JP5509545B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device and an image forming apparatus using the fixing device, and more particularly to a technique for shortening a warm-up time in a fixing device using an induction heating fixing belt.

In recent years, in the field of image forming apparatuses such as printers and copiers, those equipped with a fixing device of an electromagnetic induction heating method having a higher power saving effect than a fixing device using a halogen heater as a heat source are becoming widespread (for example, patent documents). 1).
FIG. 10A is a cross-sectional view showing the configuration of the electromagnetic induction heating type fixing device 300 in Patent Document 1.

As shown in the figure, the fixing device 300 has a fixing roller 302 disposed on the inner side of the circulation path of the fixing belt 301, and is positioned on the outer side of the circulation path and facing the fixing roller 302 with the fixing belt 301 interposed therebetween. A pressure roller 303 is provided, and the pressure roller 303 is urged toward the fixing belt 301 to form a fixing nip 306.
The pressure roller 303 rotates in the direction of arrow B in response to a driving force from a driving motor (not shown). This driving force is transmitted to the fixing roller 302 and the fixing belt 301 via the fixing nip 306, so that the fixing roller 302 and the fixing belt 301 are driven to rotate in the direction of arrow A.

  In addition, a magnetic flux generator 304 that generates a magnetic flux for generating heat from the heat generating layer included in the fixing belt 301 is disposed outside the circumference of the fixing belt 301 and on the opposite side of the pressure roller 303. Is done. A restricting plate 305 that contacts the back surface of the fixing belt 301 and restricts the revolving position is disposed at a position on the inner side of the revolving path that faces the magnetic flux generation unit 304. This stabilizes the relative position with the magnetic flux generation unit 304 even during the rotation of the fixing belt 301, so that the heat generation of the fixing belt 301 due to electromagnetic induction does not vary.

In such a configuration, when the magnetic flux is generated from the magnetic flux generator 304 while the fixing belt 301 is driven to rotate, a portion of the heat generating layer in the fixing belt 301 that mainly faces the magnetic flux generator 304 generates heat, and the sheet When the toner image formed on S passes through the fixing nip 310, it is heated and pressurized and thermally fixed to the sheet S.
FIG. 10B is an enlarged cross-sectional view of the fixing belt 301 and the regulation plate 305 in the wavy line T in FIG.

As shown in the figure, the fixing belt 301 is formed by laminating a release layer 3011, an elastic layer 3013, a heat generating layer 3013, and a magnetic shunt alloy layer 3014 from the outside. Further, the regulation plate 305 is formed of a low resistance non-magnetic conductive material such as copper.
The magnetic shunt alloy is a ferromagnetic material at a normal temperature, but has a property of becoming non-magnetic when the Curie temperature is exceeded, and by providing a magnetic shunt alloy layer 3014 in which the Curie temperature is appropriately set, An effect of preventing an excessive temperature rise in a portion of the fixing belt 301 where the sheet does not pass (hereinafter referred to as “non-sheet passing portion”) can be obtained.

  In other words, the fixing belt 301 is deprived of heat by the sheet S in the central portion where the sheet S is passed, but the temperature is lowered without depriving heat in the portions on both ends where the sheet does not pass. Since the voltage remains high, if the electric power is supplied to the magnetic flux generator 304 in order to maintain the central portion of the fixing belt 301 at the target temperature necessary for fixing, the temperature of the non-sheet passing portion further increases. As a result, the non-sheet passing portion of the magnetic shunt alloy layer 3014 included in the fixing belt 301 is heated to a temperature higher than the Curie temperature, and is changed from a ferromagnetic material to a non-magnetic material. This magnetic flux passes through the magnetic shunt alloy layer 3014 and reaches the regulating plate 305 this time.

