Fixing device

Abstract

According to the present invention, there is provided a fixing device for fixing a toner image formed on a recording medium to the recording medium, the fixing device comprising: a cylindrical film including a base layer and a conductive layer having a lower electrical resistance than the base layer; a slip member; a pressing member; and a restricting member having a restricting surface configured to restrict movement of the film in a longitudinal direction of the film when the film moves in the longitudinal direction of the film. In the fixing device, a relationship Dgt is satisfied with respect to the longitudinal direction; f is the width of the film, C is the width of the conductive layer, R is the distance between the two limiting surfaces, and D is the width of the pressing member.

Description

Technical Field

[0001] The present invention relates to a fixing device included in an image forming apparatus such as an electrophotographic copying machine or an electrophotographic printer. Background Art

[0002] As one mode of a fixing device installed in an electrophotographic printer or the like, Japanese Patent Application Laid-Open No. 2014-26267 discusses a fixing device in which a cylindrical film (also referred to as a belt) having a conductive layer is used and current flows to the conductive layer to cause the film to generate Joule heat.

[0003] The fixing device using a film includes a restriction member that restricts movement (deviation motion) of the film in the longitudinal direction of the film.

[0004] In the case of a structure in which the displacement movement is restricted by the restriction member, if the displacement force of the film becomes strong in a state in which the restriction member bears the end surface of the film, the film may be damaged. In a fixing device in which current flows into the film and the film generates heat, if the film is damaged at the position where the current flows, the resistance may increase, resulting in heat generation failure or abnormal heat generation. Summary of the invention

[0005] An object of the present invention is to provide a fixing device capable of suppressing an increase in the resistance of a conductive layer therein.

[0006] According to the present invention, there is provided a fixing device for fixing a colorant image formed on a recording medium to the recording medium, the fixing device comprising: a cylindrical film comprising a base layer and a conductive layer having a lower resistance than the base layer; a sliding member, the sliding member being arranged in an inner space of the film and the rotating film being in sliding contact with the sliding member; a pressing member contacting an outer peripheral surface of the film, the pressing member clamping the film together with the sliding member to form a fixing clamping portion between the film and the pressing member; and a limiting member, the limiting member having a limiting surface, the limiting surface being configured to limit the movement of the film in the longitudinal direction of the film when the film moves along the longitudinal direction of the film, wherein in the fixing device, an electric current is passed along the surrounding direction to the conductive layer so that the conductive layer generates Joule heat, and utilizes the Joule heat to heat the recording medium clamped and conveyed by the fixing clamp, thereby fixing the colorant image formed on the recording medium to the recording medium, wherein the limiting member is arranged at a position facing the end surface of the film along the longitudinal direction, wherein, relative to the longitudinal direction, the conductive layer into which the current flows along the circumferential direction is not arranged in the area of ​​the end of the film, but is arranged in the area between the areas of the end, and wherein, relative to the longitudinal direction, the relationship D>R+C–F is satisfied, wherein F is the width of the film, C is the width of the conductive layer, R is the distance between the two limiting surfaces, and D is the width of the pressing member.

[0007] 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

[0008] Figure 1 is a cross-sectional view of a schematic configuration of an image forming apparatus.

[0009] Figure 2 is a cross-sectional view of the fixing device.

[0010] Figure 3 It is a front view of the fixing unit.

[0011] Figure 4 It is an exploded perspective view of the membrane unit.

[0012] Figure 5 It is a cross-sectional structure diagram of the membrane.

[0013] Figure 6 It is a perspective view of the magnetic core and the excitation coil.

[0014] Figure 7 is a diagram showing a portion of an alternating magnetic field and an induced current.

[0015] FIG. 8A to FIG. 8D is a diagram describing the flange structure.

[0016] Fig. 9 It is a schematic diagram showing a state where film displacement has occurred.

[0017] Fig. 10A and Fig. 10B is a schematic diagram of an induced current when the resistance of a portion of a conductive layer increases.

[0018] Fig.11A and Fig. 11B is a schematic diagram for describing a film shift state in the first exemplary embodiment.

[0019] Fig. 12A and Fig. 12B is a schematic diagram describing the film shift state in Comparative Example 1.

[0020] Fig.13A and Fig. 13B is a schematic diagram describing the film shift state in Comparative Example 2.

[0021] Fig.14A and Fig. 14B is a schematic diagram describing the film shift state in Comparative Example 3.

