JP2001083821A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a fixing device where OHP sheet is not soiled by paper powder when the OHP sheet is fixed afterward even in the case that a fixing operation of paper where paper powder is often generated. SOLUTION: In this fixing device, a fixing roller 28, a press roller 30 that is rolled in contact with the fixing roller 28 at a specified pressure, a supporting roller 34 that is installed separated from the fixing roller 28, a fixing belt 36 that is hung endlessly on the supporting roller 34 and the fixing roller 28, a heating means 32 heating the fixing belt 36 and heating unfixed toner on the sheet that is passed a roller contact part between the fixing roller 28 and the press roller 30 are provided and the unfixed toner is fixed on the above sheet by having the sheet with the unfixed toner carried on its surface pass the roller contact part along one direction. In this case, the fixing belt 36 is provided with the an endless belt substrate 36a and a heat resistant release layer 36 formed on an outside surface of the belt substrate 36a and the hardness of this heat resistant release layer 36b is set to be >=30 deg. by JISA.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device used in a copier, a printer, a facsimile or the like, for melting and pressing unfixed toner on a sheet and fixing the unfixed toner on the sheet.

[0002]

2. Description of the Related Art In a recent fixing apparatus for an electrophotographic apparatus, as shown in FIG. 8, a fixing roller R1 and a heating / tension roller (hereinafter simply referred to as "heating roller") R.
A technique has been developed that combines a belt fixing method in which a fixing belt B is stretched between the three and a pressing roller R2 that presses from below through the fixing belt B and preheating of the recording medium D. Thereby, the temperature of the nip portion can be set low by preheating, and by using the fixing belt B having a small heat capacity, the temperature of the fixing belt B is rapidly cooled when passing through the nip portion, and the fixing belt B is separated from the fixing belt B at the exit of the nip portion. By increasing the cohesive force of the toner, the releasability between the fixing belt B and the toner is enhanced, and a clear fixed image with no offset can be obtained even when no oil is applied or only a small amount of oil is applied. This device is known as a fixing device that solves the problems of releasability and oil application that could not be solved by the heating roller method.

The configuration of this conventional fixing device will be briefly described below. The fixing device includes a fixing roller R1, a pressure roller R2 disposed immediately below the fixing roller R1, and a side of the fixing roller R1 (an upstream side along a recording medium conveyance direction).
And a heating roller R3 disposed in the fixing roller R1.
A fixing belt B is stretched between the heating roller R3 and the heating roller R3.

An oil application roller R4 is provided above the fixing belt B. Further, a guide plate G as a recording medium support is provided with a gap below the fixing belt B.
And a heating path P for the recording medium is formed between the lower portion of the fixing belt B and the guide plate G. The fixing belt B is
The heating roller R3 is pressed by the pressing lever U in a direction separating from the fixing roller R1 to obtain a desired tension, and is driven by the fixing roller R1 to rotate stably without slipping or loosening. Can be done.

On the other hand, inside the heating roller R3, a heating heater H is provided as a heating source. Also, the heating roller R
3, a thermistor S is provided for measuring the surface temperature. Since the thermistor S measures the temperature of the test portion in the contact state, it is not preferable to make the thermistor S contact the paper passing area of the fixing belt B. Therefore, the thermistor S is brought into contact with the non-paper passing area of the fixing belt B.

[0006]

In the conventional fixing device having the above structure, a metal belt manufactured by, for example, an electroforming method (hereinafter simply referred to as an electroformed belt) is used as a fixing belt from the viewpoint of thermal response and breaking strength. Is used as a belt base. The outer peripheral surface (surface layer) of the electroformed belt is coated with silicone rubber as a heat-resistant release layer from the viewpoint of toner release properties.

[0007] As described above, the surface of the fixing belt is coated with silicone rubber, so that the fixing belt can exhibit a releasing function. However, recently, inexpensive papers have been circulating for the purpose of reducing running costs, and among such inexpensive papers, there are papers which easily generate paper dust. As described above, when the paper on which the paper dust easily emerges is repeatedly subjected to the fixing operation, the paper dust adheres to the silicone rubber surface layer of the fixing belt and becomes soiled.

Such a stain does not substantially cause a problem when plain paper is used as a recording medium, but a sheet for an overhead project (hereinafter simply referred to as OPH) is used as the recording medium. When used, the paper dust adhering to the silicone rubber surface layer of the fixing belt is uniformly retransferred to the OHP sheet and becomes soiled with the fixing operation.

It has been pointed out that if the OHP sheet is uniformly contaminated with paper dust as described above, when the OHP sheet is projected on a screen with OHP, the projected image becomes entirely dark and difficult to read. There is a need for a solution.

The present invention has been made in view of the above-described circumstances, and a main object of the present invention is to fix an OHP sheet when fixing an OHP sheet at a later time even when a sheet that easily generates paper dust is fixed. Is to provide a fixing device that does not contaminate the paper with paper dust.

Another object of the present invention is to provide a fixing device capable of simultaneously satisfying paper dust adhesion and abrasion.

[0012]

Means for Solving the Problems To solve the above-mentioned problems,
To achieve the above object, according to the first aspect of the present invention, a fixing device includes a fixing roller, a pressure roller that rolls on the fixing roller at a predetermined pressure, and a distance from the fixing roller. A fixing roller provided, a fixing belt wrapped around the supporting roller and the fixing roller endlessly, and a heating unit that heats the fixing belt to determine an undetermined state on a sheet passing through a rolling contact portion between the fixing roller and the pressure roller. A heat generating means for heating the toner to be attached, wherein the sheet having the unfixed toner carried on its surface passes through the rolling contact portion in one direction, thereby fixing the unfixed toner on the sheet. In the fixing device, the fixing belt includes an endless belt base and a heat-resistant release layer formed on an outer surface of the belt base, and the heat-resistant release layer has a hardness of:
It is characterized by being set at 30 degrees or more according to JIS A.

