JP6146942B2 - Sheet conveying apparatus, image forming apparatus, and image reading apparatus - Google Patents

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 device where the deflection is formed in the sheet conveyed between the paper feeding roller and the conveying roller faster than the sheet conveying speed by, the noise when the deflection in the sheet is eliminated is reduced It has the characteristics.

  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 apparatus in which a deflection is formed in a sheet conveyed between a paper roller and a conveying roller, the sheet is tightly stretched when the deflection of the sheet is eliminated without reducing the sheet conveying efficiency. It is an object to appropriately prevent the generation of a loud sound.

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, the sheet feeding roller A deflection amount detecting means for detecting the deflection amount of the sheet with respect to the conveying roller and a control means for controlling the rotation speed of the paper feeding roller are provided, and the trailing edge of the sheet passes through the paper feeding roller by the control means. Before starting, the sheet conveyance speed at the sheet feeding roller is reduced so that the sheet deflection between the sheet feeding roller and the conveyance roller is eliminated. Based on the detection result of the deflection amount detecting means, the sheet conveyance speed of the paper feed roller is reduced so that the difference between the sheet conveyance speed by the conveyance roller and the sheet conveyance speed by the conveyance roller is equal to or less than a predetermined speed difference. In changing the ratio, the sheet conveying speed by the sheet feeding roller is not changed until a predetermined time has elapsed after the sheet reaches the conveying roller, and the sheet conveying speed by the sheet feeding roller is changed after the predetermined time has elapsed. I tried to slow down .

  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 the sheet conveying speed by the sheet feeding roller and the conveying roller at the time when the deflection of the sheet is eliminated. When the speed difference from the sheet conveyance speed is set to a predetermined speed difference or less, the load applied to the sheet is reduced when the deflection is eliminated, and the generation of sound when the deflection is eliminated is suppressed.

  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 decelerated so as to eliminate the deflection of the sheet, and the sheet is fixed by the conveying roller. Since the sheet is conveyed at the 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.

  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 conveyance speed at the sheet feeding roller is reduced, and 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 less than a predetermined speed difference. Therefore, the load applied to the sheet when the deflection 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 by the sheet feeding roller is only decelerated so as to eliminate the deflection of the sheet as described above, and the sheet is conveyed at a constant sheet conveying speed by the conveying roller. The sheet conveying efficiency is not lowered, and the image forming efficiency is not lowered.

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-described embodiment, the state of 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 deflection amount state of the sheet is shown. It is a schematic explanatory drawing. In the sheet conveying apparatus according to the above-described embodiment, when the amount of deflection of the sheet at the time when the leading edge of the sheet is guided to the conveying roller increases, the sheet is fed until the sheet is fed and the deflection is eliminated. FIG. 5 is a schematic explanatory diagram illustrating a sheet conveyance speed, a sheet conveyance speed by a conveyance roller, and a deflection amount state of the sheet. 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 modification example in which the deflection of the sheet generated between the sheet feeding roller and the conveying roller is eliminated is shown, and the sheet feeding until the deflection is eliminated after the sheet is fed is shown. FIG. 6 is a schematic explanatory diagram illustrating a state of a sheet conveyance speed by a paper roller, a sheet conveyance speed by a conveyance roller, and a deflection amount in a sheet. FIG. 9 is a schematic explanatory diagram showing a driving force transmission mechanism for switching the rotation speed of the paper feed roller in the modification shown in FIG. 8. FIG. 10 is a schematic block diagram illustrating a sheet conveyance control system in the modification 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 end 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 deflection amount detection sensor 61 is arranged in a curved sheet feeding conveyance path that conveys the sheet S from the sheet feeding roller 13 to the conveyance roller 21, and from the sheet feeding 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.

  Here, also in the sheet conveying apparatus of this embodiment, the peripheral speed of the paper feeding roller 13, that is, the sheet conveying speed by the paper feeding roller 13 is set to the circumferential speed of the conveying roller 21, that is, the conveying roller 21 as in the conventional case. It is faster than the sheet conveyance speed.

  Then, 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 conveying roller 21 through the sheet feeding conveyance path. At this time, the sheet S is conveyed so as to swell toward the outer guide plate 26 as described above, and a deflection is formed in the sheet S.

  Further, when the leading edge of the sheet S is guided to the transport roller 21 in a state where the deflection is formed in this way, the sheet sensor 62 detects this and outputs it to the control means 60.

