Fixing device and imaging device

Abstract

The present invention relates to a fixing device and an imaging device. The fixing device includes a first rotating component, a heating element, a second rotating component, a clamping component, a reflecting component and a supporting component. The supporting component is configured to be able to rotate to a pressurized state and a non-pressurized state, wherein the pressurized state is a state in which the first position and the second position of the supporting component are pressurized toward the second rotating component along the pressurized direction, and the non-pressurized state is a state in which the pressurized state of the supporting component is released. The supporting component includes a contact surface that contacts the reflecting component in the pressurized state. The posture taken by the contact surface is such that when the supporting component is in the non-pressurized state, the center position between the first position and the second position in the rotational axial direction is closer to the second rotating component than the first position and the second position.

Description

Technical Field

[0001] The present invention relates to a fixing device configured to fix a toner image onto a sheet, and an image forming apparatus including the fixing device. Background Art

[0002] Typically, an electrophotographic laser printer includes a fixing device configured to fix a toner image transferred to a sheet by applying heat and pressure to the toner image. Japanese Patent Application Laid-Open No. 2014-66851 discloses a fixing device comprising a cylindrical fixing belt, a heating unit configured to heat the fixing belt, and a pressure roller forming a nip portion with the fixing belt.

[0003] The heating device includes a halogen lamp that generates radiant heat, a clamping member that receives the radiant heat from the halogen lamp, a reflective plate that reflects the radiant heat from the halogen lamp back to the clamping member, and a bracket that supports the clamping member. The reflective plate is positioned by being sandwiched between the clamping member and the highly rigid bracket.

[0004] However, in the fixing device described in Japanese Patent Application Laid-Open No. 2014-66851, if the bracket flexes, the reflective plate also flexes along with it. Specifically, the bracket often flexes due to the load applied to the clamping portion while it is pressurized. If the bracket and reflective plate flex in this manner, thermal unevenness is likely to occur in the clamping portion, potentially leading to image defects such as uneven gloss. Summary of the Invention

[0005] According to a first aspect of the present invention, a fixing device includes: a first rotating member formed in an annular shape; a heating element disposed inside the first rotating member; a second rotating member that contacts an outer peripheral surface of the first rotating member and, together with the first rotating member, forms a clamping portion for fixing a toner image to a sheet; a clamping member slidably disposed relative to the inner peripheral surface of the first rotating member to clamp the first rotating member together with the second rotating member, and configured to heat the clamping portion by receiving radiant heat from the heating element; a reflecting member that reflects radiant heat from the heating element toward the clamping member; and a supporting member that supports the clamping member via the reflecting member. The supporting member is configured to be movable between a pressurized state and a non-pressurized state, wherein the pressurized state is a state in which a first position in a rotational axial direction of the supporting member and a second position different from the first position are pressed toward the second rotating member in a pressurized direction, and a state in which the pressurized state of the supporting member is released. The supporting member includes a contact surface that contacts the reflecting member in the pressurized state. The contact surface takes a posture such that a center position between the first position and the second position in the rotational axial direction is closer to the second rotating member than the first position and the second position when the support member is in a non-pressurized state.

[0006] According to a second aspect of the present invention, a fixing device includes: a first rotating member formed in an annular shape; a heating element disposed inside the first rotating member; a second rotating member that contacts an outer peripheral surface of the first rotating member and, together with the first rotating member, forms a clamping portion for fixing a toner image to a sheet; a clamping member slidably disposed relative to the inner peripheral surface of the first rotating member to clamp the first rotating member together with the second rotating member and configured to heat the clamping portion by receiving radiant heat from the heating element; a reflecting member that reflects radiant heat from the heating element toward the clamping member; and a supporting member that supports the clamping member via the reflecting member. The supporting member is configured to be movable between a pressurized state and a non-pressurized state, wherein the pressurized state is a state in which a first position and a second position different from the first position in the rotational axial direction of the supporting member are pressed toward the second rotating member in the pressurized direction, and a non-pressurized state in which the pressurized state of the supporting member is released. The outer diameter of a central portion of the second rotating member in the rotational axial direction is smaller than the outer diameters of each end portion of the second rotating member in the rotational axial direction.

[0007] According to a third aspect of the present invention, the fixing device includes: a first rotating member formed in a ring shape; a heating element arranged on the inner side of the first rotating member; a second rotating member, which contacts the outer peripheral surface of the first rotating member and forms a clamping portion together with the first rotating member for fixing the colorant image to the sheet; a clamping member, which is slidably arranged relative to the inner peripheral surface of the first rotating member to clamp the first rotating member together with the second rotating member, and is configured to heat the clamping portion by receiving radiant heat from the heating element; a supporting member, which supports the clamping member; and an elastic portion having an elastic modulus lower than the elastic modulus of the supporting member and the clamping member, the elastic portion being arranged between the supporting member and the clamping member in a pressing direction that is orthogonal to the rotational axial direction of the second rotating member and the sheet conveying direction.

[0008] 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

[0009] Figure 1A is a schematic diagram illustrating the overall configuration of a printer of the first exemplary embodiment.

[0010] Figure 1B is a schematic diagram illustrating the imaging unit of the first exemplary embodiment.

[0011] Figure 2 is a cross-sectional view illustrating the fixing device of the first exemplary embodiment.

[0012] Figure 3ASchematic diagram showing a fixing device in a non-pressurized state according to a comparative example, as viewed from a sheet conveyance direction.

[0013] Figure 3B Schematic diagram showing a fixing device in a pressurized state according to a comparative example, as viewed from a sheet conveying direction.

[0014] Figure 4 1 is a schematic diagram showing the fixing device as viewed from the sheet conveying direction.

[0015] Figure 5A 1 is a schematic diagram showing the fixing device in a non-pressurized state when viewed from the sheet conveying direction.

[0016] Figure 5B 1 is a schematic diagram showing the fixing device in a pressurized state when viewed from the sheet conveying direction.

[0017] Figure 6 is a schematic diagram illustrating a fixing device according to a modified example.

[0018] Figure 7A is a schematic diagram illustrating the fixing device in a non-pressurized state of the second exemplary embodiment as viewed from the sheet conveying direction.

[0019] Figure 7B is a schematic diagram illustrating the fixing device in a pressurized state of the second exemplary embodiment as viewed from the sheet conveying direction.

[0020] Figure 8 is a cross-sectional view illustrating a fixing device of a third exemplary embodiment.

[0021] Figure 9A is an exploded perspective view showing a supporting member and a low-elasticity member.

[0022] Figure 9B is a perspective view showing that the supporting member and the low elastic member are assembled with each other.

[0023] Figure 10A is an exploded perspective view illustrating a supporting member and a low-elasticity member according to a modification of the third exemplary embodiment.

[0024] Figure 10B is a perspective view showing that the supporting member and the low elastic member are assembled with each other.

[0025] Figure 11A is an exploded perspective view illustrating a supporting member and a low-elasticity member of a fourth exemplary embodiment.

[0026] Figure 11B is a perspective view showing that the supporting member and the low elastic member are assembled with each other.

