer is made of foaming conductive rubber, the impact force of the transfer material collision is further appropriately reduced.

In particular, according to the invention described in claim 2 , since the belt member bends not only according to the elasticity of the belt member but also according to the elastic force by the elastic force applying means, the impact force of the transfer material collision is further appropriately reduced. Is done. In particular, since the tension of the belt member is adjusted according to the thickness of the transfer material, the impact force at the time of transfer material collision that varies according to the thickness of the transfer material can be further appropriately reduced.

  In particular, according to the invention described in claim 5, since the tension of the belt member is adjusted according to the thickness of the transfer material, the impact force at the time of collision of the transfer material, which varies according to the thickness of the transfer material, is reduced. Furthermore, it can reduce appropriately.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to a first embodiment. It is a side view which shows a transfer part. It is a perspective view which shows a transcription | transfer part. It is a partially enlarged view showing a belt cross section. FIG. 6 is a diagram illustrating a state in which a leading end of a sheet collides with a belt member of a transfer unit. It is a perspective view which shows the transfer part which concerns on 2nd Embodiment. It is a figure which shows the relationship between the thickness of a paper, and the tension | tensile_strength of a belt member. It is a figure which shows the transfer part which concerns on 3rd Embodiment. It is a figure which shows the relationship between the thickness of a paper, and a collision angle. It is a figure which shows the transfer part which concerns on a modification. It is a figure which shows a mode that the front-end | tip of a paper collides with the transfer part which concerns on a modification.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<1. First Embodiment>
<1-1. Equipment overview>
FIG. 1 is a diagram illustrating a schematic configuration of an image forming apparatus 1 according to the present embodiment. The image forming apparatus 1 is an apparatus that develops an electrostatic latent image on an image carrier to form an image. Here, as an image forming apparatus, an electrophotographic apparatus, more specifically, a tandem full-color electrophotographic apparatus is illustrated.

  As shown in FIG. 1, the image forming apparatus 1 includes a plurality (specifically, four) of imaging units 10 (specifically, 10Y, 10M, 10C, and 10K). Specifically, the image forming apparatus 1 includes a yellow imaging unit 10Y, a magenta imaging unit 10M, a cyan imaging unit 10C, and a black imaging unit 10K. Each imaging unit 10 is an electrophotographic image of each color component (specifically, each component of Y (yellow), M (magenta), C (cyan), K (black)) in the final output image). It is formed by a method and transferred to an intermediate transfer belt (also referred to as an intermediate transfer member) 21. Then, the image of each color component superimposed on the intermediate transfer belt 21 is further transferred onto a sheet (transfer material) PA, whereby a full color image is formed on the sheet PA.

  The four imaging units 10 (10Y, 10M, 10C, and 10K) are arranged in the lower linear portion mainly at the lower portion of the lower linear portion of the intermediate transfer belt 21 that is wound around the driving roller 23 and the winding roller 24. Are arranged in series. Each imaging unit 10 includes a photoconductor (image carrier) 11, a charger 12, an exposure device 13, a developing device 14, a first transfer device (primary transfer device) 15, an eraser (static eliminating device) 16, and a cleaner 17. And have. Specifically, in each imaging unit 10, a charger 12, an exposure device 13, a developing device 14, a first transfer device 15, an eraser 16, and a cleaner 17 are provided so as to surround the outer periphery of the substantially cylindrical photoconductor 11. Arranged clockwise in order. Among these, the first transfer device 15 (specifically, a transfer roller) is disposed at a position facing the photoconductor 11 with the intermediate transfer belt 21 therebetween.

  The intermediate transfer belt 21 moves in the direction of the arrow AR <b> 1 by driving the driving roller 23. A transfer unit 50 is provided at a position facing the drive roller 23 with the intermediate transfer belt 21 therebetween. The transfer unit 50 will be described in detail later.

  In addition, a paper feeding unit 30 is provided below each imaging unit 10 and the transfer unit 50 (upstream on the transport path). The paper feed unit 30 includes a paper feed tray 31, a feed roller 32, a paper feed roller 33, and a suction roller 34, and is configured to supply the paper PA toward the timing rollers 41 and 42 and the transfer unit 50. Has been. Further, a fixing device 45 is provided on the downstream side in the transport direction of the paper PA that has passed the position of the transfer roller (secondary transfer roller) 51 of the transfer section 50, and the paper discharge section 46 is further downstream in the transport direction. Is provided.

