JP6693211B2 - Fixing device and image forming device - Google Patents

Description

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

  In an image forming apparatus such as a copying machine or a printer using an electrophotographic method, an unfixed toner image formed on a recording medium such as recording paper is fixed by a fixing device to form an image. As a fixing device used in such an image forming apparatus, there is a roll-roll system including a fixing roll for heating as a fixing member and a pressure roll as a pressure member.

  Further, there has been proposed a fixing device that uses an endless belt as a fixing member instead of a fixing roll and a pressure roll. The fixing belt may be of a type stretched by a plurality of support rolls, or of a type having a nip portion forming member inside and being rotationally driven by being pressed against a pressure roll in a non-stretched state. The fixing belt has a thin heat-resistant resin or the like as a base layer and has a smaller heat capacity than the roll-shaped member, so that warming-up is performed in a short time. Further, the shape of the nip portion can be freely formed by using the fixing belt.

  In the latter type of fixing device, a sliding sheet member interposed between the fixing belt and the pressing pad is provided in order to reduce sliding resistance between the fixing belt and the pressing pad that is a nip portion forming member, A lubricant is supplied to the sliding portion between the fixing belt and the sliding sheet member.

  For example, in Patent Document 1, an endless fixing belt in which a central portion in the width direction is in a tensionless state in a circumferential direction and is supported so as to be capable of circling, a heating device for heating the fixing belt, and a fixing belt Of the pressure roller, which is in contact with the outer peripheral surface of the fixing roller and is rotatably supported around the axis, and the pressure roller, which is in contact with the inner peripheral surface of the fixing belt. An undetermined state on the recording medium that has a pressing member to act and a support member that is inserted inside the fixing belt and supports the pressing member, and that passes through a fixing nip portion formed between the fixing belt and the pressure roll. A fixing device that pressurizes and heats a deposited toner image to form a fixed image is described. A glass fiber sheet impregnated with a fluororesin having good slidability and high wear resistance between a pressing pad and a fixing belt. The silicone oil on the inner surface of the fixing belt. It is described that applying a release agent and the like as a lubricant.

  In such a fixing device, in order to shorten the start-up time of the fixing device, the pressure between the fixing member and the pressing member is separated by separating the fixing member and the pressing member during non-image formation such as when the device is started up. In some cases, the pressure may be lower than that during formation, and during image formation, the two may be pressed against each other before the recording medium is conveyed.

  However, the contact between the fixing member and the pressure pad is weak during non-image formation such as when the fixing device is started up (warming up). Therefore, especially when a low viscosity type (oil etc.) is used as the lubricant, Is hard to stay in the sliding parts such as the nip and is dispersed on the inner surface of the fixing member. Only a small amount of the total lubricant amount passes through the sliding parts such as the nip when the two are pressed together. During this period, the sliding load becomes high, which may lead to quality troubles such as deterioration of paper transportability, and shortening of the life of the fixing device due to abrasion of the sliding member.

JP, 2006-047768, A

  An object of the present invention is, in a fixing device that performs an operation of lowering the pressure between a pressure member and a belt member during non-image formation than during image formation, a fixing device in which abrasion of a sliding sheet member is suppressed, and An object is to provide an image forming apparatus including the fixing device.

According to a first aspect of the present invention, a rotatable pressure member, a belt member movable while being in contact with the pressure member, and a belt member arranged to face the pressure member via the belt member, A nip portion forming member that presses a belt member against the pressure member to form a nip portion through which the recording medium passes between the pressure member and the belt member, and the nip portion forming member from the upstream side in the passage direction of the recording medium. A sliding sheet member arranged between the nip portion forming member and the belt member, a lubricant supply member for supplying a lubricant to a sliding portion between the belt member and the sliding sheet member, and the nip portion A support member for supporting the forming member and an elastic member provided between the nip portion forming member and the support member are provided, and the pressure between the pressure member and the belt member is imaged during non-image formation. Below the formation Can der be kept is, the pressing member during non-image formation, relative to the position of the pressing member during the image formation, the fixing device state Ru der the passage inclined toward the upstream side of the recording medium is there.

According to a second aspect of the present invention, an image carrier, a latent image forming unit that forms a latent image on the surface of the image carrier, a developing unit that develops the latent image with toner to form a toner image, a transfer unit that transfers the toner image onto a recording medium to fix the toner image on the recording medium, an image forming apparatus and a fixing device according to claim 1.

