JP2020038400A - Image heating device - Google Patents

Abstract

To solve the problem in which: in an image heating device of a film heating system provided with a heat conduction member 140 on the rear face of a heating heater 113, the heat conduction member 140 may be shifted or deformed in the longitudinal direction due to repetition of a heat cycle; when the shift and deformation of the heat conduction member 140 causes a contact failure with the heating heater 113, image defects including unevenness in glossiness may occur in a fixed image.SOLUTION: A regulation part 140a regulating the position of a heat conduction member 140 is provided at a portion corresponding to an area where a pressing force is relatively high in the longitudinal direction of a fixing nip No and the width in the short direction of the fixing nip is large, so as to suppress shift or deformation in the longitudinal direction of the heat conduction member 140 due to repetition of a heat cycle and prevent image defects including unevenness in glossiness and damage to a fixing member.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image heating apparatus suitable for use as a fixing device mounted on an image forming apparatus such as a copying machine of an electrophotographic system or a laser beam printer.

  As a fixing device, a heat roller system, a film (belt) heating system, and the like are conventionally known. Patent Document 1 discloses a fill heating type image heating apparatus in which a heat conducting member is provided on the back surface of a heater to suppress so-called non-paper passing portion temperature rise (heating of a recording material non-passing portion). This apparatus has a problem in that the heat conductive member is shifted with respect to the support member and the effect of suppressing the rise in the temperature of the non-sheet passing portion is reduced. This problem is solved by locking the conductive member to the support member in a direction perpendicular to the recording material conveyance direction by the locking portion.

JP 2014-238560 A

  The present invention relates to a further improvement of the above technique. That is, even if a regulating portion is provided to prevent the longitudinal direction of the heat conducting member from shifting, the heat conducting member may be shifted with respect to the heater when the heat cycle is repeated. In particular, when using an aluminum material with high thermal conductivity as the heat conductive member, or when using a thin heat conductive member to reduce the heat capacity, the strength of the heat conductive member is weak, and the force that moves due to thermal expansion is reduced. In some cases, the strength of the restricting portion was lost, and the restricting portion was deformed and shifted.

  In addition, when the regulating portion of the heat conducting member is deformed, the contact surface with the heater may be deformed, and the contact with the heater may be reduced. When the heat conducting member floats from the heater, the temperature of the heater in that portion rises, and temperature unevenness occurs in the longitudinal direction. In the case where the temperature unevenness in the longitudinal direction causes an image failure as gloss unevenness on the image, or when the temperature rise of the heater is high, heat loss of the heater holder or the pressure roller may be considered. In addition, when the heat conduction member is displaced from the heater due to the heat cycle, it is conceivable that the fixing failure at the end portion or the damage to the fixing member may occur as described above.

  An object of the present invention is to suppress the displacement and deformation of the heat conducting member.

  A typical configuration of the image heating apparatus according to the present invention for achieving the above object is a heating member having an elongated substrate and a resistance heating element formed along the length of the substrate along the length thereof and generating heat by energization, A heat conducting member having a heat conductivity higher than the heat conductivity of the substrate at least in a direction parallel to the plane with the holding member holding the heating member, which is sandwiched between the heating member and the holding member. A heat conductive member, an endless belt rotatable while an inner peripheral surface is in contact with a surface of the heating member opposite to the side of the heat conductive member, the belt being rotatable while sliding, and the heating member sandwiching the belt. A rotating member having elasticity that forms a nip with the outer surface of the belt in contact with the belt, and heats the recording material carrying an image in the nip while nipping and transporting the recording material. The member corresponds to the holding member. When the width in the recording material conveyance direction of the nip portion is a short width, the short width is a thick portion and a narrow portion in the longitudinal direction of the nip portion. In addition, the present invention is characterized in that the regulating portion is provided on a side of a portion where the short width is thicker than a middle portion between a thick portion and a thin portion.

  ADVANTAGE OF THE INVENTION According to this invention, the displacement and deformation of a heat conductive member can be suppressed.

Configuration explanatory view of a main part of the first embodiment Schematic diagram of an example of an image forming apparatus Explanatory drawing of the main part of the fixing device Block diagram of control system Assembly drawing for assembling the heat conducting member and heater to the heater holder Illustration of fixing nip adjustment Explanatory drawing of a fixing nip of a fixing device according to the first embodiment. Explanatory drawing of a fixing nip of a fixing device according to a second embodiment. Explanatory view of a main part of a fixing device according to a second embodiment. Explanatory view of a main part of a fixing device according to a third embodiment. Explanatory drawing (1) of the principal part of another Example. Explanatory drawing (2) of the principal part of another Example. Explanatory drawing (3) of the principal part of another Example. Explanatory drawing of a main part of the fixing device of Comparative Example 1.

<< Example 1 >>
(Main body configuration of image forming apparatus)
FIG. 2 is a schematic diagram of the image forming apparatus 50 in the present embodiment. The image forming apparatus 50 is an electrophotographic monochrome laser linter that directly transfers a toner image formed on a photosensitive drum 1 as an image carrier to a sheet-like recording material (hereinafter, referred to as paper) P. . Around the photosensitive drum 1, a charger 2, an exposure device 3 for irradiating the photosensitive drum 1 with the laser beam L, a developing device 5, a transfer roller 10, and a photosensitive drum cleaner are arranged in the drum rotation direction (direction of arrow R <b> 1). 16 are arranged.

  The surface of the rotating photosensitive drum 1 is charged to a negative polarity by the charger 2, and the charged surface is subjected to laser scanning exposure by the exposure device 3. The laser beam L is modulated according to the image information, and an electrostatic latent image corresponding to the scanning exposure pattern is formed on the surface of the photosensitive drum 1 (the exposed portion has a higher surface potential). The electrostatic latent image is developed as a toner image by the developing device 5 containing the black toner. The toner of this embodiment is charged to a negative polarity, and the negative toner adheres only to the electrostatic latent image portion on the photosensitive drum 1 to form a toner image on the photosensitive drum 1.

  The paper P is fed by a feed roller 4 and is transported by a transport roller 6 to a transfer nip N which is a contact portion between the photosensitive drum 1 and the transfer roller 10. A positive polarity transfer bias having a polarity opposite to the polarity of the toner is applied to the transfer roller 10 from a power supply (not shown), and the toner image on the photosensitive drum 1 is transferred onto the sheet P at the transfer nip N. . After the transfer, the transfer residual toner on the surface of the photosensitive drum 1 is removed by a photosensitive drum cleaner 16 having an elastic blade.

  The paper P carrying the toner image is conveyed and introduced into a fixing device 100 as an image heating device, and the toner image on the surface is heated and fixed. Then, the sheet is discharged onto the tray 11 as an image formed product.

(Overview of fixing device)
The fixing device 100 of this embodiment is a film (belt) heating type image heating device (OMF: on-demand fixing device) for the purpose of shortening the start-up time and reducing power consumption.

