JP5084438B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine thereof, and a fixing device installed therein, and in particular, presses and releases a fixing member and a pressure member. The present invention relates to a fixing device and an image forming apparatus.

  Conventionally, in a fixing device installed in an image forming apparatus such as a copying machine or a printer, a fixing member such as a fixing roller or a fixing belt, and a pressure member such as a pressure roller, a pressure belt, or a pressure pad; A technique for releasing the pressure contact state is known (see, for example, Patent Document 1 and Patent Document 2).

In the fixing device, the fixing member and the pressure member are brought into a pressure contact state by the pressure unit, and a nip portion (fixing nip portion) is formed between the two members. Then, the fixing member is heated by heating means such as a heater and an excitation coil, and the toner image on the recording medium conveyed toward the nip portion is fixed on the recording medium by receiving heat and pressure.
Such a fixing device is provided with a release mechanism for releasing the pressure contact state between the fixing member and the pressure member. When a jam (paper jam) occurs in the recording medium at the nip portion, the user can easily perform the jam processing by operating the release mechanism.

Here, in Patent Document 1 and the like, when the pressure release lever (release lever) is in the pressure release position, the pressure release lever moves from the pressure release position to the pressure position in conjunction with the closing operation of the cover of the image forming apparatus main body. A technique for moving to is disclosed. Furthermore, a technique is also disclosed in which a stopper that engages with the pressure release lever is provided on the housing of the apparatus in order to determine the pressure release position of the pressure release lever.
Japanese Patent Application Laid-Open No. H11-228561 discloses a technique for performing an operation of releasing the pressure contact state between the fixing member and the pressure member in conjunction with the opening operation of the cover of the image forming apparatus main body.

Japanese Patent No. 3896235 JP 2006-48005 A

In the fixing device disclosed in Patent Document 1 and the like, since a stopper that determines the pressure release position of the pressure release lever is installed in the housing of the device, the shape and size of the housing are limited. Therefore, the fixing device may be increased in size and cost.
In addition, since the fixing device disclosed in Patent Document 2 performs the operation of releasing the pressure contact state between the fixing member and the pressure member in conjunction with the opening operation of the cover of the image forming device main body, In the removed state, the pressure release position is not determined, and the operability of the fixing device alone is insufficient. Therefore, the workability of taking out the fixing device from the image forming main body (for example, jam handling work that cannot be processed without taking out the fixing device) is poor. Furthermore, the configuration of the apparatus is complicated, and the apparatus may be increased in size and cost.

  The present invention has been made to solve the above-described problems, and the structure of the apparatus is relatively simple, and the operability of releasing the pressure contact is high even with the fixing apparatus alone without increasing the size and cost of the apparatus. Another object is to provide a fixing device and an image forming apparatus.

According to a first aspect of the present invention, a fixing device forms a fixing member that heats and melts a toner image and fixes the toner image on a recording medium, and a nip portion that is pressed against the fixing member and the recording medium is conveyed. A pressure member that is urged by a biasing means and engages the pressure member or the fixing member directly or indirectly to bring the pressure member and the fixing member into a pressure contact state; A release lever that pushes the pressure lever to displace the pressure lever to release the pressure contact state of the pressure member and the fixing member, and the release lever includes the pressure member and the pressure member. A contact portion that contacts a contacted portion of the pressure lever after the displacement of the pressure lever is started and determines a release position of the pressure lever when releasing the pressure contact state of the fixing member ; Displace the pressure lever at the release position to When the member and the fixing member are returned to the pressure contact state, after the displacement of the pressure lever is started, a stop position of the pressure lever is determined by contacting the second contacted portion of the pressure lever. And the fixing position is fixed when the second contact portion and the second contacted portion are not installed at the stop position. When the position of the pressure lever that is restricted in a state where the member and the pressure member are thermally expanded, and the second contact portion and the second contacted portion are not installed The apparatus is set to a position between the position of the pressure lever which is restricted in a state where the apparatus is stopped and the fixing member and the pressure member are not thermally expanded .

