JP2017072781A - Image heating device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem in which: in an image heating device of a film heating system provided with a first heat conduction member 140 in proximity with a primary circuit member 114 and a second heat conduction member 141 in proximity with a secondary circuit member 115 on the rear face of a heating heater 113, when the distance Y between the first and second heat conduction members is set long in order to satisfy insulation performance of the primary circuit and secondary circuit, image defects including unevenness in glossiness may occur due to unevenness in temperature.SOLUTION: In order to suppress a change in distance Y between first and second heat conduction members 140 and 141 due to thermal expansion of the heat conduction members, regulation members 140a and 141a in the longitudinal direction of the first and second heat conduction members 140 and 141 are provided inside the minimum paper feeding width Xm.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image heating apparatus and an image forming apparatus including the same. This image heating device can be used as a fixing device mounted on an image forming apparatus such as an electrophotographic copying machine or a laser beam printer.

  Conventionally, a heat roller method, a film (belt) heating method, and the like are known as an image heating device (hereinafter referred to as a fixing device) for heating a recording material (hereinafter referred to as paper) carrying a toner image.

  Patent Document 1 discloses a film heating method in which a heat conduction member is provided on the back surface of a heater to suppress so-called non-sheet passing portion temperature rise (recording material non-passing portion temperature rise) and increase the productivity of small size paper. A fixing device is described. The heat conducting member is a member made of a material having a higher thermal conductivity than the substrate of the heater.

  In a film heating system, a configuration is generally adopted in which a protective element as a primary circuit member and a temperature detection element as a secondary circuit member are arranged in a heater. When a heat conduction member is provided on the back surface of the heater, a protection element and a temperature detection element are arranged with respect to the heat conduction member.

  The protective element is connected to a primary circuit that is a circuit directly connected to a commercial power source that supplies power. When the heater is abnormally heated, the protective element is activated by the abnormal temperature increase and energizes the commercial heater from the commercial power source. Shut off. The temperature detection element is not directly connected to the primary circuit, but is connected to a secondary circuit that is a circuit that is supplied with power from a device such as a transformer or a converter in the device. Used to control the input power.

  Therefore, since the primary circuit and the secondary circuit are mixed on the back side of the heater, it is desirable to insulate the primary circuit and the secondary circuit. In a configuration in which insulation between the protective element and the heat conducting member cannot be obtained, the heat conducting member arranged on the back surface of the heater together with the protective element and the temperature detecting element is also the secondary circuit side where the primary circuit side where the protective element is arranged and the temperature detecting element are arranged next time. It is desirable to ensure insulation by dividing the roadside.

JP 2014-238560 A

  However, in the configuration in which the heat conduction member is divided and provided on the back surface of the heater, the heat conduction member is not in contact with the region in contact with the back surface of the heater (the separated region between the divided heat conduction members) and As a result, heat unevenness in the longitudinal direction occurs in the fixing film (fixing belt). In particular, when a region where the heat conducting member is not in contact is wide, image defects such as uneven gloss may occur.

  On the other hand, if the interval between the divided heat conducting members is narrow, there is a possibility that insulation between the heat conducting member on the primary circuit side and the heat conducting member on the secondary circuit side cannot be secured. Further, the length of the heat conducting member in the longitudinal direction changes due to thermal expansion. The length of the heat conducting member in the longitudinal direction varies depending on the temperature condition of the fixing device and the sheet passing condition. In consideration of these, it is desired that the divided heat conducting members be separated from each other by a predetermined distance, so that it is difficult to achieve compatibility with image defects such as uneven gloss.

  The object of the present invention is a film heating type image heating apparatus, in which the heat conducting member is divided into two parts (divided) and installed, while ensuring the insulation performance of the primary circuit and the secondary circuit, the thermal unevenness This is to suppress image defects such as uneven gloss.

  In order to achieve the above object, a typical configuration of an image heating apparatus according to the present invention includes an elongated substrate, a heating member having a resistance heating element that generates heat by energization formed along the length on the substrate, and the heating. A holding member that holds the member, and a heat conductive member that has a thermal conductivity higher than that of the substrate at least in a direction parallel to the plane, and is arranged along the longitudinal direction of the heating member, and the heating member A first heat conduction member and a second heat conduction member sandwiched between the member and the holding member, and an inner peripheral surface of the heating member is in contact with a surface opposite to the heat conduction member side An endless belt that can rotate while sliding, and a rotating body that abuts on the heating member across the belt to form an outer surface of the belt and a nip portion, and an image is formed at the nip portion. While holding the recording material carrying In the image heating apparatus, the first heat conducting member and the second heat conducting member are arranged at a predetermined interval, and a regulating portion that regulates movement in the longitudinal direction with respect to the holding member, respectively. And the restricting portion is provided at a location corresponding to the inside of the passage region of the recording material of the minimum width size that can be conveyed by the image heating apparatus.

