Land vehicles – Body elevation or tilt – Loading position
Reexamination Certificate
1999-05-11
2001-05-22
Mai, Lanna (Department: 3619)
Land vehicles
Body elevation or tilt
Loading position
C280S006157, C280S006159, C280S005514
Reexamination Certificate
active
06234493
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a level control system operated by pressure media, and in particular, a level control system for a vehicle in which at least one air suspension bellow is provided for support of the vehicle frame above at least one vehicle axle, and wherein the level of the vehicle frame above the vehicle axle is determined by the prevailing pressure in the air suspension bellow.
A level control system of this type is disclosed, for example, in German patent application DE 195 46 730 A 1, which is incorporated herein by reference. In such known system, inclination of a vehicle caused by asymmetrical loading is compensated for only when leveling of the vehicle can be achieved while concurrent maintenance of a required minimum pressure level in the air suspension bellows via which the vehicle body is supported on the vehicle axles is possible. When leveling of the vehicle cannot be accomplished while the minimum pressure level is maintained, the inclined position of the vehicle body relative the vehicle axles is temporarily retained, and subsequently remains unchanged until the occurrence of a different load situation in which leveling permits maintenance of the minimum pressure level.
In the known system, a test is carried out to determine whether leveling is possible without reduction of pressure below the required minimum pressure level, in accordance with which a number of opposing control attempts are made in order to compensate for the deviation sensed by the control system. If the number of attempts do not exceed a predetermined number, maintenance of the minimum pressure level is ensured. The multiple opposing control attempts, however, require introduction and venting of air, resulting in an overall loss of air pressure affecting the air supply system.
In addition to vehicle inclinations caused by loading, inclinations of the vehicle body may result from uneven footing, such as for example, where one wheel of the vehicle axis rests atop the sidewalk.
The problem of undesirable air loss attendant the previously mentioned air admission and venting processes involved with a leveling of the vehicle in general is exaggerated in circumstances in which the vehicle inclination is the result of uneven footing as compared to a load-related inclination. All air losses which are not absolutely necessary should advantageously be avoided, particularly in level control systems where the air supply system is fed by a compressor driven by an electric motor and which provides a limited air supply.
The above stated problem is further aggravated by the fact that when the vehicle has gone from the condition of uneven footing, which resulted in the inclined position, to a footing which is again even, the air suspension bellow pressures which changed in the course of compensation while in the inclined position must again be reversed, and this again involves air loss.
In the event of vehicle inclinations caused by uneven footing, the procedure in accordance with known systems used for inclinations caused by loads cannot, therefore, be effectively applied, since application of such would exaggerate the problem of undesirable air loss.
It is therefore the object of the present invention to provide a level control system operated by pressure media of the type mentioned above in which no unnecessary air losses occur, particularly when a vehicle inclination is caused by uneven footing.
SUMMARY OF THE INVENTION
In accordance with these and other objects of the invention, there is provided a level control system for regulating a distance between a vehicle frame and a vehicle axle in a vehicle in which an inclination may occur whereby the axle is not aligned parallel to the vehicle frame. Included in the vehicle is at least one air suspension bellow for supporting the vehicle frame above the vehicle axle, the distance between the vehicle frame and the vehicle axle being determined by the pressure prevailing in the air suspension bellow. A valve arrangement is also provided for adjusting a pressure of air within the air suspension bellow. The vehicle is further equipped with at least one sensor for determining an actual distance between the vehicle frame and the vehicle axle and a regulating system for receiving a target level representative of a desired distance between the vehicle frame and the vehicle axle. The regulating system controls the valve arrangement in such manner that a control deviation produced from a difference between a target level and the actual distance corresponding thereto is minimized. By prescribing a value of the target level equalized with the current actual level, a control function of the regulating system can be deactivated. The regulating system is activated for a traveling state defined when a travel speed of the vehicle exceeds a predetermined minimum speed and no actuation of a brake takes place, and in which the target level is a target traveling level to thereby indicate the desired distance between the vehicle frame and the axle while in such state. Similarly, the regulating system is also activated for a stoppage state indicative of a stopped condition of the vehicle, the target level being a target stoppage level to thereby indicate the desired distance between the vehicle frame and the vehicle axle while in the stoppage state. The actual level of the vehicle frame relative to the vehicle axle is indicated to the regulating system for use as the target stoppage level even when the actual level reflects a vehicle inclination. The regulating system is also activated for a shunting state initiated following the stoppage state indicative of a travel condition in which a travel speed is below a predetermined minimum speed indicative of a traveling state, the target level being a target shunting level indicative of the desired distance between the vehicle frame and the vehicle axle while in the shunting state.
In accordance with embodiment of the invention, leveling of a vehicle can be advantageously applied in a more versatile manner for correction of inclinations than was heretofore permitted by the known system described above. The invention advantageously further permits implementation without any complicated processes dependant upon the possible presence of an inclined position, since the same procedure is consistently selected independent of the whether or not a vehicle inclination in fact exists.
The invention provides further advantage in that virtually no additional costs are involved in its practical realization, since a control program for a level control system already provided in a vehicle need only be modified. Moreover, since the invention utilizes target value indications which depend on the operating state of the vehicle in the leveling process, implementation thereof is facilitated.
The invention is explained in further detail through a example of an embodiment which follows read in conjunction with the accompanying drawings, in which like reference numerals designate elements providing the same function.
REFERENCES:
patent: 4678203 (1987-07-01), Rohner et al.
patent: 4965878 (1990-10-01), Yamagiwa et al.
patent: 4967360 (1990-10-01), Fukunaga et al.
patent: 5048867 (1991-09-01), Gradert
patent: 5080391 (1992-01-01), Kawabata
patent: 5082308 (1992-01-01), Jones
patent: 5083275 (1992-01-01), Kawagoe et al.
patent: 5087072 (1992-02-01), Kawarasaki
patent: 5130927 (1992-07-01), Kunishima et al.
patent: 5193849 (1993-03-01), Holzmann
patent: 5220505 (1993-06-01), Yokote et al.
patent: 5261691 (1993-11-01), Laichinger et al.
patent: 5286059 (1994-02-01), Tabe
patent: 5287277 (1994-02-01), Mine et al.
patent: 5338010 (1994-08-01), Haupt
patent: 5388857 (1995-02-01), Wernimont et al.
patent: 5499845 (1996-03-01), Geiger et al.
patent: 5684698 (1997-11-01), Fujii et al.
patent: 5769400 (1998-06-01), Holzl et al.
patent: 5855379 (1999-01-01), Buma et al.
patent: 5865453 (1999-02-01), Harada et al.
patent: 6015155 (2000-01-01), Brookes et al.
patent: 6049746 (2000-04-01), Southward et al.
patent: 6061615 (2000-05-01
Kleen Berend
Sohn Robert
Mai Lanna
Proskauer Rose LLP
To Toan
WABCO GmbH
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