  According to the first aspect of the invention, in the fixing device that performs the operation of lowering the pressure between the fixing member and the pressure member during non-image formation as compared with that during image formation, the elasticity is provided between the nip portion formation member and the support member. Provided is a fixing device in which abrasion of the sliding sheet member is suppressed as compared with the case where the member is not provided.

According to the first aspect of the invention, the sliding sheet is compared with the case where the pressing member at the time of non-image formation is not inclined to the upstream side in the passage direction of the recording medium with respect to the position of the pressing member at the time of image formation. Provided is a fixing device in which abrasion of members is suppressed.

According to the second aspect of the present invention, in the image forming apparatus including the fixing device that performs the operation of lowering the pressure of the fixing member and the pressure member during non-image formation than that during image formation, the nip portion forming member and the supporting member are provided. There is provided an image forming apparatus in which abrasion of a sliding sheet member is suppressed as compared with a case where an elastic member is not provided between the sheet and the sheet.

1 is a schematic configuration diagram showing an example of a fixing device according to an exemplary embodiment of the present invention. FIG. 6 is a schematic diagram showing a state in which a lubricant is accumulated on the entrance side of the nip portion N (the insertion side of the recording medium P) when an elastic member is provided in the fixing device according to the embodiment of the present invention. FIG. 6 is a schematic diagram showing a state in which a lubricant is accumulated at an inlet side of a nip portion N (inserting side of a recording medium P) when an elastic member having another shape is provided in the fixing device according to the embodiment of the present invention. 1 is a schematic configuration diagram showing an example of an image forming apparatus according to an embodiment of the present 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.

<Fixing device and pressure member>
An example of the fixing device according to the exemplary embodiment of the present invention is schematically shown in FIG. 1, and its configuration will be described. The fixing device according to the present exemplary embodiment will be described by taking a fixing device that employs an electromagnetic induction heating method as an example, but the present invention is not limited to this.

  As shown in FIG. 1, the fixing device 60 according to the present exemplary embodiment includes a pressure roll 62 that is a rotatable pressure member, and a fixing belt 61 that is a belt member that is movable while being in contact with the pressure roll 62. , A nip through which the recording medium P passes between the pressure roll 62 and the fixing belt 61 by being arranged so as to face the pressure roll 62 with the fixing belt 61 interposed therebetween. Portion (pressurizing portion) N, which is a nip portion forming member, and a sliding sheet member 68 disposed between the pressing pad 64 and the fixing belt 61 from the upstream side in the passage direction of the recording medium P. A lubricant supply member 67 that supplies a lubricant to the sliding portion between the fixing belt 61 and the sliding sheet member 68, a holder 65 that is a support member that supports the pressing pad 64, the pressing pad 64 and the holder 6. And a resilient member 66 provided between the.

  The pressure roll 62 is arranged so as to face the fixing belt 61, is rotated at a process speed of, for example, 140 mm / sec in the direction of arrow D, and drives the fixing belt 61. The fixing belt 61 is held in a state of being sandwiched by the pressure roll 62 and the pressing pad 64, and a nip portion N is formed between the fixing belt 61 and the pressure roll 62, and the unfixed toner is formed in the nip portion N. The recording medium P holding the image is passed, heat and pressure are applied, and the unfixed toner image is fixed on the recording medium P.

  The fixing belt 61, which is a film tubular body, is rotatably supported by a pressing pad 64, a belt guide member 63, and edge guide members (not shown) arranged at both ends of the fixing belt 61. Then, it is pressed against the pressure roll 62 at the nip portion N, and driven by the pressure roll 62 to rotate in the arrow direction.

  The above-mentioned film tubular body may be made of resin or metal. Further, when the film tubular body is used as a fixing belt, for example, a single-layer resin film or a single-layer metal film is used, but the resin layer and the metal layer may each be a multi-layer. The resin layer and the metal layer may be combined, for example, by using the film-forming film as a base material and providing an elastic layer or a release layer made of resin thereon.

  The belt guide member 63 is attached to a holder 65 arranged inside the fixing belt 61. The belt guide member 63 is formed of a plurality of ribs (not shown) directed in the rotation direction of the fixing belt 61, and reduces the contact area with the inner peripheral surface of the fixing belt 61. Further, the belt guide member 63 is formed of a heat resistant resin such as PFA (perfluoroalkyl vinyl ether copolymer) or PPS (polyphenylene sulfide) having a low friction coefficient and a low thermal conductivity. As a result, the sliding resistance between the belt guide member 63 and the inner peripheral surface of the fixing belt 61 is reduced, and heat dissipation is reduced.

