JP3919296B2 - Image heating device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image heating apparatus applied to an image forming apparatus such as a copying machine and a printer, and more particularly to an apparatus that generates heat by a magnetic induction.
[0002]
[Prior art]
In recent years, a “magnetic induction heating type” fixing device has been devised in consideration of the first print time and sufficient pressure and temperature responsiveness.
[0003]
This magnetic induction heating type fixing device applies a high-frequency current to an excitation coil (wire ring, winding (coiled wire), field winding, field coil) and generates a magnetic material surface as a heating element by a generated high-frequency magnetic field. In the apparatus, heat generated by the skin current generated in the toner is directly applied to the toner.
[0004]
In such a fixing device, the heat transfer model is very simple (for example, magnetism generation → magnetic material heat generation → rubber layer heat transfer → toner melting), and the heat transfer response is determined by heating the film using a heating roller method or a ceramic heater. It is possible to remarkably improve compared with the method.
[0005]
In such a power supply apparatus that supplies power to a magnetic induction heating type fixing device, a voltage resonance type power supply that reduces switching loss and has high cost merit is used. In this voltage resonance type power supply, the manner of oscillation of the flyback voltage when the switching element is off is a condition for reducing the switching loss.
[0006]
Therefore, the magnetic material as the heating element and the exciting coil occupy most of the development in the matching, that is, the impedance matching. In such a situation, generally, a matching transformer or a matching coil is used for matching with the load impedance.
[0007]
[Problems to be solved by the invention]
The impedance matching of the switching element by the matching transformer of the conventional example is expected to match a good switching state in principle and in operation. However, the power to be handled in the present invention is a scale of power of 1100 W or more at the time of start-up, and when the matching transformer is actually designed, the size of the transformer is determined from the magnitude of the current to flow. A cube with one side exceeding 70 mm. When a transformer having such a size is mounted, the size of the transformer occupies almost half of the size of a power supply device configured to heat the fixing device. Moreover, the cost increase of such a transformer surpasses the component cost used in the switching circuit.
[0008]
Further, since the matching coil is provided in a different place as a member different from the exciting coil, it is necessary to design a storage space or the like for that purpose, and there is a problem that the apparatus configuration becomes complicated.
[0009]
An object of the present invention is to provide an image heating apparatus that reduces switching loss without complicating the apparatus.
[0010]
Another object of the present invention is that the exciting coil for generating heat from the heat generating member has a first coil portion and a second coil portion for matching impedance between the heat generating member, and the first coil portion and the first coil portion An object of the present invention is to provide an image heating apparatus in which two coil portions are adjacent to each other.
[0011]
Other objects of the present invention will become apparent from the following description.
[0012]
[Means for Solving the Problems]
The present invention is an image heating apparatus having the following configuration.
[0013]
  (1) A heating member having a conductive layer and a magnetic field generating means having an exciting coil for generating a magnetic field, wherein the exciting coil is supplied with power from a power source by a switching circuit,MagnetismIn the image heating apparatus in which an eddy current is generated in the heat generating member by a magnetic field generated by a field generating means, the heat generating member generates heat by the eddy current, and an image on the recording material is heated by the heat, the excitation coil Has a first coil part and a second coil part for matching impedance between the first coil part and the heat generating member, and the first coil part and the second coil part are adjacent to each other. TheAnd the number of windings of the second coil part is less than the number of windings of the first coil part.An image heating apparatus.
[0014]
  (2) The magnetic coupling between the second coil portion and the heat generating member is weaker than the magnetic coupling between the first coil portion and the heat generating member.DoThe image heating apparatus according to (1).
[0015]
(3) The image heating apparatus according to (1), wherein the second coil portion is further away from the heat generating member than the first coil portion.
[0016]
(4) The image heating apparatus according to (1), wherein the first coil portion and the second coil portion are connected in series.
[0018]
  (5) A heating member having a conductive layer and a magnetic field generating means having an exciting coil for generating a magnetic field, wherein the exciting coil is supplied with electric power from a power supply by a switching circuit, and the magnetic field generating means In the image heating apparatus in which an eddy current is generated in the heat generating member by a generated magnetic field, the heat generating member generates heat by the eddy current, and an image on the recording material is heated by the heat, the exciting coil is a first coil. And a second coil portion for matching impedance between the first coil portion and the heat generating member, and the first coil portion and the second coil portion are adjacent to each other,And a support member for supporting the excitation coil, wherein the support member exists between the heating member and the excitation coil.StatueHeating device.
[0019]
  (6)The support member is an electrical insulating material.(5)The image heating apparatus described in 1.
[0020]
  (7) A heating member having a conductive layer and a magnetic field generating means having an exciting coil for generating a magnetic field, wherein the exciting coil is supplied with electric power from a power source by a switching circuit, and the magnetic field generating means In the image heating apparatus in which an eddy current is generated in the heat generating member by a generated magnetic field, the heat generating member generates heat by the eddy current, and an image on the recording material is heated by the heat, the exciting coil is a first coil. And a second coil portion for matching impedance between the first coil portion and the heat generating member, and the first coil portion and the second coil portion are adjacent to each other,The winding density of the second coil part is less than the winding density of the first coil part.StatueHeating device.
