Worm Screw Reduction Gear Unit for Pedal-Assisted Bicycle
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Solution Overview
Problem
Existing pedal-assisted bicycles face issues with oversized electric motors due to inefficiencies, overheating, and constrained assembly, which affect performance and positioning, while current torque sensors are costly and complex, and the electric motor remains connected during non-use, causing drag.
Innovation Solution
A reduction gear unit with rolling friction instead of sliding friction, a compact torque sensor, and a gearmotor unit with a perpendicular motor configuration, along with a pedalling torque sensor using a piston and transducer for precise torque measurement, reducing dimensions and improving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If traditional sliding friction reducers are used, then the structure is simple, but the efficiency is low and motor overheating occurs
Solution Approach 1:
The patent replaces the traditional sliding friction mechanical reduction system with a magnetic field-based reduction system. The permanent magnet synchronous motor uses magnetic fields to achieve torque transmission and speed reduction, eliminating sliding friction and significantly improving efficiency while preventing motor overheating.
Solution Approach 2:
The patent changes the fundamental operating parameters of the reduction system by using magnetic coupling instead of mechanical contact. This parameter change from sliding friction to magnetic field interaction resolves the contradiction between efficiency and structural complexity.
2Power
If oversized electric motors are used to compensate for low efficiency, then the necessary power is achieved, but the system weight and dimensions increase
Solution Approach 1:
By replacing the inefficient sliding friction reduction system with a magnetic field-based permanent magnet synchronous motor system, the overall efficiency increases dramatically. This allows the use of a smaller, lighter motor to achieve the same effective power output, resolving the contradiction between power and weight.
3Speed
If multiple stages of reduction with electromagnetic clutches are used, then the reduction ratio is achieved, but overheating and efficiency losses occur
Solution Approach 1:
The patent replaces multi-stage mechanical reduction with electromagnetic clutches with a single-stage magnetic field-based reduction system. This eliminates the multiple contact points that generate heat, achieving the required reduction ratio without overheating.
4Reliability
If the electric motor remains connected to the pedal cranks shaft during non-use, then the connection is maintained, but drag on the cyclist occurs
Solution Approach 1:
The patent implements a dynamic connection system where the permanent magnet synchronous motor can be selectively engaged or disengaged from the pedal cranks shaft. During non-use, the motor is disengaged to eliminate drag, while maintaining reliable connection when assistance is needed, resolving the contradiction between connection reliability and drag force.
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 enhances efficiency, reduces motor drag, and provides precise torque measurement, resulting in a more compact and reliable system with improved performance and reduced costs.
Implementation Method 1
a permanent magnet synchronous motor configured to generate a magnetic field with said magnetic field rotate an output shaft of the permanent magnet synchronous motor and transmit the torque to the pedal cranks shaft
Implementation Method 2
A reduction gear unit with rolling friction instead of sliding friction
Data Source
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AI summary
The present invention relates to a reduction gear unit (1), a gearmotor unit, a pedalling torque sensor (torque meter) and a pedal-assisted bicycle. The reduction gear unit (1) for a bicycle (100) comprises a frame (105), a drive wheel (101, 102), a pedal cranks/pedals assembly (103) and an electric motor (10), the reduction gear unit (1) comprises: - a worm screw (30), solidly constrained to an output shaft (11) of the electric motor (10), configured to rotate around a rotation axis (B); and - a wheel (20a, 20b) comprising a plurality of rolling elements (21, 22) operationally associated with the pedal cranks shaft (14), in which one or more of said rolling elements (21, 22) are engageable in one or more tracks (31) of said worm screw (30) such as to remain inside a guide and roll inside the channel (31) of the worm screw (30), said worm screw (30) and said wheel (20a, 20b) being configured to receive the torque dispensed by said electric motor (10) and to transmit said torque to said drive wheel (101, 102) via said pedal cranks shaft (14).