JPH06250565A - Heating device - Google Patents

Abstract

PURPOSE:To prevent a heat from being taken by an element such as a thermo- switch or thermo-fuse without loosing the responsiveness of the element by providing a temperature detecting element for safety countermeasure on the outside of the area where a heating element heats a body to be heated. CONSTITUTION:A heater 3 has, for example, an electric resistance material such as Ag/Pd, as a heating element 4, applied by screen printing along substantially the center part of a base 6 made alumina and the heating element 4 is coated with a glass or fluororesin thereon as a protective layer 5. A thermo- fuse 11 is set on the opposite surface to the surface on which the heating element 4 is formed on the heater 3. The part B of the heater 3 is a heating area, and recording materials of all sizes are made to passed in the direction of arrow A with the position of C as the reference. By setting the thermo-fuse 11 in this way, a partial temperature reduction of the heater by the heat being taken by the thermo-fuse 11 is eliminated in the heating area B, and the fixing failure caused only in the thermo-fuse setting part can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method in which a heating element is adhered to one side of a heat resistant film and an object to be heated is adhered to multiple sides, and heat energy is applied to the object via the heat resistant film. Heating device.

[0002]

2. Description of the Related Art This apparatus is an image heat fixing device in an image forming apparatus such as an electrophotographic copying machine, a printer or a fax machine, that is, a resin which is heated and meltable by an image forming process means such as electrophotography, electrostatic recording or magnetic recording. To the target image information formed directly or indirectly (transfer) on the surface of the recording material (electrofax sheet, electrostatic recording sheet, recording material sheet, printing paper, etc.) using toner composed of A device that heats and fixes a corresponding unfixed toner image as a permanently fixed image on the surface of the recording material bearing the image. For example, the recording material bearing the image is heated to provide surface properties (gloss, etc.) It can be widely used as a means and a device for heat-treating an image carrier, such as a device for reforming an image carrier, a device for performing hypothetical dressing, and the like.

A conventional example of a heating device used in a copying machine or the like will be described below. As the apparatus, a heating roller system in which a heating roller maintained at a predetermined temperature and a heating roller that has an elastic layer and is in pressure contact with the heating roller while nipping and transporting the recording material to heat the recording material are widely used, In addition, various methods such as a flash heating method, an oven heating method, and a hot plate heating method are known and put to practical use.

Recently, a heating body (thermal heater, hereinafter referred to as a heater) fixed directly to a metal or resin holder, a heat resistant film (fixing film) conveyed while being pressed against the heater, An unfixed image is formed on the surface of the recording material by applying heat from the heater to the recording material through the film, which has a pressure member that adheres the recording material to the heater through the film. There has been proposed a heating device of a system (film heating system) for heating and fixing the film.

According to the applicant's earlier proposal, for example, Japanese Patent Laid-Open No.
The heating device disclosed in Japanese Patent Laid-Open No. 3-313182 belongs to this, and this device is a thin heat-resistant film (sheet), a moving driving means for the film, and a fixed support on one side of the film centering the film. And the heater arranged in the opposite direction, and the other side of the heater is placed so as to face the heater, and the visible image-bearing surface of the recording material to be image-fixed as the heated material is closely attached to the heater through the film. And a pressurizing member. The film is adapted to travel at the same speed in the forward direction as the recording material to be image-fixed which is conveyed and introduced between the film and the pressure member at least during image fixing. The recording material is passed through a fixing nip portion as a fixing point formed by pressure contact between a heater and a pressure member with the recording material sandwiched therebetween. As a result, the surface of the recording material bearing the visible image is heated by the heater through the film to apply thermal energy to the visible image (unfixed toner image) to soften and melt it, and after passing through the fixing point. Fixing is performed by separating the film and the recording material at the separation point.

In such a film heating system,
A low heat capacity heating element can be used as the heater. For this reason, it is possible to save power and shorten the wait time (quick start) compared to the conventional contact heating method such as a heat roller method or a belt heating method, and other various drawbacks of the conventional heating method. It has an advantage of being able to solve and is effective.

Next, another conventional example will be described with reference to FIG. FIG. 22 is a sectional view showing a schematic structure of a conventional film heating type fixing device. In FIG. 22, 2 is an endless heat-resistant film, which is a heater 3 as a heating body.
Is externally fitted to the stay 1 as a guide member including.
The inner circumference of the endless heat-resistant film 2 and the heater 3
The outer peripheral length of the stay 1 including the film 2 is, for example, 3 m.
Therefore, the film 2 is loosely fitted to the stay 1 with a sufficient circumferential length.