  The image forming apparatus 1 prints out an image based on image data transmitted from another information processing apparatus (such as a personal computer) connected via a network or the like by using the printing mechanism as described above. Functions as a color page printer.

  Further, the transfer unit 50 described above is upstream of the vicinity of the position where the intermediate transfer belt 21 and the secondary transfer roller 51 face each other (and from the position of the timing rollers 41 and 42) in the paper transport path (transfer material transport path). Is also provided from the position on the downstream side to the vicinity of the facing position. Next, the configuration and the like of the transfer unit 50 will be described in detail.

<1-2. Transfer part 50>
2 and 3 are diagrams illustrating the configuration of the transfer unit 50 (also referred to as 50A) according to the first embodiment. FIG. 2 is a side view showing the transfer unit 50, and FIG. 3 is a perspective view showing the transfer unit 50. 3 shows only the configuration of one end side (front side in FIG. 2) of the secondary transfer roller 51 and the driven roller 52, the same applies to the other end side (back side in FIG. 2). A configuration is provided.

  As shown in FIGS. 2 and 3, the transfer unit 50 is wound around a secondary transfer roller 51, a driven roller 52 disposed substantially parallel to the secondary transfer roller 51, and both rollers 51 and 52. And an endless belt member 53.

  Each of the secondary transfer roller 51 and the driven roller 52 has a rotation axis extending in the width direction of the conveyed sheet (the depth direction in FIG. 3), and rotates about each rotation axis. The secondary transfer roller 51 is mechanically connected to a rotation drive motor (drive device), and rotates according to the rotation drive operation of the motor. That is, the secondary transfer roller 51 is a transfer roller as well as a drive roller. When the secondary transfer roller 51 rotates, the belt member 53 wound around the secondary transfer roller 51 and the driven roller 52 rotates in a circular manner.

  FIG. 4 is an enlarged cross-sectional view of the vicinity of the portion PR1 in FIG. 2 and shows a detailed configuration of the belt member 53.

  As shown in FIG. 4, the belt member 53 includes a base layer 53a and an elastic layer 53b. Specifically, the elastic layer 53b is formed by being laminated on the outer side (outer peripheral side) of the base layer 53a.

  The base layer 53a is made of a resin material such as polyimide (PI) or polyphenylene-sulfide (PPS), for example. The base layer 53a of the belt member 53 contains a substance that imparts conductivity (for example, carbon black).

  On the other hand, the elastic layer 53b is made of a conductive elastic material. Specifically, as the material of the elastic layer 53b, for example, rubber such as NBR or EPDM is used. Further, the rubber that is a material of the elastic layer 53b of the belt member 53 contains a substance that imparts conductivity (for example, carbon black). Such a conductive rubber is preferably used for the elastic layer 53b. Moreover, it is preferable that the said conductive rubber of the elastic layer 53b is what reduced hardness by foaming (namely, foamable conductive elastic member (foamable conductive rubber etc.)).

  Since the base layer 53a and the elastic force imparting layer 53b have conductivity, the toner image on the intermediate transfer belt 21 is appropriately transferred to the paper PA in response to voltage application by the secondary transfer roller 51.

  Further, the secondary transfer roller 51 and the driven roller 52 can relatively move in a direction in which the distance between them is expanded or contracted. Then, by applying an elastic force by the spring 54 in a direction that increases the relative distance between the secondary transfer roller 51 and the driven roller 52, the belt member 53 wound around the secondary transfer roller 51 and the driven roller 52 is applied to the belt member 53. A tension F is applied.

  Specifically, a spring 54 is provided between the secondary transfer roller 51 and the driven roller 52 via a fixing member 55 and a standing member 56, and appropriate elasticity is provided between the rollers 51 and 52. Power (biasing power) is given. Specifically, as shown in FIG. 3, the shaft member of the secondary transfer roller 51 is disposed through the circular hole 55 c of the fixed member 55 fixed at a predetermined position in the apparatus, and the shaft member of the driven roller 52. Is disposed through the long hole 55 d of the fixing member 55. The driven roller 52 can move in the extending direction of the long hole 55d, and the driven roller 52 and the secondary transfer roller 51 can relatively move in the direction in which the distance between them is expanded or contracted. A spring 54 is provided between the standing member 56 fixed to the fixing member 55 and the bearing portion 52 c of the driven roller 52. The spring 54 is provided in a state in which the spring 54 is contracted from the natural length, and a force in a direction that further increases the relative distance between the secondary transfer roller 51 and the driven roller 52 acts on the spring 54. An appropriate tension (tension) F acts on the belt member 53 wound around the secondary transfer roller 51 and the driven roller 52 by the elastic force of the spring 54 and the like.

