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Title:
FUEL INJECTOR FOR A COMBUSTION ENGINE
Document Type and Number:
WIPO Patent Application WO/2017/144479
Kind Code:
A1
Abstract:
A fuel injector has a head portion adapted to provide connections from and to an ECU to selectively energize an actuator to start and stop fuel injection pulses, a fuel supply connection for supplying fuel into the injector at an elevated pressure, a fuel return connection for returning fuel at a lower pressure, a fuel injection nozzle having at least one nozzle opening provided at an end of a valve guide, a valve member movable in a chamber defined within the valve guide and biased to close against a valve seat and inhibit fuel injection through the nozzle and to move within the valve chamber away from the valve seat to eject fuel through the nozzle. A circuit is provided for detecting by an electrical change whether the nozzle is open or closed. The circuit includes a conductor extending between the head of the fuel injector, either in an outer region of the body of the injector or through an isolation member for the actuator, to a position generally at a head end of the actuator, a contact member at the head end of the actuator maintained in electrical contact with the conductor and a resilient electrical link between the contact member and one of the valve member and the valve guide.

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Inventors:
LALE, Xavier (4 allée Paul Gauguin, Vendôme, Vendôme, 41100, FR)
BIMBENET, Bruno (13 bis, rue du Bon Levrault, Saint-Claude-de-Diray, 41350, FR)
TAPIN, Christophe (26 rue des Acacias, Saint Sulpice de Pommeray, 41000, FR)
BEDUNEAU, Jean-Luc (10 rue de Touraine, BLOIS, 41000, FR)
DORADOUX, Laurent (70 rue de Touraine, Herbault, Herbault, 41190, FR)
Application Number:
EP2017/053958
Publication Date:
August 31, 2017
Filing Date:
February 21, 2017
Export Citation:
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Assignee:
DELPHI INTERNATIONAL OPERATIONS LUXEMBOURG S.À R.L. (Avenue de Luxembourg, 4940 Bascharage, 4940, LU)
International Classes:
F02M47/02; F02M57/00; F02M65/00
Domestic Patent References:
WO2016008640A12016-01-21
WO2005080786A12005-09-01
Foreign References:
DE102005002796A12006-08-03
Attorney, Agent or Firm:
DELPHI FRANCE SAS (Bâtiment le Raspail - ZAC Paris Nord 2 22 avenue des Nations CS65059 Villepinte, Roissy CDG Cedex, 95972, FR)
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Claims:
Claims:

1 A fuel injector (10) having

- a head (12) provided with an electrical connector (14) adapted to provide connections (15) from and to an ECU (16) to selectively energize an actuator (18) via electrical connections (15, 102) to start and stop fuel injection pulses,

- a fuel supply connection (20) for supplying fuel into the injector (10) at an elevated pressure,

- a fuel return connection (22) for returning fuel at a lower pressure, - a fuel injection nozzle (26) assembly having

- a nozzle body (41) provided at an end with nozzle openings (28),

- a valve member (32) axially guided in the nozzle body (41) between an upper guide member (31) and a lower guide (29), the valve member (32) being adapted to be biased to close against a valve seat (38) and inhibit fuel injection through the noz- zle openings (28) or to move away from the valve seat (38) to enable fuel spray through the nozzle openings (28),

- a fuel passage (42) communicating fuel from the supply connection (20) to the nozzle openings (28),

- a branch from the fuel passage (42) to a control chamber (34), an end of the valve member (32) remote from the valve seat (38) protruding in said chamber

(34) so that fuel pressure in the chamber (34) urges the valve member (32) towards the valve seat (38) in a closed position of the nozzle, and

- a control valve (52) operated by the actuator (18) to allow fuel from control chamber (34) to pass to the return connection (22) thereby lowering the pres- sure in the chamber (34) and enabling to move the valve member (32) away from the valve seat (38) in an open position of the nozzle enabling said fuel injection, characterized in that

the fuel injector further comprises a circuit for detecting by an electrical change whether the nozzle is open or closed, the circuit extending between the electri- cal connector (14) and the upper guide member (31), the circuit including a resilient electrical link (126).

2. A fuel injector (10) in accordance with the preceding claim wherein the resilient link (126) comprises a rigid conductor member (130) and at least one axially resilient conductor member (134) arranged in series with the rigid conductor (130). 3. A fuel injector (10) in accordance with claim 2, wherein the circuit further comprises a conductor (110) arranged along the electrical connections (15, 102) for the actuator to a position generally at a head end of the actuator (18), a contact member (118) at the head end of the actuator (18) maintained in electrical contact with the conductor (110) and the resilient electrical link (126) axially extending along the actuator, from the contact member (118) to the upper guide member (31).

