JPS6161390A - Ignition plug - 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 an ignition plug Vc for an internal combustion engine, and mainly relates to a spark plug which prevents smoldering and fouling and expands the heat range.

(Prior art) The conventionally known means of improving the fouling resistance of spark plugs has been to increase the length of the insulator legs exposed to the combustion chamber side, the so-called insulation distance. However, the length of the legs has a big impact on heat resistance (gray ignition resistance)! ! Therefore, if you try to satisfy both characteristics, there is a limit to the method of increasing the insulation distance by lengthening the legs.

Therefore, as shown in FIG. 6, a step 12e'Th is provided at the tip of the leg portion 12c of the insulator 12 to make the tip smaller in diameter, and an annular auxiliary gap 19 is entirely formed opposite to this small diameter portion 12f. A spark plug (Japanese Utility Model Publication No. 56-25194) is known which is provided with a constricted portion 16c protruding from the inner wall of the mounting fitting 16.

(Problems to be Solved by the Invention) In the above-mentioned conventional spark plug, without adhesion of ordinary conductive substances such as carbon, sparks fly off in the main spark gap 18 between the center electrode 11 and the ground electrode 17, resulting in contamination. When auxiliary gap 19
It has the effect of improving stain resistance by burning off carbon etc. with the spark energy.
Compared to the electrode form of general spark plugs, the throttle part (ilf
In recent years, due to improved ignitability, the spark distance has been increased to 1tjX', and internal flashover is likely to occur even under normal conditions through the constriction, and the main spark This has the disadvantage that it becomes difficult for sparks to fly in the gap, resulting in ignition errors during acceleration and idling, and this phenomenon is particularly aggravated as the mounting screw diameter becomes smaller and the radial space is reduced. It is necessary to take design considerations into account.

(Means for Solving the Problems) The present invention has been made to improve the above-mentioned problems, and it not only increases the insulation distance, but also provides a specific dimension range to achieve thermal and shape effects. It is stain resistant by g! The aim of this project is to provide a spark plug with a high quality.

The present invention provides a spark plug having a step on the circumference so as to reduce the heat capacity i of the tip of the leg of an insulator having a center electrode exposed from the tip surface, and the tip of the leg having the step. When protruding from the end surface of the mounting bracket, and taking the diameter of the tip of the leg as its length k (B), the position of the step from the tip end of the leg 't-(C), and the dimension of the step as ■, A≦4.5m
mφ, B=0~2.0''%C=1.0~4.Off,
This spark plug satisfies the condition of D>0.1 wings, and the corner (2) of the step of the leg is formed into a sharp, sharp angle with no rounding.

(Operations and Effects of the Invention) The ignition bladder of the present invention has the following effects due to the above-mentioned configuration.

(a) The heat capacity of the tip of the leg of the insulator is small, and since the tip of the stepped metal part protrudes from the end surface of the mounting bracket, the temperature of the tip surface tends to rise, so carbon adheres when running at low speed. Easy to dry and insulation resistance does not easily decrease. Otherwise, the deposited carbon is easily burnt out and has excellent self-cleaning properties when running at low speeds.

(b) The step installed on the circumference of the insulator leg essentially extends the insulating M, and also serves as a means of completely discontinuing the leakage circuit formed by combustion products such as carbon and lead compounds. This is effective, and the effect is particularly great when the corner 't5 shape of the step is formed, and the decrease in insulation resistance value due to adhered carbon etc. can be reduced.

(c) By reducing the diameter of the center electrode and the diameter of the tip of the insulator leg, the effect of preventing sparks from flying sideways to the mounting bracket is improved, so the gap between the insulator leg and the inner wall of the mounting bracket is reduced. As a result, the inflow of carbon is suppressed and the stain resistance is improved. In addition, if the conventional method of making the entire leg part is thinner, it is not possible to obtain the required strength for practical purposes.Also, since the center electrode sealed in the leg part becomes thinner, the heat dissipation of the leg part is inhibited, and sufficient gray ignition resistance is not achieved. I won't be able to do it.

(2) Pre-ignition in spark plugs generally starts at the tip of the insulator leg, but in the spark plug of the present invention, the heat capacity at the leg tip is small, so the temperature at which pre-ignition occurs rises, and the pre-ignition occurs at the tip of the leg. There are advantages that are difficult to overcome. Furthermore, if the tip end of the leg protrudes beyond the end surface of the mounting bracket, the above effect becomes even greater.

(e) The spark plug of the present invention is highly effective in improving the performance of small plugs with small diameter screws, and greatly contributes to the reduction in weight and size of internal combustion engines. In particular, when combined with a multipolar spark plug with multiple ground electrodes, the opening volume around the electrode becomes large, which is advantageous for the growth of the flame kernel through the air-fuel mixture and improves ignition performance.

(Example〕 The spark plug of the present invention will be explained below with reference to the drawings.

FIG. 1 is a half-sectional view showing an embodiment of the spark plug of the present invention. In the figure, 1 is a center electrode made of a nickel alloy or encapsulated with tuning, the tip portion 1a of which is formed to have a smaller diameter than the base portion. ing. Reference numeral 2 denotes an insulator made of high alumina porcelain or the like, and a small diameter hole 2b at the tip is formed in the shaft hole 2a, through which the tip 1a of the center electrode 1 is inserted, and from the tip surface 2d of the leg 2c. The protruding rear end is provided with a flange portion 1b to be secured to the stepped portion of the shaft hole 2a, and the resistor 3 is sandwiched between conductive lath sealing materials 4 and integrated with the terminal electrode 5 by a known method. Heat sealed. Reference numeral 6 denotes a mounting bracket, in which an engine mounting screw 6a is disposed, and the insulator 2 protrudes from the end face 6b of the mounting bracket into the inner cavity and is fixed by known caulking or the like. Reference numeral 7 designates a spark plug which forms a spark gap 8 between a ground electrode welded to the end surface 6b of the mounting fitting and the center electrode tip surface 1c.

