JP3787426B2 - Heating device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a heating device of an electromagnetic (magnetic) induction heating system.In placeRelated.
[0002]
[Prior art]
For convenience, an image heating apparatus (fixing apparatus) that heats and fixes a toner image on a recording material in an image forming apparatus such as a copying machine or a printer will be described as an example.
[0003]
  In an image forming apparatus, a recording material (transfer material sheet, electrofax sheet, electrostatic recording paper, OHP sheet, printing paper, photo paper, photo paper, and the like is recorded by appropriate image forming process means such as an electrophotographic process, an electrostatic recording process, and a magnetic recording process. As a fixing device that heats and fixes an unfixed image (toner image) of the target image information formed and supported on a matte sheet or the like by a transfer method or a direct method as a permanently fixed image on a recording material surface, a heat roller method is used. The device was widely used. Recently, it is advantageous for energy saving and shortening wait time.the filmHeating devices have been put into practical use. Similarly, an electromagnetic induction heating apparatus has also been proposed.
[0004]
a) Heat roller type fixing device
This is based on a pressure roller pair consisting of a fixing roller (heating roller) and a pressure roller, and the roller pair is rotated so that the unfixed toner to be fixed on the fixing nip portion which is the mutual pressure contact portion of the roller pair. A recording material on which an image is formed and supported is introduced, nipped and conveyed, and an unfixed toner image is fixed on the surface of the recording material by heat of the fixing roller and a pressing force of the fixing nip portion.
[0005]
In general, the fixing roller has an aluminum hollow metal roller as a base body (core metal), and a halogen lamp as a heat source is inserted and disposed in the inner space thereof. The temperature of the halogen lamp is controlled and controlled so that the temperature is maintained.
[0006]
In particular, as a fixing device of an image forming apparatus for performing full-color image formation that requires the ability to sufficiently heat-melt and mix colors of up to four toner image layers, the core metal of the fixing roller has a high heat capacity. In addition, a rubber elastic layer for wrapping the toner image around the core metal and melting it uniformly is provided, and the toner image is heated through the rubber elastic layer. There is also a configuration in which a heat source is also provided in the pressure roller so that the pressure roller is also heated and temperature-controlled.
[0007]
However, in the heat roller type fixing device, even when the image forming apparatus is turned on and the energization of the halogen lamp, which is a heat source, is started, the fixing roller has a large heat capacity, so that the fixing roller and the like are cold. A considerable waiting time (wait time) is required until the temperature rises to a predetermined fixing temperature, and the quick start property is lacking. Also, it is necessary to energize the halogen lamp and maintain the fixing roller at a predetermined temperature control state even when the image forming apparatus is in a standby state (non-image output) so that an image forming operation can be executed at any time. There were problems such as large power consumption.
[0008]
Further, in the case of using a fixing roller having a particularly large heat capacity like the fixing device of the above-described full-color image forming apparatus, a delay occurs in temperature control and temperature increase on the surface of the fixing roller. Problems such as offset occurred.
[0009]
b) Film heating type fixing device
A film heating type fixing device has been proposed in, for example, Japanese Patent Application Laid-Open No. 63-313182, Japanese Patent Application Laid-Open No. 2-157878, Japanese Patent Application Laid-Open No. 4-44075, Japanese Patent Application Laid-Open No. 4-204980, and the like.
[0010]
That is, a nip portion is formed by sandwiching a heat resistant film (fixing film) between a ceramic heater as a heating body and a pressure roller as a pressure member, and the film of the nip portion and the pressure roller The recording material on which an unfixed toner image to be image-fixed is formed and supported is introduced and conveyed together with the film so that the heat of the ceramic heater is applied to the recording material through the film at the nip portion. Further, the unfixed toner image is fixed to the surface of the recording material by heat and pressure by the applied pressure of the nip portion.
[0011]
This film heating type fixing device can be configured as an on-demand type device using a ceramic heater and a film having a low heat capacity as a film, and energizes the ceramic heater as a heat source only when the image forming apparatus performs image formation. It is only necessary to generate heat at a predetermined fixing temperature, and the waiting time from the power-on of the image forming apparatus to the image forming executable state is short (quick start property), and the power consumption during standby is greatly reduced (saving) Power).
[0012]
c) Electromagnetic induction heating type fixing device
Japanese Utility Model Laid-Open No. 51-109736 discloses an induction heating fixing apparatus that induces a current in a fixing roller by magnetic flux and generates heat by Joule heat. This achieves a fixing process that is more efficient than a heat roller type fixing device using a halogen lamp as a heat source by directly generating heat from the fixing roller using generation of an induced current.
[0013]
However, since the energy of the alternating magnetic flux generated by the exciting coil as the magnetic field generating means is used to raise the temperature of the entire fixing roller, the heat dissipation loss is large, and the fixing energy density relative to the input energy is low and the efficiency is low.
[0014]
Therefore, in order to obtain a high density of energy that affects fixing, high-efficiency fixing is achieved by bringing the exciting coil closer to the fixing roller, which is a heating element, or by concentrating the alternating magnetic flux distribution of the exciting coil near the fixing nip. A device was devised.
[0015]
FIG. 14 shows a schematic configuration of an example of an electromagnetic induction heating type fixing device that improves the efficiency by concentrating the alternating magnetic flux distribution of the exciting coil in the fixing nip.
[0016]
Reference numeral 10 denotes a cylindrical fixing film having an electromagnetic induction heat generating layer (conductor layer, magnetic layer, resistor layer) as an electromagnetic induction heat generating rotating body.
