JP2005301018A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an induction heating type fixing device whose heating efficiency is enhanced and whose warm-up time is shortened. <P>SOLUTION: The induction heating type fixing device is constituted so that the heat capacity of the part facing a magnetic field generating means of an endless heating means may be lower than that of the magnetic field generating means. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus for forming an image on a recording material by an electrophotographic process, and a fixing device used in the image forming apparatus, and more particularly to improvement of an induction heating type heat fixing technique.

  Conventional. In electrophotographic image formation, a heat fixing device using a halogen lamp as a heat source has been widely used, but an induction current is generated by an electromagnetic induction phenomenon, and heating means is heated by heat generated by the generated induction current, The induction heating method for fixing has recently been attracting attention, researched, and put into practical use.

  The induction heating method has advantages such as a short warm-up time, no inrush current generated in the halogen lamp, no countermeasure is required, and power control is possible.

  In addition, in the induction heating method, there are a mold in which magnetic field generation is arranged outside the heating means and a mold in which the magnetic field generation is arranged inside.

Patent Document 1 describes an induction heating type fixing device in which a magnetic field generating unit is arranged outside a heating unit. Patent Document 1 describes the temperature distribution in the axial direction of a heating roller that is a component of the heating unit. In order to prevent unevenness, it has been proposed that the heat capacity of the fixing belt (component of the heating means) stretched around the heating roller is 60 J / K, preferably 40 J / K.
JP 2003-323075 A

  When the heat capacity of the heating means is set small as in Patent Document 1, the heat capacity of the heating means is smaller than the heat capacity of the magnetic field generating means in relation to the magnitude of the heat capacity of the magnetic field generating means. Then, the heat generated in the heating means moves to the magnetic field generating means by heat radiation and is absorbed by the magnetic field generating means or radiated through the magnetic field generating means, so that the heat energy is generated as a whole. There is a problem that the heating efficiency is reduced by being absorbed by the means.

  Accordingly, an object of the present invention is to solve such problems in the induction heating type fixing device, and to provide a fixing device with high heating efficiency and an image forming apparatus having such a fixing device.

