JP2011046289A - Vehicular understeer suppression device and understeer suppression method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique capable of more effectively suppressing a tendency of understeer. <P>SOLUTION: When it is determined that a vehicle has a tendency of understeer, the vehicle is gradually controlled in a sequential order depending on a reference US modified moment amount Mθ. In other words, longitudinal distribution of vehicular roll moment is changed to rear wheels 1RL, 1RR side. Next, while the longitudinal distribution of the vehicular roll moment is maintained to the rear wheels 1RL, 1RR side, braking force is generated on turning inner wheel of the rear wheels 1RL, 1RR or the braking force generated on the turning inner wheel of the rear wheels 1RL, 1RR is increased. Further, while the braking force is maintained, the longitudinal distribution of the vehicular roll moment changed to the rear wheels 1RL, 1RR side is changed again to front wheels side. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a technique for suppressing an understeer tendency of a vehicle.

  There exists patent document 1 as a prior art which suppresses the understeer tendency which generate | occur | produced in the vehicle. In this prior art, when it is determined that the vehicle is understeering when the actual yaw rate is smaller than the yaw rate obtained by subtracting the yaw rate margin from the reference yaw rate, the braking force of the left and right rear wheels is increased. As a result, the understeer tendency of the vehicle is suppressed by sliding outward in the turning direction and reducing the kinetic energy of the vehicle by deceleration. At the same time, by increasing the roll rigidity on the rear wheel side, the ground contact load of the turning outer wheel on the left and right rear wheels is increased, the tire slip limit is exceeded, and the left and right rear wheels tend to flow outwardly, Eliminate vehicle understeer tendency. Also, if the actual yaw rate is greater than the yaw rate obtained by subtracting the yaw rate margin from the reference yaw rate, but the actual roll angle exceeds the target roll angle, if it is determined that the vehicle is shifting to an understeer tendency, the left and right rear wheels turn. At the same time as increasing the braking force of the inner ring, control is performed to increase the roll rigidity on the rear wheel side.

Japanese Patent Laying-Open No. 2005-329794 (see paragraph numbers 0030 to 0039)

In the prior art, if it is determined that the vehicle has an understeer tendency, the roll rigidity on the rear wheel side of the vehicle is increased while applying a braking force, so that unintentional deceleration occurs and the driver feels uncomfortable. Further, when the slip ratio reaches the maximum friction coefficient, it is not possible to generate a sufficient braking force on the rear wheel inside the turn that generates the braking force. As a result, the suppression of the understeer tendency may be insufficient.
The present invention has been made paying attention to the above points, and an object of the present invention is to provide a technique capable of further suppressing an understeer tendency without a driver feeling uncomfortable.

In order to solve the above problems, the present invention calculates a reference US correction moment amount, which is a correction yaw moment amount for suppressing an understeer tendency, when the vehicle determines an understeer tendency, and based on the reference US correction moment amount. Control the yaw moment generated in the vehicle. In this control, the following processing is executed step by step according to the magnitude of the reference US correction moment amount.
That is, first, the front-rear distribution of the vehicle roll moment is changed so that the rear wheel side becomes larger. Next, the braking force is generated on the turning inner wheel of the rear wheel or the braking force generated on the turning inner wheel is increased in a state where the rear-wheel distribution of the vehicle roll moment is maintained as large as possible on the rear wheel side. Next, in the state where the braking state is maintained, the front-rear distribution of the vehicle roll moment maintained so that the rear wheel side becomes as large as possible is changed again so that the front wheel side becomes large.

According to the present invention, if the reference US correction moment amount is small, the understeer tendency is suppressed without generating braking or without increasing the already generated braking to suppress the understeering tendency.
Furthermore, even when the slip ratio reaches the maximum friction coefficient, the yaw moment that suppresses the understeer tendency can be increased. Thereby, the understeer tendency can be further suppressed.
Therefore, the understeer tendency can be further suppressed without causing the driver to feel uncomfortable.

It is a schematic diagram which shows the vehicle structure which concerns on embodiment based on this invention. It is a block diagram which shows the structure of a suspension control controller. It is a figure which shows various specifications. It is a block diagram which shows the structure of US correction | amendment moment amount control means. It is a figure which shows the example of the map for calculating | requiring distribution before and behind a roll. It is a figure explaining the process of a 1st and 2nd correction control means. It is a figure for demonstrating the process of an understeer control part. It is a figure for demonstrating an operation example. It is a figure explaining the change of the vertical load of a right-and-left wheel. It is a schematic diagram which shows another vehicle structure which concerns on embodiment based on this invention. It is a schematic diagram which shows another vehicle structure which concerns on embodiment based on this invention. It is a schematic diagram which shows another vehicle structure which concerns on embodiment based on this invention. It is a schematic diagram which shows another vehicle structure which concerns on embodiment based on this invention.

