JPH09160425A - Electrophotographic printer provided with paper positional deviation correction mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact inexpensive paper positional deviation correction mechanism which can be mounted even on a compact electrophotographic printer as well. SOLUTION: At the time of printing, a pressure roll for fixing 2 is pressed on a heating roll 1 with a pair of springs 16a and 16b and a pair of arms 14a and 14b. When a cam shaft 19 is rotated in a fixed direction with a motor 20, during nonprinting, cams 15a and 15b push the arms 14a and 14b against the force of the springs 16a and 16b to separate the pressure roll 2 from the heating roll 1. Since the phases or shapes of the cams 15a and 15b are difference from each other, when a printing paper is positionally deviated during a printing operation, the rotation of the motor 20 is controlled within a very small range, so that the mutual lifting quantities of the cams 15a and 15b with respect to the pressure roll are slightly different and a delicate difference in pressing force between both ends of the roll 2 is made. Thus, the positional deviation of the printing paper can be corrected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic printing apparatus such as a laser beam printer or a copying machine, and more particularly to correcting a positional deviation of a sheet on a printing sheet conveyed by a fixing mechanism section (for example, skew feeding). Correction).

[0002]

2. Description of the Related Art In an electrophotographic printer, conveyance of printing paper is extremely important in terms of print quality, effective printing speed, labor saving, and the like. In order to cope with various printing papers such as paper quality, paper thickness, and size, in addition to improvement of printing speed and printing quality, a paper position deviation correcting mechanism (skew correction mechanism) has been conventionally devised.

Among the sheet conveying mechanisms, the pressure roll type fixing mechanism has a great influence on the sheet feeding performance. Especially, in the laser beam printer for continuous sheets, the fixing mechanism is provided with a sheet position correcting mechanism. There are many practical examples.

FIG. 2 shows a fixing and sheet position deviation correcting mechanism according to a conventional method.

The fixing roll comprises a heating roll 1 and a pressure roll 2. The heating roll 1 is supported by a roll supporting unit (not shown) and is configured to rotate at a fixed position by the power of the driving unit.

The pressure roll 2 is arranged so as to face the heating roll 1, and the printing paper 3 is conveyed while being sandwiched between the heating roll 1 and the pressure roll 2.

The mechanism for pressing the pressure roll 2 against the heating roll 1 includes an arm 4 (4a, 4b) and a cam 5 (5a,
5b), steel wires 6 (6a, 6b), springs 7 (7a, 7b), etc., and these elements are arranged in pairs near both ends of the pressure roll 2 to form a pair. It constitutes a pressure roll pressing mechanism. Of these, the cams 5a and 5b also serve as a pressure roll pressing release mechanism.

The arms 4a and 4b are arranged near both ends of the pressure roll 2, and the steel wire 6 is attached to one end of the arm 4a.
a is fixed. The steel wire 6a has an end on the side opposite to the arm connected to one end of the spring 7a. Similarly arm 4
The steel wire 6b is fixed to one end of b. The steel wire 6b is connected to one end of the spring 7b at the end opposite to the arm. The other end of the spring 7a has a steel wire 8
Further, the other end of the spring 7b is also connected to the steel wire 8, so that the springs 7a and 7b are connected via the steel wire 8. The steel wire 8 is wound around the pulley 9, and the springs 7a and 7b are arranged left and right around the wire winding position of the pulley 9.

The pulley 9 is connected to the drive shaft of the motor 10. Both end shafts of the pressure roll 2 are supported by the arms 4a and 4b while enabling the pressure roll 2 to rotate. Arm 4
A cam follower 11 is disposed on each of a and 4b, and a pair of cams 5a and 5b are installed so as to contact the corresponding cam followers 11. The cams 5a and 5b are connected by a cam shaft 12, and the cam shaft 12 is rotatably supported by a frame (not shown) and can be rotated by a motor 13.

At the time of non-printing, the cam shaft 12 rotates so that the pressure roll 2 comes to a position away from the heating roll 1,
Stop. During printing, the cam shaft 12 rotates in the direction opposite to that during non-printing, and the cams 5a and 5b move toward the cam follower 1.
1 is pushed up, the arms 4a and 4b move around a fulcrum (not shown) as a center of rotation, and the pressure roll 2 is stopped at a position where it is completely pressed against the heating roll 1. At this time, spring 7
The pressure roll 2 is pressed against the heating roll 1 via the arms 4a and 4b by the pulling force of a and 7b, and the printing paper 3 is nipped by the pressure roll 2 and the heating roll 1, and is heated by the rotation of the heating roll 1. The pressure roll 2 is driven and the printing paper 3 is conveyed while being fixed. The print paper feed position is detected by a print paper feed position detection unit (not shown).

When the printing paper feed position detection unit detects that the paper feed position is shifted to the left in the feed direction, the motor 10 rotates the pulley 9 in a predetermined direction,
Contract the left spring 7a and the right spring 7b
Try to extend As a result, the pressing force on the left side of the pressure roll 2 is smaller than that on the right side, and the conveying force on the left side of the paper is smaller than that on the right side, so that the paper feeding position is shifted to the right side. In this way, the deviation of the sheet feeding position (skew) is corrected. If it skews to the right, the opposite operation is performed.