The object is achieved by the following invention.
1.
Endless heating means for heating the recording material in contact with the recording material and fixing the toner image on the recording material, and having an exothermic member that generates heat by an induced current;
Pressurizing means for pressing the recording material against the endless heating means; and
In a fixing device comprising a magnetic field generating means for generating a magnetic field for generating an induced current in the heat generating member, the magnetic field generating means being disposed outside the endless heating means,
When the heat capacity of the magnetic field generating means is CA and the heat capacity of the portion of the endless heating means facing the magnetic field generating means is CB,
CA <CB
The fixing device is characterized in that the endless heating means and the magnetic field generating means are configured so that.
2.
The endless heating means includes a fixing belt that constitutes the heat generating member, a heating portion support roller that supports the fixing belt with a heating portion, and a fixing portion support member that supports the fixing belt in the fixing portion, and the heat capacity CB is 2. The fixing according to claim 1, which is a total of a heat capacity CC of a portion of the fixing belt facing the magnetic field generating unit and a heat capacity CD of a portion of the heating unit supporting roller facing the magnetic field generating unit. apparatus.
3.
3. The fixing device according to 2 above, wherein the heating unit support roller includes a metal roller and an elastic layer formed on the metal roller.
4).
The endless heating means includes a heat generating roller that generates heat by an induced current, a fixing unit support member, and a fixing belt stretched between the heat generating roller and the fixing unit support member, and the heat capacity CB is the magnetic field of the fixing belt. 2. The fixing device according to 1, wherein the fixing device is a total of a heat capacity CC ′ of a portion facing the generating unit and a heat capacity CD ′ of a portion of the heat generating roller facing the magnetic field generating unit.
5).
The heat capacities CC and CD are:
CC <CD
The fixing device according to 2 above, wherein the fixing belt and the heating unit support roller are configured so that
6).
The heat capacities CC ′ and CD ′ are
CC '<CD'
The fixing device according to 4, wherein the fixing belt and the heating unit support roller are configured so that
7).
The fixing device according to any one of 2 to 6, wherein the fixing belt includes a release layer.
8).
The endless heating means is disposed opposite to the pressurizing means and the magnetic field generating means, has an exothermic roller that generates an induced current and generates heat by the generated current, and the heat capacity CB 2. The fixing device according to 1 above, wherein the fixing device has a heat capacity of the heat generating roller at a portion facing the magnetic field generating unit.
9.
The endless heating means is disposed opposite to the pressurizing means and the magnetic field generating means, has an exothermic roller that generates an induced current and generates heat by the generated current, and an elastic layer formed on the exothermic roller. The heat capacity CB is a total of a heat capacity of a portion of the heat generating roller facing the magnetic field generating means and a heat capacity of a portion of the elastic layer facing the magnetic field generating means. Fixing device.
10.
The endless heating means is disposed facing the pressurizing means and the magnetic field generating means, generates an induced current, and generates heat by the generated current, an elastic layer formed on the heat generating roller, and the elastic The heat capacity CB includes a heat capacity of a portion of the heat generating roller facing the magnetic field generating means, and a heat capacity of a portion of the elastic layer facing the magnetic field generating means, 2. The fixing device according to claim 1, wherein the fixing device is a total of a heat capacity of a part of the release layer facing the magnetic field generating unit.
11.
The endless heating means is disposed opposite to the pressurizing means and the magnetic field generating means and has an exothermic roller that generates an induced current and generates heat by the generated current, and a release layer formed on the exothermic roller. The heat capacity CB is a sum of a heat capacity of a portion of the heat generating roller facing the magnetic field generating means and a heat capacity of a portion of the release layer facing the magnetic field generating means. The fixing device according to 1.
12
The magnetic field generating means includes a single wire wound coil and a coil support member that supports the coil,
12. The fixing device according to claim 1, wherein the heat capacity CA is a total of a heat capacity of the coil and a heat capacity of the coil support member.
13.
13. The fixing device according to 12, wherein the fixing device includes a power source that supplies an alternating current having a frequency of 1 MHz to 10 MHz to the coil.
14
14. An image forming apparatus comprising the fixing device according to any one of 1 to 13 above.

  According to any one of the first to thirteenth inventions, heat absorbed by the magnetic field generating means or radiated through the magnetic field generating means is suppressed, so that the heat generated by the heat generating member is effectively fixed. A fixing device that is used and has high heating efficiency and can be raised to a predetermined fixing temperature with a small amount of electric power is realized.

  According to the invention of claim 12 or 13, since the magnetic field generating means having a small heat capacity is used, the heat absorbed by the magnetic field generating means or radiated through the magnetic field generating means is suppressed, and the fixing device as a whole Heating efficiency can be increased.

  According to the fourteenth aspect of the present invention, an image forming apparatus with a short warm-up time and low power consumption is realized.

  FIG. 1 is an overall view of an image forming apparatus according to an embodiment of the present invention.

  The image forming apparatus includes an automatic document feeder A, an image reading unit B, and an image forming unit C.

  The automatic document feeder A automatically feeds the documents placed on the document feed tray 1 one by one, supplies them to the image reading position, and discharges them to the paper discharge tray 2.

  The image reading unit B illuminates the document with the document illumination lamp 3 and causes the reflected light from the document to enter the image sensor 6 with the three mirrors 4 and the imaging lens 5 to generate digital image data.

The image forming unit C forms an image on the recording material P by electrophotography,
The drum-shaped photoconductor 10 is charged by the charging device 11, exposed by the exposure device 12, and developed by the developing device 13, thereby forming a toner image on the photoconductor 10.

  The formed toner image is transferred to the recording material P by the transfer device 14. The transferred photoreceptor 10 is cleaned by a cleaning device 15.

  The recording material P is stored in the recording material storage tray 20, conveyed one by one by the paper feed roller 21, adjusted in timing by the registration roller 22, and supplied between the photoconductor 10 and the transfer device 14.

