Hybrid Vehicle Clutch Control for Energy Regeneration
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Solution Overview
Problem
In hybrid vehicles with a two-motor hybrid drive system, the clutch's disengagement mechanism can lead to increased rotational speeds of the sun gear and first motor, causing inefficiencies in energy regeneration and potential durability issues, especially when the state of charge of the electric power storage device is saturated, and can result in engine restart failures and clutch wear due to improper engagement or disengagement states.
Innovation Solution
A control system that prohibits EV mode settings when the clutch is fully engaged at high vehicle speeds and disengaged at low speeds, allowing the engine to stop in EV mode, preventing excessive rotational speeds and ensuring the clutch remains engaged during vehicle stops to prevent foreign object invasion and wear, while allowing clutch engagement during acceleration requests.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the clutch is disengaged to allow the engine to stop in EV mode, then fuel economy is improved, but the rotational speed of the sun gear and first motor increases excessively causing energy regeneration inefficiency
Solution Approach 1:
The control system changes the engagement state parameter of the clutch based on vehicle speed thresholds. When vehicle speed exceeds the first threshold, the clutch is kept engaged to maintain appropriate rotational speeds for energy regeneration, while allowing engine stop at lower speeds to improve fuel economy.
2Ease of operation
If the clutch disengagement time is extended due to mechanism deterioration, then ease of operation is reduced, but the rotational speed of the sun gear and first motor increases due to vehicle speed increase during disengagement
Solution Approach 1:
The control system takes preliminary action by monitoring the disengagement time of the clutch. When the disengagement time exceeds a predetermined threshold, the system proactively prohibits EV mode setting to prevent excessive rotational speeds, addressing the issue before it causes energy regeneration inefficiency.
3Loss of energy
If the clutch remains disengaged during vehicle stops, then engine restart capability is lost, but fuel economy is improved
Solution Approach 1:
The control system uses feedback by monitoring the engagement state of the clutch and vehicle speed. When the clutch is detected to be disengaged at low speeds, the system prohibits EV mode to ensure engine restart capability is maintained, while still allowing fuel economy benefits when conditions are appropriate.
4Ease of operation
If the clutch is exposed to the outside of the vehicle in a disengaged state, then ease of operation is improved, but foreign objects or water invade the friction surface causing wear
Solution Approach 1:
The control system takes preliminary protective action by monitoring clutch engagement state and vehicle speed. When the clutch is disengaged at low speeds, EV mode is prohibited, which indirectly protects the clutch friction surface from exposure to foreign objects and water, preventing wear and maintaining durability.
Data Source
AI summary
A control system for a hybrid vehicle, the hybrid vehicle includes an engine, a first motor, a second motor, a differential mechanism, and a clutch. The control system includes a electronic control unit. The electronic control unit is configured to: (a) set an EV mode in which a vehicle travels at least by drive power of the second motor among the first motor and the second motor in a state that the engine stops, (b) prohibit setting of the EV mode in a state that the clutch is fully engaged when a vehicle speed is at least equal to a predetermined first vehicle speed threshold value, and (c) prohibit setting of the EV mode in a state that the clutch is disengaged when the vehicle speed of the vehicle that travels in the EV mode is at most equal to a predetermined second vehicle speed threshold value.