JP2002050452A - Heating body, image heating device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a heating body, an image heating device and an image forming device wherein there is no crack in the heating body and wherein a fixing property is superior and wherein they can be produced at a low cost. SOLUTION: An image developing agent carried on a recording material is given a thermal energy of the heating body, and fixed at the recording material by being passed through a nip part between the heating body and a pressed member pressure-contacted to it. The heating body has a substrate and a layer which is formed on an insulating layer installed at one side of the substrate and which generates a heat by a supply g electricity. The substrate consists of metal, and at least one concave is formed at a face opposing to a face wherein a heat generation layer is formed on the substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating element, an image heating apparatus and an image forming apparatus using the heating element, and more particularly, to an image heating apparatus and an image forming apparatus suitable for permanently fixing a toner image in electrophotography to a recording material. .

[0002]

2. Description of the Related Art Conventionally, in an image output apparatus such as a copying machine, a printer, a facsimile or the like using an appropriate image forming process such as electrophotography, electrostatic recording, magnetic recording, etc., the image is formed on a recording material by a transfer method or a direct method. As a device for fixing the developer image carried on the recording material surface, there is a film heating type image heating device. For example, JP-A-63-3131
No. 82, JP-A-2-15778, and the like.

[0003] The devices described in these documents are usually
A thin heat-resistant film, a heating element fixedly supported and arranged on one side of the film, and a heating element arranged opposite to the heating element on the other side, and the recording material is adhered to the heating element via the film. And a pressure member that forms a nip. The heating element has a heating layer composed of a resistor that generates heat when energized, and a ceramic substrate having good thermal conductivity that supports the heating layer. The energization of the heating layer is a detection output of a temperature detection element that detects the temperature of the substrate. Is controlled by Heat fixing, between the film forming the nip and the pressure member,
In the image heating apparatus, the recording material in which a developer image is formed and supported is introduced and passed, and the developing material of the recording material is heated via a film on the surface of the image carrier by a heating element, and heat energy is applied to the recording material. Is imparted to an unfixed image, and the developer is softened and melted, and adhered to a recording material.

Further, the film heating system is not limited to such a fixing device. For example, a heating device for improving the surface properties such as gloss by heating a recording material carrying an image, an image heating device for supposed wearing It can be used effectively as such.

[0005]

In these devices, each component is required to have a low heat capacity in order to quickly control the temperature to a target temperature. Need to raise the temperature. Further, higher speed is required, and the startup power consumption itself tends to be large.

[0006] In a normal operating environment, there is no particular harm caused by a design that gives priority to low heat capacity and high heat conduction in consideration of these quick starts. But, for example,
When several sheets of small-sized thick paper or envelopes are passed together in a stack, even if the paper is in a so-called paper passing area where the paper temperature is controlled at the normal temperature control temperature, the paper may not be In a certain so-called non-sheet passing area, the heating body floats from the pressing member, heat is not absorbed by the pressing member, and the surface temperature of the heating body abnormally rises. The heating element cracks due to the thermal stress caused by the heat.

To prevent this, it is known to use aluminum nitride which has higher strength and higher thermal conductivity than ceramic. However, not only is aluminum nitride very expensive, but if it is used to manufacture a heating element, on the contrary, the thermal conductivity will be too high, and the heating element will be heated from the side of the heating element opposite to the side where the heating layer is located. The heat escapes to the support, and the fixing property at the end in the longitudinal direction deteriorates. further,
The heating body substrate made of aluminum nitride must be cut from a large flat plate to a predetermined size with a cutting device using a laser beam or a diamond cutter, etc.
Processing requires expensive and special equipment, which increases costs.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved heating element, an image heating apparatus and an image forming apparatus having the heating element, which can be manufactured at low cost without cracking of the heating element, good fixability, and low cost. Is to get

[0009]

According to a first aspect of the present invention, there is provided a heating element including a substrate and a resistive layer provided on the substrate and configured to generate heat when energized. The metal substrate is formed with an insulating layer interposed, and at least one recess is formed on a surface of the metal substrate opposite to a surface on which the insulating layer and the resistance layer are formed.

A heating element according to a second aspect of the present invention includes a substrate and a resistance layer provided on the substrate and generating heat by energization. The substrate is made of metal, and the resistance layer is insulated on the metal substrate. The metal substrate is characterized in that a plurality of recesses are formed on a surface of the metal substrate opposite to a surface on which the insulating layer and the resistance layer are formed.

