fixing device

Abstract

A fixing device includes a looped belt, a rotatable press member that contacts an outer circumferential surface of the looped belt, and a sliding member on an inner side of the looped belt. The sliding member forms a nip by pinching and feeding the looped belt between itself and the rotatable press member, and slides on an inner circumferential surface of the looped belt. The rotatable press member pinches and feeds a recording material in the nip in cooperation with the belt, and fixes a toner image on the recording material by applying heat and pressure. The sliding member includes a base body that extends in a width direction of the looped belt, and the base body is made of metal and includes a plurality of protrusions that protrude toward the rotatable press member.

Description

Technical Field

[0001] The present invention relates to a fixing device for fixing an image of toner carried on a recording material onto the recording material. Background Technology

[0002] As a fixing device, the clamping portion is formed by clamping portion forming members (e.g., belt and roller) to clamp and supply recording material through the clamping portion, and to heat and pressurize the recording material. In this configuration, the clamping portion is formed between the belt and the clamping portion forming members by sliding a sliding member on the inner circumference of the belt at the clamping portion.

[0003] To ensure the quality of the image to be fixed onto the recording material, the fixing device must suppress slippage between the recording material and the tape supplied to the clamping portion, as well as slippage between the recording material and the clamping portion forming member. For this purpose, the frictional force between the tape and the sliding member needs to be less than the frictional force between the recording material and the tape, and between the recording material and the clamping portion forming member. In particular, in configurations with a wide clamping portion (where the clamping portion is wider to improve heating efficiency), it is necessary to reduce the frictional force between the tape and the sliding member.

[0004] For example, Japanese Patent Application Publication No. 2020-52354 discloses a structure in which an unevenness is formed on a sliding sheet that moves together with the inner surface of the belt in the clamping portion to reduce the friction between the sliding sheet and the belt.

[0005] When the belt and sliding member slide as described above, if the frictional force acting on the clamping portion increases, the sliding member may deform, and pressure unevenness may occur in the clamping portion. If pressure unevenness occurs, gloss unevenness may appear in the fixed image. In particular, in a wide clamping structure with a wide clamping portion, the frictional force acting on the clamping portion tends to increase.

[0006] The purpose of this invention is to provide a structure that can suppress both uneven gloss and wrinkles on the recording material. Summary of the Invention

[0007] According to one aspect of the invention, a fixing device is provided, comprising: an annular belt configured to apply heat to recording material; a rotatable pressing member contacting an outer peripheral surface of the annular belt; and a sliding member inside the annular belt, configured to form a clamping portion by clamping and supplying the belt between the sliding member itself and the rotatable pressing member, and sliding on an inner peripheral surface of the belt, wherein the rotatable pressing member cooperates with the belt to clamp and supply the recording material in the clamping portion, and fixes a toner image onto the recording material by applying heat and pressure, wherein the sliding member includes a base extending along the width direction of the belt, wherein the base is made of metal and includes a plurality of protrusions projecting toward the rotatable pressing member.

[0008] Other features of the invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0009] Figure 1 This is a schematic cross-sectional view of an imaging apparatus according to an embodiment.

[0010] Figure 2 Part (a) is a schematic cross-sectional view of the fixing apparatus according to an embodiment. Figure 2 Part (b) is Figure 2 A schematic diagram of the magnified portion A of part (a).

[0011] Figure 3 Parts (a) and (b) are schematic diagrams of the sliding member according to an embodiment. Figure 3 Part (a) is a sectional view. Figure 3 Part (b) is a plan view.

[0012] Figure 4 This is a schematic diagram illustrating the relationship between the sliding member and the belt according to an embodiment.

[0013] Figure 5 Part (a) is a schematic cross-sectional view showing the structure around the clamping part when not under pressure. Figure 5 Part (b) is a cross-sectional view schematically showing the structure around the clamping part when under pressure.

[0014] Figure 6 Part (a) is a graph showing the pressure distribution along the width of the ideal clamping portion. Figure 6 Part (b) is a schematic diagram showing the relationship between forces during the supply of recording material in the ideal clamping section.

[0015] Figure 7 Part (a) is a graph showing the pressure distribution along the width of the clamping portion in the comparative example. Figure 7 Part (b) is a schematic diagram showing the relationship between forces in the clamping section during the supply of recording material in the comparative example.

[0016] Figure 8 This is a list representing the conditions for the various sliding components used in Evaluation 1.

[0017] Figure 9 This is a graph representing the results of evaluation 1.

[0018] Figure 10 This is a graph representing the results of evaluation 2.

[0019] Figure 11 This is a graph representing the results of evaluation 3.

[0020] Figure 12 This is a graph representing the results of evaluation 4. Detailed Implementation

[0021] use Figures 1 to 12 To explain embodiments of the present invention. First, using Figure 1 The schematic structure of the imaging device in this embodiment will be explained below.

[0022] [Imaging device]

[0023] Imaging apparatus 1 is an electrophotographic full-color printer with four imaging portions Pa, Pb, Pc, and Pd, providing these four imaging portions for four colors: yellow, magenta, cyan, and black. In this embodiment, the imaging portions Pa, Pb, Pc, and Pd are arranged in a cascaded configuration along the rotation direction of the intermediate transfer belt 204 (explained later). Imaging apparatus 1 forms a toner image (image) on recording material in response to image signals from an image reading portion (document reader) 2 (which is connected to the main component 3 of the imaging apparatus) or a host device (e.g., a personal computer connected to the main component 3 of the imaging apparatus for communication). Recording materials include paper, plastic film, cloth, and other sheet materials.

