JP2010217301A - Belt conveying device and image forming apparatus - Google Patents

Abstract

Provided is a belt conveying device that is not affected by the shape of a belt end portion in belt skew sensing, and that is capable of highly accurate detection without time delay.
A belt conveyance device includes: an endless belt stretched around a plurality of rollers; drive means coupled to and driving any one of the rollers; and a belt orthogonal to the traveling direction of the endless belt. A belt speed detecting means for detecting the conveying speed of the endless belt disposed at a plurality of positions in the width direction, and a traveling direction of the endless belt based on a difference in the belt conveying speed detected by the plurality of belt speed detecting means. Belt inclination calculating means for calculating the inclination at.
[Selection] Figure 6

Description

The present invention relates to a belt conveyance device, and more particularly to various belt conveyance devices used in an image forming apparatus such as a copying machine and a printer, and an image forming apparatus including the belt conveyance device.
Further, the present invention can be used for speed control of a belt-like endless moving member that requires high-precision speed control in various devices, and in particular, an intermediate transfer belt and a photoconductor related to image formation of various image forming apparatuses. The endless moving member is suitable for speed control or position control with high accuracy. If the belt conveying apparatus is applied to a color image forming apparatus, it is possible to prevent color misregistration and the like and always form a high-quality full color image.

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus, an image forming apparatus using an endless conveying belt as an intermediate transfer belt that is a transfer medium or a recording sheet that is a transfer medium is known. The belts used in these apparatuses are stretched around a plurality of rollers and driven to circulate. At this time, the belt position in which the belt position moves in the direction perpendicular to the belt conveyance direction (main scanning direction) and the belt conveyance direction are Belt skew that tilts in the main scanning direction may occur.
When the belt is skewed, the image forming position on the transfer medium such as the intermediate transfer belt or the recording paper is shifted, which causes image distortion. Further, monochrome images of black (hereinafter referred to as K), yellow (hereinafter referred to as Y), magenta (hereinafter referred to as M), and cyan (hereinafter referred to as C) are formed, respectively. In a color image forming apparatus that obtains a color image by superimposing toner images on a transfer medium, a shift in image forming position appears as a color shift between the color toner images. All of these lead to degradation of image quality, and it is necessary to take some measures for the belt skew in order to obtain a high-quality image.

  In order to cope with the above problem, various methods have been proposed, and one of them is a method of providing a guide member near the endless belt. However, the force in the main scanning direction generated in the endless belt is regulated by bringing the shift guide member provided on the belt surface into contact with the end surface of the belt conveyance roller, and the shift of the endless belt is suppressed. The belt skew caused by the touching guide member touching in the main scanning direction and the shaking of the end face of the conveying roller cannot be suppressed, and there is a drawback in that image distortion and color misregistration due to positional deviation in the main scanning direction occur.

In contrast, in Patent Document 1 (Japanese Patent Laid-Open No. 2005-148127), in a system in which the deviation of the belt is regulated by a deviation guide member provided on the belt, the photosensitive member is based on a meandering component for one period of the belt measured in advance. The configuration for controlling the position of the latent image to be formed is described.
Further, as a method other than providing a guide member near the endless belt, in Patent Document 2 (Japanese Patent Application Laid-Open No. 2006-276427), an inclination for detecting that the endless belt is transported in an inclined state with respect to the transport direction. And when the skew detection of the endless belt is detected by the skew detection means, the image forming means distorts the image based on the skew amount of the endless belt detected by the skew detection means. The structure which correct | amends is described.

However, by providing a guide member on the endless belt as in Patent Document 1, the belt side is suppressed, and the effect of belt meandering that cannot be suppressed by the guide member is controlled on the latent image forming position on the photoreceptor. However, there are the following problems in the method of suppression.
Specifically, since the meander component for one cycle of the belt including the contact with the belt conveyance roller end surface and the deviation of the guide member in the main scanning direction is measured in advance, it is caused by the vibration of both the roller end surface and the guide member. Although belt meandering can be suppressed, it is necessary to frequently measure meandering components in order to cope with time-dependent deformation of endless belts and offset guide members and deformation due to environmental changes such as temperature and humidity. Since the forming operation is frequently interrupted, this greatly hinders the speeding up of image output. There is also a problem that it is difficult to cope with dynamic deformation due to the influence of vibration or the like. In addition, in the method of suppressing the belt deviation by providing the deviation guide member on the endless belt, when the belt is driven at a high speed, a large external force is applied to the deviation guide member, and the belt and the deviation guide member are buckled or damaged. It is difficult to speed up image output.

Further, the method of controlling the latent image forming position on the photosensitive member by detecting the belt skew without providing a guide member on the endless belt as in Patent Document 2 has the following problems.
Specifically, as a first method for detecting the belt skew, there is a method using a control signal of the steering roller. However, the steering roller corrects the belt shift by adjusting the inclination so that each part on the belt always passes through the same position after one round. Whether or not occurs is determined by the inclined state of each roller. For this reason, the skew of the belt on the image transfer surface from the photosensitive member that affects image distortion and color misregistration is not determined only by the inclination of the steering roller. If a roller other than the steering roller is tilted due to temperature fluctuations or changes over time, the belt skew cannot be accurately detected by the steering roller control signal, and accurate belt skew correction cannot be performed. .

  As a second method for detecting the belt skew, there is a method in which a mark for image position detection is formed in a non-image area of the intermediate transfer belt and detected by a mark detection means. However, in this method, in order to form the image position detection mark, it is necessary to develop the mark latent image formed on the photosensitive member with toner and transfer it onto the intermediate transfer belt. There is a problem that a large amount of toner is consumed and the image forming cost increases. Further, while a normal image is transferred from the intermediate transfer belt to a recording material such as paper, the image position detection mark needs to be removed by a cleaning member without being transferred, and the load of the intermediate transfer belt cleaning is increased. It increases and also causes a cleaning failure.

  Further, as a third method of detecting the belt skew, there is a method of detecting belt edges at a plurality of positions in the belt conveyance direction of the image transfer surface from the photosensitive member. However, in this method, since it is necessary to arrange a plurality of belt edge sensors which are essentially required to detect the belt edge for adjusting the steering roller, the cost increases. Furthermore, it is difficult to arrange a plurality of belt edge sensors in the belt conveyance direction of the image transfer surface on which a plurality of photoconductors are arranged for full-color image formation, and the size of the apparatus increases due to an increase in belt circumference. And increase costs.