The fixing device according to a second aspect of the present invention is the fixing device according to the first aspect, wherein the release lever includes a cam portion and is configured to be rotatable about a support shaft. Accordingly, the cam portion slides on the flat portion of the pressure lever to displace the pressure lever.

The fixing device according to a third aspect of the present invention is the fixing device according to the first or second aspect , wherein the pressure lever and / or the release lever are made of a metal material.

A fixing device according to a fourth aspect of the present invention is the fixing device according to any one of the first to third aspects, wherein the pressure lever is a bearing that pivotally supports the pressure member or the fixing member. And the pressure member and the fixing member are brought into a pressure contact state.

According to a fifth aspect of the present invention, in the fixing device according to the fourth aspect, the bearing is held movably with respect to the frame of the device in accordance with the displacement of the pressure lever. is there.

According to a sixth aspect of the present invention, in the fixing device according to the fifth aspect of the present invention, the bearing is engaged with a driven gear installed on the shaft of the pressure member or the fixing member. It moves on the frame around the center of rotation of the gear transmitting the force.

The fixing device according to a seventh aspect of the present invention is the fixing device according to any one of the first to sixth aspects, wherein the release lever closes a cover that can be opened and closed on the main body of the image forming apparatus. In conjunction with the operation, displacement of the pressure lever at the release position toward the pressure position is started.

An image forming apparatus according to an eighth aspect of the present invention includes the fixing device according to any one of the first to seventh aspects.

  According to the present invention, when the pressure contact state between the fixing member and the pressure member is released, after the displacement of the pressure lever is started, the release position of the pressure lever is determined by contacting the contacted portion of the pressure lever. The contact portion is provided on the release lever. As a result, it is possible to provide a fixing device and an image forming apparatus that have a relatively simple device configuration, are large in size and high in cost, and have high operability for releasing pressure contact even with a single fixing device.

Embodiment.
Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. In addition, 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.

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 in the present embodiment is a tandem 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 has been transferred at the position of the secondary transfer nip is conveyed to the nip portion of the fixing portion 20 (where the fixing belt 21 and the pressure roller 31 are in pressure contact). The color image transferred onto the surface is fixed on the recording medium P by the heat and pressure generated by the fixing belt 21 and the pressure roller 31 at the nip portion (fixing nip portion).
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.

  A cover 110 (main body cover) is installed on the side of the apparatus main body 1 so as to be openable and closable. When the cover 110 is opened around the support shaft 110a in the direction of arrow A in FIG. 1, the fixing device 20 is exposed. Then, the user or the service person performs processing (jam processing) of the jammed recording medium P at the position of the fixing device 20 with the fixing device 20 exposed, or removes the fixing device 20 from the apparatus main body 1 and fixes the fixing device 20. 20 maintenance.

Next, the configuration / operation of the fixing device 20 installed in the image forming apparatus main body 1 will be described in detail with reference to FIG.
As shown in FIG. 2, the fixing device 20 includes a fixing belt 21 as a fixing member, a fixing auxiliary roller 22, a heating roller 23, a pressure roller 31 as a pressure member, a tension roller 35, and the like.

  Here, the fixing belt 21 as a fixing member is an endless belt having a multilayer structure in which an elastic layer and a release layer are sequentially laminated on a base layer made of polyimide resin and having a layer thickness of 90 μm. The elastic layer of the fixing belt 21 has a layer thickness of about 200 μm and is formed of an elastic material such as silicone rubber, fluorine rubber, and foamable silicone rubber. The release layer of the fixing belt 21 has a layer thickness of about 20 μm, and is formed of PFA (tetrafluoroethylene bar fluoroalkyl vinyl ether copolymer resin), polyimide, polyetherimide, PES (polyether sulfide), or the like. Has been. By providing the release layer on the surface layer of the fixing belt 21, the releasability (peelability) for the toner T (toner image) is ensured. The fixing belt 21 is stretched and supported by a plurality of roller members (the fixing auxiliary roller 22, the heating roller 23, and the tension roller 35), and travels in the direction of the arrow in FIG.

