Fixing device and image forming apparatus

Abstract

The invention relates to a fixing device and an image forming apparatus. The fixing device includes a heating unit configured to heat a sheet and a facing roller facing the heating unit and forming a fixing nip together with the heating unit. The facing roller includes a roller portion including an elastic layer. The roller portion has a first end portion as an end portion of the first side in the width direction and a second end portion as an end portion of the second side in the width direction when a side where the predetermined position in the width direction is located with respect to the central portion of the roller portion is defined as a first side and a side opposite to the first side is defined as a second side. The thickness of the elastic layer of the second end is smaller than that of the elastic layer of the first end.

Description

Technical Field

[0001] The present invention relates to a fixing device used in an image forming apparatus using an electrophotographic system or an electrostatic recording system and an image forming apparatus including the fixing device. Background Art

[0002] Hitherto, for example, in an image forming apparatus of an electrophotographic system, a fixing device that fixes an unfixed toner image formed on a sheet to the sheet is used, and, for example, a film heating type fixing device is widely used as the fixing device (see JP H04-044075A). The film heating type fixing device includes a heating unit that heats the sheet and a facing roller that faces the heating unit and forms a fixing nip portion together with the heating unit. The heating unit includes a tubular film (hereinafter referred to as a fixing film) having high heat resistance and flexibility and a ceramic heater (hereinafter referred to as a heater) provided in an inner space of the fixing film.

[0003] In addition, as an imaging device, an imaging device is known that adopts a side end reference conveying method, in which the position reference in the width direction of the sheet is not set at the center in the width direction, but at one side end (see JP 2019-23681A). Such a side end reference imaging device, for example, has a conveying unit structure that abuts against a wall surface on the reference side when conveying the recording material and conveys the recording material.

[0004] However, in the case where the side end reference conveying method described in JP 2019-23681A is applied to the fixing device described in JP H04-044075A, since the temperature of the non-sheet passing portion rises to be higher than the temperature of the sheet passing portion, it is possible to generate a force that causes the fixing film to shift in the sheet width direction (hereinafter referred to as the shifting force). In the case where the fixing film is subjected to the shifting force, the end face in the direction of the shifting force pressure rotates while being pressed by the limiting component, so wear, damage, etc. may occur, and the life extension of the heating unit may be hindered. On the other hand, when the thickness of the fixing film is increased in order to extend the life, the thermal conductivity of the fixing film may be reduced, and the fixing process may also be slowed down. Summary of the invention

[0005] According to a first aspect of the present invention, a fixing device includes: a heating unit configured to heat a sheet; and a facing roller facing the heating unit and forming a fixing nip together with the heating unit. The fixing device is configured to fix a toner image carried on a sheet to the sheet by applying heat and pressure at the fixing nip. Regardless of the sheet size, one end of the sheet in the width direction intersecting the sheet conveying direction conveyed to the fixing device passes through a predetermined position of the fixing nip in the width direction. The facing roller includes a roller portion, the roller portion including a base and an elastic layer disposed around the base and having elasticity. In the case where a side where the predetermined position in the width direction is located relative to a central portion of the roller portion is defined as a first side and a side opposite to the first side is defined as a second side, the roller portion has a first end as an end of the first side in the width direction and a second end as an end of the second side in the width direction. The thickness of the elastic layer of the second end is smaller than the thickness of the elastic layer of the first end.

[0006] According to a second aspect of the present invention, a fixing device includes: a heating unit configured to heat a sheet; a facing roller facing the heating unit and forming a fixing nip together with the heating unit; and a pressing unit configured to press one of the heating unit and the facing roller toward the other of the heating unit and the facing roller. The fixing device is configured to fix a toner image carried on a sheet to the sheet by applying heat and pressure at the fixing nip. Regardless of the sheet size, one end of the sheet conveyed to the fixing device in a width direction intersecting with the sheet conveying direction passes through a predetermined position of the fixing nip in the width direction. The facing roller includes a roller portion, the roller portion including a base and an elastic layer provided around the base and having elasticity. In the case where the side where the predetermined position in the width direction is located relative to the central portion of the roller portion is defined as a first side and the side opposite to the first side is defined as a second side, the roller portion has a first end as an end of the first side in the width direction and a second end as an end of the second side in the width direction. The pressing unit is configured so that the pressing force at the first end is greater than the pressing force at the second end. The elastic layer includes a high hardness region provided on the first side, and the hardness of the elastic layer in the high hardness region is higher than the hardness of the elastic layer in the central portion.

[0007] According to a third aspect of the present invention, a fixing device includes: a heating unit configured to heat a sheet; and a facing roller facing the heating unit and forming a fixing nip together with the heating unit. The fixing device is configured to fix a toner image carried on a sheet to the sheet by applying heat and pressure at the fixing nip. Regardless of the size of the sheet, one end of the sheet in the width direction intersecting the sheet conveying direction conveyed to the fixing device passes through a predetermined position of the fixing nip in the width direction. The heating unit includes a rotatable and flexible annular rotating member, a heater disposed in the inner space of the rotating member and configured to heat the rotating member, and a limiting member. The facing roller includes a roller portion, the roller portion including a base and an elastic layer disposed around the base and having elasticity. In the case where the side where the predetermined position in the width direction is located relative to the central portion of the roller portion is defined as a first side and the side opposite to the first side is defined as a second side, the limiting member has a limiting surface, the limiting surface is configured to contact the end surface of the rotating member on the second side in the width direction to limit the movement of the rotating member toward the second side. The rotating member includes a base layer and an elastic layer disposed around the base layer and containing a filler. The base layer has a protrusion that protrudes relative to the elastic layer in a first direction directed from a first side to a second side in the width direction and is configured to contact a restriction surface in the width direction.

[0008] According to a fourth aspect of the present invention, a fixing device comprises: a heating unit configured to heat a sheet; and a facing roller facing the heating unit and forming a fixing nip together with the heating unit. The fixing device is configured to fix a toner image carried on a sheet to the sheet by applying heat and pressure at the fixing nip. Regardless of the size of the sheet, one end of the sheet conveyed to the fixing device in a width direction intersecting with the sheet conveying direction passes through a predetermined position of the fixing nip in the width direction. The heat unit comprises a rotatable and flexible annular rotating member, a heater disposed in an internal space of the rotating member and configured to heat the rotating member, a first supporting member disposed in the internal space and configured to support the heater, and a second supporting member disposed in the internal space and configured to support the first supporting member. The facing roller comprises a roller portion, the roller portion comprising a base and an elastic layer disposed around the base and having elasticity. In the case where the side where the predetermined position in the width direction is located relative to the central part of the roller portion is defined as a first side and the side opposite to the first side is defined as a second side, the first supporting member includes: a first guide portion provided on the first side in the width direction and configured to guide the rotating member at a position upstream of the fixing nip portion in the sheet conveying direction; and a second guide portion provided on the second side in the width direction and configured to guide the rotating member at a position upstream of the fixing nip portion in the sheet conveying direction. The second supporting member has a facing portion which is farther away from the fixing nip portion than the first guide portion and the second guide portion in an orthogonal direction orthogonal to the sheet conveying direction and the width direction and faces an upstream portion of the inner peripheral surface of the rotating member in the sheet conveying direction. A distance from the facing portion to an upstream end of the second guide portion in the sheet conveying direction is longer than a distance from the facing portion to an upstream end of the first guide portion in the sheet conveying direction.

[0009] According to a fifth aspect of the present invention, a fixing device comprises: a heating unit configured to heat a sheet; and a facing roller facing the heating unit and forming a fixing nip together with the heating unit. The fixing device is configured to fix a toner image carried on a sheet to the sheet by applying heat and pressure at the fixing nip. Regardless of the size of the sheet, one end of the sheet conveyed to the fixing device in a width direction intersecting with the sheet conveying direction passes through a predetermined position of the fixing nip in the width direction. The heating unit comprises a rotatable and flexible annular rotating member, a heater disposed in an internal space of the rotating member and configured to heat the rotating member, a first supporting member disposed in the internal space and configured to support the heater, and a second supporting member disposed in the internal space and configured to support the first supporting member. The facing roller comprises a roller portion, the roller portion comprising a base and an elastic layer disposed around the base and having elasticity. The second supporting member has a facing portion at an end portion on the opposite side to the roller portion with respect to the fixing nip portion in a direction orthogonal to the sheet conveying direction and the width direction, the facing portion facing an upstream portion of the inner peripheral surface of the rotating member in the sheet conveying direction. The heating unit includes a cover provided on the opposite side to the predetermined position with respect to the center portion of the roller portion in the width direction, the cover being provided between the facing portion of the second supporting member and the upstream portion of the inner peripheral surface of the rotating member in the sheet conveying direction.

[0010] According to a sixth aspect of the present invention, a fixing device comprises: a heating unit configured to heat a sheet; and a facing roller facing the heating unit and forming a fixing nip together with the heating unit. The fixing device is configured to fix a toner image carried on a sheet to the sheet by applying heat and pressure at the fixing nip. Regardless of the size of the sheet, one end of the sheet conveyed to the fixing device in a width direction intersecting with the sheet conveying direction passes through a predetermined position of the fixing nip in the width direction. The heating unit comprises a rotatable and flexible annular rotating member, a heater disposed in an internal space of the rotating member and configured to heat the rotating member, and a limiting member. The facing roller comprises a roller portion, the roller portion comprising a base and an elastic layer disposed around the base and having elasticity. In the case where the side where the predetermined position in the width direction is located relative to the central part of the roller portion is defined as a first side and the side opposite to the first side is defined as a second side, the limiting member has: a limiting surface configured to contact with the end surface of the rotating member on the second side in the width direction to limit the movement of the rotating member toward the second side; and a guide portion provided to protrude from the limiting surface toward the rotating member in the width direction and configured to guide the rotating member by contacting with the inner peripheral surface of the rotating member. The limiting member is configured to be movable to a first position and a second position so that the guide portion of the limiting member located at the second position is located further upstream in the sheet conveying direction than the guide portion of the limiting member located at the first position, and is configured to move from the first position to the second position by the rotating member pushing the limiting surface in a first direction from the first side to the second side when the limiting member is located at the first position.

[0011] According to a seventh aspect of the present invention, an image forming apparatus includes: an image forming unit configured to form a toner image on a sheet; and the fixing device configured to fix the toner image formed by the image forming unit onto the sheet.

[0012] Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1A is a schematic cross-sectional view showing an imaging apparatus according to a first embodiment.

[0014] Figure 1B is a plan view showing the skew feed correction device according to the first embodiment.

[0015] Figure 2 is a schematic cross-sectional view of the fixing device according to the first embodiment.

[0016] Figure 3 is a schematic side view of the fixing device according to the first embodiment.

[0017] Figure 4A and Figure 4B is a view showing a fixing device according to a first embodiment, wherein Figure 4A is a cross-sectional view facing the roller, Figure 4B is a graph showing the outer diameter of the facing roller in the width direction.

[0018] Figure 5A is a schematic side view of the fixing device according to the first embodiment.

[0019] Figure 5B is a graph showing temperature distribution of the facing roller in the width direction according to the first embodiment.

[0020] Fig. 6A is a schematic cross-sectional view of facing rolls according to Comparative Examples 1 and 2.

[0021] Figure 6B is a graph showing the outer diameters of the facing rollers according to Comparative Examples 1 and 2 in the width direction.

[0022] Fig. 7A is a sectional view of a facing roller of a fixing device according to a second embodiment.

[0023] Figure 7B is a schematic side view of a fixing device according to a second embodiment.

[0024] Figure 8 is a cross-sectional view showing a fixing film and a flange according to a comparative example.

[0025] Fig. 9A is a cross-sectional view of a fixing film of a fixing device according to a third embodiment.

[0026] Fig. 9B is a sectional view of a fixing film and a flange of a fixing device according to a third embodiment.

[0027] Fig. 10A is a cross-sectional view showing a fixing film and a flange on a first side of a fixing device according to a third embodiment.

[0028] Fig. 10B is a cross-sectional view showing a fixing film and a flange on a second side of a fixing device according to a third embodiment.

[0029] Fig.11A is a cross-sectional view showing a fixing film according to Comparative Example 3.

[0030] Fig. 11B is a cross-sectional view showing a fixing film according to Comparative Example 4.

[0031] Fig. 12A is a side view showing a fixing device according to a fourth embodiment.

[0032] Fig. 12B is a graph showing temperature distribution in the width direction of the facing roller of the fixing device according to the fourth embodiment.

[0033] Fig. 12C is a graph showing a conveying speed distribution in the width direction of a facing roller of a fixing device according to a fourth embodiment.

[0034] Fig.13A is a cross-sectional view of the heating unit according to Comparative Example 5 when fixing a letter-size sheet, when viewed from above.

[0035] Fig. 13B is a cross-sectional view of the heating unit according to Comparative Example 5 when fixing an A6 size sheet, when viewed from above.

[0036] Fig.14A It is a cross-sectional view when the heating unit according to Comparative Example 5 is fixed to a letter-size sheet, as viewed from the front.

[0037] Fig. 14B It is a cross-sectional view when the heating unit according to Comparative Example 5 is fixed to an A6 size sheet, as viewed from the front.

[0038] Fig.15 : is an explanatory diagram showing a force acting on the fixing film in a case where an intersection angle is formed between the facing roller and the fixing film.

[0039] Fig.16A is a cross-sectional view of the heating unit according to the fourth embodiment when fixing a letter-size sheet, when viewed from above.

[0040] Fig. 16B is a cross-sectional view when the heating unit according to the fourth embodiment is fixed to an A6 size sheet, as viewed from above.

[0041] Fig.17A is a cross-sectional view of a heating unit according to a fourth embodiment when fixing a letter-size sheet, when viewed from the front.

[0042] Fig. 17B is a cross-sectional view of a heating unit according to the fourth embodiment when fixing an A6 size sheet, as viewed from the front.

[0043] Fig.18 is a cross-sectional view of a heating unit according to a fifth embodiment when viewed from above.

[0044] Fig.19A is a cross-sectional view of the heating unit according to the fifth embodiment when fixing a letter-size sheet, when viewed from the front.

[0045] Fig.19Bis a cross-sectional view of a heating unit according to the fifth embodiment when fixing an A6 size sheet, as viewed from the front.

[0046] Fig. 20A is an explanatory diagram when the flange of the fixing device according to the sixth embodiment is located at the first position.

[0047] Fig. 20B is an explanatory diagram when the flange of the fixing device according to the sixth embodiment is located at the second position.

[0048] Fig.21A : is an explanatory diagram showing a heating unit according to a sixth embodiment when a flange is located at a first position.

[0049] Fig.21B : is an explanatory diagram showing the heating unit according to the sixth embodiment when the flange is located at the second position. DETAILED DESCRIPTION

[0050] First embodiment

[0051] First, a first embodiment of the present invention will be described. An image forming apparatus 100 is an electrophotographic laser beam printer that forms a monochrome toner image. Figure 1A 1 is an overall schematic cross-sectional view showing the imaging apparatus 100 according to the first embodiment.

[0052] In the following, Figure 1A and Figure 1B The directions are defined in the same way as the arrows in the diagram indicate directions. That is, Figure 1A The upper direction in the drawings is called the upper direction U, the lower direction in the drawings is called the lower direction D, the right direction in the drawings is called the front direction F (front direction), the left direction in the drawings is called the back direction B (back direction), the front direction in the drawings is called the left direction L, and the back direction in the drawings is called the right direction R (see Figure 1B ).like Figure 1B As shown in the figure, the left-right direction is referred to as a width direction W intersecting with the sheet conveying direction DF (in the present embodiment, the width direction W is orthogonal to the sheet conveying direction DF).

[0053] Schematic configuration of imaging device

[0054] The image forming apparatus 100 includes an image forming unit 140 that forms a toner image on a sheet as a recording material, a feeding unit 150 that feeds the sheet to the image forming unit 140, a skew feed correction device 19, and a fixing device 6 that heats and fixes the toner image on the sheet to the sheet. The image forming unit 140 includes a photosensitive drum 1, which is a drum-type electrophotographic photosensitive member as an image bearing member. The photosensitive drum 1 is rotatably supported by an apparatus main body 100a forming a housing of the image forming apparatus 100. The image forming unit 140 includes a charging roller 2, a laser scanner 3, a developing device 4, a transfer roller 5, and a cleaning device 8 that are sequentially arranged in a rotation direction around the outer peripheral surface of the photosensitive drum 1.

