Hydraulic Steering Measuring Motor Inversion
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Solution Overview
Problem
Hydraulic steering systems exhibit a dead zone or time gap when changing steering directions, making steering difficult and uncomfortable.
Innovation Solution
The measuring motor is arranged in one of the working lines, allowing for immediate response to steering direction changes, and includes features like a neutral position for the control valve, throttling means, and an over center valve to ensure hydraulic pressure is maintained, enabling direct steering and emergency operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the measuring motor is arranged in the high pressure line before the control valve, then the steering system can meter hydraulic fluid to control the steering angle, but a dead zone or time gap occurs when changing steering direction
Solution Approach 1:
The patent inverts the conventional arrangement by placing the measuring motor in the return line (low pressure side) instead of the high pressure supply line. This reversal allows the measuring motor to immediately respond to pressure changes from the control valve during direction changes, eliminating the dead zone while maintaining precise steering angle control through the same metering function.
2Ease of operation
If the control valve switches flow paths during steering direction change, then steering control is achieved, but a time gap occurs before the steering motor reacts
Solution Approach 1:
The measuring motor positioned in the return line provides immediate feedback on the actual steering motor displacement. During control valve switching, the measuring motor detects pressure changes and adjusts the steering motor position in real-time, creating a feedback loop that eliminates response delays and improves steering control responsiveness.
3Force
If the high pressure port supplies hydraulic fluid to working ports, then steering force is generated, but the system cannot maintain operation when supply pressure is insufficient
Solution Approach 1:
The measuring motor is designed with multi-functionality: during normal operation it meters hydraulic fluid for precise steering control, but when supply pressure becomes insufficient, it automatically functions as an auxiliary pump to maintain system pressure and ensure continuous steering operation, thereby improving reliability without adding separate components.
4Ease of operation
If throttling means are added to control flow between high pressure and low pressure ports, then flow rate is controlled and working ports are protected from excessive pressure, but system complexity increases
Solution Approach 1:
The throttling means are integrated directly into the control valve body, merging the flow control function with the existing steering control mechanism. This combination allows flow rate control and working port pressure protection without requiring separate throttling devices, thereby maintaining ease of operation while minimizing additional structural complexity.
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 eliminates the dead zone, providing comfortable steering and ensuring continuous operation by generating necessary hydraulic pressure, even in low supply conditions, through the measuring motor's auxiliary pumping function.
Implementation Method 1
The measuring motor acts on the control valve in a sense to close the above mentioned flow path when an amount of hydraulic fluid corresponding to the intended steering angle of the steering member has been delivered or metered to the respective working port
Implementation Method 2
a symmetrically acting steering motor, said steering device comprising a supply port arrangement having a high pressure port and a low pressure port
Data Source
AI summary
A hydraulic steering system (1) is provided having a steering device (2) and a symmetrically acting steering motor (3), said steering device (2) comprising a supply port arrangement having a high pressure port (P) and a low pressure port (T), a working port arrangement having two working ports (L, R), a control valve (14), two working lines (18, 19) each connecting said control valve (14) with one of said working ports (L, R), and a measuring motor (23). Such a hydraulic steering system should show a comfortable steering behavior. To this end said measuring motor (23) is arranged in one of said working lines (18, 19).