EP3368763A1

EP3368763A1 - Fuel injector

Info

Publication number: EP3368763A1
Application number: EP16785177.3A
Authority: EP
Inventors: Thierry Thibault; Legrand PHILIPPE
Original assignee: Delphi Technologies IP Ltd
Current assignee: Delphi Technologies IP Ltd
Priority date: 2015-10-29
Filing date: 2016-10-24
Publication date: 2018-09-05
Anticipated expiration: 2036-10-24
Also published as: FR3043144A1; EP3368763B1; FR3043144B1; WO2017072081A1

Abstract

A fuel injector for an internal combustion engine, comprising: an injection nozzle (12) with a body (16) in which a needle (14) is arranged; a control chamber (46) collaborating with a control valve driven by an actuator. A device for detecting the position of the needle comprises a contactor element (62) actuated by the upper part of the needle (42), the device being designed so that the contactor element is in contact, in the closed position, with terminal-forming element (64) of the position detection device, and so that the lifting of the needle causes a break in contact. The contactor element may be a spring, installed in the control chamber (46) and which is deformed radially in the closed position so as to touch an end of a rod and thus close the detection circuit.

Description

FUEL INJECTOR Technical field

The present invention generally relates to the field of fuel injectors and more precisely to an injector equipped with a device for detecting the position of the needle. State of the art

A fuel injector conventionally comprises a needle controlled opening and closing depending on the pressure in a control chamber, which pressure is a function of the position of a control solenoid valve. These small displacements are carried out at high speed and, the regularly increased performances now require for an optimal control a feedback as to the real position of the needle. Devices are known in which a sensor is arranged on the injector, or an injector in which the surfaces of the body components are electrically insulated so that a measurement of electrical resistance can be made between two elements of the body of the injector. . These complex and expensive devices have not yet proven their industrial realism and should be offered a simple and effective device.

For example, FR 3 013 080 in which the injector comprises resistive surface coatings arranged on several contact surfaces between parts, and in which the overall electrical resistivity of the injector between the body of the solenoid actuator and the injector body varies by at least three different intermittent ohmic values according to the kinetics of the injection needle of the injector.

A difficulty in the proposed systems is related to the tolerances on the needle that cause misalignment / misalignment with the seat. Indeed, it happens that the tip of the needle laterally touches the nozzle body, just at the periphery of the seat, generating anticipated openings / closures relative to the actual opening or closing. Object of the invention

The object of the present invention is to provide a fuel injector with another opening detection device having good reliability.

General description of the invention

With this objective in mind, the present invention provides a fuel injector for an internal combustion engine, comprising an injection nozzle with a body in which is arranged a movable needle between a closed position (PF), wherein a first end of the needle rests on a seat and closes the injection ports of the nozzle, and a fully open position (PO), in which the first end of the needle is lifted from its seat and allows injection. A control chamber is filled, in operation, with fuel so as to exert pressure on the second end of the needle. A control valve is associated with the control chamber for selectively varying the fuel pressure in the control chamber and thereby controlling an opening or closing movement of the needle, the control valve being driven by an actuator .

According to the invention, the injector comprises a device for detecting the position of the needle defining a detection circuit, the detection device comprising a contact element actuated by the upper part of the needle, the device being designed of so that the contactor member is in closed contact with a terminal member of the position detecting device, thereby closing the detection circuit, and so that the lifting of the needle interrupts the contact between the contactor element and the terminal element, thereby opening the detection circuit.

The detection device according to the invention therefore comprises the contactor element and the terminal, which cooperate in the manner of a switch. The contactor element is actuated by the movement of the needle. The actuation of the contact element by the upper part of the needle can be direct or indirect. This detection principle allows to avoid the implementation of insulating and resistive layers at the needle.

The detection circuit is closed when the contactor element is in contact with the terminal; and the circuit opens when the needle rises and changes the contactor element. The moment of the interruption of the electrical contact between the contactor element and the terminal, that is to say the closed circuit transition open circuit, is here an indication of the timing of the opening of the needle. Conversely, when the needle returns to its seat at the end of the actuation sequence the contactor will come into contact again with the terminal, closing the circuit.

The detection of the position of the needle in the upper part thereof avoids the problems of alignment of the needle at its seat, likely in known solutions to generate false contacts. It should be noted here that the guide clearance of the needle partly at the top (at the top guide) where the contactor element is positioned and the terminal is reduced when the pressure increases, thereby improving the quality of the contact.

