Stationary Torque Sensor via Differential Gear Inversion

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing torque measurement systems for gearboxes are complex, costly, and inaccurate, especially at extreme temperatures, and rely on unreliable methods such as rotating torque sensors or temperature-sensitive strain gauges.

Innovation Solution

A stationary sensor measures output torque by detecting deformation or force applied by a torsionally compliant or rigid measurement member connected to a differential gear system, which reacts to the rotation of the gearbox, using a measurement gear train to amplify signals and a force sensor to provide accurate torque readings.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a rotating torque sensor is used to measure output torque, then torque measurement capability is achieved, but system complexity and cost increase and reliability decreases

Engineering Contradiction:

Improveoutput torque measurementVSAvoidsystem complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

Instead of using a rotating sensor to directly measure torque on the rotating shaft, the invention inverts the approach by using a stationary sensor to measure the reaction torque on a stationary component. The differential gear system converts the rotational torque measurement into a stationary reaction force measurement, eliminating the need for rotating sensors and slip rings.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The invention introduces a differential gear system as an intermediary mechanism between the rotating output shaft and the stationary sensor. This intermediary converts the rotational motion and torque into a stationary reaction force that can be measured by a fixed sensor, avoiding the complexity of rotating sensor interfaces.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If strain gauges are used at mounting points to measure force, then torque measurement is possible, but implementation difficulty increases and temperature accuracy deteriorates

Engineering Contradiction:

Improveforce measurementVSAvoidimplementation difficulty

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The differential gear system acts as an intermediary that converts torque measurement into a more easily measurable reaction force on a stationary component. This intermediary mechanism simplifies the measurement setup and improves implementation ease while maintaining measurement accuracy.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention replaces traditional strain gauge mounting on rotating shafts or mounting points with a mechanical lever arm system that amplifies and translates the torque into a measurable force on a stationary sensor, improving both ease of manufacture and temperature stability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Device complexity

If calculated torque methods are used based on motor parameters, then measurement simplicity is achieved, but accuracy deteriorates due to unknown gear efficiency and drag variations

Engineering Contradiction:

Improvemeasurement system simplicityVSAvoidoutput torque accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The invention replaces electrical calculation methods with a direct mechanical measurement system. By using a differential gear system with a stationary sensor that directly measures the reaction torque, the system achieves both simplicity and accuracy without relying on motor parameter calculations or knowledge of gear efficiency variations.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 a simple, economical, and highly accurate method for measuring output torque, independent of temperature extremes and rotating interfaces, enhancing reliability and reducing costs.

Implementation Method 1

the measurement member is a torsionally compliant member arranged to undergo torsional deformation due to angular displacement of the measurement output element

Methodology Applied

Scientific EffectTorsional deformation: Deformation

Implementation Method 2

a stationary sensor is arranged to detect a deformation of the measurement member or a force applied by the measurement member due to rotation of the measurement output element, wherein the deformation or the force is proportional to the output torque

Methodology Applied

Scientific EffectForce detection: Force

Data Source

PatentEP3411683B1Gearbox torque measurement system

Publication Date: 2022.01.12 MOOG INC

Figure 1~2
Figure 3~4
Figure 5~6

AI summary

A torque transmission apparatus incorporates a differential gear system and a stationary sensor connected to the differential gear system for measuring output torque. The stationary sensor may be connected to a measurement output element of the differential gear system by a torsionally compliant measurement member, wherein the stationary sensor measures torsional deformation of the measurement member. The torsional deformation may be measured directly, or it may be measured following amplification by a gear train. A rotary position sensor may be used as the stationary sensor. Alternatively, the stationary sensor may be connected to the measurement output element of the differential gear system by way of a rigid measurement member, wherein the stationary sensor measures force applied by the measurement member. In this alternative, a force sensor may be used as the stationary sensor.