Automatic Transmission Shift Control Neutral State Timing
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Solution Overview
Problem
Existing automatic transmission shift control methods are inefficient in shortening the time required for shifting gears, particularly when shifting from first to second gear, due to slow engine speed increase and potential shock during gear changes.
Innovation Solution
A control apparatus and method that strategically disengage and re-engage frictional engagement elements to implement gear ratios, allowing the input shaft revolution number to increase quickly by entering a neutral state, thereby shortening the shifting time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If conventional shift control methods are used to engage frictional engagement elements, then gear shifting is achieved, but the time required for shifting is prolonged due to slow engine speed increase
Solution Approach 1:
The control apparatus starts disengagement of the first and second frictional engagement elements before the engine speed has fully increased, preparing the transmission for the neutral state in advance. This preliminary action allows the system to transition more quickly into the neutral state where engine speed can increase without being constrained by engaged elements, thereby reducing overall shifting time.
Solution Approach 2:
The control apparatus dynamically adjusts the engagement and disengagement timing of frictional engagement elements based on real-time transmission state. By transitioning elements between engaged and disengaged states according to engine speed conditions, the system optimizes the balance between maintaining gear connection and allowing engine speed increase, thus reducing shifting time while controlling shock.
2Productivity
If frictional engagement elements are engaged quickly to reduce shifting time, then shifting speed increases, but shock and retardation occur during gear changes
Solution Approach 1:
The control apparatus enters a neutral state where the first and second frictional engagement elements are disengaged before completing the engagement of the third and fourth elements. This neutral state acts as a cushioning phase that allows engine speed to increase and synchronizes the input shaft speed, preventing shock and retardation when the new gear engagement is completed.
Solution Approach 2:
The neutral state serves as an intermediary state between the first gear and second gear. During this intermediate state, the transmission temporarily disconnects the engine from the output shaft, allowing engine speed to increase freely and input shaft speed to synchronize. This intermediary phase mediates the transition, preventing direct shock between the engaged elements during gear changes.
3Loss of time
If the transmission enters a neutral state during shifting, then shifting time is reduced, but adverse effects may occur from neutral state transitions
Solution Approach 1:
The control apparatus continuously monitors transmission state and engine speed, and uses this feedback to control the timing and sequence of frictional engagement element operations. During the neutral state transition, the ECU adjusts engagement timing based on real-time conditions, ensuring that the transition is completed reliably while maintaining shifting stability and preventing adverse effects.
Data Source
AI summary
An ECU executes a program including the steps of: starting disengagement of a C2 clutch and a B1 brake when downshifting a transmission implementing gears in accordance with combinations of engaged clutches and brakes from sixth gear to third gear, or disengagement of the C2 clutch and a B3 brake when downshifting from fifth gear to second gear; when at least one of the C2 clutch and the B1 brake, or at least one of the C2 clutch and the B3 brake, is completely disengaged, starting engagement of a C1 clutch and the B3 brake when downshifting from sixth gear to third gear, or engagement of the C1 clutch and the B1 brake when downshifting from fifth gear to second gear.