Heating device and image forming apparatus

Abstract

The invention relates to a heating apparatus and an image forming apparatus. The heating device includes: a first rotating member having an internal space in which a heating member and a holding member are provided; a second rotating member that contacts an outer circumferential surface of the first rotating member; and a frame integrally supporting the heating member, the holding member, the first rotating member, and the second rotating member, in which the second rotating member forms a nip between the first rotating member and the second rotating member, the holding member holding the heating member, and the holding member holding the first rotating member and the second rotating member. The heating member is configured such that at least a portion of at least one end surface of the heating member in a longitudinal direction thereof is exposed in the longitudinal direction, and the frame is configured such that at least the portion of the heating member exposed from the holding member is also exposed out of the frame.

Description

[0001] This application is a divisional application of the invention patent application named "Heating device and imaging device", filed on August 3, 2021, and with application number 202110883670.2. Technical Field

[0002] The present invention relates to a heating device and an image forming device. Background Art

[0003] As a heating device for toner used in an electrophotographic system, a heat roller type heating device, a film heating type heating device, and the like are known.

[0004] In Japanese Patent Application Publication No. H04-044075, a film heating type heating device includes: a heater having a resistance heating element on a ceramic substrate; a fixing film heated and rotated by the heater; and a pressure roller forming a nip portion by contacting the fixing film. Here, a recording material carrying an unfixed toner image is heated while being conveyed through the nip portion. By this heating, the toner image on the recording material is fixed to the recording material.

[0005] However, the heat capacity of the film heating type heating device is small, so, for example, when a small-sized paper is passed through the heating device, the area (non-paper passing area) other than the area (paper passing area) where the paper passes through the fixing member (e.g., fixing film, pressure roller) heats up faster than the paper passing area. If the temperature in the non-paper passing area rises like this and the temperature of the fixing member exceeds the heat-resistant temperature, the safety of the heating device is reduced. Therefore, for example, it is necessary to suppress the temperature rise in the non-paper passing area by increasing the time interval of the paper passing, and thus, the productivity of printing small-sized paper is reduced.

[0006] To solve this problem, Japanese Patent Application Publication No. 2018-36490 discloses a technology for cooling the non-paper-passing area by sending air to the edge of the heating device using a cooling fan. However, even if a cooling fan is used, if printing on small-sized paper is repeatedly performed, the non-paper-passing area may not be sufficiently cooled and may heat up.

[0007] Therefore, in the conventional heating device, a decrease in productivity in printing small-sized sheets due to a temperature rise in the non-paper-passing area has become a problem. Summary of the invention

[0008] An object of the present invention is to provide a heating device capable of controlling a decrease in productivity when printing small-sized paper.

[0009] One aspect of the present invention is: a heating device comprising: a heating member including a heating element; a holding member for holding the heating member; a first rotating member, the first rotating member having an internal space, the heating member and the holding member being arranged in the internal space; a second rotating member, the second rotating member contacting the outer peripheral surface of the first rotating member; and a frame, the frame integrally supporting the heating member, the holding member, the first rotating member and the second rotating member, wherein the second rotating member forms a clamping portion between the first rotating member and the second rotating member, the holding member holds the heating member so that at least a portion of at least one end surface of the heating member in a longitudinal direction thereof is exposed in the longitudinal direction, and the frame is configured so that at least the portion of the heating member exposed from the holding member is also exposed from the frame.

[0010] Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a diagram depicting an imaging device according to Embodiment 1;

[0012] Figure 2A and Figure 2B is a diagram depicting a heating device according to Example 1;

[0013] Figure 3A and Figure 3B is a diagram depicting a heating device according to Example 1;

[0014] Figure 4 is a diagram depicting a heater according to Embodiment 1;

[0015] Figure 5 is a diagram depicting connection between a heater holder and a heater according to Embodiment 1;

[0016] FIG. 6A to FIG. 6C is a diagram depicting the shape of a heater holder according to Embodiment 1;

[0017] Figure 7 is a diagram depicting a side view of a heating device according to Example 1;

[0018] Figure 8 is a diagram depicting a side view of a heating device according to a comparative example;

[0019] 9A to 9C is a diagram depicting the shape of a heater holder according to Embodiment 2;

[0020] Fig.10is a diagram depicting a side view of a heating device according to Example 2;

[0021] FIG. 11A to FIG. 11C is a diagram depicting the shape of a heater holder according to Embodiment 3;

[0022] Fig.12 is a diagram depicting a side view of a heating device according to Example 3;

[0023] Fig.13 is a diagram depicting a heating device according to another embodiment;

[0024] Fig.14A and Fig. 14B is a diagram depicting a heating device according to another embodiment; and

[0025] Fig.15A and Fig. 15B is a diagram depicting a heater according to a comparative example. DETAILED DESCRIPTION

[0026] (Problems with the heating device) First, a problem that may occur when a film heating type heating device is used in an image forming device will be described in detail. The film heating type heating device here uses a film with a small heat capacity as a fixing member, so the time until the fixing member reaches (rises to) a predetermined temperature can be reduced compared to the heat roller of the heat roller type heating device. In addition, in the case of the film heating type heating device with a short rise time, it is not necessary to heat the fixing member during standby, so that power consumption can be controlled to be low.

[0027] Fig.15A denoted is a heater used for the heating device, which is a heater 1013 as a comparative example of each embodiment described later. Fig.15A 1 is a cross-sectional view of the heater 1013. The heater 1013 includes resistance heating elements 2001 and 2002, which heat the fixing film by contacting the fixing film. Fig.15A As shown, in the heater 1013, the resistance heating elements 2001 and 2002 are arranged in series on the ceramic substrate 2007 through the conductor 2003. The conductive electrode units 2004 and 2005 are respectively arranged on one edge of the resistance heating element 2001 and on one edge of the resistance heating element 2002. The resistance heating elements 2001 and 2002 are heated by the current flowing from the electrode units 2004 and 2005 to the resistance heating elements 2001 and 2002 (to energize them).

[0028] Since the heater 1013 contacts the inner surface of the fixing film with a small heat capacity (directly heats the fixing film), the temperature of the fixing member (fixing film, pressure roller) rises uniformly and rapidly in the longitudinal direction (the direction perpendicular to the conveying direction of the recording material). Then, if a recording material (small-sized paper) with a narrow width in the longitudinal direction of the heater 1013 passes continuously, the temperature in the non-paper-passing area (the area other than the area where the paper passes (paper-passing area)) of the fixing film rises much more than the paper-passing area. This is because in the paper-passing area, heat is transferred to the recording material being conveyed, but in the non-paper-passing area, the recording material to which heat is transferred is not transferred. In addition, in the heater 1013 according to the comparative example, each surface of the heater 1013 except the surface in contact with the fixing film is covered by the heater retainer, so not much heat is released to the outside.

