From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Varying valve velocity to increase port-area in an internal combustion engine.
| Identifier | ExFiles\Box 147\4\ scan0174 | |
| Date | 13th August 1940 guessed | |
| to drive the valve with a varying velocity which is greater than the mean velocity during the periods in which the valves are in register, whereby the circum- ferential lengths of the ports are greater, with the same 5 timing of the opening and closing of the fixed port, than if the valve is rotated uniformly at its mean velocity. It will be clear that the greater the varia- tion of velocity provided during the revolution of the valve, the greater will be the increase in port-area 10 obtainable, but practical considerations will usually limit the permissible variations in velocity and this invention, therefore, includes as a feature, the use of a driving gear which gives a comparatively small range of velocity variation, up to, say, 20% above and below the 15 mean velocity. When used with an internal-combustion engine, in which a single port in the valve registers successively with the inlet-port and with the exhaust-port, it may be that the additional length obtainable in this way for the 20 inlet port is achieved at the expense of the exhaust-port- opening, but it is more important to increase the size of the inlet-port, and, moreover, the pressure available to expel the exhaust gases is adequate, whereas that available for taking in the inlet gases is usually small. 25 In any case, it is easy to provide both inlet and exhaust ports which have larger areas than with a poppet-valve. The speed-variation of the valve during each revolution may be obtained by any known or convenient mechanism between the crankshaft and the valve spindle, 30 and one suitable construction for a 4-stroke engine will 3. | ||