JPH0776436A - Paper sheet conveying device for image forming device - Google Patents

Abstract

PURPOSE:To convey a paper sheet satisfactorily by setting the nip pressure of a conveying roller device larger at the center of the sheet and smaller at the sides of it in a register device formed by combining a register roller device with the conveying roller device. CONSTITUTION:In a register device 1 installed in an image forming device, a conveying roller device 10 is positioned in the upstream from a register roller device 2 positioned just before an image copying position and, in a drive roller member 11, roller members 13, 13a, and 13b are arranged on a drive shaft 12. Also, in a nip roller for pressing a sheet against the drive roller member, a nip roller member 16 at the center of it is supported by a strong spring 18 and nip rollers 16a and 16b on both sides of it are supported through weak springs 18a and 18b. Then a large nip pressure is given to a sheet P by a roller device at the center of it during the conveying of the sheet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conveying roller device arranged in a sheet conveying path of an image forming apparatus, and more particularly, to a register device arranged immediately before an image transfer portion or the like when aligning sheets. The present invention relates to an apparatus that can set a large conveyance force for a sheet at a central portion of a sheet conveyance path and prevent an excessive skew (diagonal feed) or the like from occurring in the sheet.

[0002]

2. Description of the Related Art In an image forming apparatus such as a printer or a copying machine, a sheet is taken out from a sheet feeding member such as a sheet feeding tray arranged in a sheet feeding section and conveyed by a plurality of conveying roller devices arranged in a sheet conveying path. Then, a mechanism for feeding paper from the image forming apparatus such as the photosensitive drum toward the image transfer position is configured. In the sheet conveying device provided in the image forming apparatus, a plurality of roller members provided in a skewered shape on a shaft arranged in a direction perpendicular to the sheet conveying direction is often used. Then, a driving mechanism is arranged on one of the roller members arranged on one side of the front and back sides of the paper to constitute a driving roller member, and the other roller member is constituted as a nip roller member provided with a biasing means such as a spring. The conveyance operation can be performed while the paper is nipped between the roller members.

In the above-mentioned conveying roller device, with respect to a long shaft arranged across the sheet conveying path in the width direction,
A plurality of roller members arranged at a predetermined interval is used, and there is a problem that the shaft is easily bent because a nip pressure is set for the transport roller device. When the shaft is bent, there is a problem that the nip pressure is large at the side of the paper and weak at the center, and it is difficult to set a good conveyance action for the paper.

Therefore, in a conventional sheet conveying device, as disclosed in, for example, Japanese Utility Model Laid-Open No. 3-23135,
It has been proposed that the roller member located in the central portion of the paper transport path be made of a hard roller and the roller member located at the side portion be made of a soft roller member. Also, the actual development 6
In the example disclosed in Japanese Laid-Open Patent Publication No. 4-43038, it is also proposed that the roller member provided on the shaft has a large diameter at the central portion and a small roller at the side portion. In the transport roller device as shown in each of the conventional examples, even when the shaft is bent, a uniform transport action can be given to the entire width direction of the paper.

[0005]

However, as shown in the above-mentioned prior art example, even when a conveying roller device capable of imparting a uniform conveying force in the width direction of the sheet is used, it is arranged at the end of the sheet conveying path. A problem remains when configuring a resist device that does. In other words, when the front end of the paper is abutted against the registration roller device arranged immediately in front of the image transfer portion from the photoconductor drum to form a loop on the paper for alignment, the alignment action of the paper causes In some cases, the paper may be inclined with respect to the paper transport path. When the aligned paper is sent toward the image transfer unit, not only when the nip pressure for the paper is different, but also when the nip pressure is evenly applied, the flexibility of the paper is limited. The problem of paper wrinkling is likely to occur.

