JP2015132722A - Fixing apparatus, sliding member, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing apparatus configured to prevent temperature increase in a non-paper passing area of a nip part.SOLUTION: A fixing apparatus 60 includes: a rotatable fixing roll 61; an endless belt 62 which moves in contact with the fixing roll 61; a pressure pad 64 arranged to face the fixing roll 61 across the endless belt 62, and bringing the endless belt 62 into pressure contact with the fixing roll 61 to form a nip part N where a sheet P passes, between the fixing roll 61 and the endless belt 62; and a slide sheet 68 for reducing sliding resistance between the pressure pad 64 and the endless belt 62. The slide sheet 68 is arranged in the nip part N and downstream of the nip part N in a passing direction of the sheet P. Thermal conductivity in a nip-part non-corresponding section is higher than that in a nip-part corresponding section which corresponds to the nip part N.

Description

  The present invention relates to a fixing device, a sliding member, and an image forming apparatus.

  In an image forming apparatus such as a copying machine or a printer using an electrophotographic system, for example, a photosensitive member (photosensitive drum) formed in a drum shape is charged, and the photosensitive drum is controlled by light controlled based on image information. An electrostatic latent image is formed on the photosensitive drum by exposure. The electrostatic latent image is converted into a visible image (toner image) with toner, and the toner image is transferred from the photosensitive drum to a recording medium such as paper, and then the toner image is fixed on the paper by a fixing device. Yes.

  For example, as shown in FIG. 4, a fixing device used in such an image forming apparatus includes a heating source 114 inside a cylindrical core 111, a heat-resistant elastic layer 112 on the core 111, and an outer periphery thereof. The fixing roll 110 formed by laminating the release layer 113 on the surface, the heat-resistant elastic body layer 122 on the core 121 and the heat-resistant resin coating or It comprises a pressure roll 120 formed by laminating a release layer 123 made of a heat-resistant rubber film or the like. Then, the sheet holding the unfixed toner image is passed through the nip portion between the fixing roll 110 and the pressure roll 120, and the unfixed toner image is heated and pressed to form the sheet. The toner image is fixed. Such a fixing device is called a roll nip method, a two-roll method, or a heating roll method, and is generally widely used.

  By the way, in the roll nip type fixing device, it is desired to increase the width of the nip portion in proportion to the fixing speed so that a sufficient amount of heat can be supplied to the toner and the paper.

  In order to realize a fixing device corresponding to the speeding up of the image forming apparatus, the applicant of the present invention has a fixing roll that is a rotatable fixing member whose surface is elastically deformed, and an endless belt that can run while being in contact with the fixing roll. A pressure pad that is a pressure applying member disposed in a non-rotating state on the inner surface side of the endless belt, and a sheet-like sliding member having a low frictional resistance between the pressure pad and the endless belt. Thus, the endless belt can be brought into pressure contact with the fixing roll so as to form a contact surface with the fixing roll through the sliding member, and a recording medium such as paper can be passed between the endless belt and the fixing roll. And a technology relating to a fixing device configured to locally elastically deform the nip portion of the surface of the fixing roll on the exit side of the recording medium is proposed (for example, , See Patent Documents 1 and 2).

  In a fixing device (referred to as “free belt nip method”) described in Patent Documents 1 and 2, instead of a pressure roll in a conventional roll nip type fixing device, for example, an elastic material portion of a nip portion on the recording medium inlet side The endless belt is brought into pressure contact with the fixing roll using a pressure pad provided with a plurality of pressure portions of the extreme pressure portion on the outlet side. By adopting such a configuration, the width of the nip portion formed by the fixing roll and the endless belt can be easily made larger than the width of the nip portion formed by the conventional fixing roll and pressure roll. In addition, since a nip pressure that is as uniform and high as possible can be applied to the nip portion, it is possible to cope with a high speed, and it is easy to reduce the size of the apparatus.

  Furthermore, since the heat capacity of the endless belt pressed against the fixing roll is small, and the pressure pad is arranged in a non-rotating state, a configuration in which heat transmitted from the fixing roll is difficult to be dissipated to the outside is realized. Therefore, even when rotation of the fixing roll is started, the amount of heat taken from the fixing roll to the endless belt side is small, the thermal efficiency at the time of melting the toner can be increased, and the amount of temperature decrease at the nip portion is also small. The toner has an advantage that the fixing property of the toner can be improved, and has been put into practical use as a compact and high-speed energy-saving fixing device.

  On the other hand, as a sliding member used in such a fixing device, in Patent Document 3, a heat-resistant woven fabric formed by weaving heat-resistant fibers orthogonally is used as a base layer, and the weft component of the heat-resistant woven fabric is the length of the heating device. It is described that the heat transfer performance per unit time of the weft yarn of the heat-resistant woven fabric exceeds the heat transfer performance per unit time of the warp yarn.

  Patent Document 4 describes a sliding member made of a thermally conductive anisotropic material having a higher thermal conductivity in the plane direction than in the thickness direction.

  Patent Document 5 describes a pressing member in which a contact portion that contacts a heat-generating rotating body is formed of a heat-resistant member including bubbles or an air layer.

Japanese Patent Application Laid-Open No. 11-133776 JP 2005-148618 A Japanese Patent Laid-Open No. 6-194981 JP 2006-267410 A Japanese Patent Laid-Open No. 10-074003

  An object of the present invention is to provide a fixing device in which a temperature rise in a non-sheet passing region where a recording medium does not pass through a nip portion is suppressed, a sliding member provided in the fixing device, and an image forming apparatus provided with the fixing device. There is to do.

  The invention according to claim 1 is disposed so as to face the rotating member through the endless belt member, a rotatable rotating member, an endless belt member movable while contacting the rotating member, and the endless belt member. A nip portion forming member that presses a belt member against the rotating member to form a nip portion through which a recording medium passes between the rotating member and the endless belt member; and the nip portion forming member and the endless belt member. A sheet-like sliding member that reduces a frictional resistance between the nip portion and the nip portion, and at least the downstream side of the nip portion in the passing direction of the recording medium. In order to fix the toner image held on the recording medium, the thermal conductivity of the non-nip portion corresponding portion other than the nip portion corresponding portion is higher than the thermal conductivity of the nip portion corresponding portion corresponding to the portion. It is a of the fixing device.

  The invention according to claim 2 is the fixing device according to claim 1, wherein the sliding member is arranged from the upstream side of the nip portion to the nip portion and the downstream side of the nip portion.

  The invention according to claim 3 is the fixing device according to claim 1, wherein the endless belt member is a pressure belt on a side not in contact with the toner image.

  According to a fourth aspect of the present invention, in the first or second aspect, the endless belt member is a fixing belt on a side in contact with the toner image, and no heat generating member exists on the inner surface side of the endless belt member of the nip portion. The fixing device described.

  The invention according to claim 5 is any one of claims 1 to 4, wherein the non-corresponding portion of the sliding member has a thermal conductivity equal to or higher than the thermal conductivity of the base material layer of the endless belt member. The fixing device according to (1).

  According to a sixth aspect of the present invention, the sliding member is composed of a multilayer including at least a base material layer and a surface layer, and the thermal conductivity of at least one layer other than the surface layer of the nip portion corresponding portion. The fixing device according to claim 1, wherein at least one layer other than the surface layer of the nip portion non-corresponding portion has high thermal conductivity.

  The invention according to claim 7 is characterized in that at least one layer other than the surface layer of the non-nip portion corresponding portion is provided with respect to the thermal conductivity of the material constituting at least one layer other than the surface layer of the nip portion corresponding portion. The fixing device according to claim 6, wherein the constituent material has high thermal conductivity.

  According to an eighth aspect of the present invention, at least one layer other than the surface layer of the nip non-corresponding portion includes a thermally conductive filler, and the heat of the nip non-corresponding portion with respect to the nip corresponding portion. The fixing device according to claim 6, wherein the compounding amount of the conductive filler is high.

  The invention according to claim 9 is characterized in that the sliding member is rotatable in the circumferential direction of the endless belt, and the nip portion corresponding portion is provided when the recording medium passes or nip is pressed. 9. The device according to claim 1, wherein the nip portion is disposed at the nip portion and moves in such a manner that the non-nip portion-corresponding portion is disposed at the nip portion when the recording medium is not passed or nip pressure is not applied. The fixing device according to any one of the above items.

  The invention which concerns on Claim 10 is arrange | positioned so that the said rotation member may be opposed via the said endless belt member, the endless belt member which can be moved while contacting the said rotation member, and the said endless A toner image held on the recording medium, comprising: a nip portion forming member that presses the belt member against the rotating member to form a nip portion through which the recording medium passes between the rotating member and the endless belt member. Is provided in a fixing device for fixing the nip portion, reduces the frictional resistance between the nip portion forming member and the endless belt member, and the thermal conductivity of the nip portion corresponding portion corresponding to the nip portion, The sliding member has a high thermal conductivity in the non-nip portion corresponding portion other than the nip portion corresponding portion.

