JP2001313160A - Heating member and heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent those problems that in order to pursue the characteristics of the short start up time required for an induction heater, a thin cored bar metal is used for the fixation roller, which in turn causes abnormal rise of temperature in the area where paper does not pass when small size of paper is used, while on the other hand the temperature of the fixation roller balls at its edge portion due to the discharge of the temperature from edge portion after start when a roller of a straight shape is used. SOLUTION: The heater comprises a magnetic metal layer which generates Joule heat on the surface of the cored bar by induction current, and the thickness of the magnetic metal layer is made different in the longitudinal direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating member having a magnetic metal layer for generating Joule heat by a dielectric current on the surface of a cored bar, and to a heating device provided with a pressing member which presses against the heating member. .

[0002]

2. Description of the Related Art As a heating device for heating and fixing a toner image transferred onto a sheet such as a recording paper or a transfer material as a recording medium by an image forming means such as an electrophotographic copying machine, a sheet is used. There is a heating device having a fixing roller also referred to as a heating roller for thermally fusing the upper toner image, and a pressing roller for pressing the fixing roller to hold a sheet.

The fixing roller is formed in a hollow shape, and a heating element is held on a central axis of the fixing roller by holding means. This heating element is formed of, for example, a tubular heating heater such as a halogen lamp, and generates heat when a predetermined voltage is applied. Since the halogen lamp is located at the center axis of the fixing roller, heat generated from the halogen lamp is uniformly radiated to the inner wall of the fixing roller, and the temperature distribution of the outer wall of the fixing roller becomes uniform in the circumferential direction.

The outer wall of the fixing roller is heated until its temperature reaches a temperature suitable for fixing (for example, 150 to 200 ° C.). In this state, the fixing roller and the pressure roller rotate in the opposite directions while being pressed against each other, and pinch the toner-adhered sheet at a pressure contact portion (hereinafter also referred to as a nip portion) between the fixing roller, the pressure roller, and both rollers. Then, the toner image on the sheet is melted by the heat of the fixing roller, and is fixed to the sheet by the pressure applied from both rollers.

However, in the above-described heating device having a heating element composed of a halogen lamp or the like, since the fixing roller is heated by using the radiant heat from the halogen lamp, the temperature of the fixing roller is reduced after the power is turned on. It takes a relatively long time to reach a predetermined temperature suitable for fixing (hereinafter referred to as "warm-up time"). However, during this temperature rise period, the user cannot use the copying machine, and is forced to wait for a long time, resulting in poor operability.

In order to improve the operability, it is conceivable to apply a large amount of electric power to the fixing roller to shorten the warm-up time. However, the power consumption of the heating device is increased, which is against energy saving. Occurred. For this reason, in order to increase the value of products such as electrophotographic copying machines, attention and emphasis has been placed on achieving both energy saving (low power consumption) and improved operability (quick print) of a heating device. Have been.

[0007] As an apparatus that meets such a demand, Japanese Unexamined Patent Publication No.
As shown in JP-A-9-33787, an induction heating type heating device using high-frequency induction as a heating source has been proposed. In this induction heating device, a coil is concentrically arranged inside a hollow fixing roller made of a metal conductor, and a high-frequency magnetic field generated by flowing a high-frequency current through this coil generates an induced eddy current in the fixing roller, The fixing roller itself generates Joule heat by the skin resistance of the fixing roller itself. According to the heating device of the induction heating system, the electric-heat conversion efficiency is extremely improved, so that the warm-up time can be reduced.

[0008]

However, in the above-mentioned conventional induction heating type heating device, in order to pursue the characteristic of the induction heating type that the start-up time is short, the thickness of the core metal as a fixing roller is reduced. Uses thin metal. For this reason, for example, when small-sized paper is passed, there has been a problem that the temperature of the non-paper passing area rises abnormally. Also, when using a straight roller, heat escapes more rapidly from the end immediately after startup,
There was a phenomenon that the temperature at the end of the fixing roller was lowered.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem of the prior art.
It is another object of the present invention to provide a heating member having a uniform temperature distribution that does not cause a drop in end temperature and having a short startup time, and a heating device capable of quickly heating using the heating member.

[0010]

According to the present invention, there is provided a heating member and a heating device having the following constitution.

(1) A heating member having a magnetic metal layer for generating Joule heat by an induced current on the surface of a cored bar, wherein the thickness of the magnetic metal layer varies in the longitudinal direction.

(2) The heating member according to (1), wherein the thickness at the center of the magnetic metal layer is smaller than the thickness at the end.

(3) The heating member according to (1), wherein the thickness of the core metal differs in the longitudinal direction.

(4) The heating member according to (1), wherein the thickness of the central portion of the core in the longitudinal direction is larger than the thickness of the end portion.

(5) The heating member according to any one of (1) to (4), wherein the induced current is an eddy current generated by the intersection of magnetic fluxes.

