JP2020196358A - Vehicle attitude controller - Google Patents

Abstract

To provide a vehicle attitude controller capable of suppressing floating of an inside rear part of a vehicle body when turning, in a vehicle whose roll axis is forward tilted.SOLUTION: A vehicle attitude controller for controlling an attitude of a vehicle (1) whose roll axis is forward tilted includes: a brake actuator (8); and a brake controller (14a) which generates braking force by transmitting a control signal to the brake actuator, on the basis of a travel state of the vehicle. The brake controller executes vehicle attitude control for suppressing floating of an inside rear part of a vehicle body (1a) by causing the braking force to act on rotating inside rear wheels of the vehicle, in turning of the vehicle according to operations to turn the steering wheel (6) of the vehicle away from a center position. The braking force caused to act on the inside rear wheels of the vehicle according to the vehicle attitude control is set so that deceleration in a vertical direction for suppressing floating of the inside rear part of the vehicle body is equal to a predetermined value or less.SELECTED DRAWING: Figure 8

Description

The present invention relates to a vehicle attitude control device, and more particularly to a vehicle attitude control device that controls the attitude of a vehicle in which a wheel suspension device is configured so that the roll axis of the vehicle body tilts forward.

Japanese Patent No. 5193885 (Patent Document 1) describes a vehicle motion control device. In this vehicle motion control device, different braking force or driving force is applied to the left and right wheels based on the control command value of the yaw moment calculated from the skid information of the vehicle. As a result, in the invention described in Patent Document 1, acceleration / deceleration linked to the steering wheel operation is automatically performed, skidding is reduced in the limit operation region, 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 the yaw moment to the vehicle by applying different braking force or driving force to the left and right wheels based on the steering wheel operation of the driver. It is said.

On the other hand, it is also attempted to improve the posture of the vehicle when turning by setting the base suspension of the vehicle. That is, by setting the base suspension so that the vehicle is likely to cause a pitching motion, proper diagonal rolls are naturally generated in the vehicle body even when turning at low lateral acceleration. .. Specifically, by setting the base suspension of the vehicle so that the roll axis of the vehicle body tilts forward (the front side of the vehicle body is lowered), the vehicle body is likely to cause a pitching motion, which is appropriate when turning. Diagonal rolls can be produced.

Patent No. 5193885

However, if the base suspension is set so that pitching motion is generated in the vehicle body when turning in the low lateral acceleration region and an appropriate diagonal roll is generated, the vehicle is turning in a region where the lateral acceleration is large to some extent. There is a problem that the inner rear part of the vehicle body is easily lifted. 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 while turning. That is, even in the lateral acceleration region where the lateral acceleration is relatively small and the turning performance of the vehicle is not substantially affected, the inner rear portion of the vehicle body during turning may be lifted. In this way, in a vehicle in which the roll axis of the vehicle body is set to tilt forward, even in a region where the lateral acceleration is not so large, the rear part of the vehicle body inside the turning vehicle may be lifted, and the driver. And may give anxiety to the occupants. If a braking force is applied to the inner rear wheels in order to solve the problem of floating inside the vehicle body, an excessive yaw moment may act on the vehicle, which may rather impair the vehicle's kinetic performance. ..

Therefore, according to the present invention, 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 lift of the inner rear portion of the vehicle body during turning while suppressing the deterioration of the vehicle's kinetic performance. It is an object of the present invention to provide a vehicle attitude control device capable of providing a vehicle attitude control device.

In order to solve the above-mentioned problems, the present invention is a vehicle attitude control device for controlling the attitude of a vehicle in which a wheel suspension device is configured so that the roll axis of the vehicle tilts forward, and a braking force is applied to the wheels of the vehicle. It has a brake actuator that acts on the vehicle and a brake control device that sends a control signal to the brake actuator to generate a braking force based on the running state of the vehicle, and the brake control device is used for cutting operation of the steering wheel of the vehicle. Based on the vehicle attitude control, it is configured to execute vehicle attitude control that suppresses the lifting of the inside rear of the vehicle body by applying a braking force to the inner rear wheels of the vehicle while turning. The braking force acting on the inner rear wheels of the vehicle is characterized in that the deceleration in the vertical direction, which suppresses the lifting of the inner rear part of the vehicle body, is set to be equal to or less than a predetermined value.

In a vehicle in which the wheel suspension device is configured so that the roll axis of the vehicle body tilts forward, pitching motion is likely to occur, and a diagonal roll can be generated even when the vehicle has a small lateral acceleration. Performance can be improved. However, in a vehicle in which the roll axis is tilted forward in this way, when the lateral acceleration during turning increases to some extent, the inner rear part of the vehicle body tends to rise, which causes anxiety to the driver and occupants. Unique technical challenges arise. The present invention solves such a technical problem peculiar to a vehicle in which the roll axis of the vehicle body is tilted forward. Further, if a braking force is applied to the inner rear wheels of the vehicle in order to suppress the lifting of the inner rear portion of the vehicle body, a yaw moment is applied to the vehicle, which affects the turning performance of the vehicle. According to the present invention configured as described above, when the vehicle is turning based on the cutting operation of the steering wheel of the vehicle, a braking force is applied to the inner rear wheels of the turning vehicle to act on the inner rear of the vehicle body. It is configured to execute vehicle attitude control that suppresses lifting, and the braking force applied to the inner rear wheels of the vehicle based on vehicle attitude control is a vertical deceleration that suppresses lifting inside and behind the vehicle body. It is set to be less than or equal to a predetermined value. The braking force acting on the inner rear wheels is not enough to substantially add a yaw moment to the vehicle, but suppresses the lifting of the inner rear part of the vehicle body while suppressing the influence on the turning performance of the vehicle, and the driver. It acts to make it less likely to give anxiety to the occupants. In the present specification, the "vertical deceleration that suppresses the lifting of the inside and rear of the vehicle body" refers to the acceleration in the direction of sinking the inside and rear portion of the vehicle body when the vehicle is turning. Further, in the present specification, the "vertical acceleration that lifts the inside rear of the vehicle body" means the acceleration in the direction that lifts the inside rear portion of the vehicle body upward when the vehicle turns.

In the present invention, the mass of the vehicle is preferably 960 kg to 1060 kg, and the brake control device generates a braking force at a brake hydraulic pressure of 0.1 MPa or less in vehicle attitude control, and reduces the vehicle attitude in the vertical direction by a predetermined value or less. Produces speed.

According to the present invention configured as described above, in vehicle attitude control, a braking force is generated at a brake fluid pressure of 0.1 MPa or less for a vehicle having a mass of 960 kg to 1060 kg, so that a braking force is generated in a vertical direction of a predetermined value or less. It causes deceleration. Therefore, the braking force applied to the inner rear wheels is very small, and the braking force is not substantially applied to the turning vehicle.

In the present invention, preferably, the brake control device generates a braking force at a brake fluid pressure of 0.02 MPa or more in vehicle attitude control to cause a deceleration in the vertical direction.

According to the present invention configured as described above, in vehicle attitude control, a braking force is generated at a brake fluid pressure of 0.02 MPa or more, so that it is possible to suppress the lifting of the inner rear portion of the vehicle body during turning. It is possible to suppress the anxiety given to the driver and occupants.

