JP2012014070A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device that is capable of setting the surface speed of a recording member on an image carrier side to substantially the same surface speed as that of an image carrier even when a thick recording member is conveyed to a transfer nip, and allows reduction of a cost of the device.SOLUTION: When a paper thickness t detected by a paper thickness detection sensor 71 is a thick paper (t>t1) (YES in S3), an intermediate transfer motor 111 is controlled so that the driving current value of a transfer motor 112 is "a" (S7). In contrast, when the detected paper thickness t is a plain paper (t2<t≤t1)(S3YES,S4 NO), the intermediate transfer motor 111 is controlled so that the driving current value of the transfer motor 112 is "b" (S5). Further, when the detected paper thickness t is a thin paper (t≤t2)(S3YES,S4YES), the intermediate transfer motor 111 is controlled so that the driving current value of the transfer motor 112 is "c" (S6).

Description

  The present invention relates to an image forming apparatus such as a printer, a facsimile machine, and a copying machine.

  2. Description of the Related Art Conventionally, a transfer roller that is a transfer member that forms a transfer nip by contacting a surface of an image carrier such as a photoconductor or an intermediate transfer belt is provided, and a toner image on the image carrier is transferred to a recording member that has been conveyed to the transfer nip. An image forming apparatus for transferring the image is known.

  Patent Document 1 describes an image forming apparatus provided with a cleaning blade that contacts the surface of a transfer roller and scrapes off dirt such as toner adhering to the transfer roller. In this image forming apparatus, a load impeding the rotation is applied to the transfer roller by the contact of the cleaning blade, and therefore the transfer roller cannot be driven to rotate by following the image carrier. For this reason, the transfer roller is driven to rotate.

  In order to satisfactorily transfer the toner image on the image carrier to the recording member, it is desirable that the conveyance speed of the recording member is substantially the same as the surface velocity of the image carrier. However, the surface speed of the image carrier and the surface speed of the transfer roller vary depending on individual component variations and the environment (temperature / humidity) such as the outer diameter of the transfer roller. As a result, the surface speed of the transfer roller is different from the surface speed of the image carrier. If the surface speed of the transfer roller is different from the surface speed of the image carrier, the recording member transported to the transfer nip is affected by the surface speed of the transfer roller, and the transport speed of the recording member becomes equal to the surface speed of the image carrier. It will differ, and abnormal images, such as a magnification fluctuation, will arise.

  Patent Document 2 describes an image forming apparatus that controls the rotation speed of a transfer roller as follows. During the pre-rotation before the recording member is conveyed to the transfer nip, the transfer roller is rotated at a predetermined rotation speed, the torque of the transfer roller is detected, and the surface speed of the image carrier is determined based on the detection result. And the rotation speed of the transfer roller are controlled so that the surface speed of the transfer roller becomes the same. When the surface speed at the transfer nip of the image carrier is higher than the surface speed at the transfer nip of the transfer roller, the transfer roller receives driving assistance from the image carrier, and the torque of the transfer roller decreases. Therefore, in this case, the surface speed at the transfer nip of the transfer roller can be made substantially the same as the surface speed at the transfer nip of the image carrier by performing control to increase the rotation speed of the transfer roller. On the other hand, when the surface speed at the transfer nip of the image carrier is lower than the surface speed at the transfer nip of the transfer roller, the torque of the transfer roller increases because the image carrier acts like a brake. Therefore, in this case, the surface speed at the transfer nip of the transfer roller can be made substantially the same as the surface speed at the transfer nip of the image carrier by performing control to reduce the rotation speed of the transfer roller. Further, since only the means for detecting the torque of the transfer roller need be provided, means for detecting the rotation speed of the image carrier and means for detecting the rotation of the transfer roller are provided, Compared with the case where the rotation speed of the transfer roller is controlled to be substantially the same, the apparatus can be made inexpensive.

  However, even if the rotational speed of the transfer roller is controlled as described in Patent Document 2 and the surface speeds of the transfer roller and the image carrier are substantially the same, the magnification of the image varies depending on the thickness of the recording member. There was a problem. As a result of earnest research on this subject, the present applicant has found the following. That is, when a thick recording member is conveyed to the transfer nip, even if the surface speeds of the transfer roller and the image carrier are substantially the same, the surface speed of the recording member on the image carrier side is higher than the surface speed of the image carrier. I knew it would be faster. The reason why the surface speed of the recording member on the side of the image carrier becomes faster than the surface speed of the image carrier when the thick recording member is conveyed to the transfer nip is as follows. When the surface speed of the image carrier and the surface speed of the transfer roller are different, the applicant has confirmed through experiments that the recording member is conveyed at substantially the same speed as the surface speed of the transfer roller. . For this reason, the conveyance speed of the recording member in the transfer nip depends more on the surface speed of the transfer roller than the surface speed of the image carrier, and the recording member moves following the rotation of the transfer roller in the transfer nip. It is thought that. If the recording member is thick, the distance from the rotation center of the transfer roller to the surface of the recording member on the image carrier side is increased. As a result, the surface speed of the recording member on the image carrier side in the transfer nip becomes faster than the surface speed of the transfer roller in the transfer nip. As a result, when the rotation speed of the transfer roller is controlled so that the surface speed of the transfer roller before the recording member is sandwiched by the transfer nip and the surface speed of the image carrier are the same, The surface speed of the thick recording member on the image carrier side becomes faster than the surface speed of the image carrier.

  Thus, in order to make the surface velocity of the recording member on the image carrier side equal to the surface velocity of the image carrier, the applicant of the present invention is based on the thickness of the recording member and the image carrier and transfer roller in the transfer nip. It has been found that it is necessary to give a predetermined speed difference to the surface speed.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus capable of obtaining the following two effects. That is, the first is that even when a thick recording member is conveyed to the transfer nip, the surface speed of the recording member on the image carrier side can be made substantially the same as the surface speed of the image carrier. Second, a means for detecting the rotational speed of the image carrier and a means for detecting the rotational speed of the transfer member are provided, and the surface speed at the transfer nip of the transfer member and the surface speed at the transfer nip of the image carrier are The apparatus can be made cheaper than that in which the speed difference between the two is controlled to a predetermined value.

