Fixing device and image forming apparatus

Abstract

To prevent wear of an inner surface of a fixing belt and a slide part over time.SOLUTION: A fixing device of the present invention comprises: a sleeve-like rotating member (fixing belt 310) that has flexibility; a slide member (resistance member 370) that slides with an inner surface of the rotating member; a pressure member (pressure roller 320) that is in pressure contact with a portion facing the slide member with the rotating member therebetween to form a nip part between the rotating member and the pressure member; and lubricant between the rotating member and the slide member. The consistency of the lubricant is set to 340 or less and the elastic power of a slide surface of the rotating member is set to 58% or more, or the consistency of the lubricant is set to 275 or less and the elastic power of the slide surface of the rotating member is set to 55% or more. The surface roughness in a slide direction of the slide surface of the rotating member is made larger than the surface roughness in the slide direction of a slide surface of the slide member.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a fixing device and an image forming apparatus, and more particularly to a fixing device and an image forming apparatus in which the slidability of a fixing belt is improved and noise caused by sliding is suppressed. [Background technology]

[0002] Various types of fixing devices are known for use in electrophotographic image forming apparatuses. One of these is a sliding fixing method in which a thin fixing belt with low heat capacity is heated by a heater member (see Patent Documents 1 and 2). The heater member used is a halogen lamp or a planar heater. The fixing belt is sandwiched between a pressure roller acting as a pressure member on the outside of the fixing belt and a sliding portion that makes sliding contact with the inner surface of the fixing belt, forming a fixing nip.

[0003] In conventional sliding fixing methods, in order to suppress wear on the inner surface of the belt that comes into sliding contact with the sliding part or the planar heater, a lubricant is applied to the sliding part, and the surface roughness of the inner surface of the fixing belt in the sliding direction is made rougher than the surface roughness of the sliding part, as in Patent Document 3 (JP 2009-14893 A), for example. Summary of the Invention [Problem to be solved by the invention]

[0004] However, it has been found that it is difficult to maintain the inner surface roughness of a rotating fixing belt as described in Patent Document 3 over time, and that the inner surface roughness of the fixing belt smoothes over time due to wear. When the inner surface of the fixing belt smooths, wear on the inner surface of the belt (sliding layer such as polyimide or PTFE) increases (surface deterioration), causing stick-slip noise. Therefore, an object of the present invention is to suppress wear on the rotating members and sliding parts over time. [Means for solving the problem]

[0005] In order to solve the above-mentioned problems, the fixing device of the present invention includes a flexible sleeve-shaped rotating member, a sliding member that slides against the inner periphery of the rotating member, a pressure member that sandwiches the rotating member and presses against a portion facing the sliding member to form a nip between the rotating member and the pressure member, and a lubricant between the rotating member and the sliding member, wherein the consistency of the lubricant is 340 or less, and the elastic power of the sliding surface of the rotating member is 58% or more, or the consistency of the lubricant is 275 or less, and the elastic power of the sliding surface of the rotating member is 55% or more, and the surface roughness in the sliding direction of the sliding surface of the rotating member is greater than the surface roughness in the sliding direction of the sliding surface of the sliding member. [Effects of the Invention]

[0006] According to the present invention, wear of the rotating members and sliding parts can be suppressed over time. [Brief explanation of the drawings]

[0007] [Figure 1A] 1 is a schematic diagram illustrating the 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. 10 is a cross-sectional view of a third fixing device according to an embodiment of the present invention. [Figure 2D] FIG. 10 is a cross-sectional view of a fourth fixing device according to an embodiment of the present invention. [Figure 3A] 1A and 1B are a plan view and a cross-sectional view, respectively, of a single resistance heating element with an electrode at one end. [Figure 3B] 1A and 1B are a plan view and a cross-sectional view, respectively, of a dual resistance heating element having electrodes on both ends. [Figure 3C] FIG. 1 is a plan view of a multi-resistance heating element having electrodes on both ends. [Figure 4] FIG. 2 is a diagram showing a heating device, a power supply circuit, and a control unit. [Figure 5] 1(a) to 1(d) are diagrams illustrating a method for measuring elastic power. [Figure 6] FIG. 1 is a load-displacement diagram illustrating the difference between elastic power and rate of return. [Figure 7] FIG. 10 is a diagram showing the rank of inner surface wear of a fixing belt according to elastic power. [Figure 8] FIG. 10 is a diagram showing the correlation between elastic power and film loss. [Figure 9] 10A and 10B are diagrams illustrating how the lubricant is retained depending on the surface roughness of the fixing belt and the heater. [Figure 10A] FIG. 1 is a diagram illustrating arithmetic mean roughness. [Figure 10B] FIG. [Figure 10C] FIG. 1 is a diagram showing a load curve representing a solid portion and a space portion. [Figure 10D] 1A and 1B are diagrams showing height distributions depending on the skewness Ssk, where (a) Ssk>0 and (b) Ssk<0. [Figure 10E] FIG. 10 is a diagram showing the height distribution according to the kurtosis (Sku), where (a) is the height distribution when Sku>3 and (b) is the height distribution when Sku<3. [Figure 11A] FIG. 10 is a diagram showing the relationship between elastic power and coefficient of friction. [Figure 11B] FIG. 10 is a diagram showing the relationship between elastic power and the occurrence of abnormal noise and vibration. [Figure 11C] FIG. 10 is a diagram showing the relationship between the elastic power and the difference in the coefficient of friction. [Figure 12] 1A and 1B are schematic configuration diagrams of different types of image forming apparatuses. [Figure 13] 1A and 1B are diagrams illustrating the configuration of fixing devices of different models. [Figure 14] FIG. 2 is a plan view of a heater member of the fixing device. [Figure 15] FIG. 2 is an exploded perspective view of a heater member and a holder. [Figure 16] FIG. 2 is an exploded perspective view of a heater member, a terminal, a guide, and a stay. [Figure 17]FIG. 2 is a diagram showing the arrangement of thermistors. [Figure 18] FIG. 10 is an explanatory diagram of a groove in a guide. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, a heating device according to an embodiment of the present invention, and a fixing device and image forming apparatus (laser printer) using the heating device will be described with reference to the drawings. In this specification, the term "heating device" refers to a device that heats a sheet material with a heat generating element. The term "fixing device" refers to a device that conveys a sheet material in a direction perpendicular to the longitudinal direction through a nip formed between the heating device and a pressure applying element, thereby fixing unfixed toner on the sheet material. The term "image forming apparatus" refers to a device that includes a fixing device and forms an image by applying developer or ink to a sheet material, which is a recording medium on which an image is recorded.

[0009] A laser printer is one example of an image forming device, and the image forming device is not limited to a laser printer. In other words, the image forming device can be configured as any one of a copier, facsimile, printer, printing machine, and inkjet recording device, or as a multifunction device that combines at least two of these.

[0010] In addition, the same or corresponding parts in each drawing are denoted by the same reference numerals, and redundant 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, are not intended to limit the scope of this invention.

[0011] 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 (paper). The "recording medium" includes not only paper (paper), but also overhead projector sheets, fabrics, metal sheets, plastic films, and prepreg sheets made of carbon fibers pre-impregnated with resin.

[0012] "Recording media" includes media onto which developer or ink can be attached, recording paper, and recording sheets. "Paper" also includes not only plain paper, but also cardboard, postcards, envelopes, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, etc.

[0013] Furthermore, the term "image formation" used in the following description refers not only to the application of meaningful images such as letters and figures to a medium, but also to the application of meaningless images such as patterns to a medium.

[0014] (● Laser printer configuration) Fig. 1A is a diagram showing the schematic configuration of a color laser printer as one embodiment of an image forming apparatus 100 equipped with a heating device or fixing device 300 of the present invention. Fig. 1B also shows a simplified diagram of the principle of the color laser printer.

[0015] 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.

[0016] Each process unit 1K, 1Y, 1M, and 1C has the same configuration except that it has toner bottles 6K, 6Y, 6M, and 6C containing 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.

[0017] The process unit 1K has an image carrier 2K (e.g., a photosensitive drum), a drum cleaning device 3K, and a static eliminator. The process unit 1K also has a charging device 4K as charging means for uniformly charging the surface of the image carrier, and a developing device 5K as developing means for visualizing the electrostatic latent image formed on the image carrier. The process unit 1K is detachably mounted to the main body of the image forming apparatus 100, and consumable parts can be replaced at the same time.

[0018] The exposure device 7 is disposed above each of the process units 1K, 1Y, 1M, and 1C installed in the image forming apparatus 100. The exposure device 7 is configured to perform writing scanning in accordance with image information, that is, to reflect laser light LB from a laser diode on a mirror 7a based on image data and irradiate the image carrier 2K.

[0019] In this embodiment, the transfer device 15 is disposed below each of the process units 1K, 1Y, 1M, and 1C. This transfer device 15 corresponds to the transfer means TM in Fig. 1B. Primary transfer rollers 19K, 19Y, 19M, and 19C are disposed in contact with the intermediate transfer belt 16, facing the image carriers 2K, 2Y, 2M, and 2C, respectively.

[0020] The intermediate transfer belt 16 circulates while being stretched over primary transfer rollers 19K, 19Y, 19M, and 19C, a drive roller 18, and a driven roller 17. A 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.

[0021] The belt cleaning device 21 is installed downstream of the secondary transfer roller 20 in the running direction of the intermediate transfer belt 16. In addition, a cleaning backup roller is installed on the opposite side of the intermediate transfer belt 16 from the belt cleaning device 21.

[0022] A paper feeder 200 having a tray for stacking paper sheets 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 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 means for transporting paper sheets P.

[0023] Paper feeder 200 can be inserted into and removed from the main body of image forming apparatus 100 for paper replenishment, etc. Paper feed roller 60 and roller pair 210 are disposed above paper feeder 200, and are configured to transport the topmost paper P in paper feeder 200 toward paper feed path 32.

