JP2017167462A - Image heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image heating device that does not cause reduction in effect of heat uniformization over an entire heater substrate zone by dividing a heat uniformizing member into a plurality of sub-heat uniformizing members, or falling in reduction effect of power consumption due to blockage of heat transmitting from a non-paper feeding part to a thermistor part.SOLUTION: An image heating device includes: a cylindrical film; a heater that contacts with an inner surface of the film; a pressure member that forms a nip part via the film together with the heater; and a support member that supports the heater, in which the image heating device heats an image as conveying a recording material in the nip part. In a longitudinal direction orthogonal to a conveyance direction of the recording material, the image heating device includes: first and second heat uniformizing members 26a and 26b that contact with a surface on an opposite side of a surface, contacting with the inner surface of the film, of the heater, and have respective opposing surfaces k1 and k2 of the first and second heat uniformizing members 26a and 26b mutually spaced from each other; and a third heat uniformizing member 26c that contacts with respective surfaces m1 and m2, different from the opposing surfaces, of the first and second heat uniformizing members 26a and 26b.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a film heating type (on-demand type) image heating apparatus.

  As an image heating apparatus in an electrophotographic copying machine or printer, a film heating type fixing apparatus that heats and fixes a toner image formed on a recording material is known (Patent Document 1). In such a fixing device, when a recording material (small size paper) having a width smaller than the maximum size is continuously printed, the temperature of a region where the paper does not pass (non-sheet passing portion) in the longitudinal direction of the fixing nip portion (nip portion) is increased. A phenomenon of rising gradually (temperature increase of the non-sheet passing portion) occurs. In the case of a film heating method using a heater with a low heat capacity as the heater, the temperature rise of the non-sheet passing portion of the heater is large, the heater holding member is damaged, the durability performance of the pressure roller forming the film and the nip portion is reduced, High temperature offset of the paper passing portion is likely to occur.

  Further, as the processing speed of the image forming apparatus increases, the temperature rise of the non-sheet passing portion is likely to occur. This is because the time required for the recording material to pass through the fixing nip portion is shortened as the speed is increased, and thus the heating and fixing temperature must be increased. Also, during the continuous printing process, the time (interval) during which no recording material is present in the fixing nip portion decreases as the speed of the apparatus increases, so it becomes difficult to eliminate temperature distribution unevenness during the interval.

  In order to suppress such non-sheet passing portion temperature rise, the throughput (number of sheets passed per unit time) when small size sheets are continuously passed is reduced, or the temperature distribution in the longitudinal direction is made uniform. Therefore, a method of providing a heat radiating roller in contact with the pressure roller has been devised and implemented. However, reducing the throughput reduces the specifications of the image forming apparatus, and providing the heat radiation roller increases the cost significantly.

  Therefore, a configuration is disclosed in which a low-cost soaking member such as a thin aluminum plate is placed in contact with the heater to suppress the temperature rise of the non-sheet passing portion (Patent Document 2). As an effect of the heat equalizing member, it can be mentioned that the excessive heat of the non-sheet passing portion is conveyed to the sheet passing portion, so that the temperature can be equalized over the entire heater.

  Further, as another effect of using the heat equalizing member, the temperature of the heat equalizing member rises due to the excessive heat of the non-sheet passing portion being carried to the paper passing portion, and the thermistor disposed in contact with the heat equalizing member. The detected temperature rises above the target temperature. For this reason, the electric power consumed in order to reduce detection temperature to target temperature can be restrained low. That is, the effect of reducing power consumption occurs.

JP 63-313182 A Japanese Patent Laid-Open No. 11-84919

  However, when a soaking member that is long in the longitudinal direction of the nip portion is used, there is a possibility that a part of the soaking member (such as a positioning portion formed by bending) is damaged or the soaking member is deformed.

  Here, in the longitudinal direction of the nip portion, it is conceivable to divide the heat equalizing member into a plurality of parts and arrange the heat equalizing members side by side with a gap therebetween to reduce the expansion amount of the heat equalizing member. In this case, by dividing the heat equalizing member into a plurality of parts, the effect of heat equalization over the entire heater substrate is reduced, or the heat transfer from the non-sheet passing part to the thermistor part is cut off, resulting in an effect of reducing power consumption. A configuration that can prevent the deterioration is desired.

  An object of the present invention is to divide the heat equalizing member into a plurality of parts, thereby reducing the effect of heat equalization over the entire heater substrate or blocking heat transfer from the non-sheet passing portion to the thermistor portion. An object of the present invention is to provide an image heating apparatus capable of preventing the reduction effect from being lowered.

