JPH0412488A - Spark plug with pressure sensor - Google Patents

Abstract

PURPOSE:To prevent the occurrence of smoke pollution during an engine compatibility test with a dense air-fuel mixture in the low-temperature environment by providing a required ceramic heater on an insulator located at the leg section of the main metal of a spark plug provided with a pressure sensor. CONSTITUTION:A ceramic heater 5 coated with ceramic on an electric heating element is arranged on the surface or inside of the long leg section of an insulator 2 located at the reach section 11 on the leg section of a main metal 1 provided with a piezoelectric pressure sensor 4. When the heater 5 is excited and the surface temperature of the long leg section of the insulator 2 is forcefully increased, the carbon stuck on the long leg section is burned. Smoke pollution rarely occurs during an engine compatibility test with a dense air-fuel mixture at a low temperature, and the occurrence of such a trouble is prevented that the compatibility test is interrupted during its conduct.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention mainly relates to a spark plug with a pressure sensor used for suitability testing of newly developed engines.

[Prior Art] A spark plug with a pressure sensor is known, which consists of a center electrode, an insulator surrounding the center electrode, and a mounting bracket that holds the insulator in its inner cavity and has a pressure sensor disposed in its body. (Utility Model Application Publication No. 63-171989).

[Problems to be Solved by the Invention] In general, suitability tests for newly developed engines are conducted under various conditions, and are often conducted in low-temperature environments or in rich air-fuel mixtures.

In such cases, conventional spark plugs with pressure sensors
Smoke contamination is likely to occur, and if smoke contamination occurs, even if there is no abnormality in the pressure sensor, it will misfire, making it unusable and the test will be interrupted.

An object of the present invention is to provide a spark plug with a pressure sensor that has excellent resistance to explosion and contamination.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a method for fixing an insulator with a shaft hole by fitting it into a cylindrical main metal fitting, and inserting and fixing a center electrode into the shaft hole. , a pressure segisor in which a piezoelectric pressure sensor is disposed between a body portion with a slightly large diameter provided in the middle of the metal shell and a leg portion with a small diameter provided on the tip side thereof and having an engine mounting screw. In the spark plug with
A ceramic heater, which is an electric heating element coated with ceramic, is installed on the surface or inside of the edge body located at the leg of the metal shell.

[Function and Effects of the Invention] (Function) By energizing the ceramic heater, the surface temperature of the long leg portion of the insulator can be forcibly raised. Therefore, carbon and the like adhering to the long leg portions can be burned off.

(Effects) Even if a test engine is tested under a low-temperature environment with a rich mixture, cicada contamination is unlikely to occur. Therefore, suspension of the compliance test due to smoke contamination can be prevented.

[Example] Next, a first example of a spark plug with a pressure sensor according to the present invention will be described based on FIGS. 1 and 2.

A spark plug A with a pressure sensor is fixed by fitting an insulator 2 with a shaft hole 21 into a cylindrical main metal fitting 1, and fixing the insulator 2 with a shaft hole 21.
The center electrode 3 is inserted into the hole 1 and fixed. Further, a pressure sensor 4 is provided on the metal shell 1, and a ceramic heater 5 is provided on the insulator 2.

The metal shell 1 is made of low carbon steel, and has a reach portion 11 at the tip.
(small diameter), a hexagonal part 12 at the rear end, and a body part 13 (slightly large diameter) in the center.

The reach part 11 has screws 1 for engine mounting except for the tip.
4 is formed on the outer periphery. The end surface of this reach part 11 has gold on the firing part side, 1K61 (100% iridium,
A Keckel alloy) is welded to the outer electrode 6 on which a platinum alloy (platinum alloy, etc.) is disposed. Further, a tapered packing contact surface is formed on the inner wall of the reach portion 11, and a packing is provided around the contact surface.

The hexagonal part 12 has an outer periphery as a hexagonal opposite side (diameter smaller than the body part 13), and a talc ring and wire packing are inserted inside.

The body part 13 consists of a large diameter part and a small diameter part, and a holding fitting 15 having an angular cross-section is seam-welded 16 to the small diameter part.A gasket 17 is provided around the engine side of this holding fitting 15. It is set up.

The insulator 2 includes a long leg portion 22 at the tip and a corrugation portion 23 at the rear end, and is formed of a ceramic sintered body made of alumina. Further, the base 24 of the long leg portion 22 has a tapered shape and is in contact with the gasket.

The central electrode ft3 is made by joining an ignition cutter 32 (made of noble metal such as platinum-20% iridium alloy, 100% iridium alloy, etc.) to an electrode body 31, so that there is no gap between it and the shaft hole 21. It is formed.

