Shift Device Rotational Play Spline Design
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Solution Overview
Problem
Modern motor vehicle transmissions, particularly shift-by-wire systems, require a shift shaft to rotate relative to a fixed shift lever in certain operating situations, but existing solutions incur additional costs and complexity by requiring additional components like freewheel elements.
Innovation Solution
A spline connection with rotational play between the shift shaft and lever allows for a conditional rotational freewheel of 40° to 60°, achieved without additional components by designing the internal and external splines with radially inward and outward teeth, respectively, enabling relative rotation and torque transmission while maintaining precise angular alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a non-rotatable connection is used between shift lever and shift shaft, then the connection is simple and rigid, but the shift shaft cannot rotate relative to the fixed shift lever in certain operating situations
Solution Approach 1:
The spline connection is segmented with gaps between the teeth, allowing the shift shaft to rotate relative to the shift lever within a limited angular range while maintaining torque transmission capability. The segmented tooth structure enables both rigid connection and controlled rotation.
Solution Approach 2:
The spline connection performs multiple functions simultaneously: it transmits torque from the shift lever to the shift shaft, allows limited rotational movement for sensor alignment, and maintains a mechanical connection without requiring additional freewheel components.
2Adaptability or versatility
If a freewheel element is added to enable rotational freewheel, then the shift shaft can rotate relative to the shift lever, but additional components and costs are incurred
Solution Approach 1:
The freewheel functionality is merged into the spline connection design itself. The gaps between the spline teeth create the freewheel effect without requiring a separate freewheel mechanism, combining the torque transmission and rotational freedom functions in a single structural element.
Solution Approach 2:
The spline connection structure serves itself by using its own geometric design (gaps between teeth) to enable the freewheel function. The structure automatically provides both rigid torque transmission and controlled rotation without needing external assistance from additional components.
3Adaptability or versatility
If the spline connection has rotational play, then conditional rotational freewheel is enabled, but precision of angular alignment may be affected
Solution Approach 1:
The spline connection has different properties in different aspects: radially, the teeth provide rigid torque transmission, while circumferentially, the gaps between teeth allow controlled rotation. This local differentiation of mechanical properties enables both precision and freedom where needed.
Solution Approach 2:
The spline teeth are designed with asymmetric engagement characteristics - they transmit torque effectively in one direction while allowing limited rotation in the other direction through the gaps. This asymmetric design enables controlled rotational play without compromising overall alignment precision.
Data Source
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AI summary
The invention relates to a shift device (100) for a motor vehicle transmission, in particular for a motor vehicle automatic transmission, having a shift shaft (110) which leads to the transmission and having a shift lever (120) for actuating the shift shaft (110), wherein the shift shaft (110) and the shift lever (120) are connected to one another by means of a spline toothing connection. It is provided that the spline toothing connection is formed with rotational play, permitting a restricted rotational free travel (a) of the shift shaft (110) when the shift lever (120) is stationary. The invention also relates to a motor vehicle transmission having a shift device (100) of said type.