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

Abstract

The present invention provides 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 are less susceptible to damage to the hydraulic pump. [Solution] The control method for a work machine comprises performing a first control and performing a second control. In the first control, the target rotational speed of the prime mover for driving a hydraulic pump that discharges hydraulic fluid is switched from the rated rotational speed to a standby rotational speed lower than the rated rotational speed. In the second control, the target rotational speed is switched from the standby rotational speed to a return rotational speed higher than the standby rotational speed. Here, for at least one of the first control and the second control, the rotational speed of the prime mover is controlled so that it transitions to the target rotational speed over a transition period of time.

Description

Technical Field

[0001] The present invention relates to a control method for a working machine including a prime mover for driving a hydraulic pump that discharges hydraulic oil, a control program for a working machine, a control system for a working machine, and a working machine.

Background Art

[0002] As related art, a working machine (construction machine) including a hydraulic pump driven by a prime mover is known (for example, see Patent Document 1). The working machine according to the related art drives a plurality of hydraulic actuators including a traveling hydraulic motor by hydraulic oil (pressure oil) from the hydraulic pump.

[0003] In the working machine according to the related art, the prime mover is an electric motor. In this working machine, when the traveling hydraulic motor is operated during idling operation and switched to normal operation, as the target rotational speed of the prime mover (command rotational speed to the inverter), first, a predetermined intermediate rotational speed between a first rotational speed and a second rotational speed is output, and then the second rotational speed is output.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the related art described above, for example, when the temperature of the hydraulic oil is low in a cold region or the like and the rotational speed of the prime mover suddenly increases, there is a possibility that the hydraulic pump may be damaged due to cavitation, and this problem becomes prominent when returning the rotational speed of the prime mover from the stopped state.

[0006] The object of the present invention is 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 in which the hydraulic pump is less susceptible to damage. [Means for solving the problem]

[0007] A control method for a work machine according to one aspect of the present invention comprises performing a first control and performing a second control. In the first control, the target rotational speed of the prime mover for driving a hydraulic pump that discharges hydraulic fluid is switched from the rated rotational speed to a standby rotational speed lower than the rated rotational speed. In the second control, the target rotational speed is switched from the standby rotational speed to a return rotational speed higher than the standby rotational speed. In this control method, for at least one of the first control and the second control, the rotational speed of the prime mover is controlled so as to transition to the target rotational speed over a transition period of time.

[0008] 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.

[0009] A control system for a work machine according to one aspect of the present invention includes a control processing unit. The control processing unit is capable of performing a first control and a second control. In the first control, the target rotational speed of a prime mover for driving a hydraulic pump that discharges hydraulic fluid is switched from the rated rotational speed to a standby rotational speed lower than the rated rotational speed. In the second control, the target rotational speed is switched from the standby rotational speed to a return rotational speed higher than the standby rotational speed. Here, for at least one of the first control and the second control, the control processing unit controls the rotational speed of the prime mover so as to transition to the target rotational speed over a transition period of time.

[0010] A work machine according to one aspect of the present invention comprises a control system for the work machine and a machine body. [Effects of the Invention]

[0011] 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 in which the hydraulic pump is less susceptible to damage. [Brief explanation of the drawing]

[0012] [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 hydraulic circuit and other components of the work machine according to Embodiment 1. [Figure 3] Figure 3 is a timing chart showing an example of the operation of the control system for a work machine according to Embodiment 1. [Figure 4] Figure 4 is a timing chart showing an example of the operation of the control system for a work machine according to Embodiment 1. [Figure 5] Figure 5 is a timing chart showing an example of the operation of the control system for a work machine according to Embodiment 1. [Figure 6] Figure 6 is a timing chart showing an example of operation of the control system for a work machine according to Embodiment 1. [Figure 7] Figure 7 is a timing chart showing an example of the operation of the control system for a work machine according to Embodiment 1. [Figure 8] Figure 8 is a timing chart showing an example of the operation of the control system for a work machine according to Embodiment 1. [Figure 9] Figure 9 is a timing chart showing an example of the operation of the control system for a work machine according to Embodiment 1. [Figure 10] Figure 10 is a timing chart showing an example of the operation of a control system for a work machine according to Embodiment 1. [Modes for carrying out the invention]

[0013] 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.

[0014] (Embodiment 1) [1] Overall configuration As shown in FIG. 1, the work machine 3 according to the present 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 work machine 3 further includes a control system 1 for work machines (hereinafter also simply referred to as "control system 1"). In addition, as shown in FIGS. 1 and 2, the machine body 30 further includes a display device 2, an operation device 35, a main switch 35, an accelerator operation unit 37, and the like.

[0015] The "work machine" referred to in the present disclosure means various working machines. As an example, it is a work vehicle such as a backhoe (including a hydraulic excavator, a mini excavator, etc.), a wheel loader, and a carrier. The work machine 3 includes a working unit 33 configured to be able to execute one or more operations. The work machine 3 is not limited to a "vehicle", and may be, for example, a work flying object such as a work ship, a drone, or a multicopter. Further, the work machine 3 is not limited to a construction machine, and may be, for example, an agricultural machine (agricultural machinery) such as a rice transplanter, a tractor, or a combine. In the present embodiment, unless otherwise specified, the work machine 3 is a ride-on type backhoe, and the case where it can execute excavation work, land leveling work, trench excavation work, loading work, etc. as work will be described as an example.

[0016] In addition, in the present embodiment, for convenience of explanation, the vertical direction in the state where the working machine 3 can be used is defined as the vertical 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 operating unit 321). In other words, each direction used in the present embodiment is a direction defined based on the machine body 30 of the working machine 3. 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 do not intend to limit the usage direction (direction during use) of the working machine 3.

[0017] The working machine 3 includes a prime mover 40 (see FIG. 2) that serves as a power source. The prime mover 40 is, for example, a device that converts energy such as electricity, combustion, or heat of steam into mechanical force (power) and generates power for driving each part of the machine body 30. In the present embodiment, as an example, the prime mover 40 is an electric motor. The prime mover 40 is driven by receiving power supply from a battery 38 (see FIG. 2). In the present embodiment, the prime mover 40 is an alternating current motor and is driven by alternating current power (alternating current voltage) supplied from a drive circuit 39 (see FIG. 2) composed of an inverter circuit. The drive circuit 39 is electrically connected to the battery 38 and drives the prime mover 40 by converting the direct current voltage output from the battery 38 into an alternating current voltage and supplying it to the prime mover 40. That is, the working machine 3 includes the battery 38 and the drive circuit 39.

[0018] The output shaft of the prime mover 40 is connected to the hydraulic pump 41 (see Figure 2) via a power transmission unit, and the hydraulic pump 41 is driven by power from the prime mover 40. In the work machine 3, the prime mover 40 drives the hydraulic pump 41, and hydraulic fluid is supplied from the hydraulic pump 41 to the hydraulic actuators (including the hydraulic motor 43 and hydraulic cylinder 44, etc.) in various parts of the machine body 30, thereby driving the machine body 30. In other words, the prime mover 40 drives the hydraulic pump 41, causing it to discharge hydraulic fluid, which in turn supplies power (hydraulic fluid) to various parts of the machine body 30 of the work machine 3, thereby driving the various parts of the machine body 30.

[0019] Such a work machine 3 is controlled, for example, by a user (operator) who is seated in the driver's compartment 321 of the machine body 30 and operates the control levers of the control device 35. In other words, the power generated by the prime mover 40 is distributed to each part of the machine body 30 according to the operator's operations, so the work machine 3 operates according to the operator's operations.

[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) riding in the driver's unit 321 and performs work such as excavation. The driver's unit 321 on which the user rides is located in the slewing unit 32.

[0021] Here, the control unit 321 of the machine body 30 is equipped with a display device 2 and an operating device 35, and the user can operate the operating device 35 while viewing various information related to the work machine 3 displayed on the display device 2. For example, the display screen of the display device 2 displays information related to the operating status of the work machine 3, such as the cooling water temperature and the hydraulic oil temperature, so that the user can check the information related to the operating status of the work machine 3 necessary for operating the operating device 35 on the display device 2.

[0022] 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 blades 312. The running unit 31 further has a hydraulic motor 43 (hydraulic actuator) for driving the crawlers 311.

[0023] The slewing section 32 is located above the traveling section 31 and is configured to rotate around a rotation axis along the vertical direction D1 relative to the traveling section 31. The slewing section 32 has a hydraulic motor (hydraulic actuator) for slewing, etc. In addition to the operating section 321, the slewing section 32 is equipped with a prime mover 40 and a hydraulic pump 41, etc. Furthermore, a boom bracket 322 to which the working section 33 is attached is provided at the front end of the slewing section 32.

[0024] The work unit 33 is configured to perform one or more tasks. The work unit 33 is supported by the boom bracket 322 of the slewing unit 32 and performs tasks. The work unit 33 has a bucket 331. The bucket 331 is a type of attachment (working tool) that is attached to the body 30 of the work machine 3, and consists of any tool selected from a plurality of types of attachments according to the content of the work. For example, the bucket 331 is detachably attached to the body 30 and is replaced according to the content of the work. In addition to the bucket 331, there are various other tools 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.

[0025] The working section 33 further includes a boom 332, an arm 333, and a hydraulic actuator (including a hydraulic cylinder 44 and a hydraulic motor, etc.). The bucket 331 is attached to the tip of the arm 333.

[0026] 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 its base end, which is 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.

[0027] The work unit 33 operates by receiving power from the prime mover 40, which serves as the power source. Specifically, the prime mover 40 drives the hydraulic pump 41, and hydraulic fluid is supplied from the hydraulic pump 41 to the hydraulic 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.

[0028] 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.

[0029] The traveling section 31 and the slewing section 32, like the working section 33, operate by receiving power from the prime mover 40, 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 hydraulic pump 41 to the hydraulic motor 43 of the traveling section 31 and the hydraulic motor of the slewing section 32, etc.

