Fixing apparatus, Image forming apparatus

Abstract

The objective is to reduce the frictional force generated between the inner surface of the cylindrical member and the heating element, compared to the case where the inner surface of the cylindrical member and the element placed inside the cylindrical member are in contact with each other on the upstream and downstream sides of the nip portion in the circumferential direction of the cylindrical member. [Solution] The fixing device comprises a cylindrical member that is cylindrical in shape, extends axially, rotates around the cylindrical member, and has grease applied to its inner surface; a heating member that extends axially, contacts the inner surface, generates heat to heat the cylindrical member; and a pressurizing member that is positioned on the opposite side of the heating member across the cylindrical member, forms a nip portion that sandwiches the recording medium between itself and the heating member, and pressurizes the recording medium toward the heating member. The heating member and the pressurizing member are positioned such that, in the circumferential direction of the cylindrical member, at least one of the upstream and downstream sides of the nip portion is in a non-contact state between the inner surface and the member positioned inside the cylindrical member.

Description

Technical Field

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

Background Art

[0002] The fixing device described in Patent Document 1 includes a heating body, a fixing rotating body heated by the heating body, a guide member that guides the fixing rotating body and is included in the fixing rotating body, grease interposed between the fixing rotating body and the guide member, a pressing member that forms a nip portion by pressing against the guide member via the fixing rotating body, and driving means for rotating the pressing member forward and backward. On the downstream side of the paper passage of the guide member, when the pressing member rotates forward, a predetermined gap is generated between the fixing rotating body and the guide member, and when the pressing member rotates backward, the gap is set to be smaller than that during forward rotation, and the execution interval of the reverse rotation drive depends on the number of recording material sheets on which the fixing process has been performed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The fixing device of the image forming apparatus includes a heating member that heats the toner image formed on the recording medium, and a pressing member that presses the recording medium toward the heating member. The heating member has a circumferential cylindrical member and a heat generating member that contacts the inner peripheral surface of the cylindrical member and generates heat to heat the cylindrical member. And a nip portion for sandwiching the recording medium is formed between the heating member and the pressing member.

[0005] Here, the heating element is positioned on the opposite side of the pressurizing element, sandwiching the cylindrical element, and the recording medium, which is held in place at the nip portion, is heated by the heating element via the cylindrical element. On the other hand, grease is applied to the inner circumferential surface of the cylindrical element, and the frictional force between the inner circumferential surface of the cylindrical element and the heating element at the nip portion is reduced by the grease.

[0006] However, in the circumferential direction of the cylindrical member, the inner surface of the cylindrical member and the member positioned inside the cylindrical member may come into contact with the nip portion on both the upstream and downstream sides. By trapping grease in the area where the inner surface and the member come into contact, the grease accumulates in this area, reducing the amount of grease supplied between the heat-generating element and the cylindrical member.

[0007] The object of this disclosure is to reduce the frictional force generated between the inner surface of the cylindrical member and the heating element, compared to the case where the inner surface of the cylindrical member and the element disposed inside the cylindrical member are in contact with each other on the upstream and downstream sides of the nip portion in the circumferential direction of the cylindrical member. [Means for solving the problem]

[0008] A fixing device according to a first aspect of the present disclosure comprises a cylindrical member that is cylindrical, extends in the axial direction, is circumferential, and has grease applied to its inner surface; a heating member that extends in the axial direction, contacts the inner surface, generates heat, and heats the cylindrical member; and a pressurizing member that is positioned on the opposite side of the heating member with respect to the cylindrical member, forms a nip portion that sandwiches a recording medium between itself and the heating member, and pressurizes the recording medium toward the heating member, wherein the heating member and the pressurizing member are positioned such that, in the circumferential direction of the cylindrical member, at least one side upstream and downstream of the nip portion is in a non-contact state between the inner surface and a member positioned inside the cylindrical member.

[0009] A fixing device according to a second aspect of this disclosure is characterized in that, in the fixing device described in the first aspect, the consistency of the grease is 250 or less.

[0010] A fixing device according to a third aspect of this disclosure is characterized in that, in the fixing device described in the first aspect, when the recording medium is held between the nip portion, the inner circumferential surface and a member disposed inside the cylindrical member are in a non-contact state on the upstream side of the nip portion in the circumferential direction of the cylindrical member.

[0011] A fixing device according to a fourth aspect of this disclosure is characterized in that, in the fixing device described in the third aspect, the inner circumferential surface and the member disposed inside the cylindrical member are in a non-contact state both upstream and downstream of the nip portion in the circumferential direction.

