JP2002356120A - Motion control device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-cost motion control device for a vehicle capable of performing appropriate vehicle stabilization control without needing a sensor for detecting the motion and state quantity of the vehicle. SOLUTION: A road surface P gradient value which is the gradient of braking force and/or driving force of a wheel to the wheel slip speed, is estimated on the basis of the wheel speed of each wheel (FR or the like) of the vehicle detected by a wheel speed sensor (WS1 or the like). When the road surface μgradient value of at least one wheel becomes a prescribed value or less, control is performed to lower output of an engine(EG) and/or to increase braking force applied to at least one wheel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle motion control apparatus, and more particularly to a method for estimating a road .mu. Gradient value which is a gradient of a braking force and / or a driving force of a wheel with respect to a wheel slip speed, and based on the road .mu. The present invention relates to a vehicle motion control device that performs vehicle stabilization control.

[0002]

2. Description of the Related Art As a vehicle motion control device, for example,
As described in JP-A-2-70561, a vehicle motion control device for setting a target yaw rate of a vehicle, controlling a braking force in accordance with a result of comparison with an actual yaw rate of the vehicle, and maintaining stability during vehicle motion. It has been known.

Further, Japanese Patent Application Laid-Open No. 10-329682 proposes a vehicle rollover prevention device which avoids the possibility of rollover during turning. This publication is provided with braking force adjusting means capable of individually controlling braking forces acting on wheels of a vehicle, and in particular, vehicle state information (for example, wheels applied to left and right wheels that can indicate the possibility of rollover of the vehicle) A state detecting means (state sensor) for detecting a load, a lateral G, or a vehicle speed and a steering angle, and a possibility of the vehicle rolling over is determined from the vehicle state information detected by the state detecting means ( For example, when the difference between the left and right wheel loads is large or one of the left and right wheel loads is zero.

When the vehicle approaches [0]), it is predicted that the possibility of rollover is increased, and the braking force adjusting means is driven to apply a predetermined braking force to the front wheels among the wheels.

Further, as described in JP-A-11-189136, a minute gain of the wheel speed is calculated, and a value of a road surface μ gradient which is a gradient of braking / driving force with respect to a slip speed is calculated from the minute gain. Estimate the braking / driving force from the wheel cylinder pressure and accelerator opening, calculate the road surface condition and slip speed based on the wheel speed, road μ gradient, braking / driving force, and store the stored slip speed and road μ gradient for each road surface. It is known that a reference road surface μ gradient corresponding to the road surface condition and the slip speed is obtained based on the relationship of the following, and the wheel load is estimated based on a comparison between the road surface μ gradient and the reference road surface μ gradient.

[0005]

Problems to be Solved by the Invention JP-A-2-70 mentioned above.
In the apparatus described in Japanese Patent Application Laid-Open No. 561 and Japanese Patent Application Laid-Open No. 10-329682, for example, a yaw rate sensor, a lateral G sensor, a wheel load sensor, and the like are required as sensors for detecting vehicle motion and state quantity.

On the other hand, in the device described in Japanese Patent Application Laid-Open No. H11-189136, it is disclosed that the wheel load is estimated based on a comparison between a road surface μ gradient and a reference road surface μ gradient. This is based on the phenomenon that, as shown in FIG. 7, for example, as the vertical load applied to the wheels increases, the gradient of the braking / driving force with respect to the wheel slip speed, that is, the value of the road surface μ gradient, increases. For example, FIG. 7 shows the values of the road surface μ gradient (KFz1, KFz2) at the origin of zero braking / driving force. However, as shown in FIG. (KFz3, KFz4) are values corresponding to the wheel loads. The value of the road μ gradient described in the publication has a correlation not only with the wheel load but also with the wheel slip angle as shown in FIG. 9. As the wheel slip angle increases, the values of the road μ gradient (Kα1, Kα2 ) Are in a relationship of becoming smaller. Further, even if the front-back slip of the wheel (so-called slip ratio) increases, the road surface μ gradient value changes. After all, the road surface μ gradient value K is calculated as a function of the wheel slip ratio S, the wheel slip angle α, and the wheel load Fz as K = f (S, α,
Fz).

[0007] If the motion state of the vehicle is estimated using the road μ gradient value representing the grip state of the wheels as described above, the sensor for detecting the vehicle motion and the state quantity can be used without using a sensor. For example, when the stability of the vehicle tends to be impaired, the stability of the vehicle can be ensured by controlling the engine, the transmission and the brake to reduce the vehicle speed.

Accordingly, an object of the present invention is to provide an inexpensive vehicle motion control device capable of appropriately performing vehicle stabilization control without requiring a sensor for detecting vehicle motion or state quantity.

[0009]

In order to achieve the above object, a vehicle motion control device according to the present invention comprises a wheel speed detecting means for detecting a wheel speed of each wheel of a vehicle. A road μ gradient estimating means for estimating a road μ gradient value which is a gradient of a braking force and / or a driving force of the wheel with respect to a wheel slip speed based on a wheel speed detected by the wheel speed detecting means; When the road μ gradient value of at least one wheel estimated by the means becomes equal to or less than a predetermined value, the output of the engine mounted on the vehicle decreases, and / or
Alternatively, control means for controlling so as to increase the braking force applied to at least one wheel is provided. The road surface μ gradient value is a gradient of the braking force and / or the driving force of the wheel with respect to the wheel slip speed, and is described in Japanese Patent Application Laid-Open No. H11-189136.

