JPS62217589A - Spark plug for internal combustion engine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a spark plug for an internal combustion engine.

[Prior art]

As shown in FIGS. 2 and 3, a conventional spark plug 1 of this type has a hollow housing 10 having a shoulder 11 formed on its inner peripheral surface. The housing 10 protrudes beyond the end 12E1 of the opening 12 on the 4! It houses 20 Nokos. Insulator 20 [Yu, its one end surface 20a
It has a center electrode 30 protruding from the center electrode.

〔problem〕

One of the causes of performance deterioration of this type of spark plug related to the operating conditions of the internal combustion engine is contamination by carbon (=Irj). , 1 is particularly likely to occur.

This is because in such cases, the air-fuel ratio is low and the combustion temperature is 1α.
Since the fuel is not completely combusted, unburned carbon adheres to the insulator and the inner surface of the housing, resulting in d3 damage.

When contamination due to carbon adhesion occurs, the insulation resistance value between both electrodes decreases and mis-sparks occur or become smaller.

In order to prevent this, as shown in Japanese Patent Publication No. 53-10219 or Utility Model Publication No. 11rl 56-25194, that is, as shown in FIG. It is recommended that the gap between the two be reduced. This prevents unburned fuel from entering the housing.

Furthermore, since the discharge occurs through the carbon layer attached to the end surface 20a of the insulator 2o, this carbon layer is burned off. These solve the problem of the above-mentioned reduction in insulation resistance. However, this effect can be expected only when carbon generation is relatively small, and cannot be expected under operating conditions where carbon generation is significant (low air-fuel ratio, low combustion temperature). That is, when 14 carbon particles are attached to the end of the insulator 20, the resistance value of the outer surface of the insulator 20 decreases, so that discharge occurs from the surface of the insulator toward the circumferential surface of the opening 12 of the housing 10. If the carbon layer is thin, the carbon layer will be burned off by this discharge. However, if carbon is generated in large quantities over a long period of time, not only will it be impossible to burn off the carbon layer attached to the ends of the insulator, but the carbon layer will also extend to the outer circumferential surface of the insulator inside the housing. Become. As a result, discharge occurs not only toward the inner circumferential surface of the housing opening 12 but also toward the inner circumferential surface 13 of the housing. Since the discharge to the inner circumferential surface 13 of the housing does not easily come into contact with the new air-fuel mixture, the ignition ability is poor and ignition errors are likely to occur. For this reason,
Energy for ignition is wasted,
Engine response performance for the driver deteriorates. Furthermore, if this condition continues, the insulation resistance value of the insulator will further decrease and eventually it will become impossible to ignite.

[Means for solving problems]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a spark plug in which there is no discharge from the insulator to the inner peripheral surface of the housing, and there is no loss of discharge energy.

In order to achieve this object, in the present invention, an annular radial recess is formed on the inner circumferential surface of the housing or the outer circumferential surface of the insulator between the 11"1 part of the housing and the opening.
I am taking T-dan.

[Effect]

As mentioned above, by providing an annular recess in the inner circumferential surface of the housing or the outer circumferential surface of the insulator, the inner circumferential surface of the housing and b
! The insulation space between the outer circumferential surfaces of the child is expanded! This has the effect of suppressing leakage of discharge energy from the seventh element to the housing.

〔Example〕

The effects of the present invention will become clearer from the following description of embodiments with reference to the accompanying drawings.

A spark plug 1, which is an embodiment of the present invention shown in FIG.
0. An annular portion 15 is formed on the inner surface of the housing 10 and projects radially inward. Insulator 2
A center electrode 30 protruding from one end surface 20a of the insulator 20 is embedded within the insulator 20, and is electrically connected to a terminal (not shown) provided at the other end of the insulator 20.

One end of the ground electrode 40 is joined to the end of the opening 12 of the housing 10, and the other end is bent toward the center electrode 30.

A spark gap is defined between the end surface of center electrode 30 and the bent other end surface of ground electrode 40 .

The size of this spark gap is determined by the shoulders 15 and v of the housing.
This is determined by the engagement of the first child 20 with the n section 21 across the para 4-n 22.

An annular radial recess 16 is bored into the inner circumferential surface of the housing between the opening 12 and the shoulder 15 of the housing.

The intrusion of carbon into the outer peripheral surface of the insulator inside the housing is
It is affected by the large knurling of the minimum radial distance S between the inner circumferential surface of the housing opening 12 and the outer circumferential surface of the 4!7 children. That is, if the opening 12 is large (the distance l1iIUS is large I
J), more carbon will be attached to the outer peripheral surface of the insulator. However, if the opening 12 is made too small, carbon will become clogged between the insulator and the opening, resulting in a significant drop in insulation resistance. The inner peripheral surface of the housing opening and 11
There should be an optimal range for the radial distance tns between the outer peripheral surface of the child and the minimum radial distance Mg between the bottom surface 16a of the housing recess 16 and the outer peripheral surface of the child 20, That is, the part farthest from the opening 12 of the housing (radial distance #1 between the bottom of the recess at D and the insulator)
An optimal relationship exists between a and the distance 1lIltS if f. In order to determine these relationships, the following experiment was conducted. In the embodiment shown in FIG.
Since both the opening part 12J3 and the insulator 20 do not have a tapered part, the inner peripheral surface of the opening and b! The distance in the radial direction of the outer circumferential surface of the J child is the minimum distance in the radial direction.

