Electric work vehicle

Abstract

The present invention comprises: a battery 4; an electric motor M1 that transmits power to traveling devices 10,11 using the power of the battery 4; a temperature regulating means H that regulates the temperature of the battery 4 using electricity; and a temperature detecting means 4B that detects the temperature of the battery 4. The temperature regulating means H operates to increase the temperature of the battery 4 if the temperature detected by the temperature detecting means 4B is lower than a first set temperature.

Description

Electric Work Vehicle

[0001] The present invention relates to an electric work vehicle equipped with a battery and an electric motor that transmits power to a traveling device using electric power from the battery.

[0002] 2. Description of the Related Art In electric tractors, which are an example of electric work vehicles, some have been equipped with a cooling device for cooling the battery, as disclosed in, for example, Patent Document 1.

[0003] JP2023-95636 A

[0004] In the above-mentioned electric work vehicle, managing the battery temperature is important to ensure that the battery can be properly charged and discharged. The electric tractor disclosed in Patent Document 1 is equipped with a cooling device that cools the battery, and measures can be taken to prevent high battery temperatures. However, in cold regions, etc., if the battery is operated at a low temperature, there is a risk that the battery will not be able to properly charge and discharge. Therefore, in addition to cooling the battery, a configuration is also required to warm the battery when the battery temperature is low. In particular, in a low-temperature environment below the battery's allowable temperature range, the battery will not operate, and it will not be possible to drive the electric traction motor using the battery, nor will it be possible to charge the battery.

[0005] An object of the present invention is to provide an electric work vehicle that is capable of adjusting the temperature of the battery even in a low-temperature environment.

[0006] The characteristic configuration of the electric work vehicle of the present invention is that it is equipped with a battery, an electric motor that transmits power to the traveling device using the power of the battery, a temperature adjustment means that adjusts the temperature of the battery using the power, and a temperature detection means that detects the temperature of the battery, and the temperature adjustment means operates to increase the temperature of the battery if the temperature detected by the temperature detection means is lower than a first set temperature.

[0007] According to the present invention, when the battery temperature detected by the temperature detection means is lower than a first set temperature, the temperature adjustment means is activated to raise the battery temperature. The first set temperature is set to, for example, a low temperature equivalent to the lower limit of the battery's allowable temperature range. If the battery temperature is lower than the first set temperature, the battery may not operate. However, by using the temperature adjustment means, it is possible to adjust the battery temperature and make the battery operable.

[0008] Therefore, it is possible to provide an electric work vehicle that can adjust the battery temperature even in a low-temperature environment.

[0009] In the present invention, it is preferable that the temperature adjusting means is operated by power supplied from an external power source.

[0010] According to this configuration, even in a situation where the battery cannot operate in a low-temperature environment, the temperature of the battery can be increased by using power supplied from an external power source.

[0011] In the present invention, it is preferable that the temperature adjustment means operates using power supplied from the battery so that the temperature of the battery increases when the temperature of the battery detected by the temperature detection means is higher than the first set temperature and lower than a second set temperature that is higher than the first set temperature.

[0012] According to this configuration, the battery is operable when the battery temperature is higher than the first set temperature, and the temperature adjustment means can be operated using the battery's power. As a result, it is possible to avoid unnecessarily prolonged heating operation of the temperature adjustment means using an external power source, and by using the power stored in the battery, it is possible to reduce unnecessary power consumption.

[0013] In the present invention, it is preferable that the temperature adjusting means stops the temperature raising operation for the battery when the temperature of the battery rises to or exceeds the second set temperature.

[0014] According to this configuration, it is possible to prevent unnecessary consumption of not only power from an external power source but also battery power.

[0015] In the present invention, it is preferable that the temperature adjustment means includes a circulation flow path through which a refrigerant circulates through the inside of the battery, and a heater that heats the refrigerant, and that the heater performs heating operation using supplied power.

[0016] According to this configuration, the heating medium heated by the heater circulates through the circulation path, thereby raising the temperature of the battery. This configuration makes it possible to heat the battery with better thermal efficiency than when the battery is heated directly by the heat of the heater.