For example, when the wheel slip angle becomes excessively large and the stability and maneuverability of the vehicle are likely to be impaired,
In a situation where the road surface μ gradient value of at least one wheel is less than or equal to a predetermined value and the wheel grip / groundability tends to be lost, such as when the vehicle loses the ground contact property of the wheels and the vehicle tends to roll over, the control means Control is performed so as to decrease the output of the engine and / or increase the braking force applied to at least one wheel, and as a result, the vehicle speed decreases. The transmission may be downshifted (so-called engine braking).

[0011] The control means may be configured to, when the road surface μ gradient value of at least one of the wheels estimated by the road surface μ gradient estimating unit becomes equal to or less than a predetermined value, control the road surface μ gradient. It is preferable that the braking force applied to at least one wheel other than the wheel whose value is equal to or less than the predetermined value is controlled to be increased.

Further, the control means, when the value of at least one road surface μ gradient estimated by the road surface μ gradient estimating means is equal to or less than a predetermined value, is set forth in claim 3.
It is preferable that the braking force applied to at least one of the front wheels is controlled to be increased. Alternatively, when the road μ gradient value of at least one of the front wheels estimated by the road μ gradient estimating unit becomes equal to or less than a predetermined value, the control unit may be configured to control the rear wheel at least. It may be configured to control so as to increase the braking force applied to one side. Further, the control means may determine that the road surface μ gradient value of at least one of the wheels inside the turn estimated by the road surface μ gradient estimating means when the vehicle turns is a predetermined value. In the following cases, the braking force applied to at least one of the outer wheels may be controlled to be increased. Thus, in addition to the aforementioned decrease in vehicle speed,
A braking force difference between the front and rear and / or the left and right can be generated so as to cancel the instability of the vehicle and generate a yaw moment in a direction to improve the stability of the vehicle.

According to a sixth aspect of the present invention, there is provided a wheel speed detecting means for detecting a wheel speed of each wheel of a vehicle, and a braking force of the wheel with respect to a wheel slip speed based on the wheel speed detected by the wheel speed detecting means. And / or road μ gradient estimating means for estimating a road μ gradient value that is a gradient of driving force, and calculating a time change amount of the road μ gradient value from the road μ gradient value estimated by the road μ gradient estimating means. When the time variation of the road surface μ gradient value of one of the wheels is equal to or less than a predetermined time variation, the output of the engine mounted on the vehicle is reduced and / or the control applied to at least one wheel is reduced. Control means for controlling so as to increase the power may be provided.

According to a seventh aspect of the present invention, the time variation of the road μ gradient value of at least one wheel estimated by the road μ gradient estimating means is equal to or less than a predetermined time variation amount. In this case, it is preferable that the braking force applied to at least one wheel other than the wheel whose time variation of the road surface μ gradient value is equal to or less than a predetermined time variation is increased.

[0015]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows the overall configuration of a control system including a vehicle motion control device. The brake hydraulic system is configured as shown in FIG. 2, for example. FIG.
, An engine EG is an internal combustion engine provided with a throttle control device TH and a fuel injection device FI. In the throttle control device TH, a main throttle opening of a main throttle valve MT is controlled in accordance with an operation of an accelerator pedal AP. Further, the sub-throttle valve S of the throttle control device TH is controlled according to the output of the electronic control device ECU.
T is driven to control the sub-throttle opening,
The fuel injection device FI is driven to control the fuel injection amount.

In FIG. 1, wheels FL indicate front left wheels as viewed from the driver's seat, wheel FR indicates front right wheels, wheel RL indicates rear left wheels, and wheel RR indicates rear right wheels. , RL, RR are mounted with wheel cylinders Wfl, Wfr, Wrl, Wrr, respectively. In the present embodiment, the engine EG is connected to wheels FL and FR in front of the vehicle via a shift control device GS, and a so-called front-wheel drive system is configured. The present invention can be applied to either a rear-wheel drive system or a four-wheel drive system, and is not limited to a front-wheel drive system.

The wheels FL, FR, RL, RR are provided with wheel speed sensors WS1 to WS4, which are connected to the electronic control unit ECU, and which control the rotational speed of each wheel, that is, the number of pulses proportional to the wheel speed. Is input to the electronic control unit ECU. Further, a brake switch BS that is turned on when the brake pedal BP makes a stroke, a steering angle sensor SR that detects a steering angle of the vehicle, and hydraulic pressure sensors P1 and P2 described later are connected to the electronic control unit ECU. Also, a signal from a throttle sensor (not shown) for detecting the opening of the main throttle valve MT and the sub throttle valve ST is input to the electronic control unit ECU. The operation and non-operation of the accelerator pedal AP can be detected based on the output signal of the throttle sensor. Thus, the electronic control unit ECU is configured to drive the engine EG and / or the brake fluid pressure control unit BC. The brake fluid pressure control device BC is configured as shown in FIG. 2, and its specific configuration and operation will be described later.

