JP2003338365A - Heat generating device and fixing device by use of electromagnetic induction - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the generation of noise of other member or equipment by preventing unnecessary radiation due to leak magnetic flux. <P>SOLUTION: A short ring 230 is provided on an outer side of a support frame 190 so as to surround a storage chamber 200. An eddy current is generated in the direction of elimination of leak magnetic flux leaking to the outside among magnetic fluxes generated by making a current flow in an excited coil 220 in the short ring 230. When the eddy current is generated, a magnetic field is generated in the direction of elimination of a magnetic field of the leak magnetic flux by the Fleming's rule to prevent unnecessary radiation due to the leak magnetic flux and reduce the generation of noise of the other member or equipment. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat generating device and a fixing device using electromagnetic induction used in an electrostatic recording type image forming apparatus such as a copying machine, a facsimile, a printer, and more specifically, electromagnetic induction heating. The present invention relates to a toner image fixing device using a method.

[0002]

2. Description of the Related Art In recent years, market demands for energy saving and high speed have increased for image forming apparatuses such as printers, copying machines, and facsimiles. In order to achieve these required performances, it is important to improve the thermal efficiency of the fixing device used in the image forming apparatus.

In an image forming apparatus, an unfixed toner image is recorded on a recording material sheet, printing paper, photosensitive paper, electrostatic recording by an image transfer system or a direct system by an image forming process such as electrophotographic recording, electrostatic recording and magnetic recording. It is formed on a recording material such as paper. As a fixing device for fixing an unfixed toner image, a contact heating type fixing device such as a heat roller type, a film heating type, or an electromagnetic induction heating type is widely adopted.

As an electromagnetic induction heating type fixing device, in Japanese Patent Laid-Open No. 8-22206, Joule heat is generated by an eddy current generated in a magnetic metal member by an alternating magnetic field, and a heating body including the metal member is heated by electromagnetic induction. Technology is proposed.

[0005]

[Patent Document 1] JP-A-8-22206

[0006]

The electromagnetic induction heating type fixing device is a type in which an eddy current is generated on the surface of the conductive roller by a magnetic field generated by an exciting coil to generate heat.
Since the supporting unit made of resin or the like adjacent to the conductive roller is exposed to a high temperature, there is a problem that warpage occurs due to long-term use.

Further, there is a problem in that unnecessary radiation due to the leakage magnetic flux generated by the exciting coil causes noise in members and devices around the fixing device.

Therefore, an object of the fixing device according to the present invention is to prevent warping of a support unit such as a resin for accommodating the conductive roller.

Another object of the fixing device according to the present invention is to reduce unnecessary radiation due to the leakage magnetic flux generated by the exciting coil and reduce the influence of noise on the surroundings.

[0010]

In order to solve the above problems, the present invention provides a heating section for heating a print medium, a support frame having a storage section for storing the heating section, and a heating section for heating the heating section. Reinforcing means for reinforcing the warped portion of the storage portion of the support frame is provided.

Further, the present invention is characterized by comprising a heat generating member, an exciting coil which is arranged to face the heat generating member and heats the heat generating member by electromagnetic induction, and an annular short ring made of a metal member. It was configured.

[0012]

DETAILED DESCRIPTION OF THE INVENTION (Image Forming Apparatus) First, an outline of an image forming apparatus according to the present invention will be described. FIG. 1 is an explanatory diagram showing a configuration of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus to be described in this embodiment is
A developing device is provided for each of the four basic color toners that contribute to the color development of a color image among the devices that employ the electrophotographic method.
It is a tandem system that superimposes a four-color image on a transfer body and transfers it to a recording material all at once. However, it goes without saying that the present invention is not limited to the tandem type image forming apparatus, and can be applied to any type of image forming apparatus regardless of the number of developing devices, the presence or absence of an intermediate transfer member, and the like. .

In FIG. 1, the photosensitive drums 10a, 10
The photoconductor drums 10 are provided around b, 10c and 10d.
Charging means 20a, 20b, 20c, 20 for uniformly charging the surfaces of a, 10b, 10c, 10d to a predetermined potential.
d, charged photosensitive drums 10a, 10b, 10c,
Exposure means 3 for irradiating scanning lines 30K, 30C, 30M, and 30Y of laser beams corresponding to image data of a specific color on 10d to form an electrostatic latent image, and photoconductor drums 10a and 1a.
Developing means 40a, 40b, 40c, 40d for visualizing the electrostatic latent images formed on the photosensitive drums 10a, 10b, 10c, 10d, and the toner images visualized on the photosensitive drums 10a, 10b, 10c, 10d. -Shaped intermediate transfer belt (intermediate transfer member) 7
Transfer means 50a, 50b, 50c, 50 for transferring to 0
d, cleaning means 60a, 60b, 6 for removing the residual toner remaining on the photoconductor drums 10a, 10b, 10c, 10d after transferring the toner image from the photoconductor drums 10a, 10b, 10c, 10d to the intermediate transfer belt 70.
0c and 60d are arranged respectively.

