Work machine with automatic and manual operating control

A work machine capable of driving each actuator more speedily and more accurately by ensuring high operability in a case of operator's manual operation, while accurately supplying a hydraulic fluid at a target flow rate to the actuator without depending on a load fluctuation in a case of automatic control over a machine body in response to a command input from a controller is provided. The controller controls a plurality of auxiliary flow controllers in such a manner that supply flow rates to a plurality of directional control valves from hydraulic pumps either fluctuate in response to load fluctuations of a plurality of hydraulic actuators when an area limiting control function invalidation instruction is issued, or do not fluctuate in response to the load fluctuations of the plurality of hydraulic actuators when an area limiting control function validation instruction is issued.

TECHNICAL FIELD

The present invention relates to a work machine such as a hydraulic excavator.

BACKGROUND ART

A work machine such as a hydraulic excavator includes a machine body including a swing structure, and a work device (front device) attached to the swing structure, and the work device includes a boom (front member) connected to the swing structure vertically rotatably, an arm (front member) connected to a tip end of this boom vertically rotatably, an arm (front member) connected to a tip end of this boom vertically rotatably, a bucket (front member) connected to a tip end of this arm vertically rotatably, a boom cylinder (actuator) that drives the boom, an arm cylinder (actuator) that drives the arm, and a bucket cylinder (actuator) that drives the bucket. It is not easy to operate the front members of the work machine by corresponding manual operation levers to excavate a predetermined area, so that an operator is required to have expertise of operation. To meet the requirement, technologies for facilitating such work are proposed (Patent Documents 1 and 2).

An area limiting excavation control device for a construction machine described in Patent Document 1 includes: controller including detection means that detects a position of a front device, a computing section that computes the position of the front device from a signal from this detection means, a setting section that sets an entry prohibited area where an entry of the front device is prohibited, and a computing section that calculates a control gain of an operation lever signal from the entry prohibited area and the position of the front device; and actuator control means that controls operations of actuators from the calculated control gain. According to such a configuration, a lever operation signal is controlled in response to a distance to a demarcation line of the entry prohibited area; thus, control is exercised in such a manner that a trajectory of a bucket tip end moves automatically along a demarcation even when an operator falsely intends to move the bucket tip end to the entry prohibited area. It is thereby possible for any operator to conduct stable work with high precision without depending on operator's expertise of operation.

Meanwhile, in a hydraulic drive system described in Patent Document 2, a pressure compensating valve compensating for a pressure of a directional control valve of each actuator is disposed in series in the directional control valve. Accordingly, an operator can supply a hydraulic fluid at a flow rate in response to a lever operation amount to each actuator without influence of a load fluctuation. Furthermore, a target compensation differential pressure of the pressure compensating valve is changed in a case in which a pump is incapable of delivering a hydraulic fluid at a pump delivery flow rate equal to a target flow rate due to horsepower control or the like, whereby it is possible to supply the hydraulic fluid while the flow rate of the hydraulic fluid delivered to each actuator is reduced and a flow rate allocation ratio of the hydraulic fluid is kept. Moreover, by setting so-called downward-sloping characteristics indicating a degree of reducing the flow rate at each pressure compensating valve in response to an increase in a load pressure of the corresponding actuator itself, it is possible to impart the downward-sloping characteristics to the actuator to prevent occurrence of hunting in response to load characteristics of the actuator and to improve stability of an operation of the actuator.

PRIOR ART DOCUMENT

Patent Document

SUMMARY OF THE INVENTION

Problem to be Solved by the Invention

The construction machine described in Patent Document 1 has the following problems in a case of supposing changeover between an operator's manual operation function and a machine body automatic control function in response to a work content.

In a case of the machine body automatic control in response to a command from the controller, it is important to accurately move the tip end of the front device along a target trajectory, and it is necessary to accurately supply the hydraulic fluid at the target flow rate to each actuator for accurately moving the tip end thereof. However, in the area limiting excavation control device described in Patent Document 1, it is an opening amount of each directional control valve that is controlled in response to the lever operation amount; thus, the hydraulic fluid at the flow rate may be unstably supplied to the actuator depending on a change in a differential pressure across the valve in association with a load fluctuation of the actuator, in some cases.

In contrast, with the technology of Patent Document 2, controlling not only the opening amount of each directional control valve in response to an operation lever input amount but also the differential pressure across the directional control valve by the pressure compensating valve enables accurate supply of the hydraulic fluid at the flow rate to the actuator without depending on the load of the actuator. Accordingly, it is considered that applying the technology of Patent Document 2 to the area limiting excavation control device of Patent Document 1 makes it possible to accurately deliver the hydraulic fluid at the target flow rate to each actuator without depending on the load fluctuation even under automatic control.

However, the change in the operation of the actuator depending on the load fluctuation is one important information for determination in operator's operating the machine body via the operation lever. To implement a function capable of accurately delivering the hydraulic fluid at the target flow rate to each actuator without depending on the load fluctuation as described above means a loss of the change in the operation of the actuator in association with the load fluctuation. Owing to this, the operator possibly has a strong sense of incongruity in a feeling of operating the machine body, which disadvantageously causes degradation in operability of the machine body.

In this way, the operator's manual operation function and the machine body automatic control function of the work machine such as a hydraulic excavator differ from each other in intended performance and also differ from each other in a hydraulic system configuration suited to the intended performance for these functions. Owing to this, even when one hydraulic system of the work machine is capable of changeover between these two functions, it is difficult to achieve the performances intended for those functions.

The present invention has been achieved in light of these circumstances, and an object of the present invention is to provide a work machine capable of driving each actuator more speedily and more accurately by ensuring high operability in a case of operator's manual operation, while accurately supplying a hydraulic fluid at a target flow rate to the actuator without depending on a load fluctuation in a case of automatic control over a machine body in response to a command input from a controller.

Means for Solving the Problem

To attain the object, a work machine according to the present invention includes: a travel structure; a swing structure swingably attached onto the travel structure; a work device attached to the swing structure; a plurality of hydraulic actuators driving the swing structure or the work device; hydraulic pumps; regulators exercising horsepower control over the hydraulic pumps in response to load pressures of the plurality of hydraulic actuators; a plurality of directional control valves connected to delivery lines of the hydraulic pumps in parallel and regulating supply flow rates to the plurality of hydraulic actuators from the hydraulic pumps; operation lever devices for issuing instructions on operations of the plurality of hydraulic actuators; a pilot pump; operation pressure generation valve devices reducing a delivery pressure of the pilot pump in response to operation instruction amounts from the operation lever devices, and outputting the reduced delivery pressure as operation pressures of the plurality of directional control valves; a control validation switch for issuing an instruction to validate or invalidate an area limiting control function to prevent entry of the work device into a preset area; and a controller that controls the operation pressure generation valve devices in such a manner as to output the operation pressures in response to the operation instruction amounts from the operation lever devices in a case in which the control validation switch issues an instruction to invalidate the area limiting control function, and that controls the operation pressure generation valve devices in such a manner as to correct the operation pressures in response to the operation instruction amounts from the operation lever devices and to output the corrected operation pressures in a case in which the control validation switch issues an instruction to validate the area limiting control function. The work machine includes a plurality of auxiliary flow controllers that are connected to upstream of the plurality of directional control valves and that can limit supply flow rates to the plurality of directional control valves from the hydraulic pumps. The controller, in the case in which the control validation switch issues an instruction to invalidate the area limiting control function, controls the plurality of auxiliary flow controllers in such a manner that the supply flow rates to the plurality of directional control valves from the hydraulic pumps fluctuate in response to load fluctuations of the plurality of hydraulic actuators; and in the case in which the control validation switch issues an instruction to validate the area limiting control function, controls the plurality of auxiliary flow controllers in such a manner that the supply flow rates to the plurality of directional control valves from the hydraulic pumps do not fluctuate in response to the load fluctuations of the plurality of hydraulic actuators, and controls the plurality of auxiliary flow controllers in such a manner that the supply flow rates to the plurality of directional control valves from the hydraulic pumps are reduced in response to a pump flow rate reduction rate that is a ratio of a current delivery flow rate of each of the hydraulic pumps to a target delivery flow rate of each of the hydraulic pumps at a time of occurrence of saturation indicating that the current delivery flow rate of each of the hydraulic pumps is reduced to be lower than the target delivery flow rate of each of the hydraulic pumps due to the horsepower control.

