JP2000122460A - Fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent permanent set from occurring on an elastic body layer by pressuring force and to easily remove transfer material jammed in a fixing part even when a fixing roller and a pressure roller are provided with the elastic body layer on their surfaces. SOLUTION: When a condition is switched from an image forming condition to an image non-forming condition or when jamming occurs, a gear 97 on the output shaft of which a motor 98 is fixed is rotated in a direction shown by an arrow 97b, a gear 96 is rotated in a direction shown by an arrow 96a, and a gear 95 is rotated in a direction shown by an arrow 95b. Since a gear 109 is rotated in a direction shown by an arrow 109b, at such a time, the gear 109, a rotary shaft 110 and a gear 108 are integrally rotated and a cam 89 is rotated by about 180 deg. so as to press down a pressure frame 86 against the energizing force of a pressure spring 88. Thus, the fixing roller 81 and the pressure roller 82 do not come in contact with each other, whereby the permanent deformation is prevented from occurring on the elastic body layer by the pressuring force and the transfer material jammed in the fixing part is easily removed even when the rollers 81 and 82 are provided with the elastic body layer on their surfaces.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nip formed between a fixing rotator and a pressure rotator for holding a transfer material on which an unfixed toner image has been transferred. The present invention relates to a fixing device for thermally fixing an attached toner image to a transfer material, and an image forming apparatus including the fixing device for forming an image by an electrophotographic or electrostatic recording method, such as a copying machine, a printer, and a facsimile.

[0002]

2. Description of the Related Art A color laser beam printer will be described as an example of a conventional electrophotographic image forming apparatus.

This color laser beam printer has a drum-shaped electrophotographic photosensitive member, that is, a photosensitive drum, which is rotatably supported and rotates in one direction, at a substantially central portion thereof. Around the photosensitive drum, a primary charger for uniformly charging the photosensitive drum, laser beam exposure means for irradiating image information to form a latent image, and developing a latent image into a visible image (toner image). A plurality of developing devices and an intermediate transfer belt as an intermediate transfer member to which a visible image on the photosensitive drum is transferred are arranged. Then, the toner image formed on the photosensitive drum is transferred to the surface of the intermediate transfer belt. The residual toner on the photosensitive drum is removed by the cleaning device, and the photosensitive drum is used for the next image forming process.

[0004] By repeating such an image forming process, a multicolor toner image is superimposedly transferred onto the surface of the intermediate transfer belt. Thereafter, the multicolor toner image on the intermediate transfer belt is transferred to a transfer material fed from a feeding device. The transfer material to which the multicolor toner image has been transferred is conveyed to a fixing device by a conveyance belt, heated and pressed by a fixing roller and a pressure roller, and the toner image is transferred to the transfer material and discharged outside the apparatus.

In the above-described color laser beam printer, the fixing device needs to fix a multicolor toner image, and uses a fixing roller and a pressure roller in which an elastic layer such as rubber is formed on a metal pipe (core). , About 20kgf-40kg
The pressure roller is pressed against the fixing roller at f to form a nip necessary for fixing. This state is shown in FIG. In FIG. 6, 181 is a fixing roller, 182 is a pressure roller,
1a and 182a are elastic layers, 181b and 182b are metal pipes (core metal), and N is a nip.

[0006]

In the above-described conventional color laser beam printer (image forming apparatus), the nip N between the fixing roller 181 and the pressure roller 182 on which the elastic layers 181a and 182a of the fixing device are formed is provided. Because a load of about 20kgf to 40kgf is applied,
When the fixing roller 18 is left for a long time, as shown in FIG.
1 and the elastic layer 181 at the nip N of the pressure roller 182.
a, 182a are permanently deformed, and even if the nip N is opened, the deformation of the elastic layers 181a, 182a (the upper part of the elastic layer 181a and the lower part of the elastic layer 182a in the figure) cannot be restored. was there.

As a countermeasure, there is a method in which the fixing roller and the pressure roller are periodically rotated even when the image is not formed. However, this method cannot be performed when the power of the apparatus is turned off.

When a jam occurs for some reason during fixing of the transfer material by the fixing device, about 20 kgf to 4 kgf
Since a high pressure of 0 kgf was applied, it was extremely difficult to remove the jammed transfer material.

