GB2077851A

GB2077851A - Ignition Spark Plug

Info

Publication number: GB2077851A
Application number: GB8026069A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1980-06-13
Filing date: 1980-08-11
Publication date: 1981-12-23
Also published as: FR2484723A1; IT1132336B; FR2484723B1; GB2077851B; JPS575280A; SE8005751L; AU6187280A; IT8024032A0

Abstract

An ignition spark plug incorporates a primary valve 5 and a secondary valve 7. The primary valve 5 is a check valve disposed in a through bore 2b formed in the central electrode 2 of the plug and is adapted to prevent gas from leaving a cylinder in which the plug is installed. The secondary valve is provided within a body 10 adapted for connection to a supply lead and is adapted to act, when the valve 5 is open at the completion of a power stroke, to permit introduction of external air through ports 9a and a filter 12 to the central electrode 2 and into the cylinder, but otherwise to assume a closed position in which it closes the bore of the electrode. <IMAGE>

Description

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

It is well known that the performance of an internal combustion engine is adversely affected by unburnt residual gas which remains after the ignition stroke and raises the temperature in the cylinder. It is also known that the elevated temperature in the cylinder unfavourably promotes the generation of nitrogen oxides from the residual unburnt gas, which nitrogen oxides are discharged to atmosphere and causes environmental pollution.

To overcome the above-described problem, it has been proposed to supply fresh air into an engine to anable complete burning of the residual gas by a secondary combustion, but no satisfactory practical means for doing this has been developed.

It is also known that the pressure in the cylinder of an internal combustion engine is instantaneously deceased during the ignition and exhaust strokes. The present invention proposes to supply secondary air into the cylinder by making an efficient use of this instantaneous pressure drop in the cylinder.

A major object of the invention is to provide an ignition spark plug which, by promoting efficient secondary combustion, achieves a reduction in fuel comsumption, together with a lowered exahust gas concentration.

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, a check valve disposed in said air introduction passage and adapted to prevent escape of gas from the cylinder, and a secondary valve which is springurged towards a position in which it closes said passage and arranged in relation to the check valve such that when the check valve opens in response to a reduction in pressure in a cylinder in which the plug is installed, in use, the secondary valve opens to admit air into the cylinder through said passage.

A preferred embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a vertical sectional view of one form of the ignition spark plug of the invention; Figure 2 is an exploded perspective view of a valve chamber incorporated in the ignition spark plug of Figure 1; Figure 3 is a perspective view of a check valve shown in Figure 2; Figure 4 is a vertical sectional front elevation of a conductive tubular member constituting a secondary valve; Figure 5 is a sectional view of the conductive tubular member taken along the line V-V of Figure 4; Figure 6 is a front elevation of an outer sleeve constituting a part of the secondary valve, with part thereof removed; Figure 7 is a sectional view of the outer sleeve taken along the line VIl-VIl of Figure 6;; Figure 8 is a vertical sectional front elevation of an annular member constituting a part of the secondary valve, and Figure 9 is a sectional view of the annular member taken along the line IX-IX of Figure 8.

Referring to the drawings, reference numeral 1 denotes the body of an ignition spark plug of the invention having a threaded portion 1a for attachment to a cylinder of an internal combustion engine and hooked-electrode 1 b.

Reference numeral 2 denotes a central electrode having an intermediate large-diameter portion 2a and a through bore 2b extending vertically across the increased diameter portion 2a. The central electrode 2 as a whole is inserted into the body 1 of the ignition spark plug. A connector 2c having a screw 2c, and a communication port 2c2 is provided at the upper part of the central electrode 2.

Reference numeral 3 denotes a valve seat having a central valve port 3a, and reference numeral 4 denotes a guide tube. Reference numeral 5 designates a sintered check valve which has, as will be clearly seen from Figure 3, a pointed head portion 5a and a main body 5b, in the outer peripheral surface of which are formed a plurality of longitudinal grooves 5b, extending from the base of the pointed head portion 5a to the end of the body Sb remote from the head portion. The grooves 5b communicate at one end with a blind bore Sc extending from said remote end of the main body Sb.

As will be seen from Figure 1, the valve seat 3 is fitted to an upper part of the increased diameter portion 2a of the electrode 2 and the guide tube 4 is fitted beneath the valve seat 3. The check valve 5 is disposed in the guide tube 4 in such a manner as to be able to move up and down, the upper part of the pointed head portion 5a fitting into the valve port 3a of the valve seat 3 when the check valve 5 is moved upwards.

The symbol a generally represents a secondary valve which is composed of a conductive tubular member 6, valve member 7, outer sleeve 8, annular member 9 and a secondary electrode connecting portion 10. As will be seen from Figures 4 and 5, the conductive tubular member is an integral unit having an upper chamber 6a, lower chamber 6b and a partition wall 6d having an outer peripheral annular groove 6c. Female screw threads 6a and 6b, are formed in the upper chamber 6a and the lower chamber 6b, while a plurality of vent holes 6d, are formed in the partition wall 6d. Also, a tapered valve seat 6b, is formed in the lower chamber, while a slide bore 6a2 is formed in the base of the upper chamber 6a.

The valve member 7 comprises a valve part 7a adapted to be seated on the valve seat 6b2, a valve rod 7b and a head screw 7c. The valve rod 7b is received by the slide bore 7a2 through the partition wall 6d, and a spring 11 is disposed to act between the scew head 7c and the base of the upper chamber 6a.