The film 2 has a film thickness of 100 μm in order to reduce the heat capacity and improve the quick start property.
Below, preferably a single layer of PTFE, PFA, FEP having heat resistance of 50 μm or less and 20 μm or more, or polyimide, polyamide imide, PEEK, PES, PPS
A composite layer film in which PTFE, PFA, FEP or the like is coated on the outer peripheral surface of the above can be used. In the conventional example of FIG. 22, the outer peripheral surface of a polyimide film coated with PTFE was used.

Reference numeral 3 is a heater, and an electric resistance material such as Ag / Pd (silver palladium) is coated on the surface of a substrate made of alumina or the like to a thickness of 10 μm and a width of 1 to 3 mm by screen printing or the like. Is coated with glass or fluororesin as a protective layer.

Reference numeral 8 denotes a film pressure roller as a rotating body that drives the film 2 by forming a nip with the heater 3 sandwiching the film 2, and includes a cored bar 9 and a silicone rubber or the like which is mounted on the shaft. It is made of heat-resistant rubber 10 having good releasability, and is driven by driving means (not shown) from the end of the cored bar 9.

For temperature control, the output of the thermistor 7 provided on the heater 3 is A / D converted and taken into the CPU 110, and the heater energization power is controlled by pulse width modulation of the triac 111 based on the information, and the film is supplied. The heater 3 is controlled to a constant temperature so that the surface has a temperature sufficient for fixing an unfixed image on the recording material.

[0012]

However, according to the above-mentioned conventional example, there are the following problems. First, in a film heating type heating device, when a low heat capacity heating element is used as a heater, power can be saved and wait time can be shortened. On the other hand, since the heat capacity of the heater is small, a thermoswitch for safety measure of heat capacity is used. When a thermofuse or the like is brought into contact, heat is taken by these elements, and the temperature of that portion is lowered, so that the fixing property of the image deteriorates only in that portion. Also, a thermo switch,
If these elements are installed away from the heater in order to prevent the heat from being taken by the thermofuses and the like, the response may be delayed when the heater is out of control, and in some cases smoke may be emitted.

Next, in the conventional example shown in FIG. 22, the temperature of the heater can be maintained at a constant control temperature under any conditions, but the temperature of the film surface changes depending on various sheet passing modes of the recording material. There was a problem to do.

Further, since the heat capacity of the stay and the pressure roller is much larger than that of the fixing film, the temperature of the stay and the pressure roller greatly affects the temperature of the fixing film. In particular, since the film rotates by rubbing around the stay, the area of contact with the stay is large and the temperature of the stay becomes low. Tends to be unstable.

This is because the amount of heat supplied from the heater is not only applied to the recording material via the film, but also used as a temperature rise of the stay, the pressure roller and the like.

FIG. 23 is a schematic diagram showing changes in heater temperature, film temperature, stay temperature, and pressure roller with time during printing. The heater is controlled to a constant temperature of 180 ° C. at the start of printing. On the other hand, since the stay and the pressure roller have large heat capacities, the surface temperature gradually rises. At this time, the film temperature gradually rises while taking an intermediate value between the heater temperature and the stay temperature due to the influence of the stay and the pressure roller as described above.

Therefore, in the fixing of the first sheet, the temperature of the film becomes β ° or less, and there is a problem that fixing failure occurs.

If the heater temperature is set to be β ° C. or higher for the first sheet in order to prevent this fixing failure, the apparatus becomes warm and the film temperature becomes α ° C. or higher for the seventh and subsequent sheets, which causes high temperature offset. When the heater temperature is lowered to α ° C. or lower in order to prevent the high-temperature offset of the seventh and subsequent sheets, there is a problem that fixing failure occurs on the first sheet.

To solve this problem, it has been conventionally proposed to lower the heater temperature according to the number of prints during continuous printing, but even in this case, the film temperature is kept constant depending on how warm the apparatus is. For one
Since the proper values of the heater temperature of the first sheet and the number of sheets for lowering the heater temperature are different, it is necessary to change the control depending on each case, which complicates the control.

For example, when 10 sheets are continuously fed in 2 minutes, or at intervals of 3 minutes, at intervals of 10 minutes, and further 5 consecutive times.
There are an unlimited number of combinations of 50 sheets and 50 sheets, and it is almost impossible to control the heater temperature in all cases.

Further, in order to know whether the amount of heat applied to the recording material is sufficient to fix the toner, there is a method of performing temperature control by measuring the temperature of the film immediately after being separated from the recording material. Proposed.

However, if temperature control is performed only by detecting the surface temperature of the film, a response delay occurs in the temperature control due to the time when heat is transferred from the heater to the surface of the film.
There is a possibility that the overshoot at the start-up of the first time in the morning becomes high and the ripple of temperature control becomes large.

