Fixing device and image forming apparatus

Abstract

To facilitate transfer of heat from a heating member to an annular belt.SOLUTION: A fixing device 30 is provided with a fixing belt 53, a heating member 70 that is provided on an inner peripheral surface 56S of the fixing belt 53; a slide member 52 that is provided on an opposing surface 51B of the heating member 70 opposite to the inner peripheral surface 56S; and a pressure roller 60 that is provided on an outer peripheral surface of the fixing belt 53 and forms a nip part N between the slide member 52 and the pressure roller with the fixing belt 53 therebetween. The slide member 52 includes at least a binder resin 52B and thermally conductive filler particles 52F.SELECTED DRAWING: Figure 13

Description

[Technical field]

[0001] The present invention relates to a fixing device and an image forming apparatus, which is suitable for use in, for example, an electrophotographic printer. [Background technology]

[0002] Conventionally, as an image forming device (also called a printer), a widely used device performs printing processing by forming a developer image using toner (also called a developer) in an image forming unit based on an image supplied from a computer device or the like, transferring the developer image to a medium such as paper, and fixing the image by applying heat and pressure in a fixing device.

[0003] Some fixing devices have a heating member disposed opposite the inner circumferential surface of a circular belt, and transfer heat to the fixing belt through the opposing member at the fixing nip (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Application No. 2019-128507 Summary of the Invention [Problem to be solved by the invention]

[0005] However, although it is preferable to efficiently transfer the heat generated by the heating element provided on the inner surface of the circular belt to the circular belt, when an opposing element (sliding layer) is provided on the surface of the heating element to ensure the sliding properties of the circular belt, etc., it is difficult for the heat from the heating element to be transferred to the circular belt, especially in high-speed printing.

[0006] The present invention has been made in consideration of the above points, and aims to propose a fixing device and an image forming apparatus that can easily transfer heat from a heating member to a circular belt. [Means for solving the problem]

[0007] In order to solve the above problems, the fixing device of the present invention has the following features: The substrate layer is made of a resin material. A circular belt and a Heater included A heating element; heater Inner surface Base layer and a pressure member provided on the outer peripheral surface of the circular belt and forming a nip region between the opposing member and the circular belt via the circular belt. The opposing member contains at least resin and carbon, and has a weight blending ratio, which is the blending ratio of the added carbon to the weight ratio of the opposing member, of 11 wt% to 49 wt%. When the thickness of the opposing member is a [μm] and the weight blending ratio of the carbon is b [wt%,] the following formula (1) is satisfied (a>0.198b...(1)).

[0008] The present invention uses carbon, which has a higher thermal conductivity than resin, to improve the thermal diffusivity in the thickness direction of the heating member, thereby making it possible to reduce the limit temperature of fixing.

[0009] In the fixing device of the present invention, a circular belt having a base layer made of a resin material, a heating member including a heater provided on the inner peripheral surface side of the circular belt, and an opposing member provided on an opposing surface of the heater that faces the base layer on the inner peripheral surface, the opposing member being made of at least resin and having a thermal conductivity higher than that of resin. carbon and the weight ratio of the opposing member is carbon The weight mixture ratio is 11 [wt%] or more and 49 [wt%] or less, and the thickness of the opposing member is a [μm]. carbon If the weight blend ratio is b [wt%], the following formula (3) is satisfied (a>0.198b……(3)) Yo I did.

[0010] Furthermore, in the fixing device of the present invention, The substrate layer is made of a resin material. A circular belt and a Heater included A heating element; heater Inner surface Base layerand a facing member provided on the facing surface facing the resin, the facing member including at least a resin and a heat conductive material having a higher thermal conductivity than the resin, a volumetric blending ratio, which is a blending ratio of the heat conductive material added to the volume ratio of the facing member, is 8 [vol%] or more and 38 [vol%] or less, a thickness of the facing member is t [μm], a volumetric blending ratio of the heat conductive material is Rv [vol%], and a density of the heat conductive material is α [g / cm 3 ], resin density is β [g / cm 3 ], the following formula (4) is satisfied. I changed it to JPEG0007631710000001.jpg972.

[0011] The present invention uses a heat conductive material having a higher thermal conductivity than resin to improve the thermal diffusivity in the thickness direction of the heating member, thereby making it possible to reduce the fixing limit temperature.

[0012] Furthermore, the image forming apparatus of the present invention is provided with the fixing device described above. Effect of the Invention

[0013] According to the present invention, it is possible to realize a fixing device and an image forming apparatus that can easily transfer heat from a heating member to a circular belt. [Brief description of the drawings]

[0014] [Figure 1] FIG. 2 is a left side view illustrating a configuration of the image forming apparatus. [Diagram 2] FIG. 1 is a perspective view showing a configuration (1) of a fixing device. [Diagram 3] FIG. 4 is a front view showing the configuration (2) of the fixing device. [Figure 4] FIG. 4 is a cross-sectional view taken along the line AA in FIG. 3, showing a configuration (3) of the fixing device. [Diagram 5] 5 is an enlarged cross-sectional view of an area A in FIG. 4, showing the configuration (4) of the fixing device. [Figure 6] FIG. 2 is an exploded perspective view showing the configuration of a fixing belt unit. [Figure 7] 3 is a cross-sectional view showing a configuration of a heat diffusion member. FIG. [Figure 8] 8 is an enlarged view of FIG. 7, illustrating the configuration of a sliding member. FIG. [Figure 9] FIG. 2 is a cross-sectional view illustrating a configuration of a fixing belt. [Figure 10] FIG. 2 is a perspective view showing the configuration (1) of a pressure roller. [Figure 11] 11 is a cross-sectional view taken along the line BB in FIG. 10, showing the configuration (2) of the pressure roller. [Figure 12] 1 is a table showing thermogravimetric differential thermal analysis. [Figure 13] 13 is a table showing the determination results. [Figure 14] 1 is a table showing pressure and sliding distance. [Figure 15] 1 is a table showing the relationship between the graphite weight blend ratio and the graphite volume blend ratio and the wear depth of a sliding member. [Figure 16] 1 is a graph showing the relationship between the weight blend ratio of graphite and the wear depth of a sliding member. [Figure 17] 1 is a graph showing the relationship between the volumetric blending ratio of graphite and the wear depth of a sliding member. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, modes for carrying out the invention (hereinafter referred to as embodiments) will be described with reference to the drawings.

[0016] [1. Configuration of image forming device] As shown in Fig. 1, the image forming apparatus 1 is, for example, a printer using an electrophotographic method, and performs an image forming operation using a developer such as toner to form a black-and-white image or a color image on a recording medium P such as paper. In the following, a position close to the paper feed tray 3 as viewed from an arbitrary position on the conveying path along which the recording medium P is conveyed, or a direction toward the paper feed tray 3, is referred to as upstream. Also, a position close to a stacker 9 into which the recording medium P is discharged and stacked, or a direction toward the stacker 9, as viewed from an arbitrary position on the conveying path, is referred to as downstream. Furthermore, the direction from upstream to downstream is referred to as the conveying direction.

[0017] The image forming apparatus 1 has a box-shaped printer housing 2, inside which a paper feed tray 3, a hopping roller 4, a pair of registration rollers 5, an image forming section 10, a fixing device 30, and a pair of discharge rollers 6.

[0018] The paper feed tray 3 is disposed in the lower portion of the printer housing 2, and accommodates a stack of a plurality of recording media P. Downstream of the paper feed tray 3, a hopping roller 4 is provided.

[0019] The hopping roller 4 is in pressure contact with the surface of the recording medium P and delivers the recording medium P downstream along the conveying path. The hopping roller 4 rotates by power transmitted from a hopping motor (not shown) with the central axis of the hopping roller 4 as the rotation axis. A pair of registration rollers 5 is provided downstream of the hopping roller 4.

[0020] The registration roller pair 5 transports the recording medium P toward the image forming unit 10. When the recording medium P is transported, the leading edge of the recording medium P is abutted against the registration roller pair 5, thereby correcting skew of the recording medium P. The image forming unit 10 is provided downstream of the registration roller pair 5. The image forming unit 10 transfers an image onto the recording medium P and transports it to the fixing device 30.

[0021] The fixing device 30 applies heat and pressure to the image transferred onto the recording medium P transported from the transfer belt unit 18 of the image forming section 10, thereby fixing the image onto the recording medium P, and also transports the recording medium P along the transport path toward the discharge roller pair 6. Downstream of the fixing device 30, the discharge roller pair 6 is provided.

[0022] The pair of discharge rollers 6 transports the recording medium P toward the stacker 9. As a result, the image forming apparatus 1 discharges the recording medium P to the stacker 9, which is provided outside the printer housing 2 and which stacks the recording medium P on which the image has been fixed.

