GB2567191A

GB2567191A - Fuel injector

Info

Publication number: GB2567191A
Application number: GB1716285.0A
Authority: GB
Inventors: P Cooke Michael
Original assignee: Delphi Technologies IP Ltd
Current assignee: Delphi Technologies IP Ltd
Priority date: 2017-10-05
Filing date: 2017-10-05
Publication date: 2019-04-10
Anticipated expiration: 2037-10-05
Also published as: WO2019068566A1; GB201716285D0; GB2567191B

Abstract

A fuel injector 10 comprising a solenoid 36 adapted to generate sufficient forces to reciprocally move a needle valve member 98 between a closed position and an open position; the solenoid 36 comprising a fixed coil cooperating with an armature (106, Fig. 5) fixed to the needle 98 and, a metallic tube 60 connected to a return port and to the needle, thus reducing the needle surface pressurised by high pressure.

Description

FUEL INJECTOR

TECHNICAL FIELD

The present invention relates to a direct acting solenoid diesel fuel injector.

BACKGROUND OF THE INVENTION

Making a direct acting solenoid injector work at the pressures needed for modern diesel fuel injection equipment is a challenge because it is difficult for a solenoid to generate the high force needed to overcome the seat pressure imbalance of a conventional diesel nozzle when the needle valve member is seated in a closed position. Most approaches concentrate on multiplying the force on the solenoid (e.g. EP2530293, WO2013189636, DE 102012222043, EP2295785). These suffer from complexity and high inertia forces because the only way to get more force than the solenoid can provide is to use some form of mechanical advantage which multiplies the force using a “lever” ratio, but this also means the solenoid must move more distance and at higher velocity by the same ratio. A few attempts have been made to reduce the force imbalance from the nozzle. GB2526273 has a balancing piston which reduces the seat force, but these pistons entail guide leakage which consumes power and requires measures to catch the leakage. Application GB 1711913.2 describes a leak free force balancing concept using a spring tube compressed under pressure, but the relatively low spring tube compressibility under pressure limits the amount of assistance this can provide if a large needle lift is required for instance for Heavy Duty nozzles.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to resolve the above mentioned problems in providing a fuel injector adapted to be part of a direct fuel injection equipment of an internal combustion engine. Said injector has an elongated shape extending along a main axis and comprising a body defining an inner space. In use, fuel at high pressure enters via an inlet and, a solenoid is adapted to generate sufficient forces to reciprocally move a needle valve member between a closed position of a valve seat preventing fuel injection and, an open position of said valve seat enabling said fuel injection through spray holes drilled at a bottom end of the injector body.

Said solenoid comprises a coil fixed to said body and cooperating with a magnetic armature fixed to said needle. A metallic tube extending in said body inner space is also arranged. Said tube extends from a first end connected to a return low pressure port to a second end defining a bore wherein is slidably inserted a piston integral to the head of the needle valve member. The tube inside channel is in fluid communication with the drain and it remains at a low pressure at all-time thus reducing the needle surface pressurised by high pressure.

Also, said injector inner space is divided by a core member in an upper chamber wherein extends the tube and in a nozzle chamber wherein extends the needle, said core member being provided with a through hole for the second end of the tube and the head of the needle to be slidably engage together.

Also, the coil is positioned around said core.

Also, the fuel injector further comprises a fluid communication enabling fuel to flow between said upper chamber and said nozzle chamber.

Said fluid communication partially extending through the core. Said fluid communication partially extends through the armature.

Also, the section area of the fluid communication evolves from an open state when the needle is in closed position to a restricted state when the needle is in open position.

More precisely, the fluid communication comprises a first path defined by a first hole and a throttle having a fixed section generating, in use, a pressure difference between said upper chamber and said nozzle chambers and, a second path defined partially by a second hole, said second path having an evolving section.