According to the present invention configured as described so far, in the case in which the area limiting control function is invalid, then the flow control of the auxiliary flow controllers is made invalid, and the auxiliary flow controllers maintain openings in response to the operator's operation input amounts and split a flow for the plurality of hydraulic actuators. In this case, the operator is more sensitive to the change in each actuator operation in response to the load fluctuation of the actuator; thus, it is possible to ensure operability of the work machine at the time of the operator's operation. On the other hand, in the case in which the area limiting control function is valid, the auxiliary flow controllers can supply the hydraulic fluid at the flow rate agreeable to the target flow rate commanded by the controller to each actuator without depending on the load fluctuation of the actuator with high responsiveness and with stability; thus, it is possible to improve automatic control accuracy of the actuator. As described so far, changing over to hydraulic system characteristics suited for each of two types of operation modes, that is, an operation mode during the operator's manual operation and an operation mode during the automatic control by the controller makes it possible to ensure demanded performances in the two operation modes.

Advantages of the Invention

The work machine according to the present invention can drive each actuator more speedily and more accurately by ensuring high operability in the case of the operator's manual operation, while accurately supplying the hydraulic fluid at the target flow rate to the actuator without depending on the load fluctuation in the case of automatic control over the machine body in response to a command input from the controller.

MODES FOR CARRYING OUT THE INVENTION

A hydraulic excavator will be described hereinafter as an example of a work machine according to embodiments of the present invention with reference to the drawings. It is noted that equivalent members are denoted by same reference characters in the drawings and that repetitive description will be omitted.

FIG. 1is a side view of a hydraulic excavator according to the present embodiments.

As depicted inFIG. 1, a hydraulic excavator300includes a travel structure201, a swing structure202disposed on this travel structure201and configuring a machine body, and a work device203attached to this swing structure202and conducting earth and sand excavation work and the like.

The work device203includes a boom204vertically rotatably attached to the swing structure202, an arm205vertically rotatably attached to a tip end of the boom204, a bucket206vertically rotatably attached to a tip end of the arm205, a boom cylinder204adriving the boom204, an arm cylinder205adriving the arm205, and a bucket cylinder206adriving the bucket206.

A cabin207is provided at a front side position on the swing structure202, and a counterweight209that keeps weight balance is provided at a rear side position. A machine room208accommodating therein an engine, a hydraulic pump, and the like is provided between the cabin207and the counterweight209, and a control valve210is installed in the machine room208.

A hydraulic drive system to be described in the following embodiments is mounted in the hydraulic excavator300according to the present embodiments.

FIGS. 2A and 2Bare circuit diagrams of the hydraulic drive system according to Embodiment 1 of the present invention.

As depicted inFIGS. 2A and 2B, a hydraulic drive system400according to Embodiment 1 includes three main hydraulic pumps, for example, a first hydraulic pump1, a second hydraulic pump2, and a third hydraulic pump3each formed from, for example, a variable displacement hydraulic pump, which are driven by the engine that is not depicted. In addition, the hydraulic drive system400includes a pilot pump4driven by the engine that is not depicted, and a hydraulic operating fluid tank5that supplies hydraulic operating fluids to the first to third hydraulic pumps1,2, and3, and the pilot pump4.

A tilting angle of the first hydraulic pump1is controlled by a regulator attached to this first hydraulic pump1. The regulator of this first hydraulic pump1includes a flow control command pressure port1a, a first hydraulic pump self-pressure port1b, a second hydraulic pump self-pressure port1c. Likewise, a tilting angle of the second hydraulic pump2is controlled by a regulator attached to this second hydraulic pump2. The regulator of this second hydraulic pump2includes a flow control command pressure port2a, a second hydraulic pump self-pressure port2b, a first hydraulic pump self-pressure port2c. Furthermore, likewise, a tilting angle of the third hydraulic pump3is controlled by a regulator attached to this third hydraulic pump3. The regulator of this third hydraulic pump3includes a flow control command pressure port3aand a third hydraulic pump self-pressure port3b.

A right travel directional control valve6that controls a flow of a hydraulic fluid supplied to a right travel motor, which is not depicted, out of a pair of travel motors driving the travel structure201and that is provided most upstream is connected to the first hydraulic pump1. A bucket directional control valve7that controls a flow of a hydraulic fluid supplied to the bucket cylinder206a, a second arm directional control valve8that controls a flow of a hydraulic fluid supplied to the arm cylinder205a, and a first boom directional control valve9that controls a flow of a hydraulic fluid supplied to the boom cylinder204aare provided downstream of this right travel directional control valve6and connected to the first hydraulic pump1. The bucket directional control valve7, the second arm directional control valve8, and the first boom directional control valve9are connected in parallel via a line41connected to the right travel directional control valve and connected to the line41via lines42,43, and44.

A second boom directional control valve10that controls the flow of the hydraulic fluid supplied to the boom cylinder204a, a first arm directional control valve11that controls the flow of the hydraulic fluid supplied to the arm cylinder205a, a first attachment directional control valve12that controls a flow of a hydraulic fluid supplied to a first actuator that is not depicted and that drives, for example, a first special attachment such as a cut in-block machine provided as an alternative to the bucket206, and a left travel directional control valve13that controls driving of a left travel motor that is not depicted out of the pair of travel motors driving the travel structure201are connected to the second hydraulic pump2. The second boom directional control valve10, the first arm directional control valve11, the first attachment directional control valve12, and the left travel directional control valve13are connected to each other in parallel via a line45connected to the second hydraulic pump2and are connected to the line45via lines46,47,48, and49. Furthermore, the line49is connected to the line41via a merging valve17.

A swing directional control valve14that controls a flow of a hydraulic fluid supplied to a swing motor that is not depicted and that drives the swing structure202, a third boom directional control valve15that controls the flow of the hydraulic fluid supplied to the boom cylinder204a, and a second attachment directional control valve16that controls a flow of a hydraulic fluid supplied to a second actuator that is not depicted when a second special attachment configured with the second actuator is attached in addition to the first special attachment or when the second special attachment configured with the first actuator and the second actuator is attached as an alternative to the first special attachment are connected to the third hydraulic pump3.

The swing directional control valve14, the third boom directional control valve15, and the second attachment directional control valve16are connected to each other in parallel via a line50connected to the third hydraulic pump3and are connected to this line50via lines51,52, and53.

