Hybrid Engine Lift-Start Control via Transmission Ratio Adjustment
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Solution Overview
Problem
In hybrid vehicle engine starting control systems, the rotational difference between the engine and motor/generator can lead to heat generation and durability issues in the clutch during lift-starting, especially when the motor/generator is at high rpm, causing clutch deterioration.
Innovation Solution
A control system that adjusts the gearshift ratio of the transmission to reduce the transmission input rotation speed to a range that matches or exceeds the engine's operational rotation speed, engaging the clutch to lift-start the engine while compensating for drag torque using the motor/generator, thereby minimizing rotational differences and heat generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the motor/generator is rotating at high rpm during engine lift-starting, then the engine can be started quickly, but the rotational difference in the first clutch increases causing heat generation and clutch durability deterioration
Solution Approach 1:
The control system performs preliminary action by controlling the motor/generator rotation speed before clutch engagement. The motor/generator is accelerated to a target rotation speed that is carefully controlled to be within an acceptable range of the engine rotation speed, preventing excessive rotational difference before the clutch engages. This preliminary speed matching prevents the harmful effect of large rotational difference and heat generation while still enabling quick engine starting.
Solution Approach 2:
The control system changes the parameter of motor/generator rotation speed to optimize the starting process. By dynamically adjusting the motor/generator rotation speed to match the engine rotation speed parameters, the system minimizes the rotational difference across the clutch during engagement. This parameter control allows the clutch to engage with minimal slip and heat generation, protecting clutch durability while maintaining efficient engine starting.
2Productivity
If the first clutch engages with large rotational difference, then engine starting is achieved, but heat is generated due to slip engagement causing clutch durability deterioration
Solution Approach 1:
The control system performs preliminary speed matching by controlling the motor/generator rotation speed to be close to the engine rotation speed before clutch engagement. This preliminary action ensures that when the clutch engages, the rotational difference is minimal, preventing excessive heat generation from slip engagement while still achieving reliable engine starting.
Solution Approach 2:
The control system converts the potential harmful effect of rotational difference into a benefit by using the motor/generator's ability to precisely control its rotation speed. Instead of allowing uncontrolled high-speed engagement that would cause heat, the system uses the motor/generator's speed control capability to match speeds, turning the rotational difference from a harmful factor into a controlled parameter that enables smooth engagement without excessive heat generation.
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 suppresses clutch durability deterioration, improves fuel efficiency, and ensures successful engine starting when switching from electric to hybrid operation mode by controlling the gearshift ratio based on battery charge, vehicle speed, and driver requests, reducing heat generation and maintaining engine start capability.
Implementation Method 1
heat is generated in the first clutch due to the slip engagement associated with a large amount of slip
Data Source
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AI summary
An engine of a hybrid vehicle is lift started by reducing a rotational speed of a motor/generator (MG) of the hybrid vehicle by adjusting a gearshift ratio of a transmission (AT) coupled to the motor/generator (MG), and engaging a clutch (CL1) to couple the engine (E), while in a stopped state, to the rotating motor/generator (MG) for imparting the rotation to the engine (E).