[0022] Fig.15A and Fig. 15B is a schematic diagram describing the film shift state in Comparative Example 4. DETAILED DESCRIPTION

[0023] A first exemplary embodiment will be described. Figure 1 is a cross-sectional view of a schematic configuration of a laser beam printer 1 (hereinafter referred to as printer 1) as an image forming apparatus that forms a toner image on a recording medium P using electrophotography. The printer 1 is an A4 printer that supports a recording medium P of letter size (215.9 mm width).

[0024] The printer 1 includes a photosensitive drum 2 as an image bearing member, a charging unit 3 that charges the surface of the photosensitive drum 2 in a substantially uniform manner, and a scanner unit 4 that scans the photosensitive drum 2 with a laser beam according to image information to form an electrostatic latent image on the photosensitive drum 2. The printer 1 also includes a developing unit 5 that develops the electrostatic latent image with a toner, a transfer member 6 that transfers the toner image on the photosensitive drum 2 to a recording medium P, and a cleaning unit 7 that removes the toner that has not been transferred to the recording medium P and remains on the photosensitive drum 2. The printer 1 also includes a fixing device A that fixes the toner image that has been transferred to the recording medium P to the recording medium P. The fixing device A will be described in detail below.

[0025] A cassette 8 storing recording media P (e.g., paper) is attached to the lower portion of the printer 1. The recording media P stored in the cassette 8 are fed one by one by a roller 9. The recording media P that have been fed are conveyed by conveying rollers 10, 11, and 30, a transfer member 6, a fixing device A, etc., and finally pass through the printer 1. Figure 1 The dotted line path shown is discharged to the discharge tray 31 .

[0026] The fixing device A (fixing unit) will be described in detail. Figure 2 is a cross-sectional view of the fixing device A, Figure 3 is a front view of the fixing device A, Figure 4 is an exploded perspective view of the film unit 50. The front side of the fixing device A is an inlet side where the recording medium P enters the fixing device A, and the rear side of the fixing device A is an outlet side where the recording medium P exits the fixing device A. The left side is defined as the side when viewed from the front side of the fixing device A (i.e., Figure 3 The left side of the fixing device A is defined as the right side when viewed from the front side of the fixing device A. The fixing device A is an electromagnetic induction heating fixing device. The fixing device A is roughly divided into a film unit 50, a pressure roller 15 as a pressure member, and an equipment frame 60 including these units and rollers.

[0027] The membrane unit 50 includes a cylindrical membrane 13, a sliding member 14 with which the rotating membrane 13 is in sliding contact, a guide member 17 that holds the sliding member 14, and a metal bracket 16 that ensures the rigidity of the fixing device A. The membrane unit 50 also includes: an excitation coil 19 that is arranged in the internal space of the membrane 13 and has a spiral portion whose spiral axis is approximately parallel to the longitudinal direction of the membrane 13; and a magnetic core 18 that has an end surface and is arranged in the spiral portion. The membrane unit 50 also has a temperature sensor 20 that contacts the inner surface of the membrane 13 and detects the temperature of the membrane 13, and a flange 40 (restriction member) that is arranged at either end of the bracket 16 along the longitudinal direction of the membrane 13. The flange 40 has a restriction surface that restricts the movement of the membrane 13 in the longitudinal direction of the membrane 13 when the membrane 13 moves in the longitudinal direction of the membrane 13.

[0028] The sliding member 14, the bracket 16, and the guide member 17 are all members longer than the width (lateral length) of the film 13, and their left and right sides extend from both ends of the film 13 to the outside of the film 13. The flange 40L is fitted to the left protruding portion 16aL of the bracket 16, and the flange 40R is fitted to the right protruding portion 16aR of the bracket 16. That is, the flanges 40L and 40R are arranged at positions facing the end surface of the film 13 in the longitudinal direction of the film 13.

[0029] The film 13 will be described. Figure 5It is a cross-sectional structural diagram of the central part of the film 13 in the longitudinal direction of the film 13. The film 13 has a base layer 13a, a conductive layer 13b, a protective layer 13c, and a demolding layer 13d. In the film 13, due to the induced electromotive force, the induced current flows into the conductive layer 13b with low resistance, and the conductive layer 13b generates Joule heat. The base layer 13a is ideally made of a material having a higher resistance value than the conductive layer 13b, so as to ensure the insulation between the conductive layer 13b through which the induced current flows and the components arranged in the internal space of the film 13. The base layer 13a also needs to have heat resistance. Therefore, the material of the base layer 13a is preferably an insulating heat-resistant resin, such as polyimide, polyamide-imide, polyetheretherketone (PEEK) or polyethersulfone (PES). The base layer 13a in this exemplary embodiment has an inner diameter of 30mm, a width F of 240mm, and a thickness of about 40μm, and its material is polyimide.

