Construction machine

Abstract

To provide a construction machine which can reduce fluid resistance when a hydraulic oil passes through a control valve, by achieving optimization of a relation between a flow rate of the hydraulic oil supplied to the control valve from a hydraulic pump and an opening of the control valve.SOLUTION: A construction machine includes a controller 100. The controller 100 is constituted so as to execute pump flow rate control processing and actuator control processing. In the pump flow rate control processing, discharge flow rate control of a hydraulic pump including feedback control which reduces a differential value between an actual discharge flow rate of the hydraulic pump acquired by pump actual discharge flow rate acquisition processing and a target discharge flow rate of the same, via a regulator 29. In the actuator control processing, supply flow rate control of a hydraulic oil to a hydraulic actuator including feedback control which reduces a differential value between an actual supply flow rate of the hydraulic oil to the hydraulic actuator acquired by actuator actual supply flow rate acquisition processing and a target supply flow rate of the same, via a control valve.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a construction machine. [Background technology]

[0002] Conventionally, construction machines such as hydraulic excavators are equipped with a hydraulic drive system for driving a plurality of hydraulic actuators. This hydraulic drive system has a hydraulic pump driven by a drive source such as an engine, and drives the plurality of hydraulic actuators with hydraulic oil discharged from the hydraulic pump. Patent Document 1 listed below discloses an example of this type of hydraulic drive system.

[0003] This hydraulic drive device includes a pump regulator that controls the displacement volume of the hydraulic pump, an operation means that controls the stroke amount of a plurality of directional control valves (control valves) for distributing the hydraulic oil discharged from the hydraulic pump to each hydraulic actuator, a detection means that detects the operation amount of the operation means, a setting means that sets a target flow rate of the hydraulic oil to be supplied to the hydraulic actuator in accordance with the operation amount detected by the detection means, a flow rate determination means that determines the flow rate (actual flow rate) of the hydraulic oil actually supplied to the hydraulic actuator, and a regulator control means that controls the operation of the pump regulator so that the actual flow rate of the hydraulic oil determined by the flow rate determination means approaches the target flow rate.

[0004] According to this configuration, when the operating means is operated, the opening of the directional control valve of the hydraulic actuator corresponding to the operation is feedforward controlled to a predetermined opening according to the amount of operation. Then, with the opening of the actuator directional control valve controlled to the predetermined opening by this feedforward control, the discharge flow rate of the hydraulic pump is feedback controlled via the regulator control means so that the flow rate (actual flow rate) of the hydraulic oil actually supplied to each hydraulic actuator approaches the target flow rate (see FIG. 11 of Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 1994 / 21925 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the conventional construction machine shown in Patent Document 1, matching between the supply flow rate control of the hydraulic oil via the directional control valve for the actuator (control valve for the actuator) and the discharge flow rate control of the pump via the pump regulator (i.e., optimizing the relationship between the opening degree of the control valve and the flow rate of the hydraulic oil supplied to the control valve) is not attempted. For this reason, the supply flow rate of the hydraulic oil supplied to the control valve may become excessive with respect to the opening degree of the control valve. If the supply flow rate of the hydraulic oil supplied to the control valve becomes excessive, the fluid resistance increases when the hydraulic oil passes through the control valve, increasing the required driving force of the hydraulic pump, which in turn causes a problem of a decrease in the energy efficiency of the entire construction machine.

[0007] The present invention has been made to solve the above-mentioned problems, and aims to reduce the fluid resistance when the hydraulic oil passes through the control valve by optimizing the relationship between the flow rate of the hydraulic oil supplied from the hydraulic pump to the control valve and the opening degree of the control valve, thereby reducing the driving power of the hydraulic pump. [Means for solving the problem]

[0008] In a first aspect of the present invention, a construction machine includes a drive source, a hydraulic pump driven by the drive source, a regulator capable of changing a flow rate of hydraulic oil discharged from the hydraulic pump, a hydraulic actuator driven by the hydraulic oil discharged from the hydraulic pump, a control valve capable of changing the flow rate of hydraulic oil supplied to the hydraulic actuator, an operation device including an operation member to which an operation for driving the hydraulic actuator is applied and outputting an operation signal corresponding to the operation of the operation member, and a controller, and the controller performs an actuator actual supply flow rate acquisition process for acquiring an actual supply flow rate of hydraulic oil supplied to the hydraulic actuator, an actuator target supply flow rate calculation process for calculating a target supply flow rate of the hydraulic oil to the hydraulic actuator based on the operation signal output from the operation device, and a controller for controlling the hydraulic pump based on the target supply flow rate calculated by the actuator target supply flow rate calculation process. a pump actual discharge flow rate acquisition process that acquires an actual discharge flow rate of hydraulic oil discharged from the hydraulic pump; a pump flow rate control process that performs, via the regulator, control of the discharge flow rate of the hydraulic pump, including feedback control for reducing a difference value between the actual discharge flow rate of the hydraulic pump acquired by the pump actual discharge flow rate acquisition process and the target discharge flow rate of the hydraulic pump calculated by the pump target discharge flow rate calculation process; and an actuator flow rate control process that performs, via the control valve, control of the supply flow rate of hydraulic oil to the hydraulic actuator, including feedback control for reducing a difference value between the actual supply flow rate of hydraulic oil to the hydraulic actuator acquired by the actuator actual supply flow rate acquisition process and the target supply flow rate of hydraulic oil to the hydraulic actuator calculated by the actuator target supply flow rate calculation process.

[0009] According to this configuration, by executing both the discharge flow rate control of the hydraulic pump and the supply flow rate control of the hydraulic oil to the hydraulic actuator so as to include feedback control, it is possible to optimize (match) the relationship between the actual supply flow rate of the hydraulic oil supplied from the hydraulic pump to the control valve and the opening of the control valve, thereby reducing the fluid resistance when the hydraulic oil passes through the control valve. That is, when the discharge flow rate of the hydraulic oil from the hydraulic pump is feedback-controlled via a regulator and the supply flow rate of the hydraulic oil to the hydraulic actuator is feedforward-controlled via a control valve, as in the conventional case, a situation may occur in which the opening of the control valve is too small for the supply flow rate of the hydraulic oil supplied from the hydraulic pump. As a result, the fluid resistance when the hydraulic oil passes through the control valve increases, which increases the driving power of the hydraulic pump, and ultimately causes a problem of a decrease in the energy efficiency of the entire construction machine. In contrast, according to the present configuration, not only the actual discharge flow rate of the hydraulic pump but also the actual supply flow rate of hydraulic oil to each actuator is controlled based on feedback control, so that the relationship between the actual supply flow rate of hydraulic oil supplied from the hydraulic pump to the control valve and the opening degree of the control valve can be optimized to prevent excess supply of hydraulic oil to the control valve, thereby avoiding the problem of reduced energy efficiency caused by an increase in the driving power of the hydraulic pump described above.

[0010] In a second invention, in the first invention, a plurality of the hydraulic actuators are provided, and the control valve is provided for each of the plurality of hydraulic actuators, the actuator actual supply flow rate acquisition process is a process of acquiring an actual supply flow rate of the hydraulic oil supplied to each of the plurality of hydraulic actuators, the actuator target supply flow rate calculation process is a process of calculating a target supply flow rate of the hydraulic oil for each of the plurality of hydraulic actuators, the pump actual discharge flow rate acquisition process is a process of calculating a sum of the actual supply flow rates of the hydraulic oil supplied to each of the plurality of hydraulic actuators and acquiring the calculated sum as the actual discharge flow rate of the hydraulic pump, and the pump target discharge flow rate calculation process is a process of calculating the sum of the target supply flow rates of each of the plurality of hydraulic actuators calculated by the actuator target supply flow rate calculation process. It is preferable that the feedback control included in the pump flow rate control process is control to operate the regulator so as to reduce a difference value between the actual discharge flow rate of the hydraulic pump acquired by the pump actual discharge flow rate acquisition process and the target discharge flow rate of the hydraulic pump, which is the sum of the target supply flow rates of the multiple hydraulic actuators calculated by the pump target discharge flow rate calculation process, and that the feedback control included in the actuator flow rate control process is control to operate the control valve so as to reduce a difference value between the actual supply flow rate of hydraulic oil of each of the multiple hydraulic actuators acquired by the actuator actual supply flow rate acquisition process and the target supply flow rate of hydraulic oil of each of the multiple hydraulic actuators calculated by the actuator target supply flow rate calculation process.

[0011] According to this configuration, when a construction machine has multiple hydraulic actuators, the relationship between the opening degree of each control valve provided for each hydraulic actuator and the actual supply flow rate of hydraulic oil supplied from the hydraulic pump to each control valve can be optimized to reduce the fluid resistance when the hydraulic oil passes through each control valve. That is, according to this configuration, the discharge flow rate control of the hydraulic pump is executed in parallel with the feedback control of the supply flow rate of hydraulic oil to each actuator via each control valve. In this discharge flow rate control of the hydraulic pump, the actual discharge flow rate of the hydraulic pump is feedback-controlled so that the total value of the actual supply flow rate of hydraulic oil supplied from the hydraulic pump to each hydraulic actuator (i.e., the actual discharge flow rate of the hydraulic pump) approaches the target discharge flow rate (more specifically, so that the difference between the total value and the target discharge flow rate becomes small). Therefore, by controlling the aperture of each control valve while statically determining the total value of the hydraulic oil supplied to each hydraulic actuator, it is possible to prevent control interference (a situation in which an event occurs in which one is stabilized and then the other is destabilized, causing the controlled quantity to oscillate and not converge) between the control of the discharge flow rate of the hydraulic pump and the control of the supply flow rate of the hydraulic oil to each actuator by each control valve. By extension, it is possible to reduce the drive power of the hydraulic pump by optimizing the actual supply flow rate of the hydraulic oil supplied from the hydraulic pump to each control valve and the aperture of each control valve.

[0012] In a third invention, in the second invention, it is preferable that the responsiveness of the discharge flow rate control of the hydraulic pump in the pump flow rate control process is lower than the responsiveness of the supply flow rate control of the hydraulic oil to each hydraulic actuator in the actuator flow rate control process.

[0013] According to this configuration, by making the responsiveness of the discharge flow rate control of each hydraulic pump lower than the responsiveness of the supply flow rate control of the hydraulic oil to each hydraulic actuator, it is possible to prevent an excessive supply of hydraulic oil from the hydraulic pump to each control valve that controls the supply flow rate of the hydraulic oil to each hydraulic actuator. Therefore, the passage resistance (fluid resistance) of the hydraulic oil in each control valve is suppressed, and the drive power of the hydraulic pump can be reduced.

