JP7013433B2 - Image heating device - Google Patents

Description

The present invention relates to an image heating device.

In the heating and fixing device as an image heating device provided in an image forming device that employs an electrophotographic method, an electrostatic recording method, etc., power is not supplied to the fixing device during standby, and film heating that suppresses power consumption as low as possible. The type fixing device has been put into practical use.
In recent years, there have been various demands for image forming devices such as copiers and printers, such as faster printing speed, improved quick startability, energy saving, and compactification. Against this background, film heating type fixing devices are widely used.
In the film heating type fixing device, the film and the pressurizing member are pressure-welded, and a heater (heating body) for heating the film is arranged inside the film on the inner surface of the portion facing the pressurizing member. As a method for driving the film in such a fixing device, a method in which a drive roller is provided on the inner peripheral surface of the film to drive the film while applying tension, or a method in which a member supporting the film is loosely supported to drive the pressure roller. A method of driven rotation is known. In recent years, the latter pressure roller drive type is often adopted because the number of parts is small.

Here, in the film heating type fixing device, the temperature rise at the end described below is mentioned as an existing problem.
When the recording material is passed through the fixing device and fixed, the surface temperature of the non-passing area of the pressure roller (outside the area through which the recording material is conveyed) may rise excessively. This is because heat is partially stored in the non-passing area of the fixing nip portion where the recording material does not pass, because the heat is not taken by the recording material. This phenomenon is referred to as temperature rise at the end of the fixing device or temperature rise at the non-passing portion, and when the temperature rise at the end becomes high, it has a thermal peak, which leads to the occurrence of hot offset and melting of the heater holder.
In order to solve this problem of temperature rise at the end, it has been proposed to make the temperature distribution of the heater uniform by arranging a heat conductive member between the back surface of the heater and the heater holder as in Patent Document 1. When using a heat conductive member, it has been proposed as in Patent Document 2 that the heat conductive member is electrically divided and used to ensure safety.

Japanese Unexamined Patent Publication No. 11-841919 Japanese Unexamined Patent Publication No. 2014-123100

However, in the case of the above-mentioned conventional technology, there is a concern that the following problems may occur.
In the configuration disclosed in Patent Document 1, it is necessary to provide the heat conductive member with an insertion portion into the heater holder. This is because if the heat conductive member is not positioned in the longitudinal direction of the fixing nip portion, the heat conductive member is displaced, especially when the end portion is displaced from the temperature rising portion. This is because there is a concern that the desired effect of suppressing the temperature rise at the end may not be exhibited. However, when the heat conductive member is provided with an insertion portion into the heater holder, the heat capacity of the insertion portion becomes larger than that of the peripheral portion. Therefore, there is a concern that the soaking effect is promoted at the insertion portion, the temperature of the heater is locally lowered, and fixing failure corresponding to the width of the insertion portion is caused.
Further, when a plurality of heat conductive members are arranged as in the configuration disclosed in Patent Document 2, a gap is formed between the heat conductive members and the heat conductive members. Since the heater corresponding to the gap does not come into contact with the heat conductive member, the heat equalizing effect is reduced, the temperature of the heater rises locally, and image defects such as hot offset corresponding to the width of the gap may occur. I am concerned.

The present invention has been made in view of the above circumstances, and is a technique capable of suppressing local temperature unevenness of a heater and obtaining a good image while maintaining the heat equalizing effect of the heat conductive member. The purpose is to provide.

In order to achieve the above object, in the present invention,
A heater containing a substrate and a heating element arranged on the substrate,
A heat conductive member that is contact-arranged with the heater and for uniformizing the temperature distribution in the longitudinal direction of the heater.
A flexible sleeve that is rotatably provided and slides on the heater,
A pressure member forming the heater and the nip portion via the flexible sleeve,
Have,
In an image heating device that sandwiches, conveys, and heats a recording material on which a developer image is formed between the flexible sleeve and the pressure member in the nip portion.
The heat conductive member is provided with a first region and a second region having a smaller heat capacity per unit length in the longitudinal direction than the first region.
The heater is
The first heater region in contact with the first region and
The second heater region in contact with the second region and
Is provided,
The length of the width of the entire first heating element corresponding to the first region in the direction orthogonal to the longitudinal direction is the first length, and the length of the width of the entire second heating element corresponding to the second region. Is a second length that is longer than the first length.
The calorific value per unit length in the longitudinal direction of the first heater region is set to be larger than the calorific value per unit length in the longitudinal direction of the second heater region .

A heater containing a substrate and a heating element arranged on the substrate ,
A heat conductive member that is contact-arranged with the heater and for uniformizing the temperature distribution in the longitudinal direction of the heater.
A flexible sleeve that is rotatably provided and slides on the heater,
A pressure member forming the heater and the nip portion via the flexible sleeve,
Have,
In an image heating device that sandwiches, conveys, and heats a recording material on which a developer image is formed between the flexible sleeve and the pressure member in the nip portion.
A plurality of the heat conductive members are arranged with a gap along the longitudinal direction.
The heater is provided with a contact region in which the heat conductive member contacts and a third heater region corresponding to the gap portion.
The length of the width of the entire first heating element corresponding to the contact region in the direction orthogonal to the longitudinal direction is the first length, and the length of the width of the entire second heating element corresponding to the gap portion is the first length. It is a second length longer than the first length, and is
The calorific value per unit length in the longitudinal direction of the third heater region is set to be smaller than the calorific value per unit length in the longitudinal direction of the contact region.

According to the present invention, it is possible to suppress local temperature unevenness of the heater and obtain a good image while maintaining the heat equalizing effect of the heat conductive member.

Sectional drawing which shows the schematic structure of the image forming apparatus of embodiment The figure which shows the schematic structure of the fixing device of an embodiment. Schematic diagram showing the heater of the embodiment Schematic diagram of the configuration in which the heat conductive member is not arranged on the back surface of the heater Schematic cross-sectional view of the configuration of this embodiment in which the heat conductive member is arranged on the back surface of the heater. The figure which shows the structure which the position in the longitudinal direction of a heat conduction member is not regulated. Schematic diagram showing the dimensional relationship of the heat conductive member alone in Example 1. The figure which shows the dimensional relationship of the heat conduction member and a heater in Example 1. The figure which shows the temperature distribution measurement result in the whole length direction. The figure which shows the dimensional relationship of the heat conduction member and a heater in Example 2. Schematic diagram for explaining the cross-sectional shape of the holder in Example 2. The figure which shows the temperature distribution measurement result in the whole length direction. Schematic diagram showing the dimensional relationship of each of the heat conductive members in Example 3 as a single unit. The figure which shows the dimensional relationship of the heat conduction member and a heater in Example 3. The figure which shows the temperature distribution measurement result in the whole length direction.

