Work machine

Abstract

The present invention improves the operability of a work machine and reduces energy loss.　A storage device (7b) of this work machine (1) stores: first characteristic information (L4, L5) indicating the relationship between the rotation speed of a prime mover (9, 69) and the operation speed of a work device (20, 18); and second characteristic information indicating the relationship between the rotation speed of the prime mover and a loss occurring in the prime mover and / or a hydraulic pump (19). When an operation member (5a, 5b, 5e) is operated, a control unit (7) selects, as an optimum rotation speed (Rs), a rotation speed at which the difference (△U) between an operation speed (Us) corresponding to the operation of the operation member and a target speed (Ug) is zero or at most a first predetermined value (△Ut), and a loss (Es, Es1, Es2) corresponding to the operation of the operation member is zero or at most a second predetermined value (Et, Et1, Et2), on the basis of the first characteristic information and the second characteristic information, and the prime mover is rotated at the optimum rotation speed.

Description

Work machine

[0001] The present invention relates to a work machine such as a backhoe (excavator).

[0002] For example, in Patent Document 1, an engine as a prime mover, a work device for performing work, an accelerator pedal, and a control device for controlling the engine speed based on the first to third control characteristic lines that set the relationship between the operation amount of the accelerator pedal and the engine speed are provided. A work machine is disclosed. The control device includes a first engine speed control unit that controls the engine speed according to the first control characteristic line that prioritizes the work speed during work by the work device, and a second engine speed control unit that controls the engine speed according to the second control characteristic line that prioritizes fuel efficiency when the load is small during traveling. A third engine speed control unit that controls the engine speed according to a third control characteristic line between the first control characteristic line and the second control characteristic line when the load is large.

[0003] Japanese Patent Publication "Japanese Unexamined Patent Application Publication No. 2014 - 190235"

[0004] In a conventional work machine, when the operation amount of the accelerator is kept constant by the driver during work by the work device, the rotational speed of the prime mover is also kept at a constant rotational speed corresponding to the operation amount. Therefore, the lower the rotational speed of the prime mover, the slower the operation of the work device during operation of the work device by the operation member, resulting in a decrease in workability. The higher the rotational speed of the prime mover, the greater the energy loss.

[0005] The present invention has been made to solve the above problems of the prior art, and aims to improve the workability of the work machine and reduce energy loss.

[0006] A work machine according to one aspect of the present invention comprises a prime mover, a hydraulic pump driven by the prime mover to discharge hydraulic fluid, a work device having a hydraulic actuator operated by the hydraulic fluid, a control valve capable of switching the supply state of the hydraulic fluid to the hydraulic actuator, an operating member that can be operated in a plurality of operating directions to operate the control valve, a control device for controlling the rotational speed of the prime mover, and a storage device, wherein the storage device stores first characteristic information indicating the relationship between the rotational speed of the prime mover and the operating speed of the work device, and second characteristic information indicating the relationship between the rotational speed of the prime mover and losses occurring in at least one of the prime mover and the hydraulic pump, and when the operating member is operated, the control device selects an optimal rotational speed based on the first characteristic information and the second characteristic information such that the difference between the operating speed corresponding to the operation of the operating member and a predetermined target speed is zero or less than or equal to a first predetermined value, and the losses corresponding to the operation of the operating member are zero or less than or equal to a second predetermined value, and rotates the prime mover at the optimal rotational speed.

[0007] According to the above configuration, the workability of the work machine can be improved and energy loss can be reduced.

[0008] This is a side view of an example of a work machine. This is a schematic diagram showing an example of a hydraulic circuit installed in a work machine. This is a schematic diagram showing an example of the configuration of a work machine. This is a diagram showing an example of the control block of a work machine. This is a conceptual diagram showing an example of operation characteristic information in a graph. This is a conceptual diagram showing an example of first characteristic information in a table. This is a conceptual diagram showing an example of target loss information in a graph. This is a conceptual diagram showing an example of prime mover characteristic information in a table. This is a conceptual diagram showing an example of pump characteristic information in a table. This is a conceptual diagram showing other examples of pump characteristic information in a table. This is a conceptual diagram showing examples of first characteristic information, first loss information, and second loss information in graphs. This is a conceptual diagram showing an example of changes in the rotation speed of an electric motor, the operating position of an operating member, and the position of a work device in a graph. This is a conceptual diagram showing an example of changes in the rotation speed of a conventional electric motor, the operating position of an operating member, and the position of a work device in a graph. This is a schematic diagram showing other examples of the configuration of a work machine.

[0009] Hereinafter, one embodiment of the present invention will be described with reference to the drawings. Figure 1 is a side view of an example of a work machine 1. The work machine 1 in this embodiment is an excavator called a backhoe. The work machine according to the present invention is not limited to the work machine 1, but may be other construction machinery, agricultural machinery, or work vehicles.

[0010] The work machine 1 comprises a machine body (turntable) 2, a traveling device 10, and work devices 20, 18, etc. Furthermore, the work machine 1 is an electric work machine that is powered by an electric motor 9, which is installed inside the machine body 2 as a prime mover. The work machine according to the present invention is not limited to an electric work machine, and may also be a work machine equipped with an engine as a prime mover.

[0011] A cabin 6 is mounted on top of the aircraft body 2. Inside the cabin 6 are a driver's seat 4 where the operator sits, and control devices 5, etc. The work machine according to the present invention may have a protective mechanism such as a rops or canopy instead of a cabin 6. The control devices 5 are installed in a position that can be operated by the operator seated in the driver's seat 4.

[0012] The running device 10 supports the machine body 2 so that it can move. The running device 10 has a running frame (track frame) 11 and a running mechanism 12. The running frame 11 is a structure to which the running mechanism 12 is attached around the perimeter and which supports the machine body 2 on top. The running mechanism 12 is, for example, a crawler-type running mechanism. The running mechanism 12 is provided on the left and right sides of the running frame 11, respectively.

[0013] The running mechanism 12 includes an idler 13, a drive wheel 14, a plurality of road wheels 15, an endless crawler belt 16, and running motors ML and MR. The idler 13 is located at the front of the running frame 11. The drive wheel 14 is located at the rear of the running frame 11. The plurality of road wheels 15 are provided between the idler 13 and the drive wheel 14. The crawler belt 16 is wrapped around the idler 13, the drive wheel 14, and the road wheels 15.

[0014] The left-hand drive motor ML is included in the drive mechanism 12 located on the left side of the drive frame 11. The right-hand drive motor MR is included in the drive mechanism 12 located on the right side of the drive frame 11. These drive motors ML and MR are composed of hydraulic motors. In each drive mechanism 12, the drive wheels 14 are rotated by the power of the drive motors ML and MR, causing the crawler belt 16 to circumferentially move around.

[0015] A dozer 18 is mounted on the front of the traveling device 10. The dozer 18 is a working device that performs tasks such as cutting, pushing, and leveling soil. The dozer 18 swings up and down by the extension and retraction of the dozer cylinder C5. The dozer cylinder C5 is attached to the traveling frame 11. The dozer cylinder C5 consists of a hydraulic cylinder.

[0016] The machine body 2 is supported on the travel frame 11 via a slewing bearing 3 so as to be rotatable around the slewing axis X. A slewing motor MT is installed inside the machine body 2. The slewing motor MT is composed of a hydraulic motor. The machine body 2 rotates around the slewing axis X using the power of the slewing motor MT.

[0017] The working device 20 is connected to the front of the machine body 2. The working device 20 includes a boom 21, an arm 22, a bucket (working tool) 23, and hydraulic cylinders C1 to C5. The base end of the boom 21 is pivotally attached to a swing bracket 24 so as to be rotatable around a horizontal axis (an axis extending in the width direction of the machine body 2). As a result, the boom 21 can swing up and down (vertically). The arm 22 is pivotally attached to the tip of the boom 21 so as to be rotatable around a horizontal axis. As a result, the arm 22 can swing in the front-to-back direction or up and down direction. The bucket 23 is provided at the tip of the arm 22 so as to be able to perform shoveling and dumping operations.

[0018] In place of the bucket 23, or in addition to the bucket 23, other work tools (hydraulic attachments) that can be driven by a hydraulic actuator can be attached to the tip of the arm 22. Examples of other work tools include hydraulic breakers, hydraulic crushers, angle brooms, earth augers, pallet forks, sweepers, mowers, and snow blowers. The work device 20 performs various tasks using the attached work tools.

[0019] The swing bracket 24 swings from side to side by the extension and retraction of the swing cylinder C1 located inside the machine body 2. The boom 21 swings up and down by the extension and retraction of the boom cylinder C2. The arm 22 swings back and forth or up and down by the extension and retraction of the arm cylinder C3. The bucket 23 swings back and forth or up and down by the extension and retraction of the work tool cylinder C4 to perform shoveling and dumping operations. The swing cylinder C1, boom cylinder C2, arm cylinder C3, and work tool cylinder C4 are composed of hydraulic cylinders.

