Fixing device

Abstract

To stabilize support of heating means for a heating roller.SOLUTION: A fixing device comprises: a frame body 32; a heating roller 307 that is rotatably supported by the frame body 32; a halogen heater 306 that is provided inside the heating roller 307 and along a rotation axis direction of the heating roller 307, and heats the heating roller 307 from an inner peripheral side; a first holding part 33 that is supported on the frame body 32, and holds an end on one side in the rotation axis direction of the halogen heater 306; and a second holding part that is supported on the frame body 32, and holds an end on the other side in the rotation axis direction of the halogen heater 306. The first holding part 33 has a leaf spring 35 that urges to have a component of force in a direction toward the second holding part with respect to the rotation axis direction, and a substrate 34 that regulates the movement of the halogen heater 306 in an intersecting direction intersecting the rotation axis direction and has a higher rigidity than that of the leaf spring 35.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a fixing device for fixing a toner image formed on a recording material to the recording material.

Background Art

[0002] In image forming apparatuses such as electrophotographic apparatuses and electrostatic recording apparatuses, an unfixed toner image is formed on a sheet-like recording material, and the toner image is heated and pressurized by a fixing device to be fixed on the recording material. A fixing device using a halogen heater as a heating means is known (see Patent Document 1). In this fixing device, a halogen heater is provided so as to face the inner peripheral surface of the heating roller, and by energizing this, the heat generated from the halogen heater is transmitted to the heating belt via the heating roller. Then, while sandwiching and conveying the recording material carrying the unfixed toner image at the fixing nip portion which is the contact portion between the heating belt and the pressure rotating body, the toner image is fixed to the recording material with heat and pressure.

[0003] In this fixing device, as a support structure of the halogen heater, it has protruding portions protruding in the longitudinal direction at both ends in the longitudinal direction of the halogen heater, and through holes formed on a support member fixed to the frame. Then, the protruding portions at both ends of the halogen heater are respectively engaged with the through holes of the support member, whereby the halogen heater is fixed and supported by the support member. Here, the halogen heater may generate thermal expansion during use. If both ends of the halogen heater are fixed in the longitudinal direction by the support member, when it thermally expands, it will press the support member. For this reason, the protruding portion is supported by the through hole so as to be movable when a force equal to or greater than the threshold value is applied in the longitudinal direction, and when the halogen heater thermally expands, the protruding portion moves with respect to the through hole to absorb the displacement due to thermal expansion. That is, a halogen heater is provided so as to face the inner peripheral surface of the heating roller, and both ends of the halogen heater in the longitudinal direction are supported by a pair of support members, and the support member is fixed to the frame of the fixing device.

Prior Art Documents

Patent Documents

[0004] [Patent Document 1] Japanese Patent Publication No. 2021-189449 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, in the fixing device described in Patent Document 1 above, the support members at both ends of the halogen heater are both made of rigid (inelastic) materials. Therefore, due to the difference in the amount of thermal expansion between the fixing device frame and the halogen heater, the longitudinal positional relationship between the halogen heater and the support members shifts when heated, which can lead to unstable support and fluctuations in the heat distribution on the heating roller.

[0006] The present invention aims to provide a fixing device that can stabilize the support of a heating means to a heating roller. [Means for solving the problem]

[0007] The fixing apparatus of the present invention is a fixing apparatus for fixing a toner image formed on a recording material to the recording material, comprising: a support; a heating roller rotatably supported by the support; a heating means provided inside the heating roller along the rotation axis direction of the heating roller and heating the heating roller from the inner circumference side; and a support provided by the support, with one end of the heating means in the rotation axis direction. The heating means is supported so as to be movable in the direction of the rotation axis, and a restricting portion is provided to restrict the movement of the heating means in an intersecting direction that intersects the direction of the rotation axis. 1 Support part The other end of the heating means in the direction of the rotation axis is supported by the support and the other end of the heating means in the direction of the rotation axis. While supporting the heating means so as to be movable in the direction of the rotation axis, the movement of the heating means in the direction intersecting the direction of the rotation axis is restricted. The second Support part and, A biasing member that biases one end of the heating means in the direction of the rotation axis toward the second support member, Equipped with In a fixing device , The heating means comprises a plurality of heaters and a holding member that integrally holds the plurality of heaters, and the biasing unit is configured to bias the holding member toward the second support unit. It is characterized by the following: [Effects of the Invention]

