Land vehicles – Suspension modification enacted during travel – Suspension stiffness for ride comfort
Reexamination Certificate
1998-12-23
2001-01-23
Dickson, Paul N. (Department: 3618)
Land vehicles
Suspension modification enacted during travel
Suspension stiffness for ride comfort
Reexamination Certificate
active
06176494
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a suspension control system.
One example of a conventional suspension control system is disclosed in Japanese Patent Application Unexamined Publication (KOKAI) No. 7-232530. The conventional suspension control system judges road surface conditions on the basis of the frequency of a signal detected by a vertical acceleration sensor. The term “road surface conditions” means conditions of each particular road, for example, an undulating road that causes a low-frequency vertical acceleration signal to be generated, or a bad road that causes a high-frequency vertical acceleration signal to be generated. Then, the suspension control system adjusts a control signal for an actuator in accordance with the result of the judgment of the road surface conditions, thereby allowing a shock absorber to generate a damping force according to the result of the judgment.
Incidentally, road surface conditions cannot clearly be classified into undulating roads, bad roads, normal roads, etc. Road surface conditions often have both an undulating road component and a bad road component. That is, there are many road surfaces that are both undulating and rough. In other words, there are many cases where when road surface conditions are detected with a vertical acceleration sensor, for example, the detected signal has a high-frequency component superimposed on a low-frequency component. In such cases, according to the above-described prior art, a road that is undulating and rough is judged to be either an undulating road or a bad road, and control adapted for only an undulating road or a bad road determined by the result of the judgment is carried out. Consequently, under circumstances where steering stability if important, control for a bad road may be carried out (i.e. damping force characteristics may be set “soft”), causing the vehicle steering stability to be impaired. Alternatively, under circumstances where ride quality should be given priority, control for an undulating road may effected (i.e. damping force for a characteristics may be be set “hard”), causing the ride quality to be degraded. Thus, the prior art is likely to fail to take full advantage of a predetermined degree of importance in the suspension control.
SUMMARY OF THE INVENTION
In view of the above-described circumstances, an object of the present invention is to provide a suspension control system wherein even when it is judged that the present road surface falls into a plurality of different categories for road surface conditions, it is possible to ensure an improvement in the ride quality or in the steering stability appropriately according to the degree of importance.
The present invention provides a suspension control system including a shock absorber interposed between the body of a vehicle and an axle. The shock absorber is capable of controlling damping force through an actuator. A road surface condition detecting device outputs a signal corresponding to road surface conditions. An extraction device extracts at least two different vibration components from the signal output from the road surface condition detecting device. A damping force control device effects predetermined damping force control for each of the vibration components when the level of the vibration component exceeds a predetermined value. The damping force control device controls damping force according to a predetermined order of priority when the levels of at least two of the vibration components simultaneously exceed the respective predetermined values.
According to one embodiment of the present invention, the damping force control device effects damping force control for a high-frequency vibration component with priority relative to damping force control for a low-frequency vibration component.
According to another embodiment of the present invention, when the vehicle speed is low, the damping force control device effects damping force control for a high-frequency vibration component with priority relative to damping force control for a low-frequency vibration component, whereas when the vehicle speed is high, the damping force control device effects damping force control for a low-frequency vibration component with priority relative to damping force control for a high-frequency vibration component.
REFERENCES:
patent: 5175687 (1992-12-01), Tsutsumi et al.
patent: 5802486 (1998-09-01), Uchiyama
Ichimaru Nobuyuki
Uchiyama Masaaki
Dickson Paul N.
Fleming Faye M.
Tokico Ltd.
Wenderoth , Lind & Ponack, L.L.P.
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