Electric tractor

Abstract

The electric tractor has a vehicle body, a working machine, an electric motor, a battery, and a converter for controlling the input and output power of the battery. The electric tractor has a control device that controls the converter. The control device performs restriction processing, state of charge calculation processing, and mitigation processing. In the restriction processing, when the state of the battery satisfies the restriction condition, the control device controls the converter to limit the input and output of the battery to a specified power range. In the state of charge calculation processing, the control device calculates the state of charge of the battery when it is assumed to complete the work on the farm as an estimated state of charge. In the mitigation processing, when the estimated state of charge is greater than a first specified state of charge, the control device expands the specified power range.

Description

Technical Field

[0001] The invention relates to an electric tractor. Background Art

[0002] The electric tractor disclosed in Japanese Patent Application Laid-Open No. 2014-143965 includes a battery, an electric motor, wheels, and a working machine. The battery supplies power to the electric motor. The electric motor is driven by receiving power from the battery. The driving force from the electric motor is transmitted to the wheels and the working machine. That is, the electric tractor disclosed in Japanese Patent Application Laid-Open No. 2014-143965 travels using the electric motor as a driving source. Summary of the invention

[0003] In the technology of this electric tractor disclosed in Japanese Patent Application Laid-Open No. 2014-143965, it is known that the output of the battery is limited to a certain value or less according to the state of the battery. When the output of the battery is limited, the travel and operation of the electric tractor are limited. Therefore, if the output of the battery is limited, the electric tractor has to operate in a state of low operating efficiency after the output is limited. As a result, it takes a long time to complete the operation in the farm, and the expected operation may not be completed.

[0004] In order to solve the above-mentioned problems, the present invention provides an electric tractor, which comprises: a body that can be connected to a working machine; the working machine has a rotating body; wheels for traveling, which are installed on the body; an electric motor that drives at least one of the wheels and the rotating body; a battery that accumulates power to be supplied to the electric motor; a converter that controls the input and output power of the battery; and a control device that takes the converter as a control object, and in the electric tractor, the control device performs the following processing: a restriction processing, in which, when the state of the battery satisfies a preset restriction condition, the converter is controlled to limit the input and output of the battery to a preset specified power range; a state of charge calculation processing, in which the state of charge of the battery assumed to be completed in a preset farm is calculated as an estimated state of charge; and a mitigation processing, in which, when the estimated state of charge calculated in the state of charge calculation processing is greater than a preset first specified state of charge, the specified power range is expanded.

[0005] In the above configuration, when it is estimated that the battery's state of charge when the work in the farm is completed is greater than the first specified state of charge, the control device of the electric tractor relaxes the input and output restrictions of the battery. This can prevent the electric tractor from having to continue working in a state of low working efficiency and being unable to achieve the expected work.

[0006] In the above configuration, the electric tractor may be configured such that, when the estimated state of charge is less than a second specified state of charge, the control device determines that the restriction condition is satisfied and executes the restriction process, wherein the second specified state of charge is set to a value greater than the first specified state of charge. According to the above configuration, the input and output of the power of the battery can be restricted as the state of charge of the battery is low. As a result, the battery can be prevented from becoming over-discharged.

[0007] In the above configuration, the electric tractor can also be configured as follows: the control device further performs a work determination process, in which it is determined which of a plurality of pre-set work contents the work content performed by the work machine belongs to, and in the charge state calculation process, the estimated charge state is calculated according to the work content determined in the work determination process. According to the above configuration, the work content performed by the work machine can be reflected in the estimated charge state. Therefore, the estimated charge state can be calculated more accurately.

[0008] In the above configuration, the electric traction vehicle may be configured as follows: the electric motor drives at least the rotating body, and when the state of charge of the battery is less than the first specified state of charge, the control device further performs a forced stop process in which the converter is controlled to stop the drive of the rotating body.

[0009] According to the above configuration, the battery state of charge can be prevented from being low by stopping the driving of the rotating body of the working machine, thereby preventing other machines other than the working machine from being unable to operate due to insufficient power.

[0010] In the above configuration, the electric tractor may be provided with a notification device that notifies using at least one of sound and light, and the control device may further perform a first notification process after executing the restriction process, in which the notification device notifies information indicating that the state of charge of the battery is estimated to be low. According to the above configuration, the occupant of the electric tractor can detect the possibility that the state of charge of the battery is low. Therefore, the occupant can travel based on the state of charge of the battery.

[0011] In the above configuration, the electric tractor may be provided with a notification device that notifies using at least one of sound and light, and when the state of charge of the battery is less than a second specified state of charge, the control device further performs a second notification process in which the notification device notifies that the working machine may be stopped, wherein the second specified state of charge is set to a value greater than the first specified state of charge. According to the above configuration, the occupants of the electric tractor can detect that the state of charge of the battery is low.

[0012] In order to solve the above-mentioned problems, the present invention provides an electric tractor, comprising: a body that can be connected to a working machine; the working machine has a rotating body; wheels for traveling, which are mounted on the body; an electric motor that drives at least one of the wheels and the rotating body; a battery that accumulates power to be supplied to the electric motor; a converter that controls input and output power of the battery; and a control device that takes the converter as a control object, and in the electric tractor, the control device performs the following processing: a restriction processing, in which, when the state of the battery satisfies a preset restriction condition, the converter is controlled to limit the input and output of the battery to a preset prescribed power range; a temperature calculation processing, in which the temperature of the battery is calculated as an estimated temperature when it is assumed that the work is completed in a preset farm; and a mitigation processing, in which, when the estimated temperature calculated in the temperature calculation processing is lower than a preset first prescribed temperature, the prescribed power range is expanded.

[0013] In the above configuration, when the temperature of the battery is lower than the first predetermined temperature when the work in the farm is estimated to be completed, the control device of the electric tractor relaxes the input and output power restrictions of the battery. This can prevent the electric tractor from having to continue working in a state of low working efficiency and being unable to perform the expected work.

[0014] In the above configuration, the electric tractor may be configured such that, when the estimated temperature is greater than a second predetermined temperature, the control device determines that the restriction condition is satisfied and executes the restriction process, wherein the second predetermined temperature is set to a value lower than the first predetermined temperature. According to the above configuration, the input and output of the power of the battery can be restricted as the temperature of the battery rises. As a result, the battery can be prevented from becoming overheated.

[0015] In the above configuration, the electric tractor can also be configured as follows: the control device further performs a work determination process in which it is determined which of a plurality of pre-set work contents the work content performed by the work machine belongs to, and in the temperature calculation process, the estimated temperature is calculated according to the work content determined in the work determination process. According to the above configuration, the work content performed by the work machine can be reflected in the estimated temperature. Therefore, the estimated temperature can be calculated more accurately.

[0016] In the above configuration, the electric tractor may be configured as follows: the electric motor drives at least the rotating body, and when the temperature of the battery is higher than the first predetermined temperature, the control device further performs a forced stop process in which the converter is controlled to stop the driving of the rotating body.

[0017] According to the above configuration, by stopping the driving of the rotating body of the working machine, it is possible to suppress an excessive increase in the temperature of the battery, thereby suppressing a battery failure caused by an increase in the battery temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Features, advantages and technical and industrial significance of exemplary embodiments of the present invention are described with reference to the accompanying drawings, in which like reference numerals represent like parts, and in which:

[0019] Figure 1 This is a schematic diagram of the electric tractor.