A heating element according to a third aspect of the present invention includes a substrate and a resistance layer provided on the substrate and configured to generate heat when energized. The substrate is made of metal, and the resistance layer is insulated on the metal substrate. One recess formed on the metal substrate and extending along the longitudinal direction of the substrate on the surface opposite to the surface on which the insulating layer and the resistive layer are formed, and having a shape in a longitudinal end region different from that of the central region. Is formed.

The heating element according to the fourth aspect is the third aspect.
Wherein the width of the recess is changed along the longitudinal direction of the heating element.

The heating element according to the fifth aspect is the third aspect of the invention.
Wherein the depth of the recess is changed along the longitudinal direction of the heating body.

According to a sixth aspect of the present invention, there is provided a heating element including a substrate and a resistance layer provided on the substrate and generating heat by energization. The substrate is made of metal, and the resistance layer is insulated on the metal substrate. A plurality of recesses formed along the longitudinal direction of the substrate on the surface of the metal substrate opposite to the surface on which the insulating layer and the resistance layer are formed, and having a different shape at the longitudinal end region from that of the central region. Is formed.

According to a seventh aspect of the present invention, there is provided a heating element.
Wherein the number of the depressions is changed along the longitudinal direction of the heating element.

In the image heating apparatus according to the present invention, a fixedly supported heating element, a film sliding on the heating element, and a nip portion formed by pressing the heating element through the film. Pressurizing member, the recording material having an image held between the film and the pressing member of the nip portion is conveyed, and the recording material is heated by the heat from the heating body via the film. In an image heating apparatus for heating the above image, a heating element includes: a substrate; and a resistance layer, which is formed on an insulating layer provided on one side of the substrate and generates heat by energization. And at least one dent is formed on the surface opposite to the surface on which the resistance layer is formed.

According to a ninth aspect of the present invention, in the image heating apparatus, a nip portion is formed by pressing a fixedly supported heating element, a film sliding on the heating element, and the heating element via the film. Pressurizing member, the recording material having an image held between the film and the pressing member of the nip portion is conveyed, and the recording material is heated by the heat from the heating body via the film. In an image heating apparatus for heating an upper image, a heating element includes a substrate and a resistance layer which is formed on an insulating layer provided on one surface of the substrate and generates heat by energization. And a plurality of recesses formed on the surface opposite to the surface on which the resistance layer is formed.

According to a tenth aspect of the present invention, in the image heating apparatus, a fixedly supported heating element, a film that slides on the heating element, and a nip portion formed by pressing the heating element through the film. Pressurizing member, the recording material having an image held between the film and the pressing member of the nip portion is conveyed, and the recording material is heated by the heat from the heating body via the film. In an image heating apparatus for heating an upper image, a heating element includes a substrate and a resistance layer which is formed on an insulating layer provided on one surface of the substrate and generates heat by energization. And a surface extending in the longitudinal direction of the substrate on a surface opposite to the surface on which the resistive layer is formed, wherein one concave portion having a shape in a longitudinal end region different from that of the central region is formed.

An image heating apparatus according to an eleventh aspect is characterized in that, in the heating element according to the tenth aspect, the width of the recess is changed along the longitudinal direction of the heating element.

According to a twelfth aspect of the present invention, in the image heating apparatus according to the eleventh aspect, the depth of the recess is changed along the longitudinal direction of the heating body.

According to a thirteenth aspect of the present invention, in the image heating apparatus, a nip portion is formed by pressing a fixedly supported heating element, a film sliding on the heating element, and the heating element via the film. Pressurizing member, the recording material having an image held between the film and the pressing member of the nip portion is conveyed, and the recording material is heated by the heat from the heating body via the film. In an image heating apparatus for heating an upper image, a heating element includes a substrate and a resistance layer which is formed on an insulating layer provided on one side of the substrate and generates heat by energization. Extend along the direction,
It is characterized in that a plurality of depressions are formed which are different from those of the central region in the longitudinal end region.

According to a fourteenth aspect of the present invention, in the heating body according to the thirteenth aspect, the number of the recesses is changed along the longitudinal direction of the heating body.

According to a fifteenth aspect of the present invention, in the image heating apparatus according to any one of the eighth to fourteenth aspects, the substrate is made of stainless steel.

