JP3323714B2 - Fixing device - Google Patents

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 applying heat energy to a recording material carrying a developed image (unfixed toner image) to be heated and fixed to heat and fix the developed image.

[0002]

2. Description of the Related Art Conventionally, as a means for fixing a visible image on a recording material, a method using a heat roller is known. There are drawbacks such as a longer warm-up time. On the other hand, a fixing device using a fixing film made of a heat-resistant film has been proposed (JP-A-63-31163).
No. 3182).

The fixing device includes a fixing film made of a thin heat-resistant film, a driving roller for driving the fixing film, and a heating element fixedly supported and arranged so as to be in sliding contact with the inner peripheral surface of the fixing film. And a pressing member disposed so as to come into contact with the outer peripheral surface of the fixing film and press against the heating element via the film.

In the fixing device, the fixing film and the pressing member are driven to rotate at the same speed as the conveying speed of the recording material at least at the time of performing image fixing, and the heating member formed via the fixing film is heated. When the recording material is nipped and conveyed in the fixing nip portion of the pressure member, thermal energy of a heating element is applied to a developed image (unfixed toner image) on the recording material, so that the developed image is softened and melted. When the recording material is discharged from the fixing nip portion, the visible image is cooled and solidified and fixed on the recording material.

In a fixing device using such a fixing film, when the recording material is caught and stopped in the fixing nip portion for some reason, the fixing film and the pressing member are used so that the recording material can be easily removed. It is desirable to provide a pressure release mechanism for releasing the pressure contact with the pressure. By providing this pressure release mechanism, the unfixed toner adheres to the fixing film, which causes image deterioration in the subsequent image formation, or the fixing film is damaged by forcibly pulling out the recording material from the fixing nip portion. Can be prevented.

[0006]

However, in the above-mentioned conventional fixing device, when the heating element is heated while the pressure contact between the fixing film and the pressure member is released, the temperature rises sharply. And the fixing film may be damaged to shorten the life of the fixing film.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to prevent abnormal heating of a heating element and prevent damage to a heating element, a pressing member and a film member. It is an object of the present invention to provide a fixing device capable of improving the durability of the fixing device.

[0008]

In order to achieve the above-mentioned object, the invention according to claim 1 is provided with a predetermined tension around a heating element and a support, and the endless or endless movement of the support by rotation of the support. and a film member, a pressure member disposed to press the heating member via the film member, the pressure release means for pressurizing and pressure release the pressure member against the heating member When an abnormal condition occurs, the pressure
In the fixing device that performs removal, after the pressure is released in the event of an abnormality
Sometimes , after a lapse of a predetermined time from the start of rotation of the support and the film member , the pressing member is pressed against the heating member, and after the rotation of the film member and the pressing member starts, the pressing member is pressed.
It is characterized by energizing a heating element .

[0009] Thus, according to the first aspect of the invention, low
At least if the pressure member is not pressed by the heating element
Since there be energized heating element, rapid heating of the heating member is prevented, the heating body, is a pressure member and improve these durability is prevented that the film member is Ru damaged It is planned. In addition, the state where the heating body is cooled down without energizing the heating body
Can reduce the time to drive the film member
Therefore, the driving of the film member can be stabilized.
You.

According to a second aspect of the present invention, in the first aspect of the present invention, the heating element is provided via the fixing film.
The recording material is sandwiched between a nip formed by the pressure member and the pressure member.
The pressure of the pressure member is released when the pressure is stopped .

[0011] Thus, according to the second aspect of the invention, two
When the recording material is caught in the
Since the pressure is released, recording that is caught in the nip
Material can be easily removed for subsequent image formation.
Image deterioration and damage to the fixing film.
You.

[0012] The invention of claim 3, wherein, in the invention of claim 1, wherein, the power supply to the heating member, the film member and the pressure member wherein the pressure member is pressurized to the heating body 1
It is characterized in that it is performed after the rotation has been completed.

Therefore, according to the third aspect of the present invention, the pressure member does not rotate when the film member slips and stops due to a shock or the like that presses the pressure member or when the pressure member does not rotate due to insufficient pressure. In this case, since no current is supplied to the heating element, a rapid rise in the temperature of the heating element is prevented, and the durability of the heating element, the pressing member, and the film member is improved.

[0014]

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

<First Embodiment> FIG. 1 is a cross-sectional view showing the structure of a fixing device according to a first embodiment of the present invention, and FIG. 2 is a cross-sectional view of a main part of an image forming apparatus provided with an identification attaching device.

