METHOD FOR COMPENSATING FOR FLOW RATE OF HYDRAULIC PUMP OF CONSTRUCTION MACHINE

Abstract

A method is provided for compensating for the flow rate of a variable capacity-type hydraulic pump such that, when a manipulation lever is manipulated, a discontinuous section, which has no change in the discharge flow rate of the hydraulic pump, is eliminated.

Claims

1. A method for compensating a discharge flow rate of a hydraulic pump for a construction machine, the construction machine including a hydraulic pump connected to an engine; a hydraulic actuator that drives the working device by operating hydraulic fluid; a control valve installed in a flow path of the hydraulic pump; an operation lever outputting a signal pressure corresponding to an operation amount; means for detecting the operation amount of the operation lever; means for detecting an engine rpm; and a controller for controlling the control valve in response to the signal pressure corresponding to the operation amount and a detected signal corresponding to an engine rpm, the method comprising; detecting the signal pressure corresponding to the operation amount of the operation lever, and the engine rpm; determining a required discharge volume corresponding to the operation amount of the operation lever and a compensation ratio, and determining a required discharge volume that compensates for the engine rpm, and controlling a discharge flow rate of the hydraulic pump, wherein the controlling step includes controlling the hydraulic pump so that the discharge flow rate is derived from a sum of a required volume corresponding to the operation amount of the operation lever and a calculated volume that is obtained by multiplying a percentile compensation ratio by a difference value between the required volume corresponding to the operation amount of the operation lever and the required volume that compensates for the engine rpm.

2. The method of claim 1, wherein, the compensation ratio ranges from 100% when a spool of the control valve begins to shift by operation of the operation lever to 0% when the discharge flow rate is controlled corresponding to the operation amount, and is controlled so that the ratio value is inversely proportional to a pilot pressure and thus decreasing with the pilot pressure applied by the operation lever.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] FIG. 1(a, b) are the graphs showing a pump volume and a discharge flew rate of a hydraulic pump in response to an operation amount of the operation lever according to the conventional technology.

[0023] FIG. 1(c, d) are the graphs showing a pump volume and a discharge flow rate in response to the operation amount of the operation lever according to another conventional technology

[0024] FIG. 2 is the flow chart demonstrating a method of compensating the discharge flow rate of the hydraulic pump according to the conventional technology.

[0025] FIG. 3(a, b) are the graphs showing a pump volume and a discharge flow rate of a hydraulic pump in response to an operation amount of the operation lever according to the embodiment of the present invention.

[0026] FIG. 4 is the graph showing the functional relation between a volume compensation ratio and a pilot pressure by the operation of the operation lever in a method for compensating a discharge flow rate of a hydraulic pump according to the embodiment of the present invention.

[0027] FIG. 5 is the flow chart showing the method for compensating the discharge flow rate of the hydraulic pump according to the embodiment of the present invention.

[0028] FIG. 6 is the hydraulic circuit used for the method of compensating the discharge flow rate of the hydraulic pump according to the embodiment of the present invention.

EXPLANATION OF REFERENCE NUMERALS FOR MAIN PARTS IN THE DRAWING

[0029] 10; engine
20; variable displacement hydraulic pump
30; hydraulic actuator
40; control valve (MCV)
50; operation lever (RCV)
60; means for detecting the operation amount of the operation lever
70; means for detecting engine RPM
80; controller
90; regulator

DETAILED DESCRIPTION

[0030] Hereinafter, a method for compensating a discharge flow rate of a hydraulic pump for construction equipment according to a preferred embodiment, of the present invention will be described in detail with reference to the accompanying drawings.

[0031] FIG. 3(a, b) are the graphs showing a pump volume and a discharge flow rate in response to an operation amount of the operation lever according to the embodiment of the present invention. FIG. 4 is the graph showing the functional relation between a volume compensation ratio and a pilot pressure by the operation of the operation lever in the method for compensating the discharge flow rate of the hydraulic pump according to the embodiment of the present invention, FIG. 5 is the flow chart showing the method for compensating the discharge flow rate of the hydraulic pump according to the embodiment of the present invention. FIG. 6 is the hydraulic circuit used for the method of compensating the discharge flow rate of the hydraulic pump according to the embodiment of the present invention.

[0032] Referring to FIG. 3(a, b) to FIG. 6, the method for compensating the discharge flow rate of the hydraulic pump for construction machine according to an embodiment of the present invention is applied for the construction machine comprising;

[0033] a variable displacement hydraulic pump (20) connected to the engine (10); a hydraulic actuator (30) that drives the working device by operating the hydraulic fluid; a control valve (MCV) (40) installed in the path of the hydraulic pump (20); an operation lever (RCV) (50) outputting the signal pressure corresponding to the operation amount; a means (60) for detecting the operation amount of the operation lever (50); a means (70) for detecting the engine rpm; and a controller (80) for controlling: the control valve (40) in response to the signal pressure corresponding to the operation amount and the detected signal corresponding to the engine rpm, which are generally used in the technical field of the present invention. Therefore, the detailed explanations of those elements will be omitted.

