JPS61134776A - Heat roll of copying machine - Google Patents

Abstract

PURPOSE:To obtain a resistance layer having a necessary resistivity and a uniform and appropriate thickness to be formed easily by using a heat roll prepared by forming on the outer surface of a core the resistance layer contg. at least one of oxides, such as alumina, magnesia, or spinel, and an Ni-Cr alloy. CONSTITUTION:The resistance layer contains at least one kind of alumina, magnesia, or MgO.Al2O3, and an Ni-Cr alloy, preferably, having an Ni/Cr weight ratio of 90:10-70:30. The resistance layer is formed by the flame coating on the outer surface of the core of heat roll, and a preferably average perticle diameter of the oxide is 10-50mum.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heat roll for a copying machine in which a resistance layer is provided on the outer surface of a cylindrical core.

[Prior Art] As a heat roll used in a heat fixing device for heat fixing a toner image on copy paper, there is a known heat roll in which a resistance layer is provided on the outer surface of a cylindrical core (for example, 56
-120559, Utility Model Publication No. 58-175551). That is, by supplying electricity to this resistance layer, the heat roll is maintained in a heated state, and the toner is thermally fixed.

By the way, the resistance layer formed on the outer surface of the heat roll is required to be one that can easily form a layer having a predetermined resistance value.

[The point to be solved by the invention] Conventionally, nickel-chromium alloys and the like have been used as resistance layers, but nickel-chromium alloys have a low specific resistance, so the layer thickness has to be made small, and it is not uniform. Moreover, it is not easy to form a resistance layer having a predetermined resistance value.

Further, the above two utility model publications do not disclose the composition of the resistive layer itself at all.

[Means for Solving the Problems] In order to solve the above problems, the present invention uses alumina, magnesia, and alumina-magnesia spinel (hereinafter abbreviated as spinel) as a resistance layer formed on the outer surface of the heat roll core. ) and a nickel-chromium alloy.

The present invention will be explained in detail below.

The resistance layer of the present invention is made of alumina (AJ1203), magnesia (MgO), and spinel (MgO・Al 203).
) and a nickel-chromium alloy.

The nickel-chromium alloy preferably has a weight ratio of nickel to chromium of 90:10 to 70:30. In addition to nickel and chromium, there are also Fe, St, AM, Ti, and Y, which are commonly alloyed with these materials as resistance and heat-resistant materials.
, Ce, Mo, W, Mn, etc., in an amount of 10% by weight or less.

Alumina, magnesia and spinel are chemically stable and inexpensive. Moreover, in the temperature range from room temperature to the temperature at which the heat roll is used (usually about 200° C.), there is no phase transformation and no accompanying volume change.

The resistance layer of the present invention is usually formed on the outer surface of the heat roll core by thermal spraying, and the oxide powder preferably has an average particle size of 10 to 50 μm. When the average particle size is larger than 50 pLm, the ratio of the particle diameter to the film thickness becomes large, and the film becomes non-uniform.

The average particle size is 10#1. If it is smaller than m, it will be difficult to uniformly form the resistive layer by thermal spraying, and the adhesion strength of the resistive layer will also decrease. In other words, in order to carry out thermal spraying, the outer surface of the core is usually shot blasted to increase the surface roughness before thermal spraying, but moderately coarse particles fill all four parts of the core surface, causing the surface of the core to become rough. Even if there are bumps, fI! 4
The film is evenly deposited. However, if the particle size of the oxide powder is too small, it will not be able to smooth out surface irregularities, making it difficult to deposit an even and uniform film.

In addition, when the resistance layer is formed by thermal spraying in this way, the adhesion strength between the core and the resistance layer becomes extremely high, and the resistance layer becomes difficult to peel off from the core.

The mixing ratio of nickel chromium alloy and oxide powder is as follows:
Nickel chromium alloy 5~25% by weight, oxide powder 95~
About 75% by weight is preferable. If the nickel chromium alloy is less than 5% by weight, the resistance layer loses its homogeneity and the adhesion strength of the resistance layer to the outer surface of the core decreases. On the other hand, if the content of the nickel-chromium alloy exceeds 25% by weight, the specific resistance will decrease and the film thickness will have to be reduced accordingly, making it difficult to control the film thickness and forming a uniform resistance layer.

FIG. 3 is a graph showing the measurement results of the specific resistance of a resistance layer formed by plasma spraying a mixture of nickel chromium alloy powder and spinel powder, as detailed in Example 2, and the horizontal axis is The content of nickel-chromium alloy in the thin film is scaled.

From Figure 3, it is recognized that the specific resistance decreases as the content of the nickel-chromium alloy increases, and in particular, when the content of the nickel-chromium alloy exceeds 25% by weight, the specific resistance decreases by lXl.
It is recognized that the resistance is 0-2Ω@Cm or less.

In the present invention, the thickness of the resistance layer is 50 to 500.
The thickness is preferably about 100 to 300 μm. When the film thickness is smaller than 501 Lm, the film thickness distribution of the resistance layer tends to become non-uniform, and on the other hand, when it exceeds 5001 Lm, the heat capacity of the resistance layer itself becomes large. Moreover, it becomes easy to peel off from the outer surface of the core body.

In the heat roll of the present invention, it was found that the resistance layer formed on the surface of the core had a temperature coefficient of resistance of approximately 0 or positive near the heat fixing temperature. Figure 4 shows
As will be detailed in Example 3, this shows the measurement results of the resistance-temperature characteristics of a resistance layer formed by thermal spraying and having a composition of 15% by weight nickel-chromium alloy and the balance being alumina, and the temperature coefficient of resistance is +6 in the range of approximately 50-250℃
．． It was 7×10-'Ωcm/°C.

If the temperature coefficient of resistance near the heat fixing temperature is approximately O or positive in this manner, it becomes possible to accurately maintain the fixing temperature at a predetermined fixing temperature. Incidentally, if the temperature coefficient of resistance near the heat fixing temperature is negative and its absolute value is large, as in T i O2 shown in Figure 4, the current flowing will increase as the temperature rises near the heat fixing temperature. As a result, the amount of heat generated tends to increase, making temperature control difficult.

FIG. 1 is a sectional view showing an example of the heat roll of the present invention, and FIG. 2 is an enlarged view of the portion H in FIG. 1.

As shown in the figure, the heat roll 1 has a cylindrical shape, and the core body 2
A resistive layer 5 is deposited on the outer surface of. A bonding material 3 and an insulating material 4 are provided between the core body 2 and the resistance layer 5.

The insulating material 4 is for preventing a short circuit between the resistive layer 5 and the core 2, and the bonding material 3 is for increasing the bonding property between the core 2 and the insulating material 4. A fluororesin layer 6 is formed on the surface of the resistance layer 50 to prevent offset. Although electrodes 7 for supplying electricity to the resistance layer 5 are provided on both ends of the resistance layer 5, they may be provided on both end surfaces of the heat roll. 8 in the figure is a moisture-proof layer for preventing moisture from diffusing and penetrating into the insulating material 4.

As the core body 2, a conventional core material such as carbon steel, stainless steel, or aluminum alloy is used.

As the bonding material 3, a nickel-based alloy or the like is used, such as a nickel-aluminum-molybdenum alloy. The thickness of this bonding material 3 is 20 to 10011. About m is preferable.

Various oxide powders are used as the insulating material 4, but
In order to approximate the coefficient of thermal expansion to the resistance layer 5, it is preferable to use the same material as the oxide powder contained in the resistance layer 5. For example, when the resistance layer 5 contains spinel powder, it is preferable to use spinel as the insulating material 4 as well. If the thickness of the insulating material 4 is too thick, the heat capacity will increase, and if it is too thin, the insulation will deteriorate.
It is estimated to be about 1000 μm.

As the electrode 7 for supplying electricity to the resistance layer, a conductive metal or ceramic is used. In addition to heat-resistant polyimide resin, the moisture-proof layer 8 may be made of a fluororesin such as polytetrafluoroethylene.

When manufacturing the heat roll of the present invention, it is convenient to use a thermal spraying method to attach the binder, insulating material, resistance layer, or electrode to the outer surface of the core.

Various known methods such as plasma spraying, flame spraying, and arc spraying can be employed as the thermal spraying method, but plasma spraying is suitable for thermally spraying ceramic powder. Note that, prior to thermal spraying, it is preferable to increase the surface roughness by subjecting the core surface to a crevice blasting treatment or the like.

Note that the material and the thickness of each layer in the explanation of FIG. 2 are merely examples, and the present invention is not limited thereto.

[A resistive layer containing one or more of the core alumina, magnesia, and spinel and a nickel chromium alloy can easily have a desired resistance value, and can have a uniform and appropriate thickness. It can be done. Moreover, this makes the resistance distribution of the resistance layer uniform and reduces the heat capacity. Along with this, a resistance layer is formed on the outer surface of the core,
It is possible to rapidly raise the temperature of the heat roll.

Furthermore, if the resistance layer is formed by thermal spraying, the adhesion strength of the resistance layer to the core body will be significantly increased.

This resistive layer may have a low temperature coefficient of resistance or a positive temperature coefficient of resistance, which allows the heat roll to be accurately held at a predetermined fusing temperature.

[Example] Examples will be described below.

