JP2016032394A - Electric vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique which can avoid discharge control from being not performed normally due to a failure of a positioning sensor when performing the discharge control.SOLUTION: The electric vehicle disclosed in the specification comprises an inverter that supplies electricity to a motor for driving the vehicle and a capacitor connected to the inverter. Further, the electricity vehicle comprises a positioning sensor that detects a rotation position of a rotor of the motor, a collison sensor that detects a collision of the vehicle and a controller. The controller controls the inverter so that an electric load of the capacitor is discharged to the motor on the basis of information about the rotation position detected by the positioning sensor, and the controller, when the collision sensor detects the collision of the vehicle, stops the inverter (S5) and shuts down a current route between the capacitor and the motor. Subsequently, the controller, if there is no abnormality in the positioning sensor, controls the inverter so that the electric load of the capacitor is discharged to the motor as described above (S9).SELECTED DRAWING: Figure 2

Description

  The technology disclosed in this specification relates to an electric vehicle. The electric vehicle includes a hybrid vehicle provided with a motor together with an engine and an electric vehicle provided only with a motor. A fuel cell vehicle is also included in the electric vehicle in this specification.

  An electric vehicle travels by driving a motor using electric power from a battery or the like as an energy source. The electric power supplied to the motor is converted into AC power suitable for driving the motor using an inverter. A large current flows through the inverter to supply power to the motor. In order to smooth the large current input to the inverter, a large-capacitance capacitor is connected to the input terminal of the inverter.

  There is a need for a technique for discharging electric charge accumulated in a capacitor to ensure safety when an electric vehicle collides. Examples of the discharge technique are disclosed in Patent Document 1 and Patent Document 2. Patent Document 1 discloses a technique for discharging electric charge accumulated in a capacitor by using a resistance of a motor coil. Here, the discharge to the motor coil is performed so that the motor torque is not generated based on the detection result of the rotational position of the rotor position sensor. Patent Document 2 discloses a technique for distributing and flowing a current caused by a counter electromotive force generated until a motor stops before a capacitor starts discharging to a plurality of diodes built in the inverter. Has been. In Patent Document 2, all of the upper arm transistors of the inverter are turned off and all of the lower arm transistors are turned on, so that the current due to the back electromotive force is distributed to all of the lower arm transistors. Then, after the motor is stopped, one upper arm transistor is half-on, and the lower arm transistor connected in series with the one upper arm transistor is fully turned on to discharge the capacitor.

JP-A-10-304676 JP2012-110200A

  Patent Document 1 discloses discharge control for discharging a capacitor charge to a motor without generating motor torque. This discharge control is based on the rotational position of the rotor (rotational position with respect to the stator) detected by the position sensor so that the discharge current vector is directed in a direction parallel to the d-axis of the rotor (the direction of the magnetic flux generated by the magnetic poles of the rotor). To control the inverter. By the way, when a vehicle collides, abnormality (for example, disconnection of a signal line, etc.) may occur in a position sensor that detects the rotational position of the rotor. If the above-described discharge control is executed in a state where the position sensor is abnormal, the motor may rotate or an excessive control amount (overcurrent or overvoltage due to incorrect rotation position) may occur. In the following, it should be noted that “discharge control” means discharge control of a capacitor using the rotational position of a rotor by a position sensor unless otherwise specified.

  The technology disclosed in this specification was created in view of the above problems. The purpose is to avoid that the discharge control is not normally performed due to the failure of the position sensor when the above-described discharge control is executed.