[0023] [2. Configuration of image forming unit] The image forming section 10 is a mechanism that forms an image (toner image) and transfers the image onto the recording medium P. The image forming section 10 has four developing units 11 (developing units 11K, 11Y, 11M, and 11C), four exposure units 17 (exposure units 17K, 17Y, 17M, and 17C), and a transfer belt unit 18. The developing units 11K, 11Y, 11M, and 11C are arranged in this order along the conveying direction of the recording medium P. Hereinafter, the developing units 11K, 11Y, 11M, and 11C are collectively referred to as developing units 11, and the exposure units 17K, 17Y, 17M, and 17C are collectively referred to as exposure units 17.

[0024] The developing unit 11 forms an image using toner, which is a developer, based on print data transmitted from a higher-level device such as a personal computer. The developing units 11K, 11Y, 11M, and 11C form images of black, yellow, magenta, and cyan, respectively. The developing units 11K, 11Y, 11M, and 11C have the same configuration, except that they form images using toners of different colors. Each developing unit 11 has a photoconductor drum 12, a charging roller 13, a developing roller 14, a cleaning blade 15, and a toner storage unit 16.

[0025] Photoconductor drum 12 is a cylindrical member that carries an electrostatic latent image on its surface (surface layer portion), and is constructed using a photoconductor (e.g., an organic photoconductor). This photoconductor drum 12 rotates clockwise in FIG. 1 by power transmitted from a photoconductor motor (not shown). Photoconductor drum 12 is charged by charging roller 13 and exposed by corresponding exposure unit 17. As a result, an electrostatic latent image is formed on the surface of photoconductor drum 12. Then, as toner is supplied from developing roller 14, an image corresponding to the electrostatic latent image is formed (developed) on photoconductor drum 12.

[0026] The charging roller 13 is configured to charge the surface (surface portion) of the photosensitive drum 12. The charging roller 13 is disposed so as to be in contact with the surface (circumferential surface) of the photosensitive drum 12 and to be pressed against the photosensitive drum 12 with a predetermined pressure. The charging roller 13 rotates counterclockwise in FIG. 1 in accordance with the rotation of the photosensitive drum 12. A predetermined charging voltage is applied to the charging roller 13.

[0027] The developing roller 14 is configured to carry charged toner on its surface. The developing roller 14 is disposed so as to be in contact with the surface (circumferential side surface) of the photosensitive drum 12, and is disposed so as to be pressed against the photosensitive drum 12 with a predetermined pressure. The developing roller 14 rotates counterclockwise in FIG. 1 by power transmitted from a photosensitive motor (not shown). A predetermined developing voltage is applied to the developing roller 14.

[0028] The cleaning blade 15 is a member that scrapes off and cleans the toner remaining on the surface of the photoreceptor drum 12. This cleaning blade 15 is disposed so as to be in counter contact with the surface of the photoreceptor drum 12 and to be pressed against the photoreceptor drum 12 with a predetermined pressure.

[0029] The toner storage sections 16 are configured to store toner. Specifically, the toner storage sections 16 of the developing units 11K, 11Y, 11M, and 11C store black, yellow, magenta, and cyan toner, respectively.

[0030] The exposure units 17 (exposure units 17K, 17Y, 17M, and 17C) are mechanisms that irradiate light onto the photoconductor drums 12 of the development unit 11, and are configured using, for example, LED (Light Emitting Diode) heads. As a result, electrostatic latent images are formed on the surfaces of these photoconductor drums 12. Then, images corresponding to the electrostatic latent images are formed on the photoconductor drums 12.

[0031] The transfer belt unit 18 is a mechanism that transfers an image formed on the surface of the photosensitive drum 12 to the surface of the recording medium P by Coulomb force, and transports the recording medium P in the transport direction. The transfer belt unit 18 transports the recording medium P to which the image has been transferred, toward the fixing device 30. The transfer belt unit 18 has a transfer belt 19, a drive roller 20, a driven roller 21, four transfer rollers 22 (transfer rollers 22K, 22Y, 22M, and 22C), and a cleaning blade 23.

[0032] The transfer belt 19 is a seamless circular belt capable of carrying the recording medium P. The transfer belt 19 is tensioned by a drive roller 20 and a driven roller 21. The drive roller 20 is a rotating member that rotates to convey the recording medium P toward the fixing device 30 by the power transmitted from a belt motor (not shown), and circulates the transfer belt 19. The driven roller 21 is a member that adjusts the tension applied to the transfer belt 19 while stretching the transfer belt 19 together with the drive roller 20. The four transfer rollers 22 are rotating members that transfer an image formed on the surface of the photosensitive drum 12 of the corresponding development unit 11 onto the transfer surface of the recording medium P. The transfer rollers 22K, 22Y, 22M, and 22C are disposed opposite the photosensitive drums 12 of the development units 11K, 11Y, 11M, and 11C via the transfer belt 19, respectively. A predetermined transfer voltage is applied to each of the transfer rollers 22K, 22Y, 22M and 22C, whereby the image formed on the photoconductor drum 12 by the developing unit 11 is transferred onto the transfer surface of the recording medium P. The cleaning blade 23 is a member that scrapes off and cleans waste toner remaining on the surface of the transfer belt 19. A fixing device 30 is provided downstream of the image forming section 10.

[0033] [3. Configuration of the fixing device] 2, 3, 4, 5, 6, 7, 8, 9, 10, and 11, a detailed configuration of the fixing device 30 will be described. As shown in FIG. 2, the fixing device 30 has side frames 31L and 31R, springs 32L and 32R, levers 33L and 33R, a drive gear 35, a fixing belt unit 40, and a pressure roller 60.

[0034] The side frames 31L and 31R are members fixed to the printer housing 2 of the image forming apparatus 1 using screws or the like. As shown in FIG. 2 and FIG. 4, the spring 32L is an elastic member such as a spring, and applies a biasing force to the lever 33L. One end of the spring 32L is fixed to the side frame 31L, and the other end is fixed to the lever 33L. The spring 32R is an elastic member such as a spring, similar to the spring 32L, and applies a biasing force to the lever 33R. The lever 33L rotates in the D1 direction around the rotation fulcrum 34L along the left-right direction as a rotation axis due to the biasing force applied by the spring 32L. The lever 33L is attached to the side frame 31L. The lever 33R rotates in the D1 direction around the rotation fulcrum 34R along the left-right direction as a rotation axis due to the biasing force applied by the spring 32R, similar to the lever 33L. When the fixing device 30 is not performing a fixing operation, the levers 33L and 33R are pressed to a predetermined position by a lever fixing member (not shown). That is, since the spring 32L is pressed by the lever fixing member via the lever 33L, when the lever 33L is released from the lever fixing member, a biasing force can be applied to the lever 33L. The same is true for the spring 32R. The drive gear 35 transmits power from an annular belt motor (not shown) to the pressure roller 60.

[0035] With this configuration, when the fixing device 30 performs a fixing operation, the drive gear 35 transmits power from the circular belt motor to the pressure roller 60. In addition, the levers 33L and 33R are released from the lever fixing member in response to the operation of the drive gear 35, so that the levers 33L and 33R rotate in the D1 direction around the rotation fulcrums 34L and 34R as the rotation axes. Therefore, the fixing belt unit 40 attached to the levers 33L and 33R is pressed against the pressure roller 60, so that a nip portion N is formed between the fixing belt unit 40 and the pressure roller 60. FIG. 4 shows a state in which the nip portion N is formed between the fixing belt unit 40 and the pressure roller 60. When the recording medium P passes through the nip portion N, heat and pressure are applied to the image transferred onto the recording medium P, and the image is fixed onto the recording medium P.

[0036] [4. Configuration of the fixing belt unit] The fixing belt unit 40 is configured to apply heat to an image on the recording medium P. As shown in FIG. 4 to FIG. 6, the fixing belt unit 40 has a stay 41, a holding member 43, a heater 44, a heat retention plate 48, a heat diffusion member 50, and a fixing belt 53. The stay 41 is a member that supports the fixing belt 53. The stay 41 is fixed to the lever 33L by a screw 42L, and is fixed to the lever 33R by a screw 42R. The holding member 43 is a member that holds the heater 44, the heat retention plate 48, and the heat diffusion member 50. The holding member 43 is fixed to the stay 41. As shown in FIG. 5 and FIG. 6, the heat retention plate 48, the heater 44, the heat diffusion member 50, and the fixing belt 53 are arranged in this order from top to bottom. That is, the heat retention plate 48 faces the heater 44, the heater 44 faces the heat diffusion member 50, and the heat diffusion member 50 faces the fixing belt 53. Hereinafter, the heat diffusion member 50 and the heater 44 are collectively referred to as a heating member 70 .

