JPH10177319A - Fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film type thermal fixing device by which paper wrinkles and gloss irregularity caused by temperature rising at a non-paper passing part are prevented from occurring and an image forming device provided with this thermal fixing device. SOLUTION: Resistance heaters 610 and 620 on a ceramic substrate 601 are formed so as to consecutively change the width of the heaters from both ends parts to a central part, so that longitudinal heating distribution is changed, the calorific value of the central part of the heater 610 is large and that of both ends parts of the heater 620 is large. Two thermistors 630 and 631 are arranged on the back surface 601b of a ceramic heater 600 in a longitudinal direction, and the electric conduction ratio of the heaters 610 and 620 is controlled so that the temperature difference between the temperature of the thermistor 631 on the central part of a paper passing area and the temperature of the thermistor 630 on a paper passing area end part side becomes within 40 deg.C.

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 heating and fixing a toner image formed on a recording material, and an image forming apparatus having the fixing device, such as an electrophotographic apparatus and an electrostatic recording apparatus.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic system, which is an example of an image forming system, fixing of a visualized toner image on a recording material includes a heating roller controlled at a predetermined temperature and an elastic layer. In general, a method in which the recording material is nipped and conveyed while being heated and pressurized by a pressure roller that is in pressure contact with the heating roller (heat roller method).

However, recently, in order to realize power saving and a reduction in time from power-on to image output, Japanese Patent Application Laid-Open No. 63-313182 and Japanese Patent Application Laid-Open No.
No. 7878, etc., a heater unit comprising at least a fixedly supported heater (heater) and a heat-resistant film (fixing film) conveyed while being pressed against the heater, and the heater unit A fixing device having a pressure member for bringing the recording material into close contact with the recording material, and applying heat of a heater to the recording material via the film to heat and fix the toner image formed on the surface of the recording material. (Film heating fixing method) has been proposed.

FIG. 8 shows an example of such a film heating and fixing apparatus, which will be described below. In FIG. 8, reference numeral 60 denotes a heater unit, 65 denotes a cylindrical heat-resistant film, and a polyimide film having a thickness of 40 to 60 μm is used as a base layer, and its outer peripheral surface (surface in contact with a recording material and a toner image).
A PFA having a thickness of 5 to 20 μm and a release layer in which PTFE is dispersed in PFA. 61
Is a heater as a heating element, and has a ceramic substrate 62 having an insulating property, heat resistance, and low heat capacity whose longitudinal direction is perpendicular to the conveying direction of the recording material 20, and a resistive heating printed on the surface thereof along the longitudinal direction. Body 63 and the ceramic substrate 62
And a thermistor 64 as a temperature detecting element provided in contact with the surface opposite to the surface on which the resistance heating element 63 is formed.

The heater 61 has a film guide 66 (heater stay) having a semicircular trough shape in cross section as a support.
The recording material 20 and the toner image on the recording material 20 are heated via the heat-resistant film 65. The temperature of the heater 61 is controlled by the CPU 101 as control means in accordance with the output of the thermistor 64.
Is performed by driving the triac 55 and controlling the energization of the resistance heating element 63 from the power supply 35.

Reference numeral 67 denotes an inverted U-shaped reinforcing sheet metal provided to prevent the heater unit 60 including the heater 61, the thermistor 64, and the heater stay 66 from being deformed when pressed by the pressing roller 7. It is. Further, the fixing film 65 has an inner peripheral diameter of the reinforcing sheet metal 6.
7 is configured to be larger than the outer peripheral length of the heater unit.

On the other hand, a pressure roller 7 as a pressure member
Is pressed against the heater 61 by a pressure means (not shown) at a total pressure of 9 to 11 kgf, and the pressure roller 7 is moved in the conveying direction of the recording material 20 by a driving system (not shown). It is driven to rotate (counterclockwise). As a result, the cylindrical heat-resistant film 65 comes into close contact with the surface of the heating element of the heater 61 and slides around the film guide 66.
At this time, heat-resistant grease is interposed between the two to reduce the sliding friction of the inner surface of the film of the heater.