[0029] Fig. 15B It shows the temperature distribution in the longitudinal direction of the fixing film when small-sized paper is passed. When such small-sized paper (recording material) is passed continuously, the temperature of the non-paper-passing area of ​​the fixing member (fixing film, pressure roller) rises, such as Fig. 15B As shown. Hereinafter, such a rise in temperature in the non-paper-passing area is referred to as "non-paper-passing portion temperature rise". In the case where "non-paper-passing portion temperature rise" occurs in the fixing member, a possible control is to increase the time interval of paper passing so that the temperature in the non-paper-passing area of ​​the fixing member does not exceed the heat-resistant temperature and the temperature of the fixing member is made uniform (equalized). However, increasing the time interval of paper passing reduces the productivity of printing small-sized paper, which is a problem.

[0030] Example 1

[0031] A heating device according to Embodiment 1 will be described. The heating device according to Embodiment 1 is a film heating type heating device with low power consumption and fast temperature rise. In the heating device according to Embodiment 1, a heater holder (holding member) covers a heater (heating member) so that the end face of the heater in the longitudinal direction (longitudinal axis direction; a direction perpendicular to the conveying direction of the recording material) is exposed. Therefore, the temperature in the non-paper-passing area of ​​the fixing member does not rise rapidly. Thus, it is possible to control the decrease in productivity in printing of small-size paper in which "heat rise in the non-paper-passing portion" is prone to occur.

[0032] <Imaging Device> First, refer to Figure 1The schematic diagram in illustrative embodiment describes the configuration of an image forming apparatus 50 including a heating device 100 according to Embodiment 1. The image forming apparatus 50 is an electrophotographic type image forming apparatus that directly transfers a toner image on a photosensitive drum onto a recording material P. On the outer peripheral surface of a photosensitive drum 1 (image bearing member), a charging device 2, an exposure device 3 that emits laser light L to the photosensitive drum, a developing device 5, a transfer roller 10, and a photosensitive drum cleaner 16 are sequentially provided along the rotation direction (arrow R1 direction).

[0033] (Printing method) A method for printing a toner image on a recording material P by the imaging device 50 will be described. First, the surface of the photosensitive drum 1 (imaging unit; forming device) is charged to negative polarity by the charging device 2. Then, an electrostatic latent image is formed on the surface of the charged photosensitive drum 1 by the laser light L of the exposure device 3 (the surface potential of the exposed portion is increased). The toner of Embodiment 1 is charged to negative polarity, and by the developing device 5 filled with black toner, the negative toner adheres only to the electrostatic latent image portion on the photosensitive drum 1. Thus, a toner image (image) is formed on the photosensitive drum 1.

[0034] On the other hand, before the process of forming an electrostatic latent image onto the photosensitive drum 1 begins, the recording material P is fed by the paper feed roller 4. The paper feed control unit 330 controls the paper feed timing of the paper feed roller 4 so that the front end of the recording material P reaches the transfer nip N at the moment when the front end of the toner image on the photosensitive drum 1 reaches the transfer nip N. When the paper feed operation is completed, the conveying roller 6 conveys only one sheet of the recording material P to the transfer nip N. Then, a transfer bias with a positive polarity (opposite to the polarity of the toner) is applied to the transfer roller 10 from a power source (not shown). Thereby, the toner image on the photosensitive drum 1 is transferred to the recording material P in the transfer nip N. In other words, an unfixed toner image (image) is formed on the recording material P by the photosensitive drum 1.

[0035] After the transfer, the untransferred toner is removed from the surface of the photosensitive drum 1 by the photosensitive drum cleaner 16 including an elastic scraper. On the other hand, the recording material P carrying the toner image is transferred to the heating device 100, where the toner image is heated and fixed. In other words, the toner image (image) formed on the recording material P is fixed to the recording material P by the heating device 100. The recording material P after the toner image is fixed is discharged by the discharge roller 7 onto the paper discharge tray 45. Thus, the printing of the image on the recording material P is completed.

[0036] In the case of printing on a plurality of recording materials P continuously, feeding of the subsequent recording material starts while the toner image on the photosensitive drum 1 is being transferred to the rear end of the previous recording material. Before the moment when the leading end of the subsequent paper reaches the transfer nip N, the process of forming an electrostatic latent image on the surface of the photosensitive drum 1 also starts, and the toner image for the subsequent paper is formed on the photosensitive drum 1. When the leading end of the subsequent paper reaches the transfer nip N, the toner image is transferred to the subsequent paper. Continuous printing is achieved by repeating this operation (process).

[0037] In Embodiment 1, the surface movement speed of the photosensitive drum 1 is about 200 mm / sec, and in the case of continuous printing, the image forming device 50 can print 35 sheets per minute for LTR size (letter size) paper. In the case of continuous printing of paper having a size smaller than the LTR size, the image forming device 50 also starts printing at a speed of 35 prints per minute, just like the case of LTR size paper. Here, the image forming device 50 controls to reduce the production volume by increasing the time interval of paper feeding in the middle of continuous printing so that the temperature in the non-paper passing area of ​​the fixing member does not exceed the heat resistance temperature.

[0038] <Cooling Fan> A cooling fan 60 (cooling device) is provided in the image forming apparatus 50. The cooling fan 60 lowers the temperature of the photosensitive drum cleaner 16 and the photosensitive drum 1 by sending out air.

[0039] For example, if the printing operation is repeated, the temperature of the photosensitive drum cleaner 16 and the photosensitive drum 1 may rise due to the heat of the heating device 100 and exceed the softening point of the toner. In some cases, this may cause the waste toner in the photosensitive drum cleaner 16 to solidify, or may cause the toner in the developing device 5 to melt and adhere. In this case, poor cleaning and poor development of the photosensitive drum 1 may occur. In order to prevent this, if the printing operation is repeated and the temperature inside the imaging device 50 rises, the fan control unit 61 operates the cooling fan 60. Then the air sent by the cooling fan 60 lowers the temperature inside the imaging device 50, and the generation of poor cleaning and poor development can be controlled.

[0040] The cooling fan 60 can also cool the non-paper-passing area of ​​the heating device 100 (fixing member) whose temperature rises when small-sized paper passes. In the image forming device 50, an air duct is formed so that the air sent out by the cooling fan 60 circulates around both edges in the longitudinal direction of the heating device 100. Therefore, if small-sized paper is continuously printed, the cooling fan 60 is operated by the fan control unit 61, and the air of the cooling fan 60 is sent to the non-paper-passing area of ​​the fixing member, thereby cooling the non-paper-passing area.

[0041] <Heating Device> Next, a description will be given of the heating device 100. The heating device 100 is a film heating type heating device that achieves shortened temperature rise time and reduced power consumption. Figure 2A and Figure 2B It is a simplified assembly diagram of the heating device 100 . Figure 2A is a diagram showing the heating device 100 in a state before assembly. Figure 2B is a diagram showing the heating device 100 in a unit state after being assembled.