[0034] The method for compensating the flow rate of the hydraulic pump of the construction equipment according; to an embodiment of the present invention comprises;

[0035] a step of detecting the signal pressure corresponding to the operation amount of the operation lever (50), and the engine rpm (S100);

[0036] a step of determining a required discharge volume (q1 ) corresponding to the operation amount of the operation lever (50) and a compensation ratio (r1), and determining a required discharge volume (q2) that is compensated for the engine rpm (5200); and,

[0037] a step of inputting the control signal to the regulator (90) in order to control the hydraulic pump (20) so that the discharge flow rate is derived from the sum (=q1+(q2−q1)×r1/100) of the required volume (41) corresponding to the operation amount of the operation lever and the calculated discharge volume ((q2−q1)×r1/100) that is obtained by multiplying a percentile of the compensation ratio (r1) by the difference value (q2−q1) between the required volume (q1) corresponding to the operation amount of the operation lever and the required volume (q2) that is compensated for the engine rpm (S300).

[0038] The compensation ratio ranges from 100% (Pa) when the spool of the control valve (40) begins to shift by the operation of the operation lever (50) to 0% (Pb) when the discharge flow rate is controlled corresponding to the operation amount, and can be controlled so that the ratio value is inversely proportional to the pilot pressure and thus decreasing with the pilot pressure.

[0039] According to the aforementioned method, in a step of S100, the operation signal (Pi) corresponding to the operation amount of the operation lever (50) is detected by the means (60) for detecting the operation amount of the operation lever, and the signal for the engine rpm is detected by the means (70) for detecting the engine rpm. The signals detected by the means (60) for detecting the operation a Count of the operation lever and the means (70) for detecting engine rpm are inputted to the controller (80).

[0040] As in S200, the controller (80) determines the required discharge volume (q1) corresponding to the operation amount of the operation lever (50), the compensation ratio (r1), and the required discharge volume (q2) that is compensated for the engine rpm.

[0041] As shown in FIG. 3(a), the compensation ratio (r1) of the hydraulic pump (20) is determined in the range from 100% (Pa) when the spool of the control valve (40) begins to shift by the operation of the operation lever (50) to 0% (Pb) when the discharge flow rate is controlled corresponding to the operation amount of the operation lever (50).

[0042] As shown in FIG. 4, the compensation ratio (r1) is controlled so that the ratio value is inversely proportional to the pilot pressure and thus decreasing with the pilot pressure applied by the operation lever (50).

[0043] As in 300, the control signal is inputted to the regulator (90) in order to control the hydraulic pump (20) so that the discharge flow rate is derived from the sum (=q1+(q2−q1)×r1/100) of the required discharge volume (q1) corresponding to the operation amount of the operation lever and the calculated volume ((q2−q1)×r1/100) that is obtained by multiplying the percentile compensation ratio (r1) by the difference value (q2−q1) between the required discharge volume (q1) corresponding to the operation amount of the operation lever and the required discharge volume (q2) that is compensated for the engine rpm.

[0044] Accordingly, as shown in FIG. 3(b), the discharge flow rate (hydraulic pump volume×engine rpm) of the hydraulic pump is controlled by the graph (a) which shows (q1×s1) of the required discharge volume (q1) corresponding to the operation amount of the operation lever (50) multiplied by the arbitrary higher engine rpm (s1), and the graph (h which shows (q2×s2) of the required discharge volume (q2) compensated for the engine rpm multiplied by the arbitrary lower engine rpm (s2).

[0045] As a result, as shown in the graph (b) of FIG. 3(b), the spool of the control valve (40) gradually begins to shift from the point (Pa) where the pilot pressure (Pa) corresponding to the operation amount of the operation lever (50) is inputted to the control valve (40). Thus, it can prevent the working device from being operated abruptly when the working device is operated by the operation lever (50).

[0046] Although the present invention has been described with reference to the preferred embodiment in the attached figures, it is to be understood that various equivalent modifications and variations of the embodiments can be made by a person having an ordinary skill in the art without departing from the spirit and scope of the present invention as recited in the claims.

[0047] According to the present invention having the above-described configuration, since the discharge flow rate of the hydraulic pump can be controlled so as not to increase abruptly by eliminating the flat range of flow rate when the working device such as the boom of the excavator is operated by the operation lever, it brings the effect of improving the operability.