Centrifugal Fan Impeller Blade Tip Curvature for Mold Durability
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Solution Overview
Problem
The existing centrifugal fan impellers with outer diameter rings are prone to mold fractures due to sharp acute angles, making mass production challenging.
Innovation Solution
The impeller design features blades bent in the rotating direction at the tip end portions with a connection angle between 30° to 90°, an outer ring with thickness-reduced relief parts, and a main plate smaller than the outer ring, allowing for integrally molded construction and improved stiffness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the connection angle between the blade and outer ring is made small and sharp to improve aerodynamic performance, then the airflow efficiency is improved, but the mold is prone to fracture during mass production
Solution Approach 1:
The patent changes the geometric parameter of the connection angle from a small sharp angle to a larger angle of 30-90 degrees. This parameter modification resolves the contradiction by maintaining acceptable aerodynamic performance while eliminating the mold fracture issue caused by acute angles during injection molding.
Solution Approach 2:
The patent introduces a curved transition region at the connection between the blade and outer ring, replacing the sharp acute angle with a gradual curved surface. This curvature allows the mold to have a larger, more robust geometry that is resistant to fracture while still maintaining smooth airflow characteristics.
2Strength
If the outer ring height is increased to improve structural stiffness, then the impeller strength is improved, but the air discharge performance deteriorates due to blockage
Solution Approach 1:
The patent applies different heights of the outer ring at different locations. The outer ring has a first height at the connection region with the blade and a second height at other regions, where the first height is greater than the second height. This local variation provides enhanced stiffness where needed while maintaining open airflow passages in other areas.
Solution Approach 2:
The patent resolves the contradiction by adding vertical dimensionality variation to the outer ring structure. By creating a stepped or varied height profile in the vertical dimension, the design achieves both structural support and airflow clearance simultaneously.
Data Source
AI summary
An impeller for a centrifugal fan includes a main plate having a disc shape, a plurality of blades arranged along a circumferential direction about a center part of the main plate, and an outer ring having a ring shape connecting the respective blades. The outer ring is connected to tip end portions of the respective blades at a side of a fluid discharge opening, and each of the blades has a shape which is bent in a rotating direction of the impeller in a vicinity of the tip end portion.