JP2016128899A - Fixation device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixation device that allows reduction in size of a magnetic shunt material to reduce prime costs and allows simplification in processing to reduce processing costs.SOLUTION: A fixation device 20 includes: a belt-shaped fixation member 24; a magnetic flux generating part 27 for generating a magnetic flux; a heating member 21 that heats the fixation member 24 with heat generated by the magnetic flux; a magnetic flux control member 22 that is positioned opposite to the magnetic flux generating part 27 with the heating member 21 interposed therebetween; and a magnetic flux shielding member 23 that is positioned opposite to the magnetic flux generating part 27 with the magnetic flux control member 22 interposed therebetween. The magnetic flux control member 22 and the magnetic flux shielding member 23 include planar shape parts 22a and 23a, respectively, and the fixation member 24 is stretched along the planar shape parts 22a and 23a.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a fixing device and an image forming apparatus.

  Conventionally, an induction heating type fixing device is widely used as a fixing device used in an electrophotographic image forming apparatus. As one of the technical problems in the fixing device, an excessive temperature rise in an area outside the paper width at the time of paper passing is known. Can be mentioned. In a fixing device using an induction heating method, a configuration in which a magnetic shunt material is provided between a heating element and a magnetic shielding member is known as a countermeasure against excessive temperature rise. As a result, when the magnetic shunt material is equal to or higher than the Curie temperature, the magnetic flux generated by the exciting device is transmitted through the shunt material and shielded by the shielding member, so that excessive heating of the heating element is suppressed.

  As such a technology, a fixing device is known in which a fixing member having a conductive layer is slid with a magnetic flux control member in order to reduce the heat capacity of the heat generating portion while providing a self-temperature control function using a magnetic shunt material. (See, for example, “Patent Document 1”).

However, in the conventional fixing device using the induction heating method, when using the magnetic shunt material as a heating member, it is necessary to process the magnetic shunt material into a roller shape, which increases the manufacturing cost. It was. This is because the material cost of the magnetic shunt material itself and the processing cost for the roller processing are large, and the ratio to the manufacturing cost of the entire fixing device is large. Therefore, further improvement is required to develop a low-cost fixing device. . Even in the technique described in “Patent Document 1”, since the magnetic flux control member has an arc shape, the processing cost remains large.
The present invention solves the above-described problems, and provides a fixing device and an image forming apparatus capable of reducing the cost cost by reducing the size of the magnetic shunt material and simplifying the processing to reduce the processing cost. With the goal.

  According to the present invention, a belt-shaped fixing member, a magnetic flux generating unit that generates magnetic flux, a heating member that heats the fixing member by heat generated by the magnetic flux, and the magnetic flux generating unit are disposed opposite to each other through the heating member. A magnetic flux control member, and a magnetic flux shielding member disposed opposite to the magnetic flux generation unit via the magnetic flux control member, wherein the magnetic flux control member and the magnetic flux shielding member each have a planar shape portion, and the fixing The member is stretched in a state along each planar shape portion.

  According to the present invention, it is possible to reduce the amount of magnetic shunt material used as compared with the conventional fixing device, simplify the processing, reduce the material cost and the processing cost, and manufacture the fixing device. Can be greatly reduced.

1 is a schematic view of an image forming apparatus to which an embodiment of the present invention can be applied. 1 is a schematic view of a fixing device used in a first embodiment of the present invention. 1 is a cross-sectional view of a fixing belt used in a first embodiment of the present invention. It is the schematic explaining the structure of the coil used for the 1st Embodiment of this invention. It is the schematic explaining the path | route of the magnetic flux generated from the coil in case the magnetic flux control member in the 1st Embodiment of this invention is below Curie temperature. It is the schematic explaining the path | route of the magnetic flux generated from the coil in case the magnetic flux control member in the 1st Embodiment of this invention is more than Curie temperature. It is a principal part schematic diagram explaining the conventional fixing device. FIG. 3 is a diagram showing a temperature transition of the fixing device according to a lapse of time since the apparatus is started in the first embodiment of the present invention. FIG. 6 is a schematic diagram of a main part of a fixing device used in a second embodiment of the present invention. It is the schematic explaining the eddy current which arises in the magnetic flux control member used for the 1st Embodiment of this invention. It is the schematic explaining the magnetic flux control member used for the 3rd Embodiment of this invention. It is the schematic explaining the eddy current which arises in the magnetic flux control member used for the 3rd Embodiment of this invention. It is the schematic explaining the magnetic flux control member used for the modification of the 3rd Embodiment of this invention. It is the schematic explaining the eddy current which arises in the magnetic flux control member used for the modification of the 3rd Embodiment of this invention. It is the diagram which compared the temperature rising time after apparatus starting of the 1st Embodiment and 3rd Embodiment of this invention. It is the schematic of the fixing device used for the 4th Embodiment of this invention. It is the schematic of the fixing device used for the 5th Embodiment of this invention. FIG. 10 is a cross-sectional view of a fixing belt used in a fifth embodiment of the present invention. It is a schematic perspective view of the magnetic flux control member used for the 6th Embodiment of this invention. It is the schematic of the fixing device principal part used for the 7th Embodiment of this invention. It is the schematic of the fixing device principal part used for the 8th Embodiment of this invention. It is the schematic of the fixing belt rubbing surface in the contact member used for the 9th Embodiment of this invention.

