Drive unit for small-sized electric vehicle

Abstract

This drive unit comprises: a power storage unit (71); and a plurality of drive devices (30) that respectively drive a plurality of drive shafts of a small-sized electric vehicle. Each drive device comprises: a motor (31) that generates motive power for rotating a drive shaft; an inverter (34) that converts electric power supplied from the power storage unit and supplies the converted electric power to the motor; control circuits (32, 33, 40, 41, 42) that control the inverter; an initial diagnosis unit (40b) that performs initial diagnosis of failures in the motor, the inverter, and the control circuits when the drive unit is started; and a prescribed processing unit (40c) that, if it was diagnosed by the initial diagnosis unit that a failure has occurred in at least one of the motor, the inverter, and the control circuits, executes prescribed processing for the failure.

Description

Drive unit for small electric vehicles CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Japanese Application No. 2024-020236 filed on February 14, 2024, the contents of which are incorporated herein by reference.

[0002] The present disclosure relates to a drive unit for driving a small electric vehicle.

[0003] For example, there is a drive unit that includes a first electric drive unit that drives the left rear wheel of an electric wheelchair and a second electric drive unit that drives the right rear wheel (see Patent Document 1). The electric drive unit described in Patent Document 1 includes a motor and a reduction gear, and the rotor, stator, and power converter are housed in a motor housing that is integrated with the reduction gear. Therefore, Patent Document 1 states that the wiring that electrically connects the stator winding and the power converter can also be housed in the motor housing, simplifying the configuration of the electric drive unit.

[0004] JP 2023-102121 A

[0005] The drive unit described in Patent Document 1 aims to simplify the configuration of the electric drive device (drive device), and minimizes the configuration. Therefore, Patent Document 1 does not describe a configuration for detecting a malfunction, and if a malfunction occurs in the electric drive device, there is a risk that the electric wheelchair (small electric vehicle) will be driven in a state that interferes with its operation.

[0006] The present disclosure has been made to solve the above-mentioned problems, and its main purpose is to prevent a drive unit of a small electric vehicle from driving the small electric vehicle in a state that interferes with its operation.

[0007] A first means for solving the above problem is a drive unit comprising a power storage unit and a plurality of drive devices that respectively drive a plurality of drive shafts of a small electric vehicle, each drive device comprising: a motor that generates power to rotate the drive shaft; an inverter that converts power supplied from the power storage unit and supplies it to the motor; a control circuit that controls the inverter; an initial diagnosis unit that performs an initial diagnosis of faults in the motor, the inverter, and the control circuit when the drive unit is started; and a predetermined processing unit that performs predetermined processing for the fault when the initial diagnosis unit diagnoses that a fault has occurred in at least one of the motor, the inverter, and the control circuit.

[0008] According to the above configuration, the drive unit includes a power storage unit and a plurality of drive devices that respectively drive a plurality of drive shafts of the small electric vehicle. Each drive device includes a motor that generates power to rotate the drive shaft, an inverter that converts power supplied from the power storage unit and supplies it to the motor, and a control circuit that controls the inverter. Therefore, by controlling the inverter with the control circuit, the power supplied from the power storage unit can be converted by the inverter and supplied to the motor. Therefore, each drive shaft of the small electric vehicle can be driven by the motor of each drive device, and the running state of the small electric vehicle can be controlled.

[0009] Here, if a fault occurs in the drive device, the fault may not be detectable while the drive unit is operating. In that case, the fault may not be detected after the drive unit starts operating, and the small electric vehicle may continue to be driven in a state that interferes with its operation. In this regard, the initial diagnosis unit performs an initial diagnosis of faults in the motor, the inverter, and the control circuit when the drive unit is started. This makes it possible to detect faults that cannot be detected after the drive unit starts operating at the time of start-up of the drive unit. Then, when the initial diagnosis unit diagnoses that a fault has occurred in at least one of the motor, the inverter, and the control circuit, the predetermined processing unit executes predetermined processing for the fault. This prevents the small electric vehicle from being driven in a state that interferes with its operation.

[0010] The above and other objects, features, and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which Fig. 1 is a schematic diagram of an automated guided vehicle, Fig. 2 is a block diagram showing an electric drive unit and its peripheral configuration, Fig. 3 is a schematic diagram showing the activation of a drive unit under normal conditions, Fig. 4 is a schematic diagram showing the activation and deactivation of a drive unit under abnormal conditions, Fig. 5 is a schematic diagram showing backup control of one electric drive unit under abnormal conditions, and Fig. 6 is a schematic diagram showing backup control of multiple electric drive units under abnormal conditions.

[0011] An embodiment of the present invention will be described below with reference to the drawings, in which the drive unit is mounted on an automated guided vehicle (small electric vehicle). The automated guided vehicle is an AGV (Automatic Guided Vehicle) that is guided by a magnetic tape (magnetic line) in, for example, a factory or a warehouse.

[0012] 1 , the automated guided vehicle 10 includes a vehicle body 11, four (multiple) sets of drive wheels 12 and drive shafts 13, and a drive unit 20. Each drive wheel 12 is connected to a corresponding drive shaft 13 and rotates around the corresponding drive shaft 13. The four drive wheels 12 are the left and right front wheels and the left and right rear wheels of the automated guided vehicle 10.

