Electric vehicle

Abstract

The invention relates to an electric vehicle which suppresses overheating of elements of a buck-boost converter. The electric vehicle includes: a motor connected to a drive wheel; an inverter that drives the motor; a power storage device; a buck-boost converter that exchanges power with voltage conversion between a low-voltage-side power line to which the power storage device is connected and a high-voltage-side power line to which the inverter is connected; an auxiliary machine connected to the high-voltage-side power line; and a control device that controls the inverter, the buck-boost converter, and the auxiliary machine. When a predetermined condition that the current flowing through the elements of the buck-boost converter is in the direction from the high-voltage-side power line toward the low-voltage-side power line and is greater than a threshold value is satisfied, the control device increases the power consumption of the auxiliary machine than when the predetermined condition is not satisfied.

Description

Technical Field

[0001] This disclosure pertains to electric vehicles. Background Technology

[0002] Previously, an electric vehicle was proposed, comprising: a motor connected to drive wheels; an inverter driving the motor; an energy storage device; and a heating device consisting of a drive system cooling circuit for cooling the motor and inverter, and a hot water circuit (see, for example, Patent Document 1). In this electric vehicle, the hot water circuit recovers heat generated from the heater to a circulation path for hot water flow, and during heating, the recovered heat is used to heat the air and supply hot air into the vehicle interior. Furthermore, by using the drive system cooling circuit as a hot water circuit and the motor and inverter as heaters, a circulation circuit recovers heat generated from the motor and inverter to the drive system cooling circuit during operation.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2012-183958

[0004] In electric vehicles that, in addition to a motor connected to the drive wheels, an inverter for the drive motor, and an energy storage device, also have a buck-boost converter that exchanges power between the low-voltage side power line connected to the energy storage device and the high-voltage side power line connected to the inverter, if a relatively large current continuously flows from the high-voltage side power line to the low-voltage side power line through the buck-boost converter when the drive wheels slip and then grip the ground, the components of the buck-boost converter may overheat. Summary of the Invention

[0005] The main purpose of the electric vehicle disclosed herein is to suppress overheating of the components of the buck-boost converter.

[0006] The electric vehicle disclosed herein employs the following mechanism to achieve the aforementioned main objectives.

[0007] The electric vehicle disclosed herein includes: a motor connected to a drive wheel; an inverter driving the motor; an energy storage device; a buck-boost converter that exchanges power between a low-voltage side power line connected to the energy storage device and a high-voltage side power line connected to the inverter, with voltage conversion; an auxiliary motor connected to the high-voltage side power line; and a control device that controls the inverter, the buck-boost converter, and the auxiliary motor. The main feature of the electric vehicle is that, when a predetermined condition is met—that the current flowing through the elements of the buck-boost converter is greater than a threshold value and flows from the high-voltage side power line towards the low-voltage side power line—the control device increases the power consumption of the auxiliary motor compared to when the predetermined condition is not met.

[0008] In the electric vehicle disclosed herein, when a predetermined condition is met—that the current flowing through the components of the buck-boost converter is greater than a threshold value and flows from the high-voltage side power line to the low-voltage side power line—the power consumption of the auxiliary equipment is increased compared to when the predetermined condition is not met. This process suppresses the continuous flow of a relatively large current from the high-voltage side power line to the low-voltage side power line via the buck-boost converter. As a result, it suppresses the continuous flow of a large current through the components of the buck-boost converter, thus suppressing overheating of the components. Alternatively, the buck-boost converter may have an upper arm, a lower arm, and a reactor, and the current flowing through the components of the buck-boost converter may be detected by a current sensor that detects the current flowing through the reactor.

[0009] In the electric vehicle disclosed herein, when the predetermined condition is met due to grip loss following drive wheel slippage, the control device increases the power consumption of the auxiliary motor compared to when the predetermined condition is not met. Alternatively, when the predetermined condition is met due to motor regeneration, the control device increases the power consumption of the auxiliary motor compared to when the predetermined condition is not met. This way, overheating of the buck-boost converter components can be suppressed when the predetermined condition is met due to grip loss following drive wheel slippage or when the predetermined condition is met due to motor regeneration. Attached Figure Description

[0010] Figure 1 This is a simplified structural diagram of an electric vehicle according to an embodiment of the present disclosure.

[0011] Figure 2 This is a flowchart illustrating an example of a processing routine executed by an electronic control unit.

