Flexure-based system for measuring torque on a shaft

Abstract

A sensing device for detecting the amount of torque transmitted through a shaft. The device has a first and second section interconnected by a flexure arrangement to which permanent magnets are attached. Deflections of the flexures produce a repeatable and proportional change of magnetic flux which flows in a stationary annular ring that is concentrically mounted with respect to the shaft and separated from it by an air gap. The annular ring is instrumented with an array of magnetic field sensors that measure the changing magnetic flux.

Description

[0001]This U.S. Patent Application claims the priority of U.S. Provisional Patent Application 62 / 088,225, filed on Dec. 5, 2014.TECHNICAL FIELD[0002]This disclosure is in the field of sensors that are placed inline with a rotating shaft to determine the transmitted torque without contact and therefore without the use of slip rings, twist capsules or cable wraps.BACKGROUND[0003]In the control of a shaft driven by a motor or actuator, the position, speed and torque applied to the shaft are parameters of most interest in closing the feedback loop of the system or device. There is, therefore, need for a device that can provide these measurements without contacting the shaft as these are often not very reliable, may be expensive to implement and necessarily require the use of a slip ring or twist capsule to obtain an output electronic signal for processing. One typical contact measurement method uses strain gages which are attached to the shaft of interest; when torsional stress is appli...

AI Technical Summary

Benefits of technology

The invention is a sensor that can measure the torque and speed of a rotating shaft. It uses a flexible arrangement of beams called flexures that are attached to permanent magnets. The flexures act as springs and maintain contact with the input section of the sensor. The sensor is designed to prevent overloading the flexures and can be made from a composite of a flexible non-magnetic material and a magnetically soft material. The sensor can have multiple pairs of flexures that are axially spaced or offset from each other. The strength of the magnets used in the system can affect the number of flexures needed.

Problems solved by technology

There is, therefore, need for a device that can provide these measurements without contacting the shaft as these are often not very reliable, may be expensive to implement and necessarily require the use of a slip ring or twist capsule to obtain an output electronic signal for processing.

However, each of the referenced patents utilize complex magnetic material formulations, either as permanent magnets or as members that must exhibit magnetostriction, in order to achieve the desired data.

Furthermore, complex manufacturing and / or assembly processes render these devices costly for use in mass production markets.

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