| 摘要 |
<p>When an on/off operation selectable external indicating means (30) is switched to ON, since a control device (10) changes over a solenoid valve (26) to a position (26), the oil pressure of a pilot pump (3) is caused to act on an operating portion (24c) of a switching valve (24) and a pressing member (7d) of a cut-off valve (7). Oil drained from a head chamber (4A ) of a servo piston (4) for controlling a swash plate angle of a variable displacement hydraulic pump (2) is caused to pass through a throttle portion (25a) of a slow return valve (25) due to changing over of the switching valve (24), the reduction speed of the swash plate angle is delayed, and the absorption horsepower of the hydraulic pump (2) is increased with good response. In addition, since the oil pressure of the pilot pump (3) maintains the cut-off valve (7) at a position (7a) even against the high discharge pressure of the hydraulic pump (2), the cut-off function can be kept halted.</p> |
