JP2007304230A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an image of high quality free from image misregistration by surely restraining the movement (meandering) in the width direction, of an endless belt member laid across a plurality of rotating members in a tensioned condition through simple constitution and inexpensively. <P>SOLUTION: A belt conveying apparatus has an intermediate transfer belt 18 and a plurality of rollers 14, 15 and 16 across which the intermediate transfer belt 18 is laid in a tensioned condition and which rotationally drives the belt 18, the belt conveying apparatus is characterized in that it includes: a guide rib 19 provided on the whole periphery of the inside surface of the belt 18; and flanges 20 and 150 for regulating the belt 18 while abutting the guide rib 19 against the belt when the belt 18 moves in a direction orthogonal to the rotational moving direction, the flanges 20 and 150 are provided on two rollers 14 and 16 among the plurality of rollers. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that forms an image on a recording material using an endless belt member stretched around a plurality of rotating members.

  Conventionally, as an image forming apparatus using an endless belt member, an image forming apparatus using an intermediate transfer belt stretched around a plurality of rollers is known. An image forming method using an intermediate transfer belt is often employed in, for example, an image forming apparatus having a full color or multiple image forming function. Japanese Patent Laid-Open No. 2002-132057 (hereinafter referred to as Patent Document 1) uses the intermediate transfer belt, and sequentially transfers toner images of respective colors onto the intermediate transfer belt, and carries the toner carried on the intermediate transfer belt. An image forming apparatus that collectively transfers an image onto a recording material is disclosed.

  In the image forming apparatus disclosed in Patent Document 1, the intermediate transfer belt is stretched by three rollers. Specifically, a driving roller that rotationally drives the intermediate transfer belt, a secondary transfer opposite roller that faces a secondary transfer roller that collectively transfers a toner image onto a recording material, and a tension roller that applies tension to the intermediate transfer belt; Thus, the intermediate transfer belt is stretched. A plurality of image forming portions that form toner images of respective colors that are sequentially transferred onto the intermediate transfer belt are arranged on the belt surface between the drive roller and the tension roller, and are arranged in parallel in the belt running direction. Has been.

  Further, the image forming apparatus is provided with a shift regulating means for regulating the movement (shift) of the intermediate transfer belt in the belt width direction orthogonal to the traveling direction of the intermediate transfer belt. This deviation regulating means includes guide ribs provided on both edges of the back surface side (inner side) of the intermediate transfer belt, and both ends of a tension roller that is one of three rollers that stretch the intermediate transfer belt. And a flange having an inclination provided on the surface. Due to this deviation restricting means, a force in the width direction acts on the intermediate transfer belt, and even if the intermediate transfer belt tries to move in the width direction, one guide rib of the intermediate transfer belt is brought into contact with one flange of the roller. The contact of the intermediate transfer belt in the width direction is restricted.

JP 2002-132057 A

  However, the image forming apparatus has a configuration in which a flange that abuts and regulates the guide rib of the intermediate transfer belt is provided only on a tension roller that is one of three stretching rollers. For this reason, when the biasing force acting on the intermediate transfer belt increases, the guide rib of the intermediate transfer belt in the abutting relation pushes up the inclination of the flange of the roller and rides on the roller, and the intermediate transfer belt moves in the width direction. There is a risk of moving to a large distance. If the intermediate transfer belt moves in the width direction due to the action of such a large shifting force, the intermediate transfer belt runs meandering, the transfer position of each color toner image is shifted, and the quality of the color image is deteriorated. There is a risk that.

  Further, even if the deviation regulating means maintains the above-described abutting relationship, the intermediate transfer belt may be twisted. That is, even if the guide rib of the transfer belt hits the flange on the tension roller side and the deviation can be regulated, the deviation cannot be regulated on the opposite drive roller side through the belt surface on which the image forming unit is arranged in parallel. Will further move in the direction in which the offset force acts. As a result, the intermediate transfer belt between the tension roller and the driving roller is twisted. If the intermediate transfer belt is thus twisted, the intermediate transfer belt may be damaged. Also, if the intermediate transfer belt is conveyed in a twisted state, the intermediate transfer belt is conveyed at a position shifted from the center of the image, so the image recording accuracy in the direction orthogonal to the running direction of the intermediate transfer belt is reduced. Resulting in. In particular, in the case of a color image, since the toner images of the respective colors are sequentially transferred onto the twisted intermediate transfer belt between the tension roller and the driving roller, color misregistration occurs and image quality deteriorates. Further, in recent years, as the product speed increases, the peripheral speed of the intermediate transfer belt tends to increase and the shifting force acting on the intermediate transfer belt tends to increase. In this case, the above-described deterioration in image quality is more remarkable. It becomes.

  Therefore, an object of the present invention is to reliably regulate the movement (shift) in the width direction of the endless belt member stretched around a plurality of rotating members, and to obtain a high-quality image without positional deviation. An image forming apparatus is provided.

  In order to achieve the above object, a typical configuration of the present invention is a belt conveying device having an endless belt member and a plurality of rotating members that stretch and rotate the belt member, and the belt member. A guide member that is provided over the entire circumference of the inner surface, and a regulating member that abuts and regulates the guide member when the belt member moves in a direction orthogonal to the rotational movement direction. The at least two rotating members among the plurality of rotating members are provided.

  According to the present invention, even if a force in a direction perpendicular to the rotational movement direction is applied to the belt member, the guide member of the belt member is abutted against the restriction member of at least two rotation members, so that the guide The force with which the member tries to get over the restricting member is reduced. For this reason, the movement to the direction orthogonal to the rotational movement direction of a belt member can be controlled more reliably. As a result, the belt member can be restricted to a position within a predetermined range, and even when the belt member is used for image formation, it is possible to improve the recording accuracy in the direction perpendicular to the rotational movement direction of the belt member. A high-quality image without deviation can be obtained.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in the following embodiments should be appropriately changed according to the configuration of the apparatus to which the present invention is applied and various conditions. Therefore, unless specifically stated otherwise, the scope of the present invention is not intended to be limited thereto.

