Electric working machinery

Abstract

To provide an electric work machine which suppresses an action for connecting a power supply cable from an external power source to a main machine during driving, and can prevent occurrence of arc discharge even if the power supply cable is connected.SOLUTION: An electric work machine includes a battery, and a hydraulic actuator using a hydraulic pump driven by an electric motor using the battery as a driving power source, as a hydraulic source, and can supply power to the battery from an external power source connected to a power supply cable by selecting to supply power to the battery by a switch and detecting that rotation of the electric motor is stopped and the power supply cable is connected to a power supply port connected to the battery.SELECTED DRAWING: Figure 5D

Description

[Technical Field]

[0001] The present invention relates to an electric work machine. [Background technology]

[0002] The following Patent Document 1 describes a power supply system that drives an electric motor using a commercial power source and a battery. This power supply system supplies DC power to an electric motor. a circuit for supplying DC power from a battery to an inverter for converting the DC power into AC power and supplying the AC power; The AC power supplied from the commercial power source is converted to DC power through an AC-DC converter and then fed to the inverter. It is equipped with a power supply switching device that switches the electrical path supplied to the

[0003] The following Patent Document 2 describes a system that drives an electric motor while continuously charging a battery from an external power source. and a mode in which the electric motor is driven only by the battery. In the excavator, when an external power source is connected while the electric motor is in the mode driven only by the battery, By doing so, the electric motor can be driven while the battery continues to be charged from an external power source. A technology for transitioning to this mode has been disclosed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-228715 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-308881 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in Patent Document 1, since the commercial power supply and the battery are selected, If an electric motor is driven only by the power from the commercial power supply, the power to drive the electric motor will be Therefore, when performing work that requires a large driving force, sufficient driving force may not be obtained. Furthermore, in Patent Document 2, an external power source is required for the device while it is being driven only by the battery. There is a risk of arc discharge when connecting the power supply cable to the Furthermore, connecting a power cable to the machine while it is running on battery power alone may affect the rotation and There is a risk of causing a collision accident due to driving movements.

[0006] In view of the above problem, the present invention provides a method for connecting a power supply cable from an external power source to the device while it is in operation. This prevents arc discharge even if a power cable is connected. The object of the present invention is to provide an electric working machine that can [Means for solving the problem]

[0007] The electric working machine of the present invention is an electric working machine including a battery and a hydraulic actuator having a hydraulic pump as a hydraulic source driven by an electric motor that can use the battery as a drive power source, By switch Selection Selected R, The rotation of the electric motor is stopped, and the power supply cable is connected to the power supply port connected to the battery. Toga By detecting this, the power supply cable Turn on the relay of the power supply that converts the AC voltage supplied via It is a composition.

[0008] The electric working machine having the above configuration includes a cutoff lever that limits operation of the hydraulic actuator by cutting off pilot pressure that operates the hydraulic actuator, The configuration may be such that power cannot be supplied from the external power source to the battery unless operation of the hydraulic actuator is restricted.

[0009] The electric working machine having the above configuration may be configured so that the electric motor can be driven using only the battery as a drive power source.

[0010] In the electric working machine configured as described above, the electric motor may be configured to be able to use the external power source as a drive power source via the power supply cable. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a side view showing an electric work machine according to an embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged side view showing the periphery of a cut-off lever of the electric working machine. [Figure 3] FIG. 2 is a diagram showing a hydraulic circuit of the electric working machine. [Figure 4] FIG. 2 is a block diagram of a power supply system mounted on the electric work machine. [Figure 5A] FIG. 1 is a block diagram of a power supply system that realizes a commercial power supply mode. [Figure 5B] FIG. 1 is a block diagram of a power supply system that realizes a 2-way mode. [Figure 5C] FIG. 1 is a block diagram of a power supply system that realizes a battery mode. [Figure 5D] FIG. 1 is a block diagram of a power supply system that realizes a charging mode. [Figure 6] 10 is a flowchart showing a procedure for controlling switching of power supply modes. [Figure 7] 10 is a flowchart showing a procedure for controlling switching between a 2-way mode and a battery mode. [Figure 8] 10 is a flowchart showing a procedure for controlling switching between a 2-way mode and a battery mode according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0013] [Configuration of electric work machines] First, referring to FIGS. 1 and 2, a hydraulic excavator 1 as an example of an electrically operated working machine will be described. The outline of the structure will be explained. However, the electric work machine is not limited to the hydraulic excavator 1. The hydraulic excavator 1 includes a lower traveling body 2 and a working machine. 3 and an upper rotating body 4.