[0012] Figure 3 This is a simplified structural diagram of a hybrid vehicle, a variant example. Detailed Implementation

[0013] The embodiments (implementations) for carrying out this disclosure will be described with reference to the accompanying drawings. Figure 1 This is a simplified configuration diagram of an electric vehicle 10 according to an embodiment of the present disclosure. As shown, the electric vehicle 10 of the embodiment includes a motor 22, an inverter 24, a battery 26 as an energy storage device, a buck-boost converter 30, a heater 40, a cooling cycle device 42, and an electronic control unit 50 as a control device.

[0014] Motor 22 is configured as a three-phase AC motor, having a rotor in which permanent magnets are embedded in the rotor core and a stator in which three-phase (U-phase, V-phase, W-phase) coils are wound in the stator core. The rotor of motor 22 is connected to a drive shaft 16 via a differential gear 14 to drive wheels 12a and 12b.

[0015] Inverter 24 is connected to buck-boost converter 30 via high-voltage side power line 32. Inverter 24 includes six transistors T11-T16 as switching elements and six diodes D11-D16 connected in parallel with each of the six transistors T11-T16. Transistors T11-T16 are arranged in pairs, with their positive and negative terminals on the high-voltage side power line 32 forming the source and sink sides, respectively. Each connection point of each pair of transistors T11-T16 is connected to each of the three-phase (U-phase, V-phase, W-phase) coils of motor 22. Therefore, when voltage is applied to inverter 24, the electronic control unit 50 adjusts the ratio of the conduction time of the pairs of transistors T11-T16, thereby creating a rotating magnetic field in the three-phase coils of motor 22, driving motor 22 (rotor) to rotate. A smoothing capacitor 36 is connected to the high-voltage side power line 32.

[0016] The battery 26 is configured as, for example, a lithium-ion secondary battery or a nickel-metal hydride secondary battery, and is connected to the buck-boost converter 30 via a low-voltage side power line 34. A smoothing capacitor 38 is connected to the low-voltage side power line 34.

[0017] The buck-boost converter 30 is connected to the high-voltage side power line 32 and the low-voltage side power line 34, and includes transistors T31 and T32 (upper and lower arms) as two switching elements, two diodes D31 and D32 connected in parallel with each of the two transistors T31 and T32, and a reactor L. Transistor T31 is connected to the positive terminal of the high-voltage side power line 32. Transistor T32 is connected to the common negative terminal of transistor T31, the high-voltage side power line 32, and the low-voltage side power line 34. The reactor L is connected to the junction of the two transistors T31 and T32 and the positive terminal of the low-voltage side power line 34. The buck-boost converter 30 adjusts the ratio of the on-time of transistors T31 and T32 by the electronic control unit 50, thereby boosting the power from the low-voltage side power line 34 to supply to the high-voltage side power line 32, or stepping down the power from the high-voltage side power line 32 to supply to the low-voltage side power line 34.

[0018] Heater 40 is connected to the high-voltage side power line 32. Heater 40 is used as a heat source for heating the passenger compartment or for warming the cooling water circulating in the circulation path including battery 26. Refrigeration cycle unit 42 is used as a cold source for cooling the passenger compartment or cooling the aforementioned cooling water, and as a heat source for heating the passenger compartment. Refrigeration cycle unit 42 includes a compressor 44, a condenser, an expansion valve, and an evaporator. Compressor 44, connected to the high-voltage side power line 32, compresses the refrigerant from the evaporator to make it a high-temperature, high-pressure gaseous refrigerant. The condenser, through heat exchange with air, transforms the refrigerant from compressor 44 into a normal-temperature, high-pressure liquid refrigerant. The expansion valve depressurizes the refrigerant from the condenser to become a low-temperature, low-pressure gas-liquid mixture refrigerant. The evaporator, through heat exchange with air, transforms the refrigerant from the expansion valve into a low-temperature, low-pressure gaseous refrigerant. When heating the interior of the carriage, air heated by heat exchange with the heater 40 and / or the condenser is blown into the carriage by a blower. When cooling the interior of the carriage, air cooled by heat exchange with the evaporator is blown into the carriage by a blower. The cooling water in the circulation path is heated by the heater 40 and / or the refrigeration circulation device 42, or cooled by the refrigeration circulation device 42.