  According to the present invention, it is possible to suppress image defects such as gloss unevenness due to heat unevenness while ensuring insulation performance between the primary circuit and the secondary circuit.

Structure explanatory drawing of the principal part of Example 1 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 of assembling the heat conduction member and heater to the heater holder Structure explanatory drawing of the principal part of the comparative example 1 Illustration of other configurations Structure explanatory drawing of the principal part of Example 2

Example 1
(Body configuration of image forming apparatus)
FIG. 2 is a schematic diagram of the image forming apparatus 50 in this embodiment. The image forming apparatus 50 is an electrophotographic monochrome laser printer that directly transfers a toner image formed on a photosensitive drum 1 serving as an image carrier onto a sheet-like recording material (hereinafter referred to as paper) P. . Around the photosensitive drum 1, the charger 2, the exposure device 3 for irradiating the photosensitive drum 1 with the laser beam B, the developing device 5, the transfer roller 10, and the photosensitive drum cleaner are sequentially arranged in the drum rotation direction (arrow R1 direction). 16 is arranged.

  The surface of the rotating photosensitive drum 1 is charged with a negative polarity by the charger 2, and laser scanning exposure is performed on the charged surface by the exposure device 3. The laser beam B is modulated corresponding 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 surface potential of the exposed portion is increased). The electrostatic latent image is developed as a toner image by the developing device 5 containing black toner. The toner of this embodiment is charged with a negative polarity, and the negative toner adheres only to the electrostatic latent image portion on the photosensitive drum 1, and a toner image is formed on the photosensitive drum 1.

  The paper P is fed by the paper feed roller 4 and is transported by the transport roller 6 to a transfer nip N that is a contact portion between the photosensitive drum 1 and the transfer roller 10. A transfer bias having a positive polarity that is opposite to the polarity of the toner is applied to the transfer roller 10 from a power source (not shown), and the toner image on the photosensitive drum 1 is transferred onto the paper P at the transfer nip N. . The transfer residual toner on the surface of the photosensitive drum 1 after the transfer 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, where the toner image on the surface is heated and fixed. Then, it is discharged onto the tray 11 as an image formed product.

(Outline of fixing device)
The fixing device 100 according to the present exemplary embodiment is a film (belt) heating type image heating device (OMF: on-demand fixing device) for the purpose of shortening the startup time and reducing power consumption.

  FIG. 3A is a cross-sectional view of the main part showing an outline of the fixing device 100 in this embodiment. FIG. 3B is a schematic view of the main part in the longitudinal direction when the fixing device 100 is viewed from the upstream side (paper introduction side) in the paper conveyance direction (recording material conveyance direction: arrow A1 direction). FIG. 3B shows the fixing film 112 and the heater holder 130 so that the state of the heater 113 and the first and second heat conducting members 140 and 141 which are internal members of the fixing film 112 can be easily understood. Shown in state.

  The fixing device 100 includes 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 the fixing film 112 and the pressure roller 110 included in the film unit 101 form a nip portion (fixing nip) No.

  The film unit 101 includes a fixing film 112 that is a rotatable endless belt that is loosely fitted to an internal member. Inside the fixing film 112, there are a heater 113 as a heating member, first and second heat conducting members 140 and 141, and a heater holder 130 as a holding member that holds the heater 113 and the heat conducting members 140 and 141. Has been placed. Similarly, a protection element 114 as a primary circuit member, a temperature detection element 115 as a secondary circuit member, a stay 120 for supporting the heater holder 130, and a flange member 150 on one end side and the other end side are arranged.

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

  The heater holder 130 is a holding member that holds the heater 113 in a fixed manner, and 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) that is a heat resistant resin is used. Using. The heater holder 130 is supported by an iron stay 120 from the side opposite to the heater 113 in order to give strength.

  The pressure roller 110 is supported such that one end side and the other end side of the cored bar 117 are rotatable with respect to an apparatus housing (not shown) via a bearing 132. The film unit 101 is installed with respect to the apparatus casing so that the internal heater 113 faces the pressure roller 110 and is substantially parallel to the pressure roller 110. And the predetermined pressurization force of the arrow A2 direction by the pressurization spring 133 is applied with respect to the flange member 150 of the one end side and the other end side, respectively. With this applied pressure, the stay 120 is pressed and biased in a direction toward the pressure roller 110.

  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 elastic layers of the pressure roller 110 with respect to the pressure roller 110 with the fixing film 112 interposed therebetween. 116 is pressed against the elastic layer. The surface side of the heater 113 is in contact with the inner surface of the fixing film 112 to form an inner surface nip Ni that heats 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. .