The spark plug of the present invention has an insulator 2, as detailed in FIG.
The leg portion 2c exposed to the combustion chamber side is provided with a step 2e at the tip end protruding from the end surface 6b of the mounting bracket to form a small tip diameter portion 2f, and the step 2e portion is a small diameter hole for holding the center electrode. It is formed at the same position in y as the stepped portion 2b' of 2b. The preferred dimensional relationship for the tip of the insulator leg is that the diameter of the tip of the leg is ≦4.5 mm, and the length is B.
) = O ~ 2.0 wings, position of step from leg tip surface 2d (
C) ~1.0~4.9 ffff, step dimension (2)>
It is set to satisfy the conditions o, a, and m.

Furthermore, if the corner (G) of the step 2e is formed into a sharp corner with no rounding, it can have the function of cutting off the hearing circuit f formed by combustion products. Preferably, the above numerical conditions are set according to the diameter of the mounting screw, which is more effective in terms of stain resistance and the like.

In other words, the smaller the diameter of the screw, the greater the effect; for a screw diameter of 14 mm, it is 4.58 φ or more, for a screw diameter of 12 mm, it is 3.5 mm or more, and 1Qll.
If IF is 8.0 to φ or higher, no effect can be obtained h0
In addition, (B) and (I) have large dimensions and a large culm effect (
The B1 dimension is the level of the step on the circumference Pl(
C) ut, 0-4. Om range power 'j L <,
It is not effective if it is less than 1, Q or 4. If it exceeds Qtttwt, the mechanical strength will decrease and the durability will deteriorate. Furthermore, the diameter of the tip of the center electrode is also small according to the diameter of the mounting screw, preferably 2.
．． It is preferable to set it to 0 to 0.5 silk.

FIG. 3 shows another embodiment of the spark plug of the present invention, which differs from the above embodiment in that a plurality of ground electrodes 7 are disposed opposite the side surface 1dK of the tip end of the center electrode 1 to form a spark gap 8. The shape and dimensional relationship of the insulator leg tip of the present invention can be applied to the formed spark plug, and excellent effects such as stain resistance can be obtained.

Next, the results of the stain resistance test and heat range of the spark plug of the present invention are described in A. Fightφ, (B
) = 0.5 W, (C) ~ 2.01ff, ([) ~ 0
．． 7M, the diameter of the center electrode tip is set to 2.0 mm φ, while the conventional spark plug B is (A) ~ 5.0 mm φ with no step, and the center electrode tip is ffl 2.5 Mllφ. was used for comparison. Figure 4 shows 4 cycles, 2000
A low-temperature fouling test at -10"C on a car equipped with a CC engine shows the extent to which the insulation resistance value decreases due to carbon adhesion during cycle operation with a start-idle-low-speed driving pattern. 89, conventional spark plug B In contrast, the spark plug A of the present invention showed good performance with little decrease in insulation resistance value. Figure 5 shows the preignition resistance and the vehicle speed at which the carbon burns out due to the advance angle of preignition occurrence. This is a bar graph showing the self-cleaning performance of each spark plug 5.
This is the average value of ge. It has been confirmed that the spark plug A of the present invention has a higher pre-ignition advance angle than the conventional spark plug B, and also has a lower self-cleaning vehicle speed and an expanded heat range.
7'(.

However, the present invention is not limited to the above-mentioned embodiments, but the spark discharge surfaces of the center electrode and the ground electrode are made of Pt-Ir, Pt-Rh, Pt-Ni, etc. with excellent wear resistance. A known precious metal such as PT gold alloy may be joined according to maintenance-free requirements, and an extended shell type in which the end surface 6b of the mounting metal 6 protrudes from the combustion chamber wall surface (1 to 10 mm) may be used. The shape of the tip of the insulator leg of the present invention can also be applied to a spark plug that forms a spark gap between the corner of the tip of the spark plug and the center electrode and the side surface of an oblique ground electrode protruding from the mounting bracket so as to face the spark plug. Can be applied to advantage.

[Brief explanation of drawings]

FIG. 1 is a half-sectional view showing an embodiment of the spark plug of the present invention;
FIG. 2 is an enlarged sectional view of the main part of FIG. 1, FIG. 3 is an enlarged FFr sectional view of the main part showing another embodiment of the spark plug of the present invention, and FIG. 4 is a graph showing the results of the stain resistance test. FIG. 5 is a graph showing the heat range, and FIG. 6 is an enlarged half-sectional view of the main part of a conventional spark plug. 1... Center electrode 2... Insulator 2c... Leg part
2d... Tip surface 2e... Step 2f... Small diameter portion 6... Mounting bracket 6b... End face Patent applicant NGK Spark Plug Co., Ltd. Figure 4 Figure 5 Figure 6 Figure 2c

Claims (2)

[Claims] (1) In a spark plug that has a step on the circumference to reduce the heat capacity of the tip of the insulator leg with the center electrode exposed from the tip surface, the tip of the leg with the step is installed. It protrudes from the end surface of the metal fitting, and the diameter of the tip of the leg is (A
), its length is (B), the position of the step from the tip of the leg is (C), and the dimension of the step is (D), A≦4.5mmφ, B=0 to 2.0mm, C =1.0～
A spark plug characterized by satisfying the conditions of 4.0 mm and D>0.3 mm. (2) The spark plug according to claim 1, wherein the corner [E] of the step of the leg is formed into a sharp corner with no roundness in order to discontinuously form a leakage circuit formed by combustion products.