  The pressing pad 64 is pressed by the pressure roller 62 via the fixing belt 61 to form the nip portion N. The pressing pad 64, which is a pressing member, is supported by a holder 65, which is a supporting member, so as to press the pressure roll 62 with a load of, for example, 35 kgf by a spring, an elastic body, or the like. The pressing pad 64 includes an elastic body such as silicone rubber or fluororubber. The pressing pad 64 has a concave portion and a convex portion formed on the pressure roll 62 side. As a result, when the fixing belt 61 separates from the surface of the pressing pad 64 on the pressure roll 62 side, a rapid change in curvature occurs, and the recording medium P after fixing is easily separated from the fixing belt 61.

  A lubricant supply member 67 is arranged in the holder 65, which is a support member, in the longitudinal direction of the fixing device 60. The lubricant supply member 67 is in contact with the inner peripheral surface of the fixing belt 61, and the lubricant is supplied to the sliding portion between the fixing belt 61 and the sliding sheet member 68. Examples of the lubricant include liquid oils such as silicone oil and fluorine oil, grease obtained by mixing a solid substance and a liquid, and combinations thereof.

  The fixing device 60 can lower the pressure between the pressure roll 62 and the fixing belt 61 during non-image formation as compared with that during image formation. For example, the pressure roll 62 and the fixing belt 61 may be separated so as to be in a non-contact state at the time of non-image formation, and the pressure between the pressure roll 62 and the fixing belt 61 may be made lower than that at the time of image formation. “Non-image forming” refers to a time when the image forming apparatus is not performing an image forming operation, for example, a time when the image forming apparatus is stopped, a time when the fixing device is started (warming up), and the like. “At the time of image formation” refers to a time when the image forming apparatus is performing an image forming operation.

  As described above, at the time of non-image formation such as startup (warming up) of the fixing device, the contact between the fixing belt 61, which is a fixing member, and the pressing pad 64 is weak. When the lubricant is used, the lubricant is hard to stay in the sliding portion between the fixing belt 61 and the pressing pad 64, such as the nip portion N, and is dispersed on the inner surface of the fixing belt 61, so that the fixing belt 61 and the pressing pad 64 are pressed against each other. At this time, only a small amount of the total amount of the lubricant passes through the sliding portion such as the nip portion N, so that the sliding load becomes high for a while after the pressure contact, and the quality trouble due to the deterioration of the sheet transportability and the sliding. The life of the fixing device may be shortened due to the abrasion of the moving member.

  In the present embodiment, in the fixing device 60 that performs the operation of lowering the pressure between the pressure roll 62 and the fixing belt 61 during non-image formation as compared with that during image formation, a holder 65 that is a support member inside the fixing belt 61 By providing the elastic member 66 between the pressing pad 64 and the pressing pad 64, abrasion of the sliding sheet member 68 is suppressed as compared with the case where the elastic member is not provided between the holder 65 and the pressing pad 64. This is because the pressure between the fixing belt 61 and the pressure roller 62 is lower than that during image formation (that is, the fixing belt 61 and the pressure roller 62 are separated from each other), as shown in FIG. During non-image formation, the pressing pad 64 is appropriately pressed against the fixing belt 61 by the elastic member 66, and the lubricant 69 collects on the inlet side of the nip portion N (insert side of the recording medium P). Since the amount of the lubricant that can pass through the nip portion N increases when the pressure becomes, the sliding load after the pressure contact is reduced, the transportability of the recording medium P is stabilized, and the abrasion amount of the sliding sheet member 68 is increased. It is thought that this will lead to reduction of quality troubles and longer life of the fixing device.

  Examples of the material forming the elastic member 66 include silicone rubber and fluororubber.

  The thickness of the elastic member 66 is, for example, in the range of 0.1 mm or more and 6 mm or less, preferably in the range of 2 mm or more and 4 mm or less. If the thickness of the elastic member 66 is less than 0.1 mm, it may be difficult to obtain the effect of suppressing the wear of the sliding sheet member, and if it exceeds 6 mm, the pressure at the nip portion may become unstable.

  The elastic modulus of the elastic member 66 is, for example, in the range of 0.1 MPa or more and 10 MPa or less, and preferably in the range of 0.4 MPa or more and 2 MPa or less. If the elastic modulus of the elastic member 66 is less than 0.1 MPa or exceeds 10 MPa, it may be difficult to obtain the effect of suppressing the wear of the sliding sheet member.

