JP4541865B2 - Image heating device - Google Patents

Description

  The present invention relates to an image heating apparatus of an electromagnetic induction heating system suitable for use as a heat fixing apparatus mounted on an electrophotographic or electrostatic recording image forming apparatus.

  In recent years, various proposals have been made for a heat fixing device mounted on an image forming apparatus such as a copying machine or a laser printer in order to save energy. By shortening the start-up time, the temperature of the heat fixing device during standby can be lowered to save energy during standby, or only the part where the toner image (developer image) is formed during printing The thing which realizes energy saving by heating is mentioned.

  In an electromagnetic induction heating type heat fixing device using high frequency induction as a heating source, an exciting coil is concentrically arranged inside a hollow fixing roller made of a metal conductor, and a high frequency current is passed through the exciting coil. An induced eddy current is generated in the fixing roller by the generated high frequency magnetic field, and the fixing roller itself generates Joule heat by the skin resistance of the fixing roller itself. According to this electromagnetic induction heating type fixing device, since the electric-heat conversion efficiency is extremely improved, the warm-up time can be shortened.

  In such an electromagnetic induction heating type fixing device, a transfer material of various sizes as a material to be heated is sandwiched and conveyed at a nip portion (fixing nip portion, heating nip portion) between a fixing roller and a pressure roller in pressure contact with the fixing roller. Thus, the toner is heated and fixed on the transfer material by applying heat and pressure to the unfixed toner image on the transfer material. When the size of the transfer material is the maximum, the maximum transfer material passing area (conveyance area) of the nip portion is actually heated to a predetermined fixing temperature to fix the toner on the transfer material. It consumes more energy than fixing the toner. In addition, when a small-size transfer material having a size smaller than the maximum size is continuously nipped and conveyed at the nip portion, the non-sheet-passing region (non-conveying region) other than the small-size transfer material passing region is fixed to the toner at the nip portion. The temperature rises above the temperature (so-called non-sheet passing portion temperature rise), which causes temperature rise in the machine and thermal deterioration of the material to be heated.

As this countermeasure, as disclosed in Patent Document 1, a method of shielding a magnetic flux acting on the fixing roller by shielding a region corresponding to a non-conveying region of the transfer material with a magnetic flux shielding member is effective.
Japanese Patent Laid-Open No. 10-74009

  However, in the case of using a magnetic flux shielding member as disclosed in Patent Document 1, a magnetic flux shielding member that shields an area corresponding to a non-conveyance area of a transfer material is arranged in advance, and the shielding position is set using a driving unit. The heat generation area was changed by moving to. However, there are actually various paper sizes, and it is difficult to cope with various paper sizes. Further, the area corresponding to the transfer material conveyance area is heated even in the area where the toner image is not present, so that the effect is insufficient from the viewpoint of energy saving. In general, the ratio of the portion where the image toner is placed on the transfer material (recording paper) for image recording used in the office is almost 10% or less of the whole. Therefore, heating a portion where toner is not placed is wasteful energy consumption. In addition, the heating of the paper as the transfer material also causes problems due to the temperature rise of the paper, such as heat curling and adhesion of discharged paper.

  An object of the present invention is to provide an image heating apparatus capable of realizing selective heating and fixing of only an image on a heated material with energy saving.

  It is another object of the present invention to provide an image heating apparatus capable of realizing selective heating and fixing of only an image on a heated material using a current developer and an electromagnetic induction heat generating member.

  Another object of the present invention is to provide an image heating apparatus capable of realizing selective heating and fixing of only an image on a material to be heated in correspondence with colorization and high speed.

The configuration of a typical image heating apparatus according to the present invention includes a magnetic field generation unit and a heating member that generates electromagnetic induction heat by the action of the magnetic field generation unit, and is on a material to be heated formed based on image information. In the image heating apparatus that heats the image by the heat generating member, the surface of the heat generating member on the surface opposite to the surface to be heated has the magnetic field generating means and the surface of the heat generating member on the magnetic field generating means side. you characterized with powder coating means for coating a powder containing non-magnetic metal in accordance with the image information.