[0024] Imaging device 1 is equipped with an image reading section 2 and a main component 3. The image reading section 2 reads the original document placed on the stage glass 21. Light emitted from the light source 22 is reflected from the original document and forms an image on the CCD sensor 24 through an optical component 23 (e.g., a lens). The optical unit scans the original document in the direction of the arrow and converts the original document into a progressive sequence of electrical signal data. The image signal obtained by the CCD sensor 24 is sent to the main component 3 of the imaging device, where a control section 30 performs image processing appropriate to each imaging section, as described below. The control section 30 also receives external input as image signals from an external host device (e.g., a print server).

[0025] The main component 3 of the imaging apparatus is equipped with multiple imaging sections Pa, Pb, Pc, and Pd, each of which performs imaging based on the aforementioned image signal. Specifically, the image signal is converted into a PWM (Pulse Width Modulation) laser beam by the control unit 30. The polygon scanner 31, serving as an exposure unit, scans the laser beam according to the image signal. Then, the laser beam irradiates the photosensitive drums 200a to 200d, which serve as image-carrying components, in each imaging section Pa to Pd.

[0026] Pa is the imaging portion for yellow (Y), Pb is the imaging portion for magenta (M), Pc is the imaging portion for cyan (C), and Pd is the imaging portion for black (Bk), which together form images of the corresponding colors. Since the imaging portions Pa to Pd are largely the same, details of the imaging portion Pa for Y will be described below, while descriptions of the other imaging portions will be omitted. In the imaging portion Pa, the photosensitive drum 200a has a toner image formed on its surface based on the image signal, as described below.

[0027] The charging roller 201a, acting as a primary charger, charges the surface of the photosensitive drum 200a to a predetermined potential, preparing it for the formation of an electrostatic latent image. A laser beam from the polygon scanner 31 forms the electrostatic latent image on the surface of the photosensitive drum 200a, now charged to the predetermined potential. The developer 202a develops the electrostatic latent image on the photosensitive drum 200a to form a toner image. The primary transfer roller 203a discharges from the back of the intermediate transfer belt 204 and applies a primary transfer bias of opposite polarity to the toner, transferring the toner image from the photosensitive drum 200a onto the intermediate transfer belt 204. After the transfer, the surface of the photosensitive drum 200a is cleaned by the cleaner 207a.

[0028] The toner image on the intermediate transfer belt 204 is transferred to the next imaging section, and the toner images of various colors formed in the respective imaging section are transferred sequentially in the order of Y, M, C, and Bk, thereby forming a four-color image on its surface. The toner image that has passed through the Bk imaging section Pd (which is located downstream along the rotation direction of the intermediate transfer belt 204) is transferred to the secondary transfer section, which includes secondary transfer rollers 205 and 206. In the secondary transfer section, a secondary transfer electric field with a polarity opposite to that of the toner image on the intermediate transfer belt 204 is applied, thereby causing secondary transfer to the recording material.

[0029] Recording material is contained in cartridge 9. The recording material supplied from cartridge 9 is fed to alignment section 208 (which includes, for example, a pair of alignment rollers) and waits there. Then, alignment section 208 controls the timing so that the toner image on intermediate transfer belt 204 is aligned with the paper supply section and the recording material is supplied to secondary transfer section.

[0030] In the secondary transfer section, the recording material on which the toner image has been transferred is supplied to the fixing device 8, where the toner image on the recording material is fixed by heating and pressurizing it. The recording material that has passed through the fixing device 8 is discharged into the discharge tray 7. When performing double-sided imaging on both sides of the recording material, when the toner image transfer and fixing are completed on the first side (front) of the recording material, the front and back sides of the recording material are reversed by the reverse supply section 10, the toner image is transferred and fixed on the second side (back) of the recording material, and the recording material is stacked on the discharge tray 7.

[0031] The control unit 30 controls the entire imaging apparatus 1, as described above. Furthermore, the control unit 30 can perform various settings based on input from the operation unit 4 (which is located in the imaging apparatus 1). The control unit 30 includes a CPU (Central Processing Unit), a ROM (Read-Only Memory), and RAM (Random Access Memory). The CPU controls each part and simultaneously reads the program corresponding to the control process stored in the ROM. The RAM stores working data and input data, and the CPU performs control based on the aforementioned program by referring to the data stored in the RAM.

[0032] [Fixing device]

[0033] The following will use Figure 2 The construction of the fixing device 8 in this embodiment will be explained by parts (a) and (b). In this embodiment, a belt-heated fixing device using an annular belt is employed. Figure 2 In part (a), the X direction represents the supply direction of the recording material P (not shown), the Y direction represents the width direction of the recording material that intersects (orthogonal in this embodiment) the supply direction of the recording material, and the Z direction represents the pressing direction, i.e., the direction in which the recording material is pressed at the clamping part N. In this embodiment, the X, Y, and Z directions are each orthogonal to each other.

