JP2000338815A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a fixing device by which removal of transferr paper can be safely performed by pressure release at a fixing position and pressure return after pressure release can be automatically performed with ease and certainty by a door closing operation. SOLUTION: A pressure release means 40 of a pressure roller 23, which is in press- contact with a heat roller 22 of a fixing unit 21 via a press-contact means 30 in an approaching and separating direction X, is constituted of a pressure release lever 41 which is freely rotatably supported with an axis 44 as a supporting point O at another end 31b side of a pressure lever 31 of the press-contact means 30. The pressure release lever 41 is made to slidably correspond to a rear 16a side of a door panel 16 being capable of opening/closing on the image forming device main body 1 side with a hand hold end part 41a at one end of the pressure release lever 41 as a point of application P and, further, the pressure release lever 41 is made to slidably correspond to a fixed frame 26 on the fixing unit 21 side with another end part 41b side thereof as a force point F. The pressure release lever 41 is sliding-rotated so that the point of application P thereof is located below the supporting point O and is made to be able to lock and the pressure roller 23 is made to be movable in a separating direction to the heat roller 22 to perform pressure release.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for use in an image forming process of an image forming apparatus such as a laser printer, and more particularly, to a fixing unit of a fixing unit capable of coming in contact with and separating from a heat roller. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device in which pressure releasing means of a pressure roller to be pressed is improved.

[0002]

2. Description of the Related Art In an image forming apparatus, an electrostatic latent image based on a document image formed by an optical system is developed by a developer, and the toner image is transferred and fixed on a transfer paper to thereby form an image. Forming process.

[0003] A fixing device used in such an image forming process is usually formed as a unit with a heat roller provided with a heater therein and a pressure roller pressed against the outer peripheral surface of the heat roller. In addition, the transfer paper holding the unfixed toner is passed through a nip portion (fixing portion) between the heat roller and the pressure roller of the fixing unit, and the pressure is applied while heating and melting the toner. Thus, the toner image is fixed on the transfer paper.

A pressure roller constituting a fixing portion of the fixing unit is disposed in a pressure-contact state so as to be capable of coming in contact with and separating from the heat roller via a pressure release mechanism. By releasing the pressure contact state between the two rollers by the pressure release mechanism, it is easy to remove the transfer paper remaining in the fixing unit.

Conventionally, as a pressure release mechanism of this type of fixing device, there is a pressure release mechanism having a configuration as disclosed in, for example, Japanese Patent Application Laid-Open No. Sho 59-105668 (hereinafter referred to as Prior Example 1). The invention described in the preceding example 1
As shown in FIGS. 7 and 8, the pressure roller c is pressed against the heat roller a by the urging force of the pressure spring b. A cam portion g of a pressure release lever f rotatably supported on a fixed shaft e on the fixing unit side so as to be in contact with the fixed portion e.
When the pressure of the pressure roller c is released, as shown in FIG. 8, the pressure release lever f is manually rotated in the clockwise pressure release direction Y, and the pressure lever d is pressed by the pushing operation of the cam portion g. Is moved in contact with the heating roller a and the pressure roller c in the direction in which the heating roller a and the pressure roller c are separated from each other.

On the other hand, when the pressure of the pressure roller c is restored after the transfer paper is removed, as shown by a dashed line in FIG.
The lock is released by rotating the pressure release lever f again in the counterclockwise return direction Z in which the cam portion g is separated from the pressure lever d by manual operation.

As another conventional pressure release mechanism (hereinafter referred to as Prior Example 2), as shown in FIG. 9, a pressure roller c is pressed against a heat roller a by the urging force of a pressure spring b. Is rotatably supported on a swing shaft h that is rotatably supported in the contact and separation direction X in a pressed state, and is rotatably supported on a fixed shaft e on the fixing unit side, and is urged in a return direction Z by a return spring i. There is one having a configuration in which the pressure release lever f is brought into contact with and engaged.