[0037] The heater 44 is a plate-like member extending in the left-right direction, and is a heat source for heating the fixing belt 53. The heater 44 has a plurality of (for example, five) heat generating parts arranged along a width direction (left-right direction) perpendicular to the rotation direction of the fixing belt 53. When an image is formed on a recording medium P having a wide left-right width, such as A3 paper, the fixing belt unit 40 causes all the heat generating parts of the heater 44 to generate heat. On the other hand, when an image is formed on a recording medium P having a narrow left-right width, such as a postcard, the fixing belt unit 40 causes only the heat generating parts in the left-right center to generate heat, thereby reducing energy consumption. In this way, the fixing belt unit 40 selectively energizes the heat generating parts to generate heat depending on the width of the recording medium P in the left-right direction.

[0038] The heat retention plate 48 is a member that stores heat generated by the heater 44. In this example, the heat retention plate 48 is a plate-shaped member that extends in the left-right direction along the heater 44. The heat retention plate 48 makes it difficult for the heat generated by the heater 44 to be transferred to the side of the heat retention plate 48 opposite to the side facing the heater 44. Note that, in this example, the fixing belt unit 40 has the heat retention plate 48, but this is not limiting, and the fixing belt unit 40 does not need to have the heat retention plate 48.

[0039] Between the heater 44 and the heat retention plate 48, thermally conductive grease is applied in order to efficiently transfer the heat generated by the heater 44. Similarly, between the heater 44 and the heat diffusion member 50, thermally conductive grease is applied. The heater 44 and the heat retention plate 48 are disposed so as to be sandwiched between the holding member 43 and the heat diffusion member 50, and are fixed by the holding member 43. Note that, in this example, thermally conductive grease is applied between the heater 44 and the heat retention plate 48, but this is not limited thereto, and thermally conductive grease may not be applied. Also, between the heater 44 and the heat diffusion member 50, thermally conductive grease is applied, but this is not limited thereto, and thermally conductive grease may not be applied.

[0040] [5. Composition of heat diffusion material] The heat diffusion member 50 is a substantially flat metal plate member extending in the left-right direction along the heater 44, and is configured to transfer heat generated by the heater 44 to the fixing belt 53. The heat diffusion member 50 is shaped like a capital letter "U" when viewed from the right side, and both front and rear ends are bent upward in the vertical direction, which is the thickness direction. That is, the heat diffusion member 50 has a recess facing the heater 44. As shown in FIG. 5, the convex parts bent upward at the front-rear end of the heat diffusion member 50 are inserted into the holding grooves 49F and 49B provided in the holding member 43. Since the holding grooves 49F and 49B are wider than the convex parts of the heat diffusion member 50, the heat diffusion member 50 inserted into the holding grooves 49F and 49B can move in the thickness direction (substantially vertical direction) by the fixing belt unit 40 being pressed against the pressure roller 60. That is, when the fixing device 30 performs a fixing operation, the heat diffusion member 50 is pressed against the heater 44. At this time, the heat diffusion member 50 transfers the heat generated by the heater 44 to the fixing belt 53. As shown in FIG.

[0041] [5-1. Composition of the base material] The substrate 51 has an opposite surface 51A facing the heater 44, and an opposite surface 51B opposite to the opposite surface 51A. The substrate 51 also has a sliding member 52 formed on the opposite surface 51B. The opposite surface 51A faces an inner circumferential surface 56S (FIG. 5) of the fixing belt 53. As described above, the substrate 51 has a shape like a capital letter "U" when viewed from the right side, and both front and rear ends are bent upward in the vertical direction, which is the thickness direction. The substrate 51 equalizes the temperature difference at the joints between the heat generating portions of the heater 44.

[0042] The base material 51 is configured to include, for example, a metal having a high thermal diffusivity, which indicates the speed at which heat is transmitted. In this example, the main component of the base material 51 is aluminum (Al). Here, the main component means a component that occupies 50 [wt%] of the entire base material 51. That is, the content of Al in the base material 51 is higher than other materials. In this example, the base material 51 includes Al, but is not limited to this, and may include other metals having a high thermal diffusivity. The base material 51 may have a thermal conductivity that can equalize the temperature difference at the joints of the heat generating parts of the heater 44, and may include, for example, stainless steel (SUS), copper, or zinc (Zn). The thickness of the base material 51 is not limited to the thickness exemplified.

[0043] [5-2. Configuration of sliding members] The sliding member 52 has a sliding surface SF facing the inner peripheral surface 56S (FIG. 5) of the fixing belt 53, and is a contact member that comes into contact with the inner peripheral surface 56S of the fixing belt 53 via sliding grease GR (described later). Here, the sliding surface SF of the sliding member 52 facing the inner peripheral surface 56S of the fixing belt 53 means that the sliding surface SF is disposed opposite the inner peripheral surface 56S. In this case, "facing" also means that the sliding surface SF comes into contact with the inner peripheral surface 56S to be disposed opposite the inner peripheral surface 56S, or that the sliding surface SF is disposed opposite the inner peripheral surface 56S via another member such as sliding grease GR (described later). The heater 44 is located on the opposite side of the sliding surface SF with respect to the substrate 51. The sliding member 52 is configured to include, for example, a resin that has good slidability with the inner peripheral surface 56S of the fixing belt 53. The thickness of the sliding member 52 is preferably 2.1 μm or more and 9.7 μm or less. Here, the thickness of the sliding member 52 is the distance from the facing surface 51B of the base material 51 of the heat diffusion member 50 toward the nip portion N along a direction perpendicular to the facing surface 51B to the sliding surface SF of the sliding member 52. In addition, the thickness of the sliding member 52 is not limited to the thickness exemplified above.

[0044] [5-2-1. Composition of binder resin] 8, the sliding member 52 contains a binder resin 52B as a main component. The binder resin 52B constituting the sliding member 52 is, for example, polyamideimide (PAI) having high toughness. Here, the main component means a component that occupies 50 wt% of the entire sliding member 52. That is, the content of PAI in the sliding member 52 is higher than that of other materials.

[0045] [5-2-2. Composition of thermally conductive filler particles] Furthermore, the sliding member 52 contains a plurality of particulate fillers (hereinafter, thermally conductive filler particles 52F) of graphite as carbon, which is a thermally conductive material. The sliding member 52 contains the thermally conductive filler particles 52F of graphite, thereby further improving the sliding property and thermal conductivity.

[0046] As shown in FIG. 8, the thermally conductive filler particles 52F are distributed, for example, discretely inside the binder resin 52B. Some of the thermally conductive filler particles 52F include a portion exposed to the sliding surface SF. Therefore, a fine uneven structure is formed on the sliding surface SF. Even if the sliding surface SF is worn down by sliding against the inner circumferential surface 56S, the sliding surface SF can maintain the fine uneven structure because the thermally conductive filler particles 52F are embedded in the binder resin 52B.

[0047] In this example, for example, a PAI solvent is sprayed onto one surface of the substrate 51, and the resin is cured by heating, forming the sliding member 52 on the substrate 51. The thickness of the sliding member 52 is controlled, for example, by adjusting the number of sprays to be applied. In this example, the length of the sliding member 52 in the longitudinal direction (left-right direction) is approximately 264.9 [mm], and the length of the sliding member 52 in the lateral direction (front-back direction) is approximately 17.55 [mm]. That is, the sliding member 52 covers approximately the entire surface of the facing surface 51B of the substrate 51 facing the inner peripheral surface 56S of the fixing belt 53. The sliding surface SF of the sliding member 52 faces the fixing belt 53 as described above, and the inner peripheral surface 56S of the fixing belt 53 that rotates in a circular manner slides on the sliding surface SF.

[0048] 5 and 7, in order to improve the sliding property of the inner circumferential surface 56S against the sliding surface SF, for example, sliding grease GR is applied as a lubricant to the sliding surface SF, so that the sliding grease GR is provided between the fixing belt 53 and the sliding surface SF of the sliding member 52. Therefore, the fixing belt 53 slides on the sliding surface SF via the sliding grease GR. The sliding grease GR is, for example, a gel-like grease, and includes a silicone-based material or a fluorine-based material.

[0049] In this example, the binder resin 52B of the sliding member 52 contains PAI, but is not limited thereto and may contain other resins. Such other resins include polyimide (PI), which improves the sliding properties of the fixing belt 53 and has excellent heat resistance and mechanical strength. In addition, the sliding member 52 covers substantially the entire surface of the facing surface 51B of the base material 51 that faces the inner circumferential surface 56S of the fixing belt 53, but is not limited thereto and may instead cover, for example, a part of the facing surface 51B of the base material 51.

[0050] [6. Structure of the fixing belt] The fixing belt 53 is a circular belt stretched by the stay 41 with a predetermined tension, and is configured to be rotatably held. The fixing belt 53 has an inner peripheral surface 56S facing the sliding surface SF, and the inner peripheral surface 56S is provided to slide on the sliding surface SF. The fixing belt 53 forms a nip portion N (FIG. 5) between the fixing belt 53 and the pressure roller 60. As shown in FIG. 9, the fixing belt 53 has a surface layer 54, an elastic layer 55, and a base layer 56. That is, in the fixing belt 53, the elastic layer 55 is formed on the base layer 56, and the surface layer 54 is formed on the elastic layer 55.

