towing vehicle

Abstract

A tractor has a work machine, a lifting mechanism that lifts the work machine, a motor, a battery, a leakage detection circuit that detects a leakage in the battery, and a control device. The control device controls the lifting mechanism to be in one of a lowered state for positioning the work machine at a position that contacts a ground surface and a raised state for positioning the work machine at a position that is separated from the ground surface. When the leakage detection circuit detects a leakage in the battery while the lifting mechanism is in the lowered state (step S100: YES), the control device performs a state change process to cause the lifting mechanism to be in the raised state (step S120).

Description

TECHNICAL FIELD

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

[0002] Japanese Patent Application Publication No. 2014-143965 discloses a tractor having a battery, a motor, a lift arm, 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 from the motor is input to the rotary tiller via a PTO shaft. The lift arm is actuated by hydraulic pressure. The lift arm lifts the rotary tiller. The rotary tiller is drivable in a state in which the rotary tiller is in contact with the ground of a farm such as a farmland. By driving the rotary tiller in the state in which the rotary tiller is in contact with the ground of the farm, the farm can be tilled. SUMMARY

[0003] In the tractor of Japanese Patent Application Publication No. 2014-143965, the driving source of the rotary tiller is the motor. Therefore, the battery that supplies electric power to the motor employs a battery having a relatively large capacity and a high voltage. Therefore, in the event that some abnormality occurs in the battery and the peripheral circuit thereof, measures need to be taken so that electric current does not flow through other components. However, the tractor such as that of Japanese Patent Application Publication No. 2014-143965 is provided with devices such as the rotary tiller that are not provided in ordinary cars. Furthermore, the tractor such as that of Japanese Patent Application Publication No. 2014-143965 is not limited to traveling on a paved road surface for travel, but also travels in a muddy farm. As described above, the device configuration of the tractor such as that of Japanese Patent Application Publication No. 2014-143965 is different from that of an ordinary car, and the expected traveling environment is also different from that of an ordinary car. Therefore, as measures in the event that some abnormality occurs in the battery and the like, it is not necessarily appropriate to take the same measures as those of an ordinary car.

[0004] A tractor for solving the above-described problem includes a vehicle body, a work machine coupled to the vehicle body, a lift mechanism that lifts the work machine, a motor that is a driving source of the work machine, a battery that supplies electric power to the motor, a leakage detection circuit that detects a leakage in the battery, and a control device that controls the lift mechanism to be in 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 been moved away from the ground. The control device performs state change processing to cause the lift mechanism to be in the raised state in the case where the lift mechanism is in the lowered state and the leakage detection circuit detects the leakage in the battery.

[0005] In the above configuration, by performing the state change processing, the work machine becomes a state of having left the ground. By this, even in a state where a farm is wet and electricity easily flows, leaked electricity is prevented from flowing to the farm via the work machine. Thus, even if an electric leakage occurs in the battery and the peripheral circuit thereof, electricity is prevented from flowing in the work machine or the like.

[0006] The tractor for solving the above problem has a vehicle body, a work machine coupled to the vehicle body, a lifting mechanism that lifts the work machine, an electric motor that serves as a drive source of the work machine, a battery that supplies electric power to the electric motor, an electric leakage detection circuit that detects an electric leakage in the battery, a notification device that performs notification using at least one of light and sound, and a control device that takes the notification device as a control object and controls the lifting mechanism to one of a lowered state in which the work machine is positioned at a position at which the work machine contacts the ground and a raised state in which the work machine is positioned at a position at which the work machine has left the ground. In a case where the electric leakage detection circuit detects an electric leakage in the battery while the lifting mechanism is in the lowered state, the control device performs change notification processing to cause the notification device to notify of a content that the lifting mechanism needs to be changed to the raised state.

[0007] According to the above configuration, by the occupant causing the lifting mechanism to be in the raised state in correspondence with the change notification processing, the work machine becomes a state of having left the ground. By this, even in a state where a farm is wet and electricity easily flows, leaked electricity is prevented from flowing to the farm via the work machine. Thus, even if an electric leakage occurs in the battery and the peripheral circuit thereof, electricity is prevented from flowing in the work machine or the like.

[0008] The tractor can further have a notification device that performs notification using at least one of light and sound. In a case where the electric leakage detection circuit detects an electric leakage in the battery while the lifting mechanism is in the lowered state, the control device performs: estimation processing that estimates a water content of the ground at the time when the electric leakage is detected by the electric leakage detection circuit; determination processing that determines whether the water content is less than a predetermined prescribed water content; and evacuation notification processing that causes the notification device to notify of a content that it is possible to get off in a case where it is determined in the determination processing that the water content is less than the prescribed water content, and causes the notification device to notify of a content that it is not possible to get off in a case where it is determined in the determination processing that the water content is the prescribed water content or more.

[0009] In a case where the water content of the ground is small, electricity is difficult to flow to the ground due to a balance with the resistance of the ground. If it is in such a situation, the occupant is able to get off the vehicle. Also, if getting off, it is possible to get away from the vehicle body, so the safety of the occupant is more reliable. On the other hand, in a case where the water content of the ground is large, electricity easily flows to the ground. According to the above configuration, it is possible to prompt the occupant of a more safe evacuation method.

[0010] The traction vehicle can also have a relay that turns on / off the electrical connection between the battery and the electric motor, and the control device can perform, as a condition that the lifting mechanism is in the raised state, a disconnection process that switches the electrical connection by the relay to be disconnected in a case where it is determined in the determination process that the water content is less than the prescribed water content.

[0011] In the above configuration, after the electrical connection by the relay is switched to be disconnected, the battery becomes a non-energized state. Therefore, from then on, the electric leakage in the battery and its peripheral circuit disappears. By this, it is possible to suppress the electric leakage in the battery and its peripheral circuit to a minimum.

[0012] The control device can perform, as a condition that the lifting mechanism is in the raised state, a limitation process that limits the output from the battery in a case where the leakage detection circuit detects the electric leakage in the battery when the lifting mechanism is in the lowered state in the traction vehicle.

[0013] According to the above configuration, it is possible to suppress the amount of electric leakage in the battery and its peripheral circuit in conjunction with suppressing the output from the battery. BRIEF DESCRIPTION OF DRAWINGS

[0014] The features, advantages, and technical and industrial significance of exemplary embodiments of the application will be described in the specification, together with the drawings, wherein the same reference numerals refer to the same elements throughout the specification. The application is not limited to the embodiments disclosed, but is applicable to practice them in conjunction with the drawings.

[0015] Figure 1 is a schematic view of a traction vehicle.

[0016] Figure 2 is a view showing the electrical structure and power transmission path of a traction vehicle.

