JP2013083683A - Belt fixing device and image forming device including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secure and energy-saving belt fixing device configured to be warmed up in a short time, and to provide an image forming device including the same.SOLUTION: The fixing device 15 includes a fixing roller 15a, a pressure roller 15b, a fixing belt 64, and a heating member 60. In the fixing device 15, the fixing belt 64 is stretched between the fixing roller 15a and the heating member 60, and the heating roller 15b is arranged so as to face the fixing roller 15a across the fixing belt 64. On the outside surface of the heating member 60, a groove is formed so as to be perpendicular to or inclined with respect to the moving direction of the fixing belt 64. The groove is filled with highly heat-conductive grease to easily eliminate temperature variation to be caused by film thickness variation of a conductive film, thereby achieving uniform temperature distribution.

Description

  The present invention relates to a belt fixing device that fixes a toner image on a recording medium by heat and pressure, and an image forming apparatus using the belt fixing device.

  As a fixing device used in an electrophotographic image forming apparatus such as a copying machine or a printer, a heat roller fixing type fixing device is frequently used. A heat roller fixing type fixing device includes a roller pair (fixing roller and pressure roller) that are in pressure contact with each other, and is heated by a heating unit including a halogen heater or the like disposed inside or both of the roller pair. After the pair is heated to a predetermined temperature (fixing temperature), a recording medium such as a recording sheet on which a fixed toner image is formed is fed to the pressure contact portion (fixing nip portion) of the roller pair and passed through the pressure contact portion. The toner image is fixed on the recording paper by heat and pressure.

  By the way, in a fixing device provided in a color image forming apparatus, it is common to use an elastic roller provided with an elastic layer made of silicon rubber or the like on the surface of the fixing roller. By using an elastic roller as the fixing roller, the surface of the fixing roller is elastically deformed corresponding to the unevenness of the unfixed toner image, and comes into contact so as to cover the toner image surface. It is possible to perform heat fixing on an unfixed toner image satisfactorily. In addition, due to the strain relief effect of the elastic layer at the fixing nip, it is possible to improve the releasability for color toners that are more likely to be offset than in monochrome. Further, since the nip shape of the fixing nip is convex upward (on the fixing roller side) (so-called reverse nip shape), it is possible to improve the recording paper peeling performance without using a peeling means such as a peeling claw. The recording paper can be peeled off (self-stripping), and image defects caused by the peeling means can be eliminated.

  In the fixing device provided in such a color image forming apparatus, it is necessary to widen the nip width of the fixing nip portion in order to cope with the high speed. As a method for widening the nip width, there are methods such as increasing the thickness of the elastic layer of the fixing roller and increasing the diameter of the fixing roller. However, in a fixing roller having an elastic layer, since the thermal conductivity of the elastic layer is very low, there is a problem that the temperature of the fixing roller does not follow when the process speed is increased when there is a heating means inside the fixing roller. is there. On the other hand, when the diameter of the fixing roller is increased, there are problems that the warm-up time becomes longer and the power consumption increases.

  As a fixing device provided in a color image forming apparatus that solves such a problem, Patent Document 1 discloses that a fixing belt is stretched between a fixing roller and a heating roller, and the fixing roller and the pressure roller are interposed via the fixing belt. A belt-fixing type fixing device having a configuration in which the two are in pressure contact with each other is disclosed. In this belt fixing type fixing device, since the fixing belt having a small heat capacity is heated, the warm-up time is short, and it is not necessary to incorporate a heat source such as a halogen lamp in the fixing roller. A thick elastic layer can be provided, and a wide nip width can be secured.

  Further, in Patent Document 2, in a belt fixing type fixing device, a heating unit is used as a planar heating element to secure a contact area between the heating member and the fixing belt, and the heating member is disposed close to the fixing roller. A fixing type fixing device is disclosed. In this sheet heating belt fixing type fixing device, since the curvature of the heating member is larger than the curvature of the fixing roller, a contact area with the fixing belt is ensured and at the same time a low heat capacity is achieved. Since the sheet heating element directly heats the fixing belt, the thermal response speed is improved compared to the method of indirectly heating the heating roller using a halogen lamp or the like, and the warm-up time is further shortened or further increased. Energy saving can be achieved.

  In Patent Document 3, a high-resistance metal material such as stainless steel or a polyimide on an insulating layer made of a polyimide resin or the like on the back surface of a heat panel made of a highly heat-conductive material such as aluminum having a curved surface with an arc-shaped cross section. A heating wire composed of a material in which silver is dispersed in a resin or the like, and a planar resistance heating element having a configuration in which a plurality of patterns are bent back and forth in a direction perpendicular to the direction of movement of the fixing belt. A fixing device is disclosed. A temperature sensor that detects the temperature of the heating panel is disposed inside the heating panel.

  The fixing belt, which is a member to be heated, is installed between a heating panel fixedly disposed and a pressure pad, and a pressure roller, which is a pressing member, is pressed toward the pressure pad with the fixing belt interposed therebetween. Heat is transmitted while the fixing belt moves while sliding on the surface of the heating panel by the rotation of the pressure roller, and the fixing belt is heated to a temperature suitable for the fixing process.

  A heat fixing process is performed by passing the recording medium onto which the toner image has been transferred between a fixing belt and a pressure roller. The pressure pad can be replaced with a pressure roller (see Patent Document 3).

  Further, a method for obtaining the running stability of the fixing belt by using a lubricant on the inner surface of the fixing belt is described in Patent Document 4, and it can be analogized that there is not only a lubricating effect but also a thermal conductivity effect. . However, the effect of preventing meandering in the longitudinal direction of the belt is insufficient.

