towing vehicle

Abstract

In a case where it is determined that the towing vehicle is located at a farm, a first response process that performs a first treatment for responding to an anomaly when a first condition is satisfied, and a second response process that performs a second treatment for responding to an anomaly when a second condition is satisfied are executed. The first condition is satisfied when the second condition is satisfied, and is also satisfied in a part of a state where the second condition is not satisfied.

Description

TECHNICAL FIELD

[0001] The present application relates to a tractor. BACKGROUND

[0002] A tractor disclosed in Japanese Patent Application Publication No. 2014-143965 has a battery, a motor, and a rotary tiller. The battery supplies electric power to the motor. The motor is driven by receiving the electric power supply from the battery. The driving force of the motor causes the tractor to travel or causes the rotary tiller to operate. The tractor travels within a farm, such as a farmland. At this time, the farmland can be tilled by causing the rotary tiller to operate. SUMMARY

[0003] In the technology described in Japanese Patent Application Publication No. 2014-143965, when some kind of abnormality occurs in the electric power system from the battery to the motor, the travel of the tractor can be obstructed. Among them, the road surface of the farm has unevenness or is muddy. That is, the travel environment within the farm is worse than that of a paved road. Therefore, if the travel of the tractor is obstructed within the farm and the tractor is in a state where it cannot travel, it is not necessarily possible to adopt a response such as towing, which is applicable to a general automobile in a paved road. Therefore, when the above-described abnormality occurs within the farm, it is necessary to retreat the tractor to the outside of the farm before the tractor becomes unable to travel.

[0004] A tractor for solving the above-described problem includes: a motor as a drive source; a vehicle body that can be coupled to a work machine to travel with the driving force of the motor; a battery that supplies electric power to the motor; and an abnormality detection device that detects an abnormality in an electric system between the battery and the motor, the abnormality detection device performing: a determination process that determines whether the vehicle body is located in a farm; a first response process that performs a first treatment for responding to the abnormality when it is determined in the determination process that the vehicle body is located in the farm and a first condition that is set in advance is satisfied; and a second response process that performs a second treatment as the treatment for responding to the abnormality when it is determined in the determination process that the vehicle body is located in the farm and a second condition that is set in advance as a condition indicating the occurrence of the abnormality is satisfied, the second treatment being different from the first treatment, the first condition being satisfied when the second condition is satisfied and also being satisfied in some conditions where the second condition is not satisfied.

[0005] In the above-described configuration, the first condition is looser than the second condition, and the first condition is easier to satisfy than the second condition. Therefore, the first treatment can be performed when there is a suspicion of an abnormality, and then the second treatment can be performed when the possibility of an abnormality occurring is high. That is, in the above-described configuration, the occurrence of an abnormality is monitored in two stages, and different treatments are performed. In this way, by performing the first treatment at a stage before an abnormality occurs, the occupant or the like of the tractor can be prompted to retreat the tractor to the outside of the farm.

[0006] The tractor can also be provided with a notification device that notifies using at least one of light and sound, the work machine linked to the vehicle body, and a lifting mechanism that lifts the work machine, the abnormality detection device controls the lifting mechanism to one of a lowered state in which the work machine is positioned at a position in contact with the ground and a raised state in which the work machine is positioned at a position that has moved away from the ground, as the first treatment, the abnormality detection device causes the notification device to notify of the occurrence of the abnormality, and as the second treatment, the abnormality detection device switches the work machine to a stopped state and switches the lifting mechanism to the raised state.

[0007] According to the above configuration, by notifying of the occurrence of the abnormality as the first treatment, it is possible for the passenger or the like to grasp the situation in which the abnormality is likely to occur at an early stage. Further, by causing the work machine to be in the stopped state as the second treatment, the power consumption of the battery that accompanies the operation of the work machine thereafter disappears. Furthermore, if the lifting mechanism is in the raised state, the tractor will not be braked by the contact of the work machine with the road surface when the tractor is caused to travel thereafter. Thus, according to the above configuration, it is possible to prevent a situation in which the tractor cannot travel within the farm due to insufficient battery capacity before retreating outside the farm.

[0008] The tractor can also be provided with a notification device that notifies using at least one of light and sound, as the first treatment, the abnormality detection device causes the notification device to notify of the occurrence of the abnormality, and as the second treatment, the abnormality detection device limits the output from the battery to be less than the output of the battery in a state in which the second treatment is not performed.

[0009] According to the above configuration, by notifying of the occurrence of the abnormality as the first treatment, it is possible for the passenger or the like to grasp the situation in which the abnormality is likely to occur at an early stage. Further, by limiting the output from the battery as the second treatment, it is possible to suppress the power consumption of the battery thereafter. By performing these treatments, it is possible to prevent a situation in which the tractor cannot travel within the farm due to insufficient battery capacity before retreating outside the farm.

[0010] In the tractor, the abnormality detection device can also store in advance a necessary power that is the power per unit time necessary to move from the farm side to the road surface side across a boundary between the farm and a surrounding road surface, and as the second treatment, the abnormality detection device limits an upper limit value of the power outputtable per unit time from the battery to the necessary power.

[0011] According to the above configuration, even if the second treatment is executed, it is possible to secure the electric power necessary for moving from the farm to the road surface. That is, according to the above configuration, even in a case where the farm, such as a paddy field, is located lower than the surrounding road surface, it is possible to reliably cause the tractor to retreat outside the farm.

[0012] In the tractor, the abnormality detection device can prohibit execution of the second treatment in a case where the travel speed of the vehicle body is below a predetermined prescribed vehicle speed. If the degree of unevenness of the road surface of the farm or the degree of muddiness is large, the progress of the tractor becomes slow. A large driving force is required in a case where the travel environment of the farm is poor. Therefore, in the above configuration, in a case where the travel speed of the tractor is low and the travel environment of the farm is expected to be poor, the output restriction is prohibited. Thereby, even in a case where the travel environment of the farm is poor, it is possible to prioritize the travelability of the tractor. BRIEF DESCRIPTION OF DRAWINGS

[0013] Features, advantages, and technical and industrial significance of exemplary embodiments of the present application will be described with reference to the accompanying drawings, wherein like numerals denote like elements, and wherein:

[0014] Figure 1 is a plan view of the tractor.

[0015] Figure 2 is a view showing the electrical configuration and the power transmission path of the tractor.

[0016] Figure 3 is an explanatory view of the contents of the first treatment and the second treatment.

[0017] Figure 4 is a flowchart showing the processing steps of the abnormality countermeasure processing. DETAILED DESCRIPTION

[0018] Hereinafter, one embodiment of the tractor will be described with reference to the drawings.