  According to an eleventh aspect of the present invention, there is provided an image carrier, latent image forming means for forming a latent image on the surface of the image carrier, and developing the latent image using a developer for developing an electrostatic image to form a toner image. 10. A developing unit for forming, a transfer unit for transferring the toner image to a recording medium, and a fixing unit for fixing the toner image to the recording medium, wherein the fixing unit is any one of claims 1 to 9. An image forming apparatus which is the fixing device according to the item.

  According to the first aspect of the present invention, compared to the case where the thermal conductivity of the nip portion non-corresponding portion is not high with respect to the thermal conductivity of the nip portion corresponding portion of the sliding member, in the non-sheet passing region of the nip portion. There is provided a fixing device in which a rise in temperature is suppressed.

  According to the second aspect of the present invention, there is provided a fixing device in which the temperature rise in the non-sheet passing region of the nip portion is further suppressed as compared with the case where the sliding member is not disposed on the upstream side of the nip portion.

  According to the third aspect of the invention, when the endless belt member is a pressure belt on the side that does not contact the toner image, an effect of suppressing the temperature rise in the non-sheet passing region of the nip portion is exhibited.

  According to the fourth aspect of the present invention, when the endless belt member is the fixing belt on the side in contact with the toner image and no heat generating member is present on the inner surface side of the endless belt member of the nip portion, the non-sheet passing region of the nip portion The effect of suppressing the temperature rise is exhibited.

  According to the invention according to claim 5, the endless belt of the nip portion is compared with a case where the non-corresponding portion of the sliding member does not have a thermal conductivity equal to or higher than the thermal conductivity of the base material layer of the endless belt member. Temperature rise in the non-sheet passing region of the member is suppressed.

  According to the invention which concerns on Claim 6, compared with the case where it does not have this structure, a surface layer is comprised including highly durable materials, such as a fluororesin, and the durability of a sliding member is made high. it can.

  According to the seventh aspect of the present invention, the durability of the sliding member can be increased by configuring the surface layer to include a highly durable material such as a fluororesin as compared with the case where the present configuration is not provided. it can.

  According to the invention which concerns on Claim 8, compared with the case where it does not have this structure, a surface layer is comprised including highly durable materials, such as a fluororesin, and the durability of a sliding member can be made high. In addition, a fixing device having a sliding member having a high thermal conductivity of the non-nip portion corresponding portion with respect to the nip portion corresponding portion is easily manufactured.

  According to the ninth aspect of the present invention, there is provided a fixing device in which the temperature of the nip portion is quickly and substantially equalized after completion of fixing.

  According to the invention of claim 10, the temperature rise in the non-sheet passing region of the nip portion is suppressed compared to the case where the thermal conductivity of the non-nip portion corresponding portion is not higher than the thermal conductivity of the nip portion corresponding portion. A sliding member is provided.

  According to the invention of claim 11, in the non-sheet passing region of the nip portion, compared to the case where the thermal conductivity of the nip portion non-corresponding portion is not high with respect to the thermal conductivity of the nip portion corresponding portion of the sliding member. An image forming apparatus including a fixing device that suppresses a rise in temperature is provided.

1 is a schematic configuration diagram illustrating an example of an image forming apparatus to which a fixing device according to an embodiment of the present invention is applied. 1 is a side cross-sectional view illustrating a configuration of an example of a fixing device according to an embodiment of the present invention. FIG. 6 is a side cross-sectional view illustrating a configuration of another example of a fixing device according to an embodiment of the present invention. It is a side sectional view showing an example of a configuration of a conventional roll nip type fixing device. It is a top view which shows an example of a structure of the sliding member which concerns on embodiment of this invention. It is a top view which shows the other example of a structure of the sliding member which concerns on embodiment of this invention.

  Embodiments of the present invention will be described below. This embodiment is an example for carrying out the present invention, and the present invention is not limited to this embodiment.

  FIG. 1 is a schematic configuration diagram illustrating an example of an image forming apparatus to which the fixing device according to the present embodiment is applied. FIG. 1 shows an intermediate transfer type image forming apparatus generally called a tandem type. The image forming apparatus shown in FIG. 1 has a plurality of image forming units 1Y, 1E, on which toner images of respective color components (yellow (Y), magenta (M), cyan (C), black (B)) are formed by electrophotography. 1M, 1C, 1K, a primary transfer unit 10 for sequentially transferring (primary transfer) the color component toner images formed by the image forming units 1Y, 1M, 1C, 1K to the intermediate transfer belt 15, and the intermediate transfer belt 15 A secondary transfer unit 20 that collectively transfers (secondary transfer) the superimposed toner image transferred onto the paper (recording medium) P, and a fixing device 60 that fixes the secondary transferred image onto the paper P. ing. Moreover, it has the control part 40 which controls operation | movement of each apparatus (each part).

  Each of the image forming units 1Y, 1M, 1C, and 1K forms an electrostatic latent image on the photosensitive drum 11 and a charging device 12 that charges the photosensitive drum 11 around the photosensitive drum 11 that rotates in the arrow A direction. An exposure device 13 for writing with a laser or the like (in FIG. 1, the exposure beam is indicated by a symbol Bm), and a developing device that accommodates each color component toner and visualizes the electrostatic latent image on the photosensitive drum 11 with the toner. 14, a primary transfer roll 16 that transfers the toner image of each color component formed on the photosensitive drum 11 to the intermediate transfer belt 15 in the primary transfer unit 10, and a drum cleaner that removes residual toner on the photosensitive drum 11. Electrophotographic devices such as 17 are sequentially arranged. These image forming units 1Y, 1M, 1C, and 1K are substantially linear from the upstream side of the intermediate transfer belt 15 in the order of yellow (Y), magenta (M), cyan (C), and black (K), for example. Has been placed.

The intermediate transfer belt 15 as an intermediate transfer member is constituted by a film-like endless belt in which an appropriate amount of an antistatic agent such as carbon black is contained in a resin such as polyimide or polyamide. The volume resistivity is, for example, 10 ⁶ Ωcm or more and 10 ¹⁴ Ωcm or less, and the thickness is, for example, about 0.1 mm. The intermediate transfer belt 15 is circulated and driven (rotated) by various rolls at a predetermined speed in the direction B shown in FIG. As these various rolls, a drive roll 31 that is driven by a motor (not shown) having excellent constant speed and rotates the intermediate transfer belt 15, and extends substantially linearly along the arrangement direction of the photosensitive drums 11. A support roll 32 that supports the intermediate transfer belt 15, a tension roll 33 that functions as a correction roll that applies a constant tension to the intermediate transfer belt 15 and prevents the intermediate transfer belt 15 from meandering, and the secondary transfer unit 20. A backup roll 25 provided; and a cleaning backup roll 34 provided in a cleaning unit that scrapes off residual toner on the intermediate transfer belt 15.

The primary transfer unit 10 includes a primary transfer roll 16 that is disposed to face the photosensitive drum 11 with the intermediate transfer belt 15 interposed therebetween. The primary transfer roll 16 is composed of, for example, a shaft and a sponge layer as an elastic layer fixed around the shaft. The shaft is, for example, a cylindrical bar made of a metal such as iron or SUS. The sponge layer is formed including, for example, a blend rubber of acrylonitrile-butadiene rubber (NBR), styrene-butadiene rubber (SBR), and ethylene-propylene-diene rubber (EPDM) containing a conductive agent such as carbon black. A sponge-like cylindrical roll having a volume resistivity of 10 ⁷ Ωcm or more and 10 ⁹ Ωcm or less, for example. The primary transfer roll 16 is disposed in pressure contact with the photosensitive drum 11 with the intermediate transfer belt 15 interposed therebetween. Further, the primary transfer roll 16 has a polarity opposite to the toner charging polarity (for example, negative polarity; the same applies hereinafter). Voltage (primary transfer bias) is applied. As a result, the toner images on the respective photosensitive drums 11 are sequentially electrostatically attracted to the intermediate transfer belt 15 so as to form superimposed toner images on the intermediate transfer belt 15.

The secondary transfer unit 20 includes, for example, a secondary transfer roll 22 disposed on the toner image holding surface side of the intermediate transfer belt 15 and a backup roll 25. The backup roll 25 includes, for example, an inner layer portion containing EPDM rubber and the like, and a tubular surface layer containing EPDM and NBR blend rubber in which carbon or the like is dispersed. For example, the surface resistivity is 10 ⁷ Ω / □ to 10 ¹⁰ Ω / □, and the hardness is set to 70 ° (Asker C), for example. The backup roll 25 is disposed on the back side of the intermediate transfer belt 15 to form a counter electrode of the secondary transfer roll 22 and is in contact with a metal power supply roll 26 to which a secondary transfer bias is stably applied. Has been placed.