<1-3. Operation>
Next, a transfer operation using the transfer unit 50 will be described in detail. The transfer operation and the like are controlled by a controller (control unit) built in the image forming apparatus 1.

  After the paper PA supplied by the paper supply unit 30 and conveyed from the upstream side of the conveyance path passes through the positions of the timing rollers 41 and 42 (see FIG. 1), the secondary transfer roller 51 is driven to rotate at an appropriate timing. Start. As a result, the belt member 53 wound around the secondary transfer roller 51 and the driven roller 52 rotates clockwise. Accordingly, the belt member 53 is located on the conveyance path side of the paper PA from the upstream side (lower side in FIG. 2) to the downstream side (upper side in FIG. 2) as shown by an arrow AR2 in FIG. proceed. Here, it is assumed that the conveyance speed of the belt member 53 is substantially the same as the conveyance speed of the intermediate transfer belt 21.

  Further, the timing rollers 41 and 42 convey the paper PA, which is a transfer target of the toner image, toward the portion PT1 of the belt member 53. Then, as shown in FIG. 2, the sheet PA conveyed from the upstream side further advances along the conveyance path. When the paper PA further travels along the transport path, it collides with the portion PT1 of the belt member 53 with a collision angle θ as shown in FIG. In order to reduce the impact force at the time of collision, the collision angle θ is preferably a relatively small acute angle (specifically, 45 degrees or less). Further, the collision angle θ is more preferably 30 degrees or less.

  As shown in FIG. 2, the portion PT1 in the belt member 53 is a portion on the side of the sheet conveyance path, and is a substantially straight portion between the contact CP2 and the contact CP1. Here, the contact CP <b> 1 is a contact between the secondary transfer roller 51 and the substantially linear portion of the belt member 53, and the contact CP <b> 2 is a contact between the driven roller 52 and the substantially linear portion of the belt member 53. Further, the portion PT1 is not in contact with the outer peripheral portion of the secondary transfer roller 51 and is not in contact with the outer peripheral portion of the driven roller 52. In other words, the portion PT1 is not supported by either the secondary transfer roller 51 or the driven roller 52. Therefore, the part PT1 is also referred to as a non-supporting part. Alternatively, the portion PT1 is also expressed as a portion that can be bent in response to an external force, that is, a flexible portion.

  As shown in FIG. 5, when the paper PA collides with the portion PT <b> 1 of the belt member 53, the portion PT <b> 1 is bent by the elasticity of the spring 54 and the elasticity of the belt member 53. In particular, the collision force acting on the portion PT1 of the belt member 53 from the front end portion of the paper PA is absorbed by the portion PT1 being bent and the spring 54 being further contracted with the deformation of the elastic layer 53b. In this way, the impact force due to the collision of the paper PA is absorbed, and the impact force transmitted to the secondary transfer roller 51 and the intermediate transfer belt 21 is reduced. Therefore, adverse effects on image formation can be suppressed.

  Thereafter, the front end of the paper PA is conveyed downstream (upward in the drawing) at a speed substantially the same as the speed of the belt member 53 according to the rotation operation of the belt member 53 while being in contact with the belt member 53. The Then, the paper PA reaches the nip portion N3 (FIG. 1), which is a portion where the secondary transfer roller 51 and the driving roller 23 face each other, and further passes through the nip portion N3. When passing through the nip portion N3, the full color toner image formed on the intermediate transfer belt 21 is transferred onto the paper PA by the transfer portion 50 (particularly, voltage application to the secondary transfer roller 51).

  The toner image transferred onto the paper PA is heated by the fixing device 45 and fixed on the paper PA. Thereafter, the paper PA is discharged to the paper discharge unit 46.