[0017] Figure 3 is a flowchart showing the process procedure of a measure process. DETAILED DESCRIPTION

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

[0019] <OVERALL CONFIGURATION OF TRACTION VEHICLE>

[0020] As Figure 1As shown in the figure, the tractor 10 is provided with a vehicle 11, a work machine 20, and a lifting mechanism 30. The vehicle 11 has a plurality of wheels 12 and a vehicle body 13. The plurality of wheels 12 is linked to the vehicle body 13. The vehicle body 13 has a cabin 14. The cabin 14 is a space partitioned by the vehicle body 13. The cabin 14 is a cab into which an occupant enters.

[0021] The work machine 20 is located at the rear when viewed from the vehicle 11. The work machine 20 has a support member 22 and a rotating body 21. The support member 22 is linked to the vehicle body 13 via the lifting mechanism 30. Details of the manner of the linkage are described later. The rotating body 21 has a rotating shaft 21A supported by the support member 22 and a plurality of blades 21B. The rotating shaft 21A is orthogonal to both a direction of travel when the vehicle 11 travels and a direction of gravity. That is, the rotating shaft 21A faces sideways. Each blade 21B is linked to the rotating shaft 21A. Each blade 21B rotates integrally with the rotating shaft 21A. Note that the blade 21B is simplified to a cylindrical shape in Figure 1 The lower portion of the rotating track of the blade 21B is located below when viewed from the lowermost end of the support member 22. If the rotating shaft 21A rotates in a state in which the blade 21B is in contact with the ground 200 of a farm, the farm can be plowed. In addition, the support member 22 and the rotating body 21 are made of metal.

[0022] The lifting mechanism 30 has a plurality of arms 32 and a hydraulic device 35. The plurality of arms 32 is linked to each other. In addition, the plurality of arms 32 links the vehicle body 13 and the support member 22 of the work machine 20.

[0023] The hydraulic device 35 has a hydraulic circuit 36 and a lifting cylinder 37. The hydraulic circuit 36 supplies hydraulic pressure to the lifting cylinder 37. The lifting cylinder 37 expands and contracts in correspondence with the hydraulic pressure from the hydraulic circuit 36. The lifting cylinder 37 is linked to the arm 32. In correspondence with the expansion and contraction of the lifting cylinder 37, each arm 32 acts. In conjunction therewith, as indicated by an arrow D in the figure, Figure 1 The work machine 20 is lifted. Hereinafter, a state of the lifting mechanism 30 for placing the rotating body 21 of the work machine 20 in a position in contact with the ground 200 is referred to as a lowered state. In addition, a state of the lifting mechanism 30 for placing the rotating body 21 in a position that has been separated from the ground 200 is referred to as a raised state. In addition, Figure 1 In the figure, a position of the work machine 20 when the lifting mechanism 30 is in the lowered state is indicated by a solid line. In addition, in the figure, Figure 1 In the figure, a position of the work machine 20 when the lifting mechanism 30 is in the raised state is indicated by a double-dot chain line.

[0024] The tractor 10 has an operation table 16 and a display 15. The operation table 16 is located in the cabin 14. The display 15 is located on the operation table 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.

[0025] As shown in Figure 2 , the tractor 10 has a first switch 51, a second switch 52, and a third switch 56 as the operation section 50. The first switch 51 is a switch that is turned on / off in correspondence with whether the occupant and the tractor 10 are located in the farm. That is, the first switch 51 is a switch for inputting the position information of the tractor 10. The second switch 52 is a switch for switching the lifting mechanism 30 to the lowered state or the raised state. The third switch 56 is a reset switch for eliminating the display of the display 15 in conjunction with the measure processing described later. These first switch 51, second switch 52, and third switch 56 are located on the operation table 16, for example.

[0026] In addition, the tractor 10 has a first lever 53, a second lever 54, an ignition switch 55, and a steering wheel 57 as the operation section 50. The first lever 53 is a member for switching the start / stop of the rotation of the rotating body 21 and the rotation speed of the rotating body 21. The second lever 54 is a member for switching the traveling speed of the tractor 10. The ignition switch 55 is a member for starting the tractor 10. The ignition switch 55 is also sometimes referred to as a start switch. The steering wheel 57 is a steering member for operating the traveling direction of the tractor 10. These first lever 53, second lever 54, ignition switch 55, and steering wheel 57 are located in the cabin 14, for example. Note that the operation section 50 is schematically shown in Figure 2 , with each operation section 50 simplified.

[0027] <Power transmission path of tractor>

[0028] As shown in Figure 2 , the tractor 10 has a first motor 41, a second motor 42, a third motor 43, a power transmission mechanism 19, and a PTO 25. The first motor 41, the second motor 42, and the third motor 43 are motor generators.

[0029] The first motor 41 is a drive source for traveling of the tractor 10. The first motor 41 is linked to the wheel 12 via the power transmission mechanism 19. The power transmission mechanism 19 includes, for example, a reduction mechanism that increases torque and outputs it.

[0030] The second motor 42 is a drive source of the work machine 20. The second motor 42 is linked to the rotating body 21 of the work machine 20 via the PTO 25. The PTO 25 is a device for transmitting the torque of the second motor 42 to the rotating body 21. The PTO 25 includes, for example, a reduction mechanism.

[0031] The third electric motor 43 is the drive source for the hydraulic device 35. The third electric motor 43 is connected to the hydraulic pump in the hydraulic circuit 36. The third electric motor 43 drives the hydraulic pump. It should be noted that, as shown above, the first electric motor 41, the second electric motor 42, and the third electric motor 43 are generator-motors. Therefore, these motors can function as generators. For example, the first electric motor 41 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.

[0032] The tractor unit 10 has 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. The second rotation sensor 62 detects the rotational position of the rotor of the second motor 42. The third rotation sensor 63 detects the rotational position of the rotor of the third motor 43.

[0033] <Electrical Structure of the Tractor>

[0034] like Figure 2 As shown, the tractor unit 10 includes a power supply circuit 99. The power supply circuit 99 includes a first battery 77, a second battery 78, a positive wire 81, a negative wire 82, a positive relay 83, and a negative relay 84. Additionally, the power supply circuit 99 includes a first converter 85, a second converter 86, a first converter 71, a second converter 72, and a third converter 73.

[0035] The first battery 77 is a secondary battery. The first battery 77 is a high-voltage main battery responsible for the movement of the tractor 10, the drive of the working machinery 20, and the drive of the lifting mechanism 30. The first battery 77 receives / transmits power to the first electric motor 41, the second electric motor 42, and the third electric motor 43.

[0036] The high-potential terminal of the first battery 77 is connected to the first converter 85 via the positive wire 81. Conversely, the low-potential terminal of the first battery 77 is connected to the first converter 85 via the negative wire 82. The first converter 85 converts the voltage and outputs it.

[0037] Positive relay 83 is located in the middle of positive line 81. Negative relay 84 is located in the middle of negative line 82. Positive relay 83 and negative relay 84 connect / disconnect the electrical connection between the first battery 77 and the first converter 85.

[0038] 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.

