CVT Lock-Up Clutch Control for Hydraulic Pressure Maintenance
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Solution Overview
Problem
The challenge is to protect continuously variable transmissions in vehicles while improving fuel consumption performance, as engine stop-start technology reduces hydraulic pressure, leading to potential slippage and increased fuel consumption.
Innovation Solution
A control device is implemented with a lock-up clutch, electric motor, and device control unit that manages the clutch and motor states to maintain hydraulic pressure during vehicle deceleration and stop conditions, using an electric pump to support hydraulic oil supply when the engine is stopped.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the engine stop-start technology is implemented to improve fuel consumption, then fuel efficiency is improved, but the hydraulic pressure drops causing chain slippage in the continuously variable transmission
Solution Approach 1:
The control device activates the electric motor before the engine actually stops to maintain hydraulic pressure. When the control unit detects engine stop conditions, it promptly activates the electric motor to drive the oil pump, ensuring hydraulic pressure is maintained in advance before any potential slippage occurs, rather than waiting for pressure to drop.
Solution Approach 2:
The electric motor serves as an intermediary between the stopped engine and the oil pump. When the engine stops, the electric motor temporarily takes over as the driving force for the oil pump, maintaining hydraulic pressure without requiring the engine to remain running. This intermediary solution allows engine stop-start operation while preventing transmission slippage.
2Reliability
If the engine is kept running at idle to maintain hydraulic pressure, then transmission reliability is improved, but fuel consumption increases
Solution Approach 1:
The invention extracts the function of driving the oil pump from the engine alone. By separating the engine's primary function (power delivery) from the oil pump driving function, the system can stop the engine while using the electric motor to maintain hydraulic pressure, thereby protecting the transmission without continuous fuel consumption at idle.
Solution Approach 2:
The system dynamically changes the driving parameter of the oil pump from engine-driven (fuel-consuming) to electric motor-driven (energy-efficient during idle periods). The control unit monitors hydraulic pressure and engine state, switching between power sources optimally - using engine power when needed and electric motor power when the engine is stopped, thus protecting transmission reliability while minimizing fuel consumption.
3Reliability
If the electric motor is activated to maintain hydraulic pressure during engine stop, then hydraulic pressure is maintained preventing slippage, but the electric motor control complexity increases
Solution Approach 1:
The control unit continuously monitors hydraulic pressure from the oil pump and engine rotational state, using this feedback to determine when to activate or deactivate the electric motor. This closed-loop feedback control automatically adjusts electric motor operation based on real-time pressure conditions, maintaining hydraulic pressure reliability while managing control complexity through intelligent automation rather than manual intervention.
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 ensures minimal hydraulic pressure is maintained in the continuously variable transmission, preventing slippage and enhancing fuel efficiency by allowing the engine to be rotated by the electric motor during fuel cut-off conditions.
Implementation Method 1
an electric motor that is coupled to the engine and configured to be controlled in a powering state in which the engine is rotationally driven
Implementation Method 2
an oil pump that is configured to be driven by the engine and to supply a hydraulic oil to the continuously variable transmission
Implementation Method 3
a lock-up clutch that is disposed in a torque converter coupled to the engine and switchable between an engaged state and a released state
Data Source
AI summary
Provided is a control device for a vehicle including a continuously variable transmission. The control device includes a lock-up clutch, an oil pump, an electric motor, and a device control unit. The lock-up clutch is disposed in a torque converter coupled to the engine and switchable between an engaged state and a released state. The oil pump is driven by the engine and supplies a hydraulic oil to the continuously variable transmission. The electric motor is coupled to the engine and controlled to be in a powering state in which the engine is rotationally driven. The device control unit controls the lock-up clutch to put into the released state and controls the electric motor to put into the powering state if a discharge pressure of the oil pump falls below a threshold value at the time of a vehicle deceleration in which a fuel supply to the engine is cut off.