JP2012108186A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device that suppresses slip phenomenon of driven members due to deterioration over time or environmental change without increasing the number of components, and provides excellent image quality, and an image forming apparatus.SOLUTION: A fixing device includes: a fixing belt 21; a pressuring roller that comes into contact with an outer peripheral surface of the fixing belt 21; a contact member that is disposed at inner peripheral side of the fixing belt 21, and comes into contact with the pressuring roller via the fixing belt 21 to form a nip part; and heating means that heats the fixing belt 21. The fixing belt 21 is formed by laminating an elastic layer 21b and a release layer 21c on a base material 21a; and the base material 21a is exposed contactably with the pressuring roller in at least a part of a non-paper passage area that is an area where a recording medium does not pass at the nip part.

Description

  The present invention relates to a fixing device for fixing toner on a recording medium by heat and pressure, and image formation such as FAX, printer, copying machine or their combined machine using an electrophotographic system, electrostatic recording system, etc. equipped with the fixing device. It relates to the device.

  Conventionally, various image forming apparatuses using an electrophotographic system have been devised as image forming apparatuses such as copying machines and printers, and are well known in the art. In the image forming process, an electrostatic latent image is formed on the surface of the photosensitive drum as an image carrier, and the electrostatic latent image on the photosensitive drum is developed with a toner as a developer to be visualized and developed. The image is transferred to a recording medium (also referred to as a fixing material, paper, or recording paper) by a transfer device to carry the image, and the toner image on the recording medium is fixed by a fixing device that uses pressure or heat. is doing.

  In this fixing device, a fixing member and a pressing member constituted by opposing rollers or belts or a combination thereof are arranged so as to contact each other to form a nip portion, and a recording medium is sandwiched in the nip portion, Heat and pressure are applied to fix the toner image on the recording medium.

  As an example of the fixing device, a technique using a fixing belt stretched around a plurality of roller members as a fixing member is known (for example, see Patent Document 1). An apparatus using such a fixing belt is provided in a fixing belt (endless belt) as a fixing member, a plurality of roller members that stretch and support the fixing belt, and one of the plurality of roller members. And a heater, a pressure roller (pressure member), and the like. The heater heats the fixing belt via the roller member. Then, the toner image on the recording medium conveyed toward the nip formed between the fixing belt and the pressure roller is fixed on the recording medium by receiving heat and pressure at the nip. Belt fixing method).

  In such a fixing device, either the fixing member or the pressure member is a member that rotates by driving (drive member), and the other is a driven member that rotates with the drive member. Is a driving member, and the fixing member is a driven member.

  Here, when a sheet is passed, a recording medium is inserted into the nip portion, and most of the fixing member and the pressure member do not come into contact with each other in the nip portion, and the frictional force between them is reduced. However, there is a problem that a slip phenomenon occurs in which the image is delayed with respect to the drive member (for example, a pressure member), and the image quality is deteriorated. Further, when the fixing member slips, the heat is not diffused by the rotation, and heat is locally supplied to cause ignition.

  To solve this problem, the end surface layer in the axial direction of the pressure member is made of a material having a higher friction coefficient than the central portion, or the axial end portion has a higher load on the fixing member than the central portion. For example, there has been proposed a fixing device having a configuration in which the fixing member is reliably rotated with respect to the pressure member.

  For example, in Patent Document 2, a high friction body is provided on a non-sheet passing portion of a pressure belt that is a pressure member and a non-sheet passing portion of a heating roller that is a fixing member, and another member is provided from the inside of the pressure belt. A configuration is disclosed in which a sufficient grip is obtained and driven by being pressed against a heating roller. However, this method requires a separate member for pressing the pressure member against the fixing member, leading to an increase in the number of parts, which is disadvantageous in terms of cost. In addition, increasing the number of parts increases the heat capacity, which also reduces the thermal efficiency.

  Also, the surface layer of the fixing member is often made of a material having good releasability, such as a fluororesin, in order to ensure separation from the recording medium, the surface layer has a small coefficient of friction, and mainly elastic such as rubber. Since the friction coefficient with the recording medium is smaller than that of the pressure member constituted by the member, there is a problem that the frictional resistance at the time of passing the paper is lowered and the fixing member (driven member) slips. In order to prevent such slipping of the driven member, many techniques are known in which a portion having a high load and a high friction coefficient is provided in a non-sheet-passing portion that does not affect the image quality and the separation property of the recording medium. If another member is used to increase the load at the end as described above, the cost increases and the heat capacity (power consumption) increases. In addition, in order to improve the friction coefficient, when the release layer of the non-sheet passing portion of the fixing member is removed and the uppermost layer is a rubber material that is an elastic layer, Slip occurred due to a decrease in load) or a change in hardness due to the environment.

  The present invention has been made in view of the above-described problems in the prior art, and can suppress the slip phenomenon of the driven member due to deterioration with time or environmental change without increasing the number of parts, and can obtain good image quality. It is an object of the present invention to provide a fixing device and an image forming apparatus using the fixing device.

