Electric vehicle control device

Abstract

To suppress power consumption performance from being deteriorated a result of drive power distribution being disturbed by a drive power correction during a travel in a power consumption priority mode where a front-rear wheel drive power distribution is controlled, in an electric vehicle whose front and rear wheels are both driven by an electric motor.SOLUTION: (a) Proposed is an electric vehicle whose front and rear wheels are both driven by an electric motor. The electric vehicle has a control apparatus including a drive power correction part for correcting at least either of front-wheel drive power and rear-wheel drive power. (b) Further, the control apparatus, including a power consumption-priority travel control part for controlling travel in a range mode (a power consumption-priority mode that controls front-rear wheel drive power distribution so as to suppress power consumption, (c) inhibits the drive power correction part from correcting while traveling in the range mode, specifically correction through sprung dumping control and correction through line trace control.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a control device for an electric vehicle in which both the front and rear wheels are driven by electric motors, and more particularly to a control device for an electric vehicle having an electricity efficiency priority mode in which power consumption is reduced. [Background technology]

[0002] Various driving force correction units have been proposed for correcting the driving force of a vehicle. Patent Document 1 describes a technology that stabilizes vehicle behavior during cornering by setting a target value for the yaw rate at the beginning of a turn when the steering angle begins to change, calculating a yaw moment for controlling the yaw rate to the target value, calculating a correction amount for a torque command value for a power source corresponding to the yaw moment, i.e., a correction amount for the driving force, and controlling the power source to achieve the torque command value corrected by the correction amount. Patent Document 2 describes a technology that calculates a damping torque for suppressing sprung vibration and adds the damping torque to the torque of an electric motor used as a power source. In this case, the damping torque corresponds to the correction amount for the driving force. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-133811 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-241818 [Patent Document 3] Patent Publication No. 2021-88247 Summary of the Invention [Problem to be solved by the invention]

[0004] Patent Document 3 describes an electric vehicle in which both the front and rear wheels are driven by electric motors (see Figures 1 and 5 of the document), and it is conceivable to apply the driving force correction techniques described in Patent Documents 1, 2, etc. to such an electric vehicle. In that case, although it is not yet publicly known, if driving force correction by the driving force correction technique intervenes when driving in an electricity efficiency priority mode that controls the distribution of driving force between the front and rear wheels to suppress power consumption and extend driving distance, the distribution of driving force between the front and rear wheels will change, compromising the electricity efficiency that suppresses power consumption and potentially shortening the driving distance.

[0005] The present invention has been made against the background of the above circumstances, and its purpose is to prevent a loss of electricity efficiency performance due to a disruption in driving force distribution caused by driving force correction when driving in an electricity efficiency priority mode in which the driving force distribution between the front and rear wheels is controlled in an electric vehicle in which both the front and rear wheels are driven by electric motors. [Means for solving the problem]

[0006] In order to achieve this object, the first invention is a front wheel a front wheel drive unit having a front electric motor for driving the rear wheel A rear wheel drive unit having a rear motor that drives the front and rear wheels, and a front and rear wheel independent drive type having a rear motor that drives the front and rear wheels, A control device for an electric vehicle includes a driving force correction unit that corrects at least one of front wheel driving force and rear wheel driving force, and (a) includes an electricity efficiency priority driving control unit that controls the distribution of driving force between the front and rear wheels so as to suppress power consumption, and (b) limits the correction by the driving force correction unit when driving in the electricity efficiency priority mode. (c) the power consumption priority mode is a mode in which the vehicle is driven by preferentially using one of the front wheel drive unit and the rear wheel drive unit, whichever is determined to have lower power consumption. It is characterized by:

[0007] In addition, the above Priority use can take various forms in which the driving force distribution rate (sharing ratio) of one of the front or rear wheel drive units is higher than usual, such as always driving using only one of the front or rear wheel drive units, basically driving using only one of the front or rear wheel drive units while additionally using the other drive unit, or using both front and rear wheel drive units while the driving force distribution rate (sharing ratio) of one drive unit is higher than usual.

