Liquid Filter Volume Compensation With Integrated Dual Sealing

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Solution Overview

Problem

Existing liquid filters face challenges with volume changes due to temperature fluctuations, risking damage to the filter housing and requiring multiple sealing elements that complicate logistics and assembly, increasing the risk of leaks and fluidic short circuits.

Innovation Solution

A volume compensation element with integrated sealing areas that ensures both external and internal sealing, eliminating the need for separate O-rings and simplifying assembly by integrating the sealing functions into a single, elastically compressible component.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If multiple separate sealing elements (O-rings) are used for external and internal sealing, then sealing reliability is improved, but device complexity and assembly difficulty increase

Engineering Contradiction:
Improvesealing reliabilityVSAvoidnumber of sealing elements
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent combines multiple separate sealing elements (external sealing O-ring and internal sealing O-ring) into a single integrated sealing element. This sealing element has a complex geometry that allows it to simultaneously provide both external sealing between the filter element and housing, and internal sealing to prevent fluidic short circuits between clean and raw sides. The integration reduces the number of parts from two separate O-rings to one, simplifying logistics and assembly while maintaining dual sealing functions.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The integrated sealing element performs multiple sealing functions simultaneously. It provides external sealing at the interface between the filter element and housing, and internal sealing to prevent fluid bypass between the clean and raw sides. This multi-functional design allows a single component to replace what previously required two separate specialized sealing elements, reducing complexity while maintaining comprehensive sealing coverage.

Inventive Principle:
Principle #6Universality (Multi-functionality)

2Reliability

If multiple separate sealing elements are used, then sealing coverage is improved, but assembly errors and logistics complexity increase

Engineering Contradiction:
Improvesealing coverageVSAvoidassembly simplicity
Core Design Contradiction:
ReliabilityVSEase of operation

Solution Approach 1:

The patent merges the functions of multiple sealing elements into a single integrated component that is installed in one assembly operation. This eliminates the risk of assembly errors such as forgetting to install a sealing element or mixing up different types of O-rings. The single sealing element is designed with specific geometric features that guide its correct positioning and ensure both external and internal sealing functions are activated simultaneously during assembly.

Inventive Principle:
Principle #5Merging (Combining)

3Object-affected harmful factors

If a volume compensation element is added to handle temperature-induced volume changes, then housing damage is prevented, but device complexity and assembly steps increase

Engineering Contradiction:
Improvehousing damage from volume expansionVSAvoidnumber of components
Core Design Contradiction:
Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent integrates the volume compensation element with the filter element as a single integrated component rather than a separate part. The filter element includes an expandable cavity or compliant structure that allows it to accommodate volume changes of the filtered liquid due to temperature fluctuations. This integration adds only one component to the system while providing both filtration and thermal expansion compensation functions.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The integrated filter element serves dual purposes: it performs the primary filtration function by separating particles from the liquid, and simultaneously acts as a volume compensation element that expands or contracts to accommodate thermal volume changes of the liquid. This multi-functional design prevents housing damage from expansion forces while maintaining the filtration capability, without requiring a separate dedicated volume compensation component.

Inventive Principle:
Principle #6Universality (Multi-functionality)

4Stability of the object's composition

If the volume compensation element is securely fixed, then positional stability is improved, but device complexity increases

Engineering Contradiction:
Improveposition stability of volume compensation elementVSAvoidfixing mechanism complexity
Core Design Contradiction:
Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The patent combines the volume compensation element with the filter element structure, eliminating the need for separate fixing mechanisms. The integrated design uses the filter element's own structural features (such as rigid end caps or anchoring points) to secure the volume compensation portion in place. This integration provides positional stability through the inherent structural relationship between components rather than adding complex external fixing devices.

Inventive Principle:
Principle #5Merging (Combining)

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 effectively prevents housing damage and simplifies the assembly process by ensuring reliable sealing and simplifies the assembly of the sealing and reduces the risk of leaks and fluidic short circuits, enhancing the reliability of the sealing and simplifies the assembly and reduces the risk of leaks and fluidic short circuits.

Implementation Method 1

This element is not filled with the liquid but is elastically deformable. If the volume of the liquid inside the housing increases, the volume compensation element is compressed by the additional volume

Methodology Applied
Scientific EffectElastic deformation: Elasticity

Implementation Method 2

a filter element is known in which a fluidic short circuit between the clean side and the raw side (internal sealing) is prevented by a ring seal which is arranged in a sealing groove of an end cap of the filter element

Methodology Applied
Scientific EffectPhysical separation with sealing: Physical Containment

Data Source

PatentEP4037803B1Liquid filter and volume-equalizing element for a liquid filter
Publication Date: 2026.01.07 ROBERT BOSCH GMBH
  • EP4037803B1 patent drawingFigure 1
  • EP4037803B1 patent drawingFigure 2a
  • EP4037803B1 patent drawingFigure 2b

AI summary

The invention relates to a liquid filter. The liquid filter has a housing (2) with a cover (3) and also has an inflow (4) for a liquid and an outflow (5) for the liquid as well as a filter insert (20), which is arranged in an interior (6) of the housing (2) and has a first end cap (21), which is directed towards the cover (3), a second end cap (22) and a filter medium (23), which is arranged in an axial direction (A) between the two end caps (21, 22), wherein the filter insert (20) separates a clean side (7) from a dirty side (8). The liquid filter also has a volume-equalizing element (40) with a central body (41), which can be compressed in an elastically reversible manner and has a central-body interior space (42), wherein the central-body interior space (42), in a non-compressed state, encloses an initial volume and, in a compressed state, encloses an end volume, wherein the difference between the end volume and initial volume corresponds to at least 35% of a maximum change in volume of the liquid in the liquid filter (1) over a temperature range between +90° C and -40° C under normal pressure. The volume-equalizing element (40) here has a first sealing region (50), which surrounds the central body (41), wherein the first sealing region (50) is designed so that, when the liquid filter (1) is in the fully fitted state, said first sealing region interacts with the housing (2) and the cover (3) such that the interior (6) of the housing is sealed in a fluid-tight manner from an exterior space (9) of the liquid filter (1). The volume-equalizing element (40) here has a second sealing region (60), which surrounds the central body (41), wherein the second sealing region (60) is designed to prevent a fluidic short circuit between the clean side (7) and the dirty side (8).