JP2016118602A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that conveys a sheet while suppressing the occurrence of looping of a sheet and suppressing a phenomenon where a sheet is strongly pushed into image forming means.SOLUTION: An image forming apparatus 1 comprises: a registration roller pair 2; a motor M1 that drives the registration roller pair 2; a control part 100 that controls the motor M1 to control the conveyance speed of the registration roller pair 2; and image forming means that conveys a sheet P while forming an image on the sheet P conveyed by the registration roller pair 2. The control part 100 controls the drive of the registration roller pair 2 to reduce the conveyance speed of the sheet P by two or more stages during a process from when the leading end of the sheet P reaches the image forming means until when the rear end of the sheet P passes through the registration roller pair 2, and make the conveyance speed when the rear end of the sheet P passes through the registration roller pair 2 slower than the conveyance speed by the image forming means.SELECTED DRAWING: Figure 6

Description

  The present invention relates to an image forming apparatus that conveys a sheet while forming an image on the sheet conveyed by a conveying unit that conveys the sheet.

  In Patent Document 1, after the leading edge of a strong sheet has entered the secondary transfer nip between the intermediate transfer member and the transfer member, the conveyance speed of the conveyance roller pair is reduced below the conveyance speed of the intermediate transfer member and the transfer member. A configuration is disclosed. According to such a configuration, a loop formed between the secondary transfer nip and the conveyance roller pair in the sheet is reduced.

JP 2010-009022 A

  However, in the technique described in Patent Document 1, before the trailing edge of the sheet passes through the pair of conveyance rollers, the speed of the pair of conveyance rollers is increased to a speed substantially equal to the conveyance speed of the intermediate transfer member and the transfer member.

  For this reason, the loop shape between the secondary transfer nip and the conveyance roller pair is set to be large again. Due to the size of the loop shape, when the trailing edge of the sheet passes through the pair of conveying rollers, the sheet may be violated, and the pre-image defect at the secondary transfer nip may be deteriorated.

  In addition, a thick and glossy sheet having a low stiffness may cause a pre-image defect in the secondary transfer nip due to the sheet being strongly pushed into the secondary transfer nip.

  When the trailing edge of the sheet passes through the conveying roller pair, the sheet becomes unsteady, and the load on the intermediate transfer member becomes large due to the absence of conveyance assist of the conveying roller pair on the sheet, so that the pre-image at the primary transfer nip is increased. There is also a possibility of causing a defect.

  SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide an image forming apparatus that conveys a sheet while suppressing the phenomenon of excessively pushing the sheet into the image forming unit while suppressing the occurrence of excessive loops in the sheet. And

  In order to achieve the above object, an image forming apparatus of the present invention includes a conveying unit that conveys a sheet, a driving unit that drives the conveying unit, and a control that controls the conveying unit by controlling the driving unit. And an image forming unit that conveys the sheet while forming an image on the sheet conveyed by the conveying unit, and the control unit is configured to transfer the sheet after the leading edge of the sheet reaches the image forming unit. In the process until the trailing edge passes through the conveying unit, the sheet is decelerated in two or more stages so that the conveying speed when the trailing edge of the sheet exits the conveying unit is slower than the conveying speed of the image forming unit. The driving of the conveying means is controlled.

  According to the present invention, it is possible to convey the sheet while suppressing the phenomenon that the sheet is strongly pushed into the image forming unit while suppressing the occurrence of excessive loops in the sheet.

1 is a cross-sectional view illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. It is sectional drawing which shows a cassette, a pick-up roller, a feed roller, and a separation roller. It is a block diagram of a control part and an actuator. It is sectional drawing which shows a mode that a sheet | seat is conveyed. It is a control graph of ON / OFF of an electromagnetic clutch. It is a graph which shows the relationship between the rotation speed of a motor when a sheet | seat is fed from a cassette, and time.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be exemplarily described in detail with reference to the drawings. However, since the dimensions, materials, shapes, relative positions, etc. of the components described in this embodiment are appropriately changed depending on the configuration of the apparatus to which the invention is applied and various conditions, there is no specific description. As long as the scope of the invention is not limited to these, it is not intended.

