Electric Vehicle Clutch Torque Sharing Control
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Solution Overview
Problem
In electric vehicles with a motor and automatic transmission, the torque sharing rate of the second clutch during shift transitions is often imprecise, leading to clutch slipping or excessive torque sharing, which can result in erroneous gear shift inertia phase determination and prolonged engine start request response.
Innovation Solution
An electric vehicle control device that includes a motor, automatic transmission, shift control means, a frictional engagement element, and control means for switching the torque sharing rate, delaying the torque sharing rate switch from the start to the end of gear shift and continuously adjusting it based on the shifting procedure, ensuring precise engagement capacity control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the torque sharing rate is switched using gear shift start and end as triggers, then the control is simple to implement, but the engagement capacity precision of the frictional engagement element deteriorates
Solution Approach 1:
The torque sharing rate is changed from a static step function (switching only at gear shift start/end) to a dynamic continuous function that adjusts based on the shifting procedure progress. The control device calculates the shifting procedure progress based on rotational speed changes and continuously adjusts the torque sharing rate accordingly, making the control parameter adaptive to the real-time state of the frictional engagement element.
Solution Approach 2:
The control device introduces feedback by monitoring the actual shifting procedure progress (through rotational speed changes) and using this information to adjust the torque sharing rate. The feedback loop ensures that the torque sharing rate accurately reflects the current engagement state, allowing for precise control of the frictional engagement element's engagement capacity throughout the gear shift process.
2Reliability
If the torque sharing rate becomes smaller than intended during shift transition, then the control is conservative, but the second clutch slips and causes erroneous gear shift inertia phase determination
Solution Approach 1:
The control device performs preliminary action by proactively adjusting the torque sharing rate based on the predicted shifting procedure progress. Instead of reacting to slip or erroneous determination after they occur, the system anticipates the engagement state changes and pre-adjusts the torque sharing rate to maintain optimal engagement capacity throughout the transition, preventing slip and ensuring accurate inertia phase determination.
3Strength
If the torque sharing rate becomes larger than intended during shift transition, then the second clutch engagement is strong, but the slip-in time from engine start request to clutch slip begins to prolong
Solution Approach 1:
The torque sharing rate is dynamically adjusted to match the actual engagement state of the frictional engagement element. During engine start, the system detects the changing engagement conditions and adjusts the torque sharing rate in real-time, allowing the clutch to engage smoothly without excessive initial torque that would prolong slip-in time, while still ensuring sufficient engagement strength when needed.
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 approach ensures precise engagement capacity of the frictional engagement element by appropriately switching the torque sharing rate during shift transitions, preventing slipping and reducing engine start request latency.
Implementation Method 1
a frictional engagement element disposed in a power transmission path between the motor and driving wheels, and engaged or slip-engaged as an element other than a shifting element that is involved in the gear shift of the automatic transmission
Data Source
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AI summary
The present invention ensures the required engagement capacity precision of a frictional engagement element by appropriately switching a torque sharing rate during a shift transition period. Provided is a control device for an FR hybrid vehicle equipped with a motor/generator (MG), an automatic transmission (AT), an AT controller (7), a second clutch (CL2), a control unit (71) for switching the CL2 torque sharing rate, a torque/oil pressure command converter (72), and an oil pressure/electric current command converter (73). The second clutch (CL2) is disposed in a power transmission path from the motor/generator (MG) to the left and right rear wheels (RL, RR). The control unit (71) for switching the CL2 torque sharing rate delays switching the torque sharing rate of the second clutch (CL2) during a shift transition period until the start of the shifting procedure, and continuously switches the current gear sharing rate to a subsequent gear sharing rate in accordance with the degree of the shifting procedure when the shifting procedure starts.