  FIG. 1 shows a full-color printer (hereinafter referred to as a printer) 100 as an image forming apparatus to which an embodiment of the present invention can be applied. In the figure, the printer 100 has a document scanning device (not shown) mounted on the upper portion of the apparatus main body 101, and a discharge tray 17 used as an in-body discharge section is formed on the upper surface of the main body located below the document scanning apparatus. Has been.

  Inside the apparatus main body 101, the visible images formed on the photosensitive drums 120Y (yellow), 120C (cyan), 120M (magenta), and 120Bk (black) face each photosensitive drum 120 in the direction of arrow A1. Are sequentially transferred to a transfer belt 11 that can be moved to the right. This transfer process is a primary transfer process, and each image is sequentially transferred onto the transfer belt 11 to form a superimposed transfer image. Thereafter, the secondary transfer process is performed on the paper P, whereby the superimposed transfer image is collectively transferred onto the paper P.

  Around the photosensitive drum 120, an apparatus for performing an image forming process as the photosensitive drum 120 rotates is disposed. The following is a description of the photoconductor 120Bk that performs black image formation. A charging device 30Bk that performs image forming processing, a developing device 40Bk, a primary transfer roller 12Bk, and a cleaning device 50Bk are arranged along the rotation direction of the photosensitive drum 120Bk. For writing performed after charging, an optical scanning device 8 described later is used.

  In the superimposing transfer on the transfer belt 11, visible images formed on the respective photosensitive drums 120 are sequentially superimposed and transferred onto the transfer belt 11 in the process in which the transfer belt 11 moves in the direction of the arrow A <b> 1. The primary transfer process is performed from the upstream side in the direction of arrow A1 by applying a transfer bias using primary transfer rollers 12Y, 12C, 12M, and 12Bk arranged to face the respective photosensitive drums 120 with the transfer belt 11 interposed therebetween. It is performed sequentially toward the downstream side.

  Each photosensitive drum 120 is housed in a process cartridge, and is arranged in the order of yellow, cyan, magenta, and black from the upstream side in the direction of the arrow A1. Each photosensitive drum 120 is provided in an image station for forming an image of each color. As a configuration for executing the primary transfer process, a transfer belt unit 10 including a transfer belt 11 and each primary transfer roller 12 facing each photoconductor drum 120 with the transfer belt 11 interposed therebetween is used. The image superimposed and transferred onto the transfer belt 11 is collectively transferred onto the paper P by the secondary transfer roller 5 constituted by a roller that rotates following the movement of the transfer belt 11.

  In addition to the above-described process cartridge and transfer belt unit 10, the printer 100 is provided with an optical scanning device 8 disposed to face the lower side of the four image stations, and a belt cleaning device 13 for cleaning the transfer belt 11. It has been.

  The optical scanning device 8 is equipped with a semiconductor laser as a light source, a coupling lens, an fθ lens, a toroidal lens, a mirror, a polygon mirror, and the like. In the optical scanning device 8, writing light Lb corresponding to each color with respect to each photosensitive drum 120 (in FIG. 1, for convenience, only the image station of the black image is marked, but other image stations are also included. The same). Thereby, an electrostatic latent image is formed on each photosensitive drum 120.

  The printer 100 sets the registration timing of the paper P fed from the paper feeding device 61 and the paper feeding device 61 that feeds the paper P onto which the images superimposed and transferred in the secondary transfer process are collectively transferred. A registration roller pair 4 for feeding to the next transfer position is provided. The printer 100 also includes a sensor (not shown) that detects that the leading edge of the paper P has reached the registration roller pair 4.

  The paper P onto which the toner images superimposed and transferred onto the transfer belt 11 in the secondary transfer process are transferred collectively is conveyed to a fixing device 20 to be described later, and the toner image is fixed. The fixed paper P is discharged toward a paper discharge tray 17 provided outside the apparatus main body 101 via a paper discharge roller 7. Reference numerals 9Y, 9C, 9M, and 9Bk in FIG. 1 indicate new toner replenishing tanks for the developing devices provided in the image stations of the respective colors.

