Image heating device

Abstract

To provide a configuration in which a plurality of heaters are provided inside a heat roller and a plurality of terminals of the heater are arranged while the plurality of terminals can easily be inserted into the heat roller.SOLUTION: A heater unit includes a first halogen heater, a second halogen heater, and a pair of holders. The first halogen heater has: a first heat generation unit; a first glass tube; a second heat generation unit; a second glass tube; and a pair of first support portions supporting both ends of the first glass tube and both ends of the second glass tube. The second halogen heater has a third heat generation unit, a third glass tube, and a pair of second support portions supporting both ends of the third glass tube. A pair of holders fit into both the first support portions and the second support portions and hold the first halogen heater and the second halogen heater such that the pair of holders can be inserted into / pulled from a heat roller integrally with the first halogen heater and the second halogen heater.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an image heating device that heats a toner image carried on a recording material. [Background technology]

[0002] 2. Description of the Related Art As a fixing device, which is an example of an image heating device, a configuration in which a plurality of heaters are arranged inside a roller has been known in the past (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-45273 Summary of the Invention [Problem to be solved by the invention]

[0004] In a configuration in which a heater is provided inside the roller, the heater must be inserted and removed from the roller in the direction of the rotation axis during assembly or maintenance of the device. This can be difficult when there are multiple heaters, especially when the heaters have multiple terminals. For example, while holding one end of the heater while inserting it into the roller, it is not possible to hold the other end until it emerges from inside the roller.

[0005] When there is only one heater, it is relatively easy to insert it by holding one end of the heater while controlling the position and posture of the other end so that the heater does not come into contact with the inside of the roller.In contrast, when there are multiple heaters with multiple terminals, the insertion process is more difficult because it is necessary to control the relative positions and postures of the heaters to prevent them from coming into contact with each other, in addition to preventing the heaters from coming into contact with the roller.

[0006] The present invention aims to provide a configuration in which a plurality of heaters are provided inside a roller and a plurality of heater terminals are arranged, and in which the plurality of terminals can be easily inserted into the roller. [Means for solving the problem]

[0007] The present invention is an image heating device that heats a toner image carried on a recording material at a nip portion, comprising: a rotatable heating roller; and a heater unit that is provided inside the heating roller and can be inserted into and removed from the heating roller along the rotational axis direction of the heating roller, wherein the heater unit comprises: a first halogen heater having a first heating portion, a first glass tube that covers the first heating portion, a second heating portion, a second glass tube that covers the second heating portion, and a pair of first support portions that support both ends of the first glass tube and both ends of the second glass tube; a second halogen heater having a third heating portion, a third glass tube that covers the third heating portion, and a pair of second support portions that support both ends of the third glass tube; and a pair of holders that fit into the first support portions and the second support portions, respectively, and hold the first halogen heater and the second halogen heater integrally with the first halogen heater and the second halogen heater so that they can be inserted into and removed from the heating roller. [Effects of the Invention]

[0008] According to the present invention, a plurality of heaters are provided inside the roller, and a plurality of heater terminals are arranged, so that the plurality of terminals can be easily inserted into the roller. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view showing a schematic configuration of an image forming apparatus according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view showing a schematic configuration of a fixing device according to the embodiment. [Figure 3] 1A is a perspective view of a heating roller in which a halogen heater according to an embodiment is disposed, as viewed from one end side, and FIG. 1B is a perspective view of a heating roller in which a halogen heater according to an embodiment is disposed, as viewed from the other end side. [Figure 4]FIG. 4 is a diagram showing the light distribution of a halogen heater according to the embodiment. [Figure 5] FIG. 3 is a perspective view of one end side of a plurality of halogen heaters held by a holding portion according to the embodiment. [Figure 6] FIG. 2 is a plan view of a holder according to the embodiment. [Figure 7] FIG. 2 is a cross-sectional view of a heating roller in which a halogen heater is disposed according to the embodiment. [Figure 8] (a) Enlarged view of the left part of Figure 7, (b) Enlarged view of the right part of Figure 7. [Figure 9] FIG. 4 is a view of the holder as seen from the direction of the rotation axis of the heating roller. DETAILED DESCRIPTION OF THE INVENTION

[0010] The embodiment will be described with reference to Figures 1 to 9. First, the schematic configuration of an image forming apparatus according to the present embodiment will be described with reference to Figure 1.

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

[0012] The image forming apparatus 1 comprises an image reading unit 2 and an image forming apparatus main body 3. The image reading unit 2 reads an original placed on a platen glass 21. Light emitted from a light source 22 is reflected by the original and forms an image on a CCD sensor 24 via optical components 23 such as a lens. This optical unit scans in the direction of the arrow, converting the original into a line-by-line electrical signal data stream. The image signal obtained by the CCD sensor 24 is sent to the image forming apparatus main body 3, where it is subjected to image processing in accordance with each image forming unit (described later) by a control unit 30. The control unit 30 also receives external inputs as image signals from external host devices such as a print server.