[0020] Figure 2 This is a diagram showing the electrical structure and power transmission path of an electric tractor.

[0021] Figure 3 This is a flowchart of the estimated power consumption calculation control executed by the control device of the electric traction vehicle according to the first embodiment.

[0022] Figure 4 This is a flowchart of farm departure power calculation control executed by the control device for the electric traction vehicle according to the first embodiment.

[0023] Figure 5 This is a flowchart of the input / output limiting control executed by the control device for the electric traction vehicle according to the first embodiment.

[0024] Figure 6 This is a flowchart of the input / output limiting control executed by the control device for the electric traction vehicle according to the second embodiment. DETAILED DESCRIPTION

[0025] <First embodiment>

[0026] <Overall structure of electric tractor>

[0027] like Figure 1 As shown, the electric tractor 10 includes a vehicle 11, a working machine 20, and a support mechanism 30. The vehicle 11 has a plurality of wheels 12 and a vehicle body 13. The plurality of wheels 12 are connected to the vehicle body 13. The vehicle body 13 can be connected to the working machine 20 via the support mechanism 30.

[0028] When viewed from the vehicle 11, the working machine 20 is located at the rear. The working machine 20 includes, for example, a plurality of blades 21 for tilling as a rotating body. The working machine 20 can till the farm by rotating the blades 21 while the blades 21 are in contact with the ground GR of the farm. Figure 1In the figure, the plurality of blades 21 are simplified into a cylindrical shape. In addition, although the blades 21 are provided as the working machine 20, the working machine 20 can be replaced with, for example, a working machine for spreading fertilizer, a working machine for transplanting rice, a working machine for reinforcing ridges, etc. In addition, each of these various working machines has a rotating body that rotates based on the power from the PTO 25 described later.

[0029] The support mechanism 30 connects the vehicle body 13 and the working machine 20. The support mechanism 30 has a support shaft 31. Although not shown in the figure, the support mechanism 30 also includes a plurality of rods, a hydraulic circuit, a control valve, a hydraulic cylinder, etc. in addition to the support shaft 31. The hydraulic cylinder is actuated by turning on / off the control valve, etc. in the support mechanism 30. As a result, the working machine 20 rotates around the support shaft 31. Specifically, the working machine 20 rotates the plurality of blades 21 around the support shaft 31 in the approach direction D1 or the departure direction D2. The approach direction D1 is a direction in which the plurality of blades 21 approach the ground GR. The departure direction D2 is a direction in which the plurality of blades 21 depart from the ground GR.

[0030] <Power transmission path of electric tractor>

[0031] like Figure 2 As shown, the electric tractor 10 includes a first motor 41, a second motor 42, a third motor 43, a power transmission mechanism 19, a PTO 25, and a hydraulic device 35. The first motor 41, the second motor 42, and the third motor 43 are generator motors. It should be noted that "PTO" stands for "power take-off".

[0032] The first motor 41 is a driving source for driving the electric tractor 10. The first motor 41 is connected to the wheels 12 via the power transmission mechanism 19. That is, the wheels 12 are wheels for driving that are rotated by the driving force from the first motor 41. The power transmission mechanism 19 includes, for example, a speed reduction mechanism that increases and outputs torque.

[0033] The second motor 42 is a driving source for the blade 21 in the working machine 20. The second motor 42 is connected to the blade 21 of the working machine 20 via the PTO 25. The PTO 25 is a device for transmitting the torque of the second motor 42 to the blade 21. The PTO 25 includes, for example, a speed reduction mechanism.

[0034] The third motor 43 is a driving source of the hydraulic device 35. The third motor 43 drives the hydraulic device 35. The hydraulic device 35 generates hydraulic pressure based on the driving force from the third motor 43. The hydraulic pressure generated by the hydraulic device 35 is supplied to the support mechanism 30. As described above, the support mechanism 30 can rotate the working machine 20 in the approach direction D1 and the separation direction D2 based on the supplied hydraulic pressure.

[0035] It should be noted that, as described above, the first motor 41 is a generator motor. Therefore, the first motor 41 can function as a generator. Specifically, the first motor 41 can function as a generator when the electric tractor 10 is decelerated. At this time, a regenerative braking force corresponding to the amount of power generated by the first motor 41 is generated in the electric tractor 10.

[0036] <Electrical structure of electric tractor>

[0037] like Figure 2 As shown, the electric tractor 10 includes a power supply circuit 99. The power supply circuit 99 includes a battery 77, an inverter 85, a first converter 71, a second converter 72, and a third converter 73.

[0038] The battery 77 is a secondary battery. The battery 77 is a high-voltage battery responsible for the travel of the electric tractor 10, the drive of the working machine 20, and the drive of the support mechanism 30. The battery 77 stores electric power to be supplied to the first motor 41, the second motor 42, and the third motor 43. The inverter 85 is connected to the battery 77. The inverter 85 converts the voltage of the input electric power and outputs it.

[0039] The first converter 71 and the second converter 72 are connected to the converter 85. The first converter 71 and the second converter 72 are connected in parallel with each other with respect to the converter 85. The first converter 71 is connected to the first motor 41. The first converter 71 performs DC / AC power conversion between the converter 85 and the first motor 41. The second converter 72 is connected to the second motor 42. The second converter 72 performs DC / AC power conversion between the converter 85 and the second motor 42.

[0040] The third converter 73 is connected to the battery 77. The third converter 73 is connected in parallel with the inverter 85. The third converter 73 is connected to the third electric motor 43. The third converter 73 performs direct current / alternating current power conversion between the battery 77 and the third electric motor 43.

[0041] The electric tractor 10 includes an acceleration sensor 61 , a battery temperature sensor 62 , and a current and voltage sensor 63 .

[0042] The acceleration sensor 61 is located in the vehicle body 13 of the electric tractor 10. The acceleration sensor 61 detects the acceleration IA generated in the vehicle body 13. The acceleration IA is a vector value and includes information related to the direction. In addition, the gravitational acceleration acts on the electric tractor 10. Therefore, the acceleration sensor 61 also functions as a tilt sensor that detects the tilt angle of the vehicle body 13.

[0043] The battery temperature sensor 62 is built in the battery 77. The battery temperature sensor 62 detects the temperature T1 of the battery 77. The current and voltage sensor 63 detects the voltage of the battery 77 and the current from the battery 77 as the battery information BI.

[0044] <General structure of control device, etc.>

[0045] The electric tractor 10 includes a control device 100 , a display 80 , a GPS device 50 , and a wireless communication device 51 .

[0046] The display 80 is installed in the cabin of the vehicle body 13. The cabin refers to a space for passengers to sit in when the passengers drive the electric tractor 10. The display 80 can display various information. In addition, the display 80 has a built-in touch panel to receive input from the passengers. Thus, the passengers can input information to the electric tractor 10 through the display 80. The display 80 is one of the notification devices that notify by at least one of sound and light.

[0047] The GPS device 50 is mounted on the vehicle body 13. The GPS device 50 receives a signal related to current position information PI of the electric tractor 10 from a GPS satellite.

[0048] The wireless communication device 51 is mounted on the vehicle body 13. The wireless communication device 51 can communicate with a weather server (not shown) via a wireless communication network. The wireless communication device 51 receives weather information WI corresponding to the current position specified based on the position information PI. The weather information WI includes information such as the presence of precipitation or the absence of precipitation.

[0049] The control device 100 controls the first converter 71, the second converter 72, the third converter 73, etc. The control device 100 controls the first converter 71 to drive the electric tractor 10 or stops the driving of the electric tractor 10. In addition, the control device 100 controls the second converter 72 to operate or stop the blades 21 of the working machine 20. That is, the control device 100 controls the input and output power of the battery 77 by controlling the first converter 71 and the second converter 72.

[0050] The control device 100 controls the display 80. The control device 100 outputs a display signal J1 for causing the display 80 to display various information to the display 80. After receiving the display signal J1, the display 80 displays the content corresponding to the display signal J1. In addition, when the passenger uses the display 80 to input, the control device 100 receives the information J2 input by the passenger through the display 80.

[0051] The control device 100 obtains a signal indicating the acceleration IA of the vehicle body 13 from the acceleration sensor 61. The control device 100 obtains a signal indicating the temperature T1 of the battery 77 from the battery temperature sensor 62. The control device 100 obtains a signal indicating the battery information BI from the current and voltage sensor 63. As described above, the battery information BI includes information on the voltage and current of the battery 77. The control device 100 receives a signal related to the position information PI via the GPS device 50. It should be noted that the control device 100 repeatedly obtains the signals from the above-mentioned sensors at every unit time.

[0052] The control device 100 requests the weather server (not shown) for the weather information WI at the current location via the wireless communication device 51. The control device 100 receives the weather information WI transmitted in response to the request via the wireless communication device 51.

[0053] The control device 100 stores an electric power map M. The electric power map M is a map generated and updated by the estimated electric power consumption calculation control described later. The electric power map M stores a plurality of operation contents that can be performed by the electric tractor 10. The plurality of operation contents are, for example, tillage, fertilizer spreading, rice transplanting, ridge reinforcement, etc. The electric power map M shows the estimated electric power consumption for each operation content. The estimated electric power consumption is an estimated value of the electric power of the battery 77 consumed by the electric tractor 10 until the operation is completed in a preset farm.

[0054] In addition, the control device 100 stores an electric power map M corresponding to the weather information WI. The control device 100 stores a first electric power map M1 used when there is no precipitation and a second electric power map M2 used when there is precipitation as the electric power map M. The first electric power map M1 and the second electric power map M2 store the same type of work content.

[0055] The control device 100 can be configured as one or more processors that perform various processes according to a computer program (software). It should be noted that the control device 100 can also be configured as a circuit (circuitry) including one or more dedicated hardware circuits such as application-specific integrated circuits (ASICs) that perform at least a part of the various processes, or a combination thereof. The processor includes a memory such as a CPU, RAM, and ROM. The memory stores program codes or instructions configured to enable the CPU to perform processes. The memory, i.e., a computer-readable medium, includes various available media that are general or dedicated and can be accessed by a computer. The control device 100 has an electrically rewritable non-volatile memory, i.e., a storage device. The control device 100 stores a program for executing the estimated power consumption calculation control, farm disconnection power calculation control, and input / output limitation control described later in the non-volatile memory, i.e., the storage device.

[0056] <About estimated power consumption calculation control>

[0057] The control device 100 starts the estimated power consumption calculation control when the electric tractor 10 enters the farm from outside the farm. That is, the control device 100 obtains the current position information PI of the electric tractor 10 from the GPS device 50. In addition, based on the obtained position information PI, the control device 100 determines whether the current position of the electric tractor 10 is within the area of ​​the farm input in advance. Then, the control device 100 performs the estimated power consumption calculation control on the condition that the last position information PI is outside the area of ​​the farm and the current position information PI is within the area of ​​the farm. In addition, the area of ​​the farm is input by the occupant using the display 80, etc. and is pre-stored in the control device 100.

[0058] like Figure 3 As shown, if the estimated power consumption calculation control is started, the control device 100 first executes the processing of step S11. In step S11, the control device 100 obtains the current state of charge of the battery 77, that is, the state of charge at the moment when the electric tractor 10 starts working on the farm, as the initial state of charge. Specifically, the control device 100 obtains the battery information BI from the battery 77. In addition, the control device 100 obtains the temperature T1 from the battery temperature sensor 62. The control device 100 calculates the initial state of charge based on the battery information BI and the temperature T1. The state of charge refers to the ratio of the amount of electricity stored in the battery 77 to the amount of electricity in the fully charged state of the battery 77, for example, expressed as a percentage. Then, the processing of the control device 100 jumps to step S12.

[0059] In step S12, the control device 100 obtains the content of the next operation to be performed by the electric tractor 10. Specifically, first, the control device 100 outputs a display signal J1 to the display 80 to start displaying a message on the display 80. The content of the message includes information urging the operator to select which type of operation the next operation to be performed belongs to. In addition, the control device 100 receives information J2 of the operation content selected by the operator through the display 80.

[0060] In addition, in step S12, the control device 100 requests the weather server via the wireless communication device 51 for weather information WI corresponding to the current position of the electric tractor 10. And the control device 100 receives the weather information WI via the wireless communication device 51. The control device 100 determines whether there is precipitation or no precipitation based on the received weather information WI. Then, the processing of the control device 100 jumps to step S13.

[0061] In step S13, the control device 100 determines whether the electric tractor 10 has completed the operation. Specifically, the control device 100 determines that the operation has been completed when the driving distance of the electric tractor 10 is greater than a predetermined distance and the second converter 72 does not drive the second motor 42. The above-mentioned predetermined distance is preset as the driving distance required to complete the operation on the farm when the electric tractor 10 is driving while working on the farm. In the case of a negative determination in step S13 (S13: No), the control device 100 executes the processing of step S13 again. In addition, in the case of an affirmative determination in step S13 (S13: Yes), the processing of the control device 100 jumps to step S14.

[0062] In step S14, the control device 100 obtains the state of charge of the battery 77 when step S14 is executed, that is, the state of charge at the time when the electric tractor 10 completes the work in the farm, as the completed state of charge. Specifically, the control device 100 obtains the battery information BI and the temperature T1 in the same manner as S11. Then, the control device 100 calculates the completed state of charge based on the battery information BI and the temperature T1. Then, the processing of the control device 100 jumps to step S15.

[0063] In step S15, the control device 100 calculates the power consumed by the operation, that is, the consumed power, based on the initial state of charge and the completed state of charge. Specifically, the control device 100 subtracts the completed state of charge from the initial state of charge to calculate the state of charge of the consumed battery 77. Then, the control device 100 converts the state of charge of the consumed battery 77 into power (Ah) to calculate the consumed power. Then, the processing of the control device 100 jumps to step S16.

[0064] In step S16, the control device 100 first determines the power map M to be updated. Specifically, if the weather information WI acquired in step S12 includes information that there is no precipitation, the control device 100 determines it as the first power map M1. In addition, if the weather information WI acquired in step S12 includes information that there is precipitation, it is determined to be the second power map M2. In addition, the control device 100 refers to the estimated power consumption corresponding to the information J2 of the work content acquired in step S12 in the referenced power map M.

[0065] Then, the control device 100 calculates a new estimated power consumption. The new estimated power consumption is calculated by the following formula using the reflection rate α. The reflection rate α is a fixed value that is set in advance as a value greater than 0 and less than or equal to 1.

