Control method for work machines, control program for work machines, control system for work machines, and work machines

Abstract

To provide a control method of a work machine, a control program for a work machine, a control system for a work machine, and a work machine that facilitate improving an efficiency of a motor while suppressing functions and performance required to a pump.SOLUTION: A work machine 3 comprises: a motor 41 operating by receiving power from a power source (a battery 22); and a pump 42 driven by the motor 41 and discharging a working fluid to an actuator. A control method of the work machine 3 includes adjusting a rotation speed of the motor 41 when driving the motor 41 so that a torque of the motor 41 does not exceed a torque upper limit. The torque upper limit is set in accordance with the rotation speed of the motor 41.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a control method for a working machine, a control program for a working machine, a control system for a working machine, and a working machine, which are used for a working machine including a pump that is driven by a motor operating under power supply and discharges a working fluid to an actuator.

Background Art

[0002] As related art, a working machine (hydraulic excavator) including a motor (electric motor), a variable displacement pump (hydraulic pump) driven by the motor, and a plurality of actuators driven by a working fluid (pressure oil) discharged from the pump is known (see, for example, Patent Document 1). The working machine according to the related art controls so that the absorption torque of the pump does not exceed a preset maximum torque by reducing the discharge flow rate of the pump when the discharge pressure of the pump increases.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the above related art, as the pump, it is necessary to use a variable displacement pump whose discharge flow rate can be adjusted. Further, in order to improve the efficiency of the motor (suppress the power consumption), a higher-performance variable displacement pump is required.

[0005] An object of the present invention is to provide a control method for a working machine, a control program for a working machine, a control system for a working machine, and a working machine, which are easy to improve the efficiency of a motor while suppressing the functions and performance required for the pump.

Means for Solving the Problems

[0006] A control method for a work machine according to one aspect of the present invention is a control method for a work machine comprising a motor that operates by receiving power from a power source, and a pump driven by the motor that discharges a working fluid to an actuator, wherein when the motor is driven, the rotational speed of the motor is adjusted so that the torque of the motor does not exceed a torque upper limit. The torque upper limit is set in correspondence with the rotational speed.

[0007] A control program for a work machine according to one aspect of the present invention is a program that causes one or more processors to execute a control method for the work machine.

[0008] A control system for a work machine according to one aspect of the present invention is used to control a work machine comprising a motor that operates by receiving power from a power source, and a pump driven by the motor that discharges a working fluid to an actuator. The control system for the work machine includes an adjustment processing unit. When driving the motor, the adjustment processing unit adjusts the rotational speed of the motor so that the torque of the motor does not exceed a torque upper limit. The torque upper limit is set in correspondence with the rotational speed.

[0009] A working machine according to one aspect of the present invention comprises a control system for the working machine and a machine body on which the motor and the pump are mounted. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a control method for a work machine, a control program for a work machine, a control system for a work machine, and a work machine that can easily improve the efficiency of a motor while suppressing the functions and performance required of a pump. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a schematic perspective view showing the overall configuration of the work machine according to Embodiment 1. [Figure 2]Figure 2 is a schematic diagram showing the electrical circuit and other components of the work machine according to Embodiment 1. [Figure 3] Figure 3 is a schematic circuit diagram showing an example of an inverter for a work machine according to Embodiment 1. [Figure 4] Figure 4 is an explanatory diagram showing an example of a two-dimensional map representing the correlation between the torque upper limit and rotational speed used in the control method of the work machine according to Embodiment 1. [Figure 5] Figure 5 is an explanatory diagram showing an example of rotational speed control in normal mode using the control method for the work machine according to Embodiment 1. [Figure 6] Figure 6 is an explanatory diagram showing an example of rotational speed control in eco mode using the control method for a work machine according to Embodiment 1. [Figure 7] Figure 7 is an explanatory diagram showing an example of switching control from normal mode to eco mode using the control method for a work machine according to Embodiment 1. [Figure 8] Figure 8 is an explanatory diagram showing an example of switching control from eco mode to normal mode using the control method for a work machine according to Embodiment 1. [Figure 9] Figure 9 is a flowchart showing an example of the operation of the control system for a work machine according to Embodiment 1. [Figure 10] Figure 10 is an explanatory diagram showing an example of rotational speed control by the control method for a work machine according to Embodiment 2. [Modes for carrying out the invention]

[0012] The embodiments of the present invention will be described below with reference to the attached drawings. The following embodiments are examples that embody the present invention and are not intended to limit the technical scope of the present invention.

[0013] (Embodiment 1) [1] Overall structure As shown in FIG. 1, the working machine 3 according to this embodiment includes a traveling unit 31, a turning unit 32, and a working unit 33 on the machine body 30. Further, as shown in FIG. 2, the working machine 3 further includes a control system 1 for working machines (hereinafter also simply referred to as "control system 1").

[0014] As used in this disclosure, "working machine" means various working machines. As an example, it is a working vehicle such as a backhoe (including hydraulic excavators, mini excavators, etc.), a wheel loader, and a carrier. The working machine 3 includes a working unit 33 configured to be able to execute one or more operations. The working machine 3 is not limited to a "vehicle", and may be, for example, a working flying object such as a working ship, a drone, or a multicopter. Further, the working machine 3 is not limited to construction machinery (construction machines), and may be, for example, agricultural machinery (agricultural machines) such as a rice transplanter, a tractor, or a combine. In this embodiment, unless otherwise specified, the working machine 3 is a backhoe with a lifting function (crane function), and an example will be given to explain the case where, in addition to the lifting work, excavation work, leveling work, trench excavation work, or loading work can be executed as work.

[0015] In this embodiment, for convenience of explanation, the vertical direction in the state where the working machine 3 can be used is defined as the up-down direction D1. Further, in the non-turning state of the turning unit 32, the front-rear direction D2 and the left-right direction D3 are defined based on the direction seen from the user (operator) boarding the working machine 3 (the cab 321). In other words, each direction used in this embodiment is a direction defined based on the machine body 30 of the working machine 3, and the direction in which the machine body 30 moves when the working machine 3 moves forward is "front", and the direction in which the machine body 30 moves when the working machine 3 moves backward is "rear". Similarly, the direction in which the front end of the machine body 30 moves when the working machine 3 turns right is "right", and the direction in which the front end of the machine body 30 moves when the working machine 3 turns left is "left". However, these directions are not intended to limit the use direction (direction during use) of the working machine 3.

