Coordinated Engine Start Torque in Cold Hybrid Powertrains
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Solution Overview
Problem
In hybrid electric vehicles, very cold temperatures reduce the output of high voltage batteries, making it difficult for electric motors to crank the engine alone, and low voltage starters experience belt slip, hindering engine starting.
Innovation Solution
An electronic controller coordinates the actuation of both the electric machine and the belt integrated starter-generator (BISG) to apply torques to the engine, using the electric machine to provide initial torque through a disconnect clutch and the BISG to provide additional torque once an engine speed threshold is reached.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electric motor alone is used to crank the engine, then the structure is simple, but in very cold temperatures the battery output is significantly reduced making the torque insufficient to start the engine
Solution Approach 1:
The patent combines two different starting systems (electric motor and belt integrated starter) into a hybrid starting system. The controller coordinates both systems to work together, merging their torque outputs to ensure reliable engine starting in cold temperatures while maintaining the ability to operate with either system independently.
Solution Approach 2:
The starting system is segmented into two independent components: the electric motor and the belt integrated starter. Each component can operate independently or in coordination, allowing the system to adapt to different temperature conditions and battery states without requiring complete system redesign.
2Force
If the low voltage starter is used to assist in cold temperatures, then the torque is increased, but the belt experiences slip reducing effectiveness
Solution Approach 1:
The controller continuously monitors engine speed and torque requirements, dynamically adjusting the operation of the belt integrated starter and electric motor. When belt slip is detected or anticipated, the controller increases electric motor contribution to compensate, ensuring reliable starting despite belt limitations.
Solution Approach 2:
The system changes operational parameters based on temperature and battery state. In very cold temperatures, the controller modifies the torque distribution between the electric motor and belt starter, and adjusts engagement timing to optimize performance while accounting for reduced battery output and increased belt slip risk.
3Force
If both electric motor and belt integrated starter are coordinated to start the engine, then the torque is sufficient in cold temperatures, but the control complexity increases
Solution Approach 1:
The control system automatically determines the optimal torque distribution between the electric motor and belt integrated starter based on real-time sensor data including temperature, battery state, and engine speed. The system self-regulates without requiring manual intervention, managing the complexity internally while presenting a simple interface.
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 coordinated approach ensures reliable engine starting in very cold temperatures by combining the torques from the electric machine and the BISG, overcoming the limitations of reduced battery power and belt slip.
Implementation Method 1
the electric machine to apply a first torque to the engine
Implementation Method 2
An electric machine selectively coupled with the engine by a clutch
Implementation Method 3
the BISG may experience belt slip
Implementation Method 4
the method includes using a starter to apply a second torque to the engine
Data Source
AI summary
A vehicle includes an engine and an electric machine coupled to a transmission element. The electric machine is also selectively coupled with the engine by a clutch. The vehicle includes a belt integrated starter-generator (BISG) operatively coupled to the engine. An electronic controller includes one or more inputs adapted to receive a temperature measurement and a request to start the engine. The electronic controller is programmed to, in response to the one or more inputs receiving the request to start the engine and the temperature measurement less than a threshold temperature measurement, effect actuation of the electric machine and close the clutch to apply a first torque to the engine. The electronic controller is further programmed to, in response to an engine speed achieving an engine speed threshold, effect actuation of the BISG to apply a second torque to the engine.