Automatic Transmission Shift Arm Control for Rapid Gear Engagement
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Solution Overview
Problem
Conventional automatic transmission systems with dog clutches face challenges in performing gear changes quickly and reliably due to issues like rounded corners on engaging surfaces, leading to incomplete engagement and failure in rapid gear shifts.
Innovation Solution
An automatic transmission device with a clutch actuator, shift actuator, and detection systems that control the engagement and disengagement of gears, ensuring sufficient engagement time and using friction forces to maintain engagement during gear changes, allowing for quicker and more reliable shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the shift arm is returned to the neutral position at the same time as the dog fitting, then the gear change time is shortened, but the engagement reliability deteriorates due to rounded corners on engaging surfaces
Solution Approach 1:
The patent applies preliminary action by starting to return the shift arm to the neutral position before the dog fitting is completed. The control device initiates the shift arm return movement while the clutch is in the half-clutch state, before the engaging portions are fully engaged. This allows the shift arm to reach the neutral position earlier, shortening the overall gear change time while the clutch friction plates maintain engagement through friction during the transition period.
Solution Approach 2:
The patent changes the parameter of clutch engagement state by introducing a half-clutch state where the clutch is partially engaged. During this half-clutch state, the clutch friction plates are in contact but not fully engaged, allowing torque transmission through friction while permitting the shift arm to return to neutral. This parameter change enables the shift arm to move freely during the critical engagement period without compromising reliability.
2Reliability
If the shift arm is returned to the neutral position after half clutch control is finished, then the engagement is ensured, but the gear change time is extended
Solution Approach 1:
The control device initiates the shift arm return movement in advance, before the half clutch control is completed. The shift arm starts returning to the neutral position while the clutch is still in the half-clutch state, rather than waiting for the engagement to be fully secured. This preliminary action reduces the waiting time while the clutch friction maintains engagement.
Solution Approach 2:
The patent maintains continuous useful action by having the clutch friction plates continuously transmit torque throughout the gear change process. The clutch remains in a controlled engagement state (half-clutch) during the entire period when the shift arm is returning to neutral, ensuring uninterrupted torque transmission and engagement reliability throughout the transition.
3Reliability
If the corners of engaging portions are rounded due to long-term use, then the dog fitting becomes unreliable, but the gear change speed cannot be increased
Solution Approach 1:
The patent substitutes the mechanical dog clutch engagement system with a friction-based clutch system for the critical engagement phase. Instead of relying on the precision mechanical fit of dog clutch engaging portions (which deteriorate with rounded corners), the system uses the friction between clutch friction plates to maintain engagement. This allows the shift arm to move freely during engagement without requiring precise mechanical alignment, enabling faster gear changes even with worn dog clutch surfaces.
Solution Approach 2:
The clutch friction plates serve as an intermediary between the engine torque and the transmission gears during the gear change process. The friction-based clutch transmission provides a buffer that allows the shift arm to return to neutral while maintaining torque transmission, decoupling the reliability of dog fitting from the speed of gear change. The intermediary friction connection compensates for the rounded corners of the dog clutch engaging portions.
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
Enables continuous gear changes within a short time frame with certainty by ensuring proper engagement and disengagement of gears, reducing the time between shifts and improving the reliability of the gear change process.
Implementation Method 1
a friction clutch (46) located between the engine (45) and the transmission mechanism (43) and configured to convey and cut off a torque from the engine (45) to the transmission mechanism (43)
Data Source
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AI summary
With an automatic transmission device 40, at the time of change of gear position of a transmission mechanism 43, when, after a movable gear is engaged with a fixed gear, an engagement detection section 155 detects that the engagement has not been kept for a prescribed time duration while a clutch is in a half clutch state, a shift actuator control device 140 gives a driving force, continuously or again, to a shift arm 425 for moving the shift arm 425 from a neutral position toward a gear position change position. When the engagement detection section 155 detects that the engagement of the movable gear and the fixed gear has been kept for the prescribed time duration while the clutch is in a half clutch state, the shift actuator control device 140 returns the shift arm 425 to the neutral position.