Fixing device and image forming apparatus

Abstract

The present invention provides a fixing device and an image forming apparatus. The fixing device (30) includes a belt (44), a pressure roller (34), a heater (46), and a holding member (72). The heater (46) extends in an axial direction orthogonal to the conveyance direction and heats the belt (44). Further, the heater (46) has a contact portion (47) and a non-contact portion (48) that contacts the inner circumferential surface (45A). The non-contact portion (48) is disposed on both outer sides of the contact portion (47), has a second end portion (68) thicker than the thickness of the first end portion (64) of the contact portion (47), and does not contact the belt (44). The holding member (72) contacts the second end portion (68) in the conveyance direction, thereby holding the heater (46).

Description

Technical Field

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

[0002] Patent Document 1 discloses a fixing device having: a heating element; a heating element holding member that fixedly holds the heating element; a fixing sleeve that slides with the heating element and includes a metal base layer having flexibility and in the shape of an endless belt; and a pressing member that forms a nip with the heating element via the fixing sleeve and fixes a conveyed heated body by sandwiching it between the fixing sleeve and the pressing member using the nip portion. The heating element protrudes from the heating element holding member toward the sliding surface side, and in the fixing device configured in this way, the shape of the end face edge portion of the sliding portion of the protruding heating element is R0.2 or more.

[0003] [Prior Art Documents]

[0004] [Patent Documents]

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2006-292867 Summary of the Invention

[0006] [Problems to be Solved by the Invention]

[0007] An object of the present invention is to provide a fixing device and an image forming apparatus that suppress a phenomenon in which the position of a heating member deviates in the conveyance direction when the rotating body rotates in a configuration having a heating member that contacts a rotating body that conveys a recording medium by rotation and has a thickness at an end portion in the conveyance direction that is thinner than that at the central portion.

[0008] [Technical Means for Solving the Problems]

[0009] The fixing device according to the first aspect includes: a rotating body that is hollow and rotates about its own axis; a pressing member that presses a recording medium together with the rotating body and conveys the recording medium in the conveyance direction as the rotating body rotates; a heating member that is disposed in contact with the inner peripheral surface of the rotating body and extends in an axial direction orthogonal to the conveyance direction to heat the rotating body, and the heating member has a contact portion and a non-contact portion, at least a part of the contact portion contacts the inner peripheral surface, the non-contact portion is disposed on both outer sides of the contact portion in the axial direction, has a second end portion thicker than a first end portion of the contact portion on the downstream side in the conveyance direction, and does not contact the rotating body; and a holding member that contacts at least the second end portion in the conveyance direction to hold the heating member.

[0010] In the contact portion of the fixing device of the second embodiment, the first end portions are formed on the upstream side and the downstream side in the conveyance direction, and in the non-contact portion, the second end portions are formed on the upstream side and the downstream side in the conveyance direction. The holding member contacts the second end portions on the upstream side and the downstream side in the conveyance direction in the conveyance direction.

[0011] A part of the first end portion of the fixing device of the third embodiment is formed as a chamfered portion when viewed from the axial direction.

[0012] A part of the second end portion of the fixing device of the fourth embodiment protrudes outward more than the chamfered portion when viewed from the axial direction.

[0013] The holding member of the fixing device of the fifth embodiment contacts a part in the thickness direction of the first end portion in the conveyance direction.

[0014] In the fixing device of the sixth embodiment, a first height in the thickness direction of a portion of the holding member facing the first end portion in the conveyance direction is the same as a second height in the thickness direction of a portion of the holding member facing the second end portion in the conveyance direction.

[0015] The image forming apparatus of the seventh embodiment includes: an image forming member that forms a developer image on a recording medium; and the fixing device according to any one of the first to sixth embodiments that fixes the developer image to the recording medium by heating and pressing.

[0016] [Advantages of the Invention]

[0017] According to the fixing device of the first embodiment, in a configuration having a heating member that contacts a rotating body that conveys a recording medium by rotation and the thickness of the end portion in the conveyance direction is thinner than the thickness of the central portion, compared with a configuration that only holds the thin end portion, it is possible to suppress the phenomenon that the position of the heating member deviates in the conveyance direction when the rotating body rotates.

[0018] According to the fixing device of the second embodiment, when the recording medium is drawn out to the upstream side in the conveyance direction, compared with a configuration having no holding member on the upstream side in the conveyance direction, it is possible to suppress the phenomenon that the position of the heating member deviates.

