Heating device and image forming apparatus

Abstract

To normally assemble a flange member to a heating device assembled with a plane heater, a holder, and a stay.SOLUTION: A flange member 42 is provided with a cylindrical part 42a that is formed to be able to face an inner peripheral surface of a fixing belt 22, a regulating part 42b that is formed to be able to contact an end face of the fixing belt 22 and regulates the movement in a width direction of the fixing belt 22, a notch part 42c that is formed in a portion corresponding to a nip part to extend over the cylindrical part 42a and the regulating part 42b, and a bridge-like part 42b2 that is bridged to close the notch part 42c at a position outside the regulating part 42b in the width direction. A gap M between the bridge part 42b2 and a plane heater 24 is configured to be smaller than the depth N of a recess 23a in the holder 23 to which the plane heater 24 is fitted.SELECTED DRAWING: Figure 9

Description

Technical Field

[0001] The present invention relates to a heating device such as a fixing device equipped with a planar heater, and an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a multifunction machine equipped with the same.

Background Art

[0002] Conventionally, in a fixing device (heating device) in an image forming apparatus such as a copying machine or a printer, a planar heater (heating resistor) has been known as a heating means for heating a fixing belt (for example, see Patent Document 1).

[0003] Specifically, the fixing device of Patent Document 1 includes a fixing belt, a pressure roller (pressure rotating body), a planar heater (heater) that is pressure-contact with the pressure roller via the fixing belt, a holder (heater holder) that holds the planar heater, a stay that holds and reinforces the holder, a pair of flange members (support members) that respectively hold both end portions in the width direction of the stay, and a device frame (housing) that holds the flange members so as to be slidable in the pressure direction. Then, the pressure roller is rotationally driven by a driving means, and due to the frictional resistance with the pressure roller in the nip portion, the fixing belt also rotates passively (rotates along) as the pressure roller rotates. Then, the fixing belt is heated by the planar heater, and the toner image on the sheet conveyed toward the nip portion is fixed on the sheet by receiving heat and pressure in the nip portion.

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the conventional technology, when assembling a flange member by relatively moving it in the width direction with respect to a state in which a planar heater, a holder, and a stay are assembled, there are cases where a flange member in a partially deformed state is assembled, or the flange member is assembled in a state where the planar heater is not properly set in the holder. As a result, there is a possibility that the planar heater may be displaced from the nip portion and set, or the planar heater, the holder, etc. may be damaged.

[0005] The present invention has been made to solve the above-described problems, and an object thereof is to provide a heating device and an image forming apparatus that can properly assemble a flange member with respect to a state in which a planar heater, a holder, and a stay are assembled.

Means for Solving the Problems

[0006] The heating device according to the present invention includes a planar heater extending in the width direction, a belt member heated by the planar heater, a pressurizing rotating body that forms a nip portion through which a sheet is conveyed by pressing against the planar heater via the belt member, a holder that holds the planar heater over the width direction, a stay that holds the holder, a pair of flange members that respectively hold both width direction ends of the stay and can hold both width direction ends of the belt member, a housing that movably holds the pair of flange members in a direction in which the distance from the pressurizing rotating body is changed, and a biasing member that biases the pair of flange members in a direction approaching the pressurizing rotating body. At least one of the pair of flange members includes a cylindrical portion formed to face the inner peripheral surface of the belt member, a restricting portion formed to contact the end surface of the belt member and restrict the movement of the belt member in the width direction, a notch portion formed in a portion corresponding to the nip portion so as to straddle the cylindrical portion and the restricting portion, and a bridging portion bridging so as to close the notch portion at a position outside the cylindrical portion in the width direction in the restricting portion. The gap between the bridging portion and the planar heater is smaller than the depth of the recess in the holder into which the planar heater is fitted. [Effect of the Invention]

[0007] According to the present invention, it is possible to provide a heating device and an image forming apparatus that can normally assemble a flange member to a state in which a planar heater, a holder, and a stay are assembled. [Brief Description of the Drawings]

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Figure 19

Figure 20

Figure 21

Figure 22

Figure 23

Figure 24

Figure 25

Figure 26

Figure 27

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In each figure, the same or corresponding parts are denoted by the same reference numerals, and the redundant description thereof will be simplified or omitted as appropriate.

[0010] First, with reference to FIG. 1, the overall configuration and operation of the image forming apparatus 1 will be described. As shown in FIG. 1, the image forming apparatus 1 in the present embodiment is a tandem type color printer. In a bottle storage section 101 above the image forming apparatus main body 1, four toner bottles 102Y, 102M, 102C, and 102K corresponding to respective colors (yellow, magenta, cyan, black) are detachably (replaceably) installed. Below the bottle storage section 101, an intermediate transfer unit 85 is disposed. Image forming units 4Y, 4M, 4C, and 4K corresponding to respective colors (yellow, magenta, cyan, black) are arranged in parallel so as to face an intermediate transfer belt 78 of the intermediate transfer unit 85.

[0011] In each of the image forming units 4Y, 4M, 4C, and 4K, a photosensitive drum 5Y, 5M, 5C, or 5K is disposed. Further, around each of the photosensitive drums 5Y, 5M, 5C, and 5K, a charging section 75, a developing section 76, a cleaning section 77, a charge removing section, etc. are disposed. Then, on the surface of each of the photosensitive drums 5Y, 5M, 5C, and 5K, an image forming process (charging process, exposure process, developing process, transfer process, cleaning process) is performed, and an image of each color is formed on the surface of each of the photosensitive drums 5Y, 5M, 5C, and 5K.

[0012] The photosensitive drums 5Y, 5M, 5C, and 5K are rotationally driven in the clockwise direction of FIG. 1 by a motor. And at the position of the charging section 75, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K are uniformly charged (this is the charging process). Thereafter, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K reach the irradiation position of the laser beam L emitted from the exposure section 3, and an electrostatic latent image corresponding to each color is formed by exposure scanning at this position (this is the exposure process).

[0013] Thereafter, the surfaces of the photoreceptor drums 5Y, 5M, 5C, and 5K reach the position facing the developing unit 76, and at this position, the electrostatic latent image is developed to form toner images of respective colors (this is the developing process). Thereafter, the surfaces of the photoreceptor drums 5Y, 5M, 5C, and 5K reach the position facing the intermediate transfer belt 78 and the first transfer bias rollers 79Y, 79M, 79C, and 79K, and at this position, the toner images on the photoreceptor drums 5Y, 5M, 5C, and 5K are transferred onto the intermediate transfer belt 78 (this is the first transfer process). At this time, a small amount of untransferred toner remains on the surfaces of the photoreceptor drums 5Y, 5M, 5C, and 5K.

[0014] Thereafter, the surfaces of the photoreceptor drums 5Y, 5M, 5C, and 5K reach the position facing the cleaning unit 77, and at this position, the untransferred toner remaining on the photoreceptor drums 5Y, 5M, 5C, and 5K is mechanically recovered by the cleaning blade of the cleaning unit 77 (this is the cleaning process). Finally, the surfaces of the photoreceptor drums 5Y, 5M, 5C, and 5K reach the position facing the charge removing unit, and at this position, the residual potential on the photoreceptor drums 5Y, 5M, 5C, and 5K is removed. Thus, a series of image forming processes performed on the photoreceptor drums 5Y, 5M, 5C, and 5K are completed.

[0015] Thereafter, the toner images of respective colors formed on each photoreceptor drum through the developing process are transferred and overlapped onto the surface of the intermediate transfer belt 78. Thus, a color image is formed on the intermediate transfer belt 78. Here, the intermediate transfer unit 85 is composed of the intermediate transfer belt 78, four first transfer bias rollers 79Y, 79M, 79C, and 79K, a second transfer backup roller 82, a cleaning backup roller 83, a tension roller 84, an intermediate transfer cleaning unit 80, etc. The intermediate transfer belt 78 is stretched and supported by three rollers 82 to 84, and is endlessly moved in the direction of the arrow in FIG. 1 by the rotational drive of one roller 82.