A first object of the present invention is to solve the above problems and provide a heating device in which heat is not taken by the element such as thermoswitch or thermofuse without impairing the response of the element. Especially.

A second object of the present invention is to provide a heating device capable of optimizing the temperature of the film without complicating the control.

[0025]

According to the first invention of the present application,
The first object is to attach a heating body to one side of the heat resistant film and a heated body to the other side of the heat resistant film, and to apply heat energy of the heating body to the heated body through the heat resistant film. In the above, it is achieved by providing the temperature detecting element for safety measures outside the region for heating the heated body of the heating body.

According to the second invention of the present application, the second object is a support for supporting the heating body, and an endlessly movable film stretched so as to contact the heating body and the support. A pressure member arranged so as to be pressed against the heating body via the film, a temperature detecting means for detecting the temperature of the heating body, and a predetermined temperature based on the temperature detected by the temperature detecting means. A temperature control means for maintaining the set temperature, and a heating device for applying the thermal energy of the heating body to the recording material by sandwiching and conveying the recording material at the pressure contact portion, and detecting the temperature of the support body. This is achieved by providing a temperature detecting means for the support, and the temperature control means is set to correct the set temperature based on the temperature detected by the temperature detecting means for the support.

Further, according to the third invention of the present application, the second object is a support for supporting the heating body, and an endlessly movable film stretched so as to contact the heating body and the support. A pressure member arranged so as to be pressed against the heating body via the film, a temperature detecting means for detecting the temperature of the heating body, and a predetermined temperature based on the temperature detected by the temperature detecting means. A temperature control means for maintaining a set temperature, and a heating device for applying the thermal energy of the heating body to the recording material by sandwiching and conveying the recording material at the pressure contact part, and a film for detecting the temperature of the film. The temperature control means is provided, and the temperature control means is set to correct the set temperature based on the temperature detected by the film temperature detection means.

[0028]

According to the first invention of the present application, the temperature detecting element for safety measures is provided in order to prevent an accident due to the abnormal temperature rise of the heating element. Since it is installed outside the area to be heated, the desired responsiveness is maintained without depriving the heat energy applied to the object to be heated.

Further, according to the second and third inventions of the present application, the temperature of the heating body is controlled to be a predetermined temperature based on the temperature detected by the temperature detecting means. The temperature depends on the temperature of the support of the film or the pressing member due to the low heat capacity of the film. Therefore, the temperature of the film is always appropriate by detecting the temperature of the support of the film or the film itself by a temperature detecting means other than the temperature detecting means and appropriately changing the control temperature based on the detected temperature. Value is maintained.

[0030]

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

<First Embodiment> First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a sectional view showing a schematic configuration of a tensionless film heating type fixing device as an embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a horizontally long stay made of heat-resistant resin, which serves as an inner surface guide member for a film 2 which will be described later.

Reference numeral 3 denotes a heater. The heater 3 is made of an electric resistance material such as Ag / Pd (silver-palladium) as a heating element 4 and has a thickness of 10 μm along a substantially central portion of a substrate 6 made of alumina or the like. A width of 1 to 3 mm is applied by screen printing or the like, and glass, a fluororesin or the like is coated thereon as a protective layer 5.

2 is an endless heat-resistant film,
The stay 1 including the heater 3 is externally fitted. The inner peripheral length of the endless heat-resistant film 2 and the outer peripheral length of the stay 1 including the heater 3 are larger than those of the film 2 by, for example, 3 mm. The length fits loosely with a margin.

The film 2 has a total thickness of 10 in order to reduce the heat capacity and improve the quick start property.
It is possible to use a film of a single layer or a composite layer having a heat resistance, releasability, strength and durability of 0 μm or less, preferably 40 μm or less and 20 μm or more.

Reference numeral 8 denotes a film pressure roller as a rotating body which drives the film 2 by sandwiching the film 2 with the heater 3 to form the fixing nip portion. And a roller portion 10 made of a heat-resistant rubber elastic body having good releasability, and the end portion of the central shaft 7 is driven by a driving means (not shown).

In this embodiment, the thermo fuse 11 is installed in the fixing device as described above at the position shown in FIG. Figure 2
In, the thermofuse 11 is installed on the surface of the heater 3 opposite to the surface on which the heating element is formed. The portion B of the heater is a heating region, and recording materials of all sizes are fed in the direction of arrow A with reference to the position of C. By installing the thermofuses 11 in this way, the temperature drop of the heater due to the heat being taken by the thermofuses 11 in the heating area B is not partially reduced, and it is possible to prevent fixing failure that occurs only in the thermofuses installation parts. . Further, according to the experiments conducted by the inventors, the response to the runaway is faster in the case where the apparatus is placed in contact with the non-image area as in this embodiment, as compared with the case where the apparatus is placed in the heating area B without contact. I knew that.