[First Embodiment]
First, a schematic configuration of an image forming apparatus including the belt conveyance device according to the present embodiment will be described. FIG. 1 is an overall configuration diagram illustrating an embodiment of an image forming apparatus.

<Overall configuration>
The image forming apparatus is configured as a color laser printer which is one form of a color image forming apparatus. First, the overall configuration of the color laser printer will be described with reference to FIG.

  The color laser printer includes an intermediate transfer belt 18 as an endless belt member. In addition, four color image forming units of yellow (Y), magenta (M), cyan (C), and black (K) are provided along the intermediate transfer belt 18. Then, the toner images of the respective colors formed by the respective image forming portions are multiplex-transferred onto the intermediate transfer belt 18, and then transferred onto the recording material, and the recording material onto which the four-color toner images have been transferred is fixed. A full-color permanent image is obtained.

  The intermediate transfer belt 18 is suspended from a plurality of rotating members. Specifically, it is suspended and installed on three rollers, ie, a driving roller 14 as the rotating member, a secondary transfer counter roller 15 and a tension roller 16, and together with these driving rollers 14 and the like, an intermediate transfer as a belt conveying device. The unit 13 is configured. The intermediate transfer belt 18 is driven to rotate in the direction of the arrow in the figure by driving by the driving roller 14. Here, three rollers are illustrated as the plurality of rotating members, but the number of rollers is not limited to this.

  Each image forming unit has a drum-type electrophotographic photosensitive member, that is, a photosensitive drum 1 (1Y, 1M, 1C, 1K) as an image carrier. Furthermore, a process means for acting on the photosensitive drum 1 is provided around it. Specifically, the charging roller 5 (5K, 5M, 5C, 5K), the developing unit 4 (4Y, 4M, 4C, 4K), and a drum cleaner (not shown) are provided. A laser scanner 6 (6Y, 6M, 6C, 6K) is disposed above each photosensitive drum 1. Further, below each photosensitive drum 1, a primary transfer charger (not shown) facing the photosensitive drum 1 with the intermediate transfer belt 18 interposed therebetween is arranged. Among these, the photosensitive drum 1, the charging roller 5, the developing device 4, and the drum cleaner are integrated in the holder container 3 (3Y to 3K) and are detachably installed in the printer main body. The process unit is replaceable.

  The photosensitive drum 1 has an organic photoconductor layer coated on the outside of an aluminum cylinder. The photosensitive drum 1 is rotatably supported by the holder container 3 and is rotated in the counterclockwise direction in the drawing by transmitting a driving force from a driving motor (not shown) at one end at the rear of the drawing at the time of image formation. Is done. The charging roller 5 is a contact-type charging unit, and applies a voltage to the charging roller 5 in contact with the surface of the photosensitive drum 1 to uniformly charge the surface of the photosensitive drum 1 to a predetermined polarity and potential.

  The laser scanner 6 as an exposure means includes a laser diode (not shown), a polygon mirror 6a (6Ya, 6Ma, 6Ca, 6Ka), an imaging lens 6b (6Yb, 6Mb, 6Cb, 6Kb) and the like. When an image signal is given to the laser diode, the laser diode irradiates the polygon mirror 6a with image light corresponding to the image signal. Then, the polygon mirror 6a that rotates at high speed by the scanner motor reflects the image light, and the surface of the photosensitive drum 1 that rotates at a constant speed is selectively exposed through the imaging lens 6b. An electrostatic latent image is formed on the surface.

  The developing device 4 has a sleeve 4S (4YS, 4MS, 4CS, 4KS) disposed at a position facing the photosensitive drum 1 with a minute interval. The developing unit 4 contains yellow (Y), magenta (M), cyan (C), and black (K) developers, here, a two-component developer in which a non-magnetic toner and a magnetic carrier are mixed. ing. Each developing device 4 feeds the stored developer to the sleeve 4S by a feed mechanism, and coats the developer on the surface of the sleeve 4S that rotates in the clockwise direction in the figure. Each developing device 4 conveys the coated developer to a developing position facing the photosensitive drum 1 by the sleeve 4S, and develops the electrostatic latent image formed on the photosensitive drum 1 with a developer of a corresponding color. Thus, it is visualized as a toner image.

  The toner images of the respective colors on the photosensitive drum 1 are transferred while being superimposed on the intermediate transfer belt 18. Here, the intermediate transfer belt 18 is formed of a seamless resin belt having a circumferential length of about 1000 mm. The intermediate transfer belt 18 is supported by the printer main body with the driving roller 14 as a fulcrum, and transmits the driving force of a driving motor (not shown) at one end of the driving roller 14, so that the peripheral speed of the photosensitive drum 1 according to the image forming operation. Synchronously with, it is rotated in the clockwise direction. Further, the intermediate transfer belt 18 can be easily attached to and detached from the intermediate transfer unit 13 in the right direction in the drawing.

  Below the intermediate transfer belt 18, a cassette 7 containing a plurality of recording materials P is installed. The cassette 7, the pickup roller 8, the feed roller 9, the double feed prevention retard roller 10, the guide plate 11, the transport roller 61, and the registration roller pair 12 constitute a feeding unit. At the time of image formation, the rollers 8, 9, and 10 are driven and rotated in accordance with the image forming operation to separate and feed the recording material P in the cassette 7 one by one. And, it reaches the registration roller pair 12 via the conveying roller 61 and the like. During the image forming operation, the registration roller pair 12 performs a non-rotating operation for allowing the recording material P to stand still and a rotating operation for conveying the recording material P toward the intermediate transfer belt 18 in a predetermined sequence. The image and the recording material P at the time of the transfer process are aligned.

