JP5545030B2 - Paper feeding and conveying apparatus and image forming apparatus - Google Patents

Description

  The present invention feeds a sheet to a transfer position at a predetermined timing in order to transfer a toner image held on the surface of an intermediate transfer member onto the sheet in an image forming apparatus such as a printer, a copier, or a facsimile. The present invention relates to a sheet feeding / conveying apparatus and an image forming apparatus.

  In an image forming unit of an image forming apparatus such as a printer, an electrophotographic copying machine, or a facsimile machine, a toner image formed on a photosensitive member or an intermediate transfer member is transferred to paper (not limited to paper) by a transfer device. In other words, it means that an image including OHP is formed, and is transferred onto a recording medium or recording medium or recording paper) and fixed, and then the paper on which the toner image is fixed is removed from the machine. To be discharged. At this time, the sheet fed by the sheet feeding roller of the sheet feeding device is conveyed by the conveying roller, and is temporarily stopped with the leading end abutted against a pair of registration rollers arranged in front of the transfer device, and the photosensitive member or The registration roller pair is driven in synchronization with the movement and timing of the toner image on the intermediate transfer member, and the sheet is fed to the transfer position. However, since the paper transport speed and the entry speed into the registration roller pair are increasing in order to achieve high image quality, high speed, and high productivity, the paper that has been fed toward the transfer position by the paper feeding device The collision noise (hereinafter referred to as “registration collision noise”) when the front end of the roller collides with the registration roller in a stopped state is relatively loud and annoying. For this reason, reduction of the collision noise has been conventionally demanded.

  Therefore, in order to solve this problem, in Patent Document 1, after detecting the leading edge of a sheet by a sensor provided immediately before the registration roller, the conveyance speed of the paper feed roller and the conveyance roller is decreased by decelerating the stepping motor. Therefore, although the resist collision noise can be reduced, the print productivity of the image forming apparatus is greatly reduced by the deceleration of the paper feed roller and the transport roller. Similarly, Patent Document 2 discloses that after the leading edge of a sheet is detected by a sensor provided immediately before the registration roller, the conveyance speed of the paper feed roller and the conveyance roller is decreased, and thereby the registration collision noise can be reduced. However, print productivity is greatly reduced.

  Further, Patent Document 3 discloses a method in which a pair of conveying rollers provided immediately before a registration roller is separated by using a solenoid or the like to release a grip force on a sheet so as not to disturb a registration function. Noise due to the operation of other mechanical parts and collision noise due to the collision of the pair of transport rollers are generated. In particular, a high speed machine is likely to generate a large noise because the conveyance roller repeatedly contacts and separates at high speed. Further, since the conveyance speed at the front end of the sheet is not reduced, the resist collision noise is not reduced. In addition, the configuration is complicated and the number of parts is large, resulting in an increase in space and cost.

  Further, Patent Document 4 discloses a configuration in which a sponge roller is provided at a position upstream of the registration roller in the transport direction and downstream of the sheet bending position. According to this configuration, since the paper passes through the sponge roller before contacting the registration roller, the paper can be brought into contact with the registration roller after the collision force at the leading edge of the paper is once buffered by the sponge roller. It is possible to reduce the collision force at the time of roller contact, and hence to reduce the resist collision noise. However, there is a possibility that the sponge roller itself may prevent the sheet from being bent and skew correction due to the bending, and the leading edge of the sheet being conveyed may jam due to the conveyance resistance when passing through the sponge roller.

  Even if the sponge roller is configured so as to be able to contact and separate from the paper, the responsiveness from the detection of the leading edge of the paper when the sponge roller is brought into contact with the paper immediately after the leading edge of the paper is passed through the sponge roller will be improved. Then, since the sponge roller must be brought into contact with the opposing roller quickly, a new noise is generated. That is, it was not possible to instantaneously obtain a braking effect for paper conveyance at a position as close as possible to the registration rollers. In order to bring the paper into contact with the registration roller slowly, it is necessary to increase the distance from the registration roller to the sponge roller so that it does not reach the registration roller after the passage of the leading edge of the paper is detected and before the braking action is applied. Then, it becomes necessary to dispose the sponge roller at the position where the sheet is bent, which interferes with skew correction due to the bending.

