Internal-combustion engines – Valve – Rotary
Patent
1987-09-22
1989-08-01
Wolfe, Willis R.
Internal-combustion engines
Valve
Rotary
123 80BA, 123190E, F01L 710, F01L 716
Patent
active
048525324
DESCRIPTION:
BRIEF SUMMARY
This invention relates to rotary valves for internal combustion engines in which a continuously rotating valve member incorporated in the cylinder-head replaces the conventionally used poppet valves.
Such rotary valves have been developed since the inception of the internal combustion engine. The arguments for their use include the improved smoothness of operation, the more rapid and precise opening and closing of the valve ports and the larger port openings that can be provided.
Most efforts have been made in the past to apply the rotary valve to single cylinder engines of high performance because of its ability to provide the large port openings needed when such engines are operated at very high speeds. In most cases these engines were air cooled. None of these developments has proved successful to a point where the engines went into mass production, primarily because of the difficulties experienced in sealing the valves and preventing rapid deterioration of sealing and journal surfaces due to heating and distortion resulting from the passage of hot exhaust gases through the rotary valve. Attempts to apply the rotary valve to multi-cylinder engines have been even less successful.
The overriding emphasis today is placed upon improved efficiency, control of emissions and on achieving reduced engine weight rather than achieving optimum engine performance for a given displacement volume as is the past. The rotary valve offers advantages in all three areas.
Firstly, the use of a rotary valve dispenses with the exhaust poppet valve (the head of which may reach temperatures as high as 900 degrees Centigrade) and so eliminates the prime cause of pre-ignition of the incoming charge of gas, and reduces the tendency to "knock" in an engine of given compression ratio. By permitting a higher compression ratio, greater efficiency and cooler running may be obtained.
Secondly, the instantaneous start and finish of valve opening characteristic of the rotary valve allows less valve "overlap" to be used, that is, the period of time, or angular rotation of the crankshaft during which the exhaust and intake valves are both open. Thus, with the poppet valve system, the exhaust and inlet valves commence and finish their motion from rest, and hence it is common practice to "overlap" such valves by an angle which may vary from about 40.degree. up to about 90.degree. rotation of the crankshaft in order to improve engine breathing. This matters little if the engine is designed primarily for maximum power output for a given displacement volume, but when such an engine with a large valve "overlap" is operated at low speeds or idle it runs very roughly and, in addition, unburnt gas passes from the inlet to the exhaust ports causing emission of unburnt hydro- carbons. This "overlap" can be virtually eliminated with the rotary valve, yet the large and rapid port openings of the rotary valve more than compensate for any loss of "breathing" attributable to the elimination of "overlap".
Thirdly, a rotary valve engine can be lighter and of less overall height than a poppet valve engine.
The basic problem with the rotary valve is that sealing must be achieved between surfaces when they are in rubbing contact whereas in the poppet valve system the sufaces are at rest when sealing. Two conditions of sealing are of particular importance. Firstly, the sealing of gas during combustion, when the gas reaches a pressure of several hundred P.S.I. at a temperature of about two thousand degrees F., and secondly the prevention of the entry of even minute quantities of oil into the combustion chamber during operation of the engine at low manifold pressure. Proper sealing in these two extreme cases and in the many intermediate cases is possible only if surface contact or near-surface contact is achieved.
Now the rotary valve as generally proposed comprises a cylindrical valve member or rotor journalled for rotation in a bore in the cylinder-head transverse to the piston axis. The rotor is hollow, having a bore extending from each end and terminating at a
REFERENCES:
patent: 3871340 (1975-03-01), Zimmerman
patent: 3892220 (1975-07-01), Franz
patent: 4019487 (1977-04-01), Guenther
patent: 4036184 (1977-07-01), Guenther
patent: 4404934 (1983-09-01), Asaka et al.
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