Next, the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram illustrating a configuration of a vehicle according to the present embodiment.
(Constitution)
As shown in FIG. 1, the vehicle according to the present embodiment has two front wheels 1FL and 1FR and two rear wheels 1RL and 1RR. In addition, braking devices 2FL to 2RR such as disc brake devices are individually attached to the wheels 1FL to 1RR. The braking devices 2FL to 2RR for each wheel apply a braking force according to a braking command from the braking controller 3 to the corresponding wheels 1FL to 1RR.

  Next, the suspension configuration of each wheel will be described. The rotation support members 4FL to 4RR rotatably support the corresponding wheels 1FL to 1RR. The suspension links 5FL to 5RR connect the rotation support members 4FL to 4RR to the vehicle body 7 so as to be able to swing up and down. Further, the lower ends of the shock absorbers 6FL to 6RR whose shafts are directed upward and downward are connected to the suspension links 5FL to 5RR or the rotation support members 4FL to 4RR. The upper ends of the shock absorbers 6FL to 6RR are connected to the vehicle body 7.

  In addition, the front stabilizer 9 connects the left and right front wheels, and the rear stabilizer 10 connects the left and right rear wheels 1RL and 1RR. Each of the stabilizers 9 and 10 has a central portion 9a and 10a rotatably supported by the vehicle body 7, and both foot portions 9b and 10b are connected to shock absorbers 6FL to 6RR or rotation support members 4FL to 4RR, respectively. Rotary actuators 11 and 12 are provided at the central portions 9a and 10a of the stabilizers 9 and 10, respectively. The rotary actuators 11 and 12 adjust the rigidity of the stabilizers 9 and 10, that is, the roll rigidity in response to a command from the suspension controller 13. That is, the rotary actuators 11 and 12 constitute roll moment distribution adjusting means.

  A yaw rate sensor 30 as actual yaw rate detecting means for detecting the actual yaw rate of the vehicle, a turning angle sensor 31 as steering angle detecting means for detecting the turning angle of the steered wheels, and a wheel speed for detecting the rotational speed of each wheel. And a wheel speed sensor 32 as detection means. In addition, a steering direction detecting means for detecting the steering direction of the vehicle is provided. This steering direction detecting means may be constituted by the steering angle sensor 31 or a steering angle sensor 33 for detecting the steering angle of the steering wheel.

  The braking controller 3 calculates a braking force command value for each wheel in accordance with an operation amount of a brake pedal (not shown), and controls the braking force of the braking devices 2FL to 2RR for each wheel so as to be the braking force command value. To do. In addition, when a braking command is input from another controller such as the suspension control controller 13, as a control braking unit that generates braking force not depending on the driver's intention on the wheel or increases the braking force generated by the driver's intention. In operation, the braking force of the braking devices 2FL to 2RR for each wheel is controlled in accordance with the braking command.

  Moreover, the suspension controller 13 includes an understeer controller 13A as shown in FIG. The understeer control unit 13A is a processing unit that performs control for suppressing an understeer tendency generated in the vehicle. As shown in FIG. 2, the understeer control unit 13 </ b> A includes a US tendency determination unit 14, a standard US correction moment amount calculation unit 15, and a US correction moment amount control unit 16.

The US tendency determining means 14 determines whether or not the vehicle has an understeer tendency. For example, the following first US tendency determination method or second US tendency determination method may be employed to determine whether the tendency is an understeer tendency.
A first US tendency determination method will be described. When the first US tendency determination method is set as shown in FIG. 3, the actual yaw rate γ ₀ is smaller than the preset yaw rate threshold value Δγ with respect to the target yaw rate γ _t as in the determination of the following equation (1). In this case, it is determined that there is an understeer tendency.
γ _t − γ ₀ ≧ Δγ (1)

Here, as the actual yaw rate γ ₀ , for example, an observation value acquired by the yaw rate sensor 30 is used. Alternatively, a value estimated by known means is used as the actual yaw rate γ ₀ .
The yaw rate threshold value Δγ is obtained by evaluating the value in advance through experiments.
The target yaw rate γ _t is calculated by the following equation (2).
γ _t = (V × δ) / L (2)
here,
L: Wheel base of vehicle δ: Actual turning angle of steered wheels V: Vehicle body speed

The vehicle body speed V is obtained by the following equation (3), for example. The wheel speed is acquired from the wheel speed sensor 32.
V = (wheel speed) × (2π × (tire radius)) (3)
δ is the actual steering angle of the steered wheels. The actual rudder angle may be detected directly, or may be estimated by the following equation (4), for example. The steering angle may be acquired from the steering angle sensor 33.
δ = (steering angle) × (steering gear ratio) (4)

The second US tendency determination method is a determination method based on the skid angle. That is, when set as shown in FIG. 3, the side slip angle β ₀ at the center of gravity of the vehicle is smaller than the preset side slip angle threshold Δβ with respect to the target side slip angle β _t as shown in the following equation (5). In this case, it is determined that there is an understeer tendency.
β _t − β ₀ ≧ Δβ (5)

The skid angle threshold value Δβ is obtained by evaluating a value in advance through experiments.
The target side slip angle β _t is calculated by the following equation (6), for example.
β _t = (Lr × δ) / L (6)
here,
Lr: distance between the center of gravity of the vehicle and the rear wheel axle δ: actual turning angle of the steered wheels L: wheel base