With the above configuration, the recording material 20 is guided between the film 65 and the pressure roller 7 and passes through the fixing nip, whereby the toner image on the recording material is fixed.

The above-described film heat fixing method can reduce the heat capacity of the heater section to several tenths and can generate heat at a high temperature as compared with a conventional heat roller type fixing apparatus. Since a body can be used, the time required for the heated portion to reach a temperature at which fixing can be performed can be several seconds. Therefore, a so-called on-demand fixing, which has been difficult to achieve in the fixing device of the heat roller type, can be performed.

[0010]

However, in the above-mentioned film type heat fixing, the above-mentioned on-demand fixing is possible because the heater is in close contact with the recording material through a low heat capacity film to transfer heat. If a recording material with a relatively short width is continuously conveyed with respect to the longitudinal width of the body, the surface temperature difference between the paper passing portion and the non-paper passing portion of the pressure roller to which the heater is in close contact via the film increases, and In the longitudinal direction of the pressure roller, the outer diameter and the coefficient of friction sometimes changed.

Therefore, since a stress having a component in the longitudinal direction is applied to the film, paper wrinkles and gloss unevenness are likely to occur.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a film-type heat fixing device which does not cause paper wrinkles and uneven gloss due to a non-sheet passing portion temperature rise, and an image forming apparatus provided with the heat fixing device. And

[0013]

According to a first aspect of the present invention, there is provided a heating element fixedly supported by a support, means for detecting a temperature of the heating element, A heat-resistant film conveyed while being pressed against the heating body, and a pressing member for bringing the recording material into close contact with the heating body via the heat-resistant film, and the heat of the heating body is applied to the heat-resistant film. In the fixing device for fixing an unfixed image formed on the recording material surface to the recording material surface by applying the fixing member to the recording material surface, the heating element has a plurality of resistance heating elements and the plurality of resistance heating elements. At least two of the heating elements have different longitudinal heat generation distributions, and a control means is set such that an energization ratio to the plurality of resistance heating elements can be switched according to the longitudinal width of the recording material to be used. It is achieved by having.

According to a second aspect of the present invention,
The object of the present invention is that the heating element of the first invention has a plurality of temperature detecting elements in the longitudinal direction, and the control means controls the resistances having different heat generation distributions in the longitudinal direction according to the output of the temperature detecting elements. This is achieved by changing the energization ratio to the heating element.

Further, according to a third aspect of the present invention, the above object is to provide an electric power supply apparatus according to the first or second aspect, wherein a current supply ratio to a plurality of resistance heating elements having different longitudinal heat generation distributions is defined by: This is achieved by changing the temperature of the pressure member, the calculated value of the temperature of the pressure member by simulation, or the number of prints, the printing time, and the like, according to parameters that can assume the temperature of the pressure roller.

According to a fourth aspect of the present invention,
The object is to provide a heating element fixedly supported by a support, a means for detecting the temperature of the heating element, a heat-resistant film conveyed while being pressed against the heating element, and a heat-resistant film. And a pressure member for bringing the recording material into close contact with the heating member, and applying the heat of the heating member to the recording material via the heat-resistant film to form an unfixed image formed on the recording material surface. In an image forming apparatus that forms an image by fixing to a recording material surface, the heating element has a plurality of resistance heating elements, and at least two of the plurality of resistance heating elements have a longitudinal heat generation distribution that is different from each other. In contrast, this is achieved by providing a control unit that is set so that the energization ratio for the plurality of resistance heating elements can be switched in accordance with the longitudinal width of the recording material to be used.

Further, according to a fifth aspect of the present invention, there is provided a heating element according to the fourth aspect, wherein the heating element has a plurality of temperature detecting elements in a longitudinal direction, and the control means controls the temperature detecting element. In accordance with the output of the element, the heat generation distribution in the longitudinal direction is achieved by changing the energization ratio to the different resistance heating elements.

