JP2000233732A - Vehicular motion control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a tire from applying an excessive load when tire air pressure goes down during car's traveling. SOLUTION: This motion control device is equipped with a tire air pressure detecting means PT detecting the tire air pressure of each wheel WL, a tire load detecting means LT detecting the load acting on each tire of these wheels WL, and an upper limit value setting means UL setting an upper limit value of the load to the tire of the air pressure lowering wheel according to the tire air pressure when the tire air pressure of the wheel detected by the air pressure detecting means PT is lowered to the specified value, respectively. Furthermore, when it is equipped with a control means CT and it detects the tire air pressure less than the specified value during vehicle's traveling, it controls braking force and or driving force to these wheels WL so as to make the tire load not exceed the upper limit value as to the air pressure lowered wheel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motion control device for a vehicle, and more particularly, to a device for applying a braking force to each wheel during vehicle motion including turning of the vehicle, regardless of whether a brake pedal is operated or not. The present invention relates to a vehicle motion control device that stabilizes a vehicle motion state by controlling a driving force.

[0002]

2. Description of the Related Art In recent years, attention has been paid to means for controlling the motion characteristics, particularly the turning characteristics, of a vehicle. For example, Japanese Patent Laid-Open No. 2-1
No. 71373 discloses that the state of a turning vehicle is detected,
The purpose is to maintain the stability of the vehicle by controlling the vehicle speed, and at the time of turning the vehicle, estimate the limit at which stable turning can be performed based on the output from the sensor group that detects the turning state. 2. Description of the Related Art A vehicle brake device has been proposed in which a vehicle is decelerated when approaching a limit.

[0003]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Application Laid-Open No. 2-171 is disclosed.
In the device described in Japanese Patent Publication No. 373, the vehicle is decelerated when the turning state approaches the limit.
No action is taken when the vehicle condition is abnormal. For example, when the air pressure of a tire is low, an excessive load is applied to the tire when a braking force or a lateral force is applied to the tire according to a normal control condition even if the vehicle is turning.

Accordingly, an object of the present invention is to provide a vehicle motion control apparatus that does not apply an excessive load to a tire when the air pressure of the tire decreases during traveling.

[0005]

In order to solve the above-mentioned problems, the present invention provides an air pressure detecting means for detecting a tire air pressure of each wheel of a vehicle, and a tire of each wheel. A tire load detecting means for detecting a load acting on the tire, and when the tire pressure of the wheel detected by the air pressure detecting means falls below a predetermined value, the upper limit of the load on the tire of the tire with the reduced air pressure according to the tire pressure. An upper limit value setting means for setting a value, and when the air pressure detecting means detects a tire pressure equal to or less than the predetermined value while the vehicle is running, a tire load detected by the tire load detecting means with respect to the wheel having a decreased air pressure is a tire load. Control means for controlling a braking force and / or a driving force for each of the wheels so as not to exceed the upper limit value.

The loads acting on the tires of the respective wheels include a braking force applied to the wheels when the vehicle is braking, and a lateral force applied to the wheels when the vehicle turns, for example. As the air pressure detecting means, for example, there is an air pressure sensor mounted on each wheel to detect the air pressure of each tire, and as the tire load detecting means, for example, connected to a wheel cylinder of each wheel to detect wheel cylinder hydraulic pressure There is a pressure sensor that detects the lateral acceleration of the vehicle, a lateral acceleration sensor that detects the lateral acceleration of the vehicle, and a load sensor that detects the load on each wheel, and calculates the lateral force on the wheels based on the detection results.

[0007] The control means may include a braking force limiting means for limiting a braking force to the wheel with reduced air pressure according to a tire pressure of the wheel with reduced air pressure when braking the vehicle. It is good to have it.

Alternatively, the control means may include a lateral force restricting means for restricting a lateral force applied to the air pressure lowering wheel according to a tire pressure of the air pressure lowering wheel when the vehicle turns. It may be provided. It is to be noted that the vehicle is provided with lateral acceleration detecting means for detecting the lateral acceleration of the vehicle, and the lateral force on the wheels can be calculated based on the lateral acceleration detected by the lateral acceleration detecting means.

Further, as set forth in claim 4, a tire pressure detecting means for detecting a tire pressure of each wheel of the vehicle, a tire load detecting means for detecting a load acting on a tire of each wheel, and the tire pressure detecting means Upper limit value setting means for setting an upper limit value of a load on a tire of the tire having a reduced pressure according to the tire pressure when the tire pressure of the wheel detected by the means falls below a predetermined value; and When the air pressure detecting means detects a tire air pressure equal to or less than the predetermined value, each of the tires other than the air pressure lowering wheel is controlled so that the tire load detected by the tire load detecting means with respect to the air pressure lowering wheel does not exceed the upper limit value. It may be configured to include a braking force control unit that applies a braking force to the wheel. Further, when the air pressure detecting means detects a tire air pressure equal to or less than the predetermined value while the vehicle is running, the tire load detected by the tire load detecting means with respect to the wheel with reduced air pressure does not exceed the upper limit value. To
For example, a driving force control unit that reduces the throttle opening to reduce the driving force on the vehicle may be provided.

