JP2014153660A - Belt driving device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a belt driving device configured to prevent degradation of original functions of a tension-applying stretching member and a driving stretching member even if the attitude of an inclining stretching member is changed, and to provide an image forming apparatus including the same.SOLUTION: A driving stretching member, such as a driving roller 301, applies moving force to an endless belt 300. A tension-applying stretching member is supported so as to be displaced in a moving direction with respect to a belt surface of the endless belt 300 in contact therewith, and applies a force toward the belt surface of the endless belt 300. The above stretching members are other than stretching members located adjacent upstream in a belt moving direction of an inclining stretching member which can be inclined to change relative attitude with respect to the belt surface of the end less belt 300 in contact therewith.

Description

  The present invention relates to a belt driving device for endlessly moving an endless belt member that is stretched by four or more rollers as stretching members, and an image of a copying machine, a facsimile, a printer, or the like provided with the belt driving device. The present invention relates to a forming apparatus.

  Many conventional electrophotographic image forming apparatuses use an endless belt, which is an endless belt member, as an image carrier such as a photosensitive member or an intermediate transfer member. In addition, in a conventional image forming apparatus including not only an electrophotographic system but also an ink-jet system, an apparatus using an endless belt is also known as a transport unit that transports a recording material such as a recording sheet. In general, such an endless belt obtains the rotational driving force of the driving roller while being stretched by a plurality of rollers including a driving roller that is a driving stretching member and a tension roller that is a tension applying stretching member. Then, endless driving is performed so as to move endlessly along the sub-scanning direction orthogonal to the main scanning direction.

  The endless belt is circulated and driven by a plurality of rollers. At this time, the belt is shifted in the sub-scanning direction of the endless belt, and the belt slanting in which the stretched region with the belt is inclined in the main scanning direction. May occur. If the belt is shifted, the endless belt may come off the roller, or the end of the endless belt may come into contact with the side plate that supports the shaft portion of the roller. In addition, belt skew occurs in a primary transfer region of an endless intermediate transfer belt as an intermediate transfer member, and belt skew occurs in a transfer region of a paper conveyance belt as a conveyance unit. As a result, the image forming position on the transfer medium such as the intermediate transfer belt or the recording paper is displaced, which causes image distortion. Further, in a color image forming apparatus in which black, yellow, magenta, and cyan single color images are formed and superimposed on a transfer medium to obtain a color image, the image forming position shifts between the color toner images. Appears as a color shift.

  All of these lead to degradation of image quality, and it is necessary to take some measures for the belt shift and the belt skew in order to obtain a high-quality image. Conventionally, various countermeasures for correcting belt deviation and belt skew have been proposed. In particular, as disclosed in Patent Documents 1 to 3, a tilting stretcher that can tilt freely among rollers that stretch an endless belt. A countermeasure for changing the attitude of the steering roller as a member is effective.

  In the belt driving devices disclosed in Patent Documents 1 to 3, as a countermeasure for correcting the belt shift and the belt skew, one end of the rotating shaft of the steering roller is displaced with respect to the other end. Thereby, the relative attitude | position of the said steering roller is changed with respect to the endless belt part contact | abutted to a steering roller. When the attitude of the steering roller is changed in this way, the approach angle of the endless belt with respect to the steering roller changes, and the endless belt moves endlessly. The endless belt portion in contact with the steering roller receives a force for displacing the endless belt portion in the belt width direction from the steering roller, and is displaced in the belt width direction. The endless belt portion in contact with the steering roller is displaced in the belt width direction. Then, the angle formed by the belt width direction of the belt stretched portion stretched between the steering roller and a roller adjacent thereto (hereinafter referred to as an adjacent roller) and the main scanning direction changes, and the belt is skewed. It can be corrected.

  Further, when the endless belt portion that contacts the steering roller is displaced in the belt width direction, the force is transmitted to the endless belt portion that contacts the adjacent roller of the steering roller, so that the endless belt portion is also displaced in the belt width direction. Works. When the endless belt portion contacting the adjacent roller is also displaced in the belt width direction by this force, the displacement force in the belt width direction is also transmitted to the endless belt portion contacting the adjacent roller due to this displacement. By causing such a phenomenon to occur in a chain on the entire endless belt, the endless belt can be displaced in the belt width direction as a whole, and belt misalignment can be corrected.

  However, when the attitude of the steering roller is changed to correct the belt deviation or the belt skew, the steering roller abuts on one end side and the other end side in the belt width direction of the endless belt portion that abuts the steering roller. A difference occurs in the pressure with which the surface pushes the endless belt portion of the endless belt (hereinafter referred to as pressing force). Therefore, there is a difference in the tension acting on the endless belt along the endless movement direction of the endless belt (hereinafter referred to as belt tension) between one end side and the other end side in the belt width direction. When such a belt tension difference occurs in the belt width direction, the belt tension difference also occurs between one end side and the other end side in the belt width direction in the rollers other than the steering roller that stretches the endless belt. Acts as a force to tilt the roller shaft.

