JPH06348175A - Image heating device - Google Patents

Abstract

PURPOSE:To prevent a film member from adhering onto a heating means and a heating body by changing a time from the stoppage of current supply to the heating body after completion of fixing processing to the stoppage of driving of a film member. CONSTITUTION:A time tau1 is the time at which the final fixing processing has been completed and a current to a heater is shut down by a signal from an MPU. A temperature T2 of a second thermister at that time is, for example, 250 deg.C because the temperature at a non-sheet passing area is increased by the continuous sheet passing of a small-sized paper sheet, which is higher by 70 deg.C than the detected temperature T1 of 180 deg.C of a first thermister at that time. The temperature T2 lowers rapidly with time, and it reaches 190 deg.C at a time tau2 that is 5sec. after the time tau1. Then the driving of a fixing film is stopped at the time tau2 to prevent the inner surface of the fixing film at that time and the heater from adhering onto the outer surface of the fixing film and the surface of a pressurizing roller, respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image heating apparatus for heating an image on a recording material, and more particularly to an image heating apparatus suitable for an apparatus for heating and fixing an unfixed image on a recording material.

[0002]

2. Description of the Related Art Conventionally, as an image heating apparatus for heating and fixing an unfixed image and modifying the surface property of an image, a heat roller and a pressure roller are used to sandwich and convey a recording supporting an image. Although the roller method has been widely used, in such a heat roller method, since the heat capacity of the heating roller is large, it takes a long time to heat the heat roller to a predetermined fixing temperature (so-called warm-up time). There was a problem. Therefore, in JP-A-63-313182, JP-A-2-157878, and the like, a heater having a low thermal capacity, such as a thermal head, is used with a thin film that slides on the thermal head to shorten the warm-up time. A film heating system was proposed.

A heater used in this type of apparatus has an electric heating layer whose longitudinal direction is a direction intersecting the moving and passing direction of the recording material, and each part of the effective length region of the heating layer has a predetermined length per unit length. It generates heat with an amount of heat generation, and the effective full-length area of this heat generating layer has a length dimension corresponding to the width of the maximum size recording material that can be used by being supplied to an image forming apparatus incorporating this heating device. . When the heating process is performed, the effective area of the heating layer is energized to generate heat with a predetermined heat generation amount per unit length regardless of the width of the recording material used, so that the recording material having the maximum width can be used. Heat treatment is applied to the surface of the recording material even if it has a width of various sizes smaller than that.

[0004]

However, according to the above-mentioned conventional example, when the width of the recording material supplied to the apparatus is smaller than the maximum width, the so-called non-sheet passing portion in the non-sheet passing portion in the longitudinal direction of the heater. There is a problem that the temperature rises. In such a state, after heating a large number of sheets in succession and stopping the film supply at the same time as stopping the power supply to the heater, the film, the heater and the pressurizing means are still in a high temperature state. Because they are pressed against each other,
When the adhesion between the film and the heater or between the film and the pressing means increases, and when the heat treatment is restarted again after that, it is necessary to overcome the above adhesion and drive the film and the pressing means. Therefore, it is necessary to increase the torque of the drive source, which causes a problem of increasing the size of the device. Furthermore, when pulling apart the closely attached parts,
There was a risk of damaging the film.

In order to solve such a problem, it is sufficient to stop the supply of electric power to the heater after the heat treatment and then continue the film running until the heater or the like is sufficiently cooled. If the film is run for such a long time, the running time of the film becomes long, the wear of the film and the heater due to sliding with the heater increases, and the time until the device stops becomes long Another problem of deterioration of the property occurs.

An object of the present invention is to solve the above-mentioned problems, to increase the abrasion of the film and the heater, and to prolong the time until the apparatus stops, after the power supply to the heater is stopped. An object of the present invention is to provide an image heating apparatus that does not increase the adhesion between the film and the pressing means.