[0030] The actuators provided in various parts of the machine body 30 (hydraulic actuators including a hydraulic motor 43 and a hydraulic cylinder 44 in this embodiment) operate in response to the operation of the control device 35. In other words, the work machine 3 according to this embodiment is equipped with actuators that operate in response to the operation of the control device 35. Therefore, the work machine 3 will perform various operations such as forward and backward movement by the travel unit 31, rotation by the slewing unit 32, and excavation work by the work unit 33 in response to the operation of the control device 35 by the user (operator).

[0031] 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 oil) oil passages, dotted lines indicate low-pressure (pilot oil) oil passages, and dashed arrows indicate the paths of electrical signals. Furthermore, the thick line (solid line) between the prime mover 40 and the hydraulic pump 41 indicates the physical connection between the prime mover 40 (output shaft) and the hydraulic pump 41.

[0032] As shown in Figure 2, the work machine 3 includes a hydraulic pump 41, a hydraulic motor 43 (not shown in Figure 2), a hydraulic cylinder 44, a prime mover 40, a battery 38, and a drive circuit 39, as well as a pilot pump 42, a remote control valve 45, a control valve 461, a cutoff switch 462, a cutoff lever 463, a temperature sensor 47, a directional control valve 48, a hydraulic oil tank 49, a main switch 36, and an accelerator operating unit 37, etc.

[0033] The hydraulic fluid from the hydraulic pump 41, driven by the prime mover 40, is supplied to the hydraulic motor 43 of the travel section 31, the hydraulic motor of the slewing section 32, and the hydraulic cylinder 44 of the work section 33, etc. This drives the hydraulic actuators such as the hydraulic motor 43 and the hydraulic cylinder 44.

[0034] The drive circuit 39 drives the prime mover 40 at any desired rotational speed. In other words, by controlling the rotational speed of the prime mover 40, the drive circuit 39 can control the rotational speed of the hydraulic pump 41 driven by the prime mover 40, and thereby change the discharge amount of hydraulic fluid from the hydraulic pump 41. Thus, in this embodiment, the flow rate of hydraulic fluid supplied from the hydraulic pump 41 is not fixed but can be changed (variable) by appropriate means. The drive circuit 39 may change the rotational speed of the prime mover 40 continuously and steplessly, or it may change it in steps (for example, in 2 steps, 5 steps, or 10 steps).

[0035] Hydraulic actuators such as the hydraulic motor 43 and hydraulic cylinder 44 are equipped with a pilot-operated directional control valve 48 that can switch the direction and flow rate of the hydraulic fluid from the hydraulic pump 41. The directional control valve 48 is driven by pilot oil supplied from the pilot pump 42, which serves as an input command.

[0036] Here, for example, a remote control valve 45 is provided in the supply path for pilot oil to the directional control valve 48 corresponding to the hydraulic cylinder 44 of the work unit 33. The remote control valve 45 outputs work operation commands for the work unit 33 in response to the operation of the operating device 35 (operating lever). The work operation commands instruct the work unit 33 to perform operations such as extending and retracting. In addition, the flow rate of pilot oil supplied from the pilot pump 42 to the remote control valve 45 can be adjusted by the control valve 461.

[0037] The control valve 461 is an electromagnetic control valve (solenoid valve) and is inserted between the remote control valve 45 and the pilot pump 42. The control valve 461 is connected to the power supply via a cutoff switch 462 and operates according to the current supplied from the power supply. Here, the control valve 461 is assumed to be an (electromagnetic) proportional control valve, but it is not limited to this and may be an on-off valve that can switch between opening and closing the flow path, for example.

[0038] The control valve 461 opens the pilot oil passage when energized, i.e., when current as a control signal is supplied, and closes the pilot oil passage when de-energized, i.e., when current as a control signal is cut off. As a result, when the current (control signal) supplied to the control valve 461 is cut off, the hydraulic actuator (hydraulic cylinder 44, etc.) corresponding to the remote control valve 45 becomes unable to drive, and the hydraulic actuator is forcibly stopped without operation of the operating device 35.

[0039] Similarly, a remote control valve is also provided in the supply passage for pilot oil to the directional control valve corresponding to the hydraulic motor 43 of the travel unit 31. This remote control valve outputs a travel operation command for the travel unit 31 in response to the operation of the operating device 35 (operating lever). The travel operation command instructs the travel unit 31 to travel (forward or backward, etc.). Furthermore, a remote control valve is also provided in the supply passage for pilot oil to the directional control valve corresponding to the hydraulic motor of the slewing unit 32. This remote control valve outputs a slewing operation command for the slewing unit 32 in response to the operation of the operating device 35 (operating lever). The slewing operation command instructs the slewing unit 32 to slewing (left turn or right turn, etc.). A control valve 461 is also inserted between these remote control valves and the pilot pump 42.

[0040] The cutoff switch 462 is linked to the cutoff lever 463. The cutoff lever 463 is located in the control unit 321 of the machine body 30 and accepts operation input from the user (operator). In this embodiment, as an example, the cutoff lever 463 can be operated along the vertical direction D1. When the cutoff lever 463 is in the "up position", which is the upper end of its movable range, the cutoff switch 462 is "off", and when the cutoff lever 463 is in the "down position", which is the lower end of its movable range, the cutoff switch 462 is "on". The cutoff switch 462 is connected to the control system 1, and the on / off state of the cutoff switch 462, that is, the operating state of the cutoff lever 463, is monitored by the control system 1.

[0041] Therefore, when the cutoff lever 463 is in the "down position," the control valve 461 becomes energized, and the hydraulic actuator (hydraulic cylinder 44, etc.) is driven by the operation of the operating device 35. Conversely, when the cutoff lever 463 is in the "up position," the control valve 461 becomes de-energized, and the hydraulic actuator is forcibly stopped without operation of the operating device 35. For this reason, in order to drive the hydraulic actuator (hydraulic cylinder 44, etc.), the user (operator) needs to operate the cutoff lever 463 to the "down position."

[0042] Furthermore, since the slewing section 32 and the traveling section 31 are operated by hydraulic fluid supplied from the hydraulic pump 41 to the hydraulic actuator (hydraulic motor 43, etc.), if the cutoff lever 463 is in the "up position", the slewing section 32 and the traveling section 31 will also become inoperable. In other words, if the cutoff lever 463 is in the "up position", the working section 33, the slewing section 32, and the traveling section 31 are all forcibly rendered inoperable.

[0043] In this embodiment, the state in which the cutoff lever 463 is in the "up position," that is, the state in which the work machine 3 cannot be operated, is defined as the "locked state." On the other hand, the state in which the cutoff lever 463 is in the "down position," that is, the state in which the work machine 3 can be operated, is defined as the "unlocked state."

[0044] In short, the cutoff switch 462 is in a "locked state" when it is off, where the operation of the work machine 3 is restricted (including prohibited), and in an "unlocked state" when it is on, where the operation of the work machine 3 is not restricted. When the cutoff lever 463 is in the "up position" and the cutoff switch 462 is in the locked state (off), the operation of the work machine 3 is forcibly restricted without operation of the operating device 35. The cutoff lever 463 is the lever that is operated when locking the operation of the work machine 3 in this way, and is synonymous with the gate lock lever.

[0045] The operating device 35 is located in the operating section 321 of the machine body 30 and is a user interface for receiving operation input from the user (operator). The operating device 35 includes, for example, an operating lever and controls the remote control valve 45 according to the amount of operation of the operating lever. This allows the operator to operate the operating device 35 to activate the remote control valve 45, instruct the direction and flow rate of hydraulic fluid from the hydraulic pump 41, and operate the work machine 3.

[0046] The temperature sensor 47 detects the temperature of the hydraulic fluid discharged from the hydraulic pump 41 (hydraulic fluid temperature). Specifically, in this embodiment, the temperature sensor 47 is located in the hydraulic fluid tank 49 that stores the hydraulic fluid, and detects the temperature of the hydraulic fluid stored in the hydraulic fluid tank 49. Since the hydraulic pump 41 draws up the hydraulic fluid stored in the hydraulic fluid tank 49 and discharges it, the temperature sensor 47 detects the temperature of the hydraulic fluid discharged from the hydraulic pump 41. The temperature sensor 47 is connected to the control system 1, and the temperature detection signal indicating the temperature (hydraulic fluid temperature) detected by the temperature sensor 47 is input to the control system 1.

[0047] Here, the temperature sensor 47 is an example of a detection unit for detecting the state quantity of the hydraulic fluid. In this disclosure, "state quantity" refers to a physical quantity that represents the state of an object (in this case, hydraulic fluid), and means a value that is determined according to the state. Examples include temperature, viscosity, pressure, volume, density, or type of oil. In this embodiment, the temperature sensor 47 detects the temperature of the hydraulic fluid discharged from the hydraulic pump 41 as the state quantity of the hydraulic fluid.

[0048] The main switch 36 is located in the control unit 321 of the machine body 30 and is operated by the user (operator) when starting the work machine 3. While the main switch 36 is off, the machine body 30 (including the travel unit 31, slewing unit 32, and work unit 33) is not in a state to operate in response to the operation of the control device 35. Only when the main switch 36 is turned on does the machine body 30 become capable of operating in response to the operation of the control device 35. Also, when the main switch 36 is turned on, power is supplied to the display device 2, etc. In this embodiment, as an example, the main switch 36 is linked to the key cylinder and is turned on when the prime mover 40 is started using the key.

[0049] The accelerator control unit 37 is located in the driver's unit 321 of the machine body 30 and is operated by the user (operator) when starting the work machine 3. The accelerator control unit 37 is a device operated to set the rated rotational speed of the prime mover 40, and is, for example, an accelerator dial, an accelerator lever, or an accelerator pedal. The accelerator control unit 37 is connected to the control system 1, and the operation signal generated by the operation of the accelerator control unit 37 is input to the control system 1. In this embodiment, as an example, the accelerator control unit 37 is a rotary dial-type control unit that sets the rated rotational speed of the prime mover 40 according to its rotational position.

[0050] The control system 1 primarily consists of a computer system having, for example, 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, or it may primarily consist of one processor or multiple processors. The control system 1 will be explained in detail in the section "[2] Configuration of the Control System".

[0051] The display device 2 is located in the control unit 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. The display device 2 accepts various operations from the user by outputting electrical signals corresponding to the user's operations, for example. This allows the user (operator) to view the display screen shown on the display device 2 and to operate the display device 2 as needed.

