JPH09260021A - Spark plug for temperature measurement - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spark plug for temperature measurement, which has high durability with the speed of increasing gap being slow. SOLUTION: This spark plug comprises a cylindrical body attachment with an outer electrode being extended in the tip surface 11, insulator with an axial hole 21 fixed in the body, a center electrode 3 which forms axially a insertion hole 31 with bottom, extending the electrode tip 32 from the insulator tip 22 and being fixed in the axial hole 21, and sheathed thermo-couple inserted in the insertion hole 31, the tip of a sheath 41 is welded to the bottom of the insertion hole 31. In this case, the sheath tip 41 of the sheathed thermo-couple inserted into the insertion hole 31 is first welded to the bottom of the insertion hole 31, then the tip of the molten alloy 45 is cut and removed so that the molten alloy 45 is exposed to outside at the top inner circumference of the center electrode 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature measuring spark plug for detecting the center electrode tip temperature by a sheath thermocouple inserted in a bottomed insertion hole formed in the axial direction of a center electrode.

[0002]

2. Description of the Related Art When a new engine is prototyped, a plug compatibility test is conducted in order to find a spark plug that can bring out the performance of the engine. This plug compatibility test starts with
A temperature measurement test is performed using a spark plug for temperature measurement, and the search range is narrowed down based on the measured center electrode tip temperature.

For this temperature measurement test, conventionally, a bottomed insertion hole is opened in the axial direction of the center electrode, a sheath thermocouple is inserted into this insertion hole, and the sheath tip is joined to the hole bottom by welding. Spark plug is used.

[0004]

In this conventional spark plug for temperature measurement, when the sheath tip is welded to the hole bottom, the joint portion (sheath tip and center electrode tip) is melted and the center electrode tip is entirely molten alloy. Become a part.

Since the melt-solidified alloy is more likely to wear sparks (the gap increasing rate is faster) than the center electrode base material due to segregation of components (microscopic), the conventional temperature measuring spark plug has a short life. Have challenges.

An object of the present invention is to provide a temperature measuring spark plug having a slow gap increasing speed and excellent durability.

[0007]

In order to solve the above-mentioned problems,
The present invention employs the following configuration. (1) A tubular metal shell with an outer electrode protruding from the tip surface,
An insulator with a shaft hole fixed in the metal shell, a bottomed insertion hole formed in the axial direction, and a tip of the electrode protruding from the tip surface of the insulator and fixed in the shaft hole; A sheath thermocouple inserted into the hole is provided, and the sheath tip and a part of the electrode tip are melted and solidified through a melt-solidified alloy,
In the temperature measuring spark plug in which the tip of the solid sheath is welded to the hole bottom of the insertion hole, the molten solidified alloy was formed so as to be exposed to the outside only at the inner peripheral portion of the end surface of the center electrode.

(2) A cylindrical metal shell having an outer electrode protruding from the front end surface thereof, an insulator having a shaft hole fixed in the metal shell, and a bottomed insertion hole are formed in the axial direction to form an electrode. A center electrode having a tip protruding from the tip surface of the insulator and fixed in the shaft hole, and a sheath thermocouple inserted into the insertion hole are provided, and the sheath tip and a part of the electrode tip are melted and solidified. In a spark plug for temperature measurement in which the solid sheath tip is welded to the hole bottom of the insertion hole through a solidified alloy, the sheath tip of the sheath thermocouple inserted into the insertion hole is inserted into the hole of the insertion hole. After welding to the bottom, the tip of the center electrode was ground or cut off to expose the melt-solidified alloy to the outside only at the inner peripheral portion of the end face of the center electrode.

(3) A cylindrical metal shell having an outer electrode projecting from the tip surface, an insulator with a shaft hole fixed in the metal shell, and a bottomed insertion hole are formed in the axial direction to form an electrode. A center electrode having a tip portion projected from the tip surface of the insulator and fixed in the shaft hole, and a sheath thermocouple inserted into the insertion hole are provided so that the side surface and the outer peripheral portion of the end surface of the center electrode do not melt. The sheath tip of the sheath thermocouple was welded to the hole bottom of the insertion hole.

