Motor car

Abstract

To suppress supplying of excessive current from a battery to a motor in a motor car.SOLUTION: This motor car comprises: a motor that drives wheels; a battery that supplies power to the motor; a voltage sensor that detects output voltage of the battery; an accelerator pedal operated to adjust an output of the motor; and a power control unit that adjusts the power supplied from the battery to the motor in accordance with the accelerator opening of the accelerator pedal and the detected voltage of the voltage sensor.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The technology disclosed in this specification relates to an electric vehicle. The term "electric vehicle" broadly refers to a vehicle whose wheels are driven by a motor, and includes, for example, battery electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and fuel cell electric vehicles. [Background technology]

[0002] Patent Document 1 describes an electric vehicle. This electric vehicle includes a motor that drives the wheels, a battery that supplies power to the motor, and a power control unit. The power control unit has a built-in inverter and adjusts the power supplied from the battery to the motor. This power control unit is configured to limit the value of the current flowing through the motor when the rotation speed of the motor is zero. This prevents the switching elements of the inverter from overheating. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-9954 A Summary of the Invention [Problem to be solved by the invention]

[0004] Normally, the power supply from the battery to the motor is set according to the accelerator opening. That is, when the accelerator opening is at a maximum, the power supply from the battery to the motor is also set at a maximum. However, if the above-mentioned power supply is set at a maximum when, for example, the remaining charge of the battery is significantly reduced and the output voltage of the battery is significantly reduced, an excessive current may be supplied from the battery to the motor to compensate for the reduced output voltage. In this case, even inside the power control unit, a current exceeding a permissible value may flow through, for example, a switching element of an inverter.

[0005] In view of the above, the present specification provides a technique that can avoid or suppress an excessive current being supplied from a battery to a motor. [Means for solving the problem]

[0006] The technology disclosed in this specification is embodied in an electric vehicle that drives wheels by a motor. This electric vehicle includes the motor, a battery that supplies power to the motor, a voltage sensor that detects the output voltage of the battery, an accelerator pedal that is operated to adjust the output of the motor, and a power control unit that adjusts the supply power supplied from the battery to the motor in response to the accelerator opening of the accelerator pedal and the voltage detected by the voltage sensor.

[0007] The power control unit sets a target value of the supplied power in accordance with the accelerator opening, and when the accelerator opening is in a predetermined high opening range and the detected voltage is in a predetermined low voltage range, reduces the set target value at a predetermined rate.

[0008] According to the above-mentioned configuration, when the battery voltage is low and, for example, the accelerator pedal is fully depressed, the target value of the power supply from the battery to the motor is reduced at a predetermined rate. This prevents or suppresses excessive current from being supplied from the battery to the motor. Inside the power control unit, for example, a current exceeding a permissible value is prevented from flowing through a switching element of an inverter. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is a block diagram showing the configuration of an electric vehicle 10. [Diagram 2] 4 is a flowchart showing an example of a series of control procedures executed by the power control unit 20. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] An electric vehicle 10 according to the embodiment will be described with reference to the drawings. As an example, the electric vehicle 10 according to the embodiment is a so-called battery electric vehicle (BEV). Note that the configuration described in the embodiment is not limited to battery electric vehicles, and can be similarly adopted in other types of electric vehicles.

[0011] As shown in Fig. 1, an electric vehicle 10 includes a motor 12, a battery 14, a voltage sensor 16, an accelerator pedal 18, and a power control unit 20. The battery 14 is a high-voltage battery. Note that high voltage here means an operating voltage exceeding 60 V DC. The battery 14 has multiple built-in secondary battery cells, which may be, for example, lithium-ion cells.

[0012] The motor 12 is a device that drives wheels (not shown) of the electric vehicle 10 by power supplied from the battery 14. The motor 12 is electrically connected to the battery 14 and mechanically connected to the wheels. Although not particularly limited, the motor 12 is a three-phase AC motor. The wheels driven by the motor 12 may be the front wheels or the rear wheels. As an example, in the electric vehicle 10 of this embodiment, the motor 12 is connected to a pair of front wheels via a reduction gear and a differential device. Note that, in another embodiment, the motor 12 may be a so-called in-wheel motor. In this case, the electric vehicle 10 can be provided with a plurality of motors 12 according to the number of drive wheels.

[0013] The voltage sensor 16 is provided between the battery 14 and the motor 12. The voltage sensor 16 detects the output voltage of the battery 14. The voltage sensor 16 is electrically connected to the power control unit 20, and the detected voltage of the voltage sensor 16 (i.e., the output voltage of the battery 14) is taught to the control device 28 of the power control unit 20. Note that the specific configuration and arrangement of the voltage sensor 16 are not particularly limited.

[0014] The accelerator pedal 18 is disposed within the passenger compartment of the electric vehicle 10, and is operated by a passenger of the electric vehicle 10. The accelerator pedal 18 outputs a signal corresponding to the amount of operation by the passenger, i.e., the accelerator opening. The accelerator pedal 18 is electrically connected to the power control unit 20, and the signal output from the accelerator pedal 18 (i.e., the output voltage of the battery 14) is instructed to a control device 28 of the power control unit 20. The specific configuration and arrangement of the accelerator pedal 18 are not particularly limited. It should be noted that the accelerator pedal 18 referred to here is not limited to one operated by the foot of the passenger.

