Transmission Shift Element Pressure Control Against Disengagement
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Solution Overview
Problem
Form-locking shift elements in transmissions experience unintentional disengagement due to rapid torque buildup or hydraulic failures, leading to inefficient operation and potential mechanical issues, as they require precise synchronization and are prone to flank jamming and out-of-mesh positions, which existing control methods struggle to manage effectively.
Innovation Solution
A method involving a hydraulic pump-driven transmission with sensors to monitor the position of form-locking shift elements, determining reference values for engaged and disengaged states, and adjusting hydraulic pressure to prevent undesirable operating condition changes, using threshold values to trigger countermeasures such as increasing drive torque or reducing hydraulic pressure to maintain desired engagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If form-locking shift elements are used to eliminate drag torques, then transmission efficiency is improved, but the risk of unintentional disengagement increases due to rapid torque buildup and hydraulic failures
Solution Approach 1:
The control unit proactively monitors the position of the form-locking shift element and detects deviations from the desired engaged position before complete disengagement occurs. By identifying partial disengagement states early, the control unit can trigger countermeasures such as increasing hydraulic pressure or applying braking torque to prevent full disengagement, thus maintaining reliability while preserving the efficiency benefits of form-locking elements.
Solution Approach 2:
The system implements continuous feedback monitoring of the shift element position using sensors (e.g., Hall effect sensors, magnetoresistive sensors) that detect the position of ferromagnetic components on the shift element. This feedback loop enables the control unit to compare actual position with desired position and dynamically adjust hydraulic pressure or apply corrective torques to maintain proper engagement, preventing unintentional disengagement while allowing the form-locking element to remain engaged for efficiency.
2Reliability
If sensor-based monitoring is implemented to detect disengagement, then reliability is improved, but device complexity increases
Solution Approach 1:
The form-locking shift element incorporates ferromagnetic components (such as ferromagnetic rings or coated surfaces) that interact with the sensor field, enabling the shift element itself to provide the sensing function. This integration means the shift element serves both its mechanical locking function and as a target for position detection, reducing the need for separate complex sensing mechanisms and simplifying the overall system while maintaining reliable disengagement detection.
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 allows for early detection and prevention of unintentional disengagement, ensuring stable operation by maintaining the shift element in its intended condition, thereby enhancing transmission efficiency and reliability.
Implementation Method 1
The current position of the shift-element half is determined with the aid of a sensor
Data Source
AI summary
A method for operating a transmission (3) is provided, which includes a hydraulic pump drivable on a transmission-input end and at least one form-locking shift element (A, F). One of the shift-element halves is displaceable between a first end position and a second end position with a hydraulic pressure of the hydraulic pump. The current position of the shift-element half is detected with a sensor and is stored as a specified end-position value if the shift-element half is located in one of the end positions, the hydraulic pump is driven, and the shift-element half is actuated, with the hydraulic pressure, towards the current end position. When the hydraulic pressure is less than a threshold value, a deviation is determined between the current position of the shift-element half and the specified end-position value. The hydraulic pressure is increased when the deviation is greater than a threshold value.