Linear Compressor Yoke-Magnet Mounting for Thermal Expansion

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Solution Overview

Problem

Linear compressors with linear electric motors are prone to damage from severe temperature changes due to coolant compression, which can reduce their service life and operational reliability.

Innovation Solution

A linear compressor design featuring a yoke-magnet arrangement with a spring mechanism that allows for axial movement and tolerance compensation, ensuring reliable operation under temperature changes, utilizing a yoke with shoulders or projections to limit magnetic ring movement and a spring for axial pressure, and optionally using an insert for spring support.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the linear compressor uses a rigid yoke-magnet arrangement fixed directly to the cylinder, then the structure is simple and strong, but the component is damaged by severe temperature changes during operation

Engineering Contradiction:
Improveoperational reliabilityVSAvoidtemperature changes
Core Design Contradiction:
ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies the dynamics principle by replacing the rigid fixed connection with a dynamic spring-based suspension system. The yoke-magnet arrangement is no longer rigidly fixed but can move axially within controlled limits, allowing the system to adapt dynamically to temperature-induced dimensional changes while maintaining operational stability

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The patent implements parameter changes by introducing a spring mechanism that alters the mechanical state of the yoke-magnet arrangement. The spring constant and pre-compression force are carefully selected to provide appropriate compliance under thermal stress, changing the system's mechanical parameters from rigid to elastically compliant

Inventive Principle:
Principle #35Parameter changes

2Object-affected harmful factors

If the yoke-magnet arrangement is allowed to move freely on the cylinder, then thermal expansion is accommodated, but axial movement of the magnetic ring damages the component

Engineering Contradiction:
Improvethermal expansionVSAvoidcomponent strength
Core Design Contradiction:
Object-affected harmful factorsVSStrength

Solution Approach 1:

The patent applies local quality by differentiating the constraints at different locations: the spring provides compliant support at the base to accommodate thermal expansion, while the yoke shoulder provides a rigid stop at the magnetic ring location to prevent excessive movement and protect component strength

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The patent implements beforehand cushioning by pre-compressing the spring between the cylinder stop and the yoke. This pre-compression creates a cushioning effect that absorbs thermal expansion forces before they can damage the magnetic ring, while still maintaining sufficient constraint to prevent uncontrolled movement

Inventive Principle:
Principle #11Beforehand cushioning (Prior cushioning)

3Reliability

If a spring mechanism is introduced to accommodate thermal expansion, then operational reliability improves, but the device complexity increases

Engineering Contradiction:
Improveoperational reliabilityVSAvoidstructure complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies merging by combining multiple functions into the spring component: it serves as both a thermal compensation element and a positioning element for the yoke-magnet arrangement. The spring simultaneously accommodates thermal expansion and maintains proper axial positioning, reducing the need for separate components

Inventive Principle:
Principle #5Merging (Combining)

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 design minimizes friction, reduces energy loss, and maintains operational reliability by accommodating thermal expansion, enhancing the compressor's durability and efficiency.

Implementation Method 1

The spring (8) is pressed against a stop (9) on the cylinder (7) and limiting an axial movement of the yoke-magnet-arrangement (5, 6) on the cylinder (7)

Methodology Applied
Scientific EffectElasticity: Elasticity

Implementation Method 2

a linear electric motor comprising a stator (2) with a coil (3) and a movable system (4)... creates a magnetic field which acts on the mover and consequently moves the cylinder

Methodology Applied
Scientific EffectElectromagnetic force: Lorentz Force

Implementation Method 3

The yoke is used to distribute the magnetic field so that the driving force of the linear electric motor is amplified

Methodology Applied
Scientific EffectMagnetic field distribution: Magnetic Field

Data Source

PatentEP4685349A1Linear compressor with a linear electric motor and household appliance
Publication Date: 2026.01.28 BSH HAUSGERATE GMBH
  • EP4685349A1 patent drawingFigure 1
  • EP4685349A1 patent drawingFigure 2a~2d
  • EP4685349A1 patent drawingFigure 3a~3d

AI summary

Disclosed is a linear compressor for a household appliance, for instance a refrigerator, wherein a yoke-magnet-arrangement is clamped in such a way on a cylinder of a cylinder-piston arrangement that temperature expansions of the yoke-magnet-arrangement are enabled; in particular by forcing the yoke-magnet-arrangement via a spring force against a fixed stop of the cylinder, and a household appliance.