[0008] No.2 The invention is 1 The control device for an electric vehicle of the present invention is characterized by comprising an opposite-sign torque limiting unit that limits a change in the positive torque command value when the torque command value that controls the output of the front wheel drive unit and the torque command value that controls the output of the rear wheel drive unit are of different positive and negative signs when the electric vehicle is accelerating. [Effects of the Invention]

[0009] In such an electric vehicle control device, when driving in an electricity consumption priority mode in which the distribution of driving force between the front and rear wheels is controlled to reduce power consumption, the correction by the driving force correction unit is limited. This prevents the intervention of the driving force correction unit from changing the distribution of driving force between the front and rear wheels, which would result in a loss of electricity consumption performance, and ensures an appropriate driving distance. In addition, in an electric vehicle with independent front and rear wheel drive that has separate front and rear wheel drive units, the power consumption priority mode allows the vehicle to run using a predetermined drive unit that consumes less power, either the front wheel drive unit or the rear wheel drive unit, thereby appropriately reducing power consumption and extending the driving distance.

[0011] No. 2 In the present invention, when the torque command value for the front-wheel drive unit and the torque command value for the rear-wheel drive unit differ in sign during acceleration of an electric vehicle, the change in the positive torque command value is limited, thereby suppressing deterioration in drivability and vehicle stability due to the difference in sign between the front and rear wheel drive forces. However, if such a torque limiting unit for wrong sign is provided, during re-acceleration in an electricity efficiency-prioritized mode that prioritizes the use of one drive unit, the torque command value for one drive unit becomes positive and the torque command value for the other drive unit becomes negative due to the intervention of the driving force correcting unit, and torque limiting is performed on one drive unit due to the difference in sign, which could restrict the acceleration of the electric vehicle and reduce drivability. In the present invention, correction by the driving force correcting unit is limited during driving in the electricity efficiency-prioritized mode, thereby suppressing the difference in sign between the torque command values ​​and suppressing deterioration in drivability due to the torque limiting associated with the difference in sign. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a diagram illustrating a schematic configuration of a drive system of an electric vehicle to which the present invention is applied, and also showing essential parts of control functions. [Figure 2]2 is a diagram illustrating the characteristics of a plurality of types of driving modes that can be switched by a driving mode switching control unit that the electronic control device of FIG. 1 has functionally. [Figure 3] 3 is a diagram specifically explaining the difference between the range mode and the eco mode in FIG. 2 in comparison with the normal mode. FIG. [Figure 4] 2 is a flowchart illustrating a specific example of sprung vibration damping control by a sprung vibration damping control unit that is functionally provided in the electronic control device of FIG. 1. [Figure 5] 1. FIG. 4 is a diagram specifically explaining torque limitation by a wrong sign torque limiting unit functionally provided in the electronic control device of FIG. [Figure 6] 10 is an example of a time chart illustrating changes in the operating state of each unit when torque is limited by a torque limiting unit when a wrong sign occurs when the electric vehicle is re-accelerated. [Figure 7] 10 is a flowchart illustrating an operation for prohibiting sprung vibration damping control and line tracing control during running in a range mode. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention is applicable to a control device for a front-wheel-independent drive electric vehicle having separate front-wheel drive units and rear-wheel drive units, for example. However, it can also be applied to a drive force distribution electric vehicle having a single drive force source device with an electric motor and a drive force distribution device capable of controlling the drive force distribution to the front and rear wheels. The drive unit or drive force source device may have only an electric motor as a power source, or it can be a hybrid or plug-in hybrid device having another power source such as an engine (internal combustion engine) in addition to the electric motor. When only an electric motor is used as a power source, the vehicle may be a battery electric vehicle (BEV) equipped only with a power storage device such as a battery as a power source, or it may be equipped with a power generation device such as a generator or fuel cell rotated by the engine. The electric motor generates mechanical rotational force from electric power, but it may also have the function of a generator that generates electricity when rotated.

