Hydraulic Steering Unit Variable Orifice Arrangement
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Solution Overview
Problem
Hydraulic steering units with neutral open orifices face challenges in maintaining smooth steering behavior and minimizing dead band, particularly in closed-center solutions where fluid flow interruption is necessary.
Innovation Solution
A further variable orifice arrangement is introduced between the supply and working port arrangements, which remains closed in neutral position, allowing the bridge arrangement to maintain smooth operation by opening when the steering unit is actuated, and optionally including a measuring motor, main orifice, and variable tank orifices to control fluid flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If neutral open orifices are used in the bridge arrangement, then smooth steering behavior is achieved, but dead band increases and steering responsiveness deteriorates
Solution Approach 1:
The orifice arrangement is divided into two functional groups: a first orifice arrangement (main orifice, tank orifices) that is closed in neutral position to eliminate dead band, and a second orifice arrangement (bridge arrangement with neutral open orifices) that provides smooth steering when activated. This segmentation allows each arrangement to fulfill its specific function without compromising the other.
Solution Approach 2:
The first orifice arrangement is pre-configured in a closed state in neutral position, creating a ready-to-activate system. When steering input is applied, the orifices in the first arrangement open immediately to allow fluid flow through the bridge arrangement, eliminating the dead band effect while maintaining smooth steering characteristics.
2Measurement precision
If closed-center solution is implemented with fluid flow interruption in neutral position, then steering precision is improved, but smooth steering operation becomes difficult
Solution Approach 1:
The system segments the orifice arrangements into two distinct groups with different neutral position configurations. The first orifice arrangement implements closed-center solution for precision, while the second orifice arrangement (with neutral open orifices) ensures smooth operation when steering is activated, resolving the contradiction between precision and operability.
Solution Approach 2:
The system dynamically switches between different orifice configurations based on operating conditions. In neutral position, the first orifice arrangement is closed for precision. When steering input is detected, the system transitions to allowing flow through the bridge arrangement via the second orifices, providing smooth dynamic response.
3Loss of time
If a further variable orifice arrangement is added between supply and working port arrangements, then dead band is eliminated, but device complexity increases
Solution Approach 1:
The complex orifice system is segmented into two functional arrangements: the first orifice arrangement (main orifice, first left/right orifices, second left/right orifices) that handles closed-center solution and flow interruption, and the second orifice arrangement (bridge arrangement with neutral open orifices) that handles smooth steering. This segmentation organizes the complexity into manageable functional modules.
Solution Approach 2:
The first orifice arrangement serves multiple functions: it provides closed-center solution, interrupts fluid flow in neutral position, and enables immediate flow when activated. The bridge arrangement with neutral open orifices provides smooth steering operation. Together, they achieve both dead band elimination and smooth operation without requiring a completely new system design.
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 configuration ensures no dead band and provides a comfortable steering experience by allowing immediate fluid flow through the bridge arrangement when actuated, maintaining smooth steering and functioning as a closed-center solution.
Implementation Method 1
Hydraulic fluid under pressure from the pressure port flows through the first left orifice, the left working flow path to the left working port
Implementation Method 2
a bridge arrangement of variable neutral open orifices, said bridge arrangement comprising a first left orifice connected to the main flow path and to the left working flow path
Data Source
AI summary
A hydraulic steering unit (1) is described comprising a supply port arrangement having a pressure port (P) connected to a main flow path (5) and a tank port (T) connected to a tank flow path (6), a working port arrangement having a left working port (L) connected to a left working flow path (7) and a right working port (R) connected to a right working flow path (8), a bridge arrangement (14) of variable neutral open orifices, said bridge arrangement (14) comprising a first left orifice (A2L) connected to a main flow path (5) and to the left working flow path (7), a first right orifice (A2R) connected to a main flow path (5) and to the right working flow path (8), a second left orifice (A3L) connected to the left working flow path (7) and to the tank flow path (6), and a second right orifice (A3R) connected to the right working flow path (8) and to the tank flow path (6). Such a steering unit has a good steering behavior but can function as a closed-center solution. To this end a further variable orifice arrangement is arranged between the supply port (P) arrangement and the working port arrangement (T), which further orifice arrangement is closed in neutral position.