[0014] According to a fourth aspect of the present invention, in the third aspect of the present invention, in the pump flow rate control process, a pump flow rate command signal specifying a discharge flow rate of the hydraulic oil discharged from the hydraulic pump is output from the controller, and the regulator is configured to operate the hydraulic pump at a discharge flow rate corresponding to the pump flow rate command signal output from the controller by the pump flow rate control process. In the pump flow rate control process, when the discharge flow rate control is executed, a control for outputting the pump flow rate command signal for reducing a deviation between a target discharge flow rate of the hydraulic oil to the hydraulic pump calculated by the pump target discharge flow rate calculation process and an actual discharge flow rate of the hydraulic oil to the hydraulic pump calculated by the pump actual discharge flow rate acquisition process is executed as the feedback control, and a feedforward control for outputting the pump flow rate command signal set in advance according to the target discharge flow rate of the hydraulic pump is executed in parallel with the feedback control. In the actuator flow rate control process, an actuator flow rate command signal specifying a supply flow rate of the hydraulic oil to be supplied to each of the plurality of hydraulic actuators is output from the controller, and a plurality of control valves are configured to supply hydraulic oil at a flow rate corresponding to an actuator flow rate command signal output from the controller by the actuator flow rate control process to each hydraulic actuator corresponding to each control valve, and in the actuator flow rate control process, when executing the supply flow rate control, a control is executed as the feedback control to output an actuator flow rate command signal for reducing a deviation between a target supply flow rate of the hydraulic oil to the plurality of hydraulic actuators calculated by the actuator target supply flow rate calculation process and an actual supply flow rate of the hydraulic oil to each hydraulic actuator acquired by the actuator actual supply flow rate acquisition process, and a feedforward control is executed in parallel with the feedback control to calculate and output a preset actuator flow rate command signal corresponding to the target supply flow rate of the hydraulic oil to each hydraulic actuator, and in the pump flow rate control process, when executing the feedforward control, the target discharge flow rate of the hydraulic pump, which is an input of the feedforward control, is corrected by multiplying it by a preset correction factor that is greater than 0 and less than 1,It is preferable to output a preset pump flow rate command signal corresponding to the corrected target discharge flow rate, thereby making the responsiveness of the discharge flow rate control of the hydraulic pump lower than the responsiveness of the supply flow rate control of the hydraulic oil to each of the hydraulic actuators.

[0015] According to this configuration, the discharge flow rate control of the hydraulic pump and the supply flow rate control of the hydraulic oil to each hydraulic actuator are realized by combining feedback control and feedforward control, and the target discharge flow rate of the feedforward control executed in the discharge flow rate control of the hydraulic pump is corrected to a smaller value than the actual value by multiplying it by a predetermined correction factor that is greater than 0 and smaller than 1, so that the responsiveness of the discharge flow rate control of the hydraulic pump can be easily reduced by a simple calculation. Also, the responsiveness of the discharge flow rate control of the hydraulic pump can be easily adjusted by simply adjusting this correction factor without changing the hardware configuration.

[0016] A fifth aspect of the invention is directed to the fourth aspect of the invention, further comprising a memory unit which pre-stores feedforward corresponding data which specifies the supply flow rate of hydraulic oil to each of the plurality of hydraulic actuators and an actuator flow command signal corresponding to the supply flow rate, and in the actuator flow control process, when executing the feedforward control, the actuator flow command signal for each of the hydraulic actuators is calculated and output based on the target supply flow rate of hydraulic oil to each of the hydraulic actuators calculated by the actuator target supply flow rate calculation process and the feedforward corresponding data stored in the memory unit, and it is preferable that the feedforward corresponding data is set so that each control valve corresponding to each of the plurality of hydraulic actuators does not operate at a dead band opening which does not follow changes in the actuator flow command signal.

[0017] According to this configuration, when controlling the supply flow rate of hydraulic oil to each hydraulic actuator, the opening control of each control valve based on the feedforward control can be quickly controlled without being affected by the dead zone of each control valve. Therefore, the operation delay (time lag) of each control valve can be reduced to improve the operation response. This makes it possible to prevent an excessive supply of hydraulic oil to each control valve due to a delay in the operation of each control valve during, for example, an increase in the flow rate of the hydraulic pump. In turn, the fluid resistance when the hydraulic oil passes through each control valve can be reduced to reduce the drive power of the hydraulic pump.

[0018] A sixth invention is the first invention, further comprising a machine body, a rotating body mounted on the machine body so as to be rotatable about a predetermined rotating axis, a hydraulic rotating motor for driving the rotating body about the predetermined rotating axis, a work attachment mounted on the rotating body, and a hydraulic working cylinder for driving the work attachment, wherein a plurality of hydraulic actuators are provided, and the plurality of hydraulic actuators include the swing motor and the working cylinder, and the pump actual discharge flow rate acquisition process acquires an actual discharge flow rate for work supplied to the working cylinder out of the actual discharge flow rates of hydraulic oil discharged from the hydraulic pump, and an actual discharge flow rate for swing supplied to the swing motor out of the actual discharge flow rates of hydraulic oil discharged from the hydraulic pump, and the pump target discharge flow rate calculation process acquires a target supply flow rate of hydraulic oil to the working cylinder calculated by the actuator target supply flow rate calculation process as a working target discharge flow rate which is the flow rate of hydraulic oil to be supplied to the working cylinder out of the hydraulic oil discharged from the hydraulic pump, and the actuator target supply flow rate calculation process acquires a target supply flow rate of hydraulic oil to the working cylinder calculated by the actuator target supply flow rate calculation process as a working target discharge flow rate which is the flow rate of hydraulic oil to be supplied to the working cylinder out of the hydraulic oil discharged from the hydraulic pump, and a target supply flow rate of hydraulic oil to the swing motor outputted from the hydraulic pump is calculated as a target discharge flow rate for swing, which is the flow rate of hydraulic oil to be supplied to the swing motor from the hydraulic pump, and the pump flow rate control process includes a work pump flow rate control process that performs discharge flow rate control of the hydraulic pump via the regulator, including feedback control that reduces a difference value between the actual discharge flow rate for work acquired by the actual pump discharge flow rate acquisition process and the target discharge flow rate for work calculated by the target pump discharge flow rate calculation process, and a swing pump flow rate control process that performs discharge flow rate control of the hydraulic pump via the regulator, including feedback control that reduces a difference value between the actual discharge flow rate for swing acquired by the actual pump discharge flow rate acquisition process and the target discharge flow rate for swing calculated by the target pump discharge flow rate calculation process, and it is preferable that the responsiveness of the feedback control performed in the swing pump flow rate control process is reduced below the responsiveness of the feedback control performed in the work pump flow rate control process.

[0019] According to this configuration, it is possible to prevent the actual supply flow rate of hydraulic oil to the swing motor from being excessively large relative to the opening of the control valve for the swing motor. That is, after intensive research, the inventors have found that the dynamic characteristics of the swing motor are gentler than the dynamic characteristics of the working cylinder. In this configuration, based on such knowledge, the pump flow rate control section is composed of a swing pump flow rate control section and a working pump flow rate control section, and the responsiveness of the feedback control in the discharge flow rate control of the hydraulic oil for the swing motor executed by the swing pump flow rate control section is made lower than the responsiveness of the feedback control in the discharge flow rate control of the hydraulic oil for the working cylinder executed by the working pump flow rate control section (by gently following the target of the discharge flow rate of the hydraulic oil for the swing motor), thereby preventing the hydraulic oil from being excessively supplied to the control valve for the swing motor. This reduces the fluid resistance when the hydraulic oil passes through the control valve for the swing motor, reducing the driving power of the hydraulic pump, and ultimately preventing a decrease in the energy efficiency of the entire construction machine. Effect of the Invention

[0020] According to the present invention, by optimizing the relationship between the flow rate of hydraulic oil supplied from the hydraulic pump to the control valve and the opening degree of the control valve, the fluid resistance when the hydraulic oil passes through the control valve can be reduced, thereby reducing the driving power of the hydraulic pump. [Brief description of the drawings]

[0021] [Figure 1] 1 is a schematic diagram showing an overall configuration of a hydraulic excavator according to a first embodiment of the present invention. FIG. [Diagram 2] FIG. 2 is a circuit diagram showing hydraulic circuit sections related to a boom cylinder and a bucket cylinder extracted from a hydraulic circuit provided in the hydraulic excavator. [Diagram 3] FIG. 2 is a block diagram showing the configuration of a control system including a controller. [Figure 4A] FIG. 4 is a block diagram for illustrating an overview of feedback control and feedforward control executed by a pump flow rate control unit. [Figure 4B]FIG. 4 is a block diagram for illustrating an overview of feedback control and feedforward control executed in actuator flow control sections (boom cylinder flow control section and bucket cylinder flow control section). [Diagram 5] 11 is a graph showing the relationship between the flow rate of hydraulic oil flowing through the boom control valve and the command current of the boom pilot solenoid valve when the differential pressure ΔP between the upstream and downstream sides of the valve opening of the boom control valve is changed to three different values. [Figure 6] 5 is a flowchart showing details of the control of the discharge flow rate of the hydraulic pump and the control of the supply flow rate of hydraulic oil to the boom cylinder and the bucket cylinder, which are executed by the controller. [Figure 7] 5 is a flowchart showing details of the control of the discharge flow rate of the hydraulic pump and the control of the supply flow rate of hydraulic oil to the boom cylinder and the bucket cylinder, which are executed by the controller. [Figure 8] 6 is a graph showing the results of control of the discharge flow rate of a hydraulic pump and control of the supply flow rate of hydraulic oil to a boom cylinder and a bucket cylinder, which are executed by a controller. [Figure 9] FIG. 4 is a view corresponding to FIG. 3 and showing a comparative example of the first embodiment. [Figure 10] FIG. 11 is a circuit diagram showing hydraulic circuit sections related to an arm cylinder and a swing motor extracted from a hydraulic circuit provided in a hydraulic excavator according to a second embodiment. [Figure 11] FIG. 5 is a view corresponding to FIG. 3 and showing a second embodiment. [Figure 12] 13 is a graph showing the results of calculating, by simulation, the change over time in the flow rate of hydraulic oil actually supplied to the arm cylinder and the swing motor in the hydraulic excavator according to the second embodiment. [Figure 13] 13 is a graph showing the results of calculations, by simulation, of the change over time in the actual flow rate of hydraulic oil supplied to the arm cylinder and the swing motor in the hydraulic excavator according to a comparative example of the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0023] (First embodiment) 1 shows a hydraulic excavator A, which is an example of a construction machine according to a first embodiment of the present invention. The hydraulic excavator A includes a lower traveling body 1 (an example of a machine body), an upper rotating body 2, which is a rotating body mounted on the lower traveling body 1 so as to be rotatable about a rotating axis X, a work attachment 3 attached to the upper rotating body 2, and a swing motor 10, which is a hydraulic motor that drives the upper rotating body 2 around the rotating axis X (around the swing axis) relative to the lower traveling body 1.

[0024] A cab 2a serving as an operator's room is provided at a front portion in the front-rear direction of the upper rotating body 2, and the work attachment 3 is mounted on the cab 2a. An engine room 2b is provided at a rear portion of the upper rotating body 2.

[0025] The working attachment 3 includes a boom 4, an arm 5, a bucket 6, a boom cylinder 7, an arm cylinder 8, and a bucket cylinder 9. Each of the cylinders 7 to 9 (an example of a hydraulic actuator) is configured by an extendable hydraulic cylinder. The boom 4 has a base end connected to the upper rotating body 2 so as to be rotatable in the hoisting direction, and a tip end on the opposite side. The arm 5 has a base end rotatably connected to the tip end of the boom 4, and a tip end on the opposite side, and the bucket 6 is rotatably attached to the tip end of the arm 5. The boom cylinder 7 is interposed between the boom 4 and the upper rotating body 2 so as to hoist the boom 4 in accordance with its telescopic movement. Similarly, the arm cylinder 8 is interposed between the boom 4 and the arm 5 so as to rotate the arm 5 by its telescopic movement, and the bucket cylinder 9 is interposed between the arm 5 and the bucket 6 so as to rotate the bucket 6 by its telescopic movement.