[0013] The drive unit 20 is housed in the vehicle body 11. The drive unit 20 includes four (multiple) sets of electric drive devices 30 and brakes 60, a host controller 70, a battery 71, an MCU relay 73, a brake relay 75, and sensors 77. Each set of electric drive devices 30 and brakes 60 corresponds to each set of drive wheels 12 and drive axles 13. In Fig. 1, power supply lines PL1 and PL2 are indicated by solid lines, and the signal line SL is indicated by a dashed line.

[0014] Each electric drive unit 30 (drive unit) drives each drive shaft 13. Each electric drive unit 30 is fixed to the vehicle body 11. Each electric drive unit 30 includes an MCU (Motor Control Unit) and a reducer 59.

[0015] Each MCU (each electric drive unit 30) is connected to a battery 71 via a power supply line PL1. An MCU relay 73 is provided on the power supply line PL1 between the battery 71 and the four MCUs. The MCU relay 73 (high-order relay) is switched between an ON state, in which power is supplied from the battery 71 to the four MCUs (electric drive units 30), and an OFF state, in which power to the four MCUs is cut off. When the MCU relay 73 is in the ON state, each MCU is driven by power supplied from the battery 71.

[0016] The reducer 59 is, for example, a planetary gear mechanism, a cycloid gear mechanism, etc. The reducer 59 reduces the rotation speed of the motor 31 (see FIG. 2) of the MCU and transmits the reduced rotation speed to the drive shaft 13.

[0017] Each brake 60 (brake device) brakes each drive axle 13. Each brake 60 is fixed to the vehicle body 11. Each brake 60 is connected to a battery 71 via a power supply line PL2. A brake relay 75 is provided on the power supply line PL2 between the battery 71 and each of the four brakes 60. The brake relay 75 (brake device relay) is switched between an ON state, in which power is supplied from the battery 71 to each of the four brakes 60, and an OFF state, in which power is cut off from each of the four brakes 60. When the brake relay 75 is in the ON state, each of the brakes 60 is driven by power supplied from the battery 71. Each of the brakes 60 is, for example, a non-excitation actuated electromagnetic brake that brakes each of the drive axles 13 when no power is supplied. The braking force applied by each of the brakes 60 to each of the drive axles 13 can also be controlled by each of the MCUs or the host controller 70.

[0018] The host controller 70 (control unit) is composed of an ECU (Electronic Control Unit) equipped with, for example, a CPU, ROM, RAM, an input / output interface, etc. The host controller 70 and the four MCUs are connected to each other via a signal line SL. The signal line SL is a signal line that meets, for example, the CAN (Controller Area Network) communication standard. The host controller 70 and the four MCUs transmit and receive information to each other via the signal line SL. The host controller 70 controls the four MCUs (electric drive devices 30) by inputting commands to each MCU via the signal line SL. The host controller 70 switches the MCU relay 73 and the brake relay 75 between the on state and the off state. The host controller 70 maintains the MCU relay 73 and the brake relay 75 in the on state while the drive unit 20 is operating.

[0019] The sensors 77 include, for example, an abnormality stop button, a collision detection switch, a magnetic sensor that detects the magnetism of the magnetic tape, a position information sensor that reads floor position information, a human presence sensor that detects people, etc. The detection results of the sensors 77 are input to the upper controller 70.

[0020] 2 is a block diagram showing the electric drive unit 30 and its peripheral configuration. Since the four electric drive units 30 have the same configuration, one electric drive unit 30 will be described as an example.

[0021] The electric drive device 30 includes two power supply line relays 32, a battery reverse connection prevention relay 33, an inverter 34, a current sensor 41, and an angle sensor 42. Each electric drive device 30 includes one motor 31, a reducer 59, and a controller 40.

[0022] The inverter 34 of each system is connected to the MCU relay 73 (battery 71 ) via the power supply line relay 32 and the battery reverse connection prevention relay 33 .

[0023] The power supply line relay 32 (predetermined relay) is switchable between an ON state in which power is supplied from the battery 71 to the inverter 34 and an OFF state in which the power is cut off. The reverse battery connection prevention relay 33 corrects reverse connection when the battery 71 is connected with reverse polarity (reverse connection). The reverse battery connection prevention relay 33 (predetermined relay) can be switched between an ON state in which power is supplied from the battery 71 to the inverter 34 and an OFF state in which the power is cut off.

[0024] The inverter 34 is, for example, a three-phase inverter, and includes a plurality of switching elements corresponding to the respective phases, and converts the supplied DC power into AC power. The inverter 34 inputs (supplies) the AC power to the motor 31.

[0025] The motor 31 is, for example, a three-phase motor, and includes one rotor (not shown) and two systems of stator windings 31 a. AC power is input to the stator windings 31 a of each system from the inverter 34 of each system.

[0026] The current sensor 41 of each system detects the current flowing through the stator winding 31 a of the corresponding system. The angle sensor 42 of each system detects the electrical angle (angle) of the rotor. The current sensor 41 and the angle sensor 42 input the detection results to the controller 40.