An image forming apparatus according to a sixteenth aspect is provided with the image heating device according to any one of the eighth to fifteenth aspects.

[0025]

The heating element according to the first aspect, the image heating apparatus according to the eighth aspect, and the image forming apparatus according to the sixteenth aspect are incorporated in the image heating apparatus because the substrate of the heating element is made of metal. Sometimes, the heating element floats from the pressure member,
Even if heat is no longer absorbed by the pressing member and the surface temperature of the heating element rises abnormally, the substrate does not break due to thermal stress caused by the abnormal temperature rise. The dent reduces the contact area with the member supporting the heating element, and furthermore, acts as a heat insulating layer to suppress heat from escaping from the heating element to the member supporting the heating element. Body, image heating device or image forming device. In addition, the manufacturing and processing of the substrate of the heating element can be performed without expensive equipment, and the material cost of the substrate is low. Therefore, the heating element, the image heating apparatus, or the image forming apparatus can be manufactured at low cost.

The heating element according to the second aspect of the invention, the image heating apparatus according to the ninth aspect of the invention, and the image forming apparatus according to the sixteenth aspect of the present invention have no cracks in the heating element, have good fixing properties, and are manufactured at low cost. In addition to this, even if the width of the heating body substrate is increased for speeding up, a high heat insulating effect can be obtained without lowering the strength of the heating body.

[0027] The heating element according to any one of claims 3 to 7,
The image heating apparatus according to the tenth and fourteenth aspects of the present invention and the image forming apparatus according to the sixteenth aspect of the present invention do not crack the heating element, have good fixing properties, can be manufactured at low cost, and have a long heating element. Since the amount of heat insulation in the hand direction can be changed, uneven fixing in the longitudinal direction of the recording material can be eliminated. That is, the higher the speed of the image heating apparatus and the image forming apparatus, the more severe the fixing property of the longitudinal end of the heating element becomes, and it becomes difficult to keep the fixing property uniform over the entire length of the recording material. The shape of the recess in the direction end region is different from that of the central region, for example,
By increasing the width, depth or number of the recesses at the longitudinal end, the temperature distribution at the longitudinal end of the heating element can be improved, so that uniform fixing can be performed over the entire longitudinal direction of the recording material.

[0028]

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

The image forming apparatus described as an embodiment is, for example, a laser beam printer, and the image heating apparatus is configured for this, that is, a heat fixing apparatus.

(Embodiment 1) As shown in FIG. 1, this heat fixing device includes a film 1, a support 2, a heating body 3, and a pressing means 4.

The film 1 is an endless film that extends long in the front-rear direction of the drawing and is externally fitted to a support 2 serving as a film guide. The film itself is made of a heat-resistant synthetic resin film or metal foil having a thickness of 100 μm or less, preferably 50 μm or less, and 20 μm or more in order to reduce the heat capacity and improve the quick start property. For example, film 1 is made of PTFE resin, P
FA resin, FEP resin single layer film, or polyimide resin, polyamide imide resin, PEEK resin, P
PTFE, PF on the surface of ES resin, PPS resin, etc.
A composite layer film coated with A resin, FEP resin or the like can be employed. Here, the surface of the polyimide resin film is coated with a PTFE resin.

The support 2 has a substantially half-moon cross section, and has substantially the same length as the film 1. Although not shown, end guides are attached to both ends. The end guide has a flange for stopping the film 1 from coming out and a socket for a connector for connecting the heating element 3 to a power source.

The pressing means 4 is in the form of a roller, and presses the film 1 against the heating body 3 to form a nip portion N, and rotates the recording paper P to feed the recording paper P between the film 1 and the heating body 3. While being conveyed, the transfer material P is pressed against the heating element 3 via the film 1 at the nip portion N. This pressure roller has a shaft 4A and an elastic layer 4B made of heat-resistant rubber having good releasability such as silicone rubber.

The heating element 3 extends parallel to the film 1.
It is narrow and elongated, and includes a substrate 20 and a layer 6 formed on an insulating layer 21 on the substrate and generating heat by energization. Attachment to the support 2 is performed by fitting into a seat provided on the lower surface of the support 2 in the longitudinal direction of the support 2 and fixing to the support 2.

FIGS. 2 to 5 show the details of the heating element 3.

