JP2012236657A - Sheet conveying device, image forming apparatus, and image reading device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly prevent the generation of large noise when a slack in a sheet conveyed from a paper feed roller to a conveyance roller is removed.SOLUTION: When removing a slack generated in a conveyed sheet S between a paper feed roller 13 and a conveyance roller 21, a control means 60 for controlling a rotation speed of the paper feed roller is provided. The slack amount of the sheet between the paper feed roller and the conveyance roller is reduced by reducing the sheet conveyance speed in the paper feed roller before a trailing end of the sheet passes through the paper feed roller. In accordance with the slack amount of the sheet at this point of time, the sheet conveyance speed in the paper feed roller is controlled by the control means, and a speed difference of the sheet conveyance speed between the paper feed roller and the conveyance roller at the point when the slack of the sheet is removed is equal to or lower than a predetermined speed difference.

Description

  The present invention relates to a sheet conveying apparatus that conveys a sheet in an image forming apparatus, an image reading apparatus, or the like. In particular, a sheet feeding roller that feeds and conveys the sheet and a sheet conveying roller that is provided downstream of the sheet feeding direction in the sheet conveying direction and conveys the sheet are provided. In the sheet conveying apparatus in which the deflection of the sheet conveyed between the paper feeding roller and the conveying roller is faster than the sheet conveying speed of the sheet, the deflection of the sheet is eliminated without reducing the sheet conveying efficiency. This is characterized in that the generation of sound at the time is reduced and the deflection of the sheet can be eliminated in a short time.

  For example, in an image forming apparatus such as a copying machine or a printer, in order to feed a sheet stacked on a paper feed cassette into the machine and carry it in, the uppermost sheet stacked on the paper feed cassette is used. Pickup roller that picks up, paper feed roller that pulls out the picked up sheet from the paper cassette to the paper feed conveyance path, and this paper feed roller, facing the paper feed roller, prevents two or more sheets from being stacked and conveyed A separating roller is provided.

  A torque limiter is provided on the rotating shaft of the separation roller. When a rotational force exceeding the rotation limiting force of the torque limiter is applied to the separation roller, the separation roller rotates.

  Here, the rotation limit force of the torque limiter is set to be larger than the friction force between the sheets, and is set to be smaller than the friction force between the sheet and the separation roller. It prevents it from being conveyed.

  Further, in the sheet feeding and conveying path, a conveying roller is provided at a position downstream of the sheet feeding direction and the separating roller in the sheet conveying direction, and the sheet conveying speed by the conveying roller is fed. The sheet is transported at a speed lower than the sheet transport speed by the roller to prevent the sheet from being pulled between the paper feed roller and the transport roller during the transport.

  Here, until the sheet is guided from the sheet feeding roller to the conveying roller through the sheet feeding conveyance path, a deflection is formed on the sheet conveyed in the sheet feeding conveyance path, and the sheet is conveyed as described above. When the sheet conveying speed by the roller is set lower than the sheet conveying speed by the sheet feeding roller, the deflection of the sheet between the sheet feeding roller and the conveying roller is further increased.

  If a large space is provided in the sheet feeding / conveying path so that such sheet deflection is sufficiently accommodated in the sheet feeding / conveying path between the sheet feeding roller and the conveying roller, the apparatus becomes large. There are problems such as.

  For this reason, conventionally, the sheet feeding roller is stopped from rotating after a certain period of time has passed since the sheet is guided from the sheet feeding roller through the sheet feeding conveyance path to the conveyance roller.

  When the rotation of the paper feed roller is stopped and only the transport roller is rotated at a constant speed in this way, the deflection in the sheet is drastically reduced, and when the deflection is eliminated, the sheet is tensioned. The seat itself produces a loud noise. It is known that this sound becomes louder as the speed at which the deflection is eliminated is higher.

  In the image forming apparatus disclosed in Patent Document 1, in the secondary sheet feeding after the deflection is formed on the sheet, the registration roller is driven before the conveyance roller, and the deflection on the sheet is eliminated. Until then, the driving speed of the driving means for driving the registration roller and the conveying roller is controlled stepwise to prevent the sheet from being strongly hit against the guide.

  However, since the image forming apparatus disclosed in Patent Document 1 increases the rotational speed of the registration roller in a stepwise manner, the rising speed when the sheet is conveyed by the registration roller is slow, and the sheet is conveyed. There is a drawback that the efficiency is lowered and the image forming efficiency is lowered.