[0020] The travel device 10 is driven by the travel motors ML and MR, causing the work machine 1 to move. The work machine 1 moves by traveling, changes the orientation of the machine body 2 by the slewing motor MT, and changes the posture (position and orientation) of the work devices 20 and 18 by the hydraulic cylinders C1 to C5 to perform work such as excavation. The travel motors ML and MR, the slewing motor MT, and the hydraulic cylinders C1 to C5 are hydraulic actuators provided on the work machine 1 and are driven by hydraulic fluid.

[0021] Figure 2 is a schematic diagram of an example of a hydraulic circuit K provided in the work machine 1. The hydraulic circuit K is equipped with hydraulic components such as hydraulic actuators C1 to C5, ML, MR, MT, control valve unit CV, hydraulic pumps 19 and 29, operating valves PV1 to PV6, and an oil passage 50.

[0022] The multiple hydraulic pumps 19 and 29 are each driven by the power of the electric motor 9 to discharge hydraulic fluid. Specifically, the first hydraulic pump 19 sucks hydraulic fluid stored in the hydraulic fluid tank 48 and then discharges the hydraulic fluid into the oil passage 51 toward the control valve unit CV. The first hydraulic pump 19 is an operating pump that discharges hydraulic fluid to operate the hydraulic actuators C1 to C5, ML, MR, and MT. The second hydraulic pump 29 sucks hydraulic fluid stored in the hydraulic fluid tank 48 and then discharges the hydraulic fluid into the oil passage 52 to output hydraulic pressure for signaling or control. In other words, the second hydraulic pump 29 is a pilot pump that discharges pilot oil. In Figure 2, one first hydraulic pump 19 and one second hydraulic pump 29 are shown, but the number of first hydraulic pumps 19 and second hydraulic pumps 29 can be appropriately determined according to the number and performance of the hydraulic actuators C1 to C5, ML, MR, and MT.

[0023] The control valve unit CV includes multiple control valves V1 to V8. The multiple control valves V1 to V8 are provided in correspondence with multiple hydraulic actuators C1 to C5, ML, MR, and MT. The swing control valve V1 corresponds to the swing cylinder C1. The boom control valve V2 corresponds to the boom cylinder C2. The arm control valve V3 corresponds to the arm cylinder C3. The bucket control valve V4 corresponds to the work tool cylinder C4. The dozer control valve V5 corresponds to the dozer cylinder C5. The left-side travel control valve V6 corresponds to the left-side travel motor ML. The right-side travel control valve V7 corresponds to the right-side travel motor MR. The slewing control valve V8 corresponds to the slewing motor MT.

[0024] Each control valve V1 to V8 is supplied with hydraulic fluid discharged from the first hydraulic pump 19. Each control valve V1 to V8 is composed of a three-position switching valve that can be switched between positions V1a to V8a and V1b to V8b that supply hydraulic fluid to the corresponding hydraulic actuators C1 to C5, ML, MR, and MT, and a neutral position V1c to V8c that shuts off the hydraulic fluid. When the spools provided in each control valve V1 to V8 move and each control valve V1 to V8 switches to the first supply position V1a to V8a, and when it switches to the second supply position V1b to V8b, the direction of hydraulic fluid supply to the corresponding hydraulic actuators C1 to C5, ML, MR, and MT differs. The opening degree of each control valve V1 to V8 at each supply position V1a to V8a and V1b to V8b changes according to the position of the spool of each control valve V1 to V8. Each control valve V1 to V8 can switch the supply state of hydraulic fluid from the first hydraulic pump 19 to the corresponding hydraulic actuators C1 to C5, ML, MR, and MT by changing its position and opening degree. In other words, the control valves V1 to V8 control the supply, shut-off, supply direction, supply amount, and supply pressure of hydraulic fluid to the corresponding hydraulic actuators C1 to C5, ML, MR, and MT.

[0025] The work machine 1 is equipped with a plurality of operating members 5a to 5f. The plurality of operating members 5a to 5f are located inside the cabin 6 and are operated by the operator seated in the driver's seat 4. Operating members 5a and 5b are work levers for operating the work device 20. By swinging operating member 5a from side to side, the control valve V1 is switched to supply positions V1a and V1b, the swing cylinder C1 is extended and retracted, and the swing bracket 24 is swung from side to side. By swinging operating member 5a back and forth, the control valve V2 is switched to supply positions V2a and V2b, the boom cylinder C2 is extended and retracted, and the boom 21 is swung up and down. The operating member 5b, when swung from side to side, switches the control valve V3 to supply positions V3a and V3b, extends and retracts the arm cylinder C3, causing the arm 22 to swing up and down. When swung back and forth, it switches the control valve V4 to supply positions V4a and V4b, extends and retracts the work tool cylinder C4, causing the work tool such as the bucket 23 to swing back and forth.

[0026] Operating members 5c and 5d are travel levers for operating the travel device 10. Operating member 5c, when swung back and forth, switches the control valve V6 to supply positions V6a and V6b, causing the left travel motor ML to rotate forward or backward, thereby moving the left travel device 10 forward or backward. Operating member 5d, when swung back and forth, switches the control valve V7 to supply positions V7a and V7b, causing the right travel motor MR to rotate forward or backward, thereby moving the right travel device 10 forward or backward. Operating member 5e, when swung back and forth, switches the control valve V5 to supply positions V5a and V5b, extending and retracting the dozer cylinder C5, and swinging the dozer 18 up and down. The operating member 5f is a swivel lever that, when swung from side to side, switches the control valve V8 to supply positions V8a and V8b, causing the swivel motor MT to rotate in the forward or reverse direction, thereby swiveling the machine body 2 left and right around the swivel axis X.

[0027] When each operating member 5a to 5f is in the neutral position, it sets the corresponding control valves V1 to V8 to the neutral position V1c to V8c, stopping the corresponding hydraulic actuators C1 to C5, ML, MR, and MT. Note that the operating members 5a to 5f may be other operating members besides levers, such as pedals, sliders, or push buttons.

[0028] Multiple operating members 5a to 5f and multiple operating valves PV1 to PV6 are included in the control device 5. Multiple operating valves PV1 and PV2 are provided to correspond to the operating direction of operating members 5a and 5b, the supply positions V1a to V4b of control valves V1 to V4, and the operating direction (extension and contraction) of hydraulic actuators C1 to C4. Multiple operating valves PV3 to PV6 are provided to correspond to the operating direction of operating members 5c to 5f, the supply positions V5a to V8a of control valves V5 to V8, and the operating direction of hydraulic actuators ML, MR, C5, and MT. Pilot oil, which is a control hydraulic fluid, is supplied to each operating valve PV1 to PV6 from the second hydraulic pump 29. Each operating valve PV1 to PV6 opens and closes in conjunction with the operation of the corresponding operating member 5a to 5f, and the degree of opening is changed to adjust the pressure of the pilot oil flowing through the second oil passage 52.

[0029] More specifically, when the operator of the work machine 1 operates each of the operating members 5a to 5f, each of the operating valves PV1 to PV6 is activated according to the direction and amount of operation of each of the operating members 5a to 5f. Pilot oil at a flow rate proportional to the amount of operation of each of the operating valves PV1 to PV6 acts from each of the operating valves PV1 to PV6 to the pressure receiving parts V1d to V8d and V1e to V8e of one of the control valves V1 to V8. As a result, the spools of each of the control valves V1 to V8 move in a straight line, each of the control valves V1 to V8 switches to one of the supply positions, and the opening degree of each of the control valves V1 to V8 is changed. Then, hydraulic oil at a flow rate proportional to the amount of movement of the spools of each of the control valves V1 to V8 is supplied to the corresponding hydraulic actuators C1 to C5, ML, MR, and MT in the direction corresponding to the switched supply position of each of the control valves V1 to V8. Then, each hydraulic actuator C1 to C5, ML, MR, and MT operates according to the amount and direction of hydraulic fluid supplied from each control valve V1 to V8.

[0030] The oil passage 50 is a passage that connects the various parts of the hydraulic circuit K and supplies hydraulic fluid or pilot oil to each part. The oil passage 50 includes a first oil passage 51 and a second oil passage 52. The first oil passage 51 is connected to the first hydraulic pump 19 and the hydraulic actuators C1 to C5, ML, MR, and MT. The first oil passage 51 includes a main oil passage 51a, a branch oil passage 51b, and reciprocating oil passages 51c, 51d, and a discharge oil passage 51e. The main oil passage 51a is a passage through which the hydraulic fluid discharged by the first hydraulic pump 19 flows toward the control valve unit CV. The control valve unit CV is provided with a plurality of branch oil passages 51b that branch off from the main oil passage 51a. Control valves V1 to V8 are connected to each branch oil passage 51b, respectively.

[0031] The reciprocating oil passages 51c and 51d are flow paths that connect the corresponding control valves V1 to V8 to the hydraulic actuators C1 to C5, ML, MR, and MT in pairs. That is, the reciprocating oil passages 51c and 51d are flow paths that supply hydraulic fluid from the connected control valves V1 to V8 to the hydraulic actuators C1 to C5, ML, MR, and MT, and return hydraulic fluid from the hydraulic actuators C1 to C5, ML, MR, and MT to the control valves V1 to V8. The discharge oil passage 51f is connected to each control valve V1 to V8 and the hydraulic fluid tank 48. The discharge oil passage 51f is a flow path that discharges the hydraulic fluid that has returned from each hydraulic actuator C1 to C5, ML, MR, and MT to each control valve V1 to V8 into the hydraulic fluid tank 48.