[0010]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows an embodiment of a motion control device according to the present invention, in which a brake fluid pressure is applied from a brake fluid pressure control device BC to each wheel WL of a vehicle according to at least a brake pedal operation, and at least an accelerator operation is performed. The opening and closing of the throttle valve of the internal combustion engine EG is controlled according to the driving force to control the driving force. In the vehicle, the tire pressure detecting means PT for detecting the tire pressure of each wheel WL, the tire load detecting means LT for detecting the load acting on the tire of each wheel WL, and the tire pressure of the wheel detected by the tire pressure detecting means PT. An upper limit value setting means UL is provided for setting an upper limit value of the load on the tire of the tire having a reduced air pressure according to the tire air pressure when the tire pressure falls below a predetermined value. Further, the control means C
T is provided, and when the tire pressure detecting means PT detects a tire pressure equal to or less than a predetermined value while the vehicle is running,
The braking force and / or the driving force for each wheel WL is controlled so that the tire load detected by the tire load detecting means LT does not exceed the upper limit value with respect to the wheel with reduced air pressure.

The control means CT may be provided with braking force limiting means BL for limiting the braking force on the wheel with reduced air pressure in accordance with the tire pressure of the wheel with reduced air pressure when braking the vehicle. It is also possible to provide a lateral force limiting means YL that limits the lateral force on the wheel with reduced air pressure according to the tire pressure of the wheel with reduced air pressure.

FIG. 2 shows an overall structure of a vehicle including the motion control device. An engine EG is an internal combustion engine having a throttle control device TH and a fuel injection device FI. In the throttle control device TH, an accelerator pedal AP is used. The main throttle opening of the main throttle valve MT is controlled in accordance with the operation of. Further, the sub-throttle valve ST of the throttle control device TH is driven to control the sub-throttle opening in accordance with the output of the electronic control unit ECU, and the fuel injection device FI is driven to control the fuel injection amount. It is configured. The engine EG of the present embodiment is connected to wheels FL,
FR, so-called front-wheel drive system is configured. For the braking system, wheels FL, FR, RL, RR
The wheel cylinders Wfl, Wfr, Wrl, Wr
r are mounted, and these wheel cylinders Wfl
And the like, a brake fluid pressure control device BC is connected. still,
The wheel FL indicates the front left wheel when viewed from the driver's seat, the wheel FR indicates the front right wheel, the wheel RL indicates the rear left wheel, and the wheel RR indicates the rear right wheel. In the present embodiment, a so-called X pipe is configured. I have.

The wheels FL, FR, RL, RR are provided with wheel speed sensors WS1 to WS4, which are connected to the electronic control unit ECU. The rotation speed of each wheel, that is, the number of pulses proportional to the wheel speed, Is input to the electronic control unit ECU. Further, the brake switch BS which is turned on when the brake pedal BP is depressed, the steering angle θ of the wheels FL and FR in front of the vehicle.
The front wheel steering angle sensor SSf for detecting f, the lateral acceleration sensor YG for detecting the lateral acceleration of the vehicle, and the changing speed of the vehicle rotation angle (yaw angle) around a vertical axis passing through the center of gravity of the vehicle, that is, the yaw angular speed (yaw rate) is detected. A yaw rate sensor YS or the like is connected to the electronic control unit ECU. Further, tire pressure sensors APS1 to APS4 for detecting the tire pressure (Pa **) of each wheel, and the load (N *) on each wheel.
*) And wheel cylinder pressure sensors WPS1 to WPS4 for detecting the fluid pressure in each wheel cylinder, and these are connected to the electronic control unit ECU (**). Is each wheel
FR etc.).

The electronic control unit ECU of the present embodiment has a configuration shown in FIG.
As shown in FIG. 1, a microcomputer CMP comprising a processing unit CPU, a memory ROM, a RAM, an input port IPT, an output port OPT, and the like, which are interconnected via a bus, is provided. The wheel speed sensor WS
1 to WS4, brake switch BS, front wheel steering angle sensor SSf, yaw rate sensor YS, lateral acceleration sensor YG,
Tire pressure sensors APS1 to APS4, wheel load sensors LS1 to LS4, wheel cylinder hydraulic pressure sensor W
The output signals of PS1 to WPS4 etc.
It is configured to be input to the processing unit CPU from the input port IPT via P. Also,
The output port OPT is configured to output control signals to the throttle control device TH and the brake fluid pressure control device BC via the drive circuit ACT.

In the microcomputer CMP,
The memory ROM stores programs for various processes including the flowcharts shown in FIGS. 3 to 9, the processing unit CPU executes the programs while an ignition switch (not shown) is closed, and the memory RAM executes the programs. Temporarily stores the variable data required for the execution of For each control such as throttle control,
Alternatively, a plurality of microcomputers may be configured by appropriately combining related controls, and the microcomputers may be electrically connected to each other.

