JP5857685B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device and an image forming apparatus, and more particularly to a technique for preventing damage to a fixing belt in a resistance heating element type fixing device.

In recent years, a resistance heating element type fixing device has attracted attention as a fixing device that can save energy with a simple device configuration.
In the resistance heating element type fixing device, if the power supply is intermittently interrupted due to poor contact with the resistance heating element of the power supply brush that is in sliding contact with the resistance heating element and supplies power to the resistance heating element, the resistance heating element The amount of heat generated fluctuates, resulting in poor fixing. For example, as shown in FIG. 7, the backing member having a C-shaped cross section is brought into contact with the inner peripheral surface of the fixing belt, and the backing member of the fixing belt is not in contact with the problem. The pressure roller is pressed against the inner peripheral surface while being urged.

  At a position facing the pressing roller across the fixing belt, a power supply brush is disposed so as to be in contact with an electrode provided on the outer peripheral surface of the fixing belt. Further, the pressure roller is brought into pressure contact with the fixing belt so as to face the backing member. In this way, the power supply brush can be reliably brought into contact with the electrode, so that the power supply can be stabilized and fixing failure can be prevented (see Patent Document 1).

JP-A-9-16013

However, in the fixing device according to the above-described prior art, since the backing member and the pressing roller are in contact with the fixing belt over the entire length in the rotation axis direction of the fixing belt, the heat of the fixing belt Escape to the pressure roller. For this reason, there is a problem that heat loss is large and warm-up time is long.
The present invention has been made in view of the above-described problems, and is a resistance heating element type fixing device and image forming capable of performing stable power supply over a long period of time while suppressing a decrease in thermal efficiency. An object is to provide an apparatus.

In order to achieve the above object, a fixing device according to the present invention includes a fixing nip formed by pressing a pressing member against an outer peripheral surface of an endless fixing belt having a resistance heating element layer that generates heat when energized. A fixing device for fixing a toner image by passing a recording sheet, wherein the pressing member is provided at a position facing the pressure member inside the fixing belt and supports the fixing belt at the fixing nip position. A pair of annular members that are rotatably supported together with the fixing belt, and are fitted outside the pressing members in the rotational axis direction of the fixing belt, and are fitted in openings at both ends of the fixing belt, and at least a pair of power supply members When brought into contact with the outer peripheral surface of the annular member, and a plurality of support rollers for supporting the annular member by a driven rotating in the annular member, The fixing belt is provided with a pair of electrode portions on the outer peripheral surfaces of both ends, and the pair of power supply members are opposed to the annular members from the outer peripheral surface side of the fixing belt at positions facing the pair of annular members, respectively. Urged and arranged to feed power from the pair of electrode portions to the resistance heating element layer, and the rotation center of the annular member has a position where the plurality of support rollers contact the annular member, and the feeding member Is located inside a polygon connecting positions where the fixing belt contacts the fixing belt .

  In this way, the electrical contact between the power supply member and the fixing belt is stabilized by urging the power supply member against the annular member that contacts the inner peripheral surface of the fixing belt only at the end portion of the fixing belt. Therefore, it is possible to suppress heat loss due to heat conduction from the fixing belt to the annular member and to prevent uneven fixing. Further, instability of power feeding due to wear of the power feeding member or the like can be suppressed.

Note that the fitting of the annular member to the opening at both ends of the fixing belt means that the annular member is fitted to the fixing belt so that the inner peripheral surface of the fixing belt is pressed against the outer peripheral surface of the annular member at the end of the fixing belt. Say.
In this case, the fixing belt may be fixedly disposed inside and may include a supporting member that supports the pressing member, or may be supported by the supporting member and disposed at the center of rotation of the annular member. An interposition member interposed between the support member and the annular member and rotatably supporting the annular member may be provided.