  (8) The image heating apparatus according to (7), wherein the magnetic coupling between the second coil portion and the heat generating member is weaker than the magnetic coupling between the first coil portion and the heat generating member.
  (9) The image heating apparatus according to (7), wherein the second coil portion is further away from the heat generating member than the first coil portion.
  (10) The image heating apparatus according to (7), wherein the first coil portion and the second coil portion are connected in series.
[0021]
    (11)The heat generating member is an endless film (1)Or (5) or (7)The image heating apparatus described in 1.
[0022]
  (12)The exciting coil is present inside the film.(11)The image heating apparatus described in 1.
[0023]
  (13) The image heating apparatus according to (11), wherein the exciting coil exists outside the film.
  (14)The heating member and a roller for forming a nip are provided, and a recording material carrying an unfixed image at the nip is nipped and conveyed, and the unfixed image is fixed on the recording material (1)Or (5) or (7)The image heating apparatus described in 1.
[0024]
<Operation>
That is, instead of degrading the magnetic coupling to the first coil portion whose primary purpose (first function) is to magnetically couple to the heat generating member having the conductive layer (first function) and making it magnetically loosely coupled. Since the second coil part whose main purpose is to ensure the leakage inductance (second function) is composed of one exciting coil, impedance matching between the first coil part of the exciting coil and the heating member is taken. Therefore, it is relatively easy to construct a magnetic circuit capable of zero-cross switching without requiring a matching transformer.
[0025]
Since the first coil portion and the second coil portion are adjacent to each other and are configured as one excitation coil, it is not necessary to design a storage space for the matching coil separately from the excitation coil, and the apparatus configuration can be simplified. .
[0026]
Therefore, an image heating apparatus that reduces switching loss without complicating the apparatus can be provided for the magnetic induction heating type image heating apparatus.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a schematic configuration diagram of an example of an image forming apparatus. The image forming apparatus of this example is an electrophotographic color printer.
[0028]
Reference numeral 101 denotes an electrophotographic photosensitive drum (image bearing member) made of an organic photosensitive member or an amorphous silicon photosensitive member, which is rotationally driven in a counterclockwise direction indicated by an arrow at a predetermined process speed (peripheral speed).
[0029]
The photosensitive drum 101 is uniformly charged with a predetermined polarity and potential by a charging device 102 such as a charging roller during its rotation.
[0030]
Next, the charged surface is subjected to a scanning exposure process of target image information by a laser beam 103 output from a laser optical box (laser scanner) 110. The laser optical box 110 outputs a laser beam 103 modulated (on / off) corresponding to a time-series electric digital pixel signal of target image information from an image signal generation device such as an image reading device (not shown) to rotate the photoconductor. The drum surface is subjected to scanning exposure, and an electrostatic latent image corresponding to target image information scanned and exposed on the surface of the rotary photosensitive drum 101 is formed by this scanning exposure. Reference numeral 109 denotes a mirror that deflects the output laser light from the laser optical box 110 to the exposure position of the photosensitive drum 101.
[0031]
In the case of full-color image formation, scanning exposure / latent image formation is performed on a first color separation component image of a target full-color image, for example, a yellow component image, and the latent image is subjected to yellow development in the four-color developing device 104. The yellow toner image is developed by the operation of the device 104Y. The yellow toner image is transferred onto the surface of the intermediate transfer drum 105 at a primary transfer portion T1 which is a contact portion (or proximity portion) between the photosensitive drum 101 and the intermediate transfer drum 105. The surface of the rotating photosensitive drum 101 after the transfer of the toner image to the surface of the intermediate transfer drum 105 is cleaned by the cleaner 107 after removal of adhesion residues such as transfer residual toner.
[0032]
The process cycle of charging / scanning exposure / development / primary transfer / cleaning as described above includes a second color separation component image (for example, magenta component image, magenta developer 104M is activated) of the target full-color image, The color separation component images (for example, the cyan component image and the cyan developing device 104C are operated) and the fourth color separation component image (for example, the black component image and the black developing device 104BK are operated) are sequentially executed for the intermediate The toner images of four colors of yellow toner image, magenta toner image, cyan toner image, and black toner image are sequentially superimposed and transferred onto the surface of the transfer drum 105, and a color toner image corresponding to the target full-color image is synthesized and formed. .
[0033]
The intermediate transfer drum 105 has a middle resistance elastic layer and a high resistance surface layer on a metal drum. The intermediate transfer drum 105 is in contact with or close to the photosensitive drum 101 at an approximately same peripheral speed as the photosensitive drum 101. The toner image on the photosensitive drum 101 side is transferred to the surface side of the intermediate transfer drum 105 by applying a bias potential to the metal drum of the intermediate transfer drum 105 and rotating the clockwise rotation as shown in FIG. Let
[0034]
The color toner image synthesized and formed on the surface of the rotary intermediate transfer drum 105 is transferred to the secondary transfer portion T2 at the secondary transfer portion T2 which is a contact nip portion between the rotary intermediate transfer drum 105 and the transfer roller 106. Are transferred onto the surface of the recording material P fed at a predetermined timing from a paper feeding unit (not shown). The transfer roller 106 supplies a charge having a polarity opposite to that of the toner from the back surface of the recording material P, thereby sequentially transferring the combined color toner images sequentially from the surface of the intermediate transfer drum 105 to the recording material P side.