JP-A-10-30796 JP 2002-333788 A JP 2003-287970 A JP 2004-286929 A

  However, the heating member is a planar heating element in which a resistance heating element is used as the planar heating element, and an electrical insulating layer and a resistance heating layer are laminated on the substrate, and the resistance heating layer is attached to the substrate. On the other hand, in the belt fixing method formed on the fixing belt side, peeling occurs because the linear expansion coefficients of the base material, the electrical insulating layer, and the resistance heating layer are different, and the heating layer peels off, which is a safety problem. In addition, since the curvature of the heating member is larger than the curvature of the fixing roller, the fixing belt does not smoothly enter or exit from the contact, resulting in uneven rotation of the fixing belt and further the life of the fixing belt. Shorter.

  Further, as in the above-described direct heating type fixing device, a resistance heating element is arranged inside the heating panel, and the resistance heating element is a band-like resistance heating element that is folded back multiple times in the direction perpendicular to the direction of movement of the fixing belt. In the configuration described above, there is a possibility that non-uniformity of heat generation does not occur over the entire fixing belt. However, the resistance heating element is formed by attaching a thin metal plate such as SUS and a polyimide resin plate, and a folded pattern and terminal on the thin metal plate side. Is a heating element obtained by etching and leaving only the metal in the pattern part, and if this is placed on the back side of the heating panel, for example, by bonding or mechanically pressing, it will inevitably come into contact A non-uniform portion of the thermal resistance is generated, and the SUS thin plate is peeled off due to a difference in thermal expansion coefficient, so that the portion overheats and emits smoke from the organic insulating layer. Ri there is a safety problem.

  On the other hand, it is conceivable to arrange a ceramic heater made of an inorganic material in the heating panel section. However, it is possible to efficiently transfer heat from the flat ceramic heater to the fixing belt. Difficult in terms of

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems and provide a safe and energy-saving belt fixing device capable of warming up in a short time and an image forming apparatus using the same. .

The present invention is a fixing device for fixing a toner image carried on a recording medium by heating and pressing on the recording medium,
A fixing member, a heating member, an endless fixing belt stretched between the fixing member and the heating member, and a pressure member facing the fixing member via the fixing belt,
The heating member has a substantially semi-cylindrical shape, and a conductive film that generates heat by energization is formed on one surface in the thickness direction of the insulating layer in the heating portion that heats the fixing belt in contact with the fixing belt. A groove is formed on the surface in sliding contact with the fixing belt so as to have a right angle or an inclined angle with respect to the direction in which the fixing belt moves.

  According to this belt fixing device, by forming a groove on the outer surface of the heating member so as to be perpendicular or inclined with respect to the moving direction of the fixing belt, temperature variations due to film thickness variations of the conductive film can be made uniform easily. Can be realized.

  In the belt fixing device of the present invention, the groove is filled with highly heat conductive grease.

  In addition, according to this belt fixing device, by filling the groove with highly heat-conductive grease, heat conduction and diffusion are performed along the groove, so that the temperature of the groove becomes uniform. The temperature distribution is more uniform in the longitudinal direction.

  In the belt fixing device of the present invention, the groove formed at a right angle or an inclination angle with respect to the direction in which the fixing belt moves has the heating unit having a direction perpendicular to the moving direction of the fixing belt as a longitudinal direction. It is characterized in that it is formed as a contrast at the longitudinal central part of.

  Also, according to this belt fixing device, by arranging a groove so as to be a contrast at the longitudinal center portion of the heating unit, the fixing belt has a low shifting speed, and uses a fixing belt having high flexibility and good releasability. It becomes possible to do. Therefore, a high-quality image can be stably obtained, and the life of the fixing belt is extended.

  In the belt fixing device of the present invention, the heating member has the grooves formed in the moving direction of the fixing belt at both longitudinal end portions of the heating unit having a longitudinal direction as a direction orthogonal to the moving direction of the fixing belt. It is characterized by that.

  Further, according to this belt fixing device, it is possible to prevent the high heat conductive grease from leaking outside the necessary area of the heating unit and contaminating the surface of the fixing belt (the surface in contact with the image).

  In the belt fixing device according to the aspect of the invention, the heating member may move in the moving direction of the fixing belt rather than the groove formed at a right angle or an inclination angle with respect to the moving direction of the fixing belt inside the longitudinal direction of the heating member. The groove is formed deeply.

  Further, according to this belt fixing device, when the grease moves from the inner side in the longitudinal direction to the outer side with the rotational movement of the fixing belt, the grease can be prevented from overflowing from the outer groove.

  In the belt fixing device of the present invention, the conductive film that generates heat when energized uses a material selected from ITO, aluminum-added zinc oxide, gallium-added zinc oxide, fluorine-added tin oxide, and niobium-added titanium dioxide. And

  Further, according to this belt fixing device, in order to suppress the contact thermal resistance, it is necessary that the heating element is formed in close contact with the base material, and therefore a material that can be formed by vapor deposition or the like is used. Used. Furthermore, since it is possible to form a transparent conductive film, it is possible to exclude a defective film formation in a manufacturing process in a short time, and quality control becomes easy.

  In the belt fixing device of the present invention, the heating member is characterized in that the base material is glass.

  Further, according to this belt fixing device, the heating member has a thermal expansion coefficient close to that of the ITO film, can suppress the peeling of the conductive film due to heating / cooling, and can extend the life.

  In the belt fixing device of the present invention, the conductive film has a first heating area corresponding to a narrow recording sheet and a second heating area corresponding to a wide recording sheet, and supplies power to the conductive film. The heating region is controlled by supplying power to the power supply film.