According to the sixth aspect of the present invention,
The object of the present invention is to provide a power supply ratio for a plurality of resistance heating elements having different longitudinal heat generation distributions according to the fourth invention or the fifth invention, wherein the temperature of the pressure member or the calculated value of the temperature of the pressure member by simulation is calculated. Alternatively, it is achieved by changing the temperature of the pressure roller according to a parameter that can be assumed, such as the number of prints and the print time.

That is, in the first aspect of the present invention, the heating element has a plurality of resistance heating elements, and at least two of the plurality of resistance heating elements have different heat generation distributions in the longitudinal direction. The energization ratio for the plurality of resistance heating elements is
Since the recording material is set so as to be switched in accordance with the longitudinal width of the recording material used, in the case of a recording material having a width over the entire longitudinal direction, heating is performed over the entire region. By performing energization to the resistance heating element at the energization ratio, good fixing is performed.On the other hand, in the case of a recording material having a width shorter than the entire width, the non-passing area of the recording material passes. Since the resistance heating element is energized at an energization ratio such that the amount of heat generated is smaller than that in the center of the area, the temperature rise in the non-passing area of the recording material is eliminated.

Further, in the second invention according to the present application, the heating element according to the first invention has a plurality of temperature detecting elements in a longitudinal direction, and the control means responds to an output of the temperature detecting element. Since the power distribution ratio to the heating elements having different heat generation distributions in the longitudinal direction is changed, the recording material having a width over the entire area in the longitudinal direction is heated so that the temperature in the entire area becomes uniform. For the recording material shorter than the width over the entire area, heating is performed so that the temperature in the non-passing region of the recording material does not rise extremely than the passing region.

Further, in the third invention according to the present application, the energization ratio to the plurality of resistance heating elements having different longitudinal heat generation distributions of the first invention or the second invention is determined by the temperature of the pressing member. Alternatively, the calculated value of the temperature of the pressing member by simulation or the number of prints, the printing time, etc., are changed according to the parameters that can assume the pressure roller temperature, so even if a plurality of temperature sensing elements are not provided In addition, appropriate fixing is performed according to the width of the recording material.

In the fourth invention according to the present application, the heating element of the fixing device has a plurality of resistance heating elements, and at least two of the plurality of resistance heating elements have a longitudinal heat generation distribution. Are different from each other, and the energization ratios for the plurality of resistance heating elements are set so as to be switched according to the longitudinal width of the recording material to be used, so that the recording material having a width over the entire region in the longitudinal direction is used. In this case, good heating is performed so that uniform heating is performed over the entire region in the longitudinal direction, and heat is uniformly applied to the heating elements having different heat distributions, so that good fixing is performed and a good image is obtained. On the other hand, in the case of a recording material having a width shorter than the width over the entire area, the heating elements having different heat generation distributions are arranged so that the non-passing area of the recording material generates less heat than the central part of the passing area. On the other hand, by increasing the energization ratio to the heating element having a high heat generation amount at the central portion in the longitudinal direction, the temperature rise in the non-passing area of the recording material is eliminated, so that a good image without wrinkling of the recording material and uneven gloss is obtained.

Further, in the fifth invention according to the present application, the heating element according to the fourth invention has a plurality of temperature detecting elements in a longitudinal direction, and the control means responds to an output of the temperature detecting element. Since the power distribution ratio to the heating elements having different heat generation distributions in the longitudinal direction is changed, the recording material having a width over the entire area in the longitudinal direction is heated so that the temperature in the entire area becomes uniform. For a recording material shorter than the width over the entire area, heating is performed such that the temperature in the non-passing region of the recording material does not rise extremely than that in the passing region, and a good image is obtained.

In the sixth invention according to the present application, the energization ratio of the plurality of resistance heating elements having different longitudinal heat generation distributions according to the fourth invention or the fifth invention is determined by the temperature of the pressing member. Alternatively, the calculated value of the temperature of the pressing member by simulation or the number of prints, the printing time, etc., are changed according to the parameters that can assume the pressure roller temperature, so even if a plurality of temperature sensing elements are not provided In addition, appropriate fixing is performed according to the width of the recording material, and a good image is obtained.