Hereinafter, embodiments for carrying out the present invention will be exemplified in detail with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment should be appropriately changed depending on the configuration of the apparatus to which the invention is applied and various conditions, and the present invention The scope is not intended to be limited to the following embodiments.

(1) Image Forming Device FIG. 1 is a cross-sectional view showing a schematic configuration of the image forming device of the present embodiment. In this embodiment, a transfer type electrophotographic process type laser printer will be described as an image forming apparatus.
In FIG. 1, reference numeral 1 denotes a rotary drum type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) as an image carrier, which is rotationally driven at a predetermined frequency (process speed) in the direction of arrow a. The photosensitive drum 1 has a structure in which a photosensitive material layer such as OPC / amorphous Si is formed on the outer peripheral surface of a cylinder (drum) -shaped conductive substrate such as aluminum or nickel. The surface of the photosensitive drum 1 is uniformly charged to a predetermined polarity and potential by the charging roller 2 in the rotation process. After that, the laser beam scanner 3 performs a scanning exposure L with a laser beam corresponding to the image information on the charged surface of the photosensitive drum 1, so that a latent image (static) corresponding to the target image information is performed on the surface of the photosensitive drum 1. Electrolatent image) is formed. The latent image is developed by the toner (developer) T in the developing apparatus 4 and visualized. As the developing method, a jumping developing method, a two-component developing method, a FEED developing method, or the like is used, and it is often used in combination with image exposure and reverse development.

On the other hand, the recording materials P housed in the feeding cassette 9 are fed out one by one by the drive of the feeding roller 8, and the pressure contact portion between the photosensitive drum 1 and the transfer roller 5 is passed through a sheet path having a guide / resist roller. It is supplied to the transfer nip portion, which is, at a predetermined control timing. Then, when a positive transfer bias is applied to the transfer roller 5 by the transfer bias application power supply, the negative electrode toner image (developer image) on the surface of the photosensitive drum 1 is transferred onto the recording material P at the transfer nip portion. Toner.
After that, the recording material P on which the toner image is transferred at the transfer nip portion is introduced into a heat fixing device (hereinafter, fixing device) 6 as an image heating device and undergoes a heat fixing process of the toner image. The fixing device 6 will be described in detail in the section (2). The recording material P that has passed through the fixing device 6 is printed out on the discharge tray through a sheet path having a transport roller, a guide, and a discharge roller. Further, the surface of the photosensitive drum 1 that has passed through the transfer nip portion is cleaned by a cleaning device 7 for removing deposits such as transfer residual toner, and is repeatedly subjected to image drawing.

(2) Fixing device 6
2A and 2B are views showing a schematic configuration of the fixing device 6 of the present embodiment, FIG. 2A is a sectional view of the fixing device 6, FIG. 2B is a sectional view of a heater, and FIG. 2C is a sectional view of the heater. It is an exploded perspective view of the fixing device 6.
The fixing device 6 of the present embodiment is basically a film heating type fixing device including a fixing assembly 10 and a pressure roller 20 that are pressed against each other to form a nip portion N. As shown in FIGS. 2A and 2C, the fixing assembly 10 mainly receives pressure from the fixing film 13, the heater 11, the heat conductive member 17, the holder 12, and the pressure spring 15 to press the holder 12. It is composed of a metal stay 14 that presses against the pressure roller 20.

[Fixing film 13]
The fixing film 13 is rotatably provided and corresponds to a flexible sleeve that slides on the heater 11. In the present embodiment, the fixing film 13 is a heat-resistant film set to a total thickness of 200 μm or less in order to enable quick start. The fixing film 13 is formed of a heat-resistant resin such as polyimide, polyamide-imide, or PEEK, or a pure metal or alloy such as SUS, Al, Ni, Cu, or Zn having heat resistance and thermal conductivity as a base layer. In the case of a resin base layer, a heat conductive powder such as BN, alumina, or Al may be mixed in order to improve the heat conductivity. Further, in order to form a fixing device having a long life, the fixing film 13 having sufficient strength and excellent durability needs to have a total thickness of 20 μm or more. Therefore, the optimum total thickness of the fixing film 13 is 20 μm or more and 200 μm or less.

Further, in order to prevent offset and ensure the separability of the recording material, a fluororesin such as PTFE, PFA, FEP, ETFE, CTFE, PVDF, and a heat-resistant resin having good releasability such as silicone resin are mixed or independently on the surface layer. It is coated to form a releasable layer. Here, PTFE is polytetrafluoroethylene, PFA is tetrafluoroethylene perfluoroalkyl vinyl ether copolymer, and FEP is tetrafluoroethylene hexafluoropropylene copolymer. ETFE is an ethylene tetrafluoroethylene copolymer, CTFE is polychlorotrifluoroethylene, and PVDF is polyvinylidene fluoride.

As a coating method, the outer surface of the fixing film 13 may be etched and then the releaseable layer may be dipped, or a powder spray or the like may be applied. Alternatively, a method may be used in which the surface of the fixing film 13 is covered with a resin formed in a tube shape. Alternatively, a method may be used in which the outer surface of the fixing film 13 is blasted and then a primer layer as an adhesive is applied to cover the releasable layer. In this embodiment, a fixing film having a total thickness of 75 μm and an outer diameter of φ18 mm is used, which comprises a PFA having a surface layer (release layer) having a thickness of 10 μm, a primer layer having a thickness of 5 μm, and a base layer having a thickness of 60 μm.

[Heater 11]
As shown in FIG. 2B, the heater 11 as a heating member heats the nip portion N by coming into contact with the inner surface of the fixing film 13. The heater 11 has a low heat capacity plate shape. Then, on the surface of the insulating ceramic substrate 11a such as alumina or aluminum nitride, a resistance heating element 11b such as Ag / Pd (silver-palladium), _RuO2 , _Ta2N , etc. is attached to the screen along the longitudinal direction of the nip portion N. It is formed by printing or the like. At this time, the resistance heating element 11b is formed to have a thickness of about 10 μm and a width of about 1 to 5 mm.
A protective layer 11c is provided on the surface of the heater 11 in contact with the fixing film 13 to protect the resistance heating element within a range that does not impair the thermal efficiency. It is desirable that the thickness of the protective layer is sufficiently thin and the surface property is good, and a glass coat having a thickness of about 30 to 200 μm is generally used. In the following description, the longitudinal direction in the nip portion N is simply referred to as the longitudinal direction.