[0008] According to the present invention, the support of the heating means for the heating roller can be stabilized. [Brief explanation of the drawing]

[0009] [Figure 1] A schematic cross-sectional view of the image forming apparatus according to an embodiment. [Figure 2] (a) A schematic cross-sectional view of the fixing device according to the embodiment, and (b) A schematic diagram showing an enlarged view of part A in (a). [Figure 3] A cross-sectional view showing one end of a halogen heater according to an embodiment. [Figure 4] A perspective view showing one end of a halogen heater according to an embodiment. [Figure 5] A cross-sectional view showing the other end of the halogen heater according to the embodiment. [Figure 6] A cross-sectional view showing one end of a halogen heater according to a comparative example. [Figure 7] A perspective view showing one end of a halogen heater according to a comparative example. [Modes for carrying out the invention]

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to Figures 1 to 5. First, the schematic configuration of the image forming apparatus of this embodiment will be described using Figure 1.

[0011] [Image forming apparatus] The image forming apparatus 1 is an electrophotographic full-color printer having four image forming units Pa, Pb, Pc, and Pd, corresponding to four colors: yellow, magenta, cyan, and black. In this embodiment, the image forming units Pa, Pb, Pc, and Pd are arranged in a tandem configuration along the rotation direction of the intermediate transfer belt 204, which will be described later. The image forming apparatus 1 forms a toner image (image) on a recording material in response to an image reading unit (document reader) 2 connected to the image forming apparatus body 3 or an image signal from a host device such as a personal computer that is communicatively connected to the image forming apparatus body 3. Examples of recording materials include paper, plastic film, and sheet materials such as cloth.

[0012] The image forming apparatus 1 comprises an image reading unit 2 and an image forming apparatus body 3. The image reading unit 2 reads a document placed on the document glass 21. Light emitted from a light source 22 is reflected by the document and formed as an image on a CCD sensor 24 via an optical system component 23 such as a lens. By scanning in the direction of the arrow, this optical system unit converts the document into a series of electrical signal data for each line. The image signal obtained by the CCD sensor 24 is sent to the image forming apparatus body 3, where the control unit 30 performs image processing according to each image forming unit, which will be described later. The control unit 30 also receives external input as an image signal from an external host device such as a print server.

[0013] The main body of the image forming apparatus 3 is equipped with multiple image forming units Pa, Pb, Pc, and Pd, and each image forming unit performs image formation based on the image signal described above. That is, the image signal is converted into a laser beam controlled by PWM (pulse width modulation) by the control unit 30. The polygon scanner 31, which acts as an exposure device, scans the laser beam according to the image signal. The laser beam is then irradiated onto the photosensitive drums 200a to 200d, which serve as image carriers for each image forming unit Pa, Pb, Pc, and Pd.

[0014] Pa is the image forming unit for yellow (Y), Pb is for magenta (M), Pc is for cyan (C), and Pd is for black (Bk), each forming an image of the corresponding color. Since the image forming units Pa, Pb, Pc, and Pd are substantially the same, the details of the Y image forming unit Pa will be explained below, and the explanations of the other image forming units will be omitted. In the image forming unit Pa, a toner image is formed on the surface of the photosensitive drum 200a based on the image signal, as described below.

[0015] The charging roller 201a as a primary charger charges the surface of the photosensitive drum 200a to a predetermined potential to prepare for electrostatic latent image formation. An electrostatic latent image is formed on the surface of the photosensitive drum 200a charged to a predetermined potential by the laser beam from the polygon scanner 31. The developing unit 202a develops the electrostatic latent image on the photosensitive drum 200a to form a toner image. The primary transfer roller 203a discharges from the back of the intermediate transfer belt 204 and applies a primary transfer bias of the opposite polarity to the toner, and transfers the toner image on the photosensitive drum 200a onto the intermediate transfer belt 204. The photosensitive drum 200a after transfer is cleaned on its surface by the cleaner 207a.

