Control devices for electric vehicles

Abstract

To enable electric vehicles to run with more appropriate torque that meets user requirements. [Solution] A control device for an electric vehicle equipped with a motor for driving, which limits the torque output from the motor when predetermined conditions are met, determines whether the electric vehicle is traveling on a straight road based on the amount of change in the accelerator opening, and when it is determined that the electric vehicle is traveling on a straight road, even if the predetermined conditions are met, the limit on the torque output from the motor is relaxed compared to when it is determined that the electric vehicle is not traveling on a straight road. As a result, the electric vehicle can be driven with a more appropriate torque that meets the user's requirements.

Description

Technical Field

[0001] The present disclosure relates to a control device for an electric vehicle.

Background Art

[0002] Conventionally, as a control device for this type of electric vehicle, there has been proposed one including a traveling motor and a battery that exchanges power with the motor (see, for example, Patent Document 1). In this device, by limiting the torque of the motor, heating of the battery is prevented and the battery is protected at low temperatures.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above-described control device for an electric vehicle, even when the user requests torque for traveling such as in a circuit, the torque output from the motor may be limited and the torque for traveling may not satisfy the user's request.

[0005] The main object of the control device for an electric vehicle of the present disclosure is to make the electric vehicle travel at a more appropriate torque that satisfies the user's request.

Means for Solving the Problems

[0006] The electric vehicle control device of this disclosure employs the following means to achieve the above-mentioned main objective. The electric vehicle control device of this disclosure is used in an electric vehicle equipped with a motor for driving, and is an electric vehicle control device that limits the torque output from the motor when predetermined conditions are met, and determines whether the electric vehicle is traveling on a straight road based on the amount of change in the accelerator opening, and when it is determined that the electric vehicle is traveling on a straight road, even if the predetermined conditions are met, the limit on the torque output from the motor is relaxed compared to when it is determined that the electric vehicle is not traveling on a straight road. With the above configuration, the electric vehicle control device of this disclosure can drive the electric vehicle with a more appropriate torque that meets the user's requirements. [Brief explanation of the drawing]

[0007] [Figure 1] A diagram showing the general configuration of a hybrid vehicle. [Figure 2] A flowchart showing an example of a processing routine executed by HVECU. [Figure 3] An explanatory diagram illustrating the relationship between the battery charge ratio, vehicle speed, and whether or not there is an output limit. [Modes for carrying out the invention]

[0008] Embodiments of this disclosure will be described with reference to the drawings. Figure 1 is a schematic diagram showing the configuration of a hybrid vehicle according to an embodiment of this disclosure. As shown in Figure 1, the hybrid vehicle 20 of the embodiment includes an engine 22, a planetary gear 30, motors MG1 and MG2, inverters 41 and 42, a battery 50, and a hybrid electronic control unit (hereinafter referred to as HVECU) 70. Here, the control device 21 corresponds to the HVECU 70.

[0009] Engine 22 is configured as an internal combustion engine that outputs power using gasoline, diesel fuel, or the like. This engine 22 is controlled by the HVECU 70.

[0010] The planetary gear 30 is configured as a single-pinion type planetary gear mechanism. The rotor of the motor MG1 is connected to the sun gear of the planetary gear 30. The drive shaft 36, which is connected to the drive wheels 39a and 39b via a differential gear 38, is connected to the ring gear of the planetary gear 30. The crankshaft 23 of the engine 22 is connected to the carrier of the planetary gear 30 via a damper 28.

[0011] Motor MG1 is configured, for example, as a synchronous regenerative motor, and as described above, its rotor is connected to the sun gear of the planetary gear 30. Motor MG2 (motor for driving) is configured, for example, as a synchronous regenerative motor, and its rotor is connected to the drive shaft 36. Inverters 41 and 42 are used to drive motors MG1 and MG2 and are connected to the battery 50 via the power line 54. Motors MG1 and MG2 are driven by the HVECU 70, which controls the switching of multiple switching elements (not shown) of inverters 41 and 42.

[0012] The battery 50 is configured as, for example, a lithium-ion secondary battery or a nickel-metal hydride secondary battery, and as described above, is connected to inverters 41 and 42 via power lines 54. This battery 50 is managed by HVECU 70.

