Automatic Transmission Shift Element Protection
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Solution Overview
Problem
Automatic transmissions face performance issues due to shift elements failing to adjust between engaged and disengaged states, leading to potential damage and over-determination, particularly when a shift element sticks in an engaged configuration.
Innovation Solution
A method for operating an automatic transmission that involves commanding a positive shifting element to actuate and measuring its speed differential or position, and opening non-positive shifting elements if the positive element does not properly actuate, thereby terminating power flow to protect the transmission from damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If shift elements are used to adjust gear ratios, then transmission performance is improved, but reliability deteriorates when shift elements fail to adjust properly between engaged and disengaged states
Solution Approach 1:
The control unit monitors the operational state of positive shifting elements and uses this feedback to determine when to open non-positive shifting elements. When a positive shifting element fails to actuate properly, the control unit detects this condition and responds by opening the corresponding non-positive shifting element to prevent transmission damage.
Solution Approach 2:
The system takes preliminary protective action by opening non-positive shifting elements before damage can occur to the transmission. When a positive shifting element is detected to be stuck or malfunctioning, the control unit proactively opens the non-positive shifting element to prevent the transmission from entering an overdetermined state.
2Ease of operation
If shift elements are commanded to actuate, then gear shifting is achieved, but harmful factors increase when shift elements stick in engaged configuration
Solution Approach 1:
The system converts the harmful condition of a stuck positive shifting element into a beneficial protective action. When a positive shifting element fails to disengage, the control unit responds by opening the non-positive shifting element, which terminates power flow and prevents damage to the transmission components.
Solution Approach 2:
The non-positive shifting element acts as an intermediary protective mechanism. When the positive shifting element fails in its primary function, the non-positive shifting element serves as a backup safety device that opens to terminate power flow and protect the transmission from harmful overdetermination conditions.
3Power
If non-positive shifting elements remain closed, then power flow is maintained, but transmission damage occurs when positive shifting elements malfunction
Solution Approach 1:
The state of non-positive shifting elements is made dynamic rather than static. Instead of remaining constantly closed, the non-positive shifting element dynamically changes state based on the operational condition of positive shifting elements, opening when needed to protect the transmission and closing when safe to maintain power flow.
Data Source
AI summary
A method for operating an automatic transmission is provided. The method includes commanding a positive shifting element to actuate to a disengaged configuration or an engaged configuration and opening at least one non-positive shifting element if the positive shifting element does not properly actuate. Opening the at least one non-positive shifting element may terminate power flow from the automatic transmission in order to protect the automatic transmission.