Belt device, fixing device and image forming apparatus

Abstract

To prevent wear of a belt and generation of an unusual sound effectively over time.SOLUTION: A belt device comprises: a rotatable endless belt 310; a slide member 330 that slides relative to an inner peripheral surface of the belt 310; a pressure member 320 that is in contact with the slide member 330 with the belt 310 therebetween to form a nip part SN between the belt 310 and the pressure member; and lubricant that is interposed between the inner peripheral surface of the belt 310 and the slide member 330. Of slide surfaces on which the belt 310 and the slide member 330 slide, the slide surface of the belt 310 has an elastic power of 55% or more, and the surface roughness of the slide surface of the slide member 330 is larger than the surface roughness of the slide surface of the belt 310.SELECTED DRAWING: Figure 2A

Description

[Technical field]

[0001] The present invention relates to a belt device, a fixing device, and an image forming apparatus. [Background technology]

[0002] 2. Description of the Related Art Fixing devices using an endless belt are known as belt devices mounted in image forming apparatuses such as copiers and printers.

[0003] Generally, in the case of a belt-type fixing device, when the belt rotates, the belt slides against members such as a heater or a pad arranged inside the belt, which causes a problem of abnormal noise being generated by the sliding of the belt.

[0004] To address this problem, the following Patent Document 1 (JP 2020-148943 A) proposes a method of applying a lubricant to the sliding points between the belt and the heater to suppress the generation of abnormal noise, and further making the surface roughness of the sliding surface of the heater that slides relative to the belt greater than the surface roughness of the inner surface of the belt. Summary of the Invention [Problem to be solved by the invention]

[0005] However, it has been found that even if the surface roughness of the sliding member that slides relative to the belt of a heater or the like is increased as described above, the belt wears over time, and the wear powder of the belt absorbs the lubricant, accelerating the wear of the belt and making it more likely to generate abnormal noise. For this reason, it has been difficult with conventional techniques to effectively and continuously suppress belt wear and abnormal noise. [Means for solving the problem]

[0006] In order to solve the above problems, the present invention provides a belt device including a rotatable endless belt, a sliding member that slides relatively against the inner peripheral surface of the belt, a pressure member that contacts the sliding member via the belt to form a nip between the belt and the sliding member, and a lubricant that is interposed between the inner peripheral surface of the belt and the sliding member, wherein the elastic power of the sliding surface of the belt is 1 / 2 the sliding surface between the belt and the sliding member. 62 % or more, and the surface roughness of the sliding surface of the sliding member is greater than the surface roughness of the sliding surface of the belt. Effect of the Invention

[0007] According to the present invention, belt wear and abnormal noise generation can be effectively suppressed over time. [Brief description of the drawings]

[0008] [Figure 1A] 1 is a schematic diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 1B] 1 is a diagram illustrating the principle of an image forming apparatus according to an embodiment of the present invention. [Figure 2A] 1 is a cross-sectional view of a first fixing device according to an embodiment of the present invention. [Figure 2B] FIG. 4 is a cross-sectional view of a second fixing device according to an embodiment of the present invention. [Figure 2C] FIG. 11 is a cross-sectional view of a third fixing device according to an embodiment of the present invention. [Figure 2D] FIG. 11 is a cross-sectional view of a fourth fixing device according to an embodiment of the present invention. [Diagram 3] FIG. 2A is a diagram showing the lubricant retention state when the surface roughness of the fixing belt is greater than that of the heater, and FIG. 2B is a diagram showing the lubricant retention state when the surface roughness of the heater is greater than that of the fixing belt. [Figure 4A] FIG. 2 is a diagram for explaining the arithmetic mean roughness Sa. [Figure 4B] FIG. [Figure 4C] FIG. 1 is a diagram showing a load curve representing a solid portion and a space portion. [Figure 4D] 13A is a diagram showing the height distribution when the deviation degree Ssk>0, and FIG. 13B is a diagram showing the height distribution when the deviation degree Ssk<0. [Figure 4E] 13A is a diagram showing the height distribution when the kurtosis Sku>3, and FIG. 13B is a diagram showing the height distribution when the kurtosis Sku<3. [Diagram 5] 1(a) to 1(d) are diagrams illustrating a method for measuring elastic power. [Figure 6] FIG. 11 is a diagram showing the relationship between elastic power and abrasion resistance rank of a fixing belt. [Figure 7] FIG. 1 is a diagram for explaining the difference between elastic power and return rate. [Figure 8A] FIG. 1A is a plan view of a single-type resistive heating element having an electrode at one end, and FIG. 1B is a cross-sectional view of the single-type resistive heating element. [Figure 8B] FIG. 1 is a plan view of a dual-type resistance heating element having electrodes on both ends. [Figure 3C] FIG. 2 is a plan view of a multi-type resistance heating element having electrodes on both ends. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, a belt device according to an embodiment of the present invention, and a fixing device and an image forming device (laser printer) using the belt device will be described with reference to the drawings. In addition, the "belt device" in the present invention means a device including a rotatable endless belt, a sliding member having a sliding surface that slides relatively against the inner peripheral surface of the belt, a pressure member that contacts the sliding member via the belt and forms a nip between the belt and the sliding member, and a lubricant interposed between the inner peripheral surface of the belt and the sliding member. In addition, the "fixing device" means a device that conveys a sheet member, which is a recording medium on which an image is recorded, to the nip between the belt and the pressure member, and fixes unfixed toner onto the sheet member. In addition, the "image forming device" means a device that includes a fixing device and adheres a developer or ink to the sheet member to form an image.

[0010] A laser printer is one example of an image forming device. Therefore, the "image forming device" in the present invention is not limited to a laser printer. In other words, the image forming device can be any one of a copier, a facsimile, a printer, a printing machine, and an inkjet recording device, or can be configured as a multifunction machine that combines at least two or more of these.

[0011] In addition, the same or corresponding parts in each drawing are given the same reference numerals, and the repeated explanations are appropriately simplified or omitted. Furthermore, the dimensions, materials, shapes, relative positions, etc. in the explanations of each component are examples, and unless otherwise specified, the scope of this invention is not limited to them.

[0012] In the following embodiments, the "recording medium" which is the sheet member of the present invention will be described as "paper", but the "recording medium" is not limited to paper. The "recording medium" includes not only paper but also OHP sheets, fabrics, metal sheets, plastic films, and prepreg sheets in which carbon fibers are pre-impregnated with resin.

[0013] All media to which a developer or ink can be attached, recording paper, and recording sheets are included in the "recording media." In addition, "paper" includes not only plain paper, but also cardboard, postcards, envelopes, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, etc.

[0014] Furthermore, the term "image formation" used in the following description refers not only to the application of meaningful images, such as characters and figures, to a medium, but also to the application of meaningless images, such as patterns, to a medium.

[0015] <Laser printer configuration> Fig. 1A is a schematic diagram showing the configuration of a color laser printer as an embodiment of an image forming apparatus 100 equipped with a belt device or fixing device 300 of the present invention. Fig. 1B is a simplified diagram showing the principle of the color laser printer.

[0016] The image forming apparatus 100 includes four process units 1K, 1Y, 1M, and 1C as image forming means. These process units form images using developers of the respective colors of black (K), yellow (Y), magenta (M), and cyan (C), which correspond to the color separation components of a color image.

[0017] The process units 1K, 1Y, 1M, and 1C have the same configuration, except that they have toner bottles 6K, 6Y, 6M, and 6C that contain unused toner of different colors. Therefore, the configuration of one process unit 1K will be described below, and descriptions of the other process units 1Y, 1M, and 1C will be omitted.