  The recording material P on which the toner image is transferred by the transfer device 14 is fixed by the fixing device 30, conveyed by the paper discharge roller 24, and discharged to the paper discharge tray 25.

  FIG. 2 shows an example of the fixing device 30 according to the embodiment of the present invention.

  The fixing device 30 is an induction heating type fixing device, and includes an endless heating means D, magnetic field generating means 33 and 34, and a pressure roller 38 as a pressure means.

  The endless heating means D includes a metal roller 31 as a core metal, an elastic layer 32 formed on the metal roller 31, and an endless fixing belt 35 as a heat generating member.

  The fixing belt 35 is stretched around a heating unit support roller including a metal roller 31 and an elastic layer 32 and a fixing unit support roller including a cored bar 36 and an elastic layer 37 formed thereon, and is driven by a motor (not shown). It is circulated and moved as indicated by the arrow by driving the rotating fixing unit support roller.

  The magnetic field generating means 33 and 34 are arranged opposite to the endless heating means D, and the pressure roller 38 is in pressure contact with the fixing belt 35 supported by the fixing unit supporting roller.

  As shown in FIG. 3, the magnetic field generating means 33 and 34 are each composed of a coil support member 33a and a coil 33b wound around the coil support member 33a. The coil 33b may be a litz wire used in a conventional induction heating type fixing device, that is, a bundle wire, but is preferably a single wire type. The single wire coil is a coil in which one coil is wound around the support member 33a.

  However, the single wire type coil has one input terminal 33b1 and one output terminal 33b2 as shown in FIG. 3, and constitutes one excitation circuit E having an AC power supply AC, or as shown in FIG. A plurality of input terminals 33b1, 33b3, 33b5 and a plurality of output terminals 33b2, 33b4, 33b6, and a plurality of excitation circuits E1, E2. Although what comprises E3 may be included, it is preferable to comprise an excitation circuit by one line | wire connected to one power supply.

  The AC power supply AC supplies an AC current having a frequency of 1 MHz to 10 MHz to the coil 33b.

  Thus, rapid heating becomes possible by heating with a current having a higher frequency than in the prior art.

  When the frequency of the alternating current is lower than 1 MHz, there is a possibility that only the magnetic flux passes through the surface of the heat generating member and the whole heat generating member does not generate heat. If it is higher than 10 MHz, much of the magnetic flux is formed through the heat generating member, and there is a possibility that heat generation is not sufficient.

  The magnetic field generation means 34 also has the same structure as the magnetic field generation means 33 described above.

  In the example shown in FIGS. 3 and 4, the coil 33b is wound substantially parallel to the moving direction of the fixing belt 35, but as shown in FIG. 5, the direction almost perpendicular to the moving direction, that is, Alternatively, the support member 33a may be wound in the longitudinal direction.

  The fixing belt 35 is made of a metal such as aluminum, iron, nickel, platinum, silver, etc., generates an eddy current in the fixing belt 35 by the magnetic field generated by the magnetic field generating means 33, 34, and generates heat by the generated eddy current. The fixing belt 35 may have a release layer such as a fluororesin on the surface thereof in order to prevent the recording material P from being wound or offset.

  The elastic layer 32 is made of a heat resistant elastic body such as foamed silicon rubber.

  The elastic layer 37 is made of a heat-resistant elastic material such as foamable silicon rubber.

  By supplying an alternating current to the coil 33b, an eddy current is induced in the metal roller 31, and Joule heat is generated by the eddy current to heat the fixing belt 35.

  The recording material P is heated by the fixing belt 35 that moves as indicated by the arrow in FIG. 2, and the toner image T on the recording material P is heated and fixed.

  The relationship between the heat capacity of the endless heating means and the heat capacity of the magnetic field generating means will be described with reference to FIG.

  As shown in FIG. 6, the magnetic field generating means 33 is disposed to face the endless heating means D.

  The part of the endless heating means D facing the magnetic field generating means 33 is defined as follows. In the following description, the magnetic field generating unit 33 is described, but the same conditions regarding the heat capacity are set for the magnetic field generating unit 34.