Also, the magnetic armature cooperates with the core to define together said second path of the fluid communication. The opening section of said second path increases continuously from a first state when the needle is in open position to a second state when the needle moves to the closed position.

In said first state, said second path is fully closed, the open state of the fluid communication being the fixed section of the throttle.

The fuel injector further comprises an adjusting member fixed to the injector body and defining a thrust face against which abuts the top end face of the tube. Said adjusting member is a cylinder fixed in a bore extending through the body of the injector, said cylindrical adjusting member comprising an upper inlet portion fixed in said bore and a lower portion defining said thrust face.

Said lower portion is provided with an inner conduit opening in said thrust face and interconnecting the tube inner channel to the low pressure drain port.

Also, the cylindrical adjusting member is press fitted in said bore.

Also, the cylindrical adjusting member is threaded and tightened in said bore.

Also, the adjusting member is provided with engagement means for complementary attachment of a tool enabling a positioning adjustment of the adjusting member in said bore.

Also, the adjusting member is further provided with a hole defining the fuel inlet. Said hole extends from an opening in its outer end to a blind bottom end.

Also the adjusting member further comprises a filter arranged in said hole, said filter comprising a plurality of micro-drillings extending from said hole to said inner chamber.

Also, the needle valve member is axially guided between a lower guiding means and an upper guiding means defined between an armature peripheral face and a complementary face of the injector body.

BRIEF DESCRIPTION OF THE DRAWINGS

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

Figure 1 is an axial view of a fuel injector as per the invention.

Figure 2 is an axial section of the injector of figure 1.

Figure 3 is a detail of the nozzle of the injector of figure 1.

Figures 4 is a section of a detail of the upper end of the injector of figure

1.

Figures 5, 6 and 7 are three detailed sections of the injector of figure 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In reference to the figures 1, 2 and 3 is generally described a diesel fuel injector 10 of a direct injection equipment of an internal combustion engine. The injector 10 has an elongated shape extending along a longitudinal axis X that is adapted to be inserted and clamped in a well provided in the engine block. Said injector 10 comprises an actuation assembly 12 (upper part of the figure) and a nozzle assembly 14 (lower part of the figure) fixed together by an injector capnut 16 abutting at an end against a shoulder of the nozzle and, firmly tightened at the other end, onto the actuation assembly. In use, fuel at high pressure, that can be 3000 bars or above, is delivered to the injector entering via a fuel inlet 18 arranged in the top of the actuation assembly 12 and flowing inside the injector toward spray holes 20 arranged in the opposite tip end 22 of the injector, for said fuel to be sprayed in a cylinder of the engine. To ease and clarify the description the arbitrary top-down orientation of the figures is utilised therefore words and expression such as “top, down, above, below, upper, under” are used without any limitation intention.

The actuation assembly 12 comprises a tubular actuator body 24 defining an inner chamber 26, also identified as upper chamber 26, surrounded by a peripheral wall 28 extending about said longitudinal axis X, from an upper end 30 where is provided said fuel inlet 18 to a lower end 34 defining a transverse lower face 35 wherein opens said upper chamber 26, said lower face 35 being limited to the annular area surrounding said opening. The peripheral wall 28 is further provided with a longitudinal groove 29 arranged on its outer face and extending between the upper and the lower ends. Over the upper end 30 of the body is engaged a plastic moulded electric connection assembly 31 defining an opening for said body engagement, and comprising an electrical connector 32 from where extends a lengthy arm wherein are overmoulded electrical wires 33, said wires 33 being arranged in said longitudinal groove 29.