  As described above, according to the image forming apparatus 1, when the paper PA collides with the belt member 53, the portion PT1 (flexible portion) of the belt member 53 bends, thereby causing the paper PA to collide. Impact force is eased. That is, it is possible to satisfactorily reduce the impact force generated during image transfer.

  In particular, since the belt member 53 has the elastic layer 53b on the outer peripheral side thereof, the impact force due to the collision of the paper PA is reduced by the elastic force of the elastic layer 53b in the portion PT1. Further, by using a foamable rubber for the elastic layer 53b, a suitable shock absorbing force can be obtained.

  Further, the secondary transfer roller 51 and the driven roller 52 are provided so as to be relatively movable in a state where an elastic force is applied between them by a spring 54. Therefore, the portion PT1 bends not only according to the elasticity of the belt member 53 but also according to the elasticity of the spring 54. Thereby, the impact force due to the collision of the paper PA is more appropriately absorbed.

<2. Second Embodiment>
<2-1. Overview>
The second embodiment is a modification of the first embodiment. Below, it demonstrates centering on difference with 1st Embodiment.

  FIG. 6 is a perspective view showing a transfer unit 50 (specifically, 50B) according to the second embodiment.

  As shown in FIG. 6, the transfer unit 50 </ b> B includes an eccentric cam 57 and a motor 58, and can adjust the tension of the belt member 53. Specifically, in the first embodiment, one end of the spring 54 is fixed to the standing member 56, but in the second embodiment, the one end of the spring 54 is fixed to the eccentric cam 57. When the eccentric cam 57 is rotated by the motor 58, the length of the spring 54 is changed. As a result, the elastic force by the spring 54 is changed, and the tension F of the belt member 53 is changed. As described above, the eccentric cam 57 and the motor 58 function as an adjustment unit that adjusts the elastic force of the spring 54 and the tension F of the belt member 53.

  In this embodiment, the tension F of the belt member 53 is changed according to the thickness D of the paper PA to be transferred. The thickness D of the paper PA is detected by, for example, a paper thickness sensor 61 (see FIG. 1) provided on the upstream side of the transfer unit 50 in the paper transport path.

<2-2. Operation>
Next, the operation according to the second embodiment will be described in detail.

  After the paper PA supplied by the paper supply unit 30 and conveyed from the upstream side of the conveyance path passes through the positions of the timing rollers 41 and 42 (see FIG. 1), the secondary transfer roller 51 is driven to rotate at an appropriate timing. Start. As a result, the belt member 53 wound around the secondary transfer roller 51 and the driven roller 52 rotates clockwise, and the belt member 53 moves from the upstream side of the conveyance path to the downstream side on the conveyance path side of the paper PA. Proceed toward.

  When the paper PA passes the position of the timing rollers 41 and 42, the paper thickness sensor 61 detects the paper thickness D. Then, the tension F of the belt member 53 is adjusted according to the detected thickness D. Specifically, the eccentric cam 57 is rotated by driving the motor 58 and the length of the spring 54 is changed, whereby the tension F of the belt member 53 is adjusted.

  FIG. 7 is a diagram illustrating how the tension F is changed. As shown in FIG. 7, the tension F of the belt member 53 is set to decrease as the thickness D of the sheet PA increases.

  For example, when the thickness D is a relatively small value D1, the repulsive force of the spring 54 is reduced by further shortening the spring 54 that is shorter than the natural length (that is, by increasing the amount of contraction of the spring 54 from the natural length). By increasing the tension F, the tension F of the belt member 53 is adjusted to a relatively large value F1. Conversely, when the thickness D is a relatively large value D2 (> D1), the repulsive force (biasing force) of the spring 54 is reduced by reducing the contraction amount from the natural length of the spring 54, and the belt member 53. Is adjusted to a relatively small value F2 (<F1).

  When the adjustment operation of the tension F is completed, the sheet PA conveyed from the upstream side collides with the portion PT1 of the belt member 53 in a state having a certain collision angle θ.

  When the sheet PA collides with the portion PT1 of the belt member 53, the portion PT1 bends due to the elasticity of the spring 54 and the elasticity of the belt member 53. In particular, the collision force acting on the portion PT1 of the belt member 53 from the front end portion of the paper PA is absorbed by the portion PT1 being bent and the spring 54 being further contracted with the deformation of the elastic layer 53b. In this way, the impact force due to the collision of the paper PA is absorbed, and the impact force transmitted to the secondary transfer roller 51 and the intermediate transfer belt 21 is reduced. Therefore, adverse effects on image formation can be suppressed.