The electronic control unit ECU has a microcomputer CMP, and as shown in FIG.
T, output port OPT, processing unit CPU,
The memory ROM, the memory RAM, and the timer TMR are interconnected via a bus. The wheel speed sensor WS
1 to WS4, brake switch BS, steering angle sensor S
Output signals from the R, hydraulic pressure sensors P1, P2, etc. are configured to be input to the processing unit CPU from the input port IPT via an amplifier circuit (typically represented by AMP). Further, control signals are output from the output port OPT to the throttle control device TH and the brake fluid pressure control device BC via a drive circuit (typically represented by ACT). In the microcomputer CMP, the memory ROM stores a program corresponding to the flowchart shown in FIG. 3 and the like. The processing unit CPU executes the program while an ignition switch (not shown) is closed. Temporarily stores variable data necessary for executing the program. Thus, in the electronic control unit ECU,
The road μ gradient estimating means and the control means of the present invention are configured, and are processed as described later.

In this embodiment configured as described above, vehicle stabilization control is performed by the electronic control unit ECU as follows. When an ignition switch (not shown) is closed, initialization is first performed in step 101 of FIG. 3, and after various calculated values are cleared, the process proceeds to step 102 and thereafter, and the processing of steps 102 to 110 is performed. Is repeated at a predetermined cycle. In step 102, output signals of the wheel speed sensors WS1 to WS4, the brake switch BS, the steering angle sensor SR, the hydraulic pressure sensors P1 and P2, etc. are read, and these are filtered in step 103 and sequentially stored in the memory. .

Next, the routine proceeds to step 104, where it is determined whether the vehicle is traveling straight or turning based on the steering angle signal detected by the steering angle sensor SR. A turn or a left turn is identified. Thereafter, the routine proceeds to step 105, where the road surface μ gradient values Kfr, Kfl, Krr, Krl of the respective wheels are obtained from the signals of the wheel speed sensors WS1 to WS4.
Is required. These road surface μ gradient values can be calculated, for example, in Japanese Unexamined Patent Application Publication No. 11-189136,
No. 78843 (wheel torsional vibration model),
0-114263 (wheel deceleration model), JP-A-2
The calculation is performed by the method disclosed in Japanese Patent Application Publication No. 000-108863 (suspension resonance model). Further, in step 106, the road surface μ gradient values Kfr, Kfl, Krr, K
rl (represented by K **) is differentiated by time,
Time variation DKfr, DKfl, DKr of μ gradient value of each road surface
r and DKrl (represented by DK **) are calculated.

Then, in step 107, the road surface μ
It is determined whether or not the vehicle stabilization control based on the gradient value has been executed. If the vehicle stabilization control has not been executed, the process proceeds to step 108, where a control start determination is performed. It is determined whether or not is satisfied. This control start determination is performed based on the road surface μ gradient value of each wheel. For example, when the road surface μ gradient value of at least one of the road surface μ gradient values K ** of each wheel becomes equal to or less than a predetermined value. Then, it is determined that the grip / groundability of the wheel is lost and the vehicle is becoming unstable. Alternatively, it may be determined whether or not a situation in which the wheel grip suddenly decreases is performed, and the vehicle stabilization control may be performed based on the determination result. In this case, the time change amount DK of the road surface μ gradient value may be determined. ** is used. Furthermore, the road surface μ gradient value K **
The control start determination may be made based on a combination of the time change amount DK ** and the time change amount DK **.

If it is determined in step 108 that the control start condition is satisfied, the routine proceeds to step 110, where vehicle stabilization control is performed. That is, in order to eliminate the tendency of the vehicle to be unstable, such as excessive oversteer, excessive understeer, or vehicle rollover tendency, the vehicle speed is controlled to decrease. Specifically, by reducing the throttle opening, the fuel supply is suppressed to reduce the engine output, or by automatically downshifting, the engine brake is applied, and the braking force is applied to each wheel. By giving, the vehicle speed can be reduced. Further, in order to improve the tendency of the vehicle to be unstable, it is effective to control the yaw moment by applying a braking force to the wheels.

In the vehicle stabilizing control of step 110, when a braking force is applied to the wheels, the road surface μ gradient value is large based on the road surface μ gradient value K ** of each wheel, that is, grip / groundability. It is desirable to apply a braking force to a wheel that can afford. In addition, on a road surface having a low maximum friction coefficient μmax between wheels and the road surface such as an icy road surface, there is a possibility that the drive wheels may be locked by the engine brake, and the vehicle stability may be impaired. For this reason, when the road surface μmax is equal to or less than a predetermined value (for example, 0.2 to 0.3 or less), it is desirable not to use the engine brake as the vehicle speed reducing means.

The above-described vehicle stabilization control is executed until the control end condition is satisfied. If it is determined in step 109 that the wheel grip degree has recovered, that is, if the road surface μ gradient value K ** has decreased, the wheel stabilization control is performed. If the road μ gradient value K ** has recovered to the predetermined value, it is determined that the control end condition has been satisfied, and the routine returns to step 102 without performing the control of step 110.