A solenoid assembly 36 comprising an electrical coil 38 arranged around a core member 40, or magnetic pole piece 40, is inserted in the lower part of said upper chamber 26. The core member 40, better shown on figures 5, 6 and 7 is substantially cylindrical axially extending from an upper face 42, inside the upper chamber 26 to an opposed transverse under face 44. Between said opposed faces

42, 44 the core member defines a peripheral face complementary inserted in the lower end 34 of the actuator body, the core under face 44 being in approximately flush surface continuity with the annular lower face 35 of the actuator body. The coil 38 is wound in an annular shape and, it is engaged around said core peripheral face in an annular recess defined between the core and the inner face of the body

24. The core 40 is further provided with an axial through hole 46 comprising a top conical portion 48 largely opening in said upper face 42, said portion narrowing down for joining a central cylindrical portion 50 that downwardly joins a steeper lower conical portion 52 slightly widening toward an opening in said under face 44. The coil 38 is electrically connected to terminals of the connector 32 via the overmoulded electrical wires 33 extending in said longitudinal groove 29.

The actuator body 24 is also provided with flats 58 arranged in the upper part in the vicinity to the inlet 18 and of the connector 32 so that, when placed in the well of the engine block, the fuel inlet 18, the electric connector 32 and said flats 58 protrude outside the well enabling clamping of the injector to the engine block.

Inside the upper chamber 26 is arranged a tube 60 defining an inner channel 61. Said tube 60 extends from a first end 62, or tube upper end 62, defining a top-end-face 63 to, a second end 64, or tube lower end 64, defining an adjusted bore 65 which opening is surrounded by an annular down-end-face 66. In the upper end 62 the inner channel 61 opens in the centre of said top-end-face 63 and, at the opposite lower end 64, said channel 61 joins the adjusted bore 65 opening in the centre of said down-end-face 66.

The tube 60 is kept in place between an adjusting member 67 fixed in a bore 68 provided at the very top of the actuator body 24 and, a spring 69 compressed below the tube 60 and upwardly pushing on the down-end-face 66.

The adjusting member 67 defines a thrust face 70 against which the tube top-end-face 63 complementary abuts and, as shown, said faces define a sealed seat wherein said thrust face 70 defines a male conical face complementary engaged within said top end face 63 that defines a female conical face. In alternative embodiments not shown the sealed seat is defined with other complementary geometries such as flat faces or spherical faces.

Further described in reference to figure 4, the adjusting member 67 is cylindrical integrally comprising an upper inlet portion 71 defining the fuel inlet 18 of the injector and, a lower drain connector portion 72 defining a low pressure connector for the tube inner channel 61, the male conical thrust face 70 being the lower end face of said connector portion 72.

The upper inlet portion 71 comprises an axial blind bore 73 surrounded by a peripheral wall having an upper part 74 which outer face is threaded and complementary tightened in the bore 68 of the injector body and, a slightly narrower lower part 75 provided with micro holes radially drilled through said peripheral wall and opening at both ends in the blind bore 73, and in an annular gap G defined between the wall outer face and the bore 68 of the injector body. Said micro holes define together a filter 80 so that, in use, fuel entering the fuel inlet 18 flows in the bore 68 then in the blind hole 73, through said filter 80 prior to fill the upper chamber 26. In use, particles and debris present in the fuel are trapped at the bottom of said blind hole 73.

Also, the blind hole 73 is internally threaded 78 for complementary engagement of a tool, not shown, adapted to axially push-in or pull-out the adjusting member 67 in the bore 68 therefore enabling fine tuning of the position of the tube first end 62. Other complementary tool engagement means can be chosen.

The lower drain connector portion 72 downwardly extending from said upper inlet portion 71 to said male conical thrust face 70 has a cross section just fitted to said bore 68 and provided with axially extending flats 76 or channels enabling fuel to flow from said annular gap G down in said upper chamber 26. Inside the lower drain portion 72, the adjusting member 67 further comprises an inner conduit 77 having a first axial X portion opening at the tip end of the male conical thrust face 70, where it connects to the tube inner channel 61 and, a second radial portion opening in the outer face of said lower drain connector portion 72 in an area between said flats 76 where the inner conduit 77 sealingly connects to a drain port 79 arranged in the injector body. To ensure said sealing connection between the adjusting member 67 and the bore 68, the lower drain portion 72 is inserted in the bore 68 with a small interference fit sufficient for the sealing but still enabling axial tuning of the adjusting member 67 location.

