JP6614816B2 - Image heating device - Google Patents

Description

  The present invention relates to an image heating apparatus.

In a heat fixing device as an image heating device provided in an image forming apparatus that employs an electrophotographic method, an electrostatic recording method, etc., film heating that does not supply power to the fixing device during standby and keeps power consumption as low as possible This type of fixing device has been put into practical use.
In recent years, image forming apparatuses such as copiers and printers have various demands such as higher printing speed, improved quick start performance, energy saving and downsizing. Under such a background, film heating type fixing devices are widely used.
In a film heating type fixing device, a film and a pressure member are disposed in pressure contact with each other, and a heater (heating body) for heating the film is disposed on the inner surface of the portion facing the pressure member. As a driving method of the film in such a fixing device, a driving roller is provided on the inner peripheral surface of the film and driven while applying tension to the film, or a pressure roller is driven by loosely supporting a film supporting member. There is known a method in which the motor is driven and rotated. In recent years, since the number of components is small, the latter pressure roller drive type is often employed.

Here, in the fixing device of the film heating system, the temperature rise at the end described below is cited as an existing problem.
When the recording material is passed through the fixing device and fixed, the surface temperature of the non-passage area of the pressure roller (outside the area through which the recording material is conveyed) may be excessively increased. This is because, in the non-sheet passing area where the recording material does not pass in the fixing nip portion, heat is partially stored as much as there is no heat removal by the recording material. This phenomenon is called temperature rise at the end of the fixing device or temperature rise at the non-sheet passing portion. When the temperature rise at the end reaches a high temperature, it has a thermal peak, leading to the occurrence of hot offset, melting of the heater holder, and the like.
In order to solve the problem of the temperature rise at the end, a proposal has been made to make the temperature distribution of the heater uniform by disposing a heat conducting member between the back surface of the heater and the heater holder as in Patent Document 1. In the use of the heat conducting member, as in Patent Document 2, a proposal has been made to use it in an electrically divided manner to ensure safety.

JP 11-84919 A JP 2014-123100 A

However, in the case of the conventional technology as described above, there are concerns that the following problems will occur.
In the configuration disclosed in Patent Document 1, it is necessary to provide the heat conducting member with an insertion portion to the heater holder. This is because, if the longitudinal direction of the fixing nip portion is not performed with respect to the heat conducting member, the heat conducting member has shifted, particularly when the end temperature rising portion has shifted. This is because there is a concern that the desired end-part temperature rise suppressing effect is not exhibited. However, when the insertion part to the heater holder is provided in the heat conducting member, the heat capacity of the insertion part is larger than that of the peripheral part. Therefore, there is a concern that the soaking effect is promoted at the insertion portion, the heater temperature is locally lowered, and fixing failure corresponding to the width of the insertion portion is caused.
Further, when a plurality of heat conducting members are arranged as in the configuration disclosed in Patent Document 2, a gap is formed between the heat conducting member and the heat conducting member. Since the heater corresponding to the gap portion does not come into contact with the heat conducting member, the heat equalization effect is reduced, the heater temperature is locally increased, and image defects such as hot offset corresponding to the width of the gap portion may be caused. Concerned.

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

In order to achieve the above object, the present invention provides:
A heater,
A heat conducting member that is disposed in contact with the heater and uniformizes the temperature distribution of the heater;
A flexible sleeve which is rotatably provided and slides on the heater;
A pressure member that forms a nip portion with the heater via the flexible sleeve;
Have
In the image heating apparatus for sandwiching and conveying the recording material on which the developer image is formed between the flexible sleeve and the pressure member in the nip portion,
The heat conducting member is provided with a first region and a second region having a smaller heat capacity per unit area than the first region,
The heater includes
A first heater region in which a temperature for heating the nip portion is controlled by contact of the first region among regions of the heater for heating the nip portion;
A second heater region in which a temperature for heating the nip portion is controlled by contact of the second region among the heater regions for heating the nip portion;
Is provided ,
The calorific value of the previous SL first heater region, larger set than the heating value of the second heater region, a temperature in the region of the nip portion is heated by the first heater region, heated by the second heater region The difference between the temperature of the nip region and the temperature of the nip portion is zero or smaller than when the heat generation amount of the first heater region and the heat generation amount of the second heater region are the same. Features.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to suppress a local temperature nonuniformity of a heater and to obtain a favorable image, maintaining the soaking effect of a heat conductive member.

Sectional drawing which shows schematic structure of the image forming apparatus of embodiment. 1 is a diagram illustrating a schematic configuration of a fixing device according to an embodiment. Schematic showing the heater of the embodiment Schematic of a configuration without a heat conducting member on the back of the heater Schematic sectional view of the configuration of the present embodiment in which a heat conducting member is arranged on the back surface of the heater The figure which shows the structure where the position of the longitudinal direction of a heat conductive member is not controlled Schematic which shows the dimensional relationship of the heat conductive member single-piece | unit in Example 1. FIG. The figure which shows the dimensional relationship of the heat conductive member and heater in Example 1. FIG. The figure which shows the temperature distribution measurement result in the whole length direction The figure which shows the dimensional relationship of the heat conductive member and heater in Example 2. FIG. Schematic for demonstrating 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 which shows the dimensional relationship in the single-piece | unit of each heat conductive member in Example 3. FIG. The figure which shows the dimensional relationship of the heat conductive member and heater in Example 3. The figure which shows the temperature distribution measurement result in the whole length direction

  DETAILED DESCRIPTION Exemplary embodiments for carrying out the present invention will be described in detail below with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment should be appropriately changed according to the configuration of the apparatus to which the invention is applied and various conditions. It is not intended to limit the scope to the following embodiments.