[0019] The electronic control unit 50 includes a microcomputer with a CPU, ROM, RAM, flash memory, input / output ports, and communication ports, various drive circuits, and various logic ICs. The electronic control unit 50 receives signals from various sensors. For example, it receives the rotational speeds Nwa and Nwb of the drive wheels 12a and 12b from the speed sensors 13a and 13b mounted on the drive wheels 12a and 12b. The electronic control unit 50 also receives the rotational position θm of the motor 22 from the rotational position sensor 22a, which detects the rotational position of the motor 22's rotor, and the phase currents Iu, Iv, and Iw of each phase of the motor 22 from the current sensors 22u, 32v, and 32w mounted on each phase of the motor 22. The electronic control unit 50 also receives the voltage Vb of the battery 26 from the voltage sensor 26v mounted between the terminals of the battery 26, and the current Ib of the battery 26 from the current sensor 26i mounted on the output terminals of the battery 26. The electronic control unit 50 is also input to the current IL of the reactor L from the current sensor 30i of the reactor L connected in series with the buck-boost converter 30, the voltage VH of the capacitor 36 (high voltage side power line 32) from the voltage sensor 36v installed between the terminals of the capacitor 36, and the voltage VL of the capacitor 38 (low voltage side power line 34) from the voltage sensor 38v installed between the terminals of the capacitor 38. The electronic control unit 50 is also input to the switch signal from the power switch 60, the shift position SP from the shift sensor 62 which detects the operating position of the shift lever 61, the accelerator opening Acc from the accelerator pedal position sensor 64 which detects the amount of pedal pressure of the accelerator pedal 63, the brake pedal position BP from the brake pedal position sensor 66 which detects the amount of pedal pressure of the brake pedal 65, and the vehicle speed V from the vehicle speed sensor 67.

[0020] The electronic control unit 50 outputs various control signals. For example, it outputs control signals for transistors T11 to T16 of the inverter 24 and for transistors T31 and T32 of the buck-boost converter 30. It also outputs control signals for the heater 40 and for the compressor 44 of the refrigeration cycle unit 42. The electronic control unit 50 calculates the electrical angle θe and rotational speed Nm of the motor 22 based on the rotational position θm of the rotor of the motor 22 from the rotational position sensor 22a. The electronic control unit 50 calculates the state of charge (SOC) of the battery 26 based on the accumulated value of the current Ib of the battery 26 from the current sensor 26i.

[0021] In the electric vehicle 10 configured in this way, the electronic control unit 50 sets the required torque Td* (required by the drive shaft 16) for driving based on the accelerator opening Acc and the vehicle speed V. This required torque Td* is output to the drive shaft 16 and set as the torque command Tm* for the motor 22. The motor 22 is driven by the torque command Tm*, and the switching control of transistors T11 to T16 of the inverter 24 is performed. Furthermore, the electronic control unit 50 sets the target voltage VH* of the high-voltage side power line 32 based on the torque command Tm* and the speed Nm of the motor 22. The target current IL* of the reactor L is calculated through voltage feedback control, whereby the difference between the voltage VH of the high-voltage side power line 32 and the target voltage VH* is canceled out. Next, the duty cycle command D* is calculated through current feedback control, whereby the difference between the current IL of the reactor L and the target current IL* is canceled out. The calculated duty cycle command D* is used to control the switching of transistors T31 and T32 of the buck-boost converter 30.

[0022] Next, the operation of the electric vehicle 10 according to the embodiment will be explained. In particular, the operation of the drive wheels 12a and 12b when they grip the ground after slipping will be explained. Figure 2 This is a flowchart illustrating an example of a processing routine executed by the electronic control unit 50. This routine is repeatedly executed for a specified time after detecting a situation where the drive wheels 12a and 12b slip and subsequently gain traction. Furthermore, the slippage of the drive wheels 12a and 12b, and the subsequent traction, can be detected, for example, using the change in rotational speeds Nwa and Nwb of the drive wheels 12a and 12b per unit time from the speed sensors 13a and 13b, i.e., the rate of change of rotational speed ΔNwa and ΔNwb.