[0017]
Reference numeral 16 denotes a saddle-shaped film guide member having a substantially semicircular arc shape in cross section, and the cylindrical fixing film 10 is loosely fitted outside the film guide member 16.
[0018]
Reference numeral 15 denotes a magnetic field generating means disposed inside the film guide member 16, which includes an exciting coil 18 and an E-type magnetic core (core material) 17.
[0019]
Reference numeral 30 denotes an elastic pressure roller. The fixing film 10 is sandwiched between the lower surface of the film guide member 16 so as to form a fixing nip portion N having a predetermined width with a predetermined pressing force, and are pressed against each other. The magnetic core 17 of the magnetic field generating means 15 is disposed at a position corresponding to the fixing nip N. The pressure roller 30 is rotationally driven by the driving means M in the counterclockwise direction indicated by the arrow. A rotational force acts on the fixing film 10 by the frictional force between the pressure roller 30 and the outer surface of the fixing film 10 by the rotational driving of the pressure roller 30, and the fixing film 10 has its inner surface at the fixing nip portion N as a film guide. The outer periphery of the film guide member 16 is rotationally driven at a peripheral speed substantially corresponding to the rotational peripheral speed of the pressure roller 30 in the clockwise direction indicated by the arrow while sliding in close contact with the lower surface of the member 16 (pressure roller drive system) ).
[0020]
The film guide member 16 serves to pressurize the fixing nip N, support the exciting coil 18 and the magnetic core 17 as the magnetic field generating means 15, support the fixing film 10, and transport stability during rotation of the film 10. do. The film guide member 16 is an insulating member that does not hinder the passage of magnetic flux, and a material that can withstand a high load is used.
[0021]
The temperature of the fixing nip portion N is detected by the temperature detecting means 26 brought into contact with the pressure roller 30, and based on this, the current supply to the exciting coil 18 is controlled so that a predetermined temperature is maintained. The temperature is adjusted.
[0022]
Thus, the pressure roller 30 is driven to rotate, and the cylindrical fixing film 10 rotates around the outer periphery of the film guide member 16, and the fixing film 10 is supplied with power from the excitation circuit to the excitation coil 18 as described above. The recording material P on which the unfixed toner image t is formed by the image forming means (not shown) is transferred to the fixing nip in a state where the fixing nip portion N rises to a predetermined temperature and is temperature-controlled. The fixing film 10 is introduced between the fixing film 10 of the portion N and the pressure roller 30 with the image surface facing upward, that is, facing the fixing film surface, and is sandwiched with the image surface being in close contact with the outer surface of the fixing film 10. 10 is conveyed along the fixing nip portion N together with 10. In the process of being conveyed through the fixing nip N, the fixing film 10 is heated by electromagnetic 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 10 and discharged and conveyed.
[0023]
[Problems to be solved by the invention]
In the above-described electromagnetic induction type fixing device in which the fixing film 10 generates heat as shown in FIG. 14, since the heat capacity of the fixing film 10 is small and the thickness is thin, the thermal conductivity in the longitudinal direction of the film is low. For this reason, when a recording material having a width smaller than that of the fixing film 10 is passed, the heat of a portion (non-sheet passing portion) through which the recording material does not pass is not taken away by the recording material. In this case, the temperature of the film rises (non-sheet passing portion temperature rise).
[0024]
For this reason, for example, when printing, for example, A4 size paper next to small size paper such as an envelope, the temperature of the non-sheet passing portion after passing the small size paper reaches the toner offset temperature. When the size paper is passed, the toner on the A4 size paper is offset to the fixing film, which causes a problem that a good fixed image cannot be obtained. For this reason, in order to solve the temperature increase in the non-sheet passing portion, it is necessary to reduce the throughput and greatly reduce the number of sheets that are passed per minute.
[0025]
  Accordingly, an object of the present invention is to provide an electromagnetic induction heating type heating device.In placeIn the heating nip portion, the good heat conduction member is disposed at a position facing the pressure member, thereby reducing the temperature rise at the non-sheet passing portion and increasing the throughput when the small size paper is passed. With the goal.
[0026]
[Means for Solving the Problems]
  The present invention provides a heating apparatus having the following configuration.In placeis there.
[0027]
  [1]: a magnetic field generating means, a member that generates electromagnetic induction heat by the action of the magnetic field of the magnetic field generating means, and a pressure member that forms a heating nip portion of the material to be heated in mutual pressure contact with the electromagnetic induction heat generating member And a heating device that heats the material to be heated by the heat generated by the electromagnetic induction heating member,
  A good heat conducting member at a position facing the pressure member through the electromagnetic induction heating member of the heating nip portionAnd the magnetic field generating means is disposed at a position where the influence of the magnetic field generated by the magnetic field generating means is not given to the good heat conducting member.A heating device characterized by that.
[0028]
  [2]:in frontThe electromagnetic induction heating element is a rotating bodyClaim 1Heating device.
[0030]
  [3]:in frontThe thermal conductivity k of the good thermal conductive member is
k ≧ 70 [W · m^-1・ K^-1]
It is characterized byAccording to [1]Heating device.
[0031]
  [4]:in frontThe good heat conducting member is a non-magnetic memberAccording to [1]Heating device.
[0032]
  [5]:in frontThe heat conductive member is a non-magnetic metalAccording to [1]Heating device.
[0035]
  [6]:in frontThe magnetic field generating means comprises an exciting coil and a core, and the good heat conducting member is disposed at a position separating the core from the exciting coil.According to [1]Heating device.
