JP7274103B2 - Vehicle attitude control device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle attitude control system, and more particularly to a vehicle attitude control system for controlling the attitude of a vehicle having wheel suspensions configured such that the roll axis of the vehicle body is tilted forward.

Japanese Patent No. 5193885 (Patent Document 1) describes a motion control device for a vehicle. In this vehicle motion control device, different braking forces or driving forces are applied to the left and right wheels based on the yaw moment control command value calculated from the side slip information of the vehicle. As a result, in the invention described in Patent Document 1, acceleration and deceleration are automatically performed in conjunction with the steering wheel operation, skidding is reduced in the limit driving range, and safety performance is improved. That is, in the invention described in Patent Document 1, the yaw motion of the vehicle is controlled by directly applying a yaw moment to the vehicle by applying different braking forces or driving forces to the left and right wheels based on the steering wheel operation of the driver. and

On the other hand, attempts have been made to improve the posture of the vehicle during turning by setting the base suspension of the vehicle. In other words, by setting the base suspension so that the vehicle easily pitches, even when turning with low lateral acceleration, the vehicle body naturally generates an appropriate diagonal roll. . Specifically, by setting the base suspension of the vehicle so that the roll axis of the vehicle body is tilted forward (the front side of the vehicle body is lowered), the vehicle body becomes more prone to pitching motion, and the proper turning motion is achieved. Diagonalol can be produced.

Patent No. 5193885

However, if the base suspension is set so that pitching motion occurs in the vehicle body when turning in a low lateral acceleration region and an appropriate diagonal roll is generated, then in a region where the lateral acceleration is relatively high, the A problem arises in that the inner rear part of the vehicle body tends to be lifted up. Such a phenomenon also occurs in a region where the lateral acceleration is much smaller than the lateral acceleration that causes the vehicle to skid during turning. That is, even in a lateral acceleration range in which the lateral acceleration is relatively small and does not substantially affect the turning performance of the vehicle, the inner rear portion of the vehicle body during turning may rise. In this way, in a vehicle that is set so that the roll axis of the vehicle body is tilted forward, even in an area where the lateral acceleration is not very large, the inside rear portion of the vehicle body may be lifted up while the vehicle is turning. and may cause discomfort to passengers.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a vehicle attitude control system capable of suppressing lifting of the inner rear portion of the vehicle body during turning in a vehicle in which the suspension is set so that the roll axis of the vehicle body tilts forward. and

In order to solve the above-described problems, the present invention provides a vehicle posture control device for controlling the posture of a vehicle in which a wheel suspension system is configured such that the roll axis of the vehicle body is tilted forward. A lateral acceleration sensor that detects acceleration, a brake actuator that applies a braking force to the wheels of the vehicle, a brake control device that generates a braking force by sending a control signal to the brake actuator based on the running state of the vehicle, and a vehicle. and a wheel speed sensor for detecting the wheel speed of the rear wheels. A braking force larger than when the lateral acceleration is small is applied to the inner rear wheels of the vehicle during turning to perform vehicle attitude control to suppress the lifting of the inner rear wheel of the vehicle. The braking force applied to the inner rear wheels of the vehicle is set based on the detected difference in wheel speed between the inner rear wheels and the outer rear wheels and the lateral acceleration of the vehicle.

A vehicle with a wheel suspension system configured so that the roll axis of the vehicle body tilts forward tends to generate pitching motion, and can generate a diagonal roll even when the vehicle turns with a small lateral acceleration. It can improve performance. However, in a vehicle with the roll axis tilted forward in this way, if the lateral acceleration during turning increases to a certain extent, the inner rear part of the vehicle body tends to rise, giving the driver and passengers a sense of uneasiness. A unique technical challenge arises. The present invention solves the technical problem unique to such a vehicle in which the roll axis of the vehicle body is tilted forward. According to the present invention configured as described above, when the vehicle is turning based on the turning operation of the steering wheel, when the lateral acceleration of the vehicle is large, a larger braking force is applied than when the lateral acceleration of the vehicle is small. It acts on the inside rear wheels of the turning vehicle. When a braking force is applied to the inner rear wheel of the vehicle, a force acts to pull down the inner rear portion of the vehicle body via the wheel suspension, thereby suppressing the lifting of the inner rear portion of the vehicle body. The braking force applied to the inside rear wheel does not substantially affect the turning performance of the vehicle, but rather suppresses the lifting of the inside rear wheel of the vehicle, making it difficult for the driver and passengers to feel uneasy. acts on

The lifting of the vehicle body affects the ground load of the rear wheels of the vehicle, and when the inner rear wheel of the vehicle body lifts, the difference in wheel speed between the inner rear wheels and the outer rear wheels of the vehicle changes. In the present invention configured as described above, the braking force applied to the inner rear wheels of the vehicle is set based on the difference in wheel speed between the inner rear wheels and the outer rear wheels and the lateral acceleration of the vehicle. The braking force for suppressing the lifting of the inner rear part of the vehicle body can be set more accurately.

Preferably, the present invention further includes a vehicle speed sensor for detecting the speed of the vehicle, and the brake control device applies a larger braking force when the vehicle speed detected by the vehicle speed sensor is high than when the vehicle speed is low. Act on the inside rear wheels of the vehicle inside.

According to the present invention configured as described above, when the vehicle speed is high, a larger braking force is applied to the inner rear wheels of the vehicle during turning than when the vehicle speed is low, so that appropriate braking is performed according to the vehicle speed. Power can be set.

In the present invention, preferably, an accelerator opening sensor is further provided, and the brake control device provides a larger braking force when the accelerator opening detected by the accelerator opening sensor is large than when the accelerator opening is small. on the inside rear wheels of the turning vehicle.

According to the present invention configured as described above, when the accelerator opening is large, a larger braking force is applied to the inner rear wheels of the vehicle during turning than when the accelerator opening is small. An appropriate braking force can be set according to the

In the present invention, preferably, the vehicle further has a steering angle sensor for detecting a steering angle of a steering wheel of the vehicle, and the brake control device detects a steering angle detected by the steering angle sensor by turning the steering wheel to a predetermined value. In the following cases, the vehicle attitude control is not executed.

According to the present invention configured as described above, when the steering angle due to the turning operation of the steering wheel is equal to or less than the predetermined value, the vehicle attitude control is not executed. It is possible to prevent posture control from intervening and giving the driver a sense of discomfort.

In the present invention, preferably, the brake control device is configured to be capable of executing vehicle attitude control in the low road friction mode and vehicle attitude control in the high road friction mode, and the low road friction mode and the high road friction mode are the same. Different braking forces are generated with respect to lateral acceleration.

The effect of the braking force applied to the inner rear wheel of the vehicle during turning to suppress the vehicle from lifting up differs depending on the magnitude of the road surface friction. According to the present invention configured as described above, different braking forces are generated for the same lateral acceleration in the low road friction mode and the high road friction mode. can be set.

In the present invention, preferably, the brake control device is configured to be capable of executing vehicle attitude control in a high road friction mode and vehicle attitude control in a low road friction mode, and in the high road friction mode, the lateral acceleration of the vehicle is set to the first In the low road friction mode, vehicle attitude control is executed when the lateral acceleration of the vehicle reaches or exceeds a second lateral acceleration different from the first lateral acceleration. be.

The braking force exerted on the inner rear wheel of the vehicle during turning has a different effect of suppressing lift-off depending on the magnitude of road surface friction, and the level of lateral acceleration to which the vehicle attitude control should intervene also varies. According to the present invention configured as described above, vehicle attitude control is executed when the lateral acceleration exceeds the first lateral acceleration in the high road friction mode, and when the lateral acceleration exceeds the second lateral acceleration in the low road friction mode. Therefore, the vehicle attitude control can be started at an appropriate timing according to the road surface friction.

Preferably, the present invention further includes a vehicle speed sensor that detects the speed of the vehicle, and the brake control device changes the conditions for starting vehicle attitude control according to the vehicle speed detected by the vehicle speed sensor.

The effect of the braking force applied to the inside rear wheel of the vehicle during turning to suppress the uplift varies depending on the speed of the vehicle. According to the present invention configured as described above, since the condition for starting the execution of vehicle attitude control is changed according to the vehicle speed, the execution of vehicle attitude control can be started at an appropriate timing according to the vehicle speed. .

In the present invention, the wheel suspension preferably includes a link mechanism for suspending the axle of the rear wheel with respect to the vehicle body, and the link mechanism rotates the axle around a predetermined center of suspension. It is suspended and the center of suspension is located above the axle.

According to the present invention configured as described above, the link mechanism that suspends the axle of the rear wheel with respect to the vehicle body suspends the axle so that the axle rotates around a predetermined center of suspension. By positioning the center of suspension above the axle, when a braking force is applied to the rear wheels, the component of the force that pulls the vehicle downward via the link mechanism becomes greater, resulting in a more effective inner rear portion of the vehicle. can be suppressed.

In the present invention, preferably, the vehicle mechanically controls the wheel speed difference between the inner rear wheels and the outer rear wheels according to the torque respectively acting on the inner rear wheels and the outer rear wheels of the vehicle during turning. The vehicle attitude control device further has an accelerator opening sensor, and the brake control device increases the speed of change in the accelerator opening detected by the accelerator opening sensor, To reduce the braking force acting on the inner rear wheels of a turning vehicle.

According to the present invention configured as described above, the vehicle is equipped with a mechanical limited slip differential device, and due to its function, the larger the accelerator opening, the more rapidly the wheel speed difference between the inner rear wheel and the outer rear wheel is reduced. is reduced. In addition to the action of the differential limiting device, when the brake control device applies braking force to the inner rear wheels based on vehicle attitude control, the change in the wheel speed difference between the inner rear wheels and the outer rear wheels becomes excessive. There is a possibility that the driver may feel uncomfortable. According to the present invention configured as described above, the braking force applied to the inside rear wheel is reduced as the rate of change of the accelerator opening is increased, so that the sense of discomfort given to the driver can be suppressed.

In the present invention, preferably, the brake control device is configured to generate the same braking force regardless of road surface friction on the road surface when the same lateral acceleration is acting on the vehicle during travel. In addition, when the wheel speed difference between the inner rear wheels and the outer rear wheels of the vehicle during turning is equal to or less than a predetermined threshold value, no braking force is applied.

