Planetary Roller Screw Telescopic Spindle With Slip-Free Tooth Meshing
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Solution Overview
Problem
Existing planetary roller screw drives for telescopic spindles suffer from slippage issues that lead to inaccuracies in positioning due to varying speeds between the spindle and ring gear sleeve, making them unsuitable for precise actuation.
Innovation Solution
A planetary roller screw design with a rotatably mounted spindle, a non-rotatable ring gear axially displaceable within a housing, and a nut also axially displaceable relative to the ring gear, featuring external teeth that prevent slippage and allow for relative axial displacement, enabling a compact telescopic spindle configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If planetary rollers roll on the spindle and ring gear sleeve with different speeds depending on diameter ratios, then synchronous lifting movement is achieved, but pitch differences produce slippage that leads to positioning inaccuracies
Solution Approach 1:
The patent replaces the traditional rolling contact mechanism with a meshing tooth engagement mechanism. The external teeth on the spindle and planetary rollers, along with the internal teeth on the ring gear sleeve, create a positive engagement system that eliminates slippage by converting the rolling friction-based transmission into a tooth-meshing mechanical transmission, ensuring precise positioning without pitch differences.
Solution Approach 2:
The patent introduces external teeth with specific tooth counts (spindle: 20 teeth, planetary rollers: 10 teeth, ring gear sleeve: 40 teeth) to change the transmission parameters. This tooth-based parameter system replaces the diameter ratio-based rolling system, creating fixed mechanical relationships that prevent slippage while maintaining the synchronous lifting function.
2Measurement precision
If external teeth are introduced on the spindle and planetary rollers, then slippage is prevented and positioning accuracy is improved, but the device complexity increases
Solution Approach 1:
The external teeth on the planetary rollers serve multiple functions simultaneously: they prevent slippage during rotation, enable axial displacement through the overlapping section design, and maintain the lifting function. This multi-functionality reduces the need for separate components, thereby limiting the increase in device complexity despite the added precision mechanism.
Solution Approach 2:
The patent merges the threading function and toothing function into a single integrated component structure. The external teeth are introduced into the external thread of the spindle and planetary rollers, creating an overlapping section where both functions coexist, eliminating the need for separate threaded and geared components.
3Volume of moving object
If the planetary roller screw is designed for compact telescopic configuration, then space is reduced, but relative axial displacement between spindle and planetary rollers must be enabled
Solution Approach 1:
The patent creates a dynamic axial displacement capability through the overlapping section design. The external teeth and external threads are arranged to overlap axially, allowing the planetary rollers to move axially relative to the spindle while maintaining engagement. This dynamic configuration enables telescopic extension and retraction without requiring excessive space, as the displacement occurs within the existing component envelope.
Solution Approach 2:
The telescopic spindle design nests the planetary rollers within the annular space between the spindle and ring gear sleeve. The compact arrangement allows the planetary rollers to be positioned axially within this nested configuration, enabling telescopic movement while maintaining a compact overall volume. The overlapping tooth and thread sections allow axial displacement within this nested structure.
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 solution reduces slippage and allows for precise positioning, enabling the use of planetary roller screws as compact telescopic spindles with improved accuracy and a larger adjustment range.
Implementation Method 1
the external teeth of the spindle meshing with the external teeth of the planetary rollers
Implementation Method 2
a set of planetary rollers rolls on the one hand on a central spindle and on the other hand on an internal thread of a ring gear sleeve
Data Source
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AI summary
The present invention relates to a planetary roller screw drive with a spindle having an external thread, a screw nut with an internal thread, and with planetary rollers arranged between the spindle and the screw nut, each having an external thread that engages with both the external thread of the spindle and the internal thread of the screw nut, wherein both the spindle and the planetary rollers furthermore each have external teeth, and wherein the external teeth of the spindle mesh with the external teeth of the planetary rollers.According to the invention, the external teeth of the spindle are inserted into the external thread of the spindle and/or the external teeth of the planetary rollers are inserted into the external thread of the planetary rollers, so that the spindle and/or planetary rollers have a superimposed section in which the respective external thread and the respective external teeth overlap, such that a relative axial displacement between the spindle and the planetary rollers is possible.