[0019] According to the fixing device of the third embodiment, compared with a configuration in which the first end portion has a step when viewed from the axial direction, it is possible to suppress wear of the rotating body caused by contact with the rotating body.

[0020] According to the fixing device of the fourth embodiment, it is possible to increase the thickness of the second end portion within the thickness range of the portion other than the first end portion in the contact portion.

[0021] The fixing device according to the fifth aspect can suppress deviation in the conveyance direction of the heating member as compared with a configuration in which the holding member and the first end portion are non-contact.

[0022] The fixing device according to the sixth aspect can suppress deformation of the first end portion in a case where the entire first end portion is deformed in the conveyance direction as compared with a configuration in which the first height is lower than the second height.

[0023] The image forming apparatus according to the seventh aspect can suppress image defects caused by deviation of the heating member as compared with a configuration in which deviation of the contact portion of the heating member is not restricted. Description of the Drawings

[0024] Figure 1 is a front view of the image forming apparatus of the present embodiment.

[0025] Figure 2 is a longitudinal sectional view of the fixing device of the present embodiment.

[0026] Figure 3 is a bottom view of the belt, heating member, and holding member of the present embodiment as viewed from the nip portion side.

[0027] Figure 4 is a longitudinal sectional view of the heater of the present embodiment ( Figure 3 sectional view taken along line 4-4).

[0028] Figure 5 is a partial perspective view showing a part of the heating member of the present embodiment.

[0029] Figure 6 is a partial sectional view of the heating member and the holding member of the present embodiment ( Figure 3 a part of the sectional view taken along line 6-6).

[0030] Figure 7 is a partial sectional view of the heating member and the holding member of the present embodiment ( Figure 3 a part of the sectional view taken along line 7-7).

[0031] Figure 8 is a partially enlarged sectional view of the heating member of the present embodiment.

[0032] Figure 9 is a partial perspective view showing a part of the heating member of a modified example of the present embodiment.

[0033] [Description of Reference Numerals]

[0034] 10: Image forming apparatus

[0035] 16: Image forming unit (an example of an image forming member)

[0036] 30: Fixing device

[0037] 34: Pressing roller (an example of a pressing member)

[0038] 44: Belt (an example of a rotating body)

[0039] 45A: Inner peripheral surface

[0040] 46: Heater (an example of a heating member)

[0041] 47: Contact portion

[0042] 48: Non-contact portion

[0043] 64: First end portion

[0044] 65: Chamfered portion

[0045] 68: Second end portion

[0046] 72: Holding member

[0047] 90: Fixing device

[0048] 92: Heater (an example of a heating member)

[0049] 96: First end portion

[0050] 97: Chamfered portion

[0051] G: Toner image (an example of a developer image)

[0052] ha: First height

[0053] hb: Second height. Detailed implementation manners

[0054] As an example of the image forming apparatus and the fixing device of the present embodiment, the image forming apparatus 10 and the fixing device 30 will be described.

[0055] 〔Overall configuration〕

[0056] Figure 1 The image forming apparatus 10 is shown. The image forming apparatus 10 is configured to include the following parts: a housing portion 12 that houses the paper P; a conveyance portion 14 that conveys the paper P; an image forming portion 16 that forms a toner image G on the paper P; a control portion 18 that controls the operations of the respective parts of the image forming apparatus 10; and a fixing device 30. In the following description, for the image forming apparatus 10, the height direction will be referred to as the "apparatus height direction", the depth direction will be referred to as the "apparatus depth direction", and the left-right direction will be referred to as the "apparatus width direction". The apparatus height direction, the apparatus depth direction, and the apparatus width direction are orthogonal to each other.

[0057] The sheet P is an example of a recording medium. The toner image G is an example of a developer image. The conveying unit 14 conveys the sheet P from the housing unit 12 toward the upper side in the apparatus height direction along the conveyance path T. The image forming unit 16 is an example of an image forming member. Further, as an example, the image forming unit 16 is configured to perform the processes of charging, exposure, development, and transfer, which are the existing electrophotographic methods, using monochromatic or multicolor toner to form the toner image G on the sheet P.

[0058] 〔Main Component Configuration〕

[0059] Next, the fixing device 30 will be described.

