Transaxle Sump Bellows for Fluid Expansion Accommodation

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Solution Overview

Problem

Hydrostatic transaxles face issues with fluid expansion and contraction, leading to leaks, contamination, and space inefficiency due to external fluid expansion tanks and sump vents, which can damage components and limit vehicle configuration versatility.

Innovation Solution

A sealed sump within the transaxle case using a bellows assembly as a flexible partition to accommodate fluid expansion and contraction, integrated into the axle support structure, reducing the need for external components and maintaining hydraulic fluid containment within the housing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If an external fluid expansion tank or reservoir is used to accommodate sump fluid expansion and contraction, then the transaxle can handle fluid volume changes, but the device complexity increases and external space is required

Engineering Contradiction:

Improvefluid expansion accommodationVSAvoidexternal components

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent combines the fluid expansion accommodation function with the existing sump structure by integrating a collapsible bladder directly into the sump. This merging eliminates the need for separate external expansion tanks and hoses, reducing device complexity while maintaining the ability to handle fluid volume changes during operation

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The collapsible bladder is nested within the sump structure, allowing the expansion accommodation mechanism to be contained within the existing transaxle housing. This nesting approach eliminates external components while providing the necessary fluid volume compensation

Inventive Principle:

Principle #7Nested doll (Nesting)

2Reliability

If a sump vent is used to allow fluid expansion, then fluid volume changes can be accommodated, but leaks and contamination can occur

Engineering Contradiction:

Improvefluid expansion accommodationVSAvoidleaks and contamination

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent converts the harmful effect of fluid expansion (which causes leaks through vents) into a beneficial contained expansion within the collapsible bladder. The bladder safely absorbs expansion forces internally, preventing the need for vents that could leak or allow contamination

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The collapsible bladder acts as a flexible membrane that contains the hydraulic fluid while accommodating volume changes. This flexible enclosure prevents leaks and contamination by maintaining a sealed environment, eliminating the need for vent openings that would compromise the seal

Inventive Principle:

Principle #30Flexible shells and thin films

3Device complexity

If an internal bellows is used for fluid expansion, then external components are eliminated, but the transaxle housing size must increase

Engineering Contradiction:

Improveintegrated designVSAvoidhousing size

Core Design Contradiction:

Device complexityVSVolume of stationary object

Solution Approach 1:

The collapsible bladder uses a flexible membrane structure that can expand and contract within the existing sump volume. This flexible design allows fluid expansion accommodation without requiring additional rigid housing space, unlike traditional bellows designs

Inventive Principle:

Principle #30Flexible shells and thin films

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 efficiently utilizes space and material, preventing leaks and contamination while maintaining optimal oil pressure, even in cold conditions, thus enhancing the reliability and versatility of transaxle designs.

Implementation Method 1

a flexible partition separating the sump from an air chamber formed by a group of elements comprising the flexible partition, a portion of the main housing axle support structure

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 2

a biasing member can be used to pressurize the sump oil or sump fluid in a transaxle that will be operated in a cold environment so that transaxle case oil pressure does not drop below atmospheric pressure

Methodology Applied

Scientific EffectMechanical Force: Mechanical Force

Data Source

PatentUS9469191B1Transaxle fluid expansion and contraction accommodation apparatus

Publication Date: 2016.10.18 HYDRO GEAR LP

AI summary

An apparatus for accommodating fluid expansion and contraction within an axle housing or axle support structure of a hydrostatic transaxle is provided. A partitioning element separates the hydraulic fluid from an air chamber created at least partially by the partitioning element and the partitioning element has an internal volume that is in communication with the primary sump and the partitioning element expands to increase the size of its internal volume and thereby expand the volume of the sump.