JP5611134B2 - Coil manufacturing cartridge, induction heating coil manufactured using the same, and fixing device - Google Patents

Description

  The present invention relates to an induction heating coil used in an induction heating type fixing device mounted on an image forming apparatus such as a copying machine, a printer, and a facsimile, and more particularly to a cartridge for manufacturing the induction heating coil.

  In a conventional image forming apparatus using an electrophotographic system, a heat source is built in at least one roller of a pair of fixing rollers that form a nip, or a heat source is arranged outside to form a heating roller. A heat roller fixing method is widely used in which a paper carrying an unfixed toner image is inserted into a nip portion and heated and pressed to fix the toner image on the paper.

  Further, instead of the heating roller, an endless fixing belt heated by a heat source is used, and a sheet carrying an unfixed toner image is inserted into a nip portion between the fixing belt and a pressure member pressed against the fixing belt. A belt fixing method for fixing a toner image on paper has been developed. This belt fixing method can reduce the heat capacity by reducing the heat capacity compared to the heat roller fixing method, and can reduce power consumption.

  As a heating method for such a heating roller and a fixing belt, a lamp method in which heating is performed by a lamp such as a halogen lamp is known. However, due to a recent reduction in warm-up time and a demand for energy saving, an alternating magnetic field is used as a magnetic conductor. An induction heating (IH: Induction Heating) system in which heating is performed by interlinking and generating eddy currents has been proposed.

  In the induction heating method, a high frequency magnetic flux is generated by applying a high frequency current to an induction heating coil in which a litz wire is wound along the outer peripheral surface of a bobbin extending in the width direction of a heating roller or a fixing belt. This high-frequency magnetic flux acts on the induction heating layer of the heating roller or fixing belt, and an eddy current is generated around the magnetic flux of the induction heating layer. Therefore, Joule heat due to the inherent resistance of the material in the induction heating layer is generated and heated. The roller or fixing belt is heated.

  By the way, in the induction heating type fixing device, if the longitudinal dimension of the induction heating coil is substantially the same as the width dimension of the heating roller or the fixing belt, the induction heating coil is disposed at both ends of the heating roller or the fixing belt in the width direction. A turn part (folded part) will face. Here, since the magnetic flux generated in the turn portion is smaller than the magnetic flux generated in the straight portion other than the turn portion, it is possible to efficiently heat the heating roller facing the turn portion, or both ends in the width direction of the fixing belt. This was not possible, leading to uneven fixing temperature and energy loss.

  Further, the above problem can be solved by making the linear portion of the induction heating coil longer than the width direction dimension of the heating roller or the fixing belt. However, since the induction heating portion including the induction heating coil is enlarged, It was an obstacle to downsizing and downsizing.

  Therefore, a configuration has been proposed in which the magnetic flux generated in the induction heating coil is effectively used without increasing the size of the apparatus by reducing the width of the turn portion of the induction heating coil. An induction heating device is disclosed in which a turn portion is stacked and wound in a direction perpendicular to the longitudinal direction of a heating member (heating roller). In Patent Document 2, the linear portion of the coil is arranged in a planar shape along the outer peripheral surface of the member to be heated (heat roller), and the turn portion of the coil has a plurality of stages less than the number of turns of the coil. An induction heating device is disclosed that is arranged in a stack.

JP 2002-43049 A JP 2008-270215 A

  However, the Litz wire is regulated in order to stack the litz wire in the vertical direction at the turn portion of the induction heating coil as in Patent Document 1 and to stack and arrange in multiple stages as in Patent Document 2. A coil manufacturing apparatus that winds in an aligned manner is required. Moreover, in the induction heating coil of patent document 1, although the method of starting up only the turn part of the induction heating coil which wound the litz wire in the horizontal direction in the vertical direction is also considered, the number of manufacturing processes increases. Therefore, there is a problem that the manufacturing cost of the induction heating coil increases.

  In view of the above problems, an object of the present invention is to provide a coil manufacturing cartridge that can easily and inexpensively manufacture an induction heating coil having a narrow turn portion and a small energy loss.

  In order to achieve the above object, the present invention provides a first cartridge having a concave surface that is curved in an arc shape when viewed from the end in the longitudinal direction, and is attachable to and detachable from the first cartridge. A second cartridge having an arcuate convex surface opposed to each other; a core portion formed on either the bottom of the concave surface or the top portion of the convex surface and wound with a litz wire; and a circumferential direction of the core portion A coil guide portion having an arcuate cross section formed by the concave surface and the convex surface on the outside; and a coupling means for coupling or uncoupling the first cartridge and the second cartridge via the winding core portion. An interval h1 between the coil guide portions at both ends in the longitudinal direction of the first cartridge and the second cartridge is a front side on a side surface in the longitudinal direction of the first cartridge and the second cartridge. Is a broad for manufacturing a coil cartridge than the distance h2 of the coil guide portion.

