Fluid-pressure and analogous brake systems – Speed-controlled – With yaw control
Reexamination Certificate
2001-04-26
2002-12-10
Graham, Matthew C. (Department: 3683)
Fluid-pressure and analogous brake systems
Speed-controlled
With yaw control
C303S170000, C303S189000
Reexamination Certificate
active
06491358
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a braking force control system of a vehicle which adequately distributes the braking force in braking.
2. Description of the Related Art
In recent years, there have been proposed various braking control systems which make use of constitutions of anti-lock braking systems (ABS) and control distribution of braking force in normal braking to be more adequate one.
For example, in JP-A-10-119744, there is disclosed one which, when deceleration of a vehicle reaches a specified value and a vehicle speed exceeds a specified speed, independently increases, reduces or holds braking oil pressure of each of right and left rear wheels so that braking force distribution between rear and front wheels becomes an approximately ideal one to perform independent braking control for carrying out sufficient braking.
During a braking operation, for example, road surface friction coefficients (road surface friction) with respect to left and right wheels are greatly asymmetric in some cases. Namely, when a wheel on one side of a vehicle is on a dry road surface (high friction road) and a wheel on the other side thereof is on, for example, an ice plate (low friction road), a very high yawing moment occurs in some cases when the vehicle is braked.
Therefore, in a related art ABS control operation, in order to prevent the stability of the vehicle from being lost by applying a large braking force to a wheel on the side of a high friction road, a select-low control, in which a brake on a high friction road side is controlled in accordance with a brake on a low friction road side, i.e., on the side of a large slipping condition, is employed in many cases.
In general, the above-described independent braking control is suitable for a case where the obtainment of a sufficient braking force is required, while the above-described select-low control is suitable for a case where the minimization of the occurrence of a yawing moment and the obtainment of a sufficient vehicle stability are required. Therefore, it is desired that these controls can be carried out in a suitably selected manner in accordance with the variously changing traveling condition of a vehicle.
Further, in a braking operation, also important is a method of generating a braking pressure for producing a braking force. Especially, when a braking pressure is rapidly increased on a split friction road or with a load on a vehicle greatly different at left and right parts thereof, and in other similar cases, a yawing moment occurs in the vehicle. This would cause the vehicle to become unstable, or an unpleasant rolling behavior to be left during the turning with a high lateral acceleration.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above-mentioned circumstances, and provides a braking force distribution control apparatus for vehicles, capable of carrying out a reliable and stable braking operation finely and in a well-balanced manner by suitably selecting various braking controls in accordance with variously changing traveling condition of a vehicle, and executing a selected control, without adding a special complicated mechanism to the apparatus.
To attain the above object, according to a first aspect of the invention, there is provided a braking force distribution control apparatus for a vehicle, including: a lateral acceleration detecting unit detecting a lateral acceleration of the vehicle; a longitudinal acceleration detecting unit detecting a longitudinal acceleration of the vehicle; a vehicle speed detecting unit detecting a vehicle speed; and a braking control unit adapted to select and execute, one of a select-low control and an independent braking control in accordance with the lateral acceleration, the longitudinal acceleration and the vehicle speed when preset conditions for brake operating time are satisfied, the select-low control controlling braking forces of left and right wheels depending on a wheel on the side with a large slipping condition, the independent braking control independently controlling the braking force for each wheel depending on the slipping condition of each wheel.
In the braking force distribution control apparatus according to the first aspect, the lateral acceleration of a vehicle is detected by the lateral acceleration detecting unit, the longitudinal acceleration of the vehicle by the longitudinal acceleration detecting unit, and a vehicle speed by the vehicle speed detecting unit. The braking control device is adapted to select, when preset conditions for a braking operation are satisfied, either of a select-low control in which a wheel braking force for a left wheel and a right wheel is controlled in accordance with lateral acceleration, longitudinal acceleration and vehicle speed and correspondingly to a wheel on the side with a large slipping condition, and an independent braking control in which the braking force for each wheel is controlled independently and correspondingly to the slipping condition of each wheel, and then execute a selected control.
In addition, in the above braking force distribution control apparatus, when the preset conditions for a braking operation are satisfied, the braking control unit is adapted to select, either of the select-low control and the independent braking control in accordance with the vehicle speed in a case where the lateral acceleration is in a preset high region and then execute the selected control; select either of the select-low control and the independent braking control in accordance with the vehicle speed and the longitudinal acceleration in a case where the lateral acceleration is in a preset intermediate region, and then execute the selected control; and select and execute the select-low control in a case where the lateral acceleration is in a preset low region.
This braking force distribution control apparatus is so constituted that, for example, when the lateral acceleration is in a preset high region with a vehicle speed being low, a sufficient braking operation can be carried out by selectively executing an independent braking control, and so that, when the lateral acceleration is in the same region with a vehicle speed being high, the safety can be secured by selectively executing a select-low control. The apparatus is also so constituted that, when the lateral acceleration is in a preset intermediate region with the longitudinal acceleration being high, a judgement that a vehicle is traveling on a high friction road is given; when a vehicle speed is low, a sufficient braking operation can be carried out by executing an independent braking control; and, when a vehicle speed is high, the stability can be secured by selectively executing a select-low control. The apparatus is also so constituted that, when the longitudinal acceleration is low in this case, the stability can be secured by selectively executing a select-low control. The apparatus is formed so that, when the lateral acceleration is in a preset low region, the stability can be secured by selectively executing a select-low control.
Further, in the above braking force distribution control apparatus according to the first aspect, the select-low control and the independent braking control are carried out for the rear wheels.
Moreover, according to a second aspect of the invention, there is provided a braking force distribution control apparatus for a vehicle, including: a lateral acceleration detecting unit detecting a lateral acceleration of the vehicle; a longitudinal acceleration detecting unit detecting a longitudinal acceleration of the vehicle; and a braking control unit adapted to select and execute at least one of a select-low control, an independent braking control and a stepwise pressure increase control in accordance with the lateral acceleration and the longitudinal acceleration when preset conditions for brake operating time are satisfied, the select-low control controlling braking forces of left and right wheels depending on a wheel on the side with a large slipp
Akiyama Tohru
Soejima Yuji
Fuji Jukogyo Kabushiki Kaisha
Graham Matthew C.
Smith , Gambrell & Russell, LLP
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