  Further, according to this belt fixing device, the heating region of the vapor deposition film can be easily divided by patterning the arrangement of the electrodes without performing a mask in the vapor deposition film formation process and etching after the film formation. be able to. As a result, even if the size of the recording paper changes, it is possible to prevent overheating in an area where there is no paper, which is safe and energy saving.

  The present invention is an image forming apparatus including the fixing device.

  As described above in detail, in the present invention, the substantially semi-cylindrical heating member is made of an inorganic material ensuring high-temperature heat resistance, the heat generating layer is formed on the substrate, and the surface of the fixing belt is formed on the surface of the substrate. Grooves arranged at right angles or at an inclination angle with respect to the moving direction and grooves in the same direction as the fixing belt moving direction are formed outside the grooves in the longitudinal direction of the heating member. Since it is filled with heat-conducting grease, the fixing belt has no rotation unevenness and uniform temperature distribution without temperature unevenness throughout the fixing belt, so that it is possible to provide energy-saving and high-quality images.

1 is a diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a cross-sectional view illustrating a configuration of a fixing device according to a first embodiment of the present invention. FIG. 4 is a diagram illustrating a configuration of a heating member included in the fixing device. It is a figure which shows the groove | channel formed in the outer surface of a heating member. It is sectional drawing which shows the structure of the planar heating element which is the 1st example of a heating member. It is a figure which shows the heat_generation | fever area | region formed with the electrically conductive film and electrode which generate | occur | produce with electricity.

  Hereinafter, a plurality of embodiments of the present invention will be described.

  FIG. 1 is a diagram illustrating a configuration of an image forming apparatus 100 according to an embodiment of the present invention. The image forming apparatus 100 is an apparatus that forms multicolor and single color images on recording paper based on image data of a read original document or image data transmitted via a network or the like. The image forming apparatus 100 includes an exposure unit 10, a photosensitive drum 101 (101a to 101d), a developing device 102 (102a to 102d), a charging roller 103 (103a to 103d), a cleaning unit 104 (104a to 104d), and an intermediate transfer belt. 11, a primary transfer roller 13 (13a to 13d), a secondary transfer roller 14, a fixing device 15, paper transport paths P1, P2, and P3, a paper feed cassette 16, a manual paper feed tray 17, and a paper discharge tray 18. .

  The image forming apparatus 100 corresponds to the hues of four colors of cyan (C), magenta (M), and yellow (Y), which are three subtractive primary colors obtained by color separation of black (K) and a color image. Using the image data, image formation is performed in the image forming units Pa to Pd corresponding to each hue. Each of the image forming portions Pa to Pd has the same configuration. For example, the black (K) image forming portion Pa includes a photosensitive drum 101a, a developing device 102a, a charging roller 103a, a transfer roller 13a, a cleaning unit 104a, and the like. Composed. The image forming portions Pa to Pd are arranged in a line in the moving direction (sub-scanning direction) of the intermediate transfer belt 11.

  The charging roller 103 is a contact-type charger that uniformly charges the surface of the photosensitive drum 101 to a predetermined potential. Instead of the charging roller 103, a contact type charger using a charging brush or a non-contact type charger using a charging wire may be used.

  The exposure unit 10 includes a semiconductor laser (not shown), a polygon mirror 4, a first reflection mirror 7, a second reflection mirror 8, and the like. Black (K), cyan (C), magenta (M), and yellow (Y). Each of the photosensitive drums 101a to 101d is irradiated with a light beam such as a laser beam modulated by the image data of each hue. Each of the photosensitive drums 101a to 101d forms an electrostatic latent image based on image data of each hue of black (K), cyan (C), magenta (M), and yellow (Y).

  The developing device 102 supplies toner as a developer to the surface of the photosensitive drum 101 on which the electrostatic latent image is formed, and develops the electrostatic latent image into a toner image. Each of the developing devices 102a to 102d contains toner of each hue of black (K), cyan (C), magenta (M), and yellow (Y), and is formed on each of the photosensitive drums 101a to 101d. The electrostatic latent image of each hue is visualized into a toner image of each hue. The cleaning unit 104 removes and collects toner remaining on the surface of the photosensitive drum 101 after development and image transfer.

  The intermediate transfer belt 11 is disposed above the photosensitive drum 101, and is stretched between the driving roller 11a and the driven roller 11b to form a loop-shaped moving path. The outer peripheral surface of the intermediate transfer belt 11 faces the photosensitive drum 101d, the photosensitive drum 101c, the photosensitive drum 101b, and the photosensitive drum 101a in this order. Primary transfer rollers 13a to 13d are arranged at positions facing the respective photosensitive drums 101a to 101d with the intermediate transfer belt 11 interposed therebetween. Each of the positions where the intermediate transfer belt 11 faces the photosensitive drums 101a to 101d is a primary transfer position. The intermediate transfer belt 11 is formed of a film having a thickness of about 100 to 150 μm.

  The primary transfer rollers 13a to 13d have constant voltage control of a primary transfer bias opposite to the charging polarity of the toner in order to transfer the toner images carried on the surfaces of the photosensitive drums 101a to 101d onto the intermediate transfer belt 11. Applied. As a result, the toner images of the respective colors formed on the photosensitive drums 101a to 101d are sequentially transferred onto the outer peripheral surface of the intermediate transfer belt 11, and a full-color toner image is formed on the outer peripheral surface of the intermediate transfer belt 11. .

