Steering Apparatus with Mixed-Diameter Ball Screw Elements
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Solution Overview
Problem
Conventional steering apparatuses experience increased steering load and power consumption due to ball clogging in the ball screw mechanism, where adjacent rolling elements contact each other, leading to friction and reduced durability.
Innovation Solution
A steering apparatus with a ball screw mechanism that incorporates large-diameter and small-diameter rolling elements, where the small-diameter elements are disposed between the large-diameter ones, allowing only the large-diameter elements to transmit power at lower loads and both elements to transmit power at higher loads, reducing friction and improving durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If rolling elements are arranged with prescribed intervals in the ball screw mechanism, then smooth rotation with low resistance is achieved, but ball clogging occurs when gap between rolling elements is reduced, leading to increased friction and steering load
Solution Approach 1:
The patent applies parameter changes by varying the diameter of rolling elements. Large-diameter rolling elements are positioned at both ends of the circulation passage where gap reduction occurs, while small-diameter rolling elements are positioned in the intermediate region. This diameter parameter variation prevents ball clogging at critical locations while maintaining smooth rotation elsewhere, thereby reducing steering load without compromising reliability.
2Power
If rolling elements are arranged densely to handle high power transmission, then power transmission capability is improved, but friction increases due to contact between adjacent rolling elements
Solution Approach 1:
The patent applies local quality by creating different rolling element density zones along the circulation passage. The first and second regions at both ends have large-diameter rolling elements that prevent clogging and maintain low friction, while the intermediate region has small-diameter rolling elements that can be arranged more densely to handle higher power transmission demands. This local differentiation allows high power transmission capability without excessive friction losses.
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
This configuration reduces friction and maintains smooth relative rotation between the ball screw portion and nut, minimizing steering load and enhancing durability by adjusting the power transmission based on load conditions.
Implementation Method 1
a first screw groove (21b1) formed on an outer peripheral surface of the rack shaft (21), a second screw groove (33a1) formed on an inner peripheral surface of the ball nut (33a) so as to correspond to the first screw groove (21b1), and a plurality of balls (38) arranged and accommodated in a circulation passage (50)
Data Source
AI summary
A steering apparatus includes a steering shaft; a steered shaft; a ball screw mechanism; and a motor. A plurality of rolling elements includes large-diameter rolling elements and small-diameter rolling elements. A prescribed diameter difference is set such that when a magnitude of power transmitted between a first screw groove and a second screw groove is a prescribed value or less, only the large-diameter rolling elements transmit the power between the first screw groove and the second screw groove, and when the magnitude of the power transmitted between the first screw groove and the second screw groove exceeds the prescribed value, both the large-diameter rolling elements and the small-diameter rolling elements transmit the power.