In the present embodiment configured as described above, a series of processes such as braking steering control and anti-skid control are performed by the electronic control unit ECU, and when an ignition switch (not shown) is closed. Execution of the program corresponding to the flowcharts of FIGS. 3 to 9 and the like starts. 3 and 4 show the entire control operation of the vehicle.
First, in step 101, the microcomputer CMP is initialized, and various calculated values are cleared. Next, in step 102, the detection signals of the wheel speed sensors WS1 to WS4 are read, and the front wheel steering angle sensor SSf
(The steering angle θf), the detected yaw rate γa of the yaw rate sensor YS and the detected acceleration of the lateral acceleration sensor YG (that is, the actual lateral acceleration and represented by Gya). Further, the air pressure (Pa **) of each wheel detected by the tire pressure sensors APS1 to APS4 is read, and the load (N **) on each wheel detected by the wheel load sensors LS1 to LS4 is read.

Next, the routine proceeds to step 103, where the wheel speed Vw ** of each wheel is calculated, and these are differentiated to obtain the wheel acceleration DVw ** of each wheel. Subsequently, in step 104, the maximum value of the wheel speed Vw ** of each wheel is calculated as the estimated vehicle speed Vso at the position of the center of gravity of the vehicle (Vso = MAX (Vw **)). Also, the wheel speed V of each wheel
An estimated vehicle speed Vso ** is obtained for each wheel based on w **, and if necessary, normalization is performed to reduce an error based on a difference between the inner and outer wheels when the vehicle turns. Further, the estimated vehicle speed Vso is differentiated, and an estimated vehicle acceleration (including an estimated vehicle deceleration having the opposite sign) DVso at the position of the vehicle center of gravity is calculated.

Next, in step 105, the wheel speed V of each wheel obtained in steps 102 and 103 is calculated.
Based on w ** and the estimated vehicle speed Vso ** (or the normalized estimated vehicle speed), the actual slip ratio Sa ** of each wheel is Sa ** =
(Vso **-Vw **) / Vso **. next,
In step 106, based on the estimated vehicle body acceleration DVso at the position of the center of gravity of the vehicle and the actual lateral acceleration Gya of the detection signal of the lateral acceleration sensor YG, the road surface friction coefficient μ is approximately (DVso ² +
Gya ² ) calculated as ^1/2 . Further, as means for detecting the road surface friction coefficient, various means such as a sensor for directly detecting the road surface friction coefficient can be used.

In step 107, the load on the tire, that is, the upper limit of the tire braking force and the tire lateral force, is set, which will be described later with reference to FIG. Subsequently, in steps 108 and 109, the vehicle body slip angular velocity Dβ is calculated, and the vehicle body slip angle β is calculated. The vehicle body slip angle β represents the slip of the vehicle body with respect to the traveling direction of the vehicle as an angle, and can be calculated and estimated as follows. That is, the vehicle body side slip angular velocity Dβ is a differential value dβ / dt of the vehicle body side slip angle β, and can be obtained as Dβ = Gya / Vso−γa in step 108, which is integrated in step 109 and β
= ∫ (Gya / Vso-γa) dt, and the vehicle body slip angle β
Can be requested.

Then, the routine proceeds to step 110, where a braking steering control mode is set, and a target slip ratio to be used for braking steering control is set as described later. The braking force on each wheel is controlled. This braking steering control is superimposed on control in all control modes described later.
Thereafter, the routine proceeds to step 111, where it is determined whether or not the anti-skid control start condition is satisfied. If the start condition is satisfied and it is determined that the anti-skid control is to be started at the time of braking steering, the initial specifying control ends immediately and step 112 Is set to a control mode for performing both braking steering control and anti-skid control.

If it is determined in step 111 that the anti-skid control start condition is not satisfied, the process proceeds to step 113, where it is determined whether the front-rear braking force distribution control start condition is satisfied. If it is determined that the braking force distribution control has been started, the routine proceeds to step 114, where a control mode for performing both the braking steering control and the longitudinal braking force distribution control is set. Is satisfied or not. If it is determined that the traction control is started during the braking steering control, the control mode is set to perform both the braking steering control and the traction control in step 116, and if neither control is determined to be started during the braking steering control, In step 117, it is determined whether the brake steering control start condition is satisfied.

If it is determined in step 117 that the braking steering control is to be started, the routine proceeds to step 118, where a control mode in which only the braking steering control is performed is set. Then, after performing hydraulic servo control in step 119 based on these control modes, the process returns to step 102. In the front / rear braking force distribution control mode, the distribution of the braking force applied to the rear wheels to the braking force applied to the front wheels is controlled so as to maintain stability of the vehicle during braking of the vehicle. Step 117
If it is determined that the conditions for starting the braking steering control are not satisfied, the solenoids of all the solenoid valves are turned off in step 120, and the process returns to step 102. In addition, based on steps 112, 114, 116, and 118, the sub-throttle opening of the throttle control device TH is adjusted according to the motion state of the vehicle as necessary, the output of the engine EG is reduced, and the driving force is limited. .

FIG. 5 shows the specific processing contents of the brake steering control in step 110 of FIG. 4. The brake steering control includes oversteer suppression control and understeer suppression control. And / or a target slip ratio corresponding to the understeer suppression control is set. First, in steps 201 and 202, the start and end of the oversteer suppression control and the understeer suppression control are determined.

