CONTROL VALVE OF A FUEL INJECTOR

Abstract

 A control valve (16) of a fuel injector is provided with a cylindrical valve body (42) extending along a main axis from an upper face (44) to a lower face (46), said body (42) being provided with a large cylindrical shallow recess (48) opening in said upper face (44) and in the bottom of which opens a valve distributor bore (50) axially extending toward the lower face (46). The control valve further has a magnetic armature-stem assembly (62) and, guiding means (56) for slidably guiding the armature-stem assembly (62) into the valve bore (50) and with seating means (70, 72, 74), distinct and independent means from the guiding means (56), for opening or closing a fluid communication between a high pressure conduit (112) and a return conduit (110), both conduits opening in said bore (50).

Description

TECHNICAL FIELD

[0001] The present invention relates to a fuel injector and more particularly to a control valve.

BACKGROUND OF THE INVENTION

[0002] Fuel injectors known in the art are provided with control valve controlling the fuel pressure in a control chamber that cooperates with a valve needle in order to enable or forbid fuel spray.

[0003] The control valve comprises a cylindrical body extending axially from an upper face to a lower face and provided with a shallow recess opening in the upper face and from the center of the bottom of which extends toward the lower face a valve bore in which open a high pressure conduit in fluid communication with said control chamber and, a return conduit in fluid communication with a low pressure reservoir. A cylindrical sleeve is fixedly arranged in the bore by means of two press fitted annular areas, one being at the upper extremity of the bore, the other being at the lower extremity of the bore. Inside the sleeve is slidably arranged the stem of an armature-stem assembly that cooperates with a coil generating a magnetic field. The high pressure conduit laterally opens in the bore, between the press fit annular areas and, the return conduit comprises the shallow recess that creates a low pressure chamber.

[0004] The armature-stem assembly slides between an upper position where it opens a valve seat creating a fluid communication between the high pressure conduit and the return conduit and, a lower position wherein said valve seat is closed. The valve seat comprises a fixed face that is an upper face of the sleeve and a mobile face that is a conical face of the stem arranged just under the armature.

[0005] It has been observed that, in use, under the influence of the high pressure fuel surrounding the sleeve, said sleeve shrinks in diameter and consequently to stretch out in length. These variations are of micrometers, or even sub-micrometers, but still the elongations generate micro displacement that are not prevented by the press fit areas and that are detrimental to the correct operation of the control valve, especially in that the valve seat slowly displaces.

SUMMARY OF THE INVENTION

[0006] Accordingly, it is an object of the present invention to solve the above mentioned problems in providing a control valve of a fuel injector, said valve being provided with a cylindrical valve body extending along a main axis from an upper face to a lower face. The body is provided with a large cylindrical shallow recess opening in said upper face and in the bottom of which opens a valve distributor bore axially extending toward the lower face. The control valve is further provided with a magnetic armature-stem assembly, the magnetic armature having a thick disc-shape in the centre of which is enshrined and crimped a cylindrical stem shaft extending perpendicularly from the armature to a lower extremity and, guiding means for slidably guiding the armature-stem assembly into the valve bore and with, seating means, for opening or closing a fluid communication between a high pressure conduit and a return conduit, both conduits opening in said bore.

[0007] The seating means and the guiding means are distinct and independent means.

[0008] More particularly, the guiding means is a cylindrical sleeve extending from an upper extremity to a lower extremity and fixedly press fitted in the valve bore, the stem being slidably engaged in said sleeve and, the seating means comprises a valve seat having a fixed face surrounding the opening of the return conduit cooperating with a mobile face integral to the stem.

[0009] Also, the sleeve is fixed in the bore by means of a single annular area of interference with the bore. Particularly, the single annular area of interference is a proximal an extremity of the sleeve and the fixed face of the valve seat is proximal the opposite extremity of the sleeve.

[0010] The valve bore opens in the lower face of the body, said single annular area of interference being proximal to said lower face and, the valve seat is in the opening of bore in the bottom of the recess, the fixed face being the interconnecting face surrounding the opening of the valve bore in the recess, the mobile face being a conical face of the stem proximal the armature.