[0016] The working machine 3 according to this embodiment has at least a part of a drive device that generates power electrified. In this embodiment, as an example, the working machine 3 is an electric (electrical) working machine that uses only the motor 41 (see FIG. 2) as a power source. The motor 41 is an electric motor that generates power by receiving supply of electric power (electrical energy). More specifically, the motor 41 is an alternating current motor (alternating current electric motor) driven by alternating current power supplied from the inverter 21 (see FIG. 2).

[0017] The power generated by the motor 41 is used at least for driving the pump 42 (see FIG. 2) in the drive device. In this embodiment, furthermore, the motor 41 also functions as a generator and performs a power generation operation of converting the power (rotational force) applied to the output shaft of the motor 41 into electric power (electrical energy). The electric power generated by the motor 41 is output to the battery 22 (see FIG. 2) via the inverter 21. The drive mode and the power generation mode of the motor 41 are switched by an integrated controller that controls the entire working machine 3.

[0018] In the working machine 3, as described above, the pump 42 is driven by the motor 41, and hydraulic oil is supplied from the pump 42 to hydraulic actuators (including the hydraulic motor 43 and the hydraulic cylinder 44, etc.) of each part of the machine body 30, whereby the machine body 30 is driven. That is, the hydraulic oil is an example of the "actuating fluid", and by being discharged from the pump 42 to the hydraulic actuator (including the hydraulic motor 43 and the hydraulic cylinder 44, etc.), the actuator is driven. The hydraulic actuator is an example of the "actuator", and is driven by utilizing the fluid power (pressure × flow rate) of the actuating fluid (hydraulic oil), and converts the fluid power into mechanical power. Further, the working machine 3 is controlled, for example, by a user (operator) boarding the cab 321 of the machine body 30 operating an operation lever or the like of the operating device.

[0019] That is, the working machine 3 includes a motor 41 that operates by receiving power supply from a power source (battery 22), and a pump 42 that is driven by the motor 41 and discharges an actuating fluid to the actuator.

[0020] In this embodiment, as described above, it is assumed that the work machine 3 is a ride-on type backhoe, so the work unit 33 is driven according to the operation of the user (operator) who is seated in the driver's cab 321 and performs work such as excavation. The driver's cab 321 in which the user sits is located in the slewing unit 32.

[0021] The running unit 31 has a driving function and is configured to be able to travel on the ground (including turning). The running unit 31 has, for example, a pair of left and right crawlers 311 and a blade 312. The running unit 31 further has a hydraulic motor 43 (actuator) for driving the crawlers 311.

[0022] The slewing section 32 is located above the traveling section 31 and is configured to rotate around a rotation axis perpendicular to the traveling section 31. The slewing section 32 has a hydraulic motor (actuator) for slewing. The slewing section 32 is equipped with a driver's cab 321 and a pump 42, among other things. Furthermore, a boom bracket 322 to which the working section 33 is attached is provided at the front end of the slewing section 32.

[0023] The work unit 33 is configured to perform operations including lifting operations. The work unit 33 is supported by the boom bracket 322 of the slewing unit 32 and performs operations. The work unit 33 has a bucket 331, a boom 332, an arm 333, etc. The work unit 33 further has actuators (including a hydraulic cylinder 44 and a hydraulic motor, etc.) for driving each part.

[0024] The bucket 331 is a type of attachment (working tool) that is mounted on the machine body 30 of the work machine 3, and consists of any tool selected from several types of attachments according to the nature of the work. For example, the bucket 331 is detachably mounted to the machine body 30 and can be replaced according to the nature of the work. In addition to the bucket 331, various other tools can be used as attachments for the work machine 3, such as breakers, augers, crushers, forks, fork claws, steel frame cutters, asphalt milling machines, brush cutters, rippers, mulchers, tilt rotators, and tampers. The work unit 33 performs its work by driving the bucket 331 with power from the drive unit.

[0025] The boom 332 is rotatably supported by the boom bracket 322 of the slewing section 32. Specifically, the boom 332 is rotatably supported by the boom bracket 322 around a rotation axis along the horizontal direction. The boom 332 has a shape that extends upward from the base end supported by the boom bracket 322. The arm 333 is connected to the tip of the boom 332. The arm 333 is rotatably supported relative to the boom 332 around a rotation axis along the horizontal direction. A bucket 331 is attached to the tip of the arm 333.

[0026] The work unit 33 operates by receiving power from the motor 41, which serves as the power source. Specifically, the motor 41 drives the pump 42, and the pump 42 supplies working fluid (hydraulic oil) to the actuators (hydraulic cylinders 44, etc.) of the work unit 33, thereby causing each part of the work unit 33 (bucket 331, boom 332, and arm 333) to operate.

[0027] In this embodiment, the work unit 33 has a multi-joint structure in which the boom 332 and the arm 333 are configured to rotate independently. That is, by each of the boom 332 and the arm 333 rotating around a rotation axis along the horizontal direction, the multi-joint work unit 33 including the boom 332 and the arm 333 can be extended or folded as a whole.

[0028] The traveling section 31 and the slewing section 32, like the working section 33, operate by receiving power from the motor 41, which serves as the power source. In other words, the slewing section 32 and the traveling section 31 operate when hydraulic fluid is supplied from the pump 42 to the hydraulic motor 43 of the traveling section 31 and the hydraulic motor of the slewing section 32, etc.

[0029] The motor 41 is mounted on the swivel section 32 along with the pump 42 and other components. The motor 41 is driven by power supplied from the battery 22 (more precisely, the inverter 21 electrically connected to the battery 22) which serves as the power source.

[0030] Figure 2 schematically shows the hydraulic and electrical circuits (electrical connection relationships) of the work machine 3 according to this embodiment. In Figure 2, solid lines indicate high-pressure (hydraulic fluid) oil passages, and dashed lines indicate electrical connection paths (arrows on the dashed lines indicate electrical signal paths).