JP 2005-154119 A

  According to the present invention, the sheet conveying speed of the sheet feeding roller that feeds and conveys the sheet is faster than the sheet conveying speed of the conveying roller that is provided on the downstream side of the sheet feeding direction with respect to the sheet conveying direction. In a sheet conveying device in which a deflection is formed in a sheet conveyed between a paper roller and a conveying roller, a large noise is generated when the deflection of the sheet is eliminated without reducing the sheet conveying efficiency. An object of the present invention is to prevent the sheet flexure in a short time while preventing it appropriately.

  In the present invention, in order to solve the above-described problems, a sheet feeding roller that feeds and conveys a sheet, and a conveyance roller that conveys the sheet by being provided downstream of the sheet feeding roller in the sheet conveying direction are provided. In the sheet conveying apparatus in which the sheet conveying speed by the sheet feeding roller is faster than the sheet conveying speed by the conveying roller and the sheet conveyed between the sheet feeding roller and the conveying roller is bent, Control means for controlling the rotation speed is provided, and before the trailing edge of the sheet passes through the sheet feeding roller, the sheet conveying speed in the sheet feeding roller is reduced to reduce the amount of deflection of the sheet between the sheet feeding roller and the conveying roller. According to the amount of deflection of the sheet at this point, the sheet feeding roller and the conveying roller At the time when the deflection of the sheet is eliminated during, and so that the speed difference between the sheet conveying speed of the sheet conveying speed and the conveying roller by the paper feed roller below a predetermined speed difference.

  Thus, before the trailing edge of the sheet passes through the sheet feeding roller, the sheet conveying speed by the sheet feeding roller is reduced, and then the sheet conveying speed by the sheet feeding roller is controlled to eliminate the sheet deflection. If the difference in speed between the sheet conveyance speed by the paper feed roller and the sheet conveyance speed by the conveyance roller is less than the predetermined speed difference, the load applied to the sheet is reduced when the deflection is eliminated, and the sound at the time of eliminating the deflection is reduced. Is suppressed.

  Further, in the present invention, at the stage where the sheet is conveyed by the conveying roller as described above, the sheet conveying speed by the sheet feeding roller is only controlled so as to eliminate the deflection of the sheet. Since the sheet is conveyed at a constant sheet conveyance speed, the sheet conveyance efficiency does not decrease.

  Here, when the difference between the sheet conveyance speed by the sheet feeding roller and the sheet conveyance speed by the conveyance roller at the time when the sheet deflection is eliminated as described above is less than a predetermined speed difference, In order to sufficiently suppress the occurrence, it is preferable to set the speed difference to 100 mm / s or less.

  Further, by the above control means, the difference in speed between the sheet conveyance speed by the sheet feeding roller and the sheet conveyance speed by the conveyance roller at the time when the deflection of the sheet is eliminated as described above is equal to or less than a predetermined speed difference. In controlling the sheet conveying speed by the sheet feeding roller, a deflection amount detecting means for detecting the deflection amount of the sheet between the sheet feeding roller and the conveying roller is provided, and the sheet amount conveying by the sheet feeding roller is performed by the deflection amount detecting means. It is detected that the amount of deflection of the sheet has reached a predetermined amount of deflection by decelerating the speed, or the amount of deflection of the sheet when the sheet conveying speed of the paper feed roller is decelerated is detected and fed by the above control means. The sheet conveyance speed in the paper roller can be controlled. Also, the amount of deflection of the sheet at the time when the sheet conveying speed at the sheet feeding roller is decelerated is calculated from the type of sheet to be conveyed, the sheet conveying speed by the sheet feeding roller, the sheet conveying speed by the conveying roller, and the like. The sheet conveying speed in the sheet feeding roller can be controlled by the control means.

  In the image forming apparatus according to the present invention, the sheet conveying apparatus as described above is used to convey a sheet of recording paper or the like accommodated in a sheet feeding cassette or the like.

  In the image reading apparatus according to the present invention, the sheet conveying apparatus as described above is used to convey a document sheet set on a document feeding tray or the like.

  In the sheet conveying apparatus of the present invention, the trailing edge of the sheet is used as the sheet feeding roller and the conveying roller whose sheet conveying speed is slower than that of the sheet feeding roller. Before passing, the sheet conveying speed at the sheet feeding roller is reduced to reduce the sheet deflection amount between the sheet feeding roller and the conveying roller, and the sheet is fed by the control means according to the sheet deflection amount at this time. The sheet conveyance speed at the roller is controlled so that the difference between the sheet conveyance speed by the sheet feeding roller and the sheet conveyance speed by the conveyance roller at the time when the deflection of the sheet is eliminated is equal to or less than a predetermined speed difference. The load applied to the seat when it is eliminated is reduced, and the generation of sound when the deflection is eliminated is suppressed.

