JPH0139015B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a glow plug used for preheating the sub-combustion chamber or combustion chamber of a diesel engine, in which two types of heating elements are incorporated in the glow plug to function as a self-temperature control type. Regarding connection method.

In general, diesel engines have poor starting performance at low temperatures, so by installing a glow plug in the auxiliary combustion chamber or combustion chamber and passing an electric current through it to generate heat, it is possible to raise the intake air temperature or use it as an ignition source to start the engine. Methods are being used to improve sexual performance. By the way, what is required of this type of glow plug is that it can function as a quick heating type by supplying a large amount of power to the heating element built inside at the initial stage of energization to improve its temperature rise characteristics and to function as a fast heating type. In order to prevent melting of the body, the saturation temperature is set to an appropriate value to prevent overheating, and stable heat generation characteristics can be obtained. It is possible to satisfy the performance such as guaranteeing the performance.

In the conventionally well-known general sheath type glow plug, in which a heat-resistant metal sheath is filled with heat-resistant insulating powder and a coiled heating element made of a type of material such as nickel is buried, the power supplied to the glow plug is is limited to prevent adverse effects on various parts including the heating element, which poses a problem in terms of temperature rise characteristics, and in order to function as a fast heating type,
In order to prevent overheating of the heating element, it is necessary to provide a separate temperature control means, which has the drawback of increasing the cost of the entire device.

In addition, glow plugs have been proposed that use heating elements made of two different materials with different temperature coefficients of resistance, in order to improve the above-mentioned temperature rise characteristics and have self-temperature control means. Although this kind of structure functions as a fast-heating type to some extent, it is difficult to manufacture and expensive, and its heat generation characteristics are not good, so it is difficult to say that it can satisfy all of the above-mentioned performances. Ta. This is because this kind of traditional glow plug,
A heating element with a small temperature coefficient of resistance is provided on the tip side, and a heating element with a large temperature coefficient of resistance is provided on the rear side, and the resistance fluctuation due to temperature change of the rear heating element is used to make the heating element on the tip side immediately after energization. However, since both heating elements are placed too close to each other, the temperature of the heating element on the rear end rises too quickly due to the thermal influence from the front end. This is because the power supplied to the tip side is controlled. Due to these problems, it lacked heat generating properties and was unable to exhibit its effectiveness as a rapid heating type.

For this reason, the present inventors conducted various research and development to effectively utilize the advantages of using a heating element made of two types of materials as described above. Paying attention to the fact that because they are placed so close together, they are affected by heat, which shortens the time for large current to flow in the initial stage of energization.
As a solution to this problem, the patent application
No. 65994, we first proposed an inexpensive glow plug for diesel engines that has excellent heat generation characteristics that are stable and quick to heat up.

To briefly explain this using FIGS. 1 and 2, reference numeral 1 in the figure is a sheath made of a heat-resistant metal material such as stainless steel, 2 is a housing that holds this sheath 1 at the tip, and this housing 2 An electrode rod 4 is concentrically attached to the rear end of the electrode rod 4 via an insulating bush 3, and the tip of the electrode rod 4 is inserted into the sheath 1.

In the inner space on the distal end side of the sheath 1,
A first spiral heating element 5 (hereinafter referred to as the first heating element) made of a conductive material with a small temperature coefficient of resistance, such as iron chromium or nickel chromium alloy, is disposed along the axial direction. One end is electrically connected to the sheath 1.

Further, in the inner space on the rear end side of the sheath 1, a nickel or carbon content of, for example, 0.25% is provided between the first heating element 5 and the electrode rod 4 on the rear end side of the sheath 1. A second spiral heating element 6 (hereinafter referred to as the second heating element) formed of a conductive material with a large temperature coefficient of resistance such as the following low carbon steel (hereinafter referred to as low carbon steel) is disposed, and The heating elements 5 and 6 are embedded in the sheath 1 with heat-resistant insulating powder 1a such as magnesia. Here, the second heating element 6 not only acts as a heat generation source itself, but also supplies a large amount of electric power to the first heating element 5 because its resistance value is small immediately after the start of energization. It is possible,
In addition, the resistance value increases as the energization time elapses, reducing the power supplied to the glow plug, thereby keeping the saturation temperature of the glow plug itself low and also functioning as a temperature control means to prevent overheating.