  FIG. 3A is a cross-sectional view of a main part schematically illustrating the fixing device 100 according to the present exemplary embodiment. FIG. 3B is a schematic view of a main portion in the longitudinal direction of the fixing device 100 as viewed from the upstream side (paper introduction side) in the paper transport direction (recording material transport direction: arrow A1 direction). FIG. 3B shows the fixing film 112 and the heater holder 130 in a transparent state so that the state of the heater 113 and the heat conducting member 140 as the internal members of the fixing film 112 can be easily understood.

  The fixing device 100 has a film unit (belt unit) 101 and a pressure roller 110 as a rotating body having elasticity. The film unit 101 and the pressure roller 110 are arranged substantially in parallel, and a nip portion (fixing nip) No is formed by the fixing film 112 and the pressure roller 110 of the film unit 101.

  The film unit 101 has a fixing film 112 that is a rotatable endless belt that is loosely fitted to the internal member. Inside the fixing film 112, a heater 113 as a heating member, a heat conductive member 140, and a heater holder 130 as a holding member for holding the heater 113 and the heat conductive member 140 are arranged. Similarly, a temperature detecting element (temperature sensor) 115, a stay 120 supporting the heater holder 130, and one end side and the other end side flange member 150 are arranged.

  The flange members 150 on one end and the other end are fitted and fixedly installed on one end and the other end of the stay 120, respectively. The fixing film 112 is located between the flange seat 150a of the flange member 150 on one end side and the other end side.

  The heater holder 130 is a holding member for fixing and holding the heater 113. The heater holder 130 is preferably made of a material having a low heat capacity so that the heat of the heater 113 is not easily removed. In this embodiment, a liquid crystal polymer (LCP) which is a heat-resistant resin is used. Using. The heater holder 130 is supported from the side opposite to the heater 113 by an iron stay 120 to provide strength.

  One end and the other end of the cored bar 117 of the pressure roller 110 are rotatably supported by a device housing (not shown) via a bearing 132. The film unit 101 is installed with respect to the apparatus housing with the internal heater 113 facing the pressure roller 110 and substantially parallel to the pressure roller 110. A predetermined pressing force is applied to the one end side and the other end side flange member 150 by the pressing spring 114 in the direction of arrow A2. With this pressing force, the stay 120 is pressed and urged in a direction toward the pressure roller 110 side.

  Therefore, the surface (first surface) of the heater 113 held by the heater holder 130 and a part of the surface of the heater holder 130 are separated from the elastic layer of the pressure roller 110 with respect to the pressure roller 110 with the fixing film 112 interposed therebetween. It is pressed against the elastic layer 116. The front side of the heater 113 contacts the inner surface of the fixing film 112 to form an inner nip Ni for heating the fixing film 112 from the inner surface. Then, the pressure roller 110 is pressed against the heater 113 so as to sandwich the fixing film 112, and a fixing nip (nip portion) No is formed between the outer surface of the fixing film 112 and the pressure roller 110. .

  The pressure roller 110 is driven by a driving force of a motor (drive source) M controlled by a control unit 500 (FIG. 4) with respect to a drive gear 131 provided on the core bar 117 via a power transmission mechanism (not shown). After being transmitted, it is rotationally driven at a predetermined speed in the counterclockwise direction of arrow R1 in FIG. In this embodiment, the pressure roller 110 rotates at a surface moving speed of 200 mm / sec.

  As the pressure roller 110 is driven to rotate, the fixing film 112 is driven to rotate. That is, the fixing film 112 slides while the inner peripheral surface thereof is in contact with the surface of the heater 113 and a part of the surface of the heater holder 130 in the fixing nip No. It is driven to rotate in the clockwise direction of arrow R2.

  The flange seat portions 150a of the flange members 150 at the one end side and the other end side respectively receive the end faces of the fixing film, thereby restricting the one-side movement in the longitudinal width direction accompanying the rotation of the fixing film 112. Further, the film inner surface guide portions 150b of the flange member 150 at one end and the other end respectively support the both ends of the fixing film 112 from the inside of the film and guide the rotation of the fixing film 112 (rotation trajectory determination).

  The heater 113 is heated rapidly by the heat generated by the power supply unit 501 (FIG. 4) controlled by the control unit 500, and the temperature of the heater 113 is detected by the temperature detection element 115. The control unit 500 controls the power supplied from the power supply unit 501 to the heater 113 so that the temperature of the heater 113 is raised to a predetermined temperature and controlled based on the temperature information fed back from the temperature detection element 115. .

  In a state where the pressure roller 110 is driven to rotate and the heater 113 is raised to a predetermined temperature and the temperature is adjusted, the sheet P on which the unfixed toner image T is formed in the image forming unit is fixed in the direction of arrow A1. It is transported to the nip No. and introduced. The paper P is introduced such that the image surface faces the fixing film 112. Then, the paper P is nipped and conveyed at the fixing nip No. and heated and pressed by the heat of the fixing film 112 heated by the heater 113 and the nip pressure, so that the unfixed toner image T is fixed on the paper P as a fixed image. You.

  In the apparatus according to the present embodiment, the paper P of various width sizes, large and small, is passed by a so-called center reference conveyance at the center of the paper width. In FIG. 3B, Wg is the longitudinal width of the elastic layer 116 of the pressure roller 110. X is the width of the passage area of the maximum width paper (large paper) usable (conveyable) to the apparatus, that is, the maximum paper passing width. Wg> X. The longitudinal width of the fixing film 112 is larger than Wg. Further, the inner surfaces of the one end side and the other end side of the fixing film 112 are supported by the film inner surface guide portions 150b of the flange members 150 at the one end side and the other end side outside the maximum sheet passing width X, respectively.

(Fixing film)
In a free state in which the fixing film 112 of the present embodiment is not deformed by an external force, the fixing film 112 is a heat-resistant member having a thin and substantially cylindrical shape having an outer diameter of 20 mm due to its own elasticity. It has a multilayer structure in the thickness direction. The layer structure of the fixing film 112 includes a base layer 126 for maintaining the strength of the film and a release layer 127 for reducing the adhesion of dirt to the surface.

  The material of the base layer 126 is required to have heat resistance because it receives the heat of the heater 113. Further, strength is required for sliding with the heater 113. Therefore, a metal such as SUS (Stainless Used Steel: stainless steel) or nickel, or a heat-resistant resin such as polyimide is preferably used. Metals can be made thinner because of their strength compared to resins, and have high thermal conductivity, so that the heat of the heater 113 can be easily transmitted to the surface of the fixing film 112. Resin has an advantage that it has a small heat capacity and is easily heated because it has a lower specific gravity than metal. The resin can be formed at low cost because a thin film can be formed by coating and molding.

  In this embodiment, a polyimide resin is used as a material of the base layer 126 of the fixing film 112, and a carbon-based filler is added to improve the thermal conductivity and strength. The smaller the thickness of the base layer 126 is, the more easily the heat of the heater 113 is transmitted to the surface of the fixing film, but the strength is reduced. Therefore, the thickness is preferably about 15 μm to 100 μm.