The start / end determination of the oversteer suppression control performed in step 201 is made based on whether or not the vehicle is in a control area indicated by oblique lines in FIG. That is, the vehicle body slip angle β and the vehicle body slip angular velocity Dβ at the time of determination are
When the vehicle enters the control region according to the value of, the oversteer suppression control is started, and when the vehicle leaves the control region, the oversteer suppression control is terminated, and the control is performed as indicated by the arrow curve in FIG. Further, the braking force of each wheel is controlled so that the control amount increases from the start reference straight line toward the outside of the control region.

On the other hand, the start / end determination of the understeer suppression control performed in step 202 is performed based on whether or not the vehicle is in a control area indicated by oblique lines in FIG. That is, at the time of determination, according to the change of the actual lateral acceleration Gya with respect to the target lateral acceleration Gyt, understeer suppression control is started when the vehicle deviates from the ideal state indicated by the one-dot chain line and enters the control region. Is ended, and control is performed as indicated by the arrow curve in FIG.

Subsequently, it is determined in step 203 whether or not the oversteer suppression control is being controlled, and if not, it is determined in step 204 whether or not the understeer suppression control is being controlled. If not, the process proceeds directly to step 209. When it is determined in step 204 that the vehicle is understeer suppression control, the process proceeds to step 205, and the target slip ratio of each wheel is set for understeer suppression control described later. If it is determined in step 203 that the vehicle is in the oversteer suppression control, the process proceeds to step 206 to determine whether or not the vehicle is understeer suppression control. Is set for If it is determined in step 206 that the understeer suppression control is being performed, the oversteer suppression control and the understeer suppression control are performed simultaneously, and in step 208, a target slip ratio for simultaneous control is set.

The target slip ratio of each wheel in step 205 is as follows: the front wheel on the outside of the turn is set to Stufo, the front wheel on the inside of the turn is set to Stufi, and the rear wheel on the inside of the turn is Sturi.
Is set to As for the sign of the slip ratio (S) shown here, "t" represents "target" and represents "actual measurement" described later.
Compared to "a". "u" is "understeer suppression control"
"F" represents "front wheel", "r" represents "rear wheel", "o" represents "outside", and "i" represents "inside".

The target slip ratio of each wheel in step 207 is set to Stefo for the front wheel on the outside of the turn and to Steri for the rear wheel on the inside of the turn. Here, “e” represents “oversteer suppression control”. And step 208
The target slip ratios of the respective wheels are set such that the front wheel on the outside of the turn is set to Stefo, the front wheel on the inside of the turn is set at Stufi, and the rear wheel on the inside of the turn is set at Sturi. That is,
When the oversteer suppression control and the understeer suppression control are performed simultaneously, the front wheels on the outside of the turn are set in the same manner as the target slip ratio of the oversteer suppression control, and the wheels on the inside of the turn are all set in the same manner as the target slip rate of the understeer suppression control. Is set. In any case, the rear wheels on the outside of the turn (ie, the driven wheels in the front-wheel drive vehicle) are not controlled because the estimated vehicle speed is set.

The vehicle slip angle β and the vehicle slip angular velocity Dβ are used for setting the target slip ratio for the oversteer suppression control in step 207. The target lateral acceleration Gyt is used for setting the target slip ratio for the understeer suppression control. And the actual lateral acceleration Gya.
For example, the target slip ratio Stefo of the front wheel on the outside of the turn used for the oversteer suppression control is Stefo = K1 · β + K2.
The target slip ratio Steri of the rear wheel on the inside of the turn is set to “0”. Here, K1 and K2 are constants, which are set to values for controlling the pressing direction (direction for increasing the braking force).

On the other hand, the target slip ratio for the understeer suppression control is set as follows based on the deviation ΔGy between the target lateral acceleration Gyt and the actual lateral acceleration Gya. That is,
The target slip ratio Stufo for the front wheel outside the turning is K3
ΔGy is set, and the constant K3 is set to a value for controlling the pressurizing direction (or the depressurizing direction). The target slip ratio Sturi for the rear wheel on the inside of the turn is set to K4 · ΔGy, and the constant K4 is set to a value for controlling the pressing direction. Similarly, the target slip ratio Stufi for the front wheel inside the turn is set to K5ＫΔGy, and the constant K5 is set to a value for controlling the pressing direction. And step 2
At 09, the tire lateral force is limited, which will be described later with reference to FIG.

FIG. 6 shows the processing of the hydraulic servo control performed in step 119 of FIG. 4. The slip ratio servo control of the wheel cylinder hydraulic pressure is performed for each wheel. First, in step 301, the target slip rate set in the above-described step 205, 207 or 208 is read, and further, the target slip rate set in the tire lateral force limitation in step 209 (this will be described later). ) Is added and used as the target slip ratio St ** of each wheel.

Subsequently, in step 302, the slip ratio deviation ΔSt ** is calculated for each wheel, and in step 303, the vehicle body acceleration deviation ΔDVso ** is calculated.
In step 302, the target slip ratio S of each wheel
The difference between t ** and the actual slip ratio Sa ** is calculated to determine the slip ratio deviation ΔSt ** (ΔSt ** = St ** − Sa *
*). In step 303, the difference between the estimated vehicle acceleration DVso at the position of the center of gravity of the vehicle and the wheel acceleration DVw ** of the wheel to be controlled is calculated, and the vehicle acceleration deviation ΔDV is calculated.
so ** is required. The actual slip ratio S of each wheel at this time
The calculation of a ** and the vehicle body acceleration deviation ΔDVso ** differ depending on the control mode such as anti-skid control, traction control, etc., but the description thereof will be omitted.

