JPH08202198A - Fixing device for electrophotographic device - Google Patents

Abstract

PURPOSE: To eliminate the variance of the fixing coefficient of a toner image with respect to a recording paper and to prevent the recording paper from wrinkling at a fixing time. CONSTITUTION: A compression spring 5 is made to intervene between both end parts of a pressure adjustment member 11 disposed along in the shaft direction of a pressure roller 4 and a bearing 3. The adjustment member 11 is freely turnably fitted to a pressure adjustment member shaft 13 in a state where the spring 5 can elongate and contract. The shaft 13 is disposed at such a position that the corresponding spring 5 is pressured by both ends of the adjustment member 11. Therefore, when the variance of a pair of springs 5 is found, the adjustment member 11 is turned around the shaft 13 as a center according to the variance. When this turning action is stopped, such a state where one of a pair of springs 5 contracts and the other thereof elongates is maintained. As the result, even when the variance of a pair of springs 5 is found, the pressure force of the roller 4 in the shaft direction with respect to a heat roller 2 is balanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for thermally fixing a toner image transferred onto a recording sheet in an electrophotographic apparatus such as a laser beam printer or a copying machine.

[0002]

2. Description of the Related Art Conventionally, a fixing device of this type is shown in FIG.
And the one shown in FIG. 7 is known. In this fixing device, a pair of bearings 1, 1 are used to rotatably support a heat roller 2, and a pair of bearings 3 are provided with a pressure roller shaft 4A projecting at both ends so as to rotate in pressure contact with the heat roller 2. The pressure roller 4 supported by 3 and the pair of bearings 3, 3 are supported by a frame (not shown) so as to move back and forth toward the heat roller 2. One end of each of the pair of compression springs 5 and 5 is attached to the pair of bearings 3 and 3, and the compression springs 5 and 5 are attached.
The other end of each of 5 is attached to a pair of pressure levers 6 and 6 rotatable about a shaft 6A.

In the above-mentioned conventional structure, when the pair of pressure levers 6 and 6 are in the fixing position as shown in FIG. 7, the compression spring is in a compressed state and the pressure of the compression spring 5 causes a pair of pressing forces. The pressure roller bearings 3, 3 move toward the heat roller 2, and the pressure roller 4 is pressed against the heat roller 2. In this way, the pressure roller 4 presses against the heat roller 2 by utilizing the force generated by compressing the pair of compression springs 5, so that the pressure roller is caused by the variation in the spring constant of the pair of compression springs 5. In the axial direction of 4, the pressure applied to the heat roller 2 varies. This variation becomes larger as the device becomes smaller. This is because the stroke of the compression spring 5 is short, and compensation is made with a large spring constant. Therefore, there is a problem that the fixing rate of the toner image on the recording sheet varies in the axial direction of the heat roller and wrinkles are generated on the recording sheet due to the variation of the pressing force.

By the way, as a conventional technique related to the above-mentioned fixing device, a fixing device described in JP-A-1-307786 and a fixing device described in JP-A-2-254480 are known. In the former device described in the publication,
The force of the pair of pressure springs that bring the pressure roller into pressure contact with the heat roller is made different from each other to prevent wrinkling of the recording paper passing between the heat roller and the pressure roller during fixing. ing. Further, in the latter conventional device, the compression amount of the compression spring that presses the pressure roller against the heat roller is changed according to the thickness of the recording paper so that a constant fixing strength can always be obtained regardless of the thickness of the recording paper. I have to.

[0005]

However, in the conventional device described in the above publication, the problem already described in the description of the fixing device shown in FIGS. 6 and 7, that is, the pressure roller 4 is pressed against the heat roller 2. No consideration is given to eliminating the variation in the pressing force applied to the heat roller 2 in the axial direction of the pressure roller 4 due to the variation in the spring constant of the pair of compression springs 5 and 5. Therefore, the problem that the fixing rate of the toner image on the recording sheet varies in the axial direction of the heat roller due to the variation of the pressing force and the recording sheet has wrinkles cannot be solved.

The present invention has been made in view of the above circumstances, and eliminates the variation in the toner image fixing rate in the width direction of the recording sheet and eliminates the wrinkling of the recording sheet during the toner image fixing. It is an object of the present invention to provide a fixing device for an electrophotographic device.