First, a schematic configuration of the image forming apparatus will be described with reference to FIG.

The image forming apparatus shown in FIG. 2 is an electrophotographic copying machine of a fixed original platen / movable optical system / rotary drum type / transfer type. In this image forming apparatus, an original is placed on a fixed original platen glass 20. When the copy start key (not shown) is pressed after setting the necessary copy conditions and placing the photosensitive drum 19, the photosensitive drum 39 is driven to rotate at a predetermined peripheral speed in a direction indicated by an arrow (clockwise) in the figure.

The light source 21 (22 is a reflection shade) and the first mirror 23 move along the lower surface of the original table glass 20 from the home position on the left side of the glass to the right side of the glass at a predetermined speed V. 24 and the third mirror 25
By moving at a speed of 1/2, the platen glass 20
The downward image surface of the original 19 placed on the upper surface is illuminated and scanned from the left side to the right side, and the original surface reflected light of the illumination scanning light is reflected by the imaging lens 29 and the fixed fourth to sixth mirrors 26, 27, 2.
Then, the surface of the photosensitive drum 39 is subjected to image forming exposure (slit exposure) through the interface 8.

The surface of the photosensitive drum 39 is uniformly charged to a predetermined positive or negative potential by the primary charger 30 before the image forming exposure is performed, and the charged surface is exposed. Thus, an electrostatic latent image having a pattern corresponding to the document image is sequentially formed on the surface of the photosensitive drum 39. Then, the electrostatic latent image formed on the surface of the photosensitive drum 39 is visualized as a toner image by the developing roller 32 of the developing device 31.

On the other hand, a recording material P is fed by a paper feeding roller 51, and the recording material P is introduced into a transfer portion between the photosensitive drum 39 and the transfer charger 34 at a predetermined timing through a guide 33. When receiving the transfer corona, the recording material P comes into contact with the photosensitive drum 39, and the toner image carried on the photosensitive drum 39 is sequentially transferred to the lower surface of the recording material P.

The recording material P that has passed through the transfer portion is subjected to the charge removal of the back surface by the charge removing needle 35 while the photosensitive drum 3
Nine surfaces are sequentially separated from each other, and the transport unit 38 and the entrance guide 10
After the toner image is fixed to the fixing device 60 according to the present invention through the above-described process and is fixed to a toner image as described later, the toner image is discharged out of the apparatus as an image formed product. The surface of the photosensitive drum 39 after the transfer is cleaned and removed by the cleaning blade 37 of the cleaning device 36, and the toner is repeatedly used for image formation.

Next, details of the fixing device 60 according to the present invention will be described with reference to FIG.

In the fixing device 60 shown in FIG. 1, reference numeral 6 denotes an endless belt-shaped fixing film made of a thin heat-resistant film. The fixing film 6 comprises a left driving roller 7, a right driven roller 8, and both rollers. It is stretched between the linear heater 1 having a low heat capacity and fixed below the space between the heaters 7 and 8.

The driven roller 8 also serves as a tension roller for applying tension in the direction in which the fixing film 6 is stretched outward. The driving roller 7 whose surface is coated with silicone rubber or the like to increase the friction coefficient is rotated clockwise. When done
The fixing film 6 is rotated clockwise at a predetermined peripheral speed without wrinkles, meandering, and speed delay.

Reference numeral 9 denotes a pressing roller as pressing means. The pressing roller 9 has a rubber elastic layer having a high releasability such as silicone rubber, and has a longitudinal length of 350 mm and a diameter of 350 mm. It is set to 25 mm. This pressure roller 9
The recording material P is pressed against the lower surface of the heater 1 by a biasing means such as a spring with a contact force of, for example, 5 to 10 kgf, with the lower portion of the fixing film 6 sandwiched between the heater 1 and the fixing member. Rotates counterclockwise in the forward direction in the transport direction.

Reference numeral 13 denotes a cleaning roller disposed so as to be in pressure contact with the pressure roller 9. The cleaning roller 13 is formed of an aluminum rod, and is, for example, 200 to 2000 g / cm. cm and a pressure of 9 cm.

