INJECTOR FOR INTRODUCING A FLUID WITH IMPROVED JET PREPARATION

Abstract

An injector for injecting a fluid, in particular for injecting fuel, includes at least one closing element for opening and closing at least one through opening. The through opening includes an injection hole having a first center axis, and a preliminary stage having a second center axis. The first center axis of the injection hole and the second center axis of the preliminary stage of at least one of the through openings diverge.

Claims

1. An injector for injecting a fluid, comprising: at least one closing element for opening and closing at least one through opening; wherein the through opening includes an injection hole having a first center axis, and a preliminary stage having a second center axis, and wherein the first center axis of the injection hole and the second center axis of the preliminary stage of at least one of the through openings diverging.

2. The injector of claim 1, wherein the first center axis is situated in parallel to and spaced apart from the second center axis.

3. The injector of claim 1, wherein the second center axis is oriented at an angle) with respect to the first center axis.

4. The injector of claim 1, wherein the second center axis intersects the first center axis within the through opening.

5. The injector of claim 1, wherein the preliminary stage is situated behind the injection hole in the flow direction through the through opening.

6. The injector of claim 1, wherein the injection hole and/or the preliminary stage has a cylindrical, divergent, or convergent flow channel.

7. The injector of claim 1, wherein the length of the injection hole in the flow direction is smaller than the length of the preliminary stage.

8. The injector of claim 1, wherein an area ratio of the smallest area of the injection hole through which flow passes to the smallest area of the preliminary stage through which flow passes is 1:1.3 to 1:12.

9. The injector of claim 1, wherein the center of mass of a jet is situated at the end of the injection hole, on the center axis of the preliminary stage.

10. The injector of claim 1, wherein the injector includes at least one flow pocket.

11. The injector of claim 1, wherein the fluid is a fuel.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG. 1 shows a schematic side view of an injector according to a first exemplary embodiment of the present invention.

[0019] FIG. 2 shows a schematic, enlarged partial sectional view of the injector according to FIG. 1.

[0020] FIG. 3 shows a schematic, enlarged partial sectional view of the injector along section line Y-Y according to FIG. 2.

[0021] FIG. 4 shows a schematic detailed view of a through opening of the injector according to the first exemplary embodiment of the present invention.

[0022] FIG. 5 shows a schematic detailed view according to a second exemplary embodiment of the present invention.

DETAILED DESCRIPTION

[0023] A fuel injector according to a first exemplary embodiment of the present invention is described in greater detail below with reference to FIGS. 1 through 4.

[0024] As is apparent from FIG. 1, injector 1 includes a housing 3, an actuator 60, and a closing element 5 in the form of a valve needle. Closing element 5 opens up and closes a through opening 20 in housing 3 or, as shown in FIG. 2, in an injection hole disk 8 fixedly situated in housing 3. FIGS. 1 and 2 show the closed state of injector 1.

[0025] Injector 1 is an inwardly opening injector 1, the opening direction being opposite outflow direction A from injector 1.

[0026] Actuator 60 is a magnetic actuator, and includes an armature 61 and a coil 62. Closing element 5 is movable in axial direction X-X due to the cooperation of actuator 60 and armature 61. A resetting element 66 holds closing element 5 in the closed position shown in FIGS. 1 and 2. It is self-evident that actuator 60 may also be configured as a piezo actuator.

[0027] Injector 1 also includes a pressure chamber 4 that encompasses the interior of housing 3. Pressure chamber 4 is filled with fluid or fuel 10 to be introduced. A high pressure which may be up to 35010.sup.5 Pa prevails in pressure chamber 4, depending on the medium to be introduced.

[0028] Closing element 5 is apparent in greater detail in FIG. 2. Closing element 5 is configured as a valve needle with a valve ball 51 and a stop 55. In addition, housing 3 is provided with a supply line area 50 that extends in axial direction X-X of injector 1 from a closing element seat 6, opposite outflow direction A, along longitudinal axis X-X. Supply line area 50 together with closing element 5 forms an annular space that is part of pressure chamber 4, through which fuel 10 is guided to closing element seat 6 in outflow direction A.

[0029] Injector 1 is situated directly at a combustion chamber 2, and may be configured as a fuel injector 1 for the direct injection of fuel 10. However, fuel 10 may be gaseous or liquid.

[0030] Injector 1 according to the first exemplary embodiment functions as follows. When an opening operation is initiated, an actuator force is exerted on armature 60 by actuator 61, so that armature 60 together with closing element 5 is moved linearly in axial direction X-X, opposite outflow direction A.

[0031] Due to the movement of closing element 5, which takes place opposite the elastic force of resetting element 66, an annular space between valve ball 51 and closing element seat 6 is opened, and fuel 10 flows through this annular space into an inflow area 7. Inflow area 7 conducts fuel 10 to a through opening 20, through which fuel 10 is conducted from pressure chamber 4 into combustion chamber 2. In the idle state of injector 1 illustrated in FIGS. 1 and 2, valve ball 51 is pressed against closing element seat 6 due to the elastic force of resetting element 66, so that inflow area 7 may be closed off or separated from the remaining pressure chamber 4 in a gas- and fluid-tight manner. For this purpose, the shape of closing element seat 6 is adapted to the shape of valve ball 51.

[0032] FIG. 3 shows a section of injector 1 according to FIG. 2 along a plane in section line Y-Y. Multiple flow pockets 52 and webs 53 are situated in housing 3 over the circumference. Flow pockets 52 increase the effective cross section through which flow passes in axial direction X-X of injector 1 in the area of supply line area 50, so that fuel 10 may flow quickly and with low pressure loss through this cross-sectional enlargement and into inflow area 7, and thus into through opening 20. For this purpose, flow pockets 52 may be provided in housing 3, so that one or multiple webs 53 is/are formed between flow pockets 52. Webs 53 form bearing surfaces and guide surfaces for valve ball 51 or closing element 5, and support it in the radial direction. Flow pockets 52 and webs 53 accordingly extend from closing element seat 6 in axial direction X-X of injector 1, which may be over an entire stroke distance which valve ball 51 traverses during opening and closing.

