Construction machinery

Abstract

Provided is a construction machine comprising first and second hydraulic actuators that are driven by first and second hydraulic pumps, respectively, and that drive a front work machine, a third hydraulic actuator that is driven by the second hydraulic pump, a solenoid valve that controls hydraulic oil to the second hydraulic actuator, an operation device that operates the front work machine, and a controller that controls the solenoid valve and the first and second hydraulic pumps on the basis of the distance between the front work machine and a target construction surface and an operation signal, wherein the controller calculates an upper limit speed of the second hydraulic actuator on the basis of a flow rate difference between the maximum read flow rate of the second hydraulic pump and a supply flow rate to the third hydraulic actuator, calculates a target speed of the second hydraulic actuator by limiting a requested speed for the second hydraulic actuator according to the operation signal to the upper limit speed, and controls the solenoid valve and the second hydraulic pump according to the target speed.

Description

Technical Field

[0001] The present invention relates to construction machinery such as hydraulic excavators.

Background Art

[0002] In recent years, with the utilization of ICT, information-based construction is being introduced at construction sites, and construction machinery having a machine control (hereinafter abbreviated as MC) function for automatically or semi-automatically controlling a front work machine according to the designed terrain (target construction surface) at the construction site is becoming widespread. In this specification, "automatic control" refers to control in which a controller drives a hydraulic actuator that is not being operated by an operator, and "semi-automatic control" refers to control in which the operation of a hydraulic actuator being operated by an operator is corrected by the controller intervening in the operator's operation.

[0003] By the way, at a construction site, even during work using the MC function, an operator may operate a hydraulic actuator other than the hydraulic actuator targeted by the MC. For example, during driving of a front work machine using the MC function, when the machine body cannot be made to face the construction surface due to the working environment, or when expanding the working range to suppress the number of times the machine body moves, the operator operates an attachment such as a positioning cylinder or a tilt rotator, or performs a turning operation of the revolving body.

[0004] In MC control, the target flow rate for driving the hydraulic actuators at a target speed corresponding to the operator's actions is calculated, and the discharge flow rate of the hydraulic pump and the pilot pressure of the control valve may be controlled accordingly. When multiple hydraulic actuators are operating in combination, the discharge flow rate of the hydraulic pump is determined according to the target speed and target flow rate of each hydraulic actuator, but the maximum flow rate that the hydraulic pump can discharge is determined by the specifications of the hydraulic pump. Therefore, if the total target flow rate of the multiple hydraulic actuators being driven exceeds the maximum discharge flow rate of the hydraulic pump, each hydraulic actuator may not be driven at its target speed. In this case, the accuracy of MC control may decrease, making it impossible to shape the construction site as designed, or to manually operate the machine as intended by the operator.

[0005] As a technology to solve this problem, Patent Document 1 discloses a hydraulic control device that, when the maximum discharge flow rate of a hydraulic pump is insufficient for the total target flow rate of multiple hydraulic actuators, combines the discharge oil from another hydraulic pump to compensate for the shortfall. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2007-100779 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] Generally, when multiple hydraulic actuators connected to the same hydraulic pump operate simultaneously, the discharged oil from the hydraulic pump tends to flow more easily to the hydraulic actuator with the lower load pressure. On the other hand, the less the oil flow splits and merges in the oil passages connecting the hydraulic actuators and hydraulic pumps, the less the load pressure affects the control of the supply flow rate to each hydraulic actuator. For this reason, in MC control, it is desirable to reduce the number of hydraulic pumps and hydraulic actuators connected to the same oil passage and to suppress the splitting and merging of the discharged oil from the hydraulic pumps.

[0008] In contrast, the hydraulic control device described in Patent Document 1 ensures the target flow rate of the hydraulic actuator by merging the discharge oil from another hydraulic pump when the maximum discharge flow rate of the hydraulic pump is insufficient for the target flow rate of the hydraulic actuator. However, in such a configuration, the number of points where the discharge oil from the hydraulic pump is divided and where it is merged increases, making it more susceptible to the influence of the load pressure of each hydraulic actuator, and the division during combined operation becomes more complex, which may reduce the accuracy of MC control.

[0009] One example of work using MC control is what is called excavation work. Excavation work is a leveling operation in which the boom and arm are linked to excavate the ground in front of the machine so that the height of the excavation surface is uniform. In this case, for example, when the boom cylinder is driven by the first hydraulic pump and the arm cylinder is driven by the second hydraulic pump, the hydraulic actuator and hydraulic pump have a one-to-one relationship, and the accuracy of MC control is maintained without flow division or merging. In this excavation work, there are cases in which a slewing operation is performed while the boom and arm are being driven under MC control, with the intention of expanding the leveling area without moving the machine body. In this case, if the circuit configuration is such that the slewing motor is driven by the second hydraulic pump, the discharge oil from the second hydraulic pump is divided between the arm cylinder and the slewing motor, unlike when the excavation work is performed by the movement of the boom and arm alone. In this situation, if the total target flow rate of the arm cylinder and slewing motor exceeds the maximum discharge flow rate of the second hydraulic pump due to the operator's operation, the maximum discharge flow rate of the second hydraulic pump will be insufficient for the target flow rate. In this example, the technology described in Patent Document 1 ensures the target flow rates for the arm cylinder and the slewing motor by merging the discharge oil from the first hydraulic pump into the oil passage of the second hydraulic pump. However, by merging the discharge oils from the first and second hydraulic pumps in this way, not only the discharge oil from the second hydraulic pump but also the discharge oil from the first hydraulic pump is diverted to the boom cylinder, arm cylinder, and slewing motor. As a result, the load pressure of the first hydraulic pump and boom cylinder begins to affect the MC control related to excavation work, which may lead to a decrease in the accuracy of the MC control.

[0010] The object of the present invention is to provide a construction machine that can suppress a decrease in the accuracy of MC control while ensuring good responsiveness to the operator's intended operation, even when a hydraulic actuator that is not subject to MC control is operated during MC control. [Means for solving the problem]

[0011] To achieve the above objective, the present invention provides a vehicle body, a front work implement attached to the vehicle body, a first hydraulic pump and a second hydraulic pump mounted on the vehicle body, a first hydraulic actuator driven by the discharge oil of the first hydraulic pump to drive the front work implement, a second hydraulic actuator driven by the discharge oil of the second hydraulic pump to drive the front work implement, a third hydraulic actuator driven by the discharge oil of the second hydraulic pump, a directional control valve that controls the flow of pressurized oil from the second hydraulic pump to the second hydraulic actuator, a solenoid valve that generates pilot pressure to drive the directional control valve, an operating device for operating the front work implement, a sensor that detects a state quantity corresponding to the operation of the third hydraulic actuator, and controls the solenoid valve, the first hydraulic pump and the second hydraulic pump based on the target surface distance, which is the distance between a specific point on the front work implement and a preset target construction surface, and an operation signal corresponding to the operation of the operating device. In a construction machine equipped with a controller, the controller calculates the supply flow rate of pressurized oil from the second hydraulic pump to the third hydraulic actuator based on the output of the sensor, calculates the upper limit speed of the second hydraulic actuator based on the flow rate difference between the maximum flow rate that the second hydraulic pump can discharge and the supply flow rate to the third hydraulic actuator, compares the requested speed of the second hydraulic actuator in response to the operation signal with the upper limit speed, calculates the requested speed as the target speed of the second hydraulic actuator if the requested speed is less than or equal to the upper limit speed, calculates the upper limit speed as the target speed if the requested speed exceeds the upper limit speed, calculates the flow rate of the second hydraulic actuator in accordance with the target speed of the second hydraulic actuator and the supply flow rate to the third hydraulic actuator to calculate the target flow rate of the second hydraulic pump, controls the solenoid valve based on the target speed and controls the second hydraulic pump based on the target flow rate. [Effects of the Invention]

