Transmission Gain Control Valve Shift Quality
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Solution Overview
Problem
Automatic transmissions face challenges in efficiently managing clutch gain during shifts, particularly due to variations in turbine torque, which can lead to inaccurate torque capacity control and potential clutch slip, especially when transitioning between gear ratios.
Innovation Solution
A transmission system with a gain control valve and a controller that adjusts line pressure based on turbine torque, maintaining pressure above a switching threshold during shifts and limiting engine torque if below the threshold to prevent gain switching, thereby ensuring accurate torque capacity control of shift elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the controller adjusts line pressure based on turbine torque during shifts, then torque capacity control accuracy is improved, but the system complexity increases due to the gain control valve and pressure switching mechanism
Solution Approach 1:
The gain control valve acts as an intermediary component that automatically switches between different gain values based on line pressure thresholds. This mediator handles the complexity of adaptive control, allowing the controller to maintain accurate torque capacity control without implementing complex real-time calculations for gain adjustment.
Solution Approach 2:
The system changes the gain parameter dynamically by switching between a first gain value and a second gain value based on whether the line pressure exceeds a threshold. This parameter change approach allows the system to adapt to different operating conditions (high vs. low turbine torque) while maintaining simple control logic.
2Adaptability or versatility
If the gain control valve switches state during a shift, then the torque capacity adapts to changing conditions, but clutch slip occurs due to inaccurate torque control
Solution Approach 1:
The controller determines in advance whether the turbine torque exceeds the threshold at the beginning of a shift and proactively adjusts the line pressure or limits engine torque accordingly. This preliminary action ensures the gain control valve remains in the appropriate state throughout the entire shift duration, preventing clutch slip caused by mid-shift gain switching.
Solution Approach 2:
The system takes preliminary anti-action by limiting engine torque or maintaining line pressure above the threshold before the shift completes, specifically preventing the gain control valve from switching state during the critical shift period when clutch engagement reliability is most vulnerable.
3Reliability
If the controller limits engine torque during shifts to prevent gain switching, then clutch slip is minimized, but power transmission efficiency is reduced
Solution Approach 1:
The controller applies torque limiting only partially - specifically during the shift duration and only when the turbine torque is below the threshold. This partial action is sufficient to prevent gain switching and ensure reliable clutch engagement, while minimizing the impact on overall power transmission efficiency by not continuously limiting torque.
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 solution ensures precise torque control during shifts, minimizing clutch slip and maintaining optimal engine performance across various gear ratios by dynamically adjusting clutch torque capacity based on turbine torque conditions.
Implementation Method 1
the valve body includes a gain control valve configured to alter a relationship between a commanded current and a resulting shift element torque capacity in response to a pressure in the line pressure circuit exceeding a switching threshold
Implementation Method 2
Between shifts, the controller is programmed to set the pressure in the line pressure circuit as a function of a turbine torque. During a shift, if the turbine torque exceeds a threshold at a beginning of the shift, the controller may maintain the pressure in the line pressure circuit above the switching threshold throughout the shift
Implementation Method 3
If the turbine torque is less than the threshold at the beginning of the shift, the controller limits an engine torque level throughout the shift such that the gain control valve does not change state
Implementation Method 4
The valve body is configured to route fluid at controlled pressure from a line pressure circuit to the shift elements
Implementation Method 5
The fluid is pressurized and circulated by an engine driven pump. The fluid absorbs heat that is generated by friction within the transmission
Data Source
AI summary
In a transmission hydraulic control system, a gain control valve may be used to switch between a low gain and a high gain based on line pressure. Line pressure may be controlled as a function of turbine torque. If the gain of a holding element or oncoming element changes during a shift as a result of changing turbine torque, shift quality may degrade. If the gain is set low at the beginning of the shift, the controller limits engine torque to ensure that the line pressure is not increased beyond a level that would cause a gain switch. If the gain is set high at the beginning of a shift, the controller maintains the line pressure high enough to prevent a switch to low gain, even if turbine torque drops.