[0011] In a particular embodiment, the high pressure conduit laterally opens in the valve bore and the shallow recess is part to the return conduit, the sleeve being provided with radial through holes enabling, in use the high pressure fuel to flow from the high pressure conduit, through the sleeve and into the return conduit.

[0012] In specific embodiments, the valve bore is a through bore opening in the recess and in the lower face of the body, the single annular area of interference being proximal to the recess an, the valve seat is in the opening of bore in the lower face of the valve body, the mobile face of the valve seat being the lower extremity of the stem adapted to cooperate with a fixed face surrounding a return conduit provided in a nozzle body and opening axially in the valve bore.

[0013] The invention also extends to an arrangement of a control valve as described above and a nozzle assembly. The upper face of the nozzle body is in surface sealing abutment against the lower face of the control valve and, the opening of the return conduit in the upper face of said nozzle body is axially centred in the opening of the valve bore in the lower face of the valve body. The fixed face of the seat is the face surrounding the opening of the return conduit in said upper face of the nozzle body.

[0014] The invention further extends to a fuel injector comprising a control valve as mentioned above.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The present invention is now described by way of example with reference to the accompanying drawings in which:

Figure 1 is a longitudinal section of a fuel injector provided with a control valve as per the invention.

Figure 2 is a section of a control valve as per a first embodiment of the invention.

Figure 3 is a section of a control valve as per a second embodiment not part to the invention.

Figure 4 is a section of a control valve as per a third embodiment of the invention.

Figure 5 is a magnified view of the control valve of figure 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] As per figure 1 is represented a fuel injector 10 extending along a longitudinal axis A1 and which comprises from top to bottom, according to the non-limiting orientation of the figure, a head 12, an actuation member 14, a control valve 16 and a nozzle assembly 18.

[0017] As mentioned, the orientation of figure 1 will serve the description and for clarity and simplification purposes terms such as "right, left, high, low, over, under, upper, lower, above or below" may be utilized without intention to limit the scope of the application.

[0018] The head 12 in integral to the top of the actuation member 14 and is provided with an inlet 20, adapted to be connected to a high pressure fuel source such as a common rail reservoir, and also with an outlet 22, barely visible on the figure, adapted to be connected a low pressure return line leading to a low pressure reservoir.

[0019] The actuation member 14 comprises an elongated body 24, also identified as a "nozzle holder body, or NHB", mainly cylindrical, extending from the head 12 to a lower transversal face 26. Externally, in the vicinity of said lower face 26, the body 24 is provided with a male thread 28 for complementary engagement of the female thread 30 of a capnut 32.

[0020] Internally, the body 24 is provided with a bore 34 extending along a second axis A2, parallel and distinct from the longitudinal axis A1, said bore 34 opening in the lower face 26 and, in said bore 34 is fixedly arranged an electrical coil 36 whose underside is flush with the lower face 26 of the body 24. From the top of the coil 36 extend, through a specific channel, electrical connecting members 37, such as rigid cables, which connect to a connector 38 enabling electrical link of the coil 36 to a non-represented control unit. The coil 36 itself is further provided with a central bore 39 opening on said underside and in which is arranged a valve spring 40 slightly protruding out of said bore 39.

[0021] The body 24 is further provided with fuel conduit that will be detailed later.

[0022] The control valve 16 comprises a cylindrical body 42 which extends from an upper face 44, arranged in sealing abutment against the lower face 26 of the actuator body, to a lower face 46. Internally, the valve body 42 is provided with a wide and shallow recess 48 opening in said upper face 44 and from the bottom of which extends along the second axis A2 and toward the lower face 46 a hydraulic distributor bore 50.

[0023] The injector represented on figure 1 which serves this description is just a non-limiting example of injector and numerous alternative embodiments exist and will be mentioned but, those alternatives which would be unintentionally omitted would not be excluded for the scope of protection provided by the claims. As an example, the longitudinal axis A1 and the second axis A2 have been described as distinct and parallel. This offset, introduced originally in patent EP1693563, presents numerous advantages but injectors having both axes coincident exist and can also benefit from the teachings of the present invention.

