JPH1195584A - Fixing device with induction heating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain high reliability and safety by disposing an induction coil part having a core for generating an induced magnet flux and an induction coil, outside a fixing roller. SOLUTION: The induction coil part 3 is arranged in the side surface (outside) of the fixing roller 1, with a gap. The gap between the induction coil part, 3 and the fixing roller 1 is provided to make both ends of the gap uniform. The induction coil part 3 consists of the core 31 of a ferromagnetic body such as ferrite, a bobbin 32 made of resin excellent in heat resistance and insulation and the induction coil 33 having a magnet wire wound on the bobbin 32. Since the induction coil part 3 is disposed outside the fixing roller 1 by this method, only a part of the induction coil part 3 is directly affected by the heat generation of the roller 1, regardless of the fact that the coil part 3 is affected by the heat generation of the roller 1. Moreover, the coil part 3 is not a hermetically sealed part in the fixing roller 1, not to be so greatly affected (rise in the ambient temp.).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device in an image forming apparatus such as a copying machine, a printer, and a facsimile, and more particularly, to an induction heating type fixing device.

[0002]

2. Description of the Related Art As a fixing device in an image forming apparatus such as a copying machine, a printer, and a facsimile, there is known an induction heating type in which a peripheral wall of a fixing roller generates Joule heat by an induced current. In a conventional induction heating type fixing device, an electromagnetic induction heating means having an induction coil is arranged inside a rotating hollow roller (fixing roller), and a high-frequency current is applied to this means to generate an induction magnetic flux. An induced current is generated in the conductive layer on the outer periphery of the roller, and the surface of the roller is heated and controlled to a predetermined temperature (generally about 180 ° C.) by Joule heat accompanying the induced current.

[0003]

In the conventional apparatus having such a configuration, the induction coil portion is disposed inside the fixing roller, and is almost in a state of being almost sealed. Therefore, when the surface temperature of the fixing roller is set to a predetermined temperature (control temperature), the temperature of the induction coil approaches the predetermined surface temperature of the fixing roller over time because the atmosphere of the induction coil faces the inner wall of the fixing roller. Furthermore, the ambient temperature of the induction coil is raised by heat generated by the copper loss (ohm loss) of the induction coil itself. As a result, the induction coil is exposed to an atmosphere higher than the surface temperature of the fixing roller.

For this reason, the temperature of the induction coil becomes high, such as 200 ° C. to 250 ° C., and there is a problem that safety, durability and reliability are uneasy. In addition, since a special material having high heat resistance must be used as the wire material of the induction coil, the cost of the induction coil and the entire device is inevitably increased, which hinders the spread of the induction heating type fixing device. .

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems in the prior art and to provide an induction heating type fixing device having high reliability and safety at a low cost.

[0006]

According to the present invention, there is provided an induction heating type fixing apparatus comprising a fixing roller and a pressure roller, wherein the fixing roller is an induction heating type heating roller. This problem is solved by disposing an induction coil unit having a core for generating a magnetic flux and an induction coil outside the fixing roller.

Further, the present invention proposes to dispose the induction coil portion inside the pressure roller in order to solve the above-mentioned problem. Further, the present invention proposes that the core member of the pressure roller is made of a non-magnetic metal in order to solve the above problem.

Further, in order to solve the above-mentioned problems, the present invention proposes that the induction coil is wound around the fixing roller in the axial direction of the fixing roller. Further, the present invention proposes, in order to solve the above-mentioned problem, that the core around which the induction coil is wound has a fixing roller proximity part larger than the induction coil winding part.

Further, in order to solve the above-mentioned problems, the present invention proposes that the induction coil section has a heat insulating / insulating member. Further, according to the present invention, in order to solve the above-mentioned problems, a core metal member of the fixing roller is disposed on a first core metal member made of a good magnetic metal and on an inner peripheral side of the first metal core member. It is proposed that the composite material is composed of a non-magnetic material and a second metal core member made of a good heat conductive metal.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIGS. 1A and 1B show a main part of a fixing device according to an embodiment of the present invention. FIG. 1A is a sectional view, and FIG. 1B is a side view. The fixing device shown in FIG. 1 includes a fixing roller (heating roller) 1, a pressure roller 2, and an induction coil unit 3.