A pressure sensor71athat detects a bottom-side pressure and a pressure sensor71bthat detects a rod-side pressure are provided at the boom cylinder204a. Likewise, a pressure sensor72athat detects a bottom-side pressure and a pressure sensor72bthat detects a rod-side pressure are provided at the arm cylinder205a. Furthermore, likewise, a pressure sensor73athat detects a bottom-side pressure and a pressure sensor73bthat detects a rod-side pressure are provided at the bucket cylinder206a. Moreover, a stroke sensor74that detects an amount of strokes of the boom cylinder204a, a stroke sensor75that detects an amount of strokes of the arm cylinder205a, and a stroke sensor76that detects an amount of strokes of the bucket cylinder206aare provided for the purpose of acquiring an operation state of the machine body. It is noted that type of means for acquiring the operation state of the machine body cover a broad range such as an inclination sensor, a rotational angle sensor, and an IMU, and are not limited to the stroke sensors described above.

Auxiliary flow controllers21,22, and23that limit flow rates of the hydraulic fluids supplied to the directional control valves from the first hydraulic pump1at a time of a combined operation are provided at the line42connected to the bucket directional control valve7, the line43connected to the second arm directional control valve8, and the line44connected to the first boom directional control valve9, respectively.

Auxiliary flow controllers24and25that limit flow rates of the hydraulic fluids supplied to the directional control valves10and11from the second hydraulic pump2at the time of the combined operation are provided at the line46connected to the second boom directional control valve10and the line47connected to the first arm directional control valve11, respectively. In Embodiment 1, the auxiliary flow controller24is configured with a sheet-shaped main valve31that forms an auxiliary variable throttle, a feedback throttle31bthat changes an opening area thereof in response to a movement amount of a valve body31aof the main valve31, that is provided at the valve body31a, and that serves as a control variable throttle, and a hydraulic variable throttle valve32that serves as a pilot variable throttle. A housing incorporating therein the main valve31has a first pressure chamber31cformed in a connection portion where the main valve31is connected to the line46, a second pressure chamber31dformed in a connection portion of a line57between the main valve31and the second boom directional control valve10, and a third pressure chamber31eformed in such a manner as to communicate with the first pressure chamber31cvia the feedback throttle31b. The third pressure chamber31eis connected to the hydraulic variable throttle valve32by a line63a, the hydraulic variable throttle valve32is connected to the line57by a line63b, and these lines63aand63bform a pilot line63.

A pressure signal port32aof the hydraulic variable throttle valve32is connected to an output port of a proportional solenoid pressure reducing valve35, a supply port of the proportional solenoid pressure reducing valve35is connected to the pilot pump4, and a tank port of the hydraulic variable throttle valve32is connected to the hydraulic operating fluid tank5.

A pressure sensor77is provided at the line45connected to the second hydraulic pump. A pressure sensor78is provided at the line57connecting the second boom directional control valve10to the auxiliary flow controller24. A pressure sensor79ais provided at a line connecting the second boom directional control valve10to a bottom side of the boom cylinder204a. A pressure sensor79bis provided at a line connecting the second boom directional control valve10to a rod side of the boom cylinder204a. A pressure sensor80is provided at a line58connecting the first arm directional control valve11to the auxiliary flow controller25. A pressure sensor81ais provided at a line connecting the first arm directional control valve11to a bottom side of the arm cylinder205a. A pressure sensor81bis provided at a line connecting the first arm directional control valve11to a rod side of the arm cylinder205a.

While partial configurations are not depicted for the sake of simple description, auxiliary flow controllers21to29and surrounding instruments, lines, and interconnections are all identical in configuration to those described above.

This hydraulic drive system400according to Embodiment 1 is configured with an operation lever91aand a pilot valve92athat can change over positions of each of the first boom directional control valve9, the second boom directional control valve10, the third boom directional control valve15, and the bucket directional control valve7, and an operation lever91band a pilot valve92bthat can change over positions of each of the first arm directional control valve11and the second arm directional control valve8. Pressure sensors102that detect that the boom204, the arm205, and the bucket206are operated are provided in lines97connecting the pilot valves92aand92bto a selector valve unit93. It is noted that to avoid complicated description, a swing operation device that operates the swing directional control valve14to change over positions thereof, a right travel operation device that operates the right travel directional control valve6to change over positions thereof, a left travel operation device that operates the left travel directional control valve13to change over positions thereof, a first attachment operation device that operates the first attachment directional control valve12to change over positions thereof, and a second attachment operation device that operates the second attachment directional control valve16to change over positions thereof are not depicted.

The selector valve unit93is connected to the flow control command ports of the first to third hydraulic pumps1,2, and3via lines98, connected to pilot ports of the directional control valves via lines99, and connected to a solenoid proportional valve unit94via lines100and101.

FIG. 3is a configuration diagram of the selector valve unit93. As depicted inFIG. 3, the selector valve unit93incorporates therein a plurality of solenoid selector valves93asubjected to position control by a command from a controller95. A position of each solenoid selector valve93ais changed over to a position A depicted inFIG. 3when a control validation switch96issues an instruction on invalidation of an area limiting control function, and the position thereof is changed over to a position B depicted inFIG. 3when the control validation switch96issues an instruction on validation of the area limiting control function. When the solenoid selector valve93ais at the position A depicted inFIG. 3, a pilot pressure signal inputted from the line97is output to the pilot port of each directional control valve or the flow control command pressure ports3a,3b, and3cof the first to third hydraulic pumps1,2, and3via the line98or99. One the other hand, when the solenoid selector valve93ais at the position B, the pilot pressure signal inputted from the line97is output to the solenoid proportional valve unit94via the line100. At the same time, a pilot pressure signal inputted from the solenoid proportional valve unit94via the line101is output to the pilot port of each directional control valve or the flow control command pressure ports3a,3b, and3cof the first to third hydraulic pumps1,2, and3via the line98or99.

FIG. 4is a configuration diagram of the solenoid proportional valve unit94. As depicted inFIG. 4, the solenoid proportional valve unit94incorporates therein a plurality of proportional solenoid pressure reducing valves94aopening amounts of which are each controlled by a command from the controller95. The pilot pressure signal inputted from one line100is corrected by the corresponding proportional solenoid pressure reducing valve94aand output to the selector valve unit93via the corresponding line101.

The hydraulic drive system400according to Embodiment 1 includes the controller95, and output values from the pressure sensors71a,71b,72a,72b,73a,73b,77,78,79a,79b,80,81a, and81b, output values from the stroke sensors74,75, and76, and a command value of the control validation switch96are input to the controller95. Furthermore, the controller95outputs commands to each selector valve provided in the selector valve unit93, each solenoid valve provided in the solenoid proportional valve unit94, and proportional solenoid pressure reducing valves35and36(as well as proportional solenoid pressure reducing valves that are not depicted).

FIG. 5is a functional block diagram of the controller95. InFIG. 5, the controller95has an input section95a, a control validation determination section95b, a machine body posture computing section95c, a demanded flow rate computing section95d, a target flow rate computing section95e, a corrected target flow rate computing section95f, a target pump flow rate computing section95g, a pump flow rate reduction rate computing section95h, an actuator flow rate computing section95i, a current pump flow rate computing section95j, and an output section95k.

