Automatic Transmission Skip Shift Control via Sequential Clutch Actuation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional shift control methods for automatic transmissions face challenges in efficiently performing a 6 to 3 skip shift, resulting in long shifting times, poor shift feel, and shift shock due to the difficulty in simultaneously controlling hydraulic pressure for multiple frictional elements, leading to intermediate shift-speed issues and torque fluctuations.
Innovation Solution
A shift control method that simultaneously releases the first and second frictional elements and engages the third and fourth frictional elements, with controlled hydraulic pressure patterns to prevent intermediate shift-speeds, including reducing hydraulic pressure to zero and maintaining pre-fill and stand-by pressures, while increasing turbine speed and engine torque reduction to facilitate smooth transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If two frictional elements are released and two other frictional elements are engaged simultaneously during a 6 to 3 skip shift, then shifting time is reduced and shift feel is improved, but hydraulic pressure control becomes extremely difficult
Solution Approach 1:
The patent segments the skip shift process into two distinct sequential stages: first releasing two frictional elements (clutches C1 and C2), then after a predetermined time delay, engaging two other frictional elements (brake B1 and clutch C3). This segmentation avoids the complexity of simultaneous four-element control while achieving the skip shift function.
Solution Approach 2:
The patent applies preliminary action by releasing the off-going clutches (C1 and C2) before engaging the on-coming brake (B1) and clutch (C3). The predetermined time delay allows the release process to begin before the engagement process starts, ensuring smooth transition without requiring simultaneous complex control of all four elements.
2Device complexity
If a 6 to 4 shift is completed before performing a 4 to 3 shift to achieve a 6 to 3 skip shift, then hydraulic pressure control is simplified, but shifting time increases and shift feel deteriorates
Solution Approach 1:
The patent performs the release of off-going clutches as a preliminary action before engaging the on-coming brake and clutch. The predetermined time delay ensures that the release process is initiated but not completed before engagement begins, creating an overlapping period that reduces total shift time while maintaining control simplicity.
3Loss of time
If overlapping shift control is performed where a second shift from an intermediate shift-speed to the final shift-speed is overlapped with a first shift from the current shift-speed to the intermediate shift-speed, then shifting time is reduced, but output torque fluctuates seriously and double shift feel occurs
Solution Approach 1:
The patent extracts the intermediate shift-speed stage from the shift process by directly transitioning from 6th gear to 3rd gear through sequential clutch release and brake engagement. This eliminates the intermediate 4th gear state, preventing output torque fluctuations and double shift feel while still achieving time reduction through overlapping operations.
4Ease of operation
If turbine speed is increased without controlling hydraulic pressure during the skip shift process, then shift feel is improved by preventing intermediate shift-speed achievement, but shift shock may occur
Solution Approach 1:
The patent applies beforehand cushioning by controlling the engagement timing of the on-coming brake and clutch to occur after a predetermined time delay following clutch release. This timing control cushions the transition process, allowing turbine speed to increase naturally while preventing abrupt engagement that would cause shift shock, thus improving shift feel without harmful effects.
Data Source
AI summary
A shift control method of an automatic transmission controls a skip shift from a first shift-speed achieved by engagements of first and second frictional elements to a second shift-speed achieved by engagements of third and fourth frictional elements, wherein the engagements of the third and fourth frictional elements is controlled after completion of releases of the first and second frictional elements.