[0014] The driving force correction unit includes various controls for correcting at least one of the front wheel driving force and the rear wheel driving force, such as a behavior stabilization control unit that corrects at least one of the front wheel driving force and the rear wheel driving force to stabilize the behavior of the electric vehicle during driving, or a sprung mass vibration damping control unit that calculates a driving force vibration damping compensation value to suppress sprung mass vibration and corrects at least one of the front wheel driving force and the rear wheel driving force based on the driving force vibration damping compensation value. However, it is sufficient that at least one of the corrections by the driving force correction unit is limited when driving in the electricity efficiency priority mode. The limit on the correction by the driving force correction unit can be various, such as completely prohibiting the correction, reducing the correction amount by a certain percentage or a certain amount, or setting an upper limit on the correction amount. Note that the driving force may be replaced with driving torque or driving power.

[0015] The power consumption priority mode is a driving mode that controls the distribution of driving force between the front and rear wheels to reduce power consumption in order to extend the driving distance, and can also be expressed as eco mode, range mode, etc. In the power consumption priority mode, in addition to controlling the distribution of driving force between the front and rear wheels, various controls that can reduce power consumption may be used in combination, such as air conditioning restrictions, meter / display brightness restrictions, vehicle speed restrictions, driving force restrictions, and soft acceleration processing that smooths the change in driving force more than usual in response to acceleration requests.

[0016] The torque limiting unit for wrong sign limits the change in the positive torque command value when the torque command value for the front wheel drive unit and the torque command value for the rear wheel drive unit differ in sign due to differences in the smoothing process of the torque command value or correction by the driving force correcting unit when accelerating the electric vehicle, and for example, the upper limit rate (upper limit of the rate of change) of the torque command value is set to 0, but it is also possible to simply lower the upper limit rate to make the rate of increase and change (gradient) of the torque command value smaller. When such a torque limiting unit for wrong sign is provided, the present invention has the exceptional effect of suppressing sign mismatch by limiting the correction by the driving force correcting unit, and thereby suppressing a decrease in drivability due to torque limiting associated with the sign mismatch, but the present invention can also be applied to a control device for an electric vehicle that does not have a torque limiting unit for wrong sign. [Example]

[0017] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 1 is a diagram illustrating the schematic configuration of a drive system of an electric vehicle 10 to which the present invention is applied, and also shows the main parts of the control functions of an electronic control device 50. The electric vehicle 10 is equipped with a front-wheel drive unit 14 mounted on the front of the vehicle to drive and rotate left and right front wheels 12, and a rear-wheel drive unit 18 mounted on the rear of the vehicle to drive and rotate left and right rear wheels 16, which are separate and spaced apart from each other. The front-wheel drive unit 14 is equipped with only a front electric motor 22 as a power source, and is also equipped with a transaxle 24 that changes the speed of the rotation of the front electric motor 22 and transmits it to the left and right front wheels 12, and the front electric motor 22 is connected to a battery 30 via a front PCU (Power Control Unit) 28 that has an inverter and the like. The rear-wheel drive unit 18 is equipped with only a rear electric motor 32 as a power source, and a transaxle 34 that changes the speed of the rotation of the rear electric motor 32 and transmits it to the left and right rear wheels 16, and the rear electric motor 32 is connected to a battery 30 via a rear PCU 38 that has an inverter and the like. The front electric motor 22 and the rear electric motor 32 are both so-called motor generators that function as generators that generate electricity when rotated. The electric vehicle 10 is a front-rear wheel independent drive electric vehicle, a BEV (Battery Electric Vehicle) that is equipped with only a battery 30 as a power source.

[0018] The electric vehicle 10 is equipped with an electronic control unit 50 as a control device that executes various types of control, including torque control of the front wheel drive unit 14 and the rear wheel drive unit 18. The electronic control unit 50 is configured to include a so-called microcomputer equipped with, for example, a CPU, RAM, ROM, an input / output interface, etc. The CPU executes various types of control of the electric vehicle 10 by performing signal processing according to programs stored in advance in the ROM while utilizing the temporary storage function of the RAM.