[0052] As shown in Figure 2, the display device 2 comprises a control unit 21, an operation unit 22, and a display unit 23. The display device 2 is configured to communicate with the control system 1 and can exchange data with the control system 1. In this embodiment, as an example, the display device 2 is a dedicated device used in the work machine 3.

[0053] The control unit 21 controls the display device 2 according to data from the control system 1. Specifically, the control unit 21 outputs electrical signals corresponding to user operations received by the operation unit 22, and displays the display screen generated by the control system 1 on the display unit 23.

[0054] The operation unit 22 is a user interface for receiving user (operator) input for the display screen shown on the display unit 23. The operation unit 22 accepts various operations from the user, for example, by outputting electrical signals corresponding to the user's operations.

[0055] The display unit 23 is a user interface for presenting information to the user (operator), such as a liquid crystal display or an organic EL display that displays various types of information. The display unit 23 presents various types of information to the user through display.

[0056] Furthermore, in addition to the above-described configuration, the machine body 30 is further equipped with a drive system and a communication terminal, etc. The drive system is a device for supplying power to the attachment of the work unit 33, and consists of a device (mechanism) such as a PTO (Power take-off) for extracting power from the prime mover 40 as power for driving the attachment, which consists of hydraulic equipment. In addition, the machine body 30 is equipped with various sensors (including a camera) for detecting objects to be detected in the monitoring area around the work machine 3, such as a camera that takes images of the area around the machine body 30.

[0057] [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 of the machine body 30 (including the traveling section 31, the turning section 32, and the working section 33, etc.). In this embodiment, 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.

[0058] As shown in Figure 2, the control system 1 comprises an acquisition processing unit 11 and a control processing unit 12. 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 (acquisition processing unit 11, 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.

[0059] The control system 1 is configured to communicate with devices provided in various parts of the aircraft body 30. Specifically, the control system 1 is connected to at least the drive circuit 39, the prime mover 40, the main switch 36, the accelerator control unit 37, the temperature sensor 47, the display device 2, and the cutoff switch 462. This allows the control system 1 to control the drive circuit 39 and the display device 2, and to acquire the rotational speed of the prime mover 40, the operating status of the accelerator control unit 37, and the detection results (hydraulic oil temperature) of the temperature sensor 47. Here, the control system 1 may exchange various types of information (data) directly with each device, or indirectly via a relay or the like. The control system 1 and the devices provided in various parts of the aircraft body 30 can communicate using a communication method such as CAN (Controller Area Network), for example.

[0060] The acquisition processing unit 11 performs an acquisition process to acquire the rotational speed of the prime mover 40, the operating state of the accelerator control unit 37, and the detection result (hydraulic oil temperature) of the temperature sensor 47. In this embodiment, the acquisition processing unit 11 acquires the rotational speed of the prime mover 40, the operating state of the accelerator control unit 37, and the detection result (hydraulic oil temperature) of the temperature sensor 47 periodically or irregularly.

[0061] Furthermore, the data acquisition processing unit 11 can periodically or irregularly acquire information such as the on / off status of the main switch 36 and the cutoff switch 462 through the data acquisition process. Here, the data acquisition processing unit 11 can also acquire the outputs (sensor signals) of the fuel level sensor, coolant temperature sensor, and hydraulic oil temperature sensor. The data acquisition processing unit 11 may acquire various data directly from various sensors (including cameras) or indirectly via an electronic control unit. The data acquired by the data acquisition processing unit 11 is stored, for example, in memory.

[0062] The control processing unit 12 adjusts the rotational speed of the prime mover 40 by controlling the drive circuit 39. Here, the control processing unit 12 sets a target rotational speed for the prime mover 40 and controls the rotational speed of the prime mover 40 using the drive circuit 39 so that the actual rotational speed of the prime mover 40, which is acquired by the acquisition processing unit 11 from the prime mover 40, approaches the target rotational speed. Specifically, if the actual rotational speed of the prime mover 40 is lower than the target rotational speed, the control processing unit 12 controls the drive circuit 39 to increase the rotational speed of the prime mover 40 (make it faster). Conversely, if the actual rotational speed of the prime mover 40 is higher than the target rotational speed, the control processing unit 12 controls the drive circuit 39 to decrease the rotational speed of the prime mover 40 (make it slower).

[0063] Incidentally, the control processing unit 12 can perform decelerator control, stop control, decelerator release control, and stop release control as controls to automatically change the target rotational speed of the prime mover 40.

[0064] Deceleration control is a control mechanism that switches the target rotational speed of the prime mover 40 from the rated rotational speed to a first specific rotational speed lower than the rated rotational speed. In other words, the control processing unit 12 has an auto-deceleration function that automatically reduces the rotational speed of the prime mover 40. For example, if the work unit 33 or the like is not operating and the output of the prime mover 40 is not required for a certain period of time, the control processing unit 12 outputs a control signal to the drive circuit 39 to reduce the target rotational speed and executes deceleration control to reduce the rotational speed of the prime mover 40.

[0065] Desel release control is a control that releases desel control, and specifically, it is a control that switches the target rotational speed of the prime mover 40 from a first specific rotational speed to a second specific rotational speed that is higher than the first specific rotational speed.

[0066] In other words, when the auto-deceleration function is activated, the control processing unit 12 switches the rotational speed of the prime mover 40 to a low idle speed (first specific rotational speed) that is lower than the rated rotational speed. On the other hand, when the auto-deceleration function is deactivated, the control processing unit 12 switches the rotational speed of the prime mover 40 to a high idle speed (second specific rotational speed) that is higher than the first specific rotational speed. In other words, the control processing unit 12 can automatically lower the rotational speed of the prime mover 40 through deceleration control and automatically increase the rotational speed of the prime mover 40 through deceleration release control. In this way, by keeping the rotational speed of the prime mover 40 low as needed, it is possible to reduce the noise and vibration generated by the prime mover 40, suppress energy (electricity) consumption by the prime mover 40, and suppress the occurrence of a time lag due to the restart of the prime mover 40.

[0067] Stop control is a control that stops the prime mover 40 and sets the target rotational speed to zero (0). In other words, the control processing unit 12 has an auto-stop function that automatically reduces the rotational speed of the prime mover 40 to zero (i.e., stops it). For example, if the work unit 33, etc., is not operating and the output of the prime mover 40 is not required for a certain period of time, the control processing unit 12 outputs a control signal to the drive circuit 39 to stop operation and executes stop control that stops the prime mover 40 in a manner that allows it to be restarted.

[0068] The stop release control is a control that releases the stop control, and specifically involves starting the prime mover 40 that has been stopped by the stop control and setting the target rotational speed of the prime mover 40 to a third specific rotational speed.

[0069] In other words, when the auto-stop function is activated, the control processing unit 12 temporarily stops the prime mover 40 (i.e., in a manner that allows it to be restarted by the control processing unit 12), thereby reducing the rotational speed of the prime mover 40 to zero. On the other hand, when the auto-stop function is released, the control processing unit 12 restarts the prime mover 40 and increases its rotational speed to a third specific rotational speed. In other words, the control processing unit 12 can automatically stop the prime mover 40 through stop control and automatically start (restart) the prime mover 40 through stop release control. By temporarily stopping the prime mover 40 as needed in this way, it is possible to further reduce the noise and vibration generated by the prime mover 40, as well as further suppress the energy (electricity) consumption of the prime mover 40.

[0070] Furthermore, the auto-deceleration function and the auto-stop function can each be switched on or off. The auto-deceleration function and the auto-stop function can be switched on or off by the user (operator), for example, by operating the auto-deceleration switch and auto-stop switch located on the control unit 321. In other words, if the auto-deceleration switch is on, the auto-deceleration function is enabled; if the auto-deceleration switch is off, the auto-deceleration function is disabled. Similarly, if the auto-stop switch is on, the auto-stop function is enabled; if the auto-stop switch is off, the auto-stop function is disabled.

[0071] [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 3 to 10.

[0072] 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 2.

[0073] Here, the control system 1 executes the following various processes related to the control method when a specific preset start operation is performed to execute the control program. The start operation is, for example, the operation to start the prime mover 40 of the work machine 3, that is, the operation to turn on the main switch 36. On the other hand, the control system 1 terminates the following various processes related to the control method when a specific preset end operation is performed. The end operation is, for example, the operation to stop the prime mover 40 of the work machine 3, that is, the operation to turn off the main switch 36.

[0074] [3.1] Desel control and desel release control First, we will describe the control method according to this embodiment, that is, the operation of the control system 1 according to this embodiment, specifically the operations related to deceleration control and deceleration release control.

[0075] The control processing unit 12 of the control system 1, when the auto-decel function is enabled (i.e., the auto-decel switch is on) and predetermined deceleration conditions are met, executes deceleration control to switch the target rotational speed of the prime mover 40 from the rated rotational speed to a first specific rotational speed lower than the rated rotational speed. The deceleration conditions are the conditions for executing deceleration control, and the control processing unit 12 reduces the target rotational speed of the prime mover 40 when the deceleration conditions are met.

[0076] In this embodiment, the deceleration conditions include conditions related to the operation of the work machine 3. That is, conditions related to the operator's operation of the work machine 3 (also called "operation-related conditions") are included in the deceleration conditions. Therefore, the operator's operation of the work machine 3 is reflected in whether or not the deceleration conditions are met, that is, whether or not deceleration control is performed. Consequently, for example, in situations where the work unit 33, etc., is not operating and the output of the prime mover 40 is not required, it is possible to perform deceleration control to reduce the target rotational speed of the prime mover 40 by satisfying the deceleration conditions based on the operator's operation of the work machine 3 at that time. In other words, it is possible for the operator to decide whether or not to perform deceleration control.