[0060] Figure 2 The illustrated fixing device 30 includes: a frame 32 as a device body; a heating unit 40 provided inside the frame 32 and disposed on one side with respect to the conveyance path T for conveying the sheet P; and a pressure roller 34 provided inside the frame 32 and disposed on the other side with respect to the conveyance path T. As an example, the extending direction of the conveyance path T (the conveyance direction of the sheet P) coincides with the apparatus height direction. In the fixing device 30, as an example of the conveyance method of the sheet P, a center registration method is adopted, and in the center registration method, the center of the conveyance path T in the apparatus depth direction coincides with the center of the sheet P at the same position to convey the sheet P. The fixing device 30 fixes the toner image G to the sheet P by heating and pressing it.

[0061] <Pressure Roller>

[0062] The pressure roller 34 is an example of a pressure member and includes a shaft member 35 having the apparatus depth direction as the axial direction, an elastic layer 36, and a release layer 37. The shaft member 35 is supported by a bearing (not shown) and rotates by a motor (not shown). Further, the shaft member 35 is pressed toward the heating unit 40 side with respect to the conveyance path T by a pressing member including a spring (not shown). And the pressure roller 34 presses the sheet P together with a belt 44 described later, and conveys the sheet P in the conveyance direction as the belt 44 rotates.

[0063] <Heating Unit>

[0064] As an example, the heating unit 40 includes a support frame 42, a belt 44, a heater 46, a holding member 72, and a temperature detection unit (not shown). In addition, in the non-sheet-passing state of the sheet P, the portion where the outer peripheral surface of the belt 44 contacts the outer peripheral surface of the pressure roller 34 is referred to as the nip portion NP. The temperature detection unit is configured to include a thermistor (not shown) and a thermostat and is used for controlling the fixing temperature at the nip portion NP and suppressing an excessive temperature rise.

[0065] (Support Frame)

[0066] The support frame 42 is a member that is long in the depth direction of the apparatus. When viewed from the depth direction of the apparatus, the cross-sectional shape of the support frame 42 is U-shaped and open toward the pressure roller 34 side. Moreover, both end portions of the support frame 42 in the depth direction of the apparatus are supported by side plates (not shown) of the frame body 32, and the central portion is disposed inside a belt 44 described later.

[0067] In the following description, the axial direction (long side direction) of the support frame 42 and the belt 44 is referred to as the Z direction. Moreover, the conveyance direction that is orthogonal to the Z direction and conveys the sheet P in the fixing device 30 is referred to as the X direction. Further, the direction that is orthogonal to the X direction and the Z direction and is the thickness direction of a heater 46 described later is referred to as the Y direction. In the present embodiment, as an example, the Z direction coincides with the depth direction of the apparatus, the X direction coincides with the height direction of the apparatus, and the Y direction coincides with the width direction of the apparatus.

[0068] When distinguishing one side and the other side with respect to the center in the X direction, they are referred to as the upper side and the lower side in accordance with the height direction of the apparatus. When distinguishing one side and the other side with respect to the center in the Y direction, they are referred to as the heating side and the pressure side. When distinguishing one side and the other side with respect to the center in the Z direction, they are referred to as the back side and the front side in accordance with the depth direction of the apparatus.

[0069] (Belt)

[0070] The belt 44 is an example of a hollow and rotatable rotating body about its own axis, and is formed in a cylindrical shape (seamless). The surface on the inner side in the thickness direction of the belt 44 is referred to as the inner peripheral surface 45A. The surface on the outer side in the thickness direction of the belt 44 is referred to as the outer peripheral surface 45B. The axial direction of the belt 44 is the Z direction.

[0071] Moreover, as an example, the belt 44 is a member made of a polyimide resin having a fluorine coating applied to the outer peripheral surface 45B. Both end portions of the belt 44 in the Z direction are rotatably supported by cap members (not shown). Further, the belt 44 rotates in the direction of arrow R in the drawing following (driven by) the rotation of the pressure roller 34, and thereby conveys the sheet P in the X direction.

[0072] As Figure 3 shown, the length of the belt 44 in the Z direction is set to L1 [mm]. The length L1 is longer than the length of the sheet P in the Z direction, which is the maximum size used in the image forming apparatus 10 (see Figure 1 ).

[0073] (Heater)

[0074] Figure 2The illustrated heater 46 is an example of a heating member. Moreover, the heater 46 is disposed in contact with the inner peripheral surface 45A and extends in the Z direction orthogonal to the X direction and the Y direction. And the heater 46 is configured to generate heat by being energized from a power source (not shown) to heat the belt 44.

