JP6186937B2 - Endless belt device and image forming apparatus - Google Patents

Description

  The present invention relates to an endless belt device in which an endless belt is stretched by applying tension by a plurality of rollers and is moved around by a driving roller, and an image using the endless belt of the endless belt device as an intermediate transfer belt or a recording material conveying belt. The present invention relates to a forming apparatus.

BACKGROUND ART Endless belt devices in which an endless belt is stretched by applying tension by a plurality of rollers and moved around by a driving roller are used in various industrial fields.
For example, in an electrophotographic image forming apparatus, an intermediate transfer belt that is an endless belt is used as an intermediate transfer material, or a recording material conveyance belt that is an endless belt as a means for conveying a recording material such as paper as a transfer medium The one using is known.
Such an endless belt device is stretched by a plurality of rollers, and is driven to rotate by rotation of a driving roller. At that time, there may occur a belt shift in which the belt position moves in the belt width direction (main scanning direction) perpendicular to the moving direction of the endless belt, or a belt skew in which the belt moving direction is inclined in the main scanning direction. is there.

When the belt is deviated or the belt is skewed, the image forming position on the intermediate transfer belt as a transfer medium or the recording material is displaced, which causes image distortion.
Also, black (K), yellow (Y), magenta (M), and cyan (C) single color images are formed on the image carrier, transferred onto the transfer medium, and the color image is transferred. There is a color image forming apparatus to obtain.
In the color image forming apparatus, a shift in image forming position appears as a color shift between toner images of the respective colors. All of these lead to degradation of image quality, and it is necessary to take measures against the belt shift and the belt skew in order to obtain a high-quality image.

In order to cope with this problem, various methods have been proposed. As one of the methods, for example, as shown in Patent Document 1, an offset guide member is provided on an endless belt that is an intermediate transfer belt or a recording material conveyance belt. There is a way.
This method regulates the force in the belt width direction (main scanning direction) generated in the endless belt by bringing a guide member provided on the surface of the endless belt into contact with the end face of the belt conveying roller or inserting it into the groove. Thus, the endless belt is prevented from shifting.

However, with this method, it is possible to suppress the deflection that is the position fluctuation in the main scanning direction of the shift guide member formed on the endless belt and the belt skew caused by the position fluctuation in the main scanning direction of the end surface of the conveying roller and the groove. Can not. For this reason, there is a drawback in that a position shift in the main scanning direction occurs and image distortion and color shift occur.
Further, when the endless belt is driven at a high speed, a large external force is applied to the shift guide member, and the belt and the shift guide member are likely to buckle or break, and it is difficult to increase the image output speed.

Therefore, as described in Patent Document 2, for example, the belt shift and skew of the endless belt in the main scanning direction are accurately detected, and the latent image formation in the main scanning direction on the image carrier is performed based on the detection information. There is a method for correcting the position.
According to this method, since a member that hinders belt high-speed driving, such as a shift guide member, is not used, the image output speed can be increased. In addition, since the image forming position on the image carrier is corrected in accordance with the endless belt shift and skew, image distortion and color misregistration can be prevented.

  Further, as described in, for example, Patent Document 3, a position in the width direction of an endless belt that moves around, such as an intermediate transfer belt, is detected to calculate a shift and skew, and the shift and skew are determined as endless. There is also a correction method using two steering rollers that stretch the belt.

  Further, Patent Document 4 includes a shift adjustment mechanism that includes a first adjustment mechanism that moves one end of one steering roller in a first direction and a second adjustment mechanism that moves one end of the steering roller in a second direction. An image forming apparatus having the same is disclosed. Then, when adjusting the deviation of the endless belt that is the paper conveying belt, the first and second adjustments are performed when the endless belt is moved quickly in the main scanning direction that is the width direction and when it is moved accurately. The mechanism is used properly.

  Further, Patent Document 5 discloses that the correction amount of the position in the width direction of the intermediate transfer belt is increased by inclining two adjacent steering rollers integrally. It also describes that the two steering rollers are subjected to a surface treatment so as to have a higher coefficient of friction than the other rollers to maintain the belt restraining force of the steering roller in the correction operation.

  However, as described in Patent Document 2, when correcting image distortion and color shift due to endless belt skew or skew according to the image forming position, the inclination of the endless belt is not directly corrected. Therefore, the required image forming position correction amount for the detected endless belt shift or skew varies due to variations in product assembly accuracy, environmental conditions, etc., and high accuracy correction cannot be performed. There is a limit to the conversion.

In addition, as described in Patent Document 3, when correcting not only the shift but also the skew by the steering roller, specifically, the two steering rollers are respectively unique as in the configuration disclosed in Patent Document 4. It is necessary to correct the skew and skew by tilting to.
At this time, in order to sufficiently secure the correction sensitivity obtained with respect to the inclination of each steering roller and the linearity of the sensitivity in the necessary correction range, restrictions on the layout of the rollers that stretch the belt increase. In order to increase the correction sensitivity, it is well known that the diameter of the steering roller should be increased, but this is an obstacle to downsizing and cost reduction of the apparatus.

On the other hand, in the image forming apparatus described in Patent Document 5, the correction sensitivity is increased by increasing the steering roller diameter by inclining two adjacent rollers together.
However, even in this case, if the distance between the steering roller and the adjacent roller on the upstream side in the circumferential movement direction of the endless belt is small, the sensitivity of the correction obtained with respect to the inclination of the steering roller and the necessity Sensitivity linearity in a wide correction range cannot be obtained.
For this reason, it is necessary to increase the distance between the steering roller and the adjacent roller on the upstream side, but this causes a problem that the apparatus becomes larger and the cost becomes higher.

