JPS6029853B2 - How to assemble glow plugs - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for assembling a glove lug for a diesel engine, and more particularly to a method for assembling a globe lug in which a ceramic heater is attached to the tip of the globe lug via a metal protection pipe.

Generally, a diesel engine is provided with a globe lug in the combustion chamber for the purpose of improving startability.

In recent years, ceramic glove lugs have been used to improve the reliability of these glove lugs.

As shown in Fig. 1, this ceramic globe lug P has a heater 3 fixed to the tip of a hollow metal plug via a metal protection pipe 2, and is embedded in the heater 3. One end of the heating element made of a metal wire is grounded to the plug housing 1, and the other end is connected to the lead wire 5. The lead wire 5 is formed by bundling a large number of sacrificial conducting wires, and the outer periphery of the lead wire 5 is protected by a sleeve 6 made of an insulating heat-resistant material and connected to an external connection terminal 7.

8 is an insulating protection member, which connects the external connection terminal 7 with a plug/.
The terminal 7 is electrically insulated, and a nut 9 is screwed onto a screw formed at the end of the terminal 7 to connect the conductor.

Now, when assembling the glove lug, a heater 3 with a built-in heating element is prepared, this heater 3 is joined to the metal protection pipe 2 by silver brazing, and then this protection pipe 2 is plugged. The housing 1' was joined using the same silver brazing process.

However, the method of silver brazing between ceramic materials and metal pipes requires advanced technology, and depending on variations in the material and manufacturing method, brazing may be incomplete. If this metal pipe is brazed to a plug housing after the brazing treatment, there is a drawback that the airtightness of the brazed portion between the ceramic and the metal pipe is reduced due to the influence of the heat.

Therefore, when a globe lug with reduced airtightness is attached to a swirl chamber type combustion chamber of a diesel engine, there is a problem in that gas inside the cylinder leaks. Furthermore, ceramic materials have almost no change in volume even at high temperatures during brazing, but metal protective pipes thermally expand at high temperatures during brazing and shrink when cooled after brazing, so the above-mentioned glove The problem with the lugs was that after the brazing process, the ceramic heater was tightened against the metal protection pipe, which caused compression cracks to easily occur, reducing the durability and reliability of the globe lugs.

This invention was made in order to eliminate the drawbacks of the conventional globe lugs having ceramic heaters, and its purpose is to connect ceramic heaters and metal protection pipes with a small gap between them. By brazing the joint between the protective pipe and the plug housing, the former is brazed at a high temperature and the latter at a lower temperature, and by assembling with a temperature difference during brazing. An object of the present invention is to provide a glove lug that has high airtightness at a brazed joint and is free from compression cracks.

The present invention, which achieves the above object, is a method of assembling a globe lug for preheating a diesel engine, in which a ceramic heater is attached to a plug housing via a metal protection pipe, and the diameter is 0. The ceramic heater is inserted into a metal protection pipe having a large inner diameter inside and outside on the 18th side so that the gap is almost uniform, and the step part is joined using a brazing material with a high melting point. Insert the pipe into the plug housing and
The brazing material is characterized in that the brazing material has an internal and external melting point lower than that of the brazing material by 200q○ to join them together. Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is an enlarged partial sectional view of the main part of the tip of a glove lug P showing an embodiment of the present invention.

In this invention, in order to protect the ceramic heater 3 at the tip of the globe lug P, the heater insertion hole 2a of the metal protection pipe 2 interposed between the heater 3 and the plug housing 1 is inserted into the heater 3. The heater 3 is formed into the same shape, which is slightly larger than the outer peripheral shape, so that when the heater 3 is inserted into the insertion hole 2a, the gap Q between the two is in the range of 0.18±17.

In this invention, no particular gap is provided at the joint between the metal protection pipe 2 and the plug housing 1, but if necessary, a gap smaller than the gap Q, for example, a slight gap between the inside and outside of the 0.07 willow. It may be provided. The method of the present invention for assembling the glove lug P configured in this way is to first fit the metal protection pipe 2 into the ceramic heater 3 so that the gap Q is uniform, and then fit the metal protection pipe 2 into the ceramic heater 3. The stepped portion A of the protective pipe 2 and the protective pipe 2 are welded by silver brazing. The brazing material used here has a relatively high melting point.
Next, this protective pipe 2 to which the heater 3 has been joined is inserted into the plug housing 1, and the B portion is welded by silver brazing using high frequency or the like in the same manner as described above.

At this time, since the brazing process is performed between metals, it is sufficient to use a material with a relatively low melting point.
The brazing material used for brazing the and protective pipe 2 is more fused.
Use one with a score about 200q0 lower. Therefore, due to the brazing temperature difference of 2000C at the time of joining, in the method for assembling the globe lug P of the present invention, due to the influence of heat during the brazing process between the protective pipe 2 and the plug housing, the brazing process is performed first. The brazing between the ceramic heater 3 and the protection pipe 2 does not change (deteriorate), and the airtightness of the brazing portion of the heater 3 and the protection pipe 2 is not impaired. Furthermore, since a gap exists between the ceramic heater 3 and the metal protection pipe 2 even after the globe lug is assembled, thermal deformation of the protection pipe 3 is absorbed by this gap, and compressive stress is applied to the ceramic material. This prevents compression failure of the ceramic heater.

As explained above, in the present invention, in the assembling method of a globe lug in which a ceramic heater is attached to a plug housing via a metal protection pipe, there is a small gap between the heater and the protection pipe that takes into account the thermal shrinkage of the metal protection pipe. In addition to providing a gap, the brazing temperature in this gap is approximately 200 OO higher than the brazing temperature in the joint between the protection pipe and the plug casing, thereby improving the airtightness of the brazed part. Furthermore, since the ceramic material is not subjected to thermal stress, there is no gas leakage from the brazed joint when the globe lug according to the method of the present invention is installed in a diesel engine, and the reliability of the globe lug is maintained. This has the effect of improving durability and durability.

[Brief explanation of drawings]

FIG. 1 is a side sectional view showing a schematic structure of a glove lug equipped with a ceramic heater, and FIG. 2 is an enlarged partial sectional view of the main part of the tip of the glove lug showing an assembly method of the present invention. 1... Plug housing, 2... Protective pipe, 3... Ceramic heater, P... Globe lug,
Q: Gap, A, B: Brazed portion. Figure 1 Figure 2

Claims (1)

[Claims] 1. A method for assembling a glow plug for preheating a diesel engine, in which a ceramic heater is attached to a plug housing via a metal protection pipe, the glow plug being made of metal and having an inner diameter that is 0.18 mm larger inside and outside than the outside diameter of the ceramic heater. Insert the ceramic heater into the protection pipe so that the gap is almost uniform, and join the step part using brazing material with high spacing, and then insert the metal protection pipe into the plug housing. , 200℃ higher than the brazing material
A method for assembling a glow plug characterized by joining the inner and outer parts using brazing material with a low melting point.