[0042] Will be referenced in Figure 2A 1 and 10 , while describing the assembly process of the heating device 100, the configuration of the heating device 100 is described. First, the core rod 117 of the pressure roller 110 is placed on the bearings 132 provided on both edges of the fixing frame 70 made of iron. Then, the driving gear 131 is provided to the core rod 117.

[0043] Then, the resistance heating element of the heater 113 is mounted so as to face the pressure roller 110 side, and the back side (the side opposite to the surface on which the resistance heating element is mounted) is held by the heater holder 130 made of heat-resistant resin. In the heater 113, two resistance heating elements are arranged in series on the ceramic substrate, just like the comparative example (see Fig.15A ). In addition, a temperature detection element 115 for detecting the substrate temperature of the heater is provided on the back side of the heater 113. Here, the heater holder 130 is supported from the opposite side of the heater 113 by a bracket 120 made of iron to enhance the holding strength.

[0044] The fixing film 112 is inserted into a member in which the heater 113, the temperature detection element 115, the heater holder 130, and the bracket 120 are assembled. A fixing flange 150 is mounted on each edge of the fixing film 112 to regulate deviation of the fixing film in the longitudinal direction.

[0045] The fixing flange 150 on each edge is pressed by the pressure spring 114, and the film unit (a unit including a heater, a heater holder, and a bracket in the fixing film and having the fixing flange assembled on each edge) is pressed by the pressure roller 110. By pressing the pressure spring 114 with the fixing cover 71, the fixing cover 71 is closed to the fixing frame 70. Then the fixing frame 70 integrally supports the film unit and the pressure roller 110, thereby completing Figure 2B The assembly of the units of the heating device 100 is shown in FIG.

[0046] Figure 3A is from Figure 2B The heating device 100 viewed from the arrow L side in FIG. 1 is at the position of the temperature detection element 115 ( Figure 2B Schematic cross-sectional view along the longitudinal direction along the dotted line D). Figure 3BIt is a schematic diagram viewed from the upstream side in the conveying direction of the recording material P. Figure 3B The heating device 100 is shown in which the fixing film 112 is transparent (indicated by a dotted line) in order to observe the internal state more clearly.

[0047] like Figure 3A As shown, the heater 113 (heating element) is held by a heater holder 130 (holding member). In addition, a fixing film 112 (first rotating member) is provided, the inner surface of which contacts the heater 113 and the heater holder 130, and which has a flexible tubular shape. In other words, the heater 113 and the heater holder 130 are provided in the inner space of the fixing film 112. The heater 113 contacts the inner surface of the fixing film 112 to form an inner surface clamping portion Ni, thereby heating the fixing film 112 from the inside. A heat transfer member or the like may be provided between the heater 113 and the inner surface of the fixing film 112.

[0048] The heater 113 and the pressure roller 110 hold the fixing film 112 therebetween. Thus, the pressure roller 110 (second rotating member) facing the heater 113 forms a fixing nip No so as to nip the fixing film 112. Figure 3A When the recording material P is conveyed to the fixing nip No in the direction of arrow A1 shown in FIG. 1 (when the recording material P passes through the fixing nip No), the recording material P and the toner image T are heated, and the toner image T is fixed to the recording material P.

[0049] The pressure roller 110 rotates while pressing the outer surface (peripheral surface) of the fixing film 112. Specifically, as Figure 3B As shown, the pressure roller 110 receives power from a driving source (not shown) to a driving gear 131 provided on the edge of the core bar 117, and is driven (rotated) in the direction of arrow R1. When the pressure roller 110 is driven in the direction of arrow R1, the fixing film 112 receives power from the pressure roller 110 in the fixing nip No, and rotates in the direction of arrow R2.

[0050] In some cases, the fixing film 112 may be set in a state of being deviated to the left or right in the longitudinal direction. In order to prevent this, a fixing flange 150 for controlling the deviation is provided at each edge of the fixing film 112 in a manner of interfitting with each end of the bracket 120. Due to the fixing flange 150, the inner surface of the fixing film 112 is supported at a position outside the paper passing area X.

[0051] (Fixing Film) The fixing film 112 in a tubular state (a state not pressed by the pressure roller 110) has The fixing film 112 has an outer diameter of 1.1 mm and a multi-layer structure in the thickness direction. 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.

[0052] As the material of the base layer 126, metals such as stainless steel (SUS) and nickel or heat-resistant resins such as polyimide can be used. This is because the base layer 126 receives heat from the heater 113, so it needs to have heat resistance, and because the base layer contacts the heater 113, it also needs to have strength.

[0053] Compared with using resin as a material, metal is easier to thin due to its strength and has higher thermal conductivity. Therefore, if metal is used for the base layer 126, the heat of the heater 113 can be more easily transferred to the surface of the fixing film 112. On the other hand, compared with using metal as a material, resin with a lower specific gravity has a smaller heat capacity and is easier to warm. In addition, if resin is used, a thin film can be formed by coating, so the cost of forming the film can be reduced.

[0054] In Embodiment 1, polyimide resin is used as the material of the base layer 126, and carbon filler is added to improve thermal conductivity and strength. As the base layer 126 becomes thinner, it is easier to transfer the heat of the heater 113 to the surface of the pressure roller 110, but the strength decreases. Therefore, the thickness of the base layer 126 is preferably about 15 μm to 100 μm, and is 50 μm in Embodiment 1.

[0055] On the other hand, as the material of the release layer 127, fluororesins such as perfluoroalkoxy resin (PFA), polytetrafluoroethylene resin (PTFE), tetrafluoroethylene / hexafluoropropylene resin (FEP) can be used. In Embodiment 1, PFA is used as the material of the release layer 127, which is superior in release and heat resistance among fluororesins. The release layer 127 can be formed by covering the base layer 126 with a tube, or the release layer 127 can be formed by coating the surface of the base layer 126 with a coating material. In Embodiment 1, the release layer 127 is formed by coating the base layer 126 with a coating material having excellent film coating properties. As the release layer 127 becomes thinner, it is easier to transfer the heat of the heater 113 to the surface of the fixing film 112, but if the release layer 127 is too thin, the durability decreases. Therefore, the thickness of the release layer 127 is preferably about 5μm to 30μm, and 10μm in Embodiment 1.

