Fuel Injector Force Amplifier for Needle Drift
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Solution Overview
Problem
Existing fuel injectors with direct electromagnetic actuation suffer from early drift and incomplete elimination of pressure variations in fuel distribution due to the relatively weak force exerted by the solenoid actuator on the needle, leading to inconsistent fuel supply through injection holes.
Innovation Solution
A fuel injector design incorporating a force amplifier mechanism that utilizes a hydraulic amplification chamber and dampers to amplify the electromagnetic force and return spring force, ensuring the needle's precise movement between open and closed positions, thereby stabilizing fuel pressure and distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a direct electromagnetic actuator is used to open or close the needle, then the device complexity is reduced, but the force exerted on the needle is insufficient leading to early drift and pressure variations
Solution Approach 1:
A magnetic armature is introduced as an intermediary between the electromagnetic actuator and the needle. The armature is attracted by the solenoid and transmits this force to the needle through a shaft, amplifying the effective force applied to the needle while maintaining the simplicity of the electromagnetic actuator design.
Solution Approach 2:
A hydraulic amplification chamber is introduced where high-pressure fuel acts on a thrust face with a larger area than the solenoid's effective area. This creates a mechanical advantage that amplifies the force generated by the solenoid, allowing the needle to overcome fuel pressure more effectively and reduce early drift.
2Reliability
If the needle is hydraulically balanced to reduce drift, then the force requirement is reduced, but pressure variations in fuel distribution are not completely eliminated
Solution Approach 1:
The high-pressure fuel channel is designed to extend through the armature, shaft, and needle bore in sequence, establishing a predetermined pressure distribution path. This preliminary arrangement of pressure zones ensures that fuel pressure is evenly distributed to all injection holes before the needle opens, preventing variations in fuel delivery.
Solution Approach 2:
The hydraulic amplification chamber creates a feedback mechanism where fuel pressure acts on the thrust face to assist the solenoid force. The pressure distribution through the extended channel provides continuous feedback to maintain balanced forces on the needle, ensuring consistent fuel supply and eliminating early drift.
3Force
If the solenoid force is increased to eliminate drift, then the force on the needle is sufficient, but the device complexity and energy consumption increase
Solution Approach 1:
The hydraulic amplification chamber uses high-pressure fuel (already present in the system) to amplify the solenoid force. Instead of increasing solenoid power consumption, the system leverages the existing fuel pressure to create a mechanical advantage, reducing energy requirements while maintaining sufficient needle actuation force.
Solution Approach 2:
The system changes the effective force parameter by introducing the hydraulic amplification mechanism. The force amplification ratio is determined by the area ratio between the thrust face and the solenoid's effective area, allowing sufficient needle force with reduced solenoid power consumption.
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 solution effectively reduces early drift and stabilizes fuel pressure distribution, ensuring consistent and efficient fuel delivery to internal combustion engines by amplifying the forces applied to the needle, thus improving the injector's performance.
Implementation Method 1
an actuator (18) comprising a solenoid (44) fixed in the injector body (16) and generating when it is electrically powered an opening force on the magnetic armature (48)
Implementation Method 2
a return spring (58) generating a closing force on the piston (22) when the solenoid is not fed
Implementation Method 3
a force amplifier (56) arranged between the shaft (50) and the needle (14), the piston (22) moving under the action of an electromagnetic force generated by the solenoid as well as under the action of a force generated by the return spring so that the resultant of the two forces is applied to the piston is transmitted and amplified to the needle
Implementation Method 4
The shaft (50) further comprises a first damper (64) arranged in the second section (76) of the HP channel (24) so that the first damper (64) slows down a pressure wave generated by the armature (48)
Implementation Method 5
The shaft (50) further comprises a second damper (66) arranged in the second section (76) of the HP channel (24), between the first high pressure chamber (59) and a second high pressure chamber (67) so that the second damper (66) slows the movement of the armature (48)
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
A fuel injector (10) arranged to deliver fuel to an engine, the injector comprising: an injector body (16) extending along a longitudinal axis (X) comprising a bore (26) and a high-pressure chamber (56), and a needle (14) arranged so as to slide in the bore (26) between a top guide (20) and a bottom guide (21), a piston (22) comprising a magnetic armature (48) and a shaft (50) extending along the longitudinal axis (X), an actuator (18) comprising a fixed solenoid (44) generating, when electrically powered, an opening force on the magnetic armature (48), and a return spring (58) generating a closing force on the piston (22) when the solenoid (44) is not powered, characterised in that the injector (10) comprises a high-pressure channel (24), and in that the injector (10) also comprises a force amplifier (56) arranged between the shaft (50) and the needle (14).