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

BACKGROUND OF THE INVENTION

A fuel injector comprises the stack-up of a nozzle assembly, a control valve and an actuator assembly. The control valve indirectly controls the motions of a valve member, arranged in the nozzle assembly, by retaining or releasing fuel at high pressure in a control chamber also arranged in the nozzle assembly. This is done by opening and closing a fluid communication between the control chamber and a low pressure reservoir.

The control valve has a cylindrical body extending between a first transverse face adapted to be in sealing surface contact against a face of the actuator assembly and, a second transverse face adapted to be in sealing surface contact against an upper face of the nozzle assembly. In the valve body extend an inlet line and an outlet line, the inlet line having a main inlet conduit and a restricted inlet conduit and, the outlet line having a restricted outlet conduit, a main outlet conduit and a valve as such.

The main inlet conduit extends between the two transverse faces and, in use, fuel at high pressure flows from an upper inlet conduit extending in the actuator assembly, then through said main inlet conduit, then in a nozzle conduit extending in the nozzle assembly. In the valve body, the restricted inlet conduit extends from a first T-junction, where it joins the main inlet conduit, to the second transverse face where it opens in a location that, in use, is in fluid communication with the control chamber.

The restricted outlet conduit opens in the second transverse face, in a location that in use is also in fluid communication with the control chamber, and then it extends to a second T-junction where it joins the main outlet conduit. Said main outlet conduit also opens in the second transverse face, but in a location that in use is sealingly closed by the upper face of the nozzle assembly, then it extends to a valve bore, in which is slidably arranged a valve spool controlling a valve seat, that is said fluid communication between the control chamber and a low pressure reservoir. The main outlet conduit has a large cross section while the restricted outlet conduit has a much smaller cross section creating a restrictor through which only a restricted flow of fuel may flow to exit the control chamber.

While the main inlet conduit and the main outlet conduit have large cross section, the restricted inlet conduit and the restricted outlet conduit have small calibrated cross section creating flow restrictors through which only a limited flow of fuel may enter or exit the control chamber.

The restricted conduits are difficult to manufacture, difficult to clean and, as the maximum operational pressure of the fuel injectors regularly increases, said restricted conduits are areas of stress concentration where cracks may occur and propagate in the valve body.

SUMMARY OF THE INVENTION

It is an object of the invention to resolve or at least mitigate the above mentioned problem by proposing a body of the control valve of a fuel injector.

The body extends along a main axis from a first transverse face, adapted to be in surface contact against an actuator assembly and, a second transverse face, adapted to be in 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. The valve body is provided with:

an inlet line wherein, in use, flows high pressure fuel, the inlet line comprising a main inlet conduit extending between said two transverse faces, and also with a restricted inlet conduit extending between an opening in the second transverse face, that in use is in fluid communication with the control chamber, and the main inlet conduit and with,

an outlet line wherein, 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 the main outlet conduit in the second transverse face is sealed in use by the upper face of the nozzle assembly, and also with 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 extends and opens on the main outlet conduit.

At least one of the restricted inlet conduit or the restricted outlet conduit is a groove formed on the surface of the second transverse face so that, in use, said groove is sealingly covered and closed by the upper face of the nozzle assembly.

In another embodiment both the restricted inlet conduit and the restricted outlet conduit are grooves formed on the surface of the second transverse face.

The invention further extends to a control valve assembly having a control valve body as described in the preceding paragraphs.

The invention further extends to a fuel injector having a control valve assembly as described in the preceding paragraph.

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 axial section of a fuel injector.

- Figure 2 is a semitransparent isometric view of a valve body enabling to visualize the various internal channels therein made.

- Figure 3 is another semitransparent isometric view of the valve body focusing on the lower face of the body.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In reference to figure 1 is described a fuel injector 10 extending along a main axis XI and which comprises the stack-up of nozzle assembly 12 over which are a control valve assembly 14 then an actuator assembly 16.

The nozzle assembly 12 comprises the complementary arrangement of an elongated cylindrical nozzle body 18 extending from a transverse upper face 20 of to a pointy tip 22. The nozzle body 18 is also provided with an internal axial bore 24 in which a needle valve 26 is slidably arranged and guided between an upper guide 28 and a lower guide 30. The upper guide 28 comprises the top end 32 of the needle 26 adjusted in a guiding bore 34, the volume of said bore 34 that is above the top end 32 of the needle 26 forming a needle valve control chamber 36. The lower guide 30 comprises a cylindrical face of the needle 26 adjusted in a lower portion of the bore 24.