[0013] The image forming apparatus main body 3 includes multiple image forming units Pa, Pb, Pc, and Pd, and each image forming unit forms an image based on the image signal. That is, the image signal is converted into a laser beam that is PWM (pulse width modulation) controlled by a control unit 30. A polygon scanner 31 serving as an exposure device scans the laser beam in accordance with the image signal. The laser beam is then irradiated onto photosensitive drums 200a to 200d serving as image carriers of each image forming unit Pa to Pd.

[0014] Note that Pa is a yellow (Y) image forming unit, Pb is a magenta (M) image forming unit, Pc is a cyan (C) image forming unit, and Pd is a black (Bk) image forming unit, each forming an image of the corresponding color. Since the image forming units Pa to Pd are substantially identical, the Y image forming unit Pa will be described in detail below, and descriptions 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 an image signal, as will be described below.

[0015] A charging roller 201a, which serves as a primary charger, charges the surface of the photosensitive drum 200a to a predetermined potential to prepare for the formation of an electrostatic latent image. A laser beam from a polygon scanner 31 forms an electrostatic latent image on the surface of the photosensitive drum 200a, which has been charged to a predetermined potential. A developing unit 202a develops the electrostatic latent image on the photosensitive drum 200a to form a toner image. A primary transfer roller 203a discharges electricity from the back surface of the intermediate transfer belt 204 and applies a primary transfer bias of opposite polarity to the toner, transferring the toner image on the photosensitive drum 200a onto the intermediate transfer belt 204. After transfer, the surface of the photosensitive drum 200a is cleaned by a cleaner 207a.

[0016] The toner image on intermediate transfer belt 204 is then conveyed to the next image forming station, where the toner images of each color formed at each image forming station are transferred in the order of Y, M, C, and Bk, forming a four-color image on the surface. The toner image that has passed through Bk image forming station Pd, which is located at the most downstream side in the rotation direction of intermediate transfer belt 204, is conveyed to a secondary transfer station made up of a pair of secondary transfer rollers 205 and 206. In the secondary transfer station, a secondary transfer electric field of opposite polarity to the toner image on intermediate transfer belt 204 is applied, thereby secondarily transferring the toner image onto the recording material.

[0017] The recording material is stored in a cassette 9, and the recording material fed from the cassette 9 is transported to a registration unit 208, which is made up of, for example, a pair of registration rollers, and waits at the registration unit 208. Thereafter, 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 position of the paper, and the recording material is transported to a secondary transfer unit.

[0018] The recording material onto which the toner image has been transferred in the secondary transfer section is transported to a fixing device 8, where the toner image carried on the recording material is fixed to the recording material by heating and pressing. The recording material that has passed through the fixing device 8 is discharged onto a discharge tray 7. When forming images on both sides of the recording material, after the toner image has been transferred and fixed onto the first side (front side) of the recording material, the recording material is turned over via a reversing conveyance section 10, and the toner image is transferred and fixed onto the second side (rear side) of the recording material, and the recording material is then stacked on the discharge tray 7.

[0019] As described above, the control unit 30 controls the entire image forming apparatus 1. The control unit 30 can also perform various settings based on inputs from the operation unit 4 and display unit 5 of the image forming apparatus 1. The operation unit 4 and display unit 5 are provided in the image forming apparatus 1 and are, for example, a touch panel or buttons that can be operated by touch.

[0020] Such a control unit 30 has a CPU (Central Processing Unit), ROM (Read Only Memory), and RAM (Random Access Memory). The CPU controls each unit by reading a program corresponding to a control procedure stored in the ROM. In addition, working data and input data are stored in the RAM, and the CPU performs control by referring to the data stored in the RAM based on the aforementioned program, etc.

[0021] [Fixing device] Next, the configuration of fixing device 8 as an image heating device in this embodiment will be described with reference to FIG. 2. In this embodiment, a fixing device of a belt heating type using an endless belt is adopted. In FIG. 2, the recording material is transported from right to left as indicated by arrow α. Fixing device 8 has a heating unit 300 having a fixing belt 310 as an endless rotatable belt member, and a pressure roller 330 as a pressure rotating body that contacts fixing belt 310 and forms a nip portion N together with fixing belt 310.

[0022] The heating unit 300 includes the above-described fixing belt 310, a fixing pad 320 serving as a nip portion forming member and a pad member, and a heating roller 340 and a tension roller 350 serving as tension members. The pressure roller 330 serving as a driving rotor rotates in contact with the outer peripheral surface of the fixing belt 310 and also serves as a driving roller that applies a driving force to the fixing belt 310.

[0023] The endless fixing belt 310 has thermal conductivity, heat resistance, and the like, and is, for example, a thin-walled cylindrical shape with an inner diameter of 120 mm. In this embodiment, it has a three-layer structure consisting of a base layer, an elastic layer on the outer periphery of the base layer, and a release layer on the outer periphery of the elastic layer. The base layer is 60 μm thick and made of polyimide resin (PI), the elastic layer is 300 μm thick and made of silicone rubber, and the release layer is 30 μm thick and made of PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin) as a fluororesin. The fixing belt 310 is stretched by a fixing pad 320, a heating roller 340, and a tension roller 350.

