| 摘要 |
PROBLEM TO BE SOLVED: To promptly carries out change-over in a gear shifter interposed in a transmission system to a hydraulic pump without evolving discontinuous portions in characteristics before and after the change-over in the gear shifter. SOLUTION: A gear shifter 5 capable of two-speed change-over, high and low, is interposed in the middle of a transmission system run from an engine E to a hydraulic pump 4. A lead pressure oil passage 16 branched at the middle of the discharge oil passage 15 of the hydraulic pump 4 is connected to the change-over clutch 6 of the gear shifter 5. A pressure sensitive valve V2 is interposed in the middle of the lead pressure oil passage 16. The pressure sensitive valve V2 is communicated with the discharge oil passage 15 through a pilot oil passage 20. Elevated internal pressure in the discharge oil passage 15 by steering operation opens the pressure sensitive valve V2. Stored pressure in an accumulator A in the middle of the lead pressure oil passage 16 is introduced in the change-over clutch 6 to change-over the gear shifter 5 to the high- speed side, resulting in high-speed driving. |