According to the present invention configured as described above, when the same lateral acceleration is acting on the vehicle in motion, the same braking force is generated irrespective of the road surface friction on the road in motion. Therefore, there is no need to change the control according to the road friction, and the control algorithm can be configured simply. Further, according to the present invention configured as described above, braking force is not applied when the wheel speed difference is equal to or less than the predetermined threshold value, so excessive intervention of braking force by the brake control device is suppressed. In addition, in a situation where a braking force is required, an appropriate braking force can be applied to suppress the lifting of the inner rear portion of the vehicle during turning.

According to the vehicle attitude control device of the present invention, even in a vehicle in which the suspension is set so that the roll axis of the vehicle body tilts forward, it is possible to suppress the inner rear portion of the vehicle body from being lifted up during turning.

1 is a layout diagram showing the overall configuration of a vehicle equipped with a vehicle attitude control system according to a first embodiment of the present invention; FIG. FIG. 2 is a diagram schematically showing, from the rear of the vehicle, a structure for suspending an axle of a rear wheel with respect to the vehicle body of the vehicle equipped with the vehicle attitude control device according to the first embodiment of the present invention; 1 is a diagram showing a roll axis of a vehicle body equipped with a vehicle attitude control system according to a first embodiment of the present invention; FIG. FIG. 4 is a diagram schematically illustrating forces acting on the vehicle body when a braking force is applied to the rear wheels of the vehicle equipped with the vehicle attitude control device according to the first embodiment of the present invention; 1 is a block diagram showing a PCM, sensors, etc. mounted on a vehicle equipped with a vehicle attitude control system according to a first embodiment of the present invention; FIG. 4 is a flow chart showing the action of the vehicle attitude control system according to the first embodiment of the present invention; 7 is a flowchart of a subroutine called from the flowchart shown in FIG. 6; 4 is a time chart showing the action of the vehicle attitude control system according to the first embodiment of the present invention on a normal road surface; 5 is a time chart showing the action of the vehicle attitude control system according to the first embodiment of the present invention on a road surface with a low friction coefficient; 4 is a map for setting a wheel speed difference threshold in the vehicle attitude control system according to the first embodiment of the present invention. 4 is a map of steering angle gains multiplied by basic command values in the vehicle attitude control system according to the first embodiment of the present invention. 4 is a map of an accelerator opening change speed gain to be multiplied by a basic command value in the vehicle attitude control system according to the first embodiment of the present invention; 5 is a map of accelerator opening degree gains multiplied by a basic command value in the vehicle attitude control system according to the first embodiment of the present invention; 4 is a map of lateral acceleration gains multiplied by basic command values in the vehicle attitude control system according to the first embodiment of the present invention; 5 is a map of vehicle speed gains multiplied by a basic command value in the vehicle attitude control system according to the first embodiment of the present invention; 5 is a map of accelerator opening degree gains multiplied by a basic command value in the vehicle attitude control system according to the first embodiment of the present invention; 4 is a map of lateral acceleration gains multiplied by basic command values in the vehicle attitude control system according to the first embodiment of the present invention; 5 is a map of vehicle speed gains multiplied by a basic command value in the vehicle attitude control system according to the first embodiment of the present invention; 4 is a map of a differential rotation gain multiplied by a basic command value for brake LSD control in the vehicle attitude control system according to the first embodiment of the present invention; 9 is a flowchart showing processing for determining command values in a vehicle attitude control system according to a second embodiment of the present invention; 9 is a map of differential rotation gains multiplied by basic command values for brake LSD control in the vehicle attitude control system according to the second embodiment of the present invention.

Preferred embodiments of the present invention will now be described with reference to the accompanying drawings.
First, a vehicle equipped with a vehicle attitude control system according to a first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a layout diagram showing the overall configuration of a vehicle equipped with a vehicle attitude control system according to a first embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a vehicle equipped with a vehicle attitude control system according to this embodiment.
Left and right front wheels 2a and 2b, which are steered wheels, are provided at the front portion of the vehicle body of the vehicle 1, and left and right rear wheels 2c and 2d, which are drive wheels, are provided at the rear portion of the vehicle body. Front wheels 2a, 2b and rear wheels 2c, 2d of the vehicle 1 are respectively supported by suspensions 3, which are wheel suspension devices, with respect to the vehicle body 1a. An engine 4, which is a prime mover for driving the rear wheels 2c and 2d, is mounted on the front portion of the vehicle body 1a of the vehicle 1. As shown in FIG. In this embodiment, the engine 4 is a gasoline engine, but an internal combustion engine such as a diesel engine or an electric motor can also be used as the prime mover. In this embodiment, the vehicle 1 is a so-called FR vehicle in which an engine 4 mounted on the front of the vehicle body 1a drives rear wheels 2c and 2d via a transmission 4a, a propeller shaft 4b, and a differential gear 4c. . Moreover, preferably, the differential gear 4c is provided with a mechanical limited-slip differential device 4d (LSD: Limited-Slip Differential Gear). By providing the differential limiting device 4d, even when the grounding performance of one rear wheel is reduced, a relatively large driving force can be applied to the other rear wheel. However, the present invention can be applied to any drive type vehicle such as a so-called RR vehicle in which an engine mounted in the rear part of the vehicle body drives the rear wheels, or an FF vehicle in which the engine mounted in the front part of the vehicle body drives the front wheels. can be done.

The vehicle 1 is also equipped with a steering device 7 that steers the front wheels 2a and 2b based on the rotation operation of the steering wheel 6. As shown in FIG.
Further, the vehicle 1 includes a brake control system that supplies brake fluid pressure to wheel cylinders and brake calipers (not shown) of the brake device 8, which are brake actuators provided for each wheel. The brake control system includes a hydraulic pump 10 that generates the brake fluid pressure required to generate braking force in the brake device 8 provided for each wheel. The hydraulic pump 10 is driven by electric power supplied from, for example, a battery (not shown), and generates braking force in each brake device 8 even when the brake pedal (not shown) is not depressed. It is possible to generate the brake hydraulic pressure necessary for

The brake control system also includes a valve unit 12 (a valve unit 12 ( Specifically, it has a solenoid valve). For example, the opening of the valve unit 12 is changed by adjusting the amount of power supplied from the battery to the valve unit 12 . The brake control system also includes a hydraulic pressure sensor 13 that detects the hydraulic pressure supplied from the hydraulic pump 10 to the brake device 8 of each wheel. The hydraulic pressure sensor 13 is arranged, for example, at a connecting portion between each valve unit 12 and a hydraulic pressure supply line on the downstream side thereof, detects the hydraulic pressure on the downstream side of each valve unit 12, and outputs the detected value to PCM (Power-train control module) 14.

Furthermore, the brake control system calculates the hydraulic pressure to be independently supplied to each of the wheel cylinders and brake calipers of each wheel based on the braking force command value input from the PCM 14 and the detection value of the hydraulic pressure sensor 13. The rotational speed of the hydraulic pressure pump 10 and the opening degree of the valve unit 12 are controlled according to the hydraulic pressure of .

Next, a suspension structure of a vehicle equipped with the vehicle attitude control system according to the present embodiment and a roll axis of the vehicle body will be described with reference to FIGS. 2 to 4. FIG.
FIG. 2 is a diagram schematically showing the structure for suspending the axles of the rear wheels 2c and 2d from the vehicle body 1a of the vehicle 1, viewed from the rear of the vehicle. FIG. 3 is a diagram showing the roll axis of the vehicle body of the vehicle equipped with the vehicle attitude control system according to the present embodiment. FIG. 4 is a diagram schematically illustrating forces acting on the vehicle body when braking force is applied to the rear wheels of the vehicle.

As shown in FIG. 2 , the axle 2 e of the left rear wheel 2 c of the vehicle 1 is supported by the suspension 3 with respect to the vehicle body 1 a of the vehicle 1 . Specifically, in the example shown in FIG. 2, an axle 2e of a rear wheel 2c is supported by an upper arm 3a and a lower arm 3b, which are link mechanisms that constitute the suspension 3. As shown in FIG. In this manner, lines extending from the upper arm 3a and the lower arm 3b connecting the vehicle body 1a and the rear wheel 2c intersect at the intersection point _P1 . A straight line connecting the intersection point P ₁ and the ground contact point P ₂ of the rear wheel 2c intersects the central axis line A of the vehicle body 1a at a point _PrR . This point P _rR is the central point of the rolling motion of the rear portion of the vehicle body 1a, and the rear portion of the vehicle body 1a rolls around this point P _rR . Since the vehicle 1 is bilaterally symmetrical, the same point P _rR becomes the center point of the rolling motion even when the center point of the rolling motion is obtained for the right rear wheel 2d. The center point _PrF of the rolling motion can also be similarly obtained for the suspension 3 that suspends the front wheels 2a and 2b of the vehicle 1. FIG.

FIG. 3 is a diagram in which the center point P _rR of the rolling motion at the rear portion of the vehicle body 1a and the center point P _rF of the rolling motion at the front portion of the vehicle body 1a obtained in this manner are projected from the side of the vehicle 1. As shown in FIG. The axis _Ar connecting the center point P _rR of the rolling motion of the rear portion of the vehicle body 1a and the center point P _rF of the front portion thereof is the center axis line of the rolling motion of the vehicle body 1a. Therefore, the vehicle body 1a of the vehicle 1 basically rolls around the roll axis _Ar . Further, as shown in FIG. 3, in the present embodiment, the roll axis _Ar of the vehicle 1 is tilted forward so that the front side of the vehicle 1 is lowered. By tilting the roll axis _Ar of the vehicle 1 forward in this manner, an appropriate diagonal roll can be naturally generated when the vehicle 1 turns, thereby improving the turning performance of the vehicle 1. be able to.

Next, forces acting on the vehicle body 1a when braking forces are applied to the rear wheels 2c and 2d of the vehicle 1 will be described with reference to FIG.
As described above, the rear wheels 2c and 2d are suspended by the upper arm 3a and the lower arm 3b that constitute the suspension 3. As shown in FIG. The wheels may be suspended by various suspensions, but in all cases the axles of the wheels can be regarded as pivotally suspended about a given virtual center of suspension. . As shown in FIG. 4, in this embodiment, the rear wheel 2d is suspended so as to rotate around a suspension center point P _S . In this embodiment, the suspension center point P _S is located above the axle 2e of the rear wheel 2d.

により計算することができる。さらに、車両１のホイールベースをｌ_r、車両１の重心Ｇと懸架中心点Ｐ_Sとの間の水平距離をＸ_rとすると、車体１ａの後部を引き下げるように作用するモーメントＭ_alは、数式（１）により計算することができる。

Here, when the braking force is applied to the rear wheel 2d, the rear wheel 2d moves the vehicle body 1a along the line segment l ₁ connecting the rear wheel 2d, the ground contact point P2 of the road surface, and the suspension center point P _S . Pull back backwards. Assuming that the angle between the line segment _l1 and the road surface is _θal , and the frictional force acting between the road surface and the rear wheel 2d is _Fx , the component of the force that pulls the vehicle body 1a downward is:

can be calculated by Further, when the wheelbase of the vehicle 1 is _lr , and the horizontal distance between the center of gravity G of the vehicle 1 and the suspension center point _Ps is _Xr , the _{moment Mal} acting to pull down the rear portion of the vehicle body 1a is given by the following formula: (1) can be calculated.

Thus, by applying a braking force to the rear wheels 2c or 2d of the vehicle 1, the rear portion of the vehicle body 1a can be pulled down. Further, in this embodiment, since the suspension center point P _S is positioned higher than the axle 2e of the rear wheels, the force for pulling down the vehicle body 1a is relatively large.

Next, various sensors mounted on the vehicle 1 will be described with reference to FIG.
FIG. 5 is a block diagram showing the PCM 14 mounted on the vehicle 1 and the sensors and the like connected thereto.

As shown in FIG. 5, the vehicle 1 includes a steering angle sensor 16 for detecting the rotation angle of the steering wheel 6, an accelerator opening sensor 18 for detecting the amount of depression of the accelerator pedal (accelerator opening), and a sensor for detecting the vehicle speed. A vehicle speed sensor 20 is mounted, and detection signals thereof are input to the PCM 14 . Further, the vehicle 1 includes a lateral acceleration sensor 22 for detecting lateral acceleration acting on the vehicle 1, a wheel speed sensor 24 for detecting the wheel speed of each wheel of the vehicle 1, and a valve unit 12 (Fig. 1) downstream side of the valve unit 12 (Fig. 1). A hydraulic pressure sensor 13 for detecting hydraulic pressure is mounted, and detection signals thereof are also input to the PCM 14 . In this embodiment, a sensor for directly measuring lateral acceleration is mounted on vehicle 1 as lateral acceleration sensor 22 . However, the lateral acceleration sensor 22 does not necessarily have to be a sensor that directly measures the lateral acceleration, and the lateral acceleration can be obtained from the detected value measured by another sensor. As used herein, "lateral acceleration sensor" shall include any sensor used to determine lateral acceleration.

Furthermore, the vehicle 1 is configured so that the driver can select a low road friction mode or a high road friction mode according to the road surface conditions during driving. A setting switch 26 is provided. When the driver selects the low road friction mode or the high road friction mode according to the road surface condition with the mode setting switch 26, this setting is input to the PCM 14, and as will be described later, vehicle attitude control according to the road surface condition is performed. executed.

On the other hand, the PCM 14 includes a brake control unit 14a that is a brake control device for controlling the brake device 8, a turning control unit 14b that executes turning control for improving the turning performance of the vehicle 1, and a turning control unit 14b that controls turning of the vehicle 1. A side-slip prevention control unit 14c is built in to perform side-slip prevention control for suppressing side-slip. As will be described later, each of these controllers is configured to send control signals to the engine 4 and brake device 8 to execute vehicle attitude control, turning control, and sideslip prevention control, respectively.

The vehicle attitude control system according to the first embodiment of the present invention includes a steering angle sensor 16 that sends a signal to the PCM 14, an accelerator opening sensor 18, a vehicle speed sensor 20, a lateral acceleration sensor 22, a wheel speed sensor 24, a mode setting switch 26, and , a brake control unit 14a, a turning control unit 14b, and a sideslip prevention control unit 14c built in the PCM 14; It should be noted that the above-described configuration of the vehicle attitude control device can be partially omitted according to the application.

Each control unit of these PCM 14 includes a CPU, various programs interpreted and executed on the CPU (including a basic control program such as an OS and an application program that is started on the OS and realizes a specific function), and programs and It is composed of a computer (not shown) having an internal memory such as ROM and RAM for storing various data.

Next, operation of the vehicle attitude control system according to the first embodiment of the present invention will be described with reference to FIGS. 6 to 19. FIG.
FIG. 6 is a flow chart showing the action of the vehicle attitude control system. FIG. 7 is a flowchart of a subroutine called from the flowchart shown in FIG. FIG. 8 is a time chart showing the action of the vehicle attitude control system on a normal road surface. FIG. 9 is a time chart showing the action of the vehicle attitude control system on a road surface with a low coefficient of friction. 10 to 19 are maps showing various gains used when determining vehicle attitude control command values by the vehicle attitude control system.

The flowchart shown in FIG. 6 is mainly repeatedly executed in the PCM 14 at predetermined time intervals, and is executed to automatically apply a braking force to the vehicle 1 for the purpose of vehicle attitude control and the like.

First, in step S1 of FIG. 6, detection signals from various sensors are read into the PCM 14 from various sensors. The detection signal read in step S1 is used for processing in steps S2 to S4. Specifically, in step S1, a steering angle (rotation angle of the steering wheel 6) [deg] signal from the steering angle sensor 16, an accelerator opening [%] signal from the accelerator opening sensor 18, a vehicle speed sensor A signal of vehicle speed [km/h] from 20 is read. Further, in step S1, the signal of the lateral acceleration [G] from the lateral acceleration sensor 22, the wheel speed [m/sec] of each wheel from the wheel speed sensor 24, and the brake hydraulic pressure [MPa] from the hydraulic pressure sensor 13 are signal is read. A selection signal is read from the mode setting switch 26 to indicate whether the driver is currently selecting the low road friction mode or the high road friction mode.

Next, in step S2, command value determination processing based on vehicle attitude control is executed. Specifically, as the vehicle attitude control, when the vehicle 1 is turning based on the turning operation of the steering wheel 6 of the vehicle 1, in order to suppress the lifting of the inner rear part of the vehicle body 1a of the vehicle 1 during turning, the Apply braking force to the inner rear wheel. For example, when the vehicle 1 turns to the left in FIG. 1, a braking force is applied to the left rear wheel 2c to suppress the lifting of the left rear portion of the vehicle body 1a. In step S2, the flowchart shown in FIG. 7 is called as a subroutine to determine the command value of the braking force to be applied to the inner rear wheels for vehicle attitude control. This vehicle attitude control is executed in a region where the lateral acceleration of the vehicle 1 during cornering is relatively small. 1 braking force is applied.

Preferably, a hydraulic pressure of 0.02 MPa or more and 0.1 MPa or less is applied to the brake device 8 by the hydraulic pump 10 to apply a braking force for vehicle attitude control to the vehicle 1 having a mass of about 960 kg or more and about 1060 kg or less. Generated by adding As a result, when the vehicle 1 turns, the inside rear portion of the vehicle body 1a tends to rise with a certain acceleration. The following small deceleration is given, and the lifting of the inside rear of the car body is suppressed.

Next, in step S3, a command value determination process based on turning control is executed. The turning control is a control executed by the turning control section 14b of the PCM 14 for the purpose of improving the turning performance of the vehicle 1 when the steering angular velocity of the steering wheel 6 exceeds a predetermined value. Further, in this turning control, adjustment of the torque generated by the engine 4 and/or application of braking force by the brake device 8 are executed. When a braking force is applied to the vehicle 1 in turning control, the braking force is applied to the inner rear wheels of the vehicle 1 during turning to generate a yaw moment in the turning direction of the vehicle 1, thereby improving the turning performance of the vehicle 1. are improving.

In the vehicle attitude control for determining the command value in step S2, a braking force is applied to the inner rear wheels of the vehicle 1 during turning, but the turning control is executed in a region where the lateral acceleration is relatively large compared to the vehicle attitude control. In turning control, a larger braking force is applied than in vehicle attitude control. That is, the vehicle attitude control is executed for the purpose of suppressing the lifting of the inner rear portion of the vehicle body 1a when the vehicle 1 turns, whereas the turning control imparts a yaw moment to the vehicle 1 to improve turning performance. It is executed for the purpose of allowing the vehicle to move, and is completely different from turning control. In the present embodiment, the braking force applied for turning control is applied to the brake device 8 by the hydraulic pump 10 with a hydraulic pressure of 0.2 MPa or more and 0.5 MPa or less, which is larger than that for vehicle attitude control. Generated by

Next, in step S4, a command value determination process based on side slip prevention control is executed. Sideslip prevention control is control that is executed by the sideslip prevention control section 14c of the PCM 14 in order to suppress or prevent the vehicle 1 from skidding when turning. This skid prevention control is a control that is executed based on the steering angle of the steering wheel 6 and the lateral acceleration of the vehicle 1, and is executed in a region where the lateral acceleration is much higher than that of the turning control. In the sideslip prevention control, an appropriate braking force is applied to each wheel of the vehicle 1 in order to restore the running state of the vehicle 1 to the cornering run intended by the driver. The braking force applied in sideslip prevention control is much larger than that in turning control. In this embodiment, the braking force acting for skid prevention control is generated by applying a hydraulic pressure of 20 MPa or more, which is greater than that for turning control, to the brake device 8 by the hydraulic pump 10 .

Further, in step S5, based on the command values determined in steps S2 to S4, the PCM 14 transmits a control signal to the braking device 8 to apply the braking force to the vehicle 1. end the processing of The above-described vehicle attitude control, turning control, and sideslip prevention control all apply a braking force to the vehicle 1, but are executed in different running states, and usually these controls are superimposed. is not actually executed.

Next, referring to FIGS. 7 to 19, a command value determination process by vehicle attitude control will be described.
As described above, the flowchart shown in FIG. 7 is a subroutine called from step S2 in the flowchart of FIG. 8 and 9 are time charts showing an example of braking force generated when vehicle attitude control is executed. FIG. 8 shows the case where the vehicle 1 runs on a normal road surface (high-friction road surface), and FIG. 9 shows the case where the vehicle 1 runs on a constant-friction road surface such as a snowy road. In the time charts shown in FIGS. 8 and 9, the horizontal axis represents time, and the vertical axis represents values detected by the steering angle sensor 16, the accelerator opening sensor 18, and the wheel speed sensor 24 in order from the top. 4 shows the wheel speed of the rear wheel and the braking command value given to the inside rear wheel.

First, in step S11 of FIG. 7, the wheel speed difference between the left and right rear wheels 2c and 2d of the vehicle 1 is calculated. Specifically, in step S1 of FIG. 6, the wheel speed difference between the left and right rear wheels 2c and 2d is calculated based on the wheel speed of each wheel read from the wheel speed sensor 24. FIG.

Next, in step S11, it is determined whether or not the "vehicle attitude control flag" is "true". The "vehicle attitude control flag" is changed to "true" when the vehicle 1 starts turning and vehicle attitude control is started based on a predetermined condition, and the cut steering wheel 6 is turned back to turn. is a flag that returns to "false" when the In the example of the time chart shown in FIG. 8, the vehicle 1 has not started turning at time _t0 , so the "vehicle attitude control flag" is "false", and the process of the flowchart of FIG. 7 proceeds to step S16. .

In step S16, the wheel speeds of the inner rear wheel and the outer rear wheel of the vehicle that is turning are compared. If the outer wheel speed is higher, the process proceeds to step S17. The process proceeds to step S21. When the rear wheels are not slipping, the wheel speed of the outer rear wheels is high, and when the inner rear wheels are slipping to some extent, this relationship is reversed. In the example of FIG. 8, the steering wheel 6 is turned by the driver at time _t1 , and the wheel speed of the outer rear wheels of the vehicle 1 that has started turning is high, and the wheel speed of the inner rear wheels is low. goes to step S17.

In step S17, the difference in wheel speed between the outer rear wheel and the inner rear wheel (outer wheel speed - inner wheel speed) is the first wheel speed difference _Ta [m/sec], which is the threshold value of the wheel speed difference. It is determined whether it is greater than If the wheel speed difference between the outer and inner wheels is equal to or less than the first wheel speed difference _Ta , the processing from step S23 onward is executed, and the braking force is not applied by the vehicle attitude control, and the flow chart shown in FIG. terminates the one-time processing of That is, the wheel speed difference between the left and right rear wheels may also be caused by an error in the wheel speed sensor 24, and if the vehicle attitude control is intervened based on a minute wheel speed difference, the driver may feel uncomfortable. Vehicle attitude control is not executed when the wheel speed difference is very small. Note that the first wheel speed difference _Ta , which is the threshold value of the wheel speed difference, is changed based on the vehicle speed of the vehicle 1 . A specific setting of the wheel speed difference threshold will be described later with reference to FIG.

In the example of FIG. 8, when the driver turns the steering wheel 6 at time t ₁ and the vehicle 1 starts turning, the wheel speed difference gradually increases, and the wheel speed difference is the first wheel speed difference. When the speed difference T _a is exceeded, the processing from step S18 onwards is executed.
In step S18, the lateral acceleration detected by the lateral acceleration sensor 22 is higher than a predetermined first lateral acceleration GY _a [G] (1 [G]=9.81 [m/sec ² ]), and the vehicle speed sensor It is determined whether the vehicle speed detected by 20 is higher than a predetermined first vehicle speed V _a [km/h]. If the lateral acceleration is equal to or less than the first lateral acceleration GY _a or the vehicle speed is equal to or less than the first vehicle speed V _a , the processing from step S23 onwards is executed, and braking force is applied by vehicle attitude control. Then, one processing of the flow chart shown in FIG. 7 ends. That is, when the lateral acceleration or vehicle speed is very low, there is little need for vehicle attitude control to intervene, and unnecessary intervention may give the driver a sense of discomfort, so vehicle attitude control is not executed.

On the other hand, when the lateral acceleration exceeds the first lateral acceleration GY _a and the vehicle speed exceeds the first vehicle speed V _a , the processing from step S19 onwards is executed, and braking force is applied by vehicle attitude control. . First, in step S19, the vehicle attitude control flag is changed to "true". In step S19, when the vehicle attitude control flag is changed to "true", the process in the flowchart of FIG. 7 proceeds from step S12 to step S13 during that time. However, in the example shown in FIG. 8, since the mode setting switch 26 has selected the high road friction mode, the process of the flowchart of FIG.

Next, in step S20, a basic command value F _b1 [N] for vehicle attitude control is determined based on the wheel speed difference between the left and right rear wheels. That is, the braking force applied to the inner rear wheels of the vehicle 1 is set based on the difference in wheel speed between the inner rear wheels and the outer rear wheels. This basic command value F _b1 is a command value for the braking force to be applied to the inner rear wheel of the vehicle 1 that is turning _, and a predetermined _coefficient C Calculated by equation (2) by multiplying by _m1 .

Further, in step S25, the basic command value _Fb1 calculated in step S20 is multiplied by various gains to determine the final command value _F1 for vehicle attitude control. The specific processing executed in step S25 will be described later. Next, in step S26, the command values calculated for each control are compared, and the maximum command value is selected as the final command value.

That is, in the flowchart shown in FIG. 7, in addition to the first braking force by the vehicle attitude control calculated in step S20, as will be described later, the lower limit braking force by the pre-brake LSD control calculated in step S15, step S22 A second braking force due to the brake LSD control calculated in is also calculated. At step S26, the maximum braking force is selected from the calculated braking forces, and one processing of the flow chart shown in FIG. 7 ends. When the processing of the flowchart of FIG. 7 is completed, the processing proceeds to step S5 of the flowchart of FIG. 6, where the braking device 8 is controlled so that the selected braking force is applied.

In the example shown in FIG. 8, after the steering wheel 6 starts to be turned at time _t1 , the difference between the wheel speed of the outer rear wheels and the inner rear wheels of the vehicle 1 increases. The braking force command value calculated in (2) also increases. As a result, the braking force applied to the inner rear wheels of the vehicle 1 during turning also increases (time t ₁ to t ₂ in FIG. 8). Next, at time t ₂ in FIG. 8, the driver starts depressing the accelerator pedal, and the wheel speed difference between the left and right rear wheels becomes constant (time t ₂ to t ₃ in FIG. 8). During this period, the command value of the braking force calculated by the formula (2) also becomes constant while maintaining the maximum value.

Next, at time _t3 in FIG. 8, when the driver finishes turning the steering wheel 6 and shifts to holding the steering wheel, the vehicle 1 enters a steady turning state. Along with this, the wheel speeds of the inner and outer rear wheels increase, and the wheel speed difference between the inner and outer rear wheels decreases (time t ₃ to t ₄ in FIG. 8). As a result, the braking force command value calculated by Equation (2) also decreases. Furthermore, at time _t4 in FIG. 8, the wheel speed difference between the inner rear wheel and the outer rear wheel becomes equal to _or less than the first wheel speed difference Ta. , and the command value based on vehicle attitude control becomes zero.

Next, at time _t5 in FIG. 8, the slip of the inner rear wheel increases, the wheel speeds of the inner rear wheel and the outer rear wheel reverse, and the wheel speed of the inner rear wheel increases. As a result, the process in the flowchart of FIG. 7 proceeds from step S16 to step S21, and the processes from step S21 onward in the flowchart of FIG. 7 are executed.

In step S21, it is determined whether or not the wheel speed difference between the outer rear wheel and the inner rear wheel (inner wheel speed - outer wheel speed) is greater than the second wheel speed difference _Tb [m/sec]. be. If the wheel speed difference between the outer and inner wheels is equal to or less than the second wheel speed difference _Tb , the processing from step S23 onward is executed, and the braking force is not applied by the brake LSD control, and the flow chart shown in FIG. terminates the one-time processing of That is, the wheel speed difference between the left and right rear wheels may also be caused by an error in the wheel speed sensor 24, and if the brake LSD control is intervened based on a minute wheel speed difference, the driver may feel uncomfortable. Brake LSD control is not executed when the wheel speed difference is very small.

On the other hand, when the wheel speed difference between the outer rear wheel and the inner rear wheel is larger than the second wheel speed difference _Tb , the process proceeds to step S22, and a second braking force command value based on the brake LSD control is calculated. In this way, the brake control unit 14a applies the second braking force to the inner rear wheels when the wheel speed of the inner rear wheels of the vehicle 1 becomes faster than the wheel speed of the outer rear wheels while the vehicle 1 is turning. Let The brake LSD control is a control for applying brakes to the wheels that are spinning to reduce the wheel speed and avoid the spinning state. ₈ , the wheel speed of the inner drive wheels (rear wheels in this embodiment) of the vehicle 1 during turning exceeds _the wheel speed of the outer drive wheels. The inner drive wheels are starting to spin. When the wheel speed difference increases due to the idle rotation of the inner wheels, the driving force is not transmitted to the outer rear wheels via the differential gear 4c, so braking force is applied to the inner wheels to increase the wheel speed of the inner wheels. Lower.

In step S22, a basic command value F _b2 [N] for brake LSD control is determined based on the wheel speed difference between the left and right rear wheels. The basic command value F _b2 of the braking force by this brake LSD control is the command value of the braking force applied to the inner rear wheel of the turning vehicle 1, and the inner wheel speed V _i and the outer wheel speed V _o is calculated by Equation (3) by multiplying the difference between , by a predetermined coefficient C _m2 .

In the example shown in FIG. 8, at time _t5 , application of braking force based on the brake LSD control is started, whereby the wheel speed of the inner rear wheel is reduced, and at time _t6 , the inner rear wheel and the outer The wheel speed difference between the rear wheels is almost zero. After the wheel speed difference becomes almost zero at time _t6 , the processing in the flowchart of FIG. is not given (time t ₆ to t ₇ in FIG. 8).

Further, in the example shown in FIG. 8, the driver starts to turn the steering wheel 6 back at time _t6 , and at time _t7 completes the turning back and returns to the straight-ahead state to finish turning.
In step S23, it is determined based on the detected value of the steering angle sensor 16 whether or not the steering wheel 6 has been returned. When completed, the process proceeds to step S24. In the present embodiment, the brake control unit 14a controls the vehicle attitude during the period from when the turning operation of the steering wheel ₆ is started at time _t1 in FIG. , to generate a braking force with a brake fluid pressure of about 0.1 MPa or less.

In step S24, the "vehicle posture control flag" is changed to "false" because the steering back is completed and the turning travel is finished. After that, when the flowchart shown in FIG. 7 is executed, the processing proceeds from step S12 to step S16. In this state, even if the mode setting switch 26 is set to the low road friction mode, the braking force based on the pre-brake LSD control is not applied.

Next, referring to FIG. 9, vehicle attitude control when the mode setting switch 26 is set to the low road friction mode will be described.
The time chart shown in FIG. 9 shows an example of vehicle attitude control when the low road friction mode is set. When the low road surface friction mode is set, the flow chart of FIG. 7 differs from the time chart of FIG. 8 in that the processes from step S14 onward are executed. In the processing after step S14, the braking force based on the pre-brake LSD control is calculated. In the time chart of FIG. 9, a solid line indicates a command value for vehicle attitude control, a dashed line indicates a command value for pre-brake LSD control, and a one-dot chain line indicates a command value for brake LSD control.

In this embodiment, the low road friction mode and the high road friction mode are switched by setting the mode setting switch 26 by the driver. On the other hand, as a modification, the present invention can be configured so that each mode is automatically selected together with the setting of the mode setting switch 26 or instead of setting the mode setting switch 26 . For example, the friction coefficient of the road surface is estimated according to the outside air temperature sensor, rain sensor, wiper operation status, slip state of the drive wheels, etc. mounted on the vehicle 1, and if the friction coefficient is equal to or less than a predetermined value, automatic The brake control unit 14a can also be configured so as to set the low road friction mode automatically. In this case, the brake control section 14a also functions as a friction coefficient estimating section that estimates the friction coefficient of the road surface on which the vehicle 1 is traveling.

First, when the driver starts turning the steering wheel 6 at time _t11 in FIG. 9, a wheel speed difference is generated between the inner rear wheel and the outer rear wheel, and vehicle attitude control is started. As a result, in the flowchart of FIG. 7, steps S11->S12->S16->S17->S18->S19->S20->S25->S26 are executed. As a result of this process, when the vehicle attitude control flag is changed to "true" in step S19, the process proceeds from step S12 to step S13 when the flowchart of FIG. is executed.

In step S13, it is determined whether or not the low road friction mode is set. In the example of the time chart of FIG. 9, the low road friction mode is set, so the process proceeds to step S14. In step S14, it is determined whether or not the lateral acceleration detected by lateral acceleration sensor 22 is higher than a predetermined second lateral acceleration GY _b [G]. If the lateral acceleration is equal to or less than the second lateral acceleration _GYb , the process proceeds to step S16, and no braking force is applied by the pre-brake LSD control. In this embodiment, the second lateral acceleration _GYb is set to a value smaller than the first lateral acceleration _GYa . That is, when the lateral acceleration is extremely low, there is little need to intervene in the pre-brake LSD control, and unnecessary intervention may give the driver a sense of discomfort, so the pre-brake LSD control is not executed.

On the other hand, when the lateral acceleration is greater than the second lateral acceleration _GYb , the process proceeds to step S15, and the basic command value _Fb3 of the lower limit braking force by the pre-brake LSD control is determined. In step S15, the basic command value _Fb3 is calculated by Equation (4) by multiplying the maximum value of the most recently set basic command value _Fb1 for vehicle attitude control by a predetermined coefficient _Cm3 .

In this embodiment, the coefficient C _m3 is set to a positive value less than one. That is, the basic command value _Fb3 for the pre-brake LSD control is always set to a value smaller than the maximum value of the basic command value _Fb1 for the vehicle attitude control. In the example shown in FIG. 9, between time t ₁₁ and t ₁₂ , the basic command value F _b1 for vehicle attitude control tends to increase, so its maximum value is updated as needed, and is multiplied by coefficient C _m3 . The basic command value F _b3 also increases. Next, between times t ₁₂ and t ₁₃ , since the basic command value F _b1 for vehicle attitude control is constant at the maximum value, the maximum value is also _constant , and the basic command value F The value of _b3 also becomes a constant value. Further, after time _t13 , the basic command value _Fb1 for vehicle attitude control tends to decrease, but the maximum value is held, and the value of the basic command value _Fb3 obtained by multiplying the maximum value by the coefficient _Cm3 is also held. . The basic command value _Fb3 based on this pre-brake LSD control is maintained until the turning travel is completed at time _t17 and the vehicle attitude control flag is changed to "false" (steps S23→S24). Thus, after the first braking force is applied by the vehicle attitude control, even if the wheel speed difference between the inner rear wheel and the outer rear wheel is reduced, the predetermined lower limit braking force is applied until the turn is completed. The above braking force is maintained.

Thus, the braking force based on the pre-brake LSD control starts applying the braking force again by the brake LSD control after the application of the braking force based on the vehicle attitude control is completed (after time _t14 in FIG. 9). At time t ₁₅ in FIG. 9 ), the braking force applied to the inner rear wheels of the vehicle 1 changes in a short period of time, and is applied for the purpose of suppressing the feeling of discomfort given to the driver. On the other hand, when the high road friction mode is selected, there are few cases where braking force is applied by brake LSD control after application of braking force by vehicle attitude control is completed, and brake LSD control is executed. Even when the brake is applied, the applied braking force is relatively small. Therefore, in the present embodiment, the lower limit braking force by the pre-brake LSD control is set when the low road friction mode is selected, and when the high road friction mode is selected, the pre-brake LSD control is set to It is not executed (steps S13→S16 in FIG. 7). Alternatively, as a modified example, the present invention can be configured so that the pre-brake LSD control is executed even when the high road friction mode is selected. In this case, it is preferable to set the coefficient C _m3 in the high road friction mode to be smaller than the coefficient C _m3 in the low road friction mode.

Subsequently, in the example shown in FIG. 9, the inside rear wheel slips during times t ₁₅ to t ₁₆ , and the basic command value F _b2 for brake LSD control is set. Thus, in the example shown in FIG. 9, the basic command value F _b1 is set by the vehicle attitude control during times t ₁₁ to t ₁₄ , and the basic command value F _b3 by the pre-brake LSD control is set during times t ₁₁ to t ₁₇ . A basic command value F _b2 for brake LSD control is set at times t ₁₅ to t ₁₆ .

In step S25 of FIG. 7, each gain to be multiplied by each basic command value is set, and command values _F1 , _F2 and _F3 obtained by multiplying each basic command value by the gain are calculated. Furthermore, in step S26, these command values F ₁ , F ₂ and F ₃ are compared, the largest command value is adopted, and braking force is applied to the inner rear wheel based on this. The setting of the gain to be multiplied by each basic command value in step S25 will be described later with reference to FIGS. 11 to 19. FIG.

Next, referring to FIG. 10, the setting of the wheel speed difference threshold value (first wheel speed difference T _a ) used in step S17 of FIG. 7 will be described.
FIG. 10 is an example of a map for setting the threshold value of the wheel speed difference, and the value of the first wheel speed difference _Ta [m/sec] in step S17 of FIG. set. The value of the first wheel speed difference T _a is changed based on the vehicle speed of the vehicle 1 detected by the vehicle speed sensor 20 . As shown in FIG. 10, the value of the first wheel speed difference _Ta is maximum when the vehicle speed is 0, decreases as the vehicle speed increases, and reaches a substantially constant value above a predetermined vehicle speed _V1 . Preferably, the value of the vehicle speed V ₁ is set to about 80 to about 110 [km/h] per hour _. /sec].

Thus, by changing the threshold value of the wheel speed difference according to the vehicle speed, the condition for starting the execution of the vehicle attitude control is changed. That is, by setting the first wheel speed difference _Ta , which is the threshold value of the wheel speed difference, it becomes difficult for the vehicle attitude control executed in step S18 and subsequent steps in FIG. 7 to intervene in the low vehicle speed region. That is, in a region where the vehicle speed is low, an error is likely to occur in the measured value of the wheel speed, and if the vehicle attitude control is executed with a minute wheel speed difference, the vehicle attitude control may be executed based on the measurement error. In order to suppress such unnecessary vehicle attitude control intervention, in the present embodiment, the value of the first wheel speed difference _Ta is set as shown in FIG.

Next, gains to be multiplied by each basic command value in step S25 of FIG. 7 will be described with reference to FIGS. 11 to 19. FIG.
FIG. 11 shows the steering angle gain set based on the steering angle and multiplied by the basic command value _Fb1 for vehicle attitude control. FIG. 12 shows an accelerator opening changing speed gain which is set based on the changing speed of the accelerator opening and multiplied by the basic command value _Fb1 for vehicle attitude control. 13 to 15 are maps applied when the high road friction mode is set. FIG. 13 is a map of the accelerator opening gain that is set based on the accelerator opening and multiplied by the basic command value _Fb1 for vehicle attitude control. FIG. 14 is a map of lateral acceleration gains set based on the lateral acceleration and multiplied by the basic command value _Fb1 for vehicle attitude control. FIG. 15 is a map of vehicle speed gains set based on the vehicle speed and multiplied by the basic command value _Fb1 for vehicle attitude control.

16 to 18 are maps that are applied when the low road friction mode is set. FIG. 16 is a map of the accelerator opening gain that is set based on the accelerator opening and multiplied by the basic command value _Fb1 for vehicle attitude control. FIG. 17 is a map of lateral acceleration gains set based on the lateral acceleration and multiplied by the basic command value _Fb1 for vehicle attitude control. FIG. 18 is a map of vehicle speed gains set based on the vehicle speed and multiplied by the basic command value _Fb1 for vehicle attitude control. Also, FIG. 19 is a map of the differential rotation gain that is set based on the inner and outer wheel speed difference and multiplied by the basic command value _Fb2 for the brake LSD control.

As shown in FIG. 11, the steering angle gain G _θ is zero when the steering angle θ [deg] is equal to or less than the first steering angle θ ₁ , increases when θ ₁ or more, and becomes It is set to converge to "1". By setting the steering angle gain G _θ in this way, in a region where the steering angle is equal to or less than the first steering angle θ ₁ , substantially no vehicle attitude control is executed and control intervention is not performed (steering angle By multiplying by the gain _Gθ , the vehicle attitude control command value becomes zero.). As a result, it is possible to prevent the vehicle attitude control from intervening due to fine steering with respect to the steering wheel 6 and giving the driver a sense of discomfort. Preferably, the value of the first steering angle θ ₁ is set to about 3.5 to about 6.0 [deg], and below this value, the value of the steering angle gain G _θ is set to zero. .

As shown in FIG. 12, the accelerator opening change speed gain G _AV is "1.2" in the region where the accelerator opening change speed A _V [%/sec] is near zero, and decreases as the change speed increases. Then, it is set to converge to "0.5" at a predetermined rate of change or higher. Here, when the accelerator pedal (not shown) of the vehicle 1 is rapidly depressed (accelerator opening change rate is large), the wheel speed difference (differential rotation) between the inner rear wheel and the outer rear wheel increases, causing the differential gear 4c to shift. The limited slip differential device 4d provided at actuates. Due to the action of the differential limiting device 4d, the wheel speed difference is rapidly reduced.

When the vehicle attitude control is activated in conjunction with the action of the limited slip differential device 4d and a large braking force acts on the inner rear wheel, the speed of change in the wheel speed difference becomes too large, giving the driver a sense of discomfort. Sometimes. Therefore, by setting the accelerator opening change speed gain _GAV , the braking force applied by the vehicle attitude control is reduced in a situation where the accelerator pedal (not shown) is rapidly depressed. That is, by multiplying the acceleration opening change speed gain G _AV set as shown in FIG. The braking force acting on is reduced. This prevents the driver from feeling uncomfortable due to an excessive increase in the speed of change of the wheel speed difference.

As shown in FIG. 13, the accelerator opening gain G _aH increases as the accelerator opening [%] increases, becomes "1" at the first accelerator opening _A1 , and becomes "1" at the first accelerator opening _A1 or higher. is set to converge to a predetermined value greater than "1". By setting the accelerator opening gain G _aH in this way, the command value for vehicle attitude control becomes smaller as the accelerator opening decreases. That is, in a region where the accelerator opening is small, the inner rear portion of the vehicle body 1a is less likely to be lifted. Preferably, the value _of the first accelerator opening A ₁ is set to about 45 to about 60 [%]. The accelerator opening gain G _aH is set to be "1" or more.

As shown in FIG. 14, the lateral acceleration gain G _lH is zero when the lateral acceleration a _l [G] is equal to or less than the first lateral acceleration a _l1 , increases when the lateral acceleration a l [ _G ] is equal to or greater than a is set to converge to "1" at . By setting the lateral acceleration gain _GlH in this way, when the lateral acceleration of the vehicle 1 is large, a larger braking force acts on the inner rear wheels of the vehicle 1 during turning than when the lateral acceleration of the vehicle 1 is small. be done. Further, by setting the lateral acceleration gain G _lH as shown in FIG. 14, in a region where the lateral acceleration is equal to or less than the first lateral acceleration a _l1 , intervention of the vehicle posture control is substantially prevented (lateral acceleration gain G By multiplying by _lH , the vehicle attitude control command value becomes zero.) That is, in a region where the lateral acceleration _al is very small, the rear inner portion of the vehicle body 1a is less likely to rise, so unnecessary vehicle attitude control intervention is used to prevent the driver from feeling discomfort. Preferably, the value of the first lateral acceleration a _l1 is set to about 0.22 to about 0.35 [G], and the value of the lateral acceleration gain G _lH is set to zero below this value. .

As shown in FIG. 15, the vehicle speed gain G _VH gradually increases as the vehicle speed [km/h] increases, becomes "1" at the first vehicle speed _V1 , and relatively sharply increases at the first vehicle speed _V1 or higher. set to increase. By setting the vehicle speed gain G _VH in this way, the command value for vehicle attitude control increases as the vehicle speed increases. Acts on the rear wheels. That is, in a region where the vehicle speed is low, the inner rear portion of the vehicle body 1a is less likely to lift. is strongly intervening. Preferably, the value _of the first vehicle speed _V1 is set to about 95 to about 115 [km/h]. Set _VH to increase.

In step S25 of FIG. 7, when the high road friction mode is selected, the steering angle gain G θ set based on _FIG . 11 and the steering angle gain G _θ set based on FIG. Accelerator opening change speed gain _GAV set based on FIG. 13, accelerator opening gain G _aH set based on FIG. 13, lateral acceleration gain _GlH set based on FIG. is multiplied by the vehicle speed gain G _VH , and the command value F ₁ for vehicle attitude control is calculated by Equation (5).

On the other hand, when the low road friction mode is selected, the accelerator opening gain, the lateral acceleration gain, and the vehicle speed gain are different from those when the high road friction mode is selected. are set using .

As shown in FIG. 16, when the low road surface friction mode is selected, the accelerator opening gain G _aL increases as the accelerator opening [%] increases, and at the second accelerator opening _A2 "1", and is set to a predetermined value larger than "1" at the second accelerator opening A2 or _more . By setting the accelerator opening gain G _aL in this manner, the command value for vehicle attitude control becomes smaller as the accelerator opening decreases. Further, the second accelerator opening _A2 at which the accelerator opening gain G _aL in the low road friction mode is "1" is the first accelerator opening at which the accelerator opening gain G _aH in the high road friction mode is "1". It is set larger than the opening degree _A1 . Preferably, the value of the second accelerator opening A ₂ is set to about 60 to about 75 [%], below this value the accelerator opening gain G _aL is set to "1" or below, and above this value, The accelerator opening gain G _aL is set to be "1" or more.

As shown in FIG. 17, when the low road friction mode is selected, the lateral acceleration gain G _lL is zero in the region where the lateral acceleration a _l [G] is equal to or lower than the second lateral acceleration a _l2 , It is set so that it increases when the second lateral acceleration is equal to or greater than a _l2 and converges to "1" when the lateral acceleration is equal to or greater than a predetermined lateral acceleration. In this way, in the low road friction mode, a different lateral acceleration gain is set than in the high road friction mode. different braking forces are generated. Further, by setting the lateral acceleration gain G _lL in this way, in a region where the lateral acceleration is equal to or lower than the second lateral acceleration a _l2 , the intervention of the vehicle attitude control is substantially prevented (the lateral acceleration gain G _lL is By multiplying it, the vehicle attitude control command value becomes zero.) Further, in the present embodiment, the second lateral acceleration al2 at which the lateral acceleration gain G _lL is greater than zero in the low road friction mode is the second lateral acceleration a _l2 at which the lateral acceleration gain G _lH is greater than zero in the high road friction mode. Unlike the lateral acceleration a _l1 of 1, it is set smaller than the first lateral acceleration a _l1 . That is, in the low road friction mode, vehicle attitude control intervenes from a state where the lateral acceleration is smaller than in the high road friction mode. Preferably, the value of the second lateral acceleration a _l2 is set to about 0.02 to about 0.15 [G], and the value of the lateral acceleration gain G _lL is set to zero below this value. .

As shown in FIG. 18, when the low road friction mode is selected, the vehicle speed gain _GVL is set to zero below the second vehicle speed _V2 , increases above the second vehicle speed _V2 , and reaches a predetermined value. is set to converge to a predetermined value smaller than "1" at a vehicle speed of . Therefore, when the vehicle speed is high, a larger braking force is applied to the inner rear wheels of the turning vehicle than when the vehicle speed is low. Further, by setting the vehicle speed gain _GVL in this manner, the vehicle attitude control does not intervene below the second vehicle speed _V2 , and the command value by the vehicle attitude control is reduced even in the high vehicle speed region. That is, when the low road friction mode is selected, the intervention of the vehicle attitude control is suppressed at any vehicle speed compared to the high road friction mode. That is, the braking force of the vehicle attitude control suppresses the slippage of the inner rear wheel. Preferably, the value of the second vehicle speed V ₂ is set to about 15 to about 30 [km/h], and the vehicle speed gain G _VL converges to about 0.3 to about 0.6 in the region where the vehicle speed is high. The vehicle speed gain _GVL is set as follows.

In step S25 of FIG. 7, when the low road friction mode is selected, the steering angle gain G θ set based on _FIG . 11 and the steering angle gain G _θ set based on FIG. Accelerator opening change speed gain _GAV set based on , accelerator opening gain G _aL set based on FIG. 16, lateral acceleration gain _GlL set based on FIG. 17, and set based on FIG. is multiplied by the vehicle speed gain _GVL , and the command value _F1 for vehicle attitude control is calculated by the equation (6).

Next, with reference to FIG. 19, the differential rotation gain _GDL that is multiplied by the basic command value _Fb2 for the brake LSD control when the low road friction mode is selected will be described. Note that when the high road friction mode is selected, the differential rotation gain _GDH is always "1".
As shown in FIG. 19, _the differential rotation gain _GDL is set to "1" when the differential rotation D between the inner ring and the outer ring is equal to or less than the first differential rotation _D1 [m/sec], is set to converge to a predetermined value greater than "1". By setting the differential rotation gain _GDL in this manner, the command value for the brake LSD control increases when the differential rotation becomes equal to or greater than the first differential rotation _D1 . That is, when the low road friction mode is selected, the braking force to be applied when the inner wheel slips is set larger than when the high road friction mode is selected, and the inner wheel slip is strengthened. Suppress. Preferably, the value of the first differential rotation D ₁ is set to about 8 to about 12 [m/sec], and above this value, the brake LSD control command value is increased. Further, preferably, the differential rotation gain G _DL is set so as to converge to approximately 1.3 to approximately 1.6 in a region where the differential rotation D is large.

In step S25 of FIG. 7, when the low road friction mode is selected, the basic command value F _b2 for brake LSD control is multiplied by the differential rotation gain G _DL set based on FIG. A command value _F2 for the brake LSD control is calculated by (7). On the other hand, when the high road friction mode is selected, the differential rotation gain _GDH is always "1", so the basic command value _Fb2 is directly set to the command value _F2 .

As described above, in step S25 of FIG. 7, the command value F1 for vehicle attitude control is calculated by the formula (5) or ( ₆ ) based on the basic command value _Fb1 for vehicle attitude control. Furthermore, the command value _F2 is calculated by Equation (7) based on the basic command value _Fb2 for the brake LSD control, or the basic command value _Fb2 is used as it is as the command value _F2 .

Further, when the low road friction mode is selected, the command value _F3 for the pre-brake LSD control is calculated by multiplying the basic command value _Fb3 by a gain similar to that for vehicle attitude control. That is, the command value _F3 is calculated by the following formula (8). As described above, the pre-brake LSD control is applied for the purpose of suppressing a change in the braking force after the application of the braking force based on the vehicle attitude control is completed until the braking force is applied by the brake LSD control. ing. Therefore, the command value for the pre-brake LSD control is also multiplied by a gain similar to that for the vehicle attitude control, and the braking force is set so as to be smoothly connected to the vehicle attitude control.

On the other hand, when the high road surface friction mode is selected, as described above, the pre-brake LSD control is not executed (pre-brake LSD control command value F ₃ =0). However, as a modification, if the present invention is configured so that the pre-brake LSD control is executed even when the high road friction mode is selected, the command value _F3 is calculated by the following formula (9). can do. As a result, even in the high road friction mode, the braking force can be set so as to be smoothly connected to the vehicle attitude control.

Further, in step S26 of FIG. 7, the vehicle attitude control command value _F1 , the brake LSD control command value _F2 , and the pre-brake LSD control command value _F3 calculated as described above are compared, The largest command value is finally determined as the command value for the braking force acting on the inner rear wheel. When the braking force command value is determined in step S26 of FIG. 7, the process proceeds to step S5 of the flowchart of FIG. 6, and in step S5, the brake device 8 is controlled based on the determined command value.

According to the vehicle attitude control system of the first embodiment of the present invention, when the vehicle 1 turns when the vehicle is turning based on the turning operation of the steering wheel, when the lateral acceleration _al of the vehicle 1 is large, the lateral acceleration al of the vehicle 1 _is A larger braking force is applied to the inner rear wheels of the vehicle during a turn than when .DELTA. When a braking force (command value F ₁ ) is applied to the inner rear wheel of the vehicle 1, a force acts to pull down the inner rear portion of the vehicle body 1a via the suspension 3, which is a wheel suspension device, and the inner rear portion of the vehicle body 1a is pulled downward. Floating is suppressed.

Further, according to the vehicle attitude control system of the present embodiment, the inner side of the vehicle 1 is calculated based on the difference in wheel speed between the inner rear wheels and the outer rear wheels (step S16 in FIG. 7) and the lateral acceleration _al of the vehicle 1. Since the braking force (command value F ₁ ) applied to the rear wheels is set, the braking force for suppressing the lifting of the inner rear portion of the vehicle body 1a can be set more accurately.

Furthermore, according to the vehicle attitude control system of the present embodiment, when the vehicle speed V is high, a larger braking force is applied to the inside rear wheels of the vehicle 1 during turning than when the vehicle speed V is low (FIGS. 15 and 15). 18), an appropriate braking force corresponding to the vehicle speed V can be set.

Further, according to the vehicle attitude control system of the present embodiment, when the accelerator opening is large, a larger braking force acts on the inner rear wheels of the vehicle during turning than when the accelerator opening is small (FIG. 13). , FIG. 16), it is possible to set an appropriate braking force according to the degree of opening of the accelerator.

Furthermore, according to the vehicle attitude control system of the present embodiment, when the steering angle θ due to the turning operation of the steering wheel 6 is less than or equal to a predetermined value, vehicle attitude control is not executed (braking force by vehicle attitude control=0). (FIG. 11), it is possible to prevent the vehicle attitude control from intervening based on fine steering unintended by the driver and giving the driver a sense of discomfort.

Further, according to the vehicle attitude control system of the present embodiment, different braking forces are generated with respect to the same lateral acceleration in the low road friction mode (FIG. 17) and the high road friction mode (FIG. 14). An appropriate braking force can be set according to the friction.

Furthermore, according to the vehicle attitude control system of the present embodiment, when the lateral acceleration becomes equal to or greater than the first lateral acceleration _al1 in the high road friction mode (FIG. 14), the lateral acceleration becomes equal to or greater than the second lateral acceleration _al2 in the low road friction mode. Since the vehicle attitude control is executed when this occurs (FIG. 17), the vehicle attitude control can be started at an appropriate time according to the road surface friction.

Further, according to the vehicle attitude control system of the present embodiment, the condition for starting the execution of the vehicle attitude control (step S17 in FIG. 7, FIG. 10) is changed according to the vehicle speed V. Vehicle attitude control can be started in a timely manner.

Furthermore, according to the vehicle attitude control system of the present embodiment, the upper arm 3a and the lower arm 3b, which are link mechanisms for suspending the axles of the rear wheels 2c and 2d with respect to the vehicle body 1a, rotate around the predetermined suspension center P _S . The axle 2e is suspended so that the axle rotates (Fig. 4). Since the center of suspension P _S is located above the axle 2e, when a braking force is applied to the rear wheels 2c or 2d, the component of the force that pulls the vehicle body 1a downward via the upper arm 3a and the lower arm 3b. is increased, it is possible to more effectively suppress the floating of the rear portion of the vehicle body.

In addition, in the vehicle attitude control system of the present embodiment, the vehicle 1 is provided with the mechanical limited slip differential device 4d, and due to its function, the wheels of the inner rear wheels and the outer rear wheels are rapidly displaced as the accelerator opening increases. speed difference is reduced. In addition to the action of the differential limiting device 4d, when the brake control unit 14a applies a braking force to the inner rear wheels based on vehicle attitude control, the change in the wheel speed difference between the inner rear wheels and the outer rear wheels becomes excessive. This may cause the driver to feel uncomfortable. According to the vehicle attitude control system of the present embodiment, the braking force applied to the inside rear wheel is reduced as the rate of change of the accelerator opening is increased (FIG. 12), so that the sense of discomfort given to the driver can be suppressed. .

Next, a vehicle attitude control system according to a second embodiment of the present invention will be described with reference to FIGS. 20 and 21. FIG.
In the vehicle attitude control system of the present embodiment, the braking force applied by the vehicle attitude control is determined by the same control algorithm regardless of the road friction of the road surface on which the vehicle 1 is running. It differs from one embodiment. Therefore, only the points of the second embodiment of the present invention that are different from those of the first embodiment will be described here, and descriptions of the same configurations, actions, and effects will be omitted. That is, in the above-described first embodiment, different vehicle attitude controls are executed depending on whether the low road friction mode is selected or the high road friction mode is selected. In contrast, in the present embodiment, if the same lateral acceleration is acting on the vehicle 1, the same braking force is applied regardless of the road surface friction of the road surface.

FIG. 20 is a flowchart showing processing for determining a command value in vehicle attitude control in this embodiment, and is a flowchart corresponding to FIG. 7 of the first embodiment.
In the flowchart according to the first embodiment shown in FIG. 7, it is determined in step S13 whether or not the low road friction mode is selected. A command value for the pre-brake LSD control has been set. On the other hand, when the low road friction mode is not selected (high road friction mode), the pre-brake LSD control is not executed.

In contrast, in the present embodiment, there is no selection of the "low road friction mode" or "high road friction mode", and the command value for the pre-brake LSD control is set regardless of the road friction. That is, in this embodiment, as shown in FIG. 20, the vehicle attitude control flag is "true" (step S112), and the lateral acceleration detected by the lateral acceleration sensor 22 is the predetermined second lateral acceleration _GYb. When it is higher than [G] (step S113), in step S114, the basic command value _Fb3 of the lower limit braking force by the pre-brake LSD control is always determined. The flowchart shown in FIG. 20 is the same as the flowchart shown in FIG. 7 except that there is no selection between the low road friction mode and the high road friction mode. That is, in step S114, the basic command value F _b3 is obtained by multiplying the maximum value of the most recently set basic command value F _b1 for vehicle attitude control by a predetermined coefficient C _m3 irrespective of the road surface friction. 10).

Further, in this embodiment, the basic command value F _b1 [N] for vehicle attitude control calculated in step S119 of FIG. determined based on That is, the basic command value F _b1 is a command value for the braking force applied to the inner rear wheel of the vehicle 1 that is turning, and is a predetermined coefficient for the difference between the outer wheel speed V _o and the inner wheel speed V _i It is calculated by equation (11) by multiplying by C _m1 .

Furthermore, in this embodiment, the basic command value F _b2 [N] for brake LSD control calculated in step S121 of FIG. determined based on That is, the basic command value _Fb2 of the braking force by the brake LSD control is the command value of the braking force applied to the inner rear wheels of the vehicle 1 that is turning, and the inner wheel speed _Vi and the outer wheel speed V It is calculated according to equation (12) by multiplying the difference of _o by a predetermined coefficient C _m2 .

In step S124 of FIG. 20, the basic command values F _b1 , F _b2 , and F _b3 calculated as described above are multiplied by respective gains to obtain a command value F ₁ for vehicle attitude control and a command value F 1 for brake LSD control. A command value F ₂ and a command value F ₃ for pre-brake LSD control are calculated.

That is, the vehicle attitude control command value _F1 is composed of a basic command value _Fb1 , a steering angle gain _Gθ , an accelerator opening change speed gain _GAV , an accelerator opening gain _Ga , a lateral acceleration gain _Gl , and a vehicle speed gain. Multiplied by G _V and calculated by Equation (13).

Here, the same gains as those set in the first embodiment can be used for the steering angle gain G _θ and the accelerator opening rate change speed gain G _AV in Equation (13). Further, the accelerator opening gain G _a , the lateral acceleration gain G _l , and the vehicle speed gain G _V are the accelerator opening gain G aH and the lateral acceleration gain G _aH set when the high road friction mode is selected in the first embodiment. The same gain as acceleration gain G _lH and vehicle speed gain G _VH can be used. Alternatively, gains different from the gains set in the first embodiment can be set.

Furthermore, the command value _F2 for the brake LSD control is calculated by the formula (14) by multiplying the basic command value _Fb2 for the brake LSD control by the differential rotation gain G _D . Here, the differential rotation gain G _D is set based on the map shown in FIG. In the first embodiment described above, when the low road friction mode is selected, the differential rotation gain G _DL is set based on the map shown in FIG. 19, and the high road friction mode is selected. , the differential rotation gain _GDH was always set to "1". On the other hand, in this embodiment, the differential rotation gain _GD is set based on the map shown in FIG. 21 regardless of the road surface friction.

FIG. 21 is a map used to set the differential rotation gain G _D .
As shown in FIG. 21, the differential rotation gain G _D is set to a value of approximately 0.8 or less in a region where the differential rotation D [m/sec] between the inner and outer rings is low, and increases to 1 as the differential rotation D increases. is set to converge to . By setting the differential rotation gain G _D in this manner, the differential rotation increases and the command value for the brake LSD control increases. Further, since the differential rotation gain G _D converges to "1" as the differential rotation D increases, the command value for the brake LSD control does not become excessive even when the road surface friction is large.

Further, the command value _F3 for the pre-brake LSD control is calculated by multiplying the basic command value _Fb3 by a gain similar to that for vehicle attitude control. That is, the command value _F3 is calculated by the following formula (15). The pre-brake LSD control is applied for the purpose of suppressing a change in the braking force until the braking force is applied by the brake LSD control after the application of the braking force based on the vehicle attitude control is completed. Therefore, the command value for the pre-brake LSD control is also multiplied by a gain similar to that for the vehicle attitude control, and the braking force is set so as to be smoothly connected to the vehicle attitude control.

Next, in step S125 of FIG. 20, the vehicle attitude control command value F ₁ , the brake LSD control command value F ₂ , and the pre-brake LSD control command value F ₃ , which are calculated by the formulas (13) to (15), respectively. are compared, and the largest command value is finally determined as the command value for the braking force acting on the inner rear wheel. Further, similar to the above-described first embodiment, the braking device 8 is controlled based on the braking force command value determined in step S125 of FIG.

In the above-described first embodiment, different command values are calculated and applied by the brake device 8 depending on whether the high road friction mode is selected or the low road friction mode is selected. The motive power was also different. On the other hand, in the present embodiment, there is no selection regarding the road surface friction, and if the running state of the vehicle 1 such as the lateral acceleration acting on the vehicle 1 is the same, the braking force is the same regardless of the road friction of the running road surface. is generated by the braking device 8 .

Further, in this embodiment, in step S116 of FIG. 20, when the wheel speed difference between the inner rear wheel and the outer rear wheel of the vehicle 1 during turning is equal to or less than the first wheel speed difference _Ta [m/sec]. , the process proceeds to step S122. Therefore, the basic command value F _b1 [N] for vehicle attitude control is not set in step S119 (F _b1 =0). Similarly, in step S120 of FIG. 20, when the wheel speed difference between the outer rear wheel and the inner rear wheel (inner wheel speed - outer wheel speed) is equal to or less than the second wheel speed difference T _b [m/sec]. , the process proceeds to step S122. Therefore, in step S121, the basic command value F _b2 [N] for brake LSD control is not set (F _b2 =0). Further, since the basic command value F _b3 for the pre-brake LSD control is a basic command value calculated by multiplying the maximum value of the basic command value F _b1 by a predetermined coefficient C _m3 , the basic command value F _b1 =0. If so, the basic command value F _b3 also becomes zero.

Thus, in this embodiment, when the wheel speed difference between the inner rear wheels and the outer rear wheels of the vehicle 1 during turning is equal to or less than a predetermined threshold value, the basic command values F _b1 , F _b2 , and F _b3 are Both are zero, and no braking force is applied by the braking device 8 .

According to the vehicle control device of the second embodiment of the present invention, when the same lateral acceleration is acting on the vehicle 1 during travel, the same braking force is generated regardless of the road surface friction during travel. Therefore, it is not necessary to change the control according to the road surface friction, and the control algorithm can be configured simply. Further, according to the vehicle control device of the present embodiment, braking force is not applied when the wheel speed difference is equal to or less than the predetermined threshold value, so excessive intervention of the braking force by the braking device 8 can be suppressed. In addition, in a situation where braking force is required, an appropriate braking force can be applied to prevent the inner rear portion of the vehicle 1 from being lifted up during turning.

Although the vehicle attitude control system according to the embodiment of the present invention has been described above, various modifications can be made to the embodiment described above. In particular, in the above-described embodiment, the vehicle attitude control system of the present invention is applied to a rear-wheel drive vehicle, but the present invention can be applied to any drive system vehicle such as a four-wheel drive vehicle.

1 vehicle 1a vehicle body 2a, 2b front wheels 2c, 2d rear wheels 2e axle 3 suspension (wheel suspension device)
3a upper arm (link mechanism)
3b lower arm (link mechanism)
4 engine 4a transmission 4b propeller shaft 4c differential gear 4d differential limiter 6 steering wheel 7 steering device 8 brake device (brake actuator)
10 hydraulic pump 12 valve unit 13 hydraulic pressure sensor 14 PCM
14a brake control unit (brake control device)
14b turning control unit 14c sideslip prevention control unit 16 steering angle sensor 18 accelerator opening sensor 20 vehicle speed sensor 22 lateral acceleration sensor 24 wheel speed sensor 26 mode setting switch

Claims (13)

A vehicle posture control device for controlling the posture of a vehicle in which a wheel suspension device is configured so that the roll axis of the vehicle body is tilted forward,
a lateral acceleration sensor that detects the lateral acceleration of a running vehicle;
a brake actuator that applies a braking force to the wheels of the vehicle;
a brake control device for generating a braking force by sending a control signal to the brake actuator based on the running state of the vehicle;
a wheel speed sensor that detects the wheel speed of the rear wheels of the vehicle;
has
When the vehicle is turning based on the turning operation of the steering wheel of the vehicle, the brake control device applies a larger braking force to the vehicle during turning when the lateral acceleration of the vehicle is large than when the lateral acceleration of the vehicle is small. Executes vehicle attitude control that acts on the inside rear wheel to suppress the lifting of the inside rear part of the vehicle body,
Further, the brake control device sets the braking force to be applied to the inner rear wheels of the vehicle based on the difference in wheel speed between the inner rear wheels and the outer rear wheels detected by the wheel speed sensor and the lateral acceleration of the vehicle. A vehicle attitude control device characterized by : Further, a vehicle speed sensor for detecting the speed of the vehicle is provided, and when the vehicle speed detected by the vehicle speed sensor is high, the brake control device applies a larger braking force than when the vehicle speed is low. 2. The vehicle attitude control system according to claim 1 , wherein the rear wheels are acted upon. Further, an accelerator opening sensor is provided, and when the accelerator opening detected by the accelerator opening sensor is large, the brake control device applies a larger braking force than when the accelerator opening is small. 3. The vehicle attitude control system according to claim 1 or 2, wherein the inner rear wheel of the vehicle. Further, a steering angle sensor for detecting a steering angle of a steering wheel of the vehicle is provided, and the brake control device detects when the steering angle detected by the steering angle sensor due to the turning operation of the steering wheel is equal to or less than a predetermined value. 4. The vehicle attitude control system according to any one of claims 1 to 3 , wherein the vehicle attitude control is not executed. The brake control device is configured to be capable of executing vehicle attitude control in a low road friction mode and vehicle attitude control in a high road friction mode. 5. The vehicle attitude control system according to claim 1, wherein different braking forces are generated at different positions. The brake control device is configured to be capable of executing vehicle attitude control in a high road friction mode and vehicle attitude control in a low road friction mode. In the low road surface friction mode, the vehicle attitude control is performed when the lateral acceleration of the vehicle becomes greater than or equal to a second lateral acceleration different from the first lateral acceleration. Item 6. The vehicle attitude control device according to any one of Items 1 to 5 . Further comprising a vehicle speed sensor for detecting the speed of the vehicle, wherein the brake control device changes conditions for starting execution of the vehicle attitude control according to the vehicle speed detected by the vehicle speed sensor . The vehicle attitude control device according to any one of Claims 1 to 1. The wheel suspension system includes a link mechanism for suspending the axle of the rear wheel with respect to the vehicle body, the link mechanism suspending the axle so that the axle rotates around a predetermined center of suspension, and 8. The vehicle attitude control system according to claim 1, wherein the center of suspension is located above the axle. The vehicle is a mechanical limited slip differential that mechanically controls the wheel speed difference between the inner rear wheels and the outer rear wheels according to the torque acting on the inner rear wheels and the outer rear wheels of the vehicle during turning. The vehicle attitude control device further has an accelerator opening sensor, and the brake control device increases the rate of change of the accelerator opening detected by the accelerator opening sensor, the more the vehicle is turning. 9. The vehicle attitude control system according to any one of claims 1 to 8 , wherein a braking force acting on the inner rear wheels of the vehicle is reduced. Further comprising a vehicle speed sensor for detecting the speed of the vehicle, wherein the brake control device changes conditions for starting execution of the vehicle attitude control according to the vehicle speed detected by the vehicle speed sensor . The vehicle attitude control device according to any one of Claims 1 to 1. The wheel suspension system includes a link mechanism for suspending the axle of the rear wheel with respect to the vehicle body, the link mechanism suspending the axle so that the axle rotates around a predetermined center of suspension, and 11. The vehicle attitude control system according to any one of claims 1 to 4 and 10 , wherein the center of suspension is located above the axle. The vehicle is a mechanical limited slip differential that mechanically controls the wheel speed difference between the inner rear wheels and the outer rear wheels according to the torque acting on the inner rear wheels and the outer rear wheels of the vehicle during turning. The vehicle attitude control device further has an accelerator opening sensor, and the brake control device increases the rate of change of the accelerator opening detected by the accelerator opening sensor, the more the vehicle is turning. 12. The vehicle attitude control system according to any one of claims 1 to 4 , 10 and 11, wherein the braking force acting on the inner rear wheels of the vehicle is reduced. The brake control device is configured to generate the same braking force regardless of the road surface friction of the traveling road surface when the same lateral acceleration is acting on the vehicle while the vehicle is turning. 13. The vehicle posture according to any one of claims 1 to 4 and 10 to 12 , wherein the braking force is not applied when the wheel speed difference between the inner rear wheel and the outer rear wheel is equal to or less than a predetermined threshold value. Control device.

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