Automatic Transmission Hydraulics for Pump Flow Diagnosis
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Solution Overview
Problem
The operational reliability of hydraulic systems in dual-clutch transmissions is compromised due to the lack of a reliable method to determine the actual delivery volume flow of the hydraulic pump without a separate volume meter, leading to potential malfunctions.
Innovation Solution
Incorporating a diagnostic module that uses piston speed measurements to diagnose the delivery volume flow by comparing actual volume flow to a target volume flow, with the control valve adjusting piston strokes and speeds in the hydraulic positioning cylinder to determine displacement volume, allowing for inference of pump delivery volume without additional sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a separate volume meter is installed to measure the actual delivery volume flow of the hydraulic pump, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent uses the hydraulic positioning cylinder as an intermediary element to indirectly measure the delivery volume flow of the hydraulic pump. Instead of directly measuring pump output with a volume meter, the system measures the piston speed in the positioning cylinder, which reflects the hydraulic fluid flow. This intermediary measurement approach achieves accurate delivery volume flow determination without adding complex sensing equipment to the pump itself.
Solution Approach 2:
The hydraulic positioning cylinder serves dual purposes: it performs its primary function of positioning control while simultaneously providing measurement data for delivery volume flow diagnosis. The existing piston speed measurement capability of the positioning cylinder is leveraged for the additional diagnostic function, eliminating the need for separate measurement devices and reducing overall system complexity.
2Device complexity
If piston speed measurements are used to diagnose delivery volume flow, then device complexity is reduced, but measurement precision may be affected by boundary conditions
Solution Approach 1:
The system performs preliminary actions to establish appropriate boundary conditions before conducting the delivery volume flow diagnosis. The control unit prepares the hydraulic system by ensuring the accumulator is charged and the positioning cylinder is in a known state, which creates optimal conditions for accurate measurement. This preliminary preparation ensures that piston speed measurements accurately reflect pump delivery volume without interference from transient system conditions.
Solution Approach 2:
The control unit continuously monitors piston speed measurements and compares them against expected values to diagnose delivery volume flow conditions. This feedback mechanism allows the system to detect deviations and identify pump malfunctions. The control unit can also adjust system parameters based on the diagnosis results, creating a closed-loop system that maintains measurement accuracy through continuous monitoring and adjustment.
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 ensures operational reliability by accurately diagnosing faults and determining delivery volume flow, reducing sensor complexity and measurement inaccuracies, while maintaining constant accumulator pressure during diagnosis.
Implementation Method 1
a hydraulic charge pump, which delivers hydraulic fluid into the hydraulic system in a charging operation in order to increase the accumulator pressure
Implementation Method 2
a pressure accumulator for supplying an accumulator pressure in the hydraulic system
Implementation Method 3
a control valve is positioned, which can be controlled by an electronic control unit and can be used to adjust the hydraulic pressure applied to the clutch hydraulic cylinder
Implementation Method 4
The above-mentioned piston speed can be determined easily by a sensor system, for example, by means of a position sensor described hereafter, which detects the piston strokes of the hydraulic positioning cylinder
Implementation Method 5
The clutches and the gear selectors for engaging the gears are actuated via hydraulic cylinders, which are controlled hydraulically via a hydraulic system
Data Source
AI summary
A hydraulic system for an automatic transmission of a motor vehicle. A high pressure circuit in which a pressure accumulator, at least one clutch as well as gear selectors and at least one hydraulic pump are arranged, which can be controlled by an electronic control unit. The pressure accumulator can be connected to a hydraulic positioning cylinder via at least one hydraulic path, wherein a control valve that can be controlled by the control unit is arranged upstream thereof, with which a hydraulic pressure at the hydraulic positioning cylinder can be adjusted, and which control valve can be moved between two through-flow positions in order to move a piston in opposing piston strokes via opposing piston travel paths as well as piston speeds in the hydraulic positioning cylinder.