Servo Piston Area Ratio for Band Drag Reduction
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Solution Overview
Problem
In high-performance applications of GM Powerglide transmissions, increased line pressure causes a force imbalance due to the area differential between the release and apply sides of the servo piston, leading to band drag in high gear, which the original release springs are not designed to handle effectively.
Innovation Solution
The design includes a servo assembly with a servo pin and multiple pistons, where the total release area is greater than or equal to the total apply area, allowing pressurized release oil to act on a larger surface, thereby increasing the release force without compromising the ability to engage the band, and includes a replacement method for existing servo assemblies to enhance release force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If line pressure is increased for better clutch holding power and quicker shifts, then clutch holding power and shift speed are improved, but force imbalance occurs due to area differential between release and apply sides, causing band drag in high gear
Solution Approach 1:
The patent changes the geometric parameters of the servo piston by providing a release side with a larger surface area than the apply side. This parameter modification allows the piston to respond appropriately to increased line pressure by generating sufficient release force to overcome the apply force and prevent band drag, while still maintaining effective clutch holding power when needed.
Solution Approach 2:
The patent applies a counterbalancing principle by designing the release side area to be greater than the apply side area. This creates a natural counterweight effect where the larger release area generates proportionally greater release force to counterbalance the increased apply force resulting from higher line pressure, thereby preventing the harmful band drag effect.
2Power
If original release springs are used with increased line pressure, then clutch holding power is improved, but release capability deteriorates due to force imbalance
Solution Approach 1:
The patent changes the geometric parameter of the servo piston by providing a larger release side area. This modification allows the system to maintain reliable release capability even when using original release springs with increased line pressure, because the larger release area generates sufficient release force to counterbalance the increased apply force, preventing the force imbalance that would otherwise cause band drag.
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 configuration allows for increased line pressure without negatively impacting the servo's ability to release, maintaining or improving performance by reducing the force required for clutch engagement and release, and potentially reducing the need for stronger release springs.
Implementation Method 1
pressurized release oil to a release side of the servo piston... causing the piston to retract back to the release position
Implementation Method 2
pressurized apply oil is directed to apply side of servo piston, causing the servo piston and servo pin to move from a released position to an applied position
Data Source
AI summary
Methods of modifying a GM Powerglide low range servo assembly for high line pressure applications as well as replacement components for Powerglide low range servo assemblies and replacement low range servo assemblies.