As shown in FIG. 2, the pressure sensor 4 includes an annular packing 41 arranged on the inner bottom of a hollow ring-shaped metal case 40, the upper inner wall of which is electrically insulated with insulating substrates 42 and 43, and an annular electrode 44. It is sandwiched between an annular insulating plate 45 and an annular piezoelectric element 46, and an output cable 47 is electrically connected to the electrode 44. Note that the output cable 47 is connected to a pressure detection device (not shown) through the guide hole 10.

The ceramic heater 5 is disposed on the center surface of the insulator 2 located at the reach portion 11 of the metal shell 1, and is made by covering an electric heating element such as tungsten or platinum with a ceramic mainly composed of alumina. In addition, 50 is a waterproof O-ring,
51 and 52 are lead electrodes. The lead electrode 51 is connected to the packing, and the electric current Vi! 52 are electrically connected to respective terminal terminals 53 provided around the corrugation portion 23. When performing an engine suitability test, this ceramic heater 5 is energized when smoke contamination is likely to occur (at low temperatures, during startup, etc.).

A method for manufacturing the main parts of the spark plug A with a pressure sensor will be described.

(1) Mix tungsten powder and alumina powder, add a binder, and produce tungsten paste for each application (for heating elements, lead electrodes, and heater terminals).

(2) Print the above tungsten paste at a predetermined position on the green insulator.

(3) Fitting the ignition electrode 32 into the shaft hole of the unfired insulator,
The unfired electrode body, which is made by adding conductive metal powder to glass powder, is heated in a heating furnace while being pressed with a center shaft (not shown).
i1.3 and insulator 2 are co-fired together. The tungsten paste is applied to the ceramic heater 5 and the lead electrode 51.
．． 52, which becomes the heater terminal 53.

(4) Assemble the spark plug body except the holding fitting 15 and gasket 17.

(5) Pass the output cable 47 through the guide hole 10 from below,
The pressure sensor 4 is fitted into the reach portion 11 from below in the figure, and brought into contact with the stepped portion 18 of the body portion 13.

(6) Seam weld 16 the holding fitting 15 to the small diameter portion of the metal shell 1 while pressing the pressure sensor 4 against the stepped portion 18 using the holding fitting 15.

(7) Attach the gasket 17 and complete.

Next, the effects of the spark plug A with a pressure sensor will be described.

(A) By energizing the ceramic heater 5, the surface temperature of the long leg portion 22 of the insulator 2 can be increased to improve self-cleaning performance. For this reason, even if an engine suitability test is performed in a low-temperature environment with a rich air-fuel mixture, carbon or the like is unlikely to adhere to the long leg portion 22, and smoke staining is extremely unlikely to occur.

(a) The firing electrode 32 is thin with a diameter of 1 mm. In addition, shaft hole 2
There is no gap between 1 and the firing electrode 32. Therefore, the insulation path in the radial direction is secured, and the creepage distance between the firing electrode 32 and the heater 5 is also secured. Therefore, even if a severe compliance test is performed, no problems (penetration, flashover) will occur due to the arrangement of the ceramic heater 5.

(1) The ignition electrode 32 is made of a noble metal such as platinum-20% iridium alloy, and the outer type 'IE! 6 is 100% iridium,
A noble metal 61 such as a platinum alloy is disposed on the firing part side. Therefore, even if severe compliance tests are performed for a long time or continuously, electrode wear due to sparks is extremely small, resulting in excellent durability.

[Brief explanation of the drawing]

1 and 2 show a first embodiment of the invention. FIG. 1 is a partial sectional view of a spark plug with a pressure sensor, and FIG. 2 is a sectional view of a main part thereof. In the figure 1... Metal shell 2... Insulator 3... Center electrode 4... Pressure sensor 5... Ceramic heater 11... Reach part (leg part) 13... Body part 14
...Screw (engine mounting screw) 21...Shaft hole A.
・・Spark plug with pressure sensor Diagram 2

Claims (1)

[Scope of Claims] 1) An insulator with a shaft hole is fitted and fixed into a cylindrical metal shell, a center electrode is inserted and fixed into the shaft hole, and a slightly diameter insulator provided in the middle of the metal shell In a spark plug with a pressure sensor, a piezoelectric pressure sensor is disposed between a large body part and a small diameter leg part provided on the tip side of the body part and having an engine mounting screw. A spark plug with a pressure sensor, characterized in that a ceramic heater, which is an electric heating element coated with ceramic, is disposed on the surface or inside of an insulator.