US3802403A

US3802403A - Run-on prevention means for spark-ignition internal combustion engines including evaporative loss canisters

Info

Publication number: US3802403A
Application number: US00254857A
Authority: US
Inventors: R Dewick; T Hoare
Original assignee: Meakers Realisations Ltd
Current assignee: Meakers Realisations Ltd
Priority date: 1971-05-20
Filing date: 1972-05-19
Publication date: 1974-04-09
Anticipated expiration: 1991-04-09

Abstract

A spark ignition engine is precluded from running-on or diseling by providing a solenoid valve which terminates the delivery of fuel to the induction system of the engine in the period during which the engine continues to rotate (due to the energy stored in the flywheel) after the ignition has been switched off. The solenoid is only energised for the period between the ignition being switched off and the engine ceasing to rotate.

Description

United States Patent [191 Dewick et a1.

[ Apr. 9, 1974 1 RUN-ON PREVENTION MEANS FOR SPARK-IGNITION INTERNAL COMBUSTION ENGINES INCLUDING EVAPORATIVE LOSS CANISTERS [75] Inventors Richard Henry Dewick, Redditch;

Terence Graham Hoa're, Birmingham, both of England [73] Assignee: British Leyland (Austin-Morris) Limited, Birmingham, England 22 Filed: May 19, 1972 211 App]. No.5 254,857

301 Foreign Application Priority Data May 20, 1971 Great Britain 15972/71 [52] US. CL... 123/136, 123/DIG. 11, 123/198 DB, v 123/198 DC [51] Int. Cl. F02m 37/01), F0213 77/08 [58] Field of Search. 123/DIG. 11, 198 D, 198 DC, 123/198 DB, 136

[56] References Cited 3,093,124 6/1963 Wentworth 123/136 3,577,966 5/1971 Collingwood et a1. 123/198 DC 3,191,587 6/1965 Hall 123/136 3,354,877 11/1967 Z'ub et a1. 123/D1G. 11 3,398,731 8/1968 Johansson.... 123/198 D 3,482,562 12/1969 Ranft l23/D1G. 11 3,678,912 7/1972 Hensler 123/198 D X Primary Examiner-Al Lawrence Smith Attorney, Agent, or Firm-Brisebois & Kruger [5 7] ABSTRACT A spark ignition engine is precluded from running-on or diseling by providing a solenoid valve which terminates the delivery of fuel to the induction system of the engine in the period during which the engine continues to rotate (due to the energy stored in the flywheel) after. the ignition has been switched off. The solenoid .is only energised for the period between the ignition being switched off and the engine ceasing to 4 Claims, 2 Drawing Figures /2 :1 Q. l. :1 i

' C2 047' qua wage PATENTED APR 9 I974 SHEET 2 [1F 2 BACKGROUND OF THE INVENTION This invention relates to spark-ignition internal combustion (i.c.) engines.

Modern high-compression, spark-ignition i.c. engines are rather prone to exhibit the phenomenon of running-on after the ignition has been switched off. This propensity is attributable to the use of retarded ignition at idling (which necessitates a larger degree of throttle valve opening than would otherwise suffice to give the required idling speed), in conjunction with the use of fuel of lower octane rating than that recommended for the particular engine concerned.

The purpose of this invention is to preclude the occurrence of running-on, by providing means effective automatically to terminate the delivery of fuel to the induction system of the engine in the period during which the engine continues to rotate (due to the energy stored in its flywheel) after the ignition has been switched off. I

SUMMARY OF THE INVENTION In a preferred form of the invention a spark ignition internal combustion engine having an intake manifold, a fuel reservoir, a carburetter float chamber, a fuel vapour storage device having a first and second end with vapor absorbing means disposed therebetween; the improvement which comprises:

a. a fuel vapour distributing valve assembly including:

I. a first duct connecting the valve with the first end of the vapour storage device; II. a second duct connecting the valve with an evacuable means; III. a third duct connecting the valve to atmospheric air; b. a first conduit linking the float chamber the the second end of the vapour storage device; c. a second conduit linking the fuel reservoir to the second end of the vapour storage device; and

d. a purge conduit linking the crank case of the en-' gine to the second end of the vapour storage device.

According to one aspect of the preferred form the first duct means includes an evaporative loss canister.

According to another aspect of the preferred form the second duct means includes an evaporative loss canister.