[0051] In this example, the surface layer 54 is composed of a copolymer (PFA) of tetrafluoroethylene and perfluoroalkylvinylether. The thickness of the surface layer 54 is, for example, 20 [μm]. It is desirable that the thickness of the surface layer 54 is large enough to follow the deformation of the elastic layer 55. On the other hand, if the thickness of the surface layer 54 is too small, wrinkles will occur in the surface layer 54 due to sliding with the pressure roller 60 or the recording medium P, so the thickness of the surface layer 54 is preferably 10 to 50 [μm]. In addition, it is desirable that the surface layer 54 has heat resistance that can withstand the fixing temperature and has a release property that makes it difficult for toner remaining on the fixing belt 53 and paper powder derived from the recording medium P to stick to it, and is preferably made of a fluorine-substituted material. Note that the material of the surface layer 54 is not limited to the exemplified material, and the thickness of the surface layer 54 is not limited to the exemplified thickness.

[0052] In this example, the elastic layer 55 is made of silicone rubber having heat resistance that can withstand the fixing temperature. The rubber hardness of the elastic layer 55 is, for example, 12 degrees, and the thickness of the elastic layer 55 is, for example, 200 [μm]. It is desirable that the elastic layer 55 has a rubber hardness and thickness that can form the nip portion N. On the other hand, it is desirable that the elastic layer 55 suppresses the heat loss of the heat generated from the heater 44 and efficiently transfers the heat generated from the heater 44 to the outer peripheral surface (toner contact surface) of the fixing belt 53. If the thickness of the elastic layer 55 is large, a uniform nip portion N is easily formed, but the heat capacity becomes large and the heat loss becomes large, which is not preferable. The thickness of the elastic layer 55 is preferably 50 to 500 [μm]. In addition, the rubber hardness of the elastic layer 55 is preferably 10 to 60 degrees in order to increase the uniformity of the nip portion N. In this example, the elastic layer 55 contains silicone rubber, but is not limited to this and may contain other materials having heat resistance that can withstand the fixing temperature. The elastic layer 55 may contain, for example, fluororubber. The thickness of the elastic layer 55 is not limited to the thickness shown in the example.

[0053] In this example, the base layer 56 is configured to include polyimide (PI), and the main component of the base layer 56 is PI. Here, the main component means a component that occupies 50 [wt%] of the entire base layer 56. That is, the content of PI in the base layer 56 is higher than other materials. The inner diameter of the base layer 56 is, for example, 30 [mm], and the thickness of the base layer 56 is, for example, 80 [μm]. The base layer 56 imparts durability and mechanical strength to the fixing belt 53, and is excellent in mechanical strength, repeated bending resistance, and buckling resistance. That is, the base layer 56 has a large Young's modulus and a high buckling strength, so that the fixing belt 53 is unlikely to break. In this example, the base layer 56 includes PI, but is not limited thereto, and may instead include other materials having high heat resistance, a large Young's modulus, and a high buckling strength. The base layer 56 may include, for example, stainless steel or polyether ether ketone (PEEK). In particular, a resin material having excellent heat resistance is preferable, for example, polytetrafluoroethylene (PTFE). The base layer 56 may contain a material to which a conductive filler containing a metal element such as carbon black or zinc is added, and in this case, the base layer 56 can exhibit conductivity. The base layer 56 may contain PTFE to which a filler such as boron nitride is added, and in this case, the sliding property and thermal conductivity of the base layer 56 can be improved. The thickness of the base layer 56 is not limited to the thickness exemplified.

[0054] [7. Configuration of pressure roller] As shown in FIG. 10 and FIG. 11, the pressure roller 60 is a rotating member that is provided so as to be able to come into contact with the outer circumferential surface of the fixing belt 53 in the fixing belt unit 40 so as to form a nip portion N between the pressure roller 60 and the fixing belt unit 40, and applies pressure to the image on the recording medium P. The outer diameter of the pressure roller 60 is 40 [mm], and the hardness of the pressure roller 60 is preferably 50 to 65 degrees. The pressure roller 60 has a surface layer 61, an adhesive layer 62, an elastic layer 63, and a shaft 64. That is, the pressure roller 60 has the elastic layer 63 formed on the shaft 64, the adhesive layer 62 formed on the elastic layer 63, and the surface layer 61 formed on the adhesive layer 62. An adhesive layer may be provided between the shaft 64 and the elastic layer 63.

[0055] In this example, the surface layer 61 is composed of PFA. The thickness of the surface layer 61 is, for example, 30 [μm]. The surface layer 61 slides against the recording medium P and the fixing belt 53. The thickness of the surface layer 61 is desirably large enough to follow the deformation of the elastic layer 63, similar to the surface layer 54 of the fixing belt 53. On the other hand, if the thickness of the surface layer 61 is too small, wrinkles will occur in the surface layer 61 due to sliding with the fixing belt 53 or the recording medium P, so the thickness of the surface layer 61 is desirably 15 to 50 [μm]. In addition, the surface layer 61 is desirably heat-resistant enough to withstand the fixing temperature and has a releasing property that makes it difficult for the toner remaining on the fixing belt 53 and paper powder derived from the recording medium P to stick to it, and is desirably made of a fluorine-substituted material. The material of the surface layer 61 is not limited to the exemplified material, and the thickness of the surface layer 61 is not limited to the exemplified thickness.

[0056] In this example, the adhesive layer 62 is composed of a silicone adhesive that has sufficient adhesive strength, is added with a conductive material, and can withstand the fixing temperature. The adhesive layer 62 bonds the elastic layer 63 and the surface layer 61 to suppress peeling of the surface layer 61 from the elastic layer 63 and the occurrence of wrinkles. Since the adhesive layer 62 is conductive, it suppresses, for example, accumulation of electric charge on the pressure roller 60 during continuous printing, and electrostatic adhesion of paper powder, etc. In this example, the adhesive layer 62 is added with a conductive material, but the present invention is not limited to this, and the conductive material may not be added. The material of the adhesive layer 62 is not limited to the exemplified material.

[0057] In this example, the elastic layer 63 is composed of a silicone sponge having foamed cells to which a conductive material is added. The thickness of the elastic layer 63 is, for example, 4 [mm]. Since the elastic layer 63 is conductive, for example, in continuous printing, the charge on the pressure roller 60 is accumulated, and paper powder and the like are prevented from electrostatically adhering. It is desirable that the elastic layer 63 has a rubber hardness and thickness capable of forming the nip portion N. It is also desirable that the elastic layer 63 has a heat storage property so as not to lose the amount of heat transferred from the fixing belt 53 to the image and the recording medium P. It is also preferable that the cell diameter of the foamed cells is small so that no nip marks remain in the pressurized nip portion N, and specifically, it is preferable that the average cell diameter of the foamed cells is 20 to 250 [μm]. In this example, the average cell diameter is 100 [μm]. The average cell diameter was measured by cutting the silicone sponge with a razor or the like, observing it with a CCD (Charged-coupled devices) microscope, measuring the cell diameters of 10 pieces within the observation viewing angle, and averaging these values ​​to obtain the measured value. In this example, a conductive material is added to the elastic layer 63, but this is not limited thereto, and the elastic layer 63 may not have a conductive material added thereto. In addition, the elastic layer 63 includes a silicone sponge, but this is not limited thereto, and other materials may be included. The elastic layer 63 may include, for example, solid rubber. The thickness of the elastic layer 63 is not limited to the thickness shown in the example.

[0058] The shaft 64 is a pressure-resistant member that is not deformed by the fixing pressure, and is configured to include, for example, solid stainless steel (SUS304). In this example, the shaft 64 includes SUS304, but is not limited to this, and may instead include other materials. In this example, a solid shaft is used, but is not limited to this, and instead, for example, a hollow shaft may be used.

[0059] [8. Operation of image forming device] In this configuration, the image forming apparatus 1 forms an image on the recording medium P as follows. That is, when the image forming apparatus 1 receives print data from a host device, it rotates the photoconductor drum 12 of the developing unit 11 to perform an image forming process.

[0060] In the image forming apparatus 1, the photoconductor drum 12, the surface of which has been charged in the developing unit 11, is selectively irradiated with light from the exposure unit 17, thereby forming an electrostatic latent image on the surface of the photoconductor drum 12. Then, an image is formed on the photoconductor drum 12 in accordance with the electrostatic latent image.

[0061] The image forming apparatus 1 transmits power from a hopping motor (not shown) to rotate the hopping roller 4, and feeds the recording medium P toward the pair of registration rollers 5. The pair of registration rollers 5 transport the recording medium P toward the image forming unit 10. At that time, the front edge of the recording medium P is abutted against the pair of registration rollers 5, so that skew of the recording medium P is corrected.