[0031] As shown in Figure 2, the work machine 3 includes a motor 41, a pump 42 driven by the motor 41, and actuators 40 such as a hydraulic motor 43 and a hydraulic cylinder 44, as well as an inverter 21, a battery 22, a control valve 45, and a relief valve 46. Furthermore, the work machine 3 includes a rotation speed setting unit 34 and a mode switching unit 35.

[0032] Motor 41 is an AC motor driven by AC power supplied from inverter 21. The hydraulic fluid from pump 42, driven by motor 41, is supplied to actuators 40 such as the hydraulic motor 43 of the travel section 31 (see Figure 1), the hydraulic motor of the slewing section 32, and the hydraulic cylinder 44 of the work section 33 (see Figure 1). This drives the actuators 40, which are hydraulic actuators.

[0033] In this embodiment, pump 42 is a constant-displacement gear pump. Generally, positive displacement pumps, such as hydraulic pumps, include variable-displacement pumps, which can change the amount of hydraulic fluid discharged per rotation of the drive shaft, and constant-displacement pumps (also called fixed-displacement or constant-discharge pumps), which have a constant (fixed) amount of hydraulic fluid discharged per rotation of the drive shaft. Furthermore, pumps are classified into several types depending on the drive method, such as gear pumps, vane pumps, and piston pumps. In the work machine 3 of this embodiment, a constant-displacement gear pump with a relatively simple structure is used as pump 42, making it relatively resistant to foreign matter and available at low cost.

[0034] The control valve 45 is installed in the hydraulic fluid path (oil passage) to each actuator 40 and is a valve that controls the flow direction of the hydraulic fluid supplied from the pump 42, determining the starting, stopping, or operating direction of the actuator 40. In this embodiment, as an example, the control valve 45 is a pilot-operated directional control valve that can switch the direction and flow rate of the hydraulic fluid from the pump 42, and is driven by pilot oil supplied from a pilot pump, which serves as an input command. Here, for example, a remote control valve is provided in the pilot oil supply passage to the control valve 45, and the pilot oil supplied to the control valve 45 is adjusted according to the operation of an operating device (operating lever).

[0035] The relief valve 46 sets the relief pressure, which is the maximum value of the (discharge) pressure of the pump 42. The relief valve 46 is connected to the oil passage from the pump 42 to the control valve 45. When the hydraulic pressure, which is the pressure of the hydraulic fluid in the oil passage (hydraulic circuit), exceeds the relief pressure, the relief valve 46 activates and reduces the hydraulic pressure to below the relief pressure.

[0036] The inverter 21 has an input capacitor 211 and converts the DC voltage across the input capacitor 211 into an AC voltage for output. The input capacitor 211 is located in the input stage of the inverter 21 (i.e., between the input terminals of the inverter 21) and is electrically connected to the battery 22 via a bus line. The output terminals of the inverter 21 are electrically connected to the motor 41. Therefore, the inverter 21 drives the motor 41, which is an AC motor, by converting the DC voltage applied from the battery 22 to the input capacitor 211 into an AC voltage and outputting it to the motor 41. The inverter 21 is controlled by a control signal from the control system 1 and performs a power conversion operation from DC power to AC power in accordance with the control signal.

[0037] Figure 3 is a schematic circuit diagram showing a specific configuration example of the inverter 21. As shown in Figure 3, the inverter 21 has an input capacitor 211 in addition to a plurality (six in this case) of switching elements Q1 to Q6. Each switching element Q1 to Q6 is made of a transistor and is individually controlled on / off according to a control signal from the control system 1. Here, a pair of switching elements Q1, Q2, a pair of switching elements Q3, Q4, and a pair of switching elements Q5, Q6 are each electrically connected in series across the input capacitor 211. A motor 41 is connected to a terminal located at the midpoint of the three-phase arm formed by each pair of these switching elements. As a result, when the inverter 21 is operating, three-phase AC power is supplied to the motor 41, and the motor 41 is driven.

[0038] Battery 22 is an example of a "power source" that supplies DC power to the inverter 21, etc. In this embodiment, as an example, battery 22 is a rechargeable secondary battery (energy storage device), such as a lithium-ion battery. Battery 22 is electrically connected to the bus line. As a result, when battery 22 has sufficient remaining capacity, a DC voltage is applied from battery 22 to the inverter 21, etc. via the bus line.

[0039] The control system 1 primarily consists of a computer system having one or more processors such as a CPU (Central Processing Unit) and one or more memories such as ROM (Read Only Memory) and RAM (Random Access Memory), and performs various processes (information processing). In this embodiment, the control system 1 is an integrated controller that controls the entire work machine 3, and consists of, for example, an electronic control unit (ECU). However, the control system 1 may be provided separately from the integrated controller. The control system 1 will be explained in detail in the section "[2] Configuration of the Control System".

[0040] The rotation speed setting unit 34 accepts user (operator) input to set the target rotation speed of the motor 41 that drives the pump 42. The rotation speed setting unit 34 has an operating unit such as a potentiometer or rotary encoder, and accepts user input by outputting an electrical signal corresponding to the user's input to the control system 1.

[0041] The mode switching unit 35 accepts user (operator) input to switch the operating mode of the work machine 3. Here, the operating mode of the work machine 3 is selectively selected from a plurality of modes, including at least a normal mode and an eco mode. In other words, the work machine 3 operates in the operating mode selectively selected by the mode switching unit 35 from among the plurality of modes, and the operating mode switches when a different operating mode is selected by the mode switching unit 35. The normal mode is an operating mode in which the maximum output value of the motor 41 that drives the pump 42 is set to a steady value, and the eco mode is an operating mode in which the maximum output value of the motor 41 that drives the pump 42 is set to an energy-saving value lower than the steady value. In other words, in eco mode, the work machine 3 can reduce the power consumption of the motor 41 by suppressing the maximum output (power) of the actuator 40 driven by the working fluid supplied from the pump 42, compared to the normal mode.