  A swingable transfer roller 60 is installed on the surface side of the intermediate transfer belt 18 at the location of the secondary transfer counter roller 15 to form a secondary transfer portion T2. The transfer roller 60 is formed by winding a metal shaft with a medium resistance foamed elastic body, can swing up and down in the figure, and is rotationally driven by a driving force to the metal shaft. While the four-color toner image is formed on the intermediate transfer belt 18, the transfer roller 60 is positioned below so that the toner image on the intermediate transfer belt 18 does not disturb the image until it reaches the secondary transfer portion T2. However, it is separated from the intermediate transfer belt 18. Thereafter, the transfer roller 60 is moved to an upper position by a cam member (not shown) in accordance with the timing of transferring the color image to the recording material P, and is pressed against the intermediate transfer belt 18 through the recording material P with a predetermined pressure. .

  At the same time, a bias is applied to the transfer roller 60, and the toner image on the intermediate transfer belt 18 is transferred to the recording material P. Since the intermediate transfer belt 18 and the transfer roller 60 are respectively driven, the recording material P sandwiched between the two is transported at a predetermined speed in the left direction of the drawing at the same time as the transfer process, and is the next process. It is sent toward the fixing device 50.

  The fixing device 50 fixes the toner image transferred onto the recording material P. As shown in FIG. 1, the fixing device 51 applies heat to the recording material P, and presses the recording material P against the fixing roller 51. A pressure roller 52 for rotating the rollers 51 and 52. Each of the rollers 51 and 52 is formed hollow and has a heater (not shown) inside. The recording material P onto which the toner image has been transferred is nipped and conveyed by the fixing roller 51 and the pressure roller 52, and the toner image is fixed to the recording material P by applying heat and pressure therebetween.

<Description of configuration of intermediate transfer belt>
Further, the intermediate transfer belt 18 is provided with a tension applying mechanism using a compression spring 21 at the tension roller 16. As a result, even if the peripheral length of the intermediate transfer belt 18 changes due to changes in temperature and humidity in the printer main body and diameter, the tension of the intermediate transfer belt 18 is maintained constant.

  As shown in FIG. 2, the tension applying mechanism compresses between the end surface 22b of the tension bearing 22 in which the shaft 16a of the tension roller 16 is rotatably fitted and the wall surface 23b of the frame 23 of the intermediate transfer unit 13. The spring 21 is attached with a predetermined pressure. The shaft 16 a of the tension roller 16 is further supported by a tensioner 17. A conductive polyacetal resin is used as the material of the tension bearing 22, and the tension roller 16 is electrically grounded. Although the tension roller shaft 16a and the tensioner 17 rotate and slide, the load applied to the inner wall of the bearing portion of the tensioner 17 is reduced, and the wear on the inner wall becomes almost zero.

  On the other hand, the inner wall 22a of the tension bearing 22 and the tension roller shaft 16a are worn, but there is no change in the positional relationship between the tensioner 17 and the tension roller 16, and the relative positional relationship between the tension roller 16 and the blade 31 of the cleaning unit 30. Will not change. Further, although the mounting dimension of the compression spring 21 slightly changes due to wear of the inner wall 22a of the tension bearing 22 and the tension roller shaft 16a, the intermediate transfer belt 18 does not slip due to a pressure drop due to the change.

  Here, the conductive polyacetal resin is used for the tension bearing 22, but the same effect can be obtained by using, for example, an iron-based or copper-based oil-impregnated sintered material.

<Explanation of deviation control means>
Further, a deviation regulating means is provided for regulating movement of the intermediate transfer belt 18 in the belt width direction orthogonal to the rotational movement direction, that is, deviation of the belt 18. The shift regulating means includes a guide rib 19 as a guide member provided over the entire inner surface of the intermediate transfer belt 18 and a regulating member that abuts and regulates the guide rib 19 when the intermediate transfer belt 18 moves in the width direction. As flanges 20 and 150. This will be described in detail below with reference to FIGS. FIG. 3 is a schematic configuration diagram around the intermediate transfer unit. 4 and 5 are views showing a cross section of an arrow O portion in FIG. 4 and 5, an arrow K indicates the front side of the apparatus, and an arrow J indicates the conveyance direction of the intermediate transfer belt 18. CL indicates the center position of the image. Since the image center CL is orthogonal to the axis center of the drive roller 14, the image center CL is parallel to the conveyance direction of the intermediate transfer belt 18.

  As shown in FIGS. 3 and 4, the guide rib 19 as the guide member is made of rubber, and is provided on both edges of the back surface side of the intermediate transfer belt 18 over the entire circumference. Here, the guide ribs 19 are attached to both edges on the back side of the intermediate transfer belt 18 with an adhesive. Further, the flanges 20 and 150 as the regulating members are provided on two rollers 14 and 16 among the plurality of rollers 14, 15 and 16 that stretch the intermediate transfer belt 18. More specifically, the flange 20 as the first restricting member is provided on the tension roller 16 as the first rotating member on the upstream side in the rotational movement direction (the direction of arrow J in FIG. 3) of the belt 18 via the photosensitive drum 1. . Further, the flange 150 as the second regulating member is provided on the drive roller 14 as the second rotating member on the downstream side in the rotational movement direction of the belt 18 (in the direction of arrow J in FIG. 3) via the photosensitive drum 1. The flanges 20 and 150 are formed of resin, and have inclined surfaces that abut against the guide ribs 19 and regulate them. Further, the flanges 20 and 150 are provided at both axial ends of the rollers 14 and 16 so as to correspond to the guide ribs 19, respectively.

  With the above-described configuration, even if an offset force in the width direction acts on the intermediate transfer belt 18 and the intermediate transfer belt 18 tries to move in the width direction, one guide rib 19 of the intermediate transfer belt 18 is tension roller on the tension roller side. It hits 16 corresponding flanges 20. Further, the drive roller abuts against the corresponding flange 150 of the drive roller 14. That is, the shift of the intermediate transfer belt 18 is regulated on the tension roller side and the driving roller side. Thereby, the force of the guide rib 19 overcoming the flanges 20 and 150 is reduced, and the movement (shift) of the intermediate transfer belt 18 in the width direction can be more reliably regulated.