[0012]

According to the prior art, a mechanism for pressing the pressure roll during printing and releasing the pressure during non-printing, and a mechanism for changing the pressing force at both ends of the pressure roll during the printing operation. Were required separately, and each was composed of a link mechanism, a motor, and the like.

Therefore, the device becomes complicated and large, and the cost of the device also increases, so that it is not possible to cope with the recent miniaturization. For this reason, there are some small-sized, low-speed laser beam printers for continuous paper that do not have a paper position deviation correction mechanism.

An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a small-sized and low-cost sheet misalignment correction mechanism which can be mounted on a small electrophotographic printer.
An object of the present invention is to realize an electrophotographic printing apparatus having high printing quality and high reliability for various printing papers.

[0015]

In order to achieve the above object, the present invention is configured as follows.

That is, a pressure roll for fixing, a pair of pressure roll pressing mechanisms for applying a pressing force to the pressure roll at both end positions of the pressure roll, and a pressure roll pressing for releasing the pressing force. In an electrophotographic printing apparatus including a release mechanism, the pressure roll pressing release mechanism is driven by a motor that can rotate in forward and reverse directions.
When a pair of cams are provided, the pressure roll comes into contact with and separates from the opposite roll due to the forward and reverse rotational displacements of the cams, and the pair of cams are misaligned on the printing paper during the printing operation. The motor can be controlled to rotate in a minute range, and the lift amount of the cams with respect to the pressure roll may be set to be slightly different at least in this minute range of rotation, whereby a mechanism for correcting the positional deviation of the printing paper is provided. It consists of.

According to the above construction, when the printing paper is misaligned during the printing operation, the motor of the pressing release mechanism is selected in either the forward direction or the reverse direction to control the minute rotation. As a result, the lift amount given to the pressure roll of the pair of cams against the force (for example, spring force) of the pair of pressure roll pressing mechanisms is slightly different between the cams. There is a slight difference in the pressing force (the difference between the left and right pressing forces can be increased on the left side or the right side by changing the rotation direction of the cam). As a result, the left and right conveying force of the conveyed printing paper is changed, and the misalignment is corrected by increasing the pressing force on the side opposite to the offset direction of the paper.

It is possible to control the conveyance of the printing paper by interlocking the position deviation correcting mechanism with the printing paper feeding position detecting section.

The sheet position deviation correcting mechanism configured as described above can also serve as the cam mechanism of the pressure roll pressing release mechanism, which originally did not operate during printing. The two functions (pressurizing roll pressing release function and position deviation correcting function) which are conventionally configured and realized by two mechanisms can be achieved by one mechanism.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment according to the present invention, in which (a) is a perspective view of an essential part thereof, and (b) is a side view showing the arrangement of a pair of cams used in the pressure roll pressing release mechanism. FIG.

The heating roll 1 is constructed so that it can rotate at a fixed position by a supporting portion and a driving portion (not shown). Pressure roll 2
Is located opposite to the heating roll 1 with the printing paper 3 sandwiched therebetween.

The pressure roll 2 has a structure that is movable in the radial direction along a guide groove (not shown).

The pressure roll pressing mechanism is composed of the arm 14 (1
4a, 14b), a cam 15 (15a, 15b), and a spring 16 (16a, 16b), and these elements are arranged near the both ends of the pressure roll 2 in groups to form a pair. It constitutes a pressure roll pressing mechanism. Of these, the cams 15a and 15b also serve as a pressure roll pressing release mechanism.

The arms 14a and 14b have a bearing 1 at one end.
7, and is rotatably supported by a frame (not shown). The other end of each of the arms 14a and 14b has a spring 16
One ends of a and 16b are connected and pulled toward the heating roll 1.

The pair of cams 15a and 15b are provided on the arm 14
It is installed at a position where it comes into contact with the cam followers 18 provided on a and 14b. These cams 15a and 15b are arranged on a common cam shaft (rotary shaft) 19, and the cam shaft 19 is rotatably supported by a frame (not shown) and can be rotated by a motor 20.

A rotatable shaft 21 projects from both ends of the pressure roll 2, and the shaft 21 is always in contact with a part of the arm.

During non-printing, the cam shaft 19 is rotated in one direction by the motor 2 so that the cams 15a, 15b are rotated.
Pushes down the arms 14a and 14b via the cam followers 18, the pressure roll 2 comes to a position away from the heating roll 1, and stops.

During printing, the cam shaft 19 rotates in the opposite direction to that during non-printing, so that the cam 15 separates from the cam follower 18, and the force of the spring 16 causes the pressure roll 2 to rotate.
Stops at a position where it completely contacts heating roll 1. At this time, the spring 16 presses the pressure roll 2 against the opposing roll (heating roll) 1. In this way, the printing paper 3
Is sandwiched between the pressure roll 2 and the heating roll 1, and by the rotation of the heating roll 1, the pressure roll 2 is driven and the printing paper 3 is conveyed while being fixed. The print paper feed position is detected by a print paper feed position detection unit (not shown).