  On the other hand, among the rollers that stretch the endless belt, there is usually a tension roller for applying a desired belt tension to the endless belt. In general, the tension roller is supported so as to be able to move forward and backward with respect to the endless belt portion in contact with the tension roller, and receives a biasing force in a direction toward the surface of the endless belt by the biasing means. Yes. When an adjacent roller adjacent to the steering roller is used as the tension roller, the posture of the steering roller is changed. Then, a difference in belt tension occurs between the one end side and the other end side in the belt width direction on the tension roller adjacent to the steering roller, and a force that tilts the axis of the tension roller acts. In response to this, the axis of the tension roller is inclined and the posture of the tension roller changes. Such a change in the posture of the tension roller has an effect of reducing a difference in belt tension in the belt width direction that has occurred in the endless belt. However, when the attitude of the steering roller is changed to correct the belt shift or belt skew, the tension roller's attitude changes so much that the tension roller is properly applied to the endless belt. The original tension function may be disturbed.

  Also, among the rollers that stretch the endless belt, there is usually a driving roller that applies a desired belt driving force to the endless belt and moves it endlessly at a desired moving speed. The drive roller rotates at a desired rotational speed while maintaining a predetermined static frictional force with the endless belt portion of the endless belt. Thereby, the endless belt can move endlessly at a desired moving speed while obtaining a desired belt driving force. When the adjacent roller adjacent to the steering roller is used as the driving roller having such a configuration, the axial direction of the steering roller and the axial direction of the driving roller are not parallel when the attitude of the steering roller is changed. As a result, the belt stretched portion stretched between the steering roller and the drive roller is twisted. At this time, a force that moves in the axial direction of the steering roller acts on the belt stretch portion. The force is transmitted to the drive roller side through the twisted belt stretch portion. As a result, the force in the axial direction of the steering roller that is not parallel to the axial direction of the driving roller acts on the endless belt portion in contact with the driving roller.

  This force component is decomposed into a force component in the axial direction of the drive roller and a force component in a direction perpendicular to the axial direction of the drive roller. The component of force in the direction perpendicular to the axial direction of the drive roller is generated on the contact surface with the endless belt portion of the drive roller as the pressing force. This pressing force changes from one end side to the other end side in the axial direction of the driving roller according to the attitude of the steering roller. When the attitude of the steering roller is changed and the pressing force exceeds a predetermined value, a static friction force having a predetermined value in the axial direction with the endless belt portion of the endless belt cannot be maintained. As a result, a phenomenon occurs in which the endless belt portion in contact with the driving roller slides in the axial direction of the driving roller. When this slipping phenomenon occurs, a dynamic frictional force is generated in the axial direction in the endless belt portion that contacts the driving roller, and a static friction force of a predetermined value with the endless belt portion of the endless belt can be maintained by this dynamic frictional force. It becomes difficult. As a result, the endless belt cannot be moved endlessly at a desired moving speed. Therefore, there is a possibility that the original function of the drive roller is hindered.

  The present invention has been made in view of the above problems, and its object is to inhibit the original functions of the tension applying tension member and the driving tension member even if the posture of the tilting tension member is changed. It is an object of the present invention to provide a belt driving device and an image forming apparatus including the belt driving device.

  In order to achieve the above object, a first aspect of the present invention provides a belt drive device for endlessly moving an endless belt member stretched on four or more stretch members, and applies a moving force to the endless belt. The belt of the endless belt that abuts the driving tension member and the tension applying tension member that is supported so as to be displaceable in a direction that advances and retreats with respect to the belt surface of the endless belt that abuts and biases toward the belt surface of the endless belt In order to change the relative posture with respect to the surface, a tilting stretchable member that is freely tiltable is a stretchable member other than the stretchable member adjacent to the upstream side in the belt moving direction.

  As an experiment, in the case of a belt driving device in which an endless belt member is stretched by four or more tension members and moved endlessly, one of the four or more tension members is a tilting tension member. To do. A tension member other than the tension member adjacent to the upstream side of the tilting tension member in the belt moving direction was used as a driving tension member. And the load which arises on the contact surface which contact | abuts the endless belt part of all the tension members is changed by changing the attitude | position of a tilting tension member. Based on the measurement results, verification is made on which stretch member other than the tilt stretch member is subjected to the load generated on the contact surface that abuts on the endless belt portion of the tilt stretch member caused by the change in the posture of the tilt stretch member. An experiment was conducted. As a result of this experiment, the load generated on the contact surface that contacts the endless belt portion of the tilting tension member contacts the endless belt portion of the tensioning member adjacent to the upstream side of the tilting tension member in the belt moving direction. Acts on the tangent surface. And it turned out that there are few tension members adjacent to the further downstream side of the tension member and the downstream side of the tilting tension member in the belt movement direction. Therefore, in the present invention, the drive tension member and the tension applying tension member are not tension members adjacent to the upstream side of the tilting tension member in the belt moving direction, but are tension members other than the tension member. As a result, the load generated on the contact surfaces of the drive tension member and the tension applying tension member contacting the endless belt portion is the same as the load generated on the contact surface of the tilt tension member contacting the endless belt portion. The load can be made smaller than the load applied to the contact surface that contacts the endless belt portion of the stretch member adjacent to the upstream side of the belt in the belt movement direction. Therefore, even if the posture of the tilting tension member is changed, a specific effect is obtained that the original functions of the tension applying tension member and the driving tension member are hardly hindered.