[0019] The electronic control unit 50 receives various information required for control from various sensors provided on the electric vehicle 10. For example, from a front electric motor rotation speed sensor 70, a rear electric motor rotation speed sensor 72, an accelerator opening sensor 74, a steering angle sensor 76, a vehicle longitudinal acceleration sensor 78, a vehicle lateral acceleration sensor 80, a wheel speed sensor 82, an SOC sensor 84, a range selection device 86 such as a shift lever that can select a plurality of driving ranges, a mode selection device 88 that can select a plurality of driving modes, etc., a front electric motor rotation speed Nmf that is the rotation speed of the front electric motor 22, a rear electric motor rotation speed Nmr that is the rotation speed of the rear electric motor 32, an accelerator opening θacc that represents the acceleration request amount (such as the amount of depression of the accelerator pedal) by the driver, a steering angle Φ that corresponds to the amount of rotational operation of the steering wheel, a longitudinal acceleration Ga of the electric vehicle 10, a lateral acceleration Gb of the electric vehicle 10, wheel speeds Nwfl, Nwfr, Nwrl, and Nwrr of the front wheels 12 and the rear wheels 16 (hereinafter, wheel speed Nw Signals are supplied that represent the vehicle speed V, a state-of-charge value SOC corresponding to the remaining charge of the battery 30, a selected driving range Sra, a selected driving mode Smo, etc. Based on the wheel speeds Nwfl, Nwfr, Nwrl, and Nwrr, the vehicle speed V is calculated, for example, from the average value thereof. The state-of-charge value SOC is calculated from the voltage of the battery 30, but can also be calculated from the charge / discharge amount. The multiple driving ranges include, for example, a D range that allows forward driving according to the accelerator opening θacc, an R range that allows reverse driving according to the accelerator opening θacc, an N range that disables driving according to the accelerator opening θacc, and a P range for parking.

[0020] The multiple driving modes are driving modes for forward driving in D range, such as sport mode, which emphasizes driving performance over fuel economy by reducing power consumption; normal mode, which balances fuel economy and driving performance; eco mode, which emphasizes fuel economy (i.e., cruising distance) over driving performance; and range mode, which maximizes driving distance at the expense of driving performance and air conditioning comfort. In this embodiment, these four driving modes are selectable, and the relationships between driving performance, air conditioning comfort, and cruising distance (driving distance) are determined as shown in Figure 2. These driving modes are established by the driving mode switching control unit 62, which is functionally included in the electronic control unit 50, which controls the electric vehicle 10. Figure 3 specifically explains the differences between range mode and eco mode, comparing it with normal mode. In range mode, vehicle speed and driving force are limited, and the brightness of the meter and display is also limited. Soft acceleration softens the initial driving force of the accelerator pedal opening θacc, and softens the driving force to the same extent in range mode and eco mode. Air conditioning restrictions are implemented in both range mode and eco mode to reduce power consumption by limiting the operation of air conditioning devices such as air conditioners. However, the degree of restriction is greater in range mode. For example, in eco mode, operation continues at a specified output, whereas in range mode, the operation of the air conditioning device is turned off (stopped).

[0021] The front-rear driving force distribution control reduces power consumption and extends driving distance by preferentially using the front-wheel drive unit 14 or the rear-wheel drive unit 18, whichever consumes less power. Specifically, if the front PCU 28 uses a Si-based semiconductor while the rear PCU 38 uses a more efficient semiconductor such as SiC or GaN, the rear-wheel drive unit 18 equipped with the rear PCU 38 is used preferentially. This front-rear driving force distribution control is performed in both range mode and eco mode, but range mode gives a higher degree of priority to the use of the rear-wheel drive units. For example, in eco mode, both drive units 14 and 18 are used at a predetermined driving force distribution rate to perform four-wheel drive, while in range mode, the rear-wheel drive unit 18 has a driving force distribution rate of 100%, performing two-wheel drive using only the rear wheels 16. In this embodiment, range mode corresponds to the power consumption priority mode, and the rear-wheel drive unit 18 corresponds to the drive unit used preferentially in the power consumption priority mode.

[0022] The electronic control unit 50 functionally comprises a driving force control unit 52, a driving force correction unit 54, a wrong-sign torque limiting unit 60, and a driving mode switching control unit 62. The driving force correction unit 54 comprises a sprung vibration damping control unit 56 and a line tracing control unit 58, and the driving mode switching control unit 62 comprises a range mode control unit 64. The electronic control unit 50 corresponds to the control device of the electric vehicle 10.

