JP2008058560A - Belt drive device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a belt driving device and an image forming apparatus having the belt driving device capable of correcting a deviation of an endless belt quickly and surely without increasing the cost of the entire apparatus.
SOLUTION: An endless belt 40 and a plurality of stretching rollers 41 to 46 for stretching the endless belt, one of the plurality of stretching rollers being a driving roller 41 and the other being an endless belt. In the belt drive device that is the alignment adjustment roller 46 for correcting the deviation, the alignment adjustment roller 46 is applied to the endless belt 40 from the outer surface thereof at an adjacent position upstream or downstream of the drive roller 41 in the belt traveling direction. It is provided so as to correct the offset of the endless belt.
[Selection] Figure 3

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a belt driving device that has an endless belt and drives and rotates the belt driving device, and an image forming apparatus such as a copying machine, a printer, a facsimile machine, and a scanner equipped with the device. The present invention relates to a belt driving device that corrects a belt deviation and an image forming apparatus including the belt driving device.

  2. Description of the Related Art Conventionally, as an image forming apparatus such as a copying machine or a printer, an apparatus including an intermediate transfer belt formed of an endless belt, a photosensitive belt, a transfer conveyance belt, and the like is known. These endless belts may be offset or meander in a direction perpendicular to the traveling direction due to the rotation thereof. When such an endless belt misalignment phenomenon occurs, for example, in an image forming apparatus that forms a color image, the position of the toner image of each color is shifted and the color shift is caused. There was a problem of becoming.

  In order to solve such a problem, in a belt driving device having an endless belt, in particular, in the color image forming apparatus as described above, it is necessary to appropriately and quickly correct a deviation or meandering of the endless belt. . Several belt drive devices that can correct the deviation of the endless belt are already proposed. For example, a flange is provided on the side of the photosensitive member that abuts the endless belt to regulate the deviation phenomenon of the belt of the endless belt (see, for example, Patent Document 1), and a rib or the like is provided at the belt edge of the endless belt. (See, for example, Patent Documents 2 and 3), a guide for biasing the endless belt by providing a spring-biased guide at the outer end of the driven roller (see, for example, Patent Document 4), etc. It has been known. In addition, one of a plurality of rollers on which an endless belt is stretched can adjust the inclination of the shaft, and the endlessness can be adjusted by adjusting the inclination of the roller shaft (hereinafter referred to as “alignment adjustment”). A belt that corrects the deviation of the belt is also known (see, for example, Patent Documents 5 to 7). The belt driving device as described in Patent Documents 5 to 7 is compared with the belt driving device as described in Patent Documents 1 to 4 that forcibly eliminates the deviation of the endless belt. Thus, the load applied to the endless belt is small, so that there is an advantage that the durability and reliability of the belt are high.

By the way, when correcting the deviation of the endless belt with a mechanism as described in Patent Documents 5 to 7, a roller for correcting this deviation (hereinafter referred to as an “alignment adjustment roller”) has a surface frictional resistance. Higher grip force on the belt is advantageous because the response of the endless belt offset correction to the alignment adjustment control is higher. In many cases, the driving roller has such a function that the frictional resistance of the surface is high and the gripping force against the belt is strong. However, since the driving roller is connected to the driving means, there is a problem that it is not suitable for use as an alignment adjusting roller. In addition, it is conceivable that such an alignment adjusting roller has the same configuration as that of a driving roller having a high frictional resistance on its surface. Therefore, there is a problem in that the configuration of the alignment adjusting roller similar to that of the driving roller leads to an increase in the cost of the entire apparatus.
JP 2001-183911 A JP 2004-191714 A Japanese Patent Laid-Open No. 2005-200192 JP 2000-155480 A JP 2004-35200 A JP 2001-117374 A JP 2001-80782 A

  SUMMARY OF THE INVENTION Accordingly, the present invention solves the problems of the prior art and provides a belt driving device and an image forming apparatus equipped with the belt driving device that can quickly and reliably correct the deviation of the endless belt without increasing the cost of the entire device. The purpose is to provide.

  In order to solve the above-mentioned problem, the invention described in claim 1 includes an endless belt and a plurality of stretching rollers that stretch the endless belt, and one of the plurality of stretching rollers is a driving roller. The other one is a belt driving device in which the alignment adjusting roller is used to correct the deviation of the endless belt, and the alignment adjusting roller is arranged at an adjacent position upstream or downstream of the driving roller in the belt traveling direction. The endless belt is brought into contact with the outer surface to correct a deviation of the endless belt.

  According to a second aspect of the present invention, in the first aspect, one of the plurality of stretching rollers is a tension roller that applies tension to the endless belt, and the tension roller and the driving roller are arranged in the belt traveling direction. An alignment adjusting roller is disposed between and adjacent to them.

  According to a third aspect of the present invention, in the first or second aspect, the detecting means for detecting the positional deviation of the edge portion of the endless belt, and the control means for controlling the alignment adjusting roller based on information obtained by the detecting means. And is provided.

  According to a fourth aspect of the present invention, there is provided an image forming apparatus comprising the belt driving device according to any one of the first to third aspects.

