GB2319296A

GB2319296A - I.c. engine with valves actuated electrically, eg electromagnetically

Info

Publication number: GB2319296A
Application number: GB9623567A
Authority: GB
Inventors: Bernard Owen
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-11-13
Filing date: 1996-11-13
Publication date: 1998-05-20
Also published as: GB9623567D0

Abstract

The inlet and/or exhaust valves 17,18 include actuation means electrically connected to the engine management system whereby the opening and/or closing of the valves is controlled according to the prevailing operating conditions and power demanded of the engine. Each valve 17,18 may be actuated electromagnetically with an annular solenoid 27,28 disposed around the valve stem which may include a part 29,30 of paramagnetic material. When the engine is not running, the valves may be held closed by weak springs 21,22. In use, the engine management system delivers electrical power to the lower part of the solenoid 27,28 to open the valve and to the upper part of the solenoid, assisted by the spring 21,22, to close the valve. The two parts of each solenoid may be wound in the same or opposite senses. The engine is able to operate at high efficiency over its full operating range.

Description

INTERNAL COMBUSTION ENGINE This invention relates to internal combustion engines having inlet and exhaust valves and in particular provides such an engine having an improved valve control system.

Conventionally, inlet and exhaust valves, commonly referred to as poppet valves, in four-stroke internal combustion engines are actuated by cams. However, although the engine's requirements for the exact timing of the opening and closing of the valves vary according to the speed at which the engine is running, the opening and closing of the valves is of necessity non-variable, being determined by the profile of the cam lobes. Thus, cam lobe design is a compromise between the extremes represented by the ideal conditions for idling or lowpower use on the one hand and high speed or high-power use on the other hand. The result is that the engine operates under reduced efficiency over at least some of its operating range, compared with what would be theoretically possible if the valves were controlled according to the instantaneous requirements having regard to the operating speed, conditions and power demands being placed on the engine.

Attempts have been made to provide engines with valves which are actuated by different cams according to the engine speed, but such proposals are of necessity technically complex and would find utility only in highperformance engines.

It is an object of the present invention to provide an internal combustion engine in which the valves are actuated in response to the instantaneously-prevailing operating conditions and power demands.

Accordingly, in one aspect the invention provides an internal combustion engine having inlet and exhaust valves, in which at least the inlet or the exhaust valves include actuation means electrically connected to the engine management system, whereby the opening and/or closing of the valves is controlled by the engine management system according to the operating conditions and power demanded of the engine.

The actuation means may comprise for example an electric motor operatively connected to each respective valve stem but, preferably, the said valves are actuated electromagnetically and comprise a magnetic material, the actuation means comprising means for producing a magnetic field in operative proximity to each said valve to open and/or close the valve, the power and/or duration of the magnetic field being determined by the engine management system. Conveniently, at least part of the valve stem is made from a magnetic material, the remainder of the valve being made from a non-magnetic material such as titanium which is both light in weight and is resistant to high temperatures. The valve stem may be surrounded along part of its length by a solenoid through which an electric current is passed under the control of the engine management system to produce a magnetic force to open and/or close the valve, preferably to open the valve, a biassing force being provided to urge it towards and to maintain it in the closed position in the absence of the magnetic force. However, in a preferred arrangement the actuation means is adapted both to open and to close the valves under electromagnetic force, for example, by arranging for the solenoid windings to be in two parts, preferably arranged end to end, with means to divert the current from one part to the other to open o close the valve. The respective parts may be wound ir the same sense, whereby the polarity is represented b ABAB along the length of the solenoid, or in opposit senses whereby the polarity may be represented as ABBA Alternatively, the actuation means may be arranged tc pass current through the solenoid in opposing directions, in order to provide for both opening and closing of th valves under magnetic control. A relatively weak sprint or other biassing means may be provided to maintain th valves in the closed position when the engine is not running, or movement-limiting means may be provided te prevent the valves from coming to rest in a positior where they would be struck by a piston.

