Controller of electric vehicle

Abstract

To provide a controller of an electric vehicle which can reduce the risk that load is deviated to either one of electric motor systems at front wheels and rear wheels to limit output thereof.SOLUTION: In a traveling state where a slip detection part 42 of a controller of an electric vehicle does not detect slip, a leveling control device 44 calculates and sets a front wheel request driving force Tff and a rear wheel request driving force Tfr based on a first electric motor margin value FMSI subtracting MG1 current load value Img1 during traveling from a first load resistance value Img1MX of an electric motor system MG1sys, a second electric motor margin value RMSI subtracting MG2 current load value Img2 during traveling from a second load resistance value Img2MX of an electric motor system MG2sys, and a request driving force Tf of the vehicle through an expression (1) and an expression (2) in which K1 and K2 are moduli: Tff=Tr×[K1×FMSI / (FMSI+RMSI)] ... (1); and Tfr=Tr×[K2×RMSI / (FMSI+RMSI)] ... (2).SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Electric vehicles equipped with an electric motor that drives main drive wheels or auxiliary drive wheels are known. The electric motor and its drive circuit (hereinafter referred to as the electric motor system) are provided with temperature protection. For example, if the temperature of the electric motor system exceeds a predetermined value due to heat generation caused by continuous high load, an output limit is imposed on the electric motor to ensure reliability and safety. Since the imposition of an output limit can impede driving, techniques have been disclosed for controlling the output in advance to avoid the output limit, i.e., to prevent the electric motor system from excessively increasing in temperature. For example, the output control described in Patent Document 1 is one such technique. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-220802 Summary of the Invention [Problem to be solved by the invention]

[0004] The technology described in Patent Document 1 is output control for an auxiliary electric motor that assists the main drive source, but such output control is also required in electric vehicles equipped with a first electric motor that drives the front wheels and a second electric motor that drives the rear wheels. In such electric vehicles, driving force is distributed between the front wheels and the rear wheels to improve drivability, but driving force distribution that prioritizes drivability can result in an uneven load on either the front or rear wheel electric motor system, posing a risk of output restriction.

[0005] The present invention has been made against the background of the above circumstances, and its purpose is to provide a control device for an electric vehicle that can reduce the risk of output restriction due to an uneven load on either the front or rear wheel electric motor system. [Means for solving the problem]

[0006] The gist of a first invention is a control device for an electric vehicle including (a) a first electric motor for driving front wheels and a second electric motor for driving rear wheels, (b) a slip detection unit for detecting slippage of the front wheels and the rear wheels, and a load leveling control unit for leveling the load on the first electric motor and the second electric motor, and (c) when the slip detection unit is not detecting slippage and the vehicle is in a running state, the load leveling control unit sets a maximum current that can be loaded on the first electric motor as a maximum value. a first motor margin value FMSI obtained by subtracting a current load value of the first motor while the vehicle is running from a first load tolerance value set as the maximum current that can be loaded to the second motor; a second motor margin value RMSI obtained by subtracting a current load value of the second motor while the vehicle is running from a second load tolerance value set as the maximum current that can be loaded to the second motor; and a vehicle required driving force Tf, according to the following equations (1) and (2): Tff=Tf×[K1×FMSI / (FMSI+RMSI)]···(1) Tfr=Tf×[K2×RMSI / (FMSI+RMSI)]···(2) However, K1 and K2 are coefficients [Effects of the Invention]

[0007] According to the first aspect of the present invention, when the slip detection unit is not detecting a slip and the vehicle is in a running state, the leveling control unit calculates and sets a front-wheel required driving force Tff to the front wheels and a rear-wheel required driving force Tfr to the rear wheels according to equations (1) and (2) using a first motor margin value FMSI obtained by subtracting a current load value of the first electric motor while the vehicle is running from a first load tolerance value set as a maximum current that can be loaded to the first electric motor, a second electric motor margin value RMSI obtained by subtracting a current load value of the second electric motor while the vehicle is running from a second load tolerance value set as a maximum current that can be loaded to the second electric motor, and a vehicle required driving force Tf. As a result, in a normal running state in which no slip is occurring and driving force distribution between the front and rear wheels to avoid slip is not required, a larger required driving force is distributed to the first electric motor or the second electric motor with a larger load margin value, thereby leveling the load and reducing the risk of the first electric motor or the second electric motor being subject to output limitation. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating a schematic configuration of a vehicle to which the present invention is applied, and is also a diagram illustrating main parts of control functions and control systems for various controls in the vehicle. [Figure 2] 4 is a flowchart illustrating a main part of the control operation of the electronic control device, and is a flowchart illustrating the control operation for leveling the load between the first electric motor and the second electric motor. [Figure 3] 1 and 2. FIG. 4 is a view corresponding to FIG. 1, showing another embodiment of a vehicle to which the present invention is applied. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. [Example]

[0010] FIG. 1 is a diagram illustrating the general configuration of a vehicle 10 to which the present invention is applied, and also illustrates the main parts of the control functions and control systems for various controls in the vehicle 10.