In the present invention, preferably, the brake control device uses a brake fluid pressure of 0.1 MPa or less in vehicle attitude control from the start of the steering wheel turning operation to the end of the steering wheel turning back operation. It is configured to generate braking force.

According to the present invention configured as described above, since a braking force is generated with a brake hydraulic pressure of 0.1 MPa or less from the start of the turning operation to the end of the turning operation of the steering wheel, the vehicle is substantially subjected to turning. No yaw moment is added to the wheel, and the effect on turning performance can be reliably eliminated.

In the present invention, preferably, it further has a turning control unit that executes turning control for improving the turning performance of the vehicle, and this turning control unit exerts a braking force on the inner rear wheels of the vehicle during turning. This is configured to generate a yaw moment in the vehicle, and in turning control, a braking force is applied to the inner rear wheels of the vehicle with a brake fluid pressure of 0.2 MPa or more and 0.5 MPa or less.

According to the present invention configured as described above, the turning control unit applies a braking force to the inner rear wheels of the turning vehicle at a brake fluid pressure of 0.2 MPa or more and 0.5 MPa or less to generate a yaw moment. Therefore, in a situation where turning control is required, a sufficient yaw moment is applied to the vehicle, and the turning performance of the vehicle can be improved.

In the present invention, preferably, there is a skid prevention control unit that executes skid prevention control for suppressing skidding when the vehicle is turning, and this skid prevention control unit acts a braking force on the vehicle while turning. By doing so, it is configured to suppress the sideslip of the vehicle, and in the sideslip prevention control, a braking force is applied to the wheels of the vehicle with a brake fluid pressure of 20 MPa or more.

According to the present invention configured as described above, since the sideslip prevention control unit exerts a braking force on the turning vehicle with a brake fluid pressure of 20 MPa or more, it is sufficient for the vehicle in a situation where sideslip prevention control is required. Braking force is applied, and it is possible to prevent the vehicle from skidding.

In the present invention, preferably, the wheel suspension device includes a link mechanism for suspending the axles of the rear wheels with respect to the vehicle body, and the link mechanism rotates the axles so that the axles rotate around a predetermined suspension center. Along with the suspension, the suspension center is located above the axle.

According to the present invention configured as described above, the link mechanism for suspending the axles of the rear wheels with respect to the vehicle body suspends the axles so that the axles rotate around a predetermined suspension center. Since the suspension center is located above the axle, when a braking force is applied to the rear wheels, the component of the force that pulls the vehicle body downward via the link mechanism becomes large, so the rear part inside the vehicle body is more effective. It is possible to suppress the floating of.

According to the vehicle attitude control device of the present invention, in a vehicle in which the suspension is set so that the roll axis of the vehicle body tilts forward, the inner rear portion of the vehicle body is lifted during turning while suppressing deterioration of the vehicle's kinetic performance. Can be suppressed.

It is a layout figure which shows the whole structure of the vehicle which mounted the vehicle attitude control device by embodiment of this invention. It is a figure which shows typically the structure which suspends the axle of a rear wheel with respect to the vehicle body of the vehicle which mounts the vehicle attitude control device by embodiment of this invention from the rear of a vehicle. It is a figure which shows the roll axis of the vehicle body of the vehicle which mounts the vehicle attitude control device by embodiment of this invention. It is a figure which schematically explains the force acting on the vehicle body when the braking force is applied to the rear wheel of the vehicle which mounts the vehicle attitude control device according to the embodiment of this invention. It is a block diagram which shows the PCM, the sensor and the like mounted on the vehicle equipped with the vehicle attitude control device according to the embodiment of the present invention. It is a flowchart which shows the operation of the vehicle attitude control device by embodiment of this invention. It is a flowchart of a subroutine called from the flowchart shown in FIG. It is a time chart which shows the operation on the normal road surface of the vehicle attitude control device by embodiment of this invention. It is a time chart which shows the action on the road surface of the vehicle attitude control device by embodiment of this invention with a low friction coefficient. It is a map for setting the threshold value of the wheel speed difference in the vehicle attitude control device according to the embodiment of the present invention. It is a map of the steering angle gain multiplied by the basic command value in the vehicle attitude control device according to the embodiment of the present invention. It is a map of the accelerator opening gain to be multiplied by the basic command value in the vehicle attitude control device according to the embodiment of the present invention. It is a map of the lateral acceleration gain multiplied by the basic command value in the vehicle attitude control device according to the embodiment of the present invention. It is a map of the vehicle speed gain multiplied by the basic command value in the vehicle attitude control device according to the embodiment of the present invention. It is a map of the accelerator opening gain to be multiplied by the basic command value in the vehicle attitude control device according to the embodiment of the present invention. It is a map of the lateral acceleration gain multiplied by the basic command value in the vehicle attitude control device according to the embodiment of the present invention. It is a map of the vehicle speed gain multiplied by the basic command value in the vehicle attitude control device according to the embodiment of the present invention. It is a map of the differential rotation gain to be multiplied by the basic command value by the brake LSD control in the vehicle attitude control device according to the embodiment of this invention.

Next, a preferred embodiment of the present invention will be described with reference to the accompanying drawings.
First, with reference to FIG. 1, a vehicle equipped with a vehicle attitude control device according to an embodiment of the present invention will be described. FIG. 1 is a layout diagram showing an overall configuration of a vehicle equipped with a vehicle attitude control device according to an embodiment of the present invention.

In FIG. 1, reference numeral 1 indicates a vehicle equipped with the vehicle attitude control device according to the present embodiment.
Left and right front wheels 2a and 2b, which are steering wheels, are provided on 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 on the rear portion of the vehicle body, respectively. The front wheels 2a and 2b and the rear wheels 2c and 2d of the vehicle 1 are supported by the suspension 3 which is a wheel suspension device with respect to the vehicle body 1a, respectively. Further, 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. In the present embodiment, the engine 4 is a gasoline engine, but an internal combustion engine such as a diesel engine or a motor driven by electric power can also be used as a prime mover. Further, in the present embodiment, the vehicle 1 is a so-called FR vehicle in which the rear wheels 2c and 2d are driven by the engine 4 mounted on the front portion of the vehicle body 1a via the transmission 4a, the propeller shaft 4b, and the differential gear 4c. .. However, the present invention is applied to a vehicle having an arbitrary drive system, such as a so-called RR vehicle in which the rear wheels are driven by an engine mounted on the rear portion of the vehicle body or an FF vehicle in which the front wheels are driven by an engine mounted on the front portion of the vehicle body. Can be done.

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

Further, the brake control system includes a valve unit 12 (which is provided in the hydraulic pressure supply line to the brake device 8 of each wheel and controls the hydraulic pressure supplied from the hydraulic pump 10 to the brake device 8 of each wheel. Specifically, it is equipped with a solenoid valve). For example, the opening degree of the valve unit 12 is changed by adjusting the amount of electric power supplied from the battery to the valve unit 12. Further, the brake control system includes a hydraulic pressure sensor 13 that detects the hydraulic pressure supplied from the hydraulic pressure pump 10 to the brake device 8 of each wheel. The hydraulic pressure sensor 13 is arranged, for example, at a connection 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 determines the detected value by PCM (Power-train). Output to Control Module) 14.

