Internal-combustion engines – Multiple cylinder – Cylinders in-line
Patent
1990-04-12
1991-12-31
Okonsky, David A.
Internal-combustion engines
Multiple cylinder
Cylinders in-line
123190D, 123666, F01L 700
Patent
active
050762192
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an internal-combustion engine with distribution by rotary shutter.
In the internal-combustion engines with a piston driven in a reciprocating movement, the distribution is conventionally obtained by means of cam-controlled sliding valves.
This device is noisy, subject to wear and energy-consuming and offers the gases only a limited passage cross-section. To increase the passage cross-section, the lift of the valves has to be increased, thus making it necessary to increase the force of the return springs and consequently reinforce the control members, thereby increasing their inertia and as a result making it necessary to increase the force of the return springs even further Thus a limit is quickly reached beyond which systems with more than two valves per cylinder have to be considered, but this is a costly solution entailing further noise and friction At all events, this known distribution makes it unavoidable to choose for the combustion chamber somewhat flattened shapes which are not ideal and which are governed by the need to give the valves the largest possible diameter and to provide between the valves and piston the clearance necessary for their relative movement when the piston is near its top dead centre.
The documents DE-A-3,327,810, FR-A-1,571,711 and US-A-4,359,981 propose to provide, on the cylinder head and on the piston, faces which come very near each-other and compress the gas situated between them when the piston reaches its top dead centre, in such a manner as to create turbulences in the combustion chamber at the moment of ignition. These turbulences are considered to accelerate the propagation of the combustion, in spite of the more or less favourable forms of the chamber which are set forth hereinabove. According to DE-A-3,327,810, the form of the chamber remains very flat. According to FR-A-1,571,711 and US-A-435,981, the chamber is more compact but its walls define together with at least one of the valves in the opening position constrictions which impair the breathing of the engine. Furthermore, the teaching of the three documents appears to be incompatible with the presence of four valves per cylinder. The teaching of these three documents is therefore, on an overall basis, opposed to a good circulation of the gases in the engine.
Moreover, the presence of this face of the piston which closely approaches a corresponding face of the cylinder head when the piston is at top dead centre has consequential effects on the pressure distribution on the piston. During the ascent of the piston, the pressure is greater on this face of the piston than on the remainder of the piston. During the combustion, the opposite applies, this face is partially sheltered from the commencement of combustion. This leads to tilting torques on the piston.
WO-A-87 01415 also discloses an engine in which the distribution is ensured by means of a bell adjacent to the inner face of the cylinder head and driven in rotation in such a way that a slot of the bell selectively exposes intake and exhaust ports. Disadvantages arising as a result of the reciprocating movement of the valves are therefore eliminated. The breathing of the engine is excellent. However, this known structure also has disadvantages. With it, it is difficult to increase the compression ratio, whilst at the same time still giving the combustion chamber a shape favourable to combustion. On the other hand, the bell has to absorb a considerable shock at the start of each expansion. It has, moreover, been found that the slot provided through this bell had a disadvantage: the bell is not balanced about its axis of rotation and this can lead to vibrations and frictional forces which are very detrimental between the outer surface of the bell and the fixed wall of the cylinder head. WO-87/01415 mentions, in its FIG. 1, an item of prior art permitting the construction of a relatively compact combustion chamber and the limiting of the pressure on the piston and the bell at commencement of expansion, since a face of the bell
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