Electric vehicle

Abstract

To suppress overheating of an element of a step-up / down converter.SOLUTION: An electric vehicle includes a motor connected to a driving wheel, an inverter that drives the motor, a power storage device, a step-up / down converter that exchanges electric power with voltage conversion between a low-voltage power line to which the power storage device is connected and a high-voltage power line to which the inverter is connected, an auxiliary device connected to the high-voltage power line, and a control device that controls the inverter, the step-up / down converter, and the auxiliary device. The control device is configured to increase power consumption of the auxiliary device when a predetermined condition that a current flowing through an element of the buck-boost converter flows from the high voltage-side power line toward the low voltage-side power line and is greater than a threshold value is satisfied, as compared with a case where the predetermined condition is not satisfied.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to electric vehicles. [Background technology]

[0002] Conventionally, an electric vehicle has been proposed that includes a motor connected to drive wheels, an inverter that drives the motor, an electric storage device, and a heating device that includes a drivetrain cooling circuit and a hot water circuit for cooling the motor and inverter (see, for example, Patent Document 1). In this electric vehicle, the hot water circuit recovers heat generated by a heater in a circulation path through which hot water flows, and during heating, the recovered heat is used to heat air and supply hot air to the vehicle interior. In addition, by using the drivetrain cooling circuit as the hot water circuit and the motor and inverter as the heater, heat generated by the motor and inverter is recovered in the circulation path of the drivetrain cooling circuit while the vehicle is running. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-183958 Summary of the Invention [Problem to be solved by the invention]

[0004] In an electric vehicle that includes a motor connected to a drive wheel, an inverter that drives the motor, a power storage device, and also a step-up / step-down converter that exchanges power with voltage conversion between a low-voltage power line to which the power storage device is connected and a high-voltage power line to which the inverter is connected, if a relatively large current continues to flow from the high-voltage power line to the low-voltage power line via the step-up / step-down converter when, for example, the drive wheel slips and then grips, there is a risk that the elements of the step-up / step-down converter will overheat.

[0005] The electric vehicle of the present disclosure has a primary objective of preventing overheating of the elements of the step-up / step-down converter. [Means for solving the problem]

[0006] The electric vehicle of the present disclosure employs the following measures to achieve the above-mentioned main object.

[0007] The electric vehicle of the present disclosure includes: a motor connected to a drive wheel; an inverter that drives the motor; a power storage device; a step-up / step-down converter that exchanges power with voltage conversion between a low-voltage power line to which the power storage device is connected and a high-voltage power line to which the inverter is connected; an auxiliary device connected to the high-voltage side power line; a control device that controls the inverter, the step-up / step-down converter, and the auxiliary equipment; An electric vehicle comprising: When a predetermined condition is satisfied that the current flowing through the elements of the step-up / step-down converter is in a direction from the high-voltage side power line to the low-voltage side power line and is greater than a threshold, the control device increases the power consumption of the auxiliary equipment compared to when the predetermined condition is not satisfied. The gist of this is as follows.

[0008] In the electric vehicle disclosed herein, when a predetermined condition is met in which a current flowing through an element of the buck-boost converter is in a direction from the high-voltage power line to the low-voltage power line and is greater than a threshold, the power consumption of the auxiliary equipment is increased compared to when the predetermined condition is not met. This process can prevent a relatively large current from continuously flowing from the high-voltage power line to the low-voltage power line via the buck-boost converter. As a result, a relatively large current is prevented from continuously flowing through the element of the buck-boost converter, and overheating of the element of the buck-boost converter can be prevented. Here, the buck-boost converter may have an upper arm, a lower arm, and a reactor, and the current flowing through the element 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, the control device may increase the power consumption of the accessories when the predetermined condition is met due to grip after slip of the drive wheels, compared to when the predetermined condition is not met. Also, the control device may increase the power consumption of the accessories when the predetermined condition is met due to regeneration of power by the motor, compared to when the predetermined condition is not met. In this way, overheating of elements of the buck-boost converter can be suppressed when the predetermined condition is met due to grip after slip of the drive wheels or when the predetermined condition is met due to regeneration of power by the motor. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic configuration diagram of an electric vehicle according to an embodiment of the present disclosure. [Figure 2] 4 is a flowchart showing an example of a processing routine executed by an electronic control unit. [Figure 3] FIG. 10 is a schematic diagram of a hybrid vehicle according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0011] An embodiment of the present disclosure will be described with reference to the drawings. Fig. 1 is a schematic diagram of an electric vehicle 10 according to an embodiment of the present disclosure. As shown in the figure, the electric vehicle 10 according to the embodiment includes a motor 22, an inverter 24, a battery 26 as a power storage device, a step-up / step-down converter 30, a heater 40, a refrigeration cycle 42, and an electronic control unit 50 as a control device.

