Starter Motor Flywheel Magnetic Pole Configuration for Torque Control
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Solution Overview
Problem
Conventional starter motors for vehicles face challenges in achieving both engine startability and vehicle mountability due to noise and durability issues associated with high-speed rotation and the need for a torque output, which is often addressed by using swing-back or decompression functions that compromise size and versatility.
Innovation Solution
The engine unit incorporates a starter motor with a four-stroke engine body, an inner stator, and a flywheel with a high number of magnetic poles, allowing the control device to supply current to the windings to overcome high-load regions during engine start, optimizing torque continuity and reducing size while maintaining high angular velocity and magnetic flux density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a speed reducer is used to reduce rotation speed, then the starter motor can output necessary torque, but noise and durability problems occur
Solution Approach 1:
The invention extracts and removes the speed reducer from the starter motor system. By directly connecting the motor to the crankshaft without a speed reducer, the patent eliminates the source of noise and durability problems while maintaining the ability to output necessary torque through direct drive.
Solution Approach 2:
The patent replaces the mechanical speed reduction system with an electrical control system. By controlling the current supplied to the winding and utilizing the high angular velocity from the large number of magnetic poles, the system achieves torque control without mechanical gears, thereby eliminating noise and improving durability.
2Volume of moving object
If the starter motor is downsized for vehicle mountability, then the motor size is reduced, but the torque output becomes insufficient
Solution Approach 1:
The invention changes key parameters of the motor system: increasing the number of magnetic poles to 10 or more (creating high angular velocity) and optimizing the current supply control. These parameter changes enable a downsized motor to generate sufficient torque through high-speed rotation and controlled current input, resolving the contradiction between size and torque output.
3Force
If the number of magnetic pole faces is increased, then the magnetic flux density increases and leakage flux is reduced, but the complexity of the flywheel increases
Solution Approach 1:
The flywheel is segmented into multiple independent magnetic pole faces (10 or more), with each pole face being a separate permanent magnet or magnetized region. This segmentation allows for increased magnetic flux density while maintaining manufacturing feasibility, as each pole can be independently positioned and configured to optimize performance without requiring a completely complex redesign.
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 ensures efficient engine startability and improved vehicle mountability without relying on swing-back or decompression functions, enhancing torque output and reducing power generation current, thus improving engine startability and vehicle performance.
Implementation Method 1
a starter motor including an inner stator and a flywheel, the inner stator including a stator core and windings of plurality of phases, the stator core having a plurality of slots arranged at intervals with respect to a circumferential direction, the windings being arranged so as to pass through the slots
Implementation Method 2
the flywheel including a permanent magnet part and a back yoke, the permanent magnet part being provided outside the inner stator with respect to a radial direction
Data Source
Figure 1(a)~1(b)
Figure 2
Figure 3
AI summary
Provided is an engine unit that achieves improvement in both engine startability and vehicle mountability without use of a swing-back function and a decompression function, and, when used in combination with the swing-back function and/or the decompression function, achieves further improvement in the engine startability and the vehicle mountability. An engine unit mounted to a vehicle includes a starter motor. A flywheel provided in the starter motor includes magnetic pole faces that are provided on inner circumferential surfaces of permanent magnet parts with respect to a radial direction of the starter motor. The magnetic pole faces are arranged side by side in a circumferential direction of the starter motor. The number of the magnetic pole faces is more than 2/3 of the number of slots. At least at a time of starting a four-stroke engine body, a control device changes a current supplied to a winding of each phase, to thereby enable the flywheel to rotate with overcoming of a high-load region.