Four-Bar Linkage Steering Interface for Hydrostatic Transmission Speed Control
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Solution Overview
Problem
Existing steering systems for dual path hydrostatic ground wheel drive motors exhibit an undesirable increase in turning speed as the steering input is pivoted from the neutral position, leading to undesirable steering characteristics.
Innovation Solution
A mechanical linkage interface is designed to separately receive speed/direction and steering inputs, utilizing a hydraulic steering cylinder with a fixed barrel and piston rod to couple with a pivotable input member, which decreases the rate of displacement change of the pumps as the steering cylinder moves from the neutral position, thereby reducing the speed of steering during a turn.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a conventional four-bar linkage interface is used to control pump displacement for steering, then the steering input can be transmitted to the pumps, but the turning speed increases as the steering input is pivoted from the neutral position, resulting in undesirable steering characteristics
Solution Approach 1:
The patent changes the geometric parameters of the four-bar linkage, specifically the length and pivot positions of the linkage members. By carefully selecting these parameters, the linkage transforms the steering cylinder's linear motion into pump displacement changes at a reduced rate, preventing excessive turning speed while maintaining steering controllability
Solution Approach 2:
The four-bar linkage acts as an intermediary mechanism between the steering cylinder and the pump displacement control arms. It mediates the motion transmission by converting the steering input motion into a modified motion pattern that delivers pump displacement changes at a controlled rate, thereby resolving the contradiction between steering input transmission and turning speed control
2Adaptability or versatility
If the steering cylinder is moved further from the neutral position to increase steering input, then more steering authority is achieved, but the rate of change of pump displacement increases, causing faster turning speed that is not desirable
Solution Approach 1:
The patent modifies the kinematic parameters of the linkage system to create a non-linear relationship between steering cylinder displacement and pump displacement rate. The linkage geometry is designed so that even as the steering cylinder moves further from neutral to increase steering authority, the resulting pump displacement changes occur at a moderated rate, preventing excessive turning speed
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 effectively mitigates the undesirable increase in turning speed, providing a more controlled and desirable steering characteristic by maintaining a consistent steering speed as the steering input increases, enhancing operator experience.
Implementation Method 1
a steering input being provided by a hydraulic steering cylinder having a fixed barrel containing a piston rod
Data Source
AI summary
A four-bar linkage is provided as a mechanical interface for transferring respective outputs from a speed/direction control device and a hydraulic steering cylinder to displacement control arms of a pair of pumps of a dual-path hydrostatic transmission including a pair of motors respectively coupled for driving a pair of front wheels of a vehicle. The hydraulic steering cylinder is fixed and has a piston rod slidably coupled to an input arm of the four-bar linkage in such a way that a rotation speed decrease occurs as the arm and a linked control plate are pivoted from a neutral position, the control plate transferring pivotal movement to effect differential movement of the displacement control arms. This results in the vehicle speed decreasing during a turn.