JP2017003606A - Belt fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress wear and drive torque of a fixing belt by preventing contact between the fixing belt and a fixing member at portions other than a nip part.SOLUTION: A heating roller 71 is disposed at a position separated from a fixing pad 74 as a fixing member, and a fixing belt 73 is laid over the heating roller 71 and fixing pad 74. The fixing member is separated from an inner peripheral surface of the fixing belt 73 at shoulder parts 74a located outside the entrance and exit of a nip part N.SELECTED DRAWING: Figure 2A

Description

The present invention relates to a belt fixing device and an image forming apparatus.

In recent years, a belt fixing method has been adopted as a fixing device used in an electrophotographic image forming apparatus such as a copying machine or a printer. In this belt fixing method, a fixing belt is wound around a fixing roller or a fixing pad and a heating roller, and the fixing roller or the fixing pad and the pressure roller are brought into pressure contact with each other via the fixing belt. In order to prevent the fixing belt from slipping and to increase the heat transfer efficiency from the heating roller to the fixing belt, tension is applied to the fixing belt to bring the fixing belt and the heating roller into close contact with each other.

In recent years, in order to reduce the size and cost of the belt fixing method, a fixing device using a fixing pad rather than a fixing roller tends to be used as disclosed in, for example, Japanese Patent Application Laid-Open No. 2004-286932. . In the apparatus using the fixing pad, as shown in FIGS. 7A and 7B, the fixing belt 73 to which a predetermined tension is applied is in sliding contact with the fixing pad 74, so that the driving torque of the fixing belt 73 is increased. is there.

Further, since the fixing belt 73 is in sliding contact with the fixing pad 74, there is another problem that the fixing belt 73 is easily worn. In particular, when a belt stretching member that applies tension to the fixing belt 73 is disposed, there is a problem that the fixing belt 73 is worn due to friction between the belt stretching member and the fixing belt 73.

An object of the present invention is to suppress wear and driving torque of the fixing belt.

In order to solve the above-described problems, the present invention provides a method in which a heated fixing belt is slid between a pressure member and a fixing member while the pressure member and the fixing member are in pressure contact with each other. The recording medium carrying the visualized developer is passed through the formed nip portion, so that the developer on the recording medium is transferred to the recording medium by the heat of the fixing belt and the pressure of the nip portion. In the fixing device configured to be heat-sealed on the heating roller, a heating roller is disposed at a position separated from the fixing member, the fixing belt is looped between the heating roller and the fixing member, and the nip portion In the belt fixing device, the shoulder portion of the fixing member located outside at least one of the inlet side and the outlet side of the fixing member is separated from the inner peripheral surface of the fixing belt.

In the present invention, since the shoulder portion of the fixing member located outside at least one of the inlet side and the outlet side of the nip portion is separated from the inner peripheral surface of the fixing belt, it is possible to suppress the wear and driving torque of the fixing belt. it can.

1 is a schematic view of an image forming apparatus according to an embodiment of the present invention. 1 is a schematic cross-sectional view of a belt fixing device according to an embodiment of the present invention. It is a schematic sectional drawing of the belt fixing device which concerns on embodiment of this invention which added the tension | tensile_strength provision member. It is a perspective view of a belt fixing device and an end support plate. 6 is a graph showing the relationship between the linear pressure of the belt fixing device and the R shape of the fixing belt. 2A and 2B are plan views of the fixing device shown in FIGS. 2A and 2B, where FIG. 2A is a state where the fixing belt is separated from the pressure roller, FIG. 2B is a state where the fixing belt is in contact with the pressure roller, and FIG. FIG. 4 is a plan view showing a state in which the fixing belt is in contact with the pressure roller and the fixing pad is in contact with the pressure roller. It is a top view similar to FIG. 5 which shows the deformation | transformation embodiment of this invention. (A) and (b) are schematic sectional views of a belt fixing device of a conventional image forming apparatus.

Embodiments of the present invention will be described below with reference to the drawings. In each of the drawings for explaining the embodiments of the present invention, constituent elements such as members and components having the same function or shape are described once by giving the same reference numerals as much as possible. Then, the explanation is omitted.

(Image forming device)
First, an overall configuration and operation of an image forming apparatus according to an embodiment of the present invention will be described with reference to FIG. The image forming apparatus 1 according to the present embodiment is a general electrophotographic color printer. However, the present invention is not limited to this. The configuration of the present invention can also be applied to an image forming apparatus such as a monochrome printer, other printers, a copier, a facsimile, or a complex machine thereof.

In the center of the apparatus main body of the image forming apparatus 1, four process units 2Y, 2M, 2C, and 2Bk as image forming units are arranged. Each process unit 2Y, 2M, 2C, 2Bk contains developers of different colors of yellow (Y), magenta (M), cyan (C), and black (Bk) corresponding to the color separation components of the color image. The configuration is the same except that.

Specifically, each process unit 2Y, 2M, 2C, 2Bk supplies a photosensitive member as a latent image carrier, a charging device as a charging means for charging the surface of the photosensitive member, and a developer to the surface of the photosensitive member. A developing device as a developing means for cleaning, a cleaning device as a cleaning means for cleaning the surface of the photoreceptor, and the like.

As the developer, for example, a toner containing oil-containing silica as an external additive can be used. The toner may be either pulverized toner or polymerized toner. In the embodiment, 2 parts of hydrophobic silica RY50 (manufactured by Aerosil) is added to 100 parts of toner, and a 20 L Henschel mixer is used to perform a mixing process at a peripheral speed of 40 m / sec for 5 minutes. Thereafter, the mixture was passed through a sieve having an opening of 75 microns to obtain a developer toner.

The process units 2Y, 2M, 2C, and 2Bk are configured to be detachable from the apparatus main body of the image forming apparatus 1. In the present embodiment, as shown by the one-dot chain line in FIG. 1, each process unit 2Y, 2M, 2C, 2Bk is removed upward by rotating the upper cover 3 of the apparatus main body upward, or vice versa. It can be attached from above.

Above each process unit 2Y, 2M, 2C, 2Bk, an exposure device 4 for exposing the surface of the photoreceptor is disposed. The exposure apparatus 4 is attached to the upper cover 3, and when the upper cover 3 is opened, the exposure apparatus 4 is retracted together with the upper cover 3 from above the process units 2Y, 2M, 2C, and 2Bk. With this configuration, the exposure apparatus 4 does not interfere with the process unit attaching / detaching operation.

