JP2012071904A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that can change selected torque in a small space and at low cost.SOLUTION: An oil dumper 130 which permits the following rotation of a separation roller 123 when the selected torque or larger is applied to a separation roller 123, inhibits the following rotation when rotation torque not larger than the set torque is made to act thereon, and increases and decreases the set torque accompanied by an increase and decrease of the rotation speed of the separation roller 123 is connected to the separation roller 123. A control unit changes the rotation speed of the separation roller 123 according to the information of a sheet inputted from an input unit and changes the selected torque of the oil dumper 130.

Description

  The present invention relates to an image forming apparatus, and more particularly to a configuration of a sheet separating unit for separating and feeding sheets one by one to an image forming unit.

  Conventional image forming apparatuses such as printers, copiers, and facsimile machines form an image on a sheet fed by a sheet feeding apparatus. Here, when feeding sheets, double feeding of sheets in which two or more sheets are fed may occur. Therefore, in order to prevent such multi-feeding of sheets, conventionally, a sheet separating unit for separating and feeding the sheets one by one is provided. Such a sheet separating unit includes a feeding roller, a separation roller that is in pressure contact with the feeding roller and has a built-in torque limiter, or a retard roller.

  By the way, in the conventional sheet separation unit, in order to prevent double feeding, the relationship between the friction force between the double fed sheets and the torque setting torque is important, but the friction coefficient of the sheet differs depending on the type, The optimum set torque varies depending on the type (thickness) of the sheet. Therefore, conventionally, in order to change the set torque of the torque limiter depending on the thickness of the sheet, there is a type in which a plurality of torque limiters having different set torques are provided and the connection destinations are changed (see Patent Document 1).

JP 2002-2992 A

  However, an image forming apparatus having such a conventional sheet separating unit requires a plurality of torque limiters having different set torques, and also requires a switching means for changing the connection destination, which increases the number of parts. It leads to cost increase. Furthermore, a space for installing a plurality of torque limiters and switching means is required, leading to an increase in the size of the apparatus.

  Accordingly, the present invention has been made in view of such a situation, and an object of the present invention is to provide an image forming apparatus capable of changing a set torque in a small space and at a low cost.

  The present invention provides an image forming apparatus comprising: a separation roller formed by a conveyance roller that conveys a sheet; and a separation roller that is in pressure contact with the conveyance roller and that can rotate following the conveyance roller. When the rotation torque more than the set torque acts on the separation roller, the rotation of the separation roller is allowed, and when the rotation torque less than the set torque acts, the follow-up rotation is blocked and the rotation speed of the separation roller is reduced. A torque adding unit that increases or decreases the set torque in accordance with the increase / decrease, an input unit that inputs sheet information, and a torque adding unit that increases / decreases the rotation speed of the separation roller according to the sheet information input from the input unit. And a control unit for changing the set torque.

  According to the present invention, it is possible to change the set torque in a small space and at a low cost by providing the separation roller with a torque addition unit that increases or decreases the set torque as the rotational speed of the separation roller increases or decreases.

1 is an overall configuration diagram of a full-color laser printer that is an example of an image forming apparatus according to a first embodiment of the present invention. FIG. FIG. 3 is a diagram illustrating a configuration of a sheet feeding device provided in the full color laser printer. FIG. 4 is a diagram illustrating a sheet separating operation by a separation roller of the sheet feeding device. The control block diagram of the said sheet feeding apparatus. (A) is a figure which shows the relationship between the rotational speed of the oil damper provided in the said separation roller, and setting torque, (b) is a figure which shows the relationship of the sheet feeding torque with respect to the kind of sheet | seat. The figure explaining the other structure of the said sheet feeding apparatus. FIG. 10 is a diagram illustrating a configuration of a sheet feeding device provided in an image forming apparatus according to a second embodiment of the present invention. The figure explaining the other structure of the said sheet feeding apparatus. FIG. 10 is a diagram illustrating a configuration of a sheet feeding device provided in an image forming apparatus according to a third embodiment of the present invention. The figure which shows the relationship between the rotational speed and each set torque in each sheet position of the said sheet feeding apparatus. The figure explaining the other structure of the said sheet feeding apparatus.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. FIG. 1 is an overall configuration diagram of a full-color laser printer which is an example of an image forming apparatus according to a first embodiment of the present invention. In FIG. 1, 100 is a full-color laser printer, and 100A is a full-color laser printer main body (hereinafter referred to as a printer main body). The printer main body 101A as the apparatus main body is provided with an image forming unit 100B that forms an image on a sheet, a sheet feeding device 120 that feeds the sheet, and the like.

