Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Indication or control of braking – acceleration – or deceleration
Reexamination Certificate
2000-08-09
2001-11-27
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Indication or control of braking, acceleration, or deceleration
C701S041000, C701S071000, C303S188000, C180S197000, C180S445000
Reexamination Certificate
active
06324458
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device for controlling a running behavior of a vehicle such as an automobile, and more particularly, to a device for controlling a turn running behavior of such a vehicle for a higher stability in a forward turn running as well as in a rearward turn running.
2. Description of the Prior Art
In the art of running behavior control of four-wheeled vehicles, an oversteer control (anti-spin control) and an understeer control (anti-driftout control) are well known. In the conventional turn behavior control devices, an oversteering condition is generally judged by an oversteer index based upon the slip angle of the vehicle body increasing beyond a threshold value in a direction opposite to a turning direction, and when it occurs, a front wheel serving at the outside of a turn is braked to generate an anti-spin moment in the vehicle around the braked front outside wheel, with or without a simultaneous reduction control of engine torque. When the front outside wheel is braked to control the oversteering, the cornering force of the braked front outside wheel decreases, so that the front outside wheel might slip to the outside of the turn. Such a front outside slip of the vehicle contributes to the oversteer control. On the other hand, an understeering condition is generally judged by an understeer index based upon a deviation of the actual yaw rate of the vehicle from a theoretical yaw rate calculated based upon the steering angle and the vehicle speed, and when it occurs, a rear wheel or wheels are braked to decelerate the vehicle, with a particular effect that when a rear wheel serving at the inside of a turn is braked, a turn assist yaw moment is generated in the vehicle around the braked rear inside wheel. A simultaneous reduction control of engine torque may also be made. When the rear wheel or wheels are braked to control the understeering, the cornering force of the braked rear wheels decreases, so that the rear wheels might slip to the outside of the turn. Such a rear outside slip of the vehicle contributes to the understeer control.
When a vehicle equipped with such a conventional turn behavior control device is put into an oversteering condition in a rearward turn running, its intrinsic front wheel (virtually rear wheel) serving at the outside of the turn will be braked, when the control device still operates. The braking of the virtually rear outside wheel generates an anti-spin moment in the vehicle around the braked virtually rear outside wheel, also to be effective as an oversteer control. However, the braked virtually rear outside wheel is liable to slip to the outside of the turn, and when it occurs, it cancels the oversteer control.
On the other hand, when a vehicle equipped with such a conventional turn behavior control device is put into an understeering condition in a rearward turn running, its intrinsic rear wheel (virtually front wheel) serving at the inside of the turn may be braked. The braking of the virtually front inside wheel generates an anti-driftout moment in the vehicle around the braked virtually front inside wheel, also to be effective as an understeer control. However, the braked virtually front inside wheel is liable to slip to the outside of the turn, and when it occurs, it cancels the understeer control.
In view of the above-mentioned drawback in the operation of the conventional turn behavior control in a rearward drive, it has been proposed by Japanese Patent Laid-open Publication 7-11645 to adapt such a turn behavior control to a rearward drive of a vehicle with such a modification that a braking for an oversteer control in a rearward drive is applied to a virtually front (intrinsically rear) wheel serving at the outside of the turn, while a braking for an understeer control in a rearward drive is applied to a virtually rear (intrinsically front) wheel serving at the inside of the turn.
Apart from the above matter concerned with the forward/rearward drive, with respect to the rearward turn running performance of the four-wheeled vehicles, it is noted that the vehicles are generally highly liable to deviate from a running course intended by the driver, so that the stability of the rearward turn drive of the vehicle is generally very low. An essential cause for such a turn trace instability in the rearward drive would be an inexperience of most drivers to the rearward drive, but another essential cause is considered to reside in the fact that, in the rearward drive, the point of contact of each of a pair of steered wheels with the ground surface is located ahead of the point of the steering axis of each of the pair of steered wheels traversing the ground surface along the direction of running movement of the vehicle, so that, when the pair of steered wheels are non-driven wheels, the force applied to each of the pair of steered wheels from the ground surface has an effect of augmenting a steering angle input thereto by the steering system.
SUMMARY OF THE INVENTION
In view of the above-mentioned geometric difference in the virtual steering construction from the actual steering construction of the four-wheeled vehicle due to a reversal of the drive direction of the vehicle and the accompanying inversion of the feedback performance in the steering operation from a stable negative feedback to an unstable positive feedback, it is a primary object of the present invention to provide a device for controlling a turn running behavior of a four-wheeled vehicle at each best mode in a forward as well as rearward drive of the vehicle.
According to the present invention, the above-mentioned primary object is accomplished by a device for controlling a turn running behavior of a vehicle having a vehicle body, front left, front right, rear left and rear right wheels, an engine for driving at least a rear pair or a front pair of the wheels, a steering system for steering at least the front pair or the rear pair of the wheels, and a brake system for braking each of the wheels, comprising:
means for detecting at least one parameter with respect to the turn running behavior of the vehicle in addition to a drive direction thereof, the one parameter being indicative of changes of degree of desirability of the turn running behavior control according to changes of a magnitude thereof,
means for calculating an amount for the turn running behavior control based upon the turn running parameters detected by the turn running behavior parameter detection means,
means for determining a start of the turn running behavior control according to the one turn running behavior parameter traversing a threshold value determined therefor, and
means for executing the turn running behavior control by operating at least one of the engine and the brake system according to the turn running behavior control amount,
wherein the turn running behavior control start determination means change the threshold value in a rearward drive of the vehicle as compared in a forward drive thereof such that the turn running behavior control is started at a lower degree of the desirability thereof in the rearward drive than in the forward drive.
By a four-wheeled vehicle being controlled of its turn running behavior by such a turn running behavior control device, the turn running behavior control is started at an earlier stage of progress of a liability to a turn running instability when the vehicle is driven rearward than it is driven forward, so that the higher liability to the turn running instability of the vehicle in the rearward drive is effectively suppressed by such an earlier counteraction thereto before the vehicle is put into a substantial turn running instability.
In the turn running behavior control device of the above-mentioned basic construction, the turn running behavior control start determination means may determine the one turn running behavior parameter to traverse the threshold value according to a control start determination formula common to the forward and rearward drive, the common control start deter
Nagae Akira
Ohtake Hirotada
Takagi Masashi
Arthur Gertrude
Cuchlinski Jr. William A.
Oliff & Berridg,e PLC
Toyota Jidosha & Kabushiki Kaisha
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