JP2006145622A - Image forming apparatus and transfer position control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress, at a low cost, the fluctuation of an image position on a transfer material in case of a change in the circumferential length of the intermediate transfer belt of an image forming apparatus which transfers an image to the intermediate transfer belt having a tensioner and further transfers the image to a transfer material. <P>SOLUTION: A color shift detection sensor or density detection sensor 20 is disposed between a position beyond the range where a tension roller 19 moves in accordance with the fluctuation in the circumferential length of the belt and the position of a secondary transfer roller 18. Elongation of the intermediate transfer belt 12 is detected by measuring time needed for a lateral line as a circumferential detection mark on the intermediate transfer belt 12, formed by an exposure means, to be detected by the color shift detection sensor or density detection sensor 20, which is an optical sensor. Based upon the result of the detection, time needed for the transfer material to reach the nip of the secondary transfer roller 18 is adjusted. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus and a transfer position control method, and more particularly, to an image forming apparatus such as a color copying machine or a color printer having a configuration in which an image is transferred to an endless belt-shaped image carrier and further transferred to a transfer material. And a transfer position control method thereof.

  In a conventional image forming apparatus, an intermediate transfer belt unit is manufactured at a low cost, and the intermediate transfer belt unit is shortened in order to shorten the transport path from paper feed to paper discharge in order to reduce the overall size of the apparatus and shorten the first printout time. The unit has a biaxial configuration with the minimum number of stretches, and is configured to perform secondary transfer on one end side of an intermediate transfer belt having a biaxial configuration. For this reason, the opposing roller of the secondary transfer roller is a drive roller, and the other end is a tension roller. For example, the image forming apparatus disclosed in Patent Document 1.

  Further, in the image forming apparatus disclosed in Patent Document 1, since the transfer material conveyance direction in the secondary transfer roller portion is a direction from the lower paper feed cassette to the upper paper discharge tray, the intermediate transfer belt has a tension after the primary transfer. The process proceeds to the secondary transfer roller via the roller, and the belt length from the primary transfer to the secondary transfer is substantially equal to the belt circumferential length.

  Hereinafter, a conventional image forming apparatus will be described with reference to FIG. 1 is a paper feed cassette, 2 is a paper feed roller, 3 is a registration roller, 4 is a fixing device, 5 is a paper discharge roller, and 6 is a paper discharge tray. The photosensitive drums 7 to 10 are exposed by 11 laser scanners, and develop yellow, magenta, cyan, and black toners by developing means (not shown), respectively. The intermediate transfer belt 12 is brought into contact with the photosensitive drums 7 to 10 by primary transfer rollers 13 to 16 and rotates in the direction of arrow A in the figure. The intermediate transfer belt 12 has a biaxial configuration, and a driving roller 17 is disposed opposite to the secondary transfer roller 18. The tension roller 19 applies tension to the intermediate transfer belt 12, and the belt material is mainly PI (polyimide) from the viewpoint of durability and transferability.

  Further, the optical sensor 20 detects toner on the intermediate transfer belt 12 at a position where the vibration of the belt surface is suppressed by the backup rollers 20-B1 and 20-B2, and based on the density and the time until the detection, The amount of color misregistration is detected.

  Next, the operation will be described. The transfer material fed from the paper feed cassette 1 by the paper feed roller 2 is conveyed to the registration roller 3 at the leading end and temporarily stops. Here, the intermediate transfer belt 12 driven by the driving roller 17 runs around the toner on the photosensitive drums 7 to 10 which is exposed by the laser scanner 11 and then developed, and travels in the direction of arrow A in the figure to sequentially perform primary transfer. The image is transferred onto the intermediate transfer belt 12 by the rollers 13-16. The registration roller 3 is rotated in accordance with the transferred image on the intermediate transfer belt 12, and the temporarily stopped transfer material is conveyed to the nip of the secondary transfer roller 18. The transfer material to which the image has been transferred is fixed on the image by the fixing device 4 and is discharged onto the discharge tray 6 by the discharge roller 5.

  Next, a method for conveying the transfer material to the nip of the secondary transfer roller in accordance with the image on the intermediate transfer belt 12 will be described. The transfer material reaches the nip of the secondary transfer roller 18 at the time when the image on the intermediate transfer belt 12 reaches the nip of the secondary transfer roller 18 with reference to the exposure start of the photosensitive drum 7 of the laser scanner 11 as a reference. By rotating the registration roller 3, the image on the intermediate transfer belt 12 is transferred to an appropriate position on the transfer material. In the case of an in-line image forming apparatus using the intermediate transfer belt 12, the above-described method is generally used as a method for aligning the image on the intermediate transfer belt 12 and the position of the transfer material.