FIG. 4 shows an embodiment in which an oversteering tendency of the vehicle is detected to suppress excessive oversteering. The processing of steps 101 to 105 is substantially the same as that of steps 101 to 105 in FIG. In the present embodiment, it is determined in step 107 whether or not the oversteer suppression control based on the road surface μ gradient value has been executed. If not, the process proceeds to step 121 where a control start determination is made, and the oversteer suppression control is executed. It is determined whether the start condition is satisfied. That is, the rear wheel RR,
When at least one of the road surface μ gradient values K ** of the RL falls below a predetermined value K1, it is determined that the grip of the rear wheels has been lost and the vehicle has an oversteer tendency.
At 23, vehicle stabilization control by oversteer suppression control is performed.

More specifically, at least one of throttle closing drive, fuel cut, shift down, and application of braking force is executed to reduce the vehicle speed. Further, in order to generate an outward yaw moment that suppresses the tendency to oversteer, a braking force is applied to the front wheels outside the turning direction. Further, it is also effective to apply a braking force to the rear outside wheel. As the object of the wheel that applies the braking force,
Priority is given to a wheel having a high road surface μ gradient value K **, that is, a wheel having a sufficient wheel grip.

The above-described vehicle stabilization control is terminated when the road surface μ gradient value K ** of the rear wheel whose wheel grip degree has decreased has recovered to a predetermined value K2 or more. That is, step 107 in FIG.
Is determined to be under control, and the routine proceeds to step 122, where it is determined that the control end condition is satisfied when it is determined that the road surface μ gradient value K ** of the rear wheels has recovered to the predetermined value K2 or more, The process returns to step 102 without performing the control of step 123.

In the embodiment of FIG. 4, the determination of the oversteer tendency is made based on the road surface μ gradient value K ** of the rear wheel. In addition, as described below, the road surface μ gradient value of the rear wheel is determined. May be determined based on the time change amount (DK **), the deviation of the road μ gradient value between the rear wheel and the front wheel, and the deviation of the time variation between the road μ gradient values of the rear wheel and the front wheel. . That is, (a) when at least one of the road wheel μ gradient values of the rear wheels decreases below a predetermined value, (b) the time change amount of at least one of the road wheel μ gradient values of the rear wheels exceeds the predetermined value in the decreasing direction. (D) When the road surface μ gradient value of the rear wheel decreases and the deviation from the road surface μ gradient value of the front wheel exceeds a predetermined value, (d) the road surface μ gradient value of the rear wheel Is reduced, and when the time change of the rear wheel road surface μ gradient value exceeds the predetermined value (abruptly) with respect to the time change amount of the front wheel road surface μ gradient value, it can be determined that the vehicle is oversteering.
Further, (e) can be determined by combining any one or more of the above (a) to (d).

Means for reducing the vehicle speed in the above-mentioned oversteer suppression control include (a) closing drive of the throttle, (b) fuel cut, (c) downshift,
(D) The application of a braking force to the turning inner front wheel, and (e) a combination of one or more of the above (a) to (d). As means for generating an outward yaw moment in addition to reducing the vehicle speed, (A) braking force applied to the turning outer front wheel, (B) braking force applied to the turning outer rear wheel, and (C) There are combinations.

FIG. 5 shows an embodiment in which the understeering tendency of the vehicle is detected to suppress excessive understeering. The processing in steps 101 to 105 is substantially the same as that in steps 101 to 105 in FIG. In the present embodiment, it is determined in step 107 whether or not the understeer suppression control based on the road surface μ gradient value has been executed. If not, the process proceeds to step 131, where the control start determination is performed, and the understeer suppression control is performed. It is determined whether the start condition is satisfied. That is, the front wheels FR,
If at least one of the road μ gradient values K ** of the FLs falls below a predetermined value K3, it is determined that the grip of the front wheels has been lost and the vehicle has an understeer tendency, and step 133 is executed.
, Vehicle stabilization control by understeer suppression control is performed.

More specifically, at least one of throttle closing drive, fuel cut, shift down, and application of braking force is executed to reduce the vehicle speed. Further, in order to generate an inward yaw moment, a braking force is applied to the turning inner rear wheel. Further, it is also effective to apply a braking force to the front wheel inside the turning. Also in the present embodiment, the road surface μ
Priority is given to a wheel having a high gradient value K **, that is, a wheel having a sufficient wheel grip.

The vehicle stabilization control in step 133 ends when the road surface μ gradient value K ** of the rear wheel whose wheel grip degree has decreased has recovered to a predetermined value K4 or more. That is, it is determined in step 107 of FIG.
When it is determined that the road surface μ gradient value K ** of the rear wheels has recovered to the predetermined value K4 or more, it is determined that the control end condition has been satisfied, and the control of step 133 is not performed. Return to step 102.

In the embodiment of FIG. 5, the understeer tendency is determined based on the road surface μ gradient value K ** of the front wheels. In addition, as will be described below, the time of the road surface μ gradient value of the front wheels is determined. The understeer tendency may be determined based on the variation (DK **), the deviation of the road μ gradient value between the front wheel and the rear wheel, and the deviation of the time variation between the road μ gradient values of the front and rear wheels. That is, (a) when at least one road surface μ gradient value of the front wheels decreases below a predetermined value, (b) the time change amount of at least one road surface μ gradient value of the front wheels exceeds the predetermined value in a decreasing direction (suddenly). (C) when (c) the road surface μ gradient value of the front wheel decreases, and when the deviation from the road surface μ gradient value of the rear wheel exceeds a predetermined value, (d) the road surface μ gradient value of the front wheel decreases. If the time change of the front wheel road surface gradient value with respect to the rear wheel road surface gradient value exceeds a predetermined value (abruptly), it can be determined that the vehicle is understeering.
Further, (e) can be determined by combining any one or more of the above (a) to (d).

