JP2009046091A - Braking force control device, driving force control device, and braking and driving force control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stabilize a vehicle behavior while maintaining appropriate deceleration capability. <P>SOLUTION: A hydraulic braking force control device 30 which controls a braking force generation device (hydraulic braking means 21FL, 21FR, 21RL, 21RR or brake actuator 23, etc) that can apply braking forces of individual magnitudes to at least rear wheels 10RL, 10RR comprises: a lateral force calculation means for obtaining a lateral force of the highμroad-side rear wheel 10RL (10RR) which can suppress the vehicle yaw moment generated by the difference between the highμroad-side wheel and the lowμroad-side wheel when a brake is applied at traveling on the road-span surface; a maximum frictional force calculation means for obtaining a maximum frictional force of the rear wheel 10RL (10RR) based on a road friction factor of the highμroad and on the tread weight of the highμroad-side rear wheel 10RL (10RR) when the brake is applied at traveling on the road-span surface; and a target braking force calculation means for obtaining a braking force acting on the highμroad-side rear wheel 10RL (10RR) based on the lateral force and on the maximum frictional force when the brake is applied at traveling on the road-span surface. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a braking force control device that controls braking force generated on a wheel, a driving force control device that controls driving force generated on a wheel, and a braking / driving force that controls braking force and driving force generated on a wheel. The present invention relates to a control device.

  2. Description of the Related Art Conventionally, a technique for suppressing disturbance of vehicle behavior during braking force control or driving force control is known. For example, Patent Document 1 below discloses a technique for stabilizing the behavior of a vehicle by reducing the yaw moment generated in the vehicle during ABS control. In Patent Document 1, an increase in braking force of at least one wheel is limited, thereby reducing the yaw moment.

  In Patent Document 2 below, a target slip rate of each wheel is set from the yaw rate and wheel speed, and the vehicle behavior is stabilized by controlling the braking force of each wheel based on the target slip rate. Is disclosed. Further, in Patent Document 3 below, on a straddle road surface, a braking force reduction amount of a road surface wheel having a high road surface friction coefficient is limited according to a braking force reduction amount of a road surface wheel having a low road surface friction coefficient. Thus, a technique for stabilizing the behavior of a vehicle is disclosed.

JP-A-6-156248 JP-A-5-65059 Japanese Patent Laid-Open No. 7-132816

  However, since the road surface condition is not taken into consideration in the technology of the above-mentioned Patent Document 1, there is a possibility that the braking force is limited more than necessary, and the deceleration performance of the vehicle is lowered than desired. is there. Such an inconvenience can also be considered during driving force control. In other words, in order to suppress the yaw moment acting on the vehicle, the driving force of a certain wheel may be reduced, but if the reduction allowance is not set appropriately, the vehicle behavior can be stabilized even if the vehicle behavior is stabilized. The power may be reduced.

  Therefore, the present invention improves the disadvantages of the conventional example, and provides a braking force control device that makes it possible to stabilize the behavior of the vehicle while exhibiting good deceleration performance, and the behavior of the vehicle while exhibiting good acceleration performance. It is an object of the present invention to provide a driving force control device that makes it possible to stabilize the vehicle and a braking / driving force control device that makes it possible to stabilize the behavior of the vehicle while exhibiting good deceleration performance and acceleration performance.

  In order to achieve the above object, according to the first aspect of the present invention, a braking force generating device capable of applying a braking force of an individual magnitude to at least the left and right wheels of the rear axle in the vehicle traveling direction is controlled. In the braking force control device, the road surface with the high friction coefficient capable of suppressing the yaw moment of the vehicle caused by the difference in braking force between the wheels on the road surface side with the high friction coefficient and the road surface side with the low friction coefficient during the straddle road surface braking operation. Lateral force calculation means for obtaining the lateral force of the wheel on the rear side in the vehicle traveling direction, and the road surface friction coefficient on the road surface with a high friction coefficient and the ground load on the wheel on the rear side in the vehicle traveling direction on the road surface side with the high friction coefficient. Based on the maximum frictional force calculation means for obtaining the maximum frictional force of the wheel during straddle road surface braking operation, and the road side vehicle traveling method with a high friction coefficient during straddle road surface braking operation based on the lateral force and the maximum frictional force Includes a target braking force calculating means, the determining the braking force exerting against the rear wheel.

  The braking force control device according to claim 1 applies the braking force obtained by the target braking force calculation means to the wheels on the rear side in the vehicle traveling direction on the road surface side having a high friction coefficient, so A lateral force for suppressing the yaw moment generated by the braking force difference can be generated. Therefore, in the vehicle during the straddling road surface braking operation, the yaw moment is suppressed and the behavior is stabilized. Further, at that time, the maximum frictional force of the wheel is generated by the braking force and the lateral force with respect to the wheel, and the braking force becomes a minimum magnitude that can be secured while stabilizing the behavior of the vehicle. Therefore, the vehicle braking force having a magnitude that does not impair the deceleration performance requested by the driver can be applied to the vehicle.

  In order to achieve the above object, according to the second aspect of the present invention, there is provided a braking force generator capable of applying a braking force of an individual magnitude to at least the left and right wheels of the rear axle in the vehicle traveling direction. In a braking / driving force control device that controls a driving force generating device capable of applying a driving force of an individual magnitude to the left and right wheels, a road surface side having a high friction coefficient at the time of braking operation or driving operation of the straddling road surface Lateral force calculation means for determining the lateral force of the wheel on the rear side in the vehicle traveling direction on the road surface side of the high friction coefficient capable of suppressing the yaw moment of the vehicle generated by the difference in braking force between the wheels on the road surface side of the low friction coefficient On the basis of the road friction coefficient of the road surface having a high friction coefficient and the ground contact load on the wheel on the rear side in the vehicle traveling direction on the road surface side of the high friction coefficient. The maximum frictional force calculation means for determining the force, and the braking force that acts on the rear wheel in the vehicle traveling direction on the road surface side with a high friction coefficient during the braking operation or driving operation of the straddle road surface based on the lateral force and the maximum friction force Or a target braking / driving force calculating means for obtaining a driving force.

  The braking / driving force control device according to claim 2 applies the braking force determined by the target braking / driving force calculating means during the straddling road surface braking operation to the wheel on the rear side in the vehicle traveling direction on the road surface side having a high friction coefficient. Thus, similarly to the braking force control apparatus according to the first aspect, it is possible to stabilize the behavior of the vehicle and secure the vehicle braking force. Further, the braking / driving force control device according to claim 2 applies the driving force obtained by the target braking / driving force calculating means during the straddling road surface driving operation to the wheel on the rear side in the vehicle traveling direction on the road surface side having a high friction coefficient. By acting, it is possible to generate a lateral force for suppressing the yaw moment generated by the difference in driving force between the left and right wheels. Therefore, in the vehicle during the straddle road surface driving operation, the yaw moment is suppressed and the behavior is stabilized. Further, at that time, the maximum frictional force of the wheel is generated by the driving force and the lateral force with respect to the wheel, and the driving force becomes a minimum magnitude that can be secured while stabilizing the behavior of the vehicle. Therefore, the vehicle driving force having a magnitude that does not impair the acceleration performance requested by the driver can be applied to the vehicle.

  In order to achieve the above object, according to the third aspect of the present invention, a braking force generator capable of applying a braking force of an individual magnitude to each wheel and an individual magnitude for each wheel. Each wheel capable of suppressing the yaw moment of a vehicle generated when changing to a road surface with a different friction coefficient in accordance with a steering operation in a braking / driving force control device that controls a driving force generating device capable of exerting a large driving force A lateral force calculating means for obtaining a lateral force in the vehicle, a maximum frictional force calculating means for obtaining a maximum frictional force of each wheel at the time of transfer based on a road surface friction coefficient of a grounded road surface and a ground contact load on the road surface, And a target braking / driving force calculating means for obtaining a braking force or a driving force to be applied to each wheel during the transfer based on the lateral force and the maximum frictional force.

  The braking / driving force control apparatus according to claim 3 applies the braking force obtained by the target braking / driving force calculating means to each wheel when the vehicle is transferred to a road surface having a different friction coefficient associated with the steering operation. A lateral force necessary for stabilizing the behavior can be generated on the wheel. Therefore, in the vehicle, the yaw moment generated at the time of transfer is suppressed, and the behavior is stabilized. Further, at that time, the maximum frictional force of the wheel is generated by the braking force and the lateral force with respect to the wheel, and the braking force becomes a minimum magnitude that can be secured while stabilizing the behavior of the vehicle. Therefore, the vehicle braking force having a magnitude that does not impair the deceleration performance requested by the driver can be applied to the vehicle. Furthermore, the braking / driving force control device according to claim 3 is configured to apply the driving force obtained by the target braking / driving force calculating means to each wheel when transferring to a road surface having a different friction coefficient associated with a steering operation. A lateral force necessary for stabilizing the behavior of the vehicle can be generated on the wheels. Therefore, in the vehicle, the yaw moment generated at the time of transfer is suppressed, and the behavior is stabilized. Further, at that time, the maximum frictional force of the wheel is generated by the driving force and the lateral force with respect to the wheel, and the driving force becomes a minimum magnitude that can be secured while stabilizing the behavior of the vehicle. Therefore, the vehicle driving force having a magnitude that does not impair the acceleration performance requested by the driver can be applied to the vehicle.

  In order to achieve the above object, in the invention described in claim 4, in the driving force control device for controlling the driving force generator capable of applying a driving force of an individual size to each wheel, Lateral force calculation means for obtaining lateral force at each wheel capable of suppressing the yaw moment of the vehicle generated when changing to a road surface with a different friction coefficient due to a steering operation, a road surface friction coefficient of a grounded road surface and the road surface Maximum frictional force calculating means for determining the maximum frictional force of each wheel at the time of transfer based on the ground load, and target driving for determining a driving force to be applied to each wheel at the time of transfer based on the lateral force and the maximum frictional force Force calculating means.

  The driving force control apparatus according to claim 4 applies the driving force obtained by the target driving force calculating means to each wheel when transferring to a road surface having a different friction coefficient due to a steering operation. Similar to the braking / driving force control device, it is possible to stabilize the behavior of the vehicle and to secure the vehicle driving force.

  The braking force control device according to the present invention can generate a lateral force required for stabilizing the behavior of the vehicle while suppressing a decrease in braking force more than necessary at each wheel, so that the behavior of the vehicle is stabilized. Can also exhibit good deceleration performance. Further, the driving force control device according to the present invention can generate a lateral force required for stabilizing the behavior of the vehicle while suppressing a decrease in the driving force more than necessary at each wheel, so that the behavior of the vehicle is stabilized. Good acceleration performance can be exhibited while trying. Further, the braking / driving force control device according to the present invention can generate a lateral force required to stabilize the behavior of the vehicle while suppressing a decrease in braking force (or driving force) more than necessary at each wheel. Good deceleration performance (or acceleration performance) can be exhibited while stabilizing the behavior of the vehicle.

  Hereinafter, embodiments of a braking force control device, a driving force control device, and a braking / driving force control device according to the present invention will be described in detail with reference to the drawings. The present invention is not limited to the embodiments.

  A braking force control apparatus according to a first embodiment of the present invention will be described with reference to FIGS.

  First, the configuration of the braking force control apparatus according to the first embodiment will be described with reference to FIG. FIG. 1 shows an example of a vehicle to which the braking force control apparatus of the first embodiment is applied.

The vehicle according to the first embodiment is provided with a braking force generator that can apply a braking force of an individual magnitude to at least the left and right wheels of the rear axle in the vehicle traveling direction. For example, here, a braking force is applied to each of the wheels 10FL, 10FR, 10RL, and 10RR, thereby generating a braking force Fb _fl , Fb _fr , Fb _rl , and Fb _rr having individual magnitudes, respectively. The thing provided with the generator is illustrated. In this vehicle, the operation of the braking force generator is controlled, and the braking force for controlling the braking forces Fb _fl , Fb _fr , Fb _rl , and Fb _rr of the respective wheels 10FL, 10FR, 10RL, and 10RR is controlled. A control device is provided. The braking force control device includes a CPU (central processing unit) (not shown), a ROM (Read Only Memory) that stores a predetermined braking force control program in advance, and a RAM (Random Access) that temporarily stores the calculation results of the CPU. Memory) and an electronic control unit (ECU) configured by a backup RAM or the like that stores information prepared in advance.

