Engine Clutch Touchpoint Learning in Hybrid Electric Vehicles
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Solution Overview
Problem
Hybrid electric vehicles face challenges in accurately learning the touchpoint of the engine clutch, which is affected by wear, leading to increased hydraulic pressure requirements and inefficient learning processes, especially when the engine is off, resulting in prolonged learning times and potential fuel loss.
Innovation Solution
A method for learning the touchpoint of the engine clutch by adjusting the engagement hydraulic pressure in a stepwise manner using a first and second motor, allowing touchpoint learning after starting the motor while the engine is off, with the first controller unit controlling the motors to maintain specific speeds and the second controller unit determining the touchpoint based on torque changes, thereby stabilizing the engine shaft clutch speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the engine is on during touchpoint learning, then the learning process can proceed using idle RPM, but the learning time is prolonged due to idle stabilization requirements and fuel is consumed
Solution Approach 1:
The patent changes the operational parameters from engine idle RPM to motor-driven RPM. The control unit controls the motor to rotate at a predetermined RPM that corresponds to the touchpoint condition, eliminating the need for idle stabilization while maintaining accurate touchpoint detection through torque change monitoring
Solution Approach 2:
The patent replaces the mechanical engine idle operation with an electrical motor-driven system. Instead of relying on the engine's natural idle characteristics, the motor is controlled to achieve the required RPM and torque conditions for touchpoint learning, enabling faster and more efficient learning without fuel consumption
2Loss of energy
If the engine is off during touchpoint learning, then fuel loss is reduced, but the learning process cannot proceed as the engine is not running
Solution Approach 1:
The patent makes the motor serve multiple functions: it acts as both a propulsion device and a substitute for the engine during touchpoint learning. The motor can operate independently to provide the necessary RPM and torque for learning without requiring the engine to be running, enabling learning in engine-off conditions
Solution Approach 2:
The motor serves as an intermediary between the battery and the clutch system during learning. It transmits rotational force to the clutch assembly through the transmission, enabling the touchpoint learning process to occur without direct engine involvement while still achieving the mechanical conditions needed for accurate learning
3Reliability
If continuous use of the engine clutch occurs, then the clutch wears and the touchpoint changes, but increasing engagement hydraulic pressure to compensate increases system complexity
Solution Approach 1:
The patent performs touchpoint learning at regular intervals to proactively detect and adapt to clutch wear before it significantly impacts performance. By periodically updating the touchpoint reference values based on actual clutch behavior, the system maintains accurate control without needing to increase hydraulic pressure or add complex compensation mechanisms
Solution Approach 2:
The patent implements a feedback mechanism where the control unit continuously monitors torque changes during clutch engagement and uses this information to identify and update touchpoint values. This adaptive feedback loop compensates for clutch wear by dynamically adjusting the learned touchpoint parameters, maintaining reliable operation without increasing system complexity
Data Source
AI summary
A hybrid electric vehicle (HEV) includes an engine, a first motor directly connected to the engine through a first shaft, a second motor directly connected to a second shaft, and an engine clutch of which one end is connected to the first shaft and the other end is connected to the second shaft so as to selectively connect the first shaft and the second shaft. The (HEV) includes a first controller unit configured to control each of the first motor and the second motor and a second controller unit configured to determine whether a preconfigured touch point learning condition is satisfied, control the first and second motors to respective first and second speeds when the learning condition is satisfied, and learn a touch point of the engine clutch on the basis of a torque change of the first motor or the second motor.