[0042] In this embodiment, as an example, the mode switching unit 35 is implemented by a display device (monitor) located in the driver's cab 321 of the machine body 30. The display device is a user interface that receives operation input from the user (operator) and outputs various information to the user. The display device consists of, for example, a touch panel display and accepts various operations from the user by outputting electrical signals corresponding to the user's operation to the control system 1. As a result, the user (operator) can view the display screen shown on the display device and operate the display device as needed.

[0043] In addition to the above-described configuration, the machine body 30 is further equipped with an operating lever, a cutoff lever, a communication terminal, a charging circuit (for charging the battery 22), and various electrical equipment. The electrical equipment (including facilities) includes various devices such as a display device, lighting equipment, communication equipment, and air conditioning equipment. The display device is located in the operator's cab 321 of the machine body 30 and is a user interface for receiving operation input from the user (operator) and outputting various information to the user. Furthermore, the machine body 30 is equipped with sensors for monitoring the operating status of the machine body 30, such as a hydraulic oil temperature sensor, sensors (including cameras, etc.) for monitoring the surroundings of the machine body 30, and an hour meter for measuring operating time. The machine body 30 is also equipped with sensors for detecting the status of the cutoff lever and main switch, etc.

[0044] [2] Control system configuration Next, the configuration of the control system 1 according to this embodiment will be described with reference to Figure 2. The control system 1 controls each part (including the inverter 21, etc.) of the machine body 30 of the work machine 3. The control system 1 is a component of the work machine 3 and together with the machine body 30, etc., constitutes the work machine 3. In other words, the work machine 3 according to this embodiment comprises at least the control system 1 and the machine body 30 (including the traveling section 31, the rotating section 32, and the working section 33) on which the motor 41 and the pump 42 are mounted.

[0045] The control system 1 is used to control a work machine 3 equipped with a motor 41 and a pump 42, and includes an adjustment processing unit 12 as shown in Figure 2. The control system 1 further includes a control processing unit 11, a switching processing unit 13, and a storage unit 14. In this embodiment, as an example, the control system 1 mainly consists of a computer system having one or more processors, so these multiple functional units (adjustment processing unit 12, etc.) are realized by one or more processors executing a control program for the work machine. These multiple functional units included in the control system 1 may be distributed and provided in multiple housings, or they may be provided in a single housing.

[0046] The control system 1 is configured to communicate with devices provided in various parts of the machine body 30. In other words, the control system 1 is connected to at least the inverter 21, the rotation speed setting unit 34, and the mode switching unit 35. This allows the control system 1 to control the inverter 21 and other devices, and to acquire electrical signals (corresponding to user operations) from the rotation speed setting unit 34 and the mode switching unit 35. Here, the control system 1 may exchange various types of information (data) directly with each device, or indirectly via a relay or the like.

[0047] The control processing unit 11 executes control processing to drive the motor 41. Here, the control processing unit 11 specifies the rotational speed of the motor 41 by a rotational speed command and controls the motor 41 so that it operates at the target rotational speed included in the rotational speed command. The rotational speed and torque of the motor 41 are fed back (from the inverter 21) to the control system 1 (control processing unit 11).

[0048] In this embodiment, the control processing unit 11 controls the inverter 21 to perform "rotational speed control," which controls the rotational speed (rotational velocity) of the motor 41. Specifically, the control processing unit 11 adjusts the rotational speed of the motor 41 by adjusting the frequency of the AC power supplied from the inverter 21 to the motor 41. Here, the control processing unit 11 adjusts the rotational speed of the motor 41 so that the rotational speed of the motor 41 fed back from the inverter 21 approaches the "target rotational speed," which is the target value of the motor 41's rotational speed. As a result, the rotational speed of the motor 41 is controlled to the target rotational speed.

[0049] When the motor 41 is driven, the adjustment processing unit 12 performs an adjustment process to adjust the rotational speed of the motor 41 so that the torque of the motor 41 does not exceed a torque upper limit value that is set in accordance with the rotational speed of the motor 41. In other words, when the control processing unit 11 drives the motor 41 by rotational speed control, the adjustment processing unit 12 adjusts the target rotational speed so that the torque of the motor 41 does not exceed the torque upper limit value. Here, the torque upper limit value is set in accordance with the rotational speed of the motor 41 and is a value that is uniquely determined according to the rotational speed of the motor 41.

[0050] The switching processing unit 13 performs a switching process to switch the operating mode of the work machine 3. Specifically, the switching processing unit 13 switches the operating mode of the work machine 3 between at least normal mode and eco mode in response to the electrical signal output from the mode switching unit 35. In other words, when the mode switching unit 35 selects normal mode, the switching processing unit 13 sets the operating mode of the work machine 3 to normal mode, and when the mode switching unit 35 selects eco mode, the switching processing unit 13 sets the operating mode of the work machine 3 to eco mode.

[0051] The memory unit 14 stores information such as the correspondence between the torque upper limit and the rotational speed of the motor 41. In this embodiment, as an example, the memory unit 14 consists of a non-volatile memory. The information stored in the memory unit 14 that shows the correspondence between the torque upper limit and the rotational speed of the motor 41 is, for example, two-dimensional map data representing the correlation between the torque upper limit and the rotational speed of the motor 41.

[0052] [3] Control method for working machinery The following describes an example of a control method (hereinafter simply referred to as "control method") for the work machine 3, which is mainly performed by the control system 1, with reference to Figures 4 to 9.

[0053] The control method according to this embodiment is executed by a control system 1, which mainly consists of a computer system; in other words, it is embodied in a control program for a work machine (hereinafter simply referred to as the "control program"). That is, the control program according to this embodiment is a computer program that causes one or more processors to execute each process related to the control method. Such a control program may be executed in cooperation with, for example, the control system 1 and the display device.

[0054] Here, the control system 1 executes the following various processes related to the control method when a specific pre-set start operation is performed to execute the control program. The start operation is, for example, the operation to start the work machine 3. On the other hand, the control system 1 terminates the following various processes related to the control method when a specific pre-set end operation is performed. The end operation is, for example, the operation to stop the work machine 3.

[0055] [3.1] Adjustment process First, the adjustment process included in the control method according to this embodiment will be described. As described above, the adjustment process is a process of adjusting the rotational speed (of the motor 41) so that the torque of the motor 41 does not exceed the upper torque value set in relation to the rotational speed of the motor 41 when the motor 41 is driven.