  According to a fifth aspect of the present invention, in the fourth aspect, the alignment adjusting roller and the two stretching rollers located on both sides of the alignment adjusting roller are disposed at positions that support a belt surface on which an image of an endless belt is formed. It is characterized by not.

  According to a sixth aspect of the present invention, in the fourth or fifth aspect, the endless belt is an intermediate transfer belt, a primary transfer unit that transfers an image on the photosensitive drum onto the intermediate transfer belt, and an intermediate transfer belt And a secondary transfer unit having a secondary transfer counter roller for transferring the image on the transfer material, and the alignment adjusting roller is located at an adjacent position upstream or downstream of the secondary transfer counter roller in the belt traveling direction. Are not arranged.

  According to a seventh aspect of the present invention, in the fourth or fifth aspect, the endless belt conveys a transfer material on a belt surface facing the photosensitive drum, and an image formed on the photosensitive drum on the belt surface. It is characterized by being directly transferred onto a transfer material.

  The present invention is as described above, and includes an endless belt and a plurality of stretching rollers that stretch the endless belt, one of the plurality of stretching rollers being a driving roller, and the other being an endless. In the belt drive device that is an alignment adjustment roller that corrects the deviation of the belt, the alignment adjustment roller is arranged at an adjacent position upstream or downstream of the drive roller in the belt traveling direction, and the outer surface of the endless belt In other words, the alignment adjustment roller configured to be able to adjust the alignment is arranged outside the endless belt and next to the roller. Since the drive roller that drives and rotates the endless belt is arranged, the endless belt is wound around the drive roller and alignment adjustment roller. There were both increased, it can be expected excellent effects that the response of the endless belt deviation modifications to the operation of the alignment adjustment is improved. In addition, since the above effect can be exhibited by such a simple mechanism, the deviation correction of the endless belt can be performed quickly and reliably without increasing the cost of the entire apparatus.

An embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a configuration diagram showing an outline of the overall configuration of a four-tandem color image forming apparatus as an example of the image forming apparatus, and FIG. 2 is a yellow toner image forming unit of the color image forming apparatus of FIG. FIG. 4 is an enlarged cross-sectional view showing the configuration of FIG.

  In the figure, reference numeral 1 denotes an image forming apparatus. The image forming apparatus 1 includes image information obtained by color-separating the surface of a charged photosensitive drum for each predetermined color into a predetermined color input from a scanner or the like. The image forming section 3 is formed by an exposure apparatus 2 that selectively exposes a laser beam based on the image, an image forming section 3 that forms a toner image for each predetermined color on the photoreceptor exposed by the exposure apparatus 2, and an image forming section 3. The toner image of each color is transferred onto a transfer paper (transfer material), and the transfer belt unit 4 that transports the transfer paper to the fixing device, the paper feeding unit 5 that supplies the transfer paper to the transfer belt unit 4, and the transfer paper A pair of registration rollers 6 that synchronize the timing of supply and transfer, a belt fixing type fixing device 7 that fixes the toner image transferred to the transfer paper, a paper discharge unit 8 that discharges and stocks the transfer paper, Is equipped.

  The image forming unit 3 is located substantially at the center of the image forming apparatus 1 and is photosensitive for each predetermined color (yellow: Y, magenta: M, cyan: C, black: K) along a transfer conveyance belt 40 described later. This is a so-called quadruple tandem type in which four toner image forming portions 3Y, 3M, 3C, and 3K having body drums Y, M, C, and K are arranged in a line, as shown in FIG. The toner image forming portions of the respective colors are arranged so as to be inclined obliquely upward in the order of Y, M, C, and K. The toner image forming units 3Y, 3M, 3C, and 3K for the respective colors have the same configuration except that the colors of the toners to be used are different from each other. Therefore, the yellow toner image forming unit is representatively the yellow toner image forming unit. The toner image forming unit 3Y for use will be described below, and description of the others will be omitted.

  As shown in FIG. 2, the toner image forming unit 3Y includes a process unit 30Y and a developing device 31Y. Since the process unit 30Y is a known unit, a detailed description is omitted. In addition to the photosensitive drum Y, a brush roller 301Y for applying a lubricant to the photosensitive drum Y, a cleaning unit 302Y for cleaning the photosensitive drum Y, The charging roller 303Y uniformly charges the photosensitive drum Y, the cleaning roller 304Y that cleans the surface of the charging roller 303Y, and the like. Further, since the developing device 31Y is also known in the same manner, a detailed description thereof is omitted, but a developing roll 311Y, a first transport screw 312Y, and a second transport that are arranged so as to partially expose the opening of the developing case 310Y. A screw 313Y, a developing doctor 314Y, a toner concentration sensor 315Y, a communication unit 316Y with a powder pump (not shown), and the like are included.

