INTEGRATED FILTER-INJECTOR

This invention is concerned with an integrated filter which prevents the holes of injector nozzles in fuel injection systems having a precise mechanical structure as commonly used in internal combustion engines, from being clogged by solid particles resulting from fuel or injection system.

The basic function of high pressure injection systems used in internal combustion engines is to inject fuel through the injector nozzle in order to create the required air/fuel mixture in a manner to ensure full combustion in the cylinder which forms the combustion chamber, within the operating range of the engine, in other words, depending on the revolution speed of the engine and on the power taken off therefrom. As the legal restrictions on exhaust gas emissions of internal combustion engines have been made narrower, the formation of a good air/fuel mixture in a manner to ensure full combustion gradually becomes of greater importance in view of the emissions resulting from combustion as well as of the efficiency. For above reasons, in order to create a good mixture in the cylinder and to obtain the conditions for full combustion, substantial developments have been achieved in the fuel injection systems. Along with starting to use such developments particularly in hole drilling methods (such as laser drilling) in mass production, diameters of holes in an injector nozzle have been gradually made smaller, which, in turn, ensures that the fuel injected into the cylinder under high pressure is broken into smaller droplets, hence forming a mixture with air quickly. However, the smaller diameters of holes in the injector nozzle as mentioned above have brought along the risk of complete or partial clogging of these holes even by very small solid particles in the fuel, which, in turn, causes the engine to lose power or to become completely inoperable, depending on the increased flow resistance of the injected fuel in the injector nozzle. Furthermore, since the structure of fuel cluster injected through such narrowed and reshaped cross-sections of holes in the injector nozzle will be impaired, it may cause deviations from the conditions of forming a proper mixture determined during design and development stage as well as increases in exhaust emissions by effecting the combustion event in the cylinder. The aforesaid narrowing or clogging in the injector nozzle may be due to solid particles or due to wears in pump, fuel line and injector in the fuel injection system, and it also depends on the quality of fuel used. Such a case may cause a substantial increase in maintenance expenses in addition to occurrence of such adversities as loss of power in the engine and increase in exhaust emissions, depending on the aforesaid conditions.

By this invention, an integrated filter applicable to any type of fuel injectors, which prevents the injector nozzle holes to be clogged by solid particles resulting from the fuel itself or from the injection system as aforesaid having a precise mechanical structure is proposed and explained herein.

The filter mentioned here is named as an integrated filter since it is directly incorporated within the injector body. Direct incorporation of the filtering system within the injector body does not require major modifications due to simplicity of its structure. The clogging of a part of the holes provided on the filter element over time does not cause a substantial narrowing of cross-section because of the numerous holes provided on an integrated filter element and thus the increase in resistance against fuel flow is prevented. Furthermore, thanks to a collection volume provided in the integrated filter, which has a structure to allow accumulation of solid particles, an integrated filter element will have a longer operation life. The use of such an integrated filter will also eliminate the need for installing a separate external filter element in the fuel injection system. On the other hand, the requirement for a pressure chamber in the fuel line within an injector in the fuel injection system will also be eliminated, because the pressure fluctuations will be avoided thanks to the capillary holes provided on the integrated filter element. An additional acquisition that may be achieved with an integrated filter is that by determining the chamfer size of an injector needle, it can be ensured that the external surface of the needle covers a portion of the holes provided on the filter when the needle is in closed position, thus changing the cross-section of flow in the course of injection process proceeding from the start of injection and that hence a step-by-step injection becomes possible.

Drawings explaining the invention are as follows :

Figure 1. Injector unit provided with an integrated filter. Figure 2. An integrated filter element.

Detailed explanation of the invention :

The unit being the subject matter of the invention, which is defined as an integrated filter, is incorporated within the injector body (1) located at the very end of the fuel injection system as seen in Figure 1, while the detailed view of an integrated filter unit is shown in Figure 2. Fuel from injection pump passing through the fuel line and/or in common rail systems, through a valve located at the injector inlet reaches the filter volume (2) provided at a location closer to the upper side of the injector body. In ordinary injectors, the integrated filter element is usually positioned where the pressure chamber is located in the fuel line within the injector. In general, the volume (2) within the injector body reached by the fuel before it is filtered has a ring shape, with its internal surface forming the filtration surface (3). Both the ring-shaped volume (2) and the filtration surface (3) are sized according to the structure of the injector body. On the internal surface of the ring-shaped filtration surface (4), an injector needle (5) is provided. There are numerous holes (6) drilled through in the ring-shaped surface (3, 4) defined as the filtration surface. These holes (6) provided in the filtration surface (3, 4) are defined as the filtration holes (6) which function to filter the fuel. The quantity and diameter of such holes (6), in other words, their total cross-sectional area, are sized to minimize pressure drop or pressure loss during fuel flow. Another important condition is that the diameter of the aforesaid filtration holes (6) should be smaller than that of the injection holes (8) provided in the injector nozzle (7). In such case, those of the solid particles in the fuel system which have sizes equal to or greater than the cross-section of the injection holes (8) provided in the injector nozzle (7) are prevented from passing through the filtration holes (6). Thus the clogging of injection holes (8) provided in the injector nozzle (7) in a fuel system by solid particles contained in fuel is avoided. Filtration holes with very small diameter (6) can be manufactured easily by such methods as laser drilling which have now started to be used in mass production. On the other hand, the depth and geometry (10) of the filter volume (2) connected to the fuel line (9) of an integrated filter are also of importance from functional viewpoint. Filter volume (2) is made such that it will further continue downward to some extent (10) starting from those of the filtration holes (6) provided in filtration surface (3, 4) which are located at the lower row relative to the injector body (11). The volume (12) at the lower surface where no filtration holes (6) are provided forms a zone defined as the collection volume (12) which has been sized in a manner to allow solid particles caught in the filter element to accumulate therein. Thus the accumulation of solid particles in a fuel system in front of the filtration holes (6), clogging the said holes and reducing the cross- section of flow is prevented, which, in turn, ensures that an integrated filter will have a longer operation life. The filtration and the particles collection feature of an integrated filter as explained above also eliminates the requirement for use of a separate external fuel filter. In general, the injector needle (5) located at the center of the injector body (1) has a chamfered (13) structure. The needle surface extended in size (14) by the chamfer (13) on injector needle is in contact with the internal surface (4) of the filtration ring. The needle surface extended in size (14) by the chamfer (13) can be sized such that the filtration holes (6) located on the inner surface (4) of filtration ring will be partially closed when the injector needle (5) is in closed position, in other words, when no injection operation is performed through the injection holes (8) in injector nozzle (7). Such a design that allows the external surface of needle (5) to cover a portion of the filtration holes (15) located on filtration ring when the needle is in closed position changes the cross-section of flow in the course of injection process proceeding from the start of injection, hence making a step-by- step injection possible. Such a structure, besides its filtration action, is of use in preventing combustion knock or sudden pressure increase in the cylinder due to ignition delay of the injected fuel, particularly in diesel engines. With its simple structure, an integrated filter has the possibility of use in the injectors provided in a series or a distributor type of pumping systems, in the electromagnetic- or piezoelectric-controlled high pressure common rail systems and in the unit pump systems containing a combined pump and injector.