In the lower part of the injector 10, the nozzle assembly 14 has a nozzle body 86 extending along the main axis X from a transverse upper face 88 down to said tip end 22, said upper face 88 being pressed in sealing surface contact against the transverse lower face 35 of the actuator body. The nozzle body internally defines a nozzle chamber 90 surrounded by a peripheral wall 92 that comprises a large upper portion defining a large portion 94 of the nozzle chamber and, a narrow lower portion defining a narrow portion 96 of the nozzle chamber, said narrow portion ending with said tip end 22.

In said nozzle chamber 90 is axially X guided a needle valve member 98 having a generally thin cylindrical core extending from a pointy end 101 that cooperates with a seating face 102 provided on the inner side of the peripheral wall 92 and defining a valve seat 103 right above said spray holes 20 to, a head 100 having an upper extension 105 defining a piston 105 slidably inserted in the adjusted bore 65 of the tube lower end 64, the needle head 100 defining a shoulder 104 at the joining intersection of the core to the piston 105. The bore 65 and the piston 105 are closely matched in diameter defining a slide fit preventing in use, the high pressure fuel to enter the tube and leak to the drain, ensuring that the tube inner channel 61 remains at low pressure.

A magnetic armature 106 is fixed to said needle 98. More precisely, said armature 106 has a general disc-like shape defining a cylindrical peripheral face 108 extending between a flat upper face 110 facing the under face 44 of the core member and, an opposed under face 112 facing said large portion 94 of the nozzle chamber. The armature 106 is provided with an axial through hole 113 extending between said opposed faces 110, 112 and in which is inserted the piston 105, the armature under face 112 abutting the shoulder 104 of the needle. On the other side, said piston 105 protrudes out of the hole 113 above the armature upper face 110 and is slidably inserted in the adjusted bore 65 ending the tube inner channel 61. The spring 69 upwardly pushing the tube 60 is compressed between said annular face 66 of the tube and a spring seat member 82 arranged on the armature upper face 110.

In an alternative shown on figure 5, the magnetic armature 106 is provided with a first through hole 114, on the right side of the figure, extending from an opening in the upper face 110, facing the lower conical portion 52 of the hole of the core member 40, to an opening in the under face 112, said through hole 114 defining a throttle 116 having a restricted cross-section.

In said alternative of figure 5, the magnetic armature 106 is further provided with a larger second through hole 118 also extending between said armature upper 110 and under 112 faces.

In another alternative presented in figure 6, the magnetic armature 106 is only provided with the first through hole 114 defining the throttle 116. It does not have a second though hole.

In practice, in the alternative of figure 5 there would be a plurality of second holes 118 equispaced on a pitch circle around the armature in order to avoid non-axial magnetic and hydraulic forces. There would also be a plurality of holes 114, 116 as well to minimise the radial space they take up so that the hole 52 through the solenoid does not need to be too big, which would lose solenoid force.

In another aspect of the invention shown on figure 5, the needle 98 is axially guided between a lower guiding means 120 and an upper guiding means 122, both guiding means defining enlarged portions of the needle adjusted to slide against the inner face of the narrow portion 96 of the nozzle chamber.

In the alternative of figure 7, the upper guiding means 122 is defined in the large portion 94 of the nozzle chamber, between the peripheral face 108 of the armature adjusted to slide against the inner face of the peripheral wall 92 of the nozzle.

In use, the injector 10 is arranged in a fuel injection equipment provided on an internal combustion engine and, fuel at high pressure, that can be 3000 bars and above, is delivered and enters the injector 10 via the fuel inlet 18. There it is filtered 80 from particles prior to fill the upper chamber 26 and to flow around the tube 60 in the through hole 46 of the core member. Then the fuel flows through the holes and throttle 116 of the armature and in the nozzle chamber 90, large 94 and narrow 96 portions. As said, the tube inner channel 61 remains at low pressure while the tube outside is subject to the high pressure of the upper chamber 26.