The present invention provided to solve the above problems is as follows. In addition, the site | part and code | symbol etc. which respond | correspond in the form for implementing this invention in a parenthesis are shown.
[1] A rotating endless belt fixing member (fixing belt 21), a pressure member (pressure roller 31) in contact with the outer peripheral surface of the fixing member, and an inner peripheral side of the fixing member, An abutting member (abutting member 26, reinforcing member 23) for forming a nip portion for fixing unfixed toner on the recording medium passing through the fixing member in contact with the pressure member to the recording medium; Heating means (heating member 22, heater 25 or induction heating unit 50) for heating the fixing member, and the fixing member has an elastic layer (elastic layer 21b) and a release layer on a base material (base material 21a). (Release layer 21c) is laminated, and at least a part of the non-sheet passing portion that is a region through which the recording medium does not pass in the nip portion, the base material is exposed to be in contact with the pressure member. A fixing device (fixing device 2) 0, FIGS. 2-7).
[2] The fixing device according to [1] (FIG. 4), wherein the exposed portion of the substrate has irregularities on the surface thereof.
[3] The fixing device according to [2] (FIG. 4), wherein the unevenness has a shape that improves a grip force with respect to the pressure member.
[4] The concave and convex portions are arranged such that rib-shaped convex portions (convex portions 21d) having a certain length are arranged on the outer periphery of the base material with the longitudinal direction of the convex portions being inclined with respect to the axial direction of the pressing member. The fixing device according to [2] or [3] above (FIG. 4).
[5] The outer diameter of the exposed portion of the base material is larger than the outer diameter of the base material in a paper passing portion that is a region through which the recording medium passes in the nip portion. The fixing device according to any one of 1] to [4] (FIG. 3).
[6] The pressurizing member has an outer diameter corresponding to an exposed portion of the base material that is larger than an outer diameter of the pressurizing member in a paper passing portion where the recording medium passes in the nip portion. The fixing device according to any one of [1] to [4], which is large (FIG. 5).
[7] An image forming apparatus (image forming apparatus 1, FIG. 1) comprising the fixing device (fixing apparatus 20) according to any one of [1] to [6].

According to the fixing device of the present invention, a base material made of a metal material is added without providing an elastic layer and a release layer in at least a part of the non-sheet passing portion which is a region through which the recording medium does not pass in the nip portion of the fixing member. Since it is exposed so as to be able to contact the pressure member, it is possible to suppress a decrease in hardness due to deterioration over time and a change in hardness due to the environment in the exposed portion of the base material of the non-sheet passing portion. Since a strong driving force can be applied, the fixing operation can be performed without slipping stably for a long period of time.
According to the image forming apparatus of the present invention, since the fixing device of the present invention is provided, it is possible to form an image with good image quality.

1 is a cross-sectional view showing an overall configuration of an image forming apparatus according to the present invention. 1 is a cross-sectional view showing a basic configuration (1) of a fixing device according to the present invention. FIG. 3 is a schematic diagram illustrating a configuration example (1) of a fixing belt used in the fixing device of the present invention. FIG. 6 is a main part external view showing a configuration example (2) of a fixing belt used in the fixing device of the present invention. FIG. 6 is a schematic diagram illustrating a configuration example (3) of a fixing belt used in the fixing device of the present invention. FIG. 3 is a cross-sectional view showing a basic configuration (2) of the fixing device according to the present invention. FIG. 3 is a cross-sectional view showing a basic configuration (3) of the fixing device according to the present invention.

The configurations of the fixing device and the image forming apparatus according to the present invention will be described below.
A configuration example of the entire image forming apparatus according to the present invention will be described with reference to FIG.
As shown in FIG. 1, the image forming apparatus 1 is a tandem type color printer. Four bottles 102Y, 102M, 102C, and 102K corresponding to the respective colors (yellow, magenta, cyan, and black) are detachably (replaceable) installed in the bottle housing portion 101 above the image forming apparatus main body 1. ing.
An intermediate transfer unit 85 is disposed below the bottle housing portion 101. Image forming units 4Y, 4M, 4C, and 4K corresponding to the respective colors (yellow, magenta, cyan, and black) are arranged in parallel so as to face the intermediate transfer belt 78 of the intermediate transfer unit 85.

  Photosensitive drums 5Y, 5M, 5C, and 5K are disposed in the image forming units 4Y, 4M, 4C, and 4K, respectively. Further, around each of the photosensitive drums 5Y, 5M, 5C, and 5K, a charging unit 75, a developing unit 76, a cleaning unit 77, a charge eliminating unit (not shown), and the like are disposed. Then, an image forming process (charging process, exposure process, development process, transfer process, cleaning process) is performed on each of the photoconductive drums 5Y, 5M, 5C, and 5K. An image of each color is formed on 5K.

The photosensitive drums 5Y, 5M, 5C, and 5K are rotationally driven in a clockwise direction in FIG. 1 by a drive motor (not shown). Then, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K are uniformly charged at the position of the charging unit 75 (a charging process).
Thereafter, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K reach the irradiation position of the laser light L emitted from the exposure unit 3, and electrostatic latent images corresponding to the respective colors are formed by exposure scanning at this position. (It is an exposure process.)