It is a schematic diagram which shows the structure of the belt drive device used for the analysis. FIG. 6 is a characteristic diagram showing a detection result in the case of steering condition 1; FIG. 6 is a characteristic diagram showing a detection result in the case of steering condition 2. 1 is a schematic diagram illustrating a configuration of an image forming apparatus to which the present invention is applied. It is a schematic perspective view which shows the structure of a belt drive part. It is a perspective view which shows the structure of a belt shift and skew detection means. FIG. 2 is a block diagram illustrating a configuration of an apparatus that corrects a latent image forming position on an image carrier in order to correct an image forming position in the main scanning direction on an intermediate transfer belt.

First, the principle of the belt driving device of the present invention will be outlined.
In the configuration in which the belt deviation or the belt skew is corrected by the steering roller in the belt driving device, the posture of the steering roller is changed. It is desirable that the tension change in the belt width direction caused thereby does not affect the tension function by the tension roller or the like, the image forming function by the primary transfer unit or the secondary transfer unit, or the belt drive function by the drive roller or the like. As a result of the following analysis, it has been clarified that the roller in which the tension change in the belt width direction caused by the steering roller is limited to some extent by the layout.

  FIG. 1 is a schematic diagram showing a configuration of a belt driving device used for analysis. In the figure, a belt 300 is rotationally driven by a driving roller 301. Then, the driven roller 302 is tilted in the direction a (steering condition (1)) orthogonal to the tension direction A and the driven roller 303 in the direction b (steering condition (2)) orthogonal to the tension direction B. Tilted. In this case, the axial load and the load direction applied to the contact surface of the driving roller 301 and the driven rollers 302, 303, 304, and 305 with the belt 300, and the position in the main scanning direction where the belt 300 deformed thereby travels. Was detected.

  The detection results are shown in FIGS. FIG. 2 shows the detection result for the steering condition (1), and FIG. 3 shows the detection result for the steering condition (2). As can be seen from the detection result in the case of the steering condition 1 as shown in FIG. 2, the driven roller 302 changes the attitude of the driven roller 302 according to the steering condition 1. Then, the contact surface of the driven roller 303 adjacent to the upstream side of the driven roller 302 is added to the contact surface of the driven roller 302 with the belt 300 in the direction opposite to the load direction of the driven roller 302. The load is larger than the load. The belt 300 is largely deformed in the belt width direction between the driven roller 302 and the driven roller 303 adjacent to the upstream side thereof. However, the axial load applied to the contact surface of the driven roller 304 adjacent to the upstream side of the driven roller 303 with the belt 300 is smaller than the load on the driven roller 303.

  The axial load applied to the contact surface of the drive roller 301 adjacent to the upstream side of the driven roller 304 with the belt 300 is smaller than the load on the driven roller 304. The axial load applied to the contact surface of the driven roller 305 adjacent to the upstream side of the drive roller 301 and adjacent to the downstream side of the driven roller 302 is slightly larger than the load on the drive roller 301. However, it is at least smaller than the load on the driven roller 302 and the load on the driven roller 303. This is considered that the driven roller 305 is adjacent to the downstream side of the driven roller 302, so that the load on the driven roller 302 has some influence on the driven roller 302. And it became clear that the deformation in the belt width direction of the belt 300 is small in the driving roller 301 and the driven rollers 302 and 305.

  As can be seen from the detection result in the case of the steering condition 2 as shown in FIG. 3, the driven roller 303 changes the attitude of the driven roller 303 according to the steering condition 2. Then, the contact surface of the driven roller 304 adjacent to the upstream side of the driven roller 303 is added to the contact surface of the driven roller 303 with the belt 300 in the direction opposite to the load direction of the driven roller 303. The load is larger than the load. The belt 300 is largely deformed in the belt width direction between the driven roller 303 and the driven roller 304 adjacent to the upstream side thereof. However, the load applied to the contact surface of the driving roller 301 adjacent to the upstream side of the driven roller 304 with the belt 300 is smaller than the load on the driven roller 304. Further, the axial load applied to the contact surface of the driven roller 305 adjacent to the upstream side of the drive roller 301 with the belt 300 is smaller than the load on the drive roller 301. The axial load applied to the contact surface of the driven roller 302 adjacent to the upstream side of the driven roller 305 and adjacent to the downstream side of the driven roller 303 is based on the load on the driven roller 303 or the load on the driven roller 304. small. Due to the influence, the belt 300 is largely deformed in the belt width direction between the driven roller 303 to be steered and the driven roller 304 adjacent to the upstream side thereof. And it became clear that the deformation in the belt width direction of the belt 300 is small in the driving roller 301 and the driven rollers 302 and 305.

