Worm Gear Bearing Spring Layout for Quiet Steering Preload
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Solution Overview
Problem
Existing electromechanical steering systems suffer from noise due to uneven preload and load distribution in the bearing, leading to potential damage and limited radial travel, which is addressed by a spring element with uniformly distributed force and preload.
Innovation Solution
A spring element with annular base body and spring arms arranged circumferentially, providing uniform preload and load distribution through a rolling bearing, reducing noise and preventing damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a spring-type preload element is used to preload the worm gear bearing, then the bearing is preloaded axially and radially, but the preload is not constant and noise occurs due to friction
Solution Approach 1:
The spring element is divided into multiple spring arms (at least two, preferably three or four) arranged circumferentially around the longitudinal axis. Each spring arm independently contacts the worm wheel at different circumferential positions, distributing the preload force uniformly around the circumference. This segmentation eliminates the tilting moment and friction noise associated with single-element springs while maintaining constant radial preload on the bearing.
Solution Approach 2:
The spring arms are designed with asymmetric geometry relative to the longitudinal axis, with each spring arm having a specific orientation angle. This asymmetric arrangement ensures that the spring arms make contact with the worm wheel at optimally spaced positions, creating uniform radial preload while preventing tilting moments that would cause noise and uneven bearing loading.
2Reliability
If wave springs are used for preloading, then the bearing is preloaded, but a flat (symmetrical) load distribution is not possible and a tilting moment occurs
Solution Approach 1:
The spring element is divided into multiple spring arms (at least two, preferably three or four) arranged circumferentially around the longitudinal axis. Each spring arm independently contacts the worm wheel at different circumferential positions, distributing the preload force uniformly around the circumference. This segmentation eliminates the tilting moment and friction noise associated with single-element springs while maintaining constant radial preload on the bearing.
Solution Approach 2:
The spring arms are positioned and dimensioned to create equipotential load distribution around the bearing. By arranging the spring arms at specific circumferential intervals and orienting them at appropriate angles, the system achieves uniform radial preload at all contact points, eliminating tilting moments and ensuring stable, balanced loading conditions.
3Volume of moving object
If a compact spring design is used, then space is saved, but the radial travel available for achieving a large spring deflection is minimal
Solution Approach 1:
The spring element utilizes the circumferential dimension around the longitudinal axis rather than only radial or axial dimensions. By arranging spring arms circumferentially and allowing them to deflect in multiple directions (radially and circumferentially), the design achieves large effective deflection capacity within a compact radial envelope, solving the space-travel contradiction.
Solution Approach 2:
The spring arms are designed as flexible beam structures with optimized cross-sections that provide high deflection capability in radial and circumferential directions while maintaining minimal radial height. The flexible geometry allows large spring deflection for absorbing axial play and thermal expansion without requiring significant radial space.
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 achieves a quiet operation with improved preload and load distribution, minimizing noise and preventing bearing damage, while allowing for radial movement and compensating for axial play and thermal expansion.
Implementation Method 1
a spring element is arranged in the direction of the longitudinal axis between the inner ring of the second bearing and the worm wheel
Data Source
Figure 1
Figure 2~3
Figure 4~5A
AI summary
An electromechanical steering system for a motor vehicle, with a reduction gear (1) comprising a worm (4) and a worm wheel (3), wherein the worm wheel (3) is rotatably mounted about a longitudinal axis (100) in a gear housing (12) on a first end face in a first bearing (13) and on a second end face in a second bearing (13), wherein the two bearings (13) have an outer ring (15) and an inner ring (14, 140), between which rolling bodies (16) are arranged, wherein the inner rings (14, 140) are non-rotatably arranged on a shaft (2) driven by the worm wheel (3), and the outer rings (15) are located in the gear housing (12), and wherein a spring element (22) is arranged in the direction of the longitudinal axis (100) between the inner ring (140) of the second bearing (13) and the worm wheel (3), the spring element (22) having an at least partially annular main body (220) which, when installed, extends coaxially with respect to the longitudinal axis (100) and from the outer circumferential side (221) of which spring arms (222), which are spaced apart from the longitudinal axis (100), branch off in the circumferential direction, wherein at least one spring arm (222) has a free end (223), and the spring arm comprises a first limb (222a) which points away from the longitudinal axis (100) and a second limb (222b) which runs at least partially parallel to the longitudinal axis (100) and on which the free end (223) is formed.