Example 1 As shown in Figure 2, a binding material, an insulating material, a resistance layer, a fluororesin (polytetrafluoroethylene) layer, an electrode, and a moisture-proof layer were formed on the surface of a stainless steel (SUS430) core body, and a heat roll was applied. Manufactured. The binding material, insulating material, and resistance layer were formed by plasma spraying, the electrodes by flame spraying, and the resin by coating.

The specific conditions are shown below.

Core inner diameter 28mm outer diameter
30mm Length of body part 290.5mm Binding material N1-A-Mo alloy Ni89.5% A-text 5.5% Mo5.0% Thickness 5oI1. m Insulating material Spinel thickness 300μm Resistance layer Nickel chromium alloy 5% (Ni80
%, Cr2O%) Spinel 95% Thickness 170 gm Average particle size of powder before thermal spraying Nickel chromium alloy 25 m Spinel 25 m Fluororesin layer Thickness 200 μm Electrode
Cu-Zn alloy thickness 600J1. m width 4mm moisture barrier layer
The amount of power required to heat the resistive layer formed using polyimide resin having a width of 2 mm or more from room temperature to 200° C. was 600 W×1 minute. Further, although the temperature was repeatedly heated, the characteristics hardly changed.

Note that the temperature coefficient of resistance of this resistance layer is ÷f1. ? X 10-
'The temperature was ΩCm/℃.

Example 2 A heat roll was manufactured in the same manner as in Example 1, except that the blending ratio of the nickel chromium alloy and spinel constituting the resistance layer was varied.

Measure the specific resistance of the resistance layer of each heat roll. The results are shown in Figure 3.

From Figure 3, the specific resistance decreases as the nickel-chromium alloy content increases, especially when the nickel-chromium alloy content increases to 25%.
It is recognized that when the amount exceeds % by weight, the specific resistance becomes a considerably small value.

Example 3 A resistive layer was prepared with an average grain size of about 2511. 15% by weight of a nickel-chromium alloy of m and alumina powder with an average particle size of about 25 gm8
A heat roll was manufactured in the same manner as in Example 1, except that it was formed by plasma spraying using 5% by weight and that the alumina was coated with nickel chromium with a particle size of several μm, and the temperature coefficient of resistance of the resistance layer was measured. .

For comparison, titania (T i
A heat roll having a resistance layer formed in the same manner was manufactured using 02), and the temperature coefficient of resistance was measured.

These results are shown in FIG.

From FIG. 4, the resistance layer of the heat roll according to the present invention is +6
．． It is observed that it has a temperature coefficient of resistance of 7XIO-'Ωcm/°C. Further, it is recognized that the one using T i O2 has a negative temperature coefficient of resistance of -233X-'ΩCm/°C and a large absolute value.

[Effects] As described above, the heat roll of the present invention uses a nickel-chromium alloy and one or more oxides of alumina, magnesia, and spinel as the resistance layer formed on the outer surface of the core. A resistive layer having a desired resistance value can be easily formed, and a resistive layer having a uniform and appropriate thickness can be obtained. Then, it becomes possible to make the resistance distribution of the resistance layer uniform and to reduce the heat capacity of the resistance layer. Further, in combination with the fact that the resistance layer is formed on the outer surface of the core, the temperature of the heat roll can be increased rapidly.

Furthermore, in the heat roll of the present invention, the adhesion strength of the resistance layer to the core body is increased, and the temperature coefficient of resistance of the resistance layer near the fixing temperature is approximately 0 or positive, so that the heat roll can be accurately maintained at a predetermined fixing temperature. It is also possible to hold it.

[Brief explanation of drawings]

Figure 1 is an axial cross-sectional view of the heat roll, and Figure 2 is a cross-sectional view of the heat roll.
It is an enlarged view of the main part of the figure. Moreover, FIGS. 3 and 4 are graphs showing the measurement results of characteristics in the examples, respectively. 1... Heat roll, 2... Core body. 4... Insulating material, 5... Resistance layer.

Claims (4)

[Claims] (1) In a heat roll for a copying machine in which a resistance layer is provided on the outer surface of a cylindrical core, the resistance layer consists of one or more oxides of alumina, magnesia, and alumina/magnesia spinel, and nickel chromium. A heat roll for a copying machine, characterized in that it has a resistance layer comprising an alloy. (2) The copying machine according to claim 1, wherein the resistance layer is a resistance layer containing 5 to 25% by weight of a nickel-chromium alloy and 95 to 75% by weight of an oxide. heat roll. (3) A copy according to claim 1 or 2, wherein the resistance layer and the insulating layer are formed by plasma spraying, and the average particle size of the oxide powder for spraying is 10 to 50 μm. machine heat roll. (4) The heat roll for a copying machine according to any one of claims 1 to 3, wherein the resistance layer has a thickness of 50 to 500 μm.