[0019] <Overall configuration of tractor>

[0020] As shown in Figure 1 , the tractor 10 is provided with a vehicle 11. The vehicle 11 is provided with a vehicle body 13 and a plurality of wheels 12. The plurality of wheels 12 are linked to the vehicle body 13. The vehicle body 13 is provided with a cabin 14. The cabin 14 is a space partitioned by the vehicle body 13. The cabin 14 is a control room into which an occupant enters.

[0021] The vehicle 11 is provided with an operation platform 16 and a display 15. The operation platform 16 is located in the cabin 14. The display 15 is located on the operation platform 16. The display 15 is capable of displaying various information. That is, the display 15 is a notification device that notifies various information by light.

[0022] The tractor 10 is provided with a work machine 20. The work machine 20 is located at the rear when viewed from the vehicle 11. The work machine 20 is provided with a support body 22 and a rotating body 21. The support body 22 is linked to the vehicle body 13 via a lift mechanism 30 described later. The rotating body 21 is provided with a rotating shaft 21A and a plurality of blades 21B. The rotating shaft 21A is rotatably supported by the support body 22. The plurality of blades 21B rotate integrally with the rotating shaft 21A. In Figure 1 , the blades 21B are simply illustrated as cylindrical shapes. If the rotating shaft 21A is rotated in a state where the blades 21B are in contact with the ground 200 of the farm, the farm can be plowed.

[0023] The tractor 10 is provided with the lift mechanism 30. The lift mechanism 30 is provided with a plurality of arms 32 and a hydraulic device 35. The plurality of arms 32 are linked to each other. In addition, the plurality of arms 32 link the vehicle body 13 and the support body 22 of the work machine 20. The hydraulic device 35 generates hydraulic pressure. Each of the arms 32 is actuated in accordance with the hydraulic pressure. Consequently, as indicated by an arrow D of Figure 1 , the work machine 20 is lifted. At the same time, the rotating body 21 of the work machine 20 is brought into contact with or separated from the ground 200. Hereinafter, a state of the lift mechanism 30 for positioning the rotating body 21 of the work machine 20 at a position where the rotating body 21 is in contact with the ground 200 is referred to as a lowered state. In addition, a state of the lift mechanism 30 for positioning the rotating body 21 at a position where the rotating body 21 has been separated from the ground 200 is referred to as a raised state. In Figure 1 , the position of the work machine 20 when the lift mechanism 30 is in the lowered state is indicated by a solid line. In addition, in Figure 1 , the position of the work machine 20 when the lift mechanism 30 is in the raised state is indicated by a double-dot chain line.

[0024] As indicated in Figure 2 , the tractor 10 is provided with a vehicle speed sensor 59. The vehicle speed sensor 59 detects a travel speed of the vehicle 11 as a vehicle speed SP. The tractor 10 is provided with a plurality of switches and levers as operation portions. The plurality of switches and levers include switches and levers for an occupant to switch the travel speed of the tractor 10 or for the occupant to actuate the work machine 20 and the lift mechanism 30. One of the plurality of switches is a start switch 55 for instructing the start of the tractor 10. One of the plurality of switches is a position information switch 51 that is turned on / off by the occupant in accordance with whether the tractor 10 is positioned inside or outside the farm. One of the plurality of switches is a reset switch 52 for canceling the display of the display 15 in association with an abnormality coping process described later. These start switch 55, position information switch 51, and reset switch 52 are located on the operation platform 16, for example. In addition, as indicated in Figure 1 , the vehicle 11 is provided with a steering wheel 57 for steering.

[0025] <Power transmission path of tractor>

[0026] AsFigure 2 As shown, the tractor 10 includes a first electric motor 41, a second electric motor 42, a third electric motor 43, a power transmission mechanism 19, and a PTO 25. The first electric motor 41, the second electric motor 42, and the third electric motor 43 are generator motors.

[0027] The first electric motor 41 is the drive source for moving the tractor 10. The first electric motor 41 is connected to the wheels 12 via a power transmission mechanism 19. The power transmission mechanism 19 includes, for example, a reduction gear that increases and outputs torque.

[0028] The second electric motor 42 is the drive source for the working machine 20. The second electric motor 42 is connected to the rotating body 21 of the working machine 20 via a PTO 25. The PTO 25 is a device for transmitting the torque of the second electric motor 42 to the rotating body 21. The PTO 25 includes, for example, a reduction gear mechanism.

[0029] The third electric motor 43 is the drive source for the hydraulic system 35. The third electric motor 43 is connected to the hydraulic pump of the hydraulic system 35. The third electric motor 43 drives the hydraulic pump. As described above, the first electric motor 41, the second electric motor 42, and the third electric motor 43 are generator electric motors. Therefore, these electric motors can function as generators. For example, as the first electric motor 41, it can function as a generator when the tractor 10 decelerates. At this time, regenerative braking force corresponding to the power generated by the first electric motor 41 is generated in the tractor 10.

[0030] The tractor 10 is equipped with a first rotation sensor 61, a second rotation sensor 62, and a third rotation sensor 63. The first rotation sensor 61 detects the rotational position of the rotor of the first motor 41 as a first position A1. The second rotation sensor 62 detects the rotational position of the rotor of the second motor 42 as a second position A2. The third rotation sensor 63 detects the rotational position of the rotor of the third motor 43 as a third position A3.

[0031] <Electrical Configuration of the Tractor>

[0032] like Figure 2 As shown, the tractor unit 10 includes a power supply circuit 99. The power supply circuit 99 is mounted on the vehicle body 13. The power supply circuit 99 includes a battery 77, a positive wire 81, a negative wire 82, a positive relay 83, and a negative relay 84. Furthermore, the power supply circuit 99 includes a first converter 85, a first transformer 71, a second transformer 72, and a third transformer 73. Additionally, the power supply circuit 99 includes a current sensor 91, a voltage sensor 92, and a temperature sensor 93.

[0033] The battery 77 is a secondary battery. The battery 77 performs output and reception of electric power with the first motor 41, the second motor 42, and the third motor 43. A voltage sensor 92 is connected between the terminals of the battery 77. The voltage sensor 92 detects an output voltage of the battery 77 as a battery voltage 92V. A temperature sensor 93 is attached to the battery 77. The temperature sensor 93 detects a temperature of the battery 77 as a battery temperature 93T.

[0034] The positive line 81 connects a terminal of the high potential side of the battery 77 to the first converter 85. The negative line 82 connects a terminal of the low potential side of the battery 77 to the first converter 85. The first converter 85 converts the magnitude of the voltage and outputs.