Further, the brake control system calculates the hydraulic pressure to be independently supplied to 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, and these are calculated. The rotation speed of the hydraulic pump 10 and the opening degree of the valve unit 12 are controlled according to the hydraulic pressure of.

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

As shown in FIG. 2, the axle 2e of the rear wheel 2c on the left side of the vehicle 1 is supported by the suspension 3 with respect to the vehicle body 1a of the vehicle 1. Specifically, in the example shown in FIG. 2, the axle 2e of the rear wheel 2c is supported by the upper arm 3a and the lower arm 3b, which are link mechanisms constituting the suspension 3. Thus, upper arm 3a for connecting the vehicle body 1a and the rear wheels 2c, line extended lower arm 3b intersect at an intersection P _1. The straight line connecting the intersection P ₁ and the ground contact point P ₂ of the rear wheels 2c intersects the central axis A of the vehicle body 1a at the point _{Pr R.} This point _PrR is the center point of the rolling motion at the rear portion of the vehicle body 1a, and the rear portion of the vehicle body 1a makes a rolling motion around this point _PrR . Since the vehicle 1 is symmetrical, the same point _PrR is the center point of the rolling motion even when the center point of the rolling motion is obtained for the rear wheel 2d on the right side. Further, the center point _PrF of the rolling motion can be obtained in the same manner for the suspension 3 suspending the front wheels 2a and 2b of the vehicle 1.

Figure 3 is thus determined was the rolling motion in the rear portion of the body 1a center point P _rR, and the center point P _rF of the rolling motion in the front, a diagram obtained by projecting from the side of the vehicle 1. Axis A _r connecting the rear of the center point P _rR and the front of the center point P _rF of the rolling motion of the vehicle body 1a is, the vehicle body 1a is central axis when rolling motion. Therefore, the vehicle body 1a of the vehicle 1 basically makes a rolling motion 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. Thus, by keeping tilted forward roll axis A _r of the vehicle 1, when the vehicle 1 is turning motion can be generated proper die gona roll naturally, improve the turning performance of the vehicle 1 be able to.

Next, with reference to FIG. 4, the force acting on the vehicle body 1a when the braking force is applied to the rear wheels 2c and 2d of the vehicle 1 will be described.
As described above, the rear wheels 2c and 2d are suspended by the upper arm 3a and the lower arm 3b constituting the suspension 3. The wheels may be suspended by various suspensions, in which case the axles of the wheels can be considered to be suspended so as to rotate around a virtual predetermined suspension center. .. As shown in FIG. 4, in the present embodiment, the rear wheels 2d is suspended to pivot about a suspension center point P _S. In the present 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 allowed to act braking force to the rear wheels 2d, the rear wheels 2d includes a ground point P2 of the rear wheel 2d and the road surface, along line l ₁ connecting the suspension center point P _S, the vehicle body 1a Pull back. Assuming that the angle formed by this line segment l ₁ and the road surface is θ _al and the frictional force acting between the road surface and the rear wheels 2d is F _x , the component of the force that pulls the vehicle body 1a downward is

Can be calculated by. Furthermore, the wheelbase of l _r vehicle 1, the horizontal distance between the center of gravity G and the suspension center point P _S of the vehicle 1 and X _r, the moment M _al that act to lower the rear portion of the vehicle body 1a is formula It can be calculated according to (1).

In this way, 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. In the present embodiment, since the position of the suspension the center point P _S is positioned higher than the axle 2e of the rear wheel, the force to lower 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 a PCM14 mounted on the vehicle 1, a sensor connected to the PCM14, and the like.

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

Further, the vehicle 1 is configured so that the driver can select a low road surface friction mode or a high road surface friction mode according to the state of the road surface during traveling, and a mode for selecting these modes. A setting switch 26 is provided. When the driver selects the low road surface friction mode or the high road surface friction mode according to the road surface condition by the mode setting switch 26, this setting is input to the PCM 14, and the vehicle attitude control according to the road surface condition is performed as described later. Will be executed.

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

The vehicle attitude control device according to the 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 PCM14. It is composed of a brake control unit 14a, a turning control unit 14b, a sideslip prevention control unit 14c, an engine 4 controlled by the PCM 14, a brake device 8, and the like built into the vehicle. The above configuration of the vehicle attitude control device may be partially omitted according to the application.

Each control unit of these PCM 14s 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. It is composed of a computer (not shown above) equipped with an internal memory such as a ROM or RAM for storing various types of data.

Next, the operation of the vehicle attitude control device according to the embodiment of the present invention will be described with reference to FIGS. 6 to 18.
FIG. 6 is a flowchart showing the operation of the vehicle attitude control device. FIG. 7 is a flowchart of a subroutine called from the flowchart shown in FIG. FIG. 8 is a time chart showing the operation of the vehicle attitude control device on a normal road surface. FIG. 9 is a time chart showing the operation of the vehicle attitude control device on a road surface having a low coefficient of friction. 10 to 18 are maps showing various gains used when determining a vehicle attitude control command value by the vehicle attitude control device.

The flowchart shown in FIG. 6 is repeatedly executed mainly 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, the detection signals of each sensor are read from various sensors into the PCM 14. The detection signal read in step S1 is used for processing in steps S2 to S4. Specifically, in step S1, the steering angle (rotation angle of the steering wheel 6) [deg] signal from the steering angle sensor 16, the accelerator opening [%] signal from the accelerator opening sensor 18, and the vehicle speed sensor. The signal of the 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. Signal is read. Further, from the mode setting switch 26, a selection signal indicating whether the low road surface friction mode is currently selected or the high road surface friction mode is selected is read by the driver.

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

Preferably, the hydraulic pump 10 applies a braking force of 0.02 MPa or more and 0.1 MPa or less to the braking device 8 for the vehicle 1 having a mass of about 960 kg or more and about 1060 kg or less for controlling the vehicle attitude. Generated by adding. As a result, when the vehicle 1 is turning, the inner rear part of the vehicle body 1a tends to rise at a certain acceleration, but by applying the braking force set as described above, a predetermined value is applied in the vertical direction of the vehicle body 1a. The following small deceleration is given, and the lifting of the inside and rear of the vehicle body is suppressed. In the present embodiment, when a hydraulic pressure of about 0.1 MPa is applied to the brake device 8, a deceleration of about 0.001 G is given in the vertical direction as an example, and the lifting of the inside and rear of the vehicle body is suppressed. Will be done.

Next, in step S3, the command value determination process based on the turning control is executed. The turning control is a control executed by the turning control unit 14b of the PCM 14 when the steering angular velocity of the steering wheel 6 exceeds a predetermined value for the purpose of improving the turning performance of the vehicle 1. Further, in this turning control, the torque generated by the engine 4 is adjusted and / or the braking force is applied by the braking device 8. When a braking force is applied to the vehicle 1 in the turning control, the yaw moment in the turning direction is generated in the vehicle 1 by applying the braking force to the inner rear wheels of the vehicle 1 during turning, and the turning performance of the vehicle 1 Is 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 turning vehicle 1, but the turning control is executed in a region where the lateral acceleration is relatively larger than 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 inner rear portion of the vehicle body 1a from being lifted when the vehicle 1 is turning, whereas the turning control is applied to the vehicle 1 to improve the turning performance. It is executed for the purpose of making it, and is completely different from the turning control. In the present embodiment, the braking force applied for turning control is 0.2 MPa or more and 0.5 MPa or less, which is larger than the vehicle attitude control, applied to the braking device 8 by the hydraulic pump 10. Is generated by.