Here, the exposing means 30 is the photosensitive drum 1
It is arranged with a predetermined inclination with respect to 0a, 10b, 10c and 10d. Further, the intermediate transfer belt 70 rotates in the direction of arrow A in the illustrated case. In addition,
At the image forming stations Pa, Pb, Pc and Pd, a black image, a cyan image, a magenta image and a yellow image are formed respectively. Then, the photosensitive drum 10a,
The monochromatic images of the respective colors formed on 10b, 10c, and 10d are sequentially transferred and superposed on the intermediate transfer belt 70 to form a full-color image.

At the lower part of the apparatus, there is provided a paper feed cassette 100 in which a sheet material 90 such as printing paper is stored. Then, the sheet material 90 is sent one by one from the paper feed cassette 100 to the paper transport path by the paper feed roller 80.

A sheet material transfer roller 110, which is in contact with the outer peripheral surface of the intermediate transfer belt 70 for a predetermined amount on the sheet conveying path, and transfers the color image formed on the intermediate transfer belt 70 to the sheet material 90, a sheet material. A fixing device 120 for fixing the color image transferred on the sheet 90 to the sheet material 90 by pressure and heat accompanying the nip rotation of the rollers is arranged.

In the image forming apparatus having such a structure,
First, the charging unit 20a and the exposure unit 30 of the image forming station Pa form a latent image of a black component color of image information on the photoconductor drum 10a. This latent image is visualized as a black toner image by the developing means 40a having the black toner by the developing means 40a, and the transfer means 50 is formed.
The black toner image is transferred onto the intermediate transfer belt 70 by a.

On the other hand, while the black toner image is being transferred to the intermediate transfer belt 70, the image forming station Pb
Then, a latent image of a cyan component color is formed, and then the developing unit 4
At 0b, the cyan toner image is visualized by the cyan toner. Then, the cyan toner image is transferred by the transfer means 50b of the image station Pb onto the intermediate transfer belt 7 where the transfer of the black toner image is completed at the previous image station Pa, and is superposed on the black toner image.

Thereafter, image formation is performed on the magenta toner image and the yellow toner image by the same method, and when the four color toner images are superposed on the intermediate transfer belt 70, the paper feeding roller 80 is used to feed the paper cassette 100. The toner images of four colors are collectively transferred onto the sheet material 90 fed from the sheet material by the sheet material transfer roller 110. Then, the transferred toner image is heated and fixed on the sheet material 90 by the fixing device 120, and a full color image is formed on the sheet material 90.

(Fixing Device) The fixing device used in the image forming apparatus according to the present invention will be described below.

FIG. 2 is an explanatory view showing the structure of the fixing device used in the image forming apparatus according to the embodiment of the present invention. FIG. 4 is an explanatory view showing the structure of the heating roller constituting the fixing device of FIG. 2 in a broken manner.

The fixing device shown in FIG. 2 has an induction heating means 18
Heating roller 130 heated by electromagnetic induction of 0, and fixing roller 140 arranged in parallel with heating roller 130
An endless belt-shaped heat-resistant belt (toner heating medium) that is stretched between the heating roller 130 and the fixing roller 140, is heated by the heating roller 130, and is rotated in the direction of arrow B by the rotation of at least one of these rollers. 1
50 and the fixing roller 140 via the heat resistant belt 150.
And a pressure roller 160 that rotates in the forward direction with respect to the heat resistant belt 150.

The heating roller 130 is made of, for example, a hollow cylindrical magnetic metal member such as iron, cobalt, nickel, or an alloy of these metals, has an outer diameter of 20 mm and a wall thickness of 0.3 mm, for example, and heats it with a low heat capacity. It has a fast configuration.

The heating roller 130, as shown in FIG.
Both ends thereof are rotatably supported by bearings 132 fixed to a supporting side plate 131 made of a galvanized steel plate. The heating roller 130 is rotationally driven by a driving unit (not shown) of the apparatus body. The heating roller 130 is
It is composed of a magnetic material which is an alloy of iron, nickel and chromium, and its Curie point is adjusted to be 300 ° C. or higher. The heating roller 130 has a thickness of 0.3.
It is formed in a pipe shape of mm.

The surface of the heating roller 130 is coated with a release layer (not shown) made of a fluororesin having a thickness of 20 μm in order to impart releasability. As the release layer, resins and rubbers having good release properties such as PTFE, PFA, FEP, silicone rubber, and fluororubber may be used alone or in combination. When the heating roller 130 is used for fixing a monochrome image, only releasability needs to be secured, but when the heating roller 130 is used for fixing a color image, it is desirable to impart elasticity. In that case, Needs to form a thicker rubber layer.

In FIG. 2, the fixing roller 140 includes a core metal 140a made of metal such as stainless steel,
The elastic member 140b is made of a heat-resistant silicone rubber in a solid or foamed state and covered with a core metal 140a. Then, in order to form a contact portion (fixing nip portion N) having a predetermined width between the pressure roller 160 and the fixing roller 140 by the pressing force from the pressure roller 160, the pressure roller 160 and the fixing roller 140 are formed. The outer diameter is, for example, 30 mm
As a degree, the heating roller 130 is made larger.