[0035] The positive relay 83 is located in the middle of the positive line 81. The negative relay 84 is located in the middle of the negative line 82. The positive relay 83 and the negative relay 84 turn on / off the electric connection between the battery 77 and the first converter 85.

[0036] The current sensor 91 is attached to the middle of the positive line 81. Specifically, the current sensor 91 is attached between the battery 77 and the positive relay 83 on the positive line 81. The current sensor 91 detects a charge / discharge current flowing through the battery 77 as a battery current 91A.

[0037] The first inverter 71 and the second inverter 72 are connected to the first converter 85. The first inverter 71 and the second inverter 72 are connected in parallel to each other. The first inverter 71 is connected to the first motor 41. The first inverter 71 performs DC / AC power conversion between the first converter 85 and the first motor 41. The second inverter 72 is connected to the second motor 42. The second inverter 72 performs DC / AC power conversion between the first converter 85 and the second motor 42.

[0038] The third inverter 73 is connected to the battery 77. The third inverter 73 is connected in parallel to the first converter 85. The third inverter 73 is connected to the third motor 43. The third inverter 73 performs DC / AC power conversion between the battery 77 and the third motor 43.

[0039] <Outline of Control Device>

[0040] The towing vehicle 10 is provided with a control device 100. The control device 100 can be configured as one or more processors that execute various processes according to a computer program (software). Note that the control device 100 can also be configured as one or more dedicated hardware circuits, such as an application specific integrated circuit (ASIC), that execute at least a part of the various processes, or a circuitry that includes a combination thereof. The processor includes a CPU 102, a memory such as a RAM and a ROM 104. The memory stores program codes or instructions that cause the CPU 102 to execute processes. The memory, which is a computer-readable medium, includes various available media that are general-purpose or specific-purpose and that are accessible by a computer. The control device 100 has a nonvolatile memory, which is a storage device, that can be electrically rewritten.

[0041] The control device 100 receives signals from the various operation units. That is, the control device 100 receives a signal 55N from the start switch 55. The control device 100 receives a signal 51N from the position information switch 51. The control device 100 receives a signal 52N from the reset switch 52.

[0042] Further, the control device 100 receives detection signals from various sensors. The control device 100 receives a vehicle speed SP detected by a vehicle speed sensor 59. The control device 100 receives a battery current 91A detected by a current sensor 91. The control device 100 receives a battery voltage 92V detected by a voltage sensor 92. The control device 100 receives a battery temperature 93T detected by a temperature sensor 93. The control device 100 calculates a state of charge SOC of the battery 77 on the basis of these battery current 91A, battery voltage 92V, and battery temperature 93T. The state of charge SOC of the battery 77 is a value obtained by dividing a remaining capacity of the battery 77 by a full charge capacity.

[0043] The control device 100 receives a first position A1 detected by the first rotation sensor 61, a second position A2 detected by the second rotation sensor 62, and a third position A3 detected by the third rotation sensor 63. The control device 100 calculates a rotational speed, which is a first rotational speed Smg1, of a rotor of the first motor 41 on the basis of the first position A1. Likewise, the control device 100 calculates a rotational speed, which is a second rotational speed Smg2, of a rotor of the second motor 42 on the basis of the second position A2. Likewise, the control device 100 calculates a rotational speed, which is a third rotational speed Smg3, of a rotor of the third motor 43 on the basis of the third position A3.

[0044] The control device 100 takes the first motor 41 as a control target. The control device 100 causes the tractor 10 to travel or causes the tractor 10 to stop traveling by controlling the first motor 41. The control device 100 substantially controls the first motor 41 by controlling the first inverter 71. The control device 100 refers to the first rotational speed Smg1 when controlling the first motor 41. The control device 100 stores a plurality of target travel speeds that are set in advance. The control device 100 controls the first motor 41 based on one of the plurality of target travel speeds, for example, in response to an instruction from an occupant.

[0045] The control device 100 takes the working machine 20 as a control target. Specifically, the control device 100 controls the working machine 20 through control of the second motor 42. That is, the control device 100 causes the rotary body 21 to rotate or causes the rotary body 21 to stop rotating by controlling the second motor 42. The control device 100 substantially controls the second motor 42 by controlling the second inverter 72. The control device 100 refers to the second rotational speed Smg2 when controlling the second motor 42. The control device 100 causes the rotary body 21 to rotate or causes the rotary body 21 to stop rotating, for example, in response to an instruction from an occupant.

[0046] The control device 100 takes the lifting mechanism 30 as a control target. Specifically, the control device 100 controls the hydraulic pressure generated by the hydraulic device 35 through control of the third motor 43 and a control valve or the like of a hydraulic circuit in the hydraulic device 35. Thereby, the lifting mechanism 30 becomes the raised state or the lowered state. The control device 100 substantially controls the third motor 43 by controlling the third inverter 73. The control device 100 refers to the third rotational speed Smg3 when controlling the third motor 43. The control device 100 causes the lifting mechanism 30 to become the raised state or the lowered state, for example, in response to an instruction from an occupant.

[0047] The control device 100 takes the display 15 as a control target. The control device 100 outputs a display signal for displaying various information on the display 15 to the display 15. The display 15 displays the content corresponding to the display signal when receiving the display signal.

[0048] The control device 100 takes the positive electrode relay 83 and the negative electrode relay 84 as control targets. That is, the control device 100 switches the on / off of the electrical connection of the positive electrode relay 83 and the negative electrode relay 84 according to the on / off of the start switch 55.

[0049] <Function as an abnormality detection device>

[0050] The control device 100 functions as an anomaly detection device, detecting anomalies in the electrical system between the battery 77 and the first motor 41. As described above, the electrical system between the battery 77 and the first motor 41 includes the battery 77, positive wire 81, negative wire 82, positive relay 83, negative relay 84, first converter 85, first inverter 71, and first motor 41. In this embodiment, the control device 100 detects anomalies in the battery 77 as an anomaly in the electrical system between the battery 77 and the first motor 41. Here, "anomaly in the battery 77" refers to an anomaly within the range where power can be supplied from the battery 77 to the first motor 41, rather than a malfunction where power cannot be supplied from the battery 77 to the first motor 41. That is, a state where power can be supplied from the battery 77 to the first motor 41, enabling the tractor 10 to move, but the battery 77 is not entirely functioning, is termed an anomaly in the battery 77.