Further, the toner image is fixed by passing a recording sheet through a fixing nip formed by pressing a pressing member against the outer peripheral surface of an endless fixing belt having a resistance heating element layer that generates heat when energized. A fixing device provided at a position facing the pressure member inside the fixing belt, and a pressing member that supports the fixing belt at the fixing nip position, and is rotatably supported together with the fixing belt; Outside the pressing member in the direction of the rotation axis of the fixing belt, at a position where the pair of annular members fitted in the openings at both ends of the fixing belt, at least a pair of power supply members, and the annular member are fitted. wherein the outer peripheral surface of the fixing belt in contact, and a plurality of support rollers for supporting the annular member by a driven rotating the fixing belt The fixing belt unit pair of electrodes provided on the outer circumferential surface of both end portions, the pair of power supply members with respect to the annular member from the outer peripheral surface of the fixing belt at a position opposed to each of the pair of annular members The resistance heating element layer is fed from the pair of electrode portions, and the center of rotation of the annular member is a position where the plurality of support rollers and the feeding member abut against the fixing belt. It may be located inside the connected polygon. In any case, the effect of the present invention is not changed.

Further, at least one of the pair of annular members is provided with a drive transmission gear, the roller-shaped pressurizing member is driven to rotate, and the annular member is driven to rotate via the drive transmission gear. Thus, if the fixing belt rotates, slip between the fixing belt and the pressure member can be prevented.
An image forming apparatus according to the present invention includes the fixing device according to the present invention. Therefore, the fixing device according to the present invention has the above-described effects.

1 is a diagram illustrating a main configuration of an image forming apparatus according to the present invention. 2A and 2B are cross-sectional perspective views illustrating the main configuration of the fixing device 100, where FIG. 1A illustrates a cross-section including a rotation axis of the fixing belt, and FIG. 2B illustrates a cross-section perpendicular to the rotation axis of the fixing belt. 2 is a cross-sectional view illustrating a layer configuration of a fixing belt 200. FIG. It is a figure which shows the cross-sectional shape of the press pad 220. FIG. FIG. 9 is a cross-sectional perspective view showing a main configuration of a fixing device 100 according to a modified example of the present invention, where (a) shows a cross section including a rotation shaft of the fixing belt 200, and (b) shows a rotation shaft of the fixing belt 200. A vertical section is shown. FIG. 9 is a cross-sectional perspective view showing a main configuration of a fixing device 100 according to a modified example of the present invention, where (a) shows a cross section including a rotation shaft of the fixing belt 200, and (b) shows a rotation shaft of the fixing belt 200. A vertical section is shown. It is an external appearance perspective view which shows the main structures of the fixing device of the resistance heating element system which concerns on a prior art.

Hereinafter, embodiments of a fixing device and an image forming apparatus according to the present invention will be described with reference to the drawings.
[1] Configuration of Image Forming Apparatus First, the configuration of the image forming apparatus according to the present invention will be described.
FIG. 1 is a diagram showing a main configuration of an image forming apparatus according to the present invention. The image forming apparatus 1 is a so-called intermediate transfer type color image forming apparatus, and includes image forming units 101Y to 101K as shown in FIG. Each of the image forming units 101Y to 101K has the same configuration, and the outer peripheral surface of the cylindrical photosensitive drum 102 is uniformly charged by the charging device 103 to obtain a predetermined potential, and then the charged region is charged. The exposure device 104 performs image exposure according to the document image, and forms an electrostatic latent image.

  The developing device 105 develops the electrostatic latent image by supplying each color toner of YMCK supplied from the toner cartridges 108Y to 108K onto the outer peripheral surface of the photosensitive drum 102 by the developing roller 105a to which a developing bias is applied. A visible toner image is obtained. A primary transfer voltage is applied to the primary transfer roller 106, and a visible toner image is primarily transferred from the outer peripheral surface of the photosensitive drum 102 onto the intermediate transfer belt 110 by electrostatically adsorbing toner. After the primary transfer of the visible toner image onto the intermediate transfer belt 110, the toner remaining on the outer peripheral surface of the photosensitive drum 102 is removed by the cleaning device 107.

  The intermediate transfer belt 110 is stretched between a secondary transfer counter roller 111 and a driven roller 112, and is driven in the direction of arrow A by being driven and rotated by the secondary transfer counter roller 111 rotated by a drive source (not shown). While rotating, toner images of each color of YMCK are sequentially primary-transferred. The driven roller 112 is driven to rotate by a frictional force with the intermediate transfer belt 110 that rotates.

