JPH03159087A - Spark plug for internal combustion engine - Google Patents

Abstract

PURPOSE:To enable the easy connection of a light conductor and an optical fiber coaxially by providing a terminal for the insertion of the light conductor and optical fiber, internally connecting the conductor to the optical fiber and supplying high voltage to a center electrode. CONSTITUTION:There is provided a terminal 6 having a light conductor 4 and an optical fiber 5 inserted, connecting the light conductor 4 and optical fiber 5 tn each other internally, electrically connecting a center electrode 3 to a high voltage cable, and supplying high voltage to the center electrode 3. By inserting both of the light conductor 4 and optical fiber 5 into the terminal 6 as aforementioned, it becomes unnecessary to take care of positioning the light conductor 4 and the optical fiber 5, and both are easily positioned for connection. According to the aforesaid construction, the light conductor 4 and optical fiber 5 can be easily connected to each other approximately coaxially.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a spark plug used in internal combustion engines such as automobiles.

[Prior Art] In Utility Model Application Publication No. 61-133991, a terminal for supplying a high voltage to a center electrode also serves as an optical connector for coupling an optical fiber to a glass rod arranged in the axis of the center electrode. A spark plug for an internal combustion engine is disclosed. In addition, in this type of spark 1 lug, it is known that if the glass rod and the optical fiber are not coupled coaxially, a transmission loss of combustion light transmitted from the glass rod to the optical fiber will occur.

[Problems to be Solved by the Invention] However, in the conventional spark plug described above, the end of the glass rod is exposed to the outside from the end surface of the terminal, so it is difficult to connect the glass rod and the optical fiber coaxially. At this time, it was necessary to pay sufficient attention to the positioning of the axial center position of the glass rod and the axial center position of the optical fiber.

For this reason, since the glass rod and the optical fiber cannot be easily coupled coaxially, there is a problem that the assembling workability of assembling the optical fiber to the spark plug is reduced.

SUMMARY OF THE INVENTION An object of the present invention is to provide a spark plug for an internal combustion engine in which a light guide and an optical fiber can be easily coupled coaxially.

[Means for Solving the Problem] The spark plug for an internal combustion engine of the present invention has one end face facing the combustion chamber of the internal combustion engine, and the other end face connected to an optical fiber.
a light guide that guides combustion light to the optical fiber; a center electrode that is arranged to cover the outer periphery of the light guide and to which a high voltage is applied from a high-voltage cable; and a center electrode into which the light guide and the optical fiber are inserted; A terminal is provided that connects the light guide and the optical fiber, electrically connects the center electrode and the high-voltage cable, and supplies a high voltage to the center electrode.

[Function] By inserting both the light guide and the optical fiber into the inside of the terminal, the light guide and the optical fiber can be easily positioned without paying attention to the positioning of the light guide and the optical fiber. are connected approximately on the same axis.

[Effects of the Invention] Since the light guide and the optical fiber can be easily coupled almost on the same axis, the assembly work efficiency when assembling the light guide and the optical fiber can be improved, and the transmission from the light guide to the optical fiber can be improved. The transmission loss of combustion light can be reduced.

[Example] A spark plug for an internal combustion engine according to the present invention will be described based on an example shown in the drawings.

1 to 3 show a spark lug for use in an internal combustion engine of an automobile or the like, which uses the material of the present invention.

This spark plug 1 includes a cylindrical insulator 2, a tubular center electrode 3 held by the insulator 2, a light guide 4 held by the center electrode 3, and a center electrode 3 that supplies a high voltage to a center electric fi3. It is equipped with a tubular terminal 6 for supplying high voltage to. Note that 11 is an outer electrode that forms a gap with the tip end surface of the center electrode 3. Reference numeral 12 denotes a mounting fitting fixed to the outer periphery of the insulator 2. This mounting bracket 12 has an outer electrode 11 joined to its distal end surface by a joining method such as welding, and a mounting thread 13 for mounting on an internal combustion engine is formed on its outer periphery.

The insulator 2 is made of alumina or aluminum nitride and has an axial hole 23 that is open at the front end 21 and the rear end 22.
has. Further, the center electrode 3 is inserted through the insulator 2 from a long leg portion 24 projecting into a combustion chamber (not shown) of an internal combustion engine to a rear end side portion 25 disposed outside the combustion chamber.

The center electrode 3 is fitted into the shaft hole 23 of the long leg portion 24 . Further, an inner peripheral screw 26 for fastening the terminal 6 is formed in the shaft hole 23 of the rear end side portion 25. Note that the inner periphery of the shaft hole 23 in the rear end side portion 25 and the terminal 6 are joined together with a cement seal or a glass seal.