Subsequently, the routine proceeds to step 304, where one parameter Y ** used for the brake fluid pressure control in each control mode is calculated as Gs ** · ΔSt **. Where G
s ** is a gain, which is shown in FIG. 12 according to the vehicle body slip angle β.
Is set as shown by the solid line. Step 305
, Another parameter X used for brake fluid pressure control
** is calculated as Gd ** · ΔDVso **. The gain Gd ** at this time is a constant value as shown by a broken line in FIG. Thereafter, the process proceeds to step 306, where the hydraulic mode is set for each wheel according to the control map shown in FIG. 13 based on the parameters X ** and Y **. In FIG. 13, respective areas of a rapid pressure reduction area, a pulse pressure reduction area, a holding area, a pulse pressure increase area, and a rapid pressure increase area are set in advance. ,
It is determined which area corresponds. In the non-control state, the hydraulic mode is not set (the solenoid is off).

Next, at step 307, the tire braking force is limited, which will be described later with reference to FIG. On the other hand, when the region determined this time in step 306 is switched from the pressure increase to the pressure decrease or the pressure decrease to the pressure increase from the region previously determined, it is necessary to make the fall or rise of the brake fluid pressure smooth. Therefore, the pressure increase / decrease compensation processing is performed in step 308. For example, when switching from the rapid pressure reduction mode to the pulse pressure increase mode, rapid pressure increase control is performed, and the time is determined based on the duration of the immediately preceding rapid pressure reduction mode. Step 30 is performed in accordance with the hydraulic mode, the specific hydraulic mode, and the pressure increase / decrease compensation processing.
In step 9, the hydraulic pressure control solenoid is driven, the solenoid of the brake hydraulic pressure control device BC is driven, and the braking force of each wheel is controlled. This brake fluid pressure control device BC
Will be described later with reference to FIG. In the above embodiment, the control is performed based on the slip ratio. However, as the control target, in addition to the slip ratio, a target value corresponding to a braking force applied to each wheel such as a brake fluid pressure of a wheel cylinder of each wheel. Any value may be used.

Next, with reference to FIGS. 7 to 9, the limitation of the tire lateral force and the limitation of the tire braking force according to the tire air pressure will be described. FIG. 7 shows a process for setting the load on the tire set in step 107, that is, the upper limit value of the tire braking force and the tire lateral force.
01, lateral acceleration Gx in the x and y directions with respect to the vehicle
It is determined whether or not the absolute values of a and Gya are lower than predetermined values Kx and Ky, respectively. This is because, for example, when the front-rear lateral load on the vehicle is large, the load on the tire is large. Therefore, when the upper limit value is calculated, it is a condition that such a load is not applied to the tire. Only when both the absolute values of Gxa and Gya are below the predetermined values Kx and Ky, the routine proceeds to steps 402 and 403, where the upper limit values of the tire braking force and the tire lateral force are calculated.

In step 402, the upper limit value Pwu of the wheel cylinder fluid pressure is set to 30 MPa for the wheel having the normal tire pressure Pa ** (predetermined value), and the tire pressure Pa ** is increased from the predetermined value. The upper limit value Pwu of the wheel cylinder fluid pressure is set to decrease proportionally as the pressure decreases. In step 403, the upper limit Gyu of the lateral acceleration is set to (1.5 / 4 G) for the wheel having the normal tire pressure Pa **, and the tire pressure P
As a ** decreases from a predetermined value, upper limit Gyu of lateral acceleration
Is set to decrease proportionally. Here, the lateral acceleration indicates a value of 1.5 G as a vehicle, and the lateral acceleration of each wheel is equally distributed. Therefore, as shown in FIG. 7, the upper limit Gyu of the lateral acceleration of each wheel is (1.5 / 4 G). And The lateral acceleration is obtained by multiplying the lateral acceleration of the vehicle by the mass of the vehicle.

FIG. 8 shows the processing for limiting the lateral force of the tire performed in step 209.
, The lateral acceleration Gyt ** given to each wheel is | Gya
| · Μ ** · N ** / Σμ ** · N **
Here, Gya is the lateral acceleration of the vehicle, μ ** is the coefficient of friction at each wheel, and N ** is the load at each wheel. The lateral acceleration Gyt ** calculated in this way is compared with the upper limit Gyu in step 502, and if it exceeds the upper limit Gyu, the routine proceeds to step 503, where the tire lateral force restriction control flag is set (1). Proceeding to step 504, the target slip ratio is corrected.

