JP2012027355A - Fixation device and image formation device having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a belt fixation device with a heating member having a resistance heating element in which the uniform fixation performance can be achieved at highly effective heat transmittance by making it possible to adapt for increase in temperature for paper non passing part without deterioration of durability from breaking of wire or detachment and the like even in the case of the variation in thickness of the resistance heating element.SOLUTION: In a belt fixation device with a heating member having a resistance heating element, the heating member is made from a resistance heating element generating heat by a heat dissipation member and through electric conduction. The resistance heating element is arranged on the inner surface of the heat dissipation member and has a heating region and a plurality of non-heated regions formed in the heating region.

Description

  The present invention relates to a fixing device including a heating member and an image forming apparatus including the fixing device.

  In various image forming apparatuses such as a printer using a belt fixing type fixing apparatus having a small heat capacity, when the fixing apparatus is adapted to high speed while corresponding to recording papers of various sizes, it is called non-sheet passing portion temperature rise. A problem occurs. This is because the temperature of the fixing nip portion in the non-sheet passing portion, which is a region where the recording paper is not passed, when continuously passing a small-sized recording paper with a small width with respect to the longitudinal direction of the heating member of the fixing device. When the temperature rises excessively and exceeds the heat resistance temperature of the peripheral members, the fixing device is damaged due to thermal deformation or causes the local expansion of the pressure roller, and then when normal size recording paper is passed, Fixing unevenness occurs in the longitudinal direction of the heating member, and wrinkles are caused by recording paper transport unevenness. In particular, when the heat capacity of the fixing roller is reduced in order to shorten the warm-up time, the thermal conductivity in the paper width direction is lowered, and this problem becomes more remarkable.

  For such non-sheet passing temperature rise, the process speed is reduced only when a small size recording paper is passed, or the throughput, that is, the feeding interval of the recording paper is increased, or printing is paused. However, in either case, the print productivity for small-size recording paper is reduced. In addition, in the fixing device in which the heat source is a halogen lamp, a plurality of lamps corresponding to the paper width are separately used to cope with the temperature rise of the non-sheet passing portion. However, this has a disadvantage that the device becomes complicated. Have.

  As a heating apparatus that solves the problem of non-sheet passing portion temperature rise, there is a method of Patent Document 1.

  FIG. 11 is a diagram showing the heating device of Patent Document 1. As shown in FIG. By providing a plurality of resistance heating elements 101, 102 on the substrate 100, an arbitrary temperature gradient can be given in the short direction of the substrate 100, the fixing property can be improved, and further, the resistance heating elements 101, 102. It is disclosed that the amount of heat generated can be increased by narrowing the width of, and the temperature drop at both ends is prevented.

JP 2008-233367 A

  However, in Patent Document 1, the amount of heat generated is uneven due to the thickness variation of the resistance heating element. The portion where the heat generation amount was large was thin, the current amount per unit area of the resistance heating element was large, and the resistance heating element was disconnected or peeled off.

  Therefore, a method of heating the fixing belt by installing a ceramic heater with a heating element embedded in the ceramic on the heating member is conceivable. However, in the case of using this ceramic heater, there is a method of forming it in the same plane for patterning in one ceramic heater. However, if the pattern is formed on the same plane, the installation area of the heating element Should be taken widely, which is undesirable.

  The present application has been made in view of the above-described problems. The purpose of the belt fixing device is provided with a heating member having a resistance heating element. Even if the thickness of the resistance heating element varies, disconnection, peeling, etc. The durability is not reduced, the warm-up time is short, the temperature followability of the fixing roller during high-speed printing is good, and it is possible to cope with the temperature rise of the non-sheet-passing part, and heating unevenness and heat transfer efficiency are reduced. It is an object of the present invention to provide a fixing device that can suppress generation and achieve uniform fixing performance with high heat transfer efficiency.

  Another object of the present invention is to provide an image forming apparatus provided with the fixing device.

  The present invention includes an endless fixing belt stretched between a fixing member and a heating member, and a pressure member at a position facing the fixing member via the fixing belt. A fixing device for fixing a toner image carried on a recording medium by applying heat and pressure on the recording medium at a fixing nip formed by the fixing belt, wherein the heating member is energized with a heat radiating member. The resistance heating element has a heat generation area and a plurality of non-heat generation areas formed in the heat generation area, and is disposed inside the heat dissipation member. It is what.

  Further, the present invention is characterized in that the resistance heating element is provided with electrode pairs at both ends in a direction in which the fixing belt slides, and the heating region is energized by the electrode pairs. Is.

  Further, the present invention is characterized in that the area of the non-heat generating region is larger than the area of the non-heat generating region disposed at both ends in the direction in which the fixing belt slides.

  Further, the present invention is characterized in that the electrode pair is arranged at a position other than the both ends.

  In the present invention, it is preferable that the heat dissipating member has a substantially arc shape.

  In the present invention, it is preferable that the heating member is fixed so as to be pressed against the fixing belt by a pressing member.

