Fluid Pump Rotor Asymmetry for Stable Shaft Engagement
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Solution Overview
Problem
In inscribed gear type fluid pumps, the lack of correction for perpendicularity of the tooth flank during assembly leads to instability in discharging and pulsating performance, requiring strict management of the inner rotor's direction relative to the outer rotor to avoid performance issues.
Innovation Solution
A fluid-pump inner rotor design with a through hole and shaft member configuration, where the fitting strength between specific regions is optimized to allow for radial enlargement and stable engagement, reducing the slope of the tooth flank and enabling assembly from either end face, with serration and guide portions for secure alignment and centering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the inner rotor is assembled with strict direction management to correct tooth flank perpendicularity, then discharging performance and pulsating performance are stabilized, but assembly complexity and manufacturing cost increase
Solution Approach 1:
The invention introduces asymmetric features including a keyed structure on the shaft member that engages with a corresponding keyway in the rotor member, and an asymmetric pressing portion that applies force at a specific location. This asymmetry creates a predetermined assembly direction without requiring complex external management, as the asymmetric features naturally guide the components into the correct orientation during assembly
Solution Approach 2:
The shaft member's pressing portion automatically applies pressing force to the tooth flank during the assembly process itself, causing radial enlargement of the rotor member that corrects the tooth flank perpendicularity. This self-correcting mechanism eliminates the need for separate correction steps or complex assembly management, as the assembly act itself performs the correction function
2Manufacturing precision
If the shaft member is made with high fitting strength to the first hole region, then the tooth flank perpendicularity is corrected through radial enlargement, but the manufacturing precision requirements increase
Solution Approach 1:
The invention applies pressing force locally at a specific region of the rotor member through the shaft member's pressing portion, rather than uniformly across the entire component. This localized pressing causes radial enlargement specifically at the tooth flank region that requires correction, while leaving other areas unaffected. The local quality approach allows precision correction without requiring high manufacturing precision across the entire component
Solution Approach 2:
The invention utilizes the elastic-plastic deformation characteristics of the rotor member material, where the pressing force temporarily exceeds the yield strength to create permanent radial enlargement. By controlling the fitting strength parameters of the shaft member and pressing portion geometry, the desired perpendicularity correction is achieved through controlled parameter changes rather than precision manufacturing
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 enhances the assembly stability and reduces noise by ensuring proper engagement and reducing the frequency of engagement failures, allowing for easier assembly and lower manufacturing costs by eliminating the need for additional correction steps.
Implementation Method 1
the outer face of the shaft member will press the inner face of the through hole towards the outer radial side of the rotor member. Therefore, if the pressing force applied from the outer face of the shaft member to the inner face of the through hole is large, this tends to cause a radial enlargement in the rotor member
Implementation Method 2
the first shaft region includes in a circumferential direction a serration portion having a plurality of groove portions extending along the direction of the rotational axis
Data Source
AI summary
Provided is a fluid-pump inner rotor that can be easily fitted to an outer rotor. This fluid-pump inner rotor includes a rotor member having a through hole along a rotational axis and a shaft member fitted in the through hole. Fitting strength between a first hole region provided in an inner face of the through hole of the rotor member which region extends along a rotational axis of the rotor member from one of end faces thereof perpendicular to this rotational axis and a first shaft region provided in an outer face of the shaft member is set greater than fitting strength between a second hole region provided in the inner face of the through hole of the rotor member and a second shaft region provided in the outer face of the shaft member.