4. A fuel injector (10) in accordance with claim 3 wherein the conductor (110) and the resilient electrical link (126) are directed parallel to a longitudinal axis (X) of the actuator.

5. A fuel injector (10) in accordance with either of the claims 3 or 4, wherein the electrical connections (15) for the actuator (18) are electrically isolated by an isolation member (102) extending through an axial bore (112) provided in the injector body between the head (12) and the actuator (18), and wherein the insulated conductor (110) for the circuit is arranged inside the insolation member (102) along the electrical links (15).

6. A fuel injector (10) in accordance with either of the claims 3 or 4, wherein the electrical connections (15) for the actuator (18) are electrically isolated by an isolation member (102) extending through an axial bore (112) provided in the injector body between the head (12) and the actuator (18), and wherein the insulated conductor (110) for the circuit is arranged outside and along the insolation member (102).

7. A fuel injector (10) in accordance with any one of the claims 3 to 6, wherein the end part (116) of the insulated conductor (110) opposite to the head (12) is bent through approximately a right angle to contact the contact member (118).

8. A fuel injector (10) in accordance with any one of the claims 3 or 6, wherein the contact member (118) is a disc member generally arranged on the head of the actu- ator (18), said disc (118) having an upper or lower face in electrical contact with the conductor (110) and the lower face in electrical contact with the resilient electrical link (126). 9. A fuel injector (10) in accordance with claim 8, wherein the disc (118) is provided with a nose portion (119) radially extending beyond the actuator, the resilient electrical link (126) being in contact with the under face of said nose portion (119).

10. A fuel injector (10) in accordance with any one of the claims 3 to 9, wherein the conductor (110) is welded or brazed to the disc (118).

11. A fuel injector (10) in accordance with any one of the claims 3 to 9, wherein the contact member (118) is urged by a compression spring (120) into contact with an end (116) of the conductor (110) positioned at the head end of the actuator (18).

12. A fuel injector (10) in accordance with any one of the claims 1 or 2, wherein the circuit extends along a straight direction parallel and radially offset to the longitudinal axis (X) of the injector, said circuit going from the head (12) of the injector to the upper guide member (31).

13. A fuel injector (10) in accordance with any one of the preceding claims, wherein the resilient electrical link (126) is a coil spring (136).

14. A fuel injector (10) in accordance with claim 13, wherein the coil spring (136) comprises a first portion (138) having touching turns, said portion being axially non- resilient and, an second portion (140) wherein the turns of the spring are distant from one another, said second portion being resilient.

15. A fuel injector (10) in accordance claim 14, wherein the coil spring (136) is fur- ther provided with a third portion (142), the turns of the spring of said third portion

(142) being distant from one another, said third portion (142) being axially resilient and wherein, the first portion (138) is a central portion of the coil spring (136), the second portion (138) is an extreme portion of the spring in contact with the upper guide mem- ber (31) and, the third portion (142) is an opposite extreme portion of the spring (136) in electrical contact with the contact member (118).

16. A fuel injector (10) in accordance with any one of the preceding claims, where- in the electrical circuit comprises a resistive coating, such as diamond like carbon (DLC), applied to at least one of the valve seat (38) and a region of the valve member (32) cooperating with the valve seat (38) or, on an element incorporated in the valve member (32).

Description:
FUEL INJECTOR FOR A COMBUSTION ENGINE The present invention relates to a fuel injector for a combustion engine.

More specifically it relates to a kind of fuel injector having a head provided with an electrical connector adapted to provide connections from and to an ECU to selectively energize an actuator via electrical connections to start and stop fuel injection pulses, a fuel supply connection for supplying fuel into the injector at an elevated pressure, a fuel return connection for returning fuel at a lower pressure, a fuel injection nozzle assembly having a nozzle body provided at an end with nozzle openings, a valve member axially guided in the nozzle body between an upper guide member and a lower guide, the valve member being adapted to be biased to close against a valve seat and inhibit fuel injection through the nozzle openings or to move away from the valve seat to enable fuel spray through the nozzle openings, a fuel passage communicating fuel from the supply connection to the nozzle openings, a branch from the fuel passage to a control chamber, an end of the valve member remote from the valve seat protruding in said chamber so that fuel pressure in the chamber urges the valve member towards the valve seat in a closed position of the nozzle, and a control valve operated by the actuator to allow fuel from control chamber to pass to the return connection thereby lowering the pressure in the chamber and enabling to move the valve member away from the valve seat in an open position of the nozzle enabling said fuel injection.