[0027] The controller 40 includes a microcomputer and an ASIC (Application Specific Integrated Circuit). The microcomputer is configured, for example, by an ECU including a CPU, memory (ROM, RAM, etc.), an input / output interface, etc. The ASIC is an IC optimized for controlling the motor 31, etc. The controller 40 switches the power line relays 32 and the reverse battery connection prevention relays 33 of each system between an on state and an off state. Specifically, the controller 40 maintains the power line relays 32 and the reverse battery connection prevention relays 33 in an on state while the MCU (electric drive device 30) is operating. The controller 40 executes programs stored in the memory to realize the functions of a motor control unit 40a, a diagnosis unit 40b (initial diagnosis unit, diagnosis unit), and a predetermined processing unit 40c. The motor control unit 40a controls the inverters 34 of each system based on commands from the host controller 70 and detection results of the current sensors 41 and angle sensors 42 of each system.

[0028] The power supply line relay 32, the battery reverse connection prevention relay 33, the controller 40, the current sensor 41, and the angle sensor 42 constitute a control circuit that controls the inverter 34.

[0029] When the upper controller 70 determines that the automatic guided vehicle 10 has been instructed to travel straight ahead, it sends a rotational speed command value to the controller 40 of each MCU so that the left and right drive wheels 12 are rotated in the same direction and at the same rotational speed.

[0030] When the host controller 70 determines that braking of the automated guided vehicle 10 has been instructed, it transmits a torque command value to the controller 40 of each MCU so as to cause each motor 31 to generate a braking torque. This applies a braking force to the automated guided vehicle 10, and the automated guided vehicle 10 then stops. The host controller 70 can also control the braking force acting on each drive shaft 13 by controlling each brake 60.

[0031] When the upper controller 70 determines that the unmanned guided vehicle 10 has been instructed to turn, it rotates the left and right drive wheels 12 in the same direction and sends a rotation speed command value to the controller 40 of each MCU so that the rotation speed of the drive wheel 12 in the instructed turning direction is lower than the rotation speed of the remaining drive wheels 12.

[0032] The host controller 70 can also transmit rotational speed command values ​​to the controllers 40 of the respective MCUs so as to rotate the left and right drive wheels 12 in opposite directions. In this case, the automated guided vehicle 10 performs a pivot turn.

[0033] 3 is a schematic diagram showing the normal start-up of the drive unit 20. Here, the movement of signals (information) through the signal line SL is indicated by arrows (the same applies to the following figures).

[0034] The diagnostic unit 40b (functions as an initial diagnostic unit) performs an initial diagnosis of faults (normal or not) in the motor 31, inverter 34, and control circuit (power line relay 32, battery reverse connection prevention relay 33, controller 40, current sensor 41, and angle sensor 42) when the drive unit 20 is started.

[0035] The faults of the motor 31 include breaks and short circuits in the stator windings 31a, etc. The faults of the inverter 34 include breaks and short circuits in the wiring of the inverter 34, and malfunctions of the switching elements.

[0036] Here, since the power supply line relay 32 and the battery reverse connection prevention relay 33 must be maintained in the ON state while the MCU (electric drive device 30) is operating, it is not possible to diagnose faults in the power supply line relay 32 and the battery reverse connection prevention relay 33 while the electric drive device 30 is operating. When the drive unit 20 is started, the diagnosing unit 40b performs an initial diagnosis of whether the power supply line relay 32 and the battery reverse connection prevention relay 33 can be switched from the ON state to the OFF state. After the initial diagnosis, the diagnosing unit 40b maintains the power supply line relay 32 and the battery reverse connection prevention relay 33 in the ON state.

[0037] Faults in the controller 40 include malfunctions of the microcomputer and ASIC, program execution errors, etc. Here, because the ASIC is always operating while the electric drive device 30 is in operation, it is not possible to diagnose ASIC faults while the electric drive device 30 is in operation. The diagnosing unit 40b performs an initial diagnosis of whether the ASIC is operating normally when the drive unit 20 is started up. Note that the power supply line relay 32, the battery reverse connection prevention relay 33, and the ASIC correspond to predetermined parts that can be diagnosed when the drive unit 20 is started up, but cannot be diagnosed while the drive unit 20 is in operation.

[0038] Failures of the current sensor 41 and the angle sensor 42 include breaks and short circuits in the wiring, abnormalities in the detected values, and the like.

[0039] The diagnostic unit 40b (functioning as an initial diagnostic unit) diagnoses whether communication between the electric drive unit 30 and the host controller 70 is normal. Specifically, the diagnostic unit 40b diagnoses whether communication with the host controller 70 is established, whether data transmission and reception with the host controller 70 is normal, etc. The diagnostic unit 40b (functioning as an initial diagnostic unit) checks notifications (presence or absence of notification, notification content) from the host controller 70 to the electric drive unit 30. Notifications from the host controller 70 to the electric drive unit 30 include, for example, whether the other electric drive units 30 are normal, the control state of the electric drive unit 30 (normal control, backup control), etc. The diagnostic unit 40b inputs the results of the initial diagnosis to the host controller 70.