  The electric vehicle disclosed in this specification includes a motor that drives the vehicle, an inverter that supplies electric power to the motor, and a capacitor that is connected in parallel to the input terminal of the inverter. The electric vehicle includes a position sensor that detects the rotational position of the rotor of the motor, a collision sensor that detects a collision of the vehicle, and a controller. The controller controls the inverter to discharge the capacitor charge to the motor based on the rotational position detected by the position sensor. When the collision sensor detects a vehicle collision, the controller stops the inverter and interrupts the current path between the capacitor and the motor. Subsequently, if there is no abnormality in the position sensor, the controller controls the inverter to discharge the capacitor charge to the motor based on the rotational position of the rotor as described above. Note that there are a pre-crash sensor, an airbag sensor, and the like as a collision sensor for detecting a collision of a vehicle. Further, means for determining abnormality of the position sensor will be described in the embodiment.

  According to this configuration, after the collision is detected, the capacitor charge is not released to the motor until it is determined that there is no abnormality in the position sensor. That is, discharge control is not performed. Then, after it is determined that there is no abnormality in the position sensor, discharge control is performed. Discharge control is not performed when an abnormality has occurred in the position sensor. Details and further improvements of the technology disclosed in this specification will be described in the following “DETAILED DESCRIPTION”.

It is a block diagram of the electric power system of the electric vehicle of an Example. It is a flowchart of discharge control.

  A hybrid vehicle 2 that is an electric vehicle according to an embodiment will be described with reference to the drawings. In FIG. 1, the block diagram of the electric power system of the hybrid vehicle 2 is shown. The hybrid vehicle 2 of the embodiment includes an engine 6 and a three-phase AC motor (hereinafter referred to as a motor 8) for traveling. The output of the engine 6 and the output of the motor 8 are combined by the power distribution mechanism 7 and transmitted to the axle 9. The power distribution mechanism 7 may distribute the output of the engine 6 to the axle 9 and the motor 8 in some cases. In that case, the hybrid vehicle 2 generates power with the motor 8 while traveling with the power of the engine 6. The generated power is charged in a battery 3 described later. Furthermore, the hybrid vehicle 2 may generate electric power by reversely driving the motor 8 using the kinetic energy of the vehicle during braking, and may charge the battery 3 with the electric power.

  The hybrid vehicle 2 includes a power converter 5, a system main relay 4, and a battery 3. The electric power stored in the battery 3 is supplied to the motor 8 through the system main relay 4 and the power converter 5. As shown in FIG. 1, a motor 8 is connected to an output end of the power converter 5, and a battery 3 is connected to an input end of the power converter 2 with a system main relay 4 interposed therebetween. In the hybrid vehicle 2, current may flow from the motor 8 to the battery 3 (for example, in the case of braking described above). In this specification, for convenience of explanation, the side to which the motor 8 of the power converter 5 is connected is referred to as an “output end”, and the side to which the battery 3 is connected is referred to as an “input end”. Similarly, with respect to a voltage converter 12 and an inverter 13 described later built in the power converter 5, the side where the motor 8 is located is referred to as an “output end”, and the side where the battery 3 is located is referred to as an “input end”. .

  The electric power stored in the battery 3 is converted from DC power to AC power by the power converter 5 and supplied to the motor 8. The power converter 5 includes a voltage converter 12 that boosts the voltage of DC power and an inverter 13 that converts DC power into AC power. Further, as described above, the motor 8 may function as a generator for charging the battery 3. In this case, the voltage converter 12 functions as a step-down converter for stepping down the electric power from the motor 8 and charging the battery 3. As shown in FIG. 1, the input end of the power converter 5 is connected to the input end of the voltage converter 12. The output end of the voltage converter 12 is connected to the input end of the inverter 13. The output terminal of the inverter 13 is connected to the output terminal of the power converter 5.

  A circuit configuration of the voltage converter 12 will be described. A reactor L1 and a transistor T7 are connected between the input terminal and the output terminal of the high potential side line of the voltage converter 12. The input terminal and the output terminal of the line on the low potential side of the voltage converter 12 are directly connected. A transistor T8 is connected between the reactor L1 and the low potential side line. Diodes are connected in antiparallel to the transistors T7 and T8. A filter capacitor C2 is connected in parallel to the input end of the voltage converter 12. The voltage converter 12 functions as a step-up converter by controlling on / off of the transistor T8, and functions as a step-down converter by controlling on / off of the transistor T7. Since the voltage converter 12 is a well-known technique, the details are omitted. Note that “turning on” a transistor means turning the transistor into a conductive state, and “turning off” the transistor means turning off the transistor.