  In the present invention, the endless fixing belt is stretched between the fixing member and a driven member, and the heating member is fixed so as to be pressed against the fixing belt from the inside of the fixing belt. Further, it is arranged at a position different from that of the driven member.

  Further, according to the present invention, the resistance heating element includes a control unit that controls energization, a detection unit that detects the temperature of the surface of the fixing belt, and a belt surface temperature detected by the detection unit within a predetermined temperature range. And an energization control unit for controlling energization to the resistance heating element.

  Further, the present invention is characterized in that the heat radiation member is coated with a coating made of at least one of PTFE resin containing fluorine and PFA resin on the surface on which the fixing belt slides. is there.

According to the resistance heating element of the present invention, since there is a non-heat generation region, even when the thickness is thin, the amount of current per unit area decreases and the amount of heat generation decreases. The body does not cause disconnection or peeling. Furthermore, since the resistance heating element is controlled in heat generation by forming a plurality of heat generation areas and non-heat generation areas, finer temperature control is possible.

  Furthermore, since the resistance heating element is provided with electrode pairs at both ends in the direction in which the fixing belt slides, and the heating area is energized by the electrode pair, the temperature of the heating area can be controlled with high efficiency.

  According to the resistance heating element of the present invention, since the area of the non-heat generation region at both ends in the direction in which the fixing belt slides is increased, the heat generation amount at both ends increases, and the temperature decrease at both ends can be compensated. It becomes easy to adjust.

  In the resistance heating element of the present invention, in addition to the both ends in the direction in which the fixing belt slides, electrode pairs for energizing the heat generating area corresponding to the width of the small-sized paper are disposed. Temperature control can be performed independently, excessive temperature rise can be suppressed, and durability of the fixing belt and the heating member can be ensured.

  Furthermore, since the fixing belt can be smoothly slid by using the heat radiating member having a substantially arc shape, the adhesion between the fixing belt and the surface of the heat radiating member is improved, and the heat transfer efficiency to the fixing belt is improved.

  Further, since the heating member is pressed against the fixing belt by the pressing member, the tension of the fixing belt can be controlled to be constant, the adhesion between the fixing belt and the surface of the heat radiating member is further increased, and the transmission to the fixing belt is achieved. Thermal efficiency is improved. Furthermore, since the surface temperature of the fixing belt becomes uniform and the surface pressure on which the fixing belt slides is made uniform, it is possible to suppress the meandering of the fixing belt, and the durability of the surface of the fixing belt and the heat radiating member is improved. Can do.

  Further, the endless fixing belt is stretched between the fixing member and the driven member, and the heating member is fixed so as to be pressed against the fixing belt from the inside of the fixing belt, and is located at a position different from the driven member. Since the heating member is arranged in the portion where the fixing belt is less bent, the load applied to the heating member is reduced, and the member for maintaining the rigidity of the resistance heating element can be simplified. This leads to a reduction in the heat capacity of the resistance heating element and achieves high heat transfer efficiency.

  Furthermore, since an energization control unit that controls energization to the resistance heating element is provided, high-precision temperature control with excellent responsiveness by suppressing heating unevenness is possible, and a good image without image defects is provided. be able to.

  Furthermore, the heat radiation member has a coating made of at least one of PTFE resin and PFA resin containing fluorine on the surface on which the fixing belt slides, thereby reducing the sliding resistance between the fixing belt and the heat radiation member. Thus, durability of the fixing belt and the heat radiating member can be improved.

  Furthermore, according to the present invention, the image forming apparatus includes the fixing device, so that the warm-up time is short, high-speed printing can be performed, and an image without fixing unevenness can be formed.

1 is a schematic cross-sectional view illustrating a configuration of an image forming apparatus including a fixing unit according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view illustrating a configuration of a fixing unit according to the first embodiment of the present invention. 2 is a block diagram illustrating an electrical configuration of a fixing unit. FIG. It is the schematic which shows the structure of the resistance heating element which the heating member which is the 1st Embodiment of this invention has. (A) It is the schematic seen from the longitudinal direction of the heat radiating member. (B) It is the schematic which shows the structure of a cross section. It is the schematic which shows the structure of the resistance heating element which the heating member which is the 2nd Embodiment of this invention has. FIG. 3 is a schematic diagram illustrating a configuration of a heating member included in a fixing unit according to an embodiment of the present invention. It is the schematic which looked at the resistive heating element which the heating member which is the 2nd Embodiment of this invention has from the longitudinal direction of the heat radiating member. It is the schematic which shows the structure of the resistance heating element which is embodiment of this invention. (A) It is the schematic seen from the upper surface. (B) It is a figure which shows an equivalent circuit. It is the schematic which shows the structure of the resistance heating element used as the reference example with respect to embodiment of this invention. (A) It is the schematic seen from the upper surface. (B) It is a figure which shows an equivalent circuit. It is the schematic which looked at the resistive heating body which the heating member which is the 3rd Embodiment of this invention has from the longitudinal direction of the heat radiating member. It is the schematic which shows the structure of the resistance heating element used as the prior art example with respect to embodiment of this invention.