(6) A magnetic metal layer for generating Joule heat by an induced current is provided on the surface of the metal core, and the thickness of the magnetic metal layer is different from the heating member in the longitudinal direction. A heating device, comprising:

(7) The heating device according to (6), wherein the thickness of the center portion of the magnetic metal layer is smaller than the thickness of the end portion.

(8) The heating device according to (6), wherein the thickness of the cored bar varies in the longitudinal direction.

(9) The heating device according to (6), wherein the thickness of the central portion of the core in the longitudinal direction is larger than the thickness of the end portion.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

(Embodiment 1) Hereinafter, Embodiment 1 of the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view schematically showing an induction heating device according to Embodiment 1 of the present invention, in which a fixing roller 1 is provided on a surface of a straight iron core metal cylinder 1a having an outer diameter of 40 [mm]. For example, PTFE 10 to 50 [μm] or PFA 10
層 50 [μm] layer 1b is provided.

The pressure roller 2 comprises a hollow cored bar 14 and an elastic layer 15 which is a heat-resistant rubber layer formed on the outer peripheral surface thereof.
Consists of Bearing portions are formed at both ends of the pressure roller 2, and are rotatably attached to a fixing unit frame (not shown).

The fixing roller 1 is also rotatably supported by the fixing unit frame similarly to the pressure roller 2, and is configured to drive only the fixing roller 1. Pressure roller 2
Is pressed against 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 about 30 [kg weight] by a mechanism (not shown) using a spring or the like in the rotation axis direction of the fixing roller 1.
Pressurized with a load of In that case, the width (nip width) of the press contact portion is about 6 [mm]. However, the nip width may be changed by changing the load depending on circumstances.

FIG. 2 illustrates the principle of heating in the fixing nip. The magnetic flux generated by the current applied to the induction coil 3 by the excitation circuit 16 is guided to the high magnetic permeability core 4 and generates a magnetic flux 33 and an eddy current 34 in the core of the fixing roller 1 in the fixing nip N. The eddy current 34 and the fixing roller 1
Heat is generated by the specific resistance of

The induction coil 3 is disposed inside a holder 5 made of a heat-resistant resin such as PPS, PEEK, or phenol resin so as to be wound around the core 4. An alternating current of 10 to 100 [kHz] is applied to the induction coil 3. The magnetic flux 33 induced by the alternating current causes an eddy current 34 to flow on the inner surface of the fixing roller 1 which is a conductive layer, and generates Joule heat. In order to increase the heat generation, the number of turns of the induction coil 3 may be increased, the core 4 may be made of ferrite or permalloy having a high magnetic permeability and a low residual magnetic velocity density, or the frequency of the alternating current may be increased.

The temperature sensor 6 is disposed so as to be in contact with the surface of the fixing roller 1, and the power supply to the induction coil 3 is increased or decreased based on the detection signal of the temperature sensor 6, whereby the surface temperature of the fixing roller 1 is increased. Is automatically controlled so as to reach a predetermined constant temperature.

The conveyance guide 7 is arranged at a position for guiding the transfer material 9 conveyed while carrying the unfixed toner image 8 to a pressure contact portion (nip group) between the fixing roller 1 and the pressure roller 2. . The separation claw 10 is disposed in contact with or close to the surface of the fixing roller 1 on the transfer material discharge side.

Next, referring to FIG. 3, the fixing roller 1 of the present invention will be described.
Will be described in detail. The iron core 1a of the fixing roller 1 (this embodiment; referred to as a roller) has a central portion (line A in the figure).
Has a wall thickness of 0.4 mm and an end portion (line B in the drawing) of 1 mm. The induction coil 3 is arranged parallel to the longitudinal axis, and the distance from the induction coil 3 to the inner surface of the fixing roller 1 is smaller at the end.

In order to compare the fixing roller 1 used in the present embodiment with a conventional one, a heat roller having a heat capacity of 0.7 m
A fixing roller having a uniform thickness of m (comparative example; referred to as a roller) was prepared, and the power required to maintain a constant temperature was measured.

FIG. 4 shows that a high-frequency AC voltage of 60 kHz, 100 V, initial 1300 W was applied to each of the rollers, the surface temperature of the fixing roller was raised from room temperature to 200 ° C., and about 30 sheets were passed. 1 shows an initial temperature distribution in the longitudinal direction.

According to this, the temperature of the roller at the initial stage of sheet passing is smaller than that of the roller. This is because the heat capacity at both ends is larger than that at the center, so it is expected that the rise will be slow and the temperature will drop at the ends. It is considered that the amount of heat generated by the heat treatment increased, and as a result, the temperature distribution in the longitudinal direction became uniform.

Next, the temperature control temperature was fixed at 180 ° C., and small-size paper (B5 paper) was passed at a speed of 30 sheets / min.
The average power during paper passing was 750 W. FIG. 5 shows the roller and the temperature of the surface of the fixing roller when the roller is used.