[0026] Fig. 2 is a diagram showing a hydraulic circuit of a hydraulic excavator A according to this embodiment. As shown in Fig. 2, the hydraulic excavator A includes a hydraulic pump 20, an engine 21 (one example of a drive source), a boom control valve 22, a bucket control valve 23, a boom pilot solenoid valve 24, a bucket pilot solenoid valve 25, a relief valve 26, a first operating device 27, a second operating device 28, a boom speed sensor 35, a bucket speed sensor 36, a controller 100, and a data storage unit 110. Note that in the hydraulic circuit of Fig. 2, only a hydraulic circuit unit B1 related to the boom cylinder 7 and the bucket cylinder 9 is extracted and shown, and hydraulic circuit units related to the arm cylinder 8 and the swing motor 10 are omitted from the illustration.

[0027] The hydraulic pump 20 is a variable displacement hydraulic pump, and is connected to an output shaft of an engine 21 housed in the engine room. The hydraulic pump 20 is driven by the engine 21, thereby discharging hydraulic oil from a tank. A pump regulator 29 is attached to the hydraulic pump 20. The hydraulic pump 20 is configured to change the pump displacement by changing the tilt angle based on a command current input from a controller 100 to the pump regulator 29, thereby changing the amount of hydraulic oil discharged.

[0028] The pump regulator 29 receives an input of a command current (an example of a pump flow command signal) specifying the discharge flow rate of the hydraulic pump 20 from the controller 100, and operates the hydraulic pump 20 so that the discharge flow rate of the hydraulic pump 20 becomes a flow rate corresponding to the command current.

[0029] The boom control valve 22 (an example of a control valve) is disposed between the hydraulic pump 20 and the boom cylinder 7 to control the supply and discharge of hydraulic oil to the boom cylinder 7. The boom control valve 22 is configured, for example, as a hydraulic pilot type three-position directional control valve. Specifically, the boom control valve 22 is configured to be switchable between a neutral position where the supply and discharge of hydraulic oil to the boom cylinder 7 is stopped, a first position where the boom cylinder 7 can be driven in the extension direction, and a second position where the boom cylinder 7 can be driven in the retraction direction by changing the position of a spool accommodated therein. The boom control valve 22 strokes the spool upon receiving pilot pressure from a boom pilot solenoid valve 24 described later. The boom control valve 22 is configured to be able to adjust the supply flow rate of hydraulic oil supplied to the boom cylinder 7 by changing the stroke amount when the spool is moved from the neutral position to the first position or the second position. Thus, the boom control valve 22 functions as a control valve capable of adjusting the flow rate of hydraulic oil supplied to the boom cylinder 7. The control valve is not limited to a three-position directional control valve, and may be, for example, a throttle valve or the like provided separately from the three-position directional control valve.

[0030] The bucket control valve 23 (an example of a control valve) is disposed between the hydraulic pump 20 and the bucket cylinder 9 to control the supply and discharge of hydraulic oil to the bucket cylinder 9. The bucket control valve 23 is configured, for example, as a hydraulic pilot type three-position directional control valve. Specifically, the bucket control valve 23 is configured to be switchable between a neutral position where the supply and discharge of hydraulic oil to the bucket cylinder 9 is stopped, a first position where the bucket cylinder 9 can be driven in the extension direction, and a second position where the bucket cylinder 9 can be driven in the contraction direction by changing the position of a spool housed therein. The bucket control valve 23 strokes the spool upon receiving pilot pressure from a bucket pilot solenoid valve, which will be described later. The bucket control valve 23 is configured to be able to adjust the supply flow rate of hydraulic oil supplied to the bucket cylinder 9 by changing the stroke position of the spool in the first position or the second position. Thus, the bucket control valve 23 functions as a control valve that can adjust the flow rate of hydraulic oil supplied to the bucket cylinder 9. The control valve is not limited to a three-position directional control valve, and may be, for example, a throttle valve or the like provided separately from the three-position directional control valve.

[0031] The boom pilot solenoid valve 24 is interposed between a pilot hydraulic source (not shown, for example, a pilot pump driven by the engine 21) and the boom control valve 22. The boom pilot solenoid valve 24 opens upon receiving a command current corresponding to the operation output from the controller 100 when a boom operation is applied to an operation member 27a of a first operation device 27 described later, and supplies pilot pressure from the pilot hydraulic source to the boom control valve 22. Specifically, when a boom operation is applied to the operation member 27a, the boom pilot solenoid valve 24 opens to allow pilot pressure to be supplied to a pilot port corresponding to the direction of the boom operation, out of a pair of pilot ports provided in the boom control valve 22.

[0032] The bucket pilot solenoid valve 25 is interposed between a pilot hydraulic source (not shown) (for example, a pilot pump driven by the engine 21) and the bucket control valve 23. When a bucket operation is applied to an operating member 28a of a second operating device 28 described below, the bucket pilot solenoid valve 25 opens upon receiving a command current corresponding to the operation output from controller 100, and supplies pilot pressure from the pilot hydraulic source to the bucket control valve 23. Specifically, when a bucket operation is applied to the operating member 28a, the bucket pilot solenoid valve 25 opens to allow pilot pressure to be supplied to one of a pair of pilot ports provided in the bucket control valve 23 that corresponds to the direction of the bucket operation.

[0033] The relief valve 26 is provided in the relief flow passage 30 and operates to open and close the relief flow passage 30. The relief flow passage 30 is a flow passage that directly connects a pump line and a tank line so that the hydraulic oil discharged from the hydraulic pump 20 is released to a tank, bypassing the boom control valve 22 and the bucket control valve 23. The relief valve 26 opens so as to limit the pump pressure, which is the pressure of the hydraulic oil discharged from the hydraulic pump 20, to a pressure equal to or lower than a preset relief set pressure.

[0034] The first operating device 27 has an operating member 27a to which a boom operation is given for commanding the operation of the boom cylinder 7. The operating member 27a is provided in the cab 2a so that an operator in the cab 2a can operate it. The first operating device 27 receives a boom operation and outputs a command signal corresponding to the boom operation. The command signal output from the first operating device 27 is input to the controller 100.

[0035] The second operating device 28 has an operating member 28a to which a bucket operation is given in order to command the operation of the bucket cylinder 9. The operating member 28a is provided in the cab 2a so that an operator in the cab 2a can operate it. The second operating device 28 receives the bucket operation and outputs a command signal corresponding to the bucket operation. The command signal output from the second operating device 28 is input to the controller 100.

[0036] When the controller 100 receives an input of a command signal corresponding to the boom operation from the first operating device 27, it opens and closes the boom pilot solenoid valve 24 so that the pilot pressure corresponding to the command signal is input to the pilot port of the boom control valve 22 (the pilot port of the pair of pilot ports that corresponds to the command signal).

[0037] When controller 100 receives an input of a command signal corresponding to the bucket operation from second operating device 28, it opens and closes bucket pilot solenoid valve 25 so that pilot pressure corresponding to the command signal is input to a pilot port of bucket control valve 23 (the pilot port of the pair of pilot ports that corresponds to the command signal).

[0038] The boom speed sensor 35 is a sensor that detects the extension / retraction speed of the boom cylinder 7. The bucket speed sensor 36 is a sensor that detects the extension / retraction speed of the bucket cylinder 9. The boom speed sensor 35 and the bucket speed sensor 36 each output a speed signal indicating the detected speed to the controller 100.

[0039] The data storage unit 110 is configured, for example, with an external hard disk or the like, and stores current-flow rate correspondence data, which will be described later. Note that the function of the data storage unit 110 may be included in the controller 100.

[0040] [Controller Details] FIG. 3 is a block diagram showing a configuration of a control system including a controller 100. As shown in FIG. 3, the controller 100 is configured by a computer including, for example, a CPU, a memory, and the like. The controller 100 has, as functional units, a boom target supply flow rate calculation unit 101, a bucket target supply flow rate calculation unit 102, a pump target discharge flow rate calculation unit 103, a boom cylinder actual supply flow rate acquisition unit 104, a bucket cylinder actual supply flow rate acquisition unit 105, a pump actual discharge flow rate acquisition unit 106, a pump flow rate control unit 107, and an actuator flow rate control unit 108. The actuator flow rate control unit 108 includes a boom cylinder flow rate control unit 108a and a bucket cylinder flow rate control unit 108b. These functional units are realized by the controller 100 executing a computer program stored in advance in a storage medium such as a ROM.

[0041] Boom target supply flow rate calculation unit 101 (an example of an actuator target supply flow rate calculation unit) calculates a target supply flow rate of hydraulic oil to boom cylinder 7 corresponding to the operation amount of operating member 27a output from first operating device 27. Specifically, boom target supply flow rate calculation unit 101 receives an operation signal (e.g., a current signal) of said operating member 27a from first operating device 27, recognizes the operation amount of operating member 27a based on the received operation signal, and calculates a target supply flow rate to boom cylinder 7 based on the recognized operation amount. This target supply flow rate may be calculated based on target flow rate data in which the relationship between the operation amount of operating member 27a and the target supply flow rate of boom cylinder 7 is previously associated, or may be calculated by proportional calculation based on a target supply flow rate corresponding to a maximum operation amount of operating member 27a stored in advance.

[0042] The bucket target supply flow rate calculation unit 102 (an example of an actuator target supply flow rate calculation unit) calculates a target supply flow rate of hydraulic oil to the bucket cylinder 9 according to the operation amount of the operating member 28a output from the second operating device 28. Specifically, the bucket target supply flow rate calculation unit 102 receives an operation signal (e.g., a current signal) of the operating member 28a from the second operating device 28, recognizes the operation amount of the operating member 28a based on the received operation signal, and calculates the target supply flow rate to the bucket cylinder 9 based on the recognized operation amount. This target supply flow rate may be calculated based on target flow rate data in which the relationship between the operation amount of the operating member 28a and the target supply flow rate of the bucket cylinder 9 is previously associated, or may be calculated by proportional calculation based on a target supply flow rate corresponding to a maximum operation amount of the operating member 28a that is previously stored.

[0043] The pump target discharge flow rate calculation unit 103 calculates the total flow rate (total value) of the target supply flow rate of hydraulic oil to the boom cylinder 7 calculated by the boom target supply flow rate calculation unit 101 and the target supply flow rate of hydraulic oil to the bucket cylinder 9 calculated by the bucket target supply flow rate calculation unit 102 as the target discharge flow rate of the hydraulic pump 20.

[0044] Boom cylinder actual supply flow rate acquiring unit 104 (an example of an actuator actual supply flow rate acquiring unit) acquires the actual supply flow rate of hydraulic oil to boom cylinder 7. Specifically, boom cylinder actual supply flow rate acquiring unit 104 calculates the extension / retraction speed of boom cylinder 7 based on the speed signal received from boom speed sensor 35. Then, boom cylinder actual supply flow rate acquiring unit 104 calculates (acquires) the actual supply flow rate of hydraulic oil to boom cylinder 7 based on the extension / retraction speed of boom cylinder 7 and the cross-sectional area of ​​the cylinder chamber.