[0038]
    <Action>
  (1)A good heat conduction member is provided at a position facing the pressure member via the electromagnetic induction heating member of the heating nip portion, and the magnetic field generation means influences the good heat by the magnetic field generated by the magnetic field generation means. It is arranged at a position not to give to the conductive memberByHeatingHeat conduction at the nip is improved, and the material to be heated with a narrow widthHeatingEven when the nip portion is passed, the temperature rise of the non-sheet passing portion can be suppressed.
[0040]
(3) The thermal conductivity k of the good heat conducting member is k ≧ 70 [w · m^-1・ K^-1As a result, good thermal conductivity is secured.
[0041]
(4) Since the good heat conducting member is a non-magnetic member, it does not generate heat due to the magnetic field of the magnetic field generating means, so the location of the magnetic field generating means can be arbitrarily set, and the degree of freedom in design is improved. This facilitates downsizing of the device.
[0043]
DETAILED DESCRIPTION OF THE INVENTION
(1) Example of image forming apparatus
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.
[0044]
Reference numeral 101 denotes a photosensitive drum (image carrier) 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 (circumferential speed).
[0045]
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.
[0046]
Next, the charged surface is subjected to scanning exposure processing of target image information by laser light 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. By scanning and exposing the drum 101 surface, an electrostatic latent image corresponding to the target image information is formed on the drum 101 surface. Reference numeral 109 denotes a mirror that deflects the output laser beam 103 from the laser optical box 110 to the exposure position of the photosensitive drum 101.
[0047]
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 to the surface of the intermediate transfer drum 105 at the primary transfer portion T1 which is a contact portion (or proximity portion) between the photosensitive drum 101 and the intermediate transfer drum 105. 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 the same peripheral speed as that of the photosensitive drum 101. The toner image on the photosensitive drum 101 side is transferred to the surface of the intermediate transfer drum 105 by the potential difference from the photosensitive drum 101 by being driven to rotate clockwise.
[0048]
The surface of the rotary 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 adhered residues such as transfer residual toner.
[0049]
The process cycle of charging, scanning exposure, development, primary transfer, and cleaning as described above includes a second color separation component image (for example, a magenta component image, the magenta developer 104M is activated) of a target full color image, and a third color. Each color separation component image of the separation component image (for example, cyan component image, cyan developing device 104C is activated) and the fourth color separation component image (for example, the black component image, black developing device 104BK is activated) is sequentially executed for intermediate transfer Four color toner images of a yellow toner image, a magenta toner image, a cyan toner image, and a black toner image are sequentially superimposed and transferred onto the surface of the body drum 105, and a color toner image corresponding to the target full-color image is synthesized and formed. .
[0050]
The color toner image is transferred to the secondary transfer portion T2 from a paper feeding portion (not shown) at a predetermined timing in the secondary transfer portion T2 which is a contact nip portion between the rotating intermediate transfer drum 105 and the transfer roller 106. It is transferred onto the surface of the recording material P that has been fed. The transfer roller 106 batch-transfers the combined color toner image from the surface of the intermediate transfer drum 105 to the recording material P side by supplying a charge having a polarity opposite to that of the toner from the back surface of the recording material P.
[0051]
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 the image heating device (fixing device) 100, and undergoes a heat fixing process for an unfixed toner image to obtain a color image. The formed product is discharged to a discharge tray (not shown) outside the apparatus. The fixing device 100 will be described in detail in the next section (2).
[0052]
After the color toner image has been transferred to the recording material P, the rotating intermediate transfer drum 105 is cleaned by the cleaner 108 after removal of adhering residues such as transfer residual toner and paper dust. The cleaner 108 is held in a non-contact state with the intermediate transfer drum 105 during normal times (when a toner image is synthesized), and the secondary transfer of the color toner image from the intermediate transfer drum 105 to the recording material P is performed. In the execution process, the toner image is held in contact with the surface of the intermediate transfer drum 105 after the toner image is transferred.
[0053]
Also, the transfer roller 106 is always held in a non-contact state with the intermediate transfer drum 105, and the intermediate transfer drum 105 is covered 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. The recording material P is held in contact.
[0054]
This example apparatus can also execute a mono-color image print mode such as a self-black image. A double-sided image print mode or a multiple image print mode can also be executed.
[0055]
In the double-sided image print mode, the recording material P that has been printed on the first side of the image heated from the image heating device 100 is turned upside down via a recirculation conveyance mechanism (not shown) and sent again to the secondary transfer portion T2. Upon receiving the toner image transfer on the second side, the toner image is again introduced into the image heating apparatus 100 and the toner image is fixed on the second side, whereby a double-sided image print is output.
[0056]
In the multiple image print mode, the recording material P on which the first image has been printed out of the image heating apparatus 100 is sent again to the secondary transfer portion T2 through the recirculation conveyance mechanism (not shown) without being turned upside down. Then, the second toner image is transferred to the surface on which the first image has been printed, and is again introduced into the image heating apparatus 100 and undergoes the second toner image fixing process, whereby a multiple image print is output.
[0057]
In this example, a toner containing a low softening material is used.
[0058]
(2) Fixing device (heating means) 100
2 is a cross-sectional side view of the main part of the fixing device 100 of this example, FIG. 3 is a front view of the main part, and FIG. 4 is a longitudinal front view of the main part.
[0059]
This example apparatus 100 is an apparatus of a pressure roller driving system and an electromagnetic induction heating system using a cylindrical electromagnetic induction heat-generating film, similarly to the fixing apparatus of FIG. Constituent members / portions common to those in the apparatus of FIG.