An embodiment in which the belt driving device of the present invention is applied to a transfer unit of an image forming apparatus will be described.
FIG. 4 is a schematic diagram showing the configuration of an image forming apparatus to which the present invention is applied. FIG. 5 is a schematic perspective view showing the configuration of the belt driving unit. A printer 100 as an image forming apparatus shown in FIG. 4 uses four photosensitive drums provided with developing devices in parallel, and forms a full-color image on an intermediate transfer belt. In this printer 100, four image carriers (hereinafter referred to as photosensitive drums) 101, 102, 103, and 104 are rotationally driven in the direction of an arrow (counterclockwise) during image formation, and the surfaces thereof are charged by chargers 111, 112, 113 and 114 are uniformly charged. Thereafter, exposure is performed according to the input image information by the exposure devices 121, 122, 123, and 124, and an electrostatic latent image is formed. Then, the yellow developing unit 131 attaches toner to the electrostatic latent image on the photosensitive drum 101 and develops it as a yellow toner image. Next, the magenta developing unit 132 attaches toner to the electrostatic latent image on the photosensitive drum 102 and develops it as a magenta toner image. Then, the cyan developing unit 133 attaches toner to the electrostatic latent image on the photosensitive drum 103 and develops it as a cyan toner image. Finally, the black developing unit 134 attaches toner to the electrostatic latent image on the photosensitive drum 104 and develops it as a black toner image.

  The yellow toner image, the magenta toner image, the cyan toner image, and the black toner image are in contact with the photosensitive drums 101, 102, 103, and 104 and move on the intermediate transfer belt 200 that moves endlessly in the direction of the arrow. Primary transfer is performed. Thereafter, four color toner images are superimposed on the intermediate transfer belt 200. The four color toner images are secondarily transferred to the recording material P conveyed by a conveyance roller 225 from a paper feed cassette (not shown). The recording material P that has been secondarily transferred is transported to the fixing device 227 by the belt transport mechanism 226 and fixed, whereby a full color image can be obtained.

  As shown in FIGS. 4 and 5, the intermediate transfer belt 200 is stretched by a plurality of substantially parallel rollers, and is driven in the belt conveyance direction by one drive roller 211 among them. While the driving roller 211 and the driven rollers 212, 213, and 214 are fixed at predetermined positions, both ends of the rotation shaft of the tension roller 215 are urged in the tension direction indicated by the arrow, thereby applying tension to the intermediate transfer belt 200. ing. Both ends of the rotating shaft of the steering roller 216 are supported by a pivot bearing or the like so as to be swingable in a direction perpendicular to the roller rotating shaft, and one end side is tensioned by an actuator 217 serving as a first shift / slanting correction means. Is supported so as to be able to reciprocate in a direction orthogonal to the direction. Both ends of the rotating shaft of the steering roller 218 are supported by a pivot bearing or the like so as to be swingable in a direction orthogonal to the roller rotating shaft, and one end side is tensioned by an actuator 219 which is a second deviation / skew correction means. Is supported so as to be able to reciprocate in a direction orthogonal to the direction. A secondary transfer roller 220 that applies a voltage for secondary transfer is disposed at a position facing the driven roller 214 via the intermediate transfer belt 200. Further, primary transfer rollers 221, 222, 223, and 224 that apply a voltage for primary transfer are disposed at positions facing the photosensitive drums 101, 102, 103, and 104 via the intermediate transfer belt 200. Has been.

  Based on the belt deviation detection information and the belt skew detection information, the actuators 217 and 219 are driven to swing the steering rollers 216 and 218 so as to correct movement and inclination in the belt main scanning direction. Thereby, the belt shift and the belt skew are controlled within a certain range. Here, the adjustment sensitivity of the belt shift and the belt skew by the actuator 217 and the adjustment sensitivity of the belt shift and the belt skew by the actuator 219 are known. If stable and constant, the ratio of driving the actuators 217 and 219 with respect to the belt deviation detection information and the ratio of driving the actuators 217 and 219 with respect to the belt skew detection information are set optimally in advance. Thereby, it is possible to independently control the deviation of the belt and the skew of the belt by the two actuators.