[0066] (New estimated power consumption) = (estimated power consumption) + (reflection rate α) × (power consumption - estimated power consumption)

[0067] Then, the control device 100 updates the estimated power consumption belonging to the above-mentioned work content to the new estimated power consumption in the referred power map M. Then, the estimated power consumption calculation control by the control device 100 is completed.

[0068] <For farms to be freed from power calculation control>

[0069] The control device 100 starts the farm departure power calculation control when the electric tractor 10 enters the farm from outside the farm. The control device 100 can also process each process of the farm departure power calculation control in parallel with each process of the estimated power consumption calculation control.

[0070] like Figure 4 As shown, if the farm starts to disconnect from the power calculation control, the control device 100 first performs the processing of step S20. In step S20, the initial state of charge is obtained in the same manner as in the above-mentioned step S11. That is, the control device 100 calculates the initial state of charge based on the battery information BI and the temperature T1. Then, the processing of the control device 100 jumps to step S21.

[0071] In step S21, the control device 100 first calculates the operation rate. Specifically, the control device 100 obtains the state of charge of the battery 77 at the time of processing in step S21. Specifically, the control device 100 obtains the battery information BI from the battery 77. In addition, the control device 100 obtains the temperature T1 from the battery temperature sensor 62. The control device 100 calculates the state of charge of the battery 77 based on the battery information BI and the temperature T1. Then, the control device 100 subtracts the state of charge of the battery 77 at the time of processing in step S21 from the initial state of charge to calculate the consumed state of charge. In addition, the control device 100 converts the estimated consumed power into the state of charge of the battery 77 and calculates the state of charge required to complete the operation. Then, the control device 100 calculates the ratio of the consumed state of charge to the state of charge required to complete the operation as the operation rate.

[0072] Then, the control device 100 determines whether the operation rate is greater than a predetermined operation rate. The predetermined operation rate is determined as a value at which the operation in the farm is completed or considered to be substantially completed at the time of step S21. The predetermined operation rate is, for example, set to a value of 90% or more. In the case of a negative determination in step S21 (S21: No), the processing of the control device 100 jumps to step S28.

[0073] In step S28, the control device 100 determines whether the electric tractor 10 has been separated from the farm to the outside of the farm. Specifically, when the last position information PI is within the farm area and the current position information PI is outside the farm area, the control device 100 determines that it has been separated from the farm. In the case of a positive determination in step S28 (S28: Yes), the farm separation power calculation control performed by the control device 100 is completed. In the case of a negative determination in step S28 (S28: No), the control device 100 performs the process of step S21 again.

[0074] On the other hand, in the case of an affirmative determination in step S21 (S21: Yes), the processing of the control device 100 jumps to step S22. In step S22, the control device 100 determines whether the electric tractor 10 begins to detach from the farm. Specifically, the control device 100 obtains the acceleration IA from the acceleration sensor 61. Then, the control device 100 calculates the inclination angle of the vehicle body 13 based on the acceleration IA. Here, the inclination angle of the vehicle body 13 refers to the angle of the acute angle formed by the upper and lower axes of the vehicle body 13 and the vertical axis extending in the gravity direction. Therefore, when the electric tractor 10 is traveling on a horizontal plane, the inclination angle of the vehicle body 13 is 0. The control device 100 determines whether the state in which the inclination angle of the vehicle body 13 is greater than a predetermined specified angle continues for more than a predetermined specified period. If the determination is affirmative, the control device 100 determines that the electric tractor 10 begins to detach from the farm. An example of the above-mentioned specified period is a few seconds.

[0075] If a negative determination is made in step S22 (S22: No), the control device 100 executes the process of step S22 again. If a positive determination is made in step S22 (S22: Yes), the process of the control device 100 jumps to step S23.

[0076] In step S23, the control device 100 starts to obtain the power of the battery 77. That is, the control device 100 obtains the battery information BI at each unit time. The control device 100 calculates the power (W) of the battery 77 at each unit time based on the battery information BI. In addition, the control device 100 may obtain the battery information BI at a time shorter than the unit time, and calculate the average power in the unit time as the output power of the battery 77 at each unit time. Starting from the processing of step S23, the control device 100 calculates the output power of the battery 77 at each unit time. Then, the processing of the control device 100 jumps to step S24.

[0077] In step S24, the control device 100 determines whether the electric tractor 10 has completed the separation from the farm. Specifically, the control device 100 obtains the acceleration IA from the acceleration sensor 61. The control device 100 determines whether the state in which the inclination angle of the vehicle body 13 is less than the above-mentioned prescribed angle continues for a certain period of time. If the determination is affirmative, the control device 100 determines that the electric tractor 10 has completed the separation from the farm. An example of the above-mentioned prescribed period is several seconds.

[0078] If the determination in step S24 is negative (S24: No), the control device 100 executes the process of step S24 again. On the other hand, if the determination in step S24 is positive (S24: Yes), the control device 100 ends the acquisition of power. Then, the process of the control device 100 jumps to step S25.

[0079] In step S25, the control device 100 acquires the largest value of the output power per unit time calculated from step S23 as the deviated maximum power and stores it. Then, the process of the control device 100 jumps to step S26.

[0080] In step S26, the control device 100 determines whether the maximum power for separation determined in step S25 is greater than the maximum power for separation learning value stored in the control device 100. The maximum power for separation learning value is a value determined in the previous farm power for separation calculation control and stored in the control device 100. In addition, when the maximum power for separation learning value is not stored, the control device 100 treats the maximum power for separation learning value as 0.

[0081] If a negative determination is made in step S26 (S26: No), the farm disconnection power calculation control by the control device 100 ends. On the other hand, if an affirmative determination is made in step S26 (S26: Yes), the process of the control device 100 jumps to step S27.

[0082] In step S27, the control device 100 stores the maximum power for separation acquired in step S25 as the maximum power for separation learning value. That is, the control device 100 updates the maximum power for separation learning value. Then, the farm separation power calculation control performed by the control device 100 ends.

[0083] <Regarding input and output limit control>

[0084] The control device 100 starts the input / output limit control when the electric tractor 10 enters the farm from outside the farm. The control device 100 can perform the input / output limit control processes in parallel with the farm exit power calculation control processes and the estimated power consumption calculation control processes.

[0085] like Figure 5 As shown, after starting the input / output limiting control, the control device 100 first executes the process of step S101.

[0086] In step S101, the control device 100 acquires the initial state of charge similarly to the above step S11. That is, the control device 100 calculates the initial state of charge based on the battery information BI and the temperature T1. Then, the process of the control device 100 jumps to step S102.

[0087] In step S102, the control device 100 obtains the content of the work to be performed next by the electric tractor 10, similarly to the above-mentioned step S12. In addition, in step S102, the control device 100 receives weather information WI, similarly to the above-mentioned step S12. The control device 100 determines whether there is precipitation or no precipitation based on the received weather information WI. Step S102 is a work determination process for determining which of the multiple pre-set work contents the work content performed by the work machine 20 belongs to. Then, the process of the control device 100 jumps to step S103.

[0088] In step S103, the control device 100 refers to the power map M corresponding to the weather information WI, similarly to step S16. That is, the control device 100 refers to the first power map M1 or the second power map M2. Then, the control device 100 refers to the estimated power consumption corresponding to the acquired work content in the referenced power map M. Then, the processing of the control device 100 jumps to step S104.