  In parallel with the above, in the paper feed cassette 120 containing the recording sheet S, the recording sheet S is sent out one by one by the pickup roller 121, and the secondary transfer counter roller 111 and the secondary transfer roller 113 form 2. It is conveyed to the next transfer nip. A secondary transfer bias is applied to the secondary transfer roller 113, and the toner image carried on the intermediate transfer belt 110 is electrostatically transferred to the recording sheet S in the secondary transfer nip.

The recording sheet S carrying the toner image is conveyed to the resistance heating element type fixing device 100, where the toner image is thermally fixed. Thereafter, the recording sheet S is discharged onto the paper discharge tray 131 by the paper discharge roller 130. On the other hand, the toner remaining on the intermediate transfer belt 110 after the secondary transfer is conveyed in the direction of arrow A and then removed by the cleaning device 109.
[2] Configuration of Fixing Device 100 Next, the configuration of the fixing device 100 will be described.

  2A and 2B are cross-sectional perspective views showing the main configuration of the fixing device 100, wherein FIG. 2A shows a cross section including the rotation axis of the fixing belt, and FIG. 2B shows a cross section perpendicular to the rotation axis of the fixing belt. . As shown in FIG. 1, the fixing device 100 includes an endless fixing belt 200 having a resistance heating element layer, a pressure roller 210 that presses against the fixing belt 200 to form a fixing nip, and pressure is applied via the fixing belt 200. A pressing pad 220 that faces the roller 210 and a housing 230 that houses these members are provided.

  FIG. 3 is a cross-sectional view showing the layer configuration of the fixing belt 200. As shown in FIG. 3, the fixing belt 200 has a configuration in which a resistance heating element layer 300, a reinforcing layer 301, an elastic layer 302, a release layer 303, and an electrode portion 203 are sequentially stacked from the inner periphery side. The portion 203 is electrically connected to the resistance heating element layer 300 so as to cover an end portion of the fixing belt 200 in the rotation axis direction. The resistance heating element layer 300 is adjusted to a predetermined electrical resistivity by dispersing a conductive filler in a resin. Polyimide (PI), polyphenylene sulfide (PPS), and polyether ether ketone (PEEK) may be used as the resin material, and the polyimide having the highest heat resistance is used. desirable.

  Conductive fillers include powders of metals such as silver (Ag), copper (Cu), aluminum (Al), magnesium (Mg), nickel (Ni), carbon such as graphite, carbon black, carbon nanofibers, and carbon nanotubes. It is desirable to use compound powders and high ionic conductor powders of inorganic compounds such as silver iodide (AgI) and copper iodide (CuI), and two or more kinds of them may be mixed and dispersed.

  The conductive filler is preferably in the form of a fiber in order to increase the contact probability between fillers with a small content and facilitate percolation. Carbon compounds and high ionic conductors have a negative temperature coefficient (NTC) in which the volume resistivity decreases as the temperature increases, and are used to impart NTC characteristics to the resistance heating element layer 300. . In particular, the high ionic conductor is useful because it does not lower the mechanical strength of the resistance heating element layer 300.

  However, with only a carbon compound or a high ion conductor, the electric resistivity of the resistance heating element layer 300 is adjusted so that the power consumption of the fixing device is within a range of about 500 [W] to 1500 [W] with a commercial power source. Therefore, it is desirable to adjust the electrical resistivity by using metal fine particles together. As the metal fine particles, needle-shaped or flake-shaped silver or nickel is preferably used, and the particle diameter is preferably in the range of 0.01 [μm] to 10 [μm]. In this way, it is possible to obtain the resistance heating element layer 300 having a uniform volume resistivity by being intertwined linearly with the carbon compound or the high ionic conductor.

  The conductive filler to be dispersed in the heat-resistant resin should be within the range of 50 [wt%] to 300 [wt%] of the metal fine particles with respect to the weight of the heat-resistant resin, and the carbon compound and the high ionic conductor [ It is preferably in the range of 5 wt%] to 100 [wt%]. If the conductive filler is too much, the electrical resistivity is too low to be used, and if it is too low, the electrical resistivity is too high to be used.