[0060]
The magnetic cores 17a, 17b, and 17c are members having high magnetic permeability, and are preferably made of a material used for a transformer core such as ferrite or permalloy, and more preferably ferrite having a low loss even at 100 kHz or more.
[0061]
An excitation circuit 27 (FIG. 5) is connected to the excitation coil 18 at the power feeding portions 18a and 18b. The excitation circuit 27 can generate a high frequency of 20 kHz to 500 kHz by a switching power supply.
[0062]
The exciting coil 18 generates an alternating magnetic flux by the alternating current (high-frequency current) supplied from the exciting circuit 27.
[0063]
Reference numerals 16a and 16b denote saddle-shaped film guide members having a substantially semicircular arc cross-section, which form a substantially cylindrical body with the opening sides facing each other, and loosely fix the fixing film 10 which is a cylindrical electromagnetic induction heat generating film on the outside. It is fitted outside.
[0064]
The film guide member 16a holds magnetic cores 17a, 17b, and 17c as magnetic field generating means and an excitation coil 18 inside.
[0065]
Further, as shown in FIG. 2, the film guide member 16a is provided with a good heat conducting member 40 in the longitudinal direction in the drawing as opposed to the pressure roller 30 in the nip portion N and inside the fixing film 10. It is.
[0066]
In this example, iron is used for the good heat conducting member 40. The good thermal conductive member 40 has a thermal conductivity k of k = 72 [w · m^-1・ K^-1], And the thickness is 1 [mm].
[0067]
The good heat conducting member 40 is prevented from generating heat by the exciting coil 18 and the magnetic cores 17a, 17b and 17c which are magnetic field generating means. That is, it is arranged outside this magnetic field so as not to be affected by the generated magnetic field. This is because if the magnetic metal such as iron is disposed in the magnetic field generated from the magnetic field generating means, the iron itself generates heat.
[0068]
When the iron itself as the good heat conducting member 40 generates heat, when the small-size paper passes through the nip portion N, the non-sheet passing portion temperature rise occurs as in the heating by the fixing film 10. The effect for reducing the temperature increase of the non-sheet passing portion is reduced. Therefore, the good heat conducting member 40 is preferably arranged outside the magnetic field generated from the magnetic field generating means. Specifically, the good heat conducting member 40 is disposed at a position separating the magnetic core 17c from the exciting coil 18, and is located outside the magnetic path by the exciting coil 18 to affect the good heat conducting body 40. I am trying not to.
[0069]
Reference numeral 22 denotes a laterally long pressurizing rigid stay disposed in contact with the inner surface plane portion of the film guide member 16b in which the magnetic cores 17a, 17b, and 17c and the exciting coil 18 are disposed.
[0070]
Reference numeral 19 denotes an insulating member for insulating the magnetic cores 17a, 17b, and 17c and the exciting coil 18 from the pressurizing rigid stay 22.
[0071]
23a and 23b are flange members that are fitted around the left and right ends of the assembly of the film guide members 16a and 16b, are rotatably mounted while fixing the left and right positions, and restrict and hold the end portions of the fixing film 10.
[0072]
The pressure roller 30 as a pressure member includes a cored bar 30a, and a heat-resistant / elastic material layer 30b made of silicone rubber, fluororubber, fluororesin, or the like, which is concentrically molded and coated around the cored bar. The both ends of the cored bar 30a are rotatably held between the chassis side plates (not shown) of the apparatus.
[0073]
A pressing force is applied to the pressurizing rigid stay 22 by contracting the pressurizing springs 25a and 25b between both ends of the pressurizing rigid stay 22 and the spring receiving members 29a and 29b on the apparatus chassis side. As a result, the lower surface of the good heat conducting member 40 disposed on the lower surface of the film guide member 16a and the upper surface of the pressure roller 30 are pressed against each other with the fixing film 10 interposed therebetween to form a fixing nip portion N having a predetermined width.
[0074]
The pressure roller 30 is rotationally driven by the driving means M in the counterclockwise direction indicated by the arrow. A rotational force acts on the fixing film 10 by a frictional force between the pressure roller 30 and the outer surface of the fixing film 10 by the rotational driving of the pressure roller 30, and the inner surface of the fixing film 10 has good heat at the fixing nip N. The outer periphery of the film guide members 16a and 16b is rotated in a clockwise direction indicated by an arrow with a peripheral speed substantially corresponding to the rotational peripheral speed of the pressure roller 30 while sliding in close contact with the lower surface of the conductive member 40.
[0075]
In this case, in order to reduce the mutual sliding frictional force between the lower surface of the good heat conductive member 40 and the inner surface of the fixing film 10 in the fixing nip portion N, the lower surface of the good heat conductive member 40 and the fixing film 10 in the fixing nip portion N. A lubricant such as heat-resistant grease can be interposed between the inner surface and the lower surface of the good heat conducting member 40 can be covered with the lubricating member. This is because the surface slipperiness is not good as in the case where iron is used as the good heat conducting member 40, or when the finishing process is simplified, the sliding fixing film 10 is damaged and the fixing film is damaged. 10 is to prevent the durability of 10 from deteriorating. Further, as shown in FIG. 5, convex rib portions 16e are formed on the peripheral surface of the film guide member 16a at predetermined intervals along the length thereof, and the peripheral surface of the film guide member 16a and the inner surface of the fixing film 10 are formed. The contact sliding resistance is reduced to reduce the rotational load of the fixing film 10. Such a convex rib part can be similarly formed on the film guide member 16b.