According to a second aspect of the present invention, there is provided a fixing device, comprising: a fixing roller; a pressure roller which rolls on the fixing roller at a predetermined pressure; and a distance from the fixing roller. And a fixing belt that is endlessly stretched between the supporting roller and the fixing roller. The fixing belt is heated, and the unfixed sheet on the sheet passing through the rolling contact portion between the fixing roller and the pressure roller is heated. A fixing unit for fixing the unfixed toner on the sheet by passing the sheet having the unfixed toner carried on the surface thereof in one direction along the rolling contact portion; In the apparatus, the fixing belt includes an endless belt base and a heat-resistant release layer formed on an outer surface of the belt base, and a 100% modulus load of the heat-resistant release layer is 3 mm. It is characterized in that it is set to 5MPa or less.

According to a third aspect of the present invention, there is provided a fixing device, comprising: a fixing roller; a pressure roller which rolls on the fixing roller at a predetermined pressure; and a distance from the fixing roller. And a fixing belt that is endlessly stretched between the supporting roller and the fixing roller. The fixing belt is heated, and the unfixed sheet on the sheet passing through the rolling contact portion between the fixing roller and the pressure roller is heated. A fixing unit for fixing the unfixed toner on the sheet by passing the sheet having the unfixed toner carried on the surface thereof in one direction along the rolling contact portion; In the apparatus, the fixing belt includes an endless belt base and a heat-resistant release layer formed on an outer surface of the belt base.
It is characterized in that it is set to 30 degrees or more in ISA and the 100% modulus load of the heat-resistant release layer is set to 3.5 MPa or less.

According to a fourth aspect of the present invention, in the fixing apparatus, the heat-resistant release layer is formed to have elasticity.

According to a fifth aspect of the present invention, in the fixing device, the heat-resistant elastic release layer is formed of silicone rubber.

According to a sixth aspect of the present invention, there is provided a fixing device, wherein the belt base is formed of an electroformed belt.

According to a seventh aspect of the present invention, in the fixing device, the belt base is made of a polyimide resin.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of an embodiment of a fixing device according to the present invention will be described below in detail with reference to the accompanying drawings.

First, as shown in FIG. 1, the fixing device 10 of this embodiment is fixed to a frame of an electronic image forming apparatus (not shown) such as an electronic printer as a housing structure. Housing 1
The housing 12 includes a bottom plate 14 directly fixed on the apparatus frame, side plates 16 standing upright from both left and right side edges of the bottom plate 14, and a substantially upper right portion of the side plate 16 in FIG. And a left cover part 20 attached to the side plate 16 so as to cover substantially the left side thereof.

Here, the upper cover part 18 is fixedly attached to the side plate 16, and at the upper right part thereof,
The swing lever 22 is swingably supported so that the left side in the figure is opened around the first support shaft 24 located on the right side in the figure. On the other hand, the left cover part 20
Is swingably attached to the side plate 16 such that the upper part is opened around the support shaft 26.

Further, the fixing device 10 has a roller configuration, in which a fixing roller 28 rotatably supported on a side plate 16 around a fixed axis is provided, and substantially below (specifically, obliquely below) the fixing roller 28. A pressure roller 30 rotatably supported by the side plate 16 around a fixed axis set in parallel with the fixing axis of the fixing roller 28 in a state of being in contact with the roller, and substantially above the fixing roller 28 (specifically, Is mounted on the swing lever 22 in a state of being located obliquely upward), and is configured to include a support roller 34 supported rotatably about its own central axis.

The fixing device 10 includes a support roller 3
4, a first lamp such as a halogen lamp.
And a heating source 32 disposed inside the pressure roller 30.
For example, it further includes a second heating source 33 such as a halogen lamp, and a fixing belt (heat transfer belt) 36 endlessly wound around the fixing roller 28 and the support roller 34. That is, in this embodiment, the support roller 34 is
The halogen lamp 32 functions as a built-in heating roller. In the following description, the roller 34 will be described as a heating roller.

The fixing roller 2 will be described in detail later.
8 is configured as an elastic roller, while the pressure roller 30
Is composed of a roller having a higher on-roller hardness than the elastic roller. On the other hand, the fixing roller 28 and the pressure roller 3
As shown in FIG. 2, the distance D between the centers of rotation with respect to 0 is
The radius is set slightly but shorter than the sum (R1 + R2) of the radius R1 of the fixing roller 28 and the radius of the pressing roller 30R2. As a result, at the mutual rolling contact portion (nip portion) of the fixing roller 28 and the pressure roller 30, the two roll contact each other with a predetermined pressure contact force P <b> 1, whereby the fixing roller 2
8 will be brought into a concave state at the rolling contact portion. That is, a sufficient nip width is secured.

The fixing device 10 includes a fixing belt 3
6, a silicone oil is applied to the outer surface of the fixing belt 36, and an oil applying roller 38 for cleaning the outer surface of the fixing belt 36 is brought into pressure contact with the oil applying roller 38 in a state of being orthogonal to the fixing belt 36. 3
First coil spring 4 for applying predetermined tension to 6
0, and a second coil spring 42 that urges the heating roller 34 in a direction away from the fixing roller 28 and applies a predetermined tension to the fixing belt 36 in cooperation with the first coil spring 40. I have.

The lower right portion of the upper cover 18 in the figure is bent inward, and is located below the bent piece, and is separated from the bent piece by the guide plate 44. It is fixed to. From between the upper cover portion 18 and the guide plate 44, a sheet (hereinafter, simply referred to as an unfixed sheet) carrying unfixed toner on the upper surface is moved in one direction (conveying direction) indicated by an arrow in the drawing. An inlet port 46 is defined along the interior of the housing 12.

