Fuel Injector Needle Conical Seating for Stable Detection
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Solution Overview
Problem
Existing fuel injectors experience unstable closed loop detection signals due to needle lift hesitations and misalignment issues during opening, leading to erroneous detection of needle opening and closing.
Innovation Solution
A fuel injector design featuring a symmetrically shaped needle with a conical seating face and annular collar, combined with a three-way control valve arrangement, ensures stable needle lift and reduces misalignment, providing a clean electric contact and faster needle opening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional needle design with simple seating face is used, then the device complexity is low, but the needle lift stability deteriorates leading to unstable detection signals
Solution Approach 1:
The needle seating face is designed with a conical geometry (curved surface) instead of a flat surface. This conical shape guides the needle tip to lift axially in a controlled manner, preventing radial deviations and side contacts with the seat, thereby ensuring stable detection signals during needle opening.
Solution Approach 2:
The needle structure incorporates asymmetric features including a collar with specific geometry and a conical seating face with defined angle. This asymmetric design creates specific flow patterns and force distributions that promote stable axial lift and prevent cavitation-induced hesitations during needle opening.
2Productivity
If the needle opening speed is increased, then the productivity is improved, but the measurement precision of needle position deteriorates due to unstable detection signals
Solution Approach 1:
The conical seating face geometry guides the needle to open smoothly and rapidly along the axial direction. The curved surface ensures that the needle tip maintains proper alignment during high-speed opening, preventing radial deviations that would cause unstable detection signals even at high opening speeds.
Solution Approach 2:
The conical angle of the seating face is specifically optimized to balance needle opening speed and detection stability. This parameter change allows the needle to open quickly while maintaining stable axial movement, ensuring both high productivity and accurate position detection.
3Speed
If a simple valve arrangement is used, then the device complexity is low, but the needle opening speed deteriorates
Solution Approach 1:
The valve arrangement is segmented into multiple independent components including a control valve, a main valve, and a three-way valve. This segmentation allows each valve to perform a specific function (control pressure, main flow, drainage) enabling rapid needle opening through coordinated action of multiple valves working in parallel.
Solution Approach 2:
The valve arrangement uses hydraulic principles to control needle opening. The three-way valve rapidly drains control pressure from the needle control chamber, and the main valve opens fuel supply, creating a hydraulic force imbalance that drives the needle open at high speed.
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
The design promotes axial needle lift, reducing radial deviations and side contacts, resulting in a stable closed loop detection signal and improved fuel flow, enhancing the precision and reliability of fuel injection.
Implementation Method 1
the needle forms a switch in a detection circuit
Implementation Method 2
During early opening of the needle (i.e. within the first few microns of lift), cavitation may appear between the needle and the nozzle seat, leading to a hesitating electrical contact
Data Source
Figure 1
Figure 2~4
Figure 3
AI summary
A fuel injector comprises a nozzle (12) with a body (24) defining an internal bore (28) in which a needle (30) is axially moveable and having a spray extremity with injection orifice(s). The needle has an axially symmetrical shaft portion (32) which is tapered at an end (34) and defines a male seating face (44) that cooperates with a female tapered seating face (46) in the needle bore (28), upstream of the injection orifice(s). The said needle (30) includes a protruding annular collar (36) that divides the internal volume of nozzle bore (28), the collar (36) including substantially symmetrically configured passage means (36.1). A control valve arrangement (14) including a three-way valve pilots the needle via a control chamber (50). The injector includes a detection circuit (58) in which the needle (30) forms a switch. The female tapered seating face (46) is generally conical and the male tapered seating face (44) includes a conical surface having an angle (β) of greater than 75°.