Electro-Hydraulic Transmission Control for Safe Multi-Range Shifting
Find Innovative SolutionsGenerate Solutions
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 engagement and fault tolerance during electrical power loss.
Innovation Solution
An electro-hydraulic control system with a controller, fluid source, torque-transmitting mechanisms, and a network of pressure control solenoids and valves that selectively apply hydraulic pressure to achieve various gear ranges, including a mechanism to default to safe states in case of power loss, ensuring only two torque-transmitting mechanisms are active in each range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple torque-transmitting mechanisms are used to achieve multiple gear ranges, 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 divided into multiple independent trim systems (first through fifth trim systems), each responsible for controlling a specific torque-transmitting mechanism. This segmentation allows each subsystem to be managed independently, reducing the overall control complexity while enabling multiple gear ranges through coordinated operation of these modular trim systems
Solution Approach 2:
The controller pre-determines the state of each torque-transmitting mechanism based on the desired gear range before actual shifting occurs. By calculating and preparing the required clutch/brake engagement states in advance, the system can execute smooth transitions between ranges without increasing real-time control complexity
2Manufacturing precision
If multiple torque-transmitting mechanisms are controlled to achieve precise clutch engagement, then desirable shift quality is improved, but the difficulty of controlling the system increases
Solution Approach 1:
The controller continuously monitors the state of torque-transmitting mechanisms and adjusts trim valve positions accordingly to achieve precise clutch engagement. This closed-loop feedback control ensures desirable shift quality while automating the complex coordination required for multi-clutch operations
Solution Approach 2:
Trim valves serve as intermediary devices between the controller and torque-transmitting mechanisms, providing fine-adjustment control of hydraulic pressure to each clutch/brake. This intermediary layer simplifies the controller's task by handling the precise pressure modulation required for smooth clutch engagement
3Reliability
If fault tolerance mechanisms are implemented for power loss scenarios, then transmission protection is improved, but the device complexity increases
Solution Approach 1:
Instead of actively managing all clutch states during normal operation and then recovering from faults, the system is designed to default to a safe state (unapplied torque-transmitting mechanisms) upon power loss. This inverted approach simplifies the fault tolerance mechanism by relying on passive spring-return or default positioning of trim valves rather than active recovery 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
The system effectively manages multiple gear ranges with precise clutch engagement and fault tolerance, ensuring smooth operation and protecting the transmission during electrical power loss by defaulting to safe states.
Implementation Method 1
a network of pressure control solenoids and valves that selectively apply hydraulic pressure to achieve various gear ranges
Implementation Method 2
when the third shift valve is in its de-stroked position, the third shift valve blocks fluid communication between the fluid source and at least two of the torque-transmitting mechanisms
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.