Automatic Transmission Control System Reverse Inhibit Logic
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Solution Overview
Problem
Conventional automatic transmission systems with reverse inhibit control mechanisms increase device size, weight, and production costs, and may fail to perform reverse inhibit control if the position sensor fails.
Innovation Solution
A control system that avoids using a cut-off valve and employs an avoidance unit to shift to a forward speed that does not engage the first friction engagement element if the detection unit fails, ensuring reverse shift speed suppression even if the detection unit fails, and engages the second friction engagement element based on the reverse range pressure to prevent reverse shift speed formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cut-off valve is provided to perform reverse inhibit control, then reverse inhibit control can be achieved, but device size, weight, and production costs increase
Solution Approach 1:
The invention extracts and eliminates the cut-off valve from the hydraulic system by implementing reverse inhibit control through software logic in the control unit. The control unit monitors detection unit status and prevents reverse shift speed formation through control signals to the shift control valve, removing the need for the physical cut-off valve and its associated hydraulic passages.
Solution Approach 2:
The invention replaces the mechanical/hydraulic cut-off valve with an electronic control system. The control unit uses detection unit status signals to generate control signals that regulate the shift control valve, substituting a mechanical pressure cutoff mechanism with an electronically controlled hydraulic regulation system.
2Productivity
If the first friction engagement element remains engaged during detection unit failure, then forward travel can continue, but reverse shift speed may be formed if reverse range is selected in error
Solution Approach 1:
The invention dynamically adjusts the engagement state of the first friction engagement element based on detection unit status. During normal operation, the element engages/disengages according to shift requirements. When detection unit failure is detected, the control unit maintains the element in an engaged state regardless of shift lever position, dynamically adapting the system behavior to ensure safety while maintaining forward travel capability.
Data Source
AI summary
A control system for an automatic transmission that does not require a cut-off valve, and that can inhibit a reverse control even if a detection unit for detecting a shift range fails. The control system includes a first friction engagement element, which is engaged in predetermined forward and reverse shift speeds, a detection unit that detects a shift range from shift ranges that include a forward range and a reverse range; a failure judgment unit for judging failure of the detection unit, and an avoidance unit for shifting to a forward shift speed that does not engage the first friction engagement element if the failure judgment unit determines that the detection unit has failed.