[0039] The third inverter 73 is connected to the first 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 first battery 77 and the third motor 43.

[0040] The second converter 86 is connected to the first battery 77. The second converter 86 is connected in parallel to the first converter 85. The second converter 86 outputs after converting the magnitude of voltage. The second converter 86 is connected to the second battery 78. The second battery 78 is a secondary battery. The second battery 78 is an auxiliary battery whose voltage is lower than that of the first battery 77. The second battery 78 is connected to, for example, the display 15, the operation sections 50, and the control device 100 to be described later, which are low-voltage devices.

[0041] <Leakage Detection Circuit>

[0042] The power supply circuit 99 has a leakage detection circuit 90. The leakage detection circuit 90 is a circuit for detecting a leakage in the first battery 77. The leakage detection circuit 90 includes a first resistor 91, a capacitor 92, a second resistor 93, a transmitter 94, a voltmeter 95, and a monitoring circuit 96. The first resistor 91 is connected between a terminal on the low potential side of the first battery 77 and the vehicle body 13 which is a ground. The first resistor 91 has a resistance value of several mega ohms. The first terminal of the capacitor 92 is connected to the terminal on the low potential side of the first battery 77. The second terminal of the capacitor 92 is connected to the transmitter 94 via the second resistor 93. The transmitter 94 is connected to the vehicle body 13 which is a ground. The transmitter 94 outputs a pulse signal of a specific frequency. The voltmeter 95 detects the voltage at the connection point between the capacitor 92 and the second resistor 93.

[0043] The monitoring circuit 96 monitors the voltage detected by the voltmeter 95. In the case where the voltage detected by the voltmeter 95 is below a prescribed voltage, the monitoring circuit 96 detects a leak in the first battery 77. In this case, the monitoring circuit 96 outputs a leak detection signal E. Here, in the case where a leak occurs in the first battery 77, the resistance value, i.e., the insulation resistance value, of the first resistor 91 decreases. Also, the voltage at the connection point between the capacitor 92 and the second resistor 93 decreases. The maximum value of the resistance value that the first resistor 91 can take in the case where a leak occurs in the first battery 77 is called the leak resistance value. The prescribed voltage described above is the voltage at the connection point between the capacitor 92 and the second resistor 93 when the resistance value of the first resistor 91 becomes the leak resistance value. The prescribed voltage described above is determined in advance, for example, by experiment, in correspondence with the leak resistance value described above. Also, not only in the case of a leak in the first battery 77, but also in the case where a leak occurs in the electrical system of the peripheral circuit of the first battery 77, such as the negative electrode line 82, the voltage at the connection point between the capacitor 92 and the second resistor 93 decreases. In this case, if the voltage is below the prescribed voltage, the monitoring circuit 96 also outputs the leak detection signal E, considering that a leak has occurred in the first battery 77.

[0044] <Outline of Control Device>

[0045] The towing vehicle 10 has a control device 100. The control device 100 can be configured as one or more processors that execute various processes according to computer programs (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 configure the CPU 102 to execute processes. The memory, i.e., the computer readable medium, includes various available media that can be accessed by a computer, which can be general or specific. The control device 100 has a nonvolatile memory, i.e., a storage device, that can be electrically rewritten.

[0046] The control device 100 receives the leak detection signal E from the leak detection circuit 90. In addition, the control device 100 receives the signal P from each operation section 50. Note that the control device 100 receives the signal from each switch and each lever individually, but in the present specification and the drawings, the signal from each operation section 50 is uniformly labeled with the reference sign P.

[0047] The control device 100 receives the detection signal Al of the first rotation sensor 61, the detection signal A2 of the second rotation sensor 62, and the detection signal A3 of the third rotation sensor 63. The control device 100 calculates the rotational speed of the rotor of the first motor 41, i.e., the first rotational speed Smgl, based on the detection signal Al of the first rotation sensor 61. Similarly, the control device 100 calculates the rotational speed of the rotor of the second motor 42, i.e., the second rotational speed Smg2, based on the detection signal A2 of the second rotation sensor 62. Similarly, the control device 100 calculates the rotational speed of the rotor of the third motor 43, i.e., the third rotational speed Smg3, based on the detection signal A3 of the third rotation sensor 63.

[0048] The control device 100 takes the first motor 41 as a control target. The control device 100 causes the tractor 10 to travel or stops the travel of the tractor 10 by controlling the first motor 41. Note that the control device 100 substantially controls the first motor 41 by controlling the first inverter 71. The control device 100 controls the first motor 41 with reference to the first rotational speed Smgl so as to be able to achieve the travel speed of the tractor 10 instructed by the passenger through the second lever 54.

[0049] The control device 100 takes the work machine 20 as a control target. Specifically, the control device 100 controls the work machine 20 through the control of the second motor 42. That is, the control device 100 causes the rotary body 21 to rotate or stops the rotation of the rotary body 21 by controlling the second motor 42. Note that the control device 100 substantially controls the second motor 42 by controlling the second inverter 72. The control device 100 controls the second motor 42 with reference to the second rotational speed Smg2 so as to be able to achieve the rotational speed of the rotary body 21 instructed by the passenger through the first lever 53. The control device 100 stores a plurality of target rotational speeds in advance as information for achieving the rotational speed of the rotary body 21 instructed by the passenger. The target rotational speed is a target value for the rotational speed of the second motor 42. In detail, the control device 100 stores a plurality of target rotational speeds in correspondence with the switching positions of the first lever 53. The control device 100 controls the second motor 42 based on these target rotational speeds.

[0050] The control device 100 takes the lifting mechanism 30 as a control target. Specifically, the control device 100 controls the hydraulic pressure supplied to the lifting cylinder 37 by controlling the third motor 43 and a control valve and the like in the hydraulic circuit 36. This causes the lifting mechanism 30 to be in the raised state or the lowered state. Note that the control device 100 substantially controls the third motor 43 by controlling the third inverter 73. The control device 100 controls the third motor 43 with reference to the third rotational speed Smg3 so as to be able to achieve the state of the lifting mechanism 30 instructed by the passenger through the second switch 52. In addition, the control device 100 opens / closes the control valve in the hydraulic circuit 36 in correspondence with the control of the third motor 43.

[0051] The control device 100 takes the display 15 as a control target. The control device 100 outputs a display signal J for causing the display 15 to display various information to the display 15. The display 15, upon receiving the display signal J, displays contents corresponding to the display signal J.

[0052] The control device 100 takes the positive relay 83 and the negative relay 84 as control targets. That is, the control device 100 switches the on / off of the electrical connection by the positive relay 83 and the negative relay 84 in accordance with the on / off of the ignition switch 55. Note that if the electrical connection by the positive relay 83 and the negative relay 84 is on, the first battery 77 becomes in an energized state. That is, the first battery 77 supplies electric power to each device connected to the first battery 77. On the other hand, if the electrical connection by the positive relay 83 and the negative relay 84 is off, the first battery 77 becomes in a non-energized state. Even in this case, the control device 100 maintains the activated state due to the supply of electric power from the second battery 78. This is the same for the display 15.