In the above-described configuration, the first and second heating elements 5 and 6 are connected such that their spiral portions face each other with a predetermined gap. That is, by providing a certain gap between the spiral portions of both heating elements 5 and 6, the conventional problem of thermal influence from the first heating element 5 on the tip side on the second heating element 6 can be avoided. This allows the time interval to be maintained, thereby temporally delaying the current control by the second heating element 6, extending the time for supplying large power to the first heating element 5, and rapidly making the first heating element 5 red-hot, resulting in temperature rise characteristics. This makes it possible to significantly improve the

In the figure, reference numeral 1b denotes a guide rod made of a heat-resistant insulating material such as ceramic, which is disposed to penetrate through both the heating elements 5 and 6 and hold them in a predetermined position.
In addition to improving the ease of assembling both heating elements 5 and 6,
This is useful for properly maintaining the gap between the above-mentioned heating elements 5 and 6 and for stabilizing the heat generation characteristics.

Further, the above-mentioned heating elements 5 and 6 are connected in such a manner that heat transfer within the gap is minimized. As shown in FIG. 2, the connection structure is as shown in FIG.
The end surfaces of linear end portions 5b and 6b extending in the axial direction from a and 6a, respectively, are brought into contact with each other at their intermediate portions, and connected by plasma arc welding or the like, or as shown in FIG. It is considered that the linear ends 5b and 6b are overlapped and connected by spot welding or the like.

However, in the glow plug configured as described above, each linear end 5 of both heating elements 5, 6
Some problems have arisen in connection of b and 6b. That is, when the end faces of the straight end portions 5b, 6b of both heating elements 5, 6 are joined together and welded by plasma arc welding or the like, the welded portion 7 is closer to the heating elements 5, 6 as shown in FIG. There is a risk that the heat-generating elements 5 and 6 may easily protrude outside and come into contact with the inner wall of the sheath 1, and furthermore, the wire diameters and outer diameters of both heating elements 5 and 6 are quite small, making welding work difficult. There were flaws.

Moreover, the linear ends 5b, 6b of both heating elements 5, 6
As is clear from Fig. 5, when they are overlapped within a predetermined gap (GAP) and connected by spot welding, as shown in Fig. 6a, the electrodes are inserted from both sides of the overlapping part. It is necessary to bring the electrodes 8a and 8b into contact with each other, but since the wire diameters of both the heating elements 5 and 6 are small, as shown in FIG.
If the two heating elements 5 and 6 are sandwiched together at point b, the positions of both heating elements 5 and 6 will be shifted from each other, making it difficult to weld. This poses a problem in terms of workability and reliability during welding. There was a drawback that it was difficult to maintain the concentricity of the heating elements 5 and 6.

The present invention has been made in view of the above circumstances, and the straight part extending from the end of the spiral part of one heating element is overlapped with the end of the spiral part of the other heating element so as to intersect with each other. By welding the overlapping parts, it is possible to easily and reliably weld and connect both heating elements, greatly improving workability and reliability during welding. The present invention provides a method for connecting a heating element of a glow plug for a diesel engine, which makes it possible to maintain the concentricity of the glow plug.

Hereinafter, the present invention will be explained in detail using embodiments shown in the drawings.

Figures 7a and 7b show an embodiment of the heating element connection method according to the present invention, and in these figures, the same or corresponding parts as in Figures 1 to 6 are designated by the same numbers. ing.

