JP2014109756A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device capable of preventing a heater from being deprived of heat by members ensuring a nip (stay and pad), and preventing a part not in contact with a belt material from being heated, so as to transfer heat of the heater to the belt material at the maximum efficiency.SOLUTION: A fixing device includes: a pressure rotating body; an endless belt member that has flexibility, and runs in a predetermined direction to heat and fuse a toner image; a stationary member that is in pressure contact with the pressure rotating body with the belt member therebetween, and is fixedly provided on an inner peripheral surface side of the belt member so as to form a nip part with the pressure rotating body at which a recording material having a toner image on the surface is conveyed; and a reinforcement member that is fixedly provided on the inner peripheral surface side of the belt member to be in contact with the stationary member so as to reinforce the stationary member. The reinforcement member has an opening, and further a heat transfer member that covers the opening and is in contact with the belt member, and heating means that is provided between the reinforcement member and the heat transfer member.

Description

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

Conventionally, a heat roller fixing device is known as a fixing device used in an image forming apparatus such as a printer or a copying machine.
In the heat roller fixing device, a heat source such as a halogen lamp is provided inside, and the heated nip portion is fixed to a contact nip portion (fixing nip portion) of two heating rollers (fixing roller and pressure roller) that are pressed against each other and rotated. Then, the recording medium on which the unfixed toner image is placed is passed, where the toner image is melted and fixed on the recording medium.

On the other hand, in recent years, due to increasing demands for energy saving of devices and shortening of the wait time, fixing devices that employ a heating device using a belt or a thin film instead of a heating roller are widely adopted. This fixing device is a so-called on-demand type that realizes a low heat capacity of the fixing device, improves heat transfer efficiency to the recording medium, and greatly shortens the waiting time required for heating (warm-up time). is there.
In this type of fixing device, a configuration in which the belt material is directly heated from a heating means (heater) is conceivable. However, it is difficult to ensure safety during runaway due to an increase in temperature rise rate and to uniformly heat the sleeve. Therefore, such a fixing device is already known in which a heat transfer member is indirectly transferred to the belt member by mounting a metal heat transfer member inside the belt member.

However, in the conventional indirect heating method using a metal heat transfer member, heat can be transferred only to the portion where the heat transfer member and the belt material are in contact, but the non-contact portion is also heated by the heater. There was a problem of reducing the thermal efficiency of the heater.
In addition, there are members (stays, pads, etc.) that secure not only the heat transfer member but also the nip in the vicinity of the heater inside the belt material, so that the above member is also deprived of heat, and further the problem of lowering the heat efficiency of the heater was there.

Here, the fixing device described in Patent Document 1 uses a main part that heats the heat transfer member directly and heat conduction from the main part for the purpose of reducing the heat capacity of the part that is not directly heated from the heat transfer member to the belt material. There is a slave portion to be heated, and a configuration is disclosed in which the heat capacity of the slave portion is smaller than that of the main portion.
However, in such a configuration, there is a limit in reducing the heat capacity of the portion where the belt material is not directly heated, and the problem of heating the portion (secondary portion) where the belt material is not directly heated cannot be solved. Moreover, in order to reduce the heat capacity of the slave, changing the thickness or making a hole raises the problem of increasing the manufacturing cost of the heat transfer member.

  In addition, the fixing device described in Patent Document 2 includes a light emitting means inside the fixing belt for the purpose of reducing the heat capacity of the heat generating member and obtaining high heating efficiency, and shortening the warm-up time and reducing power consumption. The heat transfer roller is disposed, and the fixing belt is heated via the heat transfer roller. However, in such a configuration, it is necessary to heat the entire heat transfer roller, and heat is released by heat radiation in a portion that is not in contact with the heat transfer roller. Has not been resolved.

  The present invention has been made in view of the above problems in the prior art, prevents heat from being taken away by members (stays, pads, etc.) that secure the nip, and heats portions that are not in contact with the belt material. It is an object of the present invention to provide a fixing device that can prevent heat from being transferred to a belt member with maximum efficiency.

  In order to solve the above problems, a fixing device according to the present invention includes a pressure rotator, an endless belt member that is flexible and travels in a predetermined direction to heat and melt a toner image, and the belt member. On the inner peripheral surface side of the belt member so as to form a nip portion with the pressure rotator on which a recording medium having a toner image on the surface is conveyed. A fixing member that is fixedly provided, and a reinforcing member that is fixedly provided on the inner peripheral surface side of the belt member and that abuts on the fixing member and reinforces the fixing member. And a heat transfer member that covers the opening and contacts the belt member, and a heating means provided between the reinforcing member and the heat transfer member.