The actual side slip angle β ₀ is calculated by, for example, integrating the following equation (7).
(Dβ / dt) = (α _y / V) −γ ₀ (7)
here,
α _y : lateral acceleration of the center of gravity point V: vehicle body speed γ ₀ : yaw rate

Further, when the standard US correction moment amount calculation means 15 determines that the vehicle has an understeer tendency based on the determination by the US tendency determination means 14, the reference US correction moment amount which is a correction yaw moment amount in the oversteer direction for suppressing the understeer tendency. The amount Mθ is calculated.
When it is determined that the first US tendency determination method is an understeer tendency, the reference US correction moment amount Mθ is calculated by the following equation (8), for example.
Mθ = I × {(dγ _t / dt) − (dγ ₀ / dt)} (8)
here,
I: Yaw moment of inertia of vehicle γ _t : Target yaw rate γ ₀ : Actual yaw rate

When it is determined that the second US tendency determination method is an understeer tendency, the reference US correction moment amount Mθ is calculated by the following equation (9), for example.
Mθ = I × (Lr / V) × {(dβ _t / dt) − (dβ ₀ / dt)}
... (9)
here,
Lr: distance between the center of gravity of the vehicle and the rear wheels 1RL, 1RR axle β _t : target side slip angle β ₀ : actual side slip angle

  The US correction moment amount control means 16 is based on the reference US correction moment amount Mθ calculated by the reference US correction moment amount calculation means 15 and the yaw moment in the oversteer direction for suppressing the understeer tendency (hereinafter simply referred to as the US correction moment amount). (Also called). As shown in FIG. 4, the US correction moment amount control means 16 includes a first correction control means 16A for changing the front / rear distribution of the vehicle roll moment toward the rear wheels 1RL, 1RR, and the turning inner wheels of the rear wheels 1RL, 1RR. A second correction control means 16B for generating a braking force or increasing a braking force generated in the turning inner wheel, and a third modification for re-changing the front-rear distribution of the vehicle roll moment that is closer to the rear wheel to the front wheel side. It has correction control means 16C and roll moment distribution command value output means 16D. Then, the US correction moment amount control means 16 carries out in the order of the first correction control means 16A, the second correction control means 16B, and the third correction control means 16C in accordance with the increase of the reference US correction moment amount Mθ.

  When the first correction control means 16A determines that the vehicle has an understeer tendency based on the determination of the US tendency determination means 14, the first correction control means 16A does not use the braking controller 3 but distributes the front and rear distribution of the vehicle roll moment via the roll moment distribution adjustment means. The modified yaw moment is generated by changing the wheels 1RL and 1RR to be larger. The first correction control means 16A includes roll moment estimation means 16Aa and roll moment distribution change means 16Ab.

The roll moment estimating means 16Aa estimates the roll moment amount MR of the vehicle.
The roll moment amount MR is estimated by, for example, the following equation (10).
Estimated roll moment MR = K × δ × V (10)
here,
K: Gain obtained in advance δ: Actual steering angle V: Vehicle body speed

The estimated roll moment amount MR may be obtained from the lateral acceleration at the center of gravity.
The roll moment distribution changing means 16Ab distributes the front and rear of the vehicle roll moment for generating the reference US correction moment amount Mθ based on the reference US correction moment amount Mθ and the roll moment amount MR estimated by the roll moment estimation means 16Aa. calculate.

For example, the amount of yaw moment generated when the front-rear distribution is changed in an actual vehicle is measured in advance. Then, as shown in FIG. 5, the reference US correction moment amount Mθ, the estimated roll moment amount MR, and the roll moment front distribution are mapped. In FIG. 5, the corresponding variable increases as any axis goes in the direction of the arrow. FIG. 5 illustrates the case where the lateral acceleration at the center of gravity, which is proportional to the estimated roll moment MR, is used as a variable instead of the estimated roll moment MR, but instead of the lateral acceleration at the center of gravity. The same is true for the estimated roll moment amount MR.
Here, obtaining the roll moment front distribution using the map is synonymous with calculating the amount of change of the vehicle roll moment before and after the rear wheels 1RL and 1RR.

Then, the roll moment distribution command value output means 16D outputs the distribution command value calculated by the roll moment distribution change means 16Ab to the rotary actuators 11 and 12 constituting the roll moment distribution adjustment means. When the front / rear distribution is changed closer to the rear wheels 1RL, 1RR, the rigidity of the stabilizer 10 on the rear wheels 1RL, 1RR side may be relatively increased, or the rigidity of the stabilizer 9 on the front wheel side may be decreased.
Here, the amount of yaw moment for suppressing understeer, which is generated by changing the distribution before and after the roll moment of the vehicle, is also referred to as a first US correction moment amount M1.

