JPH09151487A - Hydraulic pump control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the maximum drive speed of a boom cylinder at the time of a boom elevating operation, cause the drop of the speed at the time of a boom lowering operation, and maintain the hydraulic fluid amount required for each actuator at the time of a combined operation for lowering the boom and crowding an arm, as well as a combined operation for crowding a bucket. SOLUTION: The function generator 151 of a controller computes the first target displacement volume θn of a hydraulic pump on the basis of negative control pressure. Also, function generators 141 and 142, and a maximum value selection part 143 compute the first and the second limit values θ and θv corresponding to an arm crowding operation variable as well as a bucket crowding operation variable, and output the larger value thereof as the third limit value θav. Furthermore, a setting part 144, a tilt and rotation amount selector part 145, and a minimum value selection part 147 use θn as target displacement volume θ when a boom lowering operation is not detected, and control the maximum value of θn so as not to exceed θav when the boom lowering operation is detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic pump control device provided in a hydraulic drive system for a hydraulic working machine such as a hydraulic excavator, and more particularly to a hydraulic pump control system for controlling the flow rate of a hydraulic pump that drives a plurality of hydraulic actuators. Regarding the device.

[0002]

2. Description of the Related Art Generally, a hydraulic drive system for a hydraulic working machine such as a hydraulic excavator controls a variable displacement hydraulic pump, a plurality of hydraulic actuators driven by the hydraulic pump, and the drive of these hydraulic actuators. A plurality of center bypass type flow control valves, and a center bypass path in which the center bypasses of these flow control valves are connected in series, and as a control device for a hydraulic pump provided in such a hydraulic drive system. Is Japanese Patent Laid-Open No. 1-259.
As described in Japanese Patent No. 21, the flow resistance means, such as a fixed throttle, which is installed on the downstream side of the center bypass passage and generates a negative control pressure in the center bypass passage, and the negative control pressure generated in the center bypass passage are detected. Based on the pressure sensor, the controller that calculates the target displacement of the hydraulic pump (the tilting amount of the swash plate) and outputs an electric signal in accordance with the predetermined characteristics based on the detection value of the pressure sensor, and the electric signal Some are equipped with a regulator that is driven to control the displacement of the hydraulic pump.

In such a hydraulic pump control device, when all the flow control valves are in the neutral position, that is, when no hydraulic actuator is driven, the center bypass of each flow control valve is fully opened. The total amount of discharge flow from the hydraulic pump flows through the center bypass passage, the negative control pressure detected by the pressure sensor becomes maximum, and the controller calculates the minimum target displacement according to the predetermined characteristics. The displacement (discharge flow rate) is controlled to be the minimum. Then, for example, when the corresponding flow rate control valve is operated to drive one hydraulic actuator, the center bypass of the flow rate control valve is throttled, the flow rate flowing through the center bypass passage is reduced, and the negative control pressure detected by the pressure sensor is also reduced. The target displacement volume calculated by the controller increases in accordance with the predetermined characteristics, the hydraulic pump increases the displacement volume, and the flow rate from the hydraulic pump is sufficient to drive the hydraulic actuator. Pressure oil is discharged.

[0004]

By the way, in the conventional hydraulic pump control device, the displacement of the hydraulic pump is based on the operation amount of the operating lever of each hydraulic actuator, regardless of the hydraulic actuator to be driven. The negative control pressure generated is uniquely determined by a characteristic predetermined by the controller. However, the preferable drive speed of the hydraulic actuator in the hydraulic excavator differs depending on each hydraulic actuator, and in normal operation, the operating lever is often fully operated.

As a preferable drive speed, it is desirable that the boom cylinder has a high maximum drive speed in work efficiency in boom raising operation.

On the other hand, when the boom is lowered alone, it is difficult to stop the boom at an accurate position due to the large inertia caused by the weight of the front part including the boom. Therefore, it is desirable that the maximum drive speed of the boom cylinder be small. . In addition, the combined operation of lowering the boom and arm cloud requires hydraulic oil in both the boom cylinder and arm cylinder. Therefore, in order to maintain the boom cylinder drive speed during the single boom lowering operation, the discharge flow rate of the hydraulic pump must be maintained. The boom must be lowered and increased more than when operated alone. Further, in the combined operation of lowering the boom, arm crowd, and bucket cloud, hydraulic oil flows through each of the boom cylinder, arm cylinder, and bucket cylinder, so it is necessary to secure the amount of hydraulic oil required by each actuator.

