Transmission Valve Open-Loop Control for Flow-Force Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Modern vehicle transmissions with reduced hydraulic circuit size and smaller valve cross-sections face challenges in ensuring comfortable and reliable gear ratio changes due to increased impact of flow effects and flow forces, which existing open-loop control methods fail to adequately address.
Innovation Solution
The method involves calculating and accounting for the volume flow rate through the valve in addition to pressure values to determine the control current, considering system properties and flow effects, allowing for precise adjustment of clutch pressure and improved shifting characteristics in a compact design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the hydraulic circuit size is reduced and smaller valve cross-sections are used, then the installation space is reduced, but the flow effects and flow forces increase making gear ratio changes less comfortable and reliable
Solution Approach 1:
The patent introduces a feedback mechanism by calculating the actual volume flow rate through the valve based on the control current and valve characteristics, then using this calculated flow rate information to adjust subsequent control commands. This feedback loop compensates for the increased flow effects in compact valves, maintaining reliable gear ratio changes despite the reduced hydraulic circuit size.
Solution Approach 2:
The patent changes the control parameters from purely pressure-based control to a combined approach using control current, calculated volume flow rate, and pressure. By monitoring and adjusting based on multiple parameters including the actual flow rate through the valve, the system compensates for the heightened sensitivity to flow effects in smaller valves, ensuring consistent performance.
2Volume of moving object
If the hydraulic circuit size is reduced and smaller valve cross-sections are used, then the installation space is reduced, but the flow effects and flow forces increase affecting shifting comfort
Solution Approach 1:
The feedback mechanism calculates the actual volume flow rate and uses this information to dynamically adjust control commands, ensuring smooth and comfortable gear transitions. By continuously monitoring the flow rate through the smaller valve cross-section and adapting the control strategy, the system maintains shifting comfort despite the reduced hydraulic circuit size.
Solution Approach 2:
The patent implements dynamic control by continuously calculating the volume flow rate based on current valve position and control current, then adapting subsequent control actions based on this real-time flow information. This dynamic adjustment ensures comfortable gear shifts by compensating for the increased flow effects that occur in smaller, more compact valve designs.
3Device complexity
If existing open-loop control methods are used with smaller valve cross-sections, then the device complexity is reduced, but the ability to compensate for flow effects is insufficient
Solution Approach 1:
The patent enhances the control system by introducing feedback based on calculated volume flow rate. The control unit calculates the actual flow rate through the valve using the control current and valve characteristics, then uses this information to compensate for flow effects in subsequent control decisions. This feedback approach provides reliable flow effect compensation without requiring additional hardware sensors.
Solution Approach 2:
The control unit performs self-service by calculating its own operating state (volume flow rate through the valve) based on its control current output and known valve characteristics. This self-calculated feedback enables the system to compensate for flow effects using its existing computational resources, avoiding the need for additional measurement devices while maintaining reliable control.
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 enables efficient and precise adjustment of clutch pressure, ensuring comfortable and reliable gear ratio changes even in compact designs, reducing the impact of fluctuating conditions and potentially eliminating the need for pressure sensors, while maintaining cost-effectiveness and reliability.
Implementation Method 1
an electrically controllable valve in a vehicle transmission that includes a hydraulic circuit, wherein the valve sets a defined pressure in the hydraulic circuit as a function of a control current
Implementation Method 2
a hydraulic circuit, wherein the valve sets a defined pressure in the hydraulic circuit as a function of a control current in order to selectively actuate a clutch
Data Source
AI summary
A vehicle transmission includes a hydraulic circuit and a control unit. The control unit is configured to: obtain (20) a target pressure specification; convert (26) the target pressure specification into a target volume flow rate; determine (42) a valve volume flow rate as a function of the target volume flow rate and as a function of parameters that represent system properties of the hydraulic circuit; determine (46) a pressure drop at a valve due to flow forces as a function of the valve volume flow rate; determine (48) a compensated valve output pressure as a function of the valve volume flow rate and the pressure drop; determine (58) the electric control current as a function of the compensated valve output pressure; and activate a valve with the electric control current.