GB2568468A

GB2568468A - Injector

Info

Publication number: GB2568468A
Application number: GB1718841.8A
Authority: GB
Inventors: Shi Junmei; Muller-Girard Otto Jr
Original assignee: Delphi Automotive Systems Luxembourg SA
Current assignee: Delphi Technologies IP Ltd; BorgWarner Luxembourg Automotive Systems SA
Priority date: 2017-11-15
Filing date: 2017-11-15
Publication date: 2019-05-22
Also published as: GB201718841D0

Abstract

A nozzle assembly of an injector and an injector are disclosed. The nozzle has a body which cooperates with a valve member to control an outlet path. The outlet comprises a guidance channel 72 which leads to a spray hole 60, 62. The grooves 72 and outlet orifice 60,62 are arranged to force the flow to swirl S when entering the spray hole 60,62. There may be several branches 74 of the channel leading to the spray hole. The nozzle may include a plurality of spray holes which may be joined by the guidance channel. The application extends to a Selective Catalytic Reduction (SCR) injector adapted to spray into the exhaust pipe on an internal combustion engine. The induction of swirl enhances the atomization performance of the nozzle, allowing for the number of holes needed to be minimised. This reduces machining costs and increases plugging resistance.

Description

TECHNICAL FIELD

The present invention relates to the nozzle assembly of a low pressure injection valve or injector, e.g. injectors for port fuel injection, selective catalytic reagent (SCR) injection, water or hydrogen injection.

BACKGROUND OF THE INVENTION

Low pressure injectors are used to meter and atomize various liquids used in an internal combustion engine or its exhaust gas treatment components. Typically the injector also directs the atomized spray in an particular geometry towards a defined target. The spray droplet size and spray pattern geometry have a direct effect on the operational efficiency and output emissions of the internal combustion engine (ICE). The design of the injector must minimize deposit formation and have robust performance against the deposits that do form. Smaller spray droplet can be created by reducing the spray hole size and in the same time increasing the number of holes in the director plate to deliver a given flow rate. There are practical limits to the size of the holes. Furthermore smaller holes are more prone to plugging. More holes increase the cost of the director plate as more machining operations are required to make the holes. In this invention we seek to enhance the atomization performance of a low pressure liquid atomizer at a given spray hole size by using specifically designed flow guidance channels. This allows to minimize the number of holes necessary meet spray particle size requirements. This reduces cost and improves plugging resistance.

SUMMARY OF THE INVENTION

The invention is outlined for a low pressure liquid atomizer based on a Selective catalytic reduction (SCR) injector. Accordingly, it is an object of the present invention to resolve or at least mitigate the above mentioned problems in providing a nozzle assembly of an injector extending along a main axis and having a body and a valve member cooperating, in use, to control access of a fluid flow to an outlet path comprising a guidance channel. Said guidance channel has an upstream portion wherein, in use, the flow enters and, a downstream portion wherefrom the flow exits via a spray hole, the guidance channel and the spray hole being arranged to force the flow to a swirl motion when entering said spray hole.

The spray hole may be drilled with an offset relative to the direction of said downstream portion.

The spray hole may comprise a large entry portion joining via a shoulder a narrow exit portion, said large entry portion forming a step hole wherein the flow enters and swirl.

The guidance channel may comprise a circus for the flow to swirl, said circus being arranged at the end of the downstream portion, the spray hole opening in said circus.

The guidance channel may comprise several branches each leading to the spray hole.

The nozzle assembly may comprises a plurality of spray holes, all spray holes being substantially equidistant from the nozzle main axis.

In an embodiment, the guidance channel joins several spray holes.

The guidance channel may comprise an arcuate portion.

The guidance channel may comprises a straight portion.

The nozzle assembly may further comprise a flow director member arranged to cover the nozzle body, said outlet path being provided in said flow director member.

The flow director member closes an opening of the body and partially defines a sac volume, the upstream portion of the guidance channel opening in said sac to the downstream portion being outside said sac and being covered by the body.

The invention extends to an injector comprising a nozzle assembly as described above.

In a particular embodiment, said injector may be a SCR injector adapted to spray a reagent fluid in the exhaust pipe of an internal combustion engine.

In another embodiment, said injector may be a gasoline injector for spraying gasoline fuel in the cylinders of an engine.

In yet another embodiment, said injector is a water injector for spraying water.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is now described by way of example with reference to the accompanying drawings in which:

Figure 1 is an axial section of the nozzle of a SCR injector as per the invention.