[0051] As part of the function of the aforementioned anomaly detection device, the control device 100 can perform fail-safe processing. Fail-safe processing is a process used to detect anomalies or precursors to anomalies in the battery 77 and to respond to these anomalies or precursors. For example... Figure 3 As shown, fail-safe procedures include farm-specific fail-safe procedures and general fail-safe procedures. Farm-specific fail-safe procedures are performed when the tractor 10 is located on a farm. General fail-safe procedures are performed when the tractor 10 is located outside the farm, i.e., when the tractor 10 is traveling on a paved road.

[0052] <Fault-Safe Handling for Farms>

[0053] In fail-safe procedures for farm use, when a pre-set first condition is met, the control device 100 performs a first farm-specific procedure as a response to an anomaly in battery 77. For example... Figure 3 As shown, the first action for farm use involves displaying a first message on the display 15. The first message includes a suspicion that the battery 77 is malfunctioning (hereinafter referred to as "suspicion") and a requirement to move the tractor 10 away from the farm. That is, in the first action for farm use, a response is taken to the precursory abnormality of the battery 77, referred to as "suspicion." In this embodiment's first action, by responding to the precursory abnormality of the battery 77, an abnormality is addressed before it actually occurs. Furthermore, this first action is the first response action in farm-use fail-safe procedures.

[0054] The control device 100 stores in advance a first condition. The first condition is that the state of charge SOC of the battery 77 is equal to or lower than a first value Ll. The first value Ll is, for example, 20 [%]. The first value Ll is set in advance, for example, by experiment or simulation, to a value at which, as the state of charge SOC of the battery 77, the battery 77 is still normal, but if the current situation continues and the battery 77 continues to output electric power, the battery 77 is likely to be irreversibly deteriorated due to overdischarge or the like.

[0055] In the farm safety process, when the second condition set in advance is established, the control device 100 performs a farm second treatment as a measure for dealing with an abnormality of the battery 77. As shown in Figure 3 The farm second treatment includes the following three. One of the farm second treatments is to display a second message on the display 15. The content of the second message includes content that the battery 77 is likely to have an abnormality. In addition, one of the farm second treatments is to switch the work machine 20 to a stopped state and switch the lifting mechanism 30 to a raised state. In addition, one of the farm second treatments is to limit the output from the battery 77 to be less than the output of the battery 77 in a state where the second treatment is not performed. The output limitation of the battery 77 will be described later in detail. In addition, the process of performing the above-mentioned second treatment is a second countermeasure process in the farm safety process.

[0056] The control device 100 stores in advance a second condition. The second condition is set in advance as a condition in which an abnormality occurs in the battery 77. The second condition is that the state of charge SOC of the battery 77 is equal to or lower than a second value L2. The second value L2 is a value smaller than the first value Ll, for example, 5 [%]. The second value L2 is a value determined, for example, by experiment or simulation, as a value at which the output voltage of the battery 77 is relatively low compared to the rated output voltage, and the likelihood of an abnormality occurring in the battery 77, such as overdischarge, is extremely high in the battery 77. By comparing the second condition and the first condition, it is understood that the above-mentioned first condition is a condition that is established when the second condition is established and is also established in part of the conditions in which the second condition is not established.

[0057] The output limitation of the battery 77 will be described. Specifically, limiting the output of the battery 77 means limiting the upper limit value of the electric power that can be output from the battery 77 per unit time. That is, in the second treatment, the control device 100 sets the output upper limit value Wout as the upper limit of the total amount of electric power that can be output from the battery 77 per unit time. Also, the control device 100 controls the first motor 41, the second motor 42, and the third motor 43 within a range in which the electric power output from the battery 77 does not exceed the output upper limit value Wout.

[0058] The control device 100 stores in advance a second treatment-related output upper limit value Wout. Here, a farm such as a paddy field is located at a level lower than that of a surrounding road surface. A ramp for entering and exiting the farm is provided at the boundary between the farm and the road surface. The necessary electric power per unit time necessary to move from the farm side to the road surface side over the ramp is referred to as necessary electric power. The control device 100 stores this necessary electric power as the second treatment-related output upper limit value Wout. The above-mentioned necessary electric power is determined, for example, by experiment or simulation. Further, the inclination angle of the above-mentioned ramp differs depending on the farm. Here, the maximum value of the inclination angle that can be achieved by the ramp of the farm is referred to as the maximum inclination angle. As the inclination angle of the ramp at the time of setting the above-mentioned necessary electric power, the maximum inclination angle is estimated.

[0059] In a case where the vehicle speed SP of the tractor 10 is below a prescribed vehicle speed SPK, the control device 100 prohibits the output limitation of the battery 77. That is, in a case where the vehicle speed SP of the tractor 10 is below the prescribed vehicle speed SPK, even if the second condition is established, the control device 100 does not perform the output limitation of the battery 77. Here, the road surface of the farm can be poor in terms of, for example, the degree of unevenness or the degree of muddiness. When the tractor 10 travels in such an environment, the vehicle speed SP of the tractor 10 is often slow. Also, when the tractor 10 travels in such an environment, the tractor 10 requests a considerable driving force, and requests electric power supply from the battery 77 sufficient to output the driving force. Therefore, the output limitation of the battery 77 is prohibited when the vehicle speed SP of the tractor 10 is considerably low, so that sufficient electric power supply can be performed when the tractor 10 travels in the above-mentioned environment. The above-mentioned prescribed vehicle speed SPK is set in advance, for example, by experiment or simulation, as the maximum value of the vehicle speed SP that can be achieved by the tractor 10 when the travel environment of the farm is expected to be poor. As an example, the prescribed vehicle speed SPK is 1 to 3 km / h.

[0060] <Normally-used fail-safe processing>

[0061] In the normally-used fail-safe processing, when the above-mentioned first condition is established, the control device 100 performs normally-used first processing for coping with the abnormality of the battery 77. As the normally-used first processing, for example, the control device 100 performs the output limitation of the battery 77. As the normally-used first processing, for example, the control device 100 performs the output limitation of the battery 77. Figure 3As shown, the normally used first treatment is to cause a third message to be displayed on the display 15. The content of the third message includes content indicating that there is a suspicion that the battery 77 is abnormal, and content indicating that entry into the farm is prohibited. Further, in the normally used fail-safe processing, when the above-described second condition is satisfied, the control device 100 performs normally used second treatment for coping with the abnormality of the battery 77. The normally used second treatment includes the following two contents. One of the normally used second treatment is to cause a fourth message to be displayed on the display 15. The content of the fourth message includes content indicating that it is highly likely that the battery 77 is abnormal. Further, one of the normally used second treatment is to limit the output of the battery 77. The control device 100 stores an output upper limit value Wout related to the normally used second treatment in advance. The electric power necessary per unit time for causing the tractor 10 to travel at the lowest value among the plurality of target travel speeds set to the tractor 10 on the premise that the tractor 10 travels on a paved road is referred to as the minimum travel electric power. The control device 100 stores this minimum travel electric power as the output upper limit value Wout of the battery 77 related to the normally used second treatment. The minimum travel electric power is determined, for example, by experiment or simulation. The minimum travel electric power is smaller than the necessary electric power.