Here, the guide plate 44 is mounted so as to be inclined upward and leftward in the figure so that the height thereof increases as it enters the housing 12. On the other hand, the leading end of the guide plate 44, that is, the lower right end in the drawing, is an endless sheet transport end disposed in the electronic printer and adjacent to the entrance port 46 on the right side in the drawing. The guide plate 44 is positioned so as to face the outlet end of the belt EB, and the leading end of the guide plate 44, that is, the upper left end in the figure, is a rolling contact portion (nip) between the fixing roller 28 and the pressure roller 30. Part)
Is positioned so as to face the.

Then, the leading end of the unfixed sheet conveyed through the endless belt EB toward the fixing device 10 in one direction (conveying direction) indicated by an arrow in FIG. The unfixed sheet guided by the guide plate 44 is set so that it is conveyed obliquely upward, and the leading end of the unfixed sheet first contacts the outer peripheral surface of the pressure roller 30. The fixing roller 28 is configured to move along the outer peripheral surface of the pressure roller 30 and to be guided to a rolling contact portion between the fixing roller 28 and the pressure roller 30.

On the other hand, the fixing roller 28 and the pressing roller 30
Thus, a sheet discharge path 48 for discharging a sheet (hereinafter, referred to as a fixed sheet) on which the unfixed toner is fixed by thermocompression bonding is formed. In this embodiment, the sheet discharge path 48 is The fixed sheet is set to be discharged upward in a substantially upright state.

A lower discharge roller 50 is rotatably supported by the left cover portion 20 in a state between the discharge path 48 and the rolling contact portion. The lower discharge roller 50 is described later. A configuration is adopted in which a driving force from the driving mechanism 52 is obtained and the rotation is performed at a speed equal to or higher than that of the pressure roller 30 (for example, a rotation speed set 5% faster than the speed of the pressure roller 30). Have been. The lower discharge roller 50 includes:
In a state of rolling contact from obliquely above, the upper discharge roller 54 is in rolling contact with the plate spring 56 with a predetermined elastic force. The position of the upper discharge roller 54 is set such that a line connecting the center positions of the upper discharge roller 54 and the lower discharge roller 50 is substantially orthogonal to the discharge path of the fixed sheet. Have been.

In the fixing device 10 having such a schematic configuration, the unfixed sheet S conveyed onto the guide plate 44 via the endless belt EB by the conveying mechanism.
The lower surface where no unfixed toner is attached
The fixing belt 36 is guided toward a rolling contact portion (nip portion) between the fixing roller 28 and the pressure roller 30 around which the fixing belt 36 is wound. It is set so that the unfixed toner is thermocompressed and fixed on the sheet by being inserted. Hereinafter, the various components described above will be sequentially described individually.

{Description of Fixing Roller 28} The fixing roller 28 includes a core 28A rotatably supported by a side plate 16 via a bearing (not shown), and a core 28A.
And a roller body 28B coaxially disposed around the outer periphery of the roller A and around which the fixing belt 36 is wound. The roller outer diameter is set to 38.0 mm in this embodiment. Here, in this embodiment, the core 28A has a diameter of 25 mm.
roller body 28B
Is formed of a silicone rubber heat-resistant elastic body (specifically, 18 degrees in JIS A hardness on a roller) attached to the outer periphery of the cored bar 28A with a thickness of 6.5 mm.

A first driven gear 58 is coaxially mounted on a shaft disposed at one end of the cored bar 28A via a one-way clutch 60 which will be described in detail later. A transmission gear 62 that constitutes a part of the drive mechanism 52, which will be described in detail later, meshes with the one driven gear 58. In this manner, the driving force from the driving mechanism 52 is transmitted to the first driven gear 58 via the transmission gear 62 as a clockwise rotational force in the drawing, and the one-way clutch 60
The rotational force is transmitted to the fixing roller 28 via the fixing roller 28.

{Description of the Pressure Roller 30} As described above, the pressure roller 30 incorporating the second heating source 33 is rotatably supported by the side plate 16 via a bearing (not shown). 30A and a roller main body 30B coaxially disposed on the outer periphery of the cored bar 30A, and the roller outer diameter is set to 35 mm. Here, in this embodiment, the core metal part 30A is formed of an iron pipe having an inner diameter of 22 mm and an outer diameter of 32 mm, and the roller body 30B
Is a silicone rubber heat-resistant elastic body attached to the outer periphery of the cored bar 30A with a thickness of 1.5 mm (specifically, ASKER on a roller harder than the fixing roller 28 described above).
C hardness of 74 to 75 degrees).

The shaft provided at one end of the cored bar 30A has a second driven gear 64 coaxially fixed thereto. The second driven gear 64 is connected to the first driven gear 64 described above. Gear 58
The driving force from this is transmitted to the second driven gear 64 via the first driven gear 58, and the pressing roller 30 moves in the counterclockwise direction opposite to the fixing roller 28. It is configured to be driven to rotate.

In this embodiment, the pressure roller 30 is set as the main drive for conveying the unfixed sheet, and the peripheral speed of the fixing roller 28 is increased even when the fixing roller 28 is thermally expanded. The gear ratio of the first and second driven gears 58 and 64 is set so that the peripheral speed of the pressure roller 30 does not become faster. That is, the rotation speed when the fixing roller 28 is rotated by the second driven gear 64 is the rotation speed of the fixing belt 36.
The rotation speed is set to be slightly lower than the rotation speed at the time of rotation by frictional engagement with the pressure roller 30 through the roller.

