JPH03110778A - Built-in photo-sensor type spark plug - Google Patents

Abstract

PURPOSE:To measure the temperature in a combustion chamber and the combustion light signal stably and to obtain an excellent durability by providing an ignition electrode baked integrally with an insulator which is inserted at the top of an axial hole. CONSTITUTION:A metal plate 31 consisting of a high solder material presenting a conical trapezoid, whose tip is connected electrically with an ignition electrode 30, is connected to the ignition electrode 30 and the taper 21 at the igniter side, and the ignition electrode 30 is baked integrally together with an insulator 2 which is inserted to the top of an axial hole 23. As a result, no clearance is genenated between the ignition electrode 30 or the insulator 2, and the axial hole 23, and no combustion gas invades into the axial hole 23. Consequently, the top end surface of a photo-waveguide body 14 is never contaminated with carbon or the like, the temperature in a combustion chamber and the combustion light signal can be measured stably, no deterioration of the photo-waveguide body 4 owing to the contamination is generated, and ignition electrode 30 is fixed closely to the insulator 2 without generating a removal and the like. An excellent durability can be obtained, accordingly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a spark plug that measures the temperature of a combustion chamber of an internal combustion engine and a combustion light signal.

[Prior Art] An internal combustion engine in which an optical waveguide is provided in the shaft hole of an insulator of a spark plug so as to be exposed to the combustion chamber, and a heat-resistant metal covering that does not transmit light is provided on the tip surface of the optical waveguide. A spark plug that measures the temperature and combustion waveform of a combustion chamber of an engine is known (Japanese Patent Laid-Open No. 17-163841).

[Problems to be Solved by the Invention] However, in conventional spark plugs, when the heat-resistant metal coating is repeatedly exposed to the high temperature and high pressure combustion gas of an internal combustion engine, the bonding strength between the coating and the optical waveguide is low, so and peel it off.

An object of the present invention is to provide a spark plug with a built-in optical sensor that can stably measure the temperature of a combustion chamber and a combustion light signal, and has excellent durability.

[Means for Solving the Problems] The present invention provides a cylindrical metal shell having an outer electrode formed at its tip;
an insulator that has a tapered shaft hole on the firing part side and the base side and is fitted into and fixed to the cylindrical metal shell; and an insulator that is fitted into the tip of the shaft hole and is fired integrally with the insulator. an ignition electrode, a metal plate made of a high brazing material having a truncated cone shape that is engaged with the taper on the ignition part side and whose tip is electrically connected to the ignition electrode, whose tip is electrically connected to the metal plate and whose rear end is on the base side; a conductor located behind the taper of the shaft, a tubular terminal electrode inserted from the rear end of the shaft hole, and a central conductor made of conductive glass that seals the terminal electrode and the conductor within the shaft hole; , and an optical waveguide that is inserted through the center conductor and transmits infrared rays.

[Actions and Effects of the Invention 1 The spark glove with a built-in photosensor of the present invention has the following effects.

(A) The tip is electrically connected to the ignition electrode, and a truncated conical metal plate made of high brazing material is engaged with the ignition electrode and the taper on the ignition part side. Therefore, when inserting the firing electrode into the green insulator, the firing electrode can be inserted in either direction, and the firing electrode has a high degree of freedom in shape. For example, if the firing part of the firing electrode is shaped like a brim, electrode wear will be reduced.

(b) The ignition electrode is fitted into the tip of the shaft hole and fired integrally with the insulator. Therefore, there is no gap between the ignition electrode and the shaft hole of the insulator, and combustion gas does not enter into the shaft hole.
The tip surface of the optical waveguide is not contaminated with carbon, etc., and the temperature of the combustion chamber and the combustion light signal can be measured stably.

(c) Spark plugs with a built-in optical sensor have excellent durability because the optical waveguide does not deteriorate due to contamination, and the ignition electrode is tightly fixed to the insulator and does not become loose.

[Example] A first example of the optical sensor built-in plug according to the present invention is described below.
This will be explained based on FIGS.

The optical sensor built-in plug A has a cylindrical metal shell 1 with an outer electrode 11 welded to the tip thereof, and a shaft hole 23 in which tapers 21 and 22 are formed, and is fitted and fixed into the cylindrical metal shell 1. an insulator 2, a firing electrode 30 fitted into the tip of the shaft hole 23 and fired integrally with the insulator 2, and the taper 2.
1 and whose tip is electrically connected to the ignition electrode 30 , the metal plate 31 is made of high brazing material and has a truncated cone shape, whose tip is electrically connected to the metal plate 31 and whose rear end is located behind the taper 22 A conductor 32 , a tubular terminal electrode 33 inserted from the rear end of the shaft hole 23 , and a central conductor 3 made of conductive glass 34 that seals the terminal electrode 33 and the conductor 32 in the shaft hole 23 . , an optical fiber 4 inserted through the central conductor 3 and transmitting infrared rays.

