Patent Application
20130327855
The invention relates generally to injectors, and more particularly, an orifice disc for a fuel injector which provides sufficient atomization of fuel.
Injectors are a commonly used device for injecting fuel into the cylinders of an internal combustion engine. One of the ways to improve the efficiency of an engine is to inject the fuel in an “atomized” form. Fuel that is atomized burns much more efficiently, allowing as much of the fuel to be used as possible.
Different fuel injectors are often used with different types of fuel, which have different material properties, and react differently to various temperature changes. One such type of fuel is ethanol, which freezes or solidifies during cold weather conditions. Many attempts have been made to improve the operation of a fuel injector used with ethanol to eliminate freezing of the ethanol.
Spray generation, or atomization, is created by the fluid stream breaking into droplets, while being directed in a specific direction. Breakup of the fluid stream is further enhanced by keeping the fluid turbulent as it exits the orifice hole. One of the factors that influence the atomization of the fluid is the shape of the exit orifice or exit aperture through which the fluid passes as the fluid exits the injector. Some injectors include a plate which may have several exit apertures through which the fluid passes. If the fluid flow becomes laminar, or streamlined, to the wall of the exit aperture, the fluid droplets become elongated and create large droplets, or “ligaments.” The definition of the size of a ligament is quantified by the particle size measurement of Sauter Mean Diameter (SMD).
One of the contributing factors to this particle size is the ratio of the material thickness or depth of the wall of the exit aperture to the diameter of the wall of the exit aperture, referred to as the L/D ratio. As the depth or thickness of the exit aperture is minimized, atomization is improved. However, using a plate which is of a single thickness and minimizing the thickness of the exit aperture to improve atomization also requires that the material used to create the plate be minimized in thickness as well, which then reduces the weld properties of the plate, increasing the difficulty in welding the plate to the injector during assembly.
When the thickness of the exit aperture is above a certain value, such as 0.006 inches, and the L/D ratio approaches 1.0, the fluid, or fuel in liquid form, reattaches to the wall of the aperture, causing ligaments and larger droplets. The ligaments often build up in the injector, which causes problems during cold starts.
Accordingly, there is a need for a plate having an exit aperture or orifice used in a fuel injector which reduces droplet size, and therefore reduces or eliminates the formation of ligaments and large droplets, where the plate still maintains desirable weld properties.
The present invention is an orifice plate used as part of a fuel injector. The orifice plate has a base portion, an offset portion integrally formed with the base portion, and a flow entry side, where the base portion and the offset portion are part of the flow entry side. The orifice plate also includes a flow exit side, where the base portion and the offset portion are also part of the flow exit side. The orifice plate also has a recessed surface formed as part of the offset portion such that the recessed surface is located on the flow entry side, and a raised surface formed as part of the offset portion, where the raised surface is located on the flow exit side. An inner side wall is adjacent the recessed surface, and an outer side wall is adjacent the raised surface. A plurality of exit apertures is integrally formed with the offset portion. Each of the plurality of exit apertures includes a plurality of stepped portions, and each exit aperture is of a depth which is twice the size of the inner diameter, to provide optimal atomization of fuel as the fuel passes through each of the exit apertures.
It is an object of the present invention to provide an orifice plate which is made of a single piece of material, or a single plate, with a plurality of exit apertures, where the plurality of exit apertures provide improved atomization of fuel flowing through an injector.
It is another object of this invention to control flow rate through an orifice plate by controlling the flow diameter of the orifice, and coining during the manufacturing process.
It is yet another object of this invention to control the spray pattern through the use of dimple geometry, and to improve breakup of the fuel flow through locally reduced material thickness.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.
The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:
The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.
An orifice plate having a stepped orifice aperture or hole according to embodiments of the present invention is shown in the Figures generally at 10. The plate 10 has at least one, but in some embodiments has a plurality of stepped apertures, shown generally at 12, which allow fluid, such as fuel, to pass through.
The plate 10 is a single piece part, and has base portion 14 and an offset portion 16. The offset portion 16 forms a recessed surface 18 on the flow entry side, shown generally at 20, and also forms a raised surface 22 on the flow exit side, shown generally at 24. Surrounding the recessed surface 18 is an inner side wall 26 which is substantially parallel to an outer side wall 28, and the outer side wall 28 is adjacent to the raised surface 22. The offset portion 16 is curved or at least partially spherical in shape, such that each of the plurality of stepped apertures 12 are at an angle relative to the center of the plate 10.
Each stepped aperture 12 includes at least one stepped portion, and in the embodiments shown in the Figures, a plurality of stepped portions. More specifically, each stepped aperture 12 includes a first stepped portion, shown generally at 30, a second stepped portion, shown generally at 32, and a third stepped portion, shown generally at 34. Each stepped portion 30,32,34 includes various surfaces. The first stepped portion 30 has a first inner diameter (ID) surface 36 and a first step surface 38, the second stepped portion 32 includes a second ID surface 40 and a second step surface 42, and the third stepped portion 34 includes a third ID surface 44.
Each stepped portion 30,32,34 includes an inner diameter, and a depth. The first stepped portion 30 includes a first inner diameter 46, which is about 0.025 inches, and a first depth 48, which is about 0.003 inches. The second stepped portion 32 includes a second inner diameter 50, which is about 0.014 inches, and a second depth 52, which is about 0.0015 inches. The third stepped portion 34 includes a third inner diameter 54 which is about 0.007 inches, and a third depth 56, which is also about 0.0015 inches. The third stepped portion 34 also includes the aperture 58 (which may also be referred to as an exit orifice) through which the fuel flows through. Each of the inner diameters 46,50,54 and the depths 48,52,56 may be changed to allow the orifice plate 10 to be used in different applications.
The third stepped portion 34 having the third inner diameter 54 and the third depth 56 is such that the ratio between the two is as low as possible. However, while the thickness of the third depth 56 is reduced to improve breakup of the jet stream of fuel and increasing atomization, the thickness of the third depth 56 must be thick enough to meet weld robustness requirements. In a preferred embodiment, the third depth 56 is twice the size of the third inner diameter 54. In one embodiment, the third depth 56 is approximately 0.0030 inches; however, it is within the scope of the invention that the third depth 56 may be of other dimensions as well.
The orifice plate 10 may be produced in a number of ways. In an embodiment, a series of progressive dies are used to form the plate 10. A flow diagram describing the process used to create the plate 10 is shown in
The second step 104 is a flatten operation to prepare the blank 60 for the second punching operation. The third step 106 is to form the second stepped portion 32 using a second punch, as shown in
The sixth step 112 is to displace a portion of the plate 10 to form the offset portion 16. This is also accomplished by using a punch having at least a rounded portion, or a partially spherical shape. Each aperture 58 includes an axis 62, and the offset portion 16 is curved or at least partially spherical in shape such that each aperture 58 is located at an angle 64 relative to a central axis or vertical axis 66, where the vertical axis 66 extends through the center of the plate 10, best seen in
The seventh step 114 is to cut the tabs 68 from the base portion 14, shown in
Referring again to
The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.