In order to achieve the above object, an invention according to claim 1 is directed to an image carrier, a transfer member that contacts the image carrier to form a transfer nip, and an image carrier drive unit that rotationally drives the image carrier. In the image forming apparatus, comprising: a transfer driving unit that rotationally drives the transfer member; and conveying the recording member to the transfer nip, and transferring the toner image on the image carrier to the recording member at the transfer nip. And a torque for setting the torque of the transfer member when the transfer member and the image carrier are in contact with each other based on the detection result of the recording member detection means. A setting unit; and a control unit that controls the transfer driving unit and / or the image carrier driving unit so that the torque of the transfer member becomes a torque set by the torque setting unit. And it is characterized in and.
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the control means sets the torque between the start of the image forming operation and the time when the recording member reaches the transfer nip. The transfer driving means and / or the image carrier driving means are controlled so that the transfer member rotates with a torque set by the means.
According to a third aspect of the present invention, in the image forming apparatus of the first or second aspect, the transfer member is rotated when the transfer member and the image carrier are in contact with each other, and the transfer member is rotated at a specified rotational speed. Torque detection means for detecting the torque of the member is provided, and the control means controls the image carrier driving means based on the detection result of the torque detection means so that the torque set by the torque setting means is obtained. It is a feature.
According to a fourth aspect of the present invention, in the image forming apparatus of the third aspect, the torque detecting means detects the torque of the transfer member based on a drive current value to the transfer drive means. It is.
According to a fifth aspect of the present invention, in the image forming apparatus according to the third or fourth aspect, the torque setting means is configured to set the torque of the transfer member lower as the recording member becomes thicker. It is what.
According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the third to fifth aspects, the latent image carrier, toner image forming means for forming a toner image on the latent image carrier, and the latent image carrier. Transfer means for transferring the upper toner image to the image carrier and latent image carrier drive means for rotationally driving the latent image carrier, and the control means include the image carrier drive means and the latent image. The carrier driving means is controlled.

As described above, as the surface speed at the transfer nip of the transfer member becomes slower than the surface speed at the transfer nip of the image carrier, the force that the image carrier assists the rotation of the transfer member increases. Torque decreases. On the other hand, as the surface speed at the transfer nip of the transfer member becomes faster than the surface speed of the transfer member of the image carrier, the image carrier becomes a brake for rotation of the transfer member, and the torque of the transfer member increases. Therefore, the difference between the surface speed of the image carrier and the surface speed of the transfer member at the transfer nip can be found from the torque of the transfer member. Therefore, by controlling the rotation speed of the transfer member and / or the image carrier so that the torque of the transfer member becomes a predetermined value, the difference between the surface speed of the image carrier and the surface speed of the transfer member in the transfer nip can be reduced. It can be a predetermined value. Therefore, the present invention sets the torque value of the transfer member based on the thickness of the recording member, and controls the rotation of the transfer member and / or the image carrier so that the torque of the transfer member becomes the torque value. As a result, the difference in surface speed between the transfer member and the image carrier is such that when the recording member is conveyed to the transfer nip, the surface speed of the recording member on the image carrier side is substantially the same as the surface speed of the image carrier. Can be a speed difference. As a result, even when a thick recording member is conveyed to the transfer nip, the surface speed of the recording member on the image carrier side can be made substantially the same as the surface speed of the image carrier, and a good image can be obtained. it can.
Further, according to the present invention, the rotational speed of the transfer member and / or the image carrier is controlled so that the torque of the transfer member becomes a set torque, so that the transfer member and the image carrier are in the transfer nip. The speed difference is set to a predetermined value. Therefore, when controlling the rotation of the transfer member to set the transfer member torque to the set torque, the drive current value input to the transfer drive means when the transfer member torque is the set torque is stored in advance. By storing the drive current value stored in the storage means and inputting the drive current value stored in the storage means to the transfer drive means, the difference in surface speed between the transfer member and the image carrier in the transfer nip can be set to a predetermined value. Further, when controlling the rotation of the image carrier, if a torque detection means for detecting the torque of the transfer member is provided and the rotation of the image carrier is controlled so that the torque of the transfer member becomes a set torque, The difference in surface speed between the transfer member and the image carrier in the transfer nip can be set to a predetermined value. In other words, when the rotation of the transfer member is controlled, a storage means may be provided, and when the rotation of the image carrier is controlled, a torque detection means for detecting the torque of the transfer member may be provided. Therefore, a means for detecting the rotation speed of the transfer member and a means for detecting the rotation speed of the image carrier are provided so that the difference between the rotation speed of the transfer member and the rotation speed of the image carrier becomes a predetermined value. By controlling the distance between the transfer member and the image carrier, it is possible to reduce the cost of the apparatus as compared with the case where the difference in surface speed at the transfer nip between the transfer member and the image carrier is a predetermined value.

  According to the present invention, even when a thick recording member is transported to the transfer nip, the transport speed of the recording member can be made substantially the same as the surface speed of the image carrier, and a good image can be obtained. . Further, a means for detecting the rotation speed of the image carrier and a means for detecting the rotation of the transfer member are provided, and the speed between the surface speed at the transfer nip of the transfer member and the surface speed at the transfer nip of the image carrier. The apparatus can be made cheaper than that in which the difference is controlled to a predetermined value.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment. FIG. 3 is an enlarged schematic diagram illustrating a secondary transfer nip and the surrounding configuration of the image forming apparatus. FIG. 4 is a diagram illustrating a relationship between a surface speed difference between a secondary transfer roller and an intermediate transfer belt and a drive current to a transfer motor. 2 is a diagram illustrating the image forming apparatus and a control unit. FIG. Control flow of image forming operation. The control flow of the modification 1. FIG. 4 is a diagram illustrating a relationship between a speed difference between the surface speed of the intermediate transfer belt and the surface speed of the secondary transfer roller when the basic rotation speed of the secondary transfer roller is reduced, and a drive current value at that time. The control flow of the modification 2.

  FIG. 1 is a schematic configuration diagram showing an example of an image forming apparatus to which the present invention is applied. In the figure, reference numeral 100 denotes a tandem intermediate transfer image forming apparatus main body as an image forming apparatus, and reference numeral 200 denotes an image forming apparatus main body 100 placed on the upper surface and a transfer sheet S as a sheet-like recording member inside. Each of the stored paper feed tables is shown.

  A tandem intermediate transfer type image forming unit (hereinafter referred to as a tandem type image forming unit) 20 in which a plurality of image forming units 1Y, 1M, 1C, and 1K are arranged in parallel is provided inside the image forming apparatus main body 100. Is provided. Note that the subscripts Y, M, C, and K attached to the above symbols indicate yellow, magenta, cyan, and black colors, respectively.

  The image forming apparatus main body 100 is provided with an intermediate transfer belt 10 that is an endless belt-shaped image carrier near the center. The intermediate transfer belt 10 is wound around a plurality of support rollers 13, 14, 15, 16 and the like so as to be able to rotate and convey clockwise in the drawing.

