Electric vehicle control system

Abstract

To provide a control system of an electric vehicle that can suppress running resistance while suppressing energy consumption.SOLUTION: A control system of an electric vehicle is provided with: a rotary electric machine that drives wheels of an electric vehicle; a battery for driving that supplies electric power to the rotary electric machine; a pressure boosting device that boosts electric power of the battery for driving; and a control device that controls the electric vehicle. The control device performs boosting control of making the boosting device boost the electric power and regenerative output suppression control of suppressing regenerative output that is generated by the rotary electric machine. The control device preferentially executes the boosting control, when rotation speed of the rotary electric machine is above first rotation speed, in a state where the rotary electric machine is dragged round by the wheels.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a control system for an electric vehicle. [Background technology]

[0002] Conventionally, there is known a control system for an electric vehicle in which the wheels are driven by a motor (see, for example, Patent Document 1). In such an electric vehicle, an induced voltage corresponding to the rotation speed of the motor is generated as the motor rotates along with the wheels. When the induced voltage becomes higher than the voltage of the drive battery that supplies power to the motor, current flows from the motor to the drive battery, and the motor enters a regenerative state. When the motor enters a regenerative state, it creates running resistance. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-240442 Summary of the Invention [Problem to be solved by the invention]

[0004] In the control system for an electric vehicle disclosed in Patent Document 1, the motor is controlled so that the regenerative output of the motor is zero in order to suppress the induced voltage. Such control to suppress the regenerative output consumes a lot of energy. Furthermore, it is difficult to accurately set the regenerative output to zero with this control.

[0005] An object of the present disclosure is to provide a control system for an electric vehicle that can reduce running resistance while suppressing energy consumption. [Means for solving the problem]

[0006] The control system for an electric vehicle according to the present disclosure includes a rotating electric machine that drives the wheels of the electric vehicle, a drive battery that supplies power to the rotating electric machine, a boost device that boosts the power of the drive battery, and a control device that controls the electric vehicle, wherein the control device has boost control that boosts the power using the boost device, and regenerative output suppression control that suppresses the regenerative output generated by the rotating electric machine, and the control device prioritizes executing the boost control when the rotation speed of the rotating electric machine is equal to or higher than a first rotation speed while the rotating electric machine is being rotated by the wheels.

[0007] According to this electric vehicle control system, the control device increases the voltage of the drive battery through voltage boost control. This causes the control device to increase the motor rotation speed at which the induced voltage becomes higher than the voltage of the drive battery. Because the control device prioritizes voltage boost control, it can reduce the frequency with which it executes regenerative output suppression control. As a result, this electric vehicle control system can reduce running resistance while suppressing energy consumption. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide a control system for an electric vehicle that can reduce running resistance while suppressing energy consumption. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a system diagram of an electric vehicle according to one embodiment of the present disclosure. [Figure 2] 4 is a flowchart showing a control procedure executed by a control device according to an embodiment of the present disclosure. [Figure 3] 4 is a timing chart illustrating an example of control executed by a control device according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings.

[0011] As shown in FIG. 1 , the control system 3 of the electric vehicle C includes an internal combustion engine 1, a motor (FrM: an example of a rotating electric machine) 2, a generator (GEN) 4, a drive battery (BT) 6, a transaxle 8, a vehicle control device (an example of a control device) 12, an engine control device 14 that controls the internal combustion engine 1, an accelerator pedal 16 operated by a user of the electric vehicle C, an inverter 18 that controls the motor 2 and the generator 4, a charger 20 that can be connected to an external power source, a DC-DC converter (DC-DC: an example of a boost device) 24, and a shifter 26. The control system 3 of the electric vehicle C may also include a power supply device 22 that can supply power to external devices such as home appliances, and a charge button (not shown) that the user uses to instruct charging. In this embodiment, the electric vehicle C is a plug-in hybrid vehicle (PHEV) that can store power from an external power source in the drive battery 6 using the charger 20. The shifter 26 is a device that selects, for example, N range, D range, etc. The shifter 26 is electrically connected to the vehicle control unit 12 and transmits the selected range to the vehicle control unit 12 .

[0012] The motor 2 is connected to the wheel C1 via the transaxle 8 and the axle 10, and drives the wheel C1. In this embodiment, the motor 2 is a three-phase AC motor having multiple coils and multiple permanent magnets. When the wheel C1 rotates, the motor 2 rotates along with the wheel C1 via the transaxle 8 and the axle 10. At this time, an induced voltage Mv is generated as the permanent magnet passes through the coil. The induced voltage Mv increases as the rotation speed of the motor 2 increases.

