JP2024052373A - Work Machine - Google Patents

Abstract

A work machine capable of maintaining a balance between the operating speeds of a plurality of hydraulic actuators when the output of a prime mover is limited is provided.
[Solution] The work machine calculates a pump flow rate limit value of the pressurized oil that the hydraulic pump can discharge based on a predetermined output limit value of the prime mover and the discharge pressure of the hydraulic pump detected by a discharge pressure sensor, calculates a required speed for each of a plurality of hydraulic actuators based on an operation amount detected by an operation amount detection sensor, calculates a pump flow rate estimate that is an estimate of the flow rate of pressurized oil that the hydraulic pump should discharge in order to satisfy the calculated plurality of required speeds, calculates a plurality of target speeds by correcting each of the plurality of required speeds based on a ratio between the pump flow rate limit value and the pump flow rate estimate, and controls at least one of the prime mover, the hydraulic pump, and a plurality of flow control valves so that each of the plurality of hydraulic actuators operates at the target speed.
[Selected figure] Figure 7

Description

The present invention relates to a work machine equipped with multiple hydraulic actuators.

In a work machine such as a hydraulic excavator, each link of the working device, such as the boom and arm, is connected by a rotary or linear joint, and rotates or moves in a translational manner by a hydraulic actuator (e.g., hydraulic motor, hydraulic cylinder). The hydraulic actuator is operated by hydraulic oil supplied from a hydraulic pump that is driven to rotate by a prime mover (e.g., engine, electric motor).

To control the speed, acceleration, and force of the work equipment, it is necessary to control the rotational torque or thrust applied to each joint. On the other hand, there is an upper limit to the output energy and torque of the prime mover, so if the driving energy of the hydraulic actuator becomes excessive, it is necessary to control it so that it does not exceed the upper limit of the output energy of the prime mover, for example by reducing the discharge capacity of the variable capacity hydraulic pump.

To solve this problem, for example, Patent Document 1 discloses a method for controlling the pump's discharge capacity within a range that does not exceed the output energy of the prime mover by calculating the flow rate limit value by dividing the energy limit value by the current pump discharge pressure.

Japanese Patent No. 5985165

However, when multiple hydraulic actuators are operated in a combined manner, limiting energy using the method of Patent Document 1 may cause the balance of the operating speeds of the hydraulic actuators to be lost. This can result in the work machine operating in an unintended manner by the user.

The present invention was made in consideration of the above-mentioned circumstances, and its purpose is to provide a work machine that can maintain a balance between the operating speeds of multiple hydraulic actuators when the output of the prime mover is limited.

In order to achieve the above object, the present invention provides a work machine including a prime mover that generates a driving force, a hydraulic pump that discharges pressurized oil by the driving force of the prime mover, a discharge pressure sensor that detects the discharge pressure of the hydraulic pump, a plurality of hydraulic actuators that operate by the pressurized oil supplied from the hydraulic pump, a plurality of flow control valves that control the supply and discharge amount of pressurized oil to and from each of the plurality of hydraulic actuators, an operating device that operates each of the plurality of hydraulic actuators, an operation amount detection sensor that detects the operation amount by the operating device, and a controller that controls the prime mover, the hydraulic pump, and at least one of the plurality of flow control valves, the controller detecting a predetermined output limit value of the prime mover and the discharge pressure sensor. The system is characterized in that it calculates a pump flow rate limit value of the pressure oil that the hydraulic pump can discharge based on the discharge pressure of the hydraulic pump detected by the operation amount detection sensor, calculates a required speed for each of the multiple hydraulic actuators based on the operation amount detected by the operation amount detection sensor, calculates a pump flow rate estimate value that is an estimate of the flow rate of the pressure oil that the hydraulic pump should discharge in order to satisfy the calculated multiple required speeds, calculates multiple target speeds by correcting each of the multiple required speeds based on the ratio between the pump flow rate limit value and the pump flow rate estimate value, and controls the prime mover, the hydraulic pump, and at least one of the multiple flow control valves so that each of the multiple hydraulic actuators operates at the target speed.

According to the present invention, it is possible to maintain a balance between the operating speeds of multiple hydraulic actuators when the output of the prime mover is limited. Problems, configurations, and effects other than those described above will become clear from the description of the following embodiments.

FIG. 2 is a side view of the hydraulic excavator. FIG. 2 is a diagram showing a drive circuit of a hydraulic excavator. FIG. 2 is a hardware configuration diagram of the hydraulic excavator 1. FIG. 2 is a functional block diagram of a controller. FIG. 4 is a detailed diagram of a required speed calculation unit. FIG. 4 is a detailed diagram of a rotation speed control unit. FIG. 4 is a detailed diagram of an output limiting unit. FIG. 4 is a detailed diagram of a target pressure calculation unit applied to a hydraulic cylinder. FIG. 4 is a detailed diagram of a target pressure calculation unit applied to the hydraulic motor. FIG. 4 is a detailed diagram of a valve control unit that performs meter-in control. FIG. 4 is a detailed diagram of a valve control unit that performs meter-out control. FIG. 4 is a detailed view of the pump control unit. 1 is a schematic diagram of a hydraulic circuit mounted on a hydraulic excavator. FIG. 11 is a drive path diagram showing another combination of hydraulic actuators for performing a composite operation.

An embodiment of a hydraulic excavator 1 (working machine) according to the present invention will be described with reference to the drawings. Note that specific examples of the working machine are not limited to the hydraulic excavator 1, and may be wheel loaders, cranes, dump trucks, etc. Furthermore, unless otherwise specified, the terms front, back, left, right, and front in this specification are based on the viewpoint of an operator who is riding on and operating the hydraulic excavator 1.

Figure 1 is a side view of a hydraulic excavator 1. As shown in Figure 1, the hydraulic excavator 1 includes a lower traveling body 2 and an upper rotating body 3 supported by the lower traveling body 2. The lower traveling body 2 and the upper rotating body 3 are an example of a vehicle body. The lower traveling body 2 includes a pair of left and right crawlers 4 which are endless tracks. The pair of left and right crawlers 4 rotate independently when driven by a traveling motor 5. As a result, the hydraulic excavator 1 travels. However, the lower traveling body 2 may be of a wheeled type instead of the crawlers 4.

The upper rotating body 3 is supported on the lower running body 2 so that it can rotate by a rotating motor 6. The upper rotating body 3 mainly comprises a rotating frame 7 that serves as a base, a cab (driver's seat) 8 located on the front left side of the rotating frame 7, a counterweight 9 located at the rear of the rotating frame 7, and a front work machine 10 (working device) attached to the front center of the rotating frame 7 so that it can rotate up and down.