[0024] The pair of registration rollers 250, which serves as a separation and conveyance means, is disposed immediately upstream of the secondary transfer roller 20 in the conveyance direction, and can temporarily stop the paper P fed from the paper feeder 200. This temporary stop causes slack in the leading edge of the paper P, correcting any skew in the paper P.

[0025] 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.

[0026] A transport roller 240 is disposed at the downstream end of the paper feed device 200 to transport the paper upward after it has 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.

[0027] The roller pair 210 is made up of a pair of upper and lower rollers. The roller pair 210 can be of an FRR separation type or an FR separation type.

[0028] In the FRR separation method, a separation roller (return roller) to which a fixed 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 the FR separation method, 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.

[0029] In this embodiment, the roller pair 210 is configured using the FRR separation method. That is, the roller pair 210 is configured with an upper feed roller 220 that transports 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.

[0030] The separation roller 230 is biased by a biasing means such as a spring toward the feed roller 220. The feed roller 60 rotates counterclockwise in FIG. 1A by transmitting the driving force of the feed roller 220 via a clutch means.

[0031] The paper P, which has been struck by the pair of registration rollers 250 and has a loosened leading edge, 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. The toner image formed on the intermediate transfer belt 16 is then electrostatically transferred with high precision to the desired transfer position on the sent-out paper P by a bias applied at the secondary transfer nip.

[0032] The post-transfer conveying 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 near the upper end of the post-transfer conveying path 33.

[0033] Fixing device 300 includes fixing belt 310 as a rotating member incorporating a heating device, and pressure roller 320 as a pressure member that rotates while contacting fixing belt 310 with a predetermined pressure. Fixing device 300 can be of various types as shown in Figs. 2A to 2D described later, but here we will explain the type shown in Fig. 2A.

[0034] The post-fixing transport path 35 is disposed above the fixing device 300, and branches at the upper end of the post-fixing transport path 35 into a paper discharge path 36 and a reversing transport path 41. A switching member 42 is disposed at this branching point, and the switching member 42 swings around a swing shaft 42a. A pair of paper discharge rollers 37 is disposed near the open end of the paper discharge path 36.

[0035] The reverse conveying path 41 merges with the paper feed path 32 at the other end opposite 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 top of the image forming apparatus 100 and has a recessed shape facing inward of the image forming apparatus 100.

[0036] 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.

[0037] In the image forming apparatus 100 of this embodiment, a certain distance is required from the paper feed roller 60 to the secondary transfer roller 20 due to the transfer paper transport. The powder container 10 is installed in the dead space created by this distance, thereby reducing the overall size of the laser printer.

[0038] Transfer cover 8 is installed on top of paper feed device 200, directly in front of the paper feed device 200 in the direction of removal. Opening this transfer cover 8 makes it possible to inspect the inside of image forming apparatus 100. Transfer cover 8 is equipped with a manual paper feed roller 45 for manual paper feed and a manual paper feed tray 46 for manual paper feed.

[0039] (● 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.

[0040] 1A, the paper feed roller 60 rotates in response to a paper feed signal from the control unit of the image forming apparatus 100. The paper feed roller 60 then separates only the topmost sheet of the stack of paper sheets P stacked in the paper feed device 200 and sends it to the paper feed path 32.

[0041] 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, the paper P becomes loose 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.

[0042] In the case of manual paper feeding, a stack of sheets of paper loaded on manual tray 46 is conveyed one by one, starting from the top sheet, through 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 for paper feeding from paper feeder 200.

[0043] 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 LB based on image data.

[0044] The potential of the surface of the image carrier 2K irradiated with the laser beam LB drops, forming an electrostatic latent image. The developing device 5K has a developer carrier that carries 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 has been formed.

[0045] The image carrier 2K to which the toner has been transferred forms (develops) a black toner image on its surface. The toner image formed on the image carrier 2K is then transferred to the intermediate transfer belt 16.

[0046] The drum cleaning device 3K removes 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 static eliminator eliminates residual charge on the image carrier 2K from which the residual toner has been removed by the cleaning device 3K.

[0047] Similarly, in the process units 1Y, 1M, and 1C for the respective colors, toner images are formed on the image carriers 2Y, 2M, and 2C, and then transferred onto the intermediate transfer belt 16 so that the toner images of the respective colors are superimposed on each other.

[0048] 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 at a predetermined timing while nipping the paper that has been abutted against them, and transports the paper to the secondary transfer nip of the secondary transfer roller 20 in time with the timing at which the toner images formed by superimposing transfer onto the intermediate transfer belt 16 are suitably transferred. In this way, the toner images on the intermediate transfer belt 16 are transferred onto the paper P sent out by the pair of registration rollers 250.

[0049] The paper P onto which the toner image has been transferred is transported to the fixing device 300 via 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 the unfixed toner image is fixed to the paper P by applying heat and pressure. 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.

[0050] 1A, at the timing when the paper sheet 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 conveyance path 35. The paper sheet P sent out from the fixing device 300 is then sent out to the paper discharge path 36 via the post-fixing conveyance path 35. The paper discharge roller pair 37 pinches the paper sheet P sent out to the paper discharge path 36 and rotates to discharge the paper sheet P onto the paper discharge tray 44, thereby completing the single-sided printing.

[0051] Next, double-sided printing will be described. As in single-sided printing, the fixing device 300 sends the paper P to the paper discharge path 36. When double-sided printing is performed, the pair of paper discharge rollers 37 are driven to rotate to transport a portion of the paper P outside the image forming apparatus 100.

[0052] 1A, the switching member 42 swings about the swing shaft 42a, and closes the upper end of the post-fixing conveyance path 35. Almost simultaneously with the closing of the upper end of the post-fixing conveyance 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 conveyance path 41.

[0053] The paper P sent to the reverse conveying path 41 passes through the reverse conveying roller pair 43 and reaches the registration roller pair 250. The registration roller pair 250 then determines the optimal timing (synchronization) for transferring the toner image formed on the intermediate transfer belt 16 to the non-transferred surface of the paper P, and sends the paper P to the secondary transfer nip.

[0054] Then, when the paper P passes through the secondary transfer nip, the secondary transfer roller 20 and the drive roller 18 transfer the toner image onto the non-transferred surface (back surface) of the paper P. Then, the paper P onto which the toner image has been transferred is transported to the fixing device 300 via the post-transfer transport path 33.

[0055] The fixing device 300 sandwiches the conveyed paper P between a fixing belt 310 and a pressure roller 320, and applies heat and pressure to fix the unfixed toner image to the back surface of the paper P. In this way, the paper P with the toner images fixed on both sides is sent out from the fixing device 300 to a post-fixing conveyance path 35.

[0056] 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. The paper P sent out from the fixing device 300 is then sent out to the paper discharge path 36 via the fixing transport path. The paper discharge roller pair 37 pinches the paper P sent out to the paper discharge path 36, and rotates to discharge the paper onto the paper discharge tray 44, thereby completing double-sided printing.

[0057] After the toner image on the intermediate transfer belt 16 is transferred to the paper P, residual toner remains on the intermediate transfer belt 16. The belt cleaning device 21 removes this residual toner from the intermediate transfer belt 16. The toner removed from the intermediate transfer belt 16 is transported to the powder container 10 by the waste toner transport means and collected in the powder container 10.

[0058] (● Fixing device) Next, a further description will be given below of the heating device and the first to fourth fixing devices 300 according to the embodiment of the present invention. The heating device of this embodiment is for heating the fixing belt 310 of the fixing device 300.

[0059] As shown in FIG. 2A, the first fixing device is composed of a thin fixing belt 310 with low heat capacity and a pressure roller 320. Fixing belt 310 has a cylindrical substrate, for example, with an outer diameter of 25 mm and a thickness of 40 to 120 μm, whose main component is polyimide (PI). By using polyimide as the main component, a high elastic power can be ensured (for example, approximately 20 to 40% in the case of PAI). Furthermore, by using polyimide, if the substrate is PI-based, no inner coating is required, and if the substrate is not PI, a PI-based paint may be applied.

[0060] 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 fixing belt 310. An elastic layer made of rubber or the like and having a thickness of 50 to 500 μm may be provided between the base and the release layer.

[0061] Alternatively, only an adhesive layer may be interposed between the substrate and the release layer without an elastic layer. The polyimide substrate is highly flexible, allowing the belt to conform well to the shape of the nip entrance, making it easy to supply grease to the belt by capillary action.

[0062] Furthermore, when maintaining the same belt surface temperature, the presence of an elastic layer necessitates a higher temperature on the inner surface of the belt, i.e., the sliding surface, due to its insulating effect. Without an elastic layer, the heat conductivity from the inner surface to the outer surface of the belt is improved, allowing the heater temperature to be set lower, which is beneficial in preventing the evaporation of the lubricant and extending the belt's lifespan. Patent Document 5 (Patent Publication No. 6061606) proposes a fixing device that uses polyimide on the inner surface of the belt and adjusts the loss modulus of the polyimide to improve wear resistance, but does not achieve sufficient wear resistance.

[0063] Furthermore, the substrate of fixing belt 310 is not limited to polyimide, but may be a heat-resistant resin such as PEEK, or a metal substrate such as nickel (Ni), SUS, etc. The inner circumferential surface of fixing belt 310 may be coated with polyimide, PTFE, or the like as a sliding layer.

[0064] 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 formed on the surface of core 321, and a release layer 323 formed on the outside of elastic layer 322. Elastic layer 322 is made of silicone rubber, and has a thickness of, for example, 3.5 mm.

[0065] To improve releasability, it is desirable to form a release layer 323 made of a fluororesin layer having a thickness of, for example, about 40 μm on the surface of the elastic layer 322. A pressure roller 320 is pressed against the fixing belt 310 by a biasing means.

[0066] A roll-shaped heat equalizing member 389 is disposed around the outer periphery of fixing belt 310 so as to be rotatable and detachable from the outer periphery of fixing belt 310. Heat equalizing member 389 eliminates temperature unevenness in the axial direction of fixing belt 310, and is made of a material such as aluminum or copper that has high thermal conductivity in the axial direction.

