Overrunning Clutch Friction Decoupling for Low-Loss Engagement
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Solution Overview
Problem
Existing one-way clutches for engaging and disengaging motors, such as those in bicycles with auxiliary drives, suffer from efficiency losses due to constant friction torque caused by pressure springs and friction elements, leading to reduced performance.
Innovation Solution
A one-way clutch design featuring a friction clutch with adjustable friction regions that allow for temporary frictional contact only when necessary, decoupling in other areas to minimize friction and enhance efficiency, utilizing a combination of magnetic and mechanical components for rotation inhibition and axial displacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pressure spring and friction element are used to maintain frictional contact for torque transmission, then the clutch can reliably engage and disengage the motor, but constant friction torque acts on the toothed body in both axial positions causing efficiency losses
Solution Approach 1:
The friction element is designed to dynamically change its contact state with the toothed body. It transitions from a friction-free state in the first axial position to a frictional contact state in the second axial position, and back again. This dynamic adaptation allows the clutch to maintain reliability during engagement/disengagement while minimizing energy losses during coasting or neutral states.
Solution Approach 2:
The frictional contact parameter is changed based on the axial position of the toothed body. In the first axial position, the friction element is displaced axially to eliminate contact and reduce friction to zero. In the second axial position, the friction element engages with the toothed body to provide necessary frictional torque for reliable engagement. This parameter change resolves the contradiction between reliability and energy efficiency.
2Reliability
If friction elements are preloaded by pressure springs to ensure continuous contact, then engagement reliability is improved, but friction losses increase in both engaged and disengaged states
Solution Approach 1:
The axial coupling path is segmented into distinct zones: a first axial position where the friction element is disengaged from the toothed body, and a second axial position where engagement occurs. The friction element is selectively activated only in the engagement zone, while remaining inactive in the disengaged zone. This segmentation allows the system to achieve reliable engagement when needed while minimizing energy consumption during non-engagement periods.
Solution Approach 2:
The friction element operates in a periodic manner, being activated only during the engagement phase and deactivated during the disengaged phase. This periodic action pattern ensures that friction forces are applied only when necessary for reliable engagement, rather than continuously, thereby reducing overall energy consumption while maintaining engagement reliability.
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 solution significantly reduces friction losses by up to 50%, improving the overall efficiency of the clutch mechanism and ensuring smooth operation across various operating states without unnecessary friction, thus enhancing the performance of motor-assisted bicycles.
Implementation Method 1
the at least one friction region of the first friction clutch part moves relative to the second friction clutch part in at least one intermediate position of the axial coupling path of the toothed body and exerts a rotational inhibition on the toothed body
Data Source
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AI summary
The present invention relates to a freewheel clutch for engaging and disengaging a motor, comprising a drive side connectable to the motor, an output side connectable to the motor, an axially acting geared clutch, and a friction device. The drive side has a gear body of the geared clutch displaceably arranged along an axial clutch path between a first axial position and a second axial position. The output side has a gear section of the geared clutch connected to the gear body in the second axial position. The friction clutch is operatively connected to the gear body. The friction device is designed as a friction clutch comprising a first friction clutch part with a friction section and a second friction clutch part comprising a friction section that can be brought into frictional contact with the at least one friction section of the first friction clutch part.The friction clutch is configured such that, when the gear body is moved from the first axial position to the second axial position and/or from the second axial position to the first axial position, the at least one friction area of the first friction clutch part moves relative to the second friction clutch part in at least one intermediate position of the axial clutch travel of the gear body, thereby exerting a rotational restraint on the gear body. In the second axial position of the gear body, the first friction clutch part is disengaged from the second friction clutch part. The invention also relates to a drive device with such a freewheel clutch and to a bicycle with such a drive device.