  The image forming unit 100B includes process cartridges 103a to 103d that form toner images of four colors of yellow, magenta, cyan, and black. The process cartridges 103a to 103d include photosensitive drums 101a to 101d, which are image carriers, and are detachably attached to the printer main body 101A.

  The image forming unit 100B is disposed vertically below the process cartridges 103a to 103d, and irradiates a laser beam based on image information to form a scanner unit 109 that forms an electrostatic latent image on the photosensitive drums 101a to 101d. I have. Here, each of the process cartridges 103a to 103d is composed of developing units 104a to 104d that visualize toner images by attaching toner to electrostatic latent images, and cleaner units 105a to 105d. The developing units 104a to 104d include developing rollers 106a to 106d, developer application rollers 107a to 107d, and a toner container. The cleaner units 105a to 105d include photosensitive drums 101a to 101d, charging rollers 102a to 102d for uniformly charging the surface of the photosensitive drum, drum cleaning blades 108a to 108d, and waste toner containers.

  In FIG. 1, reference numeral 110 denotes an intermediate transfer belt unit. The intermediate transfer belt unit 110 includes an intermediate transfer belt 110e and primary transfer rollers 110a to 110d disposed on the inner side of the intermediate transfer belt 110e. Yes. The intermediate transfer belt 110e is stretched around a driving roller 110f and a tension roller 110g, and the tension roller 110g applies tension in the direction of arrow T. The primary transfer rollers 110a to 110d are disposed to face the respective photosensitive drums 101a to 101d, and are configured to apply a transfer bias by a bias applying unit (not shown). Then, by applying a primary transfer bias to the intermediate transfer belt 110e by the primary transfer rollers 110a to 110d, each color toner image on the photosensitive drum is sequentially transferred to the intermediate transfer belt 110e. A full-color image is formed in.

  A secondary transfer unit 113 includes a driving roller 110f and a secondary transfer roller 113a, and sequentially transfers a full color image formed on the intermediate transfer belt 110e to a sheet. A fixing unit 115 fixes the toner image by applying heat and pressure to the toner image formed on the sheet. The fixing roller 115a includes a heater (not shown) therein, and a pressure roller that is in pressure contact with the fixing roller 115a. 115b.

  The sheet feeding device 120 includes a sheet feeding cassette 200 that is detachably attached to the printer main body 101A, a feed roller 122 that constitutes a sheet feeding unit that feeds the sheet S stored in the sheet feeding cassette 200, and the like. is doing. When the sheet S stored in the sheet cassette 200 is fed, the feed roller 122 pressed against the sheet S is rotated to send out the sheet S. The sheet S sent out in this way is then separated one by one by a separation unit composed of a feed roller 122 and a separation roller 123 that is in pressure contact with the feed roller 122, and then conveyed to the registration roller pair 114. The

  Next, an image forming operation of the full color laser printer 100 configured as described above will be described. When an image signal is input to the scanner unit 109 from a personal computer (not shown) or the like, a laser beam corresponding to the image signal is emitted from the scanner unit 109 onto the photosensitive drum. At this time, the surfaces of the photosensitive drums 101a to 101d are uniformly charged to a predetermined polarity and potential in advance by the charging rollers 102a to 102d, and the surface of the photosensitive drums 101a to 101d is exposed to laser light from the scanner unit 109. An image is formed. Thereafter, the electrostatic latent images are developed by the developing units 104a to 104d and visualized.

  For example, the scanner unit 109 first irradiates the photosensitive drum 101a with laser light based on the image signal of the yellow component color of the document, thereby forming a yellow electrostatic latent image on the photosensitive drum. The yellow electrostatic latent image is developed with yellow toner from the developing unit 104a and visualized as a yellow toner image. Thereafter, with the rotation of the photosensitive drum 101a, the toner image arrives at the primary transfer portion where the photosensitive drum 101a and the intermediate transfer belt 110e come into contact with each other. In this primary transfer portion, the yellow toner image on the photosensitive drum is transferred onto the intermediate transfer belt by the primary transfer bias applied to the primary transfer roller 110a.

