JPS6218707Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) The invention aims to improve the temperature rise characteristics of the sheathed heat generating part of a glow plug for a diesel engine.
This relates to a glow plug designed to improve engine output.

(Prior technology) Glow plugs currently in general use as glow plugs for diesel engines are
As described in Publication No. 46-31293, a heating wire is placed inside a heat-resistant metal pipe, and the space between the heating wire and the heat-resistant metal pipe is tightly filled with heat-resistant electrical insulating powder and fixed. The sheath type heat generating part of the glow plug is configured by the above.

(Problem to be solved by the invention) However, in the glow plug with the above configuration, the heating wire itself is not exposed to the high temperature combustion gas atmosphere in the combustion chamber of the engine, so it has an advantage in terms of durability. On the other hand, when a glow plug generates heat due to energization, there is a time delay until the temperature generated in the heating wire is transmitted to the heat-resistant metal pipe via the heat-resistant electrical insulating powder, so the temperature of the sheath-shaped heat-generating part of the glow plug rises slowly. It was hot.

In addition, glow plugs are essentially unnecessary once the engine has started, but because they protrude into the combustion chamber of the engine, they have poor mixing properties between air and fuel, inhibiting the formation of an air-fuel mixture, and thus inhibiting combustion. The drawback was that the efficiency deteriorated and the original output was not produced.

(Means for Solving the Problem) The present invention is equipped with a sheath-type heating section configured by sealing a heating wire together with heat-resistant electrical insulating powder inside a heat-resistant metal pipe. The glow plug has a structure in which the outer diameter is narrow and the root region excluding the tip region is thicker than the tip region, and this plug is attached to a diesel engine so that the tip region of the plug is inside the combustion chamber of the engine. The combustion chamber is made to protrude and the root region is made to face the mounting hole in the wall of the combustion chamber through a gap.

(Embodiment) The present invention will be described below with reference to an embodiment shown in the drawings. In FIG. 1, reference numeral 1 denotes a pipe made of a heat-resistant metal such as stainless steel, and has a shape in which one end is open and the other end is closed. Reference numeral 2 denotes a coiled heating wire made of nichrome wire or the like, and one end of the heating wire 2 is joined to the inside of the closed end of the heat-resistant metal pipe 1 by welding or the like. Reference numeral 3 denotes a heat-resistant electrical insulating powder made of magnesia or the like, which is densely filled in the space between the heat-resistant metal pipe 1 and the heating wire 2 to form the sheathed heating section 7. Reference numeral 4 denotes a center shaft made of heat-resistant metal, one end of which is joined to one end of the heating wire 2 by welding or the like, while the other end is electrically connected to a terminal nut 5 to which a lead wire is connected from a power source (not shown). The above-mentioned sheath type heat generating part 7
As shown in FIG. 3, the tip region 1a protruding into the swirl-type combustion chamber 8 of the diesel engine is narrowly narrowed to an outer diameter of 3 mm, for example, and the other root portion 1b excluding this tip region For example, outer diameter 5
It is thickened to mm. As shown in FIG. 3, this root region 1b faces a mounting hole in the wall of the cylinder head 12 of the combustion chamber 8 through a gap. Reference numeral 6 denotes a plug body for attaching a glow plug, and the heat-resistant metal pipe 1 is bonded and fixed to the plug body 6 by brazing or the like. In addition, in FIG. 3, 9 is a fuel injection valve, 10 is a communication hole,
Reference numeral 11 indicates a main combustion chamber, and reference numeral 13 indicates a housing of the combustion chamber.