The cab 8 defines an internal space in which an operator who operates the hydraulic excavator 1 sits. The internal space of the cab 8 also includes a seat on which the operator sits, and operating devices that are operated by the operator seated in the seat.

The operating device receives operations from an operator to operate the hydraulic excavator 1. When the operator operates the operating device, the lower traveling body 2 travels, the upper rotating body 3 rotates, and the front working machine 10 operates. Specific examples of the operating device include a lever, a steering wheel, an accelerator pedal, a brake pedal, and a switch. The operating device includes at least a boom operating lever 41, an arm operating lever 42, and an EC dial 43, as described below with reference to FIG. 3, for example.

The front work machine 10 includes a boom 11 supported on the upper rotating body 3 so that it can be raised and lowered, an arm 12 supported rotatably at the tip of the boom 11, a bucket 13 supported rotatably at the tip of the arm 12, a boom cylinder 14 that drives the boom 11, an arm cylinder 15 that drives the arm 12, and a bucket cylinder 16 that drives the bucket 13. The counterweight 9 is used to balance the weight of the front work machine 10, and is a heavy object that has an arc shape when viewed from above.

The travel motor 5, the swing motor 6, the boom cylinder 14, the arm cylinder 15, and the bucket cylinder 16 are examples of hydraulic actuators that operate by supplying and discharging hydraulic oil (pressurized oil). In other words, the hydraulic excavator 1 is equipped with multiple hydraulic actuators. However, specific examples of hydraulic actuators are not limited to these.

Figure 2 is a diagram showing the drive circuit of the hydraulic excavator 1. Note that while Figure 2 shows only the hydraulic circuits for driving the boom cylinder 14 and the arm cylinder 15, the hydraulic excavator 1 also includes hydraulic circuits for driving other hydraulic actuators (i.e., the travel motor 5, the swing motor 6, and the bucket cylinder 16). As shown in Figure 2, the hydraulic excavator 1 mainly includes an engine 20 (prime mover), a hydraulic oil tank 21, a hydraulic pump 22 (hydraulic pump), directional control valves 23 and 24, meter-in control valves 25 and 26, opening control valves 27 and 28, a relief valve 29, a bleed-off valve 30, and pressure sensors 31, 32, 33, 34, and 35.

The engine 20 generates a driving force for driving the hydraulic excavator 1. However, specific examples of the driving source are not limited to the engine 20, and may be an electric motor or the like. The hydraulic oil tank 21 stores hydraulic oil. The hydraulic pump 22 rotates by the driving force of the engine 20 and discharges the hydraulic oil stored in the hydraulic oil tank 21. The hydraulic pump 22 is a variable displacement type such as a swash plate type or an inclined axis type. The discharge capacity of the hydraulic pump 22 is controlled by a regulator 22a.

The directional control valve 23, the meter-in control valve 25, and the opening control valve 27 are hydraulic components for operating (extending and retracting) the boom cylinder 14. The directional control valve 24, the meter-in control valve 26, and the opening control valve 28 are hydraulic components for operating (extending and retracting) the arm cylinder 15. Since these hydraulic components have a common configuration, the following will explain the hydraulic components 23, 25, and 27 for operating the boom cylinder 14.

The directional control valve 23 is disposed on the flow path from the hydraulic pump 22 to the boom cylinder 14, and on the flow path from the boom cylinder 14 to the hydraulic oil tank 21. The directional control valve 23 is an electromagnetic proportional control valve that controls the supply direction of hydraulic oil to the boom cylinder 14 under the control of the controller 50. More specifically, the directional control valve 23 has a spool that moves between a stop position A, an extended position B, and a retracted position C in response to a command current being supplied to ports 23a and 23b.

The stop position A is a position where the supply and discharge of hydraulic oil to the boom cylinder 14 is stopped. The extension position B is a position where the hydraulic oil discharged from the hydraulic pump 22 is supplied to the bottom chamber of the boom cylinder 14, and the hydraulic oil discharged from the rod chamber of the boom cylinder 14 is returned to the hydraulic oil tank 21. This causes the boom cylinder 14 to extend. The contraction position C is a position where the hydraulic oil discharged from the hydraulic pump 22 is supplied to the rod chamber of the boom cylinder 14, and the hydraulic oil discharged from the bottom chamber of the boom cylinder 14 is returned to the hydraulic oil tank 21. This causes the boom cylinder 14 to contract. Also, the closer the spool is to the stop position A, the less hydraulic oil is supplied to and discharged from the boom cylinder 14. On the other hand, the closer the spool is to the extension position B or the contraction position C, the more hydraulic oil is supplied to and discharged from the boom cylinder 14.

The initial position of the spool of the directional control valve 23 (the position when no command current is supplied to either port 23a or 23b) is the stop position A. When a command current is supplied to port 23a, the spool of the directional control valve 23 moves from the stop position A toward the extended position B. When a command current is supplied to port 23b, the spool of the directional control valve 23 moves from the stop position A toward the retracted position C. The spool of the directional control valve 23 moves closer to the extended position B or the retracted position C as the command current supplied to ports 23a and 23b increases. On the other hand, when the supply of the command current to ports 23a and 23b is stopped, the spool of the directional control valve 23 returns to the stop position A.

The meter-in control valve 25 is disposed in the flow path from the hydraulic pump 22 to the directional control valve 23. In other words, the meter-in control valve 25 is disposed upstream of the directional control valve 23. The meter-in control valve 25 controls the flow rate of hydraulic oil discharged by the hydraulic pump 22 and supplied to the boom cylinder 14 through the directional control valve 23. More specifically, the meter-in control valve 25 increases or decreases the flow rate of pressure oil supplied to the directional control valve 23 by controlling the back pressure with the opening control valve 27.

The opening control valve 27 controls the flow rate of hydraulic oil supplied from the hydraulic pump 22 to the directional control valve 23 through the meter-in control valve 25 (i.e., the opening of the meter-in control valve 25) by controlling the back pressure of the meter-in control valve 25. The opening control valve 27 is an electromagnetic proportional control valve that controls the flow rate of hydraulic oil passing through the meter-in control valve 25 under the control of the controller 50. The opening control valve 27 has a spool that moves between a supply position D and a shutoff position E when a command current is supplied.

