Vehicle braking / driving force control device

Abstract

A vehicle braking / driving force control device for performing vehicle motion control, comprising: actuators (30fl, 30fr, 30rl, 30rr) which independently drive a left front wheel (10fl), a right front wheel (10fr), a left rear wheel (10r1) and a right rear wheel (10rr), respectively, and thereby generate a braking / driving force representing both a braking force and a driving force on the left front wheel (10fl), the right front wheel (10fr), the left rear wheel (10rl) and the right rear wheel (10rr), respectively; andsuspension mechanisms (20fl, 20fr, 20rl, 20rr) which independently couple the left front wheel (10fl), the right front wheel (10fr), the left rear wheel (10rl) and the right rear wheel (10rr) to a vehicle body, respectively, and apply the braking / driving force to the left front wheel (10fl), the right front wheel (10fr), the left rear wheel (10r1) and the right rear wheel (10rr), driven by the respective actuators (30fl, 30fr, 30rl, 30rr),into a force in a height direction of the vehicle body (B) such that the conversion rate of the conversion of the braking / driving force into the force in the height direction of the vehicle body (B) is different for the front wheels (10fl, 10fr) and the rear wheels (10r1, 10rr), characterized in that: the vehicle braking / driving force control device further comprises: distribution setting means (50) for setting, when the vehicle motion control is performed, a force distribution of a driver-requested braking / driving force (F*), which is set based on an operation amount of a driver, to the front wheels (10fl, 10fr) and the rear wheels (10rl, 10rr) such that a distributed driver-requested braking / driving force (Fdx) for each of the suspension mechanisms (20rl, 20rr) wheels coupled with a higher conversion rate (10rl,10rr) is greater than a distributed driver-requested braking / driving force (Fdx) for each of the wheels (10fl, 10fr) coupled to the suspension mechanisms (20fl, 20fr) with a smaller conversion rate, and that a proportion of the driver-requested braking / driving force (F*) on the wheels (10rl, 10rr) coupled to the suspension mechanisms (20rl, 20rr) with a larger conversion rate is greater when the vehicle motion control is executed than when the vehicle control is not executed; a target braking / driving force calculation means (50) for calculating, when the vehicle motion control is executed, target braking / driving forces (Fx) for the left front wheel (10fl), the right front wheel (10fr), the left rear wheel (10rl), and the right rear wheel, respectively (10rr),wherein each of the target braking / driving forces (Fx) comprises the driver-requested braking / driving force (Fdx) and a motion control braking / driving force (Fcx) necessary for vehicle motion control; andan actuator control means (35, 50) for controlling operations of the actuators (30fl, 30fr, 30rl, 30rr) by following the target braking / driving forces (Fx).

Description

1. Field of the InventionThe present invention relates to a vehicle braking / driving force control device for independently controlling a driving force and a braking force of each of four wheels (left and right front wheels and left and right rear wheels) of a vehicle.2. Description of the Prior ArtThere is known a vehicle braking / driving force control apparatus for independently controlling a driving force and a braking force (collectively referred to as braking / driving force) of four wheels of a vehicle. For example, in a vehicle having an in-wheel motor as a form of an electric vehicle, a motor is disposed in or near a wheel of the vehicle that is directly driven by the motor. The motors provided for the respective wheels can be controlled independently of one another for driving. In the vehicle with the wheel hub motors, each motor is individually controlled for travel with electrical energy or for regeneration, so that drive torques and braking torques on the individual wheels are individually controlled and thus the travel and the movement of the vehicle are regulated.A vehicle braking / driving force control apparatus according to the preamble of claim 1 is disclosed in JP 2009-143 310 A, wherein in the vehicle travel control apparatus described therein, yaw motion during turning of a vehicle is controlled by controlling driving forces of in-wheel motors so as to prevent roll behavior generated in response to a suspension characteristic of the vehicle as a result of control of the yaw motion.For better understanding of the present invention, reference is further made to JP 2007-161 032 A, which discloses a device capable of changing a distribution of driving forces between front and rear wheels, and US 2013 / 0 218 388 A1, which discloses a control system for controlling braking and driving forces of a vehicle.However, when the braking / driving forces are controlled to the wheels (i.e., the braking or driving forces transmitted to the wheels) so as to control the vehicle movement, there arises a problem that the braking / driving forces are preferably applied to the front wheel side or preferably to the rear wheel side (i.e., not uniformly applied to the front wheel side and the rear wheel side) and a certain wheel reaches an output limit value earlier than the other wheels. This problem will be described below.Each wheel is coupled to a vehicle body via a suspension mechanism. Generally, as shown in FIG. 3, a current rotation center Cf of a suspension mechanism for coupling a front wheel 10 fto a vehicle body B is positioned behind and above the front wheel 10 f, and a current rotation center Cr of a suspension mechanism for coupling a rear wheel 10 rto the vehicle body B is positioned in front of and above the rear wheel 10 r. Therefore, when a driving torque is applied to the front wheel 10 f, a force Ff 1 acts forward in the traveling direction of the vehicle at a ground contact point of the front wheel 10 f, and a vertical force Fzf 1 (a vertically downward force component acting on the suspension mechanism) that acts on the vehicle body B via the suspension mechanism is generated by the force Ff 1 acting on the ground contact point of the front wheel 10 f. Thus, as a result of the driving of the front wheel 10f, a force acts in the lowering direction of the vehicle body B. In contrast, when a braking torque is applied to the front wheel 10f, a force Ff2 acts at the ground contact point of the front wheel 10f rearward in the traveling direction of the vehicle, and a vertical force Fzf2 (a vertically upward force component acting on the suspension mechanism) that urges the vehicle body B upward via the suspension mechanism is generated by the force Ff2 acting at the ground contact point of the front wheel 10f. Thus, as a result of the deceleration of the front wheel 10f, a force acts in the raising direction of the vehicle body B.On the other hand, the direction of a corresponding vertical force on the rear wheel 10r is opposite to that on the front wheel 10f. In other words, when a driving torque is applied to the rear wheel 10 r, a force Fr 1 in the traveling direction of the vehicle acts forward at a ground contact point of the rear wheel 10 r, and a vertical force Fzr 1 (an upward vertical force component acting on the suspension mechanism) that urges the vehicle body B upward via the suspension mechanism is generated by the force Fr 1 at the ground contact point of the rear wheel 10 r. Thus, as a result of the driving of the rear wheel 10 r, a force acts in the raising direction of the vehicle body B. In contrast, when a braking torque is applied to the rear wheel 10 f, a force Fr 2 acts at the ground contact point of the rear wheel 10 rbackward in the traveling direction of the vehicle, and a vertical force Fzr 2 (a vertically downward force component acting on the suspension mechanism) that acts on the vehicle body B via the suspension mechanism is generated by the force Fr 2 at the ground contact point of the rear wheel 10 r. Thus, as a result of the deceleration of the rear wheel 10r, the force acts in the lowering direction of the vehicle body B.When an angle formed between a horizontal ground surface and a line connecting the ground contact point of the front wheel 10 fto the present rotation center Cf is denoted by θf and an angle formed between the horizontal ground surface and a line connecting the ground contact point of the rear wheel 10 rto the present rotation center Cr is denoted by θr, an amount of the vertical force is a value obtained by multiplying the braking / driving force Ff (Ff 1 or Ff 2) by tan (θf) for the front wheel 10 fside and an amount of the vertical force is a value obtained by multiplying the braking / driving force Fr (Fr 1 or Fr 2) by tan (θr) for the rear wheel 10 rside. The terms tan(θf) and tan(θr) represent conversion rates for converting the braking / driving forces into the vertical forces acting on the vehicle body B. The angle θr is larger than the angle θf (θf<θr) due to the structure of the suspension mechanism in an ordinary vehicle. Thus, the suspension mechanism for the front wheel 10f is smaller in conversion rate than the suspension mechanism for the rear wheel 10r. Therefore, control ranges for the braking / driving forces on the front wheel 10f side and the rear wheel 10r side are equal to