[0034] The fixing device 8 includes a fixing belt (hereinafter referred to as the "belt") 301, a support 302, a pressure pad (hereinafter referred to as the "pad") 303, a sliding member 304, a pressure roller 305, a heating roller 307, and a thermistor 308. The belt 301 is an annular, rotatable, heated rotating member. The pressure roller 305, which forms a clamping portion, is a pressure rotating member that contacts the outer periphery of the belt 301 to form a clamping portion N for clamping and supplying recording material.

[0035] The sliding member 304 slides against the inner circumference of the belt 301 within the clamping portion N. A pad 303, serving as a support member, is located inside the belt 301 to hold the sliding member 304 and the belt 301 between the pressure roller 305, thereby supporting the sliding member 304. The sliding member 304 is arranged to cover the outer circumference of the pad 303 on the belt 301 side. A support post 302 is located inside the belt 301, opposite the clamping portion N across the pad 303, and supports the pad 303. A heating roller 307 is located inside the belt 301 to stretch and heat the belt 301. A thermistor 308, serving as a temperature sensing member, detects the temperature of the belt 301. The various structures are described in detail below.

[0036] The strip 301 possesses thermal conductivity and heat resistance, and is a thin-walled cylindrical shape. In this embodiment, the strip 301 has a three-layer structure, comprising a base layer 301a, an elastic layer 301b on the outer periphery of the base layer 301a, and a separable layer 301c on the outer periphery of the elastic layer, as shown below. Figure 2 Part (b) is shown.

[0037] The base layer 301a is, for example, 80 μm thick and is made of polyimide resin (PI). The elastic layer 301b is, for example, 300 μm thick and is made of silicone rubber. The separable layer 301c is, for example, 30 μm thick and is made of PFA (polyvinyl fluoride tetrafluoride / perfluoroalkoxyethylene copolymer resin), which is a fluoropolymer. The belt 301 is stretched by a pad 303 and a heated roller 307. In this embodiment, the outer diameter of the belt 301 is 150 mm.

[0038] A pad 303 is located inside the belt 301, facing the pressure roller 305 across the belt 301, and forms a clamping portion N that clamps and supplies recording material between the belt 301 and the pressure roller 305. In this embodiment, the pad 303 is a generally plate-shaped member that is longer along the width direction of the belt 301 (the longitudinal direction intersecting the rotation direction of the belt 301 and the rotation axis direction of the heating roller 307). The pad 303 is pressed against the pressure roller 305 across the belt 301 to form the clamping portion N. The material of the pad 303 is LCP (liquid crystal polymer) resin. The pad 303 has a crown-shaped profile in a direction perpendicular to the supply direction to compensate for deformation caused by the deflection of the support column 302 during pressurization. A sliding member 304 is positioned between the pad 303 and the belt 301. Details of the sliding member 304 are described below.

[0039] The pad 303 is supported by a support post 302, which acts as a support member located inside the belt 301. Specifically, the support post 302 is located on the side of the pad 303 opposite to the pressure roller 305 and supports the pad 303. The support post 302 is a rigid reinforcing member with a relatively long rigidity along the longitudinal direction of the belt 301 and contacts the pad 303 to support it. In other words, when the pressure roller 305 presses down on the pad 303, the support post 302 provides strength to the pad 303 and ensures the pressing pressure in the clamping portion N.

[0040] The support column 302 is made of a metal such as stainless steel, and its cross-section (transverse section) orthogonal to the longitudinal direction of the support column 302 intersects the rotation direction of the belt 301. For example, the support column 302 is made of pultruded SUS304 (stainless steel) with a wall thickness of 3 mm, and its strength is ensured by forming a hollow section with a roughly square cross-section. The support column 302 can be formed into a roughly rectangular shape in cross-section by combining multiple metal sheets and fixing them together by welding or other means.

[0041] The material for support column 302 is not limited to stainless steel, as long as its strength can be guaranteed.

[0042] A heating roller 307 is located inside the belt 301 and, together with a pad 303, tensions the belt 301. The heating roller 307 is formed into a cylindrical shape from a metal such as aluminum or stainless steel and includes a halogen heater 306 as a heat source for heating the belt 301. The heating roller 307 is heated to a predetermined temperature by the halogen heater 306.

[0043] The heating roller 307 is also a control roller, with its center of rotation at one end or near the center along the longitudinal direction, and controls the position of the belt 301 along the main scanning direction by generating a front-to-back tension difference by rotating it relative to the belt 301. The heating roller 307 is also a tensioning roller, which is attached by a spring supported by a frame (not shown) to apply a predetermined tension to the belt 301.

[0044] In this embodiment, the heating roller 307 is formed of, for example, a 1 mm thick stainless steel tube. Although a single halogen heater 306 can be used, multiple halogen heaters are desirable to control the temperature distribution of the heating roller 307 along the longitudinal direction (rotation axis direction). Multiple halogen heaters 306 have different light distributions along the longitudinal direction, and the illumination ratio is controlled according to the size of the recording material. In this embodiment, three halogen heaters 306 are arranged. The heat source is not limited to halogen heaters; it can also be other heaters capable of heating the heating roller 307, such as a carbon heater.

