JP2000056604A - Fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain the temperature rise of a magnetic substance core and an exciting coil by oppositely arranging the magnetic substance core in the axial direction of the fixing roller, winding the exciting coil round the magnetic substance core in the axial direction and providing a means for cooling the magnetic substance core and the exciting coil. SOLUTION: The fixing roller 1 and a pressure roller 2 are rotatably supported, and only the roller 1 is driven. The roller 2 press-contacts with the surface of the roller 1 and is submissively rotated by frictional force at a press-contact part (nip part). Then, the magnetic substance core 9 is oppositely arranged in the axial direction of the roller 1 and the exciting coil 8 is wound round the core 9 in the axial direction. In such a case, the means for cooling the core 9 and the coil 8 is a heat sink 10 equipped with a heat radiation part 10a using an aluminum plate and a connection part 10b connected with the core 9, and comes in contact with the core 9 over the axial direction of the roller 1. Therefore, heat storage is avoided by the heat sink 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fixing device for fusing and fixing a toner image on a transfer material in an image forming apparatus.

[0002]

2. Description of the Related Art An image forming apparatus using an electrophotographic method is:
Normally, a transfer material and a toner made of a resin, a magnetic material, a colorant, and the like, which are electrostatically carried on the transfer material, are pressed and rotated at a pressure contact portion (nip portion) of a fixing roller and a pressure roller which are pressed and rotated with each other. It has a fixing device that fuses and fixes by applying heat and pressure while nipping and conveying.

In such a fixing device, as a means for heating, an electromagnetic induction heating system is used in which an eddy current is generated in a conductive layer (heat generating source) provided on the inner surface of the fixing roller by magnetic flux from an exciting coil and heat is generated by Joule heat. Things have been suggested.

In this method, since the heat generating source can be arranged very close to the toner carried on the transfer material, the surface of the fixing roller is activated when the fixing device is started, as compared with the conventional heat roller method using a halogen lamp. This is characterized in that the time required for the temperature to reach an appropriate temperature for fixing can be shortened.

Another feature is that the heat transfer path from the heat source to the toner is short and simple, so that the heat efficiency is high.

[0006]

However, when a large number of small-sized transfer materials are continuously fixed, the excitation coil itself at the end may generate heat due to a skin effect due to the passage of a high-frequency current or the like. Heat is stored due to self-heating due to hysteresis loss of the core of the part, expensive heat-resistant resin is required for coating the coil, or the core exceeds the unique Curie point,
Problems such as loss of magnetism occur.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to suppress the temperature rise of a magnetic core and an exciting coil of a fixing device in an electromagnetic induction heating system. is there.

[0008]

According to the present invention, an eddy current is generated in a conductive layer provided on a fixing roller by an induction heating means having a magnetic core and an exciting coil. In a fixing device of an electromagnetic induction heating system for generating heat, the magnetic core is disposed to face along the axial direction of the fixing roller, and the exciting coil is wound around the magnetic core in the axial direction. It is characterized by comprising means for cooling the core and the exciting coil.

Preferably, the cooling means is made of a material which is in contact with the magnetic core and the exciting coil but is not magnetically coupled, and is arranged along the axial direction of the fixing roller.

[0010] Preferably, the cooling means is a heat sink.

It is preferable that the induction heating means is disposed inside a fixing roller.

It is preferable that the induction heating means is provided outside the fixing roller. With the above configuration,
For example, when a large amount of small-size transfer material is continuously fixed,
Due to the skin effect and the like caused by the passage of the high-frequency current, the heat generated by the exciting coil itself and the heat storage of the magnetic core by self-heating due to the hysteresis loss are avoided by the cooling means, and the temperature rise of the magnetic core and the exciting coil is suppressed.

The image forming apparatus includes the above-described fixing device through which the transfer material on which the toner image is formed by the image forming means is passed.

[0014]

(Embodiment 1) FIG. 1 is a drawing showing the features of the present invention best, and is a schematic view of a cross section of a fixing device TS according to a first embodiment of the present invention.

The fixing roller 1 is provided with an iron core metal cylinder having an outer diameter of 40 (mm) and a thickness of 0.7 (mm), for example, PTFE of 10 to 50 (μm) in order to enhance the surface releasability.
Alternatively, a layer of PFA 10 to 50 (μm) may be provided.

As another material of the fixing roller 1, 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, among the non-magnetic materials, a conductive material such as a metal can be used by forming the material into a thin film.

The pressure roller 2 has a rubber strength having a thickness of 5 (mm) according to JIS A on the outer circumference of an iron core having an outer diameter of 20 (mm).
In order to enhance the releasability of the surface as in the case of the fixing roller 1, for example, PTFE 10 to 50 (μ
m) and a layer of PFA 10 to 50 (μm), and the outer diameter is 30 (mm).

The fixing roller 1 and the pressure roller 2 are rotatably supported, so that only the fixing roller 1 is driven. The pressure roller 2 is in pressure contact with the surface of the fixing roller 1 and is arranged so as to be driven to rotate by frictional force at a pressure contact portion (nip portion).