[0018] The process unit 1K has an image carrier 2K (e.g., a photosensitive drum), a drum cleaning device 3K, and a charge removal device. The process unit 1K further has a charging device 4K as a charging means for uniformly charging the surface of the image carrier, and a developing device 5K as a developing means for performing visible image processing of the electrostatic latent image formed on the image carrier. The process unit 1K is detachably mounted on the main body of the image forming apparatus 100, and consumable parts can be replaced at the same time.

[0019] The exposure unit 7 is disposed above each of the process units 1K, 1Y, 1M, and 1C installed in the image forming apparatus 100. The exposure unit 7 is configured to perform writing scanning according to image information, that is, to reflect laser light L from a laser diode by a mirror 7a based on image data and irradiate the image carrier 2K.

[0020] In this embodiment, the transfer device 15 is disposed below each of the process units 1K, 1Y, 1M, and 1C. The transfer device 15 corresponds to the transfer means TM in Fig. 1B. The primary transfer rollers 19K, 19Y, 19M, and 19C are disposed in contact with the intermediate transfer belt 16 and facing the image carriers 2K, 2Y, 2M, and 2C, respectively.

[0021] The intermediate transfer belt 16 circulates around the primary transfer rollers 19K, 19Y, 19M, and 19C, the drive roller 18, and the driven roller 17. The secondary transfer roller 20 is disposed opposite the drive roller 18 and in contact with the intermediate transfer belt 16. If the image carriers 2K, 2Y, 2M, and 2C are the first image carriers for the respective colors, then the intermediate transfer belt 16 is the second image carrier that combines these images.

[0022] The belt cleaning device 21 is disposed downstream of the secondary transfer roller 20 in the running direction of the intermediate transfer belt 16. In addition, a cleaning backup roller is disposed on the opposite side of the intermediate transfer belt 16 to the belt cleaning device 21.

[0023] A paper feeder 200 having a tray for stacking paper P is installed below the image forming apparatus 100. This paper feeder 200 constitutes a recording medium supply section, and is capable of storing a large number of sheets of paper P as recording media in a bundle. The paper feeder 200 is unitized with a paper feed roller 60 and a roller pair 210 as a conveying means for the paper P.

[0024] The paper feed device 200 can be inserted into and removed from the main body of the image forming apparatus 100 for the purpose of replenishing paper, etc. The paper feed roller 60 and the roller pair 210 are disposed above the paper feed device 200, and are configured to transport the topmost paper P of the paper feed device 200 toward the paper feed path 32.

[0025] The pair of registration rollers 250 as a separation conveying means are disposed immediately upstream of the secondary transfer roller 20 in the conveying direction, and can temporarily stop the paper P fed from the paper feeding device 200. This temporary stop creates slack in the leading edge of the paper P, and corrects the skew of the paper P.

[0026] A registration sensor RS is disposed immediately upstream in the conveying direction of the registration roller pair 250, and this registration sensor RS detects the passage of the leading edge of the paper. After the registration sensor RS detects the passage of the leading edge of the paper, when a predetermined time has elapsed, the paper is abutted against the registration roller pair 250 and temporarily stops.

[0027] A transport roller 240 is disposed at the downstream end of the paper feed device 200 to transport the paper upward, the paper having been transported to the right from the roller pair 210. As shown in FIG 1A, the transport roller 240 transports the paper upward toward the registration roller pair 250.

[0028] The roller pair 210 is composed of a pair of upper and lower rollers. The roller pair 210 may be of an FRR separation type or an FR separation type.

[0029] The FRR separation method is a method in which a separation roller (return roller) to which a certain amount of torque is applied in the counter-feed direction by the drive shaft via a torque limiter is pressed against the feed roller to separate the paper at the nip between the rollers.In contrast, the FR separation method is a method in which a separation roller (friction roller) supported on a fixed shaft is pressed against the feed roller via a torque limiter to separate the paper at the nip between the rollers.

[0030] In this embodiment, the roller pair 210 is configured as an FRR separation type. That is, the roller pair 210 is configured with an upper feed roller 220 that transports the paper into the machine, and a lower separation roller 230 that is given a driving force by a drive shaft via a torque limiter in the opposite direction to the feed roller 220.

[0031] The separation roller 230 is biased by a biasing means such as a spring toward the feed roller 220. The feed roller 60 is rotated counterclockwise in FIG. 1A by the driving force of the feed roller 220 being transmitted via a clutch means.

[0032] The paper P abutted against the pair of registration rollers 250 is sent to the secondary transfer nip (transfer nip N in FIG. 1B) between the secondary transfer roller 20 and the drive roller 18 in time for the toner image formed on the intermediate transfer belt 16 to be suitably transferred. Then, the toner image formed on the intermediate transfer belt 16 is electrostatically transferred to the desired transfer position with high precision by a bias applied to the secondary transfer nip.

[0033] The post-transfer transport path 33 is disposed above the secondary transfer nip between the secondary transfer roller 20 and the drive roller 18. The fixing device 300 is disposed in the vicinity of the upper end of the post-transfer transport path 33.

[0034] The fixing device 300 includes a fixing belt 310 formed of an endless belt, and a pressure roller 320 as a pressure member that rotates while contacting the fixing belt 310 with a predetermined pressure.

[0035] The post-fixing transport path 35 is disposed above the fixing device 300, and branches into a paper discharge path 36 and a reversing transport path 41 at the upper end of the post-fixing transport path 35. A switching member 42 is disposed at this branching point, and the switching member 42 is adapted to swing about its swing shaft 42a. In addition, a pair of paper discharge rollers 37 is disposed near the open end of the paper discharge path 36.

[0036] The reverse conveying path 41 merges with the paper feed path 32 at the other end opposite to the branching portion. A pair of reverse conveying rollers 43 is disposed midway along the reverse conveying path 41. The paper output tray 44 is disposed on the upper portion of the image forming apparatus 100, forming a concave shape facing inward of the image forming apparatus 100.

[0037] The powder container 10 (for example, a toner container) is disposed between the transfer device 15 and the paper feed device 200. The powder container 10 is detachably attached to the main body of the image forming apparatus 100.

[0038] In the image forming apparatus 100 of this embodiment, a certain distance is necessary between the paper feed roller 60 and the secondary transfer roller 20 due to the relationship with the transfer paper transport. The powder container 10 is installed in the dead space generated in this distance, thereby making the entire laser printer smaller.

[0039] The transfer cover 8 is installed on the top of the paper feed device 200, in front of the paper feed device 200 in the pull-out direction. By opening the transfer cover 8, it is possible to inspect the inside of the image forming apparatus 100. The transfer cover 8 is provided with a manual feed roller 45 for manual paper feed and a manual feed tray 46 for manual paper feed.

[0040] <Laser printer operation> Next, the basic operation of the laser printer according to this embodiment will be described below with reference to Fig. 1A. First, single-sided printing will be described.

[0041] The paper feed roller 60 rotates in response to a paper feed signal from the control unit of the image forming apparatus 100. Then, the paper feed roller 60 separates only the topmost sheet of the stack of sheets P stacked in the paper feed device 200, and sends it to the paper feed path 32.

[0042] When the leading edge of the paper P sent out by the paper feed roller 60 and the roller pair 210 reaches the nip of the registration roller pair 250, it forms a slack and waits in that state. Then, the toner image formed on the intermediate transfer belt 16 is transferred to the paper P at the optimal timing (synchronization), and the leading edge skew of the paper P is corrected.

