Transmission Gearbox Front Coupling to Reduce Shift Noise
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Solution Overview
Problem
Transmission gearboxes in motor vehicles, particularly in motorcycles and scooters, experience noisy engagements and shifting due to the 'hammer blow' effect caused by the interaction of toothed wheels, leading to discomfort during driving.
Innovation Solution
A transmission gearbox design featuring a coupling wheel with a coupling slot having a shallow recess and a coupling tooth with reduced size, allowing for a backlash-free engagement that reduces noise by slowing down the idle wheel's angular speed and distributing the engagement force, thereby minimizing the 'hammering' effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional toothed wheels are engaged frontally with the inner wall of the slot, then gear engagement is achieved, but hammer blow noise and vibration occur
Solution Approach 1:
The coupling slot includes a portion of shallow recess that extends for at least an angular sector of the slot, creating a pre-engagement zone before the tooth reaches the through-portion. This preliminary action allows the tooth to gradually engage with the recess rather than abruptly hitting the inner wall, thereby reducing hammer blow noise while maintaining manufacturing simplicity
Solution Approach 2:
The shallow recess acts as a cushioning zone that absorbs the impact energy before the tooth fully engages with the through-portion of the slot. This beforehand cushioning prevents the direct hammer blow against the inner wall by providing a gradual engagement path that reduces shock and vibration
Data Source
Figure 1
Figure 1A~1A'
Figure 1B~1B'
AI summary
A transmission gearbox, in particular of a motor vehicle, is described comprising: a primary shaft receiving a driving torque by means of a primary transmission; a secondary shaft connected to the primary shaft. On the secondary shaft: an idle wheel revolvingly non-working on the secondary shaft comprising at least a coupling slot, and at least a coupling wheel revolvingly integral to the secondary shaft comprising a corresponding coupling tooth are assembled, respectively. The coupling wheel is arranged adjacent to the idle wheel and it can be axially moved so as to translate axially between a free configuration, wherein it is disengaged with respect to the idle wheel, and an engaged configuration, wherein it is engaged with the idle wheel by implementing a front coupling between the coupling tooth and the coupling slot for transmitting the motion between the primary shaft and the secondary shaft. The coupling slot comprises a portion of shallow recess extending for at least an angular sector of the same, so as to define a first through-portion and a second closed portion of the slot. The second closed portion allows to intercept and guide the tooth coupling towards the first through-portion, by reducing noisiness both in the engaging phase and during operation.