JP2003015455A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stable high-quality fixing device free from irregular density caused by the permanent set of a fixing roller or a pressure roller in spite of simple constitution. SOLUTION: In this fixing device, a toner image is fixed by making paper to which the toner image is transferred pass through space between the fixing roller and the pressure roller rotating while press-contacting with each other. The fixing device is provided with a press-contact means for making the fixing roller press-contact with the pressure roller, a release means for releasing the press-contact of the fixing roller with the pressure roller and a trigger means for actuating the release means. The release means is a cam for releasing the press-contact by rotating submissively to the rotation of at least either of the fixing roller and the pressure roller when the release means is actuated by the trigger means.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device used in copying machines, printers and the like.

[0002]

2. Description of the Related Art In a fixing device having a fixing roller for heating and fixing a toner image on a sheet, and a pressure roller for pressing the sheet to the fixing roller, either the fixing roller or the pressure roller is generally used. An elastic layer made of silicon rubber or the like is formed on one or both outer circumferences.

In such a fixing device, since the fixing roller and the pressure roller are pressed against each other with a large force and the pressure per unit area is also large, the roller surface is permanently deformed when left stationary for a long period of time.

In order to prevent this, a means for manually releasing the pressure contact between the fixing roller and the pressure roller is provided from the time the image forming apparatus is manufactured to the time it is used. When the image forming apparatus is used while the pressure contact is released when the sheet is loaded on the sheet, there are problems such as discharge of the sheet carrying the unfixed toner image and sheet jamming.

Further, when the pressing force between the fixing roller and the pressure roller is large, the elasticity of the fixing roller or the pressure roller is released even if the image forming apparatus finishes the operation for one day and the pressure contact is released. Deformation of the layer may not be recovered, and uneven fixing and uneven image gloss may occur when the image forming apparatus is used the next day. As a measure to solve this problem, a method of releasing the pressure contact after each copy is considered.

To solve the above problem, Japanese Patent Laid-Open No. 11-125
Japanese Patent Laid-Open No. 985 proposes a fixing device capable of automatically performing the pressure contact and the pressure contact release by using a motor and a cam, as shown in FIG.

[0007] Hereinafter, as a first embodiment of a conventional fixing device, a proposed embodiment of the fixing device will be described with reference to FIG.
This will be described with reference to the schematic diagram of.

FIG. 9A is a schematic view showing a state where the fixing roller and the pressure roller are in pressure contact with each other, and FIG. 9B is a state in which the pressure contact between the fixing roller and the pressure roller is released. It is a schematic diagram which shows.

In the figure, the fixing roller 27 and the pressure roller 28 face each other in the vertical direction, and the pressure roller 28 is biased by a roller pressure spring 246 in a direction in which the fixing roller 27 is pressed by a pressing lever 248. Has been done. The pressure contact lever 248 has a bearing 245 that rotatably fits and holds the pressure roller 28 in the center, and a round hole formed in the vicinity of the left end and a lever rotation shaft 2 fixed to the fixing device main body.
49 is rotatably fitted, the lower surface near the right end is abutted against the roller pressing spring 246 and is urged upward, and the upper surface near the right end is in contact with the outer circumference of the pressure release cam 295. Touching.

The pressure contact releasing cam 295 is formed of a cam portion having a disk-shaped outer peripheral shape and a hole portion provided at a rotation center position eccentric from the cam portion.

The cam rotation shaft 296 has a press contact release cam 295.
Is fixed through the hole and is rotatably fitted to cam bearings (not shown) fixed to the fixing device main body near both ends. The cam rotation shaft 296 is connected to a cam drive motor (not shown) so as to be rotationally driven by a connection mechanism (not shown) such as a gear.

In FIG. 9 (a), the cam drive motor is energized by the control of a control unit (not shown), the pressure contact release cam 295 is rotated in the direction of the arrow, and the outer peripheral portion having a short distance from the center is pressure contacted. At a position where it comes into contact with the lever 248, a sensor (not shown) that detects the position of the pressure contact release cam 295, the pressure contact lever 248, or the like is operated to stop the rotation of the cam drive motor. In this state, the fixing roller 27 and the pressure roller 28 are in pressure contact with each other.

In FIG. 9B, the cam drive motor is energized to rotate the pressure contact release cam 295, and the outer peripheral portion having a long distance from the center of the pressure contact release cam 295 is pressed by the pressure contact lever 2.
At the position where it comes into contact with 48, the sensor is actuated and the rotation of the cam drive motor is stopped. In this state, the pressure contact between the fixing roller 27 and the pressure roller 28 is released.

