JP2001194936A - Heater, fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such problem that the temperature control is hard and the fixing efficiency is lowered even when the temperature of a heating element is controlled, and also to solve such problems that a fixing film at the end part of the heating element in the longitudinal direction, a pressure roller and the like are damaged, and the end parts whose temperature rises are offset when a large-sized paper being equal to or over the small-sized paper is passed after the small-sized paper is passed because the temperature of the whole area of the heating element is lowered when maximum-sized paper is passed, that of the central part of the heating element where the paper is passed is lowered but that of both end parts of the heating element being the paper non-passing parts becomes higher in comparison with the central part when the small-sized paper is passed with a center as a reference. SOLUTION: On the heater provided with the heating elements generating heat by being energized at the surface of an insulating substrate, the plural different-width heating elements are arranged side by side along in the longitudinal direction on the insulating substrate and the narrow heating elements are arranged at an upstream side in the width direction of the insulating substrate in the advancing direction of a recording material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heater provided with a heating element which generates heat when energized on the surface of an insulating substrate, and heats and fixes unfixed toner on a recording material (hereinafter referred to as recording paper or paper) using the heater as a heat source. The present invention relates to a fixing device and an image forming apparatus such as a copier, a printer, a facsimile, and the like using an electrophotographic method to which the fixing device is applied.

[0002]

2. Description of the Related Art Conventionally, a copying machine based on the above electrophotographic method,
2. Description of the Related Art A fixing device applied to an image forming apparatus such as a printer employs a contact heating type heat roller fixing method having good thermal efficiency and safety, and an energy saving type film heating method.

The above-mentioned fixing device of the film heating type is disclosed in, for example, JP-A-63-313182 and JP-A-2-157.
878, JP-A-4-44075 to JP-A-4-44075
-44083, JP-A-4-204980-
As described in JP-A-4-2094984, a heat-resistant film (hereinafter, referred to as a fixing film or a film), which is a heating rotator, is formed by a pressing rotator (hereinafter, referred to as a pressure roller). The recording paper carrying the unfixed toner image is introduced into the fixing nip formed by the heater and the pressure roller with the fixing film sandwiched therebetween, and the recording paper is conveyed together with the fixing film. An unfixed toner image is fixed on a recording paper as a permanent image by heat from a heating body applied through a fixing film and a pressing force of a fixing nip portion.

In this fixing device of the film heating type, a linear heating element having a low heat capacity can be used as a heating element provided in a heater, and a thin film having a low heat capacity can be used as a film. (Quick start property) is possible.

In this type of film heating type fixing device, a driving roller is provided on the inner peripheral surface of the film to drive the fixing film, and the film is driven while applying tension to the film. A method in which the film is driven to rotate with respect to the pressurizing rotary body by fitting and driving the pressurizing rotary body is known. However, in recent years, since the number of components is small, the latter pressurizing rotary body is required. A drive system is often employed.

As a specific example, FIG. 7 is a configuration diagram showing a conventional fixing device, and FIG. 7A is a cross-sectional view of a film heating type fixing device employing a pressing rotary member driving method.
FIG. 2B is a front view showing the relationship between the film 3 and the pressure roller 4. In the figure, a pressure roller 4 is formed by forming a release layer 4a on the surface of a heat-resistant rubber layer 4b having a core 4c, and is rotatably supported on the lower frame 6 'of the fixing device by the core 4c. Have been.

[0007] The fixing-side metal stay 5 pressed down by pressing means (not shown) provided on the upper frame 6 of the fixing device.
And a cylindrical fixing film 3, which is rotated and conveyed along the heater holder 2 also serving as a film guide member together with the rotation of the pressure roller 4 by the frictional force acting on the interface due to the frictional force acting on the interface. A fixing nip portion is formed between them. The recording material 8 is conveyed along the fixing entrance guide 7, and is heated and pressed by the heater 1 via the fixing film 3 when passing through the fixing nip, whereby the unfixed toner is fixed and discharged along the paper discharge guide 7 '. Is done.