  FIG. 1 is a cross-sectional view showing a configuration of an image forming apparatus 1 according to an embodiment of the present invention. The image forming apparatus 1 is a color laser beam printer and includes an apparatus main body 1A as an “image forming apparatus main body”. A plurality of (here, four) cartridges 10 (10Y, 10M, 10C, 10Bk) are mounted inside the apparatus main body 1A. A photosensitive drum 20 as an “image carrier” is disposed inside each of the cartridges 10.

  A cassette 24 for storing sheets P is mounted on the lower side inside the apparatus main body 1A. In the conveyance path of the sheet P conveyed from the cassette 24, a pickup roller 21, a feed roller 22, a separation roller 23, and the like are arranged in order from the cassette 24 side in the sheet conveyance direction.

  The pickup roller 21 as “feeding means” feeds the sheet P inside the cassette 24. The feed roller 22 and the separation roller 23 as “separation means” separate the sheets P fed by the pickup roller 21 one by one.

  A pair of registration rollers 2 as “conveying means” for conveying the sheet P in synchronization with the timing of the image is arranged downstream of the feed roller 22 and the separation roller 23 in the sheet conveying direction L. That is, the feed roller 22 and the separation roller 23 are disposed upstream of the registration roller pair 2 in the sheet conveyance direction L. Further, a top sensor 3 as a detecting unit for detecting the position and jam of the sheet P is disposed immediately downstream of the registration roller pair 2 in the sheet conveying direction L. A scanner unit 4 (exposure device) is provided above the cassette 24. Above the scanner unit 4, the four cartridges 10 described above are arranged.

  The intermediate transfer unit 5 is disposed above the cartridge 10 so as to face the cartridge 10. The intermediate transfer unit 5 includes an intermediate transfer belt 6, a primary transfer roller 7, a driving roller 8, a tension roller 9, a cleaning device 11, and a secondary transfer roller 12.

  The intermediate transfer belt 6 as an “intermediate transfer member” is disposed downstream of the registration roller pair 2 in the sheet conveyance direction L, and the toner image formed on the photosensitive drum 20 is primarily transferred. The secondary transfer roller 12 as “transfer means” secondarily transfers the toner image primarily transferred to the intermediate transfer belt 6 onto the sheet P conveyed by the registration roller pair 2. The “image forming unit” includes the above-described photoreceptor drum 20, intermediate transfer belt 6, secondary transfer roller 12, charging roller, exposure device 4, primary transfer roller 7, and fixing unit 13. Such an “image forming unit” conveys the sheet P while forming an image on the sheet P conveyed by the registration roller pair 2.

  The secondary transfer roller 12 is disposed on the right side of the intermediate transfer unit 5 at a position facing the drive roller 8 via the intermediate transfer belt 6. The primary transfer roller 7, the driving roller 8, and the tension roller 9 are disposed inside the intermediate transfer belt 6 and suspend the intermediate transfer belt 6. A cleaning device 11 is disposed at a position facing the tension roller 9 via the intermediate transfer belt 6.

  A fixing unit 13 is disposed above the intermediate transfer unit 5 and the secondary transfer roller 12. A discharge roller pair 14 and a reversing unit 15 are disposed at the upper left portion of the fixing unit 13. The reversing unit 15 includes a reversing roller pair 16 and a flapper 17 that is a branching unit.

  Next, an image forming operation of the image forming apparatus 1 will be described. The image forming apparatus 1 shown in FIG. 1 sequentially transfers toner images formed by the scanner unit 4 and the photosensitive drum 20 on the intermediate transfer belt 6 that rotates counterclockwise (arrow X direction) (primary transfer). ) And superimpose the toner images of the respective colors. As a result, a full-color toner image is formed on the intermediate transfer belt 6.

  The sheet P stored in the cassette 24 is picked by the pickup roller 21, separated at the separation nip between the feed roller 22 and the separation roller 23, and conveyed to the registration roller pair 2.

