JP6303506B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a printer, a facsimile machine, or a multifunction machine having at least two functions thereof.

  In the image forming apparatus of the above type, belt devices such as an intermediate transfer belt, a photoreceptor belt, and a paper conveying belt are often used. For example, a sensor for detecting the density and / or position of the toner mark carried on the belt may be disposed around the intermediate transfer belt and the photosensitive belt in order to perform density adjustment and alignment adjustment. Many.

  In general, it is important for the light receiving / emitting section of the density detection sensor to maintain the focal length with the object to be measured with high accuracy. If the focal distance with the object to be measured is deviated, the sensor characteristics change. Detection accuracy decreases. In order to prevent this, it is known to arrange a backup member that stabilizes the running of the transfer belt surface facing the sensor to reduce the influence of noise due to vibration or the like. At this time, as one method for reducing the rubbing load on the belt by the backup member, there is a method of flocking on the belt rubbing surface of the backup member.

Such a method is effective in reducing the frictional load on the belt at the beginning, but there is a problem that the effect is reduced as hair fall progresses by use.
Therefore, in order to prevent the fall of the flocked hair, a method of reducing the amount of fall of the hair by putting an operation of reversing the belt at a constant interval has already been proposed.

  In this belt reverse rotation method, the interval can be changed under certain conditions, but basically the reverse rotation operation must be performed at a constant belt travel distance interval or the like. If this interval is too wide, a sufficient effect for preventing hair fall cannot be obtained. On the other hand, if the interval is too narrow, if the transfer cleaning blade is always in contact, the blade will be damaged, resulting in poor cleaning. Further, when the belt cannot be completely separated from the photosensitive member, the photosensitive member and the belt are rubbed and damaged, and an image defect occurs. Furthermore, since the reverse rotation operation is frequently performed, there is a problem that the number of sheets to be passed per minute is reduced and the specification is reduced as a product.

  By the way, the purpose of Patent Document 1 is to prevent abnormal noise due to hair fall, and as shown in the timing chart of FIG. A method of performing a reverse rotation operation for returning is disclosed.

  However, even with the method described in Patent Document 1, if the interval is too wide, a sufficient effect of preventing hair fall cannot be obtained. Conversely, if the interval is too narrow, problems such as poor cleaning and rubbing of the photoreceptor are solved. It was difficult to do.

  SUMMARY OF THE INVENTION In view of the above-described conventional problems, an object of the present invention is to provide an image forming apparatus capable of performing a recovery operation for improving the fall of a flock at an optimum time for each apparatus.

In order to solve the above-described problems, the present invention includes a belt that is stretched and rotated by a plurality of rollers, and is arranged between the rollers, abutting against the inner surface of the belt, and having flocked on the side that abuts on the belt. A rotation member that monitors the rotational torque of the belt that rotates in a predetermined direction during an image forming operation, and when the rotational torque exceeds a certain threshold value, In an image forming apparatus that performs a recovery operation for recovery, the rotational torque value of the belt when it is started from a state of being stationary for a predetermined time or more and the torque value when the torque increase is stopped by continuing the rotation are measured. Then, an image forming apparatus is proposed in which a torque increase amount is determined from a difference between both torque values, and the threshold value is set based on the increase amount.
Further, the present invention includes a belt that is stretched and rotated by a plurality of rollers, and a backup member that is disposed between the rollers, contacts the inner surface of the belt, and has a flocking on the side that contacts the belt. The rotational torque of the belt rotating in a predetermined direction during the image forming operation is monitored, and when the rotational torque exceeds a threshold value, a recovery operation is performed to recover the fall of the flocked hair other than the image forming operation. In the image forming apparatus, the initial torque value recorded in the manufacturing process and the torque value when the rotation continues and the torque increase stops are measured, and the torque increase amount is determined from the difference between the two torque values. The present invention proposes an image forming apparatus characterized in that the threshold is set.
Furthermore, the present invention includes a belt that is stretched and rotated by a plurality of rollers, and a backup member that is disposed between the rollers, abuts against the inner surface of the belt, and has flocking on the abutment side of the belt. The rotational torque of the belt rotating in a predetermined direction during the image forming operation is monitored, and when the rotational torque exceeds a threshold value, a recovery operation is performed to recover the fall of the flocked hair other than the image forming operation. In the image forming apparatus, the recovery operation is a repetitive operation of repeating the reverse rotation of rotating the belt in the direction opposite to the rotation direction at the time of image formation when the threshold value is reached, and then repeating normal rotation and reverse rotation. The present invention proposes an image forming apparatus characterized in that the operation ends at the last reverse rotation.
Furthermore, the present invention includes a belt that is stretched and rotated by a plurality of rollers, and a backup member that is disposed between the rollers and that abuts against the inner surface of the belt and includes flocking on the abutting side of the belt. And monitoring the rotational torque of the belt that rotates in a predetermined direction during the image forming operation, and performing a recovery operation to recover the fall of the flocked hair other than the image forming operation when the rotational torque exceeds a certain threshold value. In the image forming apparatus to be implemented, there is proposed an image forming apparatus characterized in that, when the decrease in rotational torque after performing the recovery operation is small, the execution time of the recovery operation is lengthened.
Finally, the present invention includes a belt that is stretched and rotated by a plurality of rollers, and a backup member that is disposed between the rollers and that abuts against the inner surface of the belt and includes flocking on the abutting side of the belt. And monitoring the rotational torque of the belt that rotates in a predetermined direction during the image forming operation, and performing a recovery operation to recover the fall of the flocked hair other than the image forming operation when the rotational torque exceeds a certain threshold value. In the image forming apparatus to be implemented, there is proposed an image forming apparatus characterized by resetting the threshold value again when a decrease in rotational torque after performing the recovery operation is small.