[0030] The conductive layer 13b is a resistance heat generating member having a lower resistance than the base layer 13a and the protective layer 13c.

[0031] The material of the conductive layer 13b is preferably a metal with a low volume resistivity, such as iron, copper, silver, aluminum, nickel, chromium, tungsten, SUS304 (stainless steel) containing these metals, or a nickel-chromium alloy. Conductors such as carbon fiber reinforced plastics (CFRP) or carbon nanotubes can be used as long as their volume resistivity is low. The method for forming the conductive layer 13b is coating, electroplating, sputtering, evaporation, etc. The conductive layer 13b in this exemplary embodiment is formed of copper with a thickness of about 2μm by electroplating. The width (lateral length) of the conductive layer 13b is greater than the width of the maximum size of the recording medium P available in the printer 1, and is smaller than the width of the base layer 13a. In the present exemplary embodiment, the conductive layer 13b is formed on the base layer 13a by electroplating, wherein both ends of the base layer 13a are shielded by 8mm so that the conductive layer 13b has a width C of 224mm. Because the conductive layer 13b does not exist in the areas of the two ends of the film 13, the film 13 in the areas of the two ends has Figure 5 The cross section shown is with the conductive layer 13b removed.

[0032] The protective layer 13c is provided to prevent the conductive layer 13b made of copper from being degraded by oxidation. For the same reason as the base layer 13a, the resistance of the protective layer 13c is ideally higher than that of the conductive layer 13b, and is preferably made of an insulating heat-resistant resin. The protective layer 13c in this exemplary embodiment is made of polyimide with a thickness of about 20 μm.

[0033] The material of the release layer 13d is preferably a material with excellent release properties and heat resistance, such as perfluoroalkoxyalkane (PFA), polytetrafluoroethylene (PTFE) or fluorinated ethylene propylene (FEP). The release layer 13d in this exemplary embodiment is a PFA tube with a thickness of about 15 μm. An elastic layer composed of sponge or rubber can be provided between the release layer 13d and the protective layer 13c. The provision of the elastic layer allows the surface of the film 13 to easily follow the concave and convex on the surface of the recording medium P, thereby improving the adhesion to the colorant image. This makes it possible to reduce uneven heating of the colorant image and obtain a good image with less uneven gloss. In order to enhance the adhesion between the layers, a primer layer can be provided between the layers.

[0034] The sliding member 14 will be described. The sliding member 14 is required to have excellent sliding properties and heat resistance on the inner surface of the film 13. The sliding member 14 in this exemplary embodiment is formed by a substrate having a surface layer on the surface, and the film 13 is in sliding contact with the surface layer. The substrate is preferably a heat-resistant resin (such as polyimide, polyamide-imide, PEEK or PES) or a metal (such as aluminum or iron). In this exemplary embodiment, pure aluminum with a thickness of 0.8mm is used as the substrate. The surface layer is a PTFE coating with a thickness of about 30μm, which has low sliding resistance on the inner surface of the film 13 and excellent heat resistance and wear resistance. A heat-resistant lubricant is between the sliding member 14 and the film 13 to further reduce the sliding resistance between the sliding member 14 and the film 13. As a lubricant, a fluorine-based or silicon-based grease or lubricating oil is preferred. The lubricant in this exemplary embodiment is a fluorine grease mixed with PTFE as a thickener.

[0035] The guide member 17 will be described. The guide member 17 is a member made of a heat-resistant resin, and supports the sliding member 14, and has a function of guiding the rotation of the film 13. The guide member 17 has a groove portion on the lower surface along the longitudinal direction of the film 13, and the sliding member 14 is fitted into the groove portion and supported by the groove portion so that the surface of the film 13 that is in sliding contact with it faces the outside. As a material for the guide member 17, a heat-resistant resin such as a liquid crystal polymer, a phenolic resin, polyphenylene sulfide (PPS) or PEEK is preferred. In the present exemplary embodiment, the guide member 17 is made of a liquid crystal polymer.