In the above-described conventional hydraulic pump control device, in order to efficiently perform the work, the characteristics of the controller are selected so that the boom cylinder can be driven at a satisfactory speed during the boom raising operation. Is normal. Therefore, in this case, if the operating lever is fully operated during the boom lowering operation alone, the boom cylinder becomes overspeed, and it becomes difficult to stop the boom cylinder at an accurate position. In addition, the combined operation of lowering the boom and the arm cloud, or the combined operation of lowering the boom, arm cloud, and bucket cloud cannot increase the discharge flow rate of the hydraulic pump more than when operating only the lower boom. Operability is reduced.

The object of the present invention is to increase the maximum drive speed of the boom cylinder during the boom raising operation, and to decrease the maximum drive speed of the boom cylinder during the boom lowering operation. By providing a hydraulic pump control device that can increase the discharge flow rate of the hydraulic pump and secure the amount of hydraulic oil required by each actuator during combined operation of lowering, arm cloud, and bucket cloud compared to when operating the boom alone. is there.

[0009]

[Means for Solving the Problems]

(1) In order to solve the above problems, the present invention provides a variable displacement hydraulic pump, a plurality of hydraulic actuators including a boom cylinder, an arm cylinder, and a bucket cylinder that are driven by the hydraulic pump, and a plurality of these hydraulic actuators. A plurality of center bypass type flow control valves including a flow control valve for boom, a flow control valve for arm, and a flow control valve for bucket, and a center bypass path in which the center bypasses of these flow control valves are connected in series. The target displacement for output is calculated based on the negative control pressure generated by the flow resistance means installed on the downstream side of the center bypass passage, which is provided in the hydraulic drive device having the discharge flow rate of the hydraulic pump. In the hydraulic pump control device for controlling, the negative generated in the center bypass passage is controlled. Control means for detecting the control pressure, and first target displacement calculation means for calculating the first target displacement of the hydraulic pump according to a first characteristic determined in advance based on the detection value of the pressure detection means. A first operation detecting means for detecting whether or not the boom flow control valve is operated in a boom lowering direction, an operation amount of the arm flow control valve in an arm cloud direction, and a bucket of the bucket flow control valve. The operation of the arm flow control valve in the arm cloud direction of the arm flow control valve based on the second and third operation detection means for respectively detecting the operation amount in the cloud direction and the detection values of the second and third operation detection means. The first limit value of the first target displacement according to the amount and the first limit value according to the operation amount of the bucket flow control valve in the bucket cloud direction. A maximum target displacement limit value calculating means for calculating a second limit value of the target displacement and outputting the larger one of the first and second limit values as a third limit value; and the first operation detection. When the operation of the boom flow rate control valve in the boom lowering direction is not detected by the means, the first target displacement is set as the output target displacement, and the first operation detection means determines the boom flow control valve. When an operation in the boom lowering direction is detected, an output target displacement volume calculation means for limiting the maximum value of the first target displacement volume so as not to exceed the third limit value and setting the output target displacement volume. Is provided.

In the above hydraulic pump control device, when the boom flow control valve is operated in the boom raising direction, the detection value of the pressure detecting means for detecting the negative control pressure changes, and the first target displacement volume calculating means. Then, according to the predetermined first characteristic, the first value corresponding to the detected value
The target displacement of is calculated. On the other hand, at this time, the first operation detection means detects that the boom flow control valve is not operated in the boom lowering direction, and the output target displacement calculation means outputs the first target displacement for output. The target displacement is set, and the discharge flow rate of the hydraulic pump is controlled by the first target displacement. Therefore, the discharge flow rate of the hydraulic pump becomes a large flow rate according to the first characteristic, the maximum drive speed of the boom cylinder can be increased, and the work can be efficiently performed.

When the boom flow control valve is operated in the boom lowering direction, the first target displacement calculation means calculates the first target displacement as described above, and the second and third operations are performed. The detection means detects the operation amount of the arm flow rate control valve in the arm cloud direction and the operation amount of the bucket flow rate control valve in the bucket cloud direction, and the maximum target displacement volume limit value calculation means calculates the first target displacement volume. A small value is calculated as the first and second limit values of, and the small value is output as the third limit value. On the other hand, at this time, the first operation detection means detects that the boom flow control valve is operated in the boom lowering direction, and the output target displacement calculation means determines that the maximum value of the first target displacement is The hydraulic pump is controlled so as not to exceed the third limit value, and the first target displacement for which the maximum value is small is set as the target displacement for output. For this reason, the maximum drive speed of the boom cylinder is suppressed to a low value, and the boom can be stopped at an accurate position.