[0025]

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. 6 is a diagram illustrating a main part of a laser printer according to an embodiment of the present invention. In FIG. 6, reference numeral 1 denotes an organic photosensitive drum as an image carrier. A charging roller 2 as a charging member is provided on the upper portion of the photosensitive drum 1, and the surface of the photosensitive drum 1 is uniformly charged by the charging roller 2. Then, when the charged surface is irradiated with laser light from the laser exposure device 3, an electrostatic latent image is formed on the surface. The developer is conveyed to a portion facing the developing device 4 provided with a developing blade, a one-component magnetic toner, and the like, and is visualized as a toner image by the toner of the developing device 4. On the other hand, the recording material 20 accommodated in the cassette 11
When the recording material supply roller 10 conveys the photosensitive drum 1 to the opposing portion of the transfer roller 5, the transfer roller 5
A transfer voltage is applied to transfer the toner image onto the recording material 20, and the recording material 20 is conveyed to a fixing device including the heater unit 6 and the pressure roller 7. Then, the toner image is fixed on the recording material 20 by this fixing device, and is discharged outside the apparatus. The surface of the photosensitive drum 1 after the transfer is cleaned by the cleaning blade 8 and used for the next image formation.

Next, the fixing device in the above-described image forming apparatus will be described in detail with reference to FIG. As shown in FIG. 5, the fixing device of the present embodiment is a film heating and fixing device. In FIG. 5, reference numeral 6 denotes a heater unit. The heater unit 6 includes a heater 600 as a heater, a film guide 660 (heater stay) having a semicircular trough cross section as a support for supporting the heater 600, and a heater roller 6. An inverted U-shaped replenishing sheet metal 670 provided so as not to be deformed when pressed, and a cylindrical heat-resistant film 650
And

The heater 600 includes a ceramic substrate 601 having an insulating property, heat resistance, and low heat capacity and having a longitudinal direction perpendicular to the conveying direction of the recording material 20, a heater 610 and a heater 620 as resistance heating elements, and a temperature detecting element. The device includes a thermistor 630 as an element and another thermistor (thermistor 631 shown in FIG. 1). The heater 610 and the heater 620 are exposed to the film guide 660, and are insulated and fixedly supported. ing.

A pressure roller 7 as a pressure member is disposed below the heater unit 6 as described above. The pressure roller 7 is composed of a metal core 71 and an elastic material made of silicone rubber. It is composed of a layer 72 and a surface layer 73 made of a fluorine-based resin. The pressure roller 7 is pressed against the heater unit 6 by a pressure unit (not shown) at a total pressure of 9 to 11 kgf, and is driven in a driving system (not shown) in the conveying direction of the recording material 20. ) To rotate (counterclockwise). As a result, the cylindrical heat-resistant film 650 comes into close contact with the surface of the heating element of the heater 600 and slides,
It rotates around the film guide 660.

With the above configuration, the nip portion N between the heater unit 6 and the pressure roller 7 whose temperature is controlled is
The toner image is fixed on the recording material 20 by nipping and conveying the recording material 20. However, when the recording material having a relatively short width relative to the longitudinal width of the heating element is continuously conveyed, the heater is interposed via the film 650. The surface temperature difference between the paper passing portion and the non-paper passing portion of the pressure roller 7 to which the pressure roller 600 adheres is increased, and the outer diameter and the friction coefficient are changed in the longitudinal direction of the pressure roller 7, and the film 650 is formed.
However, since a stress having a component in the longitudinal direction is applied, paper wrinkling and gloss unevenness are likely to occur.

Therefore, in this embodiment, two resistance heating elements 610 and 620 having different heat generation distributions in the longitudinal direction and two thermistors 630 and 631 are disposed in the longitudinal direction and the two thermistors 630 and 631 are disposed. The power supplied to the two resistance heating elements 610 and 620 is controlled independently so that the resistance value of the pressure roller 7 is within a certain value.
Is controlled within a certain range irrespective of the paper size to be conveyed.