each other, but the control range for the vertical force of the front wheel 10f side is smaller than that for the rear wheel 10r side. In other words, the range of the vertical force that can be generated by controlling the braking / driving force for the front wheel 10 fis narrower than the range of the vertical force that can be generated by controlling the braking / driving force for the rear wheel 10 r.Therefore, first, the braking / driving force of the front wheel 10 fpreferably tends to exceed a control range (upper limit value) of the in-wheel motor when the driver required braking / driving force is ensured in response to the operation amount by the driver and the vertical forces for the motion control of the vehicle are generated. As a result, the control range for the vehicle motion control narrows.This also applies to a vehicle in which the conversion rate for converting the braking / driving force into the vertical force of the suspension mechanism for the rear wheel 10 ris smaller than that of the suspension mechanism for the front wheel 10 f, and in this case, the braking / driving force of the rear wheel 10 rfirst tends to exceed the in-wheel motor control range (upper limit value).The present invention has been made in view of the above-described problem, and it is an object of the present invention to prevent the driving force limit value from being reached as low as possible in each wheel when the braking / driving forces of the wheels are used for vehicle motion control.To achieve the above object, a vehicle braking / driving force control device for performing vehicle motion control according to the present invention includes actuators that independently drive a left front wheel, a right front wheel, a left rear wheel, and a right rear wheel, respectively, thereby generating a braking / driving force representing both a braking force and a driving force to the left front wheel, the right front wheel, the left rear wheel, and the right rear wheel, respectively, and suspension mechanisms that independently couple the left front wheel, the right front wheel, the left rear wheel, and the right rear wheel to a vehicle body, and thus convert the braking / driving force to the left front wheel, the right front wheel, the left rear wheel, and the right rear wheel, driven by the respective actuators, into a force in a height direction of the vehicle body, the conversion rate of converting the braking / driving force into the force in the height direction of the vehicle body is different for the front wheels and the rear wheels. The vehicle braking / driving force control device is characterized in that: the vehicle braking / driving force control device further comprises: distribution setting means for setting, when the vehicle motion control is performed, a force distribution of a driver-requested braking / driving force set based on an operation amount of a driver to the front wheels and the rear wheels such that a distributed driver-requested braking / driving force for each of the wheels coupled to the suspension mechanisms having a greater conversion rate is greater than a distributed driver-requested braking / driving force for each of the wheels coupled to the suspension mechanisms having a smaller conversion rate, and that a proportion of the driver-requested braking / driving force to the wheels coupled to the suspension mechanisms having a greater conversion rate is greater, when the vehicle motion control is executed as when the vehicle control is not executed; target braking / driving force calculating means for calculating, when the vehicle motion control is executed, target braking / driving forces for the left front wheel, the right front wheel, the left rear wheel and the right rear wheel, respectively, each of the target braking / driving forces including the driver-requested braking / driving force and a motion control braking / driving force necessary for the vehicle motion control; and actuator control means for controlling operations of the actuators by following the target braking / driving forces.According to the present invention, the front left wheel, the front right wheel, the rear left wheel, and the rear right wheel are coupled to the vehicle body via suspension mechanisms independently provided for the respective wheels. The actuators apply the driving forces and the braking forces to the individual wheels. For example, a wheel hub motor installed in a wheel is used as an actuator. The braking / driving force of the actuator driven wheel is converted into the force in the vertical direction of the vehicle body by the suspension mechanism. Vehicle movements can be controlled by controlling the vertical forces. For example, a roll state, a pitch state, and a lift state of the vehicle may be controlled. The target braking / driving force calculation means calculates, based on the driver's operation amount such as an accelerator operation amount and a brake operation amount, the target braking / driving forces for the four wheels including the driver's requested braking / driving force and the motion control braking / driving force necessary for the vehicle motion control. The actuator control means controls the operations of the actuators by following the target braking / driving forces.The suspension mechanisms are designed such that the conversion rates for converting the braking / driving forces into the forces in the vertical direction of the vehicle body are different for the front wheel side and the rear wheel side. For example, the conversion rate is a value corresponding to an amount of an angle formed between a horizontal ground surface and a line connecting a ground contact point of the wheel to a current rotation center of the suspension mechanism for coupling the wheel in a side view of the vehicle. This configuration prevents the angle formed between the horizontal bottom surface and the line connecting the ground contact point of the front wheel to the present rotation center of the suspension mechanism and the angle formed between the horizontal bottom surface and the line connecting the ground contact point of the rear wheel to the present rotation center of the suspension mechanism from being equal. Therefore, the range of the vertical force that can be generated by the control of the braking / driving forces on the wheels is different for the front wheel and the rear wheel, and the range is narrower for the wheel coupled to the suspension mechanism having the smaller conversion rate. Accordingly, the driver-requested braking / driving force is ensured, and when the vertical forces for vehicle motion control are generated, the braking / driving force of the wheel coupled to the suspension mechanism with a smaller conversion rate first tends to exceed a control range (a travel limit value of the actuator or a travel limit value determined by road surface friction).Thus, according to the present invention, the distribution setting means sets the distribution of the driver-requested braking / driving force to the front wheels and the rear wheels such that the proportion of the driver-requested braking / driving force of the wheels coupled to the suspension mechanisms having a larger conversion rate is larger than that of the wheels coupled to the suspension mechanisms having a smaller conversion rate. Accordingly, on the wheel coupled to the suspension mechanism having the smaller conversion rate, the driver-demanded braking / driving force is given, and a widely effective braking / driving force range available for the vehicle motion control can be ensured, so that the braking / driving force hardly reaches the driving force limit value.The distribution switching means switches the distribution of the driver-requested braking / driving force to the front wheels and the rear wheels so that a proportion of the driver-requested braking / driving force of the wheels coupled to the suspension mechanisms with a larger conversion rate is larger when the vehicle motion control is executed than when the vehicle motion control is not executed. Then, when at least the vehicle motion control is executed, the distribution setting means sets the distribution of the driver-requested braking / driving force to the front wheels and the rear wheels such that the proportion of the driver-requested braking / driving force of the wheels coupled to the suspension mechanisms having a larger conversion rate is larger than that of the wheels coupled to the suspension mechanisms having a smaller conversion rate. Accordingly, when the vehicle motion control is executed, a more effective driving force range available for the vehicle motion control can be secured to the wheel coupled to the suspension mechanism with a small conversion rate, and the braking / driving force hardly reaches the driving force limit value.According to an advantageous aspect of the present invention, the vehicle braking / driving force control device is characterized in that when the vehicle motion control is not executed, the distribution setting means sets the force distribution so that the distributed driver-requested braking / driving forces for the left front wheel, the right front wheel, the left rear wheel, and the right rear wheel are the same.According to the advantageous development, when the vehicle movement control