(4) In the sheath thermocouple having any one of the above-mentioned constitutions (1) to (3), two different kinds of metal wires inserted in the sheath are electrically connected to the tip of the solid sheath. It is a grounded type.

[0011]

[Operation and effect of the invention]

[Claim 1] The temperature measuring spark plug is a sheath thermoelectric device in which a solid sheath tip is welded to a hole bottom of an insertion hole through a melt-solidified alloy in which a sheath tip and a part of an electrode tip are melt-solidified. The melt-solidified alloy is formed so as to be exposed to the outside only at the inner peripheral portion of the end surface of the center electrode.

Since spark discharge is likely to occur at the outer edge of the end surface of the center electrode, the electrode consumption due to the spark discharge progresses faster at the outer peripheral portion of the end surface of the center electrode than at the inner peripheral portion of the end surface for the same material. However, since the molten solidified alloy, which is more susceptible to spark consumption than the center electrode base material, is formed so as to be exposed to the outside only at the inner circumference of the end face of the center electrode, the center electrode is consumed and the gap The rate of increase can be slowed. Therefore, the temperature measurement spark plug has excellent durability.

[Claim 2] In the temperature measurement spark plug, the solid sheath tip is welded to the hole bottom of the insertion hole through the melt-solidified alloy in which the sheath tip and a part of the electrode tip are melt-solidified. A sheath thermocouple that is inserted into the insertion hole, welds the sheath tip of the sheath thermocouple to the bottom of the insertion hole, and then polishes or removes the tip of the center electrode to remove the end surface of the center electrode. The molten solidified alloy is formed so that it is exposed to the outside only at the inner peripheral portion.

Since spark discharge is likely to occur at the outer edge of the end surface of the center electrode, the electrode consumption due to the spark discharge progresses faster at the outer peripheral portion of the end surface of the center electrode than at the inner peripheral portion of the end surface when the same material is used. However, by grinding or cutting off the tip of the center electrode after welding (processing is simple and the cost rises only slightly), a melt-solidified alloy that is more likely to wear sparks than the center electrode base material Since it is formed so as to be exposed to the outside only at the inner peripheral portion of the end face, the electrode consumption of the center electrode occurs on average, and the gap increasing speed can be slowed. Therefore, the spark plug for temperature measurement has excellent durability and does not cause a significant increase in cost.

[Claim 3] In the spark plug for temperature measurement, the solid sheath tip is welded to the hole bottom of the insertion hole through the melt-solidified alloy in which the sheath tip and a part of the electrode tip are melt-solidified. The sheath thermocouple is provided, and the sheath tip of the sheath thermocouple is welded to the hole bottom of the insertion hole so as not to melt the side surface and the outer peripheral portion of the end surface of the center electrode.

Since spark discharge is likely to occur at the outer edge of the end surface of the center electrode, the electrode consumption due to the spark discharge progresses faster at the outer peripheral portion of the end surface of the center electrode than at the inner peripheral portion of the end surface when the same material is used. However, since the sheath tip of the sheath thermocouple is welded to the hole bottom of the insertion hole so that the side surface and the outer periphery of the end surface of the center electrode do not melt, a melt-solidified alloy (sparks are more easily consumed than the base material of the center electrode) Are not formed on the side surface and the outer peripheral portion of the end surface of the center electrode. For this reason, since the center electrode is consumed on average, the gap increasing rate can be slowed.
Therefore, the temperature measurement spark plug has excellent durability.

[Claim 4] The sheath thermocouple uses a ground type in which two different types of metal wires inserted in the sheath are electrically connected to the tip of a solid sheath. Therefore, the metal wire can be protected and the temperature measuring contact can be set substantially at the tip of the center electrode. Further, a high voltage can be easily applied to the center electrode via the sheath.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention (Claim 1,
(Corresponding to 2 and 4) will be described based on FIGS. The spark plug A for temperature measurement shown in FIGS. 1 and 2 has a cylindrical metal shell 1 having an outer electrode 12, an insulator 2 with a shaft hole 21 fixed in the metal shell 1, and a bottomed metal shell 1. The insertion hole 31 is formed in the axial direction, and the electrode tip portion 32 is attached to the insulator tip surface 2
A center electrode 3 protruding from 2 and fixed in the shaft hole 21;
The sheath thermocouple 4 inserted in the insertion hole 31 is provided.