  The leading edge of the sheet P conveyed to the registration roller pair 2 is detected by a top sensor 3 provided downstream of the registration roller pair 2 in the sheet conveyance direction L. And based on the detection result of the top sensor 3, the conveyance speed of the registration roller pair 2 is accelerated or decelerated. As a result, the sheet P is conveyed to the transfer position T2 in synchronism with the toner image on the intermediate transfer belt 6. At the transfer position T2, the sheet P is nipped by the intermediate transfer belt 6 and the secondary transfer roller 12, and the sheet P is conveyed at a constant speed, and the toner image is transferred to the sheet P. The sheet P to which the toner image has been transferred at the transfer position T2 is conveyed to the fixing unit 13.

  In the fixing unit 13, the toner image transferred to the sheet P is fixed by the pressure roller 13a and the heating roller 13b. The sheet P on which the toner image is fixed is discharged to the discharge tray 25 at the upper part of the apparatus by the discharge roller pair 14. Here, it is assumed that the sheet conveying apparatus 200 includes a feed roller 22, a separation roller 23, and a registration roller pair 2. The intermediate transfer belt 6, the driving roller 8, and the secondary transfer roller 12 also convey the sheet P, but are included in the image forming unit.

  FIG. 2 is a cross-sectional view showing the cassette 24, the pickup roller 21, the feed roller 22, and the separation roller 23. The pickup roller 21 as a “feeding unit” feeds the sheet P stored in the cassette 24. The pickup roller 21 picks up and conveys the sheet P toward the separation nip N formed by the feed roller 22 and the separation roller 23.

  The feed roller 22 and the separation roller 23 as “separation means” separate the sheets P one by one. The separation roller 23 has a torque limiter 26 inside. The torque limiter 26 is mounted in a state where the D-shaped shaft portion 26 a does not rotate with respect to the holder 28. The holder 28 is configured to be rotatable around a rotation center 28a, and the separation roller 23 is pressed against the feed roller 22 via the holder 28 by a compression spring 27. In a state where the sheet P is nipped between the feed roller 22 and the separation roller 23, the separation roller 23 rotates in the arrow direction (counterclockwise) in FIG.

  When the feed roller 22 is rotating and when a single sheet is being conveyed, the separation roller 23 is driven by the conveyed sheet P and is opposite to the arrow direction in FIG. 2 (clockwise). Rotate to. When a plurality of sheets P are conveyed by the pickup roller 21 while being overlapped, the separation roller 23 does not rotate. As a result, the sheets P are separated one by one. The pickup roller 21 and the feed roller 22 separate and convey the sheet P one by one to the registration roller pair 2 arranged downstream thereof.

  FIG. 3 is a block diagram of the control unit 100 and the actuator. The control unit 100 as “control means” of the image forming apparatus 1 is connected to the motor M1, the motor M2, the top sensor 3, and the electromagnetic clutch CR, and controls the driving thereof. The motor M1 as “driving means” rotates (drives) the pickup roller 21, the feed roller 22, and the registration roller pair 2.

  The control unit 100 controls the conveyance speed of the pickup roller 21, the feed roller 22, and the registration roller pair 2 by controlling the driving of the motor M <b> 1. The drive from the motor M1 to the pickup roller 21 and the feed roller 22 is connected (ON) and disconnected (OFF) by an electromagnetic clutch CR as a clutch means. The motor M2 rotates the drive roller 8. When the driving roller 8 rotates in the arrow direction of FIG. 4, the intermediate transfer belt 6 of the intermediate transfer unit 5 similarly rotates in the arrow direction of FIG.

  Although details will be described later with reference to FIG. 4, the control unit 100 determines that the leading end of the sheet P reaches the secondary transfer roller 12 as “image forming unit” and then the trailing end of the sheet P moves the registration roller pair 2. In the process until exit, the sheet P is decelerated in two or more stages, and the transport speed when the trailing edge of the sheet P exits the registration roller pair 2 becomes slower than the transport speed of the intermediate transfer belt 6 as the “image forming unit”. Thus, the drive of the motor M1 is controlled.