[0056] (Pressure Roller) The outer diameter of the pressure roller 110 is In the pressure roller 110, as Figure 3A As shown, the mandrel 117 ( An elastic layer 116 (foam rubber) is formed on the pressure roller 110 (iron rod), and the elastic layer is foam silicone rubber with a thickness of 4 mm. If the heat capacity and thermal conductivity of the pressure roller 110 are high, the heat on the surface of the pressure roller 110 is easily absorbed into the inside, so the surface temperature of the pressure roller 110 does not rise rapidly. On the other hand, if a material with low heat capacity and thermal conductivity but high heat resistance effect is used for the pressure roller 110, the rising time of the surface temperature of the pressure roller 110 can be shortened. The thermal conductivity of the foam rubber generated by foaming silicone rubber is 0.11 to 0.16 W / m·K, which is lower than the thermal conductivity of solid rubber, which is about 0.25 to 0.29 W / m·K. The specific gravity related to heat capacity is about 1.05 to 1.30 in the case of solid rubber and about 0.45 to 0.85 in the case of foam rubber. In other words, the heat capacity of foam rubber is lower than that of solid rubber. Therefore, if foam rubber is used for the elastic layer 116 , the rising time of the surface temperature of the pressing roller 110 can be shortened.

[0057] When the outer diameter of the pressure roller 110 is small, the heat capacity is small, but if the outer diameter is too small, the width of the fixing nip No is reduced. Therefore, in Embodiment 1, the outer diameter of the pressure roller 110 is Furthermore, if the elastic layer 116 is too thin, heat is transferred from the elastic layer 116 to the metal core rod 117, so the elastic layer 116 needs to have an appropriate thickness. Therefore, in Embodiment 1, the thickness of the elastic layer 116 is 4 mm.

[0058] When the pressure roller 110 is heated, heat is released from the end faces of the elastic layer 116 and the core rod 117, so the temperature of the edge of the elastic layer 116 decreases. This means that if the width Wg of the elastic layer 116 in the longitudinal direction is too short relative to the maximum paper width of the recording material to be conveyed, the fixability of the toner image T on the edge of the recording material P is easily reduced. On the other hand, if the width Wg is too wide, the width of the image forming device 50 must be increased. Therefore, in Embodiment 1, the width Wg of the elastic layer 116 in the longitudinal direction is 226 mm, that is, 5 mm longer on both sides than the letter size 216 mm (the maximum width of the recording material that can be conveyed).

[0059] A release layer 118 made of a perfluoroalkoxy resin (PFA) is formed on the outer periphery of the elastic layer 116. The release layer 118 may be a layer formed by covering the elastic layer 116 with a tube, or a layer formed by coating the surface of the elastic layer 116 with a coating material, as in the case of the release layer 127 of the fixing film 112. In Embodiment 1, the release layer 118 is a layer formed by covering the surface of the elastic layer 116 with a tube having good durability. As a material of the release layer 118, a fluororesin such as PTFE and FEP, or a fluororubber or silicone rubber having good release properties can be used.

[0060] When the surface hardness of the pressure roller 110 becomes lower, even if the pressure of the pressure roller 110 is low (even if the pressure is light), the width of the fixing nip No can be increased. However, if the surface hardness of the pressure roller 110 is too low, the durability of the pressure roller 110 is reduced. Therefore, in Embodiment 1, the surface hardness of the pressure roller 110 is 40° Asker-C hardness (4.9N load).

[0061] The pressure roller 110 is rotated along the Figure 3A The surface moves in the direction of arrow R1 at a speed of 200 mm / sec.

[0062] (Heater) For the heater 113, a heater (heating member) in which a resistance heating element is provided in series on a ceramic substrate is used. In the heater 113, a resistance heating element made of Ag / Pd (silver palladium) is coated to 10 μm on the surface of an alumina substrate (width in the conveying direction of the recording material P: Wh=6 mm, thickness: H=1 mm) by screen printing. In addition, glass covers the substrate on which the resistance heating element is coated to a thickness of 50 μm as a heating element protective layer.

[0063] Figure 4 is along Figure 3A Schematic diagram of the heater 113 observed in the direction of the arrow A3 indicated in FIG. If the width W of the resistance heating elements 201 and 202 in the longitudinal direction is too narrow relative to the maximum paper passing width of the conveyed recording material, the fixability of the toner image on the edge of the recording material is easily reduced due to the heat release at the edge of the pressure roller 110. On the other hand, if the width W is too wide relative to the maximum paper passing width of the conveyed recording material, the temperature in the non-paper passing area of ​​the fixing member in contact with the heater 113 is easily increased. Taking these aspects into consideration, in Embodiment 1, the width W of the resistance heating elements 201 and 202 in the longitudinal direction is 218 mm, that is, 1 mm longer on the left and right than the letter size of 216 mm (the maximum width of the recording material that can be conveyed in the imaging device 50).

[0064] The resistance heating elements 201 and 202 are arranged in series on the substrate 207 through the conductor 203, and are covered with the heating element protection layer 209. The conductive electrode units 204 and 205 are respectively arranged on the edge of the resistance heating element 201 and the edge of the resistance heating element 202. The resistance heating elements 201, 202 are heated by the power supplied from the electrode units 204, 205. In Example 1, the width Wb of the substrate 207 in the longitudinal direction is 270 mm, which is sufficiently longer than the width W, so that the resistance heating elements 201 and 202, the conductor 203, the electrode units 204 and 205, and the heating element protection layer 209 are accommodated on the substrate 207.

[0065] In addition, if Figure 2A and Figure 3A As shown, a temperature detection element 115 is provided on the back side of the heater 113, and the temperature detection element detects the temperature of the ceramic substrate which rises with the heating of the resistance heating elements 201 and 202. The temperature of the heater 113 is adjusted by controlling the current that the electrode units 204 and 205 allow to flow into the resistance heating elements 201 and 202 according to the signal of the temperature detection element 115.

[0066] (Heater Holder) The heater holder 130 (holding member) is preferably made of a material with low heat capacity so that not much heat is transferred from the heater holder 130 when the heater 113 is activated. In Embodiment 1, liquid crystal polymer (LCP) as a heat-resistant resin is used for the heater holder 130.

[0067] like Figure 5 As shown in FIG. 1 , a recess O slightly larger than the heater 113 is formed in the heater holder 130. When the heater 113 is inserted into the recess O, the heater 113 is held (connected). The heater holder 130 also fixes (determines) the position of the heater 113 in the longitudinal direction and the position of the recording material P in the conveying direction. In Embodiment 1, among the respective wall portions constituting the recess O of the heater holder 130, the wall portion corresponding to (facing) the end face of the heater 113 in the longitudinal direction is formed into a concave shape ( Figure 5 omitted).

[0068] Fig. 6A and Figure 6B It is depicted along Figure 3A 1 is a diagram of the heater holder 130 viewed in the direction of arrow A3 shown in FIG. Fig. 6A It is a diagram depicting only the heater holder 130 . Figure 6B 1 is a diagram depicting a state in which the heater 113 is held by the heater holder 130 . Figure 6C is to describe the Figure 6B 1 is a diagram showing the side surface of the heater holder 130 viewed in the arrow L direction and the arrow R direction shown in FIG.