The elastic member 140b of the fixing roller 140 has a wall thickness of, for example, about 3 to 8 mm and a hardness of, for example, 15 mm.
-50 ° (Asker hardness: JIS A hardness of 6-
It is about 25 °). With this configuration, the heat capacity of the heating roller 130 is smaller than that of the fixing roller 140, so that the heating roller 130 is rapidly heated and the warm-up time is shortened.

The heat resistant belt 150 stretched between the heating roller 130 and the fixing roller 140 is the induction heating means 18
It is heated while it is in contact with the heating roller 130 heated by 0. The inner surface of the heat resistant belt 150 is continuously heated by the rotation of the heating roller 130 and the fixing roller 140, and as a result, the entire belt is heated.

The heat-resistant belt 150 is provided so as to cover the surface of a heat-generating layer made of, for example, a magnetic metal such as iron, cobalt, nickel, etc. or an alloy having such a base material as a base material. A composite layer belt including a release layer made of an elastic member such as silicone rubber or fluororubber.

When the composite layer belt is used, in addition to the heating from the induction heating means 180 to the heat resistant belt 150 through the heating roller 130, the induction heating means 180 can directly heat the heat resistant belt 150. Further, as another effect, the heat generation efficiency is improved and the heat generation response becomes faster.

Even if for some reason, for example, a foreign substance is mixed between the heat-resistant belt 150 and the heating roller 130 to cause a gap, heat is generated due to electromagnetic induction of the heat-generating layer of the heat-resistant belt 150. Since the belt 150 itself generates heat, temperature unevenness is small and fixing reliability is high.

The thickness of the heating layer is 20 μm to 50 μm.
About μm is desirable, and about 30 μm is particularly desirable.

As described above, when the heat generating layer is made of a material having a magnetic metal such as iron, cobalt, nickel or the like or an alloy having such a base material as a base material, and the thickness thereof is larger than 50 μm. In addition, the strain stress generated when the belt is rotated becomes large, which causes the generation of cracks due to shearing force and the extreme decrease in mechanical strength. If the thickness of the heat generating layer is less than 20 μm, the composite layer belt may be damaged by cracking or the like due to the thrust load applied to the belt end portion due to the meandering during belt rotation.

On the other hand, the thickness of the release layer is 100 μm.
To about 300 μm is desirable, and about 200 μm is particularly desirable. By doing so, the toner image T formed on the recording material 90 is sufficiently covered by the surface layer portion of the heat resistant belt 150, so that the toner image T can be uniformly heated and melted.

When the thickness of the release layer is less than 100 μm, the heat capacity of the heat resistant belt 150 becomes small and the belt surface temperature rapidly decreases in the toner fixing step.
The fixing performance cannot be sufficiently secured. Further, when the thickness of the release layer is larger than 300 μm, the heat capacity of the heat resistant belt 150 becomes large and the warm-up time becomes long. In addition, in the toner fixing step, the belt surface temperature is less likely to decrease, the effect of agglomeration of the melted toner at the outlet of the fixing unit cannot be obtained, and the releasability of the belt decreases, so that the toner adheres to the belt. Hot offset occurs.

The inner surface of the heat generating layer may be coated with a resin for the purpose of preventing metal oxidation and improving the contact property with the heating roller 130.

As the base material of the heat resistant belt 150,
Instead of the heat generating layer made of the above metal, a resin layer having heat resistance such as a fluorine resin, a polyimide resin, a polyamide resin, a polyamideimide resin, a PEEK resin, a PES resin, or a PPS resin may be used. The use of the resin layer has an effect of making it difficult to break.

If the base material is composed of a resin layer which is a resin member having high heat resistance, the heat resistant belt 150 is used as the heating roller 1.
The heating roller 13 is easily adhered according to the curvature of 30.
The heat of 0 is efficiently transferred to the heat resistant belt 150. However, the heat transfer property itself is higher in the metal layer.

In this case, the thickness of the resin layer is 20 μm.
The thickness is preferably about m to 150 μm, and more preferably about 75 μm. If the thickness of the resin layer is less than 20 μm, mechanical strength against meandering during belt rotation cannot be obtained. Further, when the thickness of the resin layer is larger than 150 μm, the thermal conductivity of the resin is small, so that the heat transfer efficiency from the heating roller 130 to the release layer of the heat resistant belt 150 is lowered, and the fixing performance is lowered. Occur.

Next, the pressure roller 160 comprises a core metal 160a made of a cylindrical member made of metal having high heat conductivity such as copper or aluminum, and heat resistance and toner separation provided on the surface of the core metal 160a. It is composed of an elastic member 160b having high moldability. In addition to the above metals, SUS may be used for the core 160a.

The pressure roller 160 presses the fixing roller 140 via the heat resistant belt 150 to form the fixing nip portion N. In the present embodiment, the hardness of the pressure roller 160 is the same as that of the fixing roller 140. When the pressure roller 160 is made harder than the pressure roller 160, the pressure roller 160 bites into the fixing roller 140 (and the heat resistant belt 150). By this biting, the recording material 90 follows the circumferential shape of the surface of the pressure roller 160. 90 has the effect of making it easy to separate from the surface of the heat resistant belt 150.