[0016] Also, the toner image on the intermediate transfer belt 204 is conveyed to the next image forming unit, and in the order of Y, M, C, Bk, the toner images of each color formed in each image forming unit are sequentially transferred, and a four-color image is formed on its surface. Then, the toner image that has passed through the Bk image forming unit Pd at the most downstream in the rotation direction of the intermediate transfer belt 204 is conveyed to the secondary transfer unit composed of the secondary transfer roller pair 205 and 206. Then, in the secondary transfer unit, a secondary transfer electric field of the opposite polarity to the toner image on the intermediate transfer belt 204 is applied, and secondary transfer is performed onto the recording material.

[0017] The recording material is accommodated in the cassette 9, and the recording material fed from the cassette 9 is conveyed to the registration unit 208 composed of, for example, a pair of registration rollers and waits in the registration unit 208. Then, the timing of the registration unit 208 is controlled to align the position of the toner image on the intermediate transfer belt 204 with the paper, and the recording material is conveyed to the secondary transfer unit.

[0018] The recording material onto which the toner image has been transferred in the secondary transfer unit is transported to the fixing unit 8, where it is heated and pressurized to fix the toner image onto the recording material. The recording material that has passed through the fixing unit 8 is discharged to the discharge tray 7. When image formation is performed on both sides of the recording material, once the transfer and fixing of the toner image to the first side (front) of the recording material is complete, the front and back sides of the recording material are reversed via the reversal transport unit 10, and the toner image is transferred and fixed to the second side (back) of the recording material, which is then loaded onto the discharge tray 7.

[0019] The control unit 30 controls the entire image forming apparatus 1 as described above. The control unit 30 can also perform various settings based on input from the operation unit 4 of the image forming apparatus 1. This control unit 30 includes a CPU (Central Processing Unit), ROM (Read Only Memory), and RAM (Random Access Memory). The CPU controls each part while reading programs corresponding to control procedures stored in the ROM. The RAM stores working data and input data, and the CPU controls the apparatus by referring to the data stored in the RAM based on the aforementioned programs.

[0020] [Fusing device] Next, the configuration of the fixing device 8 in this embodiment will be described using Figures 2(a) and 2(b). In this embodiment, a belt heating type fixing device using an endless belt is employed. In Figure 2(a), the X direction is the transport direction of the recording material (not shown in the figure), the Y direction is the width direction of the recording material that intersects (orthogonal in this embodiment) the transport direction of the recording material, and the Z direction is the pressurizing direction in which the recording material is pressurized at the fixing nip section N. In this embodiment, the X, Y, and Z directions are all orthogonal to each other.

[0021] The fixing device 8 includes a fixing belt 301, a stay 302, a pad 303 (pressure pad), a sliding member 304, a pressure roller 305, a heating roller 307, a thermistor 308, and the like. The fixing belt 301 is an endless, rotatable heating rotating body. The pressure roller 305, as a nip-forming member, is a pressure rotating body that contacts the outer circumferential surface of the fixing belt 301 and forms a fixing nip portion N that grips and conveys the recording material between itself and the fixing belt 301. That is, the pressure roller 305 is an example of an opposing member that grips the fixing belt 301 between itself and the sliding member 304 and forms a fixing nip portion N that grips and conveys the recording material between itself and the fixing belt 301.

[0022] The sliding member 304 slides against the inner circumferential surface of the fixing belt 301 at the fixing nip portion N. The pad 303, acting as a backup member, is positioned inside the fixing belt 301 so as to sandwich the sliding member 304 and the fixing belt 301 between itself and the pressure roller 305, thereby backing up the sliding member 304. The sliding member 304 is positioned so as to cover the outer circumferential surface of the pad 303 on the fixing belt 301 side. The stay 302 is positioned inside the fixing belt 301, sandwiching the pad 303 and on the opposite side of the fixing nip portion N, to support the pad 303. The heating roller 307 is positioned inside the fixing belt 301 so as to tension the fixing belt 301 and heats the fixing belt 301. The thermistor 308, acting as a temperature sensing member, detects the temperature of the fixing belt 301. Each component will be described in detail below.