  In the pressure roller 110, a driving force of a motor (drive source) M controlled by a control unit 500 ((a) of FIG. 4) with respect to a drive gear 131 provided on a metal core 117 is a power transmission mechanism (not shown). ) Is transmitted through. Thus, the pressure roller 110 is rotationally driven at a predetermined speed in the counterclockwise direction indicated by the arrow R1 in FIG. In the present embodiment, the pressure roller 110 rotates at a surface moving speed of 150 mm / sec.

  As the pressure roller 110 rotates, the fixing film 112 rotates. That is, the inner peripheral surface of the fixing film 112 slides in contact with the surface of the heater 113 and a part of the surface of the heater holder 130 at the fixing nip No. while the heater 113, the heater holder 130, and the stay 120 are outside. It rotates following the clockwise direction of arrow R2.

  The flanges 150 on the one end side and the other end side of the flange member 150 receive the end face of the fixing film, thereby restricting the displacement in the longitudinal width direction as the fixing film 112 rotates. Further, the film inner surface guide portions 150b of the flange member 150 on one end side and the other end side respectively support the both end portions of the fixing film 112 from the inner side of the film to guide the rotation of the fixing film 112 (rotation trajectory determination).

  The heater 113 receives heat from the primary circuit (AC circuit) 502 of the power supply circuit 501 (FIG. 4A) controlled by the control unit 500, generates heat, and is heated rapidly. The temperature of the heater 113 is detected by the temperature detection element 115 of the secondary circuit (DC circuit) 505. Based on the temperature information fed back from the temperature detection element 115, the controller 500 controls the power supply control circuit 504 so that the temperature of the heater 113 is raised to a predetermined temperature and is adjusted to supply to the heater 113. Adjust the power. The power supply circuit 501 that supplies power to the heater 113 shown in FIG. 4A will be described later.

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

  In the apparatus of the present embodiment, the paper P having various sizes of large and small is passed by so-called central reference conveyance centering on 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 size paper (large size paper) that can be used (conveyable) by the apparatus, that is, the maximum sheet passing width. The maximum sheet passing width X in this embodiment is a letter size width of 216 mm. Wg> X. Xm is the width of the passing area of the minimum width size paper (small size paper) that can be used in the apparatus, that is, the minimum sheet passing width. The minimum sheet passing width Xm in this embodiment is 76 mm. The longitudinal width of the fixing film 112 is larger than Wg.

  The inner surfaces of one end side and the other end side of the fixing film 112 are supported by film inner surface guide portions 150b of the flange members 150 on the one end side and the other end side outside the maximum sheet passing width X, respectively.

(Fixing film)
The fixing film 112 of the present embodiment is a flexible heat-resistant member having a thin and substantially cylindrical shape with its outer diameter of φ20 mm in its free state in which it is not deformed by applying an external force. 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 adhesion of dirt to the surface.

  The material of the base layer 126 is required to have heat resistance because it receives heat from the heater 113. Moreover, since it slides with the heater 113, strength is also required. For this reason, a metal such as SUS (Stainless Used Steel) or nickel, or a heat resistant resin such as polyimide may be used. Since the metal is stronger than the resin, it can be thinned and has high thermal conductivity, so that the heat of the heater 113 is easily transferred to the surface of the fixing film 112. On the other hand, since resin has a smaller specific gravity than metal, there is an advantage that the heat capacity is small and the resin is easily heated. In addition, the resin can be molded at low cost because a thin film can be formed by coating.

  In this embodiment, a polyimide resin is used as the 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 thinner the base layer 126 is, the easier it is to transfer the heat of the heater 113 to the surface of the fixing film, but the strength is reduced. Therefore, the thickness is preferably about 15 μm to 100 μm, and in this embodiment, 50 μm.

  The material of the release layer 127 of the fixing film 112 is preferably a fluororesin such as perfluoroalkoxy resin (PFA), polytetrafluoroethylene resin (PTFE), tetrafluoroethylene-hexafluoropropylene resin (FEP). In this example, among the fluororesins, PFA having excellent releasability and heat resistance was used.

  The release layer 127 may be a tube-covered one or a surface coated with a paint, and in this example, the release layer 127 was formed by a coating excellent in thin-wall molding. The thinner the release layer 127 is, the easier it is to transfer the heat of the heater 113 to the surface of the fixing film 112. However, if the release layer 127 is too thin, the durability is lowered, and is preferably about 5 μm to 30 μm.