  As shown in FIG. 3, the pressure pad 64 at the time of non-image formation (upper diagram of FIG. 3) is located upstream of the position of the pressure pad 64 at the time of image formation (lower diagram of FIG. 3) in the passage direction of the recording medium P. It is preferable that it is inclined to the side (the side where the recording medium P is inserted into the nip portion N). With this configuration, the lubricant 69 is more likely to be accumulated at the inlet side of the nip portion N (the insertion side of the recording medium P) than in the case of FIG. 2, so that the pressure at the time of image formation (lower figure in FIG. 3) is reached. Since the amount of the lubricant that can pass through the nip portion N becomes larger, the sliding load after the pressure contact is further reduced. For example, the shape of the elastic member 66 may be, for example, not a normal rectangular parallelepiped as shown in FIG. 2 but a quadrangular pyramid trapezoid as shown in FIG. For example, when an elastic member 66 having a quadrangular pyramid trapezoid or a quadrangular pyramid shape as shown in FIG. 3 (upper diagram) is used, the elastic member 66 is compressed and has a substantially long length during image formation (lower diagram in FIG. 3). It becomes a rectangular shape. As a method of inclining the pressing pad 64 at the time of non-image formation to the upstream side in the passage direction of the recording medium P with respect to the position of the pressing pad 64 at the time of image formation, the elastic member 66 remains rectangular. As the thickness of the pressing pad 64, there may be mentioned a method of making the thickness of the nip portion N on the inlet side thicker than the thickness of the nip portion N on the outlet side.

  The peeling auxiliary member 70 disposed near the downstream side of the nip portion N is held by the baffle holder 72 in a direction (counter direction) in which the peeling baffle 71 faces the rotation direction of the fixing belt 61. Further, the sliding sheet member 68 is disposed between the pressing pad 64 and the fixing belt 61, and the sliding resistance between the inner peripheral surface of the fixing belt 61 and the pressing pad 64 is reduced. In the present embodiment, the sliding sheet member 68 may be configured separately from the pressing pad 64, and at least both ends may be fixed to the holder 65.

  The fixing device 60 includes a magnetic field generation unit 85 as an example of a heating member that heats the fixing belt 61 with a magnetic field generated by an alternating current.

  The magnetic field generation unit 85 has a curved shape whose cross section follows the shape of the fixing belt 61, and is installed at a gap of about 0.5 mm to 2 mm from the outer peripheral surface of the fixing belt 61. The magnetic field generation unit 85 includes an exciting coil 851 that generates a magnetic field, a coil support member 852 that holds the exciting coil 851, and an exciting circuit 853 that supplies a current to the exciting coil 851.

The exciting coil 851 is formed, for example, by winding about 16 to 20 copper wires having a diameter of 0.5 mm, which are insulated from each other, in a closed ring shape such as an oval shape, an elliptical shape, or a rectangular shape. Use the one that has been used. An alternating magnetic field H is generated around the exciting coil 851 by applying an alternating current of a predetermined frequency to the exciting coil 851 by the exciting circuit 853. When the AC magnetic field H traverses the metal layer of the fixing belt 61, an eddy current I is generated so as to generate a magnetic field that hinders the change of the AC magnetic field H by an electromagnetic induction effect. The frequency of the alternating current applied to the exciting coil 851 is set to, for example, 10 kHz to 50 kHz. When the eddy current I flows through the metal layer of the fixing belt 61, Joule heat is generated by the electric power W (W = I ² R) proportional to the resistance value R of the metal layer, and the fixing belt 61 is heated.

  The coil support member 852 is made of, for example, a heat-resistant non-magnetic material. Examples of such non-magnetic materials include heat resistant resins such as heat resistant glass, polycarbonate, polyether sulfone and PPS, and heat resistant resins obtained by mixing glass fibers with these.

  In this 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 fixing belt 61. However, the heating member may be a radiation lamp heating element or a resistance heating element. Can also be adopted.

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

  In the fixing device 60, the fixing belt 61 is driven to rotate as the pressure roller 62 rotates in the direction of arrow D, and is exposed to the magnetic field generated by the exciting coil 851. At this time, an eddy current is generated in the metal layer in the fixing belt 61, and the outer peripheral surface of the fixing belt 61 is heated to a temperature at which fixing is possible. The fixing belt 61 heated in this way moves to the nip portion N with the pressure roll 62. The recording medium P provided with the unfixed toner image on its surface is carried into the fixing device 60 via the fixing inlet guide 56 by the conveying means. When the recording medium P passes through the nip portion N between the fixing belt 61 and the pressure roll 62, the unfixed toner image is heated by the fixing belt 61 and fixed on the surface of the recording medium P. After that, the recording medium P on which the image is formed is conveyed by the conveying unit and is ejected from the fixing device 60. Further, the fixing belt 61, which has finished the fixing process in the nip portion N and the surface temperature of the outer peripheral surface thereof has decreased, rotates toward the exciting coil 851 and is heated again in preparation for the next fixing process.

