Rack-and-pinion steering backlash noise reduction
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Solution Overview
Problem
Rack and pinion steering systems experience disruptive operating noises due to excessive radial play and backlash in the toothing, particularly when driving over obstacles, which is caused by the superelevation of the profile reference line decreasing towards the axial ends.
Innovation Solution
The profile reference line of the rack's toothing is designed with a superelevation from its center to the axial ends to minimize backlash in the outer areas, allowing for minimal radial play without jamming, and this design can be overcome by wheel restoring forces or an actuator, maintaining normal steering behavior.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the profile reference line superelevation decreases towards the axial ends to prevent tooth binding, then the teeth are prevented from binding at outer edges, but radial play and backlash increase causing rattling noise
Solution Approach 1:
The patent applies local quality by differentiating the superelevation behavior in different regions of the rack teeth. The profile reference line has increased superelevation towards the axial ends specifically in the outer toothing areas, while maintaining appropriate superelevation characteristics in the central region. This localized modification minimizes backlash where it matters most (at the ends) without causing binding in the central region.
Solution Approach 2:
The patent changes the geometric parameters of the tooth profile by modifying the superelevation characteristics of the profile reference line. Specifically, the superelevation is increased towards the axial ends of the rack teeth, which alters the contact mechanics between the pinion and rack. This parameter change reduces backlash in the outer areas while preventing binding, thereby eliminating rattling noise during operation.
2Object-generated harmful factors
If the profile reference line superelevation is increased towards the axial ends to minimize backlash, then radial play is minimized reducing noise, but jamming or blocking may occur
Solution Approach 1:
The patent applies local quality by implementing increased superelevation specifically in the outer toothing areas rather than uniformly across the entire rack. This localized approach minimizes backlash and radial play in the regions where it causes noise, while preserving sufficient clearance in the central region to prevent jamming during normal steering operations.
Solution Approach 2:
The patent applies partial action by increasing superelevation only in the outer areas of the rack teeth where backlash primarily occurs, rather than applying it uniformly across the entire tooth profile. This partial modification is sufficient to reduce noise without creating excessive clearance reduction that would lead to jamming, thus achieving the optimal balance.
Data Source
Figure 1~2
Figure 3~4
AI summary
The invention relates to a rack-and-pinion steering (1), in particular for a motor vehicle, with a steering-gear housing (2) and a pinion (3) which is mounted in the steering-gear housing (2), and with a rack (4) which, by means of its toothing (5), forms a gear train together with the pinion (3) and is held in an axially displaceable manner in the steering-gear housing (2). In order to provide a rack-and-pinion steering in which annoying operating noises are avoided, it is provided that the profile reference line (6) and/or the head line (7) of the toothing (5) of the rack (4) has a camber (h) from its centre (8) to its axial ends (9, 9').