Next, to explain the operation of the glow plug of the present invention having the above structure, when the preheating energization is started, the current led from the power supply (not shown) flows from the terminal nut 5 to the heating wire 2 via the center shaft 4. It flows through the heat-resistant metal pipe 1 from the stopper 6 to the engine ground. The heat generated by the sheathed heat generating part 7 due to energization is as follows:
The heat generated in the heating wire 2 is transferred to the heat-resistant metal pipe 1 through the heat-resistant electric insulating powder 3, and the heat can be transferred in a short time according to the present invention. To explain this relationship using the experimental numerical characteristic diagram shown in Figure 2, the temperature curve of the straight-shaped sheathed heat generating part (outer diameter 5 mm) of the conventional glow plug is curve b, and the temperature curve of the seeded glow plug according to the present invention is curve b. Mold heating part (tip outer diameter 3mm)
The temperature curve will be the temperature curve or the a curve.Compared to this, the time from the start of energization to reaching 800℃ is 15
It can be seen that the present invention saves about 7 seconds, which is 8 seconds. In addition, in an engine output characteristic experiment, when tests were conducted using a diesel engine with the structure shown in Figure 3 using the conventional glow plug and the invented glow plug with the above-mentioned dimensions, the invented glow plug had a lower output than the conventional one. We confirmed that it can be uploaded.

It goes without saying that the glow plug of the present invention can also be applied to diesel engines having structures as shown in FIGS. 4 and 5. This figure 4 and 5
In the figure, the same reference numerals as in FIG. 3 indicate the same configurations as in FIG.
6 is a combustion chamber, and 17 is a piston.

In the above embodiment, the outer diameter of the part of the sheathed heat generating part protruding into the combustion chamber was set to 3 mm.
It is clear that the thinner the material, the more effective it will be.
Further, although the entire portion of the sheathed heat generating portion that protrudes into the combustion chamber is made thinner, it is of course possible to make a portion of that portion thinner.

According to experiments by the present inventor, it was found that the size of the tip region 1a of the sheathed heat generating section 7 should be 80 to 50% of the size of the root region 1b. 80
If the pre-combustion time of the glow plug exceeds 50%, the pre-combustion time of the glow plug is about the same as that of conventional glow plugs, and if it falls below 50%, the coil-shaped heating wire 2 may be crushed or come into contact with the inner wall of the pipe 1, causing electrical damage. Insulation becomes defective.

(Effects of the Invention) As described above, the glow plug of the present invention has a sheathed heat generating section in which the outer diameter of the tip region protruding into the combustion chamber of the diesel engine is made thinner than the other root region. Because the heat generated by the heating wire of the mold heating part can be quickly transferred to the heat-resistant metal pipe, the temperature of the sheathing force heating part rises extremely quickly, which reduces the preheating time of the glow plug required to start the diesel engine. This has the effect of making it shorter. In addition, by reducing the outer diameter of the sheathed heat generating part, the volume of the part that protrudes into the combustion chamber of the diesel engine is reduced, improving the mixing of fuel and air, thus improving combustion efficiency and increasing output. This has the effect of improving fuel efficiency.

Furthermore, in the present invention, the root region of the glow plug has a larger outer diameter than the tip region, and since the root region faces the plug mounting hole through the gap, the root region has a large heat capacity, and the heat of the root region is difficult to be absorbed by the inner wall of the plug mounting hole, so the root region is maintained at a high temperature, so that the temperature of the tip region following the root region is This has the effect of suppressing the decline.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an embodiment of the glow plug for diesel engines according to the present invention, Fig. 2 is a characteristic diagram explaining the effects of the present invention, and Figs. FIG. 3 is a cross-sectional view showing an example of how the plug is attached. 1...Heat-resistant metal pipe, 2...Heating wire, 3...
...Heat-resistant electric insulating powder, 7...Seed-type heat generating part, 8
... Vortex type combustion chamber, 14 ... Pre-combustion chamber, 16 ...
combustion chamber.

Claims (1)

[Scope of utility model registration request] It is equipped with a sheath-shaped heating section consisting of heat-resistant electrical insulating powder and heat-generating wires sealed inside a pipe made of heat-resistant metal. The glow plug has a structure in which the tip region is thicker than the tip region, and when this plug is attached to a diesel engine, the tip region of the plug projects into the combustion chamber of the engine, and the root region extends into the combustion chamber. A glow plug device for a diesel engine, characterized in that it faces a mounting hole in a wall through a gap.