Hydraulic Steering Unit End Stop Feedback
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Hydraulic steering units exhibit different end stop feelings in both steering directions due to varying fluid pressure, leading to an uneven steering experience.
Innovation Solution
The introduction of back pressure means controlled by valve elements and friction means between valve elements and the housing or rotating parts of the measuring motor, ensuring consistent end stop feedback by altering the characteristics of orifices and generating required back pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the measuring motor is arranged in a working line between the steering valve arrangement and a working port, then steering precision is improved, but end stop feeling becomes uneven in different steering directions
Solution Approach 1:
The invention applies preliminary anti-action by introducing back pressure means that generate opposing pressure on the measuring motor before the end stop position is reached. This back pressure compensates for the natural pressure difference that would otherwise occur, ensuring that the driver experiences consistent end stop feeling in both steering directions. The back pressure means are activated in advance to prevent the uneven end stop feeling from occurring.
2Reliability
If friction means are applied to hold one valve element in place, then back pressure generation is improved, but valve element movement freedom deteriorates
Solution Approach 1:
The invention applies local quality by selectively applying friction means to only one valve element (the spool) while leaving the other valve element (the sleeve) free to move. This localized application of friction ensures that back pressure is generated reliably through the spool's restricted movement, while the sleeve retains the freedom to move as needed for normal steering operation. The friction means are applied locally at specific contact surfaces rather than throughout the entire valve assembly.
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 consistent end stop feelings in both steering directions, enhancing the steering experience by maintaining pressure on the measuring motor, even at low rotation speeds, thus eliminating the 'steer through' phenomenon and ensuring a hard end stop is felt uniformly.
Implementation Method 1
friction means are provided between one of the valve elements and the housing or a rotating part of the measuring motor and the housing, respectively
Implementation Method 2
the friction means comprise a compressed elastic element between the sleeve and the housing
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A hydraulic steering unit (2) is described, the steering unit (2) comprising a supply port arrangement having a supply port (P) and a return port (T), a working port arrangement having two working ports (LR), a steering valve arrangement having two valve elements (32, 33) arranged in a housing (30, 38, 39) and being moveable in relation to each other to change characteristics of orifices, and a measuring motor (9) arranged in a line between the steering valve arrangement and one of the working ports (LR). A hydraulic steering unit should create similar end stop sealings in both steering directions. To this end, backpressure means are provided generating a backpressure on the measuring motor (9), wherein the backpressure means are controlled by the valve element (32, 33), and friction means (43, 43') are provided between one of the valve elements (33) and the housing (30, 38, 39) or a rotating part of the measuring motor (9) and the housing (30, 38, 39), respectively.