Electric work vehicle

Abstract

To provide an electric work vehicle taking the same behavior as a work vehicle using an engine as a power source.SOLUTION: An electric work vehicle is equipped with a battery 4 that is mounted on a machine body, an inverter 14 that converts DC power based on the output of the battery 4 into AD power, a motor M that is driven by the AD power converted by the inverter 14, a rotation number information obtaining portion 41 that obtains rotation number information indicating the rotation number of the motor M, a traveling device 42 that is driven by the motor M, an operation tool 43 that changes a request rotation number required for the motor M, a memory portion 45 that stores an output map regulating a relationship between a torque value that the motor M can output and a rotation number of the motor M, and a control portion 44 that drives the inverter 14 on the basis of the rotation number information, the request rotation number, the output map to control a current flowing the motor M. The output map, in a high rotation area in which the rotation number of the motor M becomes a predetermined rotation number or more, is set to be similar to a shape in the high rotation area of torque curve of an engine.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to an electric work vehicle that runs on electrical energy. [Background technology]

[0002] Conventionally, electric work vehicles that run on electrical energy as a power source have been used. An example of such an electric work vehicle is described in Patent Document 1, the source of which is shown below.

[0003] Patent Document 1 describes an electric work vehicle that includes a battery, a motor that is driven by power supplied from the battery, and a traveling device that is driven by the motor. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-957 Summary of the Invention [Problem to be solved by the invention]

[0005] In addition to the electric work vehicles mentioned above, there are also work vehicles that use an engine as a power source. The motor that is the power source of an electric work vehicle has a linear or nearly linear characteristic in the relationship between rotation speed and output torque. On the other hand, with an engine, for example, when trying to obtain high torque at a low rotation speed, the engine may stop (so-called stall). Also, the engine has a characteristic that the outputtable torque decreases as the rotation speed increases. For example, some users who switch from an engine-powered work vehicle to an electric work vehicle may feel uncomfortable because the relationship between the motor rotation speed and output torque differs from the relationship between the engine rotation speed and output torque, and the behavior is different.

[0006] Therefore, there is a demand for an electric work vehicle that behaves in the same way as a work vehicle powered by an engine. [Means for solving the problem]

[0007] A characteristic configuration of an electric work vehicle according to the present invention includes a battery mounted on a vehicle body, an inverter that converts DC power based on the output of the battery into AC power, a motor that is driven by the AC power converted by the inverter, a rotation speed information acquisition unit that acquires rotation speed information indicating the rotation speed of the motor, a traveling device driven by the motor, an operating tool that changes a requested rotation speed requested of the motor, a storage unit that stores an output map that defines the relationship between a torque value that the motor can output and the rotation speed of the motor, and a control unit that drives the inverter based on the rotation speed information, the requested rotation speed, and the output map to control a current flowing through the motor, and the output map includes a high rotation speed region where the rotation speed of the motor is at least equal to or higher than a predetermined rotation speed. and a low rotation region in which the rotation speed of the motor is at least less than the predetermined rotation speed, and in only the high rotation region of the high rotation region and the low rotation region, The difference is that the torque curve is set to a shape similar to the shape in the high revolution range of the torque curve that defines the relationship between the output torque of the engine equipped in the non-electric work vehicle and the revolution speed of the engine.

[0008] With this configuration, in the high rotation range where the motor rotation speed is at least equal to or higher than a predetermined rotation speed, the relationship between the torque value that the motor can output and the motor rotation speed can be made closer to the relationship between the engine output torque and the engine rotation speed, thereby making it possible to make the behavior of the electric work vehicle similar to that of a work vehicle powered by an engine.

[0009] It is also preferable that the high rotation region in the output map is defined such that the torque value that can be output by the motor decreases as the rotation speed of the motor increases from the predetermined rotation speed.

[0010] Since the torque that an engine can output decreases when its rotation speed exceeds a predetermined rotation speed, this configuration allows the motor characteristics to be made closer to the engine characteristics, making it possible to make the behavior of the electric work vehicle closer to the behavior of a work vehicle powered by an engine.

[0011] Preferably, the output map is defined so that the motor is stopped when the rotation speed of the motor becomes equal to or lower than a first rotation speed that is set in advance.