is not executed, the tire forces are equalized, so that the vehicle stability is improved.According to another advantageous development of the present invention, the vehicle braking / driving force control device is characterized in that the vehicle movement control comprises a vehicle yaw movement control.When the vehicle yaw motion control is executed, phase-reverse braking / driving forces (a driving force on a turned outer wheel and a braking force on a turned inner wheel) are set to the left and right wheels as the motion control braking / driving forces. Accordingly, the vertical force acting on the vehicle body via the front-left wheel suspension mechanism and the vertical force acting on the vehicle body via the front-right wheel suspension mechanism are opposed, resulting in a roll moment on the vehicle body on the front-wheel side. Further, the vertical force acting on the vehicle body via the suspension mechanism for the left rear wheel and the vertical force acting on the vehicle body via the suspension mechanism for the right rear wheel are opposed to each other, resulting in a roll moment on the vehicle body on the rear wheel side. In this case, the roll torques on the front wheel side and the rear wheel side are opposite, but the amount of roll torque is larger on the wheel side coupled to the suspension mechanisms having a larger conversion rate of the vertical force. In order to prevent roll generated by the yaw motion control of the vehicle body, the roll control needs to be executed so that the roll torque generated on the front wheel side and the roll torque generated on the rear wheel side are balanced. The braking / driving force of the wheel coupled to the suspension mechanism having the smaller conversion rate needs to be larger than the braking / driving force of the wheel coupled to the suspension mechanism having the larger conversion rate in order to prevent the vehicle body from rolling. However, as a result of the increase, the motion control braking / driving force necessary for the outer wheel locked to the suspension mechanism having the smaller conversion rate is increased.Further, according to the modification, the distribution of the driver required braking / driving force is switched to the front wheels and the rear wheels so that the proportion of the driver required braking / driving force of the wheels coupled to the suspension mechanisms having a larger conversion rate is larger when the vehicle yaw motion control is executed than when the vehicle yaw motion control is not executed. Then, when at least the vehicle yaw motion control is executed, the distribution setting means sets the distribution of the driver-requested braking / driving force to the front wheels and the rear wheels so that the proportion of the driver-requested braking / driving force is larger for the wheels coupled to the suspension mechanisms having a larger conversion rate than for the wheels coupled to the suspension mechanisms having a smaller conversion rate. Thus, safety is secured in applying the motion control braking / driving force for the yaw motion control and the roll control for the wheel coupled to the suspension mechanism having the smaller conversion rate. As a result, the steered outer wheel coupled to the link mechanism with the smaller conversion rate hardly reaches the travel limit value, so that the roll control during the yaw motion control can be performed very well. Further, when the yaw motion control is not executed, the distributions of the driver-requested braking / driving force to the left front wheel, the right front wheel, the left rear wheel, and the right rear wheel can be adjusted, and thus the tire generation forces can be adjusted, resulting in an improvement in the vehicle stability.According to an advantageous aspect of the present invention, the vehicle braking / driving force control apparatus is characterized in that when the vehicle yaw motion control is executed, the target braking / driving force calculation means calculates the motion control braking / driving forces so that a front wheel roll moment generated by the driving forces of the front wheels and a rear wheel roll moment generated by the driving forces of the rear wheels are balanced.When the vehicle yaw motion control is executed on a vehicle including suspension mechanisms having different conversion rates of the vertical forces on the front wheel side and the rear wheel side, the front wheel roll torque generated by the driving forces of the front wheels and the rear wheel roll torque generated by the driving forces of the rear wheels are opposite in direction but different in amount. Thus, the target braking / driving force calculating means calculates the motion control braking / driving forces for the respective wheels so that the front wheel roll torque and the rear wheel roll torque are balanced. In this case, the distribution of the driver-requested braking / driving force to the front wheels and the rear wheels is adjusted so that the proportion of the driver-requested braking / driving force of the wheels coupled to the suspension mechanisms having a larger conversion rate of the vertical force is larger than that of the wheels coupled to the suspension mechanisms having a smaller conversion rate of the vertical force. Consequently, rolling of the vehicle body can be prevented very well.According to another advantageous aspect of the present invention, the vehicle braking / driving force control device is characterized in that when the vehicle motion control is performed, the distribution setting means sets the force distribution so that reserve vertical forces that can act on the vehicle body by the braking / driving forces on the front left wheel, the front right wheel, the rear left wheel, and the rear right wheel via the suspension mechanisms are equal to each other for the front wheels and the rear wheels.According to the advantageous feature of the present invention, the reserve force adjusting means adjusts the ratio of the proportions of the driver-demanded braking / driving force to the front and rear wheels so that the reserve vertical forces which can act on the vehicle body by braking / driving forces on the wheels via the suspension mechanisms are equal on the front wheel side and the rear wheel side. Therefore, when the vehicle motion control is executed, the distribution of the braking / driving forces to the front and rear wheels can be more balanced. Accordingly, the braking / driving force to a specific wheel is prevented from reaching the threshold value early.According to another advantageous aspect of the present invention, the vehicle braking / driving force control device is characterized in that, when the vehicle motion control is performed and the driver required braking / driving force is less than a set value set in advance, the distribution setting means sets the force distribution so that the driver required braking / driving force acts only on the wheels coupled to the suspension mechanisms having a larger conversion rate.The reserve vertical forces that can act on the vehicle body by the braking / driving forces on the wheels via the suspension mechanisms may be equalized between the front wheel side and the rear wheel side when the driver-demanded braking / driving force becomes smaller than a certain value. Thus, according to the advantageous feature, the means for setting, when the driver-demanded braking / driving force is smaller than a preset setting value, the ratio of the proportions to the front wheels and the rear wheels so that the driver-demanded braking / driving force acts only on the wheels coupled to the suspension mechanisms having the larger conversion rate. In other words, the driver-demanded braking / driving force is not distributed to the wheels coupled to the suspension mechanisms with the smaller conversion rate. Accordingly, when the driver required braking / driving force is small, the driver required braking / driving force can be appropriately distributed to the front and rear wheels.According to another advantageous aspect of the present invention, the vehicle braking / driving force control device is characterized in that, when the vehicle motion control is performed, the distribution setting means detects a motion state amount of a vehicle and sets the force distribution depending on the motion state amount. In this case, the ratio adjusting state amount of the share sets the proportion of the driver-requested rear-wheel-side braking / driving force to increase as the moving state amount increases.According to another advantageous aspect of the present invention, the vehicle braking / driving force control device is characterized in that, when the vehicle motion control is performed, the distribution setting means sets the force distribution such that the distribution ratio increases as the motion state amount increases.In the above description, reference numerals used in the embodiment are placed in parentheses and assigned to each configuration of the invention corresponding to the embodiment in order to facilitate the intelligibility of the invention, but no configuration requirement of the invention is limited to the embodiment specified by the reference numerals. FIG. 1 is a schematic configuration diagram of a vehicle in which a vehicle braking / driving force control device according to an embodiment of the present invention is installed. FIG. 2 is a flowchart showing a motor drive control routine. FIG. 3 is a diagram showing a relationship between control ranges of braking / driving forces and control ranges of vertical forces. FIG. 4 is a graph showing braking / driving forces on front and rear wheels required for compensating the rolling torques. FIG. 5 is a diagram showing proportions of driver-requested driving forces, feedback driving forces, and target driving forces of the four wheels when a driver-requested driving force is distributed uniformly. FIG. 6 is a diagram showing the driver required distributed driving forces, the feedback driving forces, and the target driving forces to the four wheels when the driver required driving force is distributed more to the rear wheels. FIG. 7 is a characteristic of a driving force distribution coefficient α. FIG. 8 is a characteristic of the control driving forces during the yaw motion.Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 schematically shows a configuration of a vehicle 1 to which a vehicle braking / driving force control device according to this embodiment is mounted.The vehicle 1 includes a front left wheel 10 fl, a front right wheel 10 fr, a rear left wheel 10 rl, and a rear right wheel 10rr. The front left wheel 10 fl, the front right wheel 10 fr, the rear left wheel 10 rl, and the rear right wheel 10rr are suspended from a vehicle body B via independent wheel suspensions 20 fl, 20 fr, 20 rl, and 20rr, respectively.The suspensions 20 fl, 20 fr, 20 rl, and 20rr are coupling structures for coupling the vehicle body B to the wheels 10 fl, 10 fr, 10 rl, and 10rr, respectively, and include link mechanisms 21 fl, 21 fr, 21 rl, and 21rr formed by suspension arms and the like, suspension springs 22 fl, 22 fr, 22 rl, and 22rr for supporting loads in the vertical direction and absorbing shocks, and shock absorbers 23 fl, 23 fr, 23 rl, and 23rr for damping vibrations of a sprung mass (vehicle body B). The suspension mechanisms according to the present invention include instantaneous center-of-rotation determining members that include all the unsprung mass motion determining members, not only the link mechanisms 21 fl, 21 fr, 21 rl, and 21rr, and represent the entire suspensions 20 fl, 20 fr, 20 rl, and 20rr including the suspension springs 22 fl, 22 fr, 22 rl, and 22rr and the shock absorbers 23 fl, 23 fr, 23 rl, and 23rr in addition to the link mechanisms 21 fl, 21 fr, 21 rl, and 21rr. A well-known four-wheel independent suspension such as a strut or a suspension arm may be used as each of the suspensions 20 fl, 20 fr, 20 rl, and 20rr.Motors 30 fl, 30 fr, 30 rl, and 30rr are installed in the front left wheel 10 fl, the front right wheel 10 fr, the rear left wheel 10 rl, and the rear right wheel 10rr, respectively. The motors 30 fl, 30 fr, 30 rl, and 30rr, which are so-called in-wheel motors, are respectively disposed at unsprung positions of the vehicle 1 together with the front left wheel 10 fl, the front right wheel 10 fr, the rear left wheel 10 rl, and the rear right wheel 10rr, and are coupled to the front left wheel 10 fl, the front right wheel 10 fr, the rear left wheel 10 rl, and the rear right wheel 10rr for power transmission. In the vehicle 1, rotations of the motors 30 fl, 30 fr, 30 rl, and 30rr can be independently controlled so as to independently control the driving forces and braking forces to be generated at the front left wheel 10 fl, the front right wheel 10 fr, the rear left wheel 10 rl, and the rear right wheel 10 rr, respectively.Hereinafter, the wheels 10 fl, 10 fr, 10 rl, and 10rr, the suspensions 20 fl, 20 fr, 20 rl, and 20rr, the link mechanisms 21 fl, 21 fr, 21 rl, and 21rr, the suspension springs 22 fl, 22 fr, 22 rl, and 22rr, the shock absorbers 23 fl, 23 fr, 23 rl, and 23rr, and the motors 30 fl, 30 fr, 30 rl, and 30rr are collectively referred to as the wheel 10, the suspension 20, the link mechanism 21, the suspension spring 22, the shock absorber 23, and the motor 30, respectively, unless a specific (no specific) needs to be identified. Further, when the front wheels 10fl and 10fr and the rear wheels 10rl and 10rr are to be distinguished from each other and identified from the wheels 10fl, 10fr, 10rl and 10rr, the front wheels 10fl and 10fr are referred to as the front wheel 10f and the rear wheels 10rl and 10rr are referred to as the rear wheel 10r. Similarly, for the suspension 20, the link mechanism 21, the suspension spring 22, the shock absorber 23, and the motor 30, where when they are identified as being on the front wheel side, they are identified as the front wheel suspension 20 f, the front wheel link mechanism 21 f, the front wheel suspension spring 22 f, the front wheel shock absorber 23 f, and the front wheel motor 30 f, respectively, and where when they are identified as being on the rear wheel side, they are identified as the rear wheel suspension 20 r, the rear wheel link mechanism 21 r, the rear wheel suspension spring 22 r, the rear wheel shock absorber 23 r, and the rear wheel motor 30 r, respectively.For example, brushless motors are used as the motors 30. The motors 30 are each connected to a motor driver 35. The motor driver 35 includes, for example, a four inverters, so that a total of four inverters are provided for the motors 30. The motor driver 35 converts a direct current supplied from a battery 60 into alternating currents which are supplied to each of the motors 30 independently of each other. Accordingly, the driving of the motors 30 is controlled to generate torques to transmit driving forces to respective wheels 10. Such a state in which an electric current is supplied to the motors 30 to generate a driving torque, respectively, is referred to as a power-driven traveling operation.Further, each motor 30 functions as an electric generator for generating electric power from the rotational energy of each wheel 10, and charges the battery 60 with the electric power thus generated via the motor driver 35. The braking torque generated by the generation of electrical power by the motors 30 is applied to the wheel 10 via a braking force. Although a brake device is provided for each wheel 10, the present invention is not directed to it, and is not further considered here.The motor driver 35 is connected to an electric control / regulation unit 50. The electric control / feedback control unit 50 (hereinafter referred to as ECU 50) includes a microcomputer having a CPU, a ROM, and a RAM as main components, and executes various programs to independently feedback control the operations of the individual motors 30. The ECU 50 is connected to an operation state detector 40 for detecting an operation state of operations performed by the driver for controlling the vehicle and a motion state detector 45 for detecting a motion state of the vehicle, and inputs detection signals output from the detectors 40 and 45.The operation state detection device 40 includes an accelerator sensor for detecting an accelerator operation amount by the driver based on a depression amount (or an angle or a pressure) of an accelerator pedal, a brake sensor for detecting a brake operation amount by the driver based on a depression amount (or an angle or a pressure) of a brake pedal, a steering angle sensor for detecting a steering operation amount of an operation of a steering wheel by the driver, and the like. The motion state detecting device 45 includes an appropriate combination of a vehicle speed sensor for detecting a traveling speed of a vehicle body B, a yaw rate sensor for detecting a yaw rate of the vehicle body B, a sprung mass acceleration sensor for detecting a vertical acceleration of the vehicle body B (sprung mass) at each wheel position, a lateral acceleration sensor for detecting a lateral acceleration in the lateral direction of the vehicle body B, a pitch rate sensor for detecting a pitch rate of the vehicle body B, a roll rate sensor for detecting a roll rate of the vehicle body B, a stroke sensor for detecting a stroke amount of each suspension 20, and the like, a sensor for detecting an acceleration of an unsprung mass, for detecting a vertical acceleration of an unsprung mass of each wheel 10, and the like. A direction or sign of a sensor value with a direction element is identified as a function of its sign.As shown in FIG. 3, the suspension 20 for suspending each wheel 10 is configured such that, in the side view of the vehicle, a present center of rotation Cf (a present center of the front wheel 10 fwith respect to the vehicle body B) of the front wheel suspension 20 fis positioned behind and above the front wheel 10 fand a present center of rotation Cr (a present center of the rear wheel 10 rwith respect to the vehicle body B) of the rear wheel suspension 20 ris positioned in front of and above the rear wheel 10 r. Further, when an angle (a small angle) between a horizontal ground surface and a line connecting a ground contact point of the front wheel 10 fto the present rotation center Cf is denoted by θf, and an angle (a small angle) between the horizontal ground surface and a line connecting a ground contact point of the rear wheel 10 rto the present rotation center Cr is denoted by θr, a relationship where θr is larger than θf is satisfied (θf<θr). Hereinafter, θf is referred to as an instantaneous rotation angle θf, and θr is referred to as an instantaneous rotation angle θr.In this configuration (geometry) of the suspension 20, when a driving torque is applied to the front wheel 10 f, as shown in FIG. 3, a force Ff 1 at the ground contact point of the front wheel 10 facts forward in a traveling direction of the vehicle, and a vertical force Fzf 1 (a vertically downward force component acting on the front wheel suspension 20 f) that acts on the vehicle body B downward via the front wheel suspension 20 fis generated by the force Ff 1 at the ground contact point of the front wheel 10 f. Thus, the force in the lowering direction of the vehicle body B acts as a result of the driving of the front wheel 10f. In contrast, when a braking torque is applied to the front wheel 10 f, a force Ff 2 at the ground contact point of the front wheel 10 fappears rearward in the traveling direction of the vehicle, and a vertical force Fzf 2 (a vertically upward force component acting on the front wheel suspension 20 f) that acts upward on the vehicle body B via the front wheel suspension 20 fis generated by the force Ff 2 at the ground contact point of the front wheel 10 f. Thus, as a result of deceleration of the front wheel 10 f, the force acts in the raising direction of the vehicle body B. Further, when a driving torque is applied to the rear wheel 10 r, a force Fr 1 acts at a ground contact point of the rear wheel 10 rtowards the front of the vehicle, and a vertical force Fzr 1 (a vertically upward force component acting on the rear wheel suspension 20 r) that urges the vehicle body B upward via the rear wheel suspension 20 ris generated by the force Fr 1 at the ground contact point of the rear wheel 10 r. Thus, as a result of the driving of the rear wheel 10 r, the force acts in the raising direction of the vehicle body B. In contrast, when a braking torque is applied to the rear wheel 10 r, a force Fr 2 acts at the ground contact point of the rear wheel 10 rin the rearward direction of the vehicle, and a vertical force Fzr 2 (a vertically downward force component acting on the rear wheel suspension 20 r) applied to the vehicle body B via the rear wheel suspension 20 ris generated by the force Fr 2 at the ground contact point of the rear wheel 10 r. Thus, as a result of the deceleration of the rear wheel 10r, the force acts in the lowering direction of the vehicle body B.In this way, the suspension 20 converts the driving force and the braking force on the wheel 10 into the force in the vertical direction of the vehicle body B.The force in the vertical direction on the vehicle body B can be applied to the wheel 10 by regulating the driving force or the braking force, resulting in regulation of the state of motion of the vehicle. Hereinafter, the driving force and the braking force are collectively referred to as driving force unless differentiation is necessary. The braking force may be treated as a negative driving force. Further, when an amount of the driving force or the braking force is discussed, the amount represents an absolute value thereof.The ECU 50 calculates a driver required braking / driving force (hereinafter referred to as a driver required driving force F*) based on the accelerator operation amount and the brake operation amount detected by the operation state detection device 40, and calculates a motion control braking / driving force (hereinafter referred to as a control driving force Fcx) independently for each of the four wheels based on the vehicle motion state detected by the motion state detection device 45. Subsequently, the ECU 50 sets a sum of the feedback drive force Fcx and a driver-requested distributed drive force Fdx obtained by distributing the driver-requested drive force F* to the four wheels as a target braking / drive force (hereinafter referred to as target drive force Fx) for each of the wheels 10. The ECU 50 controls the motor driver 35 to generate an output torque corresponding to the target driving force Fx at each motor 30.An amount of the vertical force acting on the vehicle body B is a value obtained by multiplying the driving force Ff (Ff 1 or Ff 2) by tan(θf) for the front wheel 10 fside and a value obtained by multiplying the driving force Fr (Frl or Fr 2) by tan(θr) for the rear wheel 10 rside. The terms tan(θf) and tan(θr) each represent a conversion rate for converting the driving force into the vertical force to the vehicle body B. A control range of the driving force to the front wheel 10 fand a control range of the driving force to the rear wheel 10 rare the same, but the actual rotation angle θf of the front wheel suspension 20 fis smaller than the actual rotation angle θr of the rear wheel suspension 20 r, so that the range of the vertical force that can be generated by controlling the driving force to the front wheel 10 fis narrower than the range of the vertical force that can be generated by controlling the driving force to the rear wheel 10 r. Accordingly, when the motion control for the vehicle body is executed by generating the vertical force, the driving force to the front wheel 10f tends to exceed the control range (the upper limit value) first. In other words, while a reserve force of the driving force remains on the rear wheel 10 r, the driving force on the front wheel 10 fmay already exceed the control range (the upper limit value).For example, as shown in FIG. 5, a case is considered in which the engine 30 is controlled so as to generate a yawing motion of the vehicle in a right turn. When a yaw motion is generated, the control drive force Fcx in the forward direction is applied to a turned outer wheel, and the control drive force Fcx equal in magnitude but opposite to the control drive force Fcx applied to the turned outer wheel is applied to a turned inner wheel. In this situation, different vertical forces are applied to the right and left sides of the vehicle body B, so that, as shown in FIG. 4, roll torques Mxf and Mxr act. The front wheel roll torque Mxf generated by the driving force Ffl to the front wheel 10f is opposed to the rear wheel roll torque Mxr generated by the driving force Fr1 to the rear wheel 10r. In this case, when the driving forces are generated to the front wheel 10 fand the rear wheel 10 rby the same amount, the amount of the vertical force (upward) generated to the rear wheel 10 rby the driving force Fr 1 is larger than the amount of the vertical force (downward) generated to the front wheel 10 fby the driving force Ff 1. Accordingly, the rear wheel roll torque Mxr is larger than the front wheel roll torque Mxf. Thus, the front wheel roll torque Mxf and the rear wheel roll torque Mxr must balance each other, and as shown in FIG. 4, the driving force Ff1 to the front wheel 10f must be larger than the driving force Fr1 to the rear wheel 10r. In other words, in order for the vertical force Fzf 1 generated by the driving force Ff 1 on the front wheel 10 fand the vertical force Fzr 1 generated by the driving force Fr 1 on the rear wheel 10 rto have the same amount, the driving force Ff 1 on the front wheel 10 fmust be larger than the driving force Fr 1 on the rear wheel 10 r.The target driving force Fx of the motor 30 on each wheel 10 is set as a sum of the driver-requested distributed driving force Fdx and the control driving force Fcx for the vehicle motion control. Hitherto, the driver required distributed driving force Fdx has been set to a value (F* / 4) obtained by equal distributing the driver required driving force F* set depending on the operation amount by the driver to the four wheels. Therefore, for example, when the roll control is executed to balance (match) the front wheel roll torque Mxf and the rear wheel roll torque Mxr during the yaw motion of the vehicle, as described above and shown in FIG. 5, the control drive force Fcx for the front wheel 10 fis larger than the control drive force Fcx for the rear wheel. Accordingly, the target driving force Fx for the front wheel 10fl, which is a turned-in outer front wheel, first exceeds the control range (the upper limit value) of the motor 30.Thus, in this embodiment, the proportions of the driving forces to the front and rear wheels are equalized, whereby the target driving force Fx of each wheel is controlled so that the upper limit value of the control range of the motor 30 is difficult to reach.FIG. 2 shows a motor drive control routine for solving the problem. The ECU 50 repeats motor drive control routine in a predetermined short cycle. When this routine is started, the ECU 50 first detects the operation state by the driver and the vehicle moving state in step S 11. In this case, the ECU 50 acquires the accelerator operation amount, the brake operation amount, and the steering operation amount acquired from the sensor values of the operation state detector 40, and acquires motion state amounts, the degrees of the vehicle speed and motion states (the yaw motion, the roll motion, the pitch motion, and the lift motion) of the vehicle body acquired from the sensor values acquired by the motion state detector 45.Subsequently, in step S 12, the ECU 50 calculates the driver required driving force F* based on the accelerator operation amount and the brake operation amount. The driver-requested driving force F* is a driver-requested