[0012] Motor 22 is configured as a three-phase AC motor and includes a rotor with a permanent magnet embedded in a rotor core and a stator with three-phase (U-phase, V-phase, W-phase) coils wound around a stator core. The rotor of motor 22 is connected to drive shaft 16, which is connected to drive wheels 12a, 12b via differential gear 14.

[0013] Inverter 24 is connected to step-up / step-down converter 30 via high-voltage power line 32. Inverter 24 includes six switching elements, transistors T11-T16, and six diodes D11-D16 connected in parallel to each of the six transistors T11-T16. Transistors T11-T16 are arranged in pairs, two at a time, so as to be on the source side and two at the sink side of the positive and negative lines of high-voltage power line 32, respectively. The junctions of paired transistors T11-T16 are connected to the three-phase (U-phase, V-phase, W-phase) coils of motor 22, respectively. Therefore, when voltage is applied to inverter 24, electronic control unit 50 adjusts the proportion of the on-time of paired transistors T11-T16, thereby generating a rotating magnetic field in the three-phase coils of motor 22 and driving the motor 22 (rotor). A smoothing capacitor 36 is connected to high-voltage power line 32.

[0014] Battery 26 is configured as, for example, a lithium ion secondary battery or a nickel-metal hydride secondary battery, and is connected to step-up / step-down converter 30 via low-voltage side power line 34. A smoothing capacitor 38 is connected to low-voltage side power line 34.

[0015] The step-up / step-down converter 30 is connected to a high-voltage power line 32 and a low-voltage power line 34, and includes two switching elements: transistors T31 and T32 (upper arm and lower arm), two diodes D31 and D32 connected in parallel to the two transistors T31 and T32, respectively, and a reactor L. The transistor T31 is connected to the positive electrode line of the high-voltage power line 32. The transistor T32 is connected to the transistor T31 and to a common negative electrode line of the high-voltage power line 32 and the low-voltage power line 34. The reactor L is connected to the connection point of the two transistors T31 and T32 and to the positive electrode line of the low-voltage power line 34. The step-up / step-down converter 30 boosts the power on the low-voltage side power line 34 and supplies it to the high-voltage side power line 32, or reduces the power on the high-voltage side power line 32 and supplies it to the low-voltage side power line 34, by adjusting the ratio of the on-time of the transistors T31 and T32 using the electronic control unit 50.

[0016] The heater 40 is connected to the high-voltage power line 32. The heater 40 is used as a heat source for heating the vehicle interior and for raising the temperature of the coolant circulating through a circulation path including the battery 26. The refrigeration cycle 42 is used as a cold source for cooling the vehicle interior and for cooling the coolant, and as a heat source for heating the vehicle interior. The refrigeration cycle 42 includes a compressor 44, a condenser, an expansion valve, and an evaporator. The compressor 44 is connected to the high-voltage power line 32 and compresses the refrigerant from the evaporator to produce a high-temperature, high-pressure gaseous refrigerant. The condenser converts the refrigerant from the compressor 44 into a room-temperature, high-pressure liquid refrigerant through heat exchange with air. The expansion valve decompresses the refrigerant from the condenser to produce a low-temperature, low-pressure gas-liquid mixture refrigerant. The evaporator converts the refrigerant from the expansion valve into a low-temperature, low-pressure gaseous refrigerant through heat exchange with air. When heating the vehicle interior, air heated by heat exchange with the heater 40 and / or the condenser is blown into the vehicle interior by the blower. When cooling the vehicle interior, air cooled by heat exchange with the evaporator is blown into the vehicle interior by the blower. The cooling water in the circulation flow path is heated by the heater 40 and / or the refrigeration cycle 42, and cooled by the refrigeration cycle 42.