  In the sheet conveying apparatus of the present invention, the sheet conveying speed is controlled only by the sheet feeding roller so as to eliminate the deflection of the sheet as described above, and the sheet is conveyed by the conveying roller at a constant sheet conveying speed. The sheet conveying efficiency is not lowered, and the image forming efficiency is not lowered.

  Further, in the sheet conveying apparatus of the present invention, before controlling the sheet conveying speed in the sheet feeding roller by the control means, the sheet conveying speed in the sheet feeding roller is greatly reduced to greatly reduce the deflection amount of the sheet, and thereafter The control means controls the sheet conveying speed of the sheet feeding roller, and the difference in speed between the sheet conveying speed by the sheet feeding roller and the sheet conveying speed by the conveying roller at the time when the deflection of the sheet is eliminated is less than a predetermined speed difference. The sheet deflection can be eliminated in a short time.

1 is a schematic explanatory diagram of an image forming apparatus provided with a sheet conveying apparatus according to an embodiment of the present invention. It is a schematic block diagram showing a sheet conveyance control system in the sheet conveyance apparatus according to the embodiment. In the sheet conveying apparatus according to the above-described embodiment, it is a schematic explanatory view showing, in an enlarged manner, a location where a sheet feeding roller, a separation roller, and a conveying roller are arranged. In the sheet conveying apparatus according to the above embodiment, the sheet conveying speed by the sheet feeding roller until the deflection is eliminated after the sheet is fed, the sheet conveying speed by the conveying roller, and the state of increase / decrease in the amount of deflection in the sheet. It is the shown schematic explanatory drawing. In the sheet conveying apparatus according to the above-described embodiment, when the ratio of reducing the sheet conveying speed by the sheet feeding roller is large and the deflection amount in the sheet reaches a predetermined deflection amount, the sheet conveyance between the conveying roller and the sheet feeding roller is performed. FIG. 6 is a schematic explanatory diagram illustrating a sheet conveyance speed by a sheet feeding roller, a sheet conveyance speed by a conveyance roller, and an increase / decrease state of a deflection amount in a sheet when a speed difference from a speed exceeds a predetermined speed difference. In the sheet conveying apparatus according to the above embodiment, a graph showing a relationship between a difference in sheet conveying speed between the conveying roller and the sheet feeding roller at the time when the deflection is eliminated and a sound pressure level generated when the deflection is eliminated. is there. 5 is a flowchart illustrating an operation for eliminating a sheet deflection generated between a sheet feeding roller and a conveying roller in the sheet conveying apparatus according to the embodiment. In the sheet conveying apparatus according to the above-described embodiment, a schematic explanation showing an example in which a clutch mechanism for controlling on / off of transmission of rotation to the sheet feeding roller is provided in the rotation transmission mechanism for transmitting rotation to the sheet feeding roller. FIG. FIG. 9 is a schematic block diagram of a sheet conveyance control system to which control for turning on and off a clutch mechanism is added in the example illustrated in FIG. 8. 1 is a schematic explanatory diagram of an image reading apparatus provided with a sheet conveying apparatus according to an embodiment of the present invention.

  Next, a sheet conveying apparatus according to an embodiment of the present invention will be specifically described with reference to the accompanying drawings. Note that the sheet conveying apparatus according to the present invention is not limited to the one shown in the following embodiment, and can be implemented with appropriate modifications within a range not changing the gist thereof.

  FIG. 1 shows an image forming apparatus provided with the sheet conveying apparatus of this embodiment.

  The image forming apparatus is, for example, a printer that forms an image on a sheet based on image data or text data input from the outside via a network or the like. A path 20, an image forming unit 30, a fixing unit 40, a paper discharge unit 50, and the like are provided.

  Here, the paper supply unit 10 includes a paper supply cassette 11, a pickup roller 12, a paper supply roller 13, a separation roller 14, and the like. When the pickup roller 12 rotates, the sheet S stacked on the push-up plate 11b urged by the spring 11a in the paper feed cassette 11 is placed between the paper feed roller 13 and the separation roller 14. Is sent to.

  Further, a torque limiter (not shown) is provided on the rotating shaft of the separation roller 14. The rotation limiting force of the torque limiter is set to be larger than the friction force between the sheets S, but is set to be smaller than the friction force between the sheet S and the separation roller 14.