  The pressure roll 62 has a base material 621, an elastic layer 622, and a release layer 623 in order.

  Examples of the base material 621 include a solid cylindrical metal member and the like. Examples of the metal forming the metal member include iron and aluminum.

  Examples of the elastic material forming the elastic layer 622 include silicone rubber, fluorinated silicone rubber, fluororubber, and the like, and silicone rubber is preferable in terms of heat resistance, hardness, and the like.

  The thickness of the elastic layer 622 is, for example, preferably in the range of 200 μm or more and 5 mm or less, and more preferably in the range of 450 μm or more and 2 mm or less. If the thickness of the elastic layer 622 is less than 200 μm, sufficient heat insulation may not be obtained, and if it exceeds 5 mm, thermal expansion may be too large.

  Examples of the material forming the release layer 623 include fluororesins such as tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA).

  The film thickness of the release layer 623 is, for example, in the range of 5 μm or more and 300 μm or less.

  In the fixing device 60 according to the present exemplary embodiment, a fixing belt is used as a fixing member, a pressure roll is used as a pressure member, and the elastic member is provided on the fixing belt side. Although the fixing device has been described, the present invention is not limited to this, and a fixing roll may be used as the fixing member, a pressure belt may be used as the pressure member, and the elastic member may be provided on the pressure belt side. Then, a so-called belt-belt type fixing device having a configuration in which a fixing belt as a fixing member and a pressure belt as a pressure member are applied, and the elastic member is provided on either the fixing belt side or the pressure belt side. May be

[Image forming device]
The image forming apparatus according to the present exemplary embodiment includes an image carrier, a latent image forming unit that forms a latent image on the surface of the image carrier, a developing unit that develops the latent image with toner to form a toner image, and a toner. A transfer unit that transfers the image to the recording medium, and the fixing device that fixes the toner image on the recording medium are provided.

  FIG. 4 shows a schematic configuration of an example of an image forming apparatus to which the fixing device according to the present embodiment is applied. Here, an intermediate transfer type image forming apparatus generally called a tandem type will be described as an example.

  FIG. 4 is a schematic configuration diagram showing an example of the image forming apparatus according to the present exemplary embodiment. The image forming apparatus 100 in FIG. 4 is an intermediate transfer type image forming apparatus generally called a tandem type, and includes a plurality of image forming units 1Y, 1M, 1C and 1K on which toner images of respective color components are formed by an electrophotographic method. And a primary transfer portion 10 for sequentially transferring (primary transfer) each color component toner image formed by each of the image forming units 1Y, 1M, 1C, 1K to the intermediate transfer belt 15, and a superimposition transferred on the intermediate transfer belt 15. A secondary transfer unit 20 that collectively transfers (secondarily transfers) a toner image onto a recording medium P, which is a recording medium, and a fixing device 60 that fixes the secondary transferred image on the recording medium P are provided. The fixing device 60 is the fixing device. The image forming apparatus 100 also includes a control unit 40 that controls the operation of each device (each unit).

  Each of the image forming units 1Y, 1M, 1C, and 1K of the image forming apparatus 100 includes a photosensitive drum 11 that rotates in the direction of arrow A, as an example of an image holding member that holds a toner image formed on the surface.

  A charger 12 for charging the photosensitive drum 11 is provided around the photoconductor drum 11 as an example of a charging unit for charging the surface of the image carrier, and a latent image is formed on the surface of the image carrier charged by the charging unit. As an example of a latent image forming means for forming a latent image, a laser exposure device 13 (an exposure beam is shown by a symbol Bm in the drawing) for writing an electrostatic latent image on the photoconductor drum 11 is provided. In addition, toners of respective color components are contained around the photosensitive drum 11 as an example of a developing unit that develops the latent image formed on the surface of the image carrier by the latent image forming unit with toner to form a toner image. A developing device 14 that visualizes the electrostatic latent image on the photoconductor drum 11 with toner is provided, and the toner images of the respective color components formed on the photoconductor drum 11 are transferred to the intermediate transfer belt 15 at the primary transfer portion 10. There is provided a primary transfer roll 16 for transferring to.

  Further, a drum cleaner 17 for removing residual toner on the photosensitive drum 11 is provided around the photosensitive drum 11, and the charger 12, the laser exposure device 13, the developing device 14, the primary transfer roll 16 and the drum cleaner are provided. Seventeen electrophotographic devices are sequentially arranged along the rotation direction of the photosensitive drum 11. These image forming units 1Y, 1M, 1C and 1K are arranged substantially linearly from the upstream side of the intermediate transfer belt 15 in the order of yellow (Y), magenta (M), cyan (C) and black (K). To be done.

