Elliptical Ball Screw Recirculation Path for Compact Packaging

Solution Overview

Problem

The existing ball screw assemblies in vehicle power steering systems face limitations in packaging and manufacturing due to a large envelope required for the ball recirculation tube, which restricts smaller pitch designs and complicates the manufacturing process with complex geometry, leading to potential interference with adjacent ball tracks.

Innovation Solution

A ball screw assembly with a recirculation path defined by segments of elliptical arcs, where the first and second ellipses are in a common plane, reducing the overall package envelope by incorporating a third segment that deviates from the first ellipse to connect the first and second segments, thereby minimizing the mating envelope and simplifying manufacturing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a traditional ball recirculation tube with elliptical trajectory is used, then noise reduction and functionality are improved, but the packaging envelope becomes large and manufacturing complexity increases

Engineering Contradiction:

ImprovenoiseVSAvoidpackaging envelope

Core Design Contradiction:

Object-affected harmful factorsVSVolume of stationary object

Solution Approach 1:

The recirculation path is divided into multiple segments: a first segment following a first ellipse, a second segment following a second ellipse, and a third segment connecting them. This segmentation allows each segment to be optimized independently, reducing the overall envelope volume while maintaining noise reduction functionality through controlled ball recirculation

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention transitions from a single-plane elliptical recirculation path to a multi-segment path that utilizes multiple planes and dimensions. The third segment connects the first and second elliptical segments in a way that reduces the overall packaging envelope by utilizing spatial arrangement in multiple dimensions rather than confining the entire path to one ellipse

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Object-affected harmful factors

If a traditional ball recirculation tube with elliptical trajectory is used, then noise reduction and functionality are improved, but manufacturing complexity increases due to complex geometry

Engineering Contradiction:

ImprovenoiseVSAvoidmanufacturing process capability

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The recirculation path is divided into multiple segments: a first segment following a first ellipse, a second segment following a second ellipse, and a third segment connecting them. This segmentation allows each segment to be optimized independently, reducing the overall envelope volume while maintaining noise reduction functionality through controlled ball recirculation

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention changes the geometric parameters of the recirculation path by using multiple ellipses with different orientations and dimensions rather than a single ellipse. This parameter change simplifies manufacturing by allowing each segment to be formed with standard machining operations while achieving the desired noise reduction through the multi-segment configuration

Inventive Principle:

Principle #35Parameter changes

3Volume of stationary object

If a smaller pitch design is attempted, then packaging space is reduced, but interference occurs between the ball recirculation path and adjacent ball tracks

Engineering Contradiction:

Improvepackaging envelopeVSAvoidinterference between ball recirculation path and ball tracks

Core Design Contradiction:

Volume of stationary objectVSReliability

Solution Approach 1:

The invention transitions from a single-plane elliptical recirculation path to a multi-segment path that utilizes multiple planes and dimensions. The third segment connects the first and second elliptical segments in a way that reduces the overall packaging envelope by utilizing spatial arrangement in multiple dimensions rather than confining the entire path to one ellipse

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The multi-segment elliptical configuration allows different portions of the recirculation path to be positioned in different spatial locations and orientations. This local optimization ensures that each segment is strategically placed to avoid interference with adjacent ball tracks while maintaining the overall compactness of the design

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS9802640B2Ball screw assembly

Publication Date: 2017.10.31 STEERING SOLUTIONS IP HOLDING CORP

AI summary

A ball screw assembly includes a helical path for a plurality of balls to be routed through, the helical path extending from a first end to a second end. The ball screw assembly also includes a recirculation path extending from a first transition location to a second transition location. The recirculation path includes a first segment defined by a first arc portion of a first ellipse. The recirculation path also includes a second segment defined by a second arc portion of the first ellipse. The recirculation path further includes a third segment defined by an arc of a second ellipse, wherein the first ellipse and the second ellipse are disposed in a common plane.