Hydraulic fluid circuit for full case hydraulic unit

摘要

An improved hydraulic apparatus is disclosed having a hydraulic device (14) receiving conditioned hydraulic fluid directly from an inlet port (62) in a case (12) full of hydraulic fluid (16) with the conditioned hydraulic fluid having a characteristic which is better than the characteristic of the fluid within the case. The characteristic may be that the hydraulic fluid is cooled to a temperature below the temperature of the hydraulic fluid within the case, is filtered, or is deaerated. Cooled hydraulic fluid is supplied from a heat exchanger (58) in fluid communication between an outlet port of the case and the inlet port of the case to supply the hydraulic fluid contained within the case. The hydraulic fluid is filtered by a filter (54) external to the case. A deaerator (65) may be located in a fluid circuit external to the case between a scavenge pump (50) and the inlet port (67). Hydraulic fluid is pumped by a charge pump (26) to the input port (72) of the hydraulic device. Fluid line (74) connects the inlet port of the case to an input port of a charge pump so that cooled hydraulic fluid flows directly from the inlet port to the input port of the charge pump. The charge pump has a steady state flow rate of pumping hydraulic fluid to the hydraulic device which is less than a steady state rate at which cooled and filtered hydraulic fluid is supplied to the inlet port of the case which causes excess cooled hydraulic fluid to enter the case from the fluid line through interior case port (80).