When the arm flow control valve is operated in the arm cloud direction at the same time as the boom lowering operation, the operation amount of the arm flow control valve in the arm cloud direction is increased by more than 0 in the second operation detecting means. The maximum target displacement volume limit value calculating means calculates a value increased as a first limit value of the first target displacement volume in accordance with the increased arm cloud operation amount, and a third limit value is calculated. The increased value is output as the value. Therefore, in the output target displacement calculation means, the maximum value of the first target displacement is limited according to the increased third limit value, and the discharge flow rate of the hydraulic pump increases as compared with the boom lowering single operation. . Therefore, the flow rate required by the arm cylinder can be secured, and proper front operation can be realized.

When the bucket flow control valve is further operated in the bucket cloud direction simultaneously with the boom lowering operation and the arm cloud operation, the operation amount of the arm flow control valve in the bucket cloud direction is detected by the third operation detecting means. Also 0
Is detected as an increased value, and the maximum target displacement limit value calculation means calculates the first target displacement by the first target displacement.
And as the second limit value, an increased value is calculated according to the increased arm cloud operation amount and the bucket cloud operation amount, and the larger of these increased values is selected and output as the third limit value. . Therefore, in the output target displacement calculation means, the maximum value of the first target displacement is limited according to the increased limit value, and the discharge flow rate of the hydraulic pump is increased as compared with the boom lowering alone operation, and the arm displacement is increased. Whether the cloud operation amount or the bucket cloud operation amount is large, the discharge flow rate of the hydraulic pump increases according to the larger operation amount. For this reason,
The flow rates required for the arm cylinder and the bucket cylinder can be secured, and proper front operation can be realized.

(2) In the above hydraulic pump controller,
Preferably, the maximum target displacement limit value calculating means has a second characteristic of the hydraulic pump according to a second characteristic different from the first characteristic predetermined based on the detection value of the first operation detecting means. A second target displacement calculation means for calculating a target displacement as the limit value, and a third characteristic different from the first characteristic predetermined based on the detection value of the second operation detecting means. A third target displacement calculation means for calculating the third target displacement of the hydraulic pump as the limit value, and a larger one of the second and third target displacements is selected to select the third limit value. And a maximum value selecting means for outputting as.

(3) Here, preferably, the first characteristic is a characteristic that the first target displacement is increased from a predetermined minimum value to a predetermined maximum value as the detection value of the pressure detecting means decreases. Yes, the second and third characteristics are the second to third characteristics from a predetermined minimum value to a predetermined maximum value as the detection values of the first and second operation detecting means increase, respectively.
And the third target displacement volume increases, and the predetermined minimum value of the second and third characteristics is smaller than the predetermined maximum value of the first characteristic.

(4) Further, preferably, the predetermined maximum value of the second and third characteristics is equal to the predetermined maximum value of the first characteristic.

(5) In the hydraulic pump control device, preferably, the output target displacement calculation means detects the operation of the boom flow rate control valve in the boom lowering direction by the first operation detection means. If not, a constant value is output, and when the operation in the boom lowering direction is detected, the switching means that outputs the third limit value output by the maximum displacement volume limit value calculation means, and the first target displacement volume It has minimum value selecting means for selecting the smaller one of the first target displacement calculated by the calculating means and the output value from the switching means.

(6) Here, preferably, the constant value is equal to a predetermined maximum value of the first characteristic.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

Referring to FIG. 1, a hydraulic drive system according to an embodiment of the present invention is a variable displacement hydraulic pump 1 having a displacement displacement mechanism (hereinafter represented by a swash plate) 1a.
A plurality of hydraulic actuators driven by the hydraulic pump 1, that is, a boom cylinder 6, an arm cylinder 7, a bucket cylinder 8 and a plurality of center bypass type flow control valves 10, 11 for controlling the driving of these hydraulic actuators. 12 and a center bypass passage 5 to which the center bypasses of these flow control valves are connected in series, the upstream side of the center bypass passage 5 is connected to the hydraulic pump 1, and the downstream side is connected to the tank. In addition, each input port of the flow control valves 10 to 12 is a bypass line 1
It is connected in parallel to the hydraulic pump 1 via 4.

The flow rate control valves 10 to 12 are hydraulic pilot operating valves, respectively, and are operated by pilot pressures A to F output from operating lever devices 62 and 63 shown in FIG. 2, respectively. That is, the operation lever device 62 has boom pilot valves 62a, 62b and bucket pilot valves 62c, 62d, and a common operation lever 62e for selectively operating these pilot valves,
The pilot valves 62a, 62b and 62c, 62d are operated according to the respective operation amounts of the operation lever 62e in the four orthogonal directions, and the pilot pressure A according to the operation amounts,
B, C, and D are output. The operation lever device 63 has arm pilot valves 63a, 63b and turning pilot valves 63c, 63d, and a common operation lever 63e for selectively operating these pilot valves, and the pilot valves 63a, 63b and 63c, 63d. Is operated according to the respective operation amounts of the operation lever 63e in the four orthogonal directions, and the pilot pressures E, F, and
Outputs G and H. The pilot pressures G and F are used to operate a turning flow control valve of a hydraulic drive device (not shown).