The intermediate transfer belt 15, which is an intermediate transfer member, is composed of a film-shaped pressure belt in which a resin such as polyimide or polyamide is used as a base layer and an appropriate amount of an antistatic agent such as carbon black is contained. The volume resistivity is formed to be, for example, 10 ⁶ Ωcm or more and 10 ¹⁴ Ωcm or less, and the thickness thereof is, for example, about 0.1 mm.

  The intermediate transfer belt 15 is cyclically driven (rotated) in various directions by the various rolls in the direction B shown in FIG. As the various rolls, a driving roll 31 that is driven by a motor (not shown) having excellent constant speed to rotate the intermediate transfer belt 15, and an intermediate transfer that extends in a substantially linear shape along the arrangement direction of the photosensitive drums 11 A support roll 32 that supports the belt 15, a tension roll 33 that functions as a correction roll that applies a predetermined tension to the intermediate transfer belt 15 and suppresses meandering of the intermediate transfer belt 15, and a backup provided in the secondary transfer unit 20. The roll 25 and the cleaning backup roll 34 provided in the cleaning unit for scraping off the residual toner on the intermediate transfer belt 15 are provided.

The primary transfer section 10 is composed of a primary transfer roll 16 arranged to face the photoconductor 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 rod made of metal such as iron or SUS. The sponge layer is formed of, for example, a blend rubber of nitrile rubber (NBR) mixed with a conductive agent such as carbon black, styrene rubber (SBR), and ethylene propylene rubber (EPDM), and has a volume resistivity of, for example, 10 ^7. It is a sponge-like cylindrical roll having a resistance of ⁵ Ωcm or more and 10 ^8.5 Ωcm or less.

  The primary transfer roll 16 is arranged in pressure contact with the photoconductor drum 11 with the intermediate transfer belt 15 interposed therebetween, and the primary transfer roll 16 has a voltage (a negative polarity, for example, the same applies hereinafter) of a polarity opposite to the charging polarity of the toner. A primary transfer bias) is applied. As a result, the toner images on the respective photoconductor drums 11 are sequentially electrostatically attracted to the intermediate transfer belt 15 to form a superimposed toner image on the intermediate transfer belt 15.

  The secondary transfer unit 20 is a backup roll 25 and a secondary transfer unit disposed on the toner image holding surface side of the intermediate transfer belt 15 as an example of a transfer unit that transfers the toner image formed by the developing unit to a recording medium. And a roll 22.

The backup roll 25 is made of, for example, a tube made of a blend rubber of EPDM and NBR whose surface is dispersed with carbon, and the inside thereof is made of EPDM rubber. The surface resistivity is, for example, 10 ⁷ Ω / □ or more and 10 ¹⁰ Ω / □ or less, and the hardness is, for example, 70 ° (Asker C: manufactured by Kobunshi Keiki Co., Ltd., the same applies hereinafter). Is set to. The backup roll 25 is arranged on the back surface side of the intermediate transfer belt 15 and constitutes an opposite electrode of the secondary transfer roll 22, and a metal power supply roll 26 to which a secondary transfer bias is stably applied is arranged in contact therewith. ing.

The secondary transfer roll 22 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 rod made of metal such as iron or SUS. The sponge layer is formed of, for example, a blend rubber of NBR, SBR, and EPDM mixed with a conductive agent such as carbon black, and has, for example, a sponge-like shape having a volume resistivity of 10 ^7.5 Ωcm or more and 10 ^8.5 Ωcm or less. It is a cylindrical roll.

  The secondary transfer roll 22 is arranged in pressure contact with the backup roll 25 with the intermediate transfer belt 15 interposed therebetween, and the secondary transfer roll 22 is grounded so that 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 recording medium P conveyed to the unit 20.

  An intermediate transfer belt cleaner that removes residual toner, paper dust, etc. on the intermediate transfer belt 15 after the secondary transfer and cleans the surface of the intermediate transfer belt 15 is provided downstream of the secondary transfer unit 20 of the intermediate transfer belt 15. 35 is provided so as to be able to approach and separate.

  A reference sensor (home position sensor) 42 that generates a reference signal that serves as a reference for timing image formation in each of the image forming units 1Y, 1M, 1C, and 1K is provided on the upstream side of the yellow image forming unit 1Y. To be done. Further, an image density sensor 43 for adjusting image quality is arranged 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 to generate a reference signal, and each image forming unit is instructed by the control unit 40 based on the recognition of the reference signal. 1Y, 1M, 1C and 1K are configured to start image formation.