[0017] In the present invention, it is preferable that a power conversion device is provided that converts power supplied from an external power source into on-board power, and that the temperature adjustment means switches the power supply state so that, if the temperature of the battery is lower than the first set temperature, the temperature adjustment means converts the power into power that can be supplied to the heater as on-board power and supplies it to the heater, and if the temperature of the battery is higher than the first set temperature, the temperature adjustment means converts the power into power that can be supplied to the battery as on-board power and supplies it to the battery.

[0018] With this configuration, the supply state of power from the external power source can be switched between supplying power to the heater and supplying power to the battery, allowing for good operation of the temperature adjustment means at low temperatures and charging of the battery during normal operation.

[0019] In the present invention, it is preferable that the battery is not charged if the temperature of the battery is lower than the first set temperature.

[0020] According to this configuration, the battery is not charged when the temperature is lower than the first set temperature, which makes it easier to avoid problems such as early deterioration of the battery.

[0021] In the present invention, it is preferable that the battery not be discharged if the temperature of the battery is lower than the first set temperature.

[0022] According to this configuration, the battery does not discharge in a low temperature state that is lower than the first set temperature, so that it is easy to avoid inconveniences such as early deterioration of the battery.

[0023] In the present invention, it is preferable that the battery includes a plurality of unit batteries, the temperature detection means is configured to detect the temperature of each of the plurality of unit batteries, and the temperature adjustment means is activated when the lowest temperature of the plurality of unit batteries is lower than the first set temperature.

[0024] In a battery having multiple unit cells, the characteristics of each unit cell vary, and so do temperature changes. Therefore, in this configuration, the lowest temperature detected for each of the multiple unit cells is used to determine whether to activate the temperature adjustment means. For example, if the average of multiple temperatures is used, some unit cells with temperatures lower than the average may be adversely affected and become inoperable. However, in this configuration, such disadvantages are avoided and temperature adjustment can be performed satisfactorily.

[0025] In the present invention, it is preferable that power can be transmitted to a working device using the electric power of the battery.

[0026] According to this configuration, power is transmitted to the working device using an electric motor, hydraulic equipment, or the like that is powered by the battery, and various works can be performed while the vehicle body is traveling.

[0027] In the present invention, it is preferable that a second battery different from the battery is provided and capable of supplying power to the electrical equipment, and that the second battery is capable of supplying power to the electrical equipment at a temperature lower than the first set temperature.

[0028] According to this configuration, even if the battery temperature is below the first set temperature, power is also supplied from the second battery to the electrical components for operating the temperature adjustment means, so that the temperature adjustment means can be operated smoothly.

[0029] In the present invention, it is preferable that the battery is a lithium ion battery and the second battery is a lead storage battery.

[0030] According to this configuration, a lithium-ion battery has a narrow operating temperature range and is likely to become inoperable below the first set temperature. In contrast, a lead-acid battery has a wider operating temperature range than a lithium-ion battery and can supply power even below the first set temperature. Therefore, by using a lead-acid battery as the second battery, power can be supplied to the electrical components that operate the temperature adjustment means even below the first set temperature.

[0031] Fig. 1 is an overall side view of an electric tractor. Fig. 2 is an overall plan view of an electric tractor. Fig. 3 is a block diagram showing a power system and a power system of an electric tractor. Fig. 4 is a front view of a main part showing a battery and devices arranged around the battery. Fig. 5 is a side view of a main part showing a battery, a temperature control unit, etc. Fig. 6 is a flowchart of a control operation.

[0032] An embodiment of an electric work vehicle according to the present invention will be described with reference to the drawings, with the case being that it is applied to an electric tractor as an example of an electric work vehicle. In the following description, unless otherwise specified, the direction of arrow F in the drawings will be referred to as "forward," the direction of arrow B as "rear," the direction of arrow L as "left," and the direction of arrow R as "right." Furthermore, the direction of arrow U in the drawings will be referred to as "upward," and the direction of arrow D as "downward."

[0033] 1 and 2, right and left front wheels 10 (corresponding to the "traveling device" according to the present invention) are provided at the front of the machine body 1, and right and left rear wheels 11 (corresponding to the "traveling device" according to the present invention), which are the rear traveling devices, are provided at the rear of the machine body 1. The machine body 1 supports the front wheels 10 and the rear wheels 11.