[0053] <Outline of Measure Processing>

[0054] The control device 100 can control various parts as control targets even without an instruction from the occupant through each operation section 50. As one of the processes, the control device 100 can execute measure processing. The measure processing is a process for taking measures against the occurrence of a leakage current in the first battery 77. The control device 100 performs the above-described measure processing in a state where the lifting mechanism 30 is in the lowered state and the electrical connection by the positive relay 83 and the negative relay 84 is on. Note that the state where the control device 100 performs the measure processing is mainly a state where the rotating body 21 of the work machine 20 is in operation, that is, is in the process of farming a field.

[0055] As a part of the measure processing, the control device 100 performs signal reception processing, state change processing, estimation processing, determination processing, evacuation notification processing, disconnection processing, and restriction processing.

[0056] In the signal reception processing, the control device 100 receives a leakage current detection signal E from the leakage current detection circuit 90. If the control device 100 receives the leakage current detection signal E, that is, if a leakage current occurs in the first battery 77 and its peripheral circuit, the control device 100 performs each of the state change processing, the estimation processing, the determination processing, the evacuation notification processing, the disconnection processing, and the restriction processing.

[0057] In the state change processing, the control device 100 changes the state of the lifting mechanism 30. At the start of the measure processing, the lifting mechanism 30 is in the lowered state. The control device 100 causes the lifting mechanism 30 in the lowered state to be in the raised state.

[0058] In the estimation processing, the control device 100 estimates the moisture content of the ground 200 at the time when the leakage detection circuit 90 detects the leakage in the first battery 77 (hereinafter referred to as the leakage-time moisture content) K. The value obtained by subtracting the second rotational speed Smg2 from the target rotational speed of the second motor 42 is referred to as a difference. In the estimation processing, the control device 100 calculates the leakage-time moisture content K based on the difference at the time when the leakage detection circuit 90 detects the leakage in the first battery 77 (hereinafter referred to as the leakage-time difference) ΔSmg2. Note that the moisture content of the ground 200 refers to the percentage (%) of moisture contained in the ground 200.

[0059] Now, it is assumed that the lifting mechanism 30 is in the lowered state and the rotating body 21 is rotating. At this time, if the moisture content of the ground 200 is large, the rotating body 21 receives resistance accordingly, and the rotating body 21 becomes difficult to rotate. As a result, the second rotational speed Smg2 deviates from the target rotational speed. That is, the second rotational speed Smg2 becomes lower than the target rotational speed. By utilizing this causal relationship, the moisture content of the ground 200 can be calculated in association with the above-described difference.

[0060] The control device 100 stores, in advance, a moisture content chart as information for calculating the leakage-time moisture content K. The moisture content chart determines the correspondence between the above-described difference and the moisture content of the ground 200. The moisture content chart is, for example, created based on experiments. In the moisture content chart, it is roughly the case that the larger the difference, the larger the moisture content of the ground 200. The control device 100 estimates the leakage-time moisture content K based on this moisture content chart.

[0061] In the determination processing, the control device 100 determines whether or not the leakage-time moisture content K calculated in the estimation processing is less than a prescribed moisture content KZ. The control device 100 stores, in advance, the prescribed moisture content KZ. The prescribed moisture content KZ is, for example, determined through experiments as a moisture content that ensures the safety of the occupant getting off the tractor 10 also in consideration of the resistance corresponding to the moisture content of the ground 200. Further, in the above-described moisture content chart, the moisture content of the ground 200 when the difference is 0 is less than the prescribed moisture content KZ.

[0062] In the evacuation notification processing, the control device 100 causes the display 15 to display the content that it is possible to get off in the case where it is determined in the determination processing that the leakage-time moisture content K is less than the prescribed moisture content KZ. On the other hand, in the evacuation notification processing, the control device 100 causes the display 15 to display the content that it is not possible to get off in the case where it is determined in the determination processing that the leakage-time moisture content K is the prescribed moisture content KZ or more.

[0063] In the disconnection processing, the control device 100 switches the electrical connection by the positive relay 83 and the negative relay 84 to be disconnected in a case where the control device 100 determines that the leakage current is present and the water content K is less than the prescribed water content KZ in the determination processing.

[0064] In the restriction processing, the control device 100 restricts the output from the first battery 77. That is, in the control processing, the control device 100 sets an output upper limit value Wout as an upper limit of the total amount of the electric quantity (Wh) consumed by the first battery 77 per unit time, with respect to the electric quantity (Wh) which is the product of the electric power and the time. The control device 100 controls the first motor 41, the second motor 42, and the third motor 43 in a range where the electric quantity consumed by the first battery 77 does not exceed the output upper limit value Wout. The control device 100 stores the output upper limit value Wout in advance. The output upper limit value Wout is determined, for example, by experiment, as a value satisfying the following three conditions.

[0065] (A) In a state where the leakage current in the first battery 77 is generated, even if the energized state of the first battery 77 continues, no problem occurs in each part of the tractor 10.

[0066] (B) In a state where the leakage current in the first battery 77 is generated, even if the energized state of the first battery 77 continues, it is to the extent that, for example, the amount of discharge to the ground 200 via the wheels 12 can be ignored.

[0067] (C) The tractor 10 is able to climb a slope for entering and exiting the farm.

[0068] Note that, for (C), the inclination angle of the slope differs depending on the farm. The maximum value of the inclination angle that the slope of the farm can take is referred to as the maximum inclination angle. The inclination angle of the slope for (C) is estimated to be the maximum inclination angle.

[0069] <Details of the Measure Processing>

[0070] If the execution condition of the measure processing is satisfied, the control device 100 starts the measure processing. The control device 100 stores the execution condition in advance. The execution condition is satisfied by all of the following three items.

[0071] (i) The tractor 10 is located in the farm.

[0072] (ii) The lifting mechanism 30 is in the lowered state.

[0073] (iii) The electrical connection by the positive relay 83 and the negative relay 84 is on.

[0074] The control device 100 determines whether the execution condition is met based on the signal P from the operation unit 50 and the current control status related to the controlled object. Specifically, when the control device 100 receives a signal P indicating an ON state from the first switch 51, it determines that condition (i) is met. Furthermore, when the control device 100 receives a signal P from the second switch 52 indicating that the lifting mechanism 30 is in a DR state, it determines that condition (ii) is met. Additionally, when the control device 100 receives a signal P indicating an ON state from the ignition switch 55, it determines that condition (iii) is met.