[0013] The HVECU70, although not shown in the diagram, is configured as a microprocessor centered around a CPU, and in addition to the CPU, it is equipped with ROM for storing processing programs, RAM for temporarily storing data, input / output ports, and communication ports. The HVECU70 receives the following inputs via its input ports: crank angle θcr from a crank position sensor (not shown) that detects the rotational position of the crankshaft 23 of the engine 22; rotational positions θm1 and θm2 of the rotors of motors MG1 and MG2 from rotational position sensors (not shown) that detect the rotational positions of the rotors of motors MG1 and MG2; the voltage Vb of the battery 50 from a voltage sensor (not shown) attached between the terminals of the battery 50; the current Ib of the battery 50 from a current sensor (not shown) attached to the output terminal of the battery 50; the temperature Tb of the battery 50 from a temperature sensor (not shown) attached to the battery 50; the ignition signal from the ignition switch 80; the accelerator opening Acc from an accelerator pedal position sensor 84 that detects the amount the accelerator pedal 83 is pressed; and the vehicle speed V from a vehicle speed sensor 88. The HVECU70 outputs various control signals for operating the engine 22, as well as switching control signals to multiple switching elements (not shown) of inverters 41 and 42, via its output ports. The HVECU70 calculates the rotational speed of the crankshaft 23, i.e., the rotational speed Ne of the engine 22, based on the crank angle θcr from the crank position sensor; calculates the rotational speeds Nm1 and Nm2 based on the rotational positions θm1 and θm2 of the rotors of motors MG1 and MG2 from the rotational position sensors; and calculates the charge level (SOC) of the battery 50 based on the integrated value of the current Ib from the current sensor. The charge level (SOC) is the ratio of the amount of power that can be discharged from the battery 50 to the total capacity of the battery 50. The HVECU70 also sets an output limit Wout, which is the maximum allowable output power that the battery 50 may output, based on the charge level (SOC) and the temperature Tb of the battery 50. The output limit Wout of the battery 50 is set with a certain margin to prevent the battery 50 from degrading.

[0014] In the hybrid vehicle 20 of this embodiment, the vehicle operates in a hybrid driving mode (HV driving mode) in which the engine 22 is operated, or in an electric driving mode (EV driving mode) in which the engine 22 is stopped.

[0015] In HV driving mode, driving control is basically performed as follows: The HVECU70 first sets the required torque Td* (to be output to the drive shaft 36) based on the accelerator opening Acc and vehicle speed V. Next, it calculates the driving required power Pd* requested by the driver by multiplying the set required torque Td* by the rotational speed Nd of the drive shaft 36. Here, the rotational speed Nd of the drive shaft 36 can be the rotational speed Nm2 of the motor MG2 or the rotational speed obtained by multiplying the vehicle speed V by a conversion factor. Then, it sets the engine required power Pe* required for the vehicle by subtracting the battery 50 charge / discharge required power Pb* (a positive value when the battery 50 is discharging) from the calculated driving required power Pd*. Next, the target rotational speed Ne* and target torque Te* of the engine 22, and the torque commands Tm1* and Tm2* of the motors MG1 and MG2 are set so that the engine required power Pe* is output from the engine 22 and the required torque Td* is output to the drive shaft 36 within the range of the battery 50's output limit Wout. The HVECU 70 controls the intake air volume, fuel injection, and ignition of the engine 22 so that the engine 22 is operated based on the target rotational speed Ne* and target torque Te*, and also controls the switching of the transistors of the inverters 41 and 42 so that the motors MG1 and MG2 are driven by the torque commands Tm1* and Tm2*. When driving in this HV driving mode, when the engine required power Pe* falls below the threshold Pref, it is determined that the condition for stopping the engine 22 has been met, and the engine 22 is stopped and the system switches to EV driving.

[0016] In EV driving mode, driving control is basically performed as follows: First, the HVECU70 sets the requested torque Td* using the same process as when driving in HV mode as described above. Next, it sets the torque command Tm1* of motor MG1 to a value of 0. Then, it sets the torque command Tm2* of motor MG2 so that the requested torque Td* is output to the drive shaft 36 within the output limit Wout of battery 50. As described above, the HVECU70 controls inverters 41 and 42.

[0017] Next, the operation of the hybrid vehicle 20 equipped with the control device of the embodiment configured in this way, particularly its operation when driving on a circuit, will be described. Figure 2 is a flowchart of an example of a processing routine executed by the HVECU. This routine is repeatedly executed at predetermined intervals (for example, every few milliseconds) when a navigation system (not shown) detects that the current position of the hybrid vehicle 20 is within the circuit.

[0018] When this routine is executed, the CPU of the HVECU70 receives the accelerator opening degree Acc from the accelerator pedal position sensor 84, the vehicle speed V from the vehicle speed sensor 88, the charge level SOC, and the previous opening degree Accpre (S100). The previous opening degree Accpre is the accelerator opening degree Acc from the accelerator pedal position sensor 84 that was input when this routine was executed last time. When this routine is executed for the first time after the ignition switch 80 is turned on, the previous opening degree Accpre is set to its initial value of 0.

