Land vehicles – Wheeled – Running gear
Patent
1987-01-09
1988-05-10
Rice, Kenneth R.
Land vehicles
Wheeled
Running gear
280710, 280714, B60G 1126
Patent
active
047430460
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to vehicle suspension systems and more particularly, to a vehicle suspension system in which control means incorporating a micro processor or computer controls the damping of a shock absorber to optimize riding and handling characteristics under a wide range of driving conditions. The control means comprise sensors which provide signals to the micro processor which are representative of the vehicle riding comfort. The control means actively affect the shock absorber operation utilizing programmed algorithms.
STATE OF THE ART
In the U.S. Pat. No. 4,154,461, May 15, 1979, a concept of a dual state shock absorber for a vehicle wheel is introduced.
In said patent there is arranged a throttling valve, combining the upper and lower fluid chambers of a shock absorber cylinder, said valve being fixed in one of two different positions under the influence of an external control means. By this arrangement the shock absorber would offer either "soft", i.e. low damping or "stiff", i.e. high damping, respectively, to resist either compressive or expansive movements of the shock absorber.
The decision whether the damping should be stiff or soft is made dependent on the sensor signals y, representing the vehicle vertical velocity (positive upwards), and the signal indicating the compression or expansion sense of the shock absorber as expressed by (y-x). Here x is the vertical displacement upwards of the wheel and therefore (y-x) is positive for expansion and negative for compression of the shock absorber.
It is also shown by said patent that the decision about soft or stiff damping could be made entirely dependent on the sign of the variable S=y.multidot.(y-x). Obviously the arrangement according to said patent would call for two sensors; one sensor being an accelerometer on the car body to yield y and one sensor indicating the compression or expansion of the shock absorber.
The present invention relates to a hydraulic shock absorber including a generally vertical cylinder receiving therein hydraulic liquid, a piston working in the cylinder and partioning the interior thereof into two liquid chambers,
an upper and a lower chamber,
two sets of one or more damping force generating check valves mounted on the piston, one set generating the damping force in the expansion stroke and another set allowing free flow from the lower to the upper chamber in the compression stroke,
a piston rod secured to the piston extending through the end of the cylnder to the outside, said sets of valves constituting connections between the two liquid chambers, a liquid reservoir connected to the lower liquid chamber by a third set of check valves generating the damping force in the compression stroke and allowing a return free flow from the reservoir to the lower chamber in the expansion stroke.
The invention presents a mechanical design to improve the speed and accuracy of the damping control and to simplify the sensor installation. This is achieved by a circuit forming a connection between the two liquid chambers, a further circuit connecting the reservoir to the lower liquid chamber, each of the two circuits including a controllable first check valve and second check valve, respectively, that can each take two states of operation under the action of a control means, in a first state locking the valve in a closed position cutting off the forward flow through the check valve, and in a second state allowing a free forward flow through the check valve, whereas the check valve in the first state as well as in the second state block the reverse flow of both circuits.
In a second embodiment the control means comprise a locking device keeping the check valve head in sealing engagement with the valve seat to cut off the forward flow.
In a third embodiment the locking device comprises a rocking lever barring the valve head in its sealed engagement in one position and setting the valve head free in one or more further positions.
In a fourth embodiment the control means for the check valves co
REFERENCES:
patent: 4000910 (1977-01-01), Unruh et al.
patent: 4154461 (1979-05-01), Schnittger
patent: 4468050 (1984-08-01), Woods et al.
patent: 4468739 (1984-08-01), Woods et al.
patent: 4591186 (1986-05-01), Ashiba
Rice Kenneth R.
Wittenberg Malcolm B.
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