  Further, as shown in FIG. 6, a detection line 201 is formed on the surface of the intermediate transfer belt 200 at a fixed position in the main scanning direction over the entire circumference in the transport direction. Belt offset / skew detection means 202a and 202b are arranged at a predetermined interval at a position facing the detection line 201 so that the position of the detection line 201 in the main scanning direction can be detected. By detecting the position of the detection line 201 in the main scanning direction sequentially, the belt shift can be detected. Further, as shown in FIGS. 4 and 5, two belt deviation / slanting detection means 202a and 202b are arranged at a predetermined interval in the sub-scanning direction in the primary transfer portion of the intermediate transfer belt 200. Yes. The belt skew can be detected by sequentially detecting the difference in the position in the main scanning direction of the detection lines detected by the two belt deviation / skew detection means 202a and 202b. In this configuration, belt shift and belt skew are detected by detecting movement in the belt main scanning direction of a detection line formed in advance on the intermediate transfer belt with high accuracy. For this reason, for example, as in the technique described in Japanese Patent Application Laid-Open No. 2000-233843, the belt edge position and the belt skew are detected by detecting the position of the belt edge. Then, it is not necessary to refer to the edge data measured in advance or to store the data obtained by averaging the periodic fluctuations of the edge position in the storage means. As a result, it is possible to detect and control the belt at high speed without waste time with a lower cost configuration.

  This principle was applied to the printer 100 of this embodiment shown in FIGS. That is, the steering roller 216 corresponding to the driven roller 302 in FIG. 1, the steering roller 218 corresponding to the driven roller 303, and the driven roller 213 corresponding to the driven roller 304 have a function of applying tension to the intermediate transfer belt 200. Absent. The tension roller 215 has a tension function. Thereby, even if the steering operation is performed by the steering rollers 216 and 218, the axial force applied to the contact surface of the tension roller 215 with the intermediate transfer belt 200 is small. Note that the change in tension in the belt width direction caused by the tension roller 215 and the accompanying twist of the belt are not problematic.

  Further, in the printer 100 shown in FIGS. 4 and 5, the steering roller 216, the steering roller 218, and the driven roller 213 do not constitute a primary transfer portion or a secondary transfer portion involved in image formation. The primary transfer portion or the secondary transfer portion is configured by primary transfer rollers 221, 222, 223, 224, or a driven roller 214. For this reason, even if the steering operation is performed by the steering rollers 216 and 218, the force applied to the contact surfaces of the primary transfer rollers 221, 222, 223, and 224 and the driven roller 214 with the intermediate transfer belt 200 is small. Note that the change in tension in the belt width direction caused by the primary transfer rollers 221, 222, 223, and 224 and the driven roller 214 and the accompanying change in pressure in the belt width direction of each transfer portion are not problematic.

  Further, the steering roller 216, the steering roller 218, and the driven roller 213 are not rollers that convey and drive the intermediate transfer belt 200, but the rollers that convey and drive are driving rollers 211. For this reason, even if the steering operation is performed by the steering rollers 216 and 218, the axial force applied to the contact surface of the driving roller 211 with the belt is small. Further, the belt width direction tension change caused by the driving roller 211 and the accompanying driving force change in the belt width direction are not at a problem level.

  With the above configuration, the twist of the belt caused by the steering operation is small, and belt slack and wrinkle and wrinkle in the tilt detection unit do not become a problem. For this reason, it is possible to accurately detect the belt shift and inclination and to correct the belt shift and skew with high accuracy. As a result, in a monochrome image forming apparatus in which a single color image formed with one image carrier is primarily transferred to an intermediate transfer belt and then secondarily transferred to a transfer material, the image forming position on the transfer material is prevented from being displaced and distorted. It is possible to output images without any problem. Further, in a color image forming apparatus that sequentially transfers a single color image formed by a plurality of image carriers to an intermediate transfer belt in order, and then secondary-transfers the multiple color image to a transfer material, the image forming position on the transfer material is determined. Misregistration is prevented, and image output without color misregistration is possible. Further, the belt width direction transfer pressure change in the image transfer portion caused by the steering operation, the belt width direction driving force change in the belt drive roller caused by the steering operation, and the accompanying influence on the conveyance drive are not a problem. For this reason, image defects can be prevented, and high-quality image output is possible.

  Next, a correction device for correcting the influence of the belt skew in addition to the belt skew correction by the steering roller will be described. FIG. 7 is a block diagram showing the configuration of an apparatus for correcting the latent image forming position on the image carrier in order to correct the image forming position on the intermediate transfer belt in the main scanning direction. In the figure, the image signal transferred from the printer driver unit 400 is input to the image signal generation unit 501 constituting the image writing control unit 500. Engine control information from the engine control unit 600 is also input to the image writing control unit 500. The image signal generation unit 501 performs image processing on the input image signal by processing according to engine control information. At this time, since the image signal generation unit 501 actually develops the image on the recording paper, the image signal generation unit 501 performs processing with a pixel clock signal (wclk) that defines the minimum pixel used for image formation. The pixel clock signal is generated by the pixel clock generation unit 502 by using the information from the engine control unit 600 such as the resolution, the photosensitive drum linear velocity, and the like to generate a clock signal (wclk) having a predetermined frequency. Input to the circuit unit 503. The actual image signal subjected to image processing by the image signal generation unit 501 is input to the writing position control unit 504.