The pressure release mechanism in the prior art example 2 operates by manually operating the pressure in the open state of a door panel D provided on the image forming apparatus main body (not shown) side by a hinge connection when a jam occurs. Action point P of release lever f
The handle end on the side is tilted and rotated in the pressure releasing direction Y in the clockwise direction on the door side against the urging force of the return spring i with the fixed shaft e as the fulcrum O to apply the swing axis h of the pressure roller c. The pressure spring b is moved in the contact / separation direction X away from the heat roller a against the urging force of the pressure spring b. As a result, the pressure roller c
Is released, and the end of the pressure release lever f on the force point F side is abutted on the fixing frame j of the fixing unit, whereby the pressure release state of the pressure roller c is maintained. Thus, the pressure release lever f can be locked in a tilted state.

On the other hand, the pressure release lever f after the transfer paper is removed
Is operated by the pivotal movement of the door panel D when the door panel D is closed, by bringing the handle end of the pressure release lever f on the operating point P side into contact with the rear side of the door panel D so that the door panel D can be slidably contacted. The pressure release lever f is slidably rotated in the return direction Z in the counterclockwise direction to the unlocked position in conjunction with the pushing operation accompanying the hinge rotation at the time. This allows
The return is automatically performed by the biasing force of the return spring i.

[0010]

However, in the above-described pressure release mechanism of the fixing device having the conventional structure, as in the first prior art, the pressure of the pressure roller c is manually restored after the transfer paper is removed. Therefore, a great deal of force is required to unlock the pressure release lever f. In addition, it is often the case that the return operation of the pressure release lever f is forgotten and the opening / closing door (not shown) of the inspection port of the image forming apparatus main body is closed while the pressure of the pressure roller c is released. In addition, since the restart of the image forming apparatus main body becomes impossible, it is necessary to open the door again and perform the returning operation of the pressure release lever f, which is troublesome.

In the pressure release mechanism in which the return operation of the pressure release lever f after the transfer paper is removed is linked to the closing operation of the door panel D as in the preceding example 2, the pressure of the pressure roller c In the release state, the operation point P of the pressure release lever f is always positioned above the fulcrum O in order to smoothly perform the return operation of the pressure release lever f with a light force, and the door is closed by turning the hinge of the door panel D. It is designed to be linked with the push-up operation at the time. Therefore, it is difficult for the image forming apparatus main body to mechanically correspond to a model having various door opening / closing mechanisms and shapes, such as a door that opens and closes in the horizontal direction, or a model that requires space saving. It is.

In addition, since the abutment state between the end of the pressure release lever f on the force point F side and the fixing frame j of the fixing unit is unstable, it is difficult to remove the transfer paper during the pressure release state. If the operator accidentally touches the pressure release lever f lightly due to an operation error or the like, the pressure release lever f is automatically returned by the urging force of the return spring i. Further, since the pressure spring b for urging the pressure roller c into the pressure contact state with respect to the heat-retaining roller a has a strong spring force, the pressure roller c elastically and strongly returns to the pressure. If a finger is pinched in a fixing portion between the heat roller a and the pressure roller c, there is a risk that an injury is likely to occur.

The present invention has been made in view of the above circumstances, and it is possible to safely remove transfer paper by releasing pressure at a fixing portion when a jam such as a paper jam occurs, and to restore pressure after releasing pressure. To provide a fixing device capable of automatically and easily performing a door closing operation, and increasing the versatility of an image forming apparatus having various opening and closing forms and shapes of a door panel. With the goal.

[0014]

SUMMARY OF THE INVENTION The present invention is a fixing device incorporated in an image forming apparatus main body having an opening / closing door, wherein the opening / closing door is opened and transfer paper can be removed. In order to solve the above-mentioned problem, a fixing device according to claim 1, wherein the heating roller, a pressing roller positioned below the heating roller and pressed against the heating roller, and A pressure contact means for pressure-contacting the heat roller so that the pressure roller can be brought into and away from the heat roller; and a pressure release means for releasing the pressure contact state of the pressure roller pressed against the heat roller by releasing the pressure on the pressure contact means. is there. The pressure release means has an operation point at one end slidable on the back surface of the opening and closing door in the closed state, and is rotatably supported on a shaft provided at the other end side as a fulcrum. When opening the opening / closing door, the action point is:
When the pressure roller is rotated below the fulcrum, the pressure on the pressure unit is released, and the pressure roller is separated from the heat roller. When the opening / closing door is closed, an action point which is one end of the pressure releasing means slides on the opening / closing door, is pivoted upward from the fulcrum about the shaft as a fulcrum, and pressurizes the pressure means, A pressure roller is pressed against the heat roller.