[0024] The fixing pad 320, which serves as a nip portion forming member, is disposed inside the fixing belt 310 so as to face the pressure roller 330 with the fixing belt 310 sandwiched therebetween, and forms a nip portion N between the fixing belt 310 and the pressure roller 330, which sandwiches and conveys the recording material. In this embodiment, the fixing pad 320 is a substantially plate-shaped member that is long in the width direction of the fixing belt 310 (the longitudinal direction intersecting the rotation direction of the fixing belt 310, the direction of the rotation axis of the heating roller 340). The fixing pad 320 is pressed against the pressure roller 330 with the fixing belt 310 sandwiched therebetween, thereby forming the nip portion N. The fixing pad 320 is made of LCP (liquid crystal polymer) resin.

[0025] At least a portion of the portion of fixing pad 320 that forms nip portion N is formed in a flat shape. That is, the portion that comes into contact with the inner circumferential surface of fixing belt 310 via lubricating sheet 370 (described later) is formed in a substantially flat shape, making the shape of the nip portion substantially flat. This configuration can prevent wrinkles and image misalignment from occurring on the envelope, particularly when a toner image is fixed to an envelope as a recording material.

[0026] The fixing pad 320 is supported by a stay 360 serving as a support member disposed inside the fixing belt 310. That is, the stay 360 is disposed on the opposite side of the fixing pad 320 from the pressure roller 330, and supports the fixing pad 320. Such a stay 360 is a reinforcing member having long rigidity along the longitudinal direction of the fixing belt 310, and contacts the fixing pad 320 to back it up. That is, the stay 360 provides strength to the fixing pad 320 and ensures the pressure force at the nip N when the fixing pad 320 is pressed by the pressure roller 330.

[0027] The stay 360 is made of a metal such as stainless steel, and has a substantially rectangular cross section (transverse cross section) perpendicular to the longitudinal direction of the stay 360, which intersects with the rotation direction of the fixing belt 310. For example, the stay 360 is made of a 3 mm thick drawn material of SUS304 (stainless steel), and the transverse cross section is formed into a hollow, substantially square shape to ensure strength. Note that the stay 360 may also be formed into a substantially rectangular cross section by combining multiple metal plates and fixing them together by welding or the like. The material of the stay 360 is not limited to stainless steel as long as strength can be ensured.

[0028] A lubricating sheet 370 is interposed between the fixing pad 320 and the fixing belt 310. In this embodiment, a PTFE (polytetrafluoroethylene) coated PI (polyimide) sheet with a thickness of 100 μm is used as the lubricating sheet 370. The PI sheet has 100 μm protrusions formed at 1 mm intervals, which reduces the contact area with the fixing belt 310 and thereby reduces sliding resistance.

[0029] A lubricant is applied in advance to the surface of the lubricating sheet 370 that comes into contact with the fixing belt 310 to improve sliding properties. In this embodiment, oil is used as the lubricant. Silicone oil is preferably used as the oil from the viewpoint of heat resistance, and oils of various viscosities are used depending on the conditions of use. Oils with too high a viscosity tend to have poor fluidity when applied, so oils with a viscosity of 30,000 cSt or less are typically used. Specific examples of such oils include, but are not limited to, dimethyl silicone oil, amino-modified silicone oil, and fluorine-modified silicone oil.

[0030] In this embodiment, the fixing belt 310 further includes a lubricant application roll 395 as a lubricant application member that applies a lubricant to the inner circumferential surface of the fixing belt 310. This applies a lubricant to the inner circumferential surface of the fixing belt 310. The lubricant application roll 395 is disposed between the fixing pad 320 and the heating roller 340 and contacts the inner surface of the fixing belt 310. The lubricant application roll 395 is composed of a shaft and a lubricant retention layer. Examples of materials that can be used to form the shaft include aluminum, iron, stainless steel, and brass. The lubricant retention layer is a layer that is impregnated with and retains the lubricant to be applied, and the lubricant impregnated in this layer seeps out and is applied to the inner surface of the fixing belt 310. Porous materials and fibrous materials are used as the material for the lubricant application roll 395.

[0031] 2, the heating roller 340 is disposed inside the fixing belt 310 and tensions the fixing belt 310 together with the fixing pad 320 and the tension roller 350. As described above, the inner peripheral surface of the fixing belt 310 is coated with a lubricant, and the heating roller 340 tensions the fixing belt 310 via this lubricant. The heating roller 340 is disposed downstream of the fixing pad 320 and upstream of the tension roller 350 in terms of the rotation direction of the fixing belt 310. This allows the driving force of the heating roller 340 to directly pull the fixing belt 310 that has passed through the nip portion N without passing through a tension roller.

[0032] Heating roller 340 is formed into a cylindrical shape from metal such as aluminum or stainless steel, and has a plurality of halogen heaters 341, 342, and 343 disposed therein as heaters for heating fixing belt 310. Heating roller 340 is heated to a predetermined temperature by 341, 342, and 343.