[0040] Furthermore, when the drive unit 20 is started, the host controller 70 performs an initial diagnosis to determine whether the MCU relay 73 can be switched from an ON state to an OFF state. After the initial diagnosis, the host controller 70 maintains the MCU relay 73 in the ON state. When the drive unit 20 is started, the host controller 70 performs an initial diagnosis to determine whether the brake relay 75 can be switched from an ON state to an OFF state. After the initial diagnosis, the host controller 70 maintains the brake relay 75 in the ON state. In other words, the host controller 70 performs an initial diagnosis (diagnosis) of a fault external to the electric drive device 30 of the drive unit 20.

[0041] If the results of the initial diagnosis input from each electric drive device 30 and the results of the initial diagnosis performed by the host controller 70 itself are all normal, the host controller 70 starts operation of each electric drive device 30, i.e., the drive unit 20. At this time, the host controller 70 notifies each electric drive device 30 that the other electric drive devices 30 are normal and that the other electric drive devices 30 are performing normal control.

[0042] 4 is a schematic diagram showing the start / stop behavior of the drive unit 20 in the event of an abnormality. Here, an example will be described in which the electric drive unit 30 corresponding to the right front wheel of the automated guided vehicle 10 fails (an abnormality occurs).

[0043] For example, suppose that the diagnostic unit 40b (functioning as an initial diagnostic unit) of the electric drive unit 30 corresponding to the right front wheel diagnoses during initial diagnosis that a fault has occurred that prevents the power line relay 32 from being switched from an on state to an off state.

[0044] The predetermined processing unit 40c switches the battery reverse connection prevention relay 33 to the OFF state (safety processing, predetermined processing) when the diagnosing unit 40b diagnoses that a fault has occurred in the power supply line relay 32. That is, the predetermined processing unit 40c stops the supply of power to the inverter 34 when the diagnosing unit 40b diagnoses that a fault has occurred in at least one of the motor 31, the inverter 34, and the control circuit (the power supply line relay 32, the battery reverse connection prevention relay 33, the controller 40, the current sensor 41, and the angle sensor 42) in the initial diagnosis. Note that the predetermined processing unit 40c switches the power supply line relay 32 to the OFF state (safety processing, predetermined processing) when the diagnosing unit 40b diagnoses that a fault has occurred in, for example, the battery reverse connection prevention relay 33. The safety processing is processing to ensure the safety of the automatic guided vehicle 10.

[0045] When the diagnosing unit 40b diagnoses that a fault has occurred in the power supply line relay 32, the predetermined processing unit 40c notifies the host controller 70 that a fault has occurred in the power supply line relay 32 (notification processing, predetermined processing). That is, when the diagnosing unit 40b diagnoses in the initial diagnosis that a fault has occurred in at least one of the motor 31, the inverter 34, and the control circuit (the power supply line relay 32, the battery reverse connection prevention relay 33, the controller 40, the current sensor 41, and the angle sensor 42), the predetermined processing unit 40c notifies the host controller 70 of which of these components has the fault (notification processing, predetermined processing). In this way, when the diagnosing unit 40b diagnoses that a fault has occurred in at least one of the motor 31, the inverter 34, and the control circuit, the predetermined processing unit 40c executes notification processing (predetermined processing for a fault) to notify the host controller 70 of the occurrence of the fault.

[0046] When the host controller 70 receives a notification that a fault has occurred from any of the electric drive devices 30, it switches off the MCU relay 73 and the brake relay 75. In other words, when the diagnostic unit 40b of any of the electric drive devices 30 diagnoses that a fault has occurred, the host controller 70 switches off the MCU relay 73 and the brake relay 75. This stops the activation of the drive unit 20.

[0047] If the host controller 70 diagnoses that the MCU relay 73 cannot be switched from the on state to the off state when the drive unit 20 is started, the host controller 70 may switch the brake relay 75 to the off state and stop the start of the drive unit 20. Furthermore, if the host controller 70 diagnoses that the brake relay 75 cannot be switched from the on state to the off state when the drive unit 20 is started, the host controller 70 may switch the MCU relay 73 to the off state and stop the start of the drive unit 20. The host controller 70 may then indicate the location of the failure in the drive unit 20 using a warning light (not shown) or the like.

[0048] The present embodiment described above in detail has the following advantages.

[0049] The diagnosing unit 40b initially diagnoses faults in the motor 31, inverter 34, and control circuit (power supply line relay 32, battery reverse connection prevention relay 33, controller 40, current sensor 41, and angle sensor 42) when the drive unit 20 is started. Therefore, faults that cannot be detected after the drive unit 20 has started operating can be detected when the drive unit 20 is started. The predetermined processing unit 40c then executes predetermined processing for the fault when the diagnosing unit 40b diagnoses that a fault has occurred in at least one of the motor 31, inverter 34, and control circuit. This prevents the automated guided vehicle 10 from being driven in a state that would impede its operation. Examples of states that would impede operation include a state in which the faulty motor 31 is locked, a state in which the faulty motor 31 can only generate an output that is less than the command value, and a state in which the faulty motor 31 can only generate an output that exceeds the command value.