(Pressure roller)
The pressure roller 110 of this embodiment has an outer diameter of φ20 mm, and an elastic layer 116 (foamed rubber) having a thickness of 4 mm obtained by foaming silicone rubber on an iron cored bar 117 of φ12 mm. When the pressure roller 110 has a large heat capacity and a high thermal conductivity, the 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 a low heat capacity, 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 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 related 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 also a low heat capacity. Therefore, this foamed rubber can shorten the rise time of the pressure roller 110 surface temperature.

  If the outer diameter of the pressure roller 110 is smaller, the heat capacity can be suppressed. 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 example, the outer diameter was set to φ20 mm. As for the thickness of the elastic layer 116, if it is too thin, heat will escape to the metal core, so an appropriate thickness is required. In this embodiment, the elastic layer 116 has a thickness of 4 mm.

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

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

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

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

  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 sheet conveyance 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 with a thickness of 50 μm as a heating element protective layer 209 thereon. The heating element protective layer 209 is shown only in FIG. 1A, and is omitted in (c) and (d).

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

  The longitudinal width W of the resistance heating elements 201 and 202 is 218 mm which is longer by 1 mm at both ends so that letter-size paper having a width of 216 mm corresponding to the maximum sheet passing width X can be sufficiently heated in the present embodiment.

  One end of the two resistance heating elements 201 and 202 on the substrate 207 is connected in series via the conductor 203 and is conductive. Conductive electrodes 204 and 205 are provided on the other end sides of the resistance heating elements 201 and 202, respectively. When the electrodes 204 and 205 are energized, 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 were accommodated.

(Power circuit)
A power supply circuit 501 for supplying power to the heater 113 shown in FIG. 4A will be described. The power supply circuit 501 includes a commercial power source (commercial AC power source) 503, a power feeding control circuit (triac) 504, a protection element 114, an electrode unit 205, a resistance heating element 202, a conductor 203, a resistance heating element 201, and an electrode unit 204 in series. A primary circuit (AC circuit) 502 is connected. The power supply control circuit 503 is controlled by the control unit 500. Further, the power supply circuit 501 includes a secondary circuit (DC circuit) 505 in which the temperature detection element 115 is connected to the control unit 500.

  The protection element 114 is a primary circuit member that is activated when the heater 113 is abnormally heated and interrupts energization of the primary circuit 502, that is, interrupts energization from the commercial power source 503 to the heater 113. For example, it is an energization interruption member that has an internal switch such as a temperature fuse, a thermo switch, a thermostat, etc., and operates by an abnormal temperature rise of the heater 113 to interrupt energization.

  In the embodiment, the protective element 114 is inserted through a hole 130c provided in the heater holder 130 as shown in FIG. 4B, and is a first heat conduction member to be described later with respect to the back surface of the substrate 207 of the heater 113. The contact is made via 140. That is, the protection element 114 detects the temperature of the heater 113 through the first heat conducting member 140.

  The temperature detection element 115 is a primary circuit member for controlling the temperature of the heater 113, and is, for example, a thermistor. This temperature detection element 115 is also inserted through a hole 130 d provided in the heater holder 130 and is in contact with the back surface of the substrate 207 of the heater 113 via a second heat conduction member 141 described later. That is, the temperature detection element 115 also detects the temperature of the heater 113 via the second heat conducting member 141.

  The control unit 500 controls the power supply control circuit 504 according to the detected temperature information of the temperature detection element 115, and appropriately controls the current flowing from the electrode units 204 and 205 to the resistance heating elements 201 and 202 in the power supply circuit 501. Thus, the temperature of the heater 113 is adjusted.

  Both the protection element 114 and the temperature detection element 115 are installed at a position that falls within the minimum sheet passing width Xm with respect to the heater 113 in order to detect the temperature in the sheet passing state with respect to the apparatus. . In order to avoid complication of the drawing, the protection element 114 and the temperature detection element 115 are not shown in the drawings other than FIGS.

(Heat conduction member)
On the back surface (second surface) of the heater 113, as shown in FIGS. 1B to 1D, the first and second heat conducting members 140 for equalizing the temperature of the heater 113 are used. , 141 are provided. In other words, the heat conducting members 140 and 141 are divided into the first and second portions in the central portion in the longitudinal direction in the conveyance region of the paper P. The first and second heat conducting members 140 and 141 are arranged side by side in the longitudinal direction of the back surface of the heater at a position substantially corresponding to the longitudinal width W of the resistance heating elements 201 and 202.

  The heat conducting members 140 and 141 are members having a heat conductivity higher than at least the substrate 207 of the heater 113 in a direction parallel to the plane, and are interposed between the heater 113 and the holder 130. Has been.