  A circuit configuration of the inverter 13 will be described. The inverter 13 has a configuration in which three sets of series circuits of two transistors are connected in parallel (T1 and T4, T2 and T5, T3 and T6). A diode is connected in antiparallel to each transistor. The high potential side of the three sets of series circuits is connected to the input terminal on the high potential side of the inverter 13. The low potential side of the three sets of series circuits is connected to the input terminal on the low potential side of the inverter 13. Three-phase alternating current phases (U phase, V phase, W phase) are output from the midpoint of the three sets of series circuits. When the controller 15 described later controls ON / OFF of the transistors T1-T6, the inverter 13 converts DC power into AC power, or converts AC power into DC power. Since the inverter 13 is a well-known technique, the details are omitted.

  In the circuit of the inverter 13, the current path from the input terminal on the high potential side of DC current to the motor 8 is called “upper arm”, and the current path from the motor to the input terminal on the low potential side of DC power is “ It is called the “lower arm”. That is, as shown in FIG. 1, the transistors T1, T2, and T3 are included in the “upper arm”, and the transistors T4, T5, and T6 are included in the “lower arm”. Hereinafter, for convenience of explanation, a line connecting the input terminal on the high potential side of the inverter 13 and the output terminal on the high potential side of the voltage converter 12 is referred to as a high potential line P, and the input terminal on the low potential side of the inverter 13 is A line connecting the output terminals on the low potential side of the voltage converter 12 is referred to as a low potential line N.

  As shown in FIG. 1, a smoothing capacitor C <b> 1 is connected in parallel to the input terminal of the inverter 13. In other words, the smoothing capacitor C1 is connected between the high potential line P and the low potential line N. The smoothing capacitor C1 smoothes the pulsating flow of power supplied from the voltage converter 12 to the inverter 13.

  An IGBT (Insulated Gate Bipolar Transistor) is used for the transistors T1 to T8. However, this transistor may be another transistor, for example, a MOSFET (Metal Oxide Semiconductor Field Effect Transistor). Alternatively, different types of transistors may be used for the power converter 5 in the future. The technology disclosed herein does not depend on the type of transistor.

  The hybrid vehicle 2 includes a position sensor 14. The position sensor 14 is attached to the rotating shaft of the motor 8 and detects the rotational position (angle) of the rotor of the motor 8 with respect to the stator. The position sensor 14 is sometimes called a resolver. The signal output from the position sensor 14 is a sine wave whose amplitude is modulated according to the rotational position of the rotor, and the rotational position of the rotor can be calculated from the amplitude. Since the position sensor 14 is a well-known technique, a detailed description thereof will be omitted.

  The hybrid vehicle 2 includes a collision sensor 16 that detects a collision of the vehicle. As the collision sensor, an airbag sensor, a pre-crash sensor, or the like is used. The airbag sensor is a sensor that detects the impact of a vehicle collision, and is mainly used for operating the airbag when the vehicle collides. On the other hand, the pre-crash sensor is a sensor that detects that there is a high probability that the vehicle collides with an object ahead. The probability that the vehicle will collide is comprehensively determined based on, for example, information from a camera mounted on the vehicle, information from a radar or the like that measures the distance between the vehicles, and information on the running state such as the vehicle speed. A system constituted by a device such as a camera or radar and a CPU that calculates information may be referred to as a pre-crash sensor. In this specification, when the probability that the vehicle will collide is high, the vehicle will eventually collide. Therefore, the sensor (pre-crash sensor) that detects the high probability that the vehicle will collide is also referred to as “detecting vehicle collision. To be included in the “collision sensor”.