  FIG. 1 is an example of a schematic cross-sectional view illustrating a configuration of an image forming apparatus 1 including a fixing unit 2 according to an embodiment of the present invention. The image forming apparatus 1 is an apparatus that forms multi-color and single-color images on recording paper based on read image data of a document or image data transmitted via a network or the like. The image forming apparatus 1 includes first to fourth visible image forming units 51, 52, 53, 54, an intermediate transfer belt 55, a secondary transfer unit 56, a fixing unit 2, an internal paper feeding unit 57, and a manual paper feeding unit 58. Prepare. A toner image is formed by the first to fourth visible image forming units 51, 52, 53, 54, the intermediate transfer belt 55 and the secondary transfer unit 56.

  The first visible image forming unit 51 includes a photoreceptor 59, a charging unit 60, an optical system unit E, a developing unit 61, and a primary transfer unit 62. A charging unit 60, a developing unit 61, and a cleaning unit 63 are disposed around the photosensitive member 59 serving as an electrostatic latent image carrier.

  By these units, a toner image is formed on the photoreceptor 59, and the toner image is transferred to the intermediate transfer belt 55. In the optical system unit E, the data from the light source 64 is arranged so as to reach the four sets of photoconductors 59, 65, 66 and 67. The primary transfer unit 62 is disposed in pressure contact with the first visible image forming unit 51 via the intermediate transfer belt 55.

  The other second to fourth visible image forming units 52, 53 and 54 have the same configuration as the first visible image forming unit 51. The developing units 61 of the units 51, 52, 53, and 54 store toner of yellow (Y), magenta (M), cyan (C), and black (K).

  On the intermediate transfer belt 55, toner images of respective colors are transferred to form a color toner image. The intermediate transfer belt 55 is rotated by tension rollers 68 and 69. The intermediate transfer belt 55 is formed of a film having a thickness of about 100 to 150 μm.

  The waste toner box 70 is disposed in contact with the intermediate transfer belt 55 on the tension roller 69 side.

  The secondary transfer unit 56 transfers the color toner image formed on the intermediate transfer belt 55 onto the recording paper. The secondary transfer unit 56 is disposed in contact with the intermediate transfer belt 55 on the tension roller 68 side.

  The fixing unit 2 is a fixing device of the present invention. The fixing unit 2 is disposed on the downstream side of the secondary transfer unit 56. The fixing unit 2 includes a fixing member 3 and a pressure member 4, and the pressure member 4 is pressed against the fixing member 3 with a predetermined pressure by a pressure mechanism (not shown).

  Next, an image forming process in the image forming apparatus 1 will be described. After the surface of the photoconductor 59 is uniformly charged by the charging unit 60, the surface of the photoconductor 59 is laser-exposed according to image data by the optical system unit E to form an electrostatic latent image on the surface of the photoconductor 59. . The charging unit 60 employs a charging roller system in order to charge the surface of the photoreceptor 59 uniformly and without generating ozone as much as possible. Thereafter, the developing unit 61 develops the electrostatic latent image on the photoconductor 59 and visualizes the toner image.

  Further, the visualized toner image is transferred onto the intermediate transfer belt 55 by the primary transfer unit 62 to which a bias voltage having a polarity opposite to that of the toner is applied. The other second to fourth visible image forming units 52, 53 and 54 operate in the same manner, and sequentially transfer the toner images onto the intermediate transfer belt 55. The primary transfer unit 62 is formed by coating the surface of a shaft made of a metal such as stainless steel having a diameter of 8 to 10 mm with a conductive elastic material such as EPDM (ethylene propylene diene copolymer rubber), urethane foam or the like. It is the comprised transfer roller. The toner image on the intermediate transfer belt 55 is conveyed to the secondary transfer unit 56.

  Then, by the secondary transfer unit 56 in which a bias voltage having a polarity opposite to that of the toner is applied to the recording paper supplied from the paper feeding roller 73 of the internal paper feeding unit 57 or the paper feeding roller 74 of the manual paper feeding unit 58, The toner image is transferred to the recording paper.

  The recording paper carrying the toner image is conveyed to the fixing unit 2 and sufficiently heated by the fixing member 3 and the pressure member 4 so that the toner image is fused to the recording paper and discharged to the outside. The size of the recording paper corresponds to the maximum A3 size, and the heating width by the fixing unit 2 corresponds to the A4 horizontal size.

  Next, the configuration of the fixing unit 2 according to the embodiment of the present invention will be described.

  FIG. 2 is a schematic cross-sectional view showing the configuration of the fixing unit 2 according to the first embodiment of the present invention.

  The fixing unit 2 includes a fixing roller 3 as a fixing member 3, a pressure roller 4 as a pressure member 4, an endless fixing belt 5, and a heating member 6 for heating the fixing belt 5. Yes. The fixing belt 5 is stretched between the fixing roller 3 and the heating member 6. The heating member 6 is fixed and slides with the inner surface of the fixing belt 5.

