Hybrid Vehicle Engine Start Inhibition at Low Clutch Slip Speeds
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
When transitioning from electrically driven (EV) mode to hybrid electric vehicle (HEV) mode, conventional systems cause discomfort to the driver due to engine starting issues at low vehicle speeds where the second clutch cannot slip, leading to inadequate torque capacity.
Innovation Solution
Preventing the internal combustion engine from starting when the input or output rotation speed is lower than a predetermined value and the friction engagement elements are impermissible to slip, thereby allowing the vehicle to maintain a comfortable driving experience.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the engine is started at low vehicle speeds where the second clutch cannot slip, then the transition from EV mode to HEV mode is achieved, but driver discomfort occurs due to inadequate torque capacity
Solution Approach 1:
The control device prevents engine start requests from being executed when rotation speeds are below predetermined thresholds and the second clutch cannot slip. By anticipating the problematic condition (inadequate torque capacity at low speeds) and blocking the engine start request beforehand, the system avoids the driver discomfort that would result from attempting to start the engine under unsuitable conditions.
Solution Approach 2:
The system dynamically adjusts engine start permission based on real-time rotation speed conditions and second clutch slip capability. The control device continuously monitors input and output rotation speeds of the transmission, and only permits engine start when conditions are favorable (rotation speeds above thresholds and clutch capable of slipping), thereby adapting the mode transition process to current operating conditions to maintain driver comfort.
2Adaptability or versatility
If the second clutch torque capacity is lowered to enable engine starting, then engine start from EV mode is enabled, but torque transmission capability is insufficient at low speeds
Solution Approach 1:
The control device changes the operational parameters (rotation speed thresholds) that determine when engine start is permitted. By establishing predetermined rotation speed thresholds and only allowing engine start when both input and output rotation speeds exceed these thresholds, the system ensures that sufficient torque capacity is available in the second clutch during engine starting, avoiding the torque transmission insufficiency that occurs at low speeds.
3Productivity
If engine start is permitted at low rotation speeds, then mode transition is achieved, but the risk of engine stall increases
Solution Approach 1:
The control device performs preliminary verification of rotation speed conditions before permitting engine start. By checking whether input and output rotation speeds are above predetermined thresholds and whether the second clutch can slip, the system ensures that engine starting will occur under favorable conditions with adequate torque capacity, thereby preventing engine stall and maintaining reliable engine operation while still enabling efficient mode transition.
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 solution alleviates driver discomfort by canceling engine start requests at low speeds, ensuring a smoother transition and reducing the risk of engine stall, while maintaining efficient power management.
Implementation Method 1
the friction engagement elements being impermissible to slip
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A control system (60) for a hybrid vehicle (1) includes a mode selection unit (200) for start request of an engine (10); a slip determination unit (410) for determining whether or not a second clutch (25) is allowed to slip; and a start determination unit (420) for determining whether or not to allow the engine (10) to start. The start determination unit (420) prevents the engine (10) from starting when an input rotation speed (Ni) or an output rotation speed (No) (= vehicle speed (VSP)) of an automatic transmission (40) is less than a predetermined value in the presence of the start request of the engine (10) from the mode selection unit (200) and the slip determination unit (410) determines that the second clutch (25) is not allowed to slip.