According to a second aspect of the present invention, in the first aspect of the invention, the pressure releasing means has one end face forming the action point formed into an elliptical curved surface.

According to a third aspect of the present invention, in the fixing device according to the first or second aspect, the pressure releasing means has an action point in a plurality of steps in an upward direction in conjunction with a closing operation of the opening and closing door. It is characterized by sliding and rotating.

According to a fourth aspect of the present invention, in the third aspect of the present invention, the surface of the opening / closing door on which the point of action of the pressure releasing means slides is an inclined surface and a vertical surface.

According to a fifth aspect of the present invention, in the fixing device according to any one of the first to fourth aspects, the fixing device abuts on the other end of the pressure releasing means to stop the downward rotation of the action point when the pressure is released. It has a stopper.

According to a sixth aspect of the present invention, in the fixing device according to the fifth aspect, the pressure releasing means has an arcuate curved surface at the other end that contacts the stopper with the rotation. And

According to a seventh aspect of the present invention, in the fixing device according to the fifth or sixth aspect, the pressure releasing means is provided with a locking surface at the other end which comes into contact with the stopper when the downward rotation of the working point is stopped. Has a flat surface.

The fixing device according to the eighth aspect of the present invention provides the fixing device according to the fifth and sixth aspects.
In the invention according to the seventh aspect, the pressure contact means is rotatably supported at one end and elastically supported at the other end so as to support the pressure roller so as to be movable in a direction of contacting and separating from the heat roller. The pressure roller is urged in a direction of pressing the heat roller against the heat roller, and the pressure roller is moved by the movable means in the direction of contact and separation with the heat roller by the pressure at one end of the pressure releasing means. The pressure release means is provided with the shaft at the other end of the pressure contact means. When the pressure is released by opening the opening / closing door, the other end of the pressure releasing means comes into contact with the stopper to stop the rotation, and at the same time, the pressure contacting means is brought into a pressure released state against the urging of the elastic body. keep.
When the opening / closing door is closed, the other end of the pressure releasing unit is separated from the stopper, and the other end of the pressing unit is moved in a pressing direction of the pressing roller against the heat-heating roller by the bias of the elastic body.

That is, the fixing device according to the present invention employs the above-described configuration so that the point of action of the pressure releasing means is located below the fulcrum, and the pressure roller is moved away from the heat-supply roller. The pressure relief is made possible by moving the pressure relief means, so that even if the length of the pressure release means is short or the installation space in the apparatus body is narrow, the rotation stroke can be increased, The separation stroke width of the pressure roller with respect to the roller can be increased, whereby the transfer paper can be removed smoothly, and the entire apparatus can be reduced in size and space. Further, when the opening / closing door is closed, the action point which is one end of the pressure releasing means slides on the opening / closing door and causes the pressing means to press the pressure roller against the heat retaining roller. Then, since the pressure releasing means automatically returns to the pressure contact state, the returning operation is not forgotten as in the related art.

[0023]

FIG. 1 is a block diagram showing an embodiment of the present invention.
This will be described in detail with reference to the drawings shown in FIGS.
FIG. 1 schematically shows an entire configuration of an image forming process of an image forming apparatus in which a fixing device according to the present invention is incorporated, for example, a laser printer. Reference numeral 1 denotes a laser printer main body.

The image forming process of the laser printer main body 1 is based on a document (not shown) placed on the document placing table 2.
Is read by the scanning of the optical unit 3, the data of the read document image is converted into a digital signal, and is transferred to the LSU unit (laser optical system unit) 4. This LSU
The unit 4 has a built-in polygon mirror 5, and a laser beam emitted from the polygon mirror 5 forms an original image on the transfer roller 6.

The surface of the transfer roller 6 is uniformly charged by a charge 7 and an electrostatic image of a document image is formed by irradiation with a laser beam. The electrostatic image formed on the transfer roller 6 is developed with toner supplied from the developing unit 8.