[0017] The electronic control unit 50 includes a microcomputer with a CPU, ROM, RAM, flash memory, input / output ports, and communication ports, as well as various drive circuits and logic ICs. The electronic control unit 50 receives signals from various sensors. For example, the electronic control unit 50 receives rotation speeds Nwa and Nwb of the drive wheels 12a and 12b from rotation speed sensors 13a and 13b attached to the drive wheels 12a and 12b. The electronic control unit 50 also receives the rotational position θm of the rotor of the motor 22 from a rotational position sensor 22a that detects the rotational position of the rotor of the motor 22, and the phase currents Iu, Iv, and Iw of each phase of the motor 22 from current sensors 22u, 32v, and 32w attached to each phase of the motor 22. The electronic control unit 50 also receives the voltage Vb of the battery 26 from a voltage sensor 26v attached between the terminals of the battery 26 and the current Ib of the battery 26 from a current sensor 26i attached to the output terminal of the battery 26. Electronic control unit 50 also receives as inputs a current IL of reactor L from current sensor 30i attached in series to reactor L of step-up / step-down converter 30, a voltage VH of capacitor 36 (high-voltage side power line 32) from voltage sensor 36v attached between the terminals of capacitor 36, and a voltage VL of capacitor 38 (low-voltage side power line 34) from voltage sensor 38v attached between the terminals of capacitor 38. Electronic control unit 50 also receives as inputs a switch signal from power switch 60, a shift position SP from shift sensor 62 that detects the operating position of shift lever 61, an accelerator opening Acc from accelerator pedal position sensor 64 that detects the depression amount of accelerator pedal 63, a brake pedal position BP from brake pedal position sensor 66 that detects the depression amount of brake pedal 65, and vehicle speed V from vehicle speed sensor 67.

[0018] The electronic control unit 50 outputs various control signals. For example, the electronic control unit 50 outputs a control signal to the transistors T11 to T16 of the inverter 24 and a control signal to the transistors T31 and T32 of the step-up / step-down converter 30. The electronic control unit 50 also outputs a control signal to the heater 40 and a control signal to the compressor 44 of the refrigeration cycle 42. The electronic control unit 50 calculates the electrical angle θe and rotation 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 power storage rate SOC of the battery 26 based on the integrated value of the current Ib of the battery 26 from the current sensor 26i.

[0019] In electric vehicle 10 of this embodiment configured as described above, electronic control unit 50 sets a required torque Td* required for traveling (required of drive shaft 16) based on accelerator pedal position Acc and vehicle speed V, sets torque command Tm* for motor 22 so that the set required torque Td* is output to drive shaft 16, and performs switching control of transistors T11-T16 of inverter 24 so that motor 22 is driven by torque command Tm*. Electronic control unit 50 also sets a target voltage VH* for high-voltage power line 32 for motor 22 based on torque command Tm* and rotation speed Nm, and calculates target current IL* for reactor L by voltage feedback control so that the difference between voltage VH on high-voltage power line 32 and target voltage VH* is canceled out. Next, a duty command D* is calculated by current feedback control so that the difference between the current IL of the reactor L and the target current IL* is canceled out, and the calculated duty command D* is used to control the switching of the transistors T31 and T32 of the step-up / step-down converter 30.

[0020] Next, the operation of the electric vehicle 10 of this embodiment will be described. In particular, the operation when the drive wheels 12a, 12b slip and then grip will be described. FIG. 2 is a flowchart showing an example of a processing routine executed by the electronic control unit 50. This routine is repeatedly executed for a predetermined time after it is detected that the drive wheels 12a, 12b have slipped and then gripped. Note that the slip of the drive wheels 12a, 12b and the subsequent grip can be detected, for example, using the rotation speed change rates ΔNwa, ΔNwb, which are the amount of change per unit time in the rotation speeds Nwa, Nwb of the drive wheels 12a, 12b from the rotation speed sensors 13a, 13b.

[0021] 2 is executed, electronic control unit 50 receives current IL (positive in the direction from low-voltage power line 34 to high-voltage power line 32) of reactor L from current sensor 30i (step S100), and determines whether a predetermined condition is met in which input current IL of reactor L is negative and its absolute value is greater than threshold value ILref (steps S110, S120). Here, threshold value ILref is a threshold value used to determine whether a relatively large current is flowing from high-voltage power line 32 to low-voltage power line 34 via step-up / step-down converter 30. If drive wheels 12a, 12b slip while the vehicle is traveling, i.e., if rotation speeds Nwa, Nwb of drive wheels 12a, 12b increase rapidly, rotation speed Nm of motor 22 also increases rapidly, and power consumption Pm of motor 22 also increases rapidly. Then, when drive wheels 12a, 12b grip, i.e., when rotation speeds Nwa, Nwb of drive wheels 12a, 12b suddenly decrease, rotation speed Nm of motor 22 suddenly decreases, resulting in a sudden decrease in power consumption of motor 22. At this time, in the above-described control of step-up / step-down converter 30, target voltage VH* of high-voltage power line 32 may become sufficiently lower than voltage VH, target current IL* of reactor L may become negative and its absolute value may become relatively large, and current IL of reactor L may become negative and its absolute value may become relatively large (a relatively large current may flow from high-voltage power line 32 to low-voltage power line 34 via step-up / step-down converter 30). The processes of steps S110 and S120 are performed to detect such an event.