In the case of the film heating type heating device as in the present invention, the advantage that the rising time is faster is conversely compared with the conventional heating roller type heating device, on the contrary, the rate of temperature rise is high even when the heater is out of control. The thermo protector also needs to have a faster response than those of the heat roller type or the like. Therefore, the present embodiment is an effective means also for such a problem.

<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.

In this embodiment, a heater 3 as shown in FIG. 3 is used in the same fixing device as in the first embodiment. The heater 3 lowers the heat generation amount of the heating element 4a in the non-heating region on the heater 3, that is, the thermofuse installation position by 40% with respect to the heating region B. As a specific method, the width of the heating element 4a is widened to reduce the resistance of the heating element 4a.
By doing so, when the controlled temperature in the heating region B is maintained at 180 ° C., the temperature of the heater 3 in the thermofuse installation portion drops to about 140 ° C. In this way, by changing the ratio of the amount of heat generated by the heating element 4b in the heating region B and the heating value of the heating element 4a in the thermofuse installation portion, the temperature of the thermofuse installation portion can be set freely no matter how many times the fixing temperature is set. You can Therefore, for example, the use temperature of the thermofuse can be lowered, and the deterioration of the thermofuse due to heat can be mitigated, and the reliability and durability of the thermofuse can be significantly improved.

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

In this embodiment, a heater 3 as shown in FIG. 4 is used in the same fixing device as in the first embodiment. In this heater 3, the heating element 4a 'of the thermofuse installation portion has a temperature characteristic of resistance as shown in FIG. That is, at low temperature, the heating area B
Although the efficiency is lower than that of the heating element 4b 'used for the above, the resistance efficiency becomes lower than that of the heating element 4b' used for the heating region B as the temperature rises. In order to obtain such characteristics, in this embodiment, carbon black or the like was mixed with PI, phenol resin, or the like as the material of the heating element, and the characteristics were controlled by the blending amount of carbon black or the like. The heating temperature is based on the same idea as in Example 2, the heating area B is 180 ° C., and the thermofuse installation portion is about 140 ° C.
I am doing it. By using this embodiment, at the time of start-up, the resistance of the thermofuse installation portion is larger than that in the heating region B, and since the thermofuse installation portion is connected in series, the amount of heat generated is large, and therefore the rate of temperature rise is also high. This can speed up the response of the thermofuse at start-up, which is in a disadvantageous condition because the thermofuse is cold. Further, in the heating element used in this example, the low efficiency of the heating element 4a 'of the thermofuse installation portion and the low efficiency of the heating element 4b' of the heating portion are reversed at the boundary of 140 ° C, so that the overshoot of the thermofuse installation portion does not occur. Since the temperature of the thermofuse installation part during heating and the abnormal temperature rise due to runaway can be detected and set relatively close to the temperature at which the thermofuse operates, the thermofuse can be quickly activated even against runaway from normal use. The fuse can be activated.

This embodiment can be used in combination with the second embodiment, and the performance at the time of startup can be improved.

<Fourth Embodiment> Next, a fourth embodiment of the present invention will be described with reference to FIGS. FIG. 6 is a sectional view showing the schematic arrangement of the fixing device according to this embodiment. In FIG. 6, reference numeral 112 denotes a thermistor as a temperature detecting element, which is adhered to the inner wall of the stay 1 and detects the temperature of the stay 1. The output is A / D converted and taken into the CPU 110. Also, the thermistor 11
As shown in FIG. 7, reference numeral 2 designates a position in the longitudinal direction of the stay. When the sheet is fed on the basis of the left end of the figure, it is attached to the central portion of the sheet feeding area of the smallest size recording material to be fed to the apparatus. is there. This is because the thermistor is always placed in the paper passing area for all paper sizes that can be passed and the influence of the paper type is detected.

The parts of this embodiment other than the above are substantially the same as those of the conventional example shown in FIG.

In this embodiment, the control temperature of the heater 3 is changed according to the temperature of the stay 1. That is, when the temperature of the stay 1 is low and more heat energy is required to keep the temperature of the fixing film 2 at the optimum fixing temperature, the control temperature of the heater 3 is set high. Also,
When the temperature of the stay 1 is high and the temperature of the film 2 can be maintained at the fixing temperature even with a small amount of heat energy, the control temperature of the heater 3 is lowered.