[0045] A bucket cylinder actual supply flow rate acquiring unit 105 (an example of an actuator actual supply flow rate acquiring unit) acquires the actual supply flow rate of hydraulic oil to the bucket cylinder 9. Specifically, the bucket cylinder actual supply flow rate acquiring unit 105 calculates the extension / contraction speed of the bucket cylinder 9 based on a speed signal received from the bucket speed sensor 36. Then, the bucket cylinder actual supply flow rate acquiring unit 105 calculates (acquires) the actual supply flow rate of hydraulic oil to the bucket cylinder 9 based on the extension / contraction speed of the bucket cylinder 9 and the cross-sectional area of ​​the cylinder chamber.

[0046] The pump actual discharge flow rate acquisition unit 106 calculates the sum of the actual supply flow rate of hydraulic oil to the boom cylinder 7 acquired by the boom cylinder actual supply flow rate acquisition unit 104 and the actual supply flow rate of hydraulic oil to the bucket cylinder 9 acquired by the bucket cylinder actual supply flow rate acquisition unit 105, and acquires the calculated sum as the actual discharge flow rate of the hydraulic pump 20.

[0047] The pump flow rate control unit 107 determines (calculates) a command current for operating the hydraulic pump 20 at the target discharge flow rate (for bringing the actual discharge flow rate of the hydraulic pump 20 closer to the target discharge flow rate) by executing, in parallel, a feedback control for controlling the hydraulic pump 20 via the pump regulator 29 and a feedforward control, described later, so as to reduce the difference between the actual discharge flow rate of the hydraulic pump 20 acquired by the pump actual discharge flow rate acquisition unit 106 and the target discharge flow rate of the hydraulic pump 20 calculated by the pump target discharge flow rate calculation unit 103 (in other words, so that the deviation becomes zero). The determined command current (pump flow rate command signal) is input to the pump regulator 29.

[0048] The boom cylinder flow rate control unit 108a determines (calculates) a command current for controlling the actual supply flow rate of hydraulic oil to the boom cylinder 7 to the target supply flow rate (to approach the target supply flow rate) by executing, in parallel, feedback control that controls the boom control valve 22 so as to reduce the difference value (so that the deviation becomes zero) between the actual supply flow rate of hydraulic oil to the boom cylinder 7 acquired by the boom cylinder actual supply flow rate acquisition unit 104 and the target supply flow rate of hydraulic oil to the boom cylinder 7 calculated by the boom target supply flow rate calculation unit 101, and feedforward control, which will be described later. The determined command current (actuator flow rate command signal) is input to the boom pilot solenoid valve 24.

[0049] The bucket cylinder flow rate control unit 108b determines (calculates) a command current for controlling the actual supply flow rate of hydraulic oil to the bucket cylinder 9 to the target supply flow rate (to approach the target supply flow rate) by executing, in parallel, a feedback control that controls the bucket control valve 23 so as to reduce a difference value (so that the deviation becomes zero) between the actual supply flow rate of hydraulic oil to the bucket cylinder 9 acquired by the bucket cylinder actual supply flow rate acquisition unit 105 and the target supply flow rate of hydraulic oil to the bucket cylinder 9 calculated by the bucket target supply flow rate calculation unit 102, and a feedback control described later. The determined command current (actuator flow rate command signal) is input to the bucket pilot solenoid valve 25.

[0050] FIG. 4A is a control block diagram for explaining an overview of the feedback control and feedforward control executed by pump flow rate control unit 107.

[0051] As shown in FIG. 4A, the pump flow rate control section 107 includes a feedforward control section 1071 and a feedback control section 1072.

[0052] The feedforward control unit 1071 acquires the target discharge flow rate of the hydraulic pump 20 calculated by the pump target discharge flow rate calculation unit 103, corrects the acquired target discharge flow rate by multiplying it by a correction factor G (for example, G=0.6 in this example) that is less than 1, and calculates a command current I to the pump regulator 29 based on the feedforward control based on the corrected target discharge flow rate and preset flow rate-current correspondence data (corresponding to feedforward correspondence data). FFp Determine.

[0053] Here, the flow rate-current correspondence data is graph data that specifies the correspondence relationship between the discharge flow rate of the hydraulic pump 20 (horizontal axis in the figure) and the command current to the pump regulator 29 that is required to operate the hydraulic pump 20 at this discharge flow rate (vertical axis in the figure), as shown in the block of the feedforward control unit 1071 in Fig. 4A, for example. The flow rate-current correspondence data is acquired by the manufacturer by performing operational tests and theoretical calculations in advance before product shipment, and is stored in advance in the data storage unit 110. Note that the flow rate-current correspondence data is not limited to graph data, and may be, for example, table data listing numerical values.

[0054] The feedback control unit 1072 uses feedback control to control the command current I FBp In this example, PID control is used as an example of feedback control. Specifically, the feedback control unit 1072 determines a command current I FBp Determine (calculate).

[0055] I FBp = Kp×e+Ki×∫e·dt+Kd×de / dt ···· Formula (1) Here, Kp is the proportional gain, Ki is the integral gain, Kd is the differential gain, and e is the control deviation. The control deviation e is given by the following equation (2).

[0056] Control deviation e = Qtp-Qrp Equation (2) Here, Qtp is the target discharge flow rate of the hydraulic pump 20, and Qrp is the actual discharge flow rate of the hydraulic pump 20.

[0057] The pump flow rate control unit 107 then outputs a command current I FFp and a command current I FBp The combined command current (I p =I FFp +I FBp ) is expressed as the pump command current I p to the pump regulator 29.

[0058] FIG. 4B is a control block diagram for illustrating an overview of the feedback control and feedforward control executed by boom cylinder flow control section 108a and bucket cylinder flow control section 108b (both are examples of actuator flow control sections 108).

[0059] As shown in FIG. 4B, the boom cylinder flow rate control section 108a has a feedforward control section 1081 and a feedback control section 1082.

[0060] The feedforward control unit 1081 acquires the target supply flow rate of hydraulic oil to the boom cylinder 7 calculated by the boom target supply flow rate calculation unit 101, and based on the acquired target supply flow rate and preset flow rate-current correspondence data, calculates a command current I to the boom pilot solenoid valve 24 based on the feedforward control. FFbm Determine.

[0061] Here, the flow rate-current correspondence data is composed of graph data that defines the correspondence relationship between the supply flow rate of hydraulic oil to boom cylinder 7 (horizontal axis in the figure) and the command current to boom pilot solenoid valve 24 required to ensure this supply flow rate (vertical axis in the figure), as shown in the block of feedforward control unit 1081 in Fig. 4B, for example. The flow rate-current correspondence data is obtained by the manufacturer by performing operational tests and theoretical calculations in advance before product shipment, and is stored in advance in the data storage unit 110.

[0062] Here, in this example, the flow rate-current correspondence data may be created so that the pressure difference between the upstream and downstream sides of the valve opening of the boom control valve 22 (more specifically, the pressure difference between the upstream and downstream sides of the spool) becomes a predetermined differential pressure that has been set in advance.

[0063] FIG. 5 is a graph showing the relationship between the supply flow rate of hydraulic oil to the boom control valve 22 (horizontal axis) and the command current to the boom pilot solenoid valve 24 required to ensure this supply flow rate when the differential pressure ΔP is changed to three different values ​​(vertical axis).

[0064] As shown in this figure, if the flow rate of hydraulic oil flowing through the boom control valve 22 is the same, the smaller the differential pressure ΔP, the larger the valve opening must be set to ensure the flow rate, and therefore the command current to the boom pilot solenoid valve 24 also becomes larger. That is, in FIG. 5, as the differential pressure ΔP decreases from 2.0 MPa to 1.0 MPa to 0.5 MPa, the slope of the line in the graph also becomes larger (for the same flow rate, the command current becomes larger and the valve opening also increases). However, in the case where the boom control valve 22 is configured as a spool-driven directional control valve as in this example, when the command current becomes equal to or exceeds a predetermined current Im (i.e., when the valve opening becomes equal to or exceeds a predetermined opening), a transition occurs to a dead zone (a state in which the valve opening does not change even if the command current changes and the flow rate remains constant, or a state in which the valve opening changes when the command current changes but the flow rate is small, resulting in a dead zone in the differential pressure adjustment (the differential pressure ΔP does not change)). Since the control responsiveness of the boom control valve 22 drops significantly in the dead zone, it is necessary to prevent the boom control valve 22 from transitioning to the dead zone during execution of supply flow rate control of hydraulic oil to the boom control valve 22. Therefore, in this embodiment, the target differential pressure ΔP between the upstream and downstream sides of the boom control valve 22 when creating flow rate-current correspondence data is set to a predetermined differential pressure (for example, 1.0 MPa in this example), so that the command current to the boom pilot solenoid valve 24 becomes less than the predetermined current Im in a predetermined usage flow rate range R (a range equal to or less than the maximum flow rate determined at the design stage) (in other words, the valve opening of the boom control valve 22 becomes less than the lower limit opening of the opening range that becomes the dead zone).

[0065] The feedback control unit 1082 controls the command current I FBbm In this embodiment, PID control is used as an example of the feedback control. Specifically, the feedback control unit 1082 determines a command current I FBbm Determine (calculate).

[0066] I FBbm= Kp×e+Ki×∫e·dt+Kd×de / dt...Equation (3) Here, Kp is the proportional gain, Ki is the integral gain, Kd is the differential gain, and e is the control deviation. The control deviation e is given by the following equation (4).

[0067] Control deviation e = Qtbm-Qrbm Equation (4) Here, Qtbm is the target supply flow rate of hydraulic oil to the boom cylinder 7, and Qrm is the actual supply flow rate of hydraulic oil to the boom cylinder 7.

[0068] Then, the boom cylinder flow rate control unit 108a outputs a command current I FFbm and a command current I FBbm The combined command current (I bm =I FFbm +I FBbm ) is the boom command current I bm and outputs the signal to the boom pilot solenoid valve 24.

[0069] 4B, like the boom cylinder flow control unit 108a, the bucket cylinder flow control unit 108b has a feedforward control unit 1081 and a feedback control unit 1082. The specific content of the control process and the procedure for determining the target differential pressure ΔP when creating the flow-current correspondence data are similar to the control process in the boom cylinder flow control unit 108a described above, and therefore detailed description thereof will be omitted.

[0070] Then, the bucket cylinder flow rate control unit 108b controls the command current I FFbu and a command current I FBbu The combined command current (I bu =I FFbu +IFBbu ) is expressed as the bucket command current I bu and outputs the result as the bucket pilot solenoid valve.

[0071] [Control process flow by the controller] 6 and 7 are flow charts showing the details of the discharge flow rate control of the hydraulic pump 20 and the supply flow rate control of the hydraulic oil to the boom cylinder 7 and the bucket cylinder 9, which are executed by the above-mentioned controller 100.

[0072] In step S1, it is determined whether or not operation signals for each operating member 27a, 28a have been received from the first operating device 27 and the second operating device 28. If the determination is NO, the process returns (repeats the processing of step S1), whereas if the determination is YES, the process proceeds to step S2.

[0073] In step S2, the boom target supply flow rate calculation unit 101 and the bucket target supply flow rate calculation unit 102 calculate the target supply flow rates of hydraulic oil to the boom cylinder 7 and the bucket cylinder 9, respectively.