[0075] After the control device 100 initiates the action processing based on the fulfillment of the execution conditions, it proceeds to step S100. For example... Figure 3 As shown, in step S100, the control device 100 determines whether the leakage detection circuit 90 has detected leakage in the first battery 77. Specifically, the control device 100 receives a leakage detection signal E from the leakage detection circuit 90. If the control device 100 cannot receive the leakage detection signal E, it determines that no leakage has been detected (step S100: No). In this case, the control device 100 terminates a series of processes in the action procedure. Then, if the execution condition is met, the control device 100 performs step S100 again.

[0076] On the other hand, in step S100, if the control device 100 receives a leakage detection signal E, it determines that a leakage has been detected (step S100: Yes). In this case, the control device 100 proceeds the process to step S110. It should be noted that the process in step S100 is the signal receiving process described above.

[0077] In step S110, the control device 100 calculates the water content K at the time of leakage. When calculating the water content K at the time of leakage, the control device 100 first refers to the latest target rotational speed and the latest second rotational speed Smg2. Then, the control device 100 calculates the leakage time difference value ΔSmg2 as the value obtained by subtracting the latest second rotational speed Smg2 from the latest target rotational speed. The leakage time difference value ΔSmg2, as described above, is the difference when the leakage detection circuit 90 detects leakage in the first battery 77. Then, the control device 100 refers to a water content chart. Then, the control device 100 calculates the water content corresponding to the leakage time difference value ΔSmg2 in the water content chart as the water content K at the time of leakage. Afterward, the control device 100 advances the process to step S120. It should be noted that the process in step S110 is the above-described estimation process.

[0078] In step S120, the control device 100 controls the second electric motor 42 to stop the revolving body 21 of the work machine 20. That is, the control device 100 stops the second electric motor 42. Further, it is also possible that the rotation of the revolving body 21 is stopped at the point of time when the process of step S120 is performed. In this case, the control device 100 maintains the revolving body 21 in the stopped state. In addition, in step S120, the control device 100 controls the third electric motor 43 and the hydraulic circuit 36 and the like to change the state of the lifting mechanism 30 to the raised state. After the rotation of the revolving body 21 is stopped and the change of the state of the lifting mechanism 30 is completed, the control device 100 advances the process to step S130. Further, the control device 100 can grasp that the rotation of the revolving body 21 is stopped based on the case where the second rotational speed Smg2 is changed to 0. In addition, the control device 100 can grasp that the change of the state of the lifting mechanism 30 is completed based on the case where a certain time elapses after the signal is output to the control valve and the like of the third electric motor 43 and the hydraulic circuit 36. Note that the process of step S120 is the above-described state change process.

[0079] In step S130, the control device 100 determines whether the moisture content K at the time of the electric leakage is less than the prescribed moisture content KZ. Specifically, the control device 100 compares the magnitude relation between the moisture content K at the time of the electric leakage calculated in step S110 and the prescribed moisture content KZ. Then, the control device 100 determines whether the moisture content K at the time of the electric leakage is less than the prescribed moisture content KZ. In the case where the moisture content K at the time of the electric leakage is the prescribed moisture content KZ or more (step S130: No), the control device 100 advances the process to step S210. Note that the process of step S130 is the above-described determination process.

[0080] In step S210, the control device 100 causes the display 15 to start displaying a message. The content of the message includes information of the content that the electric leakage has occurred, the content that it is not possible to get off, and the content that it is necessary to make the tractor 10 travel away from the farm. That is, the control device 100 starts the output of the display signal J related to the above-described content. If the display 15 receives the display signal J, the display 15 starts the display of the above-described content. The control device 100 advances the process to step S220 after performing the process of step S210.

[0081] In step S220, the control device 100 starts the output limitation of the first battery 77. That is, the control device 100 sets the output upper limit value Wout as an upper limit of the amount of electric power consumable by the first battery 77. Note that the second motor 42 is stopped at the time point when the process of step S220 is performed after the second motor 42 is stopped in the process of step S120. Also, the lift mechanism 30 is not operated after the lift mechanism 30 is brought to the ascending state by the process of step S120. That is, the third motor 43 is also stopped at the time point when the process of step S220 is performed. Thus, the control device 100 virtually performs the above-described output limitation with respect to the electric power supply to the first motor 41. The control device 100 advances the process to step S230 after performing the process of step S220.

[0082] In step S230, the control device 100 determines whether the tractor 10 has left the farm. The process of step S230 is a process for ascertaining whether the occupant has driven the tractor 10 outside the farm in response to the display of the display 15 accompanying the process of step S210. The control device 100 determines whether the determination content of step S230 is satisfied in correspondence with the operation state of the first switch 51. The control device 100 performs the process of step S230 again in a case where the control device 100 receives the signal P indicating the on state from the first switch 51, that is, in a case where the tractor 10 is located within the farm (step S230: No). The control device 100 repeats the process of step S230 until the control device 100 receives the signal P indicating the off state from the first switch 51, that is, until the tractor 10 is located outside the farm. The control device 100 advances the process to step S240 if the control device 100 receives the signal P indicating the off state from the first switch 51 (step S230: Yes).

[0083] In step S240, the control device 100 ends the output limitation from the first battery 77. Then, the control device 100 ends the series of processes of the measure process. Note that the process of limiting the output from the first battery 77 during the process from step S220 to the present step S240 is the above-described limitation process.

[0084] Note that the display of the display 15 started in conjunction with the process of step S210 continues until the occupant operates the third switch 56 for resetting. If the third switch 56 for resetting is operated, the control device 100 ends the output of the display signal J to the display 15. In conjunction therewith, the display 15 ends the message display. The timing at which the third switch 56 is operated by the occupant is, for example, various timings such as after the tractor 10 is driven outside the farm, when the tractor 10 is put into a repair factory, and the like. The process from the start of the output of the display signal J to the display 15 in step S210 to the end of the output of the display signal J is the above-described evacuation notification process.

[0085] In addition, in the case where the water content K at the time of the leakage is smaller than the prescribed water content KZ (step S130: YES), the control device 100 advances the process to step S140.

[0086] In step S140, the control device 100 causes the display 15 to start displaying a message. The content of the message includes information of the content that the leakage has occurred, the content that it is possible to get off, and the content that it is necessary to get off the tractor 10 and leave the farm. That is, the control device 100 starts the output of the display signal J related to the above content. The display 15, if receiving the display signal J, starts the display of the above content. The control device 100, after executing the process of step S140, advances the process to step S150.

[0087] In step S150, the control device 100 performs a preparation process for disconnecting the electrical connection by the positive relay 83 and the negative relay 84. Here, at the stage of performing the process of step S150, the electrical connection by the positive relay 83 and the negative relay 84 is ON. Then, under the condition that the electrical connection by the positive relay 83 and the negative relay 84 is ON, the control device 100 is executing a plurality of processes related to each device in the state of being powered by the first battery 77. One example of the plurality of processes is a process for causing the first converter 85 to perform step-up. Before disconnecting the electrical connection by the positive relay 83 and the negative relay 84, it is necessary to end the above process in advance and to stop the operation of each device in advance. By this content, at the time of disconnecting the electrical connection by the positive relay 83 and the negative relay 84, no burden is given to each device. Therefore, in the process of step S150, the control device 100 ends each process which needs to end the process in advance in accordance with the case of disconnecting the electrical connection by the positive relay 83 and the negative relay 84. During this period, the control device 100 restricts the output from the first battery 77. The content of the output restriction is the same as the process performed in the process of steps S220 to S240. That is, the control device 100 also performs the above restriction process in this step S150. The control device 100, after executing the process of step S150, advances the process to step S160.