[0027] Figure 12A is an exploded perspective view illustrating a supporting member and a low-elasticity member according to a modification of the fourth exemplary embodiment.

[0028] Figure 12B is a perspective view showing that the supporting member and the low elastic member are assembled with each other. DETAILED DESCRIPTION

[0029] First Exemplary Embodiment

[0030] Overall structure

[0031] Exemplary embodiments of the present disclosure will be described below with reference to the accompanying drawings. Figure 1A 1 is a schematic diagram showing a printer 1 as an image forming apparatus of the first exemplary embodiment. Figure 1A As shown, the printer 1 includes an apparatus body 2 , an image reading device 3 provided above the apparatus body 2 , and an image forming unit 10 provided in the apparatus body 2 and configured to form an image on a sheet.

[0032] like Figure 1B As shown, the imaging unit 10 includes an electrophotographic imaging section 100 and a fixing device 106. When the imaging section 100 is instructed to start imaging, the photosensitive drum 101, serving as a photosensitive member, rotates, and the surface of the photosensitive drum is uniformly charged by the charging roller 102. The exposure unit 103 then outputs a laser beam modulated according to image data transmitted from the image reading device 3 or an external computer to scan the surface of the photosensitive drum 101, thereby forming an electrostatic latent image. This electrostatic latent image is visualized or developed by toner supplied from the developing unit 104 and becomes a toner image T.

[0033] In parallel with this imaging operation, a sheet feeding operation is performed to feed sheets P stacked on a cassette or manual feed tray (not shown) to the imaging unit 10. The sheets P thus fed are conveyed to the imaging unit 10 in synchronization with the advancement of the imaging operation of the imaging portion 100.

[0034] The toner image T carried on the photosensitive drum 101 is then transferred to a sheet P by a transfer roller 105. The toner remaining on the photosensitive drum 101 after the toner image is transferred is collected by a cleaning unit 107. The sheet P to which the unfixed toner image has been transferred is conveyed to a fixing device 106. The fixing device 106 melts the toner using heat and pressure, and fixes the toner image T to the sheet P. The sheet P to which the toner image T has been fixed is discharged from the imaging apparatus by a pair of discharge rollers and other devices.

[0035] Fixing device

[0036] Next, we will refer to Figure 2 The fixing device 106 of this exemplary embodiment will be described. Figure 2As shown, the fixing device 106 includes an endless fixing belt 201, a heating unit 200 for heating the fixing belt 201, and a pressure roller 202 for sandwiching the fixing belt 201 together with the heating unit 200. Note that the fixing belt 201 includes a film-like member.

[0037] The fixing belt 201 as the first rotating member is made of a polyimide resin having high thermal conductivity and low heat capacity and is a flexible endless belt. Note that the fixing belt 201 may be formed of other resins or metals such as stainless steel.

[0038] The fixing belt 201 is rotatably provided and lubricant is applied to the inner peripheral surface of the fixing belt 201 to ensure sliding performance relative to the gripping member 204 described later. Then, guide members (not shown) are provided on both end portions of the fixing belt 201 in the rotational axial direction (hereinafter referred to as "axial direction X") to guide the rotation of the fixing belt 201 and restrict the movement of the fixing belt 201 in the rotational axial direction.

[0039] The heating unit 200 is arranged on the inner circumference side of the fixing belt 201 and includes a halogen lamp 203, a clamping member 204, a reflective plate 205, and a support member 206. The halogen lamp 203, which serves as a heating element, is arranged with a certain space relative to the fixing belt 201 and the clamping member 204 so as to emit radiant heat and heat the fixing belt 201. The temperature of the radiant heat from the halogen lamp 203 varies depending on the amount of supply from an unillustrated power supply. In the case of this exemplary embodiment, the temperature of the radiant heat emitted by the halogen lamp 203 is adjusted according to the control of the supply amount by a control unit (not shown), so that the temperature of the clamping portion N detected by a temperature sensor (not shown) is maintained at a predetermined temperature. Note that the heating element is not limited to a halogen lamp and may be another heating element.

[0040] The clamping member 204 is a long member that is arranged so as not to rotate relative to the rotating fixing belt 201 and that is slidable relative to the inner circumference of the fixing belt 201, extending in the axial direction X. While the halogen lamp 203 emits radiant heat to heat the fixing belt 201, the clamping member 204 receives the radiant heat from the halogen lamp 203, as described above. Specifically, the clamping member 204 includes a heat receiving surface 204a that faces the halogen lamp 203 and receives the radiant heat from the halogen lamp 203.

[0041] The reflective plate 205, serving as a reflective member, reflects the radiant heat emitted from the halogen lamp 203 toward the clamping member 204. The reflective plate 205 is arranged at a predetermined distance from the halogen lamp 203, covering the halogen lamp 203. The reflective plate 205 is formed from, for example, an aluminum plate having a high reflectivity for infrared and far-infrared radiation, by bending the plate so that its cross-section is substantially U-shaped. The clamping portion N can be rapidly heated by effectively utilizing the radiant heat from the halogen lamp 203 via the clamping member 204. This is because the radiant heat from the halogen lamp 203 is collected by the reflective plate 205 and then brought to the clamping member 204.

[0042] More specifically, the reflective plate 205 includes a reflective portion 205a having an inner surface that receives radiant heat, and flange portions 205b extending from both ends of the reflective portion 205a in the sheet conveying direction Y and in a direction opposite to the sheet conveying direction Y. The reflective plate 205 is formed by press-molding a 400 μm thick aluminum plate, which is then mirror-polished to achieve high reflectivity. The reflective plate 205 is preferably very thin, within a range that allows it to maintain its shape. This is because if the heat capacity of the reflective plate 205 is large, the ratio of heat consumed by the halogen lamp 203 to increase the temperature of the reflective plate 205 increases, and the heating efficiency of the clamping member 204 decreases.

[0043] The support member 206 is a structure having a predetermined rigidity for supporting the clamping member 204, and is formed into a shape arranged along the outer surface of the reflective plate 205 by using a metal having excellent strength (for example, stainless steel and spring steel). More specifically, the support member 206 supports both end portions of the clamping member 204 in the sheet conveying direction Y (which is the short side direction of the clamping member 204) in the pressing direction Z via the flange portion 205b of the reflective plate 205.

[0044] Since the flange portion 205 b of the reflecting plate 205 is clamped by the support member 206 and the clamping member 204 in the pressurizing direction Z, displacement of the reflecting plate 205 in the pressurizing direction Z can be suppressed. In addition, since the flange portion 205 b of the reflecting plate 205 is supported by the highly rigid support member 206, the shape of the reflecting plate 205 in the axial direction X can be advantageously maintained over the entire length of the reflecting plate 205. A gap is also provided between the reflecting portion 205 a and the support member 206 to reduce heat escape from the clamping member 204 to the support member 206.

[0045] In the present exemplary embodiment, the supporting member 206 presses the nip member 204 in the pressing direction Z, and the fixing belt 201 is pressed from the inside toward the pressing roller 202 by the pressed nip member 204 , thereby more reliably forming the nip portion N.