[0045] The tape 301 is heated by a heating roller 307 heated by a halogen heater 306, and the tape is controlled to a predetermined target temperature based on the temperature detected by a thermistor 308, according to the type of recording material. The thermistor 308 is positioned close to the center of the tape 301 and opposite the outer periphery of the tape 301 (the entire size of the recording material that can be fixed by the fixing device 8 passes through the center). The thermistor 308 detects the temperature of the tape 301, and the control unit 30 controls the power supplied to the halogen heater 306 so that the temperature detected by the thermistor 308 becomes the target temperature. The thermistor 308 can be a non-contact sensor arranged immediately adjacent to the outer periphery of the tape 301, or it can be a contact sensor arranged in contact with the outer periphery of the tape 301.

[0046] The pressure roller 305 rotates in contact with the outer periphery of the belt 301 and is also a drive roller that applies driving force to the belt 301. In this embodiment, the heating roller 307 is also driven by a drive source (e.g., a drive motor) to provide driving force to the belt 301. However, applying driving force to the heating roller 307 can be omitted. The pressure roller 305 is a roller having a metal core (shaft) 305c, an elastic layer 305b on the outer periphery of the core 305c, and a separable layer 305a on the outer periphery of the elastic layer. The metal core 305c is made of stainless steel and has a diameter of, for example, 72 mm. The elastic layer 305b is made of conductive silicone rubber and has a thickness of, for example, 8 mm. The separable layer 305a is made of PFA (polyvinyl fluoride tetrafluoride / perfluoroalkoxyethylene copolymer resin), which is a fluoropolymer, and has a thickness of, for example, 100 μm. The pressure roller 305 is rotatably supported by the frame (not shown) of the fixing device 8, and a gear is fixed at one end and connected to a drive source (e.g., a drive motor, not shown) via the gear to drive rotation.

[0047] The fixing device 8 holds and supplies the recording material P carrying the toner image in the fixing clamping portion N formed between the belt 301 and the pressure roller 305 while heating the toner image. Therefore, the fixing device 8 fixes the toner image onto the recording material P while holding and supplying it. Thus, it requires both the ability to apply heat and pressure, as well as the ability to supply the recording material P. The pressure roller 305 is pressed against the sliding member 304 via the belt 301 by a drive roller (not shown). In this embodiment, the pressure (NF) applied in the clamping portion N during imaging (i.e., the load value applied to the pad 303 and the pressure roller 305) is 1600 N. The width of the clamping portion N in the X direction (the supply direction of the recording material) is set to 24.5 mm, and the width in the Y direction (the width direction of the recording material) is set to 326 mm.

[0048] The length (clamping width) of the clamping portion N along the supply direction (X direction) is formed by the sliding member 304 (which presses against the pressure roller 305 via the belt 301). When the pressure (NF) applied at the clamping portion N is less than 900N, a non-contact area begins to appear between the sliding member 304 and the belt 301, and the required clamping width cannot be maintained. Therefore, in this embodiment, the pressure (NF) applied at the clamping portion N (that is, the load value applied to the pad 303 and the pressure roller 305) is set to 900N or higher.

[0049] [Sliding component]

[0050] exist Figure 3 The detailed construction of the sliding member 304 is shown in parts (a) and (b). Figure 3 Part (a) is a cross-sectional view of the sliding member 304 when cut along the supply direction, and part (b) is a plan view of the sliding member 304 viewed from the side of the contact surface between the belt 301 and the sliding member 304. The sliding member 304 is fixed to the support 302 via the pad 303 using screws or the like. The sliding member 304 may be an integral part of the pad 303. It is also acceptable for the sliding member 304 to be partially fixed to the support 302 or the pad 303. For example, both ends of the sliding member 304 along the Y direction (width direction) may be fixed to the pad 303 using screws or the like.

[0051] The sliding member 304 is composed of a base material layer 304a and a sliding layer 304c. A plurality of protrusions (undulating portions) 304b are formed on the side of the base material layer 304a that slides against the belt 301, protruding toward the inner peripheral surface of the belt 301. The sliding layer 304c is provided to cover the surface of the base material layer 304a on the side that slides against the belt 301 (which includes the plurality of protrusions 304b).

[0052] The base material layer 304a should have sufficient heat resistance and strength. Materials include stainless steel, copper, aluminum, and engineering plastics (PI (polyimide), PEEK (polyether ether ketone), LCP (liquid crystal polymer), etc.). In this embodiment, metallic materials, such as stainless steel, copper, and aluminum, are preferred. In this embodiment, a 300 μm thick PI layer is used as the base material layer 304a.

[0053] Multiple protrusions 304b are integrally formed of the same material as the base layer 304a and are positioned in the clamping portion N along the material supply direction (X direction) and width direction (Y direction), the width direction intersecting the supply direction. Multiple protrusions 304b are provided such that the total area of ​​the front ends of all the protrusions 304b is 90% or greater of the total area of ​​the side surface of the sliding member 304 that slides against the inner surface of the band 301.

[0054] The distance d between the centers of adjacent protrusions 304b relative to the supply direction and the distance d between the centers of adjacent protrusions 304b relative to the width direction are each 1.25 mm or greater, preferably 1.4 mm or greater. In this embodiment, the spacing of the plurality of protrusions 304b is the same along the supply direction and the width direction to ensure uniform sliding characteristics with the belt 301, and the corresponding spacing d is 1.4 mm. However, when the pressure distribution is different between the width direction and the supply direction, the spacing of the protrusions along each direction can be changed according to the pressure distribution.

