JP2003316092A - Paper feeding device and image forming apparatus using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably feed paper by making feeding speed variable and absorbing the looseness of the paper in a paper feeding device used in an image forming apparatus such as a copying machine. <P>SOLUTION: The paper feeding device has a pair of resist rollers 8 and a transfer roller 6 for transferring an image to transfer paper 5 on the downstream side of the rollers 8 in the feeding direction of the paper 5, and the paper feeding force of the roller 6 is stronger than that of the rollers 8 and the width of the roller 6 is equal to or above the width of the paper 5. In the device, the feeding speed of the rollers 8 is made variable. The rotating speed of the rollers 8 is changed based on output from a paper detection means 9 positioned on the upstream side of the rollers 8 in the paper feeding direction and a sensor 7 positioned on the downstream side thereof. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper conveying device used for an unspecified paper conveying device such as a copying machine or a printer and an image forming apparatus using the same.

[0002]

2. Description of the Related Art Conventionally, the problems to be solved by the invention
In a paper transporting device such as a mono-color copying machine, when the image formed by the image forming device is transferred onto the transfer paper, the transfer speed of the registration roller is adjusted so that the transfer speed of the transfer paper matches the peripheral speed of the image forming device. It was complicated. This is because the registration roller determines the transport speed of the transfer paper, and the speed deviation of the roller directly leads to the image length deviation on the transfer paper.

However, in recent years, an image forming apparatus has been developed which is provided with a dedicated roller having a conveying force for transferring an image onto a transfer sheet, and which transfers the image while properly holding the transfer sheet while applying a transfer bias. However, skew correction or the like of the transfer paper requires that the registration rollers located upstream in the conveyance direction still have a function, so that two pairs of conveyance rollers having a large conveyance force are adjacent to each other on the conveyance path. Will be done. At this time, the span between rollers is reduced in order to secure the corresponding minimum paper width. Therefore, if the conveyance force is different between these rollers, the paper may be pulled or excessively loosened between the rollers, which may cause a variation in the image length.

Therefore, it is an object of the present invention to make it possible to carry out stable conveyance by varying the conveyance speed in the above-mentioned paper conveying apparatus to absorb the slack of the paper.

[0005]

In order to achieve the above object, a paper conveying apparatus according to claim 1 of the present invention is for transferring an image onto a transfer paper downstream of a pair of registration rollers and the transfer paper conveying direction. In the image forming apparatus having a transfer roller, the paper conveying force of the transfer roller is larger than the conveying force of the registration roller pair, and the width of the transfer roller is equal to or larger than the paper width of the transfer sheet, the conveyance of the registration roller pair is performed. It is characterized by having a means for varying the speed.

According to a second aspect of the present invention, in order to achieve the above object, in the paper conveying apparatus according to the first aspect, the paper detecting means in which the conveying speed varying means is located upstream of the registration roller pair in the paper conveying direction. The rotation speed of the registration roller pair is changed based on the outputs of the means and a sensor located downstream of the registration roller pair in the paper conveyance direction.

According to a third aspect of the present invention, in order to achieve the above object, in the paper conveying apparatus according to the first aspect, the paper detecting means in which the conveying speed varying means is located upstream of the registration roller pair in the paper conveying direction. The transfer speed of the pair of registration rollers is varied depending on the means and the transfer mode of the transfer paper.

According to a fourth aspect of the present invention, in order to achieve the above object, in the paper transporting device of the first aspect, the transport speed varying means is a storage content of storage means for transporting length of the transfer paper. The transfer speed of the registration roller pair is made variable after a lapse of a predetermined time from the rotation start timing of the registration roller pair.

An image forming apparatus according to a fifth aspect of the present invention is characterized by using the paper conveying apparatus according to any one of the first to fourth aspects to achieve the above object.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a conceptual side cross-sectional view showing a main part configuration of an image forming apparatus using an embodiment of a paper conveying apparatus according to the present invention. In the figure, 1 is a paper feed table, 2 is a paper feed roller set, 3 is a conveying path, 4 is an image forming belt, 5 is transfer paper, 6 is a transfer roller, 7 is a slack detecting means, 8 is a registration roller,
9 is a paper detection means.

The transfer papers 5 loaded on the paper feed table 1 are separated one by one by the paper feed roller set 2 and sent through the conveyance path 3, and when reaching the registration rollers 8, a certain amount of slack is provided for skew correction. And then stop.

Next, after the image formed by the image forming device is transferred to the image forming belt 3, when the leading edge of the image on the belt 3 reaches the transfer roller 6, the leading end of the transfer paper 5 coincides with the leading edge of the image. The registration roller 8 starts to rotate at the same timing.

Here, the transfer roller 6 and the registration roller 8
If the paper is pulled between them, the aspect ratio of the transferred image is changed. Therefore, the registration roller conveyance speed is set higher than the transfer roller conveyance speed and the paper is conveyed while being slackened. Further, if the slack is excessively large, a fold may occur, or the transfer paper 5 may be exposed when the trailing edge of the transfer paper 5 passes through the registration roller 8, and the image may be disturbed. For this reason, it is desirable that the speeds between the rollers are equal, but since differences due to variations in parts and the like will always occur, the transport speed is set within an allowable range to ensure a minimum slack in the paper.

The amount of slack differs depending on the type and length of the transfer paper 5 and the environment. In particular, slack is created between the transfer roller 6 and the registration roller 8 according to the length of the transfer paper 5 in the transport direction, but the slack height increases as the amount of slack increases.