[0056] In this embodiment, as an example, correspondence relationships G1 and G2 between the torque upper limit and the rotational speed of the motor 41, as shown in Figure 4, are pre-registered (stored) in the storage unit 14, and the adjustment processing unit 12 performs adjustment processing using these correspondence relationships G1 and G2. Here, correspondence relationship G1 shows the relationship between the torque upper limit and the rotational speed of the motor 41 when the operating mode of the work machine 3 is in "normal mode," and correspondence relationship G2 shows the relationship between the torque upper limit and the rotational speed of the motor 41 when the operating mode of the work machine 3 is in "eco mode." In other words, when the operating mode of the work machine 3 is in "normal mode," the adjustment processing unit 12 uses correspondence relationship G1 to adjust the rotational speed of the motor 41 so that the torque of the motor 41 does not exceed the torque upper limit. On the other hand, when the operating mode of the work machine 3 is in "eco mode," the adjustment processing unit 12 uses correspondence relationship G2 to adjust the rotational speed of the motor 41 so that the torque of the motor 41 does not exceed the torque upper limit.

[0057] In Figure 4, the horizontal axis represents the rotational speed (rotational velocity) of the motor 41 [rpm], and the vertical axis represents the torque of the motor 41 [Nm]. Corresponding relationships G1 and G2 represent the upper torque limits corresponding to each rotational speed. For example, in "normal mode," the adjustment processing unit 12 adjusts the rotational speed of the motor 41 within the range of correspondence G1 or less so that the torque of the motor 41 is less than or equal to the upper torque limit defined by correspondence G1. Similarly, in "eco mode," the adjustment processing unit 12 adjusts the rotational speed of the motor 41 within the range of correspondence G2 or less so that the torque of the motor 41 is less than or equal to the upper torque limit defined by correspondence G2.

[0058] Here, the maximum torque defined by correspondences G1 and G2 is T2 [Nm], and the maximum rotational speed defined by correspondences G1 and G2 is N2 [rpm]. According to correspondences G1 and G2, as the rotational speed of motor 41 decreases from the maximum rotational speed N2 [rpm], the torque upper limit gradually increases and plateaus at the maximum torque T2 [Nm]. Furthermore, correspondence G2 is set to a range less than or equal to the torque upper limit of correspondence G1 for the same rotational speed, so that the output of motor 41 (i.e., the input of pump 42), which is expressed as the product of rotational speed and torque, is smaller than that of correspondence G1.

[0059] Furthermore, the torque upper limit includes a value higher than the "relief torque," which is the torque corresponding to the relief pressure set as the maximum discharge pressure of the pump 42. In other words, in the example in Figure 4, if the relief torque is T1 [Nm], then the maximum torque T2 [Nm], which is the maximum value of the torque upper limit defined by the correspondence G1 and G2, is set to a value higher (larger) than the relief torque T1 [Nm]. As a result, for example, when increasing the rotational speed of the motor 41 from the rotational speed N1 [rpm] corresponding to the relief torque T1 [Nm], it is possible to generate a torque in the motor 41 that exceeds the relief torque T1 [Nm] and accelerate the motor 41 with that torque.

[0060] According to the correspondence relationship G1 described above, in "normal mode," adjustment processing as illustrated in Figure 5 is performed. That is, for example, as shown in Figure 5, when the load on the actuator 40 increases while the motor 41 is driven at a rotational speed N3 [rpm] and a torque T3 [Nm], the torque of the motor 41 increases. In this case, if the torque of the motor 41 increases to a relief torque T1 [Nm], the adjustment processing unit 12 reduces the rotational speed of the motor 41 to a rotational speed N1 [rpm] corresponding to the relief torque T1 [Nm], according to the correspondence relationship G1. In other words, by increasing the torque of the motor 41 and raising the discharge pressure of the pump 42, while reducing the rotational speed of the motor 41 and decreasing the discharge flow rate of the pump 42, the output of the motor 41 (i.e., the input of the pump 42) can be kept approximately constant.

[0061] Furthermore, according to the correspondence relationship G2 described above, in "eco mode," adjustment processing as illustrated in Figure 6 is performed. That is, for example, as shown in Figure 6, when the load on the actuator 40 increases while the motor 41 is driven at a rotational speed N4 [rpm] and a torque T4 [Nm], the torque of the motor 41 increases. In this case, if the torque of the motor 41 increases to T5 [Nm], the adjustment processing unit 12 reduces the rotational speed of the motor 41 to a rotational speed N5 [rpm] corresponding to the torque T5 [Nm], according to the correspondence relationship G2. In other words, by increasing the torque of the motor 41 and raising the discharge pressure of the pump 42, while reducing the rotational speed of the motor 41 and decreasing the discharge flow rate of the pump 42, the output of the motor 41 (i.e., the input of the pump 42) can be kept approximately constant.

[0062] In this embodiment, the adjustment processing unit 12 basically adjusts the rotational speed of the motor 41 according to the torque of the motor 41. That is, if the torque of the motor 41 increases, the adjustment processing unit 12 decreases the rotational speed of the motor 41 according to the corresponding relationship G1, G2, and conversely, if the torque of the motor 41 decreases, it increases the rotational speed of the motor 41 according to the corresponding relationship G1, G2. As a result, the adjustment processing unit 12 can maintain the motor output (output of the motor 41), which is expressed as the product of the rotational speed and the upper limit of the torque, at a predetermined value (steady-state value).

[0063] Here, the output of motor 41 (input to pump 42), which is expressed as the product of the rotational speed and torque of motor 41, and the output of pump 42, which is expressed as the product of the discharge flow rate and discharge pressure of pump 42, should be the same if the losses of pump 42 are ignored. Therefore, by keeping the output of motor 41 approximately constant through the adjustment process described above, the output of pump 42 will also be kept approximately constant.