  Therefore, in view of these conventional problems, the present invention performs transfer from a sheet feeding device without deteriorating print productivity and registration function, or generating noise when a roller is separated by a roller separation mechanism. An object of the present invention is to provide a sheet feeding / conveying device and an image forming apparatus capable of reducing a registration collision sound when the leading edge of a sheet fed / conveyed toward a position collides with a registration roller.

According to the present invention, this object is achieved by a sheet feeding unit that separates and feeds sheets one by one, a conveyance unit that conveys a sheet fed from the sheet feeding unit in a conveyance path, and the conveyance unit. A speed reducing member that reduces the linear velocity at the leading edge of the paper in a paper feeding and conveying apparatus having a registration roller that is disposed on the downstream side of the paper and has a registration roller that feeds the paper conveyed through the conveyance path to the image transfer unit at a predetermined timing; Opposing means facing this are arranged upstream of the registration rollers and downstream of the conveying means, the speed reduction member is connected to the driving means, and the speed reduction member has a distance from the rotating shaft to the outer peripheral surface. The decelerating member is not decelerated, and before the leading edge of the sheet conveyed by the conveying unit hits the registration roller, the decelerating member has a linear velocity on the outer circumferential surface of the longest diameter that is farthest from the rotation axis. Above Rotated controlled by the driving means to be lower than the linear velocity of paper by the feed means, the sheet is sandwiched by the counter means with the major axis outer peripheral surface of the speed reduction member, connected to the drive means controlling means for controlling the And a detection means for outputting a signal to the control means for detecting the leading edge of the paper that has been arranged and conveyed near the upstream side of the registration roller, and the control means is connected to the detection means. When the drive means is controlled by a detection signal from the means, and the leading edge of the sheet is detected by the detection means, the speed reduction member is opposed to the long-diameter outer peripheral surface of the speed reduction member by the drive means and the control means. is rotationally controlled in the position for holding the sheet by means, then, controlled to rotate to a position that does not interfere with the bending formation of the paper when the leading end of the sheet has reached the registration roller It is resolved by the.

  The deceleration member preferably has a cam shape.

  Further, a paper thickness detecting means for detecting the thickness of the paper is arranged on the upstream side of the conveying means and connected to the control means, and the linear velocity of the speed reducing member is set according to the detection information of the paper thickness detecting means. Preferably it is controlled.

Further, it is preferable that the linear velocity of the speed reducing member when the paper is thick is smaller than that when the paper is thin.
Further, the distance from the detection position of the leading edge of the sheet by the detecting means to the nip of the registration roller is L, and the speed reducing member is moved from the initial setting position to the position where the sheet is clamped by the long-diameter outer peripheral surface and the opposing means. When the rotation angle is θ, the angular velocity of the deceleration member is ω, and the linear velocity of the paper is V, it is preferable that the relationship L> (θ × V) / ω holds.

Further, it is preferable that an elastic member is attached to the speed reduction member so as to cover the outer circumference of the long diameter.
Furthermore, it is preferable that the image forming apparatus according to the present invention includes the above-described sheet feeding / conveying device.

  As described above, according to the present invention, the speed reducing member whose distance from the rotating shaft to the outer peripheral surface is not constant before the leading end of the sheet hits the registration roller is not most decelerated from the rotating shaft. Since the linear speed of the separated outer circumference of the long diameter is rotated so as to be slower than the linear speed of the paper by the conveying means, the paper is pinched by the opposed means with the outer circumference of the long diameter of the speed reduction member. Only the linear velocity is reduced, and the resist collision noise is reduced. At this time, since the conveying means is not decelerated, the print productivity is not lowered, and the decelerating member has a constant distance from the rotating shaft to the outer peripheral surface, so that registration with the registration rollers is not hindered. Further, since it is not necessary to provide a roller separation mechanism, no noise is generated.

