Hydraulic Shift Control via Pressure Compensating Cavity Fill Level
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Solution Overview
Problem
Hydraulic actuation of shift elements in vehicle transmissions experiences faulty pressure control and compromised gear shift quality due to rapid changes in pressure supply, particularly in hybrid vehicles or those with start/stop engine functions, when the pressure compensating cavity is not fully filled or is empty.
Innovation Solution
A method that accounts for the fill level of the pressure compensating cavity in the control of hydraulically actuated shift elements, considering rotational speed, temperature, system pressure, leakage, and consumer flow rates to ensure accurate fill level determination and adjust control parameters like actuating pressure, filling pressure, and filling time for smooth engagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the pressure supply of the hydraulic system is activated again after being stopped, then the pressure chamber can be filled quickly, but the pressure compensating cavity may not be fully filled causing faulty pressure control
Solution Approach 1:
The control unit determines the fill level of the pressure compensating cavity before activating the pressure supply to the pressure chamber. This preliminary assessment allows the system to prepare appropriate control parameters, ensuring that the pressure chamber is filled correctly even when the pressure compensating cavity is not yet fully filled, thus preventing faulty pressure control while maintaining quick response.
Solution Approach 2:
The control unit dynamically adjusts control parameters (such as filling pressure or filling time) based on the real-time fill level of the pressure compensating cavity. This dynamic adaptation allows the system to optimize the filling process of the pressure chamber according to the actual state of the pressure compensating cavity, resolving the contradiction between speed and reliability.
2Speed
If the pressure compensating cavity is empty or partially empty, then the system responds quickly to pressure supply activation, but the gear shift quality deteriorates due to faulty pressure control
Solution Approach 1:
The control unit continuously monitors the fill level of the pressure compensating cavity and uses this feedback information to determine appropriate control parameters for the pressure chamber. This feedback mechanism ensures that the system can quickly respond to pressure supply activation while maintaining gear shift quality by adapting control parameters to the actual fill level condition.
Solution Approach 2:
The control unit changes control parameters (such as filling pressure, filling time, or actuating pressure) based on the fill level of the pressure compensating cavity. When the cavity is partially filled, the control parameters are adjusted to compensate for the insufficient centrifugal force, thereby maintaining smooth gear shift engagement despite the quick response requirement.
3Force
If the rotational speed of the pressure chamber increases, then the centrifugal forces increase improving pressure compensation, but the pressure in the pressure chamber increases due to centrifugal forces
Solution Approach 1:
The pressure compensating cavity filled with hydraulic fluid acts as a counterbalance to the centrifugal forces in the pressure chamber. As the pressure chamber rotates, the hydraulic fluid in the pressure compensating cavity generates opposing centrifugal forces that compensate for the pressure increase in the pressure chamber, thereby stabilizing the force acting on the shift element despite increased rotational speed.
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
Enables a comfortable, jerk-free engagement of shift elements even during short-term pressure supply activation, preventing undesired torque transmission and maintaining gear shift quality by accurately compensating for centrifugal forces and fluid dynamics.
Implementation Method 1
If the rotational speed of the pressure chamber increases, the pressure in the pressure chamber increases due to the centrifugal forces acting on the hydraulic fluid. This rotational pressure can be compensated for by providing a pressure compensating cavity.
Implementation Method 2
a pressure chamber is filled with hydraulic fluid by an electronically controlled hydraulic system in order to actuate the shift element
Data Source
AI summary
A method for controlling a hydraulically actuated shift element of a vehicle transmission (G) includes determining a fill level of a pressure compensating cavity (2) associated with a pressure chamber (1) and controlling pressurizing of the pressure chamber (1) with hydraulic fluid based at least in part on the determined fill level of the pressure compensating cavity (2). The pressure chamber (1) is fillable with the hydraulic fluid by an electronically controlled hydraulic system in order to actuate the shift element.