JPS602455Y2 - Ceramic glow plug - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement of a ceramic glow plug used as a starting aid for diesel engines and the like.

Recently, in glow plugs used as a starting aid for diesel engines, etc., the heating element is made of ceramic material, and a heating element that is more powerful than metals such as tungsten, which has excellent heat resistance and rapid heating properties, is printed inside. Buried ones are being tried.

However, as shown in FIG. 1, this type of ceramic glow plug 1 has its heating element 4 attached to the plug body 2 via a heat-resistant metal protective tube 3; There is a drawback that the heating element 4 is easily damaged due to the difference in thermal expansion coefficient between the manufactured heating element 4 and the protective tube 3, thermal stress, external mechanical stress, etc.

Note that 5 indicates a heating element embedded inside the heating element 4.

Furthermore, in Japanese Utility Model Publication No. 39-6610, an insulator 4 with a center shaft 5 (center electrode rod) fixed is housed in the metal shell 1, although not between the protective tube and the ceramic heating element. A preheating plug for a diesel engine is described in which a heat-resistant powder 6 is interposed between the two and sealed and fixed.

This heat-resistant powder is thought to be filled in to protect the insulator 4 from external mechanical forces, and the filling is performed by caulking the upper end of the metal shell 1.

As described above, if the metal shell 1 is simply caulked, there is a risk that rainwater or water droplets from the car wash may enter from the outside, solidify the powder, and cause the powder to lose its function as a cushioning material.

Furthermore, when the heat-resistant powder 6 is simply sealed between the insulator 4 and the metal shell 1, the temperature difference between the two is small, so even though it can act as a mechanical buffer, it has little effect as a thermal buffer. I can't wait.

The present invention aims to overcome the above-mentioned drawbacks and provide a durable and reliable ceramic glow plug.

An example of this will be described below with reference to FIG.

Fig. 2 shows a side cross section of the main part of the ceramic glow plug 10 according to the present invention, and in the figure, 40 is a heating element made of a ceramic material and having a heating element 50 embedded therein by printing or the like. , the plug body 2 on its outer periphery
A heat-resistant metal protection tube 30 having an inner diameter moderately larger than the outer diameter of the heating element 40 is fitted on the zero side, and a heat-insulating heat-resistant material such as magnesium oxide or ceramic material is inserted into the gap formed between them. A metal sealing material O2 is filled at both ends of the powder-filled part.
Rings 71 and 72 are fitted, and the protection tube 30 is caulked 31 and drawn 32 on the outside thereof, so that the powder 60 is enclosed.

The front end 33 of the protective tube 30 is extended appropriately from the constricted portion 32, and is rounded to prevent the heating element 40 from breaking.

Since the ceramic glow plug according to the present invention is constructed as described above, when it is installed and used in a diesel engine or the like, it has the following functions and effects.

That is, since the coefficient of thermal expansion of the metal protective tube 30 is larger than that of the ceramic heating element 40, the protective tube 30 receives high heat from the heating element 40 and the combustion gas in the combustion chamber during engine operation. When the engine is stopped, the protective tube 30 contracts as the engine cools and applies tensile stress to the heating element 40, causing tensile cracks and shrinkage cracks, respectively. However, due to the presence of the powder 60, the thermal stress as described above is absorbed and relaxed, and damage to the heating element 40 is prevented.

In addition, the heating element 40 is mainly caused by vibrations during engine operation.
Since the external mechanical stress is also absorbed and relaxed by the powder 60, there is an advantage that the damage prevention effect of the heating element 40 can be further improved.

Furthermore, since metal sealing materials (O-rings 71 and 72) are fitted to both ends of the powder light bulb, leakage of the powder 60 can be prevented.

In particular, leakage toward the combustion chamber side where the tip side of the heating element 40 protrudes causes increased wear on the cylinder bore and cylinder liner. Therefore, preventing the powder 60 from leaking improves the durability and reliability of the engine. It has the effect of further improving the

Further, the metal sealing material has the effect of preventing infiltration of liquid droplets such as unburned portions of the injected fuel from the injection nozzle, suppressing solidification and qualitative deterioration of the powder 60, and has the effect of suppressing the solidification and qualitative deterioration of the powder 60. This also has the effect of preventing the infiltration of the sintering gas and preventing the functional deterioration of the powder due to carbon contamination.

Therefore, the effect of preventing damage to the heating element 40 is significantly increased, so that it is possible to provide a durable and reliable ceramic glow plug.

[Brief explanation of drawings]

Figure 1 is a side sectional view of a conventional ceramic glow plug.
FIG. 2 is a side sectional view of the main parts of the glow plug according to the embodiment of the present invention. 10; Ceramic glow plug, 20; Plug body,
30; protection tube, 40; heating element, 50; heating element,
60: Powder made of heat-resistant material, 71.72: O-ring of metal sealing material.

Claims (1)

[Scope of utility model registration request] A protective tube is attached to the plug body, a gap is provided between the protective tube and the outer circumference of the ceramic heating element, the gap is filled with powder made of a heat-resistant material, and the powder-filled portion is A ceramic glow plug characterized by having metal sealing material fitted on both ends.