[0023] If executed Figure 2In the processing routine, the electronic control unit 50 receives the current IL (positive value in the direction from the low-voltage side power line 34 to the high-voltage side power line 32) from the reactor L of the current sensor 30i (step S100), and determines whether the condition that the input current IL of the reactor L is negative and its absolute value is greater than the threshold ILref is met (steps S110, S120). Here, the threshold ILref is the threshold used to determine whether a relatively large current flows from the high-voltage side power line 32 to the low-voltage side power line 34 via the buck-boost converter 30. If the drive wheels 12a and 12b slip during vehicle operation, i.e., the rotational speeds Nwa and Nwb of the drive wheels 12a and 12b suddenly increase, the rotational speed Nm of the motor 22 also suddenly increases, and therefore the power consumption Pm of the motor 22 suddenly increases. Furthermore, if the drive wheels 12a and 12b subsequently grip the ground, i.e., the rotational speeds Nwa and Nwb of the drive wheels 12a and 12b decrease sharply, the rotational speed Nm of the motor 22 will also decrease sharply, thus the power consumption of the motor 22 will decrease sharply. At this time, in the above-described control of the buck-boost converter 30, the following possibility exists: the target voltage VH* of the high-voltage side power line 32 becomes sufficiently lower than the voltage VH, the target current IL* of the reactor L becomes negative and its absolute value becomes relatively large, and the current IL of the reactor L becomes negative and its absolute value becomes relatively large (a relatively large current flows from the high-voltage side power line 32 to the low-voltage side power line 34 via the buck-boost converter 30). The processing in steps S110 and S120 is for detecting such phenomena.

[0024] In steps S110 and S120, the routine ends when the current IL of reactor L is 0 or positive, or when the current IL of reactor L is negative and its absolute value is below the threshold ILref, i.e. when the specified conditions are not met.

[0025] In steps S110 and S120, when the current IL of reactor L is negative and its absolute value is greater than the threshold ILref, i.e., when the specified condition is met, the power consumption of heater 40 is increased compared to when the specified condition is not met (step S130), and the routine ends. In the process of step S130, the power consumption of heater 40 is increased by starting to drive heater 40 from a stop, or the power consumption of heater 40 during driving is increased. Through this process, when the specified condition is met, the power consumption of heater 40 can be increased compared to when the specified condition is met, thus suppressing a relatively large current continuously flowing from the high-voltage side power line 32 to the low-voltage side power line 34 via buck-boost converter 30. As a result, it is possible to suppress the continuous flow of a large current through the components of buck-boost converter 30 (e.g., transistor T31), and suppress overheating of the components of buck-boost converter 30.

[0026] In the electric vehicle 10 described above, when a predetermined condition is met where the current IL of the reactor L is negative and its absolute value is greater than the threshold ILref after the drive wheels 12a and 12b slip, the power consumption of the heater 40 increases compared to when the predetermined condition is not met. This suppresses the continuous flow of large currents through the components of the buck-boost converter 30 (e.g., transistor T31), and suppresses overheating of the components of the buck-boost converter 30.

[0027] In the above-described embodiments, when the predetermined condition is met due to gripping after the drive wheels 12a and 12b slip, the power consumption of heater 40 is increased compared to when the predetermined condition is not met, but this is not a limitation. For example, when the predetermined condition is met due to regeneration of motor 22, such as when the driver depresses the brake pedal 65 sharply, the power consumption of heater 40 may also be increased compared to when the predetermined condition is not met. In addition, besides when gripping after the drive wheels 12a and 12b slip and when motor 22 regenerates, the power consumption of heater 40 may also be increased compared to when the predetermined condition is not met, even when the predetermined condition is met.

[0028] In the above-described embodiments, when the specified conditions are met, the power consumption of the heater 40 is increased compared to when the specified conditions are not met, but this is not a limitation. For example, the power consumption of the compressor 44 of the refrigeration cycle device 42 may be increased in addition to increasing the power consumption of the heater 40, or alternatively.

[0029] In the above embodiment, both the heater 40 of the electric vehicle 10 and the compressor 44 of the refrigeration cycle device 42 are connected to the high-voltage side power line 32, but this is not a limitation. For example, one of the heater 40 and the compressor 44 may be connected to the high-voltage side power line 32, and the other may be connected to the low-voltage side power line 34. In this case, when the specified conditions are met, the power consumption of the one of the heater 40 and the compressor 44 connected to the high-voltage side power line 32 may be increased compared to when the specified conditions are not met.

[0030] In the above-described embodiment, the electric vehicle 10 includes a battery 26 as an energy storage device, but is not limited to this. For example, as an energy storage device, a capacitor may be included in addition to or in place of the battery.

[0031] In the above-described embodiment, the electric vehicle 10 includes a motor 22 connected to a drive shaft 16 connected to the drive wheels 12a and 12b via a differential gear 14, but is not limited thereto. For example, it may also include two in-wheel motors respectively mounted (connected) to the drive wheels 12a and 12b.