Next, in step S4, a command value determination process based on the sideslip prevention control is executed. The sideslip prevention control is a control executed by the sideslip prevention control unit 14c of the PCM 14 in order to suppress or prevent the vehicle 1 from skidding when turning. This sideslip prevention control is a control 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 larger than the turning control. In the sideslip prevention control, an appropriate braking force is applied to each wheel of the vehicle 1 in order to return the traveling state of the vehicle 1 to the turning traveling intended by the driver. The braking force applied in the sideslip prevention control is much larger than that in the turning control. In the present embodiment, the braking force acting for the sideslip prevention control is generated by applying a hydraulic pressure of 20 MPa or more, which is larger than that of the turning control, to the braking device 8 by the hydraulic pump 10.

Further, in step S5, a control signal is transmitted to the braking device 8 by the PCM 14 based on the command values determined in steps S2 to S4, braking force is applied to the vehicle 1, and the flowchart shown in FIG. 6 is performed once. Ends the processing of. The vehicle attitude control, turning control, and sideslip prevention control described above all exert a braking force on the vehicle 1, but they are executed in different running states, and these controls are usually superposed. It is never executed.

Next, the process of determining the command value by the vehicle attitude control will be described with reference to FIGS. 7 to 18.
As described above, the flowchart shown in FIG. 7 is a subroutine called from step S2 of the flowchart of FIG. 6, and is executed by the brake control unit 14a of the PCM 14. 8 and 9 are time charts showing an example of the braking force generated when the vehicle attitude control is executed. FIG. 8 shows a case where the vehicle 1 travels on a normal road surface (high friction road surface), and FIG. 9 shows a case where the vehicle 1 travels on a constant friction road surface such as a snowy road. In the time charts shown in FIGS. 8 and 9, the horizontal axis is time, and the vertical axis is detected by the steering angle sensor 16 detection value, the accelerator opening sensor 18 detection value, and the wheel speed sensor 24 in order from the top. The wheel speed of the rear wheels and the braking command value given to the inner rear wheels are shown.

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.

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 the vehicle attitude control is started based on a predetermined condition, and the cut steering wheel 6 is turned back and turned. Is a flag that is returned to "false" when is finished. In the example of the time chart shown in FIG. 8, since the vehicle 1 has not started turning at time t ₀ , the “vehicle attitude control flag” is “false”, and the processing 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 turning vehicle are compared, and if the outer wheel speed is high, the process proceeds to step S17, and if the inner wheel speed is high, the speed is increased. The process proceeds to step S21. When no slip occurs in each of the rear wheels, the wheel speed of the outer rear wheel is high, and when a certain degree of slip occurs in the inner rear wheel, this relationship is reversed. In the example of FIG. 8, at time t ₁ is cut start of the steering wheel 6 by the driver, wheel speed of the outer rear wheel of the vehicle 1 that initiated the pivot is high, has become lower wheel speed of the inner rear wheel, flowcharts The process proceeds 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. Is determined to be greater than. If wheel speed difference between the outer and inner is less than the first wheel speed difference T _a is executed step S23 following processes, without application of braking force by the vehicle posture control is performed, the flow chart shown in FIG. 7 Ends one process of. That is, the difference in wheel speed between the left and right rear wheels may also be caused by an error in the wheel speed sensor 24, and if vehicle attitude control is intervened based on a minute difference in wheel speed, the driver may feel uncomfortable. When the wheel speed difference is small, vehicle attitude control is not executed. The first wheel speed difference T _a is a threshold of the wheel speed difference is changed based on the vehicle speed of the vehicle 1. The specific setting of the wheel speed difference threshold value will be described later with reference to FIG.

In the example of FIG. 8, by the driver performing a turning operation of the steering wheel 6 at time t _1, the vehicle 1 starts turning, wheel speed difference is gradually increased, wheel speed difference is the first wheel it exceeds the speed difference T _a, so that step S18 following processing is executed.
In step S18, the lateral acceleration detected by the lateral acceleration sensor 22 is higher than the predetermined first lateral acceleration GY _a [G] (1 [G] = 9.81 [m / sec ² ]), and the vehicle speed sensor. vehicle speed detected by the 20 whether high is determined than a predetermined first vehicle speed V _a [km / h]. When the lateral acceleration is 1st lateral acceleration GY _a or less, or the vehicle speed is 1st vehicle speed V _a or less, the process of step S23 or less is executed, and the braking force is applied by the vehicle attitude control. Instead, one process of the flowchart shown in FIG. 7 is completed. That is, when the lateral acceleration or the vehicle speed is very low, there is little need to intervene in the vehicle attitude control, and unnecessary intervention may give the driver a sense of discomfort. Therefore, the vehicle attitude control is not executed.

On the other hand, the lateral acceleration exceeds the first lateral acceleration GY _a, and the vehicle speed when it exceeds the first vehicle speed V _a, the step S19 does the following, application of braking force by the vehicle posture control is performed .. First, in step S19, the vehicle attitude control flag is changed to "true". When the vehicle attitude control flag is changed to "true" in step S19, the process in the flowchart of FIG. 7 proceeds from step S12 to S13 during that time. However, in the example shown in FIG. 8, since the high road surface friction mode is selected by the mode setting switch 26, the processing of the flowchart of FIG. 7 proceeds from step S13 to S16, and the processing in steps S14 and S15 is not executed.

Next, in step S20, the basic command value F _b1 [N] for vehicle attitude control is determined based on the difference in wheel speed between the left and right rear wheels. That is, the braking force acting on 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 of the braking force applied to the inner rear wheel of the turning vehicle 1, and is a predetermined coefficient C for the difference between the outer wheel speed V _o and the inner wheel speed V _i. It is calculated by the formula (2) by multiplying by _m1 .

Further, in step S25, various gains are multiplied by the basic command value F _b1 calculated in step S20 to determine the final command value F ₁ for vehicle attitude control. The specific processing executed in step S25 will be described later. Next, in step S26, the command values calculated in 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 calculated in step S20 by vehicle attitude control, the lower limit braking force calculated in step S15 by Pre-brake LSD control, step S22, as described later. The second braking force by the brake LSD control calculated in is also calculated. In step S26, the maximum braking force is selected from these calculated braking forces, and one process of the flowchart shown in FIG. 7 is completed. When the processing of the flowchart of FIG. 7 is completed, the processing proceeds to step S5 of the flowchart of FIG. 6, and the braking device 8 is controlled so that the braking force selected there acts.

In the example shown in FIG. 8, after the cut of the steering wheel 6 is started at time t _1, since the wheel speed of the outside rear wheel of the vehicle 1, the difference in wheel speed of the inner rear wheel is increased, the formula The command value of the braking force 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). Then, at time t ₂ in FIG. 8, the driver starts depressing the accelerator pedal, and the difference in wheel speed between the left and right rear wheels becomes constant accordingly (time t _{2 to} t _{3 in} FIG. 8). During this period, the command value of the braking force calculated by the mathematical formula (2) also becomes constant while maintaining the maximum value.

Next, at time t ₃ in FIG. 8, the driver ends the notch of the steering wheel 6, shifting to the steering holding, the vehicle 1 is in a steady turning state. Along with this, the wheel speeds of the inner and outer rear wheels increase, and the difference in wheel speed between the inner rear wheels and the outer rear wheels decreases (time t _{3 to} t _{4 in} FIG. 8). As a result, the command value of the braking force calculated by the mathematical formula (2) is also reduced. Further, at time t ₄ in FIG. 8, since the wheel speed difference between the rear wheel of the rear wheels and outside the inner is less than the first wheel speed difference T _a, the processing in the flowchart of FIG. 7, step S17 → S23 The command value based on the vehicle attitude control becomes zero.

Then, at time t ₅ in FIG. 8, a slip of the inner rear wheel is increased, and reverses the wheel speed of the rear wheel of the rear wheels and outside the inner, the higher the wheel speed of the inner rear wheel. As a result, the process in the flowchart of FIG. 7 proceeds from step S16 to S21, and the process of step S21 or less in the flowchart of FIG. 7 is 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 larger than the second wheel speed difference T _b [m / sec]. To. When the difference between the outer and inner wheel speeds is less than or equal to the second wheel speed difference T _b , the process of step S23 or less is executed, and the braking force is not applied by the brake LSD control, and the flowchart shown in FIG. 7 is shown. Ends one process of. That is, the difference in wheel speed 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 difference in wheel speed, the driver may feel uncomfortable. When the wheel speed difference is small, the brake LSD control is not executed.

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 T _{b, the process} proceeds to step S22, and the command value of the second braking force based on the brake LSD control is calculated. As described above, the brake control unit 14a exerts a second braking force on the inner rear wheels when the wheel speed of the inner rear wheels of the vehicle 1 becomes faster than the wheel speeds of the outer rear wheels while the vehicle 1 is turning. Let me. The brake LSD control is a control for braking a wheel that is idling to reduce the wheel speed and avoiding an idling state. That is, as shown at times t _{5 to} t ₆ in FIG. 8, the wheel speed of the inner drive wheels (rear wheels in this embodiment) of the turning vehicle 1 exceeds the wheel speed of the outer drive wheels. Then the inner drive wheels are starting to spin. When the wheel speed difference becomes large due to the idling 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. Decrease.

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

In the example shown in FIG. 8, at time t _5, application of a braking force based on the brake LSD control is started, thereby lowering the wheel speed of the rear wheels of the inner, at time t ₆ the inside rear wheel and an outer The wheel speed difference between the rear wheels is almost zero. After the wheel speed difference becomes almost zero at time t ₆ , the processing in the flowchart of FIG. 7 proceeds as in step S16 → S21 → S23 or step S16 → S17 → S23, and the braking force on the inner rear wheel Is not given (time t _{6 to} t _{7 in} FIG. 8).

Further, in the example shown in FIG. 8, the driver starts turning back of the steering wheel 6 at time t ₆ , completes turning back at time t ₇ , returns to the straight-ahead state, and ends the turning run.
In step S23, it is determined whether or not the turning back of the steering wheel 6 is completed based on the detection value of the steering angle sensor 16, and if the turning back is not completed, the process proceeds to step S25 and the turning back is performed. When completed, the process proceeds to step S24. In the present embodiment, the brake control unit 14a is, after the turning operation of the steering wheel 6 is started at time t ₁ in FIG. 8, in the vehicle attitude control until the returning operation is completed at time t ₇ , A braking force is generated at a brake fluid pressure of about 0.1 MPa or less.

In step S24, since the turning back is completed and the turning run is completed, the "vehicle attitude control flag" is changed to "false". After that, when the flowchart shown in FIG. 7 is executed, the process proceeds from step S12 to S16. In this state, even when the low road surface friction mode is set by the mode setting switch 26, the braking force based on the Pre brake LSD control is not applied.

Next, with reference to FIG. 9, the vehicle attitude control when the low road surface friction mode is set by the mode setting switch 26 will be described.
The time chart shown in FIG. 9 shows an example of vehicle attitude control when the low road surface friction mode is set. When the low road surface friction mode is set, the flowchart of FIG. 7 is different from the time chart of FIG. 8 in that the processing of step S14 or lower is executed. In the process of step S14 and subsequent steps, the braking force based on the Pre-brake LSD control is calculated. In the time chart of FIG. 9, the command value by the vehicle attitude control is shown by a solid line, the command value by the Pre brake LSD control is shown by a broken line, and the command value by the brake LSD control is shown by a dashed line.

In the present embodiment, the low road surface friction mode and the high road surface friction mode are switched by the setting of 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 the setting of the mode setting switch 26. For example, the friction coefficient of the road surface is estimated according to the outside air temperature sensor, rainfall sensor, wiper operating condition, driving wheel slip condition, etc. mounted on the vehicle 1, and when the friction coefficient is equal to or less than a predetermined value, it is automatically performed. The brake control unit 14a can also be configured so as to set the low road surface friction mode. In this case, the brake control unit 14a also functions as a friction coefficient estimation unit that estimates the friction coefficient of the road surface on which the vehicle 1 is traveling.

First, the driver at the time t ₁₁ of FIG. 9 starts the notch of the steering wheel 6, wheel speed difference is generated between the rear wheels of rear wheels and outside the inner, vehicle posture control is started. As a result, in the flowchart of FIG. 7, the processes of steps S11 → S12 → S16 → S17 → S18 → S19 → S20 → S25 → S26 are executed. By this process, when the vehicle attitude control flag is changed to "true" in step S19, the process proceeds from step S12 to S13 the next time the flowchart of FIG. 7 is executed, and the process of step S13 and subsequent steps is performed. Is executed.

In step S13, it is determined whether or not the low road surface friction mode is set. In the example of the time chart of FIG. 9, since the low road surface friction mode is set, the process proceeds to step S14. In step S14, it is determined whether or not the lateral acceleration detected by the lateral acceleration sensor 22 is higher than the predetermined second lateral acceleration GY _b [G]. When the lateral acceleration is equal to or less than the second lateral acceleration GY _b , the process proceeds to step S16, and the braking force is not applied by the Pre-brake LSD control. In the present embodiment, the second lateral acceleration GY _b is set to a value smaller than the first lateral acceleration GY _a . That is, when the lateral acceleration is very low, there is little need to intervene in the Pre-brake LSD control, and unnecessary intervention may give the driver a sense of discomfort. Therefore, the Pre-brake LSD control is not executed.

On the other hand, when the lateral acceleration is larger than the second lateral acceleration GY _b , the process proceeds to step S15, and the basic command value F _b3 of the lower limit braking force by the Pre brake LSD control is determined. In step S15, the basic command value F _b3 is calculated by the mathematical formula (4) 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 .

In this embodiment, the coefficient C _m3 is set to a positive value less than 1. That is, the basic command value F _b3 by the Pre-brake LSD control is always set to a value smaller than the maximum value of the basic command value F _b1 of the vehicle attitude control. In the example shown in FIG. 9, during the time t ₁₁ ~t _12, since the basic command value F _b1 of the vehicle attitude control tends to increase, the maximum value is also updated from time to time, multiplied by the coefficient C _m3 thereto The value of the basic command value F _b3 also increases. Next, from time t _{12 to} t ₁₃ , the basic command value F _{b1 for} vehicle attitude control becomes constant at the maximum value, so the maximum value also becomes a constant value, and the basic command value F obtained by multiplying this by the coefficient C _m3. The value of _b3 is also constant. Further, the time t ₁₃ after the basic command value F _b1 of the vehicle attitude control is made to decrease, the maximum value is held and also maintained the value of the basic command value F _b3 multiplied this coefficient C _m3 .. Basic command value F _b3 by the Pre brake LSD control, turning is completed at time t _17, it is maintained until the vehicle attitude control flag is changed to "false" (step S23 → S24). In this way, after applying the first braking force by vehicle attitude control, even if the wheel speed difference between the inner rear wheel and the outer rear wheel decreases, a predetermined lower limit braking force is applied until the turning is completed. The above braking force is maintained.

Thus, the braking force based on the Pre brake LSD control, (after time t ₁₄ of FIG. 9) after the application of the braking force based on the vehicle attitude control is completed, application of the braking force is started by the brake LSD control again ( When the time t ₁₅₎ is the 9, the braking force short time is applied to the inner rear wheel of the vehicle 1 is changed, it is applied for the purpose of suppressing the discomfort to the driver. On the other hand, when the high road surface friction mode is selected, it is rare that the braking force is applied by the brake LSD control after the braking force is applied by the vehicle attitude control, and the brake LSD control is executed. Even if it is applied, the braking force applied 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 surface friction mode is selected, and when the high road surface friction mode is selected, the Pre brake LSD control is performed. It is not executed (steps S13 → S16 in FIG. 7). Alternatively, as a modification, the present invention can be configured so that the Pre-brake LSD control is executed even when the high road surface friction mode is selected. In this case, it is preferable to set the coefficient C _m3 in the high road surface friction mode to be smaller than the coefficient C _m3 in the low road surface friction mode.

Subsequently, in the example shown in FIG. 9, at time t ₁₅ ~t _16, slip is generated in the inner rear wheel, the basic command value F _b2 of the brake LSD control is set. Thus, in the example shown in FIG. 9, at time t ₁₁ ~t ₁₄ is set basic command value F _b1 by the vehicle attitude control, the basic command value F _b3 by Pre brake LSD control at time t ₁₁ ~t ₁₇ is is set, the basic command value F _b2 of the brake LSD control is set at time t ₁₅ ~t _16.

In step S25 of FIG. 7, each gain to be multiplied by each basic command value is set, and command values F ₁ , F ₂ , and F ₃ obtained by multiplying each basic command value by a gain are calculated, respectively. Further, in step S26, these command values F ₁ , F ₂ , and F ₃ are compared, the largest command value is adopted, and a 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 18.

Next, with reference to FIG. 10, the setting of the wheel speed difference threshold value (first wheel speed difference _Ta ) 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. 7 is based on the map 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 T _a is the maximum in a vehicle speed 0, and decreases with increasing vehicle speed becomes substantially constant value at a predetermined vehicle speeds V _{1 to} more. Preferably, sets the value of the vehicle speeds V _{1 to} about 80 to about 110 [km / h] degrees per hour, this value or more, the first wheel speed difference T _a = about 0.02 to about 0.05 [m Set to [/ sec].

In this way, 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 T _a is a threshold wheel speed difference, a low vehicle speed region, the vehicle attitude control is less likely to intervene executed in the following step S18 in FIG. 7. 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 the intervention of such unwanted vehicle attitude control, in the present embodiment, the value of the first wheel speed difference T _a is set as shown in FIG. 10.

Next, with reference to FIGS. 11 to 18, the gain to be multiplied by each basic command value in step S25 of FIG. 7 will be described.
FIG. 11 is a steering angle gain that is set based on the steering angle and is multiplied by the basic command value F _b1 by vehicle attitude control. Further, FIGS. 12 to 14 are maps applied when the high road surface friction mode is set. FIG. 12 is a map of the accelerator opening gain, which is set based on the accelerator opening and is multiplied by the basic command value F _b1 by the vehicle attitude control. FIG. 13 is a map of the lateral acceleration gain that is set based on the lateral acceleration and multiplied by the basic command value F _b1 by the vehicle attitude control. FIG. 14 is a map of the vehicle speed gain set based on the vehicle speed and multiplied by the basic command value F _b1 by the vehicle attitude control.

Further, FIGS. 15 to 17 are maps applied when the low road surface friction mode is set. FIG. 15 is a map of the accelerator opening gain, which is set based on the accelerator opening and is multiplied by the basic command value F _b1 by the vehicle attitude control. FIG. 16 is a map of the lateral acceleration gain that is set based on the lateral acceleration and multiplied by the basic command value F _b1 by the vehicle attitude control. FIG. 17 is a map of the vehicle speed gain set based on the vehicle speed and multiplied by the basic command value F _b1 by the vehicle attitude control. Further, FIG. 18 is a map of the differential rotation gain which is set based on the difference between the inner and outer wheel speeds and is multiplied by the basic command value F _b2 by the brake LSD control.

As shown in FIG. 11, the steering angle gain G _θ is zero in the region where the steering angle θ [deg] is equal to or less than the _first steering angle θ ₁ , increases at θ ₁ or more, and increases at the predetermined steering angle or more. It is set to converge to "1". By setting the steering angle gain G _θ in this way, in the region where the steering angle is the first steering angle θ ₁ or less, the vehicle attitude control is substantially not executed and the control intervention is not performed (steering angle). By multiplying the gain G _θ , the command value for vehicle attitude control becomes zero.) As a result, the vehicle attitude control intervenes due to the fine steering of the steering wheel 6 to prevent the driver from feeling uncomfortable. Preferably, the value of the first steering angle θ ₁ is set to about 3.5 to about 6.0 [deg], and the value of the steering angle gain G _θ is set to be zero below this value. ..

As shown in FIG. 12, the accelerator opening gain G _aH increases with increase in the accelerator opening [%], "1" in the first accelerator opening A _1, and the first accelerator opening A ₁ or more Is set to converge to a predetermined value larger than "1". By setting the accelerator opening gain G _aH in this way, the command value by the vehicle attitude control becomes smaller as the accelerator opening decreases. That is, in a region where the accelerator opening is small, the rear part of the inside of the vehicle body 1a is unlikely to be lifted, so that unnecessary intervention of vehicle attitude control suppresses the driver from feeling uncomfortable. Preferably, the first value of the accelerator opening degree A ₁ is set to about 45 to about 60 [%] extent, this value or less, the accelerator opening gain G _aH not more than "1", this value or more, The accelerator opening gain G _aH is set to be "1" or more.

As shown in FIG. 13, the lateral acceleration gain G _lH is zero in the region where the lateral acceleration a _l [G] is equal to or less than the first lateral acceleration a _l1 , and increases at a _l1 or more to exceed a predetermined lateral acceleration. Is set to converge to "1". By setting the lateral acceleration gain G _lH 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 turning vehicle 1 than when the lateral acceleration of the vehicle 1 is small. Will be done. _Further, by setting the lateral acceleration gain G _lH as shown in FIG. 13, in the region where the lateral acceleration is equal to or less than the first lateral acceleration a _l1 , the intervention of the vehicle attitude control is substantially eliminated (lateral acceleration gain G). _By multiplying by _lH , the command value of vehicle attitude control becomes zero.) That is, in a region where the lateral acceleration a _l is minute, the rear part of the inside of the vehicle body 1a is unlikely to be lifted, so that unnecessary intervention of vehicle attitude control suppresses the driver from feeling uncomfortable. Preferably, the value of the first lateral acceleration a _l1 is set to about 0.22 to about 0.35 [G], and below this value, the value of the lateral acceleration gain G _lH is set to zero. ..