Accordingly, a first object of the present invention is to prevent the elastic layer from being permanently deformed by the pressing force even if the fixing roller and the pressure roller have the elastic layer.

A second object of the present invention is to make it possible to easily remove a transfer material jammed in a fixing unit.

[0011]

In order to achieve the above object, the present invention comprises a rotatable fixing rotator and a rotatable pressure rotator, wherein the fixing rotator and the pressing rotator are provided. Between the fixing rotator and the pressurizing rotator by heating by a heating means provided at least in one of the fixing rotator and the pressing rotator. In a fixing device for thermally fixing the unfixed toner image to the recording medium, a pressure is applied to a swingable swing member that rotatably supports the pressure rotator, and the pressure rotator is pressed against the fixing rotator. Pressurizing means for applying pressure for pressurizing, and pressurizing releasing means for releasing the pressing state of the pressurizing rotator against the fixing rotator against the pressing force of the pressing means, The pressure releasing unit is a cam that is rotationally driven by a driving unit. The rotation of the cam causes the swinging member to swing against the pressing force of the pressing unit to release the pressurized state of the fixing rotator and the pressing rotator, and the driving unit includes: It is characterized by being driven by a drive source for rotating the fixing rotator and the pressure rotator.

The image forming apparatus further includes a rotatable fixing rotator and a rotatable pressure rotator, and an unfixed toner image is formed in a nip formed between the fixing rotator and the pressing rotator. A fixing device for nipping and transporting the transferred recording medium and thermally fixing the unfixed toner image to the recording medium by heating by a heating unit provided at least in one of the fixing rotator and the pressing rotator. A pressurizing means for applying pressure for pressurizing the pressurizing rotator against the fixing rotator by pressing a oscillating swing member rotatably supporting the pressurizing rotator; Pressurizing release means for releasing the pressure contact of the pressurizing rotator against the fixing rotator against the pressing force of the pressurizing means, wherein the pressurizing release means is driven by a driving means, And a toggle machine groove operated by rotation of the cam. The operation of the cam and the toggle mechanism causes the swinging member to swing against the pressing force of the pressing unit, thereby releasing the pressurized state of the fixing rotator and the pressing rotator. The fixing rotator and the pressure rotator are driven by a driving source for rotating the fixing rotator and the pressing rotator.

[0013] Further, there is provided a drive switching means for selectively switching the rotational driving of the fixing rotator and the pressing rotator and the rotational driving of the cam.

The drive switching means is a one-way clutch provided in a drive path for driving the fixing rotator and the pressurizing rotator and a drive path for the cam. The drive transmission is switched according to the drive direction.

Further, the driving source is a stepping motor.

Further, the cam is provided with a flat portion for maintaining the pressure release state.

Further, the pressurization of the fixing rotator and the pressurizing rotator by the pressurizing means and the pressurization release by the cam are selectively performed.

The pressure release by the cam is performed during non-image formation, and the pressure release by the cam is performed at the time of jam detection.

Further, in the image forming apparatus according to the present invention, the toner image formed on the image carrier is transferred to a transfer material, and the toner image is fixed on the transfer material. It is characterized by having the fixing device described in the item.

[0020]

Embodiments of the present invention will be described below in detail with reference to the drawings.

Embodiment 1 FIG. 1 is a schematic sectional view showing an image forming apparatus provided with a fixing device according to the present embodiment. In the present embodiment, a four-color full-color laser beam printer employing an electrophotographic method is exemplified as one mode of the image forming apparatus.

The image forming apparatus A shown in FIG. 1 has a drum-type electrophotographic photosensitive member (hereinafter referred to as a "photosensitive drum") as an image carrier.
1). The photoconductor drum 1 is driven to rotate in a direction indicated by an arrow (counterclockwise) by a driver's throw (not shown).

A charging device 2 for uniformly charging the surface of the photosensitive drum 1 in order according to the direction of rotation of the photosensitive drum 1 irradiates a laser beam based on image information to irradiate the photosensitive drum 1 with an electrostatic charge. An exposure device 3 for forming a latent image, a developing device 4 for attaching toner to the electrostatic latent image and developing it as a toner image, a transfer unit 5 where the toner image on the photosensitive drum 1 is primarily transferred, and after the primary transfer A cleaning device 6 for removing the transfer residual toner remaining on the surface of the photosensitive drum 1 is provided.