  FIG. 5 shows an assembly view (disassembled perspective view) when the heat conducting members 140 and 141 and the heater 113 are assembled to the heater holder 130. The heater holder 130 is provided with a groove 130b so that the heat conducting members 140 and 141 and the heater 113 are sufficiently accommodated. After the two heat conducting members 140 and 141 are fitted into the groove 130b of the heater holder 130, the heater 113 is fitted.

  Further, the heat conducting members 140 and 141 are provided with restricting portions 140a and 141a for restricting displacement in the longitudinal direction from the heater holder 130. The restricting portions 140a and 141a of the heat conducting members 140 and 141 are formed by bending a part of the heat conducting members 140 and 141 as shown in FIG.

  On the other hand, the heater holder 130 is provided with a restriction groove 130a so that the restriction portions 140a and 141a of the heat conducting members 140 and 141 are fitted. The heat conducting members 140 and 141 and the heater holder 130 are regulated in the longitudinal direction by fitting the regulating portions 140 a and 141 a of the heat conducting member into the regulating grooves 130 a of the heater holder 130.

  As the material of the heat conductive members 140 and 141, the higher the thermal conductivity than the material of the substrate 207 of the heater 113, the more effective the temperature of the members such as the heater 113, the fixing film 112, and the pressure roller 118 is equalized. high. As the heat conducting members 140 and 141, there are a case where a silver paste having a high heat conductivity is applied and a case where a metal plate such as a graphite sheet or an aluminum plate is contacted.

  When a sheet or a metal plate is used as the heat conducting members 140 and 141, there is an advantage that the heat capacity of the heat conducting member 140 can be easily adjusted by the thickness. In the present embodiment, aluminum (aluminum) plates that have relatively high heat conductivity among metals and can be installed at low cost are used as the heat conduction members 140 and 141. As the thickness of the heat conducting members 140 and 141 increases, the effect of leveling the temperature increases. Therefore, as described above, a job for continuously passing small-size paper having a narrow width relative to the longitudinal width W of the resistance heating elements 201 and 202 is used. Productivity is improved.

  However, since the heat capacity is increased, the rise time of the heater 113 is delayed. For this reason, it is desirable to adjust the material and thickness of the heat conducting member 140 in accordance with the balance between the productivity when continuously passing small-size paper and the rise time of the heater 113.

  The heat conducting members 140 and 141 of the present embodiment use aluminum plates having a thickness t of 0.5 mm and a width (short width) in the paper transport direction A1 of 6 mm which is the same as the short width Wh of the substrate 207 of the heater 113. It was.

  As described above, the first and second heat conducting members 140 and 141 are in contact with the protection element 114 as a primary circuit member and the temperature detection element 115 as a secondary circuit member, respectively. Therefore, the first heat conducting member 140 on the protection element 114 side is treated as a primary circuit, and the second heat conducting member 141 on the temperature detecting element 115 side is treated as a secondary circuit.

  Therefore, it is desirable to arrange the first heat conducting member 140 and the second heat conducting member 141 with a predetermined distance in order to ensure insulation from each other. 1B is a schematic view of the heater 113 and the first and second heat conducting members 140 and 141 as viewed from the direction of the arrow A2 in FIG. 3A (first and second heat conducting members 140). , 141 is a schematic diagram on the back side of the heater 113). As shown in FIG. 1B, the first and second heat conducting members 140 and 141 are installed (disposed at a predetermined interval) by a predetermined distance Y in the longitudinal center portion of the heater 113. Yes. In this embodiment, the predetermined distance Y is 4 mm.

  The longer the longitudinal width of the first and second heat conducting members 140 and 141 is, the higher the effect of smoothing the heat in the longitudinal direction is. Since heat dissipation is facilitated, the fixability at the end in the width direction of a large sheet may be reduced. For this reason, it is desirable to adjust the positions of the longitudinal width end portions of the first and second heat conducting members 140 and 141 in accordance with the balance between the productivity of small size paper and the fixability of the width direction end portion of the large size paper.

  In the present embodiment, the entire longitudinal width (position on one end side and the other end side) of the first and second heat conducting members 140 and 141 is made 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 separation distance Y between the first and second heat conducting members 140 and 141 is 4 mm, the first and second heat conducting members 140 and 141 are respectively provided. The longitudinal width Wa is 107 mm.

(Positioning part of heat conduction member)
In the present embodiment, restricting portions 140a and 141a for restricting the positions in the longitudinal direction of the heat conducting members 140 and 141 are provided at locations corresponding to the inside of the minimum sheet passing width Xm in the longitudinal direction. It is characterized by suppressing the shift in the longitudinal direction of the.

  FIG. 1C is a schematic cross-sectional view in the longitudinal direction in which the first and second heat conducting members 140 and 141 and the heater 113 are fitted into the heater holder 130. The restricting portions 140a and 141a of the first and second heat conducting members 140 and 141 are installed inside the minimum sheet passing width Xm, and the distances L from the inner ends of the heat conducting members 140 and 141 are each 4 mm. .