As shown in FIG. 3, the hydraulic excavator on which the above hydraulic drive system is mounted has a lower traveling body 100, an upper revolving superstructure 101, and a work front mechanism 102. The work front mechanism 102 is a boom 103. The boom 103 is moved up and down by the boom cylinder 6, the arm 104 is moved back and forth by the arm cylinder 7, and the bucket 105 is moved up and down and front and back by the bucket cylinder 8. 101 is turned by a turning motor (not shown).

The above hydraulic drive system is equipped with the hydraulic pump control system of this embodiment. The hydraulic pump control apparatus according to the present embodiment controls the amount of tilt of the swash plate 1a of the hydraulic pump 1 (displacement volume of the hydraulic pump 1).
A fixed throttle 20 installed on the downstream side of the center bypass passage 5 for generating a negative control pressure in the center bypass passage 5, and a pressure sensor 21 for detecting the negative control pressure generated in the center bypass passage 5.
A pressure sensor 16 for detecting whether or not the pilot pressure B acts on the boom lowering side of the boom flow control valve 10;
A pressure sensor 24 that detects a pilot pressure E that acts on the arm cloud side of the arm flow control valve 11, and a pressure sensor 18 that detects a pilot pressure C that acts on the bucket cloud side of the bucket flow control valve 12; The detection values Pn, Sb, Pa of the pressure sensors 21, 16, 23, 18
Electric signal (current) I
Is provided, and a proportional solenoid valve 25 that operates by the electric signal I. The control pressure output from the proportional solenoid valve 25 is input to the regulator 19.

The pressure sensor 16 is, for example, a pilot pressure B.
Is a pressure switch that is OFF when the value is below a predetermined value, and is ON when the value exceeds a predetermined value. Further, instead of the pressure switch, a sensor similar to the pressure sensors 23 and 18 is used to input the detected pilot pressure B to the controller 24, and a predetermined pressure is used as a threshold value. The operation may be determined.

The regulator 19 comprises a hydraulic cylinder 2 for tilting the swash plate 1a, a servo valve 3 for horsepower control, and a servo valve 4 for flow rate control. The servo valve 3 for horsepower control is provided.
The discharge pressure of the hydraulic pump 1 acts on one end of the swash plate to control the swash plate tilt amount so that the pump discharge pressure does not exceed the limit value.
The proportional solenoid valve 2 is provided at one end of the servo valve 4 for controlling the flow rate.
The control pressure output from 5 acts to control the tilting amount of the swash plate so that the pump flow rate corresponding to the control pressure is obtained.

FIG. 4 is a block diagram showing the functions of the controller 24 shown in FIG. The controller 24 is a function generator 151 that calculates a target tilt amount (target displacement volume) θn according to the detected value Pn of the negative control pressure detected by the pressure sensor 21, and the arm cloud pilot detected by the pressure sensor 23. A function generator 141 that calculates a target tilt amount θa corresponding to the detected value Pa of the pressure E, and a target tilt amount θv that corresponds to the detected value Pv of the pilot pressure C of the bucket cloud detected by the pressure sensor 18. The maximum value selection for selecting the larger of the target tilt amount θa output from the function generator 142 and the function generator 141 and the target tilt amount θv output from the function generator 142 and outputting it as the target tilt amount θav Detection value S of the portion 143 and the pressure sensor 16
When b is OFF, that is, when the boom is not lowered and the pilot pressure B is not detected, the predetermined target tilt amount θc stored in the setting unit 144 is output and the pressure sensor 16 is output.
Is ON, that is, when the boom lowering operation is performed and the pilot pressure B is detected, the tilt amount switching unit 145 that outputs the target tilt amount θav output from the maximum value selecting unit 143 and the function generator. The target displacement amount θn output from 151 and the target displacement amount θ * output from the displacement amount switching unit 145 are selected to be smaller, and the target displacement amount θ for output is selected.
And a function generator 148 that calculates a current value I (command value) according to the target tilt amount θ, and the current value I obtained by the function generator 146 is not shown in the figure. Is supplied to the proportional solenoid valve 25, the power supply device outputs an electric signal corresponding to the current value I.

