Planetary Roller Screw Preload Structure for Low-Play Assembly
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Solution Overview
Problem
Existing planetary roller screws require complex installation processes and significant space for achieving freedom from play, which is a challenge in cost-effective and space-constrained automotive applications, particularly in front-axle and rear-axle steering systems.
Innovation Solution
A planetary roller screw design featuring axially divided nut parts with interlocking sleeve-like extensions and a pre-loading device that adjusts axial play without additional components within the roller carrier, utilizing support bearings to achieve axial pre-load and reduce installation space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If spacer or screw sleeves are installed to achieve freedom from play between nut parts, then radial alignment and fit of nut parts are improved, but device complexity and installation space requirements increase
Solution Approach 1:
The patent merges the alignment function into the nut parts themselves through interlocking sleeve-like extensions. The extensions protrude from one nut part and engage with corresponding recesses in the other nut part, creating automatic radial alignment when the nut parts are assembled. This eliminates the need for separate spacer components or screw sleeves, reducing device complexity while maintaining precise radial alignment and freedom from play between the nut parts.
2Manufacturing precision
If complex measures like spacers or screw sleeves are used to eliminate play, then freedom from play in engagement is achieved, but installation space within planetary roller carrier increases
Solution Approach 1:
The alignment function is merged into the nut parts themselves through interlocking sleeve-like extensions. These extensions are integrated directly into the nut part structure, eliminating the need for separate spacer components or screw sleeves that would occupy additional installation space within the planetary roller carrier. The extensions create automatic radial alignment and freedom from play while minimizing space requirements.
Solution Approach 2:
The sleeve-like extensions are designed to nest within each other when the nut parts are assembled. The extensions protrude from one nut part and engage with corresponding recesses in the other nut part, creating a nested configuration that achieves radial alignment and freedom from play while occupying minimal installation space within the planetary roller carrier.
3Manufacturing precision
If additional components are used to connect nut parts, then radial alignment and fit are improved, but ease of manufacture decreases
Solution Approach 1:
The alignment function is merged into the nut parts themselves through interlocking sleeve-like extensions. This integration eliminates the need for separate alignment components, reducing the total number of parts that need to be manufactured, inventoried, and assembled. The extensions are formed as integral parts of the nut components, simplifying the manufacturing process while ensuring precise radial fit and alignment.
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 design simplifies manufacturing, reduces installation space, and allows for efficient axial pre-loading, making it suitable for cost-effective and space-saving applications in motor vehicle steering systems while maintaining pitch-true performance.
Implementation Method 1
planetary rollers arranged between the threaded spindle and the nut, which intermesh with their planet-side groove profile on the one hand with a groove profile on the nut side and on the other hand with a thread profile of the threaded spindle
Implementation Method 2
threaded spindle with a thread profile, wherein the planetary rollers intermesh with the thread profile
Implementation Method 3
The two nut parts can have sleeve-like extensions facing one another that are coaxial with the nut parts and interlock with little radial play, i.e., overlap one another other axially
Implementation Method 4
One complete revolution of the planetary roller carrier is equivalent to a spindle feed corresponding in its amount to the pitch of the thread of the threaded spindle
Data Source
AI summary
The disclosure relates to a planetary roller screw having: a nut arranged on a threaded spindle and divided crosswise to a spindle axis into two nut parts; planetary rollers arranged between the threaded spindle and the nut distributed over the circumference, the planetary rollers intermeshing with the nut parts and with the threaded spindle; a rotatingly driven planetary roller carrier arranged on the threaded spindle, in pockets of which, arranged distributed over the circumference, the planetary rollers are mounted, held at a distance in the circumferential direction, so as to be rotatable about the planetary roller axis; and a housing in which the planetary roller carrier is rotatably mounted. A pre-loading device is provided in order to adjust an axial pre-load between the housing and the planetary rollers.