[0012] The present invention aims to provide a construction machine that can suppress a decrease in the accuracy of MC control while ensuring good responsiveness to manual operations intended by the operator, even when a hydraulic actuator that is not subject to MC control is manually operated during MC control. [Brief explanation of the drawing]

[0013] [Figure 1] Side view of a hydraulic excavator, an example of a construction machine according to the first embodiment of the present invention. [Figure 2] Hydraulic circuit diagram of the main part of a hydraulic system mounted on a construction machine according to the first embodiment of the present invention. [Figure 3] A schematic diagram illustrating the logic of MC control by a controller provided in a construction machine according to the first embodiment of the present invention. [Figure 4] Functional block diagram showing details of the target speed calculation process (Figure 3) by the controller provided in the construction machine according to the first embodiment of the present invention. [Figure 5] Functional block diagram showing details of the pump flow rate calculation process (Figure 3) by the controller provided in the construction machine according to the first embodiment of the present invention. [Figure 6] This figure shows an example of the changes in the target flow rate of the second hydraulic pump and the target flow rate of the arm cylinder within it when a slewing operation is interrupted during MC control in the first embodiment of the present invention. [Figure 7] A schematic diagram illustrating the logic of MC control by a controller provided in a construction machine according to the second embodiment of the present invention. [Figure 8] A functional block diagram showing the details of the target speed calculation process (Figure 7) performed by the controller provided in the construction machine according to the second embodiment of the present invention. [Figure 9] Functional block diagram showing details of the target speed calculation process by the controller provided in the construction machine according to the third embodiment of the present invention. [Figure 10] This diagram illustrates an example where the difference between the target speed and the estimated actual speed of the second hydraulic actuator rapidly increases in a short period of time. [Modes for carrying out the invention]

[0014] Embodiments of the present invention will be described below with reference to the drawings.

[0015] (First Embodiment) 1. Construction Machinery FIG. 1 is a side view of a hydraulic excavator which is an example of a construction machine according to the first embodiment of the present invention. In the present embodiment, a hydraulic excavator equipped with a bucket 23 as an attachment at the tip of a front working machine 20 (working device) will be described as an example of a construction machine. However, the present invention can also be applied to a hydraulic excavator equipped with an attachment other than a bucket, or other types of construction machines such as a wheel loader or a bulldozer. In the present specification, the front of the cab 16 (the right side in FIG. 1) is defined as the front of the hydraulic excavator (strictly speaking, the revolving body 12).

[0016] The hydraulic excavator shown in the figure includes a vehicle body 10 and a front working machine 20 attached to the vehicle body 10. The vehicle body 10 includes a traveling body 11 and a revolving body 12.

[0017] The traveling body 11 includes crawler-type left and right traveling devices 13 having endless track belts in the present embodiment, and the left and right traveling devices 13 are respectively driven by left and right traveling motors 14 to travel. A hydraulic motor is used as the traveling motor 14.

[0018] The revolving body 12 is provided on the upper part of the traveling body 11 so as to be rotatable via a slewing device 15. The slewing device 15 connecting the traveling body 11 and the revolving body 12 includes a slewing motor 34, and when the slewing motor 34 is driven, the revolving body 12 rotates around a vertical central axis with respect to the traveling body 11. The slewing motor 34 is a hydraulic actuator (hydraulic motor). A cab 16 for an operator to board is provided at the front part (the front left side in the present embodiment) of the revolving body 12. A machine room 17 for housing hydraulic pumps P1, P2 (FIG. 2), etc. is provided on the rear side of the cab 16 in the revolving body 12, and a counterweight 18 for balancing the weight with the front working machine 20 is mounted on the rear end.

[0019] The front work implement 20 is a multi-jointed work arm for performing tasks such as excavating earth and sand, and is connected to the front of the slewing body 12 (to the right of the driver's cab 16 in this embodiment). This front work implement 20 consists of a boom 21, an arm 22, and a bucket 23. The boom 21 is connected by a pin to the slewing frame 19, which is the base frame of the slewing body 12, and rotates up and down relative to the slewing body 12 as the boom cylinder 31 extends and retracts. Both ends of the boom cylinder 31 are rotatably connected to the boom 21 and the slewing body 12. The arm 22 is connected by a pin to the tip of the boom 21 and rotates forward and backward relative to the boom 21 as the arm cylinder 32 extends and retracts. Both ends of the arm cylinder 32 are rotatably connected to the arm 22 and the boom 21. The bucket 23 is connected by a pin to the tip of the arm 22 and rotates relative to the arm 22 as the bucket cylinder 33 extends and retracts. The base end of the bucket cylinder 33 is connected to the arm 22, and the tip is connected to the bucket 23 via a link. The boom cylinder 31, arm cylinder 32, and bucket cylinder 33 that drive the front work equipment 20 are hydraulic actuators.

[0020] Furthermore, angle detectors D1-D3 are provided at the pivot points of the boom 21, arm 22, and bucket 23, respectively, and angle detector D4 is provided on the slewing device 15 of the slewing body 12. Angle detector D1 is a detector that detects a state quantity corresponding to the movement of the boom 21, which is a driven member driven by the boom cylinder 31, and in this embodiment it detects the rotation angle of the boom 21 relative to the slewing frame 19 and outputs it to the controller 50. Angle detector D2 is a detector that detects a state quantity corresponding to the movement of the arm 22, which is a driven member driven by the arm cylinder 32, and in this embodiment it detects the rotation angle of the arm 22 relative to the boom 21 and outputs it to the controller 50. Angle detector D3 is a detector that detects a state quantity corresponding to the movement of the bucket 23, which is a driven member driven by the bucket cylinder 33, and in this embodiment it detects the rotation angle of the bucket 23 relative to the arm 22 and outputs it to the controller 50. Angle detector D4 is a detector that detects state quantities corresponding to the movement of the slewing body 12, which is a driven member driven by the slewing motor 34. In this embodiment, it detects the rotation angle of the slewing body 12 relative to the traveling body 11 and outputs it to the controller 50. In MC control, the posture of the front work equipment 20 is calculated based on the output (detection signal) of angle detectors D1-S5. Also, the slewing speed of the slewing body 12 is calculated based on the output (detection signal) of angle detector D4. Angle detectors D1-D4 are examples of detectors that detect the movement of driven members (boom 21, arm 22, bucket 23, slewing body 12) driven by the corresponding hydraulic actuators. The amount of change in each rotation angle detected by angle detectors D1-D4 is an example of a state quantity whose change corresponds to the movement of the corresponding hydraulic actuator.