On the other hand, the secondary transfer roll 22 includes, for example, a shaft and a sponge layer as an elastic layer fixed around the shaft. The shaft is, for example, a cylindrical bar made of a metal such as iron or SUS. The sponge layer is formed, for example, by including a blend rubber of NBR, SBR, and EPDM blended with a conductive agent such as carbon black. For example, a sponge-like cylindrical roll having a volume resistivity of 10 ⁷ Ωcm to 10 ⁹ Ωcm It is. The secondary transfer roll 22 is placed in pressure contact with the backup roll 25 with the intermediate transfer belt 15 interposed therebetween. Further, the secondary transfer roll 22 is grounded and a secondary transfer bias is formed between the secondary transfer roll 22 and the backup roll 25. The toner image is secondarily transferred onto the paper P conveyed to the next transfer unit 20.

  On the downstream side of the secondary transfer portion 20 of the intermediate transfer belt 15, an intermediate transfer belt cleaner that removes residual toner, paper dust, and the like on the intermediate transfer belt 15 after the secondary transfer and cleans the surface of the intermediate transfer belt 15. 35 is detachably provided. On the other hand, on the upstream side of the yellow image forming unit 1Y, a reference sensor (home position sensor) 42 that generates a reference signal for taking image forming timing in each of the image forming units 1Y, 1M, 1C, 1K is disposed. Yes. An image density sensor 43 for adjusting image quality is disposed on the downstream side of the black image forming unit 1K. The reference sensor 42 recognizes a predetermined mark provided on the back side of the intermediate transfer belt 15 and generates a reference signal. Each image formation is performed according to an instruction from the control unit 40 based on the recognition of the reference signal. The units 1Y, 1M, 1C, and 1K are configured to start image formation.

  Further, as the paper transport system, for example, a paper tray 50 that stores paper P, a pick-up roll 51 that picks up and transports the paper P accumulated in the paper tray 50 at a predetermined timing, and a pick-up roll 51 feeds out the paper. A transport roll 52 that transports the transported paper P, a transport chute 53 that feeds the paper P transported by the transport roll 52 to the secondary transfer unit 20, and a paper that is transported after being secondarily transferred by the secondary transfer roll 22. A conveyance belt 55 that conveys P to the fixing device 60 and a fixing entrance guide 56 that guides the paper P to the fixing device 60 are provided.

  Next, a basic image forming process of the image forming apparatus using the fixing device according to the present embodiment will be described.

  In the image forming apparatus as shown in FIG. 1, image data output from an image reading device (IIT) (not shown), a personal computer (PC) (not shown), or the like is received by an image processing device (IPS) (see FIG. 1). The image forming operation is performed by the image forming units 1Y, 1M, 1C, and 1K. In IPS, predetermined image processing such as shading correction, position shift correction, brightness / color space conversion, gamma correction, frame deletion, color editing, moving editing, and the like is performed on input reflectance data. Applied. The image data that has been subjected to the image processing is converted into color material gradation data of four colors Y, M, C, and K, and is output to the exposure device 13.

  The exposure device 13 irradiates the photosensitive drums 11 of the image forming units 1Y, 1M, 1C, and 1K with, for example, an exposure beam Bm emitted from a semiconductor laser according to the input color material gradation data. In each of the photosensitive drums 11 of the image forming units 1Y, 1M, 1C, and 1K, the surface is charged by the charging device 12, and then the surface is scanned and exposed by the exposure device 13 to form an electrostatic latent image. The formed electrostatic latent image is developed as a toner image of each color of Y, M, C, K by each image forming unit 1Y, 1M, 1C, 1K. The toner images formed on the photosensitive drums 11 of the image forming units 1Y, 1M, 1C, and 1K are transferred onto the intermediate transfer belt 15 in the primary transfer unit 10 where the photosensitive drums 11 and the intermediate transfer belt 15 are in contact with each other. Transcribed. More specifically, in the primary transfer unit 10, a voltage (primary transfer bias) having a polarity opposite to the charging polarity (negative polarity) of the toner is applied to the base material of the intermediate transfer belt 15 by the primary transfer roll 16. Primary transfer is performed by sequentially superposing the toner images on the surface of the intermediate transfer belt 15.

  After the toner images are sequentially primary transferred onto the surface of the intermediate transfer belt 15, the intermediate transfer belt 15 moves and the toner image is conveyed to the secondary transfer unit 20. When the toner image is transported to the secondary transfer unit 20, in the paper transport system, the pick-up roll 51 rotates in accordance with the timing at which the toner image is transported to the secondary transfer unit 20, and the predetermined size from the paper tray 50 is reached. Paper P is supplied. The paper P supplied by the pickup roll 51 is transported by the transport roll 52 and reaches the secondary transfer unit 20 via the transport chute 53. Before reaching the secondary transfer unit 20, the paper P is temporarily stopped, and the registration roller (not shown) rotates in accordance with the movement timing of the intermediate transfer belt 15 on which the toner image is held. And the position of the toner image are aligned.

  In the secondary transfer unit 20, the secondary transfer roll 22 is pressed against the backup roll 25 via the intermediate transfer belt 15. At this time, the sheet P conveyed at the same timing is sandwiched between the intermediate transfer belt 15 and the secondary transfer roll 22. At this time, when a voltage (secondary transfer bias) having the same polarity as the toner charging polarity (negative polarity) is applied from the power supply roll 26, a transfer electric field is formed between the secondary transfer roll 22 and the backup roll 25. Is done. The unfixed toner image held on the intermediate transfer belt 15 is collectively electrostatically transferred onto the paper P in the secondary transfer unit 20 pressed by the secondary transfer roll 22 and the backup roll 25. .

  Thereafter, the sheet P on which the toner image has been electrostatically transferred is transported as it is while being peeled off from the intermediate transfer belt 15 by the secondary transfer roll 22, and transported downstream of the secondary transfer roll 22 in the sheet transport direction. It is conveyed to the belt 55. The conveying belt 55 conveys the paper P to the fixing device 60 in accordance with the optimum conveying speed in the fixing device 60. The unfixed toner image on the paper P conveyed to the fixing device 60 is fixed on the paper P by being subjected to a fixing process by heat and pressure by the fixing device 60. Then, the paper P on which the fixed image is formed is conveyed to a paper discharge placement unit provided in a discharge unit of the image forming apparatus.

  On the other hand, after the transfer to the paper P is completed, the residual toner remaining on the intermediate transfer belt 15 is conveyed to the cleaning unit as the intermediate transfer belt 15 rotates, and is cleaned by the cleaning backup roll 34 and the intermediate transfer belt cleaner 35. It is removed from the intermediate transfer belt 15.

  Next, the fixing device 60 used in the image forming apparatus according to the present embodiment will be described. FIG. 2 is a side sectional view showing an example of the configuration of the fixing device 60 according to the present embodiment. The fixing device 60 includes a fixing roll 61 as an example of a rotatable rotating member, an endless belt 62 as an example of an endless belt member that can move while contacting the fixing roll 61, and the fixing roll 61 via the endless belt 62. Pressure as an example of a nip portion forming member that presses the endless belt 62 against the fixing roll 61 to form a nip portion N through which the paper P passes between the fixing roll 61 and the endless belt 62. The main part is composed of a pad 64 and a sliding sheet 68 as an example of a sheet-like sliding member that reduces the sliding resistance between the pressure pad 64 and the endless belt 62. The sliding sheet 68 will be described later.

  The fixing roll 61 is, for example, a cylindrical roll configured by laminating a heat-resistant elastic body layer 612 and a release layer 613 around a metal core (cylindrical cored bar) 611 and is rotatably supported. And rotated at a predetermined surface speed (for example, 194 mm / sec). The fixing roll 61 is formed of, for example, a so-called straight roll whose outer diameter is substantially uniform in the axial direction.

  Inside the fixing roll 61, for example, a halogen heater 66 having a rating of 600 W is disposed as a heating source. On the other hand, a temperature sensor 69 is disposed in contact with the surface of the fixing roll 61. The control unit 40 of the image forming apparatus in FIG. 1 controls the lighting of the halogen heater 66 based on the temperature measurement value by the temperature sensor 69, and the surface temperature of the fixing roll 61 is a preset temperature (for example, 175 ° C.). Have been adjusted to maintain.

  The endless belt 62 is a seamless belt whose original shape is formed in a cylindrical shape or the like so that defects due to the seam are not generated in the output image as much as possible. The endless belt 62 is rotatably supported by a pressure pad 64 disposed in the endless belt 62, a belt guide member 63, and edge guide members (not shown) disposed at both ends of the endless belt 62. Has been. And it arrange | positions so that it may press-contact with the fixing roll 61 in the nip part N, and it follows the fixing roll 61 and rotates (for example, rotation speed 194 mm / sec) in the arrow direction.