  Since the belt edge is detected as a signal for belt deviation control by the steering roller, the edge data detected by the edge sensor has a shape including the shape of the belt edge. For this reason, in order to control the meandering of the belt with reference to the edge data measured in advance, it is necessary to synchronize with the belt, so a detection signal from the belt home sensor for detecting the home position of the belt is required. Further, a so-called “belt meander” that moves in a direction perpendicular to the conveyance direction may occur in the intermediate transfer belt due to a manufacturing error of the intermediate transfer belt. Therefore, the edge of the intermediate transfer belt is detected by an edge sensor, and by controlling the steering roller according to the end position of the intermediate transfer belt detected by the edge sensor, “belt meandering” is prevented, When controlling the end position of the transfer belt to be constant, even if the intermediate transfer belt is controlled so that the end position of the intermediate transfer belt is constant, the end position of the intermediate transfer belt itself is the predetermined position. There is a possibility that “belt meandering” may remain, for example, when the position is periodically deviated from the position. Therefore, the periodic fluctuation of the end position of the intermediate transfer belt is detected by the edge sensor in advance without controlling the steering roller, and the periodic fluctuation of the end position of the intermediate transfer belt is averaged. The stored data is stored in a storage means provided in a steering control circuit or the like. Then, based on the fluctuation information of the end position of the intermediate transfer belt stored in the storage means, a change in the end position of the intermediate transfer belt that actually occurs is detected to prevent “belt meandering”. Has been. Due to these factors, an increase in apparatus cost is inevitable.

  Therefore, the present invention has been made in view of the above problems, and it is possible to greatly speed up image output without using a configuration that obstructs belt high-speed driving such as a shift guide member, With a low-cost configuration, the movement (shift) of the endless belt in the main scanning direction is accurately detected and corrected, and the skew of the endless belt is accurately detected, and the image carrier image forming position is corrected reliably. Accordingly, an object of the present invention is to realize an image forming apparatus capable of greatly improving the image quality of an output image that can prevent image distortion and color misregistration due to misregistration in the main scanning direction.

  According to the present invention, the belt conveying device includes an endless belt stretched around a plurality of rollers, a driving unit that is connected to and drives any one of the rollers, and a traveling direction of the endless belt. Belt speed detecting means for detecting the conveying speed of the endless belt, and the endless belt from the difference in belt conveying speed detected by the plurality of belt speed detecting means, respectively. This is solved by comprising belt inclination calculating means for calculating the inclination in the running direction.

  The belt conveying device includes an endless belt stretched around a plurality of rollers, a driving unit that is connected to and drives any one of the rollers, and a width direction of the belt orthogonal to the traveling direction of the endless belt. The belt conveyance distance detection means for detecting the conveyance distance of the endless belt and the difference in belt conveyance distance detected by the plurality of belt conveyance distance detection means, and the inclination of the endless belt in the traveling direction are arranged at a plurality of locations. It is also preferable to comprise belt inclination calculating means for calculating.

Further, the belt speed detecting means includes a scale portion composed of marks continuously provided on the endless belt at predetermined intervals in the running direction, a mark detecting means for detecting the mark on the scale portion, and a detection result of the mark detecting means. And belt speed calculating means for calculating the speed of the endless belt based on the above.
The belt conveyance distance detection means includes a scale portion made of marks continuously provided at predetermined intervals in the traveling direction of the endless belt, a mark detection means for detecting the mark on the scale portion, and detection by the mark detection means. It is preferable to comprise belt moving distance calculating means for calculating the moving distance of the endless belt based on the result.

Further, the belt inclination calculating means is configured to determine the travel direction of the endless belt based on the time difference between the mark detection signals obtained from the plurality of mark detecting means and the result calculated by the belt speed calculating means or the belt moving distance calculating means. It is preferable to calculate the slope relative to.
The scale portions are provided at both ends in the belt width direction orthogonal to the running direction of the endless belt, and the mark detection means are provided at both ends in the belt width direction so as to correspond to the scale portions. And preferred.

Further, it is preferable that the mark detection means is disposed in the vicinity of an intermediate position of the length of the endless belt in the traveling direction.
In addition, it is preferable that the interval between the marks on the scale portion provided at one end of the endless belt in the belt width direction and the interval between the marks on the scale portion provided at the other end are substantially the same.

Moreover, it is preferable that the interval between the marks provided at one end in the belt width direction of the endless belt is larger than the interval between the marks provided at the other end.
Also, the scale portion provided at one end in the belt width direction of the endless belt is provided with one or a plurality of mark interval discontinuous portions having different mark intervals, and the mark interval is not provided at the other end portion. It is preferable that a specific mark different from the mark provided at one end is provided at a position corresponding to the continuous portion.

The specific mark is a mark for detecting a discontinuous portion of the mark interval, and it is preferable that the mark detection means outputs a discontinuity detection signal when the specific mark is detected.
Further, it is preferable that belt misalignment detection means is provided which is disposed at a plurality of positions in the belt width direction orthogonal to the running direction of the endless belt and detects the position of the endless belt in the belt width direction.

Further, the belt deviation detecting means includes a scale portion composed of marks continuously provided at predetermined intervals in the running direction on the endless belt, a mark detecting means for detecting the mark on the scale portion, and a detection result of the mark detecting means. And a belt shift amount calculating means for calculating a change in the position of the endless belt in the belt width direction.
Further, it is preferable to have a belt deviation correcting means for correcting the belt deviation for moving the endless belt in the belt width direction based on the detection result from the belt deviation detecting means.
The mark detection means is preferably a one-dimensional or two-dimensional sensor.

An image forming apparatus according to the present invention includes a plurality of photoconductors, a latent image forming unit that forms a latent image on the photoconductor, a developing unit that visualizes the latent image formed by the latent image forming unit, An intermediate transfer member that primarily transfers a visible image formed on the photosensitive member; and a secondary transfer unit that transfers the transfer image transferred onto the intermediate transfer member to a recording medium. A belt conveying device is preferable.
The image forming apparatus further includes a latent image forming position correcting unit that corrects a position in the main scanning direction of the latent image formed on the photoconductor, and the latent image forming position correcting unit is based on the calculation result of the belt inclination calculating unit. It is preferable to correct the formation position of the latent image formed above.

According to the belt conveyance device according to the present invention, without using a shift guide member or the like, a scale portion composed of a plurality of marks continuously provided at regular intervals in the sub-scanning direction at both ends of the endless belt, and these marks By using mark detection means arranged at both ends of the endless belt in the main scanning direction orthogonal to the sub-scanning direction for reading, the mark detection signal is not affected by the belt end shape in belt skew sensing. Is used to determine the skew angle based on the moving speed or the moving distance, and based on this, the skew correction and image correction can be performed.
Furthermore, according to the present invention, since the belt conveyance speed and the moving distance can be detected, the belt conveyance speed can be detected and controlled without adding a separate sensor, and cost reduction can be achieved. The

  Also, since the mark is formed with a certain size in the main scanning direction, the amount of light received and the intensity of the mark detection means arranged at both ends change, and based on this, the movement distance of the belt in the main scanning direction is changed. Calculated accurately and easily.

In addition, an inexpensive and highly accurate one-dimensional or two-dimensional image sensor can be used as the mark detection means.
Further, by using a shift correction means for moving the endless belt in the main scanning direction, the shift of the belt can be corrected accurately and easily without using a shift guide member or the like.