[0043] In the case of manual paper feeding, a stack of papers stacked on manual feed tray 46 is conveyed one by one, starting from the topmost paper, through a part of reverse conveyance path 41 by manual paper feed roller 45 to the nip of registration roller pair 250. The subsequent operation is the same as that of paper feeding from paper feeder 200.

[0044] Here, the image forming operation will be described for one process unit 1K, and the description of the other process units 1Y, 1M, and 1C will be omitted. First, the charging device 4K uniformly charges the surface of the image carrier 2K to a high potential. Then, the exposure device 7 irradiates the surface of the image carrier 2K with laser light L based on image data.

[0045] An electrostatic latent image is formed on the surface of the image carrier 2K irradiated with the laser light L by lowering the electric potential of the irradiated portion. The developing device 5K has a developer carrier that carries a developer containing toner, and transfers unused black toner supplied from a toner bottle 6K via the developer carrier to the surface portion of the image carrier 2K on which the electrostatic latent image is formed.

[0046] The image carrier 2K to which the toner has been transferred forms (develops) a black toner image on its surface. Then, the toner image formed on the image carrier 2K is transferred to the intermediate transfer belt 16.

[0047] The drum cleaning device 3K removes the residual toner adhering to the surface of the image carrier 2K after the intermediate transfer process. The removed residual toner is sent by a waste toner transport means to a waste toner storage section in the process unit 1K and collected. In addition, the charge removing device removes the residual charge of the image carrier 2K from which the residual toner has been removed by the cleaning device 3K.

[0048] In the process units 1Y, 1M, and 1C of the respective colors, toner images are similarly formed on the image carriers 2Y, 2M, and 2C, and the toner images of the respective colors are transferred onto the intermediate transfer belt 16 so as to be superimposed on each other.

[0049] The intermediate transfer belt 16, onto which the toner images of each color have been transferred so as to be superimposed, travels to the secondary transfer nip between the secondary transfer roller 20 and the drive roller 18. Meanwhile, the pair of registration rollers 250 rotates while pinching the abutted paper P at a predetermined timing, and transports the paper P to the secondary transfer nip of the secondary transfer roller 20 in accordance with the timing at which the toner images on the intermediate transfer belt 16 are suitably transferred. In this way, the toner image on the intermediate transfer belt 16 is transferred to the paper P sent out by the pair of registration rollers 250.

[0050] After the toner image is transferred to the paper P, the toner remaining on the intermediate transfer belt 16 is removed by a belt cleaning device 21. The toner removed from the intermediate transfer belt 16 is then transported by a waste toner transport means to the powder container 10 and collected in the powder container 10.

[0051] The paper P onto which the toner image has been transferred is transported to the fixing device 300 through a post-transfer transport path 33. The paper P transported to the fixing device 300 is then sandwiched between a fixing belt 310 and a pressure roller 320, and is heated and pressed, so that the unfixed toner image is fixed to the paper P. The paper P onto which the toner image has been fixed is sent from the fixing device 300 to a post-fixing transport path 35.

[0052] 1A , when the paper P is sent out from the fixing device 300, the switching member 42 is in a position that opens the vicinity of the upper end of the post-fixing transport path 35. In this state, the paper P sent out from the fixing device 300 is sent out to the paper discharge path 36 via the post-fixing transport path 35. Then, the paper discharge roller pair 37 pinches the paper P sent out to the paper discharge path 36 and rotates, thereby discharging the paper P to the paper discharge tray 44. This completes single-sided printing.

[0053] Next, a case where double-sided printing is performed will be described. In the case of double-sided printing, a toner image is first transferred to the paper P in the same manner as in the case of single-sided printing, and the unfixed toner image is fixed to the paper P in the fixing device 300. Thereafter, the paper P is sent out from the fixing device 300 to the paper discharge path 36, and at the timing when the rear end of the paper P passes the switching member 42, the switching member 42 swings around the swing shaft 42a as shown by the dotted line in FIG. 1A, and closes the upper end of the post-fixing conveying path 35. Furthermore, almost simultaneously with the closing of the upper end of the post-fixing conveying path 35, the pair of paper discharge rollers 37 rotates in the direction opposite to the direction in which the paper P is conveyed out of the image forming apparatus 100, and sends the paper P to the reverse conveying path 41.

[0054] The paper P sent to the reverse conveying path 41 passes through a pair of reverse conveying rollers 43 and reaches a pair of registration rollers 250. Then, the paper P is temporarily stopped by the pair of registration rollers 250 to correct the leading edge skew, and then sent to the secondary transfer nip at an optimal timing.

[0055] Then, the toner image for the back side, which is formed through the same process as the image forming process described above, is transferred to the paper P. Thereafter, the paper P is transported to the fixing device 300 through the post-transfer transport path 33, and is sandwiched between the fixing belt 310 and the pressure roller 320, and is heated and pressed, so that the unfixed toner image is fixed to the back side of the paper P.

[0056] In this manner, the paper P having the toner images fixed on both sides thereof is sent from the fixing device 300 to the post-fixing transport path 35. At this time, the switching member 42 has been returned to the position shown by the solid line in FIG. 1A, that is, the position that opens the vicinity of the upper end of the post-fixing transport path 35.

[0057] As a result, the paper P sent out from the fixing device 300 is sent to the paper discharge path 36 via the post-fixing transport path 35, and is discharged onto the paper discharge tray 44 by the paper discharge roller pair 37. In this manner, double-sided printing is completed.

[0058] <Fixing device> Next, the fixing device 300 according to the embodiment of the present invention will be further described. The fixing device 300 can be of various types as shown in Figs. 2A to 2D described later, but first, a first fixing device 300 shown in Fig. 2A will be described.

[0059] As shown in FIG. 2A, the first fixing device 300 includes, in addition to the fixing belt 310 and the pressure roller 320, a heater 330 as a heat source, a heater holder 340 as a heat source holding member, and a stay 350 as a support member.

[0060] The fixing belt 310 is an endless thin belt, and has a cylindrical substrate mainly made of polyimide (PI) with an outer diameter of 25 mm and a thickness of 40 to 120 μm. The material of the substrate of the fixing belt 310 is not limited to polyimide, but may be a heat-resistant resin such as PEEK, or a metal material such as nickel or SUS. When a metal material is used as the substrate material, a sliding layer made of polyimide, PTFE, or the like may be provided on the inner peripheral surface of the substrate.

[0061] In order to enhance durability and ensure releasability, a release layer made of fluorine-based resin such as PFA or PTFE and having a thickness of 5 to 50 μm is formed on the outermost surface of the fixing belt 310. In addition, an elastic layer made of rubber or the like and having a thickness of 50 to 500 μm may be provided between the base material and the release layer.

[0062] Pressure roller 320 has an outer diameter of, for example, 25 mm, and is composed of a solid iron core 321, an elastic layer 322 provided on the outer peripheral surface of this core 321, and a release layer 323 provided on the outer peripheral surface of elastic layer 322. Elastic layer 322 is formed of silicone rubber having a thickness of, for example, 3.5 mm, and release layer 323 is formed of a fluororesin layer having a thickness of, for example, about 40 μm.

[0063] The pressure roller 320 is pressed toward the fixing belt 310 by a biasing member such as a spring, and is in pressure contact with the outer circumferential surface of the fixing belt 310. As a result, a fixing nip SN is formed between the fixing belt 310 and the pressure roller 320 (at the contact point).

[0064] A heater holder 340 and a stay 350 are disposed inside the fixing belt 310 .

