JPH03110779A - Built-in photo-sensor type spark plug - Google Patents

Abstract

PURPOSE:To prevent a deterioration of the anti-preignition property (heat- resisting property) and to measure the temperature in a combustion chamber continuously by forming the long leg part of an insulator with aluminum nitride, inserting an ignition electrode to the top of an axial hole, and baking the insulator and the ignition electrode at a time. CONSTITUTION:The long leg part 4 of an insulator 3 is formed of aluminum nitride, a small diameter part 42 and a taper or a step 42a following the small diameter part 42 are formed at the top of the axial hole 31 of the insulator 3, and furthermore, an ignition electrode 6 made of a heat-resisting metal or cermet is inserted, and they are baked simultaneously. As a result, the heat generated in a combustion chamber can be radiated sufficiently smooth out of the combustion chamber by the high heat conductivity of the aluminum nitride, the generation of a preignition resulting from the heated plug is prevented, the connection of the ignition electrode 6 and the tube-form insulator 3 is rigid, an excellent durability is secured, and a contamination of a photo- conductor by the combustion gas can be prevented. Consequently, the temperature in the combustion chamber can be measured continuously.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is used to measure temperature changes and combustion light signals at the tip of the center electrode of a spark plug during operation of an internal combustion engine. The present invention relates to a spark plug with a built-in photosensor that detects infrared light emitted from the inner surface of the tip of a center electrode via an inserted light guide.

[Prior Art] In general, it is necessary to continuously measure the temperature inside the combustion chamber of an internal combustion engine during operation to accurately determine whether the combustion temperature is appropriate and whether the engine is operating normally. Delicious.

Conventionally, in order to continuously measure the temperature inside the combustion chamber during operation, a light guide such as a quartz glass rod or an optical fiber is inserted through the terminal electrode and center electrode of the spark plug, and the end face of the light guide is inserted. In order to prevent the (light-receiving surface) from being contaminated by combustion gas and causing problems in measurement, a light-shielding and thermally conductive coating of graphite, silver, gold, etc. is formed on the end surface of the light guide. A spark plug with a built-in optical sensor is known that detects infrared light emitted from the combustion chamber through the combustion chamber and measures temperature changes in the combustion chamber (Japanese Patent Application Laid-open No. 163841/1983).

[Problems to be Solved by the Invention] However, in this conventional spark plug with a built-in optical sensor, the bonding strength between the coating and the light guide is high, so the coating cannot be exposed to the high-temperature, high-pressure combustion gas 2 of an internal combustion engine. When exposed repeatedly,
Due to differences in thermal expansion, etc., the chicks tend to peel off easily, and there are problems with durability.

In addition, the spark plug with the above structure has quartz glass (0,0032 cal/
cm sec 'C), etc., the insulator is made of alumina (A 1203) and is prone to over-oxidation, resulting in a problem that the preignition resistance (heat resistance) of the spark plug is extremely reduced. .

The purpose of the present invention is to prevent deterioration of preignition resistance (image quality), strengthen the coating of the light guide, prevent pollution of the light guide by combustion gas, and ensure that temperature measurement in the combustion chamber is continued. An object of the present invention is to provide a spark plug with a built-in optical sensor that can perform

[Means for Solving the Problems] In order to solve the above problems, the spark plug with a built-in photosensor of the present invention includes a cylindrical metal shell having an outer electrode protruding from its tip, and a spark plug held by the metal shell. An insulator with a shaft hole, a center electrode with a shaft hole and a terminal electrode with a shaft hole, which are held in series inside the insulator, and a shaft hole of the center electrode with a shaft hole and a terminal electrode with a shaft hole. In a spark plug with a built-in optical sensor, the insulator has at least a long leg portion made of aluminum nitride, and (B) the tip of the shaft hole of the insulator has a small diameter. The technical means is to form a tapered part or a step part following the small diameter part, fit a firing electrode made of a heat-resistant metal or cermet into the tip of the shaft hole, and fire the same at the same time.

[Function and Effects of the Invention] The spark plug with a built-in photosensor of the present invention has the structure (A) and (effect) the high thermal conductivity of aluminum nitride, so that the combustion heat generated in the combustion chamber can be sufficiently radiated to the outside. This can be done smoothly, the occurrence of preignition caused by a hot plug is prevented, and (effect) preignition resistance (heat resistance) is improved.