Specifically, a table of heater control temperatures corresponding to stay temperatures as shown in FIG. 8 is used as the data CP.
It is held in advance in the memory inside the U110 or connected to the CPU110. Then, the output of the thermistor 112 that detects the stay temperature is A / D converted to convert the output from the CPU.
By 110, read in a constant cycle or indefinite cycle,
The control temperature of the heater 3 is determined at any time by referring to the table in the memory and comparing the output value with the table each time.

FIG. 9 shows changes with time in the heater temperature, film temperature, and stay temperature during continuous printing in the fixing device to which this embodiment is applied. First, at the time of starting the heater A, the heater temperature is set by the above procedure. Next, when continuous sheet feeding is continued, the stay gradually warms, the control temperature of the heater is changed in B according to the table of FIG. 8, and the same control is repeated in C.

As described above, by changing the control temperature of the heating element at any time according to the temperature of the stay, the heater temperature is always switched at an appropriate timing even when the fixing device is sufficiently cooled and 50 sheets are continuously fed. The temperature of the fixing film can be kept almost constant.

<Fifth Embodiment> Next, a fifth embodiment of the present invention will be described with reference to FIGS. The same parts as those of the fourth embodiment are designated by the same reference numerals and the description thereof will be omitted.

In the present embodiment, as shown in FIG. 10, the thermistors attached to the stay 1 are arranged near the reference end of conveyance at two places, a paper passing area and a non-paper passing area. This is in the vicinity of the thermistor 7 that controls the temperature of the heater, and is the region where the control temperature is most stable in the longitudinal direction of the stay 1.

The temperature of the stay 1 during paper passing differs between the paper passing area and the non-paper passing area, and is generally higher in the non-paper passing area. Further, the temperature difference between the paper passing area and the non-paper passing area differs depending on the type and thickness of the recording material to be passed, and the thicker the temperature difference, the greater the temperature difference.

In the present embodiment, the control temperature of the heater 3 is changed by estimating the thickness of the recording material being passed from the stay temperatures at the two places, the sheet passing area and the non-sheet passing area. That is, generally, as compared with thin paper, thick paper requires more heat to fix an image. Therefore, when the temperature difference is small when the thin paper is fed, the temperature of the heater 3 is set to be low and the temperature of the thick paper is passed. If the difference is large, the control temperature of the heater 3 is increased.

Specifically, a table as shown in FIG. 11 is prepared in advance, and the control temperature is switched by referring to the output values of the two thermistors and the table. As a result, the heater can be controlled to an optimum temperature regardless of the environment and the sheet passing mode.

<Sixth Embodiment> Next, a sixth embodiment of the present invention will be described with reference to FIGS. The same parts as those of the fourth embodiment are designated by the same reference numerals and the description thereof will be omitted.

In the present embodiment, the thermistors are provided at two places of the stay 1 as shown in FIG. 12 in order to control the conveyance interval according to the temperature rise in the non-sheet passing portion when the small size sheets are continuously passed. Install. In the drawing, the thermistor 112a is substantially the center of the paper passing area of the smallest size recording material that is passed through the apparatus when the paper is passed on the left end of the drawing.
b is arranged in the non-sheet passing area on the opposite side of the conveyance reference end. The thermistor 112a is a sensor for changing the control temperature of the heating element according to the temperature of the stay 1 as in the case of the fourth embodiment, and the thermistor 112b is used for continuously passing small size paper such as B5, envelopes and postcards. It is a sensor for controlling the interval between sheets, which is the conveyance interval, according to the temperature rise in the non-sheet passing portion.

FIG. 13 is a thermistor 112 in the case where an envelope (width 105 × length 241 mm) in which the temperature rise in the non-sheet passing portion is severe by using the temperature control of the fourth embodiment and the sheet interval is 50 mm.
a is the stay temperature of the thermistor 112b. As can be seen from this figure, the temperatures of the thermistors 112a and 112b differ by about 120 ° C. when 30 or more sheets are continuously passed, and at this time, the temperature of the non-sheet passing area (thermistor 112b) is about 250 ° C. Becomes This temperature is the heat resistant temperature of the stay which is a phenolic resin (approximately 240 ° C to 25 ° C).
(0 ° C.), which causes thermal deterioration and deformation of the stay.

Therefore, in the present embodiment, the thermistor 1 which is the temperature of the stay 1 in the non-sheet-passing portion after the small-sized paper is continuously passed through it
If the temperature of part 12b exceeds 200 ° C, then 50
The distance between the sheets was increased from 100 mm to 100 mm, the throughput was reduced, and the temperature difference between the paper passing portion and the non-paper passing portion was alleviated to prevent thermal deterioration and deformation of the stay.

