Hybrid Vehicle Engine Start Control During Downshift
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Solution Overview
Problem
In hybrid vehicles, the existing engine start control methods during automatic transmission shift control often result in increased thermal load and potential damage to the engine connecting and disconnecting device due to prolonged engine speed synchronization, especially when downshifting with a large speed difference between the motor and engine speeds.
Innovation Solution
A control device that dynamically selects between two engine start methods based on motor speed, allowing for a lower gear position downshift during engine start, reducing thermal load and inertia-related shocks by switching to the second starting method when the motor speed exceeds a predetermined value, thereby minimizing damage and improving shift responsiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the engine start control is executed during downshift control of the automatic transmission, then the engine can be started and the engine connecting and disconnecting device can be fully engaged, but the thermal load on the engine connecting and disconnecting device increases and may cause damage
Solution Approach 1:
The control device determines whether downshift control is being executed before initiating engine start control. If downshift control is detected, the control device waits until the downshift is completed before starting the engine, thereby preventing the engine connecting and disconnecting device from experiencing excessive thermal load during the gear shifting process
Solution Approach 2:
The control device continuously monitors the operational state of the automatic transmission to detect whether downshift control is being executed. Based on this feedback information, the engine start control is conditionally inhibited or permitted, ensuring that engine starting does not occur during periods when the engine connecting and disconnecting device would be subjected to harmful thermal conditions
2Object-affected harmful factors
If the gear position as destination of downshift is restricted to relatively high gear position during engine start, then thermal load on engine connecting and disconnecting device is reduced, but the driveability deteriorates due to delayed downshift to target gear position
Solution Approach 1:
The control device dynamically adjusts the engine start strategy based on the real-time state of downshift control. When downshift control is detected, the system determines whether to inhibit engine start or permit it with modified parameters, allowing flexible adaptation to different driving conditions and transmission states to balance thermal protection with driveability requirements
Solution Approach 2:
The control device changes the operational parameters of engine start control based on the downshift state. By monitoring whether downshift control is being executed and adjusting the engine start timing or method accordingly, the system optimizes the balance between reducing thermal load on the engine connecting and disconnecting device and maintaining acceptable driveability
3Speed
If skip gearshift is performed with large increase in motor speed, then the downshift response is faster, but the speed difference between motor speed and engine speed increases, causing longer synchronization time and increased thermal load
Solution Approach 1:
The control device detects skip gearshift operations in advance by monitoring the automatic transmission control state. When a skip downshift is detected, the system proactively adjusts engine start control parameters or timing to account for the larger speed difference, reducing the synchronization time and preventing excessive thermal load on the engine connecting and disconnecting device
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
The solution effectively reduces thermal load on the engine connecting and disconnecting device and minimizes inertia-related shocks, enabling prompt and efficient downshift to target gear positions while maintaining driveability and reducing the risk of damage.
Implementation Method 1
an engine connecting and disconnecting device of a frictional engagement type
Data Source
AI summary
A control device of a hybrid vehicle including an engine, motor that receives power from the engine via an engine connecting and disconnecting device, and automatic transmission, starts the engine in a first starting method in which the engine performs ignition and rotates by itself after the engine speed is increased to be equal to or higher than a predetermined rotational speed through slipping engagement of the engine connecting and disconnecting device, or a second starting method in which the engine performs ignition and rotates by itself from a stage before the engine speed reaches the predetermined rotational speed, and controls the automatic transmission to permit a lower gear position to be established according to shift conditions when the engine is started in the second starting method during a downshift of the automatic transmission, as compared with when the engine is started in the first starting method during the downshift.