Japanese Patent Laid-Open No. 2000-162891 (see page 4, FIG. 1)

  However, PI, which is an intermediate transfer belt material, is very expensive, and other materials such as PET (polyethylene terephthalate) and PVDF (polyvinylidene fluoride) may be used to reduce the cost of the image forming apparatus. It becomes the solution. When the belt material is changed to PET or PVDF in the conventional example, the distance from the primary transfer to the secondary transfer is long as described above, and the tension roller is arranged between them, and the start of exposure to the photosensitive drum of the laser scanner is a reference. In addition, since the transfer material is conveyed to the secondary transfer and the image on the belt is aligned with the position of the transfer material, there are the following problems.

  Compared to PI, the linear expansion coefficients of PET and PVDF are large, and the degree of fluctuation of the belt circumferential length is large for the same temperature change. Further, in the conventional example, since the distance from the primary transfer to the secondary transfer is long, the absolute value of the circumference variation amount becomes large.

  1. As a result of the above, since the circumference variation is absorbed by the movement of the tension roller due to the tension roller arrangement, the distance from the primary transfer to the secondary transfer is increased by the circumference variation amount.

  2. As a result, and the above-described conveyance control is performed, the position of the image on the belt and the transfer material is deviated before and after the belt circumference variation.

  An object of the invention related to the present application is to provide an image forming apparatus capable of aligning the position of the transfer material and the image regardless of the belt material, and capable of forming a good image at a low cost, and a transfer position control method thereof. Is to provide.

  In order to achieve the above object, according to one aspect of the present invention, an endless belt-like image carrier whose circumference is changed by being maintained at a predetermined tension, and an image transferred to the image carrier are transferred. In an image forming apparatus comprising a transfer means for transferring to a material and a transport means for transporting the transfer material to the transfer means, the image carrier that is driven to rotate at a predetermined peripheral speed is used for detecting a change in circumference. Marking means for transferring the mark, mark detection means for detecting the mark on the image carrier, the transfer timing, the detected timing, the peripheral speed of the image carrier, and the marking means Control means for controlling the rotation timing of the image carrier so as to compensate for the change in the circumference and transfer the image to a desired position of the transfer material based on the positions of the mark detection means and the transfer means; Provided image recording device To provide.

  Apart from this, the present invention is an endless belt-shaped image carrier that is maintained at a predetermined tension by a tension means and is driven to circulate at a predetermined peripheral speed, and is upstream of the tension means in the rotation direction. An image carrier on which an image formed by the image forming means at the first position is primarily transferred, a transport means for transporting the transfer material to a second position downstream of the pulling means, and the image on the transfer material. An image forming apparatus comprising: a transfer unit that secondarily transfers a primary transfer image on a carrier at a second position; and a mark for detecting a change in circumference of the image carrier at a predetermined timing. Marking means to be formed on the image sensor and a third position downstream of the tensioning means in the circumferential direction and upstream of the second position and spaced apart from the second position by a predetermined distance. Until the mark transferred to the body reaches Detecting means for detecting a gap between the detection result and the second and third positions so as to compensate for the change in circumference between the first and second positions and transfer the image to a desired position of the transfer material. The image recording apparatus may include a control unit that controls the rotation timing of the image carrier based on the control unit.

  Apart from this, the present invention is an endless belt-shaped image carrier that is maintained at a predetermined tension by a tension means and is driven to circulate at a predetermined peripheral speed, and is upstream of the tension means in the rotation direction. An image carrier on which an image formed by the image forming means at the first position is primarily transferred, a transport means for transporting the transfer material to a second position downstream of the pulling means, and the image on the transfer material. In a transfer position control method of an image forming apparatus comprising a transfer means for secondary transfer of a primary transfer image on a carrier at a second position, a mark for detecting a change in circumference of the image carrier is set at a predetermined timing. A step of forming the image forming unit at a third position that is downstream of the pulling unit in the circumferential direction and upstream of the second position and separated from the second position by a predetermined distance; The mark transferred to the image carrier A step of detecting a time until the image is transferred, and the detection result and the second and third so as to compensate for the change in the circumference between the first and second positions and transfer the image to a desired position of the transfer material. And a step of controlling the turning timing of the image carrier based on the position.

