Dog Clutch Dual Ring Cam Groove Abrasion Prevention
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Solution Overview
Problem
The existing dog clutch design, as described in JP 5707119 B, experiences abrasion and reduced transmission efficiency due to the dog ring coming into contact with the fork when torque changes direction, leading to disengagement issues.
Innovation Solution
The dog clutch incorporates a dual dog ring system with cam grooves and springs, where the first dog ring engages with the gear using a slope surface for high-speed engagement and the second dog ring engages with a parallel surface to prevent disengagement thrust, ensuring the dog rings do not move into contact with the fork, thus preventing abrasion and enhancing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a slope surface is formed on the release side of the dog ring to enable high-speed disengagement, then disengagement speed is improved, but the dog ring undergoes unintended thrust in the release direction when torque changes to coast direction, causing contact with the fork and abrasion
Solution Approach 1:
The dog ring is divided into two separate components: a first dog ring for positive rotation direction engagement and a second dog ring for negative rotation direction engagement. Each dog ring has its own dedicated cam groove with specific surface characteristics (first parallel surface, first slope surface, second parallel surface, second slope surface). This segmentation allows each surface to be optimized for its specific function without interference from the other direction's requirements.
Solution Approach 2:
Different surfaces of the cam groove are given different geometric qualities tailored to specific functions: the first parallel surface and second parallel surface provide axial guidance and prevent unintended thrust, while the first slope surface enables high-speed engagement for positive rotation. This local differentiation of surface properties ensures each area performs its designated function optimally.
2Speed
If the dog ring is designed to engage with a single slope surface for high-speed engagement, then engagement speed is improved, but the dog ring cannot prevent unintended movement in the disengaging direction when torque direction changes
Solution Approach 1:
The cam groove is segmented into four distinct surfaces: first parallel surface, first slope surface, second parallel surface, and second slope surface. The first dog ring engages with surfaces optimized for positive rotation direction, while the second dog ring engages with surfaces optimized for negative rotation direction. This segmentation allows high-speed engagement through slope surfaces while parallel surfaces prevent unintended movement, eliminating the need for precise fork position control.
Solution Approach 2:
The cam groove employs asymmetric surface configurations where the first slope surface is inclined for high-speed engagement in one direction, while the second slope surface and parallel surfaces are configured to prevent disengagement thrust in the opposite direction. This asymmetric design allows the system to achieve high-speed engagement without requiring precise control of the fork's axial position.
3Device complexity
If a single dog ring system is used, then the structure is simple, but the system cannot simultaneously optimize for both positive and negative rotation direction engagement without causing fork contact and abrasion
Solution Approach 1:
The single dog ring is segmented into two functionally independent dog rings: the first dog ring for positive rotation direction and the second dog ring for negative rotation direction. Each ring has its own engagement surfaces and interacts with specific portions of the cam groove. This segmentation resolves the conflict between structural simplicity and reliability by creating a modular system where each component is optimized for its specific function.
Solution Approach 2:
The dual dog ring system provides multi-functionality by enabling the transmission system to handle both positive and negative rotation directions with optimized engagement characteristics for each direction. The first dog ring and second dog ring together create a universal solution that maintains high transmission efficiency in both rotation directions without causing fork contact or abrasion.
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
This design effectively prevents contact between the dog rings and the fork, reducing abrasion and increasing transmission efficiency by allowing smooth engagement and disengagement at high speeds without increasing the axial movement speed of the fork.
Implementation Method 1
The first dog ring includes first cam protrusions each configured to be engaged with the first slope surface of the corresponding cam groove to transmit the torque in the positive rotation between the first dog ring and the power transmission shaft
Implementation Method 2
springs configured to pull the first dog ring and the second dog ring to bring the first dog ring and the second dog ring into pressure contact with each other axially
Implementation Method 3
cam grooves axially extending on the power transmission shaft. The cam grooves each include, on a surface in the positive rotation direction, a first parallel surface parallel to an axial direction and a first slope surface inclined from the first parallel surface
Data Source
AI summary
A dog clutch includes a gear (40) mounted on a power transmission shaft (30), first and second dog rings (10, 20), a fork (60), springs (65), and cam grooves (31). The cam grooves (31) each include a first slope surface (36) inclined from the axial direction toward the positive rotation direction as the first slope surface (36) approaches the gear (40) and a second parallel surface (37) parallel to the axial direction. The first dog ring (10) includes first cam protrusions (16) to be engaged with the respective first slope surfaces (36), and the second dog ring (20) includes second cam protrusions (26) to be engaged with the respective second parallel surfaces (37). This structure prevents the dog rings and the fork from coming into contact with each other, thereby avoiding generation of abrasion and increasing the transmission efficiency.