Fuel injectors of this kind are known per se and indeed the actuator can either be a so- lenoid type actuator or a piezoelectric actuator. Irrespective of the specific design of actuator that is used, the operation of the control valve to direct fuel from the branch to the return connection lowers the pressure operating in the chamber and enables the valve member to move away from the valve seat in an open position of the nozzle enabling a fuel injection pulse.

Once the control valve is closed, by a signal sent from the ECU to the actuator, the pressure in the branch increases again, and thus the pressure operating on the end face of the valve member increases, so that the valve member is again urged towards the valve seat. As explained above the valve member is biased towards the valve seat, generally by a spring such as a compression coil springs, so that the valve member always moves in the closing direction once the elevated fuel pressure from the branch acts on the end face of the valve member. Once the nozzle is closed, by virtue of the valve member sealing against the valve seat, the net hydraulic force operating on the valve member is towards the valve seat. This is the case because the area of the valve member in the chamber above the valve seat on which the fuel pressure acts is less than the area of the end face of the valve member on which the same pressure acts. The resultant force together with the force of the biasing means is always sufficient to hold the valve member in contact with the valve seat against the force of the combustion pressure acting on the valve ember via the nozzle openings at the combustion side of the valve seat. It is now known that major improvement in the control of fuel injection equipment and of the injection event is obtained with a so called closed-loop control method, which makes it possible to more accurately control the opening and closing of the fuel injector and thus the quantity of fuel injected in each injection pulse. In such method, executed by an electronic control unit (ECU) that controls the operation of the fuel injec- tion equipment and in particular the control valve of the fuel injector, the fuel injector is provided with close loop means enabling an electrical signal to be generated when the valve member reaches the closed position. In other embodiments, the signal can also take a specific value when the valve member is in the fully open position. Such close loop means typically comprise the electrical insulation of the needle relative to the noz- zle body, with the exception of the moving seating face and fixed seating face that are electrically conductive. In this way the needle and nozzle body cooperate as an electrical switch part of an electrical circuit which is closed when the needle is in closed position and which is open when the needle is either in ballistic mode or in fully open position. Consequently, a 0-1 step signal can be measured and entered in an electronic control unit (ECU) controlling the fuel injection equipment as a feedback signal which is taken into account in the parameters of the control algorithm of the fuel injectionequipment.

Such close loop means have been disclosed following various embodiments in applications PCT/EP2014/073662, F 1456783 and FR1457078.

In the invention described in our non-pre-published UK application GB1S41007.5 there is provided a nozzle assembly in which an electrical circuit comprises the valve needle, the nozzle body, isolation means preventing electrical contact between the needle member and the nozzle body when the needle is in ballistic mode, between the open and the closed positions, so that an electrical signal enabling contact detection between the two seating faces is able to determine whether the valve member is in sealing contact with the valve seat. This makes it possible to more accurately time the start and finish of each fuel injection pulse:

The object underlying the present invention is to improve a fuel injector of the initially named kind by providing advantageous arrangements for an electrical path for transmitting the electrical switching signal through the injector in order to detect by an electrical change whether the nozzle is open or closed. According to the present invention the fuel injector of the initially named kind further comprises a circuit for detecting by an electrical change whether the nozzle is open or closed, the circuit extending between the electrical connector and the upper guide member, the circuit including a resilient electrical link. A large variety of designs can be considered for the resilient electrical link of the invention.

Thus, in one embodiment of the invention, the resilient link expediently comprises a rigid conductor member and at least one axially resilient conductor member arranged in series with the rigid conductor. The axially resilient conductor member can comprise a spring contact member. This may either take the form of a resilient element such as a coil spring or a leaf spring or may be formed by solid contact pins resiliently supported on the rigid conductor member, for example a conductive bar or tube with hollow ends supporting coil springs urging the contact pins outwardly. The resilient electrical link is provided with insulation except at the free ends of the contact pins.

