JP2006042416A - Electric vehicle and its control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To more accurately measure the travel resistance in running of an electric vehicle. <P>SOLUTION: When coasting run for measuring the travel resistance is instructed, an inverter 26 to drive a motor 22 is shut down, and when vehicle speed is larger than given vehicle speed Vref, a system main relay 30 to perform electric connection and break between the inverter 26 and a battery 24 is switched off, and when the vehicle speed is under the given vehicle speed Vref, the system main relay 30 is kept ON. Hereby, the regenerative braking of the motor 22 is prevented regardless of vehicle speed, therefore it can be put in a complete nondrive state. Accordingly, the travel resistance can be measured more accurately by measuring the travel resistance in this nondrive state. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electric vehicle and a control method thereof.

Conventionally, this type of electric vehicle has been proposed that includes a motor that is connected to an axle via a differential gear and exchanges electric power with a battery via an inverter (for example, see Patent Document 1). In this electric vehicle, when the non-driving state is selected during traveling, the switching element of the inverter is subjected to switching control so that the torque output from the motor becomes 0 when the rotational speed of the motor is equal to or higher than a predetermined rotational speed. When the number of revolutions of the motor becomes less than the predetermined number of revolutions, the switching element of the inverter is shut off, and the back electromotive voltage exceeding the voltage of the battery is generated in the motor to suppress the motor from being regeneratively braked. Is secured.
JP-A-6-225402

  Ensuring a non-driving state while traveling in an electric vehicle is considered as an important problem. Here, when the non-driving state is secured, energy loss due to switching of the switching element when the torque output from the motor is set to the value 0 is suppressed, or the torque output from the motor is more reliably set to the value 0. Therefore, it is desirable that the switching element of the inverter be cut off.

  In addition, securing the non-driving state during traveling is also important for ensuring the accuracy when measuring the traveling resistance of the vehicle.

  An object of the electric vehicle and the control method thereof according to the present invention is to more appropriately ensure the non-driving state of the axle. Another object of the present invention is to make it possible to more accurately measure the running resistance of a vehicle.

  The electric vehicle and the control method thereof according to the present invention employ the following means in order to achieve at least a part of the above object.

The electric vehicle of the present invention is
An electric vehicle comprising an electric motor connected to an axle,
Charge / discharge power storage means;
A drive circuit connected to the power storage means and connected to the electric motor to drive the electric motor by operating a power adjustment element;
A connection blocking means capable of electrically connecting and disconnecting the power storage means and the drive circuit;
And a control means for controlling the connection cut-off means to stop the power adjustment element and to put into a cut-off state when traveling under a predetermined condition is instructed when the connection cut-off means is in a connected state. To do.

In the electric vehicle according to the present invention, the power adjustment is performed when the traveling under the predetermined condition is instructed when the connection blocking means capable of electrical connection and disconnection between the power storage means and the drive circuit for driving the electric motor is in the connected state. Since the connection cut-off means is controlled so as to stop the element and set the cut-off state, the non-driven state of the axle can be secured more appropriately. Further, the energy efficiency can be improved as compared with the case where the non-driving state is ensured by operating the power adjustment element. Here, the “power adjustment element” includes a switching element.

  The electric vehicle according to the present invention includes vehicle speed detection means for detecting a vehicle speed, and the control means travels according to the predetermined condition when the connection blocking means is in a connected state and the detected vehicle speed is less than a predetermined vehicle speed. Can be a means for maintaining the connection state. By doing so, it is possible to suppress frequent disconnection of the connection blocking means during traveling.

  In the electric vehicle of the present invention, the predetermined condition may be a condition that is satisfied when the shift operation is performed to the neutral position. By so doing, the axle can be brought into a non-driven state when operated to the neutral position.

  Furthermore, in the electric vehicle of the present invention, the predetermined condition may be a condition that is satisfied when traveling in a traveling resistance measurement mode for measuring a traveling resistance of the vehicle is instructed. In this way, since the running resistance can be measured after securing the non-driving state of the axle, the running resistance can be measured more accurately.