[0055] The image forming apparatus 100 according to the first embodiment includes a control unit 31. The control unit 31 controls the image forming unit 140, the feeding unit 150, the fixing device 6, etc. The control unit 31 includes a central processing unit (CPU) and a memory such as a read-only memory (ROM) or a random access memory (RAM), and the memory stores various programs required for image forming. The control unit 31 receives a print signal from an external device such as a host computer, and executes a predetermined image forming control sequence based on the print signal.

[0056] When the control unit 31 executes the control sequence, the drum motor (not shown) is driven to rotate, and the photosensitive drum 1 rotates in the direction of the arrow at a predetermined peripheral speed (process speed). The surface of the rotating photosensitive drum 1 is uniformly charged to a predetermined potential of the same polarity as the toner (negative polarity in this embodiment) by the charging roller 2. The laser scanner 3 scans the charged surface of the photosensitive drum 1 with a laser beam LB based on image information to expose the surface of the photosensitive drum 1. By this exposure, the charge of the exposure portion is removed, and an electrostatic latent image is formed on the surface of the photosensitive drum 1.

[0057] The developing device 4 includes a developing roller 41 and a toner container 42 for storing toner. The toner is rubbed by a member such as a polyurethane scraper (not shown) and charged to a predetermined polarity (negative polarity in this embodiment). When a negative potential is applied to the developing roller 41 by a developing voltage power supply (not shown), the developing device 4 attaches the toner to the electrostatic latent image on the surface of the photosensitive drum 1 by using the potential difference, and develops the electrostatic latent image into a toner image T. When a positive potential having a polarity opposite to that of the toner is applied to the transfer roller 5, the toner image T formed on the surface of the photosensitive drum 1 is transferred to the sheet S by using the potential difference caused by the transfer voltage.

[0058] On the other hand, the feeding unit 150 includes a feeding roller 11 and a conveying drive motor (not shown) driving the feeding roller 11. The control unit 31 drives the conveying drive motor to rotate, and the feeding roller 11 rotates to feed the sheet S supported and stored in the cassette 7 to the conveying path. The sheet S is conveyed to the skew feed correction device 19.

[0059] like Figure 1B As shown, the skew feed correction device 19 includes a plurality of conveying roller pairs 14 and 15, skew roller pairs 17a, 17b and 17c, and a side abutment plate 18. For example, in a case where a sheet S is conveyed in a skewed state by the plurality of conveying roller pairs 14 and 15 in the sheet conveying direction DF, the skew feed correction device 19 operates as follows. First, when the sheet S reaches the skew roller pairs 17a, 17b and 17c, a conveying force is applied to the sheet S in the width direction W in addition to the sheet conveying direction DF, so that the sheet S is conveyed while moving toward the side abutment plate 18. When the side ends of the sheet S abut against the side abutment plate 18, the skew roller pairs 17a, 17b and 17c slide, so that the sheet S rotates and is aligned with the side abutment plate 18, thereby correcting the skew. Furthermore, for example, even in a case where the sheet S is conveyed in the sheet conveying direction DF by the plurality of conveying roller pairs 14 and 15 in a non-skewed state, the sheet is conveyed in such a manner that the sheet S is aligned with the side abutment plate 18 by the skew roller pairs 17a, 17b, and 17c. In the present embodiment, the abutment surface of the side abutment plate 18 is set to the sheet passing reference position P0. Therefore, the sheet S is conveyed to the transfer nip N1 of the imaging unit 140 and the fixing nip N2 of the fixing device 6 based on the side end reference, wherein one end of the sheet S in the width direction W passes through the sheet passing reference position P0 (predetermined position) regardless of the size of the sheet. That is, the skew feed correction device 19 is an example of a conveying unit that is provided upstream of the imaging unit 140 in the sheet conveying direction DF, and conveys the sheet in the sheet conveying direction DF while moving the sheet in the width direction W so that one end of the sheet passes through the sheet passing reference position P0 of the fixing nip N2.

[0060] An alignment roller pair 16 is provided downstream of the skew feed correction device 19 and upstream of the transfer nip N1 between the surface of the photosensitive drum 1 and the outer peripheral surface of the transfer roller 5. The control unit 31 adjusts the conveyance timing of the sheet S by the alignment roller pair 16, and starts the conveyance of the sheet S so that the toner image is transferred from the photosensitive drum 1 to the sheet S at the transfer nip N1. In the present embodiment, the case where the skew feed correction device 19 is applied to convey the sheet by aligning the sheet with the side abutment plate 18 by the skew roller pair 17a, 17b, and 17c in order to realize the side end reference has been described, but the present technology is not limited thereto. For example, the skew feed correction device 19 is not necessarily provided, and the side end reference may be realized by positioning the sheet in the width direction by moving the alignment roller pair in the width direction in a state where the sheet is clamped by the alignment roller pair or the like.

[0061] The toner image formed on the surface of the photosensitive drum 1 is transferred to the sheet, and the sheet S to which the toner image has been transferred is conveyed to the fixing device 6 along the conveying guide 10, and the toner image on the sheet S is heated and pressurized by the fixing device 6 to be heated and fixed to the sheet S. The sheet S to which the toner image T is fixed is conveyed in the order of the conveying roller pair 12 and the discharge roller pair 13, and discharged to the discharge tray 100b set on the upper surface of the device body 100a. The residual toner remaining on the surface of the photosensitive drum 1 after the toner image is transferred to the sheet S is removed by the cleaning blade 81 of the cleaning device 8 and accumulated in the cleaning device 8. The imaging is sequentially performed by repeating the above-mentioned operation. The imaging device 100 according to the first embodiment can form an image at a printing speed of 70 sheets / minute, for example, in the case of an A4 size sheet.

[0062] Fixing device

[0063] Next, we will refer to Figure 2 and Figure 3 The fixing device 6 is described. Figure 2 is a cross-sectional view of the fixing device 6, Figure 3 The fixing nip N2 is a schematic diagram of the fixing nip N2 viewed from the upstream (front side) in the sheet conveying direction DF. The fixing device 6 fixes the toner image formed by the imaging unit 140 onto the sheet. The fixing device 6 includes a heating unit 60 that heats the sheet S, a facing roller 61 that faces the heating unit 60 and forms the fixing nip N2 together with the heating unit 60, and a pressing unit 48 (see FIG. Figure 3 ). The facing roller 61 is driven to rotate by the driving gear 47 and is driven to rotate in the R1 direction. The fixing film 25 is driven to rotate by the facing roller 61 that contacts the fixing film 25 at the fixing nip N2 and is driven to rotate in the R2 direction opposite to the R1 direction. The fixing device 6 clamps the sheet S at the fixing nip N2 and applies heat and pressure to fix the toner image T carried on the sheet S to the sheet S.

[0064] Facing Roller

[0065] The facing roller 61 includes a roller portion 26 that forms the fixing nip N2 together with the heating unit 60, and shaft portions 264a and 264b that are continuously provided from the roller portion 26 on both sides of the roller portion 26 in the width direction W. The shaft portions 264a and 264b are rotatably supported by a frame (not shown) of the fixing device 6. The roller portion 26 includes a base portion 261 as a shaft core, an elastic layer 262 that is an example of a second elastic layer having elasticity and is provided around the base portion 261, and a release layer 263 that is provided around the elastic layer 262.

[0066] In the present embodiment, in the width direction W, the side where the sheet passes through the reference position P0 relative to the center portion PC of the roller portion 26 is referred to as the first side W1, and the side opposite to the first side W1 is referred to as the second side W2. That is, the first side W1 is the left direction L side in the width direction W, and the second side W2 is the right direction R side in the width direction W. The right direction R is a first direction pointing from the first side W1 to the second side W2 along the width direction W. In the width direction W, the roller portion 26 has a first end 26a as an end of the first side W1 and a second end 26b as an end of the second side W2. In the present specification, the first side W1 not only refers to the side where the sheet passes through the reference position P0 relative to the center portion PC of the roller portion 26 in the width direction W, but also may refer to the direction from the side where the sheet does not pass through the reference position P0 toward the side where the sheet passes through the reference position P0 (the left direction L in the present embodiment). Similarly, in this specification, the second side W2 can refer not only to the side opposite to the first side W1 in the width direction W, but also to the direction from the side where the sheet passes the reference position P0 toward the side where the sheet does not pass the reference position P0 (the right direction R in this embodiment).

[0067] In the present embodiment, the outer diameter of the center portion PC of the roller portion 26 in the width direction W is about 25 mm. The base portion 261 is made of a metal material such as aluminum or iron and has a solid or hollow shape. In the present embodiment, the base portion 261 is made of aluminum and has a solid shape. The elastic layer 262 is made of heat-resistant silicone rubber and is made conductive by adding a conductive material such as carbon.

[0068] The release layer 263 in contact with the outer surface of the fixing film 25 is a releasable tube having a thickness of 10 to 80 μm and is made of a fluororesin such as PFA, PTFE or FEP. Here, PFA is an abbreviation of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, PTFE is an abbreviation of polytetrafluoroethylene (tetrafluoride), and FEP is an abbreviation of tetrafluoroethylene-hexafluoropropylene copolymer (4,6-fluorinated).

[0069] From the viewpoint of preventing charging accompanying the passage of the sheet, it is preferable that the release layer 263 has conductivity. However, on the other hand, when a conductive material is added to impart conductivity, the release property is deteriorated, and there is a possibility that a mixture of toner and paper powder adheres to the roller portion 26 (hereinafter referred to as roller contamination). It is known that a method of applying an electric potential to the base 261 while using a high-resistance fluororesin material as the release layer 263 can effectively suppress charging and roller contamination. Therefore, in the present embodiment, the release layer 263 of the roller portion 26 is a PFA tube with a thickness of 30 μm, and a potential of +300 V is applied to the base 261.

[0070] Heating unit

[0071] like Figure 2 and Figure 3 As shown, the heating unit 60 includes a heater 20, a heater support 29, a bracket 22 made of metal, a tubular fixing film 25, and flanges 40a and 40b. A power supply control unit 272 connected to a commercial AC power source 27 supplies power to the base 261 based on a signal from a control circuit 271.

[0072] Heater

[0073] The heater 20 is disposed in the internal space of the fixing film 25, and heats the fixing film 25. The heater 20 includes a heat-resistant heater substrate 201 made of aluminum nitride, aluminum oxide, or the like. A resistor pattern 202 serving as a conductive heating resistor layer that generates heat by energizing is formed on the surface of the heater substrate 201 by, for example, screen printing. The resistor pattern 202 is covered with a heat-resistant covering material 203, and a thermistor 204 serving as a temperature detection member that detects the temperature of the heater 20 is provided on the covering material 203. In the present embodiment, a case where the heater substrate 201 is made of ceramics such as aluminum nitride or aluminum oxide has been described, but the present technology is not limited thereto, and the heater substrate 201 may also be made of metal. In this case, a configuration in which an insulating layer made of glass or the like is provided on the surface of the heater substrate 201 and a resistor pattern 202 is provided on the insulating layer may be adopted.

[0074] Heater support

[0075] The heater support 29 is a holding member that holds the heater 20 serving as a heating body. That is, the heater support 29 is an example of a first supporting member, is disposed in the internal space of the fixing film 25, and supports the heater 20. A heat-resistant resin such as a liquid crystal polymer, a phenolic resin, PPS, or PEEK is used as a material for the heater support 29. The heater support 29 serves as a supporting member that supports the heater 20, and also serves as a guide member that guides the fixing film 25 to rotate.

[0076] Bracket

[0077] The bracket 22 is an example of a second supporting member, is disposed in the inner space of the fixing film 25, and supports the heater holder 29. The bracket 22 is fixedly supported by a frame (not shown) of the fixing device 6.

[0078] Fusing film

[0079] The fixing film 25 is an example of a rotatable and flexible annular rotating member, and is cylindrical with a diameter of 24 mm in this embodiment. The fixing film 25 is loosely fitted on the heater support 29 from the outside so that there is a gap between them. The fixing film 25 is formed by stacking a base layer 251, an elastic layer 252 as an example of a first elastic layer arranged around the base layer 251, and a surface layer 253 arranged around the elastic layer 252. A heat-resistant resin material with low heat capacity, such as a general material such as polyimide, polyamide-imide, PEEK or PES, is used as a material for the base layer 251. The thickness of the base layer 251 is preferably 18 μm or more and 150 μm or less, because it is necessary to reduce the heat capacity to achieve quick start performance and also meet the mechanical strength requirements. The base layer 251 according to the first embodiment is a cylindrical polyimide base layer with a thickness of 70 μm.

[0080] The elastic layer 252 is made of a material having elasticity represented by silicone rubber. By providing the elastic layer 252, the toner image T can be wrapped and heat can be applied uniformly, so that a high-quality image without unevenness can be obtained. Since the elastic layer 252 has low thermal conductivity in the case of only silicone rubber, a thermally conductive filler made of an inorganic material is added. A filler containing ceramic powder, metal oxide powder, or metal powder can be used as a filler. In the present embodiment, a thermally conductive filler such as aluminum oxide, metal silicon, silicon carbide, or zinc oxide is added as a filler to give the elastic layer 252 high thermal conductivity. In a high-speed machine such as the imaging device 100 according to the first embodiment, the addition amount (content) of the filler can be appropriately adjusted to ensure a thermal conductivity of 0.9 W / m·K or more. In the present embodiment, aluminum oxide and metal silicon are added as thermally conductive fillers to the rubber material of the elastic layer 252, thereby ensuring a thermal conductivity of 1.5 W / m·K. The thickness of the elastic layer 252 is 270 μm.

[0081] As a release layer, the surface layer 253 needs to have high release properties and high wear resistance to the toner. Fluororesins such as PFA, PTFE or FEP are used as the material of the surface layer 253. The surface layer 253 is formed by a coating or a tube layer obtained by firing a resin dispersion. In addition, conductivity can be imparted by adding additives such as carbon or ion conductive materials to the fluororesin. In the surface layer 253 according to the first embodiment, a fluororesin (PFA) is used as the material, no conductive material is added, and a tube layer with a thickness of 25 μm is used.

[0082] Flange

[0083] Next, we will refer to Figure 3 The flanges 40a and 40b according to the present embodiment are described. Figure 3, the fixing film 25 is indicated by a dotted line and is shown in a manner that its interior is visible. The fixing film 25 may deviate to the left or right in the width direction W. The flanges 40a and 40b are arranged to abut against both ends of the fixing film 25 in the width direction W to control the deviation. The first flange 40a is arranged to face the end surface 25a of the first side W1 of the fixing film 25 in the width direction W, and the second flange 40b is arranged to face the end surface 25b of the second side W2 of the fixing film 25 in the width direction W.

[0084] The first flange 40a includes a limiting surface 41a and a guide portion 42a. The second flange 40b is an example of a limiting component and includes a limiting surface 41b and a guide portion 42b. Since the first flange 40a and the second flange 40b have a horizontally symmetrical shape, the second flange 40b will be mainly described below. The limiting surface 41b limits the movement of the fixing film 25 to the second side W2 (right direction R) by contacting the end surface 25b of the second side W2 of the fixing film 25 in the width direction W. The guide portion 42b is arranged to protrude from the limiting surface 41b toward the fixing film 25 in the left direction L, and contact the inner peripheral surface of the fixing film 25 to guide the fixing film 25.

[0085] For example, when the fixing film 25 deviates in the right direction R, the end surface 25b of the fixing film 25 abuts against the limiting surface 41b of the second flange 40b to limit the deviation. The guide portion 42b contacts the inner peripheral surface of the fixing film 25 and guides the inner peripheral surface of the fixing film 25 in the end region adjacent to the end surface 25b of the fixing film 25. Figure 3 In this embodiment, the guide portion 42a of the first flange 40a and the inner peripheral surface of the fixing film 25 contact each other in the contact area SL, and the guide portion 42b of the second flange 40b and the inner peripheral surface of the fixing film 25 contact each other in the contact area SR.

[0086] For example, when the inner peripheral surface of the fixing film 25 and the guide portion 42b of the second flange 40b slide while contacting each other in the contact area SR, the heat required for fixing the toner escapes from the fixing film 25 toward the second flange 40b. Therefore, the guide portion 42b of the second flange 40b is set outside the maximum conveyance area Ar0 (in the right direction R) in the width direction W, which is the conveyance area for the maximum width sheet. Similarly, the guide portion 42a of the first flange 40a is set outside the maximum conveyance area Ar0 (in the left direction L) in the width direction W.

[0087] The material of the flanges 40a and 40b preferably has the same hardness as the base layer 251 of the fixing film 25 as a sliding counterpart. This is because: when the hardness of the flanges 40a and 40b is higher than the hardness of the base layer 251 of the fixing film 25, wear occurs on the inner peripheral surface of the base layer 251 of the fixing film 25, and conversely, when the hardness of the flanges 40a and 40b is lower than the hardness of the base layer 251, wear occurs on the outer peripheral surface of the guide portions 42a and 42b. Therefore, in the present embodiment, liquid crystal polymer (LCP) is used as the material of the flanges 40a and 40b.

