The present invention relates to a construction machine such as a hydraulic excavator.
In a construction machine (e.g. a hydraulic excavator), a hydraulic fluid delivered from a hydraulic pump is caused to flow into one of oil chambers of a hydraulic actuator (meter-in), the hydraulic fluid is caused to be discharged from the other oil chamber of the hydraulic actuator to a tank (meter-out), and thereby the hydraulic actuator is operated. The flow rate of the hydraulic fluid to flow into the one of the oil chambers of the hydraulic actuator (meter-in flow rate) is adjusted by a meter-in valve, for example, and the flow rate of the hydraulic fluid to be discharged from the other oil chamber of the hydraulic actuator to the tank (meter-out flow rate) is adjusted by a meter-out valve, for example. The valve bodies of these valves are moved according to lever operation by an operator or target velocities of the hydraulic actuator calculated at a controller. Typically, the rates of flows passing through the valves are determined by the opening areas of the valves (the movement amounts of the valve bodies), and the differential pressures across the valves. Among them, the differential pressures across the valves vary depending on the magnitude of a load acting on the hydraulic actuator. Accordingly, the opening areas of the valves are adjusted by the operator by means of lever operation and by the controller by means of a control signal for the meter-in valve, and the flow rate of the hydraulic fluid to be supplied to and discharged from the hydraulic actuator, that is, the operation velocity of the hydraulic actuator, is controlled.
In addition, in a case where the hydraulic fluid is supplied from the one hydraulic pump to a plurality of hydraulic actuators also, the meter-in flow rate of each hydraulic actuator is determined by the opening area of each meter-in valve and the differential pressure across the meter-in valve. In a case where the magnitudes of loads acting on the plurality of hydraulic actuators are different from each other, the hydraulic fluid is easily flown to a hydraulic actuator receiving a lower load, and thus the simultaneous supplying of the hydraulic fluid (generating branch flows of the hydraulic fluid) to the plurality of hydraulic actuators requires adjustment of the opening areas of the meter-in valves according to the differential pressures across the meter-in valves.
For example, the technique of Patent Document 1 is configure such that there are provided a stroke sensor (valve position sensor) that senses the stroke of a control valve and pressure sensors that sense the pressures before and after the control valve, and on the basis of signals from these sensors and a signal from a main controller, a valve controller electrically controls the opening of the control valve.
Patent Document 1: JP-1994-117408-A
However, there is a fear about a hydraulic circuit of a construction machine described in Patent Document 1 that the operation velocity of each hydraulic actuator cannot be controlled accurately depending on load conditions of a plurality of hydraulic actuators. This is because hydrodynamic forces that act on control valves, errors of valve position sensors and errors of pressure sensors are not taken into consideration.
For example, in a case where loads that act on respective of the plurality of hydraulic actuators significantly differ, a differential pressure across a meter-in valve corresponding to a hydraulic actuator receiving a lower load (a pressure difference between the delivery pressure of a hydraulic pump and the load pressure on the hydraulic actuator) increases. Typically, as the differential pressure across a meter-in valve increases, the opening area required for obtaining a desired meter-in flow rate decreases, and the flow rate (the flow rate per unit opening area) increases by a corresponding amount. As a result, a hydrodynamic force that acts on the valve body increases, and errors of the opening area of the meter-in valve easily occur. In addition, since a change amount of the meter-in flow rate in relation to a change amount of the opening area of the meter-in valve increases, flow rate errors increase in relation to the errors of the opening area of the meter-in valve. That is, as the differential pressure across the meter-in valve increases, flow rate errors caused by a hydrodynamic force, and by errors of the valve position sensor increase.
On the other hand, in a case where loads that act on the plurality of hydraulic actuators are very close to each other, the meter-in pressures of the hydraulic actuators become almost equal to supply pressures. Accordingly, errors of the pressure sensors relatively increase in relation to the differential pressures across the meter-in valves, and it becomes difficult to compute desired target opening areas from measurement values of the differential pressures across the meter-in valves. That is, as the differential pressures across the meter-in valves decrease, flow rate errors caused by errors of the pressure sensors increase.
The present invention has been made in view of the problems described above, and an object of the present invention is to provide a construction machine that can control branch flows from a hydraulic pump to a plurality of hydraulic actuators highly precisely without being affected by load conditions.
