Land vehicles – Skates – Ball type roller skates
Patent
1989-09-15
1990-11-20
Rice, Kenneth R.
Land vehicles
Skates
Ball type roller skates
280707, 280708, 280DIG1, B60G 1700
Patent
active
049713604
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a height adjustment system for an air suspension of a vehicle having an oscillation damper and comprising air springs, solenoid valve means for controlling air flow through the air springs, a distance sensor for sensing the distance between the vehicle body and a respective axle, and control means for controlling operation of the valve means in accordance with the distance. Such a system is known from EP-A-0091017 wherein compressed air is admitted to the air spring when a distance sensor senses that the height of the vehicle body is below a lower threshold, and air is released from the air spring when the distance sensor senses that the body height is above an upper threshold. As a result of frictional forces in the damper, the adjustment travel extends beyond that at closing of the solenoid valve arrangement. An attempt to compensate for this overshoot is made by appropriate choice of the upper and lower thresholds. However, this does not take into account the fact that the amount of overshoot depends also on the velocity of vertical movement of the vehicle body relative to the axle at the instant of closing of the valve arrangement and possibly other factors.
SUMMARY OF THE INVENTION
The object of the invention is to avoid this disadvantage.
The above object is achieved in accordance with the invention, by providing a height adjustment system in which the instant or the height at which the solenoid valve means closes, depends on the velocity of the vertical movement of the vehicle body relative to the vehicle axle. By an appropriate choice of parameters, the range of error in the adjusted height can be substantially reduced.
The invention is readily realized by the use of a characteristic curve stored in a memory. Sufficient accuracy can be obtained by selecting a threshold which is proportional to the velocity of vertical movement of the vehicle body relative to the axle at least over a portion of the characteristic curve, and by providing a characteristic curve which extends from a minimum threshold at which the velocity is within the degree of accuracy of measurement and calculation, to a maximum threshold at which the velocity of vertical movement is at the maximum that can be expected when the available compressed air supply is taken into consideration.
The characteristic curve can be determined empirically or by trial and error.
However, in a particularly advantageous embodiment, the stored characteristic can be corrected or a choice out of a range of stored characteristics can be made. This has the advantage that compensation can be made for changes which occur in the friction and damping characteristics while the vehicle is in use.
The present invention both as to its construction so to its method of operation, together with additional objects and advantages thereof, will be best understood from the following detailed description of the preferred embodiments with reference to the appended drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagram of an air suspension system for a vehicle fitted with a height adjustment system,
FIG. 2 is a block diagram of the height adjustment system according to the invention, and
FIG. 3 is a graph showing the characteristic curve stored in a memory of the height adjustment system.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows diagrammatically a part of a vehicle body 10 attached to an axle 12 by an air suspension 14. The air suspension 14 comprises an air spring bellows 16, an oscillation damper 18 and a height measuring sensor 20, each arranged between the vehicle body 10 and the axle 12. The height measuring sensor 20 can be a simple potentiometer or a variable resistor. The air spring bellows 16 is filled and emptied as required by a compressed air reservoir 22 and a solenoid valve arrangement 24. The reservoir 22 is charged from a compressor (not shown) via a line 26 containing a non-return valve 28. The valve arrangement 24 comprises a 3-port, 2-position valve 30
REFERENCES:
patent: 4696489 (1987-09-01), Fujishiro et al.
Fahrnschon Matthias
Pischke Jurgen
Tillhon Engelbert
Zehaczek Helmut
Rice Kenneth R.
Robert & Bosch GmbH
Striker Michael J.
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