[0007]

According to the present invention, the above object is to provide a heating element extending in the width direction of a recording material and an endless or endless movable element while sliding on the heating element. A film member provided, a pressurizing unit arranged so as to be in pressure contact with the heating body via the film member, a plurality of temperature detecting units for detecting the temperature of the heating unit, and a temperature detecting unit of the temperature detecting unit. An energization control unit that controls energization to the heating body so that a temperature detected by at least one of the temperature detection units has a predetermined value, and a driving unit that drives the film member and the pressing unit at a predetermined timing. However, in the image heating apparatus that applies thermal energy to the recording material by sandwiching and transporting the recording material at the pressure contact portion between the film member and the pressure applying means, the temperature detecting means can be used by being supplied to the image heating apparatus. Minimum width The driving means is disposed at at least two places, a first area through which the recording material passes and a second area outside the first area, and the driving means heats the recording material after the heating process is completed. After the power supply to the body is stopped, it is set to stop driving the film member or the pressurizing unit when the temperature detected by the temperature detecting unit in the second region becomes equal to or lower than a predetermined temperature. Achieved by

[0008]

According to the present invention, energization to the heating body is stopped by the energization control means after the heat treatment of the recording material is finished, but when the heat treatment of the recording material having the minimum width is performed, the recording material is not passed. Since the temperature in the area is a predetermined high temperature,
When the temperature of the non-sheet passing area has dropped to a predetermined low temperature, the driving of the film member or the pressing means is stopped. As a result, the adhesion between the inner surface of the film member and the heating element or between the outer surface of the film member and the pressing means becomes smaller than in the conventional case, and an increase in driving torque during re-driving and damage to the film are prevented.

[0009]

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

<Embodiment 1> First, Embodiment 1 of the present invention will be described with reference to FIGS. FIG. 1 is a side sectional view of a first embodiment apparatus in which the present invention is applied to a fixing device of an electrophotographic copying machine.

In FIG. 1, reference numeral 6 is an endless belt-shaped fixing film, which is hung around the driving roller 7, the driven roller 8 and the low heat capacity linear heater 1 and is rotatably movable. Since the fixing film 6 is repeatedly subjected to heat fixing of the toner image, heat resistance, releasability,
A thin film having excellent durability and generally 100 μm or less, preferably 40 μm or less is used. In this embodiment,
PTFE (tetrafluoroethylene resin) is applied to the outer peripheral surface of a thin endless belt made of metal such as nickel and SUS, which has a high heat resistance such as 20 μm thick polyimide, polyetherimide, polyethersulfone, and polyetheretherketone. , A low surface energy resin such as PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer resin), or a releasable coating layer in which a conductive material such as carbon black is added to these resins is applied to a thickness of 10 μm. An endless belt having a total thickness of 30 μm is used.

A tension is applied to the fixing film 6 by a driven roller 8 in an outward tension direction, and the surface of the fixing film 6 is coated with silicone rubber or the like to come into contact with a driving roller 7 having a higher friction coefficient. Along with the clockwise rotation of the drive roller 7, the drive roller 7 is rotationally driven in the clockwise direction at a predetermined peripheral speed without wrinkles or meandering speed delay.

Next, the heater 1 having a low heat capacity has a thickness of 1.0 mm, a width of 10 mm, and a longitudinal length of 3 in this embodiment.
A resistance material such as silver palladium or ruthenium oxide having a thickness of 10 μm and a width of 1.0 mm is applied to a 40 mm alumina substrate 2 to form a heat generating layer 3, and a thickness of 10 μm is further formed thereon.
The protective layer 4 made of glass or the like is formed in consideration of sliding with the film 6, and is fixedly supported by being attached and held on the heater support 11.

The heater support 11 has a heat insulating property, a high heat resistance, and a rigidity for adiabatically supporting the heater 1 with respect to the fixing device 60 and the image forming apparatus. For example, PPS (polyphenylene sulfite), PEEK (polyether). Etherketone) liquid High heat resistant resin such as polymer is composed of a composite material of these resins and ceramics, metal or the like.