Further, by making the interval between the marks provided at both ends the same, the belt moving speed and moving distance can be calculated easily and accurately using the mark detection signal.
In addition, since the interval between the marks provided at the other end is larger than the interval between the marks provided at one end, the relatively costly scale portion is only on one side, and the other is only the mark. Is cheaper.

Also, a mark having a single or a plurality of seams is provided at one end, and a specific mark different from the mark is provided at the same position in the main scanning direction corresponding to the seam at the other end. It is also possible to deal with seams that normally occur.
Further, the specific mark is a mark for detecting discontinuity, and the mark detecting means outputs a discontinuity detection signal when detecting the specific mark, and can cope with a mark shift of one pitch or more.
In addition, since the mark detection means is disposed in the vicinity of the intermediate position in the sub-scanning direction on the transfer surface of the endless belt, it is possible to avoid deformation due to large deformation of the endless belt in the vicinity of the driving roller, and to deform in the belt surface Can be minimized.

It is a figure which shows 1st Example of the belt conveying apparatus which concerns on this invention. It is a schematic diagram of the belt conveying apparatus of FIG. FIG. 5 is a diagram illustrating a principle of detecting belt skew by calculating a difference in speed and a moving distance of an intermediate transfer belt. It is a figure which shows the mode of change of speed v1, v2 when the skew state of a belt changes. It is a figure which shows the mode of a change of the movement distance when the skew state of a belt changes. It is the figure which showed typically 2nd Example of the belt conveying apparatus which concerns on this invention. It is a figure which shows the example of the mark detection means as a scale which consists of the optical mark which concerns on this invention, and a sensor. 5 is a diagram illustrating an example of a scale unit 202 using a reflective mark 201. FIG. It is a figure which shows the relationship between the time of the signal in a sensor, and signal strength. It is explanatory drawing of belt skew detection, and is a figure which shows a mode that belt skew occurred. It is a figure which shows the signal waveform in the state which belt skewing generate | occur | produced. It is a figure which shows the movement distance when the skew angle of a belt changes from (theta) 1 to (theta) 2. FIG. It is a figure which shows 3rd Example of the belt conveying apparatus which concerns on this invention. It is a figure which shows 4th Example of the belt conveying apparatus which concerns on this invention. It is the figure which showed typically one Example of the belt shift | offset | difference detection means applied to the belt conveying apparatus which concerns on this invention. FIG. 16 is a diagram showing signal waveforms when the intermediate transfer belt moves in the main scanning direction in FIG. 15, that is, when a belt shift occurs. It is a schematic diagram of a sensor unit when an image sensor is used as another embodiment of the belt deviation detecting means. It is a figure which shows the arrangement | positioning of a mark and a line sensor when a line sensor is used as an image pick-up element as another Example of a belt shift | offset | difference detection means. FIG. 3 is a block diagram illustrating a configuration of a latent image formation position correcting unit in the image forming apparatus according to the present invention. It is a figure which shows the belt deviation correction means which concerns on this invention. 1 is a diagram schematically illustrating an example of a color image forming apparatus. It is a figure which shows a part of another image forming apparatus which concerns on this invention.

FIG. 21 schematically shows an example of the color image forming apparatus 1. First, the image forming apparatus 1 will be described.
In the color image forming apparatus 1, the apparatus main body 100 is placed on a paper feed table 200 as illustrated. A scanner 300 is mounted on the apparatus main body 100, and an automatic document feeder (ADF) 400 is mounted thereon. In the apparatus main body 100, a transfer device 20 having an intermediate transfer belt 10 that is a belt-like endless moving member is provided at substantially the center thereof. The intermediate transfer belt 10 includes a driving roller 9 and two driven rollers 15 and 16. It is stretched between them and rotates clockwise in FIG.

The intermediate transfer belt 10 is configured so that residual toner remaining on the surface after image transfer is removed by a cleaning device 17 provided on the left side of the driven roller 15. Yellow (Y), magenta (M), and cyan along the moving direction of the intermediate transfer belt 10 above the linear portion spanned between the driving roller 9 and the driven roller 15 of the intermediate transfer belt 10. (D) Four drum-shaped photoconductors 40Y, 40M, 40C, and 40Bk (hereinafter simply referred to as photoconductors 40 if not specified) of black (Bk) are arranged at predetermined intervals. . Then, four primary transfer rollers 62 are provided inside the intermediate transfer belt 10 so as to oppose the respective photoreceptors 40 and sandwich the intermediate transfer belt 10 therebetween.
As shown in FIG. 22, the intermediate transfer belt 10 may be further provided with a tension roller 19 for adjusting the belt tension.

Each of the four photoconductors 40 can be rotated counterclockwise as shown in FIG. 22, and around each photoconductor 40, a charging device for yellow 111, a charging device for magenta 112, as charging means, A cyan charging device 113 and a black charging device 114 are arranged. Further, a yellow developing device 131, a magenta developing device 132, a cyan developing device 133, and a black developing device 134 are arranged as developing means. Further, the above-described primary transfer roller 62 and a photoconductor cleaning device and a charge eliminating device (not shown) are provided, and each constitutes an image forming unit 18. An exposure unit 21 is provided above the four image forming units 18, and as shown in FIG. 22, a yellow exposure device 121, a magenta exposure device 122, and a cyan exposure device 123 are provided. A black exposure device 124 is disposed.
The toner images of the respective colors formed on the respective photoreceptors by the charging device, the exposure device, and the developing device are directly superimposed on the intermediate transfer belt 10 and sequentially transferred.
On the other hand, on the lower side of the intermediate transfer belt 10, a secondary transfer device 22 serving as a transfer unit that transfers the toner image on the intermediate transfer belt 10 to a sheet P that is a recording sheet is provided. The secondary transfer device 22 is a belt in which a secondary transfer belt 24 that is an endless belt is stretched between two rollers 23 and 23, and the secondary transfer belt 24 is subjected to secondary transfer via the intermediate transfer belt 10. It presses against the opposing roller 16.

The secondary transfer device 22 collectively transfers the toner images on the intermediate transfer belt 10 onto a sheet P fed between the secondary transfer belt 24 and the intermediate transfer belt 10.
A fixing device 25 for fixing the toner image on the sheet P is provided downstream of the secondary transfer device 22 in the sheet conveying direction. A pressure roller 27 is pressed against the fixing belt 26 which is an endless belt. Yes.
The secondary transfer device 22 also functions to convey the sheet after image transfer to the fixing device 25. Further, the secondary transfer device 22 may be a transfer device using a transfer roller or a non-contact charger. A sheet reversing device 28 is provided below the secondary transfer device 22 for reversing the sheet when images are formed on both sides of the sheet.

As described above, the apparatus main body 100 constitutes an indirect transfer tandem color image forming apparatus 1.
When color copying is performed by the color image forming apparatus 1, a document is set on the document table 30 of the automatic document feeder 400. When the document is manually set, the automatic document feeder 400 is opened, the document is set on the contact glass 32 of the scanner 300, and the automatic document feeder 400 is closed and pressed.