  According to the above configuration, the surface including the nonmagnetic metal is coated on the surface of the electromagnetic induction heat generating member on the magnetic field generating means side, so that selective heating and fixing of only the image on the heated material can be realized with energy saving. . Further, it is possible to realize selective heating and fixing of only the image on the heated material while using the current developer and the electromagnetic induction heat generating member. It is also possible to cope with colorization and high speed.

  An image heating apparatus according to the present invention is a copying machine that transfers an unfixed image with toner to a recording material that is a heated material to be conveyed by an image forming mechanism as an image forming unit, and heat-fixes the unfixed image on a recording material. The best mode is used in an image forming apparatus such as a printer.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(1) Example of Image Forming Apparatus FIG. 1 is a schematic configuration diagram of an example of an image forming apparatus in which an electromagnetic induction heating type image heating apparatus according to an embodiment of the present invention is mounted as a fixing device. The image forming apparatus 100 according to the present embodiment is an image forming apparatus (a copying machine, a printer, a facsimile, or a complex machine thereof) using a transfer type electrophotographic process and a laser scanning exposure method.

  Reference numeral 101 denotes an original platen glass. An original O is placed on the original platen glass 101 with the image surface facing downward according to a predetermined placement standard, and the original cover 102 is placed on the original plate. When the copy start key is pressed, the image photoelectric reading device (reader unit) 103 including the moving optical system operates to photoelectrically read the image information on the downward image surface of the document O on the document table glass 101. An original document feeder (ADF, RDF) may be mounted on the platen glass 101 to automatically feed the document onto the platen glass 101.

  In an image forming mechanism as image forming means, a rotating drum type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) 104 is rotationally driven in a clockwise direction indicated by an arrow at a predetermined peripheral speed. The photosensitive drum 104 is uniformly charged with a predetermined polarity and potential by the charging device 105 during the rotation process, and is uniformly charged by receiving image exposure L by the image writing device 106 on the uniformly charged surface. The potential of the exposed bright portion of the surface is attenuated, and an electrostatic latent image corresponding to the exposure pattern is formed on the surface of the photosensitive drum 104. In this example, the image writing device 106 is a laser scanner, and is modulated in response to a time-series electric digital pixel signal of document image information photoelectrically read by the photoelectric reading device 103 in accordance with a command from a controller (not shown). The laser beam L is output, and the uniformly charged surface of the rotating photosensitive drum 104 is scanned and exposed to form an electrostatic latent image corresponding to the document image information.

  Next, the electrostatic latent image is developed as a toner image by the developing device 107, and at the position of the transfer charging device 108, a predetermined portion is applied from the paper feeding mechanism portion side to a transfer portion that is a facing portion between the photosensitive drum 104 and the transfer charging device 108. Is electrostatically transferred from the surface of the photosensitive drum 104 to the recording material S as the heated material fed at the control timing. The above is the configuration of the image forming mechanism.

  In the case of the image forming apparatus of this example, the sheet feeding mechanism section includes first to fourth cassette sheet feeding sections 109 to 112, an MP tray (multi-purpose tray) 113, and a reverse refeed section 114. From there, the recording material S is selectively fed to the transfer section. Reference numeral 115 denotes a registration roller for timing-feeding the recording material to the transfer unit.

  The recording material that has received the transfer of the toner image from the surface of the photosensitive drum 104 at the transfer unit is separated from the surface of the photosensitive drum 104 and conveyed to a heat fixing device (hereinafter referred to as a fixing device) 116 to fix the unfixed toner image. In response to the processing, the paper is discharged onto a paper discharge tray 118 outside the apparatus by a paper discharge roller 117.

  On the other hand, the surface of the photosensitive drum 104 after separation of the recording material is cleaned by the cleaning device 119 after removal of adhering contaminants such as toner remaining after transfer, and is repeatedly used for image formation.