  FIG. 1D shows the state of expansion of the first and second heat conducting members 140 and 141 when the paper is passed through the minimum paper passing width Xm. When a sheet having the minimum sheet passing width Xm is passed, the temperature of the first and second heat conducting members 140 and 141 is the temperature adjustment temperature for fixing in the sheet passing area. In the part, the temperature rises due to the temperature rise in the non-sheet passing part.

  Since the elongation due to thermal expansion is proportional to the temperature rise, the elongation due to thermal expansion of the first and second heat conducting members 140 and 141 is large in the non-sheet passing portion and small in the sheet passing portion. Therefore, as shown by the arrow in FIG. 1 (d), the first and second heat conducting members 140 and 141 have a large extension toward the outer end side in the longitudinal direction, but they extend toward the inner end side. Is small. Accordingly, the predetermined distance Y of 4 mm between the first heat conducting member 140 and the second heat conducting member 141 is almost maintained.

  Here, the comparative example 1 shown to (a) of FIG. 6 is demonstrated. 6 (a) corresponds to FIG. 1 (d) in this embodiment, and the restriction portions 140a and 141a of the first and second heat conducting members 140 and 141 and the restriction groove 130a of the heater holder 130 are formed. Except for the position in the longitudinal direction, the configuration is the same as that of the present embodiment, and the same reference numerals are used to omit the description.

  In the configuration of Comparative Example 1 in FIG. 6A, the elongation due to the thermal expansion of each of the first and second heat conducting members 140 and 141 is on the outer end side and the inner end side in the longitudinal direction of the member. The restricting portions 140a and 141a are installed near the longitudinal center of the heat conducting member so as to be substantially uniform. Therefore, the distance L between the inner end portion of the first heat conducting member 140 and the restricting portion 140a and the distance L between the inner end portion of the second heat conducting member 141 and the restricting portion 140a are each 70 mm. The separation distance Y between the first and second heat conducting members 140 and 141 is 4 mm as in the present embodiment.

  In the configuration of the comparative example 1, there are the restricting portions 140a and 141a of the first and second heat conducting members 140 and 141 outside the minimum sheet passing width Xm. Therefore, when a sheet corresponding to the minimum sheet passing width Xm is passed, as shown in FIG. 6B, the first and second heat conducting members 140 and 141 expand due to the temperature rise of the non-sheet passing portion. It also extends to the inner end side. That is, the distance between the inner end portions of the first heat conducting member 140 and the second heat conducting member 141 is reduced.

  As a result, the predetermined distance Y of 4 mm between the first heat conducting member 140 and the second heat conducting member 141 is not maintained, and the distance is further reduced, and the distance between the first and second heat conducting members is reduced. In other words, the insulation performance of the primary circuit and the secondary circuit is degraded.

(Verification of effect)
For the configuration of Example 1 and the configuration of Comparative Example 1, evaluation of thermal unevenness and evaluation of whether insulation between the first and second heat conducting members 140 and 141 was ensured were performed.

  Evaluation of thermal unevenness was carried out by passing 10 sheets of 100% print pattern on the entire surface, since printing with a uniform image pattern with a large amount of applied toner tends to cause image defects such as gloss unevenness due to thermal unevenness. When there was no gloss unevenness, it was marked as ◯, and when even one sheet was glossy unevenness was marked as x.

  Moreover, regarding the insulation performance between the first and second heat conducting members 140 and 141, it was confirmed whether or not a discharge occurred when a voltage assuming a lightning surge was applied. In the evaluation, a voltage of 6 kV was applied 6 times to the primary circuit while paper was being passed, and the presence or absence of discharge was confirmed. A case where there was no discharge between the first and second heat conducting members 140 and 141 was marked with ◯, and a case where there was a discharge was marked with x.

In each evaluation, when using a letter size Xerox 4200 (basis weight 75 g / m ² ) having a maximum sheet passing width X: 216 mm and a paper cut from the Xerox 4200 having a minimum sheet passing width Xm of 76 mm. Evaluated.

  The fixing temperature was adjusted so that the temperature detecting element 115 would be 180 ° C., and the letter size paper having the maximum paper passing width X was passed at 25 ppm. In the paper having the minimum paper passing width Xm, the paper was passed at a speed of 15 ppm so as not to exceed the heat resistance temperature of the heater holder 130 and the pressure roller 110 due to the temperature rise of the non-paper passing portion.

  Further, as Comparative Example 2, the same configuration as that of Comparative Example 1 was also evaluated in the case where the inner portions of the first and second heat conducting members 140 and 141 were shortened so that the separation distance Y was 5 mm. The evaluation results are shown in Table 1.