  According to the present invention, in the coil manufacturing cartridge having the above-described configuration, h1 / h2 is 1.1 to 1.2.

  Further, the present invention provides the coil manufacturing cartridge having the above-described configuration, wherein the coupling means includes a boss projecting from an upper surface of the core portion and having a thread formed on an outer peripheral surface thereof, and the concave surface or the convex surface facing the boss. And a nut that is screwed into a thread of the boss protruding through the boss hole.

  According to the present invention, in the coil manufacturing cartridge having the above-described configuration, the concave surface and the convex surface are spaced apart from each other in the circumferential direction of the core portion at both ends in the longitudinal direction of the first cartridge and the second cartridge. It is characterized by the formation of an inclined surface in the direction to be.

  In addition, the present invention is an induction heating coil manufactured using the coil manufacturing cartridge having the above-described configuration, and when viewed from a direction perpendicular to the concave surface and the convex surface, the first cartridge and the second cartridge The induction heating coil is such that the coil width of the turn portion formed at both ends in the longitudinal direction is narrower than the coil width of the linear portion formed along the longitudinal direction of the first cartridge and the second cartridge.

  The present invention also provides a fixing device including an induction heating unit that generates a magnetic flux by causing an electric current to flow through the induction heating coil having the above-described configuration, and induction-heats an induction heating layer provided on the heating member by the magnetic flux.

  According to the first configuration of the present invention, the interval h1 at both ends in the longitudinal direction of the coil guide portion having a circular arc cross section formed by the concave surface of the first cartridge and the convex surface of the second cartridge is set on the side surface in the longitudinal direction. By making it wider than the interval h2, it is possible to manufacture an induction heating coil in which the width of the turn part is narrow and the energy loss is small only by winding the litz wire around the core part along the coil guide part.

  According to the second configuration of the present invention, in the coil manufacturing cartridge of the first configuration, the ratio of the interval h1 at both ends in the longitudinal direction to the interval h2 at the side surface in the longitudinal direction of the coil guide portion is 1. By setting it as 1-1.2, the fall of workability | operativity at the time of winding a litz wire can be suppressed, narrowing the width | variety of the turn part of an induction heating coil.

  Further, according to the third configuration of the present invention, in the coil manufacturing cartridge having the first or second configuration, as the coupling means for coupling or releasing the coupling between the first cartridge and the second cartridge, A boss projecting on the upper surface and having a thread formed on the outer peripheral surface, a boss hole formed on a concave surface or a convex surface facing the boss, and a boss thread projecting through the boss hole. By using the nut to be screwed, the first cartridge and the second cartridge can be connected or released with a simple configuration.

  According to the fourth configuration of the present invention, in the coil manufacturing cartridge having any one of the first to third configurations, the winding core portion is provided at both longitudinal ends of the first cartridge and the second cartridge. By forming an inclined surface in a direction in which the concave surface and the convex surface are separated toward the outer side in the circumferential direction, the litz wire is guided to the coil guide portion along the inclined surface when winding the litz wire. Can be smoothly wound.

  Further, according to the fifth configuration of the present invention, by manufacturing the induction heating coil using the coil manufacturing cartridge having any one of the first to fourth configurations, the direction perpendicular to the concave surface and the convex surface can be obtained. When viewed, the coil width of the turn portion formed at both ends of the first cartridge and the second cartridge is narrower than the coil width of the straight portion formed along the longitudinal side surface of the first cartridge and the second cartridge. Become. Thereby, the ratio of the linear part in the longitudinal direction of a coil becomes large, and the induction heating coil which can use effectively the magnetic flux which generate | occur | produces in a coil can be manufactured simply and at low cost.

  In addition, according to the sixth configuration of the present invention, an induction heating unit that generates a magnetic flux by causing a current to flow through the induction heating coil of the fifth configuration, and induction-heats the induction heating layer provided on the heating member by the magnetic flux. The induction heating unit including the induction heating coil does not increase in size, and the fixing device is compact and has little energy loss.

Schematic sectional view of an image forming apparatus equipped with a fixing device using an induction heating coil manufactured according to the present invention. Side sectional view of a fixing device 16 using an induction heating coil manufactured according to the present invention. The top view of the induction heating part 25 used for the fixing device 16 The exploded perspective view of the cartridge 40 for coil manufacture of this invention The side view which looked at the cartridge 40 for coil manufacture of this invention from the edge part side of a longitudinal direction Side cross-sectional view of cartridge 40 wound with induction heating coil 29 cut perpendicularly to the longitudinal direction Side sectional view of the end of the cartridge 40 around which the induction heating coil 29 is wound, cut in parallel to the longitudinal direction Side sectional view of the cartridge 40 in which the litz wire pressing member 51 is inserted into the coil guide portion 50 from the side surface in the longitudinal direction, cut perpendicularly to the longitudinal direction. Side sectional view of the cartridge 40 from which the second cartridge 43 has been removed cut perpendicularly to the longitudinal direction. Side surface sectional drawing which cut | disconnected the edge part of the cartridge 40 which removed the 2nd cartridge 43 in parallel with respect to the longitudinal direction

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing the configuration of an image forming apparatus equipped with a fixing device using an induction heating coil manufactured according to the present invention. Here, a tandem color image forming apparatus is shown. In the main body of the color printer 100, four image forming portions Pa, Pb, Pc, and Pd are sequentially arranged from the upstream side in the movement direction of the intermediate transfer belt 8 (the right side in FIG. 1). These image forming portions Pa to Pd are provided corresponding to images of four different colors (magenta, cyan, yellow, and black), and magenta, cyan, and yellow are respectively subjected to charging, exposure, development, and transfer processes. And a black image are sequentially formed.

