JPS6385676A - Heat roll for electrophotography - Google Patents

Abstract

PURPOSE:To permit easy transmission of the heat at both ends of a heat roll to the central part and to uniformize the temp. in respective axial positions by providing a heat conductive layer consisting of a material such as copper alloy or aluminum alloy having good heat conductivity on the outside periphery of a cylindrical base body or the inside periphery of a protective layer. CONSTITUTION:The heat conductive layer 2 is provided on the outside periphery of the cylindrical base body 1 made of iron by thermally spraying the material such as aluminum alloy or copper alloy having good heat conductivity thereto. A bond layer 3, an insulating layer 4, a heating resistor layer 5 and the protective layer 6 are successively provided on the outside periphery of such layer 2 to form the heat roll. Electrodes 7 are respectively provided to both ends in the axial direction of the heating resistor layer 5 and electric power is supplied to the layer 5 through said electrodes, by which said layer is heated. The quantity of heat conduction is too small if the thickness of the layer 2 is smaller than 100mum and a quick start characteristic is poor if the thickness is larger than 1,000mum; therefore, the desirable thickness thereof is 300-1,000mum. The temp. distribution over the entire part of the heat roll is thereby uniformized.

Description

Detailed Description of the Invention "Field of Industrial Application" The present invention relates to a heat roll for an electrophotographic heat fixing machine that heats and fixes toner on copy paper, and particularly relates to a heat roll in which the temperature distribution of the heat roll is made uniform. be.

``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 Unexamined Patent Publication No. 81-132974).

When making copies using 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. A heat roll equipped with a The temperature at both ends is lower than that at 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.

For this reason, when trying to maintain the heating temperature at the center of the heat roll to ensure fixing performance, both ends were heated to over 240°C, causing problems such as burning the copy paper and melting the resin layer on the surface. .

Therefore, an object of the present invention is to make it easier to transfer the heat from both ends of the heat roll to the center, thereby making the temperature uniform at each axial position of the heat roll.

"Means to solve problems" The present invention is applied to the outer periphery of a cylindrical base made of iron.

A bonding layer, an insulating layer, a heating resistor layer, and a protective layer are provided.

This is a heat roll for electrophotography in which a heat conductive layer is provided on the outer periphery of a cylindrical substrate or the outer periphery of a heating resistor layer.

The cylindrical base is made of iron because it has a small coefficient of thermal expansion and is less likely to damage the insulating layer, heating resistor layer, and protective layer provided on the outer periphery.

A metal with good thermal conductivity, such as a copper alloy or an aluminum alloy, was used as the heat conductive layer, and its thickness was set to 300 to 1000 gm to obtain sufficient heat conduction and improve quick start performance. Further, if the heat roll is formed to have a small diameter of 20 mm or less, the copy paper can be easily peeled off, and the warm-up time is short, which is convenient when manufacturing a small-sized copying machine.

"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 a heat conductive layer is provided at the inner or outer circumference of the heating resistor, heat from both ends is transmitted to the center via the heat conductive layer, preventing heat loss in the center. . Therefore, even if copies are made continuously, the toner on the copy paper can be reliably and clearly heated and fixed.

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

A thermally conductive layer 2 is provided on the outer periphery of a cylindrical iron base l by spraying a material with good thermal conductivity such as an aluminum alloy or a copper alloy, and a bonding layer 3 and an insulating layer are sequentially formed on the outer periphery of this thermally conductive layer 2. 4. A heating resistor layer 5 and a protective layer 6 are provided to form a heat roll.

Note that if the insulating layer 4 is made of a material that strongly adheres to the thermally conductive layer,
Bonding layer 3 is not required.

Electrodes 7 are provided at both axial ends of the heat generating resistor layer 5, and the heat generating resistor layer 5 is heated by supplying electric power through these electrodes.

The thickness of the thermally conductive layer 2 is desirably 300 to 100 gm because if it is thinner than 100 #Lm, the amount of heat conduction will be too small, and if it is thicker than 1000 μm, the quick start performance will be poor.

In the above heat roll, the quick start performance was measured by changing the thickness of the heat conductive layer 2 made of aluminum alloy, and the results are shown in FIG. The outer diameter of the heat roll is 30
mm, and the axial length was 350 mm.

As shown in Figure 2, the thermal conductive layer thickness is 1000m7
It can be seen that below z, the waiting time is shorter than the conventional halogen lamp method, which is desirable.

Next, the surface temperature at each axial position of the heat roll was measured when a 5-minute diameter A4 sheet of A4 paper was continuously copied vertically immediately after the temperature was raised using a copying machine equipped with the above heat roll, and the results are shown in Figure 3. .

In this case, the axial length of the heat roll was 350 mm, the outer diameter was 30 mm, and the thickness of the aluminum alloy heat conductive layer was 500 g.

For comparison, the temperature distribution of the heat roll when the same continuous copying was performed using a heat roll of the same shape but without the heat conductive layer 2 of the present invention is also shown in Figure 3. Also shown.

As can be seen from FIG. 3, the temperature difference between both ends and the center of the heat roll in the present invention is smaller than that in the comparative example, which is desirable. This is considered to be because the heat roll of the present invention has the heat conductive layer 2, so that heat from both ends is transmitted to the center.

In the explanation given below, the heat conductive layer 2 is provided on the outer periphery of the cylindrical substrate 1, but it may be provided on the inner periphery of the protective layer 6 instead. A thermally conductive layer is provided, and a protective layer 6 is provided around the outer periphery of this thermally conductive layer.

Further, a heat conductive layer may be provided both on the outer periphery of the cylindrical substrate 1 and on the inner periphery of the protective layer 6. In this case as well, the temperature of the entire outer surface of the heat roll can be uniformly maintained as in the above embodiment. can. The temperature distribution in this case is shown in FIG.

Furthermore, if the outer diameter of the heat roll is formed to be as small as 20 layers or less, the copy paper can be easily peeled off, and the roll can be applied to small-sized copying machines.

"Effects of the Invention" Since the heat roll of the present invention has a cylindrical base made of iron, its coefficient of thermal expansion is low and desirable, but its thermal conductivity is low.However, a heat conductive layer is provided on the outer periphery of the cylindrical base. This makes it easier to transfer heat in the axial direction of the heat roll, and when continuous copying is performed with a copying machine, heat is taken away from the center of the heat roll by the copy paper, but heat is transferred to both axial ends through the heat conductive layer. The heat is transmitted to the center, making the temperature distribution uniform throughout the heat roll. Therefore, even if you make continuous copies,
Toner can be reliably and clearly heat-fixed on copy paper.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the heat roll of the present invention, and FIG. 2 is a graph showing the quick start properties of the heat roll of the present invention.
Both FIG. 3 and FIG. 4 are graphs showing the temperature distribution of the heat rolls of the present invention and the comparative example.

Claims (4)

[Claims] (1) In an electrophotographic heat roll in which a heating resistor layer is provided on the outer periphery of an iron cylindrical substrate via an insulating layer and a protective layer is provided on the outermost periphery, the outer periphery of the cylindrical substrate or the inner periphery of the protective layer is used. A heat roll for electrophotography, comprising: a heat conductive layer made of a material with good thermal conductivity such as a copper alloy or an aluminum alloy. (2) The heat roll for electrophotography according to claim 1, wherein the heat conductive layer is provided on both the outer periphery of the cylindrical substrate and the inner periphery of the protective layer. (3) The heat roll for electrophotography according to claim 1, wherein the heat conductive layer has a thickness of 300 to 1000 μm. (4) The heat roll for electrophotography according to claim 1, wherein the heat roll has an outer diameter of 20 mm or less.