JP5441772B2 - Image heating device - Google Patents

Description

  The present invention relates to an image fixing device mounted on an image forming apparatus such as a copying machine, a facsimile machine, a printer, or a multi-function machine for forming an image on a recording material by an appropriate image forming process such as an electrophotographic system or an electrostatic recording system. The present invention relates to an image heating apparatus of an electromagnetic induction heating method suitable for use as an apparatus.

  As an image heating device, there is a fixing device that heats an unfixed image on a recording material to fix or presuppose it as a fixed image, and a gloss increasing device that increases the gloss of the image by heating the image fixed on the recording material. Can be mentioned. In addition, an image heating apparatus for drying ink in an image forming apparatus that forms an image with a liquid containing a dye or a pigment, such as an ink jet method, can be used.

  As an electromagnetic induction heating type fixing device, an exciting coil that generates a magnetic field (magnetic flux) by applying a high-frequency current, a fixing roller that generates heat by the action of the magnetic field, and pressurization that forms a nip portion in contact with the fixing roller And a roller are known. The recording material carrying the unfixed toner image is nipped and conveyed at the nip portion, whereby the toner image is heated and fixed on the recording material. According to the electromagnetic induction heating type fixing device, an induction current (eddy current) is generated in the conductive layer (electromagnetic induction heating element) of the fixing roller by applying a magnetic field to the fixing roller, and due to the skin resistance of the fixing roller itself. The fixing roller itself generates Joule heat. For this reason, it is possible to shorten the warm-up time from the start of energization to the exciting coil until the time when the fixing roller is heated to the fixable temperature.

  As an arrangement of the exciting coils in such an electromagnetic induction heating type fixing device, there is one in which a plurality of coils are arranged along the entire circumference of the fixing roller so as to generate heat over the entire circumference of the fixing roller. Patent Document 1 proposes a heat generating device provided with magnetic flux generating means inside a roller body. The magnetic flux generating means includes an iron core, a holding frame made of a non-magnetic material that is disposed outside the iron core and extends in the axial direction of the roller body, and a plurality of guides wound around the outer circumference of the holding frame at intervals. And a coil. The mechanical strength of the magnetic flux generating means itself is secured by providing an insulating spacer between the iron core and the induction coil. In addition, by providing insulating spacers between a plurality of induction coils, it is possible to maintain the necessary spacing between adjacent induction coils, so that there is no cancellation of the magnetic flux generated between each other, and the surface temperature of the rotating roller body To avoid the decline.

JP 2000-277246 A

  In the electromagnetic induction heating type fixing device, in order to secure the heat generation efficiency of the fixing roller, not only the iron core (magnetic core) and the exciting coil wound around the iron core but also the exciting coil and the fixing roller are made as close as possible and fixed. It is necessary to keep the distance.

  An object of the present invention is to provide an image heating apparatus capable of maintaining a constant creepage distance for ensuring insulation of a coil from a heating rotator so that the coil and a magnetic core can be brought close to each other.

  In order to achieve the above object, the image heating apparatus according to the present invention includes a cylindrical heating rotator that generates heat by the action of magnetic flux, and a heating rotator that is disposed inside the heating rotator and generates magnetic flux. An image heating apparatus for heating an image carried by a recording material by heat of the heating rotator, wherein the magnetic flux generation means includes a plurality of magnetic cores and a plurality of the magnetic materials. A core holder for holding the body core along the axial direction of the heating rotator, and two coil holders having a semi-cylindrical shape combined in a cylindrical shape, and arranged in a non-contact manner inside the heating rotator Two coil holders and two coils that generate magnetic flux, and two semicircular coils disposed in each of the two coil holders along the axial direction of the heating rotator. , Each of the two coil holders has a coil locking portion on the inner surface of each end portion in the circumferential direction of the semi-cylindrical shape, and the coil locking portion holds the both ends in the circumferential direction of the coil so that the coil is engaged with the coil. It is pressed against the inner surface in the circumferential direction between the stoppers, and is combined with the core holder at both ends of the semi-cylindrical shape in the circumferential direction, and the core holder is combined in a cylindrical shape. A plurality of the magnetic cores are held inside the one coil holder with a certain gap from the two coils.

  ADVANTAGE OF THE INVENTION According to this invention, the creeping distance for ensuring the insulation from the heating rotary body of a coil can be kept constant, and the image heating apparatus which enabled the coil and the magnetic body core to adjoin can be provided.