[0032] The hydraulic fluid discharged from the first hydraulic pump 19 flows through the main oil passage 51a and the branch oil passage 51b to the control valves V1 to V8. When the control valves V1 to V8 are in any of the supply positions V1a to V8a or V1b to V8b, the hydraulic fluid passes through the supply positions V1a to V8a or V1b to V8b and through one of the connected reciprocating oil passages 51c or 51d to be supplied to the corresponding hydraulic actuators C1 to C5, ML, MR, and MT. The hydraulic fluid discharged from the corresponding hydraulic actuators C1 to C5, ML, MR, and MT returns to the connected control valves V1 to V8 through one of the reciprocating oil passages 51c or 51d, passes through any of the supply positions V1a to V8a or V1b to V8b of the control valves V1 to V8, and is discharged into the discharge oil passage 51f.

[0033] Furthermore, when the control valves V1 to V8 are in the neutral position V1c to V8c, the hydraulic fluid that flows from the branch oil passage 51b to the control valves V1 to V8 is not supplied to the hydraulic actuators C1 to C5, ML, MR, and MT, but passes through the neutral position V1c to V8c and is discharged into the discharge oil passage 52f. An oil cooler 37 is provided in the discharge oil passage 51f. The hydraulic fluid discharged into the discharge oil passage 52f is cooled by the oil cooler 37 and then flows into the hydraulic fluid tank 48. As described above, the first oil passage 51 is arranged to circulate the hydraulic fluid to the hydraulic fluid tank 48, the first hydraulic pump 19, and the control valves V1 to V8 of the control valve unit CV, or to the hydraulic actuators C1 to C5, ML, MR, and MT.

[0034] The second oil passage 52 includes a discharge oil passage 52a, a branch oil passage 52b, and pilot oil passages 52c and 52d. The discharge oil passage 52a is a passage through which pilot oil discharged by the second hydraulic pump 29 flows toward the operating valves PV1 to PV6. The pilot oil passages 52c and 52d are passages connecting the corresponding operating valves PV1 to PV6 to the pressure receiving sections V1d to V8d and V1e to V8e of the control valves V1 to V8. In Figure 2, for convenience, the intermediate sections of the pilot oil passages 52c and 52d are not shown, and the connection relationships are indicated by numbers in parentheses.

[0035] When operating members 5a to 5f are not operated, pilot oil flowing through the discharge oil passage 52a is discharged through the discharge oil passage 52e. When any of the operating members 5a to 5f are operated, the operating valves PV1 to PV6 corresponding to the operating direction of the operated operating member 5a to 5f are opened. As a result, the pilot oil flowing through the discharge oil passage 52a acts on the pressure receiving parts V1d to V8d and V1e to V8e of the corresponding control valves V1 to V8, passing through the opened operating valves PV1 to PV6 and the pilot oil passages 52c and 52d connected thereto. Then, one of the control valves V1 to V8 switches to the corresponding supply position V1a to V8a and V1b to V8b, and the hydraulic fluid from the first hydraulic pump 19 passes through the switched control valves V1 to V8 and is supplied to the corresponding hydraulic actuators C1 to C5, ML, MR, and MT. Then, the corresponding hydraulic actuators C1 to C5, ML, MR, and MT are operated by the pressure of the supplied hydraulic fluid, and the corresponding work devices 20, 18 and travel device 10 are driven. In other words, the work devices 20, 18 and travel device 10 are operated by the power of the hydraulic actuators C1 to C5, ML, MR, and MT that they are equipped with.

[0036] Figure 3 is a schematic diagram showing an example of the configuration of the implement 1. More specifically, Figure 3 shows an example of the configuration of the rotational speed control system incorporated into the implement 1. The implement 1 is equipped with a control device 7, a battery unit 30, an inverter 38, a PDU (Power Distribution Unit) 39, a key switch 41, a mode switch 58, an accelerator dial 42, a pressure sensor 43, a temperature sensor 44, and position sensors 49a to 49e.

[0037] The control device 7 includes a processor 7a, such as a CPU, and a memory 7b. The memory 7b includes volatile memory and non-volatile memory. The control device 7 (processor 7a) is a controller that controls the operation of each part of the work machine 1 and executes predetermined processes. Various types of information, control data, and software programs are stored in the memory 7b in a read-write manner. The memory 7b is an example of a storage device. Other storage devices may be built into the control device 7, or may be provided separately in the work machine 1. Furthermore, such storage devices may consist of at least one of the following: non-volatile memory, SSD (Solid State Drive), and hard disk.

[0038] The battery unit 30 has multiple battery packs 31 and 32. Each battery pack 31 and 32 is a secondary battery (storage battery) such as a lithium-ion battery, composed of at least one battery, and is capable of discharging high-voltage power, for example, 200V to 400V. Each battery constituting each battery pack 31 and 32 has multiple cells inside, and these multiple cells are electrically connected in series and / or parallel. The battery packs 31 and 32 are connected in parallel to each other. In Figure 3, the battery unit 30 is provided with two battery packs 31 and 32, but the number of battery packs that the battery unit 30 has is not limited to two, and may be three or more.

[0039] The PDU 39 has a switching circuit that switches the power supply source. The control device 7 uses the PDU 39 to discharge from either the battery pack 31 or 32, or to discharge from both the battery pack 31 and 32. The inverter 38 is a drive device (drive circuit) that has a drive circuit for driving the electric motor 9. The electric motor 9 is composed of, for example, a permanent magnet embedded type three-phase AC synchronous motor. The inverter 38 converts the DC power input from the battery unit 30 via the PDU 39 into three-phase AC power, and supplies this three-phase AC power to the electric motor 9 to drive the electric motor 9. The inverter 38 can also arbitrarily adjust the current and voltage of the power supplied to the electric motor 9. The control device 7 uses the inverter 38 to control the rotation, stopping, direction of rotation, and rotation speed of the electric motor 9.

[0040] The key switch 41, mode switch 58, and accelerator dial 42 are located inside the cabin 6 and are operated by the driver seated in the driver's seat 4. The key switch 41 is operated to start and stop the implement 1. Specifically, by turning the key switch 41 ON, the control device 7 starts the electric motor 9 and also starts other parts of the implement 1. Conversely, by turning the key switch 41 OFF, the control device 7 stops the electric motor 9 and also stops other parts of the implement 1. The mode switch 58 is an operation switch that is operated to switch the mode performed by the implement 1 to one of the first mode, second mode, or third mode. For example, the first mode is the standard mode for the implement 1, the second mode is a higher-output mode than the first mode, and the third mode is a lower-output mode than the first mode.

[0041] The accelerator dial 42 is rotated to input the target rotational speed of the electric motor 9. For example, the range of angles in which the accelerator dial 42 can be rotated corresponds to the range in which the target rotational speed of the electric motor 9 can be input. By changing the operating position of the accelerator dial 42, the target rotational speed of the electric motor 9 can also be changed. Specifically, the control device 7 determines (calculates) the target rotational speed of the electric motor 9 according to the operating state of the accelerator dial 42 (whether or not it is operated and the operating position). The accelerator dial 42 is an example of an accelerator operating member and input device (input interface) for inputting the target rotational speed. Alternatively or in addition to this, accelerator operating members other than dials, such as push buttons, tumbler switches, and pedals, may be provided on the work machine 1 as input devices for inputting the target rotational speed of the electric motor 9.

[0042] In place of, or in addition to, the mode switch 58 and accelerator dial 42, a plurality of software keys for inputting modes and target rotational speeds may be provided on the display screen of the user interface on the work implement 1. In this case, the operator inputs either a mode or a target rotational speed by operating one of the software keys via the user interface. Alternatively, a signal indicating either a mode or a target rotational speed may be transmitted from a remote device capable of remotely controlling the work implement 1, and this signal may be received (input) by the communication device 46. In this case, the operator inputs either a mode or a target rotational speed for the electric motor 9 by operating the user interface on the remote device.

[0043] The pressure sensor 43 is connected to the main oil passage 51a of the first oil passage 51, as shown in Figure 2, for example, and detects (measures) the pressure of the hydraulic fluid flowing through the main oil passage 51a. That is, the pressure sensor 43 detects the pump pressure, which is the pressure of the hydraulic fluid discharged from the first hydraulic pump 19 toward the control valves V1 to V8 of the control valve unit CV.

[0044] When none of the operating members 5a to 5f is being operated, all of the control valves V1 to V8 are in their neutral positions V1c to V8c, and none of the hydraulic actuators C1 to C5, ML, MR, and MT is operating. Therefore, the working devices 20 and 18 and the traveling device 10 are stopped (working pause state, non-traveling state). At this time, the pressure of the hydraulic oil detected by the pressure sensor 43 is about atmospheric pressure.

