JPS58168819A - Heater of glow plug - Google Patents

Abstract

PURPOSE:To improve the durability of the titled device by a method wherein a heater is formed in double helical shape by winding a pair of thin wires which extended forward with the proper insulating interval from the base bottom where said thin wire of a heat generating coil is folded. CONSTITUTION:The heater 1 of a glow plug is formed in double helical shape by winding a pair of heat generating wires which extended forward with the proper insulating interval from a base bottom 11a where a heat generating coil 11 is folded. The positive and negative pole side terminals T1, T2 are both extended from each forward end of said heat generating coil. Thereby, the straight parts for taking out the terminals from said heat generating coil can be provided at each low temperature part of the heater. Thus, the disadvantage of said heater is solved without decreasing of mass production efficiency. Further, because of the extreme minimanizing of the varation in thermal expansion between a sintering material 12 of surrounding silicone nitride, the durability of the heater can be improved without posibility of breaking of wire, even when the pre-heating speed is more increased by flowing of larger amount of electrical current in the heater.

Description

[Detailed Description of the Invention] Compared to other ceramics, silicon nitride sintered bodies have significantly superior thermal attack strength and hot fighting mechanical strength, and have high thermal conductivity. Alternatively, a heating wire made of thin wires of heat-resistant metal with a melting point such as Liao is inserted and pressure-molded into a columnar shape, and then sintered.The heating wire is drilled inside the heater. It is attracting attention as a heater for rapid preheating glow plugs that almost instantaneously raises the surface temperature to 100 to 10 OOC to start a diesel engine. There are 6 and 9 problems with exposing the surface of the solid.

In other words, a heating coil made of Wt or Mo! ! [Diameter/
Ii The round wire that is fired together with silicon nitride needs to be made thin, and usually a thin wire of about A-2 is used, and because of the relationship between the wire and the silicon nitride on the circumference, metal As used in sheathed heaters tightly packed in a chain, the heating wire is bent in the opposite direction from one end, passing through the center of the heating wire and exposed to the upper end surface of the silicon nitride sintered body. When a straight section is provided as a positive electrode side terminal, it is extended from the heating wire ring due to the difference in thermal expansion between the heating wire and the surrounding silicon nitride sintered body that occurs during expansion and contraction due to heating and cooling during use. The long straight part in the axial direction, especially the tip of the heater, is cut in the high temperature range.
A serious problem is that even when heaters are manufactured by hot pressing, it is common for wires to break during cooling.As a countermeasure for this, Q, which is made of the same material as the heating wire ring but twice the wire diameter,
In this case, we connected the wire rod with φ to one end of the heating wire by caulking it to one end of the heating wire as the edge of the positive electrode side, and inserted it upward through the center of the heating wire as before, in this case. could not solve the problem of lead wires breaking in the high temperature area near the connection with the heating wire ring below.

The above-mentioned disconnection was made by bending the heating coil from the center into a U-shape and inserting it straight from the front end of each of the heating coils in the U row facing upward while maintaining the insulation gap. One of the i1 portions is used as a positive electrode side terminal and is exposed on the upper end surface of the silicon nitride sintered body or on the outer surface close to the front end surface and connected to the center electrode, and the other is used as a negative electrode side terminal and is connected to the above positive electrode side terminal with an insulation interval. This can be solved by attaching I11 to the shaft hole of the metal shell by exposing it to the outer surface slightly below, but in this case, the winding diameter of the heat-generating ring will inevitably be small and the rigid W, Mo %
O^Melting Point Occupation Area Not only is coiling difficult, but silicon nitride, which is formed by digging and sintering heat-generating rings arranged in rows, has difficulty achieving uniform density, and the rate of temperature rise on the surface of the coils varies. There were other drawbacks. This can be improved to some extent by making the cross-sectional shape of the silicon nitride sintered body elliptical to correspond to the heating wires arranged in a row, but this is not an essential solution to O%. Special means were required to seal the shaped heater into the shaft hole of the metal shell, which resulted in another drawback that reduced mass productivity.

The present invention has succeeded in solving the above-mentioned problems in the heater for a diesel engine, in which a heat-generating coil made of thin wires of heat-resistant metal is bored into a columnar sintered body of silicon nitride. , will be explained with reference to the drawings.