[0077] Here, the conditions related to the operation of the work machine 3 included in the deceleration conditions (operation-related conditions) include the fact that the operating device 35 of the work machine 3 has not been operated for a specified time. Specifically, if the operating device 35 includes an operating lever, the state in which the operating device 35 is not operated is defined as the state in which the operating device 35 is not operated when the user (operator) is not operating the operating lever and the operating lever is in the neutral position. When the operating device 35 is not operated, the work machine 3 is in a standby state, and the various parts of the machine body 30 (traveling section 31, slewing section 32, and working section 33) do not operate. Therefore, in situations where the standby state of the work machine 3 continues for a specified time or longer, and the output of the prime mover 40 is not required, the deceleration conditions are met, and deceleration control can be performed. In other words, when a situation in which the output of the prime mover 40 is not required continues for a specified time or longer, there is little need to immediately operate the work machine 3, and in such cases, deceleration control can be performed to reduce the noise and vibration generated by the prime mover 40, as well as to suppress the energy (electricity) consumption of the prime mover 40.

[0078] Furthermore, the deceleration condition also includes the state in which the accelerator control unit 37 remains unoperated for a specified period of time or longer. In other words, if the operating device 35 for operating the running unit 31 and the work unit 33 of the machine body 30, as well as the accelerator control unit 37, remain unoperated for a specified period of time (for example, about 3 seconds) or longer, the control processing unit 12 reduces the target rotational speed of the prime mover 40 from the rated rotational speed to a low idle rotational speed (first specific rotational speed) that is lower than the rated rotational speed.

[0079] Meanwhile, the control processing unit 12 of the control system 1 executes deceleration release control, which switches the target rotational speed of the prime mover 40 from a first specific rotational speed to a second specific rotational speed higher than the first specific rotational speed, when predetermined deceleration release conditions are met during deceleration control. The deceleration release conditions are the conditions for executing deceleration release control, and the control processing unit 12 increases the target rotational speed of the prime mover 40 when the deceleration release conditions are met.

[0080] In this embodiment, the deceleration release condition includes conditions related to the operation of the work machine 3. That is, conditions related to the operator's operation of the work machine 3 (operation-related conditions) are also included in the deceleration release condition. Therefore, the operator's operation of the work machine 3 is reflected in whether or not the deceleration release condition is met, that is, whether or not deceleration release control is performed. Consequently, when the target rotational speed of the prime mover 40 is suppressed to a low idle speed (first specific rotational speed) by deceleration control, for example, in a situation where the output of the prime mover 40 is needed to operate the work unit 33, etc., it is possible to perform deceleration release control to increase the target rotational speed of the prime mover 40 by meeting the deceleration release condition based on the operator's operation of the work machine 3 at that time. In other words, it is possible for the operator to decide whether or not to perform deceleration release control.

[0081] Here, the conditions related to the operation of the work machine 3 included in the deceleration release conditions (operation-related conditions) include the operation of the operating device 35 of the work machine 3. Specifically, if the operating device 35 includes an operating lever, the deceleration release conditions include the operation of the operating lever to a position other than the neutral position. Therefore, when the target rotational speed of the prime mover 40 is suppressed to a low idle speed (first specific rotational speed) by deceleration control, and a situation arises where the output of the prime mover 40 is required, the deceleration release conditions are met, and deceleration release control can be performed.

[0082] Furthermore, the deceleration release condition also includes the operation of the accelerator control unit 37. In other words, during deceleration control, if either the operating device 35 for operating the running unit 31 and the work unit 33 of the machine body 30, or the accelerator control unit 37 is operated, the control processing unit 12 increases the target rotational speed of the prime mover 40 from the low idle speed (first specific rotational speed) to the high idle speed (second specific rotational speed), which is higher than the first specific rotational speed.

[0083] Furthermore, the deceleration release condition also includes the deactivation of the auto-deceleration function. In other words, after deceleration control is performed with the auto-deceleration switch ON and the auto-deceleration function enabled, if the auto-deceleration switch is turned OFF and the auto-deceleration function is disabled, the deceleration release condition is met, and the control processing unit 12 switches the target rotational speed of the prime mover 40 from the first specific rotational speed to the second specific rotational speed.

[0084] In this embodiment, the second specific rotational speed is the same as the rated rotational speed. In other words, the target rotational speed of the prime mover 40 is switched from the rated rotational speed to the first specific rotational speed by deceleration control, and then switched back from the first specific rotational speed to the rated rotational speed (second specific rotational speed) by deceleration release control. Therefore, when the prime mover 40 is driven at the rated rotational speed, the rotational speed of the prime mover 40 is reduced by deceleration control and restored by deceleration release control.

[0085] The rated rotational speed changes according to the operation of the accelerator control unit 37. In other words, the rotational speed of the prime mover 40 before deceleration control is performed (rated rotational speed) is not constant and can be set arbitrarily by the operator. This makes it possible to set the rated rotational speed according to the operation of the work machine 3, for example, by setting it higher when performing heavy load work and lower when performing light load work.

[0086] In the following, we assume that multiple rotational speeds (four in this case) of V21, V22, V23, and V24 can be set as the rated rotational speed V2, as shown in Figure 3. The rotational speeds V21, V22, V23, and V24 increase in the order of "V21" (lowest), "V22", "V23", and "V24" (fastest). <V22<V23<V24)。

[0087] Incidentally, in both deceleration control and deceleration release control, the control processing unit 12 does not switch the rotational speed of the prime mover 40 all at once, but rather gradually changes the rotational speed of the prime mover 40 over a certain period of transition time to reach the target rotational speed.

[0088] Figure 3 shows the rotational speed of the prime mover 40 as it changes due to deceleration control and deceleration release control, with the horizontal axis representing time. The control processing unit 12 gradually changes the actual rotational speed of the prime mover 40 (actual rotational speed) by changing the target rotational speed of the prime mover 40 during deceleration control and deceleration release control, as shown in Figure 3. Figure 3 shows the change in rotational speed of the prime mover 40 when the rated rotational speed V2 is set to rotational speeds V21, V22, V23, and V24, respectively.

[0089] Specifically, as shown in the upper part of Figure 3, during deceleration control, the control processing unit 12 gradually reduces the rotational speed of the prime mover 40 from the rated rotational speed V2 to the first specific rotational speed V1. The rotational speed of the prime mover 40 decreases with a certain slope from time t1 as time progresses, and is maintained at the first specific rotational speed V1 when it reaches that point. Here, the slope of the graph in Figure 3 corresponds to the amount of change in the rotational speed of the prime mover 40 per unit time, and is also called the "rate of change in rotational speed".

[0090] In the example in Figure 3, the rate of change of rotational speed during deceleration control is the same (uniform) regardless of whether the rated rotational speed V2 before deceleration control is V21, V22, V23, or V24. Therefore, the transition time (t3-t1) required for the rotational speed to transition to the first specific rotational speed V1 by deceleration control when the rated rotational speed V2 is V22 is longer than the transition time (t2-t1) required when the rated rotational speed V2 is V21. Similarly, the transition time (t4-t1) when the rated rotational speed V2 is V23 is even longer, and the transition time (t5-t1) when the rated rotational speed V2 is V24 is even longer.

[0091] Furthermore, as shown in the lower part of Figure 3, during deceleration control, the control processing unit 12 gradually increases the rotational speed of the prime mover 40 from the first specific rotational speed V1 to the rated rotational speed V2 (second specific rotational speed). The rotational speed of the prime mover 40 decreases with a certain slope from time t1 as time progresses, and is maintained at the rated rotational speed V2 when it reaches that speed.

[0092] In the example shown in Figure 3, the rate of change in rotational speed during deceleration release control is the same (uniform) regardless of whether the rated rotational speed V2 after deceleration release control (i.e., the same as before deceleration control) is V21, V22, V23, or V24. Therefore, the transition time (t3-t1) required for the rotational speed to transition from the first specific rotational speed V1 to rotational speed V22 due to deceleration release control is longer than the transition time (t2-t1) required for the rotational speed to transition from the first specific rotational speed V1 to rotational speed V21 due to deceleration release control. Similarly, the transition time (t4-t1) when the rated rotational speed V2 is V23 is even longer, and the transition time (t5-t1) when the rated rotational speed V2 is V24 is even longer.

[0093] As described above, the control method according to this embodiment includes: executing a first control to switch the target rotational speed of the prime mover 40 for driving the hydraulic pump 41 that discharges hydraulic fluid from the rated rotational speed to a standby rotational speed lower than the rated rotational speed; and executing a second control to switch the target rotational speed from the standby rotational speed to a return rotational speed higher than the standby rotational speed. Here, (the control processing unit 12) controls the rotational speed of the prime mover 40 so as to transition to the target rotational speed over a transition period of time for at least one of the first control and the second control.

[0094] In this embodiment, as described above, it is possible to perform deceleration control, which switches the target rotational speed of the prime mover 40 from the rated rotational speed to a first specific rotational speed lower than the rated rotational speed, and deceleration release control, which switches the target rotational speed of the prime mover 40 from the first specific rotational speed to a second specific rotational speed higher than the first specific rotational speed. Therefore, "deceleration control" is an example of "first control," and "deceleration release control" is an example of "second control." Also, "first specific rotational speed" is an example of "standby rotational speed," and "second specific rotational speed" is an example of "recovery rotational speed."

[0095] In short, in the control method according to this embodiment, for at least one of the first control (deceleration control) and the second control (deceleration release control), the rotational speed of the prime mover 40 is controlled so as to gradually transition to the target rotational speed over a transition period, rather than switching the rotational speed of the prime mover 40 all at once.

[0096] This makes it possible to suppress the occurrence of cavitation in the hydraulic pump 41 caused by a rapid change in the rotational speed of the prime mover 40 when the temperature of the hydraulic oil (hydraulic oil temperature) is low, for example in cold regions. If the rotational speed of the prime mover 40 increases rapidly when the hydraulic oil temperature is relatively low, the suction port of the hydraulic pump 41 will become negatively pressurized, causing cavitation and potentially leading to deterioration of the hydraulic pump 41. In contrast, in this embodiment, by controlling the rotational speed of the prime mover 40 so that it gradually transitions to the target rotational speed over a transition period for at least one of the first control and the second control, the occurrence of cavitation and other issues can be suppressed, and a control method for the work machine 3, a control program for the work machine, a control system 1, and the work machine 3 can be provided that are less susceptible to damage to the hydraulic pump 41.

[0097] In this embodiment, the rotational speed of the prime mover 40 is controlled so that it gradually transitions to the target rotational speed over a transition period, both for the first and second control. Therefore, as shown in Figure 3, problems caused by abrupt changes in the rotational speed of the prime mover 40 can be avoided in both the deceleration control and the deceleration release control.