According to yet another aspect of the preferred form the control means includes a solenoid and associated circuitry which operates, when the engine has been running and is switched off, to cause the valve to switch from a first position in which the valve links the third duct to the first duct to a second position in which the valve links the first duct to the third duct. Preferably the circuitry includes an engine lubricant pressure switch which, when enginelubricant pressure drops below a predetermined value, causes the solenoid to allow the valve to change from the second to the first position.

According to yet a further aspect of the preferred form the evacuable means comprises the carburetter or an inlet manifold to the engine.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described with reference to the accompanying drawings of which:

FIG. 1 is a diagram of a fuel-feed system for an i.c. engine according to the invention; and

FIG, 2 is a sectioned view of a valve incorporated in the system of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Reference should now be made to FIG. 1.

Petrol 11 from a carburetter float chamber 12 passes to the throttle bore 13 of a carburetter 14 by way of orifice 15. The area of the orifice 15 is governed by the position of a tapered needle 16 whose position relative to the orifice can be varied by way of piston 17 in a known way.

Free volume 18 in float chamber 12 is linked to evaporative loss canister 21 by way of first conduit 22. The canister 21 contains a mass of carbon granules 23 which serve to define spaces 24, 25 respectively above and below the granules 23. Space 24 has opening into it besides first conduit 22: a purge conduit 26 from rocker box cover 27 of internal combustion engine 28; and second conduit 29 from free space above fuel in fuel tank 30. From lower space 25 of canister 21 first duct 31 passes to valve 20.

Plunger 35 of valve 20 is biassed by compression spring 37 to urge valve head 36 into contact with seating 38. The plunger 35 also carries another valve head 40 which is adapted to contact seating 41 when the biassing action of the spring 37 is overcome by the passage of current through solenoid 42. The valve 20 has second duct 43 connecting volume 44 defined within are not shown. The valve opens to atmospheric air by way of third duct 46. Solenoid 42 is connected by way of switch 47 to a battery 48. The solenoid 42 is connected to earth by way of oil pressure sensitive switch 49. The crankcase of engine 28 is coupled to throttle bore 13 by way of an oil separator 45. In this way vapours within the crankcase are extracted and fed to the inlet manifold.

With engine 28 running switch 47 is open and engine oil pressure switch 49 is kept closed. Solenoid 42 is consequently unenergised and plunger 35 is freely urged by spring 37 to maintain head 36 on seating 38. Pressure in space 25 of the canister 21 is similar to that within first duct 31 which opens to atmosphere by way of third duct 46. Pressure in space 24 is slightly less than that in space 25 due to pressure drop across the granules 23 but this pressure is still higher than that in bore 13 of carburetter 14. A pressure drop therefor exists acting by way of first conduit 22 to drive fuel 11 into bore 13 by way of orifice 15. The purge conduit 26 serves to maintain a vacuum in space 24 so drawing vapour into the engine crankcase. On switching the ignition of engine 28 off switch 47 is closed causing the plunger 35 to be drawn, by the action of the field created by the current flowing through the solenoid, against the action of the spring to lift head 36 clear of seating 38 and thereafter to seat head 40 on seating 41. Because of this first conduit 31, and so space 25 in canister 21, is coupled to vacuum normally existing in inlet manifold by way of second duct 43. This vacuum is much greater than that provided by way of purge conduit 26 with the engine running. The resulting pressure drop across mass of granules 23 causes pressure in space 24 to be reduced so drawing any fuel vapour in purge conduit 26 and second conduit 29 and, more particularly, in first conduit 22 into space 24 and on into the granules 23. The granules serve to trap the fuel vapour. In addition the pressure drop acting to drive fuel 11 into bore 13 by way of orifice is removed with the result that no further fuel can pass which could result in running-on of the engine.

The pressure sensitive switch 49 after switching off the ignition will remain closed until the engine oil pressure drops below a preset value. Thereafter switch 49 opens so causing the solenoid 23 to be de-energised. Plunger 35 is then urged by the spring 37 to drive head 36 onto seating 38 and drive head 40 off seating 41 so opening first duct 31 to atmosphere by way of third duct 46.

It will be appreciated that the embodiment does not require a continuous current drain on the battery 48 while the engine is running. The solenoid 42 is only energised by a current flowing for the relative short period between the ignition being switched off and the engine oil pressure falling substantially below a value that could be sustained by the engine running on.