[0011] In FIG. 1, an electric vehicle (hereinafter referred to as vehicle) 10 includes a pair of front wheels 12 (12L, 12R), a pair of rear wheels 14 (14L, 14R), a battery 20, a front wheel drive unit 16 that drives the front wheels 12 via a front drive shaft 34, and a rear wheel drive unit 18 that drives the rear wheel 14R via a rear drive shaft 36.

[0012] The front wheel drive unit 16 includes an electric motor system MG1sys that uses an electric motor MG1 as a power source, a reduction mechanism 22, a front differential 24, etc. The driving force from the electric motor MG1 is transmitted to the front wheels 12 via the reduction mechanism 22 and the front differential 24.

[0013] The rear wheel drive unit 18 includes an electric motor system MG2sys powered by an electric motor MG2, a reduction gear mechanism 26, a rear differential 28, etc. The driving force from the electric motor MG2 is transmitted to the rear wheels 14 via the reduction gear mechanism 26 and the rear differential 28.

[0014] The electric motor system MG1sys includes an electric motor MG1 and an inverter 30. The electric motor MG1 is a so-called motor generator. The inverter 30 performs control such as converting DC power from a battery 20 into AC power and supplying it to the electric motor MG1, and converting AC power generated by the electric motor MG1 into DC power and supplying it to the battery 20. An MG1 control command signal Smg1 for controlling the driving force of the electric motor MG1 is output to the inverter 30 from an electronic control device 40 (described later). The DC current from the battery 20 to the inverter 30 is detected as an MG1 current load value Img1 [A] by a motor current sensor 86 (described later). Furthermore, a maximum value of the MG1 current load value Img1, i.e., a first load tolerance value Img1MX [A], which is the maximum value of the current that can be loaded onto the electric motor MG1, is set in the electric motor system MG1sys. The first load tolerance value Img1MX is suitably set by design or experimentation depending on the performance and characteristics (allowable current, heat resistance) of the electric motor MG1, the inverter 30, the connecting wiring from the battery 20 to the first electric motor, and the connecting components. The electric motor system MG1sys corresponds to the "first electric motor" in this invention.

[0015] The motor system MG2sys includes a motor MG2 and an inverter 32. The motor MG2 and the inverter 32 have the same functions as the motor MG1 and the inverter 30, respectively, and therefore a detailed description thereof will be omitted. An MG2 control command signal Smg2 for controlling the driving force of the motor MG2 is output to the inverter 32 from an electronic control device 40 (described later). The DC current from the battery 20 to the inverter 32 is detected as an MG2 current load value Img2 [A] by a motor current sensor 86 (described later). Similarly to the motor system MG1sys, the motor system MG2sys is set with a second load tolerance value Img2MX [A]. The second load tolerance value Img2MX is suitably set by design or experimentation depending on the performance and characteristics (allowable current, heat resistance) of the motor MG2, the inverter 32, the connecting wiring from the battery 20 to the second motor, and the connected components. The motor system MG2sys corresponds to the "second motor" in this invention.

[0016] The electronic control device 40 is configured to include, for example, a so-called microcomputer. Various signals (such as vehicle speed V, accelerator opening θacc which is the amount of accelerator operation indicating the magnitude of the driver's acceleration operation, MG1 current load value Img1, MG2 current load value Img2, front wheel rotation speeds Nwfl, Nwfr which are the rotation speeds of the front wheels 12L, 12R, and rear wheel rotation speeds Nwrl, Nwrr which are the rotation speeds of the rear wheels 14L, 14R) based on detection values ​​by various sensors (such as a vehicle speed sensor 80, an accelerator opening sensor 82, a motor current sensor 86, and a wheel speed sensor 88) provided on the vehicle 10 are respectively supplied to the electronic control device 40.

[0017] The wheel speed sensor 88 includes a front wheel rotation speed sensor that detects front wheel rotation speeds Nwfl, Nwfr and outputs signals of the front wheel rotation speeds Nwfl, Nwfr, and a rear wheel rotation speed sensor that detects rear wheel rotation speeds Nwrl, Nwrr and outputs signals of the rear wheel rotation speeds Nwrl, Nwrr. The front wheel rotation speeds Nwfl, Nwfr and the rear wheel rotation speeds Nwrl, Nwrr each correspond to the wheel speed Nw.