This design ensures good electrical contact is always achieved despite manufacturing tolerances and avoids the need to provide brazed or crimped connections. In one particularly preferred embodiment the resilient electrical link is formed by a coil spring. This is a relatively inexpensive embodiment to realize. The coil spring can be resilient over its whole length or can comprise a first portion having touching turns, said portion being axially non-resilient and a second portion in which the turns of the spring are distant from one another, said second portion being resilient. In another embodiment the coil spring forming the resilient link is further provided with a third portion, the turns of the spring of said third portion being distant from one another, said third portion thereby being axially resilient. In this design the first portion is a central portion of the coil spring the second portion is an extreme portion of the spring in contact with the upper guide member and the third portion is an opposite extreme portion of the spring in electrical contact with the contact member. The coil spring is expediently provided with insulation other than at its ends generating electrical contact with the contact member and the upper guide member.

In one embodiment the circuit for detecting by an electrical change whether the nozzle is open or closed further comprises a conductor arranged along the electrical connections for the actuator to a position generally at a head end of the actuator, a contact member at the head end of the actuator maintained in electrical contact with the conductor and the resilient electrical link axially extending along the actuator, from the contact member to the upper guide member.

This arrangement reflects the fact that the alignment of the actuator relative to the body of the fuel injector and above all the angular position of the electrical link relative to the actuator as well as the relative position of the conductor at the junction between the actuator isolation member and the actuator can vary on assembly of the fuel injec- tor due to manufacturing tolerances. By using a contact member of sufficient areal extent electrical contact problems due to alignment tolerances can be avoided.

The conductor and the resilient electrical link are directed parallel to a longitudinal axis of the actuator, but are not necessarily in line with one another but can rather be offset radially relative to each other.

In one basic embodiment of the invention the electrical connections for the actuator are conveniently electrically isolated by an isolation member extending through an axial bore provided in the injector body between the head and the actuator, and the insulat- ed conductor for the circuit for detecting by an electrical change whether the nozzle is open or closed is expediently arranged inside the insolation member along the electrical connections to the actuator. Thus the connections between the actuator and the head can extend through an axial bore or one or more axially parallel bores in an isolation member for the actuator extending between the head and the actuator and the conductor for the circuit detecting the closing of the valve member can extend through the same bore or one of the axial bores or through another axially directed bore of the isolation member. This enables a compact arrangement and facilitates the electrical connections to the ECU (engine control unit) at the head of the injector.

In an alternative basic embodiment of the invention the electrical connections for the actuator are electrically isolated by an isolation member extending through an axial bore provided in the injector body between the head and the actuator, and the insulated conductor for the circuit for detecting by an electrical change whether the nozzle is open or closed is arranged outside and along the isolation member.

In the above described embodiments of the invention the end part of the insulated con- ductor of the circuit for detecting by an electrical change whether the nozzle is open or closed is bent opposite to the head, i.e. remote from the head, through approximately a right angle to contact the contact member.

The contact member is expediently designed as a disc member generally arranged on the head of the actuator, said disc having an upper or lower face in electrical contact with the conductor and the lower face in electrical contact with the resilient electrical link. This design is particularly advantageous for the assembly of the fuel injector and of the electrical circuit for detecting by an electrical change whether the nozzle is open or closed.

The disc may expediently be provided with a nose portion radially extending beyond the actuator, the resilient electrical link being in contact with the under face of said nose portion. The conductor for the circuit for detecting by an electrical change whether the nozzle is open or closed may expediently be welded or brazed to the disc.

The resilient link ensures good contact to the contact member and to the respective one of the valve member or valve guide irrespective of thermal growth that may occur in use.

The contact member preferably comprises an axial disc generally coaxial to the actuator and surrounding the axial isolation member for the actuator extending between the head and the actuator The axial disc can readily be contact the conductor and the electrical link at least over a range of angles adapted to cope with misalignment of the end of the conductor and the electrical link.

In such an arrangement the contact member can be urged by a compression coil spring surrounding the isolation member for the actuator into contact with an end of the conductor positioned at the head end of the actuator. This embodiment is compact, simple to assemble and relatively inexpensive to realize.

The resilient link ensures good contact to the contact member and to the respective one of the valve member or valve guide irrespective of thermal growth that may occur in use.

In one embodiment the circuit for detecting by an electrical change whether the nozzle is open or closed generally extends along a straight direction parallel and radially offset to the longitudinal axis of the injector, said circuit going from the head of the injector to the upper guide member.

The invention can be used with a variety of actuators such as a solenoid and a piezoelectric actuator.

Finally, in a particularly preferred design of the invention, the electrical circuit for detecting by an electrical change whether the nozzle is open or closed comprises a resistive coating, such as diamond like carbon (DLC), applied to at least one of the valve seat and a region of the valve member cooperating with the valve seat or on an element incorporated in the valve member.