The input section95aacquires a signal from the control validation switch96and sensor output values. The control validation determination section95bdetermines whether to validate or invalidate area limiting control on the basis of the signal from the control validation switch96. The machine body posture computing section95ccomputes postures of the swing structure202and the work device203on the basis of the sensor output values. The demanded flow rate computing section95dcomputes a demanded flow rate of each actuator on the basis of the sensor output values. The target flow rate computing section95ecomputes a target flow rate of each actuator on the basis of a posture of the machine body and the demanded flow rate. The target pump flow rate computing section95gcomputes a target delivery flow rate (target pump flow rate) of each hydraulic pump on the basis of the target flow rate of each actuator outputted from the target flow rate computing section95e. The actuator flow rate computing section95icomputes a current flow rate of each actuator on the basis of the sensor output values. The current pump flow rate computing section95jcomputes a current delivery flow rate (current pump flow rate) of each hydraulic pump on the basis of the current flow rate of each actuator outputted from the actuator flow rate computing section95i. The pump flow rate reduction rate computing section95hcomputes a delivery flow rate reduction rate (pump flow rate reduction rate) of each hydraulic pump on the basis of the target pump flow rate and the current pump flow rate. The corrected target flow rate computing section95fcomputes a corrected target flow rate of each actuator on the basis of the target flow rate outputted from the target flow rate computing section95eand the pump flow rate reduction rate outputted from the pump flow rate reduction rate computing section95h. The output section95kgenerates command electrical signals on the basis of a determination result from the control validation determination section95b, the corrected target flow rate from the corrected target flow rate computing section95f, and the pressure sensor output values from the input section95a, and outputs the generated command electrical signals to the selector valve unit93, the solenoid proportional valve unit94, and the proportional solenoid pressure reducing valves35and36.

FIG. 6Ais a flowchart depicting computing processing by the controller95according to Embodiment 1. The controller95determines whether the control validation switch96is turned on (Step S100), executes control invalidation processing (Step S200) in a case of determining that the control validation switch96is turned off (NO), and executes control validation processing (Step S300) in a case of determining that the control validation switch96is turned on (YES).

FIG. 6Bis a flowchart depicting details of the control invalidation processing (Step S200). The controller95changes the selector valve unit93to be turned off (Step S201), and determines whether an operation lever input is absent (Step S202).

The controller95ends the control invalidation processing (Step S200) in a case of determining in Step S202that an operation lever input is absent (YES).

In a case of determining in Step S202that an operation lever input is present (NO), the controller95causes the pilot valves92aand92bto generate pilot command pressures in response to operation lever input amounts (Step S203), open the directional control valves in response to the pilot command pressures (Step S204), and delivers a hydraulic fluid to each actuator to actuate the actuator (Step S205). Subsequently to Step S205, the controller determines whether flow split is necessary for a plurality of actuators (Step S206).

In a case of determining in Step S206that flow split is not necessary (NO), the controller95does not output command electrical signals to the proportional solenoid pressure reducing valves35and36(Step S207), fully opens the pilot variable throttles32and34(Step S208), fully opens the main valves31and33of the auxiliary flow controllers24and25in response to openings of the pilot variable throttles (Step S209), and ends the control invalidation processing (Step S200).

In a case of determining in Step S206that flow split is not necessary (YES), the controller95outputs command electrical signals to the proportional solenoid pressure reducing valves35and36(Step S210), opens the pilot variable throttles32and34in response to command pressures from the proportional solenoid pressure reducing valves35and36(Step S211), opens the main valves31and33of the auxiliary flow controllers24and25in response to openings of the pilot variable throttles (Step S212), controls flow rates of the main valves31,33, and the like (flow rates delivered to the actuators from the directional control valves) (Step S213), and ends the control invalidation processing (Step S200).

FIG. 6Cis a flowchart depicting details of the control validation processing (Step S300). The controller95changes the selector valve unit93to be turned on (Step S301), and determines whether an operation lever input is absent (Step S302).

In a case of determining in Step S302that an operation lever input is absent (YES), the controller95ends the control validation processing (Step S300).

In a case of determining in Step S302that an operation lever input is present (NO), the controller95causes each proportional solenoid pressure reducing valve94aof the solenoid proportional valve unit94to generate a pilot command pressure in response to the operation lever input amount (Step S303), opens the directional control valves in response to the pilot command pressures (Step S304), and delivers a hydraulic fluid to each actuator to actuate the actuator (Step S305).

Subsequently to Step S305, the controller95causes the demanded flow rate computing section95dto calculate the demanded flow rate of each actuator (Step S306), causes the target flow rate computing section95eto calculate the target flow rate of each actuator (Step S307), causes the target pump flow rate computing section95gto calculate the target pump flow rate of each hydraulic pump (Step S308), causes the actuator flow rate computing section95ito calculate the current flow rate of each actuator (Step S309), causes the current pump flow rate computing section95jto calculate the current pump flow rate of each hydraulic pump (Step S310), and causes the pump flow rate reduction rate computing section95hto calculate a pump flow rate reduction rate α from the target pump flow rate and the current pump flow rate of each hydraulic pump (Step S311). Subsequently to Step311, the controller95determines whether the pump flow rate reduction rate a is lower than 1 (that is, each hydraulic pump is in a saturated state in which the flow rate of the hydraulic fluid that can be actually delivered from the hydraulic pump is lower than the target pump flow rate) (Step S312).

In a case of determining in Step S312that the hydraulic pump is not in a saturated state (NO), the controller95causes the output section95kto calculate command electrical signals on the basis of the target flow rate of each actuator and the differential pressures across the auxiliary flow controllers24and25(Step S313) and to output the command electrical signals to the proportional solenoid pressure reducing valves35and36(Step S314), opens the pilot variable throttles32and34in response to the command pressures from the proportional solenoid pressure reducing valves35and36(Step S315), opens the main valves31and33of the auxiliary flow controllers24and25in response to the openings of the pilot variable throttles (Step S316), controls the flow rates of the main valves31and33(flow rates delivered from the directional control valves to the actuators) (Step S317), and ends the control validation processing (Step S300).

In a case of determining in Step S312that the hydraulic pump is in a saturated state (YES), the controller95causes the corrected target flow rate computing section95fto calculate the corrected target flow rate by multiplying the target flow rate of each actuator by the pump flow rate reduction rate α (Step S318), causes the output section95kto calculate the command electrical signals on the basis of the corrected target flow rates and the differential pressures across the auxiliary flow controllers24and25(Step S319) and to output the command electrical signals to the proportional solenoid pressure reducing valves35and36(Step S320), opens the pilot variable throttles32and34in response to the command pressures from the proportional solenoid pressure reducing valves35and36(Step S321), opens the main valves31and33of the auxiliary flow controllers24and25in response to the openings of the pilot variable throttles (Step S321), controls the flow rates of the main valves31and33(flow rates delivered from the directional control valves to the actuators) (Step S323), and ends the control validation processing (Step S300).

While the directional control valves, the auxiliary flow controllers, and the proportional solenoid pressure reducing valves for the boom204and the arm205are referred to as specific objects to be controlled in the above description, the flows depicted inFIGS. 6A to 6Care executed to all of the directional control valves, the auxiliary flow controllers, and the proportional solenoid pressure reducing valves including those not depicted.