[0016] The four primary transfer bias rollers 79Y, 79M, 79C, and 79K sandwich the intermediate transfer belt 78 between the photosensitive drums 5Y, 5M, 5C, and 5K, respectively, to form a primary transfer nip. A transfer bias opposite to the polarity of the toner is applied to the primary transfer bias rollers 79Y, 79M, 79C, and 79K. Then, the intermediate transfer belt 78 travels in the direction of the arrow and sequentially passes through the primary transfer nips of the respective primary transfer bias rollers 79Y, 79M, 79C, and 79K. Thus, the toner images of each color on the photosensitive drums 5Y, 5M, 5C, and 5K are primarily transferred onto the intermediate transfer belt 78 in an overlapping manner.

[0017] After that, the intermediate transfer belt 78 on which the toner images of each color are transferred in an overlapping manner reaches the position opposite to the secondary transfer roller 89. At this position, the secondary transfer backup roller 82 sandwiches the intermediate transfer belt 78 between itself and the secondary transfer roller 89 to form a secondary transfer nip. Then, the four-color toner image formed on the intermediate transfer belt 78 is transferred onto the sheet P conveyed to the position of this secondary transfer nip. At this time, untransferred toner that has not been transferred to the sheet P remains on the intermediate transfer belt 78. After that, the intermediate transfer belt 78 reaches the position of the intermediate transfer cleaning unit 80. And at this position, the untransferred toner on the intermediate transfer belt 78 is recovered. Thus, a series of transfer processes performed on the intermediate transfer belt 78 are completed.

[0018] Here, the sheet P conveyed to the position of the secondary transfer nip is conveyed from the paper feed unit 12 disposed below the apparatus main body 1 via the paper feed roller 97, the registration roller pair 98 (timing roller pair), and the like. Specifically, a plurality of sheets P such as paper are stacked and stored in the paper feed unit 12. When the paper feed roller 97 is rotationally driven in the counterclockwise direction in FIG. 1, the uppermost sheet P is fed toward the space between the rollers of the registration roller pair 98.

[0019] The sheet P conveyed to the resist roller pair 98 stops once at the position of the roller nip of the resist roller pair 98 whose rotational drive has been stopped. Then, in synchronization with the color image on the intermediate transfer belt 78, the resist roller pair 98 is rotationally driven, and the sheet P is conveyed toward the secondary transfer nip. In this way, a desired color image is transferred onto the sheet P.

[0020] Thereafter, the sheet P onto which the color image has been transferred at the position of the secondary transfer nip is conveyed to the position of the fixing device 20. And at this position, the color image transferred onto the surface is fixed onto the sheet P by the heat and pressure of the fixing belt 22 and the pressure roller 31 (fixing process). Thereafter, the sheet P passes between the rollers of the paper discharge roller pair 99 and is discharged out of the apparatus. The sheet P discharged out of the apparatus by the paper discharge roller pair 99 is sequentially stacked on the stack unit 100 as an output image. In this way, a series of image forming processes in the image forming apparatus is completed.

[0021] Next, with reference to FIGS. 2 to 8 and the like, the configuration and operation of the fixing device 20 as a heating device installed in the image forming apparatus main body 1 will be described in detail. Referring to FIGS. 2 to 5 and the like, the fixing device 20 as a heating device includes a fixing belt 22 as a belt member, a stay 30 (reinforcing member), a planar heater 24 as a heating means (heating element), a holder 23, a stay 30, a pair of flange members 42, a pressure roller 31 as a pressure rotating body, a temperature detection sensor 40 (temperature detection means), and the like. Note that the fixing device 20 can be attached to and detached from the image forming apparatus main body 1 by opening and closing the opening / closing cover 110 (see FIG. 1) of the image forming apparatus main body 1 around the hinge 110a. Also, in the present embodiment, the fixing belt 22, the planar heater 24, the holder 23, the stay 30, and the pair of flange members 42 are unitized (sub-assembled) as a fixing side unit 21 (see FIGS. 4 and the like).

[0022] Here, the fixing belt 22 (fixing rotating body) is an endless belt member that circumscribes the pressure roller 31 and rotates passively as the pressure roller 31 rotates. The fixing belt 22 is a thin and flexible endless belt that rotates (passively rotates) in the direction of the arrow in Fig. 2 (counterclockwise). The fixing belt 22 has a base material layer, an elastic layer, and a release layer sequentially laminated from the inner peripheral surface (the surface that slides against the planar heater 24), and the overall thickness is set to 1 mm or less. The base material layer of the fixing belt 22 has a layer thickness of 30 to 50 μm and is formed of a metal material such as nickel or stainless steel or a resin material such as polyimide. The elastic layer of the fixing belt 22 has a layer thickness of 100 to 300 μm and is formed of a rubber material such as silicone rubber, foamed silicone rubber, or fluororubber. By providing the elastic layer, minute irregularities on the surface of the fixing belt 22 in the nip portion are not formed, heat is uniformly transmitted to the toner image T on the sheet P, and the generation of a smooth skin image is suppressed. The release layer of the fixing belt 22 has a layer thickness of 5 to 50 μm and is formed of materials such as PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), PTFE (polytetrafluoroethylene), polyimide, polyetherimide, PES (polyethersulfone), etc. By providing the release layer, the releasability (peelability) with respect to the toner T (toner image) is ensured.

[0023] On the inner side (inner peripheral surface side) of the fixing belt 22, a planar heater 24, a holder 23, a stay 30, etc. are installed. Here, the planar heater 24 is arranged to extend in the width direction (the direction perpendicular to the plane of FIG. 2). And the planar heater 24 is pressed against the pressure roller 31 via the fixing belt 22 on the inner side (inner peripheral surface side) of the fixing belt 22 to form a nip portion (fixing nip) through which the sheet P is conveyed. That is, the planar heater 24 is installed so as to be in sliding contact with the inner peripheral surface of the fixing belt 22. And when the planar heater 24 is pressed against the pressure roller 31 via the fixing belt 22, a nip portion through which the sheet P is conveyed is formed. In this way, the planar heater 24 functions as a member (nip portion forming member) that forms the nip portion (fixing nip). Note that for the planar heater 24, in order to reduce the sliding resistance with the fixing belt 22, a sheet-like member made of a low-friction material such as PTFE can be covered on its surface or a surface layer can be provided. Furthermore, a resistor pattern 26 (see FIG. 6 etc.) is formed on the portion of the planar heater 24 that is in sliding contact with the inner peripheral surface of the fixing belt 22. And electric power is supplied from a power supply portion (not shown) to the resistor pattern 26 (heating resistor), and when the resistor pattern 26 generates heat due to its resistance, the fixing belt 22 is heated. In this way, the planar heater 24 also functions as a heating means (heating body) that heats the fixing belt 22.

[0024] In the present embodiment, the planar heater 24 is held by a holder 23 (holding member). The holder 23 has a recess 23a (see FIGS. 12 and 13 etc.) formed therein, and the planar heater 24 is fitted into the recess 23a, thereby holding the planar heater 24 over the width direction. Note that the holder 23 is held by a stay 30 in a state where the planar heater 24 is held. And the stay 30 holding the planar heater 24 and the holder 23 has both end portions in its width direction held by the housing 43 (first frame 43a) of the fixing device 20 via flange members 42 respectively (see FIG. 3 etc.).

