Actuating Current Reference Determination for Transmission Shifting Elements
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Solution Overview
Problem
Existing methods for determining the reference value of an actuating current for electro-hydraulically actuated frictional shifting elements in continuously variable power-branched transmissions are inadequate, leading to shifting jerks and discomfort due to tolerance variations in electrical components, which affect the transmission capacity and shifting comfort.
Innovation Solution
A method that determines the reference value of the actuating current by considering the complete actuation chain, including electrical, hydraulic, and mechanical elements, by reducing the actuating current until a rotational speed difference exceeds a predefined limit, ensuring the shifting element operates at a defined zero-capacity point, allowing for precise actuation and improved comfort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a reference value for actuating current is determined using existing methods, then the shifting element can be actuated, but tolerance variations in electrical components cause the reference value to be inaccurate, leading to shifting jerks and discomfort
Solution Approach 1:
The patent applies feedback by monitoring the actual rotational speed difference between the two clutch halves during the actuation process and using this information to dynamically adjust the actuating current. The control unit continuously compares the actual speed difference with the target condition (speed difference exceeding the predefined limit) and modifies the current accordingly, ensuring the clutch reaches the desired operating point despite component tolerances.
Solution Approach 2:
The system performs self-calibration by automatically determining the correct reference value for actuating current through a calibration routine that uses the actual operating conditions (rotational speed difference) as feedback. The control unit stores the determined reference value in non-volatile memory for future use, enabling the system to self-adjust without external intervention and compensate for manufacturing tolerances in electrical components.
2Measurement precision
If the actuating current is reduced to determine the zero-capacity point, then the defined operating point can be accurately identified, but the process requires precise control of the complete actuation chain
Solution Approach 1:
The patent replaces direct mechanical measurement of clutch capacity with an electrical/control-based measurement approach. Instead of mechanically sensing the clutch engagement state, the system uses electrical sensors to measure rotational speed difference and a control unit to process this information and determine the zero-capacity point, simplifying the measurement while maintaining precision.
Solution Approach 2:
The system changes the operating parameter from a static reference value to a dynamically determined value based on actual rotational speed measurements. By varying the actuating current and monitoring the resulting rotational speed difference, the system identifies the precise zero-capacity point through parameter variation and feedback, ensuring accurate determination despite actuation chain complexities.
Data Source
AI summary
A method is described for determining a reference value of an actuating current that corresponds to a defined operating point of an electro-hydraulically actuated frictional shifting element of a continuously variable power-branched transmission, at which the shifting element transmission capacity is zero, and starting from which an increase of actuating force immediately increases the transmission capacity. The actuating current reference value of the shifting element, when closed with a further shifting element decoupled from the transmission output and when a transmission input rotational speed is higher than a defined threshold, is reduced until a rotational speed difference between the rotational speeds of the shifting element halves exceeds a predefined limit value such that, at the time when the limit value is exceeded, the reference value of the actuating current is the reference value of the actuating current that corresponds to the defined operating point of the shifting element.