[0035]
The recording material P that has passed through the secondary transfer portion T2 is separated from the surface of the intermediate transfer drum 105 and introduced into an image heating device (fixing device) 100, and undergoes a heat fixing process for an unfixed toner image to form a color image formed product. Are discharged to a discharge tray (not shown) outside the machine. The fixing device 100 will be described in detail later.
[0036]
After the color toner image is transferred to the recording material P, the rotating intermediate transfer drum 105 is cleaned by the cleaner 108 after removal of the adhering residue such as transfer residual toner and paper dust. The cleaner 108 is always held in a non-contact state with the intermediate transfer drum 105, and is in contact with the intermediate transfer drum 105 during the secondary transfer of the color toner image from the intermediate transfer drum 105 to the recording material P. Retained.
[0037]
Also, the transfer roller 106 is always held in a non-contact state with the intermediate transfer drum 105, and the recording material is transferred to the intermediate transfer drum 105 during the secondary transfer of the color toner image from the intermediate transfer drum 105 to the recording material P. The contact state is maintained via P.
[0038]
A mono-color image print mode such as a monochrome image can also be executed. A double-sided image print mode or a multiple image print mode can also be executed.
[0039]
In the double-sided image print mode, the recording material P on which the first-side image has been printed that has left the image heating apparatus 100 is turned upside down via a recirculation conveyance mechanism (not shown) and sent again to the secondary transfer portion T2. Upon receipt of the toner image transfer on the surface, the toner image is again introduced into the image heating apparatus 100 and undergoes toner image fixing processing on the two surfaces to output a double-sided image print.
[0040]
In the multiple image print mode, the first image printed recording material P that has exited the image heating apparatus 100 is sent to the secondary transfer portion T2 again without being turned upside down via a recirculation conveyance mechanism (not shown). A second toner image transfer is received on the surface on which the first image has been printed, and the image is again introduced into the image heating apparatus 100 and undergoes a second toner image fixing process, whereby a multiple image print is output.
[0041]
In this example, a toner containing a low softening substance is used.
[0042]
The fixing device 100 of this example is a pressure roller driving method and magnetic induction heating method device using a cylindrical magnetic induction heat generating film (metal heating film) as a fixing film.
[0043]
2A is a cross-sectional side view of the main part of the fixing device 100, FIG. 2B is an enlarged model view of a part thereof, FIG. 3 is a front view of the device 100, and FIG. is there. Reference numeral 1 denotes a magnetic induction heat generating film (hereinafter referred to as a fixing film) which is a cylindrical heat generating member. The fixing film 1 of this example has a conductive layer (metal layer, resistor layer, magnetic layer) 1a as a heating element that generates magnetic induction heat, as shown in FIG. A release layer made of a cylindrical nickel film layer (hereinafter referred to as a metal layer) having a thickness of 50 μm, an elastic layer 1b made of silicone rubber or the like covering its outer peripheral surface, and a fluororesin or the like covering its outer periphery. It is a laminated film material consisting of three layers of layer 1c. The elastic layer 1b and the release layer 1c serve to improve the toner image fixability and to improve the toner release property.
[0044]
When magnetic flux acts on the metal layer 1a as the conductive layer, an eddy current is generated in the metal layer 1a, and the metal layer 1a generates heat by magnetic induction. The metal layer 1a is made of 10 other than nickel.^-Five-10^-Ten Any metal or metal compound that is a good electrical conductor of Ω · cm may be used, and more preferably, a pure metal layer such as iron or cobalt exhibiting ferromagnetism having a high magnetic permeability or a compound thereof can be used.
[0045]
The elastic layer 1b serves to cause the surface of the fixing film 1 to follow the irregularities of the toner layer even in the case of a four-color superimposed color toner image having a thick toner layer. The altitude is preferably 60 ° (JIS-A) or less, more preferably 45 ° (JIS-A) or less. Thermal conductivity λ is 6 × 10^-Four~ 2x10^-3[Cal / cm · sec · deg. ] Is good.
[0046]
For the release layer 1c, in addition to fluorine resins such as PFA, PTFE, and FEP, a material having good release properties and heat resistance such as silicone resin, silicone rubber, fluorine rubber, and silicone rubber can be selected. The thickness is preferably 20 to 100 μm.
[0047]
The cylindrical fixing film 1 is loosely fitted on a cylindrical body constituted by a core holder 2 and a film guide member 3.
[0048]
The core holder 2 is a lower member, and the film guide member 3 is an upper member, each of which has a substantially semicircular shape with a substantially semicircular cross-sectional shape in cross section, thereby forming a substantially cylindrical body. In the center of the inner bottom surface of the lower core holder 2, two parallel rib plates 2a and 2a are provided along the length of the holder with a gap therebetween, and the first core is interposed between the rib plates 2a and 2a. 5 is dropped and held. FIG. 5 is an external perspective view of the core holder 2. Reference numeral 2b denotes a film inner surface guide rib provided on the outer surface of the core holder 2 (rib height of about 0.5 mm).
[0049]
The core holder 2 and the film guide member 3 are electrically insulating and heat resistant members. For example, it is a molded article such as phenol resin, fluorine resin, polyimide resin, polyamide resin, polyamideimide resin, PEEK resin, PES resin, PPS resin, PFA resin, PTFE resin, FEP resin, and LCP resin.
[0050]
Reference numeral 4 denotes an exciting coil (wire ring) which is configured by winding an electric wire around a boat shape substantially corresponding to the inner surface of the lower core holder 2 having a substantially semicircular arc shape in cross section. FIG. 6 is an external perspective view of the exciting coil. This boat-shaped exciting coil 4 is held on the inner surface of the core holder 2.
[0051]
Reference numerals 7 and 8 denote a spacer plate and a flat plate cover plate, which are sequentially placed on the core holder 2 holding the exciting coil 4 and the first core 5. Numerals 6 and 6 are a pair of left and right second cores that are bonded and held in advance on the back surface of the spacer plate 7. The second cores 6 and 6 are positioned at the upper left and right sides of the exciting coil 4 with the first core 5 in the middle by the spacer plate 7 being placed on the core holder 2 in a predetermined manner. The arrangement configuration is a T-shaped cross section.
[0052]
The first core 5 and the second cores 6 and 6 are horizontally long ferromagnetic and high magnetic permeability members having the longitudinal direction of the core holder 2 as the longitudinal direction, and are preferably made of a material used for a transformer core such as ferrite and permalloy. It is preferable to use ferrite with a low loss at 20 to 100 kHz.
[0053]
Reference numeral 9 denotes a laterally long stay for pressurization, which is integrally attached in advance to the center of the upper surface of the flat cover plate 8. Both ends of the stay 9 are protruded outward from both longitudinal ends of the flat cover plate 8 (FIGS. 3 and 4).
[0054]
As described above, the spacer plate 7 and the flat cover plate 8 are sequentially covered on the core holder 2, and the film guide member 3 is further covered. Then, the cylindrical fixing film 1 is loosely fitted on the assembly. Further, ring-shaped film end regulating flange members 10 and 10 are fitted on both ends of the assembly. By fitting the ring-shaped film end regulating flange member to the core holder 2 and the film guide member 3, the flange member becomes a tag and the assemblies 1 to 10 are held in an assembled state.
[0055]
Reference numeral 15 denotes an elastic pressure roller as a pressure rotating member, which includes a core metal 15a and a silicone rubber layer 15b formed concentrically around the core metal. The pressure roller 15 is rotatably supported between the front and back side plates (not shown) of the fixing device.
[0056]
Above the pressure roller 15, the assemblies 1 to 10 are arranged substantially parallel to the roller with the core holder 2 side facing down. Then, the pressure springs 12 and 12 are contracted between the spring receivers 11 and 11 serving as immovable members and the stay end portions on both ends of the pressurizing laterally long stay 9, respectively. As a result, the contraction reaction force f · f of the pressure springs 12 and 12 acts on the end of the stay and the stay 9 is pushed down, so that the lower surface of the core holder 2 and the pressure roller 15 sandwich the fixing film 1. The fixing nip portion N having a predetermined width is formed by being pressurized with a predetermined load (10 to 50 kg).
[0057]
The pressure roller 15 is driven by a drive source M through a drive transmission system and is rotationally driven at a predetermined peripheral speed in a counterclockwise direction indicated by an arrow in FIG. ). As the pressure roller 15 rotates, the rotation pressure roller 15 and the fixing film 1 are fixed to the cylindrical fixing film 1 loosely fitted outside the core holder 2 and the film guide 3 at the fixing nip N. Rotational force acts on the cylindrical fixing film 1 by the frictional force with the outer surface of the core, and the cylindrical fixing film 1 adheres to the outer surface of the core holder 2 and the film guide 3 at the fixing nip portion N so that the lower surface of the core holder 2 is closely attached While being slid, the rotating state is rotated at a peripheral speed substantially corresponding to the rotational peripheral speed of the pressure roller 15 in the clockwise direction indicated by the arrow.
[0058]
The film end regulating flange members 10 and 10 receive the end of the fixing film 1 when the fixing film 1 is rotated, and serve to regulate the movement of the fixing film along the length of the core holder.
[0059]
The exciting coil 4 generates a high-frequency magnetic field by a high-frequency current (alternating current) supplied from an exciting circuit (such as a power supply and a switching circuit having a capacitive impedance) S. The high frequency magnetic field is concentrated and distributed in the vicinity of the fixing nip N by the first core 5 corresponding to the position of the fixing nip N. The magnetic flux of the high frequency magnetic field generates an eddy current in the metal layer 1a as the heating element layer of the fixing film 1 described above. This eddy current generates Joule heat in the metal layer due to the specific resistance of the metal layer 1a (heat generation due to eddy current loss). That is, the metal layer 1a of the fixing film 1 generates heat by magnetic induction.
[0060]
FIG. 13 shows a schematic configuration of the excitation circuit S. 20 is a noise filter, 21 is a filter capacitor, 22 is a resonant capacitor, 23 is a switching element, and 24 is a freewheeling diode.
[0061]
The DC power supply circuit is a control circuit. The fixing is started by the fixing permission signal. First, when a fixing permission signal is received, the switching control circuit generates a gate pulse so that the switching element repeats appropriate on-time and off-time. When the switching element is turned on, a current flows from the rectifier circuit to the exciting coil, and when the switching element is turned off, the current of the exciting coil flows to the resonance capacitor (from the freewheeling diode to the filter capacitor). In this circuit, the longer the ON time, the more electric power is supplied to the exciting coil, and the electric power increases (the amount of heat generated increases).
[0062]
The temperature adjustment is performed by controlling the ON time width based on the temperature information detected by the thermistor 13 which is a temperature measuring means.
[0063]
The temperature of the fixing nip N is detected by the temperature detection element 13, and the detected temperature information is input to the control system C (FIG. 6), and the power supply (current supply) from the power supply in the excitation circuit S to the excitation coil 4 is performed. By being controlled by the control system C, the temperature of the fixing nip portion N is adjusted so as to be maintained at a predetermined temperature.
[0064]
In this example, the temperature detecting element 13 is a thermistor disposed on the lower surface of the core holder corresponding to the fixing nip N. The thermistor 13 is formed as a thin stainless plate, and this stainless plate is adhered to the outer surface of the core holder 2 and is covered with an insulating protective tape to protect the outer surface.
[0065]
  In this example, the exciting coil 4 is concentrated and distributed in the vicinity of the fixing nip portion N, thereby generating a generated magnetic field in a desired heating region of the metal layer 1a of the fixing film 1.ThreadingTherefore, an efficient fixing device can be realized.
[0066]
Thus, the pressure roller 15 is rotationally driven, and the cylindrical fixing film 1 is rotated accordingly, and the magnetic induction heat generation of the fixing film 1 is performed as described above by feeding power from the exciting circuit S to the exciting coil 4. When the fixing nip portion N rises to a predetermined temperature and is adjusted in temperature, the recording material P on which the unfixed toner image t conveyed from the image forming portion is formed is connected to the fixing film 1 in the fixing nip portion N. The image surface is introduced between the pressure roller 15 upward, that is, the image surface is opposed to the fixing film surface, and the image surface is brought into close contact with the outer surface of the fixing film 1 in the fixing nip portion N together with the fixing film 1. The fixing nip portion N is nipped and conveyed. In the process in which the recording material P is nipped and conveyed together with the fixing film 1 through the fixing nip N, the fixing film 1 is heated by magnetic induction heat generation, and the unfixed toner image t on the recording material P is heated and fixed. When the recording material P passes through the fixing nip portion N, it is separated from the outer surface of the rotary fixing film 1 and discharged and conveyed.
[0067]
In this example, the exciting coil 4 uses a bundle (bundle wire) of a plurality of thin copper wires, each of which is coated with insulation, as an electric wire constituting the coil. Forming. As the insulating coating, it is preferable to use a coating having heat resistance in consideration of heat conduction by heat generation of the fixing film 1. For example, the heat resistance temperature of the coating with polyimide is 220 ° C.
[0068]
2A and 2B, 4a of the windings of the exciting coil 4 is a first coil portion that is adjacent to the metal layer 1a of the fixing film 1 via an insulating material so as to be magnetically coupled. Winding. The insulating material is the core holder 2 in this example. The thickness of the core holder 2 is 1 to 5 mm.
[0069]
Reference numeral 4b denotes a winding that is a second coil portion that is not magnetically coupled to the metal layer 1a of the fixing film 1 or weaker than the first 4a.
[0070]
The exciting coil 4 in this example has a two-layer winding configuration of the first winding 4a and the second winding 4b, and the first and second windings 4a and 4b are adjacent to each other, and It is wound around the metal layer 1a of the fixing film 1 so as to generate magnetic flux in the same direction. The first winding 4a and the second winding 4b are connected in series and are supplied with power from a power source by a switching circuit having a capacitive impedance. The number of turns of the second winding 4b is smaller than that of the first winding 4a.
[0071]
FIG. 2B shows the state of magnetic flux in such a configuration. That is, the main magnetic flux mainly formed by the first winding passes through the T-shaped second core 6 and the first core 5 and is magnetically coupled to the metal layer 1a of the fixing film 1, and again the second core 6 Pass through to the first core 5.
[0072]
There are various paths of leakage magnetic flux formed mainly by the second winding that is not magnetically coupled to the metal layer 1a of the fixing film 1, but due to the effect of the shape of the first core 5 and the second cores 6 and 6, A path through the insulator (core holder 2) between the fixing film 1 outside the first winding 4a and entering the second core 6 and the first core 5, and the first winding 4a and the second winding A path that passes between the windings 4b and passes through the second core 6 and the first core 5 is considered to be the main one.
[0073]
Of these, the distance between the first winding 4a and the metal layer 1a of the fixing film 1 is required to maintain the distance to the extent that the efficiency is not deteriorated to some extent without being in close contact with the idea that the efficiency and leakage magnetic flux are ensured. There is. In this example apparatus, the core holder 2 functions as an insulating material between the two 4a and 1a, and its thickness is about 1 mm to 5 mm so that the distance between the two 4a and 1a is kept at a convenient distance. Further, a magnetic flux that is not coupled to the metal layer 1a of the fixing film 1 due to the magnetic flux passing between the first winding 4a and the second winding 4b is secured.