[0021] 2. Hydraulic System Figure 2 is a hydraulic circuit diagram of the main components of the hydraulic system installed in the hydraulic excavator shown in Figure 1. In Figure 2, the circuits that drive the boom cylinder 31, arm cylinder 32, bucket cylinder 33, and swing motor 34 are shown separately.

[0022] The hydraulic system shown in Figure 2 comprises multiple (two in this embodiment) hydraulic pumps P1, P2, a pilot pump P3, a directional control valve Vn, solenoid valves Sn1, Sn2, an operating device Ln, and a controller 50. n is a natural number from 1 to 4 (n=1,2,3,4).

[0023] 2-1. Hydraulic pump Hydraulic pumps P1 and P2 are the hydraulic power sources for each hydraulic actuator mounted on the excavator, such as the boom cylinder 31, arm cylinder 32, bucket cylinder 33, and swing motor 34, and are mounted in the vehicle body 10 (machine room 17) together with the prime mover E. Hydraulic pumps P1 and P2 are driven by the prime mover E, draw in hydraulic fluid from the hydraulic fluid tank T, pressurize it, and discharge pressurized oil to drive the corresponding hydraulic actuators. In Figure 2, the prime mover E is shown as an engine (internal combustion engine), but an electric motor may also be used as the prime mover E. Hydraulic pumps P1 and P2 are variable displacement pumps whose capacity is controlled by pump regulators R1 and R2, respectively. Figure 2 illustrates a hydraulic system equipped with two hydraulic pumps P1 and P2, but a hydraulic system may be equipped with three or more hydraulic pumps.

[0024] The pressurized oil discharged from the hydraulic pump P1 flows through the pump line PL1, which is the discharge oil passage for the hydraulic pump P1, and is supplied to the boom cylinder 31 and bucket cylinder 33 via directional control valves V1 and V3. The return oil discharged from the boom cylinder 31 and bucket cylinder 33 flows into the tank line TL via directional control valves V1 and V3 and returns to the hydraulic oil tank T. Although not shown in the diagram, the pump line PL1 and the tank line TL are connected via a relief valve that regulates the maximum pressure of the pump line PL1.

[0025] Similarly, the pressurized oil discharged from the hydraulic pump P2 flows through the pump line PL2, which is the discharge oil passage for the hydraulic pump P2, and is supplied to the arm cylinder 32 and the swing motor 34 via the directional control valves V2 and V4. The return oil discharged from the arm cylinder 32 and the swing motor 34 flows into the tank line TL via the directional control valves V2 and V4 and returns to the hydraulic oil tank T. Although not shown in the diagram, the pump line PL2 and the tank line TL are connected via a relief valve that regulates the maximum pressure of the pump line PL2.

[0026] In the hydraulic system of this embodiment, pump lines PL1 and PL2 are independent of each other, and the pressurized oil flowing through pump lines PL1 and PL2 is not combined and supplied to the hydraulic actuator. That is, there is no oil passage that bypasses the boom cylinder 31, arm cylinder 32, bucket cylinder 33, and swing motor 34 and directly connects pump lines PL1 and PL2. However, although it is desirable for pump lines PL1 and PL2 to be independent, it is also possible to configure the system so that pump lines PL1 and PL2 are connected and the discharged oil from hydraulic pumps P1 and P2 is combined and supplied to the same hydraulic actuator.

[0027] 2-2. Pilot Pump The pilot pump P3 is a fixed-displacement pump that outputs the primary pressure (starting pressure) of the pilot pressure that drives a hydraulically driven control valve, such as a directional control valve Vn, included in the hydraulic system. This pilot pump P3 is driven by the prime mover E, just like the hydraulic pumps P1 and P2. However, the pilot pump P3 may also be driven by a power source separate from the prime mover E.

[0028] 2-3. Directional control valve The directional control valve Vn (n=1,2,3,4) controls the flow (direction and flow rate) of pressurized oil supplied to the boom cylinder 31, arm cylinder 32, bucket cylinder 33, and swing motor 34.

[0029] The directional control valve V1 is used for boom driving. The spool is driven by pilot pressure input to its pilot oil chamber and the restoring force of a spring, controlling the supply, discharge, and stopping of pressurized oil to the boom cylinder 31. Each port of the directional control valve V1 is connected to the pump line PL1 and tank line TL of the hydraulic pump P1, as well as the bottom side oil chamber and rod side oil chamber of the boom cylinder 31. When the pump line PL1 is connected to the bottom side oil chamber by the directional control valve V1, the boom cylinder 31 extends and the boom 21 moves upward. Conversely, when the pump line PL1 is connected to the rod side oil chamber by the directional control valve V1, the boom cylinder 31 retracts and the boom 21 moves downward. If no pilot pressure is acting on the pilot oil chamber, the spool of the directional control valve V1 returns to the neutral position due to the restoring force of the spring, disconnecting the boom cylinder 31 from the pump line PL1 and tank line TL, and stopping the boom cylinder 31.

[0030] Similar to the directional control valve V1 for the boom cylinder 31, the directional control valve V2 for the arm cylinder 32, the directional control valve V3 for the bucket cylinder 33, and the directional control valve V4 for the swing motor 34 are also driven by pilot pressure and the restoring force of a spring.

[0031] Each port of the directional control valve V3 for bucket drive is connected to the pump line PL1 of the hydraulic pump P1, the tank line TL, and the bottom and rod side oil chambers of the bucket cylinder 33. When the directional control valve V3 connects the pump line PL1 to the bottom side oil chamber of the bucket cylinder 33, the bucket cylinder 33 extends and the bucket 23 performs a clouding action. Conversely, when the directional control valve V3 connects the pump line PL1 to the rod side oil chamber of the bucket cylinder 33, the bucket cylinder 33 retracts and the bucket 23 performs a dumping action. When the directional control valve V3 returns to the neutral position, the bucket cylinder 33 stops.

[0032] Each port of the directional control valve V2 for driving the arm is connected to the pump line PL2 of the hydraulic pump P2, the tank line TL, and the bottom oil chamber and rod oil chamber of the arm cylinder 32. When the directional control valve V2 connects the pump line PL2 to the bottom oil chamber of the arm cylinder 32, the arm cylinder 32 extends and the arm 22 performs a clouding motion. Conversely, when the directional control valve V2 connects the pump line PL2 to the rod oil chamber of the arm cylinder 32, the arm cylinder 32 retracts and the arm 22 performs a dumping motion. When the directional control valve V2 returns to the neutral position, the arm cylinder 32 stops.

[0033] Each port of the directional control valve V4 for slewing drive is connected to the pump line PL2 of the hydraulic pump P2, the tank line TL, and one port and the other port of the slewing motor 34. When the directional control valve V4 connects the pump line PL2 to one port of the slewing motor 34, the slewing motor 34 rotates forward, causing the slewing body 12 to slewing to one side in the left-right direction. Conversely, when the directional control valve V4 connects the pump line PL2 to the other port of the slewing motor 34, the slewing motor 34 rotates backward, causing the slewing body 12 to slewing to the other side in the left-right direction. When the directional control valve V4 returns to the neutral position, the slewing motor 34 stops.

