GB2027124A

GB2027124A - I.C. engine idle speed control method and valve therefor

Info

Publication number: GB2027124A
Application number: GB7923064A
Authority: GB
Original assignee: Canadian Fram Ltd
Current assignee: Canadian Fram Ltd
Priority date: 1978-08-03
Filing date: 1979-07-03
Publication date: 1980-02-13
Also published as: IT7924839A0; DE2927749A1; FR2432613A1; JPS5523389A; IT1122670B

Abstract

An engine having a carburetter or fuel injection system with a fuel-air ratio controller responsive to an exhaust oxygen sensor has a valve 66 which is opened to admit air to the intake manifold in response to the decrease in manifold vacuum in the diaphragm chamber 44 resulting from a decrease in engine idling speed. The ratio controller responds to the sensed extra air to provide extra fuel and thus restore the idling speed. <IMAGE>

Description

SPECIFICATION Idle speed control method and valve therefor This invention relates to an idle control mechanism for a vehicle engine.

To assure proper control of vehicle exhaust emission, and to achieve maximum fuel economy, it is desirable to set engine idle speed as low as possible. However, if the idle speed is set too low, the engine will stall during idle conditions when an increased load is placed on the engine.

Accordingly, it is desirable to have a mechanism which is responsive to the vehicle engine load to adjust the fuel fed to the vehicle engine accordingly, so that a relatively low, but constant, engine idle speed is attained under varying vehicle engine loading conditions. Furthermore, automobiles in the near future will be equipped with increasingly sophisticated fuel management systems.For example, at least one European vehicle is today equipped with a fuel management system which includes an oxygen sensor in the exhaust gas system and a fuel management device (which may either be an electronic carburetor or a fuel injection system) which is responsive to the oxygen level in the exhaust gas as measured by the exhaust gas oxygen sensors to control fuel feed to the engine accordingly, so that a "closed loop" system is attained in which emissions are minimized and fuel economy is maximized.

Accordingly, the present invention provides a method of controlling the idle speed of an internal combustion engine having an intake manifold, comprising the steps of measuring the oxygen content of the engine exhaust gas, adjusting the fuel flow to the engine as a function of the oxygen content of the exhaust gas increases, characterized in that it further comprises the steps of measuring the load on the engine, and enriching the oxygen content in the engine intake manifold when the load on the vehicle is increased, to thereby increase the oxygen content of the exhaust gas to cause the fuel flow to the engine to Increase.

The invention will now be described with reference to the accompanying drawings, wherein: Figure 1 is a schematic illustration of a vehicle engine and fuel management system which uses an idle speed control valve made pursuant to the teachings of the present invention; and Figure 2 is a longitudinal cross-sectional view of an idle speed control valve of the type used in Figure 1.

Referring now to the drawings, a vehicle engine and fuel management system generally indicated by the numeral 10 includes the vehicle engine 12 having an induction manifold 14 into which the fuel management system generally indicated by the numeral 1 6 delivers fuel. The fuel management system 1 6 further includes an oxygen sensor 1 8 located in the engine exhaust system manifold 20. The fuel management system 16 and oxygen sensor 18 may be a part of an electronic fuel injection as disclosed in U.S. Patent 3 815 561 (Seitz petal), or may be an electronically controlled carburetor of a type recently introduced into the vehicle art. The system 10 further includes an idle speed control valve 22, which is made pursuant to the teachings of the present invention.The idle control valve 22 includes an outlet 24 for injecting atmospheric air into the manifold 14, and a vacuum signal line 26, which communicates the manifold vacuum level to the idle control 22.

Referring now to Figure 2 of the drawings, the idle speed control valve generally indicated by the numeral 22 includes a housing 24 comprising an upper section 27 and a lower section 28. A circumferentially extending bead 30 circumscribes the outer perimeter of an annular fiexible member 32 located in the chamber 34 defined by the housing 24. The bead 30 is clamped at the juncture of the housing sections 26 and 28so that the member 32 is retained on the housing 24.

Another circumferentially extending bead 36 circumscribes the inner perimeter of the annular member 32, and is clamped between an upper diaphragm plate 38 and a lower diaphragm plate 40. Accordingly, the flexible member 32, and the diaphragm plates 38 and 40, cooperate to define a movable diaphragm 42 which is capable of axial movement within the housing 24. The diaphragm 42 divides the chamber 34 into an upper section 44 and a lower section 46. A spring 48 located in the upper section 44 yield ably urges the diaphragm 42 downwardly viewing Figure 2. An inlet tube 50 having an orifice 52 receives an end of the vacuum tube 26, so that the section 44 is connected to engine manifold vacuum through the tube 50 and the vacuum line 26.

The lower section 46 is communicated to ambient atmosphere through the openings 54 in the wall of the housing 25. An annular conventional filter member 56 is located in the lower section 46 of the chamber 34, and filters the incoming ambient air communicated into the section 46. The lower section 28 of the housing 25 further includes a tubular , ion 58 which communicates the lower section'46 of the chamber 34 with the outlet 24 through an intermediate chamber 60.A valve stem 62 is secured to the diaphragm 42, and is guided in a bore 63 defined by tubular portion 58 by circumferentially spaced vanes 64, which guide the valve stem 62 within the bore 63, but permit substantially uninhibited communication around the vanes 64 from the lower section 46 of chamber 34 into the intermediate chamber 60. A tapering valve member 66 is carried by the lowermost end (viewing Figure 2) of the valve stem 62. The tapering, circumferentially extending portion 68 of the valve member 66 defines a valve surface which cooperates with a circumferentially extending valve seat 70 at the lowermost edge (viewing Figure 2) of the tubular portion 58 to define a flow restricting orifice A therebetween.It will be noted that, when the diaphragm 42 is disposed in the uppermost position (viewing the Figure), the tapering portion 68 of the valve member 66 will be brought into sealing engagement with valve seat 70, to thereby terminate communication of ambient atmospheric air to the outlet 24. However, when the valve member 66 is disposed in an intermediate position, the size of the orifice A will be varied according to the position of the valve member 66, thereby permitting metered fluid communication between the lower section 46 of the chamber 34 and the outlet 24.