1 is a schematic configuration diagram of a color image forming apparatus for applying a paper feeding / conveying device according to the present invention. FIG. 3 is a schematic configuration diagram of a main part (registration part) of the first embodiment of the paper feeding / conveying device of the present invention, and shows an initial phase of a deceleration member 72; It is a schematic block diagram of the principal part (registration part) of 1st Embodiment of the paper feeding conveyance apparatus of this invention, and has shown the phase of the deceleration member 72 which produces a deceleration effect | action. FIG. 3 is a schematic configuration diagram of a main part (registration part) of the first embodiment of the sheet feeding / conveying device of the present invention, and shows a phase in which the speed reducing member 72 is rotated in a direction that does not prevent the sheet from being bent. 4 is a schematic perspective view of a speed reduction member 72 and a roller 73. FIG. FIG. 6 is a schematic perspective view of another embodiment of a deceleration member 72 and a roller 73. 4 is a schematic plan view of a plurality of deceleration members 72 and rollers 73. FIG. 6 is a schematic plan view showing another configuration of a plurality of deceleration members 72 and rollers 73. FIG. It is a schematic block diagram of the principal part (registration part) of 2nd Embodiment of the paper feeding conveyance apparatus of this invention. It is a schematic block diagram of the principal part (registration part) of 3rd Embodiment of the paper feeding conveyance apparatus of this invention. FIG. 6 is a schematic cross-sectional view showing another embodiment of the deceleration member 72. It is the figure which showed the relationship between the conveyance speed of the conventional conveyance roller, and time. It is the figure which showed the relationship between the conveyance speed of the conveyance roller of this invention, and time.

FIG. 1 schematically shows an example of a color image forming apparatus 1 for applying a paper feeding and conveying apparatus according to the present invention. First, the image forming apparatus 1 will be described.
In the color image forming apparatus 1, the apparatus main body 100 is placed on a paper feed table 200 as illustrated. A scanner 300 is mounted on the apparatus main body 100, and an automatic document feeder (ADF) 400 is mounted thereon. In the apparatus main body 100, a transfer device having an intermediate transfer belt 10 which is a belt-like endless moving member is provided in the approximate center, and the intermediate transfer belt 10 is provided between a driving roller 14 and two driven rollers 15 and 16. 1 so as to rotate clockwise in FIG.

  The intermediate transfer belt 10 is configured so that residual toner remaining on the surface after image transfer is removed by a cleaning device 17 provided on the left side of the driven roller 15. Yellow (Y), magenta (M), and cyan along the direction of movement of the intermediate transfer belt 10 above the linear portion spanned between the driving roller 14 and the driven roller 15 of the intermediate transfer belt 10. (D) Four drum-shaped photoconductors 40Y, 40M, 40C, and 40Bk (hereinafter simply referred to as photoconductors 40 if not specified) of black (Bk) are arranged at predetermined intervals. . Four primary transfer rollers 58 are provided inside the intermediate transfer belt 10 so as to sandwich the intermediate transfer belt 10 so as to face the respective photoreceptors 40.

Each of the four photoconductors 40 can rotate counterclockwise in FIG. 1, and around each photoconductor 40 is a charging device, a developing device 60, the above-described primary transfer roller 58, and the photoconductor. A cleaning device and a static elimination device are provided, and each constitutes an image forming unit 18. A common exposure device 21 is provided above the four image forming units 18.
Each image (toner image) formed on each photoconductor is successively transferred onto the intermediate transfer belt 10 in a superimposed manner.
On the other hand, on the lower side of the intermediate transfer belt 10, a secondary transfer device 22 including a transfer unit that transfers an image on the intermediate transfer belt 10 onto a sheet P that is a recording sheet is provided. The secondary transfer device 22 has a secondary transfer belt 24, which is an endless belt, spanned between two rollers 23, 23, and the secondary transfer belt 24 is driven by the driven roller 16 via the intermediate transfer belt 10. It comes to be pressed against.

The secondary transfer device 22 collectively transfers the toner images on the intermediate transfer belt 10 onto the paper P that is fed between the secondary transfer belt 24 and the intermediate transfer belt 10.
A fixing device 25 that fixes the toner image on the paper P is disposed downstream of the secondary transfer device 22 in the paper conveyance direction. A pressure roller 27 is pressed against the fixing belt 26 that is an endless belt. Yes.
Note that the secondary transfer device 22 also functions to convey the sheet after image transfer to the fixing device 25. Further, the secondary transfer device 22 may be a transfer device using a transfer roller or a non-contact charger. Below the secondary transfer device 22, a paper reversing device 28 is provided for reversing the paper when images are formed on both sides of the paper.