[0076]
FIG. 6 schematically shows the state of alternating magnetic flux from the exciting coil 18 and the magnetic cores 17a, 17b, and 17c, which are magnetic field generating means. A magnetic flux C represents a part of the generated alternating magnetic flux.
[0077]
The alternating magnetic flux C guided to the magnetic cores 17a, 17b, and 17c is vortexed in the electromagnetic induction heating layer 1 of the fixing film 10 between the magnetic cores 17a and 17b and between the magnetic cores 17a and 17c. Generate current. This eddy current causes Joule heat (eddy current loss) to be generated in the electromagnetic induction heat generating layer 1 by the specific resistance of the electromagnetic induction heat generating layer 1. The calorific value Q here is determined by the density of the magnetic flux passing through the electromagnetic induction heat generating layer 1, and shows a distribution as shown in the graph of FIG. In the graph of FIG. 6, the vertical axis indicates the circumferential position in the fixing film 10 represented by an angle θ with the center of the magnetic core 17 a being 0, and the horizontal axis is the heat generation in the electromagnetic induction heating layer 1 of the fixing film 10. The quantity Q is indicated. Here, when the maximum heat generation amount is Q, the heat generation region H is defined as a region where the heat generation amount is Q / e or more. This is a region where the amount of heat generated for fixing can be obtained.
[0078]
The heat generation of the fixing film 10 is controlled so that the temperature of the fixing nip N is maintained at a predetermined level by controlling the current supply to the exciting coil 18 by a temperature control system including temperature detecting means. . Reference numeral 26 denotes a temperature sensor such as a thermistor for detecting the temperature of the fixing film 10. In this example, the temperature sensor 26 is disposed on the inner surface of the fixing film 10 immediately after the fixing nip N (on the downstream side in the film rotation direction). Based on the temperature of the sensor 26, the temperature of the fixing nip N is controlled.
[0079]
Thus, the pressure roller 30 is driven to rotate, and the cylindrical fixing film 10 rotates around the outer periphery of the film guide member 16, and electromagnetic induction heat generation of the fixing film 10 is performed by supplying power to the excitation coil 18. In a state where the fixing nip N rises to a predetermined temperature and is adjusted in temperature, the recording material P on which the unfixed toner image t is formed as described above is formed between the fixing film 10 and the pressure roller 30 in the fixing nip N. It is introduced with the image surface facing upward, that is, facing the fixing film surface, and conveyed while the image surface is in close contact with the outer surface of the fixing film 10. In this process, the fixing film 10 is heated by heat generated by electromagnetic induction. Thus, the unfixed toner image t is heat-fixed on the recording material P. When the recording material P passes through the fixing nip portion N, it is separated from the outer surface of the rotary fixing film 10 and discharged and conveyed. The heat-fixed toner image on the recording material is cooled to a permanently fixed image after passing through the fixing nip.
[0080]
In this example, a toner containing a low softening substance is used in the toner t. Therefore, an oil application mechanism for preventing offset is not provided in the fixing device, but when a toner containing no low softening substance is used. An oil application mechanism may be provided. In addition, when a toner containing a low softening substance is used, oil application or cooling separation may be performed.
[0081]
A) Excitation coil 18
The exciting coil 18 is a conductive wire (electric wire) that constitutes a coil (wire ring), which is a bundle of a plurality of thin copper wires each coated with an insulation coating (bundled wire). A coil is formed. In this example, the exciting coil 18 is formed by winding 12 turns.
[0082]
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 10. In this example, polyimide coating is used and the heat-resistant temperature is 220 ° C.
[0083]
Here, pressure may be applied from the outside of the exciting coil 18 to improve the density.
[0084]
The shape of the exciting coil 18 is made to follow the curved surface of the heat generating layer as shown in FIG. In this example, the distance between the heat generation of the fixing film 10 and the exciting coil 18 is set to be approximately 2 mm.
[0085]
The material of the film guide members 16a and 16b is preferably a material that has excellent insulation and good heat resistance in order to ensure insulation from the fixing film 10. For example, a phenol resin, a fluorine resin, a polyimide resin, a polyamide resin, a polyamideimide resin, a PEEK resin, a PES resin, a PPS resin, a PFA resin, a PTFE resin, an FEP resin, an LCP resin, or the like may be selected.
[0086]
When the distances between the magnetic cores 17a, 17b, 17c and the exciting coil 18 and the heat generating layer of the fixing film are as close as possible, the magnetic flux absorption efficiency is higher. However, when this distance exceeds 5 mm, this efficiency is increased. It is better to make it within 5 mm because it is remarkably lowered. If the distance is within 5 mm, the distance between the heating layer of the fixing film 10 and the exciting coil 18 does not have to be constant.
[0087]
With respect to the lead wires from the film guide member 16a of the exciting coil 18, that is, 18a and 18b (FIG. 5), an insulating coating is applied to the outside of the bundled wire for the portion outside the film guide member 16a.
