JPH0238391Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a spark plug that has a built-in pressure pickup that detects the pressure in the combustion chamber of an internal combustion engine and converts it into an electrical signal.

(Prior art) In order to control combustion conditions such as ignition timing, emissions, output, and fuel efficiency of internal combustion engines, there are various spark plugs equipped with a built-in pressure pickup that detects changes in pressure within the combustion chamber and converts them into electrical signals. A conventional example of this device, which has been devised and used, is shown in FIG. 3, in which FIG. 3A is a longitudinal front view of the main part, and FIG. In A of the same figure, 1
3 is a ceramic insulator with a center electrode 2 inserted and fixed therein, and 3 is a hexagonal part 3-1 which becomes a plug wrench fitting part when installing a plug in the cylinder head with a mounting bracket, and a body part. 3-2 and a threaded portion 3-3, which fixedly support the insulator 1 from the outer periphery, and an outer electrode 4 protruding from the tip of the threaded portion 3-3 and a tip portion 2-1 of the center electrode 2. A spark gap is formed between the insulator 1 and the high voltage terminal 5 fixed to the center electrode 2 at the rear end of the insulator 1 for connecting the center electrode to a high voltage lead wire. Reference numeral 6 denotes a pressure pickup section (pressure sensor), which is explained in the enlarged sectional view of the main part shown in FIG.
2, 6-2', and metal seat plates 6-3, 6 above and below it.
-3' is stacked, the inside and outside of the ring are covered with insulators 6-4, 6-4', and the lead wire 6-6 is connected to the terminal leg 6-5 of the internal electrode 6-1. It's connected and connected. An annular groove 3-4 is formed in the lower end surface of the body 3-2 of the mounting bracket 3.
4 Small hole 3-6 drilled in thin side wall 3-5 on the outer periphery
The terminal leg 6-5 of the pressure pick-up part is insulated and inserted through the annular pressure pick-up part 6, and the annular pressure pick-up part 6 is housed in the recessed groove 3-4 and fixed by caulking the thin side wall 3-5 inward. ing. The part indicated by the broken line in the figure shows the state before the side wall 3-5 is caulked.

FIG. 4 shows another conventional example, in which an annular groove 3-8 is provided at the lower end of the body 3-2 of the mounting bracket 3 and opens into the mounting seat surface 3-7. A pressure sensor 7 incorporating a molded piezoelectric element is housed in the groove 3-8 and fixed by welding a diaphragm 8 made of an annular thin plate, and a lead wire 9 for taking out the output from the pressure sensor 7 is connected to the mounting bracket. A lead-out hole 3-9 provided toward the inner cavity of the body 3-2 of No. 3, and a lead-out hole 1 provided in the large-diameter portion of the insulator 1.
A structure in which the head is taken out through -1 toward the head side is known. Note that 3-10 is an introduction hole for guiding the combustion chamber pressure of the internal combustion engine (not shown) to the pressure sensor 7, and the structure of the pressure sensor 7 is the same as described above except that the lead wire 9 is led out from the top surface of the sensor. This is the same or similar to the conventional pressure sensor 6 shown in FIG. 3B.

(Problem to be solved by the invention) In the conventional spark plug with a built-in pressure pick-up as described above, the amount of gas inside the cylinder leaking from between the cylinder head and the threaded part of the mounting bracket is approximately 60 kg.
f/cm ² and invades the pressure pick-up part,
There is a problem that this gas causes changes in the pressure pickup part over time, worsening the insulation resistance.Also, since the entire circumference of the diaphragm is welded to maintain airtightness, not only is welding complicated, but also the piezoelectric element There was a risk that the materials would be destroyed due to heating.

(Means for solving the problem) The present invention was made to solve the above problems, and the body of the mounting bracket has a structure consisting of a large diameter part and a small diameter part below it, and the body part is made of metal. An annular metal-coated pressure sensor hermetically encapsulated by a case is fitted in contact with the lower end surface of the large diameter part and the side surface of the small diameter part of the body of the mounting bracket, and the outer peripheral upper end of the metal case of the pressure sensor is fitted. Either connect the edge to the lower end of the outer periphery of the large diameter part of the body of the mounting bracket with a low melting point metal such as solder, or fit an annular holding bracket with an L-shaped cross section and an outer wall and a bottom wall to the outside of the pressure sensor. The pressure sensor is fixed by spot or seam welding the upper edge of the outer wall to the outer periphery of the shoulder of the body of the mounting bracket, and the inner wall of the metal case of the pressure sensor and the small diameter part of the body of the mounting bracket are fixed. This spark plug has a built-in pressure pickup and has an O-ring made of heat-resistant rubber or hollow metal inserted between the two.

(Function) As described above, since the pressure pickup part itself is hermetically encapsulated by the metal case, the components inside the metal case do not come into direct contact with gas. Furthermore, since an O-ring is installed between the pressure sensor and the mounting metal body, gas leakage between the mounting metal body and the inner diameter side of the pressure sensor can be prevented. Incidentally, when the spark plug is screwed onto the cylinder head, the space between the pressure pickup portion and the cylinder head is kept airtight by using a copper gasket or the like as in the past.