The characteristic of the function generator 151 has a predetermined maximum value θn1 and a predetermined minimum value θn2, and when the detection value Pn decreases within a predetermined range of the detection value Pn, the target tilt amount θn corresponding to this decrease. Is the minimum value θn2 to the maximum value θn
It is a characteristic that increases to 1.

The characteristic of the function generator 141 has a predetermined maximum value θa1 and a predetermined minimum value θa2. When the detected value Pa increases within a predetermined range of the detected value Pa, the target tilt amount θa increases in accordance with this increase. Is the minimum value θa2 to the maximum value θa
It is a characteristic that increases to 1. Where θa1 = θn1,
θn2 <θa2 <θn1 (for example, θa2 = 0.6θn
1) is set.

The characteristics of the function generator 142 are as follows.
1 is a function generator having the same characteristics as 1, and has a predetermined maximum value θv1 (= θa1) and a predetermined minimum value θv2 (= θa).
2), the tilt amount θv increases from the minimum value θv2 to the maximum value θv1 as the detected value Pv increases within a predetermined range of the detected value Pv.

A predetermined target tilt amount θ in the setting unit 144
c is, for example, a constant value, and θc = θn1 (= θa1, θ
v1) is set.

In the above, the pressure sensor 21 constitutes pressure detecting means for detecting the negative control pressure generated in the center bypass passage 5, and the function generator 151 is
A first target displacement volume θn of the hydraulic pump 1 according to a first characteristic that is predetermined based on the detection value of the pressure detection means.
The pressure sensor 16 constitutes a first target displacement calculating means for calculating, and the pressure sensor 16 constitutes a first operation detecting means for detecting whether or not the boom flow control valve 10 is operated in the boom lowering direction. , 18 respectively constitute second and third operation detecting means for detecting the operation amount of the arm flow control valve 11 in the arm cloud direction and the operation amount of the bucket flow control valve 12 in the bucket cloud direction, respectively. Function generators 141 and 142 and maximum value selection unit 1
Reference numeral 43 denotes a first limit value θa of the first target displacement according to the operation amount of the arm flow rate control valve in the arm cloud direction and the bucket based on the detection values of the second and third operation detection means, respectively. The second limit value θv of the first target displacement according to the operation amount of the flow control valve for the bucket cloud direction is calculated, and the larger one of the first and second limit values is set as the third limit value θav. The setting unit 144, the tilting amount switching unit 145, and the minimum value selecting unit 147, which constitute the maximum target displacement volume limit value calculating means for outputting, operate the boom flow rate control valve in the boom lowering direction by the first operation detecting means. Is not detected, the first target displacement θn is set as the output target displacement θ, and when the operation of the boom flow control valve in the boom lowering direction is detected by the first operation detecting means, the first target displacement θn is detected. An output target displacement volume calculating means is configured to limit the maximum value of the displacement volume θn so as not to exceed the third limit value θav and to set the output target displacement volume θ. Next, the operation of this embodiment will be described. First, when neither of the operation levers 62e and 63e is operated and any of the flow rate control valves 10 to 12 is in the neutral position, the center bypass of each flow rate control valve is fully opened, and the discharge flow rate of the hydraulic pump 1 is reduced. The entire amount flows through the center bypass passage 5, the negative control pressure generated by the fixed throttle 20 becomes maximum, and the detection value Pn of the pressure sensor 21 also becomes maximum. The detection value Pn of the pressure sensor 21 is input to the function generator 151 of the controller 24, and the target tilt amount θ
The minimum value θn2 is calculated as n.

When any of the flow control valves 10 to 12 is in the neutral position, the boom lowering pilot pressure B is not output and the detection value Sb of the pressure sensor 16 is OFF.
Therefore, the tilt amount switching unit 145 outputs the predetermined target tilt amount θc of the setting unit 144. Here, as described above, since θc = θn1 (> θn2), the minimum value selection unit 1
At 47, θn (= θn2) is set as the target tilt amount θ for output.
Is selected, the electrical signal corresponding to θn2 is output to the proportional solenoid valve 25.
Is output to Therefore, the swash plate 1a of the hydraulic pump 1 is tilted so as to have the minimum target tilt amount θn2.
The discharge flow rate is kept to a minimum.

Next, when the operator fully operates the operating lever 62e alone in the extending direction of the boom cylinder 6 (boom raising direction), the flow control valve 10 is driven leftward in FIG. 1, and the center of the flow control valve 10 is driven. As the bypass is throttled, the flow rate flowing through the center bypass passage 5 decreases and the fixed throttle 2
The negative control pressure generated by 0 and the detection value Pn of the pressure sensor 21 decrease as the operation amount of the operation lever 62e increases. The detected value Pn of the pressure sensor 21 is input to the function generator 151 of the controller 24, and the target displacement amount θn calculated by the function generator 151 changes from the minimum value θn2 to the maximum value θn1.