  Next, the fixing device 20 used in the first embodiment of the present invention will be described. As shown in FIG. 2, the fixing device 20 includes a heating member 21 that generates heat by induction heating, a magnetic flux control member 22 made of a magnetic material for performing temperature control spontaneously, a magnetic flux shielding member 23 made of aluminum, and a fixing roller. 25 and a tension member 28. Further, the fixing device 20 includes a fixing belt 24 as a fixing member stretched by a fixing roller 25 and a stretching member 28, and an induction heating coil as a magnetic flux generation unit arranged to face the heating member 21 via the fixing belt 24. 27. Further, the fixing device 20 includes a pressure roller 26 as a pressing member that contacts the fixing roller 25 via the fixing belt 24. The magnetic flux control member 22 is formed with a planar portion 22a, and the aluminum member 23 is formed with a planar portion 23a.

  In the above-described configuration, the heating member 21 has the planar shape portion 21a, the magnetic flux control member 22 has the planar shape portion 22a, and the magnetic flux shielding member 23 has the planar shape portion 23a, and the stretching member that stretches the fixing belt 24. 28, the fixing belt 24 is stretched in a state having a flat portion. This flat portion is defined as a heating unit 24 a of the fixing belt 24.

  The heating member 21 is made of a non-magnetic material because it needs to transmit magnetic flux. Specific examples include SUS304, which is nonmagnetic stainless steel, and a liquid crystal polymer, which is a resin having high heat resistance. As the heating member 21, a Cu layer having a thickness of about 3 to 15 μm may be formed as a heat generation layer made of a highly conductive member on the surface layer of a member made of metal or resin. High resistance metal is generally known as a metal suitable for induction heating, but by substituting a highly conductive member into a thin layer, the substantial resistance of the heat generation layer can be set arbitrarily, and heat generation. The amount can be improved. The heat generating layer only needs to have good conductivity, and other metal layers such as silver, aluminum, magnesium, or nickel which is a magnetic substance may be used. Further, the surface layer of the Cu layer may be further plated with nickel or the like for the purpose of rust prevention.

  A magnetic shunt alloy having a Curie temperature of about 100 to 250 ° C. is used for the magnetic flux control member 22 disposed closer to the fixing roller 25 than the heating member 21, and specific examples include Fe—Ni—Cr alloys. It is done. A desired Curie point can be obtained by adjusting the amount of each material added, processing conditions, and the like. A magnetic flux shielding member 23 is disposed closer to the fixing roller 25 than the magnetic flux control member 22, thereby enabling the temperature rise to be stopped near the Curie temperature of the magnetic flux control member 22. The magnetic flux shielding member is optimally formed of aluminum that is non-magnetic and has a large loss.

The thickness of the magnetic flux shielding member 23 is desirably thicker than the penetration depth of the induction magnetic field generated from the coil. The penetration depth δ is expressed by the following equation. δ = {ρ / (πμf)} ^1/2
Here, ρ is the volume resistivity (Ω · m) of the material, μ is the magnetic permeability (H / m) of the material, and f is the frequency (Hz) of the alternating current that excites the material. For example, when the frequency of the alternating current is 60 kHz, the penetration depth δ of aluminum is about 0.34 mm. If the thickness of the magnetic flux shielding member is larger than the penetration depth, the magnetic flux that has entered the magnetic flux shielding member loses energy in the member and cannot pass through the magnetic flux control member 22, so There is no need to make it significantly thicker. From the above, when the aluminum member 23 is used as the magnetic flux shielding member, the thickness is preferably 0.6 to 2.0 mm.

  The heating member 21 and the magnetic flux control member 22 may be bonded to each other or non-bonded. In the case of non-bonding, the heating member 21 and the magnetic flux control member 22 may be in contact with each other or separated from each other. In order to increase the heating efficiency, it is desirable that the heating member 21 is rubbed against the fixing belt 24. In this case, a material layer having a low frictional resistance can be formed on the surface layer of the heating member 21. As a material used here, a material having a low coefficient of friction and high heat resistance and high thermal conductivity is desirable. Specific examples include polyimide and fluororesin.

  The fixing roller 25 includes a metal core 25a made of, for example, stainless steel or carbon steel, and an elastic member 25b covered with a core metal 25a made of heat-resistant silicon rubber or the like in a solid or foamed form. . The fixing roller 25 receives a pressing force from the pressure roller 26 and forms a fixing nip portion N that is a contact portion having a predetermined width. The fixing roller 25 has an outer diameter of about 30 to 40 mm, a thickness of the elastic member 25b of about 3 to 10 mm, and a hardness of about 10 to 50 degrees (JIS-A).