[0088] Push unit

[0089] In this embodiment, if Figure 3 As shown, the pushing unit 48 pushes the heating unit 60 toward the facing roller 61. The pushing unit 48 includes: a first pushing spring 48a, which is an example of a first pushing portion that pushes the first flange 40a toward the facing roller 61; and a second pushing spring 48b, which is an example of a second pushing portion that pushes the second flange 40b toward the facing roller 61. Each of the pushing springs 48a and 48b is formed of, for example, a compression coil spring, but the type of the spring is not limited thereto, and, for example, a tension coil spring or other types of springs may also be applied.

[0090] The first urging spring 48a urges the first flange 40a and the second urging spring 48b urges the second flange 40b to apply urging force to the heater holder 29 via the bracket 22 and press the fixing film 25 against the facing roller 61. As a result, a fixing nip N is formed between the fixing film 25 and the facing roller 61.

[0091] In the present embodiment, the first push spring 48a is configured to push the first flange 40a toward the facing roller 61 and the second push spring 48b is configured to push the second flange 40b toward the facing roller 61, but the present technology is not limited thereto. For example, at least one of the first push spring 48a and the second push spring 48b may be configured to push the facing roller 61 toward the flanges 40a and 40b. That is, the first push spring 48a pushes one of the heating unit 60 and the facing roller 61 toward the other of the heating unit 60 and the facing roller 61 at the first side W1 in the width direction W. The second push spring 48b pushes one of the heating unit 60 and the facing roller 61 toward the other of the heating unit 60 and the facing roller 61 at the second side W2 in the width direction W.

[0092] Similarly, in the present embodiment, the case where the pressing unit 48 presses the heating unit 60 toward the facing roller 61 has been described, but the present technology is not limited thereto. For example, the facing roller 61 may be pressed toward the heating unit 60. That is, the pressing unit 48 presses one of the heating unit 60 and the facing roller 61 toward the other of the heating unit 60 and the facing roller 61.

[0093] Misalignment of the fixing film

[0094] Here, we will refer to Figure 5A and Figure 5B The deviation of the fixing film 25 is described. Figure 5A 1 is a schematic diagram of the fixing nip N2 when the sheet passes through based on the side end reference when viewed from the upstream (front side) in the sheet conveying direction DF, and the sheet S is gripped and conveyed at the fixing nip N2 formed by the fixing film 25 and the roller portion 26. In the present embodiment, the maximum width of the sheet S that can pass through the fixing device 6 is the width of the letter size, and the maximum conveying area Ar0 is set to the letter size. Figure 5A The illustrated sheet S is an A6 size sheet S having a size in the width direction W that is smaller than the letter size having a maximum width.

[0095] Figure 5B FIG. 2 shows the distribution of the surface temperature of the facing roller 61 in the width direction W when the A6 size sheet S passes continuously. Figure 5B As shown, the surface temperature of the facing roller 61 is relatively higher at the non-sheet passing portion Ar2 than at the sheet passing portion Ar1. In the sheet passing portion Ar1, heat is transferred from the surface of the facing roller 61 to the sheet S, and the temperature of the facing roller 61 decreases. On the other hand, in the non-sheet passing portion Ar2, since there is no sheet S, heat is continuously supplied from the fixing film 25 to the facing roller 61, and thus the temperature of the facing roller 61 increases.

[0096] Here, the facing roller 61 includes an elastic layer 262 made of heat-resistant silicone rubber and provided on the outer periphery of the base 261, and the silicone rubber has a characteristic of being easily thermally expanded at high temperatures. Therefore, due to the thermal expansion of the silicone rubber, the outer diameter of the non-sheet passing portion Ar2 of the facing roller 61 becomes larger than the outer diameter of the sheet passing portion Ar1. Therefore, the peripheral speed of the facing roller 61 is different in the width direction W, and the sheet passing portion Ar1 becomes relatively slow, while the non-sheet passing portion Ar2 becomes faster.

[0097] The facing roller 61 is driven to rotate by the driving gear 47 and is driven along Figure 5A The fixing film 25 is driven to rotate in the R1 direction at the fixing nip N2 by the facing roller 61, along Figure 5A At this time, when there is a difference in the peripheral speed of the facing roller 61, the direction in which the fixing film 25 (the fixing film 25 is driven to rotate) rotates faster, that is, Figure 5A The offset force is generated in the right direction R in the width direction W. Due to the offset force, the fixing film 25 moves in the right direction R in the width direction W and abuts against the second flange 40b. When the temperature of the non-sheet passing portion Ar2 facing the roller 61 further increases and the offset force further increases, the fixing film 25 will deform (bend) when the offset force exceeds the rigidity of the fixing film 25.

[0098] Here, the mechanism of generating the offset force will be described. When the portion of the roller portion 26 corresponding to the non-sheet passing portion Ar2 is thermally expanded due to the temperature rise of the non-sheet passing portion Ar2 and the outer diameter of the roller portion 26 increases, the peripheral speed increases. In the fixing device 6 based on the side end reference, the temperature rise of the non-sheet passing portion Ar2 occurs only on the side opposite to the reference surface in the width direction W. Therefore, in the fixing device 6 based on the side end reference, a difference in the outer diameter of the roller portion 26 is generated in the width direction W, and a difference is generated in the feeding speed of the fixing film 25 at the fixing clamping portion N2 in the width direction W. As a result, an offset force is generated toward the side where the rotation speed of the fixing film 25 is higher. As the difference in the outer diameter of the roller portion 26 in the width direction W (i.e., the temperature rise of the non-sheet passing portion Ar2) increases, the magnitude of the offset force increases.

[0099] Therefore, in the present embodiment, the change in the outer diameter after expansion is suppressed by making the thickness of the elastic layer 262 that is thermally expanded in the facing roller 61 different in the width direction W. Figure 4A and Figure 4B The facing roller 61 according to the present embodiment is described.

[0100] Figure 4A 2 is a schematic diagram showing a cross section of the facing roller 61 in the width direction W, and shows the elastic layer 262 on the outer periphery of the base 261. In the present embodiment, the roller portion 26 includes the elastic layer 262 on the base 261, and the maximum outer diameter D1 of the base 261 at the first end 26a of the roller portion 26 is smaller than the maximum outer diameter D2 of the base 261 at the second end 26b. In the present embodiment, D1 is 20 mm, and D2 is 22 mm. The shape between D1 and D2 may be a taper connecting D1 and D2, or a straight line portion with a constant outer diameter may be partially provided and the portion other than the straight line portion may be a taper.

[0101] Since the outer diameter of the roller portion 26 does not vary much in the width direction W, the thickness d2 of the elastic layer 262 at the second end portion 26b is made smaller than the thickness d1 of the elastic layer 262 at the first end portion 26a. Figure 5A As shown, even when the non-sheet passing portion Ar2 has a relatively higher temperature than the sheet passing portion Ar1, the expansion amount of the elastic layer 262 in the non-sheet passing portion Ar2 can be made smaller than the expansion amount of the elastic layer 262 in the sheet passing portion Ar1. Therefore, in terms of the outer diameter of the roller portion 26, it is possible to suppress the non-sheet passing portion Ar2 from being significantly larger than the sheet passing portion Ar1, and the generation of the offset force can be reduced.

[0102] The thickness d2 of the elastic layer 262 at the second end portion 26b is preferably 65% ​​or more and 75% or less of the thickness d1 of the elastic layer 262 at the first end portion 26a, and is about 69% in the present embodiment. In consideration of the fixing temperature and the thermal expansion coefficient of the elastic layer, when the thickness d2 of the elastic layer 262 is 65% or more and 75% or less of the thickness d1 of the elastic layer 262, the generation of the offset force can be more effectively suppressed than when the thickness d2 of the elastic layer 262 is less than 65% or greater than 75% of the thickness d1.

[0103] Figure 4B The profile when measuring the outer diameter shape of the facing roller 61 is shown, and the facing roller has an inverted crown shape, in which the outer diameter of the central portion PC is the smallest, and the outer diameter increases in a quadratic curve from the central portion PC toward the end surface PL of the first side W1 and the end surface PR of the second side W2. Since the outer diameter shape is an inverted crown shape, when the sheet S is conveyed, the outer diameter of the end of the roller portion 26 increases, the conveying speed increases, and a tensile force toward both ends in the width direction W is generated on the sheet S, so that the occurrence of paper wrinkles, etc. can be suppressed.

[0104] In the present embodiment, the maximum outer diameter of the second end portion 26b of the roller portion 26 is larger than the maximum outer diameter of the first end portion 26a. The maximum outer diameter of the first end portion 26a of the roller portion 26 is the outer diameter of the end surface PL of the roller portion 26 on the first side W1, and the maximum outer diameter of the second end portion 26b of the roller portion 26 is the outer diameter of the end surface PR of the roller portion 26 on the second side W2. As a result, for example, when the entire roller portion 26 becomes a sheet passing portion and is heated substantially uniformly as in the case of a letter-size sheet S, even when the first side W1 in the width direction W expands more than the second side W2, the difference in the outer diameter of the roller portion 26 in the width direction W can be reduced.

[0105] In this embodiment, under room temperature, the maximum outer diameter of the first end portion 26a is 24.8 mm, the maximum outer diameter of the second end portion 26b is 25.3 mm, and the outer diameter of the center portion PC is 24.7 mm. The maximum outer diameter of the second end portion 26b is preferably 101% or more and 103% or less of the maximum outer diameter of the first end portion 26a, and in this embodiment, it is 102% of the maximum outer diameter of the first end portion 26a. Considering the fixing temperature and the thermal expansion coefficient of the elastic layer, when the maximum outer diameter of the second end portion 26b is 101% or more and 103% or less of the maximum outer diameter of the first end portion 26a, the generation of the offset force can be more effectively suppressed than when the maximum outer diameter of the second end portion is less than 101% or greater than 103% of the maximum outer diameter of the first end portion 26a.

[0106] Examples and Comparative Examples

[0107] The example 1 using the facing roller 61 according to the present embodiment and the example 2 using the facing roller 61 according to the present embodiment Fig. 6A Comparative Example 1 of the facing roller 161 was subjected to a comparative experiment.

[0108] Comparative Example 1 will be described. Fig. 6A As shown, the roller portion 76 of Comparative Example 1 facing the roller 161 includes a base 761, an elastic layer 762 disposed around the base 761, and a release layer 763 disposed around the elastic layer 762. The maximum outer diameter D1 of the base 761 is 20 mm and is uniform in the width direction W. Figure 6B As shown, the outer diameter profile is a horizontally symmetrical inverted crown shape, wherein the outer diameter increases from the center PC to both ends in the width direction W. The outer diameters of the end surface PL of the first side W1 and the end surface PR of the second side W2 are 24.8 mm, and the outer diameter of the center PC is 24.7 mm.

[0109] In the comparative experiment, 20 letter-size sheets were continuously passed at a speed of 40 sheets / minute, and the temperature and outer diameter of the roller portion were measured when the trailing edge of the last 20th sheet passed through the fixing nip N2. In addition, 20 A6-size sheets were continuously passed at a speed of 75 sheets / minute, and the temperature and outer diameter of the roller portion were measured when the trailing edge of the last 20th sheet passed through the fixing nip N2. The results are shown in Table 1.

[0110] Table 1

[0111]

[0112] In Table 1, the outer diameter of PL is the maximum outer diameter of the first end of the roller, that is, the outer diameter at the end surface PL of the first side W1. The outer diameter of PR is the maximum outer diameter of the second end of the roller, that is, the outer diameter at the end surface PR of the second side W2. In the state before the sheet passes, the outer diameter of PL is 24.8 mm, and the outer diameter of PR is 25.3 mm. In Table 1, the temperature of PL is the average temperature in the half area of ​​the roller on the first side W1 relative to the center PC in the width direction W, and the temperature of PR is the average temperature in the half area of ​​the roller on the second side W2 relative to the center PC in the width direction W.

[0113] In the case where a letter-sized sheet having a maximum sheet passing width passes, in Example 1, the heated area of ​​the roller portion 26 is substantially consistent with the area where the sheet passes, so the temperature of the PL and the temperature of the PR are both 90° C. At this time, due to the expansion of the elastic layer 262, the outer diameter of the PL increases from 24.8 mm, the value before the sheet passes, to 25.5 mm, an increase of 0.7 mm. On the other hand, due to the expansion of the elastic layer 262, the outer diameter of the PR increases from 25.3 mm, the value before the sheet passes, to 25.4 mm, an increase of 0.1 mm. This difference is because the thickness of the elastic layer 262 of the roller portion 26 is different even if the temperature of the elastic layer 262 of the roller portion 26 is the same, so the expansion amount of the PL having a larger thickness of the elastic layer 262 is larger.

[0114] In Comparative Example 1, the temperature of PL and the temperature of PR were both 90° C. as in Example 1. In Comparative Example 1, since the thickness of the elastic layer 762 of the roller portion 26 was uniform in the width direction W, the amount of expansion of the elastic layer 762 was the same for PL and PR, and thus the outer diameters of PL and PR were both 25.5 mm.

[0115] Next, in the case where the A6 size sheet passes, the temperature of the PL in Example 1 is 90° C. due to the sheet passing. On the other hand, in the PR, since the non-sheet passing portion Ar2 where the sheet does not pass is generated, the temperature rises due to the temperature rise of the non-sheet passing portion Ar2, and the average temperature in the PR is 180° C. The outer diameter of the roller portion 26 is 25.5 mm in the PL, as in the case of the letter size sheet. On the other hand, since the temperature of the PR is high, the expansion amount of the elastic layer 262 increases, and thus the outer diameter is 25.6 mm.

[0116] In Comparative Example 1, the temperature of PL is 90° C. and the temperature of PR is 180° C. as in Example 1. The outer diameter of PL is 25.5 mm as in Example 1, but PR is at a high temperature of 180° C., and the thickness of the elastic layer 762 is larger, so the outer diameter is 25.9 mm.

[0117] From the results shown in Table 1, it can be seen that when an A6 size sheet is passed, the difference between the outer diameter of PL and the outer diameter of PR can be reduced in Example 1 compared with Comparative Example 1.

[0118] Next, Table 2 shows the ratio of the PR outer diameter when the PL outer diameter of the facing roller is 100% when this comparative experiment is performed.

[0119] Table 2

[0120] size Example 1 Comparative Example 1 stationery 99.6％ 100.0％ A6 100.4％ 101.6％

[0121] In Example 1, the outer diameter of PR is 99.6% when a letter-sized sheet passes through, and the outer diameter of PR is 100.4% when an A6-sized sheet passes through. In Comparative Example 1, the outer diameter of PR is 100% when a letter-sized sheet passes through, and the outer diameter of PR is 101.6% when an A6-sized sheet passes through. It can be considered that the more the outer diameter of PR exceeds 100%, the greater the peripheral speed difference between PL and PR, and the greater the offset force generated on the fixing film 25. It can be seen from the results shown in Table 2 that the offset force generated on the fixing film 25 when an A6-sized sheet passes through can be suppressed to be smaller in Example 1 than in Comparative Example 1.

[0122] Next, Table 3 shows results indicating whether deformation (buckling) of the fixing film 25 caused by the offset force occurred during the comparative experiment.

[0123] Table 3

[0124]

[0125] In Example 1, deformation of the fixing film 25 was not observed in the case of the letter-sized sheet and in the case of the A6-sized sheet. In Comparative Example 1, deformation of the fixing film 25 was not observed in the case of the letter-sized sheet, but deformation of the fixing film 25 was observed in the case of the A6-sized sheet. This is because: as the difference in outer diameter between the left and right parts of the roller portion increases, the difference in peripheral speed between PL and PR of the roller portion also increases, and for the driven rotating fixing film 25, a deviation force is generated in the direction in which the fixing film rotates faster. Therefore, in Example 1, deformation of the fixing film 25 caused by the deviation force did not occur in the case of the letter-sized sheet and in the case of the A6-sized sheet; in Comparative Example 1, it was confirmed that deformation of the fixing film 25 caused by the deviation force is likely to occur when the A6-sized sheet passes.