[0012] When the engine tries to output excessive torque when its rotation speed is lower than a predetermined rotation speed, the engine stops. Therefore, with this configuration, the motor characteristics at low rotation speeds can be made closer to the engine characteristics, making it possible to make the behavior of the electric work vehicle closer to the behavior of a work vehicle powered by an engine.

[0013] Preferably, the output map is defined so that the motor is stopped when the rotation speed of the motor becomes equal to or higher than a second rotation speed that is higher than the first rotation speed.

[0014] With this configuration, it is possible to restrict the motor from being driven at a high rotation speed, thereby making it possible to suppress deterioration of the motor.

[0015] The output map also includes a rotation speed at which the motor can rotate, the rotation speed including the first rotation speed. The above When the range is divided into a low rotation speed region and the high rotation speed region including the second rotation speed, it is preferable that the torque value that the motor can output is specified so as to increase as the rotation speed of the motor increases from the first rotation speed to the specified rotation speed.

[0016] In a low rotation speed range below a certain rotation speed, the torque that can be output by an engine increases as the rotation speed increases. Therefore, with this configuration, the motor characteristics can be made closer to the engine characteristics, and the behavior of the electric work vehicle can be made closer to the behavior of a work vehicle powered by an engine.

[0017] The characteristic configuration of the electric work vehicle of the present invention comprises a battery mounted on a body, an inverter that converts DC power based on the output of the battery into AC power, a motor driven by the AC power converted by the inverter, a rotation speed information acquisition unit that acquires rotation speed information indicating the rotation speed of the motor, a traveling device driven by the motor, an operating tool that changes the required rotation speed required of the motor, a memory unit that stores an output map that defines the relationship between the torque value that the motor can output and the rotation speed of the motor, and a control unit that drives the inverter based on the rotation speed information, the required rotation speed, and the output map to control the current flowing through the motor, wherein the output map is set in a shape similar to the shape of a torque curve in the high rotation speed region that defines the relationship between the output torque of an engine provided in a non-electric work vehicle and the rotation speed of the engine, in the high rotation speed region where the rotation speed of the motor is at least equal to or higher than a predetermined rotation speed, and the output map is specified so that the torque value is the same at any rotation speed of the motor other than when the motor is stopped, in the low rotation speed region where the rotation speed of the motor is at least below the predetermined rotation speed.

[0018] With this configuration, even when the motor rotation speed is low, it is possible to output a torque that is greater than the torque that can be output when the engine rotation speed is low. [Brief description of the drawings]

[0019] [Figure 1] FIG. [Diagram 2] FIG. 4 is a left side view showing the arrangement of an inverter and the like. [Diagram 3] FIG. [Figure 4] FIG. 2 is an explanatory diagram of a functional unit that drives a motor. [Diagram 5] 6 is a diagram showing the relationship between the operation amount of the operating tool and the required number of rotations for the motor. [Figure 6] 3 is an example of a torque curve of a motor. [Figure 7] FIG. 11 is a diagram illustrating an example of a notification by a notification unit. [Figure 8] FIG. 13 is a diagram showing an example in which state information is displayed on an output map. [Figure 9] 4 is another example of a torque curve of a motor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The electric work vehicle according to the present invention is configured to behave in the same manner as a work vehicle powered by an engine when the motor is rotating at low speed. The electric work vehicle according to the present embodiment will be described below. Note that the following description will be given by taking an example in which the electric work vehicle is a tractor.

[0021] The embodiment of the present invention will be described with reference to the drawings. In the following description, unless otherwise specified, the direction of the arrow F in the drawing is the "front" direction, the direction of the arrow B is the "rear" direction, the direction of the arrow U in the drawing is the "up" direction, and the direction of the arrow D is the "down" direction.

[0022] [Overall configuration of the tractor] The tractor of this embodiment will be described below. As shown in Fig. 1, the tractor has left and right front wheels 10, left and right rear wheels 11, and a cover member 12.

[0023] The tractor also includes a machine body frame 2 and a driving section 3. The machine body frame 2 is supported by left and right front wheels 10 and left and right rear wheels 11.

[0024] The cover member 12 is disposed at the front of the vehicle body. The driver's section 3 is provided behind the cover member 12. In other words, the cover member 12 is disposed in front of the driver's section 3.