The present invention has been made in view of the above problems, and is a compact type that can reliably correct the deviation and skew of the endless belt without using a configuration that obstructs high-speed belt driving such as a deviation guide member. An object is to realize a low-cost endless belt device.
Also, in the image forming apparatus, it is possible to reliably correct the deviation and skew of the endless belts such as the intermediate transfer belt and the recording material conveying belt with a simple and low-cost configuration, preventing image distortion and color misregistration, and outputting. Another object is to enable high-speed and high-quality images.

In order to achieve the above object, the present invention has an endless belt stretched and tensioned by a plurality of rollers, and any one of the plurality of rollers is a driving roller for rotating the endless belt, other rollers are driven rollers that rotate together with the circulating movement of the endless belt, one of the driven roller, the correction roller for correcting the width direction of the position or the circular movement direction of the inclination of the endless belt Then, one end of the rotation shaft of the correction roller is moved relative to the other end in a direction perpendicular to the direction of tension applied to the endless belt and the rotation axis of the correction roller. An adjusting means for adjusting the posture is provided, and the posture of the correcting roller is adjusted by the adjusting means, so that the position or the circumference in the width direction during the circular movement of the endless belt is adjusted. In the endless belt device for correcting the dynamic downward tilt,
The roller adjacent to the correction roller on the upstream side in the circumferential movement direction of the endless belt is a roller that is not a correction roller among the driven rollers,
The friction coefficient between the correction roller and the endless belt, and the friction coefficient between the endless belt adjacent to the correction roller on the upstream side in the circumferential movement direction of the endless belt, the endless belt The coefficient of friction is greater than the coefficient of friction between the other roller and the endless belt.

  The endless belt device according to the present invention can reliably correct the deviation and skew of the endless belt without using a configuration that obstructs the belt high-speed drive such as a side guide member. Cost reduction can be realized.

It is a perspective view which shows the structure of the layout conditions 1 of the endless belt in the endless belt apparatus used for the analysis, and the several roller which spans it. It is a perspective view showing the composition of layout condition 2 similarly. FIG. 6 is a diagram showing the relationship between the inclination of the steering roller (driven roller 5) and the belt position correction sensitivity in the belt width direction in the case of layout conditions 1 and 2. It is a figure which shows the analysis result of the deformation | transformation attitude | position of the axial load which acts on an endless belt from each roller when the inclination of a steering roller (driven roller 5) is α under layout condition 1, and the endless belt deformed thereby. It is a figure which similarly shows the analysis result in the case of the layout conditions 2. FIG. It is a figure which shows the analysis result of the deformation | transformation attitude | position of the axial load which acts on an endless belt from each roller in case the inclination of a steering roller (follower roller 5) is 2.5 (alpha) on the layout conditions 1, and it deform | transformed. It is a figure which similarly shows the analysis result in the case of the layout conditions 2. FIG.

1 is a schematic configuration diagram illustrating a main part of an embodiment of an image forming apparatus to which the present invention is applied. FIG. 6 is a perspective view showing an example of belt deviation / skew detection means for an intermediate transfer belt. FIG. 6 is a perspective view showing an example of a means for adjusting the belt shift and skew of the intermediate transfer belt. It is a block diagram which shows schematic structure of the control system in the image forming apparatus shown in FIGS. It is a schematic block diagram which shows the principal part of other embodiment of the image forming apparatus to which this invention is applied.

Hereinafter, embodiments for carrying out the present invention will be specifically described with reference to the drawings.
[Analysis of endless belt device]
First, as a result of the analysis of the endless belt device that is the subject of the present invention, it has become clear that there are layout conditions other than the diameter of the steering roller as a factor that greatly affects the belt position correction sensitivity caused by the inclination of the steering roller. So explain it.

1 and 2 show the layout conditions 1 and 2 as the layout conditions 1 and 2, respectively, of an endless belt in the endless belt apparatus used for the analysis and a plurality of rollers that stretch the belt.
In these drawings, the endless belt 1 is stretched and stretched by a driving roller 2 and four driven rollers 3 to 6, and the driving roller 2 is driven to rotate in the clockwise direction to move in the direction indicated by the arrow A. Move around (referred to as rotation). The driven rollers 3 to 6 are driven to rotate by the rotation of the endless belt 1. Among them, the driven roller 5 that is in contact with the outer surface of the endless belt 1 is a steering roller that is a correction roller that also serves as a tension roller, and rotates counterclockwise. The other driven rollers 3, 4 and 6 are in contact with the inner surface of the endless belt 1, and thus rotate in the clockwise direction.

The layout condition 1 shown in FIG. 1 and the layout condition 2 shown in FIG. 2 are as follows: the diameter of the drive roller 2 and each of the driven rollers 3 to 6, the circumferential length of the endless belt 1, the positional relationship between the driven rollers 4 and 5, the driven roller 3, Main conditions such as the wrapping range angle of the endless belt 1 at 4 and 5 are common. Further, the interval X between the driven roller 5 that is a steering roller and the driven roller 4 adjacent on the downstream side in the circumferential movement direction of the endless belt 1 is also common. However, the intervals Y1 and Y2 between the driven roller 5 and the driven roller 6 that is not a correction roller adjacent on the upstream side in the circumferential movement direction of the endless belt 1 are different, and the layout condition is different from the interval Y1 in the layout condition 1. The interval Y2 at 2 is about 1.5 times.

In layout conditions 1 and 2 shown in FIGS. 1 and 2, the endless belt 1 is rotated in the arrow A direction by the driving roller 2. Then, it is assumed that the driven roller 5 that is a steering roller is tilted in a direction indicated by an arrow C that is orthogonal to a tension direction (direction indicated by an arrow B) that is a direction in which tension is applied to the endless belt 1 and the rotation axis of the driven roller 5.
The relationship between the belt position correction sensitivity in the belt width direction (main scanning direction) obtained with respect to the inclination of the driven roller 5 that is the steering roller in the layout conditions 1 and 2 is shown in FIG.
It can be seen that the correction sensitivity at the inclination α is twice or more higher in the layout condition 2 than in the layout condition 1. From this, it can be seen that a larger belt position correction sensitivity can be obtained when the distance between the driven roller 5 as a steering roller and the driven roller 6 as an adjacent roller on the upstream side is larger.