The electric vehicle control method of the present invention includes:
An electric motor connected to the axle; chargeable / dischargeable power storage means; a drive circuit that is connected to the power storage means and that is connected to the electric motor to drive the electric motor by operating a power adjustment element; and the power storage means A connection blocking means capable of electrical connection and disconnection with the drive circuit, and a control method for an electric vehicle comprising:
The gist is to control the connection cut-off means to stop the power adjustment element and to put into a cut-off state when traveling according to a predetermined condition is instructed when the connection cut-off means is in the connected state.

  According to the electric vehicle control method of the present invention, when the connection blocking means capable of electrical connection and disconnection between the power storage means and the drive circuit for driving the electric motor is in the connected state, traveling under a predetermined condition is instructed. In this case, since the connection blocking means is controlled so as to stop the power adjusting element and set it to the blocking state, the non-driving state of the axle can be ensured more appropriately. Further, the energy efficiency can be improved as compared with the case where the non-driving state is ensured by operating the power adjustment element. Here, the “power adjustment element” includes a switching element.

  Next, the best mode for carrying out the present invention will be described using examples.

  FIG. 1 is a configuration diagram showing an outline of a configuration of an electric vehicle 20 as an embodiment of the present invention. As shown in the drawing, the electric vehicle 20 according to the embodiment includes a motor 22 connected to an axle connected to drive wheels 28a and 28b via a differential gear 29, a battery 24 that exchanges power with the motor 22, and a battery 24. An inverter 26 that converts the direct current power into a predetermined alternating current power and supplies the motor 22 to the motor 22, and a system main relay 30 that is interposed between the battery 24 and the inverter 26 and electrically connects and disconnects between the two. An electronic control unit 40 for controlling the entire vehicle is provided.

  The motor 22 is configured as a PM type synchronous generator motor including a rotor having a permanent magnet attached to an outer surface and a stator around which a three-phase coil is wound. The power output from the motor 22 is output to the drive wheels 28 a and 28 b via the differential gear 29.

  The inverter 26 includes six transistors T1 to T6 and six diodes D1 to D6 connected in antiparallel to each of the transistors T1 to T6. The transistors T1 to T6 of the inverter 26 are arranged in pairs so as to be on the source side and the sink side with respect to the positive electrode bus 26a and the negative electrode bus 26b, and the connection point between the transistors is a three-phase coil (U Phase, V phase, and W phase). Therefore, by supplying a three-phase alternating current to the three-phase coil of the motor 22 by switching the transistors T1 to T6, it is possible to rotate the motor 22 by forming a rotating magnetic field. Since the motor 22 also functions as a generator, if power is input to the motor 22, the three-phase alternating current generated by the motor 22 can be rectified by the diodes D1 to D6 to charge the battery 24.

  The electronic control unit 40 is configured as a microprocessor centered on the CPU 42, and includes a ROM 44 that stores a processing program, a RAM 46 that temporarily stores data, and an input / output port (not shown), in addition to the CPU 42. The electronic control unit 40 includes a shift position from a shift position sensor 51 that detects an operation position of the shift lever 50, an accelerator pedal position from an accelerator pedal position sensor 53 that detects an amount of depression of an accelerator pedal 52, and a brake pedal 54. The brake pedal position from the brake pedal position sensor 55 that detects the amount of depression, the vehicle speed from the vehicle speed sensor 56, the rotational position from the rotational position detection sensor 58 that detects the rotational position of the rotor of the motor 22, and the three-phase coil of the motor 22 Phase currents from current sensors 59a and 59b that detect currents flowing through the respective phases are input via the input ports. Further, the electronic control unit 40 outputs a switching control signal to the transistors T1 to T6 of the inverter 26, an on / off signal to the system main relay 30, and the like via the output port.