[0025] In this way, the fixing belt 22 is directly heated by the planar heater 24 (resistor pattern 26) installed inside thereof. Then, heat is applied to the toner image T on the sheet P from the surface of the heated fixing belt 22. Here, the output control of the planar heater 24 is performed based on the detection result of the belt surface temperature by a temperature detection sensor 40 (temperature detection means) such as a thermopile or a thermistor facing the surface of the fixing belt 22. Also, by such output control of the planar heater 24, the temperature (fixing temperature) of the fixing belt 22 can be set to a desired temperature. In the present embodiment, although the temperature detection sensor 40 for directly detecting the fixing temperature of the fixing belt 22 is installed, it is also possible to configure it to indirectly detect the fixing temperature of the fixing belt 22 by providing a temperature detection sensor such as a thermostat or a thermistor for detecting the surface temperature of the planar heater 24 (see FIG. 21). And in such a case, the temperature detection sensor in contact with the planar heater 24 can also function as a safety device for preventing overheating of the planar heater 24.

[0026] Referring to FIGS. 5 and 9, the pair of flange members 42 (guide members) guide both end portions in the width direction of the fixing belt 22 from the inner peripheral surface side so that the substantially cylindrical posture of the fixing belt 22 is maintained. Specifically, the two flange members 42 are formed of a heat-resistant resin material or the like, and are slidably fitted into both end portions in the width direction of the housing 43 of the fixing device 20, respectively. The flange member 42 is provided with a cylindrical portion 42a for holding the fixing belt 22 while maintaining the substantially cylindrical posture of the fixing belt 22, a regulating portion 42b (stopper portion) for regulating the movement in the width direction of the fixing belt 22 (belt deviation), and the like. Also, in the present embodiment, as shown in FIG. 3, the fixing belt 22 (and the planar heater 24, the holder 23, the stay 30) is configured to be pressed against the pressure roller 31 by the biasing force of the compression spring 52 (biasing member) via the flange member 42. Note that the flange member 42 is arranged at both ends in the width direction within a circumferential range excluding the nip portion so as not to interfere with the formation of the nip portion by the planar heater 24. As described above, in the present embodiment, the members that contact the inner peripheral surface of the fixing belt 22 are only the flange member 42 that loosely contacts at both ends in the width direction and the planar heater 24, and there is no other member (belt guide) that contacts the inner peripheral surface to guide the rotation of the fixing belt 22.

[0027] Here, in the present embodiment, the stay 30 is installed inside the fixing belt 22 so as to contact the pressure roller 31 via the planar heater 24 (and the holder 23) and the fixing belt 22. The stay 30 reinforces the strength of the planar heater 24 (and the holder 23) that forms the nip portion, and is held by the housing 43 via the flange member 42 (see FIGS. 2, 5, 8, 12, etc.). Then, by the stay 30 contacting the pressure roller 31 via the planar heater 24 (and the holder 23) and the fixing belt 22, it is possible to prevent the problem that the planar heater 24 (and the holder 23) is greatly deformed by receiving the pressing force of the pressure roller 31 in the nip portion. In order to satisfy the above-described functions, the stay 30 is preferably formed of a metal material having high mechanical strength such as stainless steel or iron.

[0028] Note that as the material for forming the holder 23, a resin material or a metal material can be used, but it has rigidity such that it does not bend significantly even when receiving the pressing force by the pressure roller 31, and is a resin material having heat resistance and heat insulation properties (such as liquid crystal polymer (LCP), polyamideimide (PAI), polyethersulfone (PES), polyphenylene sulfide (PPS), polyether nitrile (PEN), polyether ether ketone (PEEK), etc.).) is suitable. In the present embodiment, liquid crystal polymer (LCP) is used as the material for the holder 23.

[0029] Referring to FIG. 2, the pressure roller 31 as a pressure rotating body has an elastic layer 33 provided on a core metal 32 (shaft portion), and is rotationally driven in a predetermined direction (the clockwise direction in FIG. 2) by a drive motor (not shown). The core metal 32 of the pressure roller 31 is a hollow structure formed of a metal material. The elastic layer 33 of the pressure roller 31 is formed of a material such as foamed silicone rubber, silicone rubber, or fluororubber. In addition, a thin release layer made of PFA, PTFE, or the like can be provided on the surface layer of the elastic layer 33. The pressure roller 31 is pressed against the fixing belt 22 to form a desired nip portion between the two members. Further, referring to FIG. 3, a gear 45 (see FIG. 3) that meshes with a drive gear of a drive motor (not shown) is installed on the pressure roller 31, and the pressure roller 31 is rotationally driven in the direction of the arrow (clockwise direction) in FIG. 2. In addition, both end portions in the width direction of the pressure roller 31 are rotatably supported by the housing 43 of the fixing device 20 via bearings.

[0030] Here, referring to FIGS. 3 to 5 and the like, the housing 43 (frame) of the fixing device 20 in the present embodiment is configured to be divisible into two frames (a first frame 43a and a second frame 43b). Specifically, the first frame 43a functions as a main part of the housing 43, and has a substantially U-shaped cross section formed with a bearing portion for receiving the shaft portion of the pressure roller 31 and a guide portion 43x that fits into a groove portion 42b1 formed in a flange member 42 of the fixing side unit 21. On the other hand, the second frame 43b is a lid-shaped frame that is installed (joined) so as to cover the side of the fixing side unit 21 with respect to the first frame 43a to which the pressure roller 31 and the fixing side unit 21 are assembled. When the second frame 43b is installed with respect to the first frame 43a, a compression spring 52 (see FIG. 5) as a biasing member is interposed between the flange member 42 of the fixing side unit 21. This compression spring 52 functions as a biasing member that biases the pair of flange members 42 in a direction approaching the pressure roller 31 (pressure rotating body).

[0031] Here, referring to FIG. 6 and the like, the planar heater 24 in the present embodiment is formed of a base material 25 (base portion), a resistor pattern 26 (heating resistor), a conductor pattern 27 (relay portion), a power supply electrode 28 as an electrode, and the like. The base material 25 is made of an insulating material at least on the front surface (the surface on the side facing the inner peripheral surface of the fixing belt 22 at the nip portion). In the present embodiment, as the base material 25, one entirely formed of an insulating material (aluminum nitride (AIN) in the present embodiment) is used. The resistor pattern 26 is formed on the front surface of the base material 25. Similarly, the conductor pattern 27 is also formed on the front surface of the base material 25. The resistor pattern 26 functions as a heating resistor that generates heat due to its resistance when an electric current flows through it (when energized). The resistor pattern 26 is formed by applying a paste adjusted to a desired resistance value onto the surface of the base material 25 by screen printing or the like and then firing it to form a pattern. The conductor pattern 27 is electrically connected to the resistor pattern 26 (and the power supply electrode 28), and functions as a relay portion that allows the current input from the power supply electrode 28 to flow through the resistor pattern 26. The conductor pattern 27 is formed by applying a paste made of a highly conductive material onto the surface of the base material 25 by screen printing or the like and then firing it to form a pattern. The power supply electrode 28 is electrically connected to the conductor pattern 27 and is formed so as to be connectable to a terminal 29a (contact portion 29a1) of a connector 29 (see FIG. 7) that serves as an external terminal. Therefore, even when a surface layer having insulation and low friction is formed over the entire surface of the planar heater 24, only the power supply electrode 28 is exposed so as to be able to supply power from the surface layer. The power supply electrode 28 is formed of a silver-based material such as silver (Ag) or silver palladium (AgPd) in order to reduce heat generation due to energization. In the present embodiment, the power supply electrode 28 is formed by printing on the surface of the base material 25 by screen printing and then firing.