The conductor need not necessarily be guided through the isolation member for the actuator. It can, for example be directed parallel to an axis of the actuator in an outer region of a body of the actuator. In this case the contact member can comprise either a conductive disc or a radially directed element and the electric link comprises an insulated conducting element disposed generally parallel to an axis of the valve member, but generally further from the axis than the said conductor. Thus the radially directed con- tact member facilitates the radial offset between the conductor and the electrical link.

The invention will now be described in more detail by way of example only and with reference to embodiments of the invention as shown in the accompanying drawings in which:

Fig. 1 shows an axial section of a fuel injector in accordance with the present invention, shows a detailed view in an axial section of the central portion of the fuel injector of Fig. 1 to an enlarged scale and illustrates the arrangement of th circuit for detecting opening and closing of the nozzle, shows a detailed view in an axial section of the central portion of a fuel injector similar to that of Fig. 1 to an enlarged scale with an alternative design of resilient link for the circuit for detecting opening and closing of the nozzle,

Fig. 3 shows a schematic version of an alternative embodiment to Fig. 1 in which the conductor of the circuit extends radially outside of the isolation mem- berfor the actuator of the fuel injector, with Fig. 3A illustrating the assembly, Fig. 3B showing the circuit separated from the structure of the injector for ease of understanding and Fig. 3C showing an axial view of the contact member in the form of a conductive disc, Fig. 4 shows a schematic version of another alternative embodiment to Fig. 1 in which the conductor of the circuit extends radially outside of the isolation memberfor the actuator of the fuel injector, with Fig. 4A illustrating the assembly and Fig. 4B showing the circuit separated from the structure of the injector for ease of understanding and

Fig. 5 shows a schematic version of yet another alternative embodiment to Fig. 1 in which the conductor of the circuit extends radially outside of the isolation member for the actuator of the fuel injector, with Fig. 5A illustrating the assembly, Fig. 5B showing the circuit separated from the structure of the injector for ease of understanding and Fig. 5C showing the conductor at the interface between the isolation member for the actuator and the actuator. Turning now to Figs. 1 and 2A there can be seen a fuel injector 10 having a head 12 provided with an electrical connector 14 adapted to provide connections 15 from and to an ECU 16 to selectively energize an actuator 18 via electrical connections 15, 102 to start and stop fuel injection pulses. A fuel supply connection 20 is provided at the head 12 for supplying fuel into the injector 10 at an elevated pressure. A fuel return connection 22 is provided for returning fuel at a lower pressure to a schematically illustrated fuel storage tank 24. At the opposite end from the head portion 12 the injector 10 has a fuel injection nozzle assembly 26 having a nozzle body 41 provided at an end with nozzle openings 28. A valve member 32 is axially guided in the nozzle body 41 between an upper guide member 31 and a lower guide 29. The valve member 32 is adapted to be biased by a compression coil spring 36 to close against a valve seat 38 and inhibit fuel injection through the nozzle openings 28 or to move away from the valve seat 38 to enable fuel spray through the nozzle openings 28. The valve seat 38 is provided in the lower guide 29 just above the nozzle openings 28. A fuel passage 42 communicates fuel from the supply connection 20 to the nozzle openings 28. A branch (not shown) leads from the fuel passage 42 to a control chamber 34 and an end 33 of the valve member 32 remote from the valve seat 38 protrudes into the chamber 34. Fuel pressure in the chamber 34 urges the valve member 32 towards the valve seat 38 in a closed position of the nozzle. A control valve 52 is operated by the actuator 18 to allow fuel from control chamber 34 to pass (via a non-illustrated passage) to the return connection 22 thereby lowering the pressure in the chamber 34 and enabling the valve member 32 to move away from the valve seat 38 into an open position of the nozzle enabling said fuel injection. The fuel injector further comprises a circuit for detecting by an electrical change whether the nozzle is open or closed. The circuit extends between the electrical connector 14 and the upper guide member 31 and includes a resilient electrical link 126.

In the design shown in Fig. 1 the nozzle body 41 has separate coaxially disposed upper and lower guide members 29 and 31. However, it is not necessary for the upper and lower guide members 29, 31 to be separate parts, instead they could be formed in one part.

Irrespective of whether a one part design or a two part design is used the valve member 32 has a generally conical sealing surface 40 which seats against the generally conical valve seat 38 of the lower valve guide member 29. When the control valve 52 operates to lower the pressure in the chamber 34 the valve member 32 is able to move within the chamber 34 away from the valve seat 38 under the influence of fuel pressure in the passage 42 to eject fuel through the nozzle openings 28, i.e. to inject it into a cylinder of an associated combustion engine (not shown). The basic operation of the fuel injector is well known to persons skilled in the art and will not therefore be described further.