[0088] In step S160, the control device 100 disconnects the electrical connection by the positive relay 83 and the negative relay 84. Thereafter, the control device 100 ends the series of processes of the measure process. Note that the display of the display 15, which is started as a trigger of the process of step S140, is ended when the occupant operates the third switch 56 for reset, as described above. This is the same as the description related to the process of step S210. The process from the start of the output of the display signal J to the end of the output of the display signal J for the display 15 in step S140 is the evacuation notification process described above.

[0089] <Effects of Embodiments>

[0090] Now assume that the tractor 10 is plowing a farm. That is, the lifting mechanism 30 is in the lowered state, and the rotating body 21 of the work machine 20 is rotating. The control device 100 performs the measure process described above while plowing the farm. If the leakage detection circuit 90 detects the leakage in the first battery 77 (step S100: YES), the control device 100 stops the rotation of the rotating body 21 and makes the lifting mechanism 30 in the raised state (step S120). Thereby, the rotating body 21 is raised to a position away from the ground 200. Thereafter, if the ground 200 has a large amount of water content (step S130: NO), the control device 100 causes the display 15 to display that it is not possible to get off the tractor 10 (step S210). The occupant drives the tractor 10 away from the farm in response to the display. During this period, the control device 100 limits the output from the first battery 77 (step S220, step S240). On the other hand, if the ground 200 has a small amount of water content (step S130: YES), the control device 100 causes the display 15 to display that it is possible to get off the tractor 10 (step S140). Then, the control device 100 disconnects the electrical connection by the positive relay 83 and the negative relay 84 (step S150). In this case, the occupant gets off the tractor 10 and further evacuates outside the farm after getting off the tractor 10.

[0091] Note that, as described above, it is possible that the rotation of the rotating body 21 is stopped at the point in time when the process of step S120 is performed. In this case, the control device 100 performs the process for the case where the water content of the ground 200 is small (step S130: YES). That is, in the case where the rotation of the rotating body 21 is stopped at the point in time when the process of step S120 is performed, the leakage time difference value ΔSmg2 calculated in step S110 is 0. According to the correlation with the content of the water content chart explained earlier, if the leakage time difference value ΔSmg2 is 0, the determination of step S130 is YES. Then, the control device 100 displays the content that it is possible to get off in step S140, and disconnects the electrical connection by the positive electrode relay 83 and the negative electrode relay 84 (step S160). Here, the condition where the rotation of the rotating body 21 is stopped at the point in time when the process of step S120 is performed is the condition where the lifting mechanism 30 is in the lowered state and the rotation of the rotating body 21 is stopped. In this condition, most of the time, the tractor 10 is stopped without traveling. In this case, since each motor is stopped, the output from the first battery 77 is small. In this condition, even if leakage in the first battery 77 occurs, it does not affect the safety of the surroundings of the tractor 10. Therefore, the occupant gets off from the tractor 10 after evacuating in response to the display of the content that it is possible to get off.

[0092] EFFECTS OF THE EMBODIMENTS

[0093] (1) The ground 200 of a farm can be wet and become a state where it is easy to conduct electricity. When the farm is cultivated, the work machine 20 comes into contact with the ground 200 in such a state. Therefore, if leakage in the first battery 77 and the circuit around it occurs when the farm is cultivated, it is possible that electricity flows from the first battery 77 to the work machine 20. In addition, the first battery 77 is a high-voltage battery. Therefore, in the case where leakage in the first battery 77 occurs, the amount of leakage thereof becomes large. Thus, if current flows to the work machine 20 in association with the leakage in the first battery 77, each part of the tractor 10 including the device located on the path can have a problem.

[0094] In the present embodiment, in the case where the leakage detection circuit 90 detects leakage in the first battery 77 (step S100: YES), the lifting mechanism 30 is brought to the raised state (step S120). By this content, the work machine 20 becomes a state where it has been separated from the ground 200. Thus, even if the farm is in a state where it is easy to conduct electricity, it is possible to prevent the leaked electricity from flowing to the farm via the work machine 20. Thus, even if leakage in the first battery 77 and the circuit around it occurs, it is possible to prevent electricity from flowing in the work machine 20 and the like.

[0095] (2) In the case where the water content K is small at the time of the electric leakage, it is difficult for electricity to flow to the ground 200 due to the balance with the resistance of the ground 200. If this is the case, the occupant can get off the tractor 10. Also, if getting off, the occupant can leave the tractor 10, and thus the safety of the occupant is more reliable. On the other hand, in the case where the water content K is large at the time of the electric leakage, electricity easily flows to the ground 200.

[0096] Therefore, in the present embodiment, in the case where the water content K is smaller than the prescribed water content KZ at the time of the electric leakage (step S130: YES), the display 15 is caused to display the content that the occupant should get off and leave (step S140). On the other hand, in the case where the water content K is the prescribed water content KZ or more at the time of the electric leakage (step S130: NO), the display 15 is caused to display the content that the occupant should cause the tractor 10 to travel and leave (step S210). By displaying the above information, a safer leaving method can be prompted to the occupant.

[0097] (3) As described above, in the present embodiment, in the case where the water content K is smaller than the prescribed water content KZ at the time of the electric leakage (step S130: YES), the display 15 is caused to display the content that the occupant should get off and leave (step S140). In response to this display, the occupant gets off the tractor 10. In this case, since the tractor 10 is not operated any more from this point, it is not necessary to cause the first battery 77 to be in the energized state any more.

[0098] Therefore, in the present embodiment, after the display 15 is caused to display the content that the occupant should get off and leave, the electrical connection by the positive relay 83 and the negative relay 84 is rapidly disconnected (step S160). Therefore, from this point, the first battery 77 becomes in the non-energized state. Then, the electric leakage in the first battery 77 and the peripheral circuit disappears. Thus, the electric leakage in the first battery 77 and the peripheral circuit thereof can be suppressed to the minimum.

[0099] (4) In the present embodiment, after the lifting mechanism 30 is in the raised state, the output from the first battery 77 is limited. Specifically, in the case where the water content K is smaller than the prescribed water content KZ at the time of the electric leakage (step S130: YES), the output from the first battery 77 is limited during the preparation processing for disconnecting the electrical connection by the positive relay 83 and the negative relay 84 (step S150). Also, in the case where the water content K is the prescribed water content KZ or more at the time of the electric leakage (step S130: NO), the output from the first battery 77 is limited during the period in which the occupant causes the tractor 10 to travel to outside the farm (step S220, step S240). By limiting the output from the first battery 77 as described above, the amount of the electric leakage in the first battery 77 and the peripheral circuit thereof can be suppressed.