  The fixing auxiliary roller 22 is a cylindrical member having an outer diameter of 52 mm, in which an elastic layer 22b (layer thickness is 14 mm) made of fluorine rubber, silicone rubber, foamable silicone rubber or the like is formed on a core metal 22a such as SUS304. Then, a nip portion (fixing nip portion) is formed by contacting the pressure roller 31 as a pressure member via the fixing belt 21. The fixing auxiliary roller 22 rotates in the clockwise direction in FIG.

The heating roller 23 is a cylindrical body (thickness is 0.6 mm, outer diameter is 35 mm) made of a metal material such as aluminum, and a heater 25 (heat source) is fixed inside the cylindrical body. ing.
The heater 25 of the heating roller 23 is a halogen heater, and both ends thereof are fixed to the frame of the fixing device 20. Then, the heating roller 23 is heated by the radiant heat from the heater 25 whose output is controlled by the power supply unit (AC power supply) of the apparatus main body 1, and further on the recording medium P from the surface of the fixing belt 21 heated by the heating roller 23. Heat is applied to the toner image T. The output control of the heater 25 is performed based on the detection result of the belt surface temperature by a thermopile (not shown) that faces the surface of the fixing belt 21 in a non-contact manner. Specifically, the AC voltage is applied to the heater 25 for the energization time determined based on the detection result of the thermopile. By such output control of the heater 25, the temperature (fixing temperature) of the fixing belt 21 can be adjusted and controlled to a desired temperature (target control temperature).

The pressure roller 31 as a pressure member is formed with an elastic layer 33 having a layer thickness of 1.5 mm made of silicone rubber, fluororubber, foamable silicone rubber or the like on a hollow core metal 32 having a thickness of 1 mm. It has been done. The pressure roller 31 has an outer diameter set to about 50 mm. A thin release layer made of PFA or the like can be provided on the surface layer of the elastic layer 33.
The pressure roller 31 is pressed against the auxiliary fixing roller 22 via the fixing belt 21 by a pressure mechanism (described in detail later with reference to FIG. 3 and the like). Thus, a desired nip (fixing nip) is formed between the pressure roller 31 and the fixing belt 21. Here, the pressure roller 31 is rotationally driven by a drive motor (not shown), and details thereof will be described later with reference to FIG.
In the present embodiment, heating means such as a heater that directly heats the pressure roller 31 may be provided.

  Although not shown, a guide plate for guiding the conveyance of the recording medium P is disposed on the entrance side of the contact portion (nip portion) between the fixing belt 21 and the pressure roller 31. In addition, the recording medium P sent from the nip portion (the recording medium after the fixing process) is wound around the pressure roller 31 at a position in contact with the pressure roller 31 and in the vicinity of the exit side of the nip portion. Separation plates are installed to prevent problems with sticking.

The fixing device 20 configured as described above operates as follows.
When the power switch of the apparatus main body 1 is turned on, an AC voltage is applied (powered) from the AC power source to the heater 25, and the pressure roller 31 is driven to rotate in the direction of the arrow in FIG. At the same time, the fixing belt 21 (fixing auxiliary roller 22 and heating roller 23) is driven to rotate.
Thereafter, the recording medium P is fed from the paper feeding unit 12 and an unfixed image is carried on the recording medium P at the position of the secondary transfer nip. The recording medium P carrying the unfixed image T (toner image) is conveyed in the direction of the arrow Y10 in FIG. 2 and fed into the nip portion between the fixing belt 21 and the pressure roller 31 that are in a pressure contact state. The toner image T is fixed on the surface of the recording medium P by the heating by the fixing belt 21 and the pressing force of the fixing belt 21 (fixing auxiliary roller 22) and the pressure roller 31. Thereafter, the recording medium P sent out from the nip portion by the rotating fixing belt 21 and the pressure roller 31 is conveyed in the direction of the arrow Y11.