  Further, the bending amount of the belt member 53 is adjusted by changing the tension F of the belt member 53 as described above.

  In particular, when the paper PA is relatively thick, the belt member 53 is relatively easily bent because the tension F of the belt member 53 is set small. When a relatively thick sheet collides with the belt member 53, the impact force at the time of the collision is appropriately reduced by the belt member 53 being bent relatively large.

  Conversely, when the paper PA is relatively thin, the tension F of the belt member 53 is set to be large, so that the belt member 53 is relatively difficult to bend. When a relatively thick sheet collides with the belt member 53, the belt member 53 bends relatively small, so that the impact force at the time of the collision is appropriately reduced.

  The subsequent operation, that is, the operation after the paper PA collides with the belt member 53 is the same as in the first embodiment.

  As described above, also in the image forming apparatus according to the second embodiment, the same effect as that of the first embodiment can be obtained. In particular, since the tension F of the belt member 53 is changed according to the thickness D of the paper PA, the impact force generated at the time of image transfer can be further appropriately reduced according to the paper thickness of the paper PA. .

<3. Third Embodiment>
<3-1. Overview>
The third embodiment is a modification of the first embodiment. Below, it demonstrates centering on difference with 1st Embodiment.

  FIG. 8 is a diagram illustrating a configuration in the vicinity of the transfer unit 50 (specifically, 50C) according to the third embodiment.

  As shown in FIG. 8, the transfer unit 50C has the same configuration as the transfer unit 50A according to the first embodiment. In addition, a movable guide member 43 is provided at a position facing the portion PT1 in the transfer portion 50C.

  The guide member 43 guides the paper PA that has passed the positions of the timing rollers 41 and 42 (see FIG. 1) toward the transfer unit 50C. The guide member 43 is provided so as to be rotatable (swingable) about the axis AX11 in the direction of the double arrow in FIG. 8, and is driven by a drive mechanism (not shown).

  When the arrangement angle of the guide member 43 is changed, the traveling direction of the paper PA that is guided and advanced by the guide member 43 is changed. As a result, the leading end of the paper PA collides with the belt member 53 of the transfer unit 50C. The collision angle is changed. In this way, the guide member 43 changes the collision angle of the paper PA with respect to the transfer portion 50C.

  In this embodiment, the arrangement angle of the guide member 43 (and consequently the collision angle θ of the paper PA with respect to the transfer portion 50C) is changed according to the thickness D of the paper PA to be transferred. As described above, the thickness D of the paper PA is detected by, for example, the paper thickness sensor 61 (see FIG. 1) provided on the upstream side of the transfer unit 50 in the paper transport path.

<3-2. Operation>
Next, the operation according to the third embodiment will be described in detail.

  After the paper PA supplied by the paper supply unit 30 and conveyed from the upstream side of the conveyance path passes through the positions of the timing rollers 41 and 42 (see FIG. 1), the secondary transfer roller 51 is driven to rotate at an appropriate timing. Start. As a result, the belt member 53 wound around the secondary transfer roller 51 and the driven roller 52 rotates clockwise, and the belt member 53 moves from the upstream side of the conveyance path to the downstream side on the conveyance path side of the paper PA. Proceed toward.

  When the paper PA passes the position of the timing rollers 41 and 42, the paper thickness sensor 61 detects the paper thickness D. Then, according to the detected thickness D, the angle of the guide member 43 (and consequently the collision angle θ) is adjusted.

  FIG. 9 is a diagram showing how the collision angle θ is changed. As shown in FIG. 9, the arrangement angle of the guide member 43 is changed so that the collision angle θ decreases as the thickness D of the paper PA increases.

  For example, when the thickness D is a relatively small value D1, the guide member 43 is rotated clockwise about the axis AX11, and the angle between the guide member 43 and the portion PT1 of the belt member 53 is changed to a relatively large value. Is done. As a result, the collision angle θ becomes a relatively large value θ1 (for example, 30 degrees). Conversely, when the thickness D is a relatively large value D2 (> D1), the guide member 43 is rotated counterclockwise about the axis AX11, and the angle between the guide member 43 and the portion PT1 of the belt member 53 is It is changed to a relatively small value. As a result, the collision angle θ becomes a relatively small value θ2 (for example, 10 degrees).

