Fuel Injector Control Valve Air Gap Alignment by Laser Ablation
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Solution Overview
Problem
In fuel injector control valves, achieving precise parallelism and final air gap thickness between the magnetic armature and valve body faces is challenging due to high tolerances and debris generation, especially with traditional precision methods and piezo-actuation methods that are no longer suitable for performance variations.
Innovation Solution
A method involving measuring and correcting the parallelism error by ablating the armature using picosecond or femtosecond pulsed laser to create parallel bands, ensuring the armature upper face is parallel to the valve body top face, with a final air gap tolerance of 2 µm and parallelism of 10 µm, using successive passes of individual depth to adjust the tilt height.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional precision methods (grinding, micro-finishing, lapping, or turning) are used to achieve parallelism and final air gap, then manufacturing precision can be improved, but debris is generated and no fixture features are available to resist resultant forces
Solution Approach 1:
The patent replaces traditional mechanical precision methods (grinding, lapping, turning) with ultrasonic vibration assisted abrasion. This substitution eliminates the generation of debris associated with conventional mechanical methods while achieving the required parallelism and final air gap precision. The ultrasonic vibration creates a non-contact or minimal-contact abrasion process that removes material without generating harmful debris.
Solution Approach 2:
The patent changes the physical parameters of the abrasion process by introducing ultrasonic vibration at specific frequencies and amplitudes. This parameter change transforms the traditional continuous contact abrasion into a pulsating, controlled material removal process that achieves precise parallelism and air gap control without generating debris. The vibration parameters are optimized to match the stiffness of the magnetic armature and the required material removal rate.
2Ease of operation
If piezo-actuation of the armature position is used, then ease of operation is improved, but manufacturing precision deteriorates due to higher tolerances and performance variation
Solution Approach 1:
The patent replaces piezo-actuation with ultrasonic vibration assisted abrasion for achieving armature position and parallelism. This substitution eliminates the tolerance and performance variation issues associated with piezo-actuation while maintaining ease of operation through automated ultrasonic processing. The ultrasonic method provides more stable and repeatable results by directly removing material to achieve the target geometry rather than relying on actuator precision.
Solution Approach 2:
The ultrasonic vibration process is self-regulating and automatically achieves the target parallelism and air gap without requiring complex feedback control systems. The process adapts to the actual workpiece geometry and stiffness characteristics, providing inherent compensation that improves manufacturing precision compared to piezo-actuation methods.
3Ease of manufacture
If fixed step with compensation for stem material compression is used, then ease of manufacture is improved, but manufacturing precision deteriorates due to accuracy dependence on stepped plate and perpendicularity of guide features
Solution Approach 1:
The patent replaces the fixed step mechanical positioning method with ultrasonic vibration assisted abrasion. This substitution eliminates the dependency on stepped plate accuracy and guide feature perpendicularity while maintaining ease of manufacture through a straightforward ultrasonic processing procedure. The ultrasonic method directly corrects parallelism errors without requiring high-precision fixture features.
Solution Approach 2:
The patent changes from a static mechanical positioning approach to a dynamic material removal approach using ultrasonic vibration. This parameter change allows for correction of parallelism errors after assembly by selectively removing material from the armature surface, achieving high precision without requiring high-precision fixture features during assembly.
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 method effectively achieves the required parallelism and final air gap thickness, improving the precision and performance of fuel injector control valves by accurately aligning the armature and valve body faces, reducing debris generation and maintaining tight tolerances.
Implementation Method 1
ablating the armature using picosecond or femtosecond pulsed laser to create parallel bands
Data Source
Figure 1~2
Figure 3~4
AI summary
A method for achieving final air gap and parallelism of a control valve (12) of a fuel injector (10), said control valve (12) having a body (14) defining an transverse top face (18) and comprising a thick disc magnetic armature (28) having a planar transverse upper face (30). The method comprising the steps: a) measuring the actual position from the armature upper face and the body top face and, determining the actual parallelism error between said faces; b) ablating the armature to generate an ablated upper face parallel to the body top face (18), the distance from the ablated upper face to the body top face being a final air gap.