An outer sleeve 8 and an annular member 9 are made of electrically insulating material. As will be seen from Figures 6 and 7, the lower part of the outer sleeve 8 constitutes a skirt 8a which surrounds the central electrode 2 of the ignition spark plug. The outer sleeve 8 is provided at its intermediate portion with an annular groove 8b and a transverse bore Sc which provides a communication between the annular groove 8b and the interior of the outer sleeve 8. The aforementioned conductive tubular member 6 is fixedly fitted to the outer sleeve 8 such that the annular groove 6c of the conductive tubular member 6 communicates with the transverse bore Sc of the outer sleeve 8. A filter 1 2 is fitted in the annular groove 8b of the outer sleeve 8.

As will be seen from Figures 8 and 9, a plurality of ambient air suction ports 9a are formed in the annular member 9. The annular member 9 is fitted to the outer sleeve 8 in such a manner that the suction ports 9a communicate with the annular groove 8b of the outer sleeve 8.

The secondary electrode connecting portion 10 is provided with a screw thread 1 Oa which engages the femaie screw thread 6a1 of the upper chamber 6a of the conductive tubular member 6.

In the arrangement described above, when the internal pressure of the cylinder is high, i.e. in the compression and ignition strokes, the check valve 5 as the primary valve receives the internal pressure of the cylinder at its blind bore Sc so as to be urged against the valve seat 3 with its pointed head 5a in close contact with the valve seat 3 to close the valve bore 3a. The gas in the cylinder is thus prevented from entering the upper part of the through bore 2b of the central electrode 2. The valve part 7a of the valve member 7 of the secondary valve a is forcibly pressed against the valve seat 6b2 by means of a spring 11. Thus gas leakage is completely avoided by the presence of the secondary valve a, even when the check valve 5 has failed to be completely effective at high engine speed operation exceeding 3000 r.p.m.The internal pressure in the cylinder is instantaneously reduced to a negative level in the transient period between the ignition stroke and the subsequent exhaust stroke. Due to this negative pressure, the check valve 5 is moved away from the seat 3, and the valve part 7a of the valve member 7 is moved away from the valve seat 6b2 overcoming the force of the spring 11 as shown in Figure 1.

While the valve part 7a is kept away from the valve seat 6b2, the ambient air is sucked through the suction ports 9a of the annular member 9, filter 12 fitted in the annular groove Sb of the outer sleeve 8, annular groove 6c of the conductive tubular member 6, and then through the vent holes 6d,. The air then flows through the communication port 2c2 of the connector 2, and the upper part of the through bore 2b of the central electrode 2 of the plug body 1. The air is finally introduced into the cylinder as secondary air through the vertical grooves 5b, of the check valve 5 which is held in its lowermost position away from the seat 3 as shown in Figure 1. The air then passes through the lower part of the through bore 2b of the central electrode 2.

In operation of the internal combustion engine equipped with the ignition spark plug of the invention, the pressure in the cylinder is lowered instantaneously in the transient period between the ignition stroke and the exhaust stroke. At that instant, the ambient air is sucked through the secondary valve and charged into the cylinder through the check valve 5 disposed in the central electrode of the plug body. In consequence, the residual gas which tends to stay in the cylinder is effectively replaced with the secondary air of comparatively low temperature so that the weight and temperature of the combustion gas are lowered.In addition, the induced secondary air is effectively used in the burning reaction of the subequent explosion stroke so that the volumetric efficiency, charging efficiency and, hence, the effective pressure are substantially increased to ensure a reduction of the fuel consumption rate.

At the same time, since the temperature in the cylinder, as well as the exhaust temperature are lowered the generation of nitrogen oxides is suppressed considerably.

Furthermore, the secondary valve which is forcibly closed effectively checks the leak of gas from the combustion chamber in the cylinder, even when the check valve as the primary valve fails to operate. Also, the ambient fresh air is cleaned by the filter before it is sucked into the engine as the secondary air.

An experimental product of the ignition spark plug of the invention was attached to an ordinary petrol engine and was tested in accordance with JIS-D1003 and the fuel testing method for automobiles. In consequence, a satisfactory result was obtained in remarkable reduction of the fuel consumption rate and reduction of exhaust gas concentration which meets the requirements of relevant Government Regulations.

Claims

1. An ignition spark plug comprising a central electrode having a through bore constituting an air introduction passage, a check valve disposed in said air introduction passage and adapted to prevent escape of gas from the cylinder, and a secondary valve which is spring-urged towards a, position in which it closes said passage and arranged in relation to the check valve such that when the check valve opens in response to a reduction in pressure in a cylinder in which the plug is installed, in use, the secondary valve opens to admit air into the cylinder through said passage.

2. An ignition plug according to Claim 1 wherein the secondary valve is mounted on the plug by way of an electrically conductive tubular member forming an electrical connection between the plug electrode and an outer connection terminal, the tubular member being divided into inner and outer chambers and containing said secondary valve which has a rod extending between the chambers and cooperating with a closure spring in the outer chamber and a valve member connected to the rod and disposed in the inner chamber, the tubular member having a port communicating with the exterior at the side of the secondary valve remote from the check valve.

3. An ignition plug as claimed in Claim 2, wherein a filter is disposed over said port.

4. An ignition plug according to any one of the preceding claims wherein an enlarged intermediate portion of the air introduction passage forms a valve chamber containing the check valve and having a valve seat for cooperation with the check valve.

5. An ignition plug according to any one of the preceding claims and further comprising an instulated body having an axial through hole within which said central electrode is accommodated.

6. An ignition plug according to Claim 4 or Claim 5 and further comprising a guide sleeve surrounding the check valve in its chamber and permitting sliding of the check valve therein.

7. An ignition plug according to any one of Claims 4 to 6 wherein the check valve has a conical portion facing its cooperating valve seat and a cylindrical portion extending from the base of the conical portion.

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.

1 0. An ignition plug according to any one of the preceding claims wherein the check valve is made of sintered material.

11. An ignition plug according to any one of Claim 4 to 10 wherein the seat co-operating with the check valve is made of sintered material.

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