  When the adjustment operation of the collision angle θ is completed, the paper PA conveyed from the upstream side collides with the portion PT1 of the belt member 53 with the adjusted collision angle θ.

  When the sheet PA collides with the portion PT1 of the belt member 53, the portion PT1 bends due to the elasticity of the spring 54 and the elasticity of the belt member 53. In particular, the collision force acting on the portion PT1 of the belt member 53 from the front end portion of the paper PA is absorbed by the portion PT1 being bent and the spring 54 being further contracted with the deformation of the elastic layer 53b. In this way, the impact force due to the collision of the paper PA is absorbed, and the impact force transmitted to the secondary transfer roller 51 and the intermediate transfer belt 21 is reduced. Therefore, adverse effects on image formation can be suppressed.

  Further, as described above, by adjusting the collision angle θ of the paper PA with respect to the transfer portion 50C, it is possible to appropriately reduce the impact force itself at the time of the collision. In particular, when the paper PA is relatively thick, the impact angle θ decreases as the angle of the guide member 43 changes, so that the impact force at the time of the collision is further appropriately reduced. Conversely, when the sheet PA is relatively thin, the leading end of the sheet PA collides with the belt member 53 at a portion PT1 in the vicinity of the nip portion N3 at a relatively large collision angle θ and proceeds on the belt member 53. By doing so, the leading end portion of the sheet PA can enter the nip portion N3 in a state where the leading end portion of the sheet PA secures a good area around the intermediate transfer belt 21. Therefore, the transfer operation can be performed satisfactorily.

  The subsequent operation is the same as in the first embodiment.

  As described above, the same effect as that of the first embodiment can be obtained also in the image forming apparatus according to the third embodiment. In particular, since the collision angle θ when the paper PA collides with the belt member 53 is changed according to the thickness D of the paper PA, the impact force generated when the image is transferred is more appropriately determined according to the paper thickness. Can be reduced.

<4. Other>
Although the embodiments of the present invention have been described above, the present invention is not limited to the contents described above.

  For example, in each of the above embodiments, the case where tension is applied to the belt member 53 by the spring 54 is illustrated, but the present invention is not limited to this. Specifically, a transfer unit 50D as shown in FIGS. 10 and 11 may be provided. In the transfer unit 50D, the spring 54 as an elastic force applying means is not provided, and the positions of the central axes of the rollers 51 and 52 are set so that the relative distance between the secondary transfer roller 51 and the driven roller 52 is always the same. It is fixed. Also by using such a transfer part transfer part 50D, it is possible to reduce the impact force generated when the paper PA collides. Specifically, when the sheet PA collides with the portion PT1 of the belt member 53 of the transfer unit 50D, the portion PT1 bends with the deformation of the elastic layer 53b, thereby reducing the impact force in the collision. . In order to bend the belt member 53 more appropriately, the secondary transfer roller 51 and the driven roller 52 are relatively moved in a state where an elastic force (repulsive force) by the spring 54 is applied as in the above-described embodiments. It is preferable to provide it.

  In the second and third embodiments, the case where the thickness D of the paper PA is detected by the paper thickness sensor 61 is exemplified, but the present invention is not limited to this, and the thickness D is detected by other methods. You may do it. For example, the thickness D of the paper PA may be acquired based on the print setting content included in the print instruction transmitted from the information processing apparatus (personal computer or the like) that is the print output request source. Specifically, in the information processing apparatus of the print output request source, print setting information (information indicating paper thickness (including paper type information)) set by the operator of the information processing apparatus on the setting screen of the printer driver From this, the thickness D of the paper PA may be acquired.

  Further, in the third embodiment, the case where the movable guide member 43 is provided on the transfer surface side (left side in FIG. 8) with respect to the sheet conveyance path is exemplified, but the present invention is not limited to this. For example, the movable guide member 43 is placed on the side opposite to the transfer surface (the right side in FIG. 8) with respect to the paper transport path (specifically, between the transport path of the paper PA and the portion PT1 of the transfer section 50). You may make it provide.