On the other hand, in this embodiment, the pressure roller 30 is not located immediately below the fixing roller 28 but in the conveying direction of the unfixed sheet rather than immediately below the fixing roller 28. When a line segment passing through both center points of the heating roller 34 and the fixing roller 28 is set as a base line, the base line and the fixing roller 2
8 and the pressure roller 30 are disposed at such a position that an angle formed by a line segment passing through both center points thereof becomes a predetermined acute angle.
A line segment passing through both center points of the fixing roller 28 and the pressure roller 30 is set so as to be substantially orthogonal to the conveying direction of the unfixed sheet.

{Description of One-Way Clutch 60} The one-way clutch 60 allows the fixing roller 28 to rotate relative to the first driven gear 58 in the clockwise direction in FIG. It is configured such that the relative rotation is locked, in other words, both rotate integrally. That is, the fixing belt 36 is
And the fixing roller 28 is fixed to the fixing belt 3.
6 is frictionally engaged with the fixing roller 2 by the pressure roller 30.
8 and the fixing belt 36 are driven (rotated), the peripheral speed of the fixing roller 28 rotating clockwise in the drawing is:
The rotation speed of the fixing roller 28 is set to be slightly faster than the rotation of the first driven gear 58 because the rotation speed of the fixing roller 28 is equal to the peripheral speed of the pressure roller 30.

<< Description of Heating Roller 34 >> In this embodiment, the heating roller 34 incorporating the first heating source 32 is formed by adding an aluminum pipe core having a diameter of 30 mm and a wall thickness of 3.5 mm to a thickness of 3.5 mm. The bearings at both ends are coated with a 20 μm-thick PTFE coating layer and have a diameter of 34 mm, made of heat-resistant resin made of polyetheretherketone (PEEK).
The collar 66 of mm is inserted to prevent the fixing belt 36 from meandering and leaning.

A first heating source 32 is built in the heating roller 34. In this embodiment, the first heating source 32 is supplied from a halogen lamp 32 having a maximum output of 1 kW. It is configured. On the other hand, the second heating source 33 built in the pressure roller 30 described above is constituted by a halogen lamp having a maximum output of 250 W. Here, the maximum output allowed for the heating source of the fixing device 10 is set to 1 kW in this embodiment. That is, in this embodiment, the first heating source 32 is set so as to be able to output the maximum output itself permitted for the fixing device 10.

{Description of Fixing Belt 36} The fixing belt 36 has a size of one square centimeter of the fixing belt 36 so that the unfixed toner on the unfixed sheet S can be fixed to the fixing temperature without giving an excessive amount of heat. Heat capacity per unit is 0.
Those in the range of 002 cal / ° C to 0.025 cal / ° C are preferred. Therefore, in this embodiment, as shown in FIG. 5, the fixing belt 36 has an endless belt base 36a made of a polyimide resin having an inner diameter of 60 mm and a thickness of 100 μm, and an outer peripheral surface of the belt base 36a. (A surface layer) and a heat-resistant elastic release layer 36b of silicone rubber coated with a thickness of 200 μm.

Here, the hardness of the heat-resistant elastic release layer 36b is set to be 39 degrees in JIS A, in other words, silicone rubber having a JIS A hardness of 39 degrees is employed. Further, the 100% modulus load is set to be 1.5 MPa, in other words, 10 MPa.
Silicone rubber having a 0% modulus load of 1.5 MPa is employed.

As described above, the heat-resistant elastic release layer 36b
Is made of silicone rubber having a JIS A hardness of 39 degrees and a 100% modulus load of 1.5 MPa, and will be described in detail later. Thus, excellent performance in abrasion is exhibited.

<< Description of Oil Application Roller 38 >> The fixing device 10 is provided with an oil application roller 38 for applying a small amount of release oil on the outer peripheral surface of the fixing belt 36. Although not shown in detail, the oil application roller 38 includes a support shaft rotatably supported in a fixed state on the casing 68 and a heat-resistant paper layer in which the outer periphery of the support shaft is impregnated with silicone oil. In this embodiment, the support shaft is formed of an iron shaft having a diameter of 8 mm, and the heat-resistant paper layer has a diameter of 100 μm with a porous fluororesin film attached to its outer periphery. 2
It is formed to have a roller outer diameter of 5 mm. By configuring the oil application roller 38 in this way, it is possible to apply a small amount of stable oil to the outer peripheral surface of the fixing belt 36.

On the outer peripheral surface of the oil application roller 38, dirt (toner and the like) adhering to the outer peripheral surface of the fixing belt 36 is transferred and adheres, and is contaminated. For this reason, a cleaning brush is in contact with the outer peripheral surface of the oil application roller 38, so that the outer peripheral surface of the oil application roller 38 is constantly cleaned to remove dirt attached thereto. .

{Description of Mechanism for Applying Tension to Fixing Belt 36} As described above, in this embodiment, as a mechanism for applying tension to the fixing belt 36, the oil application roller 38 is perpendicular to the fixing belt 36. A first coil spring 40 for applying a predetermined tension to the fixing belt 36 by pressing the heating roller 34 in a direction away from the fixing roller 28 to cooperate with the first coil spring 40 A second coil spring 42 for applying a predetermined tension to the fixing belt 36.

Here, the first coil spring 40 is a casing 68 that rotatably supports the oil application roller 38.
Is attached to the left cover 20 so as to urge the fixing belt 36 toward the fixing belt 36. That is, the casing 68
The guide rib 70 attached to the side plate 16 supports the fixing belt 36 so as to be able to freely contact and separate from the fixing belt 36. Thus, when the left cover part 20 is opened to the left in the figure,
The first coil spring 40 pressing the casing 68 is separated from the casing 68, whereby the pressing state of the oil application roller 38 against the fixing belt 36 is released. When the left cover portion 20 is rotated rightward in the drawing and closed, the first coil spring 40 presses the casing 68 with the pressing force P2, and the oil application roller 38 applies a predetermined tension to the fixing belt 36. Will be pressed.