  When a start key (not shown) is pressed, when the document is set on the automatic document feeder 4, the document is fed onto the contact glass 32. When the document is manually set on the contact glass 32, the scanner 3 is immediately driven, and the first traveling body 33 and the second traveling body 34 start traveling. Then, light is emitted from the light source of the first traveling body 33 toward the document, and reflected light from the document surface is directed to the second traveling body 34, and the light is reflected by the mirror of the second traveling body 34. The light enters the reading sensor 36 through the imaging lens 35 and the content of the original is read.

  Further, when the start key is pressed, the intermediate transfer belt 10 starts to rotate. At the same time, the photoconductors 40Y, 40M, 40C, and 40K start rotating, and yellow (Y), magenta (M), cyan (C), and black (Bk) single color toners are formed on the photoconductors. The operation for forming an image is started. The toner images of the respective colors formed on the respective photoreceptors are sequentially transferred while being superimposed on the intermediate transfer belt 10 that rotates clockwise in FIG. 21 and FIG. An image is formed.

  On the other hand, when the start key described above is pressed, the paper feed roller 42 of the selected paper feed stage in the paper feed table 2 rotates, and the sheet P is fed from one selected paper feed cassette 44 in the paper bank 43. The paper is fed out, separated into one sheet by the separation roller 45, and conveyed to the paper feed path 46. The sheet P is transported to the paper feed path 48 in the apparatus main body 1 by the transport roller 47, hits the registration roller 49, and temporarily stops.

In the case of manual sheet feeding, the sheet P set on the manual tray 51 is fed out by the rotation of the sheet feeding roller 50, and is separated into one sheet by the separation roller 52 and conveyed to the manual sheet feeding path 53. Then, it hits the registration roller 49 and temporarily stops.
The registration roller 49 starts to rotate at an accurate timing in accordance with the composite color image on the intermediate transfer belt 10, and temporarily stops the sheet P between the intermediate transfer belt 10 and the secondary transfer device 22. Send it in. Then, a color image is transferred onto the sheet P by the secondary transfer device 22.

The sheet P on which the color image has been transferred is conveyed to a fixing device 25 by a secondary transfer device 22 that also functions as a conveying device, where the transferred color image is fixed by applying heat and pressure. . Thereafter, the sheet P is guided to the discharge side by the switching claw 55, is discharged onto the discharge tray 57 by the discharge roller 56, and is stacked there.
When the double-sided copy mode is selected, the sheet P on which an image is formed on one side is conveyed to the sheet reversing device 28 side by the switching claw 55, reversed there and led again to the transfer position, and this time the image is printed on the back side. After the formation, the paper is discharged onto a paper discharge tray 57 by a discharge roller 56.

FIG. 1 shows a first embodiment of a belt conveying device 11 according to the present invention.
The belt conveyance device 11 is a device that operates an intermediate transfer belt (endless belt) 10 stretched around a drive roller 9, a driven roller 15, and a secondary transfer counter roller 16 by a drive motor 12. The drive motor 12 is connected to the drive roller 9 through a speed reducer 13 connected thereto, and rotates the intermediate transfer belt 10 by rotating the drive roller 9. Further, when applied to the intermediate transfer belt 10 applied to the above-described image forming apparatus 1, the drive motor 12 is operated while sensing the belt surface speed by sensing the mark formed on the belt surface by the speed detecting means 14. By controlling, the belt surface speed can be kept constant.

Next, a method of belt skew sensing will be described.
FIG. 2 is a schematic diagram of the belt conveyance device 11, in which the drive motor 12 and the speed reducer 13 are omitted.
In FIG. 2, the speed detection means 14 is represented as speed sensors 101 and 102, and is installed at two locations in a direction orthogonal to the conveyance direction of the intermediate transfer belt 10. Although FIG. 2 shows an example in which speed sensors as speed detecting means are installed at both ends of the intermediate transfer belt 10, they need not necessarily be at both ends.

  Moreover, as the speed detection means 14, various means for measuring the surface speed can be used, and the generality of the present invention is not lost by using any of them. As an example of the speed detection means 14, for example, when the belt surface may be contacted, a rotation roller is attached to the rotary shaft of the rotary encoder, called a roller encoder, and the rotation roller is caused by friction with the contacted object. The thing which measures the rotational speed of a roller by rotating is mentioned. Non-contact measurement means include a laser Doppler velocimeter, an image detection type method such as that used in optical mice, or a method using a linear encoder sensor with a linear scale attached to the belt surface. For example, a method of calculating a speed from a signal cycle when an optical mark or a magnetic mark is periodically provided and read by a sensor that reads the mark is used.

When a mark is detected by the speed sensors 101 and 102, a mark detection signal is output. The mark detection signal is converted into speed signals 105 and 106 by the speed calculation means 103 and 104, and the speed difference is calculated by the difference calculation unit 107. For example, if the speed signal is converted into a voltage signal corresponding to the speed, the difference calculation unit 107 simply calculates the voltage difference to obtain a speed difference voltage signal. If the speed signal is converted into a frequency pulse signal corresponding to the speed, the difference calculation unit 107 may calculate the frequency difference.
The belt skew amount (belt skew amount) is calculated by the inclination calculating means 108 from the speed difference signal output from the difference calculation unit 107.

  Based on the calculated belt skew amount, for example, the inclination can be mechanically corrected by the inclination control means 109 of the belt conveyance device. Alternatively, the image generation unit 110 can correct the output image according to the distortion, or the exposure controller 115 can adjust the exposure timing to correct the image distortion due to the belt skew.

Next, the principle of detecting the belt skew by calculating the speed difference and the movement distance difference of the intermediate transfer belt 10 will be described with reference to FIG.
FIG. 3A is a schematic diagram of the belt conveyance device when there is no belt skew, and shows a state where the belt running direction (hereinafter referred to as “sub-scanning direction”) and the belt edge are parallel to each other. Yes. FIG. 3B shows a state in which the skew of the belt starts and the skew angle gradually changes. FIG. 3C shows a state in which the skew angle of the belt is constant and the skew is stable.
Here, the speed observation positions are the belt end portions in a direction orthogonal to the belt traveling direction (hereinafter referred to as “main scanning direction”), and the observed speeds are v1 and v2, respectively. Reference line A-A is shown as a line parallel to the sub-scanning direction of the belt.

FIG. 4 shows how the speeds v1 and v2 change when the skew state of the belt changes. In the initial state where the skew of the belt shown in FIG. 3A does not occur and in the state where the skew of the belt shown in FIG. 3C is stable, the conveying speed at both ends of the belt does not change and v1 = v2. Yes.
Here, let us consider a case where the skew angle θ gradually shifts as shown in FIG. 3B and the skew angle θ shifts to a stable state as shown in FIG. In the state where the skew angle gradually changes in FIG. 3B, v1 increases and v2 decreases as shown in FIG. If the skew angle becomes constant at an angle θ as shown in FIG. 3C, v1 and v2 return to the same speed as shown in FIG. 4C.
As shown in FIG. 4, the belt skew causes a speed change between the two points of the belt, so that the belt skew change can be observed by observing the speed difference.