  As a material of the release layer 127 of the fixing film 112, it is preferable to use a fluororesin such as a perfluoroalkoxy resin (PFA), a polytetrafluoroethylene resin (PTFE), and a tetrafluoroethylene-hexafluoropropylene resin (FEP). In this embodiment, PFA which is excellent in mold release property and heat resistance among fluororesins was used.

  The release layer 127 may be coated with a tube, or may be one whose surface is coated with a paint. In this embodiment, the release layer 127 is formed by a coat excellent in thin-wall molding. As the release layer 127 is thinner, the heat of the heater 113 is more easily transmitted to the surface of the fixing film 112. However, when the release layer 127 is too thin, the durability is reduced. Therefore, the thickness is preferably about 5 μm to 30 μm.

(Pressure roller)
The pressure roller 110 of the present embodiment has an outer diameter of 20 mm, and a 4-mm-thick elastic layer 116 (foamed rubber) formed by foaming silicone rubber is formed on an iron core bar 117 of 12 mm in diameter. When the pressure roller 110 has a large heat capacity and a large thermal conductivity, heat on the surface of the pressure roller 110 is easily absorbed into the inside, and the surface temperature of the pressure roller 110 is unlikely to rise. That is, a material having as low a heat capacity as possible, a low thermal conductivity and a high heat insulating effect can shorten the rise time of the surface temperature of the pressure roller 110.

  The thermal conductivity of the foamed rubber obtained by foaming the silicone rubber is 0.11 to 0.16 W / m · K, which is lower than that of solid rubber of about 0.25 to 0.29 W / m · K. The specific gravity relating to the heat capacity is about 1.05 to 1.30 for solid rubber, and about 0.45 to 0.85 for foamed rubber, which is low heat capacity. Therefore, this foamed rubber can shorten the rise time of the surface temperature of the pressure roller 110.

  The smaller the outer diameter of the pressure roller 110 is, the smaller the heat capacity is. However, if the outer diameter is too small, the short width of the fixing nip No becomes narrow, so an appropriate diameter is required. In this embodiment, the outer diameter is set to φ20 mm. Regarding the thickness of the elastic layer 116, if it is too thin, heat escapes to the metal core, so that an appropriate thickness is required. In this embodiment, the thickness of the elastic layer 116 is 4 mm.

  When the pressure roller 110 is heated, the temperature of the end portion of the elastic layer 116 tends to decrease due to heat radiation from the end face of the metal core 117 or the elastic layer 116. For this reason, if the longitudinal width Wg of the elastic layer 116 is too narrow with respect to the maximum sheet passing width X, the fixing property at the end tends to deteriorate, and if it is too wide, the width of the image forming apparatus becomes large. In this embodiment, the left and right sides are set to be longer by 5 mm than the letter size of 216 mm, which is the maximum sheet passing width X, and the longitudinal width Wg of the elastic layer 116 is set to 226 mm.

  On the elastic layer 116, a release layer 118 made of a perfluoroalkoxy resin (PFA) is formed as a release layer for the toner. The release layer 118 may be a tube coated like the release layer 127 of the fixing film 112 or a surface coated with paint, but in this embodiment, a tube having excellent durability was used.

  As a material of the release layer 118, in addition to PFA, a fluororesin such as PTFE, FEP, or the like, a fluororubber, a silicone rubber, or the like having good releasability may be used. As the surface hardness of the pressure roller 110 is lower, a fixing nip No with a small width and a short width can be obtained at a low pressure. However, if the surface hardness is too low, the durability is reduced. In this embodiment, the Asker-C hardness (4.9 N) is used. Load) at 40 °.

(Heating heater)
The heater 113 of this embodiment is a general heater used in an image heating apparatus of a film heating type. That is, it is a ceramic heater having an elongated ceramic substrate and a resistance heating element formed on the substrate along its length and generating heat by energization.

  The configuration of the heater 113 in the present embodiment will be described with reference to FIGS. FIG. 1A is a schematic diagram (a schematic diagram of the surface of the heater 113) of the heater 113 in FIG. 3A viewed from the direction of arrow A3.

  The substrate 207 of the heater 113 is an alumina substrate having a width (short width) Wh = 6 mm and a thickness H = 1 mm in the paper transport direction A1. Two parallel resistance heating elements 201 and 202 are formed on the surface of the substrate 207 along the length of the substrate. The resistance heating elements 201 and 202 are formed by coating Ag / Pd (silver palladium) with a predetermined width and a thickness of 10 μm by screen printing. The glass is covered thereon with a thickness of 50 μm as a heating element protection layer 209. The heating element protective layer 209 is shown only in FIG. 1A, and is omitted in FIGS. 1C and 1D.

  In this embodiment, the side of the heater 113 on which the glass layer 209 is formed as a heating element protective layer is the first surface (front surface) on which the inner peripheral surface of the fixing film 112 is in contact and slides, and the substrate on the opposite side. The surface is the second surface (back surface) with which the heat conductive member 140 contacts along the longitudinal direction.

  If the longitudinal width W of each of the resistance heating elements 201 and 202 is too narrow with respect to the maximum sheet passing width X, heat dissipation at the end of the pressure roller 110 tends to deteriorate the fixing property at the end of the heater. On the other hand, if the width is too large, the temperature of the non-sheet passing area when the small size paper narrower than the large size paper is continuously passed tends to increase. Therefore, if the throughput down control is performed such that the temperature is not increased and the temperature does not exceed the heat resistance temperature of the constituent members of the film unit 101 or the pressure roller 110, the throughput is reduced by increasing the paper passing interval and the productivity is reduced. Would.

  For this reason, in the present embodiment, the longitudinal width W of the anti-heating elements 201 and 202 is set to 218 mm, which is longer by 1 mm at both ends than the letter size width 216 mm corresponding to the maximum sheet passing width X in the present embodiment.

  One ends of the two resistance heating elements 201 and 202 on the substrate 207 are connected in series via a conductor 203 and are conductive. Conductive electrodes 204 and 205 are provided on the other end sides of the resistance heating elements 201 and 202, respectively. When power is supplied from the electrodes 204 and 205, the resistance heating elements 201 and 202 generate heat.

  The longitudinal width Wb of the substrate 207 of the heater 113 was set to 270 mm so that the resistance heating elements 201 and 202, the conductor 203, the electrode portions 204 and 205, and the heating element protection layer 209 could be accommodated.

  As shown in FIG. 3, on the back surface of the heater 113, a temperature detecting element 115 for detecting the temperature of the substrate 207 which has been heated in accordance with the heat generated by the resistance heating elements 201 and 202 is arranged. The control unit 500 appropriately controls the current flowing from the power supply unit 501 to the resistance heating elements 201 and 202 via the electrode units 204 and 205 according to the detected temperature information of the temperature detection element 115, so that the heater 113 Adjusting the temperature.

  The temperature detecting element 115 detects a substrate temperature of a heater portion which becomes a paper passing area for paper of any size, large and small. In this embodiment, the temperature detection element 115 is inserted into a hole provided in the heater holder 130 with respect to the back surface of the substrate 207 of the heater 113 held by the heater holder 130 and provided on the back surface of the substrate. The contact is made via a heat conducting member 140. That is, the temperature detecting element 115 detects the temperature of the heater 113 via the heat conducting member 140. It should be noted that the temperature detecting element 115 is omitted from the drawings other than FIG.