[0032] Here, referring to FIGS. 7, 8, 12(B), etc., the connector 29 is mounted so as to sandwich the end portion (widthwise end portion) of the holder 23 in a state where the planar heater 24 is held, and is set on one end side of the fixing side unit 21 (in the state of FIG. 3) mounted on the housing 43. The connector 29 has a U-shaped cross section (a cross section perpendicular to the width direction), and a terminal 29a is installed inside thereof. When the connector 29 is mounted so as to sandwich the holder 23, the contact portion 29a of the terminal 29a is electrically connected to the power supply electrode 28 of the planar heater 24. Thereby, power is supplied from the power supply unit (not shown) of the image forming apparatus main body 1 toward the planar heater 24 (resistor pattern 26) via the harness 90, the terminal 29a, and the power supply electrode 28. Although not shown, in the present embodiment, the connector 29 and the harness 90 are configured to be held by a clamp or the like on the outer surface side of the housing 43 (second frame 43b) of the fixing device 20. And, in conjunction with the operation of attaching / detaching the fixing device 20 to / from the image forming apparatus main body 1, a second connector (not shown) connected to the harness 90 is configured to be connected to / disconnected from the main body side connector (not shown) of the image forming apparatus main body 1.

[0033] Hereinafter, the normal operation of the fixing device 20 configured as described above will be briefly described. When the power switch of the apparatus main body 1 is turned on, power is supplied to the planar heater 24, and the rotation drive of the pressure roller 31 in the direction of the arrow in FIG. 2 is started. Thereby, due to the frictional force with the pressure roller 31 in the nip portion, the fixing belt 22 also rotates in a driven manner (rotates along) in the direction of the arrow in FIG. 2. Thereafter, the sheet P is fed from the paper feeding unit 12, and an unfixed color image is carried (transferred) onto the sheet P at the position of the secondary transfer roller 89. The sheet P carrying the unfixed image T (toner image) is conveyed in the direction of arrow Y10 in FIG. 2 while being guided by the guide plate, and is fed into the nip portion of the fixing belt 22 and the pressure roller 31 in a pressure contact state. Then, the toner image T is fixed on the surface of the sheet P by the heating by the fixing belt 22 heated by the planar heater 24 and the pressing force between the planar heater 24 (and the holder 23) reinforced by the stay 30 and the pressure roller 31. After that, the sheet P sent out from the nip portion is conveyed in the direction of arrow Y11.

[0034] Hereinafter, in the fixing device 20 as a heating device in the present embodiment, the characteristic configuration and operation will be described in detail. As described above with reference to FIGS. 2 to 8 and the like, the fixing device 20 as a heating device is provided with a planar heater 24, a fixing belt 22, a pressure roller 31, a holder 23, a stay 30, a pair of flange members 42, a housing 43, a compression spring 52, and the like.

[0035] The planar heater 24 extends in the width direction (the direction perpendicular to the paper surface in FIGS. 2 and 11 and the left - right direction in FIG. 12), and is formed in a substantially rectangular parallelepiped shape. The fixing belt 22 is heated by the planar heater 24, heats the toner image, and fixes it on the surface of the sheet P. The pressure roller 31 functions as a pressure - rotating body that forms a nip portion (fixing nip) through which the sheet P is conveyed by pressing against the planar heater 24 via the fixing belt 22. The holder 23 functions as a holding member that holds the planar heater 24 over the width direction, and is formed of a resin material in the present embodiment. The stay 30 holds the holder 23 and also functions as a reinforcing member that reinforces the mechanical strength of the holder 23. In the present embodiment, the stay 30 is made of a metal material, has a U - shaped cross - section, and has protruding portions (portions that fit into the flange members 42) formed at both ends in the width direction (see FIGS. 8 and the like). The pair of flange members 42 hold both ends in the width direction of the stay 30 and are configured to be able to hold both ends in the width direction of the fixing belt 22. The housing 43 holds a pair of flange members 42 so as to be movable in a direction (the left - right direction in FIGS. 2 and 15) that changes the distance from the pressure roller 31 (pressure - rotating body). The compression spring 52 functions as a biasing member that biases a pair of flange members 42 in a direction approaching the pressure roller 31 (pressure - rotating body).

[0036] Here, referring to FIGS. 9, 10, etc., in the present embodiment, a cylindrical portion 42a, a regulating portion 42b, a notch portion 42c, etc. are formed on the flange member 42. Further, a groove portion 42b1 and a bridge - shaped portion 42b2 are provided on the regulating portion 42b. The cylindrical portion 42a of the flange member 42 is formed so as to face the inner peripheral surface of the fixing belt 22, and is for maintaining the substantially cylindrical posture of the fixing belt 22. Note that the cross - section of the cylindrical portion 42a is not a complete circular outer peripheral surface due to the notch portion 42c described later, and a part of it is missing, having an arcuate outer peripheral surface. The regulating portion 42b of the flange member 42 is formed so as to be in contact with the end surface of the fixing belt 22, and regulates the movement of the fixing belt 22 in the width direction. Therefore, the wall portion adjacent to the cylindrical portion 42a of the regulating portion 42b is formed sufficiently larger than the cylindrical portion 42a. The notch portion 42c of the flange member 42 is formed in a portion corresponding to the nip portion (fixing nip) so as to straddle the cylindrical portion 42a and the regulating portion 42b. This notch portion 42c functions as a relief portion so that the nip portion is well formed by the contact between the fixing belt 22 and the pressure roller 31.

[0037] Referring to FIGS. 9, 10, etc., the bridge - shaped portion 42b2 is bridged at a position on the outer side in the width direction of the regulating portion 42b (the side opposite to the side where the cylindrical portion 42a is formed (the right side in FIG. 10), and the side away from the fixing belt 22) so as to close the notch portion 42c. That is, the regulating portion 42b has a notch portion 42c formed in the inner portion in the width direction and has a substantially U-shaped cross section, and a bridge portion 42b2 is formed in the outer portion in the width direction and has a substantially C-shaped cross section. Note that the position in the width direction where the bridge portion 42b2 is formed is a position outside the range in the width direction where the nip portion between the fixing belt 22 and the pressure roller 31 is formed.

[0038] By forming the bridge portion 42b2 on the flange member 42 in this way, compared with the case where there is no bridge portion 42b2, deformation due to resin molding (deformation in which both tip portions of the U-shape close, refer to the flange member 142 shown in FIG. 16) is less likely to occur. Further, by forming the bridge portion 42b2, the mechanical strength of the flange member 42 can be improved compared with the case where there is no bridge portion 42b2. Therefore, when the flange member 42 is relatively moved in the width direction and assembled with respect to the state in which the planar heater 24, the holder 23, and the stay 30 are assembled (the state shown in FIG. 12(A)), as shown in FIG. 12, as shown in FIG. 16, a defect such that the flange member 142 in a partially deformed state is assembled is less likely to occur, and as shown in FIG. 15, the normal flange member 42 without deformation is assembled. Therefore, it is possible to suppress a defect in which the planar heater 24 is displaced from the nip portion and set, and the planar heater 24 does not function properly and fixing failure or the like occurs, as shown as a comparative example in FIG. 16. That is, in the present embodiment, as shown in FIG. 15, the planar heater 24 is normally set in the nip portion, and the planar heater 24 functions properly.

[0039] Note that in the present embodiment, as shown in FIG. 12, when the flange member 42 is relatively moved in the width direction and assembled with respect to the state in which the planar heater 24, the holder 23, and the stay 30 are assembled, in order to improve the workability, a taper with a taper angle of about 30 to 60° can be formed on the wall surface on the upstream side in the mounting direction (the left side in FIG. 12) of the flange member 42. In particular, since the planar heater 24 is relatively vulnerable to impact, it is preferable to set the taper of the flange member 42 described above to be larger than the thickness of the planar heater 24.

