Force-Fitting Shift Element Torque Control via Dynamic Pressure
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Solution Overview
Problem
Force-fitting shift elements in automatic transmissions require high closing pressure for torque transfer, leading to increased mechanical stress and component weight, despite not always needing the maximum pressure, and existing methods do not allow for pressure reduction without compromising torque transfer security.
Innovation Solution
A method to control the closing pressure of a force-fitting shift element based on the prevailing system pressure, using an electronically or hydraulically controlled control valve to adjust the valve lift according to a control signal, allowing for reduced pressure when system pressure is below a threshold to minimize mechanical load and prevent deposit buildup, while maintaining torque transfer security.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the control valve is fully open to apply maximum system pressure to the piston, then the shift element is securely closed for torque transfer, but the mechanical stress and component weight increase unnecessarily
Solution Approach 1:
The invention dynamically changes the closing pressure parameter based on operating conditions. The control unit adjusts the valve lift of the control valve to apply only the minimum necessary closing pressure required for secure torque transfer, rather than always applying maximum system pressure. This parameter optimization resolves the contradiction by maintaining reliability while reducing unnecessary mechanical stress and component weight.
Solution Approach 2:
The invention applies partial action by providing just enough closing pressure to securely close the shift element for torque transfer, rather than applying excessive maximum pressure. The control system determines the appropriate pressure level based on the torque to be transferred, applying only the necessary portion of system pressure, thereby reducing mechanical stress without compromising torque transfer security.
2Object-generated harmful factors
If the control valve is fully open to apply maximum system pressure, then the hydraulic valve is flushed effectively, but the shift element experiences unnecessary high closing pressure
Solution Approach 1:
The control valve is opened partially rather than fully, providing just enough opening to allow hydraulic oil flow for flushing contaminants while preventing the excessive pressure transmission that would occur with full opening. This partial action resolves the contradiction by maintaining cleaning effectiveness without subjecting the shift element to unnecessarily high closing pressure.
Solution Approach 2:
The invention dynamically adjusts the valve lift parameter of the control valve based on operating conditions. By optimizing the opening degree, the system achieves effective flushing of contaminants while controlling the closing pressure applied to the shift element, thereby resolving the contradiction between cleaning effectiveness and pressure reduction.
3Stress or pressure
If the closing pressure is reduced below maximum system pressure, then the component load and weight are reduced, but the torque transfer security may be compromised
Solution Approach 1:
The control unit dynamically adjusts the closing pressure parameter based on the torque requirements and operating conditions. By optimizing this parameter, the system applies only the minimum necessary pressure for secure torque transfer, resolving the contradiction between pressure reduction and reliability maintenance.
Solution Approach 2:
The control system uses feedback from operating conditions to continuously optimize the closing pressure. Based on information about the torque to be transferred and system state, the control unit adjusts the valve lift to maintain adequate torque transfer security while minimizing closing pressure, thereby resolving the contradiction.
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 reduces mechanical load on the shift element, prevents deposit buildup on the control valve, and ensures the minimum required pressure is applied for torque transfer, optimizing component design and reducing unnecessary stress and weight.
Implementation Method 1
a hydraulic closing pressure acting on a piston against a spring force or against a counter-force acting on a different side of the piston. The closing pressure acting on the piston is predetermined by a control valve.
Implementation Method 2
A control valve is configured, through the setting of the valve lift, depending on a control signal of a control unit, to transmit the system pressure of a hydraulic circuit to the piston, or to reduce it as needed.
Implementation Method 3
If the control valve is fully closed, apart from leakage at the valve, no closing pressure applies at the piston. If the shift element is preloaded by a spring in its open position, the spring force thereby leads to the opening of the shift element.
Implementation Method 4
The driving of the engaging shift element to the maximum pressure serves the purpose of, among other things, flushing the hydraulic valve that is allocated to the shift element. Thereby, the depositing of contaminants present in the hydraulic oil at, for example, the control edges of the hydraulic valve, can be avoided.
Data Source
AI summary
A method for controlling torque transfer of a force-fitting shift element includes controlling a closing pressure at least temporarily upon presence of a closing request for the force-fitting shift element and when a prevailing system pressure of the hydraulic circuit is above a threshold value for the system pressure. The closing pressure is controlled in a manner that is different than upon the presence of the closing request for the force-fitting shift element and when the prevailing system pressure is below the threshold value for the system pressure.