Strain Sensor Back Pressure Sensing for Fluidic Nozzles
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Solution Overview
Problem
Fluid ejection devices face issues with back pressure, leading to air ingestion when pressure is too high and fluid leakage when it's too low, as existing technologies fail to reliably sense and control back pressure near nozzles.
Innovation Solution
The implementation of a strain gauge or strain sensor mounted on a flexible region of the substrate near the nozzle, which senses flexing to detect back pressure changes and adjusts the fluid pressure using a controller and pressure adjuster to maintain an optimal range, preventing air ingestion and leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If back pressure is increased to prevent fluid leakage, then fluid containment is improved, but air ingestion occurs in the nozzle
Solution Approach 1:
The patent implements a feedback mechanism where a back pressure sensor continuously monitors the actual back pressure at the nozzle, and a controller adjusts the pump speed accordingly. This closed-loop control allows the system to maintain back pressure within an optimal range that prevents both fluid leakage and air ingestion, resolving the contradiction between these two harmful effects.
Solution Approach 2:
The patent dynamically changes the operating parameters of the pump based on real-time back pressure measurements. By adjusting pump speed according to the measured back pressure, the system can adapt to varying conditions and maintain optimal pressure levels that prevent both fluid leakage and air ingestion simultaneously.
2Object-affected harmful factors
If back pressure is decreased to prevent air ingestion, then air entry is prevented, but fluid leaks through the nozzle
Solution Approach 1:
The feedback control system using back pressure sensing allows the pump speed to be dynamically adjusted to maintain optimal back pressure levels. This ensures sufficient pressure to prevent fluid leakage while avoiding excessive pressure that would cause air ingestion, thereby resolving the contradiction between these two requirements.
Solution Approach 2:
The system uses its own back pressure sensing capability to automatically regulate pump operation without external intervention. The sensor monitors actual conditions and the controller self-adjusts pump speed to maintain optimal pressure, enabling the system to prevent both fluid leakage and air ingestion autonomously.
3Measurement precision
If existing back pressure sensing technologies are used, then back pressure can be detected, but the sensing is not reliable near nozzles
Solution Approach 1:
The patent introduces a flexible diaphragm as an intermediary element that transmits back pressure changes from the nozzle region to the strain gauge sensor. This diaphragm allows accurate pressure sensing near the nozzle while protecting the sensor from direct exposure to fluid and harsh conditions, thereby improving both measurement precision and reliability.
Solution Approach 2:
The patent replaces traditional mechanical pressure sensing methods with a strain gauge-based sensor that measures pressure through deformation of a flexible diaphragm. This substitution enables more accurate and reliable back pressure measurement near the nozzle by converting pressure changes into electrical signals through strain measurement.
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 enables reliable monitoring and control of back pressure, ensuring accurate fluid ejection by maintaining optimal pressure conditions near the nozzle, thus preventing air ingestion and fluid leakage.
Implementation Method 1
The example fluidic dies and fluid displacement devices utilize a strain gauge or strain sensor mounted to or supported by a flexible region of the substrate in close proximity to a nozzle of the fluidic die. The flexing or bending of the flexible region of the substrate is sensed by the strain sensor
Data Source
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AI summary
A fluidic die may include a substrate having a flexible region opposite a fluid supply passage within the substrate, a nozzle supported by the substrate proximate the flexible region and a strain sensor on the flexible region of the substrate. The strain sensor may sense strain during flexing of the flexible region to sense fluid back pressure changes.