The cylindrical metal shell 1 (made of carbon lI4) has a distal end with a mounting screw 12 on the outer periphery and a packing surface 13 on the inner periphery, and a rear end which is caulked inward and has a wire packing 14 and an insulating powder 15 arranged thereon. and a hexagonal part 17 on which a gasket 16 is disposed.
It consists of a central part where a The outer electrode 11 (made of heat-resistant metal) protrudes to cover the tip of the insulator 2.

The insulator 2 (fired alumina body) has a small diameter leg portion 24,
It consists of a corrugated portion 25 at the rear end and a body portion 26 at the center. The group portion 24 is fixed to the packing surface 13 via the packing 18. Tapers 21,22 are conical surfaces.

A plug cap 100 is fitted onto the corrugation portion 25 .

The ignition electrode 30 is made of Pt-Ir alloy and is located in the shaft hole 2.
It consists of a rod-shaped part fitted into the insulator 3 and a flange part protruding from the front end surface of the insulator 2.

The metal plate 31 (high brazing material) has a size that fits exactly into the taper 21, and has a coefficient of thermal expansion similar to that of the insulator 2.

The conductor 32 has a cylindrical shape and is a metal tube made of a low expansion metal such as Ni-Fe alloy or Kovar.

The terminal electrode 33 is made of steel and has a tubular shape. The tip of this terminal electrode 33 is located at the center of the cylindrical metal shell 1, and the outer periphery of the tip is jagged. Terminal electrode 3
A high voltage is applied to the terminal 3 from the terminal 35.

The conductive glass 34 (mainly composed of borosilicate glass powder and copper powder) is heated and sealed in a gas-tight manner between the tip of the terminal mold [33] and the rear end of the conductor 32 in the shaft hole 23. death,
And an electrical connection between the two is being established.

Further, the optical fiber 4 is held within the shaft hole 23.

Optical fiber 4 (fluorine-containing quartz glass, outer diameter 1 m)
In m), a core with a high refractive index is surrounded by a cladding with a low refractive index. The tip end surface of this optical fiber 4 is connected to the metal plate 31.
It is brought into contact with the rear end surface of.

Note that the area between the plug cap 100 and the connector 300 is covered with four layers: a silicon layer, a Teflon layer, an aramid fiber, and a Teflon layer.

Next, the manufacturing process (main parts) of the optical sensor built-in plug A will be explained.

1) Insert the ignition electrode 30 into the tip of the shaft hole of the unfired insulator from the tip side of the shaft hole.

2) Co-fire these. The firing electrode 30 is tightly fixed to the tip inside the shaft hole 23 by shrinkage of the unfired insulator during firing.

3) Next, a metal plate 31 made of high brazing material is inserted from the rear end side of the shaft hole 23 of this insulator 2, and a conductor 32 is further inserted and heated, and the ignition electrode 30, metal plate 31, and conductor are inserted. 32 and are electrically connected by soldering.

4) Arranging the optical fiber 4 within the conductor 32.

5) Inject and press conductive glass powder from the rear end side of the shaft hole 23, and then insert the terminal electrode 33.

6) The terminal electrode 33 is heated (approximately 950° C.) while pressurizing (approximately 40 kg) to melt the conductive glass powder, and the tip of the terminal electrode 33 and the rear end optical fiber 4 of the conductor 32 are heated.
and are sealed together in the shaft hole 23 of the insulator 2.

Next, a temperature measurement test of plug A with a built-in optical sensor will be described.

As shown in FIG. 3, the optical sensor built-in plug A is screwed into a cylinder head 201 of a gasoline engine via a mounting screw 12 of a metal shell 1. As shown in FIG.

In this engine, 202 is a cylinder, 203 is a piston, 204 is an exhaust boat, and 205 is an intake boat 1 to . 20
6 is an exhaust valve, and 207 is an intake valve.

In addition, the connector 300 of the optical fiber 4 is made of lead sulfide PbS.
, a detector 301 as a detector consisting of CdS, CdSe, Si, GaAsP, and GaP, and an emissivity compensation circuit 302
, an analog-to-digital converter 303, and a linearizer 304 in this order to a digital display device 305.

Furthermore, the linearizer 304 is connected to a pen recorder 307 via a digital-to-analog converter 306.

When the engine is in operation, fuel burns in the combustion chamber 208 and the temperature of the plug tip increases to a temperature close to that of the combustion chamber 208. As the temperature of the plug tip increases, thermal radiation with a relatively long wavelength (λ=650 nm or more), that is, infrared rays, is generated from the flanged firing electrode 30 of the center conductor 3, and the optical fiber 4 receives this infrared rays. The signal is transmitted to the detector 301 through. This detector 301 converts infrared radiation into an electrical signal, which is compensated by an emissivity compensation circuit 302. The electrical signal compensated in this way is an analog
Digital converter 303 and linearizer 304
Display device through? r305 digitally displays the temperature inside the combustion chamber 208.