The release of the pressure contact is preliminarily incorporated in the program of the control unit so that it is activated by the information such as when the planned number of prints is completed or when the paper jams. This makes it possible to prevent permanent deformation of the elastic layer.

However, there is a problem that the use of a motor is expensive and power consumption increases. On the other hand, JP-A-6-3
In Japanese Patent No. 08851, as shown in FIG. 10, there is proposed a fixing device that does not use a single drive source such as a motor but automatically restores the pressure contact when in use. This proposal has a content that the pressure contact is released by a manual lever and the pressure contact is automatically performed.

As a second embodiment of the conventional fixing device, an embodiment of the proposed fixing device will be described below with reference to the schematic view of FIG.

FIG. 10A is a schematic view showing a state in which the fixing roller and the pressure roller are in pressure contact with each other, and FIG.
FIG. 6 is a schematic diagram showing a state in which the pressure contact between the fixing roller and the pressure roller is released.

In the figure, the fixing roller 27 and the pressure roller 28 face each other in the vertical direction, and the pressure roller 28 formed integrally with the rotating shaft 284 is in a direction in which the fixing roller 27 is pressed against the fixing roller 27 via a bearing 245 or the like. The roller pressure spring 24
Energized by 6.

The lever-equipped cam 297 has a circular hole formed at the center of rotation to be fitted into the rotary shaft 284 and rotatably held therein, and has a cam portion C and a lever portion L formed on its outer shape.

The bearing 245 has an inner diameter for holding the rotary shaft 284, and has a parallel portion on its side surface which is fitted into a vertically long rectangular hole formed in the fixing device main body and slides. .

The roller pressure spring 246 is a coiled compression spring, one end of which is brought into contact with a shelf portion (no reference numeral) formed on the outer frame of the fixing device main body and the other end of which is brought into contact with the lower surface of the bearing 245. The bearing 245 is pushed up so that the fixing roller 27 and the pressure roller 28 are brought into pressure contact with each other.

A lower stopper pin 2 is provided on the outer frame of the fixing device body.
98 and an upper stopper pin 299 are provided to position the lever-equipped cam 297.

In FIG. 10A, the cam 2 with a lever is provided.
97 is a position where the lever part L abuts the lower stopper pin 298, and the cam part C is a position separated from the fixing roller 27. Therefore, the pressure roller 28 is biased by the roller pressure spring 246 and is pressed against the fixing roller 27 via the bearing 245.

In FIG. 10B, the user contacts the upper stopper pin 299 with the lever portion L of the cam 297 having a lever when the image forming apparatus is not used for a long time or when a paper jam occurs in the fixing device. The state is shown in which the fixing roller 27 and the pressure roller 28 are released from the pressure contact with each other.
That is, when the lever portion L is pushed up from the position where it abuts against the lower stopper pin 298 toward the upper stopper pin 299, the cam portion C comes into contact with the outer peripheral surface of the fixing roller 27 and pushes up the lever-equipped cam 297. Since the fixing roller 27 is fixed, the roller pressure spring 2
When the lever-equipped cam 297 is pushed down via the bearing 245 and the rotary shaft 284 against the spring pressure of 46, and the lever portion L reaches the position where it abuts the upper stopper pin 299, the fixing roller 27 and the pressure roller 27 The pressure contact with 28 is released.

In this state, when the next image forming cycle is started, the fixing roller 27 starts to rotate counterclockwise as indicated by an arrow, and the cam 297 with a lever abutting against the fixing roller 27 rotates clockwise due to frictional force. When the cam portion C comes off the fixing roller 27, the lever portion L of the lever-equipped cam 297 lowers due to its own weight and hits the lower stopper pin 298 to stop.

That is, the pressure contact between the fixing roller 27 and the pressure roller 28 is restored even if the user does not operate the lever.

However, in the fixing device according to this proposal, if the user does not release the pressure contact, it is always in pressure contact, and there is a concern that the elastic layer will be permanently deformed.

The image quality has been remarkably improved by the recent technological advances, and if permanent deformation occurs in the elastic layer of the fixing roller or the pressure roller, the image quality is likely to be affected as fixing unevenness, that is, density unevenness.

[0029]

To solve the above problems, the present invention does not require the use of power such as a motor to press and release the fixing roller and the pressure roller, and the trigger means presses the press roller at any time. The stable and high-quality fixing that does not have density unevenness due to permanent deformation of the fixing roller or the pressure roller while having a simple structure that can automatically release the pressure The purpose is to provide a device.

[0030]

The object of the present invention can be achieved by the following constitutions.

(1) In the fixing device for fixing the toner image by passing the sheet on which the toner image has been transferred between the fixing roller and the pressure roller which rotate while being in pressure contact, the fixing roller and the pressure roller are fixed. It has a pressure contact means for pressure contacting the pressure roller, a release means for releasing the pressure contact between the fixing roller and the pressure roller, and a trigger means for operating the release means, and the release means includes the trigger means. The fixing device is a cam that releases the pressure contact by being driven by the rotation of at least one of the fixing roller and the pressure roller when operated by.

(2) The fixing device according to (1), wherein the cam is formed in a ring shape and is inserted into the outer periphery of the fixing roller or the pressure roller near the end in the longitudinal direction of the rotating shaft. .

(3) The fixing roller and the pressure roller are brought into pressure contact with each other by rotating at least one of the fixing roller and the pressure roller in a direction opposite to the direction in which the pressure contact is released. The fixing device according to (1) or (2).

[0034]

1 is a conceptual diagram for explaining the configuration of a color copying machine which is an example of an image forming apparatus using a fixing device according to an embodiment of the present invention.

The image forming apparatus main body GH is called a tandem type color image forming apparatus, and includes a plurality of sets of image forming units 10Y, 10M, 10C and 10K, a belt-shaped intermediate transfer member 6, a sheet feeding and conveying means, and a sheet feeding and conveying means. And a fixing device 24.

Image forming unit 1 for forming a yellow image
0Y has a charging unit 2Y, an exposing unit 3Y, a developing device 4Y, and a cleaning unit 8Y, which are arranged around a photoconductor 1Y as an image forming body. The image forming unit 10M that forms a magenta image includes a photoconductor 1M as an image forming body,
It has a charging means 2M, an exposing means 3M, a developing device 4M and a cleaning means 8M. The image forming unit 10C that forms a cyan image has a photoreceptor 1C as an image forming body, a charging unit 2C, an exposing unit 3C, a developing device 4C, and a cleaning unit 8C. Image forming unit 1 for forming a black image
0K is a photoconductor 1K as an image forming body, a charging unit 2K,
Exposure unit 3K, developing device 4K, and cleaning unit 8K
Have. Charging means 2Y, exposure means 3Y, charging means 2M
The exposing unit 3M, the charging unit 2C, the exposing unit 3C, the charging unit 2K, and the exposing unit 3K constitute a latent image forming unit.

The intermediate transfer member 6 is an endless belt,
It is stretched by a plurality of rollers and is rotatably supported.

Image forming units 10Y, 10M, 10C and 1
The image of each color formed from 0K is sequentially transferred (primary transfer) onto the rotating intermediate transfer body 6 by the transfer means 7Y, 7M, 7C and 7K to form a combined color image. The paper P stored in the paper feed cassette 20 is fed by the paper feed means 21 and fed by the paper feed rollers 22A, 22B,
The color image is transferred to the transfer unit 7A via the 22C, the registration roller 23, and the like, and the color image is transferred onto the paper P (secondary transfer). The paper P on which the color image is transferred is fixed by the fixing device 24.
Then, the sheet is fixed by the sheet ejection roller 25, is sandwiched by the sheet ejection rollers 25, and is placed on the sheet ejection tray 26 outside the apparatus.

On the other hand, after the color image is transferred onto the paper P by the transfer means 7A, the intermediate transfer member 6 which separates the paper P is
The residual toner is removed by the cleaning unit 8A.

5Y, 5M, 5C and 5K are the developing device 4
It is a toner replenishing means for replenishing Y, 4M, 4C, and 4K with new toner.

An image reading device YS including an automatic document feeding device 201 and a document image scanning exposure device 202 is installed above the image forming apparatus main body GH. The original d placed on the original table of the automatic original feeding device 201 is conveyed by the conveying means, and the image of one side or both sides of the original is scanned and exposed by the optical system of the original image scanning exposure device 202, and the line image sensor CCD is exposed. Is read.

The analog signal photoelectrically converted by the line image sensor CCD is subjected to analog processing, A / D conversion, shading correction, image compression processing, etc. in an image processing section, and then an image writing section (exposure means) 3Y, Three
Send signals to M, 3C and 3K.

The automatic document feeder 201 is provided with an automatic double-sided document conveying means. Since the automatic document feeder 201 can continuously read the contents of a large number of documents d fed from the document table and store them in the storage means (electronic RDH function), copying is possible. It is conveniently used when copying the contents of a large number of originals by the function or when transmitting a large number of originals d by the facsimile function.

FIG. 2 is a schematic partial sectional view of the fixing device according to the first embodiment of the present invention, and FIG. 3 is a schematic AA sectional view of FIG. Since the main configuration of the fixing device according to the present invention is symmetrical in the longitudinal direction of the fixing roller, only the configuration on the front side will be mainly illustrated and described.