The outer diameter of the pressure roller 160 is about 30 mm, which is the same as the fixing roller 140, but the wall pressure is, for example, 2 mm.
It is about 5 mm thinner than the fixing roller 140, and has a hardness of, for example, 20 to 60 ° (Asker hardness: JIS A).
The hardness is about 6 to 25 °), which is harder than the fixing roller 140 as described above.

Next, the structure of the induction heating means 180 will be described in detail.

As shown in FIG. 2, the induction heating means 180 for generating a magnetic flux is arranged opposite to the outer peripheral surface of the heating roller 130. The induction heating means 180 includes a heating roller 13
A support frame (coil guide member) 190 having a storage chamber 200 for storing the heating roller 130 is provided so as to cover 0. The support frame 190 is preferably made of a flame-retardant member such as resin.

The main component of the induction heating means 180 is the exciting coil 220. The principle of heat generation of the heat resistant belt 150 or the heating roller 130 by the action of the induction heating means 180 is as follows. When the exciting coil 220 is energized, a magnetic flux is generated in the hollow portion of the exciting coil 220, and when the magnetic flux intersects with the heat resistant belt 150 or the heating roller 130 via the support frame 190, the change in the magnetic flux occurs in that portion. Eddy current is generated in a direction that hinders the heat resistance, and the resistance of the heat resistant belt 150 or the heating roller 130 acts on the surface of the heat resistant belt 150 or the heating roller 130.
Generates Joule heat on the surface of.

A thermostat 210 is provided at a position of the support frame 190 opposed to the heating roller 130, and a portion for detecting the temperature of the thermostat 210 extends from the support frame 190 to the heating roller 130 and the heat resistant belt 150.
It is provided to expose partly. As a result, the temperatures of the heating roller 130 and the heat resistant belt 150 are detected, and when an abnormal temperature is detected, the power supply circuit (not shown) is forcibly cut off.

The exciting coil 220 is, for example, a long exciting coil wire wound alternately along the support frame 190 in the axial direction of the heating roller 130. The length around which the exciting coil 220 is wound is the same as the area where the heat resistant belt 150 and the heating roller 130 are in contact with each other.

With this structure, the area of the heating roller 130 that is electromagnetically induction-heated by the induction heating means 180 is maximized, and the time during which the surface of the heating roller 130 that is generating heat is in contact with the heat resistant belt 150 is also maximized. The heat transfer efficiency to the heat resistant belt 150 is increased.

Some conventional IH fixing devices do not use the support frame 190. In this case, if there is variation in the distance between the exciting coil 220 and the heat-resistant belt 150, the magnetic flux density becomes high in the portion where the distance is short, the IH efficiency becomes high, and the belt temperature becomes high. In the portion where the distance is large, the magnetic flux density is low, so that the IH efficiency is low and the belt temperature is low.

If the distance between the thermostat 210 and the heat resistant belt 150 varies, the thermostat 210 shuts off at a portion where the distance is small and the belt temperature is relatively low. Therefore, the thermostat 210 operates in a normal state. It will operate at a time when it does not occur, reliability problems will occur,
It becomes a failure state. On the other hand, in the part where the distance is large, the thermostat 21 must be used unless the belt temperature becomes relatively high.
Since 0 does not work, it does not work even at the temperature at which it originally should work, causing smoke and ignition problems.

Therefore, the IH coil is supported by the support frame 190.
The heating roller 130, the heat resistant belt 150, and the exciting coil 220 are kept at a constant distance.
The support frame 190 may be made of resin, metal, or the like. When resin is used, there is an effect that the exciting coil 220 and the heat resistant belt 150 can be electrically insulated.

The exciting coil 220 has an oscillation circuit connected to a drive power source (not shown) whose frequency is variable, and a high frequency AC current of 10 kHz to 1 MHz, preferably a high frequency AC current of 20 kHz to 800 kHz is supplied from the drive power source (not shown). Are fed to generate an alternating magnetic field. Then, in the contact area between the heating roller 130 and the heat resistant belt 150 and in the vicinity thereof, this alternating magnetic field causes the heating roller 130 to move.
And it acts on the heat generating layer of the heat resistant belt 150, and an eddy current flows in a direction in which the change of the alternating magnetic field is prevented inside these.

This eddy current generates Joule heat corresponding to the resistance of the heating layers of the heating roller 130 and the heat resistant belt 150, and mainly the heating roller 130 and the heat resistant belt 15
In the contact area with 0 and its vicinity, the heating roller 1
30 and the heat resistant belt 150 are heated by electromagnetic induction.

The heat resistant belt 1 thus heated
Reference numeral 50 denotes a belt by a temperature detecting means 240 including a thermosensitive element such as a thermistor arranged in contact with the inner surface side of the heat resistant belt 150 near the entrance side of the fixing nip portion N shown in FIG. Inner surface temperature is detected.

