Transmission Clutch Control via Pressure Pulses to Counteract Fluid Leak-Down
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Solution Overview
Problem
Automatic transmission systems face delays in clutch engagement due to hydraulic fluid leak-down in disengaged clutches, leading to objectionable surges or sags in vehicle acceleration during shifts, caused by centrifugal forces and wear over time.
Innovation Solution
A control system that includes a clutch control module which supplies pressure pulses to disengaged clutches during steady-state operation to maintain fluid levels, discontinuing the pulse before torque transmission and adjusting based on gear ratios and engagement states to ensure consistent response times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pressure is continuously applied to disengaged clutches, then fluid levels are maintained, but clutch engagement time increases and shift response becomes slower
Solution Approach 1:
The patent applies periodic pressure pulses to disengaged clutches during steady-state operation rather than continuous pressure. The pulse module selectively supplies pressure pulses at predetermined intervals to maintain fluid levels in clutch apply chambers, while the timer module monitors elapsed time and the sequence module coordinates pulsing sequences. This periodic action maintains clutch readiness without causing continuous engagement, thus preserving both fluid levels and shift response time.
2Loss of time
If pressure pulses are supplied to maintain fluid levels, then clutch response time improves, but turbine speed flares and shift noise increase
Solution Approach 1:
The patent applies pressure pulses to disengaged clutches in advance during steady-state operation before actual shift events occur. This preliminary action maintains fluid levels and clutch readiness proactively, so that when a shift is commanded, the clutch is already prepared and can engage immediately without causing turbine speed flares or shift noise. The capacity module detects when clutches begin transmitting torque to determine when to discontinue pulsing.
Solution Approach 2:
The system uses feedback from the capacity module that detects when clutches begin transmitting torque to control the pressure pulsing. The sequence module receives this feedback and discontinues pressure pulses when torque transmission is detected, preventing over-pulsing that could cause turbine speed flares or noise while maintaining the benefits of fluid level maintenance during steady-state operation.
3Reliability
If pressure pulses are applied to multiple clutches simultaneously, then all clutches maintain fluid levels, but control complexity and potential for harmful effects increase
Solution Approach 1:
The patent segments the pressure pulsing control by clutch and by timing phase. The sequence module divides clutches into groups (first group pulsed during steady-state, second group pulsed during shift events) and applies pressure pulses to individual clutches or small groups sequentially rather than all simultaneously. The timer module tracks elapsed time for each clutch independently, allowing coordinated but staggered pulsing that maintains fluid levels across all clutches while simplifying control and reducing harmful effects.
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 maintains fluid levels in clutch apply chambers, ensuring consistent clutch engagement times, reducing turbine speed flares, undesirable shift noise, and wear, thereby improving shift feel and transmission durability.
Implementation Method 1
The pulse module selectively supplies a pressure pulse to P of the M hydraulic clutches
Implementation Method 2
caused by centrifugal forces and wear over time
Data Source
AI summary
A control system for a transmission includes an actuator module, a timer module, and a pulse module. The actuator module engages N hydraulic clutches and disengages M hydraulic clutches to operate the transmission in a gear ratio, wherein N and M are integers greater than zero. The timer module determines a first period starting when the transmission begins operating in the gear ratio. The pulse module selectively supplies a pressure pulse to P of the M hydraulic clutches based on the first period, wherein P is an integer greater than zero. A method for controlling a transmission is also provided.