  In the illustrated example, an intermediate transfer belt cleaning device 17 is provided to the left of the secondary transfer counter roller 16. The intermediate transfer belt cleaning device 17 removes residual toner remaining on the intermediate transfer belt 10 after image transfer.

  Four images of yellow (Y), magenta (M), cyan (C), and black (K) are arranged on the intermediate transfer belt 10 stretched between the support roller 14 and the support roller 15 along the conveyance direction. The tandem image forming unit 20 is configured by arranging the forming units 1Y, 1M, 1C, and 1K side by side. The image forming units 1Y, 1M, 1C, and 1K of the tandem image forming unit 20 are photoreceptors 40Y, 40M, 40C as latent image carriers that carry toner images of yellow, magenta, cyan, and black, respectively. 40K.

  On the tandem type image forming unit 20, two exposure devices 21 are provided as shown in FIG. Each exposure device 21 corresponds to two image forming units (image forming unit 1Y and image forming unit 1M, image forming unit 1C and image forming unit 1K). As the exposure device 21, for example, two light source devices (semiconductor laser, semiconductor laser array, or multi-beam light source) and a coupling optical system, a common optical deflector (polygon mirror, etc.), two systems of scanning imaging optical system An optical scanning type exposure apparatus constituted by, for example, can be used. Then, each exposure device 21 exposes the photoconductors 40Y, 40M, 40C, and 40K according to the image information of each color of yellow, magenta, cyan, and black to form an electrostatic latent image.

  A charging device 3Y for uniformly charging the photoconductors 40Y, 40M, 40C, and 40K prior to the above-described exposure is provided around the photoconductors 40Y, 40M, 40C, and 40K of the image forming units 1Y, 1M, 1C, and 1K. , 3M, 3C, 3K, developing devices 18Y, 18M, 18C, 18K for developing the electrostatic latent image formed by the exposure device 21 with toner of each color, and photoconductor cleaning for removing transfer residual toner on the photoconductor 40 Devices 7Y, 7M, 7C and 7K are provided. Further, at the primary transfer position where the toner image is transferred from the photoconductors 40Y, 40M, 40C, and 40K to the intermediate transfer belt 10, the intermediate transfer belt 10 is interposed therebetween so as to face the photoconductors 40Y, 40M, 40C, and 40K. In addition, primary transfer rollers 62Y, 62M, 62C, and 62K as constituent elements of the primary transfer device 60 are provided.

  Among the plurality of support rollers that support the intermediate transfer belt 10, the support roller 14 is a drive roller that rotationally drives the intermediate transfer belt 10, and an image carrier via a drive transmission mechanism (gear, pulley, belt, etc.) not shown. It is connected to a mid-rotation motor that is a driving means. When a black single color image is formed on the intermediate transfer belt 10, the support rollers 13, 15 other than the support roller 14, the primary transfer rollers 62Y, 62M, 62C as transfer means are moved downward by a moving mechanism (not shown). The intermediate transfer belt 10 can be separated from the yellow, magenta, and cyan photoconductors 40Y, 40M, and 40C.

  A secondary transfer unit 22 is provided on the opposite side of the intermediate transfer belt 10 from the tandem image forming unit 20. The secondary transfer unit 22 presses the secondary transfer roller 29 from the front surface side of the intermediate transfer belt 10 against the secondary transfer counter roller 16 that is a support roller of the intermediate transfer belt 10 to sandwich the intermediate transfer belt 10. Then, a transfer bias is applied between the secondary transfer roller 29 and the secondary transfer counter roller 16 to form a transfer electric field, whereby the image on the intermediate transfer belt 10 is transferred to a sheet-like transfer sheet S as a transfer medium. To do.

  Also, a fixing device 25 that fixes the image on the transfer sheet S to the transfer sheet S by pressure or heat on the left side of the secondary transfer unit 22 in the drawing and downstream of the secondary transfer unit 22 in the transfer sheet transport direction. Is provided. The fixing device 25 is configured by pressing a pressure roller 27 against a fixing belt 26 which is an endless belt wound around two support rollers. Further, at least one of the two support rollers that support the fixing belt 26 is provided with a heating means (a heater, a lamp, an electromagnetic induction heating device, or the like) (not shown).

  The transfer sheet S on which the image is transferred by the secondary transfer unit 22 is transported to the fixing device 25 by the transport belt 24 supported by the two rollers 23. Of course, the conveyance belt 24 may be a fixed guide member, a conveyance roller, a conveyance roller, or the like.

  Below the secondary transfer unit 22 and the fixing device 25, there is provided a sheet reversing device 28 that inverts and conveys the transfer paper S so as to record images on both sides of the transfer paper S in parallel with the tandem image forming unit 20. ing.

  When image data is sent to the image forming apparatus main body 100 and an image formation start signal is received, the tandem image forming unit 20 rotates the support roller 14 with a drive motor (not shown) to drive the other plurality of support rollers. Following the rotation, the intermediate transfer belt 10 is rotated in the arrow direction (clockwise direction) in the figure. At the same time, in the image forming units 1Y, 1M, 1C, and 1K, the photoreceptors 40Y, 40M, 40C, and 40K are rotated counterclockwise by a drive motor (not shown), and are charged and exposed by the charging devices 3Y, 3M, 3C, and 3K. After exposure (latent image formation) by the device 21 and development processes using toners of the respective colors of the developing devices 18Y, 18M, 18C, and 18K, yellow, magenta, cyan, and black are respectively formed on the photoreceptors 40Y, 40M, 40C, and 40K. The monochrome image is formed. As the intermediate transfer belt 10 is conveyed, the single color images are sequentially transferred to the intermediate transfer belt 10 by the primary transfer rollers 62Y, 62M, 62C, and 62K, and a composite color image is formed on the intermediate transfer belt 10.

  On the other hand, one of the paper feed rollers 42 in the paper feed table 200 is selectively rotated in accordance with such an image forming operation, and the sheet-like transfer paper S is transferred from one of the paper feed cassettes 44 provided in the paper bank 43 in multiple stages. Are separated one by one by the separation roller 45 and put into the paper feed path 46, conveyed by the conveyance roller 47, led to the paper feed path 48 in the image forming apparatus main body 100, abutted against the registration roller 49 and stopped.

  In the case of manual feeding, the sheet feeding roller 50 is rotated to feed the sheet-like transfer paper (not shown) on the manual tray 51 while separating them one by one and put into the manual feeding path 53. Stop against the registration roller 49.

