Keyless Rotation Transfer Unit for Hybrid Starter Generator
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Solution Overview
Problem
Hybrid Electric Vehicles (HEVs) with Transmission Mounted Electric Devices (TMED) face challenges in maintaining pulley toughness due to thermal expansion and belt load, leading to vibrations, reduced durability, and foreign matter introduction, which affects the power transmission and noise generation.
Innovation Solution
A keyless rotation transfer unit is introduced, featuring a spline coupling between the shaft and pulley, and a flange nut screw-fastening mechanism to enhance torque transfer and axial holding force, preventing slip and foreign matter ingress, even after the designed durable period expires.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a key holding force structure is used to connect the shaft and pulley, then the pulley can be firmly fixed initially, but thermal expansion and belt load cause vibrations that reduce durability and form key gaps over time
Solution Approach 1:
The connection between shaft and pulley is segmented into multiple keyways instead of a single key connection. This distributes the holding force across multiple segments, reducing stress concentration and preventing the formation of gaps that would occur with a single key connection under thermal expansion and vibration.
Solution Approach 2:
The flange nut is pre-tightened to apply preliminary compressive force on the pulley before operation begins. This preliminary action ensures that the pulley remains firmly pressed against the shaft even when thermal expansion and vibration occur during operation, preventing the formation of gaps and maintaining connection reliability throughout the service life.
2Reliability
If the pulley is firmly fixed to prevent vibration, then durability is improved, but the structure becomes more complex with additional components
Solution Approach 1:
The flange nut serves multiple functions simultaneously: it secures the pulley to the shaft, applies preliminary compressive force to prevent vibration, and maintains contact pressure during operation. By merging these functions into a single component, the structure achieves high reliability without excessive complexity.
Solution Approach 2:
The multi-keyway structure serves both to transmit torque and to prevent relative motion between shaft and pulley under thermal expansion. This universal design achieves multiple objectives (torque transmission, vibration prevention, gap prevention) through a single integrated connection approach, avoiding the need for separate components for each function.
3Stability of the object's composition
If a bond stiffening layer is applied between bearing and stopper, then initial stability is improved, but thermal expansion causes deeper adverse effects and delamination
Solution Approach 1:
The bond stiffening layer is completely removed from the design. Instead of relying on a adhesive layer that fails under thermal expansion, the patent uses direct mechanical contact and compression through the flange nut to secure the bearing to the stopper, eliminating the thermal expansion compatibility issue entirely.
4Power
If the pulley is designed for high torque and high speed operation, then power transmission capability is improved, but thermal expansion and belt tension cause vibrations and reduce toughness
Solution Approach 1:
The flange nut applies a counteracting compressive force that offsets the destabilizing effects of thermal expansion and belt tension. This counter-force maintains the pulley's structural integrity and prevents vibrations, allowing the pulley to operate at high torque and speed without sacrificing toughness.
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 keyless rotation transfer unit stabilizes torque transfer, maintains robustness under high torque and speed conditions, and prevents foreign matter ingress, ensuring reliable operation and extended durability of the hybrid starter and generator.
Implementation Method 1
a spline configured to form a pulley coupling force between an inner circumference of a shaft hole of a pulley and an outer circumference of a keyless shaft end
Implementation Method 2
a flange nut screw-fastened to the keyless shaft end coming out of the shaft hole and configured to form a screw fastening force to press a first surface of the pulley
Implementation Method 3
the screw fastening force forms a shaft fastening force that causes a bearing to pressurize a second surface of the pulley
Data Source
AI summary
A keyless rotation transfer unit may include a spline forming a pulley coupling force between an inner circumference of a shaft hole of a pulley and an outer circumference of a keyless shaft end forming one end of a shaft, with the keyless shaft end inserted into the shaft hole, and a flange nut screw-fastened to the keyless shaft end coming out of the shaft hole and forming a screw fastening force to press one surface of the pulley. In particular, the screw fastening force forms a shaft fastening force that causes a bearing to pressurize the other surface of the pulley, the bearing is coupled to the keyless shaft end and located at the rear of the pulley, and the flange nut forms a pulley holding force using the screw fastening force and the shaft fastening force.