Movable Permanent Magnet Starter Motor for Straddle-Type Vehicle
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Solution Overview
Problem
Straddled vehicle starter motors face a trade-off between maintaining output torque characteristics and rotation speed characteristics while ensuring compactness and mountability, as reducing winding turns to achieve high rotation speed compromises low-speed torque output, and increasing magnetic force or winding size to maintain torque requires a larger motor size.
Innovation Solution
A straddled vehicle starter motor with a movable permanent magnet that adjusts its position between advanced and retarded angles relative to the brush, using an elastic member and actuator to optimize torque and speed characteristics without increasing motor size, by positioning the magnet in the advanced angle for high torque at startup and moving it to the retarded angle as speed increases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the number of turns of a winding is reduced to enable high rotation speed, then rotation speed is improved, but output torque under low rotation speed decreases
Solution Approach 1:
The patent applies the dynamics principle by making the permanent magnet position adjustable rather than fixed. The magnet can be positioned at different angles (advanced angle for high torque, retarded angle for high speed) depending on the operational requirements. This dynamic adjustment allows the motor to optimize its characteristics for different operating conditions, resolving the contradiction between torque and speed.
Solution Approach 2:
The patent changes the parameter of magnet position angle to resolve the contradiction. By adjusting the magnet position between advanced and retarded angles, the motor can change its torque-speed characteristics. This parameter change allows the same motor structure to achieve both high torque at low speed and high rotation speed by simply repositioning the magnet.
2Force
If the magnetic force is increased to maintain output torque, then output torque is improved, but the size of the motor increases
Solution Approach 1:
Instead of increasing magnetic force permanently, the patent uses a movable permanent magnet that can be positioned dynamically. This allows the motor to achieve high output torque only when needed (at advanced angle position during startup) rather than requiring continuously high magnetic force, thus maintaining compact size while providing high torque capability.
Solution Approach 2:
The patent changes the position parameter of the permanent magnet rather than changing the magnetic force magnitude. By positioning the magnet at an advanced angle, the motor achieves high torque output without increasing the magnet's strength or size, thus maintaining a compact motor design.
3Force
If the winding size is increased to supply large current, then output torque is improved, but the device complexity and size increase
Solution Approach 1:
The patent avoids increasing winding size by using a dynamic magnet positioning system. The adjustable magnet position allows the motor to achieve high torque with the existing winding configuration, thereby reducing device complexity and avoiding the need for larger or more complex windings.
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 enhances both output torque and rotation speed characteristics while maintaining a compact design, improving engine start-up performance and reducing the need for a larger battery or motor size.
Implementation Method 1
a rotor configured to be rotatable, and including a winding... a movable permanent magnet arranged so as to oppose the core with a gap therebetween
Implementation Method 2
the magnet moving unit includes an elastic member configured to bias the movable permanent magnet in the retarded angle direction with an elastic force
Data Source
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AI summary
Provided is a straddled vehicle starter motor, etc. that is able to improve output torque characteristics and rotation speed characteristics for starting up an engine with a simple configuration, while improving mountability to a vehicle. A straddled vehicle starter motor includes: a rotor; a brush; and a movable permanent magnet supported on a housing so as to be movable in a circumferential direction of the rotor independently of the rotor within an angle range including a retarded angle position and an advanced angle position, the retarded angle position being an angle position where the movable permanent magnet is displaced in a retarded angle direction relative to the brush, the advanced angle position being an angle position where the movable permanent magnet is displaced in an advanced angle direction relative to the brush when compared to the retarded angle position and where a higher torque is caused in the rotor than a torque caused in the retarded angle position, the movable magnet being configured to be located in the advanced angle position at a time point when the rotor starts rotation upon a current supply to the rotor, and to be moved in the retarded angle direction to the retarded angle position within a period in which the rotor is rotating with a current supplied to the rotor.