Ultrasonic Welding of Encoder Magnets to Carrier Pins

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Solution Overview

Problem

Existing sensor devices for detecting the rotational position of a rotating shaft face challenges in achieving a secure, non-rotatable connection between the ring magnet and the base body, with methods like injection molding and ultrasonic welding being costly and inefficient.

Innovation Solution

A sensor device with a ring-shaped sensor magnet and a carrier pin connected through a material and form-fitting method using ultrasonic welding, where the carrier pin acts as a sonotrode, and the sensor magnet has a central recess and knurling for enhanced connection, allowing for a secure and cost-effective attachment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If injection molding is used to connect the sensor magnet to the carrier pin, then a secure connection is achieved, but the manufacturing cost increases due to expensive molding tools

Engineering Contradiction:

Improveconnection securityVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent replaces the injection molding process with ultrasonic welding, substituting a complex mechanical molding system with a simpler welding process. The ultrasonic welding device uses high-frequency vibration to create a secure metallurgical bond between the carrier pin and sensor magnet without requiring expensive molding tools, thus reducing manufacturing costs while maintaining connection reliability

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the connection method from adhesive bonding (chemical parameter) to ultrasonic welding (thermal-mechanical parameters). By controlling welding parameters such as amplitude, time, and pressure, a secure connection is achieved without the need for expensive injection molding tools, resolving the contradiction between connection security and manufacturing cost

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If adhesive connections are used to attach the ring magnet to the base body, then the manufacturing process is simple, but the connection security is insufficient

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidconnection security

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent replaces adhesive connections with ultrasonic welding, substituting a chemically-based simple process with a mechanically-based welding process. The ultrasonic welding creates a strong metallurgical bond that exceeds the security of adhesive connections while maintaining manufacturing simplicity through a single-step welding process without requiring adhesive application and curing steps

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Strength

If press fit is used to fasten the ring magnet to the base body, then mechanical stresses are avoided, but the connection may twist or displace axially

Engineering Contradiction:

Improvestress avoidanceVSAvoidanti-twisting and axial displacement security

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent creates a composite connection structure where the carrier pin and sensor magnet are joined through ultrasonic welding. This welding process creates a metallurgical bond that combines the stress avoidance benefits of press fit with the anti-twisting and axial displacement security of positive mechanical connections, effectively resolving the contradiction between stress avoidance and connection security

Inventive Principle:

Principle #40Composite materials

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 method creates a reliable, cost-effective, and secure connection between the sensor magnet and the carrier pin, ensuring a stable rotational position detection without the high costs associated with traditional methods.

Implementation Method 1

initiating a high-frequency mechanical vibration in the ultrasonic range in the carrier part, pressing the carrier part into the sensor magnet with a defined contact pressure

Methodology Applied

Scientific EffectUltrasonic vibration: Ultrasonic Vibration

Implementation Method 2

The high-frequency oscillation is preferably in a range from 20 to 40 kHz, in particular around 35 kHz

Methodology Applied

Scientific EffectHeating through vibration: Ultrasonic Vibration

Implementation Method 3

the sensor magnet has plastic in its composition and is partially heated and plasticized when the high-frequency mechanical vibration is introduced into the carrier part

Methodology Applied

Scientific EffectPlastic deformation: Plasticity

Implementation Method 4

The carrier part preferably has knurling on the outside. This knurling can be cross knurling or longitudinal knurling, for example

Methodology Applied

Scientific EffectKnurling: Knurling

Implementation Method 5

After cooling, a positive and material connection is created between the magnet and the carrier pin

Methodology Applied

Scientific EffectCooling: Cooling

Data Source

PatentEP3577421B1Sensor device for capturing the rotational position of a rotating shaft with ultrasonically welded encoder magnets

Publication Date: 2021.10.20 THYSSENKRUPP PRESTA AG

Figure 1~4
Figure 5~7

AI summary

The invention relates to a sensor device for capturing the rotational position of a rotating shaft, which is rotatably mounted in a housing, with an encoder magnet (13) which is fastened on a carrier part (14) which is connected to the shaft (12), wherein the carrier part (14) is connected to the magnet (12) by means of ultrasonic welding.