  However, when image data of only a part of the hues of yellow (Y), magenta (M), cyan (C), and black (K) is input, input is performed among the four photosensitive drums 101a to 101d. The electrostatic latent image and the toner image are formed only on a part of the photoconductors 101 corresponding to the hue of the image data. For example, when forming a monochrome image, an electrostatic latent image and a toner image are formed only on the photosensitive drum 101a corresponding to the black hue, and only the black toner image is transferred to the outer peripheral surface of the intermediate transfer belt 11. Is done.

  Each of the primary transfer rollers 13a to 13d is configured by covering the surface of a shaft whose base is a metal such as stainless steel having a diameter of 8 to 10 mm with a conductive elastic material (for example, EPDM, urethane foam, etc.). A high voltage is uniformly applied to the intermediate transfer belt 11 by the elastic material.

  The toner image transferred to the outer peripheral surface of the intermediate transfer belt 11 at each primary transfer position is conveyed to a secondary transfer position that is a position facing the secondary transfer roller 14 by the rotation of the intermediate transfer belt 11. The secondary transfer roller 14 is pressed against the outer peripheral surface of the intermediate transfer belt 11 whose inner peripheral surface is in contact with the peripheral surface of the driving roller 11a at a predetermined nip pressure during image formation. When the recording paper fed from the paper feed cassette 16 or the manual paper feed tray 17 passes between the secondary transfer roller 14 and the intermediate transfer belt 11, what is the charging polarity of the toner on the secondary transfer roller 14? A high voltage of reverse polarity is applied. As a result, the toner image is transferred from the outer peripheral surface of the intermediate transfer belt 11 to the surface of the recording paper.

  Of the toner adhering to the intermediate transfer belt 11 from the photosensitive drum 101, the toner remaining on the intermediate transfer belt 11 without being transferred onto the recording paper is used for the transfer cleaning unit in order to prevent color mixing in the next process. 12 is collected.

  The recording paper on which the toner image has been transferred is guided to the fixing device 15 of the present invention, which will be described later, and is formed between the fixing belt 64 stretched between the fixing roller 15a and the heating member 60 and the pressure roller 15b. It passes through the fixing nip portion to be heated and pressurized. As a result, the toner image is firmly fixed on the surface of the recording paper. The recording paper on which the toner image is fixed is discharged onto the paper discharge tray 18 by the paper discharge roller 18a.

  Further, in the image forming apparatus 100, the recording paper stored in the paper cassette 16 is sent to the paper discharge tray 18 between the secondary transfer roller 14 and the intermediate transfer belt 11 and via the fixing device 15. A sheet transport path P1 extending in a substantially vertical direction is provided. In the paper transport path P1, a pickup roller 16a that feeds the recording paper in the paper cassette 16 one by one into the paper transport path P1, a transport roller 16b that transports the fed recording paper upward, and the recording that has been transported. A registration roller 19 that guides the paper between the secondary transfer roller 14 and the intermediate transfer belt 11 at a predetermined timing, and a paper discharge roller 18 a that discharges the recording paper to the paper discharge tray 18 are disposed.

  Further, inside the image forming apparatus 100, a paper conveyance path P2 in which a pickup roller 17a and a conveyance roller 16b are arranged is formed between the manual paper feed tray 17 and the registration rollers 19. Further, a paper transport path P3 is formed between the paper discharge roller 18a and the upstream side of the registration roller 19 in the paper transport path P1.

  The paper discharge roller 18a is rotatable in both forward and reverse directions, and is used to form a second side image when forming a single-sided image for forming an image on one side of the recording paper and for forming a double-sided image for forming an image on both sides of the recording paper. At the time of formation, the recording paper is driven in the normal rotation direction and discharged to the paper discharge tray 18. On the other hand, when the first side image is formed in the double-sided image formation, the discharge roller 18a is driven in the forward direction until the rear end of the paper passes through the fixing device 15, and then the rear end of the recording paper is sandwiched. Driven in the reverse direction, the recording paper is guided into the paper transport path P3. As a result, the recording paper on which the image is formed only on one side at the time of double-sided image formation is guided to the paper conveyance path P1 with the front and back sides and the front and rear ends reversed.

  The registration roller 19 performs the secondary transfer of the recording paper fed from the paper cassette 16 or the manual paper feed tray 17 or conveyed via the paper conveyance path P3 at a timing synchronized with the rotation of the intermediate transfer belt 11. Guided between the roller 14 and the intermediate transfer belt 11. For this reason, the registration roller 19 stops rotating when the operation of the photosensitive drum 101 and the intermediate transfer belt 11 is started, and the recording paper fed or conveyed prior to the rotation of the intermediate transfer belt 11 is registered at the front end. The movement in the paper transport path P1 is stopped in a state where it is in contact with the roller 19. Thereafter, the registration roller 19 is a position at which the secondary transfer roller 14 and the intermediate transfer belt 11 are in pressure contact with each other, and the front end portion of the recording paper and the front end portion of the toner image formed on the intermediate transfer belt 11 face each other. To start rotation.

  At the time of full color image formation in which image formation is performed in all of the image forming portions Pa to Pd, the primary transfer rollers 13a to 13d press the intermediate transfer belt 11 against all of the photosensitive drums 101a to 101d. On the other hand, at the time of monochrome image formation in which image formation is performed only in the image forming portion Pa, only the primary transfer roller 13a is brought into pressure contact with the photosensitive drum 101a.