[0126] As described above, with the fixing device 6 according to the present embodiment, the thickness d2 of the elastic layer 262 at the second end portion 26b of the roller portion 26 is smaller than the thickness d1 of the elastic layer 262 at the first end portion 26a. Therefore, even when the non-sheet passing portion Ar2 has a relatively higher temperature than the sheet passing portion Ar1, the expansion amount of the elastic layer 262 in the non-sheet passing portion Ar2 can be made smaller than the expansion amount of the elastic layer 262 in the sheet passing portion Ar1. Therefore, it is possible to suppress the non-sheet passing portion Ar2 from being significantly larger than the sheet passing portion Ar1 in terms of the outer diameter of the roller portion 26, and to reduce the generation of the offset force to the fixing film 25. As a result, in the case where the conveying method is based on the side end reference, by increasing the speed of the fixing process without increasing the thickness of the fixing film 25, and by reducing the offset force to extend the life of the heating unit 60, it is possible to achieve both an increase in the fixing process speed and an extension of the life of the heating unit 60.

[0127] With the fixing device 6 of the present embodiment, in the base portion 261 of the roller portion 26, the maximum outer diameter D2 at the second end portion 26b is smaller than the maximum outer diameter D1 at the first end portion 26a. As a result, the thickness of the elastic layer 262 at the second end portion 26b can be reduced without greatly changing the outer diameter of the roller portion 26 in the width direction W.

[0128] Second embodiment

[0129] Next, a second embodiment of the present invention will be described, which has a configuration in which the facing roller 61 according to the first embodiment is changed. Therefore, a configuration similar to the first embodiment will be described with illustration omitted or with the same reference numerals added in the drawings.

[0130] For example, Figure 5AAs shown in FIG. 1 , when the sheet passing reference position P0 is at one side and the sheet width is smaller than the maximum sheet passing width, the fixing film 25 is biased in the direction of Figure 5A The offset force is in the right direction R. One of the reasons will be described.

[0131] In the case where the sheet is paper, the paper has the property of containing moisture in the atmosphere in the paper fibers (absorbing moisture), and the moisture contained in the sheet is released as water vapor into the fixing device 6A by being rapidly heated at the fixing nip N2. When a plurality of sheets continuously pass through the fixing device 6A, the amount of water vapor generated also increases, so the water vapor easily adheres to the facing roller 61A as water droplets. When the water droplets adhere to the surface of the facing roller 61A, the friction coefficient between the surface of the facing roller 61A and the sheet decreases, so a slip phenomenon occurs in which the conveying speed of the sheet decreases relative to the peripheral speed of the facing roller 61A. When the conveying speed of the sheet decreases, the rotation speed of the fixing film 25 that contacts the sheet and rotates driven by it also decreases.

[0132] On the other hand, since water vapor is not generated in the non-sheet passing portion Ar2 where the sheet does not pass, water droplets are not easily attached to the surface of the facing roller 61A. Therefore, slipping does not occur in the non-sheet passing portion Ar2, and the rotation speed of the fixing film 25 does not decrease. Due to the above phenomenon, the rotation speed of the sheet passing portion Ar1 of the fixing film 25 becomes low, and the rotation speed of the non-sheet passing portion Ar2 becomes high, so a deflection force is generated in the direction where the rotation speed becomes high. In the case where the deflection force becomes large, when the deflection force exceeds the rigidity of the fixing film 25, the fixing film 25 is deformed.

[0133] Facing Roller

[0134] Therefore, in this embodiment, the occurrence of slippage is reduced by making the pushing force of the pushing unit 48 at the first end 26aA of the first side W1 of the roller portion 26A greater than the pushing force at the second end 26bA of the second side W2. Fig. 7A and Figure 7B The facing roller 61A according to the present embodiment is described. Fig. 7A 2 is a cross-sectional view of a roller portion 26A facing the roller 61A according to the second embodiment. The roller portion 26A includes an elastic layer 262A on the outer periphery of a base portion 261A, and includes a release layer 263A on the outer periphery of the elastic layer 262A.

[0135] Figure 7B: is a cross-sectional view of the fixing device 6A according to the present embodiment in the width direction W. The hardness of the elastic layer of the roller portion 26A is different for the region ArL provided on the first end portion 26aA side and the region ArR provided on the second end portion 26bA side, and the hardness of the region ArL is higher than the hardness of the region ArR. The region ArL is an example of a high hardness region provided in the elastic layer 262A, provided on the first side W1 in the width direction W, and having a hardness higher than the hardness of the elastic layer 262A at the center portion PC. The region ArR is an example of a low hardness region provided in the elastic layer 262A, provided on the second side W2 in the width direction W, and having a hardness lower than the hardness of the elastic layer 262A at the center portion PC. The hardness of the elastic layer 262A is adjusted by changing the mixing ratio of silicone rubber or the like as a material. In the present embodiment, the hardness of the region ArL is 60° and the hardness of the region ArR is 54° according to the Asker C hardness. Other configurations such as dimensions are the same as those of Comparative Example 1.

[0136] Furthermore, at least a portion of the area ArL is positioned to overlap with the conveying area for conveying a sheet of the minimum conveying size when viewed from an intersecting direction (e.g., an up-and-down direction) intersecting the sheet conveying direction DF and the width direction W. The area ArL is located between the center portion PC and the sheet passing reference position P0 in the width direction W. As a result, even for a sheet of the minimum conveying size, the slipping phenomenon can be reduced by increasing the pushing force of the pushing unit 48.

[0137] Push unit

[0138] for Figure 7B As for the pushing force of the first pushing spring 48a and the second pushing spring 48b of the pushing unit 48 shown in the figure on the flanges 40a and 40b, the pushing force of the first pushing spring 48a is greater than the pushing force of the second pushing spring 48b. Specifically, the pushing force of the first pushing spring 48a is 147N, and the pushing force of the second pushing spring 48b is 98N. That is, the pushing unit 48 is configured so that the pushing force at the first end 26aA is greater than the pushing force at the second end 26bA. Therefore, by increasing the pushing force of the first side W1 that is prone to slipping due to moisture, the occurrence of the slip phenomenon can be reduced.

[0139] Here, by increasing the pushing force of the high hardness region (region ArL) where the hardness of the roller portion 26A is high and reducing the pushing force of the low hardness region (region ArR) where the hardness of the roller portion 26A is low, the deformation amount of the elastic layer 262A due to the pushing force can be made equal on the left and right sides. Therefore, even when the pushing forces on the fixing film 25 on the first side W1 and the second side W2 of the roller portion 26A are different from each other, the width of the fixing nip portion N2 formed by the fixing film 25 and the facing roller 61A in the front-rear direction can be substantially constant in the width direction W.

[0140] The hardness of the elastic layer 262A in the region ArL is preferably 110% or more and 120% or less of the hardness of the elastic layer 262A in the region ArR, and is 111% in the present embodiment. In consideration of the fixing temperature and the thermal expansion coefficient of the elastic layer, when the hardness of the elastic layer 262A in the region ArL is 110% or more and 120% or less of the hardness of the elastic layer 262A in the region ArR, generation of the offset force can be more effectively suppressed than when the hardness of the elastic layer 262A in the region ArL is less than 110% or greater than 120% of the hardness of the elastic layer 262A in the region ArR.

[0141] The urging force of the first urging spring 48a is preferably 130% or more and 170% or less of the urging force of the second urging spring 48b, and in the present embodiment, is 150% of the urging force of the second urging spring 48b. Considering the fixing temperature and the thermal expansion coefficient of the elastic layer, when the urging force of the first urging spring 48a is 130% or more and 170% or less of the urging force of the second urging spring 48b, the slippage phenomenon can be more effectively reduced than when the urging force of the first urging spring 48a is less than 130% or greater than 170% of the urging force of the second urging spring 48b.

[0142] Examples and Comparative Examples

[0143] Example 2 using the facing roller 61A according to the present embodiment and Example 2 using the facing roller 61A according to the present embodiment Fig. 6A A comparative experiment was conducted with the comparative example 2 of the facing roller 161 shown in the figure. First, the hardness of the elastic layer of the roller portion and the urging force of the urging unit 48 were measured in the example 2 and the comparative example 2. The results are shown in Table 4. In the comparative example 2, the area corresponding to the ArL in the hardness is the area at the position corresponding to the area ArL in the example 2, and the area corresponding to the ArR is the area at the position corresponding to the area ArR in the example 2.

[0144] Table 4

[0145]

[0146]

[0147] As shown in Table 4, the hardness of the elastic layer of the facing roller 161 of Comparative Example 2 is substantially uniform in the width direction W, and is 57° according to Asker C hardness. The pressure applied by the pressing unit 48 of Comparative Example 2 is equal to 122.5N on the left and right sides.

[0148] As a comparative experiment, 20 letter-size sheets were continuously passed at 40 sheets / min, and 20 A6-size sheets were continuously passed at 75 sheets / min. Table 5 shows the results indicating whether deformation (buckling) of the fixing film 25 caused by the offset force occurred during the comparative experiment.

[0149] Table 5

[0150]

[0151] In Example 2, since the width of the fixing nip N2 in the front-to-rear direction is constant in the width direction W, when a letter-sized sheet is passed, there is no difference in the sheet conveying speed on the left and right sides, and thus no deformation of the fixing film 25 is observed. When an A6-sized sheet is passed, water vapor is generated due to heating of the sheet at the fixing nip N2 in the area where the sheet passes, and thus the sheet conveying speed may be reduced. However, in Example 2, the pressure of the first side W1 is increased, so that the slippage phenomenon that occurs when water droplets adhere to the surface of the roller portion 26A can be minimized. Therefore, since the speed difference on the left and right sides of the fixing film 25 can be minimized when an A6-sized sheet is passed, no deformation of the fixing film 25 is observed.

[0152] In Comparative Example 2, when a letter-size sheet is passed, since there is no difference in pressure between the left and right sides and the width of the fixing nip N2 in the front-rear direction is constant in the width direction W, there is no difference in the sheet conveying speed between the left and right sides, and deformation of the fixing film 25 is not observed. On the other hand, when an A6-size sheet is passed, the sheet conveying speed is significantly reduced due to the generation of water vapor by heating the sheet at the fixing nip N2 in the area where the sheet passes. Therefore, in the sheet passing portion Ar1, the rotation speed of the fixing film 25 is reduced due to the influence of the slip phenomenon caused by water vapor, and the offset force caused by the difference in the rotation speed of the fixing film 25 relative to the non-sheet passing portion Ar2 increases, so that the fixing film 25 is deformed (buckled).

[0153] As described above, with the fixing device 6A according to the present embodiment, the pushing force of the pushing unit 48 at the first end portion 26aA of the roller portion 26A is greater than the pushing force at the second end portion 26bA, and thus the occurrence of the slip phenomenon of the fixing film 25 due to moisture can be reduced. Therefore, the increase in the biasing force of the fixing film 25 can be suppressed and deformation can be prevented. As a result, the generation of the biasing force of the fixing film 25 can be reduced, and the fixing device 6A capable of achieving an increase in speed and an extension in life can be realized.

[0154] In the present embodiment, the case where the pushing unit 48 includes the first pushing spring 48a and the second pushing spring 48b has been described, but the present technology is not limited thereto. For example, it is also possible to have a configuration in which only the first pushing spring 48a is provided without providing the second pushing spring 48b to push by its own weight. Alternatively, it is also possible to have a configuration in which the first pushing spring 48a is not provided on the first side W1 but is provided on, for example, the second side W2, and a pushing force is applied to the first end portion 26aA by using an appropriate transmission component therebetween.

[0155] In the present embodiment, the case where the hardness difference and the urging force difference of the elastic layer 262A of the roller portion 26A in the width direction W are provided has been described, but the present technology is not limited thereto. For example, a similar effect can be obtained by only providing a hardness difference between the elastic layer 262A of the roller portion 26A on the left and right sides, or a similar effect can be obtained by only providing a pressure difference between the urging springs 48a and 48b on the left and right sides.

[0156] Third embodiment

[0157] Next, a third embodiment of the present invention will be described, and the third embodiment has a configuration in which the fixing film 25 according to the first embodiment is changed. Therefore, a configuration similar to the first embodiment will be described with illustration omitted or with the same reference numerals added in the drawings.

[0158] Here, the buckling of the fixing film 25, which is a problem in the prior art, will be described in detail. In the case where the thermally conductive filler contained in the elastic layer 252 is increased in order to achieve high thermal conductivity of the fixing film 25, the base layer 251 of the fixing film 25 is easily worn. In particular, in the case where the flanges 40a and 40b have the limiting surfaces 41a and 41b and the guide portions 42a and 42b, the wear of the inner surface of the end portion of the fixing film 25 in the width direction W (hereinafter referred to as the inner surface wear) is easy to occur. Due to the inner surface wear, the end portion of the base layer 251 of the fixing film 25 in the width direction W becomes thinner, so it is easy to buckle, which will hinder the extension of life.

[0159] Will refer to Figure 8 The mechanism by which abrasion of the inner surface of the fixing film 25 including the elastic layer 252 containing the thermally conductive filler occurs is described. Figure 8 It is a cross-sectional view of the configuration near the second flange 40 b in the fixing device according to the comparative example in which the fixing film 25 is not configured as in the present embodiment, when viewed from the upstream (front side) in the sheet conveying direction DF. Figure 8 A cross section of the fixing film 25 in the width direction W and a side surface of the second flange 40 b are shown. Figure 8 It shows that the fixing film 25 is Figure 5A The fixing film 25 is offset in the right direction R and Figure 5A In this comparative example, elements corresponding to those of the present embodiment are given the same reference numerals.

[0160] Due to the influence of the temperature rise of the non-sheet passing portion Ar2 described in the first embodiment, the fixing film 25 is subjected to a biasing force in the right direction R, and slides and rotates while being pressed by the limiting surface 41b of the second flange 40b. The fixing film 25 and the limiting surface 41b of the second flange 40b slide in the sliding area ArB. The fixing film 25 includes a base layer 251, an elastic layer 252, and a surface layer 253, and the base layer 251 and the elastic layer 252 are worn by friction with the limiting surface 41b.

[0161] The elastic layer 252 contains a thermally conductive filler. Therefore, when the elastic layer 252 is worn by the limiting surface 41b of the second flange 40b, the thermally conductive filler contained in the elastic layer 252 is scraped off from the end surface of the elastic layer 252. The scraped off portion of the thermally conductive filler passes through the sliding area ArB between the end portion of the fixing film 25 in the width direction W and the limiting surface 41b of the second flange 40b. Then, the thermally conductive filler enters the contact area SR between the inner peripheral surface of the base layer 251 of the fixing film 25 and the guide portion 42b of the second flange 40b. As a result, the thermally conductive filler is interposed in the contact area SR.

[0162] In the present embodiment, the thermally conductive filler is made of a material having a higher hardness than the polyimide which is the material of the base layer 251 of the fixing film 25. Therefore, by sliding and rotating the fixing film 25 relative to the guide portion 42b of the second flange 40b, the wear of the inner surface of the end portion of the base layer 251 in the width direction W is accelerated in the contact area SR by the thermally conductive filler interposed between the inner peripheral surface of the base layer 251 and the guide portion 42b.

[0163] When the inner surface of the base layer 251 of the fixing film 25 is worn, as the amount of the fixing film 25 used increases, the thickness of the base layer 251 decreases, resulting in reduced strength and buckling under low offset forces. Therefore, it is possible to hinder the extension of life. On the other hand, it is conceivable to increase the thickness of the base layer 251 of the fixing film 25 to suppress buckling and extend the life. However, when the thickness of the base layer 251 is too large, the fixing performance will deteriorate due to reduced thermal conductivity, and the cost will increase. As described above, for the structure according to the prior art, it is difficult to achieve both speed increase and life extension.

[0164] Therefore, in the present embodiment, the base layer 251B of the fixing film 25B protrudes toward the second side W2 in the width direction W to avoid abrasion of the elastic layer 252B. 9A to 10B The fixing film 25B according to the present embodiment is described.

[0165] Fig. 9A2 is a cross-sectional view of the fixing film 25B in the width direction W of the present embodiment. In the present embodiment, the fixing film 25B is configured such that when the end 25bB of the base layer 251B on the second side W2 in the width direction W contacts the limiting surface 41b of the second flange 40b, the elastic layer 252B does not contact the limiting surface 41b. Fig. 9A As shown, the fixing film 25B has a protrusion 254 at the end 25bB of the second side W2 in the width direction W, which is a portion that does not include the elastic layer 252B and the surface layer 253B and is formed only by the base layer 251B. In other words, in the present embodiment, at the end 25bB of the second side W2 of the fixing film 25B, the base layer 251B has a protrusion 254, which is a portion that is positioned more outward relative to the elastic layer 252B. That is, the protrusion 254 protrudes in the right direction R of the second side W2 relative to the elastic layer 252B, and can contact the restriction surface 41b of the second flange 40b in the width direction W.