  The pressure roller 4 is disposed so as to be in pressure-contact with the fixing roller 3 through the fixing belt 5. The fixing roller 3 and the heating member 6 are arranged so as to be substantially parallel in the axial direction of the fixing roller 3.

  Therefore, when the fixing belt 5 stretched between the fixing roller 3 and the heating member 6 slides, it can be prevented from meandering and the durability of the fixing belt 5 can be maintained high.

  In the fixing unit 2, the heating member 6 contacts the fixing belt 5 to heat the fixing belt 5, and the fixing nip portion 17 formed by the fixing belt 5 and the pressure roller 4 is recorded at a predetermined fixing speed or copying speed. This is an apparatus for fixing an unfixed toner image 81 carried on the recording paper 80 by heating and pressing the recording paper 80 when the paper 80 passes in the traveling direction Y0.

  The unfixed toner image 81 includes, for example, a developer such as a non-magnetic one-component developer (non-magnetic toner), a non-magnetic two-component developer (non-magnetic toner and carrier), and a magnetic developer (magnetic toner). Toner). The fixing speed is the process speed, and the copying speed is the number of copies per minute. Further, when the recording paper 80 passes through the fixing nip portion 17, the fixing belt 5 comes into contact with the toner image carrying surface of the recording paper 80.

  The heating member 6 includes a resistance heating portion 7, and the pressure roller 4 includes a heater lamp 8. As a detection part which detects the temperature of the fixing belt 5 and the pressure roller 4, a first thermistor 10 and a second thermistor 11 are provided as temperature sensors, respectively.

  Based on the surface temperature of the fixing belt 5 detected by the first thermistor 10, the energization of the resistance heating unit 7 is controlled. The first thermistor 10 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 5, the contact-type temperature detection unit may wear the surface release layer of the fixing belt 5 at the interface in contact with the fixing belt 5. In this way, if the surface release layer of the fixing belt 5 is damaged or deteriorated, the output image is affected. Further, the energization of the heater lamp 8 is controlled based on the surface temperature of the pressure roller 4 detected by the second thermistor 11.

  The fixing roller 3 has a substantially cylindrical shape and has a two-layer structure in which a core metal 12 and an elastic layer 13 are formed from the center of the substantially cylindrical shape toward the outer periphery. A metal such as iron, stainless steel, aluminum or copper, or an alloy thereof is used for the core metal. For the elastic layer 13, a heat-resistant rubber material such as silicone rubber or fluorine rubber is suitable. In the present embodiment, the fixing roller 3 has a diameter of 30 mm. The core metal 12 is made of stainless steel having a diameter of 20 mm, and the elastic layer 13 is made of silicone sponge rubber having a thickness of 5 mm. The fixing roller 3 is rotated in the rotation direction Y1 following the direction in which the fixing belt 5 is conveyed. The force when the fixing roller 3 is pressed against the pressure roller 4 via the fixing belt 5 is about 216N.

  The pressure roller 4 has a substantially cylindrical shape, and has a three-layer structure in which a metal core 14, an elastic layer 15, and a release layer 16 are formed from the substantially cylindrical center toward the outer periphery. For the metal core 14, a metal such as iron, stainless steel, aluminum copper, or an alloy thereof is used. A rubber material having heat resistance such as silicone rubber or fluorine rubber is suitable for the elastic layer 15. A fluororesin such as PFA (a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether) or PTFE (polytetrafluoroethylene) is suitable for the release layer 16. In the present embodiment, the pressure roller 4 has a diameter of 30 mm. The core metal 14 is made of STKM (carbon steel pipe for machine structural use) with a diameter of 26 mm and a wall thickness of 1 mm. The elastic layer 15 is made of silicone solid rubber with a thickness of 1 mm. In this case, a PFA tube having a thickness of 50 μm is used.

  The pressure roller 4 conveys the fixing belt 5 by being rotationally driven in the rotational direction Y2. A heater lamp 8 for heating the pressure roller 4 is disposed inside the pressure roller 4. On the basis of the surface temperature of the pressure roller 4 detected by the second thermistor 11, the heater lamp 8 emits light and infrared rays are emitted from the heater lamp 8 by supplying electric power to the heater lamp 8. As a result, the inner peripheral surface of the pressure roller 4 is heated by absorbing infrared rays, and the entire pressure roller 4 is heated. In the present embodiment, a heater lamp 8 with a rated power of 300 W is used.

  On the other hand, the heating member 6 is supplied with electric power, that is, energized, to the resistance heating portion 7 on the substrate 18 based on the surface temperature of the fixing belt 5 detected by the first thermistor 10. The resistance heating unit 7 generates heat due to Joule heat, transfers heat to the heat radiating member 19, and further transfers heat to the fixing belt 5. In this embodiment, a resistance heating part with a rated power of 1200 W is used.