  FIG. 2 is a cross-sectional view showing the configuration of the fixing device 15 according to the first embodiment of the present invention. The fixing device 15 includes a fixing roller 15a, a pressure roller 15b, a fixing belt 64, and a heating member 60. In the fixing device 15, the fixing belt 64 is stretched between the fixing roller 15 a and the heating member 60, and the pressure roller 15 b is disposed so as to face the fixing roller 15 a through the fixing belt 64. The fixing roller 15a and the heating member 60 are disposed so as to be substantially parallel in the axial direction of the fixing roller 15a. Therefore, when the fixing belt 64 stretched between the fixing roller 15a and the heating member 60 slides, it can be prevented from meandering and the durability of the fixing belt 64 can be maintained high.

  In the fixing device 15, the heating member 60 comes into contact with the fixing belt 64 to heat the fixing belt 64, and the fixing nip portion 15 c formed by the fixing belt 64 and the pressure roller 15 b has a predetermined fixing speed (this embodiment). 220 mm / sec), and a recording medium 82 which is a recording medium at a copying speed passes through and fixes an unfixed toner image 81 carried on the recording paper 82 by heating and pressing on the recording paper 82. is there.

  The unfixed toner image 81 includes, for example, a developer such as a nonmagnetic one-component developer (nonmagnetic toner), a nonmagnetic two-component developer (nonmagnetic toner and carrier), and a magnetic developer (magnetic toner). Toner). The fixing speed is a so-called process speed, and the copying speed is the number of copies per minute. When the recording paper 82 passes through the fixing nip portion 15c, the fixing belt 64 comes into contact with the surface of the recording paper 82 opposite to the toner image carrying surface.

  The fixing roller 15a is pressed against the pressure roller 15b via the fixing belt 64 to form the fixing nip portion 15c. At the same time, the fixing roller 15a is opposed to and pressed against the pressure roller 15b via the fixing belt 64, and rotates around the rotation axis. It is provided rotatably. The pressure roller 15b follows the rotation of the fixing roller 15a (rotation direction Y1) and rotates in the rotation direction Y2. The fixing roller 15a has a diameter of 30 mm and has a two-layer structure in which a core metal and an elastic layer are formed in order from the inside. The core metal includes, for example, a metal such as iron, stainless steel, aluminum, copper, or the like. An alloy or the like is used. For the elastic layer, a heat-resistant rubber material such as silicon rubber or fluorine rubber is suitable. In this embodiment, the force when the fixing roller 15a is pressed against the pressure roller 15b via the fixing belt 64 is about 216N.

  The pressure roller 15b conveys the fixing belt 64 by being driven to rotate in the rotation direction Y2 around the rotation axis by a drive motor (drive means) (not shown). The pressure roller 15b has a three-layer structure in which a metal core, an elastic layer, and a release layer are formed in this order from the inside.

  For the metal core, for example, a metal such as iron, stainless steel, aluminum, copper, or an alloy thereof is used. For the elastic layer, a rubber material having heat resistance such as silicon rubber and fluorine rubber is suitable, and for the release layer, PFA (copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether) or PTFE (polytetrafluoroethylene) is suitable. A fluororesin such as fluoroethylene) is suitable. A heater lamp 66 for heating the pressure roller 15b is disposed inside the pressure roller 15b. When a control unit described later supplies power to the heater lamp 66 from the power supply circuit (energization), the heater lamp 66 emits light, and infrared rays are emitted from the heater lamp 66. As a result, the inner peripheral surface of the pressure roller 15b is heated by absorbing infrared rays, and the entire pressure roller 15b is heated.

  The fixing belt 64 is heated to a predetermined temperature by the heating member 60, and heats the unfixed toner image 81 and the recording paper 82 that pass through the fixing nip portion 15c. The fixing belt 64 is an endless belt having a diameter of 50 mm, is suspended by the heating member 60 and the fixing roller 15a, and is wound around the fixing roller 15a at a predetermined angle. When the fixing roller 15a rotates, the fixing belt 64 follows the fixing roller 15a and rotates in the rotation direction Y1.

  The fixing belt 64 is formed of an elastomer material (for example, silicon rubber) excellent in heat resistance and elasticity as an elastic layer on the surface of a hollow cylindrical base material made of a heat resistant resin such as polyimide or a metal material such as stainless steel or nickel. Furthermore, a three-layer structure in which a synthetic resin material (for example, a fluororesin such as PFA or PTFE) having excellent heat resistance and releasability is formed on the surface as a release layer. Moreover, you may add a fluororesin internally to the polyimide of a base material. Thereby, the sliding load with the heating member 60 can be reduced.

  Further, in the fixing device 15, as a temperature detecting means, a heating element side thermistor 63 is disposed on the peripheral surface of the fixing belt 64, and a pressure roller side thermistor 65 is disposed on the peripheral surface of the pressure roller 15b. The surface temperature is detected. Based on the surface temperature of the fixing belt 64 detected by the heating element side thermistor 63, energization to the conductive film described later is controlled. The heating element side thermistor 63 in the present embodiment is a non-contact type temperature detection means, and is an infrared detection type temperature sensor. In the configuration in which the contact-type temperature detection unit is disposed in contact with the fixing belt 64, the contact-type temperature detection unit may wear the surface release layer of the fixing belt 64 at the interface in contact with the fixing belt 64. In this way, when the surface release layer of the fixing belt 64 is damaged or deteriorated, the influence is exerted on the image, resulting in a poor image. The energization of the heater lamp 66 is controlled based on the surface temperature of the pressure roller 15b detected by the pressure roller side thermistor 65.