Further, when the registration roller device is driven to feed the paper toward the image transfer portion, the width direction with respect to the paper is increased between the registration roller device and the transport roller device arranged in the upstream portion. Since the carrying action is carried out under the stress of, the paper is likely to cause wrinkles. On the other hand, when the means for adjusting the distribution state of the nip pressure of the rollers in the width direction of the paper is provided as in the conventional example, it may be possible to reduce the occurrence of paper wrinkles. . However, for example, when using means such as arranging roller members having different hardnesses in a skewered shape with respect to the shaft,
There is a problem that a lot of labor is required for manufacturing the roller member. Providing a means for adjusting the nip pressure of the sheet with respect to the transport roller device complicates the configuration of the transport roller device and increases the manufacturing cost of the image forming apparatus. Further, when the nip pressure adjusting means between the rollers is used as in the conventional example, when the balance of the nip force is lost, there is a problem that a lot of labor is required for the maintenance.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the conventional conveying roller device, and particularly, in the conveying roller device arranged corresponding to the registration device, with respect to the central part of the roller device. Sets a large nip pressure and a very small nip pressure for the roller members on the side so that paper wrinkles do not occur when the paper is conveyed to and from the registration roller device. The purpose is to provide a device.

[0008]

SUMMARY OF THE INVENTION According to the present invention, a carrying roller device arranged at a predetermined interval in the paper carrying direction and a registration roller device for abutting a paper sheet to position a leading end portion are arranged, The present invention relates to a registration device that abuts the leading end of a sheet against the nip position of the registration roller device, forms a loop on the sheet by performing additional feeding by the transport roller device, and aligns the sheets. In the present invention, the conveying roller device is arranged in the sheet conveying path, and the driving roller member having a plurality of roller members on the driving shaft, and the pressing means separately provided corresponding to each of the driving roller members. Comprising a plurality of nip roller members configured, the nip pressure for the paper in the transport roller device,
A large value is set at the central portion of the paper conveyance path in the width direction, and a small value is set at the side portions. Further, in the present invention, the nip roller member constituting the conveying roller device is separately arranged for each of the roller members arranged in the drive roller member, and the pressing force is set by the elastic member supporting the nip roller member. An elastic member having a large urging force at the central portion of the sheet conveyance path is used for the nip roller member arranged with respect to the drive roller member,
An elastic member having a small biasing force can be used for the side nip roller member.

[0009]

As described above, in the conveying roller device of the present invention, a large nip pressure is exerted only on the central portion in the width direction of the sheet, and the side portion of the sheet is controlled by the paper. The distribution of the nip force in the roller device can be set so as to exert a small nip pressure that suppresses flapping. Further, in order to set the distribution of the nip pressure as described above, a plurality of roller members are arranged on a long shaft to form a driving roller member, and the nip roller member is separately arranged with respect to the roller member. By pressing the member via the biasing means,
A means for setting the nip pressure at each roller member is configured. Then, by setting a large nip pressure only to the roller member in the central portion of the paper conveyance path, even when the paper is conveyed by the registration device, even if the paper is conveyed between the registration roller device and the conveyance roller device. As a result, it is possible to prevent extra stress from being applied to the paper and prevent paper wrinkles and the like from occurring.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A sheet conveying device of an image forming apparatus of the present invention will be described with reference to the illustrated example. The example shown in FIG. 1 shows a configuration of a registration device 1 arranged in an image forming apparatus such as a laser beam printer. A registration roller device 2 is provided immediately before a position where a toner image is transferred from a photosensitive drum or the like. Is arranged, and the transport roller device 10 is provided at an upstream portion thereof with a predetermined interval. The registration roller device 2 and the conveyance roller device 10 are configured in the same manner as a registration device provided in a conventional copying machine or the like, and the registration roller device 2 is configured by combining a driving roller 3 and a nip roller 4 and conveys the same. The roller device 10 is also configured by combining the drive roller 11 and the nip roller 15.
A curved paper guide 5 is arranged between the roller devices arranged upstream and downstream of the registration device 1 so that the size of the loop formed on the paper can be controlled.

In the registration device 1, the paper is conveyed from a paper feed tray or the like arranged in the upstream part, and after the front end of the paper is detected by the sensor S arranged immediately in front of the registration roller device 2, it is kept constant. When the time elapses, the registration roller device 2 is driven. Immediately after the leading edge of the sheet is detected by the sensor S when the sheet is conveyed, the leading edge of the sheet rushes into the nip position of the registration roller device 2 and is stopped.
When the feeding action is still added by 0, the skew of the sheet is corrected and the aligning action is given in the state where the loop R is formed on the sheet. Then, in response to a command from the control device of the image forming apparatus main body, the registration roller device 2 is driven to send the paper toward the image transfer section.