  As shown in FIG. 3, the fixing belt 24 has a laminated structure in which an elastic layer 24c is formed on a base material 24b and a release layer 24d is formed thereon. The properties required for the substrate 24b include mechanical strength when the belt is stretched, flexibility, heat resistance that can withstand use at a fixing temperature, and the like. In the present embodiment, an insulating heat-resistant resin material, polyimide, polyimide amide, PEEK, PES, PPS, fluororesin, or the like is suitable for the base material 24b for induction heating of the heating member 21. The thickness is preferably 30 to 200 μm from the relationship between heat capacity and strength. The elastic layer 24c is formed for the purpose of giving flexibility to the belt surface in order to obtain a uniform image without uneven glossiness, and desirably has a rubber hardness of 5 to 50 ° (JIS-A) and a thickness of 50 to 500 μm. Also, silicon rubber or fluorosilicone rubber is used because of heat resistance at the fixing temperature. Examples of the release layer 24d include a tetrafluoroethylene resin (PTFE), a tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer resin (PFA), and a tetrafluoroethylene / hexafluoropropylene copolymer (FEP). Examples thereof include a fluororesin or a mixture of these resins, and those obtained by dispersing these fluororesins in a heat resistant resin.

  When the release layer 24d covers the elastic layer 24c, the toner release properties are improved and the prevention of paper powder sticking can be achieved without using silicon oil or the like (oilless). However, since these resins having mold releasability generally do not have elasticity like rubber materials, if the release layer 24d is formed thick on the elastic layer 24c, the flexibility of the belt surface is impaired. Uneven gloss will occur. In order to achieve both releasability and flexibility, the film thickness of the release layer 24d needs to be 5 to 50 μm, desirably 10 to 30 μm. Moreover, a primer layer may be provided between each layer as needed, and a layer for improving durability during sliding may be provided on the inner surface of the base material 24b. Examples of the material constituting this layer include polyimide and fluororesin. Furthermore, you may equip the base material 24b with a heat generating layer, for example, can form Cu layer 3-15 micrometers on the base layer which consists of a polyimide etc., and can use this as a heat generating layer.

  The heating induction coil 27 includes a coil 27a, a magnetic core, and a case 27e. The magnetic core has a planar core 27b that is positioned behind the coil 27a at a position facing the heating member 21. Further, the magnetic core has a center core 27c and two side cores 27d that are opposed to the heating member 21 and are located closer to the heating member 21 than the planar core 27b without the coil 27a. The magnetic core forms a magnetic path for concentrating the magnetic flux generated from the coil 27 a to the heating member 21.

  A plurality of the planar cores 27b are arranged at an appropriate interval in the longitudinal direction so that the temperature distribution in the longitudinal direction, which is the paper surface direction of the heating member 21, is uniform. The magnetic core is preferably a soft magnetic material having a small coercive force and a high magnetic permeability and a high electrical resistivity. In addition to ferrite, Mn—Zn ferrite, Ni—Zn ferrite, or the like is used as the material of the core, such as permalloy. The number and interval of the planar core 27b can be adjusted as appropriate.

  The coil 27a is obtained by winding a litz wire obtained by twisting about 50 to 500 conductive wires having a diameter of about 0.05 to 0.2 mm with an insulating coating 5 to 20 times. The surface of the litz wire is provided with a fusion layer, and the fusion layer is solidified by energization heating or heating in a thermostatic bath, and the shape of the wound coil can be maintained. It is also possible to give a shape by winding a coil using a litz wire that does not hold the fusion layer and press-molding it. Since the litz wire needs to have a heat resistance equal to or higher than the fixing temperature, a resin having both heat resistance and insulation properties, such as polyamideimide and polyimide, is used for the insulation coating material of the strand. The wound coil 27a is bonded and fixed to the case 27e using a silicon adhesive or the like. Since the case 27a needs heat resistance equal to or higher than the fixing temperature, PET, liquid crystal polymer, or the like, which is a resin having high heat resistance, is used.

  As shown in FIG. 4, the coil 27 a is formed by rotating a wire bundle obtained by bundling 90 insulated copper wires having an outer diameter of 0.15 mm, and is formed so as to cover the heating member 21. It is arranged in a spiral shape over its entire width. The coil 27a is formed to have a planar shape along the fixing belt 24 in the heating member 24a with the center core 27c as an axis.

  The pressure roller 26 includes a release layer 26a, an elastic layer 26b having high heat resistance, and a cored bar 26c made of a metal cylindrical member. The pressure roller 26 is in pressure contact with the fixing roller 25 via the fixing belt 24, and a fixing nip portion N. Is forming. The pressure roller 26 has an outer diameter of 30 to 40 mm, a thickness of the elastic layer 26b of 0.3 to 5.0 mm, and a hardness of about 20 to 50 ° (JIS-A). The material needs to be heat resistant. Therefore, silicon rubber is used. Furthermore, in order to improve the releasability at the time of double-sided image formation, a release layer 26a using a fluororesin is formed on the elastic layer 26b by about 10 to 100 μm. By making the pressure roller 26 harder than the fixing roller 25, the pressure roller 26 bites into the fixing roller 25 (and the fixing belt 24) side. As a result, the recording material has a curvature that cannot follow the surface of the fixing belt 24 at the exit of the fixing nip portion N, and the releasability of the recording material can be improved.