[0015] The power control unit 20 adjusts the power supplied from the battery 14 to the motor 12 in accordance with the accelerator opening of the accelerator pedal 18 and the voltage detected by the voltage sensor 16. The specific configuration of the power control unit 20 is not particularly limited. As an example, the power control unit 20 in this embodiment includes an inverter 22 and a control device 28. The inverter 22 has a plurality of switching elements 24 and a freewheeling diode 26 connected in parallel to each switching element 24. The control device 28 controls the on / off operation of the plurality of switching elements 24. In this way, the power control unit 20 converts the DC power supplied from the battery 14 into three-phase AC power supplied to the motor 12. At this time, the power control unit 20 can freely control the rotation speed of the motor 12 by changing the frequency of the three-phase AC power supplied to the motor 12. In addition, the power control unit 20 can set a target value of the power supplied to the motor 12 in accordance with the accelerator opening, and can control the current passed through the motor 12 in accordance with the target value and the voltage detected by the voltage sensor 16.

[0016] The output control process executed by the control device 28 will be described with reference to FIG. 2. The control device 28 repeatedly executes a series of control procedures shown in FIG. 2 when the electric vehicle 10 is traveling or accelerating from a stopped state. First, the control device 28 judges whether the accelerator opening taught by the accelerator pedal 18 is 100% or not (S10). If the accelerator opening is 100% (S10: Yes), the control device 28 sets the target value Wout of the power supplied to the motor 12 to a predetermined maximum value. If the accelerator opening is not 100% (S10: No), the control device 28 sets the target value Wout according to the accelerator opening. Then, the control device 28 controls the operation of the inverter 22 according to the set target value Wout. As a result, the inverter 22 supplies power according to the target value Wout from the battery 14 to the motor 12, and as a result, the output of the motor 12 is appropriately adjusted according to the accelerator opening.

[0017] In the process of step S10, the judgment value for the accelerator opening is not limited to 100%. The process of step S10 is a process for judging whether the accelerator opening is in a predetermined high opening region, and the lower limit value that defines the high opening region may be set to a value lower than 100%. In addition, the maximum value of the target value Wout can also be appropriately set according to the range of the high opening region.

[0018] When the accelerator opening is 100% (S10: Yes) and the target value Wout is set to the maximum value (S12), the control device 28 checks the detected voltage Vb of the voltage sensor 16 (the output voltage of the battery 14). Then, the control device 28 determines whether the detected voltage Vb of the voltage sensor 16 is 10% or more higher than the normal lower limit voltage VL of the battery 14 (S16). That is, the control device 28 determines whether Vb≧voltage 1.1VL is satisfied. When the detected voltage Vb of the voltage sensor 16 is 10% or more higher than the normal lower limit voltage VL (S16: Yes), the control device 28 returns to the process of step S10 while maintaining the setting of the target value Wout at the maximum value.

[0019] On the other hand, if the result of the process in step S16 is No (i.e., if Vb<voltage 1.1VL), the target value Wout, which is set to the maximum value, is reduced at a predetermined rate, for example, 0.05% / ms. When the output voltage of the battery 14 is decreasing, the current supplied from the battery 14 to the motor 12 is increased to compensate for the decreased voltage. Therefore, if the target value Wout is set to the maximum value, a current exceeding the allowable value flows to compensate for the decreased voltage of the battery 14, and semiconductor elements such as the switching element 24 of the inverter 22 may overheat. In this regard, if the target value Wout, which is set to the maximum value, is reduced at a predetermined rate, it is possible to prevent a current exceeding the allowable value from flowing through the switching element 24, etc.

[0020] In the process executed by the control device 28 described above, the normal lower limit voltage VL used in step S16 can be changed as appropriate according to the characteristics and type of the battery 14. In addition, the reduction rate for the target value Wout used in step S18 can also be changed as appropriate according to the characteristics and type of the battery 14 or the characteristics and type of the switching element 24, etc. [Explanation of symbols]

[0021] 10: electric vehicle, 12: motor, 14: battery, 16: voltage sensor, 18: accelerator pedal, 20: power control unit, 22: inverter, 24: switching element, 26: freewheel diode, 28: control device

Claims

[Claim 1] A motor that drives the wheels; a battery for supplying power to the motor; a voltage sensor for detecting an output voltage of the battery; an accelerator pedal operated to adjust the output of the motor; a power control unit that adjusts the power supplied from the battery to the motor in response to an accelerator opening of the accelerator pedal and a voltage detected by the voltage sensor; Equipped with the power control unit sets a target value of the supplied power in accordance with the accelerator opening, and when the accelerator opening is in a predetermined high opening range and the detected voltage is in a predetermined low voltage range, reduces the set target value at a predetermined rate. Electric car.

Images