[0089] In step S104, the control device 100 converts the estimated power consumption into the state of charge. Specifically, the control device 100 calculates the ratio of the estimated power consumption to the power of the fully charged battery 77 as the state of charge. Then, the control device 100 jumps to step S105.

[0090] In step S105, the control device 100 calculates the estimated state of charge of the battery 77 when the electric tractor 10 completes the work in the farm. Specifically, the control device 100 subtracts the state of charge corresponding to the estimated power consumption from the initial state of charge to calculate the estimated state of charge. The process of step S105 is the state of charge calculation process. Then, the process of the control device 100 jumps to step S106.

[0091] In step S106, the control device 100 determines whether the estimated state of charge calculated in the state of charge calculation process is less than a pre-set second specified state of charge B. The second specified state of charge B is set to a lower limit value of the state of charge that does not cause degradation of the battery 77. In addition, the second specified state of charge B is set to a fixed value greater than the first specified state of charge A described later. In addition, the control device 100 stores the second specified state of charge B in advance.

[0092] If a negative determination is made in step S106 (S106: No), the input / output limitation control by the control device 100 ends. On the other hand, if an affirmative determination is made in step S106 (S106: Yes), the process of the control device 100 jumps to step S107.

[0093] In step S107, the control device 100 controls the first converter 71 and the second converter 72 so that the input and output power of the battery 77 falls within a predetermined power range. Here, the so-called predetermined power range is set to a narrower range than the power that can be input and output set before executing this process. For example, the predetermined power range is set to the power that can make the vehicle body 13 travel at a low speed of, for example, 3 km / h while the blades 21 of the working machine 20 are operated at a minimum rotation speed. The processing of steps S106 and S107 is the following restriction processing: when the state of the battery 77 meets the restriction condition, the first converter 71 and the second converter 72 are controlled to limit the input and output power of the battery 77 to the prescribed power range. That is, the restriction condition is that the estimated state of charge is less than the second prescribed state of charge B. Then, the processing of the control device 100 jumps to step S108.

[0094] In step S108, the control device 100 starts displaying a message on the display 80. The content of the message includes information that the state of charge of the battery 77 is estimated to be low. The process of step S108 is the first notification process. Then, the process of the control device 100 jumps to step S109.

[0095] In step S109, the control device 100 determines whether the estimated state of charge calculated in the state of charge calculation process is less than a pre-set first prescribed state of charge A. The first prescribed state of charge A is set to a lower limit value of the state of charge that can output the above-mentioned deviating from the maximum power learning value. In addition, the control device 100 stores a mapping that represents the relationship between the state of charge of the battery 77 and the power that the battery 77 can output. And, the control device 100 refers to the mapping to calculate the first prescribed state of charge A corresponding to the deviating from the maximum power learning value. In this way, although the first prescribed state of charge A is a variable value, the aforementioned second prescribed state of charge B is set to a value larger than the entire range of the first prescribed state of charge A.

[0096] If a positive determination is made in step S109 (S109: Yes), the process of the control device 100 jumps to step S111. If a negative determination is made in step S109 (S109: No), the process of the control device 100 jumps to step S110.

[0097] In step S110, the control device 100 expands the prescribed power range set in the restriction process. Specifically, the control device 100 sets the prescribed power range to the same range as the power range during normal driving before the prescribed power range is set. That is, while the restriction process is being executed, the control device 100 temporarily relaxes the power range that can be input and output from the battery 77 to the same range as during normal driving. That is, the process of step S110 is a relaxation process of expanding the prescribed power range. Then, the process of the control device 100 jumps to step S111.

[0098] In step S111, the control device 100 determines whether the current state of charge of the battery 77, that is, the current state of charge, is less than the second specified state of charge B. Specifically, the control device 100 obtains the battery information BI and the temperature T1 in the same manner as in the above step S11. Then, the control device 100 calculates the current state of charge based on the battery information BI and the temperature T1. Then, the control device 100 compares the current state of charge with the second specified state of charge B to make the above determination.

[0099] If a negative determination is made in step S111 (S111: No), the control device 100 executes the process of step S111 again. If a positive determination is made in step S111 (S111: Yes), the process of the control device 100 jumps to step S112.

[0100] In step S112, the control device 100 starts displaying a message on the display 80. The content of the message includes information that the working machine 20 may be stopped. The process of step S112 is the second notification process. Then, the process of the control device 100 jumps to step S113.

[0101] In step S113, the control device 100 determines whether the current state of charge of the battery 77, that is, the current state of charge, is less than the first specified state of charge A. Specifically, the control device 100 obtains the battery information BI and the temperature T1 again, as in the above step S11. Then, the control device 100 calculates the current state of charge based on the battery information BI and the temperature T1. Then, the control device 100 compares the current state of charge with the first specified state of charge A to make the above determination.

[0102] If a negative determination is made in step S113 (S113: No), the control device 100 executes the process of step S113 again. If a positive determination is made in step S113 (S113: Yes), the process of the control device 100 jumps to step S114.

[0103] In step S114, the control device 100 controls the second converter 72 to stop driving the blade 21 in the working machine 20. That is, the control device 100 controls the second converter 72 to stop the output of the second motor 42. The process of step S114 is a forced stop process. Then, the control device 100 ends a series of input and output limit controls.

[0104] <Function of the first embodiment>

[0105] In the first embodiment, the estimated state of charge when the work is determined to be completed is less than the second predetermined state of charge B. In this case, the control device 100 limits the input and output power within the predetermined power range so that the state of charge of the battery 77 does not drop sharply in a short time. That is, in this situation, the travel speed of the electric tractor 10 is limited, and the rotation speed of the PTO 25 is reduced.

[0106] On the other hand, the estimated state of charge is smaller than the second predetermined state of charge B and larger than the first predetermined state of charge A. In this case, the control device 100 temporarily relaxes the power range that can be input and output from the battery 77 to the same range as that during normal travel. That is, the electric tractor 10 can operate in the same manner as during normal travel.

[0107] <Effects of the First Embodiment>

[0108] (1-1) In the above embodiment, when it is estimated that the state of charge of the battery 77 when the work is completed in the farm is greater than the first specified state of charge A, the control device 100 relaxes the input and output restrictions of the battery 77 set in the restriction process. As a result, it is possible to prevent the electric tractor 10 from having to continue to perform the work in a state of low work efficiency and being unable to perform the expected work. In addition, in this case, since the state of charge of the battery 77 when the work is completed should be greater than the first specified state of charge A, the state of charge of the battery 77 will not be too small.

[0109] (1-2) In the above embodiment, the control device 100 executes the restriction process when the estimated state of charge is less than the second predetermined state of charge B. As a result, the input and output of the power of the battery 77 can be restricted as the state of charge of the battery 77 decreases. As a result, the battery 77 can be prevented from becoming over-discharged.

[0110] (1-3) The state of charge of the battery 77 consumed varies depending on the content of the work performed by the work machine 20. In the above embodiment, the control device 100 calculates the estimated state of charge corresponding to the content of the work determined in the work determination process. According to this configuration, the content of the work performed by the work machine 20 can be reflected in the calculation of the estimated state of charge. Therefore, the estimated state of charge can be calculated more accurately.

