Drive control device for electric vehicle

Abstract

To provide a drive control device for an electric vehicle capable of improving straight advancing property of the vehicle regardless of variation of characteristics of a motor and an inverter in the electric vehicle for independently controlling driving current respectively supplied to a pair of motors for independently driving right and left driving wheels respectively by using a pair of inverters.SOLUTION: According to an electronic control device (drive control device) 100 of an electric vehicle 10, a difference Δ IMG of drive current respectively supplied from a pair of a first inverter 30 and a second inverter 32 to a left and right pair of a first electric motor MG1 and a second electric motor MG2 is detected by a drive current difference sensor 58. As a result, command drive currents (signals) SImg1 and SImg2 can be adjusted so as to eliminate an output torque difference between the left and right pair of the first electric motor MG1 and the second electric motor MG2, which is caused by the difference Δ IMG of the drive current, whereby straight advancing property of the electric vehicle 10 can be improved.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a drive control device for an electric vehicle having, as drive sources, a pair of electric motors that independently drive left and right drive wheels. [Background technology]

[0002] An electric vehicle has been proposed that has a pair of electric motors that independently drive left and right drive wheels, and that uses a pair of inverters to independently control the drive currents supplied to the pair of electric motors. For example, the electric vehicle described in Patent Document 1 is such an example.

[0003] In such electric vehicles, a differential gear device is not used between the left and right drive wheels, which simplifies the power transmission mechanism and makes it possible to stabilize the behavior of the electric vehicle by applying a torque difference between the left and right drive wheels when cornering, for example. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-220448 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the pair of electric motors and the pair of inverters that respectively control the drive currents supplied thereto have variations in characteristics initially, over time, and over temperature. Even if the command drive currents for the left and right electric motors are the same, a torque difference may occur between the left and right drive wheels, causing a problem of reduced vehicle driving stability, such as the vehicle's ability to travel in a straight line.

[0006] The present invention has been made against the background of the above circumstances, and an object of the present invention is to provide a drive control device for an electric vehicle in which the drive currents supplied to a pair of electric motors that independently drive the left and right drive wheels are controlled independently using a pair of inverters, and which can improve the running stability of the vehicle regardless of variations in the characteristics of the electric motors and inverters. [Means for solving the problem]

[0007] The gist of the present invention is (a) a drive control device for an electric vehicle having a pair of electric motors that independently drive left and right drive wheels, and a pair of inverters that independently control the drive currents supplied to the pair of electric motors in accordance with command drive currents, and (b) a drive current difference sensor that detects the difference between the drive currents supplied from the pair of inverters to the pair of electric motors. Effect of the Invention

[0008] According to the drive control device for an electric vehicle of the present invention, a drive current difference sensor detects the difference between the drive currents supplied from the pair of inverters to the pair of left and right electric motors, respectively, and thus it is possible to adjust the command drive current for the inverters so as to eliminate the output torque difference between the pair of left and right electric motors based on the drive current difference, thereby improving the running stability of the electric vehicle.

[0009] Preferably, the vehicle includes an electric motor control unit that calculates a required torque for the vehicle based on the accelerator operation amount and vehicle speed from a pre-stored relationship, and outputs the command drive current to realize the required torque, and the electric motor control unit adjusts the command drive current so as to eliminate the output torque difference between the pair of left and right electric motors.

[0010] Preferably, the vehicle further comprises a pair of drive current sensors for detecting drive currents supplied to the pair of electric motors, respectively, and the electric motor control unit calibrates the relationship between the drive currents detected by the pair of drive current sensors and the command drive current for the inverter to the same level, and also momentarily corrects for variations due to the temperatures of the electric motors, inverter, etc. This enables targeted vehicle control by operating the steering wheel. [Brief description of the drawings]

[0011] [Figure 1] 1 is a diagram illustrating a schematic configuration of an electric vehicle to which the present invention is applied, and is also a diagram illustrating main parts of control functions and a control system in the electric vehicle. [Diagram 2] 2 is a diagram illustrating a drive current difference sensor and a drive current sensor provided between a high-voltage battery and an inverter that controls drive currents supplied to a pair of left and right electric motors provided in the electric vehicle of FIG. 1. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. EXAMPLES

[0013] 1, the electric vehicle 10 includes a first driving device 12l, a second driving device 12r, a pair of left and right wheels (first driving wheel 14l and second driving wheel 14r), a case 16 attached to the vehicle body, and a pair of left and right wheels (not shown). The first driving device 12l is the driving device on the left side as viewed from the front of the electric vehicle 10, i.e., on the left side in the vehicle width direction, and the second driving device 12r is the driving device on the right side in the vehicle width direction. The first driving wheel 14l is the driving wheel on the left side in the vehicle width direction, and the second driving wheel 14r is the driving wheel on the right side in the vehicle width direction.