  Next, when the portion of the intermediate transfer belt 110e carrying the yellow toner image moves, the magenta toner image formed on the photosensitive drum 101b by the same method as described above is transferred from the yellow toner image to the intermediate transfer belt. 110e is transferred. Similarly, as the intermediate transfer belt 110e moves, a cyan toner image and a black toner image are transferred onto the yellow toner image and the magenta toner image, respectively, in the primary transfer portion. As a result, a full-color toner image is formed on the intermediate transfer belt. The toner remaining on the surface of the photosensitive drum after the toner image transfer is removed by the cleaner units 105a to 105d.

  Further, in parallel with the toner image forming operation, the sheets S accommodated in the sheet feeding cassette 200 which is a sheet accommodating portion are fed by the feed roller 122 and then separated one by one by the separation roller 123, and the separated sheets are separated. S is conveyed to the registration roller pair 114. Next, the sheet conveyed to the registration roller pair 114 is conveyed to the secondary transfer unit 113 after the timing is adjusted by the registration roller pair 114. Then, the secondary transfer unit 113 applies a positive bias to the secondary transfer roller 113a, whereby the four color toner images on the intermediate transfer belt 110e are secondarily transferred to the conveyed sheet S. After the secondary transfer to the sheet S, the toner remaining on the intermediate transfer belt is removed by the transfer belt cleaning device 111, and the removed toner is collected in a waste toner collection container (not shown).

  The sheet S after the transfer of the toner image is conveyed to the fixing unit 115 and heated and pressed by the fixing roller 115a and the pressure roller 115b, and the full-color toner image is fixed on the surface thereof as a permanent image. Next, after the full-color toner image is fixed as a permanent image, the sheet S is discharged onto the discharge tray 118 by the discharge roller pair 117.

  By the way, as shown in FIG. 2A, after the sheet is fed, it is brought into pressure contact with a feed roller 122 which is a conveying roller for conveying the sheet, and inside the separating roller 123 forming the sheet separating portion, The oil damper 130 is connected as shown in FIG.

  The set torque of the oil damper 130 is set to be smaller than the frictional force received from the feed roller 122 via the sheet S when one sheet S is fed to the nip between the feed roller 122 and the separation roller 123. ing. Thus, when one sheet S is fed to the nip between the feed roller 122 and the separation roller 123, the frictional force received from the feed roller 122 via the sheet S exceeds the set torque, and the separation roller 123 is driven to rotate. .

  The set torque of the oil damper 130 is set to be larger than the frictional force generated between the sheets when two or more sheets S are fed. As a result, when the two sheets are fed to the nip, as shown in FIG. 3, the subsequent sheet Sb receives a frictional force from the preceding sheet Sa lower than the set torque of the oil damper 130, and the sheet Sb and the sheet Sa Slip occurs between the two. As a result, the separation roller 123 does not rotate, and the second and subsequent sheets S are blocked by the nip between the feed roller 122 and the separation roller 123. As described above, in the configuration using the separation roller 123, when two or more sheets S are fed, the oil damper 130 acts as a torque limiter to prevent the sheets S from being double fed.

  That is, when a rotational torque greater than the set torque acts on the separation roller 123, the oil damper 130 connected to the separation roller 123 allows the follow-up rotation of the separation roller 123 that can follow the feed roller 122. Further, when a rotational torque equal to or lower than the set torque acts, the oil damper 130 prevents the follow-up rotation of the separation roller 123. In this way, by using the oil damper 130 as a torque adding portion that applies a load in the rotation direction of the separation roller 123, it is possible to prevent the sheets S from being double fed.

  By the way, in order to prevent double feeding, the relationship between the frictional force between the preceding sheet Sa and the succeeding sheet Sb and the set torque of the oil damper 130 is important. However, since the friction coefficient varies depending on the type of the sheet S, the optimum set torque varies depending on the type of the sheet S. On the other hand, the oil damper 130 has a characteristic that the torque changes according to the rotational speed. Therefore, in the present embodiment, by utilizing the characteristics of the oil damper 130, the rotational speed of the feed roller 122 is increased or decreased according to the type of the sheet S, and the rotational speed of the separation roller 123 is increased or decreased. The set torque is changed.

