Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Vehicle subsystem or accessory control
Reexamination Certificate
2001-12-07
2003-12-30
Nguyen, Tan Q. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Vehicle subsystem or accessory control
C701S038000, C280S005515
Reexamination Certificate
active
06671596
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a control method for a suspension which is provided to a vehicle such as an automobile or the like, and more particularly relates to a control method for a suspension which is equipped with actuators which apply forces in the upwards and downwards directions to the vehicle wheels.
2. Background Art
A suspension which is fitted to a vehicle fulfills the role of giving the vehicle a more comfortable ride by absorbing shocks from the road surface with which the vehicle wheels are in contact, and generally comprises coil springs and shock absorbers which suppress vibrations of these coil springs. There is a tendency that, the smaller is the spring rate of these coil springs with which the suspension is equipped and the softer are the springs, the better is the comfort of the ride.
On the other hand, although the greater is the stiffness of the vehicle body the greater is the controllability of the vehicle, if the spring rate is reduced in order to enhance the comfort of the ride, not only can rolling when steering the vehicle round a curve, or pitching during acceleration or deceleration, easily occur, but the controllability has a tendency to decrease; and, furthermore, since the vehicle body tilts from the point of view of the passengers, it cannot be said that the comfort of the ride is good.
Since in this manner, with a conventional vehicle suspension, it is difficult to improve both the controllability and also the comfort of the ride simultaneously, therefore it often happens that the suspension characteristics are set to give either excellent ride comfort or excellent controllability, according to the character which it is desired the vehicle should possess.
In the prior art, it is known to provide a stabilizer for enhancing the roll stiffness of the vehicle body. Such a stabilizer has no function of acting as a spring when both the left wheel and the right wheel between which it is fitted move in the same sense; but, when this left wheel and right wheel move in opposite senses, one upwards and one downwards, as during rolling of the vehicle body, the stabilizer suppresses this rolling by acting as a spring. Since the stabilizer acts as a spring when the left wheel and the right wheel move in opposite senses, it becomes possible to suppress rolling without increasing the spring rate of the coil springs of the vehicle.
Moreover, since it is easy for rolling to occur when the vehicle is being steered around a curve if the ride comfort is enhanced by reducing the spring rate of the coil springs, accordingly in this case it is necessary to increase the reaction force which is generated by the stabilizer bar, either by increasing the diameter of the stabilizer bar, or by reducing the length of the portion thereof in which twisting takes place, or the like.
However, if the reaction force which is generated by the stabilizer bar is increased, then, as a result, this is equivalent to the case in which the spring rate of the coil springs is increased in circumstances in which the road surface upon which the vehicle is being driven has irregular convexities and concavities, and therefore there is the problem that there is a tendency for the comfort of the ride to be deteriorated.
SUMMARY OF THE INVENTION
The objective of the present invention is to provide a control method for a vehicle suspension which, by implementing control of actuators which apply forces in the upwards and downwards directions to the vehicle wheels according to the operational conditions of the vehicle, can simultaneously enhance both the control stability of the vehicle and also the comfort of the ride for the passengers in the vehicle.
According to a first aspect of the present invention, there is proposed a suspension control method for controlling a suspension which includes respective actuators for left and right wheels of a vehicle, and which can apply forces in the upwards and downwards direction to the left and right vehicle wheels via these actuators, wherein, while the vehicle is being driven in a straight line, control is performed by giving priority to ride comfort (for example, by skyhook control); and, while the vehicle is being driven around a curve, control is performed by giving priority to roll suppression (for example, by rolling suppression control).
According to this aspect of the present invention as described above, it is possible to reduce vibration of the vehicle body when the vehicle is being driven in a straight line, while, when the vehicle is being driven around a curve, it is possible to reduce tilting of the vehicle body, so that it is possible to enhance the comfort of the ride from the point of view of the vehicle occupants. Furthermore, it becomes possible to enhance both the control stability and also the comfort of the ride in a compatible manner, since it becomes possible to increase the apparent spring rate only when the vehicle is being driven around a curve.
In the above described suspension control method, it is desirable, if the acceleration in the forwards and rearwards direction of the vehicle is greater than a predetermined value, to perform control by giving priority to pitching suppression, even while the vehicle is being driven in a straight line.
In this case, by performing control by giving priority to pitching suppression if the acceleration in the forwards and rearwards direction of the vehicle is greater than the predetermined value, even while the vehicle is being driven in a straight line, it becomes possible to reduce tilting of the vehicle body in the forwards and rearwards direction, and it accordingly becomes possible to enhance the comfort of the ride from the point of view of the passengers in the vehicle. Furthermore, it becomes possible to enhance both the control stability and also the comfort of the ride in a compatible manner, since it becomes possible to increase the apparent spring rate only during acceleration or deceleration.
In the above described suspension control method, it is also desirable to vary the forces generated by the actuators according to the speed of the vehicle. In this case, it becomes possible to prevent deterioration of the comfort of the ride, since the forces generated by the actuators are varied according to the speed of the vehicle, and at low vehicle speed it becomes possible to perform control more minutely due to elimination of influences from convexities and concavities of the road surface.
Moreover, according to another aspect of the present invention, there is proposed a suspension control method as first described above, in which the acceleration of the vehicle in the upwards and downwards direction is detected, and, if the value of this upwards and downwards acceleration falls outside a predetermined range of values, and moreover has continued to be outside the predetermined value range for longer than a predetermined time period, then control is performed to suppress vibration of the vehicle based upon the value of the upwards and downwards acceleration which is detected.
According to this aspect of the present invention, if the change of acceleration in the upwards and downwards direction is rapid, it is possible to prevent vibration suppression control being performed for the vehicle body based upon the detected value of acceleration in the upwards and downwards direction, and as a result the comfort of the ride at this time is enhanced.
According to another aspect of the present invention, there is proposed a suspension control method as first described above, in which the acceleration of the vehicle in the upwards and downwards direction is detected, and, if the value of this upwards and downwards acceleration falls within a predetermined range of values, and moreover has continued to be within the predetermined value range for longer than a predetermined time period, then control (for example, skyhook control) is not performed to suppress vibration of the vehicle based upon the value of the upwards and downwards acceler
Kawashima Mitsunori
Kitazawa Hirokazu
Suto Shinji
Watanabe Kazuhisa
Honda Giken Kogyo Kabushiki Kaisha
Merchant & Gould P.C.
Nguyen Tan Q.
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