When the thermistor mentioned as an example of the temperature detecting means 240 detects that the temperature of the heat resistant belt 150 has reached a certain value or more, it sends a signal to a control circuit (not shown), and the control circuit turns on the IGBT. Controlled excitation coil 22
Turn off the power supply of 0. Further, when it is detected that the temperature of the heat-resistant belt 150 has become equal to or lower than a certain value, a signal is issued to the control circuit, and the control circuit controls the IGBT to excite the exciting coil 2.
Turn on the energization of 20. In this way, the heat resistant belt 1
The temperature of 50 is controlled within a certain range.

FIG. 7 is an exploded view of the external appearance of the fixing device used in the image forming apparatus according to the embodiment of the present invention.

As shown in FIGS. 2 and 7, a short ring 230 is provided outside the support frame 190 so as to surround the storage chamber 200. In the short ring 230, an eddy current is generated in a direction of canceling out a leakage magnetic flux leaking to the outside of the magnetic flux generated by passing a current through the exciting coil 220. When the eddy current is generated, a magnetic field is generated according to Fleming's law in a direction of canceling the magnetic field of the leakage magnetic flux, and unnecessary radiation due to the leakage magnetic flux can be prevented, so that noise generation of other members or devices can be reduced.

The short ring 230 can be made of, for example, highly conductive copper or aluminum.

FIG. 3 is an explanatory view showing the structure of the fixing device used in the image forming apparatus according to the embodiment of the present invention. The short ring 310 includes at least the exciting coil 220.
It suffices that it be located at a position where a magnetic flux that cancels out the leakage magnetic flux generated outside of is generated, and as shown in FIG. 3, it can be provided on the same side as the exciting coil 220 of the support frame 190. With this configuration as well, it is possible to effectively reduce the unnecessary radiation generated from the exciting coil 220 and reduce the noise generation of other members or devices.

An exciting coil core 250 is provided on the upper surface of the short ring 230 so as to surround the storage chamber 200 of the support frame 190, and above the storage ring 200 of the support frame 190 is provided above the excitation coil core 250. A C-shaped coil core 260 is provided.

By providing the exciting coil core 250 and the C-shaped coil core 260 as shown in FIG. 2 or 3, the inductance of the exciting coil 220 increases,
The electromagnetic coupling between the exciting coil 220 and the heating roller 130 is improved. Therefore, a large amount of electric power can be applied to the heating roller 130 even with the same coil current, and a fixing device with a short warm-up time can be realized.

The C-shaped coil core 260 has, for example, a width of 1
0 mm and 25 m in the rotation axis direction of the heating roller 130
Six of them are arranged at intervals of m. Thereby, the magnetic flux leaking to the outside can be captured.

When the C-shaped coil core 260 is used, the magnetic flux on the back side of the exciting coil 220 is entirely C-shaped.
Since it passes through the inside of 0, it is possible to prevent the magnetic flux from leaking backward. As a result, it is possible to prevent the peripheral conductive member from generating heat due to electromagnetic induction, and also to prevent unnecessary electromagnetic waves from being emitted, thereby reducing noise generation in other members or devices.

Reference numeral 270 denotes a housing, which is mounted on the support frame 190 in a roof shape so as to cover the C-shaped coil core 260 and the thermostat 210. Resin is suitable for the material of the housing 270, but it may be other than resin.

Further, a plurality of holes 280 are provided in the upper part of the housing 270, and the inner supporting frame 190,
The heat radiated by the exciting coil 220, the C-shaped coil core 260 and the like can be released to the outside.

A short ring 290 is attached to the support frame 190 so as to cover the housing 270. Further, the upper portion facing the hole portion 280 is opened so as not to close the hole portion 280 provided on the upper portion of the housing 270.

The short ring 290 is similar to the above-mentioned short ring 230, and has a C-shaped coil core 2
It is located on the back of 60. In the short ring 290, an eddy current is generated in a direction of canceling a slight leakage magnetic flux leaking to the outside from the back surface of the C-shaped coil core 260 or the like, so that a magnetic field is generated in a direction of canceling the magnetic field of the leakage magnetic flux, which is unnecessary due to the leakage magnetic flux. It is possible to prevent radiation and reduce the noise generation of other members or devices.

When the exciting coil 220 has a high temperature, a warp occurs in the portion of the support frame 190 facing the exciting coil 220. Further, warpage occurs not only in the heating stage but also in the forming stage of the support frame 190. The short ring 290 has an effect of preventing the warp of the support frame 190 or casting it off, and is made of, for example, a material having a high hardness such as aluminum.

The heating roller 13 with the exciting coil 220 interposed therebetween.
A shield plate 300 is attached to the opposite side of 0.

The shield plate 300 is made of, for example, a ferromagnetic metal such as iron, and shields the leakage magnetic flux leaking to the outside from the back surface of the C-shaped coil core 260 or the like to prevent unnecessary radiation and to prevent other radiation. It is possible to reduce the generation of noise in members or devices.