2 (a) and 3 (a) show a state in which the fixing roller and the pressure roller are in pressure contact with each other, and FIG. 2 (b).
And FIG. 3B shows a state in which the pressure contact between the fixing roller and the pressure roller is released.

In the figure, a fixing roller 27 having a heating source (not shown) such as a halogen heater provided therein is a fixing roller core metal 271 and a fixing roller elastic member formed on the outer periphery of the fixing roller core metal 271. The layer 272 and the like are formed.

The front side of the fixing roller core metal 271 (here, the front outer frame 241 side to be described later with respect to the center of the fixing roller in the longitudinal direction is referred to as front or front, and the rear outer frame 242 side to be described later is the opposite direction. The outer periphery in the vicinity of the end is rotatably fitted and held by the core bar bearing 244, and the core bar bearing 244 is integrally fitted and held by the bearing holder 243. Is fixed to a round hole (no reference numeral) of the front outer frame 241 forming the front surface of the fixing device body.

The outer periphery of the rear end portion of the fixing roller core metal 271 is rotatably fitted and held by the core metal bearing 244 similarly to the front side, and the core metal bearing 244 is mounted on the bearing holder 24.
3, the bearing holder 243 is fixed to a round hole (no reference numeral) of the rear outer frame 242 that forms the back surface of the fixing device main body.

The pressure roller 28 is, for example, a rotating shaft 284.
A pair of front and rear cored bar holders 283 fitted and fixed to the rotating shaft 284, a pressure roller cored bar 281 fitted and fixed to the cored bar holder 283, and formed on the outer circumference of the pressure roller cored bar 281. The pressure roller elastic layer 282 is integrally formed.

The rotary shaft 284 is rotatably fitted and held by one of the bearings 245 in the vicinity of the front end of the rotary shaft 284. The bearing 245 is a square hole (below the circular hole of the front outer frame 241). It is held slidably (without reference numeral). The rotary shaft 284 is rotatably fitted and held in the inner diameter of the other bearing 245 in the vicinity of the rear end, similarly to the front side, and the bearing 245 is provided below the round hole of the rear outer frame 242. It is slidably held in the square hole.

The pair of front and rear bearings 245 are urged by the pair of front and rear roller pressing springs 246 in the direction in which the pressure roller 28 is pressed against the fixing roller 27 via the rotary shaft 284 (upward). The roller pressing spring 246 on the front side is a coil-shaped compression spring having one end abutting on the lower surface of the bearing 245 and the other end abutting on the upper surface of the shelf (no reference numeral) protruding from the front outer frame 241. The roller pressure spring 246 on the back side has the bearing 24 at one end as in the front side.
5, and the other end is brought into contact with the upper surface of the shelf portion projecting from the rear outer frame 242.

The pair of front and rear ring-shaped cams (hereinafter, simply referred to as ring-shaped cams) 29, which are cam means, have a cam portion 291 with a thickened thickness on a part of the inner side in the circumferential direction, and the other parts. Has a substantially cylindrical shape formed by the thin portion 292.

The ring-shaped cam 29 corresponds to the fixing roller 27.
Are arranged between the front end of the fixing roller elastic layer 272 and the front outer frame 241 in the longitudinal direction of the fixing roller elastic layer 272, and between the rear end of the fixing roller elastic layer 272 and the rear outer frame 242. The fixing roller core metal 271 is inserted around the outer circumference.

When the fixing roller 27 and the pressure roller 28 are brought into pressure contact with each other, the gap T1 formed by the outer periphery of the fixing roller core metal 271 and the outer periphery of the opposing pressure roller core metal 281 is the ring-shaped cam. 29 is smaller than the maximum thickness T2 of the cam portion 291 and has the ring-shaped thin portion 292.
Is set to a value larger than the thickness T3 (T3 <T1 <
T2).

Around the ring-shaped cam 29, a pair of front and rear U-shaped restricting members 250 fixed to the front outer frame 241 and the rear outer frame 242 in the front-rear direction and the left-right direction are provided. The cam 29 is arranged around the cam 29 with a gap.

On the outer peripheral surface of the ring-shaped cam 29, there is a stopper hole 293 at a position where the phase is shifted in the axial direction.
And a detection hole 294 are formed, close to the outer peripheral surface,
A stopper mechanism 31 and a photo sensor 247 are arranged so that the stopper hole 293 and the detection hole 294 are aligned in phase in the axial direction.

A pair of front and rear stopper mechanisms (hereinafter, simply referred to as stopper mechanisms) 31 which are trigger means include, for example, a stopper claw 311, a stopper rotating shaft 312, and a connecting pin 31.
3, solenoid 34, and solenoid return spring 35
have.