driving force in a vehicle front-rear direction acting on the entire vehicle, that is, a driving force for driving. The ECU 50 stores mapping data such as a map for deriving the driver required driving force F* from the accelerator operation amount and the brake operation amount, and uses the mapping data to calculate the driver required driving force F*.Subsequently, in step S 13, the ECU 50 determines whether or not a switching condition for switching the proportions of the driver-demanded driving force F* to the front and rear wheels is satisfied. The driver-demanded driving force F* is distributed to the four wheels. The driver required driving force F* is always equally distributed to the right wheels 10 frand 10rrand the left wheels 10 fland 10 rl(1:1), but the distribution to the front wheel 10 fand the rear wheel 10 ris switched depending on whether or not the shifting condition is satisfied.In this embodiment, the switching condition is satisfied when the vehicle motion control including the yaw motion control needs to be executed, and is not satisfied when the yaw motion control does not need to be executed. For example, the switching condition is satisfied when a difference between a target yaw rate set based on the steering angle and the vehicle speed and the actual yaw rate detected by the yaw rate sensor exceeds an allowable value, and the switching condition is not satisfied when the difference does not exceed the allowable value. Thus, the shifting condition is satisfied when a steering operation is detected or when a yaw motion is detected due to a disturbance although the steering operation is not performed (the steering wheel is held at the neutral position, for example).When the shift condition is not satisfied (No in step S 13), the ECU 50 adjusts the distribution of the driver required driving force F* so as to establish equal distribution to the front and rear wheels in step S 14. In other words, the driver-demanded driving force F* is distributed equally among the four wheels 10. On the other hand, when the shift condition is satisfied (Yes in step S 13), the ECU 50 calculates a driving force distribution coefficient α for the front and rear wheels in step S 15. In this situation, the driving force distribution coefficient α represents the part of the driver-requested driving force F* transmitted to the front wheel 10 f, and (1-α) represents the part of the driver-requested driving force F* transmitted to the rear wheel 10 r. The driving force distribution coefficient α calculated in step S 15 is set so that the proportion of the driver-requested driving force F* for the rear wheel 10 ris larger than that for the front wheel 10 f.Next, the calculation of the driving force distribution coefficient α for the front and rear wheels will be described. In this embodiment, the distribution of the driver-demanded driving force F* to the front and rear wheels is adjusted so that the reserve force in the vertical direction, which can be applied to the vehicle body B by the driving force to the wheels 10 via the suspension 20, is equal between the front wheel 10 fside and the rear wheel 10 rside.1. Vertical forceWhen the driving force to the front wheel 10 fis denoted by Ff and the driving force to the rear wheel 10 ris denoted by Fr, the vertical force Fzf generated by the driving force Ff to the front wheel 10 fand the vertical force Fzr generated by the driving force Fr to the rear wheel 10 rare represented by the following equations.2. Driving forces on the front and rear wheels after distributionWhen the driver-demanded driving force F* is represented by 2×Wd and the driving force distribution coefficient for the front wheel 10 fis represented by α (0≤α≤1), the driving force distribution coefficient for the rear wheel 10 ris represented by (1-α). The driving force Ff for the front wheel 10 fand the driving force Fr for the rear wheel 10 rmay be represented by the following equations using the driving force distribution coefficient α.When α is 0, 100% of the driver required driving force F* is transmitted to the rear wheel 10 r, and when α is 1, 100% of the driver required driving force F* is transmitted to the front wheel 10 f.3. Vertical Force After DistributionThe vertical force Fzf generated by the driving force Ff to the front wheel 10 fand the vertical force Fzr generated by the driving force Fr to the rear wheel 10 rafter the distribution of the driver-required driving force F* to the front and rear wheels are represented by the following equations.4. Maximum vertical forceWhen the maximum driving force that can be generated by the front wheel 10 fand the rear wheel 10 r, respectively, is Fmax, the maximum vertical force Fzfmax that can be generated by the driving force Ff on the front wheel 10 fand the maximum vertical force Fzrmax that can be generated by the driving force Fr on the rear wheel 10 rmay be represented by the following equations.5. Reserve Vertical ForceWhen the reserve vertical force generated by the driving force Ff to the front wheel 10 fis Fzfc (referred to as front-wheel reserve vertical force Fzfc), and the reserve vertical force generated by the driving force Ff to the rear wheel 10 ris Fzrc (referred to as rear-wheel reserve vertical force Fzrc), the front-wheel reserve vertical force Fzfc and the rear-wheel reserve vertical force Fzrc may be represented by the following equations.6. Compensation of reserve vertical forcesWhen the front-wheel reserve vertical force Fzfc and the rear-wheel reserve vertical force Fzrc are matched, the driver-required driving force can be well matched, and only one wheel is prevented from reaching the travel limit value earlier. In this case, the driving force distribution coefficient α may be set as follows.In this situation, if Fd / Fmax is set to A and Or / Of is set to D, the above equation may be represented by the following equation.Symbol A is referred to as a maximum output ratio (0≤A≤1), and symbol D is referred to as a front / rear vertical force conversion ratio (D >1).The maximum output ratio A has a value proportional to the driver-demanded driving force. In this case, an accelerator opening degree may be used as the maximum output ratio A.When the equation is solved for the driving force distribution coefficient α, it is found that the driving force distribution coefficient α is considered to be 7The driving force distribution coefficient α can be represented by the following equation.The front / rear vertical force conversion ratio D is a value greater than 1, so that (1-D) is a negative value. Therefore, the driving force distribution coefficient α is a negative infinite value (α=-∞).A possible range in which the driving force distribution coefficient α may be located is 0 to 1 (0≤α≤1), and the driving force distribution coefficient α should be zero (α=0).When A=1 is substituted into the above equation, the driving force distribution coefficient α is 0.5 (α=0.5).In this situation, the maximum output ratio A satisfying α=0 must be obtained.Thus, as shown in FIG. 7, the driving force distribution coefficient α is set to zero when the maximum output ratio A is less than (D-1) / (2D), and set to (1-D+2A·D) / (2A(1+D)) when the maximum output ratio A is (D-1) / (2D) or greater.Thus, in step S 15, the ECU 50 sets the driving force distribution coefficient α to zero when the maximum output ratio A determined based on the driver required driving force F* (or the accelerator operation amount) is less than (D- 1) / (2D), and is set to (1-D+2A·D) / (2A(1+D)) when the maximum output ratio A is (D- 1) / (2D) or greater.After the ECU 50 sets the driving force distribution coefficient α in step S 14 or S 15, the ECU 50 proceeds to the processing in step S 16. In step S 16, the ECU 50 calculates the feedback drive force Fcx for each wheel 10, i.e., the feedback drive force Fcfl for the front left wheel 10 fl, the feedback drive force Fcfr for the front right wheel 10 fr, the feedback drive force Fcrl for the rear left wheel 10 rl, and the feedback drive force Fcrr for the rear right wheel 10 rr. The feedback drive force Fcx is used as a summary label for the feedback drive forces Fcfl, Fcfr, Fcrl, and Fcrr. The vehicle motion control is executed such that the difference between the target yaw rate and the actual yaw rate detected by the yaw rate sensor exceeds the allowable value, or that at least one of the roll state amount, the pitch state amount, and the lift state amount exceeds the allowable value. Thus, the processing in step S 16 is skipped when the vehicle movement control does not need to be executed.For example, the feedback drive force Fcx for each wheel 10 is calculated using a target roll moment Mx for preventing a roll motion of the vehicle body about a longitudinal axis (roll axis) passing through the center of gravity Cg of the vehicle, a target pitch moment My for preventing a pitch motion of the vehicle body about a lateral axis (pitch axis) passing through the center of gravity Cg of the vehicle, a target yaw moment Mz for rotating the vehicle body about a vertical axis (yaw axis) passing through the center of gravity Cg of the vehicle, and a target lifting force Fz for preventing a lifting motion (springs) being a vertical motion at the position of the center of gravity Cg of the vehicle. Various known calculation means