[0025] The driving section 3 has a protective frame 30, a driving seat 31, and a steering wheel 32. An operator can sit in the driving seat 31. This allows the operator to get into the driving section 3. The left and right front wheels 10 are steered by operating the steering wheel 32. The operator can perform various driving operations in the driving section 3.

[0026] The tractor is equipped with a traveling battery 4. The cover member 12 is configured to be swingable about an opening / closing axis Q that runs along the left-right direction of the vehicle body. This allows the cover member 12 to be opened and closed. When the cover member 12 is in a closed state, the traveling battery 4 is covered by the cover member 12.

[0027] As shown in Fig. 2, the tractor includes an inverter 14 and a motor M. The driving battery 4 supplies power to the inverter 14. The inverter 14 converts DC power from the driving battery 4 into AC power and supplies it to the motor M. The motor M is then driven by the AC power supplied from the inverter 14.

[0028] 2 and 3, the tractor is equipped with a hydrostatic continuously variable transmission 15 and a transmission 16. As shown in Fig. 3, the hydrostatic continuously variable transmission 15 has a hydraulic pump 15a and a hydraulic motor 15b.

[0029] The hydraulic pump 15a is driven by rotational power from the motor M. When the hydraulic pump 15a is driven, the rotational power is output from the hydraulic motor 15b. The hydrostatic continuously variable transmission 15 is configured so that the speed of the rotational power is changed between the hydraulic pump 15a and the hydraulic motor 15b. The hydrostatic continuously variable transmission 15 is also configured so that the gear ratio can be changed steplessly.

[0030] The rotational power output from the hydraulic motor 15b is transmitted to the transmission 16. The rotational power transmitted to the transmission 16 is changed in speed by a gear-type speed change mechanism of the transmission 16, and distributed to the left and right front wheels 10 and the left and right rear wheels 11. In this way, the left and right front wheels 10 and the left and right rear wheels 11 are driven.

[0031] 2 and 3, the tractor is equipped with a mid PTO shaft 17 and a rear PTO shaft 18. The rotational power output from the motor M is distributed to the hydraulic pump 15a, the mid PTO shaft 17, and the rear PTO shaft 18. This causes the mid PTO shaft 17 and the rear PTO shaft 18 to rotate.

[0032] If a working device is connected to the mid PTO shaft 17 or the rear PTO shaft 18, the working device is driven by the rotational power of the mid PTO shaft 17 or the rear PTO shaft 18. For example, as shown in Fig. 2, in this embodiment, a grass cutting device 19 is connected to the mid PTO shaft 17. The grass cutting device 19 is driven by the rotational power of the mid PTO shaft 17.

[0033] [Motor Control] Fig. 4 is a block diagram showing functional units related to driving the motor M. The block diagram of Fig. 4 shows the battery (driving battery) 4, the inverter 14, the motor M, the rotation speed information acquisition unit 41, the traveling device 42, the operation tool 43, the control unit 44, the storage unit 45, the current sensor 51, the torque calculation unit 52, and the notification unit 57. In order to drive the motor M, each functional unit is constructed of hardware or software, or both, with a CPU as a core member.

[0034] As described above, the battery 4 is mounted on the aircraft body while being covered by the cover member 12. The electric energy stored in the battery 4 is used to drive the motor M.

[0035] The inverter 14 converts DC power based on the output of the battery 4 into AC power. The output of the battery 4 is a DC voltage and a DC current output from the battery 4. Therefore, the DC power based on the output of the battery 4 corresponds to the DC power consisting of the DC voltage and the DC current output from the battery 4.