  These image forming portions Pa to Pd are provided with photosensitive drums 1a, 1b, 1c and 1d which carry visible images (toner images) of the respective colors, and are further illustrated by a driving means (not shown). In FIG. 1, an intermediate transfer belt 8 that rotates clockwise is provided adjacent to each of the image forming portions Pa to Pd. The toner images formed on the photosensitive drums 1a to 1d are sequentially primary-transferred and superimposed on the intermediate transfer belt 8 that moves while contacting the photosensitive drums 1a to 1d, and then the secondary transfer roller. 9 is secondarily transferred onto a sheet P as an example of a recording medium. Further, after being fixed on the sheet P in the fixing device 13, the sheet is discharged from the apparatus main body. An image forming process for each of the photosensitive drums 1a to 1d is executed while rotating the photosensitive drums 1a to 1d counterclockwise in FIG.

  The paper P onto which the toner image is transferred is accommodated in a paper cassette 16 disposed at the lower part of the main body of the color printer 100, and will be described later with the secondary transfer roller 9 via a paper feed roller 12a and a registration roller pair 12b. The intermediate transfer belt 8 is conveyed to a nip portion with the driving roller 11. A sheet made of dielectric resin is used for the intermediate transfer belt 8, and a (seamless) belt having no seam is mainly used. A blade-like belt cleaner 19 for removing toner remaining on the surface of the intermediate transfer belt 8 is disposed downstream of the secondary transfer roller 9 in the moving direction of the intermediate transfer belt 8.

  Next, the image forming units Pa to Pd will be described. There are chargers 2a, 2b, 2c, and 2d for charging the photosensitive drums 1a to 1d and image information on the photosensitive drums 1a to 1d around and below the photosensitive drums 1a to 1d that are rotatably arranged. The exposure device 5 for exposing the toner, the developing devices 3a, 3b, 3c and 3d for forming toner images on the photosensitive drums 1a to 1d, and the developer (toner) remaining on the photosensitive drums 1a to 1d are removed. Cleaning parts 7a, 7b, 7c and 7d are provided.

  When image data is input from a host device such as a personal computer, first, the surfaces of the photosensitive drums 1a to 1d are uniformly charged by the chargers 2a to 2d, and then light is irradiated according to the image data by the exposure device 5. The electrostatic latent images corresponding to the image data are formed on the respective photosensitive drums 1a to 1d. Each of the developing devices 3a to 3d is filled with a predetermined amount of a two-component developer containing toner of each color of magenta, cyan, yellow, and black. In addition, when the ratio of the toner in the two-component developer filled in each developing device 3a to 3d falls below a specified value due to the formation of a toner image described later, each developing device 3a to 3d is transferred from the toner container 4a to 4d. Toner is replenished. The toner in the developer is supplied onto the photosensitive drums 1a to 1d by the developing devices 3a to 3d and electrostatically adheres to the electrostatic latent image formed by the exposure from the exposure device 5. A toner image is formed.

  The primary transfer rollers 6a to 6d apply an electric field at a predetermined transfer voltage between the primary transfer rollers 6a to 6d and the photosensitive drums 1a to 1d, and magenta, cyan, yellow, and yellow on the photosensitive drums 1a to 1d. A black toner image is primarily transferred onto the intermediate transfer belt 8. These four color images are formed with a predetermined positional relationship predetermined for forming a predetermined full-color image. Thereafter, in preparation for the subsequent formation of a new electrostatic latent image, the toner remaining on the surfaces of the photosensitive drums 1a to 1d after the primary transfer is removed by the cleaning units 7a to 7d.

  The intermediate transfer belt 8 is stretched over an upstream driven roller 10 and a downstream drive roller 11, and the intermediate transfer belt 8 rotates clockwise as the drive roller 11 is rotated by a drive motor (not shown). When the rotation starts, the sheet P is conveyed from the registration roller pair 12b to the nip portion (secondary transfer nip portion) between the driving roller 11 and the secondary transfer roller 9 provided adjacent thereto at a predetermined timing. The full color image on the intermediate transfer belt 8 is transferred onto the paper P. The sheet P on which the toner image is transferred is conveyed to the fixing device 13.

  The sheet P conveyed to the fixing device 13 is heated and pressed by the fixing belt 21 and the pressure roller 23 (see FIG. 2), and the toner image is fixed on the surface of the sheet P, thereby forming a predetermined full color image. . The paper P on which the full-color image is formed is distributed in the transport direction by the branching section 14 that branches in a plurality of directions. When an image is formed on only one side of the paper P, it is discharged to the discharge tray 17 by the discharge roller pair 15 as it is.

  On the other hand, when forming images on both sides of the paper P, the paper P that has passed through the fixing device 13 is once transported in the direction of the discharge roller pair 15, and after the rear end of the paper P has passed through the branch portion 14, the discharge roller pair 15. Is rotated in the reverse direction and the conveyance direction of the branching portion 14 is switched, so that the paper P is distributed from the rear end of the paper P to the reverse conveyance path 18 and re-conveyed to the secondary transfer nip portion with the image surface reversed. Then, after the next image formed on the intermediate transfer belt 8 is transferred to the surface of the paper P where the image is not formed by the secondary transfer roller 9 and conveyed to the fixing device 13 to fix the toner image, The paper is discharged to the discharge tray 17 by the discharge roller pair 15.

  2 is a side sectional view of the fixing device 16, and FIG. 3 is a plan view of the induction heating unit 25 of the fixing device 16 as viewed from the left in FIG. FIG. 3 shows a state in which the arch core 30b is removed so that the internal configuration of the induction heating unit 25 can be seen. As shown in FIGS. 2 and 3, the fixing device 13 includes an endless fixing belt 21 that rotates counterclockwise in FIG. 2, a belt support member 22 that is inscribed in the fixing belt 21, and the fixing belt 21. And a pressure roller 23 that is pressed against the belt support member 22 and rotates in the clockwise direction in FIG. 2, and an induction heating unit 25 that is disposed on the opposite side of the pressure roller 23 with the fixing belt 21 interposed therebetween. It is a configuration.

  A separation plate 35 that separates the sheet from the fixing belt 21 and a separation plate holder 37 that supports the separation plate 35 are disposed on the downstream side of the fixing nip N with respect to the sheet conveyance direction (from the bottom to the top in FIG. 2). Has been.

  The fixing belt 21 is an endless shape formed by laminating a plurality of layers including an induction heating layer provided on the innermost side in contact with the belt support member 22 and a release layer provided on the outermost side in contact with the pressure roller 23. It is a belt. The fixing belt 21 is wound around an arc-shaped flange portion 24 that protrudes from the inner surface of a belt support member 22 and a fixing housing (not shown) and is inscribed at both end portions in the width direction of the fixing belt 21. In addition, the portion that is not in contact with the belt support member 22 is held in an arc shape with a predetermined distance from the induction heating unit 25. Instead of the flange portion 24, a support member having a cross-sectional arch shape inscribed in the fixing belt 21 may be disposed on the opposite side of the belt support member 22 (the side facing the induction heating unit 25).

  As the induction heating layer of the fixing belt 21, a metal layer obtained by plating or rolling a metal such as nickel is used. The release layer is made of a fluorine resin such as PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), and is formed by applying a paint or covering the tube. The release layer has a thickness of about 10 to 50 μm for a PFA tube and about 10 to 30 μm for a fluororesin paint.

  Further, a silicon rubber layer having a thickness of about 100 to 1000 μm may be provided as an elastic layer between the induction heating layer and the release layer. According to this configuration, the elastic layer wraps the unfixed toner image on the paper and can be fixed softly. As a result, the image quality can be improved and the high-performance fixing device 13 can be obtained.

  In addition, a heat storage layer may be provided between the induction heating layer and the release layer so that heat generated in the induction heating layer is not released, and the temperature of the surface of the fixing belt 21 can be kept uniform. As a result, higher heating efficiency can be obtained, and the effects of shortening the warm-up time and reducing power consumption can be enhanced.

  The heat storage layer is composed of silicon rubber having a high thermal conductivity, such as silica, alumina, magnesium oxide powder or the like, and a metal having a high thermal conductivity, such as aluminum, copper, nickel, etc. These are formed by covering or plating a tube-shaped product. The heat storage layer may be made of an elastic material such as silicon rubber. However, when it is made of metal, if the wall thickness is made too thick, the belt hardness increases, and the nip amount necessary to melt the toner is obtained. It will not be possible. Therefore, the thickness of the heat storage layer is 10 to 1000 μm, desirably 50 to 500 μm.

  As the configuration of the fixing belt 21 used in the present embodiment, for example, a 200 μm-thick silicon rubber layer (elastic layer) is laminated on a 35 μm-thick nickel layer (induction heating layer), and a 30 μm-thick PFA tube ( And a belt having an outer diameter of 40 mm and a width of 360 mm coated with a release layer.

  A thermistor (not shown) is provided so as to contact the surface of the fixing belt 21. The temperature of the fixing belt 21 is detected by this thermistor, and the fixing temperature is controlled by turning on / off the current flowing through the induction heating unit 25.

  Also, the dimension in the width direction of the fixing belt 21 (perpendicular to the paper surface in FIG. 2) is set smaller than the dimension in the width direction of the induction heating unit 25 and wider than the maximum sheet width passing through the fixing nip N. Has been. As a result, the induction heating unit 25 uniformly heats the entire fixing belt 21 to prevent the occurrence of uneven fixing, and the fixing belt 21 can cover the entire surface of the paper regardless of the paper size. It is possible to prevent adhesion of unfixed toner.

  The belt support member 22 is in contact with the pressure roller 23 via the fixing belt 21 to form a fixing nip portion N through which a sheet is inserted. As a material of the belt support member 22, a metal such as aluminum, a heat resistant resin, or the like is used. Further, a silicon rubber layer having a thickness of about 100 to 1000 μm is provided as an elastic layer on the contact surface with the fixing belt 21, and a PTFE (polytetrafluoroethylene) sheet is provided as a release layer on the surface of the silicon rubber layer. It is pasted.

  As a configuration of the belt support member 22 used in the present embodiment, for example, a silicon plate having a thickness of 500 μm is formed on a surface of a rectangular parallelepiped stainless steel (SUS) plate member having a width of 11 mm and a length of 300 mm facing the fixing belt 21. A rubber layer (elastic layer) is laminated, and a PTFE sheet (release layer) is further adhered to the rising portion of the opposing surface. A hollow belt support member 22 formed by bending a thin metal plate may be used.

  The pressure roller 23 is provided with an elastic layer 23b on the outer side of the cored bar 23a, for example. A pressure adjusting mechanism (not shown) for adjusting the pressure of the pressure roller 23 is disposed on the cored bar 23a. As a configuration of the pressure roller 23, for example, a roller having an outer diameter of 35 mm in which a silicon rubber layer 23b having a thickness of 7.5 mm constituting an elastic layer is provided on the outside of an aluminum core 23a having a diameter of 20 mm. It is done. The pressure roller 23 is driven to rotate clockwise by a drive motor (not shown). The surface of the pressure roller 23 may be covered with a release layer such as a PFA tube.

  The induction heating unit 25 heats the fixing belt 21 by electromagnetic induction. The induction heating unit 25 includes a coil bobbin 27, an induction heating coil 29, a core unit including a center core 30a, an arch core 30b, and a side core 30c. It arrange | positions facing so that a part of arc-shaped outer surface may be enclosed.

  The coil bobbin 27 is formed in a circular arc shape along the outer surface of the fixing belt 21. The material of the coil bobbin 27 is preferably a heat-resistant resin (for example, PPS: polyphenylene sulfide resin, PET: polyethylene terephthalate resin, LCP: liquid crystal polymer resin).

  On the coil bobbin 27, an induction heating coil 29 in which the litz wire 28 is wound a plurality of times (here, 8 times) in the longitudinal direction of the induction heating unit 25 (perpendicular to the paper surface of FIG. 2) is arranged. The induction heating coil 29 is connected to a power source (not shown). The induction heating coil 29 is fixed to the coil bobbin 27 using a heat-resistant adhesive (for example, a silicon-based adhesive).

  The litz wire 28 is obtained by bundling and twisting a plurality of thin wires (conductive wires) with an enamel layer, and further coating the outer side of the enamel layer with a fusion layer. The number of thin wires is adjusted according to the voltage of the power source connected to the litz wire 28. For example, when the voltage is 100V, a litz wire 28 having a diameter of 3.3 mm obtained by twisting 150 fine wires is used. When the voltage is 200V, a litz wire having a diameter of 1.7 to 1.8 mm obtained by twisting 75 fine wires is used. Line 28 is used.

  The center core 30 a is a ferrite core having a rectangular cross section disposed inside the induction heating coil 29. Here, the center core 30 a is disposed at both longitudinal ends of the coil bobbin 27. A plurality of pairs of arch cores 30b and a pair of side cores 30c are arranged on both sides of the center core 30a. The arch cores 30b on both sides are ferrite cores having symmetrical shapes with respect to the center core 30a and having a cross-sectional shape formed into an arch shape. The total length of each arch core 30b is longer than the region where the induction heating coil 29 is disposed. The side cores 30c on both sides are ferrite cores formed in a block shape. The side core 30c is connected to one end (upper and lower ends in FIG. 2) of each arch core 30b. Each side core 30c covers the outside of the region where the induction heating coil 29 is disposed.

  The arch core 30b is arrange | positioned in multiple places at intervals in the longitudinal direction of the induction heating part 25, for example. In the present embodiment, the interval between adjacent arch cores 30b is about 10 mm. Further, the higher the arrangement density of the arch cores 30b, the better the magnetic flux induction performance. However, even if the arrangement density of the arch cores 30b is reduced to some extent, the decrease in magnetic flux induction performance is small. Therefore, it is preferable to set the arrangement density of the arch cores 30b so that high cost performance can be obtained within a range where sufficient performance can be exhibited. Further, when adjusting the temperature distribution in the width direction of the fixing belt 21, it can be dealt with by adjusting the arrangement density of the arch cores 30 b.