[0050] The diagnosing unit 40b performs an initial diagnosis that includes diagnosing the power line relay 32, the battery reverse connection prevention relay 33, and the ASIC (predetermined locations) of the controller 40, which can be diagnosed when the drive unit 20 is started up but cannot be diagnosed while the electric drive device 30 (drive unit 20) is in operation. With this configuration, it is possible to perform an initial diagnosis of the predetermined locations that cannot be diagnosed while the electric drive device 30 is in operation, when the drive unit 20 is started up. Therefore, even if a fault occurs in a predetermined location, it is possible to detect the fault and perform predetermined processing to address the fault.

[0051] The diagnosing unit 40b performs an initial diagnosis, including diagnosing whether the power supply line relay 32 and the battery reverse connection prevention relay 33 can be switched from the ON state to the OFF state, when the drive unit 20 is started. Therefore, even if it becomes necessary to switch the power supply line relay 32 and the battery reverse connection prevention relay 33 to the OFF state while the electric drive device 30 is in operation, it is possible to prevent a situation in which the power supply line relay 32 and the battery reverse connection prevention relay 33 cannot be switched to the OFF state.

[0052] When the diagnosing unit 40b diagnoses that a fault has occurred, the predetermined processing unit 40c executes predetermined processing including stopping the supply of power to the inverter 34. Specifically, the predetermined processing is processing to switch the power supply line relay 32 and the battery reverse connection prevention relay 33 to the off state. With this configuration, when the diagnosing unit 40b diagnoses that a fault has occurred in the electric drive device 30, the motor 31 can be stopped, and the automatic guided vehicle 10 can be prevented from being driven in a state that interferes with its operation.

[0053] The drive unit 20 includes a host controller 70 that controls the plurality of electric drive devices 30. When the diagnosing unit 40b diagnoses that a fault has occurred, the predetermined processing unit 40c executes predetermined processing, including notifying the host controller 70 of the occurrence of the fault. This configuration allows the occurrence of the fault to be notified to the host controller 70, making it easier for the host controller 70 to deal with the fault.

[0054] The diagnosing unit 40b performs an initial diagnosis, including diagnosing whether communication between the electric drive unit 30 and the host controller 70 is normal and confirming notifications from the host controller 70 to the electric drive unit 30. With this configuration, the electric drive unit 30 can perform drive control after confirming that communication between the electric drive unit 30 and the host controller 70 is normal and that notifications from the host controller 70 to the electric drive unit 30 have been received.

[0055] When the drive unit 20 is started, the host controller 70 initially diagnoses whether the MCU relay 73 can be switched from the ON state to the OFF state. Therefore, if it becomes necessary to switch the MCU relay 73 to the OFF state while the drive unit 20 is operating, it is possible to prevent a situation in which the MCU relay 73 cannot be switched to the OFF state. Furthermore, if the diagnosis unit 40b of any of the electric drive devices 30 diagnoses that a fault has occurred, the host controller 70 switches the MCU relay 73 to the OFF state. Therefore, if a fault has occurred in any of the electric drive devices 30, the host controller 70 can stop all of the electric drive devices 30 together, further preventing the automatic guided vehicle 10 from being driven in a state that interferes with its operation.

[0056] When the drive unit 20 is started, the host controller 70 initially diagnoses whether the brake relay 75 can be switched from the ON state to the OFF state. Therefore, if it becomes necessary to switch the brake relay 75 to the OFF state while the drive unit 20 is operating, it is possible to prevent a situation in which the brake relay 75 cannot be switched to the OFF state. Furthermore, if the diagnosis unit 40b of any of the electric drive devices 30 diagnoses that a fault has occurred, the host controller 70 switches the brake relay 75 to the OFF state. Therefore, if a fault has occurred in any of the electric drive devices 30, the host controller 70 can stop all of the electric drive devices 30 and all of the brakes 60 collectively.

[0057] The safety measures to be taken differ depending on whether a failure occurs in at least one of the motor 31, the inverter 34, or the control circuit of the electric drive device 30 or whether a failure occurs in another part of the electric drive device 30. That is, even if the failure occurs within the electric drive device 30, the safety measures to be taken differ depending on the part of the failure. It is undesirable for the electric drive device 30 to be erroneously replaced when the failure is external to the electric drive device 30 in the drive unit 20. In this regard, the host controller 70 diagnoses failures external to the electric drive device 30 in the drive unit 20. Specifically, the host controller 70 diagnoses failures in the MCU relay 73 and the brake relay 75 when the drive unit 20 is started. When the diagnosing unit 40b diagnoses a failure in at least one of the motor 31, the inverter 34, and the control circuit, the predetermined processing unit 40c notifies the host controller 70 of which of the motor 31, the inverter 34, and the control circuit has the failure. Therefore, the host controller 70 that receives the notification can execute appropriate safety processing depending on the location of the failure within the electric drive device 30. Furthermore, when a failure has occurred in a part of the drive unit 20 that is external to the electric drive device 30, the host controller 70 can prevent erroneous display of a message indicating that the electric drive device 30 needs to be replaced.

[0058] The above embodiment can be modified as follows: The same parts as those in the above embodiment are denoted by the same reference numerals and the description thereof will be incorporated herein.