[0007]

In order to solve the above-mentioned problems, the invention according to claim 1 is characterized in that a heating roller and both ends thereof are supported by a pair of bearings so as to be rotated in pressure contact with the heating roller. A fixing device for an electrophotographic apparatus, comprising a pressure roller, and movably and reciprocally supporting the bearing toward the heat roller, the fixing device being arranged in the axial direction of the pressure roller and opposite to the heat roller. An arm-shaped pressure adjusting member is disposed at the side portion, and a pair of elastic members are interposed between both ends of the pressure adjusting member and both ends of the bearing. Of the elastic member is rotatably attached to the pressure adjusting member shaft, and both ends of the pressure adjusting member of the pressure adjusting member shaft bring the pair of elastic members into a pressed state. It is characterized in that it is arranged at a position where

According to a second aspect of the present invention, there is provided the fixing device for an electrophotographic apparatus according to the first aspect, wherein the pressure adjusting member shaft is arranged along the axial direction of the pressure roller. It is characterized in that the bearings are arranged at positions that divide the distance between the bearings into two substantially equal parts.

According to a third aspect of the present invention, there is provided the fixing device for an electrophotographic apparatus according to the first or second aspect, wherein the pressure adjusting member is a symmetrical arm about the axis of the pressure adjusting member. It is characterized by its shape.

Further, the invention according to claim 4 is based on claim 1,
2. The fixing device for an electrophotographic apparatus according to 2 or 3, wherein the pressure adjusting member includes a fixing position for pressing the pressure roller against the heat roller, and the heat roller of the pressure roller. It is characterized in that it can be selectively fixed to a non-fixing position where the pressure applied to is released.

[0011]

According to the invention of claims 1 to 3, since both ends of the pressure adjusting member are in a state of pressing the elastic member such as the compression spring toward the bearing, the pressure of the elastic member causes the pressure applied integrally with the bearing. The roller is pressed against the heat roller. Further, since the pressure adjusting member is rotatable about the axis of the pressure adjusting member, the elastic constant (spring constant) between the pair of elastic members.
When the rotation of the pressure adjusting member is stopped, the pressure adjusting member rotates about the pressure adjusting member axis. Maintain a good condition. As a result, the pressure applied to the working roller shaft by the pair of elastic members is balanced, so that the pressure applied to the heat roller in the axial direction of the pressure roller is balanced even if there is variation in the pair of elastic members.

According to another aspect of the present invention, the pressure adjusting member has a fixing position where the pressure roller is pressed against the heat roller, and a non-releasing position where the pressure roller presses the heat roller. The fixing position can be selectively fixed.
Therefore, when using the pressure adjusting member at the fixing position,
Even if there are variations in the pair of elastic members, the pressure applied to the heat roller in the axial direction of the pressure roller can be balanced, and when the recording paper jams between the pressure roller and the heat roller, the pressure adjustment member Is set to the non-fixing position, and the recording paper having the paper jam can be easily removed.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. First Embodiment FIG. 1 is a front view showing the configuration of a fixing device according to a first embodiment of the present invention, and FIG. 2 is a side view of the identification fixing device as viewed from the direction of arrows AA in FIG. Further, FIG. 3 is a schematic cross-sectional view showing the configuration of a laser beam printer incorporating the identification and attachment device. In the laser beam printer 7 of this example, as shown in FIG. 3, a photosensitive drum 9 is installed in a printing section in the middle of a conveyance path of a recording sheet 8, and a main charger and an exposure device (not shown) are provided around the photosensitive drum 2. A device, a developing device, a transfer roller and the like are arranged, and a fixing device 10 is arranged on the discharge side of the conveyance path of the recording paper 8. The toner image is formed on the recording paper 8 by forming an electrostatic latent image on the surface of the photosensitive drum 9 by the main charger and the exposure device and developing by the developing device, and the formed toner image is transferred. It is electrostatically transferred from the photosensitive drum 9 to the recording paper 8 by the roller. Then, the transferred toner image is fixed by the fixing device 10 to complete printing.