Here, the photosensitive drum 1, the charging device 2, and the cleaning device 6 are integrally formed as a cartridge to form a process cartridge B, which is detachable from the apparatus main body 14 of the image forming apparatus A. .

A transfer material S such as paper as a recording medium
The transfer material S is fed toward the transfer unit 5 in order from the upstream side in the conveyance direction, and the feeding unit 7 that conveys the transfer material S fixes the toner image on the transfer material S after the secondary transfer. An apparatus 80 is provided.

Hereinafter, the photosensitive drum 1 will be described in detail.

The photosensitive drum 1 is, for example, about 47 mm in diameter.
An organic photoconductor layer (OPC photoreceptor) is applied to the outer peripheral surface of the aluminum shilling. The photosensitive drum 1 is rotatably supported at both ends by a support member, and a driving force from a driving motor (not shown) is transmitted to one end, so that the photosensitive drum 1 is moved in the direction of the arrow (counterclockwise). Is driven to rotate.

The charging device 2 is described in, for example,
A so-called contact charging type as disclosed in JP-A-149669 can be used. The charging member is a conductive roller formed in a roller shape. The roller is brought into contact with the surface of the photosensitive drum 1, and a charging bias voltage is applied to the roller by a power supply (not shown) to thereby charge the photosensitive member. This is for uniformly charging the surface of the drum 1.

The exposure device 3 has a polygon mirror 3a, and the polygon mirror 3a is irradiated with image light corresponding to an image signal by a laser diode (not shown). The polygon mirror 3a is a scanner motor (not shown)
Is rotated at a high speed, and the reflected image light is selectively exposed to the surface of the charged photosensitive drum 1 via the imaging lens 3b, the reflection mirror 3c, and the like to form an electrostatic latent image. ing.

The developing device 4 accommodates a rotating body 4A rotatable around an axis 4d and four developing units mounted thereon, ie, toners of yellow, magenta, cyan and black, respectively. Developing units 4Y, 4M, 4C, 4B
k.

When the electrostatic latent image on the photosensitive drum 1 is developed, a predetermined developing device of a color to be attached to the electrostatic latent image is arranged at a phenomenon position. That is, the predetermined developing device is stopped at the developing position facing the photosensitive drum 1 by the indexing rotation of the rotating body 4A, and the developing sleeve 4b of the developing device is minutely spaced (about 300 μm) with respect to the photosensitive drum 1. Then, the electrostatic latent image on the photosensitive drum 1 is developed.

This development is performed as follows. The toner in the container of the developing device corresponding to the color to be developed is sent to the applying roller 4a by the feeding mechanism, and the rotating applying roller 4a is rotated.
A thin layer of toner is applied to the outer periphery of the rotating developing sleeve 4b by the toner regulating blade 4c, and a charge is applied to the toner (friction charging). By applying a developing bias between the sleeve 4b and the photosensitive drum 1 on which the electrostatic latent image is formed, a toner image is attached to the electrostatic latent image and developed as a toner image.

Each of the developing units 4Y, 4M, 4C, 4Bk
The developing sleeve 4b is connected to a high-voltage power supply (not shown) for developing each color provided in the apparatus main body 14 when each developing device is arranged at the developing position. Is selectively applied with a voltage. Each developing unit 4
Y, 4M, 4C, and 4Bk are configured to be detachable from the rotator 4A, and the rotator 4A is detachable from the apparatus body 14.

The transfer unit 5 secondary-transfers a plurality of toner images, which are sequentially primary-transferred and superposed sequentially from the photosensitive drum 1, to the transfer material S collectively.

The transfer unit 5 is moved in the direction of the arrow (clockwise).
Is provided with an intermediate transfer belt 5a that travels in the same direction. The intermediate transfer belt 5a of the present embodiment is an endless belt having a circumference of about 440 mm, and is stretched around three rollers of a driving roller 5b, a secondary transfer facing roller 5c, and a driven roller 5d. In addition, there are provided a position where the intermediate transfer belt 5a is pressed against the photosensitive drum 1 in the vicinity of the driven roller 5d and a pressing roller 5j which retreats so as to take a position where the intermediate transfer belt 5a is separated from the photosensitive drum 1. The intermediate transfer belt 5a runs in the direction of the arrow (clockwise) due to the rotation of the drive roller 5b.