  Apart from this, the present invention is an endless belt-like image carrier that is maintained at a predetermined tension by a tension means and is driven to circulate at a predetermined peripheral speed, and is upstream of the tension means in the circulation direction. An image carrier on which an image formed by the image forming means at the first position is primarily transferred, a transport means for transporting the transfer material to a second position downstream of the pulling means, and the image on the transfer material. An image forming apparatus comprising: a transfer unit that secondarily transfers a primary transfer image on a carrier at a second position; and a mark for detecting a change in circumference of the image carrier at a predetermined timing. The marking means to be formed on the image carrier and the tension means for stretching the image carrier are moved in the pulling direction, and the position on the image carrier is moved to the position of the tension means after the movement. Detection means for detecting the time until the mark arrives; The image recording apparatus may further include a control unit configured to control a rotation timing of the image carrier based on the detection result so as to compensate for a change in circumference and transfer the image to a desired position of the transfer material. .

  Apart from this, the present invention is an endless belt-shaped image carrier that is maintained at a predetermined tension by a tension means and is driven to circulate at a predetermined peripheral speed, and is upstream of the tension means in the rotation direction. An image carrier on which an image formed by the image forming means at the first position is primarily transferred, a transport means for transporting the transfer material to a second position downstream of the pulling means, and the image on the transfer material. In a transfer position control method of an image forming apparatus comprising a transfer means for secondary transfer of a primary transfer image on a carrier at a second position, a mark for detecting a change in circumference of the image carrier is set at a predetermined timing. The image forming unit forms the mark on the image carrier at the position of the pulling unit after the movement following the movement of the image carrying member in the pulling direction by the pulling unit. Detecting the time to reach, Controlling the rotation timing of the image carrier based on the detection result so as to compensate for the change in the circumference between the position and the first position and transfer the image to the desired position of the transfer material. It may be a transfer position control method.

  Apart from this, the present invention provides an endless belt-like image carrier that is stretched by a tensioning means at a first position and maintained at a predetermined tension and is driven to rotate at a predetermined peripheral speed, and a second position. In the image forming apparatus, a transfer unit that transfers the transfer material to the transfer material and a transfer unit that transfers the image transferred to the image support to the transfer material at a second position. Marking means for transferring a mark for detecting a change in length to the image carrier; and a downstream side of the first position and an upstream side of the second position in the circumferential direction of the image carrier. Mark detecting means disposed at a predetermined position spaced apart from the second position, and compensating for the circumferential change between the first position and the predetermined position so as to transfer the image to the desired position of the transfer material. The timing at which the mark detection means detects the mark and the predetermined distance Orbiting timing of the image carrying body Hazuki may be an image recording apparatus and control means for controlling.

  Apart from this, the present invention provides an endless belt-like image carrier that is stretched by a tensioning means at a first position and maintained at a predetermined tension and is driven to rotate at a predetermined peripheral speed, and a second position. In the transfer position control method of an image forming apparatus, comprising: a transfer unit that transfers a transfer material to the transfer material; and a transfer unit that transfers an image transferred to the image carrier to the transfer material at a second position. A step of transferring a mark for detecting a change in the circumference of the carrier to the image carrier; and a downstream side of the first position and an upstream side of the second position in the circulation direction of the image carrier. A detecting step for detecting the mark at a predetermined position separated from the second position by a predetermined distance; and compensating for the change in the circumferential length between the first position and the predetermined position, and an image at a desired position of the transfer material. The timing of detecting the mark in the detection step so as to transfer And it may be a transfer position control method and a step of controlling the circulating time of the image-bearing member on the basis of the predetermined distance.

  As described above, according to the present invention, it is possible to keep the position of the image on the transfer material constant even if the circumference of the endless belt-like image carrier varies, and the transfer position accuracy can be improved. It is possible to improve. Further, by using an inexpensive optical sensor as the mark detection means, or serving as a color misregistration detection sensor or a density detection sensor, it is possible to improve the transfer position accuracy without increasing the cost.

Example 1
Embodiment 1 of an image forming apparatus according to the present invention will be described below with reference to FIG. Since Example 1 is the same as the apparatus configuration of the conventional example, a control system performing different control is illustrated, and the control will be described in the order of operation. This control is performed by the time detection unit 100, the calculation unit 110, and the motor control unit 120 realized by a CPU or the like.