In addition, the correction sensitivity at the inclination 2.5α is approximately twice that at the inclination α in the layout condition 2, and the relationship of the correction sensitivity to the inclination is close to a linear behavior. On the other hand, in the case of the layout condition 1, the correction sensitivity is about 1.3 times that of the inclination α, and the correction sensitivity does not increase so much even when the inclination is increased. I understand.
From this, it can be seen that the belt position correction sensitivity closer to the linear behavior can be obtained when the distance between the steering roller and the adjacent roller on the upstream side is larger.

Here, under the above analysis conditions, the axial load acting on the endless belt 1 from each roller and the attitude of the endless belt 1 deformed thereby were obtained. FIG. 4 shows the result when the inclination of the driven roller 5 as the steering roller is α under layout condition 1, and FIG. 6 shows the result when the inclination of the driven roller 5 is 2.5α. FIG. 5 shows the result when the inclination of the driven roller 5 is α under the layout condition 2, and FIG. 7 shows the result when the inclination of the driven roller 5 is 2.5α.

  As shown in FIGS. 4 to 7, in any of the layout conditions 1 and 2, the axial force acting from each roller to the endless belt 1 is the upstream of the driven roller 5 as a steering roller and its belt conveying direction. A large force in the opposite direction is generated by the driven roller 6 on the side. As a result, the endless belt 1 is largely deformed in the width direction (main scanning direction) between the driven roller 5 and the driven roller 6 on the upstream side thereof, and is hardly deformed at other roller positions.

When the inclination α is in the case of a layout condition 2 shown in the case and Figure 5 Layout Condition 1 shown in FIG. 4, a large difference in the axial force in the opposite direction acting on the endless belt 1 in the driven roller 5 and the driven roller 6 There is no. However, the deformation in the width direction of the belt between the driven roller 5 and the driven roller 6 is larger in the case of the layout condition 2 shown in FIG.
This is because, in the case of the layout condition 2, since the distance between the driven roller 5 and the driven roller 6 is large, the layout condition is greatly deformed with respect to the axial force. The deformation state of the endless belt 1 as a whole is greatly influenced by the deformation between the driven roller 5 and the driven roller 6 as described above. For this reason, the layout condition 2 causes a greater deformation of the posture of the belt around the layout condition 1, and the belt entry angle with respect to the roller, which is the principle of belt position correction, becomes larger. For this reason, the correction sensitivity is larger in the layout condition 2 than in the layout condition 1.

Further, in the layout condition 2 shown in FIGS. 5 and 7, the deformation in the width direction of the belt between the driven roller 5 and the driven roller 6 is less than the deformation of the driven roller 5 at the inclination α with the inclination 2.5α. The deformation is about double. For this reason, the deformation state of the entire belt is also doubled, and a correction sensitivity of about twice is obtained.
On the other hand, in the layout condition 1 shown in FIGS. 4 and 6, the deformation in the width direction of the belt between the driven roller 5 and the driven roller 6 is not deformed at the inclination 2.5α compared to the deformation at the inclination α. It is about 1.3 times. For this reason, the deformation state of the entire belt is also about 1.3 times, and the correction sensitivity is about 1.3 times. This is because, as described above, under the layout condition 1, the distance between the driven roller 5 and the driven roller 6 is small and is not easily deformed by the axial force.

  In the layout condition 1, if the deformation in the width direction of the belt exceeds an allowable range with respect to the reverse axial force acting on the endless belt 1 by the driven roller 5 and the driven roller 6, the endless belt 1 and the driven roller An axial slip occurs between 5 and 6. Therefore, even if the inclination of the steering roller is increased and the reverse axial force acting on the endless belt by the steering roller and its upstream roller increases, a slip may occur between the endless belt and the roller. is there. As a result, the deformation of the belt does not increase and the correction sensitivity cannot be increased.

From this analysis result, in order to increase the belt position correction sensitivity and make the belt position correction sensitivity behave linearly with respect to the tilt of the steering roller, the belt position correction range by the steering roller can be sufficiently secured. It turns out that it is effective to do.
That is, it is effective to ensure a large distance between the steering roller and the roller adjacent to the steering roller on the upstream side in the circumferential movement direction of the endless belt. However, it is obvious that such a layout configuration is an obstacle to miniaturization of the apparatus.

Therefore, in the endless belt device according to the present invention, when the steering roller as the correction roller is the driven roller 5 in the endless belt device as shown in FIG. The coefficient of friction between the driven roller 5 and the endless belt 1 and the coefficient of friction between the driven roller 6 and the endless belt 1 adjacent to the driven roller 5 on the upstream side in the circumferential movement direction of the endless belt 1 are represented as endless. The friction coefficient between the other roller that stretches the belt 1 and the endless belt 1 is made larger. In the endless belt device of FIG. 1, the other rollers are the driving roller 2 and the driven rollers 3 and 4.
Therefore, for example, the roller surfaces of the driven rollers 5 and 6 are roughened so that the surface roughness is larger than the roller surfaces of the other rollers. Alternatively, the roller surfaces of the driven rollers 5 and 6 are coated with a material having a large friction coefficient such as rubber.

Accordingly, the gripping force of the endless belt 1 by the driven rollers 5 and 6 is maintained, and no slip occurs between the endless belt 1 and the belt position correction sensitivity with respect to the inclination of the driven roller 5 as a steering roller. Can be made to be nearly linear.
Therefore, a sufficient correction range can be ensured without increasing the distance between the driven roller 5 which is a steering roller and the driven roller 6 adjacent thereto on the upstream side in the circumferential movement direction of the endless belt 1. .
In this way, it is possible to significantly increase the speed without using a configuration that hinders high-speed belt driving such as a shift guide member, and a small size capable of reliably correcting the shift and / or skew. An endless belt device can be realized at low cost.

[One Embodiment of Image Forming Apparatus]
Next, an embodiment of an image forming apparatus provided with an endless belt device according to the present invention will be described in detail.
FIG. 8 is a schematic configuration diagram showing a main part of an embodiment of an image forming apparatus to which the present invention is applied. This image forming apparatus is a tandem type intermediate transfer type color image forming apparatus using the endless belt in the endless belt apparatus according to the present invention as an intermediate transfer belt.
In FIG. 8 and subsequent figures, the same reference numerals are given to the arrows in the directions corresponding to the arrows A, B, and C shown in FIGS.

In the image forming apparatus shown in FIG. 8, four photosensitive drums 11 to 14 as image bearing members are arranged at equal intervals in the horizontal direction with their axes parallel to each other. A charger 21 to 24 and a developing device 31 to 34 are provided along the outer periphery of each of the photosensitive drums 11 to 14. The developing unit 31 stores yellow toner, the developing unit 32 stores magenta, the developing unit 33 stores cyan, and the developing unit 34 stores black toner.
Exposure devices 41 to 44 are arranged above the respective photoconductive drums 11 to 14, and the respective laser beams L1 to L4 emitted from the exposure devices 41 to 44 are arranged on the outer peripheral surfaces of the respective photoconductive drums 11 to 14, respectively. Irradiation is performed at a position between the chargers 21 to 24 and the developing devices 31 to 34.
As a result, an image forming unit for forming toner images of a plurality of colors on the image carrier is configured.

An intermediate transfer belt device 10 that is an endless belt device according to the present invention is disposed below each of the photosensitive drums 11 to 14. In the intermediate transfer belt device 10, an intermediate transfer belt 50, which is an endless belt as an intermediate transfer member, is tensioned by a driving roller 51 and four driven rollers 52 to 55 that are arranged in parallel to each other. Has been passed.
When the drive roller 51 is driven and rotated clockwise by a drive motor (not shown), the intermediate transfer belt 50 rotates (referred to as rotation) in the direction indicated by the arrow A. As a result, the driven rollers 52, 53, and 55 that are in contact with the inner peripheral surface of the intermediate transfer belt 50 are rotated in the clockwise direction, and the driven roller 54 that is in contact with the outer peripheral surface is rotated in the counterclockwise direction.

  A substantially horizontal upper peripheral surface side between the driving roller 51 and the driven roller 52 of the intermediate transfer belt 50 is in contact with a lower portion of the outer peripheral surface of each of the photosensitive drums 11 to 14. The intermediate transfer belt 50 is pressed against the photosensitive drums 11 to 14 by primary transfer rollers 61 to 64 disposed on the inner peripheral surface side, thereby forming a primary transfer nip for each color.

Of the four driven rollers 52 to 55, the driven roller 55 arranged at the lowermost side also serves as a secondary transfer counter roller, and is opposed to the secondary transfer roller 71 with the intermediate transfer belt 50 interposed therebetween. . The secondary transfer roller 71 spans a conveyance belt 73 between the secondary transfer roller 71 and a conveyance roller 72 whose axis is parallel, and forms a secondary transfer nip between the intermediate transfer belt 50 and the conveyance belt 73. .
On the right side of FIG. 8 with respect to the secondary transfer roller 71, a sheet-like recording material P such as paper fed from a paper supply unit (not shown) is conveyed to the secondary transfer nip at a predetermined timing. A positioning roller pair 80 is provided. Further, a fixing device 90 including a fixing roller 91 and a pressure roller 92 is disposed on the downstream side of the conveying belt 73 in the conveying direction. The recording material on which the full color toner image is fixed by the fixing device 90 is discharged out of the apparatus by the discharge roller pair 85.

This image forming apparatus forms four color toner images using four photosensitive drums 11 to 14 provided with developing devices 31 to 34 in parallel, and sequentially transfers them onto the intermediate transfer belt 50. Thus, a full-color toner image is formed.
The image forming operation will be described with reference to FIG. At the time of image formation, the four photosensitive drums 11 to 14 each serving as an image carrier are rotationally driven in the direction indicated by an arrow (counterclockwise).
The surfaces of the photosensitive drums 11 to 14 are uniformly charged by the chargers 21 to 24, respectively, and then emitted from the exposure devices 41 to 44, respectively, by laser beams L1 to L4 modulated according to image information. Exposure scanning is performed to form an electrostatic latent image.

  Then, yellow toner is attached to the electrostatic latent image on the photosensitive drum 11 by the developing device 31 to develop it as a yellow toner image, and magenta toner is developed on the electrostatic latent image on the photosensitive drum 12 by the developing device 32. To develop a magenta toner image. Further, cyan toner is attached to the electrostatic latent image on the photosensitive drum 13 by the developing device 33 and developed as a cyan toner image, and black toner is developed on the electrostatic latent image on the photosensitive drum 14 by the developing device 34. To develop a black toner image.

The yellow toner image, the magenta toner image, the cyan toner image, and the black toner image are transferred to the primary transfer nip between the photosensitive drums 11 to 14 and the intermediate transfer belt 50 that rotates in the arrow A direction. Then, the images are primarily transferred onto the intermediate transfer belt 50 while being sequentially stacked. As a result, four full-color toner images are formed on the intermediate transfer belt 50.