  FIG. 4 is a control block diagram of the sheet feeding apparatus 120. A CPU 150 is a control unit provided at a predetermined position of the apparatus main body 100A, 151 is an operation unit constituting an input unit for inputting the type of the sheet S, and 152 is a drive unit for driving the feed roller 122. It is a drive motor. Then, the CPU 150 changes the rotation speed of the drive motor 152 based on the sheet information (thickness information) from the operation unit 151 and changes the rotation speed of the feed roller 122. Note that the type of the sheet S may be detected by a sensor, and sheet information may be input to the CPU 150 from the sensor.

  Here, the set torque for the type of the sheet S increases the rotational speed of the feed roller 122 and rotates following the feed roller 122 for thin paper that is likely to cause double feeding as shown in FIG. The set torque is increased by increasing the rotation speed of the separation roller 123. For thick paper that is difficult to cause double feed, the rotational speed of the separation roller 123 is slowed down by slowing down the rotational speed of the feed roller 122 to lower the set torque. This set torque may be set continuously according to the thickness of the sheet, or may be set stepwise according to a certain paper thickness range by setting user input.

  Thus, the torque of the oil damper 130 increases as the rotational speed increases. Therefore, if the rotational speed of the feed roller 122 is changed to change the rotational speed of the separation roller 123 according to the type of the sheet S, the set torque of the oil damper 130 can be prevented from being double fed. The optimum torque possible can be set.

  As described above, the setting torque can be changed in a small space and at low cost by providing the separation roller 123 with the oil damper 130 whose setting torque increases or decreases as the rotational speed of the separation roller 123 increases or decreases.

  As shown in FIG. 5B, the motor torque of the drive motor 152 required for sheet feeding is mainly occupied by the torque required for sheet conveyance and the load torque of the oil damper 130. As for the torque required for sheet conveyance, thick paper generally has a higher load torque. Further, as described above, the load torque of the oil damper 130 does not need to be set high for thick paper. For this reason, compared with the case where a torque limiter is used, the load torque required to feed thick paper can be reduced, whereby the maximum load torque applied to the drive motor 152 can be reduced, and the cost of the drive motor 152 can be reduced. be able to.

  In the above description, the case where the oil damper 130 is connected to the inside of the separation roller 123 has been described. However, as shown in FIG. 6, the oil damper 130 is connected to the shaft 123 a of the separation roller 123. Anyway. Further, a method of changing the set torque of the oil damper according to the type of the sheet S and improving the double feeding of the sheet S is a sheet feeding device using a retard roller 224 provided with means for driving the separation roller to rotate backward. It is also applicable.

  Next, a second embodiment of the present invention using such a retard roller will be described. FIG. 7 is a diagram illustrating a configuration of a sheet feeding device provided in the image forming apparatus according to the present embodiment. In FIG. 7, the same reference numerals as those in FIG. 2 described above indicate the same or corresponding parts.

  7A and 7B, reference numeral 221 denotes a paper feed roller (sheet feed roller), and 224 denotes a retard roller that presses against the feed roller 122. Reference numeral 231 denotes a drive gear rotated by the drive motor 152, 233 denotes a drive transmission gear fixed to the shaft 122a of the feed roller 122, and 232 denotes a drive transmission gear fixed to the shaft 224a of the retard roller 224. The feed roller 122 is driven in the sheet conveying direction (counterclockwise) and the retard roller 224 is rotated in the direction opposite to the sheet conveying direction (counterclockwise) by driving of the driving motor 152 that is a driving unit transmitted via the driving gear 231. ).

  Here, an oil damper 130 is connected to the inside of the retard roller 224 as shown in FIG. Then, the retard roller 224 rotates with the feed roller 122 until the sheet is picked up by the paper feed roller 221 and sent to the nip between the feed roller 122 and the retard roller 224 by the oil damper 130.

  Further, when the sheet S is fed to the nip between the feed roller 122 and the retard roller 224 and the sheet S is one sheet, the frictional force received from the feed roller 122 via the sheet S causes the set torque of the oil damper 130 to be set. The retard roller 224 is driven. On the other hand, when two or more sheets S are fed, the frictional force received from the feed roller 122 via the sheet S is lower than the set torque of the oil damper 130, so that the driving force is received via the drive transmission gear 232. The retard roller 224 is rotated in the direction opposite to the sheet conveying direction. Accordingly, the retard roller 224 pushes back the second and subsequent sheets S from the nip between the feed roller 122 and the retard roller 224.

