DC/DC Converter Voltage Adjustment for Engine Cranking Torque
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Solution Overview
Problem
Existing vehicle systems face challenges in ensuring consistent engine starting due to insufficient torque output from the electric machine, particularly when the electric energy storage device is degraded, leading to prolonged cranking times or failed engine starts.
Innovation Solution
A method is introduced where the output voltage of a DC/DC converter is adjusted in response to engine speed during cranking, increasing the torque output of the electric machine by boosting the voltage of the low voltage bus when the engine cranking speed is less than desired, ensuring the electric machine can rotate the engine at the necessary speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electric machine is supplied with electric current via a degraded electric energy storage device, then the electric machine may not output sufficient torque to rotate the engine at the desired speed, but increasing the voltage output of the DC/DC converter during engine cranking can compensate for this deficiency
Solution Approach 1:
The DC/DC converter dynamically adjusts its voltage output parameter in response to engine cranking speed. When the engine cranking speed is below the desired threshold, the converter increases voltage output to compensate for degraded energy storage device capacity, thereby maintaining sufficient electric machine torque output for reliable engine starting
Solution Approach 2:
The system implements feedback control by monitoring engine cranking speed and using this information to adjust the DC/DC converter's voltage output. The controller continuously compares actual cranking speed with desired speed and modulates the converter output accordingly, creating a closed-loop control system that ensures reliable engine starting despite component degradation
2Power
If the DC/DC converter increases voltage output during engine cranking, then the electric machine can achieve desired torque output, but this increases energy consumption from the energy storage device
Solution Approach 1:
The DC/DC converter operates dynamically by continuously adjusting its voltage output based on real-time engine cranking speed conditions. Rather than maintaining a fixed high voltage output, the converter adapts its power delivery to match actual cranking needs, optimizing the balance between torque generation and energy consumption
Solution Approach 2:
The system prepares for engine starting by monitoring energy storage device state and pre-positioning the DC/DC converter to provide necessary voltage support during cranking. This preliminary preparation ensures that when cranking is needed, the converter can immediately deliver appropriate power without excessive energy waste
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 approach enhances engine starting consistency and reduces the likelihood of engine failure by ensuring sufficient torque is generated to achieve the desired cranking speed, improving overall engine starting efficiency.
Implementation Method 1
adjusting an output voltage of a DC/DC converter that is electrically coupled to a low voltage bus
Implementation Method 2
cranking the engine via an electric machine, the electric machine electrically coupled to the low voltage bus
Data Source
AI summary
A method for operating a vehicle that includes a DC/DC converter is described. In one example, the method includes adjusting an output voltage of the DC/DC converter to increase torque of a belt integrated starter/generator. The output voltage of the DC/DC converter may be adjusted before and during engine cranking.