[0036] The magnetic flux generating device will be described. A magnetic core 18 and an exciting coil 19 as a magnetic flux generating unit are provided in the inner space of a bracket 16 having an angled C-shaped cross section. Figure 61 is a perspective view of a magnetic core 18 and an excitation coil 19, wherein the excitation coil 19 is wound around the outer circumference of the magnetic core 18 in a spiral form. The magnetic core 18 has a cylindrical shape with an end face and is arranged at the approximate center of the film 13 in the radial direction of the film 13. The magnetic core 18 plays a role in inducing the magnetic lines of force (magnetic flux) of the alternating magnetic field generated by the excitation coil 19 and forming a path (magnetic circuit) of the magnetic lines of force. The material of the magnetic core 18 is preferably a material that causes a small iron loss (hysteresis loss and eddy current loss) and has a relatively high magnetic permeability, for example, a ferromagnetic body with high magnetic permeability (such as sintered ferrite or ferrite resin) is preferred. The cross-sectional shape of the magnetic core 18 is preferably a shape that can be stored in the internal space of the film 13 and has a cross-sectional area as large as possible. Although the cross section does not have to be circular, the cross-sectional shape is preferably close to a circle because when the excitation coil 19 is wound around the magnetic core 18, the shorter length of the wire leads to a smaller copper loss (coil current Joule loss). The magnetic core 18 in this exemplary embodiment is made of ferrite with a diameter of 10 mm and a length of 245 mm. The excitation coil 19 is formed by winding a copper wire (single conductor) coated with heat-resistant polyamide-imide with a diameter of 1 to 2 mm around the magnetic core 18 in a spiral form. The number of turns is 18. The excitation coil 19 has a spiral axis parallel to the axial direction of the magnetic core 18. When a high-frequency current flows into the excitation coil 19, an induced current flows into the conductive layer 13b, and the conductive layer 13b generates heat according to the following principle. In this way, the fixing device A includes an excitation coil 19 and a magnetic core 18, the excitation coil 19 is arranged in the internal space of the film 13 and has a spiral portion with a spiral axis approximately parallel to the longitudinal direction, and the magnetic core 18 has an end face and is arranged inside the spiral portion. An alternating current (AC) voltage is applied to the excitation coil 19 to generate an induced current in the conductive layer 13b.

[0037] The principle of induction heating in the fixing device A according to the present exemplary embodiment will be described. Figure 7 1 is a conceptual diagram showing the moment when the current flowing into the exciting coil 19 in the direction of arrow I1 increases. When the high-frequency current flows into the exciting coil 19, the fixing device A forms a magnetic field in which most (more than 90%) of the magnetic flux extending from one end of the magnetic core 18 passes through the outside of the film 13 and returns to the other end of the magnetic core 18. Figure 7 In FIG. 1 , S represents a portion of the induced current (circulating current) flowing in the conductive layer 13b. When such a magnetic field is formed, the induced current flows in the direction of the arrow I2.

[0038] The temperature detection unit will be described. Since the conductive layer 13b of the film 13 generates heat based on the above principle, the temperature detection unit is ideally configured to directly detect the temperature of the film 13 itself. Figure 2As shown, the temperature sensor 20 as a temperature detection unit is in contact with the inner surface of the film 13. The temperature sensor 20 includes a leaf spring 20a fixed to the bracket 16 at one end, a thermistor (temperature detection element) 20b arranged at the other end of the leaf spring 20a, and a sponge 20c between the leaf spring 20a and the thermistor 20b. The surface of the thermistor 20b is covered with a polyimide tape (not shown) with a thickness of 50μm to ensure sliding and electrical insulation relative to the inner surface of the film 13. The sponge 20c is used as a heat insulating material for the thermistor 20b, and also has a function of flexibly fitting the thermistor 20b to the film 13 as a measurement object.

[0039] The flange 40 will be described. The flanges 40L and 40R are arranged at positions facing the end surfaces of the film 13 in the longitudinal direction of the film 13. The flange 40L and the flange 40R have symmetrical shapes and are molded products of a heat-resistant resin.