The substrate 20 is made of metal, not alumina or aluminum nitride. The material is, for example, an iron-based alloy such as stainless steel, an aluminum alloy, a copper alloy, or the like. In this embodiment, it is made of a thin stainless steel plate having a thickness of 0.3 mm. A recess 26 is provided on one surface of the substrate 20. The depression 26 is in the form of a groove having a constant width and extending straight in the longitudinal direction of the substrate 20, as is well shown in FIG.

The insulating layer 21 is made of a material having a high electrical insulating property, and is coated on the surface of the substrate 20 opposite to the surface on which the recess 26 is formed, and on the lower surface in the figure. The insulating layer 21 is, for example, a heat-resistant glass having a thickness of 50 μm, and is formed on the substrate 20 by screen printing or the like.

The heat generating layer 6 is formed of a resistance heating element that generates heat when energized. The resistance heater 6 is printed and wired on the surface of the insulating layer 21 together with the electrode 25. The resistance heating body 6 and the electrode 25 are electrically insulated from the substrate 20 made of a conductive metal by the insulating layer 21.

The protective layer 7 is made of glass, fluororesin, or the like.
1 is coated.

The electrode 25 is connected to an AC power supply by a connector (not shown), and the resistance heating element 6 generates heat over the entire length by power supplied from the AC power supply through the connector. A temperature detecting element 22 is mounted on the surface of the substrate 20 where the recess or groove 26 is formed, with an insulating layer 23 made of heat-resistant glass interposed. Temperature sensing element 22
Is made of a thermistor bead protected by glass instead of chip thermistor mounting in order to ensure insulation resistance with respect to the substrate 20 made of a conductor, and furthermore, to allow freedom of arrangement. The thermistor beads 22 constitute a part of the temperature adjusting means of the heating element 3, and are led out of the heat fixing device by a lead wire 31. The temperature adjustment is performed by A / D converting the output from the temperature detecting element 22 and taking it into the central processing unit 11, and based on the information, the central processing unit 11 converts the phase of the AC voltage applied to the heating element 3 by the triac 12. In this case, the power supplied to the resistance heating element 6 is adjusted by performing pulse modulation such as frequency control. Further, a thermal fuse 17 as a safety device is incorporated in the surface of the substrate 20 where the groove 26 is formed. The thermal fuse 17 is located inside the groove 26, is disposed on the substrate 20 via an insulating layer 24 made of heat-resistant glass, is fixed to the substrate 20, and
It is drawn out of the heat fixing device and is connected in series to the power supply circuit of the resistance heating element 6.

This heat fixing device is incorporated in, for example, an image forming apparatus as shown in FIG.

This image forming apparatus is a laser beam printer and includes therein a photosensitive drum 101 as an electrophotographic photosensitive member in the form of a drum as an image carrier. The photosensitive drum 101 is rotatably held by the apparatus main body M, and is rotationally driven at a predetermined process speed in a direction of an arrow R1 by driving means (not shown). Around the photosensitive drum 101, a charging roller 10
2, a developing device 104, a transfer device 105, and a cleaning device 106 are sequentially arranged. Further, a paper feed cassette 107 is disposed below the apparatus main body M. An unprinted transfer material P made of a sheet such as paper is stacked and stored in the paper feed cassette 107. On the upper part of the apparatus main body M, a paper discharge tray 114 for stacking and storing printed transfer materials P
Is arranged. Paper cassette 107 and photosensitive drum 1
A paper feed roller 115, a transport roller 108, and a top sensor 109 are arranged between the image forming apparatus 1 and 01. A conveyance guide 11 is provided between the photosensitive drum 101 and the paper discharge tray.
0, a heat fixing device 111, a fixing paper discharge roller 112, and a discharge roller 113 are arranged. The roller has a shaft held by a bearing in the apparatus main body M, and the guide and the sensor are fixed to the apparatus main body M.