[0059] When the diagnostic unit 40b of any of the electric drive units 30 diagnoses that a fault has occurred, the upper controller 70 may switch the MCU relay 73 to the OFF state, or the predetermined processing unit 40c of the faulty electric drive unit 30 may switch the power line relay 32 to the OFF state (safety processing, predetermined processing).

[0060] The diagnosing unit 40b (functions as a diagnosing unit) diagnoses failures (normal or not) in the motor 31, the inverter 34, and the microcomputer of the controller 40, the current sensor 41, and the angle sensor 42 among the control circuits while the drive unit 20 is in operation. In other words, the diagnosing unit 40b may diagnose parts that can be diagnosed while the drive unit 20 is in operation. Furthermore, whether the detected values ​​of the current sensor 41 and the angle sensor 42 are normal, whether the switching elements of the inverter 34 are turning on and off at the commanded timing, etc. can only be diagnosed while the electric drive device 30 is in operation. Therefore, the diagnosing unit 40b may perform a diagnosis including parts that cannot be diagnosed when the drive unit 20 is started up but can be diagnosed while the electric drive device 30 (drive unit 20) is in operation.

[0061] When the diagnosing unit 40b diagnoses that a fault has occurred in at least one of the motor 31, the inverter 34, and the control circuit while the electric drive device 30 is in operation, the predetermined processing unit 40c may execute the safety processing to ensure the safety of the automatic guided vehicle 10 and the notification processing to notify the host controller 70 of the occurrence of the fault. With this configuration, even if a fault occurs that can only be diagnosed while the electric drive device 30 is in operation or if a fault occurs after the electric drive device 30 has been started, it is possible to prevent the automatic guided vehicle 10 from being driven in a state that impedes its operation.

[0062] When the diagnosing unit 40b diagnoses that a fault has occurred in the electric drive device 30, the predetermined processing unit 40c may cause the motor control unit 40a (control circuit) to control the inverter 34 to stop the motor 31 (safety processing, predetermined processing). For example, the motor control unit 40a can control the inverter 34 so that the torque generated by the motor 31 becomes zero. With this configuration, when the diagnosing unit 40b diagnoses that a fault has occurred in the electric drive device 30, the motor control unit 40a can continue to control the inverter 34 while stopping the motor 31. This prevents the motor 31 from going out of control and prevents the automated guided vehicle 10 from being driven in a state that interferes with its operation. Note that the diagnosis of a fault by the diagnosing unit 40b may be an initial diagnosis of a fault when the drive unit 20 is started up, or a diagnosis of a fault during operation of the electric drive device 30.

[0063] Each electric drive device 30 has two systems: an inverter 34, a stator winding 31a of the motor 31, a current sensor 41, and an angle sensor 42. Therefore, as shown in FIG. 5 , when the diagnosing unit 40b diagnoses a fault in one of the two systems, the predetermined processing unit 40c may execute backup control to drive the motor 31 using only the normal system (safety processing, predetermined processing). When the diagnosing unit 40b (initial diagnosing unit) executes an initial diagnosis of the electric drive device 30 upon startup of the drive unit 20, the initial diagnosis can detect a fault that cannot be detected after the drive unit 20 has started operating, and the control can transition to backup control. When the diagnosing unit 40b (diagnosing unit) executes a diagnosis of the electric drive device 30 while the drive unit 20 is operating, the diagnosis can detect a fault that can only be diagnosed while the drive unit 20 is operating, or a fault that occurred after the drive unit 20 has started operating, and the control can transition to backup control. The electric drive device 30 may also have two controllers 40. In this case, backup control can also be performed to drive the motor 31 using only one of the two systems that is normal.

[0064] In this case, the predetermined processing unit 40c of the failed electric drive unit 30 may notify the host controller 70 that backup control is being executed (notification process, predetermined process). With this configuration, the host controller 70 can recognize that there is an electric drive unit 30 executing backup control, making it easier to execute control in response to this.

[0065] As shown in FIG. 6 , when the host controller 70 receives a notification from one of the multiple electric drive units 30 that backup control is being performed, it may cause the other electric drive units 30 to perform backup control. For example, backup control may be performed in the electric drive units 30 other than the electric drive unit 30 in which a failure has occurred, in which the motor 31 is driven using only one of the two systems (safety processing, predetermined processing). During backup control, the maximum torque that the motor 31 can output is lower than during normal control. Therefore, the host controller 70 may instruct each controller 40 to limit the maximum acceleration of the motor 31. With this configuration, when one of the multiple electric drive units 30 fails and backup control is being performed, the other electric drive units 30 can also perform backup control in accordance with the failed electric drive unit 30. Note that during backup control, the upper limit of the rotational speed of the motor 31 may be lowered compared to during normal control. Furthermore, the diagnosis of a failure by the diagnosing unit 40b may be an initial diagnosis of a failure at the start of the drive unit 20, or a diagnosis of a failure during operation of the electric drive unit 30.

[0066] - When the upper controller 70 receives a notification that a failure has occurred in one of the multiple electric drive units 30, the unmanned guided vehicle 10 may be driven using one of the two electric drive units 30 at the front and two electric drive units 30 at the rear, excluding the failed electric drive unit 30.

