GB2077350A - Ignition plug - Google Patents

Abstract

An ignition plug for igniting the mixture in a cylinder of an internal combustion engine includes a plug body 2 through which extends a central electrode 1, the electrode having a through bore 4 and a check valve 10 provided in a valve chamber defined by an enlarged portion of the bore. The check valve assumes a closed position during the combustion stroke and, at the completion of such a stroke, moves to an open position, thus permitting inflow of air into the cylinder. <IMAGE>

Description

SPECIFICATION Ignition plug The present invention relates to an ignition spark plug for internal combustion engines and particularly for petrol engines.

It is known that unburnt gas remaining in a cylinder of an internal combustion engine after completion of an explosion stroke causes the temperature within the cylinder to rise and that such a rise in temperature has an adverse effect on the engine performance. It is also known that such unburnt gas produces nitrogen oxides due to the high temperature in the cylinder and that these nitrogen oxides cause environmental pollution when discharged to the exterior.

In order to subject the unburnt gas to a secondary combustion in the cylinder, methods of blowing air into the cylinder have already been tried but none of them has been developed to a practically usable form.

It has been ascertained that the pressure in the cylinder is locally reduced at the moment of completion of an explosion stroke or at the moment of commencement of an exhaust stroke it is considered that this pressure decreasing phenomenon is caused by the burnt gas during flame propagation.

An object of the present invention is to provide an ignition plug for an internal combustion engine enabling air to enter the cylinder at the moment of completion of an explosion stroke without subjecting the internal combustion engine to any structural modification. The plug of the invention thus leads to a lowering of the temperature in the engine cylinder and allows unburnt gas remaining in the cylinder to be completely burnt, whereby the amount of substances contained in the exhaust gas causing environmental pollution is reduced and the fuel consumption of the engine can be improved.

According to the invention, an ignition spark plug for an internal combustion engine comprises a central electrode having a through bore constituting an air introduction passage, and a check valve provided in an intermediate portion of said air introduction passage and operable to permit introduction of air into the cylinder of an engine, in which the plug is installed in use, in response to a reduction in pressure in the cylinder, and to otherwise prevent escape of gas from the cylinder.

An embodiment of the present invention will be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a front elevational view partially in longitudinal section of an ignition plug of the present invention; Figure 2 is an exploded illustration of part of the plug shown in Figure 1; and Figure 3 is a perspective view of a movable valve from the embodiment shown in Figure 1.

Referring to the drawings, reference numeral 1 denotes a central electrode provided in the central portion of an ignition plug body 2. This electrode has an enlarged portion 3 in an intermediate section thereof as well as a through bore 4 extending from one end of the electrode to the other.

The enlarged portion 3 houses a valve seat 6 made of a sintered material and having a vertical bore 5, a short tube 7 adapted to hold the valve seat 6 in the enlarged portion, and a movable valve 10 made of a sintered material, said valve 10 being composed of a conical portion 8 and a cylindrical portion 9 (Figures 2 and 3) and slidably inserted in the short tube 7.

The movable valve 10 is provided at diametrically opposite locations of the outer circumferential surface of the cylindrical portion 9 thereof with longitudinal grooves 11 extending from the larger end of the conical portion 8 to the end of the cylindrical portion 9 remote therefrom.

These grooves are radially inwardly directed at said remote end of the cylindrical portion so as to communicate with a blind axial bore 12 extending inwardly from said end of the cylindrical portion.

The illustrated ignition plug further includes a hook type electrode 29, a screw portion 30 for engagement in a threaded aperture of an engine cylinder head, a washer 31, an insulator portion 32, and a terminal portion 33 for connection to a high tension lead.

The operation of the illustrated ignition plug will now be described.

When the pressure in the cylinder is high, the movable valve 10 receives the pressure at the blind bore 12, which is open at the electrode end of the plug, and the valve is moved against the valve seat 6. As a result, the bore 5 provided in the central portion of the valve seat 6 is sealed by the conical portion 8 of the valve 10 which prevents the pressure in the cylinder from leaking to the exterior.

When the pressure in the cylinder is reduced momentarily to zero, the conical end portion of the movable valve moves away from the valve seat 6 towards a seat surface 34 within the enlarged portion 3. The valve 10 slides smoothly if the short tube 7 is made of a metal, such as stainless steel, which has a low co-efficient of thermal expansion and high resistance to high temperatures.

The secondary air entering the through bore 4 in the central electrode 1 from the upper end thereof flows along the longitudinal grooves 11 in the outer circumferential surface of the cylindrical portion of the valve 10 so as to be supplied into the cylinder via that part of the through bore 4 which is below the enlarged portion 3. It will thus be seen that in the arrangement of the present invention, the valve 10 is automatically moved in accordance with variations in pressure in the cylinder to open and close the valve port with a high accuracy.