  FIG. 3 is a diagram illustrating a configuration of the heating member 60 included in the fixing device 15. FIG. 4 is a development view showing a formation state of grooves on the surface of the heating member. The heating member 60 is a member for contacting the fixing belt 64 and heating the fixing belt 64 to a predetermined temperature. The heating member 60 includes a base material 62, a conductive film and an electrode 75 described later.

  The base material 62 has a hollow roll shape, and has a substantially semi-cylindrical cross-sectional shape in which a substantially lower half is cut. A conductive film, which will be described later, is formed on the inner surface of the substantially semi-cylindrical portion, and is a portion (heating unit 20) for transferring heat generated in the conductive film to the fixing belt 64. Therefore, the base material 62 needs to be formed from a material having high heat resistance rigidity. Examples of the material constituting the substrate 62 include metals such as aluminum and glass.

  In the belt fixing device 15, heat is transferred from the heating member 60 to the fixing belt 64 with high efficiency in the heating member 60 in which a conductive film that generates heat by energization is formed on the surface of the insulating layer of the base material 62 in order to heat the belt 64. In order to achieve this, it is desirable to increase the heat transfer area. Therefore, considering the heat capacity, a heating member having a thin semi-cylindrical shape is preferable.

  In addition, a conductive film that generates heat by energization is formed on the inner surface of the substantially semi-cylindrical surface of the heating portion 20 of the base material 62 that is in contact with the fixing belt 64, and a surface that slides on the fixing belt 64. In this case, it is preferable that the groove 71 is formed so as to have an orthogonal or inclined angle with respect to the direction in which the fixing belt 64 moves.

  As a configuration for increasing the heating efficiency of the heating member 60, it is preferable from the viewpoint of heat transfer loss and durability that a conductive film that generates heat by energization is directly formed on the surface of the heating member.

  The method for forming the conductive film on the outer surface or the curved surface of the inner surface of the substantially semi-cylindrical heating member 60 is preferably selected according to the conductive film material, and is a known method such as vapor deposition, sputtering, ion plating, Spray pyrolysis, CVD, etc. can be used. However, since a sheet heating element formed on a curved surface is formed on a curved surface, the film thickness tends to vary, and the resistance value of the conductive film changes, resulting in variations in the amount of heat generated. It has been newly found that unevenness occurs in the image due to surface temperature variations. Therefore, in order to make the film thickness of the conductive film constant, it is conceivable to perform patterning by masking or etching, but patterning in film formation to a substantially semi-cylindrical curved surface is very complicated and difficult to realize. is there. Therefore, as shown in FIGS. 4A and 4B, a groove 71 is formed on the outer surface of the heating member 60 so as to be perpendicular or inclined with respect to the moving direction of the fixing belt 64. It was found that the temperature variation due to the film thickness variation of the conductive film can be easily uniformed by filling the heat conductive grease.

  Filling the groove 71 with highly heat-conducting grease causes heat conduction and diffusion along the groove 71 so that the temperature of the groove becomes uniform, and as the fixing belt 64 rotates, the fixing belt 64 is more uniform in the longitudinal direction. Temperature distribution. The depth of the groove 71 is preferably deeper than 50 μm from the standpoint of grease retention. If it is shallower than this, grease will be easily depleted and temperature distribution will occur. Also, belt slidability becomes a problem.

  As shown in FIG. 4, the groove 71 formed at a right angle or an inclination angle with respect to the direction in which the fixing belt 64 moves is the length of the heating unit having the direction perpendicular to the direction of movement of the fixing belt as the length. It is preferable that it is formed as a control at the center.

  If the spiral groove 71 is unidirectional and has an inclination with respect to the moving direction of the fixing belt 64, the belt keeps moving in one direction from the groove 71, and the end portion of the fixing belt is destroyed. Therefore, by arranging a groove so as to be a contrast at the longitudinal center portion of the heating unit 20, the fixing belt 64 has a low shifting speed, and it is possible to use the fixing belt 64 having high flexibility and good peelability. Become. Accordingly, a high-quality image can be stably obtained, and the life of the fixing belt 64 is extended.

  In the heating member 60, it is preferable that grooves 72 are formed in the moving direction of the fixing belt 64 at both longitudinal end portions of the heating unit 20 having a direction perpendicular to the moving direction of the fixing belt 64 as a longitudinal direction. In this way, it is possible to prevent the high thermal conductive grease from leaking outside the necessary area of the heating unit 20 and contaminating the fixing belt surface (surface in contact with the image).

  Further, in the heating member 60, the groove in the moving direction of the fixing belt 64 is formed deeper than the groove 71 formed at a right angle or an inclination angle with respect to the moving direction of the fixing belt 64 on the inner side in the longitudinal direction of the heating member 60. It is preferable. In this way, it is possible to prevent the grease from overflowing from the outer groove when the grease moves from the inner side in the longitudinal direction to the outer side as the fixing belt 64 rotates.

  The grooves 71 and 72 on the surface of the heating member can be formed by mechanical formation, photolithography, or laser engraving. Further, the cross-sectional shape of the groove may be V-shaped, U-shaped, or concave, but is preferably uniform. The pitch of the grooves is preferably selected appropriately from temperature variation suppression, belt slidability, and formability.

  A top coat layer 73 capable of reducing the frictional force with the fixing belt 64 may be formed on the heating unit 20. Examples of the material constituting the top coat layer 73 include at least one material of PTFE resin and PFA resin, or a glass layer having slidability. As a result, the frictional force between the heating member 60 and the fixing belt 64 can be reduced, the wear of the fixing belt 64 can be prevented, and high durability of the fixing belt 64 can be ensured. The load on the fixing roller 15a and the pressure roller 15b for driving the belt 64 can also be reduced, and the durability of the rollers 15a and 15b can be ensured and the roller can be driven with low power.