Hereinafter, the configuration and operation of the fixing device 20 that are characteristic in the present embodiment will be described with reference to FIGS.
3 is a side view showing the fixing device when the fixing belt 21 and the pressure roller 31 are in a pressure contact state, and FIG. 4 is a side view showing the fixing device when the pressure contact state is released (released state). is there. FIG. 5 is a perspective view showing a state in which the pressure roller 31 is installed on the frame 38 of the fixing device. FIG. 6 is a diagram showing the frame 38 alone. FIG. 7 is a view showing the position of the bearing 55 installed in the frame 38 in the press-contact state, and FIG. 8 is a view showing the position of the bearing 55 in the released state. FIG. 9 is a perspective view showing a state in which the gear trains 61 to 65 are installed on the frame 38. FIG. 10 is a view showing a state in which the release lever 41 is engaged with the cover 110 of the apparatus main body 1.

3 and 4, the pressure roller 31 is rotatably supported by the frame 38 via a bearing 55 (ball bearing). Similarly, the auxiliary fixing roller 22 and the heating roller 23 are also rotatably supported by the frame 38 via bearings.
The pressure mechanism of the fixing device 20 includes a pressure lever 40, a release lever 41, a spring 50 (tensile spring) as urging means, and the like. The pressure lever 40 is biased by the spring 50 (biasing means) and engages with the pressure roller 31 (indirect engagement via the bearing 55), and the pressure roller 31 and the fixing belt. This is for bringing 21 into a pressure contact state. The release lever 41 is for releasing the pressure contact state between the pressure roller 31 and the fixing belt 21 by pressing the pressure lever 40 to displace (rotate) the pressure lever 40.

Specifically, the pressure lever 40 is supported by the frame 38 so as to be rotatable about the support shaft 40a. A hooking portion 40b to which the hook of the spring 50 is connected is formed on one end side of the pressure lever 40 (at a position away from the support shaft 40a). On the other hand, the other hook of the spring 50 is connected to the hooking portion of the frame 38. The central portion of the pressure lever 40 is in contact with a bearing 55 (installed on the shaft portion 31 a of the pressure roller 31) that supports the pressure roller 31. With such a configuration, the pressure lever 40 biases the pressure roller 31 toward the fixing belt 21 by the spring force of the spring 50. As a result, a desired nip portion is formed between the pressure roller 31 and the fixing belt 21. Here, the pressure lever 40 is formed of a metal material in order to ensure mechanical strength.
Further, the pressurizing lever 40 engages with the release lever 41, and includes a flat surface portion 40c (formed by bending), a contacted portion 40d (first contacted portion), and a second contacted portion. A contact portion 40e (second contacted portion) is provided.

The release lever 41 is supported by the frame 38 so as to be rotatable about the support shaft 41a. On one end side of the release lever 41 (at a position away from the support shaft 41a), a grip portion 41b for gripping by a user or a serviceman is provided. Further, a cam portion 41 c that engages with the flat surface portion 40 c of the pressure lever 40 is formed at the center of the release lever 41. The cam portion 41c slides on the flat surface portion 40c of the pressure lever 40 and displaces the pressure lever 40 in accordance with the turning operation of the release lever 41 around the support shaft 41a.
The release lever 41 is also provided with a contact portion 41d (first contact portion) and a second contacted portion 41e (second contact portion) that engage with the pressure lever 40. . The release lever 41 is also made of a metal material in order to ensure mechanical strength.

The operation of the pressure mechanism of the fixing device 20 will be described in detail with reference to FIGS.
When releasing the pressure contact state (when moving from the pressurization position to the release position), the holding portion 41b is held and the release lever 41 is rotated about the support shaft 41a in the clockwise direction in FIG. . As a result, the flat portion 40c is pushed by the cam portion 41c, and the pressure lever 40 rotates about the support shaft 40a in the clockwise direction in FIG. 3 so as to resist the force of the spring 50. At this time, since the cam portion 41c slides on the flat surface portion 40c formed so as to face the cam portion 41c by bending with a stable frictional resistance, the operability for the operator who operates the release lever 41 is improved. Will improve. In order to further reduce the sliding resistance between the cam portion 41c and the flat portion 40c, grease can be applied or a low friction member can be installed between the cam portion 41c and the flat portion 40c.