The stopper claw 311 is rotatably mounted on the stopper rotation shaft 312 fixed to the outer frame of the fixing device main body, and the claw portion at the tip thereof is pressed against the fixing roller 27 and the pressure roller 28. The ring-shaped cam 29 is configured to be inserted into the stopper hole 293.

The solenoid 34 fixed to the outer frame of the main body of the fixing device fixes the connecting pin 313 in a round hole formed in the vicinity of the tip of the slide shaft (no reference numeral), and the connecting pin 313 of the stopper claw 311 is used. The stopper claw 311 and the solenoid 3 are inserted into the holes provided near the claw part.
4 is configured to be rotatably connected.

A solenoid return spring is inserted in the slide shaft to urge the stopper claw 311 toward the surface of the ring-shaped cam 29.

The photo sensor 247 is fixed to the fixing device main body, and when the ring-shaped cam 29 is rotated, the fixing roller 27 is fixed.
It is arranged so as to be in phase with the detection hole 294 in the axial direction.

Next, the operation of the ring-shaped cam 29 when the fixing roller 27 and the pressure roller 28 are pressed and released from each other will be described.

When the fixing roller 27 and the pressure roller 28 are brought into pressure contact with each other and fixing of one or more sheets on which an unfixed toner image is placed is completed, the stopper hole 293 of the ring-shaped cam 29 is closed. Since the solenoid 34 is in the position of the claw portion of the stopper claw 311, and the solenoid 34 is not urged, the ring-shaped cam 29 serves as the fixing roller core metal 271 and the pressure roller when the claw portion is inserted into the stopper hole 293. It is stopped at a position where it does not come into contact with the cored bar 281.

Under the control of the control unit of the image forming apparatus, the solenoid 34 is energized to pull the slide shaft against the spring pressure of the solenoid return spring 35 in order to release the pressure contact. Further, the connecting pin 31 fixed to the slide shaft
3, the stopper claw 311 is pulled toward the solenoid 34, and the stopper claw 311 rotates about the stopper rotation shaft 312, and the claw portion of the stopper claw 311 causes the stopper hole 293 of the ring-shaped cam 29.
It comes off and stands by at a position separated from the outer periphery of the ring-shaped cam 29 (see FIG. 3B).

The ring-shaped cam 29 is rotated by the frictional force between the ring-shaped cam 29 and the pressure roller 28 as the pressure roller 28 rotates, and the cam portion 291 causes the fixing roller core metal 271 and the pressure roller core metal 28.
The gap formed by 1 and 1 is reached. That is, the ring-shaped cam 29 moves to a position where it contacts the two rollers.

The cam portion 291 that has reached the gap is nipped by the frictional force between the fixing roller core metal 291 and the pressure roller core metal 281 and the maximum thickness of the cam portion 291 is larger than the gap, so the fixing roller 27 And pressure roller 28
Of the fixing roller elastic layer 272 and the pressure roller elastic layer 282 when the pressure roller 28 is pressed downward against the roller pressure spring 246 and the cam portion having the maximum thickness reaches the gap. A gap is formed between them and the pressure contact is released (see FIG. 2B).

At this time, the detection hole 294 formed in the ring-shaped cam 29 is formed so as to come to a position facing the photo sensor 247, and a signal from the photo sensor 247 is fixed via the control unit. The rotation of the roller 27 and the pressure roller 28 is stopped.

When the fixing roller 27 and the pressure roller 28 are brought into pressure contact with each other again, the ring-shaped cam 29 is restarted by drivingly rotating the fixing roller 27 under the control of the control section, and the ring-shaped cam 29 is rotated. When the cam portion 291 passes through the gap formed by the fixing roller 27 and the pressure roller 28, the pressure contact is performed.

Subsequently, the ring-shaped cam 29 continues to rotate due to the rotation of the fixing roller 27 and the stopper hole 293.
When reaches the position corresponding to the claw portion of the stopper claw 311, the urging of the solenoid 34 has already been released, the claw portion is inserted into the stopper hole 293, and the rotation of the ring-shaped cam 29 is stopped.

FIG. 4 shows a second fixing device according to the present invention.
4 is a schematic partial cross-sectional view of the embodiment of FIG.
FIG. 4A shows a state in which the fixing roller and the pressure roller are in pressure contact with each other, and FIG. 4B shows a state in which the pressure contact between the fixing roller and the pressure roller is released.

As in the first embodiment, the cam means is the pair of front and rear ring-shaped cams 29, and the trigger means is the pair of front and rear stopper mechanisms.

The difference from the first embodiment is that the stopper claw 311 is lengthened to move the solenoid 34 away from the pressure contact portion between the fixing roller 27 and the pressure roller 28, and that the U-shaped restricting member 250 is used instead. That is, the guide roller 371 and the pressing roller 381 are provided.