The fixing device 10 is rotatably supported by a pair of bearings 1 and 1, as shown in FIGS.
The heat roller 2 having a heat generating means inside, and the pressure roller 4 in which the pressure roller shaft 4A projecting at both ends so as to rotate in contact with the heat roller are rotatably supported by bearings 3 and 3, The bearings 3, 3 are supported by a frame (not shown) so as to be movable back and forth toward the heat roller 2. An arm-shaped pressure adjusting member 11 is arranged along the axial direction of the pressure roller 4 at a portion opposite to the pressure roller 4 with respect to the pressure roller 4. Spring receiving members 12, 12 are integrally attached to both ends of the pressure adjusting member 11, and the spring receiving member 1
The compression springs 5 and 5 are interposed between the bearings 2 and 12 and the bearings 3 and 3, while the other ends of the compression springs 5 and 5 are attached to the bearings 3 and 3.

As shown in FIGS. 1 and 2, the pressure adjusting member 11 is rotatably mounted around the pressure adjusting member shaft 13 so that the pair of compression springs 5 and 5 are expanded and contracted. ing. That is, the pressure adjusting member 11 passes through the rotation hole 11A formed in the center of the pressure adjusting member 11 through the pressure adjusting member shaft 13 attached to the U-shaped shaft attaching member 4, and the pressure adjusting member 11 is rotated. It is rotatable about the member member 13. The shape of the pressure adjusting member 11 is formed symmetrically with respect to the pressure adjusting member shaft 13, and the material of the pressure adjusting member 11 is preferably highly rigid.

As shown in FIG. 1, the pressure adjusting member shaft 13 is along the axial direction of the pressure roller 4 and divides the distance between the pair of left and right bearings 3, 3 into two substantially equal parts. In this position, both ends of the pressure adjusting member 11 are arranged at positions where the pair of compression springs 5 and 5 are always in a pressurized state.

In the above structure, both ends of the pressure adjusting member 11 press the compression spring 5 toward the bearing 3, so that
The pressure roller 4 is integrated with the bearing 3 by the pressure of the compression spring 5.
Is pressed against the heat roller 2. Further, the pressure adjusting member 11 is rotatable about the pressure adjusting member shaft 13, but when the pair of compression springs 5 and 5 are balanced without force variations, the pressure adjusting member 11 is not applied. The pressure adjusting member 1 does not rotate about the pressure adjusting member shaft 13.
1 maintains a state parallel to the axis of the pressure roller 4, as shown by the solid line in FIG. Therefore, the pressure applied to the bearings 3, 3 of the pair of compression springs 5, 5 is balanced, and the pressure applied to the heat roller 2 in the axial direction of the pressure roller 4 is balanced.

On the other hand, of the pair of compression springs 5 and 5, for example, when the force of the compression spring 5 on the left side of FIG. 1 is larger than the force of the compression spring 5 on the right side of FIG. It rotates counterclockwise around the pressure adjusting member shaft 13 and stops at the position of the chain double-dashed line as shown in the figure to maintain this state. As a result, as compared with the case where the pressure adjusting member 11 cannot rotate about the pressure adjusting member shaft 13 and is fixed in a state parallel to the shaft of the pressure roller 4, the left side compression spring 5 extends. While the force of pushing the corresponding bearing 3 becomes large and decreases relatively, the compression spring 5 on the right side is compressed and the force of pushing the corresponding bearing 3 increases relatively.

As a result, the pressure applied to the pressure roller shafts 3, 3 by the pair of compression springs 5, 5 is balanced, so that even if there is a variation in force between the pair of compression springs 5, 5, the pressure roller 4 will not move. The pressure applied to the heat roller 2 in the axial direction is balanced. Therefore, according to the above configuration, it is possible to eliminate the variation in the fixing rate of the toner image on the recording sheet in the width direction of the recording sheet, and it is possible to eliminate the occurrence of wrinkles on the recording sheet when fixing the toner image.