As described above, the apparatus main body 100 constitutes an indirect transfer tandem color image forming apparatus 1.
When color copying is performed by the color image forming apparatus 1, a document is set on the document table 30 of the automatic document feeder 400. When the document is manually set, the automatic document feeder 400 is opened, the document is set on the contact glass 32 of the scanner 300, and the automatic document feeder 400 is closed and pressed.

  When a start key (not shown) is pressed, when the document is set on the automatic document feeder 4, the document is fed onto the contact glass 32. When the document is manually set on the contact glass 32, the scanner 300 is immediately driven, and the first traveling body 33 and the second traveling body 34 start traveling. Then, light is emitted from the light source of the first traveling body 33 toward the document, and reflected light from the document surface is directed to the second traveling body 34, and the light is reflected by the mirror of the second traveling body 34. The light enters the reading sensor 36 through the imaging lens 35 and the content of the original is read.

  Further, when the start key is pressed, the intermediate transfer belt 10 starts to rotate. At the same time, the photoconductors 40Y, 40M, 40C, and 40K start rotating, and yellow (Y), magenta (M), cyan (C), and black (Bk) single color toners are formed on the photoconductors. The operation for forming an image is started. The toner images of the respective colors formed on the respective photoreceptors are sequentially transferred while being superimposed on the intermediate transfer belt 10 that rotates clockwise in FIG. 1, and a full-color composite color image is formed there. Is done.

  On the other hand, when the start key described above is pressed, the paper feed roller 42 of the selected paper feed stage in the paper feed table 2 rotates, and the paper P is fed from one selected paper feed cassette 44 in the paper bank 43. The paper is fed out, separated into one sheet by the separation roller 45, and conveyed to the paper feed path 46. The paper P is transported to the paper feed path 48 in the apparatus main body 1 by the transport roller 47, hits the registration roller 49 and temporarily stops. At this time, the deflection of the paper P is formed, and the skew of the paper P is corrected.

In the case of manual paper feeding, the paper P set on the manual tray 51 is fed by the rotation of the paper feeding roller 50, and is separated into one sheet by the separation roller 52 and conveyed to the manual paper feeding path 53. Then, it hits the registration roller 49 and temporarily stops.
The registration roller 49 starts to rotate at an accurate timing in accordance with the composite color image on the intermediate transfer belt 10, and temporarily stops the paper P between the intermediate transfer belt 10 and the secondary transfer device 22. Send it in. Then, a color image is transferred onto the paper P by the secondary transfer device 22.

The sheet P on which the color image has been transferred is conveyed to a fixing device 25 by a secondary transfer device 22 that also functions as a conveying device, where the transferred color image is fixed by applying heat and pressure. . Thereafter, the sheet P is guided to the discharge side by the switching claw 55, discharged onto the discharge tray 57 by the discharge roller 56, and stacked there.
When the double-sided copy mode is selected, the paper P on which an image is formed on one side is conveyed to the paper reversing device 28 side by the switching claw 55, reversed there and led again to the transfer position, and this time the image is printed on the back side. After the formation, the paper is discharged onto a paper discharge tray 57 by a discharge roller 56.
Although the color image forming apparatus has been described here, it is of course possible to apply the paper feeding / conveying apparatus according to the present invention to a monochrome image forming apparatus.

Next, a paper feeding / conveying device which is a characteristic part of the present invention will be described. FIG. 2 is a schematic configuration diagram of a main part (registration part) of the first embodiment of the paper feeding / conveying device of the present invention.
Conveying roller pairs 47a and 47b for further conveying the sheet P separated from the sheet feeding cassette 44 by the sheet feeding roller 42 and the separation roller 45 and fed in the sheet feeding path are arranged. 47a is driven by driving means 76 such as a motor connected thereto and its control means 77 (CPU, ROM, RAM, etc.). 1 is driven by driving means such as a motor (not shown) and its control means (CPU, ROM, RAM, etc.).