Thereafter, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K reach a position facing the developing device 76, and the electrostatic latent image is developed at this position to form toner images of each color (developing process). .)
Thereafter, the surfaces of the photoconductive drums 5Y, 5M, 5C, and 5K reach the positions facing the intermediate transfer belt 78 and the first transfer bias rollers 79Y, 79M, 79C, and 79K, and at these positions, the photoconductive drums 5Y, 5M. The toner images on 5C and 5K are transferred onto the intermediate transfer belt 78 (this is a primary transfer process). At this time, a small amount of untransferred toner remains on the photosensitive drums 5Y, 5M, 5C, and 5K.

Thereafter, the surfaces of the photoconductive drums 5Y, 5M, 5C, and 5K reach a position facing the cleaning unit 77, and untransferred toner remaining on the photoconductive drums 5Y, 5M, 5C, and 5K is removed at this position. 77 is mechanically collected by a cleaning blade (cleaning process).
Finally, the surfaces of the photoconductive drums 5Y, 5M, 5C, and 5K reach a position facing a neutralization unit (not shown), and the residual potential on the photoconductive drums 5Y, 5M, 5C, and 5K is removed at this position. The
Thus, a series of image forming processes performed on the photosensitive drums 5Y, 5M, 5C, and 5K is completed.

Thereafter, the toner images of the respective colors formed on the respective photosensitive drums through the developing process are transferred onto the intermediate transfer belt 78 in an overlapping manner. In this way, a color image is formed on the intermediate transfer belt 78.
Here, the intermediate transfer unit 85 includes an intermediate transfer belt 78, four primary transfer bias rollers 79Y, 79M, 79C, and 79K, a secondary transfer backup roller 82, a cleaning backup roller 83, a tension roller 84, and an intermediate transfer cleaning unit 80. , Etc. The intermediate transfer belt 78 is stretched and supported by the three rollers 82 to 84 and is endlessly moved in the direction of the arrow in FIG.

The four primary transfer bias rollers 79Y, 79M, 79C, and 79K sandwich the intermediate transfer belt 78 with the photosensitive drums 5Y, 5M, 5C, and 5K, respectively, thereby forming primary transfer nips. Then, a transfer bias reverse to the polarity of the toner is applied to the primary transfer bias rollers 79Y, 79M, 79C, and 79K.
The intermediate transfer belt 78 travels in the direction of the arrow and sequentially passes through the primary transfer nips of the primary transfer bias rollers 79Y, 79M, 79C, and 79K. In this way, the toner images of the respective colors on the photosensitive drums 5Y, 5M, 5C, and 5K are primarily transferred while being superimposed on the intermediate transfer belt 78.

Thereafter, the intermediate transfer belt 78 onto which the toner images of the respective colors are transferred in an overlapping manner reaches a position facing the secondary transfer roller 89. At this position, the secondary transfer backup roller 82 sandwiches the intermediate transfer belt 78 between the secondary transfer roller 89 and forms a secondary transfer nip. The four color toner images formed on the intermediate transfer belt 78 are transferred onto the recording medium P conveyed to the position of the secondary transfer nip. At this time, untransferred toner that has not been transferred to the recording medium P remains on the intermediate transfer belt 78.
Thereafter, the intermediate transfer belt 78 reaches the position of the intermediate transfer cleaning unit 80. At this position, the untransferred toner on the intermediate transfer belt 78 is collected.
Thus, a series of transfer processes performed on the intermediate transfer belt 78 is completed.

  Here, the recording medium P transported to the position of the secondary transfer nip is transported from the paper feeding unit 12 disposed below the apparatus main body 1 via the paper feeding roller 97 and the registration roller pair 98. It is a thing. Specifically, a plurality of recording media P such as transfer paper are stored in the paper supply unit 12 in an overlapping manner. When the paper feed roller 97 is rotationally driven in the counterclockwise direction in FIG. 1, the uppermost recording medium P is fed between the rollers of the registration roller pair 98.

  The recording medium P conveyed to the registration roller pair 98 is temporarily stopped at the position of the roller nip of the registration roller pair 98 that has stopped rotating. Then, the registration roller pair 98 is rotationally driven in synchronization with the color image on the intermediate transfer belt 78, and the recording medium P is conveyed toward the secondary transfer nip. In this way, a desired color image is transferred onto the recording medium P.

Thereafter, the recording medium P on which the color image is transferred at the position of the secondary transfer nip is conveyed to the position of the fixing device 20. At this position, the color image transferred on the surface is fixed on the recording medium P by heat and pressure generated by the fixing belt 21 and the pressure roller 31.
Thereafter, the recording medium P is discharged out of the apparatus through a pair of paper discharge rollers 99. The transferred P discharged from the apparatus by the discharge roller pair 99 is sequentially stacked on the stack unit 100 as an output image.
Thus, a series of image forming processes in the image forming apparatus is completed.