  The developer case 310Y contains a developer containing a magnetic carrier and a negatively charged yellow toner. The developer is frictionally charged while being agitated and conveyed by the first conveying screw 312Y and the second conveying screw 313Y, and is then carried on the surface of the developing roll 311Y which is a developer carrying member. Then, after the layer thickness is regulated by the developing doctor 314Y, the layer is conveyed to a developing region facing the photosensitive drum Y, where yellow toner is attached to the electrostatic latent image on the photosensitive drum Y. By this adhesion, a yellow toner image is formed on the photosensitive drum Y. On the other hand, the developer that does not adhere and consumes the toner is contained in the developing case 310Y as the surface of the developing roller 311Y (developing sleeve) rotates. Returned to The developed toner image is transferred to a transfer paper P conveyed by a transfer conveyance belt 40 described later. Further, when the density in the developing device 31Y decreases, a powder pump (not shown) is controlled based on information from the density sensor 315Y, and a yellow color is transferred from the yellow toner cartridge (not shown) through the communication portion 316Y. The toner is replenished.

The exposure device 2 is arranged above the image forming unit 3 and irradiates the photosensitive drums Y, M, C, and K with laser beams L that are modulated and polarized based on image information separated into colors. It has become.
The paper feed unit 5 is disposed below the image forming apparatus 1 and includes paper feed trays 5a and 5b, paper feed rollers 5c and 5d, and the like that store transfer paper of a predetermined size. 5e is a manual feed tray, and 5f is a paper feed roller.
Further, the fixing device 7 is disposed on the upper side of the image forming apparatus 1 that is downstream of the image forming unit 3 and the transfer belt unit 4. The fixing device 7 is of a belt fixing type provided with a pressure roller 70 and a fixing belt 71, and the fixing belt 71 is stretched around a heating roller 72 and a driving roller 73. The heating roller 72 includes heating means such as a halogen (not shown), and is configured to heat the fixing belt 71 from the inner surface. The fixing belt 71 is driven and rotated by the driving roller 73 and rotates in the direction of the arrow in the figure, and the pressure roller 70 is in contact with the outer surface. A contact portion between the pressure roller 70 and the fixing belt 71 is a fixing nip.
The paper discharge unit 8 is disposed at the top of the image forming apparatus 1 and serves as a space for stocking transfer paper on which an image has been transferred and fixed.
S shows the space in which apparatuses, members, etc. other than the above are accommodated.

The belt driving apparatus according to this embodiment will be described mainly with reference to FIG. FIG. 3 is a configuration diagram showing an outline of the transfer belt unit of the color image forming apparatus of FIG.
A transfer belt unit 4 serving as a belt driving device is disposed at a substantially central portion of the image forming apparatus 1 and below the image forming unit 3 (see FIG. 1), and functions as a belt driving device that conveys transfer paper. And a function as a direct transfer type transfer device that directly transfers from the photosensitive drum to the transfer paper. As shown in FIG. 3, the transfer belt unit 4 functions as a belt driving device, and has an endless transfer conveyance belt 40 stretched around a plurality of stretching rollers, and the transfer conveyance belt 40 is stretched from the inside. The driving roller 41 is connected to driving means (not shown) to drive and rotate the transfer / conveying belt 40 in the direction of arrow A in the drawing, and the transfer / conveying belt 40 is driven from the inside by the driving rotation of the driving roller 41. A plurality of driven rollers 42, 43, 44 that are stretched, a tension roller 45 that applies and adjusts tension by pressing the transfer conveyance belt 40 from the inside by an urging means (not shown) such as a spring, and the transfer conveyance belt An aligner that increases the amount of winding of the belt around the driving roller by pressing the belt 40 from the outside and corrects the offset of the transfer conveyance belt 40 by an alignment adjusting means described later. And a preparative adjustment roller 46.

  The arrangement of a plurality of stretching rollers that stretch the transfer conveyance belt 40 will be described. In this embodiment, the belt surface on the image forming unit 3 side of the transfer conveyance belt 40 is transferred from the photosensitive member to the transfer sheet. (See FIG. 1), and is stretched and supported by driven rollers 43 and 44. For this reason, the drive roller 41 is disposed at the position of the first stretching roller on the downstream side in the belt traveling direction from the image forming surface while avoiding the image forming surface. Then, at the position of the next downstream tension roller, the alignment adjusting roller 46 is disposed so as to press the belt from the outer surface of the transfer conveyance belt 40 to bend the loop of the transfer conveyance belt 40 inward. At the next downstream tension roller position, the tension roller 45 is disposed so as to press the transfer / conveying belt 40 from the inside to curve the belt loop outward. Further, a driven roller 42 is disposed between the driven roller 43 that supports the right end in FIG.

  In addition to the above configuration, the transfer belt unit 4 includes, as a transfer device function, an electrostatic adsorption roller 47, four transfer bias rollers 48Y, 48M, 48C, 48K, four transport support rollers 49Y, 49M, 49C, 49K, An inlet bracket 50, an outlet bracket 51, and the like are provided. The electrostatic attraction roller 47 is configured to sandwich the transfer / conveying belt 40 between the driven roller 43 and a nip formed therebetween. The electrostatic attraction roller 47 applies an electric charge to the outer surface of the transfer conveyance belt 40 by an electrostatic attraction bias applied from a power source (not shown), so that the transfer paper P is conveyed to the nip. The transfer paper P is electrostatically adsorbed.