In order to achieve the object described above, the present invention provides a construction machine including: a tank; a hydraulic pump; a first hydraulic actuator and a second hydraulic actuator each having two supply and discharge ports; a first meter-in valve provided on a hydraulic line connecting one of the supply and discharge ports of the first hydraulic actuator to the hydraulic pump; a second meter-in valve provided on a hydraulic line that establishes communication between one of the supply and discharge ports of the second hydraulic actuator and the hydraulic pump; a first meter-out valve provided on a hydraulic line that establishes communication between the other one of the supply and discharge ports of the first hydraulic actuator and the tank; a second meter-out valve provided on a hydraulic line that establishes communication between the other one of the supply and discharge ports of the second hydraulic actuator and the tank; a first pressure sensor that senses a first meter-in pressure that is a pressure on the one of the supply and discharge ports of the first hydraulic actuator; a second pressure sensor that senses a second meter-in pressure that is a pressure on the one of the supply and discharge ports of the second hydraulic actuator; a third pressure sensor that senses a supply pressure that is a delivery pressure of the hydraulic pump; and a controller having a meter-in valve control section configured to calculate a target opening area of the first meter-in valve according to a pressure difference between the supply pressure and the first meter-in pressure, and calculate a target opening area of the second meter-in valve according to a pressure difference between the supply pressure and the second meter-in pressure. The controller has a meter-out valve control section configured to calculate a target opening area of the second meter-out valve according to the pressure difference between the supply pressure and the second meter-in pressure, or calculate a target opening area of the first meter-out valve according to the pressure difference between the supply pressure and the first meter-in pressure.
According to the thus-configured present invention, by controlling the second meter-out valve according to the pressure difference between the supply pressure and the second meter-in pressure or by controlling the first meter-out valve according to the pressure difference between the supply pressure and the first meter-in pressure, the differential pressure across the first meter-in valve or the second meter-in valve that supplies the hydraulic fluid to one of that first hydraulic actuator and the second hydraulic actuator that is receiving a lower load lowers. Thereby, without being affected by load conditions of the first and second actuators, the opening areas of the first meter-in valve and the second meter-in valve increase, and change amounts of the meter-in flow rates in relation to change amounts of the opening areas decrease. Accordingly, meter-in flow-rate errors caused by a hydrodynamic force that acts on the valve body of the first meter-in valve or the second meter-in valve, or by errors of the opening area of the first meter-in valve or the second meter-in valve are reduced.
According to the present invention, it becomes possible, in a construction machine, to control branch flows from a hydraulic pump to a plurality of hydraulic actuators highly precisely without being affected by load conditions.
Hereinafter, a hydraulic excavator is explained as an example of a construction machine according to embodiments of the present invention with reference to the drawings. Note that equivalent members are given the same reference characters in the drawings, and overlapping explanations are omitted as appropriate.
A first embodiment of the present invention is explained with reference to
In
The base end of the boom 11 of the front device 15 is vertically pivotably supported at a front section of the upper swing structure 10. One end of the arm 12 is vertically pivotably supported at the tip of the boom 11. The bucket 8 is vertically pivotably supported at the other end of the arm 12 via a bucket link 8a.
The boom 11, the arm 12, the bucket 8, the upper swing structure 10 and the lower track structure 9 are driven by a boom cylinder 5, an arm cylinder 6, a bucket cylinder 7, a swing hydraulic motor 4 and left and right travel hydraulic motors 3b (only the left travel hydraulic motor is illustrated), respectively, which are hydraulic actuators.
A cab 16 in which an operator gets is provided with: a right operation lever device 1c and a left operation lever device 1d for outputting operation signals for operating the hydraulic actuators 5 to 7 of the front device 15, and the swing hydraulic motor 4 of the upper swing structure 10; and a travel right operation lever device 1a and a travel left operation lever device 1b that output operation signals for operating the left and right travel hydraulic motors 3b of the lower track structure 9.