  Moreover, the side core 30c is divided | segmented into plurality in the longitudinal direction of the induction heating part 25, The length of one is about 30-60 mm. The plurality of side cores 30c are continuously arranged in the longitudinal direction of the induction heating unit 25 without being spaced apart. The total length of the range in which the side core 30c is disposed corresponds to the length of the region in which the induction heating coil 29 is disposed. Thus, by arranging a plurality of side cores 30c continuously, there is an effect of equalizing the fluctuation width of the temperature distribution due to the arrangement of the arch core 30b. In addition, arrangement | positioning of each arch core 30b and the side core 30c is determined according to the magnetic flux density (magnetic field strength) distribution of the induction heating coil 29, for example. Since the arch core 30b is arranged at a certain distance, the side core 30c compensates for the effect of converging the magnetic flux at the location where the arch core 30b is removed, and leveles the magnetic flux density distribution (temperature distribution) in the longitudinal direction.

  The induction heating unit 25 generates a magnetic flux through the center core 30a, the arch cores 30b and the side cores 30c on both sides by supplying a high frequency current to the induction heating coil 29. The magnetic flux generated from the induction heating unit 25 acts on the induction heating layer of the fixing belt 21. As a result, an eddy current is generated around the magnetic flux of the induction heat generation layer, so Joule heat is generated by the electric resistance of the induction heat generation layer, and the fixing belt 21 generates heat.

  The current flowing through the induction heating coil 29 is controlled by the thermistor so that the fixing belt 21 has a predetermined temperature. Then, after the fixing belt 21 is heated by the induction heating unit 25 and heated to a predetermined temperature, the paper P (see FIG. 1) conveyed while being nipped by the fixing nip N is heated and pressurized. By being pressurized by the roller 23, the powdery toner on the paper P is melted and fixed on the paper P.

  As shown in FIG. 3, when the induction heating coil 29 is viewed in a plan view, the width w <b> 1 of the turn part 29 b located at both ends of the induction heating part 25 is a straight line parallel to the longitudinal direction of the induction heating part 25. It is narrower than the width w2 of the portion 29a. With this configuration, the ratio of the linear portion 29a in the longitudinal direction of the induction heating coil 29 is increased, and the fixing belt 21 has a length in the longitudinal direction substantially equal to the width in the fixing belt 21. The ratio of the straight portions 29a facing in the width direction also increases.

  Therefore, without increasing the longitudinal dimension of the induction heating coil 29, the linear portion 29a that generates a larger magnetic flux than the turn portion 29b can be widely used for heating the fixing belt 21, and the width direction of the fixing belt 21 can be increased. The entire area can be efficiently and uniformly heated, and the occurrence of fixing temperature unevenness and energy loss can be suppressed.

  4 is an exploded perspective view of the cartridge 40 for manufacturing the induction heating coil 29, and FIG. 5 is a side view of the cartridge 40 as viewed from the end side in the longitudinal direction. The cartridge 40 includes a tray-like first cartridge 41 and a second cartridge 43 that overlaps the first cartridge 41 at a predetermined interval. The first cartridge 41 and the second cartridge 43 are made of metal such as aluminum, for example.

  The first cartridge 41 has a concave surface 41a curved in an arc shape when viewed from the end in the longitudinal direction, and an elongated core portion 45 around which a litz wire is wound is formed in the longitudinal direction at the bottom of the concave surface 41a. It is formed in a rib shape along. Two bosses 47 projecting upward are formed on the core portion 45. A thread is cut on the outer peripheral surface of the boss 47.

  The second cartridge 43 has a convex surface 43a curved in an arc shape when viewed from the end in the longitudinal direction, and a boss hole 48 is formed at a position corresponding to the boss 47 at the top of the convex surface 43a. By causing the concave surface 41a of the first cartridge 41 and the convex surface 43a of the second cartridge 43 to face each other, the two bosses 47 are fitted into the boss holes 48, and the nuts 49 are screwed into the threads of the bosses 47. As shown in FIG. 4, a coil guide portion 50 having a circular arc cross section is formed between the concave surface 41a and the convex surface 43a. The interval h1 of the coil guide portion 50 at the end of the cartridge 40 is wider than the interval h2 of the coil guide portion 50 on the side surface in the longitudinal direction of the cartridge 40.

  If the ratio between the distances h1 and h2 is too small, the width w1 of the turn part 29b of the induction heating coil 29 cannot be sufficiently narrowed. On the other hand, if the ratio between the distances h1 and h2 is too large, it is difficult to align and wind the litz wire 28 and the workability is lowered. Therefore, it is preferable that h1 is about 1.1 to 1.2 times as large as h2. For example, when h2 is 3 mm, h1 is adjusted to 3.4 to 3.5 mm.