[0064] As described above, even if the pump 42 is a constant-displacement pump, the discharge flow rate of the pump 42 can be varied by controlling the motor 41, as if it were a variable-displacement pump, and the output of the pump 42 can be kept approximately constant. In other words, even with a constant-displacement pump 42, the discharge flow rate of the pump 42 can be adjusted by adjusting the rotational speed of the motor 41 that drives it, so that fluctuations in the discharge pressure of the pump 42 can be absorbed by fluctuations in the discharge flow rate, and the output of the pump 42, which is expressed as the product of the discharge flow rate and discharge pressure of the pump 42, can be kept approximately constant. As a result, it is not essential to use a variable-displacement pump that can adjust the discharge flow rate as the pump 42, and even when it is necessary to increase the efficiency of the motor 41 (to keep power consumption low), it is possible to use a pump with a relatively simple structure. Therefore, the control method according to this embodiment has the advantage that it is easy to improve the efficiency of the motor 41 while suppressing the functions and performance required of the pump 42.

[0065] Furthermore, in this embodiment, as described above, the torque limit is determined according to the rotational speed such that the torque limit decreases as the rotational speed increases. In other words, if the rotational speed of the motor 41 changes, the torque limit is automatically determined accordingly. With this configuration, it becomes easier to maintain the output of the motor 41 (input of the pump 42), which is expressed as the product of the rotational speed and torque of the motor 41, at a nearly constant level.

[0066] Furthermore, in this embodiment, as described above, the torque limit is determined according to the rotational speed so that the motor output, expressed using the rotational speed and torque limit, falls within a predetermined range. In this embodiment, as an example, the width of the predetermined range is set to be as small as possible to maintain the motor output (output of motor 41), which is expressed as the product of the rotational speed and torque limit, at a predetermined value (steady-state value). However, the predetermined range may have a certain width, in which case the motor output may fluctuate within the predetermined range without being maintained at a predetermined value. With this configuration, the output of pump 42 can be maintained at a substantially constant level, just like a variable displacement pump.

[0067] Furthermore, in this embodiment, if the rotational speed at which the torque of the motor 41 reaches the torque upper limit is defined as the maximum rotational speed, it is not essential to increase the rotational speed of the motor 41 to the maximum rotational speed; it is sufficient for the rotational speed of the motor 41 to be adjusted to a range below the maximum rotational speed. In other words, if the maximum rotational speed is defined as the maximum value of the rotational speed at which the torque does not exceed the torque upper limit, the rotational speed is adjusted to a value below the maximum rotational speed. As a result, it is possible to set the motor output (output of the motor 41) to a more appropriate value.

[0068] [3.2] Switching process Next, the switching process included in the control method according to this embodiment will be described. As described above, the switching process is the process of switching the operating mode of the work machine 3. In this embodiment, the operating mode is switched at least between normal mode and eco mode. When switching between normal mode and eco mode, the correspondence G1 and G2 used in the adjustment process are switched.

[0069] Specifically, when switching from normal mode to eco mode, the operating point is shifted from correspondence G1 to correspondence G2, for example, as shown in Figure 7. This reduces the output of motor 41, which is expressed as the product of rotational speed and torque, and thus reduces the input to motor 41, i.e., the power consumption of motor 41. There are three patterns for shifting the operating point: arrow A11, where the torque is constant and only the rotational speed is changed (decreased); arrow A12, where the rotational speed is constant and only the torque is changed (decreased); and arrow A13, where both rotational speed and torque are changed (decreased).

[0070] On the other hand, when switching from eco mode to normal mode, the operating point is shifted from correspondence G2 to correspondence G1, for example, as shown in Figure 8. As a result, the output of motor 41, which is expressed as the product of rotational speed and torque, increases, and therefore the input to motor 41, i.e., the power consumption of motor 41, increases. There are three patterns for shifting the operating point: arrow A21, where the torque is constant and only the rotational speed is changed (increased); arrow A22, where the rotational speed is constant and only the torque is changed (increased); and arrow A23, where both rotational speed and torque are changed (increased).

[0071] As explained above, the target value (predetermined value) of the motor output (output of motor 41), expressed using rotational speed and torque upper limit, is not fixed and may change depending on the operating mode, for example. For example, in eco mode, the target value of the motor output (output of motor 41) is set lower in eco mode than in normal mode. In other words, the control method according to this embodiment further includes changing the predetermined range. This makes it possible to appropriately select, for example, a state in which power consumption is reduced, such as eco mode, and a state in which work is prioritized and a larger output can be used, such as power mode.

[0072] [3.3] Flowchart Next, the overall flow of the control method will be explained with reference to Figure 9. Figure 9 is a flowchart showing an example of the control method process.

[0073] As shown in Figure 9, the switching processing unit 13 of the control system 1 first determines whether the operating mode of the work machine 3 is the normal mode (S1). If the normal mode is selected as the operating mode of the work machine 3, the switching processing unit 13 determines that it is in the normal mode (S1: Yes) and proceeds to step S2. On the other hand, if the eco mode is selected as the operating mode of the work machine 3, the switching processing unit 13 determines that it is not in the normal mode (S1: No) and proceeds to step S6.

[0074] In step S2, the adjustment processing unit 12 applies the correspondence relationship G1 (see Figure 4) as the correspondence between rotational speed and the upper limit of torque, and starts the adjustment process. Here, the adjustment processing unit 12 first refers to the correspondence relationship G1 to identify the rotational speed corresponding to the current torque of the motor 41. Then, the control processing unit 11 controls the motor 41 to the identified rotational speed (S3).

[0075] At this time, if the torque of the motor 41 exceeds the upper torque limit corresponding to the rotational speed specified in the correspondence relationship G1 due to load fluctuations of the actuator 40, etc. (S4:Yes), the adjustment processing unit 12 executes an adjustment process to reduce the rotational speed of the motor 41 (S5) and proceeds to step S4. On the other hand, if the torque of the motor 41 is less than or equal to the upper torque limit corresponding to the rotational speed specified in the correspondence relationship G1 (S4:No), the adjustment processing unit 12 terminates the series of processes without reducing the rotational speed of the motor 41.

