HYDRAULIC CIRCUIT OF CONSTRUCTION MACHINE

Abstract

A hydraulic circuit for actuating an electromagnetic proportional pressure reducing valve by a command current outputted from a controller based on an operation amount of a remote control valve, and by a secondary pressure of the pressure reducing valve, actuating a common bleed-off valve which is a hydraulic pilot type spool valve is provided. In the controller, as a correction processing for correcting characteristics of a proportional valve command value which is a current value given to the pressure reducing valve and the opening area of the spool valve, at an inflection point at which the degree of change of a pump pressure increases, an actual proportional valve command value at a time of obtaining the pump pressure is compared to a theoretical proportional valve command value of a case of no tolerance, and a correction to compensate for a difference between the both command values is performed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view schematically illustrating a hydraulic circuit according to an embodiment of the present invention;

FIG. 2 is a view illustrating a relation between proportional valve command values, valve opening areas, and pump pressures in the hydraulic circuit;

FIG. 3 is a view for explaining a method for obtaining an inflection point of a pump pressure in the hydraulic circuit;

FIG. 4 is a flowchart for explaining contents of adjustment and correction processing in the hydraulic circuit;

FIG. 5 is a view illustrating a relation of tolerances of proportional valve secondary pressure with respect to proportional valve command values; and

FIG. 6 is a flowchart for explaining contents of adjustment and correction processing by the hydraulic circuit according to another embodiment of the present invention.

Claims

1. A hydraulic circuit of construction machine comprising: operation means;a controller for outputting a command current based on an operation amount of the operation means;an electromagnetic proportional pressure reducing valve actuated by the command current outputted from the controller; anda hydraulic pilot type spool valve actuated by a secondary pressure of the electromagnetic proportional pressure reducing valve, the spool valve being adapted to change a pump pressure in response to a change in an opening area of the spool valve;wherein as a correction processing for correcting characteristics of a proportional valve command value which is a current value given to the electromagnetic proportional pressure reducing valve and the opening area of the spool valve, the controller is configured to detect a pump pressure which has been set in advance and an actual proportional valve command value at a time of obtaining the pump pressure, compare the actual proportional valve command value to a theoretical proportional valve command value at which the set pump pressure is to be obtained in the case that a tolerance of the secondary pressure with respect to the proportional valve command value does not exist, and then perform a correction to compensate for a difference between the both command values.

2. The hydraulic circuit of construction machine according to claim 1, wherein, with respect to the pump pressure, an inflection point at which a degree of change in the pump pressure largely changes to a change of the proportional valve command value is set, and the controller is configured to perform the correction based on a comparison of proportional valve command values at the inflection point.

3. The hydraulic circuit of construction machine according to claim 2, wherein a plurality of the inflection points is set, and the controller performs the correction based on a comparison of proportional valve command values at the plurality of inflection points.

4. The hydraulic circuit of construction machine according to claim 2, wherein the controller performs the correction based on a comparison of proportional valve command values at the inflection point and a point at which the tolerance of the secondary pressure with respect to the proportional valve command value becomes a minimum value.

5. The hydraulic circuit of construction machine according to claim 2, wherein the controller obtains the inflection point from a differential pressure between steps of the pump pressure which changes stepwise.