[0062] <Abnormality coping processing>

[0063] The control device 100 can execute the abnormality coping processing as a centralized processing for executing the above-described farm-use fail-safe processing and the normally used fail-safe processing. As a part of the abnormality coping processing, the control device 100 performs a determination processing in addition to the above-described farm-use fail-safe processing and the normally used fail-safe processing. The control device 100 determines whether the tractor 10 is located in the farm in the determination processing. In a case where it is determined in the determination processing that the tractor 10 is located in the farm, the control device 100 performs the farm-use fail-safe processing. Further, in a case where it is determined in the determination processing that the tractor 10 is located outside the farm, the control device 100 performs the normally used fail-safe processing.

[0064] A specific processing step of the abnormality coping processing will be described. The control device 100 repeatedly executes the abnormality coping processing at a predetermined control cycle during the period in which the start switch 55 is turned on. As shown in FIG. 8, the control device 100 first performs the processing of step S10 when starting the abnormality coping processing. In step S10, the control device 100 determines whether the tractor 10 is located in the farm. The control device 100 performs the determination of step S10 based on the signal 51N from the position information switch 51. The control device 100 determines that the tractor 10 is located in the farm when receiving the signal 51N indicating the on state from the position information switch 51 (step S10: YES). In this case, the control device 100 causes the processing to proceed to step S20. The processing of step S10 is the determination processing. Figure 4

[0065] ​In step S20, the control device 100 determines whether the state of charge SOC of the battery 77 is equal to or lower than the first value LI. Specifically, the control device 100 refers to the latest state of charge SOC. Then, the control device 100 compares the latest state of charge SOC with the first value LI stored in advance. When the latest state of charge SOC is greater than the first value LI (step S20: No), the control device 100 temporarily ends the series of processes of the abnormality coping process. In this case, the control device 100 executes again the process of step S10.

[0066] On the other hand, in step S20, when the latest state of charge SOC is equal to or lower than the first value LI (step S20: Yes), the control device 100 causes the process to proceed to step S30. In step S30, the control device 100 determines whether the state of charge SOC of the battery 77 is equal to or lower than the second value L2. Specifically, the control device 100 refers to the latest state of charge SOC. Then, the control device 100 compares the latest state of charge SOC with the second value L2 stored in advance. When the latest state of charge SOC is greater than the second value L2 (step S30: No), the control device 100 causes the process to proceed to step S40.

[0067] In step S40, the control device 100 causes the display 15 to display a first message. As the specific process of step S40, the control device 100 outputs a first display signal J1 to the display 15. The first display signal J1 is a signal for causing the display 15 to display the content that the battery 77 is abnormal, and the content that it is necessary for the tractor 10 to retreat outside the farm. When receiving the first display signal J1, the display 15 displays a message corresponding to the first display signal J1. As described above, among the messages for the fail-safe process, there are four types of first message to fourth message. The display signals for displaying these messages also have four types of first display signal J1 to fourth display signal J4. When a display signal for fail-safe other than the first display signal J1 is being output at the time when the process has proceeded to step S40, the control device 100 cancels the output of the display signal and outputs the first display signal J1. Further, if the first display signal J1 is already being output at the time when the process has proceeded to step S40, the control device 100 continues to output the first display signal J1.

[0068] The process of Step S40 is essentially a process of starting the output of the first display signal Jl. In the process other than Step S40 in the abnormality coping process, until the case where the display signal for safety other than the first display signal Jl is output, or before the reset switch 52 is operated, the control device 100 continues to output the first display signal Jl. When the process of Step S40 is executed, the control device 100 temporarily ends the series of processes of the abnormality coping process. Then, the control device 100 executes the process of Step S10 again. The process of Step S40 is the first coping process.

[0069] Further, in Step S30, when the latest state of charge SOC is the second value L2 or less (Step S30: Yes), the control device 100 makes the process proceed to Step S50. In Step S50, the control device 100 causes the display 15 to display a second message. As the specific process of Step S50, the control device 100 outputs the second display signal J2 to the display 15. The second display signal J2 is a display signal for causing the display 15 to display the content that the battery 77 is likely to be abnormal, the content that it is necessary to make the tractor 10 retreat outside the farm, and the content that the necessary treatment of each part of the tractor 10 is appropriately performed. The above-mentioned necessary treatment specifically refers to the process of stopping the work machine 20, making the lifting mechanism 30 into the raised state, and performing the output limitation of the battery 77 according to the situation. As with Step S40, when another display signal for safety is being output at the time when the process has proceeded to Step S50, the control device 100 cancels the output of the display signal and outputs the second display signal J2. Further, when the second display signal J2 is already being output at the time when the process has proceeded to Step S50, the control device 100 continues to output the second display signal J2. As with the process of Step S40, the process of Step S50 is essentially a process of starting the output of the second display signal J2. Further, as with the first display signal Jl, until the case where the display signal for safety other than the second display signal J2 is output, or before the reset switch 52 is reset, the control device 100 continues to output the second display signal J2. After the process of Step S50 is executed, the control device 100 makes the process proceed to Step S60.

[0070] In step S60, the control device 100 switches the revolving body 21 of the work machine 20 to the stopped state by controlling the second motor 42. That is, the control device 100 stops the second motor 42. In a case where the revolving body 21 is already in the stopped state at the time when the process of step S60 is performed, the control device 100 maintains the state. Further, in step S60, the control device 100 switches the lifting mechanism 30 to the raised state by controlling the third motor 43 and the hydraulic circuit or the like. In a case where the lifting mechanism 30 is already in the raised state at the time when the process of step S60 is performed, the control device 100 maintains the state. After the process of step S60 is performed, the control device 100 causes the process to proceed to step S70.

[0071] In step S70, the control device 100 determines whether the vehicle speed SP is equal to or lower than the prescribed vehicle speed SPK. The control device 100 refers to the latest vehicle speed SP. Then, the control device 100 compares the latest vehicle speed SP with the prescribed vehicle speed SPK stored in advance. When the latest vehicle speed SP is greater than the prescribed vehicle speed SPK (step S70: No), the control device 100 causes the process to proceed to step S80.