[0023] The driving force control unit 52 calculates a required driving torque Tdem at the driving wheels (front wheels 12, rear wheels 16) of the electric vehicle 10 according to a driving torque calculation map or an arithmetic expression based on, for example, the accelerator opening θacc and the vehicle speed V, and calculates a front required torque Tfdem and a rear required torque Trdem according to a predetermined front / rear driving force distribution ratio Ad. Then, the driving force control unit 52 calculates torque command values ​​Tmfs, Tmrs for the front electric motor 22 and the rear electric motor 32 that can realize the front required torque Tfdem and the rear required torque Trdem based on the gear ratio, power transmission loss, auxiliary load, etc. of the transaxles 24, 34, respectively, and controls the torques Tmf, Tmr of the front electric motor 22 and the rear electric motor 32 according to the torque command values ​​Tmfs, Tmrs. The front / rear driving force distribution ratio Ad may be set to a constant value such as 50:50, or may be variably set based on driving conditions such as the accelerator opening θacc, vehicle speed V, steering angle Φ, accelerations Ga and Gb, etc.

[0024] The driving force correction unit 54 corrects the front required torque Tfdem, rear required torque Trdem, front electric motor torque command value Tmfs, and rear electric motor torque command value Tmrs calculated by the driving force control unit 52, and in this embodiment includes a sprung vibration damping control unit 56 and a line tracing control unit 58. The sprung vibration damping control unit 56 executes sprung vibration damping control, for example, in accordance with steps SD1 to SD4 of the flowchart in Fig. 4 (hereinafter, the steps will be omitted and simply referred to as SD1 to SD4; the same applies to other flowcharts). That is, in SD1, a predetermined sprung vibration model is used to estimate pitching and bouncing based on the wheel speed Nw, required torques Tfdem and Trdem, vehicle longitudinal acceleration Ga, etc., and a driving force vibration damping compensation value for the front wheels 12 and a driving force vibration damping compensation value for the rear wheels 16 that mitigate the pitching and bouncing. SD2 calculates front electric motor damping torque Tmfdamp and rear electric motor damping torque Tmrdamp based on these driving force damping compensation values. Then, SD3 performs limiting processes such as upper and lower limit cuts on these damping torques Tmfdamp and Tmrdamp, and then SD4 corrects the front electric motor torque command value Tmfs by adding the front electric motor damping torque Tmfdamp to it, and corrects the rear electric motor torque command value Tmrs by adding the rear electric motor damping torque Tmrdamp to it. This reduces pitching and bouncing of electric vehicle 10 during acceleration and deceleration when the driving force changes.

[0025] The line tracing control unit 58 performs line tracing control, reducing torque to align the pitching phase with the roll behavior during a turn. In the electric vehicle 10 of this embodiment, which allows independent control of driving force for the front and rear wheels, torque reduction is performed on the front side, which is highly sensitive to pitching due to torque changes. Rolling and pitching occur at the beginning of a turn, and a time lag between these motions makes it difficult for the behavior of the electric vehicle 10 to stabilize. Therefore, by advancing the pitching phase by reducing torque on the front wheels 12 at the start of a turn, vehicle behavior can be quickly stabilized, improving the turning feel. The amount of torque reduction is determined in advance through experiments or other means so as to eliminate the phase difference between rolling and pitching. The line tracing control unit 58 corresponds to a behavior stabilization control unit that corrects driving force to stabilize the behavior of the electric vehicle 10 while it is running.