(1) Image Forming Apparatus FIG. 1 is a cross-sectional view showing a schematic configuration of an image forming apparatus according to 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 rotating drum type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) as an image carrier, which is rotationally driven in the direction of arrow a at a predetermined frequency (process speed). The photosensitive drum 1 has a configuration in which a photosensitive material layer such as OPC / amorphous Si is formed on the outer peripheral surface of a cylinder (drum) -like 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 during the rotation process. Thereafter, the laser beam scanner 3 scans the charged surface of the photosensitive drum 1 with a laser beam corresponding to the image information, so that a latent image (static image) corresponding to the target image information is formed on the surface of the photosensitive drum. An electrostatic latent image) is formed. The latent image is developed with toner (developer) T in the developing device 4 and visualized. As a development method, a jumping development method, a two-component development method, a FEED development method, or the like is used, and is often used in combination with image exposure and reversal development.

On the other hand, the recording material P accommodated in the feeding cassette 9 is fed one by one by driving the feeding roller 8 and passes through a sheet path having a guide / registration roller, and the pressure contact portion between the photosensitive drum 1 and the transfer roller 5. Is fed to the transfer nip portion at a predetermined control timing. When a positive transfer bias is applied to the transfer roller 5 by the transfer bias application power source, a negative toner image (developer image) on the surface of the photosensitive drum 1 is transferred onto the recording material P at the transfer nip portion. The
Thereafter, the recording material P onto which the toner image has been transferred at the transfer nip portion is introduced into a heat fixing device (hereinafter referred to as a fixing device) 6 as an image heating device and subjected to a heat fixing process of the toner image. The fixing device 6 will be described in detail in section (2). The recording material P that has passed through the fixing device 6 is printed out on a discharge tray through a sheet path having a conveyance roller, a guide, and a discharge roller. Further, the surface of the photosensitive drum 1 that has passed through the transfer nip is cleaned by the cleaning device 7 to remove deposits such as transfer residual toner, and repeatedly subjected to image formation.

(2) Fixing device 6
FIG. 2 is a diagram illustrating a schematic configuration of the fixing device 6 according to 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. 3 is an exploded perspective view of the fixing device 6. FIG.
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 in pressure contact with each other to form a nip portion N. 2A and 2C, the fixing assembly 10 mainly receives the pressing force from the fixing film 13, the heater 11, the heat conducting member 17, the holder 12, and the pressure spring 15, and the holder 12 is moved. The metal stay 14 is pressed 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 using a heat-resistant resin such as polyimide, polyamideimide, 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, heat conductive powder such as BN, alumina, and Al may be mixed in order to improve the heat conductivity. Further, in order to constitute a long-life fixing device, the fixing film 13 having sufficient strength and excellent durability needs to have a total thickness of 20 μm or more. Therefore, the total thickness of the fixing film 13 is optimally 20 μm or more and 200 μm or less.

  Furthermore, in order to prevent offset and ensure separation of the recording material, the surface layer is mixed with a heat-resistant resin having good releasability such as PTFE, PFA, FEP, ETFE, CTFE, PVDF, etc., and a silicone resin. A release layer is formed by coating. Here, PTFE is polytetrafluoroethylene, PFA is a tetrafluoroethylene perfluoroalkyl vinyl ether copolymer, and FEP is a tetrafluoroethylene hexafluoropropylene copolymer. Further, ETFE is an ethylene tetrafluoroethylene copolymer, CTFE is polychlorotrifluoroethylene, and PVDF is polyvinyldenfluoride.

  As a coating method, after the outer surface of the fixing film 13 is etched, the release layer may be dipped or a powder spray or the like may be applied. Alternatively, a method of covering the surface of the fixing film 13 with a resin formed in a tube shape may be used. Alternatively, after the outer surface of the fixing film 13 is blasted, a primer layer that is an adhesive may be applied to cover the release layer. In the present embodiment, a fixing film having a total thickness of 75 μm and an outer diameter of φ18 mm composed of PFA having a thickness of 10 μm for the surface layer (release layer), 5 μm for the primer layer, and polyimide having a thickness of 60 μm for the base layer was used.

[Heater 11]
As shown in FIG. 2B, the heater 11 as a heating member heats the nip portion N by contacting the inner surface of the fixing film 13. The heater 11 has a plate shape with a low heat capacity. Then, on the surface of the insulating ceramic substrate 11a such as alumina or aluminum nitride, along the longitudinal direction of the nip portion N, a resistance heating element 11b such as Ag / Pd (silver palladium), RuO ₂ , Ta ₂ N is provided on the screen. It is formed by printing or the like. At this time, the resistance heating element 11b is formed with a thickness of about 10 μm and a width of about 1 to 5 mm.
On the surface where the heater 11 is in contact with the fixing film 13, a protective layer 11c for protecting the resistance heating element is provided within a range that does not impair the thermal efficiency. The thickness of the protective layer is preferably thin enough to improve the surface properties, and generally a glass coat of about 30 to 200 μm is 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 heat generation amount is increased by making the width of the resistance heating element narrower than that of the other portions and increasing the partial resistance, which has been put to practical use. In the following description, a portion where the width of the resistance heating element is narrowed is referred to as a throttle portion, a 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 the width is referred to as a throttle amount. The amount of squeezing is an amount indicating the percentage of the squeezed part when the resistance value per unit area of the sensible heating element other than the squeezed part is 100%, and the thickness of the resistive heating element is constant. Assuming that there is no partial variation in the volume resistance value possessed by the resistance material, it is expressed by the following equation.
Aperture amount (%) = (resistance heating element width other than the restriction part) / (resistance heating element width of the restriction part)
Since the resistance value and the heat generation amount are proportional, the aperture amount may be considered as a ratio of the heat generation amount per unit area. The heater 11 will be described in detail in section (4).