On the other hand, the second coil spring 42 is interposed between the left end of the swing lever 22 in the figure and the side plate 16, and in other words, rotates the swing lever 22 clockwise in the figure. Then, the heating roller 3 supported by the swing lever 22
4 is the third pressing force P in the direction in which
3 so as to press it. As a result, a predetermined tension is applied to the fixing belt 36.

That is, the heating roller 34 is biased in the direction away from the fixing roller 28 via the swing lever 22 by the urging force of the second coil spring 42, whereby the heating roller 34 and the fixing roller 28 The fixing belt 36 stretched endlessly is tensioned to a predetermined tension.

As described above, the first and second coil springs 4
The fixing belt 36 frictionally engages with the pressure roller 30 by the action of the fixing belt 36 and rotates, and the fixing roller 28 slips with respect to the fixing belt 36 in accordance with the rotation of the fixing belt 36. It is driven in a stable state without slack.

{Description of Driving Mechanism 52} As shown in FIG. 3, the driving mechanism 52 for rotatingly driving the pressure roller 30 and the like is provided with the fixing device 10 mounted on an electronic printer, as shown in FIG. A transmission gear 62 meshes with an output gear GE connected to a drive source on the printer side via a gear train (not shown), and is rotationally driven by receiving a driving force from the output gear GE.
And a first driven gear 58 which is always meshed with the transmission gear 62 and is connected to the fixing roller 28 via the one-way clutch 60, and is always meshed with the first driven gear and A second driven gear 64 fixed coaxially.

The drive mechanism 52 further includes an idle gear 80 that always meshes with the transmission gear 62 described above.
The idle gear 80 always meshes with a third driven gear 74 coaxially fixed to the lower discharge roller 50, and rotates the lower discharge roller 50 at a speed equal to or higher than the peripheral speed of the pressure roller 30. It is configured to be driven.

{Other Configurations} In addition to the above-described configuration, the fixing device 10 according to the present embodiment is, as shown in FIG. 1 again, for peeling off the fixed sheet adhered to the outer peripheral surface of the pressure roller 30. The separation claw 76 and the above-described lower discharge roller 50
Paper discharge sensor 78 that detects that the leading end of the fixed sheet has been conveyed between the upper paper discharge roller 54 and the upper paper discharge roller 54 (the rolling contact portion).
And

{Description of Arrangement of Heating Roller 34} As described above, in this embodiment, the heating roller 34
Is disposed substantially above the fixing roller 28, so that the endlessly wound fixing belt 36 between the heating roller 34 and the fixing roller 28 and the guide plate 44 The unfixed sheet conveyed above is separated so as not to contact the fixing belt 36. In other words, the fixing belt 36 is
This means that the unfixed sheet conveyed above is disposed at a position outside a region where the unfixed sheet may pass.

As described above, the heating roller 34 is connected to the fixing roller 2.
8 above, no matter how the unfixed sheet in the middle of conveyance is in a curved posture (curled state),
The unfixed toner carried on the upper surface of the sheet is reliably prevented from substantially contacting the fixing belt 36 before the fixing operation, and the fixing roller 28 is prevented from disturbing the unfixed toner.
It can be guided to the rolling contact portion between the pressure roller 30 and the pressure roller 30 to fix it.

{Description of Configuration Angle of Heating Roller 34} In the fixing device 10 having the above-described configuration, as described above, the heating roller 34 is disposed substantially above the fixing roller 28 to achieve a specific effect. Can be done.
Here, in order to clearly define the range “approximately above”, as shown in FIG. 4, an experimental example will be described in which the configuration angle of the heating roller 34 is variously changed and the optimum range is obtained.

First, in this experimental example, a line segment passing through both center points of the fixing roller 28 and the pressing roller 30 is defined as a base line B, and the base line B and both center points of the fixing roller 28 and the heating roller 34 are defined. Is defined as θ, the position of the heating roller 34 is changed so that the configuration angle θ is 90 ° to 180 °, so that the fixing roller 28 and the pressure roller The frequency of occurrence of rubbing of the image at the entrance of the transfer contact portion with No. 30 and the frequency of occurrence of an abnormality at the exit of the transfer contact portion were measured for single-sided copying and double-sided copying, respectively.

Here, ± of the constituent angle θ is defined as "+" when the value measured in the counterclockwise direction from the base line B is defined as "+", and the value measured in the clockwise direction in the figure from the base line B is defined as "-". Therefore, +1
The heating roller 34 at 80 ° and the heating roller 34 at −180 ° indicate the same position.
The heating roller 34 at 105 ° and the heating roller 34 at −255 ° indicate the same position. on the other hand,
In this embodiment, the abnormality at the outlet of the transfer portion means occurrence of an offset or occurrence of a jam at the outlet of the transfer portion.

The measurement conditions are as follows.

That is, the nip width at the rolling contact portion was set to 8 mm, and the pressing force P1 for this was set to 24 kgf / one side. On the other hand, the temperature of the portion of the fixing belt 36 wound around the fixing roller 28 was set to 160 ° C., and the surface temperature of the pressure roller 30 was set to 140 ° C. Further, the conveyance speed of the unfixed sheet was set to 180 mm / sec, and the pressure roller 30 was rotated in synchronization with the conveyance speed. As the toner, A color toner manufactured by Fuji Xerox Co., Ltd. was used, and as a sheet, paper of 64 g / m 2 was used.

Thus, the constituent angle θ is set to 90 °, 1
05 °, 120 °, 150 °, 180 °, -150 °,
Divided into nine types of -120 °, -105 °, -90 °
The measurement was performed under the measurement conditions described above.

Table 1 shows the measurement results.