  For example, the pressure pad 64 is supported by a holder 65 made of metal or the like inside the endless belt 62. Then, it is arranged in a state of being pressed against the fixing roll 61 via the endless belt 62, and a nip portion N is formed with the fixing roll 61. In the pressure pad 64, a pre-nip member 64 a for securing a wide nip portion N is disposed on the inlet side (upstream side) of the nip portion N. Further, on the outlet side (downstream side) of the nip portion N, the surface of the fixing roll 61 is locally pressed to smooth the surface of the toner image and impart image gloss, and the surface of the fixing roll 61 is distorted (dented). ), And a peeling nip member 64b for forming a down curl on the paper P is disposed.

  In order to reduce the sliding resistance between the inner peripheral surface of the endless belt 62 and the pressure pad 64, a low friction sliding member as an example of a rubbing member is provided between the inner peripheral surface of the endless belt 62 and the pressure pad 64. A moving sheet 68 is provided.

  The sliding sheet 68 is fixed to the holder 65 at the upstream end of the nip portion N by a sliding sheet fixing member 631. Then, in the state of being sandwiched between the pressure pad 64 and the inner peripheral surface of the endless belt 62 along the rotation direction of the endless belt 62, the entire area of the nip portion N and at least downstream of the nip portion N in the passage direction of the paper P. It is arranged over the side. The downstream side of the nip portion N of the sliding sheet 68 is not fixed and set to a free end (free) state so that the sliding sheet 68 is not distorted. The sliding sheet 68 has a sliding resistance between the inner peripheral surface of the endless belt 62 and the pressure pad 64 under a state in which a pressing force is applied between the pressure pad 64 and the fixing roll 61 at the nip portion N. (Friction resistance) is reduced.

  In such a configuration, the fixing roll 61 is connected to a drive motor (not shown) and rotates in the direction of the arrow C. Following this rotation, the endless belt 62 also rotates in the same direction as the fixing roll 61. The sheet P on which the toner image is electrostatically transferred in the secondary transfer unit 20 of the image forming apparatus shown in FIG. 1 is guided by the fixing inlet guide 56 and conveyed to the nip N of the fixing device 60. When the paper P passes through the nip portion N, the toner image on the paper P is fixed by the pressure acting on the nip portion N and the heat supplied from the fixing roll 61. In the fixing device 60, since the nip portion N can be configured widely by the concave pre-nip member 64a that substantially follows the outer peripheral surface of the fixing roll 61, stable fixing performance is ensured.

  In the vicinity of the downstream side of the nip portion N, the paper P peeled off from the fixing roll 61 by the peeling nip member 64b is separated from the fixing roll 61 and guided to a paper discharge path toward the discharge portion of the image forming apparatus. A peeling assisting member 70 is disposed. The peeling auxiliary member 70 is held by a baffle holder 72 in a state in which the peeling baffle 71 is close to the fixing roll 61 in a direction (counter direction) opposite to the rotation direction of the fixing roll 61.

  Next, each member constituting the fixing device 60 will be described.

  In the fixing roll 61, the core 611 is formed of a metal or alloy having high thermal conductivity such as iron, aluminum (for example, A-5052 material), SUS, copper, ceramics, fiber reinforced metal (FRM), or the like. It is composed of a cylindrical body having an outer diameter of 30 mm, a wall thickness of 1.8 mm, and a length of 360 mm.

  The heat resistant elastic body layer 612 is composed of an elastic body having high heat resistance, and it is particularly preferable to use an elastic body such as rubber or elastomer having a rubber hardness of about 15 ° to 45 ° (JIS-A). Specifically, silicone rubber, fluorine rubber or the like is used. Of these, silicone rubber is preferred from the viewpoints of low surface tension and excellent elasticity. Examples of such silicone rubber include RTV (room temperature vulcanization) silicone rubber, HTV (high temperature vulcanization) silicone rubber, and the like. Specifically, polydimethyl silicone rubber ( MQ), methyl vinyl silicone rubber (VMQ), methyl phenyl silicone rubber (PMQ), fluorosilicone rubber (FVMQ) and the like. In the fixing device 60, for example, an HTV silicone rubber having a rubber hardness of 35 ° (JIS-A) is coated on the core 611 with a thickness of 600 μm. The thickness of the heat resistant elastic body layer 612 is usually 3 mm or less, preferably in the range of 0.1 mm or more and 1.5 mm or less. There is no restriction | limiting in particular as a method of forming the heat resistant elastic body layer 612 on the surface of the core 611, For example, a well-known coating method, shaping | molding, etc. are employ | adopted.

  Since the release layer 613 is formed on the outer peripheral surface of the heat resistant elastic layer 612 of the fixing roll 61, the offset of the toner image is effectively prevented, and the fixing device 60 is operated in a stable state. The material of the release layer 613 is not particularly limited as long as it shows an appropriate release property for the toner image, and examples thereof include fluorine rubber, silicone rubber, and fluorine resin. Among these materials, a fluororesin is preferable. The fluororesin is not particularly limited. For example, polytetrafluoroethylene (PTFE); tetrafluoroethylene-perfluoromethyl vinyl ether copolymer (MFA), tetrafluoroethylene-perfluoroethyl vinyl ether copolymer (EFA), And tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) such as tetrafluoroethylene-perfluoropropyl vinyl ether copolymer. Further, tetrafluoroethylene-hexafluoropropylene copolymer (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), polychlorotrifluoride ethylene (PCTFE), polyvinyl fluoride (PVF) Etc. Among these, polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoromethyl vinyl ether copolymer (MFA), and tetrafluoroethylene-perfluoroethyl vinyl ether copolymer are particularly preferred from the standpoints of heat resistance and mechanical properties. A tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) such as a combination (EFA) is preferably used.

  The thickness of the release layer 613 is usually in the range of 10 μm to 50 μm, preferably 15 μm to 30 μm. There is no restriction | limiting in particular as a method of forming the release layer 613, For example, the coating method mentioned above etc. are mentioned. Moreover, the method etc. which coat | cover the tube formed by extrusion molding are mentioned. In the fixing device 60, for example, PFA having a thickness of 30 μm is coated.

  The endless belt 62 is a seamless belt whose original shape is formed in a cylindrical shape or the like so that defects due to the seam are not generated in the output image as much as possible. The endless belt 62 includes a base material layer and a release layer (surface layer) coated on the surface (outer peripheral surface) or both surfaces of the base material layer on the fixing roll 61 side. For the base material layer, one or a mixture selected from thermosetting polyimide resin, thermoplastic polyimide resin, polyamide resin, polyamideimide resin, polybenzimidazole resin and the like is preferable from the viewpoint of heat resistance, mechanical properties, and the like. Used for.

  As the release layer (surface layer) coated on the surface of the base material layer, for example, a fluororesin is used. Here, there is no restriction | limiting in particular as a fluororesin, For example, polytetrafluoroethylene (PTFE); tetrafluoroethylene-perfluoromethyl vinyl ether copolymer (MFA), tetrafluoroethylene-perfluoroethyl vinyl ether copolymer ( EFA), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers (PFA) such as tetrafluoroethylene-perfluoropropyl vinyl ether copolymers, and the like. Further, tetrafluoroethylene-hexafluoropropylene copolymer (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), polychlorotrifluoride ethylene (PCTFE), polyvinyl fluoride (PVF) Etc. Among these, polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoromethyl vinyl ether copolymer (MFA), and tetrafluoroethylene-perfluoroethyl vinyl ether copolymer are particularly preferred from the standpoints of heat resistance and mechanical properties. A tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) such as a combination (EFA) is preferably used. The thickness of the release layer (surface layer) is usually set in the range of about 5 μm to 100 μm, preferably about 10 μm to 30 μm.

  The pressure pad 64 is disposed inside (inner surface side) of the endless belt 62, and includes the pre-nip member 64a and the peeling nip member 64b as described above. It is supported by the holder 65 so as to be pressed with a load of 35 kgf. For example, an elastic body such as silicone rubber or fluororubber, a leaf spring, or the like is used for the prenip member 64 a, and the surface on the fixing roll 61 side is formed with a concave curved surface that substantially follows the outer peripheral surface of the fixing roll 61. In the fixing device 60, for example, silicone rubber having a width of 5 mm, a thickness of 5 mm, and a length of 320 mm is used. The hardness of the pressure pad 64 is not particularly limited, and usually the JIS-A hardness is in the range of 10 ° to 40 °.

  The peeling nip member 64b is formed of a heat-resistant resin such as polyphenylene sulfide (PPS), polyimide, polyester, polyamide, or a metal such as iron, aluminum, or SUS. As the shape of the peeling nip member 64b, the outer surface shape in the nip portion N is formed as a convex curved surface having a predetermined radius of curvature. In the fixing device 60, the endless belt 62 is covered with the fixing roll 61 by a pressure pad 64 at a winding angle of about 25 ° to form a nip portion N having a width of about 6 mm.