[0075] As Figure 3 shown, the heater 46 is formed in a rectangular plate shape that is long in the Z direction and short in the X direction. Moreover, the heater 46 has: a contact portion 47 that constitutes the central portion in the Z direction; and two non-contact portions 48 that are disposed on both outer sides of the contact portion 47 in the Z direction. The contact portion 47 and the non-contact portion 48 are distinguished according to whether they have a first end portion 64 described later. Let the length of the contact portion 47 in the Z direction be L2 [mm]. The length L2 is longer than the length L1 described above. Let the length of one non-contact portion 48 in the Z direction be L3 [mm]. As an example, the length L3 is a length that is 1 / 12 or more and 1 / 8 or less of the length L2. The portion of the contact portion 47 in the Z direction except for the both end portions is in contact with the inner peripheral surface 45A (refer to Figure 2 ). The non-contact portion 48 is not in contact with the belt 44.

[0076] Figure 4 shows a longitudinal sectional view (X - Y sectional view) of the heater 46. When viewed from the Z direction, as an example, the heater 46 has a substrate 52 and a heat generating portion 54 for heating the belt 44. In addition, Figure 4 in, in order to facilitate understanding of the configuration of the heat generating portion 54, the heat generating portion 54 is shown enlarged with respect to the substrate 52, but actually, the thickness of the heat generating portion 54 in the Y direction is thinner than the thickness of the substrate 52 in the Y direction. Therefore, Figure 4 in other figures, when the heater 46 is illustrated, the outer shape of the heater 46 is regarded as being substantially the same as the outer shape of the substrate 52 and the heater 46 is shown as a plate shape.

[0077] The substrate 52 includes a rectangular plate that is long in the Z direction and short in the X direction. Moreover, as an example, the substrate 52 includes a formed body of alumina. As an example, the thickness of the substrate 52 in the Y direction is about 1 [mm]. The surface on the pressurized side in the Y direction of the substrate 52 is referred to as the surface 52A, and the surface on the heating side is referred to as the back surface 52B. As an example, the substrate 52 is obtained by cutting one of a plurality of pieces cut from a large alumina plate.

[0078] Figure 5 shows a part of the substrate 52 at the boundary between the contact portion 47 and the non-contact portion 48. In addition, the imaginary (invisible) boundary K1 between the contact portion 47 and the non-contact portion 48 is represented by a two-dot chain line. The heat generating portion 54 (refer to Figure 4 ) is omitted.

[0079] The contact portion 47 has a configuration in which a base portion 62 and a first end portion 64 are arranged in the X direction. The imaginary (invisible) boundary K2 between the base portion 62 and the first end portion 64 is represented by a two-dot chain line. Further, the boundary K2 is a boundary obtained by connecting in the Z direction imaginary points representing the positions of the X-direction starting points of a chamfered portion 65 to be described later in the X-Y cross section. As an example, the first end portion 64 is formed on the upper side (downstream side) and the lower side (upstream side) in the X direction of the contact portion 47. In other words, the base portion 62 is the portion of the contact portion 47 other than the first end portion 64, and is a plate-like portion having substantially the same thickness in the X direction and the Z direction. Further, Figure 5 shows a part of the base portion 62 and the first end portion 64 on the upper side in the X direction.

[0080] When viewed from the Z direction, a part of the first end portion 64 is formed as the chamfered portion 65. As an example, the chamfered portion 65 is configured as the portion of the first end portion 64 that is closer to the pressing side than the center in the Y direction. Further, as an example, the chamfered portion 65 is a portion chamfered by an R chamfer. In other words, when viewed from the Z direction, the chamfered portion 65 is formed in an arc shape. Further, as an example, the length of the first end portion 64 corresponding to the width in the X direction is the length of the radius of the arc-shaped portion. Here, the end face in the X direction of the first end portion 64 (the face closer to the heating side than the center in the Y direction) is referred to as the side face 64A, and the surface of the arc-shaped portion of the chamfered portion 65 is referred to as the curved surface 65A. The side face 64A is along the Y-Z plane. The curved surface 65A is formed continuously with the side face 64A. Further, when viewed from the Z direction, the curved surface 65A bulges outward.

[0081] If the thickness (height) of the side face 64A in the Y direction is t1 [mm] and the thickness of the base portion 62 in the Y direction is t2 [mm], then t1 < t2. Further, as an example, the thickness t1 is greater than or equal to 1 / 3 and less than or equal to 2 / 3 of the thickness t2.

