Fuel Injection Valve Movable Core Design for Secondary Opening
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Solution Overview
Problem
Existing fuel injection valves face issues with secondary valve opening due to collisions between the movable core and the needle flange, leading to undesirable fuel injection, and have complex assembly processes with increased components and potential thermal deformation issues.
Innovation Solution
A fuel injection valve design featuring a housing, nozzle, stationary core, needle, movable core, movable plate, first and second urging members, and a coil, where the movable core is magnetically attracted to open the valve, and the urging members control the needle's movement to prevent secondary opening, with a simplified assembly and reduced thermal sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the movable core is provided on the valve seat side of the needle to improve response, then the valve opening speed is improved, but collision between the movable core and needle flange causes secondary valve opening
Solution Approach 1:
The patent introduces a prestrike gap between the movable core and needle flange, allowing the movable core to accelerate before contacting the needle flange. This preliminary acceleration phase ensures that the needle is reliably opened without causing secondary opening, as the controlled gap prevents excessive collision force.
Solution Approach 2:
The patent introduces a movable plate as an intermediary component between the movable core and the needle. The movable plate receives the urging force from the urging member and transfers it to the needle, mediating the interaction to prevent direct collision between the movable core and needle flange, thereby eliminating secondary valve opening.
2Strength
If flanges are welded to the needle and sleeve to the movable core to provide structural support, then the mechanical strength is improved, but the number of components and welding spots increases
Solution Approach 1:
The patent merges the flange structure directly into the needle body as an integrated component, eliminating the need for separate flange pieces and their associated welding operations. This integration maintains the necessary mechanical strength while reducing the total number of components and welding spots.
Solution Approach 2:
The patent replaces the mechanical welding connection system with a press-fit or interference fit system between the movable core and sleeve. This substitution eliminates the need for welding while maintaining structural integrity, thereby reducing manufacturing complexity and the number of welding spots.
3Ease of manufacture
If welding is used to assemble flanges and sleeves to reduce component count, then the assembly process is simplified, but thermal deformation may change the acceleration distance
Solution Approach 1:
The patent replaces the welding process with a press-fit or interference fit assembly method. This mechanical connection method avoids the thermal effects of welding, preventing thermal deformation that would alter the acceleration distance. The assembly process remains simple while maintaining manufacturing precision.
Solution Approach 2:
The patent changes the assembly method from thermal (welding) to mechanical (press-fit), fundamentally altering the assembly parameters to eliminate thermal deformation. This parameter change preserves the acceleration distance precision while maintaining ease of manufacture through a simplified, non-thermal assembly process.
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 ensures rapid and reliable valve opening with minimized secondary opening, improving fuel injection precision and reducing assembly complexity while being less susceptible to thermal deformation.
Implementation Method 1
The coil generates a magnetic force upon receiving an electric power to magnetically attract the movable core toward the stationary core side.
Implementation Method 2
The first urging member urges the movable plate to urge the movable core in the closing direction. The second urging member has an urging force, which is smaller than an urging force of the first urging member. The second urging member urges the movable core to urge the movable plate in the opening direction.
Data Source
AI summary
A movable core includes a through-hole, which receives a main body of a needle therethrough, and a receiving recess, which is axially recessed in a stationary core side end surface of the movable core. The receiving recess is configured into an annular form and radially outwardly extends from the through-hole to receive a flange of the needle. A movable plate is placed on an axial side of the movable core, which is opposite from the nozzle. An axial length of the flange is smaller than an axial distance between a contact surface of the movable plate, which is contactable with the needle, and a bottom wall of the receiving recess in a contact state where the movable core and the movable plate contact with each other.