FIG. 5 shows how the moving distance changes at this time. If the speed is positive, the cumulative travel distance becomes a graph that rises to the right. Therefore, the cumulative travel distance shows differences P1, P2 from the cumulative travel distance when traveling at a constant linear speed. Since the moving distance is an integral value of the speed, a distance deviation occurs in the section where the speed in FIGS. 3B and 4B is changing (the skew angle is changing). In a state where the skew angle in FIGS. 3C and 4C is stable at a constant angle, the moving distance has a constant value with a certain deviation. If the interval between the observation positions is L at the measurement position of v1 and the measurement position of v2, d = L tan θ. Here, the difference d in the movement distance is obtained from the difference in distance obtained by integrating the respective velocities v1 and v2, and thus the skew angle θ is also obtained.
As described above, it can be seen that the “skew change” is obtained by the speed difference between the two points in the main scanning direction of the belt, and the “skew angle” is obtained by the difference in the moving distance.

FIG. 6 schematically shows a second embodiment of the belt conveying apparatus according to the present invention.
In this embodiment, a scale portion 202 composed of a plurality of marks 201 provided on the intermediate transfer belt 10 so as to be continuous at a predetermined interval in the sub-scanning direction of the intermediate transfer belt 10 indicated by an arrow, and the scale portion The mark detecting means 203 and 204 for reading the mark 201 of 202 and the calculating means for calculating the moving speed or moving distance of the intermediate transfer belt 10 based on the outputs of the mark detecting means 203 and 204.

  As shown in the figure, scale portions 202 and mark detection means 203 and 204 as sensors are arranged at both ends of the belt in the main scanning direction. The scale unit 202 and the mark detection means 203 and 204 are generally easy to use optical sensors, but may be a combination of a magnetic mark and a magnetic sensor, or a metal mark and a capacitance sensor.

  FIG. 7 shows an example of a scale made up of optical marks and mark detection means as an optical sensor in the present invention. When a mark that causes a change in reflectance is used, a reflection type optical sensor as shown in the figure can be used as the mark detection means. As shown in the figure, a light beam 208 emitted from a light source 205 such as an LED is collected by a lens 206, hits the scale unit 202, is reflected there, and the reflected light is received by a light receiving element 207.

  FIG. 8 shows an example of the scale unit 202 using the reflective mark 201. When the intermediate transfer belt 10 is black and has a low reflectance, a white scattering mark or a total reflection mark having a high reflectance can be used as the mark 201. It is desirable that the mark 201 has a length in the main scanning direction of the belt as shown in the figure so that the light beam 208 strikes the mark 201 and is stably detected even if the belt is deviated.

  FIG. 9 shows the relationship between time and signal intensity, and is an output example from the mark detection means when the intermediate transfer belt 10 is conveyed with the above-described configuration. The signal obtained by the light receiving element 207 is high because the reflection intensity is high in the mark detection part 210 from the mark having a high reflectance, and is low in a part where there is no mark having a low reflection intensity. The signal may be used as an analog voltage as it is, or may be digitized using a comparator in order to be strong against transmission noise.

  Here, if the marks 201 of the scale unit 202 are formed at regular intervals, the signal cycle from the mark detection means obtained is a cycle corresponding to the conveyance speed of the intermediate transfer belt 10. If the signal period is T and the interval between the marks 201 is P, the belt speed V is expressed by V = P / T. Further, the moving distance of the intermediate transfer belt 10 is also calculated by counting the number of detected marks 201.

Next, a method for calculating the belt skew from the time difference (phase difference) of the mark detection signals will be described with reference to FIGS. 10, 11, and 12. In FIG. 10, the alternate long and short dash line indicates the belt conveyance state where there is no belt skew, and the solid line indicates the belt conveyance state where the belt is skewed by the angle θ in the main scanning direction.
The intermediate transfer belt 10 is conveyed in a direction inclined at an angle θ on the image transfer surface due to the influence of the inclination of each roller that conveys the belt. For this reason, as shown in FIG. 10, the image formed on the image transfer surface is inclined at an angle θ, and the images (yellow (Y), magenta (M), cyan (C), The transfer position on the black (Bk) intermediate transfer belt is shifted in the main scanning direction. As a result, image distortion and color misregistration in a color image occur.

  Further, the timing at which the mark detection means 203, 204 detects the mark 201 provided for detecting the speed of the intermediate transfer belt 10 in the sub-scanning direction also changes due to the influence of the skew angle θ of the belt. Therefore, the mark 201 is formed at two locations in the main scanning direction of the belt, and the marks are detected by the mark detection means 203 and 204 disposed at positions facing the respective marks 201, whereby the skew of the intermediate transfer belt 10 is detected. Is detected.

  FIG. 11 shows signals detected by the mark detection means 203 and 204, respectively. When the skew angle θ of the intermediate transfer belt changes, the phase difference of the mark detection period at the two detection positions in the main scanning direction changes. By detecting this change in the phase difference, the intermediate transfer belt A change in the skew angle can be detected. Usually, the intermediate transfer is performed by correcting the image forming position on the photosensitive member by the image forming position correcting means in accordance with the change in the skew angle of the belt that occurs after the image forming position is adjusted when the image forming apparatus is started. By correcting the image forming position in the main scanning direction on the belt, it is possible to correct image distortion and color misregistration in a color image.

In FIG. 11, the phase difference between the detection signals from the two mark detection means 203 and 204 before the belt skew change is t1, and the phase difference between the detection signals after the belt skew change is t2. When t1 <t2, in FIG. 10, the intermediate transfer belt is rotated in the direction in which the angle θ increases (counterclockwise). Here, if the angle before the belt skew change is θ1, the angle after the belt skew change is θ2, the distance between the two mark detection means 203 and 204 is L, and the conveyance speed of the belt in the sub-scanning direction is V, As shown in FIG.
The relationship L × sin θ2−L × sin θ1 = t2 × V−t1 × V is established.
Here, since θ1 and θ2 are minute angles, sin θ is θ,
L × θ2−L × θ1 = t2 × V−t1 × V
Therefore, the angle change (θ2−θ1) changed after the adjustment of the image forming position is
θ2−θ1 = (t2−t1) V / L. From this, the change in angle (θ2−θ1) can be obtained by using the change (t2−t1) in the phase difference of the detection signals in the belt speed detection means 203 and 204.

  As described above, by using the scale unit 202 composed of the marks 201 at regular intervals and the mark detection means 203 and 204, belt skew can be easily obtained. By calculating the period at the mark sensor and the time delay between the two sensors with a counter using a high-speed clock, the speed and skew can be calculated with high accuracy, and the digital signal can be used, making it more resistant to noise. .