[0067] If the surface of the heat equalizing member 389 is coated with a material with high releasability such as PTFE or PFA, it is possible to prevent toner adhesion, etc. The heat equalizing member 389 can also be disposed on the outer periphery of the pressure roller 320.

[0068] Heat equalizing member 389 may be configured to rotate by contact with fixing belt 310, or may be rotated by a drive source. In a process for reducing the temperature difference (hereinafter referred to as a temperature difference reduction process), which will be described later, heat equalizing member 389 is brought into contact with the outer peripheral surface of fixing belt 310, and the temperature unevenness of fixing belt 310 is thermally transferred in the axial direction by heat equalizing member 389, thereby performing the temperature difference reduction process.

[0069] By providing a drive source for the heat equalizing member 389, a difference in peripheral speed can be established between it and the fixing belt 310, and it can also be given the function of smoothing the surface of the fixing belt 310. This reduces "paper edge scratches" that appear on the image surface when the fixing belt 310 wears at the edge of the paper. For this reason, it is desirable that the heat equalizing member 389 be larger than the maximum paper width and larger than the heating width of the resistance member 370, which is the heat source (width of the heat equalizing member 389 > width of the resistance member 370 > maximum paper width).

[0070] The differential temperature reduction process of the present invention includes all processes for reducing temperature unevenness in the longitudinal direction of the heat generating element 330 (fixing belt 310), and specifically includes the following processes. (1) When the temperature difference detected by the thermistors at two locations in the longitudinal direction of the heating element 330 exceeds the allowable range, the transport of the paper is temporarily stopped. (2) When the temperature difference exceeds the allowable range, the paper transport speed is temporarily reduced. (3) When the temperature difference exceeds the allowable range, the temperature equalizing member 389 is temporarily brought into contact with the fixing belt 310 or the pressure roller 320.

[0071] The allowable range can be freely set, for example, within a range of 5° C. to 15° C. Depending on the degree of deviation from the allowable range, the time for which the paper transport is temporarily stopped, the time for which the paper transport speed is temporarily reduced, or the time for which the temperature equalizing member 389 is temporarily in contact can be increased or decreased. Also, depending on the degree of deviation from the allowable range, the rate at which the paper transport speed is reduced can be increased or decreased.

[0072] If the heat equalizing member 389 is constantly in contact with the fixing belt 310 or the pressure roller 320, this will increase the heat capacity and impair quick start-up. Therefore, it is desirable to have a contact / separation mechanism (not shown) that detects the temperature rise in the non-sheet passing area and controls the heat equalizing member 389 to rotate in contact with the fixing belt 310 or the pressure roller 320 when it is determined that heat equalization is necessary.

[0073] In particular, when the heater is configured so that the width of the resistance member 370 is greater than the maximum paper width to prevent temperature drops at the edges during startup, excessive temperature rise at the edges can easily become apparent even when the maximum paper size is used due to paper registration misalignment, and the influence of the overheated edges can cause the area around the paper edge to overheat, making gloss unevenness more likely to become apparent. For this reason, in a single heater configuration, it is also effective to set the width of the resistance member 370 greater than the maximum paper width and place the monitoring thermistor TH2, described below, outside the maximum paper size in order to detect excessive temperature rise.

[0074] Regarding the arrangement of the monitoring thermistor TH2 in the cross-sectional direction, it is desirable for temperature detection purposes to arrange the thermistor on the surface of fixing belt 310 that comes into contact with the transparent toner, but it may also be arranged on the backside of the heater or inside fixing belt 310 and an appropriate prediction model used to estimate an overheating. Also, it is possible to detect an overheating by arranging the thermistor on the surface of pressure roller 320.

[0075] In particular, it becomes possible to use a less expensive sensor with lower heat resistance when the thermistor is disposed on the surface of pressure roller 320. The control sensor may also be disposed behind the heater, on the surface of fixing belt 310, or inside fixing belt 310.

[0076] A stay 350 and a heater holder 340 are disposed axially inside the fixing belt 310. The stay 350 is made of a metal channel material, and both ends of the stay 350 are supported by both side plates of the heating device. The stay 350 reliably receives the pressing force of the pressure roller 320, stably forming the fixing nip SN as a nip portion.

[0077] A sheet of paper P as a sheet member is transported through this fixing nip SN in a direction perpendicular to the longitudinal direction of the fixing belt 310 or the heat generating element 330 (or the longitudinal direction of the pressure roller 320). Here, the "perpendicular direction" does not have to be an angle of exactly 90° with the longitudinal direction. An angle of about 90° with respect to the longitudinal direction is also included in the "perpendicular direction." Here, the angle of about 90° is preferably 80° to 100°, and more preferably 85° to 95°.

[0078] Heater holder 340 is for holding base material 341 of the heating device, and is supported by stays 350. Heater holder 340 can be preferably formed from a heat-resistant resin with low thermal conductivity, such as LCP, which reduces heat transfer to heater holder 340 and enables fixing belt 310 to be heated efficiently.

[0079] The heater holder 340 is shaped to support only two points near both ends of the substrate 341 in the lateral direction in order to avoid contact with the high-temperature portion of the substrate 341. This further reduces the amount of heat flowing to the heater holder 340, enabling the fixing belt 310 to be heated efficiently.

[0080] The heating device has a resistance member 370 as a sliding member made of a resistance heating element. This resistance member 370 can be formed in a number of types as shown in Figures 3A to 3C.

[0081] In either type, resistance member 370 is formed on substrate 341, which is an elongated thin metal plate member covered with an insulating material. By directly heating the nip area with resistance member 370, the viscosity of the lubricant in the nip area can be lowered, reducing oil film breakdown and suppressing wear.

[0082] Low-cost aluminum, stainless steel, etc. are preferable as materials for the base material 341. The base material 341 is not limited to metal, and can also be made of ceramics such as alumina or aluminum nitride, or non-metallic materials with excellent heat resistance and insulation properties, such as glass or mica.

[0083] To improve the uniformity of heat in the heating device and enhance image quality, the substrate 341 may be made of a material with high thermal conductivity such as copper, graphite, graphene, etc. In this embodiment, an alumina substrate with a short side width of 8 mm, a long side width of 270 mm, and a thickness of 1.0 mm is used.

[0084] (●Single type resistance element) 3A shows a single-type resistance element 370, in which resistance elements 370 are formed in two parallel rows in series in the longitudinal direction of substrate 341. Positioning holes 330a for positioning substrate 341 are formed on one end of substrate 341. One end of each of the two rows of resistance elements 370 is connected to power supply electrodes 370c and 370d via low-resistance power supply lines 379a and 379c formed in the longitudinal direction at one end of substrate 341. These electrodes 370c and 370d are connected to a power supply means including an AC power supply 410 as shown in FIG.

[0085] The other end of resistance member 370 is connected by folding back toward the opposite longitudinal side of substrate 341 via power supply line 379b with a small resistance value formed in the short direction at the other end side of substrate 341. Resistance member 370, electrodes 370c, 370d, and power supply lines 379a to 379c are formed by screen printing to a predetermined line width and thickness.

[0086] The material of the resistance member 370 can be formed by applying a paste made of silver (Ag) or silver palladium (AgPd) and glass powder by screen printing or the like, followed by firing. The resistance value of the resistance member 370 can be set to, for example, 10 Ω at room temperature. Other resistance materials that can be used for the resistance member 370 include silver alloy (AgPt) and ruthenium oxide (RuO2).

[0087] The surfaces of resistance member 370 and power supply lines 379a-379c are covered with a thin overcoat layer or insulating layer 385. Insulating layer 385 ensures the slidability of fixing belt 310 and also ensures insulation between fixing belt 310 and resistance member 370 and power supply lines 379a-379c. Therefore, insulating layer 385 constitutes a part of the sliding member. By using heat-resistant glass for insulating layer 385, the lubricant of fixing belt 310 does not penetrate into resistance member 370 as a sliding member, which prevents oil film breakdown on the nip surface.

[0088] Heat-resistant glass having a thickness of 75 μm, for example, can be used as the material for this insulating layer 385. The resistance member 370 heats the fixing belt 310, which is in contact with the insulating layer 385 side, by heat transfer, thereby increasing its temperature, and heats and fixes the unfixed image on the paper P transported to the fixing nip SN.

[0089] Thermistor TH1, which serves as a first temperature detection element, is positioned within the minimum paper width. Thermistor TH1 can accurately detect the temperature of the fixing belt 310 in the area that contacts the paper, regardless of the size of the paper. The temperature of resistor 370 is controlled based on the temperature T1 of resistor 370 or substrate 341 detected by thermistor TH1.

[0090] A monitoring thermistor TH2 serving as a second temperature detection member is disposed near the edge of the smallest sheet of paper that is outside the range of the smallest paper and is greater than the length (width) of the resistance member 370. This thermistor TH2 has the function of monitoring temperature unevenness of the resistance member 370 or the fixing belt 310.

[0091] Then, a differential temperature reduction process is performed to uniformly heat the resistance element 370 in the longitudinal direction based on the differential temperature (=T1-T2), which is the difference between the temperature T1 detected by thermistor TH1 and the temperature T2 of the central resistance element 370-1 or the base material 341 detected by thermistor TH2. Thermistor TH2 can also detect excessive temperature rise in the non-sheet-passing area. Thermistors TH1 and TH2 can be configured as contact-type thermistors with a thermal time constant of less than one second, and are arranged in a manner that they are pressed against the back side of the base material 341 by spring 387, as shown in Figures 2A to 2D.

[0092] (●Dual type resistance element) 3B shows a dual-type resistance element, which is composed of a central resistance element 370-1 in the longitudinal center and a pair of end resistance elements 370-2 arranged on either side of the central resistance element 370-1. The opposing ends of the central resistance element 370-1 and the end resistance element 370-2 are formed at an angle (parallelogram) relative to the short-side direction of the base material 341. This angle reduces the gap between the central resistance element 370-1 and the end resistance element 370-2 when viewed from the short-side direction of the base material 341, thereby reducing the temperature drop between them.