  First, the photosensitive member 7 is exposed by a laser scanner 11, and a horizontal line, which is a circumference detection mark, is developed with yellow toner by a developing unit. Transfer is performed by the roller 13. Next, from the start of exposure, the yellow circumference detection mark transferred onto the intermediate transfer belt 12 is an optical sensor 20 for detecting the circumference detection mark (the toner density and color deviation on the intermediate transfer belt 12 are detected). The time t until it is detected is also measured. Since the time from the start of exposure to the primary transfer is uniquely determined by the process conditions, the time from the primary transfer may be measured. Since the time t measured by the optical sensor 20 is a time including the influence of expansion / contraction of the intermediate transfer belt 12, the intermediate time from the position where the optical sensor 20 is arranged to the nip of the secondary transfer roller 18 is measured at the measurement time t. The total travel time of the transfer belt 12 accurately represents the time T required to reach the secondary transfer roller 18 from the primary transfer roller 13 in that state.

  Thereafter, as in the conventional example, the leading edge of the transfer material is conveyed to the registration roller 3 as a conveying means and is temporarily stopped. Thereafter, based on the time T calculated from the measurement result, the rotation of the registration roller 3 is controlled in accordance with the timing at which the image on the intermediate transfer belt 12 reaches the nip of the secondary transfer roller 18, and the transfer material is transferred to the secondary transfer roller. It is conveyed to 18 nips.

  The transfer material onto which the image has been transferred at the nip portion of the secondary transfer roller 18 is fixed with the image and discharged onto a discharge tray as in the conventional example.

  As described above, according to the present embodiment, the circumferential length variation due to the expansion and contraction of the intermediate transfer belt 12 is absorbed by the tension roller portion, and the optical sensor 20 is disposed downstream thereof. For this reason, the distance from the optical sensor 20 to the nip of the secondary transfer roller 18 is constant even if the belt circumferential length varies, and the portion where the belt circumferential length varies varies based on the measurement result of the optical sensor 20. Therefore, it is possible to accurately maintain the image position on the transfer material at a desired position. At this time, the measurement accuracy can be increased by measuring the time from the exposure of the yellow first station farthest from the optical sensor 20 (the most upstream) or the time from the primary transfer. The installed optical sensor 20 is a sensor that is originally used to measure the amount of color misregistration, and can be implemented without increasing new costs.

  In addition, the time measurement by the optical sensor is executed once before the start of one print job, or when one print job corresponds to several hundred sheets, for example, it is executed at a predetermined time interval between sheets during continuous printing. In addition, it is possible to cope with fluctuations in the belt circumference due to the temperature rise in the machine. It may be executed whenever the temperature inside the apparatus is detected and the temperature rises by a certain level. Moreover, since it is a dual-purpose sensor, it can also be performed when detecting the amount of color shift or density.

  In addition, since the measurement time t or the time T required to reach the secondary transfer roller 18 from the primary transfer roller 13 is stored in the nonvolatile memory, it is not necessary to perform the circumference detection every time the power is turned on.

(Example 2)
A second embodiment according to the present invention will be described below with reference to FIGS. Since the second embodiment is different from the first embodiment in the arrangement around the optical sensor, different portions will be described in detail.

  In FIG. 2, the intermediate transfer belt 12 is constituted by two axes of a driving roller 17 and a tension roller 19, and primary transfer rollers 13 to 16 are disposed at portions where the intermediate transfer belt 12 contacts the photosensitive drums 7 to 10. Yes. Reference numeral 22 denotes an optical sensor.

  As shown in detail in FIG. 3, the tension roller 19 is biased leftward in the drawing by a spring 31, and this tensioner gives the intermediate transfer belt 12 a constant tension. The optical sensor 22 is held movably following the movement of the tensioner. That is, the optical sensor 22 is fixed to the support member 30 engaged with the support shaft 19a of the tension roller 19, and an optical image on the belt surface can be detected using the tension roller 19 as a backup roller.

