JP4723852B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a belt fixing device that fixes unfixed toner held on a recording medium such as paper or an OHP sheet based on print data, and an image forming apparatus including the belt fixing device.

  In an image forming apparatus such as a laser beam printer provided with a belt fixing device, it is indispensable to stably drive the belt for a long time.

  As a conventional technique, there is an example in which a porous resin fiber woven fabric or a laminate of a porous resin film on the surface of a porous resin fiber woven fabric is used as a low friction sheet, and silicone oil is used as a lubricant (see Patent Document 1). ). However, since the pores are crushed in the pressurized portion of the porous resin and the lubricant is pushed out, the lubricant is poor. Therefore, the load torque increases according to the area of the portion where the lubricant is poor. In general, most of the fibers are non-porous resin fibers. In order to make this porous, there is a method in which it is intentionally foamed or stretched in a biaxial direction because it is not made porous by stretching only in a uniaxial direction. However, in any case, it is easy to cut from the pores (cracks) at the time of fiber formation, and the productivity is low. Therefore, there is a problem that the porous resin fiber is more expensive than a general non-porous resin fiber. In addition, silicone oil has a problem of volatilizing a low molecular siloxane component at a high temperature.

  On the other hand, as a sheet-like sliding material, the sliding surface side is a porous tissue material or a porous tissue material to which a porous film is laminated and bonded, and the non-sliding surface side is a sheet-like sliding material to which a deformation preventing film is laminated and bonded. There is an example in which silicone oil is used as a lubricant (see Patent Document 2). However, the sheet-like sliding material in which the deformation preventing film is laminated and bonded is expensive. Moreover, silicone oil has high fluidity, and if a deformation preventing film that also serves as an oil barrier is not laminated and bonded, it will permeate and diffuse to other parts. When diffused, other units are contaminated and the lubricant on the sliding surface is depleted, increasing the load torque. Furthermore, there is a problem of volatilizing low molecular siloxane components at high temperatures.

  One technical problem of the belt fixing device is to stably drive the belt for a long time. When the frictional force between the belt and the sliding layer is high, the load torque increases, resulting in damage to the drive unit and scratches on the roller surface. The load torque tends to increase when the actual contact area ratio of the pressure portion of the sliding layer is large. Also, if the oil retention rate of the sliding sheet is low, the lubricant oozes out and enters between the roller and the belt, causing the belt to slip, or the lubricant on the sliding part to be depleted when driven for a long time, and the load torque increases rapidly. There is a problem to do. When the belt slips, the sheet conveyance speed is reduced, causing problems such as paper folding and image distortion.

  In addition, since the sliding sheet and the lubricant are exposed to a high temperature for a long time, there is a possibility that the thermal deterioration proceeds. If the sliding sheet is melted by heat, it is welded to the inner surface of the belt, increasing the load torque or giving off a strange odor. When the lubricant is oxidized and deteriorated at high temperatures, the frictional force increases due to carbonization and thickening. Moreover, if the volatilized low molecular weight siloxane is adsorbed to the current-carrying part, there is a possibility of causing an electrical failure.

JP 2001-228731 A

JP 2003-191389 A

  In a fixing device employing an endless belt, if the frictional force between the belt and the sliding layer is high, the load torque increases, and the drive unit may be damaged or the roller surface may be damaged. Also, if the lubricant retention rate of the sliding layer is low, the lubricant will ooze out and enter between the roller and the belt, causing the belt to slip, or for a long period of time to run out of lubricant on the sliding part, resulting in a sudden load torque. The problem of rising may occur.

  In order to solve the above-described problems, the present invention includes a roller, an endless belt that rotates following contact with the roller, a heating source inside the roller or the endless belt, and the endless belt. In the fixing device including a pressure member that pressurizes the endless belt toward the roller, a sliding layer is provided on a side where the pressure member contacts the endless belt, and the sliding layer includes at least The structure has two or more layers and holds the lubricant.

  According to the present invention, since the fixing device has two sliding layers, the retention performance of the lubricant is excellent, and the sliding frictional resistance with the endless belt can be reduced.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  First, the overall configuration of the image forming apparatus will be described with reference to FIG. In FIG. 5, reference numeral 1 denotes a photosensitive belt, which is supported so as to be capable of endless movement in the direction of arrow d. Reference numeral 2 denotes a charging brush, and reference numeral 3 denotes a charging roller. The charging brush 2 and the charging roller 3 are provided in contact with the surface of the photosensitive belt 1 to uniformly charge the surface of the photosensitive belt 1. An exposure device 4 that irradiates light onto the surface of the uniformly charged photoreceptor belt 1 exposes the photoreceptor belt 1 in dot units according to image and character information by a personal computer, an image scanner, etc. An electrostatic latent image is formed on the surface.