As discussed hereinabove, the fuel management system 16, in cooperation with the oxygen sensor 18, provides a "closed loop" fuel control for the vehicle engine 12. In other words, the oxygen sensor 1 8 senses the oxygen content of the exhaust gas stream, and the fuel management system is responsive to the oxygen content of the exhaust as sensed by the oxygen sensor to adjust fuel feed to 1 2 accordingly. For example, if the exhaust sensor 18 senses that the exhaust gas stream is rich in oxygen, a "too lean" fuel mixture is indicated, and the fuel management system 1 6 will increase fuel feed to the manifold accordingly. On the other hand, if the exhaust gas stream is deficient in oxygen, a "too rich" fuel mixture is indicated, and the fuel management system 1 6 will feed less fuel into the manifold.

Under engine idle conditions, the manifold vacuum indication of the load on the engine. For example, a high manifold vacuum indicates a low load on the engine, but when the engine load is increased, for example, by switching on the vehicle air conditioning system, the manifold vacuum level will decrease. Referring now to the valve disclosed in Figure 2, at a high manifold vacuum level, the pressure differential across the diaphragm 42 is sufficient to collapse the spring 48, to permit the valve surface 68 to sealingly engage the valve seat 70, thereby terminating communication of ambient atmospheric air from the ports 54 to the outlet 24. Accordingly, the manifold is seaied against the outside air.On the other hand, when load of the engine is increased, the manifold vacuum in section 44 of chamber 34 is decreased, thereby decreasing the pressure differential across the diaphragm 42, to permit spring 48 to bias the valve element 66 to some predetermined intermediate position, as a function of the manifold vacuum. Accordingly, the size of the orifice A is then adjusted as a function of the manifold vacuum, which is indicative of the load on the engine. Therefore, a metered communication of ambient atmospheric air is injected directly directly into the manifold 1 4 through the orifice A and the outlet tube 24. This injection of atmospheric air to the manifold 1 4 enriches the oxygen content of the manifold, which, in turn will also enrich the oxygen content of the exhaust gas stream. this enriched oxygen content of the exhaust gas stream will be sensed by the oxygen sensor as a "lean mixture" condition, and, as discussed hereinabove, will cause the fuel management system 1 6 to inject additional fuel into the manifold, to thereby maintain engine idle speed.

Claims

1. A method of controlling the idle speed of an internal combustion engine having an intake manifold, comprising the steps of measuring the oxygen content of the engine exhaust gas, adjusting the fuel flow to the engine as a function of the oxygen content of the engine exhaust gas by increasing fuel flow if the oxygen content of the exhaust gas increases, characterized in that it further comprises the steps of measuring the load on the engine, and enriching the oxygen content in the engine intake manifold when the load on the vehicle is increased, to thereby increase the oxygen content of the exhaust gas to cause the fuel flow to the engine to increase.

2. A method according to claim 1, characterized in that the load on the engine is measured by sensing the engine intake manifold vacuum level.

3. A method according to claim 2, characterized in that the oxygen content of the intake manfold is enriched by communicating ambient atmospheric air directly into the intake manifold when the load on the engine is increased.

4. A method according to claim 3, characterized in that the amount of atmospheric air communicated into the intake manifold is a function of the level of the vacuum in the intake manifold, and varies in accordance with the fluctuations in the intake manifold vacuum level.

5. A method according to claim 4, characterized in that it includes the step of providing a valve mechanism having a housing, pressure responsive means in said housing, and a valve mechanism operated by said diaphragm which controls communication of ambient atmospheric air to the intake manifold, and opening and closing said valve mechanism as a function of the pressure differential across said pressure responsive means.

6. A method according to claim 5, characterized in that the intake manifold vacuum level is communicated to one side of said pressure responsive means and ambient atmospheric pressure is communicated to the other side of said pressure responsive means.

7. A method according to claim 6, characterized in that said valve mechanism comprises a valve seat on said housing and a valye poppet mounted for movement with said pressure responsive means, and said pressure responsive means moves said valve poppet toward said valve seat when the intake manifold vacuum increases and away from said valve seat when the intake manifold vacuum level decreases.

8. A valve mechanism for carrying out the method according to either claim 6 or 7, for an internal combustion engine having an intake manifold, characterized in that it comprises a housing defining a chamber therewith in, pressure responsive means in said chamber dividing the latter into a pair of compartments, means communicating one of said compartments to the engine intake manifold, means communicating ambient atmospheric air into the other compartment, an outlet communicating the other compartment to the engine intake manifold, and valve means operated by said pressure responsive means to control communication through said outlet in response to variations in the pressure differential across the pressure responsive means.

9. A valve mechanism according to claim 8, characterized in that said valve means comprises a valve seat on a portion of the housing in said other compartment and a valve poppet mounted for movement by said pressure responsive means, said pressure responsive means moving said valve poppet toward said valve seat when the intake manifold vacuum increases and away from said valve seat when the intake manifold vacuum decreases.

10. A valve mechanism according to claim 9, characterized in that said valve poppet includes a tapered portion which cooperates with the valve seat to define a variable area orifice to control communication of atmospheric air to said outlet, the size of said orifice decreasing when the manifold vacuum level increases and the size of said orifice increasing when the manifold vacuum level decreases.

11. A method of controlling the idle speed of an internal combustion engine substantially as described and shown with reference to the accompanying drawings.