At a predetermined position outside the intermediate transfer belt 5a, there is provided a cleaning unit 5e capable of coming into contact with and separating from the surface of the intermediate transfer belt 5a. Is removed. The cleaning unit 5e contacts the charging roller 5f to the intermediate transfer belt 5a to apply the opposite charge to the toner at the time of transfer.
The toner having the opposite charge is electrostatically attached to the photosensitive drum 1 and then collected by the cleaning device 6 for the photosensitive drum 1. The method of cleaning the intermediate transfer belt 5a is not limited to the electrostatic cleaning described above, but may be a mechanical method such as a blade or a fur brush, or a method using both of them.

After the toner developed on the photosensitive drum 1 by the developing device 4 is primarily transferred to the intermediate transfer belt 5a, the cleaning device 6 is a so-called transfer remaining on the surface of the photosensitive drum 1 without being primary-transferred. This is to remove the residual toner.

The feeding / conveying unit 7 transfers the transfer material S to the transfer unit 5.
A plurality of recording media S are stored therein, and a feed cassette 7a loaded in a lower portion of the apparatus main body 14 is provided.
It has. During image formation, the pickup member 7e,
The transport roller 7b is driven and rotated in accordance with the image forming operation, separates and feeds the transfer material S in the feed cassette 7a one by one, is guided by the guide plate 7c, and passes through the registration roller 7d to the intermediate transfer belt 5a. Is to be fed.

The fixing device 80 fixes the toner image secondary-transferred to the transfer material S. The fixing device 81 presses against the fixing roller 81 as a fixing rotating body that rotates and drives the transfer material S to apply pressure to the transfer material S. Pressure roller 8 as a pressure rotating body to be applied
2 is provided. A heater (not shown) is provided in the fixing roller 81, and the toner of the toner image can be heated by heat generated by the heater (not shown).

That is, the transfer material S which has passed through the secondary transfer roller 5n for collectively transferring the toner on the intermediate transfer belt 5a
Is applied heat and pressure by a fixing roller 81 and a pressure roller 82 when passing through the fixing device 80. As a result, the toner images of a plurality of colors are fixed on the surface of the transfer material S. The configuration and operation of the fixing device 80 will be described later in more detail.

Next, the image forming operation of the above-described image forming apparatus will be described.

The photosensitive drum 1 is rotated in the direction of the arrow (counterclockwise) in synchronization with the rotation of the intermediate transfer belt 5a, and the surface of the photosensitive drum 1 is uniformly charged by the charging device 2, and is also charged by the exposure device 3. Light irradiation of a yellow image is performed to form a yellow electrostatic latent image on the photosensitive drum 1.

Simultaneously with the formation of the electrostatic latent image, the developing device 4 is driven to dispose the yellow developing device 4Y at the developing position, and the photosensitive member is so attached that the yellow toner adheres to the electrostatic latent image on the photosensitive drum 1. At the same polarity as the charging polarity of the drum 1, a voltage of substantially the same potential is applied to cause the yellow toner to adhere to the electrostatic latent image for development. And a primary transfer roller (driven roller) 5
d to the photosensitive drum 1
The upper yellow toner image is primarily transferred onto the intermediate transfer belt 5a.

When the primary transfer of the yellow toner image is completed as described above, the next developing unit rotates and is positioned at the developing position facing the photosensitive drum 1, and in the case of yellow, the magenta , Cyan, and black, an electrostatic latent image is formed, developed, and primary-transferred sequentially, and four-color toner images are superimposed on the intermediate transfer belt 5a. These toner images are collectively and secondarily transferred onto the transfer material S supplied from the supply / conveyance unit 7.

Then, the transfer material S after the secondary transfer is transported to the fixing device 80, where the toner image is fixed.
Belt 9a moving in the direction of the arrow, and belt 9
The image is formed on the discharge tray 10 outside the apparatus main body 14 by the discharge roller 9 driven by a.

Next, the structure and operation of the fixing device 80 according to the first embodiment will be described in detail with reference to FIGS. FIG. 2 is a schematic perspective view of the fixing device according to the first embodiment, and FIG. 3 is a side view thereof.

Reference numeral 81 denotes a fixing roller as a fixing rotating body, and an elastic layer 81 is provided on the outer peripheral portion of a metal pipe (core metal) 81b.
a is formed. Reference numeral 82 denotes a pressure roller as a pressure rotating body. Similarly, an elastic layer 82a is formed on the outer periphery of a metal pipe (core bar) 82b. Further, a heater (not shown) is provided in the fixing roller.