In printing, the photosensitive drum 101 is driven to rotate in the direction of arrow R1 by driving means (not shown).
The process is started by uniformly charging to a predetermined polarity and a predetermined voltage by the charging roller 102. The exposed surface of the charged photosensitive drum 101 is subjected to image exposure L based on image information by an exposure unit 103 including a laser optical system, and the charge of the exposed portion is removed, so that an electrostatic latent image is formed on the surface of the photosensitive drum. You. This electrostatic latent image is developed by the developing device 104. The developing device 104 includes the developing roller 10
4a, a developing bias is applied to the developing roller 104a to cause toner as a developer to adhere to the electrostatic latent image on the photosensitive drum 101, and the electrostatic latent image is developed as a toner image. Visualize. The toner image is transferred to the transfer device 10
5 is transferred to a transfer material P such as paper. The transfer material P in the paper feed cassette 107 is pulled out of the paper feed cassette 107 by the paper feed roller 15, conveyed by the roller 108, and passed through the top sensor 109 to the photosensitive drum 1.
The sheet is conveyed to a transfer nip portion between the transfer device 01 and the transfer device 105. At this time, the leading end of the transfer material P is detected by the top sensor 109, and the transfer material P is synchronized with the toner image on the photosensitive drum 101. A transfer bias is applied to the roller of the transfer device 105, whereby the toner image on the photosensitive drum 101 is transferred to a predetermined position on the transfer material P. The transfer material P having the unfixed image carried on the surface by the transfer is conveyed to the heat fixing device 111 according to the present invention along the conveyance guide 110, where the unfixed toner image is heated and pressed, and the transfer material P Is established. Transfer material P after toner image fixing
Is sent out to a paper discharge tray 114 by a fixing paper discharge roller 112. On the other hand, on the photosensitive drum 101 after the transfer of the toner image, the toner remaining on the surface without being transferred onto the transfer material P is removed by the cleaning blade 106a of the cleaning device 106, and is used for the next image formation.
Image formation is performed one after another by repeating these operations.

In the heat fixing, as shown in FIG. 1, a transfer material P carrying a toner image as a developer image is introduced between a film 1 forming a nip portion N and a pressure roller 4. Then, the surface of the toner image carrier of the transfer material P is heated by the heater 3 through the film 1 to apply heat energy to the unfixed image, so that the toner is softened and melted.
This is done by attaching it to

At this time, the heat fixing device according to the present invention can eliminate cracks of the heating element which occur in a conventional heating element using a substrate made of ceramic such as alumina. That is. Also in this heat fixing device, when several small-sized thick papers or envelopes are passed through the heat fixing device in a multi-sheet feeding state, the heating element 3 floats from the pressure roller 4, thereby causing the heating element 3 Abnormal temperature rise occurs in the non-paper passing area. However, in the heat fixing device according to the present invention, since the substrate 20 of the heating element 3 is made of stainless steel, even if the temperature difference between the paper passing area and the non-paper passing area becomes large, cracks may occur in the heating element substrate 20. Does not occur. Further, the grooves 26 of the heating element substrate 20 reduce the contact area of the heating element 3 with the support 2 and, at the same time, act as a heat insulating layer between the heating element 3 and the support 2, and Since the escape of heat can be suppressed, poor fixation of the toner image to the transfer material P due to the escape of heat to the longitudinal end of the heating member can be reduced, and the fixability can be improved.

Further, the manufacture of the substrate can be performed at low cost. Conventionally, alumina, aluminum nitride, and the like, which are known as substrate materials, have poor workability, and are generally cut from a large-sized plate to a predetermined size by a cutting device using a laser beam, a diamond cutter, or the like. . However, in the heating device of the present invention, the heating element substrate 20 is made of stainless steel, the raw material cost is considerably lower than that of alumina, aluminum nitride, or the like.
Even if 6 exists, the substrate can be manufactured without using an expensive processing machine such as a cutting device using a laser beam or a diamond cutter.

(Embodiment 2) FIG. 7 shows another embodiment of the heating element according to the present invention. The figure shows the surface of the substrate of the heating element opposite to the surface on which the heat generating layer is formed, and the thermistor, the thermal fuse and the like are not shown.

The substrate 20A is made of a stainless steel thin plate and has a depression on one side of the substrate, similarly to the heater substrate of the first embodiment. However, the recess 26A is composed of a plurality of narrow straight grooves, for example, three straight grooves. These grooves 26A have the same width, the same length, the same depth and the same shape, and are provided in the substrate 20A in parallel with each other and in the longitudinal direction of the substrate 20A.

An insulating layer made of an electric insulating material is formed on the surface of the substrate 20A opposite to the surface on which the groove 26A is formed. The heat generating layer is made of a resistance heating element and is formed on the insulating layer. The protective layer made of an electrical insulator is formed on the resistance heating element.

This heating element is also fitted into the support in the same manner as in the first embodiment, and a heating and fixing device is formed together with the endless film and the pressure roller. For example, a laser beam printer as shown in FIG. Be incorporated.