[0074] In step S3, the pump target discharge flow rate calculation unit 103 calculates the target discharge flow rate of the hydraulic pump 20. Specifically, the pump target discharge flow rate calculation unit 103 calculates, as the target discharge flow rate of the hydraulic pump 20, the sum of the target supply flow rate of hydraulic oil to the boom cylinder 7 calculated by the boom target supply flow rate calculation unit 101 in step S2 and the target supply flow rate of hydraulic oil to the bucket cylinder 9 calculated by the bucket target supply flow rate calculation unit 102.

[0075] In step S4, the boom cylinder actual supply flow rate acquisition unit 104 and the bucket cylinder actual supply flow rate acquisition unit 105 calculate (acquire) the actual supply flow rates of hydraulic oil to the boom cylinder 7 and the bucket cylinder 9 based on the speed signals output from the boom speed sensor 35 and the bucket speed sensor 36, respectively.

[0076] In step S5, the pump actual discharge flow rate acquisition unit 106 calculates the sum of the actual supply flow rates of hydraulic oil to the boom cylinder 7 and the bucket cylinder 9 calculated in step S4, and acquires the calculated sum of the actual supply flow rates as the actual discharge flow rate of hydraulic oil by the hydraulic pump 20.

[0077] After the process of step S5, a pump flow rate control C1 in steps S6 to S10 and an actuator flow rate control C2 in steps S10 to S14 (see FIG. 7) are executed in parallel, as described below.

[0078] In the pump flow rate control C1, the pump flow rate control unit 107 executes the above-mentioned feedforward control (steps S6 and S7) and feedback control (step S8) in parallel.

[0079] Specifically, in step S6, the feedforward control unit 1071 of the pump flow rate control unit 107 multiplies the target discharge flow rate of the hydraulic pump 20 calculated in step S3 by a correction factor G that is equal to or greater than 0 and less than 1. Then, in step S7, the feedforward control unit 1071 calculates a command current to the pump regulator 29 based on the feedforward control on the basis of the corrected target discharge flow rate and the flow rate-current correspondence data, and then proceeds to step S9.

[0080] In step S8, which is executed in parallel with step S6, the feedback control unit 1072 of the pump flow control unit 107 calculates a command current (feedback control amount) to the pump regulator 29 such that the deviation between the target discharge flow rate of the hydraulic pump 20 calculated in step S3 and the actual discharge flow rate of the hydraulic pump 20 calculated in step S5 becomes zero, and then the process proceeds to step S9.

[0081] In step S9, pump flow rate control unit 107 adds together a command current to pump regulator 29 based on feedforward control taking into account correction factor G and a command current to pump regulator 29 based on feedback control.

[0082] In step S10, the pump flow rate control unit 107 outputs the command current summed in step S9 as the pump command current to the pump regulator 29. After the process of step S10 ends, the process returns to step S1.

[0083] Referring to FIG. 7, in the actuator flow rate control C2 executed after the above-mentioned step S5, feedforward control (step S11) and feedback control (step S12) are executed in parallel.

[0084] Specifically, in step S11, the feedforward control units 1081 of the boom cylinder flow control unit 108a and the bucket cylinder flow control unit 108b respectively calculate command currents to the boom pilot solenoid valve 24 and the bucket pilot solenoid valve 25 by feedforward control. Unlike the feedforward control (steps S6 and S7) in the pump flow control unit 107 described above, this feedforward control does not correct the target flow rate using the correction factor G. Therefore, the contribution rate of the feedforward control in the actuator flow control unit 108 is higher than the contribution rate of the feedforward control in the pump flow control unit 107.

[0085] In step S12 which is executed in parallel with step S11, the feedback control units 1082 of the boom cylinder flow control unit 108a and the bucket cylinder flow control unit 108b respectively calculate command currents to the boom control valve 22 and the bucket control valve 23 by the above-mentioned feedback control.

[0086] In step S13, the boom cylinder flow control unit 108a sums up the command signals to the boom pilot solenoid valve 24 based on the feedforward control and feedback control calculated in step S12. Similarly, the bucket cylinder flow control unit 108b sums up the command currents to the bucket pilot solenoid valve 25 based on the feedforward control and feedback control calculated in step S12.

[0087] In step S14, the boom cylinder flow rate control unit 108a and the bucket cylinder flow rate control unit 108b output the command currents added together in step S13 as a boom command current and a bucket command current to the boom pilot solenoid valve 24 and the bucket pilot solenoid valve 25. After the processing of step S14 ends, the process returns to step S1.

[0088] 8 is a graph showing the results of control of the discharge flow rate of the hydraulic pump 20 and control of the supply flow rate of hydraulic oil to the boom cylinder 7 and the bucket cylinder 9, which are executed by the controller 100. The horizontal axis of this graph indicates time, and the vertical axis indicates flow rate. Line F1 indicates the target discharge flow rate of the hydraulic pump 20, line F2 indicates the target supply flow rate of hydraulic oil to the boom cylinder 7, and line F3 indicates the target supply flow rate of hydraulic oil to the bucket cylinder 9. Also, line f1 indicates the actual discharge flow rate of the hydraulic pump 20, line f2 indicates the actual supply flow rate of hydraulic oil to the boom cylinder 7, and line f3 indicates the actual supply flow rate of hydraulic oil to the bucket cylinder 9.

[0089] In this example graph, control of the discharge flow rate of the hydraulic pump 20 and control of the supply flow rate of hydraulic oil to each of the cylinders 7, 9 are started at time t1. It can be seen that between time t2 and time t3, the actual supply flow rate of hydraulic oil to at least one of the boom cylinder 7 and the bucket cylinder 9 deviates from the target supply flow rate due to disturbances, etc., and the actual discharge flow rate of the hydraulic pump 20 also deviates from the target discharge flow rate. It can be seen that from time t3 onwards, first, the actual discharge flow rate of the hydraulic pump 20 converges (sets) to the target discharge flow rate due to the effect of the feedback control described above, and then the actual supply flow rates of hydraulic oil to the boom cylinder 7 and the bucket cylinder 9 converge (sets) to the target supply flow rate due to the effect of the feedback control described above.

[0090] As described above, in this embodiment, by executing both the control of the discharge flow rate of hydraulic oil by the hydraulic pump 20 and the control of the supply flow rate of hydraulic oil to the boom cylinder 7 and the bucket cylinder 9 so as to include feedback control, it is possible to optimize the relationship between the flow rate of hydraulic oil supplied from the hydraulic pump 20 to the boom control valve 22 and the bucket control valve 23 (one example of a control valve) and the opening degree of each control valve 22, 23, thereby reducing the fluid resistance when the hydraulic oil passes through each control valve 22, 23. This in turn makes it possible to reduce the drive power of the hydraulic pump 20 and improve the energy efficiency of the entire hydraulic excavator A.

[0091] Furthermore, in this embodiment, the feedback control by the pump flow rate control unit 107 is performed so as to reduce the difference between the actual discharge flow rate of the hydraulic pump 20 acquired by the pump actual discharge flow rate acquisition unit 106 and the target discharge flow rate of the hydraulic pump 20, which is the total value of the target supply flow rates to the boom cylinder 7 and the bucket cylinder 9 (one example of a plurality of hydraulic actuators) calculated by the pump target discharge flow rate calculation unit 103.

[0092] According to this configuration, by controlling the apertures of the boom cylinder 7 and the bucket cylinder 9 while converging the discharge flow rate of the hydraulic pump 20, which is the total value of the hydraulic oil to be supplied to the boom cylinder 7 and the bucket cylinder 9, to a target discharge flow rate, it is possible to prevent control interference (a situation in which an event in which one is stabilized and then the other is destabilized is repeated, causing the controlled quantity to oscillate and not converge) between the control of the discharge flow rate of the hydraulic pump 20 and the control of the supply flow rate of hydraulic oil to the boom cylinder 7 and the bucket cylinder 9 by the boom control valve 22 and the bucket control valve 23. Furthermore, it is possible to optimize the relationship between the flow rates of hydraulic oil supplied from the hydraulic pump 20 to the boom control valve 22 and the bucket control valve 23, respectively, and the apertures of the control valves 22, 23, thereby suppressing the occurrence of fluid resistance.

[0093] Fig. 9 is a comparative example for explaining this effect. In Fig. 9, the same names are used for functional parts similar to those of the controller in Fig. 3, but the reference numerals are changed from the 100s to the 200s. Controller 200 of the comparative example has pump flow control section 207 composed of boom pump flow control section 207a and bucket pump flow control section 207b, and differs from this embodiment in that boom pump flow control section 207a and bucket pump flow control section 207b each independently execute feedback control. That is, in the controller 200 of the comparative example, the boom pump flow rate control unit 207a performs feedback control so as to bring the difference value between the actual discharge flow rate for boom cylinder 7 (equal to the actual supply flow rate acquired by the boom cylinder actual supply flow rate acquisition unit 204) among the actual discharge flow rates of the hydraulic pump 20 and its target discharge flow rate (equal to the target supply flow rate calculated by the boom target supply flow rate calculation unit 201) closer to zero, and the bucket pump flow rate control unit 207b performs feedback control so as to bring the difference value between the actual discharge flow rate for bucket cylinder 9 (equal to the actual supply flow rate acquired by the bucket cylinder actual supply flow rate acquisition unit 205) among the actual discharge flow rates of the hydraulic pump 20 and its target discharge flow rate (equal to the target supply flow rate calculated by the bucket target supply flow rate calculation unit 202) closer to zero. In this manner, in a configuration in which the boom pump flow control section 207a and the bucket pump flow control section 207b each independently execute feedback control, the command current will not stabilize unless the controlled flow rates in each pump flow control section 207a, 207b and each cylinder flow control section 208a, 208b simultaneously track the target.

[0094] In contrast to this, in this embodiment, even if the target tracking of the supply flow rate control of the hydraulic oil to the boom cylinder 7 and the bucket cylinder 9 is not established, the command current is stabilized as long as the actual discharge flow rate of the hydraulic pump 20 calculated as the sum of the actual supply flow rates of the hydraulic oil to the boom cylinder 7 and the bucket cylinder 9 tracks the target. Therefore, the above-mentioned problem of control interference can be avoided and the supply flow rates of the hydraulic oil supplied from the hydraulic pump 20 to the boom control valve 22 and the bucket control valve 23 can be optimized, and further, the drive power of the hydraulic pump 20 can be reduced by resisting the fluid resistance when the hydraulic oil passes through each of the control valves 22, 23.

[0095] Furthermore, in this embodiment, the controller 100 is configured to reduce the responsiveness of the discharge flow rate control of the hydraulic pump 20 by the pump flow rate control unit 107 to be lower than the responsiveness of the supply flow rate control of the hydraulic oil to the boom cylinder 7 and the bucket cylinder 9 by the actuator flow rate control unit 108. Specifically, the pump flow rate control unit 107 and the actuator flow rate control unit 108 are configured to execute feedforward control based on flow rate-current correspondence data in parallel with feedback control, and when the feedforward control is executed by the pump flow rate control unit 107, the target discharge flow rate of the hydraulic pump 20, which is an input to the pump flow rate control unit 107, is corrected by multiplying it by a predetermined correction factor G that is equal to or greater than 0 and less than 1, thereby realizing the reduction in the responsiveness of the discharge flow rate control of the hydraulic pump 20 described above.