  The journal part 60 b is a part formed at both ends of the heating part 20, and is fixed to the side frame 68 of the fixing device 15 so that the heating member 60 itself does not rotate due to frictional force with the fixing belt 64. Thus, since the heating member 60 itself is configured not to rotate, safety can be sufficiently ensured even if a high current is supplied to the conductive film when the conductive film generates heat.

  Further, a meandering prevention collar 67 that prevents meandering when the fixing belt 64 rotates and slides is formed in the journal portion 60 b so as to contact the end portion of the fixing belt 64. The meander-preventing collar 67 may be a color made of polyphenylene sulfide (PPS), but is not limited to this, and may have a configuration that can rotate independently of the heating member 60. . Thus, since the meandering prevention collar 67 is uniquely installed, even if the fixing belt 64 abuts against the meandering prevention collar 67, no load is applied without sliding, and the fixing belt 64 is broken. The durability of the fixing belt 64 can be maintained high.

  Next, the conductive film included in the heating member 60 will be described. FIG. 5 is a cross-sectional view illustrating a configuration of a planar heating element that is a first example of the heating member 60. FIG. 6 is a diagram showing a heat generation region formed by a conductive film and electrodes that generate heat when energized.

  In the planar heating element, a conductive film to be a heating region is formed in a planar shape on one surface in the thickness direction of the substrate. Furthermore, the planar heating element 20 is composed of a plurality of heat generating regions, and has a plurality of divided heat generating regions. In the present embodiment, the planar heating element 20 is formed with a heating area divided into two, a heating area at both ends and a heating area at the center, with respect to the longitudinal direction of the electrically insulating base material. As described above, a heat generating region is formed at the longitudinal center portion of the electrically insulating substrate, and heat generating regions are formed at both end portions.

  In each heat generating region, a conductive film that generates heat when energized with voltage applied is formed as a whole with a surface having a certain shape. Here, the conductive film is preferably made of a material selected from ITO, aluminum-added zinc oxide, gallium-added zinc oxide, fluorine-added tin oxide, and niobium-added titanium dioxide. In order to suppress the contact thermal resistance, it is necessary to form a film with the heating element in close contact with the substrate. For this purpose, it is necessary to use a material that can be formed by vapor deposition. Furthermore, since these materials can form a transparent conductive film, it is possible to exclude film formation defects in a manufacturing process in a short time, and quality control becomes easy.

  The substrate 62 may be a substrate formed of a ceramic material such as aluminum, iron, glass, or alumina, or a heat-resistant polymer material such as polyimide resin, as having high heat resistance and high rigidity. As a base material for forming a conductive film that generates heat by vapor deposition or the like, glass is preferable. The thermal expansion coefficient of the conductive film such as ITO is close, and peeling of the conductive film due to heating / cooling can be suppressed and the life can be extended.

  The heat generation region formed in the heating member 60 has a first heating region corresponding to a narrow recording sheet and a second heating region corresponding to a wide recording sheet, and a power supply film for supplying power to the conductive film 77, and the heating region is preferably controlled by supplying power to the power supply film 77. The heating region of the deposited film can be easily divided by patterning the arrangement of the electrodes without performing a mask in the process of forming the deposited film and etching after the deposition. As a result, even if the size of the recording paper changes, it is possible to prevent overheating in an area where there is no paper, which is safe and energy saving.

  In the case of a wide recording sheet, the entire recording sheet is heated by energizing the power supply terminals a and d. In the case of a narrow recording sheet, the recording sheet is energized by energizing the power supply terminals b and c. The energization control is performed by the control unit 91 so that energization is possible in a state where the heat generation area is distinguished, so that it is not necessary to heat the area that does not pass excessively and is safe and energy saving.

Electrodes and power supply terminals as the material, a volume resistivity of 5.9 × ^{10 -8} Ωcm about zinc, gold volume resistivity of about 2.05 × ^{10 -8} Ωcm, the volume resistivity is 1.55 × 10 ^{- 8} [Omega] cm approximately copper, volume resistivity and the like 1.47 × 10 ^-8 Ωcm about silver, silver or copper volume resistivity among them are small low cost are preferred.

  As described above, in the heating unit, the amount of heat generated in the longitudinal direction of the heating unit can be adjusted by switching the energization state, and the temperature distribution on the surface of the heating member is adjusted to a desired temperature distribution. Can do.

Here, the control part 91 is controlled by the control means of the main body, and is configured to control the supplied power from the temperature detected by the heating element side thermistor 63.
The power supply is interlocked with the rotation of the fixing belt 64 or the rotation of the fixing roller 15a, and safety is ensured so that power is not supplied when the fixing belt 64 is not rotating.

[Example]

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail using an Example, this invention is not limited to these Examples.

Example 1
The fixing device used in Example 1 is the fixing device described above. Detailed conditions in Example 1 were as follows.

<Fixing roller>
A stainless steel having a diameter of 30 mm, a mandrel of 15 mm in diameter, and a silicon sponge having a thickness of 7.5 mm was used.

<Pressure roller>
A 30 mm diameter PFA tube having a diameter of 30 mm and a heater lamp having a rated power of 400 W was used as the release layer.

<Fixing belt>
A 70 μm thick polyimide was used for the belt substrate, a 150 μm thick silicon rubber was used for the elastic layer, a 30 μm thick PFA tube was used for the release layer, and the winding angle θ was 185 °.

<Color to prevent meandering>
A polyphenylene sulfide (PPS) collar having an inner diameter of 28 mm, a diameter of 32 mm, and a width of 7 mm was disposed in contact with the end of the fixing belt.