  Further, a conveyance path 48 formed by guide plates 81, 82, 83 is downstream of the conveyance roller pair 47a, 47b. A rotatable reduction member 72 and a roller 73 are disposed at the end of the conveyance path 48, and the reduction member 72 is driven by a stepping motor 74 connected thereto. The stepping motor 74 is controlled by control means 75 (CPU, ROM, RAM, etc.) connected thereto. As will be described in detail later, as shown in the figure, the speed reduction member 72 is not constant in the distance from the rotating shaft to the outer peripheral surface, and has a cam shape. Registration roller pairs 49 a and 49 b for registration are arranged further downstream of the speed reduction member 72 and the roller 73. There is a further transport path between the speed reduction member 72 and the roller 73 and the registration rollers 49a and 49b, and the paper that has been transported is located near the downstream side of the speed reduction member 72 and the roller 73 and the upstream side of the registration rollers 49a and 49b. A sensor (detection means such as a photosensor) 71 for detecting passage of the tip of P is provided and connected to the control means 75. The sensor 71 and the control means 75 can accurately grasp the leading end position of the sheet P, and can cause the deceleration member 72 to accurately decelerate the sheet P before the leading end of the sheet collides with the registration roller pair 49a, 49b. it can.

  In the above configuration, when the leading edge of the sheet P conveyed downstream by the conveying roller pair 47a and 47b passes between the speed reducing member 72 and the roller 73, the speed reducing member 72 faces the initial setting direction shown in FIG. ing. Next, when the leading edge of the sheet passes through the sensor 71, a leading edge detection signal from the sensor 71 is output to the control means 75 that controls the driving of the deceleration member 72. Then, immediately before the leading edge of the sheet collides with the registration rollers 49a and 49b, the reduction member 72 is rotationally driven so that the reduction member 72 is oriented as shown in FIG. In this rotational drive, driving is performed so that the linear velocity of the outer peripheral surface 78 farthest from the rotation center of the deceleration member 72 is slower than the linear velocity of the sheet, and the sheet is sandwiched by the nip between the deceleration member 72 and the roller 73. Thus, a braking action is given to the paper. As a result, the leading edge of the sheet collides with the pair of registration rollers 49a and 49b that have stopped rotating at a speed slower than the speed before the leading edge detection, so that the registration collision noise is reduced. Thereafter, the sheet P decelerated in this manner collides with the registration roller pair 49a, 49b, where deflection is formed and skew correction is performed, and the movement and timing of the toner image on the intermediate transfer belt are synchronized with the registration roller pair 49a. , 49b are driven, and the paper P is fed to the transfer position.

  On the other hand, immediately before the collision with the registration roller pair 49a, 49b, the conveyance speed (linear speed) of only the leading edge of the paper P is reduced, but the linear speed of the conveyance roller pair 47a, 47b, that is, the linear speed of the paper P is not reduced. Therefore, print productivity is not reduced.

  Further, the deceleration member 72 is controlled by the control means 75 and the stepping motor 74 so as to be oriented as shown in FIG. 4 when forming the deflection after the leading edge of the sheet collides with the pair of registration rollers 49a and 49b. Thereby, after the sheet collides with the registration roller, the sheet can be bent without the deceleration member 72 preventing the bending, so that the registration function is not hindered. The deceleration member 72 is controlled by the control means 75 and the stepping motor 74 so as to return to the initial setting direction shown in FIG. 2 before the next sheet is conveyed.

  Since the guide plate 81 and the guide plate 82 are arranged at a predetermined interval, an opening 84 is formed. The opening 84 is bent by the difference between the slower linear speed of the outer peripheral surface 78 and the faster linear speed of the paper P by the conveying roller pairs 47a and 47b, and the paper P hits the registration roller pairs 49a and 49b. It works to release the flexure that is formed after. As a result, the skew correction due to the deflection of the paper P is ensured, and the collision sound caused by the deflection of the paper P coming into contact with the guide plate is also avoided.