[0024] In a first embodiment of the control valve 16, represented in figure 2, said distributor bore 50 is a through bore opening in the lower face 46 of the valve body. In the wide and shallow recess 48, the bore 50 opens with a narrow upper neck 52 that continues into a larger lower section 54. In said larger lower section 54 is fixedly press fitted a cylindrical sleeve 56 provided with a plurality of radial through holes 58. The sleeve 56 and the bore 54 have a single area of interference 60 which is in the vicinity of the lower face 46 of the valve body. Indeed, during the manufacturing process, the sleeve 56 is upwardly inserted in the bore 54 from said lower face 46 and, at first, the insertion is easy and requires no force at all, it is only when approaching the full insertion that the sleeve 56, provided with a slightly larger section, comes in interference with the bore 54 and a higher force is required to complete the insertion operation.

[0025] The control valve 16 further comprises a moving member slidably arranged in the sleeve 56. Said member is an armature-stem assembly 62 comprising a magnetic armature 64 that has a thick disc-shape in the centre of which is enshrined and crimped the upper extremity of a cylindrical stem shaft 66 extending perpendicularly to the armature 64 toward a lower extremity 68. As visible on the figures, the stem 66 is inserted in the sleeve 56 so the armature 64 is arranged in the recess 48.

[0026] In the bottom of the recess 48, the recess 48 and the narrow upper neck 52 connect in a female conical face, or alternatively toroidal, said face constituting the fixed face 70 of a valve seat 72, said fixed face 70 cooperating with a complementary male conical face 74 integral to the stem 66 forming the mobile face 74 of the valve seat 72.

[0027] As said, once in place in the valve body 42 the armature-stem assembly 62 can translate between an upper position, or open position OPV of the valve seat 72 where the mobile face 74 is at a distance from the fixed face 70 and, a lower position, or closed position CPV of the valve seat 72 where both faces 70, 74, are in sealing contact. The armature-stem assembly 62 is permanently solicited toward the closed position CPV by the valve spring 40 that protrudes out of the central bore 39 of the coil and abuts against the head of the stem that is flush in surface, or slightly exceed in the centre of the armature 64.

[0028] The fuel injector 10 of figure 1 further comprises, below the control valve 16, the nozzle assembly 18 which comprises a nozzle body 76 downwardly extending along the longitudinal axis A1 from an upper face 78, that is in sealing abutment against the lower face 46 of the valve body, into an upper large section 80, then into a lower thinner section 82 having a pointy lower extremity forming an injection nozzle 84 provided with a plurality of spray holes 86. The upper and lower sections 80, 82, connect through an annular shoulder 88 and, as shown on figure 1, the lower section 82 is inserted in the capnut 32 which comes in abutment against said shoulder 88 then upwardly extends over the control valve 16 and complementary threads 28, 30, on the actuation member 24.

[0029] The stack is sealed thanks to the mirror quality of the surfaces in contact and also to the important torque applied to the capnut 32.

[0030] The nozzle body 76 is provided with an axial A1 main bore 90 in which is slidably arranged a needle valve 92 guided between an upper guide 94, in the vicinity of the upper face 78 of the nozzle body, and a lower guide 96 in the vicinity of the spray holes 86. The needle 92 axially extends from a head 98 arranged in the upper guide 94 to a pointy lower extremity 100 that cooperates with the inner face of the nozzle body to form an injection valve 102 enabling, or forbidding, fuel spray through the spray holes 86.

[0031] Above the head 98 of the needle, the space in the upper guide 94 forms a control chamber 104 in which is compressed a needle spring 106 between the head 98 of the needle and the lower face 46 of the valve body that forms the ceiling of the control chamber 104. In place, the needle valve 92 is able to axially translate between an upper, or open position OPN, and a lower, or closed position of the needle CPN. In open position OPN the injection valve 102 is open enabling fuel spray and, in closed position CPN the injection valve 102 is closed preventing fuel spray.

