Hybrid Engine Start Control via Variable Torque Slip
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Solution Overview
Problem
Existing systems for hybrid electric vehicles face challenges in balancing fast acceleration response with preventing shocks when starting the internal combustion engine, especially at low requested acceleration amounts.
Innovation Solution
An engine start control device with a programmable controller that detects the requested acceleration amount using an accelerator opening sensor, controlling the frictional engagement elements to manage torque transmission and adjust the electric motor's output torque based on predetermined parameters to optimize engine start timing and torque increase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electric motor rotation speed is increased to start the internal combustion engine during low vehicle speed travel, then the engine can be started successfully, but a shock may occur due to abrupt torque increase when acceleration request is insignificant
Solution Approach 1:
The controller dynamically adjusts the electric motor rotation speed based on the requested acceleration amount. When acceleration request is significant, the motor speed is increased to enable engine start; when acceleration request is insignificant, the motor speed is limited to prevent shock. This parameter-based control resolves the contradiction by adapting the same system to different operating conditions.
2Speed
If the second frictional engagement element is controlled to slip state for fast acceleration response, then acceleration response is improved, but it becomes difficult to prevent shock during engine start
Solution Approach 1:
The system dynamically adjusts the slip ratio of the second frictional engagement element based on the requested acceleration amount. When acceleration request is significant, the slip ratio is increased for fast response; when acceleration request is insignificant, the slip ratio is reduced to prevent shock. This dynamic adaptation resolves the contradiction between response speed and shock prevention.
3Productivity
If the electric motor torque is increased rapidly to charge the battery, then battery charging efficiency is improved, but driver-intended torque may be reduced causing shock
Solution Approach 1:
The controller adjusts the electric motor torque based on the requested acceleration amount and battery charge amount. When battery charging is needed and acceleration request is significant, torque is increased rapidly for efficient charging; when acceleration request is insignificant, torque increase is limited to prevent shock. This parameter-based control resolves the contradiction between charging efficiency and shock prevention.
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 enables rapid acceleration response when needed while minimizing shocks during insignificant acceleration requests, enhancing the overall driving experience by effectively managing the transition from electric vehicle to hybrid electric vehicle mode.
Implementation Method 1
The electric motor and the internal combustion engine are connected via a first frictional engagement element
Implementation Method 2
control the second frictional engagement element to a slip state in which a torque is transmitted through a slipping operation of the second frictional engagement element
Data Source
AI summary
An engine start using an electric motor during a vehicle travel is performed by increasing an output torque of the electric motor in a slip state where a second frictional engagement element 3 connecting the electric motor 1 and a driving wheel slips. A controller determines a requested acceleration amount from a depression amount of an accelerator pedal. When the requested acceleration amount is significant, a different torque increment characteristic is applied, compared to a case where the requested acceleration amount is not significant. Thus, the internal combustion engine starts in a high response depending on the requested acceleration amount input by the driver, thereby improving a vehicle acceleration response.