Electro-Hydraulic Transmission Control for Fail-Safe Clutch Shifting
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Solution Overview
Problem
The complexity of controlling multispeed transmissions increases with the need for precise management of friction clutches and brakes, especially in scenarios with multiple forward and reverse ranges, and there is a challenge in ensuring correct clutch application and fault tolerance during electrical power loss.
Innovation Solution
An electro-hydraulic control system that includes a controller, fluid source, torque-transmitting mechanisms, trim systems, shift valves, and solenoids to selectively apply hydraulic pressure and control the engagement of torque-transmitting mechanisms, ensuring correct clutch engagement and fault tolerance by using a combination of normally high and low solenoids and pressure control mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple torque-transmitting mechanisms are used to achieve multiple gear ratios, then the transmission system can provide improved fuel economy and multiple forward/reverse ranges, but the control system complexity increases
Solution Approach 1:
The control system is segmented into multiple independent trim systems, each controlling specific torque-transmitting mechanisms. This modular approach allows complex transmission control to be divided into manageable segments, where each trim system handles specific clutch/brake combinations for different gear ranges.
Solution Approach 2:
The electro-hydraulic control system is designed with universal components that can control multiple torque-transmitting mechanisms through a standardized architecture. The controller, fluid source, and trim systems work together in a multi-functional manner to manage various gear ratios, forward/reverse ranges, and fault conditions using the same basic control structure.
2Ease of operation
If precise control of friction clutches and brakes is implemented, then desirable shift quality is achieved, but the control system requires increased complexity to ensure correct clutch application
Solution Approach 1:
Each trim system is configured with specific solenoids and valves tailored to control particular torque-transmitting mechanisms. The control architecture applies local quality by customizing the control path for each clutch/brake combination, ensuring precise hydraulic pressure delivery to the right component at the right time for smooth shifts.
Solution Approach 2:
The control system incorporates feedback mechanisms where the controller monitors the state of torque-transmitting mechanisms and adjusts solenoid activation accordingly. This feedback loop ensures correct clutch application sequences are maintained, preventing errors in the complex multi-clutch control process.
3Reliability
If fault tolerance mechanisms are added to protect against electrical power loss, then transmission protection is improved, but the control system complexity increases
Solution Approach 1:
The control system is designed with preliminary fail-safe features where the default state of solenoids and valves is configured to protect the transmission in case of power loss. Normally-closed or normally-open configurations are selected based on which state provides protection, so that upon electrical failure, the system automatically defaults to a protected state without requiring additional active control.
Solution Approach 2:
The system converts the potentially harmful effect of electrical power loss into a beneficial protective mechanism. By designing the hydraulic control architecture where loss of electrical control results in automatic engagement of protective clutch/brake combinations, the harm of power failure is transformed into a safe default operation mode that prevents transmission damage.
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
The system effectively manages multiple gear ratios and ensures reliable operation even during power loss by accurately controlling clutch engagement and disengagement, enhancing shift quality and protecting the transmission from damage.
Implementation Method 1
a first shift solenoid disposed in electrical communication with the controller, the first shift solenoid being operably controlled between an energized and de-energized states to control movement of the first and second shift valves; a second shift solenoid disposed in electrical communication with the controller, the second shift solenoid being operably controlled between an energized and de-energized states to control movement of the third shift valve
Implementation Method 2
a fluid source for supplying hydraulic fluid; a plurality of torque-transmitting mechanisms being operably selected between an applied and an unapplied state to achieve a plurality of ranges
Data Source
AI summary
An electro-hydraulic control system for a multispeed transmission having a plurality of torque-transmitting mechanisms includes a controller for operably controlling the transmission, a fluid source for supplying hydraulic fluid, and a plurality of torque-transmitting mechanisms being operably selected between an applied and an unapplied state to achieve a plurality of ranges including at least one reverse, a neutral, and a plurality of forward ranges. The system includes a plurality of trim systems having pressure control solenoids and trim valves. The system may also include one or more shift valves disposed in fluid communication with the fluid source and being capable of moving between stroked and de-stroked positions. In any given range, only two of the plurality of torque-transmitting mechanisms may be applied. Moreover, three of the plurality of pressure control solenoids are normally high solenoids, and the remaining solenoids are normally low solenoids.