Automatic Transmission Hydraulic Discharge Rate Control for Interlock Prevention
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Solution Overview
Problem
Conventional automatic transmissions experience interlock issues when shifting from forward to reverse drive ranges, especially under low oil discharge rates due to low temperatures, as the hydraulic pressure is not fully discharged from the forward range before being supplied to the reverse range.
Innovation Solution
A control apparatus with a hydraulic pressure control system and discharge rate changeover control mechanism that increases the discharge rate of hydraulic pressure from the first friction engagement element when shifting to the reverse range before the forward range is fully released, preventing interlock occurrences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hydraulic pressure is discharged via an orifice to slowly discharge the hydraulic pressure, then the discharge rate is controlled, but interlock occurs when shifting quickly or at low temperatures
Solution Approach 1:
The discharge rate control valve changes the discharge rate dynamically based on operating conditions. When the shifting operation is quick or oil temperature is low, the valve increases the discharge rate to prevent interlock. This dynamic adjustment resolves the contradiction between controlled discharge and fast shifting requirements.
Solution Approach 2:
The system changes the discharge rate parameter according to shifting speed and oil temperature conditions. By adjusting this parameter, the system can discharge hydraulic pressure fast enough to prevent interlock during quick shifts while maintaining controlled discharge under normal conditions, thus resolving the contradiction.
2Stability of the object's composition
If hydraulic pressure is discharged slowly via an orifice, then pressure control is achieved, but the friction engagement element may be supplied with pressure before complete discharge causing interlock
Solution Approach 1:
The discharge rate control valve acts as an intermediary between the fixed orifice and the friction engagement element. It dynamically adjusts the discharge rate to ensure complete pressure release before supplying pressure to the next element, preventing interlock while maintaining stable pressure control.
Solution Approach 2:
The control system monitors shifting operation speed and oil temperature, and adjusts the discharge rate accordingly. This feedback mechanism ensures that the discharge rate is increased when needed to prevent interlock, resolving the contradiction between stable pressure control and interlock prevention.
3Reliability
If the discharge rate is increased to prevent interlock during quick shifting, then shifting reliability improves, but the controlled discharge function is reduced
Solution Approach 1:
The discharge rate control valve provides dynamic discharge rate adjustment based on actual operating conditions. This dynamic control prevents interlock during quick shifts or low-temperature operations while maintaining simple controlled discharge through the orifice under normal conditions, balancing reliability and complexity.
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
This solution ensures stable shifting between drive ranges by increasing the hydraulic pressure discharge rate, thereby suppressing interlock occurrences during quick shifts or low oil discharge conditions.
Implementation Method 1
a hydraulic pressure control means for controlling supply of hydraulic pressure to the first friction engagement element and the second friction engagement element and discharge of hydraulic pressure from the first friction engagement element and the second friction engagement
Implementation Method 2
a discharge rate changeover control means for increasing a discharge rate value of the hydraulic pressure which is discharged from the first friction engagement element
Data Source
AI summary
A control apparatus for an automatic transmission including a hydraulic pressure control means for controlling supply of hydraulic pressure to a first friction engagement element and a second friction engagement element and discharge of hydraulic pressure from the first friction engagement element and the second friction engagement, and a discharge rate changeover control means for increasing a discharge rate value of the hydraulic pressure which is discharged from the first friction engagement element in a case where when shifting from one of operating ranges to the other thereof is selected, changeover to the other operating range is carried out before completing release of the first friction engagement element, so as to become larger than a discharge rate value of the hydraulic pressure which is discharged from the first friction engagement element before the changeover to the other operating range is carried out.