GB2446003A - Rotary valve system for petrol engines - Google Patents

Abstract

A rotary valve system for controlling the fuel charge inlet and the exhaust outlet of a four-stroke petrol engine comprises a single domed rotary valve A located in the combustion chamber and forming the hemi-spherical cylinder roof. The rotary valve A has preferably three openings D to coincide with a set of three port openings on the corresponding cylinder head B. As the valve rotates about its stem F the openings D uncover the next set of three port openings in sequence. Position I corresponds with the inlet of fuel/air charge, position C. to seal the chamber for compression and to uncover three spark plugs (Z, fig.6) and position E coincides with the exhaust ports. This stepping sequence follows the conventional four-stroke cycle, and the timing of the valve rotation is managed by a digitally controlled stepping motor arrangement J. The cylinder head dome B may be cast or machined with port tubes attached to achieve smooth port surfaces, and to mould port channels (K, Fig 10) such that the fuel charge will have a turbulence bias so it will swish into the combustion chamber to better mix the air and fuel.

Description

S 2446003 ROTARY VALVE SYSTEM FOR PETROL ENGINES.

The invention relates to a rotating valve system for internal combustion four-stroke petrol engines which includes a valve, cylinder head and a device to control the timely opening of the valve, which as a system may be used to allow the transfer of air and fuel into an engines combustion chamber, where the mixture is compressed and ignited to produce combustion, and then the same valve is used to exhaust the resulting gases out of the chamber, upon which the cycle then repeats, the rotating valve system being compatible with components of conventional engines.

The invention is designed to solve several problems associated with the valve mechanisms of conventional four-stroke petrol engine.

Firstly, current engines commonly utilise separate fuel inlet valves and exhaust valves, with associated springs and fittings that are normally seated across the port opening in an engine cylinder head. The valve opening and closing is usually controlled by a rotating cam and cam follower that is also contained within the cylinder head. The rotation of the camshaft is driven by a belt or chain in a fixed synchronisation such that the valves open and close at an appropriate time and do not hit the piston. The inlet and exhaust valves being controlled by separate independent cams and associated mechanics leads to a complex mechanical system. This fixed valve timing typically means that the power output of the engine normally occurs at medium engine speeds, the power output reduces at slow and fast engine speeds.

Secondly, the purpose of the valves is to provide flow of fuel and gases without disruption, but as conventional valves typically sit across the cylinder head ports they form a part barrier to this flow due to the obstruction caused by the valve stem, valve back and shape of the valve throat, that all act to block the efficient movement of fuel mixture and exhaust gases.

Thirdly, the cylinder head is typically cast from metal and the casting process can mean that the surfaces of the ports are uneven and pitted, which can impinge on the flow. In order to fully mix the air and fuel to swirl into the combustion chamber the ports need to be designed so that the fuel charge can be biased to flow past the inlet valves.

Fourthly, the cylinder head being cast from metal, together with the valves and cam mechanisms, means there is a weight high up on the engine that can be significant. The overall height of the engine is determined partly by the size of the cylinder head and in turn will require a cars engine compartment to accommodate this.

Fifthly, in a four-stroke engine the piston is effectively a pressure tight plunger that slides up and down the cylinder; the piston converts the pressure created by the combustion process into a reciprocating mechanical movement. The shape and design of the piston crown is critical to the energy conversion and determines the shape of the combustion chamber. With a conventional valve arrangement the shape of the piston face must be able to accommodate the movement of the valve into the chamber, which in turn affects the design efficiency of the piston crown.

Lastly, ignition of the compressed fuel mixture is achieved by an electric spark, in conventional engines due to the positioning and size of the valves, and the limited space in the cylinder roof, there is typically only one spark plug and this may be positioned off-centre from the middle of the chamber. As the spark ignites the fuel a burn front spreads out from the point of the spark. The mixture of the fuel may not be constant across the chamber, and due to this and the positioning of the spark plug in the chamber, as it combusts there could be a skew to the pressure build up, the resulting energy is then uneven across the piston face which could lead to additional wear and some loss of power efficiency.

An object of this invention is to provide a rotary valve system that aims to improve the flow of air and fuel into the combustion chamber by providing multiple openings simultaneously, aiding the better mixing of this fuel charge, that provides a fuller ignition and burning of the fuel by providing multiple ignition points, which in turn creates multiple burn fronts, leading to enhanced output power at all engine speeds, improving the combustion characteristics and so the exhaust emissions of fourstroke petrol engines, whilst being simple to manufacture.

Accordingly this invention will provide a single rotary valve that forms part of the combustion chamber, the valve has a number of openings that may be of varying shapes and rotates within the chamber to mesh with the corresponding multiple port openings in the cylinder head to allow air and fuel to enter the chamber, rotates to coincide with the multiple spark plugs or ignition devices and by design forms a pressure tight seal when combustion occurs, then rotates to mesh with the corresponding multiple exhaust port openings in the cylinder head to expel the gases. The cycle then repeats as required, following the typical four-stroke cycle of internal combustion engines. Because there is no obstruction to the flow of the mixture, and the charge is introduced across all parts of the chamber more efficiently and simultaneously, this will allow fuller combustion to occur resulting in higher power output.

The rotation of the valve can achieved by mechanical means but preferably may be achieved by utilising an electric motor. This would be a digitally controllable motor to move the rotary valve to each corresponding port opening in turn, with an actuator to lift the valve from the seat before it is rotated and then re-seat it at the end of each step.

All timing aspects of the step would be able to be controlled at all engine speeds, such as the time taken to step, the time at each port and when the step starts relative to the position of the piston. In doing so variable valve timing is achieved allowing the amount of charge into the chamber to be controlled and matching the appropriate burn timing characteristics, which will lead to a higher power output across the engines operating band.

The cylinder head can then be a cast or machined metal dome. Off this dome and at the port openings could be attached separate tubes to carry the fuel mixture into the combustion chamber and exhaust gases out.

This will provide the opportunity to manufacture the ports with very smooth surfaces, free of any obstructions or surface pits that would disturb the flow of the fuel charge into the combustion chamber. The tubes can be arranged into complex designs, allowing the ports to be angled such that they give a spin bias to the charge as it enters and swirls into the chamber, leading to better mixing of the air and fuel and fuller combustion, in turn reducing noxious exhaust emissions. To cool the tubes either air or liquid would be passed around them. The sealing for compression purposes within the chamber and at each cycle step would be achieved by lapping the back surface of the rotary valve with the internal surface of the cylinder head dome.

The requirements to have the complex cams and associated mechanics high up on the engine are obviated, the weight of the system is much less, boosting the overall power to weight ratio of the engine. Further, the system requires less space and height when compared to current engine design and gives the opportunity to produce more compact engine compartments leading to better front streamlining in conventional vehicle design.

A preferred embodiment of the invention is now described with reference to the accompanying drawings in which: Fig I shows the rotary valve and potential openings as seen from below; Fig 2 shows the cylinder head corresponding openings as seen from below Fig 3 shows the rotary valve from below and from side profile; Fig 4 is a section showing the rotary valve positioned within and forming the roof of the combustion chamber; Fig 5 shows an additional section of the rotary valve positioned in the chamber; Fig 6 identifies three points of spark or other form of ignition at multiple points across the chamber; Fig 7 is a section showing the valve system with the stepper motor & actuator sifting atop the cylinder head with potential port openings into the combustion chamber and the valve located in the chamber; Fig 8 shows the potential stepper motor timing at different engine speed; Fig 9 shows how the start of the step can occur at different times and be completed at different times within the same step cycle timeframe; Fig 10 is a see through of the spiral of port tubes in the cylinder head swirling to the port openings; As shown in Fig I the rotary valve A. (viewed from below) has three-valve openings D. or more. The size and shape of these openings is variable and is dependant on the total area of the valve surface and the materials used. In this preferred example of three openings the maximum segment angle for each opening is 400 and would equate to a total port opening of 33% of the combustion chamber roof area.

However this would be outside of normal tolerance for the strength of most materials, the preferred material should be able to withstand the operating temperatures, will not wear or corrode and is tolerant to impact.