At the same time, the temperature inside the combustion chamber 208 is continuously recorded by the pen recorder 307 via the digital-to-analog converter 306.

The optical sensor built-in plug A of this embodiment has the following functions and effects.

(1) The configuration in which the metal plate 31 is disposed on the taper 21 allows the firing electrode 30 to be inserted from the tip side of the shaft hole 23. Therefore, the firing portion of the firing electrode 30 can be shaped like a brim, and wear of the firing electrode 30 can be suppressed.

(2) Since the firing electrode 30 and the insulator 2 are fired at the same time, there is no gap between them. Therefore, combustion gas does not enter the shaft hole 23, and the tip end surface of the optical fiber 4 is not contaminated with carbon or the like.

That is, the output of the detector 301 does not fluctuate due to contamination, and the temperature of the combustion chamber or the combustion light signal can be stably measured.

(3) Furthermore, since these are closely bonded to the insulator 2 by co-firing, the firing electrode 30 will not fall off, and the durability of the optical sensor built-in plug A is high.

(4) Insert the optical fiber 4 into the conductor 32 from the rear end side of the shaft hole 23, fill it with conductive glass powder, and then insert the terminal electrode 33.
The rear end of the optical fiber 2 is further heat-sealed together with the optical fiber 4 to form the central conductor 3.

Thereby, the bonding strength between the center conductor 3 and the insulator 2 becomes strong, electrical continuity between the conductor 32 and the terminal electrode 33 is achieved, and the optical fiber 4 is held in the shaft hole 23.

The present invention has the following embodiments in addition to the above embodiments.

The shape of the a1 firing electrode may be a rod without a flange.

The material of the b3 ignition electrode may be Pt, Ir, or cermet. Cermet is TiCh, TiC, TiN
Titanium compounds such as Pt, Pd, or these and Au
, Ru, Ag, Rh, and other noble metals are dispersed and fired. Furthermore, as additives, Fe, Ni,
One or more metals such as Cr, Co, Fe-Ni-Cr alloy and/or AJ20s, Cr20s,
Yx O3, zr02.5i02, La20. oxides such as MO2C, TaC, SiC, B, C and nitrides such as AJN, BN, ZrN and M.

One or more types of non-oxides such as S12 may be mixed.

The C1 conductor may be as follows. An optical waveguide with a metal coating, a ceramic body that exhibits conductivity after firing.

d, the distance between the tip surface of the optical fiber 4 and the metal plate 31 is 0.
mm-2 mm is preferable.*If it exceeds 2 mm, the sensitivity will deteriorate. Note that when this distance is set to 2 mm or less, it is difficult for heat to be directly transmitted to the optical fiber 4 and deterioration of the optical fiber 4 is less likely to occur.

e. The conductive glass may be a resistor.

f, a photoelectric element (
A configuration in which a photodiode (photodiode) is arranged may also be used.

g. An optical fiber made of sapphire glass may be used as the optical waveguide.

[Brief explanation of drawings]

Fig. 1 is a partial sectional view of a main part of a plug with a built-in optical sensor showing an embodiment of the present invention, Fig. 2 is a partial sectional view showing a state in which a socket is fitted into the plug, and Fig. 3 is a partial sectional view showing a state in which the plug is used. FIG. 2 is an explanatory diagram showing a temperature measurement system. In the diagram: 1... Cylindrical metal shell 2... Insulator 3...
・Center conductor 4...Optical fiber (light waveguide) 11・
...Outer electrode 21.22...Taper 23...Shaft hole 30...Ignition electrode 31...Metal plate 32...
・Conductor 33...Tubular terminal type i 34...Conductive glass A...Plug with built-in optical sensor

Claims (1)

[Scope of Claims] 1) A cylindrical metal shell with an outer electrode formed at the tip, and a shaft hole tapered on the firing part side and the base side, and is fitted and fixed into the cylindrical metal shell. an insulator, a firing electrode that is fitted into the tip of the shaft hole and fired integrally with the insulator, and a high solder having a truncated conical shape that is engaged with the taper on the firing section side and whose tip is electrically connected to the firing electrode. a conductor whose tip end is electrically connected to the metal plate and whose rear end is located behind the taper on the base side, a tubular terminal electrode inserted from the rear end of the shaft hole, and the terminal electrode. A spark plug with a built-in optical sensor, comprising: a center conductor made of conductive glass that seals the conductor and the conductor in a shaft hole; and an optical waveguide inserted through the center conductor and transmitting infrared rays.