JPS6121819Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) This invention detects the pressure inside the engine combustion chamber,
This invention relates to a spark plug with a built-in pressure pickup that incorporates a pressure-sensitive element that converts into an electrical signal.

(Prior art) Recently, a pressure pickup unit for detecting the pressure inside the engine combustion chamber is used as a component of a control system for research on piston engine combustion characteristics (knocking, peak pressure, etc.), fuel efficiency improvement, exhaust gas countermeasures, etc. Spark plugs that combine the following are now appearing.

One of the typical structural examples of this type of spark plug (for example, see Japanese Patent Publication No. 41-5154) is as follows:
As shown in FIG. 1, when installing the spark plug 1 to the cylinder head 2, a gasket 5 is fitted into the screw seat 4 of the mounting bracket 3 of the spark plug 1.
There is a type that stores a pressure-sensitive element inside to detect pressure.

However, in this type of structure, the spark plug and the gasket incorporating the pressure-sensitive element are separate entities, and are constructed by combining them, so the seal of the pressure-sensitive element part, It is unavoidable that the mounting structure of the connector for taking out the output, the means and structure of shielding and connecting the lead wires, etc. become complicated.

The present applicant previously proposed a spark plug with a built-in pressure-sensitive element having a structure as shown in FIG. 2 for the purpose of solving the drawbacks of the conventional example.
(Refer to Utility Application No. 58-25142) This spark plug with a built-in pressure-sensitive element will be explained with reference to Fig. 2. In the figure, 6 indicates the center electrode 7.
The mounting bracket 8 consists of a large-diameter body section 8-a and a small-diameter screw section 8-b, and fixes and supports the ceramic insulator 6 from the outside according to known specifications. . A spark gap is formed between the tip of the center electrode 7 and an outer electrode 9 protruding from the tip of the mounting bracket 8, and the other end of the center electrode 7 has a terminal for connecting to a high voltage lead wire. Metal fittings 1
0 is fixed. An annular groove 11 is provided on the lower end surface of the large diameter portion of the mounting bracket 8.
Further, a through hole 12 reaching the groove 11 is bored in the upper end surface of the shoulder portion of the mounting bracket 8, and a pressure pickup portion 15-c is housed in the through hole 12. c is the pressure sensitive element 13
, an upper electrode plate 15-a equipped with a connector pin 14 protruding into the through hole 12, an insulating support plate 19, and a lower electrode plate 15-b, which are laminated, and the lower part is a presser metal fitting 16. supported by
The presser metal fitting 16 is fixed by crimping the tip side of the large-diameter body 8-a of the mounting metal fitting 8 inward, and the gasket 17 is brought into contact with it. The structure is filled with an insulator 18 and sealed. Further, 19 is an insulating support plate.

(Problems to be solved by the invention) When the spark plug with a built-in pressure-sensitive element having such a structure is installed in a cylinder head,
The large diameter body 8-a of the mounting bracket 8 allows pressure to be received on a wide surface.
Since the pressure pick-up part 15-c is housed inside, the overall structure is compact, and the lead wires can be easily shielded and the lead wires can be easily attached and detached. The lower part of the part 15-c is the mounting bracket large diameter body part 8.
- Since the presser metal fitting 16 is crimped at the tip of a and the gasket 17 is in contact with it, it is not completely sealed, and during actual operation when attached to the cylinder head, there is a difference in thermal expansion due to high temperature. This creates a gap and combustion gas enters from that part, and due to changes over time, the pressure pick-up part 1
It was subsequently discovered that there was a problem in that the insulation properties of 5-c were deteriorated and the pressure detection performance was lowered.

(Means/effects for solving the problem) The present invention has been developed in view of the above-mentioned circumstances, and as a solution to the above-mentioned problem, the present invention has been developed to solve the above-mentioned problem. An object of the present invention is to provide a spark plug with a built-in pressure pickup having a structure in which the combustion gas is completely sealed and there is no possibility that combustion gas will intrude into the pressure pickup.