[0012] A fixing device according to a fifth aspect of the present disclosure is a fixing device according to the first aspect, characterized in that, in the heating element, the upstream edge in the direction of rotation of the cylindrical member when the recording medium is sandwiched by the nip portion of the heating element is recessed downstream in the direction of rotation at the axial central portion compared to the axial ends.

[0013] A fixing device according to a sixth aspect of this disclosure is characterized in that, in the fixing device described in the fifth aspect, the edge of the heating element is curved, so that the central portion in the axial direction is recessed downstream in the circumferential direction compared to both ends in the axial direction.

[0014] An image forming apparatus according to a seventh aspect of this disclosure is characterized by comprising a forming unit for forming an image on a recording medium, and a fixing device according to any one of claims 1 to 6 for fixing the image formed on the recording medium by the forming unit onto the recording medium. [Effects of the Invention]

[0015] The fixing device according to the first aspect of this disclosure can reduce the frictional force generated between the inner surface of the cylindrical member and the heating element compared to the case where the inner surface of the cylindrical member and the element disposed inside the cylindrical member are in contact with the nip portion upstream and downstream in the circumferential direction of the cylindrical member.

[0016] The fixing device according to the second aspect of this disclosure can reduce the frictional force generated between the inner surface of the cylindrical member and the heating element, even when grease with a consistency of 250 or less is applied to the inner surface of the cylindrical member, compared to the case where the inner surface of the cylindrical member and the element disposed inside the cylindrical member are in contact with each other on the upstream and downstream sides of the nip portion in the circumferential direction of the cylindrical member.

[0017] The fixing device according to the third aspect of this disclosure can reduce the frictional force generated between the inner surface of the cylindrical member and the heating element compared to the case where the inner surface of the cylindrical member and the element disposed inside the cylindrical member are in a non-contact state only downstream of the nip portion in the circumferential direction of the cylindrical member.

[0018] The fixing device according to the fourth aspect of this disclosure can reduce the frictional force generated between the inner surface of the cylindrical member and the heating element compared to a case where the inner surface of the cylindrical member and the element disposed inside the cylindrical member are in a non-contact state on either the upstream or downstream side of the nip portion in the circumferential direction of the cylindrical member.

[0019] The fixing device according to the fifth aspect of this disclosure can reduce the amount of grease that flows outward in the axial direction when it comes into contact with the edge of the heating element, compared to the case where the edge of the heating element extends in the axial direction.

[0020] The fixing device according to the sixth aspect of this disclosure can suppress the accumulation of grease in the axial central part of the heat-generating member compared to the case where the edge is recessed on the downstream side in the circumferential direction due to the bending of the central part in the axial direction.

[0021] The image forming apparatus according to the seventh aspect of this disclosure can suppress uneven image fixing compared to a case in which a fixing device is provided in which the inner circumferential surface of the cylindrical member and a member disposed inside the cylindrical member are in contact with the nip portion on the upstream and downstream sides in the circumferential direction of the cylindrical member. [Brief explanation of the drawing]

[0022] [Figure 1] This is a schematic diagram showing an image forming apparatus according to an embodiment of the present disclosure. [Figure 2] It is a schematic configuration diagram showing an image forming unit provided in an image forming apparatus according to an embodiment of the present disclosure. [Figure 3] It is a configuration diagram showing the whole of a fixing device according to an embodiment of the present disclosure. [Figure 4] It is a plan view showing a heater etc. provided in a fixing device according to an embodiment of the present disclosure. [Figure 5] It is an enlarged view showing a nip portion of a fixing device according to an embodiment of the present disclosure. [Figure 6] It is a configuration diagram showing the whole of a fixing device according to a comparative form with respect to an embodiment of the present disclosure. [[ID=**17**]]

**Mode for Carrying Out the Invention**

[0023] An example of a fixing device and an image forming apparatus according to an embodiment of the present disclosure will be described with reference to FIGS. 1 to 6. Note that an arrow H shown in each figure is in the vertical direction and indicates the up and down direction of the apparatus. An arrow W is orthogonal to the arrow H and is in the horizontal direction and indicates the width direction of the apparatus. An arrow D is orthogonal to the arrows H and W and is in the horizontal direction and indicates the depth direction of the apparatus.

[0024] (**Overall Configuration of Image Forming Apparatus**) As shown in FIG. 1, the image forming apparatus 10 includes a housing 10a in which each component is housed. Inside the housing 10a, a housing portion 12 for housing a sheet-like recording medium P and an image forming portion 14 for forming an image on the recording medium P are provided. Further, inside the housing 10a, a conveyance portion 16 for conveying the recording medium P from the housing portion 12 to the image forming portion 14 is provided.

