Automatic Transmission Speed Change Control for Low-Speed Shock Suppression
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Solution Overview
Problem
Automatic transmission systems face challenges in accurately detecting vehicle speed at low speeds, leading to delayed speed change responses and undesired shocks during gear changes, as existing solutions either prolong speed change times or introduce shocks when trying to quicken the process.
Innovation Solution
A speed change control system for automatic transmissions that uses a vehicle speed sensor to judge if the vehicle is at a low speed, sharply increasing and then holding hydraulic pressure to reduce speed change time and minimize shocks, with distinct control phases for normal and very low vehicle speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the increasing rate of the command hydraulic pressure is set high, then the speed change time is reduced, but undesired speed change shock occurs when the clutch is engaged
Solution Approach 1:
The hydraulic pressure control is divided into multiple distinct phases: a first phase where pressure increases at a first rate to complete piston stroke, and a second phase where pressure increases at a second (higher) rate after piston stroke completion. This segmentation allows optimization of each phase independently - the first phase prioritizes shock suppression while the second phase prioritizes speed change time reduction.
Solution Approach 2:
The system performs preliminary action by completing the piston stroke at a moderate pressure increase rate before applying the high pressure increase rate. This preliminary completion of the critical piston stroke phase prepares the system for the subsequent high-rate pressure increase, ensuring that the clutch engagement shock is avoided while still achieving rapid pressure buildup for fast speed change.
2Object-affected harmful factors
If the increasing rate of the command hydraulic pressure is set low, then the speed change shock is reduced, but the speed change time cannot be reduced
Solution Approach 1:
The system dynamically adjusts the pressure increase rate based on the operational phase. The control device switches between a first (lower) pressure increase rate during piston stroke and a second (higher) pressure increase rate after piston stroke completion. This dynamic adjustment allows the system to adapt to different operational requirements at different stages of the speed change process.
Solution Approach 2:
The hydraulic pressure control is structured as periodic action with distinct time periods: a first period for piston stroke completion at a moderate pressure rate, and a second period for final pressure buildup at a higher rate. This periodic structure with clearly defined phases enables the system to balance shock suppression during the critical engagement phase while achieving rapid speed change in the subsequent phase.
3Speed
If the hydraulic pressure is sharply increased to reduce speed change time, then the speed change response is improved, but shock occurs during clutch engagement
Solution Approach 1:
The speed change process is segmented into two distinct phases with different pressure control strategies. The first phase uses a moderate pressure increase rate to complete the piston stroke, ensuring smooth clutch engagement without shock. The second phase uses a high pressure increase rate to achieve rapid speed change response. This segmentation resolves the contradiction by applying different control strategies to different stages of the same process.
Solution Approach 2:
The system performs preliminary action by completing the piston stroke at a moderate pressure rate before applying the high pressure rate. This preliminary phase prepares the clutch for engagement without causing shock, and only after this preparation is complete does the system apply the high pressure rate to achieve rapid speed change response.
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
The system effectively reduces speed change time and suppresses shocks during low-speed gear changes, ensuring rapid and smooth operation by optimizing hydraulic pressure control based on vehicle speed detection.
Implementation Method 1
a control device that controls a hydraulic pressure applied to the first frictional element based on information on a target gear ratio
Implementation Method 2
a first frictional element that changes its operation condition from a disengaged condition to an engaged condition upon issuance of a speed change instruction
Data Source
AI summary
When it is judged that a vehicle speed detected by a vehicle speed sensor is equal to or lower than a predetermined very low value, that is, for example, 5 km/h, the hydraulic pressure applied to an engaging-side frictional element is sharply increased, sharply reduced and then held higher than a given value capable of effecting a piston stroke of a corresponding piston unit until a time when the piston stroke is completed. Upon completion of the piston stroke, the hydraulic pressure is increased to a maximum value in a time that is smaller or shorter than that set when the detected vehicle speed is higher than the predetermined very low value.