1. Field of the Invention
This invention relates generally to devices for converting power from one form to another and more specifically to fluid devices for converting fluid power to shaft power and vice versa.
2. Description of the Prior Art
Heretofore, various fluid devices have been developed for converting fluid power into shaft power and vice versa. These prior fluid devices are of two types, fixed displacement and variable displacement. In a conventional fixed displacement fluid device, the power output in terms of torque and speed is a function of the power input in terms of operating pressure and flow rate. The output speed is proportional to the volumetric input. The output torque is dependent upon the pressure input. The ratio between the output speed and output torque is dependent upon the displacement.
In a conventional variable displacement fluid device, the construction permits the working relation of the internal parts to be varied so as to vary displacement. The variation of the working relations, such as changing the angular relation between the swash plate and the cylinder block changes the displacement by varying the piston stroke or the like. Therefore, when displacement is increased to increase the work potential (torque) with input flow and pressure remaining constant, output speed is proportionally reduced and efficiency increased. When displacement is decreased to increase the output speed with input flow and pressure remaining constant, work potential (torque) is proportionally reduced and efficiency is decreased. Since the highest swash plate angle with the longest piston stroke for a given displacement volume will provide maximum mechanical advantage and higher operating efficiency, varying the swash plate angle and the piston stroke will vary the power output in terms of torque and speed at a sacrifice of efficiency except when operating at a maximum swash plate angle.
Pavesi, U.S. Pat. No. 2,844,002; Steward, U.S. Pat. No. 2,997,956; Stein, U.S. Pat. No. 3,450,058; Tulp, U.S. Pat. No. 3,741,076; Abramopaulos, U.S. Pat. No. 3,757,647; and D'Yachkov, Russian Pat. No. 224,312 relate to fluid devices of the same general type as the present invention. None of the above patents disclose or suggest the present invention.