[0033] In this embodiment, the heating roller 340 is formed from a stainless steel pipe with a thickness of 1 mm, and three halogen heaters 341-343 are arranged inside. It is desirable to have multiple halogen heaters in consideration of temperature distribution control in the longitudinal direction (direction of the rotation axis) of the heating roller 340. Although three halogen heaters are used in this embodiment, two, four, or more heaters may be used. The multiple halogen heaters 341-343 have different light distributions in the longitudinal direction, and their lighting ratios are controlled according to the size of the recording material. The heaters are not limited to halogen heaters, and may be other heaters capable of heating the heating roller 340, such as carbon heaters. The fixing belt 310 is heated by the heating roller 340 heated by the halogen heaters 341-343, and is controlled to a predetermined target temperature according to the type of recording material based on temperature detection by a thermistor (not shown).

[0034] The heating roller 340 is rotatably supported by a frame 301 serving as a heating roller support portion, and a gear is fixed to one end of the heating roller 340 in the direction of its rotation axis. The gear is connected to a motor M1, serving as an auxiliary driving roller drive source, via the gear, and the heating roller 340 is driven to rotate. The fixing belt 310 is provided with a driving force by the rotation of the heating roller 340. The force applied from the heating roller 340 to the fixing belt 310 is referred to as an auxiliary driving force. The heating roller 340 may be connected to a motor M0, serving as a pressure roller drive source (described later), and driven to rotate. The drive transmission mechanism from the motor may be a mechanism other than a gear, such as a pulley and belt, or a mechanism for pressing a roller driven by a motor from an external source. In any case, in this embodiment, the peripheral speed of the heating roller 340 is set to be faster than the peripheral speed of the pressure roller 330.

[0035] The tension roller 350 is disposed inside the fixing belt 310, stretches the fixing belt 310 together with the fixing pad 320 and the heating roller 340, and rotates in response to the fixing belt 310. In this embodiment, the tension roller 350 is biased by a spring supported by the frame of the heating unit 300, and also serves as a tension roller that applies a predetermined tension to the fixing belt 310. The tension applied by the spring is 50 N in this embodiment. By applying tension to the fixing belt 310 by the tension roller 350 in this manner, the fixing belt 310 is caused to follow the fixing pad 320.

[0036] The tension roller 350 is cylindrically formed from a metal such as aluminum or stainless steel. In this embodiment, the tension roller 350 is a stainless steel or aluminum pipe with an outer diameter of 40 mm and a thickness of 1 mm, and its ends are rotatably supported by bearings (not shown). The tension roller 350 may simply be a tension roller that suspends the fixing belt 310, or may be a roller that has a steering function in addition to a function of applying tension. The steering function is, for example, a function in which the tension roller 350 tilts relative to the rotation axis direction (longitudinal direction) of the heating roller 340 to control the position (shift position) of the fixing belt 310 relative to this rotation axis direction.

[0037] The pressure roller 330, which serves as a drive roller, rotates in contact with the outer circumferential surface of the fixing belt 310, applying a driving force to the fixing belt 310. In this embodiment, the pressure roller 330 is a roller having an elastic layer formed on the outer periphery of its shaft and a release layer formed on the outer periphery of the elastic layer. The shaft is made of stainless steel, the elastic layer is 5 mm thick and made of conductive silicone rubber, and the release layer is 50 μm thick and made of PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin) as a fluororesin. The pressure roller 330 is rotatably supported by the fixing frame 380 of the fixing device 8, and a gear is fixed to one end thereof. The pressure roller 330 is connected to a motor M0, which serves as a pressure roller drive source, via the gear, and is driven to rotate.

[0038] The fixing frame 380 is provided with a heating unit positioning portion 381, a pressure frame 383, and a pressure spring 384. The heating unit 300 is positioned on the fixing frame 380 by inserting a stay 360 into the heating unit positioning portion 381 and fixing the stay 360 to the heating unit positioning portion 381 by a fixing means (not shown). The heating unit positioning portion 381 has a pressure direction regulating surface 381a that faces the pressure roller 330 and a conveying direction regulating surface 381b that is an abutting surface in the insertion direction of the heating unit 300. The stay 360 is fixed in a state where its movement is restricted by the pressure direction regulating surface 381a and the conveying direction regulating surface 381b. At this time, the pressure roller 330 is separated from the fixing belt 310.

[0039] After the heating unit 300 is positioned in the heating unit positioning portion 381, the pressure roller 330 comes into contact with the fixing belt 310 as a result of the pressure frame 383 being moved by a drive source and a cam (not shown). The pressure roller 330 is then pressed against the fixing pad 320 via the fixing belt 310. That is, in this embodiment, the pressure roller 330 also serves as a pressure member that applies pressure toward the fixing belt 310. In this embodiment, the pressure applied during image formation is 1000 N.