[0166] It is desirable to configure so that: even in a state where the fixing film 25B is located at any phase in the circumferential direction, when the base layer 251B contacts the limiting surface 41b of the second flange 40b, the elastic layer 252B does not contact the limiting surface 41b. Therefore, in the present embodiment, the protrusion 254 is continuously provided over the entire area in the circumferential direction of the fixing film 25B, and the end surface 254a of the end portion 25bB of the fixing film 25B in the width direction W is constituted by the end surface of the protrusion 254.

[0167] However, as long as the effect of this embodiment can be fully exerted, there may be a portion in the circumference of the fixing film 25B where the protrusion 254 is not provided. In the portion where the protrusion 254 is not provided, the end surface of the end of the fixing film 25B in the width direction W is composed of the base layer 251B and the elastic layer 252B (in addition, in this embodiment, there is also a surface layer 253B). The protrusion 254 is preferably provided at more than 70% of the circumference of the fixing film 25B, more preferably more than 80%, still more preferably more than 90%, and most preferably the entire circumference of the fixing film 25B. If the protrusion 254 is provided at more than 70% of the circumference of the fixing film 25B, it is more effective to prevent the elastic layer 252B from contacting the restriction surface 41b than when the protrusion 254 is provided at less than 70%. In this embodiment, since the protrusion 254 is continuously provided over the entire area of ​​the circumference of the fixing film 25B, the protrusion 254 is provided at more than 70% of the end surface of the second side W2 of the fixing film 25A.

[0168] By using the fixing film 25B according to the present embodiment, it is possible to suppress the inner surface of the fixing film 25 from being worn as described above. Fig. 9B Describe the reason. Fig. 9B4 is a schematic cross-sectional view of the vicinity of the second flange 40 b in the fixing device 6B according to the present embodiment when viewed from upstream in the conveying direction of the sheet S. FIG. Fig. 9B A cross section of the fixing film 25B in the width direction W and a side surface of the second flange 40 b are shown. Fig. 9B The fixing film 25B is shown Figure 5A The fixing film 25B is in a state where it is deviated in the right direction R and is in contact with the restriction surface 41b of the second flange 40b.

[0169] like Fig. 9B As shown, in the sliding area ArB between the end portion in the width direction W of the fixing film 25B and the limiting surface 41b of the second flange 40b, the limiting surface 41b of the second flange 40b contacts only the base layer 251B of the fixing film 25B, and does not contact the elastic layer 252B. That is, the protrusion 254 contacts the limiting surface 41b to limit the elastic layer 252B from contacting the limiting surface 41b. Therefore, the thermally conductive filler contained in the elastic layer 252B is not scraped off, or the scraping off of the thermally conductive filler is sufficiently suppressed. As a result, in the contact area SR between the inner peripheral surface of the base layer 251B of the fixing film 25B and the guide portion 42b of the second flange 40b, the inner peripheral surface of the base layer 251 of the fixing film 25B and the guide portion 42b of the second flange 40b slide without intervening the thermally conductive filler therebetween. Therefore, the wear of the inner peripheral surface of the end portion 25bB of the fixing film 25B in the width direction W can be suppressed.

[0170] As described above, according to the present embodiment, even when a biasing force is generated due to a temperature rise in the non-sheet passing portion Ar2, the inner surface of the fixing film 25B can be suppressed from being worn and the fixing film 25B can be prevented from buckling. As a result, the life of the fixing film 25B can be extended.

[0171] Length of protrusion

[0172] Next, the setting of the protrusion length of the protrusion 254 will be described. Fig. 10A 1 is a cross-sectional view of the vicinity of the second flange 40 b in the fixing device 6B according to the present embodiment when viewed from the upstream (front side) in the conveying direction of the sheet S. FIG. Fig. 10A A cross section of the fixing film 25B in the width direction W and the side surfaces of the second flange 40 b and the facing roller 61 are shown. Fig. 10A A state is shown in which the fixing film 25B is deviated in the right direction R and the fixing film 25B is in contact with the restriction surface 41 b of the second flange 40 b on the right side.

[0173] The length of the protrusion 254 of the fixing film 25B in the width direction W (hereinafter referred to as the protrusion length) is given by Fig. 10AThe protrusion length L1 is represented by the protrusion length L1 in the fixing film 25B. The protrusion length L1 is represented by a value (initial value) at the initial stage of use of the fixing film 25B (when the fixing film 25B is new). It is desirable that the protrusion length L1 is set so that the elastic layer 252B does not protrude further outward relative to the base layer 251B in the width direction W of the fixing film 25B even in consideration of, for example, expansion of the elastic layer 252B due to heating or wear of the end surface of the base layer 251B due to increased use.

[0174] From such a viewpoint, the protrusion length L1 is preferably set to be greater than 0.1 mm. When the protrusion length L1 is greater than 0.1 mm, the elastic layer 252B can be more effectively prevented from contacting the limiting surface 41b compared to the case where the protrusion length L1 is less than 0.1 mm. From the above viewpoint, the protrusion width is more preferably set to be greater than 0.5 mm. The protrusion length L1 can be arbitrarily set in consideration of the life of the fixing film 25B, etc. For example, for the fixing film 25B used in the fixing device 6B with a longer life, the protrusion length L1 can be set to be greater. However, from the viewpoint of the mechanical strength, travel stability, etc. of the fixing film 25B, the protrusion length L1 is preferably less than 10 mm. Therefore, in the present embodiment, the protrusion amount of the protrusion 254 relative to the elastic layer 252B on the second side W2 is greater than 0.1 mm and less than 10 mm.

[0175] The width of the portion of the fixing film 25B including the elastic layer 252B in the width direction W of the fixing film 25B is larger than the maximum conveying area Ar0 (see Figure 3 ) width, and the maximum conveying area Ar0 is within the range of this portion. In this embodiment, at the end of one side of the width direction W of the fixing film 25B, the protruding length L1 of the protruding portion 254 is set to 2 mm in the entire circumferential area of ​​the fixing film 25B.

[0176] In the present embodiment, the protruding length L1 is 2 mm, and the length L2 of the guide portion 42b of the second flange 40b in the width direction W of the fixing film 25B is 4 mm. In the present embodiment, even in a state where the fixing film 25B is in contact with at least the first flange 40a, the guide portion 42b of the second flange 40b and the region of the fixing film 25B having the elastic layer 252B overlap each other in the width direction W of the fixing film 25B. That is, the protruding amount of the protruding portion 254 relative to the elastic layer 252B on the second side W2, i.e., the protruding length L1, is smaller than the length L2 of the guide portion 42b in the width direction W. As described above, by overlapping the region of the fixing film 25B having the elastic layer 252B with the guide portion 42b of the second flange 40b, the high traveling stability of the fixing film 25B can be maintained. That is, the protruding length L1 is preferably set to be smaller than the length L2 of the guide portion 42b of the second flange 40b in the width direction W of the fixing film 25B.

[0177] Position of the end facing the roller

[0178] In the present embodiment, the positional relationship between the end of the fixing film 25B on the second side W2 in the width direction W and the end of the roller portion 26 facing the roller 61 is set as follows. In the present embodiment, the roller portion 26 includes a conductive base 261, an elastic layer 262, and an electrically insulating release layer 263. In addition, a potential of +300V is applied to the base 261 by using an AC power source 27. On the other hand, the fixing film 25B includes a conductive base layer 251B, an electrically insulating elastic layer 252B, and a surface layer 253B. In the present embodiment, the base layer 251B is electrically grounded from the inner peripheral surface (see Figure 2 ).

[0179] As described above, in order to obtain a good image, it is desirable to provide a predetermined potential difference between the base layer 251B of the fixing film 25B and the roller portion 26. That is, by the electric field formed by the potential difference, the toner to which a negative charge is applied is subjected to a force pressed against the sheet S, so that the scattering and deviation of the toner can be suppressed. In the case where discharge occurs between the base layer 251B of the fixing film 25B and the elastic layer 262 of the roller portion 26, the potential difference cannot be properly maintained, and thus image defects may occur. In order to properly maintain the potential difference, it is desirable to sufficiently ensure a creepage distance between the elastic layer 262 facing the roller 61 and the base layer 251B of the protrusion 254 of the fixing film 25B at the end portion in the width direction W of the fixing film 25B to suppress discharge.

[0180] Therefore, in this embodiment, at the end of the second side W2 of the fixing film 25B, the positional relationship between the end of the fixing film 25B and the end of the roller portion 26 is set as follows. Fig. 10A As shown, the area where the elastic layer 262 of the roller portion 26 and the base layer 251B of the protrusion 254 of the fixing film 25B are adjacent to each other is defined as an adjacent area ArC. At this time, in the adjacent area ArC, the end surface 255 of the elastic layer 252B and the surface layer 253B of the fixing film 25B is positioned more outward (downstream in the right direction R) relative to the end surface of the second end 26b of the elastic layer 262 of the roller portion 26. That is, the elastic layer 252B and the surface layer 253B of the fixing film 25B have an extension portion 256 that extends more outward by a length L3 in the width direction W of the fixing film 25B relative to the end surface of the second end 26b of the elastic layer 262 of the roller portion 26. That is, at the end surface 254a (see FIG. 2 ) of the protrusion 254 on the second side W2, the end surface 254a of the protrusion 254 on the second side W2 is positioned more outward (downstream in the right direction R). Fig. 9A ) is disposed closer to the second side W2 with respect to the end surface of the elastic layer 262 of the roller portion 26 on the second side W2.

[0181] As a result, the creepage distance between the elastic layer 262 of the roller portion 26 and the base layer 251B of the protruding portion 254 of the fixing film 25B can be sufficiently ensured, and the potential difference can be appropriately maintained. The length L3 of the extension portion 256 can be appropriately set according to the potential difference between the base 261 of the roller portion 26 and the base layer 251B of the fixing film 25B so that the discharge as described above can be sufficiently suppressed. In the present embodiment, the length L3 of the extension portion 256 is set to 2 mm in the entire circumferential area of ​​each of the fixing film 25B and the roller portion 26.

[0182] Considering the protruding length L1 of the protruding portion 254 and the length L3 of the extension portion 256 for ensuring the creepage distance, the end surface 254a of the protruding portion 254 of the fixing film 25B is set to be positioned further in the right direction R by (L1+L3) relative to the end surface of the second end portion 26b of the roller portion 26. In the present embodiment, the end surface 254a of the protruding portion 254 of the fixing film 25B is set to be positioned in the right direction R by 4 mm.

[0183] Protrusion

[0184] Fig. 9A The configuration of the fixing film 25B according to the present embodiment is shown in . In the present embodiment, the protrusion 254 of the fixing film 25B is provided only at one side end portion of the second side W2 opposite to the sheet passing reference position P0 . Fig. 10B 1 is a cross-sectional view of the vicinity of the first flange 40 a of the first side W1 in the fixing device 6B according to the present embodiment when viewed from upstream (front side) in the conveying direction of the sheet S. FIG. Fig. 10B A state in which the fixing film 25B is in contact with the restricting surface 41 a of the first flange 40 a of the first side W1 is shown.

[0185] In this embodiment, on the first side W1, the restriction surface 41a of the first flange 40a and the elastic layer 252B of the fixing film 25B are Fig. 10B However, on the first side W1, even with this configuration, the inner surface of the base layer 251B of the fixing film 25B is hardly worn. The reason will be described below.

[0186] Since the deflection force due to the temperature rise of the non-sheet passing portion Ar2 is not generated on the first side W1, even when the elastic layer 252B and the limiting surface 41a of the first flange 40a slide, the thermally conductive filler contained in the elastic layer 252B is not scraped off, or the scraping off of the thermally conductive filler is sufficiently suppressed. Therefore, in the contact area SL (see FIG. 25B ) between the inner peripheral surface of the base layer 251B of the fixing film 25B and the guide portion 42a of the first flange 40a, the thermally conductive filler contained in the elastic layer 252B is not scraped off, or the scraping off of the thermally conductive filler is sufficiently suppressed. Figure 3), the inner peripheral surface of the base layer 251B of the fixing film 25B and the guide portion 42a of the first flange 40a slide on each other. Therefore, the inner peripheral surface of the end of the fixing film 25B does not wear on the first side W1.

[0187] In addition, the fixing film 25B according to the present embodiment has an extension portion 256 even on the first side W1, which is extended by a length L3 further outward (left direction L) in the width direction W relative to the end surface of the end portion 26a of the elastic layer 262 facing the roller 61. Here, similar to the second side W2, it is necessary to set the length L3 to ensure the creepage distance between the elastic layer 262 facing the roller 61 and the base layer 251B of the fixing film 25B. Therefore, the length L3 can be appropriately set according to the potential difference between the base 261 of the roller portion 26 and the base layer 251B of the fixing film 25B so that the discharge can be sufficiently suppressed. In the present embodiment, on the first side W1, the length L3 of the extension portion 256 is set to 2 mm in the entire circumferential area of ​​each of the fixing film 25B and the roller portion 26.

[0188] Examples and Comparative Examples

[0189] Example 3 using the fixing film 25B according to this embodiment, Fig.11A The comparative example 3 of the fixing film 125 shown in FIG. Fig. 11B Comparative Example 4 of the fixing film 225 shown is used for comparison.

[0190] Comparative Examples 3 and 4 will be described. Fig.11A and Fig. 11B 2 is a cross-sectional view in the width direction W of the fixing films 125 and 225 used in the configurations of Comparative Examples 3 and 4. Fig.11A The configuration of the fixing film 125 of Comparative Example 3 is shown, in which the protrusions 1254 are provided at both end portions 125 a and 125 b of the fixing film 125 . Fig. 11B The configuration of the fixing film 225 of Comparative Example 4 is shown, in which no protrusions are provided at both end portions 225 a and 225 b of the fixing film 225 .

[0191] The fixing film 125 of Comparative Example 3 has protrusions 1254 at both ends in the width direction W. Therefore, scraping due to the heat of the thermally conductive filler caused by sliding between the elastic layer 252 of the fixing film 125 and the limiting surfaces 41a and 41b of the flanges 40a and 40b at both ends does not occur or is sufficiently suppressed, thereby suppressing the wear of the inner surface of the fixing film 125. However, on the other hand, compared with the fixing film 25B of Example 3, the fixing film 125 of Comparative Example 3 has disadvantages from the viewpoints of the manufacturing process and the size of the fixing device. As for the manufacturing process, compared with the fixing film 25B of Example 3, the fixing film 125 of Comparative Example 3 has disadvantages in that the process for forming the protrusion 1254 on the first side W1 is increased and the cost is increased.

[0192] In addition, the fixing film 125 of Comparative Example 3 has a disadvantage that the size of the fixing device is increased. The reason will be described below. In the fixing film 125 of Comparative Example 3, it is necessary to appropriately set the protruding length L1 of the protruding portion 1254 and the extension portion 256 (see FIG. 2 ) at both end portions 125a and 125b. Fig. 10A and Fig. 10B ). In Comparative Example 3, at both end portions 125a and 125b of the fixing film 125, the end surface of the fixing film 125 needs to be set to be positioned further outward in the width direction W by (L1+L3) relative to the end surface of the roller portion 26. That is, the size of the fixing film 125 of Comparative Example 3 needs to be increased by about 2×(L1+L3) relative to the roller portion 26 in the width direction W. For example, in the case where L1=L3=2 mm, the width of the fixing film 125 needs to be increased by 8 mm.

[0193] On the other hand, in the fixing film 25B of Example 3, the protrusion 254 is provided at the end 25bB of the second side W2, but the protrusion 254 is not provided at the end 25aB of the first side W1 (see FIG. 25B ). Fig. 9A ). As a result, the end surface of the second side W2 of the fixing film 25B of Example 3 needs to be set to be positioned outward at (L1+L3) in the width direction W, and the end surface of the first side W1 of the fixing film 25B of Example 3 needs to be set to be positioned outward at L3. That is, the size of the fixing film 25B of Example 3 needs to be increased by approximately (L1+2×L3) in the width direction W relative to the roller portion 26. Therefore, the fixing film 25B of Example 3 can be set to be approximately L1 smaller than the fixing film 125 of Comparative Example 3 in the width direction W. In Example 3, L1=L3=2mm, and the fixing film 25B of Example 3 is 6mm larger than the roller portion 26 in the width direction W.

[0194] That is, the fixing film 25B of Example 3 can be 2 mm smaller than the fixing film 125 of Comparative Example 3 in the width direction W. The limiting surfaces 41 a and 41 b of the flanges 40 a and 40 b are set to control the movement of the fixing film in the width direction W. Therefore, the interval for the fixing film is set by providing a predetermined gap according to the length of the fixing film in the width direction W to prevent the fixing film from becoming tight when thermally expanded. Therefore, the interval between the flanges 40 a and 40 b is set according to the length of the fixing film, and the interval between the flanges 40 a and 40 b of Example 3 can be set to be 2 mm smaller than that in Comparative Example 3. As a result, the size of the fixing device 6B and the image forming apparatus 100 of Example 3 can be reduced compared to Comparative Example 3.