  The electrostatic latent image formed on the photosensitive belt 1 is supplied with toner by any one of a black toner developing machine 5K, a yellow toner developing machine 5Y, a magenta toner developing machine 5M, and a cyan toner developing machine 5C. Then, the toner image is visualized and conveyed to the first transfer position T1. At the first transfer position T <b> 1, the toner image on the photoreceptor belt 1 is transferred to the surface of the intermediate transfer body 6 due to a potential difference between the photoreceptor belt 1 and the intermediate transfer body 6.

  The surface of the photosensitive belt 1 that has passed the first transfer position T1 is subjected to light irradiation from the afterimage remover 7 so that the potential is lowered below a certain level to erase the electrostatic latent image, and then the cleaning device 8 performs the first transfer. The toner remaining on the photosensitive belt 1 without being transferred at the position T1 is removed, and the next image can be formed.

  By repeating the above steps as many times as necessary by the developing machines 5K, 5Y, 5M, and 5C, a toner image corresponding to image and character information is formed on the surface of the intermediate transfer body 6.

  Thereafter, the toner image transferred onto the intermediate transfer member 6 is transferred to the recording medium supplied from the cassette 11 by the recording medium supply device 10 by the transfer device 9 at the second transfer position T2. The recording medium onto which the toner image has been transferred is peeled off from the intermediate transfer member 6 and sent to the fixing device 12, where the toner image is fixed on the recording medium and discharged by the recording medium discharge device 13.

  In FIG. 5, reference numeral 14 denotes a cleaning device that cleans the surface of the intermediate transfer member 6.

  Next, the configuration of the fixing device 12 will be described in detail with reference to FIG.

  As shown in FIG. 1, the roller 15 of the fixing device 12 includes a toner release layer 15a, an elastic layer 15b, and a support 15c. The toner release layer 15a is preferably made of fluororesin or fluororubber such as PFA or PTFE, the elastic layer 15b is made of silicone rubber or fluororubber, and the support 15c is preferably made of metal such as aluminum or iron.

  The endless belt 16 includes a surface layer 16a and a base material 16b. The surface layer 16a is preferably a fluororesin such as PFA or PTFE or fluororubber, and the substrate 16b is preferably a resin such as polyimide or polyamideimide.

  The pressure member 17 is configured using a pressing member 17a, a sliding layer 17b, and a peeling roller 17c as necessary. The pressing member 17a may be any inorganic or organic substance that has heat resistance to the operating temperature and can transmit pressure. For example, inorganic substances such as ceramic, glass, and aluminum, rubbers such as silicone rubber and fluororubber, PTFE (four Fluorinated ethylene), PFA (tetrafluoroethylene / perfluoroalkoxy vinyl ether copolymer), ETFE (ethylene / tetrafluoroethylene copolymer), FEP (tetrafluoroethylene / hexafluoropropylene copolymer), etc. Fluorine resin, PI (polyimide), PAI (polyamideimide), PPS (polyphenylene sulfide), PEEK (polyetheretherketone), LCP (liquid crystal plastic), phenolic resin, nylon, aramid, or a combination of these Is used.

  In order to reduce the frictional force, the lubricant between the endless belt 16 and the sliding layer 17b contains a modified perfluoropolyether. For example, carboxylic acid-modified perfluoropolyether, phosphoric acid-modified perfluoropolyether, alcohol-modified perfluoropolyether, amide-modified perfluoropolyether and the like are used. By adding the modified perfluoropolyether to the lubricant, the load torque of the belt fixing device can be reduced over a long period of time.

  Further, in order to prevent the lubricant from flowing out and diffusing to other parts, a thickener may be added to the lubricant to improve the oil component retention. As the thickener, for example, benton, silica gel, urea, PTFE, molybdenum disulfide, glass, carbon, BN and the like are used. In particular, PTFE particles that have high affinity for the modified perfluoropolyether and do not impair slidability are preferred. The oil component can be prevented from diffusing by adding a thickener to the lubricant.

  The material of the sliding layer 17b may be any inorganic or organic material that has heat resistance to the operating temperature, can transmit pressure, and is suitable for sliding. For example, inorganic materials such as ceramic, glass, and aluminum, silicone rubber, fluorine Rubbers such as rubber, fluorine resins such as PTFE, PFA, ETFE, and FEP, resins such as PI, PAI, PPS, PEEK, LCP, phenol resin, nylon, and aramid, or combinations thereof are used.