  In addition, the writing position control unit 504 includes a synchronization detection signal (DETP) from the synchronization detection unit 701 of the laser writing apparatus 700, a belt displacement signal (Δa) created based on the skew information of the intermediate transfer belt, and an output from the engine control unit 600. Each engine control information is input. The synchronization detection signal (DETP) is a signal for keeping the writing start position in the main scanning direction constant when the laser beam is exposed on the photosensitive drum. This signal is an output signal from the synchronization detection plate arranged outside the scanning region on the photosensitive drum of the laser beam reflected and deflected by the polygon mirror 702 in the laser writing apparatus. A light receiving element such as a photodiode is cast as a synchronization detection sensor 703 on the synchronization detection plate, and the synchronization detection sensor 703 photoelectrically converts an incident laser beam and outputs a synchronization detection signal (DETP). The belt displacement signal (Δa) is a signal indicating the displacement of the intermediate transfer belt 200 in the main scanning direction. In other words, this is a signal calculated from the belt skew information in the main transfer direction displacement of the intermediate transfer belt within the image transfer surface, which occurs during belt deviation correction by the belt deviation correction means.

  In the writing position control unit 504, a real image signal from the image signal generation unit 501 is synthesized with a synchronization detection signal (DETP) at a predetermined timing, and a signal for driving a semiconductor laser as a light source is generated. At this time, the start timing of writing the actual image signal from the synchronization detection signal is controlled according to the belt displacement signal (Δa). The writing position control unit 504 receives a skew correction clock signal (dclk) obtained by multiplying the pixel clock signal (wclk) generated by the pixel clock generation unit 502. The skew correction clock signal (dclk) is obtained by multiplying the pixel clock signal (wclk) that defines the minimum pixel that can form an image, and is a signal having a higher frequency than the pixel clock signal. The skew correction clock signal (dclk) is a clock signal having a frequency corresponding to the detection resolution of the transfer slit position sensor, and one clock of the skew correction clock signal (dclk) corresponds to one resolution of the belt skew information. doing. A belt displacement signal (Δa) calculated from the belt skew information is detected, and a synchronization detection signal (DETP) and a belt displacement signal (Δa) are input to the writing position control unit 504.

  A (= N × wclk, N is a positive integer) from the synchronization detection signal when the belt displacement signal (Δa) is 0 to the start position in the main scanning direction of the actual image signal. Then, when Δa> 0 is detected, the delay time from the synchronization detection signal to the actual image writing timing is changed to A + Δa × dclk. Then, the actual image writing start position is delayed with respect to the case where there is no belt skew. On the other hand, when Δa <0, the delay time is set to A−Δa × dclk, and the actual image writing start timing is relatively accelerated. The laser driving signal combined by the writing position control unit 504 is input to the laser driving unit 505. The semiconductor laser 704 mounted on the laser drive unit 505 is repeatedly driven to turn on / off by turning on / off the laser drive signal. A laser beam emitted by driving the semiconductor laser 704 enters a laser writing device, passes through and reflects a plurality of lenses, mirrors, and the like, and travels in the optical path. It is rotationally deflected by a polygon mirror 702 disposed in the middle of the optical path, and a laser beam is exposed on the photosensitive drum in the main scanning direction. The process from this exposure until an output image is obtained is as described above.

  With the above configuration, correction by the steering roller can be performed only on the belt, so that the apparatus can be reduced in size and cost, and slack and wrinkles of the belt on the primary transfer surface can be prevented. As a result, the image quality of the output image can be improved by correcting the latent image forming position.

  In the above analysis results, the axial force acting from the roller to the belt by the steering roller is a large force in the opposite direction between the steering roller and its upstream roller. As a result, it has been described that the belt is largely deformed in the width direction between the steering roller and the upstream roller. However, as a result of further analysis, the case where the belt winding angle of the roller adjacent to the upstream side of the steering roller, that is, the angle in the range where the belt is in contact with the entire circumference of the roller, was considered. In that case, for example, when the angle of the range where the belt is in contact with the entire circumference of the roller is approximately 40 degrees or less, the axial force acting on the belt from the roller is small, and the deformation in the belt width direction of the roller is also small. It became clear. In this case, the large force in the reverse direction works against the large axial force that acts on the belt from the steering roller. Except for rollers with a small belt wrap angle (approximately 40 degrees or less), the steering roller and upstream belt transport It is a roller having the smallest direction interval. The belt is greatly deformed in the width direction between the roller and the steering roller. For this reason, by removing a roller having a belt winding angle of approximately 40 degrees or less as a roller adjacent to the upstream side of the steering roller as in the above-described embodiment, image distortion due to image forming position deviation is prevented and image defects are prevented. The effect of the invention of reducing the factor can be obtained.