Next, the shape of the deceleration member 72 will be described.
As can be seen from FIG. 2 and the like, the deceleration member 72 has a cam shape. Here, the distance from the rotating shaft of the speed reducing member 72 to the nip between the speed reducing member 72 and the roller 73 is X1 (mm), and the longest diameter from the rotating shaft of the speed reducing member 72 to the outer peripheral surface 78 is X2 (mm). When the surfaces of the deceleration member 72 and the roller 73 are sufficiently hard and can be assumed to be rigid bodies, X1 = X2. On the other hand, when at least one surface of the speed reduction member 72 or the roller 73 has elasticity and is soft, the paper P can be braked by holding the paper P at the nip between the speed reduction member 72 and the roller 73. In addition, X2 is preferably about 0.5 mm larger than X1. The diameter of the speed reducing member 72 other than the longest diameter is shorter than X1. Thus, by making the deceleration member 72 into the shape of a cam, it is possible to reduce the resist collision noise without reducing the print productivity. Further, the reduction of the resist function due to the provision of the deceleration member 72 is also prevented.

  FIG. 5 is a schematic perspective view of the speed reduction member 72 and the roller 73. The outer peripheral surface of the roller 73 is formed in a circular shape, whereas the outer peripheral surface of the speed reduction member 72 is formed in an oval shape. In order to sandwich the paper P at the nip between the outer peripheral surface 78 of the speed reduction member 72 and the roller 73, at least the outer peripheral surface 78 farthest from the rotation shaft of the speed reduction member 72 is configured to contact the outer peripheral surface of the roller 73. Yes. On the other hand, when the outer peripheral surface 78 moves away from the paper as the speed reducing member 72 is further rotated, the outer peripheral surface of the speed reducing member 72 having a smaller diameter does not come into contact with the paper, so that subsequent deformation of the paper is not hindered.

  FIG. 6 is a schematic perspective view of another embodiment of the speed reduction member 72 and the roller 73. As shown in the drawing, a plurality of speed reducing members 72 and rollers 73 are installed in the axial direction, so that the holding of the paper P at the nip between the outer peripheral surface 78 of the speed reducing member 72 and the rollers 73 does not slip. It will be more certain.

FIG. 7 is a schematic plan view of the plurality of deceleration members 72 and rollers 73. As shown in the figure, the speed reducing member 72 is connected to a coaxial motor 91 via a coaxial joint 92, and the driving force by the motor 91 is transmitted to the speed reducing member 72.
FIG. 8 is another schematic plan view of the plurality of deceleration members 72 and the rollers 73. As shown in the figure, the speed reduction member 72 is connected to the motor 91 via a coaxial gear 94 and a gear 93 meshed with the same, and the driving force by the motor 91 is transmitted to the speed reduction member 72. Yes.

  In the method of using a solenoid or the like as in Patent Document 3 to contact and separate the speed reduction member, a certain length of solenoid stroke is required to contact and separate it, and the mechanical mechanism is attracted by magnetic force. However, according to the present invention configured as described above, it is only necessary to rotate the motor 91 several times to rotate the speed reduction member 72. Therefore, the response after the front end of the paper is detected by the sensor 71 is improved. Further, the responsiveness can be further improved by increasing the number of teeth of the gear 93 or decreasing the number of teeth of the gear 94 in FIG.

FIG. 9 is a schematic configuration diagram of a main part (registration part) of the second embodiment of the paper feeding / conveying device of the present invention.
The difference from the first embodiment is that a paper thickness detection sensor 79 for detecting the paper thickness of the paper P is installed upstream of the conveying roller pair 47a, 47b, and the paper thickness detection sensor 79 is connected to the downstream control means 75. It has been done. When the paper P passes through the paper thickness detection sensor 79, the type and the paper thickness are detected by this, and the detection information from the paper thickness detection sensor 79 is output to the control means 75 that controls the driving of the deceleration member 72. In the control means 75, the linear velocity of the pair of deceleration members 72 and 73 after receiving the leading edge detection signal from the sensor 71 is set for each paper thickness. The magnitude of the resist collision sound varies depending on the type and thickness of the paper. Generally, the thicker the paper thickness, the larger the resist collision sound, and the smaller the paper thickness. Therefore, the collision speed of the sheet to the registration roller can be changed by changing the linear velocity or the angular velocity ω of the deceleration member 72 according to the type and thickness of the sheet. For example, in the case of a thick sheet with a large registration impact sound, the linear collision speed or angular velocity ω of the deceleration member 72 may be decreased to further decrease the registration collision speed of the sheet. In this way, in the case of an arbitrary type of paper, it is possible to reduce the resist collision noise without greatly reducing print productivity.