In this case, the fixing film 3 has a thickness of 100 μm or less, more preferably 40 μm or less and 20 μm in order to reduce the heat capacity and improve the quick start property.
PTFE, PF with the above heat resistance, release property and durability
A, PPS or a single-layer film of polyimide or polyamide imide, PEEK, PES, etc.
It is composed of a composite layer film in which a release layer 3a made of a fluororesin such as FE, PFA, FEP or the like is coated or formed into a tube.

When the fixing film having the three-layer structure is used, as shown in FIG. 7B, a region where the conductive primer layer 3b is exposed at the end of the fixing film is provided, and the surface of the conductive primer layer 3b is opposed to the surface. The conductive rubber ring 4d, which is grounded via the resistor 4e, is fitted into the pressure roller core 4c at the pressure roller side end to be pressed, and the conductive rubber ring 4d is brought into pressure contact with the conductive primer layer 3b. 3 enables the conductive primer layer 3b to be grounded by resistance,
Thereby, the potential of the fixing film 3 is stabilized, and the unfixed toner image on the recording material is less likely to be adversely affected by electrostatic.

As described above, various image forming apparatuses such as printers using the above-described film heating type fixing device eliminate the need for preheating during standby due to the high heating efficiency and the rising speed, and the waiting time. It has many advantages such as the elimination of, especially, since the rotating body driving system for driving the cylindrical film by the conveying force of the pressing roller can be realized at low cost, it started from the introduction to small and low speed machines, In the future, introduction to large high-speed machines is expected.

In order to realize this high speed, first, the motor as a drive source is powered up to increase the rotation speed of the pressure roller and the fixing film, and the passage time through the fixing nip is shortened. To supply sufficient thermal energy to the paper, set the fixing temperature even higher,
It is necessary to make improvements such as increasing the pressure of the pressure roller to increase the width of the heating area, that is, the width of the fixing nip, and changing the material of the heater substrate and the fixing film to those having high heat conductivity.

[0012]

However, the above-mentioned film heating type fixing device has the following problems.

The length of the heating element in the longitudinal direction must be equal to or greater than the maximum length of the paper size to be used, and the temperature is detected by a thermistor arranged near the center of the length to control the temperature. In, when the largest size paper is passed, the heat generated by the heating element is absorbed by the paper, and the temperature of the entire heating element decreases.

On the other hand, when a sheet having a size smaller than the maximum size is passed on the basis of the center, the temperature drops only in the central portion through which the sheet passes. The temperature rises compared to the center, causing damage to the fixing film, pressure roller, etc. at the longitudinal end,
When a larger size paper is passed after the small size paper is passed, there is a problem that the heated end is offset.

In order to solve the above-mentioned problem, when small-size paper is passed, the paper-passing interval is widened, and the temperature distribution of the end heating element, the pressure roller, the fixing film, etc., which is heated between the papers, is increased. Is considered to be uniform in the longitudinal direction. Further, a method has been considered in which heating elements having patterns having different lengths and widths are provided on a substrate, and the heating elements to be driven are changed in accordance with the recording size to be passed.

FIG. 8A shows the positions of the heating elements h1 and h2 in the width direction of the heater 1 as Comparative Example 1 and the respective heating elements h.
FIG. 8B is a diagram for explaining a temperature gradient in the heater width direction when currents 1 and h2 are energized, and FIG. 8B is a plan view showing the heater 1. The heater 1 is an insulating substrate (hereinafter, simply referred to as a substrate).
Heating elements h1 and h2 having different patterns along the longitudinal direction are provided on the heating element 11 and the heating element h1 is energized when passing large-size paper, and the heating element h2 is passed when passing small-size paper. Is to be energized. The amount of heat required when fixing recording papers of various sizes is different depending on the paper size.

