Power-Assisted Bicycle Torque Sensor Vibration Isolation
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Solution Overview
Problem
In single-shaft motor drive units for power-assisted bicycles, the one-way clutch assembly can cause noise and reduce torque detection capability due to direct vibration transmission during operation, and when the battery runs out, pedaling requires excessive force due to lack of auxiliary driving force.
Innovation Solution
A power-assisted bicycle design with a cylindrical human-power transmission member and a combined force member, featuring a deceleration mechanism with reduction gears and a one-way clutch between reduction gears and the support shaft to interrupt human driving force, preventing direct vibration transmission to the torque sensor and reducing pedal force requirement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a one-way clutch is assembled into the combined force member for interrupting human driving force, then the pedal force is reduced when battery runs out, but vibrations are directly transmitted to the torque sensor causing noise and reducing torque detection capability
Solution Approach 1:
The patent divides the combined force member into two separate components: the combined force member itself and the reduction gear. The one-way clutch is assembled into the reduction gear rather than the combined force member, creating a segmented structure that isolates vibration sources from the torque sensor mounting location.
Solution Approach 2:
The reduction gear acts as an intermediary component between the combined force member and the one-way clutch. By placing the one-way clutch in the reduction gear, vibrations are filtered through the gear mechanism before reaching the combined force member, reducing direct vibration transmission to the torque sensor.
2Reliability
If the one-way clutch is disposed between the combined force member and the human driving force, then excessive force is prevented, but vibrations during clutch operation directly affect the torque sensor
Solution Approach 1:
The patent segments the force transmission path by placing the one-way clutch in the reduction gear rather than directly in the combined force member. This segmentation separates the force control function from the vibration transmission path, allowing reliable force control while reducing vibration noise.
Solution Approach 2:
The one-way clutch is extracted from the combined force member and relocated to the reduction gear. This extraction removes the primary vibration source from direct contact with the torque sensor mounting location, eliminating the harmful vibration effect while preserving the force control function.
3Power
If reduction gears are added to the deceleration mechanism, then the motor can provide sufficient auxiliary driving force, but the device complexity increases
Solution Approach 1:
The reduction gear in the deceleration mechanism serves multiple functions: it provides the necessary torque multiplication for sufficient auxiliary driving force, and simultaneously acts as the mounting location for the one-way clutch, thereby reducing overall device complexity by combining multiple functions in a single component.
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 maintains high torque detection capability while reducing the pedal force needed during pedaling, even when the battery is depleted, and prevents excessive force application, enhancing the reliability and efficiency of the power-assisted bicycle.
Implementation Method 1
a magneto-striction generation portion (31b) is formed on the outer periphery of the human-power transmission member (28), and a coil (31a) for detecting a change of magnetism on the magneto-striction generation portion (31b) is opposed to the magneto-striction generation portion (31b)
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A power-assisted bicycle is provided to satisfactorily keep torque detection capability while reducing the pedal force of a pedal during pedaling if a battery has run out. A cylindrical human-power transmission member 28 having a magneto-striction generation portion 31b of a torque sensor 31 is disposed on the outer periphery of a crankshaft 7a. A combined force member 29 for combining a human driving force and an auxiliary driving force is disposed on the outer periphery of the crankshaft 7a. An auxiliary-driving-force transmission path from a motor 21 to the combined force member 29 has a deceleration mechanism 25 that includes a plurality of reduction gears 36c and 36d and reduction gear support shafts 36a and 36b. A one-way clutch 37 for interrupting a human driving force is disposed between the reduction gears 36c and 36d and the reduction gear support shafts 36a and 36b.