[0046] The pressure roller 202 is configured to abut against the outer peripheral surface of the fixing belt 201 and is rotatably supported. In this exemplary embodiment, the pressure roller 202 is driven by a not-shown driving motor at a predetermined peripheral speed along the fixing belt 201. Figure 2 . Then, due to the friction force generated at the clamping portion N, the rotational force of the pressure roller 202 is transmitted to the fixing belt 201. Therefore, the fixing belt 201 is driven by the pressure roller 202. That is, a so-called pressure roller drive system is adopted in this exemplary embodiment. The pressure roller 202 is constructed by forming an elastic layer 202B around a metal core metal 202A serving as a rotation axis and forming a release layer 202C formed of a fluororesin such as PTFE, PFA, and FEP around the elastic layer 202B. The elastic layer 202B contains gaps therein. The elastic layer 202B and the release layer 202C constitute a roller portion 202R serving as a second rotating member.

[0047] The core metal 202A is rotatably supported by bearing portions (not shown) that support both end portions of the core metal 202A in the axial direction X. The support member 206 then presses the nip member 204 in the pressing direction Z by a load from a pressure member (not shown), thereby pressing the fixing belt 201 toward the pressure roller 202. As a result, the surface of the pressure roller 202 elastically deforms, and a nip portion N having a predetermined width in the sheet conveyance direction Y is formed by the surfaces of the pressure roller 202 and the fixing belt 201. In the present exemplary embodiment, the load W1 applied to both end portions of the support member 206 in the axial direction X is set to 9 kg per end, and a total load of 18 kg is applied to the support member 206.

[0048] Note that the pressing direction Z is a direction orthogonal to the axial direction X and the sheet conveying direction Y. Furthermore, the clamping member 204 is not limited to a member that directly contacts the fixing belt 201, but may be a member that contacts the fixing belt 201 via a sheet member having high thermal conductivity (e.g., iron alloy and aluminum).

[0049] As described above, the temperature of the nip member 204 is increased by being heated by the radiant heat from the halogen lamp 203 and the radiant heat reflected by the reflective plate 205. The sheet P on which the unfixed toner image has been formed is heated and pressurized by being nipped and conveyed by the rotating fixing belt 201 and the pressure roller 202 at the nip portion N, whereby the toner image is fixed to the sheet P.

[0050] Mechanisms causing thermal unevenness

[0051] Next, we will refer to Figures 3A to 4 The comparative example in describes the mechanism causing thermal unevenness. Figure 3A 1 is a schematic diagram showing a fixing device in a non-pressurized state according to a comparative example as viewed from a sheet conveying direction Y. Figure 3B This is a schematic diagram of the fixing device of the comparative example in a pressurized state, viewed from the sheet conveyance direction Y. The pressurized state is a state in which the support member 1206 of the comparative example is pressed toward the pressure roller 202 in the pressurizing direction Z. The non-pressurized state is a state in which the pressurized state of the support member 1206 is released, that is, a state in which no load W1 is applied to the support member 1206.

[0052] like Figure 3A As shown, the support member 1206 has a contact surface 1206a that contacts the flange portion 205b of the reflective plate 205. When the support member 1206 is in a non-pressurized state, the contact surface 1206a extends parallel to the axial direction X. When the support member 1206 is in a pressurized state, a load W1 is applied to each of the end portions of the support member 1206 in the axial direction X, and the center portion of the support member 1206 is flexed and separated from the pressure roller 202.

[0053] As the support member 1206 flexes, the center portion of the reflecting plate 205 in the axial direction X also flexes following the support member 1206 in a direction in which the center portion is separated from the pressing roller 202. Since the reflecting plate 205 flexes in this manner, internal stress is generated and the reflecting plate 205 often ends up partially deforming in a wave-like manner.

[0054] Will refer to Figure 4 The uneven radiant heat generated when the reflective plate 205 is locally deformed in a wave-like manner will be described. Figure 4 2 is a schematic diagram showing the fixing device viewed from the sheet conveying direction Y. FIG. Figure 4 The arrows described in 200 are diagrams showing the traveling directions of the radiant heat emitted from the halogen lamp 203 and reflected by the reflecting plate 205 .

[0055] For example, the reflective plate 205 deforms convexly in region S1 to approach the clamping member 204, while the reflective plate 205 deforms concavely in region S2 to separate from the clamping member 204. The temperature of the clamping member 204 in region S1' close to region S1 is unlikely to rise due to the low density of radiant heat reflected by the reflective plate 205. However, the temperature of the clamping member 206 in region S2' close to region S2 may increase due to the high density of radiant heat reflected by the reflective plate 205.

[0056] Therefore, the deformation of the reflector 205 causes temperature unevenness in the nip member 204 of the fixing device of the comparative example. If the toner image T on the sheet P is heated and fixed in this state, the glossiness of the toner image T corresponding to the high-temperature area within the nip portion N increases, thereby causing gloss unevenness.

[0057] Shape of supporting parts

[0058] The shape of the support member 206 of the present exemplary embodiment for suppressing the above-described uneven heat and uneven glossiness will be described. Figure 5A Schematic diagram of the fixing device 106 in a non-pressurized state as viewed from the sheet conveying direction Y. Figure 5B This is a schematic diagram of the fixing device 106 in a pressurized state as viewed from the sheet conveying direction Y. The pressurized state is a state in which the supporting member 206 of this exemplary embodiment is pressed toward the pressure roller 202 in the pressurizing direction Z, and the non-pressurized state is a state in which the pressurized state of the supporting member 206 is released, that is, a state in which no load W1 is applied to the supporting member 206. The supporting member 206 is configured to be transitionable between the pressurized state and the non-pressurized state.

[0059] like Figure 2 、 5A As shown in FIG5B, the support member 206 includes a contact surface 206a that contacts the flange portion 205b of the reflective plate 205 in a pressurized state. Figure 5B As shown, in the pressurized state, the support member 206 is pressed toward the pressure roller 202 in the pressurizing direction Z at a first position P1 and a second position P2 that is different from the first position P1 in the axial direction X. The first position P1 and the second position P2 are located near both ends of the support member 206 in the axial direction X, and a load W1 is applied to each of these first position P1 and second position P2.

[0060] like Figure 5A As shown, no load W1 acts on either of the first and second positions P1, P2 of the support member 206, so the support member 206 does not deform. At this time, the contact surface 206a of the support member 206 is biased toward the roller portion 202R of the pressure roller 202, causing the distance between the contact surface 206a and the roller portion 202R of the pressure roller 202 to decrease as it approaches the center portion 206b between the first and second positions P1, P2. In other words, the contact surface 206a assumes a posture such that the center position CP corresponding to the center portion 206b is closer to the roller portion 202R than the first and second positions P1, P2. In other words, the contact surface 206a has a normal crown shape that bulges toward the roller portion 202R of the pressure roller 202.