[0111] (1-4) In the above configuration, when the current state of charge of the battery 77 is less than the first predetermined state of charge A, the control device 100 forcibly stops the driving of the working machine 20. According to this configuration, by stopping the driving of the working machine 20, it is possible to ensure the power of the battery 77 required for the travel of the electric tractor 10. This can prevent the electric tractor 10 from stopping on the farm due to insufficient power.

[0112] (1-5) In the above embodiment, the control device 100 executes the first notification process via the display 80. According to this configuration, the occupant of the electric tractor 10 can detect the possibility that the state of charge of the battery 77 is low. Therefore, the occupant can travel based on the state of charge of the battery 77. In addition, the occupant can charge the battery 77 and take measures against the estimated low state of charge of the battery 77.

[0113] (1-6) In the above embodiment, the first specified state of charge A is the lower limit value of the state of charge that can output the maximum power learning value. In the input / output limit control, when the estimated state of charge is less than the first specified state of charge A, the control device 100 does not perform the mitigation process. That is, the control device 100 can make the state of charge of the battery 77 at the time of completion of the work of the working machine 20 not lower than the state of charge of the battery 77 required to leave the farm by continuing to perform the input / output limit.

[0114] (1-7) In the above embodiment, the control device 100 executes the second notification process via the display 80. With this configuration, the occupant of the electric tractor 10 can detect that the state of charge of the battery 77 is low.

[0115] (1-8) The muddy state of the farm is different depending on whether there is precipitation or not. For example, when there is precipitation, the muddiness of the farm increases compared to when there is no precipitation, and there are more muddy places. In the above embodiment, the control device 100 can selectively refer to the first power map M1 or the second power map M2 when obtaining the estimated power consumption. That is, the control device 100 can perform the estimated power consumption calculation control based on the power map M that more appropriately represents the actual farm state.

[0116] (1-9) In the above embodiment, the control device 100 executes the estimated power consumption calculation control. As a result, the control device 100 updates the estimated power consumption in the power map M. According to this configuration, the control device 100 can store the power map M reflecting the actual farm status.

[0117] (1-10) In the above embodiment, the control device 100 executes the farm disconnection power calculation control. As a result, the control device 100 updates the disconnection maximum power learning value. According to this configuration, the control device 100 can store the disconnection power reflecting the actual farm state.

[0118] <Second embodiment>

[0119] Hereinafter, a second embodiment of the electric tractor 10 will be described. The general structure, electrical structure and power transmission path of the electric tractor 10 are the same as those of the first embodiment. Hereinafter, input / output limiting control executed by the control device 100 of the electric tractor 10 of the second embodiment will be described.

[0120] <Regarding input and output limit control>

[0121] The control device 100 starts the input / output limit control when the electric tractor 10 enters the farm from outside the farm. The control device 100 can perform the input / output limit control processes in parallel with the farm exit power calculation control processes and the estimated power consumption calculation control processes.

[0122] like Figure 6 As shown in FIG. 1 , after starting the input / output limiting control, the control device 100 first performs the processing of step S201. In step S201, the control device 100 obtains the current temperature of the battery 77, that is, the temperature at the time when the electric tractor 10 starts working on the farm, as the starting temperature. Specifically, the control device 100 obtains the temperature T1 of the battery 77 from the battery temperature sensor 62. The control device 100 stores the temperature T1 as the starting temperature. Then, the processing of the control device 100 jumps to step S202.

[0123] In step S202, the control device 100 obtains the content of the work to be performed next by the electric tractor 10, similarly to the above-mentioned step S12. In addition, in step S202, the control device 100 receives weather information WI, similarly to the above-mentioned step S12. The control device 100 determines whether there is precipitation or no precipitation based on the received weather information WI. Step S202 is a work determination process for determining which of the multiple pre-set work contents the work content performed by the work machine 20 belongs to. Then, the process of the control device 100 jumps to step S203.

[0124] In step S203, the control device 100 refers to the power map M corresponding to the weather information WI, similarly to step S16. That is, the control device 100 refers to the first power map M1 or the second power map M2. Then, the control device 100 refers to the estimated power consumption corresponding to the acquired work content in the referenced power map M. Then, the processing of the control device 100 jumps to step S204.

[0125] In step S204, the control device 100 obtains the estimated temperature increase corresponding to the estimated power consumption obtained in step S203. The control device 100 stores the estimated temperature increase, which is the temperature of the battery 77 estimated to rise when the battery 77 consumes the estimated power consumption. The control device 100 stores a map indicating the relationship between the estimated power consumption and the estimated temperature increase. In the map, the estimated temperature increase is associated in such a way that the larger the estimated power consumption is, the higher the estimated temperature increase is. And the control device 100 applies the estimated power consumption obtained in step S203 to the map to obtain the estimated temperature increase. After obtaining the estimated temperature increase, the processing of the control device 100 jumps to step S205.

[0126] In step S205, the control device 100 calculates the temperature of the battery 77 when the electric tractor 10 completes the work in the farm, that is, the estimated temperature. Specifically, the control device 100 adds the start temperature and the estimated temperature rise to calculate the estimated temperature. The process of step S205 is a temperature calculation process. Then, the process of the control device 100 jumps to step S206.

[0127] In step S206, the control device 100 determines whether the estimated temperature calculated in the temperature calculation process is greater than a preset second predetermined temperature Y. The second predetermined temperature Y is set to an upper limit value of a temperature at which the battery 77 does not output an excessively low temperature and can function. In addition, the second predetermined temperature Y is set to a fixed value that is less than the first predetermined temperature X described later. In addition, the control device 100 stores the second predetermined temperature Y in advance.

[0128] If a negative determination is made in step S206 (S206: No), the input / output limitation control by the control device 100 ends. On the other hand, if an affirmative determination is made in step S206 (S206: Yes), the process of the control device 100 jumps to step S207.

[0129] In step S207, the control device 100 controls the first converter 71 and the second converter 72 so that the input and output power of the battery 77 falls within a predetermined power range. Here, the so-called predetermined power range is set in the same manner as the predetermined power range of the first embodiment. The processing of steps S206 and S207 is the following restriction processing: when the state of the battery 77 satisfies the restriction condition, the first converter 71 and the second converter 72 are controlled to restrict the input and output of the battery 77 to within the predetermined power range. That is, the restriction condition is that the estimated temperature is greater than the second predetermined temperature Y. Then, the processing of the control device 100 jumps to step S208.

[0130] In step S208, the control device 100 starts displaying a message on the display 80. The content of the message includes information that the temperature of the battery 77 is estimated to have risen. Then, the process of the control device 100 jumps to step S209.

[0131] In step S209, the control device 100 determines whether the estimated temperature calculated in the temperature calculation process is greater than a preset first predetermined temperature X. The first predetermined temperature X is set to a temperature at which irreversible degradation of the battery 77 may occur. The first predetermined temperature X is a fixed value set by a previous experiment or the like.

[0132] If a positive determination is made in step S209 (S209: Yes), the process of the control device 100 jumps to step S211. If a negative determination is made in step S209 (S209: No), the process of the control device 100 jumps to step S210.

[0133] In step S210, the control device 100 expands the prescribed power range set in the restriction process. Specifically, the control device 100 sets the prescribed power range to the same range as the power range during normal driving before the prescribed power range is set. That is, while the restriction process is being executed, the control device 100 temporarily relaxes the power range that can be input and output from the battery 77 to the same range as during normal driving. That is, the process of step S210 is a relaxation process of expanding the prescribed power range. Then, the process of the control device 100 jumps to step S211.