[0069] Since the substrate 207 thermally expands when the heater 113 is heated, the recess O of the heater holder 130 is larger than the heater 113. In Embodiment 1, the width Wn of the recess O of the heater holder 130 in the longitudinal direction is 271 mm, which is 1 mm wider than the substrate width Wb (270 mm). The width Wm of the recess O in the transverse direction (the conveying direction of the recording material P) is 6.5 mm, which is 0.5 mm wider than the substrate width Wh (6 mm). The thickness of the recess O in the depth direction is 1 mm, which is the same as the substrate thickness H of the heater 113.

[0070] like Fig. 6A and Figure 6B As shown, in the heater 113, the abutment position in the longitudinal direction is determined by the abutment portion Tn (a portion of the end surface of the heater 113 that contacts in the longitudinal direction) abutting against the heater retainer 130, and the abutment position in the lateral direction is determined by the left and right abutment portions Tkl and Tkr.

[0071] The heater holder 130 holds (covers) the heater 113 so that a portion of an end surface of the heater 113 in the longitudinal direction is exposed. Therefore, a wall portion of the heater holder 130 is concave, thereby forming a space portion a1 (gap). By forming the wall portion into a concave shape to form the space portion a1, the wall portion having the space portion a1 can be formed simultaneously with the other wall portions of the recess O by molding. In other words, there is no need to form the space portion a1 (space portion) by scraping or the like after forming the heater holder 130 in a state without the space portion a1. Therefore, the heater holder 130 having the space portion a1 can be formed easily, stably and at low cost.

[0072] like Figure 6C As shown in the side view in FIG. 1 , when the heater holder 130 is viewed in the direction of arrow R, a portion of the heater 113 is exposed. Here, in the heater 113, the electrode units 204 and 205 are arranged on the arrow L side of the resistance heating elements 201 and 202 (see FIG. 1 ). Figure 6B ). Therefore, the area (non-heating area) of the substrate 207 where the resistance heating elements 201 and 202 are not provided is longer on the L side (left side) than on the R side (right side). In a commonly used heating device, when a small size paper passes through, the temperature in the left and right paper passing areas rises, such as Fig. 15B As shown, in the case of the heater of Embodiment 1, in which the non-heating areas on the left and right sides of the substrate are different, the temperature in the non-paper-passing area on the shorter non-heating area becomes higher. Therefore, in Embodiment 1, the temperature in the non-paper-passing area on the R side (non-heating area is shorter) is more likely to rise than on the L side. Therefore, a space portion a1 is formed in the heater holder 130 to cool the R side of the heater 113.

[0073] When the space portion a1 becomes larger, the cooling effect on the temperature of the non-paper-passing area is improved, but when the space portion a1 is too large, the heater 113 may fall off during assembly, or the temperature in the edge of the heater 113 may drop when a large-sized paper passes through. Therefore, it is preferable to adjust the size of the space portion a1 according to the structure. In Embodiment 1, the size of the space portion a1 is 4 mm for the width Wa1 in the transverse direction, and the size of the space portion a1 is 0.7 mm for the height Ha1 in the thickness direction of the heater 113. In addition, in Embodiment 1, there is no space portion on the wall portion on the L side of the electrode units 204 and 205 on which the heater 113 is provided, because: the abutment portion Tn in the longitudinal direction of the heater 113 is located on the L side; and the degree of temperature rise in the non-paper-passing area when a small-sized paper passes through is relatively low.

[0074] As described above, in the heating device 100, the space portion a1 is formed on the wall portion of the heater holder 130 so that the heater 113 is exposed (visible) from the edge in the longitudinal direction of the heater 113 in the unit state. Therefore, the heat in the non-paper passing area of ​​the heater 113 can be released from the space portion a1. Therefore, in the printing of small-sized paper in which "non-paper passing portion heating" is prone to occur, the productivity does not decrease.

[0075] Figure 7 It is a view viewed from the left and right (i.e., along the direction of arrow L and the direction of arrow R). Figure 2B 100 in FIG. 100. On the R side of the heater holder 130 of the heating device 100, there is a space portion (gap) between the heater holder 130 and the fixing film 112, so that the end surface of the heater 113 becomes visible. Here, since the components other than the heater holder 130 (such as the fixing flange 150) do not cover the heater 113, the heater 113 is exposed (visible) on the R side of the heater holder 130 in the unit state. On the other hand, the heater 113 is Figure 7 In other words, in the unit state where the fixing frame 70 integrally holds the heater 113 and the heater holder 130, a portion of the end surface of the heater 113 on the R side in the longitudinal direction is exposed in the longitudinal direction. Therefore, in the fixing frame 70, at least a portion of the heater 113 exposed from the heater holder 130 is also exposed to the outside of the fixing frame 70.

[0076] In addition, in the image forming apparatus 50 of Embodiment 1, the cooling fan 60 is provided to cool the non-paper passing area, and when the small-sized paper passes, the air is sent to both edges of the heating device 100. If the heater 113 is exposed, as in the case of Embodiment 1, the air directly hits the end surface of the heated heater 113, so the cooling effect is improved. Therefore, it is possible to further control the decrease in productivity in the small-sized paper printing in which the non-paper passing area is easily heated.

[0077] <Comparison with Comparative Example> Figure 8 1 is a diagram depicting a heating device of a comparative example viewed from the left and right (L side and R side), in which both end surfaces in the longitudinal direction of the heater 113 are covered by the heater holder 130, and the heater 113 is not visible from the outside. In the heating device of the comparative example, no space portion is formed in the end surface (wall portion) in the longitudinal direction of the heater holder 130, and the fixing flange 150 covers the heater holder, so the heater is not exposed. The configuration of the heating device of the comparative example is the same as the heating device 100 according to Example 1 except for the configuration of the heater holder and the fixing flange.

[0078] By running a test with small size paper passing through, we compared Figure 8 The heating device of the comparative example shown is Figure 7 Here, a B5 size paper (basic weight: 70 g / m 2 ) were continuously passed through two heating devices at a speed of 35 sheets per minute, and the surface temperature of the corresponding pressing roller 110 was measured using a temperature recording method. The upper limit of the heat resistance temperature of the silicone rubber used for the pressing roller 110 is generally 230°C, so the number of B5 size paper prints that could be continuously passed until the surface temperature in the non-paper passing area of ​​the pressing roller 110 reached 230°C was compared.