  For this reason, when a single sheet S is fed between the paper feed roller 13 and the separation roller 14, the frictional force between the single sheet S and the separation roller 14 is the torque limiter described above. Therefore, the separation roller 14 also rotates and conveys one sheet S. On the other hand, when two or more sheets S are sent between the paper feed roller 13 and the separation roller 14, the separation roller 14 rotates because the frictional force between the sheets S is less than the rotation limiting force of the torque limiter. Instead, only the sheet S in contact with the paper feed roller 13 is conveyed by the paper feed roller 13.

  The sheet conveyance path 20 includes an image forming path 20A, a paper discharge / reverse path 20B, a double-side conveyance path 20C, and various rollers disposed on these paths.

  The image forming path 20A is provided with a conveying roller 21, a registration roller 22, a secondary transfer roller 34, a fixing unit 40, and the like, and the sheet S taken out by the paper feeding roller 13 is positioned on the downstream side thereof. Passing through the conveying roller 21, the image forming apparatus waits at a position of the registration roller 22 and is conveyed by the registration roller 22 in accordance with the image formation timing.

  A paper discharge roller 23A and a reverse roller 23B are provided in the paper discharge / reverse path 20B. In the case of single-sided printing, the sheet S that has passed through the image forming path 20A is guided to the paper discharge / reverse path 20B, and is discharged as the paper discharge roller 23A rotates in the forward direction. On the other hand, in the case of duplex printing, the single-side printed sheet S that has passed through the image forming path 20A is guided to the reverse roller 23B side by the switching claw 24, and after the reverse roller 23B rotates in the forward direction, By rotating in the opposite direction, the trailing edge of the sheet S becomes the leading edge and is guided to the duplex conveyance path 20C.

  The image forming unit 30 includes an image forming unit 30Y for yellow, an image forming unit 30M for magenta, an image forming unit 30C for cyan, an image forming unit 30K for black, and an intermediate transfer belt 33. And a secondary transfer roller 34. Each of the image forming units 30Y, 30M, 30C, and 30K includes a photosensitive drum 31, a charging device (not shown), an exposure device, a developing device, a primary transfer roller, and a cleaning device that are arranged around the photosensitive drum 31.

  Here, the toner images formed on the respective photosensitive drums 31 in the respective image forming units 30Y, 30M, 30C, and 30K are primarily transferred onto the intermediate transfer belt 33 in order, and are transferred onto the intermediate transfer belt 33. A full-color toner image is formed on the top. When the sheet S passes between the intermediate transfer belt 33 and the secondary transfer roller 34, the toner image primarily transferred onto the intermediate transfer belt 33 is transferred to one surface of the sheet S.

  The fixing unit 40 includes, for example, a heat fixing roller 41 having a heat source and a pressure roller 42 in contact with the heat fixing roller 41, and heats the sheet S on which a toner image passing between both the rollers 41, 42 is formed. Pressurize to fix the toner image transferred to the sheet S to the sheet S. The sheet S subjected to the fixing process is stacked on the paper discharge unit 50.

  FIG. 2 is a schematic block diagram showing a sheet conveyance control system in the sheet conveyance apparatus used in the image forming apparatus shown in FIG. The control means 60 composed of a microcomputer or the like includes a CPU (not shown), a memory (ROM, RAM, EEPROM, etc.) for storing a program for operating the CPU and various information, various sensors, a motor, and an electromagnetic clutch. And an I / O (input / output) interface for connecting the electromagnetic operation unit and the like to the CPU.

  As shown in FIG. 2, the control unit 60 includes a deflection amount detection sensor 61 that detects the deflection amount formed by the sheet S, and a sheet that detects that the leading edge of the sheet S has been guided to the position of the conveyance roller 21. A sensor 62, a paper feed motor driver 63 that controls a motor that rotates the paper feed roller 13, a transport motor driver 64 that controls a motor that rotates the transport roller 21, and the like are connected.

  As shown in FIG. 3, the above-described deflection amount detection sensor 61 is disposed in a curved sheet-feed conveyance path that conveys the sheet S from the sheet feed roller 13 to the conveyance roller 21. The amount of deflection in the conveyed sheet S is detected, and the result is output to the control means 60.