[0065] The heater holder 340 is a member that holds the heater 330. The heater holder 340 is preferably made of a heat-resistant material because it is likely to become hot due to the heat of the heater 330. In particular, when the heater holder 340 is made of a heat-resistant resin with low thermal conductivity such as LCP or PEEK, the heat resistance of the heater holder 340 is ensured while heat transfer from the heater 330 to the heater holder 340 is suppressed, so that the fixing belt 310 can be heated efficiently.

[0066] The stay 350 is a member that supports the heater holder 340. The stay 350 supports the surface of the heater holder 340 opposite to the surface on the fixing nip SN side, thereby suppressing the heater holder 340 from being deflected by the pressure of the pressure roller 320. As a result, a fixing nip SN of uniform width is formed between the fixing belt 310 and the pressure roller 320. Moreover, the stay 350 is preferably made of an iron-based metal material such as SUS or SECC in order to ensure its rigidity.

[0067] The heater 330 is disposed so as to extend across the longitudinal direction of the fixing belt 310 (the paper width direction intersecting the paper conveying direction), and is in contact with the inner peripheral surface of the fixing belt 310, and is a heat source that heats the fixing belt 310 from the inside. A heater that heats the pressure roller 320 may also be provided. The heater 330 according to this embodiment has a plate-shaped base material 341, a resistance heating element 370 provided on the surface of the base material 341 on the fixing nip SN side, and an insulating layer 385 that covers the resistance heating element 370. The base material 341 is made of a material that has excellent heat resistance and insulation, such as ceramics such as alumina or aluminum nitride, glass, mica, and polyimide. The base material 341 may also be made of a metal material (conductive material) such as stainless steel (SUS), iron, or aluminum, on which an insulating layer is formed. In particular, when the material of the base material 341 is a highly thermally conductive material such as aluminum, copper, silver, graphite, or graphene, the heat uniformity of the heater 330 is improved, and image quality can be improved. The resistance heating element 370 is formed, for example, by applying a paste made of a mixture of silver palladium (AgPd) and glass powder to the surface of the base material 341 by screen printing or the like, and then firing the base material 341. Resistive materials such as silver alloy (AgPt) or ruthenium oxide (RuO2) can also be used as the material for the resistance heating element 370. The insulating layer 385 is made of a material having excellent heat resistance and insulation properties, such as ceramics such as alumina or aluminum nitride, glass, mica, or polyimide.

[0068] Further, the heater 330 is provided with a thermistor TH as a temperature detection member. The output of the heater 330 is controlled based on the temperature detected by the thermistor TH, thereby maintaining the temperature of the fixing belt 310 at a predetermined temperature. In this embodiment, the thermistor TH is disposed so as to be in contact with the base material 341 of the heater 330, but the temperature detection member that detects the temperature of the heater 330 is not limited to a contact type temperature sensor, and may be a non-contact type temperature sensor.

[0069] In the fixing device according to the embodiment of the present invention, in which the heater is disposed so as to contact the inner peripheral surface of the fixing belt, when the fixing belt rotates in accordance with the rotation of the pressure roller, the fixing belt slides against the heater, which may cause problems such as abnormal noise and wear of the fixing belt.

[0070] One of the measures to improve this problem is to apply a lubricant such as grease to the sliding portion between the fixing belt and the heater. By providing a lubricant between the fixing belt and the heater, the sliding property of the fixing belt against the heater is improved, and the occurrence of abnormal noise and wear of the fixing belt can be suppressed.

[0071] <Relationship between surface roughness and lubricant retention> As a measure to suppress the occurrence of abnormal noise and wear of the fixing belt, there is a method of adjusting the surface roughness of the sliding surfaces on which the fixing belt and the heater slide.

[0072] For example, as shown in FIG. 3A, if the surface roughness of the sliding surface (inner surface) 310s of the fixing belt 310 is made larger than the surface roughness of the sliding surface 330s of the heater 330, the lubricant 50 cannot fill the space of the minute recesses on the sliding surface of the fixing belt 310, and the lubricant 50 runs out between the minute protrusions of the fixing belt 310 and the heater 330. This makes it easier for abnormal noise and wear of the fixing belt to occur. If the inner surface of the fixing belt deteriorates in a streaky manner due to sliding, uneven heating of the image occurs, which may result in abnormal images such as uneven gloss or gloss streaks.

[0073] 3B, when the surface roughness of the sliding surface 330s of the heater 330 is made larger than the surface roughness of the sliding surface 310s of the fixing belt 310, the lubricant 50 fills the spaces of the minute recesses on the inner circumferential surface of the fixing belt 310. As a result, the lubricant 50 is interposed between the minute protrusions of the fixing belt 310 and the heater 330, making it possible to suppress abnormal noise and wear of the fixing belt.

[0074] For this reason, in the fixing device according to the present invention, in order to suppress abnormal noise and wear of the fixing belt, a configuration is adopted in which the surface roughness of the sliding surface of the heater is made greater than the surface roughness of the sliding surface of the fixing belt.

[0075] <Line roughness Ra> One of the parameters that expresses surface roughness is the arithmetic mean roughness Ra, which conforms to JIS B 0031. This line roughness Ra is calculated by measuring the roughness curve on the sliding surface of the heater, extracting only a reference length (A) in the average line direction of the roughness curve, and using the following formula (1) when the direction of the average line of this extracted portion is the X-axis, the direction of the longitudinal magnification is the Y-axis, and the roughness curve is y = f(x).

[0076]

number

[0077] As described above, in order to suppress abnormal noise and wear of the fixing belt, it is preferable that the surface roughness of the sliding surface of the heater is large. Therefore, in this embodiment, the linear roughness Ra of the sliding surface of the heater in the sliding direction (the moving direction C of the fixing belt 310 in the fixing nip SN in FIG. 2A) is set to 0.2 μm or more. On the other hand, since it is preferable that the surface roughness of the sliding surface of the fixing belt is small, in this embodiment, the linear roughness Ra of the sliding surface of the fixing belt in the sliding direction is set to 0.05 μm or less. In this way, by setting the linear roughness Ra of each sliding surface of the heater and the fixing belt, the lubricant retention force of the sliding surface of the heater can be stably maintained, and abnormal noise and wear of the fixing belt can be effectively suppressed.

[0078] <Surface roughness Sa> Another parameter expressing surface roughness is the arithmetic mean height Sa, which is obtained by a measurement method conforming to ISO25178. This surface roughness Sa is a value obtained by expanding the above-mentioned line roughness Ra, which is a parameter indicating the profile curve (line roughness), into three dimensions. In other words, the surface roughness Sa represents the average of the absolute values ​​of Z(x, y) (height difference from the average surface) in the measurement area shown in FIG. 4A, and is calculated by the following formula (2).

[0079]

number

[0080] Similarly, when the surface roughness of the sliding surface of the heater is defined as the surface roughness Sa, it is preferably 0.2 μm or more. Similarly, the surface roughness Sa of the sliding surface of the fixing belt is preferably 0.05 μm or less.