(Embodiment) FIG. 3 is a half-longitudinal cross-sectional view of an embodiment of the spark plug with a built-in pressure pickup according to the present invention, and the same parts as in FIG. 2 are designated by the same reference numerals.

In the figure, the upper end surface 8'-1 of the shoulder part of the mounting bracket 8'
A through hole 12 is bored in the axial direction of the plug as in the case shown in FIG.
A ring-shaped pressure pickup portion 15-c is formed by stacking an upper electrode plate 15-a, an insulating support plate 19, and a lower electrode plate 15-b, in which a connector pin 14 for taking out an output to the outside is bored. 1
4 is disposed so as to protrude into the through hole 12, and the exposed portions of the outer periphery and bottom surface of the pressure pickup portion 15-c are covered with a ring-shaped cover fitting 20 having an L-shaped cross section. Its upper and inner end surfaces are welded to the lower surface 8'-3 of the shoulder 8'-1 and the body 8'-4 of the mounting bracket, respectively, and the open end of the through hole 12 is welded to the periphery of the connector pin 14. , which has a main part structure filled with an insulator 18 and sealed. Note that 19 is an insulating support plate.

The rest of the structure of the spark plug is the same as that shown in FIG. 2, so a description thereof will be omitted.

(Effects of the invention) As can be understood from the above explanation, the spark plug with a built-in pressure pick-up of the present invention has a storage structure in which the pressure pick-up part is completely covered and sealed. This device completely prevents carbon, harmful gases, and moisture from entering the pressure-sensitive element from entering the pressure-sensitive element, so stable pressure detection performance can be obtained. This solution can be provided as a built-in pressure spark plug.

[Brief explanation of the drawing]

Fig. 1 is a vertical cross-sectional view showing the structure of a pressure-detecting spark plug incorporating a conventional pressure-sensitive element, Fig. 2 is a half-vertical cross-sectional view showing a prior application example of a spark plug with a built-in pressure-sensitive element, and Fig. 3 1 is a half-longitudinal sectional view of a spark plug with a built-in pressure pickup according to the present invention. 1: Spark plug, 2: Cylinder head,
3, 8, 8': Mounting bracket, 4: Screw seat, 5, 1
7: Gasket, 6: Ceramic insulator, 7: Center electrode, 8-a: Large diameter body, 8-b: Small diameter thread, 8'-1: Shoulder upper end surface, 8'-2, 8 ′−
4: Torso, 8'-3: Lower end of shoulder, 9: Outer electrode,
10: Terminal fitting, 11: Groove, 12: Through hole, 1
3: Pressure sensitive element, 14: Connector pin, 15-a:
Upper electrode plate, 15-b: Lower electrode plate, 16: Holding metal fitting, 18: Insulator, 19: Insulating support plate.

Claims (1)

[Scope of utility model registration request] A ring-shaped pressure pickup portion 15-c, which is formed by laminating the pressure-sensitive element 13, an upper electrode plate 15-a with a protruding connector pin 14, an insulating support plate 19, a lower electrode plate 15-b, etc., is attached to the plug. Axial through hole 1 provided in shoulder 8'-1 of mounting bracket 8'
2, the connector pin 14 protrudes into the ring, which is disposed along the body portion 8'-2 of the mounting bracket, and the exposed portion of the outer periphery and bottom surface of the pressure pickup portion 15-c is formed into an L-shaped cross section. shaped cover metal fittings 20
The upper and inner end surfaces of the cover metal fitting 20 are welded to the lower surface 8'-3 and body part 8'-4 of the shoulder part 8'-1 of the mounting metal fitting 8', respectively, and A built-in pressure pick-up characterized by having a pressure pick-up storage structure in which the through hole 12 of the shoulder portion 8'-1 and the circumference of the connector pin 14 in the cover metal fitting 20 except for the tip are filled with an insulator 18. type spark plug.