[0072] In step S80, the control device 100 performs the output limitation of the battery 77. That is, the control device 100 sets the output upper limit value Wout of the battery 77 to the necessary electric power. In a case where the output upper limit value Wout has been set to the necessary electric power at the time when the process proceeds to step S80, the control device 100 maintains the state. After the process of step S80 is performed, the control device 100 temporarily ends the series of processes of the abnormality coping process. Then, the process of step S10 is performed again.

[0073] Further, in step S70, when the latest vehicle speed SP is equal to or lower than the prescribed vehicle speed SPK (step S70: Yes), the control device 100 causes the process to proceed to step S90. In step S90, the control device 100 prohibits the output limitation of the battery 77. Specifically, in a case where the output limitation of the battery 77 is being performed at the time when the process proceeds to step S90, the control device 100 cancels the output limitation. That is, the control device 100 releases the setting of the output upper limit value Wout. In a case where the output limitation of the battery 77 is not being performed at the time when the process proceeds to step S90, the control device 100 maintains the state. After the process of step S90 is performed, the control device 100 temporarily ends the series of processes of the abnormality coping process. Then, the process of step S10 is performed again. The processes of step S50, step S60, and step S80 are the second coping process. Further, the processes of step S20 to step S90 are the farm use failsafe process.

[0074] In step S10, the control device 100 determines that the tractor 10 is not located in the farm when it does not receive the signal 51N indicating the on state from the position information switch 51 (step S10: No). In this case, the control device 100 makes the process proceed to step S300.

[0075] In step S300, the control device 100 performs the usual fail-safe process. That is, when the latest state of charge SOC of the battery 77 is equal to or lower than the first value L1 and the state of charge SOC is greater than the second value L2, the control device 100 causes the third message to be displayed on the display 15 as the above-mentioned usual first treatment. The controller 100 substantially outputs the third display signal J3 to the display 15. The third display signal J3 is a display signal for causing the display 15 to display the content that the battery 77 is abnormal and the content indicating that entry into the farm is prohibited. The control device 100 starts the output of the third display signal J3 or continues the output of the third display signal J3 in the same manner as the output of the first display signal J1 explained in step S40.

[0076] Further, in step S300, when the latest state of charge SOC of the battery 77 is equal to or lower than the second value L2, the control device 100 limits the output of the battery 77 as the usual second treatment. The control device 100 substantially sets the upper limit value Wout of the output of the battery 77 to the minimum travel power. Further, the control device 100 causes the display 15 to display a fourth message. The controller 100 substantially outputs the fourth display signal J4 to the display 15. The fourth display signal J4 is a display signal for causing the display 15 to display the content that the battery 77 is likely to be abnormal, the content indicating that entry into the farm is prohibited, and the content that the output limitation of the battery 77 is performed. In the usual second treatment, the control device 100 starts the output limitation of the battery 77 or continues the output limitation in the same manner as the output limitation of the battery 77 explained in step S80. Further, the control device 100 starts the output of the fourth display signal J4 or continues the output of the fourth display signal J4 in the same manner as the output of the first display signal J1 explained in step S40. After the process of step S300 is executed, the control device 100 temporarily ends the series of processes of the abnormality coping process. Then, the process of step S10 is performed again.

[0077] <Effects of Embodiments>

[0078] Now, it is assumed that the tractor 10 is located in the farm (step S10: Yes). Also, the tractor 10 is performing tillage in the farm. That is, the lifting mechanism 30 is in the lowered state. Further, the work machine 20 is in operation.

[0079] Further, assume that the state of charge SOC of the battery 77 decreases for some reason. Also, assume that the state of charge SOC of the battery 77 becomes a state of being below the first value LI (step S20: YES) and being greater than the second value L2 (step S30: NO). In this case, the control device 100 displays the first message on the display 15 as the first treatment for the farm (step S40).

[0080] After that, assume that the occupant who noticed the display of the display 15 drives the tractor 10 in order to retreat the tractor 10 from the farm, but the state of charge SOC of the battery 77 becomes below the second value L2 before the retreat from the farm ends (step S30: YES). In this case, the control device 100 switches the above first message displayed on the display 15 to the second message as the second treatment for the farm (step S50). Further, the control device 100 forcibly stops the work machine 20 and forcibly makes the lift mechanism 30 into the raised state (step S60). Further, only in the case where the vehicle speed SP is greater than the prescribed vehicle speed SPK, the control device 100 performs the output limitation of the battery 77 (step S80). That is, the control device 100 sets the output upper limit value Wout of the battery 77 to the necessary electric power. By the stop of the work machine 20 and the output limitation of the battery 77, the tractor 10 drives while suppressing the electric power consumption of the battery 77. Further, since the output upper limit value Wout of the battery 77 is the necessary electric power, the tractor 10 is able to climb the slope of the boundary between the farm and the surrounding road surface.

[0081] Then, assume that the tractor 10 has completed the retreat to the outside of the farm (step S10: NO). Assume that the occupant performs the off operation of the position information switch 51 in conjunction therewith. At this time, since the state of charge SOC of the battery 77 remains below the second value L2, the control device 100 performs the second treatment for the normal use (step S300). That is, the control device 100 switches the second message displayed on the display 15 to the fourth message. Further, the control device 100 sets the output upper limit value Wout to the minimum travel electric power which is less than the necessary electric power. Then, the tractor 10 drives in a state where the electric power consumption of the battery 77 is further suppressed, for example, parks on the shoulder.

[0082] <Effects of Embodiments>

[0083] (1) In the present embodiment, the first condition is more lenient than the second condition, and the first condition is easier to satisfy than the second condition. Therefore, in the abnormality countermeasure process, the first treatment is performed when there is a suspicion of abnormality in the battery 77, and then the second treatment is performed when the possibility of abnormality in the battery 77 becomes high. In the present embodiment, on the basis of monitoring the occurrence of abnormality in two stages in this way, different treatments are performed for each stage. The treatment in the first stage when the tractor 10 is located in the farm, that is, the first treatment, reports a suspicion of abnormality in the battery 77. As the first treatment, by performing notification of a suspicion of abnormality at a stage before the occurrence of abnormality in the battery 77, the occupant is prompted to retreat the tractor 10 outside the farm before the abnormality in the battery 77 occurs.