The fuel injector 10 is normally fed with high pressure fuel from a common rail 54 (only shown in Fig. 1) of the associated engine (not shown). The common rail 54 is fed with fuel from the fuel tank 24 via a low pressure pump 56 in or at the tank 24 and via a high pressure pump 58, so that the elevated fuel pressure prevailing at the fuel supply connection 20 is around 2000 bar and above. As is well known one or more filters and fuel cut off valves (neither shown) can also be included in the fuel supply system. Moreover, in a multi-cylinder engine each cylinder is equipped with a respective fuel injector 10 and the fuel injectors are all connected to the common rail.

It will be seen from Fig. 1 that the nozzle assembly 26 and control valve assembly 52 are inside the cap nut 96, whereas the actuator 18 and the wires 14 connecting to it are located in a bore drilled in the NHB 92 (Nozzle Holder Body) to which the cap nut is con- nected by a threaded connection. The actuator 18, the control valve 52 and the valve guide members 29, 31 have finely machined mating surfaces at the junctions between them that are held together in fuel-tight manner by the cap nut 96 which has internal threads 98 engaging external threads 100 on the NHB 92. Because of this construction and the manufacturing tolerances involved there is always the possibility of slight angular misalignment of the actuator 18 relative to the control valve 52 and the nozzle assembly 26 and this makes it difficult to ensure electrical connections between the nozzle assembly and the ECU connections at the head 12 of the actuator. When it is desired to detect changes in an electrical parameter at the nozzle assembly, which occur when the valve member 32 moves away from and engages the valve seat 38, then there must necessarily be an electrical connection from the nozzle assembly to the ECU 16 so that the ECU 16 can process this change and use it to more accurately control the operation of the control valve 52 and thus of the fuel injector 10. The electri- cal circuit which is used to detect this change requires two connections. One of these is easily realized as an earth connection through the material of the fuel injector to the grounding connection for the actuator 18 and from there via one of the leads 14 to the ECU, or through the cap nut 96 and/or the NHB 92 to a common earth for the ECU. The other electrical connection must be an insulated connection which needs to be conduct- ed through the fuel injector via the third lead 17 connecting the fuel injector to the ECU. This is the so called closed loop electrical conductor, which together with the earth connection enables closed loop control of the control valve 52 and thus of the opening and closing of the valve member 32, i.e. its movement away from and towards the valve seat 38.

Different ways of realizing the closed loop connection path forming the insulated part of the circuit for detecting by an electrical change whether the nozzle is open or closed will now be discussed with reference to the figures. In the design shown in Figs. 1 and 2A the closed loop conductive path of the circuit comprises an insulated conductor 110 extending between the head 12 of the fuel injector through a central bore 112 in the isolation member 102 for the actuator 18 to a position generally at a head end 114 of the actuator 18. It should be noted that the isolation member 102 is actually part of the actuator 18, basically it is an overmoulding of insulating resin which surrounds blades or wires 15 which control the actuator (solenoid) 18. In the design of Figs. 1 and 2A the insulated conductor 110 passing through the central bore 112 is bent radially outwardly (radially outwardly directed portion 116) and lies directly beneath a disc-like contact member 118 at the head end 114 of the actuator. The contact member 118 which comprises an axial disc surrounding the isolation member 102 is urged in this embodiment by the actuator clamping spring 120, a compression coil spring, against the end portion 116 of the electrical conductor 110. The spring 120 surrounds the actuator isolation member 102 within a recess 122 of the NHB and bears against an insulating washer 124, which in turn presses the disc-like contact member into electrical contact with the bent end portion 116 of the conductor 110 from which the insulation has been removed. The disc-like contact member 118 is insulated from the armature of the actuator 18 and from the actuator isolation member 102 by suitable electrical insulation (not shown in Figs. 1 and 2). The conductor 110 is made of a metal wire and is insulated either by shrink tubing or by overmoulding it into the insulating resin of the isolation member 102 which forms part of the solenoid of the actuator. It can also be located alongside the solenoid control wire 15 and overmoulded with resin at the same time. In this case all these wires pass through the central bore 112 of the isolation member 102 and the conductor 110 is also insulated from the wires 15. This enables a particularly compact arrangement.

