JPH1167422A - Spark plug - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the fastening characteristic of a gap between a flange part and an inner wall of an axial hole in the vicinity of a center electrode, stabilize the accuracy thereof, and enable the improvement and stabilization of the heat-resistant property, by specifying a cone angle of a center electrode receiving part. SOLUTION: An axial hole 20 of an insulator 2 has a small diameter at the front side of a tapered center electrode receiving part 25 and a large diameter at the rear side. In a center electrode 5, a flange part 52 is locked to a center electrode receiving part 25 of the axial hole 20, a rod-shaped part 51 is inserted into the front side of the axial hole 20 having a small diameter to be sealed in the axial hole by a seal glass 4. The center electrode receiving part 25 is made to have a cone angle of 45-85 deg.. This relatively large cone angle can repress a surge wave of a seal glass 43 at an inner wall of the axial hole in the vicinity of the center electrode receiving part to a low level to secure the sufficient fluidity, so that the thermal shrinking characteristic of the seal part is improved without damaging the pressure transmission and consequently the heat conductive characteristic is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a glass seal type spark plug mounted on an internal combustion engine.

[0002]

2. Description of the Related Art A center electrode 101 is fitted into a shaft hole 103 of an insulator 102, a first powdered glass material, a resistor raw material, and a second powdered glass material are sequentially placed therein, and a terminal electrode is inserted into the shaft hole 103. 2. Description of the Related Art A glass seal type spark plug manufactured by inserting and melting glass by heating and then solidifying by cooling has been known. In this spark plug, the taper angle of the center electrode receiving portion 104 is set to 20 ° or more.
The angle is set to 40 ° (see FIG. 5).

[0003]

SUMMARY OF THE INVENTION The present inventors have found that the conventional spark plug (the center electrode receiving portion 104 having a taper angle of 20 ° to 40 °) has the following problems. . Since the gap (sealing portion) between the flange portion 105 and the shaft hole inner wall 107 near the center electrode receiving portion 106 is narrow and deep, the sealing glass 108 during glass sealing does not flow sufficiently, and the sealing portion 109 has uneven density. Occurs. In particular, the seal glass 108 in the vicinity of the center electrode receiving portion 106 tends to have relatively low sinterability, and thus has low thermal conductivity.

If the sealability of the seal portion 109 is low, the thermal conductivity is poor, and the heat resistance (preignition resistance) of the spark plug is reduced. When unevenness of the density occurs in the seal portion 109, the heat resistance (pre-ignition resistance) of the spark plug varies from product to product.

SUMMARY OF THE INVENTION It is an object of the present invention to improve the heat-tightness of the gap (seal portion) between the flange portion and the inner wall of the shaft hole near the center electrode receiving portion and to stabilize the density, thereby improving and stabilizing the heat resistance performance. Another object of the present invention is to provide a glass seal type spark plug which realizes the above.

[0006]

In order to solve the above-mentioned problems,
The present invention employs the following configuration. (1) a cylindrical metal shell, an insulator fixed in the metal shell, having a shaft hole whose diameter is smaller on the front side and larger on the rear side than the tapered center electrode receiving portion; A spark plug having a flange locked to the portion and a rod-shaped portion inserted into the small shaft hole on the front side, and having a center electrode sealed in the shaft hole by a seal glass, The taper angle of the center electrode receiving portion was set to 45 ° to 85 °.

(2) The configuration of the above (1), wherein the taper angle of the center electrode receiving portion is set to 60 ° to 85 ° instead of 45 ° to 85 °.

(3) The taper angle of the center electrode receiving portion is set to 75 ° to 85 ° instead of the configuration of (1) described above, wherein the taper angle of the center electrode receiving portion is set to 45 ° to 85 °.

(4) A cylindrical metal shell, an insulator fixed in the metal shell with a shaft hole having a diameter smaller on the front side and larger on the rear side than the tapered center electrode receiving portion, and a terminal. A portion of the terminal electrode is inserted into the shaft hole so that the portion protrudes from the end face of the head of the insulator. Having a flange portion to be stopped and a rod-shaped portion inserted into a small-diameter shaft hole on the front side,
The flange portion is sealed in a shaft hole by a second seal glass, and includes a second seal glass, a resistor, and a center electrode electrically connected to the terminal electrode via the first seal glass. The center electrode receiving portion has a taper angle of 45 ° to 85 °.

(5) The spark plug is provided in the above (1) to
(4) The taper angle of the flange receiving portion of the flange contacting the center electrode receiving portion is set to (taper angle of the central electrode receiving portion + 5 °) or less.

