JPH0129554Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a spark plug with a built-in pressure sensing element (pressure pickup) that detects the pressure within an engine combustion chamber and converts it into an electrical signal.

Recently, spark plugs have appeared that are combined with a pressure pickup as a detection element for research on the combustion state of piston engines, detecting knocks, improving fuel efficiency, and controlling exhaust emissions. One of the typical structural examples (for example, see Japanese Patent Publication No. 41-5154) is that when installing the spark plug 1 to the cylinder head 5 as shown in Fig. 1, the screw seat 3 of the mounting bracket 2 of the spark plug 1 is A gasket 4 is fitted into the gasket 4, and there is a type in which a pressure sensitive element (pressure pickup element) is incorporated inside the gasket 4.

However, with this type of structure, the spark plug and pressure-sensitive element are separate and have a built-in gasket, so they must be completely sealed by themselves, making it extremely difficult to install and remove the pressure pick-up. In order to solve this problem, it is conceivable to directly connect the pressure pickup element to the spark plug, but this inevitably complicates the connection and fixing means. Furthermore, in the case of the above-mentioned pickup built into the gasket, the output take-out connector takes up space in the radial direction, and it is inevitable that the connection means and structure will be complicated if the lead wires are to be shielded.

The present invention was developed in view of the above-mentioned circumstances, and consists of grooves being bored in the cylinder head side end face and sealing face of the large-diameter body of the mounting bracket that securely supports the spark plug insulator. A pressure sensitive element is inserted into the lever and fixedly supported by a presser foot, and a hole is provided through the large diameter body of the mounting bracket on the opposite side to the groove, that is, on the opposite end side to the cylinder head side. By providing a connector here, the lead wire itself can be easily attached and detached with a simple structure, and no space is required in the radial direction to take out the lead wire, and the mounting bracket also serves as a shield. Therefore, there is no need for a special shield for the lead wire, and furthermore, since processing is simple, the cost is low.

Next, the present invention will be explained with reference to the drawings. In Fig. 2, 11 is a ceramic insulator in which a center electrode 12 is inserted and fixed, and 13 is a mounting bracket that is connected to a large diameter body 13. -a and a small-diameter screw portion 13-b, which fixedly support the ceramic insulator 11 from the outside according to known specifications. Further, a spark gap is formed between the tip of the center electrode 12 and an outer electrode 14 protruding from the tip of the mounting fitting 13, and a terminal fitting 15 for connecting to a high voltage lead wire is fixedly provided. An annular groove 16 is provided on the cylinder head side end surface of the large diameter body 13-a of the mounting bracket 13.
A pressure-sensitive element 17, that is, an element made of a piezoelectric (or electrostrictive) material such as barium titanate porcelain or a pressure-electric transducer such as a semiconductor with a large piezoresistive effect, is inserted into this and pressed with a presser foot 18. 1
8 may be fixed by being crimped inwardly by the distal end side portion 16-a of the mounting fitting 13, or the crimped portion may be further partially welded and fixed if necessary.
Electrodes 19 are in contact with both surfaces of this pressure sensitive element 17. 20 is an insulating plate.

Further, a hole 21 is provided in the large-diameter body 13-a of the mounting bracket 13, extending from the end surface opposite to the cylinder head side end surface to the groove 16 into which the pressure-sensitive element 17 is inserted, and the connector pin 22 is inserted into this hole. It is attached while being protected by an insulator 23 around it, and its tip extends to the pressure sensitive element 17 mentioned above. A gasket 24 is brought into contact with the surface of the presser foot 18 of the pressure sensitive element, and is brought into airtight contact with the cylinder wall (not shown).

The present invention has the above structure, and the pressure sensitive element 17 is housed in the groove 16 provided in the cylinder head side end surface (gasket seat surface) of the large diameter body 13-a of the mounting bracket 13. Therefore, when the spark plug is installed in the cylinder head (not shown), there is no gas leakage and pressure can be received from a wide surface, and the output connector of the pressure sensing element takes up space vertically, that is, inside the mounting bracket. The overall structure is compact, the lead wires can be easily shielded, the lead wires of the pressure sensitive element can be easily attached and detached, and manufacturing is relatively easy.
Lower costs are also possible.

[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, and FIG. 2 is a vertical cross-sectional view showing the structure of an example of a spark plug with a built-in pressure-sensitive element according to the present invention. be. 1...Spark plug, 2...Mounting bracket, 3...
... Screw seat, 4 ... Gasket, 5 ... Cylinder head, 11 ... Ceramic insulator, 12 ... Center electrode, 13 ... Mounting bracket, 13-a ... Body, 1
3-b...Threaded portion, 14...Outer electrode, 15...
Terminal fitting, 16...Groove, 17...Pressure sensitive element, 18
... Presser foot, 19 ... Electrode, 20 ... Insulating plate, 2
1... Hole, 22... Connector pin, 23... Insulator, 24... Gasket.

Claims (1)

[Scope of utility model registration request] In the large-diameter body of the mounting bracket, a pressure-sensitive element is housed in a groove provided on the end face of the cylinder head.
While being fixed by a presser foot, a through hole is formed in the large diameter body of the mounting bracket from the pressure sensing element to the end surface opposite to the cylinder head, and the output of the pressure sensing element is taken out into this through hole. A spark plug with a built-in pressure-sensitive element characterized by having a connector section.