[0034] The machine body 1 has a front frame 2, a housing frame A, and a transmission case 15. The front frame 2 is connected to the front of the housing frame A, and the transmission case 15 is connected to the rear of the housing frame A, thereby forming the frame structure of the machine body 1. Electric motors M1 and M2, which serve as power sources, are housed in the housing frame A.

[0035] A front axle case 10A is attached to the front frame 2, and the right and left front wheels 10 are supported by the front axle case 10A. The front frame 2 supports the front axle case 10A. A transmission case 15 includes an axle case that transmits power to the left and right rear wheels 11, and the transmission case 15 supports the left and right rear wheels 11.

[0036] The driver's section 3, in which the operator sits, is provided above the accommodation frame A and the transmission case 15. A ROPS frame 31 is attached to the transmission case 15, extends upward, and is provided at the rear of the driver's section 3. A first battery 4 (corresponding to the "battery" according to the present invention) for driving the electric motors M1, M2 is attached to the front frame 2, and a hood 12 is provided to cover the first battery 4.

[0037] The first battery 4 is mounted and supported on the front frame 2. The front frame 2 is used to support both the first battery 4 and the front axle case 10A of the front wheel 10. The first battery 4 stores electricity for traveling, working, and hydraulic drive.

[0038] 4, the hood 12 has a swinging portion 12A that swings open and closed, and a fixed portion 12B that is fixed below the swinging portion 12A. The swinging portion 12A can swing about a horizontal axis along the left-right direction of the vehicle body, allowing the hood 12 to be opened and closed. When the swinging portion 12A is in the closed state, the first battery 4 is covered by the hood 12.

[0039] As shown in Fig. 2, the vehicle is equipped with an electric motor M1 for traveling and an electric motor M2 for working and hydraulic drive. The electric motor M1 receives power from the first battery 4 to drive the front wheels 10 and rear wheels 11. The electric motor M2 receives power from the first battery 4 to drive the working device as described below.

[0040] Two inverters 14A, 14B are provided corresponding to the two electric motors M1, M2. The electric motors M1, M2 are disposed on the rear side of the vehicle body relative to the first battery 4. The inverters 14A, 14B are provided laterally outward of the electric motors M1, M2 on the vehicle body.

[0041] The first battery 4 supplies power to two inverters 14A, 14B. Each of the inverters 14A, 14B receives DC current from the first battery 4 and converts it into three-phase AC current. The left inverter 14A converts the DC power of the first battery 4 into AC power and supplies it to the electric motor M1, thereby operating the electric motor M1. The right inverter 14B converts the DC power of the first battery 4 into AC power and supplies it to the electric motor M2, thereby operating the electric motor M2.

[0042] The left and right loader attachment portions 8 are respectively connected to the left and right side portions of the storage frame A. A working device (not shown) such as a front loader is detachably attached to each of the left and right loader attachment portions 8.

[0043] 1 and 2, the driving section 3 is provided behind the first battery 4 and the hood 12. The driving section 3 is provided with a ROP frame 31, a driver's seat 32, a steering wheel 33 for steering the front wheels 10, a step 34, a floor 35, a charging socket 36, a work travel operating tool 37, a display unit 38, and the like.

[0044] The driving section 3 is supported by a housing frame A and a transmission case 15. The electric motors M1, M2 are arranged below a floor 35 of the driving section 3 and inside the housing frame A, side by side.

[0045] Although not described in detail, the work travel operating device 37 includes an accelerator operating device for adjusting the travel speed, and operating devices for adjusting the rotational speed of the mid PTO shaft 16A and rear PTO shaft 16B, which will be described later. This allows the operator to perform various driving operations using the driving unit 3. The display unit 38 displays, for example, the vehicle body's travel status, work status, information about the first battery 4 (charge level and temperature), etc.

[0046] The charging socket 36 is provided to the right of the control handle 33 and directly above the floor 35. When the operator inserts the charger adapter into the charging socket 36, the first battery 4 is charged. The charging socket 36 receives power for charging the first battery 4. The charging socket 36 supports normal charging, which receives alternating current power (AC power) from an external power source, and fast charging, which receives high-voltage direct current power for fast charging. The fast charging standard may be, for example, CHAdeMO, CCS2, GB / T, ChaoJi, NACS, etc.