  When the trailing edge of the sheet P passes the registration roller pair 2 in the process from when the leading edge of the sheet P reaches the “image forming unit” until the trailing edge of the sheet P passes through the registration roller pair 2, The driving of the motor M1 is controlled so that the conveyance speed of the sheet P by the registration roller pair 2 is the slowest. The control unit 100 has only one speed mode that is slower than the conveying speed of the sheet P by the intermediate transfer belt 6 as “image forming means”.

  FIG. 4 is a cross-sectional view showing how the sheet P is conveyed. FIG. 5 is a control graph of ON / OFF of the electromagnetic clutch CR. As shown in FIG. 5, when the control unit 100 receives the signal for starting the feeding operation, the control unit 100 turns on the electromagnetic clutch CR and causes the pickup roller 21 and the feed roller 22 to react with each other as shown in FIG. Rotate clockwise. The sheet P is conveyed by the pickup roller 21 and the feed roller 22 and is conveyed toward the registration roller pair 2. Since the conveyance path between the separation nip N and the registration roller pair 2 is curved, the sheet P is conveyed while forming a loop shape.

  After the leading edge of the sheet P reaches the registration roller pair 2, the sheet P is conveyed by the feed roller 22 and the registration roller pair 2. If the conveying speed of the sheet P at the separation nip N is defined as Vf and the conveying speed of the sheet P at the registration roller pair 2 is defined as Vr1, the control unit 100 sets the speed relationship of the conveying speed so that Vf <Vr1. Therefore, the loop formed between the separation nip N and the registration roller pair 2 is gradually eliminated by the speed difference between Vf and Vr1, and the state shown in FIG.

  The top sensor 3 is provided downstream of the registration roller pair 2 in the sheet conveyance direction L, and detects that the leading edge of the sheet P has passed. The control unit 100 turns off the electromagnetic clutch CR at the timing shown in FIG. 5 after a predetermined time TC has elapsed since the top sensor 3 detected the leading edge of the sheet P. When the electromagnetic clutch CR is turned off, the drive transmission from the motor M1 to the pickup roller 21 and the feed roller 22 is stopped.

  In this embodiment, the pickup roller 21 and the feed roller 22 are provided with a 1 WAY gear. Therefore, even if drive transmission to the pickup roller 21 and the feed roller 22 is stopped, the pickup roller 21 and the feed roller 22 rotate following the sheet P.

  Further, until the trailing edge of the sheet P passes through the separation nip N, it is affected by the load (back tension) of the feed roller 22 and the separation roller 23. The back tension is generated by a torque limiter 26 inside the separation roller 23. When the registration roller pair 2 is affected by the back tension, a slight slip occurs between the registration roller pair 2 and the sheet P. For this reason, the conveyance speed of the sheet P by the registration roller pair 2 is slower than the peripheral speed of the registration roller pair 2.

  The sheet P conveyed by the registration roller pair 2 is conveyed toward the transfer position T2 between the drive roller 8 and the secondary transfer roller 12. As shown in FIG. 4C, at the transfer position T2, the driving roller 8 and the secondary transfer roller 12 convey the sheet P to the downstream side in the sheet conveying direction L while transferring the image to the sheet P.

  FIG. 6 is a graph showing the relationship between the rotation speed of the motor M1 and time when the sheet P is fed from the cassette 24. The number of rotations of the motor M1 represents the “calculated” conveyance speed (hereinafter referred to as peripheral speed) of the registration roller pair 2. However, the belt speed is not the speed of the motor M1, but the speed of the intermediate transfer belt 6.

  The control unit 100 transmits a feeding operation start signal to start the rotation of the motor M1 (the parts of the line J1 and the line J1, hereinafter the same for the line J). At the start of the feeding operation, the motor M1 is driven to rotate at a normal speed (line J1). In FIG. 6, “normal speed” and “belt speed” are described. “Normal speed” is the normal speed of the motor M1. “Belt speed” is the belt speed of the intermediate transfer belt 6. The normal speed of the motor M1 is a speed mode set to a speed slightly higher than the belt speed of the intermediate transfer belt 6.