[0040] Fig. 8A , Figure 8B and Figure 8C are diagrams showing the flange 40 when viewed from the inner side, the side surface, and the top surface, respectively, and Fig.8D It is a vertical cross-sectional view of flange 40. As shown in these figures, flanges 40L and 40R each have a limiting surface 40a, a guiding surface 40b, a force receiving portion 40c, an assembly portion 40d and a vertical groove portion 40e. The limiting surface 40a faces the end face of the film 13, and is the surface with which the end face of the film 13 contacts when the film 13 moves in the longitudinal direction. Therefore, the limiting surface 40a plays a role in limiting the movement (lateral offset) of the film 13, and keeps the film 13 at a predetermined position in the longitudinal direction. The guiding surface 40b guides the inner surface of the rotating film 13 in the end region of the longitudinal direction of the film 13. In other words, the guiding surface 40b supports the inner peripheral surface of the longitudinal end of the film 13 from the inside, thereby playing a role in making the film 13 follow the desired rotation trajectory. The assembly portion 40d is a portion assembled to the protruding portion 16a of the bracket 16. The assembly portion 40d has a hole for connecting the excitation coil 19 and the power supply circuit (not shown). The force receiving portion 40c is a surface that receives the biasing force of the pressurizing spring 48L or 48R for forming the fixing nip N, and the rear surface of the force receiving portion 40c is in direct contact with the protruding portion 16a of the bracket 16. The force receiving portion 40c plays a role in receiving the biasing force of the pressurizing spring 48L or 48R to press the bracket 16 downward. The flange 40 is made of a glass fiber-containing resin such as PPS, liquid crystal polymer, polyethylene terephthalate (PET), or polyamide (PA) as a material having excellent heat resistance, relatively low thermal conductivity, and excellent sliding properties. In the present exemplary embodiment, the flange 40 is made of PPS.

[0041] The pressure roller 15 contacts the outer peripheral surface of the film 13, and forms a fixing nip N with the sliding member 14 across the film 13 therebetween. The pressure roller 15 also has the function of a driving roller that rotates the film 13. The pressure roller 15 has a metal core 15a and an elastic layer 15b, which is molded concentrically around the metal core 15a in the form of a roller to cover the metal core 15a. The pressure roller 15 is a roller with an outer diameter of 30mm and a width D (length of the elastic layer 15b) of 232mm, and has a release layer 15c as a surface layer. The elastic layer 15b is ideally made of a material with excellent heat resistance, and silicone rubber, fluororubber, fluorosilicone rubber, etc. are preferred. The elastic layer 15b in this exemplary embodiment is made of silicone rubber with a thickness of about 4mm. The release layer 15c is ideally made of a material with excellent demoulding and heat resistance, and a fluorine-based resin such as PFA, PTFE or FEP is preferred. The release layer 15 c in the present exemplary embodiment is made of PFA having a thickness of about 50 μm.

[0042] The pressure roller 15 is rotatably disposed between the left and right sides of the core shaft portion 15d through the bearing member 62 between the left and right plates 61L and 61R of the device frame 60. The driving gear 47 is concentrically disposed on the right side of the core shaft portion 15d. When the driving force of a motor (not shown) controlled by a control unit (not shown) is transmitted to the gear 47, the pressure roller 15 is rotationally driven at a predetermined circumferential speed as a driven rotating body.

[0043] The pressurizing mechanism will be described. Pressurizing springs 48L and 48R are in contact with the force receiving portions 40c of flanges 40L and 40R, respectively. Pressurizing spring 48L is arranged to be compressed between the left spring receiving portion 67L of the top plate 66 of the device frame 60 and the force receiving portion 40c of the flange 40L. Pressurizing spring 48R is arranged to be compressed between the right spring receiving portion 67R of the top plate 66 of the device frame 60 and the force receiving portion 40c of the flange 40R. Due to the reaction force of pressurizing springs 48L and 48R, the biasing force acts on the left protruding portion 16aL and the right protruding portion 16aR of the bracket 16 of the film unit 50 via the flanges 40L and 40R. Therefore, the guide member 17 having the sliding member 14 and the pressurizing roller 15 overcome the elasticity of the elastic layer 15b of the pressurizing roller 15 and clamp the film 13. A fixing clamping portion N is formed between the film 13 and the pressurizing roller 15.

[0044] The pressure roller 15 and the film unit 50 are arranged substantially parallel to each other and are disposed between the side plates 61L and 61R of the device frame 60. The vertical groove portions 40e of the flanges 40L and 40R of the film unit 50 are engaged with guide slits (not shown) provided in the side plates 61L and 61R, respectively. Therefore, the flanges 40L and 40R are held to be able to slide on the side plates 61L and 61R, respectively, and are able to move toward the film 13.