Further, the image forming apparatus 1 includes a sheet feeding device 5 as a transfer material supply unit that supplies a sheet as a transfer material, and a transfer device 6 as a transfer unit that transfers an image formed by the image forming operation to the sheet. . The image forming apparatus 1 also includes a belt fixing device 7 as a fixing unit that fixes an image on a sheet, and a paper discharge roller 8 as a transfer material discharging unit that discharges the image to the outside of the device.

The transfer device 6 includes an endless intermediate transfer belt 9, four primary transfer rollers 10 as primary transfer means, a secondary transfer roller 11 as secondary transfer means, and the like. The four primary transfer rollers 10 are in contact with the photoreceptors of the process units 2Y, 2M, 2C, and 2Bk via the intermediate transfer belt 9. As a result, a primary transfer nip is formed at the contact portion between the intermediate transfer belt 9 and each photoconductor. The secondary transfer roller 11 contacts one of the rollers around which the intermediate transfer belt 9 is wound via the intermediate transfer belt 9, and a secondary transfer nip is formed at the contact portion.

In this embodiment, the secondary transfer roller 11 is attached to a front cover 12 that can be opened and closed. Therefore, as indicated by the one-dot chain line in FIG. 1, when the front cover 12 is rotated and opened forward, the secondary transfer roller 11 is separated from the intermediate transfer belt 9 accordingly. With this configuration, it becomes easy to perform a paper jam process in the secondary transfer nip.

(Image forming operation of image forming device)
Next, the image forming operation of the image forming apparatus 1 described above will be described. When the image forming operation is started, an image of each color is formed in each process unit 2Y, 2M, 2C, 2Bk. Specifically, in each process unit 2Y, 2M, 2C, and 2Bk, the photoconductor is rotationally driven, and the surface of the photoconductor is uniformly charged to a predetermined polarity by the charging device.

Next, the surface of the photoconductor is exposed by the exposure device 4 to form an electrostatic latent image. At this time, the image information exposed by the exposure device 4 is single-color image information obtained by separating a desired full-color image into color information of yellow, magenta, cyan, and black. Then, the developing device supplies toner to the electrostatic latent image on each photoconductor, and the electrostatic latent image is developed (visualized) as a toner image.

The toner images formed on the respective photoreceptors are sequentially superimposed and transferred onto the intermediate transfer belt 9 at the primary transfer nip. The toner on each photoconductor that could not be transferred to the intermediate transfer belt 9 is removed by a cleaning device.

Thereafter, the toner images on the intermediate transfer belt 9 are collectively transferred to the paper supplied from the paper feeding device 5 at the secondary transfer nip. Then, the paper that has passed through the secondary transfer nip is conveyed to the belt fixing device 7, and the toner image on the paper is fixed (heat fusion) by the belt fixing device 7. Thereafter, the paper is discharged out of the apparatus by the paper discharge roller 8.

The above description is an image forming operation when a full-color image is formed on a sheet. However, the image forming apparatus 1 can form images other than full-color images. For example, one of four process units 2Y, 2M, 2C, 2Bk is used to form a monochromatic image, or two or three process units are used to form a two-color or three-color image. It is also possible to do.

(Fixing device)
Hereinafter, an embodiment of the belt fixing device 7 of the present invention will be described with reference to FIGS. 2A to 6. The belt fixing device 7 according to the embodiment is a pad fixing method. The belt fixing device 7 is detachable from the main body. The difference between FIG. 2A and FIG. 2B is only the presence / absence of a leaf spring 90 as a tension applying member, and the other configurations are the same. The leaf spring 90 is disposed inside the fixing belt 73, but can be disposed outside the fixing belt 73. However, when the leaf spring 90 is disposed on the inner side, the fixing belt 73 swells outward, so that at least on the inlet side of the nip portion N, the shoulder portion 74a of the fixing pad 74 and the fixing belt 73 are easily brought into non-contact.

In order to make the nip width in the axial direction of the belt fixing device 7 uniform, in the present embodiment, unlike the prior art, the axial center of the pressure roller 76 connected to the first drive source is fixed. Instead, the fixing pad 74 as a fixing member is configured so as to be able to approach and separate (contact and separate) from the pressure roller 76, and the fixing pad 74 is pushed into the pressure roller 76 by the force of the urging means 81. A fixing nip N having a predetermined width is formed.

By simply pressing the fixing pad 74 into the pressure roller 76, when the elastic material 76a of the pressure roller 76 is thermally expanded, the fixing pad 74 is pushed back by the thermal expansion and the amount of pressing is changed. Then, the tension of the fixing belt 73 changes, and the fixing belt 73 moves in the axial direction due to the change in the tension, and the end of the fixing belt 73 is damaged. Further, a jam occurs when the direction of the paper passing path changes due to the change in tension.

Therefore, a structure in which the pressing amount of the fixing pad 74 does not change regardless of the thermal expansion of the elastic member 76a of the pressure roller 76 is required. In the embodiment of the present invention, the pressing amount of the fixing pad 74 against the elastic material 76a is not changed regardless of the thermal expansion of the elastic material 76a of the pressure roller 76.

That is, as described above, in the embodiment of the present invention, the fixing nip N is formed by pressing the fixing pad 74 into the elastic member 76 a of the pressure roller 76. When the fixing pad 74 is pushed in, a portion where the fixing pad 74 first contacts the pressure roller 76 via the fixing belt 73 is a portion where the elastic material 76 a is present.

As shown in FIG. 5, the fixing pad 74 is longer in the axial direction than the fixing belt 73, and both end portions of the fixing pad 74 protrude to both sides of the fixing belt 73 by a predetermined length. After the initial contact, both ends of the fixing pad 74 come into contact with the core metal land portion 76c without the elastic material 76a at both ends of the pressure roller 76. When the both ends of the fixing pad 74 are in contact with the core metal land portion 76c, the pressing of the fixing pad 74 is stopped. That is, the core metal land portion 76 c constitutes a stopper portion that restricts the position where the fixing pad 74 is closest to the pressure roller 76 by the urging means 81. Of course, the stopper portion is not limited to the above-described configuration and can be variously modified.

In this contact state, the distance between the relative axes of the pressure roller 76 and the fixing pad 74 is fixed. For this reason, even if the elastic material 76a of the pressure roller 76 undergoes thermal expansion, as long as the fixing pad 74 is pressed with a strong force that suppresses the thermal expansion, the pressing amount of the pressure roller 76 with respect to the elastic material 76a is constant. Can be kept unchanged.

