JP5179763B2 - Fixing device in image forming apparatus - Google Patents

Description

  The present invention includes a fixing roller, a fixing belt that is wound around the fixing roller and is rotatable, and a pressure roller that presses the fixing roller with the fixing belt interposed therebetween. A nip portion is formed between the pressure roller and a pressure contact surface that is in pressure contact with the inner peripheral surface of the fixing belt across the entire width on the lower side in the recording sheet moving direction than the fixing roller. A fixing member in the image forming apparatus in which the pressure contact member has a curvature along the recording sheet movement direction of the pressure contact surface that is larger than a curvature along the recording sheet movement direction on the outer peripheral surface of the fixing roller. .

In the fixing device in the image forming apparatus, even if the recording paper portion that has passed through the nip is wrapped around the fixing belt, the recording paper portion deforms following the bending deformation of the fixing belt by the strength (rigidity) of the waist. In order to ensure that the recording paper can be reliably separated (curvature separation) from the fixing belt, it is pressed over the entire circumference of the fixing belt on the lower side of the recording paper in the moving direction of the recording paper. A pressure contact member having a pressure contact surface is provided, and the fixing belt is configured to rotate while being forcibly bent and deformed on the lower side of the fixing roller, and along the recording sheet moving direction of the pressure contact surface. The curvature is set to be larger than the curvature along the recording sheet moving direction on the outer peripheral surface of the fixing roller.
In the above fixing device, conventionally, the pressure contact member is supported in a posture in which the width direction of the pressure contact surface is parallel to the axial center of the fixing roller, and the fixing belt is slid on the inner peripheral surface with respect to the pressure contact surface. (See, for example, Patent Document 1).

Japanese Patent Laid-Open No. 2003-5565

For this reason, sliding resistance between the fixing belt and the pressure contact member occurs as the fixing belt rotates, but due to the assembly accuracy of the pressure contact member with respect to the fixing belt, the belt of the pressure contact force with respect to the fixing belt on the pressure contact surface If the distribution along the width direction becomes non-uniform, the distribution along the belt width direction of the size of the sliding resistance also becomes non-uniform, and as a result, the rotation speed of the fixing belt portion having a large sliding resistance becomes the sliding resistance. However, there is a drawback that the fixing belt is easy to rotate while meandering because it is slower than the rotation speed of the fixing belt portion having a small diameter.
The present invention has been made in view of the above circumstances, and an object thereof is to prevent a situation in which a fixing belt rotates while meandering.

The first characteristic configuration of the present invention is provided with a fixing roller, a fixing belt which is wound around the fixing roller and is rotatable, and a pressure roller which presses the fixing roller with the fixing belt interposed therebetween. In addition, a nip portion is formed between the fixing belt and the pressure roller, and is pressed against the inner peripheral surface of the fixing belt over the substantially entire width on the lower side in the recording paper moving direction than the fixing roller. An image forming member having a pressure contact member provided with a pressure contact surface, the curvature of the pressure contact surface along the recording paper movement direction being set to be larger than the curvature of the outer peripheral surface of the fixing roller along the recording paper movement direction; a fixing device in the apparatus, said pressure contact member around the axis along the paper traveling direction in a direction substantially perpendicular to the fixing belt width direction at a substantially central position of the fixing belt width direction Lies in that is swingably supported along the pressing direction relative to the inner circumferential surface of the fixing belt.

[Action and effect]
The pressure contact member is supported at a substantially central position in the fixing belt width direction so as to be swingable along the pressure contact direction with respect to the inner peripheral surface of the fixing belt around an axis in a direction substantially orthogonal to the fixing belt width direction. Therefore, when the pressure contact surfaces are divided into the left and right pressure contact surface portions sandwiching the shaft core, when the sliding resistances of the left and right pressure contact surface portions are different from each other, one of the pressure contact surface portions having a large sliding resistance is slid. The pressure contact force with respect to the fixing belt decreases so that the resistance decreases, and at the same time, the other pressure contact surface portion with a small sliding resistance swings toward the side where the pressure contact force with respect to the fixing belt increases.
Accordingly, the pressure contact member can be swung so that the difference in sliding resistance between the left and right pressure contact surface portions sandwiching the shaft core can be reduced, so that the fixing belt can be prevented from rotating while meandering.

  According to a second characteristic configuration of the present invention, the pressure contact member is configured by a roller member that is rotatably supported around an axis substantially along the fixing belt width direction, and the pressure contact surface is formed by an outer peripheral surface of the roller member. It is in a certain point.