<Explanation of the flange of the deviation regulating means>
Here, the flange portion will be described in more detail. In FIG. 4, 20a and 150a are flange contact points. The flange contact points 20a and 150a are points at which the end portions 19a of the guide ribs 19 contact the inclined surfaces of the flanges 20 and 150 when the intermediate transfer belt 18 approaches the width direction. Here, the flanges 20 and 150 provided on the rollers 14 and 16 are arranged so that the distances from the image center CL to the flange contact points 20a and 150a are the same distance.

  With this configuration, a shift force in the width direction acts on the intermediate transfer belt 18, and a state when the belt 18 moves in the width direction will be described. For example, FIG. 5 shows a state in which the intermediate transfer belt 18 has approached the back side of the apparatus (the direction opposite to the arrow K direction).

  As shown in FIG. 5, the intermediate transfer belt 18 approaches the width direction, the end surface 19a of the guide rib 19 and the flange 20 come into contact with each other at the contact point 20a, and the shift is regulated. On the other hand, the end surface 19a of the guide rib 19 and the flange 150 are in contact with each other at the contact point 150a, and the deviation is regulated.

  As described above, since the guide rib 19 abuts against the flange 20 and the flange 150 on the front side of the apparatus, even if the guide rib 19 tries to ride on the flange 20 and the flange 150, the force of the guide rib 19 riding on one flange is reduced. Thereby, the deviation control of the intermediate transfer belt 18 can be more reliably performed.

  Further, since the force applied to the guide rib 19 at the flange 20 and flange 150 portions is reduced as compared with the restriction at one place, the damage of the belt such as the guide rib 19 peeling off from the intermediate transfer belt 18 can be reduced.

  Further, the guide rib 19 of the belt 18 is abutted and regulated by the flanges 20 and 150 provided on the two rollers 14 and 16 of the plurality of rollers on which the intermediate transfer belt 18 is stretched. It can be restricted to a position within the range. As a result, it is possible to improve the image recording accuracy in the direction orthogonal to the conveying direction of the belt 18 and to obtain a high-quality image free from positional deviation (color deviation).

<Description of configuration of cleaning unit>
A cleaning unit 30 is installed on the intermediate transfer belt 18. As shown in FIG. 3, the cleaning blade 30 includes a cleaning blade 31, a pressure spring 36 that presses the blade 31 against the intermediate transfer belt 18, and a cleaner container 34 that holds them.

  The toner scraped off from the intermediate transfer belt 18 by the cleaning blade 31 is collected in the cleaner container 34 as waste toner. The collected waste toner is conveyed by a screw 35 installed at the lowermost part in the cleaner container 34 and stored in a waste toner box 40 (see FIG. 1) separately installed in the apparatus main body. The screw 35 is rotated in a direction in which waste toner is conveyed by transmitting a driving force of a driving motor (not shown). In order to simplify the structure by reducing the number of motors, the driving source of the screw 35 uses the driving source of the fixing device.

  Further, a squeeze sheet 38 that is in contact with the intermediate transfer belt 18 is installed in parallel with the blade 31 on the upstream side of the cleaning blade 31 of the cleaner container 34. The squeeze sheet 38 is affixed to the sheet metal 39 with double-sided tape, and the sheet metal 39 is affixed to the cleaner container 34 with double-sided tape.

  The cleaning unit 30 will be further described later.

<Description of operation>
An operation when image formation is performed by the printer configured as described above will be described.

  First, the pickup roller 8 shown in FIG. 1 is rotated to feed the recording material P in the cassette 7, separated one by one by the feed roller 9 and the retard roller 10, and conveyed to the registration roller pair 12. On the other hand, the photosensitive drum 1 and the intermediate transfer belt 18 are rotated in a direction indicated by an arrow in FIG. 1 at a predetermined peripheral speed V (same speed as the process speed).

  Next, when an arbitrary point in the circumferential direction of the intermediate transfer belt 18 comes to the position S (S1, S2, S3, S4) in FIG. 1, the photosensitive drum 1 whose surface is uniformly charged is shown by E ( Laser exposure is performed at positions EY, EM, EC, and EK), and image formation is started. The distance from the exposure position E (image writing start position) of the photosensitive drum 1 to the contact portion (primary transfer portion) T1 (T1Y, T1M, T1C, T1K) with the intermediate transfer belt 18 counterclockwise, and the intermediate transfer belt The distance from 18 S to T1 is equal. Therefore, when the image writing start point E on the photosensitive drum 1 reaches the position of the primary transfer portion T1, the point S on the intermediate transfer belt 18 reaches the position of T1 and coincides therewith. By transferring the toner image from the photosensitive drum 1 to the intermediate transfer belt 18, an image is formed on the intermediate transfer belt 18 in the downstream direction with the S point as a leading end. The image is formed in the order of yellow, magenta, cyan, and black.

  First, a yellow image laser is irradiated by the scanner 6Y to form a yellow latent image on the photosensitive drum 1Y. Simultaneously with the formation of the latent image, the yellow developing device 4Y is driven, and a voltage having the same polarity and the same potential as the charging polarity of the photosensitive drum 1Y is applied to the sleeve 4YS of the developing device 4Y. The toner is attached and developed, and visualized as a yellow toner image. Subsequently, the yellow toner image on the photosensitive drum 1Y is primarily transferred onto the surface of the intermediate transfer belt 18 at the primary transfer portion T1Y slightly downstream of the developing portion. At this time, the intermediate transfer belt 18 is subjected to primary transfer by applying a voltage opposite to that of yellow toner through a primary transfer charger (not shown).