[0022] In steps S110 and S120, if the current IL of the reactor L is 0 or positive, or if the current IL of the reactor L is negative and its absolute value is less than or equal to the threshold value ILref, that is, if the specified condition is not met, this routine is terminated.

[0023] In steps S110 and S120, when the current IL through the reactor L is negative and its absolute value is greater than the threshold value ILref, i.e., when the predetermined condition is met, the power consumption of the heater 40 is increased compared to when the predetermined condition is not met (step S130), and the routine ends. In step S130, the power consumption of the heater 40 is increased by starting the heater 40 from a stopped state, or the power consumption of the heater 40 while it is being driven is increased. By performing such processing, when the predetermined condition is met, the power consumption of the heater 40 can be increased compared to when the predetermined condition is met, thereby preventing a relatively large current from continuing to flow from the high-voltage power line 32 to the low-voltage power line 34 via the buck-boost converter 30. As a result, a relatively large current is prevented from continuing to flow through elements of the buck-boost converter 30 (e.g., transistor T31), and overheating of the elements of the buck-boost converter 30 can be prevented.

[0024] In the electric vehicle 10 of the embodiment described above, when a predetermined condition is met in which the current IL of the reactor L is negative and its absolute value is greater than the threshold value ILref due to grip after the drive wheels 12a, 12b slip, the power consumption of the heater 40 is increased compared to when the predetermined condition is not met. This prevents a relatively large current from continuing to flow through elements of the boost-buck converter 30 (such as the transistor T31), and prevents the elements of the boost-buck converter 30 from overheating.

[0025] In the above-described embodiment, when a predetermined condition is met due to gripping of the drive wheels 12a, 12b after slipping, the power consumption of the heater 40 is increased compared to when the predetermined condition is not met. However, this is not limiting. For example, when a predetermined condition is met due to regeneration of the motor 22, such as when the driver depresses the brake pedal 65 heavily, the power consumption of the heater 40 may be increased compared to when the predetermined condition is not met. Furthermore, when a predetermined condition is met other than when gripping of the drive wheels 12a, 12b after slipping or when regeneration of the motor 22, the power consumption of the heater 40 may be increased compared to when the predetermined condition is not met.

[0026] In the above-described embodiment, when the predetermined condition is satisfied, the power consumption of the heater 40 is increased compared to when the predetermined condition is not satisfied, but this is not limiting. For example, in addition to or instead of increasing the power consumption of the heater 40, the power consumption of the compressor 44 of the refrigeration cycle 42 may be increased.

[0027] In the above-described embodiment, the electric vehicle 10 is configured such that both the heater 40 and the compressor 44 of the refrigeration cycle 42 are connected to the high-voltage power line 32, but this is not limiting. For example, one of the heater 40 and the compressor 44 may be connected to the high-voltage power line 32, and the other may be connected to the low-voltage power line 34. In this case, when a predetermined condition is met, the power consumption of the heater 40 or the compressor 44 that is connected to the high-voltage power line 32 may be increased compared to when the predetermined condition is not met.

[0028] In the above-described embodiment, the electric vehicle 10 is equipped with the battery 26 as a power storage device, but is not limited to this. For example, a capacitor or the like may be provided as a power storage device in addition to or instead of a battery.

[0029] In the above-described embodiment, the electric vehicle 10 is provided with the motor 22 connected to the drive shaft 16 which is connected to the drive wheels 12a, 12b via the differential gear 14, but is not limited to this. For example, the electric vehicle 10 may be provided with two in-wheel motors attached (connected) to the drive wheels 12a, 12b, respectively.