(Heat conduction member)
A heat conducting member 140 for equalizing the temperature of the heater 113 is provided on the back surface (second surface) of the heater 113 as shown in FIGS. The heat conductive member 140 is a member whose heat conductivity at least in a direction parallel to the plane is higher than the heat conductivity of the substrate 207 of the heater 113.

  The heat conduction member 140 is provided between the heater 113 and the holder 130. FIG. 5 is an assembly view (exploded perspective view) when assembling the heat conducting member 140 and the heater 113 to the heater holder 130. The heater holder 130 is provided with a groove 130b so that the heat conducting member 140 and the heater 113 can be sufficiently accommodated. After the two heat conducting members 140 are fitted into the groove 130b of the heater holder 130, the heater 113 is fitted.

  As the material of the heat conductive member 140, the higher the heat conductivity than the material of the substrate 207 of the heater 113, the higher the effect of equalizing the temperature of the members such as the heater 113, the fixing film 112, and the pressure roller 118. The heat conductive member 140 may be provided by applying a silver paste having high thermal conductivity, or may be in contact with a metal sheet such as a graphite sheet or an aluminum plate.

  When a sheet or a metal plate is used as the heat conducting member 140, there is an advantage that the heat capacity of the heat conducting member 140 can be easily adjusted by its thickness. In this embodiment, an aluminum (aluminum) plate which has relatively high heat conductivity and can be installed at a low cost among metals is used as the heat conductive member 140. As the thickness of the heat conducting member 140 increases, the effect of leveling the temperature increases, and therefore, as described above, the productivity of a job for continuously passing small-size paper narrower than the longitudinal width W of the resistance heating elements 201 and 202 is described. Is improved.

  However, since the heat capacity is increased, the rise time of the heater 113 is delayed. Therefore, it is desirable to adjust the material and thickness of the heat conducting member 140 by balancing the productivity when the small-size paper is continuously passed and the rising time of the heater 113.

  As the heat conducting member 140 of this embodiment, an aluminum plate having a thickness t of 0.5 mm and a width (short width) in the sheet conveying direction A1 of 6 mm, which is the same as the short width Wh of the substrate 207 of the heater 113, was used. Further, since the coefficient of thermal expansion differs between alumina, which is the substrate 207 of the heater 113, and aluminum, which is the heat conductive member 140, the heat conductive member 140 may be deformed when the heat cycle of heating and cooling is repeated. Therefore, the heat conduction member 140 of the present embodiment is configured to be divided into two at the center in the longitudinal direction in the transport region of the paper P.

  In the division of the heat conducting member 140, as the number of divisions increases, the longitudinal width of one heat conducting member 140 decreases, so that the thermal expansion length also decreases, and deformation by a heat cycle becomes difficult. However, as the number of divisions increases, the leveling effect of heat in the longitudinal direction of the heater 113 decreases. In particular, in order to equalize the temperature of the non-sheet passing portion when the small-size sheets are continuously passed in the longitudinal direction of the heater 113, it is desirable that the heat conducting member 140 be straddled between the non-sheet passing portion and the sheet passing portion. . The heat conduction member 140 of the present embodiment was configured to be divided into two at the longitudinal center.

  FIG. 1B is a schematic view of the heater 113 and the heat conducting member 140 viewed from the direction of the arrow A2 in FIG. 3A (a schematic diagram of the back side of the heater 113 in which the heat conducting member 140 is installed). It is. As shown in FIG. 1B, the heat conducting member 140 is divided into two parts at the center in the longitudinal direction, separated by a division distance Y. If the division distance Y is too large, the temperature of the heater in a portion where the heat conducting member 140 is not provided (the heater portion corresponding to the division distance Y) rises, resulting in temperature unevenness in the longitudinal direction. In the example, the division distance Y was 4 mm.

  The longer the heat conductive member 140 is, the greater the effect of equalizing the heat of the heater 113 in the longitudinal direction. Heat is easily dissipated. Therefore, the fixability of the edge of the large-size paper in the width direction may be reduced. Therefore, it is desirable to adjust the position of the end of the heat conducting member 140 in the longitudinal direction in consideration of the balance between the productivity at the time of continuous passing of small-sized paper and the fixing property of the end of the large-sized paper in the width direction.

  In the present embodiment, the longitudinal width (position of the end in the longitudinal direction) of the heat conductive member 140 is set to be the same as the longitudinal width W of the resistance heating elements 201 and 202 of the heater 113. Since the longitudinal width W of the heat generating resistors 201 and 202 is 218 mm and the division distance Y of the heat conductive member 140 is 4 mm, the longitudinal width Wa of the heat conductive member 140 is one of the divided heat conductive members on one side and the other. 140 are each 107 mm.

  The heat conducting member 140 is provided with a restricting portion 140a for restricting a deviation from the heater holder 130 in the longitudinal direction. The regulating portion 140a of the heat conducting member 140 is formed by bending a part of the heat conducting member 140 as shown in FIG. On the other hand, regulating groove 130a is provided in heater holder 130 so that regulating portion 140a of heat conducting member 140 is fitted. The heat conducting member 140 and the heater holder 130 are regulated in the longitudinal direction by fitting the regulating portion 140a of the heat conducting member 140 into the regulating groove 130a of the heater holder 130.

(Fixing nip width and pressure distribution)
Here, the width (short width) of the fixing nip No in the paper transport direction A1 and the pressure distribution in the longitudinal direction in the present embodiment will be described. The fixing nip No. in this embodiment is configured such that the short width at the end portion is larger than the short width at the center portion in the long direction. Since the temperature of the end of the pressure roller 110 is apt to decrease, the fixing property is apt to decrease. For this reason, in this embodiment, the pressing force at the end of the pressing roller 110 is set to be stronger than the pressing force at the center of the longitudinal direction, and the fixing nip No is set at the end of the lateral width at the center of the longitudinal center as described above. Are designed so that the width of the short side becomes thicker.

  FIGS. 6A and 6B show the bending in the longitudinal direction due to the pressing of the iron stay 120 and the pressing roller 110. As shown in FIG. 6A, the iron stay 120 is pressed by a pressing spring 114 from both ends. When the pressing roller 110 receives the pressing force from the bearings 132 at both ends, the iron stay 120 bends in the direction from the solid line 120a to the dotted line 120b. Then, the core metal 117 of the pressure roller 110 bends from the solid line 117a in the direction of the dotted line 117b.

  When the iron stay 120 and the pressure roller 110 bend, the pressure at the longitudinal center of the fixing nip No. is released and weakened, and the short width of the fixing nip No. is narrower at the longitudinal center of the fixing nip No. than at the end. turn into. If the width at the center of the longitudinal direction of the fixing nip No. becomes narrow, the fixing property at the center at the longitudinal direction of the fixing nip No. is reduced. Therefore, the width of the width along the length of the fixing nip No. is adjusted to ensure the fixing property. are doing.