  When the image to be formed is A3 size, the length is 420 mm. The image of A3 is formed from the point S1 of the intermediate transfer belt 18 in the downstream direction to the point L1.

  Next, when the point S1 (the leading edge of the yellow image) on the intermediate transfer belt 18 comes to the position of S2 in FIG. 1, similarly to the case of yellow, the photosensitive drum 1M is irradiated with laser by the scanner 6M to cause the latent image of the magenta image. Form an image. This latent image is developed by the magenta developing device 4M to be visualized as a magenta toner image, and the magenta toner image is transferred onto the intermediate transfer belt 18 by being superimposed on the yellow toner image by the primary transfer portion T1M.

  Similarly, when S1 (the leading edge of yellow and magenta image) on the intermediate transfer belt 18 comes to the position of S3 in FIG. 1, a laser image of the cyan image is irradiated onto the photosensitive drum 1M by the scanner 6C to form a latent image. The latent image is developed by the cyan developing device 4C to be visualized as a cyan toner image, and the cyan toner image is transferred onto the intermediate transfer belt 18 by being superimposed on the yellow and magenta toner images at the primary transfer portion T1C.

  Similarly, when S1 (the leading edge of the yellow, magenta, and cyan images) on the intermediate transfer belt 18 reaches the position of S4 in the figure, the scanner 6K irradiates the photosensitive drum 1K with the laser of the black image to form a latent image. . The latent image is developed by the black developing device 4K to be visualized as a black toner image, and the black toner image is transferred onto the intermediate transfer belt 18 on the intermediate transfer belt 18 by being superimposed on the yellow, magenta, and cyan toner images.

  As described above, the latent image is formed, developed, and primary transferred in the order of yellow, magenta, cyan, and black, and the full-color toner image of four colors of yellow, magenta, cyan, and black is superimposed on the surface of the intermediate transfer belt 18. Form an image.

  Before the transfer of the black toner image of the fourth color to the intermediate transfer belt 18 is completed, the image leading end (intermediate transfer belt position S1) of the four color superimposed toner images on the intermediate transfer belt 18 is the secondary transfer portion. Along with reaching T2, the recording material P kept on standby by the registration roller pair 12 is conveyed to the transfer portion T2 at a predetermined timing. At the same time, the transfer roller 60 that is separated from the intermediate transfer belt 18 and is waiting below is moved upward by the cam mechanism, and the transfer roller 60 is moved to the intermediate transfer belt 18 at the transfer portion T2 with the recording material P interposed therebetween. Press contact. Simultaneously with the press contact, a bias having a reverse characteristic to that of the toner is applied to the transfer roller 60, and the four color toner images on the intermediate transfer belt 18 are secondarily transferred onto the recording material P all at once.

  The recording material P onto which the four color toner images have been transferred through the secondary transfer portion T2 is peeled off from the intermediate transfer belt 18 and conveyed to the fixing device 50, where the toner images are fixed to form a full-color permanent image. The Thereafter, the sheet is discharged onto the discharge tray 65 at the upper part of the apparatus main body via the three pairs of discharge rollers 62, 63, 64, and the image forming operation is completed.

  Untransferred toner remaining on the intermediate transfer belt 18 without being transferred by the secondary transfer is removed by the blade 31 of the cleaning unit 30 in contact with the surface of the intermediate transfer belt 18, and the removed transfer residual toner is removed from the cleaner. Housed in a container 34.

<Detailed description of cleaning unit>
Here, the cleaning unit 30 is provided with an auxiliary function for preventing the intermediate transfer belt 18 from shifting. This will be described below.

  As described above, the cleaning unit 30 includes the cleaning blade 31, the pressure spring 36 that presses the blade 31 against the intermediate transfer belt 18, and the cleaner container 34 that holds them. Here, as described above, the cleaning unit 30 is installed at a position facing the tension roller 16 with the intermediate transfer belt 18 interposed therebetween. However, the installation position of the cleaning unit 30 is not limited to this and is necessary. What is necessary is just to set suitably according to.

  The cleaning blade 31 is formed by forming urethane rubber in a plate shape on a metal plate 33, and the shaft 32 held by the cleaner container 34 is set as the rotation center to the intermediate transfer belt 18 at a predetermined angle by a pressure spring 36. Press. As a result, the cleaning blade 31 is uniformly in contact with the intermediate transfer belt 18. The tension roller 16 is positioned on the opposite portion of the cleaning blade 31 to serve as a backup roller, and allows the cleaning blade 31 to contact the intermediate transfer belt 18 with a predetermined contact pressure. The transfer residual toner on the intermediate transfer belt 18 is scraped off at the point where the cleaning blade 31 comes into contact, and the intermediate transfer belt 18 is cleaned.

  The toner (waste toner) scraped off by the cleaning blade 31 is collected in the cleaner container 34 and then transported by the screw 35 installed at the lowermost part in the cleaner container 34 to be disposed separately in the apparatus main body. The toner is stored in the toner box 40.

  As an auxiliary function for preventing the shift of the intermediate transfer belt 18, as shown in FIGS. 3 and 6, end pressing members 37 positioned outside the both ends of the cleaning blade 31 are installed in the cleaning unit 30. The end pressing member 37 presses the surface of the belt 18 at a position where the guide rib 19 and the flange 20 face each other when the offset force is generated in the intermediate transfer belt 18, and the guide rib 19 contacts the flange 20. It prevents you from getting on.

  The end pressing member 37 is formed of an elastic body such as sponge. Here, the end pressing member 37 was formed in a form in which a PTFE fiber pile was bonded onto maltoprene. The end pressing member 37 was installed in the cleaner container 34 so as to have the above arrangement.