Means for reducing the vehicle speed in the understeer suppression control include (a) throttle closing drive, (b) fuel cut, (c) shift down,
(D) The application of a braking force to the turning outer front wheel, and (e) one or more combinations of the above (a) to (d). As means for generating an inward yaw moment in addition to reducing the vehicle speed, (A) braking force applied to the turning inside front wheel, (B) braking force applied to the turning inside rear wheel, and (C) There are combinations.

FIG. 6 shows an embodiment in which the tendency of the vehicle to roll over is detected and suppressed.
The process of 05 is substantially the same as steps 101 to 105 of FIG. In the present embodiment, it is determined in step 107 whether or not the vehicle stabilization control based on the road surface μ gradient value is being executed. If not, the process proceeds to step 141 to determine the control start, and to start the control. It is determined whether the condition is satisfied. That is, when the road surface μ gradient value K ** of at least one wheel inside the turn is less than the predetermined value K5, it is determined that the load loss of the wheel having the lowered road surface μ gradient value is large and the ground contact property is losing, and step At 143, vehicle stabilization control is performed.

More specifically, at least one of throttle closing drive, fuel cut, shift down, and application of braking force is executed to reduce the vehicle speed. And
In many cases, the vehicle is excessively over-steered, and as a result, the vehicle rolls over. Therefore, in order to generate an outward yaw moment that suppresses the over-steering, a braking force is applied to the turning outer front wheel. In this case, it is more effective if braking force is further applied to the turning outer rear wheel. Also in the present embodiment, as a target of the wheel to which the braking force is applied, it is preferable to give priority to a wheel having a high road surface μ gradient value K **, that is, a wheel having a margin in the contact property of the wheel.

The vehicle stabilization control in step 143 is terminated when the road surface μ gradient value K ** of the wheel having reduced contact with the ground has recovered to a predetermined value K6 or more. That is, step 10 in FIG.
7, it is determined that control is being performed, and the routine proceeds to step 142,
The road surface μ gradient value K ** of the wheel having reduced contact property is a predetermined value K6.
When it is determined that the recovery has been completed, it is determined that the control end condition has been satisfied, and the process returns to step 102 without performing the control of step 143.

In the embodiment of FIG. 6, the determination of the vehicle rollover tendency is made based on the road surface gradient value K ** of the wheel on the inside of the turn. In addition, as described below, the wheel on the inside of the turn is also used. The vehicle rollover tendency is determined based on the time change amount (DK **) of the road surface μ gradient value, the deviation of the road surface μ gradient value between the left and right wheels, and the deviation of the time change of the road surface μ gradient value between the left and right wheels. It may be that. That is, (a) when the road surface μ gradient value of at least one wheel of one side wheel (turning inner wheel) decreases to a predetermined value or less, (b) the road surface μ gradient of at least one wheel of one side wheel (turning inner wheel). If the time change of the value changes in a decreasing direction beyond the predetermined value (rapidly),
(C) When the road surface μ gradient value of one wheel (turning inner wheel) decreases and the deviation from the road surface μ gradient value of the other wheel (turning outer wheel) becomes a predetermined value or more, (d) one side wheel ( When the road μ gradient value of the inner wheel (turning inner wheel) decreases and the time change amount of the road surface μ gradient value of the other wheel (outer turning wheel) changes (rapidly) beyond a predetermined value, the vehicle rolls over. Can be determined. Further, (e) can be determined by combining any one or more of the above (a) to (d).

Means for reducing the vehicle speed in the vehicle stabilization control include (a) closing drive of the throttle, (b) fuel cut, (c) downshifting, and (d) braking force on the front wheel inside the turning. And (e) a combination of one or more of the above (a) to (d). As means for generating an outward yaw moment in addition to reducing the vehicle speed, (A) braking force applied to the turning outer front wheel, (B) braking force applied to the turning outer rear wheel, and (C) There are combinations.

Next, the structure and operation of the brake fluid pressure control device BC shown in FIG. 2 will be described. In the present embodiment, the master cylinder MC is double-pressure driven via the vacuum booster VB according to the operation of the brake pedal BP,
The brake fluid in the low pressure reservoir LRS is pressurized and the wheel F
The configuration is such that the master cylinder hydraulic pressure is output to the hydraulic systems on the R, RL side and the wheels FL, RR side. The master cylinder MC is a tandem type master cylinder, and two pressure chambers are connected to respective brake hydraulic systems. That is, the first pressure chamber MCa is connected to the brake hydraulic system on the wheels FR, RL side, and the second pressure chamber MCb is connected to the wheels F, RL.
It is connected to the brake hydraulic system on the L, RR side. Hydraulic pressure sensors P1 and P2 are connected to each brake hydraulic system, and are supplied to the aforementioned electronic control unit ECU. In the present embodiment, a so-called X pipe is configured, but it may be a front and rear pipe.