Next, the fixing device according to the present invention will be described.
FIG. 2 is a sectional view showing a basic configuration (1) of the fixing device according to the present invention. Here, a cross-sectional configuration of the sheet passing portion, which is a region through which the recording medium P passes in the nip portion, is illustrated.
As shown in FIG. 2, the fixing device 20 includes a fixing belt 21 as a fixing member, a heating member 22, a reinforcing member 23, a contact member 26 that forms a nip portion, a heater 25 as a heat source, and an application as a pressure member. The pressure roller 31 and the temperature sensor (not shown) for detecting the temperature of the fixing belt 21 and controlling the heater 25 are configured.

  Here, the fixing belt 21 as a fixing member is a thin and flexible endless belt, and rotates (runs) in an arrow direction (counterclockwise) in FIG. The fixing belt 21 is formed by sequentially laminating an elastic layer and a release layer on the base material (details will be described later), and the overall thickness is set to 1 mm or less.

Further, the diameter of the fixing belt 21 is set to be 15 to 120 mm. In the present embodiment, the diameter of the fixing belt 21 is set to 30 mm, for example.
Inside the fixing belt 21 (inner peripheral surface side), a heater 25 (heat source), a heating member 22, a reinforcing member 23, a contact member 26, and the like are fixed. As a result, the fixing belt 21 is pressed by the contact member 26 reinforced by the reinforcing member 23 to form a nip portion with the pressure roller 31.

  The heating member 22 is a substantially pipe-shaped member formed by bending a thin metal plate, for example, and is formed in a substantially circular shape so as to face the inner peripheral surface of the fixing belt 21 at a position excluding the nip portion. A concave portion is formed so as to house and hold the contact member 26 at the position of the nip portion. Further, both ends of the heating member 22 in the width direction (axial direction) are fixedly supported on the side plate of the fixing device 20.

  The reinforcing member 23 is a member having a substantially T-shaped cross section that reinforces the strength of the contact member 26 in the nip portion, and the length in the width direction (axial direction) is equal to the length in the longitudinal direction of the contact member 26. The both ends in the width direction are fixedly supported on the side plate of the fixing device 20 on the inner peripheral side of the fixing belt 21.

  The heater 25 is a halogen heater or a carbon heater, and both ends thereof are fixed to the side plate of the fixing device 20. The heating member 22 is heated by the radiant heat of the heater 25 whose output is controlled by the power supply unit of the apparatus main body. Further, the fixing belt 21 is entirely heated by the heating member 22, and heat is applied to the toner image T on the recording medium P from the surface of the heated fixing belt 21. The output control of the heater 25 is performed based on the detection result of the belt surface temperature by a temperature sensor such as a thermistor facing the surface of the fixing belt 21. Further, the temperature of the fixing belt 21 (fixing temperature) can be set to a desired temperature by such output control of the heater 25.

  The heating member 22 is fixed so as to face the entire inner peripheral surface of the fixing belt 21 excluding the position of the nip portion, and is heated by the radiant heat of the heater 25 to heat the fixing belt 21 (transmits heat). . As a material of the heating member 22, it is preferable to use a metal thermal conductor (a metal having thermal conductivity) such as aluminum, iron, and stainless steel.

  The contact member 26 is formed in a concave shape so that the surface facing the pressure roller 31 follows the curvature of the pressure roller 31. Thereby, since the recording medium P is sent out from the nip portion so as to follow the curvature of the pressure roller 31, the problem that the recording medium P after the fixing process is not attracted to the fixing belt 21 and separated is suppressed. be able to.

  Further, as a material for forming the contact member 26, a material having a certain degree of rigidity (for example, a highly rigid metal, ceramic, or the like) is used so that the contact member 26 does not bend greatly even if the pressure applied by the pressure roller 31 is applied. .).

  Here, the contact member 26 is detachably installed on the fixing device 20. Specifically, both end portions in the width direction of the contact member 26 are detachably fixed to the side plate of the fixing device 20 by screws, snap fits, or the like. As a result, even if the wear of the contact member 26 increases due to sliding contact with the fixing belt 21 over a long period of use, only the contact member 26 can be efficiently replaced (maintenance).

  The contact surface of the contact member 26 is formed of a material having a low friction coefficient so that the wear of the fixing belt 21 is reduced even if the contact member 26 and the fixing belt 21 are in sliding contact with each other. It is preferable to apply a lubricant between the belt 26 and the fixing belt 21. Specifically, by applying a surface coating such as Teflon (registered trademark), plating, DLC (diamond-like carbon), glass coating or the like to the sliding contact surface of the contact member 26, the surface roughness of the sliding contact surface is Rz = It is desirable that the thickness be 64 μm or less.

  The pressure roller 31 has a diameter of 30 mm and is formed by forming an elastic layer 33 on a hollow cylindrical cored bar 32. The elastic layer 33 of the pressure roller 31 is made of a material such as foamable silicone rubber, silicone rubber, or fluorine rubber. A thin release layer made of PFA, PTFE or the like can be provided on the surface layer of the elastic layer 33.