  The end pressing member 37 also serves as an end sealing member of the cleaning blade 31. That is, the end pressing member 37 closes the gap between the cleaner container 34 and the intermediate transfer belt 18 outside both ends of the cleaning blade 31. Thereby, the end pressing member 37 prevents the waste toner scraped off by the blade 31 from scattering or leaking out of the cleaning unit 30. Further, the end pressing member 37 also serves to make the recovery to the cleaner container 34 more reliable.

<Operation of end holding member>
The operation of the end pressing member 37 will be described. FIG. 6 shows the positional relationship between the guide rib 19, the end pressing member 37, and the flange 20 when the cleaning unit 30 is set in the intermediate transfer unit 13.

  In FIG. 6, the width of the roller body portion not including the flange 20 of the tension roller 16 is L, and the linear length of the flange 20 up to the position where the guide rib 19 abuts due to the movement in the width direction is F. The width of the guide rib 19 is G, and the length between the outer end surfaces of the end pressing members 37 at both ends of the cleaning blade 31 is B.

  The end pressing member 37 is engaged with the guide rib 19 in a state where the guide rib 19 is in contact with the flange 20 due to the movement in the width direction of the intermediate transfer belt 18, so that the end pressing member 37 does not protrude from the guide rib 19. Members 19, 20, and 37 were arranged. That is, the members 19, 20, and 37 are arranged so that the relationship of L + 2F ≦ B ≦ L + 2F + 2G is established.

  According to this, the end pressing members 37 disposed at both ends of the cleaning blade 31 are disposed at a position straddling the guide rib 19 and the flange 20 at both ends of the tension roller 16 with the intermediate transfer belt 18 interposed therebetween. For this reason, for example, as shown in FIG. 7, even if the left side guide rib 19 hits the flange 20 and rides on the flange 20 by moving toward the intermediate transfer belt 18 in the right direction, the end pressing member 37 The guide rib 19 is pushed up. Therefore, the deviation control of the intermediate transfer belt 18 by the guide rib 19 and the flange 20 can be more reliably performed.

  When the above condition is not satisfied and B> L + 2F + 2G, as shown in FIG. 8, the end pressing member 37 protrudes from the guide rib 19 that abuts against the flange 20. Then, the movement of the intermediate transfer belt 18 in the shift direction is restricted by the end pressing member 37, and the intermediate transfer belt is difficult to return in the reverse direction, and the shift regulation is difficult to function. Further, since stress is applied to the guide rib 19, problems such as peeling of the guide rib 19 from the intermediate transfer belt 18 occur as the use proceeds.

  Further, in the case of B <L + 2F, as shown in FIG. 9, the end pressing member 37 does not hit the guide rib 19 that has come into contact with the flange 20, so that the riding of the guide rib 19 cannot be pressed.

  For this reason, as described above, the members 19, 20, and 37 are arranged so that the relationship L + 2F ≦ B ≦ L + 2F + 2G is established.

  As described above, according to this embodiment, even if a force in the width direction acts on the intermediate transfer belt 18, the guide rib 19 of the belt 18 has the flanges 20 and 150 of the two stretching rollers 14 and 16. And are regulated. Therefore, the force with which the guide rib 19 tries to get over the flanges 20 and 150 is reduced, and the movement of the intermediate transfer belt 18 in the width direction can be more reliably regulated. As a result, the intermediate transfer belt 18 can be restricted to a position within a predetermined range, the image recording accuracy in the width direction of the intermediate transfer belt 18 can be improved, and high quality without positional deviation (color deviation). Can be obtained.

  Further, in the running direction of the intermediate transfer belt, the flange 20 is provided on the upstream tension roller 16 and the flange 150 is provided on the downstream drive roller 14 via the photosensitive drum 1, so that the intermediate transfer belt 18 in the width direction is provided. The image recording accuracy can be further improved. Thereby, a high-quality image without color misregistration can be obtained.

  Further, when the intermediate transfer belt 18 moves in the width direction, the end pressing member 37 presses the surface of the belt 18 at a position where the guide rib 19 and the flange 20 that are in contact with each other face each other. Riding on the flange 20 can be prevented. In this way, not only the restriction by the contact between the guide rib 19 and the flanges 20 and 150 but also the end pressing member 37 acts at the contact portion between the guide rib 19 and the flange 20, so that a more stable displacement restriction can be realized. .

[Second Embodiment]
In the first embodiment described above, the flanges 20 and 150 are arranged on the rollers 14 and 16 so that the distance from the image center CL to the flange contact points 20a and 150a is the same in the axial direction of the roller. The configuration is illustrated. In this case, when the intermediate transfer belt 18 is shifted in the width direction, the guide rib 19 first comes into contact with the flange contact point 20a or the flange contact point 150a varies depending on the dimensional tolerance of the components to be configured.

  Here, the twist of the intermediate transfer belt is given to the obtained image when the guide rib 19 hits only the flange contact point 20a on the tension roller side and when the guide rib 19 hits only the flange contact point 150a on the drive roller side. Think about the impact.

  In the configuration described above, the tension roller is disposed on the upstream side of the image forming unit in the traveling direction of the intermediate transfer belt, and the drive roller is disposed on the downstream side of the image forming unit. Therefore, when the movement of the intermediate transfer belt in the width direction is restricted only on the tension roller side, tension is applied to the intermediate transfer belt by the conveying force of the primary transfer portion facing the photosensitive drum located on the downstream side. The belt surface is uniform and there is no belt slack at the primary transfer portion. On the other hand, when the movement of the intermediate transfer belt in the width direction is restricted on the drive roller side downstream of the primary transfer portion, the belt is bent by the conveying force of the primary transfer portion, which may cause a transfer failure. .

  Therefore, in the present embodiment, the flanges 20 and 150 are attached to the intermediate transfer belt 18 so that the guide ribs 19 of the intermediate transfer belt 18 first come into contact with either one of the flanges 20 and 150 provided on the rollers 14 and 16. The structure is provided at different positions in the width direction.

