Patent ID: 7779628
Filing Date: 2010-08-24
Classification: B60K,F15B,Y02T

Abstract:
1. A hydraulic drive system for storing and releasing hydraulic fluid comprising: a high pressure storage device; a low pressure storage device; a pump-motor operating at a range of pump-motor speeds for converting between hydraulic energy and mechanical energy, said pump-motor disposed between said high pressure storage device and said low pressure storage device; a motoring mode where hydraulic energy released from said high pressure storage device is converted to mechanical energy using said pump-motor; a pumping mode where mechanical energy is converted into hydraulic energy and stored in said high pressure storage device; a neutral state where hydraulic energy is neither stored nor released from said high pressure storage device; and at least two exit states promoting a transition of said pump-motor from one of said motoring mode and said pumping mode to said neutral state, a first exit state resulting from conditions within said hydraulic drive system and a second exit state resulting from a command originating from outside said hydraulic drive system, wherein said first exit state begins at a variable rate and said second exit state begins at a constant rate.