[0026] The wrong-sign torque limiting unit 60 limits the upper rate (upper limit of the rate of change) and lower rate (lower limit of the rate of change) of the front electric motor torque command value Tmfs and the rear electric motor torque command value Tmrs according to Fig. 5 when the front electric motor torque command value Tmfs and the rear electric motor torque command value Tmrs are different in sign during acceleration or deceleration of the electric vehicle 10. That is, when the electric vehicle 10 accelerates or decelerates, the front electric motor torque command value Tmfs and the rear electric motor torque command value Tmrs may be different in sign due to differences in the smoothing process of the front electric motor torque command value Tmfs and the rear electric motor torque command value Tmrs, correction of the electric motor torque command values ​​Tmfs and Tmrs by the driving force correcting unit 54, etc., and this difference in sign may result in a deterioration in drivability and vehicle stability. The wrong-sign torque limiting unit 60 is intended to suppress such a deterioration in drivability and vehicle stability. Specifically, when the front electric motor torque command value Tmfs and the rear electric motor torque command value Tmrs are different in sign during acceleration, the upper limit rate of the torque command value Tmfs or Tmrs on the positive side, which is the leading change, is limited. On the other hand, when the front electric motor torque command value Tmfs and the rear electric motor torque command value Tmrs are different in sign during deceleration, the lower limit rate of the torque command value Tmfs or Tmrs on the negative side, which is the leading change, is limited. This reduces the difference between the positive and negative values ​​of the front electric motor torque command value Tmfs and the rear electric motor torque command value Tmrs, thereby suppressing deterioration of drivability and vehicle stability. The upper limit rate limit reduces the upper limit of the upward change rate, and the upward change rate may be set to 0. The lower limit rate limit reduces the upper limit of the downward change rate (negative change rate), and the downward change rate may be set to 0.

[0027] 6 shows a case where the required drive torque Tdem changes from negative regenerative deceleration driving to positive at time t1 in response to an acceleration request such as accelerator ON, and the front electric motor torque command value Tmfs changes to the positive side first due to smoothing processing or the like, and the upper limit rate of the front electric motor torque command value Tmfs is set to approximately 0 only while the rear electric motor torque command value Tmrs is negative (time t2-t3). In other words, until the rear electric motor torque command value Tmrs reaches 0 or a predetermined allowable value close to 0, the increase in the front electric motor torque command value Tmfs is limited and maintained at an approximately constant value, and the difference between the positive and negative values ​​of the front electric motor torque command value Tmfs and the rear electric motor torque command value Tmrs is reduced.

[0028] The driving mode switching control unit 62 changes the driving torque calculation map for driving force control by the driving force control unit 52, the front / rear driving force distribution ratio Ad, and limits the operation of the air conditioning unit so that the vehicle travels in the driving mode selected by the mode selection device 88. The range mode control unit 64, which drives in the range mode, performs various controls, such as limiting vehicle speed, limiting driving force, and controlling the front / rear driving force distribution, as shown in FIG. 3, to maximize the driving distance. The range mode can be selected arbitrarily by the driver using the mode selection device 88. However, for example, when a destination is set using a navigation system or the like, the range mode control unit 64 may calculate the possible driving distance in the current driving mode from the state of charge value SOC of the battery 30, and if the distance is shorter than the distance to the destination, suggest the selection of the range mode on a display or the like. The possible driving distance can also be calculated with greater accuracy by calculating the cumulative elevation change from map information or by using past driving data.

[0029] If driving force correction unit 54 corrects driving force while the vehicle is traveling in the range mode, the front / rear driving force distribution will change, impairing fuel economy and possibly shortening the driving distance. In response to this, driving force control unit 52 in this embodiment determines whether the range mode is selected in SR1 as shown in FIG. 7, and if the range mode is selected, executes SR2 to prohibit correction by driving force correction unit 54. Specifically, sprung vibration damping control by sprung vibration damping control unit 56 and line tracing control by line tracing control unit 58 are both prohibited, and the front electric motor torque command value Tmfs and the rear electric motor torque command value Tmrs are determined in accordance with the front / rear driving force distribution determined by range mode control unit 64. Specifically, the front electric motor torque command value Tmfs is set to 0 so that the driving force distribution rate of the rear wheel drive unit 18 is 100% and two-wheel drive running is performed using only the rear wheels 16, and the rear electric motor torque command value Tmrs is controlled so that a predetermined driving force can be obtained using only the rear wheel drive unit 18. In this embodiment, the range mode corresponds to the electricity efficiency priority mode, and the range mode control unit 64 corresponds to the electricity efficiency priority running control unit. In the range mode of this embodiment, various controls shown in FIG. 3 are executed, but it is sufficient that at least the front / rear driving force distribution control is executed. Furthermore, even in the eco mode in which front / rear driving force distribution control is performed, it is possible to limit the correction by the driving force correction unit 54 as shown in FIG. 7, and in this case, the eco mode can also be considered as the electricity efficiency priority mode of the present invention.