The hydraulic drive system400according to Embodiment 1 configured as described above is capable of the following operations and control. It is noted that a case of performing a three-combined operation of the boom204, the arm205, and the bucket206is adopted and the operation will be described for the sake of simple description.

When the control validation switch96transmits a signal to invalidate the area limiting control over the hydraulic excavator300to the controller95, the controller95changes over the hydraulic lines within the selector valve unit93in such a manner that the pilot command pressures generated from inputs to the operation levers91aand91bvia the pilot valves92aand92bdirectly act on the pilot ports of the directional control valves of the actuators. It is thereby possible to drive each actuator in response to the operator's input operation amount.

The controller95calculates target opening amounts of the hydraulic variable throttle valves on the basis of operation amounts of the boom204, the arm205, and the bucket206, and controls, for example, the opening amount of the hydraulic variable throttle valve34via the proportional solenoid pressure reducing valve36on the basis of opening characteristics of the hydraulic variable throttle valve34of the auxiliary flow controller25corresponding to the first arm directional control valve11and the operating pressure from the proportional solenoid pressure reducing valve36in such a manner that the opening amount of the hydraulic variable throttle valve34is equal to the target operation amount.

A displacement of the main valve33is determined herein only on the basis of the operator's operation input amount without depending on a load on the arm cylinder205a. Owing to this, when the load on the arm cylinder205avaries in a state of operator's maintaining an input amount of the operation lever91b, the differential pressure across the main valve33changes and the flow rate by which the main valve33splits a flow to the arm cylinder205achanges. This flow rate change is realistically reflected in a behavior of the arm cylinder205a, and operator's recognizing the change makes it possible to adjust the input of the operation lever91band to perform an operator's intended operation.

“Automatic Operation Under Area Limiting Control”

When the control validation switch96transmits a signal to validate the area limiting control over the hydraulic excavator300to the controller95, the controller95changes over the hydraulic lines within the selector valve unit93in such a manner that the pilot command pressures generated from the inputs to the operation levers91aand91bvia the pilot valves92aand92bare guided to the solenoid proportional valve unit94. The signal pressures guided to the solenoid proportional valve unit94are controlled by commands from the solenoid proportional pressure reducing valves94aprovided in the solenoid proportional valve unit94and the controller95, and guided again to the selector valve unit93. The signal pressures guided to the selector valve unit93are guided to the pilot ports of the directional control valves of the actuators.

It is thereby possible to drive each actuator under control of the controller95and the area limiting control is exercised over the hydraulic excavator300.

The controller95calculates the target flow rate of each actuator on the basis of the operation amounts of the boom204, the arm205, and the bucket206and a machine body operating state acquired from each pressure sensor and each stroke sensor, and also calculates the target pump flow rate of each hydraulic pump on the basis of the target flow rate of each actuator. At the same time, the controller95calculates a meter-in current flow rate of each actuator on the basis of the differential pressure across the directional control valve acquired from the pressure sensors80and81b(or pressure sensors80and81a) attached to front and rear portions of the directional control valve, and opening area characteristics of the directional control valve with respect to the pilot pressure acting on the pressure command port of the directional control valve, and also calculates the current pump flow rate of each hydraulic pump on the basis of the current flow rate of each actuator. Further, the controller95calculates a pump flow rate reduction rate a on the basis of the target pump flow rate and the current pump flow rate.

In a case of the pump flow rate reduction rate α=1, the controller95calculates the command electrical signal on the basis of the target flow rate of the main valve33and the differential pressure across the auxiliary flow controller25obtained from the pressure sensors77and80without correcting the target flow rate of the main valve33, and outputs a command to the pilot variable throttle34via the proportional solenoid pressure reducing valve36.

In a case of the pump flow rate reduction rate α<1, the controller95calculates the corrected target flow rate by multiplying the target flow rate of the actuator by a, calculates the command electrical signal on the basis of the corrected target flow rate of the main valve33and the differential pressure across the auxiliary flow controller25obtained from the pressure sensors77and80, and outputs a command to the pilot variable throttle34via the proportional solenoid pressure reducing valve36.

While the operation of the auxiliary flow controller25has been described above, the other auxiliary flow controller operate similarly.

According to Embodiment 1, a work machine300includes: a travel structure201; a swing structure202swingably attached onto the travel structure201; a work device203attached to the swing structure202; a plurality of hydraulic actuators204a,205a,206a, and the like driving the swing structure202or the work device203; hydraulic pumps1,2, and3; regulators1a,1b,1c,2a,2b,2c,3a, and3bexercising horsepower control over the hydraulic pumps1,2, and3in response to load pressures of the plurality of hydraulic actuators204a,205a,206a, and the like; a plurality of directional control valves connected to delivery lines of the hydraulic pumps1,2, and3in parallel and regulating supply flow rates to the plurality of hydraulic actuators from the hydraulic pumps1,2, and3; operation lever devices91aand91bfor issuing instructions on operations of the plurality of hydraulic actuators204a,205a,206a, and the like; a pilot pump4; operation pressure generation valve devices93and94reducing a delivery pressure of the pilot pump4in response to operation instruction amounts from the operation lever devices91aand91b, and outputting the reduced delivery pressure as operation pressures of the plurality of directional control valves7to12and14to16; a control validation switch96for issuing an instruction to validate or invalidate an area limiting control function to prevent entry of the work device303into a preset area; and a controller95that controls the operation pressure generation valve devices93and95in such a manner as to output the operation pressures in response to the operation instruction amounts from the operation lever devices91aand91bin a case in which the control validation switch96issues an instruction to invalidate the area limiting control function, and that controls the operation pressure generation valve devices93and94in such a manner as to correct the operation pressures in response to the operation instruction amounts from the operation lever devices91aand91band to output the corrected operation pressures in a case in which the control validation switch96issues an instruction to validate the area limiting control function. The work machine300includes a plurality of auxiliary flow controllers21to29that are connected to upstream of the plurality of directional control valves7to12and14to16and that can limit supply flow rates to the plurality of directional control valves7to12and14to16from the hydraulic pumps1,2, and3. The controller95controls the plurality of auxiliary flow controllers21to29in such a manner that the supply flow rates to the plurality of directional control valves7to12and14to16from the hydraulic pumps1,2, and3fluctuate in response to load fluctuations of the plurality of hydraulic actuators204a,205a,206a, and the like in the case in which the control validation switch96issues an instruction to invalidate the area limiting control function, controls the plurality of auxiliary flow controllers21to29in such a manner that the supply flow rates to the plurality of directional control valves7to12and14to16from the hydraulic pumps1,2, and3do not fluctuate in response to the load fluctuations of the plurality of hydraulic actuators204a,205a,206a, and the like in the case in which the control validation switch96issues an instruction to validate the area limiting control function, and controls the plurality of auxiliary flow controllers21to29in such a manner that the supply flow rates to the plurality of directional control valves7to12and14to16from the hydraulic pumps1,2, and3are reduced in response to the pump flow rate reduction rate α that is a ratio of the current delivery flow rate to the target delivery flow rate, at a time of occurrence of saturation indicating that the current delivery flow rate of each of the hydraulic pumps1,2, and3is reduced to be lower than the target delivery flow rate of each of the hydraulic pumps1,2, and3due to the horsepower control in the case in which the control validation switch96issues an instruction to validate the area limiting control function.

