Hydraulic pressure control device

Abstract

A hydraulic pressure control device comprising: a hydraulic sensor provided between a hydraulic pump and a load; a speed command arithmetic unit configured to output a speed command value Vc based on a difference between a hydraulic pressure detection value Pd from the hydraulic sensor and a hydraulic pressure command value Pc; a torque command value arithmetic unit configured to calculate a torque command value Tc based on a difference between a speed detection value Vd of a motor and the speed command value Vc; a current controller configured to control current of the motor based on the torque command value Tc; and a hydraulic pressure abnormality detector configured to detect whether a hydraulic circuit has abnormality based on the speed command value Vc and an operating condition of the load of the hydraulic circuit commanded from an upper-level control device.

Claims

1. A hydraulic pressure control device configured to provide a hydraulic pressure by a motor that rotates a hydraulic pump, the hydraulic pressure control device comprising: a hydraulic pump and a motor; a single hydraulic sensor, wherein the hydraulic sensor is provided between the hydraulic pump and at least one load in a hydraulic circuit; a speed command arithmetic unit configured to output a speed command value based on a difference between a hydraulic pressure detection value from the hydraulic sensor and a hydraulic pressure command value; a torque command value arithmetic unit configured to calculate a torque command value based on a difference between a speed detection value of the motor and the speed command value; a current controller configured to control current of the motor based on the torque command value; and a hydraulic pressure abnormality detector configured to detect whether the hydraulic circuit has abnormality based on the speed command value and an operating condition of the at least one load of the hydraulic circuit commanded from an upper-level control device, wherein the at least one load includes a plurality of loads and the plurality of loads are connected to the hydraulic pump in parallel, between the hydraulic pump and each of the loads, there is provided a respective selector switch configured to switch the loads connected to the hydraulic pump, and the single hydraulic sensor is provided between the hydraulic pump and the respective selector switches, there is no hydraulic sensor between the selector switches and the loads, the hydraulic pressure abnormality detector includes a selector that holds a threshold value which is selected when all of the selector switches are switched OFF and a threshold value which is set for each selector switch, and that outputs one of the threshold values corresponding to ON-OFF states of the selector switches, and the hydraulic pressure abnormality detector determines that an abnormality has occurred when the speed command value exceeds the threshold value which is output from the selector.

2. The hydraulic control device according to claim 1, wherein the hydraulic pressure abnormality detector performs primary delay filter processing on the speed command value.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) Preferred embodiments of the present invention will be described in detail with reference to the following figures, wherein:

(2) FIG. 1 is a block diagram illustrating an embodiment of the present invention;

(3) FIG. 2 is a block diagram illustrating a hydraulic pressure abnormality detector according to the embodiment of the present invention;

(4) FIG. 3 is a block diagram illustrating a hydraulic pressure abnormality detector according to an embodiment of the present invention;

(5) FIG. 4 is a block diagram illustrating a conventional technique; and

(6) FIG. 5 is a block diagram illustrating a hydraulic pressure abnormality detector according to the conventional technique.

DETAILED DESCRIPTION

(7) An embodiment of the present invention will be described. Elements that are similar to those of the conventional example are denoted by similar reference signs and redundant description thereof will be avoided. FIG. 1 illustrates a block diagram of a hydraulic control device of the present invention. A hydraulic pressure abnormality detector 16 detects that the hydraulic pressure is abnormal based on the switching command Ss and the speed command value Vc and reports to the upper-level control device that the hydraulic pressure is abnormal.

(8) FIG. 2 illustrates a block diagram of a specific hydraulic pressure abnormality detector of the present invention. Based on the switching command Ss, a selector 164 selects one of abnormal flow rate thresholds 161, 162, and 163. A comparator 165 compares the speed command value Vc and the selected abnormal flow rate threshold 161, 162, or 163, and reports to the upper-level control device that the hydraulic pressure is abnormal when the speed command value Vc is larger than the abnormal flow rate threshold.

(9) Specifically, the flow rate is substantially identical to the speed command value. In addition, a flow rate required upon actuation of the actuator; that is, the speed command value, can be measured in advance. Therefore, when the actuator 14a is operated in a state where a leakage amount is large due to some abnormality, the motor is operated such that the hydraulic pressure detection value Pd becomes a desired value. Thus, the speed command value becomes large. When a selector switch Sa is operated based on the switching command Ss from the selector 164, a value Aal for an actuator Aa is selected as an abnormal flow rate threshold. When the speed command value exceeds the abnormal flow rate threshold Aal, the comparator 165 reports the abnormality to the upper-level control device. When a selector switch Sb is operated based on the switching command Ss from the selector 164, a value Abl for an actuator Ab is selected as an abnormal flow rate threshold. When the speed command value exceeds the abnormal flow rate threshold Abl, the comparator 165 reports the abnormality to the upper-level control device. In addition, when no selector switch is turned on, the selector 164 selects a value A for a case where no actuator is operated as an abnormal flow rate threshold based on the switching command Ss. Thus, the comparator 165 reports the abnormality to the upper-level control device when the speed command value exceeds the abnormal flow rate threshold A even upon failure of the hydraulic pump or large leakage of the hydraulic circuit. Setting of the abnormal flow rate threshold A to a value, which is slightly larger than the value for a case where no actuator is operated, enables more strict check of the hydraulic circuit condition. In addition, report to the upper-level control device in the state becomes possible, thereby enabling preventive maintenance.

(10) FIG. 3 illustrates another block diagram of a hydraulic pressure abnormality detector of the present invention. Elements that are similar to those of the conventional example are denoted by similar reference signs and redundant description thereof will be avoided. The comparator 165 compares a filter-processed speed command value, which is a speed command value after filter processing by a low pass filter 166, and an abnormal flow rate threshold, and reports the abnormality to the upper-level control device when the speed command value Vc is larger than the abnormal flow rate threshold.

(11) Specifically, a speed detector vibrates at some amplitude due to sudden change of hydraulic pressure upon actuation of the actuators, ripple caused by the hydraulic pump during steady operation, and the like. With this vibration, the speed command value Vc also vibrates, and thus a large value should be set to the abnormal flow rate threshold so as not to detect abnormality with excessive sensitivity. In such a case, an abnormality of the hydraulic circuit can be detected more strictly and precisely by using the filter-processed speed command value as a determination value.