JPH0112278Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a fixing device for an electrophotographic printing machine or the like.

In electrophotographic printing machines, a fixing device using a heating roller is widely used. An example of a fixing device using a heating roller is shown in FIG. The fixing device includes a heating roller 1, a pressure roller 2 having a coating made of an elastic material and disposed so as to press the heating roller 1, and a hot plate member 6 that preheats the printing paper 5 and forms a path for the paper to travel. and a suction section 7 for bringing the printing paper 5 into close contact with the hot plate member 6;
The paper is sent to a buffer 9 for absorbing the difference between the paper feeding speed sent out from the tractor 8 and the paper feeding speed of the heating roller 1, and a paper processing device (not shown) that folds and stacks the printing paper 5 alternately front and back. It is composed of a pulling roller 12. During printing operation, the pressure roller 2,
The hot plate member 6 rotates around the hinge 4, brings the pressure roller 2 into pressure contact with the heating roller 1, fuses and fixes the toner image formed on the printing paper 5, and sends the printing paper 5 to a paper processing device. ing.

When printing is stopped, it is necessary to separate the heating roller 1 and the pressing roller 2 because if the pressing roller 2 and the heating roller 1 are in pressure contact, unfixed toner will adhere to the roller surface or the printing paper will change color. There is. When printing is stopped, the heating roller 1 and the pressure roller 2 are separated by the cam means 10 at the same time as the sheet is stopped, and then the roller 12 stops rotating. At this time, the buffer 9 is applying tension to the printing paper 5, and when an operation is performed to stop the suction of the suction section 7, the printing paper 5 is returned by the buffer 9 in the direction A in FIG.

In the conventional technology, the roller 12 has a small rotation inhibiting force when it is stopped (there is no brake), so it rotates in the opposite direction as the printing paper returns, and the roller rotates due to inertia, which causes the slack as shown by the two-dot chain line in FIG. The printing paper contacts the heating roller. If the printer is left as it is for a certain period of time, the toner on the printing paper 5 may adhere to the heating roller 1 or the paper may change color due to heat, which is an inconvenience.

The purpose of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and to prevent discoloration of the printing paper and toner loss due to the paper sagging and continued contact between the heating roller and the paper even when the suction of the suction unit is stopped when printing is stopped. The purpose is to prevent adhesion to the heating roller.

By providing a brake on the drive shaft of the roller 12, the present invention prevents the roller 1 from returning when the printing paper returns.
The reverse rotation speed of the printing paper 2 is reduced, and the reverse rotation is promptly stopped to prevent the printing paper 5 from sagging.

An embodiment of the present invention will be explained with reference to FIG. 2. In FIG. 2, 1 to 12 have the same names as in FIG. 1 and have the same functions. 15 is the roller 12
The drive shaft 15 is rotated by a motor 17 or the like via a transmission means such as a belt 16, for example. Further, a belt 18 is attached to the drive shaft 15 via a spring 19.

When printing is stopped, the pressure roller 2 is separated from the heating roller 1 and at the same time the roller 12 stops rotating. At this time, even if the suction of the suction 7 is stopped and the printing paper 5 is returned by the buffer 9, a brake is applied to the drive shaft of the roller 12, so the returning speed of the printing paper decreases, and the buffer 9
Since the paper stops at the same time as the heating roller 1 stops, and the rotation of the roller 12 also stops immediately, no slack is formed in the paper, and contact between the heating roller 1 and the printing paper 5 can be prevented.

A similar effect can be obtained by pressing the brake shoe 21 against the drive shaft 15 via the spring 22 as shown in FIG.

According to the present invention, by providing a brake on the drive shaft 15 of the roller 12, even if the suction of the suction section is stopped when printing is stopped, it is possible to prevent the paper from sagging, resulting in discoloration of the paper and heating of the toner. Adhesion to the roller 1 can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view showing an example of a fixing device according to the prior art, FIG. 2 is a vertical sectional view showing an embodiment of the present invention, and FIG. 3 is a roller illustrating another embodiment of the present invention. FIG. In the figure, 1 is a heating roller, 2 is a pressure roller, 9 is a buffer, 10 is a cam means, and 12 is a roller.

Claims (1)

[Scope of utility model registration request] A heating roller, a pressure roller, a cam means for bringing the pressure roller into pressure contact with the heating roller, a buffer for absorbing the difference in paper feeding speed, and a roller for sending the paper sent out from the heating roller into a paper processing device. 1. A fixing device comprising an electrophotographic printing machine, characterized in that a brake device is provided on the drive shaft of the roller.