The fixing roller 81 is rotatably supported by a fixing frame 84 via a bearing 83. The pressure roller 82 is rotatably supported by a pressure frame 86 as a swing member via a bearing 85. Pressurizing frame 86
Is supported by a support shaft 87 fixed to a fixing frame 84 so as to be swingable, and a pressing spring 88 as a pressing unit is provided.
Thus, the pressure roller 82 is urged to be pressed by the fixing roller 81.

At one end of the fixing roller 81, a gear 112 is mounted so as to rotate integrally with the fixing roller 81.

The driving force is transmitted to the gear 112 from a motor 98 as a driving source via gears 97, 96, 95, 107 and 106. The gear 107 incorporates a one-way clutch (one-way clutch) 107a.
7 is rotated only in the direction of arrow 107b.
The gear 106 rotates integrally with the gear 1.

Reference numeral 89 denotes a cam serving as a pressure releasing unit which is driven to rotate by a motor 98. The cam 89 is fixed to both sides of a cam shaft 90 rotatably supported by the fixing frame 84, and is integral with the cam shaft 90. It is designed to rotate. The cam 89 fixed to the cam shaft 90 has gears 91, 92, 93, 94, 108, 109, 95, 9
The motor 98 is driven to rotate by the motors 6 and 97.

The gear 109 incorporates a one-way clutch (one-way clutch) 109a.
Is rotated only in the direction of arrow 109b.
And the gear 108 rotates integrally therewith. still,
The fixing device 80 includes other members such as a guide member for guiding the transfer material S, but a detailed description thereof is omitted here.

The fixing device 80 rotates the pressing frame 86 against the pressing force of the pressing spring 88 by the rotation of the cam 89 to release / press the fixing roller 81 and the pressing roller. It is configured to perform.

The pressing and releasing of the fixing roller 81 and the pressing roller 82 can be selectively switched by the judgment of a CPU (not shown) as a control means. The pressure of the fixing roller 81 and the pressure roller 82 is released when an image is formed or a jam is detected.

Normally, at the time of image formation, as shown in FIG. 3A, a pressing frame 86 is pressed by a pressing spring 88, and a pressing roller 82 is pressed by a fixing roller 81. A nip N is formed at a contact portion between the pressure roller 82 and the pressure roller 82.

When the CPU (not shown) determines that this state is switched to the non-image forming state, the motor 98 rotates the gear 97 fixed to its output shaft in the direction of arrow 97b.
The gear 96 rotates in the direction of arrow 96a, and the gear 95 rotates in the direction of arrow 95b. At this time, since the gear 109 rotates in the direction of the arrow 109b, the gear 109, the rotating shaft 110, and the gear 108 rotate integrally, and the cam 89 rotates by about 180 ° as shown in FIG. The pressing frame 86 is pressed down against the urging force of the pressing spring 88. As a result, the fixing roller 81 and the pressure roller 82 come into non-contact, and the formation of the nip N is released.

At this time, the gear 107 has an arrow 107c.
However, since the idle rotation occurs between the one-way clutch (one-way clutch) 109a and the rotating shaft 111, the gear 106 and the rotating shaft 111 do not rotate. Therefore, the fixing roller 81 does not rotate.

Further, when the CPU (not shown) determines the switching from the non-image forming state to the image forming state, the motor 98 rotates in the same direction again, and the gears 97, 96, 95, 10
9, 108, 94, 93, 92, 91 via the camshaft 9
0 rotates, and as shown in FIG.
It rotates about 180 ° from the state of (B). As a result, the cam 89 and the pressing frame 86 come out of contact with each other, so that the pressing frame 86 is pushed up by the urging force of the pressing spring 88, and the pressing roller 82 is pressed by the fixing roller 81.
A nip N is formed.

In this state, when the gear 97 fixed to the output shaft of the motor 98 rotates in the direction of arrow 97a, the gear 96 rotates in the direction of arrow 96b and the gear 95 rotates in the direction of arrow 95a. At this time, since the gear 107 rotates in the direction of the arrow 107b, the gear 107, the rotating shaft 111, and the gear 10
6 rotates integrally, and can rotate the fixing roller 81 via the gear 112.