  Then, the registration roller 49 is rotated in accordance with the timing at which the image on the intermediate transfer belt 10 reaches the position of the secondary transfer unit 22, and the transfer sheet S is sent between the intermediate transfer belt 10 and the secondary transfer unit 22. Then, the secondary transfer unit 22 transfers the image from the intermediate transfer belt 10 to the transfer paper S and records a color image on the transfer paper S.

  After the image is transferred, the transfer sheet S is transported by the transport belt 24 and sent to the fixing device 25, and the fixing device 25 applies heat and pressure to fix the image on the transfer paper S. After the image is fixed by the fixing device 25, the transfer sheet S is switched by a switching claw (not shown) and is discharged out of the device by a discharge roller 56 and stacked on a paper discharge tray 57. The conveying path is switched by the switching claw and the sheet is fed into the sheet inverting device 28. The transfer sheet S sent to the sheet reversing device 28 is turned upside down and sent again to the paper feed path 48 in the image forming apparatus main body 100, and the image on the intermediate transfer belt 10 is secondarily transferred via the registration rollers 49. After being transferred to a secondary transfer position to be transferred onto the transfer paper S by the transfer unit 22, an image is recorded also on the back surface of the transfer paper S, and then discharged onto a discharge tray 57 by a discharge roller 56.

  On the other hand, in the photoconductors 40Y, 40M, 40C, and 40K after the image transfer, residual toner remaining on the photoconductors 40Y, 40M, 40C, and 40K is removed by the photoconductor cleaning devices 7Y, 7M, 7C, and 7K. Further, the residual toner remaining on the intermediate transfer belt 10 is removed from the intermediate transfer belt 10 after image transfer by the intermediate transfer belt cleaning device 17. After these cleaning steps, the image forming apparatus prepares for another image formation by the tandem image forming unit 20.

  In the present embodiment, the charging device 3, the exposure device 21, and the developing device 18 function as a toner image forming unit that forms a toner image on the photoreceptor 40 that is a latent image carrier.

  FIG. 2 is an enlarged schematic view showing the secondary transfer nip and the surrounding configuration. In the figure, the secondary transfer counter roller 16 that partially wraps the belt around its own peripheral surface inside the loop of the intermediate transfer belt 10 backs up the deformable intermediate transfer belt 10 on its peripheral surface. It plays the role of maintaining the shape along a certain curvature. A secondary transfer roller 29 is in contact with the secondary transfer counter roller 16 on the intermediate transfer belt 10 from the belt front surface side to form a secondary transfer nip.

  The secondary transfer roller 29 is rotatably held by the secondary transfer unit 22 via a bearing (not shown). The end of the secondary transfer unit 22 opposite to the rotating shaft 104 is biased toward the intermediate transfer belt 10 by a biasing coil spring 105 as biasing means. As a result, a force that rotates counterclockwise in the figure about the rotation shaft 104 is applied to the secondary transfer unit 22, and the secondary transfer roller 29 is pressed against the intermediate transfer belt 10.

  In addition, the image forming apparatus is provided with a separation unit (not shown) for separating the secondary transfer roller 29 from the intermediate transfer belt 10. When the printing operation is completed, the secondary transfer unit 22 is rotated clockwise around the rotation shaft 102 by the separation means (not shown), and the secondary transfer roller 29 is separated from the intermediate transfer belt 10.

  The secondary transfer roller 29 is rotationally driven in the counterclockwise direction in the figure by transmitting the rotational driving force of the transfer motor 112 serving as a transfer driving means via a drive transmission means such as a gear (not shown). The secondary transfer unit 22 also holds a cleaning blade 39 and a cleaning brush roller 101.

  The toner on the belt adheres to the surface of the secondary transfer roller 29 that is in contact with the front surface of the intermediate transfer belt 10 that carries the toner image. If this adhering toner is left as it is, it is transferred to the back surface of the recording sheet at the secondary transfer nip, and so-called back contamination occurs. Therefore, in this image forming apparatus, the toner is mechanically removed from the surface of the secondary transfer roller 29 by bringing the cleaning blade 39 and the cleaning brush roller 101 into contact with the surface of the secondary transfer roller 29. In such a configuration, a load impeding the rotation is applied to the secondary transfer roller 29 due to the contact of the cleaning blade 39 and the cleaning brush roller 101, so that the secondary transfer roller 29 is rotated with the intermediate transfer belt 10. Can not be driven rotated by. For this reason, the secondary transfer roller 29 is rotationally driven by the transfer motor 112 described above.

  The toner removed by the cleaning blade 39 and the cleaning brush roller 101 is transported by a transport screw 103 to a waste tank (not shown).

  The secondary transfer roller 29 includes a cored bar and an elastic layer made of an elastic member such as high-rigidity rubber fixed to the peripheral surface of the cored bar.

Next, characteristic points of the image forming apparatus will be described.
The transfer sheet S sandwiched between the intermediate transfer belt 10 and the secondary transfer roller 29 at the secondary transfer nip is conveyed by receiving driving force from the intermediate transfer belt 10 and the secondary transfer roller 29. The transfer speed of the transfer sheet S in the nip largely depends on the surface speed of the secondary transfer roller 29. For this reason, when a speed difference is generated between the secondary transfer roller 29 and the intermediate transfer belt 10, the transfer sheet S is moved by the rotational driving force of the secondary transfer roller 29, and between the intermediate transfer belt 10 and the intermediate transfer belt 10. Slip occurs.

  In the secondary transfer nip, the transfer paper S is transported by the rotation of the secondary transfer roller 29, so that the surface speed of the transfer paper S on the intermediate transfer belt side is the secondary transfer roller 29 corresponding to the paper thickness. It becomes faster than the surface speed. Therefore, when the surface speed of the intermediate transfer belt 10 in the secondary transfer nip and the surface speed of the secondary transfer roller 29 are the same, the surface speed of the transfer sheet S on the intermediate transfer belt side is higher than the surface speed of the intermediate transfer belt 10. Will also be faster. As a result, the image transferred to the transfer paper S is transferred while extending in the sub-scanning direction from the original image, and the magnification of the image fluctuates, resulting in an abnormal image.

  Therefore, in the image forming apparatus according to the present embodiment, the speed difference between the surface speed of the secondary transfer roller 29 in the secondary transfer nip and the surface speed of the intermediate transfer belt 10 differs depending on the thickness of the transfer paper S. I tried to make it.