  In the image forming apparatus 100 of the present exemplary embodiment, as a conveying unit that conveys the recording medium P, the sheet accommodation unit 50 that accommodates the recording medium P, and the recording medium P accumulated in the sheet accommodation unit 50 are taken out at a predetermined timing. A paper feed roll 51 that conveys the recording medium P fed by the paper feed roll 51, a conveyance guide 53 that conveys the recording medium P conveyed by the conveyance roll 52 to the secondary transfer unit 20, A conveyance belt 55 that conveys the recording medium P that is conveyed after being secondarily transferred by the next transfer roll 22 to the fixing device 60, and a fixing entrance guide 56 that guides the recording medium P to the fixing device 60 are provided.

  Next, a basic image forming process of the image forming apparatus according to this embodiment will be described.

  In the image forming apparatus 100 shown in FIG. 4, image data output from an image reading apparatus (not shown) or a personal computer (PC) (not shown) is subjected to predetermined image processing by an image processing apparatus (not shown), and then image formation is performed. The image forming work is executed by the units 1Y, 1M, 1C and 1K.

  The image processing device performs predetermined image processing such as shading correction, positional deviation correction, brightness / color space conversion, gamma correction, frame erasing and color editing, and moving image editing on the input reflectance data. Is applied. The image data subjected to the image processing is converted into color material gradation data of four colors of Y, M, C and K, and output to the laser exposure device 13.

  The laser exposure device 13 irradiates the photosensitive drum 11 of each of the image forming units 1Y, 1M, 1C, and 1K with an exposure beam Bm emitted from a semiconductor laser, for example, according to the input color material gradation data. The surface of each of the photoconductor drums 11 of the image forming units 1Y, 1M, 1C and 1K is charged by the charger 12, and then the surface is scanned and exposed by the laser 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 at the primary transfer portion 10 where the photosensitive drums 11 and the intermediate transfer belt 15 contact each other. Transcribed. More specifically, in the primary transfer section 10, a voltage (primary transfer bias) having a polarity opposite to the charging polarity (for example, negative polarity) of the toner is applied to the base material of the intermediate transfer belt 15 by the primary transfer roll 16, and the toner is transferred. Primary transfer is performed by sequentially superimposing the 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 images are conveyed to the secondary transfer unit 20. When the toner image is transported to the secondary transfer unit 20, the transport unit rotates the paper feed roll 51 in synchronization with the timing when the toner image is transported to the secondary transfer unit 20, and the sheet storage unit 50 presets the toner image. A recording medium P of the size is supplied. The recording medium P supplied by the paper feed roll 51 is transported by the transport roll 52 and reaches the secondary transfer unit 20 via the transport guide 53. Before reaching the secondary transfer portion 20, the recording medium P is temporarily stopped, and a registration roll (not shown) rotates in synchronization with the movement timing of the intermediate transfer belt 15 on which the toner image is held. The position of the medium P 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 recording medium P conveyed at the same timing is sandwiched between the intermediate transfer belt 15 and the secondary transfer roll 22. At that time, when a voltage (secondary transfer bias) having the same polarity as the charging polarity (for example, negative polarity) of the toner is applied from the power supply roll 26, a transfer electric field is generated between the secondary transfer roll 22 and the backup roll 25. It is formed. Then, the unfixed toner image held on the intermediate transfer belt 15 is electrostatically transferred onto the recording medium P collectively in the secondary transfer unit 20, which is pressed by the secondary transfer roll 22 and the backup roll 25. To be done.

  After that, the recording medium P to which the toner image is electrostatically transferred is conveyed as it is in a state of being separated from the intermediate transfer belt 15 by the secondary transfer roll 22, and is provided on the downstream side of the secondary transfer roll 22 in the paper conveyance direction. It is conveyed to the conveyor belt 55. The conveyance belt 55 conveys the recording medium P to the fixing device 60 at an optimum conveyance speed in the fixing device 60. The unfixed toner image on the recording medium P conveyed to the fixing device 60 is fixed on the recording medium P by being subjected to a fixing process by heat and pressure by the fixing device 60. Then, the recording medium P on which the fixed image is formed is conveyed to a discharged sheet storage section (not shown) provided in the discharge section of the image forming apparatus.

  On the other hand, after the transfer to the recording medium 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 the cleaning backup roll 34 and the intermediate transfer belt cleaner 35. Is removed from the surface of the intermediate transfer belt 15.

