Motor-Operated Compressor Back Pressure Space Design

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Solution Overview

Problem

Conventional motor-operated compressors face increased component count and oil supply issues due to the use of sealing members, leading to frictional losses and manufacturing cost increases, as the back pressure space is sealed, preventing smooth oil distribution.

Innovation Solution

A motor-operated compressor design that eliminates the need for a sealing member by forming an open back pressure space, allowing communication between the intermediate pressure space and the casing's inner space, which includes a shaft hole and radial bearing surfaces to support the rotary shaft, enabling oil flow from the discharge space to the bearing surfaces, thus maintaining internal pressure without stagnation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a sealing member is provided to seal the back pressure space, then the back pressure space can be sealed to maintain pressure, but the number of components increases and manufacturing cost increases

Engineering Contradiction:

Improveback pressure space sealingVSAvoidnumber of components

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The sealing member is completely removed from the system. The back pressure space is no longer sealed but instead allows communication between the intermediate pressure space and the inner space of the casing through the gap between the bearing and rotary shaft, eliminating the need for a sealing member while maintaining functional integrity

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The gap between the bearing and rotary shaft serves multiple functions: it allows oil to flow from the intermediate pressure space to the inner space of the casing, provides a path for pressure equalization, and eliminates the need for a separate sealing member, thereby achieving multi-functionality without additional components

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If a sealing member is used to seal the back pressure space, then pressure can be maintained, but oil supply to the back pressure space becomes stagnant causing frictional loss

Engineering Contradiction:

Improvepressure maintenanceVSAvoidfrictional loss

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The communication path through the gap between the bearing and rotary shaft ensures continuous oil flow from the intermediate pressure space to the inner space of the casing. This continuous flow prevents pressure stagnation and ensures continuous lubrication of the bearing surfaces, eliminating frictional losses while maintaining pressure control

Inventive Principle:

Principle #20Continuity of useful action

Solution Approach 2:

The system utilizes fluid dynamics by allowing oil to flow through the gap between the bearing and rotary shaft. This hydraulic approach uses the oil flow itself to maintain pressure and provide lubrication, replacing the mechanical sealing approach that caused stagnation and friction

Inventive Principle:

Principle #29Pneumatics and hydraulics

3Reliability

If the back pressure space is sealed, then internal pressure is maintained, but oil cannot be smoothly supplied leading to oil shortage

Engineering Contradiction:

Improveinternal pressure maintenanceVSAvoidoil supply

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The gap between the bearing and rotary shaft acts as an intermediary passage that mediates between the intermediate pressure space and the inner space of the casing. This intermediary path allows oil to flow smoothly while maintaining the pressure balance, solving both the pressure maintenance and oil supply requirements simultaneously

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

This design reduces manufacturing costs by eliminating the sealing member, facilitates smoother oil supply to bearing surfaces, and prevents frictional losses by maintaining internal pressure, enhancing the compressor's operational efficiency.

Implementation Method 1

an intermediate pressure space formed on one side of the second scroll to communicate with the discharge space, configured to accommodate oil flowing in from the discharge space to form back pressure supporting the second scroll toward the first scroll

Methodology Applied

Scientific EffectPressure gradient: Pressure Gradient

Implementation Method 2

the back pressure space and the inner space of the casing may communicate through a gap between an inner peripheral surface of the bearing and an outer peripheral surface of the rotary shaft

Methodology Applied

Scientific EffectFluid flow through gap:

Data Source

PatentEP3553317B1Motor-operated compressor

Publication Date: 2023.05.31 LG ELECTRONICS INC

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AI summary

Provided is a motor-operated compressor including a casing having an inner space composed of a suction space and a discharge space, a first scroll provided in the inner space of the casing, a second scroll configured to orbit in engagement with the first scroll to form a pair of two compression chambers between the first scroll and the second scroll, a rotary shaft coupled to the second scroll and configured to transfer a rotational force of a driving motor to the second scroll, and an intermediate pressure space formed on one side of the second scroll to communicate with the discharge space, configured to accommodate oil flowing in from the discharge space to form back pressure supporting the second scroll toward the first scroll, and opened toward the suction space so that a portion of the accommodated oil flows out into the suction space.