Next, the operation of the fixing device 20 configured as described above will be described.
The fixing belt 24 travels in the direction indicated by the arrow R in FIG. 2, and the heating member 21 is heated by induction heating. Specifically, the magnetic field lines are formed so as to be switched bidirectionally and alternately in the loop of the induction heating coil 27 by passing a high-frequency alternating current of 10 kHz to 1 MHz through the induction heating coil 27. By forming an alternating magnetic field in this way, an eddy current is generated in the heating member 21 and Joule heat is generated and induction heating is performed. The fixing belt 24 is heated by the heat generated from the heating member 21 as described above, and the recording paper P being conveyed and the fixing belt 24 come into contact with each other at the fixing nip portion N to heat the toner image T on the recording paper P. Melt.

  5 and 6 show the path of the lines of magnetic force generated from the induction heating coil 27. FIG. 5 shows the case where the magnetic flux control member 22 is below the Curie temperature, and FIG. 6 shows the case where the magnetic flux control member 22 is above the Curie temperature. Each is shown. In the case of FIG. 5, since the magnetic flux generated from the induction heating coil 27 passes through the inside of the magnetic flux control member 22 as in the path of the magnetic flux A in the figure, induction heating occurs in the heating member 21 and the heating member 21 is The temperature rises to a predetermined temperature. On the other hand, when the temperature of the magnetic flux control member 22 rises to be equal to or higher than the Curie temperature, the magnetic flux generated from the induction heating coil 27 passes through the magnetic flux control member 22 as shown in FIG. Then, the magnetic flux shielding member 23 is passed. Since the magnetic flux is shielded by the magnetic flux shielding member 23 in this way, it is possible to prevent overheating of the fixing device 20.

  Here, the difference between the fixing device 20 of the present invention and the conventional fixing device will be described. In the conventional fixing device, as shown in FIG. 7, a magnetic shunt alloy is formed in a roll shape to form a magnetic flux control member 81, and the fixing belt is stretched by the curved surface. Then, by providing an induction heating coil having a shape along the roll-shaped magnetic flux control member 81 at a position facing the magnetic flux control member 81 via the fixing belt, the magnetic flux control member 81 has a function as a heating member. A magnetic flux shielding member 82 is provided inside. Thus, in the conventional fixing device, it is necessary to form an expensive magnetic shunt alloy in a roll shape, and the material cost and processing cost account for a large proportion of the cost of the entire fixing device. It was a bottleneck in trying to go down.

  In the first embodiment of the present invention, the heating member 21, the magnetic flux control member 22, and the magnetic flux shielding member 23 have planar shape portions 21 a, 22 a, and 23 a, respectively, and the fixing belt 24 has each planar shape portion 21 a, 22 a, The heating unit 24a is formed by being stretched along the state 23a. With this configuration, the amount of magnetic shunt material used can be reduced as compared to the conventional fixing device, and the processing can be simplified, and the manufacturing cost of the fixing device can be greatly reduced by reducing the material cost and the processing cost. Can be lowered. Further, since the magnetic flux control member 22 has a planar shape, the induction heating coil 27 can also have a planar shape. For this reason, the clearance control between the heating member 21 and the conventional arch-shaped induction heating coil becomes easy, and the clearance is easily reduced. In particular, since the clearance can be easily reduced, the improvement of the heating efficiency can be expected.

  FIG. 8 shows the temperature transition of the fixing device 20 over time after the apparatus is started up in the first embodiment. As shown in FIG. 8, the temperature rise starts from the time of starting up the apparatus, and when the temperature reaches a target temperature (170 ° C. in this case), the temperature rise starts to slow down due to the effect of the magnetic flux control member 22 and the magnetic flux shielding member 23. Stabilizes at the target temperature. As described above, also in this configuration, the temperature of the fixing belt 24 is automatically controlled as in the conventional fixing device.

  As described above, the fixing belt 24 is provided with a flat portion, and the magnetic flux control member 22 and the magnetic flux shielding member 23 are provided with the planar shape portions 22a and 23a, so that the configuration is greatly changed as compared with the conventional fixing device. The manufacturing cost can be reduced without doing so. The present invention is intended to reduce the cost of the fixing device by simplifying the configuration of the magnetic flux control member in the fixing device using induction heating, and the fixing member, the pressure member, and the heating member may have other configurations. Good. For example, a fixing device that is pressurized and heated by a nip formed by a flexible endless and rotatable fixing member, a nip forming member inside the fixing member, and a pressure member facing the fixing member. There may be. In this fixing device, a heating member which is a heat generating layer is provided on the fixing member and induction heating is performed. Further, the fixing device uses a fixing roller as a fixing member and is pressed and heated by a nip portion formed by an opposing pressure roller. The fixing roller is provided with a heating member as a heat generation layer, and induction heating is performed. It may be configured.