[0055] By providing a plurality of protrusions 304b on the side surface of the sliding member 304 that slides against the belt 301, the contact area between the sliding member 304 and the belt 301 is reduced, thereby reducing the sliding resistance between the sliding member 304 and the belt 301.

[0056] The sliding layer 304c should be coated with a fluoropolymer (PTFE, PFA, etc.) to achieve low friction. In this embodiment, the sliding member 304 is formed by coating the surface of a base layer 304a, which includes multiple protrusions 304b, with a PTFE layer of 20 μm thickness. In this embodiment, a lubricant is applied to the inner surface of the belt 301. Therefore, the belt 301 is configured to slide smoothly against the sliding member 304. Silicone oil is used as the lubricant.

[0057] In this embodiment, the sliding member 304 is configured to cover the pad 303 both inside and outside the clamping portion N. That is, the sliding member 304 covers the entire surface of the pad 303 facing the belt 301 (except for the surface opposite to the clamping portion N). The sliding member 304 may be arranged only on the surface of the pad 303 on the clamping portion N. Although multiple protrusions 304b are provided over the entire area of ​​the sliding member 304, it is also acceptable for the multiple protrusions 304b to be arranged only in the clamping portion N when the sliding member 304 is larger than the clamping portion N.

[0058] [Factors causing uneven pressure due to deformation of sliding components]

[0059] under, Figure 4 This is used to explain the principle of pressure irregularity caused by the deformation of sliding member 304. Figure 4 It indicates from Figure 2 The clamping portion N, viewed from above, is shown, where, for illustrative purposes, the support column 302 and the pad 303 are not shown. The sliding member 304 is pressurized with pressure W by the pressure roller 305 passing through the belt 301 in the direction of the pad 303 (Z direction). The belt 301 is driven by the heating roller 307 and moves in the belt supply direction (X direction). When the coefficient of friction between the belt 301 and the sliding member 304 is μ, the sliding member 304 experiences a frictional force μW along the direction of movement of the belt 301.

[0060] As the frictional force μW increases, depending on the rigidity of the sliding member 304, the band may bend and deform along the supply direction (X direction), resulting in localized pressure irregularities in the clamping portion. When the recording material passes through the clamping portion under these localized pressure irregularities, it is found that the pressure irregularities cause uneven gloss in the image.

[0061] In conventional fixing devices, the applied pressure is relatively low, approximately 600 N, so even when the sliding member deforms, the deformation is minimal and does not cause uneven gloss. However, in fixing devices with wide clamping sections designed for high-speed fixing, it has been found that this phenomenon becomes more pronounced when high pressure of 900 N or higher is applied due to the increased area to be pressurized. In other words, in wide clamping section structures requiring high pressure of 900 N or higher (such as fixing device 8 in this embodiment), when the rigidity of the sliding member 304 is low, pressure irregularities may occur due to the deformation of the sliding member 304. This pressure irregularity then becomes a cause of uneven gloss.

[0062] [Rigidity of sliding components]

[0063] To prevent the aforementioned gloss irregularities, the rigidity of the sliding member 304 can be increased and the amount of deformation reduced. However, it has been found that when the rigidity of the sliding member 304 is increased too much, the pressure distribution along the width direction (Y direction) becomes unstable, and supply failures may occur, such as wrinkling of the recording material.

[0064] use Figure 5 Part (a) to Figure 7 Part (b) is used to explain this phenomenon. Figure 5 Parts (a) and (b) are cross-sectional views of the clamping portion from the supply direction, wherein the corresponding portions are shown in exaggerated detail. Figure 5 Part (a) shows a schematic diagram of the clamping part N not being pressurized by the pressure roller 305. Figure 5 Part (b) shows the case where the clamping part N is pressurized. For example... Figure 5 As shown in part (a), the pad 303 has a crown-shaped shape that protrudes downwards on the side of the pressure roller 305 in the unpressurized state. When the pressure roller 305 is pressurized, the support 302 deforms due to deflection (because of the high load in the wide clamping section structure), as... Figure 5 As shown in part (b), the crown shape of the pad 303 is optimized so that the desired pressure distribution is achieved in the clamping part N along the width direction (Y direction) when the support 302 deflects.

[0065] use Figure 6 Parts (a) and (b) are used to explain the pressure distribution along the width direction (Y direction) within the clamping part N and the supply force of the recording material P. Figure 6 Part (a) is a graph of the ideal pressure distribution along the width direction when the crown shape of pad 303 is optimized. Figure 6 Part (b) is a schematic diagram showing the distribution of the supply force of the recording material P at the clamping part N, the force applied to the recording material at the inlet of the clamping part N, and the rotational torque applied to the recording material P. The length of the arrow in the distribution of the supply force of the recording material P at the clamping part N indicates the magnitude of the supply force.

[0066] In the clamping portion N, the pressure at the edge is set higher than the pressure at the center along the width direction, such as... Figure 6 As shown in part (b), the supply force of the recording material P increases as it moves toward its edge in the width direction. This allows wrinkling in the recording material to be suppressed even when a recording material with low rigidity is supplied to the clamping part N by providing a torque at the inlet of the clamping part N to unfold the recording material.

