Electrohydraulic Actuator for Hydrostatic Transmission Control
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Solution Overview
Problem
Work vehicles like agricultural or utility tractors rely on mechanical linkages between foot pedals and hydrostatic transmissions, which are inefficient and lack advanced control features, necessitating a low-cost, modular electrohydraulic actuator for smoother operation and integration of electronic controls.
Innovation Solution
An electrohydraulic actuator with a piston in a cylinder, centering spring, forward and reverse pressure control valves, and an electronic controller that uses pedal position sensors to provide electrical signals for hydraulic pressure modulation, allowing for modular substitution of hydrostatic transmissions with electronic transmissions using existing components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If mechanical linkages are used between foot pedals and hydrostatic transmission, then the system is simple and reliable, but it lacks advanced control features and operational flexibility
Solution Approach 1:
The patent replaces mechanical linkages with an electrohydraulic actuator system that uses electrical signals from sensors and controllers to modulate hydraulic pressure, enabling advanced control features like cruise control, maximum speed settings, and remote operation while maintaining compatibility with existing hydrostatic transmission mechanisms
Solution Approach 2:
The electrohydraulic actuator serves multiple functions: it replaces mechanical linkages, enables electronic control features, maintains compatibility with existing hydraulic systems, and provides a modular platform for various control applications including cruise control, speed limiting, and remote operation
2Adaptability or versatility
If electrohydraulic actuator is introduced to enable electronic control features, then operational flexibility improves, but additional supporting components are required
Solution Approach 1:
The patent merges the electrohydraulic actuator directly with the existing hydrostatic transmission housing, integrating the motor, cylinder, and control valves into a single modular unit that eliminates the need for separate supporting components and reduces system complexity
Solution Approach 2:
The patent uses hydraulic fluid as an intermediary to translate electrical control signals into mechanical motion, allowing electronic controllers to operate the hydrostatic transmission without direct mechanical linkages, thereby achieving operational flexibility while minimizing additional components
3Ease of manufacture
If modular electrohydraulic actuator is used for substitution, then ease of transmission replacement improves, but manufacturing precision requirements increase
Solution Approach 1:
The patent segments the transmission system into modular components including the electrohydraulic actuator, hydrostatic transmission, and control systems, allowing the actuator to be manufactured and tested independently before integration, which facilitates easier substitution while managing precision requirements through standardized interfaces
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
Enables cost-effective implementation of features like cruise control, engine anti-stall, and remote tractor control without additional components, while allowing for seamless integration of hydrostatic and electronic transmissions, enhancing operational flexibility and efficiency.
Implementation Method 1
a centering spring urging the piston to a neutral traction drive position in the cylinder
Implementation Method 2
provide hydraulic pressure on a second side of the piston
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
An electrohydraulic actuator for a hydrostatic transmission includes a pair of pressure control valves (112,114) between a hydraulic pressure inlet line and a pair of passages to a cylinder. A piston is positioned in the cylinder between the pair of passages and is slidable in response to hydraulic pressure in the cylinder on each side of the piston. A piston rod connects the piston to a joint which is connected to the trunnion lever of the hydrostatic transmission. A pedal position sensor (108) provides electrical signals to an electronic controller (110) that selectively actuates the pair of pressure control valves.