The left and right operation lever devices 1c and 1d are electric operation lever devices that output electric signals as the operation signals. The left and right operation lever devices 1c and 1d each have an operation lever that is operated to incline forward and backward, and leftward and rightward by the operator, and an electric signal generating section that generates an electric signal according to the inclination direction and inclination amount (lever operation amount) of the operation lever. The electric signals output from the operation lever devices 1c and 1d are input to a controller 100 (illustrated in
Operation control of the boom cylinder 5, the arm cylinder 6, the bucket cylinder 7, the swing hydraulic motor 4 and the left and right travel hydraulic motors 3b is performed by controlling, with a control valve 20, the direction and flow rate of a hydraulic operating fluid supplied from a hydraulic pump device 2 driven by a prime mover such as an engine or an electric motor (an engine 14 in the present embodiment) to the hydraulic actuators 3b and 4 to 7.
The control valve 20 is driven by a control signal output from the controller 100 (illustrated in
In
The hydraulic pump device 2 includes a hydraulic pump 2a and a regulator 2b. The regulator 2b is driven by the controller 100 and adjusts the delivery flow rate of the hydraulic pump 2a. The delivery port of the hydraulic pump 2a is connected to the control valve 20 via a supply hydraulic line 21.
The bleed-off section 20a, the boom section 20b and the arm section 20c of the control valve 20 are supplied with the hydraulic fluid from the hydraulic pump 2a via the supply hydraulic line 21. In the bleed-off section 20a, a branch hydraulic line 22 branches off from the supply hydraulic line 21, and the branch hydraulic line 22 is connected to a tank 29 via a bleed-off valve 25. The bleed-off valve 25 is driven by the controller 100, and bleeds off the hydraulic fluid from the hydraulic pump 2a by establishing communication between the supply hydraulic line 21 and the tank 29.
In the boom section 20b, the supply hydraulic line 21 is connected to an actuator hydraulic line 54a (54b) via a boom meter-in valve 53a (53b). The actuator hydraulic line 54a (54b) is connected to a bottom-side oil chamber 5a (rod-side oil chamber 5b) of the boom cylinder 5. In addition, the actuator hydraulic line 54a (54b) is connected to the tank 29 via a boom meter-out valve 55a (55b). The controller 100 can supply the hydraulic fluid from the hydraulic pump 2a to the bottom-side oil chamber 5a (rod-side oil chamber 5b) of the boom cylinder 5 by driving and opening the boom meter-in valve 53a (53b). In addition, the controller 100 can discharge the hydraulic fluid in the bottom-side oil chamber 5a (rod-side oil chamber 5b) of the boom cylinder 5 to the tank 29 by driving and opening the boom meter-out valve 55a (55b). Note that since the arm section 20c has the same configuration as the boom section 20b, an explanation thereof is omitted.
The controller 100 receives inputs of: a boom operation signal and an arm operation signal from the right operation lever device 1c and the left operation lever device 1d; a supply pressure signal from a supply-pressure sensor 28 installed on the supply hydraulic line 21; a boom pressure signal from a boom pressure sensor 58a installed on the actuator hydraulic line 54a; an arm pressure signal from an arm pressure sensor 68a installed on an actuator hydraulic line 64a; a boom meter-in valve position signal from a boom meter-in valve position sensor 59a installed on the boom meter-in valve 53a; and an arm meter-in valve position signal from an arm meter-in valve position sensor 69a installed on an arm meter-in valve 63a. On the basis of these inputs, the controller 100 drives the regulator 2b, the bleed-off valve 25, the boom meter-in valves 53a and 53b, the boom meter-out valves 55a and 55b, arm meter-in valves 63a and 63b, and arm meter-out valves 65a and 65b.
Although the pressure sensors 58a and 68a are provided only on the actuator hydraulic lines 54a and 64a in the configuration in the present embodiment for simplification of explanation here, pressure sensors may be provided also on the actuator hydraulic lines 54b and 64b. In addition, valve position sensors may be provided on all of the bleed-off valve 25, the boom meter-in valves 53a and 53b, the boom meter-out valves 55a and 55b, the arm meter-in valves 63a and 63b and the arm meter-out valves 65a and 65b.
