JPS6385677A - Heat roll for electrophotography - Google Patents

Abstract

PURPOSE:To uniformize the temp. distribution of a heat roll and to prevent the exfoliation of a heating resistor layer, etc., by providing a low expansion layer made of iron or iron alloy between the outside periphery of a cylindrical base body and insulating layer. CONSTITUTION:The low expansion layer 2 made of the iron or iron alloy is provided on the outside periphery of the cylindrical base body 1 and further, the insulating layer 3, the heating resistor layer 4 made of ceramics and a protective layer 5 consisting of fluoroplastic, etc., are successively provided on the outside periphery thereof, by which the heat roll is formed. The heat roll is heated when electric power is supplied through electrodes 6 provided at both ends of the heating resistor layer 4. Since the cylindrical base body 1 is made of an aluminum or copper alloy and has good heat conductivity, the heat distribution of the heat roll can be uniformized. However, this cylindrical base body 1 has a large coefft. of thermal expansion and, therefore, the thermal expansion is limited by the low expansion layer 2 and the exfoliation of the heating resistor layer 4 of the outside peripheral insulating layer 3 is prevented.

Description

Detailed Description of the Invention "Field of Industrial Application" The present invention relates to a heat roll of an electrophotographic heat fixing machine that heats and fixes toner on copy paper, and in particular, the present invention relates to a heat roll for an electrophotographic heat fixing machine that heats and fixes toner on copy paper. This prevents peeling damage to the heating resistor layer and insulating layer that form the roll.

``Prior Art'' As a heating means for a heat roll, various methods have been proposed in which a heat generating resistor layer is provided on the outer periphery of a cylindrical base and electric power is supplied to the heat generating resistor layer (Japanese Patent Laid-Open No. 1986-1999). 723
Publication No. 90).

The present inventor also deposited a bonding layer, an insulating layer 1, a heating resistor layer, and a protective film on the outer periphery of a cylindrical base in order, and the current applied to the heating resistor layer was passed through the bearing of the heat roll to the copying machine. An application has been filed for an invention to prevent electrical leakage to the main body (Japanese Patent Application Laid-open No. 132974/1983).

When copying with a copying machine, it is desirable that the entire surface of the heat roll be heated to a uniform temperature in order to clearly and reliably fix the toner on the copy paper. The provided heat roll can be used with a copy machine for 5
During continuous copying, heat is dissipated at the center of the heat roll where the copy paper hits, while at one end there is less heat dissipation and the center of the heat roll becomes lower in temperature than both ends.

"Problems to be Solved by the Invention" When a conventional heat roll having a heat generating resistor layer is used continuously, the center becomes colder than both ends.

Therefore, when the heating temperature at the center of the heat roll is increased to ensure fixing performance, both ends are heated to 240° C. or higher, resulting in the problem of burning the copy paper or melting the resin layer on the surface.

Therefore, if the cylindrical base that forms the heat roll is made of a material with high thermal conductivity such as aluminum alloy, and an attempt is made to transfer the heat from both ends of the heat roll to the center, the heat of the cylindrical base The coefficient of expansion was large, and there were problems such as peeling of the insulating layer and heating resistor layer provided on the outer periphery.

Therefore, an object of the present invention is to make the temperature distribution of the heat roll uniform and also to prevent the exfoliation of the heating resistor layer and the like.

"Means for Solving the Problems" The present invention provides a low expansion layer made of iron or iron alloy on the outer periphery of a cylindrical substrate made of aluminum alloy or copper alloy, and an insulating layer on the outer periphery of this low expansion layer. , a heat roll provided with a heating resistor layer and a protective layer.

Since the cylindrical base is made of aluminum alloy or copper alloy,
Although the thermal conductivity is good, the coefficient of thermal expansion is large.

However, since a low expansion layer made of iron or iron alloy is provided on the outer periphery of the cylindrical base to limit the expansion of the cylindrical base, damage to the heating resistor layer and insulating layer on the outer periphery becomes difficult.

When a heat conductive layer made of aluminum alloy or copper alloy is provided on the inner periphery of the protective layer, the heat at both ends of the heat roll can be conducted not only through the cylindrical base but also through the heat conductive layer, which improves the heat distribution of the heat roll. Uniformity can be achieved.

"Function" In the heat roll of the above means, when power is supplied to the heating resistor layer, it is heated, and the outer surface of the heat roll is heated to a substantially uniform temperature. When copies are made continuously using a copying machine equipped with this heat roll, the central part of the heat roll receives more heat from the copy paper than the opposite ends. However, since the cylindrical base of the heat roll is made of aluminum alloy and has good thermal conductivity, heat from both ends of the heat roll is transferred to the center, thereby making it possible to maintain uniform heat distribution of the heat roll.