Here, there is a configuration in which the width of the resistance heating element is made narrower than the other parts to increase the partial resistance and the amount of heat generated is increased, which has been put into practical use. In the following description, the portion where the width of the resistance heating element is narrowed is referred to as a throttle portion, the portion where the width of the resistance heating element is widened is referred to as a reverse throttle portion, and the amount of change in width is referred to as a throttle amount. The throttle amount is an amount indicating what percentage of the resistance heating element other than the throttle portion is when the resistance value per unit area of the resistance heating element is 100%, and the thickness of the resistance heating element is constant. Moreover, assuming that there is no partial variation in the volume resistance value of the resistance material, it is expressed by the following equation.
Aperture amount (%) = (width of resistance heating element other than the aperture) / (width of resistance heating element in the aperture)
Since the resistance value and the calorific value are proportional to each other, the throttle amount may be considered as the ratio of the calorific value per unit area. The heater 11 will be described in detail in section (4).

[Pressurized roller 20]
The pressure roller 20 as a pressure member is an elastic roller in which an elastic layer 22 is formed on the outer peripheral side of a metal core metal 21 such as SUS, SUM, or Al. Examples of the elastic layer 22 include an elastic solid rubber layer formed of heat-resistant rubber such as silicone rubber and fluororubber, and an elastic sponge rubber layer formed by foaming silicone rubber in order to have a more heat insulating effect. Further, as the elastic layer 22, an elastic bubble rubber layer in which a hollow filler (microballoon or the like) is dispersed in the silicone rubber layer and a gas portion is provided in the cured product to enhance the heat insulating effect can be exemplified. Further, a release layer such as a perfluoroalkoxy resin (PFA) or a polytetrafluoroethylene resin (PTFE) may be formed on the outer peripheral side of the elastic layer 22. In this embodiment, a pressure roller having an outer diameter of φ20 mm using Al as the core metal 21, silicone rubber as the elastic layer 22, and PFA as the release layer was used.

[Heat conduction member 17]
The heat conductive member 17 is arranged in contact with the heater 11 to make the temperature distribution of the heater 11 uniform. In the present embodiment, the heat conductive member 17 is sandwiched and held between the heater 11 and the holder 12 as a holding member for holding the heater 11, and is an insulating ceramic substrate 11a of the heater 11 made of alumina, aluminum nitride, or the like. It is made of a material with better thermal conductivity. As the heat conductive member 17, a graphite sheet obtained by processing Al, Cu, Ag, and graphite into a sheet can be exemplified. It is desirable that the thermal conductivity of the heat conductive member 17 is at least larger than the heat conductivity of the substrate 11a of the heater 11. The heat conductive member 17 will be described in detail in section (4).

[Drive and control method of fixing device 6]
The fixing assembly 10 is pressed against the elasticity of the pressure roller 20 by the following configuration to form a predetermined nip portion N. That is, as shown in FIG. 2 (c), both ends of the metal stay 14 in the longitudinal direction protrude from the holder 12, and the spring receiving portions 14a at both ends of the stay are pressure springs 15 via the spring receiving members. Pressurized by. The load is uniformly transmitted in the longitudinal direction of the holder 12 via the stay foot portion 14b. In the nip portion N, the fixing film 13 is sandwiched between the heater 11 and the pressurizing roller 20 due to the pressing force, and is bent so as to be in close contact with the heating surface of the heater 11.

The pressurizing roller 20 obtains a driving force that rotates in the direction of the arrow in FIG. 2A from a driving gear (not shown) provided at the end of the core metal 21. This driving force is transmitted by a motor (not shown) according to a command from a CPU (not shown) that controls the control means. Along with the rotational drive of the pressure roller 20, the fixing film 13 is driven to rotate due to the frictional force with the pressure roller 20. By interposing a lubricating material such as fluorine-based or silicone-based heat-resistant grease between the fixing film 13 and the heater 11, the frictional resistance is suppressed to a low level, and the fixing film 13 can rotate smoothly.

Further, the temperature control of the heater 11 is appropriately controlled by determining the duty ratio, wave number, etc. of the voltage applied by the CPU to the energization heat generation resistance layer according to the signal of the thermistor (not shown) which is a heat sensitive element. The temperature inside the fixing nip is kept at the specified fixing set temperature. The holder 12 is provided with a through hole, and the thermistor is arranged so as to come into contact with the heat conductive member 17 through the through hole. That is, the heat sensitive element is arranged so as to sense the heat of the heater 11 via the heat conductive member 17. The recording material P holding the unfixed toner image is appropriately supplied by a supply means (not shown) at a predetermined timing, and is conveyed into the nip portion N for heat fixing. The recording material P, which is heat-fixed while being sandwiched and conveyed by the nip portion N, is guided by a discharge guide (not shown) and discharged.

(3) Effect of heat conductive member 17 In this section, the influence of heat conductive member 17 will be described in detail.
3A and 3B are schematic views showing the heater 11 of the present embodiment, FIG. 3A is a plan view of the heater 11, FIG. 3B is a sectional view of the heater 11, and FIG. 3C is a heat conductive member. 17 is a plan view and FIG. 3D is a side view of the heat conductive member 17.
As shown in FIG. 3A, the heater 11 is formed by forming a resistance heating element 11b made of Ag / Pd (silver-palladium) on an alumina substrate by screen printing, and further connecting an electric contact portion to the resistance heating element 11b. .. The two resistance heating elements 11b are connected in series and have a resistance value of 14Ω. As shown in FIG. 3B, a glass coat having a thickness of 60 μm was formed as the protective layer 11c so as to cover the resistance heating element 11b. The substrate 11a has a rectangular parallelepiped shape having a length of 270 mm in the longitudinal direction, a length of 6.0 mm in the lateral direction, and a thickness of 1 mm. Here, on the substrate 11a, the direction orthogonal to the longitudinal direction is referred to as the lateral direction. The lateral direction is the same as the transport direction (recording material transporting direction) of the recording material transported by the nip portion N.

