Tolerance-Independent Crescent Internal Gear Pump Design
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Solution Overview
Problem
Conventional crescent internal gear pumps require strict tolerances for individual components, leading to high manufacturing costs and inefficiencies due to precise machining and laborious component sorting, which is time-consuming and costly.
Innovation Solution
A tolerance-independent crescent internal gear pump design where the gear housing, ring gear, and pinion gear have the same thickness, with a shim establishing clearance between the end cover and gear housing, allowing for assembly without precise machining, and a crescent that fits into a complementary slot in the end cover, eliminating the need for chamfered edges and reducing manufacturing steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If strict tolerances are applied to individual components, then pump efficiency is improved, but manufacturing cost increases and manufacturing complexity increases
Solution Approach 1:
A shim is introduced as an intermediary component between the end cover and gear housing to precisely control the clearance. The shim acts as a mediator that compensates for tolerance variations in other components, allowing them to be manufactured with looser tolerances while still achieving the desired pump efficiency through precise clearance control at the critical interface.
Solution Approach 2:
The invention changes the approach from controlling dimensions of multiple components to controlling a single critical parameter (clearance) through the shim thickness. By shifting the tolerance control from multiple component dimensions to one shim dimension, the manufacturing complexity and cost are reduced while maintaining pump efficiency.
2Reliability
If precise machining is used to achieve tight tolerances, then pump efficiency is improved, but manufacturing time increases
Solution Approach 1:
The shim serves as a pre-manufactured intermediary component that embodies the precise clearance requirement. Instead of machining multiple components to tight tolerances, the shim is manufactured with precision and then used to set the clearance during assembly, significantly reducing the total manufacturing time while maintaining pump efficiency.
Solution Approach 2:
The clearance control function is performed in advance by manufacturing the shim with the precise thickness required. This preliminary action of creating a dedicated clearance-setting component eliminates the need for time-consuming precision machining of multiple other components during final assembly.
3Reliability
If component sorting is performed to achieve desired clearances, then pump efficiency is improved, but labor requirements increase and manufacturing cost increases
Solution Approach 1:
The shim eliminates the need for component sorting by serving as a universal intermediary that precisely controls clearance regardless of variations in other components. This single component replaces the complex sorting process, simplifying the manufacturing process while ensuring consistent pump efficiency.
Solution Approach 2:
The invention extracts the clearance control function from the assembly of multiple components and concentrates it in a single shim component. By separating and isolating the clearance-setting function, the complex sorting process is eliminated and replaced with a simple assembly operation.
4Reliability
If tolerance stack-up is accounted for in design, then pump efficiency is improved, but individual component tolerances must be tighter than necessary
Solution Approach 1:
The shim acts as a tolerance-absorbing intermediary that decouples the tolerance requirements of individual components from the final clearance requirement. This allows components to be manufactured with relaxed tolerances while the shim compensates for any variations, achieving the desired pump efficiency without unnecessarily tight component tolerances.
Data Source
AI summary
A crescent internal gear pump includes a front cover, an end cover, a ring gear and a pinion gear disposed within a gear housing in an eccentric, intermeshing relationship. The housing is disposed intermediate the front cover and the end cover. A crescent is disposed radially intermediate the ring gear and the pinion gear. The crescent partially extends into a correspondingly shaped slot in the end cover. The gear housing, the ring gear, and the pinion gear can have substantially the same thickness. A shim can be disposed intermediate the end cover and the gear housing for establishing a desired clearance therebetween.