  For example, in the first embodiment, a mechanical braking force generator that generates a braking force by applying a mechanical braking torque to each of the wheels 10FL, 10FR, 10RL, and 10RR is prepared as the braking force generator. Yes. Here, a so-called hydraulic brake is used as an example of a mechanical braking force generator that generates the mechanical braking torque by a hydraulic force and thereby generates a mechanical braking force on each of the wheels 10FL, 10FR, 10RL, and 10RR. I will give you. Therefore, in the following, this mechanical braking force generator is referred to as “hydraulic braking force generator”, and the mechanical braking torque and braking force generated by this hydraulic braking force generator are respectively referred to as “hydraulic braking torque”. And “hydraulic braking force”.

  Specifically, the hydraulic braking force generator exemplified here includes hydraulic braking means 21FL, 21FR, 21RL, 21RR including calipers, brake pads, disk rotors and the like disposed on the respective wheels 10FL, 10FR, 10RL, 10RR. The hydraulic pipes 22FL, 22FR, 22RL, and 22RR for supplying hydraulic pressure (that is, brake oil as hydraulic oil) to the calipers of these hydraulic brake means 21FL, 21FR, 21RL, and 21RR, and the respective hydraulic pipes 22FL , 22FR, 22RL, 22RR hydraulic pressure adjusting means (hereinafter referred to as "brake actuator") 23, a brake pedal 24 that is operated when the driver generates a braking force on the vehicle, Driven according to the depression of the brake pedal 24 by the driver It includes a brake master cylinder 25, the that.

  Further, although not shown, this hydraulic braking force generator is also provided with a booster for increasing the pressure generated by the depression of the brake pedal 24 and inputting it to the brake master cylinder 25.

Here, the brake actuator 23 includes an oil reservoir, an oil pump, various valve devices such as an increase / decrease control valve for increasing / decreasing the hydraulic pressure of each of the hydraulic pipes 22FL, 22FR, 22RL, 22RR, respectively. These wheels 10FL, 10FR, 10RL, and 10RR are individually configured to perform braking force control, and so-called ABS control can be performed. The pressure increase / decrease control valve is normally controlled by the brake master cylinder 25 to adjust the hydraulic pressure of the caliper in each hydraulic braking means 21FL, 21FR, 21RL, 21RR, and individually for each wheel 10FL, 10FR, 10RL, 10RR. the hydraulic braking force _{Fbo fl, Fbo fr, Fbo rl} , to generate Fbo _rr. On the other hand, this pressure increasing / decreasing control valve is also duty ratio-controlled by the hydraulic braking force control device 30 as the above-described braking force control device as necessary, and the hydraulic pressure applied to the caliper in each hydraulic braking means 21FL, 21FR, 21RL, 21RR. Are respectively adjusted to generate individual hydraulic braking forces Fbo _fl , Fbo _fr , Fbo _rl , and Fbo _rr for the respective wheels 10FL, 10FR, 10RL, and 10RR. In the first embodiment, the respective hydraulic braking force _{Fbo fl, Fbo fr, Fbo rl} , each wheel 10FL Fbo _rr is described above, 10FR, 10RL, brake force Fb _fl of _{10RR, Fb fr, Fb rl,} Fb rr It becomes.

  In the vehicle according to the first embodiment, a drive source such as an internal combustion engine (not shown) is prepared, and the drive torque from the drive source is transmitted to the drive wheels. In the case of a front-wheel drive vehicle, the front wheels 10FL, 10FR are drive wheels, in the case of a rear-wheel drive vehicle, the rear wheels 10RL, 10RR are drive wheels, and in the case of a four-wheel drive vehicle, all wheels 10FL, 10FR, 10RL are used. , 10RR becomes a drive wheel.

  By the way, the wheels 10FL, 10FR, 10RL, and 10RR do not always roll on the road surface having the same road surface friction coefficient. For example, there is a so-called straddle road surface in which the road surface on which the left wheels 10FL and 10RL are on and the road surface on which the right wheels 10FR and 10RR are on has a so-called straddle road surface, and the vehicle travels on the straddle road surface ( Hereinafter, it may be referred to as “crossing road surface travel”. When a braking operation is performed during traveling on the straddling road surface, the hydraulic braking force control device 30 converts the braking force of the wheel on the road surface having a small road surface friction coefficient (hereinafter referred to as “low μ road”) to the road surface friction coefficient. It may be lower than the wheel on the side of a large road surface (hereinafter referred to as “high μ road”). In other words, if the difference in the road friction coefficient between the low μ road and the high μ road in this case is large, the hydraulic braking force control device 30 reduces the braking force of the wheels to prevent the wheels on the low μ road side from being locked. Sometimes.

Accordingly, the yaw moment M acts around the center of gravity of the vehicle due to the difference between the left and right braking forces. For example, FIG. 2 shows an example of a straight-ahead braking state in which the left wheels 10FL and 10RL are on a low μ road and the right wheels 10FR and 10RR are on a high μ road. That is, in the vehicle shown in FIG. 2, the braking force Fb _fl of the front wheel 10FL on the left side of the braking force Fb _fr of the right front wheel 10FR, and the rear wheel 10RL on the left side of the braking force Fb _rr of the right rear wheel 10RR. Braking force _Fbrl becomes lower, and a clockwise yaw moment M is generated on the paper surface of FIG. Note that the braking force Fb _rr of wheels 10RR after the right side of Figure 2 shows an example of application prior to those of the present invention.

The magnitude and direction of the yaw moment M can be derived from Equation 1 below. In Equation 1, “d _f ” represents the tread width of the front wheels 10FL and 10FR, and “d _r ” represents the tread width of the rear wheels 10RL and 10RR.

  Here, when such a yaw moment M works, a slip angle is generated in the vehicle, which may cause a disturbance in behavior. Therefore, in order to prevent such disturbance of the vehicle behavior due to the yaw moment M, the braking force of the wheels on the high μ road side is also reduced, thereby reducing the difference between the left and right braking forces and reducing the yaw moment M. Can be considered. For example, conventionally, a so-called low select control is known in which the braking force is reduced to substantially the same magnitude on the high μ road side in accordance with the low μ road side where the braking force is low. However, when the braking force of the wheel on the high μ road side is reduced more than necessary, the disturbance of the behavior of the vehicle can be suppressed, but the braking force acting on the vehicle (hereinafter referred to as “vehicle braking force”) is greatly increased. And the speed reduction performance desired by the driver may not be exhibited.

  Therefore, in the first embodiment, the braking force control device 30 is caused to execute the braking force control so that the stabilization of the behavior of the vehicle and the desired deceleration performance can be achieved at the time of straddle road braking operation.

Specifically, in the hydraulic braking force control device 30 of the first embodiment, first, the required braking forces Fb _fl-req , Fb _fr-req , Fb _{rl-req for} all the wheels 10FL, 10FR, 10RL, 10RR are used. , Fb _rr-req is determined according to the driver's requested vehicle braking force. Regarding the required braking forces Fb _fl-req , Fb _fr-req , Fb _rl-req , and Fb _rr-req , the lock tendency and slip tendency of the wheels 10FL, 10FR, 10RL, and 10RR are taken into consideration in the same manner as before. While calculating. Therefore, at the time of straddling road surface braking operation, the required braking force of the wheel on the low μ road side is calculated to be lower than the required braking force of the wheel on the high μ road side.

Since the yaw moment M associated with the above-described difference between the left and right braking forces acts on the vehicle at that time, if the yaw moment M increases to such an extent that the behavior of the vehicle is disturbed, the hydraulic braking force control device 30 includes A yaw moment Mr (= −M) in the opposite direction that cancels the yaw moment M is generated in the vehicle. In the first embodiment, a minimum lateral force required for canceling the yaw moment M (hereinafter referred to as “lower limit lateral force”) Fs _{rx-lim is applied} to the rear wheel on the high μ road side. A yaw moment Mr is generated in the vehicle. The relationship between the yaw moment Mr and the lower limit lateral force Fs _rx-lim is expressed by the following formula 2 using the rear length Lr of the wheel base. The hydraulic braking force control device 30 according to the first embodiment is provided with a lateral force calculating means for calculating the lower limit lateral force Fs _rx-lim using the equation (2). Incidentally, the rear length Lr of the wheel base represents the shortest distance between the center of gravity of the vehicle and the axles of the rear wheels 10RL and 10RR when the vehicle is viewed from above, as shown in FIG.

Here, the maximum frictional force (maximum force that can be generated by the high μ road side rear wheel without slipping on the road surface) while applying the above-mentioned lower limit lateral force Fs _rx-lim on the high μ road side rear wheel. If that caused the fmax _rx, while suppressing a significant decrease in the braking force Fb _rx of the rear wheels of the high μ road side, it is possible to cancel the yaw moment M according to the braking force difference between the right and left. Therefore, when there is a possibility that the behavior of the vehicle is disturbed by the yaw moment M, the maximum frictional force Fmax _rx is generated while the above-mentioned lower limit lateral force Fs _rx-lim is applied to the rear wheel on the high μ road side. Therefore, the braking force that satisfies this condition is applied to the rear wheels on the high μ road side. Hereinafter, such a braking force of the rear wheel on the high μ road side is referred to as an “upper limit braking force _Fbrx-lim ”.

In other words, during straddle road braking operation, the lower limit lateral force Fs _rx-lim can be applied to the rear wheel by applying the upper braking force _Fbrx-lim to the rear wheel on the high μ road side. The yaw moment M is cancelled, and the behavior of the vehicle can be guided in the stabilization direction. Further, since the braking force of the rear wheel on the high μ road side at that time can be set to the upper limit braking force _Fbrx-lim , it can be kept to a minimum reduction that can cancel the yaw moment M. It is possible to minimize a decrease in vehicle braking force while suppressing disturbance of the vehicle.

In the first embodiment, as shown in FIG. 3 and the following expression 3, the resultant force of the lower limit lateral force Fs _rx-lim and the upper limit braking force Fb _rx-lim is the maximum friction force Fmax _rx of the rear wheel on the high μ road side. To be.

The maximum frictional force Fmax _rx can be obtained as in the following equation 4 using the maximum road surface friction coefficient μ of the high μ road and the ground load N _rx of the rear wheel on the high μ road side. The hydraulic braking force control device 30 of the first embodiment is provided with a maximum frictional force calculating means for calculating the maximum frictional force Fmax _rx using the equation (4). The maximum road surface friction coefficient μ may be estimated, for example, by using detection values of wheel speed sensors 41FL, 41FR, 41RL, 41RR provided on the wheels 10FL, 10FR, 10RL, 10RR. That is, the estimation may be performed by using the wheel speed difference between the high μ road and the low μ road or the difference in the wheel slip ratio. Further, here, the rear wheels 10RL, load meter 42RL which are respectively provided on 10RR, but to measure the vertical load N _rx of the wheels of interest from 42RR, for the vertical load N _rx, vehicle weight, vehicle center-of-gravity position, You may estimate from a wheelbase, vehicle deceleration, etc.

In the first embodiment, a calculation formula for the upper limit braking force _Fbrx-lim of the rear wheel on the high μ road side is set in advance using the above-described formulas 1 to 4, and the hydraulic control is made using the calculation formula. The power control device 30 is made to obtain the upper limit braking force _Fbrx-lim . The upper limit braking force _Fbrx-lim becomes the target braking force (required braking force) of the rear wheel on the high μ road side when there is a possibility that the behavior of the vehicle is disturbed by the straddling road surface braking operation. Therefore, the hydraulic braking force control device 30 is provided with target braking force calculation means for calculating the upper limit braking force _Fbrx-lim using the calculation formula.

For example, in the case of FIG. 2 described above (when the left wheels 10FL and 10RL are on the low μ road and the right wheels 10FR and 10RR are on the high μ road), the arithmetic expression is expressed as the following Expression 5. The This expression 5 is an arithmetic expression for obtaining the upper limit braking force _Fbrr-lim of the right rear wheel 10RR on the high μ road side shown in FIG. As shown in FIG. 2, the upper limit braking force Fb _rr-lim is combined with the lower limit lateral force Fs _rr-lim of the right rear wheel 10RR on the high μ road side to generate the maximum friction force Fmax _rr on the right rear wheel 10RR. Let When obtaining the calculation formula of Formula 5, the lower limit lateral force “Fs _rx-lim ”, the maximum frictional force “Fmax _rx ”, the upper limit braking force “Fb _rx-lim ” of Formula 2 to Formula 4 described above, For the ground load “N _rx ”, the lower limit lateral force “Fs _rr-lim ”, the maximum frictional force “Fmax _rr ”, the upper limit braking force “Fb _rr-lim ”, the ground load “N _rr ” of the right rear wheel 10RR on the high μ road side, respectively. Is replaced. Further, “A” in the formula 5 is shown in the following formula 6.

In some cases, the left wheels 10FL and 10RL ride on a high μ road and the right wheels 10FR and 10RR ride on a low μ road to perform a straddle road braking operation. In this case as well, there is a possibility that the behavior of the vehicle is disturbed by the yaw moment M due to the difference in braking force between the left and right. In this case, the upper limit braking force Fb _rl-lim of the left rear wheel 10RL on the high μ road side is set. The upper limit braking force Fb _rl-lim may be obtained for the left rear wheel 10RL. An arithmetic expression for obtaining the upper limit braking force Fb _rl-lim of the left rear wheel 10RL can be derived in the same manner as described above, and is expressed as Expression 7 below. “B” in Equation 7 is shown in Equation 8 below.

  Here, the hydraulic braking force control apparatus 30 according to the first embodiment also determines whether or not the road surface is straddling. Such determination may be performed using at least information on the front wheels 10FL and 10FR. For example, the hydraulic braking force control device 30 reads wheel speed information from wheel speed sensors 41FL and 41FR provided on the front wheels 10FL and 10FR, and slips obtained based on wheel speed differences or wheel speeds of the front wheels 10FL and 10FR. Determine from the rate difference. This determination may be performed during a braking operation or may be performed during a non-braking operation. Accordingly, when the braking operation is performed, the lower wheel speed is determined as the low μ road. On the other hand, when it is performed during the non-braking operation, the lower wheel speed or the higher slip rate is determined as the low μ road.

  In order to improve the determination accuracy of the crossing road surface determination, the wheel speed information is read from the wheel speed sensors 41FL, 41FR, 41RL, 41RR of all the wheels 10FL, 10FR, 10RL, 10RR, and the wheel speed difference in each axle is read. Or it is preferable to make a determination using a difference in slip ratio.

  Hereinafter, the operation of the braking force control apparatus (hydraulic braking force control apparatus 30) of the first embodiment will be described based on the flowchart of FIG.

Here, it is assumed that the required braking forces Fb _fl-req , Fb _fr-req , Fb _rl-req , and Fb _{rr-req of} all the wheels 10FL, 10FR, 10RL, and 10RR are already set. In the first embodiment, the required braking forces Fb _rl-req and Fb _rr-req of the rear wheels 10RL and 10RR are provisionally set until it becomes clear which of the left and right road surfaces is a high μ road or a low μ road. Set value. Further, in the first embodiment, when the road surface on the low μ road side becomes clear, the provisional required braking force of the rear wheel on the low μ road side is determined as the final set value.

  First, the hydraulic braking force control device 30 according to the first embodiment performs the determination as to whether or not the traveling road surface is a straddling road surface as described above (step ST1).

If it is determined that the road surface is not a straddling road surface, the hydraulic braking force control device 30 ends this operation. In this case, the hydraulic braking force control device 30 uses the previously set required braking forces Fb _fl-req , Fb _fr-req , Fb _rl-req , and Fb _rr-req to the respective wheels 10FL, 10FR, 10RL, 10RR. To generate.

  On the other hand, when it is determined that the road surface is a straddling road surface, the hydraulic braking force control device 30 determines whether the left or right road surface is a high μ road or a low μ road (here, a high μ road) ( Step ST2). This determination may be performed using information (wheel speed difference or the like) obtained at the time of the determination in step ST1 described above.

Then, when it is determined in step ST2 that the left side is a high μ road, the hydraulic braking force control device 30 sets a left high μ road determination flag (step ST3), and the upper limit braking force Fb _rl− of the left rear wheel 10RL. _lim is obtained from the above-described equations 7 and 8 (step ST4).

In step ST4, the required braking forces Fb _fl-req , Fb _fr-req , and Fb _rr-req of the front wheels 10FL and 10FR and the right rear wheel 10RR determined as set values are respectively set to the braking forces Fb _fl , Substitute into Fb _fr and Fb _rr . Further, in this step ST4, the road surface friction coefficient μ of the high μ road estimated from the information (wheel speed difference etc.) obtained at the time of the determination in the above step ST1 and the load meter 42RL or the vehicle weight is estimated. The ground load N _rr is substituted into Equation 7.

Subsequently, the hydraulic braking force control apparatus 30 according to the first embodiment uses the required braking force Fb _{rl-req of the} left rear wheel 10RL in which the upper limit braking force Fb _{rl-lim of the} left rear wheel 10RL is provisionally set. Is also determined (step ST5). This step ST5 determines whether or not the yaw moment M is generated in the vehicle so that the behavior of the vehicle is disturbed by applying the required braking force Fb _rl-req to the left rear wheel 10RL.

When the hydraulic braking force control device 30 determines that the upper limit braking force Fb _rl-lim is larger than the required braking force Fb _{rl-req, the} hydraulic braking force control device 30 may apply the required braking force Fb _rl-req to the left rear wheel 10RL. It is determined that the behavior of the vehicle is not disturbed, and the required braking force Fb _rl-req is set as the final required braking force Fb _rl-req of the left rear wheel 10RL (step ST6). On the other hand, when it is determined that the upper limit braking force Fb _rl-lim is equal to or less than the required braking force Fb _rl-req , the hydraulic braking force control device 30 _applies the required braking force Fb _rl-req to the left rear wheel 10RL. It is determined that the behavior of the vehicle is disturbed, and the upper limit braking force Fb _{rl-lim is set} to the final required braking force Fb _rl-req of the left rear wheel 10RL (step ST7).

Then, the hydraulic braking force control device 30 performs drive control of the brake actuator 23 so that the required braking force Fb _rl-req set in step ST6 or ST7 is applied to the left rear wheel 10RL (step ST8). . At that time, the required braking forces Fb _fl-req , Fb _fr-req , and Fb _rr-req are also output to the front wheels 10FL and 10FR and the right rear wheel 10RR.

Further, when the hydraulic braking force control device 30 determines that the right side is a high μ road in step ST2, the right side high μ road determination flag is set (step ST9), and in the same manner as the left rear wheel 10RL, The upper limit braking force Fb _rr-lim of the right rear wheel 10RR is obtained from the above _- described equations 5 and 6 (step ST10).

In step ST10, the required braking forces Fb _fl-req , Fb _fr-req , and Fb _rl-req of the front wheels 10FL and 10FR and the left rear wheel 10RL determined as set values are respectively set to the braking forces Fb _fl , Fb _fl , Substitute into Fb _fr and Fb _rl .

Subsequently, the hydraulic braking force control apparatus 30 according to the first embodiment uses the required braking force Fb _{rr-req of the} right rear wheel 10RR in which the upper limit braking force Fb _{rr-lim of the} right rear wheel 10RR is provisionally set. Is also determined as to whether or not (step ST11). This step ST11 determines whether or not the yaw moment M is generated in the vehicle so that the behavior of the vehicle is disturbed by applying the required braking force Fb _rr-req to the right rear wheel 10RR.

When the hydraulic braking force control device 30 determines that the upper limit braking force Fb _rr-lim is larger than the required braking force Fb _{rr-req, the} hydraulic braking force control device 30 may apply the required braking force Fb _rr-req to the right rear wheel 10RR. it is determined that not disturb the behavior of the vehicle, to the required braking force Fb _rr-req final set value of the required braking force Fb _rr-req of the right rear wheel 10RR (step ST12). On the other hand, when it is determined that the upper limit braking force Fb _rr-lim is equal to or less than the required braking force Fb _rr-req , the hydraulic braking force control device 30 _applies the requested braking force Fb _rr-req to the right rear wheel 10RR. It is determined that the behavior of the vehicle is disturbed, and the upper limit braking force Fb _{rr-lim is set} to the final required braking force Fb _rr-req of the right rear wheel 10RR (step ST13).

Then, the hydraulic braking force control device 30 performs drive control of the brake actuator 23 so that the required braking force Fbr _req set in step ST12 or step ST13 is applied to the right rear wheel 10RR (step ST14). . At this time, the required braking forces Fb _fl-req , Fb _fr-req , and Fb _rl-req are also output to the front wheels 10FL and 10FR and the left rear wheel 10RL.

Thereby, in the vehicle of the first embodiment, if there is a possibility of disturbing the behavior of the vehicle, the required braking force Fb _{rl-req of} the left rear wheel 10RL (or the required braking force Fb _{rr-req of the} right rear wheel 10RR). Is made lower than the provisional set value to the upper limit braking force Fb _rl-lim (or the upper limit braking force Fb _rr-lim ), and the braking force control is performed. Therefore, in this vehicle, the lateral force Fs _rl (or lateral force Fs _rr ) that is insufficient for stabilizing the behavior of the vehicle is reduced to the lower limit lateral force Fs _rl-lim (or the lower limit lateral force Fs _rr-lim ). Therefore, the yaw moment Mr described above is generated and the yaw moment Mr accompanying the difference between the left and right braking forces can be canceled out, and the behavior of the vehicle can be stabilized. In this case, the final required braking force Fb _rl-req of the left rear wheel 10RL (or the required braking force Fb _{rr-req of the} right rear wheel 10RR) becomes lower than the provisional value set previously. The left rear wheel 10RL (or the right rear wheel 10RR) generates a maximum friction force Fmax _rl of the left rear wheel 10RL (or a maximum friction force Fmax _rr of the right rear wheel 10RR), and a required braking force Fb _{rl− Since req} (or the required braking force Fb _rr-req ) is a minimum braking force that can be secured while stabilizing the behavior of the vehicle, the vehicle has a magnitude that does not impair the deceleration performance requested by the driver. The vehicle braking force can be applied. That is, since the vehicle braking force larger than the conventional low select control can be applied to the vehicle of the first embodiment, the deceleration performance can be improved.

  Thus, the braking force control device (hydraulic braking force control device 30) of the first embodiment can stabilize the behavior while maintaining the vehicle deceleration performance in a good state. Further, according to this braking force control device, the braking force of the rear wheel on the high μ road side described above is obtained each time according to the state of the straddling road surface (that is, the magnitude of the road surface friction coefficient of each of the left and right road surfaces). Since braking force control is performed, that is, there is no need to prepare control parameters (required braking force to the wheels to be controlled) in advance according to various straddling road surface conditions, etc. Cost can also be reduced.

  By the way, in the first embodiment, the case of forward movement is taken as an example. However, at the time of backward movement, the above-described control target may be changed in the same way by changing from the rear wheel to the front wheel on the high μ road side. That is, the control target of the braking force control apparatus of the first embodiment is a wheel on the rear side in the vehicle traveling direction on the high μ road side.

  Next, a second embodiment of the braking force control apparatus according to the present invention will be described with reference to FIG.

  The braking force control apparatus according to the second embodiment is configured such that the yaw moment M is canceled from an earlier stage where the slip angle is small in the braking force control apparatus according to the first embodiment described above.

Here, in the second embodiment, the same vehicle as that of the first embodiment is illustrated as an application target of the braking force control device. Accordingly, here, a hydraulic braking force control device 30 is prepared as the braking force control device. In the second embodiment, the control mode of the hydraulic braking force control device 30 is changed to specifically describe the embodiment. By canceling the yaw moment M at an early _stage by _obtaining the upper limit braking force _Fbrx-lim of the rear wheel on the high μ road side using an arithmetic expression different from Expression 5 (Expression 6) and Expression 7 (Expression 8). To stabilize the behavior of the vehicle.

Specifically, the arithmetic expression of the second embodiment is derived using the expressions 1 to 3 and the following expression 9 of the first embodiment. Expression 9 represents the relationship among the maximum frictional force Fmax _rx , the lower limit lateral force Fs _rx-lim and the upper limit braking force Fb _rx-lim in the rear wheel on the high μ road side. That is, in the second embodiment, as shown in Equation 9 and FIG. 5, the sum of the magnitudes of the lower limit lateral force Fs _rx-lim and the upper limit braking force Fb _rx-lim is the maximum friction of the rear wheel on the high μ road side. The force Fmax _rx is set.

First, an arithmetic expression when the left wheels 10FL and 10RL are on a low μ road and the right wheels 10FR and 10RR are on a high μ road to perform a straddle road braking operation is expressed as the following Expression 10. . This expression 10 is an arithmetic expression for obtaining the upper limit braking force Fb _rr-lim of the right rear wheel 10RR on the high μ road side in that case. When obtaining the calculation formula of Formula 10, the lower limit lateral force “Fs _rx-lim ”, the maximum frictional force “Fmax _rx ”, and the upper limit braking force “Fb _rx− ” of Formula 2, Formula 3 and Formula 9 described above are _{used. lim} ”, ground contact load“ N _rx ”, the lower limit lateral force“ Fs _rr-lim ”, the maximum frictional force“ Fmax _rr ”, the upper limit braking force“ Fb _rr-lim ”, the ground load Replaced with “N _rr ”. In addition, “A” in the formula 9 is the same as the formula 6 in the first embodiment.

Further, an arithmetic expression when the left wheels 10FL and 10RL are on a high μ road and the right wheels 10FR and 10RR are on a low μ road and perform a road surface braking operation is expressed as the following Expression 11. . This expression 11 is an arithmetic expression for obtaining the upper limit braking force Fb _rl-lim of the left rear wheel 10RL on the high μ road side in that case, and is derived in the same manner as the above expression 10. “B” in the formula 11 is the same as the formula 8 in the first embodiment.

Thus, in the second embodiment, the sum of the magnitudes of the lower limit lateral force Fs _rx-lim and the upper limit braking force Fb _rx-lim is set to the maximum frictional force Fmax _rx of the rear wheel on the high μ road side. Thus, an arithmetic expression for determining the upper limit braking force _Fbrx-lim of the rear wheel is set. For this reason, in the second embodiment, as shown in FIG. 5, there is a margin in the lateral force of the rear wheel on the high μ road side, and the marginal lateral force Fs _rx− necessary to cancel the yaw moment M even when the slip angle is small. _sur can be secured. Therefore, the vehicle of the second embodiment has a stable behavior because the yaw moment M is canceled earlier than the vehicle of the first embodiment.

  As described above, the braking force control device (hydraulic braking force control device 30) of the second embodiment exhibits a vehicle behavior compared to that of the first embodiment while maintaining a good deceleration performance of the vehicle. It can lead to a more stable direction. Further, according to this braking force control apparatus, since the expressions 10 and 11 are simpler than the expressions 5 and 7 of the first embodiment, that is, the square root is not included, the calculation process is simplified and the calculation process is performed. Time can be shortened.

  By the way, in the second embodiment, the case of forward movement is taken as an example. However, at the time of backward movement, the above-described control target may be changed in the same way by changing from the rear wheel to the front wheel on the high μ road side. That is, the control target of the braking force control apparatus according to the second embodiment is a wheel on the rear side in the vehicle traveling direction on the high μ road side.

  Next, a braking / driving force control device according to the present invention will be described as a third embodiment with reference to FIGS.

  First, the configuration of the braking / driving force control device according to the third embodiment will be described with reference to FIG. 6 together with an example of a vehicle to be applied. The vehicle of the third embodiment is provided with a braking force generating device and a driving force generating device capable of applying a braking force and a driving force of individual sizes to at least the left and right wheels of the rear axle in the vehicle traveling direction. It is what was done.

First, the vehicle of the third embodiment is provided with a hydraulic braking force generator (hydraulic braking means 21FL, 21FR, 21RL, 21RR, etc.) and a hydraulic braking force control device 30 similar to those of the vehicles of the first and second embodiments. Has been. That is, here, the hydraulic braking forces Fbo _fl , Fbo _fr , Fbo _rl , and Fbo _rr having individual magnitudes act on the respective wheels 10FL, 10FR, 10RL, and 10RR.

  Further, in the vehicle according to the second embodiment, motors 51FL, 51FR, 51RL, and 51RR are disposed on the respective wheels 10FL, 10FR, 10RL, and 10RR. The operation of each of the motors 51FL, 51FR, 51RL, 51RR is controlled by the motor control device 31 shown in FIG. 6, and applies motor torque to each of the wheels 10FL, 10FR, 10RL, 10RR. Here, the motor torque includes a motor power running torque and a motor regenerative torque. It is noted that each motor 51FL, 51FR, 51RL, 51RR is supplied with power from a battery 61 shown in FIG. 6 in order to generate motor power running torque. On the other hand, when the motor regeneration torque is generated, the electric power obtained thereby is stored in the battery 61.

When each of the motors 51FL, 51FR, 51RL, 51RR is driven with motor power running torque under the control of the motor control device 31, the motor driving force Fdm _fl having an individual magnitude for each of the wheels 10FL, 10FR, 10RL, 10RR. , Fdm _fr , Fdm _rl , Fdm _rr act to move the vehicle forward or backward. For example, when the vehicle is an electric vehicle, the motors 51FL, 51FR, 51RL, 51RR are used as power sources for the vehicle. In the case of a so-called hybrid vehicle in which the vehicle is also equipped with a prime mover such as an internal combustion engine, the motors 51FL, 51FR, 51RL, and 51RR serve as power sources for assisting the power of the prime mover or switching the power with the prime mover. Used. That is, each of the motors 51FL, 51FR, 51RL, and 51RR functions as a driving force generator for the vehicle.

On the other hand, when the motors 51FL, 51FR, 51RL, and 51RR are driven with motor regenerative torque under the control of the motor control device 31, motor regenerative braking forces of individual sizes are applied to the respective wheels 10FL, 10FR, 10RL, and 10RR. Fbm _fl , Fbm _fr , Fbm _rl , and Fbm _rr act to brake the vehicle. That is, each of the motors 51FL, 51FR, 51RL, and 51RR also functions as a braking force generator for the vehicle.

  Here, the vehicle according to the third embodiment is also provided with the hydraulic braking force generator as described above. Therefore, in the third embodiment, the hydraulic braking force generator and the motors 51FL, 51FR, 51RL, 51RR constitute a braking force generator.

In the braking force generator according to the third embodiment, the hydraulic regeneration force Fbo _fl , Fbo _fr , Fbo _rl , Fbo _rr by the hydraulic braking force generator and the motor regeneration by the respective motors 51 FL, 51 FR, 51 RL, 51 RR. The sum of the power Fbm _fl , Fbm _fr , Fbm _rl , Fbm _rr or the motor driving force Fdm _fl , Fdm _fr , Fdm _rl , Fdm _rr is the braking force Fb _{fl of} each wheel 10FL, 10FR, 10RL, 10RR. , Fb _fr , Fb _rl , and Fb _rr . That is, when both the hydraulic braking force generator and the motors 51FL, 51FR, 51RL, 51RR are operated, if the motors 51FL, 51FR, 51RL, 51RR are driven with the motor regenerative torque, the respective wheels 10FL, 10FR. , 10RL, 10RR have braking forces Fb _fl , Fb _fr , Fb _rl , Fb _rr that are larger than the hydraulic braking forces F bo _fl , Fbo _fr , Fbo _rl , Fbo _rr acting at that time. On the other hand, when the motors 51FL, 51FR, 51RL, 51RR are driven with the motor power running torque, the rotational force in the direction opposite to the motor regenerative torque is applied to the wheels 10FL, 10FR, 10RL, 10RR, so that the braking force Fb _{fl, Fb fr, Fb rl,} Fb rr hydraulic braking force Fbo _fl at that time, Fbo _fr, Fbo _rl, smaller than Fbo _rr.

In the third embodiment, an electronic control unit (hereinafter referred to as “brake / motor integrated ECU”) 32 that performs integrated control of the hydraulic braking force generator and the motors 51FL, 51FR, 51RL, 51RR is prepared. The brake / motor integrated ECU 32 gives a command to the hydraulic braking force control device 30 to drive the hydraulic braking force generation device to control the braking force, and gives a command to the motor control device 31 to give a motor 51FL, The braking force control or the driving force control is performed by driving 51FR, 51RL, 51RR. That is, in the third embodiment, the brake / motor integrated ECU 32, the hydraulic braking force control device 30, and the motor control device 31 constitute a braking / driving force control device. The brake / motor integrated ECU 32 of the third embodiment includes a lateral force calculating means for calculating a lower limit lateral force Fs _rx-lim described later and a maximum friction force calculating means for calculating a maximum friction force Fmax _rx described later. And a target braking / driving force calculating means for calculating an upper limit braking force _Fbrx-lim and an upper limit driving force _Fdrx-lim , which will be described later.

Also in the vehicle of the third embodiment configured as described above, the braking force of the wheel on the low μ road side may be lower than the wheel on the high μ road side during the straddle road braking operation. A yaw moment M about the center of gravity of the vehicle acts on the vehicle at such time due to the difference in braking force between the left and right sides. Therefore, when there is a possibility that the behavior of the vehicle may be disturbed by the yaw moment M, the braking force of the rear wheels on the high μ road side is also applied to the third embodiment as in the first and second embodiments. The upper limit braking force _Fbrx-lim is set. As a result, in this vehicle, the yaw moment Mr is generated by the lower limit lateral force Fs _{rx-lim at} that time, so the yaw moment M associated with the left and right braking force difference is canceled and the behavior is led to the stabilization direction. Can do. Further, the maximum frictional force Fmax _rx is generated in the rear wheel on the high μ road side by the upper limit braking force Fb _rx-lim and the lower limit lateral force Fs _rx-lim , and the required braking force Fb _{rx-req at} that time is Since the braking force is the minimum that can be secured while stabilizing the behavior of the vehicle, the vehicle must be applied with the appropriate braking force that does not impair the deceleration performance required by the driver. Will be able to.

Here, the upper limit braking force _Fbrx-lim may be generated by increasing / decreasing any one of the hydraulic braking force, motor regenerative braking force or motor driving force of the rear wheel on the high μ road side. Alternatively, both the hydraulic braking force, the motor regenerative braking force, or the motor driving force of the rear wheel on the high μ road side may be generated by increasing / decreasing control.

By the way, the brake / motor integrated ECU 32 of the third embodiment makes the driving force of the wheel lower than the wheel on the high μ road side in order to prevent the slip of the wheel on the low μ road side when accelerating traveling on the straddle road surface. Sometimes. For this reason, the yaw moment M acts on the vehicle at this time around the center of gravity of the vehicle due to the difference between the left and right driving forces. For example, FIG. 7 shows an example of a straight traveling state in which the left wheels 10FL and 10RL are on a low μ road and the right wheels 10FR and 10RR are on a high μ road. That is, in the vehicle shown in FIG. 7, the driving force Fd _fl of the left front wheel 10FL than the driving force Fd _fr of the right front wheel 10FR and the rear wheel 10RL left of the driving force Fd _rr of the right rear wheel 10RR. The driving force Fd _rl becomes lower and a counterclockwise yaw moment M is generated on the paper surface of FIG. Note that the driving force Fd _rr of the right rear wheel 10RR in FIG. 7 is an example before application of the present invention.

  The magnitude and direction of the yaw moment M can be derived from Equation 12 below.

  Here, when such a yaw moment M is applied, a slip angle may be generated in the vehicle and the behavior may be disturbed similarly to the above-described straddle road braking operation. Therefore, in order to prevent such disturbance of the vehicle behavior due to the yaw moment M, the driving force of the wheels on the high μ road side is also reduced, thereby reducing the difference between the left and right driving forces and reducing the yaw moment M. Can be considered. However, when the driving force of the wheels on the high μ road side is reduced more than necessary, the disturbance of the behavior of the vehicle can be suppressed, but the driving force acting on the vehicle (hereinafter referred to as “vehicle driving force”) is greatly increased. The acceleration performance desired by the driver may not be exhibited.

  Therefore, in the third embodiment, the brake / motor integrated ECU 32 is caused to execute driving force control so that the behavior of the vehicle can be stabilized while exhibiting a desired acceleration performance during the straddle road surface driving operation.

Specifically, the brake / motor integrated ECU 32 first receives the required driving forces Fd _fl-req , Fd _fr-req , Fd _rl-req , and Fd _rr-req for all the wheels 10FL, 10FR, 10RL, and 10RR. The vehicle is requested according to the vehicle driving force requested by the driver. The required driving forces Fd _fl-req , Fd _fr-req , Fd _rl-req , and Fd _rr-req are calculated in consideration of the slip tendency of the wheels 10FL, 10FR, 10RL, and 10RR in the same manner as before. You can do it. Therefore, during the straddle road surface driving operation, the required driving force of the wheel on the low μ road side is calculated to be lower than the required driving force of the wheel on the high μ road side.

Since the yaw moment M associated with the above-described difference between the left and right driving forces acts on the vehicle at that time, if the yaw moment M increases to such an extent that the behavior of the vehicle is disturbed, the brake / motor integrated ECU 32 has a straddle road surface. As in the braking operation, a reverse yaw moment Mr (= −M) that cancels the yaw moment M is generated in the vehicle. Here, the lower limit lateral force Fs _rx-lim having a minimum magnitude necessary for canceling the yaw moment M is applied to the rear wheel on the high μ road side, thereby generating the yaw moment Mr in the vehicle. The relationship between the yaw moment Mr and the lower limit lateral force Fs _rx-lim is expressed by the above-described equation 2 using the rear length Lr of the wheel base as in the straddle road braking operation.

Here, when the maximum frictional force Fmax _rx is generated while the above lower limit lateral force Fs _rx-lim is applied to the rear wheel on the high μ road side, the driving force Fd _rx of the rear wheel on the high μ road side is greatly increased. The yaw moment M due to the difference between the left and right driving forces can be canceled while suppressing the decrease. Therefore, when there is a possibility that the behavior of the vehicle is disturbed by the yaw moment M, the maximum frictional force Fmax _rx is generated while the above-mentioned lower limit lateral force Fs _rx-lim is applied to the rear wheel on the high μ road side. Therefore, the driving force that satisfies this condition is applied to the rear wheels on the high μ road side. Hereinafter, such a driving force of the rear wheel on the high μ road side is referred to as “upper limit driving force Fd _rx-lim ”.

That is, at the time of straddling road surface driving operation, the upper limit driving force Fd _{rx-lim is applied} to the rear wheel on the high μ road side, so that the lower limit lateral force Fs _rx-lim can be applied to the rear wheel. The yaw moment M is cancelled, and the behavior of the vehicle can be guided in the stabilization direction. Further, since the driving force of the rear wheel on the high μ road side at that time can be set to the upper limit driving force Fd _rx-lim , it can be kept to a minimum reduction that can cancel the yaw moment M. It is possible to minimize a decrease in vehicle driving force while suppressing disturbance of the vehicle.

Here, as shown in FIG. 8 and Equation 13 below, the resultant force of the lower limit lateral force Fs _rx-lim and the upper limit drive force Fd _rx-lim is set to the maximum friction force Fmax _rx of the rear wheel on the high μ road side. .

Note that the maximum frictional force Fmax _rx can be obtained by the above-described equation 4 using the maximum road surface friction coefficient μ of the high μ road and the ground load N _rx of the rear wheel on the high μ road side.

In the third embodiment, an arithmetic expression of the upper driving force Fd _rx-lim of the rear wheel on the high μ road side is set in advance using the above-described Expression 2, Expression 4, Expression 12, and Expression 13, and the expression Is used to cause the brake / motor integrated ECU ₃₂ to obtain the upper limit driving force Fd _rx-lim . Here, if this vehicle is the above-described electric vehicle, the motor driving force of the rear wheel on the high μ road side is controlled to increase or decrease, or the hydraulic braking force is applied to the rear wheel on the high μ road side to The upper limit driving force Fd _rx-lim can be generated. When this vehicle is the hybrid vehicle described above, the motor driving force or motor regenerative braking force of the rear wheel on the high μ road side is controlled to increase or decrease, or the motor regenerative braking force or hydraulic braking force is applied to the rear wheel on the high μ road side. By acting, the upper limit driving force Fd _rx-lim can be generated on the rear wheel on the high μ road side.

For example, in the case of FIG. 7 described above (when the left wheels 10FL and 10RL are on the low μ road and the right wheels 10FR and 10RR are on the high μ road), the arithmetic expression is expressed as the following Expression 14. The This expression 14 is an arithmetic expression for obtaining the upper limit driving force Fd _rr-lim of the right rear wheel 10RR on the high μ road side shown in FIG. As shown in FIG. 7, the upper limit driving force Fd _rr-lim generates a maximum frictional force Fmax _rr on the right rear wheel 10RR in combination with the lower limit lateral force Fs _rr-lim of the right rear wheel 10RR on the high μ road side. Let When obtaining the calculation formula of Formula 14, the lower limit lateral force “Fs _rx-lim ”, the maximum frictional force “Fmax _rx ”, and the upper limit drive force “Fd _rx− ” of Formula 2, Formula 4, and Formula 13 described above are _{used. lim} ”, the ground load“ N _rx ”, the lower limit lateral force“ Fs _rr-lim ”, the maximum frictional force“ Fmax _rr ”, the upper limit drive force“ Fd _rr-lim ”, and the ground load, respectively. Replaced with “N _rr ”. Further, “C” in the formula 14 is shown in the following formula 15.

In some cases, the left wheels 10FL and 10RL ride on a high μ road, and the right wheels 10FR and 10RR ride on a low μ road and perform a road surface driving operation. In this case as well, there is a possibility that the behavior of the vehicle is disturbed by the yaw moment M due to the difference between the left and right driving forces. In this case, the upper limit driving force _Fdrl-lim of the left rear wheel 10RL on the high μ road side is The upper limit driving force Fd _rl-lim may be applied to the left rear wheel 10RL. An arithmetic expression for obtaining the upper limit driving force Fd _rl-lim of the left rear wheel 10RL can be derived in the same manner as described above, and is expressed as Expression 16 below. “D” in Equation 16 is shown in Equation 17 below.

  The straddle road surface driving operation of the braking / driving force control device (brake / motor integrated ECU 32, hydraulic braking force control device 30 and motor control device 31) of the third embodiment will be described below with reference to the flowchart of FIG.

Here, it is assumed that the required driving forces Fd _fl-req , Fd _fr-req , Fd _rl-req , and Fd _{rr-req of} all the wheels 10FL, 10FR, 10RL, and 10RR are already set. In the third embodiment, the required driving forces Fd _rl-req and Fd _rr-req of the rear wheels 10RL and 10RR are provisionally determined until it becomes clear which of the left and right road surfaces is a high μ road or a low μ road. Set value. In the third embodiment, when the road surface on the low μ road side becomes clear, the provisional required driving force of the rear wheel on the low μ road side is determined as the final set value.

First, the brake / motor integrated ECU 32 of the third embodiment determines whether or not the running road surface is a straddling road surface in the same manner as in the straddling road braking operation (step ST21). The previously set required driving forces Fd _fl-req , Fd _fr-req , Fd _rl-req , Fd _rr-req are generated for the respective wheels 10FL, 10FR, 10RL, 10RR, and on the straddling road surface. For example, whether the road surface on the left or right is a high μ road or a low μ road (in this case, a high μ road) is determined in the same manner as in the road surface braking operation (step ST22).

When the brake / motor integrated ECU 32 determines that the left side is a high μ road in step ST22, the brake / motor integrated ECU 32 sets a left high μ road determination flag (step ST23), and the upper limit driving force Fd _{rl-lim of the} left rear wheel 10RL. Is obtained from Equation 16 and Equation 17 described above (step ST24).

In step ST24, the required driving forces Fd _fl-req , Fd _fr-req , and Fd _rr-req of the front wheels 10FL and 10FR and the right rear wheel 10RR determined as set values are respectively converted into driving forces Fd _fl , Substitute into Fd _fr and Fd _rr . Further, in this step ST24, the road surface friction coefficient μ of the high μ road estimated from the information (wheel speed difference etc.) obtained in the determination of the above step ST21 and the load meter 42RL or the vehicle weight is estimated. The ground load N _rr is substituted into Equation 16.

Subsequently, the brake / motor integrated ECU 32 of the third embodiment is more than the required driving force Fd _{rl-req of} the left rear wheel 10RL in which the upper limit driving force Fd _{rl-lim of the} left rear wheel 10RL is provisionally set. It is determined whether or not it is larger (step ST25). This step ST25 is to determine whether or not the yaw moment M is generated in the vehicle so that the behavior of the vehicle is disturbed by applying the required driving force Fd _rl-req to the left rear wheel 10RL.

The brake-motor integration ECU32, when judging that the upper limit driving force Fd _rl-lim is greater than the required driving force Fd _rl-req, the vehicle also exert its required driving force Fd _rl-req to the left rear wheel 10RL behavior is determined not to disturb the to the required driving force Fd _rl-req and final required driving force setting value of Fd _rl-req of the left rear wheel 10RL (step ST26). On the other hand, when it is determined that the upper limit driving force Fd _rl-lim is equal to or lower than the required driving force Fd _rl-req , the brake / motor integrated ECU 32 applies the required driving force Fd _rl-req to the left rear wheel 10RL. Is determined to be disturbed, and the upper limit driving force Fd _{rl-lim is set} to the final required driving force Fd _rl-req of the left rear wheel 10RL (step ST27).

Then, the brake / motor integrated ECU 32 performs driving force control so that the required driving force Fd _rl-req set in step ST26 or step ST27 is generated for the left rear wheel 10RL (step ST28). At this time, the required driving forces Fd _fl-req , Fd _fr-req , and Fd _rr-req are also output to the front wheels 10FL and 10FR and the right rear wheel 10RR.

In this step ST28, a command is sent to the motor control device 31 so that the required driving force Fd _{rl-req is applied} to the left rear wheel 10RL, and the motor driving force Fdm _rl of the motor 51RL of the left rear wheel 10RL is the required driving force. What is necessary is just to _{carry out} increase / decrease control so that it may become _Fdrl-req . In order to make the required driving force Fd _rl-req work on the left rear wheel 10RL, if the vehicle is the above-described electric vehicle, the current motor driving force Fdm _rl (> required driving force of the left rear wheel 10RL). Fd _rl-req ) may be kept constant, and a command may be sent to the hydraulic braking force control device 30 to apply the hydraulic braking force Fbo _rl so that the left rear wheel 10RL becomes the required driving force Fd _rl-req . When the vehicle is the hybrid vehicle described above, the left rear wheel 10RL is required to have the required driving force Fd while the driving force (> required driving force Fd _rl-req ) of the left rear wheel 10RL by the current prime mover is kept constant. _The hydraulic braking force Fbo _rl or / and the motor regenerative braking force Fbm _rl may be applied so as to be _rl-req, and the total driving force combining the current driving force of the motor and the motor driving force Fdm _rl in the left rear wheel 10RL. while keeping the (> required driving force Fd _rl-req) to constant or may exert a hydraulic braking force Fbo _rl as the left rear wheel 10RL is required driving force Fd _rl-req.

Further, when the brake / motor integrated ECU 32 determines that the right side is a high μ road in step ST22, the brake / motor integrated ECU 32 sets a right high μ road determination flag (step ST29), and performs the same operation as that for the left rear wheel 10RL. The upper limit driving force Fd _rr-lim of the rear wheel 10RR is obtained from the above _- described equations 14 and 15 (step ST30).

In step ST30, the required driving forces Fd _fl-req , Fd _fr-req , and Fd _rl-req of the front wheels 10FL and 10FR and the left rear wheel 10RL determined as set values are respectively converted into driving forces Fd _fl , Substitute into Fd _fr and Fd _rl .

Subsequently, the brake / motor integrated ECU 32 determines whether or not the upper limit driving force Fd _rr-lim of the right rear wheel 10RR is larger than the required driving force Fd _{rr-req of the} right rear wheel 10RR that is provisionally set. Is determined (step ST31). This step ST31 determines whether or not the yaw moment M is generated in the vehicle so that the behavior of the vehicle is disturbed by applying the required driving force Fd _rr-req to the right rear wheel 10RR.

The brake-motor integration ECU32, when judging that the upper limit driving force Fd _rr-lim is greater than the required driving force Fd _rr-req, the vehicle also exert its required driving force Fd _rr-req to the right rear wheel 10RR behavior is determined not to disturb the to the required driving force Fd _rr-req and final required driving force setting value of Fd _rr-req of the right rear wheel 10RR (step ST32). On the other hand, when it is determined that the upper limit driving force Fd _rr-lim is equal to or less than the required driving force Fd _rr-req , the brake / motor integrated ECU 32 applies the required driving force Fd _rr-req to the right rear wheel 10RR. The upper limit driving force Fd _{rr-lim is set} to the final required driving force Fd _rr-req of the right rear wheel 10RR (step ST33).

The brake / motor integrated ECU 32 controls the driving force in the same manner as the left rear wheel 10RL so that the required driving force Fd _rr-req set in step ST32 or step ST33 is applied to the right rear wheel 10RR. Perform (step ST34). In this case, the required driving forces Fd _fl-req , Fd _fr-req , and Fd _rl-req are also output to the front wheels 10FL and 10FR and the left rear wheel 10RL.

Accordingly, in the vehicle during the straddle road surface driving operation, if there is a possibility of disturbing the behavior of the vehicle, the required driving force Fd _{rl-req of} the left rear wheel 10RL (or the required driving force Fd _rr- of the right rear wheel 10RR _{). req} ) is lowered to the upper limit driving force Fd _rl-lim (or the upper limit driving force Fd _rr-lim ) lower than the provisional set value, and the driving force control is performed. Therefore, in this vehicle, the lateral force Fs _rl (or lateral force Fs _rr ) that is insufficient for stabilizing the behavior of the vehicle is reduced to the lower limit lateral force Fs _rl-lim (or the lower limit lateral force Fs _rr-lim ). As a result, the yaw moment Mr described above is generated and the yaw moment Mr associated with the difference between the left and right driving forces is canceled out, so that the behavior of the vehicle can be stabilized. In this case, the final required driving force Fd _rl-req of the left rear wheel 10RL (or the required driving force Fd _{rr-req of the} right rear wheel 10RR) is lower than the provisional value set previously. The left rear wheel 10RL (or the right rear wheel 10RR) generates the left rear wheel 10RL (the maximum friction force Fmax _rl of the left rear wheel 10RL (or the maximum friction force Fmax _rr of the right rear wheel 10RR)), and the required driving force Fd _{rl at} that time _-req (or the required driving force Fd _rr-req ) is the minimum driving force that can be secured while stabilizing the behavior of the vehicle, and therefore the vehicle has the driving performance requested by the driver (that is, The vehicle driving force of a size that does not impair the acceleration performance) can be applied.

  As described above, the braking / driving force control device (brake / motor integrated ECU 32, hydraulic braking force control device 30 and motor control device 31) of the third embodiment is adapted to the braking performance of the vehicle during braking operation or driving operation of the straddle road surface. The driving performance (in other words, deceleration performance and acceleration performance of the vehicle) can be stabilized while maintaining a good state. Further, according to this braking / driving force control device, the driving force of the rear wheel on the high μ road side described above is obtained each time according to the situation of the straddling road surface (that is, the magnitude of the road surface friction coefficient of each of the left and right road surfaces). Therefore, it is not necessary to prepare control parameters (required driving force for the wheel to be controlled) according to various straddling road surface conditions in advance. And cost reduction.

Here, the maximum frictional force Fmax _rx of the rear wheel on the high μ road side during the straddling road surface driving operation may be determined as the sum of the magnitudes of the lower limit lateral force Fs _rx-lim and the upper limit drive force Fd _rx-lim described above. Well, it can be expressed as in Equation 18 below and FIG. For this reason, in this case, an arithmetic expression for the upper-limit driving force Fd _rx-lim of the rear wheel on the high μ road side is set using Expression 18 and Expression 2, Expression 4, and Expression 12 described above.

First, an arithmetic expression when the left wheels 10FL and 10RL are on a low μ road and the right wheels 10FR and 10RR are on a high μ road and perform a road surface driving operation is expressed as the following Expression 19. . This equation 19 is an arithmetic equation for obtaining the upper limit driving force Fd _rr-lim of the right rear wheel 10RR on the high μ road side in that case. When obtaining the calculation formula of the formula 19, the lower limit lateral force “Fs _rx-lim ”, the maximum friction force “Fmax _rx ”, and the upper limit drive force “Fd _{rx− lim} ”, the ground load“ N _rx ”, the lower limit lateral force“ Fs _rr-lim ”, the maximum frictional force“ Fmax _rr ”, the upper limit drive force“ Fd _rr-lim ”, and the ground load, respectively. Replaced with “N _rr ”. Further, “C” in the equation 19 is the same as the equation 15 described above.

Further, an arithmetic expression when the left wheels 10FL and 10RL are on the high μ road and the right wheels 10FR and 10RR are on the low μ road and perform the road surface driving operation is expressed as the following Expression 20. . Expression 20 is an arithmetic expression for obtaining the upper limit driving force Fd _rl-lim of the left rear wheel 10RL on the high μ road side in that case, and is derived in the same manner as Expression 19 above. “D” in the equation 20 is the same as the equation 17 described above.

By determining the maximum frictional force Fmax _rx of the rear wheel on the high μ road side in this way, the lateral force of the rear wheel on the high μ road side can be afforded as shown in FIG. 10, and the yaw moment can be achieved even when the slip angle is small. The marginal lateral force Fs _rx-sur necessary for canceling M can be secured. Therefore, the behavior of the vehicle here is stabilized by canceling the yaw moment M earlier than the vehicle using Equation 13 described above. In addition, since the expressions 19 and 20 are simpler than the expressions 14 and 16 described above, that is, the square root or the like is not included, the arithmetic processing can be simplified and the arithmetic processing time can be shortened.

  By the way, in the third embodiment, the case of forward movement is taken as an example, but at the time of backward movement, the above-described control target may be changed similarly from the rear wheel to the front wheel on the high μ road side. That is, the control target of the braking / driving force control device according to the third embodiment is a wheel on the rear side in the vehicle traveling direction on the high μ road side.

  Next, another example of the braking / driving force control device according to the present invention will be described as a fourth embodiment with reference to FIG.

  When a turning operation, a lane change, or the like is performed in accordance with a driver's steering operation, the vehicle may transfer from a high μ road to a low μ road. In this case, the maximum frictional force Fmax of the wheel that has moved to the low μ road side is reduced (in other words, the friction circle is reduced), and therefore all or most of the maximum frictional force Fmax is used as the driving force Fd. As a result, the lateral force Fs required for stable running of the vehicle cannot be secured by the wheels, and the behavior of the vehicle may become unstable.

  Thus, in the fourth embodiment, a braking / driving force control device is configured that can suppress the disturbance of the behavior of the vehicle when changing to a low μ road due to a steering operation.

The braking / driving force control device of the fourth embodiment is obtained by adding a driving force control operation at the time of a low μ road transfer accompanying a steering operation in the braking / driving force control device of the above-described third embodiment. It is illustrated as being applied to a similar vehicle. Accordingly, the braking / driving force control device according to the fourth embodiment includes the brake / motor integrated ECU 32, the hydraulic braking force control device 30, and the motor control device 31, as in the third embodiment. Further, the brake / motor integrated ECU 32 of the fourth embodiment includes lateral force calculation means for calculating lower limit lateral forces Fs _fl-lim , Fs _fr-lim , Fs _rl-lim , and Fs _rr-lim , which will be described later. Maximum friction force calculating means for calculating the maximum friction forces Fmax _fl , Fmax _fr , Fmax _rl , Fmax _rr and upper limit braking forces Fb _fl-lim , Fb _fr-lim , Fb _rl-lim , Fb _{rr-lim described later.} And target braking / driving force calculating means for calculating upper limit driving forces Fd _fl-lim , Fd _fr-lim , Fd _rl-lim , and Fd _rr-lim are prepared.

Here, in the braking / driving force control device of the fourth embodiment, specifically, the minimum lateral force (lower limit lateral force) Fs _fl-lim , Fs _fr− is required for stabilizing the behavior of the vehicle. _{lim, Fs rl-lim, Fs} rr-lim is the respective wheels 10FL, 10FR, 10RL, to perform the driving force control so as to act against 10RR. For the lower limit lateral forces Fs _fl-lim , Fs _fr-lim , Fs _rl-lim , and Fs _rr-lim of the respective wheels 10FL, 10FR, 10RL, and 10RR, the right / left load distribution ratio of the vehicle when the steering operation is performed Assuming that “N _L : N _R ”, using the lower limit lateral forces Fs _f-lim and Fs _r-lim on the front wheels 10FL and 10FR and the rear wheels 10RL and 10RR and the left / right load distribution ratio N _L : N _R It can be expressed as shown in Equation 21 to Equation 24. The lower limit lateral forces Fs _f-lim , Fs _{r-lim on the} front wheels 10FL, 10FR side and rear wheels 10RL, 10RR side are the front wheels 10FL, 10FR side and rear wheels 10RL, 10RR side necessary for stabilizing the behavior of the vehicle. It is the minimum lateral force generated in each of the above.

In order to obtain the lower limit lateral forces Fs _fl-lim , Fs _fr-lim , Fs _rl-lim , and Fs _rr-lim of each wheel 10FL, 10FR, 10RL, 10RR from these formulas 21 to 24, the left-right load distribution ratio N _L : N _R and lower limit lateral forces Fs _f-lim , Fs _r-lim on the front wheels 10FL, 10FR side and rear wheels 10RL, 10RR side may be derived.

The left / right load distribution ratio N _L : N _R can be obtained from detected values of load meters 42FL, 42FR, 42RL, 42RR provided on the respective wheels 10FL, 10FR, 10RL, 10RR, for example.

On the other hand, the lower limit lateral forces Fs _f-lim and Fs _r-lim on the front wheels 10FL, 10FR side and the rear wheels 10RL, 10RR side are derived by solving the simultaneous equations of the following equations 25 and 26: And Equation 28, respectively.

The expression 25 is an arithmetic expression for obtaining the lateral force of the vehicle necessary for stabilizing the behavior of the vehicle when the steering wheel 71 shown in FIG. 6 is steered at the steering angle θ. That is, the lateral force of the vehicle can be obtained by “m × Gy” using the vehicle weight m and the vehicle lateral acceleration Gy acting on the vehicle center of gravity, and the lower limit of the front wheels 10FL, 10FR and the rear wheels 10RL, 10RR. It can also be obtained by adding the lateral forces Fs _f-lim and Fs _r-lim (Fs _f-lim + Fs _r-lim ).

Further, the expression 26 is an arithmetic expression for obtaining a yaw moment necessary for stabilizing the behavior of the vehicle (in other words, canceling the yaw moment generated by the steering operation). That is, this yaw moment is used to stabilize the behavior of the vehicle on the side of the rear wheels 10RL and 10RR and the yaw moment “Fs _f-lim × L _f ” generated to stabilize the behavior of the vehicle on the front wheels 10FL and 10FR. It is derived by the yaw moment to be generated “Fs _r-lim × L _r ”. Note that “I _Z ” in the equation 26 represents the yaw moment of inertia acting on the vehicle, and “γ” represents the yaw rate. “L _f ” is the shortest distance between the center of gravity of the vehicle when the vehicle is viewed from above and the axles of the front wheels 10FL and 10FR, and “L _r ” is the center of gravity and the rear wheel of the vehicle when the vehicle is viewed from above. The shortest distance between the 10RL and 10RR axles is shown.

