Automatic Transmission Hydraulic Flow Diagnosis Without a Flow Meter
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Solution Overview
Problem
The operational reliability of hydraulic systems in automatic transmissions is compromised due to the lack of reliable delivery volume flow measurement, especially when the hydraulic pump is not equipped with its own volume meter.
Innovation Solution
A diagnostic module within the control unit performs a delivery volumetric flow diagnosis without an additional volume meter by activating the hydraulic pump at a specific speed and actuating the control valve to determine the piston speed, allowing for the calculation of actual volume flow based on known internal geometry and sensor data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the hydraulic pump is not equipped with its own volumetric meter, then the device complexity is reduced, but the measurement precision of delivery volume flow deteriorates
Solution Approach 1:
The patent uses a diagnostic module as an intermediary that indirectly measures the hydraulic pump's delivery volume flow by monitoring the charging process of a pressure accumulator. Instead of directly measuring flow at the pump, the system measures the rate of pressure increase in the accumulator, which serves as a mediator to infer the pump's actual flow rate without requiring a volumetric meter at the pump itself.
Solution Approach 2:
The patent replaces direct mechanical flow measurement (volumetric meter) with an electrical/electronic measurement approach. The diagnostic module uses electrical sensors to detect pressure changes and calculates flow rate through electronic computation, substituting mechanical measurement hardware with an electronic diagnostic system that achieves the same measurement goal with less complexity.
2Measurement precision
If a volumetric sensor is added to measure delivery volume flow, then the measurement precision improves, but the device complexity increases
Solution Approach 1:
The patent makes existing hydraulic components serve multiple functions. The pressure accumulator, originally designed solely for energy storage, is also used as a measurement element for flow rate diagnostics. The control valve and hydraulic actuator, designed for actuation, are utilized as flow measurement devices during diagnostic operations. This multi-functionality eliminates the need for dedicated volumetric sensors.
Solution Approach 2:
The hydraulic system performs self-diagnosis using its own existing components. The system uses its pressure accumulator, control valve, and actuator to measure and evaluate the pump's delivery volume flow without requiring external measurement devices. The diagnostic module leverages the system's inherent components to provide self-verification of pump performance.
3Productivity
If the hydraulic pump operates at high speed to charge the accumulator quickly, then the productivity increases, but the reliability deteriorates due to undetected malfunctions
Solution Approach 1:
The patent implements a feedback mechanism where the diagnostic module continuously monitors the actual delivery volume flow of the hydraulic pump and compares it against expected values. This feedback allows the system to detect deviations indicating pump malfunctions, enabling timely intervention before operational safety is compromised, while allowing the pump to operate at high speeds for efficient charging.
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 accurate measurement of delivery volume flow, enabling early detection of errors and maintaining system reliability with reduced sensor technology requirements.
Implementation Method 1
a pressure accumulator (25) for providing accumulator pressure (pS) in the hydraulic system (20)
Implementation Method 2
a hydraulic pump (53) with a drive shaft (53.1) for delivering hydraulic fluid (55) to the hydraulic system (20)
Implementation Method 3
A control valve (35), which can be actuated by an electronic control unit (39), is arranged in a coupling path leading from the pressure accumulator (25) to the clutch hydraulic cylinder (23)
Implementation Method 4
The hydraulic pump's electric motor (57) can have a speed measuring device and a current draw measuring device
Data Source
Figure 1~2b
Figure 2a
Figure 3
AI summary
The invention relates to a hydraulic system for an automatic transmission of a motor vehicle, comprising a high pressure circuit (H) in which a pressure accumulator (25), at least one clutch (K1, K2) as well as gear selectors (G1 to G4) and at least one hydraulic pump (53) are arranged, which can be controlled by an electronic control unit (39), wherein the pressure accumulator (25) can be connected to a hydraulic positioning cylinder (22) via at least one hydraulic path (32), wherein a control valve (38) that can be controlled by the control unit (39) is arranged upstream thereof, with which a hydraulic pressure at the hydraulic positioning cylinder (22) can be adjusted, and which control valve (38) can be moved between two through-flow positions (D1, D2) in order to move a piston (33) in opposing piston strokes via opposing piston travel paths (s1, s2) as well as piston speeds (Formula (I)) in the hydraulic positioning cylinder (22), wherein each piston stroke is connected to a hydraulic fluid outlet (V1, V2) out of the hydraulic system. According to the invention, the control unit (39) has a diagnosis module (79) with which a diagnosis of the conveyed volume flow can be carried out, wherein an evaluation unit (114) determines an actual conveyed volume flow (Vist) and compares same with a target conveyed volume flow (Vsoll), and, in the event of a significant deviation, detects an error that can be stored in a conveyed volume flow error memory (117).