[0093] The central resistance member 370-1 is 215 mm long to fit A4 paper, and the end resistance members 370-2 are 301 mm long to fit A3 paper. This prevents A4 and A3 paper from overheating, improving productivity.

[0094] One end of the central resistance 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. Also, one end of the left end resistance 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 element 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.

[0095] The central resistor 370-1 and the end resistor 370-2 can generate heat independently, and when a voltage is applied to the electrodes 370e and 370h, the central resistor 370-1 generates heat. Similarly, when a voltage is applied to the electrodes 370e and 370f, the left end resistor 370-2 generates heat, and when a voltage is applied to the electrodes 370e and 370g, the right end resistor 370-2 generates heat.

[0096] If the electrodes 370f and 370g are connected in parallel externally, the left and right end resistance members 370-2 can be heated simultaneously. If the paper is centered, the temperature will be symmetrical, so instead of providing a thermistor on each end of the end resistance member 370-2, it is sufficient to provide one on only one side, thereby reducing costs.

[0097] The central resistance element 370-1 and the end resistance elements 370-2 are covered with a thin insulating layer 385, similar to the series resistance element 370 (FIG. 3A) described above. This insulating layer 385 can be made of heat-resistant glass with a thickness of 75 μm, for example. The insulating layer 385 insulates and protects the central resistance element 370-1, the end resistance elements 370-2, and the power supply lines 379d, 379e, 379f, and 379h, while also maintaining slidability with the fixing belt 310.

[0098] A thermistor TH1 is disposed within the minimum paper width as a temperature detection element. The temperature of the central resistor element 370-1 is controlled based on the temperature T1 of the central resistor element 370-1 or the base material 341 detected by the thermistor TH1. The temperature detection sensor (element) and the temperature control sensor (element) may be separate.

[0099] Thermistor TH3 is placed as a temperature detection element outside the range of the smallest paper width, but inside the smallest paper width of the paper that is larger than the combined length (width) of the central resistor 370-1 and the end resistor 370-2. Then, a differential temperature reduction process is performed to uniformly heat the central resistor 370-1 in the longitudinal direction based on the differential temperature (=T1-T3) between the temperature T1 detected by thermistor TH1 and the temperature T3 of the central resistor 370-1 or the base material 341 detected by thermistor TH3.

[0100] Thermistor TH3 is located outside the smallest paper size and inside the inclined portion of central resistor 370-1 to detect excessive temperature rise in non-paper passing areas when paper smaller than central resistor 370-1 is passed through. Because the heat density is low at the inclined portion, it is preferable to place thermistor TH3 in a position that does not overlap the inclined portion.

[0101] Furthermore, if the thermistor TH3 is positioned outside the largest paper among those narrower than the central resistance member 370-1 and inside the inclined portion, it is possible to detect excessive temperature rise when printing on paper other than the smallest paper. Thermistor TH3 may be configured to measure the outer peripheral temperature of pressure roller 320 without being positioned inside fixing belt 310.

[0102] Since the temperature of pressure roller 320, which comes into contact with fixing belt 310 via fixing belt 310 and has a large heat capacity, is lower than that of fixing belt 310, which is provided with a heat-generating portion, an inexpensive thermistor can be used for thermistor TH3. Also, since lead wires, which will be described later, are connected to the thermistor, an area for routing the lead wires is required when the thermistor comes into contact with a heater disposed within fixing belt 310. As the number of thermistors increases, the number of lead wires also increases, which necessitates a larger belt diameter. However, by measuring the temperature of pressure roller 320, which is in contact with fixing belt 310, the number of lead wires within fixing belt 310 can be reduced.

[0103] A thermistor TH2 as a temperature detection element is placed near the edge of the smallest piece of paper that is larger than the combined length (width) of the central resistor 370-1 and the edge resistor 370-2. The temperature of the edge resistor 370-2 is controlled based on the temperature T2 of the edge resistor 370-2 or the base material 341 detected by the thermistor TH2.

[0104] Thermistor TH4 is placed outside the paper width of the smallest sheet of paper that is larger than the combined length (width) of central resistor 370-1 and end resistor 370-2. A differential temperature reduction process is performed to uniformly heat end resistor 370-2 in the longitudinal direction based on the differential temperature (=T2-T4) between temperature T2 detected by thermistor TH2 and temperature T4 of substrate 341 detected by thermistor TH4. Thermistors TH1-TH4 can be contact-type thermistors with a thermal time constant of less than one second, and are arranged in a manner that they are pressed against the backside of substrate 341 by spring 387, as shown in Figures 2A-2D.

[0105] In this way, by using thermistors for monitoring temperature uniformity (TH2 in FIG. 3A, TH3 and TH4 in FIG. 3B) in addition to thermistors for controlling the heat source of the fixing device (TH1 in FIG. 3A, TH1 and TH2 in FIG. 3B), the transparent toner is fixed without temperature unevenness, achieving both a quick start-up and prevention of uneven gloss of the transparent toner. Furthermore, by using a heat source for the planar heater (heating element 330) with a heat pattern that allows partial heating and control as shown in FIG. 3B, high productivity can be maintained without causing uneven gloss of the transparent toner even for different paper sizes.

[0106] Furthermore, even when transparent or highly transparent toner, whose glossiness is highly temperature-dependent, is used, it is possible to prevent uneven glossiness from occurring in the formed image. That is, as shown in Figure 3B, the temperature deviation between the center and end portions of each resistance element 370-1, 370-2 and the temperature deviation between each resistance element 370-1, 370-2 are constantly monitored to ensure that they are within a certain range before paper feeding is permitted. This makes it possible to prevent uneven glossiness from occurring.

[0107] 3B shows an example in which the resistance elements are arranged symmetrically with respect to the center of the paper, with up to three blocks. However, even if the resistance elements are arranged in finer blocks, such as five or seven blocks, by similarly arranging multiple thermistors on each resistance element, it is possible to provide a system that does not cause gloss defects even when using clear toner.

[0108] (●Multi-type resistance components) 3C, the resistance member 370 can also be configured as a multi-type in which PTC elements 371 to 378 are electrically connected in parallel. The multi-type configuration makes it easier to equalize the temperature in the axial direction, which in turn makes the grease viscosity uniform in the axial direction and the amount of grease on the nip surface uniform in the axial direction.

[0109] In this multi-type, the thermistors TH1 and TH2 in Fig. 3A and the thermistors TH1 to TH4 in Fig. 3B can be arranged in the same manner. If the resistance value between the electrodes 370c and 370d at both ends in Fig. 3C is 10Ω, the resistance value of each of the PTC elements 371 to 378 is Therefore, the resistance becomes large, 80 Ω.

[0110] The PTC element is made of a material with a positive temperature coefficient of resistance, and its resistance value increases as the temperature T increases (the current I decreases, and the heater output decreases). The temperature coefficient of resistance (TCR) can be set to, for example, 1500 PPM (parts per million). This temperature coefficient of resistance can be stored in the memory of the control unit 400 (see FIG. 4), which will be described later.

[0111] PTC elements 371-378 in Fig. 3C are arranged linearly and at equal intervals in the longitudinal direction of substrate 341. Low-resistance power supply lines 370a, 370b are arranged linearly and 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 power supply lines 370a, 370b. Power supply means including AC power supply 410 is connected to electrodes 370c, 370d formed on one end of power supply lines 370a, 370b, respectively, as shown in Fig. 4.

[0112] Similar to the series resistor member 370 (FIG. 3A) described above, the PTC elements 371-378 and the power supply lines 370a, 370b are also covered with a thin insulating layer 385. This insulating layer 385 can be made of heat-resistant glass with a thickness of 75 μm, for example. The insulating layer 385 insulates and protects the PTC elements 371-378 and the power supply lines 370a, 370b, while maintaining sliding properties with the fixing belt 310.

[0113] The PTC elements 371 to 378 can be formed, for example, by applying a paste made of a mixture 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 this embodiment, the resistance value of each of the PTC elements 371 to 378 is set to 80 Ω at room temperature (total resistance value is 10 Ω).

[0114] In addition to the materials mentioned above, resistive materials such as silver alloy (AgPt) and ruthenium oxide (RuO2) may also be used for the materials of the PTC elements 371 to 378. The materials of the power supply lines 370a, 370b and the electrodes 370c, 370d can be formed by screen printing or the like using silver (Ag) or silver palladium (AgPd).

[0115] The insulating layer 385 side of the PTC elements 371 to 378 comes into contact with the fixing belt 310 and heats it, increasing the temperature of the fixing belt 310 through heat transfer, and heating and fixing an unfixed image conveyed to the fixing nip SN.

[0116] By using PTC elements 371-378, when the temperature of the PTC elements in non-paper passing areas rises due to the passage of small-sized paper, the temperature resistance dependency of the resistance heating element reduces the amount of heat generated by the PTC elements, thereby suppressing the temperature rise. Due to this feature, for example, when printing on paper narrower than the overall width of PTC elements 371-378 (for example, within the width of PTC elements 373-376), the temperature of PTC elements 371, 372, 377, and 378 outside the paper width rises because the paper does not absorb heat. This causes the resistance values ​​of these PTC elements 371, 372, 377, and 378 to rise.

[0117] Because the voltage applied to the PTC elements 371-378 is constant, the output of the PTC elements 371, 372, 377, and 378 outside the paper width is relatively lower, suppressing temperature rise at the edges. If the PTC elements 371-378 are electrically connected in series, the only way to suppress temperature rise in the resistance heating elements outside the paper width during continuous printing is to slow down the printing speed. By electrically connecting the PTC elements 371-378 in parallel, it is possible to suppress temperature rise in non-paper passing areas while maintaining the printing speed.

[0118] As the temperature of the fixing belt 310 increases, its strength decreases, making it more susceptible to wear. However, by using a multi-type resistance member 370, it is possible to prevent excessive temperature rise in non-paper passing areas even when small-sized paper is passing through, thereby suppressing wear of the fixing belt 310 and also achieving the effect of suppressing evaporation of the lubricant.