As shown in FIG. 14, the vehicle speed gain G _VH is gradually increased with increasing vehicle speed [km / h], "1" in the first vehicle speeds V _{1 to,} in the first vehicle speeds V _{1 to} more, relatively rapidly It is set to increase. By setting the vehicle speed gain G _VH in this way, the command value by vehicle attitude control increases as the vehicle speed increases, and when the vehicle speed is high, a larger braking force is applied to the inside of the turning vehicle than when the vehicle speed is low. It acts on the rear wheels. That is, while the lift of the inner rear portion of the vehicle body 1a is unlikely to occur in the region where the vehicle speed is low, the problem of the lift of the inner rear portion of the vehicle body 1a becomes remarkable as the vehicle speed increases. Is strongly intervening. Preferably, the value of the first vehicle speed V ₁ is set to about 95 to about 115 [km / h], the vehicle speed gain G _{VH is set} to "1" or less below this value, and the vehicle speed gain G is above this value. Set to increase _VH .

In step S25 of FIG. 7, when the high road surface friction mode is selected, the basic command value F _b1 for vehicle attitude control is based on the steering angle gain G _θ set based on FIG. 11 and FIG. The accelerator opening gain G _aH set according to FIG. 13, the lateral acceleration gain G _lH set based on FIG. 13, and the vehicle speed gain G _VH set based on FIG. 14 are multiplied, and the vehicle attitude is _calculated by the formula (5). The control command value F ₁ is calculated.

On the other hand, when the low road surface 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 surface friction mode is selected. Each is set using.

As shown in FIG. 15, when the low road surface friction mode is selected, the accelerator opening gain G _aL increases as the accelerator opening [%] increases, and the second accelerator opening A ₂ becomes “ It becomes 1 ”, and when the second accelerator opening A ₂ or more, it is set to be a predetermined value larger than“ 1 ”. By setting the accelerator opening gain G _aL in this way, the command value by the vehicle attitude control decreases as the accelerator opening decreases. Further, the second accelerator opening A ₂ in which the accelerator opening gain G _aL in the low road surface friction mode is “1” is the first accelerator in which the accelerator opening gain G _aH in the high road surface friction mode is “1”. The opening is set larger than A ₁ . Preferably, the value of the second accelerator opening A ₂ is set to about 60 to about 75 [%], and below this value, the accelerator opening gain G _{aL is set} to "1" or less, and above this value, The accelerator opening gain G _aL is set to be "1" or more.

As shown in FIG. 16, when the low road surface 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 less than the second lateral acceleration a _l 2. It is set to increase at the second lateral acceleration a _l2 or more and converge to "1" at a predetermined lateral acceleration or more. In this way, in the low road surface friction mode, a lateral acceleration gain different from that in the high road surface friction mode is set. Therefore, in the vehicle attitude control, in the low road surface friction mode and the high road surface friction mode, the same lateral acceleration is applied. Different braking forces are generated. Further, by setting the lateral acceleration gain G _lL in this way, in the region where the lateral acceleration is the second lateral acceleration a _l2 or less, the intervention of the vehicle attitude control is substantially eliminated (the lateral acceleration gain G _{l L} is set). By multiplying, the command value of vehicle attitude control becomes zero.) The second lateral acceleration a _l2 the lateral acceleration gain G _lL in the low road surface friction mode is greater than zero, in the present embodiment, the lateral acceleration gain G _lH is greater than zero in the high road surface 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 surface friction mode, the vehicle attitude control intervenes from a state where the lateral acceleration is smaller than in the high road surface friction mode. Preferably, the value of the second lateral acceleration a _l2 is set to about 0.02 to about 0.15 [G], and below this value, the value of the lateral acceleration gain G _{l L} is set to be zero. ..

As shown in FIG. 17, when the low road surface friction mode is selected, the vehicle speed gain G _VL is in the second speed V ₂ less is zero, increasing the second speed V ₂ or greater, predetermined It is set to converge to a predetermined value smaller than "1" at the 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 G _VL in this way, the vehicle attitude control does not intervene at the second vehicle speed V ₂ or less, and the command value by the vehicle attitude control is reduced even in the region where the vehicle speed is high. That is, when the low road surface friction mode is selected, the intervention of vehicle attitude control is suppressed at any vehicle speed as compared with the high road surface friction mode. That is, the braking force of the vehicle attitude control suppresses the occurrence of slip on the inner rear wheels. 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 a region where the vehicle speed is high. Set the vehicle speed gain G _{VL so} as to.

In step S25 of FIG. 7, when the low road surface friction mode is selected, the basic command value F _b1 for vehicle attitude control is based on the steering angle gain G _θ set based on FIG. 11 and FIG. The accelerator opening gain G _aL set according to FIG. 16, the lateral acceleration gain G _lL set based on FIG. 16, and the vehicle speed gain G _VL set based on FIG. 17 are multiplied, and the vehicle attitude is calculated by the formula (6). The control command value F ₁ is calculated.

Next, with reference to FIG. 18, when the low road surface friction mode is selected, the differential rotation gain G _DL multiplied by the basic command value F _b2 by the brake LSD control will be described. When the high road surface friction mode is selected, the differential rotation gain G _DH is always "1".
As shown in FIG. 18, the differential rotation gain G _DL 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 D ₁ [m / sec], and is equal to or greater than the first differential rotation D _1. Is set to converge to a predetermined value larger than "1". By setting the differential rotation gain G _DL in this way, when the differential rotation becomes the first differential rotation D ₁ or more, the command value of the brake LSD control becomes large. That is, when the low road surface friction mode is selected, the braking force applied when slip occurs on the inner ring is set to be larger than when the high road surface friction mode is selected, and the slip of the inner ring is made stronger. Suppress. Preferably, the value of the first differential rotation D ₁ is set to about 8 to about 12 [m / sec] so that the command value of the brake LSD control becomes large at this value or more. Further, preferably, the differential rotation gain G _DL is set so as to converge to about 1.3 to about 1.6 in a region where the differential rotation D is large.

In step S25 of FIG. 7, when the low road surface friction mode is selected, the basic command value F _b2 for the brake LSD control is multiplied by the differential rotation gain G _DL set based on FIG. According to (7), the command value F _{2 for the} brake LSD control is calculated. On the other hand, when the high road surface friction mode is selected, the differential rotation gain G _DH is always "1", so that the basic command value F _b2 value is set to the command value F ₂ as it is.

As described above, in step S25 of FIG. 7, the command value F ₁ of the vehicle attitude control is calculated by the mathematical formula (5) or (6) based on the basic command value F _b1 of the vehicle attitude control. Further, the command value F ₂ is calculated by the mathematical formula (7) based on the basic command value F _b2 of the brake LSD control, or the basic command value F _{b 2} is used as the command value F ₂ as it is.