Configuration schematic diagram of an example of an image forming apparatus Cross-sectional schematic diagram of fixing roller and pressure roller of fixing device Schematic cross-sectional view of coil unit installed inside fixing roller and fixing roller (A) is an external perspective view of a core holder holding a plurality of magnetic cores, (b) is an external perspective view from the opening side of an IH holder holding an exciting coil. (A) is an external perspective view when a core holder holding a plurality of magnetic cores and an IH holder holding an exciting coil are coupled, and (b) is an opening side of an IH holder cover holding an exciting coil. Appearance perspective view from External perspective view of coil unit

[Example 1]
(1) Example of Image Forming Apparatus FIG. 1 is a schematic configuration diagram of an example of an image forming apparatus in which the image heating apparatus according to the present invention is mounted as an image fixing apparatus. This image forming apparatus is an electrophotographic color printer.

  The image forming apparatus shown in the first embodiment has four colors different in color depending on the first, second, third, and fourth image forming units Py, Pm, Pc, and Pb arranged in parallel in the image forming apparatus. The toner image can be formed through charging, exposure, development and transfer processes.

  In the image forming apparatus according to the first exemplary embodiment, the control unit 200 executes a predetermined image formation control sequence in response to a print command output from an external apparatus (not illustrated) such as a host computer or an external scanner. A predetermined image forming operation is performed according to the above. The control unit 200 includes a CPU and a memory such as a RAM and a ROM. The memory stores an image formation control sequence and various programs necessary for image formation. When the image forming control sequence is executed, the image forming units Py, Pm, Pc, and Pb are sequentially driven, and the photosensitive drum 1 as an image carrier is rotated at a predetermined peripheral speed (process speed) in the arrow direction. . The intermediate transfer belt 7 wound around the drive roller 6a, the secondary transfer counter roller 6b, and the tension roller 6c so as to straddle the photosensitive drum 1 of each image forming unit Py, Pm, Pc, Pb is moved in the direction of the arrow by the drive roller. The photosensitive drum 1 is rotated at a peripheral speed corresponding to the rotational peripheral speed. First, in the first color yellow image forming portion Py, the outer peripheral surface (surface) of the photosensitive drum 1 is uniformly charged by the charger 2 to a predetermined polarity and potential. Next, the exposure device 3 scans and exposes the charged surface on the surface of the photosensitive drum 1 with laser light corresponding to the image data from the external device. As a result, an electrostatic latent image corresponding to the image data is formed on the surface of the photosensitive drum 1. The electrostatic latent image (electrostatic image) is developed by the developing device 4 using yellow toner (developer), and a yellow toner image (development image) is formed on the surface of the photosensitive drum 1. The same steps of charging, exposure, and development are also performed in the second color magenta image forming portion Pm, the third color cyan image forming portion Pc, and the fourth color black image forming portion Pb. Each color toner image formed on the surface of the photosensitive drum 1 in each of the image forming portions Py, Pm, Pc, and Pb is a primary transfer roller 8 disposed so as to face each of the photosensitive drums 1 with the intermediate transfer belt 7 interposed therebetween. As a result, the toner images are sequentially transferred onto the outer peripheral surface (front surface) of the intermediate transfer belt 7. As a result, a full-color toner image is formed on the surface of the intermediate transfer belt 7.

  On the other hand, the recording material P is sent from one of the two feeding cassettes 10 and 10 and is sent to the registration roller 14 through the conveying path 13a by the belt 12. Next, the recording material P is conveyed by the registration roller 14 to the secondary transfer nip portion Tn between the intermediate transfer belt 7 and the secondary transfer roller 15. The secondary transfer roller 15 is disposed so as to face the secondary transfer counter roller 6b with the intermediate transfer belt 7 interposed therebetween. The recording material P is nipped and conveyed by the intermediate transfer belt 7 and the secondary transfer roller 15 at the secondary transfer nip portion Tn. In this conveyance process, a full-color toner image on the surface of the intermediate transfer belt 7 is formed by the secondary transfer roller 15. Transferred onto the recording material P. This toner image is carried on the surface of the recording material P.

  The recording material P carrying an unfixed full-color toner image is introduced into an image fixing device (hereinafter referred to as a fixing device) 16. The recording material P is nipped and conveyed at a nip portion (described later) of the fixing device 16 and receives heat and pressure, whereby an unfixed full-color toner image is heated and fixed on the surface of the recording material P.

  When image formation is performed on one side of the recording material P, the recording material P exiting the fixing device 16 is guided to the discharge roller 18 side by the first flapper 17 a, and the discharge roller 18 discharges the recording material P to the discharge tray 19. When image formation is performed on both sides of the recording material P, the recording material P that has exited the fixing device 16 is introduced into the reverse conveying path 13b by the first flapper 17 and then conveyed rollers 19a and 19b that can be normally reversed by the second flapper 17b. Be guided to. The conveyance rollers 19a and 19b convey the recording material P to the reversing unit 13c. As a result, the recording material P is turned over. The recording material P conveyed to the reversing unit 13c is conveyed toward the third flapper 17c by the conveyance roller 19b, and the third flapper 17c guides the recording material P to the communication conveyance path 13d. Then, the recording material P is conveyed to the registration roller through the conveyance path 13a by the conveyance rollers 20a, 20b, and 20c in the communication conveyance path 13d, and a toner image is formed on the other side through the same process as the one-side image formation described above. Later, it is discharged to a discharge tray by a discharge roller. When the image forming surface (printing surface) on one side of the recording material P is on the lower side (face down), the recording material P exiting the fixing device 16 is introduced into the reverse conveyance path 13b by the first flapper 17 and then second. Guided by the flapper 17b toward the transport rollers 19a and 19b. The conveyance rollers 19a and 19b convey the recording material P to the reversing unit 13c. The recording material P conveyed to the reversing unit 13c and reversed upside down is conveyed toward the third flapper 17c by the conveying roller 19b, and the third flapper 17c guides the recording material P toward the discharge path 13e. The transport rollers 19 a and 19 b transport the recording material P to the discharge roller 18, and the discharge roller 18 discharges the recording material P to the discharge tray 19.

  After the toner image is transferred, the transfer residual toner remaining on the surface of the photosensitive drum 1 is removed by the drum cleaner 5 and used for the next image formation. After the transfer of the full-color toner image, the transfer residual toner remaining on the surface of the intermediate transfer belt 7 is removed by the belt cleaner 9 and used for the next image formation.

(2) Fixing Device In the following description, with respect to the fixing device and members constituting the fixing device, the longitudinal direction refers to a direction orthogonal to the recording material conveyance direction on the surface of the recording material. The short side direction is a direction parallel to the recording material conveyance direction on the surface of the recording material. The length is a dimension in the longitudinal direction. The width is a dimension in the short direction.

  FIG. 2 is a schematic cross-sectional view of the fixing roller and the pressure roller of the fixing device. This fixing device is an electromagnetic induction heating type fixing device.

  The fixing device 16 shown in the first embodiment includes a fixing roller 31 as a heating rotator, a pressure roller 32 as a backup member, and a coil unit 33 as a magnetic flux generating unit. The fixing roller 31, the pressure roller 32, and the coil unit 33 are all elongated in the longitudinal direction.

  The fixing roller 31 is obtained by coating a PFA tube as a release layer 31b on the outer peripheral surface of a long cylindrical (cylindrical) cored bar 31a made of high tension steel that generates heat by the action of magnetic flux. The fixing roller 31 is a cylindrical member having an outer diameter of 40.3 mm, an inner diameter of 37.9 mm, and a thickness of 1.2 mm. The fixing roller 31 is rotatably supported by a device frame (not shown) at both ends in the longitudinal direction of the cored bar 31a of the fixing roller 31 via bearings (not shown).

  The pressure roller 32 is formed by forming silicon rubber as an elastic layer 32b on the outer peripheral surface of a steel long metal core 32a having a diameter of 32 mm, and covering the PFA tube as a release layer 32c on the outer peripheral surface of the silicon rubber. is there. The outer diameter of the pressure roller 32 is 38 mm. The pressure roller 32 is disposed below the fixing roller 31 and in parallel with the fixing roller 31. Then, both ends in the longitudinal direction of the cored bar 32a of the pressure roller 32 are rotatably supported by the apparatus frame via bearings (not shown). A bearing supported by the apparatus frame so as to be movable up and down is pressed against the outer peripheral surface (surface) of the fixing roller 31 by a pressure spring with a pressure of 980 N (100 kgf). As a result, the outer peripheral surface (surface) of the pressure roller 32 comes into contact with the surface of the fixing roller 31 and the elastic layer 32b of the pressure roller 32 is elastically deformed, so that a predetermined width is provided between the surface of the pressure roller 32 and the surface of the fixing roller 31. A fixing nip portion (nip portion) N is formed.

(2-1) Configuration of Coil Unit The coil unit 33 includes a plurality of magnetic cores 34, a core holder 35, and two exciting coils 36a and 36b as two semi-cylindrical coil holders combined in a cylindrical shape. The IH holder 37a and the IH holder cover 37b are supported. The material of the core holder 35, the IH holder 37a, and the IH holder cover 37b is a liquid crystal polymer. Note that IH is an abbreviation for Induction Heating.

  As shown in FIGS. 3 and 4A, the plurality of magnetic cores 34 are each formed in a substantially square plate shape from a predetermined magnetic material. The number of magnetic cores 34 is ten.

  The core holder 35 has an elongated substrate portion 35 a in the longitudinal direction of the core holder 35. The board portion 35a is sized to fit with the opening Wa between the inner end surfaces of the circumferential end portions 37a3 and 37a3 of the IH holder and the opening Wb between the inner end portions of the circumferential end portions 37b3 and 37b3 of the IH holder cover. (Refer to FIG. 3, FIG. 4 (a), FIG. 5 (b)). The thickness of the substrate portion 35a is set to a predetermined thickness that allows the IH holder 37a and the IH holder cover 37b to be combined in a cylindrical shape. At approximately the center in the short direction of the substrate portion 35a, the core insertion hole 35b and the pair of core holding pieces 35c, 35c are provided in the same number as the number of the magnetic cores 34 along the longitudinal direction of the substrate portion 35a. The core insertion hole 35b penetrates in the thickness direction of the substrate portion 35a. The core holding pieces 35c and 35c are provided so as to protrude in the thickness direction of the substrate portion 35a on the front and back surfaces in the thickness direction of the substrate portion 35a. The core holding pieces 35c and 35c oppose each other through a gap having the same width as the opening width of the core insertion portion 35b in the short direction of the substrate portion 35a. The same number of magnetic cores 34 as the number of magnetic cores 34 are inserted from the core holding pieces 35c, 35c corresponding to the core insertion holes 35b one by one. As shown in FIG. 3, the magnetic core 34 inserted into each core insertion hole 35b is held in a state where it protrudes by a predetermined amount from the free ends of the core holding pieces 35c and 35c on the front surface and the back surface of the substrate portion 35a. It is fitted between the pieces 35c, 35c (snap fit) and fixedly held. A plurality of locking claws (locking portions) 35d1 and 35d1 projecting in the short direction of the substrate portion 35a are provided at both ends in the short direction of the back surface of the substrate portion 35a along the longitudinal direction of the substrate portion 35a. . Further, at both ends in the short direction of the surface of the substrate portion 35a, locking claws (locking portions) projecting toward the short direction of the substrate portion 35a at positions that do not overlap the locking claws 35d1 in the longitudinal direction of the substrate portion 35a. Part) 35d2 and 35d2 are provided in plural along the longitudinal direction of the substrate part 35a. On the inner side of both ends in the short direction of the back surface of the substrate portion 35a, substantially fan-shaped coil holding ribs 35e1 and 35e1 projecting in the radial direction of the IH holder 37a between the core holding pieces 35c adjacent in the longitudinal direction of the substrate portion. A plurality of substrates are provided along the longitudinal direction of the substrate portion (see FIG. 3). In addition, the substantially fan-shaped coil pressing ribs 35e1 projecting in the radial direction of the IH holder cover 37b between the core holding pieces 35c adjacent to each other in the longitudinal direction of the substrate portion also inside the both ends in the short direction of the surface of the substrate portion 35a. A plurality of 35e1 are provided along the longitudinal direction of the substrate portion (see FIG. 3).

  The IH holder 37a and the IH holder cover 37b are formed such that the outer diameter when the IH holder 37a and the IH holder cover 37b are combined in a cylindrical shape is smaller than the inner diameter of the core 31a of the fixing roller 31. In the first embodiment, the outer diameter when the IH holder 37a and the IH holder cover 37b are combined in a cylindrical shape is 32.4 mm.

  As shown in FIG. 4B, the IH holder 37a has screw fixing portions 37a1 and 37a1 at both longitudinal ends of the IH holder 37a, and a coil housing portion 37a2 between the screw fixing portions 37a1 and 37a1. Have. A plurality of locking claws (locking portions) 37a4 and 37a4 projecting inward of the coil housing portion 37a2 are provided along the longitudinal direction of the coil housing portion 37a2 at both circumferential ends 37a3 and 37a3 of the coil housing portion 37a2. (See FIGS. 3 and 4B). The plurality of locking claws 37a4 and 37a4 are provided at positions overlapping with the locking claws 35d1 and 35d1 on the back surface of the substrate portion 35a of the core holder 35 in the longitudinal direction of the coil housing portion 37a2. Further, coil locking claws (coil locking portions) 37a5 and 37a5 projecting inward of the coil housing portion are provided on the inner surfaces of the end portions 37a3 and 37a3 in the circumferential direction of the coil housing portion 37a2 in the longitudinal direction of the coil housing portion. (See FIG. 3 and FIG. 4B). The plurality of coil locking claws 37a5 and 37a5 are provided at positions that do not overlap the locking claws 37a4 and 37a4 in the longitudinal direction of the coil housing portion 37a2. At substantially the center of the arc-shaped inner surface 37a6 (see FIG. 3) between the coil locking claws 37a5 and 37a5 of the coil housing portion 37a2, there are core holding portions 37a7 along with the number of the magnetic cores 34 along the longitudinal direction of the coil housing portion 37a2. The same number is provided. The core holding part 37a7 has a frame shape that can hold the end of the magnetic core 34 projecting a predetermined amount from the free ends of the core holding pieces 35c and 35c together with the free ends of the core holding pieces 35c and 35c on the back surface of the substrate part 35a. It is formed.