[0119] The arrangement of the PTC elements 371-378 is not limited to the state shown in Figure 3C(a). In Figure 3C(a), there are gaps between the PTC elements 371-378 in the short direction, which reduces the amount of heat generated in these gaps, making it easy for uneven fixing to occur. Therefore, in Figures 3C(b) and (c), the ends of the PTC elements 371-378 overlap each other in the long direction.

[0120] In Fig. 3C(b), steps are formed by L-shaped notches at the ends of the PTC elements 371-378, and these steps overlap with the steps at the ends of the adjacent resistance heating elements. In Fig. 3C(c), inclined portions are formed by diagonal notches at the ends of the PTC elements 371-378, and these inclined portions overlap with the inclined portions at the ends of the adjacent resistance heating elements. By overlapping the ends of the PTC elements 371-378 in this way, it is possible to suppress the effect of a decrease in heat generation in the gaps between the resistance heating elements.

[0121] Furthermore, the electrodes 370c and 370d can be arranged on both ends of the PTC elements 371 to 378, or can be arranged on one side of the PTC elements 371 to 378 as shown in Figures 3C(a) to 3C(c). By arranging the electrodes 370c and 370d on one side in this way, space can be saved in the longitudinal direction.

[0122] Each of the resistive heating elements 371 to 378 in Figure 3C is composed of a strip-shaped sheet heating element, but in order to obtain the desired output (resistance value), it can also be composed of multiple PTC elements formed in a serpentine shape with a narrow line width and electrically connected in parallel.

[0123] (●Power supply circuit) 4 shows a power supply circuit that supplies power to the heating device. This power supply circuit is usually disposed on the main body side of the image forming apparatus 100.

[0124] Resistance element 370 of the heating device uses central resistance element 370-1 and end resistance element 370-2 shown in Fig. 3B. Below the heating device, a power supply circuit for supplying power to central resistance element 370-1 and end resistance element 370-2 is shown.

[0125] The power supply circuit as power control means comprises a control unit 400, an AC power supply 410, a triac 420, a current detection means 430, heater relays 441 and 442, and voltage detection means 451 and 452. The control unit 400 and the triac 420 constitute the power supply means.

[0126] An AC power supply 410, a current transformer CT of a current detection means 430, a triac 420, and heater relays 441 and 442 are arranged in series between an electrode 370e and electrodes 370g and 370h on the opposite side. In addition, a voltage detection means 451 is arranged between the electrodes 370e and 370f on one side, and a voltage detection means 452 is arranged between the electrode 370e on one side and the electrode 370h on the opposite side.

[0127] The temperatures detected by thermistors TH1 to TH4 are input to the control unit 400. Based on the temperature obtained from thermistor TH1, the control unit 400 performs duty control of the current supplied to the electrodes 370e, 370g, and 370h using the triac 420 so that the central resistor 370-1 and the end resistor 370-2 reach predetermined target temperatures.

[0128] Specifically, the triac 420 controls the current flowing through the central resistor 370-1 with a duty ratio that corresponds to the temperature difference between the current temperature of the thermistor TH1 and the target temperature. At a duty ratio of 0%, the current is zero, and at a duty ratio of 100%, the current is at its maximum.

[0129] Similarly, triac 420 duty-controls the current flowing through end resistor 370-2 with a duty ratio that corresponds to the temperature difference between the current temperature of thermistor TH2 and the target temperature. Here, "duty" refers to the ratio of the time that current is applied to resistor 370 per control cycle.

[0130] Meanwhile, the central resistor 370-1 can be subjected to differential temperature reduction processing in the manner described above based on the differential temperature between the current temperatures of thermistors TH1 and TH3. Similarly, the left and right end resistors 370-2 can be subjected to differential temperature reduction processing based on the differential temperature between the current temperatures of thermistors TH2 and TH4.

[0131] Control unit 400 can be configured with a microcomputer including a CPU, ROM, RAM, I / O interface, etc. When paper passes through fixing nip SN, heat is dissipated (heat transferred to the paper) by the paper passing through, so by controlling the supply current taking into consideration not only temperature T1 obtained from thermistor TH1 but also the heat dissipation, it is possible to control the temperature of fixing belt 310 to a desired temperature.

[0132] The current detection means 430 detects the total value of the current flowing through the resistance member 370. That is, the control unit 400 reads the magnitude of the current flowing between the electrodes 370c and 370d via the voltage generated in the secondary resistance of the current transformer CT.

[0133] Furthermore, the voltage detection means detects the voltage value E between the electrodes 370c and 370d of the resistance member 370, and the voltage E is read by the control unit 400. The control unit 400 then calculates the resistance value R (=E / I) of the resistance member 370 from the current value I and the voltage value E.

[0134] 2A, when paper P is passed from the direction of the arrow toward the fixing nip SN, the paper P is heated between the fixing belt 310 and the pressure roller 320, and the toner image is fixed to the paper P. At this time, the fixing belt 310 is heated by the heat from the resistance member 370 while sliding against the insulating layer 385 of the resistance member 370.

[0135] (Other embodiments of the fixing device) Fixing device 300 is not limited to the first fixing device in Fig. 2A. Second to fourth fixing devices will be described below with reference to Fig. 2B to Fig. 2D. As shown in Fig. 2B, the second fixing device has a pressure roller 390 on the opposite side of pressure roller 320, and heats fixing belt 310 by sandwiching it between pressure roller 390 and a heating device.

[0136] The heating device described above is disposed inside the fixing belt 310. An auxiliary stay 351 is attached to one side of the stay 350, and a nip forming member 381 is attached to the other side.

[0137] The heating device is held by this auxiliary stay 351. The nip forming member 381 contacts the pressure roller 320 via the fixing belt 310 to form the fixing nip SN.

[0138] 2C, the third fixing device has a heating device disposed inside fixing belt 310. This heating device does not include pressure roller 390 described above, but instead has base material 341 and insulating layer 385 whose cross sections are arc-shaped to match the curvature of fixing belt 310 in order to increase the circumferential contact length with fixing belt 310.

[0139] Resistance member 370 is disposed at the center of arc-shaped base material 341. The rest is the same as the second fixing device in FIG. 2B.

[0140] 2D, the fourth fixing device is configured with a heating nip HN and a fixing nip SN. That is, nip forming member 381 and stay 352 made of a metal channel material are arranged on the opposite side of pressure roller 320 from fixing belt 310, and pressure belt 334 is disposed so as to be able to rotate around nip forming member 381 and stay 352.

[0141] Then, the paper P is passed through the fixing nip SN between the pressure belt 334 and the pressure roller 320, where it is heated and fixed. The rest is the same as the first fixing device in FIG. 2A.

[0142] (●Method of manufacturing the fixing belt) Next, a description will be given of a manufacturing method of the fixing belt 310 in this embodiment. The elastic power of the inner surface (sliding surface) of the fixing belt 310 used in this embodiment is prescribed to be 55% or more under environmental conditions of a temperature of 23°C and a relative humidity of 50%. ◆Paint mixing (common) To mix the coating liquid, add 80g of NMP (N-methyl-pyrrolidone) to 100g of polyimide varnish and mix. The polyimide varnish used was U-Imide Varnish AR manufactured by Unitika Ltd. Special grade N-methyl-pyrrolidinone manufactured by Kanto Chemical was used for NMP. While stirring with a tabletop mixer, gradually add the needle-shaped inorganic filler to the above-mentioned mixed solution A 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 10 to 15 minutes to prevent it from forming lumps. The needle-shaped inorganic filler used was Tismo D manufactured by Otsuka Chemical Co., Ltd. This mixture will be called B.

[0143] ◆Painting (common) The inner surface of the fixing belt is painted by spray painting or dipping. This time we will use spray paint. Pour mixture B into the pressure tank. Rotate the fixing belt to coat the inner surface of the fixing belt. Set the rotation speed of the fixing belt in the range of 900 to 1000 rpm. This time, set it to 900 rpm.

[0144] The coating speed should be set at 30mm / s, and the coating weight for one coat on each side should be in the range of 0.7~1.2g. The application weight is adjusted by the pressure used to pump out Mixture B. This time, the pressure was 125kPa, and the coating weight for one coat on each side was 1.0g. After application, the paint is pre-dried with hot air at 200°C before being applied over the next coat. Repeat the painting and pre-drying process 3 to 4 times. After painting, the parts are placed in a drying oven at 260°C for 30 minutes to volatilize the NMP. The thickness of the sliding layer is preferably 8 to 15 μm. This time, a total of 4.2 g of Mixture B was applied, resulting in a film thickness of 11 μm.

[0145] ◆ Firing (common) Firing is carried out in a vertical far-infrared firing furnace. Far-infrared heaters are placed on both sides of the vertically positioned fixing belt, and the heaters heat an area that is longer than the length of the fixing belt. - Set the temperature of the far-infrared heater so that the fixing belt reaches the specified temperature.

[0146] ◆ Firing temperature (when elastic power is relatively high) The far-infrared heater temperature was set so that the actual temperature of the fixing belt was 360°C. Baking time is 30 minutes. The elastic power of the sliding layer after firing was measured and found to be 70.0% at room temperature (23°C) and 60.2% at 165°C.

[0147] ◆ Firing temperature (when elastic power is relatively low) The far-infrared heater temperature was set so that the actual temperature of the fixing belt was 280°C. Baking time is 30 minutes. The elastic power of the sliding layer after firing was measured and found to be 60.4% at room temperature (23°C) and 52.1% at 165°C.

[0148] (Belt roughness and noise suppression effect) Abnormal noise on sliding surfaces is caused by a lack of lubricant on the sliding surfaces. To suppress abnormal noise, it is necessary to increase the amount of lubricant on the sliding surfaces.