[0014] The lower traveling body 2 includes a pair of left and right crawlers 21, 21 and a pair of left and right traveling motors 22L, 22L. The left and right travel motors 22L, 22R are hydraulic motors that drive the left and right crawlers 21 , 21 are driven respectively to enable the hydraulic excavator 1 to move forward and backward. The traveling body 2 is provided with a blade 23 and a hydraulic cylinder for rotating the blade 23 in the vertical direction. A blade cylinder 23a is provided as a blade holder.

[0015] The work machine 3 includes a boom 31, an arm 32, and a bucket 33, which are independently driven. The boom 31, the arm 32, and the Each bucket 33 corresponds to a working part, and the hydraulic excavator 1 has a plurality of working parts.

[0016] The boom 31 is a telescopic boom whose base end is supported on the front part of the upper rotating body 4. The arm 32 is rotated by a cylinder 31a. and is rotated by an arm cylinder 32a that is movable in an expandable and contractible manner. The bucket 33 is a bucket whose base end is supported by the tip end of the arm 32 and which is movable in an extendable and retractable manner. The boom cylinder 31a, the arm cylinder 32a, The bucket cylinder 33a is composed of a hydraulic cylinder.

[0017] The upper rotating body 4 can rotate relative to the lower traveling body 2 via a rotating bearing (not shown). The upper rotating body 4 is configured to be able to operate. The upper swing body is driven by the driving force of the swing motor 43, which is a hydraulic motor. The upper rotating body 4 rotates via a rotating bearing (not shown). A plurality of hydraulic pumps (not shown in FIG. 1) driven by motors are provided. The hydraulic pumps are connected to the hydraulic motors (travel motors 22L, 22R, swing motor 43), Cylinders (blade cylinder 23a, boom cylinder 31a, arm cylinder 32a, and and bucket cylinder 33a). These are generally called hydraulic actuators.

[0018] The control section 41 is provided with a control seat 411. A pair of operation control seats are provided on the left and right of the control seat 411. A pair of drive levers 412L, 412R are arranged in front of the vehicle, and a pair of travel levers 413L, 413R are arranged in front of the vehicle. The operator sits in the operator's seat 411 and operates the work operation levers 412L, 412R, the travel By operating the levers 413L, 413R, etc., each hydraulic actuator is controlled. It can run, turn, work, etc.

[0019] The work operation levers 412L and 412R are attached integrally to the lever stand 414. From this lever stand 414, the operation levers 412L and 412R can be operated. A cut-off lever 415 for turning on and off the operation of the machine 3 is provided extending forward. The to-off lever 415 is configured to be rotatable up and down, and when rotated downward, the work The working machine 3 can be operated by operating the operating levers 412L and 412R. If the work operation levers 412L and 412R are rotated, the work machine 3 will not operate even if the work operation levers 412L and 412R are operated. The lever stand 414 is configured to be in a locked state. A cut-off switch 416 is provided to detect the rotation position of the lever 415. The off switch 416 is turned on when the cut-off lever 415 is rotated downward. When the cut-off lever 415 is rotated upward, it is turned off.

[0020] The upper revolving body 4 is provided with a power supply port (not shown), and a commercial power source 5 (external By connecting the power supply cable 51 of the commercial power supply 5, the power supply system described later can be Can be connected to 6.

[0021] The hydraulic pump that supplies pressure oil to the hydraulic actuator is an electric motor driven by electricity. The commercial power supply 5 and the battery 62 supply power to the electric motor. do.

[0022] [Hydraulic circuit configuration] FIG. 3 shows a hydraulic circuit 100 mounted on the hydraulic excavator 1. The hydraulic circuit 100 includes: , a first actuator 111, a second actuator 112, a hydraulic pump 113, and a pump Pilot pump 114, first directional control valve 115, second directional control valve 116, and operating device 117 and is equipped with.