  Further, both ends of the pressure roller 31 in the width direction are rotatably supported on the side plate of the fixing device 20 via bearings and are movable toward the contact member 26 side. The pressure roller 31 is provided with pressure means (not shown) that presses the roller shafts at both axial ends of the pressure roller 31 toward the contact member 26 side. The pressure roller 31 is pressed against the contact member 26 via the fixing belt 21 to form a desired nip portion between both members.

  Further, the pressure roller 31 is provided with a gear that meshes with a drive gear of a drive mechanism (not shown), and the pressure roller 31 is rotationally driven in an arrow direction (clockwise direction) in FIG. A heat source such as a halogen heater can be provided inside the pressure roller 31.

  When the pressure roller 31 rotates, the fixing belt 21 also rotates due to the reaction force of the frictional force with the pressure roller 31. If this frictional force is small, the fixing belt 21 slips, and heat is not diffused by rotation, so that heat is locally supplied, which causes ignition. Further, the transportability of the recording medium is lowered, and a deviation occurs in the amount of heat supplied, resulting in image quality abnormalities such as poor fixing and gloss deviation.

  Further, in order to efficiently transfer heat from the heating member 22 to the fixing belt 21, the contact property between the heating member 22 and the fixing belt 21 is important. However, when the contact property is increased, the rotational load of the fixing belt 21 increases. A slip problem occurs. Therefore, in order to prevent the fixing belt 21 from slipping, grease is applied to the inner surface of the fixing belt 21 to reduce the frictional resistance. Further, the frictional resistance may be reduced by coating the inner surface of the fixing belt 21 and the outer peripheral surface of the heating member 22 with a low sliding coating film. Further, it is desirable that the load when the fixing belt 21 is pulled and rotated in the tangential direction is 2000 g or less.

The fixing device 20 configured as described above operates as follows.
First, when the power switch of the apparatus main body is turned on, electric power is supplied to the heater 25, and the pressure roller 31 presses the contact member 26 via the fixing belt 21 by the pressing means in FIG. Rotation drive in the direction of the arrow is started. Thereby, the fixing belt 21 is also driven (rotated) in the direction of the arrow in FIG. 2 by the frictional force with the pressure roller 31.
Thereafter, the recording medium P is fed from the paper supply unit 12, and an unfixed color image is carried (transferred) on the recording medium P at the position of the secondary transfer roller 89. The recording medium P carrying the unfixed image (toner image T) is guided by a guide plate (not shown) and fed into the nip portion of the fixing belt 21 and the pressure roller 31 that are in a pressure contact state.
Then, the toner on the surface of the recording medium P is heated by the fixing belt 21 heated by the heating member 22 (heater 25) and the pressing force of the contact member 26 reinforced by the reinforcing member 23 and the pressure roller 31. The image T is fixed. Thereafter, the recording medium P is discharged from the nip portion.

  As described above, in the fixing device 20 according to the present embodiment, the fixing belt 21 is heated almost entirely in the circumferential direction by the heating member 22 without locally heating only a part of the fixing belt 21. Therefore, even when the speed of the apparatus is increased, the fixing belt 21 is sufficiently heated and the occurrence of fixing failure can be suppressed. That is, since the fixing belt 21 can be efficiently heated with a relatively simple configuration, the warm-up time and the first print time are shortened, and the size of the apparatus is reduced.

Here, the surface layer of the fixing belt 21 is made of a release layer made of a fluororesin or the like in order to ensure separation from the recording medium, has a small friction coefficient, and is mainly composed of an elastic member such as rubber. Since the friction coefficient with the recording medium is smaller than that of the pressure roller 31, there is a problem that the friction resistance at the time of passing the paper is lowered and the fixing belt 21 slips. Further, if the release layer of the non-sheet passing portion of the fixing belt 21 is removed and the uppermost layer is a rubber material that is an elastic layer in order to improve the friction coefficient, the hardness (pressing load) decreases due to the deterioration of the rubber material over time. Slip occurred due to changes in hardness due to the environment.
The inventors pay attention to a non-sheet passing portion which is an area other than the sheet passing portion where the recording medium is present in the nip portion, and intensively study to solve the problem of slipping of the fixing belt 21, thereby forming the present invention. It came to. Hereinafter, the configuration of the main part of the present invention will be described.

[Configuration of fixing belt, etc.]
According to the present invention, in the fixing device 20, the fixing belt 21 is formed by laminating an elastic layer and a release layer on a base material, and at least one of a non-sheet passing portion that is a region through which the recording medium does not pass in the nip portion. The base material is exposed to be able to come into contact with the pressure roller 31 in the portion.
As a result, the base material made of the metal material is brought into contact with the pressure roller 31 without providing the elastic layer and the release layer in at least a part of the non-sheet-passing portion where the recording medium does not pass in the nip portion of the fixing belt 21. Since it is exposed so as to be able to contact, it is possible to suppress a decrease in hardness due to deterioration with time and a change in hardness due to the environment in the exposed portion of the base material in the non-sheet passing portion. Therefore, the fixing operation can be performed without slipping stably for a long time.
Hereinafter, specific examples of the fixing belt 21 and the like will be described with reference to the drawings.