  In the double-sided copy mode, the recording material copied on the first side from the fixing device 116 is introduced into the reverse refeeding unit 114 and reversely fed back to the transfer unit, whereby the second side of the recording material is supplied. The toner image is transferred, and again passes through the fixing device 116 and is discharged as a double-sided copy onto a discharge tray 118 outside the apparatus by a discharge roller 117.

(2) Fixing device 116
2 is a front model view of the main part of the fixing device 116, FIG. 3 is a vertical cross-sectional model view of the main part of the fixing device 116, and FIG. 4 is an operation explanatory view of the powder coating means 31 of the fixing device 116.

  This fixing device 116 is a heating roller type, electromagnetic induction heating type device, and a pair of fixing members which are pressed against each other to form a fixing nip portion N, and two heating rollers 1 which are vertically parallel as pressure members. The pressure roller 2 is mainly used.

A heating roller (hereinafter referred to as a fixing roller) 1 is a hollow (cylindrical) roller (electromagnetic induction heat generating member) made of an induction heating element, and a toner release layer 1a is formed on the outer peripheral surface thereof. In this example, the toner release layer 1a is composed of 30 μm PTFE. A photosensitive layer 1b is formed on the inner peripheral surface of the fixing roller 1 as an image bearing layer. The photosensitive layer 1b is made of amorphous silicon, zinc oxide, titanium oxide or the like. The fixing roller 1 is disposed such that both ends thereof are rotatably supported via bearings 23 between the front and rear side plates 21 and 22 of the fixing device. A heating assembly (excitation coil unit) as a magnetic field (magnetic flux) generating means is provided in the inner space on the surface (photosensitive layer 1b) opposite to the recording material side (heated material side) surface (outer peripheral surface) of the fixing roller 1. ) 3 is inserted and both end portions thereof are fixedly supported non-rotatably by the first holding members 24 and 25 on the front side and the back side of the fixing device, respectively. Further, a powder coating assembly 81 as powder coating means is inserted into the inner space, and both ends thereof are fixedly supported non-rotatably by the second holding members 26 and 27 on the front side and the back side of the fixing device, respectively. Are arranged.

  The pressure roller 2 includes an iron cored bar 2a, a silicone rubber heat-resistant elastic body layer 2b formed concentrically and integrally around an outer periphery of the cored bar, and a toner release formed on the outer peripheral surface thereof. An elastic roller comprising the layer 2c. The toner release layer 2 c is the same as the toner release layer 1 a of the fixing roller 1. The pressure rollers 2 are arranged in parallel to the lower side of the fixing roller 1, and both ends of the cored bar 2 a are rotated via bearings 26 between the front and back side plates 21 and 22 of the fixing device, respectively. A fixing nip having a predetermined width as a heating unit that is held freely and is pressed against the lower surface of the fixing roller 1 by a predetermined pressing force against the elasticity of the elastic layer 2b by a biasing means (not shown). Part N is formed.

  An induction heating element constituting the fixing roller 1 as an electromagnetic induction heating member is a magnetic metal such as nickel, iron, ferromagnetic SUS, iron-nickel alloy, iron-nickel-chromium alloy, nickel-cobalt alloy (electric conductor, Magnetic material). The fixing roller 1 is preferably made of a metal such as iron, nickel, or cobalt. By using a ferromagnetic metal (a metal having a high magnetic permeability), more magnetic flux generated from the magnetic field generating means can be constrained in the ferromagnetic metal. That is, the magnetic flux density can be increased. Thereby, an eddy current is efficiently generated on the surface of the ferromagnetic metal to generate heat. The toner release layer 1a on the outer surface of the fixing roller 7 is generally composed of PTFE 10 to 50 [mu] m or PFA 10 to 50 [mu] m. Further, a rubber layer may be used inside the toner release layer 1a.