FIG. 5 is an exploded perspective view of the fixing device used in the image forming apparatus according to the embodiment of the present invention. In FIG. 5, the short ring 290 is attached to the support frame 190 so as to cover the housing 270 as described above. Further, the short ring 290 has an open upper portion facing the hole portion 280 so as not to close the hole portion 280 provided in the upper portion of the housing 270.

The exciting coil 220 is a storage chamber 200 (FIG. 3) in which the exciting coil wire is provided in the center of the support frame 190.
It is formed by winding it a plurality of times on the outer surface of the above, and a C-shaped coil core 260 is provided on the outer side thereof. C type coil core 2
60 has a width of, for example, several mm to 10 mm, and is attached so as to cover the exciting coil 220 by forming a C shape. As shown in FIG. 2, by providing a plurality of C-shaped coil cores 260 in the longitudinal direction of the exciting coil 220, the weight can be reduced as compared with the case of the plate-shaped core, and the C-shaped coil core 260 is generated by energizing the exciting coil 220. It is possible to suppress the divergence of the generated magnetic flux, reduce the leakage magnetic flux, and further reduce the generation of noise of other members or devices.

FIG. 6 is an external configuration diagram of the fixing device used in the image forming apparatus according to the embodiment of the present invention. The external appearance of the state in which the short ring 290 and the housing 270 described in FIG. Is shown.

As described above, the housing 270 is of a roof type and is attached so as to cover the support frame 190. A plurality of holes 280 are provided in the upper portion of the housing 270 to allow heat inside to escape to the outside.

The short ring 290 generates an eddy current in the direction of canceling the leakage magnetic flux, thereby generating a magnetic field in the direction of canceling the magnetic field of the leakage magnetic flux, preventing unnecessary radiation due to the leakage magnetic flux, and preventing the unnecessary radiation of other members or devices. Generation of noise can be reduced. Further, the upper portion facing the hole portion 280 is opened so as not to prevent the hole portion 280 provided in the upper portion of the housing 270.

Next, the short rings 230 and 290
However, the situation in which the leakage magnetic flux is canceled and the situation in which the shielding plate 300 shields the magnetic flux will be described with reference to FIGS. 8 to 12.

FIG. 8 is an explanatory view showing the state of the magnetic flux of the induction heating means according to the embodiment of the present invention, and FIG. 9 cancels the magnetic flux in the short ring of the induction heating means according to the embodiment of the present invention. FIG. 10 is an explanatory view showing a state, FIG. 10 is an explanatory view showing how the magnetic flux in the short ring of the induction heating means according to the embodiment of the present invention is canceled, and FIG. 11 is an induction heating means according to the embodiment of the present invention. FIG. 6 is an explanatory diagram showing a change in magnetic flux on the shielding plate of FIG. Of the constituent elements in each figure, the same constituent elements as those already described in FIG.

As indicated by arrow C in FIG. 8, the magnetic flux generated by the exciting coil 220 by applying an alternating current from an exciting circuit (not shown) to the exciting coil 220 is because the heating roller 130 has magnetism. It penetrates through the heating roller 130 in the circumferential direction and repeats the generation and disappearance. The induced current generated in the heating roller 130 due to the change of the magnetic flux almost flows only on the surface of the heating roller 130 due to the skin effect, and Joule heat is generated by the action of the resistance of the heating roller 130.

The magnetic flux penetrating the heating roller 130 in the circumferential direction passes through the inside of the cylinder and penetrates the heating roller 130 again,
The magnetic path formed by the exciting coil core 250 and the C-shaped coil core 250 is electrically connected.

However, even with such a structure, not all the magnetic flux is added to the heating roller to heat it, and some magnetic flux leaks.

Therefore, as shown in FIG. 9, the exciting coil 2
A short ring 230 is provided in the vicinity of a leakage magnetic flux (indicated by a solid line D) that passes through the hollow portion of the heating roller 130 and penetrates the heating roller 130 to leak to the outside. Since the short ring 230 is made of highly conductive copper, aluminum, or the like, a magnetic flux (indicated by a dotted line E) in a direction for canceling the change of the leakage magnetic flux is generated, and unnecessary radiation due to the leakage magnetic flux is prevented to prevent other members. Alternatively, it is possible to reduce the generation of device noise.

Further, as shown in FIG. 10, the exciting coil 2
A leakage magnetic flux (indicated by a solid line F) is generated from 20 to the back side of the C-shaped coil core 260, and the short ring 29
By generating a magnetic flux (indicated by a dotted line G) in the direction of canceling the leakage magnetic flux, it is possible to prevent unnecessary radiation due to the leakage magnetic flux and reduce noise of other members or devices.

Further, as shown in FIG. 11, the shielding plate 300
Forms a closed magnetic path so that the magnetic flux does not leak to the outside with respect to the magnetic flux (indicated by the solid line H) leaking from the exciting coil 220 to the back side of the C-shaped coil core 260 or the like, and unnecessary radiation due to the leak magnetic flux is prevented. As a result, it is possible to reduce noise generation of other members or devices.