The belt fixing device 7 is wound around a heating roller 71 including a heat source 72 such as a halogen heater, a fixing pad 74, a reinforcing stay 75 to which the fixing pad 74 is attached, and between the heating roller 71 and the fixing pad 74 so as to be able to circulate. The fixing belt 73 is included. Further, the belt fixing device 7 includes a pressure roller 76 disposed opposite to the fixing pad 74, a temperature sensor 78 that detects the temperature of the fixing belt 73, an end support plate that supports the heating roller 71 and the reinforcing stay 75. 621. When the temperature of the fixing belt 73 becomes too high, the temperature sensor 78 detects this and cuts off the power of the heat source 72.

The fixing pad 74 forms a fixing nip N with the pressure roller 76 via the fixing belt 73. The heat of the heating roller 71 is transmitted to the fixing belt 73, and the toner image T of the transfer material P introduced upward from below to the fixing nip N of FIGS. 2A and 2B is melted by the heat of the fixing belt 73. To settle. A conveying guide is disposed on the upstream side of the fixing nip N, and a separating unit and a conveying guide are disposed on the downstream side of the fixing nip N.

The rotation shaft of the heating roller 71 and the rotation shaft of the pressure roller 76 are supported by a support body disposed in the fixing device 1 at a fixed position. The rotating shaft of the heating roller 71 is supported by a circular hole 6211 of the end support plate 621 as a support as shown in FIG. 3, and the rotating shaft of the pressure roller 76 is another support plate as a support as shown in FIG. The bearing 80 is supported. The heating roller 71 and the pressure roller 76 are respectively connected to separate motors (first driving source and second driving source) as driving sources provided in the image forming apparatus via gear trains.

The fixing belt 73 is basically rotated by the action of the pressure roller 76 rotated by the first drive source, but is also driven by the rotation of the heating roller 71 rotated by the second drive source. That is, when the driving force of the pressure roller 76 is transmitted to the fixing belt 73 at the fixing nip N, the fixing belt 73 rotates and the fixing belt 73 is rotated by the rotation of the heating roller 71 on the side opposite to the fixing nip N. Auxiliary driven.

Here, the heating roller 71 can be driven at a peripheral speed of 1 to 10% higher than that of the pressure roller 76 in the same direction as the fixing belt 73. The lower limit of 1% means that the speed increases by + 1% or more even when the error is included. The reason why the speed-up driving is possible is as follows. Conventionally, a configuration for driving the fixing belt 73 is generally a configuration in which the fixing belt 73 is driven and driven by a driving force of a pressure roller 76 connected to a motor as a first driving source. In this case, the heating roller 71 only rotates following.

However, the belt transportability of the fixing belt 73 is most unstable when printing is performed, that is, when a sheet is interposed in the fixing nip N. When the fixing belt 73 is driven and driven only by the driving force of the pressure roller 76 as in the prior art, it is difficult to eliminate the conveyance instability. Therefore, the conveyance speed of the fixing belt 73 is stabilized by slightly increasing the peripheral speed of the heating roller 71 compared with the pressure roller 76.

(About the position of the rotary shaft of the pressure roller)
In the present embodiment, as described above, the rotation shaft of the pressure roller 76 is supported by the bearing 80 of the support body of the belt fixing device 7 in a fixed position. In this type of conventional belt fixing device 7, the fixing pad 74 is generally fixed to the support, and the rotation shaft of the pressure roller 76 is disposed on the support so as to be able to contact with and separate from the fixing pad 74. Yes. In this embodiment, in order to avoid the following problems, the rotary shaft of the pressure roller 76 is supported by a fixed position on a bearing 80 of the support.

That is, when the pressure roller 76 is arranged so as to be able to contact and separate from the fixing pad 74, if a gear is attached to the one end portion of the pressure roller 76 and rotated, the gear is transmitted when the rotational torque is transmitted. It also transmits tangential forces. Then, the pressing force of the pressure roller 76 against the fixing pad 74 is increased or decreased by the tangential force. Further, since the tangential force acts only on one side of the pressure roller 76 to which the gear is attached, the fixing nip width may be different in the axial direction. Therefore, when the pressing force of the pressure roller 76 increases toward the gear side end, a phenomenon occurs in which the fixing nip width becomes wider as the gear side end is approached.

In this way, when the left and right difference in the fixing nip width occurs in the axial direction, the fixing belt 73 tends to move to one side, and when the fixing belt 73 moves to one end, the end of the fixing belt 73 is the end of the fixing pad 74. It rides on the belt receiver of the part or breaks due to contact friction with the belt receiver. When tested in this embodiment, in the case where the fixing nip width was set to 5 mm, the fixing nip width was 5.3 mm on the gear driving side, and the fixing nip width was 5 mm on the center and the non-driving side. If the fixing belt 73 continues to rotate in this state, the end of the fixing belt 73 was damaged in about one hour.

In order to avoid such a problem, it is necessary to make the fixing nip width equal to the left and right in the axial direction by fixing the rotational axis of the pressure roller 76 in position. In the present embodiment, the rotation shaft of the pressure roller 76 is fixed in position, while the fixing pad 74 is disposed so as to be movable with respect to the pressure roller 76, that is, to be able to contact with and separate from the pressure roller 76. Hereinafter, the movable structure of the fixing pad 74 will be described with reference to the end support plate 621 of FIG.

(About the end support plate)
FIG. 3 is a diagram illustrating a configuration of an end support plate 621 as a support member that supports both ends of the heating roller 71 and the reinforcing stay 75 of the belt fixing device 7. The end support plate 621 is formed in a rectangular plate shape with a resin having slidability and heat resistance.

In the present embodiment, the material of the end support plate 621 is PTFE (polytetrafluoroethylene) that is less aggressive to the fixing belt 73. In addition to this, the material of the end support plate 621 may be a liquid crystal polymer, PPS (polyphenylene sulfide), PAI (polyamideimide), or the like, which is a resin having heat resistance and excellent slidability. The material of the end support plate 621 may be a heat resistant fluororesin. Thereby, both heat resistance and slidability can be achieved, and the life of the fixing belt 73 can be extended.

The end support plate 621 has a circular hole 6211 and a rectangular hole 6212 side by side. The circular hole 6211 is a shaft hole that rotatably supports the end of the rotating shaft of the heating roller 71. The rectangular hole 6212 is a stay support hole that supports the end of the reinforcing stay 75.