  The transfer bias rollers 48Y, 48M, 48C, and 48K and the transport support rollers 49Y, 49M, 49C, and 49K are configured to be able to contact and separate from the transfer transport belt 40 by a contact / separation mechanism. That is, the transfer bias rollers 48Y, 48M, 48C, and 48K and the transport support rollers 49Y, 49M, 49C, and 49K are pressed by the contact / separation mechanism toward the photosensitive drums Y, M, C, and K, respectively, and transferred. The conveyance belt 40 is sandwiched between the photosensitive drums Y, M, C, and K and the transfer conveyance belt 40 to form a transfer nip where the transfer belt 40 contacts with a predetermined length in the belt traveling direction. Further, when the transfer bias rollers 48Y, 48M, 48C, and 48K and the transport support rollers 49Y, 49M, 49C, and 49K are all separated, the transfer belt unit 4 can be attached to and detached from the main body of the image forming apparatus 1. It has become.

  These transfer bias rollers 48Y, 48M, 48C, and 48K are rollers in which a metal cored bar is covered with an elastic body such as a sponge, and each cored bar is fixed by a transfer bias power source (not shown). A current-controlled transfer bias is applied. As a result, transfer charges are applied to the inner surface of the transfer conveyance belt 40 via the transfer bias rollers 48Y, 48M, 48C, and 48K, and the transfer conveyance belt 40 and the photosensitive drums Y, M, C, and K are transferred to each transfer nip. A transfer electric field is formed between them. In this embodiment, the transfer bias rollers 48Y, 48M, 48C, and 48K are provided as transfer means. However, instead of the rollers, brushes or blades may be used. Also, a transfer charger or the like may be used.

  Of the four transfer bias rollers 48Y, 48M, 48C, and 48K, three for Y, M, and C are supported by the swing bracket 52 via bearing members (not shown). The swing bracket 52 is disposed inside the loop of the transfer conveyance belt 40, and is configured to be swingable about a rotation shaft 52a. Similarly, among the transport support rollers 49Y, 49M, 49C, and 49K, transport support rollers 49Y, 49M, and 49C for Y, M, and C are also supported by the swing bracket 52. Below the swing bracket 52 in the figure, a cam 53 that is driven to rotate about a rotation shaft 53a by a driving means (not shown) is disposed. When the cam 53 stops rotating at a position where the cam surface abuts against the swing bracket 52, the swing bracket 52 swings counterclockwise in the figure around the rotation shaft 52a, and is used for Y, M, and C. The transfer bias rollers 48Y, 48M, and 48C are brought into contact with the photosensitive drums Y, M, and C through the transfer conveyance belt 40, and transfer nips for Y, M, and C are formed. On the contrary, the cam 53 stops rotating at a position where the cam surface does not abut against the swinging bracket 52, and the swinging bracket 52 swings around the rotation shaft 52a in the clockwise direction in the drawing, and Y, M , C transfer bias rollers 48Y, 48M, and 48C move to a position where the transfer conveyance belt 40 is not pressed against the photosensitive drums Y, M, and C, the transfer nips for Y, M, and C are not formed. As described above, the contact / separation mechanism such as the transfer bias roller of the transfer belt unit 4 causes the transfer conveyance belt 40 to abut on the photosensitive drums Y, M, and C by the swing of the swing bracket 52, so that the Y, M , C transfer nips, and the transfer conveyance belt 40 is separated from the photosensitive drums Y, M, C.

  The driven rollers 42 and 43 and the electrostatic attraction roller 47 are respectively supported by an entrance bracket 50 via bearing members (not shown), and the entrance bracket 50 is disposed inside the loop of the transfer conveyance belt. The shaft is configured to be swingable about the axis of the driven roller 42.

  Further, the swing bracket 52 has a guide hole 52b near the right end in the figure, which is the end side opposite to the base end, and a pin 50a extending from the inlet bracket 50 is loosely fitted inside the guide hole 52b. . For this reason, when the cam 53 rotates in the counterclockwise direction in the drawing, the pin 50 a is pushed up by the guide hole 52 b of the swing bracket 52. Then, the inlet bracket 50 is linked to the swing of the swing bracket 52 and swings counterclockwise around the axis of the driven roller 42 to push up the driven roller 43 and the electrostatic adsorption roller 47. . Conversely, the swing bracket 52 swings clockwise in the figure, the inlet bracket 50 links to it and swings clockwise in the figure, and pushes down the driven roller 43 and the electrostatic adsorption roller 47 downward. . In this way, the belt surface facing the photosensitive drums Y, M, C, and K, which are the image forming surface and transfer paper transport surface of the transfer transport belt 40, is always maintained in a straight line.