What has been described above is merely an example, and the present invention has a specific effect for each of the following modes.
(Aspect 1)
A drive tension member such as a drive roller 301 that applies a moving force to the endless belt, and a belt that can be displaced in a direction that moves forward and backward with respect to the belt surface of the endless belt that contacts the endless belt, and is biased toward the belt surface of the endless belt. A tension member other than the tension member adjacent to the upstream side in the belt movement direction of the tilting tension member that is tiltable to change the relative posture of the tension applying tension member with respect to the belt surface of the endless belt in contact with the tension member. did. According to this, as described in the above embodiment, as an experiment, in the case of a belt driving device in which an endless belt member is stretched by four or more tension members and moved endlessly, four or more tension members are stretched. One of the members is a tilting member. A tension member other than the tension member adjacent to the upstream side of the tilting tension member in the belt moving direction was used as a driving tension member. And the load which arises on the contact surface which contact | abuts the endless belt part of all the tension members is changed by changing the attitude | position of a tilting tension member. Based on the measurement result, verify which tension member other than the tilting tension member is subjected to the load generated on the contact surface that abuts the endless belt portion of the tilting tension member caused by the posture change of the tilting tension member The experiment was conducted. As a result of this experiment, the load generated on the contact surface that contacts the endless belt portion of the tilting tension member contacts the endless belt portion of the tensioning member adjacent to the upstream side of the tilting tension member in the belt moving direction. It has been found that the number of the tension member acting on the contact surface is less on the tension member on the further upstream side of the tension member and on the downstream side of the tilting tension member in the belt moving direction. Therefore, in the present invention, the drive tension member and the tension applying tension member are not tension members adjacent to the upstream side of the tilting tension member in the belt moving direction, but are tension members other than the tension member. As a result, the load generated on the contact surfaces of the drive tension member and the tension applying tension member contacting the endless belt portion is the same as the load generated on the contact surface of the tilt tension member contacting the endless belt portion. The load can be made smaller than the load applied to the contact surface that contacts the endless belt portion of the stretch member adjacent to the upstream side of the belt in the belt movement direction. Therefore, even if the posture of the tilting tension member is changed, the original functions of the tension applying tension member and the driving tension member are hardly disturbed.
(Aspect 2)
In (Aspect 1), another tilting stretch member that moves one end in the belt width direction of any stretch member other than the tilt stretch member relative to the other end in a direction crossing the belt width direction. And the two tilting tension members are driven independently of each other to adjust the belt position in both directions in the belt width direction. According to this, as described in the above embodiment, a configuration that obstructs high-speed driving of the belt such as a belt shift guide member is not necessary, so that the image output can be speeded up.
(Aspect 3)
In (Aspect 1), the tension member adjacent to the upstream side of the tilting tension member in the belt moving direction is a tension member other than the tension member whose belt winding angle is approximately 40 degrees or less among four or more tension members. Among the tension members, the tension member having the smallest distance between the tilting tension member and the upstream side in the belt moving direction. According to this, as described in the above embodiment, a configuration that obstructs high-speed driving of the belt such as a belt shift guide member is not necessary, so that the image output can be speeded up.
(Aspect 4)
In an image forming apparatus using an endless belt that moves endlessly by a belt driving device as an image carrier that carries an image on the surface or a recording material conveying member that carries and conveys a recording material on which an image is formed on the surface. The belt driving device is used as the belt driving device. According to this, as described in the above embodiment, it is possible to realize image quality improvement by preventing image distortion due to image formation position shift and reducing the cause of image defects.
(Aspect 5)
In (Aspect 4), the visible images formed on the plurality of image carriers are sequentially transferred onto the endless belt as an intermediate transfer member, and the transfer image on the intermediate transfer member is transferred onto the transfer material as a secondary transfer. Then, a multi-color image is formed. According to this, as described in the above-described embodiment, it is possible to reliably correct the belt shift and the belt skew, thereby preventing image distortion and color shift due to image forming position shift and reducing the cause of image defects. Can achieve high image quality in color.
(Aspect 6)
In (Aspect 5), the driving stretch member for applying a moving force to the endless belt, and supported so as to be displaceable in a direction to advance and retreat with respect to the belt surface of the endless belt that contacts, and urged toward the belt surface of the endless belt. Primary transfer to a tension applying tension member, a tilting tension member that can be tilted to change the relative posture of the abutting endless belt with respect to the belt surface, and a position facing the image carrier via the endless belt A primary transfer stretch member for applying a voltage for the transfer, and a secondary transfer stretch member for applying a voltage for secondary transfer at a position facing the endless belt. The applying tension member, the primary transfer tension member, and the secondary transfer tension member are configured by using a tension member other than the tension member adjacent to the upstream side of the tilting tension member in the belt moving direction. According to this, as described in the above embodiment, the driving roller, the tension roller, the primary transfer roller, and the secondary transfer roller are configured by rollers other than the roller adjacent to the upstream side in the belt movement direction of the steering roller. . Thereby, since the action of the load in the axial direction of the steering roller is small, the original functions of the driving roller, tension roller, primary transfer roller, and secondary transfer roller can be performed. Therefore, it is possible to increase the speed of image output because there is no need for a configuration that obstructs high-speed belt driving, such as a shift guide member, and it is possible to prevent image distortion due to misalignment of the image formation with reliable correction and cause image defects. High image quality can be achieved by reducing
(Aspect 7)
In any one of (Aspect 4) to (Aspect 6), the image forming position correcting unit corrects the latent image forming position in the main scanning direction on the image carrier. According to this, as described in the above-described embodiment, a configuration that obstructs high-speed belt driving such as a belt-side guide member is not required, and thus the apparatus can be reduced in size and cost.