  As described above, after the leading edge of the sheet P passes through the top sensor 3, the control unit 100 accelerates the rotational speed of the motor M1 (the peripheral speed of the registration roller pair 2) based on the detection result of the top sensor 3 (line). J2 → line J3) and decelerate (line J3 → line J4). This is called acceleration / deceleration control. This is because the toner image on the surface of the intermediate transfer belt 6 and the transfer position of the sheet P are matched. FIG. 6 shows a case where the number of rotations of the motor M1 (the peripheral speed of the registration roller pair 2) is increased to be constant and decelerated.

  The controller 100 then returns the rotational speed of the motor M1 (the peripheral speed of the registration roller pair 2) to the normal speed once (line J5). Thereafter, the controller 100 shifts the rotation speed of the motor M1 (the peripheral speed of the registration roller pair 2) to the assist speed (lines J6 and J7).

  Until the trailing edge of the sheet P passes through the separation nip N, the rotational speed of the motor M1 (the peripheral speed of the registration roller pair 2) is affected by the load (back tension) of the separation roller 23 and the feed roller 22. The back tension is generated by a torque limiter 26 inside the separation roller 23. When the registration roller pair 2 is affected by the back tension, a slight slip occurs between the registration roller pair 2 and the sheet P. Therefore, the conveyance speed of the sheet P by the registration roller pair 2 is slower than the peripheral speed of the registration roller pair 2.

  In order to adjust the delay, the control unit 100 sets the rotational speed of the motor M1 (the peripheral speed of the registration roller pair 2) to an assist speed that is slightly higher than the normal speed (line J7). In terms of calculation, the peripheral speed of the registration roller pair 2 increases as shown in the graph of FIG. 6, but the conveyance speed at which the actual registration roller pair 2 conveys the sheet P is set to be close to the normal peripheral speed.

  Thereafter, immediately before the leading edge of the sheet P reaches the transfer position T2, the control unit 100 increases the rotational speed of the motor M1 (the peripheral speed of the registration roller pair 2) to the T2 entry speed (lines J8 and J9). This is called T2 entry control.

  When the sheet P enters the transfer position T2, the load applied to the drive roller 8 increases, and the conveyance speed of the intermediate transfer belt 6 decreases momentarily. When the conveyance speed of the intermediate transfer belt 6 is slow, the density change of the developer image occurs during the primary transfer in which the developer image on the photosensitive drum 20 is transferred to the intermediate transfer belt 6, resulting in a blurred image. In order to prevent this, immediately before the leading edge of the sheet P reaches the transfer position T2, the number of rotations of the motor M1 is increased so that the sheet P enters the transfer position T2, and the conveyance speed of the intermediate transfer belt 6 is slow. It cancels a certain amount.

  Thick paper and glossy paper that have a large transport resistance at the moment of entry to the transfer position T2 are preferred to increase the T2 input speed. Thin paper and plain paper and other materials that have a low transport resistance always require T2 entry control. I don't need it. The T2 entry speed is preferably set appropriately according to conditions such as the sheet P, use environment, and conveyance speed. If the T2 entry speed is not required, the assist control speed mode may be maintained.

  When the leading edge of the sheet P passes the transfer position T2 (after the sheet P reaches the transfer nip between the intermediate transfer belt 6 and the secondary transfer roller 12), the control unit 100 ends the T2 entry control (line). J10). Then, the control unit 100 returns the speed of the motor M1 to the assist speed (first driving speed (speed of the line J11)) again. When the trailing edge of the sheet P passes through the separation nip N (immediately after the sheet P passes through the feed roller 22 and the separation roller 23), the control unit 100 changes the speed of the motor M1 to the registration speed (the second speed). (Drive speed (speed of line J13)) (line J12, line J13).