  In order to achieve the above object, an image heating apparatus according to the present invention includes a cylindrical film, a heater that contacts the inner surface of the film, a pressure member that forms a nip portion together with the heater via the film, An image heating apparatus that heats the image while conveying the recording material on which an image is formed at the nip portion, in a longitudinal direction orthogonal to the conveyance direction of the recording material. The first and second heat equalizing members contacting the surface opposite to the surface contacting the inner surface of the film of the heater, and the opposing surfaces of the first and second heat equalizing members are mutually opposite It has a 3rd heat equalizing member which is spaced apart and contacts on each surface different from the said opposing surface of the said 1st and 2nd heat equalizing member, It is characterized by the above-mentioned.

  Another image heating apparatus according to the present invention includes a cylindrical film, a heater that contacts the inner surface of the film, a pressure member that forms a nip portion together with the heater via the film, and the heater. An image heating apparatus that heats the image while conveying the recording material on which an image is formed at the nip portion, and the heater in a longitudinal direction orthogonal to the conveyance direction of the recording material The first and second heat equalizing members that are in contact with the surface opposite to the surface that is in contact with the inner surface of the film, and the opposing surfaces of the first and second heat equalizing members are spaced apart from each other, Respective surfaces different from the opposing surfaces of the first and second heat equalizing members are in contact with each other.

  Further, another image heating apparatus according to the present invention includes a pressure member that has one surface of the fixing member that slides in contact with the heater, the other surface of the fixing member contacts the material to be heated, and is in pressure contact with the fixing member. In the image heating apparatus that forms a nip portion between the heaters, and the heat of the heater is transferred to the heated material through the fixing member by moving the fixing member and the heated material over the heater. The heater has a plurality of heat equalizing members disposed on a surface opposite to the surface sliding in contact with the fixing member, and the plurality of heat equalizing members are disposed in contact with each other. To do.

  According to the present invention, by dividing the heat equalizing member into a plurality of parts, the effect of heat equalization over the entire heater substrate is reduced, or the heat transfer from the non-sheet passing portion to the thermistor portion is interrupted to reduce the power consumption. It is possible to provide an image heating apparatus that can prevent the reduction effect from being reduced.

1 is a schematic configuration diagram illustrating a main part of an image forming apparatus equipped with an image heating apparatus according to an embodiment of the present invention. 1 is a schematic configuration diagram of an image heating apparatus according to an embodiment of the present invention. It is a top view of the heater in the image heating apparatus which concerns on embodiment of this invention. 3 is a configuration diagram of a heat equalizing member in Embodiment 1. FIG. 3 is an element diagram of each heat equalizing member in Embodiment 1. FIG. It is a block diagram of the soaking | uniform-heating member in Example 2. FIG. It is an element diagram of the heat equalizing member in Example 2. It is a block diagram of the soaking | uniform-heating member in Example 3. FIG. It is an element diagram of the heat equalizing member in Example 3. 5 is a configuration diagram of a heat equalizing member in Comparative Example 1. FIG. It is a block diagram of the heat equalization member in the comparative example 2. It is a block diagram which does not use the soaking | uniform-heating member in the comparative example 3.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<< First Embodiment >>
(Image forming device)
FIG. 1 is a schematic configuration diagram of an example of an image forming apparatus in which an image heating apparatus according to an embodiment of the present invention is mounted as a heat fixing apparatus. This image forming apparatus is a laser beam printer using a transfer type electrophotographic process.

  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 at a predetermined peripheral speed (process speed) in an arrow U direction (clockwise). The photosensitive drum 1 has a configuration in which a photosensitive material layer such as OPC, amorphous Se, or amorphous Si is formed on the outer peripheral surface of a cylinder (drum) -like conductive substrate such as aluminum or nickel.

  The photosensitive drum 1 is uniformly charged to a predetermined polarity and potential by a charging roller 2 as a charging means during the rotation process. Then, a laser beam is output from the laser beam scanner 3 to the uniformly charged surface of the photosensitive drum 1. Specifically, scanning exposure L is performed with a laser beam that is modulation-controlled (ON / OFF control) according to image information, whereby an electrostatic latent image of target image information is formed on the surface of the photosensitive drum.

  The electrostatic latent image is developed with the toner T by 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 stored in the paper feed cassette 9 is fed out one by one by driving the paper feed roller 8, and passes through the sheet path having the guide 10 and the registration roller 11, so that the photosensitive drum 1 and the transfer roller 5. The sheet is fed at a predetermined control timing to the transfer nip portion which is a pressure contact portion. Then, the toner image on the surface side of the photosensitive drum 1 is sequentially transferred onto the surface of the recording material P as the material to be heated.

  The recording material P that has exited the transfer nip is sequentially separated from the surface of the photosensitive drum 1, and is introduced by a conveying device 12 into a heat fixing device (hereinafter referred to as a fixing device) 6 as an image heating device in the direction of arrow a. The toner image is heat-fixed. The fixing device 6 will be described in detail later.

  The recording material P that has exited the fixing device 6 passes through a sheet path having a conveyance roller 13, a guide 14, and a paper discharge roller 15, and is printed out on the paper discharge tray 16.