[0025] 〔**Image Forming Portion 14**〕 As shown in Figure 1, the image forming unit 14 includes image forming units 22Y, 22M, 22C, and 22K (hereinafter referred to as "22Y~22K") that form toner images of yellow (Y), magenta (M), cyan (C), and black (K). In the following description, the Y, M, C, and K at the end of the symbols will be omitted when yellow, magenta, cyan, and black are not specifically distinguished.

[0026] Furthermore, the image forming unit 14 includes an intermediate transfer belt 24 to which the toner images formed by each color image forming unit 22 are transferred. In addition, the image forming unit 14 includes a primary transfer roll 26 that transfers the toner images formed by each color image forming unit 22 to the intermediate transfer belt 24. Furthermore, the image forming unit 14 includes a secondary transfer roll 28 that transfers the toner images transferred to the intermediate transfer belt 24 by the primary transfer roll 26 to the recording medium P.

[0027] Each color image forming unit 22 is positioned above the intermediate transfer belt 24 and is aligned in the width direction. Each image forming unit 22 has an image holder 32 that rotates in the direction of the arrow in the figure, as shown in Figure 2.

[0028] Around the image holder 32, in order from the upstream side in the rotational direction of the image holder 32, are a charging device 23, an exposure device 36, a developing device 38, and a removal device 40. The charging device 23 charges the image holder 32, and the exposure device 36 exposes the charged image holder 32 to form an electrostatic latent image on the image holder 32. Furthermore, the developing device 38 develops the electrostatic latent image formed on the image holder 32 to form a toner image. The removal device 40 comes into contact with the image holder 32 to remove any toner remaining on it. Furthermore, above the exposure device 36 for each color, as shown in Figure 1, there are toner storage sections 39 for each color that contain the toner supplied to the developing device 38.

[0029] The intermediate transfer belt 24 is formed in a triangular shape with its apex facing downwards. On the inner circumference of the intermediate transfer belt 24 are winding rolls 41, 42, 43, 44, and 45 around which the intermediate transfer belt 24 is wound. For example, the intermediate transfer belt 24 is circulated (rotated) in one direction (for example, counterclockwise in Figure 1) while in contact with the image holder 32, as the winding roll 43 is rotated.

[0030] The primary transfer rolls 26 for each color are positioned on opposite sides of the image holder 32, with the intermediate transfer belt 24 in between. The space between the primary transfer rolls 26 and the image holder 32 is designated as the first transfer position where the toner image formed on the image holder 32 is transferred to the intermediate transfer belt 24.

[0031] The secondary transfer roll 28 is positioned on the opposite side of the winding roll 42, with the intermediate transfer belt 24 in between. The space between the secondary transfer roll 28 and the winding roll 42 is designated as the second transfer position where the toner image transferred to the intermediate transfer belt 24 is transferred to the recording medium P.

[0032] The transport unit 16 includes a transport roll 46 that sends the recording medium P stored in the storage unit 12 to the transport path 48. Furthermore, the transport unit 16 includes a plurality of transport rolls 50 that transport the recording medium P to the second transfer position along the transport path 48.

[0033] Furthermore, the transport unit 16 includes a transport roll 52 that transports the recording medium P, on which the toner image has been transferred at the second transfer position, along the transport path 48. In addition, the transport unit 16 includes an discharge roll 54 that discharges the transported recording medium P from the housing 10a. A fuser device 60 is positioned between the transport roll 52 and the discharge roll 54 in the transport path 48. The fuser device 60 will be described in detail later.

[0034] (Operation of the image forming apparatus) Next, the operation of the image forming apparatus 10 will be described. Specifically, the image forming operation in which an image is formed on the recording medium P will be described.

[0035] In the image forming apparatus 10 shown in Figure 1, the recording medium P, which is fed out from the storage unit 12 by the delivery roll 46, is fed to the second transfer position by a plurality of transport rolls 50.

[0036] Meanwhile, in each color image forming unit 22, the image holder 32, which has been charged by the charging device 23 shown in Figure 2, is exposed by the exposure device 36 to form an electrostatic latent image on the image holder 32. Then, the electrostatic latent image is developed by the developing device 38 to form a toner image on the image holder 32.

[0037] The toner images of each color formed by the respective color image forming units 22 are superimposed on the intermediate transfer belt 24 at the first transfer position by the respective color primary transfer rolls 26 to form a color image. Then, the color image formed on the intermediate transfer belt 24 shown in Figure 1 is transferred to the recording medium P, which is transported by the transport roll 50, by the secondary transfer roll 28.

[0038] The recording medium P onto which the toner image has been transferred is transported to the fuser unit 60 by the transport roll 52, and the transferred toner image is fixed by the fuser unit 60. The recording medium P with the fixed toner image is discharged from the housing 10a by the discharge roll 54.