(First embodiment)
FIG. 3 is a schematic diagram showing a configuration example (1) of a fixing belt used in the fixing device of the present invention. 3A is a cross-sectional view in the axial direction of the fixing belt 21, and FIG. 3B is a cross-sectional view in the diameter direction of the fixing belt 21 in the sheet passing portion.
As shown in FIG. 3, the fixing belt 21 is an endless belt member based on a cylindrical base material 21 a made of a metal material such as stainless steel or Ni, and on the outer periphery of the base material 21 a in the paper passing portion. The elastic layer 21b made of the rubber material described above and the release layer 21c made of the fluororesin described above are laminated, and the non-passage that is a region at both end portions on the axially outer side than the paper passing portion. The paper portion is composed of only the base material 21a. Further, the outer diameter of the base material 21a in the non-sheet passing portion is larger than that of the sheet passing portion by the thickness of the elastic layer 21b and the release layer 21c, and the outer diameter of the fixing belt 21 is made uniform in the axial direction. Has been.

  The base material 21a constituting the fixing belt 21 has a layer thickness of 30 to 100 μm and is formed of a metal material such as nickel or stainless steel.

  The elastic layer 21b 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 21b, minute irregularities on the surface of the fixing belt 21 in the nip portion are not formed, and heat is uniformly transmitted to the toner image T on the recording medium P, so that generation of a scum skin image is suppressed.

  The release layer 21c has a layer thickness of 10 to 50 μm, and is made of PFA (tetrafluoroethylene barfluoroalkyl vinyl ether copolymer resin), PTFE (tetrafluoroethylene resin), polyimide, polyetherimide, PES (polyester). Ether sulfide), and the like. By providing the release layer 21c, the releasability (peelability) for the toner (toner image) is ensured.

  Note that the sheet passing portion referred to here is an amount of play in the axial direction of the fixing belt 21 in the actual apparatus mechanism or an area of the recording medium P being conveyed in an area where the recording medium P passes in an ideal state at the nip portion. It includes at least a region to which a variation in the sheet passing position in the main scanning direction (axial direction) is added. Further, the non-sheet passing portion is also a region (grip portion) having a width that can secure a grip force that can be driven and rotated without slipping the fixing belt 21 when the pressure roller 31 is pressed and rotated. The portion of the fixing belt 21 where the base material 21a is exposed may be a part of the non-sheet passing portion, but FIG. 3 shows a configuration in which the base material 21a is exposed throughout the non-sheet passing portion.

  Here, the release layer 21c has a small coefficient of friction and is advantageous for separability from the recording medium, but is a disadvantageous material for preventing the fixing belt 21 from slipping because of its small frictional force. The elastic layer 21b has a larger friction coefficient and is more advantageous for preventing slipping than the release layer 21c. However, the elastic layer 21b is permanently deformed (a phenomenon in which the shape does not return to its original state when the elastic material is left deformed for a long time). ), Etc., or a change in hardness due to the environment, a constant frictional force cannot be obtained, and slipping may occur. On the other hand, the base material 21a is a metal material, has high hardness, and is less affected by deterioration with time and environmental fluctuation.

  Therefore, in the present embodiment, the base 21a is exposed in the non-sheet passing portion of the fixing belt 21 and is in contact with the pressure roller 31, thereby increasing the surface hardness as compared with the case where the elastic layer 21b is in contact. Thus, the pressing load from the pressure roller 31 is increased so that the fixing belt 21 can be driven and rotated. In addition, it is also possible to suppress slippage due to deterioration with time and environmental fluctuations that occur when the elastic layer 21b abuts.

  Further, if the elastic layer 21b and the release layer 21c are simply not formed in the non-sheet passing portion of the fixing belt 21, the outer diameter of the sheet passing portion and the non-sheet passing portion is equal to the thickness of the two layers. A difference occurs, and the pressing load from the pressure roller 31 is reduced in the non-sheet passing portion having a small outer diameter, so that a sufficient grip force cannot be obtained.

  Therefore, the outer diameter of the exposed portion of the base material 21a (the outer diameter of the base material 21a in the non-sheet passing portion) is preferably larger than the outer diameter of the base material 21a in the paper passing portion in the nip portion. In particular, as shown in FIG. 2A, the outer diameter of the base 21a in the non-sheet passing portion is increased by the thickness of the elastic layer 21b and the release layer 21c, and the outer diameter of the fixing belt 21 is axial. It is preferable to make it uniform. As a result, the non-sheet passing portion of the fixing belt 21 can be pressed against the pressure roller 31 with a predetermined load, which is suitable for the driven rotation of the fixing belt 21. Moreover, you may provide the convex part 21d mentioned later in the base material 21a of a non-sheet passing part at this time.