  According to the present invention, it is possible to provide a fixing device capable of transferring the heat of the heater to the belt member with high efficiency.

1 is a schematic diagram illustrating an overall configuration of an image forming apparatus according to the present invention. 2 is a schematic cross-sectional view illustrating a configuration of a fixing device 20. FIG. (With contact / separation mechanism) 2 is a schematic side view showing a configuration of a fixing device 20. FIG. 2 is a schematic cross-sectional view illustrating a configuration of a fixing device 20. FIG.

  The fixing device according to the present invention includes a pressure rotator, an endless belt member that has flexibility and travels in a predetermined direction to heat and melt a toner image, and the pressure rotation via the belt member. A fixing member that is pressed against the body and fixed on the inner peripheral surface side of the belt member so as to form a nip portion with the pressure rotating body on which a recording medium having a toner image on its surface is conveyed. And a reinforcing member fixed to the inner peripheral surface side of the belt member and abutting the fixing member to reinforce the fixing member, the reinforcing member having an opening, and the opening A heat transfer member that covers the portion and contacts the belt member, and a heating means provided between the reinforcing member and the heat transfer member.

Next, the fixing device and the image forming apparatus according to the present invention will be described in more detail.
Although the embodiments described below are preferred embodiments of the present invention, various technically preferable limitations are attached thereto, but the scope of the present invention is intended to limit the present invention in the following description. Unless otherwise described, the present invention is not limited to these embodiments. Moreover, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

The embodiment of the present invention will be described in detail with reference to FIG. 1, FIG. 2, FIG. 3, and FIG.
FIG. 1 is a schematic diagram showing the overall configuration of an image forming apparatus according to the present invention. First, the configuration and operation of the entire image forming apparatus will be described with reference to FIG.

As shown in FIG. 1, the image forming apparatus 1 according to the first embodiment 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 recording medium P discharged out of 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 configuration and operation of the fixing device 20 installed in the image forming apparatus main body 1 will be described in detail with reference to FIGS. 2, 3, and 4.
FIG. 2 is a schematic diagram illustrating the configuration of the fixing device 20.

As shown in FIG. 2, the fixing device 20 includes a fixing belt 21 as a belt member, a fixing member 26, a heat transfer member 22, a reinforcing member 23 (support member), a heater 25 (heat source), and a pressurizing rotary member. The pressure roller 31, the temperature sensor 40, and the contact / separation mechanisms 51 to 53 are configured.
Here, the fixing belt 21 as a belt member is a thin and flexible endless belt, and rotates (runs) in an arrow direction (counterclockwise) in FIG.
The fixing member 26 is pressed against the pressure roller 31 via the fixing belt 21, and forms the nip portion with the pressure roller 31 to which the recording medium P having the toner image T on the surface is conveyed. The fixing belt 21 is fixed to the inner peripheral surface side.
The details of the internal configuration of the fixing belt 21 will be described later with reference to FIG.

The fixing belt 21 has a base material layer, an elastic layer, and a release layer sequentially laminated from the inner peripheral surface 21a (sliding contact surface with the fixing member 26) side, and its total thickness is 1 mm or less. Is set to
The base material layer of the fixing belt 21 has a layer thickness of 30 to 50 μm, and is preferably formed of a metal material such as nickel or stainless steel or a resin material such as polyimide, and includes a heat resistant resin.
The elastic layer of the fixing belt 21 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 21 in the nip portion are not formed, and heat is uniformly transmitted to the toner image T on the recording medium P, thereby suppressing the generation of a scum skin image.
The release layer of the fixing belt 21 has a layer thickness of 10 to 50 μm, and includes PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), PTFE (polytetrafluoroethylene), polyimide, polyetherimide, PES ( Polyether sulfide) and the like. By providing the release layer, the releasability (peelability) for the toner T (toner image) is secured.

Further, the diameter of the fixing belt 21 is set to be 15 to 120 mm.
In the first embodiment, the diameter of the fixing belt 21 is set to about 30 mm.
In recent years, the base material layer of the fixing belt 21 is often formed of an inexpensive resin material such as polyimide. However, since the heat resistant temperature is lower than that of a metal material, there are safety problems such as ignition and smoke generation.
In this embodiment, since the metal heat transfer member 22 is disposed between the fixing belt 21 and the heater 25, there is no problem of heat resistance as compared with the configuration in which the heat of the heater 25 is directly applied to the fixing belt 21. An inexpensive resin material employs a fixing belt 21 having a base material layer.