The fact that the solenoid 34 is kept away from the pressure contact portion means that it is kept away from the sheet conveyance path to avoid overcrowding of the peripheral mechanical portions. The guide roller 371 and the pressing roller 381 have ring-shaped cams 29. It has the meaning of reducing the friction caused by the contact with the peripheral members and stabilizing the operation of the ring-shaped cam 29.

In the figure, the stopper claw 311 formed of a strip-shaped plate member has a bent portion (claw portion) at the tip,
The center portion has a hole portion that fits with the stopper rotation shaft 312 and is rotatably held, and a solenoid connecting pin hole provided at a position facing the claw portion around the hole portion. The operation of the stopper claw 311 is basically the same as that of the first embodiment except that the pulling direction of the solenoid 34 is reversed in the left-right direction, and a description thereof will be omitted.

The guide roller means 37 is composed of, for example, a guide roller 371 and a roller rotating shaft 372. The guide roller 371 has an outer periphery abutting against the ring-shaped cam 29 and an inner diameter rotatably held with the roller rotating shaft 372. The roller rotation shaft 372 is a ring-shaped member that is fixed to the fixing device main body.

The ring cam restraining means 38 comprises, for example, a ring cam restraining roller 381, a restraining roller holding plate 382, a restraining roller rotating shaft 383, a roller holding plate rotating shaft 384, and a roller holding plate spring 385.

The ring cam pressing roller 381 is rotatably attached to the pressing roller rotating shaft 383, and the pressing roller rotating shaft 383 is fixed near the end of the pressing roller holding plate 382.

The roller holding plate 382 is rotatably held by fitting a hole in the vicinity of the other end of the roller holding plate 382 to a roller holding plate rotating shaft 384 fixed to the fixing device main body. The roller holding plate spring 385 biases the holding roller holding plate 382 downward.

The ring cam restraining means 38 pushes the outer circumference of the ring-shaped cam 29 downward by the ring-cam restraining roller 381 to bring the ring-shaped cam 29 and the pressure roller core metal 281 into close contact with each other, thereby ensuring the rotation operation of the ring-shaped cam 29. To

The ring-shaped cam 29 is abutted and held by the ring-cam restraining roller 381, the pressure roller core metal 281 and one of the guide rollers 371 of the pair of guide rollers 371. A gap is provided with the other guide roller 371. This gap is for ensuring the close contact between the ring-shaped cam 29 and the pressure roller core metal 281 and the other guide roller 371.
Is to prevent the ring-shaped cam 29 from coming off.

The structure and operation of the other members are the same as those in the first embodiment, and the description thereof will be omitted.

FIG. 5 shows a third fixing device according to the present invention.
5 is a schematic partial sectional view of the embodiment of FIG.
FIG. 5A shows a state in which the fixing roller and the pressure roller are in pressure contact with each other, and FIG. 5B shows a state in which the pressure contact between the fixing roller and the pressure roller is released.

In the figure, a pair of front and rear ring cam lifting mechanisms 32 serving as trigger means are, for example, a ring cam lifting plate 321, lifting pins 322, wires 323,
It is composed of a wire guide roller 324, a wire guide shaft 325, and a solenoid 34.

The lifting pin 322 is fixed near the bifurcated lower end of the ring cam lifting plate 321, and is inserted into the space formed by the upper outer peripheral surface of the fixing roller core metal 271 and the upper inner surface of the ring-shaped cam 29.

The ring cam lifting plate 321 is suspended by the wire 323 in the hole at the upper center.

The wire 323 is bent by the wire guide roller 324 and attached to the slide shaft (no reference numeral) of the solenoid 34.

The wire guide roller 324 is rotatably held by a wire guide shaft 325 fixed to the fixing device main body.

The solenoid 34 is fixed to the main body of the fixing device. When the fixing roller 27 and the pressure roller 28 are in pressure contact with each other, as shown in FIG.
The lifting pin 322 integrated with the ring cam lifting plate 321 is lifted via the wire 323, and the lower surface of the ring-shaped cam 29 is pressed against the pressure roller core metal 28.
It is separated from the outer peripheral surface of 1. At this time, the ring-shaped cam 2
The ring-shaped cam 29 stops at a position where the inner surface of the lower portion of 9 does not contact the outer peripheral surface of the lower portion of the fixing roller core 271.

After the fixing is completed, the control of the control section releases the bias of the solenoid 34 to release the pressure contact, and the lifting pin 322 integrated with the wire 323 and the ring cam lifting plate 321 is lowered by its own weight. The ring-shaped cam 29 is moved downward to move the pressure roller core metal 281.
Abutted against.

