Automatic Transmission Hydraulic Pressure Compensation for Shift Shock
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Solution Overview
Problem
Automatic transmissions experience increased shifting time and shift shock when a brake is operated during lift-foot-up shifting, leading to delayed re-acceleration due to the conventional hydraulic pressure compensation method's inefficiencies.
Innovation Solution
A method that calculates and applies a compensation hydraulic pressure to the friction member based on the vehicle's deceleration rate, adjusting the on-coming pressure by adding a compensation pressure to the base and first-order slope pressures, which increases the pressure gradient to facilitate faster synchronization and reduce shift shock.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a conventional linear hydraulic pressure control is used during lift-foot-up shifting with brake operation, then the shifting operation is simple to control, but the shifting time is increased and shift shock occurs
Solution Approach 1:
The patent applies dynamics by making the hydraulic pressure control adaptive rather than static. The control system dynamically adjusts the on-coming pressure gradient based on real-time detection of brake operation and vehicle deceleration rate. This dynamic adaptation allows the system to maintain simple operation while significantly reducing shifting time by applying steeper pressure gradients when brake operation is detected.
Solution Approach 2:
The patent changes the pressure gradient parameter dynamically based on operating conditions. When brake operation is detected during lift-foot-up shifting, the system switches from a conventional linear pressure increase to a compensated pressure profile with a steeper initial gradient. This parameter change optimizes the shifting speed without complicating the overall control mechanism.
2Device complexity
If a conventional linear hydraulic pressure control is used during lift-foot-up shifting, then the control mechanism is simple, but shift shock increases due to abrupt turbine speed synchronization
Solution Approach 1:
The system dynamically adjusts the pressure profile based on detected brake operation and deceleration rate. By making the pressure control adaptive rather than fixed, the system can smooth the turbine speed synchronization process during brake operation, reducing shift shock without adding complex mechanical components.
Solution Approach 2:
The control system uses feedback from brake operation detection and deceleration rate sensing to adjust the hydraulic pressure profile. This feedback mechanism allows the system to automatically compensate for shift shock conditions and optimize the pressure gradient in real-time, maintaining simple control architecture while reducing harmful shift shocks.
3Productivity
If the on-coming pressure gradient is increased to reduce shifting time, then shifting speed improves, but shift shock increases due to abrupt pressure changes
Solution Approach 1:
The patent optimizes the pressure gradient parameter by applying a compensated profile that is steeper than conventional linear control but carefully shaped to avoid abrupt changes. The pressure gradient is adjusted based on deceleration rate, creating an optimal balance between shifting speed and shift shock reduction.
Solution Approach 2:
The control system applies beforehand cushioning by pre-calculating and applying an optimized pressure profile that anticipates the shifting process. The compensated on-coming pressure is designed to reach the target pressure more quickly while incorporating smooth transition characteristics that prevent abrupt changes, thus cushioning against shift shock before it occurs.
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 approach allows for earlier synchronization of the turbine speed with the synchronization speed, reducing shift shock and accelerating the shifting operation by applying increased hydraulic pressure in response to deceleration, thereby improving shifting efficiency and reducing shock.
Implementation Method 1
calculating a on-coming pressure based on the calculated compensation hydraulic pressure; and applying the calculated on-coming pressure to the friction member
Data Source
AI summary
Faster shifting operation and reduced shift shock in response to a braking operation during a lift-foot-up shifting may be achieved when an automatic transmission is controlled by a method for compensating a hydraulic pressure that includes: determining whether a lift-foot-up shifting of the automatic transmission is under control; calculating a vehicle speed of a vehicle; calculating a deceleration rate of the vehicle; calculating a compensation hydraulic pressure to be applied to a friction member of the transmission, based on the deceleration rate; calculating a on-coming pressure based on the calculated compensation hydraulic pressure; and applying the calculated on-coming pressure to the friction member.