[0088]
B) Fixing film 10
FIG. 7 is a model diagram of the layer structure of the fixing film 10 in this example. The fixing film 10 of this example includes a heat generating layer 1 made of a metal film or the like as a base layer of an electromagnetic induction heat generating fixing film, an elastic layer 2 laminated on the outer surface, and a release layer 3 laminated on the outer surface. It has a composite structure. For adhesion between the heat generating layer 1 and the elastic layer 2 and adhesion between the elastic layer 2 and the release layer 3, a primer layer (not shown) may be provided between the respective layers. In the layer structure, the heat generating layer 1 is the inner surface side of the fixing film 10 having a cylindrical shape, and the release layer 3 is the outer surface side thereof. As described above, when an alternating magnetic flux acts on the heat generating layer 1, an eddy current is generated in the heat generating layer 1 and the heat generating layer 1 generates heat. The heat heats the fixing film 10 through the elastic layer 2 and the release layer 3, and heats the recording material P as the material to be heated that is passed through the fixing nip N, thereby heat-fixing the toner image. The
[0089]
a. Heat generation layer 1
The heat generating layer 1 may be a nonmagnetic metal, but a ferromagnetic metal such as nickel, iron, ferromagnetic SUS, or nickel-cobalt alloy may be used.
[0090]
The thickness is preferably thicker than the skin depth represented by the following formula and 200 μm or less. The skin depth σ [m] is the excitation circuit frequency f [Hz], permeability μ and specific resistance ρ [Ωm],
σ = 503 × (ρ / fμ)^1/2
It is expressed.
[0091]
This indicates the depth of absorption of electromagnetic waves used for electromagnetic induction, and the intensity of electromagnetic waves is 1 / e or less deeper than this, and conversely most energy is absorbed up to this depth. (FIG. 9).
[0092]
The thickness of the heat generating layer 1 is preferably 1 to 100 μm. If the thickness of the heat generating layer 1 is less than 1 μm, most of the electromagnetic energy cannot be absorbed, resulting in poor efficiency. On the other hand, if the heat generation layer exceeds 100 μm, the rigidity becomes too high, and the flexibility becomes poor, so that it is not practical to use as a rotating body. Therefore, the thickness of the heat generating layer 1 is preferably 1 to 100 μm.
[0093]
b. Elastic layer 2
The elastic layer 2 is made of silicon rubber, fluorine rubber, fluorosilicone rubber or the like, which has good heat resistance and good thermal conductivity.
[0094]
The thickness of the elastic layer 2 is preferably 10 to 500 μm. The elastic layer 2 has a thickness necessary for assuring the fixed image quality.
[0095]
When a color image is printed, a solid image is formed over a large area on the recording material P, particularly in a photographic image. In this case, if the heating surface (release layer 3) cannot follow the unevenness of the recording material or the unevenness of the toner layer, heating unevenness occurs, and gloss unevenness occurs in the image where the heat transfer amount is large and small. A portion with a large amount of heat transfer has a high glossiness, and a portion with a small amount of heat transfer has a low glossiness. If the thickness of the elastic layer 2 is 10 μm or less, the unevenness of the recording material or the toner layer cannot be fully followed and unevenness in image gloss occurs. On the other hand, when the elastic layer 2 is 1000 μm or more, the thermal resistance of the elastic layer increases and it is difficult to realize a quick start. More preferably, the thickness of the elastic layer 2 is 50 to 500 μm.
[0096]
If the hardness of the elastic layer 2 is too high, unevenness of the image gloss will occur because it cannot follow the unevenness of the recording material or toner layer. Therefore, the hardness of the elastic layer 2 is preferably 60 ° (JIS 1A) or less, more preferably 45 ° (JIS-A) or less.
[0097]
Regarding the thermal conductivity λ of the elastic layer 2,
6x10^-Four~ 2x10^-3[Cal / cm · sec · deg.]
Is good.
[0098]
Thermal conductivity o] λ is 6 × 10^-FourWhen it is smaller than [cal / cm · sec · deg.], The thermal resistance is large, and the temperature rise in the surface layer (release layer 3) of the fixing film 10 is delayed.
[0099]
Thermal conductivity λ is 2 × 10^-3When it is larger than [cal / cm · sec · deg.], The hardness becomes too high or the compression set is deteriorated.
[0100]
Therefore, the thermal conductivity is 6 × 10^-Four~ 2x10^-3[Cal / cm · sec · deg.] Is good. More preferably 8 × 10^-Four~ 1.5 × 10^-3[Cal / cm · sec · deg.] Is good.
[0101]
c. Release layer 3
For the release layer 3, a material having good release properties and heat resistance such as fluororesin, silicone resin, fluorosilicone rubber, fluororubber, silicone rubber, PFA, PTFE, and FEP can be selected.
[0102]
The thickness of the release layer 3 is preferably 1 to 100 μm. When the thickness of the release layer 3 is smaller than 1 μm, there arises a problem that a part having poor release property is formed due to coating unevenness of the coating film or durability is insufficient. Further, when the release layer exceeds 100 μm, there is a problem that heat conduction is deteriorated. In particular, in the case of a resin release layer, the hardness becomes too high and the effect of the elastic layer 2 is lost.
[0103]
As shown in FIG. 8, in the layer structure of the fixing film 10, the heat insulating layer 4 may be provided on the free surface side of the heat generating layer 1 (on the surface opposite to the elastic layer 2 side of the heat generating layer 1).
[0104]
The heat insulating layer 4 is preferably a heat resistant resin such as a fluororesin, a polyimide resin, a polyamide resin, a polyamideimide resin, a PEEK resin, a PES resin, a PPS resin, a PFA grease, a PTFE resin, or an FEP resin.