The supply position D is a position where the back pressure port of the meter-in control valve 25 is opened to supply hydraulic oil from the hydraulic pump 22 to the directional control valve 23 through the meter-in control valve 25. The shutoff position E is a position where the back pressure port of the meter-in control valve 25 is closed to shut off the supply of hydraulic oil from the hydraulic pump 22 to the directional control valve 23 through the meter-in control valve 25. As the spool of the opening control valve 27 approaches the supply position D, the amount of hydraulic oil supplied to the directional control valve 23 increases, and as the spool of the opening control valve 27 approaches the shutoff position E, the amount of hydraulic oil supplied to the directional control valve 23 decreases.

The initial position of the spool of the opening control valve 27 (the position when no command current is being supplied) is the supply position D. In addition, the spool of the opening control valve 27 moves from the supply position D to the shutoff position E when a command current is supplied. Furthermore, the spool of the opening control valve 27 approaches the shutoff position E as the command current supplied increases. On the other hand, when the supply of the command current is stopped, the spool of the opening control valve 27 returns to the supply position D.

The directional control valve 23, the meter-in control valve 25, and the opening control valve 27 are examples of flow control valves that control the amount of hydraulic oil supplied to and discharged from the boom cylinder 14. However, the specific configuration of the flow control valve is not limited to the above-mentioned example, and it may be configured with one or more valves that are directly or indirectly controlled by the controller 50. Furthermore, the flow control valve according to this embodiment performs so-called "meter-in control", which controls the flow rate of hydraulic oil supplied to the hydraulic actuator. However, the method of controlling the flow rate of hydraulic oil to the hydraulic actuator is not limited to meter-in control, and may be so-called "meter-out control", which controls the flow rate of hydraulic oil discharged from the hydraulic actuator.

The relief valve 29 returns the pressurized oil to the hydraulic oil tank 21 in order to protect the hydraulic circuit when the discharge pressure from the hydraulic pump 22 reaches the set pressure. The bleed-off valve 30 adjusts the flow rate of a portion of the pressurized oil discharged from the hydraulic pump 22 under the control of the controller 50, and returns the adjusted flow rate to the hydraulic oil tank 21.

Pressure sensor 31 (discharge pressure sensor) detects the discharge pressure discharged from hydraulic pump 22 (hereinafter referred to as "pump discharge pressure Pp"). Furthermore, pressure sensors 32, 34 detect the pressure of hydraulic oil supplied to and discharged from the bottom chambers of boom cylinder 14 and arm cylinder 15. Furthermore, pressure sensors 33, 35 detect the pressure of hydraulic oil supplied to and discharged from the rod chambers of boom cylinder 14 and arm cylinder 15. Hereinafter, the pressures detected by pressure sensors 32 to 35 will be referred to as actual pressures P _act . Then, pressure sensors 31 to 35 output pressure signals indicative of the detected pressures to controller 50.

Figure 3 is a hardware configuration diagram of the hydraulic excavator 1. As shown in Figure 3, the hydraulic excavator 1 includes a controller 50 having a CPU 51 (Central Processing Unit) and a memory 52. The memory 52 is, for example, a ROM (Read Only Memory), a RAM (Random Access Memory), a HDD (Hard Disk Drive), or a combination of these. The controller 50 realizes the processing described below by having the CPU 51 read and execute program code stored in the memory 52.

However, the specific configuration of the controller 50 is not limited to this, and may be realized by hardware such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field-Programmable Gate Array).

The controller 50 controls the engine 20, the regulator 22a, the directional control valves 23, 24, the opening amount control valves 27, 28, and the bleed-off valve 30 based on various signals acquired from the pressure sensors 31-35, the attitude sensors 36-39, the boom operating lever 41, the arm operating lever 42, and the EC dial 43. That is, the controller 50 controls the rotation speed of the engine 20, the discharge capacity of the hydraulic pump 22, and the opening amount (the magnitude of the command current supplied) of the directional control valves 23, 24, the opening amount control valves 27, 28, and the bleed-off valve 30. The controller 50 also indirectly controls the opening amount of the meter-in control valves 25, 26 by controlling the opening amount control valves 27, 28.

The attitude sensors 36 to 39 detect the attitude of the joints driven by the hydraulic actuators, and output attitude signals indicating the detection results to the controller 50. For example, the attitude sensor 36 detects the rotation angle of the upper rotating body 3, the attitude sensor 37 detects the ground angle of the boom 11, the attitude sensor 38 detects the angle of the arm 12 relative to the boom 11, and the attitude sensor 39 detects the angle of the bucket 13 relative to the arm 12. Hereinafter, these angles are referred to as "joint angle θ". However, specific examples of the attitudes detected by the attitude sensors 36 to 39 are not limited to the above-mentioned examples.

The boom operation lever 41 accepts an operator's operation to raise or lower the boom 11 (in other words, to extend or retract the boom cylinder 14). More specifically, the boom operation lever 41 accepts an operator's operation to specify the direction in which the boom cylinder 14 extends and retracts, and the amount of extension (extension/retraction speed) of the boom cylinder 14. For example, an operation to tilt the boom operation lever 41 backward corresponds to an instruction to extend the boom cylinder 14 (positive sign), and an operation to tilt the boom operation lever 41 forward corresponds to an instruction to retract the boom cylinder 14 (negative sign). Furthermore, the amount of operation of the boom operation lever 41 corresponds to the absolute value of the amount of extension (extension/retraction speed) of the boom cylinder 14.

The arm operating lever 42 receives an operator's operation to rotate the arm 12 (in other words, extend and retract the arm cylinder 15). More specifically, the arm operating lever 42 receives an operator's operation to specify the extension direction of the arm cylinder 15 and the extension amount (extension/retraction speed) of the arm cylinder 15. For example, an operation to tilt the arm operating lever 42 to the right corresponds to an instruction (positive sign) to extend the arm cylinder 15, and an operation to tilt the arm operating lever 42 to the left corresponds to an instruction (negative sign) to contract the arm cylinder 15. Furthermore, the operation amount of the arm operating lever 42 corresponds to the absolute value of the extension amount (extension/retraction speed) of the arm cylinder 15.

The combination of the telescopic direction and telescopic amount (telescopic speed) is an example of the operation amount o. However, specific examples of the operation amount o are not limited to the above examples. The operation devices such as the boom operation lever 41 and the arm operation lever 42 output operation signals indicating the operation amount o for the operation devices to the controller 50. The boom operation lever 41 and the arm operation lever 42 have operation amount detection sensors that detect the respective operation amounts o and output the operation amounts o. Note that each operation lever that operates each of the travel motor 5, the swing motor 6, and the bucket cylinder 16 further includes a respective operation amount detection sensor that outputs the respective operation amounts o. In addition, the operation devices are not limited to the form of levers, and may be pedals or switches. Furthermore, the operation amount detection sensor is not limited to a configuration that detects the operation amount o based on a current value output from an operation device such as an operation lever provided in the cab 8, and may be a configuration that detects the operation amount o from a remote operation device via a communication line via an external server. Based on the operation signals from each of the above-mentioned operation levers, the operation amount o of each operation lever may be calculated by processing in the controller 50, and as a result, the operation amount o may be detected.