Hereinafter, the structure and control method of the heater according to the present embodiment will be described in detail. As shown in FIG. 1, a resistance heating element 6 provided on a ceramic substrate 601 is provided.
10, 620 (hereinafter, heater 610, heater 620)
Is described so that the heating element width changes continuously from both ends to the center, thereby changing the longitudinal heat generation distribution. The heater 610 generates a large amount of heat at the center. And the heater 620 are designed so that the amount of heat generated at both ends is large. In the drawing, the shape of the heating element is exaggerated, the length of the heating element is 305 mm, and the width W
Is 5 mm.

The heater 610 and the heater 62
0, electrodes 615, 616, and 617 are attached. In this embodiment, the electrodes 615 and 61
6, and the resistance between the electrodes 615 and 617 is 20Ω.

The heater 610 and the heater 6 as described above
20 and a part of the electrode 615, the electrode 616, and the electrode 617 are covered with a glass coat layer 605 having a thickness of 60 μm, and the glass coat layer 605 side rubs against the film 650.

On the other hand, the back surface 6 of the ceramic heater 600
01b is provided with thermistors 630 and 631;
Electrodes 655, 656, on the surface via through holes
It is connected to the electrode 657.

The electrodes 655 and 656 are
CP as control means of printer in the present embodiment
The CPU 100 controls the driving of the triacs 51 and 52 according to the resistance values of the thermistors 630 and 631.
The power supplied from the power supply 30 to the heater 610 and the heater 620 is controlled.

In this embodiment, the two heaters 61
An example of a voltage waveform input to 0,620 is shown in FIGS. In the figure, the hatched portion indicates a region where voltage is applied.

In this embodiment, the heater 610 and the heater 620 are turned ON / OFF for each half-wave.
Control and the energization ON at a phase angle within one half-wave
The phase control in which / OFF is switched is switched for each cycle of the power supply voltage, and if one of the voltage waveforms having the same phase is energized by the wave number control, the other is energized by the phase control. Is controlled.

FIG. 2 shows an energization waveform when the heater 610 and the heater 620 are controlled at the same energization ratio (40% in two cycles of the power supply voltage waveform).
At the time of V input, the power is about 200 W, and the heat generation distribution (no-load state) in the longitudinal direction of the heater at that time is indicated by a solid line L ₁
It is represented by the curve shown by.

FIG. 3 shows that the heater 610 has an energizing ratio of 50% and the heater 620 has an energizing ratio of 20%.
% (Both power energization percentage of supply voltage 2 cycles) represents the current waveform in the case that is controlled by, heat generation distribution of the heater length of that time (unloaded state) is represented by the curve indicated by the broken line L ₂ in FIG. 4 . In addition, in FIG. 4, A is thermistor 630, B
Indicates a longitudinal position where the thermistor 631 is arranged.

As described above, by using the two heaters 610 and 620 having different longitudinal heat distributions and performing the energization independently as described above, the heat distribution of the heaters can be changed.

In this embodiment, two thermistors 63 are arranged in the longitudinal direction of the ceramic heater 600.
0,631 and the temperature of the thermistor 631 at the center of the paper passing area and the thermistor 630 at the end of the paper passing area.
Of the heater 610 and the heater 620 is controlled so that the temperature difference between the heaters 610 and 620 is within 40 ° C.

For example, as the recording material 20, A3 (P),
When a copy sheet such as A4 (L) or LTR (L) is passed, if the heater 610 and the heater 620 are energized at a substantially equal rate, the temperature difference between the two thermistors is 4
It is within 0 ° C.

A4 (P), LTR (P), LGL
(P), etc., when passing copy paper in which the temperature rise in the non-paper passing portion is likely to occur, the energization ratio of the heater 610 is set to the heater 62.
By setting it higher than 0, the temperature difference between the thermistor 630 and the thermistor 631 can be kept within 40 ° C.