A concave groove 6214 and a concave groove 6215 are formed at both upper and lower edges of the end support plate 621. These concave grooves 6214 and 6215 are for attaching the end support plate 621 to the plate-like frame of the belt fixing device 7. That is, the concave grooves 6214 and 6215 of the end support plate 621 can be engaged with the upper and lower edges of the lateral cutout formed in the plate frame from the horizontal direction.

The end support plates 621 having the same shape are arranged in parallel with each other in a pair of left and right. Accordingly, the circular hole 6211 and the stay support hole 6212 can be arranged symmetrically, and the heating roller 71 and the fixing pad 74 can be accurately paralleled. By accurately paralleling the heating roller 71 and the fixing pad 74, the lateral deviation of the belt tension that causes the meandering is prevented, and the fixing belt 73 is difficult to meander, and the life of the fixing belt can be extended.

The stay support hole 6212 supports the reinforcement stay 75 so as to be slidable in the left-right direction in FIG. The lateral width of the stay support hole 6212 is formed to be slightly wider than the reinforcement stay 75, and an urging means 81 such as a spring for urging the reinforcement stay 75 rightward in FIG.

Thus, by making the reinforcement stay 75 slidable in the left-right direction, a predetermined tension can be applied to the fixing belt 73. By applying a predetermined tension to the fixing belt 73, a predetermined curvature radius of the bent portion 73a of the fixing belt 73 (a portion adjacent to the inlet side and the outlet side of the nip portion N) is maintained. A non-contact state with the shoulder 74a is maintained. Further, even if the pressure roller 76 has a dimensional variation in the radial direction, the pressure of the nip portion N can be kept constant.

The opposing surfaces of the pair of end support plates 621 facing each other are planar meandering restricting surfaces 6213 as meandering restricting portions. The meandering restriction surface 6213 is formed on the entire surface of one end of the end support plate 621, and the entire circumferential direction of the left and right side edges of the fixing belt 73 can be brought into contact with the meandering restriction surface 6213.

In this embodiment, since the meandering restricting surface 6213 is formed on the end support plate 621 which is a support member for the heating roller 71 and the reinforcing stay 75, the belt fixing device 7 can be reduced in size and cost. The meandering restriction surface 6213 is not necessarily formed on the entire surface of one side of the end support plate 621. It may be formed only in a necessary region such as at least around the circular hole 6211 on the side opposite to the fixing pad 74. Thereby, the friction between the meandering restriction surface 6213 and the fixing belt 73 can be reduced.

In the present embodiment, since the end support plates 621 are positioned on the sides of the entire circumference of both ends of the fixing belt 73, the entire circumference of both ends of the fixing belt 73 is regulated in the width direction by the end support plates 621. That is, when the fixing belt 73 meanders in the direction of arrow C in FIG. 3, the position of the fixing belt 73 is restricted by contacting the meandering restricting surface 6213 of the end support plate 621 with the entire circumference of one end of the fixing belt 73. In short, the meandering restriction surface 6213 functions as a deviation regulating member that regulates the deviation of the fixing belt 73.

(About heating roller)

The heating roller 71 has a hollow cylindrical shape. The heating roller 71 is manufactured by processing a metal pipe material such as aluminum, iron, and stainless steel. In the embodiment, an iron pipe material having a predetermined diameter is cut into a predetermined length to form the heating roller 71.

As the heat source 72 inside the heating roller 71, a resistance heating element or a carbon heater can be used as long as the gap with the heating roller 71 is small and there is almost no gap at the end of the heating roller 71 in addition to the halogen heater. is there. Further, electromagnetic induction heating or the like can be used as the heat source 72. In the embodiment, a 550 w halogen heater is used.

The heating roller 71 of the present embodiment has a cylindrical shape whose inner diameter is 1 mm larger than the apparent diameter of the heating means. The inner surface of the heating roller 71 is painted black in order to easily absorb radiant heat from a halogen heater or the like.

A lubricant such as silicone oil or fluorine grease is applied to the inner surface of the fixing belt 73 to reduce friction between the fixing pad 74 and the sliding sheet 77. For this reason, a lubricant may be interposed between the heating roller 71 and the fixing belt 73.

The force with which the fixing pad 74 presses the pressure roller 76 is transmitted from the sliding sheet 77 to the fixing belt 73 and is received by the pressure roller 76. The heating roller 71 is directly connected to the second drive source, the rotation direction of the heating roller 71 is the same as that of the fixing belt 73, and the speed (circumferential speed) is 1 to 1 higher than that of the pressure roller 76 as described above. Each is set to be about 10% faster.

Since the heating roller 71 also has an object of assisting the conveyance of the fixing belt 73 by positively rotating, the surface of the heating roller 71 is slightly roughened in order to transmit the driving force of the heating roller 71 to the fixing belt 73 without loss. (For example, a surface roughness Ra of 10 or less), the lubricant may be easily retained. As a method of roughening the surface of the heating roller 71, a method of physically roughing such as sand blasting, a method of chemically roughing such as etching, or a method of applying a paint mixed with small diameter beads However, any method can be adopted.

The friction between the heating roller 71 and the inner surface of the fixing belt 73 is prevented from occurring due to the speed difference. As a result, only the nip portion N of the fixing pad 74 is in contact with the inner surface of the fixing belt 73 with a speed difference. As a result, the driving torque of the fixing belt 73 can be reduced.

(Fixing pad)
The fixing pad 74 as a fixing member can be made of an elastic body such as silicone rubber or fluororubber, or a metal such as heat resistant resin or phosphor bronze. In particular, phosphor bronze has a high thermal conductivity and is effective in soaking the fixing belt 73. That is, when the width direction light emitting region (heating region) of the heat source 72 is different from the width size or position of the transferred transfer material P, the heat transfer in the axial direction is promoted by the fixing pad 74 having high thermal conductivity. Thus, the temperature difference in the axial direction of the fixing belt 73 can be reduced.

The fixing pad 74 is supported by a bar-shaped reinforcing stay 75 having a rectangular cross section. The reinforcing stay 75 is urged toward the pressure roller 76 by a spring or the like, so that the fixing pad 74 is pressed against the pressure roller 76.

