Frustoconical Secondary Filter Element for Reliable Sealing

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Solution Overview

Problem

Existing air filter systems for internal combustion engines face challenges in providing a cost-effective secondary filter element with reliable sealing and reproducible positioning, especially in environments with strong vibrations, while maintaining accurate air flow characteristics for mass flow sensors.

Innovation Solution

A filter system with a secondary filter element featuring a frustoconical shape and longitudinal seams, allowing for cost-efficient manufacturing and precise positioning on a stand pipe, which reduces flow disturbances and ensures accurate air flow measurements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a secondary filter element is used to protect the clean side during filter replacement, then protection against dirt particles is improved, but the complexity of the filter system increases

Engineering Contradiction:
Improveprotection against dirt particlesVSAvoidfilter system complexity
Core Design Contradiction:
Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The secondary filter element is positioned inside the primary filter element housing, with the primary filter element resting on the free end of the supporting tube and thus on the end cap of the secondary filter element. This nested arrangement allows both filter elements to coexist in the same space, providing protection during filter replacement without requiring a completely separate system.

Inventive Principle:
Principle #7Nested doll (Nesting)

Solution Approach 2:

The secondary filter element acts as an intermediary protective barrier between the dirty environment and the clean side of the filter system. It remains in the filter housing during replacement of the main filter element, preventing dirt particles from penetrating to the clean side while allowing the primary filter element to be exchanged.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Strength

If the secondary filter element is made with metallic elements for structural integrity, then strength is improved, but thermal disposal capability deteriorates

Engineering Contradiction:
Improvestructural integrityVSAvoidthermal disposal capability
Core Design Contradiction:
StrengthVSEase of manufacture

Solution Approach 1:

The end cap of the secondary filter element is designed with a specific geometry that provides structural support where needed while maintaining compatibility with thermal disposal requirements. The frustoconical shape with defined edges offers localized strength enhancement without requiring metallic reinforcement throughout the entire structure.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The end cap features an asymmetric design with a first edge having a smaller circumference than the second edge, creating a frustoconical shape. This asymmetric geometry provides structural integrity through shape rather than material strength, allowing the use of thermally disposable materials while maintaining sufficient mechanical strength for the application.

Inventive Principle:
Principle #4Asymmetry

3Ease of operation

If the secondary filter element is positioned without precise positioning features, then ease of assembly is improved, but measurement precision of air flow deteriorates

Engineering Contradiction:
Improveease of assemblyVSAvoidair flow measurement accuracy
Core Design Contradiction:
Ease of operationVSMeasurement precision

Solution Approach 1:

The end cap is designed with asymmetric features including a first edge with smaller circumference than the second edge, creating a frustoconical shape. This asymmetric geometry provides reproducible positioning when the secondary filter element is mounted on the stand pipe, ensuring consistent orientation for accurate air flow measurements while still allowing relatively simple assembly.

Inventive Principle:
Principle #4Asymmetry

Solution Approach 2:

The end cap geometry is pre-configured with specific edge configurations that automatically guide the secondary filter element into the correct position during assembly. The frustoconical shape with defined edges creates natural positioning features that ensure reproducible orientation without requiring complex positioning mechanisms or multiple assembly steps.

Inventive Principle:
Principle #10Preliminary action

4Reliability

If the secondary filter element uses a complex sealing structure for vibration resistance, then reliability is improved, but manufacturing cost increases

Engineering Contradiction:
Improvevibration resistanceVSAvoidmanufacturing cost
Core Design Contradiction:
ReliabilityVSEase of manufacture

Solution Approach 1:

The end cap features an asymmetric frustoconical shape with a first edge having smaller circumference than the second edge. This geometric design provides inherent positioning and sealing capabilities that are resistant to vibration effects, eliminating the need for additional complex sealing structures while maintaining manufacturing simplicity.

Inventive Principle:
Principle #4Asymmetry

Solution Approach 2:

The end cap employs a frustoconical curved surface rather than flat surfaces, creating a geometry that naturally resists vibration-induced disengagement. The curved surface provides continuous contact area with the stand pipe, enhancing vibration resistance through geometric constraints rather than additional sealing components.

Inventive Principle:
Principle #14Spheroidality (Curvature)

Data Source

PatentEP4223386B1Filter system having a primary and a secondary filter element, secondary filter element and method
Publication Date: 2025.09.17 MANN HUMMEL GMBH
  • EP4223386B1 patent drawingFigure 1
  • EP4223386B1 patent drawingFigure 2
  • EP4223386B1 patent drawingFigure 3~4

AI summary

The invention relates to a filter system (100) comprising a housing (110) with a fluid inlet (102), a fluid outlet (108), a primary filter element (50) and a secondary filter element (10). The secondary filter element (10) comprises a filter medium (16) forming a frustoconical filter body (36) having at least two longitudinal seams (18, 19) extending along an axial direction (L), and two axial end edges (12, 14), a first end edge (12) having a smaller circumference than the second end edge (14). The filter body (36) comprises a first medium layer (38) and a second medium layer (40) of the filter medium (16), being cut and joined along the at least two longitudinal seams (18, 19), and forming the frustoconical filter body (36), The invention further relates to a secondary filter element (10) and a method for manufacturing such a secondary filter element (10).