[0082] The non-contact portion 48 has a base portion 66 and a second end portion 68. The imaginary (invisible) boundary K3 between the base portion 66 and the second end portion 68 is represented by a two-dot chain line. As an example, the boundary K2 and the boundary K3 are located on the same straight line along the Z direction. As an example, the second end portion 68 is formed on the upper side (downstream side) and the lower side (upstream side) in the X direction of the non-contact portion 48. In other words, the base portion 66 is the portion of the non-contact portion 48 other than the second end portion 68, and is a plate-like portion having substantially the same thickness in the X direction and the Z direction. Further, Figure 5 shows a part of the base portion 66 and the second end portion 68 on the upper side in the X direction.

[0083] When viewed from the Z direction, a part of the second end portion 68 (the part closer to the pressing side than the center in the Y direction) is formed in a rectangular shape. The thickness of the base portion 66 in the Y direction is t2 [mm]. The surface of the base portion 66 on the pressing side in the Y direction is aligned with the surface of the base portion 62 on the pressing side in the Y direction. Moreover, the side surface 68A which is the end surface in the X direction of the second end portion 68 is aligned with the side surface 64A on the same plane along the Y-Z plane.

[0084] If the thickness of the second end portion 68 in the Y direction is t3 [mm], then t3 = t2. In other words, the non-contact portion 48 has a second end portion 68 which is thicker than the first end portion 64 on the downstream side in the X direction.

[0085] As Figure 8 shown, when viewed from the Z direction, a part of the second end portion 68 protrudes outward beyond the chamfered portion 65 (the curved surface 65A). Here, the portion of the second end portion 68 that protrudes outward beyond the first end portion 64 and is located on the aforementioned boundary K1 (refer to Figure 5 ) is called the side surface 69. The side surface 69 is a plane along the X-Y plane.

[0086] As Figure 4 shown, as an example, the heating portion 54 has two resistor bodies 55, two electrodes 56 (shown as one in the figure), a protection portion 57, and a smoothing portion 58. As an example, the thickness of the entire heating portion 54 in the Y direction is about 60 [μm]. The two resistor bodies 55 are in contact with the surface 52A of the substrate 52 and are arranged at intervals in the X direction. The two resistor bodies 55 extend along the Z direction respectively in accordance with the length of the paper P in the Z direction. The two electrodes 56 are individually connected to the two end portions in the Z direction of the two resistor bodies 55.

[0087] In the heating portion 54, a power supply (not shown) is connected to the two electrodes 56, and the two resistor bodies 55 are energized from the power supply to make the two resistor bodies 55 generate heat. The protection portion 57 covers the resistor bodies 55 and the electrodes 56. The smoothing portion 58 is in contact with the inner peripheral surface 45A. Moreover, the smoothing portion 58 contains a material with a low coefficient of friction with the belt 44 to reduce the frictional resistance caused by the sliding of the belt 44.

[0088] As Figure 2 shown, the heater 46 is arranged inside the belt 44 with the Y direction as the thickness direction and is held by a holding member 72 described later. Specifically, the heater 46 is arranged on the heating side in the Y direction with respect to the belt 44 of the nip portion NP and is in contact with the inner peripheral surface 45A. In this way, at the nip portion NP, the heater 46 sandwiches the belt 44 and the paper P together with the pressing roller 34, thereby pressing and heating the belt 44 and the paper P. In addition, the load acting on the heater 46 during pressing is transmitted to the support frame 42 via the holding member 72. Therefore, the deformation of the heater 46 is suppressed.

[0089] (Retention member)

[0090] As an example, Figure 2 The shown retention member 72 is a polyimide resin member that is long in the Z direction and includes an upstream retention member 74 disposed on the lower side (upstream side) in the X direction and a downstream retention member 75 disposed on the upper side (downstream side) in the X direction.

[0091] The upstream retention member 74 and the downstream retention member 75 are mounted on the pressurized side ends of the support frame 42. Moreover, as an example, the upstream retention member 74 and the downstream retention member 75 contact the first end portion 64 (refer to Figure 5 ) and the second end portion 68 in the X direction, thereby retaining the heater 46. In other words, the retention member 72 contacts the second end portions 68 on the upstream side and the downstream side in the X direction in the X direction. Moreover, the retention member 72 contacts a part (side surface 64A) of the first end portion 64 in the thickness direction of the belt 44 in the X direction.

[0092] Here, the portion of the upstream retention member 74 that retains the heater 46 and the portion of the downstream retention member 75 that retains the heater 46 are configured to be substantially symmetric with respect to the center in the X direction. Therefore, the downstream retention member 75 will be described, and the description of the upstream retention member 74 will be omitted.