The EC dial (engine control dial) 43 is used to arbitrarily set the required rotation speed _Wr of the engine 20 by dial operation. The EC dial 43 outputs a rotation speed command signal indicating the required rotation speed _Wr set by dial operation to the controller 50. The EC dial 43 is an example of an engine rotation speed setting device that sets the required rotation speed _Wr of the engine 20. The engine rotation speed setting device is not limited to a dial type, and may be a switch, a touch panel, or the like. Furthermore, the engine rotation speed setting device is not limited to a device that sets the required rotation speed _Wr from a dial or the like provided in the cab 8, and may be configured to set the required rotation speed _Wr from a remote control device equipped with an engine rotation speed setting device via an external server through a communication line.

Figure 4 is a functional block diagram of the controller 50. As shown in Figure 4, the controller 50 mainly includes a required speed calculation unit 61, a rotation speed control unit 62, a Jacobian matrix calculation unit 63, an output limiting unit 64, a joint torque calculation unit 65, a target pressure calculation unit 66, an actual pressure calculation unit 67, a valve control unit 68, and a pump control unit 69. Each of the functional blocks 61 to 69 shown in Figure 4 is realized, for example, by the CPU 51 executing a program stored in the memory 52.

When multiple hydraulic actuators are operated in parallel (hereinafter referred to as "combined operation"), each of the function blocks 61 to 69 shown in FIG. 4 controls at least one of the engine 20, hydraulic pump 22, directional control valves 23, 24, and opening control valves 27, 28 so that the output of the engine 20 falls within the range of the output limit value E while maintaining a balance between the operating speeds of the hydraulic actuators. An example of combined operation of the boom cylinder 14 and arm cylinder 15 is described below.

The required speed calculation unit 61 calculates the required speed _vr of the boom cylinder 14 and the arm cylinder 15 based on the operation amount o acquired through the boom operation lever 41 and the arm operation lever 42. The required speed _vr is the extension/retraction speed of the boom cylinder 14 and the arm cylinder 15 corresponding to the operation amount of the boom operation lever 41 and the arm operation lever 42.

5 is a detailed diagram of the required speed calculation unit 61. As shown in FIG. 5, the required speed calculation unit 61 has required speed tables 611, 612 corresponding to the respective hydraulic actuators. The required speed table 611 holds a predetermined correspondence relationship between the operation amount o acquired through the boom operation lever 41 and the required speed _vr-Bm of the boom 11. The required speed table 612 holds a predetermined correspondence relationship between the operation amount o acquired through the arm operation lever 42 and the required speed vr _-Am of the arm 12. More specifically, the required speed tables 611, 612 hold a relationship in which the required speeds vr _-Bm , _vr-Am become faster as the operation amount o increases.

Although not shown, the memory 52 also stores required speed tables corresponding to the travel motor 5, the swing motor 6, and the bucket cylinder 16. The required speed calculation unit 61 may have an individual required speed table for each hydraulic actuator, or may have a multi-dimensional table that outputs multiple required speeds in response to multiple inputs of operation variables.

The required speed calculation unit 61 calculates a required speed _vr-Bm corresponding to the operation amount o obtained through the boom operation lever 41, based on a required speed table 611. The required speed calculation unit 61 also calculates a required speed vr _-Am corresponding to the operation amount o obtained through the arm operation lever 42, based on a required speed table 612. Then, as shown in FIG 4, the required speed calculation unit 61 outputs the calculated required speed _vr (a vector including _vr-Bm , _vr-Am ) to the output limiting unit 64.

The rotation speed control unit 62 calculates a target rotation speed W _E-t and an output limit value E based on the required rotation speed W _r obtained through the EC dial 43. The target rotation speed W _E-t is a target value for the rotation speed of the engine 20. The output limit value E is a limit value (limit value) of the output when the engine 20 is rotated at the target rotation speed W _E-t .

FIG. 6 is a detailed diagram of the rotation speed control unit 62. As shown in FIG. 6, the rotation speed control unit 62 has a target rotation speed table 621 and an output limit value table 622. The target rotation speed table 621 holds a predetermined correspondence relationship between the required rotation speed W _r and the target rotation speed W _E-t . More specifically, the target rotation speed table 621 holds a relationship in which the target rotation speed W _E-t is constant at a minimum value when the required rotation speed W _r is smaller than a lower limit value, the target rotation _speed W _E-t is constant at a maximum value when the required rotation speed W _r is larger than an upper limit value, and the target rotation speed W _E-t becomes larger as the required rotation speed W _r becomes larger between the lower limit value and the upper limit value. The output limit value table 622 holds a predetermined correspondence relationship between the target rotation speed W _E-t and the output limit value E. More specifically, the output limit value E holds a relationship in which the output limit value E becomes larger as the target rotation speed W _E-t becomes larger.

The rotation speed control unit 62 calculates a target rotation speed W _E-t corresponding to the required rotation speed _Wr based on a target rotation speed table 621. The rotation speed control unit 62 also calculates an output limit value E corresponding to the target rotation speed W _E-t based on an output limit value table 622. Then, as shown in Fig. 4, the rotation speed control unit 62 outputs the calculated target rotation speed W _E-t to the pump control unit 69, and outputs the calculated output limit value E to the output limit unit 64. The rotation speed control unit 62 also outputs the calculated target rotation speed W _E-t to an engine controller (not shown), and controls the rotation speed of the engine 20 to become the target rotation speed W _E-t .

The Jacobian matrix calculation unit 63 calculates the Jacobian matrix J based on the joint angle θ detected by the attitude sensors 37 and 38. The Jacobian matrix J is a conversion coefficient that converts the displacement velocity of the hydraulic actuator into a target joint angular velocity vector ω't (in other words, converts the link angular velocity system into an actuator velocity system). A specific method for calculating the Jacobian matrix J is already well known, as described in, for example, Non-Patent Document 1, and therefore a detailed description will be omitted. The Jacobian matrix calculation unit 63 then outputs the calculated Jacobian matrix J to the joint torque calculation unit 65.