[0061] Therefore, when the support member 206 is in the non-pressurized state, the distance between the contact surface 206a and the outer peripheral surface of the roller portion 202R is a distance d1 as a first distance at the center position CP between the first position P1 and the second position P2 in the axial direction X. Note that the distance d1 corresponds to the distance between the center portion 206b of the contact surface 206a located at the center position CP and the outer peripheral surface of the roller portion 202R.

[0062] Furthermore, at a third position P3 between the first position P1 and the center position CP in the axial direction X, the distance between the contact surface 206a and the outer peripheral surface of the roller portion 202R is a second distance d2 that is longer than the distance d1 (d2>d1).

[0063] When the support member 206 is Figure 5B As shown, when pressure is applied, the central portion of the support member 206 deforms and separates from the roller portion 202R. At this time, the contact surface 206a of the support member 206 deforms, causing the central portion 206b to separate from the roller portion 202R. Because the contact surface 206a is pre-formed so that the central portion 206b is biased toward the roller portion 202R in the non-pressurized state, the contact surface 206a assumes a nearly flat shape along the axial direction X when pressurized. This reduces wavy deformation of the reflective plate 205 supported by the support member 206 and suppresses uneven glossiness.

[0064] Note that when support member 206 is in the pressurized state, the distance between contact surface 206a and the outer peripheral surface of roller portion 202R at center position CP is distance d3, which serves as the third distance, and at third position P3 is distance d4, which serves as the fourth distance. At this time, since distance d3 is almost equal to distance d4, the difference Δ2 between distances d3 and d4 is smaller than the difference Δ1 between distances d2 and d1. That is, the following equation holds true.

[0065] Δ2=(d4-d3)<Δ1=(d2-d1)

[0066] The present exemplary embodiment, that is, the first exemplary embodiment and Figure 3A and 3B The following describes the results of confirming the waviness of the reflective plate 205 and the uneven glossiness caused by thermal unevenness in the comparative example. The contact surface 1206a of the support member 1206 in the comparative example is approximately flat in the non-pressurized state, whereas the contact surface 206a of the support member 206 in the first exemplary embodiment has a crown shape in the non-pressurized state.

[0067] Evaluations in the first exemplary embodiment and the comparative example were performed under the following conditions.

[0068] Environment: 23℃ / 50%RH

[0069] Main body: Production volume 27ppm (A4),

[0070] Processing speed: 148mm / sec.

[0071] Sheet: LTR size "HP, Brochure Paper 200 Glossy" (weight 200g / m 2) paper in a 23°C / 50%RH environment for more than 48 hours.

[0072] Print image: A completely black image

[0073] The deflection amount of the support members 206 and 1206 is defined as the amount by which the central portions of the contact surfaces 206a and 1206a of the support members 206 and 1206 are deformed in the direction of separation from the pressure roller 202 due to the transition from the non-pressurized state to the pressurized state. Specifically, the deflection amount is obtained by cutting the fixing belt 201 within a range that does not affect the deformation of the support members 206 and 1206 and measuring the shapes of the support members 206 and 1206 using a height gauge before and after pressurization.

[0074] The deflection amount of the reflective plate 205 is defined as the amount by which the central portion of the reflective plate 205 in the axial direction X is deformed in the direction away from the pressure roller 202 due to the transition from the non-pressurized state to the pressurized state. Specifically, the deflection amount was obtained by removing the halogen lamp 203 while taking care not to affect the deformation of the reflective plate 205 and measuring the shape of the inner surface of the reflective plate 205 from both longitudinal ends with a height gauge before and after pressurization.

[0075] While the support members 206 and 1206 were in the pressurized state, the waviness of the reflecting plate 205 was confirmed by visually observing the inner surface of the reflecting plate 205 from the axial direction X. Furthermore, glossiness unevenness caused by thermal unevenness was confirmed by visually observing a solid black image after printing.

[0076] Table 1 shows the deflection amount of the support member, the deflection amount of the reflection plate, the waviness of the reflection plate, and the gloss unevenness caused by thermal unevenness of the first exemplary embodiment and the comparative example evaluated by the above-described method.

[0077] Table 1:

[0078]

[0079] It can be confirmed from Table 1 that the waviness of the reflecting plate 205 is reduced and the unevenness in glossiness caused by the uneven heat is suppressed in the first exemplary embodiment.

[0080] As described above, according to the present exemplary embodiment, the contact surface 206 a is formed so that when the support member 206 is in the non-pressurizing state, the closer it is to the center portion 206 b in the axial direction X, the closer it is to the roller portion 202R of the pressure roller 202 . This arrangement makes it possible to reduce image defects such as uneven gloss.

[0081] Modification example

[0082] Figure 6: is a schematic diagram showing a fixing device of a modified example of the first exemplary embodiment. Figure 6 As shown, this modification includes a changing mechanism 50 in addition to the configuration of the first exemplary embodiment described above. The changing mechanism 50 is configured to change the load, that is, the pressing force, applied to the support member 206 in the pressing direction Z. The changing mechanism 50 can change the magnitude of the load depending on, for example, the state of the printer 1, the type of sheet to be printed, and the job.

[0083] Thus, in the present modified example, the reflecting plate 205 is not fixed to the supporting member 206 in the pressing direction Z. For example, when a load W1 acts as a first pressing force on both end portions of the supporting member 206 in the axial direction X, the reflecting plate 205 contacts the contact surface 206a of the supporting member 206 over its entire length in the axial direction X. At the same time, when a load W2 smaller than the load W1 acts as a second pressing force on both end portions of the supporting member 206 in the axial direction X, the both end portions of the reflecting plate 205 in the axial direction X separate from the contact surface 206a of the supporting member 206.

[0084] Even if the load acting on the support member 206 is changed by the changing mechanism 50 so that the reflecting plate 205 is not fixed to the supporting member 206 in the pressing direction Z, the reflecting plate 205 is less affected in its deformation. Therefore, this arrangement also makes it possible to suppress deformation or damage of the reflecting plate 205.

[0085] Note that a configuration in which the load applied to the supporting member 206 is changed by using, for example, a rotating cam may be applied to the changing mechanism 50 .

[0086] Second Exemplary Embodiment

[0087] Next, a second exemplary embodiment of the present disclosure will be described. The second exemplary embodiment is constructed by modifying the support member and pressure roller of the first exemplary embodiment. Therefore, the same components as those of the first exemplary embodiment will be described with the same reference numerals omitted or designated as such.

[0088] Figure 7A is a schematic diagram of the fixing device 106B in the non-pressurized state of the second exemplary embodiment as viewed from the sheet conveying direction Y, Figure 7B This is a schematic diagram of the fixing device 106B in a pressurized state as viewed from the sheet conveying direction Y.

[0089] The fixing device 106B of this exemplary embodiment includes a support member 2206 and a pressure roller 2202. The pressure roller 2202 includes a core metal 202A and a roller portion 2202R attached to the core metal 202A. The roller portion 2202R, which serves as the second rotating member, is configured so that its outer diameter decreases as it approaches its center portion in the axial direction X. That is, the roller portion 2202R is formed into an inverse crown shape so that the outer diameter of the center portion of the roller portion 2202R in the axial direction X is smaller than the outer diameter of each end portion of the roller portion 2202R in the axial direction X.