[0093] As Figure 6 shown, the portion of the downstream retention member 75 that retains the contact portion 47 is referred to as the first retention portion 76. The first retention portion 76 has a mounted portion 77 and a recessed portion 78. When viewed from the Z direction, the mounted portion 77 is formed in a U-shaped cross-section that opens toward the heating side in the Y direction. Moreover, in the mounted portion 77, one end portion of the support frame 42 is inserted and fixed (bonded).

[0094] When viewed from the Z direction, the recessed portion 78 has: a contact surface 78A that extends along the X direction; and a contact surface 78B that extends from the downstream end of the contact surface 78A toward the pressurized side in the Y direction. The contact surface 78A contacts the downstream end portion in the X direction of the back surface 52B of the heater 46 in the Y direction. The contact surface 78B contacts the side surface 64A of the heater 46 in the X direction. Thereby, the movement of the contact portion 47 in the X direction and the Y direction is restricted.

[0095] As Figure 7As shown, the portion of the downstream-side holding member 75 that holds the non-contact portion 48 is referred to as the second holding portion 82. The second holding portion 82 has a mounted portion 83 and a recessed portion 84. When viewed from the Z direction, the mounted portion 83 is formed in a U-shaped cross-section that opens toward the heating side in the Y direction. Moreover, one end portion of the support frame 42 is inserted and fixed (bonded) in the mounted portion 83.

[0096] When viewed from the Z direction, the recessed portion 84 has: a contact surface 84A that extends along the X direction; and a contact surface 84B that extends from the downstream-side end of the contact surface 84A toward the pressing side in the Y direction. That is, when viewed from the Z direction, the recessed portion 84 is formed in an L-shaped cross-section. The contact surface 84A is continuous with the aforementioned contact surface 78A (refer to Figure 6 ) so as to be disposed on the same plane. The contact surface 84B is continuous with the aforementioned contact surface 78B (refer to Figure 6 ) so as to be disposed on the same plane. The contact surface 84A contacts the downstream-side end in the X direction of the back surface 52B of the heater 46 in the Y direction. The contact surface 84B contacts the side surface 68A of the heater 46 in the X direction. Thereby, the movement of the non-contact portion 48 in the X direction and the Y direction is restricted.

[0097] Figure 6 and Figure 7 In, the first height ha in the thickness direction (here, the Y direction) of the portion facing the first end portion 64 in the X direction and the second height hb in the thickness direction (here, the Y direction) of the portion facing the second end portion 68 in the X direction are the same height.

[0098] At both ends in the Z direction of the upstream-side holding member 74 (refer to Figure 2 ) and the downstream-side holding member 75, heat-resistant resin members (not shown) are provided. By means of the heat-resistant resin members, the movement of the heater 46 in the Z direction is restricted. Moreover, by interposing the heat-resistant resin members, the upstream-side holding member 74 and the downstream-side holding member 75 are integrally provided. In addition, the heater 46 is not bonded to the holding member 72 in the X direction, the Y direction, and the Z direction.

[0099] 〔Function〕

[0100] Next, the functions of the fixing device 30 and the image forming apparatus 10 of the present embodiment will be described.

[0101] In Figure 2In the fixing device 30 shown, the heater 46 generates heat by being energized, whereby the belt 44 is heated. Subsequently, the sheet P on which the toner image G is formed enters between the belt 44 and the pressure roller 34 (nip portion NP), whereby the toner image G is heated and pressed and fixed to the sheet P. The sheet P on which the toner image G is fixed is discharged from the nip portion NP as the pressure roller 34 and the belt 44 rotate.

[0102] When the belt 44 and the pressure roller 34 convey the sheet P while pressing the sheet P, a force that attempts to move the contact portion 47 of the heater 46 toward the downstream side in the X direction acts on the contact portion 47 of the heater 46 (see Figure 3 ).

[0103] Here, Figure 3 The second end portion 68 of the non-contact portion 48, which is thicker than the first end portion 64 of the contact portion 47 shown, contacts the holding member 72 in the X direction and is thus held. That is, the movement of the heater 46 in the X direction is restricted by the contact between the thick-walled second end portion 68 of the heater 46 and the holding member 72. As a result, compared with a configuration in which a heater having the same cross-sectional shape as the contact portion 47 over the entire length is held, the phenomenon in which the position of the heater 46 deviates in the X direction when the belt 44 rotates is suppressed.