  Hereinafter, the configuration of the present embodiment will be described in detail with reference to FIG. FIG. 10 is a view showing a cross section of an arrow O portion of FIG. In addition, in this embodiment, since structures other than arrangement | positioning of a flange are the same as that of embodiment mentioned above, the same code | symbol shall be attached | subjected to the member which has an equivalent function, and description shall be used.

  The guide ribs 19 constituting the deviation regulating means are provided over the entire circumference of both edges of the inner surface of the intermediate transfer belt 18 as in the above-described embodiment. On the other hand, the flanges 20 and 150 as restricting members are provided at both axial ends of the rollers 14 and 16 so as to correspond to the guide ribs 19.

  Further, in the present embodiment, in the traveling direction of the intermediate transfer belt 18, the flange 150 on the drive roller 14 side on the downstream side of the image forming unit is set to the image center CL rather than the flange 20 on the tension roller 16 side on the upstream side of the image forming unit. In contrast, it is provided on the inner side in the axial direction of the roller. That is, in this embodiment, unlike the first embodiment described above, the flanges 20 and 150 are provided so that the flange contact point 150a is located at the inner side in the axial direction of the roller by a distance N with respect to the flange contact point 20a. ing. In this embodiment, the distance N is 0.5 mm. The distance N is 0.5 mm. In this embodiment, the distance between the tension side and the drive side roller is about 400 mm, and a dimensional deviation of about 1% (about 0.4 mm) occurs. The value is set to exceed.

  With this configuration, a shift force in the width direction acts on the intermediate transfer belt 18, and for example, a state when the intermediate transfer belt 18 approaches the back side of the apparatus is shown in FIG. As shown in FIG. 11, when the intermediate transfer belt 18 approaches the rear side of the apparatus, the guide rib 19 on the front side of the apparatus first comes into contact with the flange 20 at a position closer to the distance N in the roller axial direction than the flange 150, and the deviation is regulated. The

  When the offset force is further applied and the intermediate transfer belt 18 further moves in the roller axial direction toward the center of the apparatus, the guide rib 19 that is restricted by the flange 20 as shown in FIG. The As a result, the force by which the guide rib 19 tries to ride on the flange is halved by the shifting force, so that the shifting of the intermediate transfer belt 18 can be reliably controlled. Further, since the contact points 20a and 150a of the flanges 20 and 150 with the guide ribs 19 are merely shifted in the roller axis direction, the dimensional accuracy can be roughened.

  If the distance N is too large, when the intermediate transfer belt moves in the width direction, the belt is first regulated on the tension roller 16 side, and then the belt moves until it is further regulated on the drive roller 14 side, causing the twist. May increase and the belt may be damaged. For this reason, in the present embodiment, the distance N is set to 0.5 mm, which is a value that exceeds the dimensional tolerance described above, but is set to a value that is as small as possible so that the belt is not damaged by the twist described above. .

  As described above, when the intermediate transfer belt 18 is shifted in the width direction, the deviation is first regulated by the flange 20 on the tension roller 16 side, which is the upstream side of the image forming unit, and therefore the belt 18 is conveyed to the primary transfer unit. Since the tension is applied by the force and does not sag, the transfer is good. Further, when a deviation occurs in the belt 18, the deviation is first regulated by the flange 20 on the upstream side of the image forming unit, and thereafter, the deviation is regulated by the flange 150 when further approaching. As a result, the start of the shift regulation does not vary in any of the flanges 20 and 150, and a certain shift regulation is performed. Therefore, it is not necessary to make the dimensional accuracy of the flanges 20 and 150 high in the thrust direction, and even if the positional adjustment of the components constituting the intermediate transfer unit 13 in the thrust direction (roller axis direction) is not precise, the deviation is regulated. The force is always high on the tension roller 16 side. As a result, stable belt conveyance can be obtained, so that deterioration in image quality can be prevented at low cost.

  As described above, by regulating the deviation of the intermediate transfer belt 18 from the upstream side of the image forming unit as the main deviation regulating side, the belt of the primary transfer unit is not twisted, so that stable image transfer is possible.

  Further, an auxiliary function (an end pressing member 37) for preventing the intermediate transfer belt 18 from shifting is provided on the tension roller 16 side, which is the upstream side of the image forming unit. Therefore, as shown in FIG. 11, even when the guide rib 19 of the intermediate transfer belt 18 hits the flange 20 and tries to ride on the flange 20, the guide rib 19 is pushed up by the end pressing member 37. Therefore, the deviation control of the intermediate transfer belt 18 by the guide rib 19 and the flange 20 can be more reliably performed. In addition, as described above, the upstream side of the image forming unit is the main shift regulating side, so that the position of the intermediate transfer belt can be regulated more stably. Further, meandering accompanying the intermediate transfer belt 18 is prevented, and the transfer position shift of each color toner image is eliminated, and a high-quality color image can be obtained.

  As described above, according to this embodiment, the position in the width direction of the intermediate transfer belt 18 can be stably regulated within a predetermined range, and the recording accuracy in the width direction of the intermediate transfer belt 18 is improved. Therefore, it is possible to provide a high-quality image without color misregistration.

  Further, even when the frame of the apparatus supporting the intermediate transfer unit 13 is twisted due to the influence of the installation location, which becomes the twist of the intermediate transfer unit 13 and the belt 18 is displaced, as described above. First, the shift is regulated on the upstream side of the image forming unit. Therefore, stable belt conveyance can be obtained and high-quality images without color misregistration can be obtained without increasing the rigidity of the apparatus frame and without adjusting the apparatus frame and the intermediate transfer unit.

[Other Embodiments]
In the above-described embodiment, four image forming units having an image carrier and process means acting on the image carrier are used. However, the number of use is not limited, and may be appropriately set as necessary. good.