That is, according to the paper size and the paper passing direction,
When passing paper where the temperature rise at the end of the pressure roller 7 is not particularly problematic (A3 (P), A4 (L), LTR (L), etc.)
Is controlled by the heater 610 and the heater 620 at a substantially equal energization ratio, and A4 (P), LTR (P), L4
When a sheet of paper such as GL (P), which is likely to raise the temperature at the end of the pressure roller 7, is passed, the heater 610 and the heater 620 are used.
Are thermistors 630 and 63 as described above.
Control is performed at different energization ratios so that the temperature difference indicated by 1 is 40 ° C. or less.

By configuring the heater as described above and controlling the energization, it is possible to alleviate the temperature rise at the end of the pressure roller when small-size paper is passed. The change in the outer diameter of the pressure roller and the change in the coefficient of friction that occur between the paper portions can be reduced, and wrinkles that occur on the recording material can be improved.

In this embodiment, since the two heaters generate heat evenly for each period of the power supply voltage waveform, the recording material moves through the fixing nip area for two periods of the power supply voltage (50 cycles).
In the case of Hz, if the recording material passes over a time longer than 0.04 sec), the recording material is heated almost uniformly in the fixing nip, and uniform fixing properties can be obtained.

Further, the branching method, the number of branches, and the control example of the resistance heating element shown in the present embodiment are merely examples. For the resistance heating element, the heater 610 and the heater 620 do not need to have the same resistance value. For example, it is also possible to increase the amount of heat generated on the upstream side with respect to the center of the fixing nip to improve the fixing property. Regarding control, for example, phase control and wave number control may be switched for each cycle of the power supply voltage waveform.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIG. In the present embodiment, one thermistor disposed on the back surface of the heater is used, and the energization control for two heating elements having different resistance distributions is calculated according to the paper size to be passed and the simulation temperature of the pressure roller. And switching.

FIG. 7 is a front view and a back view of a fixing heater to which the present embodiment is applied, and a diagram showing a main part of a circuit for performing temperature control.

In FIG. 7, reference numeral 900 denotes a ceramic substrate 9.
10, resistance heating elements 910, 920, thermistor 632
The ceramic heater 600 is different from the ceramic heater 600 according to the first embodiment in that the number of thermistors on the back surface is one and the number of thermistor electrodes is three to two.

However, also in this embodiment, resistance heating elements 910 and 920 (hereinafter, referred to as heater 910 and heater 920) are provided on the ceramic substrate 901. , Electrodes 915, 916, and 917 are connected. Then, the heater 910, the heater 920, and the electrode 91
5, a part of the electrode 916 and the electrode 917 are covered with a glass coat layer 905 having a thickness of 60 μm.

On the other hand, the back surface 9 of the ceramic heater 900
01b is provided with a thermistor 632, which communicates with the electrodes 955 and 957 on the surface via through holes.

The electrodes 955 and 957 are connected to the CPU 10 as control means of the laser printer of this embodiment.
1 and the CPU 101 is connected to the thermistor 6
Drive control of the triac 55 and the triac 56 is performed in accordance with the resistance value of the
0, the electric power supplied to the heater 920 is controlled.

In the present embodiment, a pressure roller is used to dispose one thermistor in the paper passing area and to alleviate the temperature rise in the non-paper passing portion by using two heaters having different heat generation patterns. It is characterized in that a temperature simulation is performed, and the energization ratio for the two heaters is changed according to the temperature.

The simulation of the pressure roller temperature is as follows.
Using the thermistor temperature at the start of energization of the heater as the initial value (T ₀ ) of the pressure roller temperature, the rise ΔTa of the pressure roller temperature at the time of paper passing every 250 msec, and the pressure roller temperature of non-paper passing such as between sheets This is performed by adding the increase ΔTb of T to T ₀ . Δ in the present embodiment
Tables 1 and 2 show Ta and ΔTb, respectively.

[0057]

[Table 1]

[0058]

[Table 2]

In the present embodiment, when the simulated value of the pressure roller temperature becomes 80 ° C., the energization ratio to the two heaters is increased to further reduce the temperature rise of the pressure roller 7 in the non-sheet passing portion. Control to switch to. Heater 91 for each paper size after 80 ° C
Table 3 shows the energization ratio for 0 and 920.

[0060]

[Table 3]

By configuring the heater as in the present embodiment and controlling the energization, it is possible to control the temperature of the heater having a different heat generation pattern even with a single thermistor. Paper wrinkles, which is a problem when paper is made, can be improved.

In this embodiment, the switching of the energization ratio for the two heaters is performed by changing the pressure roller temperature 8
It was performed at 0 ° C., but this temperature is not limited,
The temperature should be changed to an appropriate temperature in accordance with the layer configuration of the pressure roller, the rigidity of the film, and the like, and may be switched in three or more steps instead of two steps.

Further, in the above-described embodiment, the CPU provided in the image forming apparatus main body is used as the control means, but the fixing device itself may be provided with the control means.

[0064]

As described above, the first embodiment according to the present application is described.
According to the invention, the heating element has a plurality of resistance heating elements,
At least two of the plurality of resistance heating elements have different longitudinal heat generation distributions, and the energization ratio for the plurality of resistance heating elements can be switched according to the longitudinal width of the recording material used. In the case of a recording material having a width over the entire area in the longitudinal direction, power is supplied to the resistance heating element at such a ratio that heating is performed over the entire area. It can be carried out. On the other hand, in the case of a recording material having a width shorter than the width over the entire area, the energization ratio to the resistance heating element is set such that the amount of heat generated in the non-passing area of the recording material is smaller than that in the center of the passing area. Is performed, the temperature rise in the non-passing area of the recording material can be eliminated, and the occurrence of wrinkles and uneven gloss of the recording material can be prevented.

According to the second aspect of the present invention,
The heating element according to the first invention has a plurality of temperature detecting elements in a longitudinal direction, and the control means supplies current to resistance heating elements having different longitudinal heat generation distributions in accordance with an output of the temperature detecting element. Since the ratio is changed, it is possible to heat the recording material having a width over the entire area in the longitudinal direction so that the temperature of the entire area becomes uniform, and to obtain a recording material shorter than the width over the entire area. On the other hand, the heating can be performed such that the temperature in the non-passing area of the recording material does not rise extremely than that in the passing area, so that good fixing without wrinkling and uneven gloss of the recording material can be performed.

Further, according to the third invention of the present application, the energization ratio to the plurality of resistance heating elements having different longitudinal heat generation distributions of the first invention or the second invention is determined by the pressing member. Since the temperature is changed according to the temperature or the calculated value of the temperature of the pressing member by simulation, appropriate fixing can be performed according to the width of the recording material even when a plurality of temperature detecting elements are not provided.

According to the fourth aspect of the present invention,
The heating element of the fixing device has a plurality of resistance heating elements, and at least two of the plurality of resistance heating elements have different heating distributions in the longitudinal direction. Since the recording material is set so as to be switched in accordance with the longitudinal width of the recording material to be applied, in the case of a recording material having a width over the entire longitudinal direction, the energization is performed so that heating is performed over the entire region. Since power is supplied to the resistance heating element at a ratio, good fixing can be performed, and a good image can be obtained. On the other hand, in the case of a recording material having a width shorter than the width over the entire area, the energization ratio to the resistance heating element is set such that the amount of heat generated in the non-passing area of the recording material is smaller than that in the center of the passing area. Is performed, the temperature rise in the non-passing area of the recording material can be eliminated, and a good image free of wrinkles and uneven gloss of the recording material can be obtained.

Further, according to the fifth invention of the present application, the heating element of the fourth invention has a plurality of temperature detecting elements in the longitudinal direction, and the control means controls the output of the temperature detecting element. Accordingly, the energization ratio to the resistance heating elements having different heat generation distributions in the longitudinal direction is changed, so that the recording material having a width over the entire longitudinal direction is heated so that the temperature in the entire region becomes uniform. For the recording material shorter than the width over the entire area, it is possible to perform heating such that the temperature in the non-passing area of the recording material does not rise extremely than in the passing area. Images can be obtained.

According to the sixth aspect of the present invention,
The energization ratio for a plurality of resistance heating elements having different heat generation distributions in the longitudinal direction of the fourth invention or the fifth invention is as follows:
Since the temperature is changed according to the temperature of the pressing member or the calculated value of the temperature of the pressing member by simulation, it is possible to perform appropriate fixing according to the width of the recording material even when a plurality of temperature detecting elements are not provided. And good images can be obtained.

[Brief description of the drawings]

FIG. 1 is a front view of a heater according to a first embodiment of the present invention, and a diagram illustrating a main part of a circuit that performs energization control.

FIG. 2 is a diagram illustrating one form of a voltage waveform input to a heater according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating one form of a voltage waveform input to a heater according to the first embodiment of the present invention.

FIG. 4 is a diagram illustrating a heat generation distribution in a longitudinal direction of the heater according to the first embodiment of the present invention.

FIG. 5 is a diagram illustrating a main part of a fixing device including a heater according to the first embodiment of the present invention.

FIG. 6 is a diagram illustrating a main part of the laser printer according to the first embodiment of the present invention.

7A and 7B are a front view of a heater according to a second embodiment of the present invention and a diagram illustrating a main part of a circuit for performing energization control.

FIG. 8 is a diagram illustrating a main part of a fixing device including a conventional heater.

[Explanation of symbols]

 7 Pressure roller (Pressing member) 20 Recording material 100, 101 CPU (Control means) 600, 900 Heater (Heating body) 610, 620, 910, 920 Resistance heating element 630, 631 Thermistor (Temperature detecting element) 650 Heat resistance Film 660 film guide (support)

Claims (6)

[Claims] 1. A heating body fixedly supported by a support,
Means for detecting the temperature of the heating element, a heat-resistant film conveyed while being pressed against the heating element, and a pressure member for bringing a recording material into close contact with the heating element via the heat-resistant film. In a fixing device for fixing an unfixed image formed on a recording material surface to the recording material surface by applying heat of the heating body to the recording material via the heat-resistant film, the heating body includes a plurality of heating members. A resistance heating element, at least two of the plurality of resistance heating elements have different heat generation distributions in the longitudinal direction, and the energization ratio to the plurality of resistance heating elements is determined by the longitudinal width of the recording material used. A fixing device comprising a control unit set to be switched according to 2. The heating element has a plurality of temperature sensing elements in a longitudinal direction, and the control means controls an energization ratio to a resistance heating element having different heating distributions in the longitudinal direction according to an output of the temperature sensing element. The fixing device according to claim 1, wherein: 3. The current supply ratio to a plurality of resistance heating elements having different longitudinal heat generation distributions is changed according to the temperature of the pressing member or a calculated value of the temperature of the pressing member by simulation. 1 or Claim 2
3. The fixing device according to claim 1. 4. A heating body fixedly supported by a support,
Means for detecting the temperature of the heating element, a heat-resistant film conveyed while being pressed against the heating element, and a pressure member for bringing a recording material into close contact with the heating element via the heat-resistant film. An image forming apparatus for forming an image by fixing an unfixed image formed on a recording material surface to a recording material surface by applying heat of the heating body to the recording material via the heat-resistant film, The heating element has a plurality of resistance heating elements, and at least two of the plurality of resistance heating elements have different longitudinal heat generation distributions. An image forming apparatus comprising: a control unit that is set so as to be switched according to the width of the material in the longitudinal direction. 5. The heating element has a plurality of temperature detecting elements in the longitudinal direction, and the control means controls the energization ratio to the resistance heating elements having different longitudinal heat generation distributions in accordance with the output of the temperature detecting element. The image forming apparatus according to claim 4, wherein: 6. The current supply ratio to a plurality of resistance heating elements having different longitudinal heat generation distributions is changed according to the temperature of the pressing member or a calculated value of the temperature of the pressing member by simulation. 4 or Claim 5
An image forming apparatus according to claim 1.