  In addition, an inner guide plate 25 and an outer guide plate 26 are provided in the paper feed conveyance path, and the sheet S that has passed between the paper feed roller 13 and the separation roller 14 passes through the outer guide plate 26. The sheet S is conveyed so as to swell, and is guided to the conveying roller 21 in a state where the sheet S is bent. In FIG. 3, the state where the sheet S is bent is indicated by a two-dot chain line, and the state where the amount of deflection is zero is indicated by a thick dotted line.

  The sheet sensor 62 is provided in the vicinity of the conveyance roller 21 in the paper feeding conveyance path, detects that the leading edge of the sheet S is guided to the position of the conveyance roller 21, and controls the result. 60.

  Then, in the sheet conveying apparatus of this embodiment, a process of eliminating the deflection in the sheet S fed by the sheet feeding roller 13 and conveyed to the conveying roller 21 as described above will be described based on FIG.

  Also in the sheet conveying apparatus of this embodiment, the sheet S is fed by the sheet feeding roller 13 and guided to the conveying roller 21, and the sheet S is conveyed by the conveying roller 21 in the initial stage as in the conventional case. The circumferential speed of the sheet feeding roller 13, that is, the sheet conveyance speed Va by the sheet feeding roller 13, is higher than the circumferential speed of the conveyance roller 21, that is, the sheet conveyance speed Vb by the conveyance roller 21.

  Here, when the sheet S is fed by the sheet feeding roller 13 as described above and the fed sheet S is conveyed by the sheet feeding roller 13 to the conveyance roller 21 through the sheet feeding conveyance path, the sheet S is In this way, the sheet S is conveyed so as to swell toward the outer guide plate 26, and the sheet S is bent.

  When the leading edge of the sheet S is guided to the conveying roller 21 in a state where the deflection is formed in this way, the sheet sensor 62 detects this and outputs the result to the control means 60. Here, the amount of deflection of the sheet when the leading edge of the sheet S is guided to the conveying roller 21 is A0. Note that the sheet S with low rigidity is guided to the conveying roller 21 along the outer guide plate 26, and the deflection amount A0 is larger than that of the sheet S with high rigidity.

  When the fact that the leading edge of the sheet S has been guided to the conveying roller 21 is output from the sheet sensor 62 to the control means 60, the control means 60 starts a timer and is guided to the conveying roller 21. The sheet feeding roller 13 is rotated at the same speed for a predetermined time t until the sheet S is properly conveyed by the conveying roller 21. In this case, since the sheet conveying speed Va by the sheet feeding roller 13 is faster than the sheet conveying speed Vb by the conveying roller 21 as described above, due to the speed difference of the sheet conveying speed between the sheet feeding roller 13 and the conveying roller 21, The amount of deflection in the sheet S increases, and the amount of deflection of the sheet that increases at this time is A1.

  Then, after the predetermined time t has elapsed as described above, the control means 60 reduces the rotation speed of the paper feed roller 13 by the paper feed motor driver 63 to keep the sheet conveyance speed Va by the paper feed roller 13 constant. Decelerate at a rate of. Here, at the stage where the sheet conveying speed Va by the sheet feeding roller 13 is decelerated in this way, the amount of deflection in the sheet S at the stage where the sheet conveying speed Va by the sheet feeding roller 13 is faster than the sheet conveying speed Vb by the conveying roller 21. Increases, and the amount of deflection in the sheet S decreases from the time when the sheet conveying speed Va by the sheet feeding roller 13 becomes slower than the sheet conveying speed Vb by the conveying roller 21. Here, the amount of deflection of the sheet S that increases in a stage where the sheet conveyance speed Va by the sheet feeding roller 13 is faster than the sheet conveyance speed Vb by the conveyance roller 21 is A2.

  In this embodiment, as described above, the sheet conveyance speed Va by the sheet feeding roller 13 is reduced to reduce the deflection amount in the sheet S, and the deflection amount in the sheet S becomes the predetermined deflection amount A4. First, this is detected by the above-described deflection amount detection sensor 61, and the result is output to the control means 60. Here, assuming that the amount of deflection reduced until the amount of deflection in the sheet S reaches a predetermined amount of deflection A4, A0 + A1 + A2 = A3 + A4.

  Further, when the deflection amount in the sheet S reaches the predetermined deflection amount A4 as described above, the control means 60 controls the rotation speed of the sheet feeding roller 13 by the sheet feeding motor driver 63, and the sheet S When the deflection is eliminated, the speed difference between the sheet transport speed Vb by the transport roller 21 and the sheet transport speed Va by the paper feed roller 13 is set to be equal to or less than a predetermined speed difference ΔV. In this case, the sheet conveyance speed Vb by the conveyance roller 21 is kept constant.