  As shown in Table 1, in the configuration of Example 1, uneven gloss due to heat unevenness and discharge could be suppressed.

  In Comparative Example 1, the gloss unevenness could be suppressed, but the discharge occurred only when the paper having the minimum width was passed. This is thought to be because the thermal expansion due to the temperature rise due to the temperature rise at the non-sheet passing portion due to the minimum width sheet passing, and the separation distance Y between the first and second heat conducting members 140 and 141 is shorter than 4 mm. It is done.

  In Comparative Example 2, since the initial separation distance Y of the first and second heat conducting members 140 and 141 was increased to 5 mm, the discharge could be suppressed. However, when the first and second heat conducting members 140 and 141 are letter-size paper having a small inward extension due to thermal expansion, gloss unevenness has occurred.

  As described above, by providing the restricting portions 140a and 141a of the first and second heat conducting members 140 and 141 inside the minimum sheet passing width Xm, the heat conducting member can be used even when sheets of various sizes having different widths are passed. The change of the thermal expansion amount to the inside of 140,141 can be suppressed. Accordingly, it is possible to suppress an image defect due to uneven gloss due to heat unevenness and secure insulation between the heat conducting members 140 and 141.

  In the first embodiment, the restricting portions 140a and 141a in the longitudinal direction of the first and second heat conducting members 140 and 141 are limited to one place. This is because if two or more restricting portions are provided, a force may be applied to the heat conducting members 140 and 141 due to the difference in expansion between the heater holder 130 and the heat conducting members 140 and 141, which may cause deformation. It is.

  Similarly, if the friction coefficient between the first and second heat conducting members 140 and 141, the heater 113, and the heater holder 130 is high, the heat conducting members 140 and 141 are restricted except for the restricting portions 140a and 141a. Deformation may occur.

  For this, for example, it is effective to apply a lubricant such as lubricating grease to the first and second heat conducting members 140 and 141. In addition, as shown in FIG. 7, a recess 130 e is provided on the contact surface between the first and second heat conducting members 140 and 141 of the heater holder 130. Thereby, it is effective to reduce the contact area between the heater holder 130 and the heat conducting members 140 and 141.

  In the first embodiment, the case where the protection element 114 and the temperature detection element 115 are in contact with the first and second heat conducting members 140 and 141, respectively, has been described. That is, the protection element 114 as a primary circuit member directly connected to the commercial power source 502 may be in the vicinity of the first heat conducting member 140, and the temperature detection element 115 as a secondary circuit member is the second. The heat conducting member 141 may be in the vicinity. This embodiment is effective when the insulation between the primary circuit member 114 and the first heat conducting member 140 and the insulation between the secondary circuit member 115 and the second heat conducting member 141 are not ensured.

  Therefore, in the present invention, the primary circuit member is brought close to the first heat conducting member includes the case where the primary circuit member is in contact with the first heat conducting member and the case where the primary circuit member is not in contact with the first heat conducting member. It is. In addition, in order for the secondary circuit member to come close to the second heat conducting member, the case where the secondary circuit member is in contact with the second heat conducting member and the case where the secondary circuit member is not in contact are included.

Example 2
A second embodiment will be described below. In the second embodiment, as a method for regulating the first and second heat conducting members 140 and 141, the first and second heat conducting members 140 and 141 are directly fixed to the heater holder 130 with an adhesive. Yes.

  In the second embodiment, the image forming apparatus that forms an unfixed toner image, the method of the fixing apparatus, the fixing film, the pressure roller, and the heater are the same as those in the first embodiment, and thus description thereof is omitted.

(Heat conduction member)
This will be described with reference to FIG. In this embodiment, an adhesive 160 is used as a method for regulating the first and second heat conducting members 140 and 141. As shown in FIG. 8B, the adhesive 160 is applied to the first and second heat conducting members 140 and 141 and bonded to the heater holder 130. The protection element 114 and the temperature detection element 115 are omitted, but are the same as those in the fixing device of the first embodiment. It is the same.

(Positioning part of heat conduction member)
The restricting portions 140a and 141a of the first and second heat conducting members are positions (adhesive portions) bonded by the adhesive 160. In the first heat conducting member 140, the distance L from the inner end portion end portion of the heat conducting member 140 at the position (adhered portion) bonded by the adhesive 160 which is the restricting portion 140a is set to 4 mm as in the first embodiment. . The distance L from the end of the inner end of the heat conducting member 141 at the position where the second heat conducting member 141 is bonded with the adhesive 160 as the restricting portion 141a is also set to 4 mm as in the first embodiment. Further, the predetermined separation distance Y between the restricting portions 140a and 141a of the first and second heat conducting members is also 4 mm as in the first embodiment.