  Further, the surface of the photosensitive drum after separation of the recording material is subjected to a removal process of adhering contaminants such as transfer residual toner by the cleaning device 7 to be cleaned and again used for image formation.

  In this embodiment, an image forming apparatus compatible with letter size paper having a process speed of 200 mm / sec is used. The toner T was mainly composed of a styrene acrylic resin, and a toner having a glass transition point of 55 to 65 ° C. in which a charge control component, a magnetic material, silica and the like were added and added as necessary.

(Fixing device)
FIG. 2 is a schematic configuration model diagram of the fixing device 6 of the present embodiment using the film heating method. In the following description, the direction perpendicular to the paper surface of FIG.

  The fixing device 6 includes a cylindrical film 23 as a fixing member, a heater 22 in which one surface of the film 23 contacts and slides, and a pressure roller that forms a fixing nip (nip portion) N with the heater 22 via the film 23. (Pressure member) 24. The heater 22 is held (supported) by a film guide member 21 serving as a heat-resistant resin holding member (supporting member). The film guide member 21 has a heater holding function and a guide function for guiding the rotation of the film 23. The film guide member 21 is, for example, a molded product of a heat resistant resin such as PPS (polyphenylene sulfite) or a liquid crystal polymer.

  The pressure roller 24 receives power from the motor M and rotates in the arrow b direction. As the pressure roller 24 rotates, the film 23 follows and rotates in the direction of arrow c. When the recording material P is nipped and conveyed (moved) in the direction of the arrow a at the nip portion N, the toner image on the recording material with which the other surface of the film 23 comes into contact is transferred to the recording material P by transferring the heat of the heater 22. It is fixed by heating. Then, the recording material P that has passed through the nip portion N is conveyed to the paper discharge tray 16.

  In FIG. 2, the heat equalizing member 26 contacts the surface of the heater 22 opposite to the surface that contacts the inner surface of the film 23, and the temperature detecting element 25 contacts the surface of the heat equalizing member 26 opposite to the heater 22. It touches.

  Regarding the temperature control of the heater 22, the output of the temperature detection element 25 is A / D converted and taken into the CPU 28, and the electric power supplied to the heater 22 by the power source (AC power source) 30 and the triac 29 based on the information is phased, Control is performed by wave number control or the like. That is, by controlling the energization so that the heater 22 is heated when the temperature detected by the temperature detecting element 25 is lower than the temperature control temperature, and when the temperature is higher than the temperature control temperature, the heater 22 is kept at a constant temperature during fixing. Kept.

The heater 22 includes a substrate 22a made of alumina (Al ₂ O ₃ ) and a heating resistor 22b mainly made of silver / palladium (Ag · Pd) formed on the substrate 22a. Further, as shown in FIGS. 3 and 4, the heater 22 has a conductive pattern 22d mainly composed of silver (Ag) and an insulating (glass in this embodiment) surface protection covering the heating resistor 22b and the conductive pattern 22d. It has the layer 22c and the electrode 22e which contacts the connector for electric power feeding. The electrode 22e is made of the same material as the conductive pattern 22d.

The material constituting the heater 22 is not limited to the above-described one, and ceramics such as high thermal conductivity aluminum nitride (AlN) is used as the substrate 22a, and ruthenium oxide (RuO ₂ ), carbon, or the like is used as the heating resistor 22b. Also good.

  FIG. 3 is a plan view of the heater 22 in the present embodiment. The substrate 22a formed of alumina has a thickness of 1 mm, a length in the longitudinal direction of 250 mm, and a length (width) in the direction perpendicular to the longitudinal direction of 8 mm. The heating resistor 22b was formed by coating an electrically resistive material made of silver palladium with a thickness of about 10 μm, a longitudinal length of 216 mm, and a width of 1.0 mm by screen printing.

  On the left side of FIG. 3, these two heating resistors 22b are electrically connected in series by a conductive pattern 22d, while on the right side of FIG. 3, a conductive pattern 22d and a feeding electrode for supplying power to the heating resistor 22b. 22e is formed. The conductive pattern 22d and the feeding electrode 22e were formed by coating with a thickness of about 10 μm by screen printing, and finally the surface glass layer 22c was formed by screen printing with a thickness of about 50 μm. The total resistance value was 20Ω.

  The thickness of the film 23 is preferably about 20 μm or more and 100 μm or less in order to ensure good thermal conductivity. The film 23 is a composite layer film in which the surface of the base layer is coated with PTFE / PFA / FEP (tetrafluoroethylene-perfluoroalkyl vinyl ether) or the like as a release layer.

  As the material of the base layer, a single layer film 23 made of PTFE (polytetrafluoroethylene), PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether), PPS, or the like is used. Alternatively, as the material of the base layer, polyimide, polyamideimide, PEEK (polyether ether ketone), PES (polyether sulfone), or the like is used.