[0134] In step S211, the control device 100 determines whether the current temperature of the battery 77, that is, the current temperature, is greater than the second predetermined temperature Y. Specifically, the control device 100 obtains the temperature T1 of the battery 77 in the same manner as in the above step S201. Then, the control device 100 uses the temperature T1 of the battery 77 obtained in step S211 as the current temperature, and compares the current temperature with the second predetermined temperature Y to perform the above determination.

[0135] If a negative determination is made in step S211 (S211: No), the control device 100 executes the process of step S211 again. If a positive determination is made in step S211 (S211: Yes), the process of the control device 100 jumps to step S212.

[0136] In step S212, the control device 100 starts displaying a message on the display 80. The content of the message includes information that the working machine 20 may be stopped. Then, the process of the control device 100 jumps to step S213.

[0137] In step S213, the control device 100 determines whether the current temperature of the battery 77, that is, the current temperature, is greater than the first predetermined temperature X. Specifically, the control device 100 acquires the temperature T1 of the battery 77 again, similarly to the above step S201. Then, the control device 100 uses the temperature T1 of the battery 77 acquired in step S213 as the current temperature, and compares the current temperature with the first predetermined temperature X to perform the above determination.

[0138] If a negative determination is made in step S213 (S213: No), the control device 100 executes the process of step S213 again. If a positive determination is made in step S213 (S213: Yes), the process of the control device 100 jumps to step S214.

[0139] In step S214, the control device 100 controls the second converter 72 to stop driving the blade 21 in the working machine 20. That is, the control device 100 controls the second converter 72 to stop the output of the second motor 42. The process of step S214 is a forced stop process. Then, the control device 100 ends a series of input and output limit controls.

[0140] <Function of the Second Embodiment>

[0141] In the second embodiment, the estimated temperature when the work is determined to be completed is higher than the second predetermined temperature Y. In this case, the control device 100 limits the input and output power within the predetermined power range so that the temperature of the battery 77 does not rise sharply in a short time. That is, in this situation, the running speed of the electric tractor 10 is limited, and the rotation speed of the PTO 25 is reduced.

[0142] On the other hand, the estimated temperature is set to be higher than the second predetermined temperature Y and lower than the first predetermined temperature X. In this case, the control device 100 temporarily relaxes the power range that can be input and output of the battery 77 to the same range as that during normal travel. That is, the electric tractor 10 can achieve input and output in the same manner as during normal travel.

[0143] <Effects of the Second Embodiment>

[0144] Next, the effects of the second embodiment will be described. The electric tractor 10 of the second embodiment achieves the following effects in addition to the effects (1-8) to (1-10) of the first embodiment.

[0145] (2-1) In the above embodiment, when it is estimated that the temperature of the battery 77 when the work in the farm is completed is lower than the first predetermined temperature X, the control device 100 relaxes the input and output restrictions of the battery 77 set in the restriction process. This can prevent the electric tractor 10 from having to continue to perform the work in a state of low work efficiency and being unable to perform the expected work. In addition, in the above case, since the temperature of the battery 77 when the work is completed should be lower than the first predetermined temperature X, the battery 77 will not become overheated.

[0146] (2-2) In the above embodiment, the control device 100 performs the limiting process when the estimated temperature is higher than the second predetermined temperature Y. According to this configuration, the input and output of the power of the battery 77 can be limited as the temperature of the battery 77 rises. This can prevent the battery 77 from becoming overheated.

[0147] (2-3) The temperature rise of the battery 77 varies depending on the content of the work performed by the work machine 20. In the above embodiment, the control device 100 calculates the estimated temperature according to the content of the work determined in the work determination process. According to this configuration, the content of the work performed by the work machine 20 can be reflected in the calculation of the estimated temperature.

[0148] (2-4) In the above embodiment, when the temperature of the battery 77 is higher than the first predetermined temperature X, the control device 100 forcibly stops the driving of the working machine 20. According to this configuration, by stopping the driving of the working machine 20, it is possible to suppress an excessive increase in the temperature of the battery 77. Thus, it is possible to suppress the occurrence of problems with the battery 77 due to an increase in the temperature of the battery 77.

[0149] <Change Example>

[0150] The present embodiment can be implemented by being modified as follows. The present embodiment and the following modified examples can be implemented by being combined with each other within a range where there is no technical contradiction.

[0151] In the above-described embodiments, the electric tractor 10 may include only one of the first motor 41 and the second motor 42. When the electric tractor 10 includes one motor, the electric tractor 10 may include a mechanism capable of distributing and transmitting the output of the motor to the power transmission mechanism 19 and the PTO 25.

[0152] In the above embodiments, the electric tractor 10 may include a drive source other than the electric motor, such as an internal combustion engine. In this example, as long as at least one of the wheel 12 and the blade 21 of the working machine 20 is driven by the electric motor, the technology of the above embodiments can be applied.

[0153] In each of the above embodiments, the control device 100 can determine the content of the work to be performed next by the electric tractor 10 by determining the type of the work machine 20. For example, if the control device 100 includes a mechanism for determining the type of the work machine 20 mounted on the PTO 25, the control device 100 can determine the content of the work to be performed next based on the type of the work machine 20.

[0154] In each of the above embodiments, the first motor 41 may be prohibited from generating electricity after the electric tractor 10 enters the farm from outside the farm until it leaves the farm from inside the farm. In the farm, the electric tractor 10 often travels at a constant speed, and even if the first motor 41 generates electricity, more power cannot be expected. On the other hand, if the first motor 41 generates electricity, the speed of the electric tractor 10 changes, which may lead to a deterioration in fuel economy. As this modification example, since the first motor 41 is prohibited from generating electricity in the farm, the above problem is less likely to occur.

[0155] In each of the above-mentioned embodiments, the estimated power consumption calculation control can be omitted by the control device 100. In this case, the estimated power consumption obtained in advance by simulation or the like can be stored in the control device 100 in the form of a map or the like.

[0156] In the above-mentioned embodiments, the occupant may input the estimated power consumption using the display 80 etc. Alternatively, the occupant may input the working time and working area etc. using the display 80, and the control device 100 may calculate the estimated power consumption based on such information.

[0157] In each of the above embodiments, the control device 100 may also include a map other than the first power map M1 and the second power map M2. For example, the control device 100 may also include a map for snowfall. In addition, the control device 100 may include only one power map M. When the control device 100 includes only one power map M, the processing related to obtaining weather information WI in each control may be omitted.

[0158] In each of the above embodiments, the reflection rate α in the estimated power consumption calculation control may be a variable value as long as it is a value greater than 0 and less than or equal to 1. For example, the reflection rate α may be a linearly increasing or decreasing value determined by a value that increases as the difference between the power consumption and the estimated power consumption decreases.

[0159] In each of the above-mentioned embodiments, the control device 100 may omit the farm-disconnected power calculation control. For example, the control device 100 may store the maximum power when disconnecting from the farm as a fixed value preset by simulation or the like.

[0160] In each of the above-mentioned embodiments, the electric tractor 10 may not include the display 80. In this case, the electric tractor 10 may include a notifier such as an indicator lamp or a speaker that notifies using at least one of sound and light. If any of the notifiers is included, the control device 100 can execute the first notification process and the second notification process. In addition, the electric tractor 10 may not include a notifier.