Let CB be the heat capacity of the portion of the endless heating means D that is bounded by the straight lines L1 and L2 that are in contact with the outline of the magnetic field generating means 33, that is, outside the coil 33b and orthogonal to the outer peripheral surface of the fixing belt 35. And when the heat capacity of the magnetic field generating means is CA,
CA <CB
Thus, the magnetic field generating means 33 and the endless heating means D are configured.

  The material constituting the endless heating means D and the structure of the endless heating means D are limited in order to ensure heat resistance and mechanical strength. Therefore, in order to achieve the above conditions, the magnetic field generating means 33 is mainly configured. This is achieved by reducing the heat capacity.

  For this purpose, the magnetic field generating means 33 is constituted by a support member 33a and a single wire type coil 33b, and the support member 33a is preferably a heat-resistant resin that is a non-magnetic material, such as PPS (polyphenyl sulfide), phenol resin. A heat resistant resin such as silicon resin is used.

  As described above, the coil 33b is not a litz wire but a single wire type, so that the mass of the entire coil can be reduced and its heat capacity can be reduced.

  Note that the heat capacity CB of the endless heating means D is represented by the following equation in the examples shown in FIGS.

CB = CC + CD + CE
In the above equation, CC is the portion of the fixing belt 35 facing the magnetic field generating means 33, that is, the heat capacity of the portion 35a defined by the straight lines L1 and L2 in FIG. 6, and CD is facing the magnetic field generating means 33 of the metal roller 31. The portion, that is, the heat capacity of the portion 31a defined by the straight lines L1 and L2 in FIG. 6, CE is the portion of the elastic layer 32 facing the magnetic field generating means 33, that is, the portion 32a defined by the straight lines L1 and L2 in FIG. Is the heat capacity.

  The heat capacity CC of the fixing belt is preferably in the following relationship with respect to the heat capacity CD of the metal roller 31 and the heat capacity CE of the elastic layer 32.

CC <CD + CE
Thus, by setting the heat capacity of the fixing belt 35 small, it is possible to increase the temperature rise speed of the fixing belt 35 and increase the circulation movement speed of the fixing belt 35, thereby enabling high-speed fixing.

  FIG. 7 shows another example of the fixing device 30.

  In FIG. 7, the endless heating means D includes a metal roller 31 and an endless fixing belt 35. In this example, the heat capacity CB of the portion facing the magnetic field generating means 33, 34 of the endless heating means D is the sum of the heat capacity CD of the facing portion of the metal roller 31 and the heat capacity CC of the facing portion of the fixing belt 35. That is, CB = CC + CD.

  As described above, the fixing device 30 is configured to satisfy CB> CA. Further, CD> CC is preferable.

  The example of the structure shown in FIG. 7 includes the following two embodiments.

  The first is to use the fixing belt 35 as a heat generating member. In this example, as described above, the fixing belt 35 is made of a metal that generates an induced current by a magnetic field and generates heat by the generated current.

  In the second example, the metal roller 31 is a heat generating member. In this example, the metal roller 31 is made of aluminum, iron, nickel, platinum or the like. The fixing belt 35 is made of a heat resistant resin such as a polyimide resin or a polyamideimide resin.

  In the example in which the metal roller 31 is a heat generating member, the above-mentioned conditions regarding the heat capacity are as follows.

CB = CC '+ CD'
However, CC ′ is the heat capacity of the portion of the fixing belt 35 made of heat resistant resin facing the magnetic field generating means 33, 34, and CD ′ is the heat capacity of the portion of the metal roller 31 as the heat generating member facing the magnetic field generating means. It is.

Also, as explained above,
It is preferable that CC ′ <CD ′.

  FIG. 8 shows still another example of the fixing device 30.

  In FIG. 8, the endless heating means D comprises a metal roller 31 and an elastic layer 32, and the heat capacity CB of the portion facing the magnetic field generating means 33, 34 of the endless heating means is equal to the heat capacity CD of the facing portion 31a of the heat generating roller 31. This is the sum of the heat capacity CE of the opposing portion of the elastic layer 32. That is, CB = CD + CE.

