JP2022060415A - Fixation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixation device that can suppress increase of the curl of a recording medium.

SOLUTION: A fixation device 100 includes: an endless belt 121; a first elastic member 123; a second elastic member 124, harder than the first elastic member 123; and a roller (heating roller 110), holding the endless belt 121 between the first elastic body 123 and the second elastic body 124, the roller having an elastic layer 112 on the outside and carrying a recording medium S between the roller and the endless belt 121 in a carrying direction. The first elastic member 123 is located in the more upstream side of the carrying direction than the second elastic member 124 is. The elastic layer 112 is softer than the first elastic body 123.

SELECTED DRAWING: Figure 2

COPYRIGHT: (C)2022,JPO&INPIT

Description

The present invention relates to a fixing device that heat-fixes a toner image on a recording medium.

Conventionally, there is known a fixing device in which a sheet-shaped recording medium is nipped with a heating roller and an endless belt to heat-fix it. An elastic body is arranged inside the endless belt, and the elastic body is pressed against the heating roller. Patent Document 1 describes a fixing device in which two elastic bodies are provided apart from each other in the transport direction of the recording medium in order to increase the nip region. In this fixing device, the hardness of the elastic body on the downstream side is larger than the hardness of the elastic body on the upstream side in order to increase the nip pressure on the downstream side and reduce the wrinkles of the recording medium.

Japanese Unexamined Patent Publication No. 2017-021068

However, if the elastic body on the upstream side is soft, when the elastic body is pressed against the heating roller, the elastic body is greatly deformed following the heating roller. Therefore, since the recording medium is heated in a bent state, there is a problem that the curl (curvature) of the recording medium that has passed through the nip portion becomes large.

Therefore, an object of the present invention is to provide a fixing device that suppresses an increase in curl of a recording medium.

In order to solve the above problems, the fixing device of the present invention is a roller having an endless belt, a first elastic body, a second elastic body harder than the first elastic body, and an elastic layer on the outer periphery thereof. An endless belt is sandwiched between the elastic body and the second elastic body, and a roller for transporting the recording medium between the elastic body and the second elastic body in the transport direction is provided. The first elastic body is located on the upstream side in the transport direction from the second elastic body. The elastic layer is softer than the first elastic body.

According to such a configuration, in the nip region between the first elastic body and the roller, the elastic layer of the roller is crushed and the recording medium sandwiched between the roller and the first elastic body approaches a flat surface, so that the recording medium is curled. Can be suppressed.

In the fixing device described above, the first elastic body may have a corner portion at the downstream end in the transport direction.

According to such a configuration, since the corner portion is provided at the downstream end of the first elastic body, the recording medium can be strongly pressed against the roller at the corner portion to warp the recording medium against the roller. Therefore, even if the recording medium is curled so as to be wound around the roller in the nip region between the first elastic body and the roller, the recording medium can be reversed and returned by pressing with the corners to reduce the curl. ..

In the fixing device described above, there may be a configuration in which a gap is provided between the first elastic body and the second elastic body in the transport direction.

With such a configuration, the nip region can be widened.

In the fixing device described above, the durometer hardness of the elastic layer may be smaller than 6, and the durometer hardness of the first elastic body may be 6 to 20.

In the fixing device described above, the durometer hardness of the second elastic body may be 60 to 90.

In the fixing device described above, the durometer hardness of the elastic layer is 5 or less, the durometer hardness of the first elastic body is 6 to 10, and the durometer hardness of the second elastic body is 70 to 90. It may be configured.

According to such a configuration, it is possible to suppress curl of the recording medium, improve the peelability of the recording medium, and suppress the drive torque of the fixing device while widening the nip width.

In the fixing device described above, the roller may be configured to have a heater.

According to the present invention, it is possible to suppress the curl of the recording medium from becoming large in the fixing device.

It is sectional drawing of the image forming apparatus provided with the fixing apparatus which concerns on this invention. It is sectional drawing which shows the fixing apparatus which concerns on embodiment. It is sectional drawing of the fixing device in the state which is not nip. It is a figure which shows the curl characteristic, the peeling characteristic, and the nip load when the hardness of the 1st elastic body and the 2nd elastic body is changed.

Next, an embodiment of the present invention will be described in detail with reference to the drawings as appropriate. In the following description, unless otherwise specified, the vertical direction shown in FIG. 1 is up and down, the right side in FIG. 1 is the front, the left side is the back, the front side of the paper is the left, and the back side of the paper is the right. Is shown.

As shown in FIG. 1, a laser printer 1 as an example of an image forming apparatus has a housing 2, a supply unit 3 for supplying a recording medium S such as a recording sheet, and a toner image for forming a toner image on the recording medium S. It mainly includes a process unit 4 and a fixing device 100.