  As a sliding member, a sliding sheet 68 is provided to reduce the sliding resistance (friction resistance) between the inner peripheral surface of the endless belt 62 and the pressure pad 64, the friction coefficient is small, and the wear resistance and heat resistance are excellent. Suitable materials are suitable. The sliding sheet 68 is disposed over the nip portion and at least the downstream side in the recording medium passing direction from the nip portion, and has at least two portions having different thermal conductivity as shown in FIGS. However, the thermal conductivity of the nip portion non-corresponding portion other than the nip portion corresponding portion is higher than the thermal conductivity of the nip portion corresponding portion corresponding to the nip portion.

  In a fixing device such as a free belt nip method, when a recording medium such as a paper having a size smaller than the maximum paper passing width is allowed to pass, for example, an A4 size paper is placed vertically with a fixing device capable of passing an A3 size paper. When passing paper or B5 size paper, both ends in the width direction of the nip area are areas where the paper does not pass (this area is referred to as “non-paper passing area”), and the heat absorption by the paper does not occur. If this is not done, a significant temperature rise may occur in the non-sheet passing region. If the temperature rises significantly, problems such as deterioration of the endless belt due to heat and damage to peripheral members may occur. In addition, thermal degradation of the sliding member and thermal degradation of a lubricant such as silicone oil applied to the surface of the sliding member are also caused. These factors increase the sliding resistance of the endless belt, and the load torque of the fixing device. Increase, paper wrinkles due to paper conveyance failure, and image misalignment may occur. In addition, the pressure distribution in the nip changes from the normal usage due to the non-uniform thermal expansion of the pressure pad, which also causes problems such as paper wrinkles, paper curl, and non-uniform fixability. There is. Further, when a sheet of A3 size or the like having the maximum sheet passing width is passed in a state where the temperature of the non-sheet passing region is significantly increased, the sheet of A3 size or the like comes into contact with the non-sheet passing region whose temperature has been significantly increased, Overheating may cause hot offset of toner or increase the curl amount of the paper. In particular, as the size and speed of the image forming apparatus are increased, the temperature rise is more rapid in the fixing device having a low heat capacity, and the temperature difference between the sheet passing area and the non-sheet passing area may be increased. For example, when the temperature rise in the non-sheet passing area becomes too high, the sheet passing fixing operation is temporarily interrupted, and the temperature increase in the non-sheet passing area is lowered by idling the fixing roll and the pressure pad, Under conditions where the temperature rise in the non-sheet passing area is high, the temperature rise is prevented by widening the sheet passing interval or by reducing the sheet passing speed. Was inconvenient. Further, a measure to bring a temperature uniforming roll made of metal or the like into contact with the surface of the fixing roll or the like can be taken, but the apparatus is increased in size accordingly, and it is difficult to achieve both miniaturization.

  In the fixing device 60 according to the present embodiment, as shown in FIGS. 5 and 6, the heat of the nip portion non-corresponding portion other than the nip portion corresponding portion is compared with the thermal conductivity of the nip portion corresponding portion corresponding to the nip portion N. Due to the high conductivity, the temperature rise in the non-sheet passing region of the nip portion N is suppressed. As a result, the temperature difference between the paper-passing area and the non-paper-passing area is quickly eliminated, and malfunctions caused by temperature rise in the non-paper-passing area during continuous paper feeding, hot offset, paper wrinkles, paper curl, etc. There is a highly reliable, small and low-cost fixing device and image forming apparatus that can be used by users who demand high image quality without reducing productivity and increasing the size of the device. Provided.

  The thermal conductivity of the non-corresponding portion of the sliding sheet 68 may be, for example, 0.7 W / m · K or more, and preferably 1.0 W / m · K or more. If the thermal conductivity of the non-nip portion corresponding to the sliding sheet 68 is less than 0.7 W / m · K, the effect of suppressing the temperature rise in the non-sheet passing region of the nip portion N may be small.

  The thermal conductivity of the portion corresponding to the nip portion of the sliding sheet 68 may be, for example, 0.7 W / m · K or less. If the thermal conductivity of the nip portion corresponding portion of the sliding sheet 68 exceeds 0.7 W / m · K, the heat from the heating side escapes to the nip portion forming member side through the sliding member in the nip portion. In some cases, heat cannot be used in the fixing nip.

  The ratio of the thermal conductivity of the non-nip-corresponding portion to the thermal conductivity of the nip-corresponding portion is, for example, preferably 2 times or more, and more preferably 3 times or more. If the ratio of the thermal conductivity of the nip non-corresponding part to the thermal conductivity of the nip part corresponding part is less than twice, the effect of suppressing the temperature rise in the non-sheet passing region of the nip part N may be small.

  The sliding sheet 68 is disposed over the nip portion N and at least the downstream side in the paper P passing direction from the nip portion N. As shown in FIG. The thermal conductivity of the nip non-corresponding part (downstream side) other than is high. The sliding sheet 68 is disposed from the upstream side of the nip portion N to the nip portion N and the downstream side of the nip portion N, and as shown in FIG. It is preferable that the heat conductivity of the non-corresponding part (upstream side and downstream side) other than the corresponding part is high. Thereby, the temperature rise in the non-sheet passing area of the nip portion N is further suppressed, and the temperature difference between the sheet passing area and the non-sheet passing area is more quickly eliminated.

  It is preferable that the non-corresponding portion of the sliding sheet 68 has a thermal conductivity equal to or higher than the thermal conductivity of the base material layer of the endless belt 62 that is an endless belt member. Thereby, the temperature rise in the non-sheet passing region of the endless belt 62 in the nip portion N is suppressed.

  In the sliding sheet 68, as a method for increasing the thermal conductivity of the nip non-corresponding portion relative to the thermal conductivity of the nip corresponding portion, for example, the sliding sheet 68 includes at least a base layer and a surface layer. And a method of increasing the thermal conductivity of at least one layer other than the surface layer of the non-nip portion corresponding portion with respect to the thermal conductivity of at least one layer other than the surface layer of the nip portion corresponding portion. It is done. In this case, it is preferable that the surface layer of the nip portion corresponding portion and the surface layer of the nip portion non-corresponding portion are made of the same material and shape having high durability such as fluororesin. Increasing the thermal conductivity of the surface layer generally tends to decrease the durability, so controlling the thermal conductivity of the sliding sheet 68 with at least one of the layers other than the surface layer, for example, the base material layer, The heat conductivity of the base material layer in the non-nip-corresponding part is higher than the heat conductivity of the base material layer in the nip-corresponding part, and the surface layer has the same highly durable material and shape such as fluororesin. By using this material, the durability of the sliding sheet 68 can be increased.

  As a method for increasing the thermal conductivity of at least one layer other than the surface layer of the nip portion non-corresponding portion with respect to the thermal conductivity of at least one layer other than the surface layer of the nip portion corresponding portion, for example, the nip portion At least one layer other than the surface layer of the nip portion, for example, the base material layer is configured with respect to the thermal conductivity of at least one layer other than the surface layer of the corresponding portion, for example, the material constituting the base material layer. What is necessary is just to make the thermal conductivity of material high.

  Examples of the base material layer corresponding to the nip part include, for example, sintered (sintered) polytetrafluoroethylene (PTFE) resin sheets, glass fiber sheets, and fluororesin-impregnated glass fibers impregnated with modified polytetrafluoroethylene. A sheet etc. are mentioned.

  Examples of the base layer of the nip non-corresponding portion include a highly heat conductive graphite sheet, a thin film metal film such as Ni electroformed, a heat resistant resin (polyimide, fluorine resin, etc.) blended with a high heat conductive filler, and the like. .

  Examples of the surface layer include a PFA-modified polytetrafluoroethylene resin sheet and a skive film sheet (cutting sheet) containing a fluororesin.

  In addition, at least one layer other than the surface layer of the nip portion non-corresponding portion, for example, a base material layer contains a heat conductive filler, and the nip portion non-corresponding portion is mixed with the heat conductive filler. The amount may be increased. According to this method, the sliding member having a high thermal conductivity of the non-nip portion corresponding portion with respect to the nip portion corresponding portion is easily manufactured.

  Examples of the thermally conductive filler include graphite, boron nitride, and carbon nanofiller.

  The content of the heat conductive filler in the nip portion corresponding part is, for example, in the range of 0% by volume or more and 10% by volume or less, and the content of the heat conductive filler in the part not corresponding to the nip part is, for example, 10% by volume or more. The range may be 50% by volume or less.

  Specifically, as the sliding sheet 68, for example, a fluororesin-impregnated glass fiber sheet impregnated with PFA-modified polytetrafluoroethylene is disposed at the nip portion corresponding portion, and a graphite sheet is disposed at the nip portion non-corresponding portion. A laminated sheet in which a heat-resistant adhesive is applied to both surfaces to form an adhesive layer, and then a PFA-modified polytetrafluoroethylene resin sheet or a skive film sheet containing a fluororesin is heat-sealed and sandwiched In addition, a polytetrafluoroethylene sheet is disposed in the nip portion corresponding portion, and a sheet containing graphite as a heat conductive filler in polytetrafluoroethylene is disposed in the nip portion non-corresponding portion, and PFA-modified polytetrafluoroethylene resin A sheet or a skive film sheet containing a fluororesin is heat-sealed and sandwiched. Laminated sheet and the like it.