[0195] Next, in the fixing film 225 of Comparative Example 4, the protrusion of the base layer 251 in the width direction W is not formed. As a result, at the end 225b of the second side W2, the elastic layer 252 of the fixing film 225 and the limiting surface 41b of the second flange 40b slide while receiving the offset force generated by the temperature increase of the non-sheet passing portion Ar2. As a result, the thermal conductive filler contained in the elastic layer 252 is scraped off, and the inner surface of the base layer 251 of the fixing film 225 is worn. Therefore, the extension of the life of the fixing film 225 is hindered. In the following, the durability test results comparing the durability performance of Example 3 and Comparative Example 4 are shown.

[0196] Print durability test

[0197] In order to compare the durability performance of Example 3 and Comparative Example 4, a comparative experiment was conducted to compare Example 3 and Comparative Example 4. Fig. 9A In the structure of Comparative Example 4, the fixing film 25B is used. Fig. 11B The fixing film 225 is shown. The configuration of the image forming apparatus of Comparative Example 4 is substantially the same as that of the image forming apparatus 100 according to the present embodiment except for the above-mentioned difference. In Comparative Example 4, constituent elements corresponding to those of the present embodiment are given the same reference numerals.

[0198] For Example 3 and Comparative Example 4, the experiment was conducted under the following conditions. The pressure applied between each fixing film and the roller portion 26 was 186.2N (19kgf). The width of the fixing nip N2 in the sheet conveying direction DF (nip width) was 9mm. As the experimental environment, the temperature was 23°C, the relative humidity was 50%, and CS068 (A4 size and 68g / cm 2 ) and PB paper (A5 size and 68g / cm 2 ) were appropriately mixed and used as evaluation sheets. Under the above conditions, in Example 3 and Comparative Example 4, a paper-passing durability test was conducted in which 200k sheets of character images were printed at a low image coverage to evaluate durability.

[0199] Table 6 shows the evaluation results of the durability test. The durability evaluation criteria are as follows. The case where the durability of the fixing film is good without any problem is evaluated as "good", and the case where a problem related to the durability of the fixing film occurs (which will cause a problem in actual use) is evaluated as "poor". For the evaluation criteria of the fixing performance, the case where the fixing performance is good without any problem is evaluated as "good", and the case where the fixing performance is insufficient is evaluated as "poor".

[0200] Table 6

[0201]

[0202]

[0203] As shown in Table 6, in Comparative Example 4, at the time of printing 100k sheets, the end 225b of the second side of the fixing film 225 in the width direction W was buckled. As a result, the sheet passing durability test was stopped because the travel of the fixing film 225 became unstable and image defects occurred. It was found that the reason for the buckling at the end 225b of the second side W2 of the fixing film 225 in the width direction W was the wear of the inner surface of the fixing film 225. That is, in Comparative Example 4, the thickness of the base layer 251 of the fixing film 225 at the end 225b of the second side W2 was reduced from the initial thickness of 70μm to about 40μm at the time of printing 100k sheets. Therefore, it can be considered that because the fixing film 225 cannot withstand the offset force applied to the fixing film 225 in the width direction W (right direction R) when the fixing film 225 abuts on the limiting surface 41b of the second flange 40b, buckling occurs at the end 225b of the fixing film 225 in the width direction W. As described above, in Comparative Example 4, it is difficult to satisfy durability.

[0204] In Example 3, when 200k sheets were printed, no problem occurred in durability and fixing performance. Therefore, it has been confirmed that, with the configuration of Example 3, the image forming apparatus 100 having the side end reference conveying configuration can achieve extended life, increased speed, and reduced size.

[0205] As described above, in the fixing device 6B according to the present embodiment, the protrusion 254 is provided at the end of the second side W2 of the fixing film 25B, so that even when the offset force to the fixing film 25B is generated, the wear of the inner surface of the fixing film 25B can be reduced and the life can be extended. As a result, the wear of the inner surface of the fixing film 25B caused by the offset force can be reduced, and the fixing device 6B capable of achieving speed increase and life extension can be realized. In addition, by using the fixing device 6B described in the present embodiment, the wear of the inner surface of the fixing film 25B can be suppressed, so that the life extension, size reduction and cost reduction can be achieved. It can be said that the structure of the present embodiment is suitable for a high-speed machine or a long-life machine that requires high durability for the fixing film 25B.

[0206] In the present embodiment, the case where the protrusion 254 is provided at the end 25bB of the second side W2 of the fixing film 25B and not at the end 25aB of the first side W1 has been described, but the present technology is not limited thereto. For example, the protrusion may be provided at the end 25aB of the first side W1. In this case, the protrusion amount of the protrusion of the end 25aB of the first side W1 may be equal to or greater than the protrusion amount of the protrusion 254 of the end 25bB of the second side W2, but from the viewpoint of size reduction, it is preferred that the protrusion amount of the protrusion of the end 25aB of the first side W1 is smaller than the protrusion amount of the protrusion 254 of the end 25bB of the second side W2.

[0207] Fourth embodiment

[0208] Next, a fourth embodiment of the present invention will be described, and the fourth embodiment has a configuration in which the heater support 29 according to the first embodiment is modified. Therefore, a configuration similar to the first embodiment will be described by omitting illustration or attaching the same reference numerals in the drawings.

[0209] In the case of passing a small-sized sheet through a fixing device based on a side end reference, the fixing film 25 may be offset in the width direction W due to the temperature rise of the non-sheet passing portion Ar2. In addition to the offset of the fixing film 25, the longitudinal shape of the fixing film 25 may also change due to the influence of the temperature rise of the non-sheet passing portion Ar2. There is a possibility that the offset force increases due to the shape change, and there is a possibility that the fixing film 25 is deprived of heat due to contact with components in the internal space and poor fixing occurs. The following will describe the mechanism of defects due to the change in the longitudinal shape of the fixing film 25 by comparing the case of passing a letter-sized sheet with a maximum sheet passing width and an A6-sized sheet with a small width.

[0210] Fig. 12A It is a schematic diagram of the sheet passing area of ​​the letter size sheet and the A6 size sheet S. Fig. 12B2 shows the surface temperature distribution of the facing roller 61 in the width direction W when the letter size sheet and the A6 size sheet are respectively passed continuously. In the case of the letter size sheet, the surface temperature of the roller portion 26 is substantially uniform in the maximum conveying area Ar0 (sheet passing portion of the letter size sheet). In the case of the A6 size sheet, due to the temperature rise of the non-sheet passing portion Ar2, the temperature of the non-sheet passing portion Ar2 is higher than the temperature of the sheet passing portion Ar1. At this time, the roller portion 26 is constructed so that Fig. 6A The outer diameter of the base 261 shown is uniform in the width direction W and the outer diameter shape is Figure 6B In the case of the horizontally symmetrical inverted crown shown in FIG. 1 , the conveying speed of the roller portion 26 in the width direction W is as follows for each dimension: Fig. 12C Distribution shown.

[0211] like Fig. 12C As shown, in the case of a letter size sheet, since the temperature of the roller portion 26 is approximately uniform in the width direction W, the conveying speed is also approximately uniform in the width direction W. In the case of an A6 size sheet, due to the increase in temperature of the non-sheet passing portion Ar2, the conveying speed in the width direction W is also distributed according to the temperature distribution of the roller portion 26 in the width direction W. This is because, since the elastic layer 262 of the roller portion 26 thermally expands according to the temperature, the outer diameter in the non-sheet passing portion Ar2 becomes larger than the outer diameter in the sheet passing portion Ar1, thereby generating an outer diameter difference and a peripheral speed difference, resulting in a conveying speed difference. The conveying speed difference in the width direction W affects the shape of the fixing film 25 in the width direction W.

[0212] Fig.13A In Comparative Example 5, when the letter-size sheet is continuously passed, the Fig. 12A The heater support 29 of Comparative Example 5 has an upstream guide portion 291 disposed upstream in the sheet conveying direction DF and a downstream guide portion 292 disposed downstream to guide the rotation of the fixing film 25 from the inside. Fig. 12C As shown in FIG. 1 , since the conveying speed distribution of the roller portion 26 in the width direction W is substantially uniform, Fig.13A The shape of the fixing film 25 in the width direction W is also shown to be substantially straight.

[0213] Fig.14A In Comparative Example 5, when the letter-size sheet is continuously passed, Fig. 12A The fixing film 25 is not in contact with the bracket 22 or the upstream guide portion 291 or the downstream guide portion 292 of the heater holder 29 which are components inside the fixing film 25 .

[0214] Next, Fig. 13B The following diagram shows the flow of A6-size sheets continuously through the Comparative Example 5 when viewed from above. Fig. 12A A cross-sectional view taken along line II in FIG. Fig. 12C As shown, since the conveying speed of the roller portion 26 is higher in the non-sheet passing portion Ar2 than in the sheet passing portion Ar1, the fixing film 25 bulges toward the downstream in the non-sheet passing portion Ar2. The posture of the fixing film 25 is similar to the state of forming an intersection angle with respect to the roller portion 26.

[0215] Here, we will refer to Fig.15 The force acting on the fixing film 25 when an intersection angle is formed between the fixing film 25 and the roller portion 26 is described. The fixing film 25 receives a force F0 from the roller portion 26 due to frictional resistance. Since the force F0 can be decomposed into a force F1 in the lateral (radial) direction of the fixing film 25 and a force F2 in the width direction W, the fixing film 25 receives a force toward the second side W2 in the width direction W (i.e., toward the second flange 40b). Therefore, as Fig. 13B As shown, a biasing force toward the side with a higher conveying speed due to the temperature rise of the non-sheet passing portion Ar2 and a biasing force due to the formed intersection angle act on the fixing film 25 together, resulting in the sag being easily caused.

[0216] Next, Fig. 14B 1 shows a cross-sectional view taken along line II-II in the case of continuously passing an A6 size sheet in Comparative Example 5. When the fixing film 25 bulges toward the downstream in the sheet conveying direction DF, the inner peripheral surface of the fixing film 25 contacts the holder 22 upstream in the sheet conveying direction DF. When the fixing film 25 contacts the holder 22 having a large heat capacity, the temperature of the fixing film 25 is greatly reduced, resulting in poor fixing.

[0217] This phenomenon is likely to occur when the gap between the fixing film 25 and the bracket 22 is narrow. For example, in the case where the outer diameter of the fixing film 25 is reduced in order to reduce the size of the fixing device, or in the case where the thickness or height of the bracket 22 is increased in order to increase the rigidity of the bracket 22, this phenomenon is likely to occur. In addition, when the base layer 251 and the elastic layer 252 of the fixing film 25 are thin and the strength of the fixing film 25 is low, even if the conveying speed difference of the roller portion 26 in the width direction W is the same, the deformation amount of the fixing film 25 will increase, so the above phenomenon is likely to occur. In addition, when the temperature difference between the sheet passing portion Ar1 and the non-sheet passing portion Ar2 of the roller portion 26 increases, the conveying speed difference of the roller portion 26 in the width direction W increases, and the deformation amount of the fixing film 25 increases. Therefore, the above phenomenon is likely to occur.

[0218] Therefore, in the present embodiment, a protruding guide portion 293 protruding toward the upstream of the upstream guide portion 291 in the sheet conveying direction DF is provided upstream of the heater support 29C, thereby preventing the fixing film 25 from contacting the internal components. FIG. 16A to FIG. 17B The heater support 29C according to the present embodiment will be described.

[0219] Fig.16A The fourth embodiment is a diagram showing a continuous flow of letter-size sheets along the Fig. 12A The configuration of the heater support 29C is different from that of the comparative example 5. In the fourth embodiment, a protruding guide portion 293 for preventing film deformation is provided upstream of the heater support 29C in the sheet conveying direction DF and on the second side W2, and the protrusion amount toward the upstream side is increased compared with the upstream guide portion 291.

[0220] Heater Mounts and Brackets

[0221] like Fig.16A and Fig.17A As shown, the heater support 29C includes a heater holding portion 290 that holds the heater 20, and an upstream guide portion 291, a downstream guide portion 292, and a protruding guide portion 293 that are integrally provided with the heater holding portion 290. In the present embodiment, the heater support 29C is made of resin and integrally formed. However, the present technology is not limited thereto, and the heater support 29C may be formed by being integrated with other components.

[0222] The upstream guide portion 291 is an example of a first guide portion, is provided on the first side W1 in the width direction W, and can guide the fixing film 25 at a position upstream of the fixing nip N2 in the sheet conveying direction DF. The downstream guide portion 292 is provided in the entire area of ​​the heater holder 29C in the width direction W, and can guide the fixing film 25 downstream of the fixing nip N2 in the sheet conveying direction DF. The protruding guide portion 293 is an example of a second guide portion, is provided on the second side W2 in the width direction W, and can guide the fixing film 25 at a position upstream of the fixing nip N2 in the sheet conveying direction DF.

[0223] The bracket 22 has a facing portion 22a facing the inner peripheral surface of the fixing film 25. Here, the orthogonal direction to the sheet conveying direction DF and the width direction W is defined as the up-down direction. The facing portion 22a is a portion of the bracket 22, and is a portion located farther from the fixing nip N2 than the upstream guide portion 291 and the protruding guide portion 293 in the up-down direction, and faces the upstream portion of the inner peripheral surface of the fixing film 25 in the sheet conveying direction DF.

[0224] In this embodiment, if Fig.17AAs shown, in the sheet conveying direction DF, the distance L4 from the facing portion 22a of the bracket 22 to the upstream end of the protruding guide portion 293 is longer than the distance L5 from the facing portion 22a to the upstream end of the upstream guide portion 291. Therefore, in the case where a portion of the second side W2 of the fixing film 25 is to be deformed downstream in the sheet conveying direction DF, the protruding guide portion 293 comes into contact with the fixing film 25 even when the deformation amount of the fixing film is small, which is different from the case where only the upstream guide portion 291 is provided on the second side W2. Therefore, before the inner peripheral surface of the fixing film 25 abuts on the facing portion 22a, the protruding guide portion 293 comes into contact with the fixing film 25, suppressing further deformation of the fixing film 25, thereby preventing the inner peripheral surface of the fixing film 25 from coming into contact with the facing portion 22a.

[0225] Fig.17A Is in the case of continuous passing of letter size sheets along Fig. 12A A cross-sectional view taken along line II-II in FIG. Fig.13A Compared with the upstream guide portion 291 of Comparative Example 5 shown in FIG. 1 , the protruding guide portion 293 protrudes toward the upstream in the sheet conveying direction DF and has a shape close to the fixing film 25 but not in contact with the fixing film 25. Fig.17A In the embodiment of the present invention, the height of the protruding guide portion 293 is greater than the height of the upstream guide portion 291 of Comparative Example 5, but the heights may be the same.

[0226] Fig. 16B According to the fourth embodiment, when A6 size sheets are continuously passed, the Fig. 12A sectional view taken along line II in FIG. The temperature rises in the non-sheet passing portion Ar2, the conveying speed of the roller portion 26 in the non-sheet passing portion Ar2 increases, and the fixing film 25 tends to bulge downstream in the sheet conveying direction DF, but the protruding guide portion 293 supports the fixing film 25 upstream to prevent deformation. Therefore, the intersection angle between the fixing film 25 and the roller portion 26 is not too large, and the increase of the offset force due to the intersection angle is prevented.

[0227] Fig. 17B According to the fourth embodiment, when A6 size sheets are continuously passed, Fig. 12A 2 is a cross-sectional view taken along line II-II in FIG. Since the protruding guide 293 supports the fixing film 25 from the inner peripheral side upstream in the sheet conveying direction DF, the fixing film 25 can be prevented from contacting the bracket 22 having a large heat capacity. The protruding guide 293 is made of the same material as the heater support 29C, for example, a heat-resistant resin such as a liquid crystal polymer, a phenolic resin, PPS, or PEEK is used. Since the heat capacity of these resins is lower than that of the bracket 22, even if they come into contact with the fixing film 25, these resins do not take away much heat, and a significant deterioration in the fixing performance is suppressed.

[0228] In the present embodiment, the contact surface of the protruding guide 293 relative to the fixing film 25 is flat. However, the contact surface is not limited to being flat, and grooves, ribs, etc. may also be provided on the surface of the protruding guide 293 to reduce the contact area with the fixing film 25. In the present embodiment, five protruding guides 293 are arranged side by side on the distal side of the second side W2. However, the number of the protruding guides 293 is not limited to five, and may be other numbers. That is, the number and position are not limited to those shown in the drawings, and any structure may be used as long as the deformation of the fixing film 25 can be suppressed.