The supply unit 3 is provided at a lower portion in the housing 2, and includes a supply tray 31 for accommodating the recording medium S and a supply mechanism 32 for transporting the recording medium S in the supply tray 31 toward the process unit 4. ing.

The process unit 4 is housed in the housing 2, and includes an exposure device 5, a process cartridge 6, and a transfer roller 63.

The exposure apparatus 5 is arranged in the upper part of the housing 2, and irradiates the surface of the photoconductor drum 61, which will be described later, with a laser beam indicated by a long-dotted line by high-speed scanning.

The process cartridge 6 is arranged below the exposure apparatus 5 and is removable from the housing 2. The process cartridge 6 supplies the photoconductor drum 61 on which the electrostatic latent image is formed, the charger 62, the toner accommodating portion 65 accommodating the toner, and the toner in the toner accommodating portion 65 to the photoconductor drum 61. It includes a roller 66 and a developing roller 64.

In this process cartridge 6, the charger 62 uniformly charges the surface of the rotating photoconductor drum 61. The exposure apparatus 5 emits a laser beam to the surface of the photoconductor drum 61 to expose the surface of the photoconductor drum 61, thereby forming an electrostatic latent image based on image data on the surface of the photoconductor drum 61.

Next, the rotationally driven developing roller 64 supplies toner to the electrostatic latent image of the photoconductor drum 61 to form a toner image on the surface of the photoconductor drum 61. After that, the toner image supported on the surface of the photoconductor drum 61 is attracted to the transfer roller 63 and placed on the recording medium S when the recording medium S is conveyed between the photoconductor drum 61 and the transfer roller 63. Transcribed.

The fixing device 100 is provided behind the process cartridge 6. The toner image transferred onto the recording medium S is thermally fixed on the recording medium S by passing through the fixing device 100.
The recording medium S on which the toner image is heat-fixed is discharged onto the discharge tray 22 by the transport rollers 23 and 24.

As shown in FIG. 2, the fixing device 100 mainly includes a heating roller 110 as an example of a roller and a pressurizing unit 120 arranged to face the heating roller 110.

The heating roller 110 is a cylindrical roller. The heating roller 110 has a raw tube 111 made of metal or the like, an elastic layer 112 provided on the outer periphery of the raw tube 111, and a heater 113 provided inside the raw tube 111. A coating having heat resistance and wear resistance may be provided on the outside of the elastic layer 112. The heating roller 110 is rotatably supported by a frame (not shown) of the fixing device 100, and is clockwise in FIG. 2 when a driving force is input from a motor (not shown) provided in the housing 2 of the laser printer 1. Drives to rotation.

The elastic layer 112 is made of rubber such as silicon rubber, for example. The elastic layer 112 is softer than the first elastic body 123 described later. Specifically, the durometer hardness of the elastic layer 112 is preferably smaller than 6, and more preferably 5 or less.

Here, the hardness is the durometer hardness defined in ISO7619-1. The durometer hardness is a value obtained from the pushing depth of the pushing needle when the specified needle is pushed into the test piece under the specified conditions.

The hardness of the silicon rubber can be adjusted by changing the ratio of the additives (silica-based filler and carbon-based filler) added at the time of production. Specifically, when the ratio of the additive is increased, the hardness of the rubber is increased. Further, the hardness can be reduced by adding a silicone-based oil. As a rubber manufacturing method, liquid injection molding or extrusion molding can be adopted. In general, low-hardness rubber is suitable for liquid injection molding, and high-hardness rubber is suitable for extrusion molding.

The heater 113 heats the elastic layer 112 of the heating roller 110. As the heater 113, for example, a halogen lamp that emits light when energized and is heated by radiant heat can be used.

The pressurizing unit 120 is pressed toward the heating roller 110 by a pressing mechanism (not shown) to form a nip portion N for thermally fixing the recording medium S. The nip portion N is formed of a first nip portion N1, a second nip portion N2, and a third nip portion N3.

The pressurizing unit 120 mainly includes an endless belt 121, a belt guide 122, a first elastic body 123, a second elastic body 124, a holder 125, a sliding sheet 126, and a stay 127. The belt guide 122, the first elastic body 123, the second elastic body 124, the holder 125, the sliding sheet 126, and the stay 127 are located inside the endless belt 121 when viewed from the width direction of the endless belt 121.

The endless belt 121 is sandwiched between the heating roller 110 and the first elastic body 123 and the second elastic body 124. The endless belt 121 is an endless belt having heat resistance and flexibility. Both ends of the endless belt 121 are rotatably supported by side guides (not shown). The endless belt 121 is provided so as to rotate counterclockwise in FIG. 2 by the rotation of the heating roller 110.
The recording medium S is conveyed between the heating roller 110 and the endless belt 121 in the conveying direction. The transport direction is equal to the direction from the inlet to the outlet of the nip portion N formed between the heating roller 110 and the endless belt 121.

The belt guide 122 is a member that is arranged so as to be in contact with the inner peripheral surface of the endless belt 121 and guides the endless belt 121.

The first elastic body 123 is located on the upstream side in the transport direction from the second elastic body 124. The first elastic body 123 sandwiches the endless belt 121 with the heating roller 110. The first elastic body 123 forms a first nip portion N1 with the heating roller 110. As shown in FIG. 3, in a state where the heating roller 110 is not in contact with the endless belt 121, the first elastic body 123 is a rectangular parallelepiped and is formed in a long shape long in the left-right direction.

The first elastic body 123 is made of rubber such as silicon rubber, for example. The first elastic body 123 is harder than the elastic layer 112 of the heating roller 110 and softer than the second elastic body 124. Specifically, the first elastic body 123 has a durometer hardness of 6 to 80, preferably 6 to 20, and even more preferably 6 to 10.

The first elastic body 123 has a corner portion 123A at the downstream end in the transport direction. More specifically, an angle substantially perpendicular to the portion where the surface of the first elastic body 123 in contact with the inner peripheral surface of the endless belt 121 and the side surface of the first elastic body 123 facing the second elastic body 124 are connected. It has a part 123A.

The second elastic body 124 is arranged on the downstream side in the transport direction at a predetermined distance from the first elastic body 123. Then, a gap 128 is provided between the first elastic body 123 and the second elastic body 124 by a predetermined distance. The second elastic body 124 sandwiches the endless belt 121 with the heating roller 110. The second elastic body 124 forms a second nip portion N2 with the heating roller 110. Further, the endless belt 121 forms a third nip portion N3 at a position corresponding to the gap 128 in the transport direction. The second elastic body 124 is a rectangular parallelepiped in a state where the heating roller 110 is not in contact with the endless belt 121, and is formed in a long shape that is long in the left-right direction. The size of the second elastic body 124 is smaller than the size of the first elastic body 123 in the direction in which the heating roller 110 and the pressurizing unit 120 are arranged, in the vertical direction in the present embodiment.

The second elastic body 124 is made of rubber such as silicon rubber, for example. The second elastic body 124 is harder than the first elastic body 123. Specifically, the second elastic body 124 has a durometer hardness of 10 to 90, preferably 60 to 90, and even more preferably 70 to 90.

The holder 125 is a member that holds the first elastic body 123 and the second elastic body 124. The sliding sheet 126 is sandwiched between the inner peripheral surface of the endless belt 121 and the first elastic body 123 and the second elastic body 124. The stay 127 is arranged between the belt guide 122 and the holder 125, and supports the belt guide 122 and the holder 125.

According to the fixing device of the present embodiment described above, the following actions and effects can be obtained.

When the recording medium S is conveyed to the fixing device 100, the recording medium S is first niped by the first nip portion N1. Since the elastic layer 112 of the heating roller 110 is softer than the first elastic body 123, in the first nip portion N1, the elastic layer 112 of the heating roller 110 is crushed and is sandwiched between the heating roller 110 and the first elastic body 123. S is heat-fixed while maintaining a shape close to a flat surface. As a result, curling of the recording medium S can be suppressed.

In the first nip portion N1, the recording medium S may be curled so as to be wound around the heating roller 110. However, since the first elastic body 123 has the corner portion 123A at the downstream end, the corner portion 123A strongly presses the recording medium S against the heating roller 110, whereby the recording medium S can be warped against the heating roller 110. .. Therefore, even when the recording medium S is curled at the first nip portion N1, the recording medium S can be returned in the reverse direction. Therefore, it is possible to prevent the curl of the recording medium S from becoming large.

Then, after passing through the first nip portion N1, the recording medium S is niped at the third nip portion N3. Since the recording medium S can be nipped even in the third nip portion N3 located corresponding to the gap 128, the nip region can be widened.

Then, after passing through the third nip portion N3, the recording medium S is niped at the second nip portion N2. In the second nip portion N2, the second elastic body 124 is considerably harder than the elastic layer 112, so that the second elastic body 124 is hardly deformed. As a result, in the second nip portion N2, the nip pressure can be increased as compared with the first nip portion N1 and the third nip portion N3, and the peelability of the recording medium S is improved.

Further, since the second elastic body 124 has a smaller vertical dimension than the first elastic body 123, the second elastic body 124 is extremely difficult to be elastically deformed.

The results of measuring the curl characteristics, the peeling characteristics, and the nip load when the hardness of the first elastic body 123 and the second elastic body 124 in the present embodiment described above are changed are shown in FIG. 4 and will be described below. ..

