Double-Helical Gearset Axial Load Cancellation
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Solution Overview
Problem
Current electric drive units using helical gears face axial loading issues, which limit the helix angle and increase noise, vibration, and harshness (NVH) concerns, as well as bearing losses due to the need for bearings to withstand axial forces.
Innovation Solution
The implementation of a double-helical gearset with axially movable components and a planetary gearset that allows self-centering, reducing axial loads by canceling out axial forces through opposing helices and using nested bearings to minimize bearing losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If helical gears are used to reduce NVH concerns, then noise and vibration are reduced, but axial loading increases on rotating components
Solution Approach 1:
The gear is segmented into two helical sections (right-hand helix and left-hand helix) with opposite helical directions. Each helix segment generates axial forces in opposite directions, causing the axial loads to cancel each other out while maintaining the noise and vibration reduction benefits of helical engagement.
2Object-affected harmful factors
If helix angle is increased to improve NVH performance, then noise and vibration reduction improves, but axial forces exerted on gears increase
Solution Approach 1:
The gear employs asymmetric helical configurations with opposite hand directions (right-hand and left-hand helices) arranged symmetrically in terms of load cancellation but asymmetric in terms of individual helix geometry. This allows each helix to operate at optimized angles for NVH performance while the combined configuration cancels axial forces.
3Force
If bearings are designed to withstand axial forces from helical gears, then axial load capacity is improved, but bearing losses increase
Solution Approach 1:
The axial forces that would normally be harmful to bearing performance are converted into a beneficial self-centering mechanism. The opposing axial forces from the double-helical configuration create a centering effect that maintains optimal gear alignment and reduces bearing loads, thereby reducing bearing losses while maintaining axial load capacity.
4Object-affected harmful factors
If double-helical gearset with self-centering is implemented, then axial loads are reduced and NVH improves, but device complexity increases
Solution Approach 1:
The patent merges multiple functions into the single double-helical gear structure: noise and vibration reduction, axial load cancellation, and self-centering capability are all achieved within one integrated gear component rather than requiring separate mechanisms for each function.
Data Source
AI summary
An electric drive unit includes an electric motor, a differential assembly, and a double-helical gearset positioned between and interconnecting the electric motor and the differential assembly and adapted to transfer rotational motion from the electric motor to the differential assembly, the double-helical gearset including a driving double-helical gear rotationally mounted onto a transfer shaft of the electric motor and including a right-hand helix, a left-hand helix and a gap extending circumferentially between the right-hand helix and the left-hand helix, and a driven double-helical gear rotationally mounted onto a housing of the differential assembly and including a right-hand helix, a left-hand helix and a gap extending circumferentially between the right-hand helix and the left-hand helix, and a park gear positioned within the gap between the right hand helix and the left hand helix of one of the driving double-helical gear and the driven double-helical gear, wherein one of the driving double-helical gear and the driven double-helical gear is axially moveable.