  Next, the operation will be described. As in the first embodiment, the photosensitive member 7 is exposed by the most upstream laser scanner 11-1, and the horizontal line that is a circumference detection mark is developed with yellow toner by a developing means (not shown), and is indicated in the direction of arrow A in the figure. The toner image is transferred by the primary transfer roller 13 onto the intermediate transfer belt 12 that has run around. Next, the time t from the start of exposure until the horizontal line, which is a yellow circumference detection mark transferred onto the intermediate transfer belt 12, is detected by the optical sensor 22, is measured. Since the time from the start of exposure to the primary transfer is uniquely determined by the process conditions, the time from the primary transfer may be measured. Unlike the conventional example 1, the time measured by the optical sensor 20 is not measured at a position where all the expansion and contraction of the intermediate transfer belt 12 is absorbed. Therefore, the time including all the expansion and contraction of the intermediate transfer belt 12 is included. is not. However, since the measurement is performed on the tensioner 19, the position of the tensioner 19 can be calculated from the measured time, and the circumference of the intermediate transfer belt 12 can be calculated from the calculated position. Similarly to Conventional Example 1, it is possible to calculate the time T to reach from the primary transfer roller 13 to the secondary transfer roller 18 including expansion and contraction of the intermediate transfer belt 12.

  Thereafter, as in the conventional example, the leading edge of the transfer material is conveyed to the registration roller 3 as a conveying means and is temporarily stopped. Thereafter, based on the time T calculated from the measurement result, the rotation of the registration roller 3 is controlled in accordance with the timing at which the image on the intermediate transfer belt 12 reaches the nip of the secondary transfer roller 18, and the transfer material is transferred to the secondary transfer roller. It is conveyed to 18 nips.

  The transfer material onto which the image has been transferred at the nip portion of the secondary transfer roller 18 is fixed with the image and discharged onto a discharge tray as in the conventional example.

  As described above, according to this embodiment, the circumferential length variation due to the expansion and contraction of the intermediate transfer belt 12 is absorbed by the tension roller portion, and the optical sensor 22 is disposed in the tension roller portion. For this reason, it is possible to calculate the time from the primary transfer roller to the nip of the secondary transfer roller 18 without the need to provide a separate backup roller at a position where all the fluctuation of the belt circumference is absorbed. Thus, the image position on the transfer material can be accurately maintained at a desired position without increasing the cost.

(Example 3)
A third embodiment according to the present invention will be described below with reference to FIG. Since the third embodiment is different from the first embodiment only in the control system, only different portions will be described. The control of this embodiment is performed by a horizontal line detection unit 140 and a motor control unit 120 realized by a CPU or the like.

  The optical sensor 20 that also serves as a sensor for detecting the toner density and color misregistration on the intermediate transfer belt 12 exceeds the range in which the tension roller 19 moves in accordance with fluctuations in the belt circumferential length, as in Conventional Example 1. Arranged between the secondary transfer rollers 18.

  Next, the operation will be described. Prior to the image to be actually printed, the photosensitive member 7 is exposed by the laser scanner 11, and the horizontal line which is a circumferential detection mark for sensor detection is developed by the developing means with yellow toner. In the figure, the image is transferred by the primary transfer roller 13 onto the intermediate transfer belt 12 circulated in the direction of arrow A in the figure. This horizontal line, which is a circumference detection mark for sensor detection, is located at a position where the transfer material reaches the nip of the secondary transfer roller 18 according to the image when the transfer material that has been temporarily stopped when detected by the optical sensor is restarted. Transcript. As a result, the registration roller 3 is rotated with the optical sensor 20 detecting a horizontal line that is a circumference detection mark for sensor detection as a trigger, and the transfer material is restarted, regardless of the expansion and contraction of the intermediate transfer belt 12. It is possible to always keep the position of the image on the transfer material at an appropriate position.

(Other)
As described above, the present invention can be applied to a system composed of a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.) but also to an apparatus composed of a single device (for example, a copying machine, a facsimile machine). May be.

  In addition, a program code of software for realizing the functions of the embodiment is provided in an apparatus or a computer in the system connected to the various devices so as to operate the various devices so as to realize the functions of the above-described embodiments. What is implemented by operating the various devices in accordance with a program stored in a computer (CPU or MPU) of the system or apparatus supplied is also included in the scope of the present invention.

  Further, in this case, the program code of the software itself realizes the functions of the above-described embodiments, and the program code itself and means for supplying the program code to the computer, for example, a storage storing the program code The medium constitutes the present invention.

  As a storage medium for storing the program code, for example, a floppy (registered trademark) disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.