The output limiting unit 64 calculates a target speed vt, a target acceleration _v't , and a target pump flow rate _Qp-t based on the required speed vr acquired from the required speed calculation unit 61, the output limit value E acquired from the rotation speed control unit ₆₂ , and the pump discharge pressure Pp detected by the pressure sensor 31. The target speed _vt is a target value ( _{vt-Bm , vt-Am} ) of the extension and retraction speed of each of the boom cylinder 14 and the arm cylinder 15. The target acceleration _v't is a target value ( _v't-Bm , v't _{- Am} ) of the acceleration for extending and retracting the boom cylinder 14 and the arm cylinder 15 at the target speeds vt- _Bm , vt-Am. The target pump flow rate Qp _-t is a target value of the discharge capacity of the hydraulic pump 22 required for extending and retracting the boom cylinder 14 and the arm cylinder 15 at the target speeds _vt -Bm, vt _-Am .

Figure 7 is a detailed diagram of the output limiting unit 64. As shown in Figure 7, the output limiting unit 64 has calculation units 641 to 646.

The calculation unit 641 calculates the pump flow rate limit value _Qlim by dividing the output limit value E by the pump discharge pressure Pp. The pump flow rate limit value _Qlim is an upper limit value (limit value) of the discharge capacity of the hydraulic pump 22 at which the output of the engine 20 falls within the output limit value E. Then, the calculation unit 641 outputs the calculated pump flow rate limit value _Qlim to the calculation unit 643.

The calculation unit 642 calculates a pump flow rate estimate Qest by integrating the product of the required speed _vr (vr _-Bm , vr _-Am ) acquired from the required speed calculation unit 61 and the oil passage cross-sectional area S (S _- Bm, S _- Am) of the corresponding hydraulic actuator. The pump flow rate estimate _{Qest is} an estimate of the flow rate of hydraulic oil that should be discharged by the hydraulic pump 22 in order to satisfy the multiple required speeds _vr-Bm , _vr-Am calculated by the required speed calculation unit 61. The calculation unit 642 then outputs the calculated pump flow rate estimate _Qest to the calculation units 643, 646.

The calculation unit 643 calculates a speed limit gain K by dividing the pump flow rate limit value _Qlim by the pump flow rate estimated value _Qest (i.e., the ratio of the pump flow rate limit value _Qlim and the pump flow rate estimated value _Qest ). The speed limit gain K is a correction coefficient for correcting the required speed _vr and the pump flow rate estimated value _Qest . When limiting the operation of the hydraulic actuator within the range of the output limit value E, the pump flow rate limit value _Qlim is smaller than the pump flow rate estimated value _Qest , so that the speed limit gain K satisfies 0≦K<1. The calculation unit 643 then outputs the speed limit gain K to the minimum value selection unit 647.

The minimum value selection unit 647 selects the smaller of the speed limit gain K output from the calculation unit 643 or a predetermined fixed value (=1). The minimum value selection unit 647 then outputs the selected value as the speed limit gain K to the calculation units 644, 646. That is, when the speed limit gain K output from the calculation unit 643 is less than 1, the minimum value selection unit 647 outputs this speed limit gain K as is. On the other hand, when the speed limit gain K output from the calculation unit 643 is 1 or greater, the minimum value selection unit 647 substitutes 1 for the speed limit gain K and outputs it.

The calculator 644 calculates a target speed _vt (a vector including vt _-Bm , vt _-Am ) by multiplying each of the multiple required speeds vr _-Bm , vr _-Am by a speed limit gain K. That is, the calculator 644 corrects each of the multiple required speeds vr _-Bm , vr-Am based on the ratio between the pump flow rate limit value _Qlim and the pump flow rate estimated value _Qest to calculate multiple target speeds vt _-Bm , vt _{-Am .} The calculator 644 then outputs the calculated target speed _vt to the calculator 645 and the joint torque calculator 65.

The calculation unit 645 calculates the required acceleration _v'r (a vector including v'r _-Bm and _v'r-Am ) by differentiating each of the multiple required velocities vr _- Bm and _vr-Am with respect to time t. Then, the calculation unit 645 outputs the calculated required acceleration _v'r to the joint torque calculation unit 65.

The calculator 646 calculates the target pump flow rate Q _p-t by multiplying the pump flow rate estimate Q _est by the speed limit gain K. That is, the calculator 646 calculates the target pump flow rate Q p- _t by correcting the pump flow rate estimate Q _est based on the ratio between the pump flow rate limit value Q _lim and the pump flow rate estimate Q est. The calculator 646 then outputs the calculated target pump flow rate Q _{p -t} to the pump control unit 69.

The joint torque calculation unit 65 calculates the target torque ft by substituting the joint angle θ detected by the attitude sensors 37, 38, the joint angular velocity θ' obtained by time-differentiating the joint angle θ, and the target velocity _vt and target acceleration v't obtained from the output limiting unit 64 into the following equations 1 and 2. The target torque ft is the target value (ft _-Bm , ft _-Bm ) of the torque when the boom cylinder 14 and the arm cylinder 15 are extended and retracted at the target velocities vt _-Bm and _vt-Am .

First, the joint torque calculation unit 65 calculates a target joint angular velocity vector ω't by substituting the target velocities vt _-Bm and _vt-Am and the Jacobian matrix J into Equation 1. The joint torque calculation unit 65 also calculates a target torque ft by substituting the joint angle θ, the joint angular velocity θ', and the target joint angular velocity vector ω't into the equation of motion of Equation 2. Then, the joint torque calculation unit 65 outputs the calculated target torque ft to the target pressure calculation unit 66.

Here, on the right side of Equation 2, the first term is the inertia term of the link member, the second term is the central force/Coriolis force term (C) and the friction term (D), and the third term is the gravity term (g is gravitational acceleration). Note that the link member dimensions, weight, friction, and other information used to calculate the coefficients of each term are known. The calculation method used by the joint torque calculation unit 65 is known as the calculated torque method, and is already well known, as described in Non-Patent Document 2, for example, so a detailed explanation will be omitted.

The target pressure calculation unit 66 calculates the target pressures (target meter- _{in pressure Pmit} , target meter-out pressure _Pmo-t ) of the pressure oil supplied to and discharged from the boom cylinder 14 and the arm cylinder 15, respectively, based on the corresponding target speeds _vt . More specifically, the target pressure calculation unit 66 calculates the target meter-in pressure Pmit, the target meter-out pressure Pmo _{- t} , and the meter-in flag σmi based on the operation amount o acquired through the boom operation lever 41 and the arm operation lever 42, and the target torque ft acquired from the joint torque calculation unit 65.