[0023] The fixing belt 301 has thermal conductivity and heat resistance, and is a thin-walled cylindrical shape. The fixing belt 301 is an example of an endless heating belt stretched on a heating roller 307. In this embodiment, as shown in Figure 2(b), the fixing belt 301 has a three-layer structure with a base layer 301a, an elastic layer 301b on the outer circumference of the base layer 301a, and a release layer 301c on the outer circumference of the release layer. The base layer 301a is, for example, 80 μm thick and made of polyimide resin (PI). The elastic layer 301b is, for example, 300 μm thick and made of silicone rubber. The release layer 301c is, for example, 30 μm thick and made of PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin) as a fluororesin. The fixing belt 301 is stretched by a pad 303 and a heating roller 307. The outer diameter of the fixing belt 301 is 150 mm in this embodiment.

[0024] The pad 303 is positioned on the inside of the fixing belt 301, facing the pressure roller 305 with the fixing belt 301 in between, and forms a fixing nip portion N that grips and conveys the recording material between the fixing belt 301 and the pressure roller 305. In other words, the pad 303 is an example of a backup member provided on the inner circumference side of the fixing belt 301 and tensioning the fixing belt 301 together with the heating roller 307. In this embodiment, the pad 303 is a roughly plate-shaped member that is long along the width direction of the fixing belt 301 (the longitudinal direction intersecting the rotation direction of the fixing belt 301, and the rotation axis direction of the heating roller 307). The fixing nip portion N is formed when the pad 303 is pressed against the pressure roller 305 with the fixing belt 301 in between. The material of the pad 303 is LCP (liquid crystal polymer) resin. A sliding member 304 is interposed between the pad 303 and the fixing belt 301.

[0025] The pad 303 is supported by a stay 302, which acts as a support member positioned inside the fixing belt 301. That is, the stay 302 is positioned on the opposite side of the pad 303 from the pressure roller 305 and supports the pad 303. Such a stay 302 is a rigid reinforcing member that is long along the longitudinal direction of the fixing belt 301, and it contacts the pad 303 to back it up. In other words, when the pad 303 is pressed by the pressure roller 305, the stay 302 provides strength to the pad 303 and ensures the applied pressure at the fixing nip portion N.

[0026] The stay 302 is made of metal such as stainless steel, and its cross-section (transverse plane) perpendicular to the longitudinal direction of the stay 302, which intersects with the rotational direction of the anchoring belt 301, is approximately rectangular. For example, the stay 302 is made of 3mm thick extruded SUS304 (stainless steel), and its strength is ensured by forming the cross-section into a roughly square hollow shape. The stay 302 may also be formed into a roughly rectangular cross-section by combining multiple sheet metal pieces and fixing them to each other by welding or other means. Furthermore, the material of the stay 302 is not limited to stainless steel as long as strength can be ensured.

[0027] The heating roller 307 is positioned inside the fixing belt 301, rotatably supported by a support, and tensions the fixing belt 301 together with the pad 303. The heating roller 307 is formed in a cylindrical shape from a metal such as aluminum or stainless steel, and a halogen heater 306 is disposed inside it as a heat source for heating the fixing belt 301. The heating roller 307 is then heated to a predetermined temperature by the halogen heater 306.

[0028] The heating roller 307 has a pivot point at one end or near the center in the longitudinal direction, and rotates relative to the fixing belt 301 to generate a tension difference in the front and rear directions, thereby controlling the position of the fixing belt 301 in the main scanning direction, and also functions as a steering roller. Furthermore, the heating roller 307 is biased by a spring supported by a frame (not shown), and also functions as a tension roller that applies a predetermined tension to the fixing belt 301.