[0090] Meanwhile, the support member 2206 includes a contact surface 2206a that contacts the reflection plate 205 in a pressurized state. The contact surface 2206a extends parallel to the axial direction X when the support member 2206 is in a non-pressurized state.

[0091] like Figure 7B As shown, when the support member 2206 is pressed, the nip member 204 presses the roller portion 2202R of the pressure roller 2202 via the fixing belt 201. Since the roller portion 2202R of this exemplary embodiment has an inverted crown shape, the closer to the center portion in the axial direction X, the weaker the nip pressure of the nip portion N.

[0092] Therefore, the deflection of the support member 2206 is small and the deflection of the reflection plate 205 is also small. Therefore, similar to the first exemplary embodiment, the waviness of the reflection plate 205 is reduced and the unevenness in glossiness caused by the unevenness in heat is also reduced.

[0093] In this exemplary embodiment, i.e., the second exemplary embodiment, the effect of suppressing uneven glossiness was confirmed. The contact surface 2206a of the support member 2206 is approximately flat in the non-pressurized state, and the crowning amount of the roller portion 2202R in the non-pressurized state is 350 μm. Note that the crowning amount corresponds to half the difference between the outer diameter of the roller portion 2202R at both ends in the axial direction X and the outer diameter of the roller portion 2202R at the center in the axial direction X.

[0094] The second exemplary embodiment was evaluated under the same conditions as the first exemplary embodiment. Table 2 shows the deflection amount of the support member, the deflection amount of the reflection plate, the waviness of the reflection plate, and the gloss unevenness caused by thermal unevenness of the second exemplary embodiment.

[0095] Table 2:

[0096]

[0097] It can be confirmed from Table 2 that the waviness of the reflection plate 205 is reduced and the unevenness in glossiness caused by the uneven heat is suppressed in the second exemplary embodiment. Therefore, image defects can be reduced.

[0098] Third Exemplary Embodiment

[0099] Next, a third exemplary embodiment of the present disclosure will be described. The third exemplary embodiment is an embodiment in which the configuration of the fixing device of the first exemplary embodiment is modified. Therefore, the same components as those of the first exemplary embodiment will be described with the same reference numerals omitted or designated as the same components.

[0100] Incidentally, in the fixing device described in Japanese Patent Application Laid-Open No. 2014-66851, the bracket supports the clamping plate via the flange portion of the reflective component. The clamping plate, the reflective component, and the bracket are formed of metal. When rigid metals come into contact with each other, the metals tend to cause uneven pressure due to their inability to conform to irregularities and other conditions on the metal surfaces. As a result, unevenness is generated in the clamping pressure distribution at the clamping portion, which may lead to image defects such as uneven gloss. The third exemplary embodiment is an example of solving this problem.

[0101] Fixing device

[0102] like Figure 8 As shown, the fixing device 3106 of the third exemplary embodiment includes a fixing belt 201 formed into an endless shape, a heating unit 200 for heating the fixing belt 201, and a pressure roller 202 that sandwiches the fixing belt 201 together with the heating unit 200. Note that the fixing belt 201 may be a film-like member.

[0103] The fixing belt 201 as the first rotating member is a flexible endless belt made of a polyimide resin having high thermal conductivity and low heat capacity. Note that the fixing belt 201 may be formed of other resins or metal such as stainless steel.

[0104] The fixing belt 201 is provided to be rotatable, and a lubricant is applied to the inner peripheral surface of the fixing belt 201 to ensure sliding performance relative to a gripping member 204 described later. Then, guide members (not shown) are provided on both end portions of the fixing belt 201 in the rotational axial direction (hereinafter referred to as the axial direction X) to guide the rotation of the fixing belt 201 and restrict the movement of the fixing belt 201 in the rotational axial direction.

[0105] The heating unit 200 is arranged on the inner peripheral side of the fixing belt 201 and includes a halogen lamp 203, a clamping member 204, a reflective plate 3205, and a supporting member 3206. The halogen lamp 203, which serves as a heating element, is arranged with space relative to the fixing belt 201 and the clamping member 204 to emit radiant heat and heat the fixing belt 201. The temperature of the radiant heat from the halogen lamp 203 varies depending on the amount of supply from an unillustrated power supply. In the case of this exemplary embodiment, the temperature of the radiant heat emitted by the halogen lamp 203 is adjusted according to the control of the supply amount by a control portion not shown, so that the temperature of the clamping portion N detected by the unillustrated temperature sensor is maintained at a predetermined temperature. Note that the heating element is not limited to a halogen lamp and may be another heating element.

[0106] The clamping member 204 is a long member that is arranged so as not to rotate relative to the rotating fixing belt 201 and that extends slidably in the axial direction X relative to the inner circumference of the fixing belt 201. When the halogen lamp 203 emits radiant heat to heat the fixing belt 201, the clamping member 204 receives the radiant heat from the halogen lamp 203, as described above. Specifically, the clamping member 204 includes a heat receiving surface 204a that faces the halogen lamp 203 and receives the radiant heat from the halogen lamp 203.

[0107] The reflective plate 3205 is a member for reflecting the radiant heat emitted from the halogen lamp 203 toward the clamping member 204. It is arranged at a predetermined distance from the halogen lamp 203, covering the halogen lamp 203. For this purpose, the reflective plate 3205 is formed from, for example, an aluminum plate having a high reflectivity for infrared and far-infrared radiation, by bending the plate so that its cross-section is roughly U-shaped. By collecting the radiant heat from the halogen lamp 203 into the clamping member 204 via the reflective plate 3205, the radiant heat from the halogen lamp 203 can be effectively utilized, and the clamping portion N can be quickly heated by the clamping member 204. Note that the reflective plate 3205 can be omitted.

[0108] The support member 3206 has a predetermined rigidity for supporting the clamping member 204, and is formed using a metal having excellent strength (such as stainless steel or spring steel) into a shape arranged along the outer surface of the reflective plate 3205. More specifically, the support member 3206 supports both end portions of the clamping member 204 in the sheet conveyance direction Y (which is the short-side direction of the clamping member 204). In the case of this exemplary embodiment, the fixing belt 201 is pressed from the inside toward the pressure roller 202 by the clamping member 204 supported by the support member 3206, so that the nip portion N can be formed more reliably.

[0109] The pressure roller 202 as the second rotating member is in contact with the outer peripheral surface of the fixing belt 201 and is rotatably supported. In this exemplary embodiment, the pressure roller 202 is rotated along the fixing belt 201 at a predetermined peripheral speed by a drive motor not shown. Figure 8 . The fixing belt 201 is rotated in the direction of the arrow in FIG. Then, due to the friction force generated in the nip portion N, the rotational force of the pressure roller 202 is transmitted to the fixing belt 201. Thus, the fixing belt 201 is driven by the pressure roller 202. That is, a so-called pressure roller drive system is adopted in this exemplary embodiment. The pressure roller 202 is constructed by forming an elastic layer 202B around a metal core 202A serving as a rotation axis, and forming a release layer 202C formed of a fluororesin (e.g., PTFE, PFA, and FEP) around the elastic layer 202B. The elastic layer 202B contains voids therein.