Furthermore, by forming the cylindrical base of the heat roll from aluminum alloy or the like, the coefficient of thermal expansion is high, but since a low expansion layer made of iron or iron alloy is provided on the outer periphery, the expansion of the cylindrical base is limited. The resistance heating element layer and the insulating layer provided on the outer periphery of the cylindrical base will not be damaged or peeled off.

"Example" An embodiment of the present invention will be explained with reference to FIG.

The heat roll has a low expansion layer 2 made of iron or iron alloy on the outer periphery of a cylindrical base 1, and an insulating layer 3, a heating resistor layer 4 made of ceramic, and a protective layer made of fluororesin etc. on the outer periphery. The heat roll is heated by supplying electric power through electrodes 6 provided at both ends of the heating resistor layer 4. Note that the low expansion layer 2 is formed by thermal spraying iron or iron alloy, so a bonding layer may be provided. F/) + Muay Tan 1 shipμ9r↓ Tatake→←廿1k 1
It firmly adheres to the firing field.

The cylindrical base 1 is made of an aluminum alloy or a copper alloy and has good thermal conductivity, so that the heat distribution of the heat roll can be made uniform. However, since this cylindrical substrate has a large coefficient of thermal expansion, the thermal expansion is limited by the low expansion layer 2, and peeling of the insulating layer 3 and heat generating resistor layer 4 on the outer periphery is prevented.

Furthermore, the low expansion layer 2 has sufficient strength to limit the thermal expansion of the cylindrical substrate 1 if it has a thickness of 300 to 1000 lumens, and is made of a material other than iron or iron alloy, and is made of a material other than iron or iron alloy. 3
Any material having an average coefficient of expansion up to 50° C. of 18×10 −6 or less can be used.

Here, in the above example, a heat roll (axial length 350 ff, 1 country, outer diameter 30
(2) Explain the temperature distribution in the axial direction. When raising the temperature with a copying machine equipped with this heat roll, after 5 minutes of heating, A4 paper is
FIG. 2 shows the temperature distribution in the axial direction of the heat roll during continuous copying. For comparison, FIG. 2 also shows the temperature distribution of a conventional heat roll (with a cylindrical base made of iron).

As can be seen from FIG. 2, the heat roll of this embodiment has a more uniform temperature distribution than the conventional example, and can be copied in a desirable state.

Furthermore, regarding the strength of the heat roll (peeling fa of each layer), none of the layers was damaged even after being used for a considerable period of time, and it is recognized that the effect of providing the low expansion layer 2 is sufficient.

Note that the increase in warming-up time was approximately 10 seconds when the thickness of the low expansion layer was 110007z.

As a modification of the heat roll of the above embodiment, a heat conductive layer made of aluminum alloy, copper alloy, etc. is further provided on the outer periphery of the heat generating resistor layer 4 via an insulating layer, and a thermal conductive layer made of aluminum alloy, copper alloy, etc. is provided on the outer periphery of the heat conductive layer.
The layer 5 may be placed on the cylindrical substrate l.
In addition to this, heat can also be transferred in the axial direction of the heat roll from this heat conductive layer.

Temperature distribution becomes more uniform.

"Effects of the Invention" The heat roll of the present invention has a cylindrical base made of aluminum alloy or copper alloy with good thermal conductivity, and a low expansion layer provided on the outer periphery of the cylindrical base. Expansion can be limited by the low expansion layer to prevent peeling of the insulating layer, heating resistor layer, etc. Further, since the cylindrical substrate has good thermal conductivity, the temperature distribution of the heat roll becomes uniform, and when a heat conductive layer is provided around the outer periphery of one heating resistor layer, the temperature distribution of the heat roll can be made even more uniform.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the heat roll of the present invention, and FIG. 2 is a graph comparing the temperature distribution of the heat roll of the present invention with that of a conventional example.

Claims (3)

[Claims] (1) In an electrophotographic heat roll in which a heating resistor layer is provided on the outer periphery of a cylindrical substrate made of aluminum alloy or copper alloy through an insulating layer, and a protective layer is provided on the outermost periphery, the outer periphery of the cylindrical substrate and A heat roll for electrophotography, characterized in that a low expansion layer made of iron or iron alloy is provided between an insulating layer. (2) The heat roll for electrophotography according to claim 1, wherein a heat conductive layer made of aluminum alloy or copper alloy is provided on the outer periphery of the heating resistor layer with an insulating layer interposed therebetween. (3) The heat roll for electrophotography according to claim 1, wherein the low expansion layer has a thickness of 300 to 1000 μm.