The resistance heating element 11b has a pattern folded back via an electric contact portion at an end portion in the longitudinal direction, and two resistance heating elements 11b extending in the longitudinal direction are arranged side by side in the recording material transport direction. The resistance heating elements 11b located upstream and downstream in the recording material transport direction are each formed to have the same shape (no drawing shape in the pattern), and the length in the longitudinal direction is 218 mm (on both sides in the longitudinal direction with respect to the paper center O). Each has a length of 109 mm), and the length in the lateral direction is 1.0 mm.
Here, the position of the center in the longitudinal direction in the region through which the recording material is conveyed is defined as the paper center O. Further, at the longitudinal end of the heater 11, the end having an electric contact portion is referred to as a feeding portion 11d, and the end having a folded pattern is referred to as a folded portion 11e. In the present embodiment, the thermistor (not shown) is arranged at a position 25 mm outside in the longitudinal direction from the paper center O. When the position of the thermistor is shown in the figure, it is shown in the figure by using the reference numeral S.
Further, the heat conductive member 17 is a uniform metal plate made of an aluminum material (pure aluminum, alloy number A1050) as shown in FIGS. 3 (c) and 3 (d), and has a length of 218 mm in the longitudinal direction. (109 mm on each side in the longitudinal direction with respect to the center O of the paper), the width is 6 mm, and the thickness is 0.3 mm.

FIG. 4A is a schematic cross-sectional view of a configuration in which the heat conductive member 17 is not arranged on the back surface of the heater 11, and FIG. 5A is a configuration of the present embodiment in which the heat conductive member 17 is arranged on the back surface of the heater 11. It is a schematic sectional view. Since the aluminum metal plate which is the heat conductive member 17 thermally expands, a gap of 1 mm or more is provided between both ends of the heat conductive member 17 in the longitudinal direction and the holder 12. Here, the back surface of the heater 11 to which the heat conductive member 17 is contact-arranged refers to the surface of the substrate 11a opposite to the surface on which the resistance heating element 11b is formed.
When the temperature rise at the end described in the background technology section becomes a problem, a recording material (recording material with a large basis weight) having a width smaller than the width of the resistance heating element 11b and a high fixing control temperature is continuously used. The case of printing is generally known.
Therefore, the evaluation method of the temperature distribution over the entire longitudinal direction is as follows. If the temperature of the temperature riser at the end exceeds 250 ° C., problems will occur in the fixing performance and the durability of the pressure roller 20, and if the temperature exceeds 300 ° C., the holder will start to melt. The evaluation method of the end temperature rise will be described in detail below.

[Evaluation method of temperature distribution over the entire longitudinal direction]
Environment: 15 ° C / 10%
Paper type: A4 (width 210 mm) size, basis weight 128 g / m ² plain paper Passing mode: Continuous printing from cold state Print speed: Approximately 220 mm / s
Fixing control temperature: 230 ° C
When 250 sheets of recording material were passed by the above-mentioned paper passing method, the surface temperature of the pressure roller 20 was measured with a thermotracer (TH9100 manufactured by Nippon Avionics Co., Ltd.).

FIG. 4B is a diagram for explaining the result of evaluating the temperature rise at the end portion in the configuration (in the comparative example) in which the heat conductive member 17 is not arranged on the back surface of the heater 11.
The temperature of the paper-passing region (the region through which the recording material is conveyed) is controlled by using a thermistor (not shown), and the surface temperature of the pressure roller 20 is stable at about 80 ° C. In the non-paper-passing region, there was a thermal peak at a position 2 to 3 mm outside from the end position of the recording material to be passed, and the maximum temperature was 270 ° C. The temperature in the non-paper-passing region exceeded 250 ° C., which caused problems in fixing performance and durability of the pressurizing roller.

FIG. 5B is a diagram for explaining the result of evaluating the temperature rise at the end in the configuration (of the present embodiment) in which the heat conductive member 17 is arranged on the back surface of the heater 11.
The temperature of the paper-passing region is controlled by using a thermistor (not shown), and the surface temperature of the pressure roller 20 is stable at about 80 ° C.
In the non-paper-passing region, although there is a thermal peak at a position 2 to 3 mm outside the edge of the recording material to be passed, the maximum temperature is 230 ° C, which is suppressed to a temperature that does not cause problems such as fixing performance. did it. By arranging a heat conductive member having a heat conductivity on the back surface of the heater 11 rather than an insulating ceramic substrate, heat can be easily transferred in the thickness direction, the width direction, and the length direction, and the temperature of the entire fixing device as a whole is local. The gradient is greatly relaxed.
The area where the recording material is passed is repeatedly heat-removed and cooled by the recording material, and the total amount of heat transferred is proportional to the temperature gradient. Will move. On the other hand, as described in the section of the problem, if the position of the heat conductive member 17 in the longitudinal direction is not regulated, there is a concern that the effect of suppressing the temperature rise at the end may not be obtained.

FIG. 6 is a diagram for explaining a configuration in which the heat conductive member 17 is arranged on the back surface of the heater 11, but the position of the heat conductive member 17 in the longitudinal direction is not regulated. FIG. 6A shows a state in which the heat conductive member 17 is arranged at a desired position as shown in FIG. 6 (b) shows a state in which the heat conductive member 17 is displaced by 1 mm to the right side (feeding portion 11d side) of the figure, and FIG. 6 (c) shows a state shown in FIG. 6 (b). The result of evaluating the temperature rise at the end when the heat conduction member 17 is displaced is shown.
As shown in FIG. 6C, the maximum temperature on the left side (folded portion 11e side) rises from 230 ° C to 250 ° C, and on the right side (feeding portion 11d side), the maximum temperature rises from 230 ° C to 210 ° C. It has improved. In the region where the maximum temperature reached 250 ° C., fixing failure occurred.
The above phenomenon is related to the heat capacity of the heat conductive member 17 immediately below the thermal peak position of the portion where the temperature is raised at the end.

6 (d) and 6 (e) are views showing the volume of the heat conductive member 17 immediately below the thermal peak position of the portion where the temperature is raised at the end. 6 (d) shows the left side (folded portion 11e side) of the heat conductive member 17 shown in FIG. 6 (b), and FIG. 6 (e) shows the heat conductive member shown in FIG. 6 (b). The right side (feeding portion 11d side) of 17 is shown. Further, FIG. 6 (d) shows that the volume is reduced by 25% because the heat conductive member 17 is displaced to the right side (feeding portion 11d side) by 1 mm, and in FIG. 6 (e), the heat conductive member 17 is on the right side. It shows that the volume increased by 25% by shifting 1 mm to (feeding portion 11d side).