FIG. 3 is a diagram showing the relationship between the surface speed difference between the secondary transfer roller 29 and the intermediate transfer belt 10 and the drive current to the transfer motor 112. FIG. 3 is a graph when the secondary transfer roller 29 is controlled to rotate at the basic rotation speed (N) and the rotation speed of the intermediate transfer belt 10 is changed.
As shown in FIG. 3, it can be seen that the drive current to the transfer motor 112 becomes smaller as the surface speed of the secondary transfer roller 29 becomes slower than the surface speed of the intermediate transfer belt 10. This is because the intermediate transfer belt 10 rotates the secondary transfer roller 29 as the surface speed at the secondary transfer nip of the secondary transfer roller 29 becomes slower than the surface speed at the secondary transfer nip of the intermediate transfer belt 10. The power to assist increases. Therefore, the torque of the secondary transfer roller 29 is reduced, and the drive current to the transfer motor 112 is reduced. On the other hand, it can be seen that the drive current to the transfer motor 112 increases as the surface speed of the secondary transfer roller 29 becomes faster than the surface speed of the intermediate transfer belt 10. This is because, as the surface speed of the secondary transfer roller 29 at the secondary transfer nip becomes faster than the surface speed of the intermediate transfer belt 10 at the secondary transfer nip, the intermediate transfer belt 10 rotates the secondary transfer roller 29. A brake is applied, and the torque of the secondary transfer roller 29 increases. As a result, the drive current to the transfer motor 112 increases.

  For example, when the drive current value to the secondary transfer roller 29 when the secondary transfer roller 29 is rotated at the basic rotational speed (N) is b, the surface speed of the intermediate transfer belt 10 is the speed of the secondary transfer roller 29. It is faster than the surface speed. In this case, the surface speed of the intermediate transfer belt 10 and the surface speed of the secondary transfer roller 29 are controlled by controlling the rotational speed of the intermediate transfer belt 10 so that the drive current value to the secondary transfer roller 29 becomes d. It can be about the same speed.

  As shown in FIG. 3, when the transfer sheet S is a thick sheet (sheet thickness t: t> t1), the value of the surface speed difference at the secondary transfer nip between the intermediate transfer belt and the secondary transfer roller 29 is A. As a result, a good image without a magnification error can be obtained. When the transfer paper S is plain paper (paper thickness t: t2 <t ≦ t1), the value of the surface speed difference at the secondary transfer nip between the intermediate transfer belt 10 and the secondary transfer roller 29 is B. As a result, a good image without a magnification error can be obtained. When the transfer paper S is thin paper (paper thickness t: t ≦ t2), a magnification error occurs when the value of the surface speed difference at the secondary transfer nip between the intermediate transfer belt 10 and the secondary transfer roller 29 is C. A good image with no image can be obtained.

  From this, the secondary transfer roller 29 is rotated at the basic rotational speed (N), and the torque of the secondary transfer roller 29 applied by the speed difference with the intermediate transfer belt 10 at the transfer nip can be found from the drive current value at that time. . Therefore, if the sheet thickness is detected and the rotation of the intermediate transfer belt 10 or the secondary transfer roller 29 is controlled so that the drive current value of the secondary transfer roller 29 becomes a predetermined value, the intermediate transfer belt 10 and the secondary transfer belt 10 The speed difference in the secondary transfer nip with the transfer roller 29 can be set to an optimum speed difference corresponding to the sheet thickness of the transfer sheet S.

FIG. 4 is a diagram illustrating the image forming apparatus and the control unit 114.
As shown in FIG. 4, a paper thickness detection sensor 71 serving as a thickness detection means is provided upstream of the registration roller 49 in the transfer paper movement direction. A displacement sensor can be used as the paper thickness detection sensor 71. Since the height of the transfer sheet S is displaced depending on the thickness of the transfer sheet S, the output value of the displacement sensor changes. Therefore, the thickness of the transfer sheet S can be detected based on the output value of the displacement sensor. As the displacement sensor, an optical or other non-contact displacement sensor may be used, or a contact displacement sensor may be used.

  Further, the thickness of the transfer paper to be conveyed may be detected by inputting information on the thickness of the paper to be conveyed by the user with an input means such as an operation panel (not shown). For example, when it is detected that the transfer sheet S is set in the paper feed cassette 44, the user is notified that the thickness information of the paper set in the paper feed cassette 44 is input. Further, a display for inputting the thickness of the transfer paper S set in the paper feed cassette 44 is performed on the operation panel. When the user inputs the thickness information of the transfer sheet S based on the display content of the operation panel, the sheet feeding cassette 44 and the thickness information are stored in association with each other in a non-illustrated nonvolatile memory.

  The control means 114 is a intermediate transfer motor 111 as an image carrier driving means for rotationally driving the intermediate transfer belt 10, and a photosensitive motor as a latent image carrier driving means for rotationally driving the photosensitive members 40Y, 40M, 40C, and 40K. 110Y, 110M, 110C, and 110K, and a transfer motor 112 are connected to control the intermediate transfer motor 111, the respective photoreceptor motors 110Y, 110M, 110C, and 110K, and the transfer motor 112. Further, a paper thickness detection sensor 71 is connected to the control means 114, and a detection result of the paper thickness detection sensor 71 is input to the control means 114. Further, the control unit 114 detects the driving current value of the transfer motor 112 and detects the torque to the secondary transfer roller 29. That is, the control means has a function as torque detection means.

FIG. 5 is a control flow of the image forming operation.
First, when image formation is instructed, the control unit 114 brings the secondary transfer roller 29 that has been separated from the intermediate transfer belt 10 into contact with the intermediate transfer belt 10, and makes the secondary transfer roller 29 have a basic rotational speed (N). (S1). As an example, by providing a rotation speed detection means for detecting the rotation speed of the secondary transfer roller 29 such as an encoder, and changing the drive current input to the transfer motor 112 based on the detection result of the rotation speed detection means, The secondary transfer roller 29 is rotated at the basic rotation speed (N).

The control unit 114 includes a non-volatile memory as a storage unit. As shown in Table 1, the non-volatile memory stores the paper thickness t and the drive current value of the transfer motor 112 in association with each other. ing. T1> t2 shown in Table 1, and a <b <c. The drive current values shown in Table 1 are obtained from FIG.

  Next, the paper thickness detection sensor 71 detects the paper thickness of the transfer paper S conveyed to the secondary transfer nip (S2). When the detected paper thickness t exceeds t1 (t> t1) (YES in S3), it is determined that the paper is thick and the drive current value of the transfer motor 112 is set to a. Then, the control unit 114 detects the drive current value input to the transfer motor 112, controls the intermediate transfer motor 111 so that the drive current of the transfer motor 112 becomes a, and controls the rotation speed of the intermediate transfer belt. (S7). As a result, the speed difference between the surface speed of the secondary transfer roller 29 in the secondary transfer nip and the surface speed of the intermediate transfer belt 10 when the thick paper passes through the secondary transfer nip is as shown in FIG. A.

