Internal combustion engine with spherical rotary valve

Abstract

A cylinder head assembly has a substantially spherical body defining a central axis of rotation normal to the cylinder central axis and comprising a passageway there through to bring the combustion chamber into intermittent fluid communication with an exhaust duct for evacuating the burnt gases, said passageway comprising a 90 deg bend with: a first opening (31) to the exhaust duct substantially parallel to, preferably coaxial with the valve central axis of rotation, and a second opening to the combustion chamber, such that by rotation of the valve round its axis of rotation, said second opening can be intermittently brought into fluid communication with the combustion chamber.

Description

FIELD OF THE INVENTION[0001]The invention relates to internal combustion engines equipped with one or more spherical rotary valves.BACKGROUND OF THE INVENTION[0002]There is a general trend to build internal combustion engines combining high specific power to keep the engine compact, with high efficiency to avoid fuel losses and air pollution. Such can be attained by enhancing the compression ratio, the valves tightness, the filling and emptying of the cylinders, etc. At the same time the reliability of the engine must be ensured.DESCRIPTION OF PRIOR ART[0003]The cylinders of conventional four stroke internal combustion engines have been for a long time equipped with only mushroom or poppet valves. However, the reciprocating motion of the valves is problematic at high revolutions because of their inertia which can lead to a synchronisation loss with the motor revolutions regime. Moreover, poppet valves induce important head losses, which is detrimental to a good cylinder filling.[000...

AI Technical Summary

Benefits of technology

[0014]The object of the invention is to provide an internal combustion engine of simple and cheap construction, delivering a high specific power coupled with high efficiency and reliability. The present invention is defined in the appended independent claims. Preferred embodiments are defined in the dependent claims.

[0022]The use of such axial flow spherical rotary valves is advantageous in many respects. It offers better flowing conditions and thus better cylinder filling / emptying conditions. As the movement of a rotary valve is continuous and not reciprocal as is the case with a poppet valve, it may run at higher revolutions than the latter. The sealing between the valve and the combustion chamber is easier to ensure, than with cylindrical rotary valves, thus maintaining higher levels of compression. Moreover, in case of two stroke engines the use of a spherical exhaust valve allows to get rid of the exhaust opening on the cylinder wall of conventional engines, thus permitting to reduce the number of ports on the cylinder wall and hence to increase the compression stroke and the compression ratio, thus yielding a higher engine efficiency.

[0023]The gist of the invention is to rotatably mount the valve in cantilever on a shaft on one side only of the valve, the one opposite the exhaust duct, to avoid extreme thermal variations and thus thermal expansion of the exhaust shaft, which would jam the bearings of the rotary valves of the prior art.

Problems solved by technology

However, the reciprocating motion of the valves is problematic at high revolutions because of their inertia which can lead to a synchronisation loss with the motor revolutions regime.

Moreover, poppet valves induce important head losses, which is detrimental to a good cylinder filling.

The incomplete closure of the exhaust outlet while unburnt gas is being transferred into the combustion chamber, however, renders traditional two stroke engines particularly polluting.

However, the irregular shape of the channels would cause important head losses detrimental to a good cylinder filling and / or emptying.

Nevertheless, cylindrical rotary valves turned out to be ineffective to seal the passage between the combustion chamber and the rotary valve.

However, the sleeve of the exhaust valve undergoes the hot temperature of the exhaust gases and may thus jam due to its thermal expansion in its race.

In the case of a curved channel, however, this construction is problematic, since on the exhaust side of the valve, the bearings are fixed to a hollow axle carrying combusted gases into the exhaust duct.

The temperature of the exhaust axle may vary from ambient when the engine is started, to several hundreds degrees when the engine has been running for a long time, thus generating large thermal expansions, impossible to be accommodated by the bearings.

The presence of bearings around the exhaust axle is thus detrimental to the operational reliability of the rotary valve as they may jam due to the thermal expansion of the valve hollow exhaust axle.

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