  Based on this, the control means 60 starts a timer, and keeps the sheet feeding roller 13 as it is for a predetermined time until the sheet S guided to the conveying roller 21 is appropriately conveyed by the conveying roller 21. Rotate at speed. In this case, since the sheet conveying speed of the sheet feeding roller 13 is faster than the sheet conveying speed of the conveying roller 21, the sheet conveying speed is different from that of the sheet feeding roller 13 due to the difference in sheet conveying speed between the sheet feeding roller 13 and the conveying roller 21. Deflection is formed in the sheet S in the paper feed conveyance path between the roller 21 and the amount of deflection in the sheet S increases. Then, the deflection amount of the sheet S at this time is detected by the deflection amount detection sensor 61 described above, and the result is output to the control means 60.

  Then, based on the deflection amount of the sheet S detected by the deflection amount detection sensor 61 in the control means 60, the sheet conveyance speed by the conveyance roller 21 when the deflection of the sheet S is eliminated, and the sheet feeding roller 13. The peripheral speed of the paper feed roller 13 rotated by the paper feed motor driver 63 is decreased so that the speed difference from the sheet transport speed by the paper feed speed becomes equal to or less than a predetermined speed difference, and the sheet transport speed by the paper feed roller 13 is reduced. Calculate the percentage. In this case, the sheet conveyance speed of the conveyance roller 21 is kept constant.

  Then, based on the result calculated by the control means 60 in this way, the sheet conveyance speed by the sheet feeding roller 13 is decelerated, and the conveyance speed difference between the sheet conveyance speed by the conveyance roller 21 and the sheet conveyance speed by the sheet supply roller 13 is reduced. After the deflection of the sheet S is eliminated in a state in which is less than a predetermined speed difference, the rotation of the paper feed roller 13 is stopped.

  In this way, 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 sheet conveyance in the sheet feeding roller 13 so as to eliminate the deflection in the sheet S. Only the speed is reduced, and the sheet conveyance speed of the conveyance roller 21 is kept constant, so that the sheet conveyance efficiency does not decrease.

  Here, the sheet conveying speed by the sheet feeding roller 13, the sheet conveying speed by the conveying roller 21, and the state of the deflection amount in the sheet S will be described with reference to FIG.

  As described above, the sheet conveying speed Va by the sheet feeding roller 13 is set higher than the sheet conveying speed Vb by the conveying roller 21, and the sheet S is conveyed by the sheet feeding roller 13 to the conveying roller 21 through the sheet conveying path. In this case, as described above, the sheet S is conveyed so as to swell toward the outer guide plate 26, and a deflection is formed in the sheet S. When the leading edge of the sheet S is guided to the conveying roller 21, The deflection amount of the sheet S at A is defined as A0.

  Then, as described above, the leading edge of the sheet S is guided to the conveyance roller 21 and the sheet feeding roller 13 is rotated at the same peripheral speed for a predetermined time t from the time when the conveyance of the sheet S by the conveyance roller 21 is started. . In this case, since the sheet conveying speed Va by the sheet feeding roller 13 is higher than the sheet conveying speed Vb by the conveying roller 21, the sheet S is bent during the predetermined time t, and the sheet S is bent at this time. Let the amount be A1. The deflection amount detection sensor 61 detects the deflection amount (A0 + A1) of the sheet S at this time.

  Based on the deflection amount (A0 + A1) of the sheet S detected in this way, the control unit 60 controls the paper feed motor driver 63 as described above, and the conveyance roller 21 at the time when the deflection of the sheet S is eliminated. The peripheral speed of the paper feed roller 13 is decreased so that the speed difference ΔV between the sheet transport speed Vb and the sheet transport speed Va by the paper feed roller 13 is equal to or less than a predetermined speed difference, and the sheet transport by the paper feed roller 13 is performed. Decrease speed Va.

  Here, when the sheet conveying speed Va by the sheet feeding roller 13 is decreased as described above, the sheet S is deflected while the sheet conveying speed Va at the sheet feeding roller 13 is higher than the sheet conveying speed Vb at the conveying roller 21. A deflection amount formed at this time is defined as A2. For this reason, the final deflection amount in the sheet S is (A0 + A1 + A2).

  When the sheet conveyance speed Va in the sheet feeding roller 13 becomes lower than the sheet conveyance speed Vb in the conveyance roller 21, the deflection in the sheet S starts to be eliminated, and the deflection elimination amount A3 becomes the same as the final deflection amount (A0 + A1 + A2). At the time A3 = (A0 + A1 + A2), the deflection is eliminated, and the conveyance speed difference ΔV between the sheet conveyance speed Vb by the conveyance roller 21 and the sheet conveyance speed Va by the paper feed roller 13 at this time is a predetermined speed. Try to be less than the difference.