By carrying out the control of this embodiment, the temperature difference between the sheet passing portion and the non-sheet passing portion is alleviated, and even if 100 small size sheets are continuously passed, there is no thermal deterioration or deformation of the stay. The temperature of the non-sheet passing area (thermistor 112b) was about 220 ° C.

Further, it is possible to prevent the film 2 from being twisted due to the temperature rise in the non-sheet passing portion when the small size sheets are continuously passed. Further, as in the case of Example 4, the non-temperature is switched at an appropriate timing, and the temperature of the fixing film can be kept substantially constant.

<Seventh Embodiment> Next, a seventh embodiment of the present invention will be described with reference to FIGS. FIG. 14 is a sectional view showing the schematic arrangement of the fixing device according to this embodiment. Figure 1
4 is a non-contact infrared temperature measuring device 212 for detecting the surface temperature of the film.
Surface temperature is detected, the output is A / D converted, CP
It is designed to be taken in by U110. The position where the temperature of the film surface is measured was set at a position 5 mm from the nip outlet in the film peripheral length.

As shown in FIG. 15, the non-contact infrared temperature measuring device 212 passes the smallest size recording material to be passed through the apparatus when the sheet is passed at the left end of the figure as shown in FIG. It is located approximately in the center of the paper area. This is because for all paper sizes that can be passed, a non-contact infrared temperature measuring device is always placed in the paper passing area to detect the influence of the paper type.

The parts of this embodiment other than the above are substantially the same as those of the conventional example shown in FIG.

In this embodiment, the control temperature of the heater is changed according to the surface temperature of the film 2 immediately after the nip.
That is, the surface temperature of the film 2 immediately after the nip is low,
When more heat energy is required to keep the temperature of the film 2 at the optimum fixing temperature, the control temperature of the heater is set high. When the surface temperature of the film 2 is high and the temperature of the film 2 can be maintained at the fixing temperature even with a small amount of heat energy, the control temperature of the heater is lowered.

Specifically, a table of heater control temperatures corresponding to the surface temperature of the film as shown in FIG. 16 is stored in advance in the CPU 110 or a memory connected to the CPU 110 as data. Then, the A / D-converted table of the non-contact infrared temperature measuring device 212 that has detected the film surface temperature is stored as data in the CPU 110 or a memory connected to the CPU 110 in advance. Then, the output of the non-contact infrared temperature measuring device 212 for detecting the film surface temperature is A / D converted to C
The PU 110 reads the data in a constant cycle or an indefinite cycle, references the table in the memory each time, compares the output value with the table, and determines the control temperature of the heater 3 at any time.

FIG. 17 shows changes with time in the heater temperature, film surface temperature, stay temperature, and pressure roller temperature during continuous printing in the fixing device to which this embodiment is applied. First, at the time of starting the heater A, the heater temperature is set by the above procedure. Next, when the continuous paper feeding is continued, the stay, the pressure roller, and the like are gradually warmed, so that the surface temperature of the film is stabilized, the control temperature of the heater is changed in B according to the table of FIG. 16, and the same in C. Repeat the control of.

As described above, by changing the heater control temperature depending on the film surface temperature at any time, the heater temperature is always switched at an appropriate timing even when the fixing device is sufficiently cooled and 50 sheets are continuously fed. The temperature of the fixing film can be kept almost constant.

<Embodiment 8> Next, an embodiment 8 of the present invention will be described with reference to FIGS. In addition, the same parts as those of the seventh embodiment are designated by the same reference numerals and the description thereof will be omitted.

In this example, as shown in FIG. 18, non-contact infrared temperature measuring devices for detecting the temperature of the film surface were arranged near the reference end of conveyance at two places, a paper passing area and a non-paper passing area. This is in the vicinity of the thermistor 7 that controls the temperature of the heater, and is the region where the controlled temperature is most stable in the longitudinal direction of the film 2.

The temperature of the film surface during paper passing differs between the paper passing area and the non-paper passing area, and is generally higher in the non-paper passing area. Further, the temperature difference between the paper passing area and the non-paper passing area differs depending on the type and thickness of the recording material to be passed, and the thicker the temperature difference, the greater the temperature difference.

In the present embodiment, the control temperature of the heater 3 is changed by inferring the thickness of the recording material that is being passed from the film surface temperature at the two places, the sheet passing area and the non-sheet passing area. That is, generally, as compared with thin paper, thick paper requires more heat to fix an image. Therefore, when the temperature difference is small when the thin paper is fed, the temperature of the heater 3 is set to be low and the temperature of the thick paper is passed. When the difference is large, the heater control temperature is raised.

Specifically, a table as shown in FIG. 19 is prepared in advance, and the control temperature is switched by referring to the output values of the two non-contact infrared temperature measuring devices and the table. As a result, the heater can be controlled to an optimum temperature regardless of the environment and the sheet passing mode.