The target meter-in pressure P _mi-t is a target value for the pressure of hydraulic oil supplied to each of the boom cylinder 14 and the arm cylinder 15 in order to extend and retract the boom cylinder 14 and the arm cylinder 15 at target speeds v t- _Bm and v t- _Am, respectively. The target meter-out pressure P _mo-t is a target value for the pressure of hydraulic oil discharged from each of the boom cylinder 14 and the arm cylinder 15 in order to extend and retract the boom cylinder 14 and the arm cylinder 15 at target speeds v _t-Bm and v _t-Am, respectively. The meter-in flag σmi is a value indicating whether hydraulic oil is supplied to the bottom chamber or the rod chamber.

Fig. 8 is a detailed view of the target pressure calculation unit 66 applied to the hydraulic cylinders (i.e., the boom cylinder 14, the arm cylinder 15, and the bucket cylinder 16) of the hydraulic actuators. Fig. 9 is a detailed view of the target pressure calculation unit 66 applied to the hydraulic motors (i.e., the travel motor 5 and the swing motor 6) of the hydraulic actuators. As shown in Figs. 8 and 9, the target pressure calculation unit 66 has target pressure calculation tables 661, 662. The target pressure calculation tables 661, 662 hold the correspondence between combinations of the operation amount o and the target torque ft and the calculation methods of the target meter-in pressure _Pmit , the target meter-out pressure _Pmot , and the meter-in flag σmi.

As shown in Figures 8 and 9, when the operation amount o is equal to or greater than the positive threshold th1, the target pressure calculation unit 66 sets the meter-in flag σmi to bottom (=1). On the other hand, when the operation amount o is equal to or less than the negative threshold -th1, the target pressure calculation unit 66 sets the meter-in flag σmi to rod (=-1). On the other hand, when the operation amount o is less than the positive threshold th1 and greater than the negative threshold -th1, it is determined that the hydraulic actuator is stopped. Then, as shown in Figure 4, the target pressure calculation unit 66 outputs the calculated meter-in flag σmi to the actual pressure calculation unit 67.

The target pressure calculation unit 66 calculates the target meter-in pressure P _mi-t and the target meter-out pressure P _mo-t according to the combination of the operation amount o and the target torque ft. Here, the constants p _{_buf1} and p _{_buf2} are fixed values that are set in advance as the minimum pressure for preventing cavitation. The constants S _b and S _r are the cross-sectional areas of the bottom side (S _b ) and the rod side (S _r ) of the hydraulic cylinder, respectively. The motor volume q _m is the motor volume of the hydraulic motor, and is a value that takes into account the reduction ratio when a reducer is present. That is, the calculation formulas for the target meter-in pressure P _mi-t and the target meter-out pressure P _mo-t are different between the hydraulic cylinder and the hydraulic motor. As shown in FIG. 4, the target pressure calculation unit 66 outputs the calculated target meter-in pressure P _mi-t and the target meter-out pressure P _mo-t to the valve control unit 68 and the pump control unit 69.

The actual pressure calculation unit 67 calculates the actual meter-in pressure P mi and the actual meter-out pressure P mo by substituting the actual pressure P _act detected by the pressure sensors 32-35 and the meter _{-in flag σ mi obtained from the target pressure calculation unit 66 into the following equation 3. The actual meter-in pressure P mi is} the actual value of the hydraulic oil supplied to the boom cylinder 14 and the arm cylinder 15. The actual meter-out pressure P _mo is the actual value of _the hydraulic oil discharged from the boom cylinder 14 and the arm cylinder 15.

In Equation 3, the actual pressure Pa is the actual pressure detected by the bottom side pressure sensors 32, 34, and the actual pressure Pb is the actual pressure detected by the rod side pressure sensors 33, 35. The actual pressure calculation unit 67 outputs the calculated actual meter-in pressure _Pmi and actual meter-out pressure _Pmo to the valve control unit 68.

Fig. 10 is a detailed diagram of the valve control unit 68 which performs meter-in control. The valve control unit 68 in Fig. 10 calculates a valve opening command i based on the operation amount o acquired through the boom operation lever 41 and the arm operation lever ₄₂ , the target meter _{-in pressure Pmit} acquired from the target pressure calculation unit 66, the measured meter-in pressure _Pmi acquired from the measured pressure calculation unit 67, the pump discharge pressure Pp detected by the pressure sensor 31, the meter-in oil passage volume Vmi, and the meter-in oil passage volume change amount _V'mi . The valve control unit 68 has a meter-in opening limit value table 681A, calculation units 682A to 685A, and a valve opening command table 686A.

The meter-in oil passage volume _Vmi is the volume of hydraulic oil to be supplied to each of the boom cylinder 14 and the arm cylinder 15. The meter-in oil passage volume change _V'mi is the volume of hydraulic oil to be supplied per unit time to each of the boom cylinder 14 and the arm cylinder 15. The valve opening command i is a value indicating the opening of each of the meter-in control valves 25, 26 required to extend and retract the boom cylinder 14 and the arm cylinder 15 at the target speeds vt _-Bm and vt _-Am , respectively (for example, the magnitude of the command current supplied to each of the opening control valves 27, 28).

When the hydraulic actuator is a hydraulic cylinder, the meter-in oil passage volume V _mi and the meter-in oil passage volume change amount V' _mi are determined by the following formula 4. On the other hand, when the hydraulic actuator is a hydraulic motor, the meter-in oil passage volume V _mi and the meter-in oil passage volume change amount V' _mi are determined by the following formula 5. Note that the initial volumes V _a0 and V _b0 are the initial values of the oil passage volumes on the bottom side (V _a0 ) and rod side (V _b0 ) of the hydraulic cylinder, respectively. Furthermore, the cylinder displacement Xc is the displacement amount of the boom cylinder 14 and the arm cylinder 15. Furthermore, Smi and Smo are the meter-in side cylinder cross-sectional area and the meter-out side cylinder cross-sectional area, respectively. Furthermore, _qm is the motor volume of the hydraulic motor described above.

The meter-in opening limit value table 681A holds a predetermined correspondence relationship between the operation amount o and the meter-in opening limit value A _mi-lim . More specifically, the meter-in opening limit value table 681A holds a relationship in which the meter-in opening limit value A _mi-lim increases as the operation amount o increases. The meter-in opening limit value A _mi-lim is a limit value for the opening area of the meter-in control valves 25, 26. The meter-in opening limit value A _mi-lim specified based on the meter-in opening limit value table 681A is output to the calculation unit 685A.