Referring to FIG. 2, a pressure roller 31 as a pressure rotator that contacts the outer peripheral surface of the fixing belt 21 at the position of the nip portion has a diameter of about 30 mm and is elastic on a hollow core metal 32. The layer 33 is formed.
The elastic layer 33 of the pressure roller 31 (pressure rotator) is formed of a material such as foamable silicone rubber, silicone rubber, or fluororubber.
A thin release layer made of PFA, PTFE or the like can be provided on the surface layer of the elastic layer 33.
The pressure roller 31 is pressed against the fixing belt 21 to form a desired nip portion between both members.

Referring to FIG. 3, the pressure roller 31 is provided with a gear 45 that meshes with a drive gear of a drive mechanism (not shown), and the pressure roller 31 is in the direction of the arrow (clockwise) in FIG. Driven by rotation.
Further, both ends of the pressure roller 31 in the width direction are rotatably supported by the side plates 43 of the fixing device 20 via bearings 42.
A heat source such as a halogen heater can be provided inside the pressure roller 31.
Note that when the elastic layer 33 of the pressure roller 31 is formed of a sponge-like material such as foamable silicone rubber, the pressure applied to the nip portion can be reduced. Can be reduced.
Furthermore, since the heat insulation of the pressure roller 31 is enhanced and the heat of the fixing belt 21 is difficult to move to the pressure roller 31 side, the heating efficiency of the fixing belt 21 is improved.

In the first embodiment, the diameter of the fixing belt 21 is formed to be equal to the diameter of the pressure roller 31, but the diameter of the fixing belt 21 is formed to be smaller than the diameter of the pressure roller 31. You can also
In that case, since the curvature of the fixing belt 21 in the nip portion is smaller than the curvature of the pressure roller 31, the recording medium P sent out from the nip portion is easily separated from the fixing belt 21.
In addition, the diameter of the fixing belt 21 can be formed to be larger than the diameter of the pressure roller 31, but the pressure roller 31 is independent of the relationship between the diameter of the fixing belt 21 and the diameter of the pressure roller 31. The applied pressure is not applied to the heat transfer member 22.

Here, referring to FIG. 2, the fixing device 20 according to the first embodiment is provided with contact / separation mechanisms 51 to 53 that contact and separate the pressure roller 31 with respect to the fixing belt 21.
Specifically, the contact / separation mechanism includes a pressure lever 51, an eccentric cam 52, a pressure spring 53, and the like.
The pressure lever 51 is rotatably supported by the side plate 43 of the fixing device 20 around a support shaft 51a provided on one end side.
The central portion of the pressure lever 51 is in contact with a bearing 43 of the pressure roller 31 (movably held in a long hole formed in the side plate 43).
A pressure spring 53 is connected to the other end of the pressure lever 51, and an eccentric cam 52 (configured to be rotatable by a drive motor (not shown)) is connected to a holding plate of the pressure spring 53. Match.

With such a configuration, the rotation of the eccentric cam 52 causes the pressure lever 51 to rotate about the support shaft 51a, and the pressure roller 31 moves in the direction of the broken line arrow in FIG.
That is, during the normal fixing process, the eccentric cam 52 is rotated in the rotational direction as shown in FIG. 2, and the pressure roller 31 presses the fixing belt 21 to form a desired nip portion.
On the other hand, when it is not during the normal fixing process (during jamming or standby), the eccentric cam 52 rotates 180 degrees from the state shown in FIG. The roller 31 separates from the fixing belt 21 (or depressurizes the fixing belt 21).

Hereinafter, the normal operation of the fixing device 20 configured as described above will be briefly described.
When the power switch of the apparatus main body 1 is turned on, electric power is supplied to the heater 25, and rotation driving of the pressure roller 31 in the direction of the arrow in FIG.
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 T (toner image) is conveyed in the direction of arrow Y10 in FIG. 2 while being guided by a guide plate (not shown), and the fixing belt 21 and the pressure roller 31 that are in a pressure contact state. It is fed into the nip part.
The toner on the surface of the recording medium P is heated by the fixing belt 21 heated by the heat transfer member 22 (heater 25) and the pressing force of the fixing member 26 reinforced by the reinforcing member 23 and the pressure roller 31. The image T is fixed.
Thereafter, the recording medium P delivered from the nip portion is conveyed in the direction of arrow Y11.