  Thereafter, when the clockwise rotation operation of the release lever 41 in FIG. 3 proceeds (after the displacement of the pressure lever is started), the first contact portion 41d eventually becomes the first contact portion 40d of the pressure lever 40. The release position (stop position) of the pressure lever 40 is determined. That is, the first contact portion 41d of the release lever 41 contacts the first contacted portion 40d of the pressure lever 40, and the clockwise rotation movement of the pressure lever 40 is restricted (in the state of FIG. 4). is there.). At this time, the moment that rotates the release lever 41 in the release direction (clockwise in FIG. 4) acts on the support shaft 41 a of the release lever 41 via the pressure lever 40 by the spring force of the spring 50. The balanced state is maintained by the contact between the portion 41d and the contacted portion 40d.

  As described above, in this embodiment, when the pressure contact state between the fixing belt 21 and the pressure roller 31 is released, the displacement of the pressure lever 40 is started and the contacted portion 40d of the pressure lever 40 is contacted. Since the abutment portion 41d that contacts and determines the release position (stop position) of the pressure lever 40 is provided in the release lever 41, the configuration of the fixing device 20 is relatively simple, and the fixing device 20 is increased in size and cost. Therefore, the operability of releasing the pressure contact can be improved even with the fixing device 20 alone.

  On the other hand, when the fixing device 20 alone is returned from the release state to the pressure contact state (when moving from the release position to the pressure position), the holding portion 41b is held and the support shaft 41a is the center. Thus, the release lever 41 is rotated counterclockwise in FIG. As a result, the pressure lever 40 moves toward the pressure position by the spring force of the spring 50 (the movement in the counterclockwise direction in FIG. 4), and the cam portion 41c slides on the flat surface portion 40c. However, the release lever 41 also rotates counterclockwise in FIG. 4 and eventually stops at the pressure position (the state shown in FIG. 3). At this time, since the pressure lever 40 is biased in the direction of the pressure position (pressure direction) by the spring 50, the force required to operate the grip portion 41b of the release lever 41 is very small. .

In the present embodiment, the release lever 41 is directed toward the pressure position of the pressure lever 40 in the release position in conjunction with the closing operation of the cover 110 that can be opened and closed in the image forming apparatus main body 1. It is comprised so that the displacement of may be started.
Specifically, referring to FIG. 10, when the fixing device 20 is installed in the image forming apparatus main body 1, when returning from the release state to the pressure contact state, the operator places the cover 110 around the support shaft 110a in FIG. When the projection 110b is closed in the direction of arrow A ', the protrusion 110b installed on the cover 110 pushes the grip 41b of the release lever 41, and then the release lever 41 and the pressure lever 40 are the same as in the manual operation described above. Will work.
With such a configuration, when the jam of the recording medium P occurs at the position of the fixing device 20 and the operator performs the above-described release operation to perform the jam processing, the operator returns the release lever 41 described above. Even when the operation is forgotten, the cover 110 is always closed when the operation of the apparatus is resumed, so that the fixing device 20 can be prevented from operating in a released state. can do.

  Here, the stop position (pressure position) of the pressure lever 40 in the pressure contact state can be determined at a position where the pressure roller 31 and the fixing belt 21 abut. That is, when the pressure roller 31 and the fixing belt 21 come into contact with each other, the rotation movement of the pressure lever 40 in the counterclockwise direction in FIG. Is done.

  In contrast, in the present embodiment, referring to FIG. 3, when the pressure lever 40 in the release position is displaced (rotated) and returned to the pressure contact state, the displacement (rotational movement) of the pressure lever 40 is restored. ) Is started, the release lever 41 is provided with a second contact portion 41e that contacts the second contacted portion 40e of the pressure lever 40 to determine the stop position (pressure position) of the pressure lever 40. Yes. That is, when the release lever 41 and the pressure lever 40 move in the pressure direction, the pressure roller 31 and the fixing belt 21 come into contact with each other before the movement of the pressure lever 40 is restricted. The contact portion 40e and the second contact portion 41e are brought into contact with each other to restrict the movement of the pressure lever 40.