At this time, the gear 109 has an arrow 109c.
However, since the idle rotation occurs between the one-way clutch (one-way clutch) 109a and the rotating shaft 110, the gear 108 and the rotating shaft 110 do not rotate. Therefore, the gears 94, 93, 92, 91 do not rotate, and the camshaft 9 does not rotate.
0 and the cam 89 do not rotate either.

In this embodiment, a stepping motor is used as the motor 98. This is the motor 98
It is necessary to rotate and stop by a certain number of rotations, and this is facilitated by using a stepping motor.

Further, the cam 89 must be stopped in a state where the pressurizing frame 86 is pressed down, and maintain the pressurized release state even when the driving force of the motor 98 is lost. Therefore, the cam 89 is moved by the urging force of the pressure spring 88.
As shown in FIGS. 2, 3A and 3B, the cam 89 is provided with a flat portion 89a so that the cam 89 does not rotate.

When the CPU (not shown) determines that the image forming signal has not been input for a certain period of time, the CPU determines that the image forming state has been switched to the non-image forming state. 81 and pressure roller 82
Is released, and when an image forming signal is input, switching from the non-image forming state to the image forming state is determined, and the fixing roller 81 and the pressing roller 82 are pressed as described above. It is configured as follows.

When the power switch (not shown) of the image forming apparatus A is turned off, the switching from the image forming state to the non-image forming state is completed, that is, as described above, The power is turned off after the pressure of the pressure roller 82 is released, and when the power is turned on,
The switching operation from the non-image forming state to the image forming state, that is, the pressing of the fixing roller 81 and the pressing roller 82 is performed as described above.

Further, when a jam is detected in the nip N, which is a fixing portion between the fixing roller 81 and the pressure roller 82, the operation of releasing the pressure between the fixing roller 81 and the pressure roller 82 is performed as described above. After the completion of the jam processing, the fixing roller 81 and the pressing roller 82 are pressurized as described above.

As described above, in the present embodiment, the fixing roller 81 and the pressure roller 82 are provided with the elastic layers 81a and 81a on the surface.
a, the elastic layers 81a, 82
a can be prevented from being permanently deformed, and
The transfer material S jammed in the nip N between the fixing roller 81 and the pressure roller 82 can be easily removed.

<Embodiment 2> FIGS. 4 and 5A,
3B is a configuration diagram and a cross-sectional view of the fixing device of the image forming apparatus according to the present embodiment. Members having the same functions as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted. Omitted. Note that the configuration of the image forming apparatus and the image forming operation are the same as those in the above-described first embodiment, and a description thereof will be omitted in this embodiment.

In the first embodiment, the cam 89 rotates, and the cam 89 directly pushes down the pressure frame 86 to release the nip N between the fixing roller 81 and the pressure roller 82 (pressure release).
However, in the present embodiment, as shown in FIGS. 4 and 5, the pressure release means is constituted by the cam 89 and the toggle mechanism 100, and the toggle mechanism 100 is operated by the rotation of the cam 89. Then, the pressure frame 86 is pressed down to release the nip N between the fixing roller 81 and the pressure roller 82 (pressure release).

4 and 5, reference numerals 101 and 102 denote link members constituting the toggle mechanism 100. The link members 101 and 102 are rotatably connected by connecting pins 103. Further, the link members 101, 10
One end of 2 is rotatably supported by the fixing frame 84, and the other end is rotatably supported by the pressing frame 86.

The pressing frame 86 is similar to the first embodiment.
Since it is swingably supported by the fixing frame 84, the connecting mechanism of the link members 101 and 102 is displaced to form the toggle mechanism 100. Other configurations are the same as those in the first embodiment, and thus description thereof is omitted.

Next, the operation of the fixing device 80 according to the present embodiment will be described.

Normally, at the time of image formation, as shown in FIG. 5A, a pressing frame 86 is pressed by a pressing spring 88, and a pressing roller 82 is pressed by a fixing roller 81. A nip N is formed at a contact portion between the pressure roller 82 and the pressure roller 82.

When the CPU (not shown) determines to switch from this state to the non-image forming state, the motor 98 rotates the gear 97 fixed to its output shaft in the direction of arrow 97b.
The gear 96 rotates in the direction of arrow 96a, and the gear 95 rotates in the direction of arrow 95b. At this time, since the gear 109 rotates in the direction of the arrow 109b, the gear 109, the rotating shaft 110, and the gear 108 rotate integrally, and the gears 94, 93, 92,
The cam shaft 90 rotates through 91 and the cam 89
° rotate.