[0014] The first driving device 12l includes a first electric motor MG1 and a first power transmission device 18l. The second driving device 12r includes a second electric motor MG2 and a second power transmission device 18r. The first driving device 12l and the second driving device 12r are basically configured symmetrically. That is, the first electric motor MG1 and the second electric motor MG2, and the first power transmission device 18l and the second power transmission device 18r are basically configured symmetrically.

[0015] The first electric motor MG1 and the second electric motor MG2 are, for example, three-phase AC rotating electric machines, so-called motor generators. The first electric motor MG1 is connected to a high-voltage battery 34 via a first inverter 30 provided in the vehicle 10. The second electric motor MG2 is connected to the high-voltage battery 34 via a second inverter 32 provided in the vehicle 10. The high-voltage battery 34 is an electricity storage device that supplies and receives electric power to the first electric motor MG1 and the second electric motor MG2. The pair of left and right first electric motors MG1 and MG2 are provided in a case 16 and function as a power source for traveling.

[0016] The first inverter 30 and the second inverter 32 control the drive current supplied to the first electric motor MG1 and the second electric motor MG2, or the regenerative current output from the first electric motor MG1 and the second electric motor MG2, in accordance with a command drive current from the electronic control device 100 described later. The first inverter 30 and the second inverter 32 are controlled by the command drive current from the electronic control device 100, whereby the first MG torque Tmg1 which is the output torque of the first electric motor MG1 and the second MG torque Tmg2 which is the output torque of the second electric motor MG2 are controlled, respectively.

[0017] The first power transmission device 18l and the second power transmission device 18r include a first counter gear 20l and a second counter gear 20r which are a pair of parallel shaft helical gears, and a first hypoid gear 22l and a second hypoid gear 22r which are a pair of bevel gears, in the case 16. The first power transmission device 18l and the second power transmission device 18r also include a pair of left and right first drive shafts 24l and second drive shafts 24r.

[0018] The first counter gear 20l, which is one of the first counter gear 20l and the second counter gear 20r, is integrally connected to the rotor shaft of the first electric motor MG1. The second counter gear 20r, which is the other of the first counter gear 20l and the second counter gear 20r, is integrally connected to the rotor shaft of the second electric motor MG2. The first hypoid gear 22l, which is one of the first hypoid gear 22l and the second hypoid gear 22r, is integrally connected to the first drive shaft 24l. The second hypoid gear 22r, which is the other of the first hypoid gear 22l and the second hypoid gear 22r, is integrally connected to the second drive shaft 24r. The first power transmission device 18l transmits the power of the first electric motor MG1 to the first driving wheel 14l via the first counter gear 20l, the first hypoid gear 22l, the first drive shaft 24l, etc. The second power transmission device 18r transmits the power of the second electric motor MG2 to the second driving wheels 14r via the second counter gear 20r, the second hypoid gear 22r, the second drive shaft 24r, etc. The first counter gear 20l and the second counter gear 20r and the first hypoid gear 22l and the second hypoid gear 22r function as a reduction gear. The first driving wheels 14l and the second driving wheels 14r may be front wheels or rear wheels.

[0019] The electric vehicle 10 includes an electronic control device 100 that functions as a control device for the electric vehicle 10 related to control of the electric motor MG etc. The electronic control device 100 includes a so-called microcomputer.

[0020] The electronic control device 100 is supplied with various signals (e.g., the first drive current Img1, the second drive current Img2, the drive current difference ΔImg, the vehicle speed sensor 60, the MG1 rotational speed sensor 62, the MG2 rotational speed sensor 64, the accelerator opening sensor 66, the brake pedal sensor 68, the steering angle sensor 70, etc.) based on detection values ​​by various sensors provided in the electric vehicle 10 (e.g., a first drive current sensor 54 that detects a first drive current Img1 of the first electric motor MG1, a second drive current sensor 56 that detects a second drive current Img2 of the second electric motor MG2, a drive current difference sensor 58 that detects a drive current difference ΔImg which is the difference between the first drive current Img1 and the second drive current Img2, a vehicle speed sensor 60, an MG1 rotational speed sensor 62, an MG2 rotational speed sensor 64, an accelerator opening sensor 66, a brake pedal sensor 68, a steering angle sensor 70, etc.). The electronic control device 100 outputs various command signals (eg, command drive currents (signals) SImg1 and SImg2, etc.) to each device (eg, the first inverter 30, the second inverter 32, etc.) provided in the vehicle 10.