Calculation unit 682A subtracts the actual meter-in pressure _Pmi from the target meter _{-in pressure Pmit} and outputs the result to calculation unit 683A. Calculation unit 682A calculates a feedback control amount V from the calculation result of calculation unit 682A by PID (Proportional-Integral-Differential) control, and outputs the calculated feedback control amount V to calculation unit 684A. Calculation unit 684A calculates a target meter-in opening A'mit-t by substituting the actual meter-in pressure _Pmi , pump discharge pressure Pp, meter-in oil passage volume _Vmi , meter-in oil passage volume change _V'mi , and feedback control amount V into the following equation 7. The target meter-in opening A'mit _{- t} is a target value for the opening area of the meter-in control valves 25, 26.

More specifically, if the meter-in opening for achieving the pressure change of the feedback control amount V is Ami, the bulk modulus of the hydraulic oil is Kβ, the density of the hydraulic oil is ρ, and the constant c is c, then Equation 6 is established. Then, Equation 7 is obtained by rearranging Equation 6 with respect to the feedback control amount V. Then, calculation unit 684A outputs the calculated target meter-in opening _A'mit to calculation unit 685A.

The calculation unit 685A outputs the smaller of the meter-in opening limit value A _mi-lim and the target meter-in opening A' _mi-t to a valve opening command table 686A. The valve opening command table 686A holds a predetermined correspondence relationship between the output value of the calculation unit 685A and the valve opening command i. More specifically, the valve opening command table 686A holds a relationship in which the valve opening command i increases as the output value of the calculation unit 685A increases. The valve control unit 68 then controls the opening of the opening control valves 27, 28 according to the valve opening command i specified based on the valve opening command table 686A. For example, the valve control unit 68 supplies a command current indicated by the valve opening command i to the opening control valves 27, 28.

Fig. 11 is a detailed diagram of the valve control unit 68 that performs meter-out control. The valve control unit 68 in Fig. 11 calculates a valve opening command i based on the operation amount o acquired through the boom operation lever 41 and the arm operation lever 42, the target meter-out pressure P _mo-t acquired from the target pressure calculation unit 66, the measured meter-out pressure P _mo acquired from the measured pressure calculation unit 67, the discharge side pressure P _ret , the meter-out oil passage volume V _mo , and the meter-out oil passage volume change amount V' _mo . The valve control unit 68 has a meter-out opening limit value table 681B, calculation units 682B to 685B, and a valve opening command table 686B.

The meter-out oil passage volume _Vmo is the volume of hydraulic oil to be discharged from each of the boom cylinder 14 and the arm cylinder 15. The meter-out oil passage volume change amount _V'mo is the volume of hydraulic oil to be discharged per unit time from each of the boom cylinder 14 and the arm cylinder 15. The discharge side pressure _Pret is the pressure of the hydraulic oil discharged to the hydraulic oil tank 21 (usually the pressure inside the hydraulic oil tank 21). The valve opening command i is a value indicating the opening amount of the meter-out side flow control valve (for example, flow control valve 72 in _FIG . 13) required to extend and _retract the boom cylinder 14 and the arm cylinder 15 at the target speeds vt-Bm and vt-Am, respectively.

When the hydraulic actuator is a hydraulic cylinder, the meter-out oil passage volume _Vmo and the meter-out oil passage volume change amount _V'mo are determined by the above formula 4. On the other hand, when the hydraulic actuator is a hydraulic motor, the meter-out oil passage volume _Vmo and the meter-out oil passage volume change amount _V'mo are determined by the above formula 5.

The meter-out opening limit value table 681B holds a predetermined correspondence relationship between the operation amount o and the meter-out opening limit value A _mo-lim . More specifically, the meter-out opening limit value table 681B holds a relationship in which the meter-out opening limit value A _mo-lim increases as the operation amount o increases. The meter-out opening limit value A _mo-lim is a limit value of the opening area of the flow control valve 72. The meter-out opening limit value A _mo-lim specified based on the meter-out opening limit value table 681B is output to the calculation unit 685B.

The calculation unit 684B calculates a target meter-out opening A' mo-t by substituting the actual meter-out pressure P _mo , the discharge side pressure P _ret , the meter-out oil passage volume V _mo , the meter-out oil passage volume change V' _mo , and the feedback control amount V into the following equation 9. The target meter-out opening A' _{mo-t is} a target value for the opening area of the flow control valve 72. More specifically, equation 9 is obtained by rearranging equation 8 with respect to the feedback control amount V. Then, the calculation unit 684B outputs the calculated target meter-out opening A' _mo-t to the calculation unit 685B.

The processing contents of the calculation units 682B to 685B are the same as those of the calculation units 682A to 685A shown in FIG. 10, although the specific parameters used are different. Also, the valve opening command table 686B has basic contents in common with the valve opening command table 686A shown in FIG. 10, although the specific parameters input are different. That is, the valve control unit 68 shown in FIG. 10 and FIG. 11 controls the opening amount of each of the multiple flow control valves based on the difference between the corresponding target pressure and the actual measured pressure.

The pump control unit 69 calculates a target pump capacity q p-t based on the pump discharge pressure Pp detected by the pressure sensor 31, the target pump flow rate Q _p-t obtained from the output limiting unit 64, the target rotation speed W _E-t obtained from the rotation speed control unit 62, and the target meter-in pressure P _mi-t obtained from the target pressure calculation unit 66. The target pump capacity q p _{- t} is a target value of the discharge capacity of the hydraulic pump 22 required to extend and retract the boom cylinder 14 and the arm cylinder 15 at the target speeds v _t-Bm and v _t-Am , respectively.

Figure 12 is a detailed diagram of the pump control unit 69. As shown in Figure 12, the pump control unit 69 has calculation units 691 to 695.

The calculation unit 691 outputs the maximum value of the multiple target meter-in pressures P _mi-t to the calculation unit 692. The calculation unit 692 subtracts the pump discharge pressure Pp from the maximum value acquired from the calculation unit 691 and outputs the result to the calculation unit 693. The calculation unit 693 calculates a pump flow rate correction value Z from the calculation result of the calculation unit 692 by PID control, and outputs the calculated pump flow rate correction value Z to the calculation unit 694. The calculation unit 693 adds the pump flow rate correction value Z to the target pump flow rate Q _p-t to calculate a corrected target pump flow rate Q' _p-t , and outputs the corrected target pump flow rate Q' _p-t to the calculation unit 695. The calculation unit 695 divides the corrected target pump flow rate Q' _p-t by the target rotation speed W _E-t to calculate a target pump capacity q _p-t . Then, the pump control unit 69 controls the regulator 22 a so that the hydraulic oil is discharged from the hydraulic pump 22 at the calculated target pump displacement q _pt .