[0029] In this embodiment, the heating roller 307 is formed from, for example, a stainless steel pipe with a thickness of 1 mm. The halogen heater 306 is provided inside the heating roller 307 along the rotation axis direction of the heating roller 307 and is an example of a heating means that heats the heating roller 307 from the inner circumference side. One halogen heater 306 may be used, but it is desirable to have multiple halogen heaters in consideration of controlling the temperature distribution in the longitudinal direction (rotation axis direction) of the heating roller 307. Multiple halogen heaters 306 have different light distributions in the longitudinal direction, and the lighting ratio is controlled according to the size of the recording material. In this embodiment, six halogen heaters 306 are arranged (see Figure 4). The halogen heater 306 consists of multiple halogen lamps (six in this embodiment) and a pair of holding members that hold their insulators together at each end, and is unitized as a heating means. This halogen heater unit will be simply referred to as halogen heater 306 below. The heating means is not limited to a halogen heater; it may also be other heaters capable of heating the heating roller 307, such as a carbon heater.

[0030] The fixing belt 301 is heated by a heating roller 307 heated by a halogen heater 306, and controlled to a predetermined target temperature according to the type of recording material based on temperature detection by a thermistor 308. The thermistor 308 is positioned opposite the outer circumferential surface of the fixing belt 301 near the center, where all sizes of recording materials that can be fixed by the fixing device 8 pass, in the width direction of the fixing belt 301. The thermistor 308 detects the temperature of the fixing belt 301, and the control unit 30 controls the power supplied to the halogen heater 306 so that the temperature detected by the thermistor 308 becomes the target temperature. The thermistor 308 may be a non-contact type sensor positioned close to the outer circumferential surface of the fixing belt 301, or a contact type sensor positioned in contact with the outer circumferential surface of the fixing belt 301.

[0031] The pressure roller 305 is a rotating drive body that rotates in contact with the outer surface of the fixing belt 301, thereby providing driving force to the fixing belt 301. In this embodiment, the heating roller 307 is also rotationally driven by a drive source (e.g., a drive motor), providing driving force to the fixing belt 301. However, the provision of driving force to the heating roller 307 may be omitted. The pressure roller 305 is a roller with a core metal (shaft) 305c, an elastic layer 305b formed on the outer circumference of the core metal 305c, and a release layer 305a formed on the outer circumference of the release layer. For example, the core metal 305c is made of stainless steel with a diameter of 72 mm. For example, the elastic layer 305b is made of conductive silicone rubber with a thickness of 8 mm. For example, the release layer 305a is made of PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin) as a fluororesin with a thickness of 100 μm. The pressure roller 305 is rotatably supported by the frame (not shown) of the fixing device 8, and a gear is fixed to one end of it. The gear is connected to a drive source (e.g., a drive motor, not shown) and rotated.

[0032] The fixing device 8 grips the recording material carrying the toner image in the fixing nip section N formed between the fixing belt 301 and the pressure roller 305, and heats the toner image while transporting it. In this way, the fixing device 8 fixes the toner image to the recording material while gripping and transporting it. Therefore, it is necessary to balance the function of applying heat and pressure with the function of transporting the recording material. The pressure roller 305 is pressed against the sliding member 304 via the fixing belt 301 by a drive source (not shown). In this embodiment, the applied pressure (NF) in the fixing nip section N during image formation is 1600N, and the width of the fixing nip section N in the X direction (direction of transport of the recording material) is set to 24.5 mm, and the width in the Y direction (width direction of the recording material) is set to 326 mm.

[0033] [Comparative example halogen heater support structure] Here, the support structure for the halogen heater 306 will be explained using the comparative examples in Figures 6 and 7. Let's consider the case where the support members at both ends of the halogen heater 306 are formed from rigid bodies, as in the fixing device described in Patent Document 1. In this case, when heated, the longitudinal positional relationship between the halogen heater 306 and the support members will shift, making the support unstable and potentially causing fluctuations in the heat distribution to the heating roller 307. To suppress this, Figures 6 and 7 show a comparative example of a configuration in which one support member is made of an elastic member such as a leaf spring and the other is made of an inelastic member, and the halogen heater 306 is biased from one side to the other by the elastic member to eliminate play. With this configuration, it is possible to maintain a stable longitudinal positional relationship between the halogen heater 306 and the support members both at room temperature and when heated.