In the brake hydraulic system on the wheels FR, RL side of the present embodiment, the first pressure chamber MCa is
F and its branch hydraulic passages MFr, MFl are connected to the wheel cylinders Wfr, Wrl, respectively. 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 in the main hydraulic path MF. Further, the first pressure chamber MCa is connected to check valves CV5 and CV6 described later via an auxiliary hydraulic pressure path MFc.
Connected between A normally closed second on-off valve SI1 (hereinafter simply referred to as on-off valve SI1) is interposed in the auxiliary hydraulic pressure passage MFc. 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 provided with normally open two-port two-position solenoid valves PC1 and PC2 (hereinafter simply referred to as valve valves PC1 and PC2). Further, check valves CV1 and CV2 are interposed in parallel with these. The check valves CV1 and CV2 allow the flow of the brake fluid in the direction of the master cylinder MC and limit the flow of the brake fluid in the direction of the wheel cylinders Wfr and Wrl. The check valves CV1 and CV2 and the first The brake fluid in the wheel cylinders Wfr, Wrl is returned to the master cylinder MC and, eventually, to the low-pressure reservoir LRS via the on-off valve SC1 at the position (illustrated). 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. In addition, the discharge-side branch hydraulic pressure passages RFr and RFl that are connected to the wheel cylinders Wfr and Wrl are respectively connected to the normally closed type hydraulic pressure passages RFr and RFl.
Port 2 position electromagnetic on-off valves PC5 and PC6 (hereinafter simply referred to as on-off valves PC5 and PC6) are interposed, and the discharge hydraulic pressure line RF where the branch hydraulic pressure lines RFr and RFl join is connected to the reservoir RS1. .

In the brake hydraulic system on the wheels FR and RL, a modulator is constituted by the on-off valves PC1, PC2, PC5 and PC6. In addition, on-off valve P
A hydraulic pump HP1 is interposed in a hydraulic passage MFp that is connected to the branch hydraulic passages MFr and MFl on the upstream side of C1 and PC2, and a reservoir RS1 is provided on the suction side thereof through check valves CV5 and CV6. It is connected. Also, the hydraulic pump HP1
Are respectively opened and closed by a check valve CV7.
It is connected to PC2. 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 can store brake fluid having a capacity necessary for various controls described later. Is configured.

The master cylinder MC is connected in communication between a check valve CV5 and a check valve CV6 on the suction side of the hydraulic pump HP1 via an auxiliary hydraulic passage MF. 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 and CV
Numeral 7 regulates the flow of the brake fluid discharged through the hydraulic pump HP1 in a certain direction.
It is integrally formed in P1. Thus, the on-off valve SI
1 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. 2 and the master cylinder MC and the suction side of the hydraulic pump HP1 are communicated at the open position. .

Further, in parallel with the on-off valve SC1, the flow of the brake fluid from the master cylinder MC in the direction of the on-off valves PC1, PC2 is restricted, and the brake fluid pressure on the on-off valves PC1, 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 predetermined differential pressure with respect to the pressure. 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 is regulated so that the discharge brake fluid of the hydraulic pump HP1 does not rise above a predetermined pressure. Also, due to the presence of the check valve AV1, the brake fluid pressure in the wheel cylinders Wfr and Wrl is increased when the brake pedal BP is depressed even when the on-off valve SC1 is in the closed position. A damper DP1 is disposed on the discharge side of the hydraulic pump HP1, and a wheel cylinder Wr on the rear wheel side is provided.
A proportioning valve PV1 is interposed in the hydraulic pressure path leading to l.

Similarly, in the brake hydraulic 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, SI2 and on-off valves PC1 to PC8 are drive-controlled by the above-mentioned electronic control unit ECU, and vehicle stabilization control is performed.

In the brake hydraulic system configured as described above, each solenoid valve is operated as shown in FIG.
And the electric motor M is stopped.
When the brake pedal BP is depressed in this state, the first and second pressure chambers MCa, MCb of the master cylinder MC are depressed.
, The master cylinder hydraulic pressure is output to the hydraulic system of the wheels FR, RL and the wheels FL, RR, respectively, and the on-off valve SC
, SC2 and on-off valves PC1 to PC8, and are supplied to the wheel cylinders Wfr, Wrl, Wfl, Wrr.

On the other hand, for example, when the braking force applied to the wheels FR is controlled, the opening / closing valve SC1 is kept in the open position, the opening / closing valve PC1 is closed, and the opening / closing valve PC5 is opened. Position. Thus, the wheel cylinder W
fr communicates with the reservoir RS1 via the on-off valve PC5,
The brake fluid in the wheel cylinder Wfr is supplied to the reservoir RS
It flows out into 1 and is decompressed.