  According to the present invention, it is possible to suppress the occurrence of abnormal noise by delaying the progress of hair fall by performing the recovery operation for improving the hair fall of the planted hair at the optimum time.

1 is a schematic diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a perspective view illustrating an intermediate transfer belt of the image forming apparatus in FIG. 1. FIG. 2 is a side configuration diagram illustrating an intermediate transfer belt of the image forming apparatus of FIG. 1. It is explanatory drawing which shows initial hair transplantation. It is explanatory drawing which shows the hair transplantation in use. It is explanatory drawing which shows the flocking of the terminal state by use. It is a graph which shows the relationship between belt travel distance and belt drive torque. It is a control block diagram which shows one Embodiment of this invention. It is a flowchart which shows control of hair transplant recovery. It is a flowchart which shows the method of a threshold value setting. It is a graph of the belt travel distance and belt drive torque which show the threshold value to set. It is a flowchart which shows control of the enhanced hair transplant recovery. It is the schematic which shows the structure of the image forming apparatus which concerns on other embodiment of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic cross-sectional view showing an example of an image forming apparatus configured as an electronic copying machine, a printer, a facsimile, or a composite machine of these. In the image forming apparatus main body 1 shown here, image forming units 2C, 2M, 2Y and 2K having first to fourth photoconductors 4C, 4M, 4Y and 4K configured as drum-shaped image carriers. Is arranged. Further, an intermediate transfer unit having an intermediate transfer belt 3 as an image carrier made of an endless belt is disposed facing the photoreceptors 4C, 4M, 4Y, and 4K. The intermediate transfer belt 3 is wound around a driving roller 5 and a tension roller 6 which will be described in detail later, and the driving roller 5 is driven counterclockwise in FIG. Is done. Note that the image forming units 2C, 2M, 2Y, and 2K and their constituent members such as photoconductors are described with reference to each color by cyan (C), magenta (M), yellow (Y), and black (K). ), But omitted when explaining all colors in common.

  Each photoconductor 4 is rotated clockwise in FIG. 1 while contacting the surface of the intermediate transfer belt 3 at a peripheral speed of 100 to 180 mm / S. A roller-shaped charging roller 7 serving as charging means is pressed against the surface of the photoconductor 4 and is rotated by the rotation of the photoconductor 4. The charger 7 is uniformly charged to a surface potential of −200 to −1000 V by applying a bias with DC or DC superimposed on DC from a high voltage power source (not shown). Subsequently, the photosensitive member 4 is exposed to image information by an exposure unit 8 which is a latent image forming unit, and an electrostatic latent image is formed. This exposure process is performed by a laser beam scanner using a laser diode or an LED. Reference numeral 9 denotes a one-component contact developing device as developing means, which visualizes the electrostatic latent image on the photosensitive member 4 as a toner image by a predetermined developing bias supplied from a high voltage power source (not shown).