Since the endless belt-shaped fixing film 6 which is driven to rotate is repeatedly subjected to the heat fixing of the toner image, the fixing film 6 generally has a heat resistance, release property and durability of 100 μm. Hereinafter, a thin heat-resistant film having a thickness of preferably 40 μm or less is used. As an example,
PTFE (polytetrafluoroethylene resin), PFA (A resin having a low surface energy such as (tetrafluoroethylene / perfluoroalkylvinyl ether copolymer resin)) or a release coating layer formed by adding a conductive material such as carbon black to these resins to a total thickness of 3 μm.
An endless belt of 0 μm is used.

The low-heat-capacity heater 1 has a resistance material such as silver-palladium or ruthenium oxide having a thickness of 10 μm and a width of 1.0 mm on an alumina substrate 2 having a thickness of 1.0 mm, a width of 10 mm and a length of 340 mm in the longitudinal direction. Coating on heating layer 3
Is formed thereon, and a 10 μm-thick fixing film 6 is further formed thereon.
The protective layer 4 is made of glass or the like in consideration of sliding with the heater support 11 and is fixed to and supported by the heater support 11.

The heater support 11 is made of a material having excellent heat insulating properties, heat resistance, and rigidity for thermally supporting the heater 1 with respect to the fixing device 60 and the image forming apparatus, for example, PPS (polyphenylene sulfide), PEEK (polyether ether). Ketones), high heat-resistant resins such as liquid crystal polymers, and composite materials of these resins with ceramics, metals, and the like.

The heat generating layer 3 of the heater 1 is energized from both ends in the longitudinal direction. The energization is performed at 100 V AC, and the heat generating layer 3 is bonded to the back surface of the alumina substrate 2 with a heat conductive silicone rubber adhesive or the like or pressed or integrated. The energization is controlled by an MPU (not shown) in accordance with the detected temperature of a thermistor 5 such as an NTC thermistor formed in a random manner.

In this embodiment, a pressure releasing means 14 is provided below the pressure roller 9 for pressing and releasing the pressure roller 9 with respect to the heater 1. A rod 14a extending upward from the pressure releasing means 14 is connected to a shaft 9a of the pressure roller 9 as shown. When the pressure releasing means 14 is driven to lower the rod 14a while the pressure roller 9 is in a pressure state as shown in FIG. 1, the pressure roller 9 is moved from the fixing film 6 and the heater 1 It is released and its pressurized state is released.

Next, the operation of the fixing device 60 will be described.

The recording material P on which the unfixed toner image T is transferred to the upper surface by the above-described image forming operation is guided by a guide 10 and is fixed via the fixing film 6 with the heater 1 and the pressure roller 9. After entering the nip portion N, the unfixed toner image T adheres to the lower surface of the fixing film 6 and causes the fixing nip portion N to overlap with the fixing film 6 without causing surface deviation, wrinkles and deviation. Passing while receiving. In the process of passing through the fixing nip portion N, the surface of the recording material P, which carries the toner image T, receives the heat of the heat generating layer 3 via the fixing film 6 while being pressed and fixed to the fixing film 6 surface. The image T is melted at a high temperature and softened and fused to the surface of the recording material P to form a toner image Ta.

In the present embodiment, the recording material P is separated from the fixing film 6 when the recording material P passes through the fixing nip N and exits. At the time of this separation, the temperature of the molten toner Ta is still higher than the glass transition point of the toner. At this separation point, the toner Ta at a temperature higher than the glass transition point has an appropriate rubber property, so that the surface of the toner image Ta at the time of separation has an appropriate uneven surface property without following the surface of the fixing film 6. Since the surface properties are maintained and the solidification is achieved by cooling, the fixed toner image Tb does not generate excessive image gloss, and a high-quality fixed toner image Tb is obtained. The recording material P separated from the fixing film 6 is guided by the paper discharge guide 12 and reaches the paper discharge roller pair 15, during which the temperature of the toner Ta, which is higher than the glass point transfer, naturally falls (natural cooling). The temperature becomes equal to or lower than the glass transition point and solidifies, whereby a fixed toner image Tb is obtained.

In the present embodiment, the heat capacity of the heat generating layer 3 and the substrate 2 of the heater 1 is small, and these are heat-insulated and supported by the heater support 11. The surface temperature rises to a sufficiently high temperature for the melting point of the toner in a short time. For this reason,
Heat the heater 1 in advance (so-called standby temperature control)
There is no need to save energy, and the temperature inside the machine can be prevented from rising.