[0034] However, when the support member is formed from a leaf spring, there is a challenge in accurately positioning it within the cross-section of the halogen heater 306. This will be explained using Figures 6 and 7. Figure 6 is a schematic diagram showing a configuration in which one side of the insulator at the end of the halogen heater 306 is supported by a leaf spring support member. Figure 7 is a perspective view showing the leaf spring support member attached to the halogen heater 306.

[0035] The halogen heater 306 is positioned facing the inner circumferential surface of the heating roller 307, and its insulator is supported by a first retaining part 133. A leaf spring 135 is provided on the first retaining part 133, and an engagement hole 137 of approximately the same size as the protrusion 136 of the heater insulator is made in the leaf spring 135, into which the protrusion 136 is inserted. The halogen heater 306 is fixed in place when the stepped portion 136a of the protrusion 136 is pressed against the edge of the engagement hole 137. The first retaining part 133 is attached to the frame 32 to determine the position of the halogen heater 306 relative to the frame 32. At this time, the leaf spring 135 biases the halogen heater 306 toward the other end, allowing the position of the halogen heater 306 in the longitudinal direction to be stably determined.

[0036] However, since the leaf spring 135 is fixed in a deformed state (solid line in Figure 6) rather than its natural state (dashed line in Figure 6), the position of the engagement hole 137 within the cross-section also changes from its natural state. As a result, a large clearance is required between the inner surface of the heating roller 307 and the halogen heater 306, taking into account the effect of deflection, which may lead to an increase in the size of the heating roller 307 and the fixing device 8 having it. Therefore, in this embodiment, the longitudinal positional relationship between the halogen heater 306 and the support member is stably supported both at room temperature and in the heated state, while accurately positioning the halogen heater 306 within the cross-section, thereby suppressing an increase in the size of the device.

[0037] [Halogen heater support structure of this embodiment] Next, the support structure of the halogen heater 306 in this embodiment will be described using Figures 3 to 5. Figure 3 is a schematic diagram showing the configuration for supporting one end of the halogen heater 306. Figure 4 is a perspective view showing the state in which the support member is attached to the halogen heater 306. Figure 5 is a schematic diagram showing the other end of the halogen heater 306. In this embodiment, one end is denoted as the positive side of the width direction Y, and the other end is denoted as the negative side of the width direction Y. Note that the width direction Y is an example of the rotation axis direction of the heating roller 307, and the conveying direction X and pressurizing direction Z are examples of intersecting directions that intersect the width direction Y.

[0038] Figures 4 and 4 5 As shown, a frame 32, which is an example of a support, is positioned at both ends of the heating roller 307 in the width direction Y and is fixed to a frame (not shown) of the fixing device 8. As shown in Figure 4, the frame 32 at one end in the width direction Y is provided with a first holding part 33 that is supported by the frame 32 and holds one end of the halogen heater 306 in the width direction Y. 5 As shown, the frame 32 at the other end in the width direction Y is provided with a second holding portion 43 that is supported by the frame 32 and holds the other end of the halogen heater 306 in the width direction Y.

[0039] As shown in Figures 4 and 5, the first retaining part 33 has a base body 34 and a leaf spring 35 attached to the base body 34. The base body 34 is a steel plate with a thickness of about 1 mm and has through holes for positioning relative to the frame body 32 and positioning bosses and burring shapes for attaching the leaf spring 35. The leaf spring 35 is a stainless steel leaf spring with a thickness of about 0.4 mm and has through holes for attachment to the base body 34. The leaf spring 35 has a fixed end 35a fixed to the base body 34 and a biasing end 35b. The base body 34 and the leaf spring 35 are made into a single component by crimping the fixed end 35a of the leaf spring 35 to the base body 34 using a burring process. Furthermore, the base body 34 has higher rigidity than the leaf spring 35.

[0040] The halogen heater 306 has a projection 36 at one end that protrudes in the width direction Y. The base body 34 has an engagement hole 37 formed at a position corresponding to the projection 36 of the halogen heater 306, with an inner diameter approximately the same as the outer diameter of the projection 36, into which the projection 36 is inserted. By engaging with the engagement hole 37, the projection 36 is movable in the width direction Y, but its movement in the transport direction X and the pressurizing direction Z is restricted. In other words, the engagement hole 37 is an example of a restricting part that restricts the movement of the halogen heater 306 in the transport direction X and the pressurizing direction Z, and because it is formed in the base body 34, it has higher rigidity than the leaf spring 35.