Since the heating elements h1 and h2 are formed by pasting a resistive material having the same resistance value with the same thickness, when each of the heating elements is driven by the same input voltage, the heat generation amount is determined by the area of the paste. Can be adjusted. In order to select a heating element to be driven according to the paper size and to generate an optimal amount of heat, the longitudinal length (1) of each of the heating elements h1 and h2 is set.
1, 12) and the width and length (w1, w2) are 11> 1
2, w1> w2.

Such a relationship is established by the heating element h1
Required to fix large-size paper by driving
No. 1 is because the amount of heat required for driving h2 and fixing the small-size paper is larger than Q2.

However, when the heating elements h1 and h2 of the heater 1 having the configuration shown in Comparative Example 1 are energized,
As shown in FIG. 8A, the temperature gradient in the substrate when the heating element h1 on the upstream side is energized is broad in the fixing nip, but when the heating element h2 on the downstream side is heated. The temperature gradient in the substrate is sharp. Further, since the heat generation peak of the heating element h2 is shifted downstream from the center of the fixing nip, it is difficult to uniformly apply heat to the recording paper in the fixing nip, and the fixing property is disadvantageous.

As a method of controlling the temperature of each of the heating elements h1 and h2, a temperature detecting means such as a thermistor may be used.
A method of controlling the temperature while monitoring the temperature on the substrate 11 by contacting the upper surface is considered.
As shown in (a) and (b), since the temperature gradient in the substrate when the narrow heating element h2 generates heat is sharp, the contact position in the width direction of the temperature detecting means such as a thermistor is determined. Precision matters.

Even if the thermistor is brought into contact with the position a where the deviation of the temperature control of the narrow heating element h2 becomes small, the temperature gradient of the heating element h2 is sharp, so that the temperature to be controlled varies widely. I will. Further, since the temperature gradient of the heating element h1 is becoming steep at the position a, the temperature control is also difficult.

FIG. 9 shows the positions of the heating elements h1, h2 in the width direction of the heater 1 as Comparative Example 2, and the respective heating elements h1, h2.
FIG. 6 is a diagram for explaining a temperature gradient in the heater width direction when the power is supplied to the heater, and both the heating elements h1 and h2 are arranged on the upstream side from the center of the fixing nip. By doing so, the temperature gradient on the substrate when the narrow heating element h2 generates heat can be made relatively broad as compared with the comparative example 1. However, since the plurality of heating elements h1 and h2 are arranged on the upstream side from the center of the fixing nip, a portion of the heating element h1 on the upstream side is separated from the fixing nip portion, and the fixing efficiency is reduced. In addition, the width of the entire substrate becomes large, and the device becomes large.

The present invention is intended to solve the above-mentioned problem. In a case where each of a plurality of heating elements is independently energized to generate heat, the heating elements are arranged so that a temperature gradient in a substrate width direction becomes broad. A heater capable of disposing a heating element in a fixing nip portion without suppressing excessive temperature rise in a non-paper passing portion and causing thermal damage to members such as a fixing film and a pressure roller. An object of the present invention is to provide a fixing device for obtaining a fixing property and an image forming apparatus for obtaining a high quality image by applying the fixing device.

[0024]

According to the present invention, there is provided a heater, a fixing device and an image forming apparatus having the following constitutions.

(1) In a heater provided with a heating element which generates heat by energization on the surface of an insulating substrate, a plurality of heating elements having different widths are arranged in parallel along the longitudinal direction on the insulating substrate to provide insulation in a recording material advancing direction. A heater characterized in that a narrow heating element is arranged on the upstream side in the substrate width direction.

(2) In a heater provided with a heating element which generates heat by energization on the surface of the insulating substrate, a plurality of heating elements are arranged in parallel along the longitudinal direction on the insulating substrate, and the width of the insulating substrate in the recording material advancing direction is changed. A heater characterized in that a heating element having a smaller resistance value per unit area is arranged on an upstream side as compared with a heating element on a downstream side.