[0074]
In such a configuration, an equivalent circuit of the exciting coil portion is written as shown in FIG. T1 is a matching transformer, L1 is an inductance of a coil corresponding to the magnetic flux coupled to the fixing film, R is an equivalent resistance of the fixing film (heated metal film) 1, and L2 is a leakage of the coil corresponding to the magnetic flux not coupled to the fixing film. Inductance.
[0075]
FIG. 7A is a circuit diagram using a conventional matching transformer T1. When the matching transformer T1 is used, an ideal waveform can be realized by using an appropriate transformer regardless of the load inductance. However, as described above, it is quite impossible to use such a transformer T1 in an actual device in terms of size and cost.
[0076]
By adjusting the leakage inductance L2 in the exciting coil 4 so as to obtain an equivalent circuit as shown in FIG. 7B, characteristics close to ideal can be realized without using the matching transformer T1.
[0077]
The voltage waveform applied to both ends of the switching element in each case, where the magnetic coupling between the exciting coil and metal is very good and the system receives a large loss, and when the leakage inductance is increased 8 (a) and (b).
[0078]
When a constant voltage is applied to a resonant circuit in which an exciting coil and a resonant capacitor are connected in parallel, and the current supply from the constant voltage source is stopped after a certain period of time, the current is generated by the energy stored in the magnetic field at both ends of the coil. The capacitor keeps flowing, and the energy stored in the electric field appears as a voltage in the capacitor, and each capacitor tries to flow current. For this reason, a voltage called a flyback voltage as shown in FIG. 8 is generated. However, when the coupling between the coil and the metal body is good and the loss due to the metal is too large, as shown in FIG. In this case, the vibration condition is not satisfied and the voltage tends to converge to a voltage centered on Vcc (voltage applied during the on-time). In this case, the switching element is turned on in the state where the voltage of Vcc is applied, and the loss accompanying switching becomes very large.
[0079]
On the other hand, by providing the second winding 4b as described above and securing a leakage magnetic flux that is not coupled to the metal layer 1a of the fixing film 1, the flyback voltage swing can be achieved as shown in FIG. Since it becomes larger and switching at zero crossing can be realized, a system with less switching loss can be realized.
[0080]
So ideally,
(Loss) = (Voltage) × (Current) = 0 × (Current) = 0
Thus, the electric power accompanying switching in the switching element can be reduced to 0, and the switching loss can be suppressed.
[0081]
Even when the first winding 4a and the second winding 4b are in close contact with each other, since the magnetic flux between the windings does not completely cancel each other, such an effect can be expected, but insulation is ensured. Therefore, an insulator may be provided between the first winding 4a and the second winding 4b in order to adjust the leakage.
[0082]
As described above, in this embodiment, the first winding portion, which is mainly intended to be magnetically coupled to the heat generating member having the conductive layer, and the magnetic coupling to the heat generating member are deliberately deteriorated to be magnetically loosely coupled. Instead, the second winding portion, which is mainly intended to ensure leakage inductance, is configured in one exciting coil, and impedance matching between the first winding portion of the exciting coil and the heat generating member is taken. Therefore, it is possible to relatively easily realize a magnetic circuit capable of zero-cross switching without requiring a matching transformer.
[0083]
Further, when the matching coil is configured separately from the exciting coil, it is necessary to design a storage space for the matching coil separately from the exciting coil. In this embodiment, the first winding portion and the second winding are required. Since the line portions are adjacent and configured as one excitation coil, it is not necessary to design a storage space for the matching coil separately from the excitation coil, and the apparatus configuration can be simplified.
[0084]
In the example described above, the winding of the exciting coil 4 is a two-layer winding of the first winding 4a and the second winding 4b. However, this may be a multilayer winding. Such another embodiment of the present invention is shown in FIG. Even in such a case, the equivalent circuit can be basically expressed as shown in FIG. 7B. Of these, the leakage of L2 includes the first layer, the second layer, the third layer,. . . Is the sum of the inductances not involved in the magnetic coupling of the winding layers 4a, 4b, 4c,.
[0085]
The same effect as described above can also be obtained by making the windings of the second and subsequent layers sparse compared to the first layer of the winding.
[0086]
Another embodiment of such a winding method is shown in FIG. The state of the magnetic flux at this time is shown in FIG.
[0087]
In order to maintain the shape of the exciting coil 4, the exciting coil 4 is held by an elastic insulator (resin or the like) having a small coefficient of thermal expansion, or a coiled wire is used as a covered wire. A suitable support may be formed by a mold or the like and wound on the mold.
[0088]
In the ideal case, the magnetic flux between the coils cancels out and leakage does not occur, but in reality it tends to increase as the distance increases, so to increase leakage without increasing the number of turns It becomes an effective means.