[0045] The distance R between the restriction surfaces 40a of the flanges 40 arranged on the left and right sides is set to be larger than the width of the film 13. In the present exemplary embodiment, the distance R between the restriction surfaces 40a of the flanges 40 is set to 246 mm.

[0046] Fig. 9 4 is a diagram showing a state in which a leftward deflection force is generated on the film 13 and the film 13 is in contact with the left flange 40L. Since the film 13 is restricted by the flange 40L, the film 13 cannot move leftward any further. In this state, if a leftward deflection force continues to be generated, a large deformation stress is applied to a portion of the film 13 corresponding to the end position E (as shown by the dotted arrow in the figure) of the pressure roller 15. As a result, the resistance value of the conductive layer 13b may increase.

[0047] Fig. 10A and 10B 1 is a schematic diagram for describing a change in the flow of the induced current when the resistance of a portion of the conductive layer 13 b is increased. Fig. 10A 1 is a conceptual diagram showing the moment when an induced current flows in the conductive layer 13b by the magnetic flux generated by the exciting coil 19 without an increase in resistance. In this case, a predetermined amount of current flows in the entire conductive layer 13b in a substantially uniform manner, and the conductive layer 13b generates heat uniformly. On the other hand, Fig. 10B The state in which the resistance of the portion indicated by the black dots in the figure is increased is shown. Since the induced current flows in a manner bypassing the black dot portion, the heat generated at the black dot portion is reduced. In addition, on both sides of the black dot portion, the current density becomes high and the heat generated increases. As described above, in a system in which a current flows into the film 13 so that the film 13 generates Joule heat, it is necessary to reduce damage to the portion into which the current flows as much as possible.

[0048] On the other hand, even if the film 13 is laterally offset to generate deformation stress at the end position E of the pressure roller 15, no problem will occur in the area where no current flows. Therefore, utilizing the fact that the width of the conductive layer 13b can be set independently of the width of the film 13, a device configuration that satisfies the following formula 1 is adopted.

[0049] D>R+C–F…(Formula 1)

[0050] Where D is the press roll width, R is the distance between flanges, C is the conductive layer width, and F is the film width.

[0051] The effectiveness of the configuration that satisfies the relationship in Formula 1 to solve the above-mentioned problem is described by comparing with the comparative example. In the comparison, the inter-flange distance R, which is the distance between the flange 40L and the flange 40R, is 246 mm, the width F of the film 13 is 240 mm, which is the same as the comparative example, and the difference between the first exemplary embodiment and the comparative example is the width C of the conductive layer 13b and the width D of the pressure roller 15. Table 1 shows the configurations in the first exemplary embodiment and comparative examples 1 and 2, the values ​​calculated by the inter-flange distance R+the conductive layer width C−the film width F, and the satisfaction / non-satisfaction of Formula 1.

[0052] Table 1

[0053] Conductive layer width C Pressing roller width D Calculation results Formula 1 <![CDATA[ 第一示例性实施例 ]]> 224mm 232mm 230mm satisfy Comparative Example 1 224mm 228mm 230mm Dissatisfied Comparative Example 2 228mm 232mm 234mm Dissatisfied

[0054] Fig.11A and Fig. 11B is a schematic diagram for describing the occurrence of film deviation in the first exemplary embodiment. Fig.11A shows a state where no film shift occurs, Fig. 11B The state in which the film deviation to the left has occurred and the left end of the film 13 is in contact with the left flange 40L is shown. In the first exemplary embodiment, the width C of the conductive layer 13b is 224 mm, the width D of the pressure roller 15 is 232 mm, and the conductive layer 13b does not exist at the end position E of the pressure roller 15 under the deformation stress. That is, the increase in the resistance of the conductive layer 13b due to the deformation stress can be suppressed.

[0055] Fig. 12A and Fig. 12B is a schematic diagram describing the occurrence of film offset in Comparative Example 1, and Fig. 12A and Fig. 12B The difference between the two is the same as in the first exemplary embodiment. In Comparative Example 1, the film 13 is shorter than that in the first exemplary embodiment, and the width of the conductive layer 13b is 224 mm, and the length of the pressure roller 15 is 228 mm. When the film 13 contacts the left flange 40L, the conductive layer 13b exists at the end position E of the pressure roller 15 under deformation stress. As a result, the resistance of the conductive layer 13b increases due to the deformation stress ( Fig. 12B NG1 in.