<Ninth Embodiment> Next, a ninth embodiment of the present invention will be described with reference to FIGS. In addition, the same parts as those of the seventh embodiment are designated by the same reference numerals and the description thereof will be omitted.

In this embodiment, in order to control the conveyance interval according to the temperature rise in the non-sheet-passing portion when small-size sheets are continuously passed, as shown in FIG. Attach an infrared thermometer. In the figure, the non-contact infrared temperature measuring device 212a is located approximately in the center of the paper-passing area of the smallest size recording material that is passed through the apparatus when the paper is passed based on the left end of the figure. Was placed in the non-sheet passing area on the side opposite to the transport reference edge. The non-contact infrared temperature measuring device 212a is a sensor for changing the control temperature of the heating body according to the film surface temperature as in the case of the seventh embodiment, and the non-contact infrared temperature measuring device 112b is a small device such as B5, an envelope or a postcard. This is a sensor for controlling the interval between sheets, which is the conveyance interval, according to the temperature rise in the non-sheet-passing portion when size paper is continuously passed.

FIG. 21 is a non-contact infrared temperature measuring device 212a in the case where an envelope (width 105 × length 241 mm) in which the temperature of the non-sheet passing portion is severely heated is continuously passed with a space of 50 mm using the temperature control of the seventh embodiment. , 212b is the film surface temperature.
As can be seen from this figure, the non-contact infrared temperature measuring device 2
The temperature of the portions 12a and 212b has a difference of about 110 ° C. when 30 or more sheets are continuously passed, and at this time, the temperature of the non-sheet passing area (non-contact infrared temperature measuring device 212b portion) is about 270 ° C. At this time, the temperature of the stay 1 in the non-sheet passing area becomes about 250 ° C. This temperature is the heat resistant temperature of the stay 1 which is a phenolic resin (about 240 ° C. to 250 ° C.).
C.) and the stay 1 is thermally deteriorated and deformed.

In view of this, in the present embodiment, when small size paper is continuously fed and the temperature of the non-contact infrared temperature measuring device 212b, which is the surface temperature of the film 2 in the non-paper feeding portion, exceeds 210 ° C., it is until then. The space between the sheets, which was 50 mm, was expanded to 100 mm, the throughput was reduced, and the temperature difference between the paper passing portion and the non-paper passing portion was alleviated to prevent thermal deterioration and deformation of the stay 1.

By carrying out the control of this embodiment, the temperature difference between the sheet passing portion and the non-sheet passing portion is alleviated, and even if 100 small size sheets are continuously passed, the stay 1 is not deteriorated by heat or deformed. The stay temperature in the non-sheet passing area was about 220 ° C. Also,
It was also possible to prevent the twisting of the film 2 due to the temperature rise in the non-sheet-passing area when the small-sized paper was continuously fed. further,
As in the case of Embodiment 7, the non-temperature is switched at an appropriate timing, and the temperature of the fixing film 2 can be kept substantially constant.

[0078]

As described above, according to the first invention of the present application, the temperature detecting element for safety measures is mounted outside the region of the heating body for heating the heated body, so that the heating body is locally located at the mounting position. It is possible to prevent the temperature from lowering, to prevent insufficient heating at that portion, and to speed up the response of the temperature detecting element for safety measures at the time of runaway.

Further, according to the second and third inventions of the present application, by providing the temperature detecting means for detecting the temperature of the support of the film or the film itself, and changing the control temperature of the heating body according to the temperature, Even in the paper passing mode, the thermal energy applied to the recording material that is passed through the apparatus can be made constant to prevent fixing failure and offset. Further, the temperature detecting means on the surface of the support or the film can control the conveyance interval according to the temperature, so that the thermal deterioration and deformation of the stay due to the temperature rise of the non-sheet passing portion when small size paper is continuously passed Can be prevented.

[Brief description of drawings]

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

FIG. 2 is a perspective view showing a schematic configuration of a heater in the apparatus shown in FIG.

FIG. 3 is a perspective view showing a schematic configuration of a heater according to a second embodiment of the present invention.

FIG. 4 is a perspective view showing a schematic configuration of a heater according to a third embodiment of the present invention.

FIG. 5 is a diagram showing resistance characteristics of a heating element according to a third embodiment.

FIG. 6 is a cross-sectional view illustrating a schematic configuration of a fixing device according to a fourth exemplary embodiment of the present invention.

7 is a diagram showing a mounting position of a temperature detecting means for a support in the apparatus shown in FIG.

FIG. 8 is a diagram showing a table for temperature control according to a fourth embodiment of the present invention.