When the wheel cylinder Wfr enters the pulse pressure increasing mode, the open / close valve PC5 is closed and the open / close valve PC1 is opened, and the master cylinder MC receives the master cylinder hydraulic pressure via the open / close valve PC1 in the open position. To the wheel cylinder Wfr. And the on-off valve PC1
Is intermittently controlled, and the brake fluid in the wheel cylinder Wfr is repeatedly increased in pressure and held, increases in a pulsed manner, and is gradually increased. When the rapid pressure increase mode is set for the wheel cylinder Wfr, the on-off valve PC5 is set to the closed position, then the on-off valve PC1 is set to the open position, and the master cylinder MC supplies the master cylinder hydraulic pressure. And
When the brake pedal BP is released, the wheel cylinder Wf
When the master cylinder hydraulic pressure is smaller than the hydraulic pressure of r,
The brake fluid in the wheel cylinder Wfr is supplied to the check valve CV1.
And the master cylinder M via the open / close valve SC1 in the open position.
C, and eventually return to the low pressure reservoir LRS. In this way, independent braking force control is performed for each wheel.

Instead of the above-mentioned brake fluid pressure control device BC,
A brake fluid pressure control system called a so-called brake-by-wire (BBW) shown in FIG. 10 may be used. This is a system in which there is no mechanical connection between the driver's brake operation and the wheel cylinder pressure control, and the system is electronically connected. That is, a fluid pressure adjusting device PCA or the like is disposed between a power fluid pressure source PW that outputs brake fluid pressure and a wheel cylinder Wfr or the like of each wheel FR, and the power fluid pressure source PW and the fluid pressure adjusting device PCA or the like. Are controlled by the electronic control unit ECU. This electronic control unit ECU includes a brake pedal BP
Is connected to an input sensor IS that detects an operation amount of the input signal and outputs a signal corresponding to the operation amount. The broken line in FIG. 10 indicates the electronic connection relationship. In addition, Pa to Pe are hydraulic pressure sensors, and both detection signals are supplied to the electronic control unit ECU.

Thus, in the brake fluid pressure control system having the above configuration, the electronic control unit ECU
Wheel cylinder W according to operation of brake pedal BP
The brake fluid pressure may be supplied to the wheel cylinder Wfr or the like independently of (independently) operation of the brake pedal BP by supplying the brake fluid pressure to the fr or the like, and the automatic pressurization may be performed.

In the configuration shown in FIG. 2 described above, communication between the master cylinder MC and the wheel cylinder Wfr and the like is required in order to actively and independently adjust the wheel cylinder fluid pressure of each wheel (automatic pressurization). Since it is necessary to shut off, the driver may feel uncomfortable when shutting off. For this reason, it is desirable that the vehicle stabilization control be performed only during the limit time. On the other hand, in the brake fluid pressure control system shown in FIG. 10, since the brake operation by the driver and the wheel cylinder fluid pressure control are not mechanically connected, the wheel cylinder fluid pressure is regulated when the wheel cylinder fluid pressure is regulated. The fluctuation of the hydraulic pressure is not transmitted to the driver. For this reason, it is possible to start the control before the vehicle limit which is the conventional control start reference. Therefore, in the brake-by-wire (BBW) brake fluid pressure control system, vehicle stabilization control can be performed smoothly before the vehicle limit.

As described above, according to each of the above embodiments,
In a situation where the road μ gradient value of at least one wheel is equal to or less than a predetermined value and the wheel grip / groundability tends to be lost, the output of the engine is reduced and / or the braking force applied to at least one wheel is increased. As a result, the vehicle speed can be reliably reduced. In addition, a braking force difference between the front and rear and / or the left and right can be generated so as to cancel the instability of the vehicle and generate a yaw moment in a direction to improve the stability of the vehicle. This eliminates the need for a sensor for detecting vehicle motion and state quantity, and allows the system to be constructed at low cost. Alternatively, in the case of constructing a system using a yaw rate sensor, an acceleration sensor, a steering angle sensor, a load sensor, and the like (not shown) for detecting a vehicle motion and a state quantity, the redundancy of the system can be further improved. .

[0054]

The present invention has the following effects because it is configured as described above. That is, in the vehicle motion control device according to the first aspect, the road surface μ of at least one wheel is provided.
When the gradient value becomes equal to or less than a predetermined value, control is performed so that the output of the engine is reduced and / or the braking force applied to at least one wheel is increased. The vehicle stabilization control can be appropriately performed with a simple and inexpensive configuration without requiring a sensor to perform the control.

Further, if the control means is configured as described in claim 2, the vehicle speed can be reliably reduced by increasing the braking force on at least one appropriate wheel.

Further, the control means is configured as described in claim 3, or is configured as described in claim 4, and further configured as described in claim 5,
In addition to the decrease in the vehicle speed described above, control can be performed in a direction to improve vehicle stability, and more appropriate vehicle stabilization control can be performed.

In the apparatus according to the sixth aspect, when the time variation of the road surface μ gradient value of at least one wheel is equal to or less than the predetermined time variation, the output of the engine is reduced, and / or Alternatively, since the control is performed so as to increase the braking force applied to at least one wheel, the vehicle stabilization control can be appropriately performed even in a situation where the wheel grip rapidly decreases.

Further, if the control means is configured as described in claim 7, it is possible to increase the braking force on an appropriate wheel even under a situation where the wheel grip suddenly decreases.

[Brief description of the drawings]

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

FIG. 2 is a block diagram illustrating a brake fluid pressure control device according to an embodiment of the present invention.

FIG. 3 is a flowchart illustrating a vehicle stabilization control process according to an embodiment of the present invention.