[0032] In the fuel injector of figure 1, the upper guide 94 is integral to the nozzle body 76. Alternative embodiments exist where the upper guide is an independent component sandwiched between the nozzle body and the control valve. The present invention can benefit all alternatives, whatever the embodiment.

[0033] The fuel injector 10 is further provided with a high pressure fuel circuit 108 and also with a return circuit 110. The high pressure circuit 108 comprises a plurality of conduits complementary arranged to enable high pressure fuel to flow from the inlet 20 to the spray holes 86 and also into the control chamber 104.

[0034] The return circuit 110 also comprises a plurality of conduits complementary arranged to enable fuel to return from the control chamber 104 to the outlet 22. In this first embodiment, the return circuit 110 comprises an evacuation conduit 112 extending from the control chamber 104 and opening in the lateral face of the distributor bore 50, then it continues through the radial through holes 58 of the sleeve 56, then upwardly in the upper neck 52 of the distributor bore where it opens in the recess 48 forming a low pressure chamber. Further conduits enable the fuel to flow from said chamber toward the outlet.

[0035] The operation of the fuel injector 10 is now briefly described.

[0036] In a first step the coil 36 is not electrically energized, it does not generate a magnetic field and so it does not attract the armature 64. Therefore the armature-stem assembly 62 is pushed by the valve spring 40 in the closed position CPV of the valve. The high pressure fuel that permanently enters via the inlet 20 pressurizes the control chamber 104 which solicits the valve needle 92 toward the closed position CPN where fuel spray is prevented.

[0037] In a second step the coil 36 is electrically energized and it generates a magnetic field that attracts the armature 64. The armature-stem assembly 62 upwardly moves into the open position OPV of the valve. The high pressure fuel contained into the control chamber 104 can now exit via the evacuation conduit 112, the through holes 58, between the fixed 70 and mobile faces 74 of the valve seat 72 and enter the low pressure chamber 48. This evacuation creates a pressure drop in the control chamber 104 and, the pressure differential thus created between the two ends of the needle 92 displaces said needle 92 toward the open position OPN enabling fuel spray.

[0038] During this second step, the high pressure fuel evacuated from the control chamber 104 gets around the sleeve 56 which shrinks and slightly elongates. As the lower extremity of the sleeve 56 is fixed in the bore 54, the elongation occurs in the upper extremity of the sleeve 56 that is free. Also, as the valve seat 72 is independent from the sleeve 56, said slight shrinking and elongation do not affect in anyway the quality to the operation of the valve seat 72.

[0039] A second embodiment of the control valve 16, not part to the invention, is now described in reference to figure 3, and by way of differences with the first embodiment.

[0040] Although the general principle of having a sleeve fixed in the hydraulic bore thank to a single area of press fit and, said sleeve not being part of the valve seat, the major difference of this second embodiment is that the sleeve is fixed by press fit in its upper area, close to the recess 48 and the valve seat 72 is at the bottom of the distributor bore 50.

[0041] As visible on figure 3, the distributor bore 50 is a blind bore and does not open in the lower face 46 of the valve body. Instead, at the lower end of the bore 50 centrally opens a return conduit 114 of smaller diameter than said bore 50, said return conduit 114 making a right angle turn to radially extend through the valve body 42, Alternatives exists with other angles than a right angle. The face surrounding the opening of the return conduit 114 forms the fixed face 70 of the valve seat 72 and, the lower extremity 68 of the stem is complementary shaped forming the mobile face 74 of the valve seat 72.

[0042] As visible on the figure, the sleeve 56 is downwardly inserted from the recess 48 and the single area of interference 60 with the bore 50 is in the upper side, in the vicinity of said recess 48. In place, the stem 66 extends through the sleeve 56 and protrudes at the lower extremity of the sleeve 56 so that the faces 70, 74, of the valve seat close in sealing contact when the armature-stem assembly 62 is in closed position CPV

[0043] Furthermore, the evacuation conduit 112 still laterally opens in the distributor bore 50 but, when the valve seat in open the fuel evacuates directly into the return conduit 114and, the sleeve 56 of this second embodiment is not provided with radial through holes.