The center electrode 3 is made of a heat-resistant metal such as a nickel alloy, and is attached to the insulator 2 with its front end surface 31 protruding from the tip 21 of the insulator 2 and its rear end surface 32 protruding from the rear end 22 of the insulator 2. It is fitted into the shaft hole 23 and held by the insulator 2. Further, the center electrode 3 is fitted into and held in the terminal 6 with the rear end surface 32 recessed from the rear end of the terminal 6. The center electrode 3 has an axial inner hole 33 that is open at the front end surface 31 and the rear end surface 32 . The light guide 4 is fitted inside the inner hole 33 .

The light guide 4 is made of translucent ceramic such as sapphire glass and has a thin rod shape. The light guide 4 has one end surface serving as a light receiving surface 41 facing the combustion chamber of the internal combustion engine, and the other end surface serving as a light emitting surface 42 that emits combustion light toward the optical fiber 5. The light guide 4 is fitted into the inner hole 33 of the center electrode 3 and fixed to the center electrode 3 using heat-resistant cement or a glass seal provided between the center electrode 3 and the light guide 4. ing. The light receiving surface 41 is flush with the front end surface 31 of the center electrode 3, and the light scattering surface 42 is flush with the rear end surface 32 of the center electrode 3.

The optical fiber 5 is made of visible quartz glass, has a core with a high refractive index, and a cladding with a low refractive index surrounding the core, and converts the combustion light transmitted from the light guide 4 into a photoelectric conversion element (photoelectric conversion element). It leads to a combustion light sensor (not shown) consisting of a diode, phototransistor), etc. The combustion light sensor determines misfire of a mixture of fuel and air by detecting combustion light within the combustion chamber.

Further, a stainless steel reinforcing tube 51 is fitted to the outer periphery of one end of the optical fiber 5. This reinforcing pipe 51
acts as a guide to guide one end of the optical fiber 5 so that it is coaxially disposed on the optical guide 4, and also protects the optical fiber 5 from bending stress applied during coupling with the optical guide 4.
A reinforcing member is provided between the optical fiber 5 and the reinforcing tube 51 to reduce collision between the outer periphery of one end of the optical fiber 5 and the inner periphery of the reinforcing tube 51. A cushioning material 52 made of polyfluoroethylene, silicone rubber, etc. is provided. The buffer material 52 attenuates vibrations during operation of the internal combustion engine that are transmitted to the reinforcing tube 51 and transmits the vibrations to one end of the optical fiber 5 .

One end of the optical fiber 5 is inserted into the terminal 6 together with the reinforcing tube 51, and one end surface is coupled to the light emitting surface 42 of the light guide 4.

The terminal 6 is fitted into the shaft hole 23 of the rear end side portion 25 and held by the insulator 2, with the rear end protruding from the rear end 22 of the insulator 2. This terminal 6 is connected to a male screw 62 and an outer peripheral screw 63 through a shaft hole 61 and a flange 65.
has.

The shaft hole 61 can be made into a central shape by fitting the center electrode 3 inside with the middle bottom. The shaft hole 61 serves as a terminal part to electrically connect &3 and the terminal 6.
Inside, it functions as a connector part that coaxially connects the light emitting surface 42 of the light guide 4 and one end surface of the optical fiber 5.

A tapered portion 64 for locking the optical connector 8 is formed at the lower end of the male screw 62 in the drawing.

The outer circumferential screw 63 is screwed into the inner circumferential screw 26 formed in the shaft hole 23 of the rear end side portion 25 of the insulator 2, so that the collar portion 65 comes into contact with the rear end of the insulator 2. Therefore, the terminal 6 is screwed into the insulator 2 and fixed.

In addition, the terminal 6 electrically connects the center electrode 3 and the high voltage cable 7, which are electrically connected via the high voltage cable 7 and an optical connector 8.9 made of conductive metal, to the center electrode 3. It supplies high voltage.

The core wire 71 of the high voltage cable 7 is connected to the optical connector 9 by caulking a crimping ring 72. 73
is a rubber cap made of silicone rubber.

This rubber cap 13 is formed with an inner circumferential groove 74 that restricts movement of the optical connector 9 in the axial direction.

The optical connector 8.9 has a shaft hole 81.9 formed in the axial direction.
One end of the optical fiber 5 and a reinforcing tube 51 are inserted into the interior of the optical fiber 5 to hold the optical fiber 5.