The temperature measuring spark plug A is screwed through a gasket 13 to a cylinder head of a gasoline engine to be subjected to a plug compatibility test in order to measure the temperature of the center electrode tip with respect to the engine speed and the like.

The metal shell 1 is made of low carbon steel and has a threaded portion 14 formed with a male screw 141 on the outer periphery and the gasket 1.
3 has a large-diameter body portion 15 and a hexagonal portion 16 for fitting a plug wrench (not shown). Also, 16
Reference numerals 1 and 162 are rings, and 163 is a sealing material such as talc.

The outer electrode 12 has a substantially J-shape, is resistance-welded to the tip surface 11 of the metal shell 1, and forms a spark gap with the tip surface of the center electrode 3. The outer electrode 12 is formed of a nickel alloy having excellent heat resistance and corrosion resistance.

The insulator 2 is formed of a ceramic sintered body mainly composed of alumina (Al ₂ O ₃ ) and includes a long leg portion 23 exposed to high-pressure gas in the combustion chamber, a large-diameter body portion 24, and a corrugation 251. The head 25 has φ2.
The shaft holes 21 of 57 (small diameter side) and φ4.7 (large diameter side) are formed in the axial direction.

In this insulator 2, the seat surface 231 is locked to the tapered surface 143 of the metal shell 1 through the packing 142, and the caulking portion 164 is caulked, whereby the insulator tip surface 2
The head 2 and the head 25 are fixed in the metal shell 1 so as to project from the tip end surface 11 of the metal shell 1 and the caulking portion 164. In addition, 144 is a gas volume into which high-pressure gas enters the combustion chamber, and 252 is a female screw portion for screwing the high-voltage terminal 5.

Center electrode 3 manufactured by cold forging
Is composed of a rod-shaped portion 33 (outer diameter φ2.5) having a circular cross section and a collar-shaped portion 34 that is locked to the shaft hole step portion 211, and has good heat resistance in a nickel alloy 35 having excellent heat resistance and corrosion resistance. A conductive metal 36 (copper alloy in this embodiment) is enclosed. In addition, a bottomed insertion hole 31 for inserting the sheath thermocouple 4 is axially formed in the center electrode 3.

5 is a high-voltage terminal, which is made of mild steel,
It has a male screw portion 51 screwed into the female screw portion 252, a terminal portion 52 into which a plug cap (not shown) is fitted, and a through hole 53 through which the sheath thermocouple 4 is inserted. 6 is a hollow seal pipe, which is located in the shaft hole 21 on the large diameter side,
It has a role of pressing the glass seal 7 and guiding the sheath thermocouple 4.

Reference numeral 7 is a glass seal, which is filled between the flange portion 34 of the center electrode 3 and the seal pipe 6 in the shaft hole 21 on the large diameter side, and the center electrode 3 and the sheath thermocouple 4 are connected to the shaft hole 21.
Seal inside. Reference numeral 8 denotes an inorganic adhesive that hermetically joins the inner wall of the shaft hole 21 and the outer periphery of the rod-shaped portion 33 of the center electrode 3.

As shown in FIG. 3, the sheath thermocouple 4 has a sheath {φ1.0 cylindrical stainless steel tube (SUS316)} 42 having a solid sheath tip 41, and a sheath tip 4.
Chromel wire 43, alumel wire 44 electrically connected to 1
(Each φ 0.3), and the sheath tip 41 is argon arc welded to the hole bottom 311 of the insertion hole 31 of the center electrode 3.

After assembly, the high voltage generated in the ignition coil (not shown) is high tension cord →
It is applied to the center electrode 3 through the plug cap, the high voltage terminal 5, and the sheath 42. Then, the center electrode 3 and the outer electrode 12
A spark discharge (0.9 mm) between and causes the mixture in the combustion chamber of the engine to ignite, the combustion temperature of the combustion gas becomes high (2000 ° C or more), and the sheath thermocouple 4 is based on the thermoelectromotive force. Detects the tip temperature of the center electrode.