The full-color toner image on the intermediate transfer belt 50 is conveyed from a sheet feeding unit (not shown), and the secondary transfer is performed on the recording material P fed to the above-described secondary transfer nip at a timing by the positioning roller pair 80. Is done. Thus, a full-color toner image is obtained on the recording material P.
The recording material P is transported in the direction of arrow E by the transport belt 73, passes through the fixing nip of the fixing roller 91 and the pressure roller 92 of the fixing device 90, and the full color toner image is fixed. It is discharged onto a discharge tray outside the machine.

FIG. 9 shows an example of belt deviation / skew detection means for the intermediate transfer belt.
On the surface of the intermediate transfer belt 50, a detection line 501 is formed over the entire circumference at a position close to one side edge at a fixed distance from the center in the main scanning direction, which is the width direction. The detection line 501 is formed with a constant width, for example, with black paint so that the reflectance is significantly different from other portions of the surface of the intermediate transfer belt 50.

  At a position on the intermediate transfer belt 50 facing the detection line 501, two line sensors 100A and 100B are provided in the moving direction (arrow A direction) of the intermediate transfer belt 50 as belt deviation / slant detection means. It is fixedly arranged at a predetermined interval. Each of the line sensors 100A and 100B has a linear light source and a light receiving element array arranged linearly along a belt width direction (main scanning direction) orthogonal to the detection line 501, and the detection line 501. The position in the main scanning direction can be detected.

  By sequentially detecting the position of the detection line 501 on the intermediate transfer belt 50 in the main scanning direction, the belt shift can be detected. Further, the belt skew can be detected by sequentially detecting the difference between the positions of the detection lines detected by the two line sensors 100A and 100B in the main scanning direction. Therefore, the detection operations of the line sensors 100A and 100B are controlled by a control unit which will be described later, and each detection signal is taken into the control unit, where the degree of belt shift and belt skew is calculated.

Thus, by detecting the position in the belt main scanning direction of the detection line 501 formed on the intermediate transfer belt 50 with high accuracy in advance, belt deviation and skew are detected. Therefore, as described in Patent Document 3, there are the following advantages compared with the case where the belt shift and skew are detected by detecting the position of the belt edge.
There is no need to refer to pre-measured edge data or to store data that averages the periodic fluctuations of the edge position in the storage means. And the control for correcting it can be performed.

FIG. 10 shows an example of means for adjusting the belt shift and skew of the intermediate transfer belt 50.
As described with reference to FIG. 8, the intermediate transfer belt 50 is stretched by five rollers whose axes are parallel to each other, and one of the drive rollers 51 is rotated by a drive motor 56. , Rotated in the direction of arrow A.
The driving roller 51 and the driven rollers 52 and 55 have their rotation shafts fixed at predetermined positions.

On the other hand, the driven roller 54 is a steering roller that is a first correction roller, and both ends 54 a and 54 b of the rotation shaft are applied with a pressing force in the tension applying direction indicated by the arrow B, and are applied to the intermediate transfer belt 50. An almost constant tension is applied. The driven roller 54 is a steering roller and corrects a shift generated in the intermediate transfer belt 50, so that both ends 54a and 54b of the rotating shaft are supported by a pivot bearing or the like so as to be movable in a direction perpendicular to the rotating axis. And the one end 54b side is supported by the actuator 57 which is a 1st adjustment means so that a reciprocation is possible in the arrow C direction. The arrow C direction is a direction orthogonal to the arrow B direction, which is a direction in which tension is applied to the intermediate transfer belt 50, and the rotation axis of the driven roller 54.

Further, the driven roller 53 on the downstream side in the circumferential movement direction of the intermediate transfer belt 50 with respect to the driven roller 54 that is the first correction roller is also a second for correcting the skew generated in the intermediate transfer belt 50. The steering roller is a correction roller, and both ends 53a and 53b of the rotating shaft are supported by a pivot bearing or the like so as to be movable in a direction perpendicular to the rotating axis. Then, one end 53b side is supported by an actuator 58, which is a second adjusting means, so as to be able to reciprocate in the direction indicated by an arrow D perpendicular to the direction in which tension is applied to the intermediate transfer belt 50 and the rotational axis of the driven roller 53. Yes.

The actuator 57 is driven based on belt deviation detection information detected by the two line sensors 100A and 100B, which are belt deviation and skew detection means, and one end 54b of the driven roller 54 is indicated by an arrow with respect to the other end 54a. Move relative to the C direction. Accordingly, the posture of the driven roller 54 is adjusted by inclining the rotation axis of the driven roller 54 so that the belt moves in the direction opposite to the movement of the generated intermediate transfer belt 50 in the main scanning direction. Then, the position in the belt width direction during the circular movement of the intermediate transfer belt 50 is corrected, and the shift of the intermediate transfer belt 50 is controlled within a certain range. Therefore, it is possible to suppress the belt shift without providing a shift guide member or the like.

Further, based on the belt skew detection information detected by the two line sensors 100A and 100B, the actuator 58 is driven to move the one end 53b of the driven roller 53 relative to the other end 53a in the direction indicated by the arrow D. . Accordingly, the posture of the driven roller 53 is adjusted by tilting the rotation shaft of the driven roller 53 so that the belt is tilted in a direction opposite to the tilt of the generated intermediate transfer belt 50 in the main scanning direction. Then, the inclination of the circumferential movement direction during the circumferential movement of the intermediate transfer belt 50 is corrected, and the skew of the intermediate transfer belt 50 is controlled within a certain range. Therefore, image distortion and color misregistration can be prevented.

In FIG. 10, the friction coefficient between the driven roller 54 and the intermediate transfer belt 50, which is a steering roller, and the friction coefficient between the driven roller 55 and the intermediate transfer belt 50 are larger than the friction coefficient between the other rollers and the intermediate transfer belt 50. Value. The driven roller 55 is a roller that is not a correction roller adjacent to the driven roller 54 on the upstream side in the circumferential movement direction of the intermediate transfer belt 50.
Specifically, this can be realized by making the roller surfaces of the driven roller 54 and the driven roller 55 rougher than the roller surfaces of the other rollers. Alternatively, it can be realized by applying a surface coating of a material having a large friction coefficient such as rubber to the roller surfaces of the driven roller 54 and the driven roller 55.