[Action and effect]
The pressure contact member is constituted by a roller member that is rotatably supported around an axis substantially along the fixing belt width direction, and the pressure contact surface is formed by the outer peripheral surface of the roller member. As a result, the roller member whose outer peripheral surface is in pressure contact with the fixing belt rotates, and the sliding resistance between the fixing belt and the pressure contact member is reduced as a whole.
Therefore, the difference in the sliding resistance between the left and right pressure contact surfaces sandwiching the shaft core is also reduced, and the situation where the fixing belt rotates while meandering can be further prevented.

  According to a third feature of the present invention, the fixing belt and the pressure roller are formed wider than the recording paper passing through the nip portion, and the side edge portion of the fixing belt and the pressure roller are mutually connected. A rotation mechanism is provided in which the fixing belt is driven and rotated by driving rotation of the pressure roller in pressure contact.

[Action and effect]
The fixing belt and the pressure roller are formed wider than the recording paper passing through the nip portion, the side edges of the fixing belt and the pressure roller are pressed against each other, and the fixing belt is driven by the rotation of the pressure roller. Since there is a rotation mechanism for driven rotation, lubricant is applied to the inner peripheral surface of the fixing roller and the pressure contact surface of the pressure contact member so that the sliding resistance between the fixing belt and the pressure contact member can be reduced as a whole. However, the fixing belt can be rotated by pressure contact between the pressure belt and the side edge of the fixing belt, that is, the fixing belt portion not including the recording paper passing through the nip portion.

Embodiments of the present invention will be described below with reference to the drawings.
[First Embodiment]
FIG. 1 shows a color laser printer as an example of an electrophotographic image forming apparatus, which includes an optical unit A, an image forming unit B, a fixing unit C, a paper feeding unit D, a paper discharge unit E, and the like. The four development transfer units 1 corresponding to black, cyan, magenta, and yellow are provided along the nipping / conveying path 3 of the recording paper 2 between the paper feeding unit D and the paper ejection unit E.

  The fixing unit C is provided with a fixing device F according to the present invention, and is wound around a cylindrical fixing roller 4 and the fixing roller 4 and the tension roller 5 as shown in FIG. A rotatable fixing belt 6 and a cylindrical pressure roller 7 that presses against the fixing roller 4 with the fixing belt 6 interposed therebetween, and is provided on the inner peripheral side of each of the fixing roller 4 and the pressure roller 7. Includes heaters 4a and 7a.

  The outer peripheral surfaces of the fixing roller 4 and the pressure roller 7 are formed of elastic materials 4b and 7b, and the hardness of the elastic material 7b of the pressure roller 7 is smaller than the hardness of the elastic material 4b of the fixing roller 4. Thus, a nip portion 8 that is recessed on the pressure roller 7 side is formed between the fixing belt 6 and the pressure roller 7.

  A long aluminum pressure contact member 10 provided with a pressure contact surface 9 that is in pressure contact with the inner peripheral surface of the fixing belt 6 on the lower side in the recording paper moving direction than the fixing roller 4 is provided. 9 is set to a curvature larger than the curvature along the recording sheet moving direction on the outer peripheral surface of the fixing roller 4.

  The pressure contact member 10 is formed in a band plate shape that is curved substantially along the pressure contact surface 9 as viewed in the width direction of the fixing belt 6, and the outer peripheral surface is covered with a fluororesin layer. An end edge 11 on the upper side in the moving direction is extended toward the outlet side of the nip 8.

  Guide plates 12 and 13 are provided on the inlet side and the outlet side of the nip portion 8 to guide the conveying posture of the recording paper 2 from the lower surface side, and the fixing belt is provided on the outlet side of the nip portion 8. 6 and a recording sheet 2 that is separated from the fixing belt 6 and a separating plate 14 that separates the recording sheet 2 in the transport direction is provided.

  As shown also in FIG. 3, a support bracket in which a swing fulcrum pin 15 inserted through a substantially central portion in the longitudinal direction of the pressure contact member 10 is fixed to a frame on the printer housing, for example, a main body frame or a fixing unit frame. 16 and screwing the pressure contact member 10 in the pressure contact direction with respect to the inner peripheral surface of the fixing belt 6 around the axis X in a direction substantially perpendicular to the fixing belt width direction at a substantially central position in the fixing belt width direction. A fixing belt portion which is supported so as to be swingable along the pressure contact surface 9 and is pressed against the pressure contact surface 9 is separated from the pressure roller 7.