  FIG. 9 shows a second embodiment of the present invention. Compared with the first embodiment described above, the second embodiment is different only in that it has a magnetic flux control member 23A instead of the magnetic flux shielding member 23, and the other configurations are the same. In the second embodiment, the warm-up time is shortened by changing the position of the magnetic flux shielding member 23A.

  FIG. 9 shows the position of the magnetic flux shielding member 23A during warm-up. In the second embodiment, the magnetic flux shielding member 23A is moved away from the magnetic flux control member 22 during warm-up by driving means (not shown) such as a motor. In this case, the heating member 21 and the magnetic flux control member 22 are heated by the magnetic flux generated from the induction heating coil 27, and the magnetic flux does not pass through the magnetic flux shielding member 23A even when the magnetic flux control member 22 becomes equal to or higher than the Curie temperature. The temperature will not stop without being consumed. Thereby, rapid start-up at the time of warm-up becomes possible. In the second embodiment, the magnetic flux shielding member 23 </ b> A is desirably separated from the magnetic flux control member 22 by about 3.0 to 5.0 mm.

  In the second embodiment, the movement of the magnetic flux shielding member 23 </ b> A is not limited to parallel movement. For example, the magnetic flux shielding member 23 </ b> A is perpendicular to the magnetic flux control member 22. Such a movement trajectory may be drawn. Further, two or more members may be arranged side by side as the magnetic flux shielding member 23A, and the same applies to the movement in that case.

  During normal driving, the position of the magnetic flux shielding member 23A returns to a position in contact with or close to the magnetic flux control member 22 as in the first embodiment, and automatic temperature control of the magnetic flux control member 22 near the Curie temperature becomes possible. As a method of moving the magnetic flux shielding member 23A, in addition to incorporating the above-described actuator such as a motor, a simple method that does not greatly change the layout, such as interlocking with the pressure depressurization mechanism of the pressure roller 26, is applied. Is possible.

  Next, a third embodiment of the present invention will be described. In the third embodiment, the heating efficiency is improved by changing the configuration of the magnetic flux control member 22. In the first embodiment, the heating member 21 and the magnetic flux control member 22 are separate members. For this reason, it is conceivable that an eddy current in a path as shown in FIG. 10 flows on the surface of the magnetic flux control member 22 due to electromagnetic induction, resulting in a loss due to heating. In order to improve the heating efficiency, it is necessary to suppress eddy current loss on the surface of the magnetic flux control member 22. One countermeasure for this is the configuration shown in FIG.

  In FIG. 11 showing the third embodiment of the present invention, a plurality of slits 22b are formed in a magnetic flux control member 22A used in place of the magnetic flux control member 22. By having such a plurality of slits 22b, a large eddy current path cannot exist on the surface of the magnetic flux control member 22A, and a small eddy current path as shown in FIG. 12 exists between the slits 22b. It becomes. For this reason, since the heat generated by the eddy current is reduced and the loss of heat generated by the magnetic flux control member 22A is reduced, the heating efficiency is improved. Each slit 22b is desirably formed so as to penetrate the magnetic flux control member 22A.

  FIG. 13 shows a magnetic flux control member 22B used in a modification of the third embodiment of the present invention. The magnetic flux control member 22B is configured by dividing the magnetic flux control member 22 into small blocks. Also in this magnetic flux control member 22B, no eddy current path is formed between the blocks, so the eddy current path flowing through the surface of the magnetic flux control member 22B becomes smaller as shown in FIG. 14, which is the same as in the third embodiment. An effect can be obtained.

  In this modification, the magnetic flux control member 22B only needs to be divided into blocks, and the blocks are separated from each other or bonded with an insulating adhesive having high heat resistance so that an insulating layer is interposed therebetween. It only has to be. When the blocks are separated from each other, a configuration in which the magnetic flux control member 22B is arranged on a resin holding member formed in a rib shape can be employed. In the third embodiment and the modification described above, the width of the slit 22b and the size of each block can be appropriately adjusted.

  FIG. 15 is a diagram comparing the temperature rising time from the start of the apparatus in the first embodiment and the third embodiment. Compared to the first embodiment, in the third embodiment, the fixing device can be started up earlier due to the influence of eddy current loss being suppressed on the surface of the magnetic flux control member 23B.