Second Embodiment Next, a second embodiment of the present invention will be described. FIG.
5 is a front view showing the configuration of a fixing device according to a second embodiment of the present invention, and FIG. 5 is a sectional view of the identification fixing device as seen from the direction of arrows BB in FIG. The fixing device of the second embodiment is different from that of the first embodiment in that a lever 16 rotatable around a shaft 15 is integrally formed on the bottom surface of a shaft mounting member 14 to which a pressure adjusting member shaft 13 is mounted. It is a point that was attached to. Further, the lever 16 releases the pressure applied to the heat roller 2 by the fixing position (the state shown in FIG. 5) in which the pressure roller 4 is pressed against the heat roller 2. It is configured such that it can be selectively fixed to the non-fixing position. Since the other parts of the second embodiment are the same as those of the first embodiment, the same components are designated by the same reference numerals and the description thereof will be omitted.

According to this second embodiment, when the lever 16 is used in the fixing position as shown in FIG. 5, even if there is a variation in the pair of compression springs 5, as in the first embodiment, the pressure roller is used. The pressure applied to the heat roller 2 in the axial direction of 4 can be balanced. Further, when the recording paper is jammed between the pressure roller 4 and the heat roller 2, the lever 16 can be set to the non-fixing position to easily remove the jammed recording paper.

The embodiment of the present invention has been described in detail above with reference to the drawings. However, the specific structure is not limited to this embodiment, and there may be a design change or the like within a range not departing from the gist of the invention. Included in this invention. A rubber elastic member may be used instead of the compression spring.

[0023]

As described above, according to the configurations of the first to third aspects of the present invention, the pressure adjusting member for pressing the pair of elastic members is rotatable, so that there is a variation in the pair of elastic members. Even if there is, the pressure applied to the heat roller in the axial direction of the pressure roller is balanced. Therefore, it is possible to eliminate the variation in the fixing rate of the toner image on the recording sheet in the width direction of the recording sheet, and to eliminate the wrinkling of the recording sheet when fixing the toner image.

According to the invention of claim 4, when the pressure adjusting member is used at the fixing position, the fixing rate of the toner image on the recording sheet can be prevented from varying in the width direction of the recording sheet. It is possible to eliminate the occurrence of wrinkles on the recording paper when the toner image is fixed. Further, when the recording paper jams between the pressure roller and the heat roller, the pressure adjusting member is set to the non-fixing position to easily remove the recording paper having the paper jam.

[Brief description of drawings]

FIG. 1 is a front view showing the configuration of a fixing device according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of the identification attachment device as seen from the direction of arrows AA in FIG.

FIG. 3 is a schematic cross-sectional view of a laser beam printer incorporating an identification and attachment device.

FIG. 4 is a front view of a fixing device according to a second embodiment of the invention.

5 is a cross-sectional view of the identification attachment device as seen from the direction of arrows BB in FIG.

FIG. 6 is a front view of a conventional device.

7 is a cross-sectional view of the identification attachment device as seen from the direction of arrows CC in FIG.

[Explanation of symbols]

 2 heat roller 3 pressure bearing 4 pressure roller 5 compression spring 11 pressure adjusting member 13 pressure adjusting member shaft 16 lever

Claims (4)

[Claims] 1. A heat roller, and a pressure roller having both ends supported by a pair of bearings so as to rotate in pressure contact with the heat roller, and the bearing is movable back and forth toward the heat roller. A fixing device for an electrophotographic apparatus which is supported, wherein an arm-shaped pressure adjusting member is arranged along the axial direction of the pressure roller and at a site opposite to the heat roller, and the pressure is applied. A pair of elastic members are interposed between both ends of the adjusting member and both ends of the bearing, and the pressure adjusting member rotates about a pressure adjusting member shaft in a state in which the pair of elastic members can expand and contract. Can be attached freely,
Further, the pressure adjusting member shaft is arranged such that both ends of the pressure adjusting member are arranged at positions where the pair of elastic members are in a pressed state. 2. The pressure adjusting member shaft is arranged along the axial direction of the pressure roller at a position that divides the distance between the pair of bearings into two substantially equal parts. Item 2. A fixing device for an electrophotographic apparatus according to Item 1. 3. The fixing device for an electrophotographic apparatus according to claim 1, wherein the pressure adjusting member has a laterally symmetrical arm shape around the axis of the pressure adjusting member. 4. The pressure adjusting member has a fixing position where the pressure roller is pressed against the heat roller, and a non-fixing position where pressure of the pressure roller is released against the heat roller. 4. The fixing device for an electrophotographic apparatus according to claim 1, wherein the fixing device can be selectively fixed to a position.