Transmission Shift Valve Pulsing for Stiction Recovery
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Solution Overview
Problem
Automatic transmissions face issues with stuck electrohydraulic valves due to frictional resistance caused by oil-born contaminants or cold temperatures, which inhibit smooth shifting by preventing clutch engagement during gear ratio changes.
Innovation Solution
A controller-programmed decontamination routine that increases pressure to the stuck valve, including a series of first pressures, higher pressures, and pressure pulses according to a duty cycle, to overcome frictional resistance and free the valve element, ensuring seamless gear shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional pressure control is used during transmission shifting, then normal operation is maintained, but frictional resistance from contaminants or cold temperatures causes valves to stick and prevents smooth shifting
Solution Approach 1:
The system performs preliminary detection during the shift process to identify when a valve is stuck, then applies a cleaning pulse sequence before the shift is fully completed. This preliminary cleaning action prevents the stuck condition from persisting and affecting subsequent shifts, thereby maintaining reliable valve operation without requiring manual service.
Solution Approach 2:
The controller applies periodic cleaning pulses to the electrohydraulic valve at specific intervals during and after the shift process. These repeated high-pressure pulses effectively remove contaminants and break up frictional resistance, allowing the valve to return to normal operation and ensuring reliable shifting performance.
2Reliability
If high pressure is continuously applied to overcome frictional resistance, then valve sticking is prevented, but energy consumption increases and normal shifting operation is disrupted
Solution Approach 1:
Instead of continuously applying high pressure, the system uses periodic cleaning pulses with specific duty cycles. The high pressure is applied only during the pulse duration, then reduced, creating a rhythmic cleaning action that overcomes frictional resistance while minimizing overall energy consumption compared to continuous high-pressure application.
Solution Approach 2:
The controller dynamically changes the pressure parameter during the shift process by switching between normal operating pressure and elevated cleaning pressure. This parameter change is timed to coincide with detection of valve sticking, allowing the system to overcome frictional resistance only when necessary and maintain energy efficiency during normal operation.
3Reliability
If pressure pulses are applied to free a stuck valve, then shifting is restored, but the control system complexity increases
Solution Approach 1:
The controller monitors shift progress and detects when a valve is stuck by comparing actual shift status with expected shift status. This feedback mechanism triggers the cleaning pulse sequence only when needed, allowing the system to restore reliable shifting without requiring complex additional hardware, as the control logic leverages existing sensors and processors.
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 decontamination routine effectively unsticks the electrohydraulic valve, allowing for smooth transmission shifting by overcoming frictional resistance and ensuring clutch engagement, thereby maintaining transmission efficiency and preventing the need for manual service.
Implementation Method 1
an electrohydraulic valve having an actuatable valve element configured to control an engagement state of the oncoming shift element
Implementation Method 2
the torque capacity of each shift element is controlled by routing fluid to the shift elements at controlled pressure
Implementation Method 3
monotonically increase current to the valve to a maximum value to overcome frictional resistance on the valve element
Data Source
AI summary
A transmission includes a gearing arrangement configured to shift speed ratios by disengaging an off-going shift element and engaging an oncoming shift element and an electrohydraulic valve having an actuatable valve element configured to control an engagement state of the oncoming shift element. A controller is programmed to, during a shift of the transmission, in response to the off-going shift element disengaging and an expected ratio change not initiating, monotonically increase current to the valve to a maximum value to overcome frictional resistance on the valve element, and programmed to, in response to expiration of a timer and the ratio change still not initiating, send a repeating pattern of high and low current signals according to a duty cycle to overcome frictional resistance of the valve element.