  FIG. 16 shows a fixing device 20A used in the fourth embodiment of the present invention. In the present invention, the magnetic flux control member 22 is positioned at a position facing the induction heating coil 27 via the heating member 21, and the magnetic flux shielding member 23 is positioned at a position facing the induction heating coil 27 via the magnetic flux control member 22. It is important that Therefore, as shown in FIG. 16, a fixing device 20 </ b> A in which the induction heating coil 27 is positioned inside the fixing belt 24 and the magnetic flux control member 22 and the magnetic flux shielding member 23 are positioned outside the fixing belt 24 may be used. . Also with this fixing device 20A, the same operational effects as those of the fixing device 20 shown in the first embodiment can be obtained.

  FIG. 17 shows a fixing device 20B used in the fifth embodiment of the present invention, and FIG. 18 shows a fixing belt 24A as a fixing member used in the fifth embodiment of the present invention. The fixing belt 24A is provided with the heating member 21 further above the release layer 24d, and the fixing device 20B is not provided with the heating member 21. According to the fifth embodiment, physical deterioration of the heating member 21 due to rubbing of the fixing belt 24A can be suppressed, and a longer-life fixing device can be obtained.

  FIG. 19 shows a magnetic flux control member used in the sixth embodiment of the present invention. A magnetic flux control member 22C used in place of the magnetic flux control members 22, 22A, 22B described above is composed of two different types of magnetic materials 22Ca, 22Cb. Each of the magnetic materials 22Ca and 22Cb is a magnetic shunt alloy, and the Curie temperature Tca of the magnetic material 22Ca is such that the temperature of the fixing belt 24 becomes a target temperature when the fixing devices 20, 20A and 20B are driven. The Curie temperature Tcb of 22Cb is configured to be lower than the Curie temperature Tca. The magnetic material 22Ca and the magnetic material 22Cb are respectively positioned at the center in the longitudinal direction of the magnetic flux control member 22C, and the width of the magnetic material 22Ca corresponds to the width of the recording paper normally used (for example, A4 size). It is configured.

  With the above configuration, since the magnetic material 22Ca is positioned at a position where normally used recording paper is passed, the fixing belt 24 is heated to a target temperature suitable for fixing the toner on the recording paper. ing. On the other hand, since the magnetic material 22Cb is located in the non-sheet passing portion and the Curie temperature Tcb is lower than the Curie temperature Tca, the temperature of the fixing belt 24 in the non-sheet passing portion is lowered, and the temperature rises in the non-sheet passing portion. Temperature is reliably suppressed. It should be noted that since there is little risk of excessive temperature rise in the area where normally used recording paper is passed, strict temperature control is not required as in non-sheet passing portions. Therefore, the magnetic material 22Ca can be made of ferrite or the like instead of the magnetic shunt alloy with the Curie temperature adjusted. In the sixth embodiment, the magnetic flux control member 22C is configured by two different types of magnetic materials 22Ca and 22Cb. However, the magnetic flux control member 22C may be configured by three or more different types of magnetic materials.

  FIG. 20 shows a seventh embodiment of the present invention. The seventh embodiment is different from the fourth embodiment described above only in that a contact member 29 is provided between the fixing belt 24 and the magnetic flux generator 27, and other configurations are different. Are the same. The contact member 29 is urged to the left in FIG. 20 by urging means (not shown), and is pressed against the heating member 21 via the fixing belt 24. In order to improve the heating efficiency, it is desirable that the heating member 21 and the fixing belt 24 are in contact with each other, and the higher the adhesion, the higher the heating efficiency. With this configuration, the adhesion between the heating member 21 and the fixing belt 24 is increased, and the thermal resistance at the interface can be reduced as compared with the case where the heating member 21 and the fixing belt 24 are merely separated or rubbed, and the heating efficiency is improved. Will improve.

  The contact member 29 is preferably made of a non-conductive material in order to prevent the heating efficiency from being impaired by the heating member 21, and is preferably made of a material having low thermal conductivity in order to suppress thermal loss. The contact member 29 is required to have high heat resistance, and therefore, a resin member such as a liquid crystal polymer is preferable. Moreover, it is desirable that the thickness of the contact member 29 is not too thick so that the dielectric heating of the heating member 21 is not impaired by the magnetic flux generated from the magnetic flux generation unit 27. Since a high pressure is not necessary to improve the adhesion between the heating member 21 and the fixing belt 24, the thickness of the contact member 29 is suitably about 2 to 3 mm. Further, a low friction material such as tetrafluoroethylene resin may be provided on the surface of the contact member 29, or a lubricant such as silicon oil or grease may be applied.

  In the seventh embodiment, in order to improve the adhesion between the contact member 29 and the heating member 21, a configuration is shown in which the contact member 29 is biased leftward in FIG. However, the contact member 29 may be brought into contact with the heating member 21 via the fixing belt 24 without urging the contact member 29 by the above-described urging means (not shown). As this structure, the structure etc. which support the contact member 29 so that the contact member 29 will be in the position which contacts the heating member 21, for example are mentioned.