[0062] Thereafter, the image forming apparatus 1 rotates the transfer belt 19 in the image forming section 10 to transport the recording medium P toward the fixing device 30. At that time, the recording medium P passes between the photoconductor drum 12 and the transfer roller 22.

[0063] In the image forming apparatus 1, when an image is formed on the surface of the photoreceptor drum 12, a transfer process is performed by the transfer belt unit 18. At that time, in the transfer belt unit 18, the transfer roller 22 attracts the image formed on the surface of the photoreceptor drum 12 while the transfer belt 19 conveys the recording medium P. As a result, the image is transferred from the photoreceptor drum 12 to the recording medium P.

[0064] When the image is transferred from the photoreceptor drum 12 to the recording medium P, the image forming apparatus 1 transports the recording medium P to the fixing device 30. When the recording medium P is transported, the fixing device 30 performs a fixing process. At that time, the fixing device 30 applies heat and pressure to the image transferred to the surface of the recording medium P, melting the image and fixing it to the recording medium P.

[0065] When the image is fixed onto the recording medium P, the image forming apparatus 1 conveys the recording medium P towards the stacker 9 and discharges the recording medium P onto the stacker 9.

[0066] [9. Behavior of heat diffusion material during fixing operation] Next, the behavior of the heat diffusion member 50 during the fixing operation when the recording medium P onto which the image has been transferred is transported from the image forming section 10 toward the fixing device 30 will be described.

[0067] When the fixing device 30 performs a fixing operation, the drive gear 35 transmits the power from the circular belt motor to the pressure roller 60. At this time, the levers 33L and 33R are released from the lever fixing member in response to the operation of the drive gear 35, so that the levers 33L and 33R rotate in the D1 direction (FIG. 4) around the rotation fulcrums 34L and 34R, respectively. Therefore, the fixing belt unit 40 is pressed against the pressure roller 60, so that a nip portion N is formed between the fixing belt unit 40 and the pressure roller 60. In this example, the length of the nip portion N in the longitudinal direction (left-right direction) is 227 mm, and the length of the nip portion N in the lateral direction (front-rear direction) perpendicular to the longitudinal direction is 8 to 11 mm. The load applied to the fixing belt unit 40 is 33 to 39 kg for the entire nip portion N, for example, 36 kg. The nip pressure for a load of 36 kg is 1.32 to 2.15 kg / cm 2 ].

[0068] The pressure roller 60 rotates by the power transmitted from the circular belt motor. The fixing belt 53 rotates with the pressure roller 60 in response to the rotation of the pressure roller 60. As a result, in the fixing belt unit 40, the inner circumferential surface 56S of the fixing belt 53 slides on the sliding surface SF of the sliding member 52 of the heat diffusion member 50 via the sliding grease GR. At this time, in the fixing belt unit 40, the heat diffusion member 50 is pressed against the heater 44. In addition, in the fixing operation, an electric wire (not shown) flows a current supplied from an external power source to each heat generating portion, so that the heater 44 generates heat. The heat generated by the heater 44 is transmitted to the heat diffusion member 50 via the thermal conductive grease, and then transmitted to the fixing belt 53 via the sliding grease GR. When the recording medium P passes through the nip portion N, the image transferred onto the recording medium P is subjected to heat transmitted from the fixing belt 53 and pressure from the nip portion N. As a result, the image is fixed onto the recording medium P.

[0069] [10. Consideration of heat diffusion materials] The heat diffusion member 50 was examined using the image forming apparatus 1 and the fixing device 30 having the above-mentioned configuration. In this examination, as shown in FIG. 8, the sliding member 52 was formed of thermally conductive filler particles 52F and binder resin 52B, and samples A, B, C, D, E, and F of the heat diffusion member 50 were prepared, each of which has a different blending ratio (i.e., graphite weight blending ratio) of the thermally conductive filler particles 52F contained in the sliding member 52. The thermal diffusivity in the thickness direction of each heat diffusion member 50 and the arithmetic mean roughness Ra of the sliding surface SF of the sliding member 52 in the heat diffusion member 50 were measured. The thickness of the heat diffusion member 50 in this embodiment was 490 [μm] for the base material 51, 10 [μm] for the sliding member 52, and 500 [μm] for the entire heat diffusion member 50.

[0070] [10-1. Measurement of graphite weight ratio] The graphite weight blending ratio in the present invention is determined from the weight loss amount in a thermogravimetric differential thermal analysis (TG-DTA measurement) of the sliding member 52. In the TG-DTA measurement, a thermogravimetric differential thermal analyzer TG / DTA 6220 (manufactured by Hitachi High-Tech Corporation) was used. The measurement conditions were as follows.

[0071] Measurement conditions: Compliant with JISK6226-2:2003 (Table TB1 in Figure 12) Measurement sample weight: 5 mg

[0072] Here, dry air is generally air from which water vapor has been removed, and its oxygen concentration is considered to be 20.9%.

[0073] The weight loss in the measurement steps 1 and 2 in Table TB1 is due to the thermal decomposition of the binder resin 52B in a nitrogen atmosphere. The weight loss in the subsequent measurement step 3 is due to the combustion of the carbon components in an oxygen atmosphere. In this measurement step 3, the weight loss occurring from 400[°C] to 600[°C] is due to the combustion of the carbon components of the thermally decomposed binder resin 52B, and the weight loss occurring from 600[°C] to 700[°C] is due to the combustion of graphite alone. For this reason, the graphite weight is the weight loss amount due to the combustion from 600[°C] to 700[°C] in an air atmosphere after the thermal decomposition in a nitrogen atmosphere, and the ratio of the graphite weight in the measured sample weight is the graphite weight blending ratio in the present invention.

[0074] [10-2. Measurement of thermal diffusivity] In the present invention, the thermal diffusivity in the thickness direction was used as an index of thermal conductivity. In this measurement, the thermal diffusivity of the heat diffusion member 50 was measured using a Thermowave Analyzer TA35 (manufactured by Bethel Corporation). The measurement conditions were as follows.

[0075] Detector: InSb Surface treatment: Both sides of the sample are blackened with graphite spray (irradiation side, detector side) Heating light: Semiconductor laser (wavelength 808[nm]) Measurement atmosphere: Air atmosphere, 25[℃]

[0076] [10-3. Roughness measurement] In this measurement, the arithmetic mean roughness Ra defined in JIS B0601:2013 was measured as an index of roughness. In this measurement, the roughness was measured using a Surfcorder SEF3500 (manufactured by Kosaka Laboratory Co., Ltd.). The measurement conditions are as follows:

[0077] Measurement direction: perpendicular to the paper feed direction Evaluation length: 4 mm ·Measurement speed: 0.5[mm / s] Cutoff value: 0.8 [mm] The roughness was measured at three points on the heat diffusion member 50, and the average value was taken as the arithmetic mean roughness Ra of the sample.

[0078] [10-4. Measurement of the fixing limit temperature] Further, in the present invention, the fixing limit temperature was measured when each of the samples A to F of the heat diffusion member 50 was used.

[0079] The fixing limit temperature is the lower limit of the surface temperature of the fixing belt 53 at which the fixing rate is 80% or more. The fixing rate is calculated by applying mending tape (manufactured by 3M) to the fixed image, moving a 5 cm wide, 500 g cylindrical weight back and forth, and then slowly peeling it off. The image density before and after this is measured with a reflection densitometer, and calculated from the following formula. Fixation rate [%] = (image density after tape removal / image density before tape removal) x 100

[0080] [10-5. Evaluation of printed images] Furthermore, in the present invention, the printed images when the heat diffusion members 50, Samples A to F, were used were evaluated.

[0081] The printed image was evaluated for the presence or absence of vertical streak-like image defects in 100% solid printing over the entire surface. When the surface roughness Ra becomes large and the sliding grease GR is not uniformly distributed between the fixing belt 53 and the heat diffusion member 50 but is biased to one area, the temperature of the surface of the fixing belt 53 becomes uneven due to differences in thermal conductivity, and vertical streaks appear as steps with different gloss. For this reason, vertical streak-like image defects are used as an evaluation item. The image was evaluated for the presence or absence of vertical streaks with a width of 1 mm or more in the printed image.

[0082] [10-6. Print image judgment results] The graphite weight blending ratio, thermal diffusivity, arithmetic mean roughness Ra, reduction in the fixing limit temperature, printed image evaluation results (presence or absence of vertical streaks), and improvement in fixing property for samples A to E of the heat diffusion member 50 used in the present invention are shown in Table TB2 in Fig. 13. For the presence or absence of vertical streaks, the symbol "o" is recorded when no vertical streaks are present, and the symbol "x" is recorded when vertical streaks are present. For the improvement in fixing property, the symbol "x" is recorded when the graphite weight blending ratio is 0 [wt%], and the symbol "o" is recorded when the fixing limit temperature is lower than when the graphite weight blending ratio is 0 [wt%].