In the heat fixing, when the transfer material on which the toner image is formed and carried is conveyed, the toner of the toner image is softened and melted by the heating element of the heating element, and is fixed on the transfer material. At this time, since the substrate 20A is made of a metal plate, there is no failure due to cracking of the heating element due to thermal stress.
Not only the fixability of the toner image to the transfer material is good, but even if the speed is increased, the fixability does not decrease. That is, in order to increase the speed of the image forming apparatus, the width of the heating body substrate is increased or the pressing force of the pressure roller is increased.
When one wide groove is formed in the substrate as in the heat fixing device shown in FIG. 5, the substrate may be bent in the thickness direction. When the substrate bends in the thickness direction, depending on the amount of the bend, the fixability deteriorates, and the fixing unevenness occurs. However, with this heating element, there is no need to provide only one large groove on the entire surface of the substrate,
As a plurality of narrow grooves 26A, increasing the strength in the thickness direction,
Even if the width is increased or the pressing force of the pressure roller is increased, the substrate 20A is prevented from bending, so that image failure due to bending does not occur. And since heat insulation can be ensured by the plurality of grooves 26A, power consumption can be reduced. The production of the heating element is also shown in FIG.
As compared with the heating body substrate of the heating and fixing device described in relation to FIG. 5, almost no extra steps are required, in other words, it can be performed at almost the same cost.

(Embodiment 3) FIG. 8 shows still another embodiment of the heating element according to the present invention. This figure also shows the surface of the substrate of the heating element opposite to the surface on which the heat generating layer is formed, and the thermistor, the thermal fuse, and the like are not shown.

The substrate 20B is also made of a thin plate of metal, for example, stainless steel. On one surface of the substrate 20B, three grooves 26B extending straight along the longitudinal direction of the substrate 20B are provided as recesses. Each of these grooves 26B has a constant width and depth, but differs in length. In other words, one groove at the center of the substrate 20B has a length reaching the longitudinal end of the substrate, but the two grooves adjacent to the longitudinal side edge are longer than the central straight groove. And is arranged only near the longitudinal end of the substrate 20B.

The insulating layer is formed by a straight groove 2 on the substrate 20B.
6B is formed on the surface opposite to the surface on which 6B is formed. The heat generating layer is made of a resistance heating element and is formed on the insulating layer. The protective layer is formed on the resistance heating element.

This heating element is also fitted into the support in the same manner as in the first embodiment, and a heating and fixing device is formed together with the endless film and the pressure roller. For example, a laser beam printer as shown in FIG. Be incorporated.

When the transfer material carrying the toner image is conveyed, the toner is softened and melted by the heating element 20B, and the toner image is fixed on the transfer material. At this time, the substrate 20B of the heating element is made of metal, and not only does not have a failure due to cracking of the heating element, but also increases the number of grooves 20B at the longitudinal end of the substrate to increase the heat insulating property at the longitudinal end of the heating element. , It is possible to secure uniform fixability in the longitudinal direction of the heating element. For example, the higher the speed of the image forming apparatus, the more severe the fixing property of the longitudinal end of the transfer material becomes, and it becomes more difficult to maintain the fixing property uniformly over the entire longitudinal direction. Like groove 2
When the number of 0B is distributed in the longitudinal direction of the heating element, the heat insulating property of the longitudinal end of the heating element is improved, and the power consumption can be reduced. The fixing can be performed without unevenness between parts. The heating element can be manufactured at almost the same cost as the heating element described with reference to FIGS.

(Embodiment 4) FIG. 9 shows another embodiment of the heating element according to the present invention. The figure shows only the substrate, and shows only the surface of the substrate opposite to the surface on which the heat generating layer is formed, and the illustration of the misters and thermal fuses is omitted.

This heating element also has a recess in the form of a longitudinal end region different from that of the central region.

The substrate 20C is made of a stainless steel thin plate. The depression 26C of the substrate 20C is formed of one groove extending along the longitudinal direction. However, the groove 26
C is distributed over the area in the longitudinal direction of the substrate. More specifically, the recess 26C has a constant depth, but has a wider width at the longitudinal end than at the center.

The heating layer is made of a resistance heating element, and
C is formed on the insulating layer from an electric insulating material formed on the surface opposite to the surface on which the recess 26C is formed. A protective layer is formed on the heat generating layer.