[0047] The housing frame A, the electric motors M1, M2, the inverters 14A, 14B, and the transmission case 15 are disposed below the floor 35. The first battery 4 is disposed above the floor 35. In addition, the first battery 4 is provided forward of the driving unit 3 so that the rear end of the first battery 4 is located forward of the front ends of the electric motors M1, M2.

[0048] 3, the power transmission device T is provided with a power transmission mechanism 15A for traveling, a power transmission mechanism 15B for working, and a hydraulic pump 15C. The transmission case 15 houses the power transmission mechanism 15A for traveling, the power transmission mechanism 15B for working, and the hydraulic pump 15C. In other words, the power transmission device T has the transmission case 15, the power transmission mechanism 15A for traveling, the power transmission mechanism 15B for working, and the hydraulic pump 15C.

[0049] The vehicle is provided with a mid PTO shaft 16A and a rear PTO shaft 16B. The work power transmission mechanism 15B receives rotational power from the electric motor M2 and distributes the rotational power to the mid PTO shaft 16A and the rear PTO shaft 16B.

[0050] The work power transmission mechanism 15B transmits work power from the electric motor M2 to the mid PTO shaft 16A and the rear PTO shaft 16B. The mid PTO shaft 16A and the rear PTO shaft 16B then supply the work power to the work device.

[0051] The hydraulic pump 15C receives rotational power from the electric motor M2 and is driven to rotate. For example, if a front loader is attached as the working device, hydraulic oil is supplied by the hydraulic pump 15C and the working device (front loader) is driven by the electric motor M2.

[0052] The implement connected to the mid-PTO shaft 16A may be, for example, a brush cutter, a rotary rake, a leaf cutter, a sprayer, etc. The mid-PTO shaft 16A may also be used as a front PTO shaft for implements attached to the front of the machine body 1. The implement connected to the rear PTO shaft 16B may be a rotary tiller, an inter-cultivation device, a ridge-making device, etc.

[0053] [Regarding the drive system of the electric tractor] As shown in Figure 3, the electric tractor is provided with a control device 20 that controls the drive of the electric motors M1, M2 in response to the operation of the work travel operating device 37. The control device 20 is a core element of the control system of the electric tractor, and is equipped with a microcomputer to execute various operational processes. The control device 20 is equipped with a temperature adjustment control section in the form of a control program that controls the operation of a temperature adjustment device for the battery, which will be described later.

[0054] The control device 20 is connected to the charge / discharge control unit 4A of the first battery 4, the inverters 14A and 14B, the electric motors M1 and M2, the charge control unit 22, the power conversion device 23, the work travel operating tool 37, the display unit 38, etc. so as to be able to communicate data via, for example, a CAN (Controller Area Network) type signal harness 21. The power conversion device 23 includes an OBC (on-board charger) and a DC / DC converter, and converts power supplied from an external power source into on-board power.

[0055] The control device 20 outputs command signals to the inverters 14A, 14B in response to commands from the work traveling operating device 37. The inverter 14A controls the output of the electric motor M1 by adjusting the three-phase AC power (voltage value, frequency, current value, etc.) supplied from the first battery 4 to the electric motor M1 in response to the command signal from the control device 20. The inverter 14B controls the output of the electric motor M2 by adjusting the three-phase AC power supplied from the first battery 4 to the electric motor M2 in response to the command signal from the control device 20.

[0056] The control device 20 controls the operation of the display unit 38. The display unit 38 displays the operating status of the electric motors M1, M2, information about the first battery 4, and the like.

[0057] The first battery 4 is a lithium-ion battery. Although not shown, the first battery 4 is configured by stacking a large number of small, low-voltage unit cells. The output voltage of the first battery 4 is, for example, 400 volts. The multiple unit cells are housed in a sealed storage case.