[0011]

[Action and effect of the invention]

[Claims 1 to 4] The diameter of the shaft hole of the insulator is smaller on the front side and larger on the rear side than the tapered center electrode receiving portion. The center electrode has a flange portion locked to the center electrode receiving portion of the shaft hole, a rod-shaped portion inserted into the small shaft hole on the front side, and sealed with a seal glass in the shaft hole.

The taper angle of the center electrode receiving portion is 45 ° to 85 ° in claim 1, 60 ° to 85 ° in claim 2,
In claim 3, the angle is set to 75 ° to 85 °. Since the taper angle of the center electrode receiving portion is set relatively large, the flow resistance of the seal glass on the inner wall of the shaft hole near the center electrode receiving portion can be suppressed low, and the flowability can be sufficiently ensured.

As a result, the sealability of the seal portion can be improved without impairing the pressure propagation during the heat sealing, and the heat conductivity can be improved. As a result, the heat resistance (pre-ignition resistance) of the spark plug is improved. Further, since the denseness of the seal portion can be made uniform, the heat resistance (pre-ignition resistance) of the spark plug becomes substantially uniform for each product.

The numerical limitation of the taper angle of the center electrode receiving portion is based on the following reason. If the taper angle of the center electrode receiving portion is less than 45 °, it may be difficult to sufficiently bring the sealing glass into the flange during glass sealing,
In some cases, the density of the seal portion may be uneven. still,
The taper angle is preferably 60 ° or more, more preferably 75 ° or more. However, if the taper angle of the center electrode receiving portion exceeds 85 °, the flange portion of the center electrode cannot be received by the center electrode receiving portion when hot pressing pressure is applied during sealing. Also, it may be difficult to keep the tip position of the center electrode within a specified size due to a slight size / angle error.

[Claim 4] The terminal electrode is inserted into the shaft hole so that the terminal portion protrudes from the head end face of the insulator, and the seal portion is sealed in the shaft hole with the first seal glass.
In this case, the flange of the center electrode locked to the center electrode receiving portion is sealed in the shaft hole with the second seal glass. Since the terminal portion of the terminal electrode protrudes from the end face of the head of the insulator, it is not necessary to use a dedicated jig or the like, so that the glass sealing operation is facilitated and the number of operation steps can be reduced. The center electrode is electrically connected to the terminal electrode via the second seal glass → the resistor → the first seal glass. The range of the taper angle of the center electrode receiving portion is set to 45 from the viewpoint of securing the fluidity of the seal glass on the inner wall of the shaft hole near the center electrode receiving portion and the ability of the center electrode receiving portion to receive the flange portion of the center electrode. ° to 85 ° (preferably 60 ° to 85 °, more preferably 75 ° to 85 °).

[Claim 5] It is preferable to set the taper angle of the flange receiving portion of the center electrode flange which is in contact with the center electrode receiving portion to be not more than (taper angle of center electrode receiving portion + 5 °). By doing so, when sealing the glass,
The seal glass can be easily wrapped around the flange, and unevenness in the density of the seal can be prevented.

For example, as shown in FIG. 6, when the taper angle of the flange receiving portion of the center electrode flange is set to be larger than the taper angle of the center electrode receiving portion, the flange receiving portion of the center electrode flange portion is set. A small space is created between the tapered surface of the center electrode and the tapered surface of the center electrode receiving portion. At the time of glass sealing, it is difficult to make the sealing glass sufficiently flow into this minute space. When the minute space is small, there is little problem. However, as the size is large, the risk of impairing the stability of the center electrode increases, and the density of the seal portion becomes uneven.

Further, for example, as shown in FIG. 7, when the taper angle of the flange receiving portion of the center electrode flange is set smaller than the taper angle of the center electrode receiving portion, the flange receiving portion of the center electrode flange is formed. It is not necessary to flow the seal glass into a minute space between the tapered surface of the portion and the tapered surface of the center electrode receiving portion. That is, it is easy to make the seal glass flow on the outer peripheral surface of the flange portion of the center electrode, and it is possible to sufficiently secure the stability of the center electrode only by making the seal glass flow in this portion, and to reduce the density of the seal portion. Can be uniform. Therefore, it is desirable to set the taper angle of the flange receiving portion of the central electrode flange portion to (the taper angle of the central electrode receiving portion + 5 °) or less.