(Embodiment) FIG. 1 shows an embodiment of a spark plug with a built-in pressure pickup according to the present invention, in which A is a partially longitudinally sectional front view, and B is an enlarged longitudinal sectional view of the main part.
In FIG. 1A, the structure other than the main parts shown in FIG. 1B is the same as that of the prior art example in FIG. 3, so a description thereof will be omitted, but the same parts are designated by the same reference numerals. Therefore, the main parts in FIG. 1A will be explained in FIG. , 7-2' and metal seat plates 7-3, 7-3' stacked above and below, the center conductor of the lead wire 9 is connected to the internal electrode 7-1, and the insulator 7 -5, 7-5', and is housed in an annular metal case 7-6. The mounting bracket body 3-2 consists of a large-diameter portion 3-2a in which a lead-out hole 3-7 for the lead wire 9 of the pressure sensor is formed, and a small-diameter portion 3-2b below the large-diameter portion 3-2a.
An annular groove 3-8 is formed on the outer periphery of the small diameter portion 3-2b. An O-ring 10 made of heat-resistant rubber or hollow metal is fitted into the concave groove 3-8, and the annular pressure sensor 7 is attached to the upper and inner surfaces of the lower end surface of the large diameter portion 3-2a of the body of the mounting bracket, respectively. 3-9
and is fitted in contact with the outer periphery of the small diameter portion 3-2b,
The upper edge of the outer periphery of the metal case 7-6 of the pressure sensor 7 is joined to the lower edge of the outer periphery of the large diameter portion 3-2a of the body of the mounting bracket with a low melting point metal such as solder.
The pressure sensor shown in Figure A is fixed and integrated with the spark plug. In addition,
In this embodiment, the piezoelectric element 7-2 and 7-2' are stacked together, but it can also be a single layer type with only 7-2, or the insulator 7-2 on the outer periphery
5′ can also be omitted.

FIG. 2 is an enlarged cross-sectional view showing the main parts of another embodiment of the spark plug with a built-in pressure pickup according to the present invention, and the structure of the other parts other than the main parts is completely the same as in Fig. 1A above. Therefore, illustration and explanation will be omitted. Further, in FIG. 2, the pressure sensor 7 is exactly the same as the pressure sensor 7 in FIG. Therefore, pressure sensor 7
In place of the structure in which the metal case of the pressure sensor is attached to the body of the mounting bracket via the O-ring 10 in the same manner as explained in FIG. , an annular holding fitting 11 having an L-shaped cross section and an outer wall 11-1 and a bottom wall 11-2 is fitted to the outside of the pressure sensor 7, and the upper edge of the outer wall 11-1 is attached to the mounting fitting body 3-. The pressure sensor is fixed to the spark plug by spot or seam welding to the outer periphery of the shoulder of the spark plug, thereby creating an integrated structure.

(Effects of the invention) As described above, the spark plug with a built-in pressure pick-up of the present invention is a pressure sensor whose pressure pick-up part is sealed by a metal case, so that gas leaking from the cylinder cannot enter the pressure pick-up part. However, there is no risk that this gas will impair the performance of the pressure sensor, resulting in improved stability and reliability. In addition, the airtightness between the pressure sensor and the mounting bracket is ensured by an O-ring, and the pressure pickup part and the cylinder head are sealed by using conventional copper gaskets, etc., so it is completely sealed. We can provide a spark plug with a built-in pressure pick-up that maintains airtightness. Furthermore, since the pressure pickup portion is manufactured separately in advance and assembled into the plug, assembly work is simplified and workability is improved.

[Brief explanation of the drawing]

Fig. 1 shows an embodiment of the spark plug with a built-in pressure pick-up of the present invention, A is a partially longitudinally sectional front view, B is an enlarged vertical sectional view of the main part, and Fig. 2 is an embodiment of the pressure pick-up of the present invention. FIGS. 3 and 4 are an enlarged longitudinal sectional view of a main part of another embodiment of a built-in spark plug, and FIGS. be. 1: Insulator, 2: Center electrode, 3: Mounting bracket, 3
-2: Body part, 3-2a: Large diameter part, 3-2b: Small diameter part,
4: Outer electrode, 5: High voltage terminal, 6, 7: Pressure sensor, 7-6: Metal case, 10: O ring, 1
1: Holding metal fittings.

Claims (1)

[Claims for Utility Model Registration] (1) A center electrode equipped with a high-voltage terminal, an insulator that surrounds and fixedly supports the center electrode, and a space between the insulator and the tip of the center electrode, which is airtightly installed in the cylinder head. In a spark plug, the body of the mounting bracket consists of a large diameter part and a small diameter part below it, and is airtight with a metal case. An annular metal-covered pressure sensor is fixed with its upper surface and inner surface respectively in contact with the lower end surface of the large diameter portion and the outer peripheral surface of the small diameter portion of the body portion, and the inner wall of the metal case of the pressure sensor and the A spark plug with a built-in pressure pick-up that is sealed with an O-ring between the small diameter part and the small diameter part. (2) A utility model in which the pressure sensor is fixed by joining the upper edge of the outer periphery of the metal coating of the pressure sensor to the outer periphery of the lower end surface of the large diameter portion of the body of the mounting bracket using a low melting point metal such as solder. A spark plug with a built-in pressure pickup as claimed in claim 1. (3) The pressure sensor is fixed by fitting an annular holding fitting having an L-shaped cross section and an outer wall and a bottom wall to the outside of the pressure sensor, and attaching the upper edge of the outer wall of the holding fitting to the body of the mounting fitting. A spark plug with a built-in pressure pick-up according to claim 1, which is made by spot or seam welding to the outer peripheral edge of the shoulder of the spark plug. (4) The spark plug with a built-in pressure pickup according to any one of claims 1 to 3, wherein the O-ring is made of heat-resistant rubber or hollow metal.