[0063]

[Table 1]

As is apparent from Table 1, when the constituent angle θ is larger than 105 ° and smaller than −105 °, that is, when the constituent angle θ is measured only in the counterclockwise direction, When the angle is within the range of from 255 ° to 255 °, there is no occurrence of image rubbing at the entrance of the transfer part and no occurrence of abnormality at the exit of the transfer part, and a good fixing operation is performed. It has been found. On the other hand, when the constituent angle θ is 10
When the angle is 5 ° or less, it was found that either an image rubbing at the entrance of the transfer part or an abnormality at the exit of the transfer part occurred, and good fixing operation was not performed.

Further, in this embodiment, since the second heating source 33 is incorporated in the pressure roller 30 constituting one of the nip portions, a sufficient amount of heat for heating the unfixed sheet S is supplied. As a result, the fixing belt 36
Even if the traveling speed is increased, a sufficient amount of heat can be supplied to the nip portion. In this way, it is possible to sufficiently cope with an increase in the paper passing speed.

Further, in this embodiment, the heating roller 34 is disposed substantially above the fixing roller 28, and more specifically, the heating roller 34 is positioned between the center of the heating roller 34 and the fixing roller 28.
When a line segment connecting the center point of the fixing roller 28 and the pressure roller 30 is a line segment connecting the center points of the fixing roller 28 and the pressure roller 30, the angle measured from the base line B is about 105 degrees to about 105 degrees. 25
Since it is disposed at a position within a range of 5 degrees, the space between the fixing belt 36 wound endlessly between the heating roller 34 and the fixing roller 28 and the guide plate 44 passes over the guide plate 44. The conveyed unfixed sheet is separated so as not to contact the fixing belt 36. In other words, this means that the fixing belt 36 is disposed at a position outside an area where the unfixed sheet conveyed on the guide plate 44 may pass.

As a result, according to this embodiment, the unfixed sheet being conveyed may be in any curved posture (curl state) due to a jump or a slack due to a difference in conveyance speed from the transfer unit. The unfixed toner carried on the upper surface of the sheet is reliably prevented from coming into contact with the fixing belt 36, and the fixing roller 2 is fixed without disturbing the unfixed toner.
8 and the pressure roller 30 can be guided to the rolling contact portion, and this can be reliably fixed.

{Verification of Adhesion of Paper Powder and Wear of Heat-Resistant Elastic Layer 36b of Fixing Belt 36} As described above, the heat-resistant elastic release layer 36b disposed on the surface layer of the fixing belt 36 includes: When using silicone rubber,
By setting the JIS A hardness to 39 degrees and the 100% modulus load to 1.5 MPa, a state in which the difficulty in adhering paper powder and the abrasion property are satisfied at the same time is achieved. This effect is not limited to the above-mentioned numerical values defining the physical properties of the silicone rubber, and the same effect can be achieved within a predetermined range. The JIS of the heat-resistant elastic release layer 36b is described below.
Verify the allowable range of A hardness and 100% modulus load.

{Verification of the allowable range of JIS A hardness that defines the adhesion of the heat-resistant elastic release layer 36b to the paper dust} Here, when the adhesion state of the paper dust is observed microscopically, the paper dust is individually adhered to the silicone rubber. It was found that it was attached in a piercing state. From this situation, it is technically imagined that the softer the rubber hardness, the more easily the paper powder adheres, and the harder the rubber hardness, the less the paper powder adheres. That is, it is considered that the difficulty of adhering the paper powder to the heat-resistant elastic release layer 36b (paper powder adhesion) depends on the rubber hardness of the silicone rubber constituting the paper powder. Therefore, the paper powder adhesion was measured according to JIS.
A hardness was measured as a parameter, and the optimum range was verified.

For this reason, a plurality of silicone rubbers having different hardnesses are prepared, and the adhesion state of paper powder at each hardness is quantitatively measured for each predetermined number of sheets passed, and the adhesion state at the time of measurement is visually observed. The test evaluated by was carried out. That is,
Continuously pass paper that easily produces paper dust with blank paper, and peel off the paper dust with cellophane tape (trade name) every predetermined number of sheets passed. Turbidity was measured with a turbidimeter. In addition, the cellotape (trade name) to which the paper powder was adhered measured by the turbidity meter was projected on a screen with OHP, and the state of darkening due to the adhesion of the paper powder was visually evaluated.

The fixing device 10 employed in the test has substantially the same configuration as that shown in FIG.
° C, and the linear velocity of the fixing belt 36 to 180 mm / sec.
The nip width between the fixing roller 28 and the pressure roller 30 is 9
mm. The hardness of the heat-resistant elastic release layer 36b is 25 degrees, 33 degrees, 39 degrees, and 5 degrees according to JIS A.
5 degrees of 2 degrees and 65 degrees (A, A,
B, C, D, E are attached. ) Was prepared.

Next, the test method will be specifically described. First, the heat-resistant elastic release layer 36b of the fixing belt 36 in the oil-less state (that is, the state in which the oil is not dipped) is
In a state in which the product is set to a predetermined JIS A hardness product, the product is incorporated into the fixing device 10, and paper in which paper dust is likely to be emitted, specifically, A4 size AR color paper (manufactured by AUSSEDAT REY) is continuously passed. The amount of adhesion to the heat-resistant elastic release layer 36b was measured every predetermined number of sheets. Here, the predetermined number is set to “0” (that is, non-sheet passing state), “20”, “50”, “100”.
Sheets ".

When the number of sheets reached the respective number, the fixing belt 36 was removed from the fixing device 10, and a cellophane tape (trade name) having a width of 16 mm was strongly adhered to the heat-resistant elastic release layer 36b, and paper powder was adhered thereto. Thereafter, the cellophane tape (trade name) was peeled off from the heat-resistant elastic release layer 36b and stuck on a glass plate. Then, a glass plate to which a cellotape (trade name) to which the paper powder was adhered was set in a turbidimeter, and the turbidity was measured.