  The second correction control means 16B determines that the reference US correction moment amount Mθ is the maximum correction yaw moment amount that can be generated by changing the vehicle roll moment front-rear distribution toward the rear wheels 1RL and 1RR. If it is determined that the amount has been exceeded, the braking force is applied to the turning inner wheels of the rear wheels 1RL and 1RR while maintaining the state in which the front and rear distribution of the vehicle roll moment is changed closer to the rear wheels 1RL and 1RR by the first correction control means 16A. The corrected yaw moment is increased by increasing the braking force generated or generated in the turning inner wheel. The second correction control means 16B includes a roll distribution limit determination means 16Ba and a turning inner wheel braking control means 16Bb.

  First, the roll distribution limit determination means 16Ba uses the above-mentioned map (FIG. 5) with the estimated roll moment amount MR and the reference US correction moment Mθ as variables, and uses the above-described map (FIG. 5) to determine the maximum possible roll moment distribution. The maximum US correction moment amount Mx which is the yaw moment amount is calculated. Next, the calculated maximum US correction moment Mx and the reference US correction moment Mθ are compared, and when the reference US correction moment Mθ exceeds the maximum US correction moment, it is determined that the roll distribution is limited.

The turning inner wheel braking control means 16Bb generates braking force on the turning inner wheels of the rear wheels 1RL and 1RR or generates them on the turning inner wheels while changing the front and rear distribution of the vehicle roll moment toward the rear wheels 1RL and 1RR. A command to increase the braking force is output to the braking controller 3.
At this time, the first yaw moment amount (first US correction moment amount M1) for suppressing understeer by changing the front and rear distribution of the vehicle roll moment toward the rear wheels 1RL and 1RR by the first correction control means 16A described above. The sum of the second yaw moment amount for suppressing understeer (hereinafter also referred to as the second US correction moment amount M2) generated by braking of the turning inner wheels of the rear wheels 1RL and 1RR is the reference US correction moment amount Mθ. As described above, the braking force generated in the turning inner wheels of the rear wheels 1RL and 1RR is calculated, and the braking force is output to the braking controller 3.
Here, the second US correction moment amount M2 is obtained by, for example, the following equation.
M2 = (braking force of turning inner wheel of rear wheel) × (rear wheel side tread / 2)

The processing of the first correction control means 16A and the second correction control means 16B is shown in FIG.
Further, when the third correction control means 16C determines that the slip ratio of the rear wheels 1RL and 1RR has reached a predetermined slip ratio threshold with a large friction coefficient between the wheels and the road surface, the braking by the braking controller 3 (control braking means) is performed. In a state where the state is maintained, the corrected yaw can be corrected by re-changing the front-rear distribution of the vehicle roll moment, which has been changed closer to the rear wheels 1RL, 1RR, via the roll moment distribution command value output means 16D so that the front wheel side becomes larger. Increase the moment. The third correction control unit 16C includes a slip ratio limit determination unit 16Ca and a roll moment redistribution unit 16Cb.

The slip ratio limit determination means 16Ca determines whether or not the slip ratio of the rear turning inner wheel has reached a specified slip ratio threshold. The prescribed slip ratio threshold is set in advance by experiments or the like. The turning inner wheel of the left and right rear wheels is specified by the turning direction of the vehicle by the steering direction detecting means. The slip ratio of the turning inner wheel may be obtained based on the wheel speed of the turning inner wheel.
When roll moment redistribution means 16Cb determines that slip ratio limit determination means 16Ca has reached the specified slip ratio threshold, based on the reference US correction moment Mθ, the front and rear distribution of the vehicle roll moment changed toward the rear wheels 1RL, 1RR side Change the to the front wheel side again.

  At this time, when the second US correction moment amount M2 generated by braking of the turning inner wheels of the rear wheels 1RL and 1RR and the front and rear distribution of the vehicle roll moment changed to the rear wheels 1RL and 1RR side are changed again to the front wheel side. The front-rear distribution of the vehicle roll moment changed to the rear wheels 1RL, 1RR side is made closer to the front wheels so that the sum with the first US correction moment amount M1 for suppressing the understeer tendency becomes the reference US correction moment amount Mθ. While changing again, the braking force is adjusted. In this case, the first US correction moment amount M1 decreases, but conversely, the second US correction moment amount M2 increases.

Processing of the control part of the US correction moment in the understeer control unit having the above configuration will be described with reference to FIG. The processing of the understeer control unit operates at a preset sampling cycle.
First, in step S10, information necessary for control is input from each sensor.
Next, in step S20, the reference US correction moment amount calculation means 15 calculates a reference US correction moment amount Mθ (= required value).
Next, in step S30, the roll distribution limit determination means 16Ba determines whether or not the reference US correction moment amount Mθ can be generated only by the first US correction moment amount M1 generated by the change in the front and rear distribution of the roll moment. If the determination is satisfied, the process proceeds to step S40. If the determination is not satisfied, the process proceeds to step S60.

  In step S40, the roll moment distribution changing means 16Ab calculates the front / rear distribution for generating the reference US correction moment Mθ. In step S50, the roll moment distribution command value output means 16D outputs the calculated front / rear distribution. As a result, the front and rear stabilizer rigidity is adjusted through the rotary actuators 11 and 12 constituting the roll moment distribution adjusting means so that the calculated front and rear distribution is obtained. Specifically, adjustment is made so that the rigidity of the stabilizer 10 of the rear wheels 1RL, 1RR is relatively higher than the rigidity of the front stabilizer 9, so that the front-rear distribution becomes larger on the rear wheels 1RL, 1RR side. Then return.

