Shift Drum Assembly With Switchable Neutral and Endless Rotation
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Solution Overview
Problem
Existing shift drum arrangements in motor vehicle transmissions face challenges in achieving endless rotation and smooth gear shifting, particularly in hybrid vehicles, where a neutral gear position is required without causing traction interruption.
Innovation Solution
A shift drum arrangement with rotatable shift contours and a switchable coupling device allows for endless rotation and neutral position switching, enabling axial displacement of switching elements to achieve neutral gear without interrupting traction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a stop element is integrated into the shift drum body to reference rotational position, then the rotational position can be detected, but the maximum rotational range is limited to less than 360 degrees
Solution Approach 1:
The shift drum body is segmented into functional zones: shifting contours for gear engagement, a reference element for position detection, and a stop element for directional control. This segmentation allows the reference element to provide precise rotational position detection while the stop element manages the physical limits of rotation, enabling the system to achieve both accurate measurement and extended operational range through multiple 360-degree rotations.
Solution Approach 2:
The shift drum body is designed to be dynamically rotatable beyond the static limit imposed by the stop element. The stop element acts as a one-way constraint that allows rotation in the shifting direction but prevents rotation in the opposite direction. This dynamic design enables the shift drum to accumulate rotational movement across multiple cycles, achieving an effective rotational range exceeding 360 degrees while maintaining precise position detection through the reference element.
2Adaptability or versatility
If a neutral gear position is implemented in a transmission with continuous gear engagement, then stationary charging function is enabled, but traction interruption occurs
Solution Approach 1:
The shifting contours are designed to guide the shifting elements through a predetermined path that includes the neutral position. The contours are shaped to ensure smooth engagement and disengagement of gear stages, allowing the transmission to pass through neutral without causing traction interruption. The preliminary design of the contour geometry ensures that the neutral position is achieved as a natural part of the shifting sequence rather than as a disruptive interruption.
Solution Approach 2:
The shifting elements act as intermediaries between the shift drum body and the gear stages. These elements are designed to smoothly transition between engaged and disengaged states, mediating the transition through the neutral position. The shifting elements ensure that the neutral gear position is achieved without causing abrupt changes in power transmission, thereby maintaining traction continuity while enabling the neutral position for stationary charging operations.
3Adaptability or versatility
If the shift drum body is designed for endless rotation, then neutral position switching is enabled, but the structural complexity increases
Solution Approach 1:
The shift drum body is designed with multi-functionality: it serves as both the rotating element that drives gear shifts and the structure that accommodates the reference element for position detection. The stop element is integrated into the drum body rather than being a separate mechanism, and the shifting contours are directly formed on the drum surface. This universal design enables endless rotation capability and neutral position switching without requiring additional complex components.
Solution Approach 2:
The shifting contours are designed in both the axial and radial dimensions of the shift drum body. This multi-dimensional contour design allows the shifting elements to be guided through complex paths that enable neutral position switching while the drum rotates endlessly. By utilizing both axial and radial dimensions, the patent achieves versatile neutral position control without increasing the fundamental rotational simplicity of the drum body.
Data Source
Figure 1a~1b
Figure 2
Figure 3
AI summary
The invention relates to a gear shift drum assembly (32) for a shift device (30) of a transmission unit, in particular for motor vehicles, comprising a gear shift drum body (34) which can be rotated about a gear shift drum axis, wherein a first and at least one second shift contour (52a, 52b) is formed on the gear shift drum body (34), extending over 360 degrees of the circumferential section of the gear shift drum body (34), wherein the first and second shift contour (52a, 52b) are formed in an axial and/or radial direction, wherein a first shift element (51a) engages in the first shift contour (52a) and a second shift element (51b) engages in the second shift contour (52a) in such a way that they can be shifted in the axial direction of the gear shift drum body (34) by rotating the gear shift drum body (34) by means of the corresponding shift contour. In order to shift into a neutral gear position, the first shift contour (52a) has an optional path (59), and the first and the second shift element (51a, 51b) can be coupled via a shiftable coupling device (200) in such a way that an axial shifting of the second shift element (51b) can be transferred onto the first shift element (51a) for the purpose of shifting into a neutral gear position associated with the optional path (59).