[0149] Increasing the surface roughness of the inner surface of the fixing belt, as in Patent Document 3 (JP 2009-14893 A), can increase the amount of lubricant retained on the inner surface of the fixing belt. Increasing the amount of lubricant retained on the inner surface of the fixing belt increases the amount of lubricant newly flowing onto the sliding surface due to rotation, which is advantageous for suppressing abnormal noise.

[0150] However, ensuring a sufficient amount of lubricant on the sliding surface to suppress noise also depends on the roughness of the heater side. As shown in Figure 9(a) below, if the surface roughness Sa2 of the heater sliding surface (insulating layer) is made larger than the surface roughness Sa1 of the inner surface of the fixing belt, the lubricant held on the inner surface of the fixing belt will flow into the sliding area.

[0151] However, this amount of lubricant is not enough to fill the recessed parts of the heater, causing the lubricant film to break down on the protruding parts of the heater. This results in noise and wear. Furthermore, the inner surface of the belt deteriorates in streaks due to sliding, causing uneven heating of the image, resulting in abnormal images such as uneven gloss and gloss streaks.

[0152] The larger the surface roughness Sa1 of the inner surface of the fixing belt, the greater the amount of grease that the fixing belt can retain. Sa1 of 0.2 μm or more is desirable because it stably retains grease in the belt, and the surface roughness Sa2 of the insulating layer of the heater, which is the opposing member, is desirably 0.05 μm or less. Note that the "surface roughness Sa" referred to in this specification refers to the surface roughness Sa in the sliding direction (belt rotation direction) in which the fixing belt slides against the heater.

[0153] By setting the surface roughness Sa2 of the heater insulating layer to 0.05 μm or less, it is possible to prevent grease conveyed from the fixing belt from entering the recesses of the heater insulating layer and causing grease shortage at the protrusions. The surface roughness Sa2 is sufficient for retaining grease in the fixing belt, but if the spatial volume Vvv of the core portion, which will be described later and represents the volume of the recesses of the unevenness, is 0.01 ml / m or less, 2 It is more desirable that the Vvv is greater than or equal to 1. The larger Vvv is, the greater the amount of grease that can be held by the fixing belt.

[0154] The lubricant may contain fluorine grease or silicone oil, which can maintain lubrication for a long period of time between sliding members under high temperature and high surface pressure, thereby suppressing wear.

[0155] Furthermore, if the fixing belt does not have an elastic layer such as rubber, the rigidity of the fixing belt will be low and the belt will be more likely to conform to the shape of the nip entrance, which will make it easier for grease to be supplied to the nip area by capillary action.

[0156] (●Method for measuring elastic power) The aforementioned elastic power can be measured by a loading-unloading test (indentation test) using a micro-surface hardness tester with a diamond indenter; the closer it is to 1 (100%), the easier the material is to deform elastically. As shown in Figure 5, diamond indenter A is pressed into sample B at a constant loading rate (loading process) from the point (a) where it makes contact with the sample, and then the indenter is held stationary for a certain period of time at the maximum displacement (b) when the set load is reached. The indenter is then further pulled up at a constant unloading rate (unloading process), and the point at which the load is no longer applied to the indenter is the plastic displacement (c).

[0157] At this time, the resulting curve of indentation depth and load is recorded as shown in Figure 5(d). From this curve, the elastic power can be calculated by calculating the ratio of the work of elastic deformation We to the total work done by indenter A on the surface layer (the work of plastic deformation Wt + the work of elastic deformation We).

[0158] The elastic power (%) can be expressed mathematically as follows: Elastic power (%) = Work load of elastic deformation We × 100 / (Work load of plastic deformation Wt + Work load of elastic deformation We)

[0159] The elastic power measurement was performed under constant temperature and humidity conditions, and in this embodiment, the elastic power refers to 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, the measurement was performed using a Fischerscope HM-2000 (manufactured by Fisher Instruments) and a Vickers indenter under 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, followed by unloading over 30 seconds. However, values ​​measured using any device with equivalent performance may be used.

[0160] The sample was measured by suspending the fixing belt of this embodiment on a metal substrate. Since the elastic power is affected by the spring characteristics of the substrate, a rigid metal plate, slide glass, or the like is suitable as the substrate.

[0161] Furthermore, because the hardness and elasticity of the layer below the crosslinked surface layer (for example, the belt substrate) also have an effect, the specified load was adjusted so that the maximum displacement would be 1 / 10 of the thickness of the inner coating to reduce these effects. Also, to eliminate the effect of the rubber and release layer on the surface of the substrate, it is desirable to peel off the surface rubber and release layer before measurement. This measurement was performed with the surface rubber and release layer peeled off.

[0162] (● Difference between elastic power and return rate) An index similar to elastic power is the return rate (see Patent Document 4: Japanese Patent No. 6036469). However, as shown in the load-displacement diagram in Figure 6, the return rate is the same for return lines 1, 2, and 3. In contrast, elastic power also includes area information, so the return rate is a different value for return lines 1, 2, and 3.

[0163] The area under the displacement-load curve during compression and unloading, expressed as the elastic power, is the energy loss, and if this difference is large, the friction force (torque) will be large. For example, even with the same return rate, the magnitude of the friction force may differ depending on the unloading profile.

[0164] Therefore, elastic power is more effective as a sliding surface characteristic because it can confirm information on frictional force in addition to wear resistance. With return rate, it is not possible to determine the presence or absence (size) of frictional force because there is no information on area.

[0165] (●Wear rank based on elastic power) As shown in Figure 7, wear tests conducted by the inventors of the present application have shown that wear resistance can be improved by increasing the elastic power of the inner surface (sliding surface) of the fixing belt and using as lubricants Grease A with a consistency of 275 and Grease B with a consistency of 340 or less. The elastic power can be measured by the indentation test shown in Figure 5 above, and the closer the power is to 1 (100%), the more easily the material is able to deform elastically.

[0166] The lubricant penetrates the sliding surface of the belt and the sliding member, but the amount of lubricant that can penetrate the sliding surface is limited by the nip pressure. A soft lubricant with high consistency is unable to withstand the nip pressure and the amount that penetrates is reduced.

[0167] In contrast, a low-consistency, hard (high-viscosity) lubricant penetrates more than a high-consistency lubricant, and is more effective at suppressing sliding wear. When the elastic power of the inner surface of the belt is high, combined with the reaction force generated by a high-viscosity, low-consistency lubricant, gaps are more likely to occur between the inner surface of the belt and the sliding member, allowing more lubricant to penetrate the sliding surface, improving wear resistance.

[0168] ·Verification configuration: [nip forming member: planar heater on the glass surface] + [fixing belt: inner surface PI-based paint] + [pressure roller] ·Lubricants: Fluorine-based grease A (penetration 275), Fluorine-based grease B (penetration 340) ·Test conditions: Repeated heating up to the assumed actual machine life (belt temperature 180°C), rotational operation test ·Martens hardness measurement condition: Penetration 1μm ·Belt hardness (H1): Approximately 500 N / mm 2 ·Heater glass surface hardness (H2): Approximately 3500 N / mm 2

[0169] As an evaluation method, an elastic work rate and universal hardness were measured using a Fischer Instruments surface film physical property tester Fischer Scope H-100, and a ten-point average roughness (Rz) was measured using a Tokyo Seimitsu surface roughness and shape measuring machine Surfcone 1400D.

[0170] With the hardness H1 of the fixing belt sliding surface and the hardness H2 of the heater glass surface in the relationship of H1 < H2, a durability test was carried out while varying the level of the elastic work rate of the belt between 45% and 65% to investigate the wear resistance. The wear ranks shown in Figure 7 are as follows: Rank 1 is a state where many clear streaks of gloss unevenness (stripes) can be seen in the image where the inner surface of the belt is worn and flattened; Rank 2 is a state where clear streaks of gloss unevenness (stripes) can be seen in the flattened image; Rank 3 is a state where faint streaks of gloss unevenness (stripes) can be seen in the flattened image; Rank 4 is a state where no gloss stripes can be seen; Rank 5 is a state where there are no wear stripes on the inner surface of the belt. In this embodiment, the practically usable range was set as wear rank 3 or higher, and the range where there is no impact on the image quality was set as wear rank 4 or higher.

[0171] Generally, when using a highly viscous soft lubricant, the deterioration of the inner surface of the belt becomes faster, and when using a low-viscosity hard lubricant, the deterioration is improved. However, when using a hard lubricant, there is a risk that the margin for the driving force limit of the device will disappear due to an increase in sliding resistance caused by wear powder generated by sliding (stopping due to torque overrun).

[0172] When using a hard lubricant, expensive, hard materials are selected for the motor and gears to ensure sufficient driving force to avoid torque overload. Also, if the torque becomes too high, the belt will not rotate smoothly with the pressure roller, which can cause paper wrinkles or even paper jams, so the pressure between the belt and pressure roller is changed.

[0173] Even when the hardness H2 of the sliding surface of the sliding member is greater than the hardness H1 of the fixing belt sliding surface, the state of internal wear varies depending on the elastic power. The test results in Figure 7 show that practical wear resistance can be ensured by using grease A, which has an elastic power of 55% or more and a consistency of 275. It can also be seen that practical wear resistance can be ensured by using grease B, which has an elastic power of 58% or more and a consistency of 340. It can also be seen that this state can be maintained with an elastic power of at least 63% or less. Practical wear resistance can be ensured by using a consistency of 340 to 265, from hardness H1 to hardness H2, but a consistency of up to hardness H3, with a consistency of 220, can also be used.

[0174] Furthermore, when the elastic power is 58% or higher, high-quality wear resistance can be ensured with Grease A, and practical wear resistance can be ensured with Grease B. Therefore, by using a belt with a high elastic power, softer lubricants can be used, widening the range of grease options.

[0175] With hard lubricants, shear stress acts on the lubricant between the belt and the sliding member, increasing sliding resistance. This increases the drive torque of the pressure roller, placing a heavy load on the driving gears and motors. To address this, it is necessary to select more expensive drive system components. If softer lubricants can be used, it will be possible to reduce drive system costs and suppress belt wear.