The sheath thermocouple 4 has an insertion hole 3 for the center electrode 3.
It is inserted into 1 through the following steps. (1) The sheath tip 41 is the hole bottom 3 of the insertion hole 31 of the center electrode 3.
The sheath thermocouple 4 is inserted from the opening side of the insertion hole 31 of the center electrode 3 so as to come into contact with 11 (see FIGS. 4 and 5). (2) The tip of the electrode tip 32 of the center electrode 3 and the tip of the sheath tip 41 of the sheath thermocouple 4 are melted and joined by argon arc welding. After solidification, the molten alloy part 45
Are rounded as shown in FIG. (3) As shown in FIGS. 7 and 8, the exposed surface 450 has a diameter of φ1.
3. The tip 46 of the molten alloy portion 45 is cut (cut length is 0.6 mm to 1 mm) so that the depth becomes 0.7 mm, the tip surface 451 is flattened, and the outer peripheral edge 452 is edge-shaped ( All around R0.2 or less).

The center electrode 3 having the sheath thermocouple 4 inserted therein
Is inserted into the shaft hole 21 and fixed to the insulator 2, and the insulator 2 is fitted into the metal shell 1 to form the spark plug A.

Next, the temperature measuring spark plug A is used.
Make a point. [A] Spark plug A for temperature measurement (see FIGS. 1 and 2)
And on the entire surface of the tip surface 451 and the side surface of the electrode tip portion 32.
Spark plug H for temperature measurement where the molten alloy part 45 is exposed
(Comparative product; see FIG. 10) and durability test (60H
z, 4 kgf / cm ^TwoPressurization) and endurance time
The amount of increase in cap (mm) was measured. As shown in FIG.
The spark plug A for degree measurement has
Approximately 1/3 of the spark plug H for measurement, slow and durable
It can be improved three times.

The spark discharge is likely to occur on the outer peripheral edge 452 of the center electrode 3, but the spark-melted solidified alloy 45, which is more likely to be consumed than the nickel alloy 35, is exposed to the outside only at the inner peripheral portion (φ1.3) of the end face of the center electrode 3. It is considered that this is because the center electrode 3 is consumed on average and the gap increasing speed becomes slower because the electrodes are formed so as to form.

[A] In the temperature measuring spark plug A, after the sheath tip 41 of the sheath thermocouple 4 inserted in the insertion hole 31 is welded to the hole bottom of the insertion hole 31, the exposed surface 450 has a diameter of 1.3. Molten alloy part 4 so that the depth becomes 0.7 mm
Cutting the tip 46 of 5 (cut length is 0.6 mm to 1 m
m), the front end surface 451 is flattened, and the outer peripheral edge 452 is edge-shaped (the entire circumference at R0.2 or less). For this reason, it is only necessary to add a cutting process, so the process is simple and the manufacturing cost rises only slightly.

[C] The sheath thermocouple 4 is a chromel wire 4
3. The ground type in which the alumel wire 44 is electrically connected to the solid sheath tip 41 is used. Therefore, the chromel wire 43,
The alumel wire 44 is protected by the sheath 42, and the temperature measuring contact can be set substantially at the tip of the center electrode 3.
Further, a high voltage can be easily applied to the center electrode 3 via the sheath 42.

Next, a second embodiment of the present invention will be described.
(Corresponding to 2 and 4) will be described based on FIG. The spark plug B for temperature measurement has a tip surface 121 of the outer electrode 12.
And the outer peripheral surface 321 of the center electrode 3 are opposed to each other, and spark discharge occurs in the spark gap between the front end surface 121 and the outer peripheral surface 321.

Spark plug B for temperature measurement of this embodiment
After welding the sheath tip 41 of the sheath thermocouple 4 inserted into the insertion hole 31 to the hole bottom of the insertion hole 31, the exposed surface 4
The tip 46 of the molten alloy portion 45 is ground so that 50 is φ1.3 and the depth is 0.7 mm, the tip surface 451 is flattened, and the outer peripheral edge 452 is edge-shaped (the entire circumference at R0.2 or less). )I have to. The temperature measuring spark plug B of this embodiment also
The effect similar to the above [a] to [c] is exhibited.

