| 摘要 |
<p>PURPOSE:To change discharging pressure of a variable capacity oil pressure pump into two steps by means of a normal relief valve by outputting respective corresponding driving signals to a discharge amount control means when instruction signals equivalent to first and second restrict values are outputted from a flow amount instruction means. CONSTITUTION:When a first restrict value is selected by a flow amount instruction means 16, a driving signal is equivalent thereto is outputted to a discharging amount control means 12, and the displacement volume of a hydraulic pump 2 is controlled so as to discharge oil of the minimum flow amount from an oil pressure pump 2. When a second restrict value is selected by the flow amount instruction means 16, oil flow of the minimum amount larger than that of the first restrict value is discharged. In override characteristic of a normal relief valve 15, its discharge pressure becomes larger, as the flow amount of oil discharged from the oil pressure pump 2 is increased. Therefore, the second pressure is larger than the first pressure. Override characteristic of the relief valve 15 is utilized by selecting the first and second restrict values by the flow amount instruction means 16 so as to switch discharging pressure of the oil pressure pump 2 into two steps.</p> |
