Hybrid Engine Start Control via Starter Motor Segmentation
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Solution Overview
Problem
In one-motor two-clutch parallel hybrid vehicles, the restricted rated torque of the motor/generator limits the electric vehicle (EV) mode range, leading to early mode changes to hybrid mode at low speeds, which degrades fuel efficiency.
Innovation Solution
An engine start control device that selects between a first engine start system using the motor/generator and a second engine start system using a starter motor based on rotation speed information, allowing the second system to be used when the rotation speed is higher than a predetermined threshold, thereby delaying the need for engine assistance and extending the EV mode range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the rated torque of the motor/generator is restricted to reduce cost and mounting space, then the motor/generator can be downsized, but the driving torque part becomes small which limits the EV mode range
Solution Approach 1:
The patent segments the engine start function into two independent systems: the first engine start system using the motor/generator and the second engine start system using a dedicated starter motor. This segmentation allows the motor/generator to be downsized for cost and space reduction while the starter motor handles engine starting, preserving the EV mode range without requiring the motor/generator to provide both propulsion and starting torque.
2Reliability
If the first clutch is engaged to start the engine with the motor/generator, then the engine can be started, but the motor/generator must provide sufficient torque for both EV travel and engine cranking which restricts its rated torque
Solution Approach 1:
The patent introduces a dedicated starter motor as an intermediary device specifically for engine starting. This intermediary handles the high-torque cranking function, allowing the motor/generator to be optimized for its primary propulsion function with a smaller rated torque while engine startability is maintained through the starter motor system.
3Reliability
If the motor/generator provides both EV travel torque and engine start torque, then engine start is ensured, but the EV mode range is narrowed at low vehicle speeds
Solution Approach 1:
The patent divides the engine start function into two separate systems operated by different control strategies. The first system (motor/generator) operates at low speeds where it can provide both propulsion and cranking torque, while the second system (starter motor) operates at higher speeds where it handles cranking alone. This segmentation allows the motor/generator to maintain full rated torque for EV travel across a wider speed range without being constrained by engine starting requirements.
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 allows continued EV travel at higher speeds without the need for engine assistance, expanding the EV mode range and improving fuel efficiency by effectively utilizing the starter motor for engine startability at higher speeds.
Implementation Method 1
a motor/generator (6), which functions as a drive source for the vehicle in addition to functioning as a generator for regenerative braking
Implementation Method 2
a second engine start system that starts the engine with a starter motor (8) for starting the engine
Data Source
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AI summary
If a vehicle speed VSP during EV travel is lower than a predetermined speed VSP_s and hence is in a low vehicle speed range available for motor travel by a motor/generator (S11), engine start control using a first engine start system with the motor/generator is executed (S12). If the vehicle speed VSP during the EV travel is the predetermined speed VSP_s or higher and hence is in a vehicle speed range unavailable for the motor travel with the motor/generator (S11), engine start control using a second engine start system with a starter motor is executed (S13) instead of the first engine start system with the motor/generator. Accordingly, the motor/generator does not have to cover an engine start torque when VSP ≥ VSP_s. A vehicle speed range available for the motor travel expands by the amount corresponding to the engine start torque, and fuel efficiency can be improved.