[0096] According to this configuration, by making the responsiveness of the discharge flow rate control of each hydraulic pump 20 lower than the responsiveness of the supply flow rate control of the hydraulic oil to the boom cylinder 7 and the bucket cylinder 9, it is possible to prevent an excessive supply of hydraulic oil from the hydraulic pump 20 to the boom control valve 22 and the bucket control valve 23 that control the supply flow rate of hydraulic oil to each cylinder 7, 9. Therefore, the fluid resistance when the hydraulic oil passes through each control valve 22, 23 is reduced, and ultimately the drive power of the hydraulic pump 20 can be reduced.

[0097] In this embodiment, the flow rate-current correspondence data (corresponding to feedforward correspondence data) used for feedforward control in the actuator flow rate control unit 108 is Each of the boom control valves 22 and the bucket control valves 23 is set so as not to operate in a dead zone opening that would cause the control valves 22, 23 to not follow changes in the command current for driving these control valves 22, 23 (more specifically, the command current for the boom pilot solenoid valve 24 and the bucket pilot solenoid valve 25).

[0098] According to this configuration, the opening degree of the boom control valve 22 and the bucket control valve 23 based on the feedforward control can be quickly controlled without being affected by the dead band of each control valve 22, 23. Therefore, the operation delay (time lag) of each boom control valve 22 and bucket control valve 23 can be reduced to improve the operation responsiveness. This makes it possible to prevent the supply flow rate of hydraulic oil to each control valve 22, 23 from becoming excessive due to a delay in the operation of the boom control valve 22 and the bucket control valve 23 in the process of increasing the flow rate of the hydraulic pump 20, for example. The fluid resistance when the hydraulic oil passes through each control valve 22, 23 can be reduced to reduce the drive power of the hydraulic pump 20.

[0099] Second embodiment 10 and 11 are views corresponding to Figs. 2 and 3, respectively, showing a second embodiment. In this embodiment, the flow rate control of the hydraulic pump 40 for supplying hydraulic oil to the arm cylinder 8 and the swing motor 10 is different from that of the first embodiment. In the following description, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0100] That is, in the first embodiment, the discharge flow rate control of the hydraulic pump (not shown in the first embodiment) for supplying hydraulic oil to the arm cylinder 8 and the swing motor 10 is performed by feedback control that reduces the difference between the actual discharge flow rate of the hydraulic pump, which is the sum of the actual supply flow rates of hydraulic oil to the arm cylinder 8 and the swing motor 10, and its target discharge flow rate, similar to the operation control of the hydraulic pump 20 that supplies hydraulic oil to the boom cylinder 7 and the bucket cylinder 9.

[0101] In contrast to this, in this embodiment, the feedback control in the discharge flow rate control of the hydraulic pump 40 is not based on the total value of the actual supply flow rate of hydraulic oil to the arm cylinder 8 and the swing motor 10, but is divided into a flow rate for the arm and a flow rate for the swing motor 10 and is executed separately, which is different from the first embodiment.

[0102] FIG. 10 is a diagram showing a hydraulic circuit section B2 related to the arm cylinder 8 and the swing motor 10 of the hydraulic excavator A according to this embodiment.

[0103] 10, the hydraulic excavator A of this embodiment includes a hydraulic pump 40, an engine 21, an arm control valve 33, a swing control valve 34, an arm pilot solenoid valve 45, a swing pilot solenoid valve 46, a relief valve 42, a third operating device 31, a fourth operating device 32, an arm speed sensor 37, a swing speed sensor 38, and a controller 150. The controller 150 may share the same hardware as the controller 100 in the first embodiment.

[0104] The hydraulic pump 40 is a variable displacement hydraulic pump, and is connected to an output shaft of the engine 21 housed in the engine room 2b. The hydraulic pump 40 is driven by the engine 21, thereby discharging hydraulic oil from a tank. A pump regulator 41 is attached to the hydraulic pump 40. The hydraulic pump 40 is configured to change the pump capacity by changing the tilt angle based on a command current input from the controller 150 to the pump regulator 41, thereby changing the discharge amount of hydraulic oil. In this embodiment, the hydraulic pump 40 is provided separately from the hydraulic pump 20 that supplies hydraulic oil to the boom cylinder 7 and the bucket cylinder 9 described in the first embodiment, but the present invention is not limited to this, and may be used as the hydraulic pump 20, for example.

[0105] The pump regulator 41 receives an input of a command current specifying the discharge flow rate of the hydraulic pump 40 from the controller 150, and operates the hydraulic pump 40 so that the discharge flow rate of the hydraulic pump 40 becomes a flow rate corresponding to the command current.

[0106] The arm control valve 33 is disposed between the hydraulic pump 40 and the arm cylinder 8 to control the supply and discharge of hydraulic oil to the arm cylinder 8. The arm control valve 33 is configured, for example, as a hydraulic pilot type three-position directional control valve. Specifically, the arm control valve 33 is configured to be switchable between a neutral position where the supply and discharge of hydraulic oil to the arm cylinder 8 is stopped, a first position where the arm cylinder 8 can be driven in the extension direction, and a second position where the arm cylinder 8 can be driven in the contraction direction by changing the position of a spool housed therein. The arm control valve 33 strokes the spool upon receiving pilot pressure from an arm pilot solenoid valve 45 described later. The arm control valve 33 is configured to be able to adjust the supply flow rate of hydraulic oil supplied to the arm cylinder 8 by changing the stroke amount when moving the spool from the neutral position to the first position or the second position. Thus, the arm control valve 33 functions as a control valve that can adjust the flow rate of hydraulic oil supplied to the arm cylinder 8 (an example of a hydraulic actuator). The control valve is not limited to a three-position directional control valve, and may be, for example, a throttle valve or the like provided separately from the three-position directional control valve.

[0107] The swing control valve 34 is disposed between the hydraulic pump 40 and the swing motor 10 to control the supply and discharge of hydraulic oil to the swing motor 10. The swing control valve 34 is configured, for example, as a hydraulic pilot type three-position directional control valve. Specifically, the swing control valve 34 is configured to be switchable between a neutral position where the supply and discharge of hydraulic oil to the swing motor 10 is stopped, a first position where the swing motor 10 can be driven in the right direction, and a second position where the swing motor 10 can be driven in the left direction by changing the position of a spool housed therein. The swing control valve 34 strokes the spool by receiving pilot pressure from a swing pilot solenoid valve 46 described later. The swing control valve 34 is configured to be able to adjust the supply flow rate of hydraulic oil supplied to the swing motor 10 by changing the stroke amount when the spool is moved from the neutral position to the first position or the second position. Thus, the swing control valve 34 functions as a control valve capable of adjusting the flow rate of hydraulic oil supplied to the swing motor 10 (one example of an actuator). Note that the control valve is not limited to a three-position directional control valve, and may be configured, for example, by a throttle valve or the like provided separately from the three-position directional control valve.

[0108] The arm pilot solenoid valve 45 is interposed between a pilot hydraulic source (e.g., a pilot pump driven by the engine 21) not shown and the arm control valve 33. When an arm operation is applied to an operation member 31a of a third operation device 31 described later, the arm pilot solenoid valve 45 opens upon receiving a command current corresponding to the operation output from a controller 150, and supplies pilot pressure from the pilot hydraulic source to the arm control valve 33. Specifically, when an arm operation is applied to the operation member 31a, the arm pilot solenoid valve 45 opens to allow pilot pressure to be supplied to a pilot port corresponding to the direction of the arm operation, out of a pair of pilot ports provided in the arm control valve 33.

[0109] The swing pilot solenoid valve 46 is interposed between a pilot hydraulic source (not shown, for example, a pilot pump driven by the engine 21) and the swing control valve 34. When a swing operation is applied to an operating member 32a of a fourth operating device 32 described later, the swing pilot solenoid valve 46 opens upon receiving a command current corresponding to the operation output from a controller 150, and supplies pilot pressure from the pilot hydraulic source to the swing control valve 34. Specifically, when a swing operation is applied to the operating member 32a, the swing pilot solenoid valve 46 opens to allow pilot pressure to be supplied to a pilot port corresponding to the direction of the swing operation, out of a pair of pilot ports provided in the swing control valve 34.

[0110] The relief valve 42 is provided in the relief flow passage 43 and operates to open and close the relief flow passage 30. The relief flow passage 43 is a flow passage that directly connects a pump line and a tank line so that the hydraulic oil discharged from the hydraulic pump 40 is released to a tank, bypassing the arm control valve 33 and the swing control valve 34. The relief valve 42 opens so as to limit the pump pressure, which is the pressure of the hydraulic oil discharged from the hydraulic pump 40, to a pressure equal to or lower than a preset relief set pressure.

[0111] The third operating device 31 has an operating member 31a to which an arm operation for commanding the operation of the arm cylinder 8 is given. The operating member 31a is provided in the cab 2a so that an operator in the cab 2a can operate it. The third operating device 31 receives the arm operation and outputs a command signal corresponding to the arm operation. The command signal output from the third operating device 31 is input to the controller 150.

[0112] The fourth operating device 32 has an operating member 32a to which a swing operation is applied in order to command the operation of the swing motor 10. The operating member 32a is provided in the cab 2a so that an operator in the cab 2a can operate it. The fourth operating device 32 receives a swing operation and outputs a command signal corresponding to the swing operation. The command signal output from the fourth operating device 32 is input to the controller 150.

[0113] When the controller 150 receives an input of a command signal corresponding to the arm operation from the third operating device 31, it opens and closes the arm pilot solenoid valve 45 so that the pilot pressure corresponding to the command signal is input to the pilot port of the arm control valve 33 (the pilot port of the pair of pilot ports that corresponds to the command signal).

[0114] When the controller 150 receives a command signal corresponding to the rotation operation from the fourth operating device 32, it opens and closes the rotation pilot solenoid valve 46 so that the pilot pressure corresponding to the command signal is input to the pilot port of the rotation control valve 34 (the pilot port of the pair of pilot ports that corresponds to the command signal).

[0115] The arm speed sensor 37 is a sensor that detects the extension / retraction speed of the arm cylinder 8. The swing speed sensor 38 is a sensor that detects the rotation speed of the swing motor 10. For example, a rotary encoder or a resolver can be used as the swing speed sensor 38. The arm speed sensor 37 and the swing speed sensor 38 each output a speed signal indicating the detected speed to the controller 150.

[0116] [Controller Details] Fig. 11 is a block diagram showing the configuration of a control system including the controller 150. As shown in Fig. 11, the controller 150 is formed by a computer including, for example, a CPU, a memory, and the like.

[0117] The controller 150 has, as functional units, an arm target supply flow rate calculation unit 151, a swing target supply flow rate calculation unit 152, an arm cylinder actual supply flow rate acquisition unit 153, a swing motor actual supply flow rate acquisition unit 154, an arm pump target discharge flow rate calculation unit 155, an arm pump actual discharge flow rate acquisition unit 157, an arm pump flow rate control unit 159 (an example of a working pump flow rate control unit), a swing pump target discharge flow rate calculation unit 156, a swing pump actual discharge flow rate acquisition unit 158, a swing pump flow rate control unit 160, and an actuator flow rate control unit 161. The actuator flow rate control unit 161 has an arm cylinder flow rate control unit 161a and a swing motor flow rate control unit 161b. These functional units are realized by the controller 150 executing a computer program stored in advance in a storage medium such as a ROM.

