Hydraulic Filter Unit with Bypass for Viscosity Management

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Solution Overview

Problem

Existing filter units in hydraulic systems face inefficiencies due to high installation space requirements and costly valve technology, particularly when operating at low temperatures and high viscosities, leading to potential particle bypass and reduced operational safety.

Innovation Solution

A filter unit design featuring a first fluid path with a filter element on both sides and a second fluid path with a stroke storage volume that allows filtered fluid to bypass the filter element at high inlet pressures, ensuring reliable particle filtration regardless of fluid viscosity and flow direction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a filter is inserted into the hydraulic line to filter out solid particles, then particle filtration is improved, but installation space requirements increase

Engineering Contradiction:
Improveparticle filtrationVSAvoidinstallation space
Core Design Contradiction:
ReliabilityVSVolume of stationary object

Solution Approach 1:

The patent combines the filter element with the housing to form an integrated filter unit, merging the filtration function with the structural housing to reduce overall installation space while maintaining effective particle filtration capability

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The filter element is nested within the housing structure, with the filter medium arranged inside the housing cavity. This nesting arrangement allows the filter to occupy minimal space while providing sufficient filtration surface area

Inventive Principle:
Principle #7Nested doll (Nesting)

2Ease of operation

If valve technology is used to ensure unidirectional fluid flow through the filter, then flow direction control is improved, but device complexity and cost increase

Engineering Contradiction:
Improveflow direction controlVSAvoidvalve technology
Core Design Contradiction:
Ease of operationVSDevice complexity

Solution Approach 1:

The patent removes the complex valve technology from the system and replaces it with a simpler passive flow control mechanism using check valves integrated into the housing, extracting the unnecessary complexity while maintaining flow direction control

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces a check valve as an intermediary element that passively controls flow direction without requiring complex active valve technology. The check valve mediates between the dual fluid paths and the filter element to ensure proper flow direction

Inventive Principle:
Principle #24Intermediary (Mediator)

3Adaptability or versatility

If a bypass function is provided for low temperature operation, then operational capability at low temperatures is improved, but particle filtration effectiveness deteriorates

Engineering Contradiction:
Improvelow temperature operationVSAvoidparticle filtration
Core Design Contradiction:
Adaptability or versatilityVSReliability

Solution Approach 1:

The patent creates a dynamic system where the check valve automatically switches between blocking and allowing bypass flow based on the pressure differential caused by fluid viscosity changes. At low temperatures, the bypass opens to maintain flow; at normal temperatures, it closes to ensure filtration

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The bypass function operates periodically based on temperature and pressure conditions. The check valve opens the bypass path during high-viscosity conditions (low temperature) and closes it during normal operating conditions, creating a periodic activation pattern that adapts to environmental changes

Inventive Principle:
Principle #19Periodic action

4Adaptability or versatility

If the filter is placed in a hydraulic line with bidirectional flow, then adaptability to flow direction changes is improved, but particle migration prevention deteriorates

Engineering Contradiction:
Improvebidirectional flow handlingVSAvoidparticle migration prevention
Core Design Contradiction:
Adaptability or versatilityVSReliability

Solution Approach 1:

The patent employs asymmetric positioning of the filter element within the housing and asymmetric arrangement of the dual fluid paths. The filter element is positioned to face one direction preferentially, creating asymmetric flow resistance that prevents particle migration while still allowing bidirectional operation

Inventive Principle:
Principle #4Asymmetry

Solution Approach 2:

The patent inverts the conventional approach by using the pressure differential caused by bidirectional flow to enhance filtration rather than overcome it. The check valve system is designed to utilize the natural pressure changes during bidirectional flow to maintain filtration effectiveness in both directions

Inventive Principle:
Principle #13The other way round (Inversion)

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 provides a compact, cost-effective particle barrier that effectively prevents solid particles from migrating through the hydraulic system, maintaining operational reliability and reducing maintenance and operational costs by ensuring filtered fluid supply even at high viscosities.

Implementation Method 1

a filter element for filtering solid particles on both sides in the first fluid path

Methodology Applied
Scientific EffectPhysical filtration: Filter (physical)

Implementation Method 2

a compression spring arranged in the second fluid path, wherein the compression spring is preloaded in the direction of the second fluid connection

Methodology Applied
Scientific EffectElastic potential energy storage: Spring

Data Source

PatentEP2926880B1Filter unit for a hydraulic system
Publication Date: 2018.01.17 SCHAEFFLER TECHNOLOGIES AG & CO KG
  • EP2926880B1 patent drawingFigure 1
  • EP2926880B1 patent drawingFigure 2~3

AI summary

The present invention relates to a filter unit for a hydraulic system, in particular for a hydraulic coupling system, for filtering solid components from a hydraulic fluid, comprising a first fluid path leading from a first fluid port to a second fluid port, wherein a filter element for filtering solid particles on both sides is provided in the first fluid path. The filter unit additionally has a second fluid path leading from the first fluid port to the second fluid port, in which a reservoir volume for receiving a self-filtering fluid volume is arranged, wherein, at a predetermined fluid inlet pressure, an outlet of the reservoir volume, fluidically connected to the fluid port serving as the fluid outlet, opens.In summary, the filter unit described above allows hydraulic fluid to flow through it, or to supply a corresponding hydraulic component with hydraulic fluid, in a simple and compact manner, regardless of whether the viscosity is relatively low or relatively high. Solid particles in the hydraulic fluid, however, cannot pass through the filter unit. Thus, the filter unit described above forms an effective particle barrier, independent of the viscosity of the hydraulic fluid.