Fuel Injector Piezoelectric Sensor Axial Preload

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Solution Overview

Problem

Existing fuel injectors face challenges in reliably detecting the closing time of the injection element over their service life due to instability in adhesive connections under high temperatures and media influences, affecting the accuracy of injection timing and exhaust gas optimization.

Innovation Solution

A fuel injector design where the sensor element is axially preloaded against a contact surface within the injector housing, eliminating adhesive connections and ensuring reliable transmission of structure-borne noise signals, with a compression spring providing adjustable contact force and a media-tight recess to protect against external influences.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If adhesive connection is used to couple sensor element to injector housing, then assembly is simplified, but reliability of signal transmission deteriorates under high temperatures and media influences

Engineering Contradiction:

Improveassembly simplicityVSAvoidsignal transmission reliability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent replaces the adhesive connection (chemical bonding) with a mechanical connection system consisting of a sensor holder and clamping element. This mechanical system provides reliable signal transmission under high temperatures and media influences while maintaining assembly simplicity through the integrated holder design.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The sensor holder acts as an intermediary component between the sensor element and the injector housing. It provides a stable mounting structure that ensures reliable mechanical and electrical connection, solving both the assembly simplicity and signal transmission reliability requirements.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of operation

If sensor element is exposed to external environment, then accessibility for installation is improved, but stability of measurement deteriorates due to mechanical and environmental influences

Engineering Contradiction:

Improveinstallation accessibilityVSAvoidmeasurement stability

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The sensor element is nested within the sensor holder, which is in turn mounted in the injector housing. This nested structure protects the sensor element from external mechanical and environmental influences while maintaining a compact design that does not compromise installation accessibility.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The sensor holder provides a protective enclosure (shell) around the sensor element, shielding it from external influences such as fuel, air, and mechanical stress, thereby ensuring measurement stability while allowing for straightforward installation.

Inventive Principle:

Principle #30Flexible shells and thin films

3Ease of manufacture

If adhesive layer is used for coupling sensor, then connection stability over service life deteriorates under high temperatures and media influences

Engineering Contradiction:

Improveconnection simplicityVSAvoidconnection durability

Core Design Contradiction:

Ease of manufactureVSDuration of action of stationary object

Solution Approach 1:

The patent replaces the adhesive layer (chemical connection) with a mechanical clamping system using a clamping element and sensor holder. This mechanical connection is durable under high temperatures and media influences throughout the service life, while the integrated holder design maintains manufacturing simplicity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

Enables precise detection of injection parameters, including opening and closing times, enhancing the control and longevity of the fuel injector by maintaining signal integrity and structural integrity under high pressures.

Implementation Method 1

a sensor element formed as a piezoelectric element

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

the axial preload can be adjusted by means of a spring element

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentEP3034854B1Fuel injector and method for recognising at least the closing time of an injector

Publication Date: 2018.06.27 ROBERT BOSCH GMBH

Figure 1
Figure 2~3

AI summary

The invention relates to a fuel injector (10) with an injector housing (11) in which an injection element (22) is movably arranged for closing and opening at least one injection orifice (16) formed in the injector housing (11), and with a sensor device (30) for detecting at least the closing time of the injection element (22), wherein the sensor device (30) comprises a sensor element (31) designed as a piezoelectric element, which is arranged in a recess (33) of the injector housing (11) in contact with the injector housing (11), and which is configured to detect the closing time of the injection element (22) based on a structure-borne sound signal. According to the invention, the sensor element (31) is provided to bear against a contact surface (35) under axial preload.