In addition, due to the configuration (B), the connection between the firing electrode and the cylindrical insulator is strong and has excellent durability.
The durability of the joint structure of the ignition electrode is improved, and it is possible to prevent the light guide from being contaminated by combustion gas.

As described above, the spark plug with built-in photosensor of the present invention has
It has excellent durability and allows continuous temperature measurement of the combustion chamber.

[Example] Next, a first example of a spark plug with a built-in optical sensor according to the present invention will be described based on FIGS. 1 to 3.

The optical sensor built-in spark plug A of this embodiment includes a cylindrical metal shell 2 having an outer electrode 21 protruding from its tip and a mounting screw 22 formed on the outer periphery, and a shaft hole 31 held in the metal shell 2. A bonded insulator (insulator) 3, a firing electrode 6 held inside the shaft hole 31 of the bonded insulator 3, and a shaft hole 71.
The center electrode (conductor) 7 with attached and the terminal electrode 8 with shaft hole 81, and the center electrode 8i! 7 and the shaft hole 71 of terminal type ai8
, 81 and the light guide 9 inserted through the shaft hole 31.
A conductive glass 10 sealed in the gap between the center electrode 7 and the terminal electrode 8 , an extension cord 11 connected to the terminal electrode 8 and a terminal nut 12 provided at its end, and the light guide 9 A covering tube 13 that covers the extending portion of the connector 14 provided at the end of the extending portion, and the bonding type insulator 3
It is comprised of a protective tube 15 and the like that is fitted onto the rear end and covers the extension cord 11 and the covering tube 13.

In the bonded insulator 3, which is the first aspect of the present invention, in this embodiment, the front end side insulator (long leg portion) 4 is made of aluminum nitride (AIN) having excellent thermal conductivity, and the rear end side insulator 4 is made of aluminum nitride (AIN), which has excellent thermal conductivity. body 5
Both are made of low-cost alumina (AI20i) and are firmly joined via a glass sealing material 32 by an annular protrusion 41 provided at the rear end and an annular recess 51 provided at the tip. There is.

The shaft hole 31 of the bonded insulator 3 is located at the tip end side insulator placement part)
From the tip side, the shaft hole portion of No. 4 has a small diameter portion 42, a medium diameter portion 43,
It consists of a large diameter portion 44.

The firing electrode 6, which is the second aspect of the present invention, is made of an Ir (iridium) alloy (Pt, Ru, Rh, Ni) in this embodiment.
It has a rod shape with a flange-like part 61 at the rear end.

In addition, in the processing process, the firing electrode 6 is first inserted from the rear fil+ into the shaft hole 31 of the tip side insulator 4 of the AIN before firing, and the tip 62 is protruded from the small diameter portion 42 of the shaft hole, and the flange-shaped portion 61 Then, it is fitted into the step portion 42a following the small diameter portion 42. Next, the firing electrode 6 is firmly fixed by firing the bonded insulator 3.

The center electrode (conductor) 7 is a fired body of molybdenum paste, and like the firing electrode 6, this fired body has a molybdenum paste tube inserted into the middle diameter part 43 of the shaft hole of the unfired tip side insulator 4. is inserted, and the insulator is fired in a reducing atmosphere to form the conductor 7.

The terminal electrode 8 is made of steel, and has a screw 8 on the outer periphery of the tip.
It has a tubular shape with 2 holes.

The conductive glass 10 has borosilicate glass powder and copper powder as main components, and electrically connects the center electrode 7 and the terminal electrode 8. Furthermore, the optical fiber 9 is held within the shaft hole 31.

The optical guide 9 is an optical fiber made of quartz glass containing IIIll of fluorine in terms of outer diameter, and has a core with a high refractive index surrounded by a cladding with a low refractive index. This light guide 9 has a distal end surface close to the rear end surface of the firing electrode 6 at an interval of 2 m5),
The extending portion is covered with a covering tube 13 consisting of four layers: a silicone layer, a Teflon layer, an aramid fiber, and a Teflon layer.

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

As shown in Figure 3, spark plug A with built-in optical sensor
The metal shell 2 is attached to the cylinder head 201 of a gasoline engine.
It is screwed through the mounting screw 22 of.

In this engine, 202 is a cylinder, 203 is a piston, 204 is an exhaust boat, 205 is an intake boat, 206 is an exhaust valve, and 207 is an intake valve.