[0104] Moreover, according to the fixing device 30, the holding member 72 is not only disposed on the downstream side in the X direction but also on the upstream side in the X direction. Therefore, for example, when the operation of the fixing device 30 stops with the sheet P sandwiched in the nip portion NP and the sheet P is pulled out toward the upstream side in the X direction, the movement of the heater 46 toward the upstream side in the X direction is restricted by the contact between the second end portion 68 and the holding member 72. Thus, when the sheet P is pulled out toward the upstream side in the X direction, since the second end portion 68 contacts the holding member 72, the phenomenon in which the position of the heater 46 deviates is suppressed compared with a configuration in which the holding member 72 exists only on the downstream side in the X direction.

[0105] Furthermore, according to the fixing device 30, a part of the first end portion 64 has a chamfered portion 65 (formed in an arc shape). As a result, compared with a configuration in which the heater 46 has a step when viewed from the Z direction, the moving belt 44 is less likely to be caught on a part of the heater 46, so that wear of the belt 44 due to contact with the first end portion 64 is suppressed. Moreover, since a part of the first end portion 64 is arc-shaped, when a plurality of substrates 52 are obtained from a single sheet of plate material, the boundary portion between adjacent substrates 52 will be formed in a groove shape. As a result, compared with a configuration without an arc-shaped portion, it is easier to cut and take out a plurality of substrates 52.

[0106] In addition, according to the fixing device 30, when viewed from the Z direction, a part of the second end portion 68 protrudes outward more than the first end portion 64. Thus, the arrangement of the second end portion 68 is less likely to be restricted by the arrangement of the first end portion 64, and therefore the thickness of the second end portion 68 can be increased within the range of the thickness of the portion (base portion 62) other than the first end portion 64 in the contact portion 47.

[0107] Moreover, according to the fixing device 30, in addition to the second end portion 68, the first end portion 64 also contacts the holding member 72. Thus, compared with the configuration in which the holding member 72 does not contact the first end portion 64, the range in which the movement of the heater 46 in the X direction is suppressed extends in the Z direction, and therefore the deviation of the heater 46 in the X direction is suppressed.

[0108] Furthermore, according to the fixing device 30, the first height ha (see Figure 6 ) of the holding member 72 is the same as the second height hb (see Figure 7 ). Therefore, when the entire first end portion 64 deforms in the X direction, even if there is a change in the height position of the first end portion 64 in the Y direction, the portion at the first height ha, which is the same height as the second height hb, suppresses the movement of the first end portion 64. Thus, compared with the configuration in which the first height ha is lower than the second height hb, the deformation of the first end portion 64 is suppressed.

[0109] According to Figure 1 the image forming apparatus 10 shown, by having the fixing device 30, the phenomenon that the position of the heater 46 deviates in the X direction is suppressed. Thus, compared with the configuration in which the deviation of the contact portion 47 of the heater 46 is not restricted, the temperature distribution of the heated toner image G in the X direction is less likely to change, and therefore image defects caused by the deviation of the heater 46 in the X direction are suppressed. For an example of image defects, there are image omissions or image stains when thermal offset occurs, for example.

[0110] Moreover, Figure 2 in the fixing device 30 shown, the heater 46 has a side surface 69 (see Figure 5 or Figure 8 ). Here, when the belt 44 is about to move toward the front side or the back side in the Z direction, the end surface of the belt 44 in the Z direction contacts the side surface 69, and thus the movement of the belt 44 in the Z direction is restricted, and therefore the skew of the belt 44 is suppressed.

[0111] In addition, the present invention is not limited to the above-described embodiments.

[0112] <Variation Example>

[0113] Figure 9 shows the fixing device 30 (see Figure 2The heater 92 in the fixing device 90 which is a modified example of (). In addition, in the fixing device 90, the components other than the heater 92 described later are the same as those of the fixing device 30, so the description thereof is omitted.

[0114] The heater 92 is an example of a heating member. Moreover, the difference of the heater 92 is that in the heater 46 (refer to Figure 4 ), the substrate 52 (refer to Figure 4 ) is replaced with a substrate 94. The components other than the substrate 94 are the same as those of the heater 46, so the description thereof is omitted.

[0115] The difference of the substrate 94 is that in the substrate 52, the arc-shaped first end portion 64 (refer to Figure 5 ) is replaced with a first end portion 96. In the substrate 94, the components other than the first end portion 96 are the same as those of the substrate 52. When viewed from the Z direction, a part of the first end portion 96 is formed as a chamfered portion 97.