On the other hand, the paper feed cassette 9
Are transported one by one via a pickup roller 10 and a registration roller pair 11.
An electric charge is added to the transfer paper 100 by the transfer charger 12, whereby a toner image, which is a developed image, is transferred onto the transfer paper 100.

The transfer paper 100 on which the toner image has been transferred is conveyed into a fixing unit 21 described later, and the toner image is fixed on the transfer paper 100 by the fixing unit 21. At the same time, the transfer paper 100 after fixing
Are discharged onto a discharge tray 14 via a discharge roller 13 and stacked.

On one side (right side in the illustrated embodiment) of the printer main body 1, an inspection port 15 is opened at a portion corresponding to an internal image forming process. , B are provided with a door panel 16 which is an openable and closable door.

That is, the fixing unit 21 described above
It is removably incorporated in the image forming process of the laser printer body 1. As shown in FIG. 2, the fixing unit 21 includes a heating roller 22 having a built-in heater (not shown) and heated and heated, and a pressing roller 23 pressed against the heating roller 22. The pressure roller 23 is supported by a movable member 24 that is movable in the direction of contact and separation with respect to the heat roller 22 via a shaft 25. 22 can be elastically pressed.

The pressure contact means 30 has a pressure lever 31, and the pressure lever 31 is provided with an operating rod 32 which is operated by being brought into contact with the movable member 24 which supports the pressure roller 23. One end 31a of the pressure lever 31 is rotatably supported by a fixing portion of the fixing unit 21 via a shaft 33, while its free other end 31b is connected to the fixing unit 2
It is supported by a pressure spring 34 which is an elastic body attached to the first fixed portion.

The pressure spring 34 is connected to the pressure lever 3
The rotation direction of the pressure roller 23 with respect to the heat roller 22
, Ie, the direction in which the movable member 24 on which the pressure roller 23 is pivotally supported is pushed up by the operating rod 32. As a result, the pressure roller 23 always maintains a pressure-contact state with the heat roller 22.

Heating roller 22 by pressing means 30
The pressure contact state between the pressure roller 23 and the pressure roller 23 can be released by the pressure releasing means 40.
Has a pressure release lever 41.

The pressure release lever 41 has one end 41
The side a is set as a handle end so as to be slidably contactable with the back surface 16a side of the door panel 16 of the laser printer main body 1, and the sliding contact surface portion 42 serving as an action point P is formed in an elliptical curved surface form. On the other hand, the other end 41b is set as a lock end so as to be slidable in contact with the fixed frame 26 of the fixing unit 21, and the corner 43a of the slidable contact surface 43 serving as a force point F at the other end is formed into an arcuate curved surface. In the embodiment, the locking surface 43b of the fixing unit 21 to the fixed frame 26 in the locked state is formed as a flat surface. This fixed frame 2
6 serves as a stopper. Further, the pressure release lever 41 is rotatably supported by a shaft 44 on the other end 31 b side of the pressure lever 31 of the pressing means 30.

On the other hand, on the rear side of the door panel 16 of the laser printer main body 1, a guide sliding contact surface comprising two surfaces, a first lower inclined surface 17 and a second upper vertical surface 18, is formed. The pressure release lever 41 is attached to the second guide sliding contact surfaces 17 and 18 with the movement of the door panel 16 when the door is closed.
The pressure release lever 41 in the pressure release state is rotated stepwise in the return direction in conjunction with the closing operation of the door panel 16 by making the sliding contact surface portion 42 of the handle end portion 41a slidably correspond to the pressure roller 23. The pressure is automatically restored.

That is, as shown in FIG. 3, the pressure release lever 41 is horizontally moved rearward of the door panel 16 of the laser printer main body 1 when the transfer paper 100 is removed due to the occurrence of a jam such as a paper jam. In the form,
Left to right) With handle A open, handle end 4
The sliding contact state with the back surface of the door panel 16 of FIG.
The support shaft 44 to the pressure lever 31 can be pivoted in a clockwise release direction with the support shaft 44 as a fulcrum O.

When the pressure release lever 41 is rotated in the pressure release direction with the door panel 16 opened, the corner 43a of the sliding contact surface 43 of the lock end 41b on the other end side is fixed to the fixing frame of the fixing unit 21. The pressure lever 31 is rotated counterclockwise against the urging force of the pressurizing spring 34 together with the rotation of the pressure release lever 41 with the corner 43a as the point of force F.