  The toner image thus formed is transferred to the intermediate transfer belt 3 by the primary transfer roller 10 as a primary transfer member. That is, a predetermined transfer bias +500 to +1000 V is commonly applied to the primary transfer roller 10 by a single high-voltage power source (not shown) to form a transfer electric field via the intermediate transfer belt 3, and a toner image is applied to the intermediate transfer belt 3. Transfer. Note that although a metal roller having a diameter of 8 to 12 mm is used as the primary transfer member of the present embodiment, a conductive blade, a conductive sponge roller, or the like can be used as the primary transfer member. It is inevitable that toner remains on the photoreceptor 4 after toner transfer, and the residual toner is removed by the cleaning device 11.

  The image forming unit 2 is a process unit in which the photoconductor 4, the charger 7, the developing device 9, and the cleaning device 11 are integrated. The image forming unit 2 forms a visible image in the order of black, yellow, magenta, and cyan when forming a full-color image, and the visible images of the respective colors are sequentially superimposed and transferred onto the abutting intermediate transfer belt 3. Thus, a full color image is formed.

FIG. 2 is a perspective view showing the intermediate transfer belt 3, and FIG.
1 to 3, the intermediate transfer belt 3 is stretched by a cleaning counter roller, a primary transfer roller 10 and a tension roller 6 in addition to the driving roller 5 and the tension roller 6, and is driven by a driving device (not shown). It is rotationally driven via a roller 5. The belt tension is applied to both sides of the tension roller 6 by a spring 12 in a direction to apply tension to the belt. The tension roller 6 in this example has an aluminum pipe shape with a diameter of 16 to 21 mm, and a flange 13 of Φ22 as shown in FIGS. 1 and 2 is press-fitted at both ends as a regulating member that regulates meandering of the belt.

  Materials used for the intermediate transfer belt 3 include PVDF (vinylidene fluoride), ETFE (ethylene-tetrafluoroethylene copolymer), PI (polyimide), PAI (polyamideimide), PC (polycarbonate), polyester, etc. A resin film-like endless belt is used by dispersing a conductive material such as black or ion conductive resin. In this embodiment, the thickness is 90 to 160 μm and the width is 230 mm to obtain a tensile elastic modulus of 1000 to 4500 M / A. The belt was used. However, the width can be freely set by the paper width or the like.

  Reference numeral 14 denotes a secondary transfer roller (see FIG. 1). The secondary transfer roller 14 is configured to have a diameter of 19 to 22 mm and a width of 222 mm (the width can be freely set by a paper width or the like) by covering an elastic body with a conductive material on a metal core metal such as SUS having a diameter of 6 mm. ing. As the material, a conductive roller, an electronic conductive type roller (EPDM) or the like is used. In this embodiment, a roller having a diameter of 20 mm and an Asker C hardness of 35 to 50 ° is used. The resistance value of the secondary transfer roller 14 is measured from the value of current flowing when the roller 14 is installed on a conductive metal plate and a voltage of 100 to 1 kV is applied between the metal core and the metal plate. Calculated. The transfer material P, which is a recording medium deposited and placed on the paper feed tray 15, is synchronized with the timing at which the leading edge of the toner image on the surface of the intermediate transfer belt 3 reaches the secondary transfer position by the paper feed roller 16 and the timing roller pair 17. Are fed. A toner image on the intermediate transfer belt 3 is transferred to the transfer material P by applying a predetermined transfer bias to the secondary transfer roller 14 from a high voltage power source (not shown). In the present embodiment, sheet feeding / conveying takes a vertical path. The transfer material P is separated from the intermediate transfer belt 3 by the curvature of the driving roller 5, and the toner image transferred to the transfer material P is fixed by the fixing device 18 and then discharged outside the apparatus.

  Reference numeral 19 denotes a transfer belt cleaning unit, which performs cleaning by scraping off toner remaining on the intermediate transfer belt 3 after secondary transfer by a cleaning blade 19a. As a material of the cleaning blade 19a, urethane rubber having a thickness of 1.5 to 3 mm and a rubber hardness of 65 to 80 ° is used, and is in contact with the intermediate transfer belt 3 by a counter. The transfer residual toner scraped off is stored in a transfer toner waste toner storage unit (not shown) through a toner conveyance path (not shown). Each roller that stretches the intermediate transfer belt 3 is supported from both sides of the intermediate transfer belt 3 by a transfer belt unit side plate (not shown).