The core portion of the fixing roller 1 is made of a first core member 11 made of a good magnetic metal such as iron or magnetic stainless steel, and a second core member 11 made of a nonmagnetic good heat conductive metal such as aluminum or copper. It is composed of a composite material with the second core member 12.
A release layer 13 having a thickness of about several tens of microns to about 1 mm is formed on the outer periphery of the first metal core member 11 with fluororesin or silicon rubber having excellent heat resistance.

1 to 5 on the side surface (external) of the fixing roller 1.
The induction coil section 3 is arranged with a gap of about mm. The gap between the induction coil unit 3 and the fixing roller 1 is
Both ends are provided so as to be uniform. The induction coil unit 3 includes a core 31 made of a ferromagnetic material such as ferrite and a laminated silicon steel sheet, a bobbin 32 generally formed of a resin having excellent heat-resistant insulation, and an induction coil generally wound on the bobbin 32 with a magnet wire. And a coil 33.

The pressure roller 2 is made of a core metal member 21 made of a non-magnetic metal such as aluminum, copper, non-magnetic stainless steel or the like, and a silicone rubber provided on the outer periphery thereof having a surface releasability and heat resistance of about 1 to 5 mm. And a release layer 22 having a thickness of

The fixing roller 1 is driven to rotate clockwise as shown by the arrow in the figure, and the pressure roller 2 is driven to rotate by the fixing roller 1. The transfer paper (not shown) is introduced between the two rollers from the right side of the figure, is conveyed by being sandwiched between the pressure nips of the fixing roller 1 and the pressure roller 2, and the unfixed toner on the transfer paper is fixed. Then, the sheet is sent to the left in the figure, and is conveyed to a sheet discharging unit (not shown). Usually, the unfixed toner on the transfer paper is
The sheet is sandwiched between nips composed of a fixing roller 1 and a pressure roller 2, melted by the heat of the fixing roller 1, and fused to transfer paper.

An induction coil 33 having a core 31 made of a ferromagnetic material such as ferrite or a laminated silicon steel plate is connected to a power supply inverter (not shown) disposed outside the fixing device. High-frequency current can be passed. A high-frequency magnetic flux is generated by the high-frequency current, and the generated magnetic flux is converted into a space on the side of the core 31 → the induction coil 33 → a space in the vicinity of the fixing roller 1 → the core metal member 11 of the fixing roller → a space in the vicinity of the fixing roller 1 →
A loop of the core 31 is formed. The magnetic flux passing through the fixing roller core member 11 at this time generates an eddy (eddy) current inside the first core member 11, and heat generated by the eddy current loss causes the portion of the fixing roller 1 close to the induction coil portion 3 to be heated. Heat.

The heat generated by the first metal core member 11 of the fixing roller 1 increases as the part is closer to the induction coil 33 and decreases as the distance from the part increases. However, the core portion of the fixing roller 1 is the first core member 1
It is composed of a composite material of the first and second core members 12,
At a frequency (several tens of KHz) generally used for induction heating, heat is not generated unless a good magnetic metal such as iron or magnetic stainless steel is used. Therefore, the second core member 12 is made of a nonmagnetic good heat conductive metal such as aluminum or copper to improve the heat conductivity and improve the temperature unevenness in the circumferential direction of the fixing roller 1. . This configuration is also effective in improving the temperature unevenness between both ends and the center of the fixing roller 1, that is, in the axial direction.

The closer the induction coil unit 3 and the fixing roller 1 are to each other, the better the distance for induction heating. However, considering the influence of the fixing temperature on the induction coil 33 and the safety, it is appropriate that the distance be about 2 to 4 mm. The thickness of the first metal core member 11 and the second metal core member 12 is 0.5 to 10 mm, depending on the fixing start-up time, the speed of copying / printing the product, and the diameter and structure of the fixing roller. What is necessary is just to determine from the range according to the specification required for the fixing unit. Specifically, in order to shorten the rise time, it is necessary to reduce the overall heat capacity (proportional to the mass), and the first core member 11 and the second core member 12 may be made thin. If a temperature regulation (width) is required, the second core member 1
2 can be dealt with by increasing the thickness. Further, when high speed (a large number of sheets fixed per unit time) is required, both the first core member 11 and the second core member 12 may be made thick. By designing these in combination, it is possible to provide an induction heating type fixing device that matches the product.

