Automatic Gearbox Actuator With Anti-Rotation Magnet Alignment
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Solution Overview
Problem
Existing actuating devices for automated manual transmissions face challenges in maintaining precise alignment of magnetic field-sensitive sensors with magnets, leading to impaired measuring accuracy due to potential rotational movements of the piston and holding device about the longitudinal center axis, especially under temperature fluctuations and vibrations.
Innovation Solution
Incorporation of a rotatably connected anti-rotation element with a hollow cylindrical geometry, which prevents self-rotation of the holding device and magnet, ensuring the magnet remains aligned with the sensor while allowing axial movement, using a combination of longitudinal ribs and a trapezoidal anti-rotation element with slight play to facilitate smooth axial displacement and minimize friction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the magnet is mounted on the piston without anti-rotation constraints, then the piston can move coaxially freely, but the magnet may rotate about the longitudinal center axis causing impaired sensor alignment and measuring accuracy
Solution Approach 1:
The holding device acts as an intermediary component between the piston and the magnet. It provides rotational constraint through its specific geometry (longitudinal ribs or asymmetric features) while allowing free axial movement of the piston. This mediator structure solves the contradiction by preventing magnet rotation without restricting the necessary piston motion.
Solution Approach 2:
The holding device is segmented into functional elements: a body portion that allows axial movement and constraint features (such as longitudinal ribs or asymmetric geometries) that prevent rotation. This segmentation enables independent control of translational and rotational degrees of freedom, resolving the contradiction between free movement and rotational prevention.
2Measurement precision
If the holding device uses strong mechanical constraints to prevent rotation, then magnet alignment is maintained, but friction increases and axial movement becomes less smooth
Solution Approach 1:
The holding device applies local quality differentiation: the contact surfaces for axial movement are designed with low friction characteristics, while the anti-rotation features (such as longitudinal ribs or asymmetric geometries) provide precise rotational constraint only in the radial direction. This localized differentiation of constraints allows smooth axial movement while maintaining magnet alignment.
3Measurement precision
If the magnet position is constrained rigidly to prevent rotation, then alignment accuracy is maintained, but mechanical stress and wear increase
Solution Approach 1:
The holding device provides dynamic constraint: it allows the piston to move axially freely while maintaining rotational constraint of the magnet. The constraint mechanism adapts to the motion requirements, providing rotation prevention only when necessary for alignment, while allowing axial movement without resistance. This dynamic approach reduces mechanical stress and wear compared to rigid constraints.
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 ensures precise axial position measurement of the piston without contact, reduces wear, and integrates easily into existing constructions, maintaining accurate sensor alignment and reducing mechanical stress, thus enhancing the reliability and efficiency of the actuating device.
Implementation Method 1
a sensor arrangement with a magnet and a magnetic field-sensitive sensor is provided
Data Source
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AI summary
The invention relates to an operating device (10) for an automatic gearbox (12) of a motor vehicle, by means of which device a selection element or shift element of the gearbox for setting a shift track or for engaging or disengaging a gear can be moved, wherein: the operating device comprises a pressure-medium-operated actuator (54) having a piston (58) and a piston rod (64) that can be connected to the selection element or shift element of the gearbox; the piston is positioned in a radially sealed manner in a cylindrical receiving space (50) of the housing (18) of the operating device and can be moved coaxially in said space; a sensor assembly (30) having a magnet (38) and a magnetic-field-sensitive sensor (32) is provided; and the magnet is positioned on the end face of the piston remote from the piston rod by means of a holding device (44) and the sensor is positioned radially with respect to the magnet on the housing. In addition, according to the invention: the holding device is connected to the piston so as to be rotatable about the central longitudinal axis (52) of the receiving space; the holding device has a hollow-cylindrical or hollow-cylindrical-segment-shaped geometry; a rod-shaped or planar anti-turn element (80) is provided which is, at least at its two ends, received interlockingly in an associated cut-out in the housing (18); and the anti-turn element passes through the holding device in a secant-like manner with little play and at a distance from the magnet, as a result of which, although an axial movement and a rotational movement of the piston are possible, a rotational movement of the holding device about the central longitudinal axis of the receiving space is prevented.