At this time, in order to correct the belt deviation, the driven roller 54, which is the first correction roller, is inclined to move, so that the axial reverse force acting on the intermediate transfer belt 50 from the driven roller 55 on the upstream side is moved. Will increase. For this reason, even if the intermediate transfer belt 50 is greatly deformed in the width direction between the driven roller 54 and the driven roller 55, the intermediate transfer belt 50 slips in the belt deformation direction between the driven rollers 54 and 55 having a large friction coefficient and the intermediate transfer belt 50. Will not occur.
Therefore, even if the inclination of the driven roller 54 is increased in order to increase the correction sensitivity, the correction sensitivity at the position in the width direction of the intermediate transfer belt 50 can be made to be nearly linear with respect to the inclination. A sufficient belt position correction range can be secured.
Here, the “upstream side” is an upstream side in the rotation direction of the intermediate transfer belt 50.

Further, as shown in FIG. 8, the driven roller 53 that is the second correction roller is spaced from the driven roller 54 that is the upstream roller, and the driven roller that is the upstream roller. It is larger than the interval with 55. Therefore, in the driven roller 53, the correction sensitivity with respect to the inclination as the correction roller can be increased, and the correction sensitivity of the belt position with respect to the inclination can be made to be nearly linear. Therefore, a sufficient correction range of the inclination with respect to the circumferential movement direction of the intermediate transfer belt 50 by the correction roller can be ensured.

In the driven roller 54 as the first correction roller, a sufficient correction range can be secured in the same manner by increasing the distance between the adjacent driven roller 55 on the upstream side. However, for this purpose, it is necessary to increase the size of the apparatus, and further, it is necessary to increase the cost.
As described above, when two correction rollers (steering rollers) are provided for belt position correction, it is necessary to secure an ideal layout condition in both correction rollers, in particular, a sufficient distance from the upstream roller. In many cases, it becomes difficult due to restrictions on the size and cost of the apparatus.

Therefore, even when the layout of the correction roller cannot sufficiently secure the interval between the adjacent rollers on the upstream side, as described above, the friction coefficient between the correction roller and the adjacent roller on the upstream side and the intermediate transfer belt, as described above. Should be increased. As a result, the grip force of the intermediate transfer belt by each roller can be maintained, and the correction sensitivity of the belt position can be made to be nearly linear with respect to the inclination of the correction roller, which is the steering roller, and the correction range is sufficiently Can be secured.
The image forming apparatus provided with such an intermediate transfer belt device 10 has a small and low-cost configuration, reliably corrects the shift and skew without reducing the driving speed of the intermediate transfer belt, and the intermediate transfer belt 50. It is possible to correct color misregistration of a plurality of color toner images transferred on the top. As a result, the color shift of the color image formed on the recording material is also reliably corrected, and a high-quality image can be output at high speed.

By changing the illustrated embodiment, another driven roller is provided between the driven roller 53 as the second correction roller and the driven roller 54 on the upstream side thereof, and the distance from the driven roller 53 is sufficient. It may be impossible to remove. In that case, the coefficient of friction between the intermediate transfer belt 50 and the driven roller 53 which is the second correction roller and the upstream adjacent roller and the intermediate transfer belt 50 is determined as the driven roller 54, the driven roller 55 and the intermediate transfer belt 50. It should be as large as the coefficient of friction between
Further, only the driven roller 54 is used as the correction roller and the actuator 57 is also used as the adjusting roller so as to correct at least one of the position in the width direction (shift) or the inclination in the circumferential movement direction of the intermediate transfer belt 50. It may be.

The correction roller is not limited to the driven roller 54 that is also a tension roller, and may be any of a plurality of driven rollers 52 to 55. However, in this embodiment, since the driven roller 55 also serves as a secondary transfer counter roller, its rotation shaft should be fixed at a fixed position, and thus is not suitable as a correction roller. In addition, a roller having a large winding angle of the intermediate transfer belt 50 is desirable because a frictional force with the intermediate transfer belt 50 is increased. The driven roller 54 that also serves as a tension roller is optimal as a correction roller.
The second correction roller may be any one of the driven rollers other than the first correction roller. However, since the above-described conditions are satisfied, the driven roller 53 is desirable in this embodiment. Become.

[Control system of image forming apparatus]
Here, a schematic configuration of a control system in the image forming apparatus described with reference to FIGS. 8 to 10 is shown in a block diagram in FIG. 11 and will be described.
In FIG. 11, a portion of the image forming apparatus excluding the intermediate transfer belt device 10 in the configuration shown in FIG. In general, the entire portion for forming an image including the intermediate transfer belt device is called a print engine. In this embodiment, the portion for controlling the intermediate transfer belt device 10 is shown in this way.

The intermediate transfer belt device 10 includes a drive motor 56 shown in FIG. 10, an actuator 57 serving as a first adjustment unit, an actuator 58 serving as a second adjustment unit, and belt deviation / skew detection also shown in FIG. Line sensors 100A and 100B as means are provided.
In addition, a control unit 30 that controls the entire image forming apparatus, an operation unit 40 that is an interface with a user, and a communication unit 60 that communicates with a host device such as a personal computer and receives print data. These units are connected to each other via a system bus 70.

The control unit 30 includes a CPU 36 that is a central processing unit, a ROM 37 that stores programs and fixed data necessary for processing, and a microcomputer such as a RAM 38 that is used as a work area of the CPU 36 and stores temporary data. ing.
The CPU 36 of the control unit 30 executes the program stored in the ROM 37 as necessary to control each unit. When the print data is received by the communication unit 60, the print data is temporarily stored in the RAM 38, developed into image data of each color for each page, the print engine 20 and the intermediate transfer belt device 10 are operated, and the above-described image is obtained. The forming process is performed.

