Fixing apparatus and image forming apparatus

Abstract

To prevent displacement of a planar heater in a sheet conveyance direction without bonding the planar heater.SOLUTION: A fixing device comprises: a cylindrical fixing belt; a pressure roller that sandwiches and conveys a sheet with the fixing belt; a planar heater 23 that has a length in a width direction intersecting a conveyance direction Y of the sheet longer than that of the fixing belt, and is in contact with an inner peripheral surface of the fixing belt; a heater holder 25 that is in contact with a second surface 232 of the planar heater 23 on the opposite side of a first surface 231 in contact with the fixing belt, and has a length in the width direction longer than that of the fixing belt; and a pair of stationary members 30 that are mounted on the heater holder 25, are in contact with both ends in the width direction of the first surface 231, and sandwich the planar heater 23 with the heater holder 25. The pair of stationary members 30 each include a downstream-side end face contact part 32 that is in contact with an end face on the downstream side in the conveyance direction Y (downstream-side end face 23ED) of the planar heater 23.SELECTED DRAWING: Figure 12

Description

[[Technical Field]]

[0001] The present invention relates to a fixing device that fixes a toner image onto a sheet, and an image forming apparatus including the fixing device. [[Background Art]]

[0002] A fixing device that heats a fixing belt using a planar heater is known. Since a planar heater is in the form of a thin plate, it has low rigidity when used alone. Therefore, the planar heater is held by a highly rigid heater holder (for example, Patent Document 1). The heater holder is provided with a recess having a depth corresponding to the thickness of the planar heater, and the planar heater is accommodated in the recess. [[Prior Art Documents]] [[Patent Documents]]

[0003] [[Patent Document 1]] Japanese Patent Application Laid-Open No. 2006-163297 [[Summary of the Invention]] [[Problem to be Solved by the Invention]]

[0004] Incidentally, in consideration of dimensional errors of the planar heater, warpage of the heater holder, and the like, the length of the recess of the heater holder in the sheet conveying direction is designed to be larger than that of the planar heater. Therefore, conventionally, the planar heater has been adhered in the recess to prevent displacement of the planar heater in the conveying direction. However, since the temperature of the planar heater during energization reaches around 200° C., volatile organic compounds may be generated from the adhesive.

[0005] In view of the above circumstances, an object of the present invention is to provide a fixing device and an image forming apparatus that can prevent displacement of a planar heater in the sheet conveying direction without adhering the planar heater. [[Means for Solving the Problem]]

[0006] To solve the above problems, the fixing device according to the present invention comprises a cylindrical fixing belt, a pressure roller, a planar heater, a heater holder, and a pair of fixing members. The pressure roller holds the sheet between itself and the fixing belt for transport. The planar heater has a length in the width direction intersecting the sheet transport direction that is longer than that of the fixing belt, and has a first surface that contacts the inner circumferential surface of the fixing belt, and a second surface opposite to the first surface. The heater holder contacts the second surface of the planar heater and has a length in the width direction that is longer than that of the fixing belt. The pair of fixing members contact both ends of the first surface of the planar heater in the width direction and are mounted on the heater holder so as to sandwich the planar heater between itself and the heater holder. The pair of fixing members have downstream end face contact portions that contact the downstream end face of the planar heater in the transport direction.

[0007] The heater holder may include an upstream end face facing portion that faces the upstream end face of the planar heater in the conveying direction.

[0008] The pair of fixing members may include an upstream end face facing portion that faces the upstream end face of the planar heater in the conveying direction.

[0009] The heater holder includes a first end-face facing portion that faces the first end face in the width direction of the planar heater, and the fixing member on the side of the second end face in the width direction of the planar heater among the pair of fixing members may include a second end-face facing portion that faces the second end face.

[0010] Of the pair of fixing members, the fixing member on the first end face side in the width direction of the planar heater may have a first end face facing portion that faces the first end face, and the fixing member on the second end face side in the width direction of the planar heater may have a second end face facing portion that faces the second end face.

[0011] The heater holder is mounted along a predetermined mounting direction and further comprises a connector that is electrically connected to the electrode portion of the planar heater, and one of the pair of fixing members is provided with an electrode protection portion that covers the planar heater upstream of the electrode portion in the mounting direction of the connector.