[0033] Through openings 20 are provided over the circumference in inflow area 7 and in housing 3 corresponding to the angular pitch of flow pockets 52, so that the circumferential positions of flow pockets 52 and of through openings 20 correspond.

[0034] Through openings 20 may be positioned, independently of one another, relative to flow pockets 52 as a function of the number of through openings 20.

[0035] An enlarged illustration of housing 3 in the area of inflow area 7 and of through opening 20 is apparent in particular in FIG. 4. Through opening 20 includes an injection hole 21 having a first center axis 22, and a preliminary stage 23 having a second center axis 24. Fuel 10 thus flows from inflow area 7 into injection hole 21 via an inlet edge 25. Injection hole 21 opens into preliminary stage 23, through which fuel 10 exits from a dome 26 of injector 1 as a jet 11 that is disaggregated into a spray 13. The diameter of preliminary stage 23 is dimensioned to be much greater than the diameter of injection hole 21. The illustrated design of through opening 20 of injector 1 is a through opening 20 with a so-called deep, narrow preliminary stage. Length L2 of preliminary stage 23 in the flow direction is dimensioned to be greater than length L1 of injection hole 21. In addition, the diameter ratio of the areas of preliminary stage 23 to injection hole 21 through which flow passes is approximately 2:1.

[0036] A separation forms at the inlet edge 25 of injection hole 21 due to intense deflection and turbulence, resulting in the formation of a nonhomogeneous channel flow in injection hole 21 with high cavitation rates. Due to short length L1 of injection hole 21, an exiting jet 11 is not uniformly directed, so that a center axis 12 of jet 11 extends at an angle with respect to first center axis 22, not coaxially. A uniformly directed jet 11 is present when jet axis 12 is oriented in parallel to center axis 22.

[0037] Preliminary stage 23 has a center axis 24 that is situated in parallel to and spaced apart from center axis 22 of injection hole 21. This eccentrically offset preliminary stage 23 results in a uniform distance between jet 11 and the wall of preliminary stage 23 over the preliminary stage circumference. This results in particular in a more homogeneous interaction with jet 11 over the circumference, so that the dome wetting and the penetration are reduced, and the jet separation angle is increased by the avoidance of a one-sided jet constriction at the preliminary stage wall due to a collision with same. The vortex system which forms in preliminary stage 23 and which is part of the entrainment flow results in re-aspiration of fuel 10 that is deposited on dome 26, and resupplies it to jet 11. In addition, the eccentrically offset arrangement of preliminary stage 23 with respect to injection hole 21 allows an increase in the system robustness with regard to manufacturing tolerances.

[0038] FIG. 5 illustrates a second exemplary embodiment according to the present invention. In contrast to the first exemplary embodiment, center axis 22 and center axis 24 are not oriented in parallel to one another in the second exemplary embodiment. Center axis 24 of preliminary stage 23 is oriented in parallel to jet axis 12, and is inclined at an angle with respect to center axis 22 of injection hole 21. Jet 11 or jet axis 12 is thus coaxial and circumferentially symmetrical on center axis 24 of preliminary stage 23. To improve the jet dispersion, i.e., the spatial expansion in the radial direction of spray 13 formed by jet 11, injection hole 21 includes a divergent flow channel. The divergent flow channel thus has a continuously increasing channel cross section in the flow direction. Angle may be in a range of 3 to 7. An intersection point S of the two center axes 22, 24 is situated within through opening 20.

[0039] In addition, inlet edge 25 of injection hole 21 may be provided with a rounding via which the separation in injection hole 21 and the cavitation rate in the flow channel of injection hole 21 are reduced. The flow straightening effect of injection hole 21 is thus improved.

[0040] It is self-evident that injection hole 21 may have a constant, i.e., cylindrical, divergent, or convergent, channel cross section. The area ratio of the narrowest injection hole cross section to the preliminary stage cross section has values of 1:1.3 to 1:12.

[0041] The specific embodiments according to the present invention share the common feature that injection hole 21 is always situated within preliminary stage 23 at the transition into preliminary stage 23. As a result, the channel cross section in the transition from injection hole 21 into preliminary stage 23 is enlarged approximately over the entire circumference. At maximum divergence of center axes 22, 24, the circumferential surface of injection hole 21 may thus merge continuously into the circumferential surface of preliminary stage 23 at a circumferential position.

[0042] In addition, it is understood that the at least one through opening 20 is provided in housing 3 or in injection hole disk 8. Injection hole disk 8 may be fastened in a gas- and fluid-tight manner to housing 3 with a form-fit and/or force-fit connection, so that the injection hole disk partially encloses inflow area 7. Injection hole disk 8 allows simple and cost-efficient customization of injector 1.

[0043] Thus, according to the present invention an injector 1 including at least one preliminary stage 23 may be provided which has a greatly improved jet preparation, also with reduced manufacturing tolerances. Due to the central orientation of the center of mass of jet 11 in preliminary stage 23, according to the present invention the dome wetting and penetration are reduced, and the jet separation angle increases due to avoidance of a one-sided jet constriction at the preliminary stage wall. As a result of the circumferentially symmetrical flow through preliminary stage 23, the self-cleaning effect is improved due to the re-aspiration of fuel 10 deposited on dome 26 via a pronounced vortex system, and the system robustness as a whole is thus increased with regard to manufacturing tolerances.