Transmission Hydraulic Flow Control for Fast Shifts Without Pressure Drop
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Solution Overview
Problem
Existing hydraulic systems in motor vehicle transmissions face issues with overloading and pressure drops due to insufficient oil supply, leading to poor shift quality and gearshift dynamics.
Innovation Solution
A method and control unit that ascertain the actual and target volumetric flow of oil, distribute excess oil based on shift element hydraulic capacity, and limit pressure actuation to prevent hydraulic system overload, ensuring high dynamics without pressure drops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the hydraulic pump delivers high volumetric flow to enable fast gear shifts, then gearshift dynamics improve, but the hydraulic system becomes overloaded causing pressure drops
Solution Approach 1:
The control unit dynamically adjusts the pressure actuation of shift elements based on real-time hydraulic capacity assessment. The method continuously monitors the actual volumetric flow deliverable by the hydraulic pump and adapts the actuation strategy accordingly, making the system flexible and responsive to changing hydraulic conditions
Solution Approach 2:
The control unit implements a feedback mechanism by ascertaining the actual volumetric flow from the hydraulic pump and using this information to limit the pressure actuation of shift elements. This closed-loop control prevents hydraulic overload by comparing actual flow capacity with the flow required for actuation
2Manufacturing precision
If multiple shift elements are actuated simultaneously to achieve complex gear changes, then gear shift quality improves, but the demand for volumetric flow exceeds pump capacity
Solution Approach 1:
The control unit segments the actuation process by distributing the limited volumetric flow to individual shift elements based on their hydraulic capacity. Instead of actuating all shift elements simultaneously with equal priority, the method divides the hydraulic resource allocation according to each element's specific requirements and importance
Solution Approach 2:
The method applies different actuation strategies to different shift elements based on their individual hydraulic capacity. The control unit assesses the hydraulic capacity of each shift element and tailors the pressure actuation accordingly, ensuring that elements with higher capacity receive appropriate flow allocation
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 high-quality gear shifts with superior gearshift dynamics while avoiding hydraulic system overload and pressure drops.
Implementation Method 1
The hydraulic system has a primary hydraulic circuit and a secondary hydraulic circuit, the primary hydraulic circuit being used for the pressure actuation of the shift elements
Data Source
AI summary
A method for operating a hydraulic system (1) of a transmission (2) of a motor vehicle i includes ascertaining an actual volumetric flow of oil that is deliverable into a primary hydraulic circuit (10) by at least one hydraulic pump (3), ascertaining a target volumetric flow of oil that is required by the primary hydraulic circuit (10), and ascertaining an excess volumetric flow of oil depending on the actual volumetric flow of oil and the target volumetric flow of oil. The excess volumetric flow of oil is distributed to shift elements of the transmission (2) to be actuated, depending on the hydraulic capacity of these shift elements, and is taken into account when limiting the pressure actuation of the shift elements of the transmission (2) to be actuated.