[0040] In this embodiment, a separating device 400 having a separating member (a separating plate in this embodiment) 401 that separates the recording material from the fixing belt 310 is provided downstream of the nip N in the recording material conveyance direction. The separating member 401 is disposed with a gap between it and the outer peripheral surface of the fixing belt 310, and separates the recording material that has passed through the nip N from the fixing belt. Specifically, the separating member 401 is disposed close to a portion of the outer peripheral surface of the fixing belt 310 that is stretched between the fixing pad 320 and the heating roller 340. The separating member 401 is formed in a blade shape, with its tip facing the outer peripheral surface of the fixing belt 310. A fluorine-based tape is attached to the metal plate of the separating member 401 to prevent toner adhesion to the recording material and image scratches due to sliding. In this embodiment, the separating member 401 is positioned with respect to the stay 360 in the recording material conveyance direction (the widthwise direction of the stay 360, the X direction) so as to be disposed with a gap between it and the outer peripheral surface of the fixing belt 310.

[0041] The fixing device 8 configured as described above sandwiches the recording material P bearing a toner image at the nip portion N formed between the fixing belt 310 and the pressure roller 330, and heats the toner image while conveying the recording material P. This melts the toner image and fixes it to the recording material. In this embodiment, during image formation, the peripheral speed of the fixing belt 310 is 300 mm / s, the pressure at the nip portion N is 1000 N, and the temperature of the fixing belt 310 is 180°C.

[0042] [Halogen heater] Next, the configuration of halogen heaters 341, 342, and 343 arranged inside heating roller 340 will be described. FIGS. 3(a) and 3(b) are schematic diagrams showing the halogen heaters 341, 342, and 343 and the vicinity of heating roller 340. FIG. 3(a) is a perspective view of the vicinity of the front end of fixing device 8, and FIG. 3(b) is a perspective view of the vicinity of the rear end of fixing device 8. The front side of fixing device 8 is the front side of image forming apparatus 1, which is the side from which an operator such as a user operates the device. The rear side of fixing device 8 is the rear side of image forming apparatus 1. The front-to-rear direction of fixing device 8 is the same as the rotational axis direction of heating roller 340, and heater unit 500 can be inserted into and removed from inside heating roller 340 from at least one side (e.g., the rear side) of the rotational axis direction of heating roller 340.

[0043] The halogen heater 341 includes three glass tubes 341a with filaments (heat generating elements) passing through them, a pair of bases 341b connected to both ends of the glass tubes as support members, and lead wires 341c connected to the bases 341b for supplying power. The glass tubes 341a cover the filaments. The pair of bases 341b support both ends of the three glass tubes 341a. In this embodiment, a halogen heater is defined as a combination of heaters with one support member (terminal) at each end. In other words, even if there are multiple heat generating elements and glass tubes, a single halogen heater is defined as a single halogen heater if there is one terminal at each end. The terminals of the lead wires 341c are connected to the power supply of the image forming apparatus main body. When power is supplied, the heating elements light up and raise the surface of the heating roller 340 to a predetermined temperature.

[0044] The other halogen heaters 342 and 343 have the same configuration except for the number of glass tubes and the light distribution of the heating element. That is, halogen heater 342 has two glass tubes 342a (see later-described FIGS. 5 and 7), a base 342b, and a lead wire 342c. Also, halogen heater 343 has one glass tube 343a (see later-described FIGS. 5 and 7), a base 343b, and a lead wire 343c.

[0045] FIG. 4 shows the light distribution of the three glass tubes 341a of the halogen heater 341 in this embodiment. The horizontal axis represents the position in the front-to-rear direction (the direction of the rotation axis of the heating roller 340), and the vertical axis represents the heat generation performance at that position. As can be seen from FIG. 4, the three glass tubes of the halogen heater 341 each have a different light distribution. That is, there is a glass tube (Lamp 2) that mainly heats the central region in the direction of the rotation axis, and glass tubes (Lamp 1 and Lamp 3) that mainly heat the end regions in the direction of the rotation axis. In this embodiment, the halogen heater 341 is Lamp 1, Lamp 2, and Lamp 3, and the halogen heater 342 is Lamp 1 and Lamp 2. The halogen heater 343 may be Lamp 3 or a heater with a flat orientation distribution in the longitudinal direction.

[0046] This allows control according to the dimension in the width direction (rotation axis direction) of the recording material. For example, when recording materials (e.g., sheets such as paper) with small width dimensions in the front-to-rear direction continuously pass through the nip portion N, both ends of the heating roller 340 in the rotation axis direction do not come into contact with the recording material, and therefore are more likely to rise in temperature than the central portion that comes into contact with the recording material. Therefore, in this case, by reducing the lighting ratio of the glass tubes (Lamp 1, Lamp 3) that mainly heat the end regions, it is possible to suppress heat accumulation at both ends of the heating roller 340 in the rotation axis direction. Similarly, each glass tube of the halogen heaters 342 and 343 has an independent light distribution. However, the present invention is not limited to this and can be applied to any configuration in which multiple halogen heaters are provided.