  On the other hand, in step S60, it is determined whether or not the reference US correction moment Mθ can be generated based on the first US correction moment amount M1 generated by the change in the front and rear distribution of the roll moment and the second US correction moment amount M2 due to the turning inner wheel braking. . If the determination is satisfied, the process proceeds to step S70. If the determination is not satisfied, the process proceeds to step S90. Specifically, the slip ratio limit determining means 16Ca determines whether or not the slip ratio of the turning inner wheels of the rear wheels 1RL and 1RR has reached a specified slip ratio threshold.

In step S70, the roll moment distribution changing means 16Ab calculates the target roll moment distribution before and after. Subsequently, in step S80, the turning inner wheel braking control means 16Bb calculates a target braking force generated in the turning inner wheel. Thereafter, the process proceeds to step S50.
As a result, the reference US correction moment Mθ is generated by the sum of the first US correction moment amount M1 obtained by making the front and rear distribution of the roll moment closer to the rear wheels 1RL and 1RR and the second US correction moment amount M2 generated by turning inner wheel braking. .

On the other hand, in step S90, the roll moment redistribution means 16Cb changes the front and rear distribution of the roll moment toward the front side, thereby performing the target roll moment front and rear distribution that reduces the first US correction moment amount M1 due to the change in the front and rear distribution of the roll moment. calculate.
Subsequently, in step S100, the turning inner wheel braking control means 16Bb calculates a target braking force generated in the turning inner wheel for generating the second US correction moment amount M2. Here, by re-changing the front / rear distribution of the roll moment to the front side, the friction circle of the turning inner wheel increases, and the second US correction moment amount M2 increases.

(Operation, action, etc.)
The understeer tendency suppressing operation in the present embodiment will be described with reference to FIG.
If the vehicle is understeering when the vehicle is turning, a reference US correction moment amount Mθ (= required value) that is a yaw moment amount in the oversteer direction for suppressing the understeering tendency is calculated.
At this time, when the reference US correction moment amount Mθ is equal to or less than the maximum specified correction yaw moment amount (= maximum US correction moment amount Mx) that can be generated by the first US correction moment amount M1 due to the change in the distribution of the roll moment. 8), the first correction control means 16A changes the front / rear distribution of the roll moment toward the rear wheels 1RL, 1RR, so that the first US correction moment amount M1 corresponding to the reference US correction moment amount Mθ is obtained. Is generated. This suppresses the understeer tendency.
In this case, since the rear wheel braking is not performed or the generated rear wheel braking is not increased, the uncomfortable feeling to the driver due to the understeer suppressing process can be suppressed small.

Here, the reason why the understeer tendency can be suppressed by the first correction control means 16A will be described.
When the vehicle is understeering during turning and the vehicle is swollen toward the turning outer wheel, the lateral force on the front wheels 1FR and 1FL has reached its limit, while the lateral force on the rear wheels 1RL and 1RR has a margin. is there. Taking this into consideration, the front and rear distribution can be changed closer to the rear wheels 1RL and 1RR so that the roll moment due to centrifugal force is relatively borne on the rear wheels 1RL and 1RR, and can be generated on the left and right front wheels 1FR and 1FL. Increase lateral force. As a result, the understeer tendency is suppressed.

  That is, as shown in FIG. 9, the vertical loads of the left and right wheels are separated from each other by the centrifugal force during turning (the positions of points a and b), but the roll moment is relatively reduced to the rear wheel 1RL, By making the burden on the 1RR side, the vertical loads of the left and right wheels approach the front wheels (positions of points a1 and b1). As a result, the lateral force that can be generated in total for the left and right wheels is increased at the front wheels. The symbol c is the average lateral force of the left and right wheels when the vertical loads of the left and right wheels are separated. Reference sign c1 is an average lateral force of the left and right wheels in the front wheel when the front-rear distribution is moved toward the rear wheel. At this time, the vertical load of the left and right wheels is displaced in the rear wheel side, but there is no problem because the rear wheel side has a sufficient lateral force.

  Further, when the reference US correction moment amount Mθ increases and the reference US correction moment amount Mθ exceeds the maximum US correction moment amount Mx that can be obtained by changing the distribution of the front and rear of the roll moment (area B in FIG. 8), the roll moment In addition to the first US correction moment amount M1 by changing the front-rear distribution to the rear wheels 1RL, 1RR side, when braking force is generated on the turning inner wheels of the rear wheels 1RL, 1RR, or when braking has already occurred By generating the second US correction moment amount M2 due to the increase in braking force, a yaw moment amount in the oversteer direction corresponding to the reference US correction moment amount Mθ is generated. This suppresses the understeer tendency.

