Steering Column Worm-Damper Assembly for Gear Rattle Reduction
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Solution Overview
Problem
Steer-by-wire systems experience gear rattle and acoustic noise due to torque reversals, which existing technologies fail to adequately address, particularly when the motor direction is reversed, and there is a need for a compact solution that provides consistent driver feedback.
Innovation Solution
A steering column assembly with a viscous damper and a second worm screw engaged with the gear, which provides passive feedback torque and reduces noise by using a fluid chamber with damping fluid and a body with projections, and a spring to bias the worm screw, ensuring engagement with the gear and reducing backlash.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a motor is used to provide feedback torque in steer-by-wire systems, then driver road feel is improved, but gear rattle and acoustic noise increase during torque reversals
Solution Approach 1:
The spring-loaded second worm screw is pre-positioned to engage with the gear before torque reversal occurs. The spring maintains constant pressure on the worm screw, ensuring it remains in contact with the gear teeth, thereby preventing backlash and noise during direction changes.
Solution Approach 2:
The second worm screw acts as an intermediary element between the gear and the housing. By engaging with the gear and being biased by the spring, it mediates the torque transmission and prevents direct impact between the gear and housing during reversals, reducing acoustic noise.
2Object-generated harmful factors
If the worm screw is always engaged with the gear to reduce rattle, then noise is reduced, but the system complexity increases
Solution Approach 1:
The second worm screw assembly is integrated into the existing motor assembly structure. The spring-loaded mechanism is combined with the motor housing and gear assembly, creating a unified structure that maintains worm-gear engagement without requiring separate noise reduction components.
3Ease of operation
If a compact motor assembly is used, then ease of fitting in vehicle is improved, but space for additional noise reduction components is reduced
Solution Approach 1:
The second worm screw serves multiple functions simultaneously: it maintains gear engagement to prevent rattle, provides passive feedback torque through spring pressure, and acts as a mechanical stop during torque reversals. This multi-functionality eliminates the need for separate noise reduction components, maintaining compact dimensions.
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 gear rattle and acoustic noise, provides consistent driver feedback, and ensures the worm screw remains engaged with the gear, even during torque reversals, enhancing the overall steering experience and system reliability.
Implementation Method 1
a damper (460) configured to provide a passive feedback torque to the steering column (414)
Implementation Method 2
the steering column assembly may further comprise biasing means configured to urge the second worm screw towards contact with the gear connected to the steering column
Data Source
AI summary
A steering column assembly for a vehicle includes an elongate steering column mounted for rotation about its longitudinal axis and configured for attachment of a steering wheel at one end. A gear is connected to the steering column at a location spaced from the steering wheel attachment location and configured to rotate with the steering column. A motor has a rotatable output shaft. A first worm screw is directly connected to and rotatable with the output shaft of the motor and engaged with the gear. A damper includes a rotatable shaft. A second worm screw is directly connected to and rotatable with the shaft of the damper and engaged with the gear. A control means is configured to operate the motor.