[0176] The elastic work rate indicates how much stress can be relaxed when the applied stress is removed, and the higher the value, the higher the stress relaxation ability. It is desirable that the inner surface of the belt be formulated so as not to leave permanent distortion with respect to the stress due to sliding.

[0177] (● Abrasion resistance) Fig. 8 is a diagram showing the correlation between the elastic work rate and the film reduction amount. A plurality of plotted points in the figure are the results of performing an abrasion resistance test using samples with different elastic work rates on the inner surface of the belt. The test was carried out in a normal temperature / normal humidity environment at a temperature of 25°C and a relative humidity of 50%. For each photoreceptor, a character test chart was formed at the black image position on 100,000 sheets of recording paper to perform the abrasion resistance test.

[0178] The film thickness at the start of the abrasion resistance test and after forming 100,000 images on the recording paper was measured to obtain the film reduction amount. The film thickness was measured using a film thickness measuring device (product name: Fischer Scope MMS, manufactured by Fischer Instruments Co., Ltd.).

[0179] It was found that as the elastic work rate increases, the film reduction amount decreases and the abrasion resistance improves. When the elastic work rate is 55% or more, the film reduction amount becomes negligible.

[0180] (● Lubricant retention state) Figs. (a)(b) schematically show the retention state of the lubricant L due to the difference in the surface roughness between the fixing belt and the heater. Let the surface roughness of the inner surface of the fixing belt be Sa1 and the surface roughness of the sliding surface (insulating layer) of the heater be Sa2. Fig. 9(a) shows a cross section of the fixing belt and the heater when Sa1 < Sa2.

[0181] Fig. 9(a) shows that since the surface roughness Sa2 of the heater is larger, the lubricant tends to transfer from the belt to the heater. In contrast, Fig. 4(b) shows a cross section of the fixing belt and the heater when the surface roughness is reversed and Sa2 < Sa1. In Fig. 4(b), since the surface roughness Sa1 of the belt is larger, it shows that the lubricant tends to transfer from the heater to the belt.

[0182] From FIG. 9, it can be seen that in order to maintain the amount of lubricant L on the inner surface of the fixing belt, it is necessary to increase the surface roughness Sa1 of the belt so that the relationship Sa2 < Sa1 holds. Also, in order to maintain such a relationship of surface roughness over time, it was also found from the results of the film reduction amount in FIG. 8 that it is necessary to set the elastic work rate to 55% or more.

[0183] (● Types of parameters of surface shape) Surface shape parameters that are sensitive to abnormal noise and sliding include the arithmetic mean roughness Sa, the protrusion valley space volume Vvv, the skewness Ssk, and the kurtosis Sku. Each parameter will be described below.

[0184] (● Arithmetic mean roughness) FIG. 10A is a diagram for explaining the arithmetic mean roughness. The arithmetic mean roughness Sa is a parameter obtained by three-dimensionally expanding Ra, which is a contour curve (line roughness) parameter. FIG. 10A represents the average of the absolute value of Z(x, y) (height difference from the average plane) in the measurement target area.

[0185] (● Load curve) The protrusion valley space volume Vvv represents the void volume of the valleys at the load area ratio p%. FIG. 10B is a diagram showing the load curve.

[0186] To calculate the protrusion valley space volume Vvv, a load curve of the surface, which is a curve representing the height from 0% to 100% of the load area ratio, is obtained. The load area ratio represents the area of the region above a certain height c. The load area ratio at height c corresponds to Smr(c) in FIG. 10B.

[0187] From this load curve, the volume of the region where the load area ratio is p% or more and 100% or less is calculated, which is the protrusion valley space volume Vvv. In this case, p = 80 is used to calculate the protrusion valley space volume Vvv.

[0188] (● Solid part and space part) Figure 10C shows a load curve showing the solid portion and the void portion. The larger the protruding valley void volume Vvv, the larger the volume of the valley, and therefore the more lubricant can be retained. As a result, the wear resistance is improved.

[0189] (● Height distribution by deviation) Fig. 10D shows the height distribution depending on the skewness Ssk. Fig. 10D(a) shows the height distribution when the skewness Ssk>0. Fig. 10D(b) shows the height distribution when the skewness Ssk<0.

[0190] The degree of distortion (skewness) Ssk represents the symmetry of the height distribution and is calculated by the following formula (Equation 1).

number

[0191] When Ssk = 0, the height distribution is symmetrical. When Ssk > 0, the surface has many fine peaks, as shown in Figure 10D(a). When Ssk < 0, the surface has many fine peaks, as shown in Figure 10D(b).

[0192] A surface with many fine peaks, as shown in Figure 10D(b), increases the contact area of ​​the sliding surface, resulting in better wear resistance. The smaller the Ssk, the better the wear resistance, so it is desirable to set the surface shape characteristic value Ssk (degree of distortion) of the sliding surface of the fixing belt to 0 or less.

[0193] (● Kurtosis) Kurtosis Sku represents the sharpness of the height distribution and is calculated using the following formula (Equation 2).

number

[0194] When Sku=3, the height distribution is normal. When Sku>3, the surface has many sharp peaks and valleys, as shown in Figure 10E(a). When Sku<3, the surface becomes flat, as shown in Figure 10E(b), and the contact area of ​​the sliding surface increases, resulting in good wear resistance.

[0195] (●Measurement method) The surface shape parameters can be measured using a VK-X100 (manufactured by Keyence) with a 50x objective lens. The sample was measured by setting the fixing belt of the present invention on a smooth surface and confirming that there was no significant tilt or waviness at the observation position.

[0196] (●Relationship between elastic power and coefficient of friction) The area under the displacement-load curve during pressure application and unloading in Figure 5, explained in terms of elastic power, is the energy loss, and the larger this difference is, the larger the friction force (torque) becomes. Figure 11A shows that changing the elastic power results in a difference in the friction coefficient (static friction coefficient and kinetic friction coefficient) of the fixing belt. The difference between the static friction coefficient and kinetic friction coefficient becomes smaller as the elastic power increases.

[0197] FIG. 11B shows the results of the following experiment to confirm the occurrence of abnormal noise and vibration when the elastic power is changed (50% → 55% → 63%). <Measurement conditions> ■ Dynamic friction coefficient: A small amount of grease was applied (Toray HP300: 50 mg), and the average value was calculated over 24 hours. Measuring instrument: Ring-on tester Cut out the belt and place it in the ring-on tester Contact: Glass φ10 Rotation speed (measurement part): 250 mm / sec Temperature: 23℃ Load: 1kg / cm 2

[0198] ■Static friction coefficient: Without grease application Contact: Glass φ10 Temperature: 23℃ Load: 1kg / cm 2

[0199] According to this experiment, even if the elastic power is changed (50% → 55% → 63%), there appears to be no change in the occurrence of abnormal noise. However, since abnormal noise occurs when vibration worsens, it was found that increasing the elastic power has the effect of suppressing the occurrence of abnormal noise and vibration in the fixing belt.

[0200] That is, by setting the elastic power to 55%, the elastic deformation ability of the fixing belt can be improved and stress during sliding can be alleviated, ensuring practical wear resistance (preventing deterioration of the belt material) while also effectively suppressing abnormal noise and vibration.In addition, by setting the elastic power to 63%, the elastic deformation ability of the fixing belt can be further improved and stress during sliding can be further alleviated, ensuring high-quality wear resistance while also effectively suppressing abnormal noise and vibration.

[0201] Simply increasing the hardness (Martens hardness) of the belt surface to improve the belt's wear resistance does not prevent deterioration of the components. Increasing the elastic power reduces the stress on the belt surface material caused by the nip sliding area, which has the effect of preventing deterioration of the component structure.

[0202] Figure 11C shows the difference between the static and dynamic friction coefficients in Figure 11A, corresponding to changes in elastic power. As is clear from the figure, the difference in friction coefficient is 0.14 or less when the elastic power is 55% or more. The smaller the difference in friction coefficient, the more effectively it can suppress the occurrence of stick-slip and the generation of abnormal noise and vibration.

[0203] (● Other embodiments of the image forming apparatus) The image forming apparatus according to the present invention is not limited to the color image forming apparatus shown in FIG. 1A, but may also be a monochrome image forming apparatus, a copying machine, a printer, a facsimile, or a combination machine of these.

[0204] 12, for example, image forming apparatus 100 of this embodiment includes image forming means 50 including a photosensitive drum and the like, a paper transport section including a pair of timing rollers 15 and the like, paper feeding device 200, fixing device 300, paper discharge device 10, and reading section 51. Paper feeding device 200 includes multiple paper feed trays, each of which stores paper of a different size.

[0205] The reading unit 51 reads an image of the document Q. The reading unit 51 generates image data from the read image. The paper feeder 200 stores a plurality of sheets of paper P and sends the sheets of paper P to a conveyance path. The timing rollers 15 convey the sheets of paper P on the conveyance path to the image forming means 50.

[0206] The image forming means 50 forms a toner image on a sheet of paper P. Specifically, the image forming means 50 includes a photosensitive drum, a charging roller, an exposure device, a developing device, a replenishing device, a transfer roller, a cleaning device, and a discharging device. The toner image represents, for example, an image of a document Q.

[0207] The fixing device 300 applies heat and pressure to the toner image to fix the toner image to the paper P. The paper P with the fixed toner image is transported to the paper discharge device 10 by a transport roller or the like. The paper discharge device 10 discharges the paper P outside the image forming apparatus 100.

[0208] Next, a fixing device 300 of this embodiment will be described. Descriptions of components common to the fixing devices of the previous embodiments will be omitted where appropriate. As shown in Fig. 13, the fixing device 300 includes a fixing belt 310, a pressure roller 320, a heater 332, a heater holder 344, a stay 350, a thermistor TH, and the like.

[0209] A fixing nip N is formed between the fixing belt 310 and the pressure roller 320. The nip width of the fixing nip N can be set to, for example, 10 mm, and the linear speed of the fixing device 300 can be set to, for example, 240 mm / s.

