This invention relates to internal combustion engines, and more particularly, relates to rotary valves for internal combustion engines.
Rotary valves have been proposed for use in internal combustion engines for some time. They have certain inherent mechanical advantages compared to the poppet valves which are conventionally used. Spring biased poppet valves have a reciprocating motion, which because of increased inertia during high speed operations may cause operational problems. Stronger springs may be employed to partially alleviate this problem, but this in turn requires more energy to open the poppet valve. The inertia of a poppet valve may be reduced by making the valve lighter, but the valve must have some minimum size and mass to perform its intended functions. More particularly, the valve must have a certain minimum size in order to provide a sufficient cross-sectional flow area, dissipate heat, and withstand mechanical stresses.
In spite of the obvious advantages of rotary motion, as compared to reciprocating motion, especially at high speeds, poppet valves continue to be used almost exclusively. This is believed to be because the rotary valves that have been designed and proposed in the past have shortcomings that are even more serious than those of existing poppet valves.
A principal problem of earlier rotary valves has been an inability to properly seal them. That is, the rotary valve comprises a rotational member which rotates within an opening in a stationary outer metallic support member. The outer support member has ducts and the inner rotatable member has ports (or openings) for selectively enabling and preventing the flow of intake and exhaust gases through the valve, in accordance with the angular position of the inner rotatable member with respect to the outer support member. It is essential to prevent or minimize the leakage of gas between the stationary and rotatable parts of the valve during the times when the valve is closed and to ensure that all the flow is through the intended channel when the valve is open. In order to accomplish this, and in view of unavoidable manufacturing tolerances between the stationary and rotating parts of metallic valves, special seals have been necessary that are often complex and susceptible to failure. This is in contrast with poppet valves in which a portion of the valve head acts as a seal without appreciable sliding and such special seals are unnecessary.
The seals of a rotary valve are subjected to unfavorable and harsh conditions. The engine temperatures are very high and the pressure within the combustion chamber, especially during the power stroke, is also very high. Thus, when intake and exhaust ports are both closed and the precompressed fuel/air mixture is in the process of rapid combustion the seals must contain this pressure in order to transfer the maximum available energy to the piston. Rotary valve designs of the past often have been complicated and often employed metal-to-metal interfaces as part of their seals, which caused rapid seal failures because of overheating or insufficient lubrication on their surfaces.
An additional problem with conventional internal combustion engines, regardless of the type of valve employed, has been the uneven distribution of fuel in the fuel/air mixture from one point to another in the combustion chamber. A relatively small quantity of fuel is mixed with a much larger quantity of air by a process involving aspiration or injection. This fuel/air mixture is introduced at a specific location and must be uniform throughout the volume of the air if a nominal fuel-to-air ratio is to represent a real ratio as opposed to a statistical average at each point in the combustion chamber. Various designs have been employed in an effort to realize this objective, but the objective remains elusive.
However, rotary valves also provide an open, unobstructed flow path into and out of the combustion chamber, which greatly improves the flow efficiency of fuel vapors and exhaust. In addition, rotary valves also require less energy to operate than poppet valves, increasing the available energy output of the engine.
In spite of the significant potential advantages of a rotary valve internal combustion engine, they have not been widely used commercially. This is largely because rotary valves tend to leak if they are loose enough to permit free rotation and seize if they are tight enough to contain the combustion pressures generated in the combustion chamber.
These and other limitations and disadvantages of the prior art are overcome by the present invention, however, and an improved rotary valve for use in an internal combustion engine that eliminates metal-to-metal contact between an inner rotatable member and an outer support member is provided.