The thickness of the resistance heating element layer 300 is arbitrary, but is preferably in the range of 5 [μm] to 100 [μm]. The electrical resistivity of the resistance heating element layer 300 should be set according to the applied voltage and power consumption, the thickness of the resistance heating element layer 300, the outer diameter of the fixing belt 200, the length in the axial direction, and the like. It is good to set it within the range from 1.0 × 10 ⁻⁶ [Ω · m] to 1.0 × 10 ⁻² [Ω · m], more preferably from 1.0 × 10 ⁻⁵ [Ω · m]. It is preferably 5.0 × 10 ⁻³ [Ω · m].

In order to adjust the electrical resistivity of the resistance heating element layer 300, conductive particles such as a metal alloy or an intermetallic compound may be appropriately dispersed. Further, in order to improve the mechanical strength of the resistance heating element layer 300, glass fibers, whiskers (single crystal fibers), titanium oxide (TiO ₂ ) fibers, potassium titanate (K ₂ O · nTiO ₂ ) fibers, etc. are dispersed. You may let them. Furthermore, in order to improve the thermal conductivity of the resistance heating element layer 300, aluminum nitride (AlN), aluminum oxide (alumina: Al ₂ O ₃ ), or the like may be dispersed.

  In consideration of manufacturing stability of the resistance heating element layer 300, an imidizing agent, a coupling agent, a surfactant, or an antifoaming agent may be used. The resistance heating element layer 300 is formed on a polyimide varnish obtained by polymerizing an aromatic tetracarboxylic dianhydride and an aromatic diamine in an organic solvent as described above. It is manufactured by uniformly dispersing a conductive filler, applying it to a mold, and performing imide conversion.

  Instead of the above, a thin metal layer may be formed as the resistance heating element layer 300. The material constituting the metal layer of the thin film should desirably have a low temperature coefficient of volume resistivity (or conductivity), such as stainless steel (SUS), nichrome (Ni-Cr), titanium (Ti), etc. It is good to use. The metal thin film layer can be formed by performing plating, sputtering, vapor deposition or the like on the resin material. In addition, prior to forming the metal thin film layer on the resin material, if the surface of the resin material is previously subjected to acid activation treatment such as etching, catalyst treatment with palladium, blast polishing treatment, plasma treatment, etc., the resin material And the adhesion strength between the metal thin film layer can be increased.

  The release layer 303 of the fixing belt 200 is made of fluorine such as perfluoroalkoxy (PFA), polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene (ETFE), or the like. The structure which gave the mold release property, such as a tube and a fluorine-type coating, is desirable, and may have electroconductivity. The thickness is arbitrary, but is preferably in the range of 5 [μm] to 100 [μm]. As the fluorine-based tube, for example, PFA350-J, 451HP-J, 951HP Plus manufactured by Mitsui DuPont Fluorochemical Co., Ltd. can be used. The contact angle between the release layer 303 and water is preferably 90 degrees or more, and preferably 110 degrees or more. Further, the surface roughness of the release layer 303 is desirably within a range of Ra: 0.01 [μm] to about 50 [μm].

  The reinforcing layer 301 is made of a resin such as polyimide or polyphenylene sulfide, and reinforces the fixing belt 200 and electrically insulates it. The elastic layer 302 is made of silicone rubber, fluorine rubber, or the like. The fixing belt 200 needs to include at least the resistance heating layer 300 and the release layer 303, and other layers may be added according to the application. The resistance heating element layer 300 may be provided on the inner peripheral side of the release layer 303, and it does not matter whether another layer is interposed between the resistance heating element layer 300 and the release layer 303.

  The pressure roller 210 is in pressure contact with the fixing belt 200 and is rotationally driven by a drive source (not shown). The pressure roller 210 is obtained by sequentially laminating an elastic layer and a release layer on the outer peripheral surface of the cored bar 210a. The outer diameter of the pressure roller 210 is arbitrary, but is preferably in the range of 20 [mm] to 100 [mm]. As with the release layer 303 of the fixing belt 200, the release layer of the pressure roller 210 preferably has a configuration provided with release properties such as PFA and PTFE fluorine-based tubes and fluorine-based coatings, and has conductivity. May be. The thickness of the release layer may be, for example, in the range from 5 [μm] to 100 [μm].