[0044] A third embodiment of the control valve 16 is now described in reference to figures 4 and 5, and also by way of differences with the previous embodiments.

[0045] The general principles remain but, for this third embodiment the distributor bore 50 is a through bore opening in the recess 48 and also in the lower face 46 of the valve body. The bore comprises an upper section of a smaller diameter and a little shorter than a lower section that is of a slightly larger diameter and slightly longer.

[0046] The sleeve 56 extends through both sections, the sleeve 56 being press fitted in interference in the upper section and being free in the lower section.

[0047] The stem 66 comprises two distinct members, an upper stem 116 enshrined and crimped in the armature and, a lower stem 118 having at its lower extremity 68 the transversal mobile face 74 of the valve seat 72. Optionally, as shown on the figure, said mobile face is provided with a small central protrusion downwardly extending and engaging without any contacts in the opening of the return conduit 114.

[0048] In this third embodiment the sleeve 56 is upwardly inserted in the bore 50 from the lower face 46 of the valve body. At first the insertion does not require efforts and when the sleeve 56 engages into the upper section then the insertion effort grows.

[0049] Once the sleeve 56 is in place, the armature-upper stem assembly is downwardly inserted from the central opening of the sleeve from the recess and, the lower stem 118 is upwardly inserted in the sleeve 56 from the opening of the bore 50 in the lower face 46 of the valve body. The upper 116 and lower 118 stems are in contact with each other but are not fixed to each other.

[0050] As visible on figure 4, and even magnified in figure 5, the return conduit 114 is entirely arranged in the nozzle body 76. It radially extends just below the upper face 78 until it reaches the second axis A2 where an axial smaller section upwardly opens in the upper face 78, exactly in the center of the opening of the bore 50 into the lower face 46 of the valve body. Alternatively, in a fuel injector having a non-integral upper guide the return conduit would be provided in said upper guide element.

[0051] Also, the evacuation conduit 112 upwardly opens in the bottom of the distribution bore 50. The upward opening of the discharge conduit 112 in the hydraulic distribution bore 50 is not closed by the lower end of the stem 68. Although the section plane of the figures represents said opening beneath end stem, said opening is permanently open.

[0052] The operation of this third embodiment is now briefly described.

[0053] At first, the coil 36 is not energized and the armature-stem assembly 62 is downwardly pushed by the valve spring 40 toward a closed position CPV of the valve. The upper stem 116 pushes the lower stem 118 which lower extremity 68 seals the return conduit 114. The high pressure built in the control chamber 104 forces the needle valve 92 into the closed position CPN forbidding injection events..

[0054] In a second step the coil 36 is energized and it upwardly attracts the magnetic armature and the upper stem 116 and, the lower stem 118 follows the upward displacement toward the open position OPV as it is being sucked by the upper stem 116 and, the fuel captive in the control chamber 104 can evacuate and flow into the return conduit 114.

[0055] The following references are utilized in this description.