Figure 2 is a bottom view of the nozzle of figure 1.

Figures 3 is an isometric top view of the nozzle of figure 1.

Figure 4 is a isometric view of a flow director member of the nozzle of figure 1.

Figures 5 and 6 are sketches of an axial section and of a detailed top view of the first embodiment of the invention.

Figures 7 and 8 are similar to figures 5 and 6 for a second embodiment of the invention.

Figures 9, 10 and 11 are three views of a third embodiment of the invention.

Figures 12, 13 and 14 are further embodiments of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention described relates to the nozzle 10 of an injector 12 adapted to spray a liquid such as water, fuel, gasoline or a reagent under relatively low pressure. The description is based on the non-limiting example of a Selective Catalytic Reagent injector 12, hereafter SCR injector 12, adapted to be arranged to spray a reagent in the exhaust pipe of an internal combustion engine.

In reference to figures 1 to 4 is described a nozzle assembly 10 of a Selective Catalytic Reagent injector 12, hereafter SCR injector 12, adapted to be arranged to spray a reagent in the exhaust pipe of an internal combustion engine. Said nozzle assembly 10 extends along a main axis X and it comprises a body 14, defining a circular opening 16 surrounded by a seat 18, a valve member comprising a pusher 20 and a ball 22 cooperating with said seat 18, a flow director member 24 defining a plurality of reagent outlet paths 26, said flow director member24 being fixed to the body 14 by a clamp member 28.

In use, the pusher 20 is moved along said main axis X by an actuator, not shown, between a closed position where the pusher 20 urges the ball 22 against the seat 16 and, an open position where the pusher retracts enabling the ball 22 to lift off the seat and to open between the ball and the seat a passage for the reagent to be sprayed via the outlet paths 26.

More precisely, the body 14 defines an inner space surrounded by a cylindrical peripheral wall 30 closed at an end by a transverse wall 32 centrally provided with said circular opening 16. The seat 18 is a frustoconical face defined at the periphery of said opening 16 and provided on the inner face of said transverse wall 32. Alternatively to conical faces, other geometries such as a curved profile can be chosen.

The flow director member24, particularly shown on figure 4, is a thin metal sheet shaped to define a main circular flat area 34 with two peripheral two raised lips 36 separated by opposed openings. The flow director member24 has an inner face 38, visible on figure 4, opposed to an outer face 40 which central area is visible on figure 2. In the embodiment presented, three outlet paths 26, further detailed afterward, are arranged in the central area of said main circular area 34 although in a non-represented alternative, a SCR injector can be provided with another quantity of outlet paths.

The clamp member 28 is also a metal sheet with a flat area 42 and a peripheral raised lip 44, the flat area 42 being provided with a large central circular hole 46.

As shown on the axial section of figure 1, the flow director member24 is sandwiched between the body 14 and the clamp member 28, the clamp lip 44 being crimped against the cylindrical wall 30 of the body and, the flat area 34 of the flow director member is urged against the outer face of the body transverse wall 32.

Through the opening 16 of the body is visible on figure 3 an inner central circular portion 48 of the inner face 38 of the flow director member and, through the hole 46 of the clamp member is visible on figure 2 an outer central circular portion 50 of the outer face 40 of the flow director member, said inner and outer central portions 48, 50 being concentric about the main axis X. Also, as shown on the section of figure 1, the body opening 16 is smaller than the clamp member hole 46 therefore said inner central circular portion 48 is smaller than the outer central circular portion 50 of the flow director member. Moreover, a flat volume, identified as a sac 51, is defined in the opening 16 of the body, between the ball 22 and said inner central circular portion 48 of the inner face 38 of the flow director member.

The outlet paths 26, enabling in use the reagent fluid to be expelled out of the injector 12, are defined on the flow director member and, each of said outlet path 26 comprises a guidance channel 52 and a spray hole 54. The guidance channel 52 is a groove dug on the inner face 38 of the flow director member outwardly extending from an upstream portion 56, that is in said inner central portion 48 of the flow director member therefore forming an open groove opening in the sac 51 to, a downstream portion 58 that is outside said inner central portion 48, said downstream portion 58 being therefore covered by the transverse wall 32 of the body and forming a closed conduit.

At the end of said downstream portion 58, the spray hole 54 is drilled extending through the flow director member24 between an opening at an entry end in the bottom of said guidance channel 52 to an opposed exit end in said outer central circular portion 50 of the outer face of the flow director member.