  The elastic layer is preferably made of a material having high heat resistance such as silicone rubber or fluorine rubber, and the thickness may be in the range of 1 [mm] to 20 [mm]. The cored bar 210a has a pipe shape with a thickness in the range of 0.1 [mm] to 10 [mm], and is made of a material such as aluminum or iron (Fe). The cored bar 210a may have a solid columnar shape or a cross-shaped arrow shape in addition to a pipe shape.

  On the inner side of the fixing belt 200, a pressing pad 220 that forms a fixing nip by being pressed against the pressure roller 210 with the fixing belt 200 interposed therebetween is fixedly disposed. The pressing pad 220 is made of rigid resin or rubber. When the pressing pad 220 is made of rubber, a sliding member having a low friction coefficient may be disposed at a location in contact with the fixing belt 200 in order to reduce the frictional resistance with the fixing belt 200. The pressing pad 220 is supported by a high-strength shaft 221 in order to suppress deformation (bending) due to nip pressure. The shaft 221 has a structure in which the cylindrical portion 221b is fitted to the prismatic portion 221a so as not to rotate. The pressing pad 220 is fixedly supported by the prismatic part 221a, and the cylindrical part 221b of the shaft 221 is fixed to the housing 230 so as not to rotate.

  FIG. 4 is a diagram illustrating a cross-sectional shape of the pressing pad 220. As shown in FIG. 4, at both ends in the rotation axis direction of the fixing belt 200, the pressing pad 220 has a cross-sectional shape 220 a that protrudes toward the pressure roller 210, and protrudes as it approaches the fixing nip. The amount is reduced to a flat cross-sectional shape 220b, and then a recessed cross-sectional shape 220c is taken at the fixing nip portion.

  The radius of curvature of the curved portion of the cross section of the pressure pad 220 gradually increases from the cross sectional shape 220a to the cross sectional shape 220b. Specifically, the cross-sectional shape 220a is substantially the same as the radius of curvature of the inner peripheral surface of the fixing belt 200, and the radius of curvature increases as the cross-sectional shape 220b is approached. The cross-sectional shape 220b is a position where the radius of curvature is infinite, that is, a position where the side in contact with the fixing belt 200 is a straight line. If the width W of the pressing pad 220 is within the range of 340 [mm] to 345 [mm], the distance D from the cross-sectional shape 220a to the cross-sectional shape 220c through the cross-sectional shape 220b is 10 [mm] to 50 [mm]. It is desirable to be within the range up to [mm].

  Further, the radius of curvature increases so as to be 30% or more of the radius of curvature of the pressure roller 210 between the cross-sectional shape 220c and the cross-sectional shape 220b. The pressing pad 220 has rigidity, and the fixing belt 220 rotates along the curved shape of the pressing pad 220 in the fixing nip. The pressure roller 210 rotates while elastically deforming its elastic layer in accordance with the curved shape of the pressing pad 220.

  The fixing belt 200 is driven and rotated by the frictional force between the fixing roller 200 and the fixing belt 200 and the pressing roller 210 when the frictional force between the inner peripheral surface of the fixing belt 200 and the pressing pad 220 is large. There is a risk of slippage between the two and rotation failure. In order to prevent such rotation failure, belt driving gears 201 are fitted on both ends of the fixing roller 200 in the rotation axis direction. When the rotation failure of the fixing belt 200 occurs, the fixing belt 200 is rotationally driven by the belt driving gear 201, and returns from the rotation failure.

  The belt drive gear 201 is rotatably supported on the shaft 221 via a bearing 202. As described above, the shaft 221 has a structure in which the cylindrical portion 221b is fitted to the prismatic portion 221a. The belt drive gear 201 includes a boss portion 201 a surrounded by the fixing belt 200 and a flange portion 201 b positioned outside the fixing belt 200. The inner peripheral side of the flange portion 201 b of the belt drive gear 201 is supported by the cylindrical portion 221 b of the shaft 221 via the bearing 202, while the outer peripheral side of the flange portion 201 b is a gear and is supported by the shaft 232. The gear 231 is engaged. The shaft 232 is also supported on the housing 230 via a bearing 233.