In internal combustion engines according to th invention, it may be desirable to provide two inlet valves and/or two exhaust valves per cylinder, as already known, one of said two valves having a smaller valve heac area than the other of said two valves, whereby th( smaller valve is easier to open against any residual pressure in the cylinder than is the larger valve and once open, relieves any such pressure to enable th larger valve to open more easily.

By "magnetic material" in this specification is meant preferably a paramagnetic material such as iron having positive susceptibility to an applied magnetic field.

Internal combustion engines according to the invention may also include suitable magnetic shielding, in order not to cause interference between the operating means o! adjacent valves but also to protect other electromechanical or electronic components fror interference.

The invention will now be described, purely diagrammatically and by way of example, with reference to the accompanying drawing, which is a cross-section through the upper part of the crankcase and cylinder head of an engine having a double row of valves.

With reference to the drawing, the engine has a cylinder block 11 defining a cylinder 12 in which moves a piston 13. The cylinder head 14 includes inlet ports 15 and exhaust ports 16 with associated valves 17, 18 slidingly carried in valve guides 19, 20. The valves are normally held in the closed position when the engine is not running, as shown for inlet valve 17, by weak springs 21, 22 mounted between the upper ends of the valve stems 23, 24 and bridging pieces 25, 26 bolted to the cylinder head casting.

The upper part of the cylinder head casting carries annular solenoids 27, 28 which surround the upper end regions of the valve stems. The solenoids are electrically connected to the engine management system, and have upper and lower parts such that they have North polarity at the upper ends of each part and South polarity at the lower ends. The valve stems have portions 29, 30 formed from a magnetic material; they are otherwise magnetically inert.

In use, the engine management system delivers electrical power to the lower part of the solenoid when the selected valve is required to open and diverts it back to the upper part of the solenoid when the valve is required to close. The magnetic field generated by the solenoid (28 as illustrated) exerts a magnetic effect on the magnetic material 30 of valve stem 24 and draws it downwards, thereby opening the valve (as illustrated, the exhaust valve). On the electrical power being applied to the other winding, the magnetic material 30 is drawn upwards and the valve closes, assisted by spring 22. Since the management system receives signals from the ignition system relating to engine speed and sensors such as engine operating temperature sensor, lambda sensor, pressure sensor and air and fuel functions, all of which are variable depending on operating conditions and engine output requirements, the amount and duration of the electrical power to the solenoids, and hence the extent and time over which the valves are open, are matched to the instantaneous conditions of the engine.

Claims

1. An internal combustion engine having inlet and exhaust valves, in which at least the inlet or exhaust valves include actuation means electrically connected to the engine management system, whereby the opening and/or closing of the valves is controlled by the engine management system according to the prevailing operating conditions and power demanded of the engine.

2. An internal combustion engine according to Claim 1, in which said at least inlet or exhaust valves comprise a magnetic material and the actuation means comprise means for producing a magnetic field in operative proximity to each said valve.

3. An internal combustion engine according to Claim 2, in which at least part of the valve stem comprises a magnetic material.

4. An internal combustion engine according to Claim 3, in which the valve stem is surrounded along part of its length by a solenoid electrically connected to the engine management system.

5. An internal combustion engine according to Claim 4, in which the solenoid comprises separate coils arranged end to end.

6. An internal combustion engine according to Claim 5, in which the coils are wound in the same sense.

7. An internal combustion engine according to Claim 5, in which the coils are wound in opposite senses.

8. An internal combustion engine according to any preceding claim, including biassing means to maintain the valves in the closed position when the engine is not running.

9. An internal combustion engine according to any preceding claim, in which said at least inlet or exhaust valves are provided as two valves per cylinder, one of said two valves having a smaller valve head area than the other of said two valves.

10. An internal combustion engine according to any of Claims 1 to 4, in which said inlet or exhaust valves are provided with means to apply a biassing force to urge the valve in a direction opposite to that of the actuation means.

11. An internal combustion engine substantially as herein described with reference to and as illustrated in the accompanying drawing.