Then, as shown in FIG.
9 presses the connecting portion of the link members 101 and 102, and the lower end of the link member 102 pushes down the pressing frame 86 against the urging force of the pressing spring 88. As a result, the fixing roller 81 and the pressure roller 82 do not contact each other, and the nip N
Is released.

Further, when the CPU (not shown) determines the switching from the non-image forming state to the image forming state, the motor 98 rotates in the same direction again, and the gears 97, 96, 95, 10
9, 108, 94, 93, 92, 91 via the camshaft 9
0 rotates, and the cam 89 moves from the state of FIG.
° rotate.

As a result, as shown in FIG. 5A, the pressing of the cam 89 against the connecting portions of the link members 101 and 102 is released, so that the pressing frame 86 is pushed up by the urging force of the pressing spring 88. , Pressure roller 8
2 is pressed by the fixing roller 81 to form a nip N.

The switching judgment by the CPU (not shown) is the same as that in the first embodiment, and the explanation is omitted here.

As described above, also in the present embodiment, the fixing roller 81 and the pressing roller 82
a, 82a, the elastic layer 81
a, 82a can be prevented from being permanently deformed, and the transfer material S jammed at the nip N between the fixing roller 81 and the pressure roller 82 can be easily removed.

Further, the pressing frame 8 is
By pressing down 6, the rotational load of the cam 89 can be reduced.

In each of the above-described embodiments, an electrophotographic laser beam printer has been exemplified as an image forming apparatus. However, the present invention is not limited to this. For example, an image forming apparatus employing another recording method such as an ink jet method may be used. It may be a device.

In each of the embodiments described above, a printer is exemplified as an image forming apparatus. However, the present invention is not limited to this, and other image forming apparatuses such as a copying machine and a facsimile may be used. .

In each of the above-described embodiments, a multicolor image forming apparatus capable of forming a color image has been exemplified. However, the present invention is not limited to this. For example, a monochrome image forming apparatus capable of forming a black and white image may be used. There may be.

[0083]

As described above, according to the present invention,
Pressing of the fixing rotator and the pressing rotator is released by oscillating the rocking member supporting the pressing rotator against the pressing force of the pressing unit by the cam as the pressure releasing unit, or Pressing the fixing rotator and the pressurizing rotator is released by oscillating the oscillating member against the pressing force of the pressurizing device by a cam and a toggle mechanism as a pressurizing releasing unit. During image formation, the pressure of the fixing rotator and the pressing rotator can be released, and even if the fixing rotator and the pressing rotator have an elastic layer on the surface, the pressing force is applied to the elastic layer. Thus, permanent deformation can be prevented.

Further, the pressurizing means can release the pressurization of the fixing rotator and the pressurizing rotator when a jam is detected, so that even if the transfer material is jammed in the fixing section, it can be easily removed. The processability is improved.

Further, the motor which is the driving source of the fixing rotator and the pressing rotator and the motor which is the driving source of the cam which is the pressure releasing means are the same, and the drive is switched according to the rotation direction of the motor. Therefore, an increase in cost can be suppressed.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus including a fixing device according to Embodiments 1 and 2 of the present invention.

FIG. 2 is a schematic perspective view of the fixing device according to the first embodiment.

FIGS. 3A and 3B are cross-sectional views of the fixing device according to the first embodiment.

FIG. 4 is a schematic perspective view of a fixing device according to a second embodiment.

FIGS. 5A and 5B are cross-sectional views of a fixing device according to a second embodiment.

FIG. 6 is a diagram illustrating a nip state between a fixing roller and a pressure roller of a fixing device in a conventional example.

FIG. 7 is a diagram showing a nip state between a fixing roller and a pressure roller of a fixing device in a conventional example.