[0036] In this embodiment, the inverter 14 is configured to have three arms A in which a first switching element Q1 and a second switching element Q2 are connected in series between a first power supply line L1 and a second power supply line L2. The first power supply line L1 is a power supply line connected to a positive terminal of two output terminals of the battery 4, and the second power supply line L2 is a power supply line connected to a negative terminal of two output terminals of the battery 4. The inverter 14 has three arms A between the first power supply line L1 and the second power supply line L2. In the following, when the three arms A are to be distinguished from one another, they are referred to as an arm A1, an arm A2, and an arm A3, respectively. In this embodiment, a P-type IGBT is used for both the first switching element Q1 and the second switching element Q2. A collector terminal of the first switching element Q1 is connected to the first power supply line L1, and an emitter terminal of the first switching element Q1 is connected to a collector terminal of the second switching element Q2. The emitter terminal of the second switching element Q2 is connected to the second power line L2. Between the emitter terminal and the collector terminal of the first switching element Q1, a diode D1 is provided, the anode terminal of which is connected to the emitter terminal and the cathode terminal of which is connected to the collector terminal. Between the emitter terminal and the collector terminal of the second switching element Q2, a diode D2 is provided, the anode terminal of which is connected to the emitter terminal and the cathode terminal of which is connected to the collector terminal. The gate terminals of the first switching element Q1 and the second switching element Q2 are connected to a control unit 44, which will be described later. In the inverter 14, the control unit 44 energizes the first switching element Q1 of one of the three arm parts A and the second switching element Q2 of one of the other two arm parts A by PWM control. As a result, the DC power of the battery 4 is converted into AC power according to the frequency of the PWM control signal.

[0037] The motor M is driven by AC power converted by the inverter 14. The three terminals of the motor M are respectively connected to a first node n1 to which the first switching element Q1 and the second switching element Q2 in the arm portion A1 are connected, a second node n2 to which the first switching element Q1 and the second switching element Q2 in the arm portion A2 are connected, and a third node n3 to which the first switching element Q1 and the second switching element Q2 in the arm portion A3 are connected. The first node n1 to which the first switching element Q1 and the second switching element Q2 in the arm portion A1 are connected is a portion to which the emitter terminal of the first switching element Q1 and the collector terminal of the second switching element Q2 constituting the arm portion A1 are connected. The second node n2 to which the first switching element Q1 and the second switching element Q2 in the arm A2 are connected is a portion to which the emitter terminal of the first switching element Q1 and the collector terminal of the second switching element Q2 constituting the arm A2 are connected. The third node n3 to which the first switching element Q1 and the second switching element Q2 in the arm A3 are connected is a portion to which the emitter terminal of the first switching element Q1 and the collector terminal of the second switching element Q2 constituting the arm A3 are connected. In FIG. 4, an example is given in which the coil of the motor M is configured with a delta connection, but the coil of the motor M may be configured with a star connection.

[0038] The rotation speed information acquisition unit 41 acquires rotation speed information indicating the rotation speed of the motor M. The rotation speed of the motor M is the rotation speed of a rotor of the motor M. Such a rotation speed can be detected, for example, by using a rotation sensor 41A having a Hall element. Also, instead of the rotation sensor 41A, it is possible to calculate the rotation speed of the motor M based on the magnitude of the current flowing through the motor M. In this case, it is preferable to calculate it based on the detection result of a current sensor 51, which will be described later. The detection result of the rotation speed of the motor M by the rotation sensor 41A is transmitted to the rotation speed information acquisition unit 41 as rotation speed information.

[0039] The traveling device 42 is driven by the motor M. In this embodiment, the traveling device 42 is a collective term for the hydrostatic continuously variable transmission 15, the transmission 16, the left and right front wheels 10, and the left and right rear wheels 11 described above. As described above, the rotational power of the motor M is transmitted to the transmission 16 via the hydrostatic continuously variable transmission 15. The rotational power transmitted to the transmission 16 is changed in speed by a gear-type shifting mechanism of the transmission 16, and distributed to the left and right front wheels 10 and the left and right rear wheels 11. As a result, the left and right front wheels 10 and the left and right rear wheels 11 are driven, and the tractor becomes capable of traveling, as described above.