However, the stop position (pressure position) in this case is a pressure lever 40 that is restricted from moving in a state where the fixing device 20 is operated and the fixing belt 21 (fixing auxiliary roller 22) and the pressure roller 31 are thermally expanded. The movement of the fixing device 20 is stopped and the fixing belt 21 (fixing auxiliary roller 22) and the pressure roller 31 are not thermally expanded (the state is cooled by being left for a long time). The position between the pressure lever 40 and the position of the pressure lever 40 is set.
Since the fixing belt 21 (fixing auxiliary roller 22) and the pressure roller 31 are thermally expanded during operation (when the fixing is possible), the pressure lever 40 is released in the release direction compared to the cold state. Has been pushed back. Therefore, by setting the stop position (pressure position) of the pressure lever 40 within the above range, when the fixing device 20 is not operated for a long time, the fixing belt 21 (fixing auxiliary roller 22) or the pressure is applied by the applied pressure. It is possible to prevent a problem that permanent deformation occurs in the roller 31. Further, when the fixing device 20 is in operation (thermal expansion), the movement of the pressure lever 40 is restricted by the contact between the pressure roller 31 and the fixing belt 21 (the second contacted portion 40e and the second contacted portion 40e). 2) Since the movement of the pressure lever 40 is not restricted by the contact with the contact portion 41e), there is no shortage of the nip width at the nip portion due to the poor pressure contact between the pressure roller 31 and the fixing belt 21. Note that when a shortage of the nip width (decrease in the nip width) occurs, a fixing failure such as a cold offset occurs on the output image.

Hereinafter, the relationship between the bearing 55 with which the pressure lever 40 engages and the frame 38 will be described in detail with reference to FIGS.
As described above, in the present embodiment, the pressure roller 31 has the shaft portion 31a with the bearing 55 (the position in the rotation axis direction is determined by the retaining ring 53) inserted. It is rotatably supported by the frame 38 via a bearing 55 (see FIG. 5). The pressure lever 40 is urged by the spring 50 to press the pressure roller 31 toward the fixing belt 21 via the bearing 55.

Here, in order to enable the pressure roller 31 to move between the pressure position and the release position, the bearing 55 that pivotally supports the pressure roller 31 moves in accordance with the displacement (rotation) of the pressure lever 40. Is held movable.
Specifically, as shown in FIG. 6, the frame 38 is formed with a deformed hole 38 c for moving the bearing 55 in the pressurizing direction / release direction. The irregular hole 38c is provided with a plurality of receiving portions 38a for restricting the movement of the bearing 55 in the rotation axis direction (the direction perpendicular to the paper surface of FIG. 6) (the other end is regulated by the retaining ring 53). ) Further, the deformed hole 38c is provided with a guide portion 38b for guiding the movement of the bearing 55 in the pressurizing direction / release direction.
With such a configuration, the bearing 55 installed in the deformed hole 38c of the frame 38 moves between the pressurization position and the release position. FIG. 7 shows a state in which the bearing 55 is in the pressurizing position (a state in the pressure contact state), and FIG. 8 shows a state in which the bearing 55 is in the release position (a state in the release state). is there.

  In the frame 38 shown in FIG. 6, a bearing that supports the fixing auxiliary roller 22 is installed in the hole 38e, and a bearing that supports the heating roller 23 is installed in the hole 38f. The stud 38 d standing on the frame 38 is provided with a gear 62 (idler gear) that meshes with a driven gear 63 installed on the shaft 31 a of the pressure roller 31 and transmits a driving force to the driven gear 63. (See also FIG. 9).

