Vacuum Pump Shaft Spherical Centering for Wear Reduction
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Solution Overview
Problem
Electric motor-driven motor-vehicle vacuum pumps with drive shafts and two bearings face challenges in service life and manufacturing costs due to unwanted radial play and leakage between the shaft and rotor, caused by assembly and production tolerances, leading to wobbling and increased wear.
Innovation Solution
Incorporating a centering area on the shaft stub within the rotor that allows for radial centering and wobbling motion, reducing radial play and leakage by enabling tolerance-dependent compensating movements without rigid connection, and utilizing spherical or convexly curved designs to minimize contact stress and play.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the rotor is rigidly connected to the shaft stub, then the radial guiding precision is improved, but the wear and service life deteriorate due to wobbling motion caused by tolerance accumulation
Solution Approach 1:
The patent applies the dynamics principle by allowing the rotor to perform controlled wobbling and tilting motions relative to the shaft stub through a spherical connection interface. This dynamic capability enables the system to accommodate angular errors and tolerance deviations during operation, preventing rigid constraint-induced wear while maintaining functional precision. The spherical interface transforms the static rigid connection into a dynamic adaptive connection that self-adjusts to tolerance variations.
2Object-generated harmful factors
If tight tolerances are applied to reduce radial play, then the leakage flow is reduced, but the manufacturing costs increase
Solution Approach 1:
The patent applies partial action by implementing centering areas only in specific regions where radial guidance is critical, rather than requiring tight tolerances throughout the entire rotor-shaft interface. The spherical connection provides sufficient centering function in the radial direction while allowing controlled motion in other degrees of freedom, achieving acceptable leakage control without the need for excessive precision in all manufacturing dimensions.
3Duration of action of moving object
If the shaft stub is spherically formed to allow wobbling motion, then the service life is improved, but the manufacturing precision of the connection deteriorates
Solution Approach 1:
The patent directly applies spheroidality by forming the shaft stub with a spherical connection interface that fits into a corresponding spherical bore in the rotor. This spherical geometry inherently accommodates angular misalignments and wobbling motions while maintaining stable contact and centering. The curved spherical surfaces provide continuous line contact that distributes loads and reduces stress concentrations, extending service life without requiring extremely tight manufacturing tolerances.
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 solution significantly reduces wear and allows for larger production and assembly tolerances, minimizing unwanted leakage and knocking, thereby enhancing the service life and reducing manufacturing costs of the vacuum pump.
Implementation Method 1
the shaft stub in the centering area is spherically formed
Implementation Method 2
the shaft stub is able to perform a sort of tipping or wobbling motion and to tilt in the rotor
Data Source
AI summary
The invention relates to an electric motor-driven motor-vehicle vacuum pump (1), having a drive shaft (3) which has, in particular, two bearings and extends with a shaft stub (5; 35; 45) into a rotor (8) which is connected fixedly to the shaft stub so as to rotate with it. In the rotor, the shaft stub has a centring region (26; 36; 46) which serves to center the rotor, without guiding the rotor in the axial direction.