[0039] (Main part configuration) Next, the fixing device 60 according to this embodiment will be described. As shown in Figure 3, the fixing device 60 includes a heating member 62 for heating the recording medium P and a pressurizing member 82 for pressurizing the recording medium P toward the heating member 62. Specifically, the heating member 62 and the pressurizing member 82 are opposite each other in the vertical direction, with the heating member 62 positioned above the pressurizing member 82.

[0040] [Heating element 62] As shown in Figure 3, the heating element 62 comprises a cylindrical fixing belt 64 and a heater 68 positioned inside the fixing belt 64. The heater 68 generates heat when a voltage is applied to it, thereby heating the fixing belt 64. The heating element 62 also comprises a support pad 70 that supports the heater 68 and a support frame 74 that supports the support pad 70. The fixing belt 64 is an example of a cylindrical member. The heater 68 is an example of a heat generating element.

[0041] - Fixing belt 64, heater 68 - As shown in Figure 3, the fixing belt 64 is cylindrical, extends in the depth direction, and rotates counterclockwise with its inner circumferential surface 64a in contact with the heater 68. The depth direction is an example of the axial direction.

[0042] Furthermore, grease G is applied to the inner circumferential surface 64a of the fixing belt 64. In this embodiment, as an example, the consistency of the grease G, as defined in JIS K 2220, is 250 or less. In other words, the grease G applied to the inner circumferential surface 64a of the fixing belt 64 is harder than grease G with a consistency greater than 250. The viscosity of the grease G at 200°C, as measured by a rheometer, is 50 to 1500 Pa·s, preferably 80 to 1000 Pa·s, and more preferably 100 to 500 Pa·s. The weight loss rate of the grease G when heated and stored at 230°C for 336 hours is 0 to 20 wt%, preferably 0 to 15 wt%, and more preferably 0 to 10 wt%.

[0043] Grease G is composed of a base oil combined with a thickener. The base oil of Grease G is a silicone oil, preferably dimethyl silicone oil, methylphenyl silicone oil, or diphenyl silicone oil, and may have partially introduced side chains. The weight-average molecular weight Mw of the silicone oil is 10,000 to 100,000, preferably 10,000 to 60,000, and more preferably 15,000 to 40,000.

[0044] Furthermore, in Grease G, one or more inorganic materials such as melamine cyanurate, boron nitride, carbon black, silica, graphite, molybdenum disulfide, zinc stearate, and tungsten disulfide are selected as components of the thickener. The average particle size (D50v) of the thickener is 0.01 to 15 μm, preferably 0.1 to 10 μm, and more preferably 0.1 to 5 μm. The weight ratio of base oil in the components of Grease G is 40 to 95 wt%, preferably 50 to 85 wt%, and more preferably 50 to 75 wt%.

[0045] The viscosity of grease G is measured by the following method: The grease sample is placed between parallel plates with a diameter of 40 mm, and the viscosity is measured using a dynamic viscoelasticity measuring device (rheometer ARES-G2, manufactured by T.A. Instruments Inc.) with a gap of 1 mm and an angular velocity of 0.1 rad / s, while the temperature is raised from 40°C to 200°C at a rate of 6°C / min.

[0046] The weight loss rate of grease G is calculated by taking a 5g sample of grease in an aluminum cup and heating it in an oven at 230°C for 336 hours, then comparing the weight before and after heating.

[0047] The average particle size of the thickener is measured by the following method: A 2g sample of grease is placed on filter paper, and 30g of THF (tetrahydrofuran) is added and filtered by suction to separate the base oil and the thickener. The separated thickener is dispersed in water, and the particle size distribution is measured using a particle size analyzer (LS13320, Beckman Coulter).

[0048] The heater 68 is a so-called planar heater, and when viewed from the depth direction, it is rectangular in shape and extends in the width direction along the conveyor path 48, and extends in the depth direction. The heater 68 is in contact with the inner circumferential surface 64a of the anchoring belt 64 at a contact surface 68b. Furthermore, the upstream edge 68a of the heater 68 in the circumferential direction of the anchoring belt 64 is open to the internal space of the anchoring belt 64. Moreover, as shown in Figure 4, the upstream edge 68a is curved such that the central part in the depth direction is recessed downstream in the circumferential direction of the anchoring belt 64 compared to both ends in the depth direction.

[0049] The portion of the fixing belt 64 that contacts the heater 68 is straight when viewed from the depth direction and follows the transport path 48. When voltage is applied to the heater 68, it generates heat throughout the entire area in contact with the fixing belt 64, thereby heating the fixing belt 64.

