Plastic Rotor Hub with Resilient Bore for Low-Temperature Stability
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Solution Overview
Problem
Existing electrically commutated small actuators face issues with rotor shrinkage at low temperatures and vibration-induced noise due to manufacturing challenges in achieving the precise bearing clearance required for plastic hubs, leading to unreliable and costly production.
Innovation Solution
A rotor design featuring a plastic hub with a resilient extension acting as a finger that exerts a radial force on the stationary shaft, combined with a bearing shell covering the extension, allowing for a larger tolerance range in manufacturing without additional costs or effort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the bearing clearance is made small to prevent rotor oscillation and noise, then the rotor stability is improved, but the plastic hub shrinks at low temperatures due to thermal expansion
Solution Approach 1:
The hub bore is designed with non-circular geometry (oval, triangular, or star-shaped) that allows dynamic adjustment of the effective bearing clearance. The resilient extension compresses radially inward to provide preloading force, creating a variable clearance system that maintains stability while accommodating thermal shrinkage through the elastic deformation of the resilient material.
Solution Approach 2:
The invention changes the geometric parameters of the hub bore from circular to non-circular shapes (oval, triangular, star-shaped). This parameter change allows the bore to deform elastically under thermal contraction while maintaining adequate bearing clearance, preventing both excessive oscillation and noise while accommodating low-temperature shrinkage.
2Reliability
If the bearing clearance is made large to accommodate thermal shrinkage, then the low temperature reliability is improved, but the rotor oscillates and produces noise
Solution Approach 1:
The resilient extension acts as a dynamic element that compresses radially inward to provide preloading force on the rotor shaft. This dynamic preloading maintains stable rotor operation by reducing clearance-induced oscillation while the non-circular bore geometry allows the system to accommodate thermal shrinkage through elastic deformation.
Solution Approach 2:
The hub is segmented into a resilient extension portion and a bearing shell portion. The resilient extension handles the preloading function to control oscillation, while the bearing shell provides the structural support and accommodates thermal deformation, dividing the functions to resolve the contradiction between stability and thermal reliability.
3Manufacturing precision
If an additional bearing bush is added to maintain appropriate bearing clearance, then the bearing clearance precision is improved, but the manufacturing complexity and cost increase
Solution Approach 1:
The invention merges the bearing clearance control function into the hub structure itself by designing the hub bore with non-circular geometry and incorporating a resilient extension directly into the injection-molded hub. This eliminates the need for separate bearing bushes or additional components, maintaining manufacturing precision while reducing device complexity and cost.
Solution Approach 2:
The hub structure serves itself by using its own resilient extension and non-circular geometry to maintain appropriate bearing clearance. The resilient material provides self-adjusting preloading force that compensates for thermal effects, eliminating the need for external bearing components and simplifying the manufacturing process.
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
The design prevents rotor shrinkage and vibration, ensuring reliable and cost-effective manufacturing by maintaining the bearing clearance, thus reducing disruptive noise and improving manufacturing reliability.
Implementation Method 1
a section of the hub is designed as a resilient extension (4) which exerts a radial force on the axis (3) arranged in the bore (3)
Data Source
Figure 1~2
Figure 3~5
AI summary
A rotor for an electric motor, comprising a hub (1) made of plastic, a magnetic ring (2) non-rotatably connected to the hub (1), and a stationary shaft, wherein the hub (1) has a bore (3) and the stationary shaft is arranged in the bore (3) so that the hub (1) can rotate about the stationary shaft, wherein a section of the hub (1) is designed as a resilient extension (4) which exerts a radial force on the shaft arranged in the bore (3), and a small actuator for a motor vehicle, wherein the small actuator comprises an electrically commutated electric motor, the electric motor comprising such a rotor.