  After the deflection in the sheet S is eliminated in this way, the rotation of the paper feed roller 13 is stopped.

  Here, when the deflection of the sheet S is eliminated as described above, the speed difference between the sheet transport speed Vb by the transport roller 21 and the sheet transport speed Va by the paper feed roller 13 becomes a predetermined speed difference ΔV or less. By doing so, the load applied to the sheet S when the deflection is eliminated is reduced, and the generation of sound when the deflection is eliminated is suppressed. In this case, the sheet conveyance speed Vb of the conveyance roller 21 is kept constant only by controlling the sheet conveyance speed Va by the paper feed roller 13 so as to eliminate the deflection of the sheet S. There is no reduction in efficiency.

  In order to eliminate the deflection in the sheet S, after the predetermined time t has passed as described above, the rotation speed of the paper feed roller 13 by the paper feed motor driver 63 is decreased by the control means 60, and the paper feed roller 13. When the rate at which the sheet conveyance speed Va is reduced is increased, the time until the deflection amount of the sheet S reaches the predetermined deflection amount A4 is shortened, and the time for eliminating the deflection of the sheet S can be shortened. Even in the case of the sheet S having a large deflection amount A0 and low rigidity, the deflection in the sheet S can be eliminated in a short time.

  Further, after the predetermined time t has elapsed as described above, the amount of deflection in the sheet S as shown in FIG. When the difference between the sheet conveying speed Vb by the conveying roller 21 and the sheet conveying speed Va by the paper feeding roller 13 exceeds the predetermined speed difference ΔV at the time when the predetermined deflection amount A4 is reached, When the sheet conveyance speed Va by the paper roller 13 is increased and the deflection of the sheet S is eliminated, the speed difference between the sheet conveyance speed Vb by the conveyance roller 21 and the sheet conveyance speed Va by the paper feed roller 13 is a predetermined value. The speed difference ΔV or less is set. Further, after the deflection of the sheet S is eliminated in this way, the rotation speed of the paper feed roller 13 is reduced, and then the rotation of the paper feed roller 13 is stopped.

  Here, the conveyance speed difference (mm / s) between the sheet conveyance speed Vb by the conveyance roller 21 and the sheet conveyance speed Va by the paper feed roller 13 when the deflection is eliminated, and the sound pressure level [ [dB] and the results are shown in FIG.

  As a result, as the transport speed difference (mm / s) becomes smaller, the sound pressure level [dB] generated when the deflection is eliminated decreases, and when the transport speed difference (mm / s) becomes 100 mm / s or less. It has been found that the sound at the time of eliminating the deflection is reduced to such an extent that it does not bother, and it is preferable that the difference in transport speed (mm / s) is 100 mm / s or less.

  Next, an operation for eliminating the deflection of the sheet S generated between the sheet feeding roller 13 and the conveying roller 21 in the sheet conveying apparatus in this embodiment will be described based on the flowchart shown in FIG.

  First, in step S <b> 1 and step S <b> 2, the sheet feeding roller 13 and the conveying roller 21 are rotated at a predetermined speed, and the sheet S is conveyed toward the conveying roller 21 by the sheet feeding roller 13.

  In step S 3, it is determined whether the leading edge of the sheet S is guided to the conveying roller 21 and the sheet sensor 62 detects the sheet S. If the sheet S is not detected, the sheet S is detected by the sheet feeding roller 13. Is conveyed toward the conveyance roller 21. On the other hand, if the sheet S is detected, the process proceeds to step S4, where a timer is started by the control means 60, and a predetermined time t for maintaining the sheet conveyance speed by the sheet feeding roller 13 is set.

  Next, in step S5, it is determined whether or not the predetermined time t has elapsed. If not, the sheet conveyance speed of the paper feed roller 13 is maintained as it is. If the predetermined time t has elapsed, step S5 is performed. Proceeding to S6, the control means 60 decelerates the sheet conveyance speed by the sheet feeding roller 13 at a constant rate.

  In step S7, the above-described deflection amount detection sensor 61 detects whether the deflection amount of the sheet S has reached the predetermined deflection amount A4. While continuing the operation of decelerating the rotation speed at a constant rate, when the predetermined deflection amount A4 is reached, the process proceeds to step S8, and the sheet conveyance speed by the conveyance roller 21 at the time when the deflection of the sheet S is eliminated. The control unit 60 controls the sheet conveying speed of the sheet feeding roller 13 so that the speed difference from the sheet conveying speed by the sheet feeding roller 13 is equal to or less than a predetermined speed difference ΔV.