[0098] Furthermore, in this embodiment, the transition time can be set individually for each of the first and second controls. In other words, it is possible to set the transition times for the first control (deceleration control) and the second control (deceleration release control) to be different, for example. For example, when the rated rotational speed V2 is the same, it is possible to set the transition time for the second control (deceleration release control) to be longer than that for the first control (deceleration control). This makes it easier to suppress the occurrence of cavitation caused by a rapid increase in the rotational speed of the prime mover 40.

[0099] Furthermore, in this embodiment, the return rotation speed is the rated rotation speed V2. In other words, the "second specific rotation speed" is an example of the "return rotation speed," and since the second specific rotation speed is the same as the rated rotation speed V2, the return rotation speed is the same as the rated rotation speed V2. As a result, the second control (deceleration release control) can restore the rotation speed of the prime mover 40 to the rotation speed before the first control (deceleration control) (rated rotation speed V2).

[0100] In this embodiment, for at least one of the first control (deceleration control) and the second control (deceleration release control), instead of fixing the rate of change of the rotational speed of the prime mover 40, a different rate of change is adopted depending on whether or not specific conditions are met. Here, as an example, of the first control (deceleration control) and the second control (deceleration release control), a different rate of change is adopted only for the second control (deceleration release control) depending on whether or not specific conditions are met.

[0101] The specific conditions include conditions related to the state quantities of the hydraulic fluid. That is, different rates of change will be adopted based on the state quantities of the hydraulic fluid (temperature, viscosity, pressure, volume, density, or type of oil, etc.). For example, by setting specific conditions such as the hydraulic fluid being at low temperature or high viscosity, which makes it easy for cavitation to occur in the hydraulic pump 41, the rotational speed of the prime mover 40 can be changed more gradually to prevent cavitation in the hydraulic pump 41.

[0102] In this embodiment, the specific condition includes a condition relating to the temperature of the hydraulic fluid (hydraulic oil temperature) detected by the temperature sensor 47 as a state quantity of the hydraulic fluid. Specifically, the specific condition includes the hydraulic oil temperature being lower than the threshold temperature. In other words, if the hydraulic oil temperature detected by the temperature sensor 47 is above the threshold temperature, the specific condition is not met, and if the hydraulic oil temperature detected by the temperature sensor 47 is lower than the threshold temperature, the specific condition is met. The threshold temperature is set appropriately depending on the type of hydraulic fluid, for example, 0°C, -5°C, or -10°C.

[0103] Figure 4 shows the rotational speed of the prime mover 40 involved in the second control (deceleration release control) for each case where the specific conditions are not met and when they are met, with the horizontal axis being the time axis. In Figure 4, the case where the hydraulic oil temperature is above the threshold temperature and the specific conditions are not met is shown in the upper section as "Hydraulic oil temperature: high temperature", and the case where the hydraulic oil temperature is below the threshold temperature and the specific conditions are met is shown in the lower section as "Hydraulic oil temperature: low temperature".

[0104] Specifically, as shown in Figure 4, even when the rotational speed of the prime mover 40 is increased from the first specific rotational speed V1 (standby rotational speed) to the same rated rotational speed V2 (return rotational speed) by deceleration release control, the rate of change differs depending on whether or not specific conditions are met. In other words, in the case where the specific conditions are met and the "hydraulic oil temperature is low," the rate of change (slope of the graph) of the rotational speed of the prime mover 40 is smaller than in the case where the specific conditions are not met and the "hydraulic oil temperature is high." As a result, for example, even when focusing on returning to the same rotational speed V24, in the case where the specific conditions are not met and the "hydraulic oil temperature is high," the rated rotational speed V2 is reached in a transition time T1, whereas in the case where the specific conditions are met and the "hydraulic oil temperature is low," it takes a longer transition time T2 (>T1) than T1 to reach the rated rotational speed V2.

[0105] Thus, in this embodiment, the transition time differs depending on whether or not specific conditions are met for at least one of the first control and the second control. Therefore, for example, by setting specific conditions such as the hydraulic fluid being at low temperature or high viscosity, which makes cavitation of the hydraulic pump 41 likely to occur, the rotational speed of the prime mover 40 can be changed more gradually to prevent cavitation from occurring when cavitation of the hydraulic pump 41 is likely to occur.

[0106] Furthermore, for at least the second control (deceleration release control), the transition time is made longer when specific conditions are met than when specific conditions are not met. This allows, for example, by setting specific conditions such as the hydraulic fluid being at low temperature or high viscosity, which makes cavitation of the hydraulic pump 41 more likely, the rotational speed of the prime mover 40 to be changed more gradually when cavitation of the hydraulic pump 41 is likely to occur, thereby preventing cavitation.

[0107] Furthermore, in this embodiment, of the first control (deceleration control) and the second control (deceleration release control), only the second control (deceleration release control) employs different rates of change depending on whether or not specific conditions are met. In other words, the first control (deceleration control) employs the same rate of change regardless of whether or not specific conditions are met. To put it another way, the change in rotational speed of the prime mover 40 in the first control (deceleration control) shown in the upper part of Figure 3 remains the same whether or not specific conditions are met (hydraulic oil temperature: high) or not (hydraulic oil temperature: low).

[0108] Furthermore, Figure 3 shows the rotational speed of the prime mover 40 as it changes under deceleration control and deceleration release control when the specific conditions are not met (hydraulic oil temperature: high). In other words, when the specific conditions are not met, the absolute value of the rate of change in rotational speed is the same, although the sign (±) is different. Therefore, for example, if we focus on the same rated rotational speed V2 (e.g., rotational speed V24), the transition time T1 is the same for the first control (deceleration control) and the second control (deceleration release control).

[0109] In other words, in this embodiment, the transition time T2 (see Figure 4) of the second control (decel release control) when the specific conditions are met is longer than the transition time T1 (see Figure 3) of the first control (decel control) when the specific conditions are met. Also, the transition time T2 (see Figure 4) of the second control when the specific conditions are met is longer than the transition time T1 (see Figure 3) of the first control when the specific conditions are not met. Furthermore, when the specific conditions are not met, the transition time T1 (see Figure 3) of the first control and the transition time T1 (see Figure 4) of the second control are the same.

[0110] This allows, for example, by specifying conditions such as the hydraulic fluid being at low temperature or high viscosity, which makes cavitation of the hydraulic pump 41 more likely, the rotational speed of the prime mover 40 can be increased more gradually to prevent cavitation from occurring in the hydraulic pump 41.

[0111] [3.2] Stop control and stop release control Next, the control method according to this embodiment, that is, the operation of the control system 1 according to this embodiment, specifically the operation related to stop control and stop release control, will be described.

[0112] The control processing unit 12 of the control system 1, when the auto-stop function is enabled (i.e., the auto-stop switch is on) and predetermined stop conditions are met, executes stop control to switch the target rotational speed of the prime mover 40 from the rated rotational speed to zero. The stop conditions are the conditions for executing stop control, and the control processing unit 12 sets the target rotational speed of the prime mover 40 to zero when the stop conditions are met.

[0113] In this embodiment, the stop condition includes conditions related to the operation of the work machine 3. That is, conditions related to the operator's operation of the work machine 3 (operation-related conditions) are included in the stop condition. Therefore, the operator's operation of the work machine 3 is reflected in whether or not the stop condition is met, that is, whether or not stop control is performed. Accordingly, for example, in a situation where the work unit 33 etc. is not operating and the output of the prime mover 40 is not required, it is possible to perform stop control to set the target rotational speed of the prime mover 40 to zero (stop the prime mover 40) by meeting the stop condition based on the operator's operation of the work machine 3 at that time. In other words, it is possible for the operator to decide whether or not to perform stop control.

[0114] Here, the conditions related to the operation of the work machine 3 included in the stop condition (operation-related conditions) include the fact that the operating device 35 of the work machine 3 has not been operated for a specified time. Specifically, if the operating device 35 includes an operating lever, the state in which the operating device 35 is not operated is defined as the state in which the operating device 35 is not operated when the user (operator) is not operating the operating lever and the operating lever is in the neutral position. When the operating device 35 is not operated, the work machine 3 is in a standby state, and the various parts of the machine body 30 (traveling section 31, slewing section 32, and working section 33) do not operate. Therefore, in situations where the standby state of the work machine 3 continues for a specified time or longer, and the output of the prime mover 40 is not required, the stop condition is met, and stop control can be performed. In other words, when a situation in which the output of the prime mover 40 is not required continues for a specified time or longer, there is little need to immediately operate the work machine 3, and in such cases, by performing stop control, it is possible to reduce the noise and vibration generated by the prime mover 40, as well as suppress the energy (electricity) consumption of the prime mover 40.

[0115] Furthermore, the stop condition also includes the state in which the accelerator control unit 37 has not been operated for a specified period of time or longer. In other words, if the operating device 35 for operating the running unit 31 and the work unit 33 of the machine body 30, as well as the accelerator control unit 37, remain unoperated for a specified period of time (for example, about 5 minutes), the control processing unit 12 sets the target rotational speed of the prime mover 40 to zero and stops the prime mover 40. Here, the specified period in the stop condition is longer than the specified period in the deceleration condition for deceleration control. For example, if the specified period in the deceleration condition is "3 seconds", the specified period in the stop condition is set to "5 minutes".

[0116] Furthermore, when the cutoff lever 463 is operated to the "up position" and the cutoff switch 462 is turned "off", the control processing unit 12 executes stop control, which switches the target rotational speed of the prime mover 40 from the rated rotational speed to zero, regardless of whether the auto-stop function is enabled or disabled. In short, when the cutoff lever 463 is operated and the work machine 3 becomes inoperable (locked), stop control is exceptionally executed even if the auto-stop function is disabled (i.e., the auto-stop switch is off).

[0117] Even if stop control is executed and the prime mover 40 stops, power is supplied to the control system 1, so the control system 1 continues to operate.