[0089]
As shown in FIG. 9, the winding structure is a winding structure of at least two layers, and the second layer winding, the third layer winding,... Are structurally separated from the heating member. The leakage inductance is obtained or the second and subsequent windings of the heat generating member are configured in a sparse manner as shown in FIG. 10, and the first function closest to the heat generating member, that is, the heat generating member, is provided. Instead of degrading the second function, i.e., the magnetic coupling to the heat generating member, to a magnetically loosely coupled function. By providing a function whose main purpose is to ensure the leakage inductance, it is possible to obtain a sufficient flyback voltage for obtaining a good switching state.
[0090]
The apparatus according to the above-described embodiment has a configuration in which the exciting coil 4 is aligned with the core 5 in the fixing nip portion N. However, as in the apparatus of FIG. The fixing film 1 is configured upstream of the fixing film 1 in the rotation direction, and the fixing film 1 is heated upstream of the fixing nip portion N in the fixing film rotation direction. It may be configured to enter the fixing nip portion N.
[0091]
In a small machine in which the diameter of the cylindrical fixing film 1 is small and an exciting coil cannot be formed in the film, the fixing is performed on the fixing nip portion N outside the fixing film 1 as in the apparatus of FIG. The same effect can be obtained by disposing the exciting coil 4 on the upstream side in the film rotation direction and using the exciting coil 4 having the above-described two or more layers of winding configurations 4a, 4b,. Reference numeral 14 denotes a facing member that forms a fixing nip N with the fixing film 1 sandwiched between the pressing roller 15 and the pressing roller 15.
[0092]
The magnetic induction exothermic fixing film 1 may be in a form in which the elastic layer 1b is omitted in the case of heat fixing such as a monochrome or one-pass multi-color image. The conductive layer 1a as a heating element can be a layer in which a metal filler is mixed into a resin. A single-layer member having only the conductive layer 1a may be used.
[0093]
The upper film guide member 3 with respect to the lower core holder 2 may be omitted.
[0094]
The exciting coil 4 may be formed by molding with an insulating resin.
[0095]
The device configuration of the fixing device 100 as a heating device is not limited to the pressure roller driving system of the embodiment. For example, an endless belt-like fixing film may be suspended between a plurality of members such as a driving roller and a tension roller, and the fixing film may be rotationally driven by a member other than the pressure roller. In addition, a long web-like member in which the fixing film is wound into a roll can be used, and the apparatus can be configured to wind and move the fixing film from the feeding shaft side to the winding shaft side at a predetermined speed.
[0096]
The conductive material (magnetic material), which is an electromagnetic induction heat generating member, may be a device having a fixed member. For example, an iron plate as a fixed electromagnetic induction heat generating member is fixedly disposed in the fixing nip portion, and this iron plate is caused to generate magnetic induction heat by an exciting coil, and the fixed iron plate and a pressure roller as a pressure member are provided. A fixing nip portion N is formed by sandwiching a heat-resistant thin film and pressing it. The heat-resistant film rotates or runs while the inner surface of the fixing nip portion is in close contact with the lower surface of the fixed iron plate by a pressure roller driving system, or a driving roller or a winding shaft. The fixed iron plate intensively receives the alternating magnetic flux generated by applying an alternating current to the exciting coil and generates magnetic induction heat. In the process where the recording material is introduced between the heat-resistant film in the fixing nip and the pressure roller and the fixing nip is held and transported together with the heat-resistant film, the heat generated from the heat generated by the fixed iron plate And the toner image is fixed.
[0097]
The pressure member 15 is not limited to a roller body, and may be a member of another form such as a rotating belt type.
[0098]
In order to supply thermal energy to the recording material also from the pressing member 15 side, a heating device such as electromagnetic induction heating is provided on the pressing member 15 side to heat and control the temperature to a predetermined temperature. You can also.
[0099]
The image forming principle and method of the image forming apparatus are not limited to the electrophotographic process, but may be any other method such as a transfer method or a direct method electrostatic recording process or magnetic recording process.
[0100]
The heating apparatus of the present invention is not limited to the image heating and fixing apparatus of the embodiment, but an image heating apparatus that heats a recording material carrying an image to improve the surface properties such as gloss, an image heating apparatus that is supposed to be worn, and the like. It can be widely used as a means / device for heat-treating a material to be heated, such as a heating / drying device or a heating laminating device.
[0101]
As mentioned above, although the Example of this invention was described, this invention is not limited to the said Example, All the deformation | transformation are possible within the technical thought of this invention.
[0102]
【The invention's effect】
As described above, according to the present invention, in the image heating apparatus of the magnetic induction heating method, the first coil portion mainly intended to be magnetically coupled to the heat generating member having the conductive layer and the magnetic coupling to the heat generating member are intentionally deteriorated. Instead of magnetically loosely coupling, the second coil part whose main purpose is to secure leakage inductance is formed by one exciting coil, and the impedance of the first coil part of the exciting coil and the heat generating member is reduced. Since matching is achieved, it is relatively easy to construct a magnetic circuit capable of zero-cross switching without the need for a matching transformer.
[0103]
Since the first coil portion and the second coil portion are adjacent to each other and are configured as one excitation coil, it is not necessary to design a storage space for the matching coil separately from the excitation coil, and the apparatus configuration can be simplified. .