  The heat dissipating member 19 is made of a metal such as aluminum, and a surface having an outer periphery with a substantially arc-shaped cross section opposite to the surface where the resistance heating unit 7 and the substrate 18 are in close contact with the fixing belt 5. The substrate 18 is made of ceramic, glass, a heat-resistant resin insulating substrate such as polyimide, PEEK (polyether ether ketone), PPS (polyphenylene sulfide), or a metal substrate such as SUS (stainless steel) or aluminum, glass or ceramic, An insulating layer such as polyimide is used, and the resistance heating portion 7 on the substrate 18 can be a metal paste containing carbon, semiconductor oxide, silver or aluminum.

  In addition to a metal such as aluminum, the heat dissipating member 19 can be a high thermal conductive ceramic such as aluminum nitride or silicon nitride. Further, the substrate 18 may be brought into direct contact with the fixing belt 5 without providing the heat radiating member 19. In that case, it is desirable to coat the portion that comes into contact with the fixing belt 5 with amorphous glass or fluorine resin to improve the slidability with the fixing belt 5.

  The fixing belt 5 has a diameter of 50 mm. The fixing belt 5 has a three-layer configuration including a base material, an elastic layer, and a release layer. The base material is formed in a hollow cylindrical shape from a heat-resistant resin such as polyimide or a metal material such as stainless steel and nickel. An elastic layer made of an elastomer material such as silicone rubber, which is excellent in heat resistance and elasticity, is formed on the surface of the base material. On the surface of the elastic layer, a release layer made of a synthetic resin material that is excellent in heat resistance and release properties, for example, a fluororesin such as PFA or PTFE is formed. In the present embodiment, polyimide having a thickness of 50 μm is used as the base material, silicone rubber having a thickness of 150 μm is used as the elastic layer, and a PFA tube having a thickness of 30 μm is used as the release layer.

  The fixing belt 5 is heated to a predetermined temperature by the heating member 6 and heats the unfixed toner image 81 and the recording paper 80 that pass through the fixing nip portion 17. The fixing belt 5 is stretched between the heating member 6 and the fixing roller 3. When the fixing roller 3 rotates, the fixing belt 5 follows the fixing roller 3 and rotates in the rotation direction Y1. Moreover, you may add a fluororesin internally to the polyimide of a base material. Thereby, the sliding load with the heating member 6 can be reduced.

  FIG. 3 is a block diagram showing an electrical configuration of the fixing unit 2 shown in FIG. The fixing unit 2 serves as temperature control means based on temperature data detected by the first thermistor 10 and the second thermistor 11 and abnormal temperature rise data of the fixing belt 5 shown in FIG. 2 detected by a thermal protector 91 described later. The control circuit 92 controls energization. Further, the control circuit 92 controls the drive motor 94 to rotate the fixing roller 3 shown in FIG. The control circuit 92 and the power supply circuit 93 that is an energization control unit are collectively controlled by a CPU 95 that is a control device that controls all operations of the fixing unit 2. In the vicinity of the peripheral surface of the fixing belt 5, a thermostat or a thermal protector 91 is provided that detects an abnormal temperature rise of the fixing belt 5 and cuts the power supply circuit 93 when the temperature rises above a predetermined temperature.

  Specifically, when receiving an image formation instruction, the CPU 95 outputs a control signal instructing the power supply circuit 93 to supply power. Here, the image formation instruction is an instruction input from an operation panel (not shown) provided on the upper surface in the vertical direction of the image forming apparatus 1 or an external device such as a computer connected to the image forming apparatus. By receiving the input, the fixing unit 2 starts the fixing processing operation.

  The power supply circuit 93 to which the control signal is input from the CPU 95 supplies power to the heater lamp 8 through the power control means 96 to heat the fixing belt 5 and supplies power to the resistance heating unit 7, and FIG. The pressure roller 4 shown in FIG. The power control means 96 also serves to control the input power to the resistance heating unit 7 to a predetermined constant value.

  When the control circuit 92 determines that the surface temperature of the fixing belt 5 and the pressure roller 4 has reached a predetermined fixing temperature based on the input signal, an unfixed toner image is displayed in the fixing nip portion 17 shown in FIG. The recording paper 80 on which 81 is formed is conveyed. At this time, the recording paper 80 shown in FIG. 2 is conveyed with the surface carrying the unfixed toner image 81 facing the fixing belt 5 side. Then, the unfixed toner image 81 on the recording paper 80 is nipped and conveyed while being in close contact with the outer peripheral surface of the fixing belt 5, whereby heat is applied from the fixing belt 5 and the recording paper is further subjected to pressure. It is fixed on the surface of 80.

  FIG. 4 is a schematic diagram showing a configuration of the resistance heating unit 7 included in the heating member 6 shown in FIG. 2 which is the first embodiment of the present invention. FIG. 4A is a schematic view of the resistance heating portion 7 as seen from the longitudinal direction of the heat radiating member 19 shown in FIG. FIG. 4B is a schematic diagram showing the configuration of the A-A ′ cross section of FIG.