[0110] The core metal 202A is rotatably supported by bearing portions (not shown) that support both end portions of the core metal 202A in the axial direction X. Then, the supporting member 3206 presses the nip member 204 in the pressing direction Z to press the fixing belt 201 toward the pressure roller 202. As a result, the surface of the pressure roller 202 is elastically deformed, and a nip portion N having a predetermined width in the sheet conveyance direction Y is formed by the surface of the pressure roller 202 and the surface of the fixing belt 201.

[0111] Note that the pressing direction Z is a direction orthogonal to the axial direction X and the sheet conveying direction Y. It is also possible to arrange the clamping member 204 so that it is not pressed in the pressing direction Z, but so that the pressure roller 202 is pressed toward the clamping member 204. Furthermore, the clamping member 204 is not limited to a member that is in direct contact with the fixing belt 201, but may be a member that is in contact with the fixing belt 201 via a sheet-like member having high thermal conductivity (e.g., iron alloy or aluminum).

[0112] As described above, the nip member 204 is heated by the radiant heat emitted from the halogen lamp 203 and the radiant heat reflected by the reflective plate 3205, thereby increasing the temperature of the fixing belt 201. The sheet P on which an unfixed toner image has been formed is subjected to heat and pressure by being nipped and conveyed by the rotating fixing belt 201 and the pressure roller 202 at the nip portion N, so that the toner image is fixed to the sheet P.

[0113] Low elasticity parts

[0114] Next, we will refer to Figures 8 to 9BThe low elastic member 207 disposed between the supporting member 3206 and the nip member 204 is described. Incidentally, the supporting member 3206 presses the nip member 204 in the pressing direction Z to form a nip portion N between the fixing belt 201 and the pressure roller 202. Therefore, the supporting member 3206 and the nip member 204 need to have a predetermined rigidity and are generally formed of metal as their material.

[0115] In this case, the support member 3206 and the clamping member 204 (i.e., metal) are in contact with each other. Because rigid metals cannot conform to surface irregularities when in contact, uneven pressure is likely to occur. If uneven contact occurs, uneven pressure is applied to the clamping member 204 by the support member 3206, resulting in uneven distribution of pressure between the clamping member 204 and the pressure roller 202, causing uneven glossiness in the toner image.

[0116] Thus, according to this exemplary embodiment, the low-elasticity member 207 made of a polyimide resin is arranged between the support member 3206 and the clamping member 204 in the pressing direction Z. The low-elasticity member 207 has a lower elastic modulus than the support member 3206 and the clamping member 204. Therefore, the low-elasticity member 207 is sandwiched between the support member 3206 and the clamping member 204 in the pressing direction Z with a predetermined pressing force, and conforms to the shapes of the support member 3206 and the clamping member 204. This arrangement enables the pressing force to be smoothly transmitted from the support member 3206 to the clamping member 204.

[0117] More specifically, the support member 3206 extends along the entire length of the sheet passing region in the axial direction X and has a U-shaped cross section. The support member 3206 includes side walls 3206 b and 3206 c extending in the pressing direction Z, and a connecting portion 3206 a extending in the sheet conveying direction Y to connect these side walls 3206 b and 3206 c.

[0118] The low-elasticity members 207 extend along the axial direction X over the entire length of the sheet passage region and are formed into a U-shaped cross section so that the opening portion faces the support member 3206. Each low-elasticity member 207 is then attached to the edge portions of the side walls 3206b and 3206c of the support member 3206. The low-elasticity members 207 attached to the side walls 3206b and 3206c are composed of the same components, and the following description will focus on the side wall 3206b and the low-elasticity members 207 attached to the side wall 3206b.

[0119] The low-elasticity member 207 includes side walls 207b and 207c extending in the pressing direction Z, and a connecting portion 207a (which serves as an elastic portion) extending in the sheet conveying direction Y to connect these side walls 207b and 207c. The side wall 3206b of the support member 3206 includes a contact surface 3206d that contacts the connecting portion 207a of the low-elasticity member 207. Since the side walls 207b and 207c of the low-elasticity member 207 clamp the side wall 3206b of the support member 3206, displacement of the low-elasticity member 207 in the sheet conveying direction Y can be reduced. The height of the contact surface 3206d of the support member 3206 in the pressing direction Z is constant throughout its entire length in the axial direction X.

[0120] Incidentally, when, for example, a low-elasticity member having a constant cross-sectional shape in the axial direction X is used, the shape of the nip portion N in the pressurized state becomes constant in the axial direction X. The problem arises in how to suppress paper wrinkles when fixing a toner image to the sheet P at the nip portion N. Since paper wrinkles are generated when the sheets P are overlapped within the nip portion N and pressurized, suppressing such paper wrinkles requires generating a force at the nip portion N that causes the sheets to expand in a direction from the center portion toward the end portions in the axial direction X.

[0121] Thus, according to this exemplary embodiment, the thickness of the connecting portion 207a of the low elastic member 207 is different between the center portion and the end portion in the axial direction X so that the sheet conveying speed at the clamping portion N increases more at the end portion in the axial direction X than at the center portion.

[0122] More specifically, the connecting portion 207a of the low-elasticity member 207 includes a central portion 207f in the axial direction X and an end portion 207g in the axial direction X. The central portion 207f, serving as the first portion, and the end portion 207g, serving as the second portion, are located at different positions in the axial direction X. Furthermore, the central portion 207f is closer to the central portion of the connecting portion 207a in the axial direction X than the end portion 207g. Thus, the low-elasticity member 207 is arranged so that the thickness h1 of the central portion 207f in the pressurizing direction Z is thicker than the thickness h2 of the end portion 207g in the pressurizing direction Z.

[0123] If the pressure roller 202 is a balloon-like roller including an elastic layer 202B with internal voids, the more the pressure roller 202 is compressed, the closer the roller surface and the core metal 202A become, and the slower the sheet conveying speed becomes. Specifically, because the thickness h1 of the center portion 207f of the low-elasticity member 207 is thicker than the thickness h2 of the end portions 207g, the clamping member 204 conforms to the shape of the low-elasticity member 207. Consequently, since the pressure roller 202 is pressed by the clamping member 204, whose center portion bulges downward, the center portion of the pressure roller 202 in the axial direction X is compressed significantly more than the end portions in the axial direction X. Consequently, the sheet conveying speed at both end portions in the axial direction X of the clamping member N becomes faster than that at the center portion, thus suppressing paper wrinkling.

[0124] Here, to compare whether paper wrinkles and uneven glossiness occur, low-elasticity members made of two different materials were prepared and placed between the support member 3206 and the clamping member 204. Table 3 shows the structural details of the low-elasticity members made of these two different materials as a comparative example and a third exemplary embodiment, respectively.