The heating layer 3 of the heater 1 has 10
An AC voltage of 0 V is applied, and the temperature of the heater 1 is adjusted by adhering or press-contacting the substrate 2 with a heat conductive silicone adhesive or the like as shown in FIG. It is detected by the formed temperature detecting element 5 such as an NTC thermistor, and energization is controlled by a microcomputer (hereinafter, referred to as MPU) 19 according to the detected temperature.

FIG. 2 is a side view of the heater 1 as seen from the paper feed side, and the heat generating layer 3 is formed in a straight line along the length of the substrate at the substantially central portion of the lower surface of the substrate 2. Reference numerals 3a and 3b denote current-carrying electrodes (input terminals) made of a good conductive material such as silver provided at the left and right ends of the heat generating layer 3. Also, e is this electrode 3
The length dimension corresponding to the width of the A3 plate (width 297 mm), which is the effective total length region of the heat generating layer 3 between a and 3d, and is the maximum size recording material that can be supplied to the apparatus and used in this embodiment. Is set to.

Further, in the case of the present embodiment, recording material sheets of various sizes are supplied on the basis of so-called one side reference, which is based on the base line a on the left end side of the heat generating layer 3.

Further, in the present embodiment, there are two temperature detecting elements 5 provided on the opposite side of the substrate 2 from the heat generating layer 3. One is the first thermistor 5A arranged inside the sheet passing area c of the A6 plate (width 105 mm) which is the smallest size that can be used in the apparatus of this embodiment, and the other is the B4 plate (width Two
The second thermistor 5B is arranged outside the paper passing area d of 57 mm) and inside the area e.

Below the heater 1, a pressure roller 9 as a pressure means having a surface layer having a good releasability such as fluorine coating and a rubber elastic layer is fixed to the lower surface of the heater 1. The film 6 is pressed against each other by an urging means such as a spring with a contact pressure of, for example, a total pressure of 5 to 10 kgf, and is rotated counterclockwise in the forward direction of the conveyance direction of the sheet P. ing.

In the apparatus of the present embodiment as described above, when the image forming apparatus starts the image forming operation by the image forming start signal, the fixing film 6 is rotated and the heater 1 is energized at a predetermined timing.

Then, the recording material sheet P carrying the unfixed toner image T on its upper surface is conveyed from a transfer portion (not shown) to the fixing device and guided by the entrance guide 10 to rapidly reach a predetermined temperature. It enters into the pressure contact portion N (fixing nip portion) between the heated heater 1 and the pressure roller 9.

Then, the unfixed toner image surface of the recording material sheet P comes into close contact with the lower surface of the fixing film 6 in the surface moving state and moves without causing surface misalignment or wrinkling, and overlaps with the fixing film 6. Then, it passes through the fixing nip portion N while receiving a narrow pressure.

As a result, the toner image bearing surface of the sheet P receives the heat of the heating element 3 via the fixing film 6, and the toner is melted at a high temperature to become the fused toner Ta softened and adhered to the sheet P surface.

In the case of this apparatus, the recording material sheet P and the fixing film 6 are separated from each other when the sheet P passes through the fixing nip portion N and exits. At the time of this separation, the temperature of the molten toner Ta is The temperature is still higher than the glass transition point of the toner. Therefore, since the binding force (adhesive force) between the sheet P and the fixing film 6 at the time of this separation is small, the sheet P hardly causes toner offset to the surface of the unfixed film 6 and the adhesive film 6 has a poor separation. The sheet P is always adhered smoothly to the surface without being wound and jammed.

Since the toner Ta having a temperature higher than the glass transition point has a proper rubber characteristic, the toner image surface at the time of separation does not follow the surface of the fixing film and has a proper uneven surface property. Since this surface property is maintained and cooling and solidification occur, the toner image surface on which the toner image has been fixed does not have an excessive image gloss, resulting in a high quality image.

The sheet P separated from the fixing film 6 in this way is guided by the paper ejection guide 12 to reach the paper ejection roller pair (not shown), but during that time, the temperature of the toner Ta is higher than the glass transition point. Is naturally cooled (naturally cooled) to a temperature equal to or lower than the glass transition point, a solidified image Tb is formed on the recording material sheet P, and is output as the image-fixed sheet P.