  In this embodiment, the short width along the length of the fixing nip No is adjusted by the thickness of the heater holder 130. As shown in FIG. 6B, the thickness K of the central portion in the longitudinal direction of the heater holder 130 is increased from the end to the central portion in the longitudinal direction of the heater holder 130 (hereinafter, referred to as crown correction of the heater holder 130). Thereby, the short width along the length of the fixing nip No is adjusted so that the fixing failure at the longitudinal center of the fixing nip No does not occur.

  In this embodiment, in consideration of the fixing property at the end of the fixing nip No. as described above, the short width at the end is about 10% larger than the short width at the center in the longitudinal direction of the fixing nip No. The crown correction of the heater holder 130 is performed. More specifically, the crown correction amount of the heater holder 130 (the difference in thickness between the center and the end of the heater holder) was set to 400 μm.

  FIG. 7A shows the short width and the pressure distribution along the length of the fixing nip No of the fixing device of this embodiment. Here, the measurement of the short width along the length of the fixing nip No. will be described. A sheet on which a solid black image is printed over the entire width of a sheet wider than the longitudinal width 226 mm of the elastic layer 116 of the pressure roller 110 is prepared. The sheet is sandwiched by the fixing nip No. and heated by the heater 113 while the driving of the pressure roller 110 is stopped. The temperature of the heater 113 is controlled to 150 ° C. by the temperature detecting element 115 and heating is performed for 10 seconds.

  Since the solid black image is heated only at the portion of the fixing nip No., the gloss increases, and the mark (pattern) of the fixing nip No. is transferred to the solid image. From the solid image to which the mark of the fixing nip No was transferred, the short width along the length of the fixing nip No was measured. The short width along the length of the fixing nip No. was measured at 10 mm intervals along the length of the fixing nip No.

  The pressure distribution along the length of the fixing nip No was measured using a surface pressure distribution measurement system (Nitta Corporation: I-SCAN: resolution in the longitudinal direction 0.5 mm).

  As shown in the measurement results of FIG. 7A, the short width of the fixing nip No is increased from the center to the both ends in the longitudinal direction of the fixing nip No, and is 8.0 mm at the center and 8 mm at each end. 0.8 mm. FIG. 7B is a schematic diagram of the pattern of the fixing nip No. At this time, the pressure distribution in the longitudinal direction of the fixing nip No. is also the same as the short width along the length of the fixing nip No. Has become. That is, it can be said that the larger the width of the fixing nip No., the higher the pressing force of the fixing nip.

(Position of regulation part of heat conduction member)
Next, the position of the regulating portion 140a of the heat conducting member 140 will be described. In the present embodiment, the regulating portion 140a that regulates the position of the heat conducting member 140 in the longitudinal direction is provided at a position corresponding to a region where the short width of the fixing nip No is large in the longitudinal direction of the fixing nip No. This is characterized in that the displacement of the heat conducting member 140 in the longitudinal direction is suppressed.

  FIG. 1C shows a schematic cross-sectional view in the longitudinal direction in which the heat conducting member 140 and the heater 113 are fitted into the heater holder 130. The longitudinal width Wc of the groove 130b of the heater holder 130 into which the heat conducting member 140 is fitted is 1 mm wider than the longitudinal width Wa (107 mm) of the heat conducting member 140 and 108 mm so as to be accommodated even when the heat conducting member 140 thermally expands. Has become.

  The fixing portion 140a that regulates the position of the heat conducting member 140 in the longitudinal direction is a fixing nip where the pressing force is high and the short width is wide in correspondence with the pattern schematic diagram of the fixing nip No of FIG. No. are provided at positions corresponding to both ends in the longitudinal direction. The longitudinal width 140aW of the regulating portion 140a of the heat conducting member 140 is 5 mm, and the regulating portion 140a is fitted into the regulating groove 130a of substantially the same width on the side of the heater holder 130, whereby the longitudinal position of the heat conducting member 140 and the heater holder 130 is regulated. ing.

Here, the position of the regulating portion 140a of the heat conducting member 140 of Comparative Example 1 will be described. FIG. 14 is a schematic cross-sectional view in which the heat conductive member 140 and the heater 113 are fitted into the heater holder 130 of Comparative Example 1. Except for the position in the longitudinal direction of the restricting portion 140a of the heat conducting member 140 and the restricting groove 130a of the heater holder, the configuration is the same as that of the present embodiment. Further, the short width and the pressure distribution along the length of the fixing nip No are the same as those of the present embodiment, and the pressure is lower at the center of the longer side than at the long end of the fixing nip No, and the short width is narrower. ((C) of FIG. 14).

  FIG. 14A is a cross-sectional view of the heater 113 before heating, and FIG. 14B is a cross-sectional view of the heater 113 when heating. In Comparative Example 1, the regulating portion 140a of the heat conducting member 140 is located at a position corresponding to the vicinity of the central portion in the longitudinal direction of the fixing nip No. Is provided.

  When the heat conduction member 140 thermally expands due to heating by the heater 113, the heat conduction member 140 and the heater 113 are displaced in the longitudinal direction due to a difference in thermal expansion. In this case, in the longitudinal direction of the fixing nip No, the place where the pressing force is high has a high frictional force between the heat conductive member 140 and the heater holder 130 and the heater 113, so that the heat conductive member 140 is hard to be displaced. The member 140 is easily shifted.

  Therefore, as in the configuration of Comparative Example 1, the heat conducting member restricting portion 140a is provided at a position corresponding to the vicinity of the longitudinal center of the fixing nip No, which is a region where the pressing force is relatively low and the short width is narrow. In such cases, the following situations are likely to occur. That is, as shown in (b), the heat conducting member 140 expands thermally toward the longitudinal center of the fixing nip No with a small frictional force. Therefore, the regulating portion 140a of the heat conductive member 140 is deformed, and the heat conductive member 140 is shifted to the longitudinal center of the fixing nip No.

  As described above, when the regulating portion 140a of the heat conductive member 140 is deformed, the contact surface of the heat conductive member 140 with the heater 113 may be deformed, and the contact with the heater 113 may be reduced. . If the heat conducting member 140 floats from the heater 113 due to deformation, the temperature of the heater 113 at that portion becomes high, and temperature unevenness occurs in the longitudinal direction. The temperature unevenness in the longitudinal direction may result in an image failure as gloss unevenness on the image, and in some cases, may cause heat loss in the heater holder 130 and the pressure roller 110.

  On the other hand, the position of the regulating portion 140a of the heat conducting member 140 in this embodiment is a region where the pressing force is high and the width of the short side is wide, as is apparent from the correspondence between (c) and (e) of FIG. The nip No. is provided at a position corresponding to both ends in the longitudinal direction.