[Pressure 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 21 made of SUS, SUM, Al or the like. Examples of the elastic layer 22 include an elastic solid rubber layer formed of heat-resistant rubber such as silicone rubber and fluorine rubber, and an elastic sponge rubber layer formed by foaming silicone rubber in order to provide a more heat insulating effect. An example of the elastic layer 22 is an elastic cellular rubber layer in which a hollow filler (such as a microballoon) is dispersed in a silicone rubber layer and a gas portion is provided in the cured product to enhance the heat insulation effect. Further, a release layer such as perfluoroalkoxy resin (PFA) or 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 is used.

[Heat conduction member 17]
The heat conducting member 17 is disposed in contact with the heater 11 to make the temperature distribution of the heater 11 uniform. In this embodiment, the heat conducting member 17 is held between a heater 11 and a holder 12 as a holding member that holds 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. Examples of the heat conducting member 17 include a graphite sheet obtained by processing Al, Cu, Ag, and graphite into a sheet shape. The thermal conductivity of the heat conductive member 17 is desirably larger than at least the thermal conductivity of the substrate 11a of the heater 11. The heat conductive member 17 will be described in detail in section (4).

[Method of Driving and Controlling 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. 2C, 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 pressed springs 15 via the spring receiving members. Is pressurized. The load is transmitted uniformly over the longitudinal direction of the holder 12 via the stay foot 14b. At the nip portion N, the fixing film 13 is bent by being sandwiched between the heater 11 and the pressure roller 20 by the applied pressure, and is in close contact with the heating surface of the heater 11.

The pressure roller 20 obtains a driving force that rotates in a direction indicated by an arrow in FIG. 2A from a driving gear (not shown) provided at the end of the cored bar 21. This driving force is transmitted by a motor (not shown) in accordance with a command from a CPU (not shown) that controls the control means. As the pressure roller 20 is driven to rotate, the fixing film 13 is driven to rotate by a frictional force with the pressure roller 20. By interposing a lubricant such as a fluorine-based or silicone-based heat resistant grease between the fixing film 13 and the heater 11, the frictional resistance is kept low, and the fixing film 13 can be rotated smoothly.

  In addition, the temperature control of the heater 11 is performed by determining and appropriately controlling the duty ratio, wave number, etc. of the voltage applied by the CPU to the energization heating resistance layer in accordance with a signal from a thermistor (not shown) which is a thermal element. The temperature in the fixing nip is kept at a predetermined fixing setting temperature. The holder 12 is provided with a through hole, and the thermistor is arranged so as to contact the heat conducting member 17 through the through hole. That is, the thermal element is arranged so as to sense the heat of the heater 11 through the heat conducting member 17. The recording material P holding the unfixed toner image is appropriately supplied by a supply unit (not shown) at a predetermined timing, and is conveyed into the nip portion N to be heated and fixed. The recording material P that is heated and fixed while being nipped and conveyed at the nip portion N is guided and discharged by a discharge guide (not shown).

(3) Influence of Heat Conducting Member 17 In this section, the influence of the heat conducting member 17 is described in detail.
FIG. 3 is a schematic view showing the heater 11 of the present embodiment, FIG. 3 (a) is a plan view of the heater 11, FIG. 3 (b) is a cross-sectional view of the heater 11, and FIG. 3 (c) is a heat conducting member. FIG. 3D is a side view of the heat conducting member 17.
As shown in FIG. 3A, the heater 11 is formed by forming a resistance heating element 11b of Ag / Pd (silver palladium) on an alumina substrate by screen printing, and further connecting an electrical contact portion to the resistance heating element 11b. . The two resistance heating elements 11b are connected in series, and the resistance value is 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 with a longitudinal length of 270 mm, a lateral length of 6.0 mm, and a thickness of 1 mm. Here, a direction perpendicular to the longitudinal direction on the substrate 11a is referred to as a short direction. The short direction is the same direction as the recording material conveyance direction (recording material conveyance direction) conveyed at the nip portion N.

The resistance heating element 11b is a pattern that is folded back at the end in the longitudinal direction via the electrical contact portion, and two resistance heating elements 11b that extend in the longitudinal direction are arranged side by side in the recording material conveyance direction. The resistance heating elements 11b positioned upstream and downstream in the recording material conveyance direction are respectively formed in the same shape (there is no diaphragm 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 sheet passing center O). 109 mm), and the length in the short direction is 1.0 mm.
Here, the center position in the longitudinal direction of the region through which the recording material passes is defined as a sheet passing center O. Further, an end portion having an electrical contact portion at an end portion in the longitudinal direction of the heater 11 is defined as a power feeding portion 11d, and an end portion having a folding pattern is defined as a folded portion 11e. In the present embodiment, the thermistor (not shown) is arranged at a position 25 mm outside from the sheet passing center O in the longitudinal direction. Regarding the position of the thermistor, in the case shown in the figure, it is shown in the figure using the symbol S.
Further, as shown in FIGS. 3C and 3D, the heat conducting member 17 is a uniform metal plate made of an aluminum material (pure aluminum, alloy number A1050) and has a length in the longitudinal direction of 218 mm. (109 mm on both sides in the longitudinal direction with respect to the sheet passing center O), 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 conducting member 17 is not disposed on the back surface of the heater 11, and FIG. 5A is a configuration of the present embodiment in which the heat conducting member 17 is disposed on the back surface of the heater 11. It is a schematic sectional drawing. Since the aluminum metal plate which is the heat conducting member 17 is thermally expanded, a gap of 1 mm or more is provided between the longitudinal ends of the heat conducting member 17 and the holder 12. Here, the back surface of the heater 11 on which the heat conducting member 17 is placed in contact refers to the surface of the substrate 11a opposite to the surface on which the resistance heating element 11b is formed.
In the case where the temperature rise at the edge described in the background art becomes a problem, a recording material (recording material having a large basis weight) having a width smaller than that of the resistance heating element 11b and a high fixing control temperature is continuously applied. The case of printing is generally known.
Therefore, the evaluation method of the temperature distribution in the entire longitudinal direction is as follows. When the temperature of the edge heating portion exceeds 250 ° C., there is a problem in the fixing performance and the durability of the pressure roller 20, and when the temperature exceeds 300 ° C., the holder starts to melt. The evaluation method of edge temperature rising is explained in full detail below.

[Method for evaluating temperature distribution in the entire longitudinal direction]
Environment: 15 ° C / 10%
Paper type: A4 (width 210 mm) size, plain weight 128 g / m ² plain paper passing mode: Continuously printing from cold state Print printing speed: about 220 mm / s
Fixing control temperature: 230 ° C
When 250 sheets of recording material were passed by the above 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 end portion temperature rise in the configuration in which the heat conducting member 17 is not disposed on the back surface of the heater 11 (comparative example).
The temperature of the paper passing area (the area that passes when the recording material is conveyed) is controlled using a thermistor (not shown), and the surface temperature of the pressure roller 20 is stable at about 80 ° C. In the non-sheet passing region, a thermal peak occurred 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-sheet passing region exceeded 250 ° C., and was a temperature at which a problem occurred in the fixing performance and the durability of the pressure roller.

FIG. 5B is a diagram for explaining the result of evaluating the end portion temperature rise in the configuration (in the present embodiment) in which the heat conducting member 17 is arranged on the back surface of the heater 11.
The temperature of the paper passing area is controlled using a thermistor (not shown), and the surface temperature of the pressure roller 20 is stable at about 80 ° C.
In the non-sheet passing area, although there is a thermal peak at a position 2 to 3 mm outside from the end position of the recording material to be passed, the maximum temperature is 230 ° C., and it is suppressed to a temperature at which no problems such as fixing performance occur. did it. By disposing a heat conductive member that is more conductive than the insulating ceramic substrate on the back surface of the heater 11, heat can be easily transferred in the thickness direction, the width direction, and the length direction. The slope is greatly relaxed.
The area through which the recording material is passed is repeatedly heated and cooled by the recording material, and the total amount of heat that moves 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 conducting member 17 in the longitudinal direction is not regulated, there is a concern that a problem that the effect of suppressing the temperature rise at the end cannot be obtained.

FIG. 6 is a diagram for explaining a configuration in which the heat conducting member 17 is arranged on the back surface of the heater 11 but the position of the heat conducting member 17 in the longitudinal direction is not restricted. FIG. 6A shows a state where the heat conducting member 17 is arranged at a desired position as shown in FIG. FIG. 6B shows a state where the heat conducting member 17 has been shifted by 1 mm to the right side of the drawing (the power feeding section 11d side), and FIG. 6C shows the state shown in FIG. The result of having evaluated the edge part temperature increase when the heat conductive member 17 has shifted | deviated is shown.
As shown in FIG. 6 (c), the maximum temperature is raised from 230 ° C. to 250 ° C. on the left side (folded portion 11e side), and the maximum temperature is increased from 230 ° C. to 210 ° C. on the right side (feeding portion 11d side). It improved. In the region where the maximum temperature reached 250 ° C., fixing failure occurred.
The above phenomenon involves the heat capacity of the heat conducting member 17 located immediately below the thermal peak position of the portion where the temperature is increased at the end.

  6 (d) and 6 (e) are views showing the volume of the heat conducting member 17 immediately below the thermal peak position of the portion where the temperature of the end is elevated. 6 (d) shows the left side (folded portion 11e side) of the heat conducting member 17 shown in FIG. 6 (b), and FIG. 6 (e) shows the heat conducting member shown in FIG. 6 (b). The right side of FIG. 17 (power supply part 11d side) is shown. Further, FIG. 6D shows that the volume is reduced by 25% because the heat conduction member 17 is shifted by 1 mm to the right side (the power feeding part 11d side). In FIG. 6E, the heat conduction member 17 is on the right side. It shows that the volume has increased by 25% due to a shift of 1 mm to the (feeding part 11d side).