The control valve assembly 14 comprises a cylindrical valve body 38 axially XI extending between a first transverse face 40, drawn on the top of the figure, and, a second transverse face 42 that is in surface sealing contact against the upper face 20 of the nozzle body 18.

The valve body 38 is now detailed in reference to figures 2 and 3. In the valve body 38 extend an inlet line 44 and an outlet line 46 in which, in use, fuel may flow to enter or exit the control chamber 36.

The inlet line 44 comprises a main inlet conduit 48 and a restricted inlet conduit 50. The main inlet conduit 48 extends between an upper opening 52 in the first transverse face 40 and a lower opening 54 in the second transverse face 42 and, the restricted inlet conduit 50 is indeed a groove formed on the surface of the second transverse face 42 and extending between the lower opening 54 and an inlet semi-spherical recess 56 also formed in the second transverse face 42.

The outlet line 46 comprises a restricted outlet conduit 58, a main outlet conduit 60 and a valve 62, itself having a hydraulic bore 64 adapted to receive in a slidable arrangement an armature-and- spool-assembly 66. The hydraulic bore 64 axially extends along a valve axis X2 that is parallel and offset from the main axis XI . This offset was introduced in EP0740068 and it presents many advantageous characteristics benefitting the injector. 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.

The hydraulic bore 64 opens in the bottom face of a large recess 68, itself opening in the first transverse face 40 of the valve body. The opening of the hydraulic bore 64 at the bottom of the recess 68 forms a valve seat 70 that may, as a function of the valve spool 66 position, open or close a fluid communication between the hydraulic bore 64 and a drain or low pressure reservoir. The main outlet conduit 60 extends in straight direction from an opening 72 in the second transverse face 42, said opening being in use sealingly closed by the upper face of the nozzle body, to an opposite end opening in the hydraulic bore 64. The restricted outlet conduit 58 is indeed also a groove formed on the surface of the second transverse face 42 and extending between the opening 72 of the main outlet conduit in the second transverse face and an outlet semi-spherical recess 74 also formed in the second transverse face 42.

All the transverse faces have mirror surface finish so, when the injector 10 is fully assembled, the second transverse face 42 is in surface contact against the transverse upper face 20 of the nozzle body and the opening 72 of the main outlet conduit in the second transverse face and the restricted conduits 50, 58, are sealingly covered and closed. To the contrary, the opening 54 of the main inlet conduit in the second transverse face is in fluid continuity with another portion of the inlet line, said another portion extending in the nozzle assembly and, the inlet and outlet recesses 56, 74, are in fluid communication with the control chamber 36.

In operation, fuel at high pressure flows in the main inlet conduit 48 and, a limited quantity of fuel flows through the restricted inlet conduit 50 to enter the control chamber 36.

When the valve seat 70 is closed, the pressure in the control chamber 36 increases and the needle valve 26 is pushed in a closed position.

When the valve seat 70 is open, the fuel pressurized in the control chamber 36 is enabled to exit and it flows through the restricted outlet conduit 58 until it joins the main outlet conduit 60 then the hydraulic bore 64.

This arrangement of restricted conduits 50, 58, as grooves in the second transverse face 42 of the valve body is easier to manufacture that the standard drilling through the body; it is easier to clean the groove after manufacturing. Also, the standard drillings have circular cross sections while the grooves enable other shapes such as a rectangular or triangular cross sections.

LIST OF REFERENCES XI main axis

X2 valve axis

10 injector

12 nozzle assembly

14 control valve assembly 16 actuator assembly

18 nozzle body

20 transverse upper face of the nozzle body

22 pointy tip of the nozzle

24 bore

26 needle

28 upper guide of the needle

30 lower guide of the needle

32 top end of the needle

34 guiding bore

36 control chamber

38 valve body

40 first transverse face of the valve body

42 second transverse face of the valve body

44 inlet line

46 outlet line

48 main inlet conduit

50 restricted inlet conduit

52 opening of the main inlet conduit in the first transverse face

54 opening of the main inlet conduit in the second transverse face

56 inlet recess

58 restricted outlet conduit

60 main outlet conduit

62 valve arrangement

64 hydraulic bore

66 armature-and- valve-spool- assembly

68 large recess

70 valve seat

72 opening of the main outlet conduit in the second transverse face

74 outlet recess