DESCRIPTION OF SYMBOLS 100 Printer 101 Photosensitive drum 102 Photosensitive drum 103 Photosensitive drum 104 Photosensitive drum 111 Charging device 112 Charging device 113 Charging device 114 Charging device 121 Exposure device 122 Exposure device 123 Exposure device 124 Exposure device 131 Exposure device 131 Yellow developing device 132 Magenta developing device 133 Cyan developing device 134 Black developing device 200 Intermediate transfer belt 201 Detection line 202a Belt shift / skew detection device 202b Belt shift / skew detection device 211 Drive roller 212 Drive roller 213 Drive roller 214 Drive roller 215 Tension roller 216 Steering roller 217 Actuator 218 Steering roller 219 Actuator 220 Secondary transfer roller 221 Primary transfer roller 222 Primary transfer roller 223 Primary transfer roller 224 Primary transfer roller 25 conveyor roller 226 belt conveying mechanism 227 fuser 228 conveying roller

JP 2011-022549 A JP 2011-095571 A

Claims (7)

In a belt driving device for endlessly moving an endless belt member stretched on four or more stretch members,
A drive tension member that applies a moving force to the endless belt, and a tension application tension member that supports the endless belt so that the endless belt can be displaced in a forward and backward direction and biases the endless belt toward the belt surface. Is a tension member other than the tension member adjacent to the upstream side in the belt movement direction of the tilting tension member that is tiltable to change the relative posture of the abutting endless belt with respect to the belt surface. Belt drive. The belt drive device according to claim 1, wherein
There is another tilting tension member that moves one end in the belt width direction of any tension member other than the tilting tension member relative to the other end in a direction crossing the belt width direction. A belt driving device characterized by adjusting the belt position in both directions in the belt width direction by driving the tilting tension members independently of each other. The belt drive device according to claim 1, wherein
The tension member adjacent to the upstream side of the tilting tension member in the belt moving direction is a tension member other than the tension member whose belt winding angle is approximately 40 degrees or less among four or more tension members. Among them, the belt driving device is characterized in that it is a tension member having the smallest distance between the tilting tension member and the upstream side in the belt movement direction. In an image forming apparatus using an endless belt that moves endlessly by a belt driving device as an image carrier that carries an image on the surface or a recording material conveying member that carries and conveys a recording material on which an image is formed on the surface. ,
An image forming apparatus using the belt driving device according to claim 1 as the belt driving device. The image forming apparatus according to claim 4.
Visible images formed on a plurality of image carriers are sequentially transferred onto the endless belt as an intermediate transfer member, and the transfer image on the intermediate transfer member is secondarily transferred onto a transfer material, so that a multi-color image is obtained. Forming an image forming apparatus. The image forming apparatus according to claim 5.
A drive tension member that applies a moving force to the endless belt, and a tension application tension member that is supported so as to be displaceable in a direction that advances and retreats with respect to the belt surface of the endless belt that abuts, and that biases the belt surface of the endless belt. A tilting stretchable member that can be tilted to change the relative posture of the abutting endless belt with respect to the belt surface, and a voltage for primary transfer at a position facing the image carrier via the endless belt. And a secondary transfer stretch member that applies a voltage for secondary transfer to a position facing the endless belt, the drive stretch member, and the tension application The tension member, the primary transfer tension member, and the secondary transfer tension member are configured by using a tension member other than the tension member adjacent to the upstream side of the tilting tension member in the belt movement direction. An image forming apparatus. The image forming apparatus according to claim 4,
An image forming apparatus comprising image forming position correcting means for correcting a latent image forming position in the main scanning direction on an image carrier.

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