  Further, in order to reduce friction at a low cost, the sliding layer 17b has a two-layer structure, and the layer 172 on the side not in contact with the inner surface of the endless belt 16 is made of PPS fiber, aramid fiber, nylon fiber having high lubricant retention. The layer 171 on the side in contact with the inner surface of the endless belt 16 is made of a woven or nonwoven fabric made of fluorine fibers such as PTFE, PFA, ETFE, FEP, etc. in order to reduce sliding resistance. Is done.

  In particular, the layer 172 preferably has a felt structure with high oil component retention, and the layer 171 preferably has a woven fabric structure with a small actual contact area ratio. Here, in order to make the lubricant retained in the layer 172 easily transfer to the layer 171, the layer 172 may have a fiber structure instead of a film that blocks the lubricant. It is better not to laminate the layers between the layers. The actual contact area ratio of the layer 171 is preferably 20% or less at a pressure of 0.12 MPa.

  If these effects can be achieved, the sliding layer may be two or more layers.

  The actual contact area ratio is the remaining area ratio obtained by subtracting the sum of the gap area of the sliding layer 17b that does not contribute to pressure transmission from the apparent contact area of the pressurized endless belt 16 and the sliding layer 17b. It is represented by 1.

Actual contact area ratio = (apparent contact area−gap part area) / (apparent contact area) × 100 Formula 1
The method for measuring the actual contact area ratio may be as follows from Equation 1. Approximately, for example, the layer 171 is pressed against a stamp stand (medium HG-2EC black / Shiyahata Co., Ltd.) with a pressure of 0.12 MPa, and the adhered black ink (SG-40 black / Shiyahata Co., Ltd.) is applied. Immediately, it is pressed onto a smooth white paper (Fine FC / manufactured by Kishu Paper Co., Ltd.) with a pressure of 0.12 MPa and transferred. Next, the transferred image is converted into an output signal by an optical microscope (VH-8000 / manufactured by KEYENCE CORPORATION), and the actual contact area to which the black ink is adhered and the blank area of the blank paper are separately calculated by calculation processing. Etc.

  The direction of the arrangement of the layer 171 may be an angle with little deformation of the texture. In particular, the angle between the weave direction and the sliding direction is preferably 30 ° to 45 °. As shown in FIG. 2, the weft direction and the sliding direction angle in the present invention are a total of three of the warp direction and the weft direction of the sliding layer on the side contacting the endless belt 16 and the intersection of the sliding direction. Among the angles a, b, and c, this is the smallest angle a.

  In FIG. 1, a separation roller 17 c may be provided to facilitate separation of the recording medium m after fixing from the roller 15. The peeling roller 17c is a metal roller such as stainless steel that has heat resistance to the operating temperature, can transmit pressure, and is driven to rotate by the endless belt 16, or a rubber roller in which a metal core is covered with fluorine rubber, silicone rubber, or the like. preferable. Further, heating sources 15d and 17d are provided in at least one of the inside of the roller 15 and the endless belt 16, and a pressure contact portion (hereinafter referred to as a nip portion) between the roller 15 and the endless belt 16 is heated. ing. The heating source may be provided only on either one. As the heating source, for example, a halogen lamp, an electromagnetic induction heating source, a PTC heater, a film heater, a ceramic heater, or the like is used. When the unfixed toner t adhering to the recording medium m passes through the nip formed by the roller 15 and the endless belt 16, it is heated and pressurized and fixed on the recording medium m.

  Specific examples will be described below with reference to FIGS. 1, 3, 4 and Table 1. FIG.

  The roller 15 includes a PFA tube having a thickness of 30 μm on the toner release layer 15a, a silicone rubber having a thickness of 0.6 mm and a hardness of 20 ° (Shore A) as an elastic layer 15b, and an aluminum having a thickness of 1 mm and a diameter of 40 mm as a support 15c. The circular tube was used.

  As the endless belt 16, a PFA tube having a thickness of 30 μm was used for the surface layer 16a, and a polyimide belt having a thickness of 50 μm and a diameter of 30 mm was used as the substrate 16b.

  The pressing member 17 includes an aluminum pad 173 on the pressing member 17a, a silicone rubber pad 174 having a hardness of 20 ° (Shore A) and a thickness of 4 mm, and a fluorine felt (manufactured by Toray Industries, Inc.) having a thickness of 0.8 mm on the sliding layer 17b. A stainless steel roller having a diameter of 8 mm was used as the peeling roller 17c.