  The pressure roller 24 includes a cored bar 24a made of iron or aluminum, an elastic layer 24b made of silicone rubber or the like, and a release layer 24c made of PFA or the like. In this embodiment, the outer diameter is 25 mm, the length is 240 mm, the thickness of the elastic layer 24 b is 3 mm, and the roller hardness is 48 ° (ASKER-C 600 g load).

(Characteristic configuration and effect of this embodiment)
The image heating apparatus according to this embodiment includes first and second heat equalizing members that are in contact with a surface opposite to a surface that is in contact with the inner surface of the heater film in a longitudinal direction perpendicular to the conveyance direction of the recording material. . The first and second soaking members are each provided with a positioning portion that is positioned on the film guide member 21 at only one location in the longitudinal direction. The opposing surfaces of the first and second soaking members are separated from each other, and the surfaces different from the opposing surfaces of the first and second soaking members are in contact with each other, or a third soaking is performed. Connect via a member.

  In this way, the heat equalizing member is divided into a plurality of parts in the longitudinal direction, and the respective heat equalizing members are in contact with each other. Therefore, the heat equalizing members are thermally connected over the entire area in the longitudinal direction. The effect of heat equalization over the entire substrate and the effect of reducing power consumption can be obtained. Furthermore, since the soaking members that are in contact with each other can expand while being in contact with each other, damage to the positioning portion of the soaking member and deformation of the soaking member can be prevented.

  Hereinafter, examples in the present embodiment will be described together with comparative examples.

Example 1
FIG. 4 is a diagram illustrating a state in which the first heat equalizing member 26 a, the second heat equalizing member 26 b, and the third heat equalizing member 26 c are arranged on the back side of the heater 22 in the fixing device of the present embodiment. is there. The first soaking member 26a and the second soaking member 26b are arranged on the back surface of the heater 22, and the surfaces k1 and k2 that face each other in the longitudinal direction are separated from each other. The third heat equalizing member 26c is in contact with different surfaces (upper surface opposite to the heater 22) m1 and m2 of the first and second heat equalizing members 26a and 26b. As the soaking member 26 (26a, 26b, 26c) in this example, an aluminum plate (JIS alloy name: A1050) having a thermal conductivity of 230 W / (m · K) and a thickness of 0.3 mm was used. The first and second heat equalizing members 26a and 26b are formed by cutting the aluminum plate into strips and bending one end as shown in FIG. 5 (a), and the positions of the film guide member 21 and the aluminum plate. Is processed into a positioning shape to fix the.

  The first and second heat equalizing members 26a and 26b have a length in the longitudinal direction of the surface in contact with the heater 22 of 105 mm and a width of 8 mm which is the same as the width of the heater 22, and the positioning portions g1 and g2 The length in the longitudinal direction is 5 mm and the width is 8 mm. As shown in FIG. 4, the positioning portions g1 and g2 are provided on one end side and the other end side in the longitudinal direction.

  On the other hand, as shown in FIG.5 (b), the 3rd soaking | uniform-heating member 26c cuts an aluminum plate in convex shape, bends a convex part, and forms the positioning shape. The size of the third heat equalizing member 26c is such that the length in the longitudinal direction of the surface in contact with the first and second heat equalizing members 26a and 26b is 26 mm, the width is 8 mm, and the length in the longitudinal direction of the positioning portion g3. Is 5 mm in width and 5 mm in width. As shown in FIG. 4, the positioning part g3 is provided in the central part in the longitudinal direction.

  Here, a method of manufacturing the heat generating unit (heater unit) by attaching the heat equalizing member 26 (26a, 26b, 26c) in the present embodiment to the heater 22 will be described below. In FIG. 4, first, the third heat equalizing member 26 c is attached to the film guide member 21. Next, the first and second soaking members 26a and 26b are attached to the film guide member 21 from above the third soaking member 26c.

  The first and second heat equalizing members 26a and 26b are arranged with their positioning portions g1 and g2 aligned with both ends of the heating resistor 22b of the heater 22, and the first and second heat equalizing members 26a and 26b. A gap of 6 mm is provided between the surfaces facing each other in the longitudinal direction. The length in the longitudinal direction of the portion where the third heat equalizing member 26c and the first and second heat equalizing members 26a and 26b are in contact with each other is 10 mm.

  Finally, the heater 22 is attached and fixed to the film guide member 21 from above the first and second heat equalizing members 26a and 26b, so that the third heat equalizing member 26c and the first heat equalizing member 26c are in the positional relationship shown in FIG. The second heat equalizing members 26a and 26b and the heater 22 are fixed in close contact with each other.

  In this embodiment, as shown in FIG. 4, a temperature detecting element 25 such as a thermistor is in contact with the surface of the first heat equalizing member 26 a opposite to the heater 22, and the temperature detected by the temperature detecting element 25 is adjusted. Accordingly, energization to the heating resistor 22b is controlled. A thermo switch 27 is in contact with the surface of the second heat equalizing member 26b opposite to the heater 22.