  As described above, the fixing device 30 is configured to satisfy CB> CA.

  FIG. 9 shows still another example of the fixing device 30.

  In FIG. 9, the endless heating means D comprises the metal roller 31, and the heat capacity CB of the portion of the endless heating means D facing the magnetic field generation means 33 facing the magnetic field generation means 33 is transferred to the magnetic field generation means 33 of the metal roller 31. It is the heat capacity CC of the part which opposes.

  FIG. 10 shows still another example of the fixing device 30. In this example, the endless heating means D is composed of a metal roller 31 and a release layer 31a formed on the metal roller 31.

  In FIG. 10, the heat capacity CB of the portion of the endless heating means D facing the magnetic field generation means 33 is opposite to the heat capacity CC of the metal roller 31 facing the magnetic field generation means 33 and the magnetic field generation means 33 of the release layer 31a. CB = CC + CF.

  FIG. 11 shows still another example of the fixing device 3. In this example, the endless heating means D includes a metal roller 31, an elastic layer 32 formed on the metal roller 31, and a mold release formed on the elastic layer 32. It consists of layer 32a.

  In FIG. 11, the heat capacity CB of the portion of the endless heating means D facing the magnetic field generating means is the heat capacity CC of the portion of the metal roller 31 facing the magnetic field generating means and the part of the elastic layer 32 facing the magnetic field generating means 33. This is the sum of the heat capacity CE and the heat capacity CG of the part of the release layer 32a facing the magnetic field generating means 33. That is, CB = CC + CE + CG.

Using the fixing device shown in FIG. 7 and having the following configuration, the warm-up time from the room temperature to the fixing temperature of 200 ° was measured. The heat capacity of the magnetic field generating means is the heat capacity of each of the magnetic field generating means 33 and 34.
1. Embodiment of the present invention Fixing belt 35: Nickel belt with a thickness of 50 μm Metal roller 31: Iron roller with a thickness of 0.5 mm Heat capacity of the portion facing the magnetic field generating means 33, 34 of the endless heating means D: 84J (heating Belt) + 536J (Metal roller) / K
Coil support member: PPS (no excitation core)
Coils 33b and 34a: Heat capacity of magnetic field generating means 33 and 34 in which a copper wire is wound in a single wire to a thickness of 1 mm: 689 J / K
Drive power: 1000W
Warm-up time: 16 seconds Comparative Example Fixing Belt 35: Nickel Belt with a Thickness of 50 μm Metal Roller 31: Iron Roller with a Thickness of 0.5 mm Heat Capacity of the Endless Heating Unit D Opposing to the Magnetic Field Generating Units 33 and 34: 84J (Heating Belt) + 536J (Metal Roller) / K
Coil supporting member: Excitation core coils 33b, 34a: Heat capacity of magnetic field generating means 33, 34 obtained by winding a litz wire of copper wire to a thickness of 5 mm: 3445 J / K
Drive power: 1000W
Warm-up time: 24 seconds As in the example, the fixing device according to the present invention greatly shortened the warm-up time.

1 is a diagram illustrating an image forming apparatus according to an embodiment of the present invention. 1 is a diagram illustrating an example of a fixing device according to an embodiment of the present invention. It is a figure which shows the example of the coil which comprises a magnetic field generation means. It is a figure which shows the other example of the coil which comprises a magnetic field generation means. It is a figure which shows the further another example of the coil which comprises a magnetic field generation means. It is a figure which shows the part which an endless heating means and a magnetic field generation means oppose. It is a figure which shows the other example of the fixing device which concerns on embodiment of this invention. It is a figure which shows the further another example of the fixing device which concerns on embodiment of this invention. It is a figure which shows the further another example of the fixing device which concerns on embodiment of this invention. It is a figure which shows the further another example of the fixing device which concerns on embodiment of this invention. It is a figure which shows the further another example of the fixing device which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 30 Fixing device 31 Metal roller 32 Elastic layer 33, 34 Magnetic field generation means 35 Fixing belt 33a Coil support member 33b Coil