[0034] 2-5. Solenoid valve Solenoid valves Sn1 and Sn2 (n=1,2,3,4) are electromagnetically driven proportional pressure reducing valves that generate pilot pressure to drive the directional control valve Vn (n=1,2,3,4). The pilot primary pressure line PL3, which is the discharge oil passage of the pilot pump P3, is connected to solenoid valves Sn1 and Sn2. Solenoid valves Sn1 and Sn2 are driven by command signals from the controller 50 and reduce the pressure in the pilot primary pressure line PL3 to generate pilot pressure (pilot secondary pressure).

[0035] Solenoid valves S11 and S12 generate pilot pressure to drive the directional control valve V1 for boom drive and output it to the pilot oil chamber of the directional control valve V1. Solenoid valve S11 is for boom raising operation; when the pilot pressure output by solenoid valve S11 is input to the directional control valve V1, the discharge oil from hydraulic pump P1 is supplied to the bottom side oil chamber of the boom cylinder 31, causing the boom cylinder 31 to extend. Solenoid valve S12 is for boom lowering operation; when the pilot pressure output by solenoid valve S12 is input to the directional control valve V1, the discharge oil from hydraulic pump P1 is supplied to the rod side oil chamber of the boom cylinder 31, causing the boom cylinder 31 to retract.

[0036] Solenoid valves S21 and S22 generate pilot pressure to drive the directional control valve V2 for driving the arm and output it to the pilot oil chamber of the directional control valve V2. Solenoid valve S21 is for arm cloud operation; when the pilot pressure output by solenoid valve S21 is input to the directional control valve V2, the discharge oil from hydraulic pump P2 is supplied to the bottom oil chamber of the arm cylinder 32, causing the arm cylinder 32 to extend. Solenoid valve S22 is for arm dump operation; when the pilot pressure output by solenoid valve S22 is input to the directional control valve V2, the discharge oil from hydraulic pump P2 is supplied to the rod-side oil chamber of the arm cylinder 32, causing the arm cylinder 32 to retract.

[0037] Solenoid valves S31 and S32 generate pilot pressure to drive the directional control valve V3 for bucket drive and output it to the pilot oil chamber of the directional control valve V3. Solenoid valve S31 is for bucket cloud operation, and when the pilot pressure output by solenoid valve S31 is input to the directional control valve V3, the discharge oil from hydraulic pump P1 is supplied to the bottom oil chamber of the bucket cylinder 33, causing the bucket cylinder 33 to extend. Solenoid valve S32 is for bucket dump operation, and when the pilot pressure output by solenoid valve S32 is input to the directional control valve V3, the discharge oil from hydraulic pump P1 is supplied to the rod-side oil chamber of the bucket cylinder 33, causing the bucket cylinder 33 to contract.

[0038] Solenoid valves S41 and S42 generate pilot pressure to drive the directional control valve V4 for slewing and output it to the pilot oil chamber of the directional control valve V4. Solenoid valve S41 is for left slewing operation, and when the pilot pressure output by solenoid valve S41 is input to the directional control valve V4, the discharge oil from hydraulic pump P2 is supplied to one port of the slewing motor 34, causing the slewing motor 34 to rotate in the forward direction. Solenoid valve S42 is for right slewing operation, and when the pilot pressure output by solenoid valve S42 is input to the directional control valve V4, the discharge oil from hydraulic pump P2 is supplied to the other port of the slewing motor 34, causing the slewing motor 34 to rotate in the reverse direction.

[0039] The pilot pressures output by solenoid valves Sn1 and Sn2 are detected by pressure sensors Ps and input to controller 50.

[0040] 2-6.Operation device Operating devices L1-L4 are operating lever devices (electric lever devices in this embodiment) that operate the directional control valves V1-V4, thereby operating the corresponding hydraulic actuators, and are installed inside the operator's cab 16. Operating device L1 is an operating lever device for boom operation that operates the boom cylinder 31. Operating device L2 is an operating lever device for arm operation that operates the arm cylinder 32. Operating device L3 is an operating lever device for bucket operation that operates the bucket cylinder 33. Operating device L4 is an operating lever device for slewing operation that operates the slewing motor 34.

[0041] Control devices L1-L4 share two control levers; for example, control devices L1 and L3 share one control lever, located on the right side of the driver's seat (not shown). Tilting this control lever left or right operates the bucket 23, and tilting it forward or backward operates the boom 21. Control devices L2 and L4 share one control lever, located on the left side of the driver's seat (not shown). Tilting this control lever left or right operates the arm 22, and tilting it forward or backward rotates the slewing body 12. The correspondence between the operating direction of these control levers and the hydraulic actuators can be changed as appropriate. Control devices L1-L4 are equipped with sensors such as potentiometers that detect the amount of lever operation and output it to the controller 50. The amount of lever operation of control devices L1-L4 detected by these sensors is an example of a state quantity whose change corresponds to the operation of the corresponding hydraulic actuator.

[0042] 3. Controller The controller 50 is an on-board computer mounted on the vehicle body 10 and has the function of controlling the hydraulic tuner that drives the front work implement 20, which in this embodiment is the boom cylinder 31 and the arm cylinder 32. The controller 50 is equipped with a calculation unit 51, a storage device 52, and signal input / output ports, etc. The calculation unit 51 performs calculation processing such as the MC control calculation unit 53 and the MC control correction unit 54, and outputs control signals to the solenoid valves Sn1, Sn2 and the pump regulators R1, R2. The storage device 52 stores, for example, data on the target construction surface of the work site that has been set in advance by the operator. The MC control calculation unit 53 and the MC control correction unit 54 are functions executed by the controller 50 (calculation unit 51), and may be virtually implemented by software or by hardware such as electronic circuits. The controller 50 receives input from angle detectors D1-D4, operating devices L1-L4, and the output (detection signals, operation signals) of each pressure sensor Ps.

[0043] In this embodiment, the MC control calculation unit 53 controls, for example, solenoid valves S11, S12, S21, and S22 in response to the target surface distance, which is the distance between a specific point on the front work implement 20 (typically the tip of the bucket 23) and a preset target construction surface, and operation signals related to the operation of the operating device L2, thereby controlling the boom cylinder 31 and arm cylinder 32 in conjunction (MC control). Although not explained here, the hydraulic excavator is equipped with a GNSS mobile station that acquires data on the position and orientation of the vehicle body 10, and an attitude sensor that detects the attitude of the vehicle body 10 (tilt angle to the front, back, left, and right). Generally, the MC control calculation unit 53 calculates the target surface distance based on data such as the position, orientation, and attitude of the vehicle body 10 relative to the target construction surface.