FIG. 13 shows a third embodiment of the belt conveying apparatus according to the present invention.
In the present embodiment, unlike the above-described embodiments, one of the marks provided on both ends of the intermediate transfer belt 10 is a scale portion 202 composed of marks 201 having a continuous pitch, and the other is either Only the same specific mark 201 with a large interval corresponding to the position of the mark 201. Since the mark 201 of any one of the scale portions 202 and the specific mark 201 are located in the main scanning direction and correspond to each other, if the deviation between the specific mark 201 and the mark 201 of the scale portion 202 is within one pitch, These speed differences or time differences are measured by the sensors 204 and 203, and the skew angle of the intermediate transfer belt 10 can be detected in the same manner as in the second embodiment.
Thereby, the scale which is relatively expensive is only on one side and only the mark is on the other side, so that the cost can be further reduced.

FIG. 14 shows a fourth embodiment of the belt conveying apparatus according to the present invention.
In the present invention, as a method of forming a mark on the intermediate transfer belt 10, a method of adhering a resin tape as a flexible member on which a plurality of marks 201 continuous at a constant interval are formed to one side in the endless movement direction of the belt. Is adopted. In addition to this method, there is a method in which the mark 201 is formed at the same time as the belt is formed, but this method cannot make the mark interval constant when the contraction rate of the entire belt is not uniform. However, according to the bonding method of the present invention, even if the contraction rate of the belt is not uniform, this does not affect the mark interval, and the mark interval can be made constant. However, due to tolerances in manufacturing the belt, the belt circumference varies depending on the manufactured belt. As a result, as shown in the drawing, seams 251 having different intervals are generated at the portion connecting the leading end and the trailing end of the resin tape.
Also, in order to keep the distance from the mark detection means 203 to the scale portion 202 constant, the both ends of the scale portion 202 are separated at the joint 251 so that the scale portion 202 does not overlap the intermediate transfer belt 10. It is necessary to attach.

Then, since the signal strength of the output of the mark detection unit 203 at the joint 251 drops for a certain time, the specific mark 201 for identifying the discontinuity corresponding to the size of the joint 251 is provided on the opposite side of the spot. It is arranged. The discontinuity specifying mark 201 is detected when it faces the mark detection means 204 as the belt moves endlessly. At this time, a constant discontinuity detection signal is continuously output. If the time during which the discontinuity detection signal is output matches the time during which the seam 251 is output, there is no speed difference between both ends of the belt. If these times are deviated, a speed difference between both ends of the belt exists. In this case, for example, by using the time difference between the leading end portion of the discontinuous detection signal and the leading end portion of the output of the joint 251 and the time difference between the trailing end portion of the output of the joint 251 and the output of the mark, the belt as in the second embodiment. Is detected.
In this embodiment, it is possible to deal with a mark shift of one pitch or more, and the mark count is not required.

FIG. 15 shows an embodiment of a means for detecting movement (belt shift) of the belt in the main scanning direction applied to the belt conveying apparatus according to the present invention.
In the present embodiment, the mark 201 of the scale unit 202 is formed in a constant size in the main scanning direction, and the light beams 220 and 221 from the mark detection means 203 and 204 are spread in the main scanning direction. is there. Then, as shown in FIG. 15, the reference detection position with respect to the mark 201 is the left mark detection means 203 (hereinafter referred to as “sensor L”) on the left, and the right mark detection means 204 (hereinafter referred to as “sensor R”). Is shifted to the right.
When a so-called belt shift occurs, the detection width of the mark changes depending on the belt position, so that the amount of light received by the left and right sensors L and R also changes. Therefore, the signal intensity of these sensors also changes, so the belt position in the main scanning direction. A change can be detected.

FIG. 16 shows signal waveforms detected by the mark detection means when the intermediate transfer belt 10 moves in the main scanning direction in this state, that is, when a belt shift occurs. When the intermediate transfer belt 10 is moved to the right side, the output of the signal 231 from the sensor R increases and the signal 230 from the sensor L decreases (see FIG. 16 (1)). On the other hand, when moving to the left side, the signal 230 of the sensor L becomes stronger and the signal 231 of the sensor R becomes weaker (see FIG. 16 (2)). If there is no deviation of the intermediate transfer belt 10, the signal intensities of the signals 230 and 231 of the sensors L and R are substantially the same (see FIG. 16 (3)).
Thus, by comparing the signal intensities of the sensors R and L, the position of the intermediate transfer belt 10 in the main scanning direction, that is, the belt shift can be detected.

  By configuring the two mark detection means 203 and 204 as described above, in addition to the moving speed of the belt and the belt skew, it is possible to measure the belt shift, so a separate sensor is used for each measurement. There is no need to provide it, and a reduction in the number of parts and cost reduction are realized.

17 and 18 show another embodiment of the belt deviation detecting means.
In this embodiment, an image sensor 241 is used instead of the light receiving element 207 of the mark sensor, and FIG. 17 is a schematic diagram of a sensor unit when the image sensor 241 is used. A light beam emitted from a light source such as an LED hits the scale unit and is reflected there. The reflected light is received by the image sensor 241 and a signal having an intensity corresponding to the amount of received light is output. The belt position data is output. FIG. 18 shows the arrangement of the mark 201 and the line sensor 241 when the line sensor 241 is used as the image sensor.

The difference between the use of the image sensor 241 and the use of the light receiving element 207 is that the movement of the mark 201 is detected as a signal change with time in the light receiving element 207, but the image sensor 241 detects the mark when the sampling is performed. The position is to be observed. Therefore, by arranging two image sensors 241 at both ends of the intermediate transfer belt 10 and sampling at the same time, position information of the mark 201 observed by each sensor can be obtained. Changes can be read directly.
Further, as shown in FIG. 15, if sensing is performed by shifting the reference detection position to the left of the scale mark 201, the left sensor L is shifted to the left and the right sensor R is shifted to the right, the main scanning direction of the mark 201 is detected. Can be read directly.
Further, as the intermediate transfer belt 10 is conveyed, each mark 201 faces the line sensor 241, and the movement of each mark 201 in the sub-scanning direction is detected based on the detected cycle. With this information, the speed of the intermediate transfer belt 10 in the sub-scanning direction can also be detected.

In addition, when the detection marks 201 described in the above embodiment are formed on the belt at equal intervals, the detection mark intervals are different due to a belt circumferential length error, so that the detection marks are formed at equal intervals over the entire belt circumference. In this case, it is necessary to obtain an optimum interval for each belt and to form the detection mark 201 with high accuracy, which causes a problem that the manufacturing cost of the belt increases.
However, it is possible to detect marks over the entire circumference of the intermediate transfer belt by providing multiple detection patterns in the main scanning direction, arranging them so as to complement the detection pattern non-formed parts, and selecting the mark detection means as appropriate. It becomes. Specifically, by shifting the start position for placing marks at regular intervals on the belt, the gap position of the gap between the first and last marks, which is different from the gap between other marks, can be shifted in the sub-scanning direction. Good. Thus, by providing a plurality of detection patterns in the main scanning direction, it is possible to form a mark shorter than the entire circumference of the intermediate transfer belt by the length of the gap portion. This facilitates mark formation and brings about an effect of cost reduction. Further, the detection mark forming operation is facilitated, and highly accurate mark formation is possible.