[0104]
Therefore, an image heating apparatus that reduces switching loss without complicating the apparatus can be provided for the magnetic induction heating type image heating apparatus.
[Brief description of the drawings]
FIG. 1 is a schematic view of an image forming apparatus to which an image heating apparatus according to an embodiment of the present invention is applied.
2A is a cross-sectional side view of the main part of the image heating apparatus, and FIG. 2B is an enlarged view of a part thereof.
FIG. 3 is a front model view of the image heating apparatus.
FIG. 4 is a longitudinal front view of the image heating apparatus.
FIG. 5 is an external perspective view of the core holder.
FIG. 6 is an external perspective view of an exciting coil.
FIG. 7 is an equivalent circuit diagram.
FIG. 8 is a diagram showing flyback voltage
FIG. 9 is a cross-sectional side view of an image heating apparatus according to another embodiment.
10A is a cross-sectional side view of a main part of an image heating apparatus according to another embodiment, and FIG. 10B is an enlarged view of a part thereof.
FIG. 11 is a cross-sectional side view of an image heating apparatus according to another embodiment.
FIG. 12 is a cross-sectional side view of an image heating apparatus according to another embodiment.
FIG. 13 shows an excitation circuit
[Explanation of symbols]
100 Fixing device (image heating device)
1 Magnetic induction exothermic film (fixing film, metal heating film)
2 Core holder (insulating material)
3 Film guide members
4 Excitation coil
4a First winding
4b Second winding
5.6 Ferrite core
7 Spacer plate
8 Flat cover plate
9 Horizontal stay for pressurization
10 Film end regulating flange member
11 Spring support
12 Pressure spring
13 Thermistor
15 Pressure elastic roller
T1 matching transformer
L1 Inductance of coil corresponding to magnetic flux combined with fixing film
R Equivalent resistance of fixing film (metal film)
L2 Leakage inductance of the coil corresponding to the magnetic flux not coupled to the fixing film
Voltage applied during Vcc on time

Claims (14)

A heat generating member having a conductive layer having a magnetic field generating means comprising an excitation coil for generating a magnetic field, the excitation coil with power from the power supplied by the switching circuit, generated by the previous Ki磁 field generating means In the image heating apparatus in which an eddy current is generated in the heat generating member by a magnetic field that is generated, the heat generating member generates heat by the eddy current, and an image on the recording material is heated by this heat.
The exciting coil has a first coil part, and a second coil part for matching impedance between the first coil part and the heat generating member, and the first coil part and the second coil part are An image heating apparatus, wherein the number of windings of the second coil part is smaller than the number of windings of the first coil part . The image heating apparatus according to claim 1, wherein the magnetic coupling between the second coil unit and the heat generating member is weaker than the magnetic coupling between the first coil unit and the heat generating member.   The image heating apparatus according to claim 1, wherein the second coil portion is further away from the heat generating member than the first coil portion.   The image heating apparatus according to claim 1, wherein the first coil unit and the second coil unit are connected in series. A heat generating member having a conductive layer; and a magnetic field generating means having an exciting coil for generating a magnetic field. The exciting coil is supplied with electric power from a power source by a switching circuit, and generates a magnetic field by the magnetic field generating means. In the image heating apparatus in which an eddy current is generated in the heat generating member, the heat generating member generates heat by the eddy current, and an image on the recording material is heated by the heat.
The exciting coil has a first coil portion and a second coil portion for matching impedance between the first coil portion and the heat generating member, and the first coil portion and the second coil portion are are adjacent to each other, a supporting member for supporting said exciting coil, wherein the support member image heating apparatus you being present between the excitation coil and the heat-generating member. The image heating apparatus according to claim 5 , wherein the support member is an electrically insulating material. A heat generating member having a conductive layer; and a magnetic field generating means having an exciting coil for generating a magnetic field. The exciting coil is supplied with electric power from a power source by a switching circuit, and generates a magnetic field by the magnetic field generating means. In the image heating apparatus in which an eddy current is generated in the heat generating member, the heat generating member generates heat by the eddy current, and an image on the recording material is heated by the heat.
The exciting coil has a first coil portion and a second coil portion for matching impedance between the first coil portion and the heat generating member, and the first coil portion and the second coil portion are are adjacent to each other, the density of winding of the second coil portion is an image heating apparatus you characterized in that less than the density of winding of the first coil portion.   The image heating apparatus according to claim 7, wherein the magnetic coupling between the second coil unit and the heat generating member is weaker than the magnetic coupling between the first coil unit and the heat generating member.   The image heating apparatus according to claim 7, wherein the second coil portion is further away from the heat generating member than the first coil portion.     The image heating apparatus according to claim 7, wherein the first coil unit and the second coil unit are connected in series. The heating member is an image heating apparatus according to claim 1 or 5 or 7, characterized in that an endless film. The image heating apparatus according to claim 11 , wherein the exciting coil is present inside the film.   The image heating apparatus according to claim 11, wherein the exciting coil is present outside the film. Has a roller for forming the heat-generating member and the nip, the recording material an unfixed image carrying at the nip is pinched and conveyed, according to claim 1 or 5 unfixed image, characterized in that it is fixed on the recording medium Or an image heating apparatus according to 7 ;

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