  FIG. 1D is a cross-sectional view when the heater 113 is heated in the present embodiment. Heated by the heater 113, the heat conducting member 140 expands toward the center of the longitudinal direction where the pressing force is low and the width is narrow at the fixing nip No (in the direction of the arrow in the figure). In this case, regulating portions 140a of the heat conductive member 140 are provided at positions corresponding to both longitudinal ends of the fixing nip No, which are regions where the frictional force between the heat conductive member 140, the heater holder 130, and the heater 113 is high. Have been. Therefore, the position of the regulating portion 140a does not shift and does not deform.

  As described above, the regulating portion 140a that regulates the longitudinal position of the heat conducting member 140 is provided at a position corresponding to a region where the pressing force is relatively high and the short width is large in the longitudinal direction of the fixing nip No. With this configuration, it is possible to suppress displacement and deformation of the heat conducting member 140 in the longitudinal direction due to repetition of the heat cycle.

(Verification of effects)
Here, a comparison of the presence / absence of the occurrence of gloss unevenness due to the temperature unevenness in the longitudinal direction of the fixing nip No in the arrangement of the heat conductive member 140 of the first embodiment and the arrangement of the heat conductive member 140 of the first comparative example. Was done.

  The arrangement of the heat conductive member 140 according to the first embodiment is the same as that shown in FIG. 1, and the regulating portion 140 a is a region where the pressing force is relatively high and the short width is large in the longitudinal direction of the fixing nip No. Are provided at positions corresponding to both ends.

  The arrangement of the heat conductive member 140 of Comparative Example 1 is the configuration shown in FIG. 14, and the regulating portion 140a is a region where the pressing force is relatively low and the short width is narrow in the longitudinal direction of the fixing nip No. Is provided at a position corresponding to the vicinity of the longitudinal central portion of the. The central position in the longitudinal direction of the restricting portion 140a in Comparative Example 1 is a position (Wd in FIG. 14A: 10 mm) 10 mm left and right away from the center of pressure.

  As a print image, gloss unevenness tends to be visible when a uniform pattern is printed on the entire surface, and gloss unevenness tends to occur particularly when a solid image with a large amount of applied toner is printed. When the fixing device 100 is cold, the heater 113 is started from a cold state, and two sheets of a full-surface solid image in which gloss unevenness is easily visible and a full-color halftone image in which the gloss non-uniformity is relatively invisible 50% are printed. Above, the presence or absence of gloss unevenness was confirmed.

  After printing, the fixing device 100 is cooled and brought into a cold state, and then two sheets of a full solid image and a full halftone image having a printing rate of 50% are printed again. This two-sheet intermittent printing is repeated 50,000 times, which is the life of the fixing device 100, that is, 100,000 sheets, and a total of 100,000 sheets of a full-size solid image and a full-size halftone image are printed on each of 50,000 sheets, and uneven gloss is generated on the image. The presence or absence was checked.

  In the arrangement of the heat conductive member 140 of Comparative Example 1, gloss unevenness occurred in the solid image after 30,000 heat cycles, and it was confirmed that the heat conductive member 140 was displaced and deformed in the longitudinal direction. Further, after 40,000 times, gloss unevenness was confirmed even in the halftone image, and the amount of deformation of the heat conductive member 140 was large.

  On the other hand, in the arrangement configuration of the heat conductive member 140 in Example 1, no gloss unevenness occurred even in the solid image at the time of 50,000 heat cycles, and no displacement or deformation in the longitudinal direction of the heat conductive member 140 was confirmed. .

  As described above, according to the arrangement of the heat conducting member 140 of the first embodiment, it is possible to suppress the displacement and deformation of the heat conducting member 140 in the longitudinal direction due to the repetition of the heat cycle. In addition, it is possible to prevent image defects due to uneven gloss and damage to constituent members.

<< Example 2 >>
A second embodiment will be described below. In the second embodiment, contrary to the first embodiment, in a configuration in which the short width of the fixing nip No is wider at the center in the longitudinal direction than at the long end of the fixing nip No, the displacement of the heat conducting member 140 in the longitudinal direction is reduced. And the deformation of the restricting portion 140a. By providing the regulating portion 140a of the heat conducting member 140 at a position corresponding to the vicinity of the longitudinal central portion of the fixing nip No having a large short width, displacement of the regulating member 140a in the longitudinal direction of the heat conducting member 140 and deformation of the regulating portion 140a are suppressed. This prevents image defects due to uneven gloss and damage to the fixing member. This will be described below.

  In the second embodiment, an image forming apparatus for forming an unfixed toner image is generally the same as in the first embodiment, and a description thereof will not be repeated. Also, in the fixing device 100 as a heating device, the basic configuration is a film heating type heating device similar to that of the first embodiment, and the same members are denoted by the same reference numerals and the description thereof will not be repeated.

  When foamed rubber is used for the elastic layer 116 of the pressure roller 110, paper wrinkling may be prevented by making the short width of the central portion of the fixing nip No larger than the short width of the end portion. When the foamed rubber is crushed by the fixing nip No., the air inside escapes and the fixing nip surface approaches the cored bar 117, so that the rotation radius of the fixing nip No. that conveys the paper P decreases. Therefore, the transport speed of the sheet P decreases as the pressing force increases in the longitudinal direction of the fixing nip No and the amount of crushing of the elastic layer 116 increases (the width of the short side of the fixing nip No increases).

  It is generally known that in order to prevent paper wrinkles, it is better to increase the transport speed of the paper P at the end portion than at the central portion in the longitudinal direction of the fixing nip No. Therefore, the elastic layer 116 of the pressure roller 110 has a configuration in which the central portion is more crushed than the longitudinal end portion in the fixing nip No. Increase the width. Thereby, the transport speed of the paper P at the longitudinal end portion of the fixing nip No. is longer than that at the longitudinal central portion, and paper wrinkles can be prevented.

  In the present embodiment, as described with reference to FIG. 6 of the first embodiment, the crown correction of the heater holder 130 is performed so that the short width at the center of the longitudinal direction is larger than the short width at the long end of the fixing nip No. Set. In the fixing device 100 according to the second embodiment, the crown correction of the heater holder 130 is performed so that the short width of the central portion of the fixing nip No is about 10% larger than the short width of the long end portion. More specifically, the crown correction amount of the heater holder 130 (difference in thickness between the center and the end of the heater holder) was set to 600 μm.

  FIG. 8A shows the short width and the pressure distribution along the length of the fixing nip No of the fixing device 100 of the second embodiment. The short width and pressure distribution along the length of the fixing nip No were measured in the same manner as in Example 1.

  As shown in the measurement result of FIG. 8A, the short width along the length of the fixing nip No is wider from both ends to the center in the longitudinal direction, the center at the center is 8.8 mm, and the length at the end is 8 mm. 0.0 mm. FIG. 8B is a schematic diagram of the pattern of the fixing nip No. At this time, the pressure distribution along the length of the fixing nip No also has the highest pressure at the central portion of the longitudinal direction, and the pressing force decreases toward both ends of the longitudinal direction, similarly to the short width along the longitudinal direction. That is, as the width of the short side of the fixing nip No is larger, the pressing force of the fixing nip No is higher.