Claims (14)

Endless heating means for heating the recording material in contact with the recording material and fixing the toner image on the recording material, and having an exothermic member that generates heat by an induced current;
Pressurizing means for pressing the recording material against the endless heating means; and
In a fixing device comprising a magnetic field generating means for generating a magnetic field for generating an induced current in the heat generating member, the magnetic field generating means being disposed outside the endless heating means,
When the heat capacity of the magnetic field generating means is CA and the heat capacity of the portion of the endless heating means facing the magnetic field generating means is CB,
CA <CB
The fixing device is characterized in that the endless heating means and the magnetic field generating means are configured so that. The endless heating means includes a fixing belt that constitutes the heat generating member, a heating portion support roller that supports the fixing belt with a heating portion, and a fixing portion support member that supports the fixing belt in the fixing portion, and the heat capacity CB is 2. The total heat capacity CC of a portion of the fixing belt facing the magnetic field generating means and a heat capacity CD of a portion of the heating unit supporting roller facing the magnetic field generating means. Fixing device. The fixing device according to claim 2, wherein the heating unit support roller includes a metal roller and an elastic layer formed on the metal roller.   The endless heating means includes a heat generating roller that generates heat by an induced current, a fixing unit support member, and a fixing belt stretched between the heat generating roller and the fixing unit support member, and the heat capacity CB is the magnetic field of the fixing belt. 2. The fixing device according to claim 1, wherein the fixing device is a total of a heat capacity CC ′ of a portion facing the generating unit and a heat capacity CD ′ of a portion of the heat generating roller facing the magnetic field generating unit. The heat capacities CC and CD are:
CC <CD
The fixing device according to claim 2, wherein the fixing belt and the heating unit support roller are configured to satisfy the following. The heat capacities CC ′ and CD ′ are
CC '<CD'
The fixing device according to claim 4, wherein the fixing belt and the heating unit support roller are configured so that The fixing device according to claim 2, wherein the fixing belt has a release layer. The endless heating means is disposed opposite to the pressurizing means and the magnetic field generating means, has an exothermic roller that generates an induced current and generates heat due to the generated current, and the heat capacity CB is the temperature of the exothermic roller. The fixing device according to claim 1, wherein the heat capacity is a heat capacity of the heat generating roller at a portion facing the magnetic field generating unit. The endless heating means is disposed opposite to the pressurizing means and the magnetic field generating means, has an exothermic roller that generates an induced current and generates heat by the generated current, and an elastic layer formed on the exothermic roller. 9. The heat capacity CB is a sum of a heat capacity of a portion of the heat generating roller facing the magnetic field generating means and a heat capacity of a portion of the elastic layer facing the magnetic field generating means. The fixing device described. The endless heating means is disposed facing the pressurizing means and the magnetic field generating means, generates an induced current, and generates heat by the generated current, an elastic layer formed on the heat generating roller, and the elastic The heat capacity CB includes a heat capacity of a portion of the heat generating roller facing the magnetic field generating means, and a heat capacity of a portion of the elastic layer facing the magnetic field generating means, The fixing device according to claim 1, wherein the fixing device is a total of a heat capacity of a part of the release layer facing the magnetic field generation unit. The endless heating means is disposed opposite to the pressurizing means and the magnetic field generating means, has a heat generating roller that generates an induced current and generates heat by the generated current, and a release layer formed on the heat generating roller. The heat capacity CB is a sum of a heat capacity of a portion of the heat generating roller facing the magnetic field generating means and a heat capacity of a portion of the release layer facing the magnetic field generating means. The fixing device according to 1. The magnetic field generating means includes a single wire wound coil and a coil support member that supports the coil,
The fixing device according to claim 1, wherein the heat capacity CA is a total of a heat capacity of the coil and a heat capacity of the coil support member. The fixing device according to claim 12, further comprising a power source that supplies alternating current having a frequency of 1 MHz to 10 MHz to the coil. An image forming apparatus comprising the fixing device according to claim 1.

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