[0118] Here, if both the deceleration condition and the stop condition are met, the control processing unit 12 activates the auto-stop function with priority over the auto-deceleration function and performs stop control to temporarily stop the prime mover 40. Since stop control is executed when the cutoff lever 463 is in the "up position", the deceleration condition does not include any conditions related to the operation of the cutoff lever 463.

[0119] On the other hand, when the control processing unit 12 of the control system 1 is executing stop control, if a predetermined stop release condition is met, it executes stop release control to switch the target rotational speed of the prime mover 40 from zero to a third specific rotational speed. The stop release condition is a condition for executing stop release control, and when the stop release condition is met, the control processing unit 12 increases the target rotational speed of the prime mover 40.

[0120] In this embodiment, the stop release condition includes conditions related to the operation of the work machine 3. That is, conditions related to the operator's operation of the work machine 3 (operation-related conditions) are also included in the stop release condition. Therefore, the operator's operation of the work machine 3 is reflected in whether or not the stop release condition is met, that is, whether or not stop release control is performed. Consequently, in a state where the target rotational speed of the prime mover 40 is suppressed to zero by stop control, for example, in a situation where the output of the prime mover 40 is needed to operate the work unit 33, it is possible to perform stop release control to increase the target rotational speed of the prime mover 40 by meeting the stop release condition based on the operator's operation of the work machine 3 at that time. In other words, it is possible for the operator to decide whether or not to perform stop release control.

[0121] Here, the conditions related to the operation of the work machine 3 included in the stop release conditions (operation-related conditions) include the operation of the operating device 35 of the work machine 3. Specifically, if the operating device 35 includes an operating lever, the stop release conditions include the operating lever being operated to a position other than the neutral position. Therefore, when the prime mover 40 is stopped due to the stop control and the target rotational speed of the prime mover 40 is set to zero, if a situation arises where the output of the prime mover 40 is needed, the stop release conditions are met, and stop release control can be performed.

[0122] Furthermore, the stop release condition also includes the operation of the accelerator control unit 37. In other words, during stop control, if either the operating device 35 for operating the running unit 31 and the work unit 33 of the machine body 30, or the accelerator control unit 37 is operated, the control processing unit 12 increases the target rotational speed of the prime mover 40 from zero to a third specific rotational speed.

[0123] Furthermore, the stop release condition also includes the case where the cutoff lever 463 is in the "down position" and the auto-stop function is disabled. In other words, after stop control is performed with the auto-stop switch ON and the auto-stop function enabled, when the auto-stop switch is turned OFF and the auto-stop function is disabled, the stop release condition is met, and the control processing unit 12 switches the target rotational speed of the prime mover 40 from zero to a third specific rotational speed.

[0124] Furthermore, if stop control is performed by operating the cutoff lever 463 to the "up position," when the cutoff lever 463 is operated to the "down position" and the cutoff switch 462 is turned "on," the control processing unit 12 performs stop release control, which switches the target rotational speed of the prime mover 40 from zero to a third specific rotational speed. In short, stop release control is performed when the cutoff lever 463 is operated and the working machine 3 changes from a state where it cannot be operated (locked state) to a state where it can be operated (unlocked state).

[0125] In this embodiment, the third specific rotational speed is the same as the second specific rotational speed. Furthermore, as described above in this embodiment, the second specific rotational speed is the same as the rated rotational speed. In other words, the target rotational speed of the prime mover 40 is switched from the rated rotational speed to zero by stop control, and then switched back from zero to the rated rotational speed (third specific rotational speed = second specific rotational speed) by stop release control. Therefore, when the prime mover 40 is operating at the rated rotational speed, the prime mover 40 will stop temporarily by stop control and then resume operation by stop release control.

[0126] Incidentally, similar to deceleration control and deceleration release control, in both stop control and stop release control, the control processing unit 12 does not switch the rotational speed of the prime mover 40 all at once, but rather gradually changes the rotational speed of the prime mover 40 over a certain period of transition time to reach the target rotational speed.

[0127] Figure 5 shows the rotational speed of the prime mover 40 as it changes due to stop control and stop release control, with the horizontal axis representing time. The control processing unit 12 gradually changes the actual rotational speed of the prime mover 40 (actual rotational speed) by changing the target rotational speed of the prime mover 40 during stop control and stop release control, as shown in Figure 5. Figure 5 shows the change in rotational speed of the prime mover 40 when the rated rotational speed V2 is set to rotational speeds V21, V22, V23, and V24, respectively.

[0128] Specifically, as shown in the upper part of Figure 5, during stop control, the control processing unit 12 gradually reduces the rotational speed of the prime mover 40 from the rated rotational speed V2 to zero (0). The rotational speed of the prime mover 40 decreases with a certain slope from time t1 as time progresses, and is maintained at zero when it reaches zero. Here, the slope of the graph in Figure 5 corresponds to the amount of change in the rotational speed of the prime mover 40 per unit time, and is also called the "rate of change in rotational speed".

[0129] In the example in Figure 5, the rate of change in rotational speed during stop control is the same (uniform) regardless of whether the rated rotational speed V2 before stop control is V21, V22, V23, or V24. Therefore, the transition time (t3-t1) required for the rotational speed to transition to zero due to stop control when the rated rotational speed V2 is V22 is longer than the transition time (t2-t1) required when the rated rotational speed V2 is V21. Similarly, the transition time (t4-t1) when the rated rotational speed V2 is V23 is even longer, and the transition time (t5-t1) when the rated rotational speed V2 is V24 is even longer.

[0130] Furthermore, as shown in the lower part of Figure 5, when performing stop release control, the control processing unit 12 gradually increases the rotational speed of the prime mover 40 from zero to the rated rotational speed V2 (third specific rotational speed). The rotational speed of the prime mover 40 decreases with a certain slope from time t1 as time progresses, and is maintained at the rated rotational speed V2 once it reaches that speed.

[0131] In the example shown in Figure 5, the rate of change in rotational speed during stop release control is the same (uniform) regardless of whether the rated rotational speed V2 after stop release control (i.e., the same as before stop control) is V21, V22, V23, or V24. Therefore, the transition time required to transition from zero rotational speed to rotational speed V22 (t3-t1) due to stop release control is longer than the transition time required to transition from zero rotational speed to rotational speed V21 (t2-t1) due to stop release control. Similarly, the transition time when the rated rotational speed V2 is V23 (t4-t1) is even longer, and the transition time when the rated rotational speed V2 is V24 (t5-t1) is even longer.

[0132] As described above, the control method according to this embodiment includes: executing a first control to switch the target rotational speed of the prime mover 40 for driving the hydraulic pump 41 that discharges hydraulic fluid from the rated rotational speed to a standby rotational speed lower than the rated rotational speed; and executing a second control to switch the target rotational speed from the standby rotational speed to a return rotational speed higher than the standby rotational speed. For at least one of the first control and the second control, the rotational speed of the prime mover 40 is controlled so that it transitions to the target rotational speed over a transition period of time.

[0133] In this embodiment, as described above, it is possible to perform stop control, which switches the target rotational speed of the prime mover 40 from the rated rotational speed to zero, and stop release control, which switches the target rotational speed of the prime mover 40 from zero to a third specific rotational speed. Therefore, "stop control" is an example of "first control," and "stop release control" is an example of "second control." Also, "zero (0)" is an example of "standby rotational speed," and "third specific rotational speed" is an example of "return rotational speed."

[0134] In short, in the control method according to this embodiment, for at least one of the first control (stop control) and the second control (stop release control), the rotational speed of the prime mover 40 is controlled so as to gradually transition to the target rotational speed over a transition period, rather than switching the rotational speed of the prime mover 40 all at once.

[0135] This makes it possible to suppress the occurrence of cavitation in the hydraulic pump 41 caused by a rapid change in the rotational speed of the prime mover 40 when the temperature of the hydraulic oil (hydraulic oil temperature) is low, for example in cold regions. If the rotational speed of the prime mover 40 increases rapidly when the hydraulic oil temperature is relatively low, the suction port of the hydraulic pump 41 will become negatively pressurized, causing cavitation and potentially leading to deterioration of the hydraulic pump 41. In contrast, in this embodiment, by controlling the rotational speed of the prime mover 40 so that it gradually transitions to the target rotational speed over a transition period for at least one of the first control and the second control, the occurrence of cavitation and other issues can be suppressed, and a control method for the work machine 3, a control program for the work machine, a control system 1, and the work machine 3 can be provided that are less susceptible to damage to the hydraulic pump 41.

[0136] In this embodiment, the rotational speed of the prime mover 40 is controlled so that it gradually transitions to the target rotational speed over a transition period, both for the first and second control. Therefore, as shown in Figure 5, problems caused by abrupt changes in the rotational speed of the prime mover 40 can be avoided in both the stop control and the stop release control.

[0137] Furthermore, in this embodiment, the transition time can be set individually for each of the first and second controls. In other words, it is possible to set the transition times for the first control (stop control) and the second control (stop release control) to be different, for example. For example, when the rated rotational speed V2 is the same, it is possible to set the transition time for the second control (stop release control) to be longer than that for the first control (stop control). This makes it easier to suppress the occurrence of cavitation caused by a rapid increase in the rotational speed of the prime mover 40.

[0138] In this embodiment, for at least one of the first control (stop control) and the second control (stop release control), instead of fixing the rate of change of the rotational speed of the prime mover 40, different rates of change are adopted depending on whether or not specific conditions are met. Here, as an example, of the first control (stop control) and the second control (stop release control), different rates of change are adopted only for the second control (stop release control) depending on whether or not specific conditions are met.

[0139] In this embodiment, the specific condition includes the fact that the temperature of the hydraulic fluid detected by the temperature sensor 47 (hydraulic fluid temperature) is lower than the threshold temperature.

[0140] Figure 6 shows the rotational speed of the prime mover 40 related to the second control (stop release control) for each case where the specific conditions are not met and when they are met, with the horizontal axis being the time axis. In Figure 6, the case where the hydraulic oil temperature is above the threshold temperature and the specific conditions are not met is shown in the upper row as "Hydraulic oil temperature: high temperature", and the case where the hydraulic oil temperature is below the threshold temperature and the specific conditions are met is shown in the lower row as "Hydraulic oil temperature: low temperature".