In
The converting sections 161 to 165 convert signals from sensors into physical values, and output the physical values. For example, from a boom pressure signal, an arm pressure signal and a supply pressure signal which are voltage values, and by using a pressure conversion map, the converting sections 161, 162 and 163 calculate and output a boom meter-in pressure, an arm meter-in pressure and a supply pressure which are pressure values. From a boom meter-in valve position signal and an arm meter-in valve position signal which are duty ratios, and by using a stroke conversion map, the converting sections 164 and 165 calculate and output a boom meter-in valve position and an arm meter-in valve position which are stroke values.
On the basis of the boom operation signal and the arm operation signal from the right operation lever device 1c and the left operation lever device 1d, the target-flow-rate calculating section 110 calculates a boom target flow rate and an arm target flow rate, and transmits the boom target flow rate and the arm target flow rate to the pump control section 120, the meter-in valve control section 130 and the meter-out valve control section 140. For example, as the backward inclination of the right operation lever device 1c relative to the machine body increases, the boom target flow rate is increased toward the positive side; as the forward inclination of the right operation lever device 1c relative to the machine body increases, the boom target flow rate is increased toward the negative side; as the rightward inclination of the left operation lever device 1d relative to the machine body increases, the arm target flow rate is increased toward the positive side; and as the leftward inclination of the left operation lever device 1d relative to the machine body increases, the arm target flow rate is increased toward the negative side.
On the basis of the boom target flow rate and the arm target flow rate, the pump control section 120 calculates a regulator control signal and a bleed-off valve control signal, and outputs the regulator control signal and the bleed-off valve control signal to the regulator 2b and the bleed-off valve 25, respectively. For example, the regulator control signal is calculated such that the hydraulic fluid is supplied from the hydraulic pump 2a in an amount equal to the total value of the absolute value of the boom target flow rate and the absolute value of the arm target flow rate, and the bleed-off valve control signal is calculated such that the bleed-off valve 25 is closed according to the regulator control signal.
On the basis of the boom target flow rate, the arm target flow rate, the boom meter-in pressure, the arm meter-in pressure and the supply pressure, the meter-in valve control section 130 calculates a boom meter-in valve target opening area and an arm meter-in valve target opening area, and outputs the boom meter-in valve target opening area and the arm meter-in valve target opening area to the valve-position control section 150. These calculations are the same as calculation methods described in Patent Document 1, for example.
On the basis of the boom target flow rate, the arm target flow rate, the boom meter-in pressure, the arm meter-in pressure and the supply pressure, the meter-out valve control section 140 calculates a boom meter-out valve target opening area and an arm meter-out valve target opening area, and outputs the boom meter-out valve target opening area and the arm meter-out valve target opening area to the valve-position control section 150. Details of the calculations performed at the meter-out valve control section 140 are mentioned below.
On the basis of the boom meter-in valve target opening area, the arm meter-in valve target opening area, the boom meter-out valve target opening area, the arm meter-out valve target opening area, the boom meter-in valve position and the arm meter-in valve position, the valve-position control section 150 calculates a boom meter-in valve control signal, an arm meter-in valve control signal, a boom meter-out valve control signal and an arm meter-out valve control signal, and outputs the boom meter-in valve control signal, the arm meter-in valve control signal, the boom meter-out valve control signal and the arm meter-out valve control signal to the boom meter-in valve 53a, the arm meter-in valve 63a, the boom meter-out valve 55b and the arm meter-out valve 65b, respectively. For example, the control signals are calculated by using a map indicating the opening area characteristics of the valves such that the valves are at valve positions according to the target opening areas. In addition, the control signals may be corrected by known feedback control according to deviations between the valve positions according to the target opening areas and valve positions acquired at the valve position sensors 59a and 69a.
In
The subtracting section 145 subtracts the boom meter-in pressure from the supply pressure to calculate the differential pressure across the meter-in valve 53a (53b), and outputs the differential pressure to the differential-pressure-reducing-opening calculating section 143.
On the basis of the boom target flow rate, the reference-discharge-opening calculating section 141 calculates a reference discharge opening area, and outputs the reference discharge opening area to the target opening selecting section 144. For example, the reference discharge opening area is calculated such that it increases as the boom target flow rate increases. For the purpose of suppressing the pressure loss that occurs due to the rate of a meter-out flow discharged from the boom, the reference discharge opening area is desirably calculated such that the opening area of the boom meter-out valve increases according to the boom target flow rate.