[0067] On the other hand, as a comparative example, Figure 7Parts (a) and (b) show the supply force of the recording material and the pressure distribution along the width direction when the recording material wrinkles, given that the rigidity of the sliding member 304 is high. Figure 7 Part (a) is a graph showing the pressure distribution along the width direction in the comparative example. (Compared to...) Figure 6 The same as part (b), Figure 7 Part (b) is a schematic diagram of the distribution of the supply force of the recording material P at the clamping part N, the force applied to the recording material at the inlet of the clamping part N, and the rotational torque applied to the recording material P in the construction of the comparative example.

[0068] and Figure 6 The pressure distribution along the width direction is different in part (a). Figure 7 In part (a), the pressure distribution along the width direction has a portion with locally higher pressure at α. This leads to... Figure 7 The supply force distribution shown in part (b) causes the recording material P to wrinkle at β by applying inward forces to each other at the inlet of the clamping part N.

[0069] The following explanation is in Figure 7 The reason for the local pressure increase at α in part (a). We consider the situation when the pressure roller 305 is pressed against the support column 302. Figure 5 The situation in part (b) is as follows. When the rigidity of the sliding member 304 is low, the sliding member 304 itself has little effect on the pressure distribution along the width direction because the sliding member 304 deforms according to the crown shape optimized by the pad 303.

[0070] However, when the rigidity of the sliding member 304 is high, the sliding member 304 itself may affect the pressure distribution along the width direction, resulting in localized high pressure, because the sliding member 304 does not deform according to the crown shape optimized by the pad 303. Even if the sliding member 304 has high rigidity, this phenomenon has little effect if the sliding member 304 does not "warp" and has low flatness. However, due to variations in mass production and processing, a small amount of "warping" may occur, resulting in high flatness. This causes the sliding member 304 to locally deviate from the shape of the pad 303, thus leading to localized high pressure, such as... Figure 7 As shown in part (a), this causes the recording material to wrinkle.

[0071] Methods for measuring various parameters

[0072] The method for measuring the Young's modulus E and thickness t of the sliding member is described below. These parameters are crucial in this embodiment. First, the method for measuring the Young's modulus E of the sliding member 304 is explained. The Young's modulus is measured using a Shimadzu AG-X tensile tester. The AG-X tensile tester is equipped with a 500N load cell and a 500N mechanical parallel tensioning clamp. During the tensile test, the temperature of the thermostat is set to 180°C, the pulling speed is set to 5 mm / min, and the thickness measurement results are pre-entered.

[0073] The thickness measurement value used above is input as the thickness value of the base material layer 304a, which has the highest strength among all layers of the sliding member 304. The elastic modulus is calculated within the range of 10N to 15N test force of the load element. This measurement begins after confirming that the temperature setting of the isothermal bath for the tensile test has reached 180°C. The dumbbell shape used during the tensile test is the dumbbell shape shown in JIS K7139-A24. After 10 measurements are taken each along the longitudinal and width (short side) directions of the sliding member 304, the average value of each measurement is taken to obtain the elastic modulus along the longitudinal and width directions. In this measurement, the average value along the longitudinal and width directions is used for the Young's modulus E (MPa) of the sliding member 304. If the sliding member 304 has multiple types and multiple sliding layers, they are all treated as one layer when performing the above process.

[0074] The method for measuring the thickness t of the sliding member 304 is described below. When measuring thickness t, a sample is prepared by cutting the sliding member 304 into four equal parts along the Y direction (width direction). The thickness t of the sliding member 304 is measured using a CT6001 digital length measuring instrument manufactured by HEIDENHAIN. The temperature and humidity conditions during measurement are 23°C and 30% respectively. For the sample divided into four equal parts, the thickness of the sample is measured at four points along the X direction (supply direction), and the average value of these four equal parts is used as the thickness t (mm) of the sliding member 304. In this measurement, if there is a sliding layer 304c (as in the case of the sliding member 304), the thickness of the base material layer 304a, excluding the sliding layer 304c, is measured.

[0075] The method for measuring the friction coefficient μ of sliding component 304 is described below. When measuring the friction coefficient μ, a 5mm square sample of the sliding portion of sliding component 304 is cut out to generate the sample. The friction coefficient is measured using an FRP2100 friction and wear tester manufactured by Reska. The temperature of the measuring stage is adjusted to 180°C to match the actual operating environment. Belt 301 is cut into a Φ50mm circular shape and attached to the sample, so that the inner surface of belt 301 slides against the sample. A kinematic viscosity of 1000 mMn is used. 2 Silicone oil was applied at a constant speed of 250 mm / s to the sliding surface of the 301 as a lubricant, and the coefficient of friction was measured under a constant speed of 250 mm / s and a load of 10 N.

[0076] [Image Verification Method]

[0077] The following explanation is used to determine in Figure 1 The evaluation method for whether any abnormal images exist in the imaging device 1 shown. During the evaluation process, a fixing device 8 with the required parameters (E, t, and W) is installed. W is the load applied to the clamping portion N. The method of changing the parameters is explained in the explanatory text of the evaluation of the embodiment described below.