[0044] In this embodiment, hydraulic pump P1 is the first hydraulic pump, hydraulic pump P2 is the second hydraulic pump, boom cylinder 31 is the first hydraulic actuator subject to MC control, and arm cylinder 32 is the second hydraulic actuator subject to MC control. The slewing motor 34 is a third hydraulic actuator not subject to MC control. For example, when the arm cloud operation is performed with the MC control function enabled and the target surface distance is less than or equal to a set value, the controller 50 controls the pump regulators R1, R2 and solenoid valves S11, S12, S21 to link the boom 21 to the arm 22 so that the tip of the bucket 23 moves along the target construction surface and scrapes the ground surface. However, even while this MC control is functioning, manual interruption operations of the bucket cylinder 33 and slewing motor 34 are possible.

[0045] The MC control correction unit 54 corrects the target speed of the hydraulic actuators involved in MC control when an asymmetric hydraulic actuator of the MC control is operated while the MC control is functioning (i.e., manual operation is combined with the MC control), and the number of hydraulic actuators simultaneously supplied with pressurized oil from the same hydraulic pump increases. For example, if a slewing operation interrupts the MC control related to the linkage between the boom 21 and the arm 22, the flow rate of pressurized oil supplied to the slewing motor 34 is calculated based on the output of the angle detector D4, and if it is determined that this will affect the MC control (the required flow rate for the arm cylinder 32 cannot be supplied by the hydraulic pump P2), the target speed of the arm cylinder 32, which shares a hydraulic power source with the slewing motor 34, is corrected. Correction here means correcting the target speed of the arm cylinder 32 in the direction of decreasing from a value corresponding to the arm operation, so that the target flow rate of the arm cylinder 32 does not exceed the flow rate obtained by subtracting the flow rate supplied to the slewing motor 34 from the maximum flow rate that the hydraulic pump P2 can discharge.

[0046] Next, a specific example of the control logic by the MC control calculation unit 53 and the MC control correction unit 54 of the controller 50 will be described.

[0047] 3-1. MC Control Figure 3 is a schematic diagram showing the logic of MC control by the controller 50 in the first embodiment. Figure 3 illustrates an MC control algorithm in which, when the arm 22 is operated by the operating device L2, the boom 21 also moves in conjunction with the arm 22, and the tip of the bucket 23 moves along the target construction surface.

[0048] In the example shown in Figure 3, the controller 50 repeatedly performs a series of processes, including swivel speed calculation 61, swivel flow rate calculation 62, target speed calculation 63, target flow rate calculation 64, and pump flow rate calculation 65, in short cycles (e.g., 0.1 s) while the MC control function is enabled.

[0049] 3-2. MC Control Calculation Unit (Basic Processing) The controller 50 performs basic processing related to MC control (corresponding to the processing content of the MC control calculation unit 53) by first calculating the target speed v2 of the arm cylinder 32 (second hydraulic actuator) based on the operation signal (arm operation amount) of the operating device L2, and also calculates the target speed v1 of the boom cylinder 31 (first hydraulic actuator) based on the target speed v2 of the arm cylinder 32, the position, orientation, attitude and target plane distance of the vehicle body 10 (target speed calculation 63). Then, the controller 50 calculates the opening command values ​​for the directional control valves V1 and V2 according to the target speeds v1 and v2, for example using a conversion table, and outputs command signals corresponding to the opening command values ​​to the corresponding solenoid valves to control the directional control valves V1 and V2.

[0050] Simultaneously, the controller 50 calculates the target flow rate Q1 of the pressurized oil to be supplied to the boom cylinder 31 (first hydraulic actuator) based on the target speed v1, and calculates the target flow rate Q2 of the pressurized oil to be supplied to the arm cylinder 32 (second hydraulic actuator) based on the target speed v2 (target flow rate calculation 64). The controller 50 then calculates the sum of the target flow rate Q1 for boom drive and the target flow rate for bucket drive as the target flow rate Qp1 for the hydraulic pump P1, and outputs a pump control command corresponding to the target flow rate Qp1 to control the hydraulic pump P1 (first hydraulic pump) (pump flow rate calculation 65). If there is no bucket operation interruption, the target flow rate Qp1 corresponds to the target flow rate Q1 for boom drive. The controller 50 also calculates the sum of the target flow rate Q2 for arm drive and the target flow rate for slewing drive as the target flow rate Qp2, and outputs a pump control command corresponding to the target flow rate Qp2 to control the hydraulic pump P2 (second hydraulic pump) (pump flow rate calculation 65). If there is no interruption for the rotation operation, the target flow rate Qp2 corresponds to the target flow rate Q2 related to the arm drive.

[0051] As a result of the processing performed by the MC control calculation unit 53 as described above, the boom cylinder 31 (first hydraulic actuator) and the arm cylinder 32 (second hydraulic actuator) are controlled in conjunction.

[0052] 3-3. MC Control Correction Unit (Correction Processing) Furthermore, the processing of the MC control calculation unit 53 described above incorporates a correction process for target speeds v1 and v2 (processing of the MC control correction unit 54), and the slewing operation and bucket operation combined with the MC control are taken into account in the target speeds v1 and v2. Specifically, if the maximum discharge flow rate Qmax of the hydraulic pumps P1 and P2 is insufficient to meet the total required flow rate of the assigned hydraulic actuators, the target speeds v1 and v2 of the hydraulic actuators involved in the MC control are limited. The processing of the MC control correction unit 54 will be explained below using the case where a slewing operation interrupts the MC control related to the interlocking control of the boom 21 and arm 22 according to the target construction surface as an example.

[0053] In the correction process related to the MC control correction unit 54, the controller 50 first calculates the rotation speed v3 of the rotating body 12 based on the output of the angle detector D4 (sensor) (rotation speed calculation 61), and then calculates the supply flow rate Q3 of pressurized oil from the hydraulic pump P2 (second hydraulic pump) to the rotation motor 34 (third hydraulic actuator) based on the rotation speed v3 (rotation flow rate calculation 62). If a rotation operation is performed by the operating device L4 and the rotating body 12 rotates in response to the rotation operation signal, a rotation speed v3 and supply flow rate Q3 with an absolute value greater than 0 are calculated. If the operating device L4 is not operated and the rotating body 12 is stopped, the calculation results for rotation speed v3 and supply flow rate Q3 will be 0.

[0054] The flow rate Q3 supplied to the swing motor 34 (third hydraulic actuator), calculated in the swing flow rate calculation 62, is reflected in the calculation of target speeds v1 and v2 in the target speed calculation 63 and in the control of hydraulic pumps P1 and P2 in the pump flow rate calculation 65. Specifically, in the target speed calculation 63, the supply flow rate Q3 is reflected in the target speed v2 of the arm cylinder 32 and also in the target speed v1 of the boom cylinder 31, which corresponds to the target speed v2. As a result, if a swing operation by the operator is combined during MC control, the control command values ​​to the solenoid valves and hydraulic pumps change.

[0055] Figure 4 is a functional block diagram showing the details of the target velocity calculation 63 process in Figure 3.