  Further, as the reference US correction moment amount Mθ increases, the second US correction moment amount M2 is increased. However, the braking force at which the slip ratio of the turning inner wheels of the rear wheels 1RL and 1RR reaches the specified slip ratio threshold value at which the friction coefficient is maximized. Then, the friction of the turning inner wheels of the rear wheels 1RL and 1RR is redistributed to the front wheel side by redistributing the front and rear distribution of the roll moment changed to the rear wheels 1RL and 1RR side by the third correction control means (region C in FIG. 8). Increase the circle. Thus, the second US correction moment amount M2 that can be generated by the braking force of the turning inner wheels of the rear wheels 1RL and 1RR is increased, and the yaw moment amount in the oversteer direction according to the reference US correction moment amount Mθ is generated.

Here, the reason why the friction circle of the turning inner wheels of the rear wheels 1RL and 1RR becomes large will be described.
In the state where the first correction control means 16A mainly receives the roll moment on the rear wheels 1RL, 1RR side with the front and rear distribution of the roll moment being closer to the rear wheels 1RL, 1RR, the left and right wheels in the rear wheels 1RL, 1RR The vertical load is separated. For this reason, the vertical load of the inner turning wheel is relatively small compared to the vertical load of the outer turning wheel. From this state, as the roll moment is redistributed from the rear wheels 1RL, 1RR side toward the front wheels, the first US correction moment amount M1 decreases, but the vertical load on the turning inner wheel increases. Thus, the friction circle is large, that is, the second US correction moment amount M2 is increased.

As a result, even if the slip ratio of the turning inner wheels of the rear wheels 1RL and 1RR reaches a specified slip ratio threshold that maximizes the friction coefficient, yaw in the oversteer direction that can be generated by braking of the turning inner wheels of the rear wheels 1RL and 1RR. Increase the amount of moment.
Here, the rotary actuators 11 and 12 constitute roll moment distribution adjusting means. The braking controller 3 constitutes a control braking means. The yaw rate sensor 30 constitutes actual yaw rate detection means. The turning angle sensor 31 or the steering angle sensor 33 constitutes a turning angle detection unit and a steering direction detection unit.

(Effect of this embodiment)
(1) The US tendency determination means 14 determines whether or not the vehicle has an understeer tendency. If the vehicle is determined to be understeered based on the determination by the US tendency determining unit 14, the reference US corrected moment amount calculating unit 15 calculates a reference US corrected moment amount Mθ that is a corrected yaw moment amount for suppressing the understeer tendency. The US correction moment amount control means 16 controls the yaw moment generated in the vehicle based on the reference US correction moment amount Mθ. The roll moment distribution adjusting means adjusts the front / rear distribution of the vehicle roll moment.

  The US correction moment amount control means 16 includes means for stepwise execution in the order of the first correction control means 16A, the second correction control means 16B, and the third correction control means 16C. When the first correction control means 16A determines that the vehicle has an understeer tendency based on the determination of the US tendency determination means 14, the front and rear distribution of the vehicle roll moment is changed to the rear wheels 1RL and 1RR side via the roll moment distribution adjustment means. To do. The second correction control means 16B determines that the reference US correction moment amount Mθ exceeds the maximum specified correction yaw moment amount that can be generated by changing the front / rear distribution of the vehicle roll moment toward the rear wheels 1RL, 1RR. Then, the braking force is generated on the turning inner wheels of the rear wheels 1RL and 1RR while maintaining the state where the front and rear distribution of the vehicle roll moment is changed closer to the rear wheels 1RL and 1RR by the first correction control means 16A. The braking force generated in the vehicle is increased. When the third correction control means 16C determines that the slip ratio of the rear wheels 1RL, 1RR has reached a preset specified slip ratio threshold, the roll moment is generated in a state in which braking force is generated on the turning inner wheels of the rear wheels 1RL, 1RR. Via the distribution adjusting means, the front-rear distribution of the vehicle roll moment changed to the rear wheels 1RL, 1RR side is changed again to the front wheel side.

With the above configuration, as the reference US correction moment Mθ increases, the first correction control means 16A, the second correction control means 16B, and the third correction control means 16C are executed in this order in order to suppress the understeer tendency. Control the generation of moments.
As a result, if the reference US correction moment amount Mθ is small, the understeer tendency is suppressed without generating braking or increasing braking that has already occurred. The braking that has already occurred is a state in which the driver is stepping on the brake pedal, for example.
Furthermore, even if the slip ratio reaches the maximum friction coefficient, the understeer tendency can be suppressed. Thereby, the understeer tendency can be further suppressed.

(2) The first correction control means 16A includes roll moment estimation means 16Aa for estimating the roll moment of the vehicle. Then, the first correction control means 16A is arranged before and after the vehicle roll moment for generating the reference US correction moment amount Mθ based on the reference US correction moment amount Mθ and the roll moment amount MR estimated by the roll moment estimation means 16Aa. Calculate the distribution.
Thereby, the front-rear distribution of the vehicle roll moment according to the reference US correction moment amount Mθ can be obtained.
(3) The roll moment distribution adjusting means adjusts the front and rear distribution of the vehicle roll moment by changing the rigidity of the stabilizers 9 and 10 connecting the left and right suspensions.
With the existing stabilizer rigidity adjusting means, the front-rear distribution of the vehicle roll moment can be adjusted by changing the front-rear roll rigidity.

