GB2053349A - Reducing i.c. engine intake manifold vacuum at overrunning - Google Patents

Abstract

A non-explosive gas (e.g. air) is supplied to the inlet manifold (2) under the control of a valve (13) which is normally closed and is operated by an electrical actuator (16) energized through a circuit including a first switch (19) which closes when the engine speed rises above idling speed and a second switch (20) which closes when the accelerator control moves to its non-operated position. When both switches are closed the valve (13) is opened to admit gas to the manifold, causing the partial vacuum to collapse and thereby preventing fuel from the carburettor (3) reaching the combustion chambers. A further switch (22) may be included in the circuit for protecting a vacuum- braking system by opening when the brake vacuum is below a predetermined value. <IMAGE>

Description

SPECIFICATION Methods and apparatus for controlling the fuel supply to an internal combustion engine.

This invention relates to methods and apparatus for controlling the fuel supply to an internal combustion engine installed in and for propelling a vehicle and has for its main object the reduction of fuel consumption by such engines whilst maintaining satisfactory performance of the engine and operation of the vehicle.

In order that an internal combustion engine shall continue to run, even when the vehicle has been brought to a halt, it is arranged that some fuel shall continue to be delivered to the combustion chambers to maintain the engine at idling speed even though the accelerator control of the vehicle has been returned to its nonoperated position. However, when the accelerator control has been returned to said position during, for example, periods of deceleration or overrun the engine is driven by the inertia of the vehicle at speeds higher than idling speed and the fuel delivered to the combustion chambers serves no useful purpose and is wasted.

According to the present invention there is provided a method of operating an internal combustion engine installed in and for propelling a vehicle, in which the supply of fuel to the engine combustion chamber or chambers is prevented whenever the following conditions coexist, namely that the accelerator control of the vehicle is in its non-operated position and that the engine revolutions per minute are above a predetermined value corresponding to the engine idling speed.

In a specific embodiment of the present invention there is provided a method, as above stated, as applied to an internal combustion engine having a carburettor wherein supply of fuel to the combustion chamber or chambers is dependent upon the existence of a partial vacuum in the engine inlet manifold, in which the supply of fuel is prevented by introducing a non-explosive gas (e.g. air) into the manifold to thereby collapse said vacuum.

In a further embodiment of the invention there is provided the method stated in the preceding paragraph, as applied to a vehicle provided with a servo-assisted braking system the operation of which is dependent upon the existence of said vacuum in the inlet manifold, in which the introduction of said gas to the manifold is discontinued upon repeated operation of the braking system.

The invention also provides, in a vehicle including an internal combustion engine for propelling the vehicle said engine having a carburettor wherein supply of fuel to the combustion chamber or chambers is dependent upon the existence of a partial vacuum in the engine inlet manifold, a source of a non-explosive gas (e.g. air) connected to the inlet manifold so as to by-pass the carburettor, normally-closed valve means for controlling the supply of said gas to the inlet manifold, a valve actuator connected to open said valve means when the actuator is energised, and control means including an engine speed monitor unit and a unit for monitoring the position of the vehicle accelerator control adapted to energise said valve actuator when the following conditions co-exist, namely that the accelerator control is in its nonoperated position, and that the engine revolutions per minute are above a predetermined value corresponding to the engine idling speed; whereby said gas is introduced into the manifold to thereby collapse said vacuum.

Also provided by the invention is a kit of parts for modifying an existing vehicle having an internal combustion engine for propelling the vehicle, said engine having a carburettor wherein supply of fuel to the combustion chamber or chambers is dependent upon the existence of a partial vacuum in the engine inlet manifold; said kit comprising a unit for insertion between the carburettor and the inlet manifold including normally-closed valve means connectable to a source of a non-explosive gas (e.g. air), an actuator for said valve means connectable to operate said valve means, control means comprising an engine speed monitor unit and a unit for monitoring the position of the vehicle accelerator control; whereby said control means may be connected to a power source to actuate said actuator when the following conditions coexist, namely that the accelerator control is in its nonoperated position, and that the engine revolutions per minute are above a predetermined value corresponding to the engine idling speed; whereby said gas is introduced into the manifold to thereby collapse said vacuum.

Embodiments of the invention will now be described with reference to the accompanying drawing in which the single Figure shows part-insection and part-schematically an engine fuel supply controlled in accordance with the present invention.

Referring to the drawing an internal combustion engine, indicated at 1, of a vehicle has an air inlet manifold 2 supplied with fuel by a carburettor 3.