[0040] The operating tool 43 changes the requested rotation speed required for the motor M. The requested rotation speed required for the motor M corresponds to a command value of the rotation speed of the rotational power that the operator wants to output from the motor M, so-called a command rotation speed. In this embodiment, the operating tool 43 corresponds to a lever configured to be swingable in the front-rear direction at the side of the driver's seat 31. The operating tool 43 is configured to rotate at a high speed as the requested rotation speed increases as the operating tool 43 is operated to tilt forward, and is configured to stably hold the position at the operated position. FIG. 5 shows the relationship between the operation amount of the operating tool 43 and the requested rotation speed for the motor M. In FIG. 5, the vertical axis is the requested rotation speed required for the motor M, and the horizontal axis is the operation amount of the operating tool 43. In the example of FIG. 5, the requested rotation speed when the operation amount is 10 [%] is N1 [rpm], and the requested rotation speed when the operation amount is 90 [%] is N2 [rpm]. The requested rotation speed is set to be proportional to the operation amount between 10 [%] and 90 [%]. The operation amount is indicated in %, where 0% is when the operating tool 43 is at the most forward position, and 100% is when it is tilted most forward. In addition, as will be described in detail later, in this example, when the operating amount is less than 10%, the required rotation speed is 0 rpm, and when the operating amount is 90% or more, the required rotation speed is N2 rpm. In this example, based on this relationship, it is possible to set the required rotation speed of the motor M according to the operating amount of the operating tool 43.

[0041] 4, in this embodiment, the amount of operation of the operating tool 43, i.e., the position in the front-rear direction, is detected by the position detector 43A. Therefore, it is possible to specify the required number of rotations required of the motor M based on the position of the operating tool 43 detected by the position detector 43A.

[0042] The storage unit 45 stores an output map that defines the relationship between the torque value that the motor M can output and the rotation speed of the motor M. The relationship between the torque value that the motor M can output and the rotation speed of the motor M is the value of the output torque that the motor M can output while maintaining the predetermined rotation speed when the motor M rotates at the predetermined rotation speed. For example, it corresponds to a torque curve that defines the relationship between the output torque of the engine and the rotation speed of the engine. The output map can be defined by at least one of a characteristic diagram and a mathematical formula, for example. Of course, it can be defined by something other than the characteristic diagram and the mathematical formula. The storage unit 45 stores an output map that indicates the value of the output torque that the motor M can output while maintaining the predetermined rotation speed when the motor M rotates at the predetermined rotation speed.

[0043] An example of such an output map is shown in FIG. 6. In the output map shown in FIG. 6, the vertical axis represents the output torque that the motor M can output, and the horizontal axis represents the rotation speed of the motor M. In FIG. 6, the output map of the motor M (torque curve of the motor M) is shown by a solid line, and the torque curve of the engine is shown by a dashed line for reference. When the rotation speed of the engine is R2, only T1 can be output as output torque, and as the rotation speed increases from R2 to R3, the output torque that can be output also increases from T1 to T3. Furthermore, as the rotation speed increases from R3 to R4, the output torque that can be output decreases from T3 to T2. Note that in FIG. 6, the relationship between T1 and T2 is T1.<T2となっているが、T1> It may be T2.

[0044] In contrast, the torque curve (output map) of the motor M is specified such that, when the rotational speeds at which the motor M can rotate are divided into a low rotational speed region including a first rotational speed R1 and a high rotational speed region including a second rotational speed R4, the torque value that the motor M can output decreases as the rotational speed of the motor M increases from a predetermined rotational speed R3. The low rotational speed region including the first rotational speed R1 is a region in which the rotational speed is equal to or greater than R1 and less than R3 in this example. Therefore, this low rotational speed region includes R1. The high rotational speed region including the second rotational speed R4 is a region in which the rotational speed is greater than R3 and equal to or less than R4 in this example. Therefore, this high rotational speed region includes R4. In this example, as shown in FIG. 6, the output map of the motor M is specified such that, when the rotational speed is between R1 and R3, which are lower than R3, a substantially constant output torque T3 can be output regardless of the rotational speed, and when the rotational speed is between R3 and R4, the output torque that the motor M can output decreases from T3 to T2 as the rotational speed increases.

[0045] In this way, the output map of motor M is set to have a shape similar to the shape of the torque curve in the high rotation region that defines the relationship between the output torque of the engine of the non-electric work vehicle and the rotation speed of the engine in the high rotation region where the rotation speed of motor M is at least equal to or higher than a predetermined rotation speed (R3 in this example). That is, in the example of Fig. 6, the torque that can be output when the rotation speed of motor M is between R3 and R4 is set to match the torque that can be output when the rotation speed of the engine of the non-electric work vehicle (tractor using an engine as a power source) is between R3 and R4, and the torque (torque value) that can be output by motor M is set to be a substantially constant value when the rotation speed of motor M is between the first rotation speed R1 and the predetermined rotation speed R3, different from the torque that can be output when the rotation speed of the engine of the non-electric work vehicle is equal to or lower than R3.

