Optical Position Sensing for Hydraulic Pump Yoke
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Solution Overview
Problem
Current variable displacement hydraulic pump/motor assemblies face challenges with position feedback, including wear from contact methods, sensor placement difficulties, and temperature sensitivity, which affect the accuracy and reliability of existing sensors.
Innovation Solution
An optical position sensing system using absolute location indicia markings in the form of bar-type patterns on movable components like yokes or swashplates, combined with an optical/electronic sensor unit fixedly located in the housing, to provide precise feedback on the component's position without physical contact, improving accuracy and ease of maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If contact methods are used for position feedback, then position sensing can be achieved, but wear of mechanical parts occurs
Solution Approach 1:
The patent replaces mechanical contact-based position feedback methods with an optical sensing system. An optical sensor reads absolute position markings directly on the movable component through a non-contact optical path, eliminating mechanical wear while maintaining measurement precision. The optical sensor detects the position of a yoke or swashplate by reading binary-coded absolute position markings without physical contact.
Solution Approach 2:
The patent introduces optical markings (binary position codes) as an intermediary between the movable component and the optical sensor. These markings serve as a non-contact interface that transfers position information from the moving part to the stationary sensor, enabling wear-free position feedback while maintaining accuracy.
2Measurement precision
If sensors are positioned to read the position of the yoke/swashplate, then position feedback is obtained, but design becomes difficult
Solution Approach 1:
The patent transitions from direct mechanical coupling or complex angular positioning to a two-dimensional optical reading plane. The optical sensor reads binary position markings that are radially arranged on the movable component, allowing position detection through a simple radial optical path rather than complex angular sensor mounting. This dimensional change simplifies the sensor positioning while maintaining measurement precision.
3Reliability
If replacement sensors are installed, then sensor failure is addressed, but recalibration is required
Solution Approach 1:
The absolute position markings on the movable component serve as a self-calibrating reference that automatically defines the zero position and scale. When an optical sensor is replaced, it simply reads these pre-encoded absolute position markings without requiring external calibration procedures. The system self-calibrates through the inherent binary position codes on the component, eliminating recalibration time and improving maintenance efficiency.
4Measurement precision
If traditional sensors are used in high temperature environments, then position sensing continues, but sensor precision deteriorates or sensor is ruined
Solution Approach 1:
The patent replaces temperature-sensitive electronic sensors with an optical sensing system that uses light to read binary position markings. The optical components (LED, photodetector, optical path) are inherently more temperature-stable than traditional potentiometers or Hall effect sensors. The binary markings on the movable component serve as a temperature-invariant reference, allowing precise position measurement even in high-temperature hydraulic environments where traditional sensors would drift or fail.
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 provides accurate and reliable position feedback, reducing wear and temperature-related issues, enabling more precise control of the pump/motor assembly while simplifying sensor replacement and maintenance.
Implementation Method 1
an optical sensor, fixedly located in the assembly housing and being located at a spaced gap from the indicia markings, is utilized for reading these indicia markings
Implementation Method 2
produces an output signal indicative of the absolute position of the movable component
Data Source
AI summary
In a variable displacement type hydraulic pump/motor assembly including at least one internally movable component, such as a yoke, a swashplate, and the means for moving the swashplate, the improvement includes imparting on this component absolute location indicia markings and the addition of an optical/electronic sensor unit capable of reading such indicia markings fixedly located on a housing of the pump/motor assembly and including an optical read head extending into the housing interior and located at a spaced distance from the indicia markings for reading same, relative to a reference location, and producing a signal indicative of the absolute position of the movable component. The signal can then, in turn, be used for controlling the displacement of the pump/motor assembly. A method for determining the absolute component position is also set forth.