Furthermore, the plurality of auxiliary flow controllers21to29have sheet-shaped main valves31,33, and the like forming auxiliary variable throttles; control variable throttles31b,33b, and the like changing opening areas in response to movement amounts of sheet valve bodies of the main valves31,33, and the like; pilot lines63,64, and the like determining movement amounts of the sheet valve bodies in response to pass-through flow rates; and pilot variable throttles32,34, and the like disposed on the pilot lines63,64, and the like and changing opening amounts in response to commands from the controller95, respectively. The controller95controls the opening amounts of the pilot variable throttles32,34, and the like in such a manner that the pass-through flow rates of the main valves31,33, and the like fluctuate in response to the load fluctuations of the plurality of hydraulic actuators204a,205a,206a, and the like in the case in which the control validation switch96issues an instruct to invalidate the area limiting control function; and controls the opening amounts of the pilot variable throttles32,34, and the like in such a manner that the pass-through flow rates of the main valves31,33, and the like do not fluctuate in response to the load fluctuations of the plurality of hydraulic actuators204a,205a,206a, and the like, and controls the opening amounts of the pilot variable throttles32,34, and the like in such a manner that the pass-through flow rates of the main valves31,33, and the like are reduced in response to the pump flow rate reduction rate a at the time of occurrence of the saturation in the case in which the control validation switch96issues an instruction to validate the area limiting control function.

Moreover, the pilot variable throttles32,34, and the like are each configured with a hydraulic variable throttle valve, the work machine300further includes: first pressure sensors77and the like provided at delivery lines of the hydraulic pumps1,2, and3; second pressure sensors78,80, and the like provided at hydraulic lines connecting the plurality of directional control valves7to12and14to16to the main valves31,33, and the like; and proportional solenoid pressure reducing valves35,36, and the like reducing the delivery pressure of the pilot pump4in response to a command from the controller95and outputs the reduced delivery pressure as the operation pressures of the hydraulic variable throttle valves32,34, and the like. The controller95calculates target opening amounts of the hydraulic variable throttle valves32,34, and the like on the basis of the operation instruction amounts from the operation lever devices91and91b, calculates current opening amounts of the hydraulic variable throttle valves32,34, and the like on the basis of opening characteristics of the hydraulic variable throttle valves32,34, and the like and operation pressures of the hydraulic variable throttle valves32,34, and the like, and controls opening amounts of the hydraulic variable throttle valves32,34, and the like via the proportional solenoid pressure reducing valves35,36, and the like in such a manner as to reduce differences between the target opening amounts and the current opening amounts in the case in which the control validation switch96issues an instruction to invalidate the area limiting control function; and calculates target pass-through flow rates of the main valves31,33, and the like on the basis of the operation instruction amounts from the operation lever devices91aand91b, calculates current pass-through flow rates of the main valves31,33, and the like on the basis of the differential pressures across the main valves31,33, and the like detected by the first pressure sensor77, the second pressure sensors78,80, and the like and the current opening amounts of the main valves31,33, and the like with respect to the operation pressures outputted from the proportional solenoid pressure reducing valves35,36, and the like, and controls the opening amounts of the hydraulic variable throttle valves32,34, and the like via the proportional solenoid pressure reducing valves35,36, and the like in such a manner as to reduce differences between the target pass-through flow rates and the current pass-through flow rates in the case in which the control validation switch96issues an instruction to validate the area limiting control function.

Moreover, the work machine300further includes a differential-pressure-across-valve sensor that detects the differential pressures across the plurality of directional control valves7to12and14to16, and calculates the current opening amounts of the plurality of directional control valves7to12and14to16on the basis of the opening characteristics of the plurality of directional control valves7to12and14to16and the operation pressures outputted from the operation pressure generation valve devices93and94. The controller95calculates current supply flow rates to the plurality of actuators204a,205a,206a, and the like from the plurality of directional control valves7to12and14to16on the basis of the differential pressures across the plurality of directional control valves7to12and14to16detected by the differential-pressure-across-valve sensor and the current opening amounts of the plurality of directional control valves7to12and14to16, and calculates the current delivery flow rates of the hydraulic pumps1,2, and3by adding up the current supply flow rates to the plurality of actuators204a,205a,206a, and the like from the plurality of directional control valves7to12and14to16.

Furthermore, the differential-pressure-across-valve sensor includes: the second pressure sensors78,80, and the like provided at the hydraulic lines connecting the plurality of directional control valves7to12and14to16to the main valves31,33, and the like; and third pressure sensors79b,81b, and the like (79a,81a, and the like) provided at hydraulic lines connecting hydraulic operating fluid supply-side ports of the plurality of hydraulic actuators204a,205a,206a, and the like to the plurality of directional control valves7to12and14to16.

According to Embodiment 1 configured as described so far, in the case in which the area limiting control function is invalid, then the flow control of the auxiliary flow controllers21to29is made invalid, and the auxiliary flow controllers21to29maintain openings in response to the operator's operation input amounts and split a flow for the plurality of hydraulic actuators. In this case, the operator is more sensitive to the change in each actuator operation in response to the load fluctuation of the actuator; thus, it is possible to ensure operability of the hydraulic excavator300at the time of the operator's operation. On the other hand, in the case in which the area limiting control function is valid, the auxiliary flow controllers21to29can supply the hydraulic fluid at the flow rate agreeable to the target flow rate commanded by the controller95to each actuator without depending on the load fluctuation of the actuator with high responsiveness and with stability; thus, it is possible to improve automatic control accuracy of the actuator. Furthermore, even in the saturated state, it is possible to maintain a flow split ratio to each actuator and to exercise automatic control without degrading actuator control accuracy. As described so far, changing over to hydraulic system characteristics suited for each of two types of operation modes, that is, an operation mode during the operator's manual operation and an operation mode during the automatic control by the controller95makes it possible to ensure demanded performances in the two operation modes.

FIGS. 7A and 7Bare circuit diagrams of a hydraulic drive system according to Embodiment 2 of the present invention.

As depicted inFIGS. 7A and 7B, a hydraulic drive system400A according to Embodiment 2 are almost similar in configurations to the hydraulic drive system400according to Embodiment 1 (depicted inFIGS. 2A and 2B) except for the following respects.

A pressure sensor111is provided at a tank line of the second boom directional control valve10, and a pressure sensor112is provided at a tank line of the first arm directional control valve11.

While partial configurations are not depicted for the sake of simple description, auxiliary flow controllers21to29and surrounding instruments, lines, and interconnections are all identical to those depicted inFIGS. 7A and 7Bin configuration. Furthermore, computing processing of the controller95is similar to that according to Embodiment 1 (depicted inFIGS. 6A, 6B, and 6C).

The hydraulic drive system400A according to Embodiment 2 is almost similar in operations to the hydraulic drive system400according to Embodiment 1 except for the following respects.

“Automatic Operation Under Area Limiting Control”

In a state in which the signal to validate the area limiting control over the hydraulic excavator300is transmitted from the control validation switch96to the controller95and an automatic operation is performed under the area limiting control, the controller95calculates the target flow rate of each actuator on the basis of the operation amounts of the boom204, the arm205, and the bucket206and the machine body operating state acquired from each pressure sensor and each stroke sensor, and also calculates the target pump flow rate of each hydraulic pump on the basis of the target flow rate of each actuator. At the same time, the controller95calculates a meter-out current flow rate of each actuator on the basis of the differential pressure across the directional control valve acquired from the pressure sensors81band112(or pressure sensors81aand112) attached to front and rear portions of the directional control valve, and the opening area characteristics of the directional control valve with respect to the pilot pressure acting on the pressure command port of the directional control valve, and also calculates the current pump flow rate of each hydraulic pump on the basis of the current flow rate of each actuator. Furthermore, the controller95calculates the pump flow rate reduction rate α on the basis of the target pump flow rate and the current pump flow rate.