In order to favour the flow, the spray hole 54 is offset relative to the guidance channel 52 so, in use, the flow is forced to a swirl S when entering the spray hole 56.

In alternatives, not shown and benefiting from the present invention, the injector is provided with more, or less, than three outlet path 26, said path 26 being either regularly arranged or non-regularly arranged. Also, the spray hole 54 shown to extend parallel to the main axis X may be arranged at an angle.

In a first embodiment presented on figures 5 and 6, the spray hole 54 comprises a large entry portion 60 opening in the guidance channel 52 followed by a narrow exit portion 62. As sketched in the axial section of figure 5, the large entry portion 60 defines a step hole at the bottom of which opens the narrow exit portion 62.

The top view of figure 6 shows that the guidance channel 52 radially extends within lateral parallel borders 64 defining a channel width W. The upstream portion 56 is inside the circular limit of the body opening 16 and, the downstream portion 58 is between said circular limit of the body opening 16 and said circular limit of the clamp hole 46. At the end of the downstream portion the spray hole is drilled with an offset D from the guidance channel radial axis. In said first embodiment, the step hole 60 is circular having a diameter equal to the width W of the guidance channel and as shown by the arrows A representing the flow, the reagent flow makes a swirl S at the downstream end when entering the step hole 60 and the exit portion 62.

In a second embodiment presented on figures 7 and 8, the spray hole 54 does not comprise an entry step hole, the narrow portion 62 directly extending from the guidance channel 52 to the outer face 40 of the flow director member.

The top view of figure 8 shows that the guidance channel 52, similarly to the first embodiment, radially extends within lateral parallel borders defining the channel width W. The upstream portion 56 is inside the circular limit of the body opening 16 and, the downstream portion 58 is between said circular limit of the body opening 16 and said circular limit of the clamp hole 46. In said second embodiment, the end of the downstream portion 58 of the guidance channel forms a circus 66 larger than and offset to the guidance channel, the circular periphery of the circus 66 being tangent to one of the lateral borders 64 of said channel. The term circus is mainly utilized in reference to the circular shape of the feature but, other terms such cylindrical recess could be used as well. The narrow spray hole 54 is decentred relative to the circus 66 and it opens in the vicinity to said circular periphery with the offset D relative to the guidance channel radial axis. As shown by the arrows A representing the flow, the reagent follows the guidance channel 52 and enters the circus 66, following the circular periphery and making a swirl S prior to enter the spray hole 54.

In said first and second embodiments, the guidance channel 52 is straight and radially aligned. In non-represented alternatives, said guidance channel 52 may be curved to initiate the swirl motion of the reagent flow in the step hole 60 (first embodiment) or in the circus 66 (second embodiment).

In a third embodiment illustrated in figures 9, 10 and 11, each outlet path 26 comprises a first guidance channel 68 and a second guidance channel 70, both channels merging in the same entry step hole 60 of a spray hole 54. Said guidance channels 68, 70 are curved, although that in another alternative they could be straight, and are limited within an inner lateral border 64i having a smaller curvature than an outer lateral border 64o.

The width W of the guidance channel is substantially half the diameter of the step hole 60 so, the outer lateral border 64o of the first guidance channel 68 (left of figure 11) tangentially merges in the step hole 60 while the inner border 64i of said first guidance channel 68 joins the step hole approximately perpendicularly. Symmetrically, the inner lateral border 64i of the second guidance channel 70 (right of figure 11) tangentially merges the step hole 60 while the outer border 64o is perpendicular to it. Both reagent flows enter said step hole 60 via said first 68 and second 70 guidance channels in diametrically opposed areas and, they form a swirl S rotating in the same direction, finally entering the narrow exit portion 62 of the spray hole.

In figure 11, the guidance channels 68, 70 are represented having a constant width W while in the alternatives of figures 9 and 10 the upstream portion 56 has a larger width W than the downstream portion 58, the channel smoothly narrowing as approaching the spray hole.

In an alternative not represented, the spray hole 54 may be entirely narrow, same as in the second embodiment without step hole, and the two guidance channels 68, 70 both arrive tangentially in a common circus 66 at the centre of which opens said spray hole 54.

Figures 12 to 14 illustrates further embodiments of the present invention where the spray holes 64 are served by several guidance channels joining and forming a guidance network 72. All said examples have three spray holes but similar principles apply to any other number of holes 54.