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

(4) Examples Hereinafter, the present invention will be described in detail with specific examples. In the examples described below, the same components as those in the above-described embodiment are denoted by the same reference numerals, and the description thereof is omitted.
Example 1
Example 1 will be described below.
FIG. 7 is a schematic diagram showing the dimensional relationship of the heat conducting member 17 alone in this embodiment, FIG. 7 (a) is a perspective view, and FIGS. 7 (b) to 7 (d) are respectively in FIG. 7 (a). It is the figure seen from the direction shown by arrow b-d. FIG. 8 is a diagram showing a dimensional relationship between the heat conducting member 17 and the heater 11 in the present embodiment.
In this example, one metal plate was used as the heat conducting member 17. As a positioning configuration in the longitudinal direction of the heat conducting member 17, a bent portion (projecting portion) 17 a that is the same body (integral) as the metal plate is provided, and the bent portion 17 a is inserted into a through hole provided in the holder 12. The configuration was combined. 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 amount of heat generated by the heater 11 when the bent portion 17a is provided on the metal plate will be described.
When the bent portion 17a is provided on the metal plate, the heat capacity of the region 17a1 including the bent portion 17a of the metal plate 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 heat capacity of the region 17a1 and the region 17a2 being different in the metal plate.
Therefore, in this embodiment, the heat generation amount of the heater 11 is set as follows based on the relationship between the heat capacity and the temperature of the heater described above.
Here, among the regions 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 of the region 17a1 of the heat conducting member 17 is the heater region 11b1. And Further, among the regions of the heater 11 that heats the nip portion N, the region in which the temperature for heating the nip portion N is controlled by contacting the region 17a2 of the heat conducting member 17 is referred to as a heater region 11b2. In addition, the area | region 17a1 is an area | region (area | region enclosed with the dotted line in the heat conductive member 17 shown in FIG. 8) including the bending part 17a among the area | regions along the transversal direction of a metal plate, and area | region 17a2 is metal It becomes an area | region other than area | region 17a1 among boards. The region 17a1 and the region 17a2 are arranged side by side in the longitudinal direction.
At this time, in the present embodiment, the amount of heat generated in the heater region 11b1 is smaller than that in 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 larger. Here, the temperature difference does not have to be zero, and may be smaller than the case where it is assumed that the heat generation amount of the heater region 11b1 and the heat generation amount of the heater region 11b2 are the same.

Hereinafter, the present embodiment will be described more specifically.
The basic shape of the heat conducting member 17 is as described with reference to FIG. 3. As shown in FIG. 7, the heat conducting member 17 is a uniform metal plate made of an aluminum material (pure aluminum, alloy number A1050). Is 218 mm long, 6 mm wide, and 0.3 mm thick. As shown in FIGS. 7B and 7C, the bent portion 17a serving as the longitudinal positioning portion of the heat conducting member 17 is positioned 80 to 84 mm away from the sheet passing center O to the left side (folded portion 11e side). In addition, it is formed in a size of 4 mm in width and 3 mm in length. In view of the shift force that may occur due to the manufacturing tolerance of the fixing device in this embodiment, the width of 4 mm or more and the length of 2 mm or more are required in order to sufficiently secure the strength of the bent portion 17a. .

In the present embodiment, the shapes and dimensions of the substrate 11a and the resistance heating element 11b of the heater 11 shown in FIG. 8 are the same as the length of the resistance heating element 11b in the heater region 11b1 corresponding to the bent portion 17a of the metal plate. This is the same as the embodiment shown in FIG.
Here, the length in the short direction of the resistance heating element 11b of the heater region 11b1 corresponding to the bent portion 17a of the metal plate was defined as L. The length in the short direction of the resistance heating element 11b in the heater region 11b2 is 1 mm. At this time, in this embodiment, L = 0.93 mm (there is a restriction shape in the resistance heating element pattern on both the upstream and downstream sides in the recording material conveyance direction), and L = 1 mm (no restriction shape in the resistance heating element pattern). This form is referred to as Comparative Example 1.
In this embodiment, the aperture shape is provided in the resistance heating element patterns on both the upstream and downstream sides in the recording material conveyance direction. However, as long as a desired heat generation amount can be obtained, one of the upstream and downstream sides in the recording material conveyance direction is provided. A diaphragm shape may be provided only for the pattern.

In performing the performance evaluation of this example and comparative example 1, the temperature distribution in the entire longitudinal direction detailed in the item (3) was measured. FIG. 9A is a diagram illustrating a temperature distribution measurement result in the entire longitudinal direction of Comparative Example 1. FIG. Although the recording material to be passed has a thermal peak at a position 2 to 3 mm outside from the end position at the nip portion N, the maximum temperature is 230 ° C., due to the effect of the metal plate as the heat conducting member 17. Edge temperature rise could be sufficiently suppressed.
However, the pressure roller surface temperature corresponding to the bent portion 17a of the metal plate became lower than the ambient temperature, resulting in temperature unevenness. The temperature non-uniformity is about 10 ° C., which may cause fixing failure.
In Comparative Example 1 and the present embodiment, the bent portion 17a is provided in the same body as the metal plate so that the metal plate does not move in the longitudinal direction. However, in Comparative Example 1, since the bent portion 17a is provided, the heat capacity of the portion is increased. More than the surroundings, a low temperature portion has occurred as a fixing device.