[0018] The electronic control unit 40 calculates the driver's requested driving force Tf[N] for the vehicle 10 by applying the accelerator opening θacc and the vehicle speed V to a predetermined driving demand amount map, for example.

[0019] Conventionally, driving force distribution has been such that the aforementioned required driving force Tf is distributed to the front wheels 12 as a front wheel required driving force Tff and to the rear wheels 14 as a rear wheel required driving force Tfr in order to improve drivability. However, with driving force distribution that prioritizes drivability, the load is biased toward either the electric motor system MG1sys that drives the front wheels 12 or the electric motor system MG2sys that drives the rear wheels 14, and there is a risk that output will be limited due to temperature protection caused by temperature rise in the electric motor systems (MG1sys, MG2sys).

[0020] Therefore, the electronic control device 40 of this embodiment equalizes the loads on the electric motor systems MG1sys and MG2 through a control operation described later in Fig. 2, thereby reducing the risk of output restriction. Fig. 2 is a flowchart illustrating the control operation for equalizing the loads on the electric motor systems (MG1sys, MG2sys).

[0021] The electronic control device 40 functionally comprises a slip detection unit 42 that detects slip, and a load leveling control unit 44 that controls load leveling of the electric motor systems (MG1sys, MG2sys).

[0022] The control operation of the electronic control unit 40 will be described below with reference to the flowchart in Figure 2. First, in step (hereinafter, "step" will be omitted) S10, the slip detection unit 42 determines whether or not slip has been detected. Slip detection is performed in a suitable manner, for example, by comparing the wheel speeds Nw (Nwfl, Nwfr, Nwrl, Nwrr) of each wheel from the wheel speed sensors 88 with the vehicle speed V, or by detecting fluctuations in the wheel speeds Nw (Nwfl, Nwfr, Nwrl, Nwrr). If the determination in S10 is negative, the routine is terminated, and the electronic control unit 40 separately performs drive force distribution when slip is detected, i.e., drive force distribution between the front and rear wheels to avoid slip.

[0023] If the determination in S10 is affirmative, in S20 corresponding to the leveling control unit 44, the motor current sensor 86 detects the current load values ​​(MG1 current load value Img1, MG2 current load value Img2) during running.

[0024] Next, in S30 corresponding to the power leveling control unit 44, a first motor margin value FMSI and a second motor margin value RMSI are calculated according to the following equations (3) and (4). FMSI = 1st load tolerance value Img1MX-MG1 current load value Img1 (3) RMSI = Second load tolerance value Img2MX-MG2 current load value Img2 (4)

[0025] Next, in S40 corresponding to the leveling control unit 44, the front wheel required driving force Tff and the rear wheel required driving force Tfr are calculated according to the following equations (1) and (2). Tff = required driving force Tf × [K1 × FMSI / (FMSI + RMSI)] (1) Tfr = required driving force Tf × [K2 × RMSI / (FMSI + RMSI)] (2) Here, K1 and K2 are arbitrary coefficients.

[0026] Next, in S50 corresponding to the leveling control unit 44, an MG1 control command signal Smg1 is output to the inverter 30 so as to realize the front wheel required driving force Tff calculated in S40. Similarly, an MG2 control command signal Smg2 is output to the inverter 32 so as to realize the rear wheel required driving force Tfr, and this routine is then terminated.

[0027] An example of calculating the front wheel required driving force Tff and rear wheel required driving force Tfr is shown below. When the first load tolerance value Img1MX = 135 [A], the second load tolerance value Img2MX = 150 [A], the MG1 current load value Img1 = 105 [A], the MG2 current load value Img2 = 100 [A], the required driving force Tf = 12000 [N], K1 = 1, and K2 = 1, FMSI=135-105=30, RMSI=150-100=50, Required front wheel driving force Tff = 12000 x [1 x 30 / (30 + 50)] = 4500 [N] Required rear wheel driving force Tfr = 12000 x [1 x 50 / (30 + 50)] = 7500 [N] A larger requested driving force is allocated to the motor system with a larger load margin, thereby leveling the loads on the electric motor system MG1sys and the electric motor system MG2sys.