  The image forming apparatus configured as described above is a light-reflective sensor in which the density and color positional image information of each color image transferred onto the intermediate transfer belt 3 is arranged to face the lower running side of the belt. 20 is read. At this time, in order to suppress the belt behavior and obtain stable and accurate data, a sheet metal backup member 21 that is in contact with the inner surface side of the intermediate transfer belt is disposed at a position facing the sensor. Further, as shown in FIGS. 3 and 4, a flock 22 is provided on the contact surface of the backup member 21 on the intermediate transfer belt 3 in order to reduce the frictional load on the belt.

  By the way, the flocks 22 are pushed by the intermediate transfer belt 3 that travels over time, and gradually fall down in one direction as shown in FIG. At this time, although the contact pressure with the intermediate transfer belt 3 is low at the waist of the flock 22, the conveyance load of the intermediate transfer belt 3 increases as the contact area increases. If this fall progresses by use, as shown in FIG. 6, the flock 22 will adhere | attach and will become rigid. In this state, the contact area of the bristles 22 with the intermediate transfer belt 3 further increases, so that the conveyance load also increases. Then, the backup member 21 vibrates in the direction of the arrow X in FIG. Further, the bristle-filled bristles 22 scrape the intermediate transfer belt 3 and easily transmit vibrations caused by stick-slip between the intermediate transfer belt 3 and the bristles 22. Further, since the bristle-filled flock 22 rubs only at the same portion of the intermediate transfer belt 3, adhesion of foreign matters increases, and the friction coefficient increases.

FIG. 7 is a graph for explaining the correlation between the belt travel distance and the belt driving torque.
The fall of the flock 22 progresses according to the travel distance of the intermediate transfer belt 3, and when reaching the point P1, the contact area between the flock 22 and the intermediate transfer belt 3 increases, and the torque value increases. Furthermore, when the belt travel by use advances and eventually reaches point P2, the state shown in FIG. 6 is reached, and abnormal noise is generated.

  At this time, it is known that if the intermediate transfer belt 3 is rotated in the direction opposite to the rotation direction at the time of image formation, the hair fall is recovered, but it is difficult to set the reverse rotation timing. The timing for reversely rotating the intermediate transfer belt 3 is too early in the state of FIG. 4 and too late in the state of FIG. Therefore, it is preferable that the state shown in FIG. 5 is slightly lowered.

FIG. 8 is a block diagram of the control unit of the present embodiment.
The drive roller 5 is provided with a torque detector 23 for detecting the rotational torque, and the torque value detected by the torque detector 23 is taken into the control unit 24. Further, the drive motor 25 of the drive roller 5 is switched not only on / off of drive but also forward / reverse switching by the control unit 24. Further, the control unit is configured to display a warning on the alarm unit 26 such as an operation panel (not shown) and notify the user when an abnormality occurs.

The controller 24 controls the reverse rotation of the intermediate transfer belt 3 based on the flowchart shown in FIG.
In FIG. 9, the driving torque of the belt driving unit of the intermediate transfer belt 3 is monitored (step A1), and it is determined whether the driving torque exceeds a threshold value (step A2). If the driving torque exceeds the threshold value, a recovery operation for recovering the fall of the flock 22 is performed (step A3).

  In such control, setting of a threshold value is important, and there are three methods for the setting. The first method is to derive and set the torque value when it reaches FIG. 5 from the experience side. If this method is the simplest setting method, it does not correspond to each machine individually, and in some cases, there is a possibility that the setting is inappropriate.

The second method is a preferable threshold value setting method in which such a problem is unlikely to occur, and will be described with reference to the flowchart of FIG.
In FIG. 10, the intermediate transfer belt 3 is rotationally driven (step 1B), and the driving torque of the belt drive unit of the intermediate transfer belt 3 is monitored (step 2B). Next, it is determined whether this rotation has passed a predetermined time from the previous rotation (step 3B). Note that the predetermined time is, for example, about 2 hours, and if it is stopped for about 2 hours, the flocked hair 22 that has fallen by the previous rotation has returned almost to its original state by its own restoring force. When step 1B is the rotation after the lapse of a predetermined time, the rotation is continued (step 4B), and then it is determined whether the increase in the rotational torque has stopped and converged (step 5B). When the increase in rotational torque converges, the torque value is measured at that time, and the amount of torque increase is determined from the difference between that value and the initial torque value at the start of rotation (step 6B). A threshold is set from the calculated increase amount (step 7B).

