Closed Impeller Shroud Protrusions for Precise Blade Brazing

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Solution Overview

Problem

Press-formed shrouds in impellers suffer from poor dimensional accuracy, leading to gaps and brazing deficiencies when joined with blades.

Innovation Solution

A closed impeller design featuring a press-formed shroud with protrusions along blade portions, where brazing material is applied only on the end portions of these protrusions, allowing precise fitting and brazing with minimal gaps, and optionally using a two-member shroud structure to adjust outer diameter.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a shroud is press-formed from sheet material, then manufacturing ease and productivity are improved, but dimensional accuracy deteriorates, causing gaps between the shroud and blades

Engineering Contradiction:

Improvemanufacturing efficiencyVSAvoiddimensional accuracy

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The shroud is press-formed as a whole structure for manufacturing efficiency, but local areas (protrusions) are selectively removed by cutting to create precise fitting surfaces. This combines the advantages of press-forming (productivity) with precision cutting (dimensional accuracy) at critical locations.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The shroud surface is segmented into two types of areas: most of the surface remains press-formed for efficiency, while specific localized portions are cut away to form protrusions that require high dimensional accuracy for proper fitting with the blades.

Inventive Principle:

Principle #1Segmentation

2Reliability

If brazing material is applied on the entire shroud surface, then coverage is complete, but material dripping increases during brazing

Engineering Contradiction:

Improvebrazing coverageVSAvoidmaterial dripping

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

Brazing material is applied selectively only on the protrusions where joining is required, rather than on the entire shroud surface. This localized application ensures complete brazing coverage at critical interfaces while preventing excessive material that would cause dripping during the brazing process.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

Brazing material is extracted from non-essential areas of the shroud surface and concentrated only on the protrusions. This removes unnecessary brazing material that would otherwise drip during brazing, while maintaining adequate material presence where joining is actually needed.

Inventive Principle:

Principle #2Taking out (Extraction)

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

Ensures strong and precise brazing with reduced assembly gaps and material dripping, enabling consistent impeller performance and ease of adjustment to desired dimensions.

Implementation Method 1

brazing the blade portions (22) and the protrusions (33) fitted together

Methodology Applied

Scientific EffectBrazing: Brazing

Implementation Method 2

brazing material (32) is provided at least on end portions of the protrusions (33)

Methodology Applied

Scientific EffectDiffusion bonding: Diffusion Welding

Data Source

PatentEP4134553B1Closed impeller and method for producing closed impeller

Publication Date: 2025.12.31 DAIKIN INDUSTRIES LTD

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AI summary

The impeller body (20) includes a plurality of blade portions (22). The shroud (30) is press formed into a shape along end portions of the blade portions (22). The shroud (30) includes a plurality of protrusions (33) on a surface facing the impeller body (20). The protrusions (33) extend along the blade portions (22) and are joined to the corresponding blade portions (22) via the brazing material (32).