The present invention includes the following embodiments in addition to the above embodiment. Insert the sheath tip 41 of the sheath thermocouple 4 into the insertion hole 3 so as not to melt the side surface and the outer peripheral portion of the end surface of the center electrode 3.
Laser welding may be performed on the hole bottom 311 of No. 1 (corresponding to claim 3).

[Brief description of drawings]

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

FIG. 2 is an enlarged view of a main part of the spark plug.

FIG. 3 is a cross-sectional view (before welding) of a sheath thermocouple.

FIG. 4 is a cross-sectional view showing how a sheath thermocouple is inserted into the insertion hole of the center electrode.

FIG. 5 is a cross-sectional view showing a sheath thermocouple inserted in an insertion hole of a center electrode.

FIG. 6 is a cross-sectional view showing a state where a sheath thermocouple is welded with argon.

FIG. 7 is a cross-sectional view showing a state of cutting the tip of the molten alloy portion.

FIG. 8 is a cross-sectional view showing a state where the tip of the molten alloy portion is cut.

FIG. 9 is a graph showing the relationship between the endurance time and the amount of increase in the gap.

FIG. 10 is a partial cross-sectional view of a spark plug according to a comparative product.

FIG. 11 is a partial sectional view of a spark plug according to a second embodiment of the present invention.

[Explanation of symbols]

 1 Metal shell 2 Insulator 3 Center electrode 4 Sheath thermocouple 11 Tip surface 12 Outer electrode 21 Shaft hole 22 Insulator tip surface 31 Insertion hole 32 Electrode tip 41 Sheath tip 42 Sheath 43 Chromel wire (metal wire) 44 Alumel wire (metal) 45) Molten alloy part (tip of center electrode) 311 Hole bottom 452 Outer peripheral edge A, B Spark plug for temperature measurement

Claims (4)

[Claims] 1. A cylindrical metal shell having an outer electrode projecting from the tip surface, an insulator with a shaft hole fixed in the metal shell, and a bottomed insertion hole formed in the axial direction to form an electrode tip. A core electrode protruding from the tip surface of the insulator and fixed in the shaft hole; and a sheath thermocouple inserted in the insertion hole. The sheath tip and a part of the electrode tip portion are melted and solidified. In the spark plug for temperature measurement, in which the tip of the solid sheath is welded to the hole bottom of the insertion hole through the alloy, the molten solidified alloy is formed so as to be exposed to the outside only at the inner peripheral portion of the end face of the center electrode. A spark plug for temperature measurement, which is characterized in that 2. A tubular metal shell having an outer electrode protruding from the tip surface, an insulator with a shaft hole fixed in the metal shell, and a bottomed insertion hole formed in the axial direction to form an electrode tip. A core electrode protruding from the tip surface of the insulator and fixed in the shaft hole; and a sheath thermocouple inserted in the insertion hole. The sheath tip and a part of the electrode tip portion are melted and solidified. In a temperature measuring spark plug in which the solid sheath tip is welded to the hole bottom of the insertion hole via an alloy, the sheath tip of the sheath thermocouple inserted into the insertion hole is fixed to the hole bottom of the insertion hole. A spark plug for temperature measurement, characterized in that the molten and solidified alloy is exposed to the outside only at the inner peripheral portion of the end surface of the center electrode by grinding or cutting off the tip of the center electrode after welding to the center electrode. 3. A cylindrical metal shell having an outer electrode protruding from the front end surface thereof, an insulator with a shaft hole fixed in the metal shell, and a bottomed insertion hole formed in the axial direction to form an electrode tip. A center electrode protruding from the tip end surface of the insulator and fixed in the shaft hole; and a sheath thermocouple inserted into the insertion hole, so that the side surface and the end surface outer peripheral portion of the center electrode do not melt,
A spark plug for temperature measurement, characterized in that the sheath tip of the sheath thermocouple is welded to the bottom of the insertion hole. 4. The temperature according to claim 1, wherein the sheath thermocouple is a ground type in which two different kinds of metal wires inserted in the sheath are electrically connected to the tip of a solid sheath. Spark plug for measurement.