When the spark plug is mounted on the engine and operated, much of the heat received by the spark plug escapes from the flange receiving portion to the insulator through the center electrode. Therefore, heat resistance can be further stabilized by increasing the contact area between the flange receiving portion and the center electrode receiving portion. In addition, since the force that pushes the center electrode toward the firing portion during hot pressing is received at this portion, the center electrode is excessively protruded due to an increase in the contact area (the tip position of the center electrode exceeds the specified dimension). Can be avoided. In order to increase the contact area between the flange receiving portion and the center electrode receiving portion, the taper angle of the flange receiving portion of the center electrode flange portion is set to −5 ° to + 5 ° with respect to the taper angle of the center electrode receiving portion. It is desirable to set within the range.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. As shown in FIG.
A cylindrical metal shell 1 having an outer electrode 10 protruding from a front end surface 111, an insulator 2 having a shaft hole 20 fixed in the metal shell 1, and a terminal portion extending from a head end surface 231 of the insulator 2. 3
The terminal electrode 3 protruding from the shaft hole 20 and inserted into the shaft hole 20, the glass sealing material 4 for sealing the seal portion 32 of the terminal electrode 3 at the back of the shaft hole, and the rod-shaped portion 51 And a center electrode 5 fixed in the shaft hole 20 so as to protrude from the shaft hole 22. The spark plug P is connected to the gasket 12
1 is screwed to a cylinder head (not shown) of the internal combustion engine, and a plug cap (not shown) is fitted to the terminal portion 31 to supply a high voltage.

The metal shell 1 is made of low carbon steel, and has a screw portion 11 formed with a screw 112 on the outer periphery, and a body portion 1 having a gasket 121 provided on the front side and a thin band 122 provided on the rear side.
2 and a hexagonal portion 13 for fitting a plug wrench. In addition, 123 is a packing, and 124 is a ring.

Insulator 2 having shaft hole 20 formed along the axis
Is formed of a ceramic sintered body mainly composed of alumina, and has a leg portion 21 located inside the screw portion 11, a large-diameter portion 23 located from the hexagonal portion 13 of the metallic shell 1 to the inside of the body portion 12, Head 2 with corrugation 232 formed on the outer circumference
4

The shaft hole 20 is located between the head portion 24 and the large-diameter portion 23, and the shaft hole portion on the front side of the tapered center electrode receiving portion 25 is slightly smaller in diameter than the center electrode diameter (φ2.6 mm). The center electrode receiving portion 2 is formed in a large
The shaft hole on the rear side of 5 has a large diameter (φ4.2 mm).

Sample No. which is an invention product 3-No. 9
Is the taper angle of the center electrode receiving portion 25 (the angle formed between the tapered surface 251 of the center electrode receiving portion 25 and the radial surface 252).
Is set to 45 ° to 85 °. In addition, the sample No. 1, No. 2, No. 10, the taper angle of the center electrode receiving portion 25 (the angle formed between the tapered surface 251 and the radial surface 252 of the center electrode receiving portion 25) is
The angles are set to 30 °, 40 °, and 90 °.

The terminal electrode 3 is made of low carbon steel, has a surface plated with nickel, and protrudes from the head end surface 231, a sealing portion 32 which is glass-sealed in the shaft hole 20, It comprises a rod-shaped part 33 connecting the part 31 and the seal part 32. The terminal portion 31 has a small diameter at the center in order to prevent the terminal portion 31 from coming off when the plug cap is fitted. The outer periphery of the seal portion 32 is processed into a screw shape or a knurl shape, and is sealed in the shaft hole 20 by the glass seal material 4 (first and second seal glasses 41 and 43).

The glass sealing material 4 is formed by melting and solidifying a glass-based material in the order of the second powdered glass material, the resistor raw material, and the first powdered glass material. It comprises a body 42 and a second sealing glass 43. The first and second powdered glass materials are obtained by mixing (1: 1) copper powder and glass powder. Resistor raw materials are glass powder, carbon powder and metal powder (Al,
Sn), a ceramic powder, and an organic binder.

The center electrode 5 has a bar portion 51 and a flange portion 52. The flange portion 52 is engaged with the tapered surface 251 of the center electrode receiving portion 25, and the tip of the bar portion 51 projects from the insulator tip surface 22. The glass sealing material 4 (second
Is sealed in the shaft hole 20 by the seal glass 43). The flange 52 has a tapered surface 521 of a barrel-shaped flange receiving portion locked to the tapered surface 251, and a V-shaped cut 522 is formed at a rear end.

The center electrode 5 is a composite material of a sheath material made of a nickel alloy and a core material (a heat conductive metal such as copper) enclosed in the sheath material. Electrode 3
Is electrically connected to

With the insulator 2 fixed so that the leg portion 21 faces downward, glass sealing of the terminal electrode 3 and the center electrode 5 is performed as follows. (1) The center electrode 5 is fitted through the shaft hole 20 on the head 24 side of the insulator 2, and the tapered surface 521 (barrel) of the flange receiving portion of the flange portion 52 is locked to the tapered surface 251 of the center electrode receiving portion 25. Then, the rod-shaped portion 51 is made to protrude from the insulator front end face 22.

