| 摘要 |
PURPOSE:To obtain the simple device and reduce the power loss of a hydraulic pump by selectively outputting the higher cylinder oil pressure among the primary and secondary cylinder oil pressures by a selecting valve and allowing the first pressure adjusting valve to perform the pressure adjusting operation by the cylinder oil pressure and to output the first line oil pressure higher by a prescribed pressure. CONSTITUTION:The higher cylinder oil pressure among the primary and secondary hydraulic cylinders 26 and 28 is selectively outputted by a selecting valve 90. The first line hydraulic pressure higher by a prescribed pressure than the cylinder oil pressure is outputted by allowing the first pressure adjusting valve 48 to operate the cylinder oil pressure outputted from the selecting valve 90 and perform pressure adjusting operation. Therefore, the need of a microcomputer and electromagnetic pressure adjusting valve for pressure-adjusting the first line pressure is avoided, and the device is made simple. Further, since the first line hydraulic pressure is adjusted on the basis of the actual cylinder oil pressure, setting of the first line hydraulic pressure higher than the hydraulic pressure estimated from the propulsion force characteristic is eliminated, and the power loss of a hydraulic pump 42 can be reduced.
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