JPH0891639A - Sheet carrying device - Google Patents

Abstract

PURPOSE: To provide a sheet carrying device having a resist roller with the structure, which is formed so that the tip of the paper sheet of small size does not pass through, without enlarging a driven roller. CONSTITUTION: Driven roller of a resist roller is formed of plural divided rollers 9a-9c so that the paper sheets 13a-13d of all the sizes abut on at least two of the rollers 9a-9c. As a result, the nipping force of the resist roller even to the paper sheet of the minimum size can be enlarged, and the paper sheets 13a-13d of all the sizes do not pass through the resist roller. As a result, the resisting with high reliability can be provided. Since the resist roller with this structure and a carrying roller having a spherical part are combined with each other, correction of skew of the paper sheet can be easily and accurately performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet conveying apparatus for an image forming apparatus, and more particularly to a sheet conveying apparatus capable of performing stable resist correction without being affected by the size of cut sheets or the strength of waist.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine or a printer, in order to align an image (latent image) formed on a photosensitive drum with a copy sheet, a sheet sent is sent. A registration roller is arranged in front of the transfer device to stop the transfer, measure the timing, and send out. As is well known, the registration roller controls the feeding and stopping of the paper by repeating the rotation and the stopping.

In this registration roller, since it is necessary to reliably stop the paper temporarily, conventionally, strong springs are hung on both ends of the pair of upper and lower rollers, and the pair of upper and lower rollers sandwich the paper. (Hereinafter referred to as nip force) is increased. However, when the nip force is increased, the nip force tends to be smaller at the central portion of the upper and lower roller pairs with respect to the end portions due to bending of the shaft of the rollers. In order to prevent this drawback, for example, in Japanese Patent Publication No. 6-2537, the driven roller is substantially drum-shaped, that is, the diameter of the roller in the central portion in the roller axial direction is made larger than that at both end portions, and the nip force at the central portion is increased. Has been disclosed to strengthen the roller so that the roller is substantially uniform over the entire length of the roller. However, in this technology, since the upper and lower roller diameters are distributed so as to be different in the axial direction, the peripheral speed of each part of the roller is different, which causes waviness in the running of the paper, which reaches the transfer part. , There is a problem of missing images.

In order to solve this problem, there has been proposed a method of disposing a pre-transfer roller for compensating for the difference in peripheral speed of each part of the roller between the registration roller and the photosensitive member. Since the distance between the registration roller and the transfer section becomes large, the time required to reach the transfer section from the registration roller varies due to the slip of the paper between the registration roller transfer section. As a result, there is a problem that the correction effect of the resist is halved.

On the other hand, it has been attempted to divide the driven roller into a plurality of parts and attach them to an upper baffle forming a sheet conveying path near the registration rollers to make the nip force of the upper and lower roller pairs uniform. In this device, when a strong spring is hung on the end of the driven roller to increase the nip force, it is necessary to make the upper baffle robust so as not to be deformed by the spring force, which is expensive.

In order to solve this drawback, a method has been proposed in which the nip force is secured by the weight of the driven roller without using the strong spring. For example, as shown in FIG. 4, driven rollers 9a, 9b, 9c made of, for example, metal are provided so as to face drive rollers 8a, 8b, 8c made of, for example, rubber, which are integrally connected by a shaft 14. , A method of ensuring the nip force by the weight of the driven rollers 9a, 9b, 9c has been proposed.

[0007]

However, in the method of ensuring the nip force by the weight of the driven rollers 9a, 9b, 9c described above, when a wide sheet conveyance path is formed, the driven roller uniformly covers the entire conveyance path. The holding members 12a and 12b are provided so as to be arranged at a relatively large interval in the axial direction of the registration roller so as to cover the above. The driven rollers 9a, 9b, 9c and sheets 13a to 13 of various sizes sent on the sheet conveying path.
The relationship with d is as shown in FIG. 5, for example.

According to the research conducted by the present inventor, the registration roller having such a structure can be used for a large size paper (for example, A2 portrait,
(A1 portrait) contacts the registration roller and is temporarily stopped, the tip does not penetrate the registration roller, but in the case of small size paper (eg A4 portrait, A3 portrait etc.), the driven roller rises, We have found a drawback that the tip often penetrates greatly. As a countermeasure against this, it is possible to easily increase the driven roller's own weight, but increasing the driven roller's own weight will increase the size of the driven roller, and recent copying machines will have higher functionality such as colorization. In view of the tendency toward or downsizing, there is a problem that a large installation space for the driven roller cannot be obtained.

An object of the present invention is to eliminate the above-mentioned problems of the prior art, and to provide a sheet conveying apparatus having a registration roller having a structure in which the leading edge of a small-sized sheet does not penetrate without increasing the size of the driven roller. Especially.