[0047] [Heater unit] The above-mentioned halogen heaters 341 to 343 can be inserted into and removed from the heating roller 340 when assembling or maintaining the device. In particular, in this embodiment, since there are multiple halogen heaters, a configuration is adopted in which the multiple halogen heaters are held together, and this configuration, i.e., heater unit 500, can be inserted into and removed from the heating roller 340. Hereinafter, this heater unit 500 and the support configuration for heater unit 500 will be described with reference to Figures 3(a) and 3(b) and Figures 5 to 9.

[0048] As shown in FIGS. 3(a), 3(b), 7, 8(a), and 8(b), the heater unit 500 is supported on both sides in the rotational axis direction of the heating roller 340 (i.e., the front and rear sides) by support plates 347 serving as a pair of support members. As shown in FIG. 5, the heater unit 500 has three halogen heaters 341-343 serving as multiple heaters, and a pair of holders 501. As described above, the halogen heaters 341-343 are disposed inside the heating roller 340, each along the rotational axis direction. The pair of holders 501 integrally hold both ends in the rotational axis direction of the three halogen heaters 341-343, and are supported by the pair of support plates 347.

[0049] Each of the pair of holding portions 501 has a resin holder 345 as a positioning member and a spring 346 as a biasing member and an annular retaining ring. The holder 345 is a member for positioning the three halogen heaters 341-343 in the circumferential direction of the heating roller 340. The spring 346 is a member for biasing the halogen heaters 341-343 toward the holder 345 to prevent the three halogen heaters 341-343 positioned in the holder 345 from separating, and fixes the bases 341b, 342b, and 343b from the outside. That is, the bases 341b, 342b, and 343b at both ends of the three halogen heaters 341-343 are constrained and fixed by the pair of holders 345 and the pair of springs 346 on the front and rear sides, respectively, so that their relative positions do not change. This will be explained in detail below.

[0050] 7 is a schematic cross-sectional view taken along the rotation axis of heating roller 340 on a plane parallel to the rotation axis of heating roller 340. For simplicity, only halogen heaters 342 and 343 are shown in FIG. 7, but halogen heater 341 also has the same support structure. FIG. 8(a) is an enlarged view of the front side of FIG. 7, and FIG. 8(b) is an enlarged view of the rear side of FIG. 7.

[0051] Fig. 6 is a view of holder 345 as viewed from the direction of the rotation axis of heating roller 340. As shown in Fig. 6, holder 345 has engagement recesses 345a, 345b, and 345c in the circumferential direction for supporting halogen heaters 341-343, respectively. Engagement recesses 345a-345c are formed so that the ends of halogen heaters 341-343 can enter into them and loosely engage with the outer circumferential surfaces of the ends. That is, engagement recess 345a is formed so that it can be loosely fitted with base 341b of halogen heater 341, engagement recess 345b is formed so that it can be loosely fitted with base 342b of halogen heater 342, and engagement recess 345c is formed so that it can be loosely fitted with base 343b of halogen heater 343 (see Fig. 5). In other words, the holder 345 is fitted to each of the bases 341b, 342b, and 343b, and holds the halogen heaters 341, 342, and 343 so that they can be inserted into and removed from the heating roller 340 integrally with the halogen heaters 341, 342, and 343.

[0052] In this embodiment, the heating roller 340 has a through-hole through which the heater unit 500 is inserted and removed, and the inner diameter of this through-hole is larger than the outer diameter of the holder 345. Because the holder 345 is insertable and removable from the through-hole of the heating roller 340, the outer diameter of the holder 345 is limited. To accommodate multiple halogen heaters and to save space, this embodiment divides the halogen heater into one with three glass tubes, one with two glass tubes, and one with one glass tube. This configuration allows for more space-saving holders than two sets of heaters with three glass tubes. Figure 9 is a view of the holder 345 as seen from the direction of the rotation axis of the heating roller 340. 9, when holder 345 is viewed from the direction of the rotation axis of heat roller 340, the center of gravity G0 of the holder in the plan view (projection surface of the holder) is inside the line (triangle in this embodiment) connecting the centers of gravity (G1, G2, G3) of each halogen heater. This configuration improves the stability of removing the halogen heater unit when inserting or removing it from heat roller 340.

[0053] As a result, both ends of the halogen heaters 341 to 343 are loosely held by a pair of holders 345. At this time, a part of the bases 341b to 343b protrudes toward the end side beyond the part held by the holder 345. This part is fixed by tightening the ring-shaped spring 346 from the outside so that the bases 341b to 343b and the holder 345 become one unit.

[0054] That is, both ends of the halogen heaters 341-343, which are loosely held by a pair of holders 345, are elastically clamped and held by a pair of springs 346. The springs 346 are ring-shaped elastic members with a portion cut out, and are arranged to include the bases 341b-343b of the halogen heaters 341-343 held by the holders 345. As the diameter of the springs 346 elastically contracts, the bases 341b-343b are pressed against the engagement recesses 345a-345c of the holders 345, respectively, thereby integrally holding the halogen heaters 341-343. As a result, the heater unit 500 is formed by integrating the halogen heaters 341-343, the pair of holders 345, and the pair of springs 346 into a single unit. Note that the configuration for holding multiple halogen heaters is not limited to this. For example, the engagement recesses of the holders may elastically deform to insert the halogen heaters, so that the halogen heaters are held by the holders alone.