[0100] (5) In the present embodiment, when the water content K at the time of the electric leakage is calculated, the second rotational speed Smg2 is used. The second rotational speed Smg2 is calculated on the basis of the detection signal A2 of the second rotation sensor 62. The second rotation sensor 62 is a sensor that is basically necessary to be provided to the tractor 10 in order to balance the control of the second motor 42. In other words, the second rotation sensor 62 is an existing sensor that is mounted to the tractor 10 even in the case where the water content K at the time of the electric leakage is not calculated. By using the existing sensor as shown in the present embodiment, it is possible to avoid an increase in the number of components and an increase in cost at the time of the estimation of the water content K at the time of the electric leakage.

[0101] <MODIFICATION EXAMPLES>

[0102] The present embodiment can be implemented by being modified as shown below. The present embodiment and the following modification examples can be implemented after being combined with each other within a range where there is no technical contradiction.

[0103] • The processing content of the measure processing is not limited to the example of the above-described embodiment. In the measure processing, the lifting mechanism 30 can be brought to the raised state when the electric leakage detection circuit 90 detects the electric leakage in the first battery 77. For example, as for the processing of step S120, the rotation of the rotating body 21 can not be stopped. Even if the rotation of the rotating body 21 is continued, as long as the lifting mechanism 30 is brought to the raised state, since the working machine 20 is separated from the ground 200, it is possible to prevent the electric current from passing through the working machine 20.

[0104] • As for the processing of step S110, the calculation method of the water content K at the time of the electric leakage is not limited to the example of the above-described embodiment. For example, a moisture sensor for detecting the water content of the ground 200 can be mounted to the tractor 10, and the water content K at the time of the electric leakage can be calculated on the basis of the detection value of the provided sensor.

[0105] • The method of the notification in the processing of step S140 and step S210 is not limited to the example of the above-described embodiment. For example, instead of or in addition to the display of the message in the display 15, voice guidance with respect to the content of the message displayed in the display 15 can be performed. In this case, as long as a speaker that is a notification device that performs the notification by using sound is provided in the tractor 10, it is possible. Also, the speaker can be made a control target of the control device 100.

[0106] • For the processes of steps S140 and S210, notification using a warning light can be performed, for example. In this case, as the notification device that performs notification using light, a warning light dedicated to the electric leakage notification in the first battery 77 can be provided. Also, the warning light can be made a control target of the control device 100. For example, if the colors of the warning lights that are lit in steps S140 and S210 are made different colors, the occupant can be made to recognize different conditions corresponding to the amount of water content K at the time of electric leakage. The notification using the warning light can be used together with at least one of the message display and the voice guidance, or notification using only the warning light can be performed.

[0107] • For the processes of steps S140 and S210, notification using a buzzer can be performed, for example. In this case, as with the modification example of the voice guidance described above, a speaker as the notification device can be provided in the tractor 10. Also, as with the modification example of the warning light, for example, if the tones in steps S140 and S210 are made different tones, the occupant can be made to recognize different conditions corresponding to the amount of water content K at the time of electric leakage. The notification using the buzzer can be used together with at least one of the message display, the voice guidance, and the warning light, or notification using only the buzzer can be performed.

[0108] • In steps S140 and S210, different methods of notification can be adopted.

[0109] • The notification processes in steps S140 and S210 can be omitted. Even in this case, as long as the lifting mechanism 30 is made to be in the raised state in the process of step S120, electric current does not flow in the work machine 20.

[0110] • The method of determining the output upper limit value Wout when the output from the first battery 77 is limited is not limited to the example of the embodiment described above. For example, in order to determine the output upper limit value Wout, only the condition (C) can be considered without considering the conditions (A) and (B). Also, it is not necessary to set a general output upper limit value Wout that can be applied in various farms. That is, if the farm in which the tractor 10 is used for tillage is limited to only a certain specific farm, an output upper limit value Wout that is appropriate for the farm can be provided. For example, the condition (C) can be set to the amount of electric current that can climb a slope of the certain specific farm. The amount of electric current that can climb the slope of the certain specific farm can be grasped from the amount of electric current that was required to climb the slope in the past.

[0111] • As indicated by the content described in the modification example above, the method of determining the output upper limit value Wout can be appropriately changed. As long as the output is limited, the amount of electric leakage in the first battery 77 and the peripheral circuit thereof can be somewhat suppressed regardless of the size of the output upper limit value Wout.

[0112] • The output upper limit value Wout in step S150 and step S220 can be different values.

[0113] • The output upper limit value Wout can also be changed while the output restriction of the first battery 77 is being performed.

[0114] • The output restriction of the first battery 77 can also be cancelled. As described above, even in this case, as long as the lifting mechanism 30 is in the raised state.

[0115] • For the processing of step S160, the control device 100 can notify the content that the ignition switch 55 needs to be turned off instead of the case where the electrical connection by the positive relay 83 and the negative relay 84 is disconnected. In this case, a notification device for notifying the content that the ignition switch 55 needs to be turned off can be provided in the towing vehicle 10. As the notification device, for example, the display 15 of the above-described embodiment can be used, or a speaker or a warning lamp can be provided in the towing vehicle 10 as described in the above-described modification. Also, the notification can be performed in the same manner as the processing of step S140 and step S210, for example, by a message display, a voice guidance, a warning lamp lighting, and a buzzer buzzing. That is, as long as the content that the ignition switch 55 needs to be turned off can be notified by at least one of light and sound.

[0116] • For the processing of step S160, the configuration of the above-described modification can be combined with the configuration of the above-described embodiment. That is, in the case where the occupant does not operate the ignition switch 55 even after the content that the ignition switch 55 needs to be turned off is notified for a certain period, the control device 100 can disconnect the electrical connection by the positive relay 83 and the negative relay 84.

[0117] • The processing of step S160 can be cancelled. That is, the configuration related to the part of disconnecting the electrical connection by the positive relay 83 and the negative relay 84 can be cancelled. As described above, even in this case, as long as the lifting mechanism 30 is in the raised state.