[0021] 2 shows the first drive current sensor 54, the second drive current sensor 56, and the drive current difference sensor 58 arranged between the high-voltage battery 34 and the first inverter 30 and the second inverter 32. The positive (+) line 72 of the first inverter 30 and the positive (+) line 74 of the second inverter 32 are connected to the positive (+) terminal of the high-voltage battery 34 via connection lines 76 and 78, respectively, and the negative (-) line 80 of the first inverter 30 and the negative (-) line 82 of the second inverter 32 are connected to the negative (-) terminal of the high-voltage battery 34 via connection lines 84 and 86, respectively. The first drive current sensor 54 is provided on the connection line 76, the second drive current sensor 56 is provided on the connection line 78, and the drive current difference sensor 58 is provided on the connection lines 76 and 78. The first drive current sensor 54, the second drive current sensor 56, and the drive current difference sensor 58 are each made of a material with high magnetic permeability such as ferrite, and are configured with an annular body through which the connection wires 76 and / or 78 pass, and a Hall element that constitutes a part of the circumferential direction of the annular body. The connection wires 76 and 78 pass through the annular body that constitutes the drive current difference sensor 58 so that currents flow in opposite directions.

[0022] The first inverter 30 includes a three-phase bridge circuit between the positive line 72 and the negative line 80, which is made up of three switching elements 88u, 88v, 88w constituting an upper arm and three switching elements 90u, 90v, 90w constituting a lower arm, and converts the DC output from the high-voltage battery 34 into three-phase AC, and supplies the drive current (AC) corresponding to a command drive current (signal) SImg1 to the first electric motor MG1. Similarly, the second inverter 32 includes a three-phase bridge circuit between the positive line 74 and the negative line 82, which is made up of three switching elements 92u, 92v, 92w constituting an upper arm and three switching elements 94u, 94v, 94w constituting a lower arm, and converts the DC output from the high-voltage battery 34 into three-phase AC, and supplies the drive current (AC) corresponding to a command drive current (signal) SImg2 to the second electric motor MG2.

[0023] The electronic control device 100 functionally includes an electric motor control unit 102 to realize various controls in the electric vehicle 10. The electric motor control unit 102 functions as a drive control device that calculates a required drive amount for the electric vehicle 10 by applying an accelerator opening θacc and a vehicle speed V to a required drive amount map 104, for example. The required drive amount is, for example, a drive torque Trdem [Nm] required for the electric vehicle 10, that is, a total required drive torque Trdem [Nm] for the first drive device 12l and the second drive device 12r. The electric motor control unit 102 outputs command drive currents (signals) SImg1 and SImg2 to the first inverter 30 and the second inverter 32, respectively, to supply a first command drive current Img1 and a second command drive current Img2 to the first electric motor MG1 and the second electric motor MG2, which cause the required drive torque Trdem (=Trdem1+Trdem2) to be output from the left and right first drive wheels 14l and second drive wheels 14r.

[0024] The required driving amount map 104 is a relationship for calculating the required driving amount that is obtained experimentally or by design and stored in advance, and is, for example, a required driving torque map. The electronic control unit 100 calculates the required driving torque Trdem based on the actual vehicle speed V and the accelerator opening θacc from the required driving torque map 104 stored in advance.

