Power Steering Joint Axial Vibration Control
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Solution Overview
Problem
Conventional power steering apparatuses experience axial vibration and rattling noise due to axial clearance between the external-teeth and internal-teeth members, leading to inefficient transmission of rotational torque and increased noise levels.
Innovation Solution
A power steering apparatus with a joint design that includes a first boss on the motor output shaft and a second boss on the worm shaft, featuring projections for torque transmission and elastic members made of metal and resin/rubber materials to absorb relative displacement and reduce axial vibration, thereby minimizing rattling noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a clearance is provided between the external-teeth member and internal-teeth member in the axial direction, then the joint can accommodate relative displacement and reduce stress concentration, but axial vibration and rattling noise are generated due to axial clearance in bearings
Solution Approach 1:
A damping member is introduced as an intermediary element between the external-teeth member and internal-teeth member. This damping member absorbs axial vibrations and prevents rattling noise while maintaining the necessary clearance for stress accommodation. The damping member acts as a mediator that eliminates the harmful vibration transmission path without compromising the joint's ability to handle relative displacement.
Solution Approach 2:
The axial clearance in the bearing is changed from a fixed value to a variable parameter through the introduction of the damping member. The damping member allows the effective clearance to dynamically adjust based on vibration conditions, absorbing energy during high-vibration states while maintaining proper clearance during normal operation. This parameter transformation resolves the contradiction between needing clearance for durability and preventing noise.
2Object-generated harmful factors
If the axial clearance in bearings is reduced to suppress vibration, then rattling noise is reduced, but the joint cannot accommodate relative displacement effectively, leading to increased stress concentration
Solution Approach 1:
The damping member serves as a mediator that decouples the vibration suppression function from the clearance requirement. It allows the bearing to maintain small axial clearance for vibration suppression while the damping member provides the necessary compliance to accommodate relative displacement between the external-teeth and internal-teeth members, preventing stress concentration.
Solution Approach 2:
The joint structure is segmented into distinct functional zones: the bearing provides precise axial positioning with minimal clearance, while the damping member provides separate compliance for radial and angular displacements. This segmentation allows each component to optimize its function without compromising the other, resolving the contradiction between vibration suppression and stress accommodation.
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 solution effectively reduces axial displacement and vibration between the motor output shaft and worm shaft, suppressing rattling noise and enhancing the durability and efficiency of the power steering system by utilizing elastic members to manage axial loads and maintain torsional rigidity.
Implementation Method 1
a first elastic member disposed between an axial end surface of the first boss and an opposed axial end surface of the second boss which is opposed to the axial end surface of the first boss, the first elastic member being made of a metal material and formed to be elastically deformable in the axial direction the motor output shaft
Implementation Method 2
a second elastic member disposed between the axial end surface of the first boss and the opposed axial end surface of the second boss, the second elastic member being made of at least one of a resin material and a rubber material, the second elastic member cooperating with the first elastic member to generate an elastic force in such a direction as to move the worm shaft away from the motor output shaft
Data Source
AI summary
A power steering apparatus including a joint including a first boss disposed on an axial end portion of a motor output shaft, first projections disposed on the first boss in the circumferential direction, a second boss disposed on an axial end portion of a worm shaft and opposed to the first boss, second projections disposed on the second boss in the circumferential direction and arranged between the adjacent first projections, a first elastic member made of metal and a second elastic member made of at least one of resin and rubber, the first and second elastic members being disposed between an axial end surface of the first boss and an opposed axial end surface of the second boss and cooperating with each other to generate an elastic force in such a direction as to move the worm shaft away from the motor output shaft.