Vehicle Steering Ball Nut Assembly for Clearance Noise Reduction
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Solution Overview
Problem
The existing steering devices for vehicles, particularly those using a rack-driven power assist or steer-by-wire systems, suffer from noise due to clearances between the ball nut and ball screw, and between the balls and the bearing, which degrade the driver's steering feel.
Innovation Solution
A steering device design that separates the ball nut into two members and uses elastic members between the nut pulley and inner rings to compensate for clearances, minimizing noise and preventing excessive friction by ensuring tight contact between the ball nut and ball screw, and within the bearing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If clearance is provided between balls and bearing components for assembly and rotation, then ease of assembly and rotation is improved, but noise is generated during operation
Solution Approach 1:
The ball nut is divided into a first ball nut member and a second ball nut member, with a bearing disposed between them. This segmentation allows the bearing to be positioned strategically to compensate for clearances between balls and bearing components, reducing noise while maintaining ease of assembly and rotation.
Solution Approach 2:
A bearing is introduced as an intermediary component between the first and second ball nut members. The bearing acts as a mediator that compensates for clearances in the ball-bearin g interface, thereby reducing noise during operation while preserving the necessary clearance for assembly and rotation.
2Ease of manufacture
If clearance is provided between ball nut and ball screw for assembly, then ease of assembly is improved, but noise and friction increase during operation
Solution Approach 1:
The ball nut is segmented into two members with a bearing between them, allowing independent optimization of clearance compensation. This enables the bearing to reduce operational noise and friction while maintaining assembly ease through proper clearance design.
Solution Approach 2:
The invention changes the clearance parameters by introducing a bearing that can compensate for clearances between balls and bearing components. This parameter adjustment reduces noise and friction during operation while preserving ease of assembly.
3Reliability
If tight contact is achieved between ball nut and ball screw, then friction is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The bearing serves as an intermediary that handles the precision requirements for clearance compensation. By placing the bearing between the ball nut members, the invention transfers the precision burden to the bearing assembly, which can more easily compensate for clearances and achieve tight contact, thereby reducing friction while managing manufacturing precision requirements.
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 effectively mitigates noise and enhances the driver's steering feel by compensating for clearances and reducing friction, improving the overall steering experience, especially in autonomous vehicles.
Implementation Method 1
a first elastic member provided between the nut pulley and the first inner ring, and a second elastic member provided between the step jaw and the second inner ring
Data Source
AI summary
According to the embodiments, it is possible to mitigate noise by compensating for the clearance inside the bearing supporting the rotation of the ball nut and the clearance between the ball nut and the ball screw and prevent excessive friction between the ball nut and the ball screw and inside the bearing to thereby allow the driver a better steering feel.