  Although the embodiments of the present invention have been described above, the present invention should not be construed as being limited to the above-described embodiments, and various modifications, changes, and improvements are possible, and ranges that satisfy the requirements of the present invention. It goes without saying that it can be realized within.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

< Reference example 1>
An image forming apparatus (ApesPort-V C7776 manufactured by Fuji Xerox) having a fixing device as shown in FIG. 1 was used to form 700,000 sheets of image by transversely flowing A4 size P paper manufactured by Fuji Xerox. An elastic member (material: silicone rubber, elastic modulus: 0.6 MPa, shape: 8 mm × 356 mm × thickness 2 mm rectangular parallelepiped) as shown in FIG. 2 is provided between the holder, which is a supporting member inside the fixing belt, and the pressing pad. ) Is provided. An operation of lowering the pressure between the fixing belt and the pressure roll during non-image formation than that during image formation was performed. The degree of wear of the sliding sheet member was visually examined and evaluated according to the following criteria. The results are shown in Table 1.
◎: Abrasion of sliding sheet member occurred after more than 700,000 sheets (no problem in practical use)
◯: Sliding sheet member was worn when more than 500,000 sheets and less than 600,000 sheets (no problem in practical use)
X: Wear of sliding sheet member occurs at 500,000 sheets or less

<Example 1 >
As the elastic member, an elastic member as shown in FIG. 3 (material: silicone rubber, elastic modulus: 0.6 MPa, shape: 8 mm × 356 mm × thickness nip portion N inlet side 4 mm, outlet side 2 mm square truncated pyramid) is used. the pressure pad of the non-image-formation, except that the relative position of the pressing pad at the time of image formation, was tilted to (insertion side of the recording medium of the nip portion N) passes upstream side of the recording medium, reference Evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

<Comparative Example 1>
Evaluation was performed in the same manner as in Reference Example 1 except that no elastic member was provided between the holder and the pressing pad. The results are shown in Table 1.

  As described above, in the fixing device of the example, abrasion of the sliding sheet member was suppressed as compared with the comparative example in which the elastic member was not provided between the pressing pad and the holder of the comparative example.

  1Y, 1M, 1C, 1K image forming unit, 10 primary transfer portion, 11 photoconductor drum, 12 charger, 13 laser exposure device, 14 developing device, 15 intermediate transfer belt, 16 primary transfer roll, 17 drum cleaner, 20 2 Next transfer unit, 22 Secondary transfer roll, 25 Backup roll, 26 Power supply roll, 31 Drive roll, 32 Support roll, 33 Tension roll, 34 Cleaning backup roll, 35 Intermediate transfer belt cleaner, 40 Control unit, 42 Reference sensor (home Position sensor), 43 image density sensor, 50 paper storage unit, 51 paper feed roll, 52 transport roll, 53 transport guide, 55 transport belt, 56 fixing inlet guide, 60 fixing device, 61 fixing belt, 62 pressure roll, 63 Belt guide member, 64 pressure pad Deposition, 65 holder, 66 elastic member, 67 lubricant supply member, 68 sliding sheet member, 69 lubricant, 70 peeling auxiliary member, 71 peeling baffle, 72 baffle holder, 85 magnetic field generating unit, 100 image forming apparatus, 621 units Material, 622 elastic layer, 623 release layer, 851 exciting coil, 852 coil supporting member, 853 exciting circuit, P recording medium.

Claims (2)

A rotatable pressure member,
A belt member movable while contacting the pressure member,
A nip portion that is arranged so as to face the pressure member via the belt member and presses the belt member against the pressure member to pass a recording medium between the pressure member and the belt member. A nip portion forming member to be formed,
A sliding sheet member arranged from the upstream side in the passing direction of the recording medium between the nip portion forming member and the belt member,
A lubricant supply member for supplying a lubricant to the sliding portion between the belt member and the sliding sheet member,
A support member for supporting the nip portion forming member,
An elastic member provided between the nip portion forming member and the supporting member,
Have
During non-image formation Ri can der to keep down than when the pressure image formation with the belt member and the pressure member,
The pressing member during non-image formation, relative to the position of the pressing member during the image formation, the fixing device according to claim state der Rukoto the passage inclined toward the upstream side of the recording medium. An image carrier,
A latent image forming means for forming a latent image on the surface of the image carrier,
Developing means for developing the latent image with toner to form a toner image;
Transfer means for transferring the toner image onto a recording medium,
To fix the toner image on the recording medium, and a fixing device according to claim 1,
An image forming apparatus comprising: