Hydrostatic Steering Drift Compensation via Valve Arrangement
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Solution Overview
Problem
Hydrostatic steering devices for commercial vehicles experience undesirable drifting of the steering handle position relative to the wheel steering angle due to hydraulic losses and pressure imbalances, leading to reduced steerability and operator irritation.
Innovation Solution
A hydrostatic steering device with a valve arrangement that compensates for leakage-related hydraulic losses or excesses by controlling an electrically actuated proportional valve and shuttle valve, connected to a high-pressure source or hydraulic reservoir, to maintain accurate wheel steering angles and prevent drifting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a hydrostatic steering system is used to enable comfortable steering of heavy commercial vehicles, then steering comfort and capability are improved, but hydraulic losses occur due to system-related leaks causing the steering handle position to drift relative to the wheel steering angle
Solution Approach 1:
The control unit continuously monitors the steering handle position and wheel steering angle, comparing the two to detect drift. When drift is detected, the system automatically activates the proportional valve to compensate for hydraulic losses, creating a closed-loop feedback mechanism that maintains positioning accuracy while preserving steering comfort.
Solution Approach 2:
The patent replaces purely mechanical steering control with an electromechanical system. An electrically actuated proportional valve is introduced to control hydraulic fluid flow, allowing electronic compensation for leakage effects. This substitution enables precise control of the steering cylinder while addressing the drift issue caused by mechanical hydraulic losses.
2Productivity
If hydraulic fluid flows through the steering orbitrol to control the steering cylinder, then steering actuation is achieved, but pressure drop and leakage flows cause the steering handle not to fully return to its centered position
Solution Approach 1:
The system dynamically adjusts hydraulic parameters by controlling the proportional valve to compensate for pressure drops and leakage flows. The control unit modifies the hydraulic fluid flow rate and pressure characteristics in real-time, ensuring that the steering handle returns reliably to its centered position while maintaining efficient steering actuation.
Solution Approach 2:
The proportional valve acts as an intermediary component between the hydraulic high-pressure source and the steering cylinder. It mediates the hydraulic flow, regulating and compensating for losses in the steering orbitrol. This intermediary device enables the system to maintain both efficient actuation and position stability by controlling the hydraulic parameters.
3Device complexity
If leakage flow is allowed to occur within the steering orbitrol, then system simplicity is maintained, but hydraulic losses reduce the volume flow through the inlet and affect steering performance
Solution Approach 1:
Instead of attempting to eliminate leakage flow entirely, the system applies partial compensation by introducing a proportional valve that provides just enough additional hydraulic flow to offset the losses. This partial action approach maintains system simplicity while adequately addressing the volume flow reduction caused by leakage, avoiding the complexity of a complete seal redesign.
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
The solution effectively corrects drifting by continuously compensating for hydraulic losses or diverting excess fluid, ensuring the steering handle returns to its neutral position and maintaining precise control over the steerable wheels, thereby enhancing operator comfort and steerability.
Implementation Method 1
the pressure gradient between the first and second orbitrol connections leads to hydraulic losses within the steering orbitrol
Implementation Method 2
an electrically actuated proportional valve connected to the high-pressure source
Implementation Method 3
an electrically actuated shuttle valve, which can be selectively connected to one of the two working chambers of the steering cylinder
Implementation Method 4
a steering orbitrol which can be controlled by means of a steering handle and by means of which a double-acting steering cylinder can be deflected
Data Source
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AI summary
A hydrostatic steering device (10) for a commercial vehicle (12) comprises a steering orbitrol (18) controllable by means of a steering handle (16), by means of which a double-acting steering cylinder (42) can be deflected according to a steering actuation occurring at the steering handle (16), in that, depending on the direction of actuation of the steering handle (16), a first orbitrol connection (26) forms an inlet (30) supplied from a hydraulic high-pressure source (28) and a second orbitrol connection (32) forms a return line (36) communicating with a hydraulic reservoir (34) for controlling opposite working chambers (38, 40) of the steering cylinder (42). In this case, a hydraulic leakage flow occurring within the steering orbitrol (18) between the first and second orbitrol connection (26, 32) can be compensated for by means of a valve arrangement (54) communicating with the high pressure source (28) and/or the hydraulic reservoir (34) with regard to the hydraulic actuation of the steering cylinder (42).