may be used to calculate these set points. For example, the ECU 50 uses the sensor values detected by the stroke sensors and the sprung mass vertical acceleration sensors to detect the positions, the speeds, and the accelerations in the vertical direction at the four wheels, thereby detecting the roll state amount, the pitch state amount, and the lift state amount, respectively, and calculates the target roll torque Mx, the target pitch torque My, and the target lift force Fz having predetermined relationships with these state amounts. Further, based on the difference between the target yaw rate set based on the steering angle and the vehicle speed and the actual yaw rate detected by the yaw rate sensor, the ECU 50 calculates the target yaw moment Mz that is set so as to eliminate the difference.The ECU 50 calculates the feedback drive forces Fcfl, Fcfr, Fcrl, and Fcrr using the following equation, for example.Here, the symbol tf represents a wheel gauge between the left and right front wheels 10f and the symbol tr represents a wheel gauge between the left and right rear wheels 10r. The symbol Lf represents a horizontal longitudinal distance between the center of gravity Cg of the vehicle and a center of the left or right front wheel 10 f, and the symbol Lr represents a horizontal longitudinal distance between the center of gravity Cg of the vehicle and a center of the left or right rear wheel 10 r.In this case, the ECU 50 selects three of the target roll torque Mx, the target pitch torque My, the target yaw torque Mz, and the target lifting force Fz to calculate the feedback drive forces Fcfl, Fcfr, Fcrl, and Fcrr, because the drive forces to be ultimately generated to the respective wheels 10 are determined by the driver-requested drive force F*. In other words, there is a boundary condition that a sum of the feedback drive forces Fcfl, Fcfr, Fcrl, and Fcrr is set to zero, so that the four target values cannot be used for calculation at the same time. In this case, when the yaw motion control is necessary, the ECU 50 preferably selects the target yaw moment Mz and the target roll moment Mx, and uses these two target values Mz and Mx and any remaining one of the target pitch moment My and the target lifting force Fz for calculation.When the yaw motion is controlled as described above, the front wheel roll torque Mxf and the rear wheel roll torque Mxr which are opposite to each other and different in magnitude from each other are generated, and roll control is executed in which the front wheel roll torque Mxf and the rear wheel roll torque Mxr are balanced. In this case, the conversion rate (tan(θf)) for converting the driving force to the front wheel 10 finto the vertical force is smaller than the conversion rate (tan(θr)) for converting the driving force to the rear wheel 10 rinto the vertical force, so that when the roll control is performed simultaneously with the yaw motion control, as shown in FIG. 8, the calculation is performed such that the control driving forces Fcfl and Fcfr for the front wheel 10 fare larger than the control driving forces Fcrl and Fcrr for the rear wheel 10 r(comparison of the absolute values).Subsequently, in step S 17, the ECU 50 calculates a final target driving force Fx for each wheel 10, that is, a target driving force Ffl for the front left wheel 10 fl, a target driving force Ffr for the front right wheel 10 fr, a target driving force Frl for the rear left wheel 10 rl, and a target driving force Frr for the rear right wheel 10 rr, by the following equations.Note that the target driving forces Ffl, Ffr, Frl, and Frr are collectively referred to as target driving force Fx.Subsequently, in step S 18, the ECU 50 converts the target driving force Fx into a target motor torque Tx for driving the motor 30, and outputs a drive command signal corresponding to the target motor torque Tx to the motor driver 35. When the target motor torque Tx represents a driving torque, a current flows from the motor driver 35 to the motor 30, and when the target motor torque Tx represents a braking torque, a current flows from the motor 30 to the battery 60 via the motor driver 35, The current running control or the regeneration control is thus applied to the motors 30, resulting in generation of the target driving force Fx on each wheel 10.The ECU 50 outputs the drive command signal to the motor driver 35 and then ends a first pass of the motor drive control routine. Subsequently, the ECU 50 repeats the motor drive control routine in the predetermined short cycle.When the yaw motion is controlled by the driving force of the engine 30, the engine travel control routine distributes the driver-demanded driving force F* more to the rear wheel 10 rthan to the front wheel 10 f. Therefore, even when a roll control is executed in which the roll torque generated on the front wheel 10 fside and the roll torque generated on the rear wheel 10 rside are balanced as shown in FIG. 6, the target driving force Fx (=F) to the front wheel 10 fl, which is the turned-in outer front wheel, can be prevented. In other words, the driver-requested distributed driving force Fdx (=Fd·a) to the front wheel 10 flis smaller than the driver-requested distributed driving force Fdx (=Fd·(1-α)) to the rear wheel 10 rl, so that a large margin for applying the control driving force Fcx on the front wheel 10 fside can be secured, and even when the roll control is executed simultaneously with the roll movement control, the target driving force Fx to the front wheel 10 fl hardly reaches the output limit value. Thus, the roll control performed during the yaw motion control can be satisfactorily performed.Further, when the yaw motion control is not executed, an equal distribution of the driver-demanded driving force F* is set to the front left wheel, the front right wheel, the rear left wheel, and the rear right wheel. As a result, the tire generation forces can be equalized, causing an improvement in vehicle stability.Further, the distribution of the driver-demanded driving force F* to the front and rear wheels is set so that the reserve vertical force acting on the vehicle body B by the driving force on the wheel 10 is the same on the front wheel 10 fside as on the rear wheel 10 rside. Therefore, the distribution of the driving force to the front and rear wheels can be made more balanced. As a result, the driving force on a specific wheel 10 is more reliably prevented from reaching the threshold value earlier. Further, when the driver required driving force F is less than a predetermined set value, the driver required driving force F* is transmitted only to the rear wheel 10 r. Accordingly, when the driver required driving force is small, the driver required driving force can be appropriately distributed to the front and rear wheels.The vehicle braking / driving force control device according to this embodiment is described above, but the present invention is not limited to the above-described embodiment, but may be modified in various ways without departing from the spirit of the invention.< Example of Distribution Switching Condition>For example, in this embodiment, the driver required driving force F* is switched from the front / rear wheel equal distribution to the rear wheel preferable distribution when the vehicle motion control including the yaw motion control is executed (S13), since the distribution of the control driving force for the yaw motion control can be set to different values for the front and rear wheels, so that the switching is particularly effective. However, the present invention is not limited to this case, but the driver required driving force F* may also be switched from the front / rear wheel equal distribution to the rear wheel preferable distribution when vehicle motion control not limited to the yaw motion control is executed. For example, in step S 13, when at least one motion state amount can be detected from a roll motion amount (such as the roll moment), a vertical motion amount (such as the vertical force), and a pitch motion amount (such as the pitch moment) of the vehicle, and the detected motion state amount exceeds a setting value (allowable value), the distribution of the driver-requested driving force F* can be switched to the front and rear wheels. Even in this case, while preventing the front wheel motor 30 ffrom reaching the output limit value earlier, a large vertical force can be generated on the front wheel 10 fside.Further, in this embodiment, when the distribution switching condition is satisfied, the distribution of the driver-requested driving force F* is switched from the front / rear wheel equal distribution to the rear wheel preferred distribution. However, for example, a configuration may be provided in which the shifting condition is not provided and in the distribution of the driver-requested driving force F*, the rear wheel 10 ris weighted more and more than the front wheel 10 f.