Crank Transmission Torque Sensing via Torsion and Magnetic Flux
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Solution Overview
Problem
Crank transmissions for vehicles lack an effective method to detect torque applied via a crankshaft, which is essential for monitoring and controlling the power generated and for applications like automatic gear shifts or coaster brakes.
Innovation Solution
A sensor system utilizing a torsion element and magnetic flux changes to detect the angular offset between the crankshaft and gear wheel, allowing for the determination of torque magnitude and direction, featuring a cost-effective, space-saving design with a transducer unit and magnetic field-sensitive sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sensor arrangement with torsion element and magnetic sensor is implemented in the crankshaft, then torque and angle of rotation can be detected, but the device complexity increases
Solution Approach 1:
The sensor system is integrated directly into the crankshaft structure, merging the sensing functions with the existing mechanical component. The first guide element is formed as part of the crankshaft, and the second guide element is integrated with the torsion element, eliminating the need for separate sensor housings and reducing overall system complexity while maintaining torque detection capability
Solution Approach 2:
A magnetic field is introduced as an intermediary between the mechanical torsion and the electrical sensor output. The torsion element's angular displacement modulates the magnetic flux through the guide elements, which is then detected by the magnetic sensor, providing a non-contact measurement method that avoids direct mechanical coupling and reduces wear
2Volume of moving object
If a torsion element is integrated into the crankshaft cavity, then space is saved and torque transmission is maintained, but the manufacturing precision requirements increase
Solution Approach 1:
The crankshaft is segmented into functional zones: the cavity housing the torsion element, the guide elements positioned at specific locations, and the sensor mounting areas. This segmentation allows each component to be manufactured and assembled separately with controlled tolerances, reducing the overall manufacturing precision requirements compared to a fully integrated monolithic design
Solution Approach 2:
Different regions of the crankshaft are designed with different quality requirements. The guide elements and torsion element interfaces require high precision, while other areas of the crankshaft can use standard manufacturing tolerances. This localized approach to quality control reduces overall manufacturing complexity and cost
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 accurate detection of torque magnitude and direction, facilitating data acquisition for power monitoring and control purposes, while being robust and operationally reliable.
Implementation Method 1
the torsion element is elastically deformable at least in certain areas, i.e. it can be deformed elastically against a restoring torque
Implementation Method 2
a transducer unit is provided for converting the angular offset into a change in a magnetic flux
Implementation Method 3
a magnetic field-sensitive sensor is provided for detecting this change
Data Source
AI summary
A crank transmission having a crankshaft for connection to at least one foot or hand crank and at least one gear wheel driven by means of the crankshaft (5) is proposed. A coupling unit is provided between the crankshaft and the gear wheel. Under load, the coupling unit has at least temporarily an angular offset between a crank-side receiving region and an output region connected to the gear wheel for receiving and outputting the torque generated via the crank.