The central portion of the fixing pad 74 forms a nip portion N by being pressed against the pressure roller 76 via the fixing belt 73. The shape of the shoulder 74a of the fixing pad 74 on the inlet side (upstream side) and the outlet side (downstream side) of the nip portion N is such that the fixing belt 73 before and after the nip portion N is not in contact with the fixing belt 73. The curved portion 73a has an arc shape with a smaller radius of curvature than the radius of curvature of the curved portion 73a. Accordingly, the bent portion 73a of the fixing belt 73 enters and exits in the tangential direction without contacting the shoulder portion 74a of the fixing pad 74 with respect to the inlet side and the outlet side of the nip portion N.

An operating member such as a lever can be connected to both ends of the reinforcing stay 75, and the reinforcing stay 75 can be moved back and forth (left and right in FIGS. 2A and 2B) by the operating member. By the back and forth movement, it is possible to switch between pressing and releasing of the fixing pad 74 against the pressure roller 76. By allowing the fixing pad 74 to be released at least during jam processing, the transfer material P can be easily removed when a jam occurs.

As shown in the cross sections of FIGS. 2A and 2B, the fixing pad 74 has a convex shape in which the pressure roller 76 swells in an arc shape. The projecting height of the convex shape toward the pressure roller 76 is maximum at the axial center, and the axial center is gradually convex by about 0.5 mm from both axial ends. The central portion in the axial direction has a convex shape with the largest overhang height.

This is because a maximum bending deflection is generated in the central portion in the axial direction due to a reaction force received from the pressure roller 76 by the fixing pad 74 and the reinforcing stay 75 as a structure thereof. In order to solve the shortage of the fixing nip pressure, the above-described convex shape is set. Depending on the magnitude of the load applied to the fixing pad 74 by the reinforcing stay 75, the structure of the reinforcing stay 75, and the size of the transfer material P such as the A3 and A4 sizes, the size of the convex shape is about 0.5 mm at the maximum.

2A and 2B, the pressure side (right side) of the fixing pad is in contact with the inner surface of the fixing belt 73 via the sliding sheet. In order to stabilize the rotation of the fixing belt 73, heat-resistant grease can be used as a lubricant between the sliding sheet and the fixing belt 73 as necessary. It is also possible to bring the pressure side of the fixing pad into direct contact with the inner surface of the fixing belt 73 without a sliding sheet. In this case, a layer having high slidability can be coated on the pressure side of the fixing pad as necessary.

These members are brought into direct contact with the inner surface of the fixing belt 73 by coating a sliding sheet or a highly slidable layer. In the embodiment, a resin pad and a sliding sheet are used. Further, the fixing belt is slid between the inner surface of the fixing belt 73 and the sliding sheet via a lubricant such as grease or silicone oil.

Here, a fixing nip N is formed using a load from the pressure roller 76 via a sliding sheet or a fixing belt 73, and the toner is thermally melted and fixed by pressure and heat in the fixing nip N. Can do.

(Fixing belt)
The fixing belt 73 is an endless belt having both flexibility and a predetermined flexural rigidity to a thin, rotating (traveling) in FIG. 2 A, an arrow direction in FIG. 2B (counterclockwise direction). The fixing belt 73 has a base material layer, an elastic layer, and a release layer sequentially laminated from the inner peripheral surface (the sliding contact surface with the fixing member 26) side, and the total thickness thereof is 1 mm or less. Is set.

The base material layer of the fixing belt 73 has a layer thickness of 30 to 50 μm and is formed of a metal material such as nickel or stainless steel or a resin material such as polyimide, polyamide, or fluororesin. In the embodiment, polyimide is used. The back surface roughness (roughness of the surface in contact with the heating roller 71) of the polyimide base material of the fixing belt 73 is Ra5 or less. Silicone oil or grease is applied to the inner surface of the fixing belt 73.

The elastic layer of the fixing belt 73 has a layer thickness of 100 to 300 μm and is formed of a rubber material such as silicone rubber, foamable silicone rubber, or fluororubber. By providing the elastic layer, minute irregularities on the surface of the fixing belt 73 in the nip portion are not formed, and heat is uniformly transmitted to the toner image T on the transfer material P, so that generation of a scum skin image is suppressed.

In the absence of an elastic layer such as a silicone rubber layer, the heat capacity is reduced and the temperature rise is improved, but the unfixed toner image cannot be uniformly crushed and the subtle unevenness of the paper surface is fixed during fixing. There arises a problem that the corresponding image remains. In order to improve this, it is necessary to provide an elastic layer such as a silicone rubber layer, preferably 100 μm or more. Due to such deformation of the elastic layer, subtle irregularities are absorbed, and the skin image is improved.

The elastic layer is covered with a release layer so as to ensure release properties (peelability) so that the toner on the transfer material P does not adhere to the fixing belt 73. The release layer has a layer thickness of 5 to 50 μm, such as PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), PTFE (polytetrafluoroethylene), polyimide, polyetherimide, PES (polyether sulfide), etc. It is made of material.

In the embodiment, an elastic material 76a having a thickness of 100 μm and a PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer) tube having a thickness of 20 μm are coated on the outermost layer. The diameter of the fixing belt 73 is set to be 15 to 120 mm. In the first embodiment, the inner diameter of the fixing belt 73 is set to 30 mm.

In the absence of a silicone rubber layer, the heat capacity is reduced and the temperature rise is improved, but the unfixed toner image cannot be uniformly crushed, and an image corresponding to subtle irregularities on the surface of the paper at the time of fixing. The problem of remaining is caused. In order to improve this, it is necessary to provide a silicone rubber layer of 100 μm or more. Due to the deformation of the silicone rubber layer, subtle irregularities are absorbed and the skin image is improved.

The tension load applied to the fixing belt 73 is 100 to 250 N when the transfer material P is A4 size. The tension load is applied by installing members such as a tension roller, a leaf spring, and a cleaning roller on the span of the fixing belt 73.

If the tension load of the fixing belt 73 is too small, the adhesion force between the fixing belt 73 and the heating roller 71 becomes insufficient, and the driving force and heat of the heating roller 71 are not sufficiently transmitted to the fixing belt 73, so Slip and insufficient heating occur. On the other hand, even if the tension load is too large, the fixing belt 73 is bent at the shoulder portion 74a of the fixing pad 74, so that the fixing belt 73 slips.

