Automatic Transmission Filter Bypass Valve Stability
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Solution Overview
Problem
Existing filter assemblies for automatic transmission fluid (ATF) allow large contaminants to reenter and recirculate due to bypass valve instability, especially at cold temperatures, causing air entrapment and pressure instability downstream of the pump.
Innovation Solution
A filter assembly with a bypass valve and screen that disperses air bubbles through a sloped channel, minimizing bypass valve opening time and ensuring smooth fluid flow, featuring a rounded valve housing for unrestricted flow and a screen with a spherical dome to filter contaminants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a bypass valve is arranged in parallel flow path with the filter element, then the valve can open to allow fluid flow during cold temperature operation, but large contaminants can reenter and recirculate through the transmission when the valve is open
Solution Approach 1:
The bypass flow path is segmented into two stages: first through the bypass valve, then through the screen. This segmentation allows the system to provide unrestricted flow through the valve while the screen segment filters out large contaminants, resolving the contradiction between maintaining high flow rate and preventing contaminant recirculation.
Solution Approach 2:
The screen acts as an intermediary element between the bypass valve and the pump inlet. It mediates the flow by allowing fluid to pass while intercepting large contaminants, thus enabling the bypass function to operate without directly introducing contaminants into the recirculation system.
2Productivity
If the bypass valve opens during cold temperature operation, then fluid can flow through the bypass path, but air may enter the filter assembly and accumulate in large bubbles causing slug-like fluid flow and pressure instability
Solution Approach 1:
The air bubble flow path is segmented and redirected through the sloped channel design. Instead of allowing large bubbles to accumulate and exit directly into the pump intake, the sloped channel segments the air flow and guides it along a controlled path, reducing the formation of slug-like flow patterns and stabilizing the fluid composition entering the pump.
Solution Approach 2:
The sloped channel incorporates curved surfaces that guide air bubbles along a smooth trajectory. The curvature of the sloped channel prevents abrupt changes in flow direction, reducing turbulence and promoting stable, continuous flow rather than slug-like interruptions, thereby maintaining fluid flow stability during bypass operation.
3Loss of time
If restrictions are present in the flow path leading to the valve inlet, then the valve can be positioned to minimize bypass opening time, but excessively long periods when the bypass valve is open occur due to high pressure differential
Solution Approach 1:
The flow path is designed with preliminary considerations for pressure management. The positioning of the valve immediately adjacent to the inlet and the rounded valve housing create favorable flow conditions before the fluid reaches the valve, reducing the pressure differential that would otherwise cause prolonged valve opening. This preliminary flow conditioning minimizes the duration of bypass operation.
Solution Approach 2:
The rounded valve housing creates a curved, unrestricted flow path that promotes smooth fluid motion toward the valve and filter housing inlet. This curvature eliminates flow restrictions and reduces pressure buildup, thereby minimizing the pressure differential across the valve and reducing the time the bypass valve remains open during cold temperature operation.
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 solution prevents bypass valve instability and air entrapment, maintaining stable pump operation by minimizing the duration of bypass valve opening and ensuring small bubble air exit, thus preventing pressure spikes and maintaining fluid flow stability.
Implementation Method 1
the valve including an orifice that opens and closes in response to differential pressure across the valve
Implementation Method 2
a screen secured to the valve housing and covering the orifice, the screen having a fine mesh for removing contaminants from the fluid that flows through the valve
Implementation Method 3
The channel increasing in elevation as distance from the second inlet along the channel length increases. When valve is open during cold temperature operation, air that accumulates in the valve passes along the channel in small, dispersed bubbles
Data Source
AI summary
A filter assembly includes a filter housing including an inlet, through which hydraulic fluid enters the housing, and an outlet, through which hydraulic fluid exits the housing, valve housing containing a bypass valve located adjacent the inlet in a chamber, the valve including an orifice that opens and closes in response to differential pressure across the valve, and a screen secured to the valve housing and covering the orifice, the screen having a fine mesh for removing contaminants from the fluid that flows through the valve.