The pressure roller 2 is pressed in the direction of the rotation axis of the fixing roller 1 by a mechanism (not shown) using a spring or the like.

The pressure roller 2 is loaded with a weight of about 30 (kg weight). In this case, the width (nip width) of the pressure contact portion is about 6 (m).
m). However, depending on circumstances, the nip width may be changed by changing the load.

The temperature sensor 3 is disposed so as to be in contact with the surface of the fixing roller 1. The power supply to the exciting coil 8 is increased or decreased based on the detection signal of the temperature sensor 3 so that the surface temperature of the fixing roller 1 is reduced. It is automatically controlled so as to reach a predetermined constant temperature.

The transport guide 4 is arranged at a position for guiding the transfer material 6 transported while carrying the unfixed toner image 5 to a nip portion between the fixing roller 1 and the pressure roller 2.

The separation claw 7 is disposed in contact with the surface of the fixing roller 1, and is provided after the transfer material 6 has passed through the nip.
If it sticks to the, it is forcibly separated to prevent jam.

Since high-frequency power of 100 to 2,000 (kW) connected to a high-frequency converter (not shown) is supplied to the exciting coil 8, a thin wire having several litres is used, and the winding is transmitted to the winding. Considering the case of heating, a heat-resistant material was used for coating.

The magnetic core 9 has a high magnetic permeability and a low loss. In the case of an alloy such as permalloy, an eddy current loss in the core increases at high frequencies, so that a laminated structure may be used. The core is used to increase the efficiency of the magnetic circuit and for magnetic shielding. The magnetic circuit portion of the coil and the core may be air-core if there is a means capable of sufficiently shielding the magnetic field. In the embodiment, 2500B manufactured by Tokin Corporation is used.

An alternating current of 10 to 100 (kHz) is applied to the exciting coil 8 by a high frequency converter. The magnetic flux induced by the alternating current passes through the combination of three magnetic cores 9 so as to have a substantially T-shaped cross section without leaking to the outside, and between the protrusions (ends of the magnetic core 9) for the first time. The eddy current leaks out of the magnetic core 9 and penetrates the conductive layer of the fixing roller 1, causing the conductive layer itself to generate Joule heat.

The cooling means according to the present embodiment comprises a connecting portion 10 for connecting a heat radiating portion 10a and a magnetic core 9 using an aluminum plate.
b, and is in contact with the magnetic core 9 in the axial direction of the fixing roller 1. If there is a margin in the axial direction and the end of the fixing roller 1 is open, the fixing roller 1 may be provided so as to protrude from the end of the fixing roller 1.

The cross-sectional areas of the magnetic core 9, the exciting coil 8, and the heat sink 10 are 67.39 mm ² and 120, respectively.
It is set as mm ^2, 182mm ^2.

In order to verify the effect of reducing the temperature rise, the above fixing device was incorporated into a GP55 (image forming apparatus) manufactured by Canon Inc., and A4 size paper was passed vertically at a speed of 30 sheets per minute. Was performed.

The temperature was measured by attaching a thermocouple to the magnetic core 9 and the exciting coil 8 at the center in the axial direction.

The temperature control of the fixing roller 1 was performed at 190 ° C.

The highest point of the temperature is saturated and reached in about 40 to 50 minutes in elapsed time when a total of 1000 sheets are passed, and the temperature was compared at this temperature.

Without heat sink 10 Exciting coil 8 232 ° C. Magnetic core 9 228 ° C. With heat sink 10 Exciting coil 8 209 ° C. Magnetic core 9 199 ° C. Effect Exciting coil 8 Δ23 ° C. Magnetic core 9 Δ29 ° C. Skin effect due to passage of high-frequency current Thus, the heat generated by the excitation coil 8 itself and the heat storage of the magnetic core 9 due to self-heating due to the hysteresis loss are avoided by the heat sink 10, and the temperature rise of the magnetic core 9 and the excitation coil 8 is suppressed.

Accordingly, there is no need to use an expensive heat-resistant resin for covering the exciting coil 8 or to prevent the magnetic core 9 from exceeding its inherent Curie point and losing magnetism. Since the temperature exceeded 230 ° C. without the heat sink 10, an expensive heat-resistant coating was required.

(Embodiment 2) In this embodiment, FIG.
The cooling means uses a copper plate 10B as shown in
The exciting coil 8, the magnetic core 9, the cross-sectional area of the aluminum plate, ^{respectively, 67.39mm 2, 120mm 2, 182mm} 2
And

An experiment was conducted with the above configuration in the same manner as in the first embodiment.

The temperature control of the fixing roller was performed at 190 ° C.

The highest point of the temperature is saturated and reaches from about 40 minutes to about 50 minutes in elapsed time when a total of 1000 sheets are passed.