[0125] Table 3:

[0126] structure Material Vertical shape Third Exemplary Embodiment polyimide resin The center portion is thicker than the longitudinal end portions Comparative Example aluminum The center portion is thicker than the longitudinal end portions

[0127] The low elastic member of the comparative example is made of aluminum, while the low elastic member of the third exemplary embodiment is made of polyimide resin, which is the arrangement in this exemplary embodiment. In the comparative example and the third exemplary embodiment, the longitudinal shape of the low elastic member, that is, the shape in the axial direction X is as follows: Figure 9A and 9B As shown, the thickness of the longitudinal center portion is thicker than that of the longitudinal end portions. Specifically, the thickness of the longitudinal center portion of the connecting portion 207a in the sheet thickness direction is 2.3 mm, and the thickness of the longitudinal end portions is 2.0 mm.

[0128] Evaluation of paper wrinkles was performed under the following conditions.

[0129] Environment: High temperature and high humidity environment (30°C / 80% RH, hereinafter referred to as H / H environment)

[0130] Main body: Production volume 27ppm (A4),

[0131] Processing speed: 148mm / sec.

[0132] Sheet (plain paper): A4 size "Red Label" paper manufactured by Océ (weight 80 g / m2) was placed in an H / H environment for more than 48 hours.

[0133] Sheet (thin paper): A4 size "CS-060F" paper manufactured by Canon Inc. (weight 60 g / m 2 ) Place in H / H environment for more than 48 hours.

[0134] Print image: All white image

[0135] Method for judging whether paper wrinkles occur: confirm a whole bundle of fed sheets by touch, and mark "X" if paper wrinkles occur even on only one sheet among 30 fed sheets, and mark "O" if paper wrinkles do not occur.

[0136] The evaluation of uneven gloss was performed under the following conditions.

[0137] Environment: High temperature and high humidity environment (30℃ / 80%RH)

[0138] Main body: Production volume 27ppm (A4),

[0139] Processing speed: 148mm / sec.

[0140] Sheet (plain paper): LTR size "HP, Brochure Paper 200 Glossy" manufactured by HP (weight 200 g / m 2 ) paper is placed in an H / H environment for more than 48 hours.

[0141] Print image: A completely black image

[0142] Judgment of whether uneven glossiness occurs: if uneven glossiness is visually observed on a uniform solid black image, it is marked as "X", and if uneven glossiness is not visually observed, it is marked as "O".

[0143] Table 4 shows the relationship between the occurrence of paper wrinkles and uneven glossiness in the comparative example and the third exemplary embodiment.

[0144] Table 4:

[0145]

[0146] Because both the comparative example and the third exemplary embodiment are constructed so that the center portion is thicker than the longitudinal end portions, the amount of pressure applied by the pressure roller 202 at the longitudinal end portions is smaller than at the longitudinal center portion, and the sheet is conveyed faster. Consequently, since the force exerted to unfold the sheet in the longitudinal end direction is higher, neither plain paper nor thin paper wrinkles. However, since aluminum is used in the comparative example and its contact properties with rigid metals are low, the pressure applied by the support member 3206 is not uniformly transmitted to the clamping member 204, resulting in uneven gloss.

[0147] Since the third exemplary embodiment uses a polyimide resin having a lower elastic modulus than metal, the contact performance with metal is good. Therefore, since the pressing force from the support member 3206 can be smoothly transmitted to the clamping member 204, no uneven glossiness occurs.

[0148] As described above, by arranging the low-elasticity member 207 between the support member 3206 and the metal clamping member 204, uneven glossiness can be reduced. The thickness of the low-elasticity member 207 is also arranged so that the thickness h1 of the center portion 207f of the low-elasticity member 207 in the axial direction X is thicker than the thickness h2 of the end portions 207g. In other words, the low-elasticity member 207, which is an elastic member, is arranged so that its thickness in the pressurizing direction Z gradually decreases from the center portion in the axial direction X to the end portions.

[0149] Although the low elastic member 207 having a 2.3 mm thick longitudinal center portion and 2.0 mm thick longitudinal end portions is used in the present exemplary embodiment, the low elastic member 207 needs to have a certain strength or greater in order to reduce uneven pressure within the clamping portion N. Therefore, the low elastic member 207 preferably has a thickness of 1.0 mm or more even at its thinner longitudinal portion.

[0150] Modification example

[0151] 10A and 10B show modified examples of the third exemplary embodiment. Figure 10A and 10B The connecting portion 307a as the elastic portion of the low elastic member 307 shown in FIG. 1 includes a center portion 307f in the axial direction X and an end portion 307g in the axial direction X. The center portion 307f as the second portion and the end portion 307g as the first portion are located at positions different from each other in the axial direction X. Furthermore, the center portion 307f is closer to the center portion of the connecting portion 307a than the end portion 307g in the axial direction X.

[0152] Then, the connecting portion 307a is arranged so that the thickness h11 of the center portion 307f in the axial direction X is thinner than the thickness h12 of the end portions 307g. In other words, the thickness of the connecting portion 307a of the low elastic member 307 in the pressing direction Z gradually increases from the center portion to the end portions. Therefore, the clamping width at the end portions in the axial direction X at the clamping portion N can be increased more than the clamping width at the center portion, and the fixing performance at the end portions of the clamping portion N can be improved.

[0153] Fourth exemplary embodiment

[0154] Next, a fourth exemplary embodiment of the present disclosure will be described. The fourth exemplary embodiment is constructed by modifying the support member and the low-elasticity member of the third exemplary embodiment. Therefore, the same components as those of the third exemplary embodiment will be described while omitting illustration or using the same reference numerals to designate them.

[0155] like Figure 11A and 11B As shown, the support member 406 extends along the axial direction X over the entire length of the sheet passing region and has a U-shaped cross section. The support member 406 includes side walls 406 b and 406 c extending in the pressing direction Z, and a connecting portion 406 a extending in the sheet conveying direction Y to connect the side walls 406 b and 406 c.

[0156] The low-elasticity member 407 made of polyimide resin extends along the axial direction X over the entire length of the sheet passing region, and is formed into a U-shape in cross section so that the opening portion faces the support member 406. Then, each low-elasticity member 407 is attached to the edge portions of the side walls 406b and 406c of the support member 406. The low-elasticity members 407 attached to the side walls 406b and 406c are composed of the same components, and the following description will focus on the side wall 406b and the low-elasticity member 407 attached to the side wall 406b.

[0157] The low-elasticity member 407 includes side walls 407b and 407c extending in the pressing direction Z, and a connecting portion 407a (which serves as an elastic portion) extending in the sheet conveying direction Y to connect these side walls 407b and 407c. The side wall 406b of the support member 406 includes a contact surface 406d that contacts the connecting portion 407a of the low-elasticity member 407. Since the side walls 407b and 407c of the low-elasticity member 407 sandwich the side wall 406b of the support member 406, displacement of the low-elasticity member 407 in the sheet conveying direction Y can be reduced.

[0158] The height of the contact surface 406d of the support member 406 in the pressurizing direction Z is not constant over the entire length in the axial direction X. More specifically, the contact surface 406d includes a center portion 406f in the axial direction X and an end portion 406g in the axial direction X. The center portion 406f, which serves as the third portion, and the end portion 406g, which serves as the fourth portion, are located at different positions in the axial direction X. With respect to the axial direction X, the center portion 406f is closer to the center of the support member 406 than the end portion 406g.