[0076] In step S6, the adjustment processing unit 12 applies the correspondence relationship G2 (see Figure 4) as the correspondence between rotational speed and the upper limit of torque, and starts the adjustment process. Here, the adjustment processing unit 12 first refers to the correspondence relationship G2 to identify the rotational speed corresponding to the current torque of the motor 41. Then, the control processing unit 11 controls the motor 41 to the identified rotational speed (S7).

[0077] At this time, if the torque of the motor 41 exceeds the upper torque limit corresponding to the rotational speed specified in the correspondence relationship G2 due to load fluctuations of the actuator 40, etc. (S8:Yes), the adjustment processing unit 12 executes an adjustment process to reduce the rotational speed of the motor 41 (S9) and proceeds to step S8. On the other hand, if the torque of the motor 41 is less than or equal to the upper torque limit corresponding to the rotational speed specified in the correspondence relationship G2 (S8:No), the adjustment processing unit 12 terminates the series of processes without reducing the rotational speed of the motor 41.

[0078] The control system 1 repeatedly executes the processes S1 to S9 described above. However, the flowchart shown in Figure 9 is merely an example, and processes may be added or omitted as appropriate, or the order of processes may be changed as appropriate.

[0079] [4] Modified form The following lists some modifications of Embodiment 1. The modifications described below can be combined and applied as appropriate.

[0080] The control system 1 in this disclosure includes a computer system. The computer system mainly consists of one or more processors and one or more memories as hardware. The functions of the control system 1 in this disclosure are realized by the execution of a program recorded in the memory of the computer system by the processor. The program may be pre-recorded in the memory of the computer system, provided via a telecommunications line, or provided on a non-temporary recording medium such as a memory card, optical disk, or hard disk drive that can be read by the computer system. Furthermore, some or all of the functional parts included in the control system 1 may be composed of electronic circuits.

[0081] Furthermore, it is not essential for control system 1 to have at least some of its functions integrated into a single housing; the components of control system 1 may be distributed across multiple housings. Conversely, functions that are distributed across multiple devices (e.g., control system 1 and rotation speed setting unit 34, etc.) in Embodiment 1 may be integrated into a single housing. Moreover, at least some of the functions of control system 1 may be implemented by the cloud (cloud computing), etc.

[0082] Furthermore, the work machine 3 is not limited to an electric type (electric type) that uses only a motor 41 as a power source, but may also be a hybrid type work machine that includes, for example, a motor 41 that generates power by receiving an electric power supply and an engine (internal combustion engine) that generates power by burning fuel as a power source. In this case, the engine may be a diesel engine that runs on light oil as fuel, or it may be an engine other than a diesel engine. The motor 41 and the engine are driven individually and each generates power, and the power generated by the motor 41 and the power generated by the engine are combined in the power transmission unit and used to drive the pump 42 in the drive unit. Therefore, for example, the motor 41 can assist the engine and generate more power than the engine alone.

[0083] Furthermore, the pump 42 is not limited to a fixed-displacement type, but may also be a variable-displacement type. In addition, the pump 42 is not limited to a gear pump, but may also be, for example, a vane pump or a piston pump.

[0084] Furthermore, the motor 41 is not limited to a motor driven by three-phase AC power, but may also be a motor driven by DC power, for example. The power source that supplies DC power to the inverter 21 is not limited to the battery 22, but may also be a primary battery or an external power source, for example.

[0085] Furthermore, the working fluid discharged by the pump 42 is not limited to hydraulic oil; for example, it may be a gas (including air) or a liquid other than oil.

[0086] Furthermore, the relationship between rotational speed and the upper limit of torque is not limited to being defined by a two-dimensional map; for example, it may be defined by a table or by a function.

[0087] (Embodiment 2) The control method for the work machine 3 according to this embodiment differs from the control method for the work machine 3 according to Embodiment 1 in that, as shown in Figure 10, the response of the rotational speed to torque when the torque decreases is low. Hereinafter, components similar to those in Embodiment 1 will be denoted by common reference numerals and their descriptions will be omitted as appropriate.

[0088] In other words, while the rotational speed is adjusted according to the torque, in this embodiment, when the torque decreases, the response of the rotational speed to the torque is lower compared to when the torque increases. Here, when the torque increases, the adjustment processing unit 12 immediately reduces the rotational speed when the torque exceeds the upper torque limit, similar to Embodiment 1. On the other hand, when the torque decreases, as shown in Figure 10, the adjustment processing unit 12 does not immediately increase the rotational speed, thereby reducing the response of the rotational speed to the torque change. This makes it possible to suppress hunting in the rotational speed of the motor 41 in situations where the load on the actuator 40 fluctuates repeatedly. As a result, the user (operator) is less likely to feel any discomfort in the operability of the work machine 3.

[0089] Specifically, the adjustment processing unit 12 maintains the rotational speed at a value corresponding to the torque before the decrease, even if the torque decreases, until the torque decreases by more than a specified range. In the example in Figure 10, we assume that when the motor 41 is driven at a rotational speed of N6 [rpm] and a torque of T6 [Nm], for example, the load on the actuator 40 decreases and the torque of the motor 41 decreases. In this case, the rotational speed is maintained at a value corresponding to the torque before the decrease (N6 [rpm]) until the torque decreases from T6 [Nm] to the threshold torque T7 [Nm]. Then, when the torque of the motor 41 reaches the threshold torque T7, the adjustment processing unit 12 increases the rotational speed of the motor 41 from N6 [rpm]. With this configuration, it becomes easier to suppress hunting of the rotational speed of the motor 41.

[0090] Here, the specified range, that is, the difference between the torque T6 [Nm] before the reduction and the threshold torque T7 [Nm], is a relative value set based on the torque T6 [Nm] before the reduction, such as 20% or 40% of the torque T6 [Nm] before the reduction. However, the specified range is not limited to a relative value based on the torque T6 [Nm] before the reduction; it may also be an absolute value, or the threshold torque T7 [Nm] may be a fixed value set independently of the torque T6 [Nm] before the reduction.