[0055] As described above, the heater unit 500 can be inserted and removed from at least one side in the direction of the rotation axis of the heat roller 340. In this embodiment, the diameter of the circumscribing circle of the pair of holding portions 501 is smaller than the minimum inner diameter r (FIG. 7) of the heat roller 340. The heater unit 500 can be inserted and removed inside the heat roller 340. Note that the outer diameter of one of the pair of holding portions 501 may be smaller than the minimum inner diameter r of the heat roller 340, and the outer diameter of the other holding portion 501 may be larger than the minimum inner diameter r. In this case, the heater unit 500 can be inserted into the heat roller 340 from one of the holding portions 501.

[0056] In either case, a pair of support plates 347 are provided at the front and rear of the heating roller 340 to fix the heater unit 500 inserted into the heating roller 340 to the frame 301 that supports the heating roller 340. As shown in FIGS. 3(a), 3(b), 7, 8(a), and 8(b), the pair of support plates 347 are fixed to the frame 301 with fixing members such as screws. The frames 301 are disposed on both sides of the heating roller 340 in the direction of its rotation axis, and rotatably support both ends of the heating roller 340. Each of the pair of support plates 347 is formed to protrude outward in the direction of the rotation axis (toward the side away from the heating roller 340) beyond the portion of the frame 301 that supports the heating roller 340. The holders 501 of the heater units 500 are supported by the support plates 347.

[0057] That is, when the heater unit 500 is placed inside the heating roller 340, the holding portions 501 at both ends protrude from the heating roller 340. The holding portions 501 are supported by the support plates 347. In other words, the pair of support plates 347 support the pair of holding portions 501 from the opposite side of the heating roller 340 in the direction of the rotation axis.

[0058] The pair of support plates 347 serving as holder support parts each have a through-hole 347a penetrating in the direction of the rotation axis. Meanwhile, the holders 345 of the pair of holding parts 501 have protrusions 345d that protrude in the direction of the rotation axis and can fit into the through-holes 347a. This allows the through-hole 347a of one of the support plates 347 to receive the protrusions 345d when the heater unit 500 is inserted into the heating roller 340 along the direction of the rotation axis.

[0059] In this embodiment, as shown in FIG. 3(a), two protrusions 345d are provided on the front holder 345, and two through-holes 347a are formed in the front support plate 347. On the other hand, as shown in FIG. 3(b), one protrusion 345d is provided on the rear holder 345, and one through-hole 347a is formed in the rear support plate 347. When arranging the heater unit 500 in the heat roller 340 with this configuration, the heater unit 500 is first inserted from the rear side of the heat roller 340. At this time, the rear support plate 347 is not fixed to the frame 301. Then, the two protrusions 345d of the front holder 345 are fitted into the through-holes 347a of the front support plate 347. This supports the front side of the heater unit 500 and determines its circumferential position. Then, the rear support plate 347 is fixed to the frame 301. At this time, one protrusion 345d of the rear holder 345 is fitted into one through-hole 347a, thereby supporting the rear side of the heater unit 500 as well.

[0060] In this embodiment, as described above, the plurality of halogen heaters 341-343 are integrated by a pair of holding portions 501 to form the heater unit 500, which is then inserted into the heating roller 340. Therefore, with a configuration in which the plurality of halogen heaters 341-343 are arranged inside the heating roller 340, the plurality of halogen heaters 341-343 can be easily inserted into the heating roller 340. For example, when one end of the heater unit 500 is held while the other end is inserted into the heating roller 340, the plurality of halogen heaters 341-343 are held by the holding portions 501, making it easy to control the relative positions and orientations of the heaters. Therefore, contact between the plurality of halogen heaters 341-343 can be prevented when the halogen heaters 341-343 are inserted. Similarly, contact between the heaters can be prevented when the halogen heaters 341-343 are removed from the heating roller 340.

[0061] <Other embodiments> In the above embodiment, a configuration in which multiple heaters are disposed within the heating roller 340 that tensions the fixing belt 310 has been described. However, the present invention is not limited to such a belt configuration, and can also be applied to a configuration in which a nip is formed by a pair of rollers and multiple heaters are disposed on one or both of these rollers. The present invention can also be applied to an external heating configuration in which the rollers are heated externally. For example, an external heating device that externally heats the heating roller that forms the nip is one in which a belt tensioned by multiple rollers is brought into contact with the heating roller. In this case, multiple heaters may be disposed on at least one of the multiple rollers that tension the belt. The present invention can also be applied to such rollers. The present invention can also be applied to a configuration in which an external heating device directly contacts a roller with the heating roller without using a belt.