[0012] The electrode protection portion may be characterized by having an opening that exposes the electrode portion and an inclined portion provided around the opening so as to be inclined toward the opening.

[0013] Furthermore, the image forming apparatus according to the present invention is characterized by comprising an imaging apparatus for forming a toner image on the sheet, and one of the fixing apparatuses for fixing the toner image on the sheet. [Effects of the Invention]

[0014] According to the present invention, it is possible to prevent the sheet heater from shifting in the sheet transport direction without having to bond the sheet heater to it. [Brief explanation of the drawing]

[0015] [Figure 1] This is a schematic front view showing the internal configuration of a printer according to one embodiment of the present invention. [Figure 2] This is a cross-sectional view of a fixing device according to one embodiment of the present invention. [Figure 3] This is a perspective view of a fixing device according to one embodiment of the present invention. [Figure 4] This is a perspective view of a fixing device excluding the fixing belt according to one embodiment of the present invention. [Figure 5] This is a perspective view of a heater holder according to one embodiment of the present invention. [Figure 6] This is a perspective view showing the front end of a heater holder according to one embodiment of the present invention. [Figure 7] This is a perspective view showing the front end of a heater holder to which a planar heater and a fixing member are attached, according to one embodiment of the present invention. [Figure 8]It is a perspective view showing a rear end portion of a heater holder according to an embodiment of the present invention. [Figure 9] It is a perspective view showing a rear end portion of a heater holder with a planar heater and a fixing member mounted according to an embodiment of the present invention. [Figure 10] It is a perspective view of a fixing member according to an embodiment of the present invention. [Figure 11] It is a perspective view of a fixing member according to an embodiment of the present invention. [Figure 12] It is a cross-sectional view of a heater holder with a planar heater and a fixing member mounted according to an embodiment of the present invention. [Figure 13] It is a view showing a second end face opposing portion according to a modification of an embodiment of the present invention. [Figure 14] It is a perspective view showing a front end portion of a heater holder supporting a planar heater according to another modification of an embodiment of the present invention. [Figure 15] It is a perspective view showing a fixing member according to another modification of an embodiment of the present invention. [Figure 16] In another modification of an embodiment of the present invention, it is a perspective view showing a front end portion of a heater holder with a planar heater mounted by a fixing member. [Figure 17] In another modification of an embodiment of the present invention, it is a perspective view showing a connector connected to a planar heater. [Figure 18A] In another modification of an embodiment of the present invention, it is a cross-sectional view showing the planar heater, the heater holder, and the connector during a process of connecting the connector to the planar heater mounted on the heater holder. [Figure 18B] In another modification of an embodiment of the present invention, it is a cross-sectional view showing the planar heater, the heater holder, and the connector during a process of connecting the connector to the planar heater mounted on the heater holder. [Figure 18C] In another modification of an embodiment of the present invention, it is a cross-sectional view showing the planar heater, the heater holder, and the connector during a process of connecting the connector to the planar heater mounted on the heater holder. [Modes for carrying out the invention]

[0016] First, the overall configuration of printer 1 (an example of an image forming apparatus) will be described. Figure 1 is a schematic front view showing the internal configuration of printer 1. Hereafter, the front side of the paper in Figure 1 will be considered the front side of printer 1, and the left and right directions will be described based on the direction in which printer 1 is viewed from the front. In each figure, U, Lo, L, R, Fr, and Rr indicate top, bottom, left, right, front, and back, respectively.

[0017] The printer 1 comprises a rectangular main housing 3. Inside the lower part of the main housing 3, there is a paper feed cassette 4 in which sheets S are stored, and a paper feed roller 5 that feeds the sheets S from the paper feed cassette 4 to the left. Above the paper feed cassette 4, there is an imaging device 6 that forms a toner image using an electrophotographic method, and to the right of the imaging device 6, there is a fuser device 7 that fixes the toner image onto the sheet S. Above the fuser device 7, there is a paper output roller 8 that ejects the sheet S with the toner image fixed on it, and a paper output tray 9 on which the ejected sheets S are stacked.

[0018] Inside the main housing 3, a transport path 10 is provided, which runs from the paper feed roller 5 through the image creation device 6 and the fixing device 7 to the paper discharge roller 8. The transport path 10 is formed using plate-shaped members that face each other with gaps between them to allow the sheet S to pass through, and transport rollers 17 that grip and transport the sheet S are provided at multiple locations in the transport direction Y. Upstream of the image creation device 6 in the transport direction Y, a registration roller 18 is provided. To the right of the fixing device 7, a reversing transport path 10R is provided, which branches off from the transport path 10 downstream of the fixing device 7 in the transport direction Y and rejoins the transport path 10 upstream of the registration roller 18 in the transport direction Y.

[0019] The imaging device 6 includes a photoreceptor drum 11 whose potential changes when exposed to light, a charging device 12 that charges the photoreceptor drum 11, an exposure device 13 that emits laser light corresponding to the image data, a developing device 14 that supplies toner to the photoreceptor drum 11, a transfer device 15 that transfers the toner image from the photoreceptor drum 11 to the sheet S, and a cleaning device 16 that removes toner remaining on the photoreceptor drum 11. A toner container 20 that supplies toner to the developing device 14 is connected to the developing device 14.

[0020] The control unit 2 comprises an arithmetic unit and a memory unit. The arithmetic unit is, for example, a CPU (Central Processing Unit). The memory unit includes storage media such as ROM (Read Only Memory), RAM (Random Access Memory), and EEPROM (Electrically Erasable Programmable Read Only Memory). The arithmetic unit performs various processes by reading and executing control programs stored in the memory unit. Note that the control unit 2 may be implemented using only integrated circuits without the use of software.

[0021] The basic image formation operation of printer 1 is as follows: When a single-sided print job is input to printer 1 from an external computer or the like, the paper feed roller 5 feeds the sheet S from the paper feed cassette 4 to the transport path 10, the registration roller 18, whose rotation has stopped, corrects the skew of the sheet S, and the registration roller 18 feeds the sheet S to the image formation device 6 at a predetermined timing. In the image formation device 6, the charging device 12 charges the photoreceptor drum 11 to a predetermined potential, the exposure device 13 writes a latent image to the photoreceptor drum 11, the developing device 14 develops the latent image using toner supplied from the toner container 20 to form a toner image, and the transfer device 15 transfers the toner image to the sheet S. Subsequently, the fixing device 7 fixes the toner image to the sheet S by melting the toner image while gripping and transporting the sheet S, and the paper discharge roller 8 discharges the sheet S to the paper discharge tray 9. In the case of double-sided printing, the sheet S on which the toner image is fixed to the first side is sent to the transport path 10 via the inversion transport path 10R, thereby transferring the toner image to the second side.

[0022] [Fusing device] Next, the fixing device 7 will be described in detail. Figure 2 is a cross-sectional view of the fixing device 7. Figure 3 is a perspective view of the fixing device 7. Figure 4 is a perspective view of the fixing device 7 excluding the fixing belt 21. Figure 5 is a perspective view of the heater holder 25.

[0023] The fixing device 7 comprises a rotatable fixing belt 21, a planar heater 23 that contacts the inner circumferential surface of the fixing belt 21 and heats the fixing belt 21, a heater holder 25 that holds the planar heater 23, a support member 24 that supports the heater holder 25, a pressure roller 27 that holds and conveys the sheet S between itself and the fixing belt 21, and a drive unit 28 such as a motor that drives the pressure roller 27. The fixing device 7 is housed in a fixing housing (not shown), and the fixing housing is fixed to the main body housing 3. In this embodiment, an example is shown in which the fixing device 7 is positioned with the pressure roller 27 located below the fixing belt 21, but the fixing device 7 may be positioned in any orientation.

[0024] [Fixing belt] The fixing belt 21 (see Figures 2 and 3) is a cylindrical endless belt with a hollow section extending in the front-to-back direction, and its length in the front-to-back direction is longer than the width of the sheet S. The fixing belt 21 comprises a base layer, an elastic layer provided on the outer circumferential surface of the base layer, and a release layer provided on the outer circumferential surface of the elastic layer (not shown), and is flexible. The base layer is made of a metal such as stainless steel or nickel alloy. The elastic layer is made of silicone rubber or the like. The release layer is made of a PFA (polytetrafluoroethylene perfluoroalkoxyethylene copolymer resin) tube or the like. In some cases, a sliding layer is formed on the inner circumferential surface of the base layer. The sliding layer is made of polyimideamide or PTFE (polytetrafluoroethylene) or the like.