(Verification of effect)
About the structure of the present Example 2, the evaluation method was used similarly to Example 1, and the thermal nonuniformity and the insulation of the 1st and 2nd heat conductive members 140 and 141 were evaluated. As a result of evaluation, neither gloss unevenness nor discharge occurred.

  Also in Example 2, uneven gloss due to heat unevenness was suppressed, and insulation of the first and second heat conducting members 140 and 141 could be secured. As in the first embodiment, the restriction portions 140a and 141a are provided at locations corresponding to the inside of the minimum sheet passing width Xm. Therefore, even when a sheet corresponding to the minimum sheet passing width X is passed, the first and second heat conducting members 140 and 141 can be prevented from thermally expanding and extending in the longitudinal direction. is there.

  In the second embodiment, the first and second heat conducting members 140 and 141 are bonded to the heater holder 130. However, the same effect can be obtained when the heat conducting members 140 and 141 are bonded to the heater 113. be able to.

  In the first and second embodiments described above, the image heating apparatus has been described by taking the fixing apparatus that heats and fixes an unfixed toner image formed on the paper (on the recording material) as an example, but is not limited thereto. The present invention can also be applied to an apparatus that increases the gloss (glossiness) of an image by reheating a toner image fixed or assumed on the paper P.

  100 ·· Image heating device (fixing device), 113 · · Heating member (heater heater), 209 · · Substrate, 201, 202 · · Resistance heating element, 130 · · Holding member (heater holder), 140 · · · Heat transfer member 141 ··· Second heat transfer member 112 · · Belt (fixing film) 110 · · Rotating body (pressure roller) No · · Nip (fixing nip) 140a, 141a · · · Restriction part, Y ... interval, Xm ... minimum paper passing width (passage area of recording material of minimum width size)

Claims (13)

A heating member having an elongated substrate and a resistance heating element that generates heat by energization formed along the length of the substrate;
A holding member for holding the heating member;
A heat conductive member having a thermal conductivity higher than that of the substrate at least in a direction parallel to the plane, and is arranged along the longitudinal direction of the heating member, between the heating member and the holding member. A first heat conducting member and a second heat conducting member sandwiched between,
An endless belt that can rotate while an inner peripheral surface is in contact with and slides on a surface of the heating member opposite to the heat conducting member;
An image heating apparatus having a rotating member that forms an nip portion and an outer surface of the belt in contact with the heating member with the belt interposed therebetween, and that heats the recording material that carries an image at the nip portion while sandwiching and conveying the recording material In
The first heat conducting member and the second heat conducting member are disposed at a predetermined interval, and each of the first heat conducting member and the second heat conducting member has a restricting portion that restricts movement in the longitudinal direction with respect to the holding member. Is provided at a position corresponding to the inside of the passage region of the recording material of the minimum width size that can be conveyed by the image heating device.   The primary circuit member directly connected to a commercial power source is in close proximity to the first heat conducting member, and the secondary circuit member is in close proximity to the second heat conducting member. Item 2. The image heating apparatus according to Item 1.   The image heating apparatus according to claim 2, wherein the primary circuit member is a protective element that is activated by an abnormal temperature rise of the heating member and interrupts energization of the primary circuit.   The image heating apparatus according to claim 2, wherein the secondary circuit member is a temperature detection element that detects a temperature of the heating member.   The image heating apparatus according to claim 1, wherein the heating member is a ceramic heater.   The image heating apparatus according to claim 1, wherein the first heat conductive member and the second heat conductive member are aluminum.   The image heating according to any one of claims 1 to 6, wherein the restricting portion is located at each longitudinal end of the first heat conducting member and the second heat conducting member. apparatus.   8. The heating according to claim 1, wherein one restricting portion is disposed for each of the first heat conducting member and the second heat conducting member. 9. apparatus.   The image heating apparatus according to claim 1, wherein lubricating grease is applied to the first heat conductive member and the second heat conductive member.   The holding member has a contact area between the first heat conductive member and the second heat conductive member by providing a recess in a contact surface between the first heat conductive member and the second heat conductive member. The image heating apparatus according to claim 1, wherein the image heating apparatus is reduced.   The image heating apparatus according to claim 1, wherein the restriction portion is fitted into a restriction groove provided in the holding member.   The said restriction | limiting part is the adhesion part by the adhesive material with respect to the said holding member of each of the said 1st heat conductive member and the said 2nd heat conductive member, The any one of Claim 1 thru | or 10 characterized by the above-mentioned. The image heating apparatus as described.   An image forming apparatus comprising the image heating apparatus according to claim 1.