Short rings 230, 290, shield plate 3
00 exhibits the effect even in each case, but by combining them, it is possible to suppress unnecessary radiation due to a larger amount of leakage magnetic flux, and it is possible to reduce the generation of noise in other members or devices.

FIG. 12 is an explanatory diagram showing the structure of a fixing device according to another embodiment of the present invention.

In the fixing device described with reference to FIG. 2, the induction heating means of the present invention is used as the fixing device configured to perform fixing through the heat resistant belt 150. As shown in FIG. It is easy to use the induction heating means including countermeasures against unnecessary radiation in the fixing device having no belt.

Reference numeral 130 is a heating roller as a heat generating member, and the heating roller 130 is rotationally driven by a driving means (not shown) of the apparatus main body. The heating roller 130 is made of iron
It is made of a magnetic material that is an alloy of nickel and chromium, and is adjusted to have a Curie point of 300 ° C. or higher, and is formed into a pipe shape having a thickness of 0.3 mm.

The surface of the heating roller 130 is coated with a release layer (not shown) made of fluororesin having a thickness of 20 μm in order to impart releasability. As the release layer, resins and rubbers having good release properties such as PTFE, PFA, FEP, silicone rubber, and fluororubber may be used alone or in combination. When the heating roller 130 is used for fixing a monochrome image, only releasability needs to be secured, but when the heating roller 130 is used for fixing a color image, it is desirable to impart elasticity. In that case, Needs to form a thicker rubber layer.

Reference numeral 160 is a pressure roller as a pressure means. The pressure roller 160 is made of silicone rubber having a hardness of JIS A65 degrees, and is pressed against the heating roller 130 with a pressing force of 20 kgf to form a nip portion. Then, in this state, the pressure roller 160 rotates as the heating roller 130 rotates.

As the material of the pressure roller 160, other heat resistant resin such as fluororubber or fluororesin or rubber may be used. Further, in order to improve wear resistance and releasability, the surface of the pressure roller 160 may be PFA, PTFE, FEP.
It is desirable to coat resin or rubber such as singly or in a mixture. Further, in order to prevent heat dissipation, the pressure roller 160 is preferably made of a material having low heat conductivity.

As described above, according to this embodiment, I
By covering the heat generating portion of the H fixing device with the support frame made of resin or the like and providing the sheet metal so as to cover the support frame, it is possible to prevent the warp of the support frame, which is likely to become hot. Further, by providing the short ring, it is possible to prevent unnecessary radiation due to a slight leakage magnetic flux leaking to the outside from the back surface of the core or the like to reduce the noise generation of other members or devices, and There is an effect that the warpage can be prevented or the warpage prevention effect of the support frame by the sheet metal can be supplemented.

[0092]

As described above, according to the present invention, the short ring / shielding plate is provided in the vicinity of the exciting coil of the heat generating device or the fixing device by electromagnetic induction heating, so that a slight leakage magnetic flux leaking from the exciting coil to the outside is caused. The effect of preventing unnecessary radiation and reducing the noise generation of other members or devices can be achieved.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a configuration of a fixing device used in the image forming apparatus according to the embodiment of the invention.

FIG. 3 is an explanatory diagram showing a configuration of a fixing device used in the image forming apparatus according to the embodiment of the invention.

FIG. 4 is an explanatory view showing the structure of a heating roller constituting the fixing device of FIG. 2 in a broken manner.

FIG. 5 is an exploded perspective view of a fixing device used in the image forming apparatus according to the embodiment of the invention.

FIG. 6 is an external configuration diagram of a fixing device used in the image forming apparatus according to the embodiment of the invention.

FIG. 7 is an external exploded view of a fixing device used in the image forming apparatus according to the embodiment of the invention.

FIG. 8 is an explanatory view showing a state of magnetic flux of the induction heating means which is an embodiment of the present invention.

FIG. 9 is an explanatory view showing how to cancel the magnetic flux in the short ring of the induction heating means which is an embodiment of the present invention.

FIG. 10 is an explanatory view showing how to cancel the magnetic flux in the short ring of the induction heating means which is an embodiment of the present invention.

FIG. 11 is an explanatory view showing a change in magnetic flux on the shield plate of the induction heating means according to the embodiment of the present invention.

FIG. 12 is an explanatory diagram showing a configuration of a fixing device according to another embodiment of the present invention.

[Explanation of symbols]

130 heating roller (131 support side plate) (132 bearings) 140 fixing roller (140a core metal) (140b elastic member) 150 heat resistant belt 160 pressure roller 160a core metal 160b elastic member 180 Induction heating means 190 support frame 200 storage room 210 thermostat 220 excitation coil 230 short ring 240 Temperature detection means 250 excitation coil core 260 C type coil core 270 housing 280 hole 290 short ring 300 shield 310 short ring

