US 5,490,068 AGranted

Suspension control system for automotive vehicle including apparatus for controlling shock absorber damping force coefficient

AssigneeAtsugi Unisia Corporation

InventorsHiroyuki Shimizu, Makoto Kimura, Toru Takahashi, Junichi Emura, Shinobu Kakizaki

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Abstract

A suspension control system for an automotive vehicle is disclosed in which, in each shock absorber, interposed between the vehicular body and tire wheel, a damping coefficient varying adjuster is provided which changes a damping coefficient at either or both of piston stroke sides according to a control signal input thereto so that the damping coefficient is set to a target damping coefficient position, at lease one sprung mass acceleration sensor and at least one sprung mass speed sensor are provided, and the control unit is provided which outputs the control signal to the damping coefficient varying means according to a result of determination of whether the vertical sprung mass acceleration exceeds a predetermined threshold value and according to a direction and magnitude of the sprung mass speed so that the damping coefficient at either or both of the stroke sides is controlled to a target damping coefficient position.

Claims29

Dependent claims

A suspension control system for an automotive vehicle, comprising:

a) at least one shock absorber, interposed between a vehicle body as a sprung mass and a tire wheel as an unsprung mass, having a piston member and a damping coefficient varying means therein, said damping coefficient varying means operatively changing its position in response to a control signal so that a damping coefficient of at least one of extension and contraction strokes of the piston member is set to a target damping coefficient exhibiting position;
b) at least one sprung mass acceleration detecting means for detecting a vertical sprung mass acceleration and outputting a vertical sprung mass acceleration signal indicative thereof;
c) high pass filtering means, having a predetermined cut-off frequency, for eliminating a lower frequency component of the vertical sprung mass acceleration indicative signal derived from said sprung mass acceleration detecting means than the predetermined cut-off frequency, said lower frequency component including a sprung mass resonance frequency component, and for passing a higher frequency component of the vertical sprung mass acceleration indicative signal from said vertical sprung mass acceleration detecting means than the predetermined cut-off frequency, said higher frequency component including an unsprung mass resonance frequency component;
d) at least one sprung mass vertical velocity detecting means for detecting a sprung mass vertical velocity and for outputting a sprung mass vertical velocity signal indicative thereof;
e) setting means for previously setting a predetermined threshold value for the high pass filtered vertical sprung mass acceleration indicative signal;
f) determining means for determining whether a value of the vertical sprung mass acceleration indicative signal passed through said high pass filtering means and derived from said sprung mass acceleration detecting means is below the predetermined threshold value;
and
g) controlling means for outputting the control signal to the damping coefficient varying means according to a result of determination of the determining means and according to a direction of the sprung mass vertical velocity signal so as to control the damping coefficient of either of extension and contraction stroke sides which is the same direction as that of the vertical sprung mass velocity signal derived from said sprung mass vertical velocity detecting means to the target damping coefficient position.

5 more elements

A method for controlling damping force characteristics of at least one stroke side of a vehicular shock absorber, said shock absorber being interposed between a sprung mass and an unsprung mass, having a vertically movable piston member and an adjuster which is so constructed and arranged as to vary its position to vary a damping force coefficient at either side of the strokes of the piston member in response to a control signal so that the damping coefficient of either of extension and contraction stroke sides of the piston member is set to a desired damping coefficient position, said method comprising the steps of:

a) detecting a vertical acceleration of the sprung mass and outputting a sprung mass acceleration indicative signal;
b) determining a vertical sprung mass velocity on the basis of the sprung mass acceleration indicative signal and outputting a vertical sprung mass velocity indicative signal;
c) eliminating a lower frequency component, including a sprung mass resonance frequency, from the sprung mass acceleration indicative signal detected in step a), said lower frequency component having a lower frequency than a predetermined cut-off frequency of a high pass filter, and passing only a higher frequency component, including an unsprung mass resonance frequency, from the sprung mass acceleration indicative signal detected in step a), said higher frequency component having a higher frequency than the predetermined cut-off frequency of the high pass filter;
d) setting a predetermined threshold value for the sprung mass acceleration indicative signal passed through said high pass filter;
e) determining whether an amplitude of said sprung mass acceleration indicative signal passed through said high pass filter is below the predetermined threshold value;
and
f) outputting the control signal to the adjuster via a pulse motor connected to the adjuster in accordance with a result of the determination in step e) and in accordance with a direction of the vertical sprung mass velocity detected in step b) so as to control the damping coefficient to the desired damping coefficient position.

4 more elements

Dependencies are inferred from the claim text.