  The sliding sheet 68 may be configured separately from the pre-nip member 64a and the peeling nip member 64b, or may be configured integrally with the pre-nip member 64a and the peeling nip member 64b.

  In the fixing device according to the present embodiment, the sliding sheet 68 is rotatable in the circumferential direction of the endless belt 62, and when the paper P passes or when the nip pressurizing the nip portion N is performed, The nip portion corresponding portion is disposed in the nip portion N, and it is preferable to move the position so that the nip portion non-corresponding portion is disposed in the nip portion N when the sheet P is not passed through or other than the nip pressurization. As a result, the temperature of the nip portion N is quickly and substantially equalized after completion of fixing.

  As a lubricant application member, a lubricant application member 67 is disposed along the longitudinal direction of the fixing device 60. The lubricant application member 67 is disposed so as to contact the inner peripheral surface of the endless belt 62 and supplies an appropriate amount of lubricant. As a result, the lubricant is supplied to the sliding portion between the endless belt 62 and the sliding sheet 68, and the sliding resistance between the endless belt 62 and the pressure pad 64 via the sliding sheet 68 is reduced. Smooth rotation is aimed at.

  As the lubricant, one that has durability against long-term use under a fixing temperature environment and can maintain wettability with the inner peripheral surface of the endless belt 62 is suitable. For example, liquid oil such as silicone oil or fluorine oil, synthetic lubricating oil grease in which a solid substance and a liquid are mixed, or a combination of these is used. Silicone oils include dimethyl silicone oil, dimethyl silicone oil with organometallic salt addition, dimethyl silicone oil with hindered amine addition, dimethyl silicone oil with organometallic salt and hindered amine addition, methylphenyl silicone oil, amino-modified silicone oil, amino-modified silicone-added amino-modified silicone. Oil, hindered amine-added amino-modified silicone oil, carboxy-modified silicone oil, silanol-modified silicone oil, sulfonic acid-modified silicone oil, and the like may be used. Further, as the fluoro oil, perfluoropolyether oil or modified perfluoropolyether oil may be used. In the fixing device 60, for example, an amino-modified silicone oil having a viscosity of 300 cSt (KF8009: manufactured by Shin-Etsu Chemical Co., Ltd.) is used.

  Here, the configuration in which the endless belt member is a pressure belt on the side not in contact with the toner image, that is, the configuration in which the endless belt is used on the pressure side and the fixing roll is used on the heating side has been described as an example. A fixing belt on the side in contact with the toner image, in which the heat generating member does not exist on the inner surface side of the endless belt member in the nip portion, that is, the pressure roller is used on the pressure side, the endless belt is used on the heating side, and the inner surface of the endless belt The structure which does not have a heat source in the side may be sufficient. An example of a configuration in which an endless belt is used on the heating side and no heating source is present on the inner surface side of the endless belt is, for example, a fixing device shown in FIG.

  FIG. 3 is a side sectional view showing another example of the configuration of the fixing device 60 according to the present embodiment. The fixing device 60 includes a pressure roll 90 as an example of a rotatable rotating member, an endless belt 62 as an example of an endless belt member that can move while contacting the pressure roll 90, and an endless belt 62. A nip portion forming member that is disposed so as to face the pressure roll 90 and forms a nip portion N through which the paper P passes between the pressure roll 90 and the endless belt 62 by pressing the endless belt 62 against the pressure roll 90. The pressure pad 64 as an example, the sliding sheet 68 as an example of a sheet-like sliding member that reduces the frictional resistance between the pressure pad 64 and the endless belt 62, and the endless by a magnetic field generated by an alternating current A main part is constituted by a magnetic field generation unit 85 as an example of a heating member that generates heat from the belt 62.

  The endless belt 62 is rotatably supported by a pressure pad 64 disposed in the endless belt 62, a belt guide member 63, and edge guide members (not shown) disposed at both ends of the endless belt 62. Has been. And it arrange | positions so that it may press-contact with the fixing roll 61 in the nip part N, and it follows the fixing roll 61 and rotates to an arrow direction.

  For example, the pressure pad 64 is supported by a holder 65 made of metal or the like inside the endless belt 62. And it arrange | positions in the state pressed by the pressurization roll 90 via the endless belt 62, and forms the nip part N between the pressurization rolls 90.

  In order to reduce the sliding resistance between the inner peripheral surface of the endless belt 62 and the pressure pad 64, a low friction sliding member as an example of a rubbing member is provided between the inner peripheral surface of the endless belt 62 and the pressure pad 64. A moving sheet 68 is provided.

  The sliding sheet 68 is sandwiched between the pressure pad 64 and the inner peripheral surface of the endless belt 62 along the rotational direction of the endless belt 62, and the entire area of the nip portion N and at least the sheet P from the nip portion N. It arrange | positions over the downstream of the passage direction. The sliding sheet 68 slides between the inner peripheral surface of the endless belt 62 and the pressure pad 64 under a state in which a pressing force is applied between the pressure pad 64 and the pressure roll 90 in the nip portion N. The resistance (friction resistance) is reduced. The sliding sheet 68 has the same configuration as that described in the fixing device 60 in FIG.

  The pressure roll 90 includes, for example, a solid iron core (columnar core) 921, a heat-resistant elastic layer 922 such as silicone sponge that covers the outer peripheral surface of the core 921, and a heat-resistant resin such as PFA. And a release layer 923 with a coating or a heat-resistant rubber coating. In addition, as a manufacturing method of the pressure roll 90, for example, a fluororesin tube in which an adhesion primer is applied to the inner peripheral surface of a PFA tube (becomes a release layer 923) and a solid shaft (becomes a core 921) Is formed in a molding die, and after injecting liquid foamed silicone rubber between the fluororesin tube and the solid shaft, the silicone rubber is vulcanized and foamed by heat treatment to form the heat resistant elastic layer 922 Is mentioned.

  The pressure roll 90 is disposed so as to face the endless belt 62, rotates in the direction of arrow D, and drives the endless belt 62. Further, a nip portion N is formed by holding the endless belt 62 between the pressure roll 90 and the pressure pad 64, and the sheet P holding the unfixed toner image is passed through the nip portion N to pass heat and Pressure is applied to fix the unfixed toner image on the paper P.

  The magnetic field generation unit 85 has a cross-sectional shape that is curved along the shape of the endless belt 62, and is installed with a gap of, for example, about 0.5 mm to 2 mm from the outer peripheral surface of the endless belt 62. The magnetic field generation unit 85 includes an excitation coil 851 that generates a magnetic field, a coil support member 852 that holds the excitation coil 851, and an excitation circuit 853 that supplies current to the excitation coil 851.

As the exciting coil 851, for example, litz wires obtained by bundling about 16 to 20 copper wires having a diameter of 0.5 mm that are insulated from each other are wound in a closed ring shape such as an oval shape, an elliptical shape, or a rectangular shape. What was formed is used. By applying an alternating current having a predetermined frequency to the exciting coil 851 by the exciting circuit 853, an alternating magnetic field H is generated around the exciting coil 851. When the AC magnetic field H crosses the metal layer of the endless belt 62, an eddy current I is generated so as to generate a magnetic field that prevents the change of the AC magnetic field H by electromagnetic induction. The frequency of the alternating current applied to the exciting coil 851 is set, for example, from 10 kHz to 50 kHz. When the eddy current I flows through the metal layer of the endless belt 62, Joule heat is generated by electric power W (W = I ² R) proportional to the resistance value R of the metal layer, and the endless belt 62 is heated.

  The coil support member 852 is made of a nonmagnetic material having heat resistance, for example. Examples of such a nonmagnetic material include heat resistant resins such as heat resistant glass, polycarbonate, polyethersulfone, and PPS, or heat resistant resins obtained by mixing glass fibers with these.

  In the present embodiment, the electromagnetic induction heating type fixing device 60 including the magnetic field generation unit 85 has been described as an example of a heating member that heats the endless belt 62. However, as the heating member, a radiation lamp heating element and a resistance heating element are used. May be adopted.

  Examples of the radiant lamp heating element include a halogen lamp. Examples of the resistance heating element include iron-chromium-aluminum, nickel-chromium, platinum, molybdenum, tantalum, tungsten, silicon carbide, molybdenum-silicide, and carbon.