(3) In a heater provided with a heating element which generates heat when energized on the surface of the insulating substrate, a plurality of heating elements are arranged in parallel along the longitudinal direction on the insulating substrate, and the width of the insulating substrate in the recording material advancing direction is set. 3. The heater according to claim 1, wherein a temperature detecting means is provided near a heating element located on the downstream side, and the temperature of the plurality of heating elements is controlled based on a detection signal of the temperature detecting means. .

(4) Any one of (1) to (3)
A heat-resistant film that presses and moves on the heater holder; and presses the heat-resistant film against the heater holder to form a fixing nip portion, and the recording material passing through the fixing nip portion is used as a heat-resistant film. And a pressurizing member for heating and fixing the unfixed toner to the recording material surface through the pressure member.

(5) In an image forming apparatus having image forming means for forming an image with unfixed toner on a recording material and fixing means for heating and fixing the unfixed toner formed and carried on the recording material to the recording material, An image forming apparatus using the fixing device according to (4) as the fixing unit.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is an enlarged view of a main part of a fixing device according to the present invention in which a heater 1 is mounted on a heater holder 2 and a pressure roller 4 is pressed against the heater 1.
Since the entire configuration of the fixing device is the same as that of the fixing device shown in FIG. 7, detailed description will be omitted. FIG. 1A illustrates the position in the width direction of the heating elements h1 and h2 of the heater 1 according to the first embodiment and the temperature gradient in the heater width direction when the heating elements h1 and h2 are energized. Figure for Figure 1
FIG. 2B is a plan view showing the heater 1.

In the first embodiment, an Ag / Pd resistance material is coated on an aluminum nitride substrate (insulating substrate) 11.
The heating elements h1 and h2 are formed by patterning a wide heating element h1 and a narrow heating element h2, and glass 12 is coated on the heating elements h1 and h2 to keep insulation from electric members such as thermistors and the film surface. .

Each of the heating elements h1 and h2 has electrodes a, b,
The current flows through the substrate 11 and heat is generated on the substrate 11. The heater to be energized is selected according to the size of the recording paper to be passed. When a large-sized recording paper is passed, the heating element h1 having a longer length in the longitudinal direction and a wider width is heated. Let
When a small-sized recording sheet of 120 mm or less in the longitudinal direction is passed, the heating element h2 having a short length in the longitudinal direction and a narrow width is generated.

In an apparatus for fixing various paper sizes, the required amount of heat differs according to the paper size, and it is desirable to change the amount of heat generated according to the size. When fixing a large-sized paper, a small-sized paper is used. Requires a larger amount of heat than when fixing.

In the first embodiment, the width of the heating element for the large size is wider than the width of the heating element for the small size.
The resistance of the entire heating element is reduced, and the amount of heat generation can be increased. Increasing the width of the large-size heating element is advantageous in terms of fixability because heat can be widely generated in the fixing nip formed by the heater and the pressure roller.

FIG. 4 shows the results when the fixing property was evaluated by varying the width of the heating element.

In the evaluation, the width w1 of the heating element h1 in FIG. 1 of the first embodiment was varied between 0.5 mm and 3.0 mm, the longitudinal length l1 was 222 mm, and the heating element h1
The evaluation was performed using a heater having the same center position in the width direction of No. 1 and having the same resistance of the entire heating element. P1 over Bo, which has irregularities on the surface of the recording paper and is disadvantageous for fixing
nd90g / m ² of LTR size (longitudinal paper size 2
16 mm), the temperature of the heater 1 was controlled to 200 ° C., and fixing was performed using a large-size heating element h1.

An evaluation pattern was printed using a printer L having a printing speed of 16 sheets / min and a recording paper conveyance speed of 94.2 (mm / sec), and the image pattern portion was rubbed. Was measured and the rate of decrease was measured to evaluate the fixability.

In this evaluation, the resistance value of the entire heating element of each sample in which the width of the heating element h1 was varied was made uniform, and the evaluation was performed with the calorific value being constant. It turns out that it is advantageous to the property.

In terms of print quality, the rate of decrease in good fixability is about 5
%, And it is understood from FIG. 5 that the width of the heating element h1 needs to be 1.0 mm or more in order to obtain good fixability. This is because if the width of the heating element h1 is too narrow compared to the fixing nip portion, the entire temperature of the substrate 11 in the width direction cannot be increased. , The toner cannot be heated and fixed in the entire fixing nip.

FIG. 5 shows that the width w1 is 1 (mm), 1.5
The results of evaluating the fixing performance of the heater 1 in which the heating elements h1 of (mm) and 3 (mm) are shifted upstream and downstream from the center of the fixing nip portion are shown. As shown in FIG. 4, it can be seen that a wider width w1 of the heating element h1 is advantageous for the fixing property. Heating element h
It can be seen that it is advantageous for the fixing property that the position 1 is arranged such that the center is located about 1 mm upstream with respect to the center of the fixing nip portion. This is presumably because a temperature gradient is generated downstream from the heating element position, and by disposing the heating element h1 at this position, the temperature gradient in the substrate width direction becomes broad.

When the heating element h1 is disposed on the downstream side with respect to the center of the fixing nip, the heating element h2 having a small width has a large rate of deteriorating the fixing property as compared with the heating element h1 having a large width. It can be seen that it is better to arrange the heating element h2 with a narrow width upstream in order to satisfy the fixability of both the heating element h2 with a small width and the heating element h1 with a large width.

In the first embodiment, a small-sized heating element h2 (width w2 = 1.5 mm, longitudinal length 12 = 1) is used.
20 mm) upstream, the center of the small-sized heating element is 2 mm upstream from the center of the fixing nip, and the large-sized heating element h
The center of 1 (width w1 = 3 mm, longitudinal length 11 = 222 mm) was placed 1.2 mm downstream from the center of the fixing nip.

With this arrangement, the temperature gradient in the width direction of the substrate can be broadened when the small-sized heating element h2 and the large-sized heating element h1 are energized, so that the heat generation with a narrow width can be achieved. In both the case where the small-sized recording paper is fixed using the body h2 and the case where the large-sized recording paper is fixed using the wide heating element h1, good fixability with a density reduction rate of 5% or less can be obtained. did it.

(Second Embodiment) FIG. 2 is an enlarged view of a main part of a fixing device according to the present invention in which a heater 1 is mounted on a heater holder 14 and a pressure roller 4 is pressed against the heater 1. Is the same as that of the fixing device shown in FIG. 7, and a detailed description thereof will be omitted. FIG. 2 (a)
Are the heating elements h1, h2 of the heater 1 according to the second embodiment.
FIG. 7 is a diagram for explaining the position in the width direction of FIG. 5 and the temperature gradient in the heater width direction when the heating elements h1 and h2 are energized;
FIG. 2B is a plan view showing the heater 1.

In the second embodiment, a heating element h1 (width w1, length 11) having a small resistance per unit area is arranged on the upstream side, and is used when a large-size sheet is passed and fixed. A heating element h2 (width w2, longitudinal length 12) having a large resistance per unit area is arranged on the downstream side, and is used when a small-size paper is passed and fixed.

The heating element h1 and the heating element h of the second embodiment
2 and the length in the longitudinal direction are as shown in FIG. 2. The resistance value of the resistance material forming the large-sized heating element h1 was used for the large-sized and small-sized heating element of Comparative Example 1. Since a resistor having a resistance value of 1/2 of the resistance material is used, the second
The heat generation amounts of the large-sized heating element and the small-sized heating element of the example of the present invention and the comparative example 1 are the same.

As in the second embodiment, the resistance material forming the large-sized heating element h1 on the upstream side is smaller than the resistance material forming the small-sized heating element h2 on the downstream side. This makes it possible to increase the calorific value by narrowing the width of the large-sized heating element h1. Therefore, the small-sized heating element disposed downstream of the large-sized heating element is also located at the center of the fixing nip. It has become possible to arrange it on the upstream side as compared with. For this reason, when the large and small heating elements h1 and h2 generate heat, the temperature gradient can be broad, and good fixing properties can be obtained.

As a means for adjusting the width of the heating element h1 without changing the heating value of the heating element h1 for large size, a low-resistance material having a different resistance value from the other heating element h2 as in the second embodiment is used. Instead of using a resistive material, a method of changing the amount and the number of coatings using a resistive material having the same resistance value can be considered.

As described above, in the second embodiment, by increasing the resistance per unit area of the heating element h1 disposed on the upstream side, the substrate when each of the heating elements h1 and h2 generates heat is increased. The temperature gradient in the width direction can be broadened, and good fixing properties can be obtained even when each of the heating elements h1 and h2 is used.

(Third Embodiment) FIG. 3 is an enlarged view of a main part of a fixing device according to the present invention in which a heater 1 is mounted on a heater holder 14 and a pressure roller 4 is pressed against the heater 1. Is the same as that of the fixing device shown in FIG. 7, and a detailed description thereof will be omitted. FIG. 3 (a)
Are the heating elements h1, h2 of the heater 1 according to the third embodiment.
FIG. 7 is a diagram for explaining the position in the width direction of FIG. 5 and the temperature gradient in the heater width direction when the heating elements h1 and h2 are energized;
FIG. 3B is a plan view showing the heater 1.

According to the third embodiment, the temperature gradient becomes broad both when the heating element h2 on the upstream side is heated and when the heating element h1 on the downstream side is heated. Also, the portion where the position of the relatively broad temperature gradient when the upstream heating element h2 is used and the position of the relatively broad temperature gradient when the downstream heating element h1 is used overlaps is the downstream heating element. Since the thermistor T is in contact with this position, the temperature of both the heating elements h1 and h2 can be easily controlled.

The control temperature of the fixing device is determined by the heating element h.
It is necessary to control the temperature of 1, h2 within a range of about ± 3 deg. In the third embodiment, a bead t1 of the thermistor T is sandwiched between sponges t2, and the surface thereof is made of aluminum t.
3. Thermistor T beads t
The mounting accuracy at the position in the width direction where the substrate 1 contacts the substrate 11 is about ± 0.5 mm. According to the third embodiment, the control temperature is the temperature difference Dh1 of the heater h1 when the substrate is mounted at the center of the position A at an intersection of ± 0.5 mm in the width direction.
(About 5 deg), the temperature difference Dh2 of the heater h2 (about 5 deg)
g) can be controlled.

As described above, in the third embodiment, the narrow heating element h2 is arranged on the upstream side, so that when a plurality of heating elements h1 and h2 are energized, the temperature gradient is broad. Since the portions overlap near the heating element on the downstream side, by providing the temperature detecting means on the vicinity of the heating element on the downstream side,
Temperature control of a plurality of heating elements can be performed, and good temperature control can be performed with a small number of components.

(Fourth Embodiment) FIG. 6 is a schematic side view of an image forming apparatus of the present invention to which the fixing devices of the first to third embodiments are applied. In the figure, a photosensitive drum 61 as an image carrier is first uniformly charged negatively by a charging means such as a charger 62 while rotating in the direction of an arrow. Image exposure is performed by 63 to form a latent image. This latent image is subjected to reversal development by a negatively charged toner of the developing device 64, and is visualized as an unfixed toner image. Then, the transfer roller 66 is transferred from the registration roller 65 serving as a recording material supply unit to the recording material 8 nipped and conveyed. And the like. After the transfer, the photosensitive drum 61 is cleaned by a cleaning means such as a blade 67 to prepare for the next image forming step.