An eddy current is generated in the regulating plate 305 by this magnetic flux. However, since it has a low resistance, it generates a magnetic flux in a direction that cancels the magnetic flux rather than generating heat as an eddy current loss. It decreases rapidly and the temperature rise is alleviated.
Thus, the conventional fixing device 300 is excellent in thermal efficiency because the fixing belt 301 itself generates heat, and the non-sheet passing portion of the belt 301 is excessively heated due to the interaction between the magnetic shunt alloy layer 301b and the regulating plate 305. The temperature can be automatically controlled so as not to occur (hereinafter referred to as “overheat suppression function”).
JP 2007-264421 A

However, since the fixing belt 301 in the conventional fixing device 300 includes the magnetic shunt alloy layer 3014, the heat capacity is increased correspondingly, which is an obstacle to further shortening the warm-up time.
In order to cope with this problem, a magnetic shunt alloy layer 3014 may be provided on the regulating plate 305 side to reduce the heat capacity of the fixing belt 301 itself. However, this time, since the heat capacity on the regulation plate 305 side becomes large, a large amount of heat generated in the fixing belt 301 is lost to the regulation plate 305 side due to heat conduction at the contact portion between the fixing belt 301 and the regulation plate 305. The warm-up time cannot be reduced as much as expected.

  An object of the present invention is to provide a fixing device capable of further shortening the warm-up time while securing an excessive temperature rise suppression function of a non-sheet passing portion using a magnetic shunt alloy.

In order to achieve the above object, the fixing device of the present embodiment is a fixing device that heats an unfixed image formed on a sheet by heating an orbitally driven belt by electromagnetic induction. A curved member that is disposed on the inner circumference of the belt that is driven and is curved along the inner circumferential surface of the belt that is driven to rotate, and is disposed on the outer periphery of the belt that is driven to rotate. And an exciting coil that generates a magnetic flux for heating the belt, and the bending member reversibly changes from a magnetic material to a non-magnetic material when the temperature exceeds a predetermined temperature. A nickel layer is formed on the surface facing the belt, and includes a metal layer made of a magnetic shunt alloy that changes, and is spaced from the bending member at a position opposite to the exciting coil of the bending member. Low Section which is curved in correspondence with the bending member with consisting Koshirubeden material in the same direction is characterized by comprising disposed arcuate flux canceling member.

The nickel layer may be formed by a plating process.
The low resistance conductive material is preferably copper or aluminum.
The present invention may also be an image forming apparatus that thermally fixes an unfixed image formed on the sheet by a fixing unit, and the fixing unit may include the above-described fixing device.

Hereinafter, an embodiment of an image forming apparatus according to the present invention will be described by taking as an example a case where it is applied to a tandem type color digital printer (hereinafter simply referred to as “printer”).
(1) Configuration of Printer FIG. 1 is a schematic cross-sectional view showing the overall configuration of the printer 1.
As shown in the figure, the printer 1 forms an image by a well-known electrophotographic system, and includes an image processing unit 10, a belt conveying unit 20, a feeding unit 30, and a fixing unit 40, and a network. When a print (print) job execution instruction is received from an external terminal device (not shown) connected to (for example, a LAN), yellow (Y), magenta (M), cyan (C) are received based on the instruction. And color image formation of black (K) color is executed.

  The image processing unit 10 includes image forming units 10Y to 10K corresponding to Y to K colors, respectively. The image forming unit 10Y includes a photosensitive drum 11Y, a charger 12Y, an exposure unit 13Y, a developing unit 14Y, a transfer roller 15Y, a cleaner for cleaning the photosensitive drum 11Y, and the like disposed around the photosensitive drum 11Y. Then, a Y-color toner image is formed on the photosensitive drum 11Y through known charging, exposure, and development processes. This configuration is the same for the other image forming units 10M to 10K, and corresponding color toner images are formed on the photosensitive drums 11M to 11K.

The feeding unit 30 feeds the recording sheets S from the sheet feeding cassette one by one to the conveyance path 35 and sends them to the belt conveyance unit 20.
The belt conveyance unit 20 includes a conveyance belt 21 that circulates in the direction of the arrow, and sequentially conveys the sheet S from the feeding unit 30 to the transfer positions of the photosensitive drums 11 </ b> Y to 11 </ b> K while being in close contact with the conveyance belt 21. . When the sheet S passes through each transfer position, the toner images on the photoconductive drums 11Y to 11K are affected by the electrostatic force generated by the electric field generated between the transfer rollers 15Y to 15K and the photoconductive drums 11Y to 11K at the respective transfer positions. Are transferred onto the sheet S in a multiple manner. After each color toner image is transferred, the sheet S is separated from the conveyance belt 21 and sent to the fixing unit 40.

The fixing unit 40 is based on an electromagnetic induction heating system including the fixing belt 101, and heats and pressurizes the sheet S sent from the conveyance belt 21 to fix each color toner image on the sheet S. The sheet S after fixing is discharged onto the discharge tray 39.
(2) Configuration of Fixing Unit FIG. 2 is a partial cross-sectional perspective view showing the configuration of the fixing unit 40, and FIG. 3 is a cross-sectional view of the main part thereof.

As shown in both drawings, the fixing unit 40 includes a fixing belt 101, a fixing roller 102, a pressure roller 103, a magnetic flux generation unit 104, and a regulation plate 105.
The fixing belt 101 is a cylindrical belt that is driven to rotate in the direction of arrow A, and has an inner diameter of about 40 [mm], and an elastic self-shape-holding belt that can hold a substantially cylindrical shape by itself is used. It has been. The belt width direction (corresponding to the rotation axis direction of the fixing roller 102) of the fixing belt 101 is longer than the width direction length of the maximum size sheet. FIG. 2 shows a state in which small-size paper having a size smaller than the maximum size passes through the fixing nip 107.

  The fixing roller 102 is formed with an elastic layer 1021 around a long and cylindrical shaft core 1022, and is arranged inside the circulation path (circulation traveling path) of the fixing belt 101. The shaft core 1022 is made of a nonmagnetic material such as aluminum or copper and a low-resistance conductive material. The elastic layer 1021 is made of silicone sponge and functions as a heat insulating layer. The outer diameter of the fixing roller 102 is, for example, about 33 [mm].

The pressure roller 103 is formed by laminating a release layer 133 around an elongated cylindrical shaft core 131 with an elastic layer 132 interposed therebetween. The pressure roller 103 is disposed outside the circulation path of the fixing belt 101, and The fixing roller 102 is pressed from the outside via the fixing belt 101 to secure a fixing nip 107 between the surface of the fixing belt 101.
The shaft core 131 is made of stainless steel, and the elastic layer 132 is made of silicone sponge or the like. The release layer 133 is made of PFA or PTFE (polytetrafluoroethylene) coat. The outer diameter of the pressure roller 103 is, for example, about 35 [mm].

The shaft core 131 may be a pipe material or a solid shaft. If the material of the shaft core 131 can secure the strength, it is possible to use a heat-resistant molded pipe such as iron or PPS (polyphenylene sulfide). It is desirable to use a nonmagnetic material that is less affected by induction heating.
The fixing roller 102 and the pressure roller 103 are rotatably supported at both axial ends of the shaft cores 1022 and 131 by a frame (not shown) via a bearing member or the like, and the pressure roller 103 is a drive motor (not shown). ) Is driven to rotate in the direction of arrow B. As the pressure roller 103 rotates, the fixing belt 101 and the fixing roller 102 are driven to rotate in the direction of arrow A.

The magnetic flux generation unit 104 includes an exciting coil 141, a main core 142, a center core 143, a hem core 144, a cover 145, and a coil bobbin 146, and is located outside the circulation path of the fixing belt 101. The fixing belt 101 is disposed along the width direction of the fixing belt 101 at a position facing the pressure roller 103.
The exciting coil 141 generates a magnetic flux for heating the heat generating layer 113 of the fixing belt 101, and is wound around the coil bobbin 146. The magnetic flux generated from the exciting coil 141 is guided to the fixing belt 101 by the main core 142 to the bottom core 144, and a portion of the heat generation layer 1013 (see FIG. 4) of the fixing belt 101 that mainly faces the magnetic flux generation unit 104 is used. Through this, an eddy current is generated in the portion of the heat generating layer 1013 to heat the heat generating layer 1013 itself.