[0116] As an example, the chamfered portion 97 is configured as a portion of the first end portion 96 that is closer to the pressing side than the center in the Y direction. Moreover, as an example, the chamfered portion 97 is a portion chamfered by C. In other words, when viewed from the Z direction, the chamfered portion 97 is formed in a shape that is cut obliquely (a shape having an inclined surface 97A). When viewed from the Z direction, the inclined surface 97A is inclined in a direction intersecting the X direction. Specifically, when viewed from the Z direction, the inclined surface 97A is inclined in a direction in which the thickness of the X-direction end portion side of the first end portion 96 is thinner than the thickness of the X-direction base portion 62 side. In this way, the first end portion is not limited to having an arc-shaped portion, and may also have an inclined surface 97A. In addition, when viewed from the Z direction, a part of the second end portion 68 protrudes outward more than the chamfered portion 97 (inclined surface 97A).

[0117] <Other Modified Examples>

[0118] In the fixing device 30, the first end portion 64 of the heater 46 may be formed only on the downstream side in the X direction. Similarly, the second end portion 68 may be formed only on the downstream side in the X direction. When viewed from the Z direction, a part of the second end portion 68 may not protrude outward more than the first end portion 64. For example, when the second end portion 68 is located on the base portion 66 side, it may not protrude outward more than the first end portion 64.

[0119] The holding member 72 may not contact the first end portion 64 and the first end portion 96 in the X direction, but may only contact the second end portion 68. The first height ha and the second height hb of the holding member 72 may also be inconsistent. For example, it may be ha = t1 and hb = t3.

[0120] The heater 46 may also protrude more than the holding member 72 to the pressurizing side (the side of the sheet P). When viewed from the Y direction, the outer shape of the non-contact portion 48 of the heater 46 is not limited to a rectangular shape, and may also be a trapezoidal shape or a polygonal shape with four or more sides. Further, the entire contact portion 47 of the heater 46 may be in contact with the inner peripheral surface 45A.

[0121] The heater 46 and the holding member 72 are not limited to being disposed at the position where the nip portion NP is formed, and may also be disposed on the upstream side in the rotation direction of the belt 44 with respect to the position where the nip portion NP is formed.

[0122] Moreover, the present invention has been described with respect to an image forming apparatus using an electrophotographic method, but is not limited to an image forming apparatus using an electrophotographic method. For example, it can also be applied to an image forming apparatus using an inkjet method, etc. The inkjet image forming apparatus holds an undried image (an unfixed ink image) formed of ink and contacts the sheet conveyed thereto, thereby fixing the unfixed ink image onto the sheet.

[0123] The present invention is not limited to the above-described embodiments, and various modifications or applications can be made without departing from the gist of the present invention.

Claims

1. A fixing device, comprising: a rotating body, which is hollow and rotates about its own axis; a pressing member, which presses a recording medium together with the rotating body and conveys the recording medium in the conveying direction as the rotating body rotates; a heating member, which is disposed in contact with the inner peripheral surface of the rotating body and extends in an axial direction orthogonal to the conveying direction to heat the rotating body, and the heating member has a contact portion and a non-contact portion, at least a part of the contact portion is in contact with the inner peripheral surface, the non-contact portion is disposed on both outer sides of the contact portion in the axial direction, and has a second end portion thicker than the thickness of the first end portion of the contact portion on the downstream side in the conveying direction and is not in contact with the rotating body; and a holding member, which is in contact with at least the second end portion in the conveying direction to hold the heating member, in the contact portion, the first end portion is formed on the upstream side and the downstream side in the conveying direction, in the non-contact portion, the second end portion is formed on the upstream side and the downstream side in the conveying direction.

2. The fixing device according to claim 1, wherein the holding member is in contact with the second end portions on the upstream side and the downstream side in the conveying direction.

3. The fixing device according to claim 1 or 2, wherein when viewed from the axial direction, a part of the first end portion is formed as a chamfered portion.

4. The fixing device according to claim 3, wherein when viewed from the axial direction, a part of the second end portion protrudes outward more than the chamfered portion.

5. The fixing device according to any one of claims 1 to 4, wherein the holding member is in contact with a part of the thickness direction of the first end portion in the conveying direction.

6. The fixing device according to claim 5, wherein a first height in the thickness direction of a portion of the holding member facing the first end portion in the conveying direction is the same as a second height in the thickness direction of a portion of the holding member facing the second end portion in the conveying direction.

7. An image forming device, comprising: an image forming section, which forms an unfixed image; and the fixing device according to any one of claims 1 to 6, which fixes the unfixed image to the recording medium by heating and pressing.

Images