Further, in this embodiment, since the pressure releasing means 14 is provided, when the recording material P stops at the fixing nip portion N, the pressure releasing means 14 is driven to By releasing the pressurized state of the roller 9, the toner in the unfixed image area that has not yet passed through the fixing device 60 stains the fixing film 6, or forcibly pulls out the recording material P sandwiched by the fixing nip N. This can prevent the fixing film 6 from being damaged.

When the image forming operation is resumed after the recording material P is removed, the pressure roller 9 is lowered, and if the heater 1 is energized in this state, the heater 1 The temperature rises too rapidly, and the heater 1 and the fixing film 6 are damaged. As a result, the life of the fixing device 60 is reduced, and in the worst case, the heater 1 and the fixing film 6 are damaged.

Therefore, in the present embodiment, the power supply to the heater 1 is started after the pressure release mechanism 14 is driven to wait until the pressure roller 9 is securely pressed. Problems can be eliminated.

That is, in the present embodiment, there is provided a microcomputer (not shown) for controlling the rotation of the drive roller 7, the operation of pressing and releasing the pressure of the pressure releasing means 14, and the energization of the heater 1. I have. Here, based on the flowchart shown in FIG. 3, the rotation of the drive roller 7, the operation of the pressure release unit 14, and the control operation of energization to the heater 1 when the image forming operation is restarted after the removal of the recording material P will be described. explain.

When the image forming operation is restarted after the recording material P stopped at the fixing nip N is removed (STEP 1),
The rotation of the drive roller 7 is started (STEP 2), and 0.5 seconds after the start of the rotation of the drive roller 7, the pressure release means 14 starts pressurizing the pressure roller 9 (STEP 3).
Then, only after a lapse of 1.5 seconds from the start of pressurization of the pressurizing roller 9 by the pressurizing release means 14, the heater 1 starts to be energized (STEPs 4 and 5) to fix an unfixed toner image ( ST
EP6).

When the fixing of the unfixed toner image is completed, the power supply to the heater 1 is stopped (STEP 7), and thereafter, the rotation of the drive roller 7 is stopped (STEP 8), and the operation is terminated (STEP 9). .

As described above, in the present embodiment,
The heater 1 is energized while the fixing film 6 and the pressure roller 9 are rotating in a pressurized state to heat the surface of the heater 1 so as to prepare for fixing of an unfixed toner image. At the same time, since the fixing film 6 and the pressure roller 9 are in a state of being heated most of the time during rotation, the rotational driving of the fixing film 6 is performed in a stable state.

The rotation drive system of the fixing film 6 is designed to operate in a state where the fixing film 6, the pressure roller 9, the heater 1 and the like are heated by the heat generated by the heater 1 (thermal expansion state). .

Second Embodiment Next, a second embodiment of the present invention will be described.

In the present embodiment, immediately after the power is turned on, or after the recording material has stopped in the apparatus for some reason, all operations related to the conveyance of the recording material are performed before the image forming operation in order to recover the recording material. A fixing device provided in an image forming apparatus that performs a so-called “pre-rotation” that discharges a recording material by operating the image forming apparatus will be described. Since the configuration of the fixing device according to this embodiment is the same as that described in the first embodiment, the same elements as those shown in FIG.

During the pre-rotation, the fixing film 6 and the pressure roller 9 used for fixing the recording material P rotate in this embodiment for about 4 seconds. Do not energize the heater 1 during this pre-rotation,
If the fixing film 6 itself is cooled and the fixing film 6 is rotationally driven, the rotation becomes unstable.

However, after the recording material P is jammed, the fixing pressure is often released. When the heater 1 is energized at the same time that the pre-rotation is started, the pressure until the pressure is increased.
A situation occurs in which the heater 1 is energized in a state where the heater 1 and the pressure roller 9 are not pressed against each other. When such a situation occurs, the temperature of the heater 1 rises abnormally during that time.
This may damage the heater 1 and the fixing film 6.
Further, the fixing film 6 may be momentarily stopped by a shock when the pressure roller 9 and the fixing film 6 are pressed against each other. In such a case, if the heater 1 is inserted, the heater 1 continues to apply heat to only a part of the fixing film 6, so that the fixing film 1 is damaged.

Therefore, in the present embodiment, the time required to start pressurization is 0.5 seconds, the time required to reliably pressurize is 1.5 seconds, and the time required for the fixing film 6 to make one rotation is 1 second. After a total of 3.0 seconds, the heater 1 is energized.

Here, the fixing device 60 according to the present embodiment is described.
The rotation of the drive roller 7 during the pre-rotation, the operation of the pressure release means 14, and the control operation of energizing the heater 1 will be described with reference to the flowchart shown in FIG.