The operating rod 32 moves in accordance with the rotation of the pressure lever 31 in the counterclockwise direction, and the movable member 24 that supports the pressure roller 23 following the movement of the operating rod 32 is a heating roller. The pressure roller 23 moves in a direction away from the pressure roller 22, whereby the pressure of the pressure roller 23 is released. At the same time, the lock end 41b of the pressure release lever 41 slides and rotates on the fixed frame 26 of the fixing unit 21, and the locking surface 43b of the sliding contact surface 43 is elastically moved by the urging force of the pressure spring 34. The pressure releasing lever 41 is locked so that the pressure releasing lever 41 is kept in abutment and the pressure releasing state of the pressure roller 23 is maintained.

At this time, the pressure release lever 41 has a rotation range θ such that the point of action P on the handle end 41a side is located below the fulcrum O. Even if the lever 41 is touched lightly, the locked state of the pressure release lever 41 is not released, and the pressure release lever 41 has a short handle end 41a side or the installation space in the laser printer main body 1. Is small, it is possible to increase the rotation stroke.

Further, the lock end portion 4 of the pressure release lever 41 which slides and rotates on the fixed frame 26 of the fixing unit 21.
Since the edge 43a of 1b has an arcuate curved surface form,
Since the sliding rotation of the fixing unit 21 with respect to the fixed frame 26 can be performed smoothly with a light load, and the locking surface 43b of the fixing unit 21 with the fixed frame 26 has a flat surface, the locked state of the pressure release lever 41 is established. Are sure.

In such a pressure released state, after removing the transfer paper 100 in the fixing unit 21, the door panel 16 of the laser printer main body 1 is horizontally moved forward (right to left in the illustrated embodiment) B in the illustrated embodiment. When the door is closed,
As shown in FIG. 4, a handle end 41 of the pressure release lever 41 is provided.
a comes into contact with a first guide sliding contact surface 17 formed by inclining rightward on a lower portion of the rear surface 16a side of the door panel 16, and the sliding operation causes the pressure release lever 41 to return in the counterclockwise return direction. Rotate up by θ1. In this case, the first stage rotation range θ1 of the pressure release lever 41 by the first guide sliding contact surface 17 is set to a range in which the action point P and the fulcrum O on the handle end 41a side are substantially at the same height. Have been.

In this state, when the door panel 16 is further moved in the front door closing direction B, the handle end 41a of the pressure release lever 41 is vertically formed on the rear side of the door panel 16 as shown in FIG. The pressure release lever 41 comes into contact with the second guide sliding contact surface 18 and is further pushed up and rotated by θ2 in the return direction by the sliding contact operation. Due to the rotation θ2 of the pressure release lever 41 in the second stage, the lock end portion 41b
Side is released from the fixed frame 26 of the fixing unit 21,
At the same time that the pressure release lever 41 is unlocked, the pressure lever 31 rotates clockwise by the urging force of the pressure spring 34.

At this time, the sliding contact surface portion 42 on the handle end 41a side of the pressure release lever 41 slidingly contacting the first and second guide sliding contact surfaces 17, 18 formed on the back side of the door panel 16 has an elliptical curved surface. Because it is formed in, compared to a form that distributes the vector load evenly like a circular curved surface,
The force is dispersed such that the vertical vector load at the action point P of the sliding contact surface portion 42 becomes larger than the horizontal vector load due to the door closing operation of the door panel 16, whereby the pressure release lever 41 returns to the return direction. Rotation can be performed with a light load.

Also, after the movable member 24 moves in the direction of pressing against the heat-storing roller 22 by the push-up operation of the operating rod 32 accompanying the rotation of the pressure lever 31, the pressure roller 23 automatically returns to the pressure state. As shown in FIG. 6, when the door panel 16 is completely closed, the pressure release lever 41 is closed.
Is completed.

In the above-described embodiment, the fixing frame 21 of the fixing unit 21 is provided with a projection for locking the lock end 41b of the pressure release lever 41 in the locked state. By restricting the rotation range θ, an inadvertent pressure return of the pressure roller 23 due to excessive rotation of the pressure release lever 41 may be prevented.

