Hydrostatic Steering Valve Leakage Compensation
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Solution Overview
Problem
Agricultural vehicles with hydrostatically driven front wheels and hydraulically steerable rear wheels face challenges in steering responsiveness due to internal leakage in mechanical steering control systems, which increases costs and complexity when trying to enhance steering sensitivity and rate control.
Innovation Solution
An automatic front steering valve supplements the primary steering valve to compensate for fluid leakage, using a position sensor and electric actuator to add fluid as needed, and an electric actuator with position feedback to center the steering control cylinder when ground speed is zero, effectively neutralizing the steering system without adding undue cost or complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a larger steering valve is selected to compensate for internal leakage, then steering responsiveness is improved, but system cost and space requirements increase
Solution Approach 1:
The steering valve system is segmented into two functional parts: a primary steering valve for normal operation and a supplemental steering valve specifically designed to compensate for internal leakage. This segmentation allows each valve to be optimized for its specific function, with the supplemental valve being smaller and more cost-effective than replacing the entire primary valve.
Solution Approach 2:
The supplemental steering valve serves multiple functions: it compensates for internal leakage in the primary valve, provides additional steering control capability, and can function independently if needed. This multi-functionality justifies its inclusion despite adding a component to the system.
2Measurement precision
If electro-hydraulic controlled ground drive is used to achieve variable steering rate, then steering control precision is improved, but system complexity and cost increase due to required redundancy
Solution Approach 1:
The system provides dynamic steering rate control by enabling the operator to select between different steering valve configurations (primary valve only, or primary plus supplemental valve). This allows the steering rate to be dynamically adjusted based on operational conditions without requiring complex electro-hydraulic control systems.
Solution Approach 2:
The supplemental steering valve acts as an intermediary component that bridges the gap between simple mechanical steering and complex electro-hydraulic steering systems. It provides enhanced control capability while maintaining the simplicity of mechanical operation and avoiding the redundancy requirements of fully electro-hydraulic systems.
3Device complexity
If internal leakage in the steering valve is accepted, then system simplicity is maintained, but steering responsiveness deteriorates under certain operating conditions
Solution Approach 1:
The system converts the harmful effect of internal leakage into a beneficial feature by using the supplemental steering valve to compensate for the leakage. What was previously a defect (leakage reducing responsiveness) becomes an opportunity to add a targeted, cost-effective compensation mechanism that improves responsiveness without redesigning the entire primary valve.
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 enhances steering responsiveness by compensating for internal leakage, allowing for electronically controlled steering rates without increasing system costs or size, thereby improving steering precision and reducing inertial resistance during turns.
Implementation Method 1
An automatic front steering valve, of a type normally provided in conjunction with the manually operated primary steering valve, is used to supplement the flow of the primary steering valve so as to compensate for the fluid flow lost by leakage
Implementation Method 2
A position sensor on the steering wheel shaft indicates steering wheel movement and turn direction
Implementation Method 3
an electric actuator with position feedback sensor for ground speed control. Whenever the actuator position sensor shows that the ground speed is set to zero and a switch in the hydro handle slot shows that the hydro handle is in the Park position, an electrical signal is sent to actuate a normally deactivated 'on-off' valve
Data Source
AI summary
An integrated steering control system includes a primary, automatic and rear control valves. A steering wheel operates the primary steering control valve and is of a type which includes a leakage characteristic. Steering wheel movement is sensed and a signal is sent which results in the automatic steering control valve being operated for adding fluid that supplied to a steering cylinder by the primary steering control valve in order to compensate for leakage, the amount of added fluid being a function of vehicle ground speed. An electric actuator with position feedback is used for ground speed control. Whenever the actuator position shows that the ground speed is set to zero and a switch in the hydro-handle slot shows that the handle is in the Park position, the automatic steering control valve is activated to move the steering cylinder to a neutral, straight ahead position, as determined by a sensor in a mechanical linkage of the steering control.