[0013] The generator 4 is connected to the internal combustion engine 1 and is capable of driving the internal combustion engine 1. The generator 4 performs motoring to drive the internal combustion engine 1 while the internal combustion engine 1 is being powered by electric power from the drive battery 6. On the other hand, the generator 4 is driven by the internal combustion engine 1 to generate electricity while the internal combustion engine 1 is in operation. Therefore, the generator 4 is a motor-generator capable of powering and generating electricity.

[0014] The drive battery 6 outputs power to the motor 2 and generator 4 via a DC-DC converter 24, and also receives power generated by the motor 2 and generator 4. The drive battery 6 also receives external power via a charger 20. The drive battery 6 in this embodiment is formed from a secondary battery such as a lithium-ion battery, and has a battery module (not shown) configured by connecting multiple battery cells in series. In this embodiment, the battery modules are further connected in series.

[0015] The drive battery 6 has a battery monitoring unit (BMU) 6a. The battery monitoring unit 6a calculates the state of charge (hereinafter referred to as SOC) of the battery module as an example of the state of charge of the drive battery 6. The battery monitoring unit 6a may also detect the state of health (hereinafter referred to as SOH) of the battery module and the drive battery 6 temperature Tb. The battery monitoring unit 6a acquires the drive battery 6 voltage Bv, the state of charge SOC, the state of health SOH, and the drive battery 6 temperature Tb, and transmits them to the vehicle control device 12.

[0016] The transaxle 8 has multiple gears and a clutch 8a. The internal combustion engine 1 is connected to the generator 4 and the axle 10 via the transaxle 8. When the clutch 8a is in a disengaged state, the transaxle 8 cuts off the power transmission between the internal combustion engine 1 and the axle 10, and when the clutch 8a is in a engaged state, the power of the internal combustion engine 1 is transmitted to the axle 10.

[0017] The vehicle control device 12 is electrically connected to the motor 2 via the inverter 18 and controls the motor 2. The vehicle control device 12 acquires an actual motor rotation speed RMrpm, which is the actual rotation speed of the motor 2, and an actual motor torque RMtq, which is the actual torque output by the motor 2. The vehicle control device 12 controls the motor 2 so that the actual motor rotation speed RMrpm and the actual motor torque RMtq become the required motor torque Mtq and required rotation speed Mrpm that the motor 2 should output. The motor 2 is actually an ECU (Electronic Control Unit) configured by a microcomputer including an arithmetic unit, a memory, an input / output buffer, etc. The vehicle control device 12 controls the motor 2 based on maps and programs stored in the memory.

[0018] In addition, the vehicle control device 12 is electrically connected to the battery monitoring unit 6a of the drive battery 6, and can obtain information such as the charging rate SOC of the drive battery 6 and the temperature Tb of the drive battery 6 from the battery monitoring unit 6a of the drive battery 6.

[0019] The vehicle control device 12 of this embodiment is further electrically connected to an engine control device 14. The engine control device 14 is electrically connected to various devices provided in the internal combustion engine 1 and controls the internal combustion engine 1. The control of the internal combustion engine 1 may be performed by the vehicle control device 12 in addition to the engine control device 14. The vehicle control device 12 may also be electrically connected to various other devices of the electric vehicle C and perform various controls.

[0020] The electric vehicle C of this embodiment has various modes, including EV mode, series mode, parallel mode, and charge mode. In EV mode, the electric vehicle C drives the motor 2 using power from the drive battery 6. In series mode, the electric vehicle C drives the generator 4 using the internal combustion engine 1 and uses the power generated by the generator 4 to drive the motor 2. In parallel mode, the electric vehicle C engages the clutch 8a and drives the axle 10 using power from the internal combustion engine 1. In charge mode, the electric vehicle C drives the generator 4 using the internal combustion engine 1 and stores the power generated by the generator 4 in the drive battery 6. In the electric vehicle C, the vehicle control device 12 switches between each mode depending on the depression state of the accelerator pedal 16 and the operation state of the charge button, and controls the motor 2 and the generator 4 via the inverter 18 and causes the engine control device 14 to control the internal combustion engine 1. The vehicle control device 12 executes each of these modes when the D range is selected by the shifter 26. When the N range is selected, the vehicle control device 12 puts the clutch 8a into a disengaged state.