  In addition, inclined surfaces 41b and 43b are formed at both longitudinal ends of the first cartridge 41 and the second cartridge 43, respectively. When the litz wire 28 is wound around the core 45, the litz wire 28 is guided to the coil guide portion 50 along the inclined surfaces 41b and 43b, so that the litz wire 28 can be smoothly wound. .

  Next, a method for manufacturing the induction heating coil 29 using the cartridge 40 will be described. First, the litz wire 28 is unwound from a reel (not shown) around which the litz wire 28 is wound, and is set along the core 45, so that the leading end on the winding start side protrudes from the cartridge 40 by a predetermined length. To do. Next, while applying a predetermined tension to the litz wire 28, the litz wire 28 is wound a predetermined number of times (for example, eight times).

  6 is a side sectional view of the cartridge 40 wound with the induction heating coil 29 cut perpendicularly to the longitudinal direction. FIG. 7 shows the end of the cartridge 40 with the induction heating coil 29 wound in the longitudinal direction. It is side surface sectional drawing cut | disconnected with respect to parallel. As shown in FIG. 6, the interval h <b> 2 of the coil guide portion 50 in the center portion in the longitudinal direction of the cartridge 40 is narrower than twice the diameter of the litz wire 28 constituting the induction heating coil 29. Therefore, when the litz wire 28 is wound around the core 45, the litz wire 28 is laminated in a zigzag manner in the linear portion 29a of the induction heating coil 29, and the litz wires 28 that contact the concave surface 41a and the convex surface 43a are contacted. The litz wires 28 are separated from each other.

  On the other hand, the distance h 1 between the coil guide portions 50 at both longitudinal ends of the cartridge 40 is approximately twice the diameter of the litz wire 28 that constitutes the induction heating coil 29. Therefore, when the litz wire 28 is wound around the core portion 45, the litz wire 28 is laminated in two layers at the turn portion 29b of the induction heating coil 29 and contacts the concave surface 41a as shown in FIG. 28 and the litz wires 28 in contact with the convex surface 43a are in close contact with each other. That is, the litz wire 28 is wound more densely in the turn portion 29b than in the straight portion 29a.

  Thereby, the litz wire 28 is sequentially wound from the back side of the coil guide portion 50 along the already wound litz wire 28, and the induction heating coil 29 having a circular arc cross section is formed along the coil guide portion 50. Rolled up. Then, while holding the wound induction heating coil 29 so as not to loosen, by cutting the reel side of the litz wire 28 so as to protrude from the cartridge 40 by a predetermined length, the winding start side of the litz wire 28, Then, both ends on the winding end side protrude from the cartridge 40. Terminals are attached to both ends of the litz wire 28.

  Next, as shown in FIG. 8, the litz wire pressing member 51 is inserted into the coil guide portion 50 from the side surface in the longitudinal direction of the cartridge 40. As a result, the litz wire 28 is compressed in the coil guide portion 50, the cross-sectional shape changes from a circular shape to a quadrangular shape, and the adjacent litz wires 28 come into close contact with each other. Further, since the pressing force of the litz wire pressing member 51 is applied to the litz wire at both ends in the longitudinal direction of the cartridge 40, the cross-sectional shape of the litz wire 28 changes from a circular shape to a square shape, and the adjacent litz wires 28 are in close contact with each other. To do.

  In this state, when a current is passed through the induction heating coil 29 via the terminals attached to both ends of the litz wire 28, the litz wire 28 self-heats to melt the surface fusion layer. Then, when the induction heating coil 29 is cooled by cutting off the current after a certain time has elapsed, the fusion layer is solidified again, and the shape of the induction heating coil 29 is fixed.

  The induction heating coil 29 having a fixed shape can be removed from the core portion 45 by loosening the nut 49 and removing the second cartridge 43. FIG. 9 is a side cross-sectional view of the cartridge 40 from which the second cartridge 43 has been removed, cut perpendicularly to the longitudinal direction. FIG. 10 shows the end of the cartridge 40 from which the second cartridge 43 has been removed parallel to the longitudinal direction. It is side surface sectional drawing cut | disconnected by. The thickness a of the turn portion 29b of the induction heating coil 29 is substantially equal to the interval h1 of the coil guide portion 50, and the thickness b of the straight portion 29a is substantially equal to the interval h2 of the coil guide portion 50. Further, the width w1 of the turn part 29b is narrower than the width w2 of the straight part 29a.

  The induction heating coil 29 removed from the cartridge 40 is attached to a coil bobbin 27 (see FIG. 2) that constitutes the induction heating unit 25. Here, since the curvature of the coil guide portion 50 is substantially the same as the curvature of the coil bobbin 27, the induction heating coil 29 corresponding to the shape of the coil bobbin 27 can be easily manufactured.