[0030] As described above, according to the electronic control device 50 of the electric vehicle 10 of this embodiment, correction by the driving force correction unit 54 is prohibited when driving in range mode in which the driving force distribution to the front and rear wheels is controlled so as to reduce power consumption. This prevents the driving force correction unit 54 from intervening to change the driving force distribution to the front and rear wheels, which would otherwise impair fuel economy, and ensures an appropriate driving distance.

[0031] Furthermore, the electric vehicle 10 of this embodiment is an electric vehicle with independent front and rear wheel drive, which has a front wheel drive unit 14 having a front electric motor 22 and a rear wheel drive unit 18 having a rear electric motor 32, and in range mode, the vehicle runs using only the rear wheel drive unit 18, which consumes less power, out of the front wheel drive unit 14 and the rear wheel drive unit 18, so power consumption can be appropriately reduced and the driving distance can be extended.

[0032] Furthermore, the vehicle is provided with a torque limiting unit 60 for wrong sign, which limits the change in the positive torque command value Tmfs or Tmrs when the front electric motor torque command value Tmfs corresponding to the torque command value for the front wheel drive unit 14 and the rear electric motor torque command value Tmrs corresponding to the torque command value for the rear wheel drive unit 18 are different in sign during acceleration of the electric vehicle 10, thereby suppressing deterioration in drivability and vehicle stability due to the difference in sign between the front and rear wheel drive forces. However, when such a torque limiting unit 60 for wrong sign is provided, if the rear electric motor torque command value Tmrs becomes positive and the front electric motor torque command value Tmfs becomes negative due to the intervention of the drive force correcting unit 54 during re-acceleration in a range mode that preferentially uses the rear wheel drive unit 18, and torque limitation is performed on the rear electric motor torque command value Tmrs due to the wrong sign, there is a possibility that acceleration of the electric vehicle 10 will be restricted and drivability will be deteriorated. In this embodiment, correction by the driving force correction unit 54 is prohibited when driving in range mode, so that a difference in sign between the front and rear electric motor torque command values ​​Tmfs, Tmrs is suppressed, and a decrease in drivability due to torque limitation resulting from the difference in sign is suppressed.

[0033] Although the embodiments of the present invention have been described in detail above with reference to the drawings, this 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]

[0034] 10: Electric vehicle 12: Front wheels 14: Front wheel drive unit 16: Rear wheels 18: Rear wheel drive unit 22: Front electric motor (electric motor) 32: Rear electric motor (electric motor) 50: Electronic control unit (control unit) 54: Driving force correction unit 60: Torque limiting unit when sign is wrong 64: Range mode control unit (electricity efficiency priority driving control unit) Tmfs: Front electric motor torque command value (torque command value) Tmrs: Rear electric motor torque command value (torque command value)

Claims

1. A control device for an electric vehicle of front and rear wheel independent drive type that is separately equipped with a front wheel drive unit having a front electric motor that drives the front wheels and a rear wheel drive unit having a rear electric motor that drives the rear wheels, the control device having a drive force correction unit that corrects at least one of the front wheel drive force and the rear wheel drive force, an electricity-saving driving control unit that drives the vehicle in an electricity-saving mode that controls the distribution of driving force between the front and rear wheels so as to reduce power consumption; limiting the correction by the driving force correction unit when traveling in the electricity consumption priority mode; The power consumption priority mode is a mode in which the vehicle is driven by preferentially using one of the front wheel drive unit and the rear wheel drive unit, whichever is determined to have lower power consumption. A control device for an electric vehicle.

2. and a torque limiting unit for limiting a change in the positive torque command value when the torque command value for controlling the output of the front wheel drive unit and the torque command value for controlling the output of the rear wheel drive unit are different in sign during acceleration of the electric vehicle. The control device for an electric vehicle according to claim 1 .

Images