The electrical contact to the bent end portion 116 takes place in a radially inner portion of the contact member 118.

The radially outer portion of the disc-like contact member 118 is in electrical contact with an insulated resilient electrical link 126 which extends between the contact member 118 and one of the valve member 32 and the valve guide member 31. In this case it connects to the valve guide member 31 through a bore in an outer portion of the body of the control valve 52 directed axially parallel to the central axis of the control valve 52. It will be appreciated that in the design of Figs. 1 and 2A, 2B the electrical contact between the bent end portion 116 of the conductor 110 and the contact member 118 and the contact between the electrical link 116 and the contact member 118 is highly insen- sitive to angular misalignment of the electrical link 126 and the conductor 110, i.e. its bent end 116.

It is also conceivable that the conductor 110 could be welded or brazed to the contact member 118.

The design is such that the insulated electrical ink passes through the NBH 92, obliquely through a bore in the upper part 31 of the valve guide 30 and then through the valve member 32 to the conical seating surface 40 of the valve member 32. An insulating layer or layer (not shown) is provided at the conical seating surface 40 or at the mating conical seat of the valve guide and the electrical resistance of this layer or these layers changes in response to contact pressure of the valve member against the valve seat 38 at the lower valve guide member 29. The lower valve guide member 29 together with the cap nut 96 and the NHB 92 forms the earth connection to the ECU. It is of course necessary to provide insulation between the valve member 32 and the upper and lower valve guide members 29 and 31 at other points where contact between these elements may occur, for example at sliding surfaces of the valve member 32 close to its lower end that serve to guide it in the lower valve guide member 29. In a design with a two part valve guide insulating layers must also be provided there between the valve member 32 and the upper part 31, and between the upper valve guide member 31 and the lower valve guide member 29 and any related structure, so that a uniquely defined electrical path exists. In this way the closed loop link enables the ECU to measure the electrical resistance between the valve member 32 and the valve seat 38 at the valve seat 38. The return path of the circuit is through the valve member 32 to the grounded structure of the fuel injector and ultimately to the ECU 16. The electrical change detected by the ECU can be at least one of a change in resistance, a change in potential and a change in current.

The resilient electrical link 126 can be realized in different ways. In the embodiment of the invention shown in Figs. 1 and 2A the resilient link 126 expediently comprises a rigid conductor member 130 and at least one axially resilient conductor member 134 arranged in series with the rigid conductor 130. The axially resilient conductor member can comprise a spring contact member 134. This may either take the form of a resilient element such as a coil spring or a leaf spring or may be formed as shown in Figs. 1 and 2A by solid contact pins resiliently supported at the rigid conductor member 130. In this example the rigid conductor member is a conductive bar or tube with hollow ends supporting coil springs (not shown) urging the contact pins 134 outwardly. The resilient electrical link is provided with insulation except at the free ends of the contact pins. Fig. 2B shows an alternative design of the resilient link 126 but is otherwise essentially identical to the design of Figs. 1 and 2A so that details of the fuel injector 10 not related to the resilient link will not be unnecessarily repeated and the previous description will be understood to apply also to Fig. 2B. In the embodiment of Fig. 2B the resilient electrical link 126 is a coil spring 136. The coil spring 136 comprises a first portion 138 having touching turns whereby this portion is axially non-resilient, at least in compression, and a second portion 140 in which the turns of the spring are distant from one another whereby the said second portion is resilient both in compression and extension. In the design of Fig. 2B the coil spring 136 is further provided with a third portion 142 in which the turns of the spring are distant from one another, whereby the third portion 142 is also axially resilient in the same way as the second portion 140. As shown the first portion 138 is a central portion of the coil spring 136, the second portion 140 is an extreme portion of the spring in contact with the upper guide member 31 and the third portion 142 is an opposite extreme portion of the spring 136 in electrical contact with the contact member 118. It is however not necessary to provide three distinct portions, just two, one stiff one and one resilient one are sufficient. It is unimportant where the resilient portion is located, it could be at either end of the rigid portion or indeed centrally disposed between two rigid portions.