<Heating member>
Base material: A glass pipe having a diameter of 28 mm and a heating part and a journal part of 1 mm and having an arc shape cut by 40% in the circumferential direction was used. A groove having a depth of 0.3 mm was formed on the outer surface by laser processing in the pattern shown in FIG.

Insulating layer on the conductive film: 30 μm thick, insulating layer made of polyimide. Conductive film: The length in the longitudinal direction, which is the direction extending corresponding to the axial direction of the fixing roller, is 330 mm. ITO was formed by vapor deposition so that the thickness of the central region in the longitudinal direction was 100 nm. Since the length of the heat generating layer in the longitudinal direction is set to 330 mm with respect to both ends, the length of the central portion in the longitudinal direction of the heat generating layer is 270 mm. The length of the central portion in the longitudinal direction of the heat generating layer is set to be smaller than the maximum width of the recording paper.
Electrode: A silver paste was applied to the arrangement shown in FIG. 6B so as to have a thickness of 10 μm and then baked.

<Thermistor>
A non-contact type was used as the heating element side thermistor, and a contact type was used as the pressure roller side thermistor.

<Fixing conditions>
Fixing nip length: 7 mm (the length of the fixing nip in the recording paper conveyance direction)
Fixing nip width: 325 mm (length corresponding to the axial direction of the fixing roller)
Fixing speed: 220mm / sec
Heating nip length: 44 mm (contact length in the recording paper conveyance direction between the fixing belt and the heating member)
Heating nip width: 330 mm (length corresponding to the axial direction of the fixing roller)
Maximum width of recording paper: 300 mm (length corresponding to the axial direction of the fixing roller)

  The heat generated from the sheet heating element (heating unit 20) of Example 1 is transmitted to the fixing belt through the base material. Grooves are formed on the surface of the base member so as to be symmetric at the center in the longitudinal direction of the heating member, and the grooves are filled with high thermal conductivity grease, so that the temperature distribution on the surface of the fixing belt is 175 ° C. plus in the longitudinal direction. It became uniform within minus 5 ° C., and a high quality image could be obtained.

  Further, by controlling the energization area during continuous printing of recording papers of different sizes, further excessive increase could be suppressed. Therefore, it is possible not only to ensure safety and maintain the life of the fixing member, but also to form an image on the recording paper in an energy-saving state.

(Comparative Example 1)
The same procedure as in Example 1 was performed except that the heating member was not formed with grooves on the outer surface of the substrate. Although the power supply to the conductive film was adjusted, the balance with the fixing temperature on the fixing belt could not be adjusted, and the temperature distribution in the longitudinal direction was 175 ° C. plus or minus 10 ° C., and the fixability of the toner image on the recording paper was non-uniform Met. Therefore, high quality image formation could not be secured.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and the design and the like within the scope not departing from the gist of the present invention are also claimed. Included in the range.

DESCRIPTION OF SYMBOLS 15 Fixing device 15a Fixing roller 15b Pressure roller 15c Fixing nip part 20 Heating part 60 Heating member 60b Journal part 62 Base material 63 Heating body side thermistor 64 Fixing belt 65 Pressure roller side thermistor 67 Meander prevention collar 68 Side frames 71, 72 Groove 73 Topcoat layer 75 Electrode 77 Power supply film 82 Recording paper 91 Control unit 100 Image forming apparatus

Claims (9)

A fixing device for fixing a toner image carried on a recording medium by applying heat and pressure on the recording medium,
A fixing member;
A heating member;
An endless fixing belt stretched between the fixing member and the heating member;
A pressure member facing the fixing member via the fixing belt;
With
The heating member is
A heating part that has a substantially semi-cylindrical shape and heats the fixing belt in contact with the fixing belt is formed with a conductive film that generates heat when energized on one surface in the thickness direction of the insulating layer. A belt fixing device, wherein a groove is formed on a surface that is in sliding contact with an angle or an angle of inclination with respect to a direction in which the fixing belt moves.   The belt fixing device according to claim 1, wherein the groove is filled with grease having high thermal conductivity.   The groove formed at a right angle or at an inclination angle with respect to the direction in which the fixing belt moves is formed as a contrast at the longitudinal central portion of the heating portion having a direction perpendicular to the moving direction of the fixing belt as a longitudinal direction. The belt fixing device according to claim 1, wherein the belt fixing device is provided.   2. The heating member is characterized in that the grooves are formed in the moving direction of the fixing belt at both longitudinal end portions of the heating portion having a direction perpendicular to the moving direction of the fixing belt as a longitudinal direction. The belt fixing device according to any one of?   In the heating member, the groove in the moving direction of the fixing belt is formed deeper than the groove formed at a right angle or an inclination angle with respect to the moving direction of the fixing belt on the inner side in the longitudinal direction of the heating member. The belt fixing device according to claim 4, wherein the belt fixing device is a belt fixing device.   6. The conductive film which generates heat by energization uses a material selected from any one of ITO, aluminum-added zinc oxide, gallium-added zinc oxide, fluorine-added tin oxide, and niobium-added titanium dioxide. The belt fixing device according to any one of the above.   The belt fixing device according to claim 1, wherein the heating member is made of glass.   The conductive film has a first heating region corresponding to a narrow recording paper, a second heating region corresponding to a wide recording paper, and a power supply film for supplying power to the conductive film, The belt fixing device according to claim 1, wherein the heating region is controlled by supplying power to the power supply film.   An image forming apparatus comprising the fixing device according to claim 1.

Images