[0056] In the target speed calculation 63 process, the controller 50 first calculates the flow rate difference Qd by subtracting the supply flow rate Q3 (swing flow rate) to the swing motor 34 from the maximum flow rate Qmax that the hydraulic pump P2 (second hydraulic pump) can discharge (process 63a). The flow rate difference Qd corresponds to the maximum flow rate that can be supplied to the arm cylinder 32 by the hydraulic pump P2 alone, without combining the discharge oil from the hydraulic pump P1 with the discharge oil from the hydraulic pump P2. Next, the controller 50 calculates the upper limit speed v2u of the arm cylinder 32 (second hydraulic actuator) that can be achieved with the flow rate difference Qd (process 63b). Simultaneously with the calculation of the upper limit speed v2u, the controller 50 calculates the required speed v2r (required arm speed) of the arm cylinder 32 (second hydraulic actuator) according to the operation signal (arm operation amount) of the operating device L2 related to arm operation (process 63c).

[0057] The controller 50 then compares the requested speed v2r of the arm cylinder 32 with the upper limit speed v2u and calculates the target speed v2 (arm target speed) of the arm cylinder 32 (second hydraulic actuator) by selecting the minimum value (process 63d). The target speed v2 is not necessarily a value corresponding to the arm operation amount (required arm speed), and can be corrected according to the slewing operation (operation of the third hydraulic actuator). Specifically, if the requested speed v2r is less than or equal to the upper limit speed v2u, the requested speed v2r is calculated as the target speed v2, and if the requested speed v2r exceeds the upper limit speed v2u, the upper limit speed v2u is calculated as the target speed v2. In other words, the target speed v2 of the arm cylinder 32 is limited by the upper limit speed v2u. To put it another way, the target speed v2 of the arm cylinder 32 is limited by the flow rate that can be supplied from the hydraulic pump P2 to the arm cylinder 32, while ensuring the supply flow rate Q3 to the slewing motor 34 according to the slewing operation.

[0058] Once the target speed v2 is calculated, the controller 50 calculates the target speed v1 (hereafter referred to as target speed v1) of the boom cylinder 31 based on the target speed v2 of the arm cylinder 32 and, for example, the vehicle attitude and the distance to the target surface (process 63e).

[0059] As explained in Figure 3, the target speeds v1 and v2 are used to calculate the command values ​​for the solenoid valves and the target flow rates Q1 and Q2 for the boom cylinder 31 and arm cylinder 32.

[0060] Figure 5 is a functional block diagram showing the details of the pump flow rate calculation 65 process in Figure 3.

[0061] In the pump flow rate calculation 65 process, the controller 50 first adds the supply flow rate Q3 (swing flow rate) to the swing motor 34 (third hydraulic actuator) to the target flow rate Q2 (arm cloud target flow rate or arm dump target flow rate) corresponding to the target speed v2 of the arm cylinder 32 (second hydraulic actuator), and calculates the target flow rate Qp2 of the hydraulic pump P2 (second hydraulic pump) (process 65a). After calculating the target flow rate Qp2, the controller 50 converts the target flow rate Qp2 into a control command value, for example, using a conversion table, and outputs a control command value (second hydraulic pump control command) based on the target flow rate Qp2 to control the hydraulic pump P2 (second hydraulic pump) (process 65c). Although not shown in Figure 5, the hydraulic pump P1 (first hydraulic pump) is also controlled in the same manner according to the target flow rate Qp1. In parallel with this, the controller 50 converts the target speeds v1 and v2 into control command values, for example, using a conversion table, outputs control command values ​​based on the target speeds v1 and v2, and controls solenoid valves S11 or S12 and S21 or S22 (Figure 3).

[0062] Since the maximum and minimum flow rates that hydraulic pump P2 can discharge are predetermined by the specifications of hydraulic pump P2, the maximum value of the target flow rate Qp2 input to process 65c is limited by the maximum discharge flow rate Qmax (maximum flow rate of the second hydraulic pump) of hydraulic pump P2, and the minimum value of the target flow rate Qp2 is limited by the minimum flow rate Qmin (minimum flow rate of the second hydraulic pump) of hydraulic pump P2 (process 65b).

[0063] Through the above process, in response to a manual interrupt operation during MC control, the control command values ​​for the solenoid valves and hydraulic pumps P1 and P2 involved in MC control are corrected, the operation related to the manual interrupt operation (swivel in the above example) is executed according to the operator's operation, and MC control is executed in parallel. For this MC control, it is determined whether the flow rate supplied to the third hydraulic actuator involved in MC control can be supplied as required even after subtracting the flow rate supplied to the third hydraulic actuator involved in the interrupt operation. If there is no shortage, the target speed of the second hydraulic actuator is output as required, and if there is a shortage, the target speed of the second hydraulic actuator is limited and corrected.

[0064] Therefore, if no manual operation such as a slewing operation interrupts MC control (or if an interruption operation occurs but the total requested flow rate remains within the maximum discharge flow rate Qmax of the hydraulic pump), the target speeds of the first and second hydraulic actuators related to MC control will not be affected. Even if, for example, the target speed of the arm cylinder 32 (second hydraulic actuator) is corrected as a result of a manual operation such as a slewing operation interrupting MC control, the target speed of the boom cylinder 31 (first hydraulic actuator) is calculated according to the target speed of the arm cylinder 32, so the trajectory of the bucket 23 does not change and the accuracy of MC control is not affected.

[0065] Figure 6 shows an example of the transition of the target flow rate Qp2 of the hydraulic pump P2 and the target flow rate Q2 of the arm cylinder 32 when a slewing operation is interrupted during MC control in this embodiment. As shown in the figure, when no slewing operation is combined during MC control, the supply flow rate Q3 to the slewing motor 34 is 0, and all of the discharged oil from the hydraulic pump P2 can be supplied to the arm cylinder 32, so the target flow rate Qp2 of the hydraulic pump P2 corresponds to the target flow rate Q2 of the arm cylinder 32. However, if a slewing operation is then combined during MC control and a supply flow rate Q3 to the slewing motor 34 is generated, simply adding the supply flow rate Q3 to the target flow rate Q2 of the arm cylinder 32 may result in a total flow rate exceeding the maximum discharge flow rate Qmax of the hydraulic pump P2, potentially causing the actual arm speed to not match the control command value. Furthermore, the slewing operation may not reach the speed corresponding to the operator's input.

[0066] In contrast, in this embodiment, even if the supply flow rate Q3 to the slewing motor 34 increases, the target flow rate Q2 of the arm cylinder 32 is limited to the difference between the maximum discharge flow rate Qmax and the supply flow rate Q3, so that the total flow rate with the supply flow rate Q3 to the slewing motor 34 does not exceed the maximum discharge flow rate Qmax of the hydraulic pump P2, due to the correction of the target speed of the arm cylinder 32 as described above. Therefore, the actual speed of the arm 22 can be matched to the control command value while ensuring slewing operation in accordance with the operator's operation.