[0079] Left Right Comparative Example Structure 40 prints 35 prints Construction of Example 1 40 prints 42 prints

[0080] In the configuration of the comparative example, the temperature rises rapidly on the right side (R side) of the heater 113, and when 35 printed sheets pass through, the surface temperature of the non-paper-passing area of ​​the pressure roller 110 reaches 230°C. On the left side (L side) of the heater 113, when 40 printed sheets pass through, the surface temperature of the non-paper-passing area of ​​the pressure roller 110 reaches 230°C. On the other hand, Figure 7In the configuration of Example 1 shown, the temperature rises rapidly on the left side (L side) of the pressure roller 110 where the heater 113 is not exposed, and when 40 printed sheets are passed, the surface temperature in the non-paper passing area of ​​the pressure roller 110 reaches 230° C., just like the comparative example. On the right side (R side) where the heater 113 is exposed, when 42 printed sheets are passed, the surface temperature in the non-paper passing area of ​​the pressure roller 110 reaches 230° C.

[0081] By forming a space portion on the wall portion of the heater holder of the heating device in the unit state, as in the case of Embodiment 1, the end surface of the heater in the longitudinal direction is exposed in the longitudinal direction, thereby being able to suppress the temperature rise rate in the non-paper passing area of ​​the fixing member. Therefore, it is possible to suppress the reduction in productivity in the small-size paper printing in which "non-paper passing portion temperature rise" is likely to occur.

[0082] Example 2

[0083] In Embodiment 2, a heating device in which the heater is exposed (visible) from both edges of the heating device in the unit state will be described. Further, in Embodiment 2, the edge on the resistance heating element side and the edge on the downstream side of the substrate of the heater are exposed. Therefore, the temperature of the non-paper passing area of ​​the heater is more easily lowered, and the decrease in productivity in small-size paper printing, in which "non-paper passing portion temperature rise" is prone to occur, can be controlled.

[0084] Unlike Embodiment 1, the image forming apparatus having the heating device according to Embodiment 2 does not include a cooling fan. Therefore, if a small-sized sheet of paper is passed in the same manner as in Embodiment 1, the non-paper-passing area of ​​the fixing member cannot be cooled by the cooling fan. Therefore, in Embodiment 2, the image forming apparatus uses the airflow (natural convection) rising toward the heating device to cool the non-paper-passing area of ​​the fixing member.

[0085] The imaging device of Embodiment 2 has the same configuration as that of Embodiment 1 except that the cooling fan 60 and the fan control unit 61 are not included. Therefore, a detailed description of the configuration of the imaging device according to Embodiment 2 is omitted. In addition, the configuration of the heating device is also a film heating type heating device, which is the same as that of Embodiment 1 except for the heater holder 130, and therefore the same components as those of Embodiment 1 are denoted by the same reference numerals, and a detailed description thereof is omitted.

[0086] (Shape of Heater Holder) The shape of the heater holder 130 according to Embodiment 2 will be described below. Fig. 9A and Fig. 9B It is depicted along Figure 3A 1 is a diagram of the heater holder 130 viewed in the direction of arrow A3 shown in FIG. Fig. 9A It is a diagram showing only the heater holder 130 . Fig. 9Bis a diagram showing the heater 113 and the heater holder 130 in a state of holding the heater 113 . Fig. 9C are along Fig. 9B 1 is a diagram of the heater holder 130 on the side viewed in the arrow L direction and the arrow R direction.

[0087] In the image forming apparatus of the second embodiment, a cooling fan for cooling the non-paper passing area is not included. Fig. 9B The wall portion on the arrow R side and the wall portion on the arrow L side are both formed in a concave shape. Since heat is released from each space portion formed by each concave wall portion, both edges of the heater 113 are easily cooled. In addition, the size of the space formed by each concave wall portion is larger than that of Embodiment 1 so that cooling is also performed by natural convection. Fig. 9C As shown, when viewed in the arrow R direction and the arrow L direction, the side surfaces of the heater 113 can be seen from the space portions of the respective wall portions of the heater holder 130 .

[0088] In the heater 113, the resistance heating elements 201 and 202 are heated by the power supplied from the electrode units 204 and 205, and therefore, the temperature of the substrate 207 becomes higher on the side closer to the resistance heating elements in the thickness direction. Fig. 9C As shown, not only the two edges of the heater 113 but also the substrate edge Hhe on the resistance heating element side (the ridge formed by the surface of the heater on the side in contact with the fixing film and the end face of the heater in the longitudinal direction) is completely exposed in the longitudinal direction. This produces a higher cooling effect. Here, the substrate edge Hhe does not need to be completely exposed in the longitudinal direction, and a cooling effect can be produced even if it is partially exposed.

[0089] The resistance heating elements 201 and 202 are uniformly arranged on the upstream and downstream sides in the conveying direction of the recording material P with respect to the center of the heater 113 in the transverse direction. Therefore, when the resistance heating elements 201 and 202 are heated during printing stop, the heating distribution becomes uniform in the upstream and downstream directions.

[0090] However, if the pressure roller 110 rotates in the R1 direction, as shown in FIG. Figure 3A As shown in the cross-sectional view in FIG. 1 , the fixing film 112 rotates in the R2 direction, and therefore, in the temperature distribution of the heater 113 during the rotation, the temperature on the downstream side in the conveying direction is higher than the temperature at the center. Therefore, in Embodiment 2, the substrate edge Hke on the downstream side (the ridge formed by the end face of the heater in the longitudinal direction and the side face of the heater on the downstream side in the transverse direction) is exposed in the longitudinal direction, as shown in FIG. Fig. 9CAs shown, at the substrate edge Hke, the temperature rises when both ends of the heater 113 rotate.

[0091] The width of the space portion a2L on both edges according to Embodiment 2 in the lateral direction and the width of the space portion a2R in the lateral direction are 6.5 mm, which is the same as the width Wm of the recess O. Due to the space portion a2L and the space portion a2R having such widths, the entire area of ​​the substrate edge Hhe of the heater 113 is exposed, and the substrate edge Hke on the downstream side is also exposed on both edges. The thickness Ha2 of the space portion a2L and the thickness Ha2 of the space portion a2R are 0.7 mm, which is the same as Embodiment 1. The abutment portion Tn for fixing the heater is formed in a convex shape on the L-side edge of the heater holder 130.

[0092] Fig.10 It depicts the image viewed from the left and right along the arrow L and arrow R directions. Figure 2B , a diagram of the heating device according to Embodiment 1 in a unit state. In the heating device according to Embodiment 2, as described above, a space portion (gap) is formed between the heater holder 130 and the fixing film 112 not only on the R side but also on the L side. Therefore, both end surfaces of the heater 113 in the longitudinal direction are exposed to the outside (visible). In addition, as Fig.10 As shown, on both the L side and the R side, components other than the heater holder 130 (e.g., the fixing flange 150) also do not cover the heater 113. In other words, in the unit state, the fixing frame 70 and the heater holder 130 are configured so that a portion of each end surface of the heater 113 in the longitudinal direction is exposed in the longitudinal direction.

[0093] As described above, the cooling fan 60 for cooling the heated non-paper-passing area is not provided in the image forming apparatus of Embodiment 2. However, the heater 113 in the unit state is exposed over a wide range, so the non-paper-passing area of ​​the fixing member is cooled by air flow (natural convection). Therefore, it is possible to suppress the decrease in productivity in printing of small-sized paper, in which "heating of the non-paper-passing portion" is likely to occur.

[0094] Comparison with Comparative Example Figure 8 The heating device according to the comparative example and the heating device according to Example 2 shown in FIG. Fig.10 In the comparative example, it is assumed that no cooling fan is provided in the imaging device, as in the second embodiment.

[0095] As in the case of Example 1, B5 size paper (basis weight: 70 g / m 2) are continuously passed through the corresponding heating device at a speed of 35 prints per minute, and the number of prints of B5 size paper that can be continuously passed until the surface temperature in the non-paper passing area of ​​the pressure roller 110 reaches 230°C is compared.

[0096] Left Right Comparative Example Structure 20 prints 15 prints Construction of Example 2 30 prints 28 prints

[0097] In the comparative example, the temperature on the right side (R side) of the heater 113 where the non-heating area is short rises rapidly, and when 15 printed sheets pass through, the surface temperature of the pressure roller in the non-paper passing area reaches 230°C. On the left side (L side) where the non-heating area is long, when 20 printed sheets pass through, the surface temperature of the non-paper passing area reaches 230°C. Fig.10 In the construction of Example 2 shown in , the temperature rises rapidly on the right side (R side), and when 28 printed sheets pass through, the surface temperature in the non-paper-passing area reaches 230°C; while on the left side (L side), when 30 printed sheets pass through, the surface temperature in the non-paper-passing area reaches 230°C.

[0098] In the case of an image forming apparatus that does not include a cooling fan, as in the case of Embodiment 2, if the end surface of the heater in the longitudinal direction is exposed from the heater holder in the longitudinal direction, the temperature rise rate in the non-paper passing area of ​​the fixing member can be suppressed. Therefore, it is possible to suppress a decrease in productivity in small-size paper printing in which "non-paper passing portion temperature rise" easily occurs.

[0099] Example 3

[0100] A heating device according to Embodiment 3 will be described. In Embodiment 3, in the heating device, both end faces of the heater in the longitudinal direction are completely visible. Therefore, the temperature rising in the non-paper passing area of ​​the heater is more easily reduced, and the decrease in productivity in small-size paper printing can be controlled.

[0101] The imaging device having the heating device according to Embodiment 3 does not include a cooling fan as in Embodiment 2. The configuration of the imaging device is the same as in Embodiments 1 and 2, and thus its description is omitted. The configuration of the heating device is a film heating type heating device, which is the same as in Embodiment 1 except for the heater holder 130, and thus the same components as in Embodiment 1 are denoted by the same reference numerals, and their detailed description is omitted.

[0102] (Shape of Heater Holder) The shape of the heater holder 130 according to Embodiment 3 will be described below. Fig.11A and Fig. 11B It is depicted along Figure 3A Schematic diagram of the heater holder 130 according to Embodiment 3 viewed in the direction of arrow A3 shown in FIG. Fig.11A is a diagram showing only the heater holder 130, Fig. 11B is a diagram showing a heater holder 130 that holds the heater 113 . Fig. 11C It is to describe the Fig. 11B 1 is a diagram of the heater holder 130 on the side viewed in the arrow L direction and the arrow R direction shown in FIG.

[0103] In the heater holder 130 of Embodiment 3, two wall portions corresponding to (facing) the two end faces of the heater 113 in the longitudinal direction are formed into a concave shape, thereby exposing the two end faces. In addition, the abutment portion of the heater 113 in the longitudinal direction does not exist, and both end faces of the heater 113 are completely exposed from the left and right. In Embodiment 3, the heater 113 is prevented from deviating or falling off by bonding it to the concave portion O of the heater holder 130. Since the end faces of the heater 113 in the longitudinal direction are completely exposed, the effect of cooling the heated non-paper-passing area is higher than that of Embodiment 2.

[0104] (Heating device in unit state) Fig.12 It depicts the observation along the arrow L and arrow R directions. Figure 2B In the heating device according to Embodiment 3, a space (gap) is formed between the heater holder 130 and the fixing film 112, and therefore, the end surface of the heater 113 is completely exposed from the left and right of the heater holder 130. Fig.12 As shown, the end faces of the heater 113 in the unit state are exposed on both the L side and the R side without any component (e.g., the fixing flange 150) other than the heater holder 130 covering the heater 113. Therefore, in the case of the image forming apparatus according to Embodiment 3, the respective end faces of the heater 113 in the unit state are fully exposed, and the non-paper passing area of ​​the fixing member can be cooled more easily by the airflow caused by natural convection.

[0105] <Comparison with Comparative Example> In Example 3, a test was also conducted by passing a small-sized paper through the Fig.12 The heating device according to Example 3 shown in FIG. Figure 8 As in the case of Example 2, a B5 size paper (basic weight: 70 g / m 2 ) are continuously passed through the corresponding heating device at a speed of 35 prints per minute, and the number of prints of B5 size paper that can be continuously passed until the surface temperature in the non-paper passing area of ​​the pressure roller 110 reaches 230°C is compared.

[0106]

[0107]

[0108] In the heating device according to Example 3, the temperature rise rate in the non-paper passing area of ​​the pressure roller is slower than that of the construction of Example 2, until the surface temperature of the pressure roller 110 in the non-paper passing area reaches 230°C, 30 printed materials pass through the right side (R side) and 32 printed materials pass through the left side (L side).

[0109] As described above, if each end surface of the heater 113 is fully exposed, the heating rate in the non-paper passing area of ​​the heater can be suppressed. Therefore, the productivity reduction in small-size paper printing, which is prone to "non-paper passing area heating", can be suppressed.

[0110] Other embodiments

[0111] In Embodiments 1 to 3, the end surface of the heater 113 in the longitudinal direction is exposed by forming the end surface (wall portion) of the heater holder 130 in the longitudinal direction into a concave shape, but the present invention is not limited thereto. Specifically, the end surface of the heater 113 in the longitudinal direction may be exposed by forming a hole opened through a part of the end surface (wall portion) of the heater holder 130 in the longitudinal direction. In addition, in Embodiments 1 to 3, the shape of the space portion in the heater holder 130 is a rectangle because it is easy to form, but it may be other polygons or a semicircle.

[0112] In Embodiments 1 to 3, an example of using an alumina substrate made of ceramic as the substrate 207 is described, but the present invention is not limited thereto. In a film heating type heating device, a high thermal conductivity ceramic such as aluminum nitride (ALN) or a metal substrate such as SUS can be used to further shorten the heating time.