[0161] In each of the above-described embodiments, the control device 100 may omit the first notification process and the second notification process.

[0162] In the above embodiments, the control device 100 may not make the power range of the battery 77 available for input and output during the mitigation process the same as that during normal travel. For example, the power range during the mitigation process may be determined to be a range that is larger than during the restriction and smaller than during normal travel.

[0163] In the first embodiment, the condition for executing the limiting process, that is, the limiting condition, is not limited to the example in the above embodiment. That is, whether to execute the limiting process may be determined based on other parameters besides the state of charge of the battery 77 .

[0164] In the first embodiment, the control device 100 may omit the state of charge calculation process. For example, the estimated state of charge may be a value input by a passenger of the electric tractor 10 via the display 80 or the like, or a preset fixed value.

[0165] In the first embodiment, the first predetermined state of charge A may not be the lower limit value of the state of charge that can output a state of charge that deviates from the maximum power learning value. For example, the first predetermined state of charge A may be set to the lower limit value of the state of charge that does not overdischarge the battery 77.

[0166] In the first embodiment described above, the control device 100 may omit the forced stop process. That is, even when the state of charge of the battery 77 is less than the first predetermined state of charge A, the control device 100 may continue to drive the blades 21 of the working machine 20. However, when the forced stop process is omitted, from the perspective of protecting the battery 77, it is preferred that the output of the working machine 20 be reduced when the state of charge of the battery 77 is less than the first predetermined state of charge A.

[0167] In the second embodiment, the condition for executing the limiting process, that is, the limiting condition, is not limited to the example in the above embodiment. That is, whether to execute the limiting process may be determined based on other parameters besides the temperature of the battery 77 .

[0168] In the second embodiment, the temperature calculation process may be omitted by the control device 100. For example, the estimated temperature may be a value input by the occupant of the electric tractor 10 via the display 80 or the like, or a preset fixed value may be used.

[0169] In the second embodiment, the control device 100 may omit the forced stop process. That is, even when the temperature of the battery 77 is higher than the first predetermined temperature X, the control device 100 may continue to drive the working machine 20. In addition, when the forced stop process is omitted, from the perspective of protecting the battery 77, it is preferable to reduce the output of the working machine 20 when the temperature of the battery 77 is higher than the first predetermined temperature X.

[0170] In the electric tractor disclosed in Japanese Patent Application Laid-Open No. 2014-143965, the state of charge of the battery may be too low when the electric tractor is operating on a farm. If the state of charge of the battery is too low, the electric tractor may not be able to detach from the farm and may stop on the farm. From the perspective of solving the above-mentioned problem, the above-mentioned embodiment only needs to include a forced stop process, and the restriction process, the state of charge calculation process, and the mitigation process may be omitted. As long as the above-mentioned forced stop process can be performed, the drive of the rotating body is stopped when the state of charge of the battery is less than a first specified state of charge, and the charging capacity of the battery is used for driving. Thereby, the risk of the electric tractor stopping and being unable to detach from the farm can be reduced.

[0171] The technical concepts derived from the above-mentioned embodiments and modifications are described below.

[0172] An electric tractor, comprising: a vehicle body capable of being coupled to a working machine; the working machine having a rotating body; wheels for traveling, mounted on the vehicle body; an electric motor, driving at least one of the wheels and the rotating body; a battery, storing electric power to be supplied to the electric motor; a converter, controlling input and output power of the battery; and a control device, which controls the converter as a control object, the electric motor at least driving the rotating body, and the control device performs a forced stop process, in which, when the state of charge of the battery is less than a first predetermined state of charge, the converter is controlled to stop driving the rotating body.

Claims

1. An electric tractor, comprising: The vehicle body can be connected to the operating machinery; Working machinery having a rotating body; Wheels for traveling, mounted on the vehicle body; A motor driving at least one of the wheel and the rotating body; a battery storing electric power to be supplied to the electric motor; a converter to control input and output power of the battery; and A control device, taking the converter as a control object, In the electric tractor, The control device performs the following processing: a limiting process in which, when the state of the battery satisfies a preset limiting condition, the converter is controlled to limit the input and output power of the battery to a preset prescribed power range; a state of charge calculation process in which the state of charge of the battery when work is assumed to be completed in a preset farm is calculated as an estimated state of charge; as well as and a mitigation process in which, when the estimated state of charge calculated in the state of charge calculation process is greater than a first predetermined state of charge, the predetermined power range is expanded.

2. The electric tractor according to claim 1, wherein: When the estimated state of charge is smaller than a second prescribed state of charge that is set to a value greater than the first prescribed state of charge, the control device determines that the restriction condition is satisfied and executes the restriction process.

3. The electric tractor according to claim 1 or 2, wherein: The control device further executes a work determination process in which it is determined to which of a plurality of pre-set work contents the work content performed by the work machine belongs. In the state of charge calculation process, the estimated state of charge is calculated according to the content of the work determined in the work determination process.

4. The electric tractor according to claim 1 or 2, wherein: The motor drives at least the rotating body. The control device further performs a forced stop process in which the converter is controlled to stop driving of the rotating body when the state of charge of the battery is less than the first prescribed state of charge.

5. The electric tractor according to claim 1 or 2, wherein: A notification device is provided, which makes notification by using at least one of sound and light, After executing the restriction process, the control device further executes a first notification process in which the annunciator notifies information indicating that the state of charge of the battery is estimated to be low.

6. The electric tractor according to claim 1 or 2, wherein: A notification device is provided, which makes notification by using at least one of sound and light, When the battery's state of charge is less than a second specified state of charge, the control device also performs a second notification process, in which the notifier notifies the working machine of information that it is possible to stop, wherein the second specified state of charge is set to a value greater than the first specified state of charge.

7. An electric tractor, comprising: The vehicle body can be connected to the operating machinery; Working machinery having a rotating body; Wheels for traveling, mounted on the vehicle body; A motor driving at least one of the wheel and the rotating body; a battery storing electric power to be supplied to the electric motor; a converter to control input and output power of the battery; and A control device, taking the converter as a control object, In the electric tractor, The control device performs the following processing: a limiting process in which, when the state of the battery satisfies a preset limiting condition, the converter is controlled to limit the input and output power of the battery to a preset prescribed power range; a temperature calculation process in which the temperature of the battery when it is assumed that work is completed in a preset farm is calculated as an estimated temperature; as well as and a mitigation process in which, when the estimated temperature calculated in the temperature calculation process is lower than a first predetermined temperature set in advance, the predetermined power range is expanded.

8. The electric tractor according to claim 7, wherein: When the estimated temperature is higher than a second predetermined temperature, the control device determines that the restriction condition is satisfied and executes the restriction process. The second predetermined temperature is set to a value lower than the first predetermined temperature.

9. The electric tractor according to claim 7 or 8, wherein: The control device further executes a work determination process in which it is determined to which of a plurality of pre-set work contents the work content performed by the work machine belongs. In the temperature calculation process, the estimated temperature is calculated according to the content of the work determined in the work determination process.

10. The electric tractor according to claim 7 or 8, wherein: The motor drives at least the rotating body. The control device further performs a forced stop process in which the converter is controlled to stop driving of the rotating body when the temperature of the battery is higher than the first predetermined temperature.

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