Dual-Sump Transmission Hydraulic Control for Parasitic Drag Reduction
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Solution Overview
Problem
In automotive transmission hydraulic systems, an excessively high fluid level in the sump due to temperature variations leads to parasitic drag and reduced lubrication efficiency, increasing fuel consumption and requiring additional engine torque to overcome resistance.
Innovation Solution
A transmission hydraulic control system incorporating a primary sump, an auxiliary sump, and an oil control valve that passively restricts flow from the auxiliary sump to the primary sump based on temperature and engine operation, using a wax motor and sliding spools to manage fluid levels and prevent excessive fluid accumulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the fluid level in the sump is high, then the sump does not become empty under cold operating conditions, but parasitic drag increases and fuel consumption increases
Solution Approach 1:
The sump is divided into two separate sumps: a primary sump that maintains adequate fluid level for cold conditions, and a secondary sump that stores excess fluid at higher temperatures. This segmentation allows the system to have different fluid levels in different locations based on operating conditions, resolving the contradiction between having enough fluid and avoiding parasitic drag.
Solution Approach 2:
A controlled flow passage with a flow restrictor acts as an intermediary between the primary and secondary sumps. This intermediary component regulates fluid transfer between sumps based on pressure differential caused by temperature changes, automatically maintaining optimal fluid levels without requiring active control systems.
2Reliability
If the fluid level in the sump is high, then the sump does not become empty under cold operating conditions, but rotating components extend into the fluid and create parasitic drag
Solution Approach 1:
The sump is divided into two separate sumps: a primary sump that maintains adequate fluid level for cold conditions, and a secondary sump that stores excess fluid at higher temperatures. This segmentation allows the system to have different fluid levels in different locations based on operating conditions, resolving the contradiction between having enough fluid and avoiding parasitic drag.
Solution Approach 2:
A controlled flow passage with a flow restrictor acts as an intermediary between the primary and secondary sumps. This intermediary component regulates fluid transfer between sumps based on pressure differential caused by temperature changes, automatically maintaining optimal fluid levels without requiring active control systems.
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 system effectively maintains optimal fluid levels in the primary sump, reducing parasitic drag, improving lubrication efficiency, and minimizing fuel consumption by dynamically adjusting fluid distribution based on temperature and engine status.
Implementation Method 1
A wax motor separates the two spools by a distance that depends upon the temperature of fluid in the fourth port
Implementation Method 2
An engine driven pump draws fluid from the primary sump and pressurizes the fluid to a line pressure
Implementation Method 3
The second spool is biased by a spring
Implementation Method 4
The position of the first spool is determined by the line pressure which biases the spool toward the second spool
Implementation Method 5
The fluid is then discharged from the gearbox components by a combination of gravitational forces and centrifugal forces generated by rotating components
Implementation Method 6
The fluid is then discharged from the gearbox components by a combination of gravitational forces and centrifugal forces generated by rotating components
Data Source
AI summary
A hydraulic control system includes a primary sump and an auxiliary sump. When the transmission fluid is warm, fluid remains in the auxiliary sump reducing the volume of oil in circulation throughout the transmission to reduce parasitic losses. An oil control valve is designed to block flow of oil from the auxiliary sump to the primary sump when the fluid is warm and to allow flow when the fluid is cold. The oil control valve also responds to transmission line pressure. At moderate temperatures, fluid is held in the auxiliary sump when the engine is running but drains back to the primary sump when the engine is off.