[0028] As described above, according to the electronic control device 40 of this embodiment, when the slip detection unit 42 is not detecting a slip during driving, the leveling control unit 44 calculates and sets the front wheel required driving force Tff to the front wheels 12 and the rear wheel required driving force Tfr to the rear wheels 14 according to equations (1) and (2) from the first motor margin value FMSI obtained by subtracting the MG1 current load value Img1 during driving from the first load tolerance value Img1MX set as the maximum current that can be loaded onto the motor system MG1sys, the second motor margin value RMSI obtained by subtracting the MG2 current load value Img2 during driving from the second load tolerance value Img2MX set as the maximum current that can be loaded onto the motor system MG2sys, and the vehicle's required driving force Tf. As a result, under normal driving conditions when no slippage is occurring and there is no need to distribute driving force between the front and rear wheels to avoid slippage, the load is leveled out by distributing the greater required driving force to the electric motor system MG1sys or the electric motor system MG2sys, which has the greater load margin, thereby reducing the risk of output restrictions being imposed on the electric motor system MG1sys or the electric motor system MG2sys.

[0029] Next, another embodiment of the present invention will be described. In the following description, parts common to the embodiments will be given the same reference numerals and the description thereof will be omitted. [Example]

[0030] 3, vehicle 50 is an example in which front wheel drive unit 16 of vehicle 10 of the first embodiment is changed to a front wheel drive unit 60 of a hybrid vehicle powered by an engine 62, electric motor MG1, electric motor MGG, etc. Front wheel drive unit 60 includes engine 62 and transaxle 64.

[0031] The output (driving force) of the engine 62 is controlled by an engine control device 66 that includes a throttle actuator, a fuel injection device, an ignition device, etc., which are provided in the vehicle 10. An engine control command signal Se for controlling the engine 62 is output from the electronic control device 40 to the engine control device 66.

[0032] The trunk axle 64 is a unit that comprises a known hybrid vehicle, and includes the power split mechanism 54, the electric motor MGG, the inverter 56, the electric motor system MG1sys (electric motor MG1, inverter 30), the front differential 24, and a group of connecting gears. The electric motor MGG and the inverter 56 have the same functions as the electric motor MG1 and the inverter 30, respectively, and therefore their description will be omitted. An MGG control command signal SmgG that controls the driving force of the electric motor MGG is output from the electronic control device 40 to the inverter 56. The driving forces from the engine 62, the electric motor MG1, and the electric motor MGG are transmitted to the front wheels 12 via the front differential 24.

[0033] The present invention can be applied to such a vehicle 50 when the engine 62 is stopped and the vehicle runs only on the electric motors, i.e., when the vehicle runs only on the electric motor MG1 (electric motor system MG1sys) and the electric motor MG2 (electric motor system MG2sys). In this case, the control operation of the flowchart in Fig. 2 is commonly applied to this embodiment as well, and the same effects as those of the first embodiment can be obtained.

[0034] The above describes in detail an embodiment of the present invention based on the drawings, but what has been described above is merely one embodiment, and the present invention can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art. [Explanation of symbols]

[0035] 10, 50: Vehicle (electric vehicle) 12 (12L, 12R): Front wheels 14 (14L, 14R): Rear wheels 40: Electronic control unit (control unit) 42: Slip detection unit 44: Leveling control unit FMSI: First motor margin value Img1MX: First load tolerance value Img2MX: Second load tolerance value Img1: Current load value Img2: Current load value MG1sys: Motor system (first motor) MG2sys: Motor system (second motor) RMSI: Second motor margin value Tf: Required driving force Tff: Front wheel required driving force Tfr: Rear wheel required driving force

Claims

[Claim 1] A control device for an electric vehicle including a first electric motor that drives front wheels and a second electric motor that drives rear wheels, a slip detection unit that detects slip of the front wheels and the rear wheels, and a load leveling control unit that performs load leveling control of the first electric motor and the second electric motor, When the slip detection unit is not detecting a slip and the vehicle is in a running state, the leveling control unit calculates and sets a front wheel required driving force Tff to the front wheels and a rear wheel required driving force Tfr to the rear wheels from a first motor margin value FMSI obtained by subtracting a current load value of the first motor while the vehicle is running from a first load tolerance value set as the maximum current that can be loaded to the first motor, a second motor margin value RMSI obtained by subtracting a current load value of the second motor while the vehicle is running from a second load tolerance value set as the maximum current that can be loaded to the second motor, and a vehicle required driving force Tf according to the following equations (1) and (2): Tff=Tf×[K1×FMSI / (FMSI+RMSI)]...(1) Tfr=Tf×[K2×RMSI / (FMSI+RMSI)]...(2) where K1 and K2 are coefficients A control device for an electric vehicle.

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