Fuel Injector Servo Valve Armature Stroke Adjustment
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Solution Overview
Problem
Existing fuel injector servo valves face challenges in precise adjustment of the armature stroke due to machining tolerances and require extensive time and effort for fine-tuning, leading to imperfect flow rate control, which is critical for modern internal-combustion engines.
Innovation Solution
The fuel injector incorporates a servo valve with a deformable sleeve and annular shims made of different materials to allow for precise adjustment of the armature stroke through controlled plastic deformation, enabling continuous and precise adjustment without the need for multiple shims or complex assembly processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If discrete calibrated shims are used to adjust the armature stroke, then the adjustment can be performed with standard machining tolerances, but the adjustment precision is limited to discrete steps (e.g., 5 μm) and requires multiple assembly attempts
Solution Approach 1:
The patent changes the physical state of the shim material from rigid to deformable through plastic deformation. By applying controlled deformation to a deformable shim, the armature stroke can be adjusted continuously rather than in discrete steps, achieving precision of 0.1 μm or better while eliminating the need for multiple assembly attempts
Solution Approach 2:
The patent introduces a deformable shim that can be dynamically adjusted during the assembly process. The shim transitions from an undeformed state to a permanently deformed state, allowing the adjustment to be made in a single operation rather than requiring iterative assembly and disassembly
2Manufacturing precision
If multiple calibrated shims are used to achieve fine adjustment, then the armature stroke can be precisely controlled, but the assembly time and operator skill requirements increase significantly
Solution Approach 1:
The patent uses a single deformable shim that can be adjusted by controlling the degree of plastic deformation. This eliminates the need to select and assemble multiple shims of different thicknesses, reducing the adjustment operation to a single step that can be performed quickly with minimal operator skill
Solution Approach 2:
The patent extracts the adjustment function from the assembly process itself. Instead of requiring precise machining and selection of multiple shims during assembly, the adjustment is performed by deforming a single shim, separating the adjustment operation from the assembly operation and making both simpler
3Speed
If the shutter is pre-loaded with a strong spring to overcome fuel pressure, then the servo valve responds promptly to electromagnet de-excitation, but the axial thrust on the shutter becomes very large (e.g., 70 N at 1800 bar)
Solution Approach 1:
The patent changes the material properties of the shutter by introducing a coating layer with different mechanical properties. The coating layer allows the shutter to deform elastically under load, enabling the system to respond quickly to pressure changes without requiring a strong pre-loading spring, thus reducing the axial thrust while maintaining response 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
This solution allows for high-precision, continuous adjustment of the armature stroke, reducing the need for multiple shims and machining precision, and eliminates the need for software compensation, resulting in a more reliable and cost-effective fuel injector with improved flow control.
Implementation Method 1
at least one shim (48) set between the flange (52) and the shoulder (49) of the casing (2), the shim (48) being made of a material having a hardness different from that of the material of the core (18) or of the casing (2) so as to cause a pre-set plastic deformation
Data Source
Figure 1
Figure 2~3
Figure 4~6
AI summary
The injector (1) with adjustable-metering servo valve (7) has a shutter (45) actuated by an armature (16) of an electromagnet (15). The armature (16) is mobile for an opening stroke defined by a surface (19) of the core (18) of the electromagnet (15), which is fixed in the casing (2) by means of a ring nut (40) and a hollow support (20) of the core (18) itself. The support (20) has a first contact surface (51) that acts on a flange (52) of the core (18). Set between the surface (19) and a shoulder (49) of the casing (2) is a shim (48) having a hardness different from that of the core (18) or of the casing (2). An annular projection (53), having a second contact surface (54), is set between the polar surface (19) and a shoulder (49) of the casing (2), the second contact surface (54) being contained at least in part in the area corresponding to the first contact surface (51), so that the stroke of the armature (16) is adjusted by means of a plastic deformation of the shim (48) or of the surface (19) of the core (18) as a function of the tightening torque of the ring nut (40).