  4 and 5, the fixing belt 6 and the pressure roller 7 are formed wider than the recording paper 2 passing through the nip portion 8, and the side edge portion of the fixing belt 6, that is, the nip portion is formed. The left and right fixing belt portions 6 a not passing through the recording paper 2 passing through the section 8 and the pressure roller 7 are brought into pressure contact with each other, and a lubricant such as grease is applied to the inner peripheral side of the fixing belt 6 and the pressure is applied. A rotation mechanism 17 that rotates the fixing belt 6 by driving rotation of the roller 7 is provided.

[Second Embodiment]
FIG. 6 shows another embodiment of the fixing device F according to the present invention. The fixing device F is wound around the fixing roller 4 and the cylindrical heating roller 18, and is freely rotatable in a state where a tension is applied by the heating roller 18. A fixing belt 6 and a cylindrical pressure roller 7 for pressing toward the fixing roller 4 are provided, and heaters 18a and 7a are provided on the inner peripheral sides of the heating roller 18 and the pressure roller 7, respectively.
Other configurations are the same as those of the first embodiment.

[Third Embodiment]
7 and 8 show another embodiment of the fixing device F according to the present invention. The pressure contact member 10 is composed of a roller member that is rotatably supported around an axis substantially along the fixing belt width direction. The surface 9 is formed by the outer peripheral surface of the roller member 10, and both end sides of the roller member 10 are rotatably supported by roller support portions 20 provided at both end portions of the roller support arm 19.

Then, the swing fulcrum pin 15 inserted through the substantially central portion of the roller support arm 19 in the longitudinal direction is screwed to the support bracket 16 fixed to the frame on the printer housing side, so that the roller member 10 is fixed in the fixing belt width direction. Is supported so as to be swingable along the pressure contact direction with respect to the inner peripheral surface of the fixing belt 6 around the axis X in a direction substantially orthogonal to the fixing belt width direction.
Other configurations are the same as those of the first embodiment.

[Other Embodiments]
1. The fixing device according to the present invention may be configured to rotate the fixing belt by driving rotation of the fixing roller.
2. In the fixing device according to the present invention, a nip portion that is recessed toward the fixing roller may be formed between the fixing belt and the pressure roller.
3. The fixing device according to the present invention may be a fixing device in an electrophotographic image forming apparatus such as a copying machine or a facsimile in addition to a laser printer.
4). The fixing device according to the present invention may be a fixing device in an electrophotographic image forming apparatus that forms a monochrome image.

Side view showing inside of image forming apparatus Side view of the main part Front view of main parts Perspective view of main parts Cross section of the main part Side view of essential parts showing the second embodiment Side view of essential parts showing the third embodiment Front view of essential parts showing a third embodiment

Explanation of symbols

2 Recording Paper 4 Fixing Roller 6 Fixing Belt 6a Side Edge 7 Pressure Roller 8 Nip Portion 9 Pressure Contact Surface 10 Pressure Contact Member (Roller Member)
17 Rotating mechanism X axis

Claims (3)

A fixing roller, a fixing belt that is wound around the fixing roller and rotatable, and a pressure roller that presses against the fixing roller with the fixing belt interposed therebetween are provided. The fixing belt and the pressure roller A nip is formed between
A pressure contact member provided with a pressure contact surface that is in pressure contact with the inner circumferential surface of the fixing belt on the lower side in the recording sheet moving direction than the fixing roller;
A fixing device in an image forming apparatus in which a curvature along the recording paper movement direction of the pressure contact surface is set to be larger than a curvature along the recording paper movement direction on the outer peripheral surface of the fixing roller;
The pressure contact member is pressed against the inner peripheral surface of the fixing belt around an axis that is substantially perpendicular to the fixing belt width direction at a substantially central position in the fixing belt width direction and that extends along the recording paper movement direction. The fixing device according to claim 1, wherein the fixing device is swingably supported along a direction. The pressure contact member is composed of a roller member that is rotatably supported around an axis substantially along the fixing belt width direction,
The fixing device according to claim 1, wherein the pressure contact surface is formed by an outer peripheral surface of the roller member. Forming the fixing belt and the pressure roller wider than the recording paper passing through the nip portion;
The fixing device according to claim 1, further comprising a rotation mechanism that presses the side edge portion of the fixing belt and the pressure roller together to rotate the fixing belt by driving rotation of the pressure roller. apparatus.

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