That is, in step 504, the target slip ratios to be added to the three wheels other than the wheels subject to the tire lateral force restriction are listed. For example, the target slip ratio Stg ** shown in step 504 is further added to the target slip ratio set in steps 205, 207, and 208 in FIG. 5 to correct the target slip ratio. Here, ** in Stg ** represents wheels, and these
"F" represents the "front wheel",
"r" stands for "rear wheel", "o" for "outside", "i" for "inside"
Respectively. Thus, for example, when the outer front wheel (fo) is subject to tire lateral force limitation, target slip rates to be added for other wheels are set as shown in the first stage. That is, the target slip ratio Stgfi to be added to the inner front wheel is set to 5%, the target slip ratio Stgro to be added to the outer rear wheel is set to 10%, and the target slip ratio Stgri to be added to the inner rear wheel is set to 2%. . by this,
Control is performed so that no lateral force is applied to the outer front wheel (fo) even when the vehicle is turning. In step 504, the throttle opening may be further controlled in the closing direction to reduce the driving force.

On the other hand, if it is determined in step 502 that the lateral acceleration Gyt ** is equal to or less than the upper limit Gyu, the process proceeds to step 505, where it is determined whether or not the tire lateral force restriction control flag is set. If the tire lateral force limit control flag has not been set, the process returns to the main routine, but if the tire lateral force limit control flag has been set, the process proceeds to step 506, where the throttle opening is gradually returned in response to the accelerator operation. It is. And step 50
When the throttle opening has a relationship corresponding to the accelerator opening in step 7, the routine proceeds to step 508, where the tire lateral force restriction control flag is reset (0).

Next, FIG. 9 shows the process of limiting the tire braking force performed in step 307. First, in step 601, it is determined whether the vehicle is being braked (during normal braking or automatic braking). If braking is in progress, in step 602, the wheel cylinder hydraulic pressure Pw ** of the wheel being braked is compared with the upper limit value Pwu. If the wheel cylinder hydraulic pressure Pw ** exceeds the upper limit value Pwu, the routine proceeds to step 603, where the hydraulic pressure is adjusted to be equal to or less than the upper limit value Pwu. That is, the hydraulic mode for the wheel cylinder is set according to the magnitude of the difference (Pw **-Pwu) between the wheel cylinder hydraulic pressure Pw ** and the upper limit value Pwu. For example,
When the difference (Pw **-Pwu) is large, the mode is set to the pulse pressure reduction mode, and the pressure is reduced until the wheel cylinder reaches the upper limit value Pwu. When the difference (Pw **-Pwu) becomes small, the hydraulic mode for the wheel cylinder is set to the holding mode or the pulse pressure increasing mode.

FIG. 14 shows a braking system including a brake fluid pressure control device BC. In response to an operation of a brake pedal BP, a master cylinder MC is provided via a vacuum booster VB.
Is boosted, the brake fluid in the low-pressure reservoir LRS is boosted, and the master cylinder hydraulic pressure is output to two brake hydraulic systems on the wheels FR and RL and on the wheels FL and RR. . The master cylinder MC is a tandem type master cylinder having two pressure chambers. One of the pressure chambers is connected to the brake hydraulic system on the wheels FR and RL, and the other pressure chamber is the brake fluid on the wheels FL and RR. It is connected to the pressure system. The master cylinder MC
Is provided with a pressure sensor PS for detecting the output hydraulic pressure (master cylinder hydraulic pressure).

In the brake hydraulic system on the wheels FR, RL side of this embodiment, one pressure chamber is connected to the wheel cylinders Wfr, Wrl via the main hydraulic path MF and the branch hydraulic paths MFr, MFl, respectively. Have been. Main hydraulic path MF
A normally open first on-off valve SC1 (which functions as a so-called cut-off valve, hereinafter simply referred to as on-off valve SC1) is interposed. One of the pressure chambers is an auxiliary hydraulic pressure path MF.
It is connected between check valves CV5 and CV6 described later via c. A normally closed second on-off valve S is provided in the auxiliary hydraulic pressure path MFc.
I1 (hereinafter simply referred to as on-off valve SI1) is interposed. Each of these on-off valves is constituted by a 2-port 2-position electromagnetic on-off valve. The branch hydraulic pressure paths MFr and MFl are normally open two-port two-position solenoid on-off valves PC1 and PC1, respectively.
2 (hereinafter simply referred to as on-off valves PC1 and PC2). In parallel with these, check valves CV1 and CV1, respectively
V2 is interposed.

The check valves CV1 and CV2 allow the flow of the brake fluid in the direction of the master cylinder MC and restrict the flow of the brake fluid in the direction of the wheel cylinders Wfr and Wrl. The brake fluid in the wheel cylinders Wfr and Wrl is supplied to the master cylinder MC via the on-off valve SC1 at the first position (the state shown).
Thus, it is configured to be returned to the low pressure reservoir LRS. Thus, when the brake pedal BP is released, the hydraulic pressure in the wheel cylinders Wfr and Wrl can quickly follow the decrease in hydraulic pressure on the master cylinder MC side. Also,
The normally closed two-port two-position solenoid on-off valves PC5 and PC6 (hereinafter simply referred to as on-off valves PC5 and PC6) are respectively connected to the discharge-side branch hydraulic pressure paths RFr and RFl that are connected to the wheel cylinders Wfr and Wrl. And the discharge hydraulic pressure line RF where the branch hydraulic pressure lines RFr and RFl merge is connected to the reservoir R
It is connected to S1.