[0141] Specifically, as shown in Figure 6, even when the rotational speed of the prime mover 40 is increased from zero (standby rotational speed) to the same rated rotational speed V2 (return rotational speed) by stop release control, the rate of change differs depending on whether or not specific conditions are met. In other words, in the case where the specific conditions are met ("hydraulic oil temperature: low"), the rate of change (slope of the graph) of the rotational speed of the prime mover 40 is smaller than in the case where the specific conditions are not met ("hydraulic oil temperature: high"). As a result, for example, even when focusing on returning to the same rotational speed V24, in the case where the specific conditions are not met ("hydraulic oil temperature: high"), the rated rotational speed V2 is reached in a transition time T1, whereas in the case where the specific conditions are met ("hydraulic oil temperature: low"), it takes a longer transition time T2 (>T1) than T1 to reach the rated rotational speed V2.

[0142] Furthermore, in this embodiment, of the first control (stop control) and the second control (stop release control), only the second control (stop release control) employs different rates of change depending on whether or not specific conditions are met. In other words, the first control (stop control) employs the same rate of change regardless of whether or not specific conditions are met. To put it another way, the change in the rotational speed of the prime mover 40 in the first control (stop control) shown in the upper part of Figure 5 remains the same whether or not specific conditions are met (hydraulic oil temperature: high) or not (hydraulic oil temperature: low).

[0143] Furthermore, Figure 5 shows the rotational speed of the prime mover 40 as it changes under stop control and stop release control when the specific conditions are not met (hydraulic oil temperature: high). In other words, when the specific conditions are not met, the absolute value of the rate of change in rotational speed is the same, although the sign (±) is different. Therefore, for example, if we focus on the same rated rotational speed V2 (e.g., rotational speed V24), the transition time T1 is the same for the first control (stop control) and the second control (stop release control).

[0144] In other words, in this embodiment, the transition time T2 (see Figure 6) of the second control (stop release control) when the specific conditions are met is longer than the transition time T1 (see Figure 5) of the first control (stop control) when the specific conditions are met. Also, the transition time T2 (see Figure 6) of the second control when the specific conditions are met is longer than the transition time T1 (see Figure 5) of the first control when the specific conditions are not met. Furthermore, when the specific conditions are not met, the transition time T1 (see Figure 5) of the first control and the transition time T1 (see Figure 6) of the second control are the same.

[0145] This allows, for example, by specifying conditions such as the hydraulic fluid being at low temperature or high viscosity, which makes cavitation of the hydraulic pump 41 more likely, the rotational speed of the prime mover 40 can be increased more gradually to prevent cavitation from occurring in the hydraulic pump 41.

[0146] [3.3] Relationship between deceleration control and stop control Next, the relationship between deceleration control and stop control will be explained with reference to Figure 7.

[0147] Figure 7 shows the rotational speed of the prime mover 40 for deceleration release control and stop release control, respectively, when specific conditions are met (hydraulic oil temperature: low), with the horizontal axis representing time. In Figure 7, the change in rotational speed of the prime mover 40 during deceleration release control is shown in the upper panel, and the change in rotational speed of the prime mover 40 during stop release control is shown in the lower panel.

[0148] When certain conditions are met, as shown in Figure 7, the amount of change in the rotational speed of the prime mover 40 per unit time differs between the deceleration release control and the stop release control. In other words, the rate of change in rotational speed differs between the case where the rotational speed of the prime mover 40 is increased from a first specific rotational speed V1 to the rated rotational speed V2 using deceleration release control and the case where the rotational speed of the prime mover 40 is increased from a stopped rotational speed of 0 to the rated rotational speed V2 using stop release control. Here, the rate of change in the rotational speed of the prime mover 40 (slope of the graph) is smaller with stop release control compared with deceleration release control.

[0149] As a result, in the case of "low operating oil temperature" that satisfies specific conditions, for example, even when focusing on increasing the rotational speed from the same first specific rotational speed V1 to rotational speed V24, with deceleration release control the rated rotational speed V2 is reached in transition time T1, whereas with stop release control it takes a longer transition time T3 (>T1) to reach the rated rotational speed V2.

[0150] In other words, the control method according to this embodiment includes executing deceleration control to switch the target rotational speed of the prime mover 40 for driving the hydraulic pump 41 that discharges hydraulic fluid from the rated rotational speed to a first specific rotational speed lower than the rated rotational speed, and executing stop control to stop the prime mover 40 and set the target rotational speed to zero. Furthermore, this control method includes executing deceleration release control to switch the target rotational speed from the first specific rotational speed to a second specific rotational speed higher than the first specific rotational speed, and executing stop release control to start the prime mover 40 and set the target rotational speed to a third specific rotational speed. Here, (the control processing unit 12) determines that, if at least certain conditions are met, the amount of change in the rotational speed of the prime mover 40 per unit time differs between deceleration control and stop control, and between deceleration release control and stop release control.

[0151] In other words, in the control method according to this embodiment, at least under certain conditions, the transition time required for the rotational speed of the prime mover 40 to reach the target rotational speed differs between deceleration control and stop control, and between deceleration release control and stop release control.

[0152] In short, in the control method according to this embodiment, the rate of change of the rotational speed of the prime mover 40 differs between deceleration control and stop control, and between deceleration release control and stop release control, at least one of which satisfies certain conditions.

[0153] This makes it possible to suppress the occurrence of cavitation in the hydraulic pump 41 caused by a rapid change in the rotational speed of the prime mover 40 when the temperature of the hydraulic fluid (hydraulic oil temperature) is low, for example, in cold regions. If the rotational speed of the prime mover 40 increases rapidly when the hydraulic oil temperature is relatively low, the suction port of the hydraulic pump 41 will become negatively pressurized, causing cavitation and potentially leading to deterioration of the hydraulic pump 41. In contrast, in this embodiment, for example, by specifying conditions such as the hydraulic fluid being low temperature or high viscosity, which are conditions that make cavitation in the hydraulic pump 41 likely to occur, the rotational speed of the prime mover 40 can be changed gradually to prevent the occurrence of cavitation in the hydraulic pump 41. As a result, it is possible to provide a control method for the work machine 3, a control program for the work machine, a control system 1, and a work machine 3 that suppress the occurrence of cavitation and other problems, and make the hydraulic pump 41 less susceptible to damage.

[0154] In this embodiment, the rate of change of the rotational speed of the prime mover 40 is made different only between the deceleration control and the stop control, and between the deceleration release control and the stop release control. In other words, between the deceleration control and the stop control, the rate of change of the rotational speed of the prime mover 40 is the same, even when certain conditions are met.

[0155] Furthermore, in this embodiment, the rate of change of the rotational speed of the prime mover 40 is made different between the deceleration release control and the stop release control only when certain conditions are met. In other words, when the specific conditions are not met, the rate of change of the rotational speed of the prime mover 40 is the same between the deceleration release control and the stop release control.

[0156] Furthermore, under certain conditions, the change in the rotational speed of the prime mover 40 per unit time is smaller with stop release control than with decel release control. This allows, for example, by setting specific conditions such as the hydraulic fluid being at low temperature or high viscosity, which makes cavitation of the hydraulic pump 41 more likely, the rotational speed of the prime mover 40 to be changed more gradually from the stop control state, thereby preventing cavitation.

[0157] In this embodiment, the rate of change of the rotational speed of the prime mover 40 is made different only between the deceleration control and the stop control, and between the deceleration release control and the stop release control, but this is not essential. For example, the rate of change of the rotational speed of the prime mover 40 may be made different between the deceleration control and the stop control if at least certain conditions are met. Alternatively, the rate of change of the rotational speed of the prime mover 40 may be made different between the deceleration control and the stop control, and between the deceleration release control and the stop release control, if at least certain conditions are met.

[0158] [3.4] Other features Next, other functions related to deceleration control, deceleration release control, stop control, or stop release control will be explained with reference to Figures 8 to 10.

[0159] As a first function, as shown in Figure 8, for at least one of the first control and the second control, the amount of change (rate of change) of the rotational speed of the prime mover 40 per unit time may differ depending on the target rotational speed. In Figure 8, with the horizontal axis being the time axis, the rotational speed of the prime mover 40 related to the second control (deceleration release control) is shown for the case where specific conditions are not met. Here, as an example, only for the second control (deceleration release control) of the two control systems, the rate of change of rotational speed differs depending on the target rotational speed.

[0160] In the example shown in Figure 8, the rate of change in rotational speed when the rotational speed transitions from the first specific rotational speed V1 to rotational speed V22 due to deceleration release control is smaller (the slope is gentler) compared to the rate of change in rotational speed when the rotational speed transitions from the first specific rotational speed V1 to rotational speed V21 due to deceleration release control. Similarly, the rate of change in rotational speed becomes even smaller when the rated rotational speed V2 is rotational speed V23, and even smaller when the rated rotational speed V2 is rotational speed V24.

[0161] With this configuration, the rate of change in rotational speed is flexibly set according to the target rotational speed of the prime mover 40, so that the rotational speed of the prime mover 40 can be changed more gradually, and cavitation can be prevented more reliably.

[0162] As a second function, as shown in Figure 9, the rated rotational speed V2 is variable, and the pattern of increase in the rotational speed of the prime mover 40 during the execution of the second control may be defined according to the rated rotational speed V2. In Figure 9, the horizontal axis is the time axis, and the rotational speed of the prime mover 40 related to the second control (deceleration release control) is shown for the case where specific conditions are not met.

[0163] With this configuration, the rotational speed increase pattern is flexibly set according to the rated rotational speed V2 of the prime mover 40, so that the rotational speed of the prime mover 40 can be changed more gradually, and cavitation can be prevented more reliably.

[0164] As a third function, as shown in Figure 10, the return rotation speed may be set in the second control according to the temperature of the hydraulic fluid. In Figure 10, with the horizontal axis being the time axis, the rotation speeds of the prime mover 40 related to the deceleration release control and the stop release control, respectively, when specific conditions are met are shown.

