Piezoelectric Injector Needle Control for Fuel Dosing Precision
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Solution Overview
Problem
Fuel injection systems in internal combustion engines face challenges in achieving precise dosing and minimizing injection quantity while ensuring repeatability, especially in part-load conditions, where high flow rate injectors are detrimental to mixture formation and can cause wall wetting.
Innovation Solution
The method involves controlling the injector needle to vary injection pressures and adjust the throttle gap, allowing for individual optimization of spray hole entry pressure, which enables precise fuel dosing and atomization, and prevents wall wetting by mechanically controlling the needle stroke and adjusting the throttle gap.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high flow rate injectors are used for nominal power, then productivity is improved, but manufacturing precision deteriorates in part-load conditions
Solution Approach 1:
The needle stroke is made dynamically adjustable through mechanical control (e.g., cam profile variation, hydraulic actuation) to vary the throttle gap opening cross-section. This allows the injection system to adapt between high flow rates for nominal power and precise low flow rates for part-load conditions, resolving the contradiction between productivity and manufacturing precision.
Solution Approach 2:
The system changes the critical parameter of needle stroke (and consequently throttle gap opening cross-section) to control spray hole entry pressure. By varying this parameter, the system achieves different injection quantities and pressures, enabling both high productivity at full load and high precision at part load.
2Object-affected harmful factors
If small pre-injection quantities are used to avoid wall wetting, then object-affected harmful factors are reduced, but manufacturing precision deteriorates due to dosing limits
Solution Approach 1:
The mechanical control system dynamically adjusts the needle stroke to precisely control the throttle gap opening cross-section. This enables accurate dosing of small pre-injection quantities while maintaining control precision, avoiding wall wetting without sacrificing dosing accuracy.
Solution Approach 2:
The patent employs mechanical control of the needle stroke (via cams, springs, or hydraulic actuators) to replace less precise control methods. This mechanical approach provides direct, reliable control over the throttle gap and injection quantity, achieving both wall wetting prevention and dosing precision.
3Manufacturing precision
If injection pressure is increased to improve atomization, then manufacturing precision is improved, but object-generated harmful factors worsen due to cavitation and wear
Solution Approach 1:
The needle stroke is dynamically controlled to optimize the balance between spray hole entry pressure and cavitation. By adjusting the throttle gap opening cross-section, the system achieves sufficient pressure for good atomization while limiting excessive pressure that would cause harmful cavitation and wear.
Solution Approach 2:
The system optimizes the parameter of needle stroke to achieve the optimal spray hole entry pressure. This parameter change enables sufficient pressure for good atomization quality while avoiding excessive pressure that would generate harmful cavitation and wear.
4Manufacturing precision
If needle stroke is increased to improve fuel dosing, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The mechanically controlled needle stroke mechanism serves multiple functions: it controls the throttle gap opening cross-section, regulates spray hole entry pressure, and determines injection quantity. This multi-functionality achieves precise fuel dosing without requiring separate control systems for each parameter, thereby limiting the increase in device complexity.
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 allows for optimized mixture formation, reduced wall wetting, and improved atomization through controlled needle lift, enabling better fuel distribution and minimizing pressure fluctuations, thereby enhancing engine performance and reducing emissions.
Implementation Method 1
The injector needle 1 is now preferably driven mechanically. For example, the injector needle moves downward in the vertical direction.
Implementation Method 2
The amount of fuel injected into the combustion chamber is the higher, the higher the pressure difference between the spray hole inlet and the spray hole outlet
Implementation Method 3
These limits are set on the one hand by the maximum possible needle stroke and on the other hand by the cavitation occurring at the needle seat and the associated wear
Implementation Method 4
The control of the needle stroke also influences the flow conditions within the blind hole, so that cleaning of the spray hole due to the increase in turbulence or Cavitation in the spray hole is made possible. Furthermore, because of the higher turbulence inside the blind hole, higher atomization of the fuel in the combustion chamber
Data Source
AI summary
The invention relates to a method for controlling a fuel injection apparatus, in particular a piezoelectric injector. Here, the fuel quantity which is injected into the combustion chamber is set by a mechanically actuable injector needle (1). Here, the injected fuel quantity depends on the pressure difference which can be set by the injector needle (1) between the spray-hole inlet and the spray-hole outlet.