  If this threshold setting is represented by a graph, it is as shown in FIG. 11. When the rotation torque at the point A is measured and the rotation continues, for example, about 100 seconds elapse, the increase in torque almost converges at the point B. Therefore, the amount of increase is calculated from the difference between the point A and the point B, and since the vicinity of the point C is almost in the state shown in FIG. The threshold value is set as a C point torque value for a time corresponding to 60 to 70% of the increase amount, and the recovery operation is executed when the torque value exceeds the threshold value. In the example of FIG. 10, the B point is 100 seconds from the start of rotation, and the C point as a threshold value is set to the torque value at 60 to 70 seconds corresponding to 60 to 70% as the threshold value.

  Thus, when the threshold value for each device is set and the monitored torque value exceeds the threshold value, the hair transplantation 22 can be prevented from falling down and not close to the occurrence of abnormal noise by executing the recovery operation. .

  By the way, if it uses over time, the restoring force of the flock 22 will become dull, and even if it implements recovery operation, it will become difficult to fall a torque value. In such a case, when the decrease in the torque value after the recovery operation is small, the recovery operation time is lengthened, or the reverse rotation / forward rotation is repeated a plurality of times. When reverse rotation and forward rotation are repeated, it is possible to prompt the flock 22 to fall down in the reverse direction by ending the drive with reverse rotation at the end. It is also effective to apply heat to the inverted flock 22 as a method for recovering the fall of the flock 22. For example, a blower duct (not shown) passing through the fixing device 18 is provided at a position where the flock 22 is warmed. In this way, it is preferable that the temperature of the flock 22 is increased by using the heat of the fixing device.

If this control is shown in the drawing, the flowchart of FIG. 12 is obtained.
First, the recovery operation described in Step 3A of FIG. 9 is performed (Step 1C). The subsequent torque value is measured (step 2C), and the decreasing rate of the measured torque value is calculated (step 3C). It is determined whether the calculated decrease rate is equal to or less than the predetermined rate (step 4C). When the decrease rate is smaller than the predetermined rate, the enhanced recovery operation is performed (step 5C). That is, the enhanced recovery operation of extending the recovery operation time described above, repeating reverse rotation and normal rotation, and applying heat to the reversed hair transplantation 22 is performed.

  Further, if the torque value does not decrease sufficiently even if the time extension or reverse rotation is repeated, the threshold is reset according to the method of FIG. When such resetting is repeated, the B point that is the convergence value reaches the level at which abnormal noise occurs in FIG. At this time, a warning such as parts replacement is issued to the user via a display panel (not shown) or the like, assuming that the hair transplantation 22 is approaching or has reached the end of its life.

  FIG. 13 is a schematic configuration diagram of a color laser printer which is an image forming apparatus to which the present invention is applied. First, the overall configuration and operation of the color laser printer will be described with reference to FIG.

  As shown in FIG. 12, an image of different colors of cyan, magenta, yellow, and black corresponding to the color separation components of the color image is formed in the center of the apparatus body (image forming apparatus body) 1 of the color laser printer. Two image forming units 2C, 2M, 2Y, and 2K are provided. Each of the image forming units 2C, 2M, 2Y, and 2K includes photoconductors 4C, 4M, 4Y, and 4K as latent image carriers. Further, around the photosensitive member 4, a charging roller 7 as a charging unit for charging the surface thereof, and a developing device as a developing unit for supplying toner to the electrostatic latent image formed on the photosensitive member 4 and developing the toner. 9 and a cleaning blade 11 as a cleaning means for cleaning the surface of the photoreceptor 4.

  Above each of the image forming units 2C, 2M, 2Y, and 2K, an exposure device 8 is disposed as a latent image forming unit that forms an electrostatic latent image on the surface of each of the photoreceptors 4C, 4M, 4Y, and 4K. Yes. The exposure device 8 includes a light source, a polygon mirror, an f-θ lens, a reflection mirror, and the like, and irradiates the surface of each photoreceptor 4 with laser light based on image data.

  On the other hand, a transfer device for transferring a toner image onto a sheet as a recording medium is disposed below the image forming units 2C, 2M, 2Y, and 2K. The transfer device includes an endless conveyance belt 3 that conveys a sheet, and four transfer rollers 10. The conveyor belt 3 is stretched in a state where a predetermined tension is applied by the drive roller 5 and the support roller 6, and the conveyor belt 3 rotates counterclockwise as the drive roller 5 rotates. It is like that. The four transfer rollers 10 are in contact with the respective photoreceptors 4 via the conveyance belt 3. Thereby, each photoconductor 4 and the conveyance belt 3 are in contact with each other, and a transfer nip for transferring a toner image is formed between them. Each transfer roller 10 is connected to a power supply (not shown) so that a predetermined direct current voltage (DC) and / or alternating current voltage (AC) is applied to each transfer roller 9.