At that time, the control unit 30 drives the drive motor 56 of the intermediate transfer belt device 10 to move the intermediate transfer belt 50 in a circular motion. During the circular movement of the intermediate transfer belt 50, the control unit 30 captures the position information of the detection line 501 shown in FIG. 9 detected by the line sensors 100A and 100B. Then, the CPU 36 calculates the amount of deviation of the position in the width direction (main scanning direction) of the intermediate transfer belt 50 and the degree of inclination in the circumferential movement direction.
The control unit 30 drives the actuators 57 and 58 according to the calculation result, and adjusts the postures of the driven rollers 54 and 53, which are the first and second correction rollers, as described above. Correct 50's and / or skew.

  The operation unit 40 includes a plurality of keys and switches that are operated by a user to perform data setting, mode selection, and the like, and a display such as a liquid crystal display panel that displays the state of the image forming apparatus, selection information, warning information, and the like. Equipped with a bowl.

[Other Embodiments of Image Forming Apparatus]
Next, another embodiment of the image forming apparatus including the endless belt device according to the present invention will be described in detail.
FIG. 12 is a schematic configuration diagram similar to FIG. 8 showing a main part of another embodiment of the image forming apparatus to which the present invention is applied. This image forming apparatus is a tandem type direct transfer type color image forming apparatus using the endless belt in the endless belt apparatus according to the present invention as a recording material conveying belt.
In FIG. 12, parts corresponding to those in FIG. 8 are denoted by the same reference numerals, and description thereof is omitted.

  In this image forming apparatus, the recording material conveying belt apparatus 10 'has the same configuration as the intermediate transfer belt apparatus 10 in the above-described image forming apparatus, but the only difference is that the endless belt is the recording material conveying belt 50'. To do. In FIG. 12, a positioning roller pair 80 is arranged on the left side of the left end of the recording material conveyance belt device 10 ', and a fixing device 90 is arranged on the right side of the right end of the recording material conveyance belt device 10'.

Since this image forming apparatus does not perform secondary transfer, a secondary transfer roller is not provided.
The primary transfer rollers 61 to 64 in FIG. 8 serve as transfer rollers, and the recording material conveyance belt 50 ′ is pressed against the lower part of the outer peripheral surface of each of the photosensitive drums 11 to 14 to form a transfer nip.
The sheet-like recording material P is formed by the positioning roller pair 80 in accordance with the timing at which the yellow, magenta, cyan, and black toner images are formed on the surfaces of the photosensitive drums 11 to 14 as image carriers. In FIG. 12, the recording material is fed from the left onto the recording material conveying belt 50 '.

The recording material P is electrostatically attracted to the surface of the recording material conveyance belt 50 ', and is conveyed rightward as the recording material conveyance belt 50' rotates in the direction of arrow A. When passing through the transfer nips between the photosensitive drums 11 to 14 and the recording material conveyance belt 50 ′, yellow, magenta, cyan, and black toner images are sequentially transferred onto the recording material P. The As a result, four full-color toner images are formed on the recording material P.
The recording material P is peeled off from the recording material conveyance belt 50 ′ at the position of the driving roller 51 and advances straight in the direction of arrow F. Then, the recording material P on which the full-color toner image is fixed when passing through the fixing device 90 is discharged onto a discharge tray outside the apparatus by a pair of discharge rollers (not shown).

Since the configuration and function of the recording material conveyance belt device 10 'are the same as those of the intermediate transfer belt device 10 in the image forming apparatus described above except that the endless belt is the recording material conveyance belt 50', description thereof will be omitted.
The configuration of the control system and the control operation are the same as those described with reference to FIG.
The image forming apparatus provided with such a recording material conveyance belt device 10 ′ is a small and low-cost configuration, and reliably corrects the deviation and skew without reducing the driving speed of the recording material conveyance belt, It is possible to reliably correct color misregistration of a plurality of color toner images transferred onto the recording material. As a result, high-quality images can be output at high speed.

As mentioned above, although embodiment of this invention has been described, this invention is not limited to this. The endless belt device according to the present invention is applicable not only to the intermediate transfer belt device and the recording material conveying belt device in the image forming apparatus but also to a photosensitive belt device, a secondary transfer belt device, and the like. Further, the image forming apparatus may be a printer, a printing apparatus, a copying apparatus, a facsimile apparatus, a multifunction machine having a plurality of functions thereof, or the like.
The type of the image forming apparatus is not limited to the tandem type, and can be applied to a revolving color image forming apparatus and an ink jet type color image forming apparatus. Other than the image forming apparatus, the present invention can also be applied to an apparatus for reforming and coating paper, a ticket vending machine using an endless belt, a precision conveying apparatus, and the like.
Further, the configurations of the above-described embodiments can be appropriately added, changed, partially omitted, and the like, and can be implemented in any combination as long as they do not contradict each other.

