Segmented Cam Clutch Switching to Prevent Sprag Jamming
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Solution Overview
Problem
Existing cam clutches face issues with unwanted jamming and high force requirements when switching between operation modes, leading to potential damage and reduced service life, due to the tilting of sprags which can result in simultaneous wedging and high surface contact, and difficulty in rolling due to arcuate curved side faces and complex contact positions.
Innovation Solution
A cam clutch design featuring an outer and inner race with coaxially arranged cams, an operation mode switching mechanism utilizing axially movable cage rings and a rotation ring to control cam orientations, restricting circumferential movement and allowing smooth mode switching between four operation modes, including a two-way lock mode, while preventing simultaneous wedging and reducing torque requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If all sprags are forced to tilt by control of the retainer when switching operation modes, then the clutch can switch between drive and freewheel modes, but the clutch cannot operate in a two-way lock mode that prohibits relative rotation between the outer race and the inner race in both forward and reverse directions
Solution Approach 1:
The clutch is divided into two independent retainer systems: a first retainer for controlling first sprags and a second retainer for controlling second sprags. Each retainer can be independently actuated, allowing the clutch to achieve four operation modes (forward drive, reverse drive, forward lock, reverse lock) without requiring all sprags to tilt simultaneously. This segmentation resolves the contradiction by enabling versatile mode switching while simplifying the control mechanism for each individual retainer.
2Ease of operation
If the wedging group of sprags tilt in the disengaging direction to switch to a freewheeling state, then the clutch can transition to freewheel mode, but the other group of sprags may tilt in the engaging direction and start wedging against the outer race and inner race before the wedging group of cams are disengaged, whereupon unwanted jamming can occur
Solution Approach 1:
The sprags are divided into two independent groups (first sprags and second sprags) controlled by separate retainers. When switching from lock mode to free mode, only the engaged sprags tilt to disengage while the other group remains in standby position. This segmentation prevents simultaneous engagement of all sprags, eliminating the jamming risk while maintaining smooth mode transitions.
Solution Approach 2:
The retainer mechanism is designed to tilt the wedging group of sprags in the disengaging direction before the other group of sprags can tilt in the engaging direction. By controlling the sequence of sprag tilting through the retainer's mechanical design, the system ensures that disengagement occurs first, preventing premature engagement and subsequent jamming.
3Strength
If all sprags are engaged with a high surface contact, then the clutch can achieve lock mode that prohibits relative rotation of the outer race and inner race, but a large force is required to change the orientation of the sprags to switch the operation mode, which may be detrimental to the engaging surfaces and raceways
Solution Approach 1:
The lock mode is achieved by engaging only one group of sprags (either first or second) while the other group remains in standby. This segmentation reduces the number of engaged sprags compared to a system where all sprags are engaged simultaneously, thereby reducing the total force required to tilt and reorient the sprags during mode switching while maintaining sufficient locking strength through the engaged group.
4Strength
If the cams or sprags have arcuate curved side faces, then the cams can provide effective wedging action, but it makes it difficult to allow the cams to roll a long distance
Solution Approach 1:
Instead of relying solely on circumferential rolling motion of the cams, the invention introduces axial movement of the retainers as an additional dimension for cam repositioning. The retainers tilt the cams by moving axially, allowing the cams to change orientation and switch between engagement and disengagement states without requiring long circumferential rolling distances. This dimensional change resolves the contradiction by maintaining effective wedging action while reducing the rolling distance requirement.
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
The design prevents unwanted jamming, ensures smooth operation, and allows for high-functionality with size reduction, improved responsiveness, and space economy by controlling cam orientations and movements through a simple structure, reducing the need for high rigidity and complex components.
Implementation Method 1
an operation mode switching mechanism that switches operation modes of the cam clutch, and a switch actuating mechanism that actuates the operation mode switching mechanism. The operation mode switching mechanism includes an outer cage ring configured to be axially movable independently of rotation of the outer race and the inner race and to change an orientation of the first cams, an inner cage ring configured to be axially movable independently of rotation of the outer race and the inner race and to change an orientation of the second cams
Implementation Method 2
a position-restricting cage ring provided between the outer cage ring and the inner cage ring and restricting a degree of freedom of circumferential movement of the outer cage ring and the inner cage ring
Implementation Method 3
The switch actuating mechanism includes an outer guide defining an axial position of the outer cage ring, an inner guide provided in a fixed position relative to the outer guide and defining an axial position of the inner cage ring, and a rotation ring circumferentially movable relative to the outer guide and the inner guide and provided for controlling the axial position of the outer cage ring and the inner cage ring
Implementation Method 4
a plurality of cams that are circumferentially arranged between the outer race and the inner race, the plurality of cams including first cams and second cams that wedge against the outer race and the inner race in different directions from each other
Data Source
AI summary
To provide a simple-structured cam clutch capable of preventing unwanted jamming of cams, thereby enabling smooth operation including switching operation between operation modes, and offering potential for higher functionality and size reduction. The plurality of cams of the cam clutch include first cams and second cams having different engaging directions. The cam clutch includes an operation mode switching mechanism for switching operation modes, and a switch actuating mechanism. The operation mode switching mechanism includes an outer cage ring, an inner cage ring, and a position-restricting cage ring. The switch actuating mechanism includes an outer guide, an inner guide, and a rotation ring circumferentially movable relative to the outer guide and inner guide and provided for controlling the axial positions of the outer cage ring and inner cage ring.