The pair of cams 15a and 15b described above are shown in FIG.
As shown in (b), the camshaft 19 is out of phase.
It is fixed to. In this embodiment, the cam 15a on the left side in the conveying direction of the three printing papers is the cam 1 on the right side when the counterclockwise direction is positive when viewed from the left side of the cam shaft 19.
It is offset by 10 degrees from 5b. In this way, by making the phases of the cams different, a misregistration correction mechanism of the printing paper is configured.

That is, when the printing paper feed position detection unit detects that the paper feed position is shifted to the left in the feed direction, the motor 20 rotates the camshaft 19 counterclockwise as viewed from the left side. . Due to this movement, the left cam 15a abuts the cam follower 18, and the arm 14a is slightly pushed back against the left spring force. As a result, the pressing force on the left side of the pressure roll 2 becomes smaller than that on the right side, and the conveying force on the left side of the paper becomes smaller than that on the right side, so that the paper feeding position shifts to the right side.

In this way, the deviation of the sheet feeding position (skew) can be corrected. If it skews to the right, the opposite operation is performed. Sampling rate of paper feeding position, rotation speed of cam shaft 19, cam 15ab
The amount of phase shift and the like are determined by the printing speed, the printing paper width, and the like.

According to the present embodiment, the paper position deviation correcting mechanism configured as described above can also be used as the cam mechanism of the pressure roll pressing release mechanism which originally did not operate during printing. In this way, the two functions (compressed roll pressing release function, position deviation correction function) that were conventionally configured and realized by two mechanisms can be achieved by one mechanism, and the number of parts is rationalized. be able to.

The present embodiment is an example in which the pair of cam phases of one cam shaft are shifted so that the left and right pressing force of the pressure roll can be varied by one motor. Even if each motor is driven independently, the number of motors will be two, but the related parts other than the motors can be rationalized.

Further, instead of the method of making the phases of the cams 15a and 15b different from each other as described above, by changing the cam shapes of the respective cams and controlling the motor as described above, the positional deviation correcting function can be obtained. Can be demonstrated.

[0035]

According to the present invention, the two functions (compressing roll pressing release function and position deviation correcting function) which have been realized by the conventional two mechanisms can be achieved by one mechanism. By streamlining, it provides a small and low-cost paper misalignment correction mechanism that can be mounted on small electrophotographic printers, and has high print quality and high reliability for a wide variety of printing paper. It becomes possible to realize an electrophotographic printing apparatus.

[Brief description of the drawings]

FIG. 1A is a perspective view showing a fixing mechanism and a misalignment correcting mechanism of an electrophotographic apparatus according to an embodiment of the present invention,
FIG. 6B is an explanatory diagram showing a phase state of the cam used in the above embodiment.

FIG. 2 is a perspective view showing a sheet misregistration correction mechanism and a fixing mechanism according to a conventional method.

[Explanation of symbols]

1 ... Heating roll, 2 ... Pressure roll, 3 ... Printing paper, 14
a, 14b ... Arm, 15a, 15b ... Cam, 16a,
16b ... Spring of pressure roll pressing mechanism, 20 ...
Cam drive motor.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Haruyuki Honda, 1060 Takeda, Hitachinaka City, Hitachinaka City, Ibaraki Prefecture, Hitachi Koki Co., Ltd. (72) Yoshinobu Gunji, 1060 Takeda, Hitachinaka City, Ibaraki Prefecture, Hitachi Koki Co., Ltd.

Claims (5)

[Claims] 1. A pressure roll for fixing, a pair of pressure roll pressing mechanisms for applying a pressing force to the pressure roll at both end positions of the pressure roll, and a pressure roll pressing for releasing the pressing force. In the electrophotographic printing apparatus including a release mechanism, the pressure roll pressing release mechanism has a pair of cams driven by motors capable of forward and reverse rotations, and the forward and reverse rotational displacements of the cams are performed. Thus, the pressure roll is brought into contact with and separated from the opposite roll, and the pair of cams can be rotationally controlled in a minute range by the motor in the case where the printing paper is misaligned during the printing operation, and At least in this minute rotation range, the amount of lift of the cams with respect to the pressure roll is set to be slightly different from each other, so that a misregistration mechanism for the misalignment of the printing paper is configured. With positive mechanism electrophotographic type printing apparatus. 2. The electrophotographic printing apparatus with a paper position deviation correcting mechanism according to claim 1, wherein the pair of cams have different phases or shapes to configure the position deviation correcting mechanism. 3. The sheet position according to claim 1, wherein the pressure roll pressing mechanism has a pair of pressing springs, and the pair of cams are arranged on a common rotary shaft. Electrophotographic printing device with misalignment correction mechanism. 4. A paper feeding position detecting unit for detecting a positional deviation of the printing paper during feeding, and is set so as to control a rotational position of the motor based on a detection signal from the paper feeding position detecting unit. An electrophotographic printing apparatus with a sheet position deviation correcting mechanism according to claim 1 or 2. 5. The electrophotographic apparatus with a sheet misregistration correction mechanism according to claim 1, wherein the pair of pressure roll pressing mechanisms and the corresponding pair of pressure roll pressing release mechanisms are independently drivable. Printing device.