When the image forming operation is started (STEP 1),
The rotation of the drive roller 7 is started (STEP 2), and 0.5 seconds after the start of the rotation of the drive roller 7, the pressure release means 14 starts pressurizing the pressure roller 9 (STEP 3).
Then, the power supply to the heater 1 is started only 2.5 seconds after the pressure release means 14 starts pressurizing the pressure roller 9 (STEPs 4 and 5), and the power supply to the heater 1 is performed only for 1 second. Then, the power supply to the heater 1 is stopped (STEPs 6 and 7), the rotation of the drive roller 7 is stopped (STEP 8), and the operation is terminated (STEP 9).

That is, the microcomputer is the heater 1
The power supply to the heater 1 is started only after a lapse of 3.0 seconds after the pressure roller 9 is pressed, and then the power supply to the heater 1 is terminated after the power supply to the heater 1 is completed for one second. Is controlled to stop.

Therefore, according to the present embodiment, since the heater 1 is energized during the pre-rotation to heat the fixing film 6, the heater 1 and the pressure roller 9, the fixing film 6 is heated.
In addition to stabilizing the driving of the fixing roller 6, the pre-heating of the fixing film 6, the heater 1, and the pressure roller 9 makes it possible to perform the fixing of the unfixed toner image that is performed subsequently.

The time required to start pressurization, the time required for pressurization, the time required for the fixing film to make one rotation, and the like differ depending on the individual fixing device. Therefore, these times are the numerical values shown in this embodiment. It is not limited to.

[0054]

As is apparent from the above description, claim 1
According to the described invention, at least the pressing member is applied to the heating body.
The heating element is not energized when not pressed
Therefore, rapid heating of the heating member is prevented, the heating body, is the effect that it is possible to improve these durability obtained prevents the pressing member and the film member Ru damaged. Also, in a state where the heating element is cooled without energizing the heating element,
The time for driving the film member can be reduced.
Therefore, the drive of the film member can be stabilized.
The above effect can be obtained.

According to the second aspect of the present invention, the nip
When the recording material is caught in
To remove the recording material between the nips.
It can be easily removed and used in subsequent image formation.
Image deterioration and damage to the fixing film can be prevented.

Further, according to the third aspect of the present invention, when the film member slips and stops due to a shock or the like that presses the pressing member, or when the pressing member does not rotate due to insufficient pressing. Because the heating element is not energized,
The effect is obtained that the durability of the heating element, the pressing member and the film member can be improved by preventing the temperature of the heating element from rising rapidly.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a fixing device according to the present invention.

FIG. 2 is a cross-sectional view of a main part of an image forming apparatus including a fixing device according to the present invention.

FIG. 3 is a flowchart showing the operation of the rotation of the drive roller, the operation of the pressure release unit, and the control operation of energizing the heater in the fixing device according to the first embodiment of the present invention.

FIG. 4 is a flowchart illustrating a pre-rotation of a driving roller, an operation of a pressure release unit, and a control operation of energizing a heater in a fixing device according to a second exemplary embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heater (heating body) 6 Fixing film (film member) 7 Driving roller (support) 8 Follower roller (support) 9 Pressure roller (pressure member) 14 Pressure release means 60 Fixing device

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03G 15/20

Claims (3)

(57) [Claims] 1. A film member which is stretched around a heating element and a support with a predetermined tension and moves endlessly or endlessly by rotation of the support, and is arranged so as to be in pressure contact with the heating element via the film member. A fixing device that has a pressure member provided and pressure release means for pressing and releasing the pressure member with respect to the heating body, and which releases the pressure of the pressure member when an abnormality occurs. At the time of return after pressurization is released in the event of an abnormality, the support and the filter
After a predetermined time has elapsed from the start of rotation of the film member, the pressing member is pressed against the heating body, and the film member and the pressing member are pressed.
A fixing device characterized in that the heating element is energized after the rotation of the member is started . 2. The method according to claim 1 , wherein the heating element is provided through the fixing film.
The recording material is pinched in the nip formed by the pressure member.
2. The fixing device according to claim 1, wherein the pressure of the pressing member is released when the pressing is stopped . Wherein energization of the heating body, according to claim 1, characterized in that the pressure member is the film member and the pressure member is pressurized to the heating body is made after one or more rotations
The fixing device as described in the above.