  The operation of the electric vehicle 20 of the embodiment configured as described above, particularly the operation when coasting to measure the running resistance of the vehicle will be described. FIG. 2 is a flowchart illustrating an example of a coasting traveling control routine executed by the electronic control unit 40 of the electric vehicle 20 according to the embodiment. This routine is executed when coasting traveling for measuring the traveling resistance of the vehicle is instructed.

  When the coasting running control routine is executed, the CPU 42 of the electronic control unit 40 first shuts down the inverter 26 (stops the switching of the transistors T1 to T6) (step S100). Subsequently, the vehicle speed V from the vehicle speed sensor 56 is input (step S110), the vehicle speed V is compared with the predetermined vehicle speed Vref (step S120), and when it is determined that the vehicle speed V is greater than the predetermined vehicle speed Vref, the system main relay 30 is turned off (step S130). Here, the predetermined vehicle speed Vref is for determining a range in which the counter electromotive voltage generated in the motor 22 is higher than the voltage on the battery 24 side. Even when the back electromotive voltage generated in the motor 22 is higher than the voltage on the battery 24 side, if the system main relay 30 is turned off, the motor 22 will not be regeneratively braked. It can be in a non-driven state. Therefore, more accurate running resistance can be measured by measuring running resistance in this non-driving state.

  When it is determined in step S120 that the vehicle speed V is equal to or lower than the predetermined vehicle speed Vref, the back electromotive voltage generated by the motor 22 is lower than the voltage on the battery 24 side. In this state, the system main relay 30 is not turned off. Since the motor 22 is not regeneratively braked, the system main relay 30 is kept on.

Then, it is determined whether or not the coasting travel has ended (step S140). When it is determined that the coasting traveling has not ended, the state of the inverter 26 and the state of the system main relay 30 are maintained, and the coasting traveling ends. When it is determined that the system main relay 30 is connected, a process of connecting the system main relay 30 is performed (step S150), and this routine is terminated. When coasting traveling for measuring the traveling resistance is instructed, since the vehicle speed is relatively high, the system main relay 30 is normally turned off. However, after coasting traveling is started, the vehicle speed decreases to a predetermined value. Even when the vehicle speed is lower than Vref, the off state of the system main relay 30 is maintained. In the embodiment, the system main relay 30 is turned off when coasting traveling for measuring traveling resistance is instructed. However, during traveling, the shift lever 50 is operated to the neutral position to instruct normal coasting traveling. In such a case, the system main relay 30 is not turned off and only the inverter 26 is shut down.

  According to the electric vehicle 20 of the embodiment described above, when the coasting for measuring the running resistance is instructed, the inverter 26 is shut down and the system main relay 30 is turned off, so that the motor 22 is regeneratively braked. And the axle can be brought into a completely non-driven state. Therefore, the running resistance can be measured more accurately by measuring the running resistance in this non-driven state. Moreover, when coasting is instructed when the vehicle speed V is equal to or lower than the predetermined vehicle speed Vref, the system main relay 30 is kept on only by shutting down the inverter 26. Therefore, the system main relay 30 is frequently turned on during traveling. It can be suppressed from being turned on / off.

  In the electric vehicle 20 of the embodiment, the system main relay 30 is turned off when the vehicle speed V is higher than the predetermined vehicle speed Vref when coasting, and the system main relay 30 is kept on when the vehicle speed V is equal to or lower than the predetermined vehicle speed Vref. However, the system main relay 30 may be turned off regardless of the vehicle speed V.

  In the electric vehicle 20 of the embodiment, the coasting traveling time control routine of FIG. 2 is executed when coasting traveling for measuring the traveling resistance is instructed, but during traveling regardless of the traveling resistance measurement. Even when the shift lever 50 is operated to the neutral position and coasting is instructed, the routine of FIG. 2 may be executed.