[0021] The inverter 18 converts the DC power supplied from the drive battery 6 into AC power and adjusts the power supplied to the motor 2, thereby controlling the power running torque (an example of power running output) of the motor 2. When the motor 2 regenerates power, the inverter 18 converts the AC power supplied from the motor 2 into DC power and adjusts the power supplied to the drive battery 6, thereby controlling the regenerative torque (an example of regenerative output) of the motor 2.

[0022] More specifically, the inverter 18 includes switching elements such as IGBTs (Insulated Gate Bipolar Transistors). When the inverter 18 acquires information on the motor required torque Mtq and required rotation speed Mrpm from the vehicle control device 12, it controls the switching elements so that the motor 2 achieves the motor required torque Mtq and required rotation speed Mrpm. The motor required torque Mtq is a positive value when the motor 2 is powered. The motor required torque Mtq is a negative value when the motor 2 is regenerating.

[0023] The DC-DC converter 24 has a boost circuit and boosts the power of the drive battery 6. More specifically, the DC-DC converter 24 is electrically connected to the vehicle control device 12. When the DC-DC converter 24 receives a boost control command from the vehicle control device 12, it flows power from the drive battery 6 into the boost circuit, thereby increasing the voltage Bv.

[0024] When measuring the running resistance of such an electric vehicle C, the user accelerates the electric vehicle C, then shifts the shifter 26 to N range and coasts the vehicle with the clutch 8a in the disengaged state. At this time, the motor 2 rotates together with the wheels C1, generating an induced voltage Mv. Also in the parallel mode, the wheels C1 are driven by the output of the internal combustion engine 1. Therefore, the motor 2 rotates together with the wheels C1, generating an induced voltage Mv.

[0025] When the induced voltage Mv becomes higher than the voltage Bv of the drive battery 6, current flows from the motor 2 to the drive battery 6. This causes regenerative torque to be generated in the motor 2. When regenerative torque is generated, the motor 2 acts as a running resistance.

[0026] To suppress the generation of such regenerative torque, the vehicle control device 12 executes voltage boost control and regenerative output suppression control. In voltage boost control, the vehicle control device 12 instructs the DC-DC converter 24 to boost the voltage Bv of the driving battery 6 to the boost voltage UBv.

[0027] In regenerative output suppression control, the vehicle control device 12 controls the motor 2 and the inverter 18 so that the actual motor torque RMtq generated by the motor 2 becomes zero. The motor 2 attempts to generate regenerative torque using the induced voltage Mv. Therefore, the actual motor torque RMtq is a negative value. To cancel out this negative actual motor torque RMtq, the vehicle control device 12 instructs the inverter 18 to generate a positive motor required torque Mtq. For this reason, regenerative output suppression control consumes more energy than voltage boost control. Furthermore, the vehicle control device 12 needs to calculate the motor required torque Mtq in accordance with the constantly changing actual motor torque RMtq. For this reason, the calculation load on the vehicle control device 12 is also greater than that of voltage boost control.

[0028] Next, the control procedure executed by the vehicle control device 12 will be described with reference to the flowchart of FIG.

[0029] In step S1, the vehicle control device 12 acquires the actual motor rotation speed RM rpm. After acquiring the actual motor rotation speed RM rpm, the vehicle control device 12 proceeds to step S2.

[0030] In step S2, the vehicle control device 12 determines whether the actual motor rotation speed RM rpm is equal to or greater than the first rotation speed R1. The first rotation speed R1 is the actual motor rotation speed RM rpm of the motor 2 when the induced voltage Mv of the motor 2 becomes greater than the voltage Bv of the drive battery 6. In this embodiment, the motor 2 is connected to the wheels C1, and therefore the actual motor rotation speed RM rpm is proportional to the vehicle speed V. Therefore, the vehicle control device 12 may use the vehicle speed V to determine whether the actual motor rotation speed RM rpm is equal to or greater than the first rotation speed R1. If the vehicle control device 12 determines that the actual motor rotation speed RM rpm is equal to or greater than the first rotation speed R1 (YES in step S2), the process proceeds to step S3.

[0031] In step S3, the vehicle control device 12 determines whether the state of charge SOC is equal to or greater than a predetermined state of charge SOCt. The predetermined state of charge SOCt is, for example, a value at which the drive battery 6 is fully charged. If the vehicle control device 12 determines that the state of charge SOC is less than the predetermined state of charge SOCt (NO in step S3), the process proceeds to step S4.