In Figure 1, l is a thin wire of heat-resistant metal such as W or Mo, wound on a coaxial wire, and connected to the front end of each of the nine heat-generating rings 'l/, which is fixed and extends upward. A pair of large diameter lead wires made of the same heat-resistant metal /J,
, /Jl) and a sintered body of silicon 9 nitride by burying these /
A columnar heater consisting of J and one lead wire h above.
The positive terminal τ1 is exposed on the upper end surface of the lat heater IO.
Then, bend the other lead 41 above to expose it on the outer surface of the heater l with an insulating distance from the positive terminal /Ja, or use the pair of leads 41 /J&, /Jl) is omitted as fever-ring//
Stretch the front ends of the terminals forward and connect the positive and negative terminals Tl.
e Ts is directly formed, but in the present invention, the heat-generating ring Iio shape is folded in half, the folded part of the thin wire of heat-resistant metal is used as the base//a, and the insulating interval is maintained from this to the front. It is characterized by being formed by winding it in the same direction so that it has a double spiral shape with a pair of elongated thin wires, and such a heating wire ring becomes the base lla as shown in Fig. 2 in detail. The bent portion is fixed to a rod-shaped jig (not shown), and the base ii.

A pair of thin lines extending forward from the double chain line l/'.

The container is obtained by winding it around the above-mentioned jig, preferably keeping it parallel to each other at equal intervals and with the same bit in the same direction, as shown by it'.

Extend both front ends of the heating coil // thus formed into a straight line, or attach a pair of leads @ / to the front end of the heating coil //.
After connecting J, , /b, round to prevent oxidation of the parts exposed from the silicon nitride sintered body that will become the positive and negative terminals T1゜T1. Apply silicon nitride powder to cover these parts shallowly. After putting it on and filling it with Wi, sintering it by hot pressing or by the usual method of pressing and firing at room temperature, the above-mentioned shallowly rounded portions are polished to form both positive and negative terminals TI and T! is exposed to complete the manufacturing process as heater l.

In addition, #I1 in the upper part of the figure in the figure - 10 positive electrode side terminal T1 and by soldering &*a, the center electrode is fixed, and the above positive electrode 1
When the 6g terminal T1 is exposed on the outer surface close to the upper end surface of the heater l as described above, it is soldered by a large-diameter collar λ.

J is a metal shell that insulates and identifies the center electrode, and J is a metal shell J that is connected and fixed to the negative terminal T1 of the heater L by soldering B1.

This is a metal tube that connects the shaft hole J/ with a brazing joint Bj to seal the heater 7. Although the assembly structure of the heater 1 consisting of these center electrodes and metal tubes is not shown in the illustration, for example, the metal tube 7 is The lower part of the heater l can be freely brought into close contact with the heater l as a thin-walled bottomed tube, or the heater l can be protected by using fine powder of a thermally conductive material.

As described above, the glow plug heater of the present invention has a double spiral structure with a bent part of the heating wire made by folding the heating wire ring into two as a base, and a pair of heating wires extending forward from this with an insulation gap maintained. Since both the positive and negative terminals were extended from the front end of the heat-generating wire ring, the straight part for pulling out the terminals from the heat-generating ring, which is a weak point, can be easily removed without sacrificing mass productivity. is installed in the low-temperature region of the heater, and significantly reduces the difference in thermal expansion with the surrounding sintered silicon nitride, so even if a large current is passed through the heater to further increase the preheating speed, there is no risk of wire breakage, and durability is greatly improved. It has a great effect on improving.

[Brief explanation of drawings]

FIG. 7 is a longitudinal sectional view showing an embodiment of the present invention, and an enlarged front view illustrating a heat generating coil used in the present invention. l...Heater, //...Heating coil, //,...
Base, Lco...Silicon nitride sintered body, TI...Positive side terminal, T2...Negative side terminal Fig. 1 11a' Fig. 2

Claims (1)

[Claims] A heating wire made of a thin wire of a heat-resistant metal was implanted in a columnar silicon nitride sintered body, and both ends of the heating wire were exposed on the surface of the silicon nitride sintered body to form a pair of positive and negative terminals. The heat-generating wire ring is formed by winding a pair of thin wires in a double spiral shape using a folded portion of a fine wire folded in half as a base and extending forward from the folded wire with an insulating gap. glow plug heater.