[0040] Here, as shown in FIGS. 9, 10, etc., the flange member 42 has a groove portion 42b1 formed on the surface opposite to the surface where the bridge-shaped portion 42b2 is formed in the restricting portion 42b (the outer surfaces located above and below in FIG. 10) so as to be slidably fitted to the guide portion 43x (see FIGS. 3 and 5) of the housing 43. Then, as described above with reference to FIG. 5 etc., by installing a compression spring 552 between the second frame 43b and the flange member 42, the flange member 42 moves in the pressing direction along the guide portion 43x (and the groove portion 42b1), and the fixing belt 22 is pressed against the pressing roller 31.

[0041] Here, referring to FIGS. 11(A) and 12(A), in the fixing device 20 of the present embodiment, a gap M (a gap in a direction orthogonal to the width direction and the conveyance direction) between the bridge-shaped portion 42b2 and the planar heater 24 is configured to be smaller than the depth N (heater restricting height) of the recess 23a in the holder 23 where the planar heater 24 is fitted (M < N). By configuring in this way, as shown in FIGS. 11(B) and 13, even when the flange member 42 is about to be assembled in a state where the planar heater 24 floats from the holder 23 without being normally set in the holder 23 (a state of riding up), the bridge-shaped portion 42b2 of the flange member 42 interferes with the end face of the planar heater 24. Therefore, the operator performing the assembly work can recognize that the planar heater 24 is not normally set in the holder 23. Therefore, the planar heater 24 is reset in the holder 23 normally, and then the flange member 42 is assembled normally as shown in FIG. 12.

[0042] In the present specification and the like, the "gap between the bridge-shaped portion and the planar heater" is defined as that in the state where the belt member (fixing belt 21) and the pressure rotating body (pressure roller 31) are in pressure contact to form a nip portion (pressurized state). That is, the "gap between the bridge-shaped portion and the planar heater" is measured in the state where the planar heater, the holder, and the stay are closer to the flange member side. Also, in the present specification and the like, the "depth (N) of the recess in the holder into which the planar heater is fitted" is defined as that at the position where the depth (N) is the deepest when there is variation in the depth (N). However, it is preferable that the depth (N) is measured on the flange member side rather than at the position at the center in the width direction or at a position outside (outer side in the width direction) with respect to the flange member.

[0043] Thus, in the present embodiment, since the gap M between the bridge-shaped portion 42b2 and the planar heater 24 is configured to be smaller than the depth N of the recess 23a of the holder 23, when the flange member 42 is relatively moved in the width direction and assembled with respect to the state in which the planar heater 24, the holder 23, and the stay 30 are assembled, it is possible to prevent the problem that the flange member 42 is assembled as it is in a state where the planar heater 24 is not properly set in the holder 23. Therefore, when the nip portion is formed, problems such as the planar heater 24 hitting against the pressure roller 31 or the holder 23 with a strong force and causing damage to the planar heater 24 or the holder 23 can also be prevented. Also, even in a case where some force is applied to the fixing side unit 21, such as when the pressure roller 31 is depressurized (or decompressed) with respect to the fixing belt 21 in a state where the fixing device 20 is incorporated, the bridge-shaped portion 42b2 functions to prevent the problem that the planar heater 24 drops off from the fixing side unit 21.

[0044] Note that, as shown in FIG. 14 as a comparative example, when the gap M between the bridge-shaped portion 42b2 and the planar heater 24 is configured to be larger than the depth N of the recess 23a of the holder 23 (M > N), even if the planar heater 24 is not properly set in the holder 23 and floats from the holder 23 and the flange member 42 is about to be assembled, the bridge-shaped portion 42b2 of the flange member 42 does not interfere with the end face of the planar heater 24. Therefore, the operator who performs the assembly will attach the flange member 42 as it is without realizing that the planar heater 24 is not properly set in the holder 23. And in such a case, as shown in FIG. 14(B), the connector 29 cannot be attached so as to sandwich the planar heater 24 and the holder 23, and they may collide with each other, and the planar heater 24, the holder 23, or the connector 29 may be damaged.

[0045] As described above with reference to FIG. 7 and the like, the connector 29 is provided with a terminal 29a that can contact the power supply electrode 28 as an electrode of the planar heater 24, and is attached from a predetermined attachment direction (the direction of the arrow in FIG. 9, which is a direction orthogonal to the width direction) so as to sandwich the planar heater 24 and the holder 23. Here, when viewed in the attachment direction (the direction of the arrow in FIG. 9), the planar heater 24 has a substantially rectangular cross-section and protrudes from the holder 23 by a predetermined length W (= the thickness of the planar heater 24 - the depth N of the recess 23a). Therefore, when attaching the connector 29 as described above, a problem such that the planar heater 24 is caught inside the connector 29 (the side where the terminal 29a is installed) and damaged is less likely to occur.

[0046] Also, referring to FIG. 11 and the like, in the present embodiment, the length of the flange member 42 in the direction corresponding to the conveyance direction of the sheet P (the vertical direction in FIG. 11) is set to be longer than the length of the holder 23 (particularly, the recess 23a) in the direction corresponding to the conveyance direction. Further, the flange member 42 is set such that the thickness in the direction corresponding to the pressing direction (the left - right direction in FIG. 11) where the pressing roller 31 (pressing rotating body) is in pressure contact is thicker than the thickness in the direction corresponding to the pressing direction of the holder 23 (particularly, the concave portion 23a). By configuring in this way, it becomes possible to stably hold the holder 23 holding the planar heater 24 with the flange member 42 via the stay 30.

[0047] Also, as described above with reference to FIG. 4 etc., the fixing device 20 in the present embodiment is unitized (sub - assembled) as a fixing side unit 21 for the purpose of improving the overall assembling workability, with the fixing belt 22, the planar heater 24, the holder 23, the stay 30, and a pair of flange members 42. Therefore, as described above, the effects of providing the bridge - shaped portion 42b2 on the flange member 42 or configuring such that the gap M between the bridge - shaped portion 42b2 and the planar heater 24 is smaller than the depth N of the concave portion 23a of the holder 23 will be effectively exhibited during the assembly of the fixing side unit 21.

[0048] <Modification Example 1> Also in the fixing device 20 in Modification Example 1, as shown in FIG. 12, the connector 29 is installed in the vicinity of the flange member 42. Here, as shown in FIG. 17, in the fixing device 20 in Modification Example 1, a protrusion 42x that restricts movement in the direction orthogonal to the mounting direction of the connector 29 (the direction of the white arrow in FIG. 17, i.e., the left - right direction in FIG. 17) is formed on the bridge - shaped portion 42b2 of the flange member 42. Specifically, the protrusion 42x is a boss with a hemispherical tip and is formed to stand up from the bridge - shaped portion 42b2 toward the inside (the side where the planar heater 24 is installed). By providing the protrusion 42x in this way, the positions of the planar heater 24, the holder 23, and the connector 29 in the flange member 42 are more likely to be accurately determined. Further, the protrusion 42x is formed at a position different from the portion (contact portion 29a1) where the terminal 29a contacts the power supply electrode 28 (electrode) in the mounting direction indicated by the white arrow. Thereby, when the flange member 42 is mounted as shown in FIG. 12, the power supply electrode 28 of the planar heater 24 contacts the protrusion 42x, and the problem of being damaged is reduced. Here, in the present embodiment, two protrusions 42x are formed so as to sandwich the portion (the position indicated by the dashed line) where the power supply electrode 28 and the terminal 29a contact each other in the mounting direction indicated by the white arrow. Specifically, two protrusions 42x are installed so as to sandwich the range X where the terminal 29a is installed. By configuring in this way, in the flange member 42, it becomes possible to support the connector 29 well-balanced by the two protrusions 42x. On the other hand, as shown in FIG. 18, the protrusion 42x can also be formed only on the downstream side in the mounting direction indicated by the white arrow. When configured in this way, it becomes easy to mount the connector 29 to the flange member 42, and it also becomes easy to determine the position of the connector 29 in the flange member 42. Although not shown in the drawings, in Modification 1, in the recess 23a of the holder 23, a cut (relief portion) for avoiding interference with the protrusion 42x when the flange member 42 is mounted can also be formed at the position of the wall portion at the widthwise end corresponding to the protrusion 42x.