[0032] In step S4, the vehicle control device 12 determines whether the temperature Tb of the drive battery 6 is equal to or lower than a predetermined temperature Tbt. The predetermined temperature Tbt is the temperature at which the drive battery 6's power acceptance capacity decreases. The predetermined temperature Tbt is, for example, zero degrees Celsius. If the vehicle control device 12 determines that the temperature Tb of the drive battery 6 is higher than the predetermined temperature Tbt (NO in step S4), the process proceeds to step S5.

[0033] In step S5, the vehicle control device 12 executes the voltage boost control in priority to the regenerative output suppression control. After executing the voltage boost control, the vehicle control device 12 proceeds to step S6.

[0034] In step S6, the vehicle control device 12 determines whether the actual motor rotation speed RM rpm is equal to or greater than a second rotation speed R2. The second rotation speed R2 is the rotation speed of the motor 2 at which the induced voltage Mv is higher than the increased voltage UBv increased by the voltage step-up control. If the vehicle control device 12 determines that the actual motor rotation speed RM rpm is equal to or greater than the second rotation speed R2, the process proceeds to step S7.

[0035] In step S7, the vehicle control device 12 executes the regenerative output suppression control. After executing the regenerative output suppression control, the vehicle control device 12 advances the process to step S1.

[0036] In step S2, if the vehicle control device 12 determines that the actual motor rotation speed RM rpm is less than the first rotation speed R1 (step S2 NO), the vehicle control device 12 proceeds to step S1 without executing either the voltage boost control or the regenerative output suppression control.

[0037] In step S3, if the vehicle control device 12 determines that the state of charge (SOC) is equal to or greater than the predetermined state of charge (SOCt) (YES in step S3), the vehicle control device 12 proceeds to step S8 and executes regenerative output suppression control. When the drive battery 6 is fully charged, the drive battery 6 has a small capacity to accept power regenerated by the motor 2. Therefore, the vehicle control device 12 executes regenerative output suppression control to lower the state of charge (SOC) of the drive battery 6.

[0038] In step S4, if the vehicle control device 12 determines that the temperature Tb of the drive battery 6 is equal to or lower than the predetermined temperature Tbt (step S4: YES), the vehicle control device 12 proceeds to step S8 and executes regenerative output suppression control. The vehicle control device 12 consumes power from the drive battery 6 through regenerative output suppression control to warm up the drive battery 6. After executing the process of step S8, the vehicle control device 12 proceeds to step S1.

[0039] In step S6, if the vehicle control device 12 determines that the actual motor rotation speed RM rpm is less than the second rotation speed R2 (step S6 NO), the vehicle control device 12 proceeds to the process in step S3 and continues to prioritize the voltage boost control.

[0040] Next, an example of the above control will be described with reference to the timing chart of FIG.

[0041] As shown from time t1 to time t2, the actual motor rotation speed RM rpm of the motor 2 increases. At this time, the vehicle control device 12 does not execute regenerative output control or voltage boost control. Such operation of the electric vehicle C occurs, for example, when accelerating in the parallel mode in the D range.

[0042] As shown from time t2 to time t4, when the actual motor rotation speed RM rpm becomes equal to or greater than the first rotation speed R1 (YES in step S2 in FIG. 2), the vehicle control device 12 prioritizes voltage boost control. However, as shown from time t2 to time t3, when the temperature Tb of the drive battery 6 is equal to or less than the predetermined temperature Tbt (YES in step S4 in FIG. 2), the vehicle control device 12 executes regenerative output suppression control to warm up the drive battery 6. This drop in drive battery 6 temperature Tb can occur not only when the electric vehicle C is accelerating in parallel mode, but also during deceleration in the N range, for example, from time t5 to time t6. As shown from time t3 to time t4, when the temperature Tb of the drive battery 6 becomes higher than the predetermined temperature Tbt (NO in step S4 in FIG. 2), the vehicle control device 12 switches to voltage boost control. At this time, the regenerative output suppression control is stopped.

[0043] As shown at time t4, when the actual motor rotation speed RM rpm becomes equal to or greater than the second rotation speed R2 (YES in step S6 in FIG. 2), the vehicle control device 12 executes regenerative output suppression control in addition to voltage boost control. Between time t4 and time t5, the actual motor rotation speed RM rpm starts to decrease. In this embodiment, the decrease in the actual motor rotation speed RM rpm occurs when, for example, the user places the shifter 26 in the N range and the electric vehicle C starts traveling.