Preferably, the detection device is designed so that the detection circuit is closed only in the closed position of the injector, and possibly in the open position, but not in the ballistic zone.

The contacting element may comprise a flexible part which is configured in the closed position of the needle so as to be in electrical contact with the terminal; the configuration of the flexible part changing when the needle leaves the closed position so as to interrupt the electrical contact with the terminal (opening of the circuit).

According to one variant, the contactor element is placed in the control chamber and the needle comprises a rod end in the control chamber which forms a contact terminal and urges the deformation of the contacting element so that the contacting element is deformed elastically when the needle is in the closed position and is in contact with the rod to establish the electrical contact, the form of the contactor element being modified during the opening stroke of the needle so that the contact is interrupted (the circuit opens).

The contacting element is for example a generally cylindrical part arranged around the needle rod, bearing against an electrically insulated stop and placed on the rod, and against a conductive stop placed in the control chamber and electrically isolated from its support. The conductive abutment may be constituted by the inner radial edge of a conductive shoulder socket mounted in the control chamber.

In particular, the contacting element may be is a helical spring, a tubular element or another elastically deformable element, in particular transversely, under the action of the needle in the closed position so that the contact element touches the rod needle, and adapted to spontaneously resume a shape in which it is not in contact with the rod when the needle leaves the closed position.

In order to detect the fully open position of the needle, the detection device may comprise a second terminal positioned in the control chamber, the needle abutting against this terminal at the end of its opening stroke, closing the circuit of detection. This second terminal can be constituted by the ceiling of the control chamber.

Alternatively, the detection device can be designed so that the contactor element moves in translation with the needle, the terminal being positioned so that the contact between the contactor element and the terminal is established in the closed position (circuit closed).

According to a variant, the needle is guided at the top by a high guide, and the device comprises a contact bushing surrounding the high guide. The contact sleeve is electrically isolated from the top guide and can slide axially thereon. The contactor element takes the form of a washer fixedly mounted on the upper part of the needle. The switch function of the detection device is thus carried out here outside the control chamber. In particular, the washer forming contactor element is positioned against a shoulder of the needle; the needle is biased in the closing direction by a needle spring surrounding the needle and resting firstly on the washer, respectively the needle shoulder, and secondly against a lower edge of the guide high. The contact sleeve extends axially on a portion of the top guide, around the spring and up to the shoulder receiving the washer.

In this embodiment, the terminal is advantageously formed by an inner radial edge of the contact sleeve, placed under the washer, so as to be in contact therewith in the closed position.

The power supply of the contact socket can be via a conductive pin through, electrically insulated, a radial flange of the top guide. An elastic contact member is preferably provided for establishing electrical contact between the pin and the conductive sleeve.

To absorb manufacturing tolerances, the contact sleeve is not fixedly mounted but is guided around the top guide. An electrically insulated spring is preferably disposed around the contact bushing so as to exert an axial force in the opening direction, in particular to compensate for wear or work. The contact sleeve is then configured so as to define with the high guide an annular cavity filled, in use, with fuel and forming an axial damping chamber limiting the axial displacement of the contact sleeve in the opening direction of the needle, when opening the injector. Although the contact bushing is not fixed mounted, the presence of the damping cavity in practice makes the contact bushing substantially static. But above all, this configuration ensures that the washer is in contact with the edge of the contact sleeve in the closed position of the needle, so that the detection circuit is closed and allows the detection of this position by the passage of the current. It remains to be noted that although the present invention was developed in the context of a diesel injector, it is entirely transferable to an injector of gasoline or any other fuel. Detailed description using the figures

Other features and characteristics of the invention will become apparent from the detailed description of at least one advantageous embodiment presented below, by way of illustration, with reference to the accompanying drawings. These show:

Figure 1 is an axial sectional view of a first embodiment of the present injector, the injector being in position (a) closed, (b), intermediate and (c) open;

Figure 2 is an axial sectional view of a second embodiment of the present injector;

Figure 3: a view of detail A of Fig.2;

Figures 4 and 5: two graphs illustrating the response (current) of the position detection device according to the stroke of the needle, for the variants of Figures 1 and 3, respectively. In these figures, the stroke of the needle is drawn in solid lines and corresponds to the axis C; and the detected signal S is shown in phantom.

FIG. 1 illustrates a first embodiment of the invention relating to a fuel injector 10, here a diesel injector, although the invention can be fully transposed to a gas injector or any other fuel, the injector 10 generally part of an injection system comprising several injectors. The description will detail the elements of the invention and will remain more succinct and general as to the surrounding elements. The injector 10 extends along a main axis A and comprises, from the bottom upwards, according to the conventional and non-limiting sense of the figures, a nozzle 12 comprising a needle 14 arranged in a nozzle body 16 and then a control valve arranged in a valve body 22 and an actuator arranged in an actuator body 26. The control valve and the actuator may be of the conventional type and are therefore not shown or described in detail. The nozzle bodies 16, valve body 22 and actuator body 26 are held together by any suitable means. Conventionally, it is possible to use a nut bearing on a shoulder of the nozzle body and screwing on the actuator body, the valve body 22 being sandwiched between the two other bodies, the three bodies and the nut forming the body of the injector.

The nozzle body 16 comprises a stepped inner axial bore 30 extending from an upper end, where it has a large diameter, to a low end closing in a point so as to form a tapered nozzle body seat 32. for controlling the access of fuel to injection ports 34 extending through the conical wall of the nozzle body 16. In the lower part, the bore 30 forms a low cylindrical guide 36 at which the needle 14 comprises a projecting annular section 38 sliding in the bottom guide 36. The passage of the fuel at this low guide is made for example by one or more grooves (straight or helical) in the wall of the low cylindrical guide or in the annular scar . The guiding of the needle in the upper part is obtained by an independent piece 40, called a high guide, arranged between the nozzle body 16 and the valve body 22 and held fixed by the assembly of the injector parts, in particular by the compression exerted by the injector nut. The high guide 40 guides the upper portion of the needle 14, referred to as the needle head 42, through a guide bore 44. The needle head 42 in combination with the valve body 22 and the bore of guide 44 define a control chamber 46.

The terms "high" and "low" are used here not only in reference to the orientation of the figure, but also in reference to the usual name given to these elements by professionals.

The needle 14 is generally cylindrical and extends axially A between the needle head 44, at the top of the figure, and a pointed end 48, at the bottom of the figure, forming a needle seat 50 cooperating with the seat valve body 32 of the body 16. When the needle rests on the seat 32 of the body it is in the closed position PF, fuel injection via the orifices 34 is prevented. The lifting of the needle 14 is obtained by adjusting the pressure in the control chamber 46, which makes it possible to bring the needle into a total open position denoted PO (typically at the upper stop), in which the fuel can pass to the injection ports 34.

As can be seen, the bottom guide 36 is close to the needle seats 50 and the nozzle body 32. Moreover, the needle 14 is provided with an annular protuberance 52, the upper face 54 of which faces the head of the nozzle. needle 42, provides a bearing surface for a spring 56 urging the needle 14 to its closed position PF in which the needle tip 48 rests on its seat 32 and closes the injection ports 34. The spring 56 is arranged under the top guide 40 and is pressed against the lower surface 58 of the top guide.

The injector 10 is moreover conventionally provided with a fuel circulation circuit which, on the one hand, allows the supply of the high pressure fuel via a high pressure circuit, brought from an inlet mouth to the orifices of the fuel. injection 34 and, on the other hand recirculation of fuel to a low pressure tank via a low pressure internal circuit. The high pressure circuit comprises in particular a bypass channel leading to the control chamber 46, chamber 46 from which the low pressure circuit leaves via a controlled outlet channel opening and closing by the control valve. When the actuator, typically an electromagnet, is electrically powered, it attracts the magnetic armature connected to the shutter member of the control valve, which opens the evacuation channel and allows the fuel trapped in the chamber of command to evacuate to the low pressure circuit. The pressure in the control chamber 46 then drops, and the needle 14 moves in the bore of the nozzle body to a fully open position PO in which the needle seat 50 is moved away from the valve body seat 32, so as to allow the injection of fuel via the injection holes 34, the top of the needle head 42 being in contact with the ceiling surface 59 (constituted by the underside of the valve body 22) of the control chamber 46.

When the actuator is not powered, the magnetic armature assembly and valve closure member is pushed by a valve spring to a position in which the discharge channel is closed which retains in the control chamber 46 the high pressure fuel that gets there. The pressure in the control chamber then rises and the needle, pushed back by the spring and by the pressure in the control chamber 46, moves towards the closed position PF in which the needle seat 50 is in sealing contact against the valve body seat 32, so as to prohibit the injection of fuel and wherein the top of the head of the needle 42 is remote from the ceiling surface 59 of the control chamber 46.

In order to accurately determine the moment of opening of the needle, the injector is equipped with a generally indicated needle position detecting device 60.

It will be appreciated that the detecting device 60 of the needle position comprises a detection circuit with a switch function actuated by the upper part 42 of the needle.

In the variant of Figure 1, the detection device 60 comprises an elastic contact member 62 placed in the control chamber 46 and which is deformed under the action of the needle 14 when in the closed position PF.

For example, the contactor member 62 may take the form of a spring associated with the needle head 42. As can be seen, the needle head includes a stem-shaped end portion 64 of reduced section, compared to the section of the needle head 42 guided by the hole 44 of the high guide 40. The rod is positioned centrally in the control chamber 46 along the axis A, and the spring contact member 62 surrounds the needle rod 64.

The reference sign 66 designates a shouldered socket made of an electrically conductive material (generally metallic), placed in the control chamber 46. The reference sign 68 designates a intermediate insulating layer, so that the sleeve 66 is electrically insulated from the top guide 40, and the latter is isolated from the valve body 22. The valve body which will constitute the starting point of the detection circuit is in fact electrically isolated no only the top guide 40 but also other surrounding parts, except at the ceiling 59 of the control chamber 46.

The rod 64 of the needle 14 passes through the shoulder 661 of the sleeve 66 and carries an isolated stop 70, for example a washer. The spring 56 rests against the abutment 70 and the shoulder 661 of the sleeve, and is, in PF of the injector, compressed so as to be deformed, here radially / transversely, and in contact with the rod 64 of needle 14.

The spring contacting element 62 and the needle rod 64 thus have functions respectively of movable contact and of switch terminal in the detection device 60. In this configuration of fig.1 which corresponds to the PF, the detection device 60 is closed, the current being able to flow between the spring 62 and the rod 64. As will be understood, the detection circuit comprises at least the elements forming the switch function. But it can be considered that the elements involved in the loop of current flow between two electric poles are also part of the detection circuit.

Referring for example to Figure 1, the conductive member 62 constituted by the spring allows the flow of current between the upper part of the injector and the needle. For example, if the valve body 59 is connected to a positive potential, the current then flows into the socket 66 with which it is in electrical contact, via the spring 62 to the needle rod 64, and therefore from the needle 14 to the mass. The path followed by the current is symbolized by the broken line arrow. The electrical detection circuit is closed, which is detected by the passage of the current.

Figure 1B shows an intermediate position of the stroke of the needle 14, between the PF and PO. The needle 14 is raised from its seat and the spring 62 is stiffened / straightened, which opened the electrical contact with the end rod 64 and thus interrupted (open circuit) the passage of the current to the needle 14 and the mass.

Advantageously, the device is designed so that the compression of the PF spring 62 is chosen for a frank electrical contact break, from the beginning of the opening stroke of the needle 14.

In FIG. 1C, the needle 14 has reached its maximum open position PO. The needle is in abutment against the ceiling 59 of the control chamber 46, that is to say that the rod 64 touches the ceiling. In this position, the current flows directly from the valve body 22 into the rod 64 and thus the needle 14, towards the ground. This closes the detection circuit again and allows detection of the maximum open position of the injector.

FIG. 4 represents on the same graph the stroke of the needle and the electrical signal (current) delivered by the detection device 60. In PF (FIG. 1A), the current flows from the spring 62 to the rod 64 and the signal Electric is at level 1. As soon as the needle comes up the circuit opens and the current drops to 0. When the needle comes to a stop (Fig.l C), the electric circuit is closed again and the current returns to 1. Although the electrical signal takes the same value in the positions PF and PO of the injector, it is possible to discriminate these two positions according to the actuation sequence.

FIG. 2 illustrates a second variant, which differs mainly in the embodiment of the designated needle position detection device 100. The detection device 100 also cooperates here with the upper part of the needle, but is placed outside the chamber control. The needle head therefore has a more conventional shape, without the rod 64, which reduces the volume of the control chamber 46. The elements that are identical or similar to those of the embodiment of FIG. 1 are designated by the same reference signs.

The detection device 100 comprises a conductive sleeve 102, also called a contact sleeve, which is mounted around the high guide 40 and is electrically isolated from that, via an insulating layer 104. Contact bushing 102 is in electrical contact with an electrical pin 106 passing through the top guide 40 through a channel 108 in which pin 106 is electrically insulated. Preferably, the contact between the pin 106 and the socket 102 is via an elastic element 1 10. The elastic element 1 10 has a low force and is intended primarily to maintain the electrical contact. It can have any suitable form. The contact portions do not necessarily have a smooth annular shape, but may include indentations etc.

The reference sign 1 12 designates a contact washer (thus electrically conductive) fixedly mounted on the needle head 42 and forming the contact member displaced by the needle 14. The washer 1 12 rests on a shoulder 54 'of an annular protuberance 52 'of the needle.

The device 100 is designed so that in PF, the washer 1 12 is in contact with the sleeve 102. In the variant, the washer 1 12 touches an inner radial edge 1 14 of the contact sleeve 102, which forms a terminal .

In this configuration, the current can flow from the pin 106 through the spring 1 10 to the contact sleeve 102. In the PF shown in Fig. 3, the washer 1 12 rests on the flange 1 14, thus closing the circuit allowing the current to flow from the washer 1 12 to the needle spring 56 and thus in the top guide 40, and to return it through the carcass of the injector towards the ground. The detection circuit is closed, which is detected by the passage of a current through the parts mentioned.

Upon actuation of the injector, the needle 14 rises from its seat, moving upwards. The washer 1 12 moves with the needle 14, which interrupts the electrical contact with the contact sleeve 102, and thus opens the circuit. The contact remains open (interrupted current) as long as the needle is spaced from the needle body seat 32. Thus during the movement of the needle, the washer 1 12 moves inside the contact sleeve 102; the outer diameter of the washer 1 12 is smaller than the inner diameter of the sleeve 102, so that the washer 1 12 never touches the sleeve 102, except in PF. FIG. 5 represents in the same graph the stroke C of the needle 14 and the electrical signal S (current) delivered by the detection device 100. The circuit is only closed at PF, when the washer 1 12 touches the rim 1 14 , which is indicated by an electrical signal at "1". As soon as the needle leaves its seat, the washer contact 1 12 / flange 1 14 is interrupted and the current goes to "0". This embodiment of the detection device 100 does not make it possible to determine the PO of the injector.

Preferably, the contact bushing 102 is configured so that there is an annular cavity 1 16 between it and the high guide 40. This annular cavity is, in use, filled with fuel and will therefore act as a chamber. amortization. Indeed, the sleeve 102 is guided around the top guide 40 and is therefore movable relative thereto. It is not fixed mounted to absorb manufacturing tolerances, which will always ensure the contact between the sleeve 102 and the contact washer 1 12 PF. For this purpose also, a compensation spring 120, isolated from the main body, is advantageously provided to ensure the contact 1 14 PF and compensate the wear of the interfaces in the system, in particular at the spring seat 56, seat of washer and contact area 1 14.

In practice, however, the sleeve 102 can be considered as quasi-fixed, since its movement is limited by the annular cavity 1 16 which forms a hydraulic blocking avoiding rapid movements of the sleeve 102.

One or more holes 18 (vents) are provided in the main portion of the bushing 102 to facilitate balancing of pressures and avoid localized pressure effects.

It will also be noted that in this second variant, the contact washer 102 forming the contacting element is an insert, fixed in operation against the shoulder 54 'of an annular portion 52'. Since the needle spring 56 is carried by the washer 102, it is not necessary to provide an annular protrusion 52 as in the variant of Fig. 1, although this is not to be excluded. So the surface support 54 'can be obtained by a simple shoulder cut into the mass of the needle 14.

In the variant of Figures 2 and 3, using a washer 1 12 reported to facilitate assembly of the assembly.

In other variations, the washer 102 could be in one piece with the needle. For example, with a suitable dimensioning of the assembly, the annular protuberance 52 of the needle of FIG. 1 can act as a contact washer.

Remains to note that in the variant of Figures 2 and 3, the detection of the PO can be done by means of an additional contactor element, shown in broken line and indicated 122, mounted on the needle head 42. The element additional contactor 122 is positioned on the needle lower than the washer 1 12. The additional contactor element 122 may also take the form of a radial protuberance of the needle 14 or a washer locked axially against a shoulder. The position of the additional contactor element 122 on the needle and its thickness are chosen so that it is in contact, in PO, with the terminal formed by the inner radial edge 1 14 of the contact sleeve 102. it will have understood, in this case the additional contactor element 122 comes to touch the lower face of the radial edge 1 14.

When such an additional contactor element 122 is present, the detection current goes to the value "1" in PO, and the current diagram corresponds to that of FIG. 4 rather than FIG.

Claims

Claims:

1. Fuel injector for an internal combustion engine, comprising:

an injection nozzle (12) with a body (16) in which is arranged a needle (14) movable between a closed position (PF), wherein a first end (48) of the needle rests on a seat (32); ) and closes the injection ports (34) of the nozzle, and a fully open position (PO), wherein the first end of the needle is lifted from its seat (32) and allows the injection;

a control chamber (46) filled, in use, with fuel so as to exert pressure on the second end (42) of the needle;

a control valve associated with the control chamber (46) for selectively varying the fuel pressure in the control chamber (46) and thereby controlling an opening or closing movement of the needle (14), the control valve being driven by an actuator;

a needle position detecting device (60; 100) defining a detection circuit;

characterized in that the needle position detecting device comprises a contactor element (62; 1 12) actuated by the upper part of the needle, the device being designed so that the contactor element is in contact in the closed position with a terminal member (64; 1 14) of the position detecting device thereby closing the detection circuit, and so that the lifting of the needle interrupts contact between the contact member and the terminal element, thereby opening the detection circuit and that,

the contactor element comprises a flexible part (62) which is configured in the closed position of the needle so as to be in electrical contact with the terminal (64); the configuration of the flexible piece (62) changing when the needle leaves the closed position so as to interrupt the electrical contact.

Fuel injector according to claim 1, characterized in that

the contactor element is placed in the control chamber

(46);

the needle comprises a rod end in the control chamber which forms a contact terminal and biases the deformation of the contactor element so that the contactor element is elastically deformed when the needle is in the closed position and is contact with the rod to establish the electrical contact, the shape of the contactor element being modified during the opening stroke of the needle so that the contact is interrupted.

3. Fuel injector according to claim 2, characterized in that the contacting element (62) is a generally cylindrical piece arranged around the needle rod, bearing against an electrically insulated abutment and placed on the rod, and against a conductive stop placed in the control chamber and electrically isolated from its support; and

preferably, the conductive abutment is constituted by the inner radial edge of a conductive shouldered sleeve mounted in the control chamber.

4. fuel injector according to claim 3, characterized in that the contacting element is a helical spring, a tubular element or another elastically deformable element, in particular transversely, under the action of the needle in the closed position so that the contact element touches the needle shaft, and adapted to spontaneously resume a shape in which it is not in contact with the rod when the needle leaves the closed position.

5. fuel injector according to any one of the preceding claims, characterized by a second terminal (59) positioned in the control chamber, the needle resting against this second terminal in the open position (PO) to close the detection circuit, said second terminal (59) being preferably formed by the ceiling of the control chamber (46).

Fuel injector according to claim 1, characterized in that the contact element (1 12) moves in translation with the needle (14) and that the terminal (64) is positioned so that the contact between the contactor element and the terminal is set in the closed position.

A fuel injector according to claim 6, wherein the needle is guided at the top by a top guide (40), characterized in that the device comprises a contact bushing (102) surrounding the top guide, the bushing contact being electrically isolated from the top guide and axially slidable thereon; and in that the contacting element takes the form of a washer (1 12) fixedly mounted on the upper part of the needle.

8. fuel injector according to claim 7, characterized in that the washer (1 12) forming contactor element is positioned against a shoulder (54 ') of the needle; in that the needle is biased in the closing direction by a needle spring (56) surrounding the needle and bearing on the one hand on the washer, respectively the needle shoulder, and on the other hand share against a lower edge of the high guide; and in that the contact bushing (102) extends, in the axial direction, over a portion of the high guide, around the spring and up to the height of the shoulder receiving the washer;

the terminal being preferably formed by an inner radial edge (1 14) of the contact sleeve, placed under the washer (1 12), so as to be in contact therewith in the closed position.

Fuel injector according to claim 8, characterized by an additional contact element (122) arranged on the needle lower than said contacting element (1 12), so as to come into contact with the edge. internal radial (1 14) of the contact sleeve (102) in the fully open position.

Fuel injector according to one of Claims 8 to 9, characterized in that

an electrically insulated spring (120) is arranged around the contact bushing so as to exert an axial force in the opening direction, in particular to compensate for wear;

the contact bushing (102) is configured so as to define with the high guide an annular cavity (1 16) filled, in use, with fuel and forming a hydraulic axial damping chamber limiting the axial displacement of the contact bush in direction of opening of the needle.