When the low road surface friction mode is selected, the command value F _{3 for} the Pre-brake LSD control is calculated by multiplying the basic command value F _{b 3} by the same gain as for the vehicle attitude control. That is, the command value F ₃ is calculated by the following mathematical 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 and before 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 the same gain as 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, the Pre-brake LSD control is not executed as described above (Pre-brake LSD control command value F ₃ = 0). However, as a modification, when the present invention is configured so that the Pre-brake LSD control is executed even when the high road surface friction mode is selected, the command value F ₃ is calculated by the following mathematical formula (9). can do. Thereby, even in the high road surface 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 command value F ₁ of the vehicle attitude control calculated as described above, the command value F ₂ of the brake LSD control, and the command value F ₃ of the Pre brake LSD control are compared. The largest command value is finally determined as the command value of the braking force acting on the inner rear wheel. When the command value of the braking force 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 braking device 8 is controlled based on the determined command value.

According to the vehicle attitude control device of the embodiment of the present invention, when the vehicle 1 is turning based on the cutting operation of the steering wheel 6 of the vehicle 1, a braking force is applied to the inner rear wheels of the turning vehicle 1. It is configured to execute vehicle attitude control (steps S2 and 7 in FIG. 6) that suppresses the lifting of the inside rear of the vehicle body 1a. The braking force applied to the inner rear wheels of the vehicle 1 based on the vehicle attitude control is set so that the deceleration in the vertical direction that suppresses the lifting of the inner rear part of the vehicle body 1a is equal to or less than a predetermined value (FIG. 7). Step S20). The braking force acting on the inner rear wheels is not such that a yaw moment is substantially added to the vehicle, and the lifting of the inner rear part of the vehicle body is suppressed while suppressing the influence on the turning performance of the vehicle 1. It acts to reduce anxiety to the driver and occupants.

Further, according to the vehicle attitude control device of the present embodiment, a braking force is generated at a brake hydraulic pressure of 0.02 MPa or more and 0.1 MPa or less in the vehicle attitude control for the vehicle 1 having a mass of 960 kg to 1060 kg. , The deceleration in the vertical direction is caused to be less than a predetermined value. Therefore, the braking force does not substantially apply the braking force to the turning vehicle 1 while suppressing the lifting of the inner rear portion of the vehicle body 1a during turning.

Further, according to the vehicle attitude control device of the present embodiment, 0.1 MPa or less is obtained from the start of the turning operation of the steering wheel 6 (time t _{1 in} FIG. 8) to the end of the turning back operation (time t _{7 in} FIG. 8). Since the braking force is generated by the brake fluid pressure of the above, the yaw moment is not substantially applied to the vehicle 1 during turning, and the influence on the turning performance can be surely eliminated.

Further, according to the vehicle attitude control device of the present embodiment, the turning control unit 14b applies a braking force to the inner rear wheels of the turning vehicle 1 with a brake fluid pressure of 0.2 MPa or more and 0.5 MPa or less. Since the yaw moment is generated (step S3 in FIG. 6), a sufficient yaw moment is given to the vehicle 1 in a situation where turning control is required, and the turning performance of the vehicle 1 can be improved.

Further, according to the vehicle attitude control device of the present embodiment, the sideslip prevention control unit 14c exerts a braking force on the turning vehicle 1 at a brake fluid pressure of 20 MPa or more (step S4 in FIG. 6), so that the sideslip prevention is prevented. In a situation where control is required, a sufficient braking force is applied to the vehicle 1 to prevent the vehicle 1 from skidding.

Further, according to the vehicle attitude control device of this embodiment, the rear wheels 2c to the vehicle body 1a, the upper arm 3a is a link mechanism for suspending an axle of 2d, lower arm 3b is around the predetermined suspension center P _S The axle 2e is suspended so that the axle rotates (FIG. 4). By this suspension center P _S is positioned higher than the axle 2e, when allowed to act braking force to the rear wheels 2c and 2d, a force pulling the upper arm 3a, and the vehicle body 1a through the lower arm 3b downward component Therefore, it is possible to more effectively suppress the lifting of the rear part inside the vehicle body.

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

1 Vehicle 1a Body 2a, 2b Front wheels 2c, 2d Rear wheels 2e Axles 3 Suspension (wheel suspension)
3a Upper arm (link mechanism)
3b Lower arm (link mechanism)
4 Engine 4a Transmission 4b Propeller shaft 4c Differential gear 6 Steering wheel 7 Steering device 8 Brake device (brake actuator)
10 Hydraulic pump 12 Valve unit 13 Hydraulic sensor 14 PCM
14a Brake control unit (brake control device)
14b Turn control unit 14c Electronic stability 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 (7)

A vehicle attitude control device that controls the attitude of a vehicle in which a wheel suspension device is configured so that the roll axis of the vehicle tilts forward.
Brake actuators that apply braking force to the wheels of the vehicle,
It has a brake control device that sends a control signal to the brake actuator and generates a braking force based on the running state of the vehicle.
The brake control device is a vehicle attitude control that suppresses the lifting of the inner rear part of the vehicle body by applying a braking force to the inner rear wheels of the turning vehicle when the vehicle is turning based on the cutting operation of the steering wheel of the vehicle. Is configured to run
The braking force applied to the inner rear wheels of the vehicle based on the vehicle attitude control is characterized in that the deceleration in the vertical direction that suppresses the lifting of the inside rear of the vehicle body is set to be equal to or less than a predetermined value. Vehicle attitude control device. The mass of the vehicle is 960 kg to 1060 kg, and the brake control device generates a braking force at a brake hydraulic pressure of 0.1 MPa or less in the vehicle attitude control, and causes a deceleration in the vertical direction of 0.1 MPa or less. The vehicle attitude control device according to claim 1. The vehicle attitude control device according to claim 2, wherein the brake control device generates a braking force at a brake fluid pressure of 0.02 MPa or more in the vehicle attitude control to cause a deceleration in the vertical direction. The brake control device applies a braking force with a brake hydraulic pressure of 0.1 MPa or less in the vehicle attitude control from the start of the steering wheel turning operation to the end of the steering wheel turning back operation. The vehicle attitude control device according to claim 2 or 3, which is configured to generate. Further, it has a turning control unit that executes turning control to improve the turning performance of the vehicle, and this turning control unit exerts a braking force on the inner rear wheels of the vehicle during turning to cause the vehicle to have a yaw moment. In the turning control, the braking force is applied to the inner rear wheels of the vehicle at a brake hydraulic pressure of 0.2 MPa or more and 0.5 MPa or less according to any one of claims 2 to 4. The vehicle attitude control device described. Further, it has a skid prevention control unit that executes skid prevention control for suppressing skidding when the vehicle is turning, and this skid prevention control unit exerts a braking force on the turning vehicle to cause the vehicle to skid. The vehicle attitude control device according to any one of claims 2 to 5, which is configured to suppress the above-mentioned electronic stability control, in which a braking force is applied to the wheels of the vehicle with a brake fluid pressure of 20 MPa or more. The wheel suspension device includes a link mechanism for suspending the axles of the rear wheels with respect to the vehicle body, and the link mechanism suspends the axles so that the axles rotate around a predetermined suspension center. The vehicle attitude control device according to any one of claims 1 to 6, wherein the suspension center is located above the axle.

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