On the basis of the boom meter-in pressure, the overrun-preventing-opening calculating section 142 calculates an overrun-preventing opening area, and outputs the overrun-preventing opening area to the target opening selecting section 144. For example, the overrun-preventing opening area is calculated such that it decreases as the value obtained by subtracting the boom meter-in pressure from a predetermined value (e.g. 5 MPa) increases. Typically, in a case where an overrun of a hydraulic actuator occurs (the hydraulic actuator is driven by free fall or by an external force, for example), the meter-in pressure becomes approximately zero. Accordingly, in the present embodiment, for the purpose of preventing an overrun of the boom 11, the overrun-preventing opening area is desirably calculated according to the boom meter-in pressure such that the boom meter-in pressure is maintained at a value sufficiently larger than zero.
On the basis of the meter-in differential pressure, the differential-pressure-reducing-opening calculating section 143 calculates a differential-pressure-reducing opening area, and outputs the differential-pressure-reducing opening area to the target opening selecting section 144. For example, the differential-pressure-reducing-opening map illustrated in
The target opening selecting section 144 selects one of the reference discharge opening area, the overrun-preventing opening area and the differential-pressure-reducing opening area, and outputs the selected one as a boom meter-out target opening area to the valve-position control section 150.
If the meter-in pressure is equal to or higher than a threshold PL (e.g. 5 MPa) at Step S1401, the process proceeds to Step S1402, and otherwise the process proceeds to Step S1420.
At Step S1420, an overrun-preventing opening area is selected as the boom meter-out target opening area, and output to the valve-position control section 150.
If the meter-in differential pressure is equal to or lower than a threshold PH (e.g. 10 MPa) at Step S1402, the process proceeds to Step S1410, and otherwise the process proceeds to Step S1430. Here, in a case where only the boom cylinder 5 is driven, the boom meter-in valve 53a (53b) is fully opened, and the rate of a flow supplied to the boom cylinder 5 is adjusted by the delivery flow rate of the hydraulic pump 2a. Accordingly, the load pressure on the boom cylinder 5 and the delivery pressure of the hydraulic pump 2a become almost equal, and the differential pressure across the boom meter-in valve 53a (53b) does not become equal to or higher than the threshold PH. The differential pressure across the boom meter-in valve 53a (53b) becomes equal to or higher than the threshold PH when the delivery pressure of the hydraulic pump 2a becomes higher than the boom meter-in pressure along with an increase of the arm meter-in pressure that occurs when the boom cylinder 5 and the arm cylinder 6 are simultaneously driven.
At Step S1430, a differential-pressure-reducing opening area is selected as the boom meter-out target opening area, and output to the valve-position control section 150.
At Step S1410, a reference discharge opening area is selected as the boom meter-out target opening area, and output to the valve-position control section 150.
As mentioned above, in a case where the boom meter-in pressure is low, since the overrun-preventing opening area is selected as the boom meter-out target opening area, an overrun of the boom 11 can be prevented. In addition, even in a case where the boom meter-in pressure is high, the differential-pressure-reducing opening area is selected as the boom meter-out target opening area when the meter-in pressure difference is large. Accordingly, meter-in flow-rate errors caused by a hydrodynamic force that acts on the valve body of the boom meter-in valve 53a (53b), and by errors of the valve position sensor 59a can be reduced. In addition, in a case where the boom meter-in pressure is high, and the meter-in differential pressure is low, since the reference discharge opening area is selected as the boom meter-out target opening area, the pressure loss that occurs due to the meter-out flow rate can be suppressed.