  Of the four transfer bias rollers, the remaining black transfer bias roller 48K is supported by the outlet bracket 51 via a bearing member (not shown). The outlet bracket 51 is disposed inside the loop of the transfer conveyance belt 40 and is configured to be swingable about the axis of the driven roller 44. Similarly, the K conveyance support roller 49K is also supported by the outlet bracket 51. As described above, the transfer bias roller 48K for K is configured such that the transfer conveyance belt 40 can be pressed against or separated from the photosensitive drum K by the swing of the outlet bracket 51. Therefore, when transferring the black monochrome toner image onto the transfer paper P, the transfer belt unit 4 swings the swing bracket 52 in the clockwise direction in FIG. , C, and a black toner image can be transferred without forming a transfer nip for Y, M, and C. As a result, it is possible to transfer a black monochromatic toner image without imposing an extra load on the photosensitive drums Y, M, and C, the transfer / conveying belt 40, and a driving system thereof.

  As shown in FIG. 1, the transfer belt unit 4 further includes a detection sensor that detects a density correction pattern formed on the transfer and transport belt 40 at a position facing the driven roller 44 and the transfer and transport belt 40. 53 and a cleaning device 54 for cleaning the outer surface of the transfer conveyance belt 40 is provided at a position downstream of the detection sensor 53 in the traveling direction of the transfer conveyance belt 40 and facing the drive roller 41 with the belt interposed therebetween. It has been. The detection sensor 53 employs a reflective sensor, and is configured to reflect light emitted from the sensor by a driven roller 44 that is a metal roller. Further, the cleaning device 54 employs a blade cleaning system, and a detection pattern written on the outer surface of the belt with a blade that can come in contact with and separate from the outer surface of the transfer conveyance belt 40 or when the paper is not passed normally (jam) The toner image transferred to the outer surface of the belt at the time of occurrence) can be cleaned and prepared for the next print.

The alignment adjusting means of the alignment adjusting roller according to this embodiment will be described mainly with reference to FIG. 4 is an enlarged perspective view showing the alignment adjusting means of the alignment adjusting roller of the image forming apparatus of FIG.
The alignment adjusting roller 46 according to this embodiment is pivotally supported by a support bracket 60 via bearings 61 and 62, and the support bracket 60 is screwed to a main body side plate of the image forming apparatus 1 (see FIG. 1). ing. Further, one of the bearing portions 61 is provided with a long hole 61a, and the other bearing portion 62 is provided with a normal circular bearing hole 62a, and both shaft end portions 46a and 46b of the alignment adjusting roller 46 are provided. Is inserted into the holes 61a and 62a. On the bearing portion 61 side, a cam motor 63 that is a stepping motor and an eccentric cam 64 that rotates according to a predetermined number of steps by driving the cam motor 63 are provided. The eccentric cam 64 rotated by a predetermined angle by the step drive of the cam motor 63 comes into contact with one shaft end portion 46a of the alignment adjusting roller 46, and this shaft end portion 46a extends in the vertical direction in the drawing along the elongated hole 61a. It is configured to slide. For this reason, when the number of steps is determined by the control means described later, the cam motor 63 rotates the eccentric cam 64 by the number of steps, and the eccentric cam 64 moves the position of one shaft end of the alignment adjustment roller 46, The angle between the roller shaft of the alignment adjusting roller 46 and the roller shaft of another stretching roller can be adjusted. That is, the alignment can be adjusted. The cam motor 63, the eccentric cam 64, the bearing 61 having a long hole 61a, and the like constitute an alignment adjusting means.

  As described above, the alignment adjusting means of the alignment adjusting roller 46 according to this embodiment has been described. For example, the alignment adjusting roller 46 is supported by the support bracket 60 via a biasing means such as a solenoid. And the angle between the roller shaft of the alignment adjustment roller 46 and the roller shaft of the other stretching roller may be adjusted by increasing or decreasing the urging state of the shaft end portions 46a and 46b of the alignment adjustment roller 46. Any configuration that can adjust the alignment of the alignment roller 46 can be replaced with a known technique.

The detection means according to this embodiment will be described mainly with reference to FIGS. FIG. 5 is a perspective view showing the belt position detection sensor of the image forming apparatus of FIG. 1 together with a part of the transfer conveyance belt, and FIG. 6 is a block diagram showing a schematic configuration of the belt position detection sensor of FIG.
The belt position detection sensor 65, which is a detection means according to this embodiment, includes a light emitting unit 65a made of, for example, a light emitting diode and a light receiving unit 65b made of, for example, a photodiode, and the light emitting unit 65a and the light receiving unit 65b. Are arranged so as to face each other across one edge portion 40a of the transfer conveyance belt 40. In the initial setting, as shown in FIG. 6, the reference position is arranged such that the end portion of the edge portion 40a of the transfer conveyance belt 40 comes on the center line of each of the light emitting portion 65a and the light receiving portion 65b. Further, the light emitting unit 65a and the light receiving unit 65b may be arranged upside down from the drawing.