Clearly the ends of the coil spring contacting the contact member 118 and the valve member 32 need to be exposed to ensure electrical contact, otherwise they are separated by appropriate electrical insulation from the structure of the fuel injector 10. One way of doing this is to use insulating shrink tubing to surround the electrical link 126. In an alternative embodiment illustrated in Figs. 3A to 3C the conductor 110 is directed parallel to an axis X of the actuator 18 in an outer region 132 of the isolation member 102 of the actuator 18. The contact member 118 can again comprise an axial disc. In this case the conductor 110 is expediently welded or brazed to a radially inner portion of the disc-like contact member 118. The electrical link 126, which can be designed in any of the ways described with reference to Figs. 1 and 2, conveniently contacts a radially outer region of the disc-like contact member 118. The enlarged end view of the disc-like contact member 118 with the nose portion 119 shown in Fig. 3C shows that this design is also insensitive to angular misalignment of the insulated conductor 110 and the electri- cal link 126. Again all parts are insulated to prevent unwanted connections to ground.

Figs. 4A and 4B illustrate another embodiment in which the insulated conductor 110 is again directed parallel to an axis X of the actuator 18 in an outer region 132 of the isolation member 102 of the actuator 18. Here the contact member 118 comprises a radially directed element and the electric link 126 comprises an insulated conducting element disposed generally parallel to an axis of the valve guide 30 but at a larger radius than the insulated conductor 110. In this embodiment the insulated conductor 110, the insulated contact member 118 and the insulated electrical link 126 can be made in one piece. The electrical link 126 preferably has a resilient contact to the upper valve guide member 31.

Finally, Figs. 5A to 5C show another alternative embodiment in which the insulated conductor 110 again passes through a central axial bore 112 of the isolation member 102 for the actuator 18. At the interface between the isolation member 102 and the actuator 18 the insulator is again bent outwardly to form an outwardly bent end portion 116. The disc-like contact member is again pressed in this embodiment against an exposed electrically conductive surface of the conductor 110. The construction is similar to that shown in Fig. 2 and again a coil spring for clamping the actuator can act on the disc-like contact member 118 via an insulating washer, although these details are not shown in this diagram. The Figs. 5A and 5B do however show that the connections 15 to the ECU lie in respective axially parallel bores in the isolation member 102 which are separated from but parallel to the central bore 112 which accommodates the closed loop link 104. This embodiment is thus distinguished from that of Figs. 1 and 2A, 2B by the fact that the disc-like contact member 118 is welded here to the conductive link 126 and the fact that the wires 15 and the conductor 110 run in separate bores of the support member. The invention also relates to a fuel injector 10 of the kind described in combination with an ECU 16 there being first and second connections 15 from the ECU 16 to the actuator 18 of the fuel injector 10, one of said connections 15 being a grounding connection and the other being a power connection, and also a third connection 17 for the said circuit (closed loop link 104) to the ECU 16.

When references are made in this specification to up or down or to upper or lower or to lifting or related expressions are used this will be understood to refer to a vertical posi- tion of the fuel injector with the nozzle openings 28 at the bottom. This does not, however, mean that the fuel injector cannot be used in other orientations and should not be interpreted restrictively.

The last portion of the conductor at the actuator end of the isolation member can be bent through approximately a right angle to contact the contact member. This is a rela- tively simple design that readily tolerates misalignment.

List of reference numerals

10 fuel injector

12 head of fuel injector

14 electrical connector

15 connections from ECU 16 to actuator 18

16 ECU

17 connection from closed loop link to ECU 16

18 actuator, solenoid or piezoelectric

20 fuel supply connection to fuel injector 10

22 fuel return connection from fuel injector 10

24 fuel storage tank

26 nozzle assembly

28 nozzle openings

29 lower part of valve guide 30

31 upper part of valve guide 30

32 valve member, needle

33 end of valve member 32 34 chamber in valve guide 30

36 spring biasing valve member 32 towards the valve seat 38

38 valve seat

40 generally conical sealing surface of the valve member 32 41 nozzle body

42 fuel passage

52 control valve

54 common rail

56 low pressure pump

58 high pressure pump

92 nozzle holder body of fuel injector 10

94 lower part of fuel injector 10

96 cap nut

98 internal thread of sleeve nut 96

100 external thread of outer sleeve 106 of upper part 92

102 insulated electrical connection

110 insulated conductor of closed loop link

112 central bore of isolation memberl02

114 head end of actuator 18

116 radially outwardly bent end portion of conductor 110

118 contact member of closed loop link

120 coil spring for clamping actuator 18

122 recess in outer sleeve 106 accommodating coil spring 120

124 washer

126 resilient electrical link

130 rigid portion of closed loop link 126

132 outer region of isolation memberl02

134 spring contact member(s)

136 coil spring forming resilient electrical link 126

138 first portion of coil spring 136

140 second portion of coil spring 136

142 third portion of coil spring 136