Direct Acting Fuel Injector Hydraulic Amplifier Chamber
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Solution Overview
Problem
Existing direct acting fuel injectors face internal volume limitations, leading to pressure wave issues and wear problems at high fuel pressures, making it difficult to achieve precise, close-timed multi-injection modes in diesel engines.
Innovation Solution
A direct acting fuel injector design with a hydraulic amplifier chamber external to the cap nut, featuring a short valve needle and a guide member that supports the plunger, allowing for precise control of injection events and reducing the need for additional components, thereby improving responsivity and reducing wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a direct acting injector design is used to eliminate control valve arrangement, then device complexity and cost are reduced, but internal volume limitations cause pressure wave issues and wear problems at high fuel pressures
Solution Approach 1:
The patent relocates the hydraulic amplifier chamber from an internal position to an external position on the injector body. This dimensional repositioning allows the chamber to be positioned in a region with greater available space, increasing its volume without compromising the compact internal structure of the injector. The external chamber is connected to the valve needle through fluid passages, maintaining the direct-acting mechanism's simplicity while eliminating the volume constraints that caused pressure wave issues.
2Volume of moving object
If internal hydraulic amplifier chamber is used, then compact design is achieved, but volume limitations prevent accurate control of close-timed injection events
Solution Approach 1:
By moving the hydraulic amplifier chamber to an external location on the injector body, the design accesses three-dimensional space that is not constrained by the internal needle and seat geometry. This external positioning allows for a larger chamber volume that can accommodate the fuel required for precise multi-injection events, while the connection to the valve needle is maintained through efficiently designed fluid passages.
3Manufacturing precision
If high fuel pressure (2500-3000 bar) is used to meet modern injection requirements, then injection precision is improved, but dilation effects cause wear problems in direct acting injectors
Solution Approach 1:
The external hydraulic amplifier chamber acts as an intermediary between the fuel supply and the valve needle. This intermediate chamber provides a larger volume that reduces pressure fluctuations and dilation effects, allowing high-pressure fuel to be delivered to the needle in a more controlled manner. The chamber absorbs some of the pressure variations, reducing the direct impact of high-pressure dilation on the needle and seat, thereby reducing wear while maintaining injection precision.
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 enables accurate control of injection events, particularly close-timed injections, with reduced wear and energy loss, enhancing system efficiency and reliability at high fuel pressures.
Implementation Method 1
The plunger acts on a chamber of fuel arranged at the upper end of a valve needle of a second, reduced diameter. The arrangement acts as a hydraulic amplifier arrangement by which the force of the plunger is transmitted to the valve needle with an amplification factor determined by the ratio of the plunger diameter to the diameter of the valve needle.
Implementation Method 2
an electromagnetic direct acting injector, a solenoid-operated actuator controls movement of a plunger, having a plunger diameter, by applying a current through a solenoid
Implementation Method 3
If the actuation force is removed by removing or reducing the current applied to the solenoid, the plunger moves downward under a spring force, reducing the volume of the control chamber and increasing fuel pressure in the control chamber so as to seat the valve needle.
Data Source
Figure 1
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Figure 4
AI summary
A direct acting fuel injector (10) for use in an internal combustion engine, the injector comprising an actuator (20); a hydraulic amplifier chamber (31) for fuel; a valve needle (14) movable within a bore (16) provided in an injector housing having a lower housing region (18a) of a first, reduced diameter (Dnoz) and an upper housing region (18b, 18c) of a second, greater diameter, wherein the upper housing region (18b, 18c) is received within a cap nut (54) of the injector, the valve needle (14) having a surface (14c) with a needle diameter (Dnoz) exposed to fuel within the hydraulic amplifier chamber (31); and a plunger (30) having a plunger diameter (Dpc) exposed to fuel within the hydraulic amplifier chamber (31), the plunger (30) being actuable by means of the actuator (20) to provide a force to the valve needle (14) with an amplification factor determined by the ratio of the plunger diameter (Dpc) to the needle diameter (Dnoz). The hydraulic amplifier chamber (31) is defined within a region of the lower housing region (18a) external to the cap nut (54).