According to the study results of the present inventors, it was found that when the heat capacity of the heat conductive member 17 is increased, the temperature of the heater 11 at the position where the heat capacity is increased is lowered, and the effect of suppressing the temperature rise at the end is high. Since the heat capacity is represented by the product of the mass of the material (the product of the volume and the specific gravity) and the specific heat, increasing the volume of the heat conductive member 17 will increase the heat capacity. That is, in the present embodiment, the change amount of the surface temperature of the pressure roller 20 is 20 ° C. (= 0.8 ° C./%) with respect to the change amount of 25% in the heat capacity of the heat conductive member 17.
From the above, it can be seen that the heat conductive member 17 must not move in the longitudinal direction and the position must be regulated in order to exert the desired effect of suppressing the temperature rise at the end portion.

(4) Examples The present invention will be described in detail below with reference to specific examples. In the examples described below, the same components as those in the above-described embodiment are designated by the same reference numerals, and the description thereof will be omitted.
(Example 1)
The first embodiment will be described below.
7A and 7B are schematic views showing the dimensional relationship of the heat conductive member 17 alone in this embodiment, FIG. 7A is a perspective view, and FIGS. 7B to 7D are FIGS. 7A. It is a figure seen from the direction indicated by arrows b to d. FIG. 8 is a diagram showing a dimensional relationship between the heat conductive member 17 and the heater 11 in this embodiment.
In this embodiment, one metal plate is used as the heat conductive member 17. Then, as a positioning configuration in the longitudinal direction of the heat conductive member 17, a bent portion (protruding portion) 17a that is the same body (integral) with the metal plate is provided, and the bent portion 17a is inserted into a through hole provided in the holder 12 and engaged. It was configured to match. The through hole was made slightly larger than the bent portion 17a in order to absorb the thermal expansion of the metal plate.

Here, the heat capacity of the metal plate and the calorific value of the heater 11 when the bent portion 17a is provided on the metal plate will be described.
When the metal plate is provided with the bent portion 17a, the heat capacity of the region 17a1 of the metal plate including the bent portion 17a is larger than the heat capacity of the region 17a2 not including the bent portion 17a. At this time, there is a concern that local temperature unevenness may occur in the heater 11 due to the difference in heat capacity between the regions 17a1 and the regions 17a2 in the metal plate.
Therefore, in this embodiment, the calorific value of the heater 11 is set as follows according to the relationship between the heat capacity and the temperature of the heater described above.
Here, of the region of the heater 11 that heats the nip portion N, the region where the temperature for heating the nip portion N is controlled (adjusted or changed) by the contact with the region 17a1 of the heat conductive member 17 is the heater region 11b1. And. Further, of the region of the heater 11 that heats the nip portion N, the region where the temperature for heating the nip portion N is controlled by the contact with the region 17a2 of the heat conductive member 17 is referred to as the heater region 11b2. The region 17a1 is a region including the bent portion 17a (a region surrounded by a dotted line in the heat conductive member 17 shown in FIG. 8) among the regions along the lateral direction of the metal plate, and the region 17a2 is a metal. The area of the board is other than the area 17a1. The regions 17a1 and 17a2 are arranged side by side in the longitudinal direction.
At this time, in this embodiment, the calorific value of the heater region 11b1 is increased from the heater region 11b2 so that the temperature difference between the heater region 11b1 and the region of the nip portion N heated in the heater region 11b2 becomes zero. Also set large. Here, the difference in temperature does not have to be zero, and may be smaller than the case where the calorific value of the heater region 11b1 and the calorific value of the heater region 11b2 are assumed to be the same.

Hereinafter, this embodiment will be described in more detail.
The basic shape of the heat conductive member 17 is as described with reference to FIG. 3, and as shown in FIG. 7, the heat conductive member 17 is a uniform metal plate made of an aluminum material (pure aluminum, alloy number A1050), and has each dimension. Has a length of 218 mm, a width of 6 mm, and a thickness of 0.3 mm. As shown in FIGS. 7 (b) and 7 (c), the bent portion 17a, which is the positioning portion in the longitudinal direction of the heat conductive member 17, is located at a position 80 to 84 mm on the left side (folded portion 11e side) from the paper center O. In addition, it is formed in a size of 4 mm in width and 3 mm in length. In consideration of the leaning force that may occur due to the manufacturing tolerance of the fixing device in this embodiment, the width must be 4 mm or more and the length must be 2 mm or more in order to sufficiently secure the strength of the bent portion 17a. ..

In this embodiment, the shapes and dimensions of the substrate 11a of the heater 11 and the resistance heating element 11b shown in FIG. 8 exclude the length of the resistance heating element 11b of the heater region 11b1 corresponding to the bent portion 17a of the metal plate in the lateral direction. The same is true for the embodiment shown in FIG.
Here, the length of the resistance heating element 11b of the heater region 11b1 corresponding to the bent portion 17a of the metal plate in the lateral direction is defined as L. The length of the resistance heating element 11b in the heater region 11b2 in the lateral direction is 1 mm. At this time, in this embodiment, L = 0.93 mm (there is a drawing shape in the resistance heating element pattern on both the upstream and downstream sides in the recording material transport direction), and L = 1 mm (there is no drawing shape in the resistance heating element pattern). This form is referred to as Comparative Example 1.
In this embodiment, a diaphragm shape is provided in the resistance heating element pattern on both the upstream and downstream sides in the recording material transport direction, but if a desired calorific value can be obtained, one of the upstream and downstream sides in the recording material transport direction can be obtained. The aperture shape may be provided only on the pattern.

In the performance evaluation of this example and comparative example 1, the temperature distribution in the entire longitudinal direction detailed in the section (3) was measured. FIG. 9A is a diagram showing the temperature distribution measurement results in the entire longitudinal direction of Comparative Example 1. Although the recording material to be passed has a thermal peak at a position 2 to 3 mm outside from the position of the end portion of the nip portion N, the maximum temperature is 230 ° C. due to the effect of the metal plate which is the heat conductive member 17. The temperature rise at the end could be sufficiently suppressed.
However, the surface temperature of the pressure roller corresponding to the bent portion 17a of the metal plate became lower than the ambient temperature, resulting in temperature unevenness. The temperature unevenness was about 10 ° C., which may cause fixing failure.
In Comparative Example 1 and this embodiment, a bent portion 17a that is the same as the metal plate is provided so that the metal plate does not move in the longitudinal direction. However, in Comparative Example 1, the heat capacity of that portion is increased by providing the bent portion 17a. It increased more than the surroundings, and there were places where the temperature was low as a fixing device.