[0083] From the results of Table TB2, it was found that the greater the graphite weight blending ratio, the more the thermal diffusivity in the thickness direction of heat diffusion member 50 improves, and the fixing limit temperature can be reduced. This is thought to be because the addition of graphite, which is thermally conductive filler particle 52F, improves the thermal conductivity of sliding member 52, allowing heat from heating member 70 to be quickly transferred to the toner on the paper surface via fixing belt 53, eliminating the need to heat fixing belt 53 excessively.

[0084] Here, if the graphite weight ratio is greater than 49 [wt%], the ratio of binder resin 52B in sliding member 52 is too small, so sliding member 52 does not adhere to substrate 51 and peels off, making it impossible to form a sliding layer, and this leads to a manufacturing limit. Therefore, if the graphite weight ratio is 49 [wt%] or less, sliding member 52 adheres to substrate 51 and can form a sliding layer.

[0085] On the other hand, it was found that the sample with a graphite weight ratio of 49 [wt%] had vertical stripe-like image defects on the printed image. This is believed to be because the apex of the graphite particle and the inner peripheral surface 56S of the fixing belt 53 come into localized contact with each other, making it difficult for the intervening sliding grease GR to spread evenly in the surface direction, resulting in localized areas with a large amount of grease and areas with a small amount of grease during sliding. Since the surface roughness of the sliding member 52 increases as the graphite weight ratio increases, even if the sliding member 52 with a graphite weight ratio exceeding 49 [wt%] can adhere to the substrate 51, it is believed that the sliding grease GR will be unevenly distributed and vertical stripe-like image defects will occur, as in the case of a graphite weight ratio of 49 [wt%].

[0086] Furthermore, it was found that samples with a graphite weight ratio of 34 wt% or less did not produce vertical streak-like image defects in printed images. For this reason, it is believed that samples with a graphite weight ratio of less than a specified value between 34 wt% and 49 wt% do not produce vertical streak-like image defects in printed images.

[0087] Thus, it was found that the fixing limit temperature can be reduced by adding graphite to sliding member 52. It was also found that image defects can be suppressed if the graphite weight blending ratio is 34 [wt %] or less.

[0088] [10-7. Measurement of wear depth of sliding components] A side effect of adding graphite to sliding member 52 is that sliding member 52 becomes more susceptible to wear, resulting in exposure of substrate 51. When substrate 51 is exposed, the sliding properties deteriorate, which increases the likelihood of scratching inner circumferential surface 56S of fixing belt 53, causing breakage of fixing belt 53. Therefore, by deriving a relationship between the amount of wear and the graphite blending ratio, and having sliding member 52 with a film thickness thicker than the amount of wear, damage to fixing belt 53 caused by exposure of substrate 51 during endurance testing of the actual machine can be suppressed.

[0089] In this measurement, a load-varying friction and wear test system HHS2000 (manufactured by Shinto Scientific Co., Ltd.) was used to measure the wear depth of the sliding member 52 by a friction and wear test using samples A to E in Table TB2, which have different graphite weight blend ratios. The measurement conditions were as follows.

[0090] Probe: SUS304 stainless steel ball φ2 [mm] ·Load: 150[g] -Sliding speed: 20 [mm / s] Sliding distance: 10m (10mm x 500 round trips) -Sliding direction: Paper feed direction

[0091] In this embodiment, the product of the load and the sliding distance in the friction wear test is equal to the product of the nip pressure and the sliding (traveling) distance of the fixing belt 53 when printing 60k sheets of A4 paper fed vertically in the actual machine, and the wear depth of the sliding member 52 during durability testing in the actual machine can be obtained. The pressure and sliding distance in the friction wear test and when printing 60k sheets of A4 paper fed vertically in the actual machine are shown in Table TB3 of FIG. 14. In this friction wear test, the sliding distance was set to 60k sheets of A4 paper fed vertically. In contrast, the life of the fixing device 30 is 50k sheets of A4 paper fed vertically. Therefore, the sliding distance in the friction wear test exceeded the life of the fixing device 30, and this is the test result when a margin was taken.

[0092] [10-8. Relationship between graphite weight ratio and film thickness of sliding material] The relationship between the graphite weight blending ratio and the wear depth for samples A to E of the heat diffusion member 50 used in the present invention is shown in Table TB4 of FIG. 15 and in the graph of FIG.

[0093] If the film thickness of sliding member 52 is thicker than the wear depth corresponding to the graphite weight blending ratio, breakage of fixing belt 53 due to exposure of substrate 51 can be suppressed. From the results of Table TB4, it was found that the wear depth increases as the graphite weight blending ratio increases, and when an approximation line is drawn in FIG. 16, it is found that, when the graphite weight blending ratio is x and the wear depth is y, the relationship y=0.198x is satisfied. From this, when the film thickness of sliding member 52 is t [μm] and the graphite weight blending ratio in sliding member 52 is Rw [wt%], breakage of fixing belt 53 can be suppressed by satisfying the relationship t>0.198Rw.

[0094] [10-9. Relationship between graphite volume ratio and film thickness of sliding material] In addition, the weight mixture ratio Rw is used as the graphite mixture ratio, but it is not limited thereto and the volume mixture ratio Rv may be used. In that case, the relationship between the film thickness and the graphite volume mixture ratio can be obtained by converting the weight mixture ratio into the volume mixture ratio as follows.

[0095] The weight of the graphite is A [g], the weight of the entire sliding member 52 is B [g], and the density of the graphite is α [g / cm 3 ], and the density of the binder resin 52B is β [g / cm 3 ], the weight blend ratio of graphite Rw [wt%] is expressed by the following formula (1).

[0096]

number

[0097] Equation (2) is derived from equation (1).

[0098]

number

[0099] Next, the volumetric blending ratio of graphite Rv [vol%] is expressed by the following formula (3).

[0100]

number

[0101] Substituting equation (2) into equation (3), we obtain the following equation (4).

[0102]

number

[0103] Furthermore, by moving Rw to the left side of equation (4), we obtain equation (5).

[0104]

number

[0105] Thus, by substituting formula (5) into the relational expression between the film thickness of slide member 52 and the graphite weight mixture ratio, the relationship between the film thickness of slide member 52 and the graphite volume mixture ratio can be derived.

[0106] That is, the film thickness of the sliding member 52 is t [μm], the volumetric blending ratio of graphite in the sliding member 52 is Rv [vol%], and the density of graphite is α [g / cm 3 ], and the density of the binder resin 52B is β [g / cm 3 ], the relationship of the following formula (6) is established, so that breakage of fixing belt 53 can be suppressed.

[0107]

number

[0108] The density of the graphite in the sliding member 52 used in the present invention is 2.2 [g / cm 3 ], and the density of the binder resin 52B is 1.4 [g / cm 3 The relationship between the graphite volumetric blending ratio and the wear depth for samples A to E of the heat diffusion member 50 is shown in table TB4 of FIG. 15 and in the graph of FIG.

[0109] If the film thickness of sliding member 52 is thicker than the wear depth corresponding to the graphite volumetric blending ratio, breakage of fixing belt 53 due to exposure of substrate 51 can be suppressed. From the results of Table TB4, it can be seen that, as with the graphite weight blending ratio, the wear depth increases as the graphite volumetric blending ratio increases. To draw the approximate curve in FIG. 17, the right side of the above-mentioned equation (5) can be substituted for x in the approximate straight line y=0.198x drawn in FIG. 16, and it was found that the relationship y=43.56x / (0.8x+140) holds when the graphite volumetric blending ratio is x and the wear depth is y. In this case, the density of the graphite in sliding member 52 used in the present invention is set to 2.2 [g / cm 3 ], and the density of the binder resin 52B is 1.44 [g / cm 3 From this, when the film thickness of sliding member 52 is t [μm] and the volumetric blending ratio of graphite in sliding member 52 is Rv [vol %], the relationship t>43.56x / (0.8x+140) is established, and therefore, breakage of fixing belt 53 can be suppressed.

[0110] [10-10. Thermal diffusivity, surface roughness, limit temperature for fixing, presence or absence of vertical streaks and fixing ability in relation to the volumetric ratio of graphite] 13, in addition to the graphite weight blending ratios of Samples A to E of heat diffusion member 50, the graphite volume blending ratios are also shown. The results of Table TB2 reveal that, similarly to the graphite weight blending ratio, the larger the graphite volume blending ratio, the more improved the thermal diffusivity in the thickness direction of heat diffusion member 50 is, and the more the fixing limit temperature can be reduced.

[0111] Here, if the graphite volumetric ratio is greater than 38 vol%, the ratio of binder resin 52B in sliding member 52 is too small, so sliding member 52 does not adhere to substrate 51 and peels off, making it impossible to form a sliding layer, which is a manufacturing limit. Therefore, if the graphite volumetric ratio is 38 vol% or less, sliding member 52 adheres to substrate 51 and can form a sliding layer.