[0118] The arm target supply flow rate calculation unit 151 calculates a target supply flow rate of hydraulic oil to the arm cylinder 8, which is determined based on the operation amount of the operating member 31a output from the third operating device 31. Specifically, the arm target supply flow rate calculation unit 151 receives an operation signal (e.g., a current signal) of the operating member 31a from the third operating device 31, recognizes the operation amount of the operating member 31a based on the received operation signal, and calculates a target supply flow rate to the arm cylinder 8 based on the recognized operation amount. This target supply flow rate may be calculated based on target flow rate data in which the relationship between the operation amount of the operating member 31a and the target supply flow rate of the arm cylinder 8 is previously associated, or may be calculated by proportional calculation based on a target supply flow rate corresponding to a maximum operation amount of the operating member 31a stored in advance.

[0119] The swing target supply flow rate calculation unit 152 calculates a target supply flow rate of hydraulic oil to the swing motor 10, which is determined based on the operation amount of the operating member 32a output from the fourth operating device 32. Specifically, the swing target supply flow rate calculation unit 152 receives an operation signal (e.g., a current signal) of the operating member 32a from the fourth operating device 32, recognizes the operation amount of the operating member 32a based on the received operation signal, and calculates a target supply flow rate to the swing motor 10 based on the recognized operation amount. This target supply flow rate may be calculated based on target flow rate data that previously associates the relationship between the operation amount of the operating member 32a and the target supply flow rate of the swing motor 10, for example, or may be calculated by proportional calculation based on a target supply flow rate corresponding to a maximum operation amount of the operating member 32a that has been previously stored.

[0120] The arm cylinder actual supply flow rate acquisition unit 153 acquires the actual supply flow rate of hydraulic oil to the arm cylinder 8 (an example of a working cylinder). Specifically, the arm cylinder actual supply flow rate acquisition unit 153 calculates the extension / retraction speed of the arm cylinder 8 based on the speed signal received from the arm speed sensor 37. Then, the arm cylinder actual supply flow rate acquisition unit 153 calculates (acquires) the actual supply flow rate of hydraulic oil to the arm cylinder 8 based on the extension / retraction speed of the arm cylinder 8 and the cross-sectional area of ​​the cylinder chamber.

[0121] The swing motor actual supply flow rate acquisition unit 154 acquires the actual supply flow rate of hydraulic oil to the swing motor 10. Specifically, the swing motor actual supply flow rate acquisition unit 154 calculates the rotation speed of the swing motor 10 based on the speed signal received from the swing speed sensor 38. Then, the swing motor actual supply flow rate acquisition unit 154 calculates (acquires) the actual supply flow rate of hydraulic oil to the swing motor 10 based on the rotation speed of the swing motor 10 and the motor capacity (including the reduction ratio setting when the vehicle body swing speed sensor is used).

[0122] An arm pump target discharge flow rate calculation unit 155 calculates the target supply flow rate of hydraulic oil to the arm cylinder 8 calculated by the arm target supply flow rate calculation unit 151 as a target discharge flow rate of hydraulic oil to be supplied to the arm cylinder 8 from the discharge flow rate of the hydraulic pump 20 (target discharge flow rate for work).

[0123] The swing pump target discharge flow rate calculation unit 156 calculates the target supply flow rate of hydraulic oil to the swing motor 10 calculated by the swing target supply flow rate calculation unit 152 as the target discharge flow rate of hydraulic oil to be supplied to the swing motor 10 from the discharge flow rate of the hydraulic pump 20 (target discharge flow rate for swing).

[0124] An arm pump actual discharge flow rate acquisition unit 157 (an example of an actuator actual discharge flow rate acquisition unit) acquires the actual supply flow rate of hydraulic oil to the arm cylinder 8 acquired by the arm cylinder actual supply flow rate acquisition unit 153 as the actual discharge flow rate of hydraulic oil for the arm cylinder 8 discharged from the hydraulic pump 20 (actual discharge flow rate for work).

[0125] The actual discharge flow rate acquisition unit for the swing pump 158 (an example of an actual discharge flow rate acquisition unit for the actuator) acquires the actual supply flow rate of hydraulic oil to the swing motor 10 acquired by the swing target supply flow rate calculation unit 152 as the actual discharge flow rate of hydraulic oil for the swing motor 10 discharged from the hydraulic pump 20 (actual discharge flow rate for swing).

[0126] An arm pump flow rate control unit 159 calculates, by feedback control, a command current to the pump regulator 41 so as to reduce a difference value (in other words, to make the deviation zero) between the target discharge flow rate for the arm of the hydraulic pump 20 acquired by an arm pump target discharge flow rate calculation unit 155 and the actual discharge flow rate for the arm of the hydraulic pump 20 acquired by an arm pump actual discharge flow rate acquisition unit 157. Note that, similarly to the first embodiment, feedforward control based on the flow rate-current correspondence data may be executed in parallel with the feedback control.

[0127] The swing pump flow rate control unit 160 calculates, by feedback control, a command current to the pump regulator 29 that reduces the difference between the target discharge flow rate of the swing hydraulic oil acquired by the swing pump target discharge flow rate calculation unit 156 and the actual discharge flow rate of the swing hydraulic oil acquired by the swing pump actual discharge flow rate acquisition unit 158 ​​(in other words, that makes the deviation zero). In this embodiment, the responsiveness of the feedback control by the swing pump flow rate control unit 160 is set lower than the responsiveness of the feedback control in the arm pump flow rate control unit 159. Note that, as in the first embodiment, feedforward control based on flow rate-current correspondence data may be executed in parallel with the feedback control.

[0128] The arm cylinder flow rate control unit 161a determines (calculates) a command current (actuator flow rate command signal) for bringing the actual supply flow rate of hydraulic oil to the arm cylinder 8 closer to the target supply flow rate by executing, in parallel, feedback control for controlling the arm control valve 33 so as to reduce the difference between the actual supply flow rate of hydraulic oil to the arm cylinder 8 acquired by the arm cylinder actual supply flow rate acquisition unit 153 and the target supply flow rate of hydraulic oil to the arm cylinder 8 calculated by the arm target supply flow rate calculation unit 151 (so as to make the deviation zero) and feedforward control based on the flow rate-current correspondence data. The determined command current is input to the arm pilot solenoid valve 45.

[0129] The swing motor flow control unit 161b executes, in parallel, feedback control for controlling the swing control valve 34 so as to reduce the difference between the actual supply flow rate of hydraulic oil to the swing motor 10 acquired by the swing motor actual supply flow rate acquisition unit 154 and the target supply flow rate of hydraulic oil to the swing motor 10 calculated by the swing target supply flow rate calculation unit 152 (so as to make the deviation zero), and feedforward control based on the flow rate-current correspondence data, thereby determining (calculating) a command current (actuator flow rate command signal) for bringing the actual supply flow rate of hydraulic oil to the swing motor 10 closer to the target supply flow rate. The determined command current is input to the swing pilot solenoid valve 46.

[0130] The feedback control and feedforward control executed in the actuator flow control section 161 (arm cylinder flow control section 161a and swing motor flow control section 161b) are similar to the feedback control and feedforward control in the actuator flow control section 108 (boom cylinder flow control section 108a and bucket cylinder flow control section 108b) described in the first embodiment, and therefore detailed description thereof will be omitted.

[0131] In addition, the feedback control executed by the arm pump flow rate control unit 159 and the swing pump flow rate control unit 160 is executed by PID control similar to the feedback control in the pump flow rate control unit 107 in the first embodiment, so a detailed description thereof will be omitted here. Note that the PID control is an example of feedback control, and the present invention is not limited to this.

[0132] As described above, in this embodiment, both the discharge flow rate control of the hydraulic oil from the hydraulic pump 20 and the supply flow rate control of the hydraulic oil to the arm cylinder 8 and the swing motor 10 are performed in a form that includes feedback control, thereby achieving the same effects as those of the first embodiment.

[0133] Moreover, in this embodiment, the pump flow control section is composed of an arm pump flow control section 159 and a swing pump flow control section 160, and the responsiveness of the feedback control in the control of the discharge flow rate of hydraulic oil for the swing motor 10 performed by the swing pump flow control section 160 is made lower than the responsiveness of the feedback control in the control of the discharge flow rate of hydraulic oil for the arm cylinder 8 performed by the arm pump flow control section 159.

[0134] This makes it possible to prevent the supply flow rate of hydraulic oil to the swing motor 10 from becoming excessively large. That is, after extensive research, the inventors have found that the dynamic characteristics of the swing motor 10 are gentler than the dynamic characteristics of the arm cylinder 8. Based on this finding, in this configuration, the responsiveness of the feedback control in the discharge flow rate control of the hydraulic oil for the swing motor 10 executed by the swing pump flow rate control unit 160 is made lower than the responsiveness of the feedback control in the discharge flow rate control of the hydraulic oil for the arm cylinder 8 executed by the arm pump flow rate control unit 159 (in other words, by making the discharge flow rate of the hydraulic oil for the swing motor 10 follow the target gently), thereby making it possible to prevent the hydraulic oil from being excessively supplied to the swing motor 10. This makes it possible to suppress an increase in the pressure of the hydraulic pump 40 caused by the excessive supply of hydraulic oil to the swing motor 10, and to reduce the driving power of the hydraulic pump 40. In turn, it is possible to prevent a decrease in the energy efficiency of the entire hydraulic excavator A.

[0135] FIG. 12 is a graph showing the results of calculation by simulation of the time change of the actual supply flow rate of hydraulic oil to the arm cylinder 8 and the swing motor 10 by the hydraulic pump 40 in the hydraulic excavator A according to this embodiment, and FIG. 13 is a diagram equivalent to FIG. 12 in a hydraulic excavator according to a comparative example of this embodiment. This comparative example differs from this embodiment in that the responsiveness of the feedback control in the discharge flow rate control of the hydraulic oil for the swing motor 10 is set to be the same as the responsiveness of the feedback control in the discharge flow rate control of the hydraulic oil for the arm cylinder 8. In FIG. 12 and FIG. 13, the upper graph shows the time change of the actual supply flow rate of hydraulic oil to the arm cylinder 8 by the hydraulic pump 40, and the lower graph shows the time change of the actual supply flow rate of hydraulic oil to the swing motor 10 by the hydraulic pump 40. In addition, the solid line in each graph is the ideal flow rate line, the dashed line is a line showing the actual simulation result, and the two-dot chain line shows the target flow rate. In each graph, the lines are shown slightly shifted so that they do not overlap and become difficult to see after the transition to a steady state (after settling); however, in reality, after the transition to the steady state, the lines overlap and coincide with the target discharge flow rate.

[0136] In the hydraulic excavator according to the comparative example, as shown in the lower graph of FIG. 13, it can be seen that the actual flow rate of hydraulic oil supplied by the hydraulic pump 40 to the swing motor 10 overshoots immediately after control starts and greatly exceeds the target discharge flow rate. When such an overshoot occurs, the excess hydraulic oil discharged from the hydraulic pump 40 is returned to the tank via the relief valve 42. This causes the hydraulic pump 40 to operate unnecessarily and reduces energy efficiency. In contrast, in the hydraulic excavator A according to the present embodiment, an overshoot like that in the comparative example does not occur (see FIG. 12), so it is possible to avoid a decrease in energy efficiency caused by the actual discharge flow rate of the hydraulic pump 40 exceeding the target discharge flow rate.

[0137] (Other embodiments) Although the hydraulic excavator A according to the embodiment of the present invention has been described above, the present invention is not limited to this, and for example, the following modified embodiments can be adopted.