The hydraulic excavator (construction machine) 600 according to the present embodiment includes: the tank 29; the hydraulic pump 2a; the boom cylinder (first hydraulic actuator) 5 and the arm cylinder (second hydraulic actuator) 6 each having two supply and discharge ports; the first meter-in valves 53a and 53b provided on the hydraulic lines 54a and 54b connecting the boom cylinder (first hydraulic actuator) 5 to the hydraulic pump 2a; the second meter-in valves 63a and 63b provided on the hydraulic lines 64a and 64b establishing communication between the arm cylinder (second hydraulic actuator) 6 and the hydraulic pump 2a; the boom meter-out valves (first meter-out valves) 55a and 55b provided on the hydraulic lines establishing communication between the boom cylinder (first hydraulic actuator) 5 and the tank 29; the arm meter-out valves (second meter-out valves) 65a and 65b provided on the hydraulic lines establishing communication between the arm cylinder (second hydraulic actuator) and the tank 29; the boom pressure sensor (first pressure sensor) 58a that senses the boom meter-in pressure (first meter-in pressure) that is the load pressure on the boom cylinder (first hydraulic actuator); the arm pressure sensor (second pressure sensor) 68a that senses the arm meter-in pressure (second meter-in pressure) that is the load pressure on the arm cylinder (second hydraulic actuator) 6; the supply-pressure sensor (third pressure sensor) 28 that senses the supply pressure that is the delivery pressure of the hydraulic pump 2a; and the controller 100 having the meter-in valve control section 130 that calculates the target opening area of the boom meter-in valve (first meter-in valve) 53a (53b) according to the pressure difference between the supply pressure and the boom meter-in pressure (first meter-in pressure), and calculates the target opening area of the arm meter-in valve (second meter-in valve) 63a (63b) according to the pressure difference between the supply pressure and the arm meter-in pressure (second meter-in pressure). The controller 100 has the meter-out valve control section 140 that calculates the target opening area of the arm meter-out valve (second meter-out valve) 63a (63b) according to the pressure difference between the supply pressure and the arm meter-in pressure (second meter-in pressure), or calculates the target opening area of the boom meter-out valve (first meter-out valve) 55a (55b) according to the pressure difference between the supply pressure and the boom meter-in pressure (first meter-in pressure).
In addition, the meter-out valve control section 140 in the present embodiment reduces the target opening area of the boom meter-out valve (first meter-out valve) 55a (55b) as the pressure difference between the supply pressure of the hydraulic pump 2a and the boom meter-in pressure (first meter-in pressure) increases, or reduces the target opening area of the arm meter-out valve (second meter-out valve) 65a (65b) as the pressure difference between the supply pressure and the arm meter-in pressure (second meter-in pressure) increases.
In addition, the hydraulic excavator (construction machine) 600 according to the present embodiment includes: the upper swing structure (machine body) 10; the boom 11 pivotably attached to the upper swing structure 10; the arm 12 pivotably attached to the boom 11; and the bucket 8 pivotably attached to a tip section of the arm 12, and includes: the boom cylinder (first hydraulic actuator) 5 that drives the boom 11; the arm cylinder (second hydraulic actuator) 6 that drives the arm 12; and the bucket cylinder (second hydraulic actuator) that drives the bucket 8.
According to the thus-configured present embodiment, by controlling the arm meter-out valve 65a (65b) according to the pressure difference between the supply pressure and the arm meter-in pressure or by controlling the boom meter-out valve 55a (55b) according to the pressure difference between the supply pressure and the boom meter-in pressure, the differential pressure across the boom meter-in valve 55a (55b) or the arm meter-in valve 63a (63b) that supplies the hydraulic fluid to one of the boom cylinder 5 and the arm cylinder 6 that is receiving a lower load lowers. Thereby, without being affected by load conditions of the boom cylinder 5 and the arm cylinder 6, the opening areas of the boom meter-in valve 55a (55b) and the arm meter-in valve 63a (63b) increase, and change amounts of the meter-in flow rates in relation to change amounts of the opening areas decrease. Accordingly, meter-in flow-rate errors caused by a hydrodynamic force that acts on the valve body of the boom meter-in valve 55a (55b) or the arm meter-in valve 63a (63b), and by errors of the opening area of the boom meter-in valve 53a (53b) or the arm meter-in valve 63a (63b) are reduced.
Note that although the controller 100 is mounted on the hydraulic excavator 600 in the configuration explained in the present embodiment, the controller 100 may be arranged separately from the hydraulic excavator 600, and the remote operation of the hydraulic excavator 600 may be enabled, for example.
A second embodiment of the present invention is explained with reference to
The present embodiment reduces meter-in flow-rate errors caused by errors of the pressure sensors 28, 58a and 68a that sense meter-in differential pressures.