[0046] Returning to FIG. 4, the control unit 44 drives the inverter 14 based on the rotation speed information, the required rotation speed, and the output map to control the current flowing through the motor M. The rotation speed information is transmitted from the rotation speed information acquisition unit 41 to the control unit 44. The detection result of the position of the operating tool 43 is transmitted from the position detection unit 43A, and the required rotation speed can be specified based on this detection result. The output map is stored in the above-mentioned storage unit 45, and is configured to be referred to by the control unit 44. The current flowing through the motor M is a current output from the inverter 14 and a current flowing through the coil of the motor M. Therefore, the control unit 44 controls the inverter 14 to control the current flowing through the coil of the motor M so that the current rotation speed of the motor M indicated by the rotation speed information becomes the required rotation speed specified by the detection result of the position detection unit 43A, and has a relationship between the torque value that the motor M can output and the rotation speed of the motor M, which is specified by the output map stored in the storage unit 45.

[0047] Specifically, when the rotation speed of the motor M is equal to or higher than R1 and lower than R3, the control unit 44 controls the current flowing through the motor M so that the output torque does not exceed T3, and when the rotation speed of the motor M is between R3 and R4, the control unit 44 controls the current flowing through the motor M so that the output torque does not exceed the torque of the output map shown in Fig. 6. This makes it possible to control the output rotational power while providing the torque that can be output from the motor M in response to the operation of the operating tool 43. In addition, since the motor M is controlled by making the torque curve of the motor M similar to the torque curve of the engine, it is possible to prevent the operator from feeling uncomfortable even when, for example, switching from a tractor powered by an engine to an electric tractor.

[0048] The control unit 44 may be configured to stop the drive of the motor M regardless of the requested rotation speed when the load of the motor M becomes higher than a preset load. The load of the motor M is the torque acting on the motor M. The preset load is a load that is desired to stop the drive of the motor M when the load acts on the motor M. For example, it is preferable to set the load based on the load acting on the engine when the engine stalls. Regardless of the requested rotation speed, it means that the rotation speed of the motor M is not made to follow the requested rotation speed requested by the operating tool 43. Stopping the drive of the motor M means that a current is not allowed to flow from the inverter 14 to the coil of the motor M. Therefore, when the torque acting on the motor M becomes higher than the preset load that is desired to stop the drive of the motor M, the control unit 44 stops the motor M by not allowing a current to flow from the inverter 14 to the coil of the motor M without making the rotation speed of the motor M follow the requested rotation speed requested by the operating tool 43.

[0049] The torque of the motor M can be calculated based on the current flowing through the motor M. The current value of the current flowing through the motor M is detected by the current sensor 51. The current flowing through the motor M is almost the same as the current flowing through the cable connecting the first node n1 and the motor M, the cable connecting the second node n2 and the motor M, and the cable connecting the third node n3 and the motor M. Therefore, the current sensor 51 may detect the current value of the current flowing through the motor M based on the current flowing through these cables. The current sensor 51 may detect the current value by using a Hall element that measures the current without breaking these cables, or may detect the current value by a voltage drop across a resistor provided between each of these cables and a reference potential (for example, ground potential). The detection result of the current value by the current sensor 51 is transmitted to the torque calculation unit 52. The detection result of the current value may be transmitted to the control unit 44, and the control unit 44 may perform PWM control of the inverter 14 while taking into account the current flowing through the motor M.

[0050] The torque calculation unit 52 calculates the torque output by the motor M based on the current value. That is, there is a predetermined relationship between the current value of the current flowing through the motor M and the torque output by the motor M. It is preferable that a map showing such a relationship is stored in advance in the torque calculation unit 52, and the output torque corresponding to the current value of the current flowing through the motor M is calculated based on the map.

[0051] In this case, the control unit 44 may stop driving the motor M when the torque output by the motor M becomes larger than a preset torque value. The torque output by the motor M is the torque calculated by the torque calculation unit 52. The control unit 44 may compare this torque with a preset torque value, and when the torque becomes larger than the torque value, it may determine that the load of the motor M is higher than the preset load and stop driving the motor M.