It should be noted that the shoulder 74 a of the fixing pad 74 should avoid a curvature of R 1 or less in order to prevent the fixing belt 73 from being bent. Since the tension or adhesion force of the fixing belt 73 cannot actually be measured, a good tension can be set without causing the above-mentioned problem by performing a weight management from 0.5 N / m to 10 N / m. . Further, it is also possible to make the shoulder portion 74 a a member different from the fixing pad 74 and to dispose a “guide plate” constituting, for example, a nip forming member in the belt inner region before and after the nip portion N without contacting the fixing belt 73. is there.

For example, when the inner diameter of the fixing belt 73 is 25 mm or less in a natural state, the fixing belt is made of a polyimide base material with a thickness of 50 μm, and the fixing belt 73 is formed using the strength (bending rigidity) of the fixing belt 73 due to the thickness. You may just make it elliptical.

(Pressure roller)
The pressure roller 76 is a hollow or solid metal roller. The pressure roller 76 is manufactured by processing a metal pipe material such as aluminum, iron, and stainless steel or a solid bar material. In the embodiment, a pressure pipe 76 is formed by cutting an iron pipe material having a predetermined diameter into a predetermined length.

A wide and shallow groove 76 b is formed in the circumferential direction on the circumferential surface of the pressure roller 76. A thermally stable elastic material 76a is provided in the groove 76b in order to ensure the width, pressure, etc. of the fixing nip N. In order to obtain the release property of the transfer material P, a release layer (PFA resin layer or PTFE resin layer) can be provided on the outer surface of the elastic material 76a. In the embodiment, the thickness of the elastic member 76a of the pressure roller 76 is 6 mm.

The elastic member 76a can be made of, for example, silicone rubber, solid rubber, or foamed sponge rubber. When sponge rubber is used, heat insulation is enhanced, and heat of the fixing belt is hardly transmitted to the core metal of the pressure roller 76. It is desirable that the heat of the fixing belt is difficult to conduct to the cored bar because accuracy of temperature control of the fixing belt is increased.

The pressure roller 76 has a cored land portion 76c without an elastic material 76a at both ends on the outer side of the groove 76b. Comparing the diameter Da of the land portion 76c and the diameter Db of the elastic material 76a, the diameter (Da = Db) is equal or the diameter Db of the elastic material 76a is larger (Da <Db).

Since the fixing pad 74 urged by the urging means 81 such as a spring is pressed against the elastic material 76 a of the pressure roller 76 as described above, the fixing pad 74 is attached to the elastic material 76 a of the pressure roller 76. The elastic material 76a is crushed and deformed in the form of biting. As a result, a predetermined nip width is formed in the fixing nip N. The nip width can be set to 5 mm, for example. Further, a heat source such as a halogen heater may be provided inside the pressure roller 76. In the embodiment, the halogen heater is only inside the heating roller 71. The pressure roller 76 is rotationally driven by a driving force transmitted from a first drive source such as a motor provided in the image forming apparatus 1 via a gear train.

(Fixing belt drive torque)
As described above, the fixing belt 73 has its bending rigidity and tension set so as to maintain no contact with the shoulder 74a of the fixing pad 74. For this reason, it is possible to reduce the wear and driving torque of the fixing belt 73 by the heating roller 71 as compared with the conventional belt fixing device as shown in FIG.

Further, in FIG. 2B, since the tension is applied to the fixing belt 73 also by the plate spring 90, the plate spring 90 is in sliding contact with the fixing belt 73 with a speed difference, but the plate spring 90 is in the traveling direction of the fixing belt 73. Change little or no. For this reason, torque increase by the leaf spring 90 with time does not occur at all or hardly. Although there is little or no torque increase, the tip sliding contact portion of the leaf spring 90 is preferably a low friction member containing fluorine, for example.

Table 1 below shows changes in the driving torque of the fixing belt 73.

Here, the driving torque of Conventional Example 1 increased after 50 hours because of friction between the fixing belt 73 and the fixing pad 74. Further, the driving torque increased after 50 hours in Conventional Example 2 because the inner surface of the fixing belt 73 was scraped and the scraped powder was mixed with grease, so that the lubricant disappeared. From the results shown in Table 1, it was found that it is desirable that the shoulder 74a of the fixing pad 74 is not in contact with the fixing belt 73 on the inlet side and the outlet side of the nip portion N in order to stably reduce the driving torque.

(Conditions for fixing belt not to contact with shoulder of fixing pad)
FIG. 4 shows conditions for preventing the fixing belt 73 from contacting the shoulder 74 a of the fixing pad 74. The R shape of the bent portion 73a was measured using polyimide having a thickness of 70 μm as the base material of the fixing belt 73. The one-dot chain line in the figure is the case of the fixing belt 73 in which the silicone rubber is 0 μm (no rubber) on the substrate, and the solid line is the fixing belt 73 in which the silicone rubber is 180 μm (rubber hardness is 1 degree) on the substrate. This is the case.

As can be seen from FIG. 4, for example, when the tension (linear pressure) applied to the fixing belt 73 without silicone rubber is 1.4 kgf / m, the curvature radius of the bent portion 73a of the fixing belt 73 is 3 mm. For this reason, in order to make the shoulder portion 74a of the fixing pad 74 non-contact at the portion, the shape of the shoulder portion 74a is set to a radius of curvature of about 2 mm (R2) so that the gap with the fixing belt 73 is about 0.5 mm. Can be. The shoulder 74a is reliably secured from the fixing belt 73 by reducing the radius of curvature of the shoulder 74a of the fixing pad 74 by about 1 mm from the radius of curvature (vertical axis in FIG. 4) of the bent portion 73a even under other tension (linear pressure). Can be separated.

Further, when there is silicone rubber on the base material of the fixing belt 73, the bending rigidity of the belt increases, so that the radius of curvature of the bent portion 73a of the fixing belt 73 increases. In this case, the radius of curvature of the shoulder portion 74a of the fixing pad 74 does not necessarily have to be increased in a range not contacting the belt. However, there is a possibility that the belt tension changes for some reason and the belt temporarily contacts the shoulder 74a of the fixing pad 74. In order to stabilize the slidability of the belt with respect to the nip portion N in such a case, it is desirable that there is no gap larger than necessary between the shoulder portion 74a and the bent portion 73a of the fixing belt 73.

(Fixing pad operation)
Of the urging force of the urging means 81 applied to the fixing pad 74, the urging force necessary for fixing is applied to the elastic member 76 a of the pressure roller 76. Other than that, it is given to the core metal land portion 76c at both axial ends of the pressure roller 76. As shown in FIG. 5A, when no load is applied to the fixing pad 74, the fixing belt 73 and the pressure roller 76 are not in contact with each other, and there is a gap between them. The fixing belt 73 is always tensioned by a biasing means 81 such as a spring in a state where the fixing belt 73 is stretched between the heating roller 71 and the fixing pad 74. The inner surface of the fixing belt 73 is in close contact with the fixing pad 74 via the sliding sheet 77.