FIG. 4 is a schematic cross-sectional view showing the configuration of the fixing device 20. The fixing device 20 will be described with reference to FIG.
A fixing member 26, a heater 25 (heating means), a heat transfer member 22, a reinforcing member 23, and the like are fixedly provided inside the fixing belt 21 (inner peripheral surface side). An infrared heater 25 serving as a heating means is provided between the reinforcing member 23 and the heat transfer member 22.
Here, the fixing member 26 is made of a heat resistant resin material such as a liquid crystal polymer.

Further, a sliding sheet 28 for reducing the sliding resistance between the fixing member 26 and the fixing belt 21 is disposed between the fixing member 26 and the fixing belt 21.
The sliding sheet member 28 is formed in a rectangular shape with a material having a small friction coefficient and excellent wear resistance and heat resistance (for example, a sheet formed of a porous fluororesin fabric).

The fixing member 26 is formed in a concave shape so that the surface on the pressure roller 31 side 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.

In the first embodiment, the shape of the fixing member 26 that forms the nip portion is formed in a concave shape, but the shape of the fixing member 26 that forms the nip portion can also be formed in a flat shape.
That is, the sliding contact surface of the fixing member 26 (the surface facing the pressure roller 31) can be formed in a planar shape.
As a result, the shape of the nip portion is substantially parallel to the image surface of the recording medium P, and the adhesion between the fixing belt 21 and the recording medium P is increased, so that the fixing property is improved.
Further, since the curvature of the fixing belt 21 on the exit side of the nip portion is increased, the recording medium P sent from the nip portion can be easily separated from the fixing belt 21.

Referring to FIG. 3, both ends of the fixing member 26 in the width direction are fixedly supported by the side plates 43 of the fixing device 20.
The fixing support of the fixing member 26 with the side plate 43 is positioned at least in the conveyance direction of the recording medium P, and the pressing direction of the pressing roller 31 is preferably positioned with the reinforcing member 23.

In addition, guide guides 41 and 42 for guiding the traveling of the fixing belt 21 are arranged on the upstream side and the downstream side of the nip portion of the fixing member 26. The guide guides 41 and 42 are made of a heat-resistant resin material such as a liquid crystal polymer, and may be formed integrally with the fixing member 26.
Thereby, the circular posture of the fixing belt 21 having flexibility is maintained to some extent, so that deterioration / breakage due to deformation of the fixing belt 21 can be reduced.

Referring to FIG. 4, heat transfer member 22 is an arc-shaped member having a thickness of 0.1 mm.
The heat transfer member 22 is formed so as to directly contact the inner peripheral surface of the fixing belt 21 at a position opposite to the nip portion, and one end thereof is fixedly supported by the reinforcing member 23. Alternatively, referring to FIG. 3, both ends in the width direction of heat transfer member 22 may be fixedly supported on side plate 43 of fixing device 20.

  Fixing of the heat transfer member 22 to the reinforcing member 23 or the side plate 43 may be directly fixed, but is fixed via the heat insulating member 22a. Thereby, it is possible to prevent the heat of the heat transfer member 22 from being transmitted to the reinforcing member 23.

The heat transfer member 22 is made of a material having a spring property, and one end thereof is fixedly supported by the reinforcing member 23, and the other end gives a biasing force to the fixing belt 21. Touching. As a result, a reduction in the contact area with the heat transfer member 22 due to floating of the fixing belt 21 during travel can be suppressed, and the heating efficiency of the fixing belt 21 can be ensured more reliably.
Further, it is preferable that a heat insulating material is sandwiched between the heat transfer member 22 and the reinforcing member 23.

An inner surface coating is applied to the side of the heat transfer member 22 opposite to the belt member in order to absorb the radiant heat (radiant light) of the heater 25.
The heat transfer member 22 is heated by the radiant heat (radiant light) of the heater 25 to heat the fixing belt 21.
That is, the heat transfer member 22 is directly heated by the heater 25 (heating means), and the fixing belt 21 is indirectly heated by the heater 25 through the heat transfer member 22.