(Modification)
(1) In the said embodiment, the rotary actuators 11 and 12 which change the rigidity of the stabilizers 9 and 10 were illustrated as roll moment distribution adjustment means. The stiffness of the stabilizers 9 and 10 may not be adjusted by the rotary actuators 11 and 12. As shown in FIG. 10, a linear actuator 20 is interposed at a connecting portion between the foot portions 9 b and 10 b of the stabilizers 9 and 10 and the suspension, and the amount of expansion and contraction of the linear actuator 20 is adjusted. , 10 may be changed.
Alternatively, as shown in FIG. 11, a linear actuator 21 is interposed between the center portions of the stabilizers 9, 10 and the vehicle body 7, and the amount of expansion / contraction of the linear actuator 21 is adjusted, so that the rigidity of each stabilizer 9, 10 is increased. May be changed.

(2) In the said embodiment, the case where the roll moment distribution adjustment means was comprised with the rigidity adjustment apparatus of the stabilizers 9 and 10 was illustrated. Instead of this or in combination, the roll moment distribution adjusting means may adjust the longitudinal distribution of the vehicle roll moment by changing the damping force of the suspension.
For example, as shown in FIG. 12, by adopting a variable damping force shock absorber as the shock absorbers 6FL to 6RR and changing the damping characteristics of the shock absorbers 6FL to 6RR of each suspension, the roll characteristics on the front wheel side and the rear wheel 1RL, The relationship between roll characteristics on the 1RR side can be changed, and the front-to-back distribution of the roll moment can be adjusted. In this case, the front / rear distribution is adjusted according to the roll speed. On the other hand, when the rigidity of the stabilizer is used, the front-rear distribution is adjusted according to the roll displacement.

(3) Further, as shown in FIG. 13, the roll moment distribution adjusting means employs an active suspension using, for example, a linear motor, as the shock absorbers 6FL to 6RR, which controls the vertical movement of the suspension by an electric mechanism. The front-rear distribution of the vehicle roll moment may be adjusted by adjusting the thrust generated in the active suspension.
In this case, the distribution of the front and rear roll moments is changed by the vertical thrust generated in each suspension.
(4) The US correction moment amount control means 16 may generate braking force on the front wheels together with the operation of the third correction control means 16C.
In this case, a front wheel braking command is output to the braking controller 3.
As a result, the vehicle is decelerated and the understeer tendency can be further suppressed.

1RL, 1RR Rear wheels 2FL to 2RR Braking device 3 Braking controller (control braking means)
6FL-6RR Shock absorber (Roll moment distribution adjusting means)
9, 10 Stabilizers 11, 12 Rotary actuator (roll moment distribution adjusting means)
13 Suspension control controller 13A Understeer control unit 14 US tendency determination means 15 Standard US correction moment amount calculation means 16 US correction moment amount control means 16A First correction control means 16Aa Roll moment estimation means 16Ab Roll moment distribution change means 16B Second correction control Means 16Ba Roll distribution limit determination means 16Bb Turning inner wheel braking control means 16C Third correction control means 16Ca Slip rate limit determination means 16Cb Roll moment redistribution means 16D Roll moment distribution command value output means 20 Linear actuator (roll moment distribution adjustment means)
21 Linear actuator (roll moment distribution adjustment means)
Mθ Standard US correction moment amount M1 First correction moment amount M2 Second correction moment amount MR Estimated roll moment amount Mx Maximum US correction moment amount

Claims (7)