Next, the operation of the paper feeding / conveying device will be described.
The paper P conveyed by the upstream conveying roller is detected by the paper thickness detection sensor 79, and detection information from the paper thickness detection sensor 79 is output to the control means 75 that controls the driving of the deceleration member 72. Is done. Then, the paper P is transported further downstream by the pair of transport rollers 47 a and 47 b, and the front end of the paper is transported between the speed reduction member 72 and the roller 73. At this time, the deceleration member 72 is oriented in the initial setting direction shown in FIG. Next, when the leading edge of the paper P passes through the sensor 71, a leading edge detection signal from the sensor 71 is output to the control means 75 that controls the driving of the deceleration member 72. The deceleration member 72 is rotationally driven at a conveyance speed (linear speed) preset in the control means 75 based on the paper thickness information from the paper thickness detection sensor 79. This rotational drive is performed so that the linear velocity of the outer peripheral surface 78 farthest from the rotational axis of the deceleration member 72 is slower than the linear velocity of the paper P. Accordingly, the paper P is braked by sandwiching the paper P at the nip between the outer peripheral surface 78 of the speed reduction member 72 and the roller 73. Thereafter, the sheet P decelerated in this manner collides with the registration roller pair 49a, 49b, where deflection is formed and skew correction is performed, and the movement and timing of the toner image on the intermediate transfer belt are synchronized with the registration roller pair 49a. , 49b are driven, and the paper P is fed to the transfer position. Here, the linear velocity preset in the control means 75 is set to be slower when the paper thickness is thicker and faster when the paper thickness is thinner.
Other configurations and operations not described here are the same as those in the first embodiment.

FIG. 10 is a schematic configuration diagram of the main part (registration part) of the third embodiment of the paper feeding / conveying device of the present invention.
As shown in the figure, the distance from the sheet leading edge detection position of the sensor 71 to the nip of the registration roller pair 49a, 49b is L (mm), and the deceleration member 72 is a position that causes the sheet P to decelerate from the initial position. The rotation angle until the sheet P is nipped by the outer peripheral surface 78 and the roller 73 is θ (rad), the angular velocity of the deceleration member 72 is ω (rad / s), and the sheet conveyance speed and linear velocity are V ( mm / s).

Here, when conditions such as L (mm) is small, the conveyance speed / linear velocity V (mm / s) is high, the rotation angle θ (rad) is large, and the angular velocity ω (rad / s) is small, deceleration occurs. Before the member 72 sandwiches the sheet P by the outer peripheral surface 78 and the roller 73 and causes a deceleration action, the leading end of the sheet may collide with the registration roller pair 49a, 49b. Therefore, in this sheet feeding / conveying device, L> (θ × V) / ω is established so as to surely cause a deceleration action by the deceleration member 72 before the leading edge of the sheet collides with the registration roller pair 49a, 49b. It is configured as follows. Accordingly, it is possible to avoid the front end of the paper from colliding with the registration roller pair 49a and 49b before the speed reduction member 72 causes the speed reduction of the paper P.
The configuration and operation of this embodiment not described here are the same as those in the first or second embodiment.

  FIG. 11 is a schematic cross-sectional view showing another embodiment of the deceleration member 72. As illustrated, a rubber member 95 such as silicone rubber having a large friction coefficient is attached to the contact surface of the speed reduction member 72 with the paper. In particular, the rubber member 95 is attached to the speed reduction member 72 so as to cover the outer peripheral surface 78 farthest from the rotation shaft of the speed reduction member 72. The rubber member 95 prevents slippage between the speed reduction member 72 and the paper P, and a more reliable speed reduction action of the paper P at the speed reduction member 72 is ensured.

Next, the print productivity of the paper feeding / conveying device of the present invention is compared with that of the prior art device that slows the conveying speed of the paper P as in Patent Documents 1 and 2.
FIG. 12 is a diagram illustrating the relationship between the conveyance speed of the conventional conveyance roller and time. If the conveyance speed of the conveyance roller is decreased from V1 to V2 before and after the leading edge of the sheet collides with the registration roller, the area of the hatched portion in FIG. The printing productivity is reduced by the length (mm).
On the other hand, FIG. 13 is a diagram showing the relationship between the conveyance speed and time of the conveyance roller of the present invention. In the present invention, before and after the leading edge of the sheet collides with the registration roller, the conveyance speed V1 of the conveyance roller 47 does not decrease and does not change, so print productivity does not decrease. Thus, according to the present invention, it is possible to increase print productivity as compared with the prior art.