As a material of the heat transfer member 22, a metal heat conductor (a metal having heat conductivity) such as aluminum, iron, and stainless steel can be used.
By setting the thickness of the heat transfer member 22 to 0.2 mm or less, the heating efficiency of the fixing belt 21 (heat transfer member 22) can be improved.
In the first embodiment, the heat transfer member 22 is formed of stainless steel having a wall thickness of 0.1 mm.

The heater 25 (heat source) is a halogen heater or a carbon heater, and both ends thereof are fixed to the side plate 43 of the fixing device 20 (see FIG. 3).
The heat transfer member 22 is heated by the radiant heat of the heater 25 whose output is controlled by the power supply unit of the apparatus body 1.
Further, the fixing belt 21 is entirely heated by the heat transfer member 22 at a position facing the nip portion, 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 the temperature sensor 40 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.
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.

In the present embodiment, since the heat transfer member 22 and the fixing belt 21 are not in contact with each other in substantially the entire circumference, the area where the heat transfer member 22 and the fixing belt 21 are in sliding contact with each other is increased, and wear of the fixing belt 21 is accelerated. Defects can be suppressed.
In addition, since the heat transfer member 22 and the fixing belt 21 are always in contact with each other, a problem that the heating efficiency of the fixing belt 21 is reduced can be suppressed.
Also, fluorine grease is applied between both members 21 and 22 so that the wear of the fixing belt 21 is reduced even if the heat transfer member 22 and the fixing belt 21 (belt member) are in sliding contact with each other. ing.
In order to reduce the sliding resistance between the heat transfer member 22 and the fixing belt 21, the sliding contact surface of the heat transfer member 22 is formed of a material having a low friction coefficient, or fluorine is applied to the inner peripheral surface of the fixing belt 21. It is also possible to form a surface layer made of the containing material.

The reinforcing member 23 (supporting member) is for reinforcing and supporting the fixing member 26 forming the nip portion, and is fixed to the inner peripheral surface side of the fixing belt 21.
The reinforcing member 23 (support member) has a U-shaped cross section and has an opening 23a. The opening 23 a faces the fixing member 26.
The heat transfer member 22 is disposed so as to cover the opening 23a. Here, covering the opening 23a means covering the entire opening.
As a result, the mechanical strength can be ensured with a small cross section, and downsizing and low heat capacity can be realized.

Referring to FIG. 3, the reinforcing member 23 is formed so that the length in the width direction is equal to that of the fixing member 26, and both end portions in the width direction are fixedly supported by the side plates 43 of the fixing device 20. .
The reinforcing member 23 comes into contact with the pressure roller 31 (pressure rotating body) via the fixing member 26, the fixing belt 21, and the sliding sheet 28, so that the fixing member 26 adds the pressure roller 31 at the nip portion. Inhibits large deformation under pressure.
The reinforcing member 23 is preferably formed of a metal material having high mechanical strength such as stainless steel or iron in order to satisfy the functions described above.

In addition, an infrared reflecting plate 44 is disposed in part or all of the U-shaped reinforcing member 23 between the U-shaped reinforcing member 23 and the heater 25.
The infrared reflector 44 is fixedly supported by the reinforcing member 23 at its end.
The infrared reflecting plate 44 may be fixed directly, but in the present embodiment, the infrared reflecting plate 44 is fixed via a heat insulating member 43a. Thereby, it is possible to prevent the heat of the infrared reflecting plate 44 from being transmitted to the reinforcing member 23.

The surface of the infrared reflector 44 facing the heater 25 is made of a material coated with high-luminance aluminum or silver coat having an infrared reflectivity of 90% or more in order to heat the heat transfer member 22 without waste.
With this infrared reflecting plate 44, it is possible to prevent heat from being taken away by members outside the infrared reflecting plate 44 as viewed from the heater 25.
The infrared reflector 44 is configured to cover the heater 25 by 180 ° or more.
Further, the heat transfer member 22 is disposed in contact with the fixing belt 21, and the contact area is configured to contact at least 60% or more of the area of the heat transfer member 22. With these configurations, it is possible to heat only the heat transfer member 22 that abuts the heat of the heater 25 on the fixing belt 21, and the thermal efficiency can be greatly improved.