  The gear 231 is a driving source (not shown) so that the rotational speed of the fixing belt 200 by the gear 231 via the belt driving gear 201 is slightly slower than the rotational speed of the fixing belt 200 by the pressure roller 210. It is driven by rotation. In addition, a torque limiter is interposed on the path for transmitting the rotational driving force from the driving source to the gear 231, and when no rotation failure occurs in the rotational driving of the fixing belt 200 by the pressure roller 210, The torque limiter idles and cuts off the transmission of rotational driving force. When a rotation failure occurs, the rotational driving force is transmitted to the gear 231 to rotate the fixing belt 200.

  On the outer peripheral surface in the vicinity of both end portions in the rotation axis direction of the fixing belt 200, electrode portions 203 are provided over the entire circumference. By causing a current to flow between the electrode portion 203 provided on one end side and the electrode portion 203 provided on the other end side, a current is caused to flow in the resistance heating element layer 300 of the fixing belt 200, and the resistance heating element layer 300. Generates heat. The electrode portion 203 is spaced from the pressing pad 220 in the direction of the rotation axis, and is disposed at a position facing the boss portion 201a of the belt drive gear 201.

  It is desirable to use a material having uniform electrical characteristics in the circumferential direction of the fixing belt 200 for the conductor used for the electrode part 203, and chemical plating or electroplating of metals such as copper, aluminum, nickel, brass and phosphor copper. Is formed on the inner peripheral surface of the fixing belt 200. In the case where the electrode portion 203 is directly formed on the resistance heating element layer 300, it is preferable to first perform chemical plating and then perform electroplating.

  As the conductor material, copper and nickel are particularly preferable, and it is even better if nickel is plated on copper. In addition to plating, copper foil or nickel foil may be adhered to the resistance heating element layer 300 with a conductive adhesive, or conductive ink or conductive paste may be applied to form the electrode portion 203. Further, when the resistance heating element layer 300 is formed in a mold, the ring-shaped electrode portion 203 may be attached to the mold and integrally formed.

  Power supply to the electrode unit 203 is performed by bringing the power supply member 204 into contact with the electrode unit 203. In addition, the power supply member 204 is supplied with power via a wire 207 from a power supply device (not shown). The power supply member 204 is held by a holding plate 205 so as to be movable in the radial direction of the fixing belt 200, and is urged toward the electrode portion 203 by a urging member 206. As the urging member 206, for example, an elastic member may be used, and a coil spring may be used. Further, as the power supply member 204, for example, a carbon brush can be used. The shape of the power supply member 204 is arbitrary, and may be slid with the fixing belt 200 or may be a rotating body that rotates following the rotation of the fixing belt 200.

  With the above configuration, the distribution of the current flowing through the resistance heating element layer 300 of the fixing belt 200 can be made uniform and the heat generation distribution can be made uniform, so that uneven fixing can be prevented. Further, even when the resistance heating element layer 300 is an intermediate layer of the fixing belt 200 and is not exposed to the inner peripheral surface side of the fixing belt 200, the electrode portion 203 is disposed so as to be exposed. Thus, power can be supplied without requiring a complicated configuration.

  In the direction of the rotation axis of the fixing belt 200, the pressure roller 210 is shorter than the pressure pad 220, and the pressure roller 210 faces the pressure pad 220 over the entire area in the direction of the rotation axis. Therefore, the press pad 220 extends from the pressure roller 210 to the end at any end in the rotation axis direction of the fixing belt 200. By adopting such a configuration, the pressing pad 220 receives the pressure contact force of the pressure roller 210 over the entire region of the pressure roller 210 in the rotation axis direction, so that local deformation of the fixing belt 200 is eliminated, The durability of the fixing device 100 can be improved.

Further, since the belt driving gear 201 contacts the fixing belt 200 only at the end portion in the rotation axis direction of the fixing belt 200, heat loss is reduced as compared with the case where the belt driving gear 201 contacts the fixing belt 200 over the entire length in the rotation axis direction. Can be small. Therefore, it is possible to suppress the influence of heat loss on the warm-up time.
Further, the biasing member 206 urges the electrode portion 203 provided on the outer peripheral surface side where the boss portion 201 a of the belt driving gear 201 is fitted on the inner peripheral surface side of the fixing belt 200. Since the power supply member 204 is brought into contact with the power supply member 204, it is possible to prevent a fixing failure caused by a contact failure between the electrode portion 203 and the power supply member 204.

[3] Modifications As described above, the present invention has been described based on the embodiments. However, the present invention is not limited to the above-described embodiments, and the following modifications can be implemented. .
(1) In the above-described embodiment, the case where the belt driving gear 201 is supported by the shaft 221 via the bearing 202 has been described. However, it is needless to say that the present invention is not limited thereto. Anyway.

  5A and 5B are cross-sectional perspective views showing the main configuration of the fixing device 100 according to this modification. FIG. 5A shows a cross-section including the rotation shaft of the fixing belt 200, and FIG. 5B shows the rotation of the fixing belt 200. A cross section perpendicular to the axis is shown. In addition, the same code | symbol is attached | subjected to the member with a corresponding member in FIG. As shown in FIG. 5A, in the fixing device 100 according to this modification, the belt drive gear 201 is no longer supported by the shaft 221, and instead shown in FIG. 5B. As shown, the two gears 231 and the power feeding member 206 are supported. Even in this case, the belt driving gear 201 can be supported and the power supply member 206 can be reliably brought into contact with the electrode portion 203. Further, since the area where the belt drive gear 201 contacts the fixing belt 200 is the same as that in the above embodiment, the heat loss can be similarly reduced.

  6A and 6B are cross-sectional perspective views showing the main configuration of the fixing device 100 according to another modification, in which FIG. 6A shows a cross section including the rotation shaft of the fixing belt 200, and FIG. 6B shows the fixing belt. A cross section perpendicular to the rotation axis 200 is shown, and corresponding members are denoted by the same reference numerals. In the fixing device 100 according to this modification, the belt driving gear 201 is no longer supported by the shaft 221, and instead, as shown in FIG. The two rollers 601 and the power supply member 206 are supported. Even in this case, the belt driving gear 201 can be supported and the power supply member 206 can be reliably brought into contact with the electrode portion 203. Therefore, the same effect as the above embodiment can be obtained.

  In FIG. 5B, the two gears 231 that support the belt driving gear 201 and the power supply member 206 are arranged so as to form a central angle of 120 degrees with respect to the rotation center of the fixing belt 200. If the triangle formed by the three contact points where the member contacts the fixing belt 200 includes the rotation center, the center angle may not be 120 degrees. Similarly in FIG. 6B, if the triangle formed by the three contact points where the three support members of the roller 601 and the power supply member 206 are in contact with the fixing belt 200 is arranged so as to include the rotation center, the center angle is obtained. May not be 120 degrees.

  (2) In the above-described embodiment, the case where the fixing belt 200 is driven to rotate by the pressure roller 210 that is rotationally driven by a drive source (not shown) has been described, but the present invention is not limited to this. Alternatively, the pressure roller 210 may be driven to rotate on the fixing belt 200 that is rotationally driven via the belt driving gear 201. When the fixing belt 200 is rotationally driven via the belt drive gear 201, a fixed pressure member that does not rotate may be used instead of the pressure roller 210.

  (3) In the above-described embodiment, the case where the belt driving gear 201 serves both the purpose of rotating the fixing belt 200 and preventing buckling has been described, but the present invention is not limited to this. Alternatively, instead of the belt driving gear 201, an annular member having no gear portion may be fitted to the fixing belt 200. Even in this case, similarly to the case where the belt driving gear 201 is fitted, the buckling and breakage of the fixing belt 200 can be prevented.

  (4) In the above embodiment, the case where the pressure roller 210 is pivotally supported by the housing 230 while being pressed against the fixing belt 200 has been described, but the present invention is not limited to this. Instead of this, the following may be used. In other words, the pressing roller 210 may be pivotally supported by an urging unit separate from the housing 230, and at the same time, the pressing roller 210 may be urged toward the fixing belt 200 by the same urging unit. In this way, the pressure contact force of the pressure roller 210 to the fixing belt 200 can be adjusted with higher accuracy.

