EP3274582B1

EP3274582B1 - Control valve arrangement

Info

Publication number: EP3274582B1
Application number: EP16702576.6A
Authority: EP
Inventors: David Bonneau; Peter Voigt; Richard Denis Jacques Alain ENTERS
Original assignee: Delphi Technologies IP Ltd
Current assignee: Delphi Technologies IP Ltd
Priority date: 2015-03-26
Filing date: 2016-02-03
Publication date: 2019-06-05
Anticipated expiration: 2036-02-03
Also published as: EP3274582A1; WO2016150603A1; CN107429651A; CN107429651B; GB201505094D0

Description

TECHNICAL FIELD

The present invention relates generally to a fuel injector and more particularly to a control valve arrangement.

BACKGROUND OF THE INVENTION

In a fuel injector, a control valve indirectly controls the motions of a valve member, also identified as a needle in reference to its elongated shape, by opening and closing an outlet conduit enabling fuel at high pressure to exit a control chamber which internal pressure solicits the needle.
The control valve comprises a cylindrical body extending between a first transverse face and a second transverse face. The body is further provided with a hydraulic bore opening in a recess, itself largely opening in the first transverse face. In the bore is slidably arranged a valve spool integral within a magnetic armature-and-spool-assembly. While the spool slides in the bore, the disc-shape armature displaces in the recess as a function of a magnetic field generated by a controlled solenoid. The spool and body further define a valve seat which opens or closes when said assembly translates. To flow the fuel from the control chamber to the hydraulic bore, the outlet conduit is usually made of two distinct straight portions. A long portion extends from the second face to the hydraulic bore. When the valve body is arranged within the injector, the transverse faces are in sealing surface contact with complementary faces of other injector bodies so, the long straight portion is then sealed at its extremity opening on the second face. The outlet conduit also comprises a short portion opening in the second face in a location that is in fluid communication with the control chamber and, said short portion extends toward the long portion and opens into it in a T-junction. In operation, when the valve seat opens, the fuel at high pressure exits the control chamber by flowing in the short portion up to the T-junction where it deviates and follows the long portion of the outlet channel until reaching the hydraulic bore. The short and long portions are typically cylindrical of relatively similar diameter. An extremely high level of mechanical stresses has been measures in the area of the T-junction and, the high frequency of the valve operation leads to mechanical damages in said T-junction area. EP1657435 discloses a fuel injector having a control valve of the prior art.

SUMMARY OF THE INVENTION

It is an object of the invention to resolve or at least mitigate the above mentioned problem with a valve body of the control valve of a fuel injector, said body extending along a main axis from a first transverse face, adapted to be in sealing surface contact against an actuator assembly and, a second transverse face adapted to be in sealing surface contact against an upper face of a nozzle assembly. The nozzle assembly is provided with a valve member moveable between a closed position and an open position under the influence of fuel pressure in a control chamber, and, the valve body is provided with an inlet line, wherein in use flows high pressure fuel toward an opening that in use is in fluid communication with the control chamber and with, an outlet line in which, in use, fuel exits the control chamber and flows to a drain or low pressure reservoir.
The outlet line comprises a valve having a valve spool slidably arranged in a hydraulic bore, a main outlet conduit extending in the valve body from the second transverse face to the hydraulic bore. The opening of said main outlet conduit in the second transverse face is sealingly closed in use, by the upper face of the nozzle assembly. The outlet line also comprises a restricted outlet conduit opening in the second transverse face in a place that, in use, is in fluid communication with the control chamber, the restricted outlet conduit extending to a T-junction where it joins the main outlet conduit.
In the area of the T-junction, the main outlet conduit has a specific non-circular cross section having a curvature bigger than the curvature of the restricted outlet conduit.
And in the area of the T-junction, the main outlet conduit has a specific non-circular cross section that is at least four times the curvature of the restricted outlet conduit and said cross section having a curvature at least four times bigger than the curvature of the restricted outlet conduit.
Also, in the area of the T-junction, the main outlet conduit has a flat face in which opens the restricted outlet conduit.
More particularly, in the area of the T-junction, the main outlet conduit has an oblong cross section, the restricted outlet conduit opening in a flat face of the oblong section.
In another embodiment, in the area of the T-junction, a portion of the main outlet conduit has an enlarged radius curvature in which opens the restricted outlet conduit.
As an example of said another embodiment, the main outlet conduit has an elliptical cross section, the restricted outlet conduit opening in the larger radius of the ellipsis, so that the axis along which extends the restricted outlet conduit perpendicularly intersects the main axis of the ellipsis.
Also, whatever the embodiment, the main outlet conduit may have a constant cross section all along its length.
To the contrary, it is possible that the specific cross section of the main outlet conduit is limited to a portion of the length, said portion comprising the T-junction.
Also, the restricted outlet conduit may have a circular cross section.
The invention further extends to a control valve assembly having a control valve body as set in any one of the preceding paragraphs.
The invention further extends to a fuel injector comprising an actuator, a nozzle assembly, and a control valve assembly as set in the preceding paragraphs.