[0067] Only some of the above-described various diagnoses may be performed in the initial diagnosis of the electric drive device 30 when the drive unit 20 is started and in the diagnosis during operation of the electric drive device 30. Furthermore, only some of the above-described various processes may be performed in the safety process and notification process (predetermined process) performed by the predetermined processing unit 40c.

[0068] One of the four (plural) electric drive units 30 may be designated as a master electric drive unit 30, and the remaining electric drive units 30 may be designated as slave electric drive units 30, with the controller 40 (control unit) of the master electric drive unit 30 controlling the slave electric drive units 30 in an integrated manner. In this case, the processing performed by the higher-level controller 70 described above can be executed by the controller 40 of the master electric drive unit 30.

[0069] The electric drive device 30 may be configured to include only one system of the inverter 34, the stator winding 31a of the motor 31, the current sensor 41, and the angle sensor 42.

[0070] In a configuration in which the drive shaft 13 is braked by causing each motor 31 to generate a braking torque, the brake 60 and the brake relay 75 may be omitted.

[0071] The automated guided vehicle 10 is not limited to a four-wheel drive automated guided vehicle having four electric drive units 30, but may be a two-wheel drive automated guided vehicle having two electric drive units 30.

[0072] The small electric vehicle to which the above-described embodiments and modified examples are applied is not limited to the automated guided vehicle 10, but may also be a one- or two-seater compact mobility vehicle such as an electric wheelchair, an automated guided robot, an agricultural robot, a construction site robot, a factory robot, a food delivery robot, a cleaning robot, an inspection robot, etc.

[0073] The above-described embodiment and modifications may be combined within the scope of possible combinations.

[0074] The following describes characteristic configurations extracted from the above-described embodiments and modified examples. [Configuration 1] A drive unit (20) for a small electric vehicle (10) including a power storage unit (71) and a plurality of drive devices (30) that respectively drive a plurality of drive shafts (13) of the small electric vehicle (10), wherein each drive device includes: a motor (31) that generates power to rotate the drive shaft; an inverter (34) that converts power supplied from the power storage unit and supplies the converted power to the motor; a control circuit (32, 33, 40, 41, 42) that controls the inverter; an initial diagnosis unit (40b) that performs an initial diagnosis of a fault in the motor, the inverter, and the control circuit when the drive unit is started; and a predetermined processing unit (40c) that performs predetermined processing for the fault when the initial diagnosis unit diagnoses that a fault has occurred in at least one of the motor, the inverter, and the control circuit. [Configuration 2] The drive unit for a small electric vehicle according to Configuration 1, wherein the initial diagnosis unit performs the initial diagnosis including diagnosing predetermined locations (32, 33) that can be diagnosed at startup of the drive unit but cannot be diagnosed while the drive device is in operation. [Configuration 3] The drive unit for a small electric vehicle according to Configuration 1 or 2, wherein the control circuit of each drive device includes a predetermined relay (32, 33) that can be switched between an on state that supplies power from the power storage unit to the inverter and an off state that cuts off the power, and the initial diagnosis unit performs the initial diagnosis including diagnosing whether the predetermined relay can be switched from the on state to the off state at startup of the drive unit. [Configuration 4] The drive unit for a small electric vehicle according to any one of Configurations 1 to 3, wherein the predetermined processing unit performs the predetermined processing including stopping the supply of power to the inverter when the initial diagnosis unit diagnoses that a fault has occurred. [Configuration 5] The drive unit for a small electric vehicle according to any one of Configurations 1 to 3, wherein the predetermined processing section executes the predetermined processing including controlling the inverter by the control circuit to stop the motor when the initial diagnosis section diagnoses that the fault has occurred.[Configuration 6] The drive unit for a small electric vehicle according to any one of Configurations 1 to 5, further comprising a control unit (70) that controls the plurality of drive devices in an integrated manner, and wherein the predetermined processing unit executes the predetermined processing including notifying the control unit of the occurrence of the failure when the initial diagnosis unit diagnoses that the failure has occurred. [Configuration 7] The drive unit for a small electric vehicle according to Configuration 6, further comprising: a control unit (70) that controls the plurality of drive devices in an integrated manner, and wherein the predetermined processing unit executes the predetermined processing including notifying the control unit of the occurrence of the failure when the initial diagnosis unit diagnoses that the failure has occurred. [Configuration 8] The drive unit for a small electric vehicle according to any one of Configurations 1 to 7, further comprising: a control unit (70) that controls the plurality of drive devices in an integrated manner, and wherein the predetermined processing unit executes the predetermined processing including backup control for driving the motor using only one of the two normal systems when the initial diagnosis unit diagnoses that the failure has occurred. [Configuration 9] The drive unit for a small electric vehicle according to Configuration 8, further comprising: a control unit that controls the plurality of drive devices in an integrated manner, and the predetermined processing unit executes the predetermined processing including notifying the control unit that the backup control is being executed. [Configuration 10] The drive unit for a small electric vehicle according to Configuration 9, further comprising: a host controller (70) that controls the plurality of drive devices in an integrated manner, and a host relay (73) that is switchable between an ON state in which power is supplied from the power storage unit to the plurality of drive devices and an OFF state in which power is cut off to the plurality of drive devices, and the host controller performs an initial diagnosis of whether the host relay can be switched from the ON state to the OFF state when the drive unit is started, and switches the host relay to the OFF state when the initial diagnosis unit of any of the drive devices diagnoses that a fault has occurred.[Configuration 12] A drive unit for a small electric vehicle as described in Configuration 11, comprising: a plurality of braking devices (60) that brake the plurality of drive shafts, respectively; and a braking device relay (75) that can be switched between an ON state in which power is supplied from the power storage unit to the plurality of braking devices and an OFF state in which power to the plurality of braking devices is cut off, wherein the upper controller, when starting up the drive unit, performs an initial diagnosis to determine whether the braking device relay can be switched from the ON state to the OFF state, and switches the braking device relay to the OFF state if the initial diagnosis unit of any of the drive devices diagnoses that the fault has occurred.