FIG. 9B is a diagram showing the temperature distribution measurement results over the entire longitudinal direction of this embodiment. Similar to the result of Comparative Example 1, the recording material to be passed has a thermal peak at a position 2 to 3 mm outside from the position of the end portion in the nip portion N, but the maximum temperature is 230 ° C. and heat conduction. Due to the effect of the metal plate which is the member 17, the temperature rise at the end could be sufficiently suppressed. Furthermore, in the bent portion 17a of the metal plate, there was no temperature unevenness as occurred in Comparative Example 1, and no image defect occurred.
This is because the drawing shape is provided in the heater region 11b1 of the resistance heating element pattern corresponding to the region 17a1 of the metal plate whose heat capacity becomes larger than the surroundings by providing the bent portion 17a. This is because the amount of heat generated in the heater region 11b1 has increased. That is, the amount of heat generated by the heater is increased by providing a diaphragm shape in the resistance heating element pattern in a region where the temperature is a concern as a fixing device.

As described above, according to the present embodiment, even when the heat conductive member 17 is provided with the positioning portion, the heat conduction member 17 is generated by increasing the calorific value of the heater 11 in the region corresponding to the positioning portion. It is possible to suppress local temperature unevenness while maintaining the effect of suppressing the temperature rise at the end of the surface. This makes it possible to obtain a better image.

Here, in this embodiment, when the heat conductive member 17 is provided with the bent portion 17a as the positioning portion, a mode for suppressing local temperature unevenness has been described, but the present invention is not limited to this. The present invention can be suitably applied when the heat conductive member for making the temperature distribution of the heater uniform is composed of a plurality of regions having different heat capacities.
That is, when there is a region in the heat conductive member in which the heat capacity is larger (smaller) than in other regions, the heat generation amount in the region of the heater corresponding to the region is increased (smaller), thereby causing the heat conductive member. It is possible to suppress local temperature unevenness while maintaining the effect of suppressing the temperature rise at the end.
Further, in the present embodiment, the bent portion 17a is the same as the metal plate, but the present invention is not limited to this, and the bent portion 17a may be configured as a separate body from the metal plate.

(Example 2)
The second embodiment will be described below. In this embodiment, the same components as those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.
FIG. 10A is a diagram showing a dimensional relationship between the heat conductive member 17 and the heater 11 in this embodiment, and FIG. 10B is a schematic perspective view showing a single heat conductive member 17 in this embodiment. .. FIG. 11 is a schematic view for explaining the cross-sectional shape of the holder 12 in this embodiment.
In this embodiment as well, as in the first embodiment, one metal plate was used as the heat conductive member 17. As a positioning configuration in the longitudinal direction of the heat conductive member 17, the bent portion 17a is provided in the first embodiment, but the following recess 17b is provided in the present embodiment. That is, in this embodiment, a recess 17b is provided by forming a shape in which the width in the lateral direction is narrower than the surroundings (hereinafter referred to as the narrow portion 17c) in a part of the metal plate, and the recess 17b is used as the holder 12. It was fitted (engaged) with the boss 12a provided in the above.

Here, the heat capacity of the metal plate and the calorific value of the heater 11 when the recess 17b is provided in the metal plate will be described.
By providing the recess 17b in the metal plate, the heat capacity of the narrow portion 17c (the region including the recess 17b in the lateral direction) of the metal plate does not include the recess 17b in the region other than the narrow portion 17c (the region including the recess 17b in the lateral direction). Region) smaller than the heat capacity of 17c1. At this time, there is a concern that local temperature unevenness may occur in the heater 11 due to the difference in heat capacity between the narrow portion 17c and the region 17c1 in the metal plate.
Therefore, in this embodiment, the calorific value of the heater 11 is set as follows. Here, in the region of the heater 11 that heats the nip portion N, the region where the temperature for heating the nip portion N is controlled by the contact with the narrow portion 17c of the heat conductive member 17 is referred to as the heater region 11b3. Further, in the present embodiment, the heater region 11b2 is a region in the region of the heater 11 that heats the nip portion N, in which the temperature for heating the nip portion N is controlled by contact with the region 17c1 of the heat conductive member 17. It becomes.
At this time, in this embodiment, the calorific value of the heater region 11b3 is increased from the heater region 11b2 so that the temperature difference between the heater region 11b2 and the region of the nip portion N heated in the heater region 11b3 becomes zero. Also set small. Here, the difference in temperature does not have to be zero, and may be smaller than the case where the calorific value of the heater region 11b2 and the calorific value of the heater region 11b3 are assumed to be the same.

Hereinafter, this embodiment will be described in more detail.
The heat conductive member 17 is a metal plate similar to that of the first embodiment, and has a length of 218 mm, a width of 6 mm, and a thickness of 0.3 mm. As shown in FIG. 10A, the recess 17b, which is the positioning portion in the longitudinal direction of the heat conductive member 17, has a width of 4 mm at a position 80 to 84 mm on the left side (folded portion 11e side) from the center O of the paper. It is formed to a depth of 3 mm.
In this embodiment, the shapes and dimensions of the substrate 11a and the resistance heating element 11b of the heater 11 shown in FIG. 10A exclude the length of the resistance heating element 11b at the position corresponding to the recess 17b of the metal plate in the lateral direction. This is the same as in Example 1 shown in FIG. For convenience of explanation, the length of the resistance heating element 11b in the heater region 11b3 corresponding to the recess 17b of the metal plate in the lateral direction is also defined as L in this embodiment.
Here, in this embodiment, L = 1.07 mm (there is a reverse drawing shape in the resistance heating element pattern on both the upstream and downstream sides in the recording material transport direction), and L = 1 mm (there is no drawing shape in the resistance heating element pattern). Let's refer to Comparative Example 2 in this form.

In the performance evaluation of this example and comparative example 2, the temperature distribution in the entire longitudinal direction detailed in the section (3) was measured. FIG. 12A is a diagram showing the temperature distribution measurement results in the entire longitudinal direction of Comparative Example 2.
In Comparative Example 2, as in Comparative Example 1, the temperature rise at the end could be sufficiently suppressed by the effect of the metal plate which is the heat conductive member 17. However, the surface temperature of the pressurized roller corresponding to the recess 17b of the metal plate became higher than the ambient temperature, resulting in temperature unevenness. The temperature unevenness was about 10 ° C., which may cause fixing failure.
In Comparative Example 2 and this embodiment, the concave portion 17b is provided in the metal plate so that the metal plate does not move in the longitudinal direction, but in Comparative Example 2, the heat capacity of the portion is reduced as compared with the surroundings by providing the concave portion 17b. , A place with high temperature has occurred as a fixing device.