[0138] In the first embodiment, the pump actual delivery flow rate obtaining unit 106 may be configured to directly obtain the actual delivery flow rate of the hydraulic pump 20 using a flow rate sensor or the like.

[0139] In each of the above-described embodiments, the actual supply flow rate acquisition units 104, 105, 153, 154 that acquire the actual supply flow rate of hydraulic oil to each hydraulic actuator may be configured to directly acquire the actual supply flow rate of hydraulic oil to each cylinder 7-9 and the swing motor 10 using a flow sensor or the like.

[0140] In each of the above-described embodiments, each of the operating devices 27, 28, 31, 32 is configured to output an electrical signal as an operating signal, but this is not limited thereto, and each of the operating devices may be configured to output a pressure signal based on a pilot pressure.

[0141] In each of the above embodiments, an example in which a plurality of hydraulic actuators are provided has been described, but the present invention is not limited to this, and the number of hydraulic actuators may be one.

[0142] In the above embodiment, the hydraulic excavator A capable of traveling on the ground has been described as an example of a construction machine, but the present invention is not limited to this and may be, for example, a construction machine fixed to the ground.

[0143] In addition, the comparative examples described in the first and second embodiments are not conventional techniques but merely comparative examples of the above-mentioned embodiments, and all of them are included in the technical scope of the present invention. In other words, the present invention may have any configuration as long as both the discharge flow rate control of the hydraulic pumps 20, 40 and the supply flow rate control of the hydraulic oil to each actuator (the boom cylinder 7, the arm cylinder 8, the bucket cylinder 9, and the swing motor 10) include feedback control.

[0144] The present invention also includes any combination of the above-described embodiments and comparative examples. [Explanation of symbols]

[0145] A: Hydraulic excavator (construction machinery) G: Correction magnification X: Rotation axis 1: Undercarriage (aircraft body) 2: Upper rotating body (rotating body) 3: Work attachment 7: Boom cylinder (hydraulic actuator) 8: Arm cylinder (hydraulic actuator) 9: Bucket cylinder (hydraulic actuator) 10: Swing motor (hydraulic actuator) 20: Hydraulic pump 21: Engine (power source) 22: Boom control valve (control valve) 23: Bucket control valve (control valve) 27: 1st operating device (operating device) 27a: Operating member 28:Second operating device (operating device) 28a: Operating member 29: Pump regulator (regulator) 31: Third operating device (operating device) 31a: Operating member 32:Fourth operating device (operating device) 32a: Operating member 33: Arm control valve (control valve) 34: Swing control valve (control valve) 40: Hydraulic pump 41: Pump regulator 100: Controller

Claims

1. A driving source; A hydraulic pump driven by the drive source; A regulator capable of changing a flow rate of hydraulic oil discharged from the hydraulic pump; a hydraulic actuator driven by hydraulic oil discharged from the hydraulic pump; a control valve capable of changing a flow rate of hydraulic oil supplied to the hydraulic actuator; an operating device including an operating member to which an operation for driving the hydraulic actuator is applied, the operating device outputting an operation signal corresponding to the operation of the operating member; and a controller. The controller: An actuator actual supply flow rate acquisition process for acquiring an actual supply flow rate of hydraulic oil supplied to the hydraulic actuator; an actuator target supply flow rate calculation process for calculating a target supply flow rate of the hydraulic oil to the hydraulic actuator based on an operation signal output from the operation device; a pump target delivery flow rate calculation process for calculating a target delivery flow rate of the hydraulic pump based on the target supply flow rate calculated by the actuator target supply flow rate calculation process; A pump actual discharge flow rate acquisition process for acquiring an actual discharge flow rate of hydraulic oil discharged from the hydraulic pump; a pump flow rate control process that executes a discharge flow rate control of the hydraulic pump via the regulator, the control including a feedback control that reduces a difference value between the actual discharge flow rate of the hydraulic pump acquired by the pump actual discharge flow rate acquisition process and the target discharge flow rate of the hydraulic pump calculated by the pump target discharge flow rate calculation process; an actuator flow rate control process that performs control of the supply flow rate of hydraulic oil to the hydraulic actuator via the control valve, the control including feedback control that reduces a difference value between the actual supply flow rate of hydraulic oil to the hydraulic actuator acquired by the actuator actual supply flow rate acquisition process and the target supply flow rate of hydraulic oil to the hydraulic actuator calculated by the actuator target supply flow rate calculation process.

2. 2. The construction machine according to claim 1, A plurality of the hydraulic actuators are provided, the control valve is provided for each of the plurality of hydraulic actuators, the actuator actual supply flow rate acquisition process is a process of acquiring an actual supply flow rate of the hydraulic oil supplied to each of the plurality of hydraulic actuators, the actuator target supply flow rate calculation process is a process of calculating a target supply flow rate of the hydraulic oil for each of the plurality of hydraulic actuators, the pump actual discharge flow rate acquisition process is a process of calculating a total value of an actual supply flow rate of the hydraulic oil supplied to each of the plurality of hydraulic actuators, and acquiring the calculated total value as an actual discharge flow rate of the hydraulic pump, the pump target delivery flow rate calculation process is a process of calculating a total value of the target supply flow rates of the plurality of hydraulic actuators calculated by the actuator target supply flow rate calculation process as a target delivery flow rate of the hydraulic pump, the feedback control included in the pump flow rate control process is control that operates the regulator so as to reduce a difference value between the actual discharge flow rate of the hydraulic pump acquired by the pump actual discharge flow rate acquisition process and the target discharge flow rate of the hydraulic pump, which is a total value of target supply flow rates of the multiple hydraulic actuators calculated by the pump target discharge flow rate calculation process; The feedback control included in the actuator flow rate control process is control that operates the control valve so as to reduce the difference value between the actual supply flow rate of hydraulic oil for each of the multiple hydraulic actuators acquired by the actuator actual supply flow rate acquisition process and the target supply flow rate of hydraulic oil for each of the multiple hydraulic actuators calculated by the actuator target supply flow rate calculation process, in a construction machinery.

3. 3. The construction machine according to claim 2, A construction machine, wherein a responsiveness of the discharge flow rate control of the hydraulic pump in the pump flow rate control process is lower than a responsiveness of the supply flow rate control of the hydraulic oil to each of the hydraulic actuators in the actuator flow rate control process.

4. 4. The construction machine according to claim 3, In the pump flow rate control process, a pump flow rate command signal that specifies a discharge flow rate of hydraulic oil discharged from the hydraulic pump is output from a controller; the regulator is configured to operate the hydraulic pump at a discharge flow rate corresponding to the pump flow rate command signal output from the controller by the pump flow rate control process, In the pump flow rate control process, when the discharge flow rate control is executed, a control for outputting the pump flow rate command signal for reducing a deviation between the target discharge flow rate of the hydraulic oil to the hydraulic pump calculated by the pump target discharge flow rate calculation process and the actual discharge flow rate of the hydraulic oil to the hydraulic pump calculated by the pump actual discharge flow rate acquisition process is executed as the feedback control, and a feedforward control for outputting the pump flow rate command signal set in advance according to the target discharge flow rate of the hydraulic pump is executed in parallel with the feedback control, In the actuator flow rate control process, an actuator flow rate command signal that specifies a supply flow rate of hydraulic oil to be supplied to each of the plurality of hydraulic actuators is output from the controller; the plurality of control valves are configured to supply hydraulic oil at a flow rate corresponding to an actuator flow rate command signal output from the controller by the actuator flow rate control process to each hydraulic actuator corresponding to each control valve; In the actuator flow rate control process, when executing the supply flow rate control, a control is executed as the feedback control to output an actuator flow rate command signal for reducing a deviation between the target supply flow rate of the hydraulic oil to the multiple hydraulic actuators calculated by the actuator target supply flow rate calculation process and the actual supply flow rate of the hydraulic oil to each of the hydraulic actuators acquired by the actuator actual supply flow rate acquisition process, and a feedforward control is executed in parallel with the feedback control to calculate and output a preset actuator flow rate command signal corresponding to the target supply flow rate of the hydraulic oil to each of the hydraulic actuators, In the pump flow rate control process, when the feedforward control is executed, the target discharge flow rate of the hydraulic pump, which is the input of the feedforward control, is corrected by multiplying it by a preset correction factor that is greater than 0 and less than 1, and a preset pump flow rate command signal corresponding to the corrected target discharge flow rate is output, thereby making the responsiveness of the discharge flow rate control of the hydraulic pump lower than the responsiveness of the supply flow rate control of the hydraulic oil to each hydraulic actuator.

5. 5. The construction machine according to claim 4, a storage unit that stores in advance feedforward corresponding data that defines a supply flow rate of hydraulic oil to each of the plurality of hydraulic actuators and an actuator flow rate command signal corresponding to the supply flow rate; in the actuator flow rate control process, when executing the feedforward control, the actuator flow rate command signal for each of the hydraulic actuators is calculated and output based on the target supply flow rate of hydraulic oil to each of the hydraulic actuators calculated by the actuator target supply flow rate calculation process and the feedforward corresponding data stored in the storage unit; The feedforward correspondence data is set so that each control valve corresponding to each of the plurality of hydraulic actuators does not operate in a dead zone opening that does not follow changes in the actuator flow command signal.

6. 2. The construction machine according to claim 1, The aircraft and A rotating body mounted on the airframe so as to be rotatable about a predetermined rotation axis; a hydraulic rotation motor that drives the rotating body around the predetermined rotation axis; A work attachment mounted on the rotating body; and a hydraulic working cylinder for driving the working attachment. A plurality of the hydraulic actuators are provided, the plurality of hydraulic actuators include the swing motor and the working cylinder, In the pump actual discharge flow rate acquisition process, an actual discharge flow rate for work supplied to the working cylinder out of the actual discharge flow rate of the hydraulic oil discharged from the hydraulic pump and an actual discharge flow rate for swing supplied to the swing motor out of the actual discharge flow rate of the hydraulic oil discharged from the hydraulic pump are acquired, In the pump target discharge flow rate calculation process, the target supply flow rate of hydraulic oil to the working cylinder calculated by the actuator target supply flow rate calculation process is acquired as a working target discharge flow rate, which is the flow rate of hydraulic oil to be supplied to the working cylinder from the hydraulic pump, and the target supply flow rate of hydraulic oil to the swing motor calculated by the actuator target supply flow rate calculation process is calculated as a swing target discharge flow rate, which is the flow rate of hydraulic oil to be supplied to the swing motor from the hydraulic pump, The pump flow rate control process includes: a working pump flow rate control process that executes a discharge flow rate control of the hydraulic pump via the regulator, the discharge flow rate control including a feedback control that reduces a difference value between the working actual discharge flow rate acquired by the pump actual discharge flow rate acquisition process and the working target discharge flow rate calculated by the pump target discharge flow rate calculation process; a swing pump flow rate control process that executes a discharge flow rate control of the hydraulic pump via the regulator, the discharge flow rate control including a feedback control that reduces a difference value between the swing actual discharge flow rate acquired by the pump actual discharge flow rate acquisition process and the swing target discharge flow rate calculated by the pump target discharge flow rate calculation process, A construction machine, wherein the responsiveness of the feedback control performed in the swing pump flow rate control process is reduced below the responsiveness of the feedback control performed in the working pump flow rate control process.

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