[0010]

In order to achieve the above-mentioned object, the invention of claim 1 suspends a sheet sent on a sheet conveying path and synchronizes with an image formed on an image forming apparatus. In a sheet conveying apparatus having a registration roller for sending out the sheet, the driven roller of the registration roller is divided into a plurality of sheets, and the leading edge of the smallest size sheet among the sheets traveling on the sheet conveyance path is It is characterized in that it is arranged so as to contact at least two driven rollers. Further, in the invention of claim 2, the smaller the size of the paper, the smaller the paper contact portion and the larger the non-contact portion,
The feature is that the driven roller is arranged.

Further, according to the invention of claim 3, a loop space for accommodating the loop of the sheet and a conveying roller composed of a driven roller of a spherical member are sequentially arranged on the upstream side of the registration roller. Is characterized by.

[0012]

According to the first aspect of the invention, all the sheets fed on the sheet conveying path come into contact with at least two driven rollers of the registration rollers. Therefore, since the nip force of the registration roller with respect to the paper becomes large,
It is possible to prevent the sheet from penetrating the registration roller, and it is possible to provide a stable registration operation.

According to the second aspect of the present invention, the frictional force exerted on the paper by the non-contact portion of the driven roller becomes larger for the smaller size paper, and a stable registration operation can be provided.

According to the third aspect of the invention, the driven roller of the spherical member absorbs the restoring force of the loop of the sheet regardless of its direction and by a constant force, so that the skew of the sheet is stable. In addition, the resist can be stably performed without being affected by the stiffness of the paper.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings. FIG. 1 is an explanatory diagram showing the configuration of a sheet conveying device of an image reproducing apparatus to which the present invention is applied. In the figure, reference numeral 2 is a cut sheet conveying path for guiding a sheet (sheet) 13 sent from a cut sheet feeding device (not shown) to the transfer section 3 of the photoconductor 1. On this cut paper transport path 2,
A registration roller unit 5 that sends the paper to the transfer unit 3 in time with the image on the photoconductor 1, and a first conveyance roller unit 6 that conveys the paper to the registration roller unit 5 provided on the upstream side thereof. Further, the second conveying roller portion 7 provided on the upstream side is arranged. The arrangement interval between the registration roller unit 5, the first conveying roller unit 6, and the second conveying roller unit 7 is determined by the minimum length of the paper conveyed to the sheet conveying device, and is at least shorter than the minimum length. Has been decided.

As will be described in detail later, the registration roller unit 5 is composed of a driving roller 8 and a driven roller 9, and the first and second conveying roller units 6 and 7 are both driving rollers 10. And a driven roller composed of a spherical member 11.

Between the registration roller section 5 and the first conveyance roller section 6, the leading edge of the sheet 13 sent by the conveyance roller sections 7 and 6 on the cut sheet conveyance path 2 is the registration roller. A loop space 4 is provided for accommodating a loop generated when the portion 5 is abutted. When the loop space 4 is generated, the first and second transport roller units 6 and 7 slide the trailing edge of the sheet to correct skew of the sheet, and the loop space 4 is excessively applied to the registration roller unit 5. The contact force is restrained from acting, and the stiff paper is restrained from exerting an excessive contact force on the registration roller portion 5.

FIG. 2 is a diagram showing the configuration of the driven roller 9 of the registration roller unit 5 which is one of the essential parts of the present invention, and the positional relationship between sheets of each size. In the example of this figure, the driven roller 9 is divided into three parts 9 a to 9 c, and each of them is attached to the cut sheet conveyance path 2 via each holding member 12. As is clear from a comparison between FIG. 2 and FIG. 5, the length of each holding member 12 in FIG. 2 is shortened, and each driven roller 9a ...
9c is configured so as to be arranged in the central portion of the cut sheet conveyance path 2 as a whole. Further, all the driven rollers 9a to 9 are divided from the paper 13 of the minimum size A4 vertical size to the maximum size A1 vertical size which is scheduled to be conveyed.
It is arranged so as to abut on c. Further, the driven rollers 9a to 9c are arranged such that the smaller the paper size, the smaller the paper contact portion and the larger the non-contact portion.

Next, the registration roller section 5 having the above-mentioned structure
First, how the sheets abut each other will be described with reference to FIG. FIG. 3 shows the smallest A4 vertical size paper 13a.
Shows the state of contact with the registration roller unit 5. When the sheet 13a comes into contact with the registration roller unit 5, the sheet 13a
The a contacts three driven rollers 9a to 9c. Therefore, the driven rollers 9a to 9c are applied to the sheet 13a by their own weight, and even if the individual driven rollers 9a to 9c have the same weight as the conventional driven roller, the weight applied to the sheet 13a, in other words, By doing so, the nip force of the registration roller is about tripled. For this reason, it is possible to prevent the driven rollers 9a to 9c from being lifted up and the front end portion of the paper from penetrating the registration roller due to the rush impact exerted on the registration roller when the paper 3a abuts.