  Note that the speed difference ΔV between the sheet conveyance speed Vb by the conveyance roller 21 and the sheet conveyance speed Va by the paper feed roller 13 at the time when the deflection of the sheet S is eliminated by the control unit 60 as described above is a predetermined speed difference. In order to reduce the peripheral speed of the paper feed roller 13 and reduce the sheet conveying speed Va by the paper feed roller 13 as described below, for example, the rigidity of the sheet S is low, and the sheet S is the outer guide plate. 26, when the deflection amount A0 of the sheet S at the time when the leading edge of the sheet S is guided to the conveyance roller 21 increases as shown in FIG. By reducing the peripheral speed and reducing the rate at which the sheet conveyance speed Va by the paper feed roller 13 decreases, the conveyance roller 21 at the time when the deflection is eliminated. A sheet conveying speed Vb, the conveying speed difference ΔV between the sheet conveying speed Va by the paper feed roller 13 is set to be below a predetermined speed difference.

  Then, the difference (mm / s) in the conveyance speed between the sheet conveyance speed Vb by the conveyance roller 21 and the sheet conveyance speed Va by the sheet feeding 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 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, when the sheet S is detected, the process proceeds to step S4, where a predetermined time t for rotating the sheet feeding roller 13 at the same peripheral speed is set by a timer.

  Next, in step S5, it is determined whether the predetermined time t has elapsed. If the predetermined time t has not elapsed, the paper feed roller 13 is rotated at the peripheral speed as it is. If the predetermined time t has elapsed, step S5 is performed. Proceeding to S 6, the deflection amount detection sensor 61 detects the deflection amount of the sheet S.

  Thereafter, in step S7, the control means 60 reduces the peripheral speed of the paper feed roller 13 to calculate the ratio of reducing the sheet conveyance speed by the paper feed roller 13, and based on this, in step S8, the feeding speed is calculated. The paper roller 13 is decelerated.

  Next, in step S9, it is determined whether the deflection of the sheet S has been eliminated. If the deflection has not been eliminated, the sheet feeding roller 13 is continuously decelerated. On the other hand, if the deflection has been eliminated, step S9 is performed. Proceeding to S10, the rotation of the paper feed roller 13 is stopped and the process ends.

  In the sheet conveying apparatus according to this embodiment, the deflection amount of the sheet S between the sheet feeding roller 13 and the conveying roller 21 is detected by the deflection amount detection sensor 61, and based on this, the control unit 60 supplies the deflection. The rate at which the sheet conveyance speed in the paper roller 13 is decelerated is determined. However, the sheet feeding roller 13 and the sheet conveyance speed are determined based on the type of the sheet S to be conveyed, the sheet conveyance speed in the sheet feeding roller 13, the sheet conveyance speed in the conveyance roller 21 It is also possible to predict the amount of deflection of the sheet S formed between the conveying rollers 21 and to determine the rate at which the sheet conveying speed of the sheet feeding roller 13 is reduced by the control means 60 based on this.

  Further, in the sheet conveying apparatus in this embodiment, the control unit 60 gradually decelerates the sheet conveying speed of the sheet feeding roller 13 at a constant rate. However, as shown in FIG. After a predetermined time t has passed since the sheet S was guided to the conveyance roller 21 and started to be conveyed by the conveyance roller 21, the sheet conveyance speed Va by the paper feed roller 13 is changed to the sheet conveyance speed Vb by the conveyance roller 21. The conveyance speed difference ΔV with respect to the sheet conveyance speed Va by the paper roller 13 is reduced at a stretch so that the deflection amount A3 becomes the same as the deflection amount (A0 + A1) in the sheet S, and the deflection is eliminated. It is also possible to maintain the sheet conveyance speed Va by the sheet feeding roller 13 in such a reduced state until the point of time. .

  Here, after a predetermined time t has elapsed since the conveyance of the sheet S by the conveyance roller 21 in this way, the sheet conveyance speed Va by the sheet supply roller 13 is changed from the sheet conveyance speed Vb by the conveyance roller 21 to the sheet supply roller. A case where the conveyance speed difference ΔV with respect to the sheet conveyance speed Va due to 13 is reduced at a stretch so as to be equal to or less than a predetermined speed difference will be described.

  As shown in FIG. 9, a first electromagnetic clutch 65 and a second electromagnetic clutch 66 are provided on the rotation shaft 13 a of the paper feed roller 13, and a gear 65 b in the first electromagnetic clutch 65 is interposed via a small-diameter intermediate gear 71. The gear 66b of the second electromagnetic clutch 66 is engaged with the large-diameter gear portion 70a provided on the drive shaft 70c of the three-stage gear 70, and the drive shaft of the three-stage gear 70 via the large-diameter intermediate gear 72. The small-diameter gear portion 70 b provided on the cushion 70 c is engaged with the drive shaft 70 c of the three-stage gear 70 and rotated by the paper feed motor driver 63. In addition, as shown in FIG. 10, the first electromagnetic clutch 65 and the second electromagnetic clutch 66 are newly connected to the control means 60.