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 a partial axial section of a fuel injector provided with a control valve arrangement as per a first embodiment of the invention.
Figure 2 is an axial section of the control valve of figure 1.
Figure 3 is a translucid isometric view of the body of the valve.
Figure 4 is a magnified detail of figure 3 viewed from the opposite direction as in figure 3.
Figures 5, 6 and 7 are detailed sketches of different embodiments of the body of the valve.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In reference to figure 1 is described a fuel injector 10 extending along a main axis X1 and which comprises the stack-up of nozzle assembly 12 over which are a control valve assembly 14 then an actuator assembly.
The nozzle assembly 12 comprises the complementary arrangement of an elongated cylindrical nozzle body 16 over which is positioned an upper guide body 18. This arrangement 16, 18, axially X1 extends from a transverse upper face 20 of the upper guide body 18 to a pointy tip 22 of the nozzle body 16. This arrangement 16, 18, is also provided with an internal axial bore 24 in which a needle 26 is slidably arranged and guided between an upper guiding means 28 and a lower guiding means 30. The upper guiding means 28 comprises the top end 32 of the needle 26 adjusted in a guiding bore 34 axially arranged in the upper guide body 18 and, the lower guiding means 30 comprises a cylindrical face 36 of the needle 26 adjusted in a lower portion 38 of the bore 24.
The control valve assembly 14 comprises a cylindrical valve body 36 axially X1 extending between a first transverse face 38, drawn on the top of the figure, and, a second transverse face 40 that is in surface sealing contact against the upper face 20 of the upper guide body 18.
Said valve body 36 is also provided with a hydraulic bore 42 that extends along a second axis X2 parallel and offset relative to the main axis X1. This offset, introduced in EP0740068 , presents many advantageous characteristics. Such an injector is used for the purpose of the present description but, the invention could also benefit other injectors were the two axis are aligned. Said hydraulic bore 42 opens in the bottom face 44 of a large recess 46, itself opening in the first transverse face 38 of the valve body.
The valve body 36 is further provided with an outlet line 48 comprising a main outlet conduit 50 and a restricted outlet conduit 52. The main outlet conduit 50 extends along an axis A50 from the second transverse face 40 of the valve body to the hydraulic bore 42 while, the restricted outlet conduit 52 extends along an axis A52 from the also from the second transverse face 40 of the valve body but joins and interconnects with the main outlet conduit 50 into a T-junction 54. As visible on figure 2, the main outlet conduit 50 and restricted outlet conduit 52 interconnect forming an angle A that is substantially a right angle and, the restricted outlet conduit 52 has, perpendicularly to its axis A52, a smaller cross section S1 than the cross section S2, perpendicular to the axis A50 of the main outlet conduit 50, the restricted outlet conduit forming a fluid restriction.
When arranged in surface sealing contact with the nozzle assembly 12, the main outlet conduit 50 is sealingly closed by the transverse upper face 20 of the upper guide and, the restricted outlet conduit 52 opens over a control chamber 56 arranged in the guiding bore 34 above the needle 26. The restricted outlet conduit 52 opens in a semi spherical outlet recess provided the ceiling face of said control chamber 56 and, therefore the outlet line 48 has an entry in the control chamber 56 and an exit in the hydraulic bore 42.
In the hydraulic bore 42 is slidably arranged an armature-and-valve-spool assembly 58 that comprises a magnetic armature 62 having the shape of a thick disc at the centre of which is inserted and crimped a spool shaft 60. The spool shaft 60 is slidable in the hydraulic bore 24 and the armature 62 moves inside the recess 46. The opening on the hydraulic bore 42 in the bottom face of the recess 46 is surrounded by a valve seat 64 that opens or closes depending on the displacements of the armature-and-valve-spool assembly 58. When in open position the control chamber 56 is put in fluid communication with a drain or low pressure reservoir via the outlet line 48, the hydraulic bore 42 and the recess 46.
Under standard operational conditions the armature-and-spool assembly 58 may commute between the closed position and an open position at a frequency of several hundred Hertz meaning that fuel pressurised at 2000 bars, or more, flows through the T-junction 54 at the same frequency generating picks of mechanical stresses in the area. To minimize, or even eliminate, damages potentially generated in the area of the T-junction 54 by said stresses, the section S2 of the main outlet conduit 50 of the outlet line 48 is made oblong, the restricted outlet conduit 52 opening in a flat side of the oblong shape.
As visible on figure 3 and magnified on figure 4 and also sketched on figure 5, the main outlet conduit 50 of the line 48 has an oblong section S2 from its opening on the second transverse face 40 of the valve body to a point situated just upstream the T-junction 54. After that point, the section S2 changes into a circular section up to the other end opening in the hydraulic bore 42.
In an alternative embodiment the main outlet conduit 50 has an oblong section all along its length from the second transverse face 40 to the hydraulic bore 42.
The important factor in this design is that, at the T-junction 54, the restricted outlet conduit 52 joins the main outlet conduit 50 in an area where the radius R2 of curvature of the main outlet conduit 50 is much larger than the radius R1 of the restricted outlet conduit 52. In the present application the expression "much larger" is to be interpreted in that the radius R2 of the section S2 of the main outlet conduit 50 is "at least four time larger" than the radius R1 of the section S1 of the restricted outlet conduit 52, measured in the area where the two conduits merge. This is mathematically given by $\frac{R 2}{R 1} \geq 4$
An extreme choice is that the restricted outlet conduit 52 opens in a flat face 66 such as in an oblong section as previously described, which by definition has an infinite radius of curvature R2. Other possible choices are sketched on figures 6 or 7 where, on figure 6 the main outlet conduit 50 has an elliptic section S2, the restricted outlet conduit opening in the area of greatest radius R2. On figure 7, the main outlet conduit 50 has a semi-circular section S2, the restricted outlet conduit 52 opening in the flat side. Many other choices of sections being possible, those presented being just example.