(Position of regulation part of heat conduction member)
Also in the second embodiment, the regulating portion 140a that regulates the position of the heat conductive member 140 in the longitudinal direction is provided at a position corresponding to a region where the short width of the fixing nip No is large in the longitudinal direction of the fixing nip No. Thereby, the displacement of the heat conducting member 140 in the longitudinal direction is suppressed.

  FIG. 9 shows the position of the regulating portion 140a of the heat conducting member 140 in the second embodiment. Similarly to the first embodiment, the heat conductive member 140 according to the second embodiment has a configuration in which the heat conduction member 140 is divided into two in the longitudinal direction corresponding to the deformation due to the heat cycle. The regulating portion 140a of the heat conducting member 140 according to the second embodiment is provided at a position corresponding to the vicinity of the central portion where the pressing force is relatively high and the short width is large in the longitudinal direction of the fixing nip No.

  As in the second embodiment, when the pressing force in the central portion is larger than the end portion in the longitudinal direction of the fixing nip No and the short width is large, the frictional force between the heat conducting member 140 and the heater holder 130 and the heater 113 is small. It is higher at the center in the longitudinal direction than at the ends. Therefore, the heat conducting member 140 heated by the heater 113 expands toward both ends of the fixing nip No having a small pressing force and a small width.

  Also in the second embodiment, since the regulating portion 140a of the heat conducting member 140 is provided in the vicinity of the central portion where the frictional force is high in the longitudinal direction of the fixing nip No., the position of the regulating portion 140a is shifted even if the heat cycle is repeated. There is no and there is no deformation.

  In the configuration of the second embodiment, the presence / absence of gloss unevenness was checked in the same manner as in the first embodiment. However, there was no gloss unevenness in the solid image until the life of the fixing device, and the longitudinal direction of the heat conductive member 140 was not changed. No displacement or deformation was found.

  Even in a configuration in which the pressing force in the central portion is longer than the end portion in the longitudinal direction of the fixing nip No and the short width is large as in the second embodiment, the heat conduction member 140 is located at a position corresponding to the region where the short width is large. The same effect as in the first embodiment can be obtained by providing the restricting portion 140a. That is, it is possible to suppress displacement or deformation of the heat conducting member 140 in the longitudinal direction due to repetition of the heat cycle.

<< Example 3 >>
In the first and second embodiments, the configuration in which the heat conducting member 140 is divided into two parts at the center in the longitudinal direction for preventing deformation is described, but the present invention is not limited to this configuration. In the third embodiment, in the configuration in which the heat conducting member 140 is not divided in the longitudinal direction, the displacement of the heat conducting member 140 in the longitudinal direction and the deformation of the regulating portion 140a are suppressed. This will be described below.

  In the third embodiment, the image forming apparatus 50 that forms an unfixed toner image is the same as in the first embodiment, and a description thereof will not be repeated. Also, in the fixing device 100, the basic configuration is the same heating device of the film heating system as in the first embodiment, and the same members are denoted by the same reference numerals and the description thereof will not be repeated. Further, similarly to the second embodiment, the configuration is such that the paper wrinkles are prevented by making the short width of the central portion of the fixing nip No longer than that of the longitudinal end. The crown correction amount of the heater holder 130 is 600 μm similarly to the second embodiment, and the short width and the pressure distribution along the length of the fixing nip No are the same distribution as the second embodiment shown in FIG.

(Position of regulation part of heat conduction member)
In the configuration of the third embodiment, the number of the heat conductive members 140 is one, and the heat conductive members 140 are provided at positions substantially corresponding to the longitudinal center portions of the fixing nip Nos having a large width in the longitudinal direction of the heat conductive members 140. A regulating section 140a for regulating is provided. FIG. 10 shows the position of the regulating portion 140a of the heat conducting member 140 according to the third embodiment. The position of the regulating portion 140a of the heat conductive member 140 of the third embodiment is provided at a position corresponding to the central longitudinal portion where the pressing force is relatively high and the short width is wide in the longitudinal direction of the fixing nip No.

  As in the case of the second embodiment, when the pressing force at the central portion in the longitudinal direction is higher than the longitudinal end portion of the fixing nip No, and the short width is large, the frictional force between the heat conducting member 140 and the heater holder 130 and the heater 113 is reduced. No is higher at the center than at the ends in the longitudinal direction. Therefore, the heat conducting member 140 heated by the heater 113 expands toward both ends of the fixing nip longitudinally with a small pressing force and a short width.

  Also in the third embodiment, the regulating portion 140a of the heat conducting member 140 is provided at a position corresponding to the central portion where the frictional force is high in the longitudinal direction of the fixing nip No. There is no displacement and no deformation.

  Even in the configuration having one heat conduction member 140 as in the configuration of the third embodiment, the longitudinal direction of the heat conduction member 140 is relatively large in the longitudinal direction of the fixing nip No. Is provided. Accordingly, it is possible to suppress the displacement or deformation of the heat conduction member 140 in the longitudinal direction due to the repetition of the heat cycle.

<< Other Examples >>
(1) In the first to third embodiments, the regulation that regulates the longitudinal position of the heat conducting member 140 at a position corresponding to a region where the pressing force is relatively high and the short width is large in the longitudinal direction of the fixing nip No. A part 140a is provided. Thus, the description has been given of suppressing the longitudinal displacement and deformation of the heat conducting member 140 due to the repetition of the heat cycle.

  In accordance with this, if the regulating portion 140a of the heat conducting member 140 is applied to the non-sheet passing area where the temperature rises outside the maximum sheet passing width X in which the sheet P can be conveyed, the heat conducting member 140 can be further shifted in the longitudinal direction. Can be suppressed. This will be described below.

  In the first to third embodiments, the configuration in which foaming rubber is used for the elastic layer 116 of the pressure roller 110 with emphasis on startup of the fixing device 100 of the monochrome image forming apparatus 50 has been described. In a fixing device used for a color image forming apparatus, solid rubber may be used for the elastic layer 116 of the pressure roller 110 in some cases.

  In a color image forming apparatus, since four colors of yellow, magenta, and cyan are printed in addition to black, the amount of applied toner is large. When the amount of toner is large, heat may be required for the pressure roller 110 in order to apply heat to the interface between the sheet P and the toner and fix the toner. Therefore, in the fixing device of the color image forming apparatus, solid rubber is often used as the elastic layer 116 of the pressure roller 110 instead of foamed rubber.

  The pressure roller 110 made of solid rubber has a higher heat capacity and heat conductivity than foamed rubber, so that the rise of the surface temperature is slowed down, but has an effect of leveling the heat in the longitudinal direction. Since the thermal conductivity is high, heat is easily transmitted to the core bar 117 as compared with the foamed rubber, and the heat at the end is also easily dissipated, so that the temperature at the end of the pressure roller 110 is easily lowered. Therefore, when solid rubber is used for the elastic layer 116 of the pressure roller 110, the longitudinal width W of the resistance heating elements 201 and 202 of the heating heater 113 is set sufficiently larger than the maximum sheet passing width X as shown in FIG. There are cases.