FIG. 9B is a diagram showing a temperature distribution measurement result in the entire longitudinal direction of the present example. Similar to the result 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 end position at the nip portion N, the maximum temperature is 230 ° C. Due to the effect of the metal plate that is the member 17, the temperature rise at the end could be sufficiently suppressed. Furthermore, there was no temperature unevenness as occurred in Comparative Example 1 in the bent portion 17a of the metal plate, and no image defect occurred.
This is because the diaphragm shape is provided in the heater region 11b1 of the resistance heating element pattern corresponding to the metal plate region 17a1 in which the heat capacity is larger than the surrounding by providing the bent portion 17a. This is because the amount of heat generated in the heater region 11b1 has increased. In other words, the heat generation amount of the heater is increased by providing a diaphragm shape in the resistance heating element pattern for a region where the temperature is likely to be low as the fixing device.

  As described above, according to the present embodiment, even when the heat conducting member 17 is provided with the positioning portion, the heat conducting member 17 can be obtained by increasing the heat generation amount of the heater 11 in the region corresponding to the positioning portion. It is possible to suppress local temperature unevenness while maintaining the edge temperature rise suppression effect. This makes it possible to obtain a better image.

Here, in the present embodiment, the mode in which local temperature unevenness is suppressed in the case where the bent portion 17a is provided as the positioning portion on the heat conducting member 17 has been described. However, the present invention is not limited to this. The present invention can be suitably applied if the heat conducting member for equalizing the temperature distribution of the heater is composed of a plurality of regions having different heat capacities.
That is, when there is a region where the heat capacity is larger (smaller) than the other regions in the heat conducting member, by increasing (smaller) the amount of heat generated in the heater region corresponding to the region, Local temperature unevenness can be suppressed while maintaining the edge temperature increase suppression effect.
In the present embodiment, the bent portion 17a is the same body as the metal plate, but is not limited thereto, and may be configured separately from the metal plate.

(Example 2)
Example 2 will be described below. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.
FIG. 10A is a diagram showing a dimensional relationship between the heat conducting member 17 and the heater 11 in the present embodiment, and FIG. 10B is a schematic perspective view showing the heat conducting member 17 alone in the present embodiment. . FIG. 11 is a schematic diagram for explaining a cross-sectional shape of the holder 12 in the present embodiment.
Also in this example, as in Example 1, one metal plate was used as the heat conducting member 17. As a positioning configuration in the longitudinal direction of the heat conducting member 17, the bent portion 17a is provided in the first embodiment, but the following concave portion 17b is provided in the present embodiment. That is, in this embodiment, a concave portion 17b is provided in a part of the metal plate by forming a shape whose width in the short side direction is narrower than the surroundings (hereinafter referred to as a narrow portion 17c). Was fitted (engaged) with the boss 12a provided on the boss 12a.

Here, the heat capacity of the metal plate and the amount of heat generated by the heater 11 when the concave portion 17b is provided in the metal plate will be described.
By providing the concave portion 17b on the metal plate, the heat capacity of the narrow portion 17c (region including the concave portion 17b in the short direction) of the metal plate does not include the concave portion 17b in the region other than the narrow portion 17c. Area) 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 heat capacities of the narrow portion 17c and the region 17c1 being different in the metal plate.
Therefore, in this embodiment, the heat generation amount of the heater 11 is set as follows. Here, of the region of the heater 11 that heats the nip portion N, the region in which the temperature at which the nip portion N is heated by contacting the narrow portion 17c of the heat conducting member 17 is referred to as a heater region 11b3. In the present embodiment, the heater region 11b2 is a region in which the temperature for heating the nip portion N is controlled by the contact of the region 17c1 of the heat conducting member 17 in the region of the heater 11 that heats the nip portion N. It becomes.
At this time, in this embodiment, the amount of heat generated in the heater region 11b3 is set to be smaller than that in 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 a smaller value. Here, the temperature difference does not have to be zero, and may be smaller than the case where it is assumed that the heat generation amount of the heater region 11b2 and the heat generation amount of the heater region 11b3 are the same.

Hereinafter, the present embodiment will be described more specifically.
The heat conducting 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. 10 (a), the concave portion 17b serving as a longitudinal positioning portion of the heat conducting member 17 has a width of 4 mm at a position 80 to 84 mm away from the sheet passing center O to the left side (folded portion 11e side). It is formed in a size of 3 mm depth.
In this embodiment, the shape and dimensions of the substrate 11a and the resistance heating element 11b of the heater 11 shown in FIG. 10A are excluding the length in the short direction of the resistance heating element 11b at the position corresponding to the concave portion 17b of the metal plate. This is the same as in the first embodiment shown in FIG. The length in the short direction of the resistance heating element 11b of the heater region 11b3 corresponding to the concave portion 17b of the metal plate is also defined as L in this embodiment for convenience of explanation.
Here, in this embodiment, L = 1.07 mm (the reverse heating shape is in the resistance heating element pattern on both upstream and downstream sides in the recording material conveyance direction), and L = 1 mm (the drawing shape is not in the resistance heating element pattern). This will be referred to as Comparative Example 2.