[0067] -effect- In this embodiment, when a hydraulic actuator not subject to MC control (e.g., a swing motor 34) is manually operated during MC control, even if the total requested flow rate of the manually operated hydraulic actuator and a hydraulic actuator connected to the same oil passage as this hydraulic actuator (e.g., an arm cylinder 32) exceeds the maximum discharge flow rate of the corresponding hydraulic pump (e.g., hydraulic pump P2), the flow rate available for use in MC control is limited by the flow rate difference Qd obtained by subtracting the requested flow rate of the manually operated hydraulic actuator from the maximum discharge flow rate. This appropriately corrects the target speed of the MC-controlled hydraulic actuator (e.g., an arm cylinder 32), and the distribution of flow rates between the MC-controlled hydraulic actuator and the manually operated hydraulic actuator can always be determined within the range of the maximum discharge flow rate Qmax of the hydraulic pump. Therefore, for example, by merging the discharge oil of hydraulic pump P1 with the discharge oil of hydraulic pump P2, the division and merging of oil passages does not increase, and the accuracy of MC control does not decrease. Furthermore, when the total requested flow rate of each hydraulic actuator reaches the maximum discharge flow rate of the hydraulic pump, a situation in which the flow rate is not distributed to each hydraulic actuator according to the control command value can be avoided. For manual operations performed during MC control, a flow rate corresponding to the amount of operation is supplied to the target hydraulic actuator, so the target hydraulic actuator is driven according to the operator's manual operation.

[0068] As described above, according to this embodiment, even if a hydraulic actuator that is not subject to MC control is manually operated during MC control, it is possible to suppress a decrease in the accuracy of MC control while ensuring good responsiveness to the manual operation intended by the operator.

[0069] (Second Embodiment) Figure 7 is a schematic diagram showing the logic of MC control by a controller provided in a construction machine according to the second embodiment of the present invention, and Figure 8 is a functional block diagram showing the details of the target speed calculation process in Figure 7. In Figures 7 and 8, elements that are the same as or corresponding to those in the first embodiment are denoted by the same reference numerals as in previously shown drawings, and their descriptions are omitted.

[0070] The difference between this embodiment and the first embodiment is that the controller 50 is equipped with a function that estimates the actual speed of the second hydraulic actuator based on the output of a detector (e.g., angle detector D2) that detects the movement of a driven member (e.g., arm 22) driven by the second hydraulic actuator (e.g., arm cylinder 32), and corrects the target flow rate Q2 of the second hydraulic actuator so that the calculated actual speed matches the target speed of the second hydraulic actuator.

[0071] In this embodiment, the controller 50 calculates an estimated value of the drive speed related to the actual extension or contraction of the arm cylinder 32 (estimated arm speed) based on the amount of change per unit time of the detection signal (arm angle) input from the angle detector D2 (process 63f). As shown in Figure 8, the target speed v2 of the arm cylinder 32 (arm target speed) calculated in process 63d is corrected by feedback control based on the estimated arm speed, and the corrected target speed v2' is output (process 63g). In the target flow rate calculation 64 (Figure 7), the target flow rate G2 is calculated based on the corrected target speed v2'. Although Figure 8 shows an example where the target speed v1 of the boom cylinder 31 is calculated based on the target speed v2, similar to the first embodiment, it is also possible to configure it to be calculated based on the corrected target speed v2.

[0072] In other respects, this embodiment is the same as the first embodiment.

[0073] With the above configuration, in addition to the same effects as in the first embodiment, the difference between the target speed v2 and the actual speed of the second hydraulic actuator (arm cylinder 32 in this example) can be reduced by feedback control. Therefore, the accuracy of MC control can be further improved.

[0074] (Third embodiment) Figure 9 is a functional block diagram showing the details of the target speed calculation process by a controller provided in a construction machine according to the third embodiment of the present invention, and corresponds to Figures 4 and 8. In Figure 9, elements that are the same as or corresponding to those in the first or second embodiment are denoted by the same reference numerals as in the previously shown drawings, and their descriptions are omitted.

[0075] The difference between this embodiment and the first and second embodiments is that the controller 50 is equipped with a function to limit the increase in the target speed v2 of the second hydraulic actuator (e.g., arm cylinder 32) due to a decrease in the supply flow rate Q3 of pressurized oil from the second hydraulic pump (e.g., hydraulic pump P2) to the third hydraulic actuator (e.g., swing motor 34).

[0076] In this embodiment, the corrected target speed v2' calculated in process 63g is output through a low-pass filter (process 63h), and the signal waveform is smoothed to limit the increase of the target speed v2'' which is then sent to the target flow rate calculation 64 (Figure 7). Figure 9 shows an example in which a low-pass filter is used in process 63h, but a rate limiter can also be used to limit the rate of increase. Also, although the example in Figure 9 illustrates a configuration in which process 63h is applied to the second embodiment, it is also possible to apply process 63h to the first embodiment (i.e., a configuration in which processes 63f and 63g are omitted). The target speed v1 of the boom cylinder 31 is shown in Figure 9 as being calculated based on the target speed v2, similar to the first and second embodiments, but it is also possible to configure it to be calculated based on the corrected target speed v2' or v2''.

[0077] In other respects, this embodiment is the same as the first embodiment.

[0078] According to the above configuration, in addition to the same effects as the first or second embodiment, when manual operation is released or the amount of operation decreases from a state in which manual operation is combined during MC control, the flow rate that can be supplied to the hydraulic actuator related to MC control (e.g., arm cylinder 32) increases sharply due to a decrease in the flow rate Q3 supplied to the hydraulic actuator related to manual operation (third hydraulic actuator), thereby suppressing abrupt changes in the target speed v2 of the hydraulic actuator related to MS control, and consequently the actual speed.

[0079] As a result, according to this embodiment, even when the difference between the target speed v2' of the arm cylinder 32 calculated in process 63g and the estimated actual speed of the arm cylinder 32 increases rapidly in a short period of time, it is possible to prevent abrupt speed changes of the arm 22 and suppress discomfort to the operator caused by shocks to the machine due to abrupt speed changes. In addition, it is possible to suppress the decrease in accuracy of MC control due to the boom 21, which is heavier than the arm 22 and has a stronger inertial effect, not following the speed change of the arm 22.

[0080] A specific example of a situation in which the difference between the target speed v2' and the estimated actual speed of the arm cylinder 32 increases rapidly in a short time is when a slewing operation interrupted during MC control is released. When the operator stops the slewing operation, the upper limit speed v2u recovers to a value that is permissible with the maximum discharge flow rate Qmax of the hydraulic pump P2, so the target speed v2 of the arm cylinder 32 increases. On the other hand, at the moment the upper limit speed v2u recovers, the estimated actual speed of the arm cylinder 32 remains at the speed when combined with the slewing operation due to the response delay. Therefore, the difference between the target speed v2' and the estimated actual speed of the arm cylinder 32 increases rapidly instantaneously. Such a situation can occur, as shown in Figure 10, for example, when the slewing operation goes from the maximum operating amount to no operation (0), when it goes from the maximum operating amount to a small operation (when the operating amount decreases), or when it goes from an intermediate operating amount smaller than the maximum operating amount to no operation (0).

[0081] (modified version) In each of the embodiments described above, in relation to the claims, hydraulic pump P1 corresponds to the first hydraulic pump, hydraulic pump P2 to the second hydraulic pump, boom cylinder 31 to the first hydraulic actuator, arm cylinder 32 to the second hydraulic actuator, and slewing motor 34 to the third hydraulic actuator. However, the invention is not limited to this example. For example, in addition to the slewing motor 34, other hydraulic actuators that may correspond to the third actuator include bucket cylinder 33, or hydraulic actuators mounted on attachments such as positioning cylinders and tilt rotators.