[0025] [Surface heater] The planar heater 23 (see Figure 2) is formed in a generally rectangular plate shape with the front-to-back direction as its longitudinal direction. The planar heater 23 comprises a base material, an insulating layer, a heating layer, and a coating layer. The base material is formed in a generally rectangular plate shape with the front-to-back direction as its longitudinal direction, using an electrically insulating material such as ceramics. The insulating layer is laminated on the lower surface of the base material using an electrically insulating material with low thermal conductivity, such as ceramics or glass. The insulating layer suppresses the transfer of heat generated by the heating layer to the base material. The heating layer is formed on the lower surface of the insulating layer using a conductive material such as a metal with high resistance. The coating layer is formed of an electrically insulating material such as ceramics with low sliding friction resistance to the fixing belt 21. The coating layer covers the heating layer, and the lower surface of the coating layer contacts the inner surface of the fixing belt 21.

[0026] [Heater holder] The heater holder 25 (see Figures 2 and 4) has the same length as the planar heater 23 in the front-to-back direction. The heater holder 25 is made of a heat-resistant resin such as liquid crystal polymer. The lower part of the heater holder 25 is provided with a first recess 251 that is elongated in the front-to-back direction and opens downwards, and the planar heater 23 is housed in the first recess 251. The left and right sides of the heater holder 25 are provided with curved surfaces 253 that have a greater curvature than the fixing belt 21.

[0027] [Support member] A support member 24 (see Figure 2), whose longitudinal direction is in the front-to-back direction, passes through the hollow portion of the fixing belt 21. The support member 24 is made of a metal such as stainless steel or aluminum alloy. The cross-section of the support member 24 perpendicular to the front-to-back direction is U-shaped and opens downwards. The upper part of the heater holder 25 is provided with a second recess 252 that is elongated in the front-to-back direction and opens upwards, and the support member 24 is fitted into the second recess 252. The support member 24 supports the heater holder 25.

[0028] [End belt holder] End belt holders 26 (see Figures 3 and 4) are provided at both the front and rear ends of the support member 24. The end belt holders 26 are supported by the main housing 3 and support the support member 24. The end belt holders 26 have cylindrical belt holding portions 26H. The belt holding portions 26H have an outer diameter corresponding to the inner diameter of the anchoring belt 21, and the belt holding portions 26H are fitted to both the front and rear ends of the anchoring belt 21. The anchoring belt 21 is rotatable along the belt holding portions 26H.

[0029] [Pressure roller] The pressure roller 27 (see Figures 2 to 4) comprises a core metal, an elastic layer provided on the outer surface of the core metal, and a release layer provided on the outer surface of the elastic layer (not shown). The core metal is made of a metal such as stainless steel. The elastic layer is made of silicone rubber or the like. The release layer is made of a PFA tube or the like. The pressure roller 27 is biased toward the fixing belt 21 by a biasing member such as a spring (not shown), thereby sandwiching the fixing belt 21 between itself and the planar heater 23, and forming a nip region N where the fixing belt 21 and the pressure roller 27 are in contact.

[0030] Next, the fixing operation of the fixing device 7 will be described. When the pressure roller 27 is driven and rotates in a predetermined direction, the fixing belt 21 rotates in accordance with the rotation of the pressure roller 27, and the inner surface of the fixing belt 21 slides against the planar heater 23. When power is supplied to the heating layer of the planar heater 23, the heating layer generates heat and the fixing belt 21 is heated. After the fixing belt 21 reaches a predetermined temperature, the sheet S on which the toner has been transferred is transported to the nip area N. In the nip area N, the sheet S is held between the fixing belt 21 and the pressure roller 27 and transported. At this time, the toner is heated and pressurized by the fixing belt 21, and the toner is fixed to the sheet S. The sheet S on which the toner has been fixed is separated from the fixing belt 21 and transported along the transport path 10.

[0031] Next, a configuration to prevent misalignment of the planar heater 23 in the transport direction Y will be described. Figure 6 is a perspective view showing the front end of the heater holder 25. Figure 7 is a perspective view showing the front end of the heater holder 25 with the planar heater 23 and fixing member 30 attached. Figure 8 is a perspective view showing the rear end of the heater holder 25. Figure 9 is a perspective view showing the rear end of the heater holder 25 with the planar heater 23 and fixing member 30 attached. Figures 10 and 11 are perspective views of the fixing member 30. Figure 12 is a cross-sectional view of the heater holder 25 with the planar heater 23 and fixing member 30 attached.

[0032] The fixing device 7 comprises a cylindrical fixing belt 21, a pressure roller 27 that holds and conveys the sheet S between itself and the fixing belt 21, a planar heater 23 whose length in the width direction intersecting the conveying direction Y of the sheet S is longer than that of the fixing belt 21 and which contacts the inner circumferential surface of the fixing belt 21, a heater holder 25 that contacts the second surface 232 of the planar heater 23 opposite to the first surface 231 that contacts the fixing belt 21 and whose length in the width direction is longer than that of the fixing belt 21, and a pair of fixing members 30 that are attached to the heater holder 25, contact both ends of the first surface 231 in the width direction, and sandwich the planar heater 23 between itself and the heater holder 25, the pair of fixing members 30 having a downstream end surface contact portion 32 that contacts the downstream end surface (downstream end surface 23ED) of the planar heater 23 in the conveying direction Y.

[0033] The heater holder 25 is provided with wedge-shaped upstream projections 25U and downstream projections 25D, respectively, on the front and rear sides of the belt holding portion 26H of the end belt holder 26 (see Figures 6 and 8). The upstream projection 25U protrudes from the side surface (left side) on the upstream side in the conveying direction Y of the heater holder 25, and the downstream projection 25D protrudes from the side surface (right side) on the downstream side in the conveying direction Y of the heater holder 25. Upstream in the conveying direction Y of the first recess 251 on the lower surface of the heater holder 25 is provided with an upstream end face opposing portion 254 that faces the upstream end face (upstream end face 23EU, see Figure 12) of the planar heater 23 in the conveying direction Y. Furthermore, a convex portion 255 is provided downstream in the conveying direction Y of the first recess 251 on the lower surface of the heater holder 25.

[0034] The fixing member 30 (see Figures 7, 9 to 12) is a plate-shaped member made of resin, metal, or the like. The fixing member 30 has a main body portion 31 whose longitudinal direction is in the transport direction Y, and both ends of the main body portion 31 in the longitudinal direction are curved upward. The upstream end of the fixing member 30 in the transport direction Y is provided with an upstream mounting portion 31U which is attached to the upstream projection portion 25U of the heater holder 25. The upstream mounting portion 31U is an opening into which the upstream projection portion 25U and the upstream end face opposing portion 254 are inserted. The downstream end of the fixing member 30 in the transport direction Y is provided with a downstream mounting portion 31D which is attached to the downstream projection portion 25D of the heater holder 25. The downstream mounting portion 31D is an opening into which the downstream projection portion 25D is inserted. The fixing member 30 is provided with a hole portion 33 into which a protrusion portion 255 is fitted.

[0035] The upper surface of the main body portion 31 of the fixing member 30 is provided with a downstream end face contact portion 32 that contacts the downstream end face 23ED of the planar heater 23. The downstream end face contact portion 32 has a convex shape with its longitudinal direction in the front-rear direction.

[0036] The planar heater 23 and the fixing member 30 are mounted as follows. First, the planar heater 23 is inserted into the first recess 251 of the heater holder 25. At this time, the second surface 232 of the planar heater 23 contacts the first recess 251. Also, the upstream end face 23EU of the planar heater 23 faces the upstream end face opposing portion 254.

[0037] Next, the fixing member 30 is attached. Specifically, when the fixing member 30 is pushed in by bringing both ends of the fixing member 30 in the transport direction Y into contact with the upstream projection 25U and the downstream projection 25D of the heater holder 25, both ends of the fixing member 30 in the transport direction Y are spread apart. The deformation of the fixing member 30 at this time is elastic deformation, and the deformation of the fixing member 30 returns to its original state when the upstream projection 25U fits into the upstream mounting part 31U and the downstream projection 25D fits into the downstream mounting part 31D. In other words, the fixing member 30 is attached to the heater holder 25 in a snap-fit ​​manner.

[0038] When the fixing member 30 is attached to the heater holder 25, the upper surface of the main body portion 31 of the fixing member 30 contacts the first surface 231 of the planar heater 23, and the planar heater 23 is sandwiched between the first recess 251 of the heater holder 25 and the fixing member 30. In this way, the planar heater 23 is fixed in the vertical direction (the direction of pressure applied by the pressure roller 27).

[0039] When the fixing belt 21 is driven, the fixing belt 21 slides against the planar heater 23 in the transport direction Y, so the planar heater 23 is subjected to frictional force in the transport direction Y. However, since the downstream end face 23ED of the planar heater 23 is in contact with the downstream end face contact portion 32 of the fixing member 30, no displacement of the planar heater 23 in the transport direction Y occurs.

[0040] As described above, the fixing device 7 according to this embodiment includes a cylindrical fixing belt 21, a pressure roller 27 that holds and conveys a sheet S between itself and the fixing belt 21, a planar heater 23 whose length in the width direction intersecting the conveying direction Y of the sheet S is longer than that of the fixing belt 21 and which contacts the inner circumferential surface of the fixing belt 21, a heater holder 25 that contacts the second surface 232 opposite to the first surface 231 of the planar heater 23 that contacts the fixing belt 21 and whose length in the width direction is longer than that of the fixing belt 21, and a pair of fixing members 30 that are attached to the heater holder 25, contact both ends of the first surface 231 in the width direction, and sandwich the planar heater 23 between itself and the heater holder 25, the pair of fixing members 30 having a downstream end surface contact portion 32 that contacts the downstream end surface (downstream end surface 23ED) of the planar heater 23 in the conveying direction Y. With this configuration, it is possible to prevent the planar heater 23 from shifting in the sheet conveying direction Y without bonding the planar heater 23.

[0041] Furthermore, according to the fixing device 7 of this embodiment, the heater holder 25 is provided with an upstream end face facing portion 254 that faces the upstream end face (upstream end face 23EU) of the planar heater 23 in the transport direction Y, so that the positioning of the planar heater 23 in the transport direction Y during assembly can be easily performed.

[0042] The above embodiment may be modified as follows.

[0043] In the above embodiment, an example is shown in which the heater holder 25 is provided with an upstream end face opposing portion 254. However, instead of the upstream end face opposing portion 254, the fixing member 30 may be provided with an upstream end face opposing portion (not shown) that faces the upstream end face 23EU of the planar heater 23. This configuration also makes it easy to position the planar heater 23 in the transport direction Y during assembly.

[0044] In addition to the configuration of the above embodiment, the heater holder 25 may include a first end face facing portion 256 that faces the first end face 23E1 in the width direction of the planar heater 23, and the fixing member 30 on the side of the second end face 23E2 in the width direction of the planar heater 23 of the pair of fixing members 30 may include a second end face facing portion 34 that faces the second end face 23E2. As an example, Figures 8 and 9 show that the heater holder 25 is provided with a first end face facing portion 256 that faces the rear end face (first end face 23E1) of the planar heater 23.

[0045] On the other hand, Figure 13 shows the second end face opposing portion 34. In this example, the second end face opposing portion 34 is provided on the front fixing member 30. The second end face opposing portion 34 is provided slightly above the center in the vertical direction of the fixing member 30 and is located forward, with a hook-shaped tip facing the front end face (second end face 23E2) of the planar heater 23. With this configuration, the widthwise positioning of the planar heater 23 during assembly can be easily performed.

[0046] Instead of the first end face opposing portion 256, the fixing member 30 on the first end face 23E1 side may be provided with a first end face opposing portion (not shown) that faces the first end face 23E1. This configuration also makes it easy to position the planar heater 23 in the width direction during assembly.

[0047] Next, the planar heater 23, which includes the electrode portion 23x, will be described with reference to Figures 14 to 16. Figure 14 is a perspective view showing the front end of the heater holder 25 to which the planar heater 23 is supported, Figure 15 is a perspective view showing the fixing member 30, and Figure 16 is a perspective view showing the front end of the heater holder 25 to which the planar heater 23 is attached by the fixing member 30.

[0048] As shown in Figure 14, a rectangular electrode portion 23x is provided at one end (front end) in the width direction of the first surface of the planar heater 23. The electrode portion 23x is electrically connected to a power supply (not shown) provided in the image forming apparatus 1 via a connector 50, which will be described later. A power supply portion 23y extends from the electrode portion 23x, and power supply lines connecting each heating element of the planar heater 23 to the electrode portion 23x are arranged therein. The current supplied from the power supply to the electrode portion 23x via the connector 50 is supplied to each heating element via the power supply portion 23y. When the planar heater 23 is supported in the first recess 251 of the heater holder 25, the electrode portion 23x is positioned outside (front) of the upstream end face opposing portion 254 and the protrusion 255 of the heater holder 25. The portion of the heater holder 25 outside (front) of the upstream end face opposing portion 254 and the protrusion 255 is the front end of the heater holder 25.

[0049] Furthermore, on the front end of the heater holder 25, a guide projection 261 is formed along the transport direction Y on the surface opposite to the surface where the first recess 251 is provided (hereinafter referred to as the bottom surface) (hereinafter referred to as the top surface).

[0050] Referring to Figure 15, the fixing member 30 will be described. The fixing member 30 has a main body portion 31 and an electrode protection portion 35 provided integrally with the main body portion 31. The main body portion 31 has the same configuration as in the embodiment described above. The electrode protection portion 35 is provided integrally with the main body portion 31 along the front side edge of the main body portion 31. The electrode protection portion 35 is formed in a rectangular shape having dimensions corresponding to the electrode portion 23x of the planar heater 23 and a thickness that allows it to be fitted into the first recess 251 of the heater holder 25. The electrode protection portion 35 has a substantially rectangular opening 37 that exposes a part of the electrode portion 23x of the planar heater 23. An inclined portion 39 is provided around the opening 37, which slopes toward the opening 37. In other words, the inclined portion 39 is formed so that its thickness gradually decreases toward the opening 37.

[0051] As shown in Figure 16, the planar heater 23 is supported in the first recess 251 of the heater holder 25, and when the planar heater 23 is attached to the heater holder 25 by the main body 31 of the fixing member 30, the electrode protection portion 35 of the fixing member 30 is fitted into the first recess 251 and contacts the first surface of the planar heater 23. As a result, the electrode portion 23x is covered by the electrode protection portion 35, and a part of the electrode portion 23x is exposed through the opening 37.

[0052] Next, the connector 50 will be described with reference to Figure 17. Figure 17 is a perspective view showing the connector 50.

[0053] The connector 50 has a rectangular parallelepiped body 51 and a lever portion 53 that is elastically deformable and connected to the body 51. A recess 55 is formed in the body 51 from one end face 51a along the longitudinal direction of the body 51. Two terminals 57 are supported on each of the opposing sides of the recess 55. Each terminal 57 is an arc-shaped leaf spring member along the longitudinal direction and is elastically deformable into a flat shape when pressed. Each terminal 57 is connected to a power source via wiring (not shown). Furthermore, a groove 59 is formed on the opposing sides of the recess 55 from the end face 51a along the longitudinal direction.

[0054] Next, with reference to Figures 18A to 18C, the process of connecting the connector 50 to the planar heater 23 mounted on the heater holder 25 will be described. Figures 18A to 18C are cross-sectional views showing the planar heater 23, heater holder 25, and connector 50 during the process of connecting the connector 50 to the planar heater 23 mounted on the heater holder 25.

[0055] First, one end face 51a (the opening of the recess 55) of the main body 51 of the connector 50 is positioned facing the front end of the heater holder 25 from the downstream side in the transport direction Y. Then, the guide projection 261 (see Figure 16) formed on the front end of the heater holder 25 is engaged with the groove 59 (see Figure 17) formed on one side of the recess 55 of the connector 50, and the connector 50 is moved upstream in the transport direction Y. The connector 50 is guided upstream in the transport direction Y along the guide projection 261, and the front end of the heater holder 25 begins to be inserted into the recess 55 of the connector 50, as shown in Figure 18A.

[0056] As the connector 50 is moved further, as shown in Figure 18B, the terminals 57 supported on both sides of the recess 55 are pressed in by the front end of the heater holder 25, and each is elastically deformed into a flat shape. Specifically, the terminal 57 supported on the upper side of the recess 55 is pressed in by the upper surface of the front end of the heater holder 25, and the terminal 57 supported on the lower side of the recess 55 is pressed in by the lower surface of the front end of the heater holder 25 and the electrode protection portion 35 of the fixing member 30.

[0057] As the connector 50 is moved further, the terminal 57 of the connector 50 reaches the inclined portion 39 of the electrode protection portion 35 on the lower surface of the front end of the heater holder 25. Since the inclined portion 39 is formed to become thinner toward the opening 37, the terminal 57 gradually begins to elastically return to its original position. Then, as shown in Figure 18C, when the front end of the heater holder 25 is fully inserted into the recess 55 of the connector 50, the terminal 57 of the connector 50 reaches the electrode portion 23x of the planar heater 23 from the opening 37 of the electrode protection portion 35, elastically returns to its original position, and contacts the electrode portion 23x with a predetermined pressure.

[0058] As described above, when the connector 50 is attached to the heater holder 25, the terminal 57 of the connector 50 moves along the electrode protection portion 35 of the fixing member 30 to the electrode portion 23x, so that the electrode portion 23x does not come into contact with the terminal 57 during movement. In this way, the electrode portion 23x is not scraped by the terminal 57 when attaching or detaching the connector 50, so wear on the electrode portion 23x is suppressed and the current supplied to the electrode portion 23x can be reliably supplied to the heating portion of the planar heater 23.

[0059] Note that the mounting direction of the connector 50 is not limited to the transport direction Y, but may also be in a direction intersecting the transport direction Y. In this case as well, since the area around the electrode portion 23x is covered by the electrode protection portion 35, the electrode portion 23x does not come into contact with the terminal 57 when the connector 50 is mounted. [Explanation of symbols]

[0060] 1. Printer (image forming apparatus) 7. Fixing device 21 Fixing belt 23 Planar heater 231 Page 1 232 2nd page 23EU Upstream end face 23ED Downstream end face 23E1 1st end face 23E2 2nd end face 23x electrode section 25 Heater holder 254 Upstream end face opposing section 256 First end face opposing portion 27 Pressure roller 30 Fixing member 31 Main body 32 Downstream end contact part 34. Second end face facing portion 35 Electrode protection part 37 Aperture 39 Slope 50 connectors

Claims

1. A cylindrical fixing belt, A pressure roller that holds and conveys the sheet between itself and the aforementioned fixing belt, A planar heater having a length in the width direction intersecting the conveying direction of the sheet longer than the fixing belt, and having a first surface that contacts the inner circumferential surface of the fixing belt and a second surface opposite to the first surface, A heater holder that contacts the second surface of the planar heater and whose length in the width direction is longer than the fixing belt, The heater holder is equipped with a pair of fixing members that contact both ends in the width direction of the first surface of the planar heater and sandwich the planar heater between themselves and the heater holder. The fixing device is characterized in that the pair of fixing members includes a downstream end face contact portion that contacts the downstream end face of the planar heater in the conveying direction.

2. The fixing device according to claim 1, characterized in that the pair of fixing members are attached to the heater holder by snap-fit ​​coupling on the upstream and downstream sides of the planar heater in the conveying direction.

3. The fixing device according to claim 1, characterized in that the heater holder has an upstream end face facing portion that faces the upstream end face of the planar heater in the conveying direction.

4. The fixing device according to claim 3, characterized in that the upstream end face opposing portion is inserted into the opening of the pair of fixing members.

5. The fixing device according to claim 1, characterized in that the pair of fixing members includes an upstream end face facing portion that faces the upstream end face of the planar heater in the conveying direction.

6. The heater holder comprises a first end face facing portion that faces the first end face in the width direction of the planar heater, The fixing device according to claim 1, characterized in that the fixing member on the second end face side in the width direction of the planar heater, of the pair of fixing members, has a second end face facing portion that faces the second end face.

7. Of the pair of fixing members, the fixing member on the first end face side in the width direction of the planar heater is provided with a first end face facing portion that faces the first end face, The fixing device according to claim 1, characterized in that the fixing member on the second end face side in the width direction of the planar heater, of the pair of fixing members, has a second end face facing portion that faces the second end face.

8. The heater holder is mounted along a predetermined mounting direction and further comprises a connector that can communicate electrically with the electrode portion of the planar heater, The fixing device according to claim 1, characterized in that one of the pair of fixing members is provided with an electrode protection portion that covers the planar heater upstream of the electrode portion in the connector mounting direction.

9. The fixing device according to claim 8, characterized in that the electrode protection portion has an opening that exposes the electrode portion and an inclined portion provided around the opening so as to be inclined toward the opening.

10. An imaging apparatus for forming a toner image on the sheet, An image forming apparatus comprising a fixing device according to claim 1 for fixing the toner image onto the sheet.

Images