FlG. 2 shows in more detail the valve of FIG. 1. Similar parts in both Figures have similar reference numerals. The valve 20 is made up of a body member 81 on which the solenoid 42 is seated by way of plate 82. The solenoid is retained on the body member 81 by a pressed metal cap 83 through which project insulated terminals 84, 85 of the solenoid. Spring 37 is located in cap 83 by a projecting stud 83a. The body member 81 has a conduit 86. As shown valve head 36 seals on seating 38 so that second duct 43 is isolated and conduit 86 is in communication with third duct 46. On passing current through solenoid 42 by way of terminals 84, 85 the plunger 35 is lifted to seat valve head 40 on seating 41 and to raise valve head 36 clear of seating 38. This causes third duct 46 to be isolated from conduit 86 and puts conduit 86 in communication with second duct 43 by way of volume 44.

The purpose of establishing normal float chamber venting after the engine has been switched off and its oil pressure has dropped is to preclude entry of petrol vapour from the float chamber into the inlet manifold which, under hot soak conditions, can render engine starting difficult.

In application to engines fitted with constant-velocity carburetters, which are distinguished by having a region of substantially constant depression between the choke and the throttle valve, this region may be preferred as the evacuable means for application to the float chamber.

In the case of those carburetters (or other metering devices) which do not have a constant depression region, when inlet manifold depression is employed as the evacuable means it may be necessary to bleed the available depression down by such means as a' small hole leading from atmosphere into the valve chamber, as application of the full depression to the float chamber might induce boiling or cause other carry-over of fuel into the inlet tract, which would be undesirable in this context.

With carburetter float chambers that have a ventilation source other than atmospheric pressure, this source would be connected to the valve chamber.

We claim:

1. In a spark ignition internal combustion engine having an intake manifold, a fuel reservoir, a carburetter float chamber, a fuel vapour storage device having a first and second end with vapour absorbing means disposed therebetween; the improvement which comprises:

a. a fuel vapour distributing valve assembly including:

I. a first duct connecting the valve with the first end of the vapour storage device;

II. a second duct connecting the valve with an evacuable means;

III. a third duct connecting the valve to atmospheric air;

b. a first conduit linking the float chamber to the second end of the vapour storage device;

c. the second conduit linking the fuel reservoir to the second end of the vapour storage device; and

d. a purge conduit linking the crank case of the engine to the second end of the vapour storage device; said valve assembly including a solenoidoperated valve having a first position, occupied when the solenoid is de-energised, linking the first duct to the third duct; and a second position, occupied when the solenoid is energised, linking the first duct with the second duct, and means for bringing said valve assembly into said second position after engine ignition has been switched off and for retaining said valve assembly in said second position only until the engine speed has dropped below the speed at which dieseling'can occur.

2. A spark ignition internal combustion engine as claimed in claim 1 in which said last-mentioned means comprises circuitry in which the solenoid operated valve is incorporated, which circuitry includes a switch responsive to engine lubricant pressure which, when said engine lubricant pressure drops below a predetermined value, causes the solenoid to be de-energised.

3. A spark ignition internal combustion engine as claimed in claim 1 in which the evacuable means comprises the carburetter.

4. A spark ignition internal combustion means as claimed in claim 1 in which the evacuable means comprises an inlet manifold to the engine.

Claims

1. In a spark ignition internal combustion engine having an intake manifold, a fuel reservoir, a carburetter float chamber, a fuel vapour storage device having a first and second end with vapour absorbing means disposed therebetween; the improvement which comprises: a. a fuel vapour distributing valve assembly including: I. a first duct connecting the valve with the first end of the vapour storage device; II. a second duct connecting the valve with an evacuable means; III. a third duct connecting the valve to atmospheric air; b. a first conduit linking the float chamber to the second end of the vapour storage device; c. the second conduit linking the fuel reservoir to the second end of the vapour storage device; and d. a purge conduit linking the crank case of the engine to the second end of the vapour storage device; said valve assembly including a solenoid-operated valve having a first position, occupied when the solenoid is de-energised, linking the first duct to the third duct; and a second position, occupied when the solenoid is energised, linking the first ducT with the second duct, and means for bringing said valve assembly into said second position after engine ignition has been switched off and for retaining said valve assembly in said second position only until the engine speed has dropped below the speed at which dieseling can occur.