[0078] The circumferential speed of the pressure roller 305 on the fixing unit 8 is set to 250 mm / sec, and the control unit 30 is controlled so that the detection temperature of the contact thermistor (not shown) of the contact heating roller 307 is 195°C. At the same time, the surface of the belt 301 is monitored using a HORIBAIT-340 infrared radiation thermometer to confirm that the surface temperature of the belt 301 is 180°C.

[0079] Then, a black toner image is formed on the recording material, and the toner image is fixed onto the recording material in the fixing device 8. An examination is then conducted to visually inspect for image defects present in the output black sample image.

[0080] The recording material used is Kokuyo's OHP film VF-1420N (A4 size) to make image defects easier to see. To further facilitate the observation of image defects caused by pressure irregularities, a dark, solid black toner image is formed on the recording material as a sample image. After using the fixing device 8, if uneven gloss or uneven density is observed in the center of the sample image, it is determined that the image has defects due to pressure irregularities caused by the deformation of the sliding member 304.

[0081] Grade 5 is defined as having no gloss irregularity at all, Grade 4 is defined as having only slight irregularity, Grade 3 is defined as having gloss irregularity that is more visible than Grade 4 but not visible from the back of the OHP film, Grade 1 is defined as having gloss irregularity that is clearly visible from the back of the OHP film, and Grade 2 is defined as having gloss irregularity between Grade 3 and Grade 1.

[0082] To examine wrinkling occurring in the recording material, a black halftone image was simultaneously output to a relatively low-stiffness recording material, CS-520 A3T (basis weight 52 g / m³), manufactured by Canon Corporation. 2 Ten consecutive sheets are fed through the fixing device 8 to check the wrinkling rate.

[0083] [Evaluation Procedures and Results]

[0084] The evaluation procedure constructed using this embodiment and the evaluation results obtained by changing the thickness and Young's modulus E of the sliding member 304 are described below. The evaluation process in evaluations 1 to 4 will be explained according to the procedure. First, various parameters of the fixing device 8 are determined, and the load value W applied to the clamping part N is set accordingly. For the sliding member 304, the Young's modulus E, thickness t, and coefficient of friction μ are measured and prepared. Then, the sliding member 304 is attached to the fixing device 8, and image verification is performed and judged respectively.

[0085] Figure 8 This illustrates the various sliding components used in the evaluation. Figures 9 to 12 The graphs represent the results of evaluations 1 through 4. An "O" in the graph indicates that no uneven gloss or wrinkles were observed in the image evaluation results, while an "×" indicates that uneven gloss or wrinkles were observed in the image evaluation results.

[0086] [Assessment 1]

[0087] In assessment 1, such as Figure 8 As shown, the material and thickness of the base material layer 304a of the sliding member 304 were changed, and the gloss irregularity level in the pressure irregularity factor was examined by changing the stiffness. The sliding member 304 used was entirely coated with PTFE as the sliding layer 304c. Due to the PTFE coating, the coefficient of friction μ was 0.03. The load value W was set to 1600 N, therefore the frictional force applied to the sliding portion between the sliding member 304 and the belt 301 was μW = 48 N. The level of gloss irregularity was evaluated according to the criteria described in the image verification evaluation method.

[0088] Pressure irregularity is caused by the deformation of the sliding member 304, which is the cause of gloss irregularity. If the rigidity of the sliding member 304 can be guaranteed to resist the frictional force applied to it, the sliding member 304 will not deform, and therefore pressure irregularity and gloss irregularity will not occur. To investigate the relationship between frictional force and the rigidity of the sliding member 304, in Figure 8 The table defines and describes a parameter called the permissible friction ratio. The permissible friction ratio is defined by the following formula (1).

[0089] Formula (1)

[0090] The numerator in formula (1) is based on the friction of the sliding member 304, and the denominator is an exponent considering the deflection stiffness of the sliding member 304, which consists of Young's modulus E (MPa), thickness t (mm) and length L (mm) along the width direction orthogonal to the supply direction of the recording material.

[0091] Figure 9 Based on Figure 8 The results are shown in a graph relating the permissible friction ratio and the gloss irregularity level. The results indicate that as the permissible friction ratio increases, the gloss irregularity level decreases, and the permissible friction ratio must be 1200 or less to satisfy gloss irregularity level 5, in which no gloss irregularity occurs.

[0092] [Evaluation 2]

[0093] In Evaluation 2, to examine the relationship between the allowable friction ratios in more detail, the material of the base layer 304a of the sliding member 304 was fixed as stainless steel, and the thickness was varied. The gloss irregularity level under pressure irregularity was also examined by changing the stiffness. As in Evaluation 1, the sliding member 304 used was entirely coated with PTFE as the sliding layer 304c. Due to the PTFE coating, the coefficient of friction μ was 0.03. The load value W was set to 1600 N, therefore the friction force on the sliding part was μW = 48 N.

[0094] Figure 10 This is a graph showing the relationship between the thickness t of the base material layer 304a of the sliding member 304 and the allowable friction ratio. The results indicate that as the thickness t increases, the allowable friction ratio decreases, and no gloss irregularities occur at allowable friction ratios of 1200 or less. These results demonstrate that by changing the thickness and Young's modulus of the sliding member 304 and setting the allowable friction ratio to 1200 or less, gloss irregularities due to pressure irregularities can be avoided.