  The heat of the generated heat is transmitted to the pressure roller 103 or the like at the position of the fixing nip 107 by the circumferential driving of the fixing belt 101, whereby the area of the fixing nip 107 (sheet passing area) is heated. Although not shown, a sensor for detecting the temperature of the fixing belt 101 is separately provided. The current temperature of the fixing belt 101 is detected based on a detection signal from the sensor, and the fixing nip 107 is detected based on the detected temperature. The power supply to the exciting coil 141 is controlled so that the temperature in the region is maintained at the target temperature. When the sheet S passes through the fixing nip 107 with the area of the fixing nip 107 maintained at the target temperature, an unfixed toner image on the sheet S is heated and pressed to be thermally fixed on the sheet S. The

  The restriction plate 105 is a long plate-like member whose length is longer than the length of the fixing belt 101 in the belt width direction, and faces the magnetic flux generation unit 104 via the fixing belt 101 inside the circulation path of the fixing belt 101. The fixing belt 101 that is disposed at a position and contacts the back surface (hereinafter referred to as “belt back surface”) 115 of the fixing belt 101 and is driven in a circulating manner is guided in the rotating direction (hereinafter referred to as “belt rotating direction”). However, the relative position between the fixing belt 101 and the magnetic flux generation unit 104 is regulated. In addition, the length direction both ends of the control board 105 are being fixed to the flame | frame which is not shown in figure.

(Materials such as fixing belt 101 and laminated structure)
4A is an enlarged cross-sectional view of the fixing belt 101, the regulating plate 105, and the fixing roller 102 in the wavy line portion S of FIG. 3, and FIG. 4B summarizes the thickness of each layer and its material in a table. It is a thing.
As shown in FIG. 4A, the fixing belt 101 is formed by laminating a release layer 1011, an elastic layer 1012, and a heat generating layer 1013 in order from the surface side.

The release layer 1011 is for enhancing the releasability with the toner, and is made of PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer) having a thickness of 30 [μm]. In addition, for example, fluororubber and fluororesins such as PTFE, FEP, and PFEP are used.
The elastic layer 1012 serves to increase the adhesion between the recording sheet and the surface of the fixing belt 101 in the fixing nip. The elastic layer 1012 is a layer of a rubber material or a resin material having heat resistance and elasticity, and is used at a fixing temperature. A heat-resistant elastomer such as silicone rubber and fluororubber that can be used can be used. In this example, a silicone rubber having a thickness of 200 [μm] is used.

The heating layer 1013 is a nickel electroformed belt having a thickness of 40 [μm].
On the other hand, the regulation plate 105 is made of a magnetic shunt alloy made of an alloy of nickel and iron and has a thickness of 200 [μm]. In this embodiment, the mixing ratio of nickel and iron is set so that the Curie temperature is about 20 ° C. higher than the temperature necessary for fixing (about 200 ° C.). The magnetic shunt alloy may further contain chromium in addition to nickel and iron.

The shaft core 1022 of the fixing roller 102 is made of copper having an outer diameter of 10 mm, and may be another low resistance conductive material such as aluminum.
The elastic layer 1021 of the fixing roller 102 is for heat-insulating and holding the heat generating layer, and a heat-resistant / elastic rubber or resin sponge (heat insulating structure) is used. By using such a material, heat insulation is maintained, the deflection of the heat generation layer is allowed, the press nip width is increased, the roller hardness is decreased, and the paper discharge performance and the recording material separation performance are improved. In this embodiment, a silicone sponge having a thickness of 13 mm is used.

(Suppressing effect of excessive temperature rise by regulating plate and shaft core)
FIGS. 5A and 5B are schematic diagrams for explaining the principle that excessive temperature rise is suppressed in the non-sheet passing portion of the fixing belt 101 due to the interaction between the regulating plate 105 and the shaft core 1022 of the fixing roller 102. FIG.
When the temperature of the magnetic shunt alloy is lower than the Curie temperature, it is a ferromagnetic body, and as shown in FIG. 5A, the alternating magnetic flux G1 generated by the exciting coil 141 is generated by the regulation plate (the magnetic shunt alloy). ) Focus toward 105. At this time, the heat generating layer 1013 generates heat due to the eddy current loss that passes through the heat generating layer 1013. The magnetic flux that has passed through the heat generation layer 1013 passes through the inside of the regulation plate 105 and returns in the direction of the exciting coil 141, so that it hardly reaches the axis 1022.

  However, heating at the non-sheet passing portion of the fixing belt 101 proceeds, and the temperature of the regulating plate 105 in contact with the fixing belt 101 rises and becomes non-magnetic when it exceeds the Curie temperature of the magnetic shunt alloy. Since the restriction plate 105 becomes non-magnetic, the magnetic flux collection effect is lost, the number of magnetic lines G2 passing through the fixing belt 101 is reduced, and the magnetic lines of force passing through the fixing belt 101 also pass through the restriction plate 105, and the shaft The core 1022 is reached and an eddy current is generated here. However, since the shaft core 1022 is formed of a low-resistance conductive material, there is little eddy current loss, and a demagnetizing effect is generated in which the magnetic flux G3 is generated in a direction that cancels the magnetic flux of the exciting coil 141 by the eddy current. For this reason, the density of magnetic flux that passes through both ends (non-sheet passing portions) where the sheet of the fixing belt 101 does not pass is further reduced (demagnetization effect).

As a result, the temperature of the non-sheet passing portion of the fixing belt 101 does not significantly exceed the Curie temperature and is prevented from reaching a high temperature that damages the fixing belt 101. The Curie temperature is not limited to the above temperature (220 ° C.), and an appropriate temperature is set depending on the configuration of the fixing unit 40.
As described above, in the present embodiment, the regulation plate 105 is formed of a magnetic shunt alloy, and the shaft core 1022 of the fixing roller 102 is formed of a low resistance conductive material. The temperature rise can be effectively suppressed, and it is no longer necessary to stack a low resistance conductive material on the regulation plate 105. Therefore, the total of the fixing roller 102 and the regulation plate 105 in the heat generation region where the magnetic flux generated by the exciting coil 141 acts greatly is combined. The heat capacity can be made smaller than before, and the heating rate can be increased by that amount, and the warm-up time can be shortened.

<Modification>
As described above, the present invention has been described based on various embodiments. However, the content of the present invention is not limited to the above embodiments, and for example, the following modifications can be considered. .
(1) The heat generating layer 1013 provided on the fixing belt 101 side in the above embodiment may be provided on the regulating plate 105 side.

6A is an enlarged cross-sectional view of the fixing belt 101, the regulating plate 105, and the fixing roller 102 in the wavy line S in FIG. 3, and FIG. 6B shows the thickness of each layer and its material. Is a table summarizing In FIG. 6A, the same reference numerals as those in FIG. 4A indicate the same components.
As shown in FIG. 6A, the fixing belt 101 is formed by laminating a release layer 1011, an elastic layer 1012 and a belt base material 1014 in order from the front side. Here, the belt base material 1014 is made of a heat-resistant resin having a thickness of 40 [μm], for example, polyimide.

On the other hand, the regulating plate 105 includes a copper heat generating layer 1051 (thickness 200 [μm]) disposed on the fixing belt 101 side and a magnetic shunt alloy (nickel / iron alloy) (thickness 200 [μm]) laminated on the opposite side. ). The heat generated by the restriction plate 105 is transmitted to the fixing belt 101.
According to the configuration of this example, since the heat generating layer is provided on the regulating plate 105 side, the belt base material 1014 is excessively laminated on the fixing belt 101 side, but the thickness thereof may be 40 μm. In the conventional configuration (FIG. 10B), the thickness of the low-resistance conductive layer on the regulating plate is 200 μm, so the total thickness of the fixing belt and the regulating plate is 160 μm thinner than that, and the total in the heat generation region is reduced. The heat capacity can be made smaller than before, which contributes to shortening the warm-up time.

The heat generating layer may be a thin layer formed of Al, Ni, or the like, for example. Its thickness is ... It may be 10 to 30 μm, desirably 15 to 20 μm. At this time, methods such as plating and vapor deposition are effective.
The magnetic shunt alloy layer needs to have a thickness of at least 100 μm in order to ensure a certain degree of rigidity.
As another material for the heat generating layer, for example, a material having a relatively high magnetic permeability μ and an appropriate resistivity ρ such as a magnetic material (magnetic metal) such as magnetic stainless steel may be used. Further, the heat generation layer may be formed by dispersing heat generation particles in a resin. Separation can be improved by using a resin-based heat generating layer.

Further, the heat generating layer and the magnetic shunt alloy layer can be formed of two clad materials.
In the present embodiment, since the heat generating portion serves as a regulating plate, the degree of freedom in selecting the fixing belt base material is high. Therefore, a resin belt that is more flexible than metal can be selected, and a configuration that is advantageous for paper separation performance can be achieved.
(2) In the above embodiment, the demagnetizing effect is ensured by forming the shaft core 1022 itself of the fixing roller 102 from a low-resistance conductive material. However, the present invention is not limited to this configuration.

For example, as shown in FIG. 8, the shaft core 1022 of the fixing roller 102 is formed of stainless steel or the like, and a similar effect can be obtained by mounting a cylindrical member 1023 made of a low resistance material on the outer periphery thereof. The cylindrical member 1023 may have a thickness of about 0.5 to 1.0 mm.
Further, instead of the cylindrical member 1023, the peripheral surface of the shaft core 1022 may be plated or vapor-deposited with a low resistance metal such as copper to a thickness of 100 μm to 200 μm.

(3) In short, the present invention affects the rate of temperature rise if the magnetic flux canceling member made of a low-resistance conductive material is provided in a position in contact with the regulating plate 105 at a position separated from the regulating plate 105. Since the purpose of reducing the heat capacity of the portion can be achieved, the magnetic flux canceling member does not necessarily have to be in the axial center portion of the fixing roller 102.
For example, as shown in the cross-sectional view of the fixing unit 40 in FIG. 7, a magnetic flux canceling member made of a low-resistance conductive material with a gap d between the regulating plate 105 and the fixing roller 102 circumferential surface. 120 may be provided. The magnetic flux canceling member 120 is substantially the same in length in the longitudinal direction as the regulating plate 105, is arranged substantially parallel to the regulating plate 105, and is held by frames (not shown) at both ends in the longitudinal direction.

  According to such a configuration, since the magnetic flux canceling member 120 is arranged with a gap d from the regulation plate 105, the axial core is not increased without increasing the heat capacity in the heat generating region, as shown in FIGS. Since the regulation plate 105 has exceeded the Curie temperature, most of the magnetic flux that has passed through it passes through the magnetic flux canceling member 120, so that much magnetic flux in the direction to cancel is generated. In addition, a higher demagnetizing effect can be obtained.

(4) Since the inner peripheral surface of the fixing belt 101 and the outer surface of the regulating plate 105 facing the fixing belt 101 are rubbed, a low friction layer is formed on both or one of the opposing surfaces for durability. May also be provided. As an example of this, FIG. 9 is a cross-sectional view of the main part showing a configuration in which the low friction layer 1053 is provided on the regulating plate 105 side in the embodiment of FIG.
The low friction layer 1053 is formed by coating heat-resistant PFA or the like with a thickness of 10 [μm], for example. Since the thickness of the low friction layer 1053 is very thin, it hardly affects the shortening of the warm-up time.