  The heating assembly 3 inserted into the inner space of the fixing roller 1 is an assembly of a holder (exterior case body) 4, an excitation coil 5, magnetic cores 6 a and 6 b, and the like. -6b is stored and held. The heating assembly 3 is inserted into the inner space of the fixing roller 1 so as to maintain a predetermined angular attitude and a predetermined gap interval in a non-contact manner with respect to the inner surface of the fixing roller 1. The front and back holding members 24 and 25 are fixedly supported non-rotatably.

  For the holder 4, a heat-resistant and non-magnetic material such as a PPS resin, PEEK resin, polyimide resin, polyamide resin, polyamideimide resin, ceramic, liquid crystal polymer, or fluororesin is suitable.

  The exciting coil 5 must generate an alternating magnetic flux sufficient for heating. For this purpose, it is necessary to have a low resistance component and a high inductance component. As the core wire of the exciting coil 5, a litz wire in which about 80 to 160 fine wires with a diameter of 0.1 to 0.3 are bundled is used. Insulated coated wires are used for the thin wires. Further, an exciting coil is formed by winding a plurality of times in a horizontal boat shape in accordance with the shape of the inner bottom surface of the holder 4 so as to go around the magnetic cores 6a and 6b. The exciting coil 5 is wound in the longitudinal direction of the fixing roller 1 and is held by the inner wall of the holder 4 and the magnetic cores 6a and 6b. Reference numerals 5 a and 5 b denote two outer lead wires (coil supply lines) of the excitation coil 5, which are connected to a power control device (excitation circuit) 52.

  The magnetic cores 6a and 6b are arranged in a T-shaped cross section. The magnetic cores 6a and 6b are high magnetic susceptibility members such as ferrite and permalloy, for example, and are preferably selected using a material with low loss.

A powder coat assembly (hereinafter referred to as a coat assembly) 31 inserted in the inner space of the fixing roller 1 fixes an aluminum-containing powder 32 stored therein as a powder containing a nonmagnetic metal according to image information. An arbitrary region of the roller inner surface photosensitive layer 1b can be selectively coated. That is, the coating area of the aluminum-containing powder 32 can be changed according to the image information. The aluminum-containing powder 32 is a resin powder containing aluminum powder inside, and is configured to include a resin for charge control. That is, the aluminum-containing powder 32 is an aluminum powder coated with a resin. In this embodiment, the aluminum-containing powder 32 is coated on the inner surface of the fixing roller by an electrophotographic process. At this time, in order to give tribo to the powder, the resin part integrated with this aluminum is charged with a resin having a desired charging tendency and stirred (the same function as the toner of the electrophotographic process). To have).

  The coat assembly 31 includes a corona charger (charging unit) 34 that charges the inner surface photosensitive layer 1b of the fixing roller 1, an LED array (exposure unit) 35 that forms an electrostatic latent image on the photosensitive layer 1b, and the electrostatic latent unit. Powder conveying roller (powder conveying means) 36 for conveying the aluminum-containing powder 32 to a region other than the image, and a powder collecting blade for collecting the aluminum-containing powder 32 coated on the photosensitive layer 1b for reuse. (Collecting means) 33 and a holder (exterior case body) 37.

  That is, the coat assembly 31 is an assembly of a corona charger 34, an LED array 35, a powder transport roller 36, a collection blade 33, and a holder 37, and the corona charger 34 is placed in a holder 37 in which the aluminum-containing powder 32 is stored. The LED array 35, the powder transport roller 36, and the powder recovery blade 33 are stored and held. The coat assembly 37 is inserted into the inner space of the fixing roller 1 so as to leave a predetermined gap between the coating assembly 37 and the heating assembly 3 at predetermined positions. The holding members 26 and 27 are fixedly supported. In the coat assembly 31, the collection blade 33, the corona charger 34, the LED array 35, and the powder transport roller 36 are arranged in that order from the downstream side of the fixing nip portion N in the rotation direction A of the fixing roller 1. The powder recovery blade 33 is disposed such that the tip thereof is in contact with the inner surface photosensitive layer 1 b of the fixing roller 1. The corona charger 34, the LED array 35, and the powder conveying roller 36 are arranged with a predetermined gap from the inner surface photosensitive layer 1b.