  On the other hand, when the detected paper thickness t is t2 <t ≦ t1 (S3YES, S4NO), it is determined as plain paper, the drive current value of the transfer motor 112 is set to b, and the drive current of the transfer motor 112 is The intermediate transfer motor 111 is controlled so as to be b, and the rotational speed of the intermediate transfer belt 10 is controlled (S5). As a result, the speed difference between the surface speed of the secondary transfer roller 29 in the secondary transfer nip and the surface speed of the intermediate transfer belt 10 when the plain paper passes through the secondary transfer nip is as shown in FIG. Becomes B.

  When the detected paper thickness t is t ≦ t2 (S3 YES, S4 YES), it is determined that the paper is thin, the drive current value of the transfer motor 112 is set to c, and the drive current of the transfer motor 112 becomes c. Then, the intermediate transfer motor 111 is controlled to control the rotation speed of the intermediate transfer belt 10 (S6). As a result, the speed difference between the surface speed of the secondary transfer roller 29 in the secondary transfer nip and the surface speed of the intermediate transfer belt 10 when the thin paper passes through the secondary transfer nip is as shown in FIG. C.

  Next, in order to prevent the surface speeds of the intermediate transfer belt 10 and the photoreceptors 40Y, 40M, 40C, and 40K from fluctuating at the primary transfer nip, the increase / decrease in the rotational speed of the intermediate transfer belt 10 and the photoreceptor motors 110Y, 110M, Control is performed to increase or decrease the rotational speeds of 110C and 110K (S8). When the drive current of the secondary transfer roller 29 reaches the set drive current value, a toner image is formed on each color photoconductor, and the transfer paper is conveyed to the secondary transfer nip at a predetermined timing (S9).

  In the present embodiment, even when the thick paper is transported to the secondary transfer nip, the surface speed of the intermediate transfer belt 10 and the surface speed of the transfer paper S on the side of the intermediate transfer belt can be made substantially the same, and a magnification error can occur. A good image with no image can be obtained. In the present embodiment, the torque (drive current) of the secondary transfer roller 29 when the secondary transfer roller 29 is rotated at a predetermined speed while the intermediate transfer belt 10 and the secondary transfer roller 29 are in contact with each other. Value), a difference in surface speed at the secondary transfer nip is detected. Since the drive current value may be detected in this way, a means for detecting the rotational speed of the intermediate transfer belt 10 and a means for detecting the rotational speed of the secondary transfer roller 29 are provided, and the surface speed difference is obtained from these rotational speeds. The apparatus can be made cheaper than the one.

  Further, for example, when the secondary transfer roller 29 expands due to an environmental change and the diameter of the secondary transfer roller 29 increases, the secondary transfer roller 29 is rotated at a predetermined rotational speed. The surface speed changes before and after roller expansion. As described above, the outer diameter of the secondary transfer roller 29, the thickness of the intermediate transfer belt 10, and the like vary depending on the environment (temperature / humidity), usage over time, and the like.・ Humidity) and changes over time. For this reason, when detecting and controlling the rotational speed of the intermediate transfer belt 10 and the secondary transfer roller 29, the change in the outer diameter of the secondary transfer roller and the change in the thickness of the intermediate transfer belt 10 as described above are detected. Unless a means is provided and the rotation speed is controlled based on the detection result, highly accurate control cannot be performed. On the other hand, in the present embodiment, control is performed based on the torque (drive current value) of the secondary transfer roller 29 generated by the surface speed difference between the intermediate transfer belt 10 and the secondary transfer roller 29 in the secondary transfer nip. High control can be performed. This is because the torque (drive current value) of the secondary transfer roller 29 is the torque (drive) of the secondary transfer roller 29 if the surface speed difference between the secondary transfer roller 29 and the intermediate transfer belt 10 is a predetermined value. This is because the (current value) becomes a predetermined value. Therefore, even if the outer diameter of the secondary transfer roller or the thickness of the intermediate transfer belt changes due to the environment (temperature / humidity) or usage over time, the torque (drive current value) of the secondary transfer roller 29 becomes a predetermined value. Thus, by controlling the rotation speed of the intermediate transfer belt 10, a predetermined speed difference can be obtained. Therefore, by detecting the rotational speed of the intermediate transfer belt and the rotational speed of the secondary transfer roller and setting the rotational speed difference to a predetermined value, the surface speed difference between the intermediate transfer belt and the secondary transfer roller is set to a predetermined value. It is possible to perform control with higher accuracy than that to be controlled. Therefore, the optimum speed difference can be set according to the thickness of the transfer sheet S, and the surface speed of the transfer sheet S on the intermediate transfer belt side and the surface speed of the intermediate transfer belt 10 can be made substantially the same. it can.

  In this embodiment, the transfer sheet S is moved to the secondary transfer nip after the surface speed difference between the secondary transfer roller 29 and the intermediate transfer belt 10 at the secondary transfer nip is controlled to be a predetermined value. Since it is conveyed, a good image can be obtained from the first sheet.

  In the above description, when the rotational speed of each photoconductor / intermediate transfer belt is controlled and the drive current to the secondary transfer roller 29 becomes the set drive current, the photoconductors 40Y, 40M, 40C, and 40K for the respective colors. In the case where a plurality of sheets are continuously printed, for example, when the rotational speed of each of the photoconductors 40Y, 40M, 40C, and 40K is changed, the first toner image is transferred to the intermediate transfer belt 10. After the transfer, it may be performed before the next image formation. The rotational speed of the intermediate transfer belt 10 may be adjusted between the time when the first toner image is transferred to the intermediate transfer belt 10 and the time when the toner image is conveyed to the secondary transfer nip. . By controlling in this way, it is possible to obtain a good image without reducing productivity.

  Next, a modified example will be described.