[Explanation of symbols]

Reference Signs List A Image forming apparatus B Process cartridge N Nip S Transfer material 1 Photoconductor drum (image carrier) 2 Charging device 3 Exposure device 3a Polygon mirror 3b Imaging lens 3c Reflection mirror 4 Developing device 4A Rotating body 4Y, 4M, 4C, 4Bk Developing device 4a Coating roller 4b Developing sleeve 4c Toner regulating blade 4d Shaft 5 Transfer unit 5a Intermediate transfer belt 5b Drive roller 5c Secondary transfer facing roller 5d Followed roller 5e Cleaning unit 5f Charging roller 5j Roller 5n Secondary transfer roller 6 Cleaning device 7 Feeding / Conveying Unit 7a Feeding Cassette 7b Conveying Roller 7c Guide Plate 7d Registration Roller 7e Pickup Member 9 Discharge Roller 9a Belt 10 Discharge Tray 14 Main Unit 80 Fixing Device 81 Fixing Roller (Fixing Rotor) 81a, 82a Body layer 81b, 82b Metal pipe 82 Pressure roller (pressure rotating body) 83, 85 Bearing 84 Fixing frame 86 Pressure frame 87 Supporting member 88 Pressure spring (pressure means) 89 Cam (pressure release means) 89a Flat Part 90 Camshaft 91 to 97 Gear 98 Motor 100 Toggle mechanism 101, 102 Link member 103 Connecting pin 106 to 109 Gear 110, 111 Rotary shaft 112 Gear 107a, 109a One-way clutch (drive switching means)

Claims (10)

[Claims] An unfixed toner image is provided in a nip formed between the fixing rotator and the pressure rotator, the fixing rotator having a rotatable fixing rotator and a rotatable pressure rotator. A fixing device that nips and conveys the transferred transfer material and thermally fixes the unfixed toner image to the recording medium by heating by a heating unit provided at least in one of the fixing rotator and the pressing rotator. A pressurizing means for applying pressure for pressing the pressurizing rotator against the fixing rotator by pressing a oscillating swinging member rotatably supporting the pressurizing rotator; Pressurizing release means for releasing the pressure contact of the pressurizing rotator against the fixing rotator against the pressing force of the pressurizing means, wherein the pressurizing release means is a cam rotationally driven by a driving means. And the pressurizing means presses the swinging member by rotation of the cam. The fixing rotator and the pressing rotator are released from the pressurized state by oscillating against the pressing force. The driving unit drives the fixing rotator and the pressing rotator to rotate. A fixing device driven by a source. 2. An image forming apparatus comprising: a rotatable fixing rotator; and a rotatable pressure rotator. An unfixed toner image is formed in a nip formed between the fixing rotator and the pressing rotator. A fixing device for nipping and transporting the transferred recording medium and thermally fixing the unfixed toner image to the recording medium by heating by a heating unit provided at least in one of the fixing rotator and the pressing rotator. A pressurizing means for applying pressure for pressing the pressurizing rotator against the fixing rotator by pressing a oscillating swinging member rotatably supporting the pressurizing rotator; Pressurizing release means for releasing the pressure contact of the pressurizing rotator against the fixing rotator against the pressing force of the pressurizing means; a cam rotatably driven by a driving means, And a toggle machine groove operated by rotation of the cam, The operation of the cam and the toggle mechanism causes the swinging member to swing against the pressing force of the pressing unit, thereby releasing the pressurized state of the fixing rotator and the pressing rotator. The fixing device is driven by a drive source that rotationally drives the fixing rotator and the pressing rotator. 3. The fixing device according to claim 1, further comprising a drive switching unit that selectively switches between the rotation drive of the fixing rotator and the pressure rotator and the rotation drive of the cam. 4. The drive switching means is a one-way clutch provided in a drive path for rotationally driving the fixing rotator and the pressure rotator and in a drive path for the cam. The fixing device according to claim 3, wherein the drive transmission is switched according to the drive direction. 5. The fixing device according to claim 1, wherein the driving source is a stepping motor. 6. The fixing device according to claim 1, wherein the cam is provided with a flat portion for maintaining a pressure released state. 7. The method according to claim 1, wherein pressurization of said fixing rotator and said pressurizing rotator by said pressurizing means and pressurization release by said cam are selectively performed. 7. The fixing device according to item 6. 8. The fixing device according to claim 1, wherein the pressure release by the cam is performed during non-image formation. 9. The fixing device according to claim 1, wherein the pressure release by the cam is performed when a jam is detected. 10. The fixing device according to claim 1, wherein a toner image formed on the image carrier is transferred to a transfer material, and the toner image is fixed to the transfer material. An image forming apparatus comprising: