EP3365548A1 - Fuel injector - Google Patents

Abstract

A mobile valve member (48) designed to be arranged in the nozzle body (30) of a fuel (F) injector (10), extends along a main axis (XI) and comprises a piston (50) formed of a male first cylinder (62) of effective diameter (DE) forming the top end of the mobile member (48) and of a second cylinder (64) provided with an internal cylindrical bore (68) of diameter (DE) and a shutoff member (52) comprising a male cylindrical shaft (84) of effective diameter (DE) which is a sliding fit in the internal bore (68), and of a member (88) extending as far as a pointed end provided with a mobile seat (56) and forming the bottom end of the mobile member (48). The mobile member (48) is hydraulically balanced and has a length between its top end and its bottom end that is variable because of the sliding of the cylindrical shaft (84) in the internal bore (68) of the piston.

Description

 Fuel injector

TECHNICAL AREA

 The present invention relates to a fuel injector more

particularly suitable for "ramp type" injection equipment

common ", the injector itself being provided with a nozzle whose needle is directly open or closed by a coil electromagnetic actuator.

BACKGROUND OF THE INVENTION

 A prior art fuel injector includes a coil and magnetic armature actuator acting directly on a valve member to open or close fuel injection holes.

 Such an injector imposes a valve member that is hydraulically balanced, or almost balanced, so that the relatively weak force exerted by

Γ solenoid actuator is sufficient to move said valve member.

SUMMARY OF THE INVENTION

 The present invention aims to remedy the disadvantages mentioned above by proposing a simple and economical solution.

 For this purpose, the invention proposes a movable valve member adapted to be arranged in the nozzle body of a fuel injector, the mobile member extending along a main axis between an upper end and a lower end provided with a movable valve seat arranged to cooperate along a circular line of effective diameter with a fixed seat arranged on the inner face of the nozzle body. The movable member is adapted to slide between a closed position in which the two valve seats are in sealing contact along said circular line preventing fuel injection and an open position in which the two valve seats are remote. one of the other allowing said injection .;

In addition, the mobile member advantageously comprises a piston formed of a first male cylinder of effective diameter forming the upper end of the mobile member and a second cylinder of larger outer diameter provided with an internal cylindrical bore of effective diameter extending axially in the second cylinder to a bottom and a shutter member formed of a cylindrical body comprising a male cylindrical shaft of effective diameter slidably fitted with clearance in the internal bore of the piston and, of a male pointed cylindrical member of larger diameter than the effective diameter, the pointed cylindrical member extending to an end in tip provided with the movable valve seat and forming the lower end of the movable member.

 Thus, advantageously, the movable valve member is

hydraulically balanced and has a variable length between its upper end and its lower end due to the sliding of the cylindrical shaft in the internal bore of the piston.

 The movable member further comprises a first compressed spring between the piston and the obturator member and continuously urging the piston and the obturator member towards an extension of the movable member.

 The shutter member further comprises a disc flange substantially arranged between the cylindrical shaft and the pointed cylinder, said flange extending radially from the cylindrical body of the shutter member to a peripheral edge provided to fit sliding against the inner face of the injector nozzle body. The flange has an upper face opposite the piston and an opposite lower face facing the valve seat. Said flange further defines a first restricted orifice and a second restricted orifice extending between the opposite faces of the flange and allowing pressurized fuel to pass at a reduced speed from one side to the other of the flange. creating a pressure difference between the faces of the collar.

 The piston is further provided with a return channel extending from the bottom of the internal bore and opening at the top end of the first cylinder.

The bore comprises a first section of diameter wider than the effective diameter and a second section of effective diameter so that the piston comprises a circular end forming a sealing lip cooperating with a circular annular surface of the upper face of the collar. The first restricted orifice being arranged outside of said circular annular surface and, the second restricted orifice being arranged inside said circular annular surface.

 The movable member is limited in extension by a mooring means preventing the shutter member from disengaging the piston and, in compression by the sealing lip in sealing abutment on the upper face of the collar.

 The invention also relates to an injection nozzle of a high-pressure fuel injector, the nozzle comprising a movable valve member produced according to the preceding paragraphs.

 The nozzle also includes a nozzle body elongate along the major axis, the body having a cylindrical lateral peripheral wall fused at one end and an upper wall at the other end. The upper wall is provided with a pressurized fuel inlet port and an axial bore opening annular guide of effective diameter and the tapered end is provided on the inner face of the wall of the nozzle body of the seat fixed valve arranged near injection holes extending through the peripheral wall.

 The movable member is arranged axially sliding in the interior space of the nozzle body, the first cylinder of the piston being slidably fitted with play in the opening annular guide, so that the movable valve seat cooperates with the fixed valve seat and that the movable assembly is slidable along the main axis between the closed position and the open position in which the movable seat is away from the fixed seat.

 The invention also extends to a fuel injector comprising an actuator and a nozzle made as previously described, the actuator being an electromagnet comprising a fixed coil and a movable magnetic armature directly attached to the piston.

BRIEF DESCRIPTION OF THE DRAWINGS

 Other features, objects and advantages of the invention will appear on reading the detailed description which follows, and with reference to the appended drawings, given by way of non-limiting example and in which:

 - Figure 1 is an overview of an injector according to the invention.

FIG. 2 is a diagram of the nozzle of the injector of FIG. 1. FIGS. 3, 4 and 5 are identical to FIG. 2 and illustrate various operating phases of the injector nozzle.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

 A fuel injector 10 shown in FIG. 1 is described

briefly to identify the main components. The injector 10 extends along a main axis XI, and comprises an actuator assembly 12, drawn at the top of the figure, and a nozzle assembly 14, drawn below.

 The actuator assembly 12 comprises a substantially cylindrical body 16 extending from an injector head 18 to a lower transverse face 20 and, in a bore 22 provided for this purpose, the body 16 encloses an electromagnet 24 comprising a coil 26 fixed in the body 16 and a movable magnetic armature 28 along the main axis XI.

 The nozzle assembly 14 also comprises a body 30 arranged in axial extension of the actuator body 16 and whose peripheral wall 32 defines an internal space V. The nozzle body 30 extends axially in a cylindrical portion from an upper face. 34 transmits in sealed surface contact with the lower face 20 of the injector body, to a portion of smaller section ending in a pointed end 36 provided with injection holes 38 extending through the peripheral wall 32 from an inlet on the inner face 40 to an outlet on the outer face 42. In addition, the nozzle body 30 comprises a fuel inlet 44, said orifice 44 being arranged in the upper face 34 and at the other end of the body 30, the inner face 40 of the peripheral wall is provided, just above the entries of the injection holes 38, with a fixed valve seat 46.

In the interior space V a movable valve member 48, also referred to as a needle by professionals, is slidably arranged along the main axis XI. The mobile member 48 is telescopic comprising mainly a cylindrical piston 50 and a shutter member 52 arranged sliding relative to each other. On the one hand the piston 50 emerges by a bore 54 of the upper face 34 of the nozzle body, this emerging part out of the nozzle body being integral with the magnetic armature 28 and, on the other hand on the opposite side, on the the pointed end 36, the shutter member is provided with a movable seat of valve 56 cooperating with the fixed seat 46. In operation, the movable valve member 48 moves axially between a closed position PF in which the movable valve seat 56 is in sealing contact against the fixed valve seat 46 along a circular line of effective diameter DE and an open position PO in which the two seats are distant from each other. In the extreme point of the nozzle body 30, under this circular line, "sub" taken in the direction of the figure, the nozzle body 30 forms a small volume known to those skilled in the art as the bag S in which open the injection holes 38.

 The actuator assembly 12 and the nozzle assembly 14 are secured to one another by an injector nut 58 which, threaded around the nozzle body 30 and resting on an outer shoulder, is screwed tightly onto the body. actuator 16.

 The injector 10 further comprises a high pressure channel 60 extending into the actuator body 16 from an inlet mouth into the lower face 20 where it communicates with the fuel inlet port 44 in the body. nozzle. The fuel F enters the interior space V the nozzle body and occupies all the available volume of said space V.

 The nozzle assembly 14 is now described in more detail with reference to FIG. 2 and following.

 The piston 50 of the movable valve member 48 is a cylindrical piece comprising a first thin cylinder 62 of outside diameter equal to the effective diameter DE and, below in the arbitrary direction of the figure, a second cylinder 64 of larger external diameter, the first and second cylinders 62, 64 joining in a transverse shoulder 66. Those skilled in the art will readily understand that the dimensions and diameters described as being equal are taken into account normal manufacturing tolerances and other games of

operation.

The second cylinder 64 of the piston is provided with a bore 68 opening into the lower face limiting the lower end to a bevelled annular surface forming sealing lip 70. From this lip 70, the bore 68 extends axially in the second cylinder 64 in a first section 72 of diameter D72 greater than the effective diameter DE and then in a second section 74 of diameter equal to the effective diameter DE. The two sections of the bore 72, 74, are connected along an inner shoulder of which the second section 74 extends to a bottom face 76 from which a return channel 78 which extends axially in the first cylinder 72 to open into the emerging part of the body nozzle.

 The shutter member 52 of the movable valve member 48 comprises three coaxial cylindrical parts, the central portion of which is a transverse disc flange 80, sometimes referred to by its English name "boost flange", whose outer diameter is slidably adjusted to the face internal 40 of the body 30. From the center of the upper face 82 of the flange 80 extends a cylindrical shaft 84 of diameter equal to the effective diameter DE, said cylindrical shaft 84 extending firstly through the first section 72 of the boring the piston and then engaging slidably fitted in the second section 74 of the piston bore. From the center of the lower face 86 of the flange 80 extends a pointed cylindrical shaft 88 of diameter D88 greater than the effective diameter DE, said pointed cylindrical shaft 88 being provided at its pointed end with the movable valve seat 56 cooperating with the fixed seat. 46 valve of the nozzle body 30.

 The flange 80 is provided on its upper face 82 with an annular sealing surface 90 cooperating with the sealing lip 70 of the piston and with two restricted orifices passing through the flange 80 between its upper face 82 and its lower face 86. The first restricted orifice 94 is arranged outside the annular sealing surface 90, that is to say between the annular surface 86 and the peripheral edge of the flange, while the second restricted orifice 96 is at the outside. inside the annular sealing surface 90.

 Due to the sliding fit of the collar 80 in the inner face of the wall of the nozzle body, the flange 80 separates the interior space V from the nozzle body into an upstream space VI situated above the collar 80, on the side of the upper face 82 and the fuel inlet port 44 in the nozzle body and, a downstream space V2 located below the collar 80, on the lower face side 86 and the holes injection 38 opening in the bag S. The restricted orifices 94, 96, thus create fluid communications between the upstream VI and downstream V2 spaces.

By engaging in the second section 74 of the bore, the cylindrical shaft 88 of diameter DE passes through the first section 72 which defines a annular chamber C1 in which opens the second restricted orifice 94 establishing a fluid communication with the downstream space V2.

 In addition, the bottom face 76 of the second bore of the piston and the end of the cylindrical shaft 84 define a return chamber C2 in which is compressed a spring 92 which tends to move the two parts 50, 52, one of them. on the other and lengthen the movable valve member 48.

 In the annular chamber C1 is arranged a docking means 98, shown diagrammatically in the figure by two annular protuberances complementary to each other and limiting said elongation of the movable valve member 48.

 The first cylinder 62 of the piston is axially guided in the bore 54 of the upper face of the nozzle body. According to the alternative of FIG. 2, the bore 54 has a diameter D54 slightly greater than the effective diameter DE of the piston and an independent annular guide 100 fitted around the first cylinder 62 guarantees the seal. The annular guide 100 has an inner diameter equal to the effective diameter DE and is held pressed against the nozzle body 30 by a second spring 102 compressed between the annular guide 100 and the shoulder 66 of the piston. The second spring 102 therefore permanently urges the piston downwardly from the figure and plates the annular guide 100 against the top of the nozzle body. The face of the guide 100 in contact with the nozzle body 30 is beveled and forms another sealing lip. In the figures the diameters and the games are represented exaggeratedly different.

 According to the alternative of FIG. 4, the annular guide 100 is integrated in a top guide 104 comprising the upper transverse face 34 of the nozzle body, face provided with the fuel inlet orifice 44, from the center of which extends the annular guide 100. Said top guide 104 is held in place compressed between the nozzle body 30 and the actuator body 16 by the injector nut 58. Said other spring 102 is then compressed between the top guide 104 and the shoulder 66 of the piston.

In operation, the first cylinder 62 of the piston is slidable in the annular guide 100 and the cylindrical shaft 84 is slid into the second section 74 of the bore in the piston. The skilled person will then understand that these sliding adjustments of male cylinders and females requires a set of operating J of a few microns, which does not prevent writing that all male and female cylinders have a diameter equal to the effective diameter OF said diameter being the nominal diameter.

 The operation of the injector 10 is now briefly presented with reference to Figures 2 to 5.

 The injector 10 is arranged within a common rail type fuel injection equipment supplying fuel with several injectors. By the inlet mouth of the injector therefore enters pressurized fuel F and, in a contemporary diesel injection equipment the

Diesel fuel pressurization can reach 2000 or 3000 bar. To illustrate this operation it is arbitrarily chosen that the fuel pressure at the inlet of the injector is 2500 bars.

 The fuel F enters the nozzle body 30 and occupies all the internal space V available.

 In a first phase, according to Figures 2 or 3, Γ electromagnet 24 is not energized, the second spring 102 pushes the piston 50 to the shutter member 52 and the shutter member 52 is itself pushed by the first spring 92 in the closed position PF, that is to say that the sealing lip 70 of the piston is in sealing contact against the annular surface 90 arranged on the upper face of the collar and the movable valve seat 56 is in leaktight contact against the fixed seat 46 along the circular line of effective diameter DE. The bag S is isolated from the volume V2. Thus, the annular chamber C1 is in communication only with the downstream space V2 via the second restricted orifice 96.

The fuel F entering the upstream space VI via the inlet port 44 passes into the downstream space V2 via the first restricted orifice 94 and then back into the annular chamber C1 via the second restricted orifice 96. The fuel passage F through the restricted orifices allows the filling of the three spaces VI, V2, C1 with fuel F at high pressure. A slight pressure difference may exist between these three spaces. In the closing phase, if 2500 bars of pressure prevail in the upstream space VI, the pressure in the downstream space V2 may be only 2200 bar and the pressure in the bag S of 2100 bar. The pressure in the annular chamber C1 is substantially equal to that in the space downstream V2 and, the return chamber C2 is permanently in communication with the low pressure, no particular pressure prevails.

 During this closed phase of the valve seat, minor static fuel leakage F takes place via the operating clearances J formed on the one hand between the cylindrical shaft 84 and the second section 74 of the bore in the piston, this leakage escaping at low pressure via the return chamber C2 and the return channel 78 and, on the other hand, between the first cylinder 62 of the piston and the annular guide 100, this leak escaping also at low pressure to join a circuit back to a low pressure tank not shown.

 Those skilled in the art will further recognize that the piston 50 is

hydraulically balanced. Indeed the cumulative surface of the faces generating on the piston a downward force is equal to the cumulative surface of the faces generating on the piston a force upwards. Thus, the forces generated by the pressure applying to the faces of the piston 50, faces distributed between the first cylinder of effective diameter DE and the second bore also of effective diameter DE, whatever the shape or the profile of said faces, s' balance.

 It is the same for the shutter member 52 whose faces under pressure extend between the cylindrical shaft of effective diameter DE and the valve seat also of effective diameter DE.

 In a second phase illustrated in FIG. 4, electromagnet 24 begins to be energized, magnetic armature 28 is attracted by the magnetic field M generated by coil 26 and, driven by the magnetic armature, piston 50 has begun to raise. The second spring 102 compresses as the first spring 92 expands, the forces of the two springs partially compensating for each other, and the electromagnet 24 then only has to overcome the difference between the spring forces. The first spring 92 holds the shutter member 52 in the closed position PF while the docking means 98 of the piston 50 and the shutter member 52 is just actuated so that the movable member 48 can not further elongate.

Since the sealing lip 70 is raised and moved away from the annular sealing surface 90, the annular chamber C1 is in fluid communication with the upstream space VI and pressurized fuel F can pass from the upstream space VI at the downstream space V2 via the two restricted orifices 94, 96, which contributes to balancing the pressures in the upstream VI and downstream V2 spaces.

 In a third phase illustrated in FIG. 5, the power supply of the electromagnet 24 is maintained and the piston 50 continues to rise. As the mooring means 98 is actuated, the piston 50 drives the shutter member 52 so that the valve seat 46, 56, opens and allows fuel F under pressure to be injected via the injection holes 38 The pressure in the bag S then increases and contributes to the opening force of the shutter member 52. The flow of fuel F passing through the first and second restricted orifices 94, 96, creates a slight differential pressure, the pressure in the the upstream space VI being slightly greater than the pressure in the downstream space V2 so as to generate a force which opposes the force of opening the pressure in the bag S. The shutter member 52 thus remains hydraulically balanced and ,

Γ electromagnet has only a small effort to provide to continue the opening of the shutter member.

 In the opening phase, if 2500 bars of pressure continue to prevail in the upstream space VI, the pressure in the downstream space V2 is about 2400 bars and the pressure in the bag S is about 2300 bars. The pressure in the annular chamber C1 is equal to that in the upstream space VI and, the return chamber C2 is still in communication with the low pressure, no particular pressure prevails.

 The length of the first spring 92 does not vary since in the second phase described above the docking means 98 is actuated and the solenoid 24 has to overcome only the compression force of the second spring 102.

 In a fourth closing phase, the supply of Γ electromagnet is interrupted and the piston 50, under the influence of the second spring 102, descends in sealing abutment against the upper face of the collar. The pressurized fuel F can no longer pass from the upstream space VI to the downstream space V2 than through the first restricted orifice 94.

The continuous injection and the pressurized fuel F can no longer move from the upstream space VI to the downstream space V2 that the first restricted orifice 94, a large pressure differential is created, the upstream pressure is the most important. important. This pressure difference causes the shutter member 52 towards the closure PF of the valve seat and stopping the injection.

 During this closing phase, if 2500 bars of pressure prevail in the upstream space VI, the pressure in the downstream space V2 may be only 2200 bars and the pressure in the bag S of 2100 bars. The pressure in the annular chamber C1 is substantially equal to that in the downstream space V2 and, the return chamber C2 is permanently in communication with the low pressure, no particular pressure prevails.

 Simulations and conclusive tests were carried out on injectors whose effective diameter is 1, 5 mm, the sum of the forces of the springs is a little more than 40N so that the seat of valve is waterproof in closed position under a pressure 250 bar to compensate for pressure in the combustion chamber, especially at the end of combustion. The electromagnet must be able to generate a force of about 65N over a course of about 250 μιη,

LIST OF REFERENCES USED

XI main axis

 V interior space of the nozzle body

 M magnetic field

 F fuel

 PF closed position

 PO open position

 Effective diameter

D72 diameter of the first boring section

 D88 diameter of the pointed shaft

 VI upstream space

 V2 downstream space

 Cl annular chamber

 C2 return room

 J operating game

 S bag

10 injector

 12 actuator assembly

 14 nozzle set

 16 actuator body

18 injector head 20 lower transverse face of the actuator body

22 reel bore

 24 electromagnet

 26 coil

 28 magnetic armature

 30 nozzle body

 32 peripheral wall of nozzle body

 34 upper transverse face of the nozzle body

36 pointed end

 38 injection holes

 40 inner face of the peripheral wall

 42 outer surface of the peripheral wall

 44 fuel inlet port in the nozzle body

46 fixed valve seat

 48 moving valve member

 50 piston

 52 shutter member

 54 bore of the upper face of the nozzle body

56 mobile valve seat

 58 injector nut

 60 high pressure channel

 62 first piston cylinder

 64 second cylinder of the piston

 66 outer shoulder of the piston

 68 piston bore

 70 sealing lip

 72 first section of the bore in the piston

74 second section of the bore in the piston

76 bottom face of the second section

 78 return channel

 80 collar

 82 upper side of the collar

 84 cylindrical shaft

 86 underside of collar

 88 pointed cylinder

 90 annular sealing surface

 92 first spring

 94 first restricted orifice

 96 second restricted orifice

 98 way of mooring

 100 ring guide

 102 second spring

 104 guide up

Claims

A movable valve member (48) adapted to be arranged in the nozzle body (30) of a fuel injector (10) (F), the movable member (48) extending along a main axis (XI) between an upper end and a lower end provided with a movable valve seat (56) adapted to cooperate along a circular line of effective diameter (DE) with a fixed seat (46) arranged on the inner face (40) the nozzle body, the movable member (48) being slidably engaged between a closed position (PF) in which the two valve seats (46, 56) are in sealing engagement along said circular line preventing fuel injection and, an open position (PO) in which the two valve seats are spaced from each other to allow said injection;  characterized in that the movable member (48) comprises:  - a piston (50) formed of a first male cylinder (62) of effective diameter (DE) forming the upper end of the movable member (48) and a second cylinder (64) of larger outer diameter provided with an inner cylindrical bore (68) of effective diameter (DE) extending axially (XI) in the second cylinder (64) to a bottom (76),  - a shutter member (52) formed of a cylindrical body comprising a cylindrical shaft (84) male effective diameter (DE) adjusted sliding with play (J) in the piston internal bore (68) and a larger diameter (D88) pointed cylindrical member (88) than the effective diameter (DE), the pointed cylindrical member (88) extending to a pointed end provided with the movable valve seat (56) and forming the lower end of the movable member (48), so that the movable valve member (48) is hydraulically balanced and has a variable length between its upper end and its lower end due to sliding of the cylindrical shaft (84) in the bore (68) internal piston. 2. mobile valve member (48) according to the preceding claim further comprising a first spring (92) compressed between the piston (50) and the shutter member (52) and continuously urging the piston and the shutter member to an extension of mobile member. 3. movable valve member (48) according to one of claims 1 or 2 wherein the shutter member (52) further comprises a disc flange (80) substantially arranged between the cylindrical shaft (84) and the pointed cylinder ( 88), said flange extending radially from the cylindrical body of the shutter member to a peripheral edge for sliding fit against the inner face (40) of the nozzle nozzle body, the collar (80) having a upper face (82) facing the piston and an opposite lower face (86) facing the valve seat, said collar further defining a first restricted orifice (94) and a second restricted orifice (96) both extending between the opposite sides of the flange and allowing fuel (F) under pressure to pass at a reduced speed from one side to the other of the collar by creating a pressure difference between the faces of the flange. 4. A movable valve member (48) according to any one of the preceding claims wherein the piston (50) is further provided with a return channel (78) extending from the bottom (76) of the bore internal (68) and opening at the top end of the first cylinder. 5. movable valve member (48) according to one of claims 3 or 4 wherein the bore (68) comprises a first section (72) of larger diameter than the effective diameter (DE) and a second section (72) 74) of effective diameter (DE) so that the piston (50) comprises a circular end forming a sealing lip (70) cooperating with a circular annular surface (90) of the upper face of the collar, the first restricted orifice (94) being arranged outside said circular annular surface (90) and the second restricted orifice (96) being arranged within said circular annular surface (90). The movable valve member (48) according to claim 5 wherein the movable member is limited in extension by a mooring means (98) preventing the shutter member (52) from disengaging from the piston (50) and, in compression by the sealing lip (70) in sealing abutment on the upper face of the collar. An injection nozzle (14) of a high pressure fuel injector, the nozzle comprising a movable valve member (48) made according to any one of the preceding claims and,  a nozzle body (30) elongated along the main axis (XI) and having a cylindrical lateral peripheral wall (32) fused at one end and an upper wall at the other end, the upper wall being provided with an orifice inlet (44) of pressurized fuel and an axial bore opening (100) of annular guide (100) of effective diameter (DE), the tapered end being provided on the inner face of the wall of the nozzle body of the fixed seat Valve assembly (46) arranged near injection holes (38) extending through the wall peripheral,  the movable member (48) being arranged axially sliding in the interior space (V) of the nozzle body, the first cylinder (62) of the piston being slidably fitted with clearance (J) in the annular guide (100) opening so that the movable valve seat (56) cooperates with the fixed valve seat (46) and the movable assembly (48) is able to slide along the main axis (XI) between the closed position (PF) and the open position (PO) in which the movable seat is away from the fixed seat. Fuel injector (10) comprising an actuator (24) and a nozzle (14) made according to claim 7, characterized in that the actuator (24) is an electromagnet comprising a fixed coil (26) and a magnetic armature ( 28) movable directly attached to the piston (50).