  In this case, when a large-size sheet corresponding to the maximum sheet passing width X is continuously passed, the pressure roller temperature in the non-sheet passing area increases. When the temperature of the pressure roller 110 rises, the pressure applied to the temperature rise portion increases due to thermal expansion. Therefore, in the non-sheet passing area, the frictional force between the heat conducting member 140, the heater holder 130, and the heater 113 increases.

  As in the configuration shown in the first embodiment, when the pressing force at the end is higher in the longitudinal direction of the fixing nip No than at the center and the width of the short side of the fixing nip No is large, the regulating portion 140a of the heat conducting member 140 is It is provided at a position corresponding to the longitudinal end of No. With this configuration, it has been described that the heat conducting member 140 is unlikely to shift.

  In addition to the configuration in which the width of the short side of the fixing nip at the end portion in the longitudinal direction of the fixing nip No. is larger than that at the center in Example 1, the non-sheet passing portion outside the maximum sheet passing width X as shown in FIG. The region is provided such that the regulating portion 140a of the heat conducting member 140 is engaged. That is, the regulating portion 140a is provided outside the passage area of the sheet of the maximum width size that can be conveyed by the apparatus in the longitudinal direction of the fixing nip No. Thereby, the displacement of the heat conducting member 140 in the longitudinal direction can be further suppressed.

  (2) In the fixing device described above, a device configuration in which a toner image is fixed on paper P by a fixing nip No formed by a fixing film 112 and a pressure roller 110 has been described. The present invention may be applied to a heating type fixing device.

  In this fixing device, a heater 113 is included in the fixing film 112 and is pressed against the outer surface of the fixing roller 300 to heat the surface of the fixing roller 300 at the heating nip N2. The configuration is such that the toner image T is fixed on the paper P at the fixing nip N1 formed by pressing the pressure roller 301 against the fixing roller 300.

  In such an external heating type fixing device, when the heat conductive member 140 is provided on the back surface of the heater 112, the regulating portion 140a of the heat conductive member 140 is provided at a place where the short width of the heating nip N2 is large in the longitudinal direction. Thus, the displacement and deformation of the heat conducting member 140 can be suppressed as in the above-described embodiments.

  (3) Although the shape of the restricting portion 140a of the heat conductive member 140 described above has been described only for the configuration in which the heat conductive member 140 is bent toward the heater holder 130 as shown in 140a of FIG. The shape of the restricting portion 140a is not limited to this shape.

  For example, as shown in (a) of FIG. 13, instead of the bent shape, the shape of the restricting portion may be the same as the contact surface with the heater 113. Further, a configuration in which a plurality of regulating portions 140a are provided on the upstream side and the downstream side in the sheet conveying direction A1 as shown in FIG. Since a plurality of regulating portions 140a can disperse and regulate the force due to the thermal expansion of the heat conducting member 140, it is possible to further suppress displacement and deformation in the longitudinal direction.

  (4) Also, a configuration has been described in which the position of the regulating portion 140a of the heat conducting member 140 described above is provided at a position corresponding to a wide area with a short width along the length of the fixing nip No. If the regulating portion 140a is provided on the side where the short width along the length of the fixing nip No is thicker than the middle between the narrow portion and the narrow portion, it is possible to reduce the displacement and deformation of the heat conducting member 140 in the longitudinal direction.

  (5) In the above embodiments, the fixing device that heats and fixes the unfixed toner image formed on the paper (on the recording material) is described as an example of the image heating device, but is not limited thereto. The present invention can be applied to an apparatus for increasing the gloss (gloss) of an image by reheating a toner image fixed or assumed on a sheet P.

  100 image heating device (fixing device), 112 belt (fixing film), 113 heating member (heating) heater, 209 substrate, 201, 202 resistance heating element, 130 holding member Heater holder), 140 heat conduction member, 140a regulating part, 110 rotating body (pressure roller), No. nip part (fixing nip), P. recording material (paper), T. Image (toner image)

Typical structure in an image heating apparatus according to the present invention for achieving the above object, the endless belt, an elongated substrate, the resistance heating element which generates heat by energization, which is formed along the longitudinal on the substrate If, have a, a heating member for heating the belt, said contact contacting surface between the belt and the opposite surface, high thermal conductivity member than the thermal conductivity of the thermal conductivity of the substrate of the heating member A holding member that holds the heating member via the heat conducting member, an urging member that applies an urging force to the holding member, and a nip portion between the belt and the heating member so as to sandwich the belt. And a pressing member that forms the nip portion through the heating member and the belt by the urging of the urging member, and the nip portion holds a recording material carrying an image. and heating while conveying, before An image heating apparatus for fixing an image on the recording material, the heat conducting member is divided into two members, one end portion positioned in the region of the thermally conductive member corresponding to the longitudinal end of the heat conducting member, said Each of the two members includes a heat conductive member and a second end located in a region of the heat conductive member corresponding to a longitudinal center portion of the heat conductive member, wherein the nip portion has a nip width in a conveying direction of the recording material. A region that gradually increases from a central longitudinal portion of the portion toward a longitudinal end portion of the nip portion, and one end of each of the two members of the heat conducting member extends in a longitudinal direction of the heating member with respect to the holding member. And a regulating portion extending in the longitudinal direction of the heating member , wherein the other end of each of the two members does not have a regulating portion extending in the longitudinal direction of the heating member. I do.

Claims (7)

A heating member having an elongated substrate and a resistance heating element formed along the length of the substrate along its length and generating heat by energization;
A holding member for holding the heating member,
A heat conductive member having a heat conductivity higher than the heat conductivity of the substrate at least in a direction parallel to the plane, and a heat conductive member sandwiched between the heating member and the holding member,
An endless belt rotatable while the inner peripheral surface is in contact with the surface of the heating member on the side opposite to the heat conduction member and slides while sliding.
A rotating body that forms a nip with the outer surface of the belt by abutting the heating member with the belt interposed therebetween; and an image heating device that heats the recording material carrying the image in the nip while nipping and conveying the recording material. At
The heat conducting member has a regulating portion that regulates movement in the longitudinal direction with respect to the holding member, and when the width of the nip portion in the recording material conveyance direction is a short width, the short side in the longitudinal direction of the nip portion is small. An image heating apparatus comprising: a thick portion and a thin portion; and the regulating portion provided on a side of a portion wider than a middle portion between the thick portion and the thin portion.   The image heating apparatus according to claim 1, wherein the heat conductive member is divided into a plurality in a longitudinal direction.   The image heating apparatus according to claim 1, wherein the short width is larger at an end portion than at a center portion in a longitudinal direction of the nip portion.   The image heating apparatus according to claim 1, wherein the short width is larger at a central portion than at an end in a longitudinal direction of the nip portion.   4. The image forming apparatus according to claim 1, wherein the restricting portion is provided outside a passage area of a recording material having a maximum width that can be conveyed by the image heating device in a longitudinal direction of the nip portion. 5. An image heating device according to the item.   The image heating apparatus according to claim 1, wherein the heat conductive member is a metal plate.   The image heating apparatus according to claim 6, wherein the metal plate is made of aluminum.

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