(5) In the above embodiment, the low resistance conductive material used for the shaft core as the magnetic flux canceling member is copper or aluminum. Examples of the low-resistance conductive material include gold and silver, but have a large cost demerit. However, there is a possibility of application when plating on the peripheral surface of the shaft core as in the modification (2).
Further, the low resistance material used for the shaft core is preferably non-magnetic in order to suppress heat generation as much as possible. This is because the elastic layer easily deteriorates due to heat generation.

(6) The material and configuration of each roller and the like are not limited to the above embodiment. It may be changed in a timely manner according to the device. Further, the shaft core may not be solid but cylindrical hollow.
(7) In the above embodiment, the tandem type color printer has been described. However, the present invention is not limited to this, and for example, a monochrome printer, or even a device having an additional function such as a copying machine or a fax machine may be used. In short, the electromagnetic induction heating method is applicable to all image forming apparatuses having a fixing device using a fixing belt , a regulation plate including a metal layer made of a magnetic shunt alloy, and a magnetic flux canceling member. is there.

The present invention can be widely applied to a fixing device using a fixing belt , a regulation plate including a metal layer made of a magnetic shunt alloy, and a magnetic flux canceling member, and an image forming apparatus using the same.

1 is a schematic cross-sectional view of a tandem color digital printer according to an embodiment of the present invention. FIG. 2 is a partial cross-sectional perspective view illustrating a configuration of a fixing unit disposed in the printer. It is a cross-sectional view showing the configuration of the fixing unit. (A) is sectional drawing for showing the laminated structure of the fixing belt and a control board in the broken-line part T of FIG. 3, (b) is a table | surface which shows the material and thickness of each layer. It is a schematic diagram for demonstrating the effect of excessive temperature rise suppression by a magnetic shunt alloy. (A) is sectional drawing for showing the laminated structure of the fixing belt and regulation board in the fixing part which concerns on the 1st modification of this invention, (b) is a table | surface which shows the material and thickness of each layer. . It is sectional drawing which shows the structure of the fixing part which concerns on the 2nd modification of this invention. FIG. 10 is a cross-sectional view illustrating a configuration of a fixing roller in a fixing unit according to a third modification of the present invention. FIG. 9 is a cross-sectional view illustrating a laminated structure of a fixing belt and a regulation plate in a fixing unit according to a fourth modification of the present invention. (A) is sectional drawing which shows the structure of the conventional electromagnetic induction heating type fixing device, (b) is an expanded sectional view which shows the laminated structure of the fixing belt and a control board.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Printer 40,300 Fixing part 101 Fixing belt 102 Fixing roller (1st roller)
103 Pressure roller (second roller)
104 Magnetic flux generator 105, 205 Restriction plate 107 Fixing nip 161 Rotating shaft of fixing roller 162 Rotating shaft 1021, 132 of pressure roller Elastic layer
1022, 131 shaft core

Claims (4)

A fixing device that heats an unfixed image formed on a sheet by heating a belt that is driven around by electromagnetic induction,
A bending member that is disposed on the inner side of the circulation path of the belt that is driven to circulate and curves along an inner peripheral surface of the belt that is driven to circulate;
An excitation coil that is disposed outside the circulation path of the belt driven to circulate, and is disposed at a position facing the bending member via the belt, and generates a magnetic flux for heating the belt,
The bending member includes a metal layer made of a magnetic shunt alloy that reversibly changes from a magnetic material to a non-magnetic material at a predetermined temperature or more, and a nickel layer is formed on a surface facing the belt,
A magnetic flux canceling member having an arcuate cross section that is made of a low-resistance conductive material and is curved in the same direction corresponding to the bending member at a position opposite to the exciting coil of the bending member and spaced from the bending member. A fixing device characterized by being arranged. The fixing device according to claim 1, wherein the nickel layer is formed by plating.   The fixing device according to claim 1, wherein the low-resistance conductive material is copper or aluminum.   An image forming apparatus for thermally fixing an unfixed image formed on the sheet by a fixing unit, comprising the fixing device according to claim 1 as the fixing unit. Image forming apparatus.

Images