[Modification 1]
FIG. 6 is a control flow diagram of the first modification.
In the image forming apparatus according to the first modification, when the transfer sheet S is a thick sheet (t> t1), the transfer speed of the transfer sheet S is controlled to decrease.
As shown in FIG. 6, when the paper thickness t exceeds t1 as a result of detection by the paper thickness detection sensor (NO in S13), the paper transport speed is reduced to 70% of the normal paper transport speed (S17). ). Specifically, the rotational speed of each photoconductor, intermediate transfer belt, secondary transfer roller, fixing roller, etc. is reduced to 70% compared to the normal time. As a result, the basic rotation speed (N) of the secondary transfer roller 29 is also set to 70% rotation speed (N ′), and the drive current value input to the transfer motor 112 is reduced by 30% in order to obtain this rotation speed. . Therefore, the relationship between the speed difference between the surface speed of the intermediate transfer belt 10 and the surface speed of the secondary transfer roller 29 and the drive current value at that time is a dotted line as shown in FIG. Therefore, when the thickness of the transfer paper exceeds t1, the drive current value to be set is set to a ′ obtained from the dotted line shown in FIG. Thereby, even when the sheet conveyance speed is set to 70%, the surface speed difference between the secondary transfer roller 29 and the intermediate transfer belt 10 in the secondary transfer nip can be set to A. Thereby, even when the thick paper is conveyed to the secondary transfer nip, the surface speed of the intermediate transfer belt 10 and the surface speed of the transfer paper S on the side of the intermediate transfer belt can be made substantially the same, and there is no magnification error. Can be obtained.

[Modification 2]
Next, Modification 2 will be described.
In this modified example 2, the rotation of the secondary transfer roller 29 is controlled so that the speed difference between the intermediate transfer belt 10 and the secondary transfer roller 29 at the secondary transfer nip is set to a predetermined value.
FIG. 8 is a control flowchart of the second modification.
First, when image formation is instructed, the control unit 114 causes the secondary transfer roller 29 that has been separated from the intermediate transfer belt 10 to contact the intermediate transfer belt 10 and rotates the secondary transfer roller 29 (S21). At this time, it is not necessary to rotate the secondary transfer roller 29 at the basic rotation speed (N) as in the first embodiment, and the rotation is simply by warm-up.

As shown in Table 2, the nonvolatile memory of the control unit 114 stores the paper thickness t and the drive current value input to the transfer motor 112 in association with each other.

  The above a1, b1, and c1 are the drive current values corresponding to the respective paper thicknesses shown in FIG. 3 (drive current values a, b, and c corresponding to the torque of the secondary transfer roller 29) with respect to the basic rotational speed (N). This is a value obtained by adding the increase / decrease of the drive current value due to the increase / decrease of the rotation speed of the secondary transfer roller 29. In the above a1, b1, and c1, the surface speed of the secondary transfer roller 29 and the surface speed of the intermediate transfer belt 10 are changed by rotating the intermediate transfer belt 10 at a predetermined rotational speed and changing the speed of the secondary transfer roller 29. Can be obtained by examining the drive current value of the transfer motor 112 at that time.

  Next, the paper thickness detection sensor 71 detects the paper thickness of the transfer paper S conveyed to the secondary transfer nip (S22). When the detected paper thickness t exceeds t1 and t> t1 (YES in S23), it is determined that the paper is thick, and the drive current value of the transfer motor is set to a1, and the drive current value a1 is input to the transfer motor 112. (S27). As a result, the speed difference between the surface speed of the secondary transfer roller 29 in the secondary transfer nip and the surface speed of the intermediate transfer belt 10 when the thick paper passes through the secondary transfer nip is A.

  On the other hand, when the detected paper thickness t is t2 <t ≦ t1 (S23 YES, S24 NO), it is determined as plain paper, the drive current value of the transfer motor 112 is set to b1, and the drive current b1 is input to the transfer motor 112. (S25). As a result, the speed difference between the surface speed of the secondary transfer roller 29 in the secondary transfer nip and the surface speed of the intermediate transfer belt 10 when the plain paper passes through the secondary transfer nip becomes B.

  When the detected paper thickness t is t ≦ t2 (S23 YES, S24 YES), it is determined that the paper is thin, the drive current value of the transfer motor 112 is set to c1, and the drive current c1 is input to the transfer motor 112 ( S26). As a result, the speed difference between the surface speed of the secondary transfer roller 29 in the secondary transfer nip and the surface speed of the intermediate transfer belt 10 when the thin paper passes through the secondary transfer nip becomes C.

  When the difference in surface speed between the intermediate transfer belt 10 and the secondary transfer roller 29 at the secondary transfer nip reaches a predetermined value, the transfer sheet S is conveyed to the secondary transfer nip.

  Also in this modified example 2, even when the thick paper is conveyed to the secondary transfer nip, the surface speed of the intermediate transfer belt 10 and the surface speed of the transfer paper S on the side of the intermediate transfer belt can be made substantially the same. A good image without error can be obtained. Further, in the second modification, it is not necessary to rotate the secondary transfer roller 29 at the basic rotation number (N). Therefore, a means for detecting the rotation number of the secondary transfer roller 29 such as an encoder becomes unnecessary, and the apparatus is It can be made cheap. Further, in Modification 2, the rotation control of the secondary transfer roller 29 is completed before the toner on the intermediate transfer belt 10 in the secondary transfer nip is conveyed (the secondary transfer roller 29 and the intermediate transfer in the secondary transfer nip are completed). The surface speed difference with the belt 10 may be a speed difference corresponding to the paper thickness). Therefore, even if the image forming operation on each of the photoconductors 40Y, 40M, 40C, and 40K is started before the rotation control of the secondary transfer roller 29 is completed, the image is not affected. Therefore, the first print can be made faster.

  In the above description, the thickness of the transfer paper S is divided into three, thick paper, plain paper, and thin paper. However, by setting this finely, it is possible to optimally transport various transfer papers. The intermediate transfer belt 10 is not limited to a belt shape supported by a plurality of rollers, and may be a drum shape. Further, the transfer member is not limited to a roller shape, and may be a belt shape supported by a plurality of rollers.

As described above, according to the image forming apparatus of the present embodiment, the intermediate transfer belt 10 that is an image carrier, the secondary transfer roller 29 that is a transfer member that contacts the intermediate transfer belt 10 and forms a transfer nip, and the intermediate transfer belt 10 are provided. A transfer motor 112 as a transfer driving means for rotating the secondary transfer roller 29, and a transfer sheet S as a recording member are conveyed to the transfer nip. Then, the toner image on the intermediate transfer belt 10 is transferred to the transfer paper S. Then, based on the detection result of the paper thickness detection sensor 71 and the paper thickness detection sensor 71 as thickness detection means for detecting the thickness of the transfer paper S as the recording member conveyed to the transfer nip, the intermediate transfer and the secondary transfer roller 29 are performed. Torque setting means (control means 114) for setting the torque of the secondary transfer roller 29 in contact with the belt 10, and the transfer motor 112 and / or so that the torque of the secondary transfer roller 29 becomes the set torque. And a control means 114 for controlling the intermediate transfer motor 111.
With this configuration, even when a thick transfer sheet S is conveyed to the transfer nip, the surface speed of the transfer sheet S on the intermediate transfer belt side can be made substantially the same as the surface speed of the intermediate transfer belt 10. A good image can be obtained. Further, a means for detecting the rotation speed of the intermediate transfer belt 10 and a means for detecting the rotation of the secondary transfer roller are provided so that the speed difference between the intermediate transfer belt and the secondary transfer roller is in a predetermined relationship. The apparatus can be made cheaper than that in which the speed difference between the surface speeds of the secondary transfer roller 29 and the intermediate transfer belt 10 in the secondary transfer nip is controlled to a predetermined value.