According to Embodiment 2, the differential-pressure-across-valve sensor that detects the differential pressures across the plurality of directional control valves7to12and14to16is configured with fourth pressure sensors79a,81a, and the like (79b,81b, and the like) provided at hydraulic lines connecting hydraulic operating fluid discharge-side ports of the plurality of hydraulic actuators204a,205a,206a, and the like to the plurality of directional control valves7to12and14to16; and fifth pressure sensors111,112, and the like provided at hydraulic lines connecting the plurality of directional control valves7to12and14to16to a hydraulic operating fluid tank5.

Embodiment 2 configured as described so far can attain the following effects in addition to similar effects to those of Embodiment 1.

Measuring the pressure of each actuator circuit and the pressure of a tank circuit on a meter-out side of each directional control valve makes it possible to accurately calculate the current flow rate of the actuator even in a hydraulic circuit prone to a deviation between an operation of the actuator and a meter-in side flow rate such as an actuator (for example, swing motor) driving a large inertial element. It is thereby possible to calculate the current pump flow rate and the pump flow rate reduction rate a more accurately, and to operate each actuator more stably with a split flow ratio during saturation.

Embodiment 3 of the present invention will be described while mainly referring to differences from Embodiment 1.

While a hydraulic drive system according to Embodiment 3 is similar in configurations to the hydraulic drive system400according to Embodiment 1 (depicted inFIGS. 2A and 2B), a content of processing by the controller95differs from that according to Embodiment 1.

FIG. 8is a functional block diagram of the controller95according to Embodiment 3. InFIG. 8, the controller95has a flow rate correction ratio computing section95land a pressure state determination section95min addition to the configurations of the controller95according to Embodiment 1 (depicted inFIG. 5).

The flow rate correction ratio computing section95lcomputes a flow rate correction ratio β by multiplying the pump flow rate reduction rate α from the pump flow rate reduction rate computing section95hby a correction ratio γ preset to each actuator. The corrected target flow rate computing section95fcomputes the corrected target flow rate of each actuator on the basis of the target flow rate from the target flow rate computing section95eand the flow rate correction ratio β from the flow rate correction ratio computing section95l. The pressure state determination section95mdetermines an actuator having a highest load pressure among the actuators for which split flow is necessary on the basis of the pressure sensor output values of the input section95a. The output section95kgenerates command electrical signals on the basis of a determination result from the control validation determination section95b, the corrected target flow rate from the corrected target flow rate computing section95f, the pressure sensor output values from the input section95a, and a determination result of the pressure state determination section95m, and outputs the generated command electrical signals to the selector valve unit93, the solenoid proportional valve unit94, and the proportional solenoid pressure reducing valves35and36.

FIG. 6Ais a flowchart depicting computing processing by a controller95A according to Embodiment 3 of the present invention. The controller95A determines whether the control validation switch96is turned on (Step S100), executes the control invalidation processing (Step S200) in the case of determining that the control validation switch96is turned off (NO), and executes control validation processing (Step S300A) in the case of determining that the control validation switch96is turned on (YES).

FIGS. 9B and 9Care flowcharts depicting details of the control validation processing (Step S300A). InFIG. 9B, Steps S301to S317are similar to those according to Embodiment 1 (depicted inFIG. 6C).

In a case of determining in Step S312that the hydraulic pump is in a saturated state (YES), the controller95causes the flow rate correction ratio computing section95lto calculate the flow rate correction ratio β by multiplying the pump flow rate reduction rate α by the correction coefficient γ preset to the actuator subjected to flow control (Step S341), causes the corrected target flow rate computing section95fto calculate the corrected target flow rate by multiplying the target flow rate of the actuator subjected to the flow control by the flow rate correction ratio β (Step S342), causes the output section95kto calculate the command electrical signals on the basis of the corrected target flow rate and the differential pressures across the auxiliary flow controllers24and25(Step S343), and causes the pressure state determination section95mto determine whether the load pressure of the actuator subjected to the flow control is highest among the actuators subjected to split flow on the basis of the pressure sensor output values from the input section95a(Step S345).

In a case of determining in Step S345that the load pressure of the actuator subjected to the flow control is not the highest load pressure among those of the actuators subjected to split flow (NO), the controller95causes the output section95kto output the command electrical signals to the proportional solenoid pressure reducing valves35and36(Step S346), opens the pilot variable throttles32and34in response to the command pressures from the proportional solenoid pressure reducing valves35and36(Step S347), opens the main valves31and33of the auxiliary flow controllers24and25in response to the openings of the pilot variable throttles (Step S348), controls the flow rates of the main valves31and33(flow rates delivered to the actuators from the directional control valves) (Step S349), and ends the control validation processing (Step S300).

In a case of determining in Step S345that the load pressure of the actuator subjected to the flow control is the highest among the actuators subjected to split flow (YES), the controller95causes the output section95knot to output command electrical signals to the proportional solenoid pressure reducing valves35and36(Step S344), fully opens the pilot variable throttles32and34in response to the command pressures (tank pressures) from the proportional solenoid pressure reducing valves35and36(Step S345), fully opens the main valves31and33of the auxiliary flow controllers24and25in response to the openings of the pilot variable throttles (Step S346), and ends the control validation processing (Step S300a).

Here, the flow rate correction ratio β, is obtained by a product between the correction coefficient γ set to each actuator and the pump flow rate reduction rate α, as depicted inFIG. 10A. In addition, the correction coefficient γ is not always constant, and may vary depending on a load pressure P1of the actuator, as exemplarily depicted inFIG. 10B.

While the directional control valves, the auxiliary flow controllers, and the proportional solenoid pressure reducing valves for the boom204and the arm205are referred to as specific objects to be controlled in the above description, the flows depicted inFIGS. 9A to 9Care executed with respect to all of the directional control valves, the auxiliary flow controllers, and the proportional solenoid pressure reducing valves including those not depicted. Furthermore, while a case of setting high the flow rate correction ratio β of each of the actuators (swing motor and boom cylinder204a) each of which drives a large inertial element and the flow rate change of each of which has a great influence on the behavior of the inertial element is exemplarily described above, the flow rate correction ratio β of each actuator is set optionally by a designer or the like in accordance with the hydraulic system, a running condition, and the like, and not limited to the content exemplarily described.

The hydraulic drive system according to Embodiment 3 is almost similar in operations to the hydraulic drive system400according to Embodiment 1 except for the following respects.