FIG. 4 is a flowchart illustrating a process for oversteer suppression control according to another embodiment of the present invention.

FIG. 5 is a flowchart illustrating a process for understeer suppression control according to still another embodiment of the present invention.

FIG. 6 is a flowchart showing a process for vehicle stabilization control according to another embodiment of the present invention.

FIG. 7 is a graph showing an example of a relationship between a braking force and a driving force with respect to a general wheel slip speed, and particularly showing a road μ gradient at an origin where the braking force or the driving force is zero.

FIG. 8 is a graph showing an example of a relationship between a wheel slip speed and a braking force or a driving force in a state where a wheel slip occurs.

FIG. 9 shows braking force or driving force against wheel slip;
It is a graph which shows the correlation about a wheel slip angle.

FIG. 10 is a block diagram showing a brake fluid pressure control system provided in another embodiment of the present invention.

[Explanation of symbols]

BP brake pedal, BS brake switch, B
C brake fluid pressure control device, FL, FR, RL, RR
Wheel, Wfl, Wfr, Wrl, Wrr Wheel cylinder,
MC master cylinder, MF main hydraulic path, MFc
Auxiliary hydraulic path, M electric motor, HP1, HP2 hydraulic pump, RS1, RS2 reservoir, SC1, SC2
First on-off valve, SI1, SI2 Second on-off valve, P
C1-PC8 open / close valve, WS1-WS4 wheel speed sensor, ECU electronic control unit

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme Court II (Reference) F02D 29/02 311 F02D 29/02 311A (72) Inventor Kenji Asano 2-1-1 Asahicho, Kariya City, Aichi Prefecture Aisin Seiki Co., Ltd. (72) Koji Umeno, 41, No. 41, Chuchu-Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture Inside Toyota Central R & D Laboratories Co., Ltd. No. 1 Inside Toyota Central Research Institute Co., Ltd. (72) Inventor Yuji Murakishi 41-Cho, Yokomichi, Oji, Nagakute-cho, Aichi-gun, Aichi Prefecture No. 1 Inside Toyota Central Research Laboratory Co., Ltd. No. 41, 41-cho, Yokomichi-cho, Machi-Da HH46 3G093 AA04 BA01 DA06 DB00 DB03 DB04 DB05 DB15 EA02 EA05 EA09 EA10 EB03 EB04 FA02 FA07 FA12 FB02

Claims (7)

[Claims] 1. A wheel speed detecting means for detecting a wheel speed of each wheel of a vehicle, and a gradient of a braking force and / or a driving force of the wheel with respect to a wheel slip speed based on a wheel speed detected by the wheel speed detecting means. Road μ gradient estimating means for estimating the road μ gradient value, and when the road μ gradient value of at least one wheel estimated by the road μ gradient estimating means becomes equal to or less than a predetermined value, the engine mounted on the vehicle is Control means for controlling so as to decrease output and / or increase braking force applied to at least one wheel. 2. The control unit according to claim 1, wherein the road surface μ gradient value becomes equal to or less than a predetermined value when the road surface μ gradient value of at least one of the wheels estimated by the road surface μ gradient estimating unit becomes equal to or less than a predetermined value. 2. The control system according to claim 1, wherein the braking force to be applied to at least one wheel other than the wheel that has been turned off is increased.
A vehicle motion control device as described in the above. 3. The braking force to be applied to at least one of the front wheels when the value of at least one road surface μ gradient estimated by the road surface μ gradient estimating device becomes equal to or less than a predetermined value. The vehicle motion control device according to claim 1, wherein the control is performed so as to increase the vehicle speed. 4. A braking force to be applied to at least one of the rear wheels when at least one of the front wheel μ gradient values estimated by the road μ gradient estimating device becomes equal to or less than a predetermined value. The vehicle motion control device according to claim 1, wherein the control is performed so as to increase the vehicle speed. 5. The controller according to claim 1, wherein when the vehicle turns, the road surface μ gradient value of at least one of the wheels on the inner side of the turn estimated by the road surface μ gradient estimator becomes less than or equal to a predetermined value. 2. The vehicle motion control device according to claim 1, wherein the control is performed so as to increase the braking force applied to at least one of the outer wheels. 6. A wheel speed detecting means for detecting a wheel speed of each wheel of a vehicle, and a gradient of a braking force and / or a driving force of the wheel with respect to a wheel slip speed based on a wheel speed detected by the wheel speed detecting means. Road μ gradient estimating means for estimating the road μ gradient value, and calculating a time change amount of the road μ gradient value from the road μ gradient value estimated by the road μ gradient estimating means, and calculating a road μ gradient value of at least one wheel. When the time change amount of the vehicle becomes equal to or less than the predetermined time change amount, control is performed so as to decrease the output of the engine mounted on the vehicle and / or increase the braking force applied to at least one wheel. A motion control device for a vehicle, comprising: a control unit. 7. The road surface μ gradient when the time variation of the road surface μ gradient value of at least one wheel estimated by the road surface μ gradient estimation device is equal to or less than a predetermined time variation. 7. The vehicle motion control device according to claim 6, wherein the control is performed so as to increase the braking force applied to at least one wheel other than the wheel whose time change amount is equal to or less than a predetermined time change amount. .