  As shown in FIG. 4A, the resistance heating element 77 includes a heat generating region 31 and a plurality of non-heat generating regions 32 formed in the heat generating region 31. A method of forming the resistance heating portion 7 will be described with reference to FIGS. First, an insulating layer 21 made of glass is formed on a planar substrate 18 made of SUS, and a paste mainly composed of silver / palladium is applied thereon by screen printing, so that a heating region 31 and a non-heating region 32 are formed. Form a pattern. And the electrode pair 20 which has silver as a main component is formed in the both ends of the longitudinal direction of the heat radiating member 19 of the board | substrate 18, and finally the glass protective layer 22 is formed on it. Each layer is formed by performing timely baking in the process of forming each layer. The substrate 18 has a length of 360 mm in the longitudinal direction, a width of 20 mm in the A-A ′ section, and a thickness of 1 mm. The resistance heating element 77 has a length in the longitudinal direction of 320 mm, a width of 16 mm in the A-A ′ section, and a thickness of 30 μm. In the non-heating region 32, the glass insulating layer 21 on the substrate 18 side and the uppermost glass protective layer 22 are in close contact with each other.

  In the example shown in FIG. 4, a plurality of non-heating regions 32 of the resistance heating element 77 are formed in the longitudinal direction of the resistance heating element 77, but as shown in FIG. The heat generation may be controlled by forming a plurality of non-heat generation regions 32, and in that case, finer temperature control becomes possible.

  FIG. 6 is a schematic diagram showing a configuration of the heating member 6 included in the fixing unit 2 according to the embodiment of the present invention. The heating member 6 is a member for contacting the fixing belt 5 and heating the fixing belt 5 to a predetermined temperature, and includes a heat radiating member 19 and a pressing member 33 in addition to the resistance heating element 77 and the substrate 18. Is done.

  As shown in FIG. 6, since the heat dissipation member 19 has a substantially arc-shaped cross section, the fixing belt 5 can be smoothly slid, so that the adhesion between the surface of the fixing belt 5 and the heat dissipation member 19 is increased. The heat transfer efficiency to the fixing belt 5 is improved. As a result, the fixing unit 2 having a short warm-up time and good temperature followability of the fixing roller 3 during high-speed printing can be obtained.

  Inside the heat radiating member 19, a resistance heating element 77 included in the heating member 6 is arranged so as to correspond to the longitudinal direction of the heat radiating member 19, and heat generated by the resistance heating element 77 is transmitted to the fixing belt 5. Therefore, the heat radiating member 19 needs to be formed from a material having high thermal conductivity. The material constituting the heat dissipating member 19 was a metal such as aluminum. The curvature of the surface sliding with the fixing belt 5 was 100 mm.

  Further, it is preferable that a top coat layer capable of reducing the frictional force with the fixing belt 5 is formed on the surface of the heat radiating member 19. Examples of the material constituting the top coat layer include at least one material of PTFE resin and PFA resin. As a result, the frictional force between the heat radiating member 19 and the fixing belt 5 can be reduced, the fixing belt 5 can be prevented from being worn, and high durability of the fixing belt 5 can be secured. Further, the load on the fixing roller 3 and the pressure roller 4 shown in FIG. 2 for driving the fixing belt 5 can be reduced, so that it can be driven with low power, and the fixing roller 3 and the pressure roller 4 can be driven. Durability can also be secured.

  Further, as shown in FIG. 6, since the heat radiating member 19 is pressed against the fixing belt 5 by the pressing member 33, the substrate 18 can be brought into close contact with the resistance heating element 77, and the substrate 18 and the resistance heating element 77 can be It can suppress bending.

  Thus, when the heat radiating member 19 is pressed against the fixing belt 5 by the pressing member 33, the tension of the fixing belt 5 can be controlled to be constant, and the adhesion between the surface of the fixing belt 5 and the heat radiating member 19 can be controlled. Since the heat transfer efficiency to the fixing belt 5 is improved, an increase in power consumption can be suppressed and energy saving can be achieved. Furthermore, since the surface temperature of the fixing belt 5 becomes uniform and the surface pressure on which the fixing belt 5 slides is made uniform, meandering of the fixing belt 5 can be suppressed. As a result, the durability of the surfaces of the fixing belt 5 and the heat radiating member 19 can also be improved.

  FIG. 7 is a schematic view of the resistance heating element 7 included in the heating member 6 shown in FIG. 2, which is the second embodiment of the present invention, as viewed from the longitudinal direction of the heat dissipation member 19 shown in FIG.

  As shown in FIG. 7, unlike FIG. 4, another pair of electrodes 40 is further provided between the pair of electrodes 20 provided at both ends in the longitudinal direction of the substrate 18. Thus, by energizing the electrode pair 40, a region having a narrower width than that between the electrode pair 20 can be heated. That is, when the small-size paper is passed without the electrode pair 40 and only the electrode pair 20, the temperature at the end in the longitudinal direction has risen, but this is suppressed. be able to. The longitudinal width of the heat generating region S of the resistance heating element 77 was 320 mm, and the amount of heat generated when a voltage of 100 V was applied was 1200 W. The width in the longitudinal direction of the heat generating region SS is 200 mm, and the amount of heat generated when a voltage of 100 V is applied is preferably controlled by controlling the voltage or current when the heat generating region SS generates heat.