[0118] • For the processing of step S120, the control device 100 can also perform change notification processing that notifies the content that the lifting mechanism 30 needs to be changed to the raised state, instead of causing the lifting mechanism 30 to be in the raised state. In this case, a notification device for notifying the content that the lifting mechanism 30 needs to be changed to the raised state can be provided in the tractor 10. As the notification device, for example, the display 15 of the above-described embodiment can be used, or a speaker or a warning lamp can be provided in the tractor 10 as shown in the above-described modification. Also, the notification can be performed in the same manner as the processing of step S140 and step S210, for example, by a message display, a voice guidance, a warning lamp lighting, and a buzzer buzzing. That is, as long as the content that the lifting mechanism 30 needs to be changed to the raised state can be notified by at least one of light and sound. If the content that the lifting mechanism 30 needs to be changed to the raised state is notified, the occupant causes the lifting mechanism 30 to be in the raised state in response to the notification. Thus, the work machine 20 becomes a state in which it has been separated from the ground 200. Thus, even if the farm is wet and becomes a state in which conduction is easy, it is possible to prevent the leaked electricity from flowing to the farm via the work machine 20. Thus, even if the leakage occurs in the first battery 77 and the peripheral circuit thereof, it is possible to prevent the electricity from flowing in the work machine 20 and the like.

[0119] • In the case where the change of the state of the lifting mechanism 30 is notified as shown in the above-described modification, the processing of disconnecting the electrical connection by the positive relay 83 and the negative relay 84 can be performed in step S160. In this case, the processing of step S160 can be prohibited from being performed until the lifting mechanism 30 is changed to the raised state. That is, there can be a case where the occupant does not operate the second switch 52 even if the notification of the change of the state of the lifting mechanism 30 is performed. If the electrical connection by the positive relay 83 and the negative relay 84 is disconnected in this state, it is not possible to change the work machine 20 to the raised state. In order to prevent this, the electrical connection by the positive relay 83 and the negative relay 84 can be disconnected with the raised state of the lifting mechanism 30 as a condition. The same operation can also be applied to the restriction of the output from the first battery 77. That is, in the case where the change of the state of the lifting mechanism 30 is notified and the restriction of the output from the first battery 77 is performed, the output restriction can be performed with the raised state of the lifting mechanism 30 as a condition.

[0120] • For the processing of step S120, the configuration that notifies the change of the state of the lifting mechanism 30 can be combined with the configuration of the above-described embodiment. That is, the control device 100 can cause the lifting mechanism 30 to be in the raised state in the case where the occupant does not operate the second switch 52 even if a certain period elapses after the content that the lifting mechanism 30 needs to be changed to the raised state is notified.

[0121] • The method for grasping whether the tractor 10 is located at the farm is not limited to the method using the first switch 51. For example, the position information of the GPS and the map information can be used. In this case, the GPS receiver is provided in the tractor 10, and the map information is stored in the control device 100.

[0122] • The configuration of the electric leakage detection circuit 90 is not limited to the example of the above-described embodiment. The electric leakage detection circuit 90 can detect the electric leakage in the first battery 77 and the peripheral circuit thereof as long as it can.

[0123] • The electric leakage detection circuit 90 can be incorporated in a part of the control device 100.

[0124] • The overall configuration of the tractor 10 is not limited to the example of the above-described embodiment. For example, the lift cylinder 37 can be configured to be mechanically driven by the third electric motor 43, not hydraulically. In this case, as long as the mechanism that converts the rotational motion of the third electric motor 43 into the linear motion exists between the third electric motor 43 and the lift cylinder 37.

[0125] • As for the operation portion 50, the operation portion configured as a switch can be changed to a lever, or the reverse change can be made. The operation portion 50 can be a component that can input the instruction from the occupant for making the various portions of the tractor 10 act to the control device 100.

[0126] • The configuration of the work machine 20 can be changed. The work machine 20 can be any machine that acts using the torque from the PTO 25.

[0127] • The tractor 10 can be configured as a hybrid vehicle that uses the electric motor and the engine as the drive source.

[0128] • The use site of the tractor 10, that is, the site where the work corresponding to the use of the work machine 20 is performed, is not limited to the farm. Regardless of the use site of the tractor 10, when the electric leakage in the first battery 77 and the peripheral circuit thereof occurs in the state where the lift mechanism 30 is in the lowered state, the lift mechanism 30 is made to be in the raised state, and thus the current can be prevented from flowing in the work machine 20.

Claims

1. A tractor having: a vehicle body; a work machine coupled to the vehicle body; a lifting mechanism that lifts the work machine; an electric motor that serves as a drive source of the work machine; a battery that supplies electric power to the electric motor; a leakage detection circuit that detects a leakage in the battery; a control device that controls the lifting mechanism as a control target; and a notification device that performs notification using at least one of light and sound, the control device controls the lifting mechanism to one of a lowered state for positioning the work machine at a position in contact with the ground and a raised state for positioning the work machine at a position away from the ground, in a case where the leakage detection circuit detects a leakage in the battery while the lifting mechanism is in the lowered state, the control device performs: a state change process that causes the lifting mechanism to be in the raised state; an estimation process that estimates a water content of the ground at a time when the leakage detection circuit detects the leakage; a determination process that determines whether the water content is less than a predetermined prescribed water content; and an evacuation notification process that causes the notification device to notify of a content that evacuation is possible in a case where the determination process determines that the water content is less than the prescribed water content, and causes the notification device to notify of a content that evacuation is impossible in a case where the determination process determines that the water content is the prescribed water content or more.

2. The tractor according to claim 1, further having a relay that turns on / off an electrical connection between the battery and the electric motor, in a case where the determination process determines that the water content is less than the prescribed water content, the control device performs a disconnection process that switches the electrical connection by the relay to be disconnected, with the condition that the lifting mechanism is in the raised state.

3. The tractor according to claim 1 or 2, in a case where the leakage detection circuit detects a leakage in the battery while the lifting mechanism is in the lowered state, the control device performs a limitation process that limits an output from the battery, with the condition that the lifting mechanism is in the raised state.

4. A tractor having: a vehicle body; a work machine coupled to the vehicle body; a lifting mechanism that lifts the work machine; an electric motor that serves as a drive source of the work machine; a battery that supplies electric power to the electric motor; a leakage detection circuit that detects a leakage in the battery; a notification device that performs notification using at least one of light and sound; and a control device that controls the notification device as a control target, the control device controls the lifting mechanism to one of a lowered state for positioning the work machine at a position in contact with the ground and a raised state for positioning the work machine at a position away from the ground, in a case where the leakage detection circuit detects a leakage in the battery while the lifting mechanism is in the lowered state, the control device performs: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The change notification process causes the notification device to notify that the lifting mechanism needs to be changed to the raised state; The estimation process estimates a water content of the ground at the time when the leakage detection circuit detects the leakage; The determination process determines whether the water content is less than a predetermined prescribed water content; and The evacuation notification process causes the notification device to notify that it is possible to get off in a case where the determination process determines that the water content is less than the prescribed water content, and causes the notification device to notify that it is not possible to get off in a case where the determination process determines that the water content is the prescribed water content or more.

5. The tow vehicle of claim 4, wherein, In a case where the leakage detection circuit detects the leakage in the battery while the lifting mechanism is in the lowered state, the control device performs a restriction process that restricts an output from the battery, with the condition that the lifting mechanism is in the raised state.

Images