Eddy Current Sensor for CVT Pulley Position and Speed Measurement
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Solution Overview
Problem
Current CVT control systems lack direct position feedback of pulleys, leading to slow control response, reduced transmission efficiency, and limited diagnostic capabilities due to high clamping forces and indirect measurement methods.
Innovation Solution
The implementation of an eddy current-based sensor system in combination with a target wheel design that allows for the measurement of both axial displacement and rotational speed of pulleys, providing direct position feedback and improving control accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If indirect measurement methods using rotational speed and oil pressure are used to determine pulley position, then device complexity is reduced, but measurement precision and control response speed deteriorate
Solution Approach 1:
The patent replaces indirect mechanical measurement methods (using rotational speed and oil pressure sensors) with a direct magnetic field-based sensing system. The magnetic sensor detects the position of magnet elements mounted on the pulley, providing precise direct position feedback without complex mechanical linkages or indirect calculation chains.
Solution Approach 2:
The patent introduces magnet elements as intermediary components mounted on the pulley wheel. These magnets serve as markers that the magnetic sensor detects to determine pulley position, enabling direct measurement while keeping the sensor system relatively simple and robust.
2Reliability
If high clamping forces are applied to prevent belt slippage, then reliability is improved, but energy losses and wear increase
Solution Approach 1:
The patent implements a feedback control system using direct position sensors on both primary and secondary pulleys. The control unit continuously monitors actual pulley positions and compares them with target positions, then dynamically adjusts clamping forces to maintain optimal belt tension only when necessary, preventing both slippage and excessive energy loss.
Solution Approach 2:
The patent transitions from static high clamping forces to dynamic, adaptive clamping force control. The system continuously adjusts clamping forces based on real-time position feedback and operational conditions, applying force only when and where needed to prevent slippage, thereby reducing unnecessary energy losses.
3Speed
If direct position feedback of pulleys is implemented, then control response speed and transmission efficiency improve, but device complexity and cost increase
Solution Approach 1:
The patent replaces complex mechanical position sensing mechanisms with simple magnetic field-based sensors. The magnetic sensors detect the position of magnet elements on the pulleys, providing direct position feedback with minimal mechanical complexity and high response speed.
Solution Approach 2:
The patent uses a universal magnetic sensing approach that can be applied to both primary and secondary pulleys with the same sensor type and magnet element design. This multi-functional solution simplifies the overall system architecture while providing comprehensive direct position feedback for both pulleys.
4Measurement precision
If magnet elements are mounted on the pulley wheel, then direct position measurement is enabled, but manufacturing complexity and cost increase
Solution Approach 1:
The patent introduces magnet elements as separate intermediary components that can be mounted on the pulley wheel after manufacturing. This approach allows the pulley itself to be manufactured using conventional methods, while the magnetic markers are added as a separate, simpler step, reducing overall manufacturing complexity.
Solution Approach 2:
The patent separates the position indication function from the pulley structure by using distinct magnet elements. This segmentation allows the pulley to be manufactured independently using standard processes, while the magnetic markers are added separately, simplifying both pulley manufacturing and sensor assembly.
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 enhances transmission and drive efficiency, reduces wear and slippage, improves diagnostic coverage, and allows for more precise control of clamping forces, leading to better reliability and driver comfort.
Implementation Method 1
The sensor probe (6) is an eddy current sensor. The frequency of the sensor signal results from a change in air gap between the sensor (6) and the target wheel (2)
Data Source
Figure 1
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Figure 4~5
AI summary
The present invention relates to an encoder device (1) , which comprises at least one target wheel (2) attachable to a rotationally and axially, with respect to the rotational axis (3), movable element, the target wheel (2) having a plurality of identical target elements (4) arranged at regular intervals around a circumference of the target wheel (2), wherein the circumferential width of each target element (4) continuously changes with the displacement along the axial direction; a sensor device (5) comprising at least one sensor probe (6) is operable to detect the target elements (4) and to provide a time-based sensor signal that represents both the rotational speed and axial displacement of the at least one target wheel (2) based on the detection of the target elements (4), and a processing unit which is operable to provide an output signal of the encoder device (1). The invention also concerns and a method of controlling a continuously variable transmission (CVT), based on the measurement of both the axial displacement of the pulleys and the rotational speed, and the determination of the slippage in a CVT transmission, based on the determination of the speed and axial displacement of both pulleys.