  The electric vehicle 20 of the embodiment has been described as applied to a normal electric vehicle that is driven only by power from the motor 22 without mounting an engine. However, if the electric vehicle has a motor connected to the axle, It can also be applied to a hybrid electric vehicle equipped with an engine. For example, as illustrated in FIG. 3, a hybrid electric machine in which an engine 121 and a motor 130 are connected to a drive shaft connected to an axle (an axle connected to the drive wheels 28 a and 28 b) via a planetary gear mechanism 131. The present invention may be applied to the automobile 120 or, as illustrated in FIG. 4, an inner rotor 232 connected to the output shaft of the engine 221 and a drive connected to an axle (an axle connected to the drive wheels 28a and 28b). The present invention may be applied to a hybrid electric vehicle 220 having an outer rotor 234 connected to a shaft and a counter-rotor motor 230 that relatively rotates both rotors by electromagnetic action.

  The best mode for carrying out the present invention has been described with reference to the embodiments. However, the present invention is not limited to these embodiments, and various modifications can be made without departing from the gist of the present invention. Of course, it can be implemented in the form.

  The present invention is applicable to the automobile industry.

It is a block diagram which shows the outline of a structure of the electric vehicle 20 as one Embodiment of this invention. It is a flowchart which shows an example of the coasting traveling time control routine performed by the electronic control unit 40 of the electric vehicle 20 of an Example. It is a block diagram which shows the outline of a structure of the electric vehicle 120 of a modification. It is a block diagram which shows the outline of a structure of the electric vehicle 220 of a modification.

Explanation of symbols

  20, 120, 220 Electric vehicle, 22 Motor, 24 Battery, 26 Inverter, 26a Positive bus, 26b Negative bus, 28a, 28b Drive wheel, 29 Differential gear, 30 System main relay, 40 Electronic control unit, 42 CPU, 44 ROM , 46 RAM, 50 shift lever, 51 shift position sensor, 52 accelerator pedal, 53 accelerator pedal position sensor, 54 brake pedal, 55 brake pedal position sensor, 56 vehicle speed sensor, 58 rotational position detection sensor, 59a, 59b current sensor, 121 , 221 engine, 130 motor, 131 planetary gear mechanism, 230 rotor motor, 232 inner rotor, 234 outer rotor.

Claims (6)

An electric vehicle comprising an electric motor connected to an axle,
Charge / discharge power storage means;
A drive circuit connected to the power storage means and connected to the electric motor to drive the electric motor by operating a power adjustment element;
A connection blocking means capable of electrically connecting and disconnecting the power storage means and the drive circuit;
An electric vehicle comprising: control means for controlling the connection cutoff means so as to stop the power adjustment element and set the cutoff state when the vehicle is instructed to run under a predetermined condition when the connection cutoff means is in the connected state. The electric vehicle according to claim 1,
Vehicle speed detection means for detecting the vehicle speed,
The control means is means for maintaining the connection state when the connection interruption means is in a connected state and when the detected traveling speed is instructed to run under the predetermined condition when the detected vehicle speed is less than the predetermined vehicle speed.   The electric vehicle according to claim 1, wherein the predetermined condition is a condition that is satisfied when a shift operation is performed to a neutral position.   The electric vehicle according to any one of claims 1 to 3, wherein the predetermined condition is a condition that is satisfied when traveling in a traveling resistance measurement mode for measuring a traveling resistance of a vehicle is instructed.   The electric vehicle according to claim 1, wherein the power adjustment element is a switching element. An electric motor connected to the axle; chargeable / dischargeable power storage means; a drive circuit that is connected to the power storage means and that is connected to the electric motor to drive the electric motor by operating a power adjustment element; and the power storage means A connection blocking means capable of electrical connection and disconnection with the drive circuit, and a control method for an electric vehicle comprising:
An electric vehicle control method for controlling the connection disconnection means to stop the power adjustment element and to enter a disconnection state when traveling according to a predetermined condition is instructed when the connection disconnection means is in a connected state.

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