Hybrid Engine Start via Disconnect Clutch Dynamics
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Hybrid electric vehicles require frequent and smooth engine restarts, which traditional starter motors may not reliably handle due to excessive usage, and rapid restarts are often necessary while the vehicle is moving.
Innovation Solution
A method involving the motor to propel the vehicle with a partially engaged disconnect clutch, gradually increasing engine speed and fueling, then fully engaging the clutch, with torque converter bypass clutch management to ensure smooth and efficient engine start transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional starter motors are used for frequent engine restarts in hybrid electric vehicles, then the engine can be restarted reliably, but the starter motor durability deteriorates due to excessive usage
Solution Approach 1:
The motor normally used for propelling the vehicle is made to serve a dual function: it acts as both the propulsion motor and the starter motor for engine restarts. This eliminates the need for a dedicated starter motor and ensures that the same motor with sufficient power and durability handles all engine restart operations in hybrid electric vehicles.
2Speed
If the engine is restarted rapidly while the vehicle is moving, then the response time is reduced, but the smoothness of the restart deteriorates
Solution Approach 1:
The disconnect clutch is controlled dynamically during engine restart by modulating its engagement state. The clutch transitions through different engagement levels (disengaged, partially engaged, fully engaged) to smoothly transfer torque from the motor to the engine crankshaft, enabling rapid yet smooth engine restarts while the vehicle is moving without disturbing vehicle torque.
Solution Approach 2:
The disconnect clutch acts as an intermediary component between the motor and the engine crankshaft during restart operations. By controlling the clutch engagement state, it mediates the torque transfer process, allowing the motor to accelerate the engine smoothly and rapidly without directly coupling the motor to the engine, thus maintaining both speed and smoothness.
3Speed
If the disconnect clutch is fully engaged immediately to start the engine, then the engine starts quickly, but vehicle torque is disturbed
Solution Approach 1:
The disconnect clutch engagement is controlled dynamically in stages rather than being fully engaged immediately. The clutch transitions from disengaged to partially engaged to fully engaged state, allowing the engine to accelerate smoothly while the motor provides assistance, thereby achieving quick engine start without sudden torque disturbances to the vehicle.
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 the reliability and smoothness of engine starts in hybrid electric vehicles, reducing wear on starter motors and enabling rapid transitions to hybrid mode without disturbing vehicle torque, thus improving durability and operational efficiency.
Implementation Method 1
using either the internal combustion engine or using a traction motor powered by electrical energy stored in a battery
Implementation Method 2
partially engaging a disconnect clutch to rotate the engine
Implementation Method 3
A torque converter bypass clutch may open or slip during the engine start process
Data Source
AI summary
Two methods may be used to start the engine of a hybrid electric vehicle while the vehicle is moving under electric power. When smoothness is most important, a disconnect clutch is partially engaged to initiate engine rotation and then released as the engine accelerates under its own power toward a motor speed. When rapid starting is most important, the disconnect clutch torque capacity is controlled to decrease the time required for the engine to accelerates to the motor speed. A torque converter bypass clutch is disengaged during the engine restart under either method. Also, the motor torque is adjusted under either method to compensate for the torque provided to the engine.