[0019] Next, the CPU of the HVECU70 determines whether the accelerator opening Acc is greater than or equal to a predetermined opening Accref (S110). The predetermined opening Accref is a threshold used to determine whether the driver's drive request is large, and is set to, for example, 80%, 85%, or 90%. If the accelerator opening Acc is less than the predetermined opening Accref, the CPU determines that the driver's drive request is not large, sets the unrestricted flag F to 0 (S170), and terminates this routine. The unrestricted flag F is a flag that indicates whether or not the torque output to the drive shaft 36 is limited within the range of the battery 50's output limit Wout. When the unrestricted flag F is set to 0, the HVECU70 CPU controls the engine 22 and motors MG1 and MG2 by setting the target rotational speed Ne* and target torque Te* of the engine 22, and the torque commands Tm1* and Tm2* of the motors MG1 and MG2, respectively, so that the requested torque Td* is output to the drive shaft 36 within the output limit Wout of the battery 50 in HV driving mode. In EV driving mode, the CPU controls the motor MG2 by setting the torque command Tm2* of the motor MG2 so that the requested torque Td* is output to the drive shaft 36 within the output limit Wout of the battery 50. This control prevents the battery 50 from being discharged with power exceeding the output limit Wout. This suppresses the deterioration of the battery 50 and electrical components such as motors MG1 and MG2, inverters 41 and 42, which deteriorate due to excessive power output from the battery 50, thereby protecting these components.

[0020] In S110, when the accelerator opening Acc is greater than or equal to a predetermined opening Accref, it is determined that the driver's driving demand is high, and subsequently, it is determined whether the charge level SOC is greater than or equal to a predetermined rate SOCref (S120) and whether the vehicle speed V is greater than or equal to a predetermined vehicle speed Vref (S130) (determining whether predetermined conditions are met). The predetermined rate SOCref and predetermined vehicle speed Vref are threshold values ​​for the charge level SOC and vehicle speed V used to determine whether to limit the torque output to the drive shaft 36 within the output limit Wout of the battery 50. The predetermined rate SOCref is set to, for example, 10%, 15%, 20%, etc. The predetermined vehicle speed Vref is set to, for example, 145km / h, 150km / h, 155km / h, etc. When the charge level SOC is equal to or greater than a predetermined SOCref and the vehicle speed V is less than a predetermined vehicle speed Vref, the CPU of the HVECU70 determines that the charge level of the battery 50 is sufficient and that even if power exceeding the output limit Wout is output from the battery 50, the impact on each component will be small, and sets the unrestricted flag F to a value of 1 (S180), and terminates this routine. When the unrestricted flag F is valued at 1, the CPU of the HVECU70 controls the engine 22 and motors MG1 and MG2 by setting the target rotational speed Ne* and target torque Te* of the engine 22, and the torque commands Tm1* and Tm2* of the motors MG1 and MG2, respectively, so that the requested torque Td* is output to the drive shaft 36 in HV driving mode. In EV driving mode, it controls the motor MG2 by setting the torque command Tm2* of the motor MG2 so that the requested torque Td* is output to the drive shaft 36. This control allows the vehicle to run while outputting the required torque Td* to the drive shaft 36 without being limited by the discharge from the battery 50 due to the output limit Wout, enabling the hybrid vehicle 20 to run with a more appropriate torque that meets the user's requirements.

[0021] When the state of charge SOC of the battery 50 is less than a predetermined ratio SOCref in S120, or when the vehicle speed V is greater than or equal to a predetermined vehicle speed Vref in S130, or when the state of charge of the battery 50 is greater than or equal to the predetermined ratio SOCref and the vehicle speed V is less than the predetermined vehicle speed Vref, it is determined that the amount of charge in the battery 50 is not sufficient, or that outputting power exceeding the output limit Wout from the battery 50 may have an adverse effect on not only the battery 50 but also each component, and it is determined whether the vehicle is traveling on a straight road (S140 to S160). The details of the determination of whether the vehicle is traveling on a straight road are as follows. First, the accelerator change amount ΔAcc is calculated by subtracting the previous opening Accpre from the accelerator opening Acc input in S100 (S140). Then, it is determined whether the accelerator change amount ΔAcc is less than or equal to a predetermined change amount dAccref (S150). The predetermined change amount dAccref is a threshold value for determining whether the change amount of the accelerator opening Acc is small. When the hybrid vehicle 20 is traveling on a straight road (straight) of the circuit, it is considered that the change in the operation amount of the accelerator pedal 83 is smaller than when traveling on a corner (corner). Therefore, S150 is a process for determining whether the traveling road is a straight road. When the accelerator change amount ΔAcc exceeds the predetermined change amount dAccref, it is determined that the vehicle is not traveling on a straight road, the non-restriction flag F is set to the value 0 (S170), and this routine is terminated. In this case, as described above, component protection can be achieved.