[0052] In addition, the control unit 44 may be configured to stop driving the motor M regardless of the requested rotation speed when the rotation speed of the motor M becomes equal to or less than a first rotation speed R1 set in advance. The rotation speed of the motor M is acquired by the rotation speed information acquisition unit 41. The preset first rotation speed is the rotation speed R1 in the case of FIG. 6, and the number of rotations per minute can be set to, for example, several hundred rotations. Therefore, the control unit 44 may stop driving the motor M when the rotation speed of the motor M acquired by the rotation speed information acquisition unit 41 becomes equal to or less than the preset rotation speed R1. In this case, the output map is specified so that the motor M is stopped when the rotation speed of the motor M becomes equal to or less than the preset first rotation speed.

[0053] Furthermore, the output map may be specified so that the motor M is stopped when the rotation speed of the motor M becomes equal to or exceeds a second rotation speed R4 that is higher than the first rotation speed R1. In the case of FIG. 6, the first rotation speed is R1, and the second rotation speed is R4. Therefore, in this case, when the rotation speed of the motor M exceeds R4, the control unit 44 may limit the current flowing through the motor M to stop the motor M.

[0054] By configuring as described above, it is possible to simulate the stall of a tractor equipped with an engine, for example. This allows an operator who has switched from a tractor equipped with an engine to use the tractor equipped with the motor M without feeling any discomfort. In addition, it is possible to suppress deterioration of the motor M caused by continuously driving the motor M at a high rotation speed.

[0055] Here, as described above, when the driving of the motor M is stopped regardless of the requested rotation speed, it is preferable that the notification unit 57 notifies the operator that the driving of the motor M has been stopped so that the operator can understand that the motor M has been stopped unintentionally. That is, when the driving of the motor M is stopped regardless of the requested rotation speed, as shown in FIG. 7, it is preferable to configure the display unit 58 provided in the driving unit 3 of the tractor to display a message such as "The motor is stopped" on the display screen, or to output a voice such as "The motor is stopped" from the speaker 59. This makes it possible for the operator to understand that the driving of the motor M has been stopped unintentionally. It is also possible to configure the notification unit 57 to notify the operator that the driving of the motor M has been stopped using a buzzer or a lamp provided on the machine body.

[0056] Also, as shown in FIG. 8, for example, the display device 58 may be configured to display an output map of the motor M on the display screen, and to display status information, which is information indicating the status of the motor M consisting of the current rotation speed of the motor M and the current output torque. In the example of FIG. 8, an example is shown in which the current rotation speed of the motor M is R5 and the output torque is T4, and an "X" mark is added to the corresponding location on the output map. By displaying the current status information on the output map in this way, it becomes possible for the driver to understand that the output torque can be further increased while maintaining the current rotation speed R5, or that the rotation speed can be further increased while maintaining the current output torque T4. The display of such status information on the output map may also be performed by the notification unit 57, and further, the notification unit 57 may be configured to display a message as shown in FIG. 8 on the display screen.

[0057] Other embodiments In the above embodiment, an example was given in which the electric work vehicle was a tractor, but the electric work vehicle may be a work vehicle other than a tractor, such as a rice transplanter, a combine harvester, construction machinery, or a lawnmower.

[0058] In the above embodiment, the motor M is a three-phase motor and the inverter 14 is described as having three arm portions A, but the motor M does not have to be a three-phase motor. In this case, the number of arm portions A of the inverter 14 may be set according to the number of phases of the motor M.

[0059] In the above embodiment, the output map is described as being specified so that the motor M stops when the rotation speed of the motor M becomes equal to or lower than the first rotation speed R1 set in advance. However, the output map can also be configured so that the motor M does not stop even when the rotation speed of the motor M becomes equal to or lower than the first rotation speed R1 set in advance.

[0060] In the above embodiment, the output map has been described as being specified so that the motor M stops when the rotation speed of the motor M becomes equal to or greater than the second rotation speed R4, which is higher than the first rotation speed R1. However, the force map can also be configured so that the motor M does not stop even when the rotation speed of the motor M becomes equal to or greater than the second rotation speed R4, which is higher than the first rotation speed R1. In this case, the motor M may be configured to stop according to the output torque of the motor M, or may be configured to stop when the rated rotation speed of the motor M, which is higher than the second rotation speed R4, is reached.