Hereinafter, the relationship between the bearing 55 with which the pressure lever 40 engages and the drive unit of the fixing device 20 will be described in detail with reference to FIG. 9.
Referring to FIG. 9, in the present embodiment, a drive motor (not shown) drives and inputs a gear 61 (drive gear), and a driven gear 63 (pressure) of the pressure roller 31 via a gear 62 (idler gear). The driving force is transmitted to the roller 31. Further, the drive gear 61 transmits the driving force to a gear 64 installed on the shaft 22a of the auxiliary fixing roller 22, and a paper discharge unit (a pair of paper discharge rollers 99 in FIG. )).
Here, although not shown, a one-way clutch is provided between the shaft 22 a of the auxiliary fixing roller 22 and the gear 64. As a result, the linear velocity of the fixing belt 21 (the linear velocity at the nip portion) is slightly smaller than the linear velocity of the pressure roller 31 (the linear velocity on the outer peripheral surface). Therefore, the fixing belt 21 is driven to rotate by contact with the pressure roller 31 due to the effect of the one-way clutch. With such a configuration, when a slip occurs between the pressure roller 31 and the recording medium P in the nip portion, the one-way clutch is locked and the recording medium P is auxiliaryly conveyed by the fixing belt 21. It will be.
In this embodiment, the pressure roller 31 functions as a main driving roller, but the fixing auxiliary roller 22 can also function as a main driving roller. Further, the fixing belt 21 can be simply driven only by the contact force with the pressure roller 31 without adopting the above-described one-way clutch configuration.

Here, in the present embodiment, the bearing 55 that pivotally supports the pressure roller 31 moves on the frame 38 around the rotation center of the idler gear 62 (a gear that transmits driving force to the driven gear 63). It is configured to do.
Specifically, referring to FIG. 6, the guide portion 38 b that guides the movement of the bearing 55 in the pressurizing direction / release direction is formed so as to draw an arc-shaped locus centering on the rotation center of the idler gear 62. Yes.
With such a configuration, the axial center pitch between the driven gear 63 and the idler gear 62 is kept constant regardless of the position of the pressure roller 31. Therefore, it is possible to prevent problems such as rotation unevenness due to the displacement of the pressure roller 31.

  As described above, in this embodiment, when the pressure contact state between the fixing belt 21 (fixing member) and the pressure roller 31 (pressure member) is released, the displacement of the pressure lever 40 is started. The release lever 41 is provided with an abutment portion 41 d that abuts against the abutted portion 40 d of the pressure lever 40 and determines the release position of the pressure lever 40. As a result, the fixing device 20 has a relatively simple configuration, and the fixing device 20 can be improved in operability of pressure contact release even with the fixing device alone 20 without increasing the size and cost.

In the present embodiment, the present invention is applied to the fixing device using the fixing belt 21 as the fixing member and the pressure roller 31 as the pressure member, but the fixing device using the fixing roller as the fixing member. (This is an apparatus that forms a nip portion by two roller members without using a belt member.) The present invention is also applied to a fixing device that uses a pressure belt or a pressure pad as a pressure member. be able to.
In the present embodiment, the present invention is applied to the fixing device 20 using the heater 25 as the heating unit. However, the electromagnetic induction heating type fixing device using the exciting coil as the heating unit, the transfer process and fixing. Of course, the present invention can also be applied to a fixing device (transfer fixing device) that performs the process simultaneously.
Even in those cases, the same effects as in the present embodiment can be obtained.

In the present embodiment, the pressure lever 40 is indirectly engaged with the pressure roller 31 via the bearing 55, but the pressure lever 40 is directly engaged with the pressure roller 31. A configuration (for example, a configuration in which the pressure lever 40 is engaged with the shaft 31a of the pressure roller 31) may be employed.
Further, in the present embodiment, the pressure lever 40 is engaged with the pressure member 31 to form a pressure contact state, but the pressure lever is a fixing member (for example, the pressure lever is engaged with the fixing roller). It is also possible to adopt a configuration in which a press-contact state is formed by engaging with.
Even in those cases, the same effects as in the present embodiment can be obtained.

