Planetary Screw Drive Actuator with Non-Rotating Roller Carrier
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Solution Overview
Problem
Existing planetary screw drive systems are complex and inefficient due to pitch changes caused by slip, requiring expensive sensor technology for precise positioning.
Innovation Solution
A planetary screw drive actuator with non-rotatingly supported planetary roller carriers and a spring assembly, allowing for slip-independent pitch and eliminating the need for distance sensors by using a rotational angle sensor and motor characteristic curve for positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional planetary screw drive systems are used with movable nut parts for pre-stressing, then pre-tensioning can be realized, but the system becomes complex and requires distance sensors for exact positioning due to pitch changes from slip
Solution Approach 1:
The patent extracts the pre-stressing function from the nut and places it in a separate pre-stressing device that acts on the planetary rollers. This separation eliminates the complexity of having a multi-functional nut while maintaining positioning accuracy without requiring distance sensors
Solution Approach 2:
The ring gear serves multiple functions: it transmits motion from the planetary rollers, provides mounting for the pre-stressing device, and enables precise positioning through its engagement with the spindle. This multi-functionality reduces overall system complexity while maintaining reliability
2Measurement precision
If distance sensors are used to register slip and maintain positioning accuracy, then exact positioning can be achieved, but the system becomes more complex and expensive
Solution Approach 1:
The patent replaces the need for electronic distance sensors with a mechanical pre-stressing system that maintains zero pitch change. The pre-stressed planetary rollers eliminate slip between the spindle and ring gear, making distance sensors unnecessary for positioning accuracy
Solution Approach 2:
The pre-stressing device automatically maintains the correct preload on the planetary rollers through its spring element, creating a self-regulating system that prevents slip without requiring external sensing or control systems
3Reliability
If sticking occurs between spindle and planetary rollers, then no axial movement occurs during rotation, but 100% slip must be registered and efficiency drops to zero
Solution Approach 1:
The pre-stressing device applies preliminary force to the planetary rollers before operation, ensuring they maintain continuous contact with the spindle. This preliminary action prevents sticking during rotation, eliminating the need to register slip and maintaining high efficiency
4Manufacturing precision
If sticking occurs between planetary rollers and ring gear nut, then 1:1 spindle pitch is achieved, but 100% slip occurs between planetary rollers and spindle and efficiency becomes very low
Solution Approach 1:
The pre-stressing device changes the contact parameters between the planetary rollers and both the spindle and ring gear. By optimizing the preload force, the system achieves both accurate pitch transmission and minimal slip, resolving the contradiction between precision and efficiency
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 solution simplifies the actuator design, maintains high efficiency, and eliminates the need for distance sensors, enabling precise axial positioning without slip-induced pitch changes.
Implementation Method 1
the pre-stressing device has a spring element that is spring loaded against the one nut part
Data Source
AI summary
An actuator with a planetary screw drive (PSD), in particular to operate a clutch of a vehicle, wherein a centric spindle having a pitch is connected non-rotatingly to a rotor of a drive and is drivable by the drive around an axis of rotation, and a plurality of planetary rollers are engaged with the spindle and mesh with a ring gear encircling the planetary rollers which has grooves in the circumferential direction, wherein both ends of the planetary rollers are positioned in a planetary roller carrier. The planetary roller carriers are supported non-rotatingly on both ends in such a way that a fixed assignment of the pitch of the spindle to an axial travel of a component that is movable axially by the PSD, which is operatively connected to an axially actuatable piston, is realized.