  In addition, the control unit 114 causes the transfer motor 112 and / or the rotation of the secondary transfer roller 29 to rotate with the set torque between the start of the image forming operation and the time when the transfer sheet S reaches the secondary transfer nip. Alternatively, the intermediate transfer motor 111 is controlled. Thereby, a good image can be obtained from the first transfer sheet S.

  Further, when the secondary transfer roller 29 and the intermediate transfer belt 10 are in contact with each other and the secondary transfer roller is rotated at the basic rotation speed (N), which is a specified rotation speed, by the control means 114 serving as torque detection means. The torque of the secondary transfer roller 29 is detected. Based on the detected torque, the intermediate transfer motor 111 is controlled so that the set torque is obtained. Thereby, the surface speeds of the intermediate transfer belt 10 and the secondary transfer roller 29 in the secondary transfer nip can be set to a predetermined value. Thereby, an optimum surface speed difference corresponding to the transfer paper S can be set.

  Specifically, the control unit 114 detects the torque of the secondary transfer roller based on the drive current value to the transfer motor 112. As described above, when the secondary transfer roller is controlled to rotate at the basic rotation speed (N), the drive current value to the transfer motor 112 changes in proportion to the torque applied to the secondary transfer roller 29. Therefore, the torque of the secondary transfer roller 29 can be detected by detecting the drive current value to the transfer motor 112.

  Further, the torque of the secondary transfer roller is set to be lower as the thickness of the transfer sheet S is larger. As described above, as the thickness of the transfer sheet S increases, the surface speed of the transfer sheet S on the intermediate transfer belt side becomes faster than the surface speed of the secondary transfer roller. Therefore, it is necessary to make the surface speed of the secondary transfer roller slower than the surface speed of the intermediate transfer belt as the thickness of the transfer sheet S increases. As described above, the torque of the secondary transfer roller decreases as the surface speed of the secondary transfer roller is made slower than the surface speed of the intermediate transfer belt. Therefore, by setting the torque of the secondary transfer roller to be lower as the transfer sheet S is thicker, even if the transfer sheet S is thicker, the surface speed of the transfer sheet S on the intermediate transfer belt 10 side and the intermediate speed are increased. The surface speed of the transfer belt 10 can be made substantially the same.

  Further, the photosensitive member 40 as a latent image carrier, a toner image forming unit (comprising the charging device 3, the exposure device 21 and the developing device 18) for forming a toner image on the photosensitive member 40, and the toner image on the photosensitive member 40 A primary transfer roller 62 as a transfer means for transferring to the intermediate transfer belt and a photoconductor motor 110Y as a latent image carrier drive means for rotating the photoconductor 40 are provided. The control unit 114 controls the photosensitive member mode 110 and the intermediate transfer motor 111. As a result, even if the rotation speed of the intermediate transfer belt is changed so that the surface speed between the secondary transfer roller and the intermediate transfer belt in the secondary transfer nip becomes a predetermined speed difference, the rotation speed of the photosensitive member is the same. Changed to As a result, the relationship between the surface speed of the photoconductor and the surface speed of the intermediate transfer belt in the primary transfer nip after the intermediate transfer belt control can be maintained at the relationship before the intermediate transfer belt control, and the image in the primary transfer can be maintained. Disturbance can be suppressed.

3: Charging device 10: Intermediate transfer belt 16: Secondary transfer counter roller 18: Developing device 21: Exposure device 22: Secondary transfer unit 29: Secondary transfer roller 40: Photoreceptor 62: Primary transfer roller 71: Paper thickness detection Sensor 110: Photoconductor motor 111: Intermediate transfer motor 112: Transfer motor 114: Control means

JP 2007-328275 A JP 2009-222814 A

Claims (6)

An image carrier;
A transfer member that contacts the image carrier and forms a transfer nip;
Image carrier driving means for rotationally driving the image carrier;
Transfer driving means for rotating the transfer member,
In the image forming apparatus for conveying the recording member to the transfer nip and transferring the toner image on the image carrier to the recording member in the transfer nip.
A thickness detecting means for detecting the thickness of the recording member conveyed to the transfer nip;
Torque setting means for setting the torque of the transfer member when the transfer member and the image carrier are in contact with each other based on the detection result of the recording member detection means;
An image forming apparatus comprising: a control unit that controls the transfer driving unit and / or the image carrier driving unit so that the torque of the transfer member becomes a torque set by the torque setting unit. The image forming apparatus according to claim 1.
The control means includes the transfer driving means and / or the transfer driving means so that the transfer member rotates at a torque set by the torque setting means between the start of the image forming operation and the arrival of the recording member at the transfer nip. Or an image forming apparatus that controls the image carrier driving means. The image forming apparatus according to claim 1 or 2,
A torque detecting means for detecting the torque of the transfer member when the transfer member is rotated at a specified rotational speed in a contact state between the transfer member and the image carrier;
The image forming apparatus according to claim 1, wherein the control means controls the image carrier driving means so that the torque set by the torque setting means is obtained based on a detection result of the torque detection means. The image forming apparatus according to claim 3.
The image forming apparatus according to claim 1, wherein the torque detection unit detects a torque of the transfer member based on a drive current value to the transfer drive unit. The image forming apparatus according to claim 3 or 4,
The image forming apparatus, wherein the torque setting unit is configured to set the torque of the transfer member lower as the recording member becomes thicker. The image forming apparatus according to any one of claims 3 to 5,
A latent image carrier;
Toner image forming means for forming a toner image on the latent image carrier;
Transfer means for transferring the toner image on the latent image carrier to the image carrier;
A latent image carrier driving means for rotationally driving the latent image carrier,
The image forming apparatus characterized in that the control means controls the image carrier driving means and the latent image carrier driving means.

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