Linear Compressor Ball-Joint Coupling for Piston Friction Reduction
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Solution Overview
Problem
Linear compressors in refrigerator appliances face efficiency issues due to friction between the piston and the chamber wall, leading to reduced performance.
Innovation Solution
A coupling system with a shaft, ball seat, ball, ball shoe, and spring is introduced to reduce friction by allowing compliant motion between the inner back iron assembly and the piston, decoupling side pull forces and minimizing radial motion transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the piston is rigidly connected to the inner back iron assembly, then the structural strength is improved, but friction losses increase due to rubbing against the chamber wall
Solution Approach 1:
The coupling is divided into multiple segments: a rigid shaft portion for strength, and flexible ball-joint portions for compliance. This segmentation allows the system to simultaneously achieve structural strength and friction reduction by distributing different functions to different segments.
Solution Approach 2:
The ball-seat and ball-shoe mechanisms act as intermediaries between the inner back iron assembly and the piston. These intermediaries provide compliant motion that absorbs misalignment and prevents direct contact between the piston and chamber wall, thereby reducing friction losses while maintaining structural integrity.
2Stability of the object's composition
If the piston is rigidly connected to the inner back iron assembly, then the structural stability is improved, but side pull forces increase causing misalignment
Solution Approach 1:
The coupling transitions from a static rigid connection to a dynamic compliant connection. The ball-seat and ball-shoe mechanisms allow the coupling to adapt its configuration in response to side pull forces, maintaining alignment between the piston and chamber axis while preserving structural stability through the rigid shaft portions.
3Loss of energy
If a compliant coupling is introduced to reduce friction, then friction losses are reduced, but the device complexity increases
Solution Approach 1:
The coupling is segmented into modular components (shaft, ball seats, ball shoes, springs) that can be manufactured and assembled separately. This segmentation reduces overall complexity by allowing each component to be optimized independently and simplifies maintenance and replacement.
Solution Approach 2:
The use of spherical ball joints instead of complex articulated mechanisms simplifies the compliant coupling design. The spherical geometry naturally provides multi-directional compliance while maintaining simple contact surfaces, reducing the number of parts and assembly complexity compared to alternative compliant mechanisms.
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 coupling system effectively reduces friction and side pull forces, enhancing the efficiency and performance of linear compressors by maintaining a uniform air gap and minimizing friction losses.
Implementation Method 1
A spring is positioned within the housing. The spring urges the ball shoe against the ball.
Implementation Method 2
The driving coil is configured for magnetically engaging the magnet in order to reciprocate the inner back iron assembly relative to the driving coil.
Data Source
AI summary
The present subject matter provides a linear compressor. The linear compressor includes a coupling that extends between an inner back iron assembly and a piston. The coupling includes a shaft and a ball seat mounted to the shaft at an end portion of the shaft. A ball is positioned on the ball seat at a seating surface of the ball seat. A ball shoe is positioned opposite the ball seat about the ball, and the ball is positioned on the seating surface of the ball shoe. A spring urges the ball shoe against the ball.