[0050] -Support pad 70, support frame 74- The support pad 70 is made of a resin material and, as shown in Figure 3, is positioned on the opposite side of the fixing belt 64 from the portion that contacts the heater 68, with the heater 68 in between. Furthermore, the width of the support pad 70 is the same as the width of the heater 68, and the support pad 70 is placed on top of the heater 68. The support pad 70 then supports the heater 68 in the depth direction.

[0051] The support frame 74 is formed by bending sheet metal and has a U-shaped cross-section with the support pad 70 side open when viewed from the depth direction. The support frame 74 supports the support pad 70 by sandwiching it from the width direction with portions of the support frame 74 at both ends. This support frame 74 extends in the depth direction and supports the support pad 70 throughout the depth direction. Furthermore, portions of the support frame 74 at both ends in the depth direction protrude from the anchoring belt 64, and these protruding portions are supported by a frame member (not shown).

[0052] [Pressurizing member 82] The pressurizing member 82 is roll-shaped and, as shown in Figure 3, is positioned on the opposite side of the conveying path 48 from the heating member 62. The pressurizing member 82 also sandwiches the fixing belt 64 between the heater 68.

[0053] In this configuration, the pressurizing member 82 rotates in the direction of the arrow (clockwise) in the figure, driven by a motor (not shown). Furthermore, the fixing belt 64 rotates in the direction of the arrow (counterclockwise) in accordance with the rotation of the pressurizing member 82.

[0054] Here, the pressurizing member 82 forms a nip portion N that sandwiches the recording medium P between itself and the heating member 62, and pressurizes the recording medium P toward the heating member 62 at this nip portion N. The heating member 62 and the pressurizing member 82 are positioned such that, in the circumferential direction of the fixing belt 64 (hereinafter referred to as the "belt circumferential direction"), the inner circumferential surface 64a and the members positioned inside the fixing belt 64 are in a non-contact state with respect to the nip portion N on the upstream and downstream sides.

[0055] Here, the nip portion N is the area where the recording medium P is pressurized toward the heating member 62 by the pressurizing member 82, as described above. The range of this nip portion N can be confirmed by placing a surface pressure measuring sheet between the heating member 62 and the pressurizing member 82. The nip portion N is the range where pressure is generated as measured by the surface pressure measuring sheet.

[0056] Furthermore, let L1 be the length of the nip portion N in the belt circumference direction. Then, the upstream side of the nip portion in the belt circumference direction is the range E1 from the upstream end P1 of the nip portion N in the belt circumference direction to the upstream side of the belt circumference direction up to length L1, as shown in Figure 5. Furthermore, the downstream side of the nip portion in the belt circumference direction is the range E2 from the downstream end P2 of the nip portion N in the belt circumference direction to the downstream side of the belt circumference direction up to length L1.

[0057] (Function of the main components) Next, the operation of the fixing device 60 will be explained together with the fixing device 160 in the comparative configuration. First, the configuration of the fixing device 160 in the comparative configuration will be explained, mainly focusing on the parts that differ from the fixing device 60 in this embodiment.

[0058] [Configuration of the fixing device 160] As shown in Figure 6, the fixing device 160 includes a heating member 162 and a pressurizing member 82. The heating member 162 includes a cylindrical fixing belt 64, a heater 168, a support pad 170, and a support frame 74.

[0059] The heater 168 is rectangular in shape and extends in the width direction when viewed from the depth direction. The heater 168 is in contact with the inner circumferential surface 64a of the fixing belt 64 at its contact surface 168b. The upstream edge 168a of the heater 168 in the belt circumference direction extends in the depth direction. The width of the heater 168 is longer than the width of the heater 68 (see Figure 3).

[0060] The support pad 170 is provided with a pair of clamping portions 170a that clamp the heater 168 from the width direction. The lower end of the clamping portion 170a on the fixing belt 64 side is positioned on the same surface as the contact surface 168b of the heater 168.

[0061] Furthermore, in the belt circumferential direction, the inner circumferential surface 64a of the anchoring belt 64 is in contact with the heater 168 and the support pad 170 on both the upstream and downstream sides of the nip portion N. Specifically, on the upstream side of the nip portion N, the inner circumferential surface 64a is in contact with one end of the heater 168 in the width direction (left side in the figure) and the lower end of one of the clamping portions 170a. In other words, on the upstream side of the nip portion N in the belt circumferential direction, a stagnant portion (B1 in the figure) is formed where grease G is trapped between the anchoring belt 64 and the anchoring belt, causing grease G to accumulate.

[0062] Furthermore, downstream of the nip portion N, the inner circumferential surface 64a is in contact with the other end of the heater 168 in the width direction (right side in the figure) and the lower end of the other clamping portion 170a. In other words, downstream of the nip portion N in the belt circumferential direction, a stagnant portion (B2 in the figure) is formed where grease G is trapped between the fixing belt 64 and the nip portion N, causing grease G to accumulate.