[0075] Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments or structures. The present disclosure also encompasses various modifications and equivalent modifications. In addition, various combinations and forms, including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure.

Claims

1. A drive unit (20) for a small electric vehicle (10), comprising a power storage unit (71) and a plurality of drive devices (30) that respectively drive a plurality of drive shafts (13) of the small electric vehicle (10), each drive device comprising: a motor (31) that generates power to rotate the drive shaft; an inverter (34) that converts power supplied from the power storage unit and supplies it to the motor; a control circuit (32, 33, 40, 41, 42) that controls the inverter; an initial diagnosis unit (40b) that performs an initial diagnosis of faults in the motor, the inverter, and the control circuit when the drive unit is started; and a predetermined processing unit (40c) that performs predetermined processing for the fault when the initial diagnosis unit diagnoses that a fault has occurred in at least one of the motor, the inverter, and the control circuit.

2. A drive unit for a small electric vehicle as described in claim 1, wherein the initial diagnosis unit performs the initial diagnosis including diagnosing predetermined locations (32, 33) that can be diagnosed when the drive unit is started but cannot be diagnosed while the drive device is in operation.

3. A drive unit for a small electric vehicle as described in claim 1 or 2, wherein the control circuit of each drive device is provided with a predetermined relay (32, 33) that can be switched between an on state in which power is supplied from the storage unit to the inverter and an off state in which the power is cut off, and the initial diagnosis unit performs the initial diagnosis when the drive unit is started, including diagnosing whether the predetermined relay can be switched from the on state to the off state.

4. A drive unit for a small electric vehicle as described in claim 1 or 2, wherein the predetermined processing unit executes the predetermined processing including stopping the supply of power to the inverter when the initial diagnosis unit diagnoses that a fault has occurred.

5. A drive unit for a small electric vehicle as described in claim 1 or 2, wherein the predetermined processing unit executes the predetermined processing including controlling the inverter by the control circuit to stop the motor when the initial diagnosis unit diagnoses that a fault has occurred.

6. A drive unit for a small electric vehicle as described in claim 1 or 2, comprising a control unit (70) that controls the plurality of drive devices in an integrated manner, and wherein the predetermined processing unit executes the predetermined processing, including notifying the control unit of the occurrence of the failure, when the initial diagnosis unit diagnoses that the failure has occurred.

7. A drive unit for a small electric vehicle as described in claim 6, wherein the initial diagnosis unit performs the initial diagnosis including diagnosing whether communication between the drive device and the control unit is normal and confirming notifications from the control unit to the drive device.

8. A drive unit for a small electric vehicle as described in claim 1 or 2, wherein each drive device has two systems of the inverter and the stator winding (31a) of the motor, or two systems of the inverter, the stator winding of the motor, and the control circuit (40), and the predetermined processing unit executes the predetermined processing including backup control for driving the motor using only one of the two systems that is normal when the initial diagnosis unit diagnoses that a failure has occurred.

9. A drive unit for a small electric vehicle as described in claim 8, comprising a control unit that controls a plurality of said drive devices in an integrated manner, and wherein said predetermined processing unit executes said predetermined processing including notifying said control unit that said backup control is being executed.

10. A drive unit for a small electric vehicle as described in claim 9, wherein when the control unit receives the notification that the backup control is being performed from one of the plurality of drive units, the control unit causes the other drive units to perform the backup control.

11. A drive unit for a small electric vehicle as described in claim 1 or 2, comprising: a host controller (70) that controls the multiple drive devices in an integrated manner; and a host relay (73) that can be switched between an on state in which power is supplied from the power storage unit to the multiple drive devices and an off state in which power is cut off to the multiple drive devices, wherein the host controller, when starting up the drive unit, performs an initial diagnosis of whether the host relay can be switched from the on state to the off state, and switches the host relay to the off state if the initial diagnosis unit of any of the drive devices diagnoses that a fault has occurred.

12. A drive unit for a small electric vehicle as described in claim 11, comprising: a plurality of braking devices (60) that respectively brake a plurality of drive shafts; and a braking device relay (75) that can be switched between an on state in which power is supplied from the storage unit to the plurality of braking devices and an off state in which power is cut off to the plurality of braking devices, wherein the upper controller, when starting up the drive unit, performs an initial diagnosis to determine whether the braking device relay can be switched from the on state to the off state, and switches the braking device relay to the off state if the initial diagnosis unit of any of the drive devices diagnoses that a fault has occurred.

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