[0159] Thus, the center portion 406f is closer to the rotation axis 202T of the pressing roller 202 than the end portion 406g in the pressing direction Z (see FIG. Figure 8That is, the contact surface 406 d is located at a position gradually away from the rotation axis 202T of the pressure roller 202 from the center portion 406 f to the both end portions 406 g in the axial direction X.

[0160] Meanwhile, the thickness of the connecting portion 407a of the low elastic member 407 in the pressing direction Z is constant over the entire length in the axial direction X. That is, the thickness of the connecting portion 407a is constant over the entire length in the axial direction X thereof.

[0161] In this exemplary embodiment, the contact surface 406d of the support member 406 is arranged so that the center portion 406f protrudes more than the end portions 406g, and the thickness of the connecting portion 407a of the low-elasticity member 407 is made constant. Therefore, the clamping member 204 conforms to the shapes of the contact surface 406d of the support member 406 and the low-elasticity member 407. Thus, the pressure roller 202 is pressed by the clamping member 204, whose center portion bulges downward, thereby suppressing wrinkles in the paper.

[0162] Since the thickness of the connecting portion 407 a of the low elastic member 407 is made constant, the heat dissipated to the supporting member 406 through the nip member 204 is uniform in the axial direction X, and dispersion in the fixing performance of the nip portion N can be reduced at each position in the axial direction X. At the same time, if the height of the contact surface 406 d of the supporting member 406 varies significantly, the low elastic member 407 cannot conform to such a shape, and thus it is necessary to optimize the shape of the contact surface 406 d by taking the flexibility of the low elastic member 407 into consideration.

[0163] Modification example

[0164] 12A and 12B show a modified example of the fourth exemplary embodiment. The support member 506 includes a contact surface 506d having a plurality of stepped portions. Therefore, the shape of the contact surface 506d is not limited to a shape curved with a constant radius of curvature, and the contact surface 506d as a whole can be arranged so that the center portion is closer to the rotation axis 202T of the pressure roller 202 than the end portions.

[0165] Other exemplary embodiments

[0166] Although the load has been applied to both end portions in the axial direction X in the first and second exemplary embodiments, the present disclosure is not limited to such a configuration. For example, the load may be applied to both end portions in the axial direction X. Figure 5B The position shown is applied to the support component at the inside in the axial direction X.

[0167] Furthermore, the first exemplary embodiment may be combined with the second exemplary embodiment. For example, the contact surface 206a may be configured to have a smaller radius of curvature than the first exemplary embodiment, and the pressure roller 2202 may have a reverse crowned roller portion 2202R having a smaller radius of curvature than the second exemplary embodiment. These may then be combined.

[0168] Although a polyimide resin with high heat resistance is used as the material of the low elastic component in the third and fourth exemplary embodiments, the present disclosure is not limited to such an arrangement. For example, the low elastic component can be formed from a highly heat-resistant material, such as a resin containing glass balloons. By using a highly heat-resistant material, it is possible to prevent the radiant heat from the halogen lamp 203 from escaping from the clamping member 204 to the support member when the temperature of the fixing device is increased. Therefore, it is possible to effectively transfer the radiant heat to the clamping portion N and accelerate the temperature increase of the fixing device.

[0169] Furthermore, although the low elasticity member is configured to contact the support member and the clamping member in the third and fourth exemplary embodiments, the present disclosure is not limited to such an arrangement. For example, a flange portion may be formed so that the reflective plate 3205 faces the contact surface of the support member, and the low elasticity member may be arranged between the flange portion and the support member.

[0170] Furthermore, although the low elastic component has been formed to have a U-shaped cross section with two side walls and a connecting portion in the third and fourth exemplary embodiments, the present disclosure is not limited to such an arrangement. For example, the two side walls may be omitted from the low elastic component.

[0171] Furthermore, in the third exemplary embodiment, the connecting portion 207a of the low-elasticity member 207 is formed so that the thickness gradually decreases from the center portion to the both end portions in the axial direction X. However, the present disclosure is not limited to such an arrangement. For example, the connecting portion 207a may be arranged so that the thickness decreases in a plurality of steps from the center portion to the both end portions.

[0172] The first to fourth exemplary embodiments and their modifications can be appropriately combined with each other.

[0173] 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 such modifications and equivalent structures and functions.

Claims

1. A fixing device comprising: a first rotating member formed in a ring shape; a heating element disposed inside the first rotating member; a second rotating member that contacts an outer peripheral surface of the first rotating member and forms, together with the first rotating member, a nip portion for fixing the toner image to the sheet; a clamping member slidably provided relative to the inner peripheral surface of the first rotating member to clamp the first rotating member together with the second rotating member, and configured to heat the clamping portion by receiving radiant heat from the heating element; a reflecting member that reflects radiant heat from the heating element toward the holding member; and a supporting member that supports the clamping member via the reflecting member, The support member is configured to be able to switch to a pressurized state and a non-pressurized state. The pressurized state is a state in which a first position in the rotational axial direction of the support member and a second position different from the first position are pressurized toward the second rotating member in a pressurizing direction. The non-pressurized state is a state in which the pressurized state of the support member is released. wherein the supporting member includes a contact surface that contacts the reflecting member in a pressurized state, and The contact surface takes a posture such that a center position between the first position and the second position in the rotational axial direction is closer to the second rotating member than the first position and the second position when the support member is in a non-pressurized state.

2. The fixing device according to claim 1, wherein With the support member in a non-pressurized state, the outer diameter of the second rotation member is constant over the entire length of the second rotation member in the rotational axial direction.

3. The fixing device according to claim 1, wherein When the support member is in a non-pressurized state, the distance between the contact surface and the outer peripheral surface of the second rotating member at the center position is a first distance, and When the support member is in the non-pressurized state, the distance between the contact surface and the outer peripheral surface of the second rotating member at a third position in the rotational axial direction between the first position and the center position is a second distance that is longer than the first distance.

4. The fixing device according to claim 3, wherein In a case where the support member is in a pressurized state, the distance between the contact surface and the outer peripheral surface of the second rotating member at the center position is a third distance, wherein, when the support member is in the pressurized state, the distance between the contact surface and the outer peripheral surface of the second rotating member at the third position is a fourth distance, and The difference between the fourth distance and the third distance is smaller than the difference between the second distance and the first distance.

5. The fixing device according to claim 1 , further comprising a changing mechanism configured to change a pressing force for pressing the supporting member in a pressing direction, in, When the support member is in a pressurized state and the pressurizing force is a first pressurizing force, the reflective member contacts the contact surface over the entire length of the reflective member in the rotational axial direction, and Here, when the support member is in a pressurized state and the pressurizing force is a second pressurizing force smaller than the first pressurizing force, both end portions of the reflective member in the rotational axial direction are separated from the contact surface.

6. The fixing device according to any one of claims 1 to 4, wherein: The reflecting member includes a flange portion clamped by the supporting member and the clamping member in the pressing direction.

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

Images