In the present embodiment, by disposing the induction coil section 3 outside the fixing roller 1, the induction coil 33 is provided.
Is the ambient temperature of the fixing device (generally, the room temperature plus about 10 to 20 ° C.). When the room temperature is set to 20 ° C., the ambient temperature of the induction coil 33 is the room temperature plus 20 ° C.
Is 40 ° C. Under this circumstance, even if the heat generated by the loss of the coil (copper loss) when a high-frequency current flows through the induction coil 33 and the temperature of the coil rises by 50 deg, the maximum temperature reached is 40 ° C. + 50 deg = 90 ° C. Insulation class A and B commonly used for winding
It is possible to use a highly versatile magnet wire such as a seed.

Although the induction coil unit 3 is disposed outside the fixing roller 1, the induction coil unit 3 is affected by the heat generated by the fixing roller 1, but the direct heat generation is limited to a part of the induction coil unit 3. In addition, since the space is not a sealed space inside the fixing roller, there is no significant effect (atmospheric temperature rise).

FIG. 2 shows a graph comparing the temperature of the induction coil in the present embodiment with that of the conventional example. As shown in this figure, the case where the surface temperature of the fixing roller 1 is controlled to 180 ° C. in the fixing device of the present embodiment. After energization is started to heat the fixing roller to the control temperature, the ambient temperature of the induction coil rises to about 40 ° C., and at this time, the temperature of the induction coil 33 is about 80 ° C. On the other hand, in the conventional example, after the start of energization, the ambient temperature of the induction coil rises to near 200 ° C., and the temperature of the induction coil rises to about 240 ° C. In the fixing device of this embodiment, it is obvious that the atmosphere of the induction coil and the temperature of the induction coil itself are kept at a low level, and the temperature difference from the conventional example is large (it does not reach a high temperature unlike the conventional example).

In order to reduce the influence of the surface temperature when the fixing roller 1 generates heat on the induction coil 33, a heat insulating member (not shown) is provided between the fixing roller 1 and the induction coil section 3. They can also be placed. As the heat insulating material, a material such as a sheet or a molded product of a heat insulating material or the like having a porous structure of ultrafine silica particles is suitable. The heat conductivity of the heat insulating material having the porous structure of the very small silica fine particles is smaller than the heat conductivity of still air, and is excellent in heat insulating performance. By disposing such a heat insulating member between the fixing roller 1 and the induction coil unit 3,
Regardless of the distance of the induction coil unit 3 from the fixing roller 1,
The temperature of the entire induction coil 33 rises substantially the same, and the reliability as a coil is improved.

Next, a second embodiment of the present invention will be described. FIG. 3 is a sectional view showing a main part of a fixing device according to a second embodiment of the present invention. In the fixing device shown in this figure, the induction coil unit 3 is disposed inside the pressure roller 2. The configurations of the fixing roller 1, the pressure roller 2, and the induction coil unit 3 are the same as those of the embodiment shown in FIG. The operation of the fixing device is the same as that of the embodiment shown in FIG.

In this embodiment, since the pressure roller 2 is interposed between the induction coil section 3 and the fixing roller 1, the influence of direct heat from the fixing roller 1 can be avoided. The temperature of the entire induction coil unit 3 can be reduced. In addition, by arranging the induction coil portion 3 inside the pressure roller 2, space can be saved, and the induction heating type fixing device can be made compact.