[0058] The first battery 4 is electrically connected to the power distribution unit 13. The power distribution unit 13 is also electrically connected to the charging socket 36, the inverters 14A and 14B, and the power conversion device 23. Therefore, the power distribution unit 13 functions as a hub that distributes power from the first battery 4 to the inverters 14A and 14B and the power conversion device 23. The power distribution unit 13 also has the function of transmitting power from the charging socket 36 to the first battery 4.

[0059] The first battery 4 is provided with a charge / discharge control unit 4A. The charge / discharge control unit 4A is configured to control the discharge current, charge current, etc. of the first battery 4 based on the output voltage, receiving voltage, heat generation temperature, etc. of the first battery 4.

[0060] The first battery 4 is provided with a temperature detection unit 4B as a temperature detection means for detecting the temperature of the first battery 4. Although not described in detail, the temperature detection unit 4B is configured to detect the temperature of each of the plurality of unit batteries.

[0061] The power conversion device 23 is electrically connected to both the charging socket 36 and the power distribution unit 13. The charging control unit 22 adjusts the power supplied from the charging socket 36. The charging control unit 22 may be, for example, a power module or PLC (Programmable Logic Controller) having a microcomputer that executes a program based on a control signal from the control device 20, or may be a relay circuit that operates based on an electrical signal from the control device 20. The charging control unit 22 controls the charging voltage and charging current for the first battery 4 when charging (including rapid charging) the first battery 4. The charging control unit 22 adjusts the power received from the charging socket 36 and supplies it to the first battery 4 as charging power.

[0062] In addition to the first battery 4, the electric tractor is equipped with a second battery 24 that supplies power to the control device 20 and other electrical equipment. The second battery 24 is a lead-acid battery. The output voltage of the second battery 24 is lower than the output voltage of the first battery 4, and supplies low-voltage (e.g., 12 volts) power to drive the electrical equipment.

[0063] The second battery 24 is charged with power supplied from the first battery 4 via a DC / DC converter provided in the power conversion device 23. The power conversion device 23 is electrically connected to each of the first battery 4 and the second battery 24, and is capable of receiving power from the first battery 4, dropping the voltage, and transmitting the power to the second battery 24. Thus, the second battery 24 can be charged with power received from the first battery 4 via the power conversion device 23.

[0064] The high-voltage equipment that receives power from the first battery 4 at high voltage tends to become hot due to heat generation. For this reason, the electric work vehicle is provided with a high-voltage equipment cooling device 26 for cooling the high-voltage equipment. The high-voltage equipment cooling device 26 is provided with a high-voltage equipment radiator 26A and pumps 26B and 26C. The pumps 26B and 26C are connected in series.

[0065] Pumps 26B, 26C pump a refrigerant that cools high-power devices that operate on electric power, such as inverters 14A, 14B, electric motors M1, M2, and power conversion device 23. When pumps 26B, 26C operate, the refrigerant flows through cooling channels in the high-power devices, such as inverters 14A, 14B, electric motors M1, M2, and power conversion device 23, to cool the high-power devices. The refrigerant heated by the high-power devices is then cooled by heat dissipation in high-voltage device radiator 26A. The order of the cooling channels in the high-power devices can be changed as appropriate.

[0066] As shown in FIG. 5 , the high-voltage equipment radiator 26A and the battery radiator 25A are arranged side by side in front of the first battery 4. A cooling fan 29 is provided behind the high-voltage equipment radiator 26A and the battery radiator 25A and in front of the first battery 4. The cooling fan 29 generates cooling air to cool the refrigerant inside the high-voltage equipment radiator 26A and the battery radiator 25A. A front grille 12f (see FIG. 1 ) is provided at the front of the hood 12, and outside air is introduced as cooling air from in front of the battery radiator 25A. The cooling fan 29 generates cooling air that flows rearward. The cooling air promotes heat dissipation from the battery radiator 25A and the high-voltage equipment radiator 26A.

[0067] [Regarding battery temperature adjustment] The electric tractor of this embodiment is equipped with a temperature adjustment means H that adjusts the temperature of the first battery 4 using electricity, and the temperature adjustment means H operates to increase the temperature of the first battery 4 if the temperature of the first battery 4 detected by the temperature detection unit 4B is lower than a first set temperature.

[0068] If the temperature of the first battery 4 is lower than a first set temperature, the temperature adjustment means H converts the power supplied from the external power source into power that can be supplied to the heater (battery heater 25C) as in-vehicle power and supplies the power to the heater (battery heater 25C). If the temperature of the first battery 4 is higher than the first set temperature, the temperature adjustment means H switches the power supply state so that the power supplied from the external power source is converted into power that can be supplied to the first battery 4 as in-vehicle power and supplies the power to the first battery 4.

[0069] The temperature adjusting means H includes a temperature adjusting device 25 for managing the temperature of the first battery 4, and a control device 20 (specifically, a temperature adjustment control unit that controls the operation of the temperature adjusting device).

[0070] The temperature adjustment device 25 will now be described. As shown in Fig. 5, the temperature adjustment device 25 is provided near the first battery 4. As shown in Fig. 3, the temperature adjustment device 25 includes a battery radiator 25A, a reservoir tank 25B, a battery heater 25C, a pump 25D, and a circulation flow path through which a refrigerant circulates inside the first battery 4 and through the above-mentioned devices. The refrigerant is, for example, an insulating oil.

[0071] The battery radiator 25A is provided between the reservoir tank 25B and an outlet of a temperature control flow path of the circulation flow path located inside the first battery 4. Therefore, the refrigerant heated in the temperature control flow path inside the first battery 4 is cooled by heat dissipation in the battery radiator 25A and returned to the reservoir tank 25B.

[0072] A refrigerant is stored in the reservoir tank 25B. The pump 25D pressurizes and pumps the refrigerant so that it circulates within the first battery 4. The battery heater 25C heats the refrigerant to raise the temperature of the first battery 4. When the pump 25D is operating, the refrigerant circulates from the reservoir tank 25B through the battery heater 25C, the pump 25D, a temperature control flow path inside the first battery 4, and the battery radiator 25A, in that order.

[0073] The control device 20 is configured to operate the temperature adjustment device 25 with power supplied from an external power source when the temperature of the first battery 4 detected by the temperature detection unit 4B is lower than a first set temperature, so as to increase the temperature of the first battery 4. The first set temperature is set to a temperature equivalent to the lower limit of the allowable temperature range of the first battery 4, for example, −19°C.

[0074] If the temperature of the first battery 4 detected by the temperature detection unit 4B is higher than a first set temperature and lower than a second set temperature (e.g., 0°C) that is higher than the first set temperature, the control device 20 operates the temperature control device 25 using power supplied from the first battery 4 so that the temperature of the first battery 4 rises.

[0075] When the temperature of the first battery 4 is lower than the first set temperature, the control device 20 operates the temperature control device 25 using power supplied from an external power source, and then when the temperature of the first battery 4 rises to or above the second set temperature, the control device 20 stops the temperature control device 25's heating operation.

[0076] Specifically, if the temperature of the first battery 4 is lower than the first set temperature, the control device 20 converts the power (AC power) from the external power source into power that can be supplied to the battery heater 25C of the temperature control device 25 and supplies it to the battery heater 25C, and if the temperature of the first battery 4 is higher than the first set temperature, the control device 20 switches the power supply state so that the power (AC power) from the external power source is converted into power that can be supplied to the first battery 4 and supplies it to the first battery 4.

[0077] The first battery 4 is not charged or discharged if the temperature of the first battery 4 detected by the temperature detection unit 4B is lower than the first set temperature.

[0078] The charging process performed by the control device 20 will be specifically described below with reference to the flowchart of FIG.

[0079] When the charging operation is started, the control device 20 determines whether the temperature of the first battery 4 detected by the temperature detection unit 4B is lower than the second set temperature Ts2 (0°C) (step #1), and whether it is lower than the first set temperature Ts1 (-19°C) (step #2). At this time, the control device 20 determines whether the lowest temperature among the plurality of unit batteries is the temperature of the first battery 4 and whether it is lower than the first set temperature Ts1.

[0080] If the temperature of the first battery 4 is lower than the first set temperature Ts1 (-19°C) and there is power (alternating current power) (AC) from an external power source (step #3), the power converter 23 (OBC) is activated to convert the AC power into DC power suitable for the battery heater 25C, and supplies power to the battery heater 25C to operate it (steps #4 and #5). That is, the power distribution unit 13 switches the energization state to switch the power supply state. At this time, the connection with the first battery 4 is cut off, and the first battery 4 is not charged or discharged.

[0081] When the temperature of the first battery 4 is lower than the first set temperature Ts1 (-19°C), it is expected that the viscosity of the heat transfer medium is high, so it is advisable to operate the battery heater 25C and then operate the pump 25D when the temperature of the refrigerant has risen and its viscosity has decreased.

[0082] When the temperature of the first battery 4 becomes higher than the first set temperature Ts1 (-19°C), the first battery 4 is switched to an operable state (steps #6 and #7). That is, the power distribution unit 13 switches the energization state to connect with the first battery 4, and the first battery 4 is placed in a state where it can be charged and discharged. Then, the power conversion device 23 (OBC) is operated to convert AC power into DC power suitable for the first battery 4, and the power supply state is switched to a state where the power is supplied to the first battery 4.

[0083] Thereafter, a charging current corresponding to the power consumption by the battery heater 25C is requested from the first battery 4, and the battery heater 25C is operated using the power from the first battery 4 (step #8). At this time, the pump 25D is also operated. This causes the temperature of the first battery 4 to rise.

[0084] When the temperature of the first battery 4 becomes higher than the second set temperature Ts2 (0°C), the operation of the battery heater 25C is stopped and the system transitions to normal charging processing (steps #9 and #10). After transitioning to normal charging processing, the system checks the state of charge of the first battery 4, and when the state of charge (SOC) decreases, charging from the external power source is performed with the external power source connected to the charging socket 36, and when charging is completed, the charging operation ends.

[0085] In step #3, if an external power source (AC power) is not connected to the charging socket 36, operation is not possible and charging is not possible, the connection between the power distribution unit 13 and the first battery 4 is severed, and the first battery 4 becomes unable to be charged or discharged (step #11).

[0086] Other Embodiments The present invention is not limited to the configurations exemplified in the above-described embodiments, and other representative embodiments of the present invention will be exemplified below.

[0087] (1) When the temperature of the first battery 4 is lower than the first set temperature Ts1 (-19°C), the temperature adjustment means H may be operated using power from the second battery 24 instead of power supplied from an external power source.

[0088] (2) When the temperature of the first battery 4 becomes higher than the first set temperature Ts1, the temperature adjustment means H may be operated using power supplied from an external power source instead of power supplied from the first battery 4.

[0089] (3) When the temperature of the first battery 4 is lower than the first set temperature Ts1 and the temperature adjustment means H performs a temperature-raising operation, the temperature-raising operation may be continued even after the temperature of the first battery 4 rises to or above the second set temperature Ts2.

[0090] (4) As the temperature adjustment means H, instead of a configuration including a circulation flow path through which the refrigerant circulates and a heater that heats the refrigerant, a configuration including an electric heater that heats from the outer periphery of the storage case of the first battery 4 may also be used.

[0091] (5) The temperature adjusting means H may be configured to operate when the average temperature of the plurality of unit batteries is lower than the first set temperature.

[0092] (6) The first battery 4 may be a battery of a type other than a lithium ion battery, and the second battery 24 may be a battery of a type other than a lead storage battery.

[0093] (7) The first set temperature Ts1 is only an example of "-19°C" and is not limited to this, and a different temperature may be set. Also, the second set temperature Ts2 is only an example of "0°C" and is not limited to this, and a different temperature may be set.

[0094] (8) In the above embodiment, an electric tractor was used as an example of an electric work vehicle, but electric work vehicles are not limited to electric tractors and can be applied to work machines that perform various tasks, such as harvesters, rice transplanters, and construction machinery.

[0095] (9) In the above embodiment, the driving device is applied to an electric vehicle driven by an electric motor M1. However, the driving device may also be applied to a hybrid vehicle that uses both driving force from battery power and driving force from an engine.

[0096] The configurations disclosed in the above-described embodiments (including other embodiments, the same applies hereinafter) can be applied in combination with the configurations disclosed in other embodiments, unless a contradiction occurs. Furthermore, the embodiments disclosed in this specification are merely examples, and the present invention is not limited to these, and can be modified as appropriate within the scope of the present invention.