Next, control of energization of the heater and fixing film rotation drive after the fixing process in this embodiment will be described. In FIG. 3, the fixing device according to the present embodiment is used, and after a predetermined number of sheets (here, 100 sheets having a small width) are continuously subjected to the fixing process, the heater is energized and the fixing film is rotated. the OFF timing, the temporal changes being shown in comparison with the time change of the second thermistor detects the temperature T _2.

In FIG. 3, time τ ₁ is the time when the final fixing process is completed, and at this time, the heater is energized by MP.
It is shut off by the signal from U19. The temperature T ₂ of the second thermistor 5B at this time is 250 ° C. due to the temperature rise of the non-sheet passing portion due to continuous feeding of small size paper, and is T ₁ which is the temperature detected by the first thermistor 5A at the same time. = 18
70 ° C higher than 0 ° C, but this temperature T ₂
Rapidly decreases with time and reaches 190 ° C. at time τ _{2 which} is 5 seconds after time τ ₁ . Therefore, in this embodiment, by stopping the driving of the fixing film 6 at this time τ ₂ , the adhesion between the inner surface of the fixing film 6 and the heater and the outer surface of the fixing film 6 and the surface of the pressure roller at this time are prevented. Prevented.

Using the structure of this embodiment, the temperature T ₁ = 180
When only one small size paper was fixed while controlling the temperature to be ° C, the temperature T ₂ was 200 ° C after the fixing was completed.
In this case, there was no problem even if the driving of the fixing film was stopped in the same manner as the end of the fixing process.

Further, using the structure of this embodiment, while controlling the temperature T ₁ to 180 ° C.
When the fixing process was continuously performed on 00 sheets, the temperature T ₂ was 260 ° C. at the end of the fixing process. After that, when the driving of the fixing film was stopped for 10 seconds, the fixing film 6
The pressure roller 9 was not damaged, and there was no inconvenience such as an increase in torque for driving the fixing film even when the fixing operation was performed again.

Comparative Example 1 In order to compare with this example,
After fixing 1000 continuous small size papers, the energization of the heater was stopped, and the fixing film was stopped within 1 second from the stop, the fixing film joined with the fluorine coating on the surface of the pressure roller, and became unusable. . Therefore, if the fixing film is stopped within 10 seconds after the power supply to the heater is stopped, the running time of the fixing film becomes long when the fixing process is performed one by one, and friction on the inner surface of the fixing film occurs, and the driving roller 7 and A slip occurred between them.

<Second Embodiment> Next, a second embodiment of the present invention will be described with reference to FIG. The same parts as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

FIG. 4 shows the ON / OFF timings of the heater energization and the fixing film rotation drive after the fixing process of 100 sheets of small size paper is continuously performed using the fixing device of the present embodiment. T _2, and in comparison with the rate of change of the detected temperature T ₂ (over dT ₂ / dt) is a diagram showing.

In this embodiment, the rate of temperature change (-dT ₂ / d
When t) is greater than or equal to the specified value v, the fixing film drive is turned off.
When (−dT ₂ / dt) <v, the fixing film drive is turned off when T ₂ drops to a predetermined value.

Generally, when only a small number of sheets are subjected to the fixing process, the amount of heat stored in the fixing device is small, so that the fixing film is not damaged even if the heater temperature is high.

However, immediately after a large amount of fixing processing, the amount of heat stored in the fixing device is large, so that it does not have to be too high.
If the driving of the fixing film is stopped immediately after the energization is stopped, the fixing film and the heater, and the fixing film and the pressure roller are exposed to high temperature / high pressure for a relatively long time, which causes problems such as sticking of the fixing film and the pressure roller. Likely to happen.

Therefore, in this experimental example, the rate of change of T ₂ is detected to detect the heat storage state of the fixing device. If the heat storage is large, the temperature change rate (-dT ₂ / dt) is small, and the heat storage is small. For example, if it is determined that the temperature change rate (-dT ₂ / dt) is large and the temperature change rate (-dT ₂ / dt) is larger than a predetermined value, the fixing film drive is turned off and the temperature change rate (-dT ₂ / dt) is changed. _{When 2} / dt) does not become larger than a predetermined value, the fixing film drive is turned off when T ₂ falls to a predetermined value, as in the first embodiment.