[0105]
Moreover, as thickness of the heat insulation layer 4, 10-1000 micrometers is preferable. When the thickness of the heat insulating layer 4 is smaller than 10 μm, the heat insulating effect cannot be obtained and the durability is insufficient. On the other hand, if it exceeds 1000 μm, the distance from the magnetic cores 17a, 17b, 17c and the exciting coil 18 to the heat generating layer 1 increases, and the magnetic flux is not sufficiently absorbed by the heat generating layer 1.
[0106]
Since the heat insulating layer 4 can insulate the heat generated in the heat generating layer 1 so as not to go to the inside of the fixing film, the heat supply efficiency to the recording material P side is improved as compared with the case without the heat insulating layer 4. Therefore, power consumption can be suppressed.
[0107]
FIG. 10 shows the surface temperature of the fixing film 10 when small-size paper is passed. In FIG. 10, the A line indicates a case where the good heat conductive material 40 is not disposed in the nip portion N, and the B line indicates a case where the good heat conductive material 40 is disposed in the nip portion N. When both are compared, in the case where the good heat conductive material 40 is disposed in the nip portion N, the temperature of the non-sheet passing portion is lower than the temperature region where the toner is offset.
[0108]
This is because the heat amount of the non-sheet passing portion in the fixing film 10 is transferred to the good heat conducting member 40, and the heat amount of the non-sheet passing portion is reduced by the heat conduction in the longitudinal direction of the good heat conducting member 40. This is because heat is transferred to the part. Thereby, the effect of reducing the power consumption at the time of passing small-size paper is also obtained.
[0109]
For example, even when small size paper such as an envelope and A4 size paper are printed alternately, the temperature of the non-sheet passing portion does not reach the toner offset temperature after passing the small size paper. Even when the paper is passed, the toner on the A4 size paper is not offset to the fixing film, and a good fixed image can be obtained.
[0110]
Further, since the temperature of the non-sheet passing portion can be lowered, even when the elastic layer 2 such as silicon rubber is provided on the fixing film 10 as in the present composition, rubber deterioration is suppressed and durability is improved. .
[0111]
In this example, iron is used as the good heat conducting member 40. However, for example, nickel (k = 83 [w · m^-1・ K^-1]) Or the like, the thermal conductivity k is k ≧ 70 [w · m^-1・ K^-1] May be used.
[0112]
(Second Embodiment)
In this example, the same reference numerals are given to the same components and parts as those in the first embodiment, and the description thereof will be omitted.
[0113]
In this example, the good thermal conductivity member 40 has a thermal conductivity k of k = 167 [W · m^-1・ K^-1The aluminum nitride, which is ceramic, is used, and the thickness is 1 [mm].
[0114]
Since aluminum nitride has better surface slipping property than a metal such as iron, sufficient slidability can be obtained without being covered with the lubricating member of the good heat conducting member 40. For this reason, it is possible to simplify the configuration of the good heat conducting member while ensuring the durability of the fixing film 10.
[0115]
Since aluminum nitride is a non-magnetic and insulating member, it is not affected by the magnetic field generated by the magnetic field generating means.
[0116]
Regarding the thermal conductivity k of the good heat conducting member 40, the iron in the first embodiment (k = 72 [w · m^-1・ K^-1]), The thermal conductivity k of aluminum nitride is about 2.3 times, so that the temperature rise of the non-sheet passing portion is higher than that of the first embodiment as shown in FIG. Reduced. For this reason, it is possible to increase the throughput while ensuring good fixability.
[0117]
In this example, aluminum nitride is used as the good heat conducting member 40. However, the good heat conducting member may be a non-magnetic good heat conducting member, such as a material such as ceramics such as beryllia and silicon carbide. Furthermore, the thermal conductivity k is k ≧ 100 [W · m^-1・ K^-1It is preferable to use a material of
[0118]
(Third embodiment)
In this example, the same reference numerals are given to the same components and parts as those in the first embodiment, and the description thereof will be omitted.
[0119]
In this example, the heat conductivity k of the good heat conducting member 40 is k = 240 [w · m^-1・ K^-1] Of aluminum is used, and its thickness is 1 [mm].
[0120]
When a non-magnetic good conductive member such as aluminum is used as the good heat conductive member 40, the good heat conductive member 40 itself does not generate heat due to the shielding effect against the magnetic field. At this time, the nonmagnetic highly conductive member is preferably thicker than the electromagnetic wave absorption depth.
[0121]
The good heat conducting member 40 may be coated or pasted with a sliding member (not shown) on the contact surface with the fixing film 10. This improves the slipperiness of the contact surface and prevents the durability of the fixing film 10 from being deteriorated.
[0122]
In this example, as shown in FIG. 12, even if the good heat conducting member 40 is positioned within the magnetic field of the heat generating means, the aluminum which is the good heat conducting member 40 shields the magnetic field, and the good heat conducting member 40 itself Does not generate heat. Therefore, it is effective for reducing the size of the fixing device 100.
[0123]
Regarding the thermal conductivity k of the good heat conducting member 40, the iron in the first embodiment (k == 72 [w · m^-1・ K^-1]) And the aluminum of this example, the thermal conductivity k is about 3.3 times. Similarly, the aluminum nitride in the second embodiment (k = 167 [w · m^-1・ K^-1] About 1.4 times as large as]). Therefore, even if the temperature rise of the non-sheet passing portion is compared with the second embodiment, it can be further reduced. For this reason, it is possible to further increase the throughput while ensuring good fixability.
[0124]
In this example, by using a non-magnetic metal good heat conducting member for the good heat conducting member 40, even if the good heat conducting member 40 is disposed in the magnetic field, the good heat conducting member does not generate heat. The fixing device 100 can be downsized while waiting for an effect equal to or greater than that of the second embodiment, and is particularly effective when mounted on a small low-speed machine.