In this case, as shown in FIG. 10, the marks 201 formed at a plurality of positions in the main scanning direction of the intermediate transfer belt 10 are detected by the mark detection means 203 and 204, respectively, and the sub-scanning direction of the intermediate transfer belt 10 is detected. And the movement in the main scanning direction are detected. In order to detect the belt speed while avoiding the gap portion, the detection signal from the mark detection 204 is switched to the other mark detection portion 203 by the switching portion when the gap portion is detected by one mark detection portion 204. By generating the detection signal, it is possible to detect the entire circumference of the intermediate transfer belt 10. Similarly, in order to detect the belt shift while avoiding the gap portion, when the gap portion is detected by one mark detection means, the switching means switches to the other mark detection means to generate a detection signal.
At this time, a circuit for calculating the position of the intermediate transfer belt 10 from the detection signals of the mark detection means 203 and 204 (detection signals obtained by switching the detection signals from the mark detection means 203 and 204 by the switching means) is provided. Can be used for speed control and belt deviation correction of the intermediate transfer belt 10 as a signal obtained by averaging the detection signals from the mark detection means 203 and 204 or a signal in which one complements the other.

  Further, as shown in FIG. 10, the mark detection means 203 and 204 may be arranged at the same position in the sub-scanning direction within the image transfer surface. The intermediate transfer belt 10 is often formed of a resin material, and the belt extends in the sub-scanning direction due to changes in environmental conditions such as temperature and humidity. Therefore, if the mark detection means 203 and 204 are arranged at different positions in the sub-scanning direction within the image transfer surface, the phase of the mark detection cycle fluctuates due to the effect of the extension of the intermediate transfer belt 10 in the sub-scanning direction. An error may occur in the detection of the line. Therefore, by arranging the mark detection means 203 and 204 at the same position in the sub-scanning direction within the image transfer surface, it is possible to minimize the influence of belt elongation due to environmental fluctuations.

  Further, as shown in FIG. 10, the mark detection means 203 and 204 may be arranged near the intermediate position in the sub-scanning direction within the image transfer surface. Since the intermediate transfer belt 10 that is often formed of a resin material has a significantly lower rigidity than the roller around which the belt 10 is wound, the intermediate transfer belt 10 may be deformed by the in-belt stress generated by the inclination of the roller. This deformation becomes large near the roller. Therefore, if the mark detection means 203 and 204 are arranged in the vicinity of the roller in the image transfer surface, an error may occur in the belt skew detection due to the deformation in the belt surface direction. Therefore, by arranging the mark detection means 203 and 204 in the vicinity of the intermediate position in the sub-scanning direction on the image transfer surface, belt skew correction and deviation correction while minimizing the influence of deformation in the belt surface direction. Can be realized.

Next, the image forming position correcting unit will be described.
As correction means for correcting the image forming position in the main scanning direction corresponding to the change in the angle of the intermediate transfer belt, a roller other than the steering roller is inclined by the same operation as the steering roller, There are means for changing the latent image forming position on the photosensitive member by providing an optical axis angle changing means in the optical path of the optical writing means for forming the latent image. Here, when the belt skew is corrected by inclining a roller other than the steering roller, the belt skew changes by correcting the belt skew, and the belt skew changes by correcting the belt skew. There is a problem that a high-function control system that performs accurate control is required and the cost increases. Also, in the case where the optical axis angle changing means is provided in the optical path of the optical writing means, it is necessary to provide highly accurate and reliable optical means, which increases the cost.

  On the other hand, FIG. 19 is a block diagram showing the configuration of the latent image forming position correcting means in the image forming apparatus according to the present invention. In the figure, the image signal transferred from the printer driver unit 601 is input to an image signal generation unit 603 constituting the image writing control unit 602. Engine control information from the engine control unit 604 is also input to the image writing control unit 602. In the image signal generation unit 603, the input image signal is subjected to image processing by processing according to engine control information. At this time, in order to actually develop the image on the recording paper, the image signal generation unit 603 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 605 based on information from the engine control unit 604 such as resolution, linear velocity of the photosensitive member, and the like, and a clock signal (wclk) having a predetermined frequency is generated. Input to the circuit unit 606. The actual image signal subjected to image processing by the image signal generation unit 603 is input to the writing position control unit 607. In addition, the writing position control unit 607 includes a belt displacement generated based on a synchronization detection signal (DETP) from the synchronization detection unit 609 of the laser writing device 608 and skew information from the belt skew detection unit 204 on the intermediate transfer belt 10. The signal (Δa) and engine control information from the engine control unit 604 are 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 photoconductor 40Bk. This signal is an output signal from the synchronization detection plate arranged outside the scanning region on the photoreceptor 40Bk of the laser beam reflected and deflected by the polygon mirror 611 in the laser writing device 608. A light receiving element such as a diode is cast as a synchronous detection sensor, and the synchronous detection sensor photoelectrically converts an incident laser beam and outputs a synchronous detection signal (DETP). The belt displacement signal (Δa) is a signal indicating the displacement in the main scanning direction of the intermediate transfer belt 10, and is inevitably generated during the belt shift correction by the belt shift correction means, and the main displacement of the intermediate transfer belt 10 in the image transfer surface. This is a signal calculated from the belt skew detection means 204 in the scanning direction. The writing position control unit 607 combines the real image signal from the image signal generation unit 603 with the synchronization detection signal (DETP) at a predetermined timing to generate a signal for driving the semiconductor laser that is a light source. 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 607 receives a skew correction clock signal (dclk) obtained by multiplying the pixel clock signal (wclk) generated by the pixel clock generation unit 605. The skew correction clock signal (dclk) is a signal having a frequency higher than that of the pixel clock signal obtained by multiplying the pixel clock signal (wclk) that defines the minimum pixel capable of forming an image. 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) is one resolution of the belt skew detection means 204. It corresponds to. A belt displacement signal (Δa) from the belt skew detection means 204 is calculated, and a synchronization detection signal (DETP) and a belt displacement signal (Δa) are input to the writing position control unit 607. Assuming that A (= N × wclk) from the synchronization detection signal when the belt displacement signal (Δa) is 0 to the start position of the actual image signal in the main scanning direction, if Δa> 0 is detected, synchronization detection is performed. The delay time from the signal to the actual image writing timing is changed to A + Δa × dclk, and 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 synthesized by the writing position control unit 607 is input to the laser driving unit 612. The semiconductor laser mounted on the laser drive unit 612 is repeatedly driven to turn on / off by turning on / off the laser drive signal. The laser beam emitted by driving the semiconductor laser is incident on the laser writing device 608, passes through and reflects a plurality of lenses, mirrors, and the like, and travels in the optical path. The light is rotated and deflected by a polygon mirror 611 disposed in the middle of the optical path, and a laser beam is exposed on the photoconductor 40Bk in the main scanning direction. The process from this exposure until an output image is obtained is as described above.

