JPS6029837Y2 - Creeping discharge type spark plug for internal combustion engine - Google Patents

Description

[Detailed description of the invention] This invention consists of a central electrode shaft of a spark plug, an insulator that is tapered in the axial direction, and is slightly recessed from the tip of the center electrode to secure the center electrode shaft. The tip of the threaded part, which holds the insulator in the stepped part in the shaft and has the mounting screw carved on the outside in the axial direction, is inside the threaded hole for installing the spark plug provided in the wall of the combustion chamber of the internal combustion engine. A spark plug mounting bracket that can be installed at a position slightly recessed from the position of the opening end, and an insulating wall of the insulator ignition part that is separated from the inside of the mounting bracket in a radial direction and is installed opposite to the center electrode. The present invention relates to a creeping discharge type spark plug for an internal combustion engine, which is provided with a ground electrode provided as described above.

Conventionally, as shown in Figures 1 and 2, the center electrode and the insulator firing part protruded too much, so they received a lot of combustion gas,
They had drawbacks such as poor ignition and lack of durability due to a large amount of deposits and carbon adhesion, or due to the adhesion of excessively rich mixed fuel due to accelerator operation.

In order to eliminate these drawbacks, the present invention creates a long and narrow space, that is, a gas volume, between the inner wall of the threaded part of the mounting bracket and the insulator ignition part in a creeping discharge type spark plug for an internal combustion engine. It is characterized by protecting the insulator ignition part from contamination.

Next, it will be explained with reference to the drawings.

Figures 1 and 2 show conventional creeping discharge type spark plugs (e.g., JP-A-50-2014, JP-A-52-145647, JP-A-52-145647,
JP-A-53-43142).

These are such that the position of the ground electrode 3 is opposite to the center electrode axis across the thin insulator wall 1, and a minute gap 5 and a creepage gap 5 are provided.
It is a creeping discharge plug with a 100 mA, which has a low discharge voltage due to the back electrode effect and has good characteristics, but it is easily contaminated.

FIG. 3 is an enlarged view of the ignition portion of a creeping discharge type ignition plug which is an embodiment of the present invention and is an improved version of the conventional type.

1 is the tip of the insulator firing part. 2 is the tip of the center electrode shaft.

3 is the end face of the ground electrode. Fig. 4 shows another embodiment in which the insulator in Fig. 3 is reinforced with a thick step in the middle of the igniting part, and this reinforced structure prevents gas from penetrating into the interior and provides durability. This is effective against staining, and the insulator becomes thinner, which improves the back electrode effect.

The specified dimensions in Figures 3 and 4 are: h: length from the ground electrode tip surface 3 to the tip 4 of the mounting bracket screw; 1: length from the same electrode tip surface 3 to the insulator tip 1; L: Length from the electrode surface 3 to the tip 2 of the center electrode, g: Distance in the radial direction from the outer periphery of the center electrode to the inner wall of the threaded part of the mounting bracket, related dimensions of 1≦g, 2/31<h≦L The annular gas volume of the ignition part is determined by 1, and if it is larger than g, the creepage gap will be higher than the required voltage, so there will be no spark, and the gas volume will also be small, resulting in poor stain resistance.

If h is smaller than the above range of 2731, the creepage gap will be small and the fouling resistance will be poor, and if it is larger than L, the fouling resistance will be good, but the spark will not be exposed to the combustion chamber side and the ignitability will be poor. So I don't like it.

The shape of the ground electrode may be annular or tripolar.

FIG. 5.6.7 shows experimental data regarding the embodiment of the present invention (FIG. 4).

In the figure, 1: one according to the present invention, 2: a conventional type, and 3: a commercially available spark plug for a rotary engine.

FIG. 5 is an ignition performance chart showing the number of errors occurring at idling speed of 7 oorpm.

Figure 6 is a durability diagram of deposit adhesion shown in terms of time until ignition failure.

FIG. 7 is a carbon stain resistance graph shown in terms of idling duration.

As described above, in the present invention, by slightly increasing the dimension of the threaded portion of the mounting bracket, the adhesion of deposits and carbon is greatly reduced, resulting in improved ignitability.

In particular, if this improved plug is applied to a rotary engine, the volume formed in the plug hole from the rotary housing surface will be larger than that of the conventional product, which will have a significant effect on improving ignition performance and therefore increasing output.

[Brief explanation of drawings]

Figures 1 and 2 show a conventional long distance creeping discharge type spark plug. 3 and 4 are enlarged views of the ignition part of the creeping discharge type ignition plug of the present invention, and 5. 6. FIG. 7 is a graph of experimental data of the embodiment of the present invention.

Claims (1)

[Scope of utility model registration request] a center electrode shaft; an insulator having an axially tapered tube shape and slightly retracted from the tip of the center electrode to secure the center electrode shaft;
is a threaded hole for mounting a spark plug, which has a tubular shape in which the stepped part in its shaft holds the insulator, and a threaded part with a mounting screw carved on the outside in the axial direction is provided in the wall of the combustion chamber of an internal combustion engine. a mounting bracket that can be installed at a position slightly retracted from the position of the inner opening end of the mounting bracket, and an insulating wall of the insulator igniting section radially separated from the inside of the mounting bracket and installed opposite to the center electrode. In a creeping discharge type spark plug for an internal combustion engine, which is equipped with a ground electrode installed as shown in FIG. The radial distance from the inner wall to the outer periphery of the center electrode is g1 The length from the end surface of the grounding electrode to the tip end surface of the threaded part is h
1 When the length from the end surface of the grounding electrode to the tip of the center electrode is L, 1≦g1 and 2/31<h≦L. A creeping discharge type spark plug for an internal combustion engine characterized by forming a gas volume.