(Example 2)
The present embodiment aims to reduce the number of points of the heat equalizing member as compared with the configuration shown in the first embodiment and to reduce the contact thermal resistance generated between different heat equalizing members. FIG. 6 is a view showing a state in which the soaking members 26 (26 a, 26 d) of this embodiment are arranged on the back surface of the heater 22. The first heat equalizing member 26a provided with the positioning portion g1 is the same as that in the first embodiment. The second heat equalizing member 26d uses the same aluminum plate as in the first embodiment, but has a shape bent in a stepped manner such that the heat equalizing members 26b and 26c in the first embodiment are integrated as shown in FIG. doing.

  As for the size of the second heat equalizing member 26d, the length in the longitudinal direction of the surface in contact with the heater 22 is 105 mm and the width is 8 mm. Moreover, the length of the longitudinal direction of the surface which is bend | folded at step shape and contacts the 1st soaking | uniform-heating member 26a is 16 mm, and width is 8 mm.

  The length of the positioning portion g2 'in the longitudinal direction is 5 mm and the width is 8 mm. The first and second heat equalizing members 26a and 26d are arranged with their positioning portions g1 and g2 'aligned with both ends of the heating resistor 22b of the heater 22, and the first and second heat equalizing members 26a A gap of 6 mm in the longitudinal direction is provided between 26d. And the length in the longitudinal direction of the part where the 1st soaking | uniform-heating member 26a and the 2nd soaking | uniform-heating member 26d mutually contact is 10 mm.

  In the present embodiment, similarly to the first embodiment, the temperature detecting element 25 is in contact with the surface of the first heat equalizing member 26a opposite to the heater 22, and the thermo switch 27 is connected to the second heat equalizing member 26d. It is in contact with the surface opposite to the heater 22.

(Example 3)
In this embodiment, in addition to measures for raising the temperature of the non-sheet passing portion and preventing damage to the heat equalizing member 26 and deformation as in the above-described embodiment, the heater 22 is prevented from being damaged electrically. is there. That is, in this embodiment, when a triac or relay used in the power supply circuit fails, the thermoswitch 27 is operated without delay even in a state where the primary current is supplied to the heater 22 without being controlled. The thermo switch 27 is operated to prevent the 22 from being damaged. Hereinafter, this configuration will be described.

  If an excessive primary current is input to the heater 22, the heater 22 is excessively heated, an excessive thermal stress is applied to the heater 22, the heater 22 is cracked, and the heater 22 may not be used. In order to prevent this, when the primary current flows, the thermo switch 27 is operated before the heater 22 is overheated and the heater 22 is cracked due to thermal stress or mechanical stress. There is a way to block.

  Here, it is desirable to shorten the time until the thermo switch 27 operates so that there is no delay as much as possible. For this reason, in this embodiment, as shown in FIG. 8, the thermo switch 27 is in direct contact with the heater 22 (substrate 22a). The first and second heat equalizing members 26f and 26g are made of the same aluminum plate as in the first embodiment. The size of the first heat equalizing member 26f is 104 mm in length in the longitudinal direction of the surface in contact with the heater 22, 8 mm in width, 5 mm in the longitudinal direction of the positioning portion g1, and 8 mm in width.

  On the other hand, the second heat equalizing member 26g is in contact with the first heat equalizing member 26f so as to bypass the thermo switch 27 as shown in FIG. Here, the size of the second heat equalizing member 26g is 104 mm in length in the longitudinal direction of the surface (26g-1) in contact with the heater 22 and 8 mm in width, and is in contact with the first heat equalizing member 26f. The length in the longitudinal direction of the portion (26g-3) is 10 mm and the width is 8 mm. Note that the length in the longitudinal direction of the positioning portion g2 ″ of the second heat equalizing member 26g is 5 mm and the width is 8 mm.

  And the part (inner wall surface) which detours the thermo switch 27 in the 2nd soaking | uniform-heating member 26g is larger than this, since the size of the thermo switch 27 is 4 mm in width (horizontal direction of FIG. 8) and 4 mm in height ( The horizontal direction in FIG. 8 is 8 mm, and the height is 6 mm. Further, the length of the outer wall surface (26g-2) in the second heat equalizing member 26g in the longitudinal direction (horizontal direction in FIG. 8) is 8 mm, and the width is 8 mm. The first and second heat equalizing members 26f and 26g are arranged with their positioning portions g1 and g2 '' aligned with both ends of the heating resistor 22b of the heater 22, and the first and second equalizing members in the longitudinal direction. A gap of 8 mm is provided between the heat members 26f and 26g.

  As in the first and second embodiments, the temperature detecting element 25 is in contact with the surface of the first heat equalizing member 26f opposite to the heater 22.