[0165] In the example shown in Figure 10, when the rotational speed transitions from the standby rotational speed (first specific rotational speed V1 or zero) to the recovery rotational speed by the second control (deceleration release control or stop release control), the recovery rotational speed is limited to an upper limit value Vlim1 or less. The upper limit value Vlim1 is determined according to the temperature of the hydraulic fluid (hydraulic oil temperature) detected by the temperature sensor 47, and the higher the hydraulic oil temperature, the larger (higher) the upper limit value Vlim1 becomes. In Figure 10, a case where the hydraulic oil temperature is relatively low is assumed, and the upper limit value Vlim1 is set to a value higher than rotational speed V22 and lower than rotational speed V23.

[0166] Therefore, even when the rated rotational speed V2 is set to rotational speed V23 or V24 by the accelerator operation unit 37, as shown in Figure 10, the return rotational speed is limited to the upper limit Vlim1 or less. As a result, once the rotational speed of the prime mover 40 rises to the upper limit Vlim1, it will not rise any further.

[0167] With this configuration, the recovery rotation speed is flexibly set according to the temperature of the hydraulic fluid, which suppresses an excessive increase in the rotation speed of the prime mover 40 and more reliably prevents the occurrence of cavitation.

[0168] The third function can also be rephrased as follows: According to the third function, the control method according to this embodiment, when certain conditions are met, performs suppression control in at least one of the deceleration release control and the stop release control to set the target rotational speed lower than the rated rotational speed V2. In short, when the operating oil temperature is below the threshold temperature, certain conditions are met, and in this case, in at least one of the deceleration release control and the stop release control, the target rotational speed after the rise is suppressed to a level lower than the rated rotational speed V2 (for example, rotational speed V23 or rotational speed V24).

[0169] Therefore, by specifying conditions such as the hydraulic fluid being at low temperature or high viscosity, which makes cavitation of the hydraulic pump 41 more likely, the target rotational speed after rising can be kept lower than the rated rotational speed V2 when cavitation of the hydraulic pump 41 is likely to occur, thereby more reliably preventing the occurrence of cavitation.

[0170] Furthermore, if certain conditions are no longer met during the execution of suppression control, the target rotational speed is set to the rated rotational speed V2. That is, when the hydraulic oil temperature rises above the threshold temperature, certain conditions are no longer met, and in this case, the upper limit Vlim1 rises, so the target rotational speed after the rise is set to the rated rotational speed V2.

[0171] Therefore, for example, if cavitation is unlikely to occur in the hydraulic pump 41, the suppression control that keeps the rotational speed of the prime mover 40 below the rated rotational speed V2 is released, and it becomes possible to increase the rotational speed of the prime mover 40 to the rated rotational speed V2.

[0172] In the first to third functions, the second control may be a stop release control, not just a deceleration release control, and the first control may be a stop control, not just a deceleration control. Furthermore, the first to third functions may each be switchable between enabled and disabled.

[0173] [4] Modified form The following lists some modifications of Embodiment 1. The modifications described below can be combined and applied as appropriate.

[0174] 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.

[0175] 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 display device 2) 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) or the like.

[0176] Furthermore, the prime mover 40, which serves as the power source for the work machine 3, is not limited to an AC motor; for example, it may be a DC motor, or even something other than an electric motor. In other words, the prime mover 40 may be a diesel engine, an internal combustion engine other than a diesel engine, or a hybrid power source including an electric motor and an internal combustion engine.

[0177] Furthermore, it is not mandatory for the second specified rotational speed to be the same as the third specified rotational speed; the second specified rotational speed may be higher or lower than the third specified rotational speed. In addition, it is not mandatory for the second specified rotational speed (recovery rotational speed) to be the same as the rated rotational speed; the second specified rotational speed (recovery rotational speed) may be higher or lower than the rated rotational speed.

[0178] Furthermore, the operating lever of the operating device 35 may be an electric operating device that accepts various operations by the user (operator) by outputting an electrical signal (operating signal) to the control system 1 in response to the user's (operator's) operation. In this case, the control system 1 can control the hydraulic actuator by, for example, controlling a control valve (solenoid valve) provided in place of the remote control valve 45 in response to the operation of the operating device 35 (operating lever).

[0179] Furthermore, it is not mandatory for the control system 1 to have both an auto-deceleration function and an auto-stop function; it may have only one of these functions.

[0180] Furthermore, the display device 2 is not limited to a dedicated device, but may be a general-purpose terminal such as a laptop computer, tablet terminal, or smartphone. Moreover, the display unit 23 is not limited to a configuration that directly displays the display screen, such as a liquid crystal display or an organic EL display, but may also be configured to display the display screen by projection, such as a projector.

[0181] Furthermore, the input method for information to the operation unit 22 may be other than push-button switches, touch panels, and operation dials. For example, the operation unit 22 may use methods such as a keyboard, a pointing device such as a mouse, voice input, gesture input, or input of operation signals from another terminal.

[0182] Furthermore, the actuators in each part of the machine body 30 are not limited to hydraulic actuators, but may also be, for example, pneumatic actuators driven by compressed air or other air pressure, or electric actuators driven by power supply, or a combination thereof.

[0183] Furthermore, the accelerator control unit 37 is not an essential component and can be omitted as appropriate. If the accelerator control unit 37 is omitted, the rated rotational speed will be fixed.

[0184] [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.

[0185] <Note 1> The first control involves switching the target rotational speed of the prime mover for driving the hydraulic pump that discharges hydraulic fluid from the rated rotational speed to a standby rotational speed lower than the rated rotational speed, The process includes performing a second control to switch the target rotational speed from the standby rotational speed to a recovery rotational speed higher than the standby rotational speed, For at least one of the first control and the second control, the rotational speed of the prime mover is controlled so as to transition to the target rotational speed over a transition period. A method for controlling industrial machinery.

[0186] <Note 2> The transition time can be set individually for each of the first control and the second control. Control method for the work machine described in Appendix 1.

[0187] <Note 3> For at least one of the first control and the second control, the transition time differs depending on whether or not a specific condition is met. A control method for the work machine described in Appendix 1 or 2.

[0188] <Note 4> At least for the second control, if the specific condition is met, the transition time is made longer than if the specific condition is not met. The control method for the work machine described in Appendix 3.

[0189] <Note 5> The transition time of the second control when the specific conditions are met is longer than the transition time of the first control when the specific conditions are met. The transition time of the second control when the specific conditions are met is longer than the transition time of the first control when the specific conditions are not met. If the above specific conditions are not met, the transition time of the first control and the transition time of the second control are the same. Control method for the work machine described in Appendix 4.

[0190] <Note 6> The aforementioned specific conditions include conditions relating to the state quantity of the hydraulic fluid, A control method for the work machine described in any of the appendices 3 to 5.

[0191] <Note 7> The return rotation speed is the rated rotation speed. A control method for the work machine described in any of the appendices 1 to 6.

[0192] <Note 8> For at least one of the first control and the second control, the amount of change in the rotational speed of the prime mover per unit time differs depending on the target rotational speed. A control method for the work machine described in any of the appendices 1 to 7.

[0193] <Note 9> The rated rotational speed is variable, and the pattern of increase in the rotational speed of the prime mover during the execution of the second control is defined according to the rated rotational speed. A control method for the work machine described in any of the appendices 1 to 8.

[0194] <Note 10> In the second control, the return rotation speed is set according to the temperature of the hydraulic fluid. A control method for the work machine described in any of the appendices 1 to 9.

[0195] <Note 11> The control method for the work machine described in any of the appendices 1 to 10, A control program for a work machine to be executed by one or more processors. [Explanation of Symbols]

[0196] 1. Control system for industrial machinery 3. Working Machines 12 Control Processing Unit 30 aircraft 40 Engine 41 Hydraulic pump T1, T2, T3 transition time V1 First specific rotation speed (standby rotation speed) V2 Rated rotation speed (recovery rotation speed)

Claims

1. The first control involves switching the target rotational speed of the prime mover for driving the hydraulic pump that discharges hydraulic fluid from the rated rotational speed to a standby rotational speed lower than the rated rotational speed, The process includes performing a second control to switch the target rotational speed from the standby rotational speed to a recovery rotational speed higher than the standby rotational speed, For at least one of the first control and the second control, the rotational speed of the prime mover is controlled so as to transition to the target rotational speed over a transition period. A method for controlling industrial machinery.

2. The transition time can be set individually for each of the first control and the second control. A method for controlling a work machine according to claim 1.

3. For at least one of the first control and the second control, the transition time differs depending on whether or not a specific condition is met. A method for controlling a work machine according to claim 1 or 2.

4. At least for the second control, if the specific condition is met, the transition time is made longer than when the specific condition is not met. A method for controlling a work machine according to claim 3.

5. The transition time of the second control when the specific conditions are met is longer than the transition time of the first control when the specific conditions are met. The transition time of the second control when the specific conditions are met is longer than the transition time of the first control when the specific conditions are not met. If the above specific conditions are not met, the transition time of the first control and the transition time of the second control are the same. A method for controlling a work machine according to claim 4.

6. The aforementioned specific conditions include conditions relating to the state quantity of the hydraulic fluid, A method for controlling a work machine according to claim 3.

7. The return rotation speed is the rated rotation speed. A method for controlling a work machine according to claim 1 or 2.

8. For at least one of the first control and the second control, the amount of change in the rotational speed of the prime mover per unit time differs depending on the target rotational speed. A method for controlling a work machine according to claim 1 or 2.

9. The rated rotational speed is variable, and the pattern of increase in the rotational speed of the prime mover during the execution of the second control is defined according to the rated rotational speed. A method for controlling a work machine according to claim 1 or 2.

10. In the second control, the return rotation speed is set according to the temperature of the hydraulic fluid. A method for controlling a work machine according to claim 1 or 2.

11. 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.

12. A first control that switches the target rotational speed of the prime mover for driving a hydraulic pump that discharges hydraulic fluid from the rated rotational speed to a standby rotational speed lower than the rated rotational speed, The system includes a control processing unit capable of performing a second control that switches the target rotational speed from the standby rotational speed to a recovery rotational speed higher than the standby rotational speed, The control processing unit controls the rotational speed of the prime mover so as to transition to the target rotational speed over a transition period of time for at least one of the first control and the second control. Control system for industrial machinery.

13. A control system for a work machine according to claim 12, Equipped with an aircraft, Agricultural machinery.

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