The connector 14 of the light guide 9 is lead sulfide (pbS, Cd).
A detector 301 made of S, CdSe, GaAsP, GaP, Si), an emissivity compensation circuit 302, an analog-to-digital converter 303, and a linearizer 304 are connected to a digital display device 305 in this order. Furthermore, the linearizer 304 is connected to a pen recorder 307 via a digital-to-analog converter 306.

As the engine operates, the temperature of the tip of the plug increases close to the temperature inside the combustion chamber 208. As the temperature of the tip of the plug increases, thermal radiation with a relatively long wavelength (λ=650 mm or more), that is, infrared light, is generated from the ignition electrode 6, and this infrared light is received by the light guide 9. The signal is transmitted to the detector 301 through. This detector 301 converts infrared light into an electrical signal, and this electrical signal is compensated by an emissivity compensation circuit 302. The electric signal thus compensated is passed through an analog-to-digital converter 303 and a linearizer 304, and the temperature inside the combustion chamber 208 is displayed digitally by a display device 305. At the same time, the digital-to-analog converter 3
The temperature of the combustion chamber 208 is continuously recorded by the pen recorder 307 via the combustion chamber 06.

Next, a second embodiment of a spark plug with a built-in photosensor according to the present invention will be explained based on FIG. > 3B is used as an integrally formed insulator. The pond is the same as in the first embodiment.

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

(a) The material of the firing electrode is Ir (iridium) or p
T may be used alone or may be a cermet. Cermet is a titanium compound such as Ti0z, Tic, TiN, Pt, Pd, or these combined with A11, Ru, Ag, Rh.
It is manufactured by dispersing precious metals such as and firing them.

Furthermore, as additives Fe, Ni, Cr, Co, Fe-
one or more base metals such as Ni-Cr alloys and/or Al2031, Cr203, Y203, Z, rO
z, S 102, La20. oxides such as Mo, C
, TaC, SiC, Ba C and other carbides and AIN,
One or more types of nitrides such as BN and ZrN and non-oxides such as Mo5iz may be mixed.

(b) The conductor may be the following: Ni-F
The tip of the shaft hole 31 of the fired insulator 4 is made of metal tubes made of low expansion metals such as e-alloy and Kovar, metal powders, optical conductors coated with metal coatings, and conductive ceramic powders. and the middle diameter portion 43, and is electrically connected to the firing electrode 6.

(C) The distance between the front end surface of the light guide and the rear end surface of the firing electrode is 0.
(2) to 21II11 are suitable. If the value exceeds 2IIIDI, the sensitivity deteriorates. Incidentally, if this distance is increased to 2 m or less, deterioration of the optical conductor due to conduction of high heat can be prevented.

(d) The conductive glass may be a resistor.

(e) The light guide may be an optical fiber made of sapphire glass.

(f) The joint portion of the joint type insulator (insulator) may be physically strengthened by a screw connection structure using a male thread and a female thread.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a main part of a first embodiment of a spark plug with a built-in optical sensor according to the present invention, FIG. 2 is a sectional view thereof, and FIG.
The figure is an explanatory diagram showing a temperature measurement system using this plug. FIG. 4 is a sectional view of a main part of the second embodiment. In the figure, 2... Metal shell 3. 3B... Insulator (insulator) 4... Tip side insulator long leg part) 5...
Rear end side insulator 6... Firing electrode 7... Center electrode with shaft hole (conductor) 8... Terminal electrode with shaft hole 9... Light conductor 21... Outer electrode 31... Shaft Hole 42...
Small diameter part 42a...Stepped part A, B...Spark plug with built-in optical sensor

Claims (1)

[Scope of Claims] 1) A cylindrical metal shell with an outer electrode protruding from its tip, an insulator with a shaft hole held in the metal shell, and a shaft held in series inside the insulator. A spark plug with a built-in optical sensor, comprising a center electrode with a hole, a terminal electrode with a shaft hole, and a light guide disposed through the shaft hole of the center electrode with a shaft hole and the terminal electrode with a shaft hole, wherein the insulation At least the long leg portion of the body is made of aluminum nitride, and the tip of the shaft hole of the insulator forms a small diameter portion and a tapered portion or a stepped portion that continues to the small diameter portion, and the tip of the shaft hole is made of heat-resistant metal or A spark plug with a built-in optical sensor that features a cermet ignition electrode fitted and fired at the same time.