(2) An appropriate amount of the second powdered glass material, the resistor material, and the first powdered glass material are sequentially loaded into the shaft hole 20 on the head 24 side of the insulator 2. (3) Connect the terminal electrode 3 to the shaft hole 20 from the head 24 side of the insulator 2.
Fit inside.

(4) The insulator 2 is heated to 800 ° C. to 950 ° C. (the first and second seal glasses 41 and 43 and the glass powder of the resistor 42 are melted), and a downward force is applied to the terminal 31. While pressing the terminal electrode 3, the bottom surface 34 of the terminal portion 31 is pressed.
Is brought into contact with the head end surface 231 of the insulator 2. (5) The insulator 2 is naturally cooled to solidify the glass sealing material 4 in a molten state, and the glass sealing of the terminal electrode 3 and the center electrode 5 is completed.

Incidentally, the insulator 2 whose glass seal has been completed
Is fitted into the metal shell 1 via the packing 123, filled with the ring 124 and the sealing material 126, and is assembled to the metal shell 1 by caulking the caulking portion 125.

Next, the heat resistance evaluation test performed by variously changing the taper angle of the center electrode receiving portion 25 and the advantages of the invention will be described. FIG. 3 shows the taper angle of the center electrode receiving portion 25 (the tapered surface 251 and the radial surface 252 of the center electrode receiving portion 25).
Sample N) with an angle of 30 ° to 90 °
o. 1 to No. 10 (5 samples per sample) were assembled to the spark plug P, and the four-cycle air-cooled single cylinder 125c
This is data obtained by plotting the advance angle at which preignition occurred with the ignition timing sequentially delayed with the engine mounted at 9000 rpm with the engine c mounted. The ignition timing is 20 ° CA
, And held for 1 minute, and changed every 1 ° CA advance angle. The taper angle of the flange 52 of the center electrode 5 (the flange 52
The angle between the tapered surface 521 of the flange receiving portion and the radial surface 252) is set to the same value as the taper angle of the center electrode receiving portion 25.

The sample No. in which the taper angle of the center electrode receiving portion 25 (the angle formed between the tapered surface 251 and the radial surface 252 of the center electrode receiving portion 25) was set to 90 °. As shown in FIG. 3, all of the spark plugs to which the ten plugs were assembled were not subjected to the heat resistance evaluation test because the center electrode 5 protruded longer than specified, as shown in FIG.

Sample No. 1 in which the taper angle of the center electrode receiving portion 25 (the angle between the tapered surface 251 and the radial surface 252 of the center electrode receiving portion 25) was set in the range of 45 ° to 85 °.
3-No. Spark plug P assembled with 9
As shown in FIG. 3, the heat resistance is improved (4 ° CA to 8 ° CA in terms of ignition advance) compared to a conventional spark plug (having a taper angle of 20 ° to 40 °), and the occurrence of preignition is suppressed. Was confirmed.

Sample No. 3-No. As shown in FIG. 3, it was confirmed that the spark plug P assembled with the spark plug 9 can reduce the variation in heat resistance (6 ° CA → 3 ° CA in terms of ignition advance) as compared with the conventional spark plug. It has been found that uniformity of quality can be realized.

The taper angle of the tapered surface 251 of the center electrode receiving portion 25 is set to 45 ° to 85 ° (sample Nos. 3 to 9).
It is considered that the spark plug P set to the above-mentioned effect has an effect of "improving pre-ignition resistance and having less variation in heat resistance and realizing uniformity of quality" for the following reasons. .

Since the taper angle of the tapered surface 251 of the center electrode receiving portion 25 is steep (60 ° to 80 °), the flow resistance of the second seal glass 43 on the inner wall of the shaft hole near the center electrode receiving portion 25 is reduced. It is kept low and fluidity is sufficiently ensured. As a result, the pressure propagation at the time of heat sealing is not impaired, so that the sealability (thermal conductivity) of the seal portion 32 can be improved.

Since the seal portion 32 has high heat-tightness, the heat conductivity is excellent, and the heat resistance (pre-ignition resistance) of the spark plug P can be improved. Since the sealability of the seal portion 32 is uniform, the heat resistance (preignition resistance) of the spark plug P can be made substantially uniform for each product.