LIST OF REFERENCES

X1: main axis
X2: valve axis
A: angle
S1: section of the short portion
S2: section of the long portion
R1: radius of the section of the short portion in the T-junction
R2: radius of the section of the long portion in the T-junction

10: injector
12: nozzle assembly
14: control valve assembly
16: nozzle body
18: upper guide body
20: transverse upper face of the upper guide
22: pointy tip of the nozzle
24: bore
26: needle
28: upper guiding means of the needle
30: lower guiding means of the needle
32: top end of the needle
34: guiding bore
36: valve body
38: first transverse face of the valve body
40: second transverse face of the valve body
42: hydraulic bore
44: bottom face of the large recess
46: large recess
48: outlet line
50: main outlet conduit
52: restricted oulet conduit
54: T-junction
56: control chamber
58: armature-and-valve-spool- assembly
60: spool shaft
62: magnetic armature
64: valve seat
66: flat face of the section of the main outlet conduit

Claims

Valve body (36) of the control valve (14) of a fuel injector (10), said body (36) extending along a main axis (X1) from a first transverse face (38), adapted to be in sealing surface contact against an actuator assembly and, a second transverse face (40) adapted to be in sealing surface contact against an upper face of a nozzle assembly that is provided with a valve member (26) moveable between a closed position and an open position under the influence of fuel pressure in a control chamber (56), said valve body (36) being provided with,
an inlet line wherein in use flows high pressure fuel toward an opening that in use is in fluid communication with the control chamber (56) and with,
an outlet line (48) in which, in use, fuel exits the control chamber (56) and flows to a drain or low pressure reservoir, said outlet line (48) comprising a valve having a valve spool (60) slidably arranged in a hydraulic bore (42), a main outlet conduit (50) extending in the valve body (36) along an axis (A50) from the second transverse face (40) to the hydraulic bore (42), the opening of said main outlet conduit (50) in the second transverse face (40) being sealingly closed in use, by the upper face of the nozzle assembly, and also with a restricted outlet conduit (52) opening in the second transverse face (40) in a place that, in use, is in fluid communication with the control chamber (56), the restricted outlet conduit (52) extending along an axis (A52) to a T-junction (54) where it joins the main outlet conduit (50),
characterized in that
in the area of the T-junction (54), the main outlet conduit (50) has a specific cross section (S2) perpendicular to its axis (A50) that is non-circular, said cross section (S2) having a curvature (R2) at least four times bigger than the curvature (R1) of the restricted outlet conduit (52).
Valve body (36) as claimed in the preceding claim wherein, in the area of the T-junction (54), the main outlet conduit (50) has a flat face (66) in which opens the restricted outlet conduit (52).
Valve body (36) as claimed in any one of the preceding claims wherein in the area of the T-junction (54), the main outlet conduit (50) has an oblong cross section, the restricted outlet conduit (52) opening in a flat face (66) of the oblong section.
Valve body (36) as claimed in claim 1 wherein in the area of the T-junction (54), a portion of the main outlet conduit (50) has an enlarged radius (R2) curvature in which opens the restricted outlet conduit (52).
Valve body (36) as claimed in claim 4 wherein in the area of the T-junction (54), the main outlet conduit (50) has an elliptical cross section, the restricted outlet conduit (52) opening in the larger radius (R2) of the ellipsis, so that the axis along which extends the restricted outlet conduit (52) perpendicularly intersects the main axis of the ellipsis.
Valve body (36) as claimed in any one of the preceding claims wherein the main outlet conduit (50) has a constant cross section all along its length.
Valve body (36) as claimed in any one of the preceding claims wherein the specific cross section (S2) of the main outlet conduit (50) is limited to a portion of the length, said portion comprising the T-junction (54).
Valve body (36) as claimed in any one of the preceding claims wherein the restricted outlet conduit (52) has a circular cross section.
Control valve assembly (14) having a control valve body (36) as claimed in any one of the preceding claims.
Fuel injector (10) comprising an actuator, a nozzle assembly, and a control valve assembly as claimed in claim 9.