In a fourth embodiment of figure 12 said guidance network 72 is starshaped, the center of the star being in the body opening 16, each of the three branches of the star radially extending to tangentially join the step hole 60 of a spray hole 54 drilled between said body opening 16 and said clamp hole 46. Said star branches have a width W that narrows as getting closer to the spray hole, the three large upstream ends joining in a central area. In other alternatives, said branches may have a constant width and said holes may be entirely narrow, without step hole, the star branches forming a circus at their downstream end.

In a fifth embodiment of figure 13, said guidance network 72 comprises three branches 74 each radially extending and passing between two spray holes from a central area inside said body opening 16 to a common circular channel 76 which outwardly surrounds the spray holes 54. Said circular channel tangentially joins all the step holes 60, or alternatively all the circus 66. Said three branches have a constant width W and their upstream portions 56 do not merge in the central area but, in an alternative, said upstream portions could merge.

In a sixth embodiment of figure 14, the spray holes are connected two by two by straight channels forming together a triangular network 72. Each of the straight channel tangentially joins a step hole, or alternatively a circus, and half way between said holes, said channels open in said body opening 16. In use, the reagent flow enters said channel in the middle of it and divides in a first sub-flow going toward a spray hole and a second sub-flow going toward the other spray hole.

LIST OF REFERENCES

X main axis

A flow

S swirl

D offset nozzle assembly

SCR injector body opening seat pusher ball flow director member outlet path clamp member cylindrical wall transverse wall flat area of the flow director member raised lip of the flow director member inner face of the flow director member outer face of the flow director member flat area of the clamp raised lip of the clamp hole in the clamp inner central circular portion of the inner face of the flow director member outer central circular portion of the outer face of the flow director member sac guidance channel - 1st and 2nd embodiment spray hole upstream portion downstream portion entry portion of the spray hole - step hole narrow exit portion of the spray hole lateral border of the guidance channel circus first guidance channel - 3rd embodiment second guidance channel - 3rd embodiment guidance network star branches circular channel

Claims

CLAIMS:

1. Nozzle assembly (10) of an injector (12) extending along a main axis (X) and having, a body (14) and a valve member (22) cooperating, in use, to control access of a fluid flow (R) to an outlet path (26) comprising a guidance channel (52) comprising an upstream portion (56) wherein, in use, the flow enters, and a downstream portion (58) wherefrom the flow exits via a spray hole (54), the guidance channel (52) and the spray hole (54) being arranged to force the flow to a swirl (S) motion when entering said spray hole.

2. Nozzle assembly (10) as claimed in the preceding claim wherein the spray hole (54) is drilled with an offset (D) relative to the direction of said downstream portion (58) .

3. Nozzle assembly (10) as claimed in claim 2 wherein the spray hole (54) comprises a large entry portion (60) joining via a shoulder a narrow exit portion (62), said large entry portion (60) forming a step hole (60) wherein the flow enters and swirl (S).

4. Nozzle assembly (10) as claimed in clam 2 wherein the guidance channel (52) comprises a circus (66) for the flow to swirl, said circus being arranged at the end of the downstream portion (58), the spray hole (54) opening in said circus (66).

5. Nozzle assembly (10) as claimed in any one of the preceding claims wherein the guidance channel (52) comprises several branches each leading to the spray hole (54).

6. Nozzle assembly (10) as claimed in any of the preceding claims comprising a plurality of spray holes (54).

7 Nozzle assembly (10) as claimed in claim 6 wherein all spray holes (54) are substantially equidistant from the nozzle main axis (X).

8. Nozzle assembly (10) as claimed in any one of the claims 6 or 7 wherein, the guidance channel (52) joins several spray holes (54).

9. Nozzle assembly (10) as claimed in any of the preceding claims wherein the guidance channel (52) comprises an arcuate portion.

10. Nozzle assembly (10) as claimed in any of the preceding claims wherein the guidance channel (52) comprises a straight portion.

11. Nozzle assembly (10) as claimed in any one of the preceding claims further comprising a flow director member (24) arranged to cover the nozzle body (14), said outlet path (26) being provided in said flow director member(24).

12. Nozzle assembly (10) as claimed in claim 11 wherein the flow director member(24) closes an opening (16) of the body and partially defines a sac (51) volume, the upstream portion (56) of the guidance channel (52) opening in said sac to the downstream portion (58) being outside said sac (51) and being covered by the body (14).

13. Injector (12) comprising a nozzle assembly (10) as claimed in any one of the preceding claims.

14. Selective Catalytic Reduction injector as claimed in claim 13 adapted to spray a reagent fluid (R) in the exhaust pipe of an internal combustion engine.