[0056] Fig.13A and Fig. 13B is a schematic diagram describing the occurrence of film offset in Comparative Example 2, and Fig.13A and Fig. 13BThe difference is the same as that in the first exemplary embodiment. In Comparative Example 2, the conductive layer 13b is wider than the conductive layer in the first exemplary embodiment, and the width of the conductive layer 13b is 228 mm, and the length of the pressure roller 15 is 232 mm. When the film 13 contacts the left flange 40L, the conductive layer 13b is present at the end position E of the pressure roller 15 under the deformation stress. As a result, the resistance of the conductive layer 13b increases due to the deformation stress ( Fig. 13B NG1 in

[0057] Fig.14A and Fig. 14B are schematic views for describing the occurrence of film deviation in Comparative Example 3, and Fig.14A and Fig. 14B The difference is the same as that in the first exemplary embodiment. As shown in Table 2, in Comparative Example 3, the width of the conductive layer is smaller than the width of the conductive layer in the first exemplary embodiment, and the width of the conductive layer 13b is 220 mm, and the width of the pressure roller 15 is 232 mm. Even in a state where the film 13 is in contact with the left flange 40L, the conductive layer 13b is not present at the end position E of the film 13 under the deformation stress. That is, an increase in the resistance of the conductive layer 13b due to the deformation stress can be suppressed.

[0058] Table 2

[0059] Conductive layer width C Pressing roller width D Calculation results Formula 1 <![CDATA[ 第一示例性实施例 ]]> 224mm 232mm 230mm satisfy Comparative Example 3 220mm 232mm 226mm satisfy

[0060] However, in a state where the film 13 is deviated, the conductive layer 13b does not completely cover the width of the maximum-size feedable recording medium for which fixability should be ensured (the maximum width T of the toner image formed on the recording medium) ( Fig. 14B NG2 in

[0061] T < C + F – R… (Formula 2)

[0062] where T is the width for ensuring fixability.

[0063] Table 3

[0064] Conductive layer width C Pressing roller width D Calculation results Formula 2 <![CDATA[ 第一示例性实施例 ]]> 224mm 232mm 218mm satisfy Comparative Example 3 220mm 232mm 214mm Dissatisfied

[0065] In the first exemplary embodiment that satisfies Formula 2, even in a state where the film 13 is deviated, the conductive layer 13b can cover the maximum width T (214.9 mm), so that a predetermined amount of heat can be applied to the recording medium P in a substantially uniform manner.

[0066] Fig.15A and Fig. 15BIt is a schematic diagram depicting the occurrence of film deviation in Comparative Example 4, and Fig.15A and Fig. 15B The difference between them is the same as in the first exemplary embodiment. In Comparative Example 4, the pressure roller 15 is longer than the pressure roller in the first exemplary embodiment, and the width of the conductive layer 13b is 220 mm, while the width of the pressure roller 15 is 236 mm. Even in a state where the film 13 is deviated and in contact with the left flange 40L, there is no conductive layer 13b at the end position E of the film 13 under the deformation stress. That is, an increase in the resistance of the conductive layer 13b due to the deformation stress can be suppressed.

[0067] Table 4

[0068] Conductive layer width C Pressing roller width D Calculation results Formula 1 <![CDATA[ 第一示例性实施例 ]]> 224mm 232mm 230mm satisfy Comparative Example 4 220mm 236mm 230mm satisfy

[0069] However, the surface of the pressure roller 15 is in sliding contact with the sliding member 14 at the right end of the pressure roller 15, and the pressure roller 15 is damaged ( Fig. 15B NG3 in

[0070] Therefore, it is preferable to increase the limiting conditions so as to further satisfy the following Formula 3.

[0071] D < F × 2 – R… (Formula 3)

[0072] Table 5

[0073] Conductive layer width C Pressing roller width D Calculation results Formula 3 <![CDATA[ 第一示例性实施例 ]]> 224mm 232mm 234mm satisfy Comparative Example 3 220mm 236mm 234mm Dissatisfied

[0074] In the first exemplary embodiment that satisfies Formula 3, the right end of the pressure roller 15 presses the sliding member 14 through the film 13 between the right end of the pressure roller 15 and the sliding member 14, and the pressure roller 15 does not directly contact the sliding member 14.

[0075] As described above, the fixing device A is configured to satisfy Formula 1 to suppress an increase in the resistance of the conductive layer 13b. In addition, satisfying Formula 2 further suppresses an increase in the resistance of the conductive layer 13b while applying a predetermined amount of heat to the recording medium P in a substantially uniform manner. Moreover, satisfying Formula 3 further suppresses an increase in the resistance of the conductive layer 13b while preventing the pressure roller 15 from directly contacting the sliding member 14.

