| 摘要 |
PURPOSE: A hydrostatic transmission system is provided to reduce the transmission shock when shifting the fourth speed of 'D' range to the third speed or second speed of the '2' range. CONSTITUTION: A 4-3 shift valve is comprises a first port(201) receiving the torque pressure by being connected with a torque pressure passage of a torque control regulator valve(21), a second port(203) connected with a fourth clutch valve(92) and selectively supplying the torque pressure supplied to the first port, a third port(205) receiving the line pressure through a passage connected with an oil pump(3), a fourth port(209) selectively connected with the third port so that the line pressure is supplied to the fourth clutch valve through the second port and the line pressure is connected with a pressure receiving chamber(207) via the fourth clutch valve, a fifth port(213) connected for the torque pressure and the line pressure passages to be selectively serviced so that operating the other pressure receiving chamber, and a sixth port(215) selectively connected with the line pressure serviced to the third port so that supplying a hydraulic pressure to the pressure receiving chamber through the fifth port.
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