  It should be noted that the present invention is not limited to the present embodiment, and it is obvious that the present embodiment can be modified as appropriate within the scope of the technical idea of the present invention, other than suggested in the present embodiment. is there. In addition, the number, position, shape, and the like of the constituent members are not limited to the present embodiment, and the number, position, shape, and the like suitable for implementing the present invention can be achieved.

1 is an overall configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention. 2 is a configuration diagram illustrating a fixing device. FIG. It is a side view showing a fixing device in a pressure contact state. FIG. 6 is a side view showing the fixing device in a released state. It is a perspective view which shows the state in which the pressure roller was installed in the flame | frame. It is a figure which shows a flame | frame. It is a figure which shows the position at the time of the press-contact state of the bearing installed in the flame | frame. It is a figure which shows the position at the time of the cancellation | release state of the bearing installed in the flame | frame. It is a perspective view which shows the state in which the gear train was installed. It is a figure which shows the state which the cancellation | release lever engaged with the cover of the apparatus main body.

Explanation of symbols

1 image forming apparatus body (apparatus body),
20 fixing device,
21 fixing belt (fixing member),
22 fixing auxiliary roller,
23 Heating roller,
25 heater (heating means),
31 Pressure roller (pressure member),
38 frames,
40 Pressure lever,
40a spindle, 40c plane part,
40d contacted part, 40e second contacted part,
41 Release lever,
41a spindle, 41c cam part,
41d contact part, 41e second contact part,
50 spring (biasing means), 55 bearing,
61-65 gear, 110 cover, P recording medium.

Claims (8)

A fixing member that heats and melts the toner image and fixes the toner image on the recording medium;
A pressure member that forms a nip portion to which the recording medium is conveyed in pressure contact with the fixing member;
A pressure lever biased by a biasing means to directly or indirectly engage the pressure member or the fixing member to bring the pressure member and the fixing member into a pressure contact state;
A release lever that pushes the pressure lever to displace the pressure lever to release the pressure contact state of the pressure member and the fixing member;
With
The release lever is
When releasing the pressure contact state of the pressure member and the fixing member, after the displacement of the pressure lever is started, the release position of the pressure lever is determined by contacting the contacted portion of the pressure lever. A contact portion ;
When the pressure lever at the release position is displaced to return the pressure member and the fixing member to the pressure contact state, the second contact of the pressure lever is started after the displacement of the pressure lever is started. A second abutting portion that abuts the contacting portion to determine a stop position of the pressure lever;
Equipped with,
The stop position is a state in which the fixing member and the pressure member are thermally expanded by operating the apparatus when the second contact portion and the second contacted portion are not installed. The position of the pressure lever, the second contact portion, and the second contacted portion are not installed, and the apparatus is stopped and the fixing member and the additional member are stopped. The fixing device is set to a position between the position of the pressure lever that is restricted in a state where there is no thermal expansion of the pressure member . The release lever includes a cam portion and is configured to be rotatable about a support shaft, and the cam portion slides on a flat portion of the pressure lever and moves the pressure lever with a rotation operation. The fixing device according to claim 1, wherein: The fixing device according to claim 1, wherein the pressure lever and / or the release lever are made of a metal material. 4. The pressure lever according to claim 1, wherein the pressure lever engages a bearing that pivotally supports the pressure member or the fixing member to bring the pressure member and the fixing member into a pressure contact state. The fixing device according to any one of the above. The fixing device according to claim 4, wherein the bearing is held movably with respect to a frame of the device in accordance with the displacement of the pressure lever. The bearing moves on the frame about a rotation center of a gear that meshes with a driven gear installed on an axis of the pressure member or the fixing member and transmits a driving force. Item 6. The fixing device according to Item 5. The release lever is configured to start displacement toward the pressure position of the pressure lever at the release position in conjunction with a closing operation of a cover that is installed in the image forming apparatus main body so as to be freely opened and closed. The fixing device according to claim 1. An image forming apparatus comprising the fixing device according to claim 1.

Images