Motor Drive Shaft Ridges for Plastic Gear Torque Coupling
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Solution Overview
Problem
Existing electric motor drive units in motor vehicles face issues with mechanical damage and temperature-related deformations due to the connection between the output shaft and plastic drive element, particularly under high torque loads, leading to potential shearing and peeling, which compromises the coupling integrity and service life.
Innovation Solution
The output shaft is designed with axially extended, chord-like ridges forming a U-bridge in the engagement area, with vent holes on the ridges, and a complementary protrusion on the drive element for a secure rotational coupling, allowing for temperature compensation and preventing mechanical damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If an interference fit is used to couple the output shaft and drive element, then a secure connection is achieved, but the coupling may shear off under high torque loads or the output shaft may peel into the drive element
Solution Approach 1:
The output shaft is segmented into multiple functional zones: a D-shaped engagement section with grooves for torque transmission, and a circular section with axially extended ridges for thermal relief. This segmentation allows each zone to perform its specialized function without compromising the other, resolving the contradiction between connection strength and coupling integrity.
Solution Approach 2:
The invention introduces axial dimensionality by extending ridges along the axial direction of the output shaft, creating a three-dimensional stress distribution pathway. This axial structure provides an additional dimension for stress relief and thermal expansion, preventing the coupling from failing under high torque loads while maintaining secure engagement.
2Weight of moving object
If the drive element is made of plastic to reduce weight, then weight is reduced, but temperature-related deformations and mechanical damage occur under high loads
Solution Approach 1:
The output shaft exhibits local quality variation: the D-shaped engagement section provides high mechanical interlocking for torque transmission, while the circular section with axially extended ridges provides thermal relief and stress distribution. This local differentiation allows the plastic drive element to maintain reliability by providing targeted structural support where needed while accommodating thermal effects in other zones.
Solution Approach 2:
The coupling system functions as a composite structure combining the metal output shaft with plastic drive element, where each material contributes its advantageous properties. The metal shaft provides structural integrity and thermal stability through its axially extended ridges, while the plastic drive element provides weight reduction and sufficient strength for power transmission, creating a balanced composite solution.
3Strength
If vent holes are made small to maintain structural integrity, then structural integrity is maintained, but deformations in the drive element are still possible during operation
Solution Approach 1:
The axially extended ridges are pre-formed on the output shaft to create stress relief pathways and thermal expansion channels before operation begins. This preliminary structural preparation prevents deformations during operation by providing predetermined pathways for stress and thermal expansion relief, eliminating the need for additional vent holes that could compromise structural integrity.
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 ensures a torsionally rigid coupling with enhanced durability and temperature control, preventing shearing and peeling, resulting in a longer service life and reliable functionality under high loads.
Implementation Method 1
to absorb temperature-related deformations of the worm or worm wheel
Implementation Method 2
to absorb temperature-related deformations of the worm or worm wheel
Implementation Method 3
the coupling between the output shaft and the drive element is realized by an interference fit
Implementation Method 4
the coupling between the output shaft and the drive element is realized by an interference fit
Data Source
AI summary
An electric motor drive unit for motor vehicle applications, which is equipped with an electric motor having an output shaft substantially circular in cross-section and with a drive element mounted on the output shaft, preferably made of plastic. The output shaft engages a receiving hole of the drive element defining at least one vent hole. According to the invention, the output shaft has, in one variant, at least in the engagement area of the receiving bore, two ridges that are spaced apart from one another and extend axially. A protrusion of the drive element engages between the ridges for rotational coupling. Furthermore, the two ridges each describe a vent hole on the outer edge.