(Comparative Example 1)
FIG. 10 is a view showing this comparative example in which a heat equalizing member that is not divided into a plurality in the longitudinal direction is arranged on the back surface of the heater 22. The material of the heat equalizing member 26e is the same aluminum plate as in the first embodiment, the size is 216 mm in length in the longitudinal direction of the surface in contact with the heater 22, the width is 8 mm, and positioning portions g3 provided at both ends. Each g4 has a length in the longitudinal direction of 5 mm and a width of 8 mm. Positioning portions g3 and g4 of the heat equalizing member 26e are arranged at both ends of the heating resistor 22b of the heater 22 as shown in FIG. The temperature detecting element 25 and the thermo switch 27 are in contact with the surface of the heat equalizing member 26e opposite to the heater 22.

(Comparative Example 2)
FIG. 11 is a view showing this comparative example in which a heat equalizing member that is divided into a plurality in the longitudinal direction but is not thermally connected is arranged on the back surface of the heater 22. The first and second heat equalizing members 26a and 26b are the same as those in the first embodiment. The first and second heat equalizing members 26a and 26b are arranged with their positioning portions g1 and g2 aligned with both ends of the heating resistor 22b of the heater 22, and the first and second heat equalizing members 26a and 26b. A gap of 6 mm is provided between them.

  The temperature detecting element 25 contacts the surface of the first heat equalizing member 26a opposite to the heater 22, and the thermo switch 27 contacts the surface of the second heat equalizing member 26b opposite to the heater 22. ing.

(Comparative Example 3)
FIG. 12 is a view showing this comparative example in which the soaking member 26 is not used. The temperature detecting element 25 and the thermo switch 27 are in contact with the surface of the heater 22 opposite to the heating resistor 22b.

(Results of non-sheet passing part temperature rise test)
As a non-sheet passing portion temperature increase test, continuous 150 sheets of 128 g / m ² , A4 size recording material were passed. Table 1 shows positioning member breakage of the soaking member, soaking member distortion, non-sheet passing portion temperature on the surface of the pressure roller 24 (temperature measured by a thermoviewer as a state of temperature rise of the non-sheet passing portion), and soaking The non-sheet passing portion temperature of the member 26 (temperature measured by attaching a thermocouple) is shown.

1) Example 1
In the configuration of Example 1 (FIG. 4), when the temperature rises, the first and second heat equalizing members 26a and 26b thermally expand into the gap provided between the two starting from the positioning portions g1 and g2. Start. The amount of thermal expansion is obtained by multiplying the length of the soaking member by the expansion coefficient (23.6 × 10 ⁻⁶ [K ⁻¹ ] for aluminum A1050) and the amount of temperature change. That is, if the temperature of the first and second soaking members 26a and 26b rises from room temperature (20 ° C.) to 230 ° C. of the non-sheet passing portion, the thermal expansion amount is about 0.56 mm.

  Since the gap (longitudinal direction) provided between the first and second soaking members 26a and 26b is 6 mm, a gap of 4.88 mm is secured between the two even after thermal expansion, and they collide with each other. There is no. On the other hand, the third heat equalizing member 26c thermally expands by about 0.07 mm in both longitudinal directions while sliding on the first and second heat equalizing members 26a and 26b around the positioning portion g3. . A gap of 2 mm is provided in the longitudinal direction between the end portion of the third heat equalizing member 26c and the film guide member 21, and does not collide after thermal expansion.

  Thus, by setting a gap with a margin so that excessive force is not applied to the inside of the positioning portion and the heat equalizing member even after expansion, damage to the positioning portion and distortion of the heat equalizing member may occur. There wasn't.

  Further, in Example 1, as a result of obtaining the soaking effect and the power consumption reduction effect by the soaking member 26, the non-sheet passing portion temperature on the surface of the pressure roller 24 is 210 ° C., and the use limit temperature of the pressure roller 24 Of 230 ° C. The non-sheet passing portion temperature of the soaking member 26 was 230 ° C.

2) Example 2
Even in the configuration of Example 2 (FIG. 6), the positioning portions g1 and g2 ′ were not damaged and the heat equalizing members 26 (26a and 26d) were not distorted. That is, when the temperature rises from room temperature to 227 ° C., the soaking members 26a and 26d thermally expand about 0.56 mm from the positioning portions g1 and g2 ′ to the gap direction between them. However, since a gap of 6 mm is provided between the two as in the first embodiment, they do not collide with each other.

  Although the surface of the soaking member 26d that contacts the soaking member 26a also expands by about 0.09 mm, a gap of 2 mm is provided between the end of the soaking member 26d and the film guide member 21, There is no collision after expansion. Thus, also in Example 2, the positioning part was not damaged and the soaking member was not distorted.

  In the configuration of the second embodiment, the non-sheet passing portion temperature on the surface of the pressure roller 24 is 207 ° C., which is an improvement over the first embodiment. This is considered to be because the contact heat resistance between the soaking members is smaller than that in Example 1, and the heat transfer effect of the entire soaking member is increased. The non-sheet passing portion temperature of the soaking member 26 was 227 ° C.