According to this embodiment, the post-rotation time of the fixing film in the case of the fixing operation of a small number of sheets can be shortened without impairing the durability of the fixing device. As a result, friction of the fixing film can be prevented. It is possible to prevent the fixing film and the drive roller from slipping.

<Third Embodiment> Next, a third embodiment of the present invention will be described. It should be noted that description of common points with the first and second embodiments is omitted.

In this embodiment, a known detection input means is used.
The width, length, and thickness of the paper to be used, the number of sheets to be fixed, and the environmental temperature are detected, and according to these information, the value of the temperature T _{2 and} the value of the temperature change rate (-dT ₂ / dt), Rotation time t ₀
Is what determines.

For example, as shown in Table 1, the temperature T _{2 at} which the post-rotation of the fixing film is stopped is changed according to the size of the paper used and the number of sheets to be subjected to the fixing process (however, the heater is the first sheet passing sheet). 200 ° C inside, 18 during paper passing after the 10th sheet
Controlled to 0 ° C). In addition, in the present embodiment, the paper having the weight of 80 g / m ² is used for description, but the same table can be created and actually used for the paper having other weights.

[0042]

[Table 1]

[0043]

As described above, according to the present invention,
Depending on the temperature of at least one temperature detecting means arranged outside the passage area of the recording material of the minimum width, by changing the time from the energization stop of the heating body after the fixing process to the drive stop of the film member, Since it is possible to minimize the running time of the film member while preventing the film member and the pressing means or the film member and the heating body from sticking to each other due to the temperature rise in the paper passing portion, it is possible to extend the life of the apparatus.

[Brief description of drawings]

FIG. 1 is a sectional view showing a schematic configuration of an image heating apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a heating element and an energization control circuit in the apparatus shown in FIG.

FIG. 3 is a diagram showing the relationship between the timing of energization of the heating element and the driving of the film member after the heat treatment and the change of the detected temperature in the non-sheet passing area in Example 1 of the present invention.

FIG. 4 shows the relationship between the timing of energization of the heating element and the driving of the film member after the heat treatment and the change in the detected temperature in the non-sheet passing area, and the rate of change of the detected temperature in Example 2 of the present invention. FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heater (heating body) 5A 1st temperature detection element (temperature detection means) 5B 2nd temperature detection element (temperature detection means) 6 Fixing film (film member) 9 Pressure roller (pressurization means) 5A 1st Temperature detection element (temperature detection means) 5B Second temperature detection element (temperature detection means) 19 MPU (energization control means)

Claims (2)

[Claims] 1. A heating element formed to extend in the width direction of a recording material, a film member disposed so as to be movable with an end or an end while sliding on the heating element, and the above-mentioned film member interposed therebetween. The pressurizing means arranged so as to come into pressure contact with the heating body, a plurality of temperature detecting means for detecting the temperature of the heating body, and the temperature detected by at least one of the temperature detecting means has a predetermined value. And a drive means for driving the film member and the pressurizing means at a predetermined timing, and recording at the press contact portion of the film member and the pressurizing means. In an image heating apparatus for applying thermal energy to a recording material by nip-conveying the material, the temperature detecting means is provided with a first area through which a recording material having a minimum width that can be supplied to the image heating apparatus and passes. , Outside the first area Is provided in at least two places with the second region of the, the driving means, after stopping the energization to the heating body after the heating treatment of the recording material, the second by the temperature detecting means. An image heating apparatus, which is set so as to stop driving of the film member or the pressurizing unit when the detected temperature of the area becomes equal to or lower than a predetermined temperature. 2. The drive means is set so as to adjust a predetermined temperature at which the drive of the film member or the pressurizing means is stopped in accordance with the rate of change of the temperature detected by the temperature detecting means in the second region. The image heating device according to claim 1.