Hybrid Engine Start Control via Variable Clutch Torque
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Solution Overview
Problem
Existing engine start control systems for hybrid electric vehicles do not differentiate between engine starts initiated by the driver's accelerator operation and those initiated by other factors, leading to uncomfortable torque fluctuations for the driver during unintended engine starts from rest.
Innovation Solution
The system introduces a dual start mode control for the hybrid electric vehicle, where the first start mode prioritizes quick engine start with higher torque capacity when initiated by the driver, and the second start mode suppresses torque fluctuations by reducing the torque capacity of the first clutch when the engine is started without driver intention, such as due to system requests or specific conditions like high oil temperature or low battery power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the transmitted torque capacity of the first clutch is increased to quickly start the engine, then the engine start speed is improved, but the torque fluctuation and shock sensation increase when the engine is started without driver intention
Solution Approach 1:
The patent applies dynamics by making the transmitted torque capacity of the first clutch adjustable based on operating conditions. The control device dynamically changes the clutch torque capacity according to whether the engine start is driver-intended or system-initiated, and according to motor-generator torque availability. This dynamic adjustment resolves the contradiction by optimizing the clutch torque capacity for each specific situation rather than using a fixed high value.
Solution Approach 2:
The patent changes the parameter of transmitted torque capacity of the first clutch based on different start conditions. When the engine is started without driver intention and motor-generator torque is sufficient, the clutch torque capacity is set to a lower value to reduce shocks. When driver intention is detected or motor-generator torque is insufficient, the clutch torque capacity is increased for faster engine starting. This parameter change strategy directly addresses the technical contradiction.
2Productivity
If the transmitted torque capacity of the first clutch is increased for fast engine starting, then the productivity is improved, but the driver comfort deteriorates during unintended engine starts
Solution Approach 1:
The patent applies local quality by differentiating the clutch torque capacity control based on the specific start condition. Instead of using a uniform high torque capacity for all engine starts, the system applies different torque capacity levels locally - lower capacity for system-initiated starts without driver intention, and higher capacity for driver-intended starts or when fast starting is necessary. This localized differentiation resolves the contradiction between productivity and driver comfort.
Solution Approach 2:
The control device uses feedback from the accelerator operation detection to determine driver intention. When accelerator operation is detected, the system infers driver intention to start the engine and adjusts clutch torque capacity accordingly. This feedback mechanism allows the system to adapt the engine starting characteristics to match driver expectations, resolving the contradiction between fast starting and driver comfort.
Data Source
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AI summary
An engine and a motor are provided. The engine and the motor are connected to each other through a first clutch whose transmitted torque capacity is adjustable. The engine is started by applying the first clutch and cranking the engine with a driving effort of the motor. A first start mode and a second start mode are employed. The first start mode is a mode in which the engine is started from rest in response to driver's accelerator operation. The second start mode is a mode in which the engine is started from rest in response to a factor other than driver's accelerator operation. The transmitted torque capacity of the first clutch during cranking of the engine is set smaller when in the second start mode than when in the first start mode.