In
The subtracting section 247 calculates a pressure difference (hereinafter, a boom-arm meter-in pressure difference) obtained by subtracting the arm meter-in pressure from the boom meter-in pressure, and outputs the boom-arm meter-in pressure difference to the pressure-difference-maintaining-opening calculating section 246.
On the basis of the boom-arm meter-in pressure difference, the pressure-difference-maintaining-opening calculating section 246 calculates a pressure-difference-maintaining opening area, and outputs the pressure-difference-maintaining opening area to the target opening selecting section 244. For example, a pressure-difference-maintaining-opening map illustrated in
The target opening selecting section 244 selects one of the reference discharge opening area, the overrun-preventing opening area, the differential-pressure-reducing opening area and the pressure-difference-maintaining opening area, and outputs the selected one as a boom meter-out target opening area to the valve-position control section 150.
If the meter-in differential pressure is equal to or lower than the threshold PH (e.g. 10 MPa) at Step S1402, and the boom-arm meter-in pressure difference is equal to or larger than a threshold PL2 (e.g. 2 MPa) at Step S2403, the process proceeds to Step S1410, and otherwise the process proceeds to Step S2460.
At Step S2460, a pressure-difference-maintaining opening area is selected as the boom meter-out target opening area, and output to the valve-position control section 150.
In a case where the boom meter-in pressure (first meter-in pressure) is higher than the arm meter-in pressure (second meter-in pressure), and the pressure difference between the boom meter-in pressure (first meter-in pressure) and the arm meter-in pressure (second meter-in pressure) is smaller than the threshold (first predetermined pressure difference), the meter-out valve control section 140 in the present embodiment reduces the target opening area of the boom meter-out valve (first meter-out valve) 55a (55b), or in a case where the arm meter-in pressure (second meter-in pressure) is higher than the boom meter-in pressure (first meter-in pressure), and the pressure difference between the arm meter-in pressure (second meter-in pressure) and the boom meter-in pressure (first meter-in pressure) is smaller than the threshold (second predetermined pressure difference), the meter-out valve control section 140 in the present embodiment reduces the target opening area of the second meter-out valve.
According to the thus-configured present embodiment, the following effects are attained in addition to effects similar to those attained with the first embodiment.
In a case where the boom meter-in pressure is higher than the arm meter-in pressure, and the pressure difference therebetween is small, the pressure-difference-maintaining opening area is selected as the target opening area of the boom meter-out valve 55a (55b). Accordingly, the meter-in pressure of the boom cylinder 5 can be maintained at a pressure higher than that of the arm cylinder 6 even at the time of excavation, and meter-in flow-rate errors caused by errors of the pressure sensors 28, 58a and 68a that sense the meter-in differential pressures can be reduced.
A third embodiment of the present invention is explained with reference to
In the present embodiment, a differential-pressure-reducing opening area is calculated without sensing a meter-in differential pressure.
In
In
On the basis of the boom meter-in target opening area, the hydrodynamic-force-reducing-opening calculating section 343 calculates a hydrodynamic-force-reducing opening area, and outputs the hydrodynamic-force-reducing opening area to the target opening selecting section 144. The hydrodynamic-force-reducing-opening calculating section 343 gradually reduces the hydrodynamic-force-reducing opening area until the boom meter-in target opening area becomes equal to or larger than a predetermined value (e.g. 5 mm2), for example. By reducing the meter-out opening area of the boom to increase the meter-out pressure, the boom meter-in target opening area can be increased to suppress a hydrodynamic force similarly to the first embodiment. In addition, as illustrated in
If the boom meter-in valve target opening area is equal to or larger than a threshold AL (e.g. 5 mm2) at Step S3402, the process proceeds to Step S1410, and otherwise the process proceeds to Step S3430.
At Step S3430, a hydrodynamic-force-reducing opening area is selected as the boom meter-out target opening area, and output to the valve-position control section 150.
In a case where the target opening area of the boom meter-in valve (first meter-in valve) 53a (53b) is smaller than the threshold (first predetermined opening area) AL, the meter-out valve control section 140 in the present embodiment reduces the target opening area of the boom meter-out valve (first meter-out valve) 55a (55b), or in a case where the target opening area of the arm meter-in valve (second meter-in valve) 63a (63b) is smaller than the threshold (second predetermined opening area), the meter-out valve control section 140 in the present embodiment reduces the target opening area of the arm meter-out valve (second meter-out valve) 65a (65b).