  In the above-described embodiment, as a process unit (cartridge) that is detachable from the main body of the image forming apparatus, a photosensitive drum and a charging unit, a developing unit, and a cleaning unit as a process unit that act on the photosensitive drum are integrally provided. A process cartridge is illustrated. However, the present invention is not limited to this, and may be a process cartridge integrally including any one of a charging unit, a developing unit, and a cleaning unit in addition to the photosensitive drum.

  Further, in the above-described embodiment, the configuration in which the process cartridge including the photosensitive drum is detachable from the main body of the image forming apparatus is illustrated, but the present invention is not limited to this. For example, it may be an image forming apparatus in which each constituent member is incorporated, or an image forming apparatus in which each constituent member is removable. The effects described above can be obtained by applying the present invention to the belt conveying device of these image forming apparatuses.

  In the above-described embodiments, the printer is exemplified as the image forming apparatus. However, the present invention is not limited to this, and other image forming apparatuses such as a copying machine and a facsimile machine, or a combination of these functions. Other image forming apparatuses such as multifunction peripherals may also be used. Further, an image forming apparatus that uses a recording material carrier as the endless belt member and sequentially superimposes and transfers the toner images of the respective colors onto the recording material carried on the recording material carrier. The same effect can be obtained by applying the present invention to these image forming apparatuses.

Overall configuration diagram showing an embodiment of an image forming apparatus A perspective view showing a tension applying mechanism of an intermediate transfer belt in an image forming apparatus Sectional view showing installation of deviation control means and cleaning unit on intermediate transfer belt The fragmentary sectional view for explaining the belt conveyance device concerning a 1st embodiment. The fragmentary sectional view for explaining the belt conveyance device concerning a 1st embodiment. Sectional drawing which shows the positional relationship of the guide rib of an intermediate transfer belt, the edge part pressing member of a cleaning unit, and the flange of a tension roller FIG. 6 is a partial cross-sectional view showing a state in which the guide rib of FIG. 6 is a partial cross-sectional view showing a state in which the end pressing member and the like in FIG. 6 are improperly arranged and the end pressing member protrudes from the intermediate transfer belt. FIG. 6 is a partial cross-sectional view showing a state in which the end pressing member or the like in FIG. 6 is improperly arranged and the end pressing member cannot press the guide rib on the flange. Partial sectional view for explaining a belt conveyance device according to a second embodiment Partial sectional view for explaining a belt conveyance device according to a second embodiment Partial sectional view for explaining a belt conveyance device according to a second embodiment

Explanation of symbols

CL ... Image center P ... Recording material T1 (T1Y, T1M, T1C, T1K) ... Primary transfer part T2 ... Secondary transfer part 1 (1Y, 1M, 1C, 1K) ... Photosensitive drum (image carrier)
4 (4Y, 4M, 4C, 4K) ... developing device (developing means)
5 (5Y, 5M, 5C, 5K) ... charging roller (charging means)
6 (6Y, 6M, 6C, 6K) ... laser scanner 13 ... intermediate transfer unit 14 ... drive roller (second rotating member)
15 ... Secondary transfer counter roller 16 ... Tension roller (first rotating member)
18 Intermediate transfer belt (endless belt member)
19: Guide rib (guide member)
20 ... Flange (first regulating member)
20a ... Flange contact point 30 ... Cleaning unit 31 ... Blade 34 ... Cleaner container 37 ... End pressing member 150 ... Flange (second regulating member)
150a ... Flange contact point

Claims (9)

A belt conveying device having an endless belt member and a plurality of rotating members that stretch and rotate the belt member,
A guide member provided over the entire circumference of the inner surface of the belt member;
A regulation member that abuts and regulates the guide member when the belt member moves in a direction orthogonal to the rotational movement direction;
The belt conveying device according to claim 1, wherein the regulating member is provided on at least two rotating members of the plurality of rotating members.   The belt conveyance device according to claim 1, wherein the rotation member provided with the regulating member is at least two rotation members that stretch the belt member to form a belt surface facing the image carrier. .   The rotating member provided with the regulating member includes a first rotating member on the upstream side in the rotational movement direction of the belt member via the image carrier and a second rotating member on the downstream side in the rotational movement direction of the belt member via the image carrier. The belt conveyance device according to claim 2, wherein the belt conveyance device is a rotating member.   When the belt member moves in a direction orthogonal to the rotational movement direction, the at least two guide members of the belt member come into contact with either one of the regulating members provided on the at least two rotational members first. The belt conveying device according to any one of claims 1 to 3, wherein the regulating members provided on the two rotating members are provided at different positions in a direction orthogonal to the rotational movement direction. The guide member is provided over the entire circumference of both edges of the inner surface of the belt member,
The restricting member is provided at both axial ends of each rotating member so as to correspond to the guide member, and the guide member comes into contact with the first restricting member rather than the first restricting member with which the guide member comes into contact first. The belt conveying device according to claim 4, wherein a second restricting member with which the guide member contacts is provided on an inner side in the axial direction of the rotating member.   When the belt member moves in a direction orthogonal to the rotational movement direction, the belt member has a pressing member that presses the surface of the belt member at a position where the guide member and the regulating member that are in abutment relationship face each other. And a belt conveying device according to any one of claims 1 to 5. An image forming unit having an image carrier and process means acting on the image carrier; an endless belt member facing the image carrier; and a plurality of rotating members that stretch and rotate the belt member. An image forming apparatus comprising:
An image forming apparatus comprising the belt conveyance device according to claim 1 as the belt conveyance device.   The image forming apparatus includes a plurality of image forming units, uses an intermediate transfer belt as the belt member, and sequentially transfers toner images of respective colors onto the intermediate transfer belt, and is carried on the intermediate transfer belt. The image forming apparatus according to claim 7, wherein the toner images are collectively transferred to a recording material.   The image forming apparatus includes a plurality of image forming units, uses a recording material carrying belt as the belt member, and sequentially transfers toner images of respective colors onto the recording material carried on the recording material carrying belt. The image forming apparatus according to claim 7.

Images