The above embodiment provides the following advantages:

According to the above embodiment, the target speeds vt _-Bm , vt _{- Am are} calculated by dividing the required speeds _vr-Bm , vr-Am of the boom cylinder 14 and the arm cylinder 15 by a common speed limit gain K. This makes it possible to maintain a balance in the extension and retraction speeds of the boom cylinder 14 and the arm cylinder 15 (i.e., the operating speeds of the boom 11 and the arm 12) even if the output of the engine 20 is limited to the output limit value E.

As a result, the arm 12 moves along the trajectory intended by the operator, although at a slower moving speed than intended by the operator. This allows the balance between the operating speeds of the boom cylinder 14 and the arm cylinder 15 to be maintained, even in a horizontal pulling operation in which the boom cylinder 14 and the arm cylinder 15 are operated in combination to move the tip of the bucket 13 horizontally in order to level soil with the tip of the bucket 13.

In the above embodiment, an example has been described in which the opening of the meter-in control valves 25, 26 is indirectly controlled by adjusting the magnitude of the command current supplied to the opening control valves 27, 28. However, the objects that are directly controlled to extend and retract the boom cylinder 14 and the arm cylinder 15 at the target speeds vt _-Bm and _vt-Am are not limited to the above example. As another example, the meter-in control valves 25, 26 may be directly controlled as solenoid proportional valves.

In the above embodiment, in the schematic diagram of the hydraulic circuit shown in FIG. 13, an example was described in which the opening amount of the meter-in side flow control valve 71 that controls the supply amount Ami of hydraulic oil to the boom cylinder 14 and the arm cylinder 15 was controlled, but the opening amount of the meter-out side flow control valve 72 that controls the discharge amount Amo of hydraulic oil from the boom cylinder 14 and the arm cylinder 15 may also be controlled.

In addition, in the above embodiment, an example of performing a combined operation of the boom cylinder 14 and the arm cylinder 15 has been described, but the combination of hydraulic actuators performing the combined operation is not limited to the above example. Figure 14 is a drive path diagram showing another combination of hydraulic actuators performing a combined operation.

As shown in FIG. 14, another example of a combined operation is to operate the swing motor 6 and the boom cylinder 14 in parallel when loading soil scooped up by the bucket 13 onto the bed of a dump truck. The configurations, arrangements, and roles of the directional control valve 74, meter-in control valve 75, opening control valve 76, and pressure sensors 77 and 78 for supplying and discharging hydraulic oil to the swing motor 6 are the same as those of the directional control valve 23, meter-in control valve 25, opening control valve 27, and pressure sensors 32 and 33 described above.

By applying the above-mentioned processing to such a combined operation, even when the soil scooped up by the bucket 13 is loaded onto the bed of a dump truck, the bucket 13 can be moved along the trajectory intended by the operator, thereby preventing the bucket 13 from coming into contact with the dump truck.

The above-described embodiments are illustrative examples of the present invention, and are not intended to limit the scope of the present invention to these embodiments. Those skilled in the art can implement the present invention in various other forms without departing from the spirit of the present invention.

1. Hydraulic excavator (work machine)
2 Lower traveling body 3 Upper rotating body 4 Crawler 5 Travel motor (hydraulic actuator)
6 Swing motor (hydraulic actuator)
7 Swing frame 8 Cab 9 Counterweight 10 Front work unit 11 Boom 12 Arm 13 Bucket 14 Boom cylinder (hydraulic actuator)
15 Arm cylinder (hydraulic actuator)
16 Bucket cylinder (hydraulic actuator)
20 Engine (prime mover)
21 hydraulic oil tank 22 hydraulic pump (hydraulic pump)
22a Regulator 23, 24 Directional control valve (flow control valve)
25, 26 Meter-in control valve (flow control valve)
27, 28 Opening amount control valve (flow control valve)
29 Relief valve 30 Bleed-off valve 31 to 35, 77, 78 Pressure sensors 36 to 39 Attitude sensor 41 Boom operation lever (operation device, operation amount detection sensor)
42 Arm operation lever (operation device, operation amount detection sensor)
43 EC dial (engine speed setting device)
50 Controller 51 CPU
52 Memory

Claims (3)

A prime mover that generates a driving force;
a hydraulic pump that discharges pressure oil by the driving force of the prime mover;
a discharge pressure sensor for detecting a discharge pressure of the hydraulic pump;
A plurality of hydraulic actuators operated by pressure oil supplied from the hydraulic pump;
a plurality of flow control valves for controlling the supply and discharge amounts of pressure oil to and from the plurality of hydraulic actuators;
an operating device that operates each of the hydraulic actuators;
an operation amount detection sensor for detecting an operation amount of the operation device;
A working machine including the prime mover, the hydraulic pump, and a controller that controls at least one of the plurality of flow control valves,
The controller:
calculating a pump flow rate limit value of pressure oil that can be discharged by the hydraulic pump based on a predetermined output limit value of the prime mover and a discharge pressure of the hydraulic pump detected by the discharge pressure sensor;
calculating a required speed for each of the hydraulic actuators based on the operation amount detected by the operation amount detection sensor;
Calculating a pump flow rate estimate value which is an estimate value of a flow rate of pressure oil to be discharged by the hydraulic pump in order to satisfy the calculated multiple required speeds;
calculating a plurality of target speeds by correcting the plurality of required speeds based on a ratio between the pump flow rate limit value and the pump flow rate estimated value;
A work machine comprising: a control unit that controls at least one of the prime mover, the hydraulic pump, and the plurality of flow control valves so that each of the plurality of hydraulic actuators operates at the target speed. 2. The work machine according to claim 1,
a plurality of pressure sensors for detecting actual pressures of pressure oil supplied to and discharged from each of the plurality of hydraulic actuators;
The controller:
calculating a target pressure of pressure oil supplied to and discharged from each of the hydraulic actuators based on the target speed;
A working machine characterized in that the opening amount of each of the plurality of flow control valves is controlled based on a difference between the target pressure and the actually measured pressure. 2. The work machine according to claim 1,
The flow control valve is
a directional control valve for controlling a supply direction of pressure oil to the hydraulic actuator;
a meter-in control valve that is disposed in a flow path from the hydraulic pump to the directional control valve and controls a flow rate of pressure oil supplied to the hydraulic actuator through the directional control valve,
The working machine, wherein the controller controls at least one of the directional control valve and the meter-in control valve.

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