Single-Cylinder Motorcycle Generator Control for Low-Speed Battery Charging
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Solution Overview
Problem
Existing engine units require increased size and decreased efficiency when operating at lowered crankshaft rotation speeds to maintain power generation, leading to higher power consumption and fuel usage.
Innovation Solution
A motorcycle engine unit with a single cylinder and a three-phase brushless generator attached directly to the crankshaft, utilizing a control device with switching parts to manage power generation and motor functions, ensuring efficient power output without increasing generator size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the crankshaft rotation speed is lowered when the vehicle is stopped, then fuel consumption and noise are reduced, but the voltage output from the generator becomes lower than the battery voltage, making battery charging difficult
Solution Approach 1:
The patent applies parameter changes by switching between two control modes: vector control for low-speed charging (when generator voltage < battery voltage) and phase control for high-speed charging (when generator voltage > battery voltage). This allows the system to maintain reliable battery charging across different crankshaft rotation speeds, resolving the contradiction between reduced fuel consumption at low speed and reliable charging capability.
2Reliability
If the size of the generator is increased to ensure sufficient power generation at low rotation speed, then battery charging capability is improved, but the mountability to the vehicle deteriorates
Solution Approach 1:
Instead of increasing generator size, the patent changes the control parameters by implementing dual control modes (vector control and phase control) that optimize the inverter's switching strategy based on the relationship between generator voltage and battery voltage. This maintains sufficient power generation capability at low rotation speeds without requiring a larger generator.
Solution Approach 2:
The patent replaces the mechanical approach of increasing generator size with an electrical control approach using dual control modes. By substituting physical enlargement with intelligent control of the inverter circuit, the system achieves reliable low-speed power generation without increasing generator dimensions.
3Power
If the wire rod thickness of the winding is increased to raise the power generation voltage at low rotation speed, then the generator output voltage is improved, but the overall power generation efficiency deteriorates
Solution Approach 1:
The patent changes the control parameters of the inverter circuit by implementing vector control at low speeds and phase control at high speeds, rather than physically increasing wire rod thickness. This maintains optimal power generation efficiency across different rotation speeds while ensuring sufficient output voltage through intelligent control rather than physical modification.
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
Ensures high-efficiency power generation and reduced load variation at lowered crankshaft speeds, minimizing noise and fuel consumption without enlarging the generator.
Implementation Method 1
an inverter including a plurality of switching parts by which a current supplied from the generator to the battery is controlled
Implementation Method 2
the control device being configured to, during at least part of a time period in which the vehicle is stopped and a voltage outputted from the generator is lower than a voltage of the battery, perform a vector control on the plurality of switching parts included in the inverter so as to raise the voltage outputted from the generator that is lower than the voltage of the battery to a voltage higher than the voltage of the battery
Implementation Method 3
a generator that generates power by being rotated along with the rotation of the crankshaft
Data Source
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AI summary
The present invention provides, for example, an engine unit that is able to ensure an amount of power generation with a high efficiency even if the rotation speed of a crankshaft is lowered when a vehicle is stopped, without any need to increase the size of a generator. The engine unit includes: a four-stroke engine body; a generator; an inverter including a plurality of switching parts; and a control device. When the vehicle is stopped and a voltage outputted from the generator is lower than the voltage of a battery, the control device performs a vector control on the plurality of switching parts so as to raise the voltage outputted from the generator that is lower than the voltage of the battery to a voltage higher than the voltage of the battery, to charge the battery.