Excitation coil 8 232 ° C. Magnetic core 9 228 ° C. With copper plate 10B Excitation coil 8 205 ° C. Magnetic core 9 195 ° C. Effect Exciting coil 8 Δ27 ° C. Magnetic core 9 Δ33 ° C. Due to the skin effect and the like caused by the passage, heat generation of the excitation coil 8 itself and heat storage of the magnetic core 9 by self-heating due to hysteresis loss are avoided by the copper plate 10B, and the temperature rise of the magnetic core 9 and the excitation coil 8 is suppressed. Was.

Accordingly, there is no need to use an expensive heat-resistant resin for covering the exciting coil 8, or to prevent the magnetic core 9 from exceeding its inherent Curie point and losing magnetism. Copper plate 10
Without B, the temperature exceeded 230 ° C., requiring an expensive heat-resistant coating.

(Embodiment 3) In this embodiment, a magnetic core 9B is disposed outside the fixing roller 1 as shown in FIG. The magnetic core 9B has a substantially E-shaped cross section,
As a cooling means, a heat sink 10C similar to that of the first embodiment is provided on two side surfaces.

The cross-sectional areas of the exciting coil 8, the magnetic core 9, and the heat sink 10C were 67.39 mm ² and 24, respectively.
0 mm ² and 182 mm ² . The magnetic core 9 uses an E-shaped magnetic core 9 connected thereto.
Part.

An experiment was conducted with the above configuration in the same manner as in the first embodiment.

The temperature control of the fixing roller was performed at 190 ° C.

The highest point of the temperature is saturated from 40 minutes to about 50 minutes in elapsed time when a total of 1000 sheets are passed,
As it reached, comparison was made at this temperature.

Without heat sink 10C Exciting coil 8 220 ° C. Magnetic core 9 231 ° C. With heat sink 10C Exciting coil 8 206 ° C. Magnetic core 9 195 ° C. Effect Exciting coil 8 Δ14 ° C. Magnetic core 9 Δ36 ° C. Skin effect due to passage of high-frequency current By the heat sink 10C, heat generation of the excitation coil 8 itself and self-heating of the magnetic core 9 due to hysteresis loss are avoided by the heat sink 10C.
The temperature rise of the magnetic core 9 and the exciting coil 8 was suppressed.

Accordingly, there is no need to use expensive heat-resistant resin for covering the exciting coil 8 or to prevent the magnetic core 9 from exceeding its inherent Curie point and losing magnetism. Since the temperature exceeded 230 ° C. without the heat sink 10C, an expensive heat-resistant coating was required.

[0049]

As described above, when a large amount of small-sized transfer material is continuously fixed, for example, due to the skin effect caused by the passage of a high-frequency current, the heat generated by the exciting coil itself and the hysteresis of the magnetic core are reduced. The heat storage of the self-heating due to the loss is avoided by the cooling means, and the temperature rise of the magnetic core and the exciting coil is suppressed.

When an expensive heat-resistant resin is required for covering the exciting coil, or when the magnetic core exceeds the inherent Curie point,
The problem of losing magnetism can be avoided. As a result, an increase in power consumption can be avoided.

[Brief description of the drawings]

FIG. 1 is a view showing a first embodiment of a fixing device according to the present invention.

FIG. 2 is a diagram showing a fixing device according to a second embodiment of the present invention.

FIG. 3 is a diagram showing a fixing device according to a third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixing roller 2 Pressure roller 3 Temperature sensor 4 Transport guide 5 Toner image 6 Transfer material 7 Separation claw 8 Excitation excitation coil 8 9 Magnetic material magnetic core 9 10 Heat sink (cooling means)

Continued on the front page (72) Inventor Yasuhiro Hayashi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Tomoichiro Ota 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. F term (reference) 2H033 AA31 BA29 BB18 BE06 3K059 AA10 AB00 AB04 AB27 AB28 AC33 AC34 AC73 AD03 AD07 AD26 AD34 AD35 CD44 CD48 CD52 CD64 CD66 CD73 CD75 CD77

Claims (6)

[Claims] 1. An electromagnetic induction heating type fixing device in which an induction heating means having a magnetic core and an exciting coil generates an eddy current in a conductive layer provided on a fixing roller to generate heat, wherein the magnetic core is the fixing member. A fixing device that is disposed to face the roller along the axial direction, the excitation coil is wound around the magnetic core in the axial direction, and a unit that cools the magnetic core and the excitation coil is provided. . 2. The cooling means is made of a material that is in contact with the magnetic core and the excitation coil but is not magnetically coupled,
The fixing device according to claim 1, wherein the fixing device is disposed along an axial direction of the fixing roller. 3. The fixing device according to claim 2, wherein the cooling unit is a heat sink. 4. The fixing device according to claim 1, wherein the induction heating unit is disposed inside a fixing roller. 5. The fixing device according to claim 1, wherein the induction heating unit is disposed outside a fixing roller. 6. An image forming apparatus comprising the fixing device according to claim 1, wherein a transfer material on which a toner image is formed by the image forming means is passed.