When the small-size paper is passed, the induction coil is close to the heat generating portion, so that the amount of heat generated at the end increases. However, since the heat capacity of the fixing roller 1 is large at the end, the temperature rise on the surface of the fixing roller is suppressed. Can be Of course, the fixing roller 1 in the present embodiment may be configured to have a cross-sectional shape as shown in FIG. 6A or FIG. 6B.

As described above, according to the present embodiment, the outer diameter of the cored bar is constant and the thickness of the end portion is thicker than that of the central portion.
It is possible to prevent an initial temperature drop and a rise in the temperature of the non-sheet passing portion when the small size sheet is passed.

(Embodiment 2) Next, another embodiment of the present invention will be described with reference to the drawings. FIG. 7 is a sectional view schematically showing a heating device according to Embodiment 2 of the present invention.
The same parts as those in the first embodiment are denoted by the same reference numerals, and redundant description will be omitted.

The fixing roller 102 comprises an iron core 104 and a release layer 103. When a high-frequency current is input to the induction coil 3, a magnetic flux is generated, and this magnetic flux is
The toner is efficiently guided to the fixing roller 102 by 406, and an eddy current is generated in the fixing roller 102 to generate heat. As described above, in the second embodiment, the fixing roller 102 is heated from the outside. (External Heating) FIG. 8 shows a roller 1 having an inverted crown shape formed by polishing a straight cored bar. In the second embodiment, an inverted crown shape of about 0.25 mm is provided, thereby preventing paper wrinkles and the like. Further, since the end portion has a large thickness and is close to the coil 3, it is possible to prevent an initial temperature decrease and a non-sheet-passing portion temperature rise during small-size sheet passing.

FIG. 9 shows the shape of the inner surface of the straight roller 1 in which the inner diameter is smaller at the end than at the center. In this case, since the thickness of the end portion is thicker than that of the center portion and the coil 3 is formed in a concave shape as viewed in the longitudinal direction of the roller, the end portion is closer to the roller. The same effect can be obtained with this configuration.

[0038]

As described above, according to the present invention, in a cylindrical heating member heated by an induced current,
Since the thickness is gradually increased or the inner diameter is gradually reduced toward both ends of the heating member, the temperature at the end of the heating member at the initial stage of heating and when the small size paper is passed. The temperature rise of the non-sheet passing portion can be reliably prevented with a simple configuration. Further, by using such a heating member, there is an effect that a heating device having a uniform temperature distribution can be easily obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a heating device according to a first embodiment of the present invention.

FIG. 2 is a diagram for explaining a heating principle of the heating device according to the first embodiment;

FIG. 3 is a schematic diagram (a fixing roller core axis direction) of a heating device according to the first embodiment and a comparative example.

FIG. 4 is a diagram showing initial temperature distribution in the longitudinal direction of the present example and a comparative example.

FIG. 5 is a diagram illustrating a temperature distribution in a longitudinal direction when a small-size sheet is passed according to the present embodiment and a comparative example.

FIG. 6 is a schematic sectional view of a heating member according to the first embodiment.

FIG. 7 is a schematic sectional view of a heating device according to a second embodiment.

FIG. 8 is a schematic diagram of a heating device according to a second embodiment.

FIG. 9 is a schematic diagram of a heating device according to a second embodiment.

[Explanation of symbols]

 1: fixing roller (heating member) 2: pressure roller (pressure member) 3: induction coil 4, 401 to 406: core (core material) 5, 25: holder (supporting member) 6: thermistor (temperature detecting element) 7: conveyance guide 8: toner image 9: transfer material 10: separation claw 16: excitation circuit 33: magnetic flux 34: eddy current

Claims (9)

[Claims] 1. A heating member having a magnetic metal layer for generating Joule heat by an induced current on the surface of a cored bar, wherein the thickness of the magnetic metal layer differs in the longitudinal direction. 2. The heating member according to claim 1, wherein the thickness of the central portion of the magnetic metal layer is smaller than the thickness of the end portion. 3. The heating member according to claim 1, wherein the thickness of the core metal differs in the longitudinal direction. 4. The heating member according to claim 1, wherein a thickness of a central portion of the core metal in a longitudinal direction is larger than a thickness of an end portion. 5. The heating member according to claim 1, wherein the induced current is an eddy current generated by the intersection of magnetic fluxes. 6. A magnetic metal layer for generating Joule heat by an induced current on a surface of a cored bar, the magnetic metal layer having a thickness different in a longitudinal direction, and being disposed in pressure contact with the heating member. And a pressing member. 7. The heating device according to claim 6, wherein the thickness of the magnetic metal layer at the center is smaller than the thickness at the ends. 8. The heating device according to claim 6, wherein the thickness of the cored bar varies in the longitudinal direction. 9. The heating apparatus according to claim 6, wherein the thickness of the central portion of the core in the longitudinal direction is larger than the thickness of the end portion.