3) Example 3
Also in Example 3 (FIG. 8), the positioning portions g1 and g2 ″ were not damaged and the soaking members 26 (26f and 26g) were not distorted. The soaking members 26f and 26g, like the first and second embodiments, thermally expand into the gap between the positioning portions g1 and g2 ''. Unlike the first and second embodiments, the thermoswitch 27 is disposed in the gap portion, but the expansion amounts of the portions 26g-1 of the heat equalizing members 26f and 26g are both about 0.55 mm. A gap of 2 mm is provided between 26 g and the thermo switch 27. For this reason, the heat equalizing members 26f and 26g and the thermo switch 27 do not collide with each other.

  Moreover, the clearance gap provided between the film guide member 21 in the longitudinal direction of the part shown by 26g-2 and 26g-3 of the soaking | uniform-heating member 26g is 2 mm. On the other hand, the total expansion amount of the 26g-1 and 26g-2 portions is about 0.59 mm, and the total expansion amount of the 26g-1, 26g-2 and 26g-3 portions is about 0.65 mm. Therefore, the soaking member 26 and the film guide member 21 do not collide with each other in each gap.

  Further, the gap between the portion 26g-2 of the heat equalizing member 26g and the film guide member 21 positioned in the upper direction in FIG. 8 is 2 mm, but the expansion amount in the height direction of the heat equalizing member 26g is about 0.03 mm. Therefore, the soaking member 26g and the film guide member 21 do not collide with each other.

  In the configuration of the third embodiment, the non-sheet passing portion temperature on the surface of the pressure roller 24 is 207 ° C., and the same effect as the second embodiment is obtained with respect to the temperature rise of the non-sheet passing portion. The non-sheet passing portion temperature of the soaking member 26 was 227 ° C.

4) Comparative Example 1
Comparative Example 1 (FIG. 10) is regulated at both ends in the longitudinal direction, unlike Examples 1, 2, and 3, in which only one end in the longitudinal direction is restricted and the other end is a free end. That is, the thermal expansion of the soaking member 26e is restricted by the positioning portions g3 and g4 at both ends in the longitudinal direction. Therefore, the expansion amount of about 1.13 mm of the heat equalizing member 26e cannot be absorbed anywhere, and excessive force is applied to the positioning portions g3 and g4 to cause damage to the positioning portions g3 and g4, or the inside of the heat equalizing member 26e. May cause distortion.

  And since the comparative example 1 was equipped with the one soaking | uniform-heating member 26e which is not divided | segmented to a longitudinal direction, the soaking | uniform-heating effect was the highest, and the non-sheet passing part temperature of the pressure roller 24 surface was the lowest with 204 degreeC. The non-sheet passing portion temperature of the soaking member 26 was 224 ° C.

5) Comparative Example 2
In the comparative example 2 (FIG. 11), the first and second heat equalizing members 26a and 26b divided in the longitudinal direction as in the first embodiment go to the gap provided between the positioning portions g1 and g2. And can be thermally expanded. For this reason, the positioning part was not damaged and the first and second heat equalizing members 26a and 26b were not distorted.

  However, since heat is not transmitted between the first and second soaking members 26a and 26b, the heat of the non-sheet passing portion temperature rise on the second soaking member 26b side is changed to the first soaking member. It cannot be transmitted to the temperature detecting element 25 in contact with 26a. For this reason, the power consumption reduction effect could not be obtained. As a result, the non-sheet-passing portion temperature on the surface of the pressure roller 24 was 223 ° C., and the non-sheet-passing portion temperature increase was worse than that in Example 1. The non-sheet passing portion temperature of the soaking member 26 was 243 ° C.

6) Comparative Example 3
Since Comparative Example 3 (FIG. 12) does not include a soaking member, the non-sheet passing portion temperature on the surface of the pressure roller 24 is 245 ° C., which is the highest temperature, and exceeds the use limit temperature 230 ° C. of the pressure roller 24. It was.

  As described above, in the present embodiment, by adopting the configuration described in the first, second, and third embodiments, the positioning portion of the heat equalizing member is prevented from being damaged and the heat equalizing member is prevented from being deformed. It becomes possible to suppress temperature.

(Measurement result of operating time of thermo switch 27)
Next, the results of measuring the operating time of the thermoswitch 27 will be described with respect to Example 3 as compared with Example 2. The largest thermal stress is applied to the heater 22 when the maximum power that can be supplied to the image forming apparatus is continuously supplied to the fixing device 6. Therefore, when the power supply voltage 120V was applied so that the maximum power was applied to the heater 22 without performing temperature control or the like, the time until the thermoswitch 27 operated and the primary current was cut off was measured. Since the resistance value of the heater 22 is 20Ω when the power supply voltage 120V is applied, the electric power supplied to the heater 22 is 720W.