  The light receiving portion 65b of the belt position detection sensor 65 is configured to generate a voltage upon receiving light from the light emitting portion 65a, and has a mechanism in which the detection voltage varies depending on the change in the amount of light received by the light receiving portion 65b. Therefore, in FIG. 6, when the position of the edge portion 40a is shifted from side to side, the degree to which the light emitted from the light emitting portion 65a is blocked by the edge portion 40a also changes. Therefore, the amount of light received by the light receiving unit 65b changes, and the detection voltage of the light receiving unit 65b also changes accordingly. With this configuration, as shown in FIG. 5, the positional deviation of the belt edge portion 40 a perpendicular to the traveling direction of the transfer conveyance belt 40 can be detected. The number of rotation steps of the cam motor 63 is determined based on the information on the detected voltage.

The control means according to this embodiment will be described mainly with reference to FIG. FIG. 7 is a block diagram illustrating a configuration example of a belt deviation correction control unit of the image forming apparatus of FIG.
FIG. 7 shows an example of control means for controlling the operation of correcting the belt misalignment of the transfer / conveying belt 40. The control means includes a control circuit 10 and a memory 11 connected to the control circuit 10. ing. The control circuit 10 is connected to a position detection sensor 65 as detection means via an A / D converter 12 and is also connected to a cam motor 63 as alignment adjustment means via a motor driver 13. Therefore, the number of steps of the cam motor 63 of the alignment adjustment roller 46 can be determined and controlled through the control circuit 10 based on the positional deviation information of the edge portion 40a of the transfer conveyance belt 40 obtained from the position detection sensor 65. it can. Further, the control circuit 10 is configured to receive a start signal 14 of the image forming apparatus, and is also connected to a counter 15.

  Next, an image forming operation of the image forming apparatus according to this embodiment will be described (see FIGS. 1 to 3). First, the transfer sheet P at the uppermost position among the transfer sheets stored in the sheet feed trays 5a and 5b and the manual feed tray 5e is fed by the sheet feed rollers 5c and 5d, and supplied and transferred by the registration roller pair 6. Are sent to the nip between the driven roller 43 and the electrostatic attraction roller 47. Here, since the charge is applied to the outer surface of the transfer / conveying belt 40 by the electrostatic attraction bias via the electrostatic attraction roller 47, when the transfer paper P reaches the nip, the transfer / conveyance is caused by electrostatic attraction. The transfer paper P is adsorbed on the outer surface of the belt 40. When transferring the full-color image onto the transfer paper P, the adsorbed transfer paper P is transferred to the yellow toner image forming unit 3Y as the first toner image forming unit as the transfer conveyance belt 40 rotates. And yellow image formation is performed here. The surface of the photosensitive drum Y is uniformly charged by the charging roller 303Y and then exposed by the exposure device 2 with the laser light L that is modulated and polarized in accordance with the yellow image information. It is formed. The formed electrostatic latent image is developed by the developing device 31Y, and a toner image is formed on the photosensitive drum Y. This toner image is transferred by the transfer bias roller 48Y at the transfer nip for Y between the photosensitive drum Y and the transfer conveyance belt 40, and a single color (yellow) image is formed on the transfer paper P. After the transfer, the photosensitive drum Y is cleaned with unnecessary toner remaining on the drum surface by the cleaning unit 302Y to prepare for the next image formation.

  As described above, the transfer paper P on which the single color (yellow) toner image is transferred by the first toner image forming unit 3Y is conveyed to the second toner image forming unit 3M by the transfer conveying belt 40. In this case as well, the toner image (magenta) formed on the photosensitive drum M is transferred onto the transfer paper P in an overlapping manner. The transfer paper P is further conveyed to the third toner image forming unit 3C (cyan) and the fourth toner image forming unit 3K (black), and similarly, the toner images of the respective colors are superimposed on the transfer paper P and transferred. As a result, a color image is formed. The transfer paper P on which the color image is formed by passing through the fourth toner image forming unit 3K is peeled off from the outer surface of the belt in the attracted state by the rapid folding of the transfer conveyance belt 40 by the driven roller 44, and the fixing device 7 is fixed to the fixing nip 7 by being heated and pressed by the fixing device 7, and then discharged to the discharge unit 8 and stocked. When transferring a black and white image to the transfer paper P, the swing bracket 52 swings away from the transfer transport belt 40, and no transfer nip for Y, M, C is formed. The black and white image is transferred to the fourth toner image forming unit 3K and transferred to the paper discharge unit 8 through the fixing device 7 as in the color image formation.

  Next, the belt misalignment correcting operation of the image forming apparatus according to this embodiment will be described. First, a belt position detection sensor 65 serving as a detection means detects a left-right positional shift (see FIGS. 5 and 6) of the edge portion 40a of the transfer conveyance belt 40 serving as an endless belt with respect to the belt traveling direction. The analog signal of the detection voltage output from 65 is converted into a digital signal by the A / D converter 12, and the digital signal is sent to the control circuit 10 (see FIG. 7). The control circuit 10 compares the positional deviation information based on the digital signal with the reference position information of the edge portion 40a stored in the memory 11 in advance, information on the relationship between the number of steps of the cam motor 63 and alignment adjustment, and the like. The number of steps of the cam motor 63 is determined, and the number of steps is commanded to the cam motor 63 via the motor driver 13. Then, the eccentric cam 64 is rotated by a predetermined angle by the cam motor 63, and the shaft end portion 46a of the alignment adjusting roller 46 is moved vertically along the elongated hole 61a in the direction perpendicular to the belt surface. , The alignment with respect to the belt surface is adjusted and acts in a direction in which the deviation of the belt of the transfer conveyance belt 40 is corrected (see FIG. 4).