In performing the performance evaluation of this example and comparative example 2, the temperature distribution in the entire longitudinal direction detailed in the item (3) was measured. FIG. 12A is a diagram illustrating a temperature distribution measurement result in the entire longitudinal direction of Comparative Example 2. FIG.
Also in the comparative example 2, similarly to the comparative example 1, the edge temperature increase could be sufficiently suppressed by the effect of the metal plate as the heat conducting member 17. However, the pressure roller surface temperature corresponding to the concave portion 17b of the metal plate became higher than the ambient temperature, resulting in temperature unevenness. The temperature non-uniformity is about 10 ° C., which may cause fixing failure.
In Comparative Example 2 and this example, the metal plate is provided with the recess 17b so that the metal plate does not move in the longitudinal direction. However, in Comparative Example 2, by providing the recess 17b, the heat capacity of that portion is reduced from the surroundings. As a fixing device, a portion with a high temperature has occurred.

FIG. 12B is a diagram showing a temperature distribution measurement result in the entire longitudinal direction of the present example. Similar to the results of Comparative Example 2 and Example 1, the edge temperature rise could be sufficiently suppressed by the effect of the metal plate as the heat conducting member 17. Further, in the concave portion 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 diaphragm 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 becomes smaller than that of the surrounding by providing the concave portion 17b. This is because the amount of heat generated in the heater region 11b3 provided with a small amount is reduced. That is, this is because the amount of heat generated by the heater is reduced by providing a reverse aperture shape in the resistance heating element pattern for a region where the temperature of the fixing device is a concern.

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

(Example 3)
Example 3 will be described below. In the present embodiment, the same components as those in the first and second embodiments are denoted by the same reference numerals, and the description thereof is omitted.
FIG. 13 is a schematic view showing the dimensional relationship of each of the heat conducting members 17 in this embodiment, FIG. 13 (a) is a perspective view, and FIGS. 13 (b) to (d) are FIG. It is the figure seen from the direction shown by arrow b-d in a). FIG. 14 is a diagram showing a dimensional relationship between the heat conducting member 17 and the heater 11 in the present embodiment.
In the present embodiment, a case where a plurality of metal plates as the heat conducting members 17 are arranged along the longitudinal direction with a gap therebetween will be described. In the following description, a case where two metal plates are used will be described. . In this embodiment, a region between the two heat conducting members 17 arranged along the longitudinal direction (a section where there is no metal plate, a gap portion) is referred to as a gap portion 18.

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

Hereinafter, the present embodiment will be described more specifically.
The heat conducting member 17 is a metal plate similar to that of Example 1, 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 sheet passing center O as shown in FIG. And the bending part 17a used as the positioning part of the longitudinal direction of the heat-conducting member 17 is 80-84 mm with respect to two metal plates on both sides of a longitudinal direction from the sheet passing center O as shown in FIG.13 (c). At a distant position, it is formed in a size of 4 mm in width and 3 mm in length. Moreover, the two heat conductive members 17 are arrange | positioned 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 lengths in the short direction of the region of the resistance heating element 11b corresponding to the bent portion 17a and the gap 18 of the metal plate. Is the same as that of the first embodiment shown in FIG.
As shown in FIG. 14, in this embodiment, the lengths in the short direction of the resistance heating element 11b in the heater region 11b1 corresponding to the bent portion 17a are defined as L1 and L2, respectively. Furthermore, the length in the short direction of the resistance heating element 11b in the heater region 11b4 corresponding to the gap 18 was defined as L3. In this embodiment, L1 = 0.93 mm, L2 = 0.93 mm, L3 = 1.1 mm (partial aperture and partial reverse aperture shape in the resistance heating element pattern on both the upstream and downstream sides in the recording material conveyance direction) To do. Further, a mode in which L1, L2, L3 = 1 mm (no diaphragm shape in the resistance heating element pattern) is referred to as Comparative Example 3.

In performing the performance evaluation of this example and comparative example 3, the temperature distribution in the entire longitudinal direction detailed in the item (3) was measured. FIG. 15A is a diagram showing a temperature distribution measurement result in the entire longitudinal direction of Comparative Example 3. FIG.
Also in the comparative example 3, similarly to the comparative example 1, the edge temperature increase could be sufficiently suppressed by the effect of each metal plate provided in the heat conducting member 17. However, the pressure roller surface temperature corresponding to the bent portion 17a of each metal plate became lower than the ambient temperature, resulting in temperature unevenness. The temperature non-uniformity is about 10 ° C., which may cause fixing failure.
Furthermore, in the space | gap part 18, temperature became higher than ambient temperature and it became temperature nonuniformity. The temperature unevenness was about 20 ° C., and there was a case where poor fixing occurred.

FIG. 15B is a diagram illustrating a temperature distribution measurement result in the entire longitudinal direction of the present example. Similar to the results of Comparative Example 3 and Example 1, the edge temperature increase could be sufficiently suppressed by the effect of each metal plate as the heat conducting member 17. In the bent portion 17 of the metal plate, the temperature unevenness as occurred in Comparative Example 3 was greatly improved to about 2 ° C., and no fixing failure occurred.
As in the first embodiment, this diaphragm shape is provided by providing a diaphragm shape in the region of the resistance heating element pattern corresponding to the region of the metal plate where the heat capacity is larger than the surrounding by providing the bent portion 17a. This is because the amount of heat generated in the resistance heating element pattern region is increased. In other words, the heat generation amount of the heater is increased by providing a diaphragm shape in the resistance heating element pattern for a region where the temperature is likely to be low as the fixing device.