[0081] <Protruding valley space volume Vvv> In addition to the line roughness Ra and the surface roughness Sa, there is a parameter expressing the surface roughness (surface shape characteristic value) called the valley spatial volume Vvv defined in ISO 25178. In the fixing device according to the present embodiment, in order to improve the wear resistance of the fixing belt, the valley spatial volume Vvv on the sliding surface of the heater is set to 0.01 ml / m 2 or more. The "protruding valley space volume Vvv" is calculated as the volume of the region where the areal load ratio is between p% and 100% in the load curve shown in FIG. 4B (the curve showing the height c where the areal load ratio Smr(c) goes from 0% to 100%). Here, the portion where the areal load ratio is 80% or more is calculated as the protruding valley space volume Vvv (see FIG. 4C). The larger the protruding valley space volume Vvv is, the larger the volume of the valleys will be, and therefore the amount of lubricant retained on the sliding surface of the heater will be. Therefore, when the protruding valley space volume Vvv on the sliding surface of the heater is set to 0.01 ml / m 2 By setting the above, the amount of lubricant held on the sliding surface of the heater is increased, and wear of the fixing belt can be effectively suppressed.

[0082] <Bias Ssk> Another parameter that indicates surface roughness (surface shape characteristic value) is the degree of skewness Ssk. The degree of skewness Ssk indicates the symmetry of the height distribution and is calculated by the following formula (3).

[0083]

number

[0084] When the degree of deviation Ssk is greater than 0, the surface has many sharp peaks (mountains), as shown in Fig. 4D(a). On the other hand, when the degree of deviation Ssk is less than 0, the surface has many round peaks (mountains), as shown in Fig. 4D(b). When the degree of deviation Ssk is 0, the height distribution is symmetrical from top to bottom.

[0085] In order to improve the wear resistance of the sliding surface of the heater, a sliding surface having many rounded apexes is preferable to a sliding surface having many sharp apexes. Therefore, in this embodiment, the deviation Ssk of the sliding surface of the heater is set to less than 0.

[0086] <Sku> Another parameter that represents surface roughness (surface shape characteristic value) is the kurtosis Sku. The kurtosis Sku represents the sharpness of the height distribution and is calculated by the following formula (4).

[0087]

number

[0088] When the sharpness Sku>3, the surface has sharp peaks (mountains) and recesses (valleys), as shown in Fig. 4E(a). On the other hand, when the sharpness Sku<3, the surface has round peaks (mountains) and recesses (valleys), as shown in Fig. 4E(b). When the sharpness Sku=3, the height distribution is a normal distribution.

[0089] In order to improve the wear resistance of the sliding surface of the heater, a sliding surface having a rounded apex is preferable to a sliding surface having a sharp apex, and therefore, in this embodiment, the sharpness Sku of the sliding surface of the heater is set to less than 3.

[0090] <Method of measuring surface shape characteristics> The above-mentioned various surface shape characteristic values ​​(line roughness Ra, surface roughness Sa, protruding valley space volume Vvv, deviation Ssk, and sharpness Sku) can be measured using a VK-X100 (manufactured by Keyence) with a 50x objective lens. The fixing belt sample is set on a smooth surface, and measurements are performed after confirming that there is no significant inclination or waviness at the observation position.

[0091] <Elastic power> As described above, in an embodiment of the present invention, the surface roughness of the sliding surface of the heater is made greater than the surface roughness of the sliding surface of the fixing belt, and further, various surface shape characteristic values ​​of the sliding surface of the heater are appropriately set, thereby making it possible to effectively suppress abnormal noise and wear of the fixing belt caused by sliding of the fixing belt.

[0092] However, when the fixing belt wears over time due to sliding, wear powder is generated, and the lubricant is absorbed by the wear powder. This reduces the lubricity at the sliding points between the fixing belt and the heater, which may cause abnormal noise. Therefore, in order to suppress the generation of such abnormal noise, it is necessary to improve the wear resistance of the fixing belt.

[0093] Therefore, the present inventors conducted a wear test on the fixing belt in order to improve the wear resistance of the fixing belt. As a result, it was found that the wear resistance of the fixing belt can be improved by increasing the elastic power of the sliding surface (inner peripheral surface) of the fixing belt. The relationship between the elastic power and the wear resistance will be described below.

[0094] First, "elastic power" is the value obtained by finding the relationship between stress and displacement from the displacement that occurs when stress is applied to a component, calculating the work of elastic deformation, and dividing that work of elastic deformation by the total work (work of elastic deformation + work of plastic deformation). In other words, the elastic power can be expressed mathematically as shown in the following formula (5). The closer the elastic power of a material is to 1 (100%), the easier it is to elastically deform.

[0095]

number

[0096] <Method for measuring elastic power> The elastic power can be measured by a loading and unloading test (indentation test) using a micro surface hardness tester with a diamond indenter. Specifically, as shown in Figure 5, diamond indenter A is pressed into sample B at a constant loading speed (loading process) from the state where diamond indenter A starts to contact sample B (state shown in Figure 5(a)), and is then stopped for a certain period of time when the indentation load reaches a set load (state shown in Figure 5(b)). After that, diamond indenter A is lifted up at a constant unloading speed (unloading process), and finally the sample B is brought into a state where no load is applied (state shown in Figure 5(c)).

[0097] The graph in FIG. 5(d) shows the relationship between the load (indentation load) and the displacement (indentation amount) at this time. In FIG. 5(d), the state shown in (a) is the state where the diamond indenter A starts to contact the sample B (the state shown in FIG. 5(a)), and the load of the diamond indenter A and the displacement of the sample B are both 0. Next, the state shown in (b) is the state where the indentation load reaches the set load (the state shown in FIG. 5(b)), and the load of the diamond indenter A and the displacement of the sample B are both maximum. Finally, the state shown in (c) is the state where the diamond indenter A is pulled up and the load is no longer applied to the sample B (the state shown in FIG. 5(c)). At this time, the load of the diamond indenter A becomes 0, but the displacement of the sample B does not become 0 because plastic deformation occurs in the sample B. In addition, in FIG. 5(d), We indicates the work amount of elastic deformation, and Wt indicates the work amount of plastic deformation.

[0098] The elastic power can be obtained by recording the relationship between load and displacement during the above-mentioned loading / unloading test (graph in Figure 5(d)), and from this relationship, calculating the ratio of the work of elastic deformation We to the total work done by diamond indenter A on the surface layer (the work of elastic deformation We + the work of plastic deformation Wt).

[0099] In the embodiment of the present invention, the elastic power was measured under constant temperature and humidity. Specifically, the elastic power in this embodiment indicates the measured value of the above test performed under environmental conditions of a temperature of 23°C and a relative humidity of 50%. In this embodiment, a load was applied using a Fischerscope HM-2000 (manufactured by Fisher Instruments) and a Vickers indenter under the conditions of a set load of 20 mN, a time to reach the maximum load of 30 seconds, and a creep time of 5 seconds, and the load was removed over 30 seconds to measure the elastic power. The elastic power may be measured using another device having equivalent performance.

[0100] In addition, in this measurement test, the fixing belt sample was suspended on a metal substrate to measure the elastic power. Since the elastic power is affected by the spring characteristics of the substrate, a rigid metal plate, slide glass, etc. are suitable as the substrate. In addition, since the hardness and elasticity of the layer below the crosslinked surface layer (e.g., the belt substrate, etc.) also have an effect, the specified load was adjusted so that the maximum displacement was 1 / 10 of the thickness of the inner coat to reduce these effects. Furthermore, in order to eliminate the effects of the rubber (elastic layer) and release layer provided on the substrate surface, it is preferable to peel off the surface rubber (elastic layer) and release layer during measurement. In this measurement test, the measurement was performed with the surface rubber and release layer peeled off.

[0101] <Elastic power and wear rank> FIG. 6 shows the relationship between the elastic power of the fixing belt obtained by the above measurement test and the wear resistance rank of the fixing belt.

