Planetary Roller Screw with Split Nut Preload and Zero Backlash
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Solution Overview
Problem
Existing planetary rolling screw drives are complex and require significant space, making them costly and inefficient for automotive applications such as rear-axle and front-axle steering actuators, where space-saving and cost-effectiveness are critical.
Innovation Solution
A simplified planetary rolling screw drive design featuring axially divided nut parts with coordinated radial play, integrated planetary rollers, and a rotary-driven carrier with adjustable axial preload, eliminating the need for additional components within the carrier for pretensioning, and utilizing support bearings for efficient force transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional planetary roller screw drives are used with preloaded nut components, then zero backlash is achieved, but the device complexity and installation space increase due to additional components like spacers or screw sleeves
Solution Approach 1:
The patent merges the functions of multiple separate components (nut components, spacers, or screw sleeves) into an integrated nut structure where the nut body itself provides the preload mechanism through its geometric design and arrangement on the threaded spindle, eliminating the need for additional pretensioning components within the planetary roller carrier
Solution Approach 2:
The nut structure serves multiple functions simultaneously: it provides the bearing surface for planetary rollers, maintains zero backlash through its geometric configuration on the threaded spindle, and integrates the preload function directly into its structure, making it a multi-functional component that replaces several separate parts
2Reliability
If conventional planetary roller screw drives with multiple components are used, then precise preload is achieved, but the installation space within the planetary roller carrier increases
Solution Approach 1:
The patent combines the preload mechanism and nut structure into a single integrated component that mounts directly on the threaded spindle, eliminating the need for separate spacers or screw sleeves within the planetary roller carrier, thereby reducing the installation space while maintaining precise preload capability
Solution Approach 2:
The patent utilizes the axial dimension of the threaded spindle more efficiently by positioning the nut components at specific axial locations that naturally provide the required preload, eliminating the need for radial or circumferential space-consuming components within the planetary roller carrier
3Reliability
If conventional planetary roller screw drives are used, then zero backlash is achieved, but the manufacturing cost increases due to complex assembly requirements
Solution Approach 1:
The patent integrates the preload function directly into the nut structure, eliminating the need for separate pretensioning components and their complex assembly procedures, thereby reducing manufacturing complexity and cost while maintaining zero backlash performance
Solution Approach 2:
The nut structure is designed with preliminary geometric features that automatically provide the required preload and zero backlash conditions upon installation, eliminating the need for complex adjustment and assembly procedures required by conventional designs with separate spacers or screw sleeves
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 reduces installation space, minimizes component mass, and ensures precise axial preload without additional components, maintaining true pitch and reducing axial play, making it suitable for space-constrained automotive applications.
Implementation Method 1
planetary roller screw drive that converts a rotational movement into a translational movement
Implementation Method 2
planetary rollers arranged between the threaded spindle and the nut... the planetary rollers roll on the threaded spindle and the nut
Data Source
Figure 1~2
Figure 3~5
AI summary
The invention relates to a planetary roller screw having: a nut (2) which is arranged on a threaded spindle (1) and is divided crosswise to the spindle axis into two nut parts (3); planetary rollers (3) arranged between the threaded spindle (1) and the nut (2) distributed over the circumference, which planetary rollers intermesh with the nut parts (3) and with the threaded spindle (1); a rotatingly driven planetary roller carrier (8) arranged on the threaded spindle (1), in pockets (9) of which, arranged distributed over the circumference, the planetary rollers (4) are mounted, held at a distance in the circumferential direction, so as to be rotatable about the planetary roller axis; and a housing (13) in which the planetary roller carrier (8) is rotatably mounted. A pre-loading device (19) is provided in order to adjust an axial pre-load between the housing (13) and the planetary rollers (4).