If necessary, a heat insulating material may be provided. In this case, if the inside of the pressure roller 2 is close to a sealed state, it is necessary to cover the entire induction coil 3. is there. If a heat insulating member is provided between the fixing roller 1 and the induction coil section 3, the temperature of the induction coil section 3 can be further reduced, and the reliability and safety can be improved. The core metal member 21 of the pressure roller 2 is a non-magnetic metal and has no direct effect on induction heating, and the pressure roller 2 is interposed (between the fixing roller 1 and the induction coil unit 3). Of the distance between the induction coil unit 3 and the fixing roller 1 due to heat (effect on induction heating)
Should be considered.

Next, a third embodiment of the present invention will be described. FIG. 4 is a sectional view showing a main part of a fixing device according to a third embodiment of the present invention. The configuration of the fixing device shown in this figure is the same as that of the above-described embodiment shown in FIG. 1 except that the structure of the induction coil unit 103 is different. The fixing roller 1 and the pressure roller 2
Is the same as that of the embodiment shown in FIG.

The induction coil section 103 comprises a core 131 and an induction coil 133. The cross-sectional shape of the core 131 is a shape in which the letter “T” is turned sideways.
31 is a two-stage column when viewed from the left and right directions in the figure. That is, the head portion 131a of "T" is a large diameter cylinder, and the "T" vertical bar portion 131b is a small diameter cylinder. An induction coil 133 is wound around the small-diameter cylindrical portion 131b.

The magnetic flux generated by the flow of the high-frequency current through the induction coil portion 103 is generated by the large-diameter portion 131a → the space in the vicinity of the fixing roller 1 → the fixing roller core metal member 11 → the space in the vicinity of the fixing roller 1 → Small diameter part 131b → large diameter part 13
Form the loop of 1a. With such a configuration, the coupling between the induction coil unit 103 and the fixing roller 1 is good, the generated magnetic flux can be efficiently transmitted to the fixing roller 1 side, and the overall heating efficiency can be increased. Become.

Here, that the coupling between the induction coil section 103 and the fixing roller 1 is good means that in this embodiment, the magnetic flux generated in the induction coil section 103 is generated in the horizontal direction (horizontal direction) in FIG. Then, since a magnetic flux is generated toward the fixing roller 1, the efficiency of induction heating of the fixing roller 1 is high. On the other hand, in the embodiment shown in FIG. 1, the magnetic flux generated in the induction coil unit 3 is as shown in FIG.
Occurs in the left-right direction (horizontal direction) of the fixing roller 1
, The heating efficiency is higher in the configuration of this embodiment.

In this embodiment, the large diameter portion 13 of the core 131 is located between the surface of the fixing roller 1 and the induction coil 133.
1a is interposed, the influence of the surface temperature of the fixing roller 1 on the induction coil 133 is reduced, and the heat insulation and insulation member is not disposed between the fixing roller 1 and the induction coil unit 103. Both the temperature and the ambient temperature of the induction coil unit 103 can be kept low.

Next, a fourth embodiment of the present invention will be described. FIG. 5 is a sectional view showing a main part of a fixing device according to a fourth embodiment of the present invention. The configuration of the fixing device shown in this figure is the same as that of the above-described embodiment shown in FIG. 4 except that the location of the induction coil unit 103 is different. Note that the configuration itself of the induction coil unit 103 is the same as that of the embodiment shown in FIG. Also,
The configurations of the fixing roller 1 and the pressure roller 2 are the same as those of the above-described embodiments shown in FIGS.

In the present embodiment, the induction coil section 103 is provided inside the pressure roller 2. Induction coil unit 103
Is the same as that of the embodiment shown in FIG. 4, and the generated magnetic flux is the large-diameter portion 131a of the core 131 → the space in the vicinity of the fixing roller 1 → the core member 11 of the fixing roller → the space in the vicinity of the fixing roller 1. A loop is formed from the small-diameter portion 131b to the large-diameter portion 131a, and the generated magnetic flux can be efficiently transmitted to the fixing roller 1 side, so that the overall efficiency with respect to heating can be increased.

The surface of the fixing roller 1 and the induction coil 1
33, the influence of the surface temperature of the fixing roller 1 is reduced, and the pressure of the induction coil 1 is reduced.
Both the temperature of 33 and the ambient temperature of the induction coil section 103 can be further reduced. And the induction coil unit 1
By arranging the inside of the pressure roller 03, space saving can be achieved, and a compact induction heating type fixing device can be configured.