A locking device 82 such as a coil spring or a leaf spring, which is locked to the tapered portion 64 of the male screw 62 formed on the outer periphery of the terminal 6, and a rear end portion of the terminal 6 are fitted to the tip side of the optical connector 8. A fitting hole 83 for insertion is formed. Further, a step portion 92 is formed in the shaft hole 91 of the optical connector 9 to lock the rear end of the reinforcing tube 51 so as to restrict movement of the reinforcing tube 51 upward in the drawing. Furthermore, a fitting hole 93 is formed at the leading end of the optical connector 9 into which the rear end portion of the optical connector 8 is fitted.

Next, the method of assembling the center electrode 3, light guide 4, optical fiber 5 and high voltage cable 7 to the terminal 6 will be explained with reference to FIGS. 1 to 3.

The center electrode 3 is held in the terminal 6 by fitting the center electrode 3 into the shaft hole 61 with an intermediate bottom. At the same time, the center electrode 3 and the terminal 6 are electrically connected.

Further, since the light guide 4 is fitted into the inner hole 33 of the center electrode 3, the axis of the light guide 4 is positioned coaxially with the axis of the shaft hole 61 of the terminal 6. Note that the positions of the rear end surface 32 of the center electrode 3 and the light emitting surface 42 of the light guide 4 are as follows:
It is arranged so as to be located above the tapered portion 64 of the terminal 6 in the figure.

On the other hand, the optical connector 9 and the core wire 71 of the high-voltage cable 7 caulk the crimping ring 12, so that the high-voltage cable 7 and the optical connector 9 are electrically connected. Then, by fitting the rear end portion of the optical connector 8 into the fitting hole 93 of the optical connector 9, the optical connector 8 and the optical connector 9 are electrically connected.

Further, one end side of the optical fiber 5 and the reinforcing tube 51 protrudes from the shaft hole 81 of the optical connector 8 and is inserted into the fitting hole 83 (37
By fitting the optical fiber 5 and the reinforcing tube 51 into the shaft hole 81.91 of the optical connector 8.9 so that the optical fiber 5 and the reinforcing tube 51 are placed in the optical connector 8.9.
It is held at 9. At this time, the rear end of the reinforcing tube 51 is restricted from moving upward in the figure by the stepped portion 92 of the optical connector 9.

By assembling as described above, an assembled body consisting of one end portion of the optical fiber 5, the reinforcing tube 51, the terminal of the high voltage cable 7, and the optical connector 8.9 is formed.

When assembling this assembly to the terminal 6, the outer periphery of one end side of the reinforcing tube 51 protruding into the fitting hole 83 of the optical connector 8 is inserted into the shaft hole 61 along the inner peripheral wall of the shaft hole 61. When the locking tool 82 of the optical connector 8 stops being inserted beyond the tapered portion 64 of the terminal 6, the optical connector 8 is inserted upwardly in the figure from the position of the tapered portion 64 of the terminal 6, as described above. Since the rear end surface 32 of the center electrode 3 and the light emitting surface 42 of the light guide 4 are located, the elastic force of the optical fiber 5 pushes the assembled body upward in the figure.
The locking tool 82 of the optical connector 8 is connected to the male screw 62 of the terminal 6.
It is latched to the tapered portion 64 of. At the same time, the male screw 62 of the terminal 6 is fitted into the fitting hole 83 of the optical connector 8, thereby establishing electrical continuity between the terminal 6 and the optical connector 8. Therefore, the center electrode 3 and the core wire 71 of the high-voltage cable 7 are electrically connected via the terminal 6, the optical connector 8.9, and the crimping ring 12.

Further, as described above, the rear end of the reinforcing tube 51 is restricted from moving upward in the figure by the stepped portion 92 of the optical connector 9, and the reinforcing tube 51
The tip of the center electrode 3 is restricted from moving downward in the drawing by the rear end surface 32 of the center electrode 3. The reinforcing pipe 51 is connected to the terminal 6
It is fitted into the shaft hole 61 of.

Therefore, it is located coaxially with the shaft hole 61 of the terminal 6, and movement of the reinforcing tube 51 in the axial direction is restricted.

Therefore, the optical fiber 5 in the reinforcing tube 51 is located coaxially with the shaft hole 61 of the terminal 6, and the reinforcing tube 51 is not separated from the light emitting surface 42 of the light guide 4 (snap-in method).