[0084] (2) In the present embodiment, as the second treatment when the tractor 10 is located in the farm, the work machine 20 is switched to a stopped state, and the lifting mechanism 30 is switched to a raised state. If the work machine 20 is brought to a stopped state, the power consumption of the battery 77 accompanying the operation of the work machine disappears thereafter. In addition, if the lifting mechanism 30 is in a raised state, the tractor 10 is not braked by contact of the rotating body 21 of the work machine 20 with the road surface when the tractor 10 is thereafter driven. Therefore, according to the present embodiment, it is possible to prevent a situation in which the tractor 10 cannot be driven in the farm due to insufficient capacity of the battery 77 before the tractor 10 is retreated outside the farm.

[0085] (3) In the present embodiment, as the second treatment when the tractor 10 is located in the farm, the output from the battery 77 is limited. If the output from the battery 77 is limited, it is possible to suppress the power consumption of the battery 77 thereafter. In addition to the above-mentioned stopping of the work machine 20, the output limitation of the battery 77 is performed, and thus it is possible to more reliably prevent a situation in which the tractor 10 cannot be driven in the farm due to insufficient capacity of the battery 77.

[0086] (4) In the present embodiment, the output upper limit value Wout at the time of performing the output limitation of the battery 77 as described in the above (3) is set to the necessary power necessary to climb an uphill slope from the farm side to the surrounding road surface side, that is, the necessary power. Therefore, even in a case where the output limitation of the battery 77 has been performed, it is possible to secure the power necessary to move from the farm to the road surface. Therefore, even in a case where the farm is located lower than the surrounding road surface, such as a paddy field, it is possible to reliably retreat the tractor 10 outside the farm.

[0087] (5) With regard to the second treatment when the tractor 10 is located in the farm, in the present embodiment, the output limitation of the battery 77 is prohibited when the vehicle speed SP is equal to or lower than a prescribed vehicle speed SPK, that is, when the driving environment in the farm is poor and a large driving force is expected to be required. By this, even in a case where the driving environment in the farm is poor, it is possible to secure that the tractor 10 can be driven.

[0088] <Modification example>

[0089] This embodiment mode can be implemented by the following modifications. This embodiment mode and the following modification examples can be implemented in combination with each other within a range not contradictory in technology.

[0090] It is not necessary to prohibit the output limitation of the battery 77 depending on the magnitude of the vehicle speed SP. For example, if the electric power of the output upper limit value Wout is set to be relatively large, the drive power necessary for running can be output even if the output limitation of the battery 77 is not prohibited.

[0091] The determination method of the necessary electric power is not limited to the example of the above embodiment mode. For example, the necessary electric power can not be a general value applicable to various farms, but can be the electric power necessary to climb a slope of a certain specific farm. If the farm plowed by the tractor 10 is limited to only a certain specific farm, the necessary electric power in that farm can be determined. The electric power necessary to climb a slope of a certain specific farm can be grasped, for example, from the electric power necessary to climb the slope in the past.

[0092] The necessary electric power can also be determined without considering the travel on the slope between the farm and the surrounding road surface. For example, depending on the farm, there can be a difference in level at the boundary with the surrounding road surface. In this case, the electric power necessary to cross over the difference in level can be determined as the necessary electric power. Further, in the case where there is no slope or difference in level, etc. between the farm and the surrounding road surface, the necessary electric power can coincide with the minimum running electric power. In this way, the necessary electric power can be the electric power necessary to move from the farm side to the road surface side across the boundary between the farm and the surrounding road surface.

[0093] Further, the necessary electric power can be determined without calculating the actual electric power necessary to move from the farm side to the road surface side by simulation or the like. For example, the necessary electric power can be determined as an electric power value larger than the minimum running electric power by a certain value, or an electric power value larger than the minimum running electric power by a certain percentage.

[0094] The output upper limit value Wout in the second treatment for the farm can be set to a value other than the necessary electric power. The output upper limit value Wout can be set to a necessary value depending on the content of the second treatment. The content of the second treatment for the farm is not limited to the example of the above embodiment mode. Two of the three contents performed in the above embodiment mode can be performed, or only one of them can be performed. Further, a treatment different from the content performed in the above embodiment mode can be performed. The second treatment for the farm can be a treatment different from the first treatment for the farm and capable of appropriately dealing with an abnormality in the farm.

[0095] The content of the first treatment for the farm is not limited to the example of the above-described embodiment. For example, the output restriction of the battery 77 can also be performed in the first treatment. The first treatment for the farm can be a treatment for coping with the abnormality of the battery 77.

[0096] The output restriction of the battery 77 can also be performed in both the first treatment and the second treatment for the farm. In this case, it can be considered that the output upper limit value Wout in the second treatment is made smaller than the output upper limit value Wout in the first treatment. As one example of this, the output upper limit value Wout in the second treatment can be set to the minimum running electric power, and the output upper limit value Wout in the first treatment can be set to the necessary electric power.

[0097] In the above-described embodiment, the first treatment for the farm is cancelled and the second treatment for the farm is performed when the second condition is established. However, the first treatment can be continued and the second treatment can be performed when the second condition is established.

[0098] The setting method of the output upper limit value Wout in the second treatment for general use is not limited to the example of the above-described embodiment. The above-described output upper limit value Wout can be made higher or lower than the minimum running electric power. If the road surface is paved, the tractor 10 can be able to be towed. Therefore, even if the above-described output upper limit value Wout is smaller than the minimum running electric power, the tractor 10 can be able to be moved to the maintenance factory.

[0099] The content of the second treatment for general use is not limited to the example of the above-described embodiment. The second treatment for general use can be a treatment that is able to appropriately cope with the abnormality outside the farm. Similarly, the content of the first treatment for general use is not limited to the example of the above-described embodiment.

[0100] The first treatment for general use can also be continued when the second condition is established, like the first treatment for the farm. The content of the first message to the fourth message is not limited to the example of the above-described embodiment. Each message can include appropriate content for conveying the current state of the battery 77 to the occupant.

[0101] The notification method in the first treatment and the second treatment for the farm is not limited to the example of the above-described embodiment. For example, instead of displaying the message on the display 15, voice guidance about the content of the message displayed on the display 15 can be performed, or in addition to displaying the message on the display 15, voice guidance about the content of the message displayed on the display 15 can be performed. In this case, as long as a speaker that is a notification device that performs notification using sound is provided on the tractor 10, it is acceptable. Furthermore, the speaker can be made a control target of the control device 100.