[0041] In this embodiment, multiple protrusions 36 are provided, for example, two or more. Multiple engagement holes 37 are also provided to engage with each of the protrusions 36. This allows the rotation of the halogen heater 306, positioned in the transport direction X and the pressurizing direction Z, to be suppressed by the protrusions 36 and engagement holes 37. Note that the number of protrusions 36 and engagement holes 37 may be three or more.

[0042] The biasing end 35b of the leaf spring 35 is positioned to overlap with the engagement hole 37 when viewed from the width direction Y. The biasing end 35b is positioned to contact the tip of the projection 36 while bending, and the reaction force of the deformation of the leaf spring 35 continuously biases the projection 36 to the negative side in the width direction Y. That is, the biasing end 35b biases the tip of the projection 36 engaged with the engagement hole 37 toward the other end.

[0043] In this embodiment, the biasing end 35b biases the protruding portion 36 in a direction along the width direction Y. However, it is not limited to biasing strictly in the width direction Y; it is sufficient to bias it in such a way that it has a component force toward the second holding portion 43 with respect to the width direction Y. Therefore, even if the biasing end 35b biases the protruding portion 36 at an angle to the width direction Y, it is sufficient that it has a component force toward the second holding portion 43 with respect to the width direction Y.

[0044] On the other hand, as shown in Figure 5, the second holding portion 43 has a base body 44 and a restricting portion 45 formed on the base body 44. The restricting portion 45 engages with the protruding portion 46 of the halogen heater 306 and restricts the movement of the halogen heater 306 in the transport direction X and pressurizing direction Z, and in the direction toward the first holding portion 33 (i.e., the positive side of the width direction Y).

[0045] At one end of the halogen heater 306, a leaf spring 35 presses the protruding portion 36 of the halogen heater 306 against the negative side in the width direction Y, while at the other end, the protruding portion 46 of the halogen heater 306 is positioned by restricting its movement with a restricting portion 45. As a result, the halogen heater 306 is positioned in the transport direction X and the pressurizing direction Z, and is also positioned in the width direction Y by abutting against the restricting portion 45 located at the other end.

[0046] As described above, according to the fixing device 8 of this embodiment, the leaf spring 35 is biased to have a component force in the direction toward the second holding part 43 with respect to the width direction Y. Furthermore, the base body 34 has higher rigidity than the leaf spring 35, and the engagement hole 37 restricts the movement of the halogen heater 306 in the transport direction X and the pressurizing direction Z. Therefore, even if the halogen heater 306 expands in the width direction Y due to heating, the deformation of the leaf spring 35 is absorbed, and fluctuations in the position of the halogen heater 306 can be suppressed, thereby suppressing fluctuations in the heat distribution to the heating roller 307. Moreover, since the movement of the halogen heater 306 in the transport direction X and the pressurizing direction Z is restricted, it is possible to suppress the size increase of the fixing device 8.

[0047] According to this embodiment, in the mounted state, the position of the halogen heater 306 within the cross-section is determined by the engagement hole 37 provided in the base 34. Therefore, since the positioning of the halogen heater 306 within the cross-section depends only on the rigid members, the position can be determined with high precision. Furthermore, the position of the halogen heater 306 in the longitudinal direction is determined by the biasing end 35b of the leaf spring 35, which causes it to be pushed to the other side with play. Therefore, even if a difference in the amount of thermal expansion occurs between the frame 32 and the halogen heater 306 when heated, the halogen heater 306 can be stably supported without causing a longitudinal displacement.

[0048] Furthermore, according to the fixing device 8 of this embodiment, the restricting portion 45 of the second holding portion 43 provided at the other end restricts the movement of the halogen heater 306 in the transport direction X and pressurizing direction Z, and in the direction toward the first holding portion 33. That is, since the halogen heater 306, which is biased from one end, can be positioned in the longitudinal direction, the positioning of the halogen heater 306 in the width direction Y can be made with high precision, and fluctuations in the heat distribution of the heating roller can be made less likely.