  In the fixing device 60, the endless belt 62 is driven and rotated by the rotation of the pressure roll 90 in the arrow D direction, and is exposed to the magnetic field generated by the excitation coil 851. At this time, an eddy current is generated in the metal layer in the endless belt 62, and the outer peripheral surface of the endless belt 62 is heated to a temperature at which fixing is possible. The endless belt 62 heated in this way moves to the nip N with the pressure roll 90. The sheet P on which the unfixed toner image is provided is carried into the fixing device 60 via the fixing inlet guide 56 by the conveying means. When the paper P passes through the nip N between the endless belt 62 and the pressure roll 90, the unfixed toner image is heated by the endless belt 62 and fixed on the surface of the paper P. Thereafter, the paper P on which the image is formed is transported by the transport unit and discharged from the fixing device 60. In addition, the endless belt 62 having finished the fixing process at the nip portion N and whose surface temperature on the outer peripheral surface has decreased rotates in the direction of the excitation coil 851 and is heated again in preparation for the next fixing process.

  In the vicinity of the downstream side of the nip portion N, there is a peeling assisting member 70 for separating the paper P peeled from the endless belt 62 from the endless belt 62 and guiding it to the paper discharge path toward the discharge portion of the image forming apparatus. Has been placed. The peeling assisting member 70 is held by a baffle holder 72 in a state where the peeling baffle 71 is close to the endless belt 62 in a direction (counter direction) opposite to the rotation direction of the endless belt 62.

  Hereinafter, although an example and a comparative example are given and the present invention is explained more concretely in detail, the present invention is not limited to the following examples.

  The fixing device shown in FIG. 2 was used for evaluation. The specifications of each component of the fixing device are as follows.

  The fixing roll has a heat resistant elasticity of silicone HTV rubber (rubber hardness 33 degrees: JIS-A) having a thickness of 600 μm on the outer peripheral surface of a cylindrical iron core having an outer diameter of 26 mm, a wall thickness of 1.8 mm, and a length of 360 mm. A body layer is provided, and a tube of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) having a thickness of 30 μm is coated as a release layer on the surface of the heat-resistant elastic layer, and the surface is close to a mirror surface state. The finished one was used. Inside the core of the fixing roll, a halogen lamp (800w) is disposed as a heating source. The surface temperature of the fixing roll was controlled by a temperature sensor and a temperature controller, which are temperature sensitive elements arranged in contact with the surface of the heated fixing roll.

  The endless belt uses a thermosetting polyimide resin having a peripheral length of 94 mm, a thickness of 80 μm, and a width of 344 mm as a base layer (thermal conductivity 0.3 W / m · K), and tetrafluoroethylene is formed on the outer peripheral surface of the base layer. A perfluoroalkyl vinyl ether copolymer (PFA) coated to a thickness of 30 μm and having a release layer was used.

  As the pressure pad for pressing the endless belt, one comprising silicone rubber having a width of 6 mm, a thickness of 5 mm and a length of 340 mm was used. As the sliding sheet, those described in the following examples and comparative examples were used, and on the surface of the sliding sheet, an amino-modified silicone oil having a viscosity of 300 cSt as a lubricant was previously prepared (manufactured by Shin-Etsu Chemical Co., Ltd .: KF8009A). 0.5 cc was applied. The size of the sliding sheet was 340 mm in width and 60 mm in length, and the pressure pad pressed the fixing roll with a load of 30 kg with a compression coil spring through an endless belt.

  The winding angle of the endless belt around the fixing roll was about 27 °, and the width of the nip portion N was about 7 mm. The driving force transmitted from the motor to the fixing roll rotated the fixing roll and the endless belt at a speed of 194 mm / sec.

<Example 1>
As a sliding sheet, it has a form as shown in FIG. 6, and a nip portion corresponding portion (330 mm × 9 mm) has a fluororesin impregnated glass cloth sheet (manufactured by Chuko Kasei Kogyo Co., Ltd.) in which a glass fiber sheet is impregnated with modified PTFE: FGF300-4, thickness 100μm, thermal conductivity 0.23W / m · K), high thermal conductivity graphite on the upstream side (330mm x 15mm) and downstream side (330mm x 15mm) of the non-corresponding nip part A sheet (PGS graphite sheet, Panasonic, thickness 100 μm, thermal conductivity 500 W / m · K) is placed, and heat-resistant adhesive fluororesin (Asahi Glass Co., Ltd., Fluon-LM-ETFE-AH) is applied on both sides. After that, a PFA-modified PTFE non-porous sheet having a thickness of 25 μm was heat-sealed (laminated) on both sides thereof, and a sheet having a thickness of 150 μm was laminated. It was used to prepare.

  A lubricant application member was arranged over the longitudinal direction of the fixing device, and 1.5 mL of 300 cSt amine-modified silicone oil was applied as a lubricant. Next, the fixing device in which the sliding sheet was fixed to the pressure pad in this manner was incorporated into an image forming apparatus (manufactured by Fuji Xerox Co., Ltd .: Color MFP DCCIV3305). The surface temperature of the fixing roll is controlled to 165 ° C., and A4 paper with a basis weight of 90 gsm is printed at a speed of 35 sheets / minute, and 200 sheets are continuously printed so that the short side of the A4 paper is almost perpendicular to the paper transport direction. Subsequently, 30 sheets of A3 size paper having a basis weight of 90 gsm were continuously run.

  The temperature of the non-passage area of the fixing roll after 200 sheets of A4 paper is continuously printed and fixed is a maximum temperature difference of 25 ° C. from the paper passage area. During that time, no paper wrinkle or fixing failure has occurred. The curl amount was 10 mm or less, and even when 30 sheets of A3 paper were continuously run, no hot offset was observed in the A3 paper outside the A4 size.

  Thereafter, a total of 100,000 sheets of A4 paper were passed under these conditions, but there was no peeling between the layers of the rolls and belts, damage to the bearings of the rolls and peripheral members, and paper wrinkles and images due to increased belt sliding torque. There was no deviation.

<Example 2>
As a sliding sheet, a PTFE sheet (heat conductivity of 1.0 W / m) having a form as shown in FIG. 6 and containing 30% by volume of graphite (UF-G, manufactured by Showa Denko) as a heat conductive filler is used. -K) is arranged on the upstream side (330 mm x 15 mm) and downstream side (330 mm x 15 mm) of the nip non-corresponding part, and the nip corresponding part does not contain a heat conductive filler (graphite) and has a thickness of 100 µm. (Thermal conductivity 0.25 W / m · K) is disposed, and both surfaces thereof are heat-bonded with a PFA-modified PTFE sheet having a thickness of 25 μm to produce a sheet having a thickness of 150 μm. It was installed and evaluated.

  The surface temperature of the fixing roll is controlled to 165 ° C., and A4 paper with a basis weight of 90 gsm is printed at a speed of 35 sheets / minute, and 200 sheets are continuously printed so that the short side of the A4 paper is almost perpendicular to the paper transport direction. Subsequently, 30 sheets of A3 size paper having a basis weight of 90 gsm were continuously run.

  The temperature of the non-passage area of the fixing roll after 200 sheets of A4 paper has been printed and fixed continuously has a maximum temperature difference of 35 ° C. from the paper passage area. During that time, no paper wrinkle or fixing failure has occurred. The curl amount was 15 mm or less, and even when 30 sheets of A3 paper were continuously run, no hot offset was observed in the A3 paper outside the A4 size.

  Thereafter, a total of 100,000 sheets of A4 paper were passed under these conditions, but there was no peeling between the layers of the rolls and belts, damage to the bearings of the rolls and peripheral members, and paper wrinkles and images due to increased belt sliding torque. There was no deviation.

<Example 3>
As a sliding sheet, a graphite sheet with a thickness of 100 μm (thermal conductivity: 500 W / m · K) is arranged on the downstream side (330 mm × 15 mm) of the nip portion non-corresponding portion. Is a fluororesin impregnated glass cloth sheet (manufactured by Chuko Kasei Kogyo Co., Ltd., FGF300-4 (thermal conductivity 0.23 W / m · K)) impregnated with modified PTFE into a glass fiber sheet having a thickness of 100 μm, and these Both sides of the film were heat-pressed with a PFA-modified PTFE sheet having a thickness of 25 μm to prepare a sheet having a thickness of 150 μm, and mounted on an image forming apparatus having the same configuration as in Example 1 for evaluation.

  The surface temperature of the fixing roll is controlled to 165 ° C., and A4 paper with a basis weight of 90 gsm is printed at a speed of 35 sheets / minute, and 200 sheets are continuously printed so that the short side of the A4 paper is almost perpendicular to the paper transport direction. Subsequently, 30 sheets of A3 size paper having a basis weight of 90 gsm were continuously run.

  The temperature of the non-passage area of the fixing roll after printing and fixing 200 sheets of A4 paper continuously is a maximum temperature difference of 32 ° C. from the paper passage area. During that time, no paper wrinkle or fixing failure has occurred. The curl amount was 15 mm or less, and even when 30 sheets of A3 paper were continuously run, no hot offset was observed in the A3 paper outside the A4 size.

  Thereafter, a total of 100,000 sheets of A4 paper were passed under these conditions, but there was no peeling between the layers of the rolls and belts, damage to the bearings of the rolls and peripheral members, and paper wrinkles and images due to increased belt sliding torque. There was no deviation.