[0113] In the case where a material having high thermal conductivity is used for the material of the substrate in this way, the thermal conductivity of the substrate can become higher than that of the glass material used for the heating element protective layer of the heater. In this case, a substrate having high thermal conductivity is used for the surface that contacts (slides) with the fixing film, and the resistance heating element can be disposed on the back side (heater holder side). Then, a functional effect similar to that of the above-described embodiment can be achieved by forming a space portion on the wall portion of the heater holder and exposing the end face of the heater in the longitudinal direction.

[0114] In the above description, the imaging device is a device that forms a monochrome image, but it may also be a color imaging device that prints an image superimposed with four colors (yellow, magenta, cyan, and black). In addition, a film heating type heating device is described, but the present invention is not limited thereto. For example, the color heating device includes: a device that uses solid rubber for the elastic layer of the pressure roller; and a film heating type device in which the elastic layer is provided on the fixing film to improve the image quality. For such a color heating device, it is also possible to achieve a functional effect similar to that of the above-described embodiment by forming a space portion on the wall portion of the heater holder and exposing the end face of the heater in the longitudinal direction.

[0115] Instead of the above-mentioned film heating type heating device, it is possible to use Fig.13 The external heating type heating device shown in FIG. Fig.13 In the heating device shown in FIG. 1 , the heater 113 is included in the fixing film 112, and the fixing roller 300 is press-contacted with the outer surface (peripheral surface) of the fixing film 112 to form a heating nip N2. Therefore, the heater 113 heats the surface of the fixing roller 300 through the fixing film 112. Then, in the fixing nip N1 formed by the pressure roller 301 press-contacting the fixing roller 300, the toner image T (image on the recording material) is fixed to the recording material P.

[0116] In such an external heating type heating device, if a space portion is formed on the wall portion of the heater holder and the end surface of the heater in the longitudinal direction is exposed in the longitudinal direction, the temperature rise rate in the non-paper passing area of ​​the heater when small-sized paper passes can be suppressed. Therefore, the temperature rise in the non-paper passing area of ​​the small-sized paper can be suppressed without complicating the device structure, and the decrease in productivity when printing small-sized paper can be controlled.

[0117] In the above-mentioned heating device in each embodiment, the diameter of the driving gear 131 is smaller on the R side, so that the side of the heater is exposed when the driving gear 131 does not cover the heater 113, as shown in FIG. Figure 7 However, in some cases, when the heating device unit is viewed from the side, the driving gear 131 may cover the heater 113, as shown in FIG. Fig. 14B As shown, because the diameter of the driving gear 131 is large, as shown in Fig.14A Even in this case, if the wall portion of the heater holder 130 is formed into a concave shape, as shown in FIG. Fig.14A As shown, the heater 113 is exposed from the heater holder 130, and a gap G into which air can flow can be formed between the heater 113 and the driving gear 131. Therefore, when the end surface of the heater 113 is exposed in the gap G, the air is sent to the end surface of the heater 113 through the space portion of the heater holder 130.

[0118] In this heating device, a space portion is formed on a wall portion of a heater holder, so that the end surface of the heater in the longitudinal direction is exposed in the longitudinal direction, and the "non-paper passing portion temperature rise" in the heating device can be suppressed. Therefore, it is possible to control the decrease in productivity when printing small-sized paper without complicating the device structure.

[0119] According to the present invention, it is possible to suppress a decrease in productivity when printing small-sized paper.

[0120] While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments.The scope of the following claims is to be accorded the broadest interpretation so as to encompass all modifications and equivalent structures and functions.

Claims

1. A heating device, comprising: a heating member comprising a heating element; a holding member for holding the heating member; a first rotating member having an inner space, wherein the heating member and the holding member are disposed in the inner space; a second rotating member contacting an outer peripheral surface of the first rotating member; and a frame integrally supporting the heating member, the holding member, the first rotating member, and the second rotating member, wherein The second rotating member forms a clamping portion between the first rotating member and the second rotating member, The holding member holds the heating member so that at least a portion of at least one end surface of the heating member in the longitudinal direction is exposed in the longitudinal direction, and The frame is configured such that at least the portion of the heating member exposed from the holding member also exposes the frame.

2. The heating device according to claim 1, wherein: The holding member has a recess into which the heating member is inserted, and Among the wall portions forming the recess, a wall portion facing at least one end surface of the heating member is concave so that at least the portion of one end surface of the heating member in the longitudinal direction is exposed in the longitudinal direction.

3. The heating device according to claim 1, wherein: The holding member holds the heating member so that at least one end surface of the heating member in the longitudinal direction is completely exposed in the longitudinal direction.

4. The heating device according to claim 1, wherein: The heating member includes electrodes for supplying power to the heating element, and The holding member holds the heating member so that an end surface in the longitudinal direction on a side where the electrode is provided for the heating element is not exposed.

5. The heating device according to claim 1, wherein: The holding member holds the heating member so that at least a portion of each end surface of the heating member in the longitudinal direction is exposed in the longitudinal direction.

6. The heating device according to claim 1, wherein: At least one end surface of the heating member in the longitudinal direction contacts the holding member.

7. The heating device according to claim 1, wherein: The holding member holds the heating member so that both end surfaces of the heating member in the longitudinal direction are completely exposed in the longitudinal direction.

8. The heating device according to claim 1, wherein: The holding member holds the heating member so that a portion of a ridge line formed by a surface of the heating member on a side in contact with the first rotating member and an end surface of the heating member in the longitudinal direction is exposed in the longitudinal direction.

9. The heating device according to claim 1, wherein: The holding member holds the heating member so that a portion of a ridge formed by an end surface of the heating member in the longitudinal direction and a side surface of the heating member in a transverse direction thereof on a downstream side in a conveying direction of a recording material is exposed in the longitudinal direction.

10. The heating device according to claim 1, wherein: The first rotating member is a tubular membrane, The second rotating member is a roller in contact with the outer peripheral surface of the film, The film is held between the heating member and the roller, and The image on the recording material is heated by the film in the nip formed between the film and the roller.

11. A heating device, comprising: a heating member comprising a heating element; a holding member for holding the heating member; a first rotating member having an inner space, wherein the heating member and the holding member are disposed in the inner space; a second rotating member contacting an outer peripheral surface of the first rotating member, wherein The second rotating member forms a clamping portion between the first rotating member and the second rotating member, The heating member includes electrodes for supplying power to the heating element, and The holding member holds the heating member so that an end surface in a longitudinal direction on a side where the electrode is provided for the heating element is not exposed.

12. An imaging device comprising: a forming device configured to form an image on a recording material; and The heating device according to any one of claims 1 to 11, the heating device being configured to heat the image formed on the recording material, wherein the recording material passes through the nip portion. 13 . The image forming apparatus according to claim 12 , further comprising a cooling device that cools the heating device by sending air to both edges of the heating device in the longitudinal direction.

Images