  In the first embodiment and the second embodiment, the technique of conveying the paper PA from the position of the timing rollers 41 and 42 toward the portion PT1 of the belt member 53 by using only the timing rollers 41 and 42 is exemplified. It is not limited to this. For example, in the first embodiment or the second embodiment, a fixed guide member 43B (not shown) is provided at a position similar to the position of the guide member 43 of the third embodiment, and the paper is placed along the guide member 43B. The paper PA may be conveyed toward the portion PT1 of the belt member 53 by guiding the PA. Further, such a guide member 43B may be disposed on the opposite side (that is, the opposite side of the sheet transfer surface) with respect to the conveyance path of the sheet PA, for example. Alternatively, the guide member 43B may be arranged on both sides of the paper transport path.

  In each of the above embodiments, a tandem color printer is exemplified as the image forming apparatus. However, the image forming apparatus is not limited to this, and the image forming apparatus is not limited to this. The idea described above may be applied. The image carrier is not limited to the intermediate transfer belt 21 and may be, for example, a photosensitive drum in a four-cycle color printer.

  Further, the image forming apparatus is not limited to an apparatus having only a printing function, and may be, for example, a multifunction machine having a scanning function and / or a copying function.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10, 10Y, 10M, 10C, 10K Imaging unit 21 Intermediate transfer belt 23 Drive roller 41, 42 Timing roller 43 (movable) Guide member 50, 50A, 50B, 50C, 50D Transfer part 51 Secondary transfer roller 51
52 driven roller 53 belt member 53a base layer 53b elastic layer 54 spring 55 fixing member 57 eccentric cam 58 motor 61 paper thickness sensor N3 nip portion PA paper PT1 flexible portion

Claims (6)

An image forming apparatus,
An image carrier for carrying a toner image;
A transfer roller facing the image carrier;
A roller member provided substantially parallel to the transfer roller;
A belt member wound around the transfer roller and the roller member;
Conveying means for conveying a transfer material, which is a transfer target of the toner image, toward a flexible portion of the belt member;
With
The belt member is to have a configured elastic layer of a conductive elastic material,
The image forming apparatus , wherein the elastic layer is made of foaming conductive rubber .   An image forming apparatus,
  An image carrier for carrying a toner image;
  A transfer roller facing the image carrier;
  A roller member provided substantially parallel to the transfer roller;
  A belt member wound around the transfer roller and the roller member;
  Conveying means for conveying a transfer material, which is a transfer target of the toner image, toward a flexible portion of the belt member;
With
  The belt member has an elastic layer made of a conductive elastic material,
  The roller member and the transfer roller can move relative to each other in the direction of expanding and contracting the distance between them,
  By applying an elastic force by an elastic force applying means in a direction that increases the relative distance between the roller member and the transfer roller, a tension is applied to the belt member wound around the transfer roller and the roller member. And
  The image forming apparatus includes:
  Adjusting means for adjusting the tension according to the thickness of the transfer material;
An image forming apparatus further comprising:   An image forming apparatus,
  An image carrier for carrying a toner image;
  A transfer roller facing the image carrier;
  A roller member provided substantially parallel to the transfer roller;
  A belt member wound around the transfer roller and the roller member;
  Conveying means for conveying a transfer material, which is a transfer target of the toner image, toward a flexible portion of the belt member;
  Changing means for changing the advancing direction of the transfer material by the conveying means and changing the collision angle when the leading end of the transfer material collides with the belt member;
With
  The belt member has an elastic layer made of a conductive elastic material,
  The image forming apparatus according to claim 1, wherein the changing unit changes the collision angle according to a thickness of the transfer material.   The image forming apparatus according to claim 2 or 3,
  Detecting means for detecting the thickness of the transfer material;
An image forming apparatus further comprising:   The image forming apparatus according to claim 2 or 3,
  The image forming apparatus, wherein the thickness of the transfer material is acquired based on a print setting content included in a print instruction.   The image forming apparatus according to any one of claims 1 to 5,
  The belt member is rotatable in a state of being wound around the transfer roller and the roller member,
  After the front end of the transfer material collides with the belt member, the front end of the transfer material is directed to the facing portion of the transfer roller and the image carrier at a speed substantially the same as the speed of the belt member in contact with the belt member. The image forming apparatus is characterized in that it proceeds.

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