Here, the height of the detection means 7 provided between the registration roller 8 and the transfer roller from the conveyance surface is set according to the allowable amount of slack. When the slack of the paper becomes large during the conveyance and the detecting means 7 detects the paper, the speed of the registration roller 8 is reduced in order to reduce the slack. This allows
Excessive slack between the registration roller 8 and the transfer roller 6 is eliminated, and when the trailing edge of the transfer paper 5 passes through the registration roller 8 there is no slack enough to disturb the image.

Further, since a large classification of paper types can be selected to some extent according to the operation mode, if the paper conveyance mode is designated in advance, the detection means 9 upstream of the registration roller 8 is provided.
The same result as described above can be obtained by detecting the rear end of the transfer paper 5 and then reducing the conveyance speed of the registration roller 8. However, since it is not possible to handle the transfer state of each transfer sheet,
The application effect is smaller than that of the above configuration.

Further, if the transport length of the transfer paper 5 is known in advance, referring to the output of the storage means that stores this length, the transfer is performed after a lapse of time from the rotation start of the registration roller 8 having a small slip ratio. The paper feed amount can be predicted, and therefore the registration roller 8 starts to rotate and the transfer speed of the registration roller 8 is reduced by a feed amount equal to or less than the length of the transfer paper 5 from the timing when the transfer paper 5 waiting for feeding is fed out. The slack of can be reduced. At this time, since it is not necessary to constantly monitor the output of the detection means 9, a configuration with a small control load can be expected.

[0018]

As described above, in the paper transfer device according to the first aspect of the present invention, in the device in which the width of the transfer roller located downstream of the registration roller pair is equal to or larger than the paper width, the conveyance speed of the registration rollers is variable. Therefore, there is an effect that the looseness of the transfer paper can be absorbed and a stable image can be obtained.

As described above, in the paper conveying apparatus according to the second aspect of the present invention, the rotation speed of the registration roller is determined from the outputs of the paper detection means located upstream of the pair of registration rollers and the paper detection means located downstream of the registration rollers. In addition to the effect common to the device according to claim 1,
There is an effect that the amount of slack can be adjusted while detecting the slack state of each transfer sheet that is being passed, and a stable image can be obtained.

As described above, according to the third aspect of the present invention, the sheet conveying device changes the conveying speed of the registration rollers depending on the output signal of the sheet detecting means located upstream of the registration roller pair and the transfer sheet conveying mode. Because I was able to
In addition to the effects common to the apparatus according to the first aspect, there is an effect that the amount of slack of the transfer paper can be adjusted and a stable image can be obtained with a configuration in which the number of detecting means installed is minimized.

As described above, the paper conveying apparatus according to the present invention conveys the contents of the transfer paper conveyance length stored in the storage means and conveys the registration rollers after a predetermined time has elapsed from the rotation start timing of the registration rollers. By making the speed variable, in addition to the effect common to the apparatus of claim 1, the amount of slack of the transfer paper can be adjusted with a configuration that does not require constant monitoring of the output of the detection means, and a stable image can be obtained. There is an effect that can be obtained.

Since the image forming apparatus according to the fifth aspect uses the sheet conveying apparatus according to the first to fourth aspects described above, the conveying speed of the registration rollers is varied to absorb the slack of the transfer sheet and stabilize the sheet. In addition to the effect of the apparatus according to claim 1 that a captured image can be obtained, according to any one of claims 2 to 4,
The same effect can be obtained with any one of the paper transporting devices.

[Brief description of drawings]

FIG. 1 is a conceptual side sectional view showing a configuration of a main part of an image forming apparatus using an embodiment of a paper conveying apparatus according to the present invention.

[Explanation of symbols]

1 Paper feed stand 2 Paper feed roller set 3 transport paths 4 imaging belt 5 Transfer paper 6 Transfer roller 7 Loosening detection means 8 Registration roller 9 Paper detection means

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2H072 AA07 AA13 AA24 AB07 BA03                       BA12 CA01 CA02 CB09 JA02                 3F049 AA01 DA12 DA14 EA10 EA12                       EA24 EA28 EA29 LA02 LA07                       LB03                 3F102 AA02 AA11 AB01 BA02 BB02                       CA03 CB01 DA08 EA03 FA04                       FA08 FA09

Claims (5)

[Claims] 1. A registration roller pair and a transfer roller for transferring an image onto a transfer sheet are provided downstream of the transfer roller in the conveyance direction, and the paper conveyance force of the transfer roller is larger than the conveyance force of the registration roller pair. A paper transporting device in which the width of the transfer roller is equal to or larger than the paper width of the transfer paper, further comprising means for varying the transport speed of the pair of registration rollers. 2. The paper transporting device according to claim 1, wherein the transport speed varying means is located upstream of the registration roller pair in the paper transport direction and downstream of the registration roller pair in the paper transport direction. A paper conveyance device characterized in that the rotational speed of the pair of registration rollers is changed based on the output from a sensor. 3. The paper carrying device according to claim 1, wherein the carrying speed varying means is a paper detecting means located upstream of the registration roller pair in the paper carrying direction and the transfer paper carrying mode, the registration roller pair. A paper transporting device, wherein the transporting speed of the paper is variable. 4. The paper transporting device according to claim 1, wherein the transport speed varying means stores the stored contents of the transporting length of the transfer paper and a predetermined time from the rotation start timing of the registration roller pair. A paper conveyance device, wherein the conveyance speed of the pair of registration rollers is variable. 5. An image forming apparatus comprising the paper conveying device according to claim 1.