  As shown in FIG. 5 (b), the IH holder cover 37b has screw fixing portions 37b1 and 37b1 at both longitudinal ends of the IH holder cover 37b, and a coil housing portion between the screw fixing portions 37b1 and 37b1. 37b2. A plurality of locking claws (locking portions) 37b4 and 37b4 projecting inward of the coil housing portion 37b2 are provided along the longitudinal direction of the coil housing portion 37b2 at both circumferential ends 37b3 and 37b3 of the coil housing portion 37b2. (See FIGS. 3 and 5B). The plurality of locking claws 37b4 and 37b4 are provided at positions that overlap with the locking claws 35d2 and 35d2 on the surface of the substrate portion 35a of the core holder 35 in the longitudinal direction of the coil housing portion 37b2. Further, coil locking claws (coil locking portions) 37b5 and 37b5 projecting toward the inside of the coil housing portion are provided on the inner surfaces of the end portions 37b3 and 37b3 in the circumferential direction of the coil housing portion 37b2 in the longitudinal direction of the coil housing portion. (See FIG. 3 and FIG. 5B). The plurality of coil locking claws 37b5 and 37b5 are provided at positions that do not overlap the locking claws 37b4 and 37b4 in the longitudinal direction of the coil housing portion 37b2. At substantially the center of the arc-shaped inner surface 37b6 (see FIG. 3) between the coil locking claws 37b5 and 37b5 of the coil housing part 37b2, there are core holding parts 37b7 along the longitudinal direction of the coil housing part 37a2. The same number is provided. The core holding portion 37b7 has a frame shape that can hold the end portion of the magnetic core 34 protruding from the free ends of the core holding pieces 35c and 35c on the back surface of the substrate portion 35a together with the free ends of the core holding pieces 35c and 35c. It is formed.

  The two exciting coils 36a and 36b are each substantially half-turned along the arc-shaped inner surfaces 37a5 and 37b5 of the coil housing portions by winding a thin wire of φ0.1 to 0.3 mm a predetermined number of times in the longitudinal direction of the coil housing portions 37a2 and 37b2. It is formed into a circular shape. The lengths of the exciting coils 36a and 36b are equal to the lengths in the coil housing portions 37a2 and 37b2. The circumferential dimensions of the arc-shaped outer surfaces 36a1, 36b1 (see FIG. 3) of the exciting coils 36a, 36b are slightly larger than the circumferential dimensions of the arc-shaped inner surfaces 37a5, 37b5 of the coil housing portions 37a2, 37b2.

  Of the two exciting coils 36a and 36b, one exciting coil 36a is accommodated in the coil accommodating portion 37a2 of the IH holder 37a along the axial direction of the fixing roller 31 (see FIG. 4B). When the exciting coil 36a is accommodated in the coil accommodating portion 37a2, the exciting coil 36a is pushed from the opening Wa toward the arc-shaped inner surface 37a6 so that the core holding portion 37a7 of the coil accommodating portion 37a2 is exposed. Then, the coil locking claws 37a5 and 37a5 of the coil housing portion 37a2 are locked to the end upper surfaces 36a2 and 36a2 (see FIG. 3) at both ends in the circumferential direction of the exciting coil 36a and hold both ends in the circumferential direction of the exciting coil 36a. . When the coil locking claws 37a5 and 37a5 are locked to both ends of the exciting coil 36a in the circumferential direction, the thin wires of the exciting coil 36a are densely packed inward in the circumferential direction along the arcuate inner surface 37a6 of the coil housing portion 37a2. Thus, the exciting coil 36a is in close contact with the arcuate outer surface 36a1 of the exciting coil 36a pressed against the arcuate inner surfaces (circumferential inner surfaces) 37a6 between the coil locking claws 37a5 and 37a5 of the coil accommodating portion 37a2. It is stored in 37a2.

  The other exciting coil 36b is accommodated in the coil accommodating portion 37b2 of the IH holder cover 37b along the axial direction of the fixing roller 31 (see FIG. 5B). When the exciting coil 36b is accommodated in the coil accommodating portion 37b2, the exciting coil 36b is pushed from the opening Wb toward the arc-shaped inner surface 37b6 so that the core holding portion 37b6 of the coil accommodating portion 37b2 is exposed. Then, the coil locking claws 37b5 and 37b5 of the coil accommodating portion 37b2 are locked to the end upper surfaces 36b2 and 36b2 (see FIG. 3) at both ends in the circumferential direction of the exciting coil 36b and hold both ends in the circumferential direction of the exciting coil 36b. . When the coil locking claws 37b5 and 37b5 are locked to both ends in the circumferential direction of the exciting coil 36b, the thin wires of the exciting coil 36b are densely packed in the circumferential direction along the arcuate inner surface 37b6 of the coil housing portion 37b2. As a result, the exciting coil 36b is in close contact with the arcuate outer surface 36b1 of the exciting coil 36b pressed against the arcuate inner surface (circumferential inner surface) 37b6 between the coil locking claws 37b5 and 37b5 of the coil accommodating portion 37b2. It is stored in the part 37a2.

  A core holder 35 holding a plurality of magnetic cores 34 is attached to the IH holder 37a in which the exciting coil 36a is housed in the coil housing portion 37a2. When the core holder 35 is attached to the coil housing portion 37a2 of the IH holder 37a, the back surface of the substrate portion 35a of the core holder 35 is opposed to the coil housing portion 37a2 directly above the opening Wa of the coil housing portion 37a2. And this core holder 35 is pushed down toward the coil accommodating part 37a2. Then, the latching claws 35d2 and 35d2 at both ends in the short direction of the back surface of the substrate portion 35a of the core holder 35 get over the latching claws 37a4 and 37a4 at both circumferential ends of the coil housing portion 37a2, and the latching claws 37a4 and 37a4. Lock (see FIG. 3). Thereby, the core holder 35 is integrally coupled to the coil housing portion 37a2 of the IH holder 37a (see FIG. 5A). When the core holder 35 and the coil housing portion 37a2 are coupled in this manner, the coil holding ribs 35e1 and 35e1 of the core holder can be used to press the exciting coil 36a in the coil housing portion so as to be in close contact with the arc-shaped inner surface 37a6 of the coil housing portion. it can.

  An IH holder cover 37b is attached to the core holder 35 coupled to the coil housing portion 37a2 of the IH holder 37a. When the core holder 35 is attached to the IH holder cover 37b, the coil housing portion 37a2 side of the IH holder cover 37b faces the surface of the substrate portion 35a of the core holder 35 directly above the surface of the substrate portion 35a. Then, the IH holder cover 37 b is pushed down toward the surface of the substrate portion 35 a of the core holder 35. Then, the locking claws 37b4 and 37b4 at both ends in the circumferential direction of the IH holder cover 37b get over the locking claws 35d1 and 35d1 at both ends in the short direction on the surface of the substrate portion 35a of the core holder 35, and the locking claws 35d1 and 35d1. Lock (see FIG. 3). As a result, the IH holder cover 37b is integrally coupled to the core holder 35 by the coil accommodating portion 37a2 of the IH holder cover 37b. That is, the IH holder 37a and the IH holder cover 37b are coupled to the core holder 35 at the circumferential end portions 37a3, 37a3, 37b3, and 37b3, respectively, and are combined in a cylindrical shape (see FIG. 6). When the coil housing portion 37a2 and the core holder 35 are coupled in this way, the exciting coil 36b in the coil housing portion can be pressed against the arc-shaped inner surface 37b6 by the coil holding ribs 35e1 and 35e1 of the core holder.

  The IH holder 37a and the IH holder cover 37b combined in a cylindrical shape are connected to the screw fixing portions 37a1 and 37a1 of the IH holder and the screw fixing portions 37b1 and 37b1 of the IH holder cover by screws 38a and 38b (see FIG. 6). And integrated.

  In the coil unit 33 shown in the first embodiment, an IH holder 37a in which an exciting coil 36a is closely attached and an IH holder cover 37b in which an exciting coil 36b is closely attached are combined in a cylindrical shape. The core holder 35 serves to fix a plurality of magnetic cores 34 in the center of the IH holder 37a and the IH holder cover 37b by snap fitting in the longitudinal direction of the IH holder 37a and the IH holder cover 37b. I'm in charge. The core holder 35 is a main body for securing strength that prevents bending in the longitudinal direction and distortion in the radial direction with respect to the IH holder 37a and the IH holder cover 37b in which the core holder 35 itself is combined in a cylindrical shape. It also plays the role of stay.

  The width of the opening Wa of the IH holder 37 a and the opening Wb of the IH holder cover 37 b is set to be slightly smaller than the width of the substrate portion 35 a of the core holder 35. For this reason, when the IH holder cover 37b and the IH holder 37a are coupled to the core holder 35, respectively, the substrate portion 35a of the core holder has the circumferential end portions 37a3 and 37a3 of the IH holder and the circumferential end portions 37b3 of the IH holder cover. 37b3 is spread. Accordingly, the IH holder and the IH holder cover can be brought into close contact with the core holder 35 by the elasticity of both ends in the circumferential direction of the IH holder 37a and the IH holder cover 37b. As a result, the IH holder 37a and the IH holder cover 37b can be prevented from being lifted from the core holder 35 serving as the main stay, and the cylindrical diameter when the IH holder and the IH holder cover are combined becomes a desired diameter. I have to. In order to ensure the above-mentioned strength and the adhesion of the IH holder and the IH holder cover to the core holder, the excitation coil is completely covered with the IH holder and the IH holder cover, and the insulation of the excitation coil from the fixing roller is ensured. There is an effect of securing the creepage distance.

  The exciting coils 36a and 36b are basically in close contact with the inner circumferential surface of the coil housing portion with the coil locking claws of the IH holder and the IH holder cover being locked. In the first embodiment, the coil holding rib 35e1 is provided on the core holder 35 in order to help prevent the exciting coil from being displaced in the radial direction of the IH holder and the IH holder cover. In FIG. 3, the direction of the current flowing through the exciting coils 36a and 36b is set so that the right half of the exciting coils 36a and 36b is upward and the left half of the exciting coils 36a and 36b is downward. By setting the current flow direction in this way, magnetic fields J1 and J2 (see FIG. 2) as indicated by broken lines are generated via the magnetic core 34. Therefore, the magnetic field between the exciting coils 34 is not canceled and efficient heat generation can be performed.

  In the coil unit 33 of the first embodiment, the fixing roller 31 and the excitation coil 34 provided in the coil unit 33 are arranged close to each other, and the distance between the fixing roller 31 and the excitation coil 34 is kept constant. Therefore, the following configuration was adopted. The exciting coils 36a and 36b are disposed inside the IH holder 37a and the IH holder cover 37b, respectively. And the coil latching claws 37a5 and 37b5 projecting from the inside of the IH holder 37a and the IH holder cover 37b are latched to the end upper surfaces 36a2 and 36b2 at both ends in the circumferential direction of the exciting coils 36a and 36b. As a result, the exciting coils 36a and 36b are pressed against the inner surfaces of the IH holder 37a and the IH holder cover 37b, that is, the arc-shaped inner surfaces 37a6 and 37b6, and are brought into close contact with the arc-shaped inner surfaces. As a result, the distance (gap) Sa (see FIG. 3) between the upper end surface of both ends in the circumferential direction of the exciting coil 36a and the open end surface of both ends in the circumferential direction of the IH holder 37a can be kept constant. Further, the distance (gap) Sb (see FIG. 3) between the upper end surface of both ends in the circumferential direction of the exciting coil 36b and the open end surface of both circumferential ends of the IH holder cover 37b can be kept constant. That is, the exciting coils 36a and 36b are locked to the coil locking claws 37a5 and 37b5 of the IH holder 37a and the IH holder cover 37b, whereby the exciting coils can be brought into close contact with the IH holder and the IH holder cover. Further, the distance between the exciting coils 36a and 36b and the fixing roller 31 is secured, and the upper end surfaces of both end portions in the circumferential direction of the exciting coils 36a and 36b are opened from the opening end surfaces of both end portions in the circumferential direction of the IH holder and IH holder cover. Can also be set low. For this reason, the IH holder 37a and the IH holder cover 37b that accommodate the exciting coils 36a and 36b and are combined in a cylindrical shape have portions that are not in contact with the exciting coil, that is, locking claws 37a4 and 37b4 provided at both ends in the circumferential direction. Arise. By locking the core holder 35 that holds the magnetic core 34 at that portion, it is possible to increase the end strength of both ends in the circumferential direction of the IH holder 37a and the IH holder cover 37b. As a result, it is possible to prevent the open ends of the circumferential end portions of the IH holder 37a and the IH holder cover 37b from being opened or dented, and the IH holder and the IH holder cover can be firmly coupled via the core holder. Increases mechanical rigidity.

