Polymer EPS Drive Pulley with Splined Shaft Retention
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Solution Overview
Problem
Existing electric power steering systems require costly post-processing and assembly methods for drive pulleys made from sintered iron, which rely on friction for torque transmission, increasing material and assembly costs.
Innovation Solution
A polymer drive pulley assembly with a radial and axial retention portion, featuring a splined engagement and arcuate portions with slots for flexibility, allowing for a press-fit or slip-fit assembly with a motor shaft, reducing material costs and simplifying the assembly process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If sintered iron is used to make the drive pulley, then the torque transmission capability is improved, but the material cost and assembly complexity increase
Solution Approach 1:
The invention changes the material parameter from sintered iron to polymer material, and changes the connection parameter from interference fit to splined engagement with press-fit or slip-fit assembly, thereby reducing material cost and assembly complexity while maintaining torque transmission capability
Solution Approach 2:
The invention uses polymer material which is cheaper than sintered iron to manufacture the drive pulley, reducing material cost without significantly compromising the functional life of the component in the steering system
2Strength
If interference fit is used to assemble the drive pulley to the motor shaft, then the torque transmission is improved, but the assembly process complexity increases
Solution Approach 1:
The invention segments the connection interface into splines on the motor shaft that engage with corresponding splines in the drive pulley's axial retention portion, replacing the monolithic interference fit with a modular splined engagement that simplifies assembly
Solution Approach 2:
The invention introduces flexibility to the axial retention portion through arcuate portions and slots, allowing dynamic adjustment during assembly to accommodate misalignment and simplify the assembly process while maintaining secure connection
3Strength
If a press machine is used to assemble the drive pulley, then the assembly strength is improved, but the equipment cost and assembly time increase
Solution Approach 1:
The splines are pre-formed on the motor shaft and the corresponding engagement features are pre-formed in the drive pulley during manufacturing, allowing for simplified assembly that does not require complex press machining operations, thereby reducing assembly time and equipment cost
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 polymer drive pulley assembly reduces material and assembly costs while maintaining effective torque transmission, offering a cost-effective and efficient solution for electric power steering systems.
Implementation Method 1
Some assist mechanisms include a pulley assembly that is actuated by the transfer of rotation from the motor shaft to a drive pulley that, in turn, drives rotation of one or more pulleys via one or more belts
Implementation Method 2
The radial retention portion transmitting a radial load of the belt to the motor shaft
Implementation Method 3
the axial retention portion including a flange protruding radially inwardly from the inner diameter of the axial retention portion to be disposed in a groove of the motor shaft to axially retain the drive pulley relative to the motor shaft
Data Source
AI summary
An electric power steering drive pulley assembly includes a motor shaft. The pulley assembly also includes a drive pulley coupled to the motor shaft. The drive pulley includes a radial retention portion having an inner diameter defining a first portion of a central opening that the motor shaft is disposed within. The drive pulley also includes an axial retention portion extending in the axial direction from the radial retention portion, the axial retention portion defining a second portion of the central opening that the motor shaft is disposed within, the inner diameter of the axial retention portion in splined engagement with the motor shaft to rotationally couple the drive pulley to the motor shaft, the axial retention portion including a flange protruding radially inwardly from the inner diameter of the axial retention portion to be disposed in a groove of the motor shaft.