WO2006018436A1

WO2006018436A1 - Sooting-controlled nozzle

Info

Publication number: WO2006018436A1
Application number: PCT/EP2005/054055
Authority: WO
Inventors: Axel Hockenberger; Enis Erkan; Ozan Alcicek
Original assignee: Robert Bosch Gmbh
Priority date: 2004-08-20
Filing date: 2005-08-17
Publication date: 2006-02-23
Also published as: TR200402080A1; EP1781933A1

Abstract

Accumulation of soot occurs over time on the area where the injection holes of injectors used in internal combustion engines open to combustion chamber, in other words, on the injector nozzle. This event starting on the injector nozzle tends to enter inside through the injection holes over time, which, in turn, causes a progressive reduction of diameter at the discharge end of an injection hole, and loss of power in the engine by a drop in flowratc brought along therewith. In order to prevent the aforesaid sooting to reduce cross-sectional area of the injection hole (2) of an injector nozzle (1 ), the discharge cross-section (3) has been provided with a new form. On the discharge area (3) of it where sooting starts, the hole is enlarged by an additional drilling operation (4) or operations (8, 9, 10,1 1 , 12, 13, 14), hence ensuring that the sooting starts on that area, and thanks to this, the soot accumulation is prevented to cause a reduction of diameter and accordingly a loss of flowrate and power. All of the additional drillings (4, 8, 9, 10,11,12,13,14) made for enlargement of the discharge end (3) of a hole on the injector nozzle (1) are made with the same drilling tools as the ones used in the main hole drilling process.

Description

DESCRIPTION

SOOTING-CONTROLLED NOZZLE

This invention is concerned with a fuel injection system, particularly relating to the geometrical structure of injection holes located on an injector nozzle and the style of forming such structure. The main consideration is to make an injection hole with its outlet being larger than its inlet. Thus the soot accumulation that occurs at the inlet of injection holes located on an injection nozzle leading to reduction of cross-section is delayed, hence extending the injector life. On the other hand, the invention explained here eliminates the manufacturing instability that arises in other methods, e.i. the differences among injector holes in mass production. One of the most important advantages brought along with this invention is that all drilling operations on the same hole can be accomplished with a single electrode and the desirable geometry can thus be obtained.

The basic function of high pressure injection systems used in internal combustion engines is to inject fuel through an injection nozzle to create a proper air/fuel mixture in a manner to provide full combustion in the combustion chamber within the operating range of the engine. In order to obtain a good air/fuel mixture in the cylinder volume, in other words, in the combustion chamber formed by a piston, cylinder head and cylinder itself which limit the combustion chamber of the engine, the geometry of injection holes on injector nozzles is of great importance. Injecting the fuel into the cylinder, or in other words, into the combustion chamber, through the injector in a very short time interval requires a high rate of fuel flow. In high pressure injection systems, even a minimum change, in other words, a reduction that may occur in the cross-sectional area of the injection holes manufactured with very narrow tolerances may cause undesirable losses in transfer of pressure of the fluid in the hydraulic system and undesirable impairments in the structure of liquid fluid cluster injected through injection holes, which, in turn, leads to substantial performance losses in high pressure hydraulic systems and injection systems and even causes the systems to become completely inoperable. Furthermore, any deviations from mixture formation conditions determined during design and development stage that occur due to reduction in the cross-section of injection holes may effect combustion process in the cylinder and hence cause increases in exhaust gas emissions. Reduction in the cross- section of injection holes may originate from clogging of narrow passages by solid particles contained in the fluid used as dragged therewith, and in addition to this, the soot accumulation in the injector nozzle also consitutes an important problem. Depending on the operating conditions of internal combustion engines, soot accumulation occurs on the walls of cylinder, piston and cylinder head that form the combustion chamber. The external surface of nozzle at the tip of the injector generally located in the cylinder head is in direct contact with the combustion chamber. Hence, similarly, the soot accumulation formed on the combustion chamber over time covers the external surface of the injector nozzle as well. The injection holes provided on an injector nozzle are also directly effected by such soot accumulation. The soot accumulated on the nozzle completely surrounds the discharge end of the fuel injection holes over time and causes reduction in cross-section by entering inside through discharge end of holes, which may then cause shortening of injector life as well as 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. Many of the injection holes of injectors currently used in internal combustion engines are completely cylindrical and a portion of them has different inlet and outlet diameters; however, they have an exact symmetry. Although atomization during injection, in other words, breaking of the injected fuel cluster into small droplets, is sufficient, the soot accumulation starting at the injector nozzles in which the injection holes are located and continuing to occur at discharge ends of holes and then in the internal surface of holes can not be prevented. In order to overcome this trouble, several practices have been tried for the channel geometry o^ injection holes located in the injector nozzle; but no efficient result could be reached due to some technical problems encountered in manufacturing. For example, after drilling through the injection hole of an injector in certain size, the electrodes used in drilling process have been changed, and the discharge end of the injection hole has been entered into again (with a thicker electrode) and exited without completing the full length of the hole. Thanks to this, a staged hole has been obtained. Thus by enlarging the cross-section closer to discharge end in the injection hole, it has been tried to retard the cross-sectional reduction effect of soot which enters inside from the discharge end and accumulates on the channel walls. But the off-centering problem arising during electrode change, that is, the unability to overlap the axes of two consecutive drilling operations, has caused production instability, in other words, a difference among injection holes produced.