[0025] During straight-ahead driving, the motor control unit 102 detects, by the drive current difference sensor 58, a difference ΔI MG When the difference ΔImg in the drive current is detected, the difference in the output torque of the pair of left and right first electric motors MG1 and MG2 is eliminated, that is, the difference ΔI MGThe command drive currents (signals) SImg1 and SImg2 are adjusted so that the difference ΔImg between the drive currents Img1 and Img2 supplied from the pair of the first inverter 30 and the second inverter 32 to the pair of the left and right first electric motors MG1 and MG2 is zero, thereby improving the straight running performance of the electric vehicle 10. That is, in straight running with the steering angle Swa being "zero", when the drive current difference sensor 58 detects the difference ΔImg between the drive currents Img1 and Img2 supplied from the pair of the first inverter 30 and the second inverter 32 to the pair of the left and right first electric motors MG1 and MG2, respectively, the command drive currents (signals) SImg1 and SImg2 are corrected so as to eliminate the output torque difference between the first electric motor MG1 and the second electric motor MG2. For example, when the steering angle Swa is "zero" and the electric vehicle 10 has a tendency to turn right, at least one of a decrease correction of the command drive current (signal) SImg1 and an increase correction of the command drive current (signal) SImg2 is executed, the magnitude of which corresponds to the steering angle Swa that causes the electric vehicle 10 to run straight. As a result, the motor control unit 102 adjusts the command drive currents SImg1 and SImg2 so as to substantially eliminate the output torque difference between the left and right first electric motors MG1 and second electric motors MG2.

[0026] Furthermore, the motor control unit 102 calibrates (corrects) the relationship between the drive current Img1 of the first electric motor MG1 and the drive current Img2 of the second electric motor MG2 detected by the pair of the first drive current sensor 54 and the second drive current sensor 56, and the command drive currents SImg1 and SImg2, and also momentarily corrects variations due to the temperatures of the first electric motor MG1 and the second electric motor MG2, the first inverter 30, the second inverter 32, etc. This enables targeted and highly accurate vehicle control by operating the steering wheel (steering angle Swa).

[0027] During straight running when the steering angle Swa is zero, the motor control unit 102 calibrates the first drive current sensor 54 and the second drive current sensor 56 (the difference between the command drive current and the actual drive current is zero) from the first drive current Img1 detected by the first drive current sensor 54 and the second drive current Img2 detected by the second drive current sensor 56 and the first command drive current SImg1 and the second command drive current SImg2. During cornering, the motor control unit 102 calibrates the drive current difference sensor 58 from the drive current difference ΔImg detected by the drive current difference sensor 58 and the difference between the first drive current Img1 and the second drive current Img2 detected by the calibrated first drive current sensor 54 and the second drive current sensor 56, respectively.

[0028] As described above, according to the electronic control device (drive control device) 100 of the electric vehicle 10 of this embodiment, the drive current difference sensor 58 detects the difference ΔI MG This detects the difference in the drive current ΔI MG The command drive currents (signals) SImg1 and SImg2 can be adjusted so as to eliminate the output torque difference between the pair of left and right electric motors, the first electric motor MG1 and the second electric motor MG2, which occurs due to the above, and the driving stability, such as the straight-line driving ability, of the electric vehicle 10 can be improved.

[0029] Although the embodiment of the present invention has been described in detail above with reference to the drawings, the present invention can be applied to other embodiments.

[0030] For example, in the above embodiment, the first drive current sensor 54 and the second drive current sensor 56 are used, but they do not necessarily have to be provided.

[0031] In the above embodiment, the drive current difference sensor 58 is used to measure the difference ΔI between the drive currents supplied to the first motor MG1 and the second motor MG2. MG However, instead of that, the first drive current I of the first motor MG1 detected by the first drive current sensor 54MG 1, and the second drive current I of the second motor MG2 detected by the second drive current sensor 56. MG Difference from 2 ΔI MG A difference calculator may be used to calculate:

[0032] In the above-described embodiment, the first drive current sensor 54 is provided on the connection line 76, the second drive current sensor 56 is provided on the connection line 78, and the drive current difference sensor 58 is provided on the connection lines 76 and 78, but the first drive current sensor 54 may be provided on the connection line 84, the second drive current sensor 56 is provided on the connection line 86, and the drive current difference sensor 58 may be provided on the connection lines 84 and 86.

[0033] It should be noted that the above is merely one embodiment, and the present invention can be embodied in various modified and improved forms based on the knowledge of those skilled in the art. [Explanation of symbols]

[0034] 10: electric vehicle, 30: first inverter, 32: second inverter, 54: first drive current sensor, 56: second drive current sensor, 58: drive current difference sensor, 100: electronic control device (control device), 102: motor control unit, MG1: first motor, MG2: second motor

Claims

[Claim 1] A drive control device for an electric vehicle having a pair of electric motors that independently drive left and right drive wheels, and a pair of inverters that independently control drive currents supplied to the pair of electric motors in accordance with command drive currents, a drive current difference sensor for detecting a difference between drive currents supplied from the pair of inverters to the pair of electric motors, A vehicle control device comprising:

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