[0102] In the wear resistance rank evaluation test, the fixing belt was assembled to the fixing device, and the fixing belt was heated to a constant temperature (fixing temperature) by a heater, and the fixing belt was rotated and stopped repeatedly until the rotation distance of the fixing belt reached its life distance. The fixing device used in this evaluation test was configured to include a fixing belt with a polyimide layer on its inner circumferential surface, a heater with a glass layer, a nip forming member (heater holder), and a pressure roller. The fixing belt was heated to a constant temperature, and the rotation and stopping were repeated until the rotation distance reached its life distance, and the wear state of the fixing belt was confirmed. As a result, the wear state of the fixing belt was determined to be at a level that could be used practically, and at a level that had no effect on image quality, and was determined to be at a wear resistance rank of "3" or higher.

[0103] From the test results shown in Figure 6, it was found that if the elastic power is 55% or more, practical wear resistance can be ensured, and furthermore, if the elastic power is 62% or more, high-quality wear resistance can be ensured. This is thought to be because the higher the elastic power of a material, the higher the stress relaxation ability when the load stress is removed, so the load caused by the sliding of the fixing belt is relieved, and the load can be prevented from remaining as permanent strain on the sliding surface (inner peripheral surface) of the fixing belt.

[0104] Therefore, in the fixing device according to the present invention, the elastic power of the sliding surface (inner peripheral surface) of the fixing belt is set to 55% or more. This improves the wear resistance of the sliding surface (inner peripheral surface) of the fixing belt, and makes it possible to effectively suppress the generation of abnormal noise at the sliding points for a long period of time. Furthermore, when the elastic power of the sliding surface (inner peripheral surface) of the fixing belt is set to 62% or more, it is possible to effectively suppress the generation of abnormal noise at the sliding points for a long period of time, prevent the generation of abnormal images such as streaked images, and provide high-quality images.

[0105] Furthermore, by setting the surface shape characteristic values ​​(line roughness Ra, surface roughness Sa, protruding valley spatial volume Vvv, deviation Ssk, and sharpness Sku) of the heater sliding surface as described above, it is possible to effectively suppress abnormal noise and wear of the fixing belt caused by the sliding of the fixing belt.

[0106] The lubricant to be interposed at the sliding portion between the heater and the fixing belt may include fluorine grease or silicone oil. By interposing such a lubricant at the sliding portion, the lubrication can be maintained for a long period of time even at the sliding portion under high temperature and high pressure, and the wear of the fixing belt can be suppressed. The lubricant is preferably applied to the heater. That is, the lubricant is applied to the heater sliding surface, which has a relatively large surface roughness, and the fixing belt is rotated, so that the excess of the lubricant on the heater sliding surface can be spread over the entire fixing belt sliding surface, which has a relatively small surface roughness. On the other hand, when the surface roughness of the fixing belt sliding surface is relatively large, the amount of lubricant required to spread over the entire fixing belt sliding surface increases, so that the amount of lubricant applied to the heater sliding surface may not be sufficient. In addition, in order to solve such a shortage of lubricant, there is a method of applying a lubricant to the entire fixing belt sliding surface, but the amount of lubricant required is larger than when the lubricant is applied to the heater. In addition, if the amount of lubricant applied is large, the lubricant may leak from both ends (openings) of the fixing belt, which may cause abnormal images such as uneven gloss. Also, it is difficult to control the manufacturing process to apply the lubricant evenly so that the lubricant does not leak from the fixing belt, and this is not realistic. Therefore, it is preferable that the lubricant is applied to the heater.

[0107] In addition, when the fixing belt has a substrate and a surface layer (release layer) provided on the outer periphery side of the substrate, and does not have an elastic layer such as a rubber layer between the surface layer (release layer) and the substrate, the rigidity is smaller than when the fixing belt has an elastic layer, and the fixing belt is more likely to deform according to the entrance shape of the nip. As a result, the adhesion of the fixing belt to the heater is increased, and the lubricant is more easily supplied to the sliding area between the heater and the fixing belt by the capillary phenomenon caused by the adhesion, and the lubrication at the sliding area is effectively obtained.

[0108] <Difference between elastic power and return rate> Here, the return rate is an index similar to the elastic power (see Patent Document 4: Japanese Patent No. 6036469). The "return rate" is a value expressed by the following formula (6), where h1 is the maximum displacement when a load is applied to the target member, and h2 is the displacement when the load is subsequently removed (see FIG. 7).

[0109]

number

[0110] For example, as shown in Fig. 7, in a graph showing the relationship between the load applied to a target member and the displacement of the target member, if the return speed (speed of return deformation) is different when the displacement of the target member changes from h1 to h2, different return lines 1, 2, and 3 are displayed according to the respective return speeds. However, the return rate does not take into account the difference in return speed and represents the ratio of the displacement difference to the maximum displacement amount, so the return rate will be the same value for all return lines.

[0111] In contrast, the elastic power is a value that indicates the energy loss when the target member elastically returns with unloading, taking into account the information on the return speed. Therefore, when the return lines 1, 2, and 3 are different from each other, the elastic power will all be different values. Therefore, even if the return rate is the same, the elastic power may differ depending on the unloading profile, and the frictional force (rotational torque) at the sliding point of the fixing belt may differ depending on the difference in the elastic power. Specifically, when the difference in energy loss obtained from the elastic power is large, the frictional force (torque) at the sliding point of the fixing belt becomes large. Therefore, as a characteristic of the sliding surface of a fixing belt or the like, the elastic power, which can confirm information on the frictional force in addition to the wear resistance, is more useful than the return rate, which cannot determine the presence or absence of frictional force or its magnitude relationship.

[0112] <Method of manufacturing the fixing belt> In the fixing belt according to the embodiment of the present invention, polyimide (PI) is used as the main component of the material constituting the cylindrical substrate. By using polyimide as the main component, high elastic power can be ensured. In addition, when a metal material is used as the material of the substrate, it is preferable to apply a polyimide-based paint to the inner peripheral surface of the substrate.

[0113] A method for manufacturing the fixing belt according to this embodiment will be described below.

[0114] <Paint Mixing> To mix the coating liquid, add 80g of NMP (N-methyl-pyrrolidone) to 100g of polyimide varnish and mix. For the polyimide varnish, use U-Imide Varnish AR manufactured by Unitika Ltd. For NMP, use special grade N-methyl-pyrrolidinone manufactured by Kanto Chemical. This mixture will be called A. While stirring the mixture A with a tabletop mixer, gradually add the needle-shaped inorganic filler and knead. Add 20g of needle-shaped inorganic filler to 100g of polyimide varnish. · The needle-shaped inorganic filler is gradually added and kneaded over a period of about 10 to 15 minutes to prevent it from forming lumps. The needle-shaped inorganic filler used is Tismo D manufactured by Otsuka Chemical Co., Ltd. This mixture will be called B.

[0115] <Painting> The method for applying the above-mentioned mixed liquid B to the inner surface of the fixing belt is spray coating or dipping coating. In this embodiment, spray painting is used as the painting method. Put mixed solution B into the pressure tank. Rotate the fixing belt to apply mixed liquid B to the inner surface of the fixing belt. The rotation speed of the fixing belt should be set within the range of 900 to 1000 rpm. In this embodiment, the rotation speed of the fixing belt is set to 900 rpm. The coating speed should be set at 30mm / s, and the coating weight in each coat should be in the range of 0.7~1.2g. The application weight is adjusted by the pressure at which Mixture B is pumped. In this embodiment, the pressure is 125 kPa, and the coating weight per application is 1.0 g. After application, the paint is pre-dried using hot air at 200°C, and then layers of paint are applied. Repeat painting and pre-drying 3 to 4 times. After painting is complete, the parts are placed in a drying oven at 260°C for 30 minutes for heat treatment to volatilize the NMP. The thickness of the sliding layer is preferably 8 to 15 μm. In this embodiment, a total of 4.2 g of Preparation B is applied to give a film thickness of 11 μm.