  As described above, the heat generation amount in the longitudinal direction of the resistance heating element 77 can be adjusted by switching the energization state so that the temperature distribution on the surfaces of the heat radiating member 19 and the fixing belt 5 becomes a desired temperature distribution. Can be adjusted. Therefore, finer temperature control is possible, and a good image free from image defects can be provided.

  The width in the longitudinal direction of the heat generating region S is set so that the width in the longitudinal direction of the resistance heating element 77 is substantially the same as the maximum sheet passing width of the recording paper 80 shown in FIG. As a result, the recording paper 80 that is passed through the fixing unit 2 shown in FIG. 2 has no temperature difference between both ends and the center, and is passed in a state in which the temperature distribution is made uniform over the entire area of the paper passing width. .

  Accordingly, it is possible to cope with papers of different sizes, and when small-size paper is continuously printed, an excessive temperature rise does not occur at both ends where the paper does not pass.

  The amount of current flowing through the resistance heating element 77 and the amount of heat generated will be described with reference to FIGS. In either case, the resistance of the resistance heating element 77 is 15Ω as a whole.

  FIG. 8A is a schematic diagram showing a configuration of a resistance heating element 77 in which a plurality of patterns of the heat generating region 31 and the non-heat generating region 32 according to the embodiment of the present invention are formed and the heat generation is controlled. FIG. 8B shows an equivalent circuit of FIG.

  On the other hand, FIG. 9A is a schematic diagram showing a configuration of a resistance heating element 77 in which a plurality of patterns of the heat generation region 31 serving as a reference example for the embodiment of the present invention is formed and heat generation is controlled. FIG. 9B shows an equivalent circuit of FIG.

  In general, the heat generating region 31 has a thickness variation, and the resistance value varies by about ± 10%. For example, assuming that variations in thickness occur in the heat generation region 31 corresponding to the resistors R1 and R2 shown in FIGS. 8B and 9B, in each heat generation region, that is, in FIG. In FIG. 9B, between R8 and the electrode pair 20, the amount of current and the amount of heat generated between the resistors R1 to R6 and the electrode pair 20 were estimated.

  Tables 1 and 2 show each heat generating region, that is, in Table 1, each of the resistors R1 to R8 and the electrode pair 20 of the present invention, and in Table 2, each heat generating region between the resistors R1 to R6 of the reference example and the electrode pair 20. The calculation results of resistance value, current amount, and calorific value corresponding to are shown.

  Table 1 shows the calculation results of the resistance value, the current amount, and the heat generation amount corresponding to each heat generation region, assuming that variations in thickness occurred in the heat generation region 31 corresponding to the resistors R1 and R2 shown in FIG. 8B. Table 2 shows the results of trial calculation of resistance values, current amounts, and heat generation amounts corresponding to the respective heat generation regions, assuming that variations in thickness occur in the heat generation regions 31 corresponding to the resistors R1 and R2 shown in FIG. 9B. Is shown.

  In both cases, it is assumed that the heating region 31 of the resistor R1 is thin and the heating region 31 of the resistor R2 is thick.

  According to this, in the case of the pattern of the heat generating region 31 as shown in FIG. 8A, since the pattern of the non-heat generating region 32 is formed, the current flows through the resistor R7 as shown in Table 1, The amount of current in the heat generating region 31 of the resistor R1 whose thickness is reduced becomes small.

  On the other hand, in the case of the pattern of the heat generation region 31 as shown in FIG. 9A, as shown in Table 2, the current amount of the heat generation region 31 of the resistor R1 whose thickness is thin does not have the resistance R7 shown in Table 1. It becomes larger than that of Table 1.

  Generally, when a large current flows through a portion where the heat generating region 31 is thin, the heat generating region 31 is likely to be disconnected or peeled off.

  That is, the current in the portion where the heat generating region 31 is thin is not increased, but if the pattern of the heat generating region 31 is reduced as in the present invention, even if the thickness of the heat generating region 31 varies, it is caused by this. Disconnection or peeling of the heat generating region 31 that occurs is less likely to occur.

  FIG. 10 illustrates a resistance heating element 77 according to another embodiment of the present invention. FIG. 10 is a schematic view of a resistance heating element 77 included in the heating member 6 shown in FIG. 2, which is the third embodiment of the present invention, as viewed from the longitudinal direction of the heat dissipation member 19 shown in FIG.

  As shown in FIG. 10, when the non-heat generating region 32 positioned on the electrode pair 20 side at both ends of the substrate 18 is expanded in the longitudinal direction, the heat generating region 31 becomes narrow, so that the amount of current per unit area increases and the substrate 18 The calorific value at both ends increases.

  In general, in order to make the temperature in the longitudinal direction uniform, it is necessary to compensate for heat escape at both ends, and increase the amount of heat generated at both ends.