[0062] Furthermore, in the above-described embodiment, the configuration was a halogen heater consisting of three heaters, a halogen heater consisting of two heaters, and a halogen heater consisting of one heater, but the present invention is not limited to this number, and a configuration of a halogen heater consisting of two heaters and a halogen heater consisting of one heater is also possible.

[0063] In the above-described embodiment, the motor M0 for the pressure roller and the motor M1 for the auxiliary drive roller are provided independently. However, a common motor may be used for the pressure roller and the auxiliary drive roller. That is, the pressure roller and the auxiliary drive roller may be driven by a common drive source. In this case, a speed change mechanism is provided between one motor and one of the rollers, and the peripheral speed of the heating roller 340 is made faster than the peripheral speed of the pressure roller 330.

[0064] In the above embodiment, the heating roller 340 is disposed downstream of the fixing pad 320 and upstream of the tension roller 350 with respect to the rotation direction of the fixing belt 310. However, the positions of the heating roller 340 and the tension roller 350 may be interchanged. That is, the heating roller 340 may be disposed downstream of the tension roller 350 and upstream of the fixing pad 320 with respect to the rotation direction of the fixing belt 310.

[0065] In the above-described embodiments, the auxiliary drive roller is provided with a halogen heater for heating the fixing belt. However, the heater may be provided on another tension member such as a steering roller instead of the auxiliary drive roller.

[0066] In addition, in each of the above-described embodiments, the nip portion forming member is the fixing pad 320, but the nip portion forming member may be a rotating body such as a roller. In addition, in each of the above-described embodiments, the driving rotating body is the pressure roller 330, but the driving rotating body may be a belt that is driven to rotate. [Explanation of symbols]

[0067] 8···Fusing device (image heating device) / 301···Frame / 310···Fusing belt (belt member) / 320···Fusing pad (nip portion forming member) / 330···Pressure roller (driving rotor) / 340···Heating roller (roller) / 341, 342, 343···Halogen heater (heater) / 345···Holder (positioning member) / 345d···Protrusion / 346···Spring (urging member) / 347···Support plate (support member) / 347a···Through hole / 500···Heater unit / 501···Holding portion

Claims

1. An image heating device that heats a toner image carried on a recording material at a nip portion, a rotatable heating roller; a heater unit provided inside the heating roller and capable of being inserted into and removed from the heating roller along the rotation axis direction of the heating roller, The heater unit comprises: a first halogen heater having a first heat generating portion, a first glass tube covering the first heat generating portion, a second heat generating portion, a second glass tube covering the second heat generating portion, and a pair of first support portions supporting both ends of the first glass tube and both ends of the second glass tube; a second halogen heater having a third heat generating portion, a third glass tube covering the third heat generating portion, and a pair of second support portions supporting both ends of the third glass tube; and a pair of holders that fit into the first support portion and the second support portion, respectively, and hold the first halogen heater and the second halogen heater integrally with the first halogen heater and the second halogen heater so that the heater can be inserted into and removed from the heating roller.

2. 2. The image heating apparatus according to claim 1, further comprising: a heat roller support portion that supports said heat roller; and a holder support portion that is provided on said heat roller support portion and engages with said holder to support said holder.

3. the second halogen heater has a fourth heat generating portion, a fourth glass tube covering the fourth heat generating portion, a fifth heat generating portion, and a fifth glass tube covering the fifth heat generating portion; 3. The image heating apparatus according to claim 1, wherein the pair of second support portions support both end portions of the third glass tube, the fourth glass tube, and the fifth glass tube.

4. the heater unit includes a third halogen heater having a sixth heat generating portion, a sixth glass tube covering the sixth heat generating portion, and a pair of third support portions supporting both ends of the sixth glass tube, 4. The image heating apparatus according to claim 3, wherein the pair of holders are fitted into the pair of third support portions to hold a third halogen heater.

5. 4. The image heating apparatus according to claim 1, wherein the heater unit is attached to the holder and has an annular retaining ring for fixing the first support portion and the second support portion from the outside.

6. 3. The image heating apparatus according to claim 2, wherein the holder has a protrusion that fits into a through-hole provided in the holder support portion in order to perform positioning with respect to the holder support portion.

7. 7. The image heating apparatus according to claim 1, wherein the nip portion is formed by a belt member and a pressure member that presses the belt member, and the heating roller stretches the belt member.

8. 8. The image heating apparatus according to claim 1, wherein the heating roller has a through hole into which the heater unit is inserted and removed, and the inner diameter of the through hole is larger than the outer diameter of the holder.

9. 9. An image heating apparatus according to claim 1, wherein the number of glass tubes of said first halogen heater is greater than the number of glass tubes of said second halogen heater.

10. 10. An image heating apparatus according to claim 1, wherein the holder is made of resin.

11. 5. An image heating apparatus according to claim 4, wherein the center of gravity of said holder in a plane when said holder is viewed from the rotation axis of said heating roller is inside a figure connecting the centers of gravity of adjacent halogen heaters.

Images