Hybrid Vehicle Engine Start Threshold Control
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Solution Overview
Problem
Hybrid vehicles experience a reduction in total torque output to the drive shaft when starting the engine in double-drive mode, leading to a feeling of slowness for the driver, especially when required torque increases beyond a certain threshold.
Innovation Solution
The hybrid vehicle employs a configuration with an engine, first and second motors, a planetary gear set, a rotation restriction mechanism, and an electronic control unit to manage drive modes, including single-drive and double-drive modes, and adjusts the start threshold based on torque history and current torque conditions to minimize torque reduction during engine start-up.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the engine is started in double-drive mode when required torque exceeds the start threshold, then the engine can be started, but the total torque output to the drive shaft reduces by a large amount causing the driver to experience a feeling of slowness
Solution Approach 1:
The patent applies dynamics by making the start threshold variable rather than fixed. The control unit adjusts the start threshold based on the rotation speed of the drive shaft, allowing the threshold to increase when rotation speed is high (reducing torque reduction feeling) and decrease when rotation speed is low (ensuring reliable engine start). This dynamic adjustment resolves the contradiction between ensuring engine start reliability and maintaining adequate torque output.
Solution Approach 2:
The patent changes the parameter of the start threshold based on the rotation speed of the drive shaft. When the rotation speed is high, the start threshold is set to a higher value, and when the rotation speed is low, the start threshold is set to a lower value. This parameter change allows the system to adapt to different operating conditions, ensuring reliable engine start while minimizing the feeling of slowness.
2Productivity
If the start threshold is set to a high value to prevent engine start, then torque output is maintained, but the engine may not start when required torque becomes larger than the threshold
Solution Approach 1:
The patent makes the start threshold dynamic by linking it to the rotation speed of the drive shaft. When rotation speed is high, the threshold can be higher without preventing necessary engine starts. When rotation speed is low, the threshold automatically decreases to ensure reliable engine start. This dynamic behavior resolves the contradiction between maintaining torque output and ensuring engine start reliability.
Solution Approach 2:
The control unit uses feedback from the rotation speed sensor to continuously monitor the drive shaft rotation speed and adjust the start threshold accordingly. This feedback mechanism ensures that the start threshold is always appropriate for the current operating condition, preventing both unnecessary engine starts and failed engine starts.
3Reliability
If the engine is started when required torque is small, then the start threshold is easily exceeded, but the driver experiences a feeling of slowness due to torque reduction
Solution Approach 1:
The patent applies dynamics by making the start threshold dependent on the rotation speed of the drive shaft. When the rotation speed is high, the threshold is higher, making it harder to exceed and preventing unnecessary engine starts that would cause torque reduction. When the rotation speed is low, the threshold is lower, allowing responsive engine start when needed. This dynamic adjustment resolves the contradiction between engine start responsiveness and maintaining torque output.
Data Source
AI summary
When there is a history that a required torque has reached a high torque range and the required torque falls within a low torque range, a start threshold is changed from a value larger than a maximum double-drive torque to a value smaller than a selection threshold for selecting a single-drive mode or a double-drive mode. When the required torque becomes larger than the start threshold, an engine is started.