  The control means 60 controls the energization of the electromagnetic operating portion 65a of the first electromagnetic clutch 65 and the electromagnetic operating portion 66a of the second electromagnetic clutch 66, and the rotational force of the gear 65b in the first electromagnetic clutch 65 is controlled. The state in which the rotational force of the gear 66b in the second electromagnetic clutch 66 is transmitted to the rotational shaft 13a of the paper feed roller 13 is switched between the state in which the rotational force is transmitted to the rotational shaft 13a of the paper feed roller 13.

  Here, when the rotation of the large-diameter gear portion 70a in the three-stage gear 70 is transmitted to the gear 65b in the first electromagnetic clutch 65, the rotation of the small-diameter gear portion 70b in the three-stage gear 70 is transmitted to the second electromagnetic clutch. As compared with the case of transmission to the gear 66 b in 66, the rotation speed of the sheet feeding roller 13 is increased, and the sheet conveyance speed Va by the sheet feeding roller 13 is increased.

  When the rotation of the large-diameter gear portion 70a in the three-stage gear 70 is transmitted to the gear 65b in the first electromagnetic clutch 65, the sheet conveyance speed Va by the paper feed roller 13 is greater than the sheet conveyance speed Vb by the conveyance roller 21. On the other hand, when the rotation of the small-diameter gear portion 70b in the three-stage gear 70 is transmitted to the gear 66b in the second electromagnetic clutch 66, the sheet conveyance speed Va by the paper feed roller 13 decreases at a stretch. As described above, the conveyance speed difference ΔV between the sheet conveyance speed Vb by the conveyance roller 21 and the sheet conveyance speed Va by the paper feed roller 13 is set to be equal to or less than a predetermined speed difference.

  If it does in this way, electricity supply with respect to the electromagnetic action part 65a of the 1st electromagnetic clutch 65 and the electromagnetic action part 66a of the 2nd electromagnetic clutch 66 is controlled by the control means 60 as mentioned above, and the gear in said 1st electromagnetic clutch 65 is controlled. By switching between a state in which the rotational force of 65 b is transmitted to the rotational shaft 13 a of the paper feed roller 13 and a state in which the rotational force of the gear 66 b in the second electromagnetic clutch 66 is transmitted to the rotational shaft 13 a of the paper feed roller 13, The sheet conveyance speed Va by the paper roller 13 can be reduced at a stretch so that the conveyance speed difference ΔV between the sheet conveyance speed Vb by the conveyance roller 21 and the sheet conveyance speed Va by the paper feed roller 13 is less than a predetermined speed difference. .

  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. 11 shows an image reading apparatus 100 image forming apparatus 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. The amount of deflection is estimated by the elapsed time since the sheet S was detected by a sensor (not shown) that detects jamming or passage of the sheet. 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.

  In such a document reading apparatus 100, a deflection eliminating sound is generated when the deflection of the sheet S is eliminated. As in the case of the sheet conveying apparatus used in the image forming apparatus, Based on the amount of deflection of the sheet S, the rotation of the sheet feeding roller 102 is controlled, and the difference in speed between the sheet conveying speed by the conveying roller 105 and the sheet conveying speed by the sheet feeding roller 102 when the deflection of the sheet S is eliminated. The peripheral speed of the paper feed roller 102 is decreased so that the sheet conveyance speed by the paper feed roller 102 is reduced so that the difference is equal to or less than a predetermined speed difference.

  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 reducing the sheet conveyance speed of 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 Feed motor driver 65 First electromagnetic clutch 66 Second electromagnetic clutch 70 Three-stage gear 100 Image reading device 102 Feed roller 103 Separating roller 104 Feed feed path 105 Transport roller 106 Registration roller S Sheet

Claims (4)

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, the deflection amount of the sheet between the sheet feeding roller and the conveying roller is detected. A deflection amount detection means and a control means for controlling the rotation speed of the paper feed roller are provided, and the control means reduces the sheet conveyance speed of the paper feed roller before the trailing edge of the sheet passes through the paper feed roller. Therefore, when the deflection of the sheet between the paper feed roller and the transport roller is eliminated, the sheet transport speed by the paper feed roller and the sheet by the transport roller are The speed difference between the transport speed to below a predetermined speed difference, based on a detection result of the deflection amount detecting means, per to change the speed reduction ratio of the sheet conveying speed in the above paper feed roller, the sheet is said The sheet conveyance speed by the sheet feeding roller is not changed until a predetermined time elapses after reaching the conveyance roller, and the sheet conveyance speed by the sheet feeding roller is controlled to be reduced after the predetermined time has elapsed. A sheet conveying apparatus.   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. 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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