[0023] The first actuator 111 is driven by pressure oil supplied from a hydraulic pump 113. The first actuator 111 is, for example, the travel motors 22L and 22R. The second actuator 112 is driven by pressure oil supplied from a hydraulic pump 113. The second actuator 112 is, for example, a boom cylinder 31a. do.

[0024] The hydraulic pump 113 is driven by an electric motor (not shown) and discharges pressure oil. The pressure oil discharged from the pump 113 flows through oil passages 113a and 113b to the first direction switching valve 114. 3, the hydraulic pressure is supplied to the hydraulic pump 113 and the second directional control valve 116. The hydraulic oil passages for the hydraulic oil supplied from the hydraulic oil supply pipe to the first actuator 111 and the second actuator 112 are provided. It is shown by a line.

[0025] The first directional control valve 115 switches the direction of the pressure oil supplied to the first actuator 111. The second directional control valve 116 is a pilot-operated directional control valve that can adjust the flow rate. The flow rate of the pressure oil supplied to the second actuator 112 can be adjusted by switching the direction of the pressure oil. It is a pilot operated directional control valve.

[0026] The pilot pump 114 is connected to a first directional control valve 115 and a second directional control valve 116. In FIG. 3, the pilot pump 114 discharges pilot pressure oil as a command. The oil passage for the pilot pressure oil supplied to the two-way switching valve 116 is shown by a broken line (note that the The oil passage for the pilot pressure oil supplied from the pilot pump 114 to the first directional control valve 115 is shown in the figure. The pilot pump 114 is connected to the first directional control valve 115 and the second directional control valve 116. The pilot pump 114 generates a pilot pressure applied to the valve 16. It is driven by a motor and discharges pressure oil to generate pilot pressure in the oil passage 114a. To generate.

[0027] The first directional control valve 115 can be switched to a plurality of positions by sliding the spool. The pilot port 115a of the first directional control valve 115 and the pilot When pilot pressure is not applied to either of the ports 115b, the spring force As a result, the first directional control valve 115 is held in the neutral position. When the pressure oil is in the pressure oil passage 113b, the pressure oil is not supplied to the first actuator 111 from the oil passage 113b.

[0028] On the other hand, the pilot port 115a or the pilot port 115 When pilot pressure is applied to b, the first directional control valve 115 moves from the neutral position to another position. The pressure oil is supplied to the first actuator via the oil passage 111a or the oil passage 111b. The pressure oil is supplied to the oil passage 111a or the oil passage 111b. The first actuator 111 is driven to rotate in the forward or reverse direction.

[0029] The second directional control valve 116 can be switched to a plurality of positions by sliding the spool. The pilot port 116a of the second directional control valve 116 and the pilot If pilot pressure is not applied to either port 116b, the spring force As a result, the second directional control valve 116 is held in the neutral position. When the pressure oil is in the pressure oil passage 113a, the pressure oil is not supplied to the second actuator 112 from the oil passage 113a.

[0030] On the other hand, the pilot port 116a or the pilot port 116 of the second directional control valve 116 When pilot pressure is applied to b, the second directional control valve 116 moves from the neutral position to another position. The pressure oil is supplied to the second actuator via the oil passage 112a or the oil passage 112b. The pressure oil is supplied to the rotor 112 via the oil passage 112a or the oil passage 112b. , the second actuator 112 expands and contracts.

[0031] The operating device 117 controls the direction and pressure of the pilot pressure oil supplied to the second directional control valve 116. The operating device 117 has a remote control valve 117a for switching. The remote control valve 117a is connected to the oil passage 114a. The remote control valve 117a is connected to the second direction switching valve 116 via an oil passage 117b and an oil passage 117c. The pilot ports 116a and 116b are connected to the remote control. The control valve 117a controls the pressure oil supplied from the pilot pump 114 via the oil passage 114a. The pilot pressure oil is supplied to the second directional control valve 116. This switches the second directional control valve 116, and the oil supplied to the second actuator 112 is The flow rate can be adjusted by switching the direction of the pressure oil.