[0116] <Firing> Firing is carried out in a vertical far-infrared furnace. Far-infrared heaters are placed on the left and right sides of the vertically placed fixing belt, and the heaters heat an area equal to or greater than the length of the fixing belt. Set the temperature of the far-infrared heater so that the fixing belt reaches the specified temperature. Set the far-infrared heater temperature so that the actual temperature of the fixing belt is 360°C. - Bake time is 30 minutes.

[0117] The elastic power of the sliding surface (inner peripheral surface) of the fixing belt manufactured as described above was measured, and the elastic power was 70.0% at room temperature of 23° C., and 60.2% when heated to 165° C. In this case, under both temperature conditions, the elastic power was 55% or more, which is the standard for improving the wear resistance of the fixing belt.

[0118] The elastic power of the fixing belt can be adjusted by changing the baking conditions of the fixing belt. Examples of other baking conditions are shown below.

[0119] <Firing> Set the far-infrared heater temperature so that the actual temperature of the fixing belt is 280°C. - Bake time is 30 minutes. The conditions other than the firing temperature and firing time are the same as those in the above manufacturing method.

[0120] When the elastic power of the sliding layer (inner surface) of the fixing belt manufactured under the other baking conditions described above was measured, the elastic power was 60.4% at room temperature of 23°C and 52.1% under heating conditions of 165°C.

[0121] In this way, when polyimide is used as the material of the base material of the fixing belt, it is possible to appropriately adjust the elastic power of the sliding surface (inner peripheral surface) of the fixing belt by changing the baking conditions of the belt. In other words, by using polyimide as the material of the base material of the fixing belt, the elastic power of the fixing belt can be easily adjusted to a desired value, and the wear resistance of the fixing belt can be improved. The material of the fixing belt according to the present invention is not limited to polyimide, and may be a heat-resistant resin such as PEEK. Also, the fixing belt may be made of a metal material such as nickel or SUS, and polyimide or PTFE may be applied to the base material.

[0122] <Another embodiment of the fixing device> Further, the fixing device according to the present invention is not limited to the embodiment shown in Fig. 2A, but may be an embodiment as shown in Fig. 2B to Fig. 2D. Hereinafter, second to fourth fixing devices will be described with reference to Fig. 2B to Fig. 2D.

[0123] The second fixing device 300 shown in FIG. 2B has a pressure roller 390 on the opposite side of the fixing belt 310 to the pressure roller 320 side, and the fixing belt 310 is sandwiched between the pressure roller 390 and a heater 330 to be heated.

[0124] Heater 330 is supported by auxiliary stay 351, which is further supported by stay 350. A nip forming member 381 is attached to the side of stay 350 opposite to the auxiliary stay 351 side, and nip forming member 381 abuts against pressure roller 320 via fixing belt 310 to form fixing nip SN.

[0125] In the third fixing device 300 shown in Fig. 2C, the above-mentioned pressure roller 390 is omitted, and the heater 330 is formed in an arc shape to match the curvature of the fixing belt 310. In this way, by forming the heater 330 in an arc shape, the contact length between the heater 330 and the fixing belt 310 in the belt rotation direction can be increased, and the heating efficiency can be improved. The other configurations are the same as those of the second fixing device shown in Fig. 2B.

[0126] A fourth fixing device 300 shown in Fig. 2D has belts 311 and 312 on either side of a pressure roller 320. A heater 330, a heater holder 340, a stay 350, etc. are arranged inside belt 311 on the left side in Fig. 2D, and heater 330 is pressed against pressure roller 320 via belt 311. A nip forming member 381 and a stay 352 are arranged inside belt 312 on the right side in Fig. 2D, and nip forming member 381 is pressed against pressure roller 320 via belt 312 to form a fixing nip SN.

[0127] <Heater configuration> The heater included in the fixing device according to the present invention may have various configurations, for example, as shown in Figures 8A to 8C. In any type of heater 330, a resistance heating element 370 is formed on a base material 341 made of an elongated thin metal plate member covered with an insulating material.

[0128] <Single type resistance heating element> 8A shows a single-type resistance heating element 370, which is arranged in series in two parallel rows in the longitudinal direction of substrate 341. One end of each of the resistance heating elements 370 in the two rows is connected to power supply electrodes 370c, 370d, respectively, via power supply lines 379a, 379c with small resistance values ​​formed in the longitudinal direction at one end side of substrate 341. These electrodes 370c, 370d are connected to power supply means including an AC power source.

[0129] The other end of each resistance heating element 370 is connected by folding back toward the opposite longitudinal side of base material 341 via a power supply line 379b with a small resistance value formed in the short direction on the other end side of base material 341. Each resistance heating element 370, each of electrodes 370c, 370d, and each of power supply lines 379a to 379c are formed to a predetermined line width and thickness by, for example, screen printing.

[0130] The surfaces of each resistance heating element 370 and each power supply line 379a-379c are covered with a thin overcoat layer or insulating layer 385. The insulating layer 385 ensures the slidability of the fixing belt and also ensures insulation between the fixing belt and each resistance heating element 370 and each power supply line 379a-379c. By using heat-resistant glass for the insulating layer 385, the lubricant in the sliding layer of the heater 330 does not penetrate into the resistance heating element 370, so that oil film breakdown on the nip surface can be suppressed.

[0131] <Dual type resistance heating element> 8B shows a dual-type resistance heating element, which is composed of a central resistance heating element 370-1 in the center in the longitudinal direction and a pair of end resistance heating elements 370-2 arranged on both sides of the central resistance heating element 370-1. The opposing ends of the central resistance heating element 370-1 and each end resistance heating element 370-2 are formed at an incline with respect to the short-side direction of the base material 341 (parallelogram). Due to this inclination, the gap between the central resistance heating element 370-1 and the end resistance heating element 370-2 is smaller when viewed from the short-side direction of the base material 341, and the temperature drop between them can be reduced.

[0132] One end of the central resistance heating element 370-1 is connected to the left electrode 370e via a power supply line 379d, and the other end is connected to the right electrode 370h via a power supply line 379f. One end of the left end resistance heating element 370-2 is connected to the left electrode 370e via a power supply line 379d, and the other end is connected to the left electrode 370f via a power supply line 379e. One end of the right end resistance member 370-2 is connected to the left electrode 370e via a power supply line 379d, and the other end is connected to the right electrode 370g via a power supply line 379h.

[0133] As described above, the central resistive heating element 370-1 and the end resistive heating element 370-2 can generate heat independently by connecting the resistive heating elements 370-1 and 370-2 to the electrodes 370e to 370h. Specifically, when a voltage is applied to the electrodes 370e and 370h, the central resistive heating element 370-1 generates heat, when a voltage is applied to the electrodes 370e and 370f, the left end resistive heating element 370-2 generates heat, and when a voltage is applied to the electrodes 370e and 370g, the right end resistive heating element 370-2 generates heat.

[0134] Furthermore, if the electrodes 370f, 370g are connected in parallel externally, the left and right end resistance heating elements 370-2 can be heated simultaneously. In that case, if the paper is centered, the temperature will be symmetrical, so instead of providing thermistors at both ends of each end resistance heating element 370-2, it is sufficient to provide a thermistor at only one side, thereby reducing costs.