The recording medium was plain paper, and the durometer hardness of each member was as follows.
Elastic layer of fixing roller 5
First elastic body 4,6,7,8,9,10,15,20
Second elastic body 40, 50, 60, 70, 80, 90

For the curl characteristics, after the recording medium is heat-fixed by the fixing device, the degree of curl of the recording medium is visually determined, and the one that is hardly curved is designated as "A", and as the curvature increases, "A" is set. It was designated as "B", "C", and "D".
As for the peeling characteristics, the characteristics of peeling from the fixing device were visually evaluated. The one with the best peelability was designated as "A", and the one with the worse peelability was designated as "B", "C", and "D".
For the nip load, the nip load for keeping the nip width of the nip portion in the transport direction constant, that is, the load for pressing the pressurizing unit against the heating roller is measured, and the one with the smallest nip load is "A". , And evaluated as "B", "C", and "D" as the nip load increased. When the nip load becomes large, it is necessary to increase the torque of the motor for rotationally driving the heating roller 110. Therefore, the smaller the nip load is, the better.

From the experimental results shown in FIG. 4, it can be seen that the curl characteristics are not good when the durometer hardness of the first elastic body 123 is 4. Further, when the durometer hardness of the second elastic body 124 is 40, 50, it can be seen that the peeling characteristics are poor and the nip load is large.
In summary, when the durometer hardness of the first elastic body 123 is 6 to 20 and the durometer hardness of the second elastic body 124 is 60 to 90, the curl of the recording medium S is widened while widening the nip width. Is suppressed.
Further, when the durometer hardness of the first elastic body 123 is 6 to 10, the nip load becomes small, so that the drive torque of the fixing device 100 can be suppressed. When the durometer hardness of the second elastic body 124 is 70 to 90, the curl characteristics can be improved.

The present invention is not limited to the above embodiment, and can be used in various forms as illustrated below. In the following description, members having substantially the same structure as those of the above-described embodiment are designated by the same reference numerals, and the description thereof will be omitted.

In the above embodiment, a monochrome laser printer is exemplified as an example of the image forming apparatus, but the image forming apparatus may be a color image forming apparatus, a copier, or a multifunction device. Further, the recording medium is not limited to paper, and may be an OHP sheet or the like.

In the above embodiment, the configuration in which the roller is a heating roller having a heater is exemplified, but the roller may not have a heater. In this case, a heater may be arranged inside the endless belt, and the endless belt may be heated by the heater. Further, a heater may be arranged outside the roller to heat the roller surface.

In the above embodiment, the configuration has a gap between the first elastic body and the second elastic body, but a configuration without a gap may be used.

In the above embodiment, the first elastic body and the second elastic body are rectangular parallelepipeds, but the elastic body is not limited to the rectangular parallelepiped and may have other shapes.

In the above embodiment, the size of the second elastic body is smaller than the size of the first elastic body in the vertical direction, but the size of the second elastic body may be larger than the size of the first elastic body.

In the above embodiment, the halogen lamp is exemplified as the heater, but the heater may be, for example, a carbon heater. Further, the heat source may be an induction heating type heater.

In addition, each element described in the said embodiment may be carried out by arbitrarily combining.

100 Fixing device 110 Heating roller 112 Elastic layer 113 Heater 121 Endless belt 123 1st elastic body 123A Corner part 124 2nd elastic body 128 Gap S Recording medium

Claims (7)

With an endless belt,
The first elastic body and
A second elastic body that is harder than the first elastic body,
A roller having an elastic layer on the outer periphery, wherein the endless belt is sandwiched between the first elastic body and the second elastic body, and the recording medium is conveyed between the endless belt and the roller in the conveying direction. Equipped with
The first elastic body is located on the upstream side in the transport direction from the second elastic body.
The elastic layer is a fixing device characterized in that it is softer than the first elastic body. The fixing device according to claim 1, wherein the first elastic body has a corner portion at a downstream end in the transport direction. The fixing device according to claim 1 or 2, wherein a gap is provided between the first elastic body and the second elastic body in the transport direction. The durometer hardness of the elastic layer is less than 6.
The fixing device according to any one of claims 1 to 3, wherein the durometer hardness of the first elastic body is 6 to 20. The fixing device according to any one of claims 1 to 4, wherein the durometer hardness of the second elastic body is 60 to 90. The durometer hardness of the elastic layer is 5 or less, and the elastic layer has a durometer hardness of 5 or less.
The durometer hardness of the first elastic body is 6 to 10, and the hardness is 6 to 10.
The fixing device according to any one of claims 1 to 3, wherein the durometer hardness of the second elastic body is 70 to 90. The fixing device according to any one of claims 1 to 6, wherein the roller has a heater.

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