[0032] An on-off valve 18 is provided in the oil passage 114a between the pilot pump 114 and the remote control valve 117a. The on-off valve 180 is configured as an electromagnetic valve and is equipped with a solenoid 180a. The solenoid 180a is connected to a cut-off switch 416. As shown in FIG. 3, the cut-off lever 415 is rotated downward to cut the guide 180a. When the off switch 416 is ON, it is energized and the on-off valve 180 is in a communicating state. As a result, pressure oil from the pilot pump 114 flows through the on-off valve 180 to the remote control valve 117a. On the other hand, as shown by the two-dot chain line in FIG. 3, the cut-off lever 415 is rotated upward. When the power is turned off, the cut-off switch 416 is turned off by the spring force. The power is no longer supplied to the switch 180a, and the on-off valve 180 is brought into a shutoff state by the biasing force of the spring. As a result, pressure oil from the pilot pump 114 is not supplied to the remote control valve 117a. Therefore, even if the operating device 117 is operated, pilot pressure is not applied to the second direction switching valve 116. Therefore, pressure oil is not supplied to the second actuator 112, and the operation of the second actuator 112 is Therefore, when the cut-off lever 415 is rotated downward, the operation of the operating device The working machine 3 can be operated by operating the operating device 117, and when it is turned upward, Even if the locking device 117 is operated, the working machine 3 is locked and does not operate.

[0033] [Power supply system configuration] 4, a power supply system that supplies power to the electric motor 7 mounted on the hydraulic excavator 1 will be described. The power supply system 6 converts the AC power supply voltage of the commercial power supply 5 into a DC power supply voltage. A power supply device 61 to be replaced, a battery 62 to charge or discharge power from the power supply device 61, and a direct an inverter 63 that converts a current power supply voltage into an AC power supply voltage; a first electric circuit 6a that supplies power to the battery 62; and a second electric circuit 6b that connects the battery 62 to the first electric circuit 6a. The electric circuit 6b is disposed between the junction 6c of the first electric circuit 6a and the second electric circuit 6b and the inverter 63. and a battery relay 64 disposed between the junction 6c and the battery 62. and a power supply relay 66 arranged between the junction 6c and the power supply 61.

[0034] The power supply unit 61 converts AC voltage supplied from the commercial power source 5 via the power supply cable 51 into DC voltage. This DC voltage is converted into a voltage by the battery via the power supply relay 66 and the battery relay 65. The DC voltage of the power supply 61 is supplied to the battery 62, and the battery 62 is charged. The power is supplied to the inverter 63 via the inverter relay 66 and the inverter relay 64 .

[0035] The battery 62 is connected to the inverter 6 via a battery relay 65 and an inverter relay 64. 3. The battery 62 is exemplified by a lithium ion battery. .

[0036] The inverter 63 converts the DC voltage supplied from the power supply 61 and / or the battery 62 into AC This AC voltage is supplied to the electric motor 7. The electric motor 7 is 4, only the hydraulic pump 113 is shown, but the hydraulic pump 113 is also shown. A plurality of pumps may be provided.

[0037] The power supply system 6 also includes a system controller 67 for controlling the power supply system 6. The system controller 67 controls the power supplied to the electric motor 7, More specifically, the system controller 67 controls the charging of the battery 62. 61, inverter 63, inverter relay 64, battery relay 65, power supply relay 6 6, etc., to drive the electric motor 7 and charge the battery 62. It is possible.

[0038] The power supply system 6 has a plurality of power supply modes shown in FIGS. 5A to 5D. As shown in FIG. 5A, the contacts of the inverter relay 64 and the power supply relay 66 are brought into contact. By disconnecting the contacts of the battery relay 65, power is supplied only from the commercial power source 5 to operate the motor. A commercial power supply mode for driving the motor 7 can be configured. This reduces the frequency of use of the battery 62, thereby extending the life of the battery 62. Even if the power supply 62 becomes abnormal, if it is in commercial power mode, work can be continued using the commercial power supply 5. It can be continued.

[0039] As shown in FIG. 5B, the power supply system 6 includes an inverter relay 64, a power supply relay By connecting the three contacts of the battery relay 62 and the commercial power supply, A 2-way mode (corresponding to the first power supply mode) in which power is supplied from the power source 5 to drive the electric motor 7. (to be configured).

[0040] As shown in FIG. 5C, the power supply system 6 includes an inverter relay 64 and a battery relay. The contacts of the relay 65 are connected and the contacts of the power supply relay 66 are disconnected, A battery mode (corresponding to a second power supply mode) in which electric power is supplied from the (which can be configured as follows.)