The ring-shaped cam 29 is rotated by a frictional force by the rotation of the pressure roller 28, and the cam portion 291 of the ring-shaped cam 29 is fixed to the fixing roller 2 in the same manner as in the first embodiment.
7 is inserted into the gap formed by the pressure roller 28, the pressure roller 28 is pushed downward, and the pressure contact with the fixing roller 27 is released (see FIG. 5B).

The configuration and operation of the other members are the same as those in the first embodiment, and the explanations thereof are omitted.

In this embodiment, since the stopper claw is unnecessary, there is an advantage that there is no impact when the stopper claw enters the stopper hole.

FIG. 6 shows a fourth fixing device according to the present invention.
6 is a schematic partial cross-sectional view of the embodiment of FIG.
6A shows a state in which the fixing roller and the pressure roller are in pressure contact with each other, and FIG. 6B shows a state in which the pressure contact between the fixing roller and the pressure roller is released. 7 is a central sectional view of FIG. 6 (b), and FIG. 8 is a side view of FIG. 6 (a).

Hereinafter, description will be made with reference to FIGS. 6, 7, and 8. In the figure, a pair of front and rear block-shaped cams 361, which is another cam means, has a tapered portion at one end and a spring hook portion formed of a hole or the like near the other end, and a pair of blocks in the middle. It has a hole into which a connecting shaft 362 for connecting the circular cam 361 is fitted, and one end of a cam return spring 363 is attached to the spring hook portion.

Assuming that the maximum thickness of the taper portion of the block-shaped cam 361 is T2, the minimum thickness is T3, and the gap between the fixing roller core metal 271 and the pressure roller core metal 281 during the pressure contact is T1, T3 <T1 The configuration is such that <T2 (see FIG. 6A).

The length of the connecting shaft 362 formed by a round bar is longer than the distance between the front outer frame 241 and the rear outer frame 242, and the front outer frame 241 and the rear outer frame 242 respectively have the same length. An elongated hole (no reference numeral) extending in the horizontal direction is formed at a substantially symmetrical position at substantially the same height as a pressure contact portion between a fixing roller and a pressure roller (not shown), and the connecting shaft 362 forms the elongated hole. It is configured to slide.

The other end of the cam return spring 363 is attached to a spring hooking member 364 fixed to the fixing device main body, which is located in a direction away from the pressure contact portion on a substantially extended line of the elongated hole. The cam return spring 363 is a block-shaped cam 361.
Is urged in a direction away from the pressure contact portion.

The block-shaped cam operating mechanism 33 as the trigger means includes a cam operating lever 331, a lever rotation shaft 332,
It is composed of a lever connecting pin 333 and a solenoid 34.

The cam actuating lever 331 has a round hole at the center thereof, which is rotatably fitted and held with the lever rotating shaft 332, and the lever connecting pin 333 is inserted into a hole provided near one end of the cam operating lever 331. The vicinity of the end of is extended to a length such that it can contact the connecting shaft 362.

Lever rotation shaft 332 and solenoid 34
Is fixed to the main body of the fixing device. Lever connecting pin 333
Is fixed in a hole provided near the end of the slide shaft of the solenoid 34.

In this embodiment, the fixing roller and the pressure roller are configured to be capable of normal rotation and reverse rotation by using a motor capable of normal and reverse rotation.

Next, the operation of this embodiment will be described. After the completion of fixing, the block-shaped cam 361 is in a position where it does not contact the fixing roller core metal 271 and the pressure roller core metal 281. However, the solenoid 34 operates to release the pressure contact under the control of the controller. Energized, Figure 6
The lever connecting pin 333 is biased in the direction of the arrow in (a).

As a result, the cam operating lever 331 is rotated clockwise, one end of the cam operating lever 331 urges the block-shaped cam 361 in the direction of the arrow via the connecting shaft 362, and the block-shaped cam 361 is fixed to the fixing roller. The core metal 271 and the pressure roller core 281 are moved to a position where they come into contact with each other.

When the tip of the taper portion of the biased block-shaped cam 361 is inserted into the gap between the fixing roller core metal 271 and the pressure roller core metal 281, the fixing roller and the pressure roller rotate together. The block-shaped cam 361 is moved in the direction of the arrow by the frictional force between the cored bars 271 and 281 and the block-shaped cam 361.

When the thickness of the taper portion of the block-shaped cam 361 exceeds the gap T1, the pressure roller core metal 281, a core metal holder (not shown), and the rotary shaft 284 are resisted against the roller pressure spring 246. Bearing 245 through
Push down to start separating the elastic layers of both rollers that were in pressure contact.