[0112] On the other hand, it was found that a vertical streak-like image defect occurred in the printed image in the sample with a graphite volumetric ratio of 38 [vol%]. Since the surface roughness of heat diffusion member 50 increases as the graphite volumetric ratio increases, even if sliding member 52 with a graphite volumetric ratio exceeding 38 [vol%] can adhere closely to substrate 51, it is considered that sliding grease GR will be unevenly distributed and vertical streak-like image defect will occur, as in the case of a graphite volumetric ratio of 38 [vol%].

[0113] Furthermore, it was found that samples with a graphite volumetric ratio of 25 vol% or less did not produce vertical streak-like image defects in printed images. For this reason, it is believed that samples with a graphite volumetric ratio of less than a specified value between 25 vol% and 38 vol% do not produce vertical streak-like image defects in printed images.

[0114] Thus, it was found that the fixing limit temperature can be reduced by adding graphite to sliding member 52. It was also found that image defects can be suppressed if the graphite volumetric blending ratio is 25 vol % or less.

[0115] [11. Effects, etc.] In the above-described configuration, the fixing device 30 of the image forming apparatus 1 is configured such that at least the binder resin 52B and the thermally conductive filler particles 52F are contained in the sliding member 52 provided on the facing surface 51B facing the inner circumferential surface 56S of the fixing belt 53 in the heating member 70 forming the nip portion N. Therefore, the fixing device 30 can improve the thermal diffusivity in the thickness direction of the heat diffusion member 50 by the thermally conductive filler particles 52F having higher thermal conductivity than the binder resin 52B, thereby reducing the fixing limit temperature.

[0116] This allows the fixing device 30 to easily transfer heat from the heater 44 to the fixing belt 53, thereby reducing the power consumption of the heater 44. Furthermore, the fixing device 30 can increase the printing speed by reducing the fixing limit temperature.

[0117] Furthermore, when the recording medium P is passed through the nip portion N, the recording medium P loses heat during the first revolution of the fixing belt 53 in the fixing device 30, but because heat can be easily transferred from the heater 44 to the fixing belt 53, the fixing belt 53 can be quickly warmed up before the second revolution of the fixing belt 53. Therefore, the fixing device 30 can ensure the fixing temperature for a medium such as thick paper that easily loses heat when the medium passes through, so that printing can be done at the same printing speed on both thin paper and thick paper, improving media compatibility.

[0118] Specifically, in the fixing device 30, the graphite weight blending ratio is set to 11 wt % or more (that is, the graphite volume blending ratio is set to 8 vol % or more).

[0119] Here, graphite, which is a carbon material, is brittle and softer than fixing belt 53 and is easily abraded, so that it can reduce the abrasion susceptibility to inner surface 56S of fixing belt 53 sliding against sliding member 52, compared to other inorganic heat transfer materials.

[0120] However, as the amount of graphite added to the sliding member 52 increases, the thermal diffusivity improves, but the surface roughness of the sliding member 52 increases, causing the sliding grease GR to become unevenly distributed on the sliding surface SF, resulting in printing defects such as vertical streak-like image defects.

[0121] In contrast, the fixing device 30 has a graphite weight mixture ratio of 49 wt% or less, and more preferably a graphite weight mixture ratio of 34 wt% or less. In terms of a graphite volume mixture ratio, the fixing device 30 has a graphite volume mixture ratio of 38 vol% or less, and more preferably a graphite volume mixture ratio of 25 vol% or less. As a result, the fixing device 30 can reduce the surface roughness of the sliding member 52 and reduce the uneven distribution of the sliding grease GR on the sliding surface SF. As a result, the fixing device 30 can reduce the occurrence of vertical streaks and maintain print quality.

[0122] Furthermore, a side effect of adding graphite to sliding member 52 is that sliding member 52 is more susceptible to wear, exposing substrate 51. When substrate 51 is exposed, the sliding properties deteriorate, which increases the likelihood of scratching inner circumferential surface 56S of fixing belt 53, causing breakage of fixing belt 53.

[0123] In contrast, the fixing device 30 is designed to satisfy the relationship t>0.198Rw, where t [μm] is the thickness of the sliding member 52 and Rw [wt %] is the weight ratio of graphite in the sliding member 52. When this is expressed in terms of the volumetric graphite ratio, the thickness of the sliding member 52 is t [μm], Rv [vol %] is the volumetric graphite ratio in the sliding member 52, and α [g / cm 3 ], and the density of the binder resin 52B is β [g / cm 3 ], the fixing device 30 is designed to satisfy the above-mentioned formula (6).

[0124] Therefore, by providing sliding member 52 having a thickness thicker than the wear amount of sliding member 52 relative to the graphite compounding ratio, fixing device 30 can suppress damage to fixing belt 53 caused by exposure of substrate 51 during actual machine endurance testing. Therefore, fixing device 30 can ensure good fixing performance while avoiding wear and scratches on inner circumferential surface 56S of fixing belt 53. In this way, by specifying the thickness of sliding member 52 relative to the graphite compounding ratio, fixing device 30 can provide sliding member 52 with sufficient durability, maintain sliding member 52 throughout the life of the device, and suppress damage to fixing belt 53.

[0125] In this manner, the fixing device 30 contains the thermally conductive filler particles 52F in the sliding member 52 at a predetermined blending ratio or less, and the film thickness of the sliding member 52 is set to a sufficient thickness according to the blending ratio of the thermally conductive filler particles 52F. This enables the fixing device 30 to improve the efficiency of heat transfer from the heating member 70 and to improve the durability of the sliding member 52, thereby achieving both an improvement in the thermal transfer efficiency of the heat diffusion member 50 and an improvement in the durability of the sliding member 52.

[0126] According to the above-mentioned configuration, the fixing device 30 of the image forming apparatus 1 includes the fixing belt 53, the heating member 70 provided on the inner surface 56S side of the fixing belt 53, the sliding member 52 provided on an opposing surface 51B of the heating member 70 that faces the inner surface 56S, and the pressure roller 60 provided on the outer surface side of the fixing belt 53 and forming a nip portion N as a nip area between the sliding member 52 and the fixing belt 53 via the pressure roller 60, and the sliding member 52 contains at least a binder resin 52B as a resin and thermally conductive filler particles 52F as carbon.

[0127] The fixing device 30 of the image forming apparatus 1 includes a fixing belt 53, a heating member 70 provided on the inner circumferential surface 56S side of the fixing belt 53, and a sliding member 52 provided on an opposing surface 51B of the heating member 70 facing the inner circumferential surface 56S. The sliding member 52 includes at least a binder resin 52B as a resin and thermally conductive filler particles 52F as a thermally conductive material having a higher thermal conductivity than the binder resin 52B. The weight blending ratio, which is the blending ratio of the thermally conductive filler particles 52F added to the weight ratio of the sliding member 52, is 11 [wt%] or more (i.e., the volume blending ratio, which is the blending ratio of the thermally conductive filler particles 52F added to the volume ratio of the sliding member 52, is 8 [vol%] or more).

[0128] Thus, in the fixing device 30, the thermal conductive filler particles 52F, which have higher thermal conductivity than the binder resin 52B, can improve the thermal diffusivity of the heat diffusion member 50 in the thickness direction, and can reduce the fixing limit temperature.

[0129] [12. Other embodiments] In the above embodiment, the thermally conductive filler particles 52F are described as being made of graphite. The present invention is not limited to this, and the thermally conductive filler particles 52F may be made of carbon black, which is the same carbon material as graphite. In addition, the thermally conductive filler particles 52F may be made of a metal, metal oxide, or metal or metal oxide coated material, such as boron nitride, aluminum oxide, or zinc oxide, as a thermally conductive material having high thermal conductivity. However, when graphite is used for the thermally conductive filler particles 52F, the graphite, which is a carbon material, is brittle and softer than the fixing belt 53 and is easily scraped off, so that the abrasion of the inner peripheral surface 56S of the fixing belt 53 that slides against the sliding member 52 can be reduced.

[0130] In the above-described embodiment, the sliding member 52 is provided on the opposing surface 51B of the heat diffusion member 50. The present invention is not limited to this, and the heat diffusion member 50 may be omitted, and the sliding member 52 may be provided on the surface of the heater 44 that faces the inner circumferential surface 56S of the fixing belt 53. However, when the heat diffusion member 50 is provided, it is possible to reduce temperature unevenness in the longitudinal direction when using the heater 44 to control a plurality of heating elements arranged in the longitudinal direction of the heater 44, and it is also possible to increase the rigidity of the entire heating member 70 compared to the case of the heater 44 alone.

