Hybrid Vehicle Engine Start Control via Road Gradient and RPM
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Solution Overview
Problem
Hybrid vehicles face challenges in optimizing engine start time, leading to inefficient fuel use, noise, vibration, and harshness (NVH) issues, especially on uphill roads, due to inaccurate torque control and frequent clutch engagement, which affects state of charge (SOC) balancing and overall fuel efficiency.
Innovation Solution
A method and device that control engine start time based on motor revolutions per minute (RPM) and road gradient, using a hybrid starter-generator to charge the battery and prevent engine clutch engagement with the motor, optimizing engine start timing to synchronize RPM and reduce unnecessary energy loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the engine start time is controlled based on motor RPM and road gradient, then fuel efficiency is improved and NVH is reduced, but the control system complexity increases
Solution Approach 1:
The controller predicts the required engine RPM and determines the optimal start time in advance before the engine is actually started. This preliminary calculation of target RPM and timing allows the engine to be started at the optimal moment, improving fuel efficiency and reducing NVH while maintaining manageable control complexity through advance planning.
Solution Approach 2:
The control system dynamically adjusts the target engine RPM and start timing based on real-time motor RPM and road gradient conditions. This dynamic adaptation allows the system to optimize engine start parameters for each specific driving scenario, improving fuel efficiency without requiring overly complex fixed-rule control logic.
2Use of energy by moving object
If the engine starts earlier to synchronize RPM with motor, then fuel efficiency improves, but the risk of improper engagement increases
Solution Approach 1:
The controller performs preliminary calculations to determine both the target engine RPM and the optimal start timing before engine initiation. By pre-calculating when to start the engine based on predicted RPM requirements, the system ensures synchronous engagement without premature or delayed starting, thus improving fuel efficiency while maintaining engagement reliability.
Solution Approach 2:
The control system continuously monitors motor RPM and road gradient, using this feedback to dynamically adjust the target engine RPM and start timing. This closed-loop feedback mechanism ensures that the engine starts at the optimal moment for RPM synchronization, improving fuel efficiency while preventing improper engagement through real-time condition assessment.
3Reliability
If the hybrid starter-generator is used to charge the battery, then SOC balance is maintained, but the system complexity increases
Solution Approach 1:
The hybrid starter-generator serves multiple functions: it can start the engine, generate electrical power to charge the battery, and operate as a motor. By utilizing this multi-functional component for both engine starting and battery charging, the system maintains SOC balance without adding separate dedicated components, thus managing system complexity while achieving reliable SOC management.
Data Source
AI summary
A method for controlling a start time of an engine in a hybrid vehicle includes: generating, by a controller, an engine start command before executing start control of the engine in response to an acceleration signal output from an acceleration pedal sensor; determining, by the controller, a gradient of a road on which the hybrid vehicle travels; controlling, by the controller, a hybrid starter-generator to operate by controlling the engine to start depending on the engine start command when it is determined that the gradient of the road is present; and controlling, by the controller, electric power of the hybrid starter-generator to charge a battery which provides electric power to a motor. The controller controls an engine clutch so that the motor is not engaged with the engine.