In this case also, the boom lowering pilot pressure B is not output, and the detection value S of the pressure sensor 16 is detected.
b is OFF, and the tilt amount switching unit 145 is the setting unit 1
A predetermined target tilt amount θc (= θn1) of 44 is output.
Therefore, the minimum value selection unit 147 selects one of θn1 and θc, for example, θn1, as the target tilt amount θ, and
An electric signal corresponding to 1 is output to the proportional solenoid valve 25. Therefore, the swash plate 1a of the hydraulic pump 1 has the maximum target tilt amount θn.
The hydraulic pump 1 is tilted so that the discharge flow rate is maximized, the boom cylinder 6 can be driven at a sufficiently high speed, and the work can be performed efficiently.

When the operator independently operates the operating lever 62e in the contracting direction of the boom cylinder 6 (boom lowering direction), the flow control valve 10 is driven to the right in FIG. The negative control pressure and the detected value Pn generated by the pressure sensor 21 decrease as the operation amount of the operation lever 62e increases, and the function generator 151 calculates the maximum value θn1 as the target tilt amount θn.

Further, in this case, since the boom lowering pilot pressure B is output, the detection value Sb of the pressure sensor 16 is turned on, and the tilting amount switching unit 145 outputs the target value output from the maximum value selecting unit 143. It is switched to output the tilt amount θav.

On the other hand, at this time, the operation lever 62e is not operated in the extension direction of the bucket cylinder 8 (bucket cloud direction), and the operation lever 63e is not operated in the extension direction of the arm cylinder 7 (arm cloud direction). Therefore, the pilot pressure C of the bucket cloud and the pilot pressure E of the arm cloud are not output, and the function generators 141 and 142 respectively output the target tilt amounts θa and θv.
Minimum values θa2 and θv2 (θa2 = θv2 <θn
1) is calculated, and the maximum value selection unit 143 calculates θa2 and θv.
2 is selected as the target tilt amount θav, and the target tilt amount θav is selected as the target tilt amount switching unit 145.
It is output to the minimum value selection unit 147.

Therefore, in the minimum value selection unit 147, θav (= θa2) is selected as the target tilt amount θ, and an electric signal corresponding to θa2 is output to the proportional solenoid valve 25. Therefore, the tilt amount of the swash plate 1a of the hydraulic pump 1 is equal to the target tilt amount θa.
It is limited to 2, and the discharge flow rate of the hydraulic pump 1 is controlled so as not to exceed the discharge flow rate corresponding to θa2. As a result, even if the operator fully operates the operation lever 62e in the boom lowering direction, the maximum drive speed of the boom cylinder 6 is suppressed to a small value, and the boom can be stopped at an accurate position.

When the operator operates the operating lever 62e in the contracting direction of the boom cylinder 6 (boom lowering direction) and simultaneously operates the operating lever 63e in the extending direction of the arm cylinder 7 (arm clouding direction) (boom lowering, Flow control valve 1)
Since both 0 and 11 are operated, the negative control pressure generated by the fixed throttle 20 becomes the minimum, the function generator 151 calculates the maximum value θn1 as the target tilt amount θn, and the tilt amount switching unit 145 The target tilt amount θav output from the maximum value selection unit 143 is switched to be output. Further, the pilot pressure E of the arm cloud is detected by the pressure sensor 23, and the limit value of the target tilting amount θn is calculated by the detection value Pa of the pressure sensor 23. That is, in the function generator 141, the operation lever 63
Target tilt amount θa that increases as the manipulated variable of e increases
Is calculated and the maximum value selection unit 143 calculates the target tilt amount θav.
The target tilt amount θa is selected as, and the target tilt amount θav (= θa) is output from the tilt amount switching unit 145 to the minimum value selection unit 147.

Therefore, in the minimum value selection unit 147, θav (= θa) is selected as the target tilt amount θ, and the electric signal corresponding to θa is output to the proportional solenoid valve 25. Therefore,
The tilt amount of the swash plate 1a of the hydraulic pump 1 is limited to the target tilt amount θa, and the discharge flow rate of the hydraulic pump 1 is controlled so as not to exceed the discharge flow rate equivalent to θa. As a result, the operator increases the operation amount of the operation lever 63e, and the target tilt amount θ
If a is increased, the discharge flow rate increases accordingly,
The flow rate required for the arm cylinder 7 can be secured. Therefore, the arm cloud operation can be reliably performed even when the boom is lowered during work such as earth and sand excavation, and a front operation suitable for work such as earth and sand excavation can be realized.

