Transmission Shaft Speed Sensing Through a Non-Ferrous Housing

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Solution Overview

Problem

Existing systems for sensing the speed of a rotating shaft, such as an input shaft in a vehicle transmission, face difficulties due to the construction of the transmission, which makes it challenging to observe the shaft's rotation effectively.

Innovation Solution

A transmission system with a sensor target coupled to a planetary gear set and a back-biased tunnel magnetoresistance sensor spaced apart by a gap, where the sensor target is composed of ferrous material and devoid of magnets, allowing the sensor to determine the rotation speed by observing windows on the target through a non-ferrous torque transfer housing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a sensor is used to observe the input shaft rotation speed, then the rotation speed can be determined, but the transmission construction makes it difficult to observe the input shaft

Engineering Contradiction:

Improverotation speed detectionVSAvoidshaft observation difficulty

Core Design Contradiction:

Measurement precisionVSDifficulty of detecting and measuring

Solution Approach 1:

The patent introduces a sensor target as an intermediary component that is easier to observe than the input shaft itself. The sensor target is positioned in a location that allows sensor observation while being mechanically coupled to the input shaft through the planetary gear set, thus mediating between the difficult-to-observe shaft and the sensor

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces direct mechanical observation of the input shaft with a magnetic field-based sensing system. Instead of mechanically attaching a sensor directly to the rotating shaft, a magnetic sensor observes magnetic targets that rotate with the shaft, substituting mechanical sensing with magnetic field interaction

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If magnets are included in the sensor target, then magnetic field interaction is enabled, but manufacturing complexity and weight increase

Engineering Contradiction:

Improvemagnetic field interactionVSAvoidmanufacturing complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent changes the magnetic properties of the sensor target by using ferrous material with specific magnetic permeability characteristics. This allows the target to interact with the magnetic field from the back-biased tunnel magnetoresistance sensor without requiring permanent magnets, thus maintaining magnetic field interaction while simplifying manufacturing

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces expensive permanent magnets with a simpler ferrous material target that can be easily manufactured and integrated into the planetary gear set. This substitution reduces manufacturing complexity and cost while maintaining the necessary magnetic interaction for sensing

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Reliability

If a gap is maintained between the sensor and sensor target, then non-contact sensing is achieved, but manufacturing precision requirements increase

Engineering Contradiction:

Improvenon-contact sensingVSAvoidgap positioning precision

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent positions the sensor and sensor target such that the magnetic field interaction occurs across a defined gap. The magnetic field penetrates the non-ferrous torque transfer housing, creating a magnetic circuit that maintains consistent flux density across the gap, effectively equalizing the magnetic potential and reducing sensitivity to gap variations

Inventive Principle:

Principle #12Equipotentiality

Solution Approach 2:

The non-ferrous torque transfer housing acts as an intermediary that allows magnetic field penetration while maintaining the physical gap between the sensor and sensor target. The non-ferrous material permits magnetic flux to pass through, enabling non-contact sensing while maintaining manufacturing tolerances

Inventive Principle:

Principle #24Intermediary (Mediator)

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 the rotation speed and direction of the shaft, reducing manufacturing complexity, weight, and energy loss, while improving fuel economy and robustness.

Implementation Method 1

The back biased tunnel magnetoresistance sensor is configured to generate a magnetic field and to observe the at least one target of the sensor target to determine a rotation speed of the shaft

Methodology Applied

Scientific EffectMagnetic field: Magnetic Field

Implementation Method 2

The sensor is a back biased tunnel magnetoresistance sensor

Methodology Applied

Scientific EffectMagnetoresistance: Magnetoresistance

Implementation Method 3

The sensor target is composed of a ferrous material

Methodology Applied

Scientific EffectFerromagnetism: Ferromagnetism

Data Source

PatentUS11754173B2Systems for shaft speed sensing

Publication Date: 2023.09.12 GM GLOBAL TECHNOLOGY OPERATIONS LLC

AI summary

A transmission system associated with a vehicle includes a shaft to rotate about an axis of rotation. The shaft is coupled to a gear set. The transmission system includes a sensor target to be coupled to the gear set and to rotate with the gear set. The sensor target includes at least one target. The transmission system includes a sensor spaced apart from the sensor target by a gap. The sensor is configured to observe the at least one target of the sensor target to determine a rotation speed of the shaft.