Here, the glass plate used was a model number S-1111 manufactured by Matsunami Glass Industry Co., Ltd. 1, having a thickness of 0.8 to 1.0 mm and a plane size of 76 × 26 mm. The turbidimeter used was a model number NDH-10001DP manufactured by Nippon Denshoku Industries Co., Ltd.

Table 2 shows the results.

[0076]

[Table 2]

As is clear from Table 2 and FIG. 6 which is a graph of the measurement results, JI indicated by sample number A was used.
In the case of the heat-resistant elastic release layer 36b made of silicone rubber having an SA hardness of 25 degrees, the turbidity of the heat-resistant elastic release layer 36b was larger than that of the other sample numbers (B to E) when 50 sheets were passed. It can be seen that the amount of adhering paper powder is large. Thereafter, as the number of sheets passed increases, the sample indicated by sample number A has a turbidity that increases proportionally, while the samples indicated by other sample numbers (BE) generally saturate. And the turbidity is stable. That is, a state in which further adhesion of the paper dust is suppressed.

The cellotape (trade name) with paper powder attached
Is defined as D (P + C), and the turbidity of the glass affixed with raw cellotape (trade name) to which paper dust is not adhered is defined as D (C). D (P) = D (P + C) ) -D (C) was defined as the turbidity D (P) of the paper dust.

Here, in the above-described test, the fixing belt 3
6 was used in an oil-less state, that is, a state in which no oil dip was performed.
6 was made in a state in which the release oil was impregnated in silicone rubber in a state where oil was dipped, and the same measurement was performed.

Table 3 shows the results.

[0081]

[Table 3]

As is evident from Table 3 and from FIG. 7 which is a graph of the measurement results, the degree of adhesion of paper dust is improved as a whole when compared with the oilless state.
Still, the turbidity of the heat-resistant elastic release layer 36b coated with silicone rubber having a JIS A hardness of 25 degrees indicated by sample number A is larger than those of the other sample numbers (B to E). And it can be seen that the amount of adhering paper powder is relatively large.

Thereafter, as the number of sheets passed increases, the sample indicated by sample number A shows that while the turbidity D (P) gradually increases while saturating, the other sample numbers (B to
In the case of E), it can be seen that the turbidity is stable in a substantially saturated state.

On the other hand, the glass to which the above-mentioned turbidity-measured paper powder is adhered to the cellotape (trade name) is adhered to OH.
It was put on P, projected on a screen, and the projected image was visually evaluated.

The results are shown in Table 4.

[0086]

[Table 4]

In the column of paper powder adhesion in Table 4, the evaluation result “」 ”indicates a case where it was evaluated that the darkness could not be recognized substantially as compared with the surroundings other than the part that transmitted the glass. And "○" indicates that the darkness is slightly recognized,
The case where evaluation is made that it hardly causes a problem (practical endurance) is shown, and “x” indicates the case where darkness is clearly recognized and evaluation is not endurable for practical use.

From Table 4, it can be seen whether the fixing belt 36 is oil-less or oil-dipped.
It has been found that a silicone rubber having an IS A hardness of 30 degrees or more has resistance to paper dust adhesion, and a JIS A hardness of less than 30 degrees has no resistance to paper powder adhesion. 6 and 7, the pass / fail judgment criterion is 10
The same result can be derived even when the turbidity D (P) is set to 15% at the time of passing 0 sheets. Conversely, it can be determined that a silicone rubber having a turbidity D (P) of more than 15% at the time of passing 100 sheets has no resistance to the adhesion of paper powder.

{Verification of Permissible Range of 100% Modulus Load that Defines Abrasion Resistance of Heat-Resistant Elastic Release Layer 36b} As described above, the adhesion state of paper powder is easier as the rubber hardness of silicone rubber is softer. It was found that the harder the rubber hardness, the more difficult it is to adhere. From this viewpoint, from the standpoint of preventing the adhesion of paper dust, the higher the rubber hardness is set, the better the result will be. On the other hand, the harder the rubber hardness, the higher the wear will be. Tends to deteriorate. Therefore, the abrasion was measured using the 100% modulus load as a parameter, and the optimum range was verified.

First, a test piece of each silicone rubber constituting the sample numbers A to E was prepared and subjected to a stress test of applying a tensile stress specified in JIS K6301 to obtain a 100% modulus load. Tensile stress (MPa) was measured until the length was doubled (that is, until the elongation reached 100%).

Next, an abrasion test was conducted to test the abrasion properties of each of the silicone rubbers constituting the above-mentioned sample numbers A to E. In this abrasion test, two silicone rubbers of each of sample numbers A to E were placed on a φ116 aluminum sample stage.
A ring-shaped test piece coated with a thickness of 00 µm is set concentrically, pressed against each test piece in two places with a wear wheel specification, and after 20,000 revolutions, the maximum wear depth is measured with a surface roughness meter. The values were measured and evaluated.

Here, a ROTARY ABRASION TESTER (taper abrasion tester) manufactured by Toyo Seiki Seisaku-Sho, Ltd. was used as the abrasion tester.
2000, and apply a pressing load of 25
0g is applied to two places and the rotation speed is 60rpm
m.

The results are shown in Table 4 above.
In the wear property column of Table 4, when the case where the wear depth is 50 is set as the threshold value for the quality judgment, the evaluation result “◎” is a value sufficiently smaller than this, that is, the case where the wear amount is small. “○” indicates a case where the wear depth near the threshold is exhibited, and “×” indicates a value considerably larger than the threshold, that is, a case where the wear amount is large.

As described above, from Table 4 in which the test results were summarized, it was confirmed that when the 100% modulus load was set to 3.5 MPa or less, there was a sufficient effect on abrasion.