Further, it goes without saying that the present invention can be variously modified and implemented without departing from the gist of the present invention.

[0046]

As is apparent from the above description, according to the fixing device of the first aspect of the present invention, the heat release roller is arranged such that the point of action of the pressure releasing means is located below the fulcrum. Since the pressure is released by moving the pressure roller in the direction away from the pressure, the rotation stroke should be increased even when the length of the pressure release means is short or the installation space in the device body is narrow. Therefore, it is possible to increase the separation stroke width of the pressure roller with respect to the heat-carrying roller, whereby the transfer paper can be removed smoothly, and the entire apparatus can be reduced in size and space. be able to. Further, when the opening / closing door is closed, the action point which is one end of the pressure releasing means slides on the opening / closing door and causes the pressing means to press the pressure roller against the heat retaining roller. Then, since the pressure releasing means automatically returns to the pressure contact state, the returning operation is not forgotten as in the related art.

Further, since the point of action of the pressure releasing means is automatically slidably brought into contact with the opening / closing door in conjunction with the closing operation of the opening / closing door, and the pressing roller is brought into pressure contact with the heat-contact roller by the pressing means. When the opening / closing door is closed, the pressure release means can be reliably returned, and the failure of restarting the image forming apparatus main body due to forgetting the return operation of the pressure release lever after removing the transfer paper as before can be avoided. Prevention It can be surely prevented.

According to the second aspect of the present invention, since one end surface forming the action point is formed into an elliptical curved surface, the vector load due to the sliding contact of the pressure releasing means which rotates in conjunction with the door closing operation is dispersed. To facilitate lightening of the rotation of the pressure release lever in the return direction, to reduce the impact at the time of return, and to be widely used for image forming apparatuses having various door panel opening / closing forms and shapes. Can be enhanced.

According to the third and fourth aspects of the present invention, the return operation of the pressure release means can be rotated in a plurality of steps in the return direction in conjunction with the closing operation of the door panel. The rotation in the return direction can be performed smoothly with a light load, and the impact at the time of return can be reduced. In particular, the pressure release means is returned to a certain extent on the inclined surface provided on the opening and closing door, and finally the pressure release means is rotated to the pressure released state on the vertical surface, so that the rotation in the return direction is light and smooth and reliably. It can be carried out.

According to the fifth aspect of the present invention, since there is provided a stopper which comes into contact with the other end of the pressure releasing means and stops the downward rotation of the working point when the pressure is released, the stopper does not deviate from the maximum pressure releasing point. Thus, the stability at the time of releasing the pressure is increased, and an accident due to a user's operation error can be prevented.

According to the sixth and seventh aspects of the present invention, the other end of the pressure releasing means abutting against the stopper has an arc-shaped curved surface, and the locking surface has a flat surface. Therefore, pressure release and pressure return operations by the pressure release lever can be reliably performed with a light load.

According to the eighth aspect of the invention, when the pressure is released by opening the opening / closing door, the other end of the pressure releasing means comes into contact with the stopper to stop the rotation, and at the same time, the urging of the elastic body is performed. In opposition, the pressure contact means is maintained in a pressure released state,
When the opening / closing door is closed, the other end of the pressure releasing unit is separated from the stopper, and the other end of the pressing unit is moved in the pressing direction of the pressing roller against the heat roller by the bias of the elastic body. It is possible to prevent an inadvertent return operation of the pressure release lever due to an operation error or the like during the transfer paper removal operation in the pressure release state as described above, whereby the transfer paper removal operation can be performed safely. At the same time, the pressure releasing means can be reliably returned by the urging of the elastic body.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of an image forming apparatus in which a fixing device according to the present invention is incorporated.

FIG. 2 is an enlarged view of a main part of the fixing device.

FIG. 3 is an explanatory diagram illustrating a pressure releasing state of a pressure roller with respect to a heat roller by a pressure releasing lever when a door panel of a pressure releasing mechanism in a fixing device is opened.

FIG. 4 is an explanatory view showing a first stage return rotation state of a pressure release lever interlocked with an opening operation of a door panel.

FIG. 5 is an explanatory view showing a second stage return rotation state of the pressure release lever interlocked with the door panel opening operation.