7 is a thermistor as a temperature detecting means of the fixing row La 1, are arranged to press is elastically contacted by the elastic member to the surface of the fixing roller 1. The temperature signal detected by the thermistor 7 is input to the control circuit 51. The temperature detection means 7 is not limited to the thermistor, and may be a temperature detection element, and may be a contact type or a non-contact type.

  A pre-fixing guide plate 8 guides the recording material S conveyed from the image forming mechanism side to the fixing device 116 to the inlet portion of the fixing nip portion N. Reference numeral 9 denotes a separation claw, which suppresses the recording material S introduced into the fixing nip portion N and exiting the fixing nip portion N from being wound around the fixing roller 1 and serves to separate the recording material S from the fixing roller 1. Reference numeral 10 denotes a post-fixing guide plate that guides the recording material S that has exited the exit of the fixing nip N to be discharged.

  When the main power switch of the image forming apparatus is turned on, the control circuit 51 activates the first driving source (first motor) M1. The rotational driving force is transmitted to a fixing roller gear G1 fixed to one end portion of the fixing roller 1 through a power transmission system, so that the fixing roller 1 has a predetermined peripheral speed in the clockwise direction indicated by an arrow A in FIG. Is rotated. The pressure roller 2 rotates in the counterclockwise direction B indicated by the arrow following the rotational driving of the fixing roller 1.

  In addition, the control circuit 51 activates a power control device (excitation circuit) 52 to supply power to the excitation coil 5 of the heating assembly 3 disposed in the fixing roller 1 from the power control device 52 via the coil supply lines 5a and 5b. (In this embodiment, a high-frequency current of 10,000 Hz) is supplied. As a result, the fixing roller 1 as an induction heating member generates induction heat (Joule heat due to eddy current loss) by the action of magnetic flux (alternating magnetic field) generated from the heating assembly 3. The temperature of the fixing roller 1 is detected by the thermistor 7 which is a temperature detecting means, and the detected temperature signal is input to the control circuit 51. The control circuit 51 supplies power from the power control device 52 to the exciting coil 5 of the heating assembly 3 so that the detected temperature of the fixing roller 1 input from the thermistor 7 is maintained at a predetermined fixing temperature, in this case 200 ° C. The power is controlled to adjust the temperature of the fixing roller.

(3) Description of Operation of Coat Assembly 31 The operation of the coat assembly 31 will be described below by taking as an example the case where the recording material S is passed through the fixing device 116.

  In the state where the fixing roller 1 and the pressure roller 2 are rotationally driven as described above, the control circuit 51 takes in image information corresponding to the unfixed toner image t formed on the recording material S from the image photoelectric reading device 103. . Based on the image information, the coating assembly 31 charges the inner surface photosensitive layer 1 b of the fixing roller 1, forms an electrostatic latent image, and develops, and starts coating the aluminum-containing powder 32.

  In FIG. 4, S is a recording material which is a heated object to be conveyed, and an unfixed toner image T is placed thereon. The coating of the aluminum-containing powder 32 on the inner surface photosensitive layer 1 b of the fixing roller 1 by the coating assembly 31 is performed so that a portion other than the toner image T on the recording material S in the nip portion N is covered with the aluminum-containing powder 32. Are performed based on the image information.