[0131] Furthermore, in the above-described embodiment, the sliding grease GR is applied to the opposing surface 51B of the sliding member 52. The present invention is not limited to this, and the sliding grease GR may be applied to the inner circumferential surface 56S of the fixing belt 53 instead of the opposing surface 51B of the sliding member 52, or the sliding grease GR may be applied to both the opposing surface 51B of the sliding member 52 and the inner circumferential surface 56S of the fixing belt 53. In short, it is only necessary to position the sliding grease GR between the opposing surface 51B of the sliding member 52 and the inner circumferential surface 56S of the fixing belt 53.

[0132] Furthermore, in the above-described embodiment, the present invention has been described as being applied to a so-called direct transfer type image forming apparatus 1 in which a toner image is directly transferred from the photoconductor drum 12 of the developing unit 11 to the recording medium P. However, the present invention is not limited to this, and the present invention may also be applied to an image forming apparatus of a so-called intermediate transfer type (or secondary transfer type) in which a toner image of each color is transferred from the photoconductor drum 12 of the developing unit 11 to an intermediate transfer belt so as to be sequentially superimposed on top of each other, and the toner image is then transferred from this intermediate transfer belt to the recording medium P.

[0133] Furthermore, in the above embodiment, the present invention has been described as being applied to a developer used in a one-component development system, but the present invention is not limited to this, and may be applied to a developer in a two-component development system in which a carrier and a toner are mixed together and friction between the carrier and the toner is used to impart an appropriate amount of charge to the toner.

[0134] Furthermore, in the above-described embodiment, the present invention has been described as being applied to an image forming apparatus 1 having four developing units 11 and forming a color image using toner of four colors. However, the present invention is not limited to this, and the present invention may be applied to an image forming apparatus having three or less or five or more developing units 11 and forming an image using toner of a predetermined number of colors.

[0135] Furthermore, in the above-described embodiment, the present invention has been described as being applied to the image forming apparatus 1, which is a single-function printer. The present invention is not limited to this, and may be applied to image forming apparatuses having various other functions, such as an MFP (Multi Function Peripheral) having the functions of a copier or facsimile machine. The present invention may also be applied to various electronic devices that form images on a recording medium P, such as paper, using a developer by electrophotography.

[0136] Furthermore, the present invention is not limited to the above-mentioned embodiment and other embodiments. That is, the scope of application of the present invention extends to embodiments in which the above-mentioned embodiment and the other embodiments are combined in part or in whole in any manner, or embodiments in which a part is extracted.

[0137] Furthermore, in the above-described embodiment, the fixing device 30 is configured as a fixing device by the fixing belt 53 as a circular belt, the heating member 70 as a heating member, the sliding member 52 as an opposing member, and the pressure roller 60 as a pressure member. However, the present invention is not limited to this, and the fixing device may be configured by a circular belt, a heating member, an opposing member, and a pressure member having various other configurations.

[0138] Furthermore, in the above-described embodiment, the fixing device 30 is configured as a fixing device by the fixing belt 53 as a circular belt, the heating member 70 as a heating member, the sliding member 52 as an opposing member, and the sliding grease GR as a lubricant. However, the present invention is not limited to this, and the fixing device may be configured by a circular belt, a heating member, an opposing member, and a lubricant having various other configurations. [Industrial Applicability]

[0139] The present invention can be used when printing images on special media using an electrophotographic image forming apparatus. [Explanation of symbols]

[0140] 1: image forming apparatus, 2: printer housing, 3: paper feed tray, 4: hopping roller, 5: pair of registration rollers, 6: pair of discharge rollers, 9: stacker, 10: image forming section, 11: development unit, 12: photoconductor drum, 13: charging roller, 14: development roller, 15: cleaning blade, 16: toner storage section, 17: exposure unit, 18: transfer belt unit, 19: transfer belt, 20: drive roller, 21: driven roller, 22: transfer roller, 23: cleaning blade, 30: fixing device, 31L, 31R: side frame, 32L, 32R: spring, 33L, 33R: lever , 34L, 34R...rotation fulcrum, 35...driving gear, 40...fixing belt unit, 41...stay, 42L, 42R...screw, 43...holding member, 44...heater, 48...heat retention plate, 49F, 49B...holding groove, 50...heat diffusion member, 51...base material, 51A...opposite surface, 51B...opposing surface, 52...sliding member, 52B...binder resin, 52F...thermally conductive filler particles, 53...fixing belt, 54, 61...surface layer, 55, 63...elastic layer, 56...base material layer, 56S...inner surface, 60...pressure roller, 62...adhesive layer, 64...shaft, 70...heating member, P...recording medium, GR...sliding grease, SF...sliding surface.

Claims

1. a circular belt having a base layer made of a resin material; a heating member including a heater provided on an inner peripheral surface side of the circular belt; a facing member provided on a facing surface of the heater that faces the base material layer of the inner circumferential surface; a pressing member provided on an outer peripheral surface side of the circular belt and forming a nip region between the pressing member and the opposing member via the circular belt; Equipped with The facing member contains at least resin and carbon, a weight mixture ratio, which is a mixture ratio of the added carbon to the weight ratio of the opposing member, is 11 [wt%] or more and 49 [wt%] or less, The thickness of the opposing member is a [μm]. When the weight blending ratio of the carbon is b [wt %], The following formula (1) is satisfied: a>0.198b...(1) A fixing device comprising:

2. a circular belt having a base layer made of a resin material; a heating member including a heat diffusion member and a heater provided on an inner peripheral surface side of the circular belt; an opposing member provided on an opposing surface of the heat diffusion member that faces the base material layer of the inner circumferential surface; a pressing member provided on an outer peripheral surface side of the circular belt and forming a nip region between the pressing member and the opposing member via the circular belt; Equipped with The facing member contains at least resin and carbon, a weight mixture ratio, which is a mixture ratio of the added carbon to the weight ratio of the opposing member, is 11 [wt%] or more and 49 [wt%] or less, The thickness of the opposing member is a [μm]. When the weight blending ratio of the carbon is b [wt %], The following formula (1) is satisfied: a>0.198b...(1) A fixing device comprising:

3. a lubricant disposed between the circular belt and the opposing member; The weight ratio of the carbon is 34 wt % or less.

3. The fixing device according to claim 1, wherein the fixing member is a fixing member having a fixing surface.

4. a circular belt having a base layer made of a resin material; a heating member including a heater provided on an inner peripheral surface side of the circular belt; a facing member provided on a facing surface of the heater that faces the base material layer of the inner circumferential surface; a pressing member provided on an outer peripheral surface side of the circular belt and forming a nip region between the pressing member and the opposing member via the circular belt; Equipped with The facing member contains at least resin and carbon, a volumetric blending ratio, which is a blending ratio of the added carbon to the volume ratio of the opposing member, is 8 [vol%] or more and 38 [vol%] or less, The thickness of the opposing member is t [μm]. The volumetric blending ratio of the carbon is Rv [vol%], The density of the carbon is α [g / cm ３ ], The density of the resin is β [g / cm ３ ], The following formula (2) is satisfied: A fixing device comprising:

5. a circular belt having a base layer made of a resin material; a heating member including a heat diffusion member and a heater provided on an inner peripheral surface side of the circular belt; an opposing member provided on an opposing surface of the heat diffusion member that faces the base material layer of the inner circumferential surface; a pressing member provided on an outer peripheral surface side of the circular belt and forming a nip region between the pressing member and the opposing member via the circular belt; Equipped with The facing member contains at least resin and carbon, a volumetric blending ratio, which is a blending ratio of the added carbon to the volume ratio of the opposing member, is 8 [vol%] or more and 38 [vol%] or less, The thickness of the opposing member is t [μm]. The volumetric blending ratio of the carbon is Rv [vol%], The density of the carbon is α [g / cm ３ ], The density of the resin is β [g / cm ３ ], The following formula (2) is satisfied: A fixing device comprising:

6. a lubricant disposed between the circular belt and the opposing member; The volumetric blending ratio of the carbon is 25 vol % or less.

6. The fixing device according to claim 4, wherein the fixing member is a fixing member having a fixing roller.

7. a circular belt having a base layer made of a resin material; a heating member including a heater provided on an inner peripheral surface side of the circular belt; a facing member provided on a facing surface of the heater that faces the base material layer of the inner circumferential surface; Equipped with the facing member includes at least a resin and carbon having a thermal conductivity higher than that of the resin, a weight mixture ratio, which is a mixture ratio of the added carbon to the weight ratio of the opposing member, is 11 [wt%] or more and 49 [wt%] or less, The thickness of the opposing member is a [μm]. When the weight blending ratio of the carbon is b [wt %], The following formula (3) is satisfied: a>0.198b...(3) A fixing device comprising:

8. The thermal diffusivity of the opposing member in the thickness direction is 38.0 mm ２ / S] or more 45.4 [mm ２ / S] or less 8. The fixing device according to claim 1, wherein the fixing member is a fixing member having a fixing member.

9. 9. An image forming apparatus comprising the fixing device according to claim 1.

Images