On the other hand, a recording material 8 carrying an unfixed toner image
The fixing roller 3 and the pressure roller 4 of the fixing device 70 according to any one of the first to third embodiments having a heater (not shown) therein through a conveyance system 68 and an entrance guide plate 69.
Is heated and pressed while being nipped and conveyed at the fixing nip portion of both rollers, so that the unfixed toner image is fixed.

According to the fourth embodiment, the first embodiment
Since any one of the fixing devices of (1) to (3) is applied, it is possible to form a high-quality image free from image defects and the like with good fixing performance.

[0058]

As described above, according to the present invention, a plurality of heating elements having different widths are arranged side by side along the longitudinal direction on the insulating substrate, and the width is set at the upstream side in the insulating substrate width direction in the recording material advancing direction. Since the heater is configured by arranging narrow heating elements, it is possible to broaden the temperature gradient in the width direction of the insulating substrate when energizing and heating each of the plurality of heating elements independently, thereby increasing the heating efficiency. There is an effect that can be.

Further, according to the present invention, a plurality of heating elements are juxtaposed on the insulating substrate along the longitudinal direction thereof, and the heating elements are arranged on the upstream side in the width direction of the insulating substrate in the recording material advancing direction as compared with the heating elements on the downstream side. Since the heater is configured by arranging a heating element having a small resistance per unit area, the entire area of the heating element on the upstream side can be reduced, that is, the width of the heating element can be reduced, and the heating element on the downstream side is also located on the upstream side. The heating elements can be arranged, and when the heating elements generate heat, the temperature gradient in the substrate width direction can be broadened, and the heating efficiency can be increased.

Further, according to the present invention, a plurality of heating elements are juxtaposed on the insulating substrate along its longitudinal direction, and the temperature is set near the heating element located on the downstream side in the width direction of the insulating substrate in the recording material advancing direction. Since the heater is configured to control the temperature of the plurality of heating elements based on the detection signal of the temperature detection means, when the heating element on the upstream side generates heat, the temperature gradient in the substrate is broadened. Also, when the downstream heating element is heated, the temperature gradient becomes broad and the temperature of both heating elements can be easily and accurately controlled.

Further, according to the present invention, since the fixing device is constituted by using any one of the heaters according to the present invention, excessive heating of the non-sheet passing portion is suppressed, and the fixing film, the pressure roller and other members are controlled. Power can be suppressed and good fixability can be obtained without causing thermal damage to the substrate. Further, since the temperature gradient in the substrate width direction becomes broad, there is an effect that a plurality of heating elements can be precisely controlled at a desired temperature with one thermistor.

According to the present invention, the image forming means for forming and carrying the unfixed toner image on the recording material and the fixing means for heating and fixing the unfixed toner image formed and carried on the recording material to the recording material are provided. Since the fixing device of the present invention is used as the fixing unit in the image forming apparatus, the image forming apparatus has good heating characteristics in heat fixing and can perform high-quality image formation without image defects and the like. There is an effect that a device can be obtained.

[Brief description of the drawings]

FIG. 1 is a plan view showing a position in a width direction of a heating element of a heater according to a first embodiment of the present invention, a temperature gradient in a heater width direction when each heating element is energized, and a heater.

FIG. 2 is a plan view showing a position in a width direction of a heating element of a heater according to a second embodiment of the present invention, a temperature gradient in a heater width direction when each heating element is energized, and a heater.

FIG. 3 is a plan view showing a position in a width direction of a heating element of a heater according to a third embodiment of the present invention, a temperature gradient in a heater width direction when each heating element is energized, and a heater.

FIG. 4 is an explanatory diagram of a width of a heating element and a decrease rate of fixability.

FIG. 5 is an explanatory diagram of the width of the heating element and the rate of decrease in fixability when the width of the heating element is varied.

FIG. 6 is a configuration diagram of an image forming apparatus according to a fourth embodiment of the present invention.