[0032] In the above-described embodiments, such as Figure 1The diagram shows the structure of an electric vehicle 10, which includes a motor 22, an inverter 24, a battery 26, a buck-boost converter 30, a heater 40, and a compressor 44 of a refrigeration cycle device 42. However, it is not limited to this structure. For example, it could be a hybrid vehicle that has the same hardware structure as the electric vehicle 10 but also includes an engine, or a fuel cell vehicle that has the same hardware structure as the electric vehicle 10 but also includes a fuel cell. In the case of a hybrid vehicle structure, for example, as... Figure 3 As shown in the modified hybrid vehicle 110, in addition to the same hardware structure as the electric vehicle 10, it may also include an engine 112, a planetary gear 114, a motor 122, and an inverter 124. In the hybrid vehicle 110, the motor 22, engine 112, and motor 122 are respectively connected to the ring gear, planet carrier, and sun gear of the planetary gear 114, and the inverter 124 driving the motor 122 is connected to the high-voltage side power line 32. Furthermore, in the case of the hybrid vehicle structure, in addition to the same hardware structure as the electric vehicle 10, a transmission may be installed between the drive shaft 16 and the motor 22, and the engine is connected to the motor 22 via a clutch.

[0033] The correspondence between the main elements of the implementation method and the main elements of the invention as recorded in the invention content column is explained. In the implementation method, motor 22 is equivalent to "motor", inverter 24 is equivalent to "inverter", battery 26 is equivalent to "energy storage device", buck-boost converter 30 is equivalent to "buck-boost converter", heater 40 is equivalent to "auxiliary machine", and electronic control unit 50 is equivalent to "control device".

[0034] Furthermore, the correspondence between the main elements of the implementation method and the main elements of the invention described in the description of the invention is merely an example used to specifically illustrate how the implementation method is used to carry out the invention described in the description of the invention, and therefore does not limit the elements of the invention described in the description of the invention. That is, the interpretation of the invention described in the description of the invention should be based on the description in that section, and the implementation method is merely a specific example of the invention described in the description of the invention.

[0035] The above describes the methods for implementing this disclosure using the embodiments, but this disclosure is not limited to such embodiments in any way, and can of course be implemented in various ways without departing from the spirit of this disclosure.

[0036] [Industrial Applicability]

[0037] This disclosure can be used in industries such as electric vehicle manufacturing.

[0038] Explanation of reference numerals in the attached figures

[0039] 10… Electric vehicle; 12a, 12b… Drive wheels; 13a… Speed ​​sensor; 14… Differential gear; 16… Drive shaft; 22… Motor; 22a… Rotary position sensor; 22u, 22v, 22w… Current sensors; 24… Inverter; 26… Battery; 26i, 30i… Current sensors; 26v, 36v, 38v… Voltage sensors; 30… Buck-boost converter; 32… High-voltage side power line; 34… Low-voltage side power line; 36, 38… Capacitors; 40… Heater; 42… Refrigeration cycle device; 44… Compressor; 50… Electronic control unit; 60… Power switch; 61… Gear shift lever; 62… Gear shift sensor; 63… Accelerator pedal; 64… Accelerator pedal position sensor; 65… Brake pedal; 66… Brake pedal position sensor; 67… Vehicle speed sensor; D11~D16, D31, D32… Diodes; T11~T16, T31, T32… Transistors.

Claims

1. An electric vehicle, comprising: The motor is connected to the drive wheel; Inverter, drives the motor; Energy storage devices; A step-up / step-down converter exchanges power between the low-voltage side power line connected to the energy storage device and the high-voltage side power line connected to the inverter, with voltage conversion. Auxiliary equipment, connected to the high-voltage side power line; and The control device controls the inverter, the buck-boost converter, and the auxiliary equipment. in, When a predetermined condition is met that the current flowing through the components of the buck-boost converter is greater than a threshold value and flows from the high-voltage side power line to the low-voltage side power line, the control device increases the power consumption of the auxiliary machine compared to when the predetermined condition is not met.

2. The electric vehicle according to claim 1, wherein, When the specified condition is met due to the slippage of the drive wheel and subsequent grip failure, the control device increases the power consumption of the auxiliary machine compared to when the specified condition is not met.

3. The electric vehicle according to claim 1, wherein, When the specified conditions are met due to the regeneration of the motor, the control device increases the power consumption of the auxiliary machine compared to when the specified conditions are not met.

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