  In the above procedure, the litz wire pressing member 51 is inserted into the coil guide portion 50 from the side surface in the longitudinal direction of the cartridge 40. However, the litz wire pressing member 51 may be further inserted from both ends in the longitudinal direction of the cartridge 40. . In this case, although the process of inserting the litz wire pressing member 51 is increased, the litz wires 28 of the turn portion 29b are securely adhered to each other, and therefore the induction heating coil 29 having a narrower width w1 of the turn portion 29b can be manufactured. it can.

  In addition, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the meaning of this invention. For example, the configuration of the fixing belt 21 and the pressure roller 23 shown in the above embodiment is a preferable example, and other configurations capable of achieving the object of the present invention can also be adopted. In the above-described embodiment, the induction heating coil 29 manufactured by the cartridge 40 of the present invention is described as an example in which the induction heating unit 25 is used for the belt fixing method in which the induction heating layer of the fixing belt 21 is heated. The present invention can be similarly applied to a heat roller fixing method in which a heating roller having an induction heating layer is provided instead of the belt 21.

  In the above embodiment, the core portion 45 is provided at the bottom of the concave surface 41 a of the first cartridge 41, but the core portion 45 may be provided at the top of the convex surface 43 a of the second cartridge 43. Further, as a coupling means for coupling or uncoupling the first cartridge 41 and the second cartridge 43, in addition to using a boss 47 and a nut 49 formed with threads, other coupling means such as bolts and clamps are used. You can also.

  Further, the induction heating coil 29 manufactured using the cartridge 40 of the present invention is not limited to the tandem color printer shown in FIG. 1, but is a digital multifunction machine, a color copying machine, an analog monochrome copying machine, or a monochrome printing machine. The present invention can be applied to the induction heating unit 25 of the fixing device 13 of various image forming apparatuses using an electrophotographic process such as a printer or a facsimile.

  INDUSTRIAL APPLICABILITY The present invention can be used for manufacturing an induction heating coil used in an induction heating portion of a fixing device of a heat roller fixing method or a belt fixing method. By using the present invention, an induction heating coil having a narrow turn portion and a small energy loss can be manufactured easily and at low cost.

13 Fixing device 21 Fixing belt (heating member)
22 belt support member 23 pressure roller 25 induction heating part 27 coil bobbin 28 litz wire 29 induction heating coil 29a linear part 29b turn part 30a center core 30b arch core 30c side core 40 cartridge 41 first cartridge 41a concave surface 43 second cartridge 43a convex surface 41b, 43b Inclined surface 45 Core part 47 Boss (coupling means)
48 Boss hole (joining means)
49 Nut (coupling means)
50 Coil guide part 51 Litz wire holding member 100 Color printer

Claims (6)

A first cartridge having a concave surface curved in an arc shape when viewed from the end in the longitudinal direction;
A second cartridge that is detachable from the first cartridge and has an arcuate convex surface facing the concave surface at a predetermined interval;
A core part formed on either the bottom of the concave surface or the top of the convex surface and wound with a litz wire;
A coil guide portion having a circular arc cross section formed by the concave surface and the convex surface on the outer side in the circumferential direction of the core portion;
A coupling means for coupling or uncoupling the first cartridge and the second cartridge via the winding core portion;
The distance h1 between the coil guide portions at both longitudinal ends of the first cartridge and the second cartridge is substantially twice the diameter of the litz wire, and the side surfaces of the first cartridge and the second cartridge in the longitudinal direction. The interval h2 between the coil guide portions in is smaller than twice the diameter of the litz wire,
The h1 and h2 are coil manufacturing cartridges that are constant in a cross-sectional direction of the coil guide portion orthogonal to the winding direction of the litz wire .   2. The coil manufacturing cartridge according to claim 1, wherein h1 / h2 is 1.1 to 1.2.   The coupling means includes a boss projecting from the upper surface of the winding core portion and having a thread formed on the outer peripheral surface thereof, a boss hole formed on the concave surface or the convex surface facing the boss and into which the boss is fitted, 3. The coil manufacturing cartridge according to claim 1, further comprising: a nut screwed into a thread of the boss protruding through a boss hole.   An inclined surface in a direction in which the concave surface and the convex surface are separated from each other toward the outer side in the circumferential direction of the core portion is formed at both longitudinal ends of the first cartridge and the second cartridge. The coil manufacturing cartridge according to any one of claims 1 to 3.   An induction heating coil manufactured using the coil manufacturing cartridge according to any one of claims 1 to 4, wherein the first cartridge and the induction cartridge when viewed from a direction perpendicular to the concave surface and the convex surface An induction heating coil in which a coil width of a turn portion formed at both longitudinal ends of the second cartridge is narrower than a coil width of a straight portion formed along the longitudinal direction of the first cartridge and the second cartridge.   A fixing device comprising an induction heating unit that generates a magnetic flux by causing an electric current to flow through the induction heating coil according to claim 5 and that induction-heats an induction heating layer provided on a heating member by the magnetic flux.

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