  The coil unit 33 according to the first embodiment is configured to cover the exciting coils 36a and 36b with an IH holder 37a and an IH holder cover 37b which are combined in a cylindrical shape and arranged in a non-contact manner inside the fixing roller 31. As a result, the creeping distance for ensuring the insulation of the exciting coils 36a and 36b from the fixing roller 31 can be kept constant. In addition, the magnetic core and the exciting coil can be brought close to each other by holding the magnetic core by the core holder at the center of the IH holder and the IH holder cover combined in a cylindrical shape. Therefore, the creeping distance between the fixing roller and the exciting coil can be secured while keeping the fixing roller and the exciting coil constant at a short distance (gap), so that the fixing roller can efficiently generate heat. In addition, since the core holder holding a plurality of magnetic cores is coupled to the IH holder and IH holder cover combined in a cylindrical shape, a dedicated spacer for securing a space between the plurality of exciting coils is not required, and assembly is possible. Can also be done easily. The magnetic flux cancellation between two exciting coils adjacent to each other in the radial direction of the IH holder combined with the two cylindrical shapes and the IH holder cover takes into account the arrangement method of the magnetic core and the direction of the current flowing through the exciting coil. I coped by doing. As a result, a temperature drop on the surface of the fixing roller can be prevented, and temperature unevenness on the surface of the fixing roller can be prevented.

(2-2) Heat Fixing Operation of Fixing Device The fixing device 16 according to the first embodiment rotationally drives a fixing motor (not shown) as a drive source in accordance with a print command, and the length of the cored bar 32a of the pressure roller 32. A drive gear (not shown) provided at the direction end is rotated in a predetermined direction. As a result, the pressure roller 32 rotates at a predetermined peripheral speed (process speed) in the direction of the arrow. The rotation of the pressure roller 32 is transmitted to the fixing roller 31 by the frictional force between the surface of the pressure roller 32 and the surface of the fixing roller 31 in the fixing nip portion N. As a result, the fixing roller 31 rotates in the arrow direction following the rotation of the pressure roller 32. An excitation circuit (not shown) supplies an alternating current to the excitation coils 36a and 36b of the coil unit 33 in accordance with the print signal. As a result, the exciting coils 36a and 36b generate an alternating magnetic flux, and the alternating magnetic flux is guided to the magnetic core 34 to generate an eddy current on the surface of the fixing roller 31. This eddy current generates Joule heat by the specific resistance of the fixing roller 31. That is, by supplying an alternating current to the exciting coils 36a and 36b, the fixing roller 31 enters an electromagnetic induction heat generation state. The temperature of the fixing roller 31 is detected by a thermistor (not shown) which is a temperature detection member. An output signal from the thermistor is captured by a control unit (not shown), and the control unit controls the excitation circuit based on the output signal so that the temperature of the fixing roller 31 maintains a predetermined fixing temperature (target temperature). In the first embodiment, the predetermined fixing temperature is set to 180 ° C. In a state where the fixing motor is driven to rotate and the fixing roller 31 is maintained at a predetermined fixing temperature, the recording material P carrying the unfixed toner image t is introduced into the fixing nip portion N (see FIG. 2). The recording material P is nipped between the surface of the fixing roller 31 and the surface of the pressure roller 32 at the fixing nip portion N, and is conveyed (nipped and conveyed) to that state. In this conveyance process, the toner image t is heated and fixed on the recording material P by receiving the heat of the fixing roller 31 and the nip pressure of the fixing nip portion N. The recording material P on which the toner image t has been heat-fixed is separated from the surface of the fixing roller 31 on the toner image carrying surface of the recording material P and discharged from the fixing nip portion N.

31: fixing roller, 33: coil unit, 34, magnetic core, 35: core holder, 35e1: coil holding rib, 36a, 36b: exciting coil, 37a: IH holder, 37a3: circumferential ends, 37a5: coil engagement Stopper, 37a6: Arc-shaped inner surface, 37b: IH holder cover, 37b3: Both ends in the circumferential direction, 37b5: Coil locking claw, 37b6: Arc-shaped inner surface, P: Recording material, t: Unfixed toner image

Claims (2)

A cylindrical heating rotator that generates heat by the action of magnetic flux, and a magnetic flux generating means that is disposed inside the heating rotator and generates magnetic flux and heats the heating rotator. In the image heating apparatus for heating the image carried by the recording material,
The magnetic flux generation means includes a plurality of magnetic cores, a core holder that holds the plurality of magnetic cores along the axial direction of the heating rotator, and two semi-cylindrical coil holders combined in a cylindrical shape. Two coil holders arranged in a non-contact manner inside the heating rotator and two coils for generating magnetic flux, each of the two coil holders along the axial direction of the heating rotator. Each of the two coil holders has a coil locking portion on the inner surface of each end portion in the circumferential direction of the semi-cylindrical shape, Both ends of the coil in the circumferential direction are held by stoppers, and the coil is pressed against the inner surface in the circumferential direction between the coil locking portions. The core holder holds a plurality of the magnetic cores with a certain gap from the two coils inside the two coil holders combined in a cylindrical shape. An image heating apparatus.   The core holder has ribs protruding in the radial direction of the two coil holders combined in a cylindrical shape, and the ribs press the two coils against the inner circumferential surface between the coil locking portions. The image heating apparatus according to claim 1.