JPH0242680Y2 - - Google Patents

Description

[Detailed description of the invention] <Technical field> This invention is a copying machine that is disposed between the paper feed section and the copying process section of an electrophotographic copying machine and transports paper in synchronization with the operation of a photoreceptor. Regarding timing rollers.

<Summary of the invention> In summary, this invention is configured by partially changing the axis diameter of the timing roller of a copying machine so that uniform pressure can be applied to sheets of different thickness. .

<Prior art and its disadvantages> In order to form a copy image of a document at a set position on copy paper in an electrophotographic copying machine, it is necessary to transport the copy paper to the copy process section in synchronization with the operation of the photoreceptor. be. For this reason, conventionally, as shown in FIG. has been set up. With the above configuration, the copy paper 17 or 18 is fed by the paper feed roller 19 or 20 prior to rotation of the photosensitive drum 14, and is stopped at the position of the timing roller 11.
After that, the timing roller 1 is rotated in synchronization with the rotation of the photoreceptor drum 14, and the paper is transferred to the photoreceptor drum 14.
and the transfer device 15 to the transfer process position.

In order to transfer the image formed on the surface of the photosensitive drum 14 over the entire surface of the copy paper in good condition, it is necessary to keep the paper conveyance speed by the timing roller 11 constant. The above-mentioned conveyance speed is affected not only by the rotational speed of the timing roller 11 but also by the contact pressure between both rollers. For example, when small thick paper such as postcards is transported as copy paper, a pressure greater than that of plain paper is applied to the surface of the copy paper, and when the trailing edge of the paper passes the timing roller 11, a large force is applied in the paper transport direction. . As a result, the small cardboard paper mentioned above is ejected in the direction of the transfer process position, which changes the paper conveyance speed and changes the contact state with the photoreceptor drum, causing a deviation in the paper conveyance direction of the copied image and deteriorating the image quality. There was a drawback.

<Purpose of the invention> In view of the above-mentioned drawbacks of the conventional technology, the purpose of this invention is to maintain the conveyance speed constant regardless of the thickness of the copy paper being conveyed from the paper feed section to the copy process section, thereby producing high-quality copied images. It is an object of the present invention to provide a timing roller for a copying machine that can be obtained.

<Structure and Effects of the Invention> This invention is based on the timing roller of a copying machine, by comparing the shaft diameter in a range perpendicular to the paper conveyance direction through which small-sized cardboard passes, with the shaft diameter outside that range. The paper is characterized by being formed to be approximately twice as small as the difference in thickness between the paper and plain paper.

With the above configuration, the contact pressure that is applied when transporting small cardboard can be made almost equal to that when transporting plain paper, and the effect in the paper transport direction that occurs when the trailing edge of the paper passes the timing roller. The force can also be kept constant. Therefore, even when the thickness of the copy paper to be transported changes, the paper transport speed does not change, and the state of contact between the surface of the photoreceptor and the surface of the copy paper can always be kept constant. Therefore, there is no deviation in the paper conveyance direction in the copied image, and high-quality copied images can always be formed.

<Embodiment> FIG. 1 is a front view in the paper conveyance direction showing the configuration of a timing roller of a copying machine which is an embodiment of this invention.

The timing roller 1 is composed of an upper roller 2 and a lower roller 3, and the copy paper is transported with a center position 6 in a direction perpendicular to the paper transport direction as a reference. In the upper roller 2, the shaft diameter of the central portion 2a in a range approximately equal to the width in the direction perpendicular to the conveyance direction of small cardboard such as postcards is smaller than the shaft diameter of the outer portion 2b. Approximate thickness difference 2
It is formed twice as small. Above upper roller 2
The lower roller 3 is in contact with the inner portion 2b, and during a copying operation, rotational force is transmitted to the shaft portions 4 and 5 in synchronization with the operation of the photosensitive drum to convey the paper.

FIGS. 2A and 2B are side views in the paper conveyance direction showing the operation of the timing roller of the copying machine.

The shaft diameter of the central part 2a of the upper roller 2 is the outer part 2b.
The shaft diameter is made smaller by approximately twice the difference in thickness between the small cardboard 8 and the plain paper 7. Therefore, the distance between the central portion 2a and the lower roller 3 is
and the lower roller 3 by an amount approximately equal to the difference in thickness between the small thick paper 8 and the plain paper 7. Therefore, as shown in FIG. 2A, the pressure that the plain paper 7 receives from the outer portion 2b when passing through the timing roller is approximately equal to the pressure that the small cardboard 8 receives from the center portion 2a. As shown in FIG. 2B, when the rear end of the copy paper passes the timing roller 1, the rear end of the small cardboard 8 rotates in the direction of arrow B with the center part 2a of the upper roller that rotates in the direction of arrow A. The conveyance force in the direction of arrow C received from the moving lower roller 3 is
It is approximately equal to the conveying force in the direction of arrow C that the rear end part receives from the outer part 2b and the lower roller 3. With the above configuration, it is possible to eliminate the difference in paper conveyance force caused by the difference in pressure between the roller and the copy paper when conveying copy paper having different thicknesses. Therefore, when conveying thick copy paper, the conveying force that acts on the trailing edge of the paper when it passes the position of the timing roller is approximately equal to the conveying force that acts on the trailing edge of plain paper. It is possible to prevent misalignment of copied images due to changes in conveyance speed that occur during conveyance of thick copy paper.

The shaft diameter of both the upper and lower rollers in the range perpendicular to the paper conveyance direction through which the small cardboard passes can be made smaller than the shaft diameter outside that range, and the shaft diameter of only the lower roller can be made smaller. A similar effect can be obtained by changing.

[Brief explanation of drawings]

FIG. 1 is a front view in the paper conveyance direction showing the structure of the timing roller of a copying machine which is an embodiment of this invention, and FIGS. 2A and 2B are side views in the paper conveyance direction showing the operation of the timing roller of the copying machine. , 3rd
The figure is a side view in the paper conveyance direction showing a schematic structure of a main part of the copying machine in which the timing roller of the copying machine is used. 1... Timing roller.

Claims (1)

[Scope of Claim for Utility Model Registration] In the timing roller of a copying machine that transports paper to a transfer process position in synchronization with the operation of a photoreceptor, the shaft diameter in the range perpendicular to the paper transport direction through which small thick paper passes, Compared to shaft diameters outside that range,
A timing roller for a copying machine is made smaller by approximately twice the difference in thickness between the above-mentioned small cardboard and plain paper.