[0030] In the above-described embodiment, as shown in FIG. 1 , the electric vehicle 10 is configured to include the motor 22, the inverter 24, the battery 26, the step-up / step-down converter 30, the heater 40, and the compressor 44 of the refrigeration cycle 42. However, the present invention is not limited to this. For example, the electric vehicle 10 may be configured as a hybrid vehicle further including an engine in addition to the hardware configuration similar to that of the electric vehicle 10, or as a fuel cell vehicle further including a fuel cell in addition to the hardware configuration similar to that of the electric vehicle 10. In the case of a hybrid vehicle configuration, for example, as shown in a modified hybrid vehicle 110 of FIG. 3 , the electric vehicle 110 may further include an engine 112, a planetary gear 114, a motor 122, and an inverter 124 in addition to the hardware configuration similar to that of the electric vehicle 10. In the hybrid vehicle 110, the motor 22, the engine 112, and the motor 122 are connected to the ring gear, the carrier, and the sun gear of the planetary gear 114, respectively, and the inverter 124 that drives the motor 122 is connected to the high-voltage power line 32. In the case of a hybrid vehicle configuration, in addition to the same hardware configuration as the electric vehicle 10, a transmission may be provided between the drive shaft 16 and the motor 22, and an engine may be connected to the motor 22 via a clutch.

[0031] The correspondence between the main elements of the embodiment and the main elements of the invention described in the "Means for Solving the Problem" section will be explained below. In the embodiment, the motor 22 corresponds to the "motor," the inverter 24 corresponds to the "inverter," the battery 26 corresponds to the "electricity storage device," the step-up / step-down converter 30 corresponds to the "step-up / step-down converter," the heater 40 corresponds to the "auxiliary device," and the electronic control unit 50 corresponds to the "control device."

[0032] The correspondence between the main elements of the embodiments and the main elements of the invention described in the "Means for Solving the Problem" section does not limit the elements of the invention described in the "Means for Solving the Problem" section, since the embodiments are examples for specifically explaining the mode for implementing the invention described in the "Means for Solving the Problem" section. In other words, the interpretation of the invention described in the "Means for Solving the Problem" section should be based on the description in that section, and the embodiments are merely specific examples of the invention described in the "Means for Solving the Problem" section.

[0033] The above describes the forms for implementing the present disclosure using embodiments, but the present disclosure is not limited to these embodiments in any way, and it goes without saying that the present disclosure can be implemented in various forms within the scope that does not deviate from the gist of the present disclosure. [Industrial Applicability]

[0034] The present disclosure is applicable to the electric vehicle manufacturing industry and the like. [Explanation of symbols]

[0035] 10 electric vehicle, 12a, 12b drive wheels, 13a rotation speed sensor, 14 differential gear, 16 drive shaft, 22 motor, 22a rotation position sensor, 22u, 22v, 22w current sensor, 24 inverter, 26 battery, 26i, 30i current sensor, 26v, 36v, 38v voltage sensor, 30 boost / buck converter, 32 high voltage side power line, 34 low voltage side power line, 36, 38 capacitor, 40 heater, 42 refrigeration cycle, 44 compressor, 50 electronic control unit, 60 power switch, 61 shift lever, 62 shift sensor, 63 accelerator pedal, 64 accelerator pedal position sensor, 65 brake pedal, 66 brake pedal position sensor, 67 vehicle speed sensor, D11 to D16, D31, D32 Diodes, T11~T16, T31, T32 transistors.

Claims

1. a motor connected to a drive wheel; an inverter that drives the motor; a power storage device; a step-up / step-down converter that exchanges power with voltage conversion between a low-voltage power line to which the power storage device is connected and a high-voltage power line to which the inverter is connected; an auxiliary device connected to the high-voltage side power line; a control device that controls the inverter, the step-up / step-down converter, and the auxiliary equipment; An electric vehicle comprising: When a predetermined condition is satisfied that the current flowing through the elements of the step-up / step-down converter is in a direction from the high-voltage side power line to the low-voltage side power line and is greater than a threshold, the control device increases the power consumption of the auxiliary equipment compared to when the predetermined condition is not satisfied. Electric car.

2. The electric vehicle according to claim 1, the control device increases the power consumption of the auxiliary device when the predetermined condition is satisfied due to grip of the drive wheels after slipping, compared to when the predetermined condition is not satisfied. Electric car.

3. The electric vehicle according to claim 1, When the predetermined condition is satisfied in association with regeneration of the motor, the control device increases the power consumption of the auxiliary device compared to when the predetermined condition is not satisfied. Electric car.

Images