[0102] As for the notification method in the first treatment and the second treatment for the farm, for example, notification can be made using a warning light. In this case, it is sufficient that the warning light is provided as the notification device using light. Also, it is sufficient that the warning light is made a control target of the control device 100. For example, if the color of the warning light that is lit is set to different colors in the first treatment and the second treatment, the occupant can grasp the difference in the situation. The notification using the warning light described above can be used together with at least one of the display of the message and the sound guidance, or the notification can be made using only the warning light.

[0103] As for the notification method in the first treatment and the second treatment for the farm, for example, notification can be made using a buzzer. In this case, as with the modification example of the sound guidance described above, it is sufficient that the speaker is provided as the notification device in the tractor 10. Also, as with the modification example of the warning light, for example, the tone color is set to different tone colors in the first treatment and the second treatment, the occupant can grasp the difference in the situation. The notification using the buzzer described above can be used together with at least one of the display of the message, the sound guidance, and the warning light, or the notification can be made using only the buzzer.

[0104] Different notification devices can be used in the first treatment and the second treatment for the farm. The modification example of the notification method described above with respect to the first treatment and the second treatment for the farm can be applied to the notification method in the first treatment and the second treatment for the general use.

[0105] Different notification devices can be used in the first treatment for the farm and the first treatment for the general use. The same applies to the second treatment for the farm and the second treatment for the general use.

[0106] The first condition and the second condition are not limited to the examples of the embodiment described above. For example, the first condition can be determined by the battery temperature 93T. In this case, for example, the first condition can be set by the battery temperature 93T being equal to or higher than a first temperature, and the second condition can be set by the battery temperature 93T being equal to or higher than a second temperature. The second temperature is a temperature higher than the first temperature. If the first temperature is set as a value at which the battery 77 is suspected to be abnormal, and the second temperature is set as a value at which the battery 77 is highly likely to be abnormal, as with the embodiment described above, it is possible to cope with the abnormality precursor and the occurrence of the abnormality. Even in the case where the first condition and the second condition are modified from the embodiment described above, it is sufficient that the second condition is determined as a condition indicating the occurrence of the abnormality. As the first condition, it is sufficient that the condition is established when the second condition is established and is also established in a part of the situation in which the second condition is not established.

[0107] The first condition and the second condition can also be defined based on different parameters. For example, the first condition can be set as a condition based on the state of charge SOC of the battery 77, and the second condition can be set as a condition based on the battery temperature 93T. Further, a plurality of parameters can be combined to define the first condition and the second condition. It is not necessary to employ the same parameters for the first condition and the second condition as long as the first condition is established when the second condition is established and the first condition is also established in a part of the conditions in which the second condition is not established.

[0108] The detection object of the abnormality is not limited to the battery 77. Any component in the electric system from the battery 77 to the first motor 41 can be the detection object of the abnormality. For example, the positive electrode line 81 can be the detection object of the abnormality. In the case where the detection object of the abnormality is changed from the above-described embodiment, it is only necessary to detect or estimate the parameter required for detecting the abnormality in the detection object with a sensor. Then, the first condition and the second condition can be defined using the parameter. For example, in detecting the abnormality of the positive electrode line 81, the temperature of the positive electrode line 81 is considered as the parameter for the abnormality detection.

[0109] In the above-described embodiment, the condition for executing the first treatment for the farm and the condition for executing the first treatment for the general purpose are the same. However, these conditions can be different from each other. The same applies to the condition for executing the second treatment for the farm and the condition for executing the second treatment for the general purpose.

[0110] The means for grasping whether the tractor 10 is located in the farm is not limited to the use of the position information switch 51. For example, the position information of the GPS and the map information can be used. In this case, a GPS receiver is provided in the tractor 10, and the map information is stored in the control device 100.

[0111] A processing device as an abnormality detection device can also be separately provided outside the control device 100. In this case, the abnormality detection device can be configured to be capable of executing the abnormality coping process and to have the notification device, the work machine 20, and the lifting mechanism 30 as control objects.

[0112] The overall configuration of the tractor 10 is not limited to the example of the above-described embodiment. The configuration of the lifting mechanism 30 can be changed. For example, in the lifting mechanism 30, a mechanical mechanism that converts the rotational motion of the third motor 43 into linear motion can be employed instead of the hydraulic device 35. The mechanical mechanism can be connected to the arm 32.

[0113] The configuration of the work machine 20 can be changed. The work machine 20 is any machine that is actuated by the torque from the PTO 25. The number of electric motors can be changed. For example, in the above-described embodiment, if each configuration is changed so that the second electric motor 42 bears the drive of the lifting mechanism 30, the third electric motor 43 can be canceled.

Claims

1. A tractor comprising: an electric motor as a drive source; a vehicle body capable of being coupled to a work machine to travel with driving force of the electric motor; a battery that supplies electric power to the electric motor; an abnormality detection device that detects an abnormality in an electric system between the battery and the electric motor; and a notification device that notifies by at least one of light and sound, wherein the abnormality detection device stores in advance a necessary electric power and a minimum travel electric power, the necessary electric power being an electric power per unit time necessary to move from a farm side to a road side across a boundary between the farm and a surrounding road surface, the minimum travel electric power being set to a value smaller than the necessary electric power, being an electric power per unit time necessary to travel on a paved road at a minimum value among a plurality of target travel speeds set in advance, the abnormality detection device performs: a determination process that determines whether the vehicle body is located in the farm; a process that causes the notification device to notify of occurrence of the abnormality when it is determined in the determination process that the vehicle body is located in the farm and a first condition set in advance is satisfied; a process that limits an upper limit value of electric power outputtable per unit time from the battery to the necessary electric power when it is determined in the determination process that the vehicle body is located in the farm and a second condition set in advance as a condition indicating occurrence of the abnormality is satisfied; a process that causes the notification device to notify of prohibition of entry into the farm when it is determined in the determination process that the vehicle body is not located in the farm and the first condition is satisfied; and a process that limits the upper limit value of electric power outputtable per unit time from the battery to a minimum travel electric power when it is determined in the determination process that the vehicle body is not located in the farm and the second condition is satisfied, the first condition being that a state of charge SOC of the battery is a first value or less, the second condition being that the state of charge SOC of the battery is a second value smaller than the first value or less, the second value being a value at which a possibility of occurrence of an abnormality in the battery is extremely high, the first condition being satisfied when the second condition is satisfied and also being satisfied in a part of conditions in which the second condition is not satisfied.

2. The tractor according to claim 1, wherein the abnormality detection device prohibits execution of the process of limiting the upper limit value to the necessary electric power when it is determined in the determination process that the vehicle body is located in the farm and in a case where a travel speed of the vehicle body is a prescribed vehicle speed set in advance or less. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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