Next, an impact test when the taper angle of the tapered surface 251 of the flange receiving portion 25 is variously changed, and advantages of the invention will be described. FIG. 4 shows that the taper angle of the center electrode receiving portion 25 is set to 50 °, and the taper angle of the flange receiving portion of the flange portion 52 of the center electrode 5 is set to +0.
°, + 5 °, and + 7 ° (1 sample 5
Book) as a spark plug P, JISB80
31 shows the results of the evaluation by the impact test specified in section 3.3. This test was conducted at a distance of 22 mm, 10 mm
A minute test was performed on each sample. The rate of change of the resistance value after the end of the test is ± 10% of the initial resistance value.
Those satisfying the following standards〇, those not meeting the standards ×
It was expressed by.

Some samples of the center electrode receiving portion 25 with a taper angle of + 7 ° are out of the standard, and it is confirmed that the impact resistance decreases as the taper angle of the flange receiving portion of the flange portion 52 increases. Was done.

When the sample subjected to this test was cut and the state of the second seal glass 43 was confirmed, the tapered surface 521 of the flange receiving portion of the flange 52 of the center electrode 5 and the tapered surface of the center electrode receiving portion 25 were checked. It has been found that there is a difference in the density of the second seal glass 43 in a minute space existing between the second seal glass 43 and the second seal glass 43. That is, the second electrode on the outer peripheral surface of the flange portion of the center electrode 5
Although the density of the seal glass 43 does not differ greatly, the density of the second seal glass 43 in the minute space described above gradually increases as the taper angle of the flange receiving portion of the flange of the center electrode 5 is set larger. Had fallen. Therefore, if the minuteness of the second seal glass 43 in the minute portion is small due to the impact test, the second seal glass 43 in this portion is easily cracked, and the stability of the center electrode 5 decreases. It is thought to be.

[Brief description of the drawings]

FIG. 1 is a sectional view of a spark plug according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a main part of the spark plug according to the embodiment of the present invention.

FIG. 1 to No. 9 is a graph showing a distribution of ignition advance angles at which preignition has occurred in a spark plug using 9 (5 each).

FIG. 4 is an explanatory diagram showing a relationship between a taper angle of a flange receiving portion and impact resistance.

FIG. 5 is a sectional view of a main part of a spark plug according to the related art and an enlarged view thereof.

FIG. 6 is an explanatory diagram in a case where a taper angle of a flange receiving portion of a flange portion of a center electrode is set to be larger than a taper angle of a central electrode receiving portion.

FIG. 7 is an explanatory diagram in the case where the taper angle of the flange receiving portion of the flange portion of the center electrode is set smaller than the taper angle of the central electrode receiving portion.

[Explanation of symbols]

 P Spark plug 1 Metal shell 2 Insulator 3 Terminal electrode 5 Center electrode 10 Outer electrode 20 Shaft hole 21 Leg length 22 Insulator tip surface 25 Center electrode receiving part 31 Terminal part 32 Seal part 41 First seal glass 42 Resistor 43 2 seal glass 51 rod-shaped part 52 flange part 111 tip surface 231 head end surface 251 taper surface

Claims (5)

[Claims] 1. A cylindrical metal shell, an insulator fixed in the metal shell having a shaft hole whose diameter is smaller on the front side and larger on the rear side than the tapered center electrode receiving portion; A spark plug having a flange locked by an electrode receiving portion, a rod-shaped portion inserted into a small-diameter shaft hole on the front side, and a center electrode sealed in the shaft hole by seal glass. A center electrode receiving portion having a taper angle of 45 to 85 degrees. 2. The spark plug according to claim 1, wherein the taper angle of the center electrode receiving portion is set to 60 ° to 85 ° instead of 45 ° to 85 °. 3. The spark plug according to claim 1, wherein a taper angle of said center electrode receiving portion is set to 75 ° to 85 ° instead of 45 ° to 85 °. 4. A cylindrical metal shell, an insulator fixed in the metal shell, having a shaft hole having a smaller diameter on the front side and a larger diameter on the rear side from the tapered center electrode receiving portion; Is inserted into the shaft hole so as to protrude from the end face of the head of the insulator, and a terminal electrode whose first sealing glass seals the seal portion in the shaft hole; And a rod-shaped portion inserted into a small-diameter shaft hole on the front side. The flange is sealed in the shaft hole by a second seal glass. A spark plug including a body and a center electrode electrically connected to the terminal electrode via the first seal glass, wherein a taper angle of the center electrode receiving portion is set to 45 ° to 85 °. And a spark plug. 5. The taper angle of the flange receiving portion of the flange portion with which the center electrode receiving portion abuts is set to (taper angle of the central electrode receiving portion + 5 °) or less. Spark plug according to Crab.