  Here, as described above, the torque of the oil damper 130 increases as the rotational speed increases. For this reason, if the rotational speed of the feed roller 122 is changed according to the type of the sheet S, the set torque of the oil damper 130 can be set to an optimum torque that can prevent double feeding. . As described above, by using the oil damper 130 as a torque applying portion to the retard roller 224, it is possible to prevent the sheet S from being double fed.

  As described above, in the present embodiment as well, the set torque of the oil damper 130 is changed by changing the rotational speed of the feed roller 122 according to the type of sheet, as in the first embodiment described above. It can be changed to prevent double feeding.

  In the above description, the oil damper 130 is connected to the inside of the retard roller 224. However, as shown in FIG. 8, the oil damper 130 is connected to the shaft 224a of the retard roller 224. Also good. In the above description, the retard roller 224 and the feed roller 122 are driven by the same drive source (drive motor 152). However, even if another drive source is used, the same effect can be obtained if the speed of the retard roller 224 is linked to the speed of the feed roller 122.

  When the retard roller 224 is driven separately from the feed roller 122 as described above, the feed roller 122 is fixed at a constant speed, and the speed of the retard roller 224 is changed, so that the multi-feed according to the sheet thickness is performed. It is possible to set performance. In this case, since the speed of the feed roller 122 can be made constant, the throughput is not affected.

  Next, a third embodiment of the present invention will be described. FIG. 9 is a diagram illustrating a configuration of the sheet feeding apparatus according to the present embodiment. In FIG. 9, the same reference numerals as those in FIG. 2 described above indicate the same or corresponding parts.

  In FIG. 9, a point A indicates a point where the feed roller 122 picks up the sheet S, a point B indicates a nip between the feed roller 122 and the separation roller 123, and a point C indicates a nip between the registration roller pair 114.

  Here, there is a problem that when the sheet S picked up by the feed roller 122 comes into contact with the separation roller 123 between the point A and the point B, the leading end of the sheet breaks. One of the factors is that the rotational speed of the separation roller 123 becomes unstable due to the load torque of the oil damper 130 connected to the separation roller 123.

  In addition, when the sheet S comes to the nip B between the feed roller 122 and the separation roller 123 between the point B and the point C, it is necessary to increase the set torque in order to prevent the sheet S from being double-fed. Further, when the sheet S comes to the nip C of the registration roller pair 114, if the set torque of the oil damper 130 is high, a large back tension is applied to the sheet S, and the conveyance distance of the sheet S may be shifted.

  Therefore, in the present embodiment, by changing the set torque of the oil damper 130 according to the conveyance position of the sheet S, improvement in folding of the leading edge of the paper, improvement of double feeding, and improvement of sheet conveyance are achieved. Yes.

  Next, a change in the set torque of the oil damper 130 according to the conveyance position of the sheet S will be described. First, between the points A and B, the set torque of the oil damper 130 is lowered so that the rotational speed of the separation roller 123 does not become unstable due to the load torque of the oil damper 130.

  For this reason, in the present embodiment, the rotation speed of the feed roller 122 is between the point A and the point B before the sheet S contacts the separation roller 123, that is, until immediately before the sheet S contacts the separation roller 123. Is slowing down (decelerating). As a result, the set torque of the oil damper 130 is lowered, and as a result, the rotation speed of the separation roller 123 is stabilized, and the tip breakage can be improved.

  In addition, between the point B point and the point C point before, that is, before the sheet S reaches the nip B between the feed roller 122 and the separation roller 123 after contacting the separation roller 123, the rotation speed of the feed roller 122 is increased ( Speed up). Thereby, the set torque of the oil damper 130 is increased, and as a result, it is possible to prevent double feeding. Further, after passing through the nip, before the sheet S reaches the nip C, the rotational speed of the feed roller 122 is decreased and the set torque of the oil damper 130 is decreased. Thereby, the back tension applied to the sheet S can be reduced, and the conveyance performance of the sheet S can be improved.

  FIG. 10 is a diagram illustrating the relationship between the rotational speed and the set torque at each conveyance position of the sheet S. Then, as shown in FIG. 10, by changing the set torque by changing the rotation speed of the feed roller 122 according to the sheet conveying position, it is possible to improve folding of the leading edge of the paper, double feeding, and improvement of the sheet conveying property. It becomes. Note that the timing for changing such a set torque is determined by the CPU based on counting pulses of the drive motor 152 or counting by a timer.

  Further, as a method for changing the rotation speed of the feed roller 122, the rotation speed may be gradually increased or gradually decreased in addition to the method shown in FIG. 10, and the same effect can be obtained in this case. . Further, a method for changing the set torque of the oil damper 130 according to the conveying position of the sheet S to improve the leading edge folding, the double feeding, and the sheet conveying property is shown in FIG. The present invention can also be applied to a sheet feeding apparatus using the.

  In the sheet feeding apparatus using the retard roller 224 as described above, the rotational speed of the feed roller 122 is changed according to the transport position of the sheet S as shown in FIG. Like that. As a result, it is possible to improve tip folding and double feeding, and improve sheet transportability. As described above, it goes without saying that the same effect can be obtained even if the retard roller 224 and the feed roller 122 are driven separately. Further, by changing the rotation speed of the feed roller 122 depending on the sheet conveyance position, the set torque can be optimized, and it is possible to improve the folding of the leading edge of the paper, the improvement of double feeding, and the improvement of the paper conveyance performance.

  Although the sheet feeding apparatus provided in the full-color laser printer 100 has been described so far, the present invention is not limited to this and can also be applied to a sheet feeding apparatus provided in a copying machine, a facsimile, or the like. Needless to say. Further, the oil damper 130 has been described as an example of the torque adding unit so far, but the present invention is not limited to this, and the same effect can be obtained as long as the load torque increases in proportion to the speed. be able to.

DESCRIPTION OF SYMBOLS 100 ... Full color laser printer, 100A ... Full color laser printer main body, 100B ... Image forming part, 120 ... Sheet feeding apparatus, 122 ... Feed roller, 123 ... Separation roller, 130 ... Oil damper, 150 ... CPU, 151 ... Operation part, 152 ... Drive motor, 200 ... Paper cassette, 221 ... Feed roller, 224 ... retard roller, S ... Sheet

Claims (8)

In an image forming apparatus including a sheet separation unit formed by a conveyance roller that conveys a sheet, and a separation roller that is in pressure contact with the conveyance roller and that can rotate following the conveyance roller.
Connected to the separation roller, if a rotational torque greater than a set torque acts on the separation roller, the follower rotation of the separation roller is allowed, and if a rotational torque less than the set torque acts, the follower rotation is prevented and A torque adding unit in which the set torque increases or decreases as the rotational speed increases or decreases;
An input unit for inputting sheet information;
A control unit that increases or decreases the rotation speed of the separation roller according to sheet information input from the input unit, and changes the set torque of the torque adding unit;
An image forming apparatus comprising: A drive unit for rotating the transport roller;
The control unit controls the driving unit according to the sheet information input from the input unit to increase or decrease the rotation speed of the transport roller, and to control the rotation speed of the separation roller that rotates following the transport roller. The image forming apparatus according to claim 1, wherein the number is increased or decreased. A drive unit for rotating the separation roller;
The image forming apparatus according to claim 1, wherein the control unit controls the driving unit according to sheet information input from the input unit to increase or decrease the rotation speed of the separation roller.   The sheet information is sheet thickness information, and the control unit reduces the set torque of the torque adding unit by reducing the rotation speed of the separation roller as the sheet is thicker. 4. The image forming apparatus according to any one of items 3.   5. The image forming apparatus according to claim 1, wherein the conveying roller separates the sheet together with the separation roller after the sheet stored in the sheet storage unit is sent out. A sheet feeding roller for feeding out the sheet stored in the sheet storage unit;
The image forming apparatus according to claim 1, wherein the conveying roller separates the sheet fed by the sheet feeding roller together with the separation roller.   The controller decelerates the rotational speed of the separation roller immediately before the sheet contacts the separation roller, and then increases the speed before the sheet reaches the nip between the conveyance roller and the separation roller. The image forming apparatus according to claim 1, wherein the image forming apparatus is decelerated. In an image forming apparatus including a sheet separation unit formed by a conveyance roller that conveys a sheet, and a separation roller that is in pressure contact with the conveyance roller and that can rotate following the conveyance roller.
When a rotation torque greater than a set torque acts on the separation roller, the follower rotation of the separation roller with respect to the transport roller is allowed. In addition, an image forming apparatus is connected, wherein a torque adding unit that increases or decreases the set torque as the rotational speed of the separation roller increases or decreases is connected.

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