Assuming that the paper 13a is impacted,
Even if the driven rollers 9a to 9c are lifted up, the driven rollers 9a and 9c with which the sheet comes into contact with the ends thereof.
Is tilted and lifted as shown. Therefore, the end portions of the driven rollers 9a and 9c on the side opposite to the sheet contact side have contact portions with the drive rollers 8a and 8c having a relatively large friction coefficient.
Since the resistance related to the rotation of the driven rollers 9a and 9c is increased, it is possible to prevent the leading edge of the sheet from penetrating from this point as well.

The above description is for the operation when the smallest A4 vertical size sheet 13a is flown into the sheet conveying path 2.
Even when the sheets 13b, 13c, and 13d having a size larger than this are flown, as can be easily understood from FIG. 2, when the registration roller 5 is brought into contact with the driven rollers 9a to 9c, the weight of three driven rollers 9a to 9c is large. The nip force can prevent the leading edge of the sheet from penetrating. Therefore, according to this embodiment, it is possible to stop the sheet of the minimum size to the sheet of the maximum size by the registration roller 5 as scheduled, and it is possible to provide a stable registration operation.

Further, in this embodiment, the registration roller 5
And the first and second conveying roller portions 6 and 7 each including the driving roller 10 and the driven roller of the spherical member 11. For this reason, when the leading edge of the sheet comes into contact with the registration roller 5 to form a loop, the restoring force on the trailing edge side of the sheet at the mountain portion of the loop is released evenly in any direction. be able to. Therefore, even if the sheet slightly skews and comes into contact with the registration roller 5, this skew can be easily eliminated, and even if a sheet having a different stiffness is brought into contact with the registration roller 5, the registration roller 5 causes The force exerted on the sheet 5 can be corrected almost uniformly, and a stable resist can be provided regardless of the stiffness of the paper.

[0023]

According to the first aspect of the present invention, a large nip force is applied even to the smallest size sheet fed on the sheet conveying device, although the small size upper roll similar to the conventional one is used. Therefore, it is possible to prevent the sheet from penetrating the resist roll, and it is possible to perform a reliable resist operation. Further, even if the paper penetrates through the resist roll, a force for suppressing this occurs, so that the penetration can be suppressed to a minimum.

According to the second aspect of the present invention, the frictional force exerted on the paper by the non-contact portion of the driven roller becomes larger for the smaller size paper, and a stable registration operation can be provided.

Further, according to the invention of claim 3, the driven roller composed of the spherical portion absorbs the restoring force of the trailing end of the sheet loop regardless of its direction, and the absorbing force is constant. It is possible to reliably perform skew correction and registration without being affected by the stiffness of the paper.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration example of a sheet conveying apparatus to which the present invention is applied.

FIG. 2 is a diagram showing a configuration of an upper roll of a resist roll of this embodiment.

FIG. 3 is a diagram showing a state in which a minimum size sheet comes into contact with the resist roll of this embodiment.

FIG. 4 is a diagram showing a state in which a minimum size sheet comes into contact with a conventional registration roll.

FIG. 5 is a diagram showing a configuration of an upper roll of a conventional resist roll.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Photoconductor, 2 ... Cut paper conveyance path, 3 ... Transfer part, 4 ... Loop space, 5 ... Registration roller part, 6 ... 1st conveyance roller part, 7 ... 2nd conveyance roller part, 8 ... Drive roller ,
9 ... driven roller, 10 ... drive roller, 11 ... spherical member,
12 ... Support member, 13a-13d ... Paper, 14 ... Shaft.

Claims (3)

[Claims] 1. A sheet conveying apparatus comprising a registration roller for temporarily stopping a sheet fed on a sheet conveying path and feeding the sheet in synchronism with an image formed on an image forming apparatus. The driven roller of the roller is divided into multiple
Further, the sheet conveying device is characterized in that among the sheets traveling on the sheet conveying path, the leading edge of the smallest size sheet is arranged so as to contact at least two driven rollers. 2. The sheet conveying apparatus according to claim 1, wherein the driven roller is arranged such that the smaller the sheet size, the smaller the sheet contact portion and the larger the non-contact portion. apparatus. 3. The sheet conveying apparatus according to claim 1, wherein a loop space for accommodating the loop of the sheet and a conveying roller including a driving roller and a driven roller of a spherical member are sequentially provided on the upstream side of the registration roller. A sheet conveying device characterized in that