An actual yaw rate detecting means for detecting the actual yaw rate of the vehicle, a turning angle detecting means for detecting the turning angle of the steered wheels, a wheel speed detecting means for detecting the rotational speed of the wheels,
US tendency determination for determining whether the vehicle is understeered based on the actual yaw rate detected by the actual yaw rate detection means, the turning angle detected by the turning angle detection means, and the wheel speed detected by the wheel speed detection means Means,
Target yaw rate calculating means for calculating a target yaw rate based on the turning angle detected by the turning angle detecting means and the wheel speed detected by the wheel speed detecting means;
When the vehicle is determined to have an understeer tendency based on the determination of the US tendency determination means, a reference US that is a corrected yaw moment amount for suppressing the understeer tendency based on the target yaw rate calculated by the target yaw rate calculation means and the actual yaw rate. A reference US correction moment amount calculating means for calculating a correction moment amount;
Roll moment distribution adjusting means for adjusting the front and rear distribution of the vehicle roll moment;
Control braking means for generating a braking force not depending on the driver's intention on the wheel or increasing the braking force generated by the driver's intention;
Steering direction detecting means for detecting the steering direction of the vehicle;
A slip ratio detecting means for detecting a slip ratio between the wheel of the turning inner wheel and the road surface based on the steering direction detected by the steering direction detecting means and the wheel speed detected by the wheel speed detecting means;
Based on the reference US correction moment amount calculated by the reference US correction moment amount calculation means and the slip ratio detected by the slip ratio detection means, the roll moment distribution adjusting means and the control braking means generate a correction yaw moment to be generated in the vehicle. US correction moment amount control means for controlling using
With
The above US correction moment amount control means is:
When the vehicle is determined to be understeered based on the determination by the US tendency determining means, the front and rear distribution of the vehicle roll moment is changed so that the rear wheel side becomes larger via the roll moment distribution adjusting means without using the control braking means. First correction control means for generating a corrected yaw moment,
After the control by the first correction control means, the standard US correction moment amount is generated by changing the front-rear distribution of the vehicle roll moment so that the rear wheel side becomes as large as possible by the first correction control means. When it is determined that the moment amount has been exceeded and this prescribed corrected yaw moment amount has been exceeded, the control braking means is applied to the turning inner wheel of the rear wheel while maintaining the front and rear distribution of the vehicle roll moment by the first correction control means. Second correction control means for increasing the correction yaw moment by generating a braking force or increasing a braking force generated in the turning inner wheel;
After the control by the second correction control means, it is determined that the slip ratio of the turning inner wheel has reached a specified slip ratio threshold value at which the friction coefficient between the wheel and the road surface is large. In the state where the braking state by the means is maintained, the front and rear distribution of the vehicle roll moment changed so that the rear wheel side is increased as much as possible through the roll moment distribution adjusting means is changed again so that the front wheel side is increased. And a third correction control means for increasing the correction yaw moment. The first correction control means, the second correction control means, and the third correction control means according to the magnitude of the reference US correction moment amount. An understeer suppression device for a vehicle characterized by using the stepwise. A roll moment estimating means for estimating the roll moment amount of the vehicle;
The first correction control means is arranged before and after a vehicle roll moment for generating a yaw moment according to the reference US correction moment quantity based on the reference US correction moment quantity and the roll moment quantity estimated by the roll moment estimation means. 2. The vehicle understeer suppression device according to claim 1, wherein the distribution is calculated.   The vehicle understeer according to claim 1 or 2, wherein the roll moment distribution adjusting means adjusts the front / rear distribution of the vehicle roll moment by changing the rigidity of a stabilizer connecting the left and right suspensions. Suppression device.   The vehicle understeer according to any one of claims 1 to 3, wherein the roll moment distribution adjusting means adjusts the longitudinal distribution of the vehicle roll moment by changing a damping force of the suspension. Suppression device. It has an active suspension that controls the vertical movement of the suspension with an electrical mechanism,
The roll moment distribution adjusting means adjusts the front / rear distribution of the vehicle roll moment by adjusting a vertical thrust generated in the active suspension, according to any one of claims 1 to 4. The vehicle understeer suppression device described.   The US correction moment amount control means generates a braking force on the front wheel or increases a braking force generated on the front wheel when the third correction control means is actuated. The understeer suppression device for a vehicle according to claim 1. Actual yaw rate detecting means for detecting the actual yaw rate of the vehicle, turning angle detecting means for detecting the turning angle of the steered wheels, roll moment distribution adjusting means for adjusting the front and rear distribution of the vehicle roll moment, and the driver's intention on the wheels Control braking means for generating non-dependent braking force or increasing the braking force generated by the driver's intention, steering direction detecting means for detecting the steering direction of the vehicle, and wheel speed detection for detecting the rotational speed of the wheel A vehicle understeer suppression method comprising:
Based on the actual yaw rate detected by the actual yaw rate detecting means, the turning angle detected by the turning angle detecting means and the wheel speed detected by the wheel speed detecting means, the step of determining that the vehicle is understeering, and Based on the steered angle detected by the steered angle detecting means and the wheel speed detected by the wheel speed detecting means, the step of calculating the target yaw rate, the target yaw rate calculated by the target yaw rate calculating means, and the actual yaw rate, A step of calculating a reference US correction moment amount, which is a correction yaw moment amount for suppressing an understeer tendency, and the roll moment distribution adjusting means according to the reference US correction moment amount without using the control braking means described below. To change the front and rear distribution of the vehicle roll moment so that the rear wheel side becomes larger A step of determining that the reference US correction moment amount exceeds a specified correction yaw moment amount generated by changing the front-rear distribution of the vehicle roll moment so that the rear wheel side becomes as large as possible, and the vehicle roll moment Generating a braking force on the turning inner wheel of the rear wheel or increasing a braking force generated on the turning inner wheel with the control braking means maintaining the rear wheel distribution as large as possible on the rear wheel side; Detecting a slip ratio between the wheel of the turning inner wheel and the road surface based on the steering direction detected by the steering direction detecting means and the wheel speed detected by the wheel speed detecting means; and the slip ratio of the wheel of the turning inner wheel Determining that the friction coefficient has reached a specified threshold value with a large friction coefficient, and maintaining the braking state by the control braking means, The step of re-changing the front-rear distribution of the vehicle roll moment maintained so that the rear wheel side is as large as possible through the roll moment distribution adjustment means is performed step by step. A method for suppressing understeer of a vehicle.

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