  When the control unit 100 decelerates the sheet P in two stages, the speed of the motor M1 is decreased from the first driving speed (the speed of the line J11) to the second driving speed (the line J13) in the first stage. (The second stage will be described later). When the trailing edge of the sheet P passes through the separation nip N, the influence of the separation means load (back tension) is eliminated. Therefore, if the assist control is maintained, the loop shape between the transfer position T2 and the registration roller pair 2 becomes large. This is to avoid this.

  The registration speed is not necessarily higher than the belt speed. In some cases, a sufficient loop shape is formed before reaching the registration speed, and it is not necessary to form a loop shape beyond that. In this case, the control unit 100 may set the registration speed to the same speed as the belt speed, or may make the registration speed slower than the belt speed if it is better to reduce the loop shape.

  Deceleration from “assist speed” to “registration speed” is the first stage of deceleration (J11, J12, J13). As the deceleration method, a rectangular deceleration method is preferable instead of the linear deceleration described by the two-dot chain line in FIG. When the controller 100 decelerates from the first drive speed (speed of line J11) to the second drive speed (speed of line J13), the control section 100 decreases the speed stepwise. This is because when the trailing edge of the sheet P passes through the separation nip N, the load on the separation means (back tension) is lost digitally at that timing, so that it is easier to obtain an effect by quickly responding to the change. .

  Next, from the “registration speed” (the speed of the motor M1 immediately after the sheet P passes through the feed roller 22 and the separation roller 23) from the second driving speed (speed of line J13), Decreasing the speed of the motor M1 when passing through the pair of conveyance rollers to the third driving speed (speed of line J15) is the second stage of deceleration (J13, J14, J15).

  That is, in the second stage, the control unit 100 reduces the speed of the motor M1 from the second drive speed (the speed of the line J13) to the third drive speed (the speed of the line J15) slower than the second drive speed. The registration missing speed is set to a speed mode that is slower than the belt speed, and is a speed from the time when the trailing edge of the sheet P finishes before the registration roller pair 2 exits.

  The registration skip speed is effective when the speed is the slowest in a series of speed modes. This is because if the pushing force of the registration roller pair 2 with respect to the transfer position T2 is the weakest, the load fluctuation when the trailing edge of the sheet P passes through the registration roller pair 2 can be minimized.

  The method of deceleration is not the linear deceleration described with a two-dot chain line in FIG. 6, but a rectangular deceleration method (lines J11, J12, J13, J14, J15). When the controller 100 decelerates from the second drive speed (speed of line J13) to the third drive speed (speed of line J15), the control section 100 decreases the speed stepwise.

  In this case, when linear deceleration is performed, the loop shape becomes smaller from the point A. When the loop shape disappears, the conveyance of the sheet P at the transfer position T2 may cause the blur of the blurred image due to slippage of the sheet P at the secondary transfer portion due to the conveyance of the sheet P of the registration roller pair 2 as a brake. There is. In order to avoid this, the registration missing speed must be set to a speed of point C indicated by a two-dot chain line, which is faster than the speed of point B indicated by a solid line.

  The size of the loop shape when the trailing edge of the sheet P passes through the registration roller pair 2 is the same as the deceleration method indicated by the solid line and the deceleration method indicated by the two-dot chain line, but the registration roller pair for the transfer position T2 is the same. The pushing force of 2 is different.

  The method of deceleration may not be two steps, but may be three steps or more. Further, a non-linear deceleration method close to a rectangular shape may be used. The optimum deceleration may be performed by taking into consideration various parameters such as the product transport roller configuration, media specifications, and transport speed.

  As described above, the control unit 100 has at least one speed mode that is slower than the conveyance speed of the sheet P by the intermediate transfer belt 6 serving as an “image forming unit”. 3rd driving speed / speed of line J15). However, a form not limited to this is also possible. For example, after setting the speed of the motor M1 to the registration skip speed, the speed of the motor M1 is once made higher than the intermediate transfer belt speed, and then the speed of the motor M1 is set again to the registration skip speed. It is also possible to make it.

  According to the configuration of the embodiment, a phenomenon in which the sheet P is strongly pressed between the intermediate transfer belt 6 as the “image forming unit” and the secondary transfer roller 12 while suppressing occurrence of excessive loops in the sheet P. The sheet P can be conveyed while suppressing this.