In the third and fourth embodiments, as in the first and second embodiments, the induction coil 10
It is possible to dispose a heat insulating member between the fixing roller 3 and the fixing roller 1.

[0034]

As described above, according to the induction heating type fixing device of the present invention, the induction coil portion is arranged outside the fixing roller, whereby the temperature rise of the induction coil can be suppressed, and the reliability is improved. An inductive heating type fixing device with improved safety can be provided at low cost.

By arranging the induction coil portion inside the pressure roller, it is possible to avoid the direct influence of heat from the fixing roller and to suppress the temperature rise of the entire induction coil portion. Further, the size of the fixing device can be reduced.

Since the core metal member of the pressure roller is made of a nonmagnetic metal, the pressure roller does not generate heat due to the magnetic flux from the induction coil portion. Since the induction coil of the induction coil is wound along the axial direction of the fixing roller, the magnetic flux generated by the induction coil is in a direction perpendicular to the fixing roller, and the coupling between the induction coil and the fixing roller is improved. In addition, the heating efficiency can be improved.

By making the size of the vicinity of the fixing roller in the core of the induction coil portion larger than that of the coil winding portion, the influence of the surface temperature of the fixing roller on the induction coil can be reduced and the temperature rise of the induction coil can be suppressed. it can.

By providing the heat insulating member in the induction coil portion, the temperature of the entire induction coil rises substantially the same regardless of the distance of the induction coil portion from the fixing roller, and the reliability of the coil can be improved. .

By forming the core member of the fixing roller from a composite material consisting of a first core member made of a good magnetic metal and a second core member made of a nonmagnetic good heat conductive metal disposed inside the first metal member. Further, it is possible to configure an induction heating type fixing device according to the rising time, temperature accuracy, and fixing speed (number of sheets fixed per unit time) of the fixing device required as a product.

[Brief description of the drawings]

1A and 1B show a main part of a fixing device according to an embodiment of the present invention, wherein FIG. 1A is a cross-sectional view and FIG. 1B is a side view.

FIG. 2 is a graph comparing the temperature of an induction coil in the present embodiment with a conventional example.

FIG. 3 is a cross-sectional view illustrating a main part of a fixing device according to a second embodiment of the invention.

FIG. 4 is a cross-sectional view illustrating a main part of a fixing device according to a third embodiment of the invention.

FIG. 5 is a sectional view showing a main part of a fixing device according to a fourth embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 fixing roller 2 pressure roller 3, 103 induction coil section 11 first metal core member 12 second metal core member 21 pressure roller core metal member 31, 131 core 32 bobbin 33, 133 induction coil 131 a fixing roller proximity portion 131 b induction Coil winding part

Claims (7)

[Claims] 1. An induction heating type fixing device having a fixing roller and a pressure roller, wherein the fixing roller is an induction heating type heating roller, comprising a core and an induction coil for generating an induction magnetic flux. An induction heating type fixing device, wherein an induction coil portion is provided outside the fixing roller. 2. The induction heating type fixing device according to claim 1, wherein the induction coil portion is disposed inside the pressure roller. 3. The induction heating type fixing device according to claim 2, wherein the core metal member of the pressure roller is made of a nonmagnetic metal. 4. The induction heating fixing device according to claim 1, wherein the induction coil is wound around the induction coil along an axial direction of the fixing roller. 5. The induction heating type fixing device according to claim 4, wherein the core around which the induction coil is wound has a fixing roller proximity portion larger than the induction coil winding portion. . 6. The induction heating type fixing apparatus according to claim 1, wherein the induction coil section has a heat insulating / insulating member. 7. The fixing roller according to claim 1, wherein said fixing roller comprises a first core member made of a good magnetic metal and a nonmagnetic good heat conductive metal disposed on an inner peripheral side of said first core member. The induction heating type fixing device according to claim 1, wherein the fixing device is a composite material including a second metal core member.