In the registration device 1 having the above-described structure, the transport roller device 10 arranged upstream of the registration roller device 2 has roller members as shown in FIG. A means for applying a large carrying force to the section is provided. In the example shown in FIG. 2, the drive roller 1 which constitutes the transport roller device 10
1 is three roller members 13 and 13 with respect to the drive shaft 12.
a and 13b are arranged, and the roller member is made of a relatively hard elastic body made of a member having a large friction coefficient such as rubber, like the conventional roller member. The nip roller 15 provided to press the paper against the roller member of the drive roller 11 corresponds to the roller members 13, ..., and has a mechanism for pressing each roller separately by using an urging means. I am configuring.

In the nip roller 15, the nip roller member 16 corresponds to the roller member 13 in the central portion of the drive roller 11, and the roller members 13 on both sides.
a and 13b, nip roller members 16a and 16
b are arranged corresponding to each other. The nip roller members 16 to 16b have respective shafts 17 ...
.About.18b so as to be able to individually apply a pressing action.
A leaf spring is used to support and press the roller member. In the transport roller device 10 having the above-described configuration, in the nip roller member 16 corresponding to the roller member 13 arranged in the central portion of the paper transport path, the spring 18 is configured to have a strong pressing force, and the side roller is configured. A mechanism for urging the nip roller members 16a, 16b corresponding to the members 13a, 13b by using springs 18a, 18b capable of setting a weak pressing force is configured. When the nip pressure in each of the roller members is set to have a difference of 1: 3 or more between the roller members on both sides and the roller member in the central portion, it is possible to exert the conveyance action on the paper in a good state.

Further, in an apparatus in which the image forming apparatus is configured to support A3 size vertical feed, only the roller device at the central portion of the carrying roller device 10 arranged upstream of the registration roller device 2 has a large carrying force. Even if the roller device on the side portion is provided with a nip pressure to such an extent that the fluttering of the sheet can be suppressed, the conveying action on the sheet can be exhibited in a good state. In the registration device 1 of the present invention configured as described above, when a loop is formed in the paper and the alignment operation of the paper is performed with the leading end of the paper P thrust into the registration roller device 2, the paper is twisted. Stress is added. Then, when the sheet thus aligned is conveyed toward the image transfer unit by driving the registration roller device 2 and the conveying roller device 10, the conveying force applied to the sheet by the conveying roller device 10 is increased. However, since it is applied only to the central portion of the paper, it is possible to prevent an extra conveyance action in the width direction of the paper from being imparted by the roller device arranged on the side portion, and it is possible to prevent the occurrence of paper wrinkles. become. Further, with respect to the paper sent out from the registration device, the registration roller device 2 applies a uniform conveying force to the entire paper, but the conveyance roller device 10 applies the conveyance force only in the central portion, so that stress is applied in the twisting direction. This makes it possible to perform the transport operation in a normal state even for the sheet in the state where the mark is added.

In the sheet conveying apparatus of the present invention, in addition to constituting the conveying roller apparatus as shown in FIG.
It is also possible to configure the transport roller device 20 as shown in FIG. In the example shown in FIG. 3, the drive roller member is configured by disposing four roller members on the roller shaft 21, and with respect to the four roller members of the drive roller member,
Nip roller members configured to exert a pressing action are arranged separately. The nip roller members 25 and 25a are supported by the springs 27 and 27a that exert a strong urging action with respect to the two drive roller members 22 and 22a arranged in the central portion of the sheet conveying path. Further, in the roller members on both sides, the drive roller members 23, 23
The nip roller members 26, 26a are arranged with respect to a, but the pressing force of these roller members is supported by springs 28, 28a so that a weak nip force can be set. In the example shown in FIG. 3, it is desirable that the roller member at the central portion is arranged at a position as close as possible to the central portion of the sheet conveying path.