[0061] In the above embodiment, in the output map shown in FIG. 6, a constant output torque T3 can be output regardless of the rotation speed from R1 to R3. However, it is also possible to configure the motor M so that the torque value that can be output by the motor M increases as the rotation speed of the motor M increases from the first rotation speed R1 to a predetermined rotation speed R3, similar to the torque curve of the engine. That is, it is also possible to configure the motor M so that the torque that can be output at the rotation speed R1 is T5, the torque that can be output at the rotation speed R2 is T1 like the torque curve of the engine, and further, the torque that can be output at the rotation speed R3 is T3. In this case, as shown in FIG. 9, it is possible to configure the motor M so that the rotation speed between R2 and R3 coincides with the torque curve of the engine. Furthermore, it is preferable to configure the motor M so that the rotation speed between R3 and R4 coincides with the torque curve of the engine, similar to the above embodiment. [Industrial Applicability]

[0062] The present invention can be used in an electric work vehicle that runs on electrical energy. [Explanation of symbols]

[0063] 4: Battery 14: Inverter 41: Rotation speed information acquisition unit 42: Running gear 43: Operating tools 44: Control unit 45: Storage section M: Motor R1: First rotation speed R3: Predetermined number of revolutions R4: 2nd rotation speed

Claims

1. A battery installed in the aircraft; an inverter for converting DC power based on the output of the battery into AC power; a motor driven by the AC power converted by the inverter; a rotation speed information acquisition unit that acquires rotation speed information indicating a rotation speed of the motor; A traveling device driven by the motor; an operating tool for changing a required rotation speed of the motor; a storage unit that stores an output map that defines a relationship between a torque value that the motor can output and a rotation speed of the motor; a control unit that drives the inverter based on the rotation speed information, the required rotation speed, and the output map to control a current flowing through the motor, The output map has a high rotation region where the motor rotation speed is at least equal to or greater than a predetermined rotation speed, and a low rotation region where the motor rotation speed is at least below the predetermined rotation speed, and in only the high rotation region of the high rotation region and low rotation region, the output map is set to a shape similar to the shape in the high rotation region of a torque curve that defines the relationship between the output torque of an engine in a non-electric work vehicle and the rotation speed of the engine.

2. 2. The electric work vehicle according to claim 1, wherein the high rotation speed region in the output map is defined such that a torque value that can be output by the motor decreases as the rotation speed of the motor increases from the predetermined rotation speed.

3. 3. The electric work vehicle according to claim 1, wherein the output map specifies that the motor is stopped when the rotation speed of the motor becomes equal to or lower than a preset first rotation speed.

4. 4. The electric work vehicle according to claim 3, wherein the output map specifies that the motor is stopped when the rotation speed of the motor becomes equal to or greater than a preset second rotation speed that is higher than the first rotation speed.

5. 5. The electric work vehicle according to claim 4, wherein the output map is defined such that, when the rotational speed at which the motor can rotate is divided into the low rotational speed region including the first rotational speed and the high rotational speed region including the second rotational speed, the torque value that the motor can output increases as the rotational speed of the motor increases from the first rotational speed to the specified rotational speed.

6. A battery mounted on the aircraft; an inverter for converting DC power based on the output of the battery into AC power; a motor driven by the AC power converted by the inverter; a rotation speed information acquisition unit that acquires rotation speed information indicating a rotation speed of the motor; A traveling device driven by the motor; an operating tool for changing a required rotation speed of the motor; a storage unit that stores an output map that defines a relationship between a torque value that the motor can output and a rotation speed of the motor; a control unit that drives the inverter based on the rotation speed information, the required rotation speed, and the output map to control a current flowing through the motor, the output map is set to have a shape similar to a shape of a torque curve in a high rotation speed region, the torque curve defining a relationship between an output torque of an engine provided in a non-electric work vehicle and the rotation speed of the engine, in a high rotation speed region where the rotation speed of the motor is at least equal to or higher than a predetermined rotation speed; An electric work vehicle in which the output map is specified so that, in a low rotation range where the motor rotation speed is at least below a predetermined rotation speed, the torque value is the same at all motor rotation speeds other than when the motor is stopped.

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