Preloaded Linear Actuator with Segmented Ball Return
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Solution Overview
Problem
Conventional linear actuator systems for vehicle clutches and brakes, particularly those using the ball-screw principle, face challenges in achieving high precision control, reliability, and cost-effectiveness, especially in heavy-duty applications, due to complex designs and increased maintenance costs.
Innovation Solution
A linear actuator system utilizing a rod and ring configuration with circumferential grooves and balls, where a control unit maintains a constant preload force to ensure balls are always clamped between the rod and ring, allowing for unidirectional actuation and reducing the need for additional components, and incorporating a cage to maintain angular positions of the balls for balanced load transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ball-screw mechanisms are used with additional channels or complex guiding structures, then the balls can be kept in contact and guided back, but the production cost increases and the system becomes more complex
Solution Approach 1:
The invention extracts the ball return function from the nut structure by using a separate return channel that is integrally formed with the rod. This separates the ball circulation path from the load-bearing nut, simplifying the nut structure while maintaining reliable ball contact and return.
Solution Approach 2:
The return channel is integrally formed with the rod, merging the ball return function into the existing rod structure. This eliminates the need for separate ball return mechanisms and reduces overall system complexity while maintaining reliability.
2Device complexity
If the number of balls is dramatically decreased to simplify the ball mechanism, then the guiding groove structure is simplified, but the load transfer to the screw becomes unbalanced
Solution Approach 1:
The invention uses multiple start threads on the rod, segmenting the ball engagement into multiple independent paths. This allows a reduced number of balls to be distributed across multiple threads, maintaining balanced load transfer while simplifying the overall ball mechanism.
Solution Approach 2:
The invention introduces multiple start threads, adding a dimensional aspect to ball engagement. Balls are distributed across multiple helical paths along the rod, enabling balanced load transfer with fewer balls by utilizing the axial dimension of the threads.
3Device complexity
If the stroke for the actuator element is limited by filling the nut thread with a chain of balls, then the ball mechanism is simplified, but the actuator stroke is restricted
Solution Approach 1:
The invention segments the ball mechanism into two independent parts: the nut containing balls for load bearing and the rod with an integrally formed return channel for ball circulation. This segmentation allows the nut to be filled with balls for simplified mechanics while the return channel provides unlimited stroke capability.
Solution Approach 2:
The return channel acts as an intermediary structure that separates the ball circulation function from the load-bearing function. This mediator allows balls to be contained in the nut for simplified mechanics while providing a separate path for ball return that does not restrict actuator stroke.
4Measurement precision
If electric motors are used to replace hydraulic or pneumatic systems, then control precision over actuation force and position is improved, but the transformation of rotational torque to linear force requires additional mechanical components
Solution Approach 1:
The invention replaces complex mechanical transmission systems with a direct ball-screw mechanism driven by the electric motor. The motor's rotational output is directly converted to linear actuation through the ball-screw principle, eliminating the need for additional mechanical transmission components while maintaining high control precision.
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 system provides reliable, high-precision linear actuation with reduced maintenance costs and simplified production, ensuring efficient operation in heavy-duty applications by maintaining continuous load and friction between the balls and components, thus optimizing the ball-screw mechanism for vehicle systems.
Implementation Method 1
the plurality of balls arranged between the ring and the rod to roll along the circumferential groove and the threads to move the other one of the ring and the rod in a longitudinally direction in response to the relative rotation
Implementation Method 2
maintaining continuous load and friction between the balls and components
Implementation Method 3
a control unit (140) configured to control the electric motor (50) to provide a constant preload force (T) acting between the rod (110) and the ring (120) without moving the other one of the ring (120) and the rod (110) in the longitudinally direction
Data Source
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AI summary
A linear actuator system (100) for providing a linear actuator force transferred from an electric motor (50), comprises: a rod (110) with threads (111); a ring (120) with at least one circumferential groove (121) facing the threads of the rod, the ring and the rod being configured to perform a relative rotation to each other, wherein one of the ring and the rod is configured to couple to the electric motor such that the electric motor is able to drive the relative rotation. The system further comprises a plurality of balls (130) arranged between the ring and the rod to roll along the circumferential groove and the threads to move the other one of the ring and the rod in a longitudinally direction in response to the relative rotation; and a control unit (140) configured to control the electric motor to provide a constant preload force acting between the rod and the ring without moving the other one of the ring and the rod in the longitudinally direction.