Brushless Starter Motor for Hybrid Engine Cranking
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Solution Overview
Problem
Conventional hybrid vehicle propulsion systems face inefficiencies in engine starting and decoupling, leading to increased fuel consumption, emissions, and perceived noise, vibration, and harshness (NVH) due to the use of brushed contact starter motors and sequential actuation, which also result in undesirable voltage drops and delayed engine restarts.
Innovation Solution
A hybrid vehicle propulsion system incorporating a brushless permanent magnet DC motor as the starter electric machine, powered by a high-voltage traction battery, which enables faster engine restarts, reduces NVH, and eliminates the need for additional voltage stabilization and mechanical actuators, allowing for quicker resumption of engine power delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional brushed contact starter motor is used to start the engine, then the engine can be started, but the system experiences increased NVH, voltage drops, and delayed restarts
Solution Approach 1:
The patent replaces the conventional brushed contact starter motor with a brushless permanent magnet DC motor. This substitution eliminates mechanical brushes and contacts, thereby eliminating NVH associated with brush contact and preventing voltage drops. The brushless motor provides reliable engine starting while removing the harmful factors of noise, vibration, and electrical instability.
Solution Approach 2:
The patent changes the operating parameters by using a high-voltage power source to power the brushless starter motor. This parameter change enables faster engine restarts and eliminates the voltage drops that occur with conventional low-voltage starter motors, while also improving overall system efficiency and reducing emissions.
2Ease of operation
If sequential actuation with mechanical actuators is used for clutch engagement, then the engine can be decoupled and re-engaged, but the process is slow and reduces responsiveness
Solution Approach 1:
The patent replaces mechanical actuators with an electrically-controlled clutch system. This substitution allows for rapid engagement and disengagement of the clutch by using electrical signals instead of mechanical actuation, thereby significantly increasing the speed of engine restart and improving overall system responsiveness while maintaining ease of operation.
3Reliability
If additional voltage stabilization components and mechanical actuators are included, then the system can function reliably, but the device complexity increases
Solution Approach 1:
The patent extracts and removes unnecessary components from the system. By using a brushless starter motor powered directly from the high-voltage battery, the system eliminates the need for additional voltage stabilization components and mechanical actuators. This reduction in component count simplifies the device while maintaining or improving reliability through the more efficient brushless motor technology.
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 provides faster engine restarts, reduced NVH, and improved responsiveness by utilizing a high-voltage power source for the starter electric machine, eliminating the need for additional boost converters and mechanical actuators, thus enhancing fuel efficiency and reducing emissions.
Implementation Method 1
A brushless permanent magnet DC motor as the starter electric machine, powered by a high-voltage traction battery
Data Source
AI summary
A vehicle propulsion system includes an engine and a first electric machine each configured to selectively provide torque to propel the vehicle. A second electric machine is coupled to the engine to provide torque to start the engine from an inactive state. A high-voltage power source is configured to power both of the first electric machine and the second electric machine over a high-voltage bus. A propulsion controller is programmed to start the engine using cranking torque output from the second electric machine powered by the high-voltage power source. The controller is also programmed to operate both of the first electric machine and the combustion engine to propel the vehicle in response to an acceleration demand greater than a threshold. The controller is further programmed to decouple the engine and propel the vehicle using the first electric machine in response to vehicle speed less than a speed threshold.