[0049] In this embodiment, the fixing device 8 has been described in which a leaf spring 35 is used as the biasing part, but it is not limited to this. For example, a compression coil spring or a torsion coil spring may be used, and the seating surface or wire portion may be used as the biasing part and brought into contact with the halogen heater 306. Alternatively, it is not limited to a metal elastic member, but a heat-resistant rubber member such as fluororubber may be used.

[0050] Furthermore, in the fixing device 8 of this embodiment, the second holding part 43 provided at the other end does not have the function of biasing in the width direction Y, but this is not limited to this. For example, a base and a biasing spring may be provided in the same way as the first holding part 33, so that the halogen heater 306 is pushed back by the biasing force. In this case, it is desirable to set a clear difference between the biasing force applied from one end and the biasing force applied from the other end so that the position of the halogen heater 306 in the longitudinal direction is kept stable. [Explanation of Symbols]

[0051] 8... Fixing device, 32... Frame (support), 33... First holding part, 34... Base, 35... Leaf spring (biasing part), 36... Protrusion, 37... Engagement hole (regulating part), 43... Second holding part, 301... Fixing belt (heating belt), 303... Pad (backup member), 305... Pressure roller (opposing member), 306... Halogen heater (heating means), 307... Heating roller, N... Fixing nip part, Y... Width direction (direction of rotation axis)

Claims

1. A fixing device for fixing a toner image formed on a recording material to the recording material, Support and A heating roller rotatably supported by the aforementioned support, A heating means is provided inside the heating roller along the rotation axis direction of the heating roller and heats the heating roller from the inner circumference side, A first support portion is provided, which is supported by the support body and supports one end of the heating means in the direction of the rotation axis so as to be movable in the direction of the rotation axis, while restricting the movement of the heating means in a direction intersecting the direction of the rotation axis, A second support portion is supported by the aforementioned support body, and while supporting the other end of the heating means in the direction of the rotation axis so as to be movable in the direction of the rotation axis, it restricts the movement of the heating means in a direction intersecting the direction of the rotation axis, A fixing device comprising a biasing part that biases one end of the heating means in the direction of the rotation axis toward the second support part, The heating means comprises a plurality of heaters and a holding member that integrally holds the plurality of heaters. The biasing portion is configured to bias the holding member toward the second support portion. A fixing device characterized by the following features.

2. The heating means has a protruding portion at one end that protrudes in the direction of the rotation axis, The first support portion has a base on which the biasing portion is provided, The restricting portion is formed in the base body and consists of an engagement hole into which the protrusion is engaged so as to be movable in the direction of the rotation axis and so as to restrict its movement in the intersecting direction. The fixing device according to feature 1.

3. The biasing portion consists of a leaf spring having a fixed end fixed to the base and a biasing end that biases the tip of the protrusion engaged with the engagement hole toward the other end. The fixing device according to feature 2.

4. The aforementioned protrusion is a first protrusion, and the aforementioned engagement hole is a first engagement hole. The holding member is provided with a second projection that protrudes along the direction of the rotation axis, The first support portion has a second engagement hole into which the second projection engages, thereby restricting the rotation of the heating means around the first projection. The fixing device according to claim 2 or 3.

5. The biasing portion does not bias the second protrusion. The fixing device according to feature 4.

6. The second engagement hole has an elongated shape with a gap between it and the second protrusion in the linear direction connecting the first protrusion and the second protrusion when viewed in the direction of the rotation axis. The fixing device according to feature 4 or 5.

7. The protrusion is positioned away from the center of the heating roller in the intersecting direction, The fixing device according to any one of claims 2 to 6.

8. The protruding portion has a shape that protrudes on the side opposite to the second support portion in the direction of the rotation axis, The fixing device according to any one of claims 2 to 7.

9. An endless heating belt stretched over the aforementioned heating roller, A backup member that tensions the heating belt together with the heating roller, The system includes an opposing member that sandwiches the heating belt between itself and the backup member, and forms a fixing nip portion that sandwiches and transports the recording material between itself and the heating belt, The fixing device according to any one of claims 1 to 8.

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