The rotary valve A. sits under the cylinder head B. and forms part of the combustion chamber roof. Fig 2 shows the cylinder head openings (viewed from below) radiating around the surface, the size and shape of these openings are determined by those on the corresponding rotary valve openings D. The sequence of rotation is to step from the inlet port opening 1. to the compression & ignition opening C. where the spark plugs or ignition devices are revealed and then on to the exhaust port opening E. The rotation shown here is clockwise but it can equally be counter-clockwise if the same step sequence is followed. Fig 3 shows the rotary valve A. from side profile where it can rotate either way about the valve stem F. Fig 4 shows the section of the cylinder head B., cylinder block X, piston Y. and the combustion chamber W. Note that the rotary valve A. does not significantly intrude into the volume of the combustion chamber W. Because the valve does not protrude into the chamber the piston crown H. can be designed such that the shape can be maximised for the best conversion of the incident combustion power.

In Fig 5 the rotary valve A. is shown to form the hemi-spherical combustion chamber roof. The rotary valve A. back forms a seal G. with the cylinder head by the surfaces being lapped against one another insitu, the preferred cylinder head is a cast or machined material as a dome. In this configuration the rotary valve A. is recessed into the cylinder head B. such that the rotary valve lip L. also form a seal at the lip edge with the cylinder head B. Fig 6 shows the rotary valve at the compression & ignition position illustrating that spark plugs or ignition devices Z. ignite the fuel charge at three points in the chamber to aid fuller combustion. The spark plugs or ignition devices are exposed at this position through the valve openings D. In Fig 7 the digitally controlled electric motor and actuator J. is preferred to sit atop the cylinder head B. in order to aid cooling and be furthest from any direct heat of the combustion. The rotary valve stem F. is preferred to be directly connected to the motor and actuator spindle arrangement. To move the rotary valve A. from one sequence position to the next the actuator first unseats and holds the valve shoulder away from the cylinder head B. The digitally controlled electric motor then rotates the whole valve through the appropriate angle (the preferred angle is 40% for three openings in the rotary valve A. as shown in Fig 1) to coincide with the next cylinder head opening. At the end of the step sequence the actuator then reseats the valve back into the cylinder head. The timing of the sequence is related to the position of the piston Y. and the speed of the engine.

The timing of the step is digitally controlled, Fig 8 shows an example of a likely step time at different engine speeds, here there are a preferred four steps per sequence, in this case the preferred step is 100 per step (other step angles or steps per sequence can occur and are only limited by the maximum step speed of the stepper motor) making the total sequence step angle of 400 between valve openings D. as mentioned above. Fig 8 assumes and shows in each case the step start time is at the beginning of the sequence and completes at the end of the sequence. This allows the valve timing to match the appropriate engine speed.

By digitally controlling the timing of the steps it is possible to delay the sequence start timing, the sequence end completion or the duration of each sequence step. Fig 9 shows an example of this for the preferred four steps per sequence step. This allows the performance to be digitally characterised to achieve the best power output for engine speed and load conditions, a further enhancement of variable valve timing.

As the preferred cylinder head is a cast or machined dome, Fig 10 shows how the ports could be formed such that the tubes spiral above the cylinder head around the chamber roof. The ports can be angled at the port openings to aid the swish of the air and fuel mixture into the combustion chamber and to spiral the exhaust gases out.

Claims (7)

1. In taking the rotary valve system as a whole, engine designers and manufacturers will have the technology to simplify the engine production.

   The rotary valve technology brings the following: 1. Significantly improving the free flow of the charge into the combustion chamber leads to a fuller combustion.
2. 2. By having three points of ignition the burn front delivers a more even energy across the piston crown returning a greater power conversion to mechanical movement.
3. 3. The control of the port opening/closing by digitally controlled electrical motor gives accurate and variable timing, delivering maximum torque across the whole power band.
4. 4. Using port tubes allows smooth port surfaces, with more flexibility to design the port bias aiding the charge swirl and improving the air/fuel mixing.
5. 5. With a fuller combustion and greater control of the charge, noxious emissions are reduced.
6. 6. The power output efficiency for a given engine size is increased, and the lighter components means a higher engine power to weight ratio.
7. 7. Reducing the number of components, by eliminating the need for camshafts, drive belts, drive gears, followers, valve mechanics and cast metal cylinder heads, will significantly reduce the time and the complexity of production.