Electric Machine Torque Key Wedge Interference Fit
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Solution Overview
Problem
The existing stator attachment methods in electric machines, such as press fitting, introduce compressive stresses that affect magnetic properties and efficiency while also causing noise, vibration, and harshness issues due to torque reactions and thermal expansion, and traditional torque keys can lead to wear and tear.
Innovation Solution
A torque key mechanism with wedges and a bolt system that creates an interference fit within a keyway to securely attach the stator to the case, increasing stiffness and reducing stress, allowing for variable keyway dimensions and eliminating press fitting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If press fitting is used to attach the stator to the case, then the stator is securely fixed, but compressive stresses are introduced that affect magnetic properties and efficiency
Solution Approach 1:
The attachment mechanism is segmented into a torque key component and a wedge mechanism, allowing the stator to be secured without direct compressive press fitting. The torque key fits into a keyway to prevent rotation, while the wedge mechanism provides axial positioning without introducing harmful compressive stresses into the stator body.
Solution Approach 2:
A wedge mechanism acts as an intermediary between the bolt and the torque key. The wedge converts the bolt's axial force into radial expansion force that secures the torque key in the keyway, eliminating the need for direct press fitting of the stator to the case while maintaining secure attachment.
2Strength
If press fitting is used to attach the stator to the case, then the stator is securely fixed, but noise, vibration, and harshness issues occur due to torque reactions and thermal expansion
Solution Approach 1:
The attachment system is divided into rotational constraint (torque key in keyway) and axial positioning (wedge mechanism), allowing each function to be optimized independently. This segmentation prevents the transmission of torque reactions and thermal expansion forces that cause noise and vibration in press-fit designs.
Solution Approach 2:
The wedge mechanism serves as an intermediary that absorbs and isolates thermal expansion and torque reaction forces. By positioning the wedge in a dedicated groove rather than directly pressing the stator to the case, the design prevents these forces from being transmitted to the stator body, thereby reducing noise and vibration.
3Stability of the object's composition
If traditional torque keys are used, then rotational constraint is provided, but wear and tear occur
Solution Approach 1:
The torque key is transformed from a static press-fit component into a dynamic wedge mechanism that can adjust its position. The wedge can move axially within the groove to accommodate thermal expansion and torque reactions, maintaining constant contact pressure and preventing wear that occurs in static torque key designs.
Solution Approach 2:
The wedge mechanism acts as an intermediary between the bolt and the torque key, distributing the securing force through a larger contact area and allowing for self-adjustment during operation. This reduces localized stress and wear on the torque key while maintaining reliable rotational constraint.
4Strength
If a bolt system is used to secure the torque key, then secure attachment is achieved, but device complexity increases
Solution Approach 1:
The rotational constraint function (torque key) and the securing mechanism (wedge and bolt) are merged into a single integrated assembly. The torque key includes the wedge mechanism as an integral part, eliminating the need for separate components and simplifying assembly while maintaining strong attachment.
Solution Approach 2:
The torque key assembly serves multiple functions: it provides rotational constraint through the keyway fit, axial positioning through the wedge mechanism, and thermal expansion accommodation through the wedge's ability to move within the groove. This multi-functionality reduces the need for additional components, offsetting the added complexity of the bolt-wedge system.
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 enhances motor efficiency by reducing compressive stress, minimizing wear and tear, and decreasing noise and vibration issues, while maintaining structural strength and durability.
Implementation Method 1
a first wedge configured to cooperate with a second wedge, wherein each wedge is configured to receive a respective portion of a bolt configured to adjust the collective force exerted on the stator and case to forcibly fix the torque key between the stator and the case
Data Source
AI summary
A stator system for an electric vehicle motor may include a stator having a torque key extending axially from a first stator end, a case configured to surround the stator and defining a case opening to receive the torque key, the case defining a keyway between the torque key and the case opening, a torque key mechanism arranged within the keyway, wherein the torque key mechanism includes a pair of reciprocally aligned wedges defining a channel through at least one of the wedges, and a bolt insertable at the channel and configured to engage the channel to move at least one wedge and create an interference fit of the torque key mechanism within the keyway to attach the stator to the case.