Controllable Coupling Assembly Backlash Asymmetry
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Solution Overview
Problem
Controllable one-way clutches can inadvertently bind in both directions due to extremely low transitional backlash, leading to a 'lock-lock' condition, where the locking elements fail to disengage as commanded.
Innovation Solution
The design includes a controllable coupling assembly with a specific configuration of forward and reverse locking elements and formations, where the number of forward locking elements and formations differs from reverse locking elements and formations, and the backlash relationships are set such that either the forward backlash is a non-zero integer multiple of the reverse backlash or vice versa, preventing inadvertent binding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of forward locking elements and reverse locking elements is made equal, then the clutch can engage symmetrically in both directions, but the clutch may inadvertently bind in both directions due to extremely low transitional backlash
Solution Approach 1:
The patent applies asymmetry by making the number of forward locking elements different from the number of reverse locking elements. Specifically, the forward clutch face has a different number of locking elements than the reverse clutch face, creating intentional asymmetry in the backlash distribution. This asymmetric configuration ensures that the transitional backlash is sufficient to prevent inadvertent binding in both directions simultaneously, while maintaining reliable engagement control.
2Measurement precision
If the backlash is reduced to achieve precise engagement, then the engagement accuracy improves, but the clutch may bind in both directions due to insufficient transitional backlash
Solution Approach 1:
The patent applies local quality by creating different backlash characteristics in different directions. The forward and reverse clutch faces are designed with different numbers of locking elements, which results in different local backlash values for forward and reverse engagement. This local differentiation ensures that each direction has appropriate transitional backlash to prevent binding, while maintaining precise engagement when locked.
Data Source
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AI summary
A controllable or selectable coupling assembly includes a plurality of forward locking elements, at least one reverse locking element and first and second coupling members supported for relative rotation about a common rotational axis. The coupling members include a first, second and third coupling faces. The first coupling face has a set of forward pockets angularly spaced about the axis. The second coupling face has a set of reverse locking formations adapted for abutting engagement with the at least one reverse locking element. The third coupling face opposes the first coupling face and has a set of forward locking formations. Either forward backlash is a non-zero integer multiple of reverse backlash or the reverse backlash is a non-zero integer multiple of the forward backlash to prevent the coupling assembly from inadvertently binding in both directions (i.e. a "lock-lock" condition) about the axis.