Fuel Injection Device Valve Timing Control for Piezoelectric Actuator
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Solution Overview
Problem
Fuel injection devices with layered piezoelectric elements face instability in valve opening behavior during small injection quantities due to premature discharging before reaching the final charging voltage, leading to increased actual injection quantities and potential cost increases from requiring high-current drive circuits.
Innovation Solution
The fuel injection device sets different valve opening starting timings based on injection quantity, using a first timing for large quantities and a second, later timing for small quantities to delay valve opening and reduce actual injection, thereby stabilizing valve behavior without needing high-current drive circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the valve opening responsiveness is improved by expanding the out orifice aperture diameter and increasing the discharge flow rate, then the valve opening speed increases, but the actual injection quantity increases for the same injection command value
Solution Approach 1:
The patent changes the timing parameter of valve opening based on the injection quantity. For minute injections, it delays the valve opening timing by setting the injection command value to start charging later or to discharge later, thereby compensating for the increased injection quantity caused by faster valve opening and achieving precise control of the actual injection quantity.
2Quantity of substance
If the injection command value is reduced to compensate for increased actual injection quantity, then the injection quantity control improves, but the injection command value becomes extremely small and less than or equal to the charging period
Solution Approach 1:
The patent segments the injection control into two independent parameters: injection quantity (determined by charging/discharging amount) and injection timing (determined by valve opening timing). By separating these controls, it can maintain a normal injection command value duration while achieving precise injection quantity control through timing adjustment, avoiding the problem of extremely small command values.
Solution Approach 2:
The patent dynamically adjusts the valve opening timing based on the injection quantity requirements. For minute injections, it delays the valve opening timing; for normal injections, it uses the standard timing. This dynamic timing adjustment allows the system to maintain adequate injection command value durations while achieving precise injection quantity control across different injection scenarios.
3Speed
If a high-current drive circuit is used to ensure sufficient charging current for the layered piezoelectric element, then the charging speed improves, but the device cost increases
Solution Approach 1:
The patent applies partial charging action by delaying the valve opening timing or reducing the charging amount specifically for minute injections, rather than requiring high charging current for all injection types. This allows the use of standard-current drive circuits while achieving the desired injection control through selective timing adjustment.
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 approach stabilizes valve opening behavior during small injection quantities and maintains high responsiveness during large injection quantities without upgrading the drive circuit, effectively managing injection quantities and reducing costs.
Implementation Method 1
a layered piezoelectric element is used. When the layered piezoelectric element that expands/shrinks by charging/discharging of the electric charge
Implementation Method 2
The fuel injector increases/decreases the fuel pressure inside the control chamber by making a high pressure fuel to flow out from and flow in to the control chamber
Data Source
AI summary
When a main injection is performed, a first timing that is a time earlier than a second timing is selected as the valve opening starting timing, and a first period that is the period of time shorter than a second period is selected as the control period. Also, when a pilot injection is performed, the second timing that is the time later than the first timing is selected as the valve opening starting timing, and the second period that is the time longer than the first period is selected as the control period. Thus, in an injector with increased valve opening responsiveness, the valve opening behavior of a control valve of the injector in fuel injection with a minute injection quantity can be stabilized without replacing a control device, particularly an EDU with that of a large current specification.