< Example of Distribution Ratio>In this embodiment, the distribution of the driver-demanded driving force F* to the front and rear wheels is set so that the reserve vertical force that can act on the vehicle body B by the driving force on the wheel 10 is equal to that on the front wheel 10 fside as on the rear wheel 10 rside (S 15). However, the present invention is not limited to this case, but for example, when the shift condition is satisfied in step S 15, a switch to a stronger portion of the rear wheel than the front wheel may be made in the distribution of the driver-requested driving force F*.Further, a configuration may be provided in which the yaw moment acting on the vehicle is detected and the distribution of the driver-demanded driving force F* to the front and rear wheels is adjusted based on this yaw moment. For example, in step S 11, the yaw motion amount (such as the yaw moment) of the vehicle may be detected, and in step S 15, distribution of the driver-requested driving force F* to the front and rear wheels may be adjusted depending on the amount of the detected yaw motion amount. In this case, the proportion of the rear wheel 10 rmay be set to increase stepwise or continuously as the yaw motion amount increases. As a result, the reserve vertical force on the front wheel 10f increases as the yaw motion amount increases, resulting in appropriate roll control caused by the yaw motion.Further, the distribution of the driver-requested driving force F* to the front and rear wheels may be adjusted depending on the motion state amount that is not limited to the yaw motion amount. For example, at least one motion state amount of the roll motion amount (such as the roll moment), the vertical motion amount (such as the vertical force), and the pitch motion amount (such as the pitch moment) of the vehicle may be detected, and in step S 15, the distribution of the driver-requested driving force F* to the front and rear wheels may be adjusted depending on the amount of this motion state amount. In this case, the proportion of the driver-requested driving force F* to the rear wheel 10 rmay be set to increase stepwise or continuously as the moving state amount increases. As a result, the reserve vertical force on the front wheel 10 fincreases as the moving state amount increases, resulting in appropriate vehicle movement control.Further, in this embodiment, when the distribution switching condition is not satisfied, the distribution of the driver-requested driving force F* to the left and right front wheels and the left and right rear wheels is equalized (S 14). However, the proportion may not always be the same. In other words, when the vehicle motion control is executed (Yes in step S 13), the distribution of the driver-requested driving force F* to the front and rear wheels may be switched such that the rear wheel 10 ris weighted more heavily in the distribution of the driver-requested driving force F* than when the vehicle motion control is not executed (No in step S 13). Of course, the distribution of the driver-demanded driving force F* to the front and rear wheels is adjusted in step S15 so that the rear wheel 10r is weighted more than the front wheel 10f.<Modifiziertes Example of Suspension Geometry>For example, this embodiment is applied to a vehicle in which the conversion rate (tan(θr)) in the rear wheel suspension 20 ris greater than the conversion rate (tan(θf)) in the front wheel suspension 20 f. However, this embodiment can also be applied to a vehicle in which the conversion rate (tan(θf)) in the front wheel suspension 20 fis larger than the conversion rate (tan(θr)) in the rear wheel suspension 20 r. In this case, the distribution of the driver-requested driving force F* to the front and rear wheels may be adjusted so that the front wheel 10 fis weighted more than the rear wheel 10 r. Thus, the relationship between the distribution of the driver-requested driving force F* to the front and rear wheels can be reversed from the embodiment also in the various modified examples described above.

Claims

A vehicle braking / driving force control apparatus for performing vehicle motion control, comprising: actuators (30fl, 30fr, 30rl, 30rr) that independently drive a front left wheel (10fl), a front right wheel (10fr), a rear left wheel (10r1), and a rear right wheel (10rr), respectively, and thereby generate a braking / driving force representing both a braking force and a driving force on the front left wheel (10fl), the front right wheel (10fr), the rear left wheel (10rl), and the rear right wheel (10rr); and suspension mechanisms (20fl, 20fr, 20rl, 20rr) that independently generate the front left wheel (10fl), the front right wheel (10fr), respectively, the left rear wheel (10rl) and the right rear wheel (10rr) are coupled to a vehicle body, respectively, and convert the braking / driving force to the left front wheel (10fl), the right front wheel (10fr), the left rear wheel (10r1), and the right rear wheel (10rr) driven by the respective actuators (30fl, 30fr, 30rl, 30rr) into a force in a height direction of the vehicle body (B) such that the conversion rate of the conversion of the braking / driving force into the force in the height direction of the vehicle body (B) is different for the front wheels (10fl, 10fr) and the rear wheels (10r1, 10rr), characterized in that: the vehicle braking / driving force control device further comprises: distribution setting means (50) for setting, when the vehicle motion control is performed, a force distribution of a driver required braking / driving force (F*) set based on a driver operation amount to the front wheels (10fl, 10fr) and the rear wheels (10rl, 10rr) such that a distributed driver required braking / driving force (Fdx) for each of the wheels (10rl, 10rr) coupled to the suspension mechanisms (20rl, 20rr) having a larger conversion rate is larger than a distributed driver required braking / driving force (Fdx) for each of the wheels (10fl, 10fr) coupled to the suspension mechanisms (20fl, 20fr) having a smaller conversion rate, and that a proportion of the driver required braking / driving force (F*) to the wheels (10rl, 10fr) coupled to the suspension mechanisms (20rl, 20rr) having a larger conversion rate of coupled wheels (10rl, 10rr) is larger when the vehicle motion control is executed than when the vehicle control is not executed; target braking / driving force calculating means (50) for calculating, when the vehicle motion control is executed, target braking / driving forces (Fx) for the left front wheel (10fl), the right front wheel (10fr), the left rear wheel (10rl), and the right rear wheel (10rr), respectively, each of the target braking / driving forces (Fx) including the driver-requested braking / driving force (Fdx) and a motion control braking / driving force (Fcx) necessary for the vehicle motion control; and actuator control means (35, 50) for controlling operations of the actuators (30fl, 30fr, 30rl, 30rr) by following the target braking / driving forces (Fx).The vehicle braking / driving force control device according to claim 1, characterized in that when the vehicle motion control is not executed, the distribution setting means sets the force distribution so that the distributed driver-requested braking / driving forces (Fdx) are equal for the left front wheel (10fl), the right front wheel (10fr), the left rear wheel (10rl), and the right rear wheel (10rr).The vehicle braking / driving force control apparatus according to claim 1 or 2, characterized in that the vehicle movement control comprises vehicle yaw movement control.The vehicle braking / driving force control apparatus according to claim 3, characterized in that when the vehicle yaw motion control is executed, the target braking / driving force calculation means (50) calculates the motion control braking / driving forces (Fcx) so that a front wheel roll torque generated by the driving forces of the front wheels (10fl, 10fr) and a rear wheel roll torque generated by the driving forces of the rear wheels (10rl, 10rr) are balanced.The vehicle braking / driving force control device according to any one of claims 1 to 4, characterized in that when the vehicle motion control is performed, the distribution setting means (50) sets the force distribution such that reserve vertical forces that can act on the vehicle body (B) by the braking / driving forces on the left front wheel (10fl), the right front wheel (10fr), the left rear wheel (10rl), and the right rear wheel (10rr) via the suspension mechanisms (20fl, 20fr, 20rl, 20rr) are equal for the front wheels (10fl, 10fr) and the rear wheels (10rl, 10rr).The vehicle braking / driving force control device according to claim 5, characterized in that when the vehicle motion control is performed and the driver required braking / driving force (F*) is less than a set value set in advance, the distribution setting means (50) sets the force distribution so that the driver required braking / driving force (F*) acts only on the wheels (10rl, 10rr) coupled to the suspension mechanisms (20rl, 20rr) with a larger conversion rate.The vehicle braking / driving force control device according to any one of claims 1 to 4, characterized in that when the vehicle motion control is performed, the distribution setting means (50) detects a motion state amount of a vehicle (1) and sets the force distribution depending on the motion state amount.The vehicle braking / driving force control device according to claim 7, characterized in that when the vehicle motion control is performed, the distribution setting means (50) sets the force distribution such that the distribution ratio increases as the motion state amount increases.

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