[0045] When at least any one of the operating members 5a to 5f is operated, the corresponding control valves V1 to V8 are switched to any of the supply positions V1a to V8a, V1b to V8b, and the corresponding hydraulic actuators C1 to C5, ML, MR, and MT are operated by the hydraulic oil supplied from the control valves V1 to V8, and the corresponding working devices 20 and 18 and the traveling device 10 are driven (working state, traveling state). At this time, the pressure of the hydraulic oil detected by the pressure sensor 43 becomes higher than atmospheric pressure.

[0046] As shown in FIG. 2, the temperature sensor 44 is connected to the oil passage 50. The temperature sensor 44 detects (measures) the temperature of the hydraulic oil. In FIG. 2, an example where the temperature sensor 44 is connected to the discharge oil passage 51e is shown, but it is not limited thereto. The temperature sensor 44 may be connected to other locations of the first oil passage 51, or may be connected to any location of the second oil passage 52, or may be installed inside the hydraulic oil tank 48 or the like. However, it is preferable that the temperature sensor 44 is not connected to a position close to the downstream side of the cooling device such as the oil cooler 37.

[0047] The position sensors 49a to 49e are composed of, for example, potentiometers. The position sensor 49a detects the operating position (swing angle) of the operating member 5a in the front-rear direction. The position sensor 49b detects the operating position of the operating member 5a in the left-right direction. The position sensor 49c detects the operating position of the operating member 5b in the front-rear direction. The position sensor 49d detects the operating position of the operating member 5b in the left-right direction. The position sensor 49e detects the operating position of the operating member 5e in the front-rear direction. Based on the output signals from the position sensors 49a to 49e, the control device 7 determines the presence or absence of operations, the operation directions, and the operating positions of the operating members 5a, 5b, and 5e, and calculates the operation amount (%) of the operating members 5a, 5b, and 5e with respect to the neutral position from the operating positions.

[0048] The control device 7 starts the electric motor 9 by the inverter 38. When the target rotational speed is input by the accelerator dial 42 or the like (or the user interface 45 or the communication device 46), the control device 7 rotates the electric motor 9 at the target rotational speed by the inverter 38. A rotational speed sensor 47 for detecting (measuring) the actual rotational speed of the rotating shaft of the electric motor 9 may be provided in the working machine 1. In this case, the control device 7 refers to the actual rotational speed of the electric motor 9 detected by the rotational speed sensor 47, and may perform feedback control on the drive of the electric motor 9 by the inverter 38 so that the actual rotational speed of the electric motor 9 matches the target rotational speed.

[0049] Further, a torque sensor 57 for detecting (measuring) the torque of the rotating shaft of the electric motor 9 may be provided in the working machine 1. Alternatively, the control device 7 may calculate the torque of the electric motor 9 based on the target rotational speed or the actual rotational speed detected by the rotational speed sensor 47. The control device 7 controls the torque of the electric motor 9 by the inverter 38.

[0050] FIG. 4 is a schematic diagram showing an example of a control block configured in the control device 7. Each control block in FIG. 4 is configured by a software program stored in the memory 7b or a logic circuit provided in the control device 7.

[0051] When the control device 7 is rotating the electric motor 9 at a target rotational speed input by the accelerator dial 42 or the like, if any of the operating members 5a, 5b, or 5e are operated in any direction, the control device 7 detects the operating position of any of the operating members 5a, 5b, or 5e operated by the position sensors 49a to 49e and calculates the actual amount of operation of the operating member 5a, 5b, or 5e. Then, the control device 7, using the target selection unit 71, determines the target speed Ug, which is the target operating speed of the work devices 20 and 18, according to the actual amount of operation. The memory 7b stores operating characteristic information that shows the relationship between the amount of operation of the operating members 5a, 5b, or 5e and the operating speed of the work devices 20 and 18.

[0052] Figure 5 is a conceptual diagram showing an example of operation characteristic information in a graph. In the graph in Figure 5, the horizontal axis represents the amount of operation of the operating members 5a, 5b, and 5e, and the vertical axis represents the operating speed of the work devices 20 and 18. The operation characteristic lines L1 to L3 shown in Figure 5 are examples of operation characteristic information. Each value shown in the operation characteristic information is a value measured in an experiment. The same applies to the values ​​shown in the other characteristic information and target loss information described later.

[0053] The operation characteristic information includes first operation characteristic information, second operation characteristic information, and third operation characteristic information, which show the relationship between the amount of operation of the operating members 5a, 5b, and 5e corresponding to the first mode, second mode, and third mode, respectively, and the operating speed of the work devices 20 and 18. The first to third operation characteristic lines L1 to L3 in Figure 5 are examples of the first to third operation characteristic information.

[0054] The operating speed indicated by the second operating characteristic line L2, which corresponds to the second mode, is set to be greater than the operating speed indicated by the first operating characteristic line L1, which corresponds to the first mode. The operating speed indicated by the third operating characteristic line L3, which corresponds to the third mode, is set to be less than the operating speed indicated by the first operating characteristic line L1, which corresponds to the first mode. In each operating characteristic line L1 to L3, the operating speed increases proportionally as the amount of manipulation increases.

[0055] When any of the operating members 5a, 5b, or 5e is operated, the control device 7 uses the target selection unit 71 to select one of the operating characteristic lines L1 to L3, which correspond to any of the first, second, or third modes that are currently in operation. The control device 7 then uses the target selection unit 71 to select one of the operating speeds from the selected operating characteristic lines L1 to L3 that corresponds to the actual amount of operation of the operating members 5a, 5b, or 5e as the target speed Ug.

[0056] Figure 5 shows an example where each operation characteristic line L1 to L3 is a straight line represented by a linear function, but it is not limited to this, and each operation characteristic line L1 to L3 may be a curve represented by another function such as a quadratic function. As another example, table data showing the first to third operation characteristic information corresponding to the first mode, second mode, and third mode may be included in the operation characteristic information. Furthermore, at least one of the first to third operation characteristic information may be set for each operating member 5a, 5b, 5e, each work device 20, 18, or each hydraulic actuator C1 to C5. Also, the target speed may be a constant value regardless of the mode, etc.

[0057] Memory 7b stores first characteristic information that shows the relationship between the rotational speed of the electric motor 9 and the operating speed of the work devices 20 and 18. Figure 6 is a conceptual diagram showing an example of the first characteristic information in graph form. The first characteristic information includes high-temperature speed characteristic information and low-temperature speed characteristic information. The high-temperature speed characteristic information is control information that shows the relationship between the rotational speed of the electric motor 9 and the operating speed of the work devices 20 and 18 when the temperature of the hydraulic oil is above a predetermined value. The low-temperature speed characteristic information is control information that shows the relationship between the rotational speed of the electric motor 9 and the operating speed of the work devices 20 and 18 when the temperature of the hydraulic oil is below a predetermined value. The high-temperature speed characteristic line L4 and the low-temperature speed characteristic line L5 shown in Figure 6 are examples of the high-temperature speed characteristic information and low-temperature speed characteristic information, respectively.

[0058] In each speed characteristic line L4 and L5, the operating speed increases proportionally as the rotational speed increases. The operating speed shown in the high-temperature speed characteristic line L4 is greater than the operating speed shown in the low-temperature speed characteristic line L5. Figure 6 shows an example where each speed characteristic line L4 and L5 are straight lines represented by linear functions, but it is not limited to this, and each speed characteristic line L4 and L5 may be a curve represented by another function such as a quadratic function. In addition, two or more predetermined values ​​for determining the temperature of the hydraulic fluid may be set, the temperature range may be divided into three or more stages, and three or more speed characteristic lines corresponding to each range may be set and included in the first characteristic information.

[0059] When the work devices 20 and 18 are in operation, losses occur in the drive systems of the work devices 20 and 18 (electric motor 9 and first hydraulic pump 19, etc.), and a target loss, which is a target value of such losses, may be set. For example, memory 7b stores target loss information that shows the relationship between the rotational speed of the electric motor 9 and the target loss (numerical value) of the drive systems of the work devices 20 and 18 (electric motor 9 and first hydraulic pump 19, etc.). Figure 7 is a conceptual diagram that shows an example of target loss information in a graph. The target loss line L6 shown in Figure 7 is an example of target loss information. In the target loss line L6, the target loss increases quadratically as the rotational speed increases.

[0060] The control device 7, using the target selection unit 71, selects the target speed Ug of the work devices 20 and 18. Then, from the speed characteristic lines L4 and L5 in Figure 6, if the temperature of the hydraulic fluid detected by the temperature sensor 44 is above a predetermined value, the high-temperature speed characteristic line L4 in Figure 6 is selected. If the temperature of the hydraulic fluid is below a predetermined value, the low-temperature speed characteristic line L4 is selected. Next, the control device 7 selects a rotational speed corresponding to the target speed Ug as the reference rotational speed Rx from either of the selected speed characteristic lines L4 or L5. Then, the control device 7, using the target selection unit 71, selects the target loss Eg corresponding to the reference rotational speed Rx from the target loss line L6 in Figure 7. Since the target speed Ug increases in the order of the third mode, first mode, and second mode according to the operation characteristic lines L1 to L3 shown in Figure 5, the reference rotational speed Rx and target loss Eg also increase in the same order.