[0229] In the present embodiment, the heater support 29C further includes an upstream guide portion 291a located on the second side W2 in the width direction W. The upstream guide portion 291a is an example of a third guide portion, and is arranged to be separated from the protruding guide portion 293 in the width direction W. In the sheet conveying direction DF, the distance L5 from the facing portion 22a to the upstream end of the upstream guide portion 291 is set to be shorter than the distance L4 from the facing portion 22b to the upstream end of the protruding guide portion 293. That is, not all guide portions arranged on the second side W2 in the width direction W of the heater support 29C have to be the protruding guide portion 293, but some of the plurality of guide portions including the other upstream guide portions 291 are the protruding guide portions 293. However, the present technology is not limited thereto, and all guide portions arranged on the second side W2 in the width direction W of the heater support 29C may be the protruding guide portions 293.

[0230] Examples and Comparative Examples

[0231] The printing durability experiment was conducted using Example 4 and Comparative Example 5 to which the heater holder 29C according to the present embodiment was applied. In the printing durability experiment, fixing films 25 having base layers 251 of different thicknesses were prepared, and the fixing films 25 having different thicknesses were respectively assembled into the fixing devices of Example 4 and Comparative Example 5. Then, 5,000 sheets of PB paper (A6 size and 68 g / cm2) were continuously passed through the fixing devices at a speed of 75 sheets / min. 2 In the fixing film 25 used in the comparative experiment, the base layer 251 had three thickness levels of 60 μm, 65 μm and 70 μm, the elastic layer 252 had a thickness of 250 μm, and the surface layer 253 had a common thickness of 12 μm.

[0232] Table 7 shows the evaluation results of durability and fixing performance. The durability evaluation criteria are as follows. The case where the durability of the fixing film 25 is good without any problem is evaluated as "good", and the case where a problem related to the durability of the fixing film 25 (which will cause a problem in actual use) occurs is evaluated as "poor". In addition, regarding the evaluation criteria of the fixing performance, the case where the fixing performance is good without any problem is evaluated as "good", and the case where the fixing performance is insufficient is evaluated as "poor".

[0233] Table 7

[0234]

[0235] In Comparative Example 5, the fixing film 25 having a base layer with a thickness of 70 μm had no problem in both fixing performance and durability. The fixing film 25 having a base layer with a thickness of 65 μm had no problem in durability, but the fixing performance deteriorated halfway during use. In the fixing film 25 having a base layer with a thickness of 60 μm, problems arose in both fixing performance and durability.

[0236] The above results show that when the thickness of the base layer 251 of the fixing film 25 is reduced, the strength of the fixing film 25 is reduced, and as a result, the shape change of the fixing film 25 in the width direction W increases due to the temperature rise of the non-sheet passing portion Ar2. When the thickness of the base layer is 65μm or 60μm, the shape change of the fixing film 25 is large, and the inner peripheral surface of the fixing film 25 is bulged downstream in the sheet conveying direction DF in the non-sheet passing portion Ar2 and contacts the bracket 22, and the heat is taken away, resulting in poor fixing. In addition, since the shape change is large and the angle of intersection with the roller portion 26 becomes larger, the offset force caused by the angle of intersection also becomes larger. When the thickness of the base layer is 65μm, there is no problem with durability, but when the thickness of the base layer is 60μm, the strength of the fixing film 25 is low, resulting in buckling at the end.

[0237] In Example 4, there are no problems with the fixing performance and durability of the base layer of all thicknesses. This is because the shape change of the fixing film 25 caused by the temperature rise of the non-sheet passing part Ar2 is suppressed by the protruding guide part 293 supported from the inner peripheral surface side, so that the fixing film 25 can also be prevented from contacting with the bracket 22. The fixing film 25 is in contact with the protruding guide part 293, but the heat capacity of the heater support 29C is low, so it does not take away too much heat, so the fixing performance is not significantly deteriorated. In addition, since the shape change is suppressed, the angle of intersection with the roller part 26 can be prevented from increasing, and the offset force can also be suppressed to a certain extent. Therefore, even when the thickness of the base layer is 60μm, buckling during use can be prevented.

[0238] In the comparative experiment, the degree of shape change was changed by changing the strength in a manner of changing the thickness of the base layer of the fixing film 25. However, the present technology is not limited to this method, and a configuration that increases the temperature difference between the sheet passing portion Ar1 and the non-sheet passing portion Ar2 or narrows the gap between the fixing film 25 and the bracket 22 can also obtain similar results.

[0239] As described above, with the heater holder 29C according to the present embodiment, the shape change is suppressed by providing the protruding guide portion 293 to support the inner peripheral surface of the fixing film 25 from the inside, and therefore, the inner peripheral surface of the fixing film 25 can be prevented from contacting the facing portion 22a. Therefore, even in a configuration in which the amount of deformation of the fixing film 25 is likely to increase due to the thinning of the fixing film 25, etc., the occurrence of poor fixing and buckling can be suppressed, and a fixing device capable of achieving increased speed and extended life can be realized.

[0240] Fifth embodiment

[0241] Next, a fifth embodiment of the present invention will be described, and the fifth embodiment has a configuration in which the bracket 22 according to the fourth embodiment is changed. Therefore, a configuration similar to the fourth embodiment will be described with illustration omitted or with the same reference numerals added in the drawings.

[0242] In this embodiment, the shape change of the fixing film 25 is suppressed by a configuration different from that of the fourth embodiment, so that poor fixing and buckling are suppressed. Figures 18 to 19B The configuration of this embodiment is described. Fig.18 is when viewed from above in the case of continuous passing of A6 size sheets according to this embodiment. Fig. 12A In the present embodiment, unlike the fixing device of Comparative Example 5, the heating unit 60D of the fixing device 6D includes a cover 50 for preventing contact provided on the second side W2 of the bracket 22 .

[0243] Fig.19A Is in the case of continuous passing of letter size sheets along Fig. 12A The cover 50 is not in contact with the fixing film 25 when a letter size sheet is passed. Fig.19B In the case of continuous passing of A6 size sheets along Fig. 12A The cover 50 supports the fixing film 25 from the inner peripheral surface side, thereby suppressing the deformation of the fixing film 25. Similar to the fourth embodiment, the fixing film 25 does not directly contact the bracket 22, so that poor fixing can be prevented. In addition, as shown in FIG. Fig.18 As shown, the shape change of the fixing film 25 is suppressed, and thus it is possible to prevent the offset force from increasing due to the increase in the intersection angle.

[0244] In the present embodiment, the heater support 29 includes a heater holding portion 290 for holding the heater 20, and an upstream guide portion 291 and a downstream guide portion 292 integrally provided with the heater holding portion 290. In the present embodiment, the protruding guide portion 293 in the fourth embodiment is not provided. The bracket 22 has a facing portion 22a similar to that in the fourth embodiment. In the present embodiment, only one cover 50 is provided. In addition, the cover 50 is arranged to extend from the upstream of the facing portion 22a toward the downstream along the upper surface of the bracket 22 in the sheet conveying direction DF, and further extends downward along the downstream side surface of the bracket. The surface of the cover 50 in contact with the fixing film 25 is a flat surface.

[0245] The cover 50 is provided between the facing portion 22a of the bracket 22 and the inner peripheral surface of the fixing film 25 upstream in the sheet conveying direction DF. Therefore, even when the fixing film 25 is deformed, it is possible to prevent the fixing film 25 from directly abutting against the facing portion 22a. The cover 50 is supported by the bracket 22. The cover 50 is made of a material having a lower thermal conductivity than the bracket 22, such as a resin or the like. As a result, the dissipation of heat can be suppressed compared to the case where the fixing film 25 directly abuts against the facing portion 22a.

[0246] As described above, in the fixing device 6D according to the present embodiment, the cover 50 is provided to support the fixing film 25 from the inside, so that the shape change can be suppressed and the inner peripheral surface of the fixing film 25 can be prevented from contacting the facing portion 22a. As a result, even in a configuration in which the amount of deformation of the fixing film 25 is likely to increase due to the thinning of the fixing film 25, etc., the occurrence of poor fixing and buckling can be suppressed, and a fixing device capable of achieving an increase in speed and a longer life can be realized.

[0247] In this embodiment, an example in which one cover 50 is provided on the second side W2 has been described, but the present technology is not limited thereto, and a plurality of covers 50 may be provided. In addition, the surface of the cover 50 in contact with the fixing film 25 is not limited to a flat surface, and a groove may be provided to reduce the contact area.

[0248] Sixth embodiment

[0249] Next, a sixth embodiment of the present invention will be described, and the sixth embodiment has a configuration in which the second flange 40b according to the first embodiment is changed. Therefore, a configuration similar to the first embodiment will be described by omitting illustration or attaching the same reference numerals in the drawings.

[0250] In the fourth and fifth embodiments, poor fixing due to contact with the bracket 22 and increase in the offset force due to the angle formed relative to the roller portion 26 caused by the change in shape of the fixing film 25 due to the temperature rise of the non-sheet passing portion Ar2 are prevented. However, the offset force itself caused by the difference in conveying speed due to the temperature rise of the non-sheet passing portion Ar2 cannot be suppressed. Therefore, in this embodiment, a displacement flange unit 43 is adopted for the second flange 40bE of the second side W2 to reduce the offset force caused by the temperature rise of the non-sheet passing portion Ar2.

[0251] Shift flange unit

[0252] Will refer to FIG. 20A to FIG. 21B The displacement flange unit 43 of the fixing device 6E according to the present embodiment is described. The displacement flange unit 43 includes a second flange 40bE, a support portion 44, and a push spring 45. The support portion 44 is fixed to a frame (not shown) of the fixing device 6E. The second flange 40bE is movably engaged with the support portion 44, and a gap having a small distance G0 in the sheet conveying direction DF is provided between the second flange 40bE and the support portion 44. The second flange 40b is supported by the support portion 44 in a movably manner.

[0253] The second flange 40bE includes a restriction surface 41bE facing the end surface of the fixing film 25 on the second side W2 and a guide portion 42bE facing the inner peripheral surface of the end portion of the fixing film 25. When the fixing film 25 moves in the width direction W, the end surface of the fixing film 25 abuts against the restriction surface 41bE. The guide portion 42bE also has a function of guiding the inner peripheral surface of the fixing film 25 when the fixing film 25 rotates.

[0254] The second flange 40bE includes a convex portion 46, which is arranged to protrude toward the second side W2 in the width direction W and has a distal end surface 46a facing an inclined direction inclined relative to the width direction W. The distal end surface 46a of the convex portion 46 is inclined so that the second side W2 in the width direction W is upstream in the sheet conveying direction DF. The support portion 44 has a concave portion 44a, which is arranged to be recessed from the end surface of the first side W1 in the width direction W toward the second side W2, and has a bottom surface 44b facing an inclined direction inclined relative to the width direction W. The bottom surface 44b of the concave portion 44a is inclined so that the second side W2 in the width direction W is upstream in the sheet conveying direction DF. That is, the support portion 44 has the bottom surface 44b of the concave portion 44a as an example of a cam surface; and the second flange 40bE has the distal end surface 46a of the convex portion 46, which abuts on the bottom surface 44b and slides, as an example of a sliding member.

[0255] In the present embodiment, the case where the distal end surface 46a of the protrusion 46 is an inclined surface that slides on the bottom surface 44b has been described, but the present technology is not limited to this. For example, the distal end of the protrusion 46 may have a curved surface shape or a spherical surface shape, or a rotatable rotating component may be provided to slide relative to the bottom surface 44b. In the present embodiment, the case where the sliding member is provided in the second flange 40bE and the cam surface is provided in the support portion 44 has been described, but the present technology is not limited to this, and this relationship may also be reversed. That is, one of the second flange 40bE and the support portion 44 may have a cam surface, and the other of the second flange 40bE and the support portion 44 may have a sliding member that abuts on the cam surface and slides.

[0256] When the second flange 40bE and the support portion 44 are combined, the convex portion 46 of the second flange 40bE fits in the concave portion 44a of the support portion 44. With this configuration, the second flange 40bE is slidably held along the concave portion 44a of the support portion 44. The urging spring 45 is an example of an urging portion, and is a compression coil spring that is contracted between the second flange 40bE and the support portion 44 and urges the second flange 40bE in a direction away from the support portion 44 (the first side W1).

[0257] Next, the operation of the shift flange unit 43 will be described. Fig. 20A 4 shows a state where no biasing force is generated on the fixing film 25. At this time, the push spring 45 pushes the second flange 40bE toward the first side. There is a gap between the limiting surface 41bE of the second flange 40bE and the end surface of the fixing film 25. In addition, there is a gap between the distal end surface of the convex portion 46 of the second flange 40bE and the bottom surface of the concave portion 44a of the support portion 44.

[0258] In this state, when the offset force F10 is generated on the fixing film 25 due to the temperature rise of the non-sheet passing portion Ar2, etc., the fixing film 25 abuts against the restriction surface 41bE. When the offset force F10 is stronger than the urging force of the urging spring 45, the fixing film 25 pushes the restriction surface 41bE toward the supporting portion 44. When the distal end surface of the convex portion 46 of the second flange 40bE reaches the bottom surface of the concave portion 44a of the supporting portion 44, the distal end surface of the convex portion 46 slides along the bottom surface of the concave portion 44a.

[0259] like Fig. 20B As shown, when the distal end surface of the convex portion 46 of the second flange 40bE slides on and abuts on the bottom surface of the concave portion 44a of the support portion 44 in the sheet conveying direction DF, the second flange 40bE moves upstream by a distance G0 along the sheet conveying path DF.

[0260] Here, Fig. 20A The position of the second flange 40bE in Fig. 20BThe position of the second flange 40bE in is defined as the second position. The second flange 40bE can be moved to the first position and the second position. In the second position, the guide portion 42bE is located further upstream in the sheet conveying direction DF than in the first position. Then, when the second flange 40bE is located in the first position, the limiting surface 41bE is pushed toward the second side W2 by the fixing film 25, and the second flange 40bE moves from the first position to the second position. The position of the limiting surface 40bE when the second flange 41bE is located in the second position is closer to the second side W2 relative to the position of the limiting surface 40bE when the second flange 41bE is located in the first position. The limiting surface 41bE of the second flange 40bE located in the first position receives a thrust from the fixing film 25 toward the second side W2 to resist the thrust of the thrust spring 45, and the bottom surface 44b and the distal end surface 46a guide the second flange 40bE toward the second position. Here, in the present embodiment, the case where the guide portion 42bE and the limiting surface 41bE are integrally formed and move integrally has been described, but the present technology is not limited thereto, and the guide portion 42bE and the limiting surface 41bE may be separate components that move independently of each other. In this case, for example, an actuator or the like may be used to move the guide portion 42bE and the limiting surface 41bE independently of each other.

[0261] When the second flange 40bE moves upstream by a distance G0 in the sheet conveying direction DF, the fixing film 25 is displaced upstream by a distance G0 only on the second side W2 and forms an intersection angle with respect to the roller portion 26. Fig.15 The effect of the fixing film 25 on the second side W2 being shifted upstream in the sheet conveying direction DF is described below. Fig.15 , the fixing film 25 is displaced upstream in the sheet conveying direction DF at the first side W1. The fixing film 25 receives a force F0 from the roller portion 26, and the force F0 can be decomposed into a component force F2 acting in the longitudinal direction of the fixing film 25 and a component force F1 acting in the transverse direction of the fixing film 25. Therefore, it can be seen that when an intersection angle is formed between the fixing film 25 and the roller portion 26, the component force F2 acts on the fixing film 25 in a direction away from the first flange 40a displaced upstream in the sheet conveying direction DF.

[0262] Fig.21A According to this embodiment, when the letter-size sheets are continuously passed, the Fig. 12A Since the displacement force due to the temperature rise of the non-sheet passing portion Ar2 is not generated, the displacement flange unit 43 does not operate.

[0263] Fig.21B According to this embodiment, when A6 size sheets are continuously passed, the Fig. 12ADue to the increase in temperature of the non-sheet passing portion Ar2 , a biasing force in a direction that pushes the restricting surface 41 bE of the displacement flange unit 43 acts on the fixing film 25 .

[0264] By the action of the displacement flange unit 43, the fixing film 25 is displaced by a distance G0 upstream in the sheet conveying direction DF while being restricted by the second flange 40bE only on the second side W2. The fixing film 25 is separated from the bracket 22 by the second flange 40bE, and the fixing film 25 does not contact the bracket 22, thereby preventing the occurrence of poor fixing. In addition, since the fixing film 25 can form an angle with the roller portion 26 to offset the offset force caused by the temperature increase of the non-sheet passing portion Ar2 by the movement of the second flange 40bE, the offset force can be reduced.