When the start signal 14 of the image forming apparatus 1 is input to the control circuit 10, the counter 15 counts the time from the start, compares this count time with a predetermined time stored in the memory 11, and determines the predetermined time. The belt offset correction operation may be repeated until time (see FIG. 7). As described above, when the belt offset correcting operation is repeated, the positional deviation of the belt is gradually converged, and the driving rotation of the belt is stabilized. Therefore, it is possible to form a high-quality image without color misregistration.
In addition, the rotation time for ½ rotation of the transfer conveyance belt 40 is stored in the memory 11 in advance, and this rotation time is compared with the time counted by the counter 15 in the control circuit 10. As described above, the belt offset correction may be periodically performed by controlling the step rotation of the cam motor 63 based on the output data from the belt position detection sensor 65 (see FIG. 7). By doing so, the belt drive rotation is always stable.

In the image forming apparatus according to this embodiment, as described above, the drive roller 41, the alignment adjustment roller 46, and the tension roller 45 from the upstream side of the tension roller that stretches the transfer conveyance belt 40. Since the transfer conveyance belt 40 is arranged in a meandering manner, the area of the transfer conveyance belt 40 in contact with the alignment adjustment roller 46 is large, in other words, in proportion to the contact area. The resistance of the belt of the transfer conveyance belt 40 when passing the alignment adjustment roller 46 is increased. Therefore, when the alignment of the alignment adjusting roller 46 is adjusted as described above, the positional deviation of the transfer conveyance belt 40 is immediately corrected. That is, the responsiveness of the offset correction of the transfer conveyance belt 40 to the alignment adjustment operation of the alignment adjustment roller 46 is improved.
In addition, since the winding amount of the transfer conveyance belt 40 around the drive roller 41 is also increased, the possibility that the drive roller 41 slips is reduced, and the transfer conveyance belt 40 can be driven and rotated stably.
Further, since the drive roller 41, the alignment adjustment roller 46, and the tension roller 45 are not arranged at the position of the stretching roller that supports and forms the image forming surface of the transfer conveyance belt 40, the operation of these rollers is not performed. The running of the belt surface when passing through the image forming surface is less affected and stable, so that an image with good image quality without positional deviation can be formed.

As described above, this embodiment has been described. However, the alignment adjustment unit, the detection unit, and the control unit are merely examples, and other well-known units can be employed. Even in such a case, it is clear that the same effect can be obtained.
Further, although the four-tandem type as the image forming apparatus and the direct transfer type transfer apparatus as the belt driving apparatus are shown and described, it is not always necessary. In short, the image forming apparatus can be applied to other image forming apparatuses as long as the image forming apparatus has an endless belt and a plurality of stretching rollers that stretch and move the endless belt. The driving device can be applied to other belt driving devices as long as a roller configured to adjust the alignment is arranged outside the endless belt and a driving roller for driving the endless belt is arranged next to the roller. Of course.

  In particular, as a belt driving device according to another embodiment, the endless belt may be an intermediate transfer belt, that is, the transfer device transfers a toner image on a photosensitive drum onto an intermediate transfer belt that is an endless belt. And a secondary transfer unit that transfers the toner image on the intermediate transfer belt onto a transfer sheet. In this case, if the running of the intermediate transfer belt becomes unstable near the secondary transfer counter roller to which the transfer bias of the secondary transfer unit is applied, the transfer quality of the image onto the transfer paper is adversely affected. Therefore, it is preferable that the alignment adjusting roller is not disposed at the position of the adjacent stretching roller upstream or downstream of the secondary transfer counter roller in the belt traveling direction. This is because the operation of the secondary transfer counter roller is less affected by the movement of the alignment adjustment roller and is stable.

  Furthermore, the shape, structure, etc. of each component shown in the drawings are merely preferred examples, and can be arbitrarily changed and modified within the scope described in the claims. is there.

  Next, a characteristic effect of the invention described in claim 2 and the following claims will be described. In addition to the above effect, according to the invention of claim 2, one of the plurality of stretching rollers is a tension roller that applies tension to the endless belt, and the tension roller and the driving roller are arranged in the belt traveling direction. Since the alignment adjustment roller is disposed between and adjacent to them, the amount of winding of the endless belt around the alignment adjustment roller is further increased as compared with the belt driving device according to claim 1. With respect to the alignment adjustment operation of the adjustment roller, the deviation phenomenon of the endless belt is corrected quickly and reliably. For this reason, the running stability of the belt can be maintained.

  Furthermore, in addition to the above-described effect, according to the invention of claim 3, a detecting means for detecting the positional deviation of the edge portion of the endless belt, and a control means for controlling the alignment adjusting roller based on information obtained by the detecting means. In other words, the operation of changing the angle of the roller shaft of the alignment adjustment roller is controlled based on the positional deviation information of the edge portion of the endless belt, and the positional deviation can be corrected. The belt offset correction can be performed automatically and accurately, and a stable belt running property without the belt offset phenomenon can be obtained.