[0061] Figure 7 shows an example where the target loss line L6 is a curve represented by a quadratic function, but it is not limited to this, and the target loss line L6 may be a straight line or curve represented by another function such as a linear function. Another example is that target loss information, which shows the numerical values ​​of the target losses corresponding to the first mode, second mode, and third mode in a table format, may be stored in memory 7b. In this case, the control device 7 selects the target loss corresponding to any one of the first mode, second mode, and third mode that is currently being executed from the target loss information using the target selection unit 71. Another example is that the target loss information may be set for each operating member 5a, 5b, 5e, each work device 20, 18, each hydraulic actuator C1 to C5, or by temperature. Also, the target loss may be a constant value regardless of the mode, etc.

[0062] Furthermore, memory 7b stores second characteristic information that shows the relationship between the rotational speed of the electric motor 9 and losses occurring in at least one of the electric motor 9 and the first hydraulic pump 19. The second characteristic information includes, for example, prime mover characteristic information that shows the relationship between the rotational speed, torque, and losses of the electric motor 9, and pump characteristic information that shows the relationship between the rotational speed of the electric motor 9, the pump pressure of the first hydraulic pump 19, and losses.

[0063] Figure 8 is a conceptual diagram showing an example of prime mover characteristic information in a table. The prime mover characteristic information in Figure 8 shows the relationship between the rotational speed, torque, and losses of the rotating shaft of the electric motor 9. Note that the display of specific numerical values ​​is omitted in Figure 8. (The same applies to Figures 9 and 10 described later.) The losses shown in Figure 8 are the power losses of the electric motor 9 (unit: W (watts)), and are, for example, the sum of iron loss, copper loss, and mechanical loss. As another example, at least one value or the sum of any two of the iron loss, copper loss, and mechanical loss of the electric motor 9 may be included as losses in the prime mover characteristic information. The prime mover characteristic information is generated according to the range of applied voltage applied to the electric motor 9. That is, memory 7b stores multiple prime mover characteristic information according to the driving state of the electric motor 9.

[0064] In each prime mover characteristic information, losses increase as the rotational speed and torque of the electric motor 9 increase. Also, the numerical values ​​and relationships of rotational speed, torque, and losses differ when the applied voltage to the electric motor 9 is different. When any of the operating members 5a, 5b, or 5e is operated, the control device 7 uses the prime mover loss extraction unit 72 to extract first loss information (information showing the relationship between rotational speed and loss enclosed by the dashed line in Figure 8) Q1, which shows the relationship between the rotational speed of the electric motor 9 corresponding to the torque of the electric motor 9 being controlled, and the losses, from the prime mover characteristic information corresponding to the range that includes the applied voltage of the electric motor 9 being controlled by the inverter 38. The first loss information Q1 extracted at this time is information corresponding to the actual applied voltage of the electric motor 9.

[0065] The control device 7 detects the applied voltage (actual applied voltage) of the electric motor 9 under control based on the control signal input to the inverter 38, for example. The control device 7 also detects the torque (actual torque) of the electric motor 9 under control using, for example, a torque sensor 57. Alternatively, the control device 7 calculates the torque (actual torque) from the current target rotational speed of the electric motor 9 under control or from the actual rotational speed of the electric motor 9 detected by the rotational speed sensor 47.

[0066] Figure 9 is a conceptual diagram showing an example of pump characteristic information in a table. The pump characteristic information in Figure 9 shows the relationship between the rotational speed of the drive gear (rotating body) of the first hydraulic pump 19, which is composed of a gear pump, the allowable peak pressure P3 of the first hydraulic pump 19, and the mechanical torque loss of the first hydraulic pump 19. Since the drive gear rotates at the same rotational speed as the rotational shaft of the electric motor 9, the rotational speed shown in the pump characteristic information in Figure 9 can be considered as the rotational shaft of the electric motor 9. The allowable peak pressure P3 is an example of the pump pressure of the first hydraulic pump 19.

[0067] Mechanical torque loss is the torque loss (in Nm (Newton meters)) that rotates the drive gear of the first hydraulic pump 19. As another example, the power loss (in W (watts)) of the first hydraulic pump 19 calculated from each mechanical torque loss may be included in the pump characteristic information. Pump characteristic information is generated for each range of hydraulic fluid temperature. In each pump characteristic information, the loss fluctuates irregularly with respect to fluctuations in rotational speed and pressure P3. Also, if the hydraulic fluid temperature is different, the numerical values ​​and relationships of rotational speed, pressure P3, and loss will also be different.

[0068] Figure 10 is a conceptual diagram showing another example of pump characteristic information in a table. The pump characteristic information in Figure 10 shows the relationship between the rotational speed of the cylinder block (rotating body) of the first hydraulic pump 19, which is composed of a piston pump, the allowable peak pressure P3 of the first hydraulic pump 19, the sum of the intermittent pressure P2 and the allowable sustained pressure P1, and the power loss of the first hydraulic pump 19. Since the cylinder block rotates at the same rotational speed as the rotation axis of the electric motor 9, the rotational speed shown in the pump characteristic information in Figure 10 can be considered as the rotation axis of the electric motor 9. Pressures P1 to P3 are examples of the pump pressure of the first hydraulic pump 19. The pump characteristic information in Figure 10 is also generated for each range of hydraulic fluid temperature. Furthermore, in each pump characteristic information in Figure 10, the loss fluctuates irregularly with respect to fluctuations in rotational speed and pressures P1 to P3, and the numerical values ​​and relationships of rotational speed, pressures P1 to P3, and loss also differ when the hydraulic fluid temperature is different.

[0069] As described above, the memory 7b stores multiple pump characteristic information corresponding to the type and operating state of the first hydraulic pump 19, as well as the temperature of the hydraulic fluid. When any of the operating members 5a, 5b, or 5e is operated, the control device 7 detects the temperature of the hydraulic fluid using the temperature sensor 44 and detects the pump pressures P1 to P3 using the pressure sensor 43. The control device 7 then uses the pump loss extraction unit 73 to extract second loss information Q2 (information showing the relationship between rotational speed and loss enclosed by the dashed line in Figure 9 or Figure 10) which shows the relationship between rotational speed and loss corresponding to the detected pressures P1 to P3 (actual pump pressure), from the pump characteristic information corresponding to the type of the first hydraulic pump 19 and the range that includes the detected hydraulic fluid temperature (actual temperature). The second loss information Q2 extracted at this time is information corresponding to the actual temperature of the hydraulic fluid.

[0070] After extracting the first loss information Q1 and the second loss information Q2, the control device 7 selects the optimal rotational speed Rs of the electric motor 9 using the rotational speed selection unit 74 based on the first characteristic information, the first loss information Q1, and the second loss information Q2. Figure 11 is a conceptual diagram showing an example of the first characteristic information, the first loss information Q1, and the second loss information Q2 in graph form. In Figure 11, the horizontal axis represents the rotational speed of the electric motor 9, the left vertical axis represents the operating speed of the work devices 20 and 18, and the right vertical axis represents the loss. In Figure 11, the high-temperature speed characteristic line L4 shown in Figure 7 is shown as an example of the first characteristic information.

[0071] The control device 7, using a rotation speed selection unit 74, calculates the sum of the losses of the electric motor 9 and the first hydraulic pump 19 corresponding to each rotation speed of the electric motor 9 included in the first loss information Q1 and second loss information Q2, and generates loss characteristic information showing the relationship between the rotation speed and the sum. The loss characteristic line L7 shown in Figure 11 is an example of loss characteristic information.

[0072] The control device 7, using a rotation speed selection unit 74, selects an optimal rotation speed Rs based on the high-temperature speed characteristic line L4 and the loss characteristic line L7, such that the difference △U between the operating speed Us of the work devices 20 and 18 corresponding to the operation of the operating members 5a, 5b, and 5e and the target speed Ug is less than or equal to a first predetermined value △Ut, and the sum of the losses Es of the electric motor 9 and the first hydraulic pump 19 corresponding to the operation is less than or equal to a second predetermined value Et. As a result, the operating speed Us corresponding to the optimal rotation speed Rs approximates the target speed Ug without deviating significantly, and the sum of losses Es corresponding to the optimal rotation speed Rs is reduced. The second predetermined value Et may be the same value as the target loss Eg (Et = Eg) or a different value from the target loss Eg (Et ≠ Eg).

[0073] As another example, the control device 7 may select as the optimal rotational speed Rs a rotational speed Rs where at least one of the difference ΔU and the total loss Es is zero, based on the high-temperature speed characteristic line L4 and the loss characteristic line L7. That is, the control device 7 may select as the optimal rotational speed Rs a rotational speed Rs where the difference ΔU is zero or less than or equal to a first predetermined value ΔUt, and the total loss Es is zero or less than or equal to a second predetermined value Et, based on the high-temperature speed characteristic line L4 and the loss characteristic line L7.

[0074] As another example, the control device 7 may select as the optimal rotational speed Rs any rotational speed Rs such that the difference ΔU is zero or less than or equal to a first predetermined value ΔUt, and the difference ΔE between the total loss Es and the target loss Eg is zero or less than or equal to a third predetermined value ΔEt, based on the high-temperature speed characteristic line L4 and the loss characteristic line L7.