  Here, the vehicle lateral acceleration Gy described above is a lateral acceleration that acts on the center of gravity of the vehicle when the steering wheel 71 is steered to the steering angle θ, and is represented by the following Expression 29. That is, the vehicle lateral acceleration Gy is estimated using the equation 29.

  Each parameter in the equation 29 is as shown below, and the parameters other than the vehicle-specific specified values are derived using known detection methods and estimation methods.

“K _f ” and “K _r ” in Expression 29 indicate the cornering power (that is, the cornering force per unit slip angle) of the front wheels 10FL and 10FR and the rear wheels 10RL and 10RR, respectively. “L” indicates the wheelbase of the vehicle. “V” indicates a vehicle speed, and “n” indicates a steering gear ratio of a steering device (not shown) including the steering wheel 71.

In addition, _"T βθ" and _"T rθ" can be represented by "L = L _f + L _r" as each formula 30 and 31 of the following.

  “S” represents a Laplace operator.

Moreover, "G _Betashita" and "G _R.theta" is a variable can be represented by the respective formulas 32 and 33 below.

Here, “K _h ” in Expression 32 is a variable, and can be obtained using Expression 34 below.

Furthermore, “ω _n ” is a transfer function and indicates the natural angular frequency of the above-described equation 29. “Ζ” is a transfer function and indicates the attenuation coefficient of the above-described expression 29. These “ω _n ” and “ζ” can be obtained using the following equations 35 and 36, respectively.

In the braking / driving force control device according to the fourth embodiment, the lower limit lateral forces Fs _fl-lim , Fs _fr-lim , Fs _rl-lim , and Fs _rr− are applied to the wheels 10FL, 10FR, 10RL, and 10RR, respectively. Driving forces Fd _fl , Fd _fr , Fd _rl , and Fd _rr that can apply _lim are generated. Here, the maximum driving force (upper limit driving force) Fd _fl-lim that can be generated while the lower limit lateral forces Fs _fl-lim , Fs _fr-lim , Fs _rl-lim , and Fs _rr-lim are applied, Let Fd _fr-lim , Fd _rl-lim , and Fd _rr-lim .

Here, after the respective wheels 10RL, upper driving force Fd _rl-lim of 10RR, the arithmetic expression of Fd _rr-lim is deformed equation of Formula 13 described above with arithmetic expression serving formula 37 of maximum friction force Fmax _rx below Using the equation 38, the following equation 39 can be derived.

That is, at the rear wheels 10RL and 10RR, the upper limit driving forces Fd _rl-lim and Fd _rr-lim are used as the driving forces, so that the lower limit lateral forces Fs _rl-lim and Fs _{rr- In} combination with _lim , the maximum frictional forces Fmax _rl and Fmax _rr work.

When calculating the upper limit driving force Fd _rl-lim of the left rear wheel 10RL, the road surface friction coefficient “μ _rx ”, the ground load “N _rx ” and the lower limit lateral force “Fs _rx-lim ” of the equation 39 are respectively left rear. Replace with the road surface friction coefficient “μ _rl ”, the ground load “N _rl ” and the lower limit lateral force “Fs _rl-lim ” in the wheel 10RL. On the other hand, when calculating the upper limit driving force Fd _rr-lim of the right rear wheel 10RR, the road surface friction coefficient “μ _rx ”, the ground load “N _rx ”, and the lower limit lateral force “Fs _rx-lim ” of the equation 39 are The road surface friction coefficient “μ _rr ”, the ground contact load “N _rr ” and the lower limit lateral force “Fs _rr-lim ” in the wheel 10RR are assumed to be replaced. The road surface friction coefficients μ _rl and μ _rr respectively represent the friction coefficients of the road surface on which the left rear wheel 10RL and the right rear wheel 10RR are riding.

Similarly to the upper limit driving forces Fd _rl-lim and Fd _{rr-lim of the} rear wheels 10RL and 10RR, the upper limit driving forces Fd _fl-lim and Fd _fr-lim are calculated for the front wheels 10FL and 10FR. The equation can be derived as the following equation 42 using the following equations 40 and 41. Accordingly, in the front wheels 10FL and 10FR, the upper limit driving forces Fd _fl-lim and Fd _fr-lim are used as the driving forces, so that the lower limit lateral forces Fs _fl-lim and Fs _fr-lim generated at that time are used. The maximum frictional forces Fmax _fl and Fmax _fr work together.

When calculating the upper limit driving force Fd _fl-lim of the left front wheel 10FL, the road surface friction coefficient “μ _fx ”, the ground load “N _fx ” and the lower limit lateral force “Fs _fx-lim ” of the equation 42 are respectively used. _{Replace with the} road surface friction coefficient “μ _fl ”, ground contact load “N _fl ” and lower limit lateral force “Fs _fl-lim ”. On the other hand, when calculating the upper limit driving force Fd _fr-lim of the right front wheel 10FR, the road surface friction coefficient “μ _fx ”, the ground load “N _fx ” and the lower limit lateral force “Fs _fx-lim ” of the equation 42 are respectively used. The road surface friction coefficient “μ _fr ”, the ground load “N _fr ”, and the lower limit lateral force “Fs _fr-lim ” in FIG. The road surface friction coefficients μ _fl and μ _fr respectively represent the friction coefficients of the road surface on which the left front wheel 10FL and the right front wheel 10FR are on.

  In the following, the driving force control operation at the time of low μ road transfer accompanying the steering operation in the braking / driving force control device (brake / motor integrated ECU 32, hydraulic braking force control device 30 and motor control device 31) of the fourth embodiment will be described with reference to FIG. It demonstrates based on the flowchart of these.

Here, the steering operation has already been performed, and the required driving forces Fd _fl-req , Fd _fr-req , Fd _rl-req , and Fd _{rr-req of} all the wheels 10FL, 10FR, 10RL, and 10RR are set as provisional values. It shall be.

First, the brake / motor integrated ECU 32 according to the fourth embodiment includes the road surface friction coefficients μ _fl , μ _fr , μ _rl , μ _rr on the road surface on which each wheel 10FL, 10FR, 10RL, 10RR is riding, and each wheel 10FL. , 10FR, 10RL, and 10RR to determine the ground loads N _fl , N _fr , N _rl , and N _rr (step ST41).

The road surface friction coefficients μ _fl , μ _fr , μ _rl , and μ _rr may be obtained by using the detected values of the wheel speed sensors 41FL, 41FR, 41RL, and 41RR of the respective wheels 10FL, 10FR, 10RL, and 10RR. For example, the road surface friction coefficients μ _fl , μ _fr , μ _rl , and μ _rr are estimated based on the wheel speed changes and slip ratio changes of the respective wheels 10FL, 10FR, 10RL, and 10RR from the detected values. do it. On the other hand, the ground loads N _fl , N _fr , N _rl and N _rr are measured from load meters 42FL, 42FR, 42RL and 42RR provided on the respective wheels 10FL, 10FR, 10RL and 10RR side.

Further, the brake / motor integrated ECU 32 provides lateral forces (lower limit lateral forces Fs _fl-lim , Fs _fr-lim , Fs _{rl-lim) of the} wheels 10FL, 10FR, 10RL, 10RR necessary for stabilizing the behavior of the vehicle. , Fs _rr-lim ) using the above equations 21 to 24 (step ST42).

Further, the brake / motor integrated ECU 32 determines the upper limit driving forces Fd _fl-lim , Fd _fr-lim , Fd _rl-lim , and Fd _rr-lim of the wheels 10FL, 10FR, 10RL, and 10RR. 39 (step ST43). In this calculation, the brake / motor integrated ECU 32 determines the road surface friction coefficients μ _fl , μ _fr , μ _rl , μ _rr and the ground loads N _fl , N _fr , N _rl , N _rr determined in step ST41 and the step ST42. The lower limit lateral forces Fs _fl-lim , Fs _fr-lim , Fs _rl-lim , and Fs _{rr-lim obtained in step 1} are used.

Subsequently, the brake / motor integrated ECU 32 determines the upper limit driving forces Fd _fl-lim , Fd _fr-lim , Fd _rl-lim , Fd _rr-lim and provisional values for each of the wheels 10FL, 10FR, 10RL, 10RR. The required driving forces Fd _fl-req , Fd _fr-req , Fd _rl-req , and Fd _rr-req are compared (step ST44).

The upper limit driving forces Fd _fl-lim , Fd _fr-lim , Fd _rl-lim , Fd _rr-lim are the required driving forces Fd _fl-req , Fd _fr-req , Fd _rl-req , Fd _rr as provisional values. _{For the} wheels 10FL, 10FR, 10RL, and 10RR larger than -req, the required driving forces Fd _fl-req , Fd _fr-req , Fd _rl-req , and Fd _rr-req as final values are used as the final required driving forces. Fd _fl-req , Fd _fr-req , Fd _rl-req , and Fd _rr-req are set (step ST45).

On the other hand, the upper limit driving forces Fd _fl-lim , Fd _fr-lim , Fd _rl-lim , Fd _rr-lim are the required driving forces Fd _fl-req , Fd _fr-req , Fd _rl-req , Fd _rr as provisional values. _{For the} wheels 10FL, 10FR, 10RL, and 10RR that are equal to or less than -req, the upper limit driving forces Fd _fl-lim , Fd _fr-lim , Fd _rl-lim , and Fd _rr-lim are determined as the final required driving force Fd _{fl -req, Fd fr-req, Fd} rl-req, is set as Fd _rr-req (step ST46).

Thereafter, the brake / motor integrated ECU 32 applies the required driving forces Fd _fl-req , Fd _fr-req , Fd _rl-req , and Fd _rr-req set in steps ST45 and ST46 to the wheels 10FL, 10FR, and 10RL, respectively. , 10 RR is executed (step ST47).

In this step ST47, the required driving forces Fd _fl-req , Fd _fr-req , Fd _rl-req , Fd _{fl -req} , Fd _rl-req , Fd _{fl -req} , Fd _rl-req , Fd _rr-req is generated.

That is, the brake / motor integrated ECU 32 causes the required driving forces Fd _fl-req , Fd _fr-req , Fd _rl-req , and Fd _rr-req to act on the wheels 10FL, 10FR, 10RL, and 10RR. A command is sent to the motor 31, and the motor driving forces Fdm _fl , Fdm _fr , Fdm _rl , Fdm _{rr of} the motors 51FL, 51FR, 51RL, 51RR are required driving forces Fd _fl-req , Fd _fr-req , Fd _rl-req , Fd _The increase / decrease control may be performed so as to be _rr-req .

When the vehicle of the fourth embodiment is the electric vehicle illustrated in the third embodiment, the motor driving forces Fdm _fl , Fdm _fr , Fdm _rl , and Fdm _rr (>) of the current wheels 10FL, 10FR, 10RL, and 10RR are as follows. While the required driving forces Fd _fl-req , Fd _fr-req , Fd _rl-req , and Fd _rr-req ) are kept constant, a command is sent to the hydraulic braking force control device 30 so that each wheel 10FL, 10FR, 10RL, 10RR The hydraulic braking forces Fbo _fl , Fbo _fr , Fbo _rl , and Fbo _rr may be applied so that the required driving forces Fd _fl-req , Fd _fr-req , Fd _rl-req , and Fd _rr-req are obtained.