Also in the sheet conveying apparatus configured as shown in FIG. 3, as in the case of the registration apparatus shown in FIG. 2, the aligning action with respect to the sheet and the action of feeding the aligned sheet toward the image transfer portion. Can be exhibited in good condition. When the transport roller device of the paper transport device as shown in FIGS. 2 and 3 is configured, the nip pressure as shown in the graph of FIG. 4 can be set. In other words, a large nip pressure is set in the roller device at the central portion of the sheet conveying path, but a small nip pressure is set at both ends so that the sheet can be conveyed. In addition, as shown in the graph of FIG.
By setting a large nip pressure in the center and setting the nip pressure at both ends to about 1/3 or less,
Even if the paper transport action of the roller devices at both ends is demonstrated,
It does not increase the stress of the fed paper and makes it possible to prevent the occurrence of paper wrinkles.

The conveying roller device for obtaining the distribution of the nip pressure as shown in the above embodiment is generally arranged in the sheet conveying path of the image forming apparatus in addition to the registration device. The present invention can also be applied to the transport roller device. Then, by exerting a large conveying force on the central portion of the sheet, the conveying force of the conveying roller device becomes uneven in the width direction of the sheet conveyed in the sheet conveying path, and skew occurs. The effect of preventing this can be exhibited. Further, as the urging member arranged with respect to the nip roller member, other arbitrary urging means can be used other than using a leaf spring as shown in the embodiment. Even when the leaf springs having the same length and strength are used, the force for urging the roller can be changed by changing the supporting position of the roller member with respect to the spring.

[0018]

Since the sheet conveying device of the image forming apparatus of the present invention is constructed as described above, the roller member at the central portion is different from the roller device arranged in plural in the width direction of the sheet. It is possible to carry out the paper conveying operation in a good state only by providing a means for setting the nip pressure at a large value. Further, when the transport roller device of the present invention is applied to the registration device, it is possible to exhibit the action of feeding aligned sheets without causing wrinkles or the like. Further, in the apparatus of the present invention, even when the twisted force in the width direction remains on the aligned paper, the paper is not moved directly between the roller devices arranged in the registration device, and the paper advances straight. It is possible to maintain the goodness.

[Brief description of drawings]

FIG. 1 is a side view showing a configuration of a registration device to which a conveyance roller device of the present invention can be applied.

FIG. 2 is an explanatory diagram of a transport roller device of the present invention.

FIG. 3 is an explanatory view of another embodiment of the transport roller device of the present invention.

FIG. 4 is a graph showing a distribution state of nip pressure in the transport roller device of the present invention.

[Explanation of symbols]

1 registration device, 2 registration roller device, 1
0 transport roller device, 11 drive roller, 12
Drive shaft, 13 roller member, 15 nip roller, 16 nip roller member, 18 spring, 20 transport roller device, 21 drive shaft, 2
2 ・ 23 roller member, 25 ・ 26 nip roller member, 27 ・ 28 spring.

Claims (2)

[Claims] 1. A conveyance roller device, which is arranged at a predetermined interval in the paper conveyance direction, and a registration roller device, which abuts the paper to position the leading end portion, are arranged at a nip position of the registration roller device. In the registration device that abuts the leading edge of the paper and forms a loop on the paper by performing additional feeding by the transport roller device and aligns the paper, the transport roller device is arranged in the paper transport path, and the drive shaft A drive roller member provided with a plurality of roller members and a plurality of nip roller members provided with separate pressing means corresponding to each of the drive roller members. The pressure is set to a large value at the center of the width direction of the paper conveyance path and a small value at the side part of the conveyance roller device of the image forming apparatus. . 2. A nip roller member constituting the transport roller device is separately arranged for each roller member arranged in the drive roller member, and a pressing force is set by an elastic member supporting the nip roller member, The nip roller member arranged with respect to the drive roller member is configured by using an elastic member having a large biasing force in the central portion of the sheet conveying path, and a small biasing force is exerted on the side nip roller member. The sheet conveying device of the image forming apparatus according to claim 1, wherein the sheet conveying device is configured by using an elastic member.