  According to the fourth to seventh aspects of the present invention, since the belt driving device according to any one of the first to third aspects is provided, the effects of the first to third aspects can be achieved in the image forming apparatus. That is, in the image forming apparatus, the running of an endless belt such as an intermediate transfer belt, a photoreceptor belt, or a conveyance belt is stabilized, and thus a stable and high-quality image can be formed.

  Furthermore, in addition to the above effect, according to the invention described in claim 5, the alignment adjusting roller and the two stretching rollers located on both sides of the alignment adjusting roller are positioned so as to support the belt surface on which the image of the endless belt is formed. Is not arranged, so the tension roller that supports the image forming surface of the endless belt, that is, the roller that supports the belt surface on which the image is first formed on the endless belt facing the photosensitive drum, is adjusted for alignment. Since the roller and the separate tension roller are always sandwiched, the running of the belt surface on which the image is formed is less affected by the movement of the alignment adjusting roller and is stabilized. Therefore, it is possible to form an image with good quality with no positional deviation.

  Furthermore, in addition to the above-described effect, according to the invention described in claim 6, the endless belt is an intermediate transfer belt, and a primary transfer unit that transfers an image on the photosensitive drum onto the intermediate transfer belt; And a secondary transfer unit having a secondary transfer counter roller for transferring the image on the belt onto the transfer material, and the alignment adjusting roller is adjacent to the upstream or downstream side of the secondary transfer counter roller in the belt traveling direction. Since it is not arranged at the position, the operation of the secondary transfer counter roller is less affected by the movement of the alignment adjustment roller and is stabilized. Therefore, it is possible to form a high-quality image without a stable color shift.

  Furthermore, in addition to the above effect, according to the invention described in claim 7, the endless belt conveys the transfer material on the belt surface facing the photosensitive drum and is formed on the photosensitive drum on the belt surface. Since the image is directly transferred onto the transfer material, the effects of claims 4 and 5 can also be achieved while using both the conveying belt and the transfer belt as one endless belt. Therefore, it is possible to reduce the cost without deteriorating the image quality.

1 is a configuration diagram showing an overall schematic configuration of a four-tandem color image forming apparatus according to an embodiment of the present invention. FIG. 3 is an enlarged cross-sectional view illustrating a configuration of a main part of the first toner image forming unit. FIG. 2 is a configuration diagram illustrating an outline of a transfer belt unit in FIG. 1. It is an expansion perspective view which shows the alignment adjustment means of a winding roller same as the above. It is a perspective view which shows the belt position detection sensor of FIG. It is a block diagram which shows schematic structure of a belt position detection sensor same as the above. It is a block diagram which shows the structural example of the control means of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 3 Image formation part Y, M, C, K Photosensitive drum (Image carrier)
4 Transfer belt unit (belt drive unit)
40 Transfer conveyor belt 41 Driving roller (stretching roller)
42, 43, 44 Driven roller (stretching roller)
45 Tension roller
46 Alignment adjustment roller (stretching roller)
63 Cam motor 64 Eccentric cam 65 Belt position detection sensor (detection means)
10 Control circuit (control means)
11 memory

Claims (7)

An endless belt and a plurality of stretching rollers for stretching the endless belt, one of the plurality of stretching rollers being a driving roller, and the other being an alignment adjusting roller for correcting the deviation of the endless belt; In the belt drive device,
The alignment adjusting roller is disposed at an adjacent position upstream or downstream of the driving roller in the belt traveling direction, and abuts on the endless belt from the outer surface thereof to correct a deviation of the endless belt. A belt drive device characterized by that.   One of the plurality of stretching rollers is a tension roller that applies tension to the endless belt, and in the belt traveling direction, between the tension roller and the driving roller and at a position adjacent thereto, The belt driving device according to claim 1, wherein an alignment adjusting roller is disposed.   The detection means which detects the position shift of the edge part of the said endless belt, and the control means which controls the said alignment adjustment roller based on the information obtained by this detection means are provided. Belt drive device.   An image forming apparatus comprising the belt driving device according to claim 1.   5. The image forming apparatus according to claim 4, wherein the alignment adjusting roller and the two stretching rollers located on both sides of the alignment adjusting roller are not disposed at a position supporting a belt surface on which an image of the endless belt is formed. The endless belt is an intermediate transfer belt;
A primary transfer unit that transfers an image on the photosensitive drum onto the intermediate transfer belt; and a secondary transfer unit that includes a secondary transfer counter roller that transfers the image on the intermediate transfer belt onto a transfer material. And
The image forming apparatus according to claim 4, wherein the alignment adjusting roller is not disposed at an adjacent position upstream or downstream of the secondary transfer counter roller in the belt traveling direction.   6. The endless belt according to claim 4, wherein the endless belt conveys the transfer material on a belt surface facing the photosensitive drum, and directly transfers the image formed on the photosensitive drum on the belt surface onto the transfer material. Image forming apparatus.

Images