Hydraulic Default Gear Control for Transmission Power Loss
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Solution Overview
Problem
Multi-speed planetary transmissions face challenges in managing default conditions, such as electrical power failures, which affect the engagement of selective couplers and result in unintended gear ratios, compromising vehicle control and safety.
Innovation Solution
A hydraulic default control system with first and second valve assemblies, each controlled by a solenoid, that shifts the transmission to predefined default speed ratios when a default condition is detected, ensuring safe operation by selectively engaging specific couplers to maintain vehicle control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the transmission operates in multiple forward and reverse speed ratios with selective couplers, then the transmission provides versatile speed control, but the system becomes vulnerable to unintended gear ratios during default conditions such as electrical power failures
Solution Approach 1:
The hydraulic default control system is pre-configured with default control subsystems that automatically engage predetermined combinations of selective couplers when a default condition occurs. This preliminary configuration ensures that upon power failure or electrical system malfunction, the transmission immediately shifts to a known safe gear ratio without requiring active control signals, thereby preventing unintended gear ratios and maintaining vehicle control
Solution Approach 2:
The default control subsystems are designed to automatically activate during default conditions without requiring external control signals. The hydraulic system self-regulates by engaging predetermined coupler combinations based on the failure mode, enabling the transmission to protect itself and maintain reliable operation during electrical system failures
2Reliability
If the hydraulic control system uses default control subsystems to manage default conditions, then the system maintains vehicle control during power failures, but the hydraulic control system complexity increases
Solution Approach 1:
The hydraulic control system is segmented into multiple independent default control subsystems, each responsible for controlling specific combinations of selective couplers. This segmentation allows each subsystem to be relatively simple and focused on a specific default scenario, rather than requiring one complex system to handle all possible failure modes. Each subsystem can be designed and tested independently, reducing overall system complexity while maintaining comprehensive coverage of default conditions
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 hydraulic default control system effectively manages default conditions by shifting the transmission to predefined speed ratios, ensuring the vehicle can be safely brought to a stop and maintaining operational stability even during power failures or other default scenarios.
Implementation Method 1
a first control valve controlled by a first solenoid and a second valve assembly having a second control valve controlled by a second solenoid
Data Source
AI summary
A multi-speed planetary transmission is operable in at least nine forward speed ratios, at least one reverse speed ratio, and at least one neutral speed ratio. A hydraulic control system for the transmission includes a hydraulic default control system and is operable to a default configuration when a default condition occurs during operation of the transmission. The hydraulic control system defaults to a forward default gear ratio during operation of the transmission in a first forward speed ratio and defaults to a default neutral speed ratio during operation of the transmission in a reverse speed ratio when a default condition occurs. The default condition may be a transmission control module (“TCM”) power failure.