[0063] [Operation of fixing devices 60 and 160] Before the fixing devices 60 and 160 are operational, the voltage applied to the heaters 68 and 168 is stopped. Furthermore, the rotation of the pressurizing member 82 is stopped.

[0064] When fixing the toner image transferred to the recording medium P, a driving force is transmitted from a motor (not shown) to the pressurizing member 82, and the pressurizing member 82 rotates in the direction of the arrow in the figures, as shown in Figures 3 and 5.

[0065] As a result, the fixing belt 64 rotates in the direction of the arrow in the figure, driven by the pressurizing member 82. The grease G applied to the inner circumferential surface 64a of the fixing belt 64 also moves along with the inner circumferential surface 64a as the fixing belt 64 rotates. Furthermore, voltage is applied to the heaters 68 and 168 from a power source (not shown). As a result, the heaters 68 and 164 generate heat, and the heaters 68 and 168 heat the rotating fixing belt 64.

[0066] In the comparative fixing device 160, as shown in Figure 6, a stagnant portion B1 where grease G accumulates is formed upstream of the nip portion N in the belt circumferential direction. The formation of the stagnant portion B1 reduces the amount of grease G supplied between the heater 168 and the fixing belt 64.

[0067] Furthermore, in the fixing device 160, a stagnation portion B2 is formed downstream of the nip portion N in the belt circumferential direction, where grease G accumulates. The formation of the stagnation portion B2 reduces the amount of grease G that moves together with the inner circumferential surface 64a as the fixing belt 64 rotates. As a result, the amount of grease G supplied between the heater 168 and the fixing belt 64 decreases.

[0068] On the other hand, in the fixing device 60 according to this embodiment, as shown in Figure 3, the heating member 62 and the pressurizing member 82 are arranged so that the inner circumferential surface 64a and the member placed inside the fixing belt 64 are in a non-contact state on the upstream and downstream sides with respect to the nip portion N.

[0069] Therefore, the formation of stagnant areas where grease G accumulates is suppressed on the upstream and downstream sides of the nip section N. As a result, the amount of grease G supplied between the heater 68 and the fixing belt 64 increases compared to the fixing device 160 in the comparative configuration.

[0070] (summary) As explained above, in the fixing device 60, the heating member 62 and the pressurizing member 82 are positioned so that the inner circumferential surface 64a and the member placed inside the fixing belt 64 are in non-contact state with respect to the nip portion N on the upstream and downstream sides. As a result, the amount of grease G supplied between the fixing belt 64 and the heater 68 increases compared to the fixing device 160 in the comparative form. In other words, the frictional force (kinetic friction) generated between the inner circumferential surface 64a of the fixing belt 64 and the heater 68 is reduced compared to the case where the inner circumferential surface 64a of the fixing belt 64 and the member placed inside the fixing belt 64 are in contact with respect to the nip portion N on the upstream and downstream sides in the belt circumferential direction.

[0071] Furthermore, in the fixing device 60, grease G with a mixing consistency of 250 or less is applied to the inner circumferential surface 64a of the fixing belt 64. In other words, grease G that is harder than grease G with a mixing consistency greater than 250 is applied to the inner circumferential surface 64a of the fixing belt 64. When such hard grease G is applied to the inner circumferential surface 64a, if stagnant portions B1 and B2 are formed as in the fixing device 160 of the comparative form, grease G tends to accumulate in the stagnant portions B1 and B2.

[0072] However, in the fixing device 60 of this embodiment, stagnant portions B1 and B2 are not formed. Therefore, even when grease with a consistency of 250 or less is applied, the frictional force generated between the inner surface 64a of the fixing belt 64 and the heater 68 is reduced compared to the case where the inner surface 64a of the fixing belt 64 and the member disposed inside the fixing belt 64 are in contact with each other on the upstream and downstream sides of the nip portion N in the belt circumferential direction.

[0073] Furthermore, in the fixing device 60, as shown in Figure 4, the edge 68a of the heater 68 is recessed downstream in the belt circumference direction at its center in the depth direction compared to both ends in the depth direction. This suppresses the flow of grease G, which moves with the rotation of the fixing belt 64, from hitting the edge of the heater 68 and flowing outward in the depth direction, compared to the case where the edge of the heater extends in the depth direction.

[0074] Furthermore, the edge 68a of the heater 68 is curved such that the central part in the depth direction is recessed downstream of the belt circumference direction of the anchoring belt 64 compared to both ends in the depth direction. This suppresses the accumulation of grease G in the central part in the depth direction of the heater 68, compared to the case where the edge is recessed downstream of the belt circumference direction due to the bending of the central part in the depth direction.