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

  As described above, in this embodiment, when a plurality of metal plates that are heat conducting members are used, the amount of heat generated by the heater 11 is increased at the positioning portion of the heat conducting 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, local temperature unevenness can be suppressed while maintaining the end temperature increase suppressing effect of the heat conducting member 17, and thus 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 is described, but the present invention is not limited to this. As a positioning configuration of each metal plate, for example, the concave portion 17b of the second embodiment may be provided. In the present embodiment, each metal plate is provided with a positioning structure, but the present invention is not limited to this. Further, in the case where a plurality of metal plates that are the heat conducting members 17 are arranged with a gap along the longitudinal direction, even if each metal plate is not provided with a positioning configuration, There is a concern that local temperature unevenness may occur in the heater 11 due to the presence of the gap. In such a case, the temperature of the heater region 11b4 of the heater 11 corresponding to the gap 18 and the temperature of the region of the nip portion N that is heated in the region of the heater 11 in contact with the metal plate (hereinafter referred to as a contact region), respectively. What is necessary is just to set the emitted-heat amount so that a difference may become zero. In other words, the amount of heat generated in the heater region 11b4 may be set smaller than that in the contact region so that the temperature difference becomes zero. Here, the temperature difference does not have to be zero, and may be smaller than the case where it is assumed that the heat generation amount of the heater region 11b4 and the heat generation amount of the contact region are the same.

  DESCRIPTION OF SYMBOLS 6 ... Fixing device, 11 ... Heater, 11b1, 11b2 ... Heater area | region, 13 ... Fixing film, 17 ... Heat conduction member, 17a1, 17a2 ... Area | region, 20 ... Pressure roller, N ... Nip part

Claims (10)

A heater,
A heat conducting member that is disposed in contact with the heater and uniformizes the temperature distribution of the heater;
A flexible sleeve which is rotatably provided and slides on the heater;
A pressure member that forms a nip portion with the heater via the flexible sleeve;
Have
In the image heating apparatus for sandwiching and conveying the recording material on which the developer image is formed between the flexible sleeve and the pressure member in the nip portion,
The heat conducting member is provided with a first region and a second region having a smaller heat capacity per unit area than the first region,
The heater includes
A first heater region in which a temperature for heating the nip portion is controlled by contact of the first region among regions of the heater for heating the nip portion;
A second heater region in which a temperature for heating the nip portion is controlled by contact of the second region among the heater regions for heating the nip portion;
Is provided ,
The calorific value of the previous SL first heater region, larger set than the heating value of the second heater region, a temperature in the region of the nip portion is heated by the first heater region, heated by the second heater region The difference between the temperature of the nip region and the temperature of the nip portion is zero or smaller than when the heat generation amount of the first heater region and the heat generation amount of the second heater region are the same. An image heating apparatus. A holding member for holding the heat conducting member;
The first region of the heat conducting member is provided with a protrusion that engages with the holding member,
2. The image heating apparatus according to claim 1, wherein the first region has the protrusion and has a larger heat capacity than the second region. A holding member for holding the heat conducting member;
The second region of the heat conducting member is provided with a recess that engages with the holding member,
2. The image heating apparatus according to claim 1, wherein the second region has the concave portion and has a smaller heat capacity than the first region. The image heating apparatus according to claim 2, wherein the protruding portion is a positioning portion that positions the heat conductive member with respect to the holding member in a longitudinal direction of the nip portion. The image heating apparatus according to claim 3, wherein the concave portion is a positioning portion that positions the heat conductive member with respect to the holding member in a longitudinal direction of the nip portion. The heater has a substrate and a heating element formed on the substrate so as to extend in the longitudinal direction of the nip portion,
In the direction perpendicular to the longitudinal direction of the heating element, the width of the heating element in the first heater region is narrower than the width of the heating element in the second heater region, so that The image heating apparatus according to claim 1, wherein a heat generation amount is set to be larger than a heat generation amount of the second heater region. A plurality of the heat conducting members are disposed with a gap along the longitudinal direction of the nip portion,
The heater is provided with a third heater region that is a region of the heater corresponding to a gap portion between adjacent heat conductive members among the plurality of heat conductive members,
The difference between the temperature of the nip region heated in the first heater region or the second heater region and the temperature of the nip region heated in the third heater region is zero, or The heat generation amount of the first heater region or the second heater region and the heat generation amount of the third heater region are assumed to be smaller than when assumed to be the same.
7. The image according to claim 1, wherein a heat generation amount of the third heater region is set to be smaller than a heat generation amount of the first heater region or the second heater region. Heating device. The heater has a substrate and a heating element formed on the substrate so as to extend in the longitudinal direction of the nip portion,
In the direction perpendicular to the longitudinal direction of the heating element, the width of the heating element in the third heater region is formed wider than the heating element in the first heater region and the heating element in the second heater region. The image heating apparatus according to claim 7, wherein a heat generation amount of the third heater region is set to be smaller than a heat generation amount of the first heater region or the second heater region. The heater has a substrate and a heating element formed on the substrate,
The thermal conductivity of the heat conductive member, An apparatus according to any one of claims 1 to 8, wherein greater than the thermal conductivity of the substrate. The heater has a substrate and a heating element formed on the substrate,
The heat conductive member, of the substrate, to any one of claims 1 to 9 wherein the heating element is formed plane, characterized in that it is placed in contact with the surface opposite The image heating apparatus described.

Images