  Table 2 shows the operation time of the thermo switch 27. While Example 2 was 4.2 seconds, Example 3 and Comparative Example 3 operated 0.6 seconds earlier, such as 3.6 seconds. This is considered to be because the time until the heat of the heater 22 is transmitted to the thermo switch 27 is delayed because the thermo switch 27 is brought into contact with the thermo switch 27 via the heat equalizing member 26d in the second embodiment. Therefore, in order to operate the thermo switch 27 faster, it is understood that the thermo switch 27 should be in direct contact with the heater 22 (substrate 22a) as in the third embodiment.

(Modification)
As mentioned above, although embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary. Incidentally, the setting of the thickness, length, and number of the heat equalizing members 26 described in each example of the present embodiment is merely an example, and is not limited to the described numerical values.

(Modification 1)
Although the soaking | uniform-heating member 26 in embodiment mentioned above was an aluminum plate, this invention is not limited to this. A metal plate other than an aluminum plate or a highly heat conductive sheet such as a graphite sheet may be used, or a mixture thereof may be used. Furthermore, you may apply | coat heat conductive grease and sliding grease to the part which soaking | uniform-heating member 26 contacts.

(Modification 2)
In the above-described embodiment, the positioning portions g1, g2, and the like are provided at the end in the longitudinal direction, but may be provided at other positions in the longitudinal direction (for example, the central portion).

21 .. Film guide member, 22 .. Heater, 22 a .. Substrate, 22 b .. Resistance heating element, 23 .. Film, 24 .. Pressure roller, 26, 26 a, 26 b, 26 c, 26 d, 26 g. Thermal member, k1, k2,... Facing surface, m1, m2 .. surface different from facing surface

Claims (13)

A tubular film,
A heater in contact with the inner surface of the film;
A pressure member that forms a nip portion with the heater through the film;
A support member for supporting the heater;
An image heating apparatus that heats the image while conveying a recording material on which an image is formed at the nip portion,
In the longitudinal direction perpendicular to the conveyance direction of the recording material, the heater has first and second heat equalizing members that are in contact with the surface opposite to the surface that is in contact with the inner surface of the film,
The opposing surfaces of the first and second soaking members are spaced apart from each other,
An image heating apparatus, comprising: a third heat equalizing member that is in contact with each of the surfaces different from the opposing surfaces of the first and second heat equalizing members.   The first and second heat equalizing members and the third heat equalizing member each have a positioning portion with respect to the support member, and each of the positioning portions is provided only in one place in the longitudinal direction. The image heating apparatus according to claim 1.   3. The image heating apparatus according to claim 2, wherein each of the first and second heat equalizing members and the third heat equalizing member includes a free end different from the positioning portion in the longitudinal direction. The positioning portion is provided at one end side and the other end side in the longitudinal direction in the first and second heat equalization members, respectively, and in the third heat equalization member, at the center portion in the longitudinal direction. The image heating apparatus according to claim 2, wherein the image heating apparatus is provided. A tubular film,
A heater in contact with the inner surface of the film;
A pressure member that forms a nip portion with the heater through the film;
A support member for supporting the heater;
An image heating apparatus that heats the image while conveying a recording material on which an image is formed at the nip portion,
In the longitudinal direction perpendicular to the conveyance direction of the recording material, the heater has first and second heat equalizing members that are in contact with the surface opposite to the surface that is in contact with the inner surface of the film,
The opposing surfaces of the first and second soaking members are spaced apart from each other,
The image heating apparatus according to claim 1, wherein surfaces of the first and second heat equalizing members that are different from the facing surfaces are in contact with each other.   6. The image heating apparatus according to claim 5, wherein one of the first and second heat equalizing members has a bent shape when viewed from the conveyance direction of the recording material.   The said 1st and 2nd soaking | uniform-heating member has a positioning part with the said supporting member, respectively, and the said positioning part is provided with only one place in the said longitudinal direction, respectively. 2. An image heating apparatus according to item 1.   The image heating apparatus according to claim 7, wherein each of the first and second heat equalizing members includes a free end different from the positioning portion in the longitudinal direction. The image heating apparatus according to claim 7, wherein the positioning portion is provided on one end side and the other end side in the longitudinal direction in the first and second heat equalizing members, respectively.   10. The image heating apparatus according to claim 1, further comprising a temperature detection element on one of the first and second soaking members. 11.   11. The image heating apparatus according to claim 1, wherein a thermo switch is provided on one of the first and second soaking members. 11.   11. The thermo switch according to claim 1, further comprising a thermo switch disposed in contact with the heater in a gap portion formed between the surfaces of the first and second heat equalizing members that are spaced apart from each other. Image heating device. One surface of the fixing member slides in contact with the heater, the other surface of the fixing member contacts the material to be heated, and a nip portion is formed between the fixing member and the pressure member that is pressed against the fixing member. In the image heating apparatus for transferring the heat of the heater to the heated material through the fixing member by moving the fixing member and the heated material,
The heater includes a plurality of heat equalizing members disposed on a surface opposite to the surface sliding with the fixing member, and the plurality of heat equalizing members are disposed in contact with each other. An image heating apparatus.