[0095] [Evaluation 3]

[0096] In Evaluation 3, to examine the relationship between the allowable friction ratio and the load, the base layer 304a of the sliding member 304 was made of stainless steel with a fixed thickness of 0.04 mm, and the gloss irregularity level in the pressure irregularity factor was examined by varying the rigidity. As in Evaluation 1, the sliding member 304 used was entirely coated with PTFE as the sliding layer 304c. Due to the PTFE coating, the coefficient of friction μ was 0.03. The load value W applied to the clamping portion N varied from 200 to 2000 N. While varying the frictional force μW applied to the sliding portion between the sliding member 304 and the belt 301, the relationship between the allowable friction ratio and the image level was investigated.

[0097] Figure 11 This is a graph showing the relationship between the permissible friction ratio and the image quality. The results indicate that as the load value W applied to the clamping portion N increases, the friction of the sliding portion increases, leading to uneven gloss. The results also show that by varying the thickness t and Young's modulus E of the sliding member 304 according to the load value W applied to the clamping portion N, and setting the permissible friction ratio to 1200 or less, gloss irregularities due to pressure irregularities can be avoided.

[0098] The results of evaluations 1 to 3 show that the following formula (2) regarding the permissible friction ratio can be satisfied in order to prevent gloss irregularities.

[0099] Formula (2)

[0100] [Evaluation 4]

[0101] In Evaluation 4, the same evaluation as in Evaluation 2 was performed by fixing the material of the base material layer 304a of the sliding member 304 to stainless steel in order to study the effect on wrinkling of the recording material when the rigidity of the sliding member 304 becomes too high. The thickness t of the sliding member 304 was varied from 0.5 to 3.5 mm to examine the degree of wrinkling of the recording material. Taking into account the local deformation along the width direction (Y direction) and the second moment of the cross section, the following formula (3) was used as an index of the rigidity of the base material layer 304a.

[0102] Formula (3)

[0103] The stiffness of the base material layer 304a shown in formula (3) is composed of the Young's modulus E (MPa) and the thickness t (mm) of the sliding member 304. Figure 12This is a graph showing the relationship between the thickness t of the base material layer 304a of the sliding member 304 and the hardness of the base material layer 304a. In the graph, O indicates that no wrinkling occurs, and × indicates that wrinkling occurs. The results show that when the thickness t of the base material layer 304a of the sliding member 304 is thinner than 2.5 mm, wrinkling of the recording material does not occur; however, when the thickness t is thicker than 3.0 mm, wrinkling of the recording material does occur. Figure 12 The curves show that the hardness requirement for the 304a base material layer, which prevents wrinkles in the recording material, is less than 2.6 × 10⁻⁶. 5 (N·mm). The results of evaluation 4 show that satisfying the following formula (4) can prevent wrinkles from appearing in the recording material.

[0104] Formula (4)

[0105] [Other embodiments]

[0106] In the above embodiments, the sliding member 304 is described as a construction example with a protrusion 304b in order to reduce the sliding resistance with the band 301. However, the present invention can also be applied to a construction in which the sliding member does not have a protrusion 304b.

[0107] Although the invention has been described with reference to exemplary embodiments, it should be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims should be interpreted in the broadest sense to cover all such variations and equivalent structures and functions.

Claims

1. A fixing device, comprising: An annular belt configured to apply heat to the recording material; A rotatable pressing member that contacts the outer peripheral surface of the annular belt; as well as A sliding member on the inner side of the annular belt, configured to form a clamping portion by clamping and supplying the annular belt between itself and the rotatable pressing member, and sliding on the inner circumferential surface of the annular belt. The rotatable pressing member cooperates with the annular belt to clamp and supply recording material in the clamping portion, and fixes the toner image onto the recording material by applying heat and pressure. The sliding member includes a base extending along the width direction of the annular band. The base is made of metal and includes multiple protrusions projecting toward the rotatable pressing member; wherein the pressing force applied to the clamping portion is less than 900 N, and... Wherein, when the load applied to the clamping part is defined as W[N], the Young's modulus of the sliding member is defined as E[MPa], the thickness of the sliding member is defined as t[mm], the coefficient of friction between the sliding member and the annular belt is defined as μ, and the length of the sliding member relative to the width direction is defined as L[mm], the sliding member satisfies the following formula: 。 2. The fixing device according to claim 1, wherein: The sliding member includes a sliding layer on the surface of its base, the sliding layer being configured to slide on the inner circumferential surface of the annular belt.

3. The fixing device according to claim 2, further comprising: A retaining member configured to retain the sliding member, wherein the retaining member is made of resin.

4. The fixing device according to claim 3, wherein: The sliding layer is made of fluoropolymer resin.

5. The fixing device according to claim 4, wherein: The retaining component is made of a different resin than the sliding layer.

6. The fixing device according to claim 1, wherein: The front end of the substrate on one side of the rotatable pressing member is flat.

7. The fixing device according to claim 3, wherein: In a cross-section perpendicular to the direction of material supply, the retaining member has a crown shape that protrudes toward the rotatable pressing member.

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