  The hybrid vehicle 2 includes a controller 15 that controls the power converter 5. The controller 15 generates a pulse signal to be sent to the voltage converter 12 and the inverter 13 and controls on / off of the transistors T1 to T8. The broken line arrows shown in FIG. 1 indicate the signal lines. Note that in FIG. 1, only signal lines to some transistors are shown, and signal lines to other transistors are omitted. The hybrid vehicle 2 determines a torque value to be output by the motor 8 based on information from the driver (accelerator opening degree, etc.) and vehicle speed. The controller 15 controls the power converter 5 based on the torque value. Further, the controller 15 may control the power converter 5 so as to discharge the electric charge stored in the smoothing capacitor C <b> 2 to the motor 8. Next, the discharge control to the motor will be described.

  The motor 8 is required to have a high output in order to drive the hybrid vehicle 2. Therefore, in the hybrid vehicle 2, the voltage of the battery 3 is boosted to several hundred volts by the boost converter and supplied to the motor 8 via the inverter 13. That is, a large current flows through the power converter 5 that supplies power to the motor 8. Therefore, a large amount of charge is stored in the capacitor provided in the power converter 5, particularly the smoothing capacitor C <b> 1. When the vehicle collides, it is desirable to discharge the electric charge of the smoothing capacitor C1 in order to ensure the safety of the driver and the worker. In the hybrid vehicle 2, when the vehicle collides, the controller 15 discharges the electric charge of the smoothing capacitor C <b> 1 to the motor 8 without generating the motor torque based on the information on the rotational position of the rotor detected by the position sensor 14. Thus, the inverter 13 is controlled. Hereinafter, this discharge control is referred to as “main discharge control” in order to distinguish it from other discharge controls. The other discharge control is, for example, control for causing the capacitor charge to flow through a discharge resistor (not shown).

  The main discharge control will be described. The three-phase AC motor is rotated by the magnetic force generated when the direction of the magnetic field generated in the rotor and the direction of the magnetic field generated in the stator intersect. In the main discharge control, the direction of the current flowing in the stator is controlled so that the direction of the magnetic field generated in the rotor (so-called d-axis) and the direction of the magnetic field generated in the stator are parallel to each other without generating motor torque. Discharge the capacitor charge to the motor. Therefore, the controller 15 performs main discharge control based on the rotational position of the rotor (rotational position with respect to the stator) detected by the position sensor 14. However, when the vehicle collides, the position sensor 14 may be abnormal. Examples of the abnormality of the position sensor 14 include a case where a signal line connected to the position sensor 14 is disconnected. If main discharge control is executed in a state where the position sensor 14 is abnormal, motor torque may be generated or an excessive amount of control may occur. The excessive control amount is, for example, an overcurrent or an overvoltage due to a malfunction of the rotational position feedback.

  When executing the main discharge control, the controller 15 of the hybrid vehicle 2 executes a process for avoiding that the electric charge of the smoothing capacitor C1 is not normally discharged due to the abnormality of the position sensor 14. FIG. 2 is a flowchart showing a process in which main discharge control is executed. The process shown in FIG. 2 is executed when the vehicle collides (including a case where the probability that the vehicle collides is high). In other words, when a collision of the vehicle is detected by the collision sensor 16, the process of the flowchart of FIG. 2 is executed.

  A process in which the main discharge control is executed will be described with reference to FIG. The controller 15 first shuts off the system main relay 4 (S2). By interrupting the system main relay 4, the current path between the power converter 5 and the battery 3 is interrupted. Moreover, the controller 15 stops the inverter 13 (S3). The controller 15 turns off all the transistors and stops the inverter 13. That is, the controller 15 interrupts between the motor 8 and the smoothing capacitor C1.