[0049] <Modification 2> As shown in FIG. 19, in the fixing device 20 in Modification 2, a leaf spring 42z as an elastic body is provided on the flange member 42. As shown in FIGS. 19(A) to 19(C), when the flange member 42 is relatively moved and mounted with respect to the holder 23 in a state where the planar heater 24 is held, the leaf spring 42z functions as an elastic body that can urge the planar heater 24 to be fitted into the recess 23a of the holder 23, and is installed on the bridge-shaped portion 42b2. Specifically, the leaf spring 42z is formed so as to apply a force (elastic force) in the direction of the arrow in FIG. 19(B) to the planar heater 24 when it contacts the planar heater 24 in the process of mounting the flange member 42. As a result, as shown in Fig. 19(A), even when the planar heater 24 is set in a state of riding on the holder 23 (floating state), as the flange member 42 is attached, the planar heater 24 is pushed into the concave portion 23a by the leaf spring 42z and is set in a normal state. In addition, in Modification 2, it is preferable that the leaf spring 42z is provided at a position different from the portion (contact portion 29a1) where the terminal 29a and the power supply electrode 28 come into contact in the attachment direction indicated by the white arrow. Thereby, when the flange member 42 is attached as shown in Fig. 19, the problem that the power supply electrode 28 of the planar heater 24 comes into contact with the leaf spring 42z and is damaged is reduced. Also, as shown in Fig. 20, a member that functions as an elastic body in the same manner as the leaf spring 42z in Fig. 19 can be integrally formed as the elastic portion 42b20 on the bridge portion 42b2 of the flange member 42.

[0050] <Modification 3> As shown in Fig. 21(A), in the fixing device 20 in Modification 3, thermostats 49 (or thermistors) for detecting the surface temperature of the planar heater 24 are installed at intervals in the width direction. These thermostats 49 are for indirectly detecting the fixing temperature of the fixing belt 22 by detecting the surface temperature of the planar heater 24 and controlling the fixing temperature, and also function as a safety device for preventing the overheating of the planar heater 24. In addition, these thermostats 49 also function as pressing members for pressing the planar heater 24 toward the side of the pressure roller 31 (pressure rotating body). Specifically, the thermostat 49 is in contact with the surface of the planar heater 24 opposite to the surface forming the nip portion (the upper surface in Fig. 21) with a predetermined contact pressure, and is configured to bias the opposite surface. In this way, since the planar heater 24 can be pushed toward the side of the pressure roller 31, a good nip portion is formed. Note that, as shown in Fig. 21(B), it is also possible to configure such that only one thermostat 49 is installed at one end side in the width direction. In that case, it is preferable to install the connector 29 at the end on the side where the thermostat 49 is installed (the right side in Fig. 21(B)). Thereby, a force in the direction of pushing the planar heater 24 into the recess 23a of the holder 23 acts by the thermostat 49 functioning as a pressing member and the bridge-shaped portion 42b2 of the flange member 42, and the mountability of the connector 29 mounted so as to sandwich the planar heater 24 and the holder 23 is improved. Also, as shown in Fig. 21(B), when the thermostat 49 is installed only at one end side in the width direction, it is preferable to form the taper (the taper formed on the wall portion on the downstream side in the mounting direction to improve the mountability) of the flange member 42 mounted on the side where the thermostat 49 is installed to be larger than the taper of the flange member 42 mounted on the side where the thermostat 49 is not installed. This is because, due to the pressing force by the thermostat 49 functioning as a pressing member, in the planar heater 24, the side where the thermostat 49 is installed may be displaced in the direction away from the holder 23 compared to the side where it is not installed, making it difficult to mount the flange member 42.

[0051] <Modification Example 4> As shown in Fig. 22, in the fixing device 20 (heating device) in Modification Example 4, the flange member 42 is formed with a pair of opposing portions 42w that oppose each other via both end portions in the short direction of the holder 23 (both upper and lower end portions in Fig. 22) with respect to the bridge-shaped portion 42b2. That is, when the state where the holder 23 holding the planar heater 24 is mounted is viewed in a cross-section orthogonal to the width direction, in the flange member 42 in Modification Example 4, both end portions in the short direction (the upper and lower direction in Fig. 22) of the holder 23 (and the planar heater 24) are each sandwiched with a gap between the bridge portion 42b2 and the opposing portion 42w. The pair of opposing portions 43w are formed such that the space where the holder 23 is mounted is substantially convex. This pair of opposing portions 42w functions as a holder restricting portion that restricts the movement of the holder 23 (and the planar heater 24) in the short side direction. By providing the pair of opposing portions 42w, even when the planar heater 24 is not properly set on the holder 23 and floats from the holder 23 and the flange member 42 is about to be assembled, since the bridge portion 42b2 of the flange member 42 interferes with the end face of the planar heater 24, the operator performing the assembly work can recognize that the planar heater 24 is not properly set on the holder 23. In particular, as a comparative example, as in the flange member 42 shown in FIG. 23, when the opposing portion 42w that opposes only one end side in the short side direction of the holder 23 is provided and the opposing portion 42w is not provided on the other end side in the short side direction of the holder 23, even when the planar heater 24 is not properly set on the holder 23 and floats from the holder 23, the holder 23 (and the planar heater 24) can be assembled in a state where the posture is inclined and not determined. Therefore, the operator performing the assembly work cannot recognize that the planar heater 24 is not properly set on the holder 23 without the bridge portion 42b2 of the flange member 42 interfering with the end face of the planar heater 24. For this reason, it is useful to form a pair of opposing portions 42w as in the flange member 42 shown in FIG. 22. Note that the pair of opposing portions 42w are set with a gap between the opposing portion 42w and the holder 23 in consideration of the thermal expansion of the related members so that they do not contact the holder 23 even when the planar heater 24 is in a heated state (even during the operation of the fixing device 20). Therefore, during the operation of the fixing device 20 (during the fixing process), it is possible to prevent problems such as the opposing portion 42w and the holder 23 contacting and deforming.