FIG. 9 is a diagram showing changes in surface temperature of a heating body, a film, and a support in Example 4 of the present invention.

FIG. 10 is a diagram showing a mounting position of a temperature detecting means for a support in Example 5 of the present invention.

FIG. 11 is a diagram showing a table for temperature control according to a fifth embodiment of the present invention.

FIG. 12 is a diagram showing a mounting position of a temperature detecting means for a support in Example 6 of the present invention.

FIG. 13 is a diagram showing changes in the surface temperature of a support in a paper passing area and a non-paper passing area in Example 6 of the present invention.

FIG. 14 is a sectional view showing a schematic configuration of a fixing device according to a seventh embodiment of the present invention.

FIG. 15 is a view showing an attachment position of a temperature detecting means for a support in the apparatus shown in FIG.

FIG. 16 is a diagram showing a table for temperature control according to a seventh embodiment of the present invention.

FIG. 17 is a diagram showing changes in surface temperature of a heating body, a film, and a support in Example 7 of the present invention.

FIG. 18 is a view showing a mounting position of a temperature detecting means for a support in Example 8 of the present invention.

FIG. 19 is a diagram showing a table for temperature control in Example 8 of the present invention.

FIG. 20 is a diagram showing a mounting position of a temperature detecting means for a support in Example 9 of the present invention.

FIG. 21 is a diagram showing changes in the surface temperature of the support in the paper passing area and the non-paper passing area in Example 9 of the present invention.

FIG. 22 is a sectional view showing a schematic configuration of a conventional device.

23 is a diagram showing temperature changes of a heating body, a support, a film, and a pressing member in the apparatus shown in FIG.

[Explanation of symbols]

1 Stay (Support) 2 Film 3 Heater (Heating Body) 8 Pressure Roller (Pressurizing Member) 11 Thermofuse (Temperature Sensing Element for Safety Measures) B Area where Heated Body Heats Heated Body P Recording Material (Covered) Heater 110 CPU (temperature control means) 112, 112 ', 112a, 112b Thermistor (temperature detection means for support) 212, 212', 212a, 212b Thermistor (temperature detection means for film)

Claims (9)

[Claims] 1. A heating device in which a heating element is adhered to one surface side of a heat resistant film and a heating element is adhered to the other surface side thereof, and heat energy of the heating element is applied to the heating element through the heat resistant film, A heating device comprising a temperature detecting element for safety measures, which is provided outside a region of the heating body for heating a heated body. 2. The heat generation amount of the heating body in the region where the temperature detecting element for safety measures is installed is set to be different from the heat generation amount of the region for heating the heated body of the heating body. Item 2. The heating device according to item 1. 3. The resistance characteristic with respect to the temperature of the heating body in the area where the temperature detecting element for safety measures is installed is set to be different from the resistance characteristic of the area where the heated body of the heating body is heated. The heating device according to claim 1. 4. A support for supporting a heating body, an endlessly movable film stretched so as to come into contact with the heating body and the support, and arranged so as to come into pressure contact with the heating body through the film. The pressure contact member, temperature detecting means for detecting the temperature of the heating body, and temperature control means for maintaining the temperature at a predetermined set temperature based on the temperature detected by the temperature detecting means. In the heating device for applying the thermal energy of the heating body to the recording material by sandwiching and transporting the recording material, the temperature control means for the support is provided for detecting the temperature of the support, and the temperature control means is A heating device is set so as to correct the set temperature based on the temperature detected by the temperature detecting means for the support. 5. The heating device according to claim 4, wherein the temperature detecting means for the support is provided at a plurality of positions of the support. 6. The heating device according to claim 4, further comprising control means set so as to appropriately adjust the recording material conveyance interval based on the temperature detected by the support temperature detection means. 7. A support for supporting the heating body, an endlessly movable film stretched so as to contact the heating body and the support, and a film provided so as to be in pressure contact with the heating body through the film. The pressure contact member, temperature detecting means for detecting the temperature of the heating body, and temperature control means for maintaining the temperature at a predetermined set temperature based on the temperature detected by the temperature detecting means. In the heating device for applying the heat energy of the heating body to the recording material by sandwiching and transporting the recording material, the temperature detecting means for the film for detecting the temperature of the film is provided, and the temperature controlling means is the film. A heating device, which is set so as to correct the set temperature based on the temperature detected by the operating temperature detecting means. 8. The heating device according to claim 7, wherein the film temperature detecting means is provided at a plurality of locations near the film. 9. The heating device according to claim 7, further comprising control means set so as to appropriately adjust the conveyance interval of the recording material based on the temperature detected by the film temperature detection means.