In the brake hydraulic system for the wheels FR and RL, the on-off valves PC1, PC2, PC5 and PC6 constitute a modulator according to the present invention. The branch hydraulic pressure path MF is located upstream of the on-off valves PC1 and PC2.
A hydraulic pump HP1 is interposed in a hydraulic passage MFp that is connected to the pumps r and MFl, and check valves CV5 and CV5 are provided on the suction side thereof.
6 is connected to the reservoir RS1. The discharge side of the hydraulic pump HP1 is connected to the check valve CV7 and the damper D.
They are connected to on-off valves PC1 and PC2 via P1. The hydraulic pump HP1 is driven by one electric motor M together with the hydraulic pump HP2, and is configured to introduce brake fluid from the suction side, increase the pressure to a predetermined pressure, and output the pressure from the discharge side. The reservoir RS1 is provided independently of the low-pressure reservoir LRS of the master cylinder MC, and can also be referred to as an accumulator. The reservoir RS1 includes a piston and a spring, and is configured to store a required amount of brake fluid for various controls. Have been.

The master cylinder MC is connected to a check valve CV5 and a check valve C on the suction side of the hydraulic pump HP1 via a hydraulic passage MFc.
It is connected to V6. The check valve CV5 prevents the flow of the brake fluid to the reservoir RS1, and allows the flow in the reverse direction. Check valves CV6, CV7
Regulates the flow of brake fluid discharged through the hydraulic pump HP1 in a certain direction.
1 are integrally formed. Thus, the on-off valve SI1
Is switched so that the communication between the master cylinder MC and the suction side of the hydraulic pump HP1 is cut off at the normal closed position shown in FIG. 14, and the master cylinder MC and the suction side of the hydraulic pump HP1 are communicated at the open position.

Further, the flow of the brake fluid from the master cylinder MC in the direction of the on-off valves PC1 and PC2 is restricted in parallel with the on-off valve SC1, so that the brake fluid pressure on the on-off valves PC1 and PC2 side becomes the brake fluid on the master cylinder MC side. The relief valve RV1 allows the flow of the brake fluid in the direction of the master cylinder MC when the pressure becomes larger than the pressure difference by a predetermined pressure or more, and allows the flow of the brake fluid in the direction of the wheel cylinders Wfr and Wrl to allow the flow in the opposite direction. A check valve AV1 for inhibiting flow is interposed. When the pressurized brake fluid discharged from the hydraulic pump HP1 becomes larger than the output hydraulic pressure of the master cylinder MC by a predetermined differential pressure or more, the relief valve RV1 supplies the brake fluid to the low-pressure reservoir LRS via the master cylinder MC. The pressure of the discharge brake fluid of the hydraulic pump HP1 is adjusted to a predetermined pressure. Also, the hydraulic pump H
A damper DP1 is disposed on the discharge side of P1, and a proportioning valve PV1 is interposed in a hydraulic path leading to a wheel cylinder Wrl on the rear wheel side.

Similarly, in the brake fluid pressure system on the wheels FL and RR, a normally open 2-port 2-position solenoid valve SC2 (first valve) including a reservoir RS2, a damper DP2 and a proportioning valve PV2. , Normally closed 2-port 2-position solenoid valve SI2 (second valve), P
C7, PC8, normally open 2-port 2-position solenoid on-off valve PC
3, PC4, check valve CV3, CV4, CV8 to CV1
0, a relief valve RV2 and a check valve AV2 are provided. The hydraulic pump HP2 is driven by the electric motor M together with the hydraulic pump HP1, and after the electric motor M is started, both the hydraulic pumps HP1 and HP2 are continuously driven.

The on-off valves SC1, SC2, SI1, SI
2 and on-off valves PC1 to PC8 are electronic control units ECU
And various controls including the above-described brake steering control are performed. For example, in order to prevent excessive oversteer, for example, it is necessary to generate a moment countering this. In the brake hydraulic system on the wheels FR and RL, the on-off valve SC1 is controlled during braking steering control.
Is switched to the closed position, the on-off valve SI1 is switched to the open position, the electric motor M is driven, and the hydraulic pump H
The brake fluid is discharged from P1. And on-off valve PC
1, PC2, PC5, and PC6 are appropriately opened and closed by the electronic control unit ECU, and the wheel cylinders Wfr, Wr
1, the pressure of the pulse is increased (slowly increased), reduced or maintained,
The braking force distribution between the front and rear wheels, including the brake fluid pressure systems on the wheels FL and RR, is controlled so as to maintain the course traceability of the vehicle.

[0049]

As described above, the present invention has the following advantages. That is, in the motion control device according to the first aspect, when a tire pressure equal to or lower than a predetermined value is detected while the vehicle is running, the braking force applied to each wheel is controlled so that the tire load does not exceed the upper limit value for the wheel having a reduced air pressure. And / or the driving force is controlled, so that the braking or turning operation can be performed smoothly without applying an excessive load to the tire of the pneumatically reduced wheel.

According to the second aspect of the present invention, when the vehicle is braked, the braking force on the wheel with reduced air pressure is limited in accordance with the tire pressure. Without the added power
The braking operation can be performed smoothly.

Further, by configuring the control means as described in claim 3, the lateral force on the wheel with reduced air pressure is limited in accordance with the tire pressure when the vehicle turns, so that the wheel with excessively low pressure is applied to the wheel with reduced pressure. The turning operation can be performed smoothly without applying any excessive lateral force.