[0075] Furthermore, the control device 7 may select as the optimal rotational speed Rs any rotational speed Rs that satisfies either the second condition that the corresponding operating speed Us is the maximum, or the third condition that the corresponding total loss Es is the minimum, within the range of rotational speeds that satisfy the first condition that the difference ΔU is less than or equal to a first predetermined value ΔUt and the total loss Es is less than or equal to a second predetermined value Et, or the difference ΔE is less than or equal to a third predetermined value ΔEt. In the example in Figure 11, the optimal rotational speed Rs that satisfies the third condition is selected.

[0076] Alternatively, the control device 7 may select as the optimal rotational speed Rs any rotational speed Rs within the range of rotational speeds that satisfy the first condition above, provided that the ratio of the difference △U to △E (△U:△E) is a predetermined ratio (a:b). In this case, the ratio (a:b) may be set to "1:1", or the first item "a" and the second item "b" may be set to different values ​​by giving weight to either the target speed Ug or the target loss Eg.

[0077] As described above, when any of the operating members 5a, 5b, or 5e is operated, the control device 7 selects the optimal rotational speed Rs for the electric motor 9 based on the first characteristic information and the second characteristic information (prime mover characteristic information and pump characteristic information). This determines the optimal rotational speed Rs corresponding to the running mode, the actual temperature of the hydraulic fluid, and the actual applied voltage to the electric motor 9. Once the control device 7 has selected the optimal rotational speed Rs, the inverter 38 rotates the electric motor 9 at that optimal rotational speed Rs.

[0078] Figure 12 is a conceptual diagram showing an example of changes in the rotation speed of the electric motor 9 of the work machine 1, the operating position of the operating member 5a, and the position of the work device 20 in a graph. Figure 13 is a conceptual diagram showing an example of changes in the rotation speed of the electric motor 9 of a conventional work machine, the operating position of the operating member 5a, and the position of the work device 20 in a graph. More specifically, Figures 12 and 13 show the change in the operating position of the operating member 5a in the front-rear direction and the change in the position of the boom 21 in the up-down direction corresponding to that operation.

[0079] In conventional work machines, if the amount of operation of the accelerator dial 42 was not changed when the operating member 5a was operated, the rotation speed of the electric motor 9 was kept constant. As a result, as shown in Figure 13, the change in the position of the boom 21 was significantly delayed in response to the change in the operating position of the operating member 5a. This delay time for the change in the position of the boom 21 was longer in the third mode than in the first mode, and also longer when the hydraulic fluid temperature was lower than when it was higher.

[0080] In contrast, with the work machine 1, when the operating member 5a is operated, even if the amount of operation of the accelerator dial 42 is not changed, the control device 7 changes the rotation speed of the electric motor 9 to the optimal rotation speed Rs. As a result, as shown in Figure 12, the delay in the position change of the boom 21 in response to the change in the operating position of the operating member 5a is smaller than in the conventional method (Figure 13). Also, the delay in the position change of the boom 21 in the third mode compared to the position change of the boom 21 in the first mode is also smaller than in the conventional method. Furthermore, the delay in the position change of the boom 21 in the low temperature state compared to the position change of the boom 21 in the high temperature state is also smaller than in the conventional method. In other words, when the operating member 5a is operated, the electric motor 9 rotates at the optimal rotation speed Rs, improving the responsiveness of the boom 21 (working device 20). Also, energy loss is reduced. Moreover, as the optimal rotation speed Rs increases, the operating speed of the working devices 20 and 18 increases, and as the optimal rotation speed Rs decreases, the amount of reduction in energy loss increases.

[0081] In the embodiments described above, an example was shown in which the prime mover characteristic information and the pump characteristic information are included in the second characteristic information, but the invention is not limited thereto. At least one of the prime mover characteristic information and the pump characteristic information may be included in the second characteristic information. In this case, when any of the operating members 5a, 5b, or 5e is operated, the control device 7 performs at least one of the following processes: extracting first loss information Q1 from the prime mover characteristic information and extracting second loss information Q2 from the pump characteristic information, and selects the optimal rotational speed Rs based on the first characteristic information and at least one of the first loss information Q1 and the second loss information Q2.

[0082] Furthermore, if at least the prime mover characteristic information is included in the second characteristic information, the control device 7 extracts at least the first loss information Q1 from the prime mover characteristic information when any of the operating members 5a, 5b, or 5e is operated. Then, based at least the first characteristic information and the first loss information Q1, the control device 7 selects as the optimal rotational speed Rs any rotational speed Rs where the difference △U between the operating speed Us corresponding to the operation of the operating members 5a, 5b, or 5e and the target speed Ug is zero or less than or equal to a first predetermined value △Ut, and the loss Es1 of the electric motor 9 corresponding to the operation is zero or less than or equal to a second predetermined value Et1. Alternatively, the control device 7 selects as the optimal rotational speed Rs any rotational speed Rs where the difference △U is zero or less than or equal to a first predetermined value △Ut, and the difference △E1 between the loss Es1 of the electric motor 9 and the target loss Eg is zero or less than or equal to a third predetermined value △Et1.

[0083] Furthermore, if at least the pump characteristic information is included in the second characteristic information, the control device 7 extracts at least the second loss information Q2 from the pump characteristic information when any of the operating members 5a, 5b, or 5e is operated. At this time, the control device 7 also extracts the second loss information Q2 corresponding to the hydraulic fluid temperature from the pump characteristic information. Then, based at least the first characteristic information and the second loss information Q2, the control device 7 selects as the optimal rotational speed Rs any rotational speed Rs such that the difference △U between the operating speed Us corresponding to the operation of the operating members 5a, 5b, or 5e and the target speed Ug is zero or less than or equal to a first predetermined value △Ut, and the loss Es2 of the first hydraulic pump 19 corresponding to the operation is zero or less than or equal to a second predetermined value Et2. Alternatively, the control device 7 selects as the optimal rotational speed Rs any rotational speed Rs such that the difference ΔU is zero or less than or equal to a first predetermined value ΔUt, and the difference ΔE2 between the loss Es2 of the first hydraulic pump 19 and the target loss Eg is less than or equal to a third predetermined value ΔEt2.

[0084] Alternatively, the second characteristic information may be information showing the relationship between the sum of the losses of the electric motor 9 and the first hydraulic pump 19 and the rotational speed of the electric motor 9. In this case, the control device 7 selects the optimal rotational speed Rs based on the first characteristic information and the second characteristic information when any of the operating members 5a, 5b, or 5e is operated.

[0085] In the embodiments described above, the present invention is illustrated by the case where the prime mover is an electric motor 9, but it is not limited to this. For example, as shown in Figure 14, the present invention is also applicable when the prime mover is an engine 69. In the embodiment of Figure 14, the control device 7 injects fuel supplied from the fuel tank 61 by the fuel pump 62 into the engine 69 using the fuel injector 63, and ignites the injected fuel with the ignition device 64 to drive the engine 69. The control device 7 also controls the rotational speed of the engine 69 by adjusting the amount of fuel injected by the fuel injector 63 and the timing of ignition by the ignition device 64. The rotational speed of the engine 69 may be detected by a rotational speed sensor. The fuel injector 63 and the ignition device 64 are drive devices that drive the engine 69. In this configuration, operation characteristic information, target loss information, first characteristic information, and second characteristic information (prime mover characteristic information, pump characteristic information) corresponding to the engine 69 are generated and stored in the memory 7b.

[0086] The work machine 1 of the embodiment described above has the configuration described in the following items and achieves the effects described therein.

[0087] (Item 1) The work machine 1 comprises prime movers 9 and 69, a hydraulic pump 19 driven by the prime movers 9 and 69 to discharge hydraulic fluid, work devices 20 and 18 having hydraulic actuators C1 to C5 that are operated by the hydraulic fluid, control valves V1 to V5 that can switch the supply state of hydraulic fluid to the hydraulic actuators C1 to C5, operating members 5a, 5b, and 5e that can be operated in multiple operating directions to switch the positions V1a to V5a, V1b to V5b, and V1c to V5c of the control valves V1 to V5 to operate the hydraulic actuators C1 to C55 and the work devices 20 and 18, a control device 7 that controls the rotational speed of the prime movers 9 and 69, and a memory device 7b, the memory device 7b contains the relationship between the rotational speed of the prime movers 9 and 69 and the operating speed of the work devices 20 and 18. The control device 7 stores first characteristic information (high-temperature speed characteristic line L4, low-temperature speed characteristic line L5) indicating the relationship between the rotational speed of the prime movers 9 and 69 and the losses generated in at least one of the prime movers 9 and 69 and the hydraulic pump 19. When the operating members 5a, 5b, and 5e are operated, the control device 7 selects an optimal rotational speed Rs based on the first characteristic information L4, L5 and the second characteristic information such that the difference △U between the operating speed Us corresponding to the operation of the operating members 5a, 5b, and 5e and a predetermined target speed Ug is zero or less than or equal to a first predetermined value △Ut, and the losses Es, Es1, Es2 corresponding to the operation of the operating members 5a, 5b, and 5e are zero or less than or equal to a second predetermined value Et, Et1, Et2, and rotates the prime movers 9 and 69 at the optimal rotational speed Rs.