  Since the loop shape between the transfer position T2 and the registration roller pair 2 can be reduced by the time the rear end of the sheet P passes through the registration roller pair 2, even if the rear end of the sheet P passes through the registration roller pair 2. The rampage of the sheet P is suppressed and pre-image defects are reduced. Further, when the trailing edge of the sheet P passes through the registration roller pair 2, the pushing force of the registration roller pair 2 with respect to the transfer position T2 is weak, so even if the trailing edge of the sheet P passes through the registration roller pair 2, the intermediate transfer belt 6 Load fluctuation is small, and pre-image defects are reduced.

  In the above-described embodiment, the registration roller pair 2 is used as the “conveying unit”. However, the present invention is not limited to this, and the pickup roller 21, the feed roller 22, and the separation roller 23 are used as the “conveying unit”. There can also be a configuration.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Registration roller pair (conveyance means)
6 Intermediate transfer belt (image forming means)
12 Secondary transfer roller (image forming means)
20 Photosensitive drum (image forming means)
21 Pickup roller (feeding means)
100 Control unit (control means)
L Sheet conveyance direction M1 Motor (drive means)
P sheet

Claims (7)

Conveying means for conveying the sheet;
Driving means for driving the conveying means;
Control means for controlling the driving means to control the conveying speed of the conveying means;
Image forming means for conveying the sheet while forming an image on the sheet conveyed by the conveying means;
With
The control means decelerates the sheet in two or more stages from the time when the leading edge of the sheet reaches the image forming means to the time when the trailing edge of the sheet exits the conveying means, and the trailing edge of the sheet is conveyed by the conveying means. An image forming apparatus, wherein the driving of the conveying unit is controlled so that a conveying speed when exiting the unit is slower than a conveying speed of the image forming unit.   The control unit is configured to transfer the conveying unit when the trailing end of the sheet passes through the conveying unit in a process from when the leading end of the sheet reaches the image forming unit until the trailing end of the sheet passes through the conveying unit. The image forming apparatus according to claim 1, wherein the driving of the driving unit is controlled so that the sheet conveyance speed by the sheet is the slowest.   In the process from the time when the leading edge of the sheet reaches the image forming means until the trailing edge of the sheet exits the conveying means, the control means sets a speed mode that is slower than the sheet conveying speed by the image forming means. The image forming apparatus according to claim 1, wherein the image forming apparatus includes a plurality of image forming apparatuses.   In the process from the time when the leading edge of the sheet reaches the image forming means until the trailing edge of the sheet exits the conveying means, the control means sets a speed mode that is slower than the sheet conveying speed by the image forming means. The image forming apparatus according to claim 1, wherein only one image forming apparatus is provided.   The image forming means transports an image carrier, an intermediate transfer body to which a toner image formed on the image carrier is primarily transferred, and a toner image primarily transferred to the intermediate transfer body by the transport means. 5. The image forming apparatus according to claim 1, further comprising: a transfer unit that performs secondary transfer onto the formed sheet. Separating means for separating the sheets fed from the feeding means for feeding the sheets one by one upstream from the conveying means in the sheet conveying direction;
The control means sets the speed of the drive means after the sheet reaches the transfer nip between the intermediate transfer body and the transfer means as a first drive speed, and the speed of the drive means immediately after the sheet exits the separation means. Is the second drive speed, and the speed of the drive means when the sheet exits the conveying means is the third drive speed. When the sheet is decelerated in two stages, the speed of the drive means is set in the first stage. The first drive speed is decelerated from the first drive speed to the second drive speed that is slower than the first drive speed, and the speed of the drive means is decreased from the second drive speed to the second drive speed in the second stage. The image forming apparatus according to claim 5, wherein the image forming apparatus is decelerated to three drive speeds.   The control means reduces the speed stepwise when decelerating from the first drive speed to the second drive speed, and increases the speed stepwise when decelerating from the second drive speed to the third drive speed. The image forming apparatus according to claim 6, wherein:

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