  In the lower part of the figure of the apparatus main body 1, a paper feed tray 15 that stores paper, a paper feed roller 16 that feeds paper from the paper feed tray 15, and the like are provided. Here, the paper P includes thick paper, postcard, envelope, plain paper, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, and the like. Further, an OHP sheet, an OHP film, or the like can be used as a recording medium.

  Further, a conveyance path R is provided in the apparatus main body 1 for discharging the paper from the paper feed tray 15 through the transfer nips of the image forming units 2C, 2M, 2Y, and 2K to the outside of the apparatus. ing. In this transport path, a pair of registration rollers 17 as timing rollers are disposed upstream of the image forming units 2C, 2M, 2Y, and 2K in the paper transport direction. On the other hand, a fixing device 18 for fixing the unfixed image transferred to the paper is disposed downstream of the image forming units 2C, 2M, 2Y, and 2K in the paper transport direction.

  A sensor 20 as a pattern detection unit is disposed at a position facing the outer peripheral surface of the transport belt 3. The sensor 20 is a reflective optical sensor and detects an image pattern formed on the conveyor belt 3 for detecting image density or detecting image position deviation. At this time, a sheet metal backup member 21 that is in contact with the inner surface of the belt 20 is disposed on the inner side of the conveyor belt 3 facing the sensor 20, and although not shown in the figure, the belt contact surface of the backup member 21 is disposed on the belt contact surface. A flock 22 is provided.

Subsequently, a basic operation of the printer according to the present embodiment will be described with reference to FIG.
When the image forming operation is started, the photoconductors 4C, 4M, 4Y, and 4K of the image forming units 2C, 2M, 2Y, and 2K are rotationally driven clockwise by a driving device (not shown), and the photoconductors 4C. The surfaces of 4M, 4Y, and 4K are uniformly charged to a predetermined polarity by the charging roller 7. Based on the image information of the original read by a reading device (not shown), the exposure device 8 irradiates the charged surface of each photoconductor 4 with laser light, and an electrostatic latent image is formed on the surface of each photoconductor 4. . At this time, the image information to be exposed on each photoconductor 4 is single-color image information obtained by separating a desired full-color image into cyan, magenta, yellow, and black color information. As the electrostatic latent image formed on the photosensitive member 4 is supplied with toner by each developing device 9, the electrostatic latent image is visualized (visualized) as a toner image.

  When the image forming operation is started, the conveyance belt 3 starts to rotate in the counterclockwise direction in the figure. Further, a constant voltage or a constant current controlled voltage having a polarity opposite to the charging polarity of the toner is applied to each transfer roller 10. Thereby, a transfer electric field is formed in the transfer nip. Further, the paper feed roller 16 starts to rotate, and the paper stored in the paper feed tray 15 is sent out to the transport path. The sheet sent to the conveyance path is timed by the registration roller 17 and is sent to the conveyance belt 3.

  When the paper is carried on the transport belt 3 and the paper passes through each transfer nip as the transport belt 3 rotates, the toner image on each photoconductor 4 is transferred to the transport belt by the transfer electric field formed in each transfer nip. 3 are sequentially superimposed and transferred onto the third sheet. Thus, a full color toner image is transferred to the paper. The toner on each photoconductor 4 that could not be transferred onto the paper is removed by the cleaning blade 11. Next, the surface of each photoconductor 4 is subjected to a static elimination action by a static elimination device (not shown), and the surface potential is initialized to prepare for the next image formation.

Thereafter, the sheet on which the toner image has been transferred is conveyed to the fixing device 18, where the toner image is fixed on the sheet by the fixing device 18, and then discharged outside the apparatus.
The above description is an image forming operation when a full-color image is formed on a sheet. A single-color image is formed using any one of the four image forming units 2C, 2M, 2Y, and 2K. Two or three image forming units can be used to form a two-color or three-color image.

