Automatic Transmission Parking Lock Control During Engine Spin-Down
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Solution Overview
Problem
Conventional hydraulic pressure control valves in vehicle automatic transmissions can cause interference between the parking rod and the regulating mechanism when power is turned ON or OFF, leading to potential damage.
Innovation Solution
The solution involves maintaining power supply to the hydraulic pressure control valve even after the vehicle's power is turned OFF, as long as the engine speed is higher than a given value, to prevent hydraulic pressure from being supplied to the parking drive mechanism, thus preventing interference with the regulating mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the hydraulic pressure control valve is used to control the parking drive mechanism, then the parking rod can be moved between locked and unlocked positions, but the parking rod may collide with the regulating mechanism when power is turned OFF or ON, causing damage
Solution Approach 1:
The controller maintains power supply to the hydraulic pressure control valve in advance during power OFF transitions (when engine speed exceeds threshold) to prevent hydraulic pressure from acting on the parking rod before the engine stops completely. This preliminary action ensures the parking rod remains stationary and avoids collision with the regulating mechanism.
Solution Approach 2:
The controller continuously monitors engine speed and uses this feedback to determine when to maintain or stop power supply to the hydraulic pressure control valve. When engine speed exceeds a predetermined threshold during power OFF, the controller maintains power supply; when engine speed is at threshold or below, the controller stops power supply. This feedback mechanism dynamically adjusts the control state to prevent damage.
2Loss of time
If power is turned OFF immediately, then the hydraulic pressure control valve stops receiving power and may allow hydraulic pressure to supply to the parking drive mechanism, but this causes the parking rod to move and collide with the regulating mechanism
Solution Approach 1:
The system performs a preliminary check of engine speed during the power OFF transition. If the engine speed exceeds the predetermined threshold, the controller preliminarily maintains power supply to the hydraulic pressure control valve, preventing hydraulic pressure from acting on the parking rod during the engine deceleration period. This preliminary maintenance of power supply avoids the harmful effect of premature power cutoff.
Solution Approach 2:
The controller changes the power supply parameter (from stopped to maintained) based on the engine speed parameter. When engine speed exceeds the threshold during power OFF, the power supply parameter is changed to maintained; when engine speed is at or below the threshold, the power supply parameter is changed to stopped. This dynamic parameter change ensures the parking rod remains stable during critical transitions.
3Ease of operation
If the hydraulic pressure control valve is designed to intercept hydraulic pressure when powered, then the system can control parking rod movement, but the valve response time is insufficient when power is turned ON, allowing hydraulic pressure to act on the parking rod
Solution Approach 1:
The controller performs a preliminary power supply action to the hydraulic pressure control valve during power ON transitions. By maintaining power supply during the initial period after power ON (until engine speed is confirmed to be at or below the threshold), the system ensures the valve is ready to intercept hydraulic pressure before the engine generates sufficient pressure to move the parking rod. This preliminary power supply compensates for the valve's response time limitation.
Solution Approach 2:
The controller rushes through the critical transition period by maintaining power supply to the hydraulic pressure control valve during the initial engine startup phase. This ensures the valve is already in the correct state (intercepting hydraulic pressure) before the engine speed rises enough to generate harmful hydraulic pressure, effectively skipping the window where damage could occur.
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 effectively prevents damage to the parking rod and the regulating mechanism by ensuring that the hydraulic pressure does not act on the parking rod when it is locked, thereby avoiding collisions and maintaining system integrity.
Implementation Method 1
a hydraulic pressure control valve which intercepts a supply of hydraulic pressure to the parking drive mechanism when power is supplied, and supplies the hydraulic pressure to the parking drive mechanism when power is not supplied
Implementation Method 2
The parking drive mechanism sets the parking rod at the locked position by biasing the parking rod, and sets the parking rod at the unlocked position using hydraulic pressure generated by an engine
Data Source
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AI summary
A control device for an automatic transmission includes a parking lock mechanism configured to lock/unlock rotation of a power transmission shaft by setting a parking rod at locked/unlocked position when the automatic transmission is in a parking range or in other ranges, a parking drive mechanism configured to set the parking rod at the unlocked position by supplying hydraulic pressure, a hydraulic pressure control valve configured to intercept the hydraulic pressure supply to the parking drive mechanism when power is supplied thereto, and supply the pressure when power is not supplied thereto, a regulating mechanism configured to regulate the movement of the parking rod at the locked position, and a controller configured to, when the parking rod is at the locked position, maintain supply of power to the valve, while an engine speed is higher than a given value, after power of a vehicle is turned OFF.