[0075] Furthermore, in the image forming apparatus 10, compared to the case where the fixing device 160 according to the comparative configuration is provided, the frictional force generated between the inner circumferential surface 64a and the heater 68 is reduced, thereby suppressing the occurrence of uneven fixing of the toner image.

[0076] Although this disclosure has been described in detail with respect to specific embodiments, it will be apparent to those skilled in the art that this disclosure is not limited to such embodiments, and that various other embodiments are possible within the scope of this disclosure. For example, in the above embodiment, the heating member 62 and the pressurizing member 82 are arranged such that the inner circumferential surface 64a and the member disposed inside the fixing belt 64 are in a non-contact state on the upstream and downstream sides with respect to the nip portion N. However, the heating member 62 and the pressurizing member 82 may be arranged such that the inner circumferential surface 64a and the member disposed inside the fixing belt 64 are in a non-contact state on at least one of the upstream and downstream sides with respect to the nip portion N in the belt circumferential direction. This reduces the frictional force generated between the inner circumferential surface 64a of the fixing belt 64 and the heater 68 compared to the case where the inner circumferential surface 64a and the member disposed inside the fixing belt 64 are in contact on both the upstream and downstream sides with respect to the nip portion N in the belt circumferential direction.

[0077] Furthermore, in the above embodiment, the heating member 62 and the pressurizing member 82 are positioned so that the inner circumferential surface 64a and the member positioned inside the fixing belt 64 are in a non-contact state on both the upstream and downstream sides of the nip portion N. However, the heating member 62 and the pressurizing member 82 may be positioned so that the inner circumferential surface 64a and the member positioned inside the fixing belt 64 are in a non-contact state only on the upstream side of the nip portion N in the belt circumferential direction. This increases the amount of grease G supplied between the heater 168 and the fixing belt 64, and reduces the frictional force generated between the inner circumferential surface 64a of the fixing belt 64 and the heater 68, compared to the case where the non-contact state is only on the downstream side of the nip portion N.

[0078] Furthermore, in the above embodiment, the heating member 62 and the pressurizing member 82 are positioned so that the inner circumferential surface 64a and the member positioned inside the fixing belt 64 are in a non-contact state on both the upstream and downstream sides of the nip portion N. As a result, compared to the case where the inner circumferential surface and the member positioned inside the fixing belt are in a non-contact state on only one side of the belt circumference relative to the nip portion N, the amount of grease G supplied between the heater 168 and the fixing belt 64 increases, and the frictional force generated between the inner circumferential surface 64a of the fixing belt 64 and the heater 68 is reduced.

[0079] Furthermore, in the above embodiment, the edge 68a of the heater 68 was recessed in the central part in the depth direction toward the downstream side in the belt circumference direction compared to both ends in the depth direction, but the edge of the heater may extend in the depth direction. However, in this case, the effect achieved by arranging the edge so that the central part in the depth direction is recessed toward the downstream side in the belt circumference direction compared to both ends in the depth direction will not be achieved.

[0080] Furthermore, in the above embodiment, the consistency of the grease G was set to 250 or less, but for example, the consistency of the grease G may be 200 or less but not exceeding 250.

[0081] (((1))) A heating member comprising a cylindrical member that is tubular, extends axially, is circumferential, and has grease applied to its inner surface, and a heating member that extends axially, contacts the inner surface, generates heat, and heats the cylindrical member, The system comprises a pressurizing member positioned on the opposite side of the heating element, sandwiching the cylindrical member, forming a nip portion that sandwiches the recording medium between itself and the heating element, and pressurizing the recording medium toward the heating element, The heating member and the pressurizing member are arranged such that, in the circumferential direction of the cylindrical member, at least one of the upstream and downstream sides with respect to the nip portion is in a non-contact state between the inner circumferential surface and the member disposed inside the cylindrical member. Fixing device.

[0082] (((2))) The fixing device described in (((1))) wherein the consistency of the grease is 250 or less.

[0083] (((3))) The fixing device according to (((1))) or (((2))), wherein, in the circumferential direction of the cylindrical member when the recording medium is held by the nip portion, the inner circumferential surface and a member disposed inside the cylindrical member are in a non-contact state on the upstream side of the nip portion.

[0084] (((4))) In the circumferential direction, the inner circumferential surface and the member disposed inside the cylindrical member are in a non-contact state on both the upstream and downstream sides with respect to the nip portion. A fixing device as described in any one of (((1))) to (((3))).

[0085] (((5))) In the heating element, the upstream edge in the direction of rotation of the cylindrical member when the recording medium is sandwiched by the nip portion is such that the central portion in the axial direction of the upstream edge in the heating element is recessed downstream in the circumferential direction compared to both ends in the axial direction. A fixing device as described in any one of (((1))) to (((4))).