Now, according to the present invention, in order to connect the first and second heating elements 5 and 6 with a predetermined gap between the spiral parts, the spiral part end 5a of one heating element 5 is extended from the spiral part end 5a. A straight end 5b as a straight part is formed by extending to the side of the other heating element 6, and the tip of this straight end 5b intersects the spiral end 6a of the other heating element 6. They are unique in that they are overlapped like this, and the two are welded at this overlapped part.

According to such a configuration, since the connecting portions of both heating elements 5 and 6 are positioned so as to intersect with each other, for example, even if the electrodes 8a and 8b are brought into contact with each other from both sides, it will not work as in the conventional case. This eliminates the problem of misalignment of the connecting parts due to the small wire diameter, and allows the heating elements 5 and 6 to be connected by simple and reliable welding. In addition to greatly improving workability and reliability during welding, it also becomes possible to maintain the concentricity of both heating elements 5 and 6, which is a great advantage.

Further, according to the present invention, it is only necessary to extend the linear end portion 5b from one heating element 5, and the other heating element 6 does not require any processing. The forming process of the straight end 5b from one side is simplified, and the required gap length can be reduced by forming the straight end 5b from one side.
Since it can be obtained by using only a single method, the precision can be made stricter, and it can be more effective in improving the heat generation characteristics of the glow plug.

In addition, in the embodiment described above, the straight portion 5b is
However, on the contrary, the second
Of course, a straight portion may be provided on the side of the heating element 6, and furthermore, the direction in which this straight portion extends does not necessarily have to be parallel to the axial direction of the heating elements 5, 6.

Furthermore, as shown in FIGS. 8a and 8b, the spiral end 6a of the other heating element 6 is bent slightly inward, and the straight end 5b from the one heating element 5 is formed at this portion. It goes without saying that the two may be connected with their tips facing each other.

In addition, in the above-mentioned embodiment, in order to weld and connect both heating elements 5 and 6, the case of spot welding is described in which the overlapped portions are held and welded from both sides by electrodes 8a and 8b. However, it will be easily understood that the present invention is not limited to this, and that the above-mentioned effects can be obtained even if various welding methods such as plasma arc welding and laser beam welding are employed.

As explained above, according to the method for connecting heating elements according to the present invention, the straight part extending from the end of the spiral part of one heating element and the end of the spiral part of the other heating element are overlapped so as to intersect with each other. Since both heating elements are welded together at this overlapping part, it is possible to easily and reliably weld and connect both heating elements, which is superior in terms of workability and reliability during welding. It is also possible to maintain the concentricity of the heating elements, and as a result, by providing a predetermined gap between the spiral portions of both heating elements, it is possible to easily and inexpensively provide a glow plug that has stable, rapid heating characteristics. It has a great effect of gaining. Particularly, according to the present invention, the effect can be exhibited when both heating elements are connected by spot welding.

[Brief explanation of drawings]

Figure 1 is a longitudinal cross-sectional side view of a glow plug for diesel engines that can exhibit excellent heat generation characteristics by providing a gap between two types of heating elements, Figure 2 is an enlarged view of its main parts, and Figure 3 is a view of both heat generating elements. Figures 4, 5 and 6 a and b showing modified examples of body connection parts
7A and 7B are side views of essential parts showing an embodiment of the heating element connection method according to the present invention, and its - line. The cross-sectional views of FIGS. 8a and 8b show another embodiment of the invention. DESCRIPTION OF SYMBOLS 1... Sheath, 2... Housing, 4... Electrode rod, 5... First heating element, 5a... Spiral part end, 5b... Straight end (straight part), 6... Second
heating element, 6a... its spiral end, 8a, 8b...
…electrode.

Claims (1)

[Claims] 1. A first helical heating element and a second helical heating element made of a material with a larger positive temperature coefficient of resistance than the first helical heating element are connected with a gap between the respective helical parts. A method for connecting heating elements that are connected at the same time, the straight part extending from the end of the spiral part of one heating element and the end of the spiral part of the other heating element are overlapped so as to intersect, and this overlapping part is welded. A method for connecting a heating element of a glow plug for a diesel engine, characterized by: