electric work vehicle

Abstract

To provide an electric work vehicle configured so that output of a battery for running the vehicle can be managed properly, even when cell voltages of battery cells constituting the battery for running cannot be detected.SOLUTION: An electric work vehicle is provided with: an electric motor 1; a battery 4 for running the vehicle constituted of a plurality of battery cells 40; an inverter 14 that supplies electric power for driving to the electric motor 1 using electric power from the battery 4 for running; a cell voltage detector 51 that detects cell voltages of the battery cells 40; and a control device 6 that when the cell voltage detector 51 cannot detect at least one cell voltage, stops output of the electric motor 1 or restricts output of the electric motor 1 to a preset limit output value, on the basis of a power supply state of the battery 4 for running.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an electric work vehicle that prevents overcharging and overdischarging of a battery by managing the charge / discharge state of the battery, thereby suppressing unexpected stops. [Background technology]

[0002] Patent Document 1 discloses a battery management device that includes a voltage sensor that detects the electromotive force (cell voltage) of each of a plurality of battery units (battery cells) that make up a battery, a voltage sensor failure detection means that detects a failure in the voltage sensors, and a battery current suppression means. This battery current suppression means suppresses the battery current when a failure in any of the voltage sensors is detected. This suppresses heat generation due to Joule heat even if an abnormality occurs in a battery unit, preventing further deterioration of the battery unit. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-357541 Summary of the Invention [Problem to be solved by the invention]

[0004] In the battery management device disclosed in Patent Document 1, when a voltage sensor failure detection means detects a failure in a voltage sensor that detects the voltage of a battery unit, the battery current is reduced. However, because reduced power is supplied from the battery to the motor, there is a risk that fatal over-discharge or over-charge may occur in the battery unit assigned to the failed voltage sensor.

[0005] In view of this situation, an object of the present invention is to provide an electric work vehicle that can appropriately manage the output of the driving battery even when it becomes impossible to detect the cell voltage of the battery cells that make up the driving battery. [Means for solving the problem]

[0006] The electric work vehicle according to the present invention comprises an electric motor that is driven to drive the vehicle body, a drive battery consisting of a plurality of battery cells, an inverter that supplies drive power to the electric motor using power from the drive battery, a cell voltage detector that detects the cell voltages of the battery cells, and a detection function that detects the cell voltage of at least one of the battery cells when the cell voltage detector is unable to detect the cell voltage. ,before a control device that stops the output of the electric motor or limits the output of the electric motor to a preset limit output value; an inverter voltage detection unit that detects a total inverter voltage of the inverter; Equipped with When the cell voltage cannot be detected and the inverter total voltage of the inverter is within a preset inverter total voltage tolerance range, the control device limits the output of the electric motor to a preset limit output value. . Moreover, an electric work vehicle according to the present invention comprises an electric motor that is driven to propel the vehicle body, a traction battery consisting of a plurality of battery cells, an inverter that supplies driving power to the electric motor using power from the traction battery, a cell voltage detector that detects the cell voltages of the battery cells, a control device that stops the output of the electric motor or limits the output of the electric motor to a preset limit output value when the cell voltage detector is unable to detect at least one of the cell voltages, and a DC / DC converter that is powered by the traction battery, and when it is unable to detect the cell voltage and the input voltage of the DC / DC converter is within a preset converter input voltage allowable range, the control device limits the output of the electric motor to the preset limit output value.

[0007] According to this configuration, if the cell voltage detector is unable to detect at least one of the cell voltages, either the electric motor output is stopped or the electric motor output is limited. At that time, if it is determined that there is a high possibility of fatal over-discharge or over-charge of the driving battery, the electric motor output is stopped and the vehicle is brought to a halt. Then, the state of the driving battery and the state of battery-related devices such as the cell voltage detector are checked. Furthermore, if it is determined that the driving battery is not imminent to fatally over-discharge or over-charge, the electric motor output is limited, allowing the electric work vehicle to travel to a location (such as a parking lot or a maintenance and inspection service center) suitable for checking the driving battery, cell voltage detector, etc.

[0008] Whether the electric motor output is stopped or the output of the electric motor is limited, this will have a significant impact on the running of the electric work vehicle, so it is preferable to notify the driver that at least one cell voltage cannot be detected by the cell voltage detector, or that the resulting selection result (output stop or output limit) is notified. For this reason, in the present invention, the driver is notified via a notification unit that the control device has decided to stop the output of the electric motor or to limit the output of the electric motor.

[0009] The battery state of the traction battery, which is the criterion for determining whether to stop the output of the electric motor or limit the output of the electric motor, can be estimated, for example, by the inverter total voltage of the inverter. Therefore, the present invention includes an inverter voltage detection unit that detects the inverter total voltage of the inverter, and the control device stops the output of the electric motor when the inverter total voltage of the inverter falls outside a preset inverter total voltage allowable range. In other words, if the inverter total voltage is low enough to indicate over-discharge of the traction battery, for example, the vehicle is stopped to avoid the risk of over-discharge. However, it is preferable to set the inverter total voltage allowable range sufficiently large to allow for a margin of error in order to avoid unexpected stops in inappropriate locations.

[0010] The battery state of the driving battery, which is the criterion for selecting whether to stop output of the electric motor or limit output of the electric motor, can also be estimated from the input voltage of a DC / DC converter powered by the driving battery. For this reason, the present invention is provided with a DC / DC converter powered by the driving battery, and the control device stops output of the electric motor when the input voltage of the DC / DC converter falls outside a preset converter input voltage allowable range. Even in this configuration, it is preferable to set the converter input voltage allowable range large enough to allow for a margin of error in order to avoid unexpected stops in inappropriate locations.

[0011] Because the basic element of a traction battery is the battery cell, if the cell voltage of one battery cell falls outside a predetermined range (permissible cell voltage range), it has a significant impact on the state of the traction battery. To solve this problem and properly manage the output of the traction battery, in the present invention, the control device stops the output of the electric motor or limits the output of the electric motor to the limited output value when the cell voltage falls outside a preset permissible cell voltage range. The permissible cell voltage range, like the permissible inverter total voltage range and the permissible converter input voltage range, is determined experimentally and empirically, taking into account factors such as the type of vehicle being worked on. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 2 is a left side view of the tractor. [Figure 2] FIG. 2 is a left side view showing the arrangement of the motor and the driving battery. [Figure 3] FIG. 2 is a schematic diagram showing the flow of power transmission. [Figure 4] FIG. 2 is a functional block diagram showing functional units of the battery system. [Figure 5] 10 is a flowchart illustrating an example of battery management control. [Figure 6] 10 is a flowchart illustrating another example of battery management control. DETAILED DESCRIPTION OF THE INVENTION

[0013] An embodiment of the present invention will be described with reference to the drawings. In the following description, unless otherwise specified, the direction of arrow F in the drawings will be defined as "front," the direction of arrow B as "rear," the direction of arrow L as "left," and the direction of arrow R as "right." The direction of arrow U in the drawings will be defined as "up," and the direction of arrow D as "down."

[0014] [Overall configuration of the tractor] The following describes a tractor as an example of an electric work vehicle according to the present invention. As shown in Figure 1, the tractor has left and right front wheels 10, left and right rear wheels 11, and a cover member 12.

[0015] The tractor comprises a machine frame 2 and a driving section 3. The machine frame 2 is supported by left and right front wheels 10 and left and right rear wheels 11. A cover member 12 is disposed at the front of the machine. The driving section 3 is provided behind the cover member 12.

[0016] The driver's section 3 has a protective frame 30, a driver's seat 31, and a steering wheel 32. The steering wheel 32 is provided so as to be operable by a driver who boards the driver's section 3 and sits in the driver's seat 31. The left and right front wheels 10 are steered by operating the steering wheel 32. The driver can perform various driving operations using the driver's section 3.

[0017] The tractor is equipped with a traction battery 4. The cover member 12 is configured to be swingable about an opening / closing axis Q that extends along the left-right direction of the vehicle body. This allows the cover member 12 to be opened and closed. When the cover member 12 is in a closed state, the traction battery 4 is covered by the cover member 12.

[0018] As shown in Fig. 2, the tractor includes an inverter 14 and an electric motor 1. The traction battery 4 supplies power to the inverter 14. The inverter 14 converts DC power from the traction battery 4 into AC power to generate drive power to be supplied to the electric motor 1. The drive power is AC power generated by the inverter 14.

[0019] 2 and 3, the tractor is equipped with a hydrostatic continuously variable transmission 15 and a transmission 16. As shown in Fig. 3, the hydrostatic continuously variable transmission 15 has a hydraulic pump 15a and a hydraulic motor 15b.

[0020] The hydraulic pump 15a is driven by rotational power from the electric motor 1. When the hydraulic pump 15a is driven, rotational power is output from the hydraulic motor 15b. The hydrostatic continuously variable transmission 15 is configured so that the speed of the rotational power is continuously changed between the hydraulic pump 15a and the hydraulic motor 15b.

[0021] The rotational power output from the hydraulic motor 15b is transmitted to the transmission 16. The rotational power transmitted to the transmission 16 is changed in speed by a gear-type speed change mechanism of the transmission 16 and distributed to the left and right front wheels 10 and the left and right rear wheels 11. In this way, the left and right front wheels 10 and the left and right rear wheels 11 are driven.

[0022] 2 and 3, the tractor is equipped with a mid PTO shaft 17 and a rear PTO shaft 18. The rotational power output from the electric motor 1 is distributed to the hydraulic pump 15a, the mid PTO shaft 17, and the rear PTO shaft 18. This causes the mid PTO shaft 17 and the rear PTO shaft 18 to rotate.

[0023] If a working device is connected to the mid PTO shaft 17 or the rear PTO shaft 18, the working device will be driven by the rotational power of the mid PTO shaft 17 or the rear PTO shaft 18. For example, as shown in FIG. 2, in this embodiment, a brush cutting device 19 is connected to the mid PTO shaft 17. The brush cutting device 19 is driven by the rotational power of the mid PTO shaft 17.

[0024] [Motor / battery control system configuration] FIG. 4 schematically shows the configuration related to the control of the traction battery 4 and the electric motor 1. The motor-battery control system includes an accelerator device 33, a key controller 34, a control device 6 that controls the operation of the electric motor 1, and an inverter 14. The accelerator device 33 is provided near the steering wheel 32. Although not shown, the accelerator device 33 includes a lever that can be swung and a potentiometer that is operated by swung operation of the lever. The accelerator device 33 is connected to the control device 6. The key controller 34 is also connected to the control device 6 and provides a key operation signal to the control device 6 based on the movement of a main key operated by the driver. The control device 6 is connected to the inverter 14 and provides a drive command to the inverter 14 in response to a command from the accelerator device 33. The inverter 14 adjusts the power supplied from the traction battery 4 to the electric motor 1 in response to a command from the control device 6 to control the output of the electric motor 1.

[0025] The control device 6 is also connected to a notification unit 35. The notification unit 35 is a general term for devices such as an operation panel, a meter panel, lamps, and buzzers that notify the driver of information, and visually or audibly notifies the driver of, for example, the vehicle's running state, working state, and information about the driving battery 4 (charge level and temperature).

[0026] The driving battery 4 can be charged from an external power source 44 via a charging unit 43. The charging unit 43 is provided with a power supply socket (not shown). The power supply socket can be connected to a power supply connector (not shown) of a charging cable from the external power source 44. The power supply socket is disposed inside the cover member 12 and is exposed to the outside when the cover member 12 is swung open. The control device 6 controls the driving of the inverter 14 and also controls the charging of the driving battery 4 by the charging unit 43.

[0027] The driving battery 4 is, for example, a lithium ion battery, and is configured by stacking a large number of battery cells 40, which are small, low-voltage unit cells. The driving battery 4 is stored in a storage case, with the outside covered in a sealed state.

[0028] A battery voltage detection unit 5 is provided to detect the battery voltage of the driving battery 4. In this embodiment, the battery voltage detection unit 5 includes a cell voltage detector 51 that detects the voltage at the connection point between multiple battery cells 40 connected in series as the cell voltage. In FIG. 4, the cell voltage detector 51 is configured to detect the cell voltage of each battery cell 40, but it may also be configured to detect the cell voltage of two or more battery cells 40 as a unit. The cell voltage detected by the cell voltage detector 51 is input to the control device 6. Although not shown, a temperature detection sensor is also provided to detect the temperature of the battery cells 40 and other internal temperatures of the driving battery 4, and the detection signal thereof is also input to the control device 6.

[0029] In addition to the traction battery 4, the tractor is equipped with an electrical equipment battery 41 that supplies power to the control device 6 and other electrical equipment. The electrical equipment battery 41 supplies low-voltage (12 volt) power to drive the electrical equipment. The electrical equipment battery 41 is charged with power supplied from the traction battery 4 via a DC / DC converter 42. The DC / DC converter 42 is drive-controlled by the control device 6.

[0030] When the cell voltage detector 51 is unable to detect at least one cell voltage, the control device 6 has the function of stopping the output of the electric motor 1 or limiting the output of the electric motor 1 to a preset limited output value based on the power supply state of the driving battery 4. To achieve this function, the control device 6 includes a battery management unit 60, an inverter voltage detection unit 61, a DC / DC converter voltage detection unit 62, and a motor drive management unit 63 to manage the output (discharge) of the driving battery 4 according to its state of charge.

[0031] The inverter voltage detection unit 61 detects the inverter total voltage of the inverter 14. The DC / DC converter voltage detection unit 62 detects the converter input voltage of the DC / DC converter 42. In FIG. 4, the inverter voltage detection unit 61 and the DC / DC converter voltage detection unit 62 are provided inside the control device 6, but they may also be provided outside the control device 6. The battery management unit 60 manages the charging and discharging of the driving battery 4 based on the cell voltage, the inverter total voltage, the converter input voltage, a signal from the accelerator device 33, a signal from the key controller 34, etc. The motor drive management unit 63 generates a drive signal for driving the electric motor 1 based on the signal from the accelerator device 33 and provides the signal to the inverter 14.

[0032] When a charging command is input with the power cable from the external power source 44 plugged into the socket of the charging unit 43, the control device 6 executes a charging program and the driving battery 4 is charged.

[0033] The control device 6 determines whether to stop the output of the electric motor 1 or to limit the output of the electric motor 1 according to a control rule that has been set in advance, and the driver is notified of the decision via the notification unit 35.

[0034] If the cell voltage detector 51 is unable to detect the cell voltage of at least one battery cell 40, the control device 6 limits the output of the electric motor 1 to a preset limit output value. Even if the cell voltage cannot be detected, this does not necessarily mean that the battery cell 40 is in an abnormal state. However, as a safety measure, the output of the electric motor 1 is first limited to take relief measures against an unexpected abnormality in a battery cell 40, i.e., an abnormality in the driving battery 4. Furthermore, a secondary method other than detecting the cell voltage with the cell voltage detector 51 is used to determine whether the driving battery 4 is abnormal, and based on the determination result, the output of the electric motor 1 is stopped, if necessary, as a secondary relief measure.

[0035] In this embodiment, an example of the secondary rescue measure, that is, the determination rule for determining whether to stop the output of the electric motor 1, is as follows. (1) When the inverter total voltage falls outside a preset inverter total voltage allowable range, the control device 6 stops the output of the electric motor 1. (2) When the input voltage of the DC / DC converter 42 falls outside a preset allowable range of the converter input voltage, the control device 6 stops the output of the electric motor 1.

[0036] Even if the cell voltage detector 51 becomes unable to detect the cell voltage of at least one battery cell 40, this does not necessarily mean that it becomes unable to detect the cell voltages of all battery cells 40, and therefore the control device 6 may determine to limit the output of the electric motor 1 or stop the output of the electric motor 1 from the cell voltage of the battery cells 40 for which the cell voltage can be detected. In other words, when the cell voltage falls outside a preset cell voltage allowable range, the control device 6 stops the output of the electric motor 1 or limits the output of the electric motor 1 to a preset limit output value.

[0037] Next, an example of management processing of the driving battery 4 (output management of the electric motor 1) by the control device 6 configured as described above will be described with reference to the flowchart of FIG.

[0038] When this battery management process is initiated, the control device 6 checks whether there is any battery cell 40 for which the cell voltage cannot be detected (#01). This check for undetectable cell voltages can be performed based on the detection results of the cell voltage detector 51. If the check for undetectable cell voltages does not detect any battery cells 40 for which the cell voltage cannot be detected (#01: No branch), a check is then performed to see if there are any battery cells 40 for which the detected cell voltage is outside a preset cell voltage tolerance range (overcharged or overdischarged state) (#02). If all cell voltages are within the cell voltage tolerance range in this check for out-of-tolerance cell voltages (#02: No branch), the battery condition of the driving battery 4 is deemed normal (#03), and motor output control for the electric motor 1 is performed normally (#04).

[0039] If at least one battery cell 40 whose cell voltage is undetectable is detected in the cell voltage detection check in step #01 (#01 Yes branch), the control device 6 notifies the notification unit 35 that a battery cell 40 whose cell voltage is undetectable has been detected (#10). Furthermore, the control device 6 uses the function of the inverter voltage detection unit 61 to check whether the inverter total voltage is outside a preset inverter total voltage allowable range (#11). If this inverter total voltage check finds that the inverter total voltage is within the inverter total voltage allowable range (#11 No branch), the traction battery 4 is deemed usable for at least a while, even though cell voltage detection is undetectable (#13). However, because future deterioration of the traction battery 4 is anticipated, the control device 6 limits the motor output of the electric motor 1 so that it does not exceed a preset output limit value (#14). At the same time, the control device 6 notifies the notification unit 35 that motor output control of the electric motor 1 will be performed (#15). This notification allows the operator to move the tractor to a suitable location for maintenance, such as a barn or repair center, without having to stop unexpectedly.

[0040] In the cell voltage out-of-range check in step #02, if any one cell voltage is outside the cell voltage allowable range (#02 Yes branch), the drive battery 4 is deemed to be abnormal (#20). In other words, if at least one battery cell 40 whose cell voltage cannot be detected is detected and any one cell voltage is outside the cell voltage allowable range, the drive battery 4 is deemed to be abnormal, and motor output control of the electric motor 1 is stopped (#21). Furthermore, the control device 6 notifies through the notification unit 35 that the drive battery 4 is deemed to be abnormal and motor output control of the electric motor 1 will be stopped (#22).

[0041] Similarly, if the inverter total voltage check in step #11 finds that the inverter total voltage is outside the inverter total voltage allowable range (#11 Yes branch), the power supply from the driving battery 4 is insufficient, the driving battery 4 is deemed to be abnormal (#20), and motor output control for the electric motor 1 is stopped (#21). Since the control device 6 considers the driving battery 4 to be abnormal, it notifies the alarm unit 35 that motor output control for the electric motor 1 will be stopped (#22).

[0042] Next, another example of the management process for the driving battery 4 (the output management process for the electric motor 1), which is different from the flowchart in FIG. 5, will be described with reference to the flowchart in FIG.

[0043] The management process of FIG. 6 differs from the management process of FIG. 5 in that, instead of checking whether the inverter total voltage is outside the preset inverter total voltage allowable range in step #11 of FIG. 5, in step #12, the control device 6 uses the function of the DC / DC converter voltage detection unit 62 to check whether the converter input voltage is outside the preset converter input voltage allowable range. If this converter input voltage check finds that the converter input voltage is within the converter input voltage allowable range (#12 No branch), the traction battery 4 is deemed usable for at least a while, even though cell voltage detection is not possible (#13). If the converter input voltage check of step #12 finds that the converter input voltage is outside the converter input voltage allowable range (#12 Yes branch), the power supply from the traction battery 4 is insufficient, and the traction battery 4 is deemed to be abnormal (#20). Otherwise, the flowchart of FIG. 6 is the same as the flowchart of FIG. 5. That is, in the management process of FIG. 6, instead of checking the inverter total voltage in the management process of FIG. 5, a check of the converter input voltage is adopted.

[0044] Another possible management process for the traction battery 4 is a combination of the flowcharts of Figure 5 and Figure 6, that is, a process that incorporates both checking the inverter total voltage in step #11 of Figure 5 and checking the converter input voltage in step #12 of Figure 6. In this management process, if the inverter total voltage is not outside the allowable range and the converter input voltage is not outside the allowable range, the traction battery 4 is considered usable for at least a while. If either the inverter total voltage or the converter input voltage is outside the allowable range, the traction battery 4 is considered to be abnormal.

[0045] In the flowchart of the management process for the driving battery 4 described above, if there is at least one battery cell 40 whose cell voltage cannot be detected and the cell voltage of at least one of the remaining battery cells 40 whose cell voltage can be detected is outside the cell voltage allowable range, i.e., if the answer to step #02 is Yes, motor output control is stopped. Alternatively, the allowable cell voltage range may be configured to include a first allowable range and a second allowable range, and if the cell voltage is outside the second allowable range, motor output control may be stopped, and if the cell voltage is within the second allowable range but outside the first allowable range, motor output may be limited. Furthermore, if the answer to step #02 is Yes, the process may jump to step #11 (FIG. 5) or step #12 (FIG. 6).

[0046] In the cell voltage detection undetectable check in step #01, if even one battery cell 40 whose cell voltage cannot be detected is detected, it is determined that the cell voltage cannot be detected. However, it may also be determined that the cell voltage cannot be detected if the cell voltage of a small number of battery cells 40 (two or more) cannot be detected.

[0047] [Another embodiment] (1) In the above embodiment, the driving battery 4 was located in front of the driving unit 3. However, instead, it may be located below the driving unit 3 or behind the driving unit 3, or it may be divided into multiple units and each unit may be located in a different location.

[0048] (2) The criteria for determining the cell voltage tolerance range, inverter total voltage tolerance range, converter input voltage tolerance range, etc. may be changed depending on whether the tractor is equipped with a work implement such as a grass cutting implement 19 or a tilling implement or whether the tractor is not equipped with a work implement, or may be changed depending on the type of work implement attached.

[0049] The configurations disclosed in the above embodiments (including other embodiments, the same applies below) can be applied in combination with configurations disclosed in other embodiments, as long as no contradiction arises. Furthermore, the embodiments disclosed in this specification are examples, and the embodiments of the present invention are not limited to these, and can be modified as appropriate within the scope that does not deviate from the purpose of the present invention. [Industrial Applicability]

[0050] The present invention is not limited to tractors, but can also be applied to various electric work vehicles such as rice transplanters, combine harvesters, and construction machinery. [Explanation of symbols]

[0051] 1: Electric motor 14: Inverter 35: Announcement unit 4: Driving battery 40: Battery cell 41: Battery for electrical equipment 42: DC / DC converter 43:Charge part 44: External power supply 5: Battery voltage detection section 51: Cell voltage detector 6: Control device 60: Battery management unit 61: Inverter voltage detection unit 62: DC / DC converter voltage detection section 63: Motor drive management unit

Claims

1. an electric motor that is driven to drive the vehicle; a driving battery consisting of a plurality of battery cells; an inverter that uses electric power from the driving battery to supply drive electric power to the electric motor; a cell voltage detector for detecting a cell voltage of the battery cell; a control device that stops the output of the electric motor or limits the output of the electric motor to a preset limit output value when the cell voltage detector becomes unable to detect at least one of the cell voltages; an inverter voltage detection unit that detects a total inverter voltage of the inverter; Equipped with When the cell voltage cannot be detected and the inverter total voltage of the inverter is within a preset inverter total voltage allowable range, the control device limits the output of the electric motor to a preset limit output value.

2. An electric work vehicle as described in claim 1, wherein the control device stops the output of the electric motor when it is impossible to detect the cell voltage and the inverter total voltage of the inverter falls outside a predetermined inverter total voltage tolerance range.

3. An electric motor driven to drive the vehicle; a driving battery consisting of a plurality of battery cells; an inverter that uses electric power from the driving battery to supply drive electric power to the electric motor; a cell voltage detector for detecting a cell voltage of the battery cell; a control device that stops the output of the electric motor or limits the output of the electric motor to a preset limit output value when the cell voltage detector becomes unable to detect at least one of the cell voltages; a DC / DC converter powered by the driving battery; Equipped with The control device limits the output of the electric motor to a preset limit output value when the cell voltage cannot be detected and the input voltage of the DC / DC converter is within a preset converter input voltage allowable range.

4. An electric work vehicle as described in Claim 3, wherein the control device stops the output of the electric motor when it is impossible to detect the cell voltage and the input voltage of the DC / DC converter falls outside the preset converter input voltage tolerance range.

5. The electric work vehicle according to any one of claims 1 to 4, wherein a notification unit notifies a driver that the control device has decided to stop output of the electric motor or to limit output of the electric motor.

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