When a load is applied to the fixing pad 74, the fixing belt 73 facing the pressure roller 76 approaches the pressure roller 76 as shown in FIG. Then, the fixing pad 74 and the fixing belt 73 start to push the elastic material 76a portion of the pressure roller 76. Thereafter, as shown in FIG. 5C, when both ends of the fixing pad 74 come into contact with both end core metal land portions 76c of the pressure roller 76, the pressing of the fixing pad 74 is finished.

Here, if the height of the metal core land portions 76 c at both ends of the pressure roller 76 and the height or thickness of the elastic material 76 a are set to desired values, the magnitude of the load acting on the elastic material 76 a via the fixing belt 73. That is, it is possible to control the magnitude of the load necessary for fixing the toner image T of the transfer material P. In the embodiment, the load applied to the fixing pad 74 is set to be about 10 to 20 N larger than the desired value.

By doing so, it is possible to apply the intended load to the elastic member 76a via the fixing belt 73 even if the height of the core metal land portion 76c and the variation in the height or thickness of the elastic member 76a are taken into consideration. It is. The desired value at this time is a load value required to act on the elastic material 76a for toner fixing in a state where the elastic material 76a of the pressure roller 76 is thermally expanded after the fixing belt 73 is heated.

The elastic material 76a is arranged so that the elastic material 76a of the pressure roller 76 and the core metal land portions 76c at both ends of the pressure roller 76 are continuous without a gap. In FIG. 5, small gaps are intentionally illustrated at both ends of the elastic member 76a in order to clarify the boundary of the elastic member 76a, but the gap is not actually provided.

If there is a gap between both end portions of the elastic material 76a and the edge of the groove 76b of the pressure roller 76, the elastic material 76a is axially moved so that the fixing pad 74 bites into the elastic material 76a to eliminate the gap. Deforms outward. Then, the deformation of the elastic material 76a leads to a pressure drop at both ends in the axial direction of the fixing nip N, and the originally required fixing nip pressure cannot be obtained at both ends in the axial direction, thereby ensuring the desired fixability. Can not be.

Further, due to the deformation of the elastic member 76a outward in the axial direction, the fixing nip width of the deformed portion becomes narrow, which may cause paper wrinkling. For this reason, it is necessary to set the axial length of the elastic member 76a so that there is no gap between both ends of the elastic member 76a.

Although the amount of thermal expansion in the radial direction of the elastic member 76a of the pressure roller 76 depends on the temperature and rubber characteristics, a thermal expansion amount of about 10% of the thickness of the elastic member 76a occurs when the temperature changes from 150 ° C to 200 ° C. In the embodiment, since the thickness of the elastic member 76a is 6 mm, it thermally expands radially outward (fixing pad 74 side) by about 0.6 mm. When the elastic material 76a thermally expands to the fixing pad 74 side by 0.6 mm, generally, the fixing pad 74 is pushed down by a little 0.6 mm.

Since the fixing belt 73 is wound around with a necessary amount of tension, it varies depending on the rubber characteristics and applied load, but even if the fixing pad 74 is pushed back and forth about 0.4 mm, it is a tension applying member. The operating range of the leaf spring is increased, and the belt tension may be reduced. As a result, the contact width between the meandering restriction flange at the end of the fixing pad 74 and the end of the fixing belt 73 is shortened, and as a result, the end of the fixing belt 73 tends to be damaged with respect to the axial direction of the fixing belt 73. In the present embodiment, the meandering restriction flange is constituted by the meandering restriction surface 6213 of the end support plate 621.

As described above, the tension compensation of the fixing belt 73 corresponding to the thermal expansion of the pressure roller 76 can be supported to some extent by the leaf spring, but stable belt running is not necessarily guaranteed. This time, the amount of thermal expansion of the pressure roller 76 is changed to check whether or not the end of the fixing belt 73 is damaged. The end of the fixing belt 73 is damaged even if the fixing pad 74 is retracted to 0.3 mm. Stable paper feeding was possible without any problems.

However, when the fixing pad 74 is retracted to 0.4 mm, the end of the fixing belt 73 is damaged by passing 1500 sheets (printing 3 sheets at 180 mm / s for about 1 hour in time and repeating a short break). Was confirmed. For this reason, the allowable backward movement length of the fixing pad 74 needs to be set including a margin for damage to the end of the fixing belt 73, and is desirably limited to an amount of backward movement of 0.2 mm or less.

When the transfer material P passes through the fixing nip N, the fixing pad 74 moves backward by the thickness of the transfer material P. Since the thickness of the transfer material P is about 0.05 to 0.1 mm, the allowable amount of retraction is about 0.1 mm when considered together with the retraction restriction amount (0.2 mm or less) of the fixing pad 74. Further, it can be seen that the fixing pad 74 should not be retracted due to the thermal expansion of the elastic member 76a of the pressure roller 76.

The stop position of the fixing pad 74 is set to the same position every time by stopping the pressing of the fixing pad 74 in a state where the fixing pad 74 is in contact with the land portion 76c of the metal core without the elastic material 76a at the end of the pressure roller 76. can do. That is, the land portion 76 c of the core metal serves as a reference for the pressing depth of the fixing pad 74.

If the contact width between the meandering restriction flange portion (meandering restriction surface 6213 in FIG. 3) of the fixing pad 74 and the end portion of the fixing belt 73 is set at the position set by the core metal land portion 76c, the fixing belt is set. It is possible to avoid the end portion damage of the belt 73 and to ensure the stable running of the fixing belt 73 over a long period of time. Even if the end of the fixing belt 73 comes into contact with the meandering restriction surface 6213, the fixing belt 73 is not in contact with the shoulder 74a of the fixing pad 74. Therefore, an increase in driving torque of the fixing belt 73 due to the contact is ignored. It is possible.