This invention is concerned with a fuel injection system, particularly relating to the geometrical structure of injection holes located on an injector nozzle and the style of forming such structure, and the main consideration is to make an injection hole with its outlet being larger than its inlet. On the other hand, the invention explained here eliminates the difference among injector holes in mass production by eliminating the aforesaid production instability. Reduction in geometrical size by sooting is only permitted after a particular working time, in other words, after the newly developed additional zone is completely filled by soot starting from low pressure zone formed by newly developed additional drilling operations. Therefore the reduction in diameter followed by the drop in flowrate is retarded to a future time, which means increasing the hole life. Furthermore, a better atomization achieved by enlarging the cross-sectional area at the injector outlet and thus by allowing a fixed quantity of fuel to cover a larger volume in the hole before its entry into combustion chamber and creation of a desirable environment with vortex foπned by impairment of the symmetry of the injected fuel profile at the time of start of combustion are among the anticipated potential improvements. This event will also ensure improvements in exhaust gas emissions by directly effecting the combustion efficiency. This new hole design has an extraordinarily alternate asymmetric structure. One of the most important advantages introduced by it is that all drilling operations on the same hole can be completed with a single electrode and that hence the desired geometry can be obtained. Since the requirement for changing electrode wire is eliminated, the requirement for matching the axes of the wires used has also been eliminated, which, in turn, means the production stability, in other words, the compliance with mass production.

Drawings explaining the invention are as follows :

Figure 1. Structure of an injector with additional partial drilling operation applied for injection hole.

Figure 2. Application of 2, 3 and 4 additional drilling operations to an injection hole by changing first the circumferential angle and then the elevation angle. Figure 3. Application of 2, 3 and 4 additional drilling operations to an injection hole by simultaneously changing both the circumferential angle and the elevation angle.

Figure 4. Λ case involving a single additional drilling operation by increasing only the elevation angle to some extent on an injector nozzle (with nozzle tip facing to left ).

Figure 5. A case involving a single additional drilling operation by increasing only the circumferential angle to some extent on an injector nozzle (with nozzle tip facing to left).

Figure 6. A case involving a single additional drilling operation by increasing both the elevation and the circumferential angles to some extent on an injector nozzle (with nozzle tip facing to left).

Detailed explanation of the invention :

As shown in Figure 1 , the invention explained under the heading "sooting-controlled nozzle head" covers additional partial drilling of hole (4) or holes at the discharge end (3) of injection holes (2) provided on an injector nozzle (1). The aforesaid application (4) as in Figure 1 is shown for one injection hole (2) provided pn the injector nozzle (1). The inlet end (5) of the injection hole (2) provided in the injector nozzle (1 ) opens to its internal volume containing fuel (6) and its outlet end (3) opens to the combustion chamber (7) of internal combustion engine. Drilling process is performed as follows: The injection hole (2) provided in the injector nozzle (1) is drilled through in required diameter by wire erosion method or by a different process. Subsequently the circumferential angle of the mechanism to which the injector nozzle (1) is connected is increased to some extent without changing the electrode or any other kind of various tools used for drilling so as to ensure entry of the same wire into the same hole (2) by a shorter distance this time than the total hole length (4) (Figures 1 and 2). Thereafter, the circumferential angle of the mechanism to which the injector nozzle is connected is reduced to some extent (for example, two-fold of the amount of increasing thereof in the previous operation) and the same process can be repeated (8). That means, the symmetrical one (8) of the additonal hole (4) relative to the vertical plain passing through the axis of the main hole (2) can also be drilled (Figure 2). As the third step, the circumferential angle of the mechanism to which the injector nozzle (1) is connected is brought to the center again and the elevation angle is increased to some extent, the additional partial drilling process can be repeated (9) (Figure 2). Thereafter, the elevation angle is reduced to some extent (for example, two- fold of the amount of increasing thereof in the previous operation) and the same process can be repeated (10) (Figure 2).