Further, the operator operates the operation lever 62e in the extension direction (bucket cloud direction) of the bucket cylinder 8 in the contraction direction of the boom cylinder 6 (boom lowering direction), and at the same time, operates the operation lever 63e in the extension direction of the arm cylinder 7 ( When operated in the arm cloud direction (when the boom is lowered, the arm cloud and the bucket cloud are combined), all of the flow control valves 10, 11, 12 are operated, so that the negative control pressure generated by the fixed throttle 20 is generated. Is minimized, the function generator 151 calculates the maximum value θn1 as the target tilt amount θn, and the tilt amount switching unit 145 is switched to output the target tilt amount θav output from the maximum value selecting unit 143. . Also,
The pilot pressure E of the arm cloud and the pilot pressure C of the bucket cloud are detected by the pressure sensors 23 and 18, and the limit value of the target tilt amount θn is calculated by the detection values Pa and Pv of these pressure sensors 23 and 18. That is, the function generator 141 calculates the target tilt amount θa that increases as the operation amount of the operation lever 63e increases, and the function generator 142 the target increase amount that increases as the operation amount of the operation lever 62e in the bucket cloud direction increases. Tilt amount θv
Is calculated and the maximum value selection unit 143 calculates the target tilt amount θav.
The larger one of the target tilt amounts θa and θv is selected as, and the target tilt amount θav is output from the tilt amount switching unit 145 to the minimum value selection unit 147.

Therefore, in the minimum value selection unit 147, θav (= θa or θv) is selected as the target tilt amount θ,
An electrical signal corresponding to θa is output to the proportional solenoid valve 25.
Therefore, the tilt amount of the swash plate 1a of the hydraulic pump 1 is limited to the target tilt amount θa or θv, and the discharge flow rate of the hydraulic pump 1 is also θ.
It is controlled so as not to exceed the discharge flow rate obtained by a or θv. This allows the operator to operate the operation lever 62e.
Regardless of whether the operation amount in the bucket cloud direction or the operation amount of the operation lever 63e is large, the hydraulic pump 1 is operated according to the target tilt amount θa or θv corresponding to the larger operation amount.
The amount of hydraulic oil required by the arm cylinder 7 and the bucket cylinder 8 can be secured while maintaining the boom cylinder drive speed during the boom lowering independent operation.

Therefore, according to this embodiment, the maximum drive speed of the boom cylinder 6 can be increased during the boom raising operation, and the maximum drive speed of the boom cylinder 6 can be reduced during the boom lowering operation. During combined operation of boom and arm cloud, or combined operation of boom lowering, arm cloud, and bucket cloud, increase the discharge flow rate of hydraulic pump 1 to secure the amount of hydraulic oil required by each actuator, compared to the case of boom lowering alone operation. You can Therefore, even if the boom is lowered during work such as earth and sand excavation, the arm cloud and bucket cloud operations can be reliably performed, and a front operation suitable for work such as earth and sand excavation can be realized.

In the above embodiment, an example in which the operation lever is detected by the pilot pressure has been described, but it may be electrically detected. Further, the regulator may be any type of regulator as long as it can reflect the target tilt amount obtained by the controller. Further, it is obvious that each function generator, the maximum value selection unit and the minimum value selection unit can be configured by a microcomputer.

[0045]

As described above, according to the present invention, since the maximum driving speed of the boom cylinder can be increased during the boom raising operation, the work can be performed efficiently and the boom cylinder operation during the boom lowering operation. Since the maximum drive speed can be reduced, the boom can be stopped at the correct position. In addition, the amount of hydraulic oil required for each actuator can be secured during combined operation of boom lowering and arm cloud operation, or combined operation of boom lowering, arm cloud, and bucket cloud operations, so boom lowering can be performed during work such as earth and sand excavation. Can reliably perform arm cloud and bucket cloud operations, and can realize front operation suitable for work such as earth and sand excavation.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram of a hydraulic pump control device of a hydraulic drive system according to an embodiment of the present invention.

FIG. 2 is a diagram showing a specific configuration of an operation lever device.

FIG. 3 is a side view of a hydraulic excavator on which the hydraulic drive system according to the present invention is mounted.

FIG. 4 is a block diagram illustrating functions of the controller shown in FIG.

