Piezoelectric Actuator Force Sensor Testing Device
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Solution Overview
Problem
Current testing devices are inadequate for simulating the long-term loads on force sensors used in fuel injectors over a vehicle's life, as they require a shorter duration endurance test that accurately replicates the operational cycles and conditions of fuel injectors, particularly for monitoring the needle closing point.
Innovation Solution
A test device utilizing a piezoelectric actuator and prestressing spring to apply defined forces at high frequency, with a rotatable lever to modulate forces and reduce stress on the actuator, allowing for in-situ measurement of piezoelectric properties under mechanical and thermal loading, enabling realistic simulation of operational conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a force sensor is subjected to endurance testing simulating the entire vehicle life, then the sensor durability can be evaluated, but the testing duration becomes excessively long
Solution Approach 1:
The patent applies periodic action by subjecting the force sensor to cyclic loading with a defined duty cycle (e.g., 10% on-time, 90% off-time) that simulates the periodic operation of fuel injectors. This allows acceleration of the testing process by repeating load cycles at higher frequencies while maintaining the relevance to actual service conditions, thereby reducing overall test duration without compromising durability evaluation
Solution Approach 2:
The patent changes the time parameter by operating the force sensor at elevated temperatures (e.g., 80°C to 150°C) during endurance testing, which accelerates degradation processes. This temperature parameter change allows the sensor to experience equivalent aging in a compressed time frame, resolving the contradiction between comprehensive durability evaluation and excessive testing duration
2Force
If the piezoelectric actuator applies the full test force Fa, then the required force magnitude is achieved, but the actuator experiences high average voltage and reduced durability
Solution Approach 1:
The piezoelectric actuator applies the full test force Fa only during the on-time portion of the duty cycle (e.g., 10%), while remaining inactive or applying minimal force during the off-time (90%). This periodic application reduces the average voltage and cumulative stress on the actuator, extending its durability while still achieving the required peak force magnitude for realistic sensor testing
Solution Approach 2:
The patent implements preliminary anti-action by using a counterweight mechanism or spring system that pre-lloads the force sensor with a baseline force. This allows the piezoelectric actuator to apply only the differential test force Fa rather than the full load, reducing the actuator's voltage requirements and improving its reliability while maintaining adequate test force levels
3Volume of moving object
If a compact testing device is used for in-situ measurement, then integration into fuel injectors is feasible, but the device complexity increases
Solution Approach 1:
The patent merges the testing device components (piezoelectric actuator, force sensor, spring element, and lever mechanism) into a single integrated assembly that fits within the fuel injector structure. This consolidation reduces the overall volume required while managing complexity through functional integration, allowing in-situ measurement without requiring separate external testing equipment
Solution Approach 2:
The force sensor serves multiple functions: it acts as both the test subject being evaluated and the measurement instrument for detecting needle closing events. The piezoelectric actuator similarly serves dual purposes as both the loading mechanism and a reference standard for piezoelectric property comparison. This multi-functionality reduces the number of separate components needed, decreasing device complexity while maintaining compact dimensions
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 the evaluation of force sensors under conditions similar to their intended application, extending sensor durability and allowing for efficient testing of multiple sensors in a compact setup, effectively simulating the wear and tear experienced by fuel injector sensors.
Implementation Method 1
The power source contains at least one piezoelectric actuator
Implementation Method 2
the power source contains at least one prestressing spring loading the force sensor or the stack of force sensors with a prestressing force F1
Data Source
Figure 1
AI summary
Test device (1) for the endurance test or in-situ measurement of the piezoelectric properties of a force sensor (2a, 2b, 2c) or a stack (22) of force sensors (2a, 2b, 2c), comprising a force source (3) for introducing a defined test force FP into the force sensor (2a, 2b, 2c) or into the stack (22) of force sensors (2a, 2b, 2c), wherein the force source (3) includes at least one piezoelectric actuator (31). Method for the endurance testing of a force sensor (2a, 2b, 2c) or a stack (22) of force sensors (2a, 2b, 2c), wherein the force sensor (2a, 2b, 2c) or the stack (22) of force sensors (2a, 2b, 2c) is subjected to a combination of at least two preload forces F1 and F2, wherein the force sensor (2a, 2b, 2c) or the stack (22) of force sensors (2a, 2b, 2c) is periodically relieved at least partially by at least one preload force F1.