  Further, in the present invention, as shown in FIG. 4, since the deceleration member 72 is rotated to a phase that does not come into contact with the deflection of the paper P or the paper P at the time of the flexure formation, the flexure formation of the paper P is not hindered. Further, since the braking action for the paper P is created only by rotating the deceleration member 72 by a predetermined phase, the number of components is small and a simple configuration is required, so that installation at low cost and space saving is possible. Further, since the speed reduction member 72 is merely rotated, no noise is generated due to this, and no noise is generated due to the operation of the solenoid and other mechanical parts when the rollers are brought into contact with and separated from each other as in Patent Document 3.

45 Separation roller (paper feeding means)
47 Conveying roller (conveying means)
49 Registration roller 72 Deceleration member 73 Roller (opposing means)
74 Stepping motor (drive means)
78 Peripheral surface (Long diameter outer peripheral surface)
P paper

JP 2003-155147 A JP-A-9-175893 Japanese Patent Laid-Open No. 11-79474 JP-A-9-86729

Claims (7)

A sheet feeding unit that separates and feeds the sheets one by one; a conveyance unit that conveys the sheet fed from the sheet feeding unit in the conveyance path; and a downstream side of the conveyance unit. In a paper feeding / conveying device having a registration roller that feeds the paper that has been conveyed to the image transfer unit at a predetermined timing,
A speed reducing member for reducing the linear velocity at the leading end of the paper and a facing means facing the speed reducing member are arranged on the upstream side of the registration roller and the downstream side of the conveying means, and the speed reducing member is connected to the driving means,
The deceleration member has a constant distance from the rotation axis to the outer peripheral surface,
The conveying means is not decelerated,
Before the leading edge of the paper conveyed by the conveying means hits the registration roller, the speed reducing member is arranged such that the linear velocity of the outer peripheral surface of the longest diameter that is farthest from the rotation axis is slower than the linear velocity of the paper by the conveying means. The rotation is controlled by the driving means, and the paper is sandwiched between the long-diameter outer peripheral surface of the deceleration member and the opposing means ,
Control means for connecting to and controlling the drive means, and detection means for outputting a signal to the control means for detecting the leading edge of the paper that is disposed near the upstream side of the registration roller and is conveyed are provided. The control means controls the driving means by a detection signal from the detection means connected thereto,
When the leading edge of the paper is detected by the detecting means, the speed reduction member is rotationally controlled by the driving means and the control means to a position where the paper is sandwiched by the long-diameter outer peripheral surface of the speed reduction member and the facing means. The sheet feeding / conveying device is controlled to rotate to a position that does not prevent the sheet from being bent when the leading edge of the sheet reaches the registration roller .   The sheet feeding / conveying device according to claim 1, wherein the deceleration member has a cam shape. A paper thickness detecting means for detecting the thickness of the paper is arranged on the upstream side of the conveying means and connected to the control means, and the linear velocity of the speed reducing member is controlled according to the detection information of the paper thickness detecting means. sheet transportation device according to claim 1 or 2, characterized in Rukoto. 4. The sheet feeding / conveying device according to claim 3 , wherein a linear velocity of the speed reduction member when the sheet is thick is smaller than that when the sheet is thin. The distance from the detection position of the leading edge of the sheet by the detection means to the nip of the registration roller is L, and the rotation angle from the initial setting position to the position where the sheet is held between the outer peripheral surface of the long diameter and the opposing means. the theta, wherein the angular velocity of the deceleration member omega, when the linear velocity of the sheet and V, L> (θ × V ) / relationship omega, characterized in that holds according to any one of claims 1-4 Paper feeding and conveying device. Sheet transportation device according to any one of claims 1 to 5, wherein the elastic member is attached to the speed reduction member so as to cover the long diameter outer circumferential surface. An image forming apparatus comprising: a sheet transportation device according to any one of claims 1-6.

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