Torque Limiter Cam Teeth Asymmetric Lead Angles
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing torque limiter designs in electric power tools, such as hammer drills, are prone to sagging of cam teeth due to collisions during operation, especially when the backlash between cam teeth is minimized, leading to rotational rattle and potential deformation.
Innovation Solution
The design incorporates cam teeth with meshing surfaces having different lead angles for forward and reverse rotations, and a relief portion on the cam teeth to prevent collisions and ensure equal torque transmission in both directions, reducing the likelihood of sagging and maintaining consistent rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the backlash between cam teeth is minimized to reduce rotational rattle, then rotational stability is improved, but cam teeth are likely to collide during torque limiter operation causing sagging
Solution Approach 1:
The patent introduces a relief portion (leading surface) on the cam teeth that allows controlled deformation and energy absorption before collision occurs. This beforehand cushioning mechanism prevents severe impacts by allowing the cam teeth to deform slightly in a controlled manner, thereby maintaining both rotational stability and preventing sagging during torque limiter operation.
Solution Approach 2:
The patent applies asymmetry by making the lead angles of meshing surfaces different between forward and reverse rotation sides. The forward rotation side has a smaller lead angle while the reverse rotation side has a larger lead angle. This asymmetric design optimizes torque transmission in both directions while preventing cam tooth collision and sagging during torque limiter operation.
2Reliability
If cam teeth are designed with different lead angles for forward and reverse rotations to prevent collision, then cam tooth durability is improved, but torque transmission symmetry may be affected
Solution Approach 1:
The patent applies asymmetry by making the lead angles of meshing surfaces different between forward and reverse rotation sides. The forward rotation side has a smaller lead angle while the reverse rotation side has a larger lead angle. This asymmetric design optimizes torque transmission in both directions while preventing cam tooth collision and sagging during torque limiter operation.
Solution Approach 2:
The patent changes the lead angle parameter of the meshing surfaces to be different for forward and reverse rotations. By optimizing these angular parameters, the patent achieves both collision prevention and equal torque transmission characteristics in both rotation directions, resolving the contradiction between durability and operational symmetry.
3Ease of operation
If the cam teeth are designed with equal lead angles for both rotations to maintain symmetry, then torque transmission is equal, but cam teeth are prone to collision and sagging during operation
Solution Approach 1:
The patent applies asymmetry by making the lead angles of meshing surfaces different between forward and reverse rotation sides. The forward rotation side has a smaller lead angle while the reverse rotation side has a larger lead angle. This asymmetric design optimizes torque transmission in both directions while preventing cam tooth collision and sagging during torque limiter operation.
Solution Approach 2:
The patent changes the lead angle parameter of the meshing surfaces to be different for forward and reverse rotations. By optimizing these angular parameters, the patent achieves both collision prevention and equal torque transmission characteristics in both rotation directions, resolving the contradiction between durability and operational symmetry.
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 configuration effectively reduces the likelihood of cam tooth collisions and sagging, while maintaining equal torque transmission in both forward and reverse rotations, thereby enhancing the operational stability and longevity of the torque limiter.
Implementation Method 1
one member of the driving side member and the driven side member is movably disposed in the axial direction with respect to the other member and is biased to the other member side with an elastic member
Data Source
AI summary
An electric power tool includes a motor, a driving side member, and a driven side member. The driving side member and the driven side member have mutually opposed surfaces. A plurality of cam teeth are respectively disposed on concentric circles on the opposed surfaces. The plurality of cam teeth have meshing surfaces inclined at predetermined lead angles. A torque limiter is formed to disengage the engagement of the meshing surfaces of the cam teeth by moving the one member in a separation direction from the other member when load of the driven side member increases. The respective cam teeth are formed such that the lead angles of the meshing surfaces are different between a forward rotation side and a reverse rotation side. A transmission torque transmitted from the driving side member to the driven side member is equal between the forward rotation and the reverse rotation.