“Automatic Operation Under Area Limiting Control”

In a state in which the signal to validate the area limiting control over the hydraulic excavator300is transmitted from the control validation switch96to the controller95and an automatic operation is performed under the area limiting control, the controller95A calculates the target flow rate of each actuator on the basis of the operation amounts of the boom204, the arm205, and the bucket206and the machine body operating state acquired from each pressure sensor and each stroke sensor, and also calculates the target pump flow rate of each hydraulic pump on the basis of the target flow rate of each actuator. At the same time, the controller95A calculates a meter-in side current flow rate of each actuator from the differential pressure across the directional control valve acquired from the pressure sensors80and81b(or pressure sensors80and81a) attached to front and rear portions of the directional control valve and an opening area calculated on the basis of the opening area characteristics of the directional control valve with respect to the pilot pressure acting on the pressure command port of the directional control valve, and also calculates the current pump flow rate of each hydraulic pump on the basis of the current flow rate of each actuator. Furthermore, the controller95A calculates the pump flow rate reduction rate α on the basis of the target pump flow rate and the current pump flow rate.

In the case of the pump flow rate reduction rate α=1, the controller95calculates the command electrical signal on the basis of the target flow rate of the main valve33and the differential pressure across the auxiliary flow controller25obtained from the pressure sensors77and80without correcting the target flow rate, and outputs the command to the pilot variable throttle34via the proportional solenoid pressure reducing valve36.

In the case of the pump flow rate reduction rate α<1, the controller95A calculates the flow rate correction ratio β, (corrected pump flow rate reduction rate) by multiplying the pump flow rate reduction rate α by the correction coefficient γ preset to each actuator. Furthermore, the controller95A calculates the corrected target flow rate by multiplying the target flow rate of each actuator by the flow rate correction ratio R, and calculates a target command electrical signal on the basis of the corrected target flow rate of the main valve33and the differential pressure across the auxiliary flow controller25obtained from the pressure sensors77and80. At the same time, the controller95determines whether the load pressure of the actuator subjected to the flow control is highest among the actuators subjected to the split flow from the pressure sensor output values.

In the case in which the load pressure of the actuator subjected to the flow control is not the highest load pressure among those of the actuators subjected to split flow, then the controller95A outputs the target command electrical signal to the proportional solenoid pressure reducing valve36, and the proportional solenoid pressure reducing valve36outputs an operation pressure of the hydraulic variable throttle valve34upon receiving the target command electrical signal.

In the case in which the load pressure of the actuator subjected to the flow control is highest among the actuators subjected to split flow, then the controller95A does not output the target command electrical signal to the proportional solenoid pressure reducing valve36, and the proportional solenoid pressure reducing valve36outputs a tank pressure as the operation pressure of the hydraulic variable throttle valve34, thereby fully opening the main valve33.

While the operation of the auxiliary flow controller25has been described above, the other auxiliary flow controller operate similarly.

According to Embodiment 3, the controller95corrects the pump flow rate reduction rate α by multiplying the pump flow rate reduction rate α by a correction coefficient γ preset to each of the plurality of hydraulic actuators204a,205a,206a, and the like, and controls the plurality of auxiliary flow controllers21to29in such a manner that the supply flow rates to the plurality of directional control valves7to12and14to16from the hydraulic pumps1,2, and3are reduced in response to a pump flow rate reduction rate β corrected for each of the plurality of hydraulic actuators204a,205a,206a, and the like in a case in which the control validation switch96issues an instruction to validate the area limiting control function and saturation occurs.

Embodiment 3 configured as described so far can attain the following effects in addition to similar effects to those of Embodiment 1.

In a case in which the actual pump delivery flow rate is lower than the target pump flow rate and the state turns into the saturated state due to the horsepower control over the pump accompanying with an increase in the load pressure of each actuator, it is possible to enhance stability of the behavior of the actuator during saturation and to operate the actuator more stably by correcting the pump flow rate reduction rate α to be increased for the actuator (for example, swing motor) having a large inertial element, preferentially delivering the hydraulic fluid to the actuator, and thereby reducing a flow rate decreasing amount with respect to the saturation.

While the embodiments of the present invention have been described in detail, the present invention is not limited to the embodiments and encompasses various modifications. For example, the above embodiments have been described in detail for facilitating understanding the present invention, and the present invention is not always limited to the embodiments having all the configurations described above. Moreover, part of the configurations of the other embodiment can be added to the configurations of a certain embodiment, and part of the configurations of the certain embodiment can be deleted or can be replaced by part of the configurations of the other embodiment.

DESCRIPTION OF REFERENCE CHARACTERS

1: First hydraulic pump1a: Flow control command pressure port (regulator)1b: First hydraulic pump self-pressure port (regulator)1c: Second hydraulic pump self-pressure port (regulator)2: Second hydraulic pump2a: Flow control command pressure port (regulator)2b: First hydraulic pump self-pressure port (regulator)2c: Second hydraulic pump self-pressure port (regulator)3: Third hydraulic pump3a: Flow control command pressure port (regulator)3b: Third hydraulic pump self-pressure port (regulator)4: Pilot pump5: Hydraulic operating fluid tank6: Right travel directional control valve7: Bucket directional control valve8: Second arm directional control valve9: First boom directional control valve10: Second boom directional control valve11: First arm directional control valve12: First attachment directional control valve13: Left travel directional control valve14: Swing directional control valve15: Third boom directional control valve16: Second attachment directional control valve17: Merging valve21: Bucket auxiliary flow controller22: Second arm auxiliary flow controller23: First boom auxiliary flow controller24: Second boom auxiliary flow controller25: First arm auxiliary flow controller26: First attachment auxiliary flow controller27: Swing auxiliary flow controller28: Third boom auxiliary flow controller29: Second attachment auxiliary flow controller31: Main valve31a: Valve body31b: Feedback throttle (control variable throttle)31c: First pressure chamber31d: Second pressure chamber31e: Third pressure chamber32: Hydraulic variable throttle valve (pilot variable throttle)32a: Pressure signal port33: Main valve33a: Valve body33b: Feedback throttle (control variable throttle)33c: First pressure chamber33d: second pressure chamber33e: Third pressure chamber34: Hydraulic variable throttle valve (pilot variable throttle)34a: Pressure signal port35: Proportional solenoid pressure reducing valve35a: Solenoid36: Proportional solenoid pressure reducing valve36a: Solenoid41to62: Line63: Pilot line63a,63b,63c: Line64: Pilot line64a,64b,64c: Line65to67: Line71a,71b,72a,72b,73a,73b: Pressure sensor74,75,76: Stroke sensor77,78,79a,79b,80,81a,81b: Pressure sensor91a,91b: Operation lever (operation lever device)92a,92b: Pilot valve93: Selector valve unit (operation pressure generation valve device)93a: Solenoid selector valve94: Solenoid proportional valve unit (operation pressure generation valve device)94a: Proportional solenoid pressure reducing valve95,95A: Controller95a: Input section95b: Control validation determination section95c: Machine body posture computing section95d: Demanded flow rate computing section95e: Target flow rate computing section95f: Corrected target flow rate computing section95g: Target pump flow rate computing section95h: Pump flow rate reduction rate computing section95i: Actuator flow rate computing section95j: Current pump flow rate computing section95k: Output section95l: Flow rate correction ratio computing section95m: Pressure state determination section96: Control validation switch97to101: Line111,112: Pressure sensor201: Travel structure202: Swing structure203: Work device204: Boom204a: Boom cylinder (hydraulic actuator)205: Arm205a: Arm cylinder (hydraulic actuator)206: Bucket206a: Bucket cylinder (hydraulic actuator)207: Cabin208: Machine room209: Counterweight210: Control valve300: Hydraulic excavator (work machine)400,400A: hydraulic drive system