Therefore, in order to simultaneously satisfy the mutually contradictory accuracy of paper powder adhesion and abrasion, JIS
It has been found that the A hardness should be set to 30 degrees or more and the 100% modulus load should be set to 3.5 MPa or less.

The silicone rubber forming the heat-resistant elastic release layer 36b in the above embodiment has a JIS A hardness of 39 degrees and a 100% modulus load of 1.5M.
Since each is set to Pa, it is within the above optimum range, and has sufficient resistance to paper dust adhesion,
It is possible to sufficiently exert an effect on abrasion.

It is needless to say that the present invention is not limited to the configuration of the above-described embodiment, but can be variously modified without departing from the gist of the present invention.

For example, in the above-described embodiment, the fixing belt 36 has been described as including the belt body 36a made of a polyimide resin. However, the present invention is not limited to such a configuration, and the fixing belt 36 of the related art can be used. As described in the section, it goes without saying that an electroformed belt can be used.

[0099]

As described above in detail, according to the present invention, even if the paper is likely to generate paper dust, the paper may be stained with the paper dust when the OHP sheet is fixed later. Thus, a fixing device having no troubles can be provided.

Further, according to the present invention, there is provided a fixing device capable of simultaneously satisfying paper powder adhesion and abrasion.

[Brief description of the drawings]

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

FIG. 2 is a diagram illustrating a rolling contact state between a fixing roller and a pressure roller.

FIG. 3 is a front view showing a configuration of a driving mechanism.

FIG. 4 is a diagram illustrating a configuration angle in an experimental example performed to check an allowable range of an arrangement position of a heating roller with respect to a fixing roller.

FIG. 5 is a front view showing a configuration of a fixing belt.

FIG. 6 is a diagram illustrating a change in the amount of paper powder adhering to a heat-resistant elastic release layer when the fixing belt is continuously fed in an oilless state.

FIG. 7 is a diagram showing a change in the amount of paper powder adhering to a heat-resistant elastic release layer when the fixing belt is continuously fed in an oil dip state.

FIG. 8 is a front view schematically showing a configuration of a conventional fixing device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Fixing device 12 Housing 14 Bottom plate 16 Side plate 18 Upper cover part 20 Left cover part 22 Swing lever 24 First support shaft 26 Second support shaft 28 Fixing roller 28A Core part 28B Roller body 30 Pressure roller 30A Core metal Part 30B Roller body 32 First heating source 33 Second heating source 34 Heating roller (supporting roller) 36 Fixing belt 36a Belt base 36b Heat-resistant elastic release layer 38 Oil application roller 40 First coil spring 42 Second coil spring 44 Guide plate 46 Inlet port 48 Discharge passage 50 Lower discharge roller 52 Drive mechanism 54 Upper discharge roller 56 Leaf spring 58 First driven gear 60 One-way clutch 62 Transmission gear 64 Second driven gear 66 Collar 68 Casing 70 Guide rib 72 Idle gear 74 third driven gear 76 peeling claw 7 8 Discharge sensor 80 First thermistor 82 Second thermistor 84 Third thermistor 86 Control device EB Endless belt GE Output gear S Unfixed sheet

Claims (7)

[Claims] An image forming apparatus comprising: a fixing roller; a pressure roller which rolls on the fixing roller at a predetermined pressure; a support roller disposed apart from the fixing roller; and an endless loop between the support roller and the fixing roller. A fixing belt that has been passed, and a heating unit that heats the fixing belt and heats unfixed toner on a sheet passing through a rolling contact portion of the fixing roller and the pressure roller, and the unfixed toner is disposed on the surface. In a fixing device for fixing the unfixed toner on the sheet by passing the carried sheet along the rolling contact portion in one direction, the fixing belt includes an endless belt base, Comprising a heat-resistant release layer formed on the outer surface of the base,
The fixing device according to claim 1, wherein the hardness of the heat-resistant release layer is set to 30 degrees or more according to JIS A. 2. A fixing roller, a pressure roller which rolls in contact with the fixing roller at a predetermined pressure, a support roller disposed apart from the fixing roller, and an endless loop between the support roller and the fixing roller. A fixing belt that has been passed, and a heating unit that heats the fixing belt and heats unfixed toner on a sheet passing through a rolling contact portion of the fixing roller and the pressure roller, and the unfixed toner is disposed on the surface. In a fixing device for fixing the unfixed toner on the sheet by passing the carried sheet along the rolling contact portion in one direction, the fixing belt includes an endless belt base, Comprising a heat-resistant release layer formed on the outer surface of the base,
The 100% modulus load of this heat-resistant release layer is 3.5M.
A fixing device characterized by being set to Pa or less. 3. A fixing roller, a pressure roller which rolls in contact with the fixing roller at a predetermined pressure, a support roller disposed apart from the fixing roller, and an endless loop between the support roller and the fixing roller. A fixing belt that has been passed, and a heating unit that heats the fixing belt and heats unfixed toner on a sheet passing through a rolling contact portion of the fixing roller and the pressure roller, and the unfixed toner is disposed on the surface. In a fixing device for fixing the unfixed toner on the sheet by passing the carried sheet along the rolling contact portion in one direction, the fixing belt includes an endless belt base, Comprising a heat-resistant release layer formed on the outer surface of the base,
The fixing device according to claim 1, wherein a hardness of the heat-resistant release layer is set to 30 degrees or more according to JIS A, and a 100% modulus load of the heat-resistant release layer is set to 3.5 MPa or less. 4. The fixing device according to claim 1, wherein the heat-resistant release layer is formed with elasticity. 5. The fixing device according to claim 4, wherein said heat-resistant elastic release layer is formed of silicone rubber. 6. The fixing device according to claim 1, wherein the belt base is formed from an electroformed belt. 7. The fixing device according to claim 1, wherein the belt base is formed of a polyimide resin.