This heating element is also fitted to the support in the same manner as in the first embodiment, and a heating fixing device is formed together with the endless film and the pressure roller. For example, a laser beam printer as shown in FIG. Be incorporated. When the transfer material carrying the toner image is conveyed from the photosensitive drum, the heating element 20C softens and melts the toner, the nip portion N presses the melted toner image against the transfer material, and the toner image is permanently fixed on the recording material. Let it. At this time, not only is there no failure due to a crack in the heating element, but also the width of the longitudinal end of the heating element in the groove 20C is increased to enhance the heat insulation at the longitudinal end of the heating element. As in the case of Example 3, uniform fixing properties can be ensured in the longitudinal direction of the heating element, and no extra processing step is required. Therefore, the heating can be performed at substantially the same cost as the heating element described in the first embodiment.

(Embodiment 5) FIG. 10 shows another embodiment of the heating element according to the present invention. The figure shows only the substrate, and shows only the surface of the substrate opposite to the surface on which the heat generating layer is formed. The thermistor and the thermal fuse are not shown.

The shape of the heating element in the end region in the longitudinal direction is different from that of the central region.

The substrate 20D is made of a stainless steel thin plate. The recess 26D is formed of a straight groove having a constant width, but the depth at the longitudinal end is formed deeper than that at the center.

The heating layer is made of a resistance heating element, and
D is formed on the insulating layer from an electric insulating material formed on the surface opposite to the surface on which the recess 26D is formed, and the protective layer is formed on the resistance heating element.

This heating element is also fitted to the support in the same manner as in Examples 1 and 2, and together with the endless film and the pressure roller, a heating fixing device is constituted.
For example, it is incorporated in a laser beam printer as shown in FIG. When the transfer material carrying the toner image is conveyed, the heat fixing device softens and melts the toner by the heating element, and fixes the toner image on the transfer material. At this time, not only is there no failure due to cracking of the heating element, but also the depth of the longitudinal end of the heating element in 20D is increased to enhance the heat insulation at the longitudinal end of the heating element. As in the heat fixing device described with reference to FIG. 9, uniform fixing properties can be secured in the longitudinal direction of the heating element, power consumption can be reduced, and As a result, the heating element can be manufactured at almost the same cost without requiring an extra processing step, and the heat fixing device and the laser beam printer can be obtained at low cost.

[0067]

As described above, according to the present invention,
There is no crack, good fixing property, and a heating element that can be manufactured at low cost can be obtained, and there is no failure due to cracking of the heating element, and the fixing property of the developer image to the transfer material is high,
In addition, the image heating apparatus and the image forming apparatus can be manufactured at low cost.

[Brief description of the drawings]

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

FIG. 2 is a bottom view of a heating element incorporated in the image heating apparatus shown in FIG.

FIG. 3 is a top view of the heating element shown in FIG. 2;

FIG. 4 is a perspective view schematically showing the heating body shown in FIGS. 2 and 3;

FIG. 5 is an enlarged sectional view taken along line AA of FIG. 4;

FIG. 6 is an explanatory diagram illustrating a configuration of an image forming apparatus of the present invention including the image heating device illustrated in FIG. 1;

FIG. 7 is a perspective view schematically illustrating a substrate in another embodiment of the heating body of the present invention.

FIG. 8 is a perspective view schematically illustrating a substrate in another embodiment of the heating body of the present invention.

FIG. 9 is a perspective view schematically illustrating a substrate in still another embodiment of the heating element of the present invention.

FIG. 10 is a perspective view schematically illustrating a substrate in still another embodiment of the heating body of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Film 3 ... Heating body 4 ... Pressurizing member 6 ... Heat generation layer 20, 20A-20D ... Substrate 26, 26A-26D ... Depression N ... Nip part P ... Transfer material

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Claims (16)

