Outer-Rotor Hermetic Reciprocating Compressor for Low Speed Fluctuation
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Solution Overview
Problem
Existing reciprocating compressors face challenges with high minimum speeds and significant speed fluctuations, particularly at low operating speeds, which affect the fixed temperature performance of refrigeration systems by causing temperature variations and inefficiencies.
Innovation Solution
The design incorporates an outer rotor type motor configuration, optimizing the moment of inertia and speed fluctuation rate by positioning the rotor outside the stator, adhering to the relationship moment of inertia ≥ internal pressure × cross-sectional area × stroke length / minimum speed², with specific coefficients for different rotor placements, thereby reducing minimum speed and fluctuation to 20% or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If an inner rotor type motor is used, then the device complexity is reduced, but the moment of inertia of the rotor is limited by the size of the stator
Solution Approach 1:
The patent inverts the conventional motor structure by placing the rotor outside the stator instead of inside. This outer rotor configuration allows the rotor to achieve a larger moment of inertia without being constrained by the stator dimensions, thereby resolving the contradiction between structural simplicity and rotational inertia requirements.
2Speed
If the moment of inertia of the rotor is increased, then the minimum speed and speed fluctuation rate are reduced, but the device complexity increases
Solution Approach 1:
By inverting the motor structure to an outer rotor configuration, the patent achieves larger moment of inertia with a more compact overall design. This inversion allows the rotor to extend outward from the stator, increasing rotational inertia while maintaining structural efficiency and reducing minimum speed fluctuations.
Solution Approach 2:
The outer rotor design utilizes the radial dimension more effectively, allowing the rotor to extend outward from the stator in a direction that maximizes moment of inertia. This dimensional approach enables higher rotational inertia without proportionally increasing the overall device footprint or complexity.
3Shape
If the rotor position is changed from inside to outside the stator, then the moment of inertia is increased, but the manufacturing precision requirements increase
Solution Approach 1:
The inverted outer rotor structure provides inherent manufacturing advantages by allowing the rotor to be mounted on the exterior of the stator assembly. This configuration simplifies alignment procedures and enables more robust mechanical connections, reducing the stringency of manufacturing precision requirements compared to inner rotor designs.
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 configuration enhances the fixed temperature performance of refrigeration systems by maintaining low minimum speeds and minimal speed fluctuations, improving temperature stability and efficiency.
Implementation Method 1
a moment of inertia of the rotor, an internal pressure of the cylinder, a cross-sectional area and a stroke length of the piston, and a minimum speed of the rotor may have a relationship as follows
Data Source
AI summary
A reciprocating compressor including a cylinder; a piston disposed to reciprocate a certain distance inside the cylinder; a connecting rod connected to the piston; a rotation shaft configured to operate the connecting rod; a rotor configured to rotate integrally with the rotation shaft; and a stator disposed inside of the rotor along a direction toward the rotation shaft or outside the rotor along the direction toward the rotation shaft. A speed fluctuation rate of the rotor is 20% or less is achieved based on consideration of a relationship between a moment of inertia of the rotor, an internal pressure of the cylinder, a cross-sectional area and a stroke length of the piston, and a minimum speed of the rotor.