Hydraulic unit

Abstract

To provide a hydraulic unit that can generate pressure and a flow rate as ordered using a variable capacity type hydraulic pump.SOLUTION: A hydraulic unit 100 includes a hydraulic controller 124 that calculates a command pump capacity q in accordance with discharge pressure P, calculates a pressure control flow rate Qp of achieving a target pressure Pd in accordance with discharge pressure P so as not to exceed a maximum allowable torque of a motor 104 and a maximum pump capacity qmax of a hydraulic pump 102, sets the smallest flow rate in the target flow rate Qd, pressure control flow rate Qp, and maximum flow rate Qmax, as a command flow rate Qr, and calculates a command rotational number N of the motor 104 on the basis of the command flow rate Qr and the command pump capacity q.SELECTED DRAWING: Figure 2

Claims

1. A variable displacement hydraulic pump, an electromagnetic proportional valve for changing the pump displacement qτ of the hydraulic pump, an inverter-driven motor for driving the hydraulic pump, a pressure sensor capable of measuring the discharge pressure P of the hydraulic pump, a hydraulic actuator driven by the hydraulic pump, and a hydraulic controller that outputs commands to the electromagnetic proportional valve and the motor and can input a target pressure Pd and a target flow rate Qd. The hydraulic controller includes a pump displacement calculation unit that calculates a commanded pump displacement q of the hydraulic pump based on the discharge pressure P so as not to exceed the maximum allowable torque τmax of the motor and the maximum pump displacement qmax of the hydraulic pump; a pressure calculation unit that calculates a pressure control flow rate Qp for achieving the target pressure Pd based on the discharge pressure P; a commanded flow rate calculation unit that selects the smallest flow rate among the target flow rate Qd, the pressure control flow rate Qp, and the maximum flow rate Qmax that the hydraulic pump can discharge as the commanded flow rate Qr; and a rotation speed calculation unit that calculates a commanded rotation speed N of the motor based on the commanded flow rate Qr and the commanded pump displacement q. A hydraulic unit, characterized by comprising the above.

2. The hydraulic unit according to claim 1, wherein the rotation speed calculation unit calculates the commanded rotation speed N according to the calculation formula N = Qr / q.

3. The hydraulic unit according to claim 1, wherein the rotation speed calculation unit calculates the commanded rotation speed N to be greater than No = Qr / q and not to exceed the maximum rotation speed Nmax.

4. The hydraulic unit according to claim 3, wherein the rotation speed calculation unit calculates the commanded rotation speed N according to the calculation formula N = min(α · No, Nmax) (where α > 1).

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