Alternatively, as described in claim 4, when a tire pressure equal to or less than a predetermined value is detected while the vehicle is running, the tire pressure lowering wheel is controlled so that the tire load does not exceed the upper limit value with respect to the tire pressure lowering wheel. May be configured to apply a braking force to each of the other wheels, and in this case,
Without excessive load being applied to the low air pressure wheel,
The braking or turning operation can be performed smoothly.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of an embodiment of a motion control device according to the present invention.

FIG. 2 is an overall configuration diagram of an embodiment of a motion control device of the present invention.

FIG. 3 is a flowchart showing a part of vehicle braking control according to the embodiment of the present invention.

FIG. 4 is a flowchart illustrating the rest of the vehicle braking control according to the embodiment of the present invention.

FIG. 5 is a flowchart illustrating a process of setting a target slip ratio used for brake steering control according to an embodiment of the present invention.

FIG. 6 is a flowchart illustrating a hydraulic servo control process according to an embodiment of the present invention.

FIG. 7 is a flowchart illustrating a calculation process of a limit value of a tire braking force and a tire lateral force according to an embodiment of the present invention.

FIG. 8 is a flowchart illustrating a process of limiting a tire lateral force according to the embodiment of the present invention.

FIG. 9 is a flowchart illustrating a process of limiting a tire braking force according to an embodiment of the present invention.

FIG. 10 is a graph showing an oversteer suppression control start / end determination area according to an embodiment of the present invention.

FIG. 11 is a graph showing an understeer suppression control start / end determination area according to an embodiment of the present invention.

FIG. 12 is a graph showing parameter calculation gains Gs ** and Gd ** for hydraulic pressure control according to an embodiment of the present invention.

FIG. 13 is a graph showing a control map according to an embodiment of the present invention.

FIG. 14 is a configuration diagram showing a hydraulic system of the vehicle motion control device of the present invention.

[Explanation of symbols]

EG engine, ECU electronic control unit, FR, F
L, RR, RL wheels, WS1 to WS4 wheel speed sensor, YG lateral acceleration sensor, YS yaw rate sensor, APS1 to APS4 tire pressure sensor, LS1
~ LS4 Wheel load sensor, WPS1 ~ WPS4 Wheel cylinder pressure sensor, MC master cylinder, B
P brake pedal, M electric motor, HP1, HP
2 hydraulic pump, RS1, RS2 reservoir, PC1
~ PC8 On-off valve, Wfr, Wfl, Wrr, Wrl Wheel cylinder, SC1, SC2 First on-off valve, SI1,
SI2 second on-off valve,

Continuation of the front page (72) Inventor Kenji Asano 2-1-1 Asahi-cho, Kariya-shi, Aichi F-term in Aisin Seiki Co., Ltd. 3D041 AA31 AA33 AA48 AA49 AA71 AB01 AC01 AC26 AD10 AD41 AD47 AD50 AD51 AE02 AE04 AE41 AF00 AF01 3D045 BB01 BB40 CC03 EE21 GG00 GG01 GG23 GG25 GG26 GG28 3D046 BB01 BB28 BB29 BB31 CC02 DD04 FF08 GG02 HH00 HH02 HH08 HH16 HH23 HH25 HH29 HH36 HH46 LL23 LL50 MM02 MM02MM

Claims (4)

[Claims] 1. A tire pressure detecting means for detecting a tire pressure of each wheel of a vehicle, a tire load detecting means for detecting a load acting on a tire of each wheel, and a tire pressure of a wheel detected by the tire pressure detecting means. Upper limit value setting means for setting an upper limit value of the load on the tire of the tire having a reduced air pressure according to the tire air pressure when the vehicle pressure is reduced to a predetermined value or less; Control means for controlling a braking force and / or a driving force on each of the wheels such that when the following tire pressure is detected, the tire load detected by the tire load detection means with respect to the wheel having a reduced air pressure does not exceed the upper limit value. A motion control device for a vehicle, comprising: 2. The braking device according to claim 1, wherein the control unit is configured to:
2. The vehicle motion control device according to claim 1, further comprising a braking force limiting unit that limits a braking force applied to the air pressure decreasing wheel according to a tire air pressure of the air pressure decreasing wheel. 3. The method according to claim 1, wherein the control unit is configured to perform
2. The vehicle motion control device according to claim 1, further comprising a lateral force limiting unit that limits a lateral force applied to the air pressure lowering wheel in accordance with a tire air pressure of the air pressure lowering wheel. 4. A tire pressure detecting means for detecting a tire pressure of each wheel of a vehicle, a tire load detecting means for detecting a load acting on a tire of each wheel, and a tire pressure of a wheel detected by the tire pressure detecting means. Upper limit value setting means for setting an upper limit value of the load on the tire of the tire having a reduced air pressure according to the tire air pressure when the vehicle pressure is reduced to a predetermined value or less; When the following tire air pressure is detected, a braking force is applied to each wheel other than the air pressure lowering wheel so that the tire load detected by the tire load detecting means with respect to the air pressure lowering wheel does not exceed the upper limit value. A motion control device for a vehicle, comprising: a power control unit.