Steer-By-Wire Coupling Rod Bearing for Thermal Backlash Control
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Solution Overview
Problem
Steer-by-wire steering systems lack an effective anti-twist protection mechanism for the coupling rod, as the traditional rack-and-pinion steering gear is absent, necessitating a new solution to prevent torsion.
Innovation Solution
A steering gear with a coupling rod mounted in a housing and equipped with a plain bearing that compensates for thermal expansions, featuring a spiral gear and a plain bearing bushing made of materials like POM or PA66GF30, which adjusts backlash for optimal tribological and acoustic performance, and forms an anti-twist device with the steering gear housing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rack-and-pinion steering gear is used, then anti-twist protection is provided through the pressure piece mechanism, but the system cannot be applied to steer-by-wire steering systems which lack a rack-and-pinion mechanism
Solution Approach 1:
The patent introduces a pressure piece as an intermediary element that directly contacts the coupling rod to provide anti-twist protection. This pressure piece acts as a mediator between the control system and the coupling rod, applying controlled force to prevent torsion without requiring a rack-and-pinion mechanism, thus enabling steer-by-wire system compatibility
Solution Approach 2:
The patent replaces the traditional rack-and-pinion mechanical steering mechanism with an electrically controlled actuator system. The anti-twist protection function is maintained through a simplified pressure piece mechanism that directly engages with the coupling rod, substituting the complex rack-and-pinion interaction with a more adaptable electronic-mechanical hybrid system
2Reliability
If thermal expansion is not compensated, then the structure remains simple, but backlash varies with temperature affecting tribological and acoustic performance
Solution Approach 1:
The patent utilizes the thermal expansion principle by designing the pressure piece with specific material properties and geometric features that allow it to expand or contract with temperature changes. This automatic thermal compensation maintains consistent backlash and contact pressure across temperature ranges, ensuring stable tribological and acoustic performance without complex active control systems
Solution Approach 2:
The patent employs parameter changes in the pressure piece design, including material selection with appropriate thermal expansion coefficients and geometric parameters that vary with temperature. These parameter variations automatically adjust the backlash and contact conditions to maintain optimal performance across different operating temperatures
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 protects the coupling rod against torsion, maintains optimal performance across temperature ranges, and provides an emergency run function, ensuring reliable operation and vibration damping.
Implementation Method 1
the plain bearing is configured to compensate for thermal expansions between the steering gear housing and the spindle nut
Implementation Method 2
the coupling rod is mounted in the steering gear housing by means of a plain bearing so as to be displaceable along a longitudinal axis
Data Source
AI summary
A steering gear for a steer-by-wire steering system of a motor vehicle may include a coupling rod mounted in a steering gear housing. A threaded spindle may be formed on the coupling rod and surrounded by a spindle nut as part of a spiral gear. The coupling rod may be displaceable along a longitudinal axis by way of the spiral gear. The coupling rod can be mounted in the steering gear housing by way of a plain bearing so as to be displaceable along the longitudinal axis. The plain bearing is configured to compensate for thermal expansions between the steering gear housing and the spindle nut.