[Explanation of symbols]

 1 Hydraulic Pump 5 Center Bypass Path 6 Boom Cylinder 7 Arm Cylinder 8 Bucket Cylinder 10-12 Flow Control Valve 16, 18, 23 Pressure Sensor 19 Regulator 20 Fixed Throttle 21 Pressure Sensor 24 Controller 25 Proportional Solenoid Valve 141, 142, 151 Function Generation 143 Maximum value selection unit 144 Setting unit 145 Tilt amount switching unit 147 Minimum value selection unit 148 Function generator

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Tsukasa Toyooka 650 Jinrachi-cho, Tsuchiura-shi, Ibaraki Hitachi Construction Machinery Co., Ltd. Tsuchiura factory (72) Inventor Shigehiro Yoshinaga 650 Kintate-cho, Tsuchiura-shi, Ibaraki Hitachi Construction Machinery Incorporated company Tsuchiura factory (72) Inventor Koji Ishikawa 650 Kandamachi, Tsuchiura city, Ibaraki prefecture Hitachi Construction Machinery Incorporated Tsuchiura factory

Claims (6)

[Claims] 1. A variable displacement hydraulic pump, a plurality of hydraulic actuators including a boom cylinder, an arm cylinder, and a bucket cylinder driven by the hydraulic pump, and a boom flow control valve for controlling the driving of these hydraulic actuators. A plurality of center bypass type flow control valves including a flow control valve for arm and a flow control valve for bucket,
The center bypass of these flow control valves is provided in a hydraulic drive device having a center bypass path connected in series, and based on the negative control pressure generated by the flow resistance means installed on the downstream side of the center bypass path. In the hydraulic pump control device that calculates the target displacement for output and controls the discharge flow rate of the hydraulic pump, the pressure detection unit that detects the negative control pressure generated in the center bypass passage, and the detection value of the pressure detection unit First determined based on
And a first operation detecting means for detecting whether or not the boom flow rate control valve is operated in the boom lowering direction. And second and third operation detecting means for respectively detecting an operation amount of the arm flow control valve in the arm cloud direction and an operation amount of the bucket flow control valve in the bucket cloud direction, and the second and third operation detection means. A first limit value of the first target displacement according to the operation amount of the arm flow control valve in the arm cloud direction and the bucket of the bucket flow control valve based on each of the detection values of the operation detection means. A second limit value of the first target displacement according to the amount of operation in the cloud direction is calculated, and the larger one of the first and second limit values is set as the third limit value. And the maximum target displacement volume limiting value calculating means for outputting Te, the first when the boom lowering direction of the operation of the boom flow control valve by the first operation detection means does not detect
When the target displacement for output is set as the target displacement for output and the operation of the boom flow rate control valve in the boom lowering direction is detected by the first operation detection means, the maximum value of the first target displacement is A hydraulic pump control device, comprising: an output target displacement volume calculating unit that limits the output target displacement volume so as not to exceed the third limit value. 2. The hydraulic pump control device according to claim 1, wherein the maximum target displacement volume limit value calculating means has the predetermined first characteristic based on the detection value of the first operation detecting means. Second target displacement calculation means for calculating the second target displacement of the hydraulic pump as the limit value according to different second characteristics, and the predetermined value based on the detection value of the second operation detection means. First
Of the second and third target displacements, a third target displacement calculation means for calculating a third target displacement of the hydraulic pump as the limit value according to a third characteristic different from the characteristic of And a maximum value selecting means for selecting a larger one and outputting it as the third limit value. 3. The hydraulic pump control device according to claim 2, wherein the first characteristic is a predetermined minimum value to a predetermined maximum value as the detected value of the pressure detecting means decreases.
Of the target displacement volume is increased, and the second and third characteristics are the minimum and the maximum values, respectively, in accordance with the increase in the detection value of the first and second operation detecting means. A second and a third target displacement volume increasing characteristics, wherein a predetermined minimum value of the second and third characteristics is smaller than a predetermined maximum value of the first characteristic. apparatus. 4. The hydraulic pump control system according to claim 3, wherein a predetermined maximum value of the second and third characteristics is equal to a predetermined maximum value of the first characteristic. apparatus. 5. The hydraulic pump control device according to claim 1, wherein the output target displacement calculation means does not detect an operation of the boom flow rate control valve in a boom lowering direction by the first operation detection means. Outputs a constant value, and when the operation in the boom lowering direction is detected, the switching means that outputs the third limit value output by the maximum displacement volume limit value calculation means, and the first target displacement volume calculation means. A hydraulic pump control device comprising: a minimum value selecting means for selecting a smaller one of the first target displacement calculated in step 1 and the output value from the switching means. 6. The hydraulic pump control device according to claim 5, wherein the constant value is equal to a predetermined maximum value of the first characteristic.