[0041] As shown in FIG. 5D, the power supply system 6 includes a battery relay 65 and a power supply relay By connecting the contacts of the inverter relay 66 and disconnecting the contacts of the inverter relay 64, the inverter is powered by the commercial power supply 5. A charging mode can be configured in which only the battery 62 is charged.

[0042] Next, we will explain the control method for switching the power supply mode. 1 is a flowchart showing the procedure for controlling the switching of the power supply mode. Then, the operator selects the power supply mode using the power supply mode selection switch. In step S1, it is determined which power supply mode has been selected. If mode 1 is selected, When this occurs, the system controller 67 controls the inverter relay 64 and the power supply relay 66. The power supply is turned on and the battery relay 65 is turned off, and the commercial power supply mode is established.

[0043] On the other hand, if mode 2 or mode 3 is selected in step S1, the next step In S2, it is determined whether the power supply device 61 is available for use. The power supply device 61 determines whether it is available for use. If the device is unusable, a control unit is provided to send an error signal to the system controller 67. When the system controller 67 receives an error signal from the power supply 61, The electric appliance 61 is determined to be unusable.

[0044] If it is determined in step S2 that the power supply device 61 is "unusable," the next step S In step 3, it is determined whether the battery 62 is usable. The battery 62 determines whether it is usable. If the device is unusable, an error signal is sent to the system controller 67. When the system controller 67 receives an error signal from the battery 62, In step S3, it is determined that the battery 62 is "unusable." If it is determined that the error is "OK", the system controller 67 issues an error notification.

[0045] On the other hand, if it is determined in step S3 that the battery 62 is "usable," the next step is In step S4, the system controller 67 turns on the battery relay 65. Then, in step S5, it is determined whether the inverter 63 is available. If it is not available, an error signal is sent to the system controller 67. The system controller 67 is provided with a control section for transmitting the output from the inverter 63. If an error signal is received, it is determined that the inverter 63 is unusable. If the inverter 63 is determined to be "unusable," the system controller 67 issues an error - Issue an alert.

[0046] On the other hand, if it is determined in step S5 that the inverter 63 is "available," the next In step S6, the system controller 67 turns on the inverter relay 64. This allows the battery motor 7 to be driven by power supplied only from the battery 62. This allows realization of a second power supply mode.

[0047] If it is determined in step S2 that the power supply device 61 is "usable," the next step S In step S7, it is determined whether the battery 62 is usable. If it is determined that the device is "unusable," the system controller 67 issues an error message. On the other hand, if it is determined in step S7 that the battery 62 is "usable", the next step is In step S 8 , the system controller 67 turns on the battery relay 65 .

[0048] Next, in step S9, it is determined which power supply mode has been selected. If it is determined that the power supply cable 51 is selected, the power supply cable 51 is connected in the next step S10. When the power supply cable 51 is connected to the power supply port, the power supply unit 61 detects this and The system controller 67 then sends a connection signal to the system controller 67. When a connection signal is received from the power supply 61, it is determined that the power supply cable 51 is connected to the power supply port. In step S10, if the power supply cable 51 is determined to be "unconnected", the system The system controller 67 issues an error notification.

[0049] On the other hand, if it is determined in step S10 that the power supply cable 51 is "connected," the next In step S11, the power supply relay 66 is turned on. A charging mode can be realized in which only the battery 62 is charged.

[0050] If it is determined in step S9 that mode 2 is selected, the next step S In step 12, it is determined whether the inverter 63 is available. If the inverter 63 is unusable, an error is reported. If it is determined that the inverter 63 is usable, the system controller 64 is The controller 67 turns on the inverter relay 64.

[0051] Next, in step S14, the connection of the power supply cable 51 is checked. In step 4, if the power supply cable 51 is determined to be "unconnected," power is supplied only from the battery 62. The battery mode (second power supply mode) is entered, in which power is supplied to drive the electric motor 7.

[0052] On the other hand, if it is determined in step S14 that the power supply cable 51 is "connected," the next In step S15, the power supply relay 66 is turned on. a two-way mode (first power supply mode) in which power is supplied from the power supply 5 to drive the electric motor 7; This can be achieved.