According to the thus-configured present embodiment, in a case where the boom meter-in valve target opening area is small (the arm meter-in pressure is higher than the boom meter-in pressure, and the pressure difference therebetween is large), the hydrodynamic-force-reducing opening area is selected as the boom meter-out target opening area, or in a case where the arm meter-in valve target opening area is small (the boom meter-in pressure is higher than the arm meter-in pressure, and the pressure difference therebetween is large), the hydrodynamic-force-reducing opening area is selected as the arm meter-out target opening area. Accordingly, similarly to the first embodiment, meter-in flow-rate errors caused by hydrodynamic forces that act on the valve bodies of the meter-in valves 53a, 53b, 63a and 63b, and by errors of the opening areas of the meter-in valves 53a, 53b, 63a and 63b can be reduced.
Note that although the differential-pressure-reducing opening area is calculated by using the meter-in target opening area in the example explained in the present embodiment, the differential-pressure-reducing opening area may be calculated on the basis of signals of the valve position sensors 59a and 69a.
Although embodiments of the present invention are mentioned in detail thus far, the present invention is not limited to the embodiments described above, and includes various modification examples. For example, although the present invention is applied to a hydraulic excavator including a bucket as a work instrument at the tip of a front device in the embodiments described above, application subjects of the present invention are not limited to this, and the present invention can be applied to hydraulic excavators including work instruments other than a bucket and construction machines other than hydraulic excavators. In addition, the embodiments described above are explained in detail in order to explain the present invention in an easy-to-understand manner, and the present invention is not necessarily limited to embodiments including all the configurations explained.
1
a: Travel right operation lever device
1
b: Travel left operation lever device
1
c: Right operation lever device
1
d: Left operation lever device
2: Hydraulic pump device
2
a: Hydraulic pump
2
b: Regulator
3
b: Travel hydraulic motor
3
b: Hydraulic actuator
4: Swing hydraulic motor (hydraulic actuator)
5: Boom cylinder (hydraulic actuator)
5
a: Bottom-side oil chamber
5
b: Rod-side oil chamber
6: Arm cylinder (hydraulic actuator)
7: Bucket cylinder (hydraulic actuator)
8: Bucket (work instrument)
8
a: Bucket link
9: Lower track structure
10: Upper swing structure (machine body)
11: Boom
12: Arm
14: Engine (prime mover)
15: Front device
16: Cab
20: Control valve
20
a: Bleed-off section
20
b: Boom section
20
c: Arm section
21: Supply hydraulic line
22: Branch hydraulic line
25: Bleed-off valve
28: Supply-pressure sensor
29: Tank
53
a,
53
b: Boom meter-in valve (first meter-in valve)
54
a,
54
b: Actuator hydraulic line
55
a,
55
b: Boom meter-out valve (first meter-out valve)
58
a: Boom pressure sensor (first pressure sensor)
59
a: Boom meter-in valve position sensor
63
a,
63
b: Arm meter-in valve (second meter-in valve)
64
a,
64
b: Actuator hydraulic line
65
a,
65
b: Arm meter-out valve (second meter-out valve)
68
a: Arm pressure sensor (second pressure sensor)
69
a: Arm meter-in valve position sensor
100: Controller
110: Target-flow-rate calculating section
120: Pump control section
130: Meter-in valve control section
140: Meter-out valve control section
141: Reference-discharge-opening calculating section
142: Overrun-preventing-opening calculating section
143: Differential-pressure-reducing-opening calculating section
144: Target opening selecting section
145: Subtracting section
150: Valve-position control section
161 to 165: Converting section
244: Target opening selecting section
246: Pressure-difference-maintaining-opening calculating section
247: Subtracting section
343: Hydrodynamic-force-reducing-opening calculating section
344: Target opening selecting section
600: Hydraulic excavator (construction machine)
Number | Date | Country | Kind |
---|---|---|---|
2018-169392 | Sep 2018 | JP | national |
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/JP2019/034581 | 9/3/2019 | WO | 00 |