In an internal combustion engine employing an ignition plug according to the present invention, the valve port is opened due to a decrease in the pressure of burnt gas in the cylinder so that air is injected into the cylinder. As a result, the residual gas in the cylinder is forced out of the cylinder by the injected air and the residual gas in the cylinder is thus replaced by the secondary air having a comparatively low temperature. In consequence, the weight and temperature of the burnt gas in the cylinder are decreased to a great extent so that the secondary air introduced into the cylinder in the above-mentioned manner is very useful to effect combustion in the following explosion stroke. This allows the volumetric efficiency, filling efficiency and working pressure to be substantially improved. Therefore, the fuel consumption can be substantially reduced.Moreover, the temperature in the cylinder after an exhaust stroke has been finished, and the temperature of the exhaust gas are decreased so that the production of nitrogen oxides can be minimised.

An experiment of an ignition plug according to the present invention was conducted as it was installed in a passenger car driven by a petrol engine of the following specification.

Type: Petrol engine, 4 stroke cycle.

Inner diameter x stroke: 88 x 82 (4 cylinder).

Displacement: 1994 cc.

Maximum output: 95 p.s15000 rpm.

Maximum torque: 16 kgm/3200 rpm.

The results of the experiment show that a car employing an ignition plug according to the present invention is superior in fuel economy to a car employing a commercially available conventional ignition plug. Namely, the fuel consumption of a car employing an ignition plug according to the present invention when the car runs at 40-80 kg/h is reduced by 25.6% as compared with a car employing a conventional ignition plug and running under the same conditions.

As is clear from the above, the ignition plug of the present invention can be installed in a commercially available internal combustion engine without modification to the engine. In the ignition plug of the present invention, a valve body in a valve chamber automatically slides therein due to a pressure differential occurring at the end of an explosion stroke or at the start of exhaust stroke without being influenced by any other factor. Therefore, the valve port is opened and closed accurately in accordance with the engine cycle so that the external air can be effectively introduced into the cylinder.

In the ignition plug of the present invention, the air-tightness thereof is never lost so that an abnormal explosion never occurs. Accordingly, the ignition plug of the present invention has a high endurance and can be used very advantageously.

Claims (12)

1. An ignition plug comprising a central electrode having a through bore constituting an air introduction passage, and a check valve provided in an intermediate portion of said air introduction passage and operable to permit introduction of air into the cylinder of an engine, in which the plug is installed in use, in response to a reduction in pressure in the cylinder, and to otherwise prevent escape of gas from the cylinder.

2. An ignition plug according to Claim 1 wherein an enlarged intermediate portion of said air introduction passage forms a valve chamber having a valve seat provided therein, the chamber containing a movable valve and a guide cylinder arranged to surround the valve.

3. An ignition plug according to Claim 1 or Claim 2, wherein said valve seat consists of a sintered material having a through bore in the central portion thereof, said movable valve consists of a sintered material composed of a conical portion and a cylindrical portion, and said cylindrical portion has longitudinal grooves extending from the larger end of said conical portion to the end of said cylindrical portion remote from said larger end and communicating with a blind bore extending from said remote end of said cylindrical portion.

4. An ignition plug according to Claim 1 comprising an insulated body having an axial through hole within which said central electrode is accommodated, the through bore of the electrode being enlarged at said intermediate location thereof to form a valve chamber within which said check valve is disposed.

5. An ignition plug according to Claim 4, further including a valve seat provided at the air inlet side of the valve chamber.

6. An ignition plug according to Claim 4 or Claim 5, further including a guide tube provided in the valve chamber to permit slidable movements of said check valve therein.

7. An ignition plug according to Claim 5 or Claim 6, wherein the check valve is composed of a conical portion and a cylindrical portion, the conical portion facing said valve seat.

8. An ignition plug according to Claim 7, wherein said cylindrical portion has at least one groove extending from the larger end of the conical portion to the end of the cylindrical portion remote from said larger end so as to communicate with the central bore of the electrode at the cylinder end of the plug when the check valve is in its open position.

9. An ignition plug according to Claim 8, wherein said remote end of the cylindrical portion is provided with a blind bore.

10. An ignition plug according to any one of Claims 4 to 9, wherein said check valve is made of a sintered material.

11. An ignition plug according to any one of Claims 5 to 10, wherein said valve seat is made of a sintered material.

12. An ignition plug for an internal combustion engine substantially as hereinbefore described with reference to the accompanying drawings.