[0076] The above exemplary embodiments disclose at least the following fixing device.

[0077] (Item 1)

[0078] A fixing device, comprising: a cylindrical film, the film including a base layer and a conductive layer having a resistance lower than that of the base layer; a sliding contact member disposed in an internal space of the film and in sliding contact with the rotating film; a pressing member contacting an outer peripheral surface of the film, the pressing member and the sliding contact member clamping the film together to form a fixing nip between the film and the pressing member; and a restricting member, the restricting member including a restricting surface that restricts movement of the film in a longitudinal direction of the film when the film moves along the longitudinal direction of the film, wherein in the fixing device, an electric current flows in a circumferential direction to the conductive layer to cause the conductive layer to generate joule heat, and the joule heat is used to heat a recording medium clamped and conveyed by the fixing nip, thereby fixing a toner image formed on the recording medium to the recording medium, the restricting member is disposed at a position facing an end surface of the film along the longitudinal direction, relative to the longitudinal direction, the conductive layer into which the electric current flows in the circumferential direction is not provided in a region of an end of the film, but is provided in a region between regions of the ends, and satisfies the relation D > R + C – F, where F is the width of the film, C is the width of the conductive layer, R is the distance between two restricting surfaces, and D is the width of the pressing member.

[0079] (Item 2)

[0080] The fixing device according to Item 1, wherein relative to the longitudinal direction, the relation T < C + F – R is satisfied, where T is the maximum width of a toner image formed on the recording medium.

[0081] (Item 3)

[0082] The fixing device according to Item 1 or Item 2, wherein the relation D < F × 2 – R is satisfied.

[0083] (Item 4)

[0084] The fixing device according to any one of Items 1 to 3, wherein the fixing device further comprises: an exciting coil disposed in the internal space of the film and including a spiral portion, the spiral portion including a spiral axis substantially parallel to the longitudinal direction; and a magnetic core having an end surface disposed inside the spiral portion, wherein an induced current is generated in the conductive layer by applying an alternating voltage to the exciting coil.

[0085] (Item 5)

[0086] The fixing device according to Item 4, wherein the induced current flows in a rotational direction of the film.

[0087] 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 for fixing a toner image formed on a recording medium to the recording medium, the fixing device comprising: A cylindrical film, the film including a base layer and a conductive layer having a lower resistance than the base layer; A sliding contact member, the sliding contact member being disposed in the inner space of the film and the rotating film being in sliding contact with the sliding contact member; A pressing member contacting the outer peripheral surface of the film, the pressing member and the sliding contact member clamping the film together to form a fixing nip between the film and the pressing member; And A restricting member, the restricting member having a restricting surface configured to restrict movement of the film in the longitudinal direction of the film when the film moves along the longitudinal direction of the film, Wherein in the fixing device, an electric current flows in a circumferential direction to the conductive layer to cause the conductive layer to generate joule heat, and the joule heat is used to heat the recording medium clamped and conveyed by the fixing nip, thereby fixing the toner image formed on the recording medium to the recording medium, Wherein the restricting member is disposed at a position facing the end surface of the film in the longitudinal direction, Wherein, with respect to the longitudinal direction, the conductive layer into which the electric current flows in the circumferential direction is not provided in the region of the end of the film, but is provided in the region between the regions of the end, and Wherein, with respect to the longitudinal direction, the relationship D>R+C–F is satisfied, where F is the width of the film, C is the width of the conductive layer, R is the distance between the two restricting surfaces, and D is the width of the pressing member.

2. The fixing device according to claim 1, wherein: With respect to the longitudinal direction, the relationship T<C+F–R is satisfied, where T is the maximum width of the toner image formed on the recording medium.

3. The fixing device according to claim 2, wherein the relationship D<F×2–R is satisfied.

4. The fixing device according to claim 1, wherein: The fixing device further comprises: An exciting coil, the exciting coil being disposed in the inner space of the film and including a spiral portion, the spiral portion including a spiral axis substantially parallel to the longitudinal direction; and A magnetic core having an end surface disposed inside the spiral portion, Wherein an induced current is generated in the conductive layer by applying an alternating voltage to the exciting coil.

5. The fixing device according to claim 4, wherein the induced current flows in the rotational direction of the film.

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