[0265] Examples and Comparative Examples

[0266] In order to confirm the effect of the present embodiment, a comparative experiment was conducted using Example 6 of the present embodiment, as well as Example 4 and Comparative Example 5. In the fixing film 25 used in the comparative experiment, the thickness of the base layer 251 was 60 μm, the thickness of the elastic layer 252 was 250 μm, and the thickness of the surface layer 253 was 12 μm. The fixing film 25 was assembled in each configuration, and the effect of the fixing film 25 on the surface of the fixing film 25 was evaluated when 500 sheets of PB paper (A6 size and 68 g / cm 2 ) and the offset force applied to the end of the fixing film.

[0267] The evaluation results of the fixing performance and the offset force are shown in Table 8. As for the evaluation criteria of the fixing performance, the case where the fixing performance was good without any problem was evaluated as "good", and the case where the fixing performance was insufficient was evaluated as "poor".

[0268] Table 8

[0269] Fixing performance Offset force Comparative Example 5 Difference 1.8kgf Example 4 good 1.1kgf Example 6 good 0.5kgf

[0270] The evaluation results of the fixing performance of Comparative Example 5 and Example 4 are as described in the fourth embodiment. In Example 6, the fixing film 25 does not contact the holder 22 by the operation of the displacement flange unit 43, so that the occurrence of poor fixing can be prevented.

[0271] In all the configurations, the temperature rise in the non-sheet passing portion Ar2 is approximately the same, but the offset force applied to the end of the fixing film 25 is 1.8 kgf in Comparative Example 5, 1.1 kgf in Example 4, and 0.5 kgf in Example 6. In Comparative Example 5, in addition to the offset force due to the temperature rise of the non-sheet passing portion Ar2, a higher value is obtained due to the influence of the offset force generated by the intersection angle caused by the shape change of the fixing film 25. In Example 4, the offset force due to the temperature rise of the non-sheet passing portion Ar2 is not different from that in Comparative Example 5, but since the shape change of the fixing film 25 in the width direction W is suppressed by the protruding guide portion 293, the intersection angle is not large, and thus the offset force can be lower than that in Comparative Example 5. In Example 6, the offset force caused by the temperature rise of the non-sheet passing portion Ar2 is offset by the shift flange unit 43, so that the offset force can be suppressed to be lower than that in Example 4.

[0272] As described above, in the fixing device 6E according to the present embodiment, the displacement flange unit 43 is provided on the second side W2, so that the displacement force caused by the temperature rise of the non-sheet passing portion Ar2 can be reduced. Therefore, even in a configuration in which the deformation amount of the fixing film 25 is easily increased due to the thinning of the fixing film 25, etc., the occurrence of poor fixing and buckling can be suppressed, and a fixing device capable of achieving speed improvement and life extension can be realized. In addition, for example, a fixing film 25 in which the base layer 251 is further thinned can also be applied, so that cost reduction can be achieved.

[0273] Other embodiments

[0274] In the above-described respective embodiments, the image forming apparatus 100 as a monochrome laser printer is described as an example, but the present technology is not limited thereto. For example, the present disclosure can be applied to an image forming apparatus as a full-color laser printer.

[0275] While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all modifications and equivalent structures and functions.

Claims

1. A fixing device, comprising: a heating unit configured to heat the sheet; and a facing roller facing the heating unit and forming a fixing nip portion together with the heating unit, wherein the fixing device is configured to fix the toner image carried on the sheet to the sheet by applying heat and pressure at a fixing nip, wherein, regardless of the sheet size, one end of the sheet conveyed to the fixing device in a width direction intersecting with the sheet conveying direction passes through a predetermined position of the fixing nip in the width direction, The facing roller includes a roller portion, and the roller portion includes a base portion and an elastic layer disposed around the base portion and having elasticity. wherein, when a side where the predetermined position in the width direction is located relative to the center portion of the roller portion is defined as a first side and a side opposite to the first side is defined as a second side, the roller portion has a first end portion as an end portion of the first side in the width direction and a second end portion as an end portion of the second side in the width direction, and The thickness of the elastic layer at the second end is smaller than the thickness of the elastic layer at the first end.

2. The fixing device according to claim 1, wherein: The maximum outer diameter of the base at the second end is greater than the maximum outer diameter of the base at the first end.

3. The fixing device according to claim 1 or 2, wherein: The outer diameter of the central portion of the roller portion is smaller than the maximum outer diameter of the first end portion and the maximum outer diameter of the second end portion.

4. The fixing device according to claim 1 or 2, wherein: The maximum outer diameter of the second end portion of the roller portion is greater than the maximum outer diameter of the first end portion.

5. The fixing device according to claim 4, wherein: The maximum outer diameter of the second end portion is not less than 101% and not more than 103% of the maximum outer diameter of the first end portion.

6. The fixing device according to claim 1 or 2, wherein: The thickness of the elastic layer at the second end portion is 65% or more and 75% or less of the thickness of the elastic layer at the first end portion.

7. The fixing device according to claim 1 or 2, wherein: The roller part includes a release layer disposed around the elastic layer.

8. A fixing device, comprising: a heating unit configured to heat the sheet; a facing roller facing the heating unit and forming a fixing nip portion together with the heating unit; and a pressing unit configured to press one of the heating unit and the facing roller toward the other of the heating unit and the facing roller, wherein the fixing device is configured to fix the toner image carried on the sheet to the sheet by applying heat and pressure at a fixing nip, wherein, regardless of the sheet size, one end of the sheet conveyed to the fixing device in a width direction intersecting with the sheet conveying direction passes through a predetermined position of the fixing nip in the width direction, The facing roller includes a roller portion, and the roller portion includes a base portion and an elastic layer disposed around the base portion and having elasticity. wherein, when a side where the predetermined position in the width direction is located relative to the center portion of the roller portion is defined as a first side and a side opposite to the first side is defined as a second side, the roller portion has a first end portion as an end portion of the first side in the width direction and a second end portion as an end portion of the second side in the width direction, wherein the pushing unit is configured such that the pushing force at the first end is greater than the pushing force at the second end, and The elastic layer includes a high hardness region arranged on the first side, and the hardness of the high hardness region is higher than that of the elastic layer in the central portion.

9. The fixing device according to claim 8, wherein: When viewed from an intersecting direction intersecting the sheet conveying direction and the width direction, at least a portion of the high hardness region overlaps with a conveying region for conveying a sheet of a minimum conveying size.

10. The fixing device according to claim 8 or 9, wherein: The elastic layer includes a low hardness region provided on the second side, and the hardness of the low hardness region is lower than that of the elastic layer in the central portion.

11. The fixing device according to claim 10, wherein: The hardness of the elastic layer in the high hardness region is 110% or more and 120% or less of the hardness of the elastic layer in the low hardness region.

12. The fixing device according to claim 8 or 9, in, The pressing unit includes: a first pressing portion configured to press one of the heating unit and the facing roller toward the other of the heating unit and the facing roller at a first side in the width direction; and a second pressing portion configured to press one of the heating unit and the facing roller toward the other of the heating unit and the facing roller at a second side in the width direction, The pressing force of the first pressing portion is not less than 130% and not more than 170% of the pressing force of the second pressing portion.

13. The fixing device according to claim 8 or 9, wherein: The high hardness region is located between the central portion and the predetermined position in the width direction.

14. A fixing device, comprising: a heating unit configured to heat the sheet; and a facing roller facing the heating unit and forming a fixing nip portion together with the heating unit, wherein the fixing device is configured to fix the toner image carried on the sheet to the sheet by applying heat and pressure at a fixing nip, wherein, regardless of the sheet size, one end of the sheet conveyed to the fixing device in a width direction intersecting with the sheet conveying direction passes through a predetermined position of the fixing nip in the width direction, The heating unit includes a rotatable and flexible annular rotating member, a heater disposed in an inner space of the rotating member and configured to heat the rotating member, and a limiting member. The facing roller includes a roller portion, and the roller portion includes a base portion and an elastic layer disposed around the base portion and having elasticity. wherein, when a side where the predetermined position in the width direction is located relative to the central portion of the roller portion is defined as a first side and a side opposite to the first side is defined as a second side, the limiting member has a limiting surface configured to contact an end surface of the rotating member on the second side in the width direction to limit movement of the rotating member toward the second side, The rotating component includes a base layer and an elastic layer disposed around the base layer and containing a filler, and The base layer has a protrusion that protrudes relative to the elastic layer in a first direction directed from the first side to the second side in the width direction, and the protrusion is configured to contact the restriction surface in the width direction.

15. The fixing device according to claim 14, wherein: The protrusion is provided in a region of 70% or more of the end surface of the rotating member on the second side.

16. The fixing device according to claim 14 or 15, wherein: The protrusion portion protrudes from the elastic layer by an amount of 0.1 mm or more and 10 mm or less on the second side in the width direction.

17. The fixing device according to claim 14 or 15, wherein: The protrusion is configured to contact the limiting surface to limit the elastic layer from contacting the limiting surface.

18. The fixing device according to claim 14 or 15, wherein: The restricting member includes a guide portion provided to protrude from the restricting surface toward the rotating member in the width direction and configured to guide the rotating member by contacting an inner peripheral surface of the rotating member.

19. The fixing device according to claim 18, wherein: The protrusion amount of the protrusion relative to the elastic layer on the second side is smaller than the length of the guide portion in the width direction.

20. The fixing device according to claim 14 or 15, in, The elastic layer is a first elastic layer, The roller portion includes a base portion and a second elastic layer which is arranged around the base portion and has elasticity. wherein the inner peripheral surface of the base layer is electrically grounded, and The end surface of the protrusion on the second side is arranged downstream in the first direction relative to the end surface of the second elastic layer on the second side.

21. The fixing device according to claim 14 or 15, wherein: The base layer is made of resin material.

22. The fixing device according to claim 14 or 15, wherein: The filler is made of inorganic material.

23. The fixing device according to claim 22, wherein: The filler includes ceramic powder, metal oxide powder, or metal powder.

24. The fixing device according to claim 23, wherein: The filler includes aluminum oxide, metallic silicon, silicon carbide, or zinc oxide.

25. A fixing device, comprising: a heating unit configured to heat the sheet; and a facing roller facing the heating unit and forming a fixing nip portion together with the heating unit, wherein the fixing device is configured to fix the toner image carried on the sheet to the sheet by applying heat and pressure at a fixing nip, wherein, regardless of the sheet size, one end of the sheet conveyed to the fixing device in a width direction intersecting with the sheet conveying direction passes through a predetermined position of the fixing nip in the width direction, The heating unit includes a rotatable and flexible annular rotating component, a heater disposed in the inner space of the rotating component and configured to heat the rotating component, a first supporting component disposed in the inner space and configured to support the heater, and a second supporting component disposed in the inner space and configured to support the first supporting component. The facing roller includes a roller portion, and the roller portion includes a base portion and an elastic layer disposed around the base portion and having elasticity. Wherein, when a side where the predetermined position in the width direction is located relative to the central part of the roller portion is defined as a first side and a side opposite to the first side is defined as a second side, the first supporting member includes: a first guide portion, which is provided on the first side in the width direction and configured to guide the rotating member at a position upstream of the fixing nip portion in the sheet conveying direction; and a second guide portion, which is provided on the second side in the width direction and configured to guide the rotating member at a position upstream of the fixing nip portion in the sheet conveying direction. wherein the second supporting member has a facing portion which is farther from the fixing nip portion than the first guide portion and the second guide portion in a direction orthogonal to the sheet conveying direction and the width direction and faces an upstream portion of the inner peripheral surface of the rotating member in the sheet conveying direction, and Here, a distance from the facing portion to an upstream end of the second guide portion in the sheet conveying direction is longer than a distance from the facing portion to an upstream end of the first guide portion in the sheet conveying direction.

26. The fixing device according to claim 25, in, the first supporting member includes a third guide portion disposed on the second side in the width direction, configured to guide the rotating member at a position upstream of the fixing nip portion in the sheet conveying direction, and disposed apart from the second guide portion in the width direction, and Here, a distance from the facing portion to an upstream end of the third guide portion in the sheet conveying direction is shorter than a distance from the facing portion to an upstream end of the second guide portion in the sheet conveying direction.

27. A fixing device, comprising: a heating unit configured to heat the sheet; and a facing roller facing the heating unit and forming a fixing nip portion together with the heating unit, wherein the fixing device is configured to fix the toner image carried on the sheet to the sheet by applying heat and pressure at a fixing nip, wherein, regardless of the sheet size, one end of the sheet conveyed to the fixing device in a width direction intersecting with the sheet conveying direction passes through a predetermined position of the fixing nip in the width direction, The heating unit includes a rotatable and flexible annular rotating component, a heater disposed in the inner space of the rotating component and configured to heat the rotating component, a first supporting component disposed in the inner space and configured to support the heater, and a second supporting component disposed in the inner space and configured to support the first supporting component. The facing roller includes a roller portion, and the roller portion includes a base portion and an elastic layer disposed around the base portion and having elasticity. wherein the second supporting member has a facing portion at an end portion on the opposite side to the roller portion relative to the fixing nip portion in a direction orthogonal to the sheet conveying direction and the width direction, the facing portion facing an upstream portion of the inner peripheral surface of the rotating member in the sheet conveying direction, and The heating unit includes a cover disposed on the side opposite to the predetermined position relative to the center of the roller portion in the width direction, the cover being disposed between the facing portion of the second supporting member and an upstream portion of the inner peripheral surface of the rotating member in the sheet conveying direction.

28. The fixing device according to claim 27, wherein: The cover is supported by the second supporting member.

29. The fixing device according to claim 27 or 28, wherein: The cover is made of a material having a lower thermal conductivity than that of the second support member.

30. A fixing device, comprising: a heating unit configured to heat the sheet; and a facing roller facing the heating unit and forming a fixing nip portion together with the heating unit, wherein the fixing device is configured to fix the toner image carried on the sheet to the sheet by applying heat and pressure at a fixing nip, wherein, regardless of the sheet size, one end of the sheet conveyed to the fixing device in a width direction intersecting with the sheet conveying direction passes through a predetermined position of the fixing nip in the width direction, The heating unit includes a rotatable and flexible annular rotating member, a heater disposed in an inner space of the rotating member and configured to heat the rotating member, and a limiting member. The facing roller includes a roller portion, and the roller portion includes a base portion and an elastic layer disposed around the base portion and having elasticity. wherein, in a case where a side where the predetermined position in the width direction is located relative to the central portion of the roller portion is defined as a first side and a side opposite to the first side is defined as a second side, the limiting component comprises: a limiting surface configured to contact an end surface of the rotating component on the second side in the width direction to limit movement of the rotating component toward the second side; and a guide portion provided to protrude from the limiting surface toward the rotating component in the width direction and configured to guide the rotating component by contacting an inner peripheral surface of the rotating component, and In which, the limiting component is configured to be able to move to a first position and a second position so that the guide portion of the limiting component located at the second position is closer upstream in the sheet conveying direction than the guide portion of the limiting component located at the first position, and is configured to move from the first position to the second position by pushing the limiting surface along a first direction from the first side to the second side by a rotating component when the limiting component is located at the first position.

31. The fixing device according to claim 30, wherein: The restriction surface when the restriction member is located at the second position is arranged downstream in the first direction than the restriction surface when the restriction member is located at the first position.

32. The fixing device according to claim 30 or 31, in, The heating unit includes a support portion configured to movably support the restriction member and an urging portion configured to urge the restriction member toward the first side relative to the support portion, wherein one of the limiting member and the supporting portion includes a cam surface, wherein the other of the limiting component and the supporting portion includes a sliding member configured to abut against the cam surface and slide, and The cam surface and the slider are configured to guide the restricting member toward the second position by receiving a pushing force from the rotating member in the first direction against the pushing force of the pushing portion through the restricting surface of the restricting member located at the first position.

33. The fixing device according to claim 30 or 31, wherein: The guide portion and the limiting surface are integrally formed.

34. An imaging device comprising: an imaging unit configured to form a toner image on a sheet; and The fixing device according to claim 1 or 2, configured to fix the toner image formed by the image forming unit onto a sheet.

35. The imaging device according to claim 34, comprising: The conveying unit is disposed upstream of the imaging unit in the sheet conveying direction and is configured to convey the sheet in the sheet conveying direction while moving the sheet in the width direction so that the one end portion of the sheet passes through the predetermined position of the fixing nip.

Images