According to the present embodiment described above, the heat transfer member that contacts the belt member in a configuration that covers the opening of the reinforcing member, and the heating means between the reinforcing member and the heat transfer member have only the opening. Since the disposed metal heat transfer member is in contact with the belt member, it is possible to prevent heating of the portion not in contact with the belt member, and to transfer the heat of the heater to the belt member with maximum efficiency. it can.
Also, a heat transfer member that contacts the belt member in a configuration that covers the opening of the reinforcing member, and a metal heat transfer member that is disposed only in the opening by having heating means between the reinforcing member and the heat transfer member Is in contact with the belt member, it is possible to prevent heating of the portion not in contact with the belt member, and to transfer the heat of the heater to the belt member with maximum efficiency.
In addition, since the opening portion faces the nip portion, the strength of the reinforcing member can be secured with a small cross-sectional area, and downsizing can be realized.
Moreover, by using an infrared heater, versatility is high, a structure is simple, and low cost is realizable.
In addition, by arranging an infrared reflector between the heating means and the reinforcing member, it is possible to prevent heat from being taken away by members (reinforcing members, fixing members, etc.) that secure the nip, and to maximize the heat of the heater. It is possible to transfer heat to the belt member with efficiency.

Further, since the infrared reflector is high-luminance aluminum having an infrared reflectance of 90% or more, the heat of the heater can be transferred to the belt member with maximum efficiency.
Further, the external reflection plate is supported and fixed by the reinforcing member, so that the infrared reflection plate can be easily arranged.
In addition, a heat insulating material is sandwiched between the infrared reflector and the reinforcing member to prevent heat from being taken away by members (reinforcing members, fixing members, etc.) that secure the nip, and to maximize the heat of the heater. Heat can be transferred to the belt member with limited efficiency.
Moreover, a heat-transfer member can be arrange | positioned easily by a structure being supported by the reinforcement member and being fixed.

In addition, since the heat insulating material is sandwiched between the heat transfer member and the reinforcing member, it is possible to prevent heat from being taken away by members (reinforcing members, fixing members, etc.) that secure the nip, and to maximize the heat of the heater. Heat can be transferred to the belt member with limited efficiency.
In addition, the heat transfer member has springiness and is in contact with the belt member, so that the contact between the belt member and the heat transfer member can be improved, and the heat of the heater is transferred to the belt member with maximum efficiency. can do.
Further, the belt member has a base material, and the base material contains a heat resistant resin, so that weight reduction can be realized at low cost.
Also, by providing these fixing devices, it is possible to provide an image forming apparatus that can transfer the heat of the heater to the belt member with maximum efficiency.

P Recording medium 20 Fixing device 21 Fixing belt 22 Heat transfer member 23 Reinforcing member 25 Heater 26 Fixing member 31 Pressure roller 41, 42 Guide guide 43 Side plate 44 Infrared reflector

JP 2010-096823 A JP 2007-192846 A

Claims (12)

A pressure rotating body;
An endless belt member having flexibility and running in a predetermined direction to heat and melt the toner image;
An inner periphery of the belt member is formed in pressure contact with the pressure rotator through the belt member and forms a nip portion with the pressure rotator to which a recording medium having a toner image on the surface is conveyed. A fixing member fixed on the surface side;
A reinforcing member fixed on the inner peripheral surface side of the belt member and abutting against the fixing member to reinforce the fixing member;
The reinforcing member has an opening,
A fixing device comprising: a heat transfer member that covers the opening and is in contact with the belt member; and a heating unit provided between the reinforcing member and the heat transfer member.   The fixing device according to claim 1, wherein the opening of the reinforcing member faces the fixing member.   The fixing device according to claim 1, wherein the heating unit is an infrared heater.   The fixing device according to claim 1, further comprising an infrared reflecting plate between the heating unit and the reinforcing member.   The fixing device according to claim 4, wherein the infrared reflecting plate is high-luminance aluminum having an infrared reflectance of 90% or more.   The fixing device according to claim 4, wherein the infrared reflecting plate is supported and fixed by the reinforcing member.   The fixing device according to claim 4, wherein a heat insulating material is sandwiched between the infrared reflecting plate and the reinforcing member.   The fixing device according to claim 1, wherein the heat transfer member is supported and fixed by the reinforcing member.   The fixing device according to claim 1, wherein a heat insulating material is sandwiched between the heat transfer member and the reinforcing member.   The fixing device according to claim 1, wherein the heat transfer member has a spring property and is in contact with the belt member. The belt member has a base material,
The fixing device according to claim 1, wherein the base material includes a heat resistant resin. An image forming apparatus comprising the fixing device according to claim 1.