  Further, when adjusting the density and positional deviation of each color image, the image forming units 2C, 2M, 2Y, and 2K function as a pattern forming unit that forms an image pattern for detection on the surface of the transport belt 3. Specifically, for image density detection, image position deviation detection, and the like on the respective photoreceptors 4 of the image forming units 2C, 2M, 2Y, and 2K, basically in the same manner as the image formation and image transfer described above. The image pattern formed on each photoconductor 4 is transferred onto the conveying belt 3 at the transfer nip position. When the image pattern reaches a position facing the sensor 20 as the conveyor belt 3 rotates, the sensor 20 detects the image pattern. Based on the detection information at this time, the image density, the image position, and the like are detected. It is corrected.

2 Image forming unit 3 Intermediate transfer belt 5 Drive roller 20 Sensor 21 Backup member 22 Flocking 23 Torque detector

Japanese Patent No. 4324515

Claims (9)

A belt that is stretched and rotated by a plurality of rollers, and a backup member that is disposed between the rollers, abuts against the inner surface of the belt, and has flocking on a side that abuts on the belt;
The rotational torque of the belt that rotates in a predetermined direction is monitored during an image forming operation, and when the rotational torque exceeds a certain threshold value, a recovery operation that recovers the fall of the flock is performed at times other than the image forming operation. In the image forming apparatus,
Measure the rotation torque value of the belt when it starts up from a standstill for a predetermined time or more, and the torque value when the rotation continues and the torque increase stops, and the amount of torque increase is calculated from the difference between the two torque values. The threshold value is set based on the increase amount.   2. The image forming apparatus according to claim 1, wherein when the recovery operation reaches the threshold value, the belt rotates in a reverse direction that rotates the belt in a direction opposite to a rotation direction during image formation. A belt that is stretched and rotated by a plurality of rollers, and a backup member that is disposed between the rollers, abuts against the inner surface of the belt, and has flocking on a side that abuts on the belt;
The rotational torque of the belt that rotates in a predetermined direction is monitored during an image forming operation, and when the rotational torque exceeds a certain threshold value, a recovery operation that recovers the fall of the flock is performed at times other than the image forming operation. In the image forming apparatus,
Measure the initial torque value recorded in the manufacturing process and the torque value when the rotation continues and the torque increase stops, determine the torque increase amount from the difference between both torque values, and set the threshold value from the increase amount An image forming apparatus. A belt that is stretched and rotated by a plurality of rollers, and a backup member that is disposed between the rollers, abuts against the inner surface of the belt, and has flocking on a side that abuts on the belt;
The rotational torque of the belt that rotates in a predetermined direction is monitored during an image forming operation, and when the rotational torque exceeds a certain threshold value, a recovery operation that recovers the fall of the flock is performed at times other than the image forming operation. In the image forming apparatus,
When the recovery operation reaches the threshold value, the recovery operation is a repetitive operation in which the belt rotates in the direction opposite to the rotation direction at the time of image formation, and then repeats normal rotation and reverse rotation, and the repetitive operation ends at the last reverse rotation. An image forming apparatus.   The image forming apparatus according to claim 4, wherein hot air is blown onto the flocked hair that has been reversely rotated. A belt that is stretched and rotated by a plurality of rollers, and a backup member that is disposed between the rollers, abuts against the inner surface of the belt, and has flocking on a side that abuts on the belt;
The rotational torque of the belt that rotates in a predetermined direction is monitored during an image forming operation, and when the rotational torque exceeds a certain threshold value, a recovery operation that recovers the fall of the flock is performed at times other than the image forming operation. In the image forming apparatus,
An image forming apparatus characterized in that, when a decrease in rotational torque after performing the recovery operation is small, the execution time of the recovery operation is lengthened. A belt that is stretched and rotated by a plurality of rollers, and a backup member that is disposed between the rollers, abuts against the inner surface of the belt, and has flocking on a side that abuts on the belt;
The rotational torque of the belt that rotates in a predetermined direction is monitored during an image forming operation, and when the rotational torque exceeds a certain threshold value, a recovery operation that recovers the fall of the flock is performed at times other than the image forming operation. In the image forming apparatus,
An image forming apparatus, wherein the threshold value is reset when the decrease in rotational torque after the recovery operation is small.   8. The image forming apparatus according to claim 4, wherein the threshold value is a preset fixed torque value. 9.   9. The image forming apparatus according to claim 1, wherein a second threshold value for issuing a warning prompting replacement is set when a certain value of the rotational torque of the belt monitored separately from the threshold value is reached. An image forming apparatus.

Images