HYDRAULIC CONTROL APPARATUS OF WORKING MACHINE

Abstract

With respect to a method of controlling a pump flow rate of a hydraulic pump, a method having a small flow rate command value is selected between a pressure feedback control for controlling the pump flow rate based on a set pressure (a cutoff pressure) and a pump pressure, and, an ordinary control for controlling the pump flow rate based on operation information, and in a case that the pressure feedback control is selected, a flow rate increasing control for increasing the flow rate command value after the case with the passage of time is performed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a hydraulic circuit of working machine according to an embodiment of the present invention;

FIG. 2 is a view illustrating a structure of a controller;

FIG. 3 is a view for explaining a pressure feedback control;

FIG. 4 is a view illustrating a relation between a pilot pressure and a flow rate command value in a positive control;

FIG. 5 is a view illustrating a relation between a pump pressure and a flow rate command value in a PQ control;

FIG. 6 is a view illustrating responses of a pressure and a flow rate according to both of the positive control and the pressure feedback control;

FIG. 7 is a flowchart for explaining an operation according to the embodiment;

FIG. 8 is a view illustrating a state that a control gain is reduced with the passage of time according to the embodiment;

FIG. 9 is a view illustrating a state that a set pressure value is increased with the passage of time according to the embodiment;

FIG. 10 is a view illustrating responses of pressures and flow rates by a flow rate increasing control according to the embodiment; and

FIG. 11 is a view for explaining a mode switching operation according to the embodiment.

Claims

1. A hydraulic control apparatus of working machine having a hydraulic circuit, the circuit comprising: a hydraulic pump;a hydraulic actuator driven by the hydraulic pump as a driving source;a control valve for controlling supply and discharge of oil with respect to the hydraulic actuator;a relief valve for setting a maximum pressure of the hydraulic circuit; andcontrol means,wherein the control means is adapted to,(i) with respect to a method of controlling a pump flow rate of the hydraulic pump, select a method having a small flow rate command value between a pressure feedback control for controlling the pump flow rate based on a set pressure as a cutoff pressure and a pump pressure, and, an ordinary control for controlling the pump flow rate based on operation information, and(ii) in a case that the pressure feedback control is selected, perform a flow rate increasing control for increasing the flow rate command value after the case with the passage of time.

2. The hydraulic control apparatus of working machine according to claim 1, wherein the control means, in the case that the pressure feedback control is selected, as a flow rate increasing control, is adapted to reduce a control gain with the passage of time.

3. The hydraulic control apparatus of working machine according to claim 1, wherein the control means, in the case that the pressure feedback control is selected, as a flow rate increasing control, is adapted to increase the set pressure with the passage of time.

4. The hydraulic control apparatus of working machine according to claim 1, wherein the control means, after the pressure feedback control is selected, in the case that the flow rate command value of the ordinary control is selected as the small value, is adapted to reset the flow rate increasing control.

5. The hydraulic control apparatus of working machine according to claim 1, wherein the control means is adapted to select on or off of the flow rate increasing control in the pressure feedback control.

6. The hydraulic control apparatus of working machine according to claim 1, the control means further comprising: mode switching means,wherein with the mode switching means, a control mode is adapted to be selected among an energy-saving mode for performing a selection of a small value of a flow rate command value between the pressure feedback control not having the flow rate increasing control and the ordinary control, an energy-saving high mode for performing the selection of the small value of the flow rate command value between the pressure feedback control having the flow rate increasing control and the ordinary control, and, a high-power mode for turning off the pressure feedback control and performing only the ordinary control.