10

injector

12

head of the injector

14

actuation member

16

control valve

18

nozzle assembly

20

inlet

22

outlet

24

actuator body

26

lower face of the actuator body

28

male thread of the actuator body

30

female thread of the capnut

32

capnut

34

bore

36

coil

37

electrical connecting members

38

connector

39

central bore

40

valve spring

42

valve body

44

upper face of the valve body

46

lower face of the valve body

48

recess - low pressure chamber

50

hydraulic distributor bore

52

narrow upper neck of the distributor bore

54

larger lower section of the distributor bore

56

sleeve

58

radial through holes

60

single area of interference

62

armature-stem assembly

64

magnetic armature

66

stem

68

lower extremity of the stem

70

fixed face of the valve seat

72

valve seat

74

mobile face of the valve seat

76

nozzle body

78

upper face of the nozzle body

80

upper large section of the nozzle body

82

lower narrower section of the nozzle body

84

injection nozzle

86

spray holes

88

shoulder face

90

main bore in the nozzle body

92

needle valve

94

upper guide

96

lower guide

98

head of the needle

100

pointy extremity of the needle

102

injection valve

104

control chamber

106

needle spring

108

high pressure fuel circuit

110

return circuit

112

evacuation conduit

114

return conduit - 2nd embodiment

116

upper stem - 3rd embodiment

118

lower stem - 3rd embodiment

120

second mobile face - 3rd embodiment

A1

longitudinal axis

A2

second axis

OPV

open position of the valve

CPV

closed position of the valve

OPN

open position of the needle

CPN

closed position of the needle

Claims

1. Control valve (16) of a fuel injector (10), said valve (16) being provided with

- a cylindrical valve body (42) extending along a main axis (A1) from an upper face (44) to a lower face (46), said body (42) being provided with a large cylindrical shallow recess (48) opening in said upper face (44) and in the bottom of which opens a valve distributor bore (50) axially extending toward the lower face (46) and with,

- a magnetic armature-stem assembly (62) provided with a magnetic armature (64) having a thick disc-shape in the centre of which is enshrined and crimped a cylindrical stem shaft (66) extending perpendicularly from the armature (64) to a lower extremity (68) and,

- guiding means (56) for slidably guiding the armature-stem assembly (62) into the valve bore (50) and with,

- seating means (70, 72, 74) for opening or closing a fluid communication between a high pressure conduit (112) and a return conduit (110), both conduits opening in said bore (50),

characterized in that
the seating means (70, 72, 74) and the guiding means (56) are distinct and independent means and wherein

- the guiding means (56) is a cylindrical sleeve (56) extending from an upper extremity to a lower extremity and fixedly press fitted in said valve bore (50), the stem (66) being slidably engaged in said sleeve (56),

- the seating means (70, 72, 74) is a valve seat (72) comprising a fixed face (70) surrounding the opening of the return conduit (110) cooperating with a mobile face (74) integral to the stem (66) and wherein

- the sleeve (56) is fixed in the bore (50) by means of a single annular area of interference (60) with the bore (50) and wherein

- the single annular area of interference (60) is a proximal an extremity of the sleeve (56) and,

- the fixed face (70) of the valve seat (72) is proximal the opposite extremity of the sleeve (72) and wherein

- the valve bore (50) is a through bore opening in the recess (48) and in the lower face (46) of the body, the single annular area of interference (60) being proximal to the recess (48) and wherein,

- the valve seat (72) is in the opening of bore (50) in the lower face (46) of the valve body, the mobile face (74) of the valve seat (72) being the lower extremity (68) of the stem adapted to cooperate with a fixed face (70) surrounding a return conduit (114) provided in a nozzle body and opening axially in the valve bore (50).

2. Control valve (16) as claimed in claim 1 wherein

- the valve bore (50) opens in the lower face (46) of the body, said single annular area of interference (60) being proximal to said lower face (46) and wherein,

- the valve seat (72) is in the opening of bore (50) in the bottom of the recess (48), the fixed face (70) being the interconnecting face surrounding the opening of the valve bore (50) in the recess (48), the mobile face (74) being a conical face of the stem (66) proximal the armature (64).

3. Control valve (16) as claimed in claim 2 wherein the high pressure conduit (112) laterally opens in the valve bore (50) and, the shallow recess (48) is part to the return conduit (110), the sleeve (56) being provided with radial through holes (58) enabling, in use the high pressure fuel to flow from the high pressure conduit (112), through the sleeve (56) and into the return conduit (110).

4. Arrangement of a control valve (16) as claimed in any one of the preceding claims and a nozzle assembly (18), the upper face (78) of the nozzle body (76) being in surface sealing abutment against the lower face (46) of the control valve and, the opening of the return conduit (114) in the upper face (78) of said nozzle body (76) is axially centred in the opening of the valve bore (50) in the lower face (46) of the valve body, the fixed face (70) of the seat (72) being the face surrounding the opening of the return conduit (114) in said upper face (78) of the nozzle body.

5. Fuel injector (10) comprising a control valve (16) as claimed in any one of the claims 1 to 4.

Drawing