  Further, a 980 W halogen lamp is used as a heating source 15d inside the roller 15 as a heating source, a film heater is used as a heating source 17d inside the endless belt 16, and a carboxylic acid-modified perfluoropolyether is used as a lubricant. A total load of 30 kgf was added to the pressure member 17 using 3 μm PTFE particles (Lublon L-2 / manufactured by Daikin Industries, Ltd.). The nip portion was heated to 160 ° C. by the halogen lamp 15d and the film heater 17d, and the peripheral speed was 200 mm / second.

  Table 1 shows the oil component retention ratio and actual contact area ratio of the sliding layer 17b, and FIG. 3 shows changes with time in load torque. Here, the oil component retention rate means that 0.5 g of a fluorine oil component (S65 / manufactured by Daikin Industries, Ltd.) is impregnated into the sliding layer 17b having a size of 30 mm in length and 18 mm in width, and is vertical for 200 hours at room temperature. It is the oil remaining rate after being left to stand.

  As shown in Table 1, the oil component retention of Example 1 was 78%, and the actual contact area ratio was 25%. The load torque at this time was 5.5 (au: arbitrary unit) with a drive time of 12.5 hours.

  The layer 172 on the side not in contact with the endless belt 16 is 0.4 mm thick aramid felt (manufactured by Fujiko Co., Ltd.), and the layer 171 on the side in contact with the endless belt 16 is 22 μm thick porous PTFE film (Poreflon / Sumitomo) Example 1 is the same as Example 1 except that it was changed to Electric Industry Co., Ltd.

  The oil component retention rate in Example 2 is as high as 86%, but the actual contact area rate is as large as 99%. The load torque at this time was 6.1 (au) at a driving time of 12.5 hours.

  The layer 172 on the side not in contact with the endless belt 16 is 0.4 mm thick PTFE woven fabric (No. 406W / manufactured by Toray Industries, Inc.), and the layer 171 on the side in contact with the endless belt 16 is 0.2 mm thick in PFA. The same as Example 1 except that the net (made by Toray Industries, Inc.) was used and the texture direction of the PFA net was changed to 45 ° with respect to the sliding direction.

  The oil component retention in Example 3 is as low as 25%, and the actual contact area ratio is as small as 1%. The load torque at this time is 1.1 (au) at a driving time of 12.5 hours, which is lower than those in the first and second embodiments, but increases to 2.2 (au) in 100 hours. is doing.

  The layer 172 on the side not contacting the endless belt 16 is 0.4 mm thick aramid felt (manufactured by Fujiko Co., Ltd.), and the layer 171 on the side contacting the endless belt 16 is 0.2 mm thick PFA net (Toray Industries, Inc.). The same as in Example 1 except that the texture direction of the PFA net is changed to 45 ° with respect to the sliding direction.

  The oil component retention ratio in Example 4 is as high as 79%, and the actual contact area ratio is as small as 1%. The load torque at this time is 1.0 (au) when the driving time is 12.5 hours, which is lower than those of Examples 1 to 3, and 1.1 (au) for 100 hours. Sustained low value.

  A method for measuring the texture direction and the texture deformation amount of the PFA net will be described below.

A 0.2 mm thick PFA net (Toray Industries, Inc.) was cut into a length of 50 mm and a width of 100 mm, the chuck area was 100 mm ² and the distance between chucks was 10 mm. It was measured. The measurement results are shown in FIG.

  From FIG. 4, it can be seen that the texture direction and the pulling direction angle are 30 ° to 45 °, and the deformation of the texture is small. Moreover, the PFA net broke when the weave direction and the pulling direction angle were 0 °. Thus, the deformation of the texture can be reduced by setting the texture direction to 30 ° to 45 ° with respect to the sliding direction.

  In the above description, the toner image formed on the belt-shaped photoreceptor is primarily transferred to the intermediate transfer member, and then the toner image transferred onto the intermediate transfer member is secondarily transferred to a recording medium such as paper. Although the description has been made on the assumption that the image forming apparatus is configured as described above, the configuration of the image forming apparatus is not limited to this, and the photosensitive member may be in the form of a drum. Further, the present invention may be applied to an image forming apparatus having a configuration in which a transfer device is provided to face a photosensitive member without using an intermediate transfer member and a toner image is directly transferred from the photosensitive member to a recording medium.

  The lubricant and the sliding layer in the present invention are applicable to OA equipment, automobiles, measuring instruments, building materials, and other industrial equipment as friction reducing materials for the pressure-contact sliding surface.