FIG. 12B is a diagram showing the temperature distribution measurement results over the entire longitudinal direction of this embodiment. Similar to the results of Comparative Example 2 and Example 1, the temperature rise at the end could be sufficiently suppressed by the effect of the metal plate which is the heat conductive member 17. Further, in the recess 17b of the metal plate, the temperature unevenness generated in Comparative Example 2 was greatly improved to about 2 ° C., and no fixing failure occurred.
This is because the reverse drawing shape is provided in the heater region 11b3 of the resistance heating element pattern corresponding to the narrow portion 17c of the metal plate whose heat capacity is smaller than that of the surroundings by providing the recess 17b. This is because the amount of heat generated in the heater region 11b3 provided with the above is reduced. That is, the amount of heat generated by the heater is reduced by providing a reverse throttle shape in the resistance heating element pattern in the region where the temperature is a concern as a fixing device.

As described above, according to the present embodiment, when the recess 17b is provided in the heat conductive member 17, the heat generation amount of the corresponding heater region 11b3 is reduced to suppress the temperature rise at the end of the heat conductive member 17. Local temperature unevenness can be suppressed while maintaining the effect. This makes it possible to obtain a better image.

(Example 3)
The third embodiment will be described below. In the present embodiment, the same components as those in the first and second embodiments are designated by the same reference numerals, and the description thereof will be omitted.
13 is a schematic view showing the dimensional relationship of each of the heat conductive members 17 in this embodiment as a single unit, FIG. 13 (a) is a perspective view, and FIGS. 13 (b) to 13 (d) are FIGS. 13 (d), respectively. It is a figure seen from the direction indicated by arrows b to d in a). FIG. 14 is a diagram showing the dimensional relationship between the heat conductive member 17 and the heater 11 in this embodiment.
In this embodiment, a case where a plurality of metal plates, which are heat conductive members 17, are arranged with a gap provided along the longitudinal direction will be described, and in the following description, a case where two metal plates are used will be described. .. In this embodiment, the region between the two heat conductive members 17 arranged along the longitudinal direction (the section where the metal plate does not exist, the gap portion) is referred to as a gap portion 18.

Here, the calorific value of the heater 11 when a plurality of metal plates are arranged with a gap provided along the longitudinal direction will be described.
When a plurality of metal plates are arranged along the longitudinal direction with a gap provided, the metal plates are not contact-arranged with respect to the heater region 11b4 of the heater 11 corresponding to the gap portion 18, so that the metal plates are locally arranged on the heater 11. There is a concern that temperature unevenness will occur.
In this embodiment, the calorific value of the heater region 11b4 is made smaller than that of the heater region 11b2 so that the temperature difference between the heater region 11b4 and the region of the nip portion N heated in the heater region 11b2 becomes zero. Set. Here, the difference in temperature does not have to be zero, and may be smaller than the case where the calorific value of the heater region 11b4 and the calorific value of the heater region 11b2 are assumed to be the same.
In this embodiment, the positioning configuration of each metal plate is the same as that of the first embodiment, and each of the bent portions 17a provided in each heat conductive member 17 is inserted into a plurality of through holes provided in the holder 12. did. By providing the bent portion 17a on the metal plate, there are regions in the metal plate having different heat capacities. At this time, heat generation in the heater region of the heater 11 corresponding to the regions of the metal plates having different heat capacities. The amount is set in the same manner as in the first embodiment.

Hereinafter, this embodiment will be described in more detail.
The heat conductive member 17 is a metal plate similar to that of the first embodiment, and has a length of 106.5 mm, a width of 6 mm, and a thickness of 0.3 mm, respectively.
In this embodiment, the two metal plates are arranged so as to be symmetrical in the longitudinal direction with respect to the paper center O as shown in FIG. 13 (b). Then, as shown in FIG. 13 (c), the bent portion 17a, which is the positioning portion in the longitudinal direction of the heat conductive member 17, is 80 to 84 mm on both sides in the longitudinal direction from the center O of the paper, respectively, with respect to the two metal plates. It is formed at a distance of 4 mm in width and 3 mm in length. Further, the two heat conductive members 17 are arranged at intervals of 5 mm in the longitudinal direction.

In this embodiment, the shape and dimensions of the substrate 11a and the resistance heating element 11b of the heater 11 shown in FIG. 14 are the length in the lateral direction of the region of the resistance heating element 11b corresponding to the bent portion 17a and the gap portion 18 of the metal plate. Except for the above, the same as in Example 1 shown in FIG.
As shown in FIG. 14, in this embodiment, the lengths of the resistance heating element 11b of the heater region 11b1 corresponding to the bent portion 17a in the lateral direction are defined as L1 and L2, respectively. Further, the length of the resistance heating element 11b in the heater region 11b4 corresponding to the gap 18 in the lateral direction is defined as L3. In this embodiment, L1 = 0.93 mm, L2 = 0.93 mm, L3 = 1.1 mm (partially drawn in the resistance heating element pattern on both the upstream and downstream sides in the recording material transport direction, and some have a reverse drawing shape). do. Further, a form in which L1, L2, L3 = 1 mm (no drawing shape in the resistance heating element pattern) is referred to as Comparative Example 3.

In the performance evaluation of this example and comparative example 3, the temperature distribution in the entire longitudinal direction detailed in the section (3) was measured. FIG. 15A is a diagram showing the temperature distribution measurement results in the entire longitudinal direction of Comparative Example 3.
In Comparative Example 3, as in Comparative Example 1, the temperature rise at the end could be sufficiently suppressed by the effect of each metal plate having the heat conductive member 17. However, the surface temperature of the pressure roller corresponding to the bent portion 17a of each metal plate became lower than the ambient temperature, resulting in temperature unevenness. The temperature unevenness was about 10 ° C., which may cause fixing failure.
Further, in the void portion 18, the temperature became higher than the ambient temperature, resulting in temperature unevenness. The temperature unevenness was about 20 ° C., and fixing defects sometimes occurred here as well.