(Second Embodiment)
FIG. 4 is an external view showing a configuration example (2) of the fixing belt used in the fixing device of the present invention, and is an enlarged view of one non-sheet passing portion of the fixing belt 21.
In the present embodiment, the configuration of the paper passing portion is the same as that of the first embodiment, and the configuration of the non-paper passing portion is different from that of the first embodiment.

  That is, the exposed part of the base material 21a (the base material 21a of the non-sheet-passing portion) has a surface shape that is different from that of the first embodiment, and has irregularities on the surface.

  As described above, since the surface hardness increases when the non-sheet-passing portion is composed only of the base material 21a, the pressing load from the pressure roller 31 increases, but the base material 21a made of a metal material is made of a rubber material. Since the friction coefficient with respect to the pressure roller 31 is smaller than that of the elastic layer 21b, the friction force in the non-sheet passing portion is smaller than that in which the uppermost layer of the non-sheet passing portion is configured by the elastic layer 21b. Further, in order to improve energy saving and durability, it is necessary to improve the contact between the heating member 22 and the fixing belt 21. The surface of the fixing belt 21 should be flat, but it is disadvantageous for slip prevention.

Therefore, in the present embodiment, the convex portion 21d is provided on the surface of the base material 21a in the non-sheet passing portion.
Accordingly, by providing the surface of the base material 21a of the non-sheet passing portion with the unevenness (convex portion 21d), the coefficient of friction with respect to the pressure roller 31 is higher than when the surface is flat, and the non-sheet passing of the fixing belt 21 is not performed. Therefore, the occurrence of slip in the driven rotation of the fixing belt 21 can be further suppressed.

  The convex portion 21d is effective in improving the frictional force. However, if the height of the convex portion 21d is high, the load is concentrated on the convex portion 21d, and the nip pressure of the paper passing portion is lowered, resulting in an image quality abnormality. Therefore, it is preferable that the convex height of the convex portion 21d is, for example, 0.01 mm to 0.1 mm.

  Further, at this time, it is preferable that the irregularities have a shape that improves the gripping force against the pressure roller 31. As shown in FIG. 4, rib-shaped convex portions 21d having a certain length are formed on the outer periphery of the base material 21a. It is preferable that the longitudinal direction of the convex portions 21 d be arranged to be inclined with respect to the axial direction of the pressure roller 31.

  A nip (contact) region N between the fixing belt 21 and the pressure roller 31 is parallel to a roller shaft core (also referred to as a roller shaft), and a convex portion 21d is formed on the surface of the substrate 21a so that its longitudinal direction is parallel to the roller shaft core. If provided, the convex portion 21d does not grip the surface of the pressure roller 31, and the timing at which the frictional force is not improved occurs.

  Therefore, as shown in FIG. 4, the convex portion 21d is inclined so that the longitudinal direction thereof has an arbitrary angle with respect to the nip (contact) region N (roller axis) of the pressure roller 31 and the fixing belt 21. Install.

As a result, the convex portion 21d is always in contact with the pressure roller 31 that is driven to rotate, and the frictional force at the non-sheet passing portion of the fixing belt 21 is further increased. Can be further suppressed.
Since the outer diameter of the pressure roller 31 and the fixing belt 21 is not an integer ratio, the contact position between the convex portion 21d and the pressure roller 31 is not always constant, and the surface condition of the pressure roller 31 is changed over time and the durability. The effect on sex is small.

(Third embodiment)
FIG. 5 is a schematic diagram showing a configuration example (3) of the fixing belt used in the fixing device of the present invention. 5A is a cross-sectional view in the axial direction of the fixing belt 21 and the pressure roller 31, and FIG. 5B is a cross-sectional view in the diameter direction of the fixing belt 21 in the sheet passing portion.

  In this embodiment, the base material 21a is exposed in the fixing belt 21 in the non-sheet passing portion, and the outer diameter is reduced by the thickness of the elastic layer 21b and the release layer 21c, while the pressure roller Reference numeral 31 denotes the pressurization in the paper passing portion where the outer diameter corresponding to the exposed portion of the base material 21a of the fixing belt 21 (the base material 21a of the non-paper passing portion) is a region through which the recording medium passes in the nip portion. The outer diameter of the roller 31 is larger.

  That is, the configuration of the present embodiment is different from that of the first embodiment (FIG. 3) in that the outer diameter of the base material 21a is constant in the fixing belt 21 and the pressure roller 31 is outside the non-sheet passing portion. The diameter is larger by the thickness of the elastic layer 21b and the release layer 21c than the outer diameter of the paper passing portion.

  Thereby, since the outer diameter of the base material 21a becomes constant, an increase in the heat capacity can be suppressed as compared with the case of the first embodiment, and the heating time of the fixing belt 21 can be shortened and the energy saving performance can be improved. Further, since the outer diameter of the non-sheet passing portion of the pressure roller 31 is increased, it is possible to suppress a decrease in the pressing load against the fixing belt 21 of the non-sheet passing portion, and the occurrence of slip in the driven rotation of the fixing belt 21. Can be prevented.