1: Endless belt 2: Drive roller
3 to 6: driven roller (5 is a steering roller as a correction roller)
10: Intermediate transfer belt device (endless belt device)
10 ': Recording material conveying belt device (endless belt device)
11-14: Photosensitive drum (image carrier)
20: Print engine 21-24: Charger 30: Control unit
31-34: Developer 36: CPU 37: ROM 38: RAM
40: operation unit 41 to 44: exposure device 50: intermediate transfer belt (endless belt)
50 ': Recording material conveying belt (endless belt) 51: Driving roller
52 to 55: driven rollers (53 and 54 are steering rollers as correction rollers, 55 is a secondary transfer counter roller) 56: drive motor
57: Actuator (first adjusting means) 58: Actuator (second adjusting means) 60: Communication unit 61 to 64: Primary transfer roller (transfer roller) 70: System bus
71: Secondary transfer roller 72: Conveying roller 73: Conveying belt
80: Positioning roller pair 85: Discharge roller pair 90: Fixing device
91: Fixing roller 92: Pressure roller 100A, 100B: Line sensor (belt deviation / skew detection means)
501: Detection line P: Recording material

JP 2005-148127 A JP 2011-2632 A JP 2000-233843 A JP 2007-163695 A JP 2009-151097 A

Claims (7)

An endless belt stretched with tension applied by a plurality of rollers is provided, and one of the plurality of rollers is a driving roller for rotating the endless belt, and the other rollers rotate around the endless belt. A driven roller that is driven by movement,
Any one of the driven rollers is a correction roller for correcting the position in the width direction of the endless belt or the inclination in the circumferential movement direction,
The posture of the correction roller is adjusted by relatively moving one end of the rotation shaft of the correction roller with respect to the other end in a direction perpendicular to the direction of applying tension to the endless belt and the rotation axis of the correction roller. Adjusting means to
In the endless belt device that adjusts the posture of the correction roller by the adjusting means to correct the position in the width direction or the inclination in the circumferential movement direction during the circumferential movement of the endless belt,
The roller adjacent to the correction roller on the upstream side in the circumferential movement direction of the endless belt is a roller that is not a correction roller among the driven rollers,
The friction coefficient between the correction roller and the endless belt, and the friction coefficient between the roller adjacent to the correction roller on the upstream side in the circumferential movement direction of the endless belt and the endless belt are: An endless belt device having a coefficient of friction larger than a coefficient of friction between another endless belt that stretches the endless belt and the endless belt. The endless belt device according to claim 1,
The correction roller is a first correction roller, and the adjustment means is a first adjustment means;
Wherein one of the rollers of the downstream side of the circular movement direction of the endless belt, to correct the width direction of the position or the circular movement direction of inclination of the endless belt with respect to the first correction roller of the driven roller A second correction roller for
One end of the rotation shaft of the second correction roller is moved relative to the other end in a direction perpendicular to the direction of tension applied to the endless belt and the rotation axis of the second correction roller. Providing a second adjusting means for adjusting the posture of the second correcting roller;
Positions in the width direction during the circular movement of the endless belt by adjusting the postures of the first correction roller and the second correction roller by the first adjustment unit and the second adjustment unit. Alternatively, an endless belt device that corrects an inclination in the circumferential movement direction. The endless belt device according to claim 2 ,
The distance between the first correction roller and the roller adjacent to the first correction roller on the upstream side in the circumferential movement direction of the endless belt is the second correction roller and the second correction roller. An endless belt device, wherein the endless belt device is smaller than an interval between adjacent rollers on the upstream side in the circumferential movement direction of the endless belt. An image forming unit that forms a toner image of a plurality of colors on the image carrier, and a primary transfer unit that sequentially superimposes and transfers the toner images of a plurality of colors formed on the image carrier by the image forming unit on the intermediate transfer belt; An image forming apparatus comprising secondary transfer means for transferring a plurality of color toner images transferred and superimposed on the intermediate transfer belt to a recording material,
The endless belt device according to claim 1, wherein the endless belt is the intermediate transfer belt, and the intermediate transfer belt is adjusted during the circular movement of the intermediate transfer belt by adjusting the posture of the correction roller by the adjusting means. An image forming apparatus that corrects color misregistration of a plurality of color toner images transferred onto the intermediate transfer belt by correcting the position in the width direction of the belt or the inclination in the circumferential movement direction. An image forming unit that forms a toner image of a plurality of colors on the image carrier, and a primary transfer unit that sequentially superimposes and transfers the toner images of a plurality of colors formed on the image carrier by the image forming unit on the intermediate transfer belt; An image forming apparatus comprising secondary transfer means for transferring a plurality of color toner images transferred and superimposed on the intermediate transfer belt to a recording material,
The endless belt device according to claim 2 , wherein the endless belt is the intermediate transfer belt, and the postures of the first and second correction rollers are adjusted by the first and second adjusting means. Thus, by correcting the position in the width direction of the intermediate transfer belt or the inclination in the direction of the circular movement during the circumferential movement of the intermediate transfer belt, the color misregistration of a plurality of color toner images transferred onto the intermediate transfer belt is corrected. An image forming apparatus characterized by correcting the above. An image forming unit for forming a toner image of a plurality of colors on the image carrier, and a toner image of a plurality of colors formed on the image carrier by the image forming unit on the recording material conveyed by the recording material conveyance belt sequentially. An image forming apparatus comprising transfer means for transferring the images in an overlapping manner,
The endless belt device according to claim 1, wherein the endless belt is the recording material conveyance belt, and the adjustment unit adjusts the posture of the correction roller to adjust the posture of the recording material conveyance belt during the circular movement. An image forming apparatus that corrects color misregistration of a plurality of color toner images transferred onto the recording material by correcting a position in a width direction of the recording material conveyance belt or an inclination in the circumferential movement direction. An image forming unit for forming a toner image of a plurality of colors on the image carrier, and a toner image of a plurality of colors formed on the image carrier by the image forming unit on the recording material conveyed by the recording material conveyance belt sequentially. An image forming apparatus comprising transfer means for transferring the images in an overlapping manner,
The endless belt device according to claim 2 , wherein the endless belt is the recording material conveyance belt, and the postures of the first and second correction rollers are adjusted by the first and second adjusting means. Then, by correcting the position in the width direction of the recording material conveyance belt or the inclination in the circumferential movement direction during the circular movement of the recording material conveyance belt, the toner images of a plurality of colors transferred onto the recording material An image forming apparatus that corrects color misregistration.

Images