The carburettor includes a fuel jet 4 within a venturi 5, an air inlet 6 and a butterfly valve or throttle 7 operated by the vehicle accelerator control (not shown). As is well understood the induction stroke in the engine cylinder or cylinders creates a partial vacuum in the manifold 2 which causes fuel, that is a fuel-air mixture, to be drawn into the combustion chamber at a rate depending upon the position of the valve 7. When the accelerator control is moved to its non-operated position the valve 7 is closed (as shown) in which condition fuel continues to be supplied to the engine at a rate sufficient to maintain the engine at idling speed.

In accordance with the invention, a unit 8 is inserted between the carburettor and the manifold and secured by bolts 9. This unit includes a first passage 10 aligned with and corresponding to the fuel-flow passage from the carburettor to the manifold and a second passage 11 communicating with the passage 10 and terminating in an air inlet 12. Within the passage 11 is a butterfly valve 13 connected to an external lever 14 which is operable from a position in which the valve 1 3 is fully closed (as shown) to a position, indicated by the broken line 15, in which the valve is open.

When the valve 13 is open, the manifold 2 is subjected to atmospheric pressure by air entering the inlet 12 and the normally-present partialvacuum in the manifold is destroyed, thereby preventing induction of fuel from the jet 4. When the valve 13 is closed, partial-vacuum is reestablished in the manifold and induction of fuel from the jet 4 is resumed.

An actuating solenoid 1 6 has its plunger 1 7 linked to the free end of the lever 14. The solenoid is energised through a circuit comprising a contactor 18 and two make-and-break switches 1 9 and 20 connected in series to a voltage source 21. A third switch 22 is shown which is optional and will be described hereinafter. When both switches 19 and 20 are closed the solenoid 1 6 is energised and the plunger 17 moves the lever 14 to the position indicated by the line 1 5, in which the valve 13 is open. When one or both switches is opened the solenoid is de-energised and the plunger 17 moves the lever 14 to the position shown in the drawing, in which the valve 13 is closed.

The switch 19 is part of an engine revolutions monitor 23 which detects the engine speed and maintains the switch 1 9 closed when said speed is above a predetermined value corresponding to the idling speed of the engine. When the engine speed falls to or below the predetermined value the switch 19 is opened, as shown. The switch 20 is part of an accelerator position monitor 24 which detects when the accelerator control of the vehicle, and therefore the throttle valve 7, is in the non-operated position (as shown) and thereupon causes the switch 20 to close, as shown. When the throttle valve 7 is in any other position the switch 20 is maintained open.

Thus, without any conscious control by the vehicle driver, supply of fuel to the manifold 2 is positively and automatically stopped when the two following conditions co-exist; namely that the engine speed is above the idling speed and the accelerator control is in the non-operated position.

In all other conditions, as the apparatus has been so far described, this overriding control of the fuel supply is removed thereby ensuring that the engine will run at idling speed when the vehicle stops and that engine speed and power can be increased by normal operation of the accelerator control.

The invention enables a substantial economy in fuel consumption to be achieved by stopping the fuel supply when the vehicle is decelerating or overrunning, as when the vehicle is descending a gradient or is being brought to a halt or when a lower gear is being selected.

In the case that the vehicle is equipped with a servo-assisted braking system the operation of which is dependent upon the existence of the aforementioned partial-vacuum in the manifold 2, then a further switch 22 is connected in series with the switches 1 9 and 20. The normally-closed switch 22 is part of a brake vacuum monitor 25 which detects when the brake vacuum falls below a predetermined minimum value and causes the switch 22 to open, thereby causing the valve 1 3 to close so the partial-vacuum in the manifold is restored.

Although the embodiment described with reference to the drawing comprises an electrically operated system for control ofthe lever 14, it is to be understood that the control can be effected by an equivalent pneumatically or hydraulically operated system.

Furthermore, the butterfly valve 13 may be replaced by any other suitable form of valve.

Although the inlet 12 has been described as open to atmospheric air,'uf may be connected to a source of some other non-explosive gas.

Further advantages of the invention include the following: a improved engine braking of the vehicle b reduced pollution of the atmosphere by unburnt fuel and oil vapour in the exhaust gases c reduced consumption of engine lubricating oil d increased spark plug life due to reduction of carbon deposits on the electrodes e reduced accretion of carbon in the combustion chambers and exhaust ports.

Apparatus for performing the invention may be incorporated into a vehicle at the design stage when the functions carried out by the unit 8 could be included integrally in the carburettor, the inlet manifold 2 or the engine's cylinder head.

Alternatively, a kit of parts may be supplied for modifying an existing vehicle which, in the illustrated embodiment, would comprise the unit 8, the actuator 16, the contactor 1 8 and the monitors 23 and 24 with, optionally, the monitor 25.

