| 摘要 |
1,117,873. Hydrostatic transmission. C. VAN DER LELY N.V. 13 April, 1966 [3 May, 1965], No. 16282/66. Heading F2C. Relates to an infinitely variable hydrostatic transmission, particularly for an agricultural tractor, comprising a rotating barrel swashplate pump 1 in closed circuit with a rotating barrel swashplate motor 2, the pump and/or motor swashplate tilt being variable. In such a transmission, to ensure that at least most of fresh cool oil supplied from a make-up pump 13 to the low-pressure motor-pump return flow path is circulated through the transmission before being drained as excess to a reservoir 15, said return flow path comprises two ducts respectively communicating with said make-up pump and said reservoir. In the transmission shown, the pump 1 is driven by an internal combustion engine or other source of rotating power and the motor 2 drives one or more ground-engaging wheels. The operation of the pump and/or motor can be arranged to reverse the vehicle, hence the highpressure flow and low-pressure return paths are interchangeable and each comprises two ducts 3, 4 and 5, 6 or vice versa. The make-up pump 13 supplies the low pressure, return, one of the ducts 3, 6 through a duet 9 and either one of oneway valves 10, 11 (that to the high-pressure flow duct closing), and excess is drained from the low pressure, return, one of the ducts 4, 5 to the reservoir 15 through a shuttle valve 17 (closing to the high-pressure flow duct), a duct 19 and a one-way valve 20 which, opening at a predetermined pressure, determines maximum pressure in the low-pressure return path. A further one-way valve 22, opening at a predetermined pressure, connects the ducts 9, 19 in the event of a duct blockage or valve failure. A cooling heat exchanger may be included in the make-up pump supply or delivery duct. |
