Power Steering Ball Nut Damping for Noise Reduction
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Solution Overview
Problem
Existing power steering systems with electromotive servo drives experience noise and wear due to metallic contact between the ball nut and the frame, primarily because conventional bearings are designed for radial forces rather than axial loads, leading to mechanical play and distortion under thermal expansion.
Innovation Solution
A power steering system design featuring a ball nut with a narrow axial web and a plastic damping element that prevents direct metallic contact, allowing the bearing to tilt and use damping inserts to reduce noise, with axial support provided by damping elements in grooves within the frame, avoiding metallic contact and enabling relative movement between the bearing and frame.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional bearings are used to support the ball nut, then radial forces are accommodated, but axial loads cause noise and wear due to metallic contact
Solution Approach 1:
A plastic damping element is introduced as an intermediary between the bearing outer ring and the frame. This damping element prevents direct metallic contact between the bearing and frame, thereby eliminating noise and wear while still supporting the ball nut under axial loads. The plastic material absorbs vibrations and provides continuous contact without the harmful effects of metal-on-metal friction.
Solution Approach 2:
The bearing support structure is modified by changing the material parameter from metal to plastic for the damping element. This material parameter change transforms the contact interface from a hard, noisy metallic contact to a softer, vibration-absorbing plastic contact that dampens noise and wear while maintaining load-bearing capability.
2Stability of the object's composition
If the bearing is rigidly mounted in the frame, then structural stability is maintained, but thermal expansion causes mechanical play and distortion
Solution Approach 1:
The bearing mounting is transformed from a rigid, fixed connection to a dynamic, compliant connection through the plastic damping element. This damping element allows controlled movement and deformation in response to thermal expansion, enabling the bearing to adapt its position while maintaining stable support. The plastic material's viscoelastic properties provide continuous adjustment to dimensional changes without creating mechanical play.
3Object-affected harmful factors
If damping elements are added to prevent metallic contact, then noise is reduced, but device complexity increases
Solution Approach 1:
The damping function is merged directly into the bearing mounting structure by integrating the plastic damping element as part of the bearing assembly. Rather than adding separate, complex damping mechanisms, the damping functionality is combined with the existing bearing outer ring, creating a unified component that provides both support and noise reduction in a single integrated element.
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 noise and wear by preventing metallic contact, providing durable and quiet operation while maintaining structural integrity under varying loads, and compensating for thermal expansion without compressing the damping elements beyond their limit.
Implementation Method 1
a plastic damping element that prevents direct metallic contact between the bearing and the frame, particularly good noise damping can be achieved
Implementation Method 2
a ball nut (1) which surrounds a lead screw (2) and engages with the lead screw (2) in such a way that rotation of the ball nut (1) displaces the lead screw (2) in the axial direction
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The invention relates to a power steering system, in particular for a motor vehicle, having a servomotor which drives an axially displaceable component via a nut (1) which is mounted in a frame (3) such that it can be rotated in a bearing (4, 5), wherein the nut (1) is in engagement with a threaded spindle (2) formed on the component and is supported in the axial direction elastically by means of spring elements (14) with respect to the frame and in the radial direction along a narrow circumferential contact surface on the frame (3), wherein the bearing (4, 5) is in contact on the outer circumferential surface of the outer ring (4) with the frame (3) on the contact surface via a web, and wherein a plastic element (7) which prevents a direct metallic contact between the bearing (4, 5) and the frame (3) is provided in the region of the web.