FIG. 7 is a configuration diagram illustrating a conventional fixing device.

FIG. 8 shows a comparative example 1 of a conventional fixing device.
It is a top view which shows the position of the width direction of the heating element of a heater, the temperature gradient in the heater width direction when each heating element is energized, and a heater.

FIG. 9 shows a comparative example 2 of a conventional fixing device.
It is a widthwise position of the heating element of the heater and a temperature gradient in a heater width direction when each heating element is energized.

[Explanation of symbols]

1 ... heater, 2 ... heater holder, 3 ... fixing film,
3a: fixing release layer 3b: conductive primer layer, 3c:
Base film, 4 ... Pressing roller, 5 ... Fixing film, 4
a: release layer, 4b: heat-resistant rubber layer, 4c: cored bar, 4d
... conductive rubber ring, 4e ... resistance, 5 ... (metal stay),
5 ': Back electrode type AlN heater, 6: Fixing unit upper frame, 6': Fixing unit lower frame, 7: Fixing unit entrance guide, 7 ': Discharge guide, 8: Recording material (recording paper or paper), 9 ... toner, 11 ... substrate, 12 ... glass, a ... electrode, b ... electrode, c ... electrode, h1 ... heating element, h2 ... heating element, w1 ... width of heating element, w2 ... width of heating element, l1 ... heat generation Length of body, 12: length of heating element, r1: resistance value of heating element, r2: resistance value of heating element, Q1: heat value of heating element, Q
2: Heat generation amount of the heating element, Dh1: Temperature variation control when the heating element h1 is controlled, Dh2: Temperature variation control when the heating element h2 is controlled, T: thermistor, t1: beads of the thermistor, t2 ... Thermistor sponge, t3 ...
Thermistor aluminum.

Continued on the front page (72) Inventor Masahiko Suzumi 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term in Canon Inc. (reference) 2H033 AA03 BA27 BE03 CA17 CA48 3K058 AA13 AA86 BA18 CA23 CA61 CE04 CE13 CE19 DA04 GA06 3K092 PP18 QA05 QB30 QB64 RF03 RF11 RF17 UA06 VV21 VV40

Claims (5)

[Claims] In a heater provided with a heating element which generates heat by energization on the surface of an insulating substrate, a plurality of heating elements having different widths are arranged on the insulating substrate along the longitudinal direction thereof, and the insulating substrate in a recording material advancing direction is provided. A heater in which a narrow heating element is arranged on the upstream side in the width direction. 2. A heater provided with a heating element which generates heat by energization on the surface of an insulating substrate, wherein a plurality of heating elements are juxtaposed on the insulating substrate along the longitudinal direction thereof, and the upstream side in the insulating substrate width direction in the recording material advancing direction. A heater characterized in that a heating element having a smaller resistance value per unit area than a heating element on the downstream side is disposed on the side. 3. A heater provided with a heating element which generates heat by energization on the surface of an insulating substrate, wherein a plurality of heating elements are juxtaposed on the insulating substrate along a longitudinal direction thereof, and a downstream side of the insulating substrate in a recording material advancing direction in a width direction of the insulating substrate. 3. The heater according to claim 1, wherein a temperature detecting means is provided near the heating element located on the side, and the temperature of the plurality of heating elements is controlled based on a detection signal of the temperature detecting means. 4. One of claims 1 to 3
A heat-resistant film that presses and moves on the heater holder; and presses the heat-resistant film against the heater holder to form a fixing nip portion, and the recording material passing through the fixing nip portion is used as a heat-resistant film. And a pressurizing member for heating and fixing the unfixed toner to the recording material surface through the pressure member. 5. An image forming apparatus comprising: an image forming means for forming an image with an unfixed toner on a recording material; and a fixing means for heating and fixing the unfixed toner formed and carried on the recording material to the recording material. An image forming apparatus using the fixing device according to claim 4 as a fixing unit.