[0125]
In this example, aluminum is used as the good heat conducting member 40. However, the good heat conducting member may be any non-magnetic good conducting member, such as brass (k = 128 [w · m^-1・ K^-1], Copper (k = 395 [w · m^-1・ K^-1], Zinc (k = 112 [w · m^-1・ K^-1]) Or the like, the thermal conductivity k is k ≧ 100 [w · m^-1・ K^-1It is particularly preferable to use the material.
[0126]
(Other embodiment examples)
1) The electromagnetic induction exothermic fixing film 10 may be configured such that the elastic layer 2 is omitted in the case of heat fixing such as a monochrome or one-pass multi-color image. The heat generating layer 1 can also be configured by mixing a metal filler into a resin. Moreover, it can also be set as the member of a heat generating layer single layer.
[0127]
2) The arrangement of the magnetic field generating means is not limited to the configuration of the above embodiment. For example, it can be arranged as shown in FIG.
[0128]
3) The pressure member 30 is not limited to a roller body, and may be a member of another form such as a rotating belt type.
[0129]
Further, in order to supply heat energy from the pressing member 30 side to the recording material P, a heating device such as electromagnetic induction heating is provided on the pressing member 30 side to heat and adjust the temperature to a predetermined temperature. You can also
[0130]
4) As shown in FIG. 13, the fixing film 10 may be suspended from the driving roller 32 and the tension roller 31.
[0131]
5) The thickness of the good heat conducting member 40 is not limited to 1 [mm], and the thickness is changed according to the required reduction amount of the non-sheet passing portion temperature rise.
[0132]
6) The heating device of the present invention is not limited to the image heating and fixing device of the above-described embodiment, but an image heating device that modifies the surface properties such as gloss by heating a recording material carrying an image, or an image heating that is assumed. It can be widely used as a means / device for heat-treating a material to be heated, such as an apparatus, a heating / drying device for a material to be heated, and a heating laminating device.
[0133]
【The invention's effect】
  As explained above,According to the present invention, a heating device of an electromagnetic induction heating system is used.In placeLeaveA good heat conduction member is provided at a position facing the pressure member via an electromagnetic induction heating member in the heating nip portion, and the magnetic field generation means takes into account the influence of the magnetic field generated by the magnetic field generation means. It is arranged at a position not given to the memberAccordingly, it is possible to reduce the temperature increase in the non-sheet passing portion and increase the throughput when the small size paper is passed.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an image forming apparatus as a first embodiment.
FIG. 2 is a cross-sectional side view of a main part of a fixing device as a heating device.
FIG. 3 is a front view of a main part of the fixing device.
FIG. 4 is a longitudinal front view of the fixing device.
FIG. 5 is a perspective view of a film guide member, an exciting coil, and a magnetic core.
FIG. 6 is a diagram showing the relationship between the magnetic flux and the amount of heat generated by the fixing film.
FIG. 7 is a schematic diagram of the layer structure of an electromagnetic induction heat-generating fixing film (Part 1).
FIG. 8 is a schematic diagram of the layer structure of an electromagnetic induction heat-generating fixing film (Part 2).
FIG. 9 is a graph showing the relationship between the heat generation layer depth and the electromagnetic wave linearity
FIG. 10 is a graph showing a non-sheet passing portion temperature increase in the first embodiment.
FIG. 11 is a graph showing the temperature rise of the non-sheet passing portion in the second embodiment.
FIG. 12 is a cross-sectional side view of an essential part of a fixing device which is a heating device according to a third embodiment.
FIG. 13 is a cross-sectional side view of an essential part of a fixing device which is a heating device according to another embodiment.
FIG. 14 is a schematic configuration diagram of a conventional electromagnetic induction heating type heating device (fixing device).
[Explanation of symbols]
1 Heat generation layer
2 Elastic layer
3 Release layer
4 Insulation layer
10 Fixing film
16 Film guide
17a-17c Magnetic core
18 Excitation coil
25a / 25b Pressure spring member
26 Temperature sensing element (thermistor)
30 Pressure roller (Pressure member)
31 Tension roller
32 Drive roller
40 Heat conduction member

Claims (6)

A magnetic field generating means, a member that generates electromagnetic induction heat by the action of the magnetic field of the magnetic field generating means, and a pressure member that forms a heating nip portion of the material to be heated by mutual pressure contact with the electromagnetic induction heating member, It is a heating device that heats the material to be heated by the heat generated by the electromagnetic induction heating member,
A good heat conduction member is provided at a position facing the pressure member via the electromagnetic induction heating member of the heating nip portion, and the magnetic field generation means influences the good heat by the magnetic field generated by the magnetic field generation means. A heating device, wherein the heating device is disposed at a position not applied to the conductive member . Heating apparatus according to claim 1, before Symbol electromagnetic induction heating element characterized in that it is a rotating body. Before Kiyonetsu thermal conductivity k of the conductive member is ^{k ≧ 70 [W · m -1} · K -1]
The heating apparatus according to claim 1, wherein: Heating apparatus according to claim 1, wherein the front Kiyonetsu conductive member is a nonmagnetic member. Heating apparatus according to claim 1, wherein the front Kiyonetsu conductive member is a nonmagnetic metal. Before SL; and a magnetic field generating means exciting coil and the core, the heating device according to claim 1, said good heat conductive member, characterized in that disposed at a position spaced a core with respect to the excitation coil.

Images