[0088] According to the configuration of item 1 above, when the operating members 5a, 5b, and 5e are operated, the prime movers 9 and 69 rotate at an optimal rotational speed Rs that takes into account the operating speed of the work devices 20 and 18 and the losses of at least one of the prime movers 9 and 69 and the hydraulic pump 19. This reduces the delay in the operation of the work devices 20 and 18, improves the workability of the work machine 1, and reduces energy loss.

[0089] (Item 2) The work machine 1 described in Item 1 above is equipped with a pressure sensor 43 that detects the pump pressure, which is the pressure of the hydraulic fluid discharged from the hydraulic pump 19. The second characteristic information includes at least one of the following: engine characteristic information that shows the relationship between the rotational speed, torque and loss of the prime movers 9 and 69, and pump characteristic information that shows the relationship between the rotational speed of the prime movers 9 and 69, the pump pressure and the loss of the hydraulic pump. The control device 7 controls the rotational speed and torque of the prime movers 9 and 69, and when the operating members 5a, 5b, and 5e are operated, it performs at least one of the following processes: extracting first loss information Q1 from the engine characteristic information that shows the relationship between the rotational speed and loss corresponding to the torque of the prime movers 9 and 69 under control, and extracting second loss information from the pump characteristic information that shows the relationship between the rotational speed and loss corresponding to the pump pressure detected by the pressure sensor 43. Based on the first characteristic information and at least one of the first loss information Q1 and the second loss information Q2, the control device 7 selects the optimal rotational speed Rs.

[0090] According to the configuration of item 2 above, when the operating members 5a, 5b, and 5e are operated, reference loss information Q1 and Q2 corresponding to the state of at least one of the prime movers 9 and 69 and the hydraulic pump 19 can be appropriately derived. Then, based on the loss information Q1 and Q2 and the first characteristic information L4 and L5, the optimal rotational speed Rs can be appropriately selected, and by rotating the prime movers 9 and 69 at the optimal rotational speed Rs, the workability of the work machine 1 can be improved and energy loss can be appropriately reduced.

[0091] (Item 3) In the work machine 1 described in Item 2 above, the second characteristic information includes prime mover characteristic information and pump characteristic information. When the operating members 5a, 5b, and 5e are operated, the control device 7 extracts first loss information Q1 from the prime mover characteristic information and second loss information Q2 from the pump characteristic information. Based on the first characteristic information, the first loss information Q1, and the second loss information Q2, the control device 7 selects an optimal rotational speed Rs such that the difference △U between the operating speed Us corresponding to the operation of the operating members 5a, 5b, and 5e and the target speed Ug is zero or less than or equal to a first predetermined value △Ut, and the sum of the losses of the prime movers 9 and 69 and the hydraulic pump 19 corresponding to the operation of the operating members 5a, 5b, and 5e, Es, is zero or less than or equal to a second predetermined value Et.

[0092] According to the configuration of item 3 above, when the operating members 5a, 5b, and 5e are operated, the prime movers 9 and 69 can be rotated at a more appropriate optimal rotational speed Rs that takes into account the operating speed of the work devices 20 and 18 and the losses of the prime movers 9 and 69 and the hydraulic pump 19. This reduces the delay in the operation of the work devices 20 and 18, improves the workability of the work machine 1, and further reduces energy loss.

[0093] (Item 4) In the work machine 1 described in item 2 or 3 above, the prime mover 9 is an electric motor, and the work machine 1 comprises a battery unit 30 including a plurality of batteries 31, 32, and an inverter 38 that supplies current from the battery unit 30 to the electric motor 9 to drive the electric motor 9, the prime mover characteristic information shows the relationship between the applied voltage value, rotational speed, torque and loss of the electric motor 9, the control device 7 controls the rotational speed and torque of the electric motor 9 with the inverter 38, and when the operating members 5a, 5b, 5e are operated, the control device 7 extracts first loss information Q1 from the prime mover characteristic information which shows the relationship between the rotational speed and loss corresponding to the applied voltage and torque of the electric motor 9 under control, selects the optimal rotational speed Rs based on at least the first characteristic information and the first loss information Q1, and rotates the electric motor 9 at the optimal rotational speed Rs with the inverter 38.

[0094] According to the configuration of item 4 above, when the operating members 5a, 5b, and 5e are operated, the first loss information Q1 corresponding to the state of the electric motor 9 can be appropriately derived, and the appropriate optimal rotation speed Rs of the electric motor 9 can be selected based on the first loss information Q1 and the first characteristic information L4 and L5. By rotating the electric motor 9 at this optimal rotation speed Rs, the delay in the operation of the work devices 20 and 18 can be reduced, improving the workability of the work machine 1 and reducing power loss.

[0095] (Item 5) In the work machine 1 described in any of the above items 2 to 4, a temperature sensor 44 is provided to detect the temperature of the hydraulic fluid, the pump characteristic information shows the relationship between the temperature of the hydraulic fluid, the rotational speed of the prime movers 9 and 69, the pump pressure and the loss of the hydraulic pump 19, and when the operating members 5a, 5b and 5e are operated, the control device 7 extracts second loss information Q2 from the pump characteristic information, which shows the relationship between the rotational speed and loss corresponding to the temperature detected by the temperature sensor 44 and the pump pressure detected by the pressure sensor 43, and selects the optimal rotational speed Rs based on at least the first characteristic information and the second loss information Q2.

[0096] According to the configuration of item 5 above, when the operating members 5a, 5b, and 5e are operated, second loss information Q2 corresponding to the pump pressure of the hydraulic pump 19 and the temperature of the hydraulic fluid can be appropriately derived, and based on the second loss information Q2 and the first characteristic information L4 and L5, an appropriate optimal rotational speed Rs with a balanced heat distribution can be selected. By rotating the prime movers 9 and 69 at this optimal rotational speed Rs, the delay in the operation of the work devices 20 and 18 can be further reduced, the workability of the work machine 1 can be further improved, and the power loss of the hydraulic pump 19 can be further reduced.

[0097] (Item 6) In the work machine 1 described in any of the above items 1 to 5, a temperature sensor 44 is provided for detecting the temperature of the hydraulic fluid, the first characteristic information shows the relationship between the temperature of the hydraulic fluid, the rotational speed of the prime movers 9 and 69, and the operating speed of the work devices 20 and 18, and the control device 7, when the operating members 5a, 5b and 5e are operated, selects an optimal rotational speed Rs corresponding to the temperature detected by the temperature sensor 44 based on the first characteristic information and the second characteristic information.

[0098] According to the configuration of item 6 above, when the operating members 5a, 5b, and 5e are operated, the prime movers 9 and 69 are rotated at an appropriate and optimal rotational speed Rs that is heat-balanced, thereby improving the workability of the work machine 1 and further reducing energy loss.

[0099] (Item 7) In the work machine 1 described in any of the above items 1 to 6, position sensors 49a to 49e are provided to detect the operating position of the operating members 5a, 5b, and 5e, and the storage device 7b stores operating characteristic information L1, L2, and L3 that shows the relationship between the amount of operation of the operating members 5a, 5b, and 5e and the operating speed of the work devices 20 and 18, and when the operating members 5a, 5b, and 5e are operated, the control device 7 calculates the actual amount of operation of the operating members 5a, 5b, and 5e from the operating position detected by the position sensors 49a to 49e, and selects the operating speed corresponding to the actual amount of operation as the target speed Ug from the operating characteristic information L1 to L3.

[0100] According to the configuration of item 7 above, when the operating members 5a, 5b, and 5e are operated, the prime movers 9 and 69 are rotated at an optimal rotational speed Rs corresponding to the amount of operation, thereby further reducing the delay in the operation of the working devices 20 and 18 and further improving the workability of the working machine 1.

[0101] (Item 8) The work machine 1 described in Item 7 above is equipped with an operation switch (mode switch) 58 that is operated to switch the mode performed by the work machine to one of the first mode, second mode, and third mode, and the operation characteristic information L1 to L3 includes first operation characteristic information (first operation characteristic line) L1 that shows the relationship between the operating amount and the operating speed corresponding to the first mode, and second operation characteristic information (second operation) that shows the relationship between the operating amount and the operating speed corresponding to the second mode and the operating speed is greater than the operating speed shown in the first operation characteristic information. The control device 7 includes a characteristic line L2 and a third operation characteristic information (third operation characteristic line) L3 that shows the relationship between the manipulated amount and the operating speed corresponding to the third mode, and the operating speed is smaller than the operating speed shown in the first operation characteristic information. When the operating members 5a, 5b, and 5e are operated, the control device 7 selects an operating speed corresponding to the actual manipulated amount as the target speed Ug from one of the first operation characteristic information L1, second operation characteristic information L2, and third operation characteristic information L3, which correspond to one of the first mode, second mode, and third mode that are currently being executed.

[0102] According to the configuration of item 8 above, when the operating members 5a, 5b, and 5e are operated, the prime movers 9 and 69 are rotated at an optimal rotational speed Rs corresponding to the amount of operation and the mode being executed, thereby further reducing the delay in the operation of the work devices 20 and 18 and further improving the workability of the work machine 1.