FIG. 6 is an explanatory diagram illustrating a state in which a pressure release lever is returned to completion in conjunction with a door panel opening operation;

FIG. 7 is an explanatory view showing a pressure release mechanism in a conventional fixing device.

FIG. 8 is an explanatory diagram illustrating a pressure release state of a pressure release mechanism in a conventional fixing device.

FIG. 9 is an explanatory view schematically showing another example of a pressure release mechanism in a conventional fixing device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image forming apparatus main body 16 Door panel 16a Back surface 17 First guide sliding contact surface 18 Second guide sliding contact surface 20 Fixing device 21 Fixing unit 22 Heat transfer roller 23 Pressure roller 24 Movable member 25 Support shaft 26 Fixed frame 30 Pressure contact Means 31 Pressure lever 31a One end 31b Other end 32 Operating rod 33 Shaft 34 Pressure spring 40 Pressure release means 41 Pressure release lever 41a One end (handle end) 41b Other end (lock end) 42 Sliding contact surface 43 Sliding contact surface 43a Corner edge 43b Locking surface 44 Axis A Door opening direction B Door closing direction F Force point O Support point P Point of action X Direction / separation direction of pressure roller Y Pressure release lever pressure release direction Z Pressure release lever return direction θ Rotation range θ1 Rotation range θ2 Rotation range

Claims (8)

[Claims] 1. A fixing device incorporated in a main body of an image forming apparatus having an opening / closing door, wherein the opening / closing door is opened to enable removal of a transfer sheet. A pressure roller that is pressed against the heat-heating roller, pressure-contact means for pressing the pressure roller so as to be able to come into contact with and separate from the heat-heat roller, and pressure-contact with the heat-heating roller by releasing the pressure on the pressure-contact means. Pressure releasing means for releasing the pressure contact state of the pressure roller, wherein the pressure releasing means has an operation point at one end thereof slidably in contact with the back surface of the opening / closing door in the closed state and at the other end side When the opening / closing door is opened and the action point is rotated below the fulcrum, the pressure on the pressure means is released, and the pressure is released. Roller is separated from the heat roller. When the opening / closing door is closed, an action point, which is one end of the pressure releasing means, slides on the opening / closing door, and is pivoted upward from the fulcrum about the axis as a fulcrum, and pressurizes the pressure means. A fixing device for pressing the pressure roller against the heat roller. 2. The fixing device according to claim 1, wherein said pressure releasing means has one end surface forming said action point formed into an elliptical curved surface. 3. An apparatus according to claim 1, wherein said pressure releasing means slides upward and downward in a plurality of steps in the direction of action thereof in conjunction with a closing operation of said opening / closing door. Fixing device. 4. The fixing device according to claim 3, wherein a surface of the opening / closing door on which the action point of the pressure releasing unit slides is a vertical surface with an inclined surface. 5. The fixing device according to claim 1, further comprising a stopper that abuts on the other end of the pressure releasing unit and stops downward rotation of the action point when the pressure is released. . 6. The fixing device according to claim 5, wherein the pressure releasing unit has an arcuate curved surface at the other end that contacts the stopper with the rotation. 7. The pressure releasing means according to claim 5, wherein the locking surface at the other end abutting on the stopper has a flat surface when the downward rotation of the point of action is stopped. Fixing device. 8. The pressure contact means is rotatably supported at one end and supports the pressure roller by an elastic body so as to support the pressure roller movably in the direction of contact and separation with respect to the heat roller. The pressure roller is urged against the heat roller in the pressure contact direction, and the pressure roller is moved in the direction in which the pressure roller is moved toward and away from the heat roller by the pressure on one end side of the pressure release means. The means is provided on the other end side of the pressure contact means, and when the opening and closing door is opened to release the pressure, the other end of the pressure release means contacts the stopper to stop the rotation, and at the same time, the elastic body In the case where the pressure contact means is kept in a pressure released state against the urging of the opening and the opening / closing door is closed, the other end of the pressure release means is separated from the stopper and the other end of the pressure contact means is biased by an elastic body. To the heat roller. 8. The fixing device according to claim 5, wherein the fixing device moves in a pressure contact direction of the pressure roller.