[0052] <Modification Example 5> As shown in FIG. 24(A), in the fixing device 20 (heating device) in Modification Example 5, the planar heater 24 is held by the holder 23 via the heat dissipation member 60. The soaking member 60 is a plate-shaped member formed of a high thermal conductivity material such as aluminum, copper, silver, graphene, or graphite, and is fitted into the recess 23a of the holder 23 together with the planar heater 24. Further, the soaking member 60 is formed so as to contact substantially the entire surface of the planar heater 24. By installing the soaking member 60 in this way, temperature unevenness (heating unevenness) is less likely to occur in the planar heater 24 itself and the fixing belt 22 heated by the planar heater 24. Further, in order to further enhance the effect of preventing such temperature unevenness, as shown in Fig. 24(B), in addition to the soaking member 60 interposed between the planar heater 24 in the recess 23a of the holder 23, a second soaking member 61 made of a high thermal conductivity material similar to the soaking member 60 can be further interposed. In that case, when the resistor pattern 26 (heating resistor) in the planar heater 24 is formed by connecting divided parts in the width direction, as shown in Fig. 24(B), a plurality of second soaking members 61 can be divided and arranged in the width direction so as to straddle the joints. Note that graphene is a flaky powder, and as shown in Fig. 25, graphene has a planar hexagonal lattice structure of carbon atoms. A graphene sheet is a sheet-like graphene, usually a single layer. Further, the graphene sheet may contain impurities in a single layer of carbon or may have a fullerene structure. The fullerene structure is generally recognized as a compound formed by condensing a polycyclic body in which the same number of carbon atoms form a cage shape with 5-membered rings and 6-membered rings. For example, C60, C70, and C80 fullerenes or other closed cage structures having 3-coordinated carbon atoms. The graphene sheet is an artificial product and can be produced, for example, by chemical vapor deposition (CVD). Commercially available products can be used for the graphene sheet. The size, thickness of the graphene sheet, or the number of layers of the graphite sheet described later is measured, for example, by a transmission electron microscope (TEM). In addition, graphite with multilayered graphene has significant thermal conductivity anisotropy. As shown in FIG. 26, graphite has layers in which the condensed six-membered ring planes of carbon atoms spread out in a planar manner, and has a crystal structure in which these layers are stacked multiple times. Between the carbon atoms in this crystal structure, adjacent carbon atoms within the layer form covalent bonds, and carbon atoms between the layers form van der Waals bonds. And the covalent bond has a greater binding force compared to the van der Waals bond, and there is a large anisotropy between the in-layer bond and the inter-layer bond. That is, by forming the heat spreader 60 (or the second heat spreader 61) with graphite, the heat transfer efficiency in the width direction of the heat spreader 60 (or the second heat spreader 61) becomes larger compared to the thickness direction (the vertical direction in FIG. 24), and heat transfer to the holder 23 can be suppressed. Therefore, the temperature unevenness in the width direction of the planar heater 24 can be efficiently suppressed, and the heat flowing out to the holder 23 side can be minimized. Further, by forming the heat spreader 60 (or the second heat spreader 61) with graphite, excellent heat resistance that does not oxidize up to about 700 degrees can be provided. The physical properties and dimensions of the graphite sheet can be appropriately changed according to the functions required for the heat spreader 60 (or the second heat spreader 61). For example, high-purity graphite or single-crystal graphite can be used, or the thickness of the graphite sheet can be increased. Thereby, its thermal conductivity anisotropy can be enhanced. Further, in order to increase the speed of the fixing device 20, a graphite sheet with a small thickness may be used to reduce the heat capacity of the fixing device 20. Also, when the width of the nip portion N or the planar heater 24 is large, the width in the width direction of the heat spreader 60 (or the second heat spreader 61) may be increased accordingly. From the viewpoint of enhancing mechanical strength, the number of layers of the graphite sheet is preferably 11 or more. Also, the graphite sheet may partially include a single-layer portion and a multi-layer portion. And even in such a configured case, the flange member 42 can be normally assembled to the one in the state where the planar heater 24, the holder 23, the stay 30, and the heat spreader 60 are assembled.

[0053] <Modification Example 6> As shown in FIG. 27, in the flange member 42 of the fixing device 20 (heating device) in Modification 6, a thick portion 42a1 is provided at a portion of the cylindrical portion 42a that faces the notch portion 42c, and a stepped portion 42b3 formed in accordance with the end shape of the stay 30 is provided in the regulating portion 42b. And also in the regulating portion 42b of the flange member 42 in Modification 6, a bridge portion 42b2 is bridged so as to close the notch portion 42c at a position outside the cylindrical portion 42a in the width direction. And the gap M between the bridge portion 42b2 and the planar heater 24 is configured to be smaller than the depth N of the recess 23a in which the planar heater 24 is fitted in the holder 23. And even when such a flange member 42 is used, the flange member 42 can be normally assembled with respect to the state in which the planar heater 24, the holder 23, and the stay 30 are assembled.

[0054] As described above, the fixing device 20 (heating device) in the present embodiment includes a planar heater 24 extending in the width direction, a fixing belt 22 (belt member) heated by the planar heater 24, a pressure roller 31 (pressure rotating body) that forms a nip portion through which the sheet P is conveyed by pressing against the planar heater 24 via the fixing belt 22, a holder 23 that holds the planar heater 24 in the width direction, a stay 30 that holds the holder 23, a pair of flange members 42 that hold both end portions in the width direction of the stay 30 and can hold both end portions in the width direction of the fixing belt 22, a housing 43 that movably holds the pair of flange members 42 in a direction in which the distance from the pressure roller 31 is changed, and a compression spring 52 (biasing member) that biases the pair of flange members 42 in a direction approaching the pressure roller 31. And at least one of the pair of flange members 42 is formed with a cylindrical portion 42a that can face the inner peripheral surface of the fixing belt 22, a regulating portion 42b that is formed to be in contact with the end surface of the fixing belt 22 and regulates the movement of the fixing belt 22 in the width direction, a notch portion 42c formed in a portion corresponding to the nip portion so as to straddle the cylindrical portion 42a and the regulating portion 42b, and a bridge portion 42b2 bridging so as to close the notch portion 42c at a position outside the cylindrical portion 42a in the width direction in the regulating portion 42b. And the gap M between the bridge portion 42b2 and the planar heater 24 is configured to be smaller than the depth N of the recess 23a in which the planar heater 24 is fitted in the holder 23. Thereby, the flange member 42 can be normally assembled to the state in which the planar heater 24, the holder 23, and the stay 30 are assembled.

[0055] In the present embodiment, the present invention is applied to the fixing device 20 in which the pressure roller 31 is used as the pressure rotating body, but the present invention can also be applied to a fixing device in which a pressure belt is used as the pressure rotating body. In addition, in this embodiment, the present invention is applied to a fixing device 20 as a heating device installed in an electrophotographic image forming apparatus 1. However, the heating device to which the present invention is applied is not limited to this, and includes a drying device as a heating device installed in an inkjet image forming apparatus (a device for drying ink on a sheet coated with ink), a fixing device as a heating device installed in a laminating device (a device for thermally bonding two laminated sheets), etc. The present invention can also be applied to these. And even in such cases, the same effects as those of this embodiment can be obtained.

[0056] It should be noted that the present invention is not limited to this embodiment, and it is obvious that within the scope of the technical idea of the present invention, this embodiment can be appropriately changed in addition to what is suggested in this embodiment. Also, the number, position, shape, etc. of the above-described constituent members are not limited to this embodiment, and can be set to appropriate numbers, positions, shapes, etc. suitable for implementing the present invention.

[0057] In this specification, etc., the "width direction" is defined as the direction orthogonal to the sheet conveyance direction and the same direction as the rotation axis direction of the fixing belt or the pressure roller.

Explanation of Reference Numerals

[0058] 1 Image forming apparatus (image forming apparatus main body), 20 Fixing device (heating device), 21 Fixing side unit, 22 Fixing belt (belt member, fixing rotating body), 23 Holder (holding member), 23a Concave portion, 24 Planar heater (heating element), 26 Resistor pattern, 28 Power supply electrode (electrode), 29 Connector, 29a Terminal, 29a1 Contact portion, 30 Stay (reinforcing member), 31 Pressing roller (pressing rotating body), 42 Flange member, 42a Cylindrical portion, 42b Restricting portion, 42b1 Groove portion, 42b2 Bridge portion (bridging portion), 42b20 Elastic portion (elastic body), 42c Notch portion, 42x Protrusion portion, 42z Leaf spring (elastic body), 42w Opposing portion, 43 Housing (frame), 43a First frame, 43b Second frame, 43x Guide portion, 49 Thermostat (pressing member), 52 Compression spring (biasing member), P Sheet (recording medium).