  That is, when the control circuit 51 captures image information, the charging bias power supply 53 is first activated. The charging bias power supply 53 supplies a charging bias to the corona charger 34, and the corona charger 34 uniformly charges the inner surface photosensitive layer 1 to a predetermined potential and polarity according to the bias. Next, the control circuit 51 controls the LED array driving circuit 54 based on the image information. The LED array drive circuit 54 controls the lighting of the LED array 35 based on the image information, and the LED array 35 irradiates light to the inner surface photosensitive layer 1b from the LED whose lighting is controlled to form a latent image corresponding to the image information. . Next, the control circuit 51 activates the second drive source (second motor) M2. The rotational driving force is transmitted to the developing roller gear G2 fixed to one end portion of the powder conveying roller 36 through the power transmission system, so that the powder conveying roller 36 is rotated in the clockwise direction of the arrow C (FIG. 4). It is rotationally driven at a predetermined peripheral speed. The aluminum-containing powder 32 is conveyed to the inner surface photosensitive layer 1b by the rotationally driven powder conveying roller 36 and is electrostatically coated on portions other than the latent image forming portion F.

  As described above, the fixing roller 1 and the pressure roller 2 are driven to rotate, and the fixing roller 1 is inductively heated by supplying power to the excitation coil 5 of the heating assembly 3 and is adjusted to a predetermined fixing temperature. The recording material S carrying the unfixed toner image T transferred electrostatically in the transfer portion of the image mechanism portion is introduced into the fixing nip portion N of the fixing device 116 and is nipped and conveyed. At this time, the portion F (FIG. 5B) of the fixing roller 1 that is in contact with the toner image T (FIG. 5A) at the nip N is a portion that is not coated with the aluminum-containing powder 32, and accordingly. The heating assembly 3 is induction-heated along with the rotation of the fixing roller 1, and the toner image T is heated and fixed at the nip portion N.

On the other hand, in the portion coated with the aluminum-containing powder 32 (coating region) F ′ (FIG. 5B), the magnetic lines of force are blocked by the aluminum-containing powder 32, and induction heating of the fixing roller 1 is suppressed. For this reason, the region where the toner image T is not placed on the recording material S is not heated, and only the F portion overlapping the toner image T in the nip portion N can be selectively heated as shown in FIG.

  The lines of magnetic force in the region coated with the aluminum-containing powder 32 penetrate the aluminum-containing powder coat portion F ′ by the penetration depth δ represented by the following formula and pass through the inside.

δ = (π * f * μ * σ) ^−1/2
(F: exciting current frequency of magnetic field generating means, μ: permeability of electromagnetic induction heat generating member, σ: conductivity of electromagnetic induction heat generating member)
Here, in the case of a nonmagnetic material such as aluminum, since the permeability is small, the penetration depth δ is increased, the resistance value of the eddy current is decreased, and Joule heat generation can be suppressed. For this reason, the aluminum-containing powder coat 32 can block the lines of magnetic force to the fixing roller 1 without generating heat.

  At this time, the thickness of the toner is more preferably larger than the penetration depth δ. By doing so, the aluminum-containing powder coat 32 can block the magnetic lines of force to the fixing roller 1 without generating heat.

For this reason, the power required for the heating assembly 3 for raising the fixing roller 1 to a temperature at which the toner image T can be fixed depends on the area of the toner image. Therefore, if the toner image area is small, it can be raised to a predetermined temperature with a small amount of power. Further, the power (input power) supplied from the power control device 52 to the heating assembly 3 via the coil supply wires 5a and 5b is controlled by the control circuit 51 based on the image information, so that printing can be performed efficiently. Energy saving can be realized. In other words, when the data amount of image information is large, the supply power is increased, and when the data amount is small, the supply power is controlled to be decreased (the input power is changed), thereby efficiently saving energy during printing. Can be realized.

  In the nipping and conveying process, the unfixed toner image T on the recording material S is fixed on the recording material surface as a permanently fixed image by the heat and nip pressure of the fixing roller 1.

In this embodiment, an example in which an area other than a toner image is coated with aluminum-containing powder according to image information has been shown. However, for example, a non-sheet passing area according to the paper size (the width of the material to be heated) Needless to say, it can also be used as a countermeasure for raising the temperature of the non-sheet-passing portion by coating only (changing the coating area of the aluminum-containing powder) .

  A second embodiment of the present invention will be described with reference to the drawings.