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Eiji Torikai             Pana, 4-62, Minoshima, Hakata-ku, Fukuoka             Sonic Communications Inc.             Within (72) Inventor Kazuhiko Soeda             Pana, 4-62, Minoshima, Hakata-ku, Fukuoka             Sonic Communications Inc.             Within (72) Inventor Tadayuki Kajiwara             Pana, 4-62, Minoshima, Hakata-ku, Fukuoka             Sonic Communications Inc.             Within (72) Inventor Tadafumi Shimizu             Pana, 4-62, Minoshima, Hakata-ku, Fukuoka             Sonic Communications Inc.             Within (72) Inventor Ikuichi Kitagawa             Pana, 4-62, Minoshima, Hakata-ku, Fukuoka             Sonic Communications Inc.             Within (72) Inventor Masahiro Sakai             Pana, 4-62, Minoshima, Hakata-ku, Fukuoka             Sonic Communications Inc.             Within (72) Inventor Kazunori Matsuo             Pana, 4-62, Minoshima, Hakata-ku, Fukuoka             Sonic Communications Inc.             Within (72) Inventor Keiichi Matsuzaki             Pana, 4-62, Minoshima, Hakata-ku, Fukuoka             Sonic Communications Inc.             Within (72) Inventor Kenji Asakura             Pana, 4-62, Minoshima, Hakata-ku, Fukuoka             Sonic Communications Inc.             Within (72) Inventor Hideki Tatematsu             Pana, 4-62, Minoshima, Hakata-ku, Fukuoka             Sonic Communications Inc.             Within F-term (reference) 2H033 AA23 AA41 BA04 BA11 BA25                       BA26 BA29 BA32 BB03 BB05                       BB06 BB23 BB33 BE06                 3K059 AB20 AB26 AB28 AD23 AD34

Claims (17)

[Claims] 1. An electromagnetic induction comprising: a heat-generating member; an exciting coil arranged to face the heat-generating member to heat the heat-generating member by electromagnetic induction; and an annular short ring made of a metal member. Had a heating device. 2. A heat generating device using electromagnetic induction, wherein the short ring is arranged on the opposite side of the heat generating member with the exciting coil interposed therebetween and along the peripheral surface of the exciting coil. 3. A heat generating device using electromagnetic induction, wherein the short ring is arranged between the exciting coil and the heat generating member along a peripheral surface of the exciting coil. 4. The shorting ring is arranged along the peripheral surface of the exciting coil on the opposite side of the heat generating member with the exciting coil sandwiched between the exciting coil and the peripheral surface of the exciting coil between the exciting coil and the heat generating member. A heating device using electromagnetic induction, comprising at least two short rings arranged along a surface. 5. The heat generating device using electromagnetic induction according to claim 1, wherein the short ring is made of diamagnetic material such as aluminum or copper having a low resistance value. 6. The heat generating device using electromagnetic induction according to claim 1, further comprising a metal shielding material arranged on the opposite side of the heat generating member with the exciting coil interposed therebetween. 7. The heat generating device using electromagnetic induction according to claim 6, wherein the metal shielding member is made of magnetic iron or silicon steel plate. 8. The exciting coil is formed so as to be curved so as to cover the heat-generating member, and has a storage chamber for storing the heat-generating member, and an opening. A heat generating device using the electromagnetic induction according to 7. 9. A fixing device for nipping and conveying a recording material at a fixing nip portion, fusing and pressurizing an unfixed toner image on the recording material to fix it on the recording medium, which is a cylindrical shape of a magnetic metal member. Of the heat generating member, an induction heating means provided with an exciting coil arranged to face the outer peripheral surface of the heat generating member and heating the heat generating member by electromagnetic induction, and pressure contact with the heat generating member or a belt member heated by the heat generating member. And a pressing member that rotates in the forward direction to form a fixing nip portion, and is provided with an annular short ring made of a metal member. 10. The fixing device using electromagnetic induction, wherein the short ring is arranged on the opposite side of the heat generating member with the exciting coil interposed therebetween and along the peripheral surface of the exciting coil. 11. A fixing device using electromagnetic induction, wherein the short ring is arranged between the exciting coil and the heat generating member along a peripheral surface of the exciting coil. 12. The short ring is arranged along the peripheral surface of the exciting coil on the opposite side of the heat generating member with the exciting coil sandwiched between the shorting ring and the peripheral portion of the exciting coil between the exciting coil and the heat generating member. At least 2 arranged along the plane
A fixing device using electromagnetic induction, comprising one or more short rings. 13. The fixing device using electromagnetic induction according to claim 9, wherein the short ring is made of diamagnetic material such as aluminum or copper having a low resistance value. 14. The fixing device using electromagnetic induction according to claim 7, further comprising a metal shielding material arranged on the opposite side of the heat generating member with the exciting coil interposed therebetween. 15. The fixing device using electromagnetic induction according to claim 14, wherein the metal shielding member is made of magnetic iron or silicon steel plate. 16. The exciting coil is formed so as to be curved so as to cover the heat-generating member and has a storage chamber for storing the heat-generating member, and an opening portion. 15. A fixing device using electromagnetic induction according to item 15. 17. A heating section for heating a print medium, a support frame having a storage section for storing the heating section, and a reinforcement for reinforcing a portion of the storage section of the support frame that is warped by heating of the heating section. And a fixing device.