First, the ambient temperature was set to -10℃, 4 cycles were carried out, and 1
The fourth cycle is to repeatedly operate a 600cc engine from idling to racing (increasing the engine speed with no load) to low-speed running as one cycle, and to determine the number of repetitions X at which continued operation is no longer possible. In this experiment, ffi (S
=0.6mtrtd3 and s=1. Q for os>
The number of repetitions is measured by changing the value of . Considering this result, it can be seen that a high repetition number X can be obtained in the range of Q(#)≧1.25(IJtI&). Furthermore, it is generally known that the number of repetitions X increases in proportion to the axial distance l between the 1;1 part of the housing and the opening (Fig. 1); , IvIa1 curve upwards and does not affect the above-mentioned relationship. In addition, the fact that the ambient temperature is set at -10°C means that the operation is under the most severe conditions imaginable in normal use, and it is more difficult for -bon to occur than for G at temperatures above this ambient temperature. I can do it. From these points (J(+m+)≧1.2s
It can be seen that (trend) is the optimal relationship for suppressing carbon adhesion.

Next, while maintaining the relationship g (M) ≧ 1.25 (am), the number of repetitions at which continuous operation becomes impossible when S is changed, The measurement results of the number of repetitions Y (point of deterioration in driving performance) until the driver feels it are shown in FIG. As is clear from Figure 5, the second
In the conventional spark plug shown in the figure, the number of times X of repeated failures is 12, and the number Y of repetitions until deterioration is 5.

However, if we keep Q (1111) = 1.28 (am) and change S, then 0.6#lII≦S≦1.
Within the range of 2#III, the result of X being 9 times or more and Y being 6 times or more is 1! # was received. Also, it can be judged from Fig. 4 that the case where G>1.28 is not much different from the case where a=1.2s (r)>1.25
(the performance characteristics are in a steady state), it can be seen that a performance curve similar to the one shown in FIG. 5 can be obtained even when G>1.25. Note that when S≦0.5 (+ya), carbon tends to become clogged between the opening 12 of the housing and the insulator, and so-called carbon bridges tend to occur, and energy leak becomes large and ignition becomes impossible.

Therefore, both distances S1g are each 0.6rnm≦S≦1
．． By setting to satisfy 2s+ and (7(INR)≧1.25(#), good radiation 1M capability can be obtained.
I can see that it will be 1.

Further, FIG. 6 shows a spark plug of another embodiment. This spark plug 1 has almost the same construction as that shown in FIG. -The stomach is
Housing 1
Gt is a tapered point. As a result, if a discharge occurs from the insulator, the discharge will be concentrated on the end face of the housing opening that is most exposed to the air-fuel mixture.
4. Decrease in fire performance can be suppressed.

In yet another embodiment shown in FIG. 7, instead of providing a recess in the inner circumferential surface of the housing, an annular radial recess is provided in the outer circumferential surface of the insulator.

The action and effect are the same as those of Moejo.

〔Effect of the invention〕

As is clear from the above description, according to the configuration of the present invention, it is possible to obtain a spark plug that does not leak discharge energy from the outer circumferential surface to the inner circumferential surface of the housing during the interval 1R, and has good ignition over a long period of time. Performance can be obtained.

[Brief explanation of drawings]

FIG. 1 is an enlarged partially cutaway sectional view of a spark plug that is an embodiment of the present invention, FIGS. 2 J3 and 3 are enlarged partially cutaway sectional views of a conventional spark plug, respectively. 4 and 5 are graphs showing experimental results showing changes in performance with changes in S and g, respectively, and FIG. 6 is an enlarged partial fracture showing a spark plug of another example. is a cross-sectional view, and
FIG. 7 is an enlarged partially cutaway sectional view showing a spark plug of still another embodiment. 10... Housing, 12... Housing opening,
15...1 part, 16...recess, 16a...recess bottom surface, 20...insulator, 30...center electrode, 40...
Ground electrode.

Claims (1)

[Claims] a hollow housing having an annular shoulder formed on the inner surface;
an insulator housed in the hollow portion of the housing; a center electrode protruding from one end surface of the insulator and extending within the insulator; one end electrically connected to the housing and the other end connected to the center a ground electrode that is bent toward the electrode and defines a predetermined spark interval between it and the center electrode, the one end surface of the insulator protruding beyond the end surface of one opening of the housing; Further, an annular radial recess is formed in the inner circumferential surface of the housing or the outer circumferential surface of the insulator between the shoulder portion of the housing and the one opening, and the inner circumferential surface of the one opening of the housing The minimum distance S (mm) in the radial direction between the outer circumferential surface of the opposing insulator is 0.6 mm
≦S≦1.2 mm, and a radius between the bottom surface of the annular recess at the part farthest from the one opening of the housing and the opposing outer circumferential surface of the insulator or inner circumferential surface of the housing. A spark plug for an internal combustion engine, characterized in that a directional distance g (mm) is g≧1.25.