  Further, by executing the program code supplied by the computer, not only the functions of the above-described embodiments are realized, but also the OS (operating system) in which the program code is running on the computer, or other application software, etc. It goes without saying that the program code is also included in the embodiment of the present invention even when the functions of the above-described embodiment are realized in cooperation with the embodiment.

  Further, after the supplied program code is stored in a memory provided in a function expansion board of a computer or a function expansion unit connected to the computer, a CPU provided in the function expansion board or function storage unit based on an instruction of the program code However, it is needless to say that the present invention also includes a case where the function of the above-described embodiment is realized by performing part or all of the actual processing.

1 is a diagram illustrating a cross section and a control system of an image forming apparatus according to a first embodiment of the present invention. It is a figure showing the cross section and control system of the image forming apparatus concerning 2nd Example of this invention. FIG. 6 is a view showing the vicinity of a tensioner of an image forming apparatus according to a second embodiment of the present invention. It is a figure showing the cross section and control system of the image forming apparatus concerning the 3rd Example of this invention. 2 is a diagram illustrating a cross section and a control system of the image forming apparatus. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Paper feed cassette 2 ... Paper feed roller 3 ... Registration roller 4 ... Fixing device 5 ... Paper discharge roller 6 ... Paper discharge tray 7-10 ... Photosensitive drum 11 ... Laser scanner 12 ... Middle Transfer belt 13 to 16 ... Primary transfer roller 17 ... Drive roller 18 ... Secondary transfer roller 19 ... Tension roller 20 ... Optical sensors 20-B1, 20-B2 ... Backup roller 22 ... Optical sensor 23 ... …… Discharge roller

Claims (13)

An endless belt-shaped image carrier that changes its circumference by maintaining a predetermined tension, a transfer means for transferring an image transferred to the image carrier to a transfer material, and the transfer material In an image forming apparatus including a conveying unit that conveys to a transfer unit,
Marking means for transferring a mark for detecting a change in circumference to the image carrier that is driven to circulate at a predetermined circumferential speed;
Mark detection means for detecting the mark on the image carrier;
Based on the transfer timing, the detected timing, the peripheral speed of the image carrier, and the positions of the marking means, the mark detection means, and the transfer means, the change in the peripheral length is compensated for and the transfer material An image recording apparatus comprising: a control unit that controls a turning timing of the image carrier so that an image is transferred to a desired position. An endless belt-shaped image carrier that is maintained at a predetermined tension by a pulling unit and is driven to rotate at a predetermined peripheral speed, and is an image forming unit at a first position upstream of the pulling unit in the rotating direction. An image carrier on which an image formed by the image is primarily transferred, a conveyance unit that conveys a transfer material to a second position downstream of the tension unit, and a primary transfer image on the image carrier on the transfer material. In an image forming apparatus provided with a transfer means for secondary transfer at a second position,
Marking means for causing the image forming means to form a mark for detecting a change in the circumference of the image carrier at a predetermined timing; and
The mark transferred to the image carrier at a third position downstream of the pulling means and upstream of the second position and spaced apart from the second position by a predetermined distance in the circumferential direction. Detecting means for detecting the time until the
Based on the detection result and the second and third positions, the image carrier is compensated so as to compensate for the circumference change between the first and second positions and transfer the image to a desired position of the transfer material. An image recording apparatus comprising: a control unit that controls the circulation timing. An endless belt-shaped image carrier that is maintained at a predetermined tension by a pulling unit and is driven to rotate at a predetermined peripheral speed, and is an image forming unit at a first position upstream of the pulling unit in the rotating direction. An image carrier on which an image formed by the image is primarily transferred, a conveyance unit that conveys a transfer material to a second position downstream of the tension unit, and a primary transfer image on the image carrier on the transfer material. In an image forming apparatus provided with a transfer means for secondary transfer at a second position,
Marking means for causing the image forming means to form a mark for detecting a change in the circumference of the image carrier at a predetermined timing; and
Detection means for detecting the time until the mark on the image carrier reaches the position of the tension means after the movement following the movement of the image carrier in the pulling direction by the tension means. When,
Control means for controlling the rotation timing of the image carrier based on the detection result so as to compensate for the change in circumference between the position and the first position and transfer the image to a desired position of the transfer material; An image recording apparatus comprising: The detection means for detecting the time to reach is a means for urging a tension roller in the pulling direction, a support member fixed to the tension roller, a mark detection means fixed to the support member, Computing means,
The calculation means calculates the circumference change based on the time until the detection means detects the mark on the image carrier, and until the arrival based on the change and the second position. The image recording apparatus according to claim 3, wherein time is calculated. An endless belt-shaped image carrier that is stretched by a tensioning means at a first position and maintained at a predetermined tension and is driven at a predetermined peripheral speed, and a conveying means that conveys a transfer material to a second position And an image forming apparatus comprising: a transfer unit that transfers the image transferred to the image carrier to the transfer material at a second position;
Marking means for transferring a mark for detecting a change in circumference of the image carrier to the image carrier;
Mark detection means disposed at a predetermined position downstream of the first position and upstream of the second position and spaced apart from the second position by a predetermined distance in the circumferential direction of the image carrier. ,
Based on the timing at which the mark detection unit detects the mark and the predetermined distance, the image is transferred to a desired position on the transfer material by compensating for the change in the circumference between the first position and the predetermined position. An image recording apparatus comprising: a control unit that controls the rotation timing of the carrier.   The image forming apparatus according to claim 1, wherein the marking unit transfers the mark at the start of one print job.   The image forming apparatus according to claim 6, wherein the marking unit further transfers the mark a plurality of times at a predetermined time interval corresponding to the size of the job during one print job.   The image forming apparatus according to claim 1, wherein the mark detection unit is an optical sensor.   The image forming apparatus according to claim 1, wherein the mark detection unit also serves as a color misregistration detection sensor or a density detection sensor.   The image forming apparatus according to claim 1, further comprising a storage unit that stores a detection result of the detection unit. An endless belt-shaped image carrier that is maintained at a predetermined tension by a pulling unit and is driven to rotate at a predetermined peripheral speed, and is an image forming unit at a first position upstream of the pulling unit in the rotating direction. An image carrier on which an image formed by the image is primarily transferred, a conveyance unit that conveys a transfer material to a second position downstream of the tension unit, and a primary transfer image on the image carrier on the transfer material. In a transfer position control method of an image forming apparatus comprising a transfer means for performing secondary transfer at a second position,
Causing the image forming means to form a mark for detecting a change in the circumference of the image carrier at a predetermined timing;
The mark transferred to the image carrier at a third position downstream of the pulling means and upstream of the second position and spaced apart from the second position by a predetermined distance in the circumferential direction. Detecting the time to reach,
Based on the detection result and the second and third positions, the image carrier is compensated so as to compensate for the change in the circumference between the first and second positions and transfer the image to a desired position of the transfer material. A transfer position control method comprising: a step of controlling rounding timing. An endless belt-shaped image carrier that is maintained at a predetermined tension by a pulling unit and is driven to rotate at a predetermined peripheral speed, and is an image forming unit at a first position upstream of the pulling unit in the rotating direction. An image carrier on which an image formed by the image is primarily transferred, a conveyance unit that conveys a transfer material to a second position downstream of the tension unit, and a primary transfer image on the image carrier on the transfer material. In a transfer position control method of an image forming apparatus comprising a transfer means for performing secondary transfer at a second position,
Causing the image forming means to form a mark for detecting a change in the circumference of the image carrier at a predetermined timing;
Following the movement of the image carrier in the pulling direction by the tension means, and detecting the time until the mark on the image carrier reaches the position of the tension means after the movement; ,
Controlling the rotation timing of the image carrier based on the detection result so as to compensate for the change in circumference between the position and the first position and transfer the image to a desired position of the transfer material. A transfer position control method comprising: An endless belt-shaped image carrier that is stretched by a tensioning means at a first position and maintained at a predetermined tension and is driven at a predetermined peripheral speed, and a conveying means that conveys a transfer material to a second position And a transfer position control method of an image forming apparatus comprising: a transfer unit that transfers the image transferred to the image carrier to the transfer material at a second position;
Transferring a mark for detecting a change in circumference of the image carrier to the image carrier;
A detection step of detecting the mark at a predetermined position downstream of the first position and upstream of the second position and spaced apart from the second position by a predetermined distance in the circumferential direction of the image carrier; ,
Based on the timing at which the mark was detected in the detection step and the predetermined distance, the image carrier is compensated so as to compensate for the change in the circumferential length between the first position and the predetermined position and transfer the image to the desired position of the transfer material. And a step of controlling the rotation timing of the holder.

Images