Electric Machine Gearbox Mounting for Tight Rotor-Stator Air Gaps
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing electric motors for vehicles with partial electric drive face challenges in achieving a reduced air gap between the rotor and stator due to increased rotor elasticity from weight savings, leading to stress and noise issues, while also requiring high power density and reduced weight.
Innovation Solution
A method for mounting an electric machine on a gearbox involves using a stator housing with a cylindrical inner surface and receiving opening, aligning it coaxially with the gearbox input shaft, securing it with a centering mandrel, and compensating for manufacturing tolerances with a pivotally connected bearing assembly to reduce the air gap and increase power density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the rotor is made lighter to reduce weight, then the weight of the electric machine is reduced, but the rotor elasticity increases causing larger air gap and reduced power density
Solution Approach 1:
A centering mandrel is introduced as an intermediary tool during assembly to precisely position the rotor relative to the stator. The mandrel fits into the hollow rotor shaft and extends into the stator cavity, providing a reference surface that ensures accurate centering and minimizes the air gap despite rotor elasticity from weight reduction.
Solution Approach 2:
The centering mandrel is inserted and secured in the stator cavity before the rotor is fully assembled and secured to the gearbox input shaft. This preliminary positioning action ensures that the rotor is pre-centered with respect to the stator, compensating for potential misalignments and tolerance accumulations that would otherwise result in a larger air gap.
2Manufacturing precision
If tolerances between gearbox input shaft and rotor shaft are reduced to minimize air gap, then power density is increased, but manufacturing complexity and cost increase
Solution Approach 1:
The centering mandrel serves as a temporary intermediary fixture that simplifies the assembly process by providing a straightforward mechanical reference for centering. Rather than requiring complex precision machining of the gearbox housing or specialized alignment equipment, the mandrel offers a simple, cost-effective solution to achieve the required air gap tolerance.
Solution Approach 2:
The hollow rotor shaft itself is utilized as part of the centering mechanism by receiving the centering mandrel. This self-service approach eliminates the need for separate, dedicated centering fixtures and leverages the existing rotor structure to achieve precise alignment, thereby reducing overall assembly complexity.
3Power
If the air gap is reduced to increase power density, then the power output is increased, but noise and vibration from rotor elasticity increase
Solution Approach 1:
The rotor is pre-centered using the centering mandrel before final securing to the input shaft. This preliminary centering action ensures that the rotor is positioned optimally with minimal air gap, maximizing power density while establishing a stable, centered position that reduces vibration and noise during operation by preventing eccentric rotation.
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The invention relates to a method for arranging an electric machine on a transmission, having the steps of: - providing a stator housing (12) which has at least one cylindrical inner lateral surface (14) and a receiving opening (16); - inserting a hollow cylindrical stator (10) into the stator housing (12) such that the stator (10) is rotationally fixed in the stator housing (12); - inserting a centering pin (20) into a stator cavity (22) of the hollow cylindrical stator (10) via the receiving opening (16) of the stator housing (12) and clamping the centering pin (20) in the stator cavity (22); - aligning the stator housing (12) on the transmission (30) such that the longitudinal axis (34) of a transmission input shaft (32) mounted in the transmission (30) is coaxial to the longitudinal direction (36) of the centering pin (20) arranged in the stator (10); - securing the stator housing (12) on the transmission (30); - removing the centering pin (20) from the stator cavity (22); - inserting a rotor (44) which has a rotor hollow shaft (50) into the stator (10); - securing the rotor (44) to the transmission input shaft (32); and - placing a bearing shield (78) which has a bearing pin (80) on the receiving opening (16) of the stator housing (12), wherein the bearing pin (80) engages into a rotor cavity (82) of the rotor hollow shaft (50) and into a pivotally attached bearing device (54) arranged in the rotor cavity (50) such that the rotor (44) is rotatably mounted about the rotor longitudinal axis.