  In this way, the amount of heat generated at both ends of the substrate 18 is increased, temperature drop at both ends of the substrate 18 can be compensated, and the amount of heat generated by the resistance heating element 77 in the longitudinal direction can be easily adjusted.

  In this manner, the temperature distribution on the surfaces of the heat dissipating member 19 and the fixing belt 5 shown in FIG. 2 can be adjusted to a desired temperature distribution. Therefore, finer temperature control is possible, and a good image free from image defects can be provided.

  Further, the width in the longitudinal direction of the resistance heating element 77 is set to be substantially the same as the maximum sheet passing width of the recording sheet 80 shown in FIG. As a result, the recording paper 80 that is passed through the fixing unit 2 shown in FIG. 2 has no temperature difference between both ends and the center, and is passed in a state in which the temperature distribution is made uniform over the entire area of the paper passing width. .

  Accordingly, it is possible to cope with papers of different sizes, and when small-size paper is continuously printed, an excessive temperature rise does not occur at both ends where the paper does not pass.

  In this embodiment, the amount of heat generated at both ends is increased by increasing the area of the non-heat generating region 32 at both ends of the substrate 18. Note that a plurality of the non-heat generating regions 32 of the resistance heating element 77 may be formed other than in the longitudinal direction, that is, in the width direction.

  As described above, since the heat generation amount of the resistance heating element 77 can be freely controlled by the shape and area of the non-heat generation region 32, the degree of freedom in the distribution of the heat generation amount is high, and the pattern arrangement of the non-heat generation region 32 with particularly high accuracy is also possible. Not needed.

  In addition, since the area of the non-heat generation amount region 32 increases as a result in the portion where the heat generation amount is large, a heat dissipation effect to the non-heat generation amount region 32 can be expected, and disconnection, peeling, etc. of the resistance heating element 77 due to temperature rise. Can be prevented.

E Optical system unit S, SS Heat generation area Y0 Travel direction Y1, Y2 Rotation direction R1 Resistance (R2-R8)
DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Fixing unit 3 Fixing roller 4 Pressure roller 5 Fixing belt 6 Heating member 7 Resistance heating part 8 Heater lamp 10 First thermistor 11 Second thermistor 12, 14 Core metal 13, 15 Elastic layer 16 Release layer 17 Fixing nip portion 18 Substrate 19 Heat radiating member 20 Electrode pair 21 Insulating layer 22 Protective layer 30 Tension roller 31 Heating region 32 Non-heating region 33 Pressing member 40 Electrode pair 51 Visible image forming unit (52 to 54)
55 Intermediate transfer belt 56 Secondary transfer unit 57 Internal paper feed unit 58 Manual paper feed unit 59 Photoconductor 60 Charging unit 61 Development unit 62 Primary transfer unit 63 Cleaning unit 64 Light source 68, 69 Tension roller 70 Waste toner box 73 Paper feed Roller 74 Paper feed roller 77 Resistance heating element 80 Recording paper 81 Unfixed toner image 91 Thermal protector 92 Control circuit 93 Power supply circuit 94 Drive motor 95 CPU
96 Power control means

Claims (10)

An endless fixing belt stretched between the fixing member and the heating member;
A pressure member is provided at a position facing and pressed against the fixing member via the fixing belt;
A fixing device that fixes a toner image carried on a recording medium by heating and pressing the recording medium at a fixing nip formed by the pressing member and the fixing belt;
The heating member is composed of a heat radiating member and a resistance heating element that generates heat when energized,
The fixing device according to claim 1, wherein the resistance heating element has a heat generating region and a plurality of non-heat generating regions formed in the heat generating region, and is disposed inside the heat radiating member.   2. The resistance heating element according to claim 1, wherein an electrode pair is disposed at both ends in a direction in which the fixing belt slides, and the heating region is energized by the electrode pair. Fixing device.   The area of the non-heat generation area is larger in the non-heat generation area disposed at both end portions than the non-heat generation area disposed in the central portion in the direction in which the fixing belt slides. The fixing device according to claim 1.   The fixing device according to claim 1, wherein the electrode pair is disposed at a position other than the both ends.   The fixing device according to claim 1, wherein the heat radiating member has a substantially arc shape.   The fixing device according to claim 1, wherein the heating member is fixed to be pressed against the fixing belt by a pressing member.   The endless fixing belt is stretched between the fixing member and a driven member, and the heating member is fixed so as to be pressed against the fixing belt from the inside of the fixing belt, and is different from the driven member. The fixing device according to claim 1, wherein the fixing device is disposed at a position. The resistance heating element includes a control device for controlling energization,
The control device is configured to detect a temperature of the fixing belt surface and an energization control for controlling energization of the resistance heating element so that the belt surface temperature detected by the detection unit is within a predetermined temperature range. The fixing device according to claim 1, further comprising a unit.   9. The heat radiating member is coated with at least one of fluorine-containing PTFE resin and PFA resin on a surface on which the fixing belt slides. The fixing device according to Item 1.   An image forming apparatus comprising the fixing device according to claim 1.