Spring devices – Vehicle – Comprising compressible fluid
Patent
1992-12-22
1994-08-16
Oberleitner, Robert J.
Spring devices
Vehicle
Comprising compressible fluid
267 6428, 280 612, 280714, B60G 1700, F16F 500
Patent
active
053380100
DESCRIPTION:
BRIEF SUMMARY
The invention in general concerns a hydropneumatic vehicle suspension. Said suspension has hydropneumatic actuators mounted between suspended and unsuspended components. A level control valve is actuated as a function of the relative position with respect to each other of the suspended and unsuspended components, and it connects the hydropneumatic actuators in a first shift position with a pressure line in a second shift position with a drain line. In another shift position said connections are locked.
A hydropneumatic suspension of the above explained type of construction is generally known by the expression level control. The pressure medium such as oil is forced into a reservoir as the axle load increases. The assembly (unsuspended components) descends. A level control valve is adjusted in a manner such that oil, for instance, from a central reservoir, is fed to the actuators until the original level is again reached. When the axle load decreases, oil flows from the reservoir. In this shift position, the level control valve connects the hydropneumatic actuators with a drain line until the original level is again produced. A hydropneumatic suspension that works according to this principle must be regarded as known already, for instance, from DE 17 80 394 A1.
To adapt a hydropneumatic vehicle suspension to different load conditions, a varied of suggestions have already been made aimed at the change of the spring temper of the hydropneumatic actuators. DE 17 55 079 B2 has disclosed an arrangement where a spring-loaded 3-way valve automatically connects the cylinder space on the piston-rod side with a drain line or with the reservoir space. Hereby the spring temper in the unloaded vehicle is lower than in the loaded vehicle.
In a wheel suspension for an agricultural multipurpose vehicle (DE 28 07 299 C2), the pressure space of the hydropneumatic actuator is connectable to a reservoir via a locking valve. Parallel with the locking valve extends a pressure line in which is inserted a 3/3-way valve. When the locking valve is closed, leaf springs assume the support of the assembly. In unloaded condition of the vehicle, a very weak spring suspension exists. By opening the locking valve, the mechanical suspension is hydropneumatically supported. The characteristic line of said suspension is then considerably steeper whereby the suspension fails more severely. By adjusting the 3/3-way valve, the pressure of the pressure medium of the hydropneumatic actuator is brought to the value required for the existing load, which value is adjusted by a manometer.
In vehicles used in agriculture, such as tractors, high axle-load differences occur. When working with an attached plow, the rear axle is heavily loaded and the front axle considerably unloaded. Reverse circumstances exist when working with a front loader. The steps known already for adapting a hydropneumatic suspension do not allow taking into consideration such different conditions of use at all.
The problem on which the invention is based consists in designing a hydropneumatic suspension in which the static pressure ratio resulting from the highest and lowest axle loads, the maximum admissible dynamic pressure, the maximum admissible pressure ratio of the reservoir and the remains of a residual amount of oil in the reservoir in the presence of a minimal axle load be sufficiently taken into consideration or ensured. The natural frequency of the assembly should be 1 hertz in a vehicle used in agriculture and building.
The problem on which the invention is based is solved by the fact that the hydropneumatic actuators are double-acting hydraulic cylinders whose head spaces are connected with a first reservoir and whose cylinder spaces, on the piston-rod side, are connected with a second reservoir. A control valve connects the second reservoir with the pressure line or separates it therefrom depending on the pressure in the first reservoir. An essential feature of the solution according to the invention consists in dividing the hydropneumatic suspension in two pressure
REFERENCES:
patent: 3550993 (1970-12-01), Peiffer
patent: 3736000 (1973-05-01), Capgvas
patent: 3741582 (1973-06-01), Eckert
patent: 3913938 (1975-10-01), Aikawa et al.
patent: 3970327 (1976-07-01), Dezelan
Research Disclosure, No. 290, Jun. 1988, New York Dan R. Kimberlin: `Active ride economy valve` p. 358.
Oberleitner Robert J.
Rutherford Kevin D.
Zahnradfabrik Friedrichshafen AG
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