  Next, the controller 15 determines whether or not the rotation of the motor is stopped before performing the main discharge control (S4). When a collision of the vehicle is detected by the collision sensor 16, the hybrid vehicle 2 is not always completely stopped. Therefore, the motor 8 may be rotating. As the motor 8 rotates, a counter electromotive force is generated in the motor 8. Therefore, a current path is required to flow current due to the counter electromotive force until the rotation of the motor 8 stops. The controller 15 turns on the transistors T4-T6 of the lower arm of the inverter that has been stopped in step S3 (S6). Note that the upper arm transistors T1 to T3 remain off by the process of step S3. As a result, a plurality of current paths are formed to connect each phase of the motor 8 and the transistors T4-T6, and the current generated by the rotation of the motor 8 can be distributed to the transistors T4-T6. Since the upper arm transistors T1-T3 remain off, the power of the smoothing capacitor C1 is maintained as it is.

  The controller 15 controls the inverter 13 to maintain the state of step S6 until the vehicle speed of the hybrid vehicle 2 reaches 0 km / hour (S4: NO). The hybrid vehicle 2 has a rotation sensor (not shown) that detects the rotation speed of the axle 9 (wheel), and the vehicle speed is calculated from the rotation speed of the axle detected by the rotation sensor. When the vehicle speed of the hybrid vehicle 2 becomes 0 km / hour (S4: YES), it is determined that the rotation of the motor 8 connected to the axle 9 has stopped, the controller 15 proceeds to step S5, and the inverter 13 is turned on again. Stop. Even when the inverter is stopped, the controller 15 turns off all the transistors. When the process proceeds to step S5 without going through step S6, the inverter 15 remains stopped by the process of step S3, and thus the controller 15 substantially skips the process of step S5. The smoothing capacitor C1 is disconnected from the motor 8 when step S5 is executed (or when step S5 is skipped).

  Next, the controller 15 diagnoses an abnormality of the position sensor 14 (S7). As described above, the signal output from the position sensor 14 is a modulated sine wave. When an abnormality occurs in the position sensor 14, an abnormality also occurs in the output signal, and the output signal becomes a constant voltage or a fragmented signal. The controller 15 determines that an abnormality has occurred in the position sensor 14 when the signal output from the position sensor 14 is different from a sine wave. When there is no abnormality in the position sensor 14 (S8: YES), the controller 15 starts main discharge control (S9). The main discharge control is continued until the residual charge of the smoothing capacitor C1 is reduced to a predetermined amount. The residual charge of the smoothing capacitor C1 is estimated from the voltage between the high potential line P and the low potential line N (hereinafter, between PN). The voltage between the PNs is monitored by the controller 15 by a voltmeter (not shown) connected between the PNs. When the voltage between the PNs is smaller than the predetermined voltage (S11: YES), the controller 15 ends the main discharge control (S12). When the voltage between the PNs is equal to or higher than the predetermined voltage (S11: NO), the controller 15 Continues main discharge control. The predetermined voltage is selected to be 60 V, for example, as a value for ensuring safety from an electric shock or the like. Note that “discharge control” described in step S12 is used as a term including both main discharge control and other discharge control described later.

  When the position sensor 14 has an abnormality (S8: NO), the controller 15 performs another discharge control different from the main discharge control (S10). As another discharge control, for example, the controller 15 discharges the electric charge of the smoothing capacitor C1 by turning on one of the transistors T1 and T4 connected in series between the PN of the inverter 13 and turning on the other half. At this time, the half-on transistor has a large resistance. This resistance functions as a discharge resistance. Further, the controller 15 may discharge by connecting another discharge resistor (not shown) to the smoothing capacitor C1. That is, a method that can perform other discharge control without using the position sensor 14 is employed. If there is an abnormality in the position sensor 14 (S8: NO), the controller 15 continues the other discharge control until the voltage between the PNs becomes smaller than the predetermined voltage, and the voltage between the PNs becomes smaller than the predetermined voltage. If so, the other discharge control is terminated (S12).

