Hydropneumatic Suspension Control Arrangement for Load-Dependent Pressure Adjustment
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Solution Overview
Problem
Hydropneumatic suspension systems in vehicles, particularly in tractors, face challenges with variable load conditions, where they stiffen disproportionately under increased load, leading to reduced driving comfort and susceptibility to pitching vibrations, and existing control arrangements are costly and complex.
Innovation Solution
A control arrangement that adjusts annular chamber pressure based on piston chamber pressure, limiting control pressure to a predetermined value, ensuring a constant annular chamber pressure at high piston chamber pressures and increasing it as piston chamber pressure decreases, using standard components and hydraulically controllable pressure-limiting valves to manage variable load conditions effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the annular chamber pressure is increased to counteract pitching vibrations at low axle loads, then the suspension stiffness increases and pitching vibrations are reduced, but the suspension becomes excessively hard when the tractor is unloaded, reducing driving comfort
Solution Approach 1:
The control arrangement dynamically adjusts the annular chamber pressure based on the piston chamber pressure. When piston chamber pressure is high (indicating heavy rear attachment), the annular chamber pressure is limited to a maximum value. When piston chamber pressure is low (indicating lighter load), the annular chamber pressure increases automatically through the pressure-limiting valve mechanism, providing higher stiffness to counteract pitching vibrations without requiring external control signals.
Solution Approach 2:
The control arrangement uses the piston chamber pressure as feedback to automatically control the annular chamber pressure. The pressure-limiting valve responds to changes in piston chamber pressure by adjusting the annular chamber pressure accordingly, creating a closed-loop control system that adapts to varying load conditions and maintains optimal suspension characteristics.
2Reliability
If a constant high annular chamber pressure is used to prevent bottoming out with heavy rear attachments, then pitching vibrations are counteracted, but the suspension is very hard when the tractor is unloaded, offering limited driving comfort
Solution Approach 1:
Instead of using a constant high annular chamber pressure, the system dynamically adjusts the pressure based on operating conditions. The pressure-limiting valve allows the annular chamber pressure to vary with piston chamber pressure, providing high pressure only when needed (heavy rear attachment) and lower pressure when the tractor is unloaded, thus preventing bottoming out while maintaining driving comfort.
Solution Approach 2:
The system changes the annular chamber pressure parameter automatically based on the piston chamber pressure level. When piston chamber pressure decreases (lighter load), the annular chamber pressure increases through the pressure-limiting valve mechanism. When piston chamber pressure is high (heavy load), the annular chamber pressure is limited, creating an inverse relationship that optimizes both bottoming out prevention and driving comfort.
3Adaptability or versatility
If a positioning piston with adjustable stop is used to control annular chamber pressure, then the pressure can be controlled inversely proportional to piston chamber pressure, but the control arrangement becomes complex and costly with no standard components
Solution Approach 1:
The invention extracts and utilizes only the essential pressure-limiting function from complex positioning piston systems. By using a simple pressure-limiting valve with a spring-loaded mechanism, the system achieves the desired inverse pressure control without requiring adjustable stops, positioning pistons, or custom control arrangements, thereby reducing complexity and enabling the use of standard components.
Solution Approach 2:
The invention replaces expensive, complex positioning piston assemblies with a simple, inexpensive pressure-limiting valve that uses standard components. The spring-loaded pressure-limiting mechanism is much more cost-effective and easier to manufacture than custom positioning piston systems, while achieving the same functional result of inverse pressure control.
4Reliability
If the suspension system is preloaded to counteract the disproportionate stiffening under increased load, then the permissible working range of the hydraulic accumulator is not exceeded, but the suspension becomes very hard when unloaded, reducing driving comfort
Solution Approach 1:
Instead of using a fixed preload, the system dynamically adjusts the annular chamber pressure based on the piston chamber pressure. This dynamic adjustment ensures that the hydraulic accumulator operates within its permissible working range under all load conditions while avoiding the excessive hardness associated with fixed high preload, thereby maintaining both reliability and driving comfort.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution provides a cost-effective, low-complexity method to adjust annular chamber pressure, enhancing driving comfort by counteracting pitching vibrations and maintaining suspension system performance across varying loads without excessive component costs or complexity.
Implementation Method 1
a hydraulically controllable pressure-limiting element (63), in particular a hydraulically controllable pressure-limiting valve, which is connected to the first pressure-limiting line (61)
Implementation Method 2
the control pressure prevailing at a control input (64) of the hydraulically controllable pressure-limiting element (63) can be subjected to a control pressure corresponding to a piston chamber pressure prevailing in the piston chamber (27)
Implementation Method 3
a first hydraulic accumulator (35) connected to the piston space (27) and acting on the piston space (27) with pressurized hydraulic fluid
Data Source
AI summary
The invention relates to a control arrangement for a hydropneumatic suspension system. The control arrangement (12) comprises a pressure supply connection (15), a return connection (16), a piston chamber connection (17) connectable to the piston chamber (27) of a suspension cylinder (25) of the hydropneumatic suspension system (10), an annular chamber connection (18) connectable to the annular chamber (29) of the suspension cylinder (25), and at least one controllable valve arrangement (40) comprising several switching positions, via which the pressure supply connection (15) and the return connection (16) can be connected to the piston chamber connection (17) and the annular chamber connection (18).The annular space connection (18) is in flow communication with the return connection (16) via a pressure limiting line (61), and a hydraulically controllable pressure limiting element with a control input (64) is connected in the pressure limiting line (61). This control input can be pressurized via a control line (66) with a control pressure corresponding to the piston chamber pressure. To further develop the control arrangement in such a way that variable annular space pressure adjustment is possible with minimal effort, low complexity, and low manufacturing costs using standard components, the control pressure can be limited to a predefinable limit pressure. The invention also relates to a hydropneumatic suspension system with such a control arrangement.