[0044] As shown at time t5, when the actual motor rotation speed RM rpm falls below the second rotation speed R2 (NO in step S6), the vehicle control device 12 stops the regenerative output suppression control and executes only the voltage boost control.

[0045] As shown from time t6 to time t7, when the state of charge SOC becomes greater than the predetermined state of charge SOCt while the boost control is being performed (YES in step S3 of FIG. 2), the vehicle control device 12 stops the boost control and performs only the regenerative output suppression control even if the actual motor rotation speed RMrpm is equal to or greater than the first rotation speed R1.

[0046] As shown from time t7 to time t8, when the state of charge SOC becomes equal to or lower than a predetermined state of charge SOCt, the vehicle control device 12 switches from the regenerative output suppression control to the voltage boost control and stops the regenerative output suppression control. As shown after time t8, when the actual motor rotation speed RM rpm becomes lower than the first rotation speed R1, the vehicle control device 12 stops the voltage boost control.

[0047] As described above, according to the present disclosure, it is possible to provide a control system 3 for an electric vehicle that can suppress running resistance while suppressing energy consumption.

[0048] <Other embodiments> Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above embodiments, and various modifications are possible within the scope of the gist of the invention. In particular, the multiple modifications described in this specification can be combined as needed.

[0049] (a) In the above embodiment, the electric vehicle C is a front-wheel-drive plug-in hybrid vehicle that drives the front wheels C1, but the present disclosure is not limited to this. The motor 2 may be a rear motor that drives the wheels C2.

[0050] (b) In the above embodiment, the electric vehicle C is described as a plug-in hybrid vehicle, but the present disclosure is not limited to this. The electric vehicle C may be an electric vehicle that runs solely on power from the drive battery 6, or a hybrid vehicle that does not have a charger 20.

[0051] (c) In the above embodiment, an example was described in which boost control was performed by the DC-DC converter 24, but the present disclosure is not limited to this. For example, a device that switches the connection of the battery modules of the driving battery 6 between parallel and series may be used, with the battery modules normally connected in parallel and only connected in series when boosting the voltage. [Explanation of symbols]

[0052] 2: Motor, 3: Control system, 6: Drive battery 12: Vehicle control device, 24: DC-DC converter C: Electric vehicle, C1: Wheel, C2: Wheel R1: First rotation speed, R2: Second rotation speed, RMrpm: Actual motor rotation speed SOC: Charging rate, SOCt: Predetermined charging rate Tb: Temperature, Tbt: Predetermined temperature

Claims

1. a rotating electric machine that drives wheels of an electric vehicle; a drive battery for supplying power to the rotating electric machine; a booster device that boosts the power of the driving battery; a control device that controls the electric vehicle; Equipped with The control device performs voltage boost control to boost the power of the driving battery using the voltage boost device; a regenerative output suppression control that suppresses a regenerative output generated by the rotary electric machine; and the control device prioritizes execution of the voltage boost control when a rotation speed of the rotating electric machine is equal to or higher than a first rotation speed in a state in which the rotating electric machine is rotated by the wheels; Electric vehicle control system.

2. the control device executes the regenerative output suppression control when the rotation speed of the rotating electric machine becomes equal to or higher than a second rotation speed while the voltage boost control is being executed. The control system for an electric vehicle according to claim 1 .

3. the control device acquires the charging rate of the drive battery, When the charging rate is equal to or higher than a predetermined charging rate, the regenerative output suppression control is executed even if the rotation speed of the rotating electric machine is equal to or higher than the first rotation speed. The control system for an electric vehicle according to claim 1 .

4. the control device acquires the charging rate of the drive battery, When the charge rate becomes equal to or higher than a predetermined charge rate while the rotation speed of the rotating electric machine is equal to or higher than the first rotation speed, the voltage boost control is switched to the regenerative output suppression control. The control system for an electric vehicle according to claim 1 .

5. The control device acquires the temperature of the driving battery, When the temperature is equal to or lower than a predetermined temperature, the regenerative output suppression control is executed even if the rotation speed of the rotating electric machine is equal to or higher than the first rotation speed. The control system for an electric vehicle according to any one of claims 1 to 4.

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