  By executing the processing shown in FIG. 2, the controller 15 detects the collision and then interrupts the current path between the smoothing capacitor C <b> 1 and the motor 8 until it is determined that there is no abnormality in the position sensor 14. The electric charge of the smoothing capacitor C1 is not discharged to the motor 8. Then, after determining that there is no abnormality in the position sensor 14, the controller 15 performs main discharge control. By performing the main discharge control in this way, it is possible to avoid that the main discharge control is not normally performed due to a failure of the position sensor 14.

  When a vehicle collides, it is desirable that the capacitor charge be discharged quickly. However, the determination of the abnormality of the position sensor 14 is made after confirming that the abnormality of the output signal (non-sine wave state) continues for a certain time, for example, 50 to 100 milliseconds. This takes into account the effect of temporary noise on the signal line. If the main discharge control is executed before the abnormality of the position sensor 14 is determined, an excessive control amount (overcurrent, overvoltage) may be generated in the inverter 13 due to the abnormality of the position sensor 14. The inverter may have a protection function for protecting the transistor from overcurrent. If the protection function is activated by an overcurrent, the inverter may stop and subsequent discharge cannot be performed. By executing the processing shown in FIG. 2, the main discharge control can be executed after reliably determining whether the position sensor 14 is abnormal.

  Hereinafter, points to be noted regarding the technology shown in the embodiments will be described. In the hybrid vehicle 2 of the embodiment, the axle and the motor rotate in conjunction with each other. Therefore, in step S4 in FIG. 2, it is confirmed that the rotation of the motor has stopped by monitoring the vehicle speed = zero. If the rotation of the axle is not necessarily the rotation of the motor, such as a clutch interposed between the motor and the axle, the process of step S4 is a determination of "Is the motor stopped?"

  Steps S4 and S6 are processes for stopping the rotation of the motor. The discharge process performed by the hybrid vehicle of the embodiment can be expressed as follows when this process is included. Based on the rotational position detected by the position sensor 14, the controller 15 discharges the electric charge of the smoothing capacitor C <b> 1 to the motor 8 without generating motor torque. When the collision sensor detects a collision of the vehicle, the controller 15 stops the rotation of the motor and stops the inverter to cut off the current path between the smoothing capacitor C1 and the motor 8. Subsequently, if there is no abnormality in the position sensor 14, the controller 15 controls the inverter 13 so as to discharge the electric charge of the smoothing capacitor C1 to the motor 8 without generating motor torque.

  Although the hybrid vehicle 2 includes one drive motor, the hybrid vehicle 2 may include two or more drive motors. In this case, even if the position sensor of one motor fails, main discharge control can be performed if the other position sensors are normal. Further, the technology disclosed in this specification can be applied not only to a hybrid vehicle but also to an electric vehicle that runs only by a motor and a fuel cell vehicle.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings can achieve a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

2: Electric vehicle 3: Battery 4: System main relay 5: Power converter 6: Engine 7: Power distribution mechanism 8: Motor 9: Axle 12: Voltage converter 13: Inverter 14: Position sensor 15: Controller 16: Collision sensor L1 : Reactor C1: Smoothing capacitor C2: Filter capacitor P: High potential line N: Low potential lines T1, T2, T3, T4, T5, T6, T7, T8: Transistor

Claims (1)

A motor for driving the vehicle;
An inverter for supplying electric power to the motor;
A capacitor connected to the input terminal of the inverter;
A position sensor for detecting the rotational position of the rotor of the motor;
A collision sensor for detecting a vehicle collision;
A controller that controls the inverter to discharge the electric charge of the capacitor to the motor based on the rotational position detected by the position sensor;
With
When the collision sensor detects a vehicle collision, the controller stops the inverter and interrupts the current path between the capacitor and the motor, and then, if the position sensor is normal, Controlling the inverter to discharge the capacitor charge to the motor;
The electric vehicle characterized by the above-mentioned.

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