From the above, in order to make the fixing nip width uniform in the axial direction, the position of the rotary shaft of the pressure roller 76 is fixed, and the land portion 76c of the metal core without the elastic material 76a at both ends of the pressure roller 76 is provided. The fixing pad 74 is pressed. The fixing pad 74 only retreats as the transfer material P passes, and the fixing pad 74 is prevented from retreating due to the temperature of the fixing belt 73, thereby realizing a stable running of the fixing belt 73. Proven to be possible. The width of the fixing belt 73 in the axial direction is shorter than the elastic material 76 a of the pressure roller 76 so that the end of the fixing belt 73 is not sandwiched between the end of the pressure roller 76 and the fixing pad 74.

Regarding the deformation of the elastic member 76a, the thickness of the elastic member 76a after the deformation is 80% or more (deformation rate less than 20%) before the deformation. This is less than 80% (deformation rate of 20% or more), and if the pressing is continued for a long time, the elasticity is somewhat lost due to permanent strain, and a predetermined contact pressure set between the fixing pad 74 and the pressure roller 76 can be secured. This is because it disappears. If a predetermined contact pressure cannot be secured, problems such as uneven fixing nip width in the axial direction, end damage due to axial movement of the fixing belt 73, and jamming may occur.

(Modified embodiment)

In the modified embodiment of FIG. 6, both end portions of the fixing pad 74 abut on the bearing portion 79 that supports the pressure roller 76 in a freely rotatable manner or the periphery of the bearing portion 79 so as to fulfill the function of the stopper portion. ing. Since the pressure roller 76 rotates, wear and frictional heat are generated between the pressure pad 76 and the fixing pad 74, but there is an advantage that friction and frictional heat are not generated because the bearing and the peripheral portion of the bearing do not rotate.

Further, not both ends of the fixing pad 74 but both ends of the reinforcing stay 75 abut on the core metal land portions 76c at both ends where the elastic material 76a of the pressure roller 76 is not provided so as to function as the stopper portion. It may be. Further, both end portions of the reinforcing stay 75 are in contact with a pair of bearing portions 79 disposed at both axial end portions of the pressure roller 76 and rotatably supporting the pressure roller 76 or the periphery of the bearing portion 79. You may make it fulfill | perform the function of the said stopper part.

Alternatively, both ends of the reinforcing stay 75 may abut on the end of the rectangular hole 6212 of the end support plate 621 so as to fulfill the function of the stopper. As described above, the stopper portion can be variously configured and is not limited to the above-described embodiment.

In the modified embodiment of FIG. 6, the core metal land portion 76 c is not used as a stopper portion, so the groove 76 b of the pressure roller 76 may not be provided. When the groove 76b is omitted, there is an advantage that the processing cost of the pressure roller 76 can be reduced. Moreover, the bearing part 79 of FIG. 6 is a conceptual thing, The shape and position are not limited to the example of illustration. For example, an end support plate 621 as shown in FIG.

The present invention has been specifically described above based on the embodiments and modified embodiments. However, the present invention is not limited to the above-described embodiments and modified embodiments, and the technical idea described in the scope of the claims is not limited. It goes without saying that various changes can be made within the range.

For example, in the embodiment, the pressure member is configured by the pressure roller 76 and the fixing member is configured by the fixing pad 74, but the pressure member and the fixing member are not limited thereto. For example, as described in Japanese Patent Application Laid-Open No. 2007-140309, the present invention can also be applied to a belt fixing apparatus having an upstream first nip formed by a roller pair and a downstream second nip formed by a pad pair.

In the embodiment, the shoulder 74a of the fixing pad 74 is not in contact with the fixing belt 73 on both the inlet side and the outlet side of the nip portion N. However, the shoulder 74a of the fixing pad 74 is not necessarily on the inlet side and the outlet side. It is not necessary to make contact with the fixing belt 73 in both cases. Depending on the model of the image forming apparatus, the shoulder 74a of the fixing pad 74 is not in contact with the fixing belt 73 only on one of the inlet side and the outlet side of the nip portion N, and on the other hand, the shoulder 74a is in contact with the fixing belt 73 as usual. May be.

1: Image forming apparatus 2Y, 2M, 2C, 2Bk: Process unit 3: Upper cover 4: Exposure device 5: Paper feeding device 6: Transfer device 7: Fixing device 8: Paper discharge roller 9: Intermediate transfer belt 10: Primary transfer Roller 11: Secondary transfer roller 12: Front cover 71: Heating roller 72: Heat source 73: Fixing belt 73a: Bending portion 74: Fixing pad 74a: Shoulder portion 75: Reinforcement stay 76: Pressure roller 76a: Elastic material 76b: Groove 76c: Core metal land portion 77: Sliding sheet 78: Temperature sensor 79: Bearing portion 80: Bearing 81: Biasing means 621: End support plate 6211: Circular hole 6212: Rectangular hole (stay support hole) 6213: Meander restriction Surface 6214: Concave groove 6215: Concave groove N: Fixing nip P: Transfer material T: Toner image

JP 2004-286932 A

Claims (7)

A heated fixing belt is slid between the pressure member and the fixing member in pressure contact with each other, and the image is visualized in a nip portion formed between the fixing belt and the pressure member. The fixing device which allows the developer on the recording medium to be thermally fused onto the recording medium by the heat of the fixing belt and the pressure of the nip portion by passing the recording medium carrying the developer. In
A heating roller is disposed at a position spaced apart from the fixing member, the fixing belt is looped between the heating roller and the fixing member, and is positioned outside at least one of the inlet side and the outlet side of the nip portion. A belt fixing device in which a shoulder portion of the fixing member is separated from an inner peripheral surface of the fixing belt.   2. The belt fixing device according to claim 1, wherein a radius of curvature of the shoulder portion of the fixing member is made smaller than a radius of curvature of the fixing belt at portions adjacent to the inlet side and the outlet side of the nip portion.   3. The belt according to claim 1, further comprising a tension applying member that increases a tension of the fixing belt by slidingly contacting the fixing belt between the fixing member and the heating roller with a predetermined pressure. Fixing device.   The fixing belt is formed of a resin such as polyimide or a metal such as nickel, and has a predetermined bending rigidity necessary for the fixing belt to be separated from a shoulder portion of the fixing member. The belt fixing device according to any one of 1 to 3.   The pressure member has a pressure roller driven by a first drive source, and the heating roller is driven at a higher speed than the pressure member by a second drive source. The belt fixing device according to any one of the above.   6. A deviation regulating member that regulates a deviation of the fixing belt by arranging the entire circumference of the fixing belt at both ends of the fixing member is disposed. The belt fixing device according to claim 1.   An image forming apparatus comprising the belt fixing device according to claim 1.

Images