Whereas in another application method, both the circumferential and the elevation angles can be changed after the drilling process of the main hole (2) and either a single additional hole (1 1) or several additional holes (1 1,12,13,14) can be drilled (Figure 3). In the injector nozzle (with nozzle tip facing to left) shown in Figure 4, a case is provided that involves only a single hole (9) drilling process where the first two additional drilling operations (4, 8) shown in Figure 2 are bypassed and only the elevation angle is increased to some extent.

In the injector nozzle (with nozzle tip facing to left) shown in Figure 5, a case is provided that involves only a single hole (4) drilling process by increasing the circumferential angle shown in Figure 2 to some extent.

In the injector nozzle (with nozzle tip facing to left) shown in Figure 6, a case is provided that involves only a single hole (1 1) drilling process by changing both the circumferential and the elevation angles shown in Figure 3. Thus, after the operations of drilling additional hole(s) (4 and/or 8), (1 1 and/or 12), (9 and/or 10), a hole geometry that appears to be a full circle (15) when looked from internal side (5) of the injector nozzle (1) and to be an ellipse (16) when looked from external side (3) of it is obtained (Figures 4, 5, 6). In additional drilling operations, the variation of circumferential angle of the mechanism to which the injector nozzle (1) is connected should be small enough not to permit cavitation in the low pressure zone formed. Thus, a very small decrease will occur in velocity and pressure at the hole outlet (3) and the effect of cross-sectional reduction by soot formation will be eliminated or ensured to occur in a longer time, hence increasing the injector nozzle life.

Claims

1 . Tlic sooling-conlrolled nozzle as described above covers an injector used as a fuel injection component in internal combustion engines and an injector nozzle ( 1 ) thereon providing entry of fuel into the combustion chamber (7) and additional drilling operations (4,8,9,10,1 1,12,13,14) at the discharge end (3) of injection holes (2) provided on the injector nozzle (1).

2. It is a system as in Claim 1, in which an injection hole (2) provided on the injector nozzle (1 ) is drilled through in the required diameter and thereafter, by increasing to some extent the circumferential angle of the mechanism to which the injector nozzle (1 ) is connected without changing the tool used for drilling, entry of the same wire into the same hole (2) by a shorter distance this time than the total hole length (4) is ensured, hence enlarging the discharge cross-section (3) of the hole.

3. It is a system as in Claim 1 and 2, in which, following the application in Request 1 , the circumferential angle of the mechanism to which the injector nozzle (1 ) is connected is reduced to some extent (for example, two-fold of the amount of increase in Request 2) and the same process can be repeated (8). That is, a symmetrical one (8) of the additional hole (2) relative to the vertical plain passing through the axis of the main hole (2) can also be drilled

4. It is a system compliant with all the aforesaid requests, in which the circumferential angle of the mechanism to which the injector nozzle (1) is connected is brought to the center again and the elevation angle is increased to some extent, and the additional partial drilling process can be repeated (9).

5. It is a system compliant with all the aforesaid requests, in which, following the application in Cliam 4, the elevation angle of the mechanism to which the injector nozzle

(1 ) is connected is reduced to some extent , (for example, two-fold of the amount of increase in Request 4) and the same process can be repeated (10).

6. It is a system as in Claim 1 , in which an injection hole (2) provided on the injector nozzle ( 1 ) is drilled, through, in the required diarrrcteraπd thereafter, by increasing to some extent the elevation angle of the mechanism to which the injector nozzle ( 1 ) is connected without changing (lie tool used for drilling, entry of the same wire into the same hole (2) by a shorter distance this time than the total hole length (4) is ensured (9), hence enlarging the discharge cross-section (3) of the hole.

7. It is system as in Claim 1 and 6, in which, following the application in Request 6, the elevation angle of the mechanism to which the injector nozzle ( 1 ) is connected is reduced to some extent (for example, two-fold of the amount of increase in Request 6) and the same process can be repeated (10).

8. It is a system as in Claim 1 , in which an injection hole (2) provided on the injector nozzle (1 ) is drilled through in the required diameter and thereafter, by changing both the circumferential angle and the elevation angle of the mechanism to which the injector nozzle (1 ) is connected without changing the tool used for drilling, entry of the same wire into the same hole (2) by a shorter distance this time than the total hole length is ensured ( 1 1 , 12, 13, 14), hence enlarging the discharge cross-section (3) of the hole.

9. It is a system compliant with all the aforesaid requests, in which the volume (4 and/or 8,9, 1 0, 1 1 , 12, 13, 14) formed by additional hole drilling operations prevents accumulation of soot entering into the injection hole (2) to cause cross-sectional reduction or retards it to occur.

1 0. It is a system compliant with all the aforesaid claims, in which a repeatability with very narrow tolerances is ensured in mass production since only the circumferential angle and/or the elevation angle of the mechanism to which the injector is connected is changed without changing the drilling tool throughout the drilling operations.