Electric Bicycle Central Axle Torque Speed Sensing Device
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Solution Overview
Problem
Current electric bike torque sensors, primarily using Hall rotational speed sensors, face issues with inaccurate measurement of static and dynamic torsional moment, inability to zero-start, and excessive power consumption, especially on level roads and downhill slopes, due to poor magnet placement and low sensitivity at high rotational speeds.
Innovation Solution
An electric-bike central-axle torque speed sensing device featuring a torque pipe with a magnetic conductive alloy sheet and a coil for detecting magnetic changes, integrated with a signal processor and a speed-sensitive Hall sensor, which allows for simultaneous detection of torque and speed signals, ensuring accurate power control and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If Hall rotational speed sensors with magnet steel are used on the central axle, then the sensor structure is simple and easy to manufacture, but the measurement accuracy of torsional moment is poor and cannot detect static torque
Solution Approach 1:
The patent replaces the traditional Hall sensor mechanical arrangement with a strain gauge-based electrical measurement system. Strain gauges are bonded to the central axle surface to directly measure deformation caused by torsional moment, converting mechanical strain into electrical signals for accurate torque detection including static conditions.
Solution Approach 2:
The patent changes the measurement parameter from magnetic field detection (Hall effect) to strain detection (resistance change). By bonding strain gauges to the axle, the system measures the physical deformation parameter directly, enabling accurate detection of both static and dynamic torsional moments without relying on rotational motion.
2Device complexity
If magnet steel is mounted on the surface of rotating components, then the sensor structure is simple, but the displacement produced due to torsion is not obvious at high rotational speeds, reducing measurement accuracy
Solution Approach 1:
The patent replaces the magnetic field-based detection system with a strain gauge measurement system that directly bonds to the central axle. This substitution eliminates reliance on magnetic steel displacement and provides direct electrical measurement of torsional deformation, maintaining accuracy across all rotational speeds.
Solution Approach 2:
The patent introduces strain gauges as an intermediary element bonded to the central axle. These gauges act as a mediator that directly senses the torsional strain in the axle material itself, providing accurate measurement without depending on the displacement of mounted components like magnetic steel.
3Ease of operation
If traditional Hall sensors are used, then the sensor can be easily installed, but the electric bike cannot zero start and consumes excessive power on level roads and downhill
Solution Approach 1:
The patent replaces the Hall sensor system with a strain gauge-based torque sensing system. This substitution enables accurate detection of minimal torque conditions, allowing the motor controller to precisely modulate power output and enable zero-start functionality while reducing unnecessary power consumption during low-demand conditions.
Solution Approach 2:
The patent implements a feedback mechanism where strain gauge measurements of actual torque demand are continuously fed to the motor control system. This feedback enables the controller to adjust motor output precisely to match actual pedaling demand, allowing zero-start capability and preventing excessive power consumption on level roads and downhill slopes.
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 device provides enhanced sensing sensitivity and accuracy, enabling zero-start capability and stable operation by processing torque and speed signals to optimize motor power output, improving energy efficiency and consistency across products.
Implementation Method 1
a coil provided on the magnetic conductive alloy sheet for detecting magnetic change
Implementation Method 2
a Hall element mounted on non-rotating components such as a frame spindle
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The present invention relates to an electric-bike central-axle torque speed sensing device, comprising a central axle (4) fitted in a five-way pipe, a left crank (13) and a right crank (14) secured on both ends of the central axle (4), and a chain wheel (16) sleeved on the central axle (4); sleeved on the central axle (4) is a torque pipe (5) that will produce circumferential deformation when it is subjected to a circumferential torsional force, the torque pipe (5) being secured at one end to the central axle (4) and secured at the other end to the chain wheel (16); on the outer wall of the torque pipe (5) is secured a circle of magnetic conductive alloy sheet (20) clinging to this torque pipe, with the magnetic conductive alloy sheet (20) provided densely with holes (17); the magnetic conductive alloy sheet (20) is provided on its periphery with a coil (19) used for detecting magnetic change, with the coil (19) connected to a motor controller via a signal processor; inside the five-way pipe is also secured a speed-sensitive Hall (18) connected to the signal processor, with the central axle (6) provided with a speed-sensitive magnet steel (12) corresponding to the speed-sensitive Hall (18). The structure of the present invention is smart and reasonable in structure, and has induction sensitivity and high accuracy.