The block-shaped cam 36 inserted in the gap.
When the thickness of 1 reaches the maximum thickness T2 of the tapered portion,
The elastic layers of both rollers are completely separated. When this state is reached, the positions of the pressure roller and the block-shaped cam 361 are detected by a sensor (not shown), and the rotation of both rollers is stopped (see FIG. 6B).

When returning to the pressure contact state again, when the block-shaped cam 361 is inserted by reversely rotating the fixing roller and the pressure roller under the control of the control section, for example, by reversing the motor capable of forward and reverse rotation. And reverse the direction (Fig. 6
(See (b)).

When the rotation progresses and the block-shaped cam 361 moves and the thickness held in the gap becomes T1,
That is, when the pressure roller comes into pressure contact with the fixing roller, the pressure contact force from both rollers against the block-shaped cam 361 becomes zero.

When this state is reached, the block-shaped cam 3
61 is urged by the spring pressure of the cam return spring 363 to move in the direction of the arrow shown in FIG.
71 and the pressure roller core 281 to a position where they do not come into contact with each other, and the connecting shaft 362 comes into contact with the ends of the slots provided in the front outer frame 241 and the rear outer frame 242 to stop (FIG. 6).
(See (a)).

Since the structure and operation of the other members are the same as those of the first embodiment, the description thereof will be omitted.

In the embodiment of the present invention, the fixing roller in which the elastic layer is formed on the outer periphery has been described. However, the fixing roller may have a release layer or a heat ray absorbing layer on the outer periphery of the elastic layer. It goes without saying that a fixing roller that does not have any type may be used.

In the present embodiment, the ring-shaped cam is inserted in the outer circumference near the end of the fixing roller, but the present embodiment can be applied to the outer circumference near the end of the pressure roller. .

Although the solenoid has been described as the trigger means in the embodiment, a cam mechanism or the like may be used.

Although no particular reference was made to the timing for releasing the pressure contact, according to the present invention, the timing can be arbitrarily set even when not used for a long time or at the end of each copy.

When pressure contact is required to perform the fixing process again, the cam automatically operates to press both rollers together with the rotation of the fixing roller or the pressure roller. No problems such as jams and discharge of unfixed paper occur.

[0116]

According to the configuration of the present invention, it is not necessary to use a motor for the power of pressure contact between the fixing roller and the pressure roller and release of pressure contact, and the pressure contact can be released at any time by a trigger means such as a solenoid. And, although it is a simple structure that the operation of pressing again is automatically performed,
It is possible to provide a stable and high-quality fixing device that does not have uneven density due to permanent deformation of the fixing roller or the pressure roller.

[Brief description of drawings]

FIG. 1 is a conceptual diagram for explaining a configuration of a color copying machine which is an example of an image forming apparatus using a fixing device according to an embodiment of the present invention.

FIG. 2 is a schematic partial sectional view of a fixing device according to a first embodiment of the present invention.

3 is a schematic AA cross-sectional view of FIG.

FIG. 4 is a schematic partial sectional view of a fixing device according to a second embodiment of the invention.

FIG. 5 is a schematic partial sectional view of a fixing device according to a third embodiment of the invention.

FIG. 6 is a schematic partial sectional view of a fixing device according to a fourth embodiment of the invention.

FIG. 7 is a central sectional view of FIG.

FIG. 8 is a side view of FIG.

FIG. 9 is a schematic diagram of a first embodiment of a conventional fixing device.

FIG. 10 is a schematic diagram of a second embodiment of a conventional fixing device.

[Explanation of symbols]

24 Fixing device 27 fixing roller 271 fixing roller core metal 28 Pressure roller 281 Pressure roller core metal 29 Ring-shaped cam 31 Stopper mechanism 33 Block-shaped cam operating mechanism 34 Solenoid 361 block cam

Claims (3)

[Claims] 1. A fixing device for fixing a toner image by passing a sheet onto which a toner image has been transferred between a fixing roller and a pressure roller that rotate while being in pressure contact with each other. A pressure roller for pressing the pressure roller; a releasing means for releasing the pressure contact between the fixing roller and the pressure roller; and a triggering means for activating the releasing means. A fixing device, which is a cam that releases the pressure contact by being driven by rotation of at least one of the fixing roller and the pressure roller when activated. 2. The fixing device according to claim 1, wherein the cam is formed in a ring shape and is inserted into an outer periphery of a rotation shaft of the fixing roller or the pressure roller near a longitudinal end thereof. 3. The fixing roller and the pressure roller are brought into pressure contact with each other by rotating at least one of the fixing roller and the pressure roller in a direction opposite to the direction in which the pressure contact is released. The fixing device according to claim 1 or 2.