In the case where the vehicle is a hybrid vehicle exemplified in the third embodiment, the driving force of each wheel 10FL, 10FR, 10RL, 10RR by the current prime mover (> required driving force Fd _fl-req , Fd _fr-req , Fd) _rl-req, while maintaining the Fd _rr-req) a constant, the respective wheels 10FL, 10FR, 10RL, 10RR is required driving force _{Fd fl-req, Fd fr-} req, Fd rl-req, the Fd _rr-req hydraulic braking force Fbo _fl, Fbo _fr as, Fbo _rl, Fbo _rr and / or the motor regenerative braking force _{Fbm fl, Fbm fr, Fbm rl} , may exert a Fbm _rr. Further, in the case of this hybrid vehicle, the total driving force (> required) combining the driving force of the current prime mover and the motor driving forces Fdm _fl , Fdm _fr , Fdm _rl , Fdm _rr in each wheel 10FL, 10FR, 10RL, 10RR. The driving forces Fd _fl-req , Fd _fr-req , Fd _rl-req , Fd _rr-req ) are kept constant, and the wheels 10FL, 10FR, 10RL, 10RR are required driving forces Fd _fl-req , Fd _{fr -req} , _{respectively. The} hydraulic braking forces Fbo _fl , Fbo _fr , Fbo _rl , and Fbo _rr may be applied so that _req , Fd _rl-req , and Fd _rr-req are obtained.

As described above, the lateral forces Fs _fl , Fs _fr , Fs _rl , and Fs _rr are insufficient by using the required driving forces Fd _fl-req , Fd _fr-req , Fd _rl-req , and Fd _rr-req as provisional values. For the wheels 10FL, 10FR, 10RL, and 10RR that cause the vehicle behavior to be disturbed, the final required driving forces Fd _fl-req , Fd _fr-req , Fd _rl-req , and Fd _{rr- are determined in step ST46. req} is lowered to upper limit driving forces Fd _fl-lim , Fd _fr-lim , Fd _rl-lim , and Fd _rr-lim lower than the provisional set value. Therefore, in the wheels 10FL, 10FR, 10RL, and 10RR, the lateral forces Fs _fl , Fs _fr , Fs _rl , and Fs _rr that are insufficient for stabilizing the behavior of the vehicle are used as the lower limit lateral forces Fs _fl-lim , Fs _{fr-lim, Fs rl-lim} , can be increased to the Fs _rr-lim, it is possible to generate a yaw moment Mr to cancel the yaw moment M generated when Noriutsuri to low μ road with the steering operation. On the other hand, even if the required driving forces Fd _fl-req , Fd _fr-req , Fd _rl-req , and Fd _rr-req are used as provisional values, the lateral forces Fs _fl , Fs sufficient to stabilize the behavior of the vehicle _fr, Fs _rl, Fs _rr possible securing of wheels 10FL, 10FR, 10RL, for 10RR, in step ST45, the temporary settings final required driving force _{Fd fl-req, Fd fr-} req, _These are set as Fd _rl-req and Fd _rr-req . Therefore, in the vehicle here, lateral forces Fs _fl , Fs _fr , Fs _rl , and Fs _rr that are large enough to stabilize the behavior can be generated by the respective wheels 10FL, 10FR, 10RL, and 10RR. Because it can, the behavior can be stabilized.

Further, in the wheels 10FL, 10FR, 10RL, and 10RR that cause the behavior of the vehicle to be disturbed, the final required driving forces Fd _fl-req , Fd _fr-req , Fd _rl-req , and Fd _rr-req are given first. Although lower than the set provisional value, the maximum frictional forces Fmax _fl , Fmax _fr , Fmax _rl , Fmax _rr are generated, and the required driving forces Fd _fl-req , Fd _fr-req , Fd _rl-req , Fd _{rr -req} is the minimum driving force that can be secured while stabilizing the behavior of the vehicle. On the other hand, in the wheels 10FL, 10FR, 10RL, and 10RR in which sufficient lateral forces Fs _fl , Fs _fr , Fs _rl , and Fs _rr are secured, the provisional values set in advance are the final required driving force Fd _{fl− It is set as req} , Fd _fr-req , Fd _rl-req , Fd _rr-req . Therefore, the vehicle driving force having a magnitude that does not impair the driving performance (that is, acceleration performance) requested by the driver can be applied to the vehicle.

  As described above, the braking / driving force control device (the brake / motor integrated ECU 32, the hydraulic braking force control device 30 and the motor control device 31) of the fourth embodiment has good acceleration performance of the vehicle when the low μ road is transferred due to the steering operation. It is possible to stabilize the behavior while maintaining a stable state.

  By the way, the braking / driving force control device of the fourth embodiment may perform the above-described driving force control even when the high μ road is transferred due to the steering operation. The behavior can be stabilized while keeping the acceleration performance in a good state.

Further, the braking / driving force control device of the fourth embodiment may perform the braking force control equivalent to the above when the braking operation is further performed at the time of the low μ road transfer accompanying the steering operation. It is possible to stabilize the behavior of the vehicle while keeping the vehicle deceleration performance in a good state when changing to a low μ road accompanying a steering operation. In this case, the upper limit driving forces Fd _fl-lim , Fd _fr-lim , Fd _rl-lim , Fd _rr-lim are used as the upper limit braking forces Fb _fl-lim , Fb _fr-lim , Fb _rl-lim , Fb _{rr-lim, respectively.} You can replace it with.

In addition, the driving force control at the time of transfer to a low μ road or a high μ road accompanying the steering operation of the fourth embodiment is applied to a vehicle equipped with a driving force control device. Also good. That is, a driving force generator capable of applying individual driving forces Fd _fl , Fd _fr , Fd _rl , Fd _rr to the wheels 10FL, 10FR, 10RL, 10RR, and the driving force generator A braking force Fb _fl , Fb _fr , Fb _rl , and Fb _rr having individual magnitudes can be applied to the wheels 10FL, 10FR, 10RL, and 10RR. It may be applied to an impossible vehicle. In this case, the driving force control device includes lateral force calculation means for calculating lower limit lateral forces Fs _fl-lim , Fs _fr-lim , Fs _rl-lim , Fs _rr-lim , and maximum frictional forces Fmax _fl , Fmax. _fr, Fmax _rl, a maximum friction force calculating means for performing calculation of Fmax _rr, upper driving force _{Fd fl-lim, Fd fr-} lim, Fd rl-lim, the target driving force calculating means for performing calculation of the Fd _rr-lim and , Is prepared.

  As described above, the braking force control device according to the present invention is useful for a technology that stabilizes the behavior of the vehicle while exhibiting good deceleration performance, and the driving force control device according to the present invention has good acceleration. It is useful for technology that stabilizes the behavior of the vehicle while demonstrating performance, and the braking / driving force control device according to the present invention is useful for technology that stabilizes the behavior of the vehicle while exhibiting good deceleration performance and acceleration performance. It is.

It is a figure which shows the structure of the braking force control apparatus which concerns on this invention. It is a figure shown about an example of the state of the vehicle at the time of the straddle road surface braking operation | movement in Example 1, and a wheel. FIG. 6 is a diagram for explaining a relationship among a maximum friction coefficient, a lower limit lateral force, and an upper limit braking force of a rear wheel on a high μ road side in the first embodiment. It is a flowchart explaining the braking force control operation | movement at the time of the straddle road surface braking operation | movement in the braking force control apparatus of Example 1. FIG. FIG. 10 is a diagram for explaining a relationship among a maximum friction coefficient, a lower limit lateral force, and an upper limit braking force of a rear wheel on a high μ road side in Example 2. It is a figure which shows the structure of the braking / driving force control apparatus which concerns on this invention. It is a figure shown about an example of the state of the vehicle at the time of the straddle road surface drive operation in Example 3, and a wheel. FIG. 10 is a diagram for explaining a relationship among a maximum friction coefficient, a lower limit lateral force, and an upper limit driving force of a rear wheel on a high μ road side in Example 3. 10 is a flowchart illustrating a driving force control operation during a straddle road surface driving operation in the braking / driving force control device according to the third embodiment. FIG. 10 is a diagram for explaining a relationship among a maximum friction coefficient, a lower limit lateral force, and an upper limit driving force of a rear wheel on a high μ road side in Example 3. 10 is a flowchart for explaining a driving force control operation at the time of a low μ road transfer accompanying a steering operation in the braking / driving force control device of the fourth embodiment.

Explanation of symbols

10FL, 10FR, 10RL, 10RR Wheels 21FL, 21FR, 21RL, 21RR Hydraulic braking means 22FL, 22FR, 22RL, 22RR Hydraulic piping 23 Brake actuator 24 Brake pedal 25 Brake master cylinder 30 Hydraulic braking force control device 31 Motor control device 32 Brake Motor integrated ECU
41FL, 41FR, 41RL, 41RR Wheel speed sensor 42FL, 42FR, 42RL, 42RR Load meter 51FL, 51FR, 51RL, 51RR Motor 71 Steering wheel

Claims (4)

In a braking force control device for controlling a braking force generator capable of exerting a braking force of an individual magnitude on at least the left and right wheels of the axle on the rear side in the vehicle traveling direction,
After the vehicle traveling direction on the road surface side of the high friction coefficient that can suppress the yaw moment of the vehicle generated by the difference in braking force between the wheels on the road surface side of the high friction coefficient and the road surface side of the low friction coefficient during the braking operation Lateral force calculation means for obtaining the lateral force of the wheel on the side,
Maximum friction for obtaining the maximum frictional force of the wheel during the straddling road surface braking operation based on the road surface friction coefficient of the road surface with the high friction coefficient and the ground contact load on the wheel on the rear side in the vehicle traveling direction on the road surface side with the high friction coefficient Force calculating means;
A target braking force calculating means for obtaining a braking force to be applied to a wheel on the rear side in the vehicle traveling direction on the road surface side with the high friction coefficient at the time of straddling road surface braking operation based on the lateral force and the maximum friction force;
A braking force control device comprising: A braking force generator capable of applying a braking force of an individual magnitude to at least the left and right wheels of the rear axle in the vehicle traveling direction and a driving force of an individual magnitude to the left and right wheels. In the braking / driving force control device for controlling the driving force generating device,
The road surface side of the high friction coefficient capable of suppressing the yaw moment of the vehicle caused by the difference in braking force between the wheels on the road surface side of the high friction coefficient and the road surface side of the low friction coefficient during braking operation or driving operation of the crossing road surface Lateral force calculating means for determining the lateral force of the wheel on the rear side in the vehicle traveling direction at
Based on the road surface friction coefficient of the road surface having the high friction coefficient and the ground load on the wheel on the rear side in the vehicle traveling direction on the road surface side of the high friction coefficient, the maximum friction of the wheel during the braking operation or driving operation of the straddle road surface Maximum frictional force calculating means for obtaining force;
Based on the lateral force and the maximum frictional force, a target braking / driving operation is performed to obtain a braking force or a driving force to be applied to a wheel on the rear side in the vehicle traveling direction on the road surface side of the high friction coefficient during a braking operation or a driving operation of the straddling road surface. Force calculating means;
A braking / driving force control device comprising: Control of a braking force generator capable of applying a braking force of an individual magnitude to each wheel and a driving force generator capable of applying an individual magnitude of a driving force to each wheel. In the braking / driving force control device to perform,
Lateral force calculation means for obtaining lateral force at each wheel capable of suppressing the yaw moment of the vehicle generated when changing to a road surface with a different friction coefficient due to a steering operation;
A maximum frictional force calculating means for obtaining a maximum frictional force of each wheel at the time of transfer based on the road surface friction coefficient of the grounded road surface and the ground load on the road surface;
Target braking / driving force calculating means for obtaining braking force or driving force to be applied to each wheel at the time of transfer based on the lateral force and the maximum frictional force;
A braking / driving force control device comprising: In a driving force control device for controlling a driving force generator capable of applying a driving force of an individual size to each wheel,
Lateral force calculation means for obtaining lateral force at each wheel capable of suppressing the yaw moment of the vehicle generated when changing to a road surface with a different friction coefficient due to a steering operation;
A maximum frictional force calculating means for obtaining a maximum frictional force of each wheel at the time of transfer based on the road surface friction coefficient of the grounded road surface and the ground load on the road surface;
Target driving force calculating means for obtaining a driving force to be applied to each wheel at the time of transfer based on the lateral force and the maximum frictional force;
A driving force control apparatus comprising:

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