FIG. 15B is a diagram showing the temperature distribution measurement results over the entire longitudinal direction of this embodiment. Similar to the results of Comparative Example 3 and Example 1, the temperature rise at the end could be sufficiently suppressed by the effect of each metal plate which is the heat conductive member 17. In the bent portion 17 of the metal plate, the temperature unevenness as in Comparative Example 3 was greatly improved to about 2 ° C., and no fixing failure occurred.
As in the first embodiment, this drawing shape is provided by providing a drawing shape in the region of the resistance heating element pattern corresponding to the region of the metal plate whose heat capacity becomes larger than the surroundings by providing the bent portion 17a. This is because the amount of heat generated in the resistance heating element pattern region has increased. That is, the amount of heat generated by the heater is increased by providing a diaphragm shape in the resistance heating element pattern in a region where the temperature is a concern as a fixing device.

Further, in the gap portion 18, the temperature unevenness as in Comparative Example 3 was greatly improved to about 3 ° C., and no image defect occurred.
This is because the reverse drawing shape is provided in the region of the resistance heating element pattern corresponding to the void portion 18 whose heat capacity is smaller than the surroundings, so that the amount of heat generated in the resistance heating element pattern region provided with the reverse drawing shape is reduced. This is because of the heat. That is, the amount of heat generated by the heater is reduced by providing a reverse throttle shape in the resistance heating element pattern in the region where the temperature is a concern as a fixing device.

As described above, in the present embodiment, when a plurality of metal plates as heat conductive members are used, the heat generation amount of the heater 11 is increased at the positioning portion of the heat conductive member 17, and the metal plates are not in contact with each other. In the heater region (gap), the amount of heat generated by the heater is reduced. As a result, it is possible to suppress local temperature unevenness while maintaining the effect of suppressing the temperature rise at the end of the heat conductive member 17, so that a better image can be obtained.

Here, in the present embodiment, the case where the bent portion 17a is provided as the positioning configuration of each metal plate as in the first embodiment has been described, but the present invention is not limited to this. As the positioning configuration of each metal plate, for example, the recess 17b of the second embodiment may be provided. Further, in the present embodiment, the positioning configuration is provided for each metal plate, but the present invention is not limited to this. Further, when a plurality of metal plates, which are heat conductive members 17, are arranged with a gap along the longitudinal direction, even if a positioning configuration is not provided for each metal plate, the metal plates may not be provided. There is a concern that local temperature unevenness may occur in the heater 11 due to the presence of the void portion. In such a case, the temperature of the heater region 11b4 of the heater 11 corresponding to the gap portion 18 and the region of the nip portion N heated in the region of the heater 11 in contact with the metal plate (hereinafter referred to as the contact region), respectively. The calorific value may be set so that the difference becomes zero. That is, the calorific value of the heater region 11b4 may be set to be smaller than that of the contact region so that the temperature difference becomes zero. Here, the difference in temperature does not have to be zero, and may be smaller than the case where the calorific value of the heater region 11b4 and the calorific value of the contact region are assumed to be the same.

6 ... Fixing device, 11 ... Heater, 11b1, 11b2 ... Heater region, 13 ... Fixing film, 17 ... Heat conductive member, 17a1, 17a2 ... Region, 20 ... Pressurized roller, N ... Nip portion

Claims (8)

A heater containing a substrate and a heating element arranged on the substrate,
A heat conductive member that is contact-arranged with the heater and for uniformizing the temperature distribution in the longitudinal direction of the heater.
A flexible sleeve that is rotatably provided and slides on the heater,
A pressure member forming the heater and the nip portion via the flexible sleeve,
Have,
In an image heating device that sandwiches, conveys, and heats a recording material on which a developer image is formed between the flexible sleeve and the pressure member in the nip portion.
The heat conductive member is provided with a first region and a second region having a smaller heat capacity per unit length in the longitudinal direction than the first region.
The heater is
The first heater region in contact with the first region and
The second heater region in contact with the second region and
Is provided,
The length of the width of the entire first heating element corresponding to the first region in the direction orthogonal to the longitudinal direction is the first length, and the length of the width of the entire second heating element corresponding to the second region. Is a second length that is longer than the first length.
The calorific value per unit length of the first heater region in the longitudinal direction is set to be larger than the calorific value per unit length of the second heater region in the longitudinal direction. Device. It has a holding member that holds the heat conductive member, and has
A protrusion that engages with the holding member is provided in the first region of the heat conductive member.
The image heating device according to claim 1, wherein the first region has a heat capacity larger than that of the second region by having the protruding portion. The image heating device according to claim 2, wherein the protruding portion is a positioning portion for positioning the heat conductive member with respect to the holding member in the longitudinal direction of the nip portion. A plurality of the heat conductive members are arranged with a gap along the longitudinal direction.
The heater is provided with a third heater region corresponding to a gap portion between adjacent heat conductive members among the plurality of heat conductive members.
The image according to any one of claims 1 to 3 , wherein the calorific value of the third heater region is set to be smaller than the calorific value of the first heater region or the second heater region. Heating device. The heating element is formed on the substrate so as to extend in the longitudinal direction.
By forming the width of the heating element in the third heater region wider than that in the heating element in the first heater region and the heating element in the second heater region in the direction orthogonal to the longitudinal direction of the heating element. The image heating device according to claim 4 , wherein the heat generation amount in the third heater region is set to be smaller than the heat generation amount in the first heater region or the second heater region. A heater containing a substrate and a heating element arranged on the substrate,
A heat conductive member that is contact-arranged with the heater and for uniformizing the temperature distribution in the longitudinal direction of the heater.
A flexible sleeve that is rotatably provided and slides on the heater,
A pressure member forming the heater and the nip portion via the flexible sleeve,
Have,
In an image heating device that sandwiches, conveys, and heats a recording material on which a developer image is formed between the flexible sleeve and the pressure member in the nip portion.
A plurality of the heat conductive members are arranged with a gap along the longitudinal direction.
The heater is provided with a contact region in which the heat conductive member contacts and a third heater region corresponding to the gap portion.
The length of the width of the entire first heating element corresponding to the contact region in the direction orthogonal to the longitudinal direction is the first length, and the length of the width of the entire second heating element corresponding to the gap portion is the first length. It is a second length longer than the first length, and is
An image heating device characterized in that the calorific value per unit length in the longitudinal direction of the third heater region is set smaller than the calorific value per unit length in the longitudinal direction of the contact region. The image heating device according to any one of claims 1 to 6 , wherein the thermal conductivity of the heat conductive member is larger than the thermal conductivity of the substrate. The invention according to any one of claims 1 to 7 , wherein the heat conductive member is arranged so as to be in contact with the surface of the substrate opposite to the surface on which the heating element is formed. The image heating device described.

Images