  Then, in a state where the sheet conveying speed in the sheet feeding roller 13 is controlled by the control unit 60 as described above, the process proceeds to step 9 to determine whether the deflection of the sheet S has been eliminated, and if the deflection has not been eliminated, When the control of the sheet conveying speed in the paper feed roller 13 is continued and the deflection is eliminated, the process proceeds to step S10, the rotation of the paper feed roller 13 is stopped and the process is terminated.

  In the sheet conveying apparatus according to this embodiment, the above-described deflection amount detection sensor is used to reduce the deflection amount in the sheet S by reducing the sheet conveyance speed Va by the sheet feeding roller 13 at a constant rate as described above. 61, it is detected that the deflection amount of the sheet S has reached a predetermined deflection amount A4, and the control unit 60 controls the sheet conveyance speed by the sheet feeding roller 13, but the sheet conveyance by the sheet feeding roller 13 is performed. When the speed is decelerated for a predetermined time, the deflection amount detection sensor 61 detects the deflection amount in the sheet S, and based on the detected deflection amount of the sheet S, the control means 60 feeds the sheet. The sheet conveying speed by the roller 13 is controlled, and the sheet by the conveying roller 21 at the time when the deflection of the sheet S is eliminated. May be the speed difference between the sheet conveying speed of the preparative conveying speed paper feed roller 13 is set to be below a predetermined speed difference [Delta] V.

  In the sheet conveying apparatus according to this embodiment, the deflection amount detection sensor 61 detects the deflection amount of the sheet S when the sheet conveyance speed Va by the sheet feeding roller 13 is reduced to reduce the deflection of the sheet S. However, the sheet S formed between the paper feed roller 13 and the transport roller 21 is determined based on the type of the sheet S to be transported, the sheet transport speed of the paper feed roller 13, the sheet transport speed of the transport roller 21, and the like. A decrease in the deflection amount of the sheet S when the deflection amount and the sheet conveyance speed by the paper feed roller 13 are decelerated is predicted, and based on this, the control means 60 controls the sheet conveyance speed at the paper feed roller 13. Is also possible.

  Further, in the sheet conveying device in this embodiment, even when the rotation of the paper feed roller 13 is stopped, the paper feed motor (not shown) for rotating the paper feed roller 13 is driven and maintained. When the next sheet S is fed by the paper feed roller 13, the rise of the rotation of the paper feed roller 13 can be accelerated to increase the rise speed of the paper feed.

  In this case, as shown in FIG. 8, a rotation transmission mechanism 70 for transmitting the rotation of the paper feed motor to the paper feed roller 13 is provided with a gear 72 having an electromagnetic clutch 71 on the rotation shaft 13a of the paper feed roller 13. The gear 72 is meshed with a gear 74 provided on a rotary shaft 73 that is rotated in accordance with the rotation of the paper feed motor, and as shown in FIG. Is connected to control on / off of the electromagnetic clutch 71.

  When the sheet feeding roller 13 is rotated by driving the sheet feeding motor, the electromagnetic clutch 71 is turned on by the control means 60 and the gear 72 rotating in mesh with the gear 74 provided on the rotating shaft 73 is rotated. The rotation is transmitted to the rotation shaft 13 a of the paper feed roller 13 to rotate the paper feed roller 13. On the other hand, even when the rotation of the sheet feeding roller 13 is stopped, when the sheet feeding motor is driven and maintained, the electromagnetic clutch 71 is turned off by the control means 60 and the rotating shaft 73 is turned on. The rotation of the gear 72 that rotates in mesh with the provided gear 74 is prevented from being transmitted to the rotation shaft 13 a of the paper feed roller 13.

  In the above embodiment, an example in which the sheet conveying device is used in the image forming apparatus has been described. However, the sheet conveying device can also be used in the image reading apparatus.

  FIG. 10 shows an image reading apparatus 100 provided with the sheet conveying apparatus of this embodiment.

  In the sheet conveying apparatus in the image reading apparatus 100, when the pickup roller 101 rotates, a sheet (document) S set on a document feeding tray (not shown) is sent between the sheet feeding roller 102 and the separation roller 103. .

  A torque limiter (not shown) is provided on the rotation shaft of the separation roller 103. Even if two or more sheets S are fed between the paper feed roller 102 and the separation roller 103 by this torque limiter, the frictional force between the sheets is less than the rotation limit force of the torque limiter. Only the sheet that does not rotate and is in contact with the paper feed roller 102 is conveyed by the paper feed roller 102.