  FIG. 21 shows an eighth embodiment of the present invention. The eighth embodiment is different from the fourth embodiment described above only in that a heating member 21A is used instead of the heating member 21, and the other configurations are the same. As described in the seventh embodiment, the heating efficiency improves as the adhesion between the heating member and the fixing belt increases. The heating member 21A is curved so that the central portion on the fixing belt 24 side protrudes, and the heating efficiency is improved by improving the adhesion by being brought into pressure contact with the fixing belt 24 stretched on each stretching member 28. Is configured to improve. With this configuration, the contact member 29 can be omitted, and the same effects as those of the seventh embodiment can be obtained at low cost. In this configuration, the contact member 29 may be disposed as in the seventh embodiment. As a result, the heating member 21A and the fixing belt 24 can be brought into close contact with each other, and the heating efficiency is reliably improved.

  In the seventh embodiment, the fixing belt 24 is rubbed while being in close contact with the contact member 29. Therefore, the fixing belt 24 may be damaged due to wear or the like during the rubbing, and the fixing device may be brought to an emergency stop. There is. Therefore, a contact member having a reduced contact area with the fixing belt 24 is shown as a ninth embodiment.

  FIG. 22 shows contact members 29A, 29B, and 29C used in the ninth embodiment of the present invention. Each contact member 29A, 29B, 29C has convex portions 29Aa, 29Ba, 29Ca and concave portions 29Ab, 29Bb, 29Cb on the sliding surface with the fixing belt 24, respectively, and only the convex portions 29Aa, 29Ba, 29Ca. Rubs against the fixing belt 24. With this configuration, the contact area with the fixing belt 24 can be reduced, the effect of the rubbing force on the fixing belt 24 can be suppressed, and the life of the fixing belt 24 can be extended. In the ninth embodiment, as in the seventh embodiment, a low friction material is provided on each of the convex portions 29Aa, 29Ba, 29Ca, or a lubricant such as silicon oil or grease is applied. Good. Furthermore, the heights of the convex portions 29Aa, 29Ba, and 29Ca may be non-uniform, and the materials of the convex portions 29Aa, 29Ba, and 29Ca and the concave portions 29Ab, 29Bb, and 29Cb may be different.

The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the specific embodiments described above, and is described in the claims unless specifically limited by the above description. Various modifications and changes can be made within the scope of the present invention.
The effects described in the embodiments of the present invention are only the most preferable effects resulting from the present invention, and the effects of the present invention are not limited to those described in the embodiments of the present invention. .

20, 20A, 20B Fixing device 21, 21A Heating member 22, 22A, 22B, 22C Magnetic flux control member 22a, 23a Planar shape portion 22b Slit 22Ca, 22Cb Magnetic body (magnetic material)
23, 23A Magnetic flux shielding member 24, 24A Fixing member (fixing belt)
26 Pressing member (Pressure roller)
27 Magnetic flux generator (heating induction coil)
29, 29A, 29B, 29C Contact member 100 Image forming apparatus (printer)
N Fixing nip

JP 2010-2603 A

Claims (10)

A belt-like fixing member;
A magnetic flux generator for generating magnetic flux,
A heating member for heating the fixing member with heat generated by the magnetic flux;
A magnetic flux control member disposed opposite to the magnetic flux generation unit via the heating member;
A magnetic flux shielding member disposed opposite to the magnetic flux generation unit via the magnetic flux control member;
Each of the magnetic flux control member and the magnetic flux shielding member has a planar shape portion, and the fixing member is stretched in a state along each planar shape portion. The fixing device according to claim 1.
The fixing device according to claim 1, wherein the magnetic flux control member is made of a magnetic material having a Curie temperature of 100 to 250 ° C. The fixing device according to claim 2.
The fixing device, wherein the magnetic flux control member includes a plurality of the magnetic bodies having different Curie temperatures. The fixing device according to any one of claims 1 to 3,
The fixing device, wherein the heating member is a non-magnetic material. In the fixing device according to any one of claims 1 to 4,
The fixing device according to claim 1, wherein the heating member and the fixing member are rubbed and have a low friction material layer on a surface layer of the heating member. In the fixing device according to any one of claims 1 to 4,
The fixing device according to claim 1, wherein a distance between the magnetic flux shielding member and the magnetic flux control member is changed when the magnetic flux shielding member is started up. In the fixing device according to any one of claims 1 to 4,
The magnetic flux control member has a plurality of slits. In the fixing device according to any one of claims 1 to 4,
A fixing device, comprising: a contact member disposed between the fixing member and the magnetic flux generation unit and configured to contact the fixing member with the heating member. The fixing device according to claim 8.
The fixing device according to claim 1, wherein the contact member has an uneven surface.   An image forming apparatus comprising the fixing device according to claim 1.

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