  FIG. 6 is a schematic longitudinal cross-sectional schematic view of the main part of an electromagnetic induction heating type fixing device used in the image forming apparatus according to the embodiment of the present invention.

The fixing device of this embodiment is obtained by forming the fixing roller 1 in the form of an endless and flexible fixing film 1A in the fixing device 116 (FIG. 3) of the first embodiment.

  In the fixing device 116 of this embodiment, an endless belt-like fixing film 1A as an electromagnetic induction heat generating member is suspended and stretched between a film guide member 60, a driving roller 61, and a tension roller 62. . A fixing nip portion N is formed by pressing the lower surface portion of the film guide member 60 and the driven rotary pressure roller 2 with the fixing film 1A interposed therebetween. The fixing film 1A is rotationally driven in the clockwise direction indicated by the arrow A by the driving roller 61, and the pressure roller 2 receives the rotational force from the fixing film 1A and is driven to rotate counterclockwise as indicated by the arrow B. The recording material S is nipped and conveyed by the fixing film 1A and the pressure roller 2 to the fixing nip portion N, whereby the toner image T on the recording material is heated and fixed on the recording material S.

Reference numeral 63 denotes powder coating means using a so-called toner jet system, which can selectively coat the aluminum-containing powder 65 stored in the holder 64 on an arbitrary area on the inner surface of the fixing film 1A. The aluminum-containing powder 65 is a resin powder containing aluminum powder inside, and is configured to include a resin for charge control. The powder coating means 63 includes a back electrode 66 for forming an electric field for causing the aluminum-containing powder 65 to fly, an insulating plate 67 provided with a large number of powder passage holes around which ring-shaped electrodes are provided, A powder conveying roller 68 for supplying the aluminum-containing powder 65 to the insulating plate 67 is configured. The back electrode 66 is disposed on the outer surface side of the fixing film 1A so as to face the insulating plate 67 with the fixing film 1A interposed therebetween. A control circuit (not shown) controls the powder coating means driving power source (not shown) on the ring electrode of the insulating plate 67 based on the image information and selectively applies a voltage from the power source, thereby fixing film 1A. Of these, the aluminum-containing powder 65 can be coated on the nip portion N that does not correspond to the toner image. The coating of the aluminum-containing powder 65 on the inner surface of the fixing film by the powder coating means 63 is timed so that a portion other than the toner image T on the recording material S in the nip portion N is covered with the aluminum powder 65. This is performed based on image information.

  Reference numeral 3 denotes a heating assembly as a magnetic flux (magnetic field) generating means, which is disposed downstream of the powder coating means 63 in the rotation direction of the fixing film 1A. The heating assembly 3 electromagnetically heats the region of the fixing film 1A that is not coated with the aluminum-containing powder 65 together with the rotation of the fixing film 1A.

  Reference numeral 68 denotes an aluminum-containing powder collecting means, which is disposed downstream of the heating assembly 3 in the rotation direction of the fixing film 1A. The aluminum-containing powder collecting means 68 electrostatically collects the aluminum-containing powder 65 by the collecting roller 70 provided on the collecting frame 69 and contacts the collecting blade 71 provided on the collecting frame 69 with the inner surface of the fixing film. Thus, the aluminum-containing powder 65 is recovered. The aluminum-containing powder recovered by the aluminum-containing powder recovery means 68 is transported to the powder coating means 63 by a transport means (not shown) and reused.

  Therefore, by using the fixing device having the above-described configuration, it is possible to realize quick start-up by belt heating with a low heat capacity and selective heating and fixing of only the toner image, realizing energy saving during standby and printing. In addition, problems such as curling due to wasted paper heating can be prevented.