The method of the invention, as broadly stated, is applicable in other ways which do not involve collapsing the partial-vacuum in an inlet manifold; for example as described in my co-pending patent applications numbered 7920082 and 7924908, the disclosures of which are incorporated herein by reference.

However from the foregoing it will be seen that from one aspect the invention may be stated broadly to provide an internal combustion enginehaving a carburettor connected by an inlet manifold to an engine combustion chamber wherein the rate of supply of fuel/air mixture by the carburettor to be consumed in the combustion chamber is a function of the level of partial vacuum obtaining in the inlet manifold, and wherein the carburettor is arranged to provide a minimum flow rate of fuel/air mixture to maintain the engine at idling speed, and means arranged to destroy at least partially and selectively the partial vacuum so as to prevent or reduce said minimum flow rate in response to a sensed operating condition of the engine indicating that said minimum flow rate is not necessary for achieving the power demanded of the engine.

Claims (8)

1. A method of operating an internal combustion engine for propelling a vehicle and having a carburettor connected by an inlet manifold to an engine combustion chamber wherein the rate of supply of fuei/air mixture by the carburettor to be consumed in the combustion chamber is a function of the level of partial vacuum obtaining in the inlet manifold, and wherein the carburettor is arranged to provide a minimum flow rate of fuel/air mixture to maintain the engine at idling speed, said method including the steps of sensing an operating condition of the engine indicating that said minimum flow rate is not necessary for achieving the power demanded of the engine and causing said partial vacuum to collapse in response to said operating condition so as to reduce said minimum flow rate.

2. A method of operating an internal combustion engine installed in and for propelling a vehicle, in which supply of fuel to the engine combustion chamber or chambers is dependent upon the existence of a partial vacuum in the engine inlet manifold, and in which the supply of fuel is inhibited by introducing a non-explosive gas (e.g. air) into the manifold thereby to collapse said vacuum whenever the following conditions coexist, namely that the accelerator control of the vehicle is in its non-operated position and that the engine revolutions per minute are above a predetermined value corresponding to the engine idling speed.

3. A method as claimed in claim 2, as applied to a vehicle provided with a servo-assisted braking system, the operation of which is dependent upon the existence of said vacuum in the inlet manifold, in which the introduction of said gas to the manifold is discontinued upon operation of the braking system.

4. An internal combustion engine for propelling a vehicle and having a carburettor connected by an inlet manifold to an engine combustion chamber wherein the rate of supply of fuel/air mixture by the carburettor to be consumed in the combustion chamber is a function of the level of partial vacuum obtaining in the inlet manifold, and wherein the carburettor is arranged to provide a minimum flow rate of fuel/air mixture to maintain the engine at idling speed, said engine comprising or being in combination with means for sensing an operating condition of the engine indicating that said minimum flow rate is not necessary for achieving the power demanded of the engine and means for causing said partial vacuum to collapse in response to said operating condition so as to reduce said minimum flow rate.

5. In a vehicle including an internal combustion engine for propelling the vehicle said engine having a carburettor wherein supply of fuel to the combustion chamber or chambers is dependent upon the existence of a partial vacuum in the engine inlet manifold, a source of a non-explosive gas (e.g. air) connected to the inlet manifold so as to by-pass the carburettor, normally-closed valve means for controlling the supply of said gas to the inlet manifold, a valve actuator connected to open said valve means when the actuator is actuated, and control means including an engine speed monitor unit and a unit for monitoring the position of the vehicle accelerator control adapted to actuate said valve actuator when the following conditions co-exist; namely that the accelerator control is in its nonoperated position, and that the engine revolutions per minute are above a predetermined value corresponding to the engine idling speed; whereby said gas is introduced into the manifold thereby to collapse said vacuum.

6. A kit of parts for modifying an existing vehicle having an internal combustion engine for propelling the vehicle, said engine having a carburettor wherein supply of fuel to the combustion chamber or chambers is dependent upon the existence of a partial vacuum in the engine inlet manifold; said kit comprising a unit for insertion between the carburettor and the inlet manifold including normally-closed valve means connectable to a source of a non-explosive gas (e.g air), an actuator for said valve means connectable to operate said valve means, control means comprising an engine speed monitor unit and a unit for monitoring the position of the vehicle accelerator control; whereby said control means may be connected to a power source to actuate said actuator when the following conditions co-exist, namely that the accelerator control is in its non-operated position, and that the engine revolutions per minute are above a predetermined value corresponding to the engine idling speed; whereby said gas is introduced into the manifold to thereby collapse said vacuum.

7. A method of operating an internal combustion engine for propelling a vehicle, substantially as herein described.

8. An internal combustion engine for propelling a motor vehicle, substantially as herein described with reference to the accompanying drawing.