[0086] (((6))) The edge of the heating element is curved, so that the central portion in the axial direction is recessed downstream in the circumferential direction compared to both ends in the axial direction. The fixing device described in (((5))).

[0087] (((7))) A forming unit that forms an image on a recording medium, A fixing device according to any one of (((1))) to (((6))) for fixing the image formed on the recording medium by the forming unit onto the recording medium, An image forming apparatus equipped with the following features.

[0088] The fixing device according to (((1))) can reduce the frictional force generated between the inner surface of the cylindrical member and the heating element compared to the case where the inner surface of the cylindrical member and the element disposed inside the cylindrical member are in contact with the element on the upstream and downstream sides of the nip portion in the circumferential direction of the cylindrical member.

[0089] The fixing device according to (((2))) can reduce the frictional force generated between the inner surface of the cylindrical member and the heating element, even when grease with a consistency of 250 or less is applied to the inner surface of the cylindrical member, compared to the case where the inner surface of the cylindrical member and the element disposed inside the cylindrical member are in contact with each other on the upstream and downstream sides of the nip portion in the circumferential direction of the cylindrical member.

[0090] The fixing device according to (((3))) can reduce the frictional force generated between the inner surface of the cylindrical member and the heating element compared to the case where the inner surface of the cylindrical member and the element placed inside the cylindrical member are in a non-contact state only on the downstream side of the nip portion in the circumferential direction of the cylindrical member.

[0091] The fixing device according to (((4))) can reduce the frictional force generated between the inner surface of the cylindrical member and the heating element compared to the case where the inner surface of the cylindrical member and the element placed inside the cylindrical member are in a non-contact state on either the upstream or downstream side of the nip portion in the circumferential direction of the cylindrical member.

[0092] The fixing device relating to (((5))) can reduce the amount of grease that flows outward in the axial direction when it comes into contact with the edge of the heating element, compared to the case where the edge of the heating element extends in the axial direction.

[0093] The fixing device relating to (((6))) can suppress the accumulation of grease in the axial central part of the heating element compared to the case where the edge is recessed on the downstream side in the circumferential direction due to the bending of the central part in the axial direction.

[0094] The image forming apparatus according to (((7))) can suppress uneven image fixing compared to the case in which a fixing device is provided in which the inner circumferential surface of the cylindrical member and a member disposed inside the cylindrical member are in contact with the nip portion on the upstream and downstream sides in the circumferential direction of the cylindrical member. [Explanation of symbols]

[0095] 10 Image forming apparatus 14 Image forming section (an example of an image forming section) 60 Fixing device 62 Heating element 64 Fixing belt (an example of a cylindrical member) 64a Inner surface 68 Heater (an example of a heating element) 68a Edge 82 Pressurizing member G Grease N Nip section

Claims

1. A heating member comprising a cylindrical member that is tubular, extends axially, is circumferential, and has grease applied to its inner surface, and a heating member that extends axially, contacts the inner surface, generates heat, and heats the cylindrical member, The system comprises a pressurizing member positioned on the opposite side of the heating element, sandwiching the cylindrical member, forming a nip portion that sandwiches the recording medium between itself and the heating element, and pressurizing the recording medium toward the heating element, The heating member and the pressurizing member are arranged such that, in the circumferential direction of the cylindrical member, at least one of the upstream and downstream sides with respect to the nip portion is in a non-contact state between the inner circumferential surface and the member disposed inside the cylindrical member. Fixing device.

2. The consistency of the grease is set to 250 or less. The fixing device according to claim 1.

3. When the recording medium is held between the nip portion, the inner circumferential surface and the member disposed inside the cylindrical member are in a non-contact state on the upstream side of the nip portion in the circumferential direction of the cylindrical member. The fixing device according to claim 1.

4. In the circumferential direction, the inner circumferential surface and the member disposed inside the cylindrical member are in a non-contact state on both the upstream and downstream sides with respect to the nip portion. The fixing device according to claim 3.

5. In the heating element, the upstream edge in the direction of rotation of the cylindrical member when the recording medium is sandwiched by the nip portion is such that the central portion in the axial direction of the upstream edge in the heating element is recessed downstream in the circumferential direction compared to both ends in the axial direction. The fixing device according to claim 1.

6. The edge of the heating element is curved, so that the central portion in the axial direction is recessed downstream in the circumferential direction compared to both ends in the axial direction. The fixing device according to claim 5.

7. A forming unit that forms an image on a recording medium, A fixing device according to any one of claims 1 to 6, for fixing an image formed on a recording medium by the forming unit onto the recording medium, An image forming apparatus equipped with the following features.

Images