1 is a cross-sectional view of a fixing device applied to an image forming apparatus of the present invention. It is explanatory drawing which shows the relationship between the texture direction of a sliding layer, and the angle of a sliding direction. 6 is a graph showing a relationship between a driving time of the fixing device and a load torque. It is a graph which shows the relationship between the texture direction of a sliding layer, and a texture deformation amount. 1 is an overall configuration diagram of an image forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 15 ... Roller, 15a ... Release layer, 15b ... Elastic layer, 15c ... Support body, 15d ... Heat source, 16 ... Endless belt, 16a ... Surface layer, 16b ... Base material, 17 ... Pressure member, 17a ... Pressing member, 17b: sliding layer, 17c: peeling roller, 17d: heating source, m: recording medium, t: toner image.

Claims (14)

A roller, an endless belt that is driven to rotate in contact with the roller, and a heating source inside the roller or the endless belt, and the endless belt faces the roller inside the endless belt. In the fixing device including a pressure member that pressurizes, the pressure member has a sliding layer on a side in contact with the endless belt, and the sliding layer includes at least two layers that are not laminated and bonded. together with, said one of two or more layers, the holding lubricant to one layer on the side not in contact with the inner surface of the endless belt, holding the layers on the side where the lubricant contacts the inner surface of the endless belt is shifted to the actual contact area ratio of the surface in contact with the inner surface of the endless belt is characterized der Rukoto 20% or less under a pressure of 0.12MPa constant Apparatus.   The fixing device according to claim 1, wherein the lubricant contains a modified perfluoropolyether.   3. The modified perfluoropolyether is any one of a carboxylic acid-modified perfluoropolyether, a phosphoric acid-modified perfluoropolyether, an alcohol-modified perfluoropolyether, and an amide-modified perfluoropolyether. The fixing device described.   The fixing device according to claim 1, wherein the lubricant contains PTFE particles. In the sliding layer, the layer on the side that contacts the inner surface of the endless belt is a fluorine fiber layer, and the layer that does not contact the inner surface of the endless belt is at least one of aramid fiber, PPS fiber, and nylon fiber. The fixing device according to claim 1.   6. The fixing device according to claim 5, wherein the layer that is at least one of the aramid fiber, the PPS fiber, and the nylon fiber is felt.   The fixing device according to claim 5, wherein the fluorine fiber layer is a woven fabric, and the weave direction is an angle of 30 to 45 ° with respect to the sliding direction.   A photoconductor having a photoconductive surface capable of forming an electrostatic latent image, a developing machine that exposes yellow, magenta, cyan, and black color toners on the photoconductor, and an intermediate for superimposing the exposed toner images. An image forming apparatus comprising: a transfer member; transfer means for transferring a toner image superimposed on the intermediate transfer member to a recording medium; and a fixing device for fixing the toner image on the recording medium to the recording medium. A roller that is driven to rotate, an endless belt that rotates following contact with the roller, a heat source inside the roller or the inside of the endless belt, and the endless belt inside the endless belt. A pressure member that pressurizes the sliding member, and a sliding layer is provided on a side where the pressure member contacts the endless belt, and the sliding layer is laminated and bonded. And having at least two or more layers, holding a lubricant in one of the two or more layers that is not in contact with the inner surface of the endless belt, and holding the retained lubricant in the endless belt. An image forming apparatus, wherein the actual contact area ratio of the surface contacting the inner surface of the endless belt is 20% or less at a pressure of 0.12 MPa.   The image forming apparatus according to claim 8, wherein the lubricant contains a modified perfluoropolyether.   The modified perfluoropolyether is any one of carboxylic acid-modified perfluoropolyether, phosphoric acid-modified perfluoropolyether, alcohol-modified perfluoropolyether, and amide-modified perfluoropolyether. The image forming apparatus described.   The image forming apparatus according to claim 8, wherein the lubricant contains PTFE particles. In the sliding layer, the layer on the side that contacts the inner surface of the endless belt is a fluorine fiber layer, and the layer that does not contact the inner surface of the endless belt is at least one of aramid fiber, PPS fiber, and nylon fiber. The image forming apparatus according to claim 8.   The image forming apparatus according to claim 12, wherein the layer that is at least one of the aramid fiber, the PPS fiber, and the nylon fiber is felt.   13. The image forming apparatus according to claim 12, wherein the fluorine fiber layer is a woven fabric, and the weave direction is an angle of 30 to 45 degrees with respect to the sliding direction.

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