JPS6026223A - Heat generating unit for use in glow plug - Google Patents

Abstract

PURPOSE:To obtain the titled heat generating unit for use in glow plug having a high starting speed and a long durability by forming an outer peripheral member by a heat resisting material and using as an inner part member a material having an electric resistance value at 1,000 deg.C which is more than three times the electric resistance value at normal temperature. CONSTITUTION:It is desirable that an alloy containing more than 10% or by weight of chromium, an alloy containing more than 15wt% thereof, or an alloy containing more than 20wt% thereof is used for the outer peripheral member. For example, as these alloys there are an iron group alloy and a nickel group alloy, for example. Between these alloys, the nickel group alloy is desirable in view of antioxidation, whereas the iron group alloy is desirable in view of the cost. As the interior member, a material which has an electric resistance value at 1,000 deg.C which is more than three times the electric resistance value at normal temperature, and in which crystal grains are difficult to grow for maintaining this characteristic for a long period of time, and which has an excellent ductility when the material is made into a complex material and subjected to elongation working is desirable. As a metal satisfying these characteristics, a nickel group metal is preferable.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a heating element for a preheating plug used for starting a diesel engine.

(Technical Background and Problems of the Invention) With the spread of diesel engines in recent years, preheating plugs with short starting times have been developed. As a result, it was found that in order to shorten the starting time, the heating element needs to have an electrical resistance value at 1000'C that is three times or more as compared to that at room temperature.

A nickel alloy consisting of nickel and 0.05 to 20% by weight of yttrium or zirconium has been developed as an alloy for heating elements that satisfies this condition.

However, this nickel alloy still has insufficient oxidation resistance. For example, when this alloy is measured by the thermal cycle test described below, its lifespan is 2,000 to 3,000 times. However, it is more desirable for the heating element to have a thermal cycle life longer than that, and a long-life heating element is desired.

(Object of the Invention) An object of the present invention is to provide a heating element having a long life as a heating element for a preheating plug that can start a diesel engine in a short time.

(Summary of the invention) In order to achieve the above object, the present invention comprises an outer peripheral member made of a heat-resistant material, and an internal member whose electrical resistance value at 1000°C is more than three times that of the electrical resistance value at room temperature. To provide a heating element for a glow plug, characterized in that it is made of a material.

In other words, by covering the internal member with the outer circumferential member, it is possible to provide a heating element that can extend the life of the internal member without reducing its function.

It is particularly important for this outer peripheral member to have acid resistance and heat resistance. Therefore, it is desirable to use an alloy containing chromium in an amount of 10% by weight or more, more preferably 15% by weight or more, and even more preferably 20% by weight or more for the outer peripheral material. This type of alloy includes, for example, iron-based and nickel-based alloys, and nickel-based alloys are preferred from the standpoint of oxidation resistance, while from the standpoint of price,
Iron-based alloys are preferred.

Examples of iron-based alloys include Fe-Or-Ni alloys and Fe-OrAl-based alloys, and examples of nickel-based alloys include nichrome alloys and Ni-Or-F alloys.
There are e-based alloys, etc.

As for internal members, the electrical resistance value at 01000°C is more than three times that at room temperature, and in order to maintain this property for a long period of time, (1) crystal grains are difficult to grow;

■When wire-drawing a composite material, it is desired that it has good ductility. Examples of metals that satisfy these characteristics include nickel-based metals.

Among the above properties, when placing particular emphasis on (1), pure nickel is desirable; when placing emphasis on property (2) and oxidation resistance, nickel-yttrium alloys and nickel-based alloys in which non-metallic compounds are dispersed are desirable. Examples of the nonmetallic compound here include oxides, nitrides, carbides, and ferrides. Comparing these alloys, the nickel-IJ alloy is easier to manufacture than the nickel-based alloy in which a non-metallic compound is dispersed because it can be manufactured by a casting method. -1 In terms of oxidation resistance, nickel-based alloys in which non-metallic compounds are dispersed are superior.

As mentioned above, the outer peripheral member and internal member of the heating element are
Each has its own characteristics. Therefore, by appropriately selecting the outer circumferential member and the inner member, a long-life heating element having respective characteristics can be manufactured.

The heating element of the present invention can be obtained, for example, as follows. A bar material as an internal member and an electric resistance welded tube as an outer peripheral member are prepared. Next, after degreasing and cleaning the surface of the bar and the inner surface of the ERW tube, the bar is inserted into the ERW tube.

Thereafter, the material is subjected to area reduction processing by rolling or the like.

By repeating the area-reducing process and annealing in this process, the heating element of the present invention can be manufactured by reducing the area to a desired diameter.

(Example of the invention) Next, the present invention will be explained in detail.

Heating elements having the compositions shown in the table were manufactured, and each was made into a 0.27 tnml round wire by rolling processing, and the electrical resistance and thermal cycle life at a predetermined temperature were measured.

Thermal cycle life is 1250'C2 seconds heating in air 2
Repeated heating measurements of air cooling for seconds were performed, and the number of times of breakage was measured. Furthermore, regarding the 6()1 constant result of the comparative example, the first
Also listed in the table.

As can be seen from this table, each Example (3, 45, 6) and each Comparative Example (1, 2) has a resistivity of 1000 at 20°C.
The value of resistivity is more than three times that of ℃. Therefore, the example (
Sample No. 34.5.6) starts the diesel engine in about the same short time as the comparative example (Sample No. 1 and 2).

On the other hand, in the thermal cycle test, as shown in the table, the lifespan of the examples (sample numbers 3, 4, 5, and 6) was significantly longer than that of the comparative examples (sample numbers 1 and 2). I understand that.

Therefore, it can be seen that, as a heating element for a tasel engine, the present invention is not only a scale that can start a tasel engine in a short time, but also has a significantly improved lifespan and is an industrially useful invention.

Blank space below (effects of the invention) The present invention has an outer peripheral member made of a heat-resistant material, and an inner member made of a heat-resistant material.
By using a material whose electrical resistance value at 000° C. is three times or more as compared to the electrical resistance value at room temperature, it is possible to provide a heating element for a glow plug that has a fast starting speed and a long life.

Representative patent attorney Kensuke Chika (and 1 other person) 11

Claims (1)

[Claims] 1. The outer peripheral member is made of a heat-resistant material, and the inner member is made of a 100%
A heating element for a glow plug, characterized in that it is made of a material whose electrical resistance value at 0°C is three times or more as compared to the electrical resistance value at room temperature. 2. The heating element for a glow plug according to claim 1, wherein the heat-resistant material is a heat-resistant alloy containing 10% by weight or more of chromium. 3. The heating element for a glow plug according to claim 2, wherein the heat-resistant alloy is a nickel-based alloy. 4. The heating element for a glow plug according to claim 2, wherein the heat-resistant alloy is an iron-based alloy. 5. The heating element for a glow plug according to claim 1, wherein the internal member is made of substantially pure nickel. 6. The heating element for a claw plug according to claim 1, wherein the internal portion # is a nickel-yttrium alloy. 7. The heating element for a glow plug according to claim 1, wherein the internal member is a nickel-based alloy in which a nonmetallic compound is dispersed.