  (5) In the above embodiment, the intermediate transfer type color image forming apparatus has been described as an example. However, the present invention is not limited to this, and the present invention is not limited to this. The present invention may be applied to a monochrome image forming apparatus. Regardless of whether the image forming apparatus is a single-function machine such as a printer, a copying machine, or a facsimile machine, or a multi-function machine (MFP) having a plurality of these functions (MFP: Multi Function Peripheral). The effects of the present invention can be obtained.

  The fixing device and the image forming apparatus according to the present invention are useful as a device for preventing the fixing belt from being damaged in the resistance heating element type fixing device.

1 ……………… Image forming apparatus 100 ………… Fixing device 200 ………… Fixing belt 201 ………… Belt drive gear 201 a ………… Boss portion 201 b ………… Flange portion 202, 233 ... bearing 203 ............... electrode portion 204 ............... feeding member 205 ............... holding plate 206 ............... biasing member 207 ............... electric wire 210 ......... ... Pressure roller 220 ......... Pressing pads 221 and 232 ... Shaft 221a ......... Pillar part 221b ......... Cylinder part 230 ......... Housing 231 ......... Gear 300 ......... ... Resistance heating element layer 301 ........... Reinforcement layer 302 ........... Elastic layer 303 ........... Release layer 601 ...........

Claims (6)

A fixing device for fixing a toner image by passing a recording sheet through a fixing nip formed by pressing a pressing member against an outer peripheral surface of an endless fixing belt having a resistance heating element layer that generates heat when energized. Because
A pressing member provided at a position facing the pressure member inside the fixing belt and supporting the fixing belt at the fixing nip position;
A pair of annular members that are rotatably supported together with the fixing belt, and are fitted on both ends of the fixing belt outside the pressing member in the rotation axis direction of the fixing belt;
At least a pair of power supply members;
A plurality of support rollers that contact the outer peripheral surface of the annular member and support the annular member by following and rotating the annular member;
The fixing belt is provided with a pair of electrode portions on the outer peripheral surfaces of both ends.
The pair of power supply members are arranged to be urged against the annular member from the outer peripheral surface side of the fixing belt at positions facing the pair of annular members, respectively, and the resistance heating element extends from the pair of electrode portions. Power the layers,
The rotation center of the annular member is located inside a polygon connecting the position where the plurality of support rollers contact the annular member and the position where the power supply member contacts the fixing belt. apparatus. A fixing device for fixing a toner image by passing a recording sheet through a fixing nip formed by pressing a pressing member against an outer peripheral surface of an endless fixing belt having a resistance heating element layer that generates heat when energized. Because
A pressing member provided at a position facing the pressure member inside the fixing belt and supporting the fixing belt at the fixing nip position;
A pair of annular members that are rotatably supported together with the fixing belt, and are fitted on both ends of the fixing belt outside the pressing member in the rotation axis direction of the fixing belt;
At least a pair of power supply members;
A plurality of support rollers that contact the outer peripheral surface of the fixing belt at a position where the annular member is fitted and support the annular member by being driven to rotate by the fixing belt;
The fixing belt is provided with a pair of electrode portions on the outer peripheral surfaces of both ends.
The pair of power supply members are arranged to be urged against the annular member from the outer peripheral surface side of the fixing belt at positions facing the pair of annular members, respectively, and the resistance heating element extends from the pair of electrode portions. Power the layers,
The fixing device according to claim 1, wherein a rotation center of the annular member is located in a polygon connected to a position where the plurality of support rollers and the power supply member are in contact with the fixing belt. The arranged fixed inside the fixing belt, a fixing device according to claim 1 or 2, characterized in that it comprises a support member for supporting the pressing member. An interposition member is provided that is supported by the support member and disposed at the center of rotation of the annular member, and is interposed between the support member and the annular member to rotatably support the annular member. The fixing device according to claim 3 . At least one of the pair of annular members is provided with a drive transmission gear,
It rollers like the pressing member is rotationally driven and, by the annular member through the drive transmission gear is rotationally driven, of claims 1 to 4, wherein the fixing belt is characterized by rotating The fixing device according to any one of the above. An image forming apparatus comprising: a fixing device according to any one of claims 1 to 5.

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