[0135] <Multi-type resistance heating element> FIG. 8C shows a multi-type resistive heating element, which has a plurality of PTC elements 371-378 electrically connected in parallel. The PTC element is made of a material having a positive temperature coefficient of resistance, and has a characteristic that the resistance value increases as the temperature increases. The temperature coefficient of resistance (TCR) can be, for example, 1500 PPM (parts per million). By making the resistive heating element such a multi-type, it becomes easier to uniformize the temperature in the longitudinal direction, so that the variation in the viscosity of the grease can be suppressed and the amount of grease on the nip surface in the longitudinal direction can be uniformed.

[0136] The PTC elements 371-378 are linearly arranged at equal intervals in the longitudinal direction of the substrate 341. Small resistance power supply lines 370a, 370b are linearly arranged parallel to each other on both sides of the short sides of each PTC element 371-378, and both ends of each PTC element 371-378 are connected to these power supply lines 370a, 370b. Each PTC element 371-378 is connected to each electrode 370c, 370d arranged on both ends of the heater 330 in the longitudinal direction via each power supply line 370a, 370b.

[0137] The PTC elements 371-378 can be formed, for example, by applying a paste made of silver palladium (AgPd) and glass powder to the base material 341 by screen printing or the like, and then firing the base material 341. In addition to the above-mentioned materials, the PTC elements 371-378 may be made of resistive materials such as silver alloy (AgPt) and ruthenium oxide (RuO2).

[0138] By using the PTC elements 371-378, when the temperature of the PTC elements in the non-paper passing area rises due to the passing of small-sized paper, the amount of heat generated by the PTC elements is reduced due to the temperature resistance dependency of the resistance heating element, and the temperature rise can be suppressed. Due to this feature, for example, when printing paper narrower than the full width of the PTC elements 371-378 (for example, within the width of the PTC elements 373-376), the temperature of the PTC elements outside the paper width rises because the heat is not absorbed by the paper. Then, the resistance value of those PTC elements rises. Here, since the voltage applied to the PTC elements 371-378 is constant, the output of the PTC elements outside the paper width relatively decreases due to the increase in resistance value, and the rise in temperature at the edge is suppressed.

[0139] Unlike the example shown in Fig. 8C, multiple PTC elements 371-378 can also be electrically connected in series. However, when multiple PTC elements 371-378 are connected in series, if the temperature of the resistance heating element outside the paper width rises during continuous printing, the printing speed must be reduced to suppress the temperature rise. In contrast, when multiple PTC elements 371-378 are electrically connected in parallel as in the example shown in Fig. 8C, the temperature rise in non-paper passing areas can be suppressed while maintaining the printing speed, which has the advantage of maintaining productivity.

[0140] Generally, the strength of a fixing belt decreases as the temperature increases, making it more susceptible to wear. However, by using a multi-type resistance heating element as shown in Fig. 8C, it is possible to prevent excessive temperature rise in non-paper passing areas when small-sized paper is passing through, which in turn prevents wear on the fixing belt and also prevents evaporation of the lubricant.

[0141] The shape of each PTC element 371 to 378 may be a rectangle as shown in FIG. 8C(a), a shape having a step at the longitudinal end as shown in FIG. 8C(b), or a parallelogram as shown in FIG. 8C(c).

[0142] In the example shown in Fig. 8C(b), a step is formed by an L-shaped notch at the end of each PTC element 371-378, and the step overlaps with the step of the adjacent PTC element. Also, in the example shown in Fig. 8C(c), the inclined portion provided at the end of each PTC element 371-378 overlaps with the inclined portion at the end of the adjacent PTC element. By overlapping the ends of each PTC element 371-378 with each other in this way, the effect of the reduction in the amount of heat generated in the gap between the PTC elements can be suppressed.

[0143] 8C, the electrodes 370c, 370d are arranged on both sides of the PTC elements 371-378 so as to sandwich them, but the electrodes 370c, 370d may be arranged on one side of the PTC elements 371-378. In that case, the heater 330 can be made smaller in size in the longitudinal direction.

[0144] Furthermore, the shape of each PTC element 371-378 is not limited to a block shape (such as a rectangle or parallelogram) as shown in FIG. 8C, but may be a linear PTC element formed into a meandering shape to obtain the desired output (resistance value).

[0145] Although the embodiment of the present invention has been described above by taking as an example a case where the present invention is applied to a fixing device, which is an example of a belt device, the present invention can also be applied to belt devices other than fixing devices. For example, the present invention can be applied to a drying device (belt device) in an inkjet image forming device that heats and dries paper with ink attached thereto while transporting it with a belt.

[0146] In the above embodiment, the case where the generation of abnormal noise at the sliding portion between the fixing belt and the heater is suppressed has been described as an example, but the present invention is also applicable to the sliding portion between the belt and nip forming member 381 shown in Fig. 2C or 2D. That is, in the present invention, the sliding member that slides relatively to the belt may be various sliding members including a nip forming member, in addition to the heater. [Explanation of symbols]

[0147] 50 Lubricants 100 Image forming device 300 Fixing device (belt device) 310 Fixing belt (belt) 310s sliding surface 320 Pressure roller (pressure member) 330 Heater (heat source, sliding member) 330s sliding surface 370 Resistance heating element (heating element) SN Fixing nip (nip part) [Prior art documents] [Patent documents]

[0148] [Patent Document 1] JP 2020-148943 A

Claims

1. A rotatable endless belt; A sliding member that slides relative to an inner circumferential surface of the belt; a pressing member that contacts the sliding member via the belt and forms a nip portion between the pressing member and the belt; a lubricant interposed between the inner circumferential surface of the belt and the sliding member; A belt device comprising: A belt device characterized in that, of the sliding surfaces on which the belt and the sliding member slide, the elastic power of the sliding surface of the belt is 62% or more, and the surface roughness of the sliding surface of the sliding member is greater than the surface roughness of the sliding surface of the belt.

2. A belt device as described in claim 1, wherein the surface roughness Sa of the sliding surface of the sliding member is 0.2 μm or more.

3. The belt device according to claim 1, wherein the linear roughness Ra in the sliding direction on the sliding surface of the sliding member is 0.2 μm or more.

4. The belt device according to claim 1, wherein the surface roughness Sa of the sliding surface of the belt is 0.05 μm or less.

5. The belt device according to claim 1, wherein the line roughness Ra in the sliding direction on the sliding surface of the belt is 0.05 μm or less.

6. The belt device according to claim 1, wherein a protruding valley space volume Vvv, which is a surface shape characteristic value of the sliding surface of the sliding member, is 0.01 ml / m 2 or more.

7. The belt device according to claim 1, wherein the degree of bias Ssk, which is a surface shape characteristic value of the sliding surface of the sliding member, is less than 0.

8. The belt device according to claim 1, wherein the surface shape characteristic value of the sliding surface of the sliding member is a sharpness Sku of less than 3.

9. A belt device according to any one of claims 1 to 8; a heat source for heating at least one of the belt and the pressure member of the belt device; A fixing device comprising:

10. The fixing device according to claim 9, wherein the heat source is a sliding member that slides relative to the inner surface of the belt.

11. The fixing device according to claim 10, wherein the heat source has a plurality of heating elements arranged along the longitudinal direction of the heat source and capable of being controlled to generate heat independently of each other.

12. An image forming apparatus comprising a belt device according to any one of claims 1 to 8, or a fixing device according to any one of claims 9 to 11.

Images