Coned Disc Spring Restriction for Steering Device Lifespan
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Coned disc springs in electric power steering devices face premature deformation due to excessive stress when deformed into a closely contacting state, leading to reduced lifespan.
Innovation Solution
A steering device configuration that includes a coned disc spring elastically supporting a ball screw mechanism's nut, with a restriction portion preventing the spring from reaching a closely contacting state, thereby reducing stress and extending its lifespan. This is achieved through a bearing and plate arrangement that restricts the spring's warp, using tapered surfaces for surface contact to distribute stress evenly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the coned disc spring is allowed to deform freely without restriction, then the steering operation resistance is reduced and smooth steering feeling is obtained, but the spring deforms into a closely contacting state causing excessive stress and shortened lifespan
Solution Approach 1:
The restriction portion is designed to prevent the coned disc spring from deforming into the closely contacting state before excessive stress can occur. By establishing a physical limit on the spring's deformation range, the restriction portion counteracts the tendency toward over-compression, thereby extending the spring's operational life while maintaining smooth steering operation.
Solution Approach 2:
The restriction portion acts as an intermediary element between the coned disc spring and the surrounding structure. It mediates the deformation process by providing a controlled stopping point, allowing the spring to deform sufficiently for smooth operation while preventing further deformation that would cause excessive stress and premature failure.
2Force
If the coned disc spring is deformed into a closely contacting state, then the elastic support force is maximized, but excessive stress is applied to the spring reducing its life
Solution Approach 1:
The restriction portion preemptively prevents the spring from reaching the closely contacting state by providing a physical barrier. This preliminary action ensures that the spring maintains optimal elastic support force without undergoing deformation that would generate excessive stress and compromise reliability.
Solution Approach 2:
The restriction portion modifies the deformation parameter range of the coned disc spring. By limiting the maximum compression distance, it changes the operational parameters to keep the spring within a safe stress range while maintaining sufficient elastic support force for proper steering operation.
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 configuration extends the life of the coned disc spring by preventing excessive stress and maintaining a higher allowable stress, allowing for a more rigid steering feel and suppressing displacement in the radial direction.
Implementation Method 1
a coned disc spring that elastically supports the nut in the axial direction of the steered shaft when the nut is relatively moved with respect to the housing in the axial direction of the steered shaft
Implementation Method 2
using tapered surfaces for surface contact to distribute stress evenly
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A steering device includes a ball screw mechanism 8 that applies a force in the axial direction to a rack shaft of a vehicle, and a bearing 20 that rotatably supports a nut 80 with respect to a housing 10. The steering device also includes a plate 31 disposed with a gap between the bearing 20 and the plate 31 in a rack shaft axial direction ZA, and a coned disc spring 32 disposed between the bearing 20 and the plate 31. The plate 31 abuts against the housing 10 in the rack shaft axial direction ZA. The coned disc spring 32 elastically supports the nut 80 in the rack shaft axial direction ZA via the bearing 20. One side surface 31c of the plate 31 that faces the coned disc spring 32 is formed in a tapered shape so as to cross a rack shaft radial direction ZB.