[0097] Each operation process in the above-described embodiments is realized by a processing circuit (circuitry) including one or more processors. The processing circuit may be configured as an integrated circuit or the like that combines one or more memories, various analog circuits, and various digital circuits in addition to the one or more processors. The one or more memories store programs (instructions) that cause the one or more processors to execute each of the processes. The one or more processors may execute each of the processes according to the program read from the one or more memories, or may execute each of the processes according to a logic circuit designed in advance to execute each of the processes. The processor may be any of various processors suitable for computer control, such as a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), and an ASIC (Application Specific Integrated Circuit). Note that the physically separated processors may cooperate with each other to execute the processes. For example, the processors installed in the physically separated computers may cooperate with each other via a network such as a LAN (Local Area Network), a WAN (Wide Area Network), or the Internet to execute the processes. The program may be installed into the memory from an external server device or the like via the network, or may be distributed in a state stored on a recording medium such as a CD-ROM (Compact Disc Read Only Memory), a DVD-ROM (Digital Versatile Disc Read Only Memory), or a semiconductor essential memory, and then installed into the memory from the storage medium.

[0098] The present invention is applicable to an electric work vehicle equipped with a battery and an electric motor that transmits power to a traveling device using electric power from the battery.

[0099] 4 First battery (battery) 4B Temperature detection unit (temperature detection means) 23 Power conversion device 24 Second battery 25C Battery heater (heater) H Temperature adjustment means Ts1 First set temperature Ts2 Second set temperature

Claims

1. Battery and An electric motor that transmits power to the traction device using the power of the aforementioned battery, A temperature control means that uses electricity to adjust the temperature of the battery, The system includes a temperature detection means for detecting the temperature of the battery, The temperature control means is an electric work vehicle that operates so that the temperature of the battery rises if the temperature detected by the temperature detection means is lower than a first set temperature.

2. The electric work vehicle according to claim 1, wherein the temperature control means is operated by power supplied from an external power source.

3. The electric work vehicle according to claim 1, wherein the temperature control means operates using power supplied from the battery so that the temperature of the battery, as detected by the temperature detection means, rises if the temperature of the battery is higher than the first set temperature and lower than a second set temperature which is higher than the first set temperature.

4. The electric work vehicle according to claim 3, wherein the temperature control means stops the heating operation for the battery when the temperature of the battery rises to or above the second set temperature.

5. The temperature control means includes a circulation path through which the refrigerant circulates via the inside of the battery, and a heater for heating the refrigerant. The electric work vehicle according to claim 1, wherein the heater performs a heating operation by the supplied power.

6. It is equipped with a power conversion device that converts power supplied from an external power source into power for use in the vehicle. The electric work vehicle according to claim 5, wherein the temperature control means switches the power supply state so that if the temperature of the battery is lower than the first set temperature, it converts the power into power that can be supplied to the heater as on-board power and supplies it to the heater, and if the temperature of the battery is higher than the first set temperature, it converts the power into power that can be supplied to the battery as on-board power and supplies it to the battery.

7. The electric work vehicle according to claim 2, wherein the battery is not charged if the temperature of the battery is lower than the first set temperature.

8. The electric work vehicle according to claim 1, wherein the battery does not discharge if the temperature of the battery is lower than the first set temperature.

9. The aforementioned battery includes a plurality of unit batteries, The temperature detection means is configured to detect the temperature for each of the plurality of unit batteries. The electric work vehicle according to claim 1, wherein the temperature control means operates if the lowest temperature among the plurality of unit batteries is lower than the first set temperature.

10. An electric work vehicle according to any one of claims 1 to 9, which is capable of transmitting power to a work device using the power of the aforementioned battery.

11. A second battery, different from the aforementioned battery, is provided, which is capable of supplying power to electrical components. The electric work vehicle according to any one of claims 1 to 9, wherein the second battery is capable of supplying power to the electrical components at a temperature lower than the first set temperature.

12. The electric work vehicle according to claim 11, wherein the battery is a lithium-ion battery and the second battery is a lead-acid battery.