  As described above, the image forming apparatus according to each embodiment is a non-magnetic metal-containing powder coated on a predetermined region of the fixing roller 1 or the fixing film 1A as an electromagnetic induction heat-generating member based on image information. The aluminum-containing powders 32 and 65 correspond to the toner image T formed and supported on the recording material S in order to block the magnetic lines of force acting on the fixing roller 1 or the fixing film 1A from the heating assembly 3 as the magnetic field generating means. It is possible to selectively prevent heating of the fixing roller 1 or the fixing film 1A in the non-existing portion, and it is possible to prevent problems due to excessive recording material heating by selective heating and fixing only the toner image portion.

  In addition, the lines of magnetic force acting on the aluminum-containing powders 32 and 65, which are non-magnetic metal-containing powders, reduce the resistance of eddy currents by increasing the penetration depth of the magnetic lines of force with respect to the non-magnetic metal. The powder itself can block the lines of magnetic force without generating heat. For this reason, energy saving during printing can be realized by selective heating and fixing only the toner image T.

  Further, no special toner is required for the fixing roller 1 or the fixing film 1A as the toner or the electromagnetic induction heat generating member, and since a normal one that is currently distributed can be used as it is, there is no problem in colorization or the like. Can be realized.

  In addition, the magnetic field effect time from the heating assembly 3 as the magnetic field generating means to the fixing roller 1 or the fixing film 1A as the electromagnetic induction heat generating member appropriately sets the distance in the direction of conveyance of the electromagnetic induction heat generating member in the magnetic force effect region. Therefore, the electromagnetic induction heat-generating member can be heated with sufficient time, so that it is possible to easily increase the speed while realizing toner image portion selective heating and fixing.

[Other]
1) In the heat fixing apparatus, the electromagnetic induction heat generating member can be configured as a single member of the electromagnetic induction heat generating member, or other material such as a heat resistant resin / ceramic including the layer of the electromagnetic induction heat generating member. It can also be configured as a composite layer material with two or more layers.

  2) In the heat fixing device, the electromagnetic induction heating of the electromagnetic induction heat generating member by the magnetic field generating means is not limited to the internal heating method of the embodiment, but the external heating method in which the magnetic flux generating means is disposed outside the electromagnetic induction heat generating member. A device configuration can also be adopted.

  3) The image heating apparatus of the present invention is not limited to the heat fixing apparatus of the embodiment, but an image heating apparatus that heats a recording material carrying an image to improve surface properties such as gloss, an image heating apparatus that is supposed to be worn, It can be used as a means / apparatus for heat-treating a recording material carrying an image widely.

Schematic configuration diagram of an example image forming apparatus having an electromagnetic induction type fixing device Front model diagram of the main part of the fixing device Longitudinal cross-sectional model of the main part of the fixing device Operation explanatory diagram of powder coating means of fixing device FIG. 6 is a diagram for explaining toner image selective heat fixing Longitudinal cross-sectional model view of the main part of another electromagnetic induction heating type fixing device used in an image forming apparatus

Explanation of symbols

1 fixing roller, 1A fixing film, 2 pressure roller, 3 heating assembly,
31 powder coat assembly (powder coat means), 32 aluminum-containing powder,
63 powder coating means, 65 aluminum-containing powder, 116 fixing device,

Claims (5)

In an image heating apparatus having a magnetic field generating means and a heat generating member that generates electromagnetic induction heat by the action of the magnetic field generating means, and that heats an image on a heated material formed based on image information by the heat generating member,
A powder containing the magnetic field generating means on the surface opposite to the surface to be heated of the heat generating member and containing a nonmagnetic metal on the surface of the heat generating member on the magnetic field generating means side according to image information. An image heating apparatus comprising powder coating means for coating . 2. The image heating apparatus according to claim 1, wherein the powder coating means changes a powder coating region in accordance with image information. 2. The image heating apparatus according to claim 1, wherein the powder coating means changes a powder coating region in accordance with a width of the material to be heated. Wherein a removing means for removing the coated powder to the heating member, according to claim 1 to 3 the powder recovered at the removing means and having a means for returning to the powder coating means Any one of the image heating apparatuses.   The image heating apparatus according to claim 1, wherein input power to the magnetic field generation unit is changed based on image information.