[0053] Next, using Figure 7, we will explain the control method for switching between 2-way mode and battery mode. When the device is in the battery mode, in step S16, the power supply cable In step S16, if the power supply cable 51 is "not connected", If it is determined that the battery mode is not reached, the battery mode is continued.

[0054] On the other hand, if it is determined in step S16 that the power supply cable 51 is "connected," the next In step S17, it is determined whether the rotation of the electric motor 7 is stopped. The motor 7 is provided with a position sensor, and the inverter 63 receives the position sensor signal from the electric motor 7. The rotation speed of the electric motor 7 is calculated by receiving information from the sensor. The information is sent to the system controller 67. The system controller 67 Based on the information on the rotation speed of the electric motor 7 received from 63, the rotation of the electric motor 7 is stopped. In step S17, it is possible to determine whether the rotation of the electric motor 7 is If the determination is "NO" and the vehicle is not stopped, the battery mode continues.

[0055] On the other hand, in step S17, if the rotation of the electric motor 7 is stopped, the answer is "YES." If so, in the next step S18, the power supply relay 66 is turned on. , it is possible to switch from battery mode to 2-way mode.

[0056] Also, in the 2-way mode, in step S19, the power supply cable 51 is connected. In step S19, if it is determined that the power supply cable 51 is "connected", Continue in 2-way mode.

[0057] On the other hand, if it is determined in step S19 that the power supply cable 51 is "not connected," In step S20, the power supply relay 66 is turned off. This turns off the 2-way mode. It is possible to realize switching from the power supply mode to the battery mode.

[0058] [Another embodiment] As shown in Figure 8, when switching from battery mode to 2-way mode, the power supply cable Check the connection of the cable 51, check that the electric motor 7 has stopped rotating, and check that the cut-off lever 4 Even if it is determined whether or not the hydraulic actuator is restricted by rotating the hydraulic actuator upward, The system controller 67 determines whether the cutoff signal sent from the cutoff switch 416 is Based on the information whether the flavor bar 415 is rotated upward or downward, the cut-off lever 4 In step S17, it is possible to determine whether the indicator 15 has been rotated upward. If it is determined that the cut-off lever 415 is turned upward in the next step S21, In step S21, it is determined whether the cut-off lever 415 is in the down position. If the answer is "NO," the battery mode continues. If the cut-off lever 415 is turned upward and the answer is "YES," the next step In step S18, the power feeder relay 66 is turned on.

[0059] Although the embodiments of the present invention have been described above with reference to the drawings, the specific configurations are as follows. The scope of the present invention should not be considered limited to the above embodiments. The invention is not limited to the description of the embodiments, but is also indicated by the scope of the claims, and is equivalent to the scope of the claims. and all changes therein within the meaning and scope of the same. [Explanation of symbols]

[0060] 1. Hydraulic excavator 5 Commercial power supply 51 Power supply cable 6 Power System 7 Electric motor 62 Battery 112 Second Actuator 113 Hydraulic Pump 415 Cut-off lever

Claims

1. A power supply that converts AC voltage supplied to a power port to which a power cable of an external power source is connected into DC voltage; a battery to which power is supplied from the power supply via a power supply relay and a battery relay; an inverter to which power is supplied from the power supply via the power supply relay and the inverter relay, and to which power is supplied from the battery via the battery relay and the inverter relay; an electric motor to which power is supplied via the inverter; a switch capable of selecting a charging mode for charging the battery; a hydraulic actuator using a hydraulic pump driven by the electric motor as a hydraulic pressure source; A controller; An electric work machine comprising: When the controller detects that the charging mode is selected by the switch and the power supply cable is connected to the power supply port, The controller separates the contacts of the inverter relay and turns on the power supply relay and the battery relay.

2. An electric work machine as described in claim 1, wherein the controller is capable of switching to a mode in which the electric motor can be driven using only the battery as a driving power source by controlling the contacts of the inverter relay and the battery relay to come into contact and the contacts of the power supply relay to be separated.

3. An electric work machine as described in claim 1 or 2, wherein the controller controls the contacts of the power supply relay and the inverter relay to be in contact while the contacts of the battery relay are separated, or controls the contacts of the power supply relay, the battery relay, and the inverter relay to be in contact, thereby enabling the electric motor to be switched to a mode in which the external power source is used as a driving power source via the power supply cable.

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