  However, since the elastic layer 33 is processed, for example, in order to change the outer diameter of the pressure roller 31 in the axial direction, the processing accuracy is lower than in the case of the first embodiment. Also in the present embodiment, the above-described convex portion 21 d may be provided on the non-sheet passing portion (base material 21 a) of the fixing belt 21.

  Although the present invention has been described with the embodiments shown in the drawings, the present invention is not limited to the embodiments shown in the drawings, and other embodiments, additions, modifications, deletions, etc. Can be changed within the range that can be conceived, and any embodiment is included in the scope of the present invention as long as the effects and advantages of the present invention are exhibited.

  For example, the basic configuration of the fixing device 20 is not limited to that shown in FIG. 2. For example, as shown in FIG. 6, instead of the heater 25 of FIG. 2, an induction heating unit 50 of an electromagnetic induction heating method is used. May be arranged on the outer peripheral side of the heating member 22, and the fixing belt 21 may be heated by the induction heating unit 50 via the heating member 22. The other configuration is the same as that shown in FIG. The reinforcing member 23 may be omitted.

  Further, the basic configuration of the fixing device 20 may be the configuration shown in FIG. Here, in the configuration shown in FIG. 2, the contact member 26 is omitted, and the heating member 22 is in contact with the pressure roller 31 via the fixing belt 21 in the nip portion. At this time, the heating member 22 has a substantially circular cross section and is formed so that the position corresponding to the nip portion is a flat surface. Further, the reinforcing member 23 is configured to support the heating member 22 at the nip portion position from the back side, and a heat insulating member 27 is provided between the reinforcing member 23 and the heating member 22 so as not to reduce the heating efficiency. Yes. The other configuration is the same as that shown in FIG.

  Further, fixing in a belt fixing device including a fixing belt wound around a plurality of rollers including a fixing roller and a heating roller, and a heating roller that presses the fixing roller via the fixing belt to form a nip portion. The present invention may be applied to a belt and a pressure roller. The pressure member may be configured as a pressure belt type instead of the heating roller 31.

  In the above-described embodiment, the configuration based on the premise that the center of the nip portion is the paper passing portion is shown. However, the paper passing method based on one of the end sides in the axial direction of the nip portion (that is, The present invention can also be applied to a case where the end side is a paper passing portion.

1. Image forming device (device main body)
3 Exposure unit 4Y, 4M, 4C, 4K Image forming unit 5Y, 5M, 5C, 5K Photosensitive drum 12 Paper feed unit 20 Fixing device 21 Fixing belt (fixing member)
21a Base material 21b Elastic layer 21c Release layer 22 Heating member 23 Reinforcing member 25 Heater (heat source)
26 Contact member 27 Heat insulation member 31 Pressure roller (pressure member)
32 Core Bar 33 Elastic Layer 50 Induction Heating Unit 75 Charging Unit 76 Developing Device 77 Cleaning Unit 78 Intermediate Transfer Belt 79Y, 79M, 79C, 79K Primary Transfer Bias Roller 80 Intermediate Transfer Cleaning Unit 82 Secondary Transfer Backup Roller 83 Cleaning Backup Roller 83 84 Tension roller 85 Intermediate transfer unit 89 Secondary transfer roller 97 Paper feed roller 98 Registration roller pair 99 Paper discharge roller pair 100 Stack part 101 Bottle storage part 102Y, 102M, 102C, 102K Toner bottle P Recording medium T Toner (toner image)

Japanese Patent Laid-Open No. 11-2982 JP 2008-165102 A

Claims (7)

A fixing member for a rotating endless belt;
A pressure member in contact with the outer peripheral surface of the fixing member;
An abutting member disposed on the inner peripheral side of the fixing member and forming a nip portion for fixing unfixed toner on the recording medium passing through the fixing member and contacting the pressure member to the recording medium; ,
Heating means for heating the fixing member,
The fixing member is formed by laminating an elastic layer and a release layer on a base material, and the base material is subjected to the pressurization in at least a part of a non-sheet passing portion which is a region through which the recording medium does not pass in the nip portion. A fixing device that is exposed so as to be in contact with a member.   The fixing device according to claim 1, wherein the exposed portion of the substrate has irregularities on a surface thereof.   The fixing device according to claim 2, wherein the unevenness has a shape that improves a grip force with respect to the pressure member.   The concave and convex portions are characterized in that rib-shaped convex portions having a certain length are arranged on the outer periphery of the substrate so that the longitudinal direction of the convex portions is inclined with respect to the axial direction of the pressing member. The fixing device according to claim 2.   5. The outer diameter of the exposed portion of the base material is larger than the outer diameter of the base material in a paper passing portion that is a region through which the recording medium passes in the nip portion. The fixing device according to any one of the above.   The pressurizing member has an outer diameter corresponding to an exposed portion of the base material that is larger than an outer diameter of the pressurizing member in a paper passing portion that is an area through which the recording medium passes in the nip portion. The fixing device according to claim 1, wherein the fixing device is characterized in that:   An image forming apparatus comprising the fixing device according to claim 1.