[0022] In S150, when the accelerator change amount ΔAcc is less than or equal to a predetermined change amount dAccref, it is determined that the hybrid vehicle 20 is traveling on a straight section of the circuit, and it is determined whether the elapsed time tac since the accelerator change amount ΔAcc became less than or equal to a predetermined change amount dAccref is greater than or equal to a predetermined time tacref (S160). The predetermined time tacref is a threshold for determining whether the state in which the accelerator change amount ΔAcc is less than or equal to a predetermined change amount dAccref, i.e., whether the straight section continues for a certain period of time, and is set to, for example, several tens of milliseconds. If the elapsed time tac is less than the predetermined time tacref, the unrestricted flag F is set to value 0 (S170), and this routine is terminated. In this case, as described above, parts can be protected. If the elapsed time tac is greater than or equal to the predetermined time tacref, it is determined that the vehicle is traveling on a straight section that continues for a certain period of time, and the unrestricted flag F is set to value 1 (S180), and this routine is terminated. In this case, as described above, the hybrid vehicle 20 can be driven with a more appropriate torque that meets the user's requirements. Figure 3 is an explanatory diagram illustrating the relationship between the charge level, vehicle speed, and the presence or absence of output limiting. When the charge level (SOC) is less than a predetermined SOCref, or when the vehicle speed V is greater than or equal to a predetermined vehicle speed Vref, the torque output to the drive shaft 36 is limited by the output limiting Wout at corners and short straight roads. However, on straight roads that continue for a certain period, the required torque Td* is output to the drive shaft 36 without being limited by the output limiting Wout. This allows the hybrid vehicle 20 to be driven with a more appropriate torque that meets the user's requirements.

[0023] In a hybrid vehicle 20 equipped with the control device of the embodiment described above, it is determined whether the hybrid vehicle 20 is traveling on a straight road based on the accelerator change amount ΔAcc. When it is determined that the hybrid vehicle 20 is continuously traveling on a straight road, the torque output to the drive shaft 36 is not limited by the output limit Wout, even if the charge storage ratio SOC is less than a predetermined ratio SOCref or the vehicle speed V is equal to or greater than a predetermined vehicle speed Vref. Therefore, the hybrid vehicle 20 can be driven with a more appropriate torque that meets the user's requirements.

[0024] In the above-described embodiment, the non-restriction flag F may be set to a value of 1 when the accelerator change amount ΔAcc is less than or equal to a predetermined change amount dAccref without considering the elapsed time tac.

[0025] In the above-described embodiment, the processing routine of FIG. 2 may be executed when a sports mode switch for instructing a sports driving mode in which the required torque Td* at the same accelerator opening Acc is set large is turned on.

[0026] In the above-described embodiment, when the non-restriction flag F is set to a value of 1, the output limit Wout of the battery 50 may be set larger than a value set based on the state of charge SOC or the temperature Tb of the battery 50 to relax the limitation of the required torque Td*.

[0027] In the above-described embodiment, the hybrid vehicle 20 may be an electric vehicle that travels on power from a motor without including an engine.

[0028] As described above, the embodiments for implementing the present disclosure have been described using the embodiments. However, the present disclosure is not limited to such embodiments, and it is needless to say that the present disclosure can be implemented in various forms without departing from the gist of the present disclosure.

Industrial Applicability

[0029] The present disclosure can be used in the manufacturing industry of control devices for electric vehicles and the like.

Description of Reference Numerals

[0030] 20 Electric vehicle, 70 Hybrid electronic control unit (HVECU70).

Claims

[Claim 1] A control device for an electric vehicle equipped with a motor for driving, which limits the torque output from the motor when predetermined conditions are met, Based on the change in accelerator opening, it is determined whether the electric vehicle is traveling on a straight road. When it is determined that the electric vehicle is traveling on a straight road, even if the predetermined conditions are met, the torque limit from the motor is relaxed compared to when it is determined that the electric vehicle is not traveling on a straight road. Control system for electric vehicles.

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