[0059] In addition, the embodiments in the present invention can also be, for example, combinations of the following Supplementary Notes 1 to 12. (Supplementary Note 1) A planar heater extending in the width direction, A belt member heated by the planar heater, A pressing rotating body that forms a nip portion through which the sheet is conveyed by pressing against the planar heater via the belt member, A holder that holds the planar heater in the width direction, A stay that holds the holder, A pair of flange members that respectively hold both ends in the width direction of the stay and can hold both ends in the width direction of the belt member, A housing that movably holds the pair of flange members respectively in a direction in which the distance from the pressing rotating body changes, A biasing member that biases the pair of flange members respectively in a direction approaching the pressing rotating body, Comprising, At least one of the pair of flange members, A cylindrical portion formed so as to be able to face the inner peripheral surface of the belt member, A regulating portion formed so as to be able to contact the end surface of the belt member and regulating the movement of the belt member in the width direction, A notch portion formed in a portion corresponding to the nip portion so as to straddle the cylindrical portion and the regulating portion, A bridge portion bridging so as to close the notch portion at a position outside the cylindrical portion in the width direction in the regulating portion, Comprising, A heating device characterized in that a gap between the bridge portion and the planar heater is smaller than a depth of a recess in which the planar heater is fitted in the holder. (Appendix 2) The heating device according to Appendix 1, characterized in that the belt member, the planar heater, the holder, the stay, and the pair of flange members are unitized. (Appendix 3) The heating device according to Appendix 1 or Appendix 2, characterized in that a connector having a terminal capable of contacting an electrode of the planar heater is mounted from a predetermined mounting direction so as to sandwich the planar heater and the holder. (Appendix 4) The connector is installed in the vicinity of the flange member, The heating device according to Appendix 3, characterized in that a protrusion for restricting movement of the bridge portion of the flange member in a direction orthogonal to the mounting direction of the connector is formed at a position different from a portion where the terminal contacts the electrode in the mounting direction. (Appendix 5) The heating device according to Appendix 4, characterized in that two protrusions are formed so as to sandwich the contacting portion in the mounting direction. (Appendix 6) The heating device according to Appendix 4, characterized in that the protrusion is formed on the downstream side in the mounting direction. (Appendix 7) The flange member, The length in the direction corresponding to the conveyance direction of the sheet is longer than the length in the direction corresponding to the conveyance direction of the holder, The heating device according to any one of Appendices 1 to 6, characterized in that the thickness in the direction corresponding to the pressing direction in which the pressing rotating body is in pressure contact is thicker than the thickness in the direction corresponding to the pressing direction of the holder. (Appendix 8) The heating device according to any one of Appendices 1 to 7, characterized in that the flange member is provided with an elastic body that can be biased so that the planar heater is fitted into the holder when the flange member is relatively moved and attached to the holder in a state where the planar heater is held. (Appendix 9) The heating device according to any one of Appendices 1 to 8, characterized by comprising a pressing member that presses the planar heater toward the pressing rotating body. (Appendix 10) The heating device according to Appendix 9, characterized in that the pressing member is a thermistor or a thermostat that biases the surface of the planar heater opposite to the surface forming the nip portion. (Appendix 11) The heating device according to any one of Appendices 1 to 10, characterized in that the flange member is formed with a groove portion that is slidably fitted to the guide portion of the housing on the surface opposite to the surface on which the bridge portion is formed in the restricting portion. (Appendix 12) The heating device according to any one of Appendices 1 to 11, characterized in that the flange member is provided with a pair of opposing portions that oppose each other through both end portions in the short side direction of the holder with respect to the bridge portion. (Appendix 13) The heating device according to Appendix 12, characterized in that the pair of opposing portions do not contact the holder even when the planar heater is in a heated state. (Appendix 14) The belt member is a fixing belt, The heating device according to any one of Appendices 1 to 13, characterized in that it is a fixing device. (Appendix 15) An image forming apparatus, characterized by comprising the heating device according to any one of Appendices 1 to 14.

Prior Art Documents

Patent Document

[0060]

Patent Document 1

Claims

1. A planar heater extending in the width direction; a belt member heated by the sheet heater; a pressure rotating body that forms a nip portion through which a sheet is conveyed by being pressed against the sheet heater via the belt member; a holder that holds the planar heater across the width; A stay for holding the holder; a pair of flange members each capable of holding both widthwise ends of the stay and holding both widthwise ends of the belt member; a housing that holds the pair of flange members so as to be movable in a direction that changes a distance between the pair of flange members and the pressurizing rotor; a biasing member that biases each of the pair of flange members in a direction approaching the pressurizing rotor; Equipped with At least one of the pair of flange members is a cylindrical portion formed to be able to face an inner circumferential surface of the belt member; a restricting portion formed to be capable of contacting an end surface of the belt member and restricting movement of the belt member in a width direction; a notch portion formed in a portion corresponding to the nip portion so as to span the cylindrical portion and the regulating portion; a bridge portion provided at an outer position of the cylindrical portion in the width direction of the restricting portion so as to bridge the notch portion; Equipped with A heating device, characterized in that a gap between the bridge-shaped portion and the planar heater is smaller than a depth of a recess in the holder into which the planar heater fits.

2. 2. The heating device according to claim 1, wherein the belt member, the sheet heater, the holder, the stays, and the pair of flange members are unitized.

3. 3. The heating device according to claim 1, wherein a connector having terminals capable of contacting electrodes of the sheet heater is mounted in a predetermined mounting direction so as to sandwich the sheet heater and the holder.

4. The connector is disposed adjacent to the flange member, The heating device according to claim 3, characterized in that the bridge-shaped portion of the flange member has a protrusion portion that limits movement of the connector in a direction perpendicular to the mounting direction, the protrusion portion being formed at a position different from the portion where the terminal contacts the electrode in the mounting direction.

5. The heating device according to claim 4 , wherein the protrusions are formed in pairs so as to sandwich the contact portion in the mounting direction.

6. The heating device according to claim 4 , wherein the protrusion is formed on a downstream side in the mounting direction.

7. The flange member is a length in a direction corresponding to a sheet conveying direction is longer than a length of the holder in the direction corresponding to the sheet conveying direction, 3. The heating device according to claim 1, wherein a thickness of the pressure rotating body in a direction corresponding to a pressure direction in which the pressure rotating body is in pressure contact is greater than a thickness of the holder in the direction corresponding to the pressure direction.

8. The heating device according to claim 1 or claim 2, characterized in that the flange member is provided with an elastic body that can be biased so that the planar heater fits into the holder when the flange member is moved relative to the holder in a state in which the planar heater is held and attached.

9. 3. The heating device according to claim 1, further comprising a pressing member for pressing the planar heater against the pressure rotating body.

10. 10. The heating device according to claim 9, wherein the pressing member is a thermistor or a thermostat that presses a surface of the planar heater opposite to a surface that forms the nip portion.

11. The heating device according to claim 1 or claim 2, characterized in that the flange member has a groove portion formed on a surface opposite to the surface on which the bridge-shaped portion is formed in the regulating portion, the groove portion being slidably fitted into the guide portion of the housing.

12. 3. The heating device according to claim 1, wherein the flange member has a pair of opposing portions that face the bridge portion across both ends of the holder in the lateral direction.

13. The heating device according to claim 12 , wherein the pair of opposing portions do not come into contact with the holder even when the sheet heater is in a heated state.

14. The belt member is a fixing belt, 3. The heating device according to claim 1, wherein the heating device is a fixing device.

15. 3. An image forming apparatus comprising the heating device according to claim 1.

Images