[0091] Furthermore, in the example shown in Figure 10, after the torque of the motor 41 reaches the threshold torque T7 [Nm], the adjustment processing unit 12 sets a target rotational speed with a margin to allow the torque of the motor 41 to increase to T8 [Nm]. In other words, the adjustment processing unit 12 sets a target rotational speed N8 [rpm] corresponding to a torque T8 [Nm] greater than the threshold torque T7 [Nm], and controls the rotational speed of the motor 41 to this rotational speed N8 [rpm]. This suppresses the occurrence of overshoot where the torque of the motor 41 exceeds the torque upper limit. Moreover, by setting such a target rotational speed, it becomes easier to secure the torque for acceleration to increase the rotational speed of the motor 41. However, it is not essential to set such a rotational speed N8 [rpm] as the target rotational speed; for example, the adjustment processing unit 12 may set the rotational speed associated with the threshold torque T7 [Nm] in the correspondence relationship G1 as the target rotational speed.

[0092] Incidentally, when torque decreases, the means of reducing the response of rotational speed to torque compared to when torque increases are not limited to maintaining rotational speed until the torque decreases by more than a specified amount, as mentioned above. For example, when torque decreases, the rotational speed may be maintained until a specified time has elapsed from the start of the torque decrease, or the rate of increase in rotational speed (acceleration) may be set low.

[0093] The configuration according to Embodiment 2 (including modified versions) can be adopted in appropriate combination with the various configurations (including modified versions) described in Embodiment 1.

[0094] [Notes on the invention] The following is an overview of the invention extracted from the above-described embodiments. Note that each configuration and processing function described below can be selected and combined as desired.

[0095] <Note 1> A motor that operates by receiving power from a power source, A control method for a work machine comprising a pump driven by the motor and discharging a working fluid to an actuator, When driving the motor, the rotational speed is adjusted so that the torque of the motor does not exceed a torque upper limit value set in relation to the rotational speed of the motor. A method for controlling industrial machinery.

[0096] <Note 2> The torque limit is determined according to the rotational speed such that the torque limit decreases as the rotational speed increases. Control method for the work machine described in Appendix 1.

[0097] <Note 3> The torque limit is determined according to the rotational speed so that the motor output, expressed using the rotational speed and the torque limit, falls within a predetermined range. A control method for the work machine described in Appendix 1 or 2.

[0098] <Note 4> The further comprising changing the predetermined range, The control method for the work machine described in Appendix 3.

[0099] <Note 5> When the maximum rotational speed is defined as the maximum value of the rotational speed at which the torque is adjusted so as not to exceed the torque upper limit, the rotational speed is adjusted to a value less than or equal to the maximum rotational speed. A control method for the work machine described in any of the appendices 1 to 4.

[0100] <Note 6> The rotational speed is adjusted according to the torque. When the torque decreases, the response of the rotational speed to the torque is lower compared to when the torque increases. A control method for the work machine described in any of the appendices 1 to 5.

[0101] <Note 7> Until the torque decreases by more than a specified amount, the rotational speed is maintained at a value corresponding to the torque before the decrease, even if the torque decreases. Control method for the work machine described in Appendix 6.

[0102] <Note 8> The torque upper limit includes a value higher than the relief torque, which is the torque corresponding to the relief pressure set as the maximum discharge pressure of the pump. A control method for the work machine described in any of the appendices 1 to 7.

[0103] <Note 9> The aforementioned pump is a constant-displacement gear pump. A control method for the work machine described in any of the appendices 1 to 8.

[0104] <Note 10> The control method for the work machine described in any of the appendices 1 to 9, A control program for a work machine to be executed by one or more processors.

[0105] The configurations described in Appendix 2 to 9 are not essential to the control method of the work machine and can be omitted as appropriate. [Explanation of Symbols]

[0106] 1. Control system for industrial machinery 3. Working Machines 12 Adjustment Processing Unit 22 Battery (Power Supply) 30 aircraft 40 Actuators 41 Motor 42 pumps

Claims

1. A motor that operates by receiving power from a power source, A control method for a work machine comprising a pump driven by the motor and discharging a working fluid to an actuator, When driving the motor, the rotational speed is adjusted so that the torque of the motor does not exceed a torque upper limit set in accordance with the rotational speed of the motor, and the rotational speed is changed in accordance with the fluctuation of the motor torque due to fluctuations in the load of the actuator. A method for controlling industrial machinery.

2. The torque limit is determined according to the rotational speed such that the torque limit decreases as the rotational speed increases. A method for controlling a work machine according to claim 1.

3. The torque limit is determined according to the rotational speed so that the motor output, expressed using the rotational speed and the torque limit, falls within a predetermined range. A method for controlling a work machine according to claim 1 or 2.

4. The further comprising changing the predetermined range, A method for controlling a work machine according to claim 3.

5. When the maximum rotational speed is defined as the maximum value of the rotational speed at which the torque is adjusted so as not to exceed the torque upper limit, the rotational speed is adjusted to a value less than or equal to the maximum rotational speed. A method for controlling a work machine according to claim 1 or 2.

6. The rotational speed is adjusted according to the torque. When the torque decreases, the response of the rotational speed to the torque is lower compared to when the torque increases. A method for controlling a work machine according to claim 1 or 2.

7. Until the torque decreases by more than a specified amount, the rotational speed is maintained at a value corresponding to the torque before the decrease, even if the torque decreases. A method for controlling a work machine according to claim 6.

8. The torque upper limit includes a value higher than the relief torque, which is the torque corresponding to the relief pressure set as the maximum discharge pressure of the pump. A method for controlling a work machine according to claim 1 or 2.

9. The aforementioned pump is a constant-displacement gear pump. A method for controlling a work machine according to claim 1 or 2.

10. A control method for a work machine according to claim 1 or 2, A control program for a work machine to be executed by one or more processors.

11. A motor that operates by receiving power from a power source, Used for controlling a work machine that includes a pump driven by the aforementioned motor and which discharges working fluid to an actuator, The motor is driven by an adjustment processing unit that adjusts the rotational speed so that the torque of the motor does not exceed a torque upper limit set in accordance with the rotational speed of the motor, and changes the rotational speed in accordance with the fluctuation of the motor's torque due to fluctuations in the load of the actuator. Control system for industrial machinery.

12. A control system for a work machine according to claim 11, The machine comprises a body on which the motor and the pump are mounted, A type of machinery used for industrial work.

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