HYDRAULIC DRIVE SYSTEM WITH NEUTRAL DRIFT COMPENSATION AND TEMPERATURE COMPENSATION FOR PRESSURE LIMITS

摘要

A hydraulic drive system (102) for storing and releasing hydraulic fluidincludes a high pressure storage device(138), a low pressure storage device (138), and a pump-motor (130) operatingat a range of pump-motor speeds for convertingbetween hydraulic energy and mechanical energy. The pump-motor is disposedbetween the high pressure device and the low pressuredevice. In normal operation, the hydraulic drive system enters a motoring modewhere hydraulic energy is released from the highpressure storage device and converted to mechanical energy using the pump-motor. It also enters a pumping mode where mechanicalenergy is converted into hydraulic energy. A neutral state exists wherehydraulic energy is neither stored nor released from the highpressure storage device. An approach for compensating for temperature changesusing varying pressure limits helps to maintain thehydraulic drive system in normal operation, thereby promoting efficiencywithin the hydraulic drive system. When the pump-motorincludes a swash-plate (216) or similar structure, compensating for driftduring normal operation helps to promote efficient operationof the hydraulic drive system.