[Claims] 1. A heating element comprising a substrate and a resistance layer provided on the substrate and generating heat by energization, wherein the substrate is made of metal, and the resistance layer is provided on the metal substrate with an insulating layer interposed. A heating element, wherein at least one dent is formed on a surface of the metal substrate opposite to a surface on which the insulating layer and the resistance layer are formed. 2. A heating element comprising a substrate and a resistance layer provided on the substrate and generating heat by energization, wherein the substrate is made of metal, and the resistance layer is provided on the metal substrate with an insulating layer interposed therebetween. And a plurality of recesses formed on a surface of the metal substrate opposite to a surface on which the insulating layer and the resistance layer are formed. 3. A heating element comprising a substrate and a resistance layer provided on the substrate and generating heat by energization, wherein the substrate is made of a metal, and the resistance layer is provided on the metal substrate with an insulating layer interposed therebetween. The metal substrate extends along the longitudinal direction of the substrate on the surface opposite to the surface on which the insulating layer and the resistive layer are formed, and is formed with one recess having a form in a longitudinal end region different from that of the central region. A heating element characterized in that: 4. The heating element according to claim 3, wherein the width of the recess is changed along the longitudinal direction of the heating element. 5. The heating element according to claim 3, wherein the depth of the recess is changed along the longitudinal direction of the heating element. 6. A heating element comprising a substrate and a resistance layer provided on the substrate and generating heat by energization, wherein the substrate is made of metal, and the resistance layer is provided on the metal substrate with an insulating layer interposed therebetween. Is formed, extending along the longitudinal direction of the substrate on the surface opposite to the surface on which the insulating layer and the resistive layer are formed, and a plurality of recesses having a shape in a longitudinal end region different from that of the central region are formed. A heating element characterized in that: 7. The heating element according to claim 6, wherein the number of the depressions is changed along the longitudinal direction of the heating element. 8. A heating body fixedly supported, a film sliding on the heating body, and a pressure member for forming a nip portion by pressing against the heating body via the film. An image heating apparatus that sandwiches and conveys a recording material carrying an image between the film and the pressing member in the nip portion and heats the image on the recording material by heat from the heating body via the film Wherein the heating element comprises a substrate and a resistive layer formed on an insulating layer provided on one side of the substrate, the resistive layer generating heat when energized. The substrate is made of metal, and is opposite to the surface on which the resistive layer and the resistive layer are formed. An image heating device characterized in that at least one recess is formed on a surface. 9. A fixedly supported heating element, a film that slides on the heating element, and a pressure member that presses against the heating element via the film to form a nip portion. An image heating apparatus that sandwiches and conveys a recording material carrying an image between the film and the pressing member in the nip portion and heats the image on the recording material by heat from the heating body via the film Wherein the heating element comprises a substrate and a resistive layer formed on an insulating layer provided on one surface of the substrate, the resistive layer being heated by energization. The substrate is made of metal and is opposite to the surface on which the insulating layer and the resistive layer are formed. An image heating device, wherein a plurality of recesses are formed on a surface. 10. A heating body fixedly supported, a film sliding on the heating body, and a pressure member for forming a nip by pressing the heating body through the film. An image heating apparatus that sandwiches and conveys a recording material carrying an image between the film and the pressing member in the nip portion and heats the image on the recording material by heat from the heating body via the film Wherein the heating element comprises a substrate and a resistive layer formed on an insulating layer provided on one surface of the substrate, the resistive layer being heated by energization. The substrate is made of metal and is opposite to the surface on which the insulating layer and the resistive layer are formed. An image heating apparatus characterized in that a surface is formed along the longitudinal direction of the substrate, and one recess is formed in the longitudinal end region, the form being different from that of the central region. 11. The heating element according to claim 10, wherein
An image heating apparatus characterized in that the width of the recess is changed along the longitudinal direction of the heating element. 12. The heating element according to claim 11,
An image heating apparatus characterized in that the depth of the recess is changed along the longitudinal direction of the heating body. 13. A heating body fixedly supported, a film sliding on the heating body, and a pressure member for pressing the heating body through the film to form a nip portion. An image heating apparatus that sandwiches and conveys a recording material carrying an image between the film and the pressing member in the nip portion and heats the image on the recording material by heat from the heating body via the film A heating element comprising: a substrate; and a resistance layer formed on an insulating layer provided on one surface of the substrate, the resistance layer generating heat when energized. The substrate is made of metal, extends along the substrate longitudinal direction, and has a longitudinal end. An image heating apparatus, wherein a plurality of depressions different in form from the central area are formed in the partial area. 14. The heating element according to claim 13, wherein
An image heating apparatus characterized in that the number of depressions is changed along the longitudinal direction of the heating element. 15. The image heating apparatus according to claim 8, wherein the substrate is made of stainless steel. 16. An image forming apparatus comprising the image heating device according to claim 8.