[0210] The fixing belt 310 has a polyimide base and a release layer, but does not have an elastic layer. The release layer is made of a heat-resistant film material such as fluororesin. The outer diameter of the fixing belt 310 can be, for example, approximately 24 mm.

[0211] Pressure roller 320 includes a core metal 321, an elastic layer 322, and a release layer 323. The outer diameter of pressure roller 320 may be, for example, 24 to 30 mm, and the thickness of elastic layer 322 may be, for example, 3 to 4 mm.

[0212] The heater 332 includes a base material, a heat insulating layer, a conductor layer including a resistance heating element, and an insulating layer, and can be formed with an overall thickness of, for example, 1 mm. The width Y of the heater 332 in the array crossing direction can be, for example, 13 mm.

[0213] As shown in Fig. 14, the conductor layer of the heater 332 includes a plurality of resistance heating elements 31, power supply lines 133, and electrode portions 134A to 134C. In this embodiment as well, as shown in the enlarged view of Fig. 13, the plurality of resistance heating elements 31 are divided into divided regions in the arrangement direction (however, although Fig. 14 only shows the divided regions within the enlarged view, in reality divided regions are provided between all of the resistance heating elements 31).

[0214] Three heat generating portions 135A to 135C are formed by the resistance heating element 31. When electricity is applied to the electrode portions 134A and 134B, the heat generating portions 135A and 135C generate heat.

[0215] Heat generating unit 135B generates heat by energizing electrode units 134A and 134C. For example, when performing a fixing operation on small-sized paper, heat generating unit 135B is made to generate heat, and when performing a fixing operation on large-sized paper, all of the heat generating units are made to generate heat.

[0216] 15, the heater holder 344 has a recess 344b that holds the heater 332. The recess 344b is provided on the heater holder 344 on the heater 332 side.

[0217] The recess 344b is composed of a surface 344b1 that is approximately parallel to the base material 30 and is recessed toward the stay 350 relative to the other surfaces of the heater 332, wall portions 344b2 provided inside the heater holder 344 on both sides in the arrangement direction of the heater holder 344 (or on one side), and wall portions 344b3 provided inside the heater holder 344 on both sides in the intersecting direction of the arrangement. The heater holder 344 has a guide portion 344a. The heater holder 344 is made of LCP (liquid crystal polymer).

[0218] 16, connector 65 includes a U-shaped housing made of resin (for example, LCP) and a plurality of contact terminals provided on the inner surface of the U-shaped housing. Connector 65 is attached so as to sandwich heater 332 and heater holder 344 together from the front and back sides.

[0219] In this state, each contact terminal makes contact (pressure contact) with each electrode portion of the heater 332, electrically connecting the heat generating portion 35 to the power supply provided in the image forming apparatus via the connector 65. This enables power to be supplied from the power supply to the heat generating portion 35. Note that, in order to ensure connection with the connector 65, at least a portion of each electrode portion 34 is not covered with an insulating layer and is exposed.

[0220] Flanges 53, which hold both ends of fixing belt 310, are provided on both sides of fixing belt 310 in the arrangement direction and hold both ends of fixing belt 310 from the inside of the belt. Flanges 53 are fixed to the housing of fixing device 300. Flanges 53 are inserted into both ends of stays 350 (see the arrow directions from flanges 53 in FIG. 16).

[0221] The direction in which the connector 65 is attached to the heater 332 and heater holder 344 is the direction that intersects the heater arrangement (see the direction of the arrow from the connector 65 in FIG. 16). When the connector 65 is attached to the heater holder 344, a convex portion on one of the connector 65 and the heater holder 344 may engage with a concave portion on the other, and the convex portion may move relatively within the concave portion. The connector 65 is attached to the heater 332 and heater holder 344 on one side in the arrangement direction, opposite the side on which the drive motor of the pressure roller 320 is provided.

[0222] 17, thermistors TH are provided facing the inner circumferential surface of fixing belt 310, at the center and end sides in the arrangement direction of fixing belt 310. Heater 332 is controlled based on the temperatures detected by the thermistors TH at the center and end sides in the arrangement direction of fixing belt 310. Note that one of these thermistors TH is provided at a position corresponding to a divided region between the resistance heating elements of heater 332, as in the above-described embodiment.

[0223] Thermostats TS are provided facing the inner circumferential surface of fixing belt 310, at the center and end sides in the arrangement direction of fixing belt 310. When the temperature of fixing belt 310 detected by thermostat TS exceeds a predetermined threshold, power supply to heater 332 is stopped.

[0224] Flanges 53 are provided on both ends of the fixing belt 310 in the arrangement direction to hold the respective ends of the fixing belt 310. The flanges 53 are made of LCP (liquid crystal polymer).

[0225] 18, a slide groove 53a is provided in the flange 53. The slide groove 53a extends in the direction in which the fixing belt 310 contacts and separates from the pressure roller 320.

[0226] An engagement portion of the housing of the fixing device 300 engages with the slide groove 53a. This engagement portion moves relatively within the slide groove 53a, so that the fixing belt 310 can move in the direction of approaching and separating from the pressure roller 320.

[0227] While the present invention has been described above based on the embodiments, it goes without saying that the present invention is not limited to the above embodiments and can be modified in various ways within the scope of the technical concept described in the claims. For example, the pressure roller 320 as the pressure member of the fixing device 300 may be configured as a pressure belt stretched between two rotating bodies. Furthermore, other heat generating elements such as a ceramic heater can also be used as the heat generating element of the fixing device 300. [Explanation of symbols]

[0228] 1K, 1Y, 1M, 1C: Process units 2K, 2Y, 2M, 2C: Image carriers 3K, 3Y, 3M, 3C: Drum cleaning device 4K, 4Y, 4M, 4C: Charging device 5K, 5Y, 5M, 5C: Developing unit 6K, 6Y, 6M, 6C: Toner bottle 7: Exposure device 7a: Mirror 8: Transfer cover 10: Powder container 15: Transfer device 16: Intermediate transfer belt 17: Driven roller 18: Drive roller 19K, 19Y, 19M, 19C: Primary transfer roller 20: Secondary transfer roller 21: Belt cleaning device 31: Resistance heating element 32: Paper feed path 33: Post-transfer transport path 35: Post-fixing transport path 36: Paper ejection path 37: Pair of paper discharge rollers 41: Reverse conveying path 42: Switching member 42a: Oscillating shaft 43: Pair of reversing conveying rollers 44: Paper output tray 45: Paper feed roller 46: Tray 60: Paper feed roller 70: Connector 71: Housing 72: Contact terminal 72a: Contact point 73: Harness 74: Highly heat conductive member 100: Image forming apparatus 101: Protrusion 102: Hole 103: Image forming apparatus body 200: Paper feeding device 210: Roller pair 220: Feeding roller 230: Separation roller 240: Conveyance roller 250: Pair of registration rollers 300: Fixing device 310: Fixing belt 320: Pressure roller 321: Core metal 322: Elastic layer 323: Release layer 324: Drive transmission gear 330: Heating element 330a: Positioning hole 333a: Electrode part 333b: Power supply line 334: Pressure belt 334: Conductive layer 340, 344: heater holder 341: substrate 350, 352: Stay 351: Auxiliary stay 370: Resistance member 370-1: Central resistance member 370-2: End resistance member 370a, 370b: Power supply line 370c~370h: Electrode 371~378: PTC element 379a~379h: Power supply line 381: Nip forming member 385: Insulation layer 387: Spring 389: Heat equalizing member 390: Pressure roller 400: Control unit 400: Control unit 410: AC power supply 420: Triac 430: Current detection means 441, 442: Heater relay 451, 452: Voltage detection means P: Paper SN: Fixing nip TH, TH1 to TH4: Thermistor TS: Thermostat TM: Transfer means [Prior art documents] [Patent documents]

[0229] [Patent Document 1] Patent No. 6336026 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-194713 [Patent Document 3] Japanese Patent Application Laid-Open No. 2009-14893 [License 4] Patent No. 6036469 [Patent Document 5] Patent No. 6061606

Claims

1. a flexible sleeve-shaped rotating member; a sliding member that slides against the inner periphery of the rotating member; a pressing member that presses against a portion of the rotating member that faces the sliding member across the rotating member to form a nip portion between the rotating member and the pressing member; In a fixing device, a lubricant is provided between the rotating member and the sliding member, The consistency of the lubricant is 340 or less, and the elastic power of the sliding surface of the rotating member is 58% or more, or the consistency of the lubricant is 275 or less, and the elastic power of the sliding surface of the rotating member is 55% or more, a fixing device characterized in that the material of the sliding surface of the rotating member contains polyimide and a needle-shaped inorganic filler, and the surface roughness Sa (arithmetic mean height) of the sliding surface in the sliding direction is 0.2 μm or more, which is larger than the surface roughness of the sliding surface of the sliding member in the sliding direction.

2. 2. The fixing device according to claim 1, wherein the elastic power of the sliding surface of said rotating member is set to 63% or more.

3. 3. The fixing device according to claim 1, wherein the sliding member has a heater.

4. 4. The fixing device according to claim 1, wherein the lubricant contains fluorine grease or silicone oil.

5. 5. The fixing device according to claim 1, wherein the sliding surface of the sliding member has a surface roughness of 0.05 [mu]m or less.

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

7. 7. The fixing device according to claim 1, wherein a deviation Ssk, which is a surface shape characteristic value of the sliding surface of the rotary member, is 0 or less.

8. 8. The fixing device according to claim 1, wherein the sliding surface of the rotary member has a surface shape characteristic value, ie, a sharpness Sku, of 3 or less.

9. 9. The fixing device according to claim 1, wherein the sliding surface of the sliding member is made of glass.

10. 10. The fixing device according to claim 1, wherein the rotating member comprises a base material, a surface layer, and an adhesive layer.

11. 11. The fixing device according to claim 1, wherein the heat generating element of the heater is divided into a plurality of parts in the longitudinal direction.

12. An image forming apparatus comprising the fixing device according to any one of claims 1 to 11.

Images