<Comparative Example 1>
As a sliding sheet, a non-porous sheet of PFA-modified PTFE is heat-sealed on both surfaces of a fluororesin-impregnated glass fiber sheet (thickness 100 μm, thermal conductivity 0.23 W / m · K) from the upstream side to the downstream side of the nip part ( And a sheet having a thickness of 140 μm (thermal conductivity 0.21 W / m · K) was used.

  The surface temperature of the fixing roll is controlled to 165 ° C., and A4 paper with a basis weight of 90 gsm is printed at a speed of 35 sheets / minute, and 200 sheets are continuously printed so that the short side of the A4 paper is almost perpendicular to the paper transport direction. Subsequently, 30 sheets of A3 size paper having a basis weight of 90 gsm were continuously run.

  The temperature of the non-passing area of the fixing roll after 200 sheets of A4 paper is continuously printed and fixed is a maximum temperature difference of 47 ° C. from the passing area. During that time, paper wrinkles are generated by 5%, and the curl amount of the paper is also When 30 sheets of A3 paper was continuously run at the maximum of 30 mm, hot offset occurred on the A3 paper portion outside the A4 size over the first 5 sheets of the 30 sheets.

  After that, when A4 paper was passed under this condition, peeling occurred between the metal core of the fixing roll and the heat-resistant elastic body layer after passing 30,000 sheets, and the bearings of the rolls of the fixing device The belt sliding torque increased due to damage and thermal deterioration of the lubricant, resulting in paper wrinkles and image misalignment.

<Comparative Example 2>
As a sliding sheet, a PTFE sheet (thermal conductivity 0.25 W / m · K) having a thickness of 100 μm that does not contain a thermally conductive filler (graphite) is provided on the upstream side (330 mm × 15 mm) and the downstream side of the non-corresponding portion (330 mm × 15 mm). The PTFE sheet (heat conductivity: 1.0 W / m) containing 30% by volume of graphite (UF-G, manufactured by Showa Denko) as a heat conductive filler having a thickness of 100 μm is disposed in the nip-corresponding portion. K) was placed, and both sides thereof were heat-pressed with a PFA-modified PTFE sheet having a thickness of 25 μm to prepare a sheet having a thickness of 150 μm, and mounted on an image forming apparatus having the same configuration as in Example 1 for evaluation.

  The surface temperature of the fixing roll is controlled to 165 ° C., and A4 paper with a basis weight of 90 gsm is printed at a speed of 35 sheets / minute, and 200 sheets are continuously printed so that the short side of the A4 paper is almost perpendicular to the paper transport direction. Subsequently, 30 sheets of A3 size paper having a basis weight of 90 gsm were continuously run.

  The temperature of the non-passage area of the fixing roll after printing and fixing 200 sheets of A4 paper continuously is a maximum temperature difference of 43 ° C. from the paper passing area. During that time, paper wrinkles and fixing defects occur 3%. The curl amount was 25 mm, and when 30 sheets of A3 paper were continuously run, three hot offsets occurred on the A3 paper outside the A4 size.

  After that, a total of 100,000 sheets of A4 paper was passed under these conditions. As a result, peeling between layers of the roll and belt, damage to the bearings and peripheral members of the roll, and paper wrinkles and image misalignment due to an increase in belt sliding torque. Did not occur.

  Thus, by using the sliding sheet of an Example, the temperature rise in the non-sheet passing area | region of a nip part was suppressed compared with the comparative example.

<Example 5>
In the fixing device of FIG. 2, when the sheet is passed through the sliding sheet 68 or when the nip is pressed to press the nip portion N, the nip portion corresponding portion is arranged in the nip portion N, and other than the passage of the paper or the nip portion. In cases other than pressurization, the position was moved so that the non-corresponding portion of the nip was disposed in the nip N.

  With this configuration, the temperature of the nip portion N is quickly and substantially uniformed after completion of fixing.

  1Y, 1M, 1C, 1K Image forming unit, 10 Primary transfer portion, 11 Photosensitive drum, 12 Charging device, 13 Exposure device, 14 Developing device, 15 Intermediate transfer belt, 16 Primary transfer roll, 17 Drum cleaner, 20 Secondary Transfer section, 22 Secondary transfer roll, 25 Backup roll, 26 Feed roll, 31 Drive roll, 32 Support roll, 33 Tension roll, 34 Cleaning backup roll, 35 Intermediate transfer belt cleaner, 40 Control section, 42 Reference sensor (home position) Sensor), 43 image density sensor, 50 paper tray, 51 pick-up roll, 52 transport roll, 53 transport chute, 55 transport belt, 56 fixing inlet guide, 60 fixing device, 61, 110 fixing roll, 111, 121, 611, 921 core Cylindrical core bar), 112, 122, 612, 922 heat resistant elastic layer, 113, 123, 613, 923 release layer, 114 heating source, 62 endless belt, 63 belt guide member, 631 sliding sheet fixing member, 64 pressure pad, 64a pre-nip member, 64b peeling nip member, 65 holder, 66 halogen heater, 67 lubricant application member, 68 sliding sheet, 69 temperature sensor, 70 peeling auxiliary member, 71 peeling baffle, 72 baffle holder, 80 edge Guide member, 85 magnetic field generation unit, 851 excitation coil, 852 coil support member, 853 excitation circuit, 90 pressure roll, P paper (recording medium).

Claims (11)

A rotatable rotating member, an endless belt member movable while being in contact with the rotating member, and an endless belt member disposed so as to face the rotating member via the endless belt member, the endless belt member being pressed against the rotating member A nip portion forming member that forms a nip portion through which a recording medium passes between the rotating member and the endless belt member, and a friction resistance between the nip portion forming member and the endless belt member is reduced. A sheet-like sliding member,
The sliding member is disposed over the nip portion and at least the downstream side in the recording medium passing direction from the nip portion, and corresponds to the nip portion with respect to the thermal conductivity of the nip portion corresponding portion corresponding to the nip portion. A fixing device for fixing a toner image held on a recording medium, characterized in that the thermal conductivity of the non-nip portion corresponding portion other than the portion is high.   The fixing device according to claim 1, wherein the sliding member is disposed from the upstream side of the nip portion to the nip portion and the downstream side of the nip portion.   The fixing device according to claim 1, wherein the endless belt member is a pressure belt on a side not in contact with the toner image.   The fixing according to claim 1, wherein the endless belt member is a fixing belt on a side in contact with the toner image, and no heat generating member is present on an inner surface side of the endless belt member of the nip portion. apparatus.   The nip portion non-corresponding portion of the sliding member has a thermal conductivity equal to or higher than the thermal conductivity of the base material layer of the endless belt member, according to any one of claims 1 to 4. Fixing device.   The sliding member is composed of a multilayer including at least a base material layer and a surface layer, and the nip portion non-corresponding portion with respect to thermal conductivity of at least one layer other than the surface layer of the nip portion corresponding portion. The fixing device according to claim 1, wherein the thermal conductivity of at least one layer other than the surface layer is high.   The thermal conductivity of the material constituting at least one layer other than the surface layer of the nip portion non-corresponding portion is different from that of the material constituting the at least one layer other than the surface layer of the nip portion corresponding portion. The fixing device according to claim 6, wherein the fixing device is high.   At least one layer other than the surface layer of the nip portion non-corresponding portion contains a heat conductive filler, and the amount of the heat conductive filler in the nip portion non-corresponding portion is higher than the nip portion corresponding portion. The fixing device according to claim 6, wherein:   The sliding member is rotatable in the circumferential direction of the endless belt, and the nip portion corresponding portion is disposed in the nip portion when the recording medium passes or when nip pressure is applied, The position of the non-nip portion-corresponding portion is moved so that the non-nip portion-corresponding portion is disposed in the nip portion when the recording medium is not passed or the nip is not pressed. The fixing device according to Item. A rotatable rotating member, an endless belt member movable while being in contact with the rotating member, and an endless belt member disposed so as to face the rotating member via the endless belt member, the endless belt member being pressed against the rotating member A fixing device for fixing a toner image held on a recording medium, comprising: a nip portion forming member that forms a nip portion through which the recording medium passes between the rotating member and the endless belt member. Provided,
Reducing the rubbing resistance between the nip forming member and the endless belt member;
A sliding member characterized in that the thermal conductivity of a non-nip portion corresponding portion other than the nip portion corresponding portion is higher than the thermal conductivity of the nip portion corresponding portion corresponding to the nip portion. An image carrier, a latent image forming unit for forming a latent image on the surface of the image carrier, a developing unit for developing the latent image using a developer for developing an electrostatic image to form a toner image, and the toner Transfer means for transferring an image to a recording medium, and fixing means for fixing the toner image to the recording medium,
The image forming apparatus according to claim 1, wherein the fixing unit is the fixing device according to claim 1.

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