Therefore, since the axis of the light guide 4 and the axis of the optical fiber 5 are located substantially coaxially, the light emitting surface 42 of the light guide 4 and one end surface of the optical fiber 5 are coupled substantially coaxially. In this way, the light guide 4 and the optical fiber 5 can be easily assembled to the terminal 6, making the assembly simple and improving the assembly workability.

Note that the shaft hole 61 of the terminal 6 functions as a terminal section for supplying a high voltage to the center electrode 3, and also functions as a connector section for coaxially connecting the axis of the light guide 4 and the axis of the optical fiber 5. Therefore, compared to a conventional plug in which the terminal and the connector are made up of separate members, the structure around the terminal is simplified and productivity can be improved.

The operation of the spark plug 1 of this embodiment is shown in FIGS. 1 and 2.
This will be explained based on the diagram.

When a mixture of fuel and air is supplied into the combustion chamber of the internal combustion engine, a high voltage is applied to the center electrode 3 from the high voltage cable 1 via the optical connector 8.9 and the terminal 6. When a high voltage is applied to the center electrode 3, a spark discharge occurs in the gap formed between the front end surface 31 of the center electrode 3 and the outer electrode 11, and the air-fuel mixture in the combustion chamber is ignited. Combustion light resulting from combustion of the air-fuel mixture is received by the light receiving surface 41 of the light guide 4 and transmitted from the light guide 4 to the optical fiber 5.

In this embodiment, the light guide 4 and the optical fiber 5 are coupled substantially coaxially by the terminal 6, which also serves as a connector for coupling the light guide 4 and the optical fiber 5, as described above. Therefore, it is possible to prevent the axial center of the light emitting surface 42 of the light guide 4 and the axial center of one end surface of the optical fiber 5 from shifting due to vibration.

Therefore, due to the misalignment between the light scattering surface 42 of the light guide 4 and one end surface of the optical fiber 5, combustion light leakage from the light emitting surface 42 of the light guide 4 to the outside of the optical fiber 5 is reduced. The transmission loss of the combustion light transmitted to 5 can be reduced. Therefore, by the combustion light sensor,
It is possible to accurately determine whether the air-fuel mixture has ignited or misfired.

In addition, by assembling the above-mentioned assembly to the spark plug 1 after installing the spark plug 1 in the internal combustion engine, the spark plug 1 can be attached to the internal combustion engine with a normal plug wrench without using any special tools. can be installed.

Furthermore, since the optical fiber 5 or the high-voltage cable 7 does not have a structure in which it protrudes in the radial and axial directions of the insulator 2 as in conventional plugs, it is possible to provide a very compact spark plug 1.

(Modified Example) In this example, the photoconductor was fitted into the inner hole of the center electrode, and the outer periphery of the photoconductor was covered with the center electrode. The center electrode may be disposed so as to cover the outer periphery of the light guide by attaching it to the center electrode.

In this embodiment, the center electrode and the terminal are formed separately, but the center electrode and the terminal may be formed integrally.

In this embodiment, sapphire glass is used as the light guide, but various translucent ceramics such as quartz glass may be used as the light guide.

In this example, the terminal and the optical fiber were coupled using a snap-in method using a locking device such as a coil spring or a leaf spring, but the terminal and the optical fiber were coupled using a bayonet lock method or a screw lock method. The bayonet lock method is a method in which the optical fiber is rotated about half a turn and positioned within the shaft hole of the terminal. The screw lock method is a method in which the optical fiber is positioned within the shaft hole of the terminal by forming an outer peripheral thread on the terminal block and an inner peripheral thread within the shaft hole of the optical connector, and then screwing the optical connector into the terminal. be.

[Brief explanation of the drawing]

1 to 3 show one embodiment of the present invention. Figure 1 is a sectional view showing the connection between a spark plug for an internal combustion engine and an assembly, Figure 2 is a sectional view of the spark plug for an internal combustion engine, and Figure 3 is a sectional view of the main parts of the spark plug for an internal combustion engine. FIG. In the diagram 1... Spark plug 3... Center electrode 4...
Light guide 5...Optical fiber 6...Terminal
7...High voltage cable 8.9...Optical connector Figure 1

Claims (1)

[Scope of Claims] 1) (a) A light guide whose one end face faces a combustion chamber of an internal combustion engine and whose other end face is connected to an optical fiber and which guides combustion light to the optical fiber; (b) an outer periphery of the light guide (c) a center electrode arranged so as to cover the center electrode and to which a high voltage is applied from a high voltage cable; A spark plug for an internal combustion engine, comprising a terminal that electrically connects an electrode and the high voltage cable to supply high voltage to the center electrode.