  Also in this sheet conveying apparatus, a deflection is formed on the sheet S in the sheet feeding / conveying path 104 between the sheet feeding roller 102 and the conveying roller 105.

  A registration roller 106 is provided on the downstream side of the conveying roller 105, and a document reading optical unit (not shown) is provided on the downstream side of the registration roller 106.

  Even in such a document reading apparatus 100, when the deflection of the sheet S is eliminated, a deflection eliminating sound is generated, but in the same manner as in the case of the sheet conveying apparatus used in the image forming apparatus. Thus, when the rotation of the sheet feeding roller 102 is controlled and the deflection of the sheet S is eliminated, the speed difference between the sheet conveying speed by the conveying roller 105 and the sheet conveying speed by the sheet feeding roller 102 is less than a predetermined speed difference. Thus, the sheet conveyance speed by the sheet feeding roller 102 is controlled.

  In this way, as in the case of the above-described image forming apparatus, the load applied to the sheet S when the deflection is eliminated is reduced, the generation of sound when the deflection is eliminated is suppressed, and the deflection in the sheet S is reduced. Since the sheet conveyance speed by the conveyance roller 105 is maintained constant only by controlling the sheet conveyance speed in the paper feed roller 102 so as to eliminate the sheet conveyance efficiency, the sheet conveyance efficiency does not decrease.

DESCRIPTION OF SYMBOLS 1 Apparatus main body 10 Paper feed part 12 Pickup roller 13 Paper feed roller 14 Separation roller 20 Sheet conveyance path 21 Conveyance roller 22 Registration roller 30 Image forming part 40 Fixing part 50 Paper discharge part 60 Control means 61 Deflection detection sensor 62 Sheet sensor 63 Feed motor driver 64 Transport motor driver 70 Rotation transmission mechanism 71 Electromagnetic clutch 72 Gear 73 Rotating shaft 74 Gear 100 Image reading device 102 Paper feed roller 103 Separating roller 104 Paper feed transport path 105 Transport roller 106 Registration roller S Sheet

Claims (8)

  A sheet feeding roller that feeds and conveys the sheet, and a sheet conveying roller that is provided downstream of the sheet feeding direction in the sheet conveying direction and conveys the sheet are provided. In a sheet conveying apparatus in which a deflection is formed in a sheet conveyed between the sheet feeding roller and the conveying roller faster than the conveying speed, a control means for controlling the rotation speed of the sheet feeding roller is provided, Before the end passes the paper feed roller, the sheet transport speed at the paper feed roller is reduced to reduce the amount of sheet deflection between the paper feed roller and the transport roller, and according to the amount of sheet deflection at this point When the sheet feeding speed between the sheet feeding roller and the conveying roller is eliminated by controlling the sheet conveying speed in the sheet feeding roller by the above control means. Kicking, the sheet conveying apparatus characterized by a speed difference between the sheet conveying speed of the sheet conveying speed and the conveying roller by the paper feed roller and below a predetermined speed difference.   2. The sheet conveying apparatus according to claim 1, wherein the difference in speed between the sheet conveying speed by the sheet feeding roller and the sheet conveying speed by the conveying roller at the time when the deflection of the sheet is eliminated is 100 mm / s or less. Sheet transport device.   3. The sheet conveying apparatus according to claim 1, further comprising a deflection amount detecting unit that detects a deflection amount of the sheet between the sheet feeding roller and the conveying roller.   4. The sheet conveyance device according to claim 3, wherein the deflection amount detecting means is configured such that the sheet conveyance speed of the sheet feeding roller is reduced and the sheet deflection amount between the sheet feeding roller and the conveyance roller is a predetermined deflection amount. And a sheet conveying device that detects that the value has reached.   5. The sheet conveying apparatus according to claim 1, wherein the rotation transmission mechanism that transmits the rotation to the sheet feeding roller controls on / off of the rotation transmission to the sheet feeding roller. A sheet conveying apparatus comprising a clutch mechanism.   6. The sheet conveying apparatus according to claim 5, wherein after the deflection of the sheet between the sheet feeding roller and the conveying roller is eliminated, the transmission of rotation to the sheet feeding roller is turned off by the clutch mechanism. Sheet transport device.   An image forming apparatus comprising the sheet conveying device according to claim 1.   An image reading apparatus comprising the sheet conveying apparatus according to claim 1.

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