[0103] (Item 9) In the work machine 1 described in any of Items 1 to 8 above, when the operating members 5a, 5b, and 5e are operated, the control device 7 selects the rotational speed as the optimal rotational speed based on the first characteristic information L4, L5 and the second characteristic information such that the difference △U between the operating speed Us corresponding to the operation of the operating members 5a, 5b, and 5e and the target speed Ug is zero or less than or equal to a first predetermined value △Ut, and the difference △E, △E1, △E2 between the losses Es, Es1, Es2 corresponding to the operation of the operating members 5a, 5b, and 5e and the predetermined target loss Eg is zero or less than or equal to a third predetermined value △Et, △Et1, △Et2.

[0104] According to the configuration of item 9 above, when the operating members 5a, 5b, and 5e are operated, the prime movers 9 and 69 rotate at the optimal rotational speed Rs, the working devices 20 and 18 operate at a speed approximating the target speed Ug, and the losses occurring in at least one of the prime movers 9 and 69 and the hydraulic pump 19 are suppressed to a value approximating the target loss. This reduces the delay in the operation of the working devices 20 and 18, improves the workability of the working machine 1, and reduces energy loss.

[0105] (Item 10) In the work machine 1 described in Item 9 above, the storage device 7b stores target loss information (target loss line) L6 that shows the relationship between the rotational speed of the prime movers 9 and 69 and the target loss, and the control device 7 selects a rotational speed corresponding to the target speed Ug from the first characteristic information as a reference rotational speed Rx, and selects a target loss Eg corresponding to the reference rotational speed Rx from the target loss information.

[0106] According to the configuration of item 10 above, the prime movers 9 and 69 can be rotated at an optimal rotational speed Rs corresponding to the amount of operation of the operating members 5a, 5b, and 5e (and the mode being executed), thereby further reducing energy loss.

[0107] Having described the present invention above, the embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than the foregoing description, and all modifications within the meaning and scope of equivalents of the claims are intended to be included.

[0108] 1 Working machine 5a, 5b, 5e Operating member 7 Control device 7b Memory (storage device) 9 Electric motor (prime mover) 18 Dozer (working device) 19 First hydraulic pump 20 Working device 30 Battery unit 31, 32 Battery 38 Inverter 43 Pressure sensor 44 Temperature sensor 49a, 49b, 49c, 49d, 49e Position sensor 58 Mode switch (operation switch) 69 Engine (prime mover) C1-C5 Hydraulic cylinder (hydraulic actuator) Es Total value of corresponding losses Es1 Loss of corresponding electric motor Es2 Loss of corresponding hydraulic pump Eg Target loss Et, Et1, Et2 Second predetermined value △E, △E1, △E2 Difference △Et, △Et1, △Et2 Third predetermined value L1 First operating characteristic line (operating characteristic information) L2 Second operating characteristic line (operating characteristic information) L3 Third operating characteristic line (operating characteristic information) L4 High temperature speed characteristic line (first characteristic information) L5 Low temperature speed characteristic line (first characteristic information) L6 Target loss line (target loss information) Q1 First loss information Q2 Second loss information Rs Optimal rotational speed Rx Reference rotational speed Us Corresponding operating speed Ug Target speed △U Difference △Ut First predetermined value V1 to V5 Control valve

Claims

1. A work machine comprising: a prime mover; a hydraulic pump driven by the prime mover to discharge hydraulic fluid; a work device having a hydraulic actuator operated by the hydraulic fluid; a control valve capable of switching the supply state of the hydraulic fluid to the hydraulic actuator; an operating member capable of operating in a plurality of operating directions for operating the control valve; a control device for controlling the rotational speed of the prime mover; and a storage device, wherein the storage device stores: first characteristic information indicating the relationship between the rotational speed of the prime mover and the operating speed of the work device; second characteristic information indicating the relationship between the rotational speed of the prime mover and losses occurring in at least one of the prime mover and the hydraulic pump; and the control device, when the operating member is operated, selects an optimal rotational speed based on the first characteristic information and the second characteristic information such that the difference between the operating speed corresponding to the operation of the operating member and a predetermined target speed is zero or less than or equal to a first predetermined value, and the losses corresponding to the operation of the operating member are zero or less than or equal to a second predetermined value, and rotates the prime mover at the optimal rotational speed.

2. The work machine according to claim 1, comprising a pressure sensor for detecting pump pressure, which is the pressure of the hydraulic fluid discharged from the hydraulic pump, wherein the second characteristic information includes at least one of: motor characteristic information showing the relationship between the rotational speed, torque and loss of the prime mover; and pump characteristic information showing the relationship between the rotational speed of the prime mover, the pump pressure and the loss of the hydraulic pump, and the control device controls the rotational speed and torque of the prime mover, and when the operating member is operated, performs at least one of the following processes: extracting first loss information from the motor characteristic information showing the relationship between the rotational speed and loss corresponding to the torque of the prime mover under control; and extracting second loss information from the pump characteristic information showing the relationship between the rotational speed and loss corresponding to the pump pressure detected by the pressure sensor, and selecting the optimal rotational speed based on the first characteristic information and at least one of the first loss information and the second loss information.

3. The work machine according to claim 2, wherein the second characteristic information includes the prime mover characteristic information and the pump characteristic information, and the control device, when the operating member is operated, extracts the first loss information from the prime mover characteristic information, extracts the second loss information from the pump characteristic information, and selects the optimal rotational speed based on the first characteristic information, the first loss information, and the second loss information such that the difference between the operating speed corresponding to the operation of the operating member and the target speed is less than or equal to the first predetermined value, and the sum of the losses of the prime mover and the hydraulic pump corresponding to the operation of the operating member is zero or less than or equal to the second predetermined value.

4. The work machine according to claim 2, wherein the prime mover is an electric motor, the work machine comprises a battery unit including a plurality of batteries, and an inverter that supplies current from the battery unit to the electric motor to drive the electric motor, the prime mover characteristic information indicates the relationship between the applied voltage value, rotational speed, torque and loss of the electric motor, the control device controls the rotational speed and torque of the electric motor with the inverter, and when the operating member is operated, extracts first loss information from the prime mover characteristic information indicating the relationship between the rotational speed corresponding to the applied voltage and torque of the electric motor under control and the loss, selects the optimal rotational speed based on at least the first characteristic information and the first loss information, and rotates the electric motor at the optimal rotational speed with the inverter.

5. The work machine according to claim 2, comprising a temperature sensor for detecting the temperature of the hydraulic fluid, the pump characteristic information indicating the relationship between the temperature of the hydraulic fluid, the rotational speed of the prime mover, the pump pressure, and the loss of the hydraulic pump, and the control device, when the operating member is operated, extracts second loss information from the pump characteristic information indicating the relationship between the rotational speed and the loss corresponding to the temperature detected by the temperature sensor and the pump pressure detected by the pressure sensor, and selects the optimal rotational speed based on at least the first characteristic information and the second loss information.

6. The work machine according to claim 1, comprising a temperature sensor for detecting the temperature of the hydraulic fluid, wherein the first characteristic information indicates the relationship between the temperature of the hydraulic fluid, the rotational speed of the prime mover, and the operating speed of the work device, and the control device, when the operating member is operated, selects the optimal rotational speed according to the temperature detected by the temperature sensor based on the first characteristic information and the second characteristic information.

7. The work machine according to claim 1, comprising a position sensor for detecting the operating position of the operating member, wherein the storage device stores operating characteristic information indicating the relationship between the amount of operation of the operating member and the operating speed of the work machine, and the control device calculates the actual amount of operation of the operating member from the operating position detected by the position sensor when the operating member is operated, and selects the operating speed corresponding to the actual amount of operation as the target speed from the operating characteristic information.

8. The work machine according to claim 7, comprising an operating switch operated to switch the mode performed by the work machine to one of a first mode, a second mode, and a third mode, wherein the operating characteristic information includes: first operating characteristic information showing the relationship between the operating amount corresponding to the first mode and the operating speed; second operating characteristic information showing the relationship between the operating amount corresponding to the second mode and the operating speed, wherein the operating speed is greater than the operating speed shown in the first operating characteristic information; and third operating characteristic information showing the relationship between the operating amount corresponding to the third mode and the operating speed, wherein the operating speed is less than the operating speed shown in the first operating characteristic information, and the control device, when the operating member is operated, selects the operating speed corresponding to the actual operating amount as the target speed from one of the first operating characteristic information, second operating characteristic information, and third operating characteristic information corresponding to one of the first mode, second mode, and third mode that is currently being performed.

9. The work machine according to claim 1, wherein the control device, when the operating member is operated, selects as the optimal rotational speed a rotational speed such that the difference between the operating speed corresponding to the operation of the operating member and the target speed is zero or less than or equal to the first predetermined value, and the difference between the loss corresponding to the operation of the operating member and a predetermined target loss is zero or less than or equal to the third predetermined value, based on the first characteristic information and the second characteristic information.

10. The work machine according to claim 9, wherein the storage device stores target loss information indicating the relationship between the rotational speed of the prime mover and the target loss, and the control device selects the rotational speed corresponding to the target speed from the first characteristic information as a reference rotational speed, and selects the target loss corresponding to the reference rotational speed from the target loss information.

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