Next, belt deviation correcting means will be described. FIG. 20 shows a belt deviation correcting means according to the present invention.
The intermediate transfer belt 10 is stretched by a plurality of substantially parallel rollers, and is driven in the belt conveyance direction by one drive roller 9 among them. The driving roller 9, the driven roller 15, and the secondary transfer counter roller 16 are fixed at predetermined positions, whereas both ends of the rotation shaft of the tension roller 19 are urged in the direction of the arrow, and the intermediate transfer belt 10 is substantially constant. It is stretched with tension.
In addition, a correction roller 29 is provided for correcting a shift generated in the intermediate transfer belt 10, that is, a movement in the main scanning direction. One end of the rotation shaft of the correction roller 29 is supported by a pivot bearing or the like so as to be swingable in the direction perpendicular to the rotation shaft, and the other end is supported by an actuator 37 so as to be reciprocally movable in the arrow direction.

  Based on the information on the belt deviation amount from the belt deviation detection means 203, 204, the actuator 37 is driven to swing the correction roller 29 so that the intermediate transfer belt 10 moves in the direction opposite to the generated movement in the main scanning direction. By doing so, the belt shift is controlled within a certain range, and the belt shift can be suppressed without providing a separate shift guide member or the like.

DESCRIPTION OF SYMBOLS 9 Drive roller 10 Intermediate transfer belt 15 Driven roller 16 Secondary transfer counter roller 29 Belt shift correction roller 201 Mark 202 Scale unit 203, 204 Mark detection means, belt skew detection means

JP-A-2005-148127 JP 2006-276427 A

Claims (17)

An endless belt stretched around a plurality of rollers;
Drive means connected to and driving any one of the rollers;
Belt speed detecting means disposed at a plurality of locations in the width direction of the belt perpendicular to the traveling direction of the endless belt, and detecting the conveying speed of the endless belt;
A belt conveying apparatus comprising belt inclination calculating means for calculating the inclination of the endless belt in the running direction from the difference in belt conveying speed detected by each of the plurality of belt speed detecting means. An endless belt stretched around a plurality of rollers;
Drive means connected to and driving any one of the rollers;
Belt transport distance detecting means disposed at a plurality of locations in the width direction of the belt orthogonal to the traveling direction of the endless belt, and detecting the transport distance of the endless belt;
A belt conveying apparatus comprising: belt inclination calculating means for calculating an inclination of the endless belt in the running direction from a difference in belt conveying distances detected by the plurality of belt conveying distance detecting means. In the belt conveyance device according to claim 1,
The belt speed detecting means includes
A scale portion composed of marks continuously provided at predetermined intervals in the traveling direction of the endless belt;
Mark detection means for detecting the mark of the scale portion;
A belt conveying device comprising: a belt speed calculating means for calculating a speed of the endless belt based on a detection result of the mark detecting means. In the belt conveyance device according to claim 2,
The belt conveyance distance detecting means includes
A scale portion composed of marks continuously provided at predetermined intervals in the traveling direction of the endless belt;
Mark detection means for detecting the mark of the scale portion;
And a belt moving distance calculating means for calculating a moving distance of the endless belt based on a detection result of the mark detecting means. In the belt conveyance device according to claim 3 or 4,
The belt inclination calculating unit is configured to determine the endless belt based on a time difference between mark detection signals obtained from the plurality of mark detecting units and a result calculated by the belt speed calculating unit or the belt moving distance calculating unit. A belt conveyance device that calculates an inclination with respect to the traveling direction of the belt. In the belt conveyance device according to claim 5,
The scale portion is provided at both ends of the belt width direction orthogonal to the traveling direction of the endless belt,
The belt conveying device according to claim 1, wherein the mark detecting means is provided at both ends in the belt width direction so as to correspond to the scale portion. In the belt conveyance device according to claim 6,
The belt conveying device according to claim 1, wherein the mark detecting means is disposed in the vicinity of an intermediate position of a length in the running direction of the endless belt. In the belt conveyance device according to claim 6 or 7,
A belt characterized in that an interval between the marks of the scale portion provided at one end portion in the belt width direction of the endless belt and an interval between the marks of the scale portion provided at the other end portion are substantially the same. Conveying device. In the belt conveyance device according to claim 6 or 7,
The belt conveying apparatus, wherein an interval between the marks provided at one end of the endless belt in the belt width direction is larger than an interval between the marks provided at the other end. In the belt conveyance device according to claim 6 or 7,
The scale portion provided at one end in the belt width direction of the endless belt is provided with one or a plurality of mark interval discontinuous portions having different mark intervals, and the other end is not provided with the mark interval. A belt conveying apparatus, wherein a specific mark different from the mark provided at the one end is provided at a position corresponding to the continuous portion. The belt conveyance device according to claim 10, wherein
The belt conveyance device according to claim 1, wherein the specific mark is a mark for detecting the mark interval discontinuous portion, and the mark detection means outputs a discontinuity detection signal when the specific mark is detected. In the belt conveyance device according to any one of claims 1 to 11,
A belt conveying apparatus comprising belt deviation detecting means disposed at a plurality of positions in the width direction of the belt perpendicular to the traveling direction of the endless belt, and detecting positions of the endless belt in the belt width direction. In the belt conveyance device according to claim 12,
The belt deviation detecting means includes
A scale portion composed of marks continuously provided at predetermined intervals in the traveling direction of the endless belt;
Mark detection means for detecting the mark of the scale portion;
A belt conveying apparatus comprising: a belt deviation amount calculating unit that calculates a change in a position of the endless belt in the belt width direction based on a detection result of the mark detecting unit. In the belt conveyance device according to claim 12 or 13,
A belt conveying apparatus comprising belt deviation correcting means for correcting a belt deviation for moving the endless belt in a belt width direction based on a detection result from the belt deviation detecting means. In the belt conveyance device according to any one of claims 3 to 14,
The belt detecting apparatus is characterized in that the mark detecting means is a one-dimensional or two-dimensional sensor. A plurality of photosensitive members, a latent image forming unit that forms a latent image on the photosensitive member, a developing unit that visualizes a latent image formed by the latent image forming unit, and a visible image formed on the photosensitive member In an image forming apparatus comprising: an intermediate transfer member that primarily transfers an image; and a secondary transfer unit that transfers a transfer image transferred onto the intermediate transfer member to a recording medium.
An image forming apparatus, wherein the intermediate transfer member is the belt conveyance device according to any one of claims 1 to 15. The image forming apparatus according to claim 16.
A latent image forming position correcting means for correcting the position of the latent image formed on the photosensitive member in the main scanning direction;
The latent image forming position correcting unit corrects a forming position of a latent image formed on the photoconductor based on a calculation result of the belt inclination calculating unit.

Images