[0082] For example, in MC control where the movement of arm 22 and boom 21 is controlled by arm operation, bucket operation may be combined with slewing operation. In this case, the hydraulic actuator that shares a hydraulic power source with the bucket cylinder 33 is the boom cylinder 31, and in relation to the description in the claims, hydraulic pump P2 corresponds to the first hydraulic pump, hydraulic pump P1 to the second hydraulic pump, arm cylinder 32 to the first hydraulic actuator, boom cylinder 31 to the second hydraulic actuator, and bucket cylinder 33 to the third hydraulic actuator. In this case, the supply flow rate Q3 of pressurized oil from hydraulic pump P1 (second hydraulic pump) to bucket cylinder 33 (third hydraulic actuator) is calculated based on the output of angle detector D3 (sensor), and the upper limit speed v1u of the boom cylinder 31 (second hydraulic actuator) that can be output with a flow rate difference Qd is calculated based on the flow rate difference Qd between the maximum discharge flow rate of hydraulic pump P1 (second hydraulic pump) and the supply flow rate Q3 to bucket cylinder 33 (third hydraulic actuator). The upper limit speed v1u is compared with the requested speed of the boom cylinder 31 (second hydraulic actuator) in response to the operation signal of the operating device L2 related to the operation (arm operation) of the front work implement 20. If the requested speed is less than or equal to the upper limit speed v1u, the requested speed is calculated as the target speed v1 of the boom cylinder 31 (second hydraulic actuator). If the requested speed exceeds the upper limit speed v1u, the upper limit speed v1u is calculated as the target speed v1. When the target speed v1 of the boom cylinder 31 is limited in this way, it is also possible to calculate the target speed v2 of the arm cylinder 32 inversely from the target speed v1 of the boom cylinder 31.

[0083] Furthermore, while we have illustrated the case where the supply flow rate Q3 to the third hydraulic actuator (e.g., swing motor 34) is calculated based on the output of an angle detector (e.g., angle detector D4), it is also possible to configure the system to calculate the supply flow rate Q3 based on the operation amount of the corresponding operating device (e.g., operating device L4).

[0084] In the embodiments described above, examples were given in which electric lever devices were used for the operating devices L1-L4. However, the operating devices L1-L4 can also be pilot-operated, where the pilot valve is mechanically operated by the operating lever. When the operating devices L1-L4 are pilot-operated, a pilot pressure is generated using the pressure of the pilot primary pressure line PL3 as the source pressure by a pilot valve (pressure reducing valve) mechanically linked to the operating lever, and the directional control valves V1-V4 are driven by this pilot pressure. In this case, for example, solenoid valves Sn1 and Sn2 for MC control are provided between the pilot valve and the corresponding directional control valve, or, by bypassing the pilot valve, between the pilot pump P3 and the directional control valve. The lever operation amount can be configured to detect the pilot pressure output by the pilot valve using a pressure sensor, or the lever operation amount itself can be detected using a potentiometer or the like.

[0085] Furthermore, while the second or third embodiment described an example of estimating the actual value of the turning speed based on the output of the angle detector D4, it is also possible to use an angular velocity meter that directly detects the angular velocity of the turn. It is also conceivable to estimate the turning speed from the amount of turning maneuver. Moreover, a configuration combining multiple of these methods may be used to prepare for sensor failure.

[0086] In addition, while an example of calculating the posture of the front work implement 20 based on the output of angle detectors D1-D3 has been described, it is also possible to use a stroke sensor (wire type, wheel type, etc., any type is acceptable) that detects the stroke of a hydraulic cylinder. It is also possible to configure the system to calculate the posture of the front work implement 20 based on the output of an acceleration sensor such as an IMU that detects the angle of a driven member such as a boom 21 relative to the direction of gravity. Furthermore, a configuration combining multiple of these methods may be used to prepare for sensor failures. [Explanation of Symbols]

[0087] 10...Vehicle body, 12...Slewing body (driven component), 20...Front work implement, 31...Boom cylinder (first hydraulic actuator), 32...Arm cylinder (second hydraulic actuator), 34...Slewing motor (third hydraulic actuator), 50...Controller, Dn...Angle detector (sensor, detector), Ln...Operating device, P1...Hydraulic pump (first hydraulic pump), P2...Hydraulic pump (second hydraulic pump), Vn...Directional control valve, Sn1, Sn2...Solenoid valves

Claims

1. The car body and, The front work machine attached to the vehicle body, The first hydraulic pump and the second hydraulic pump mounted on the vehicle body, A first hydraulic actuator, which is driven by the discharge oil of the first hydraulic pump to drive the front work implement, A second hydraulic actuator, which is driven by the discharge oil of the second hydraulic pump to drive the front work implement, A third hydraulic actuator driven by the discharge oil of the second hydraulic pump, A directional control valve that controls the flow of pressurized oil from the second hydraulic pump to the second hydraulic actuator, A solenoid valve that generates pilot pressure to drive the aforementioned directional control valve, An operating device for operating the front work machine, A sensor that detects a state variable corresponding to the operation of the third hydraulic actuator, In a construction machine comprising a controller that controls the solenoid valve, the first hydraulic pump, and the second hydraulic pump based on the target surface distance, which is the distance between a specific point on the front work machine and a preset target construction surface, and an operation signal corresponding to the operation of the operating device, The aforementioned controller, Based on the output of the sensor, the supply flow rate of pressurized oil from the second hydraulic pump to the third hydraulic actuator is calculated. Based on the flow rate difference between the maximum flow rate that the second hydraulic pump can discharge and the flow rate supplied to the third hydraulic actuator, the upper limit speed of the second hydraulic actuator is calculated. The requested speed of the second hydraulic actuator in response to the operation signal is compared with the upper limit speed. If the requested speed is less than or equal to the upper limit speed, the requested speed is used as the target speed for the second hydraulic actuator in the calculation; if the requested speed exceeds the upper limit speed, the upper limit speed is used as the target speed in the calculation; The target flow rate of the second hydraulic pump is calculated by adding the supply flow rate to the third hydraulic actuator to the flow rate corresponding to the target speed of the second hydraulic actuator. The solenoid valve is controlled based on the target speed, and the second hydraulic pump is controlled based on the target flow rate. A construction machine characterized by the following features.

2. In the construction machine described in claim 1, A construction machine characterized in that the state quantity corresponding to the operation of the third hydraulic actuator is the amount of angular change of the driven member driven by the third hydraulic actuator, or the amount of operation of the third hydraulic actuator.

3. In the construction machine described in claim 1, The system includes a detector that detects the movement of a driven member driven by the second hydraulic actuator, The aforementioned controller, Based on the output of the detector, the actual speed of the second hydraulic actuator is calculated. The target flow rate is corrected so that the actual speed matches the target speed. A construction machine characterized by the following features.

4. In the construction machine described in claim 1, The controller is characterized by limiting the increase in the target speed due to a decrease in the supply flow rate of pressurized oil from the second hydraulic pump to the third hydraulic actuator to a predetermined value in a construction machine.

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