Three steps of the injector 10 operation are now briefly described.

In a first step, the coil 38 is not energised, the needle 98 is in a closed position CP wherein the valve seat 103 is closed preventing fuel injection through the spray holes 20. The needle 98 is subject to closing forces generated by the compression spring 69 and by the high pressure force acting on needle transverse faces. As the inner channel 61 of the tube is connected to the low pressure, this relieves a proportion of said transverse faces where the high pressure force would otherwise drive the nozzle needle 98 into its seat 103.

In a subsequent second step, the coil 38 is energised generating a magnetic field that upwardly attracts the armature 106 and the needle 98 toward the core member 40. The magnetic force is sufficient to pull-up the needle 98 because the needs are reduced thanks to said piston to bore slide fit connection. The needle lifts up toward an open position OP of the valve seat 103 enabling fuel passage between the pointy end 101 of the needle and the seating face 102 of the body. As soon as the needle lifts up from the seating face 102, the high pressure fuel engages over the entire the pointy end face 101 and generates further forces opening the valve seat 103. Injection event through the spray holes 20 occurs and, the fuel having difficulties to flow through the armature, the actuation chamber 26 remains at high pressure while the pressure drops in the nozzle chamber 90.

In the embodiment of figure 5 where the armature is provided with the first through hole 114, defining the throttle 116, and with the second through hole 118, the armature upper face 110 may come in surface contact against said under face 44 closing the second through hole 118. In said embodiment, the section of the passage for the fuel to flow from the actuation chamber to the nozzle chamber varies from the sum of the sections of the throttle 116 and the second hole 118 when the needle is in closed position CP to, the section of the throttle 116 only when the needle reaches the open position OP and the second hole 118 is closed.

In a third step, energisation of the coil 38 is stopped. The needle is in open position OP. After the injection event, the pressure in the nozzle chamber 90 has dropped while the pressure in the actuation chamber 26 has substantially remained at its previous high level. The pressure difference across the armature 106 downwardly pushes the armature generating on the armature 106 and on the needle 98 a closing force pushing the armature 106 away from the core member 40 and the needle 98 toward the closed position CP.

LIST OF REFERENCES

X CP OP G

longitudinal axis closed position open position gap

10 12 14 16 18 20 22 24 26 28 29 30 31 32 33 34 35 36 38 40 42 44 46 48 50 52 58 60 61 62 63 64 65 66 67 68 69

fuel injector actuation assembly nozzle assembly capnut fuel inlet spray holes tip end actuator body inner chamber - upper chamber peripheral wall longitudinal groove upper end connection assembly electric connector electrical wires lower end lower face of the actuator body solenoid assembly coil core member - magnetic pole piece upper face under face hole top conical portion central cylindrical portion lower conical portion clamping flats tube tube inner channel tube first end - tube upper end top end face tube second end - tube lower end adjusted bore at the lower end of the tube annular face adjusting member bore at the upper end of the injector body spring

thrust face upper inlet portion lower drain connector portion blind bore upper portion of the adjusting member lower portion of the adjusting member flats inner conduit thread - tool engagement means drain port filter spring seat member nozzle body upper face of the nozzle body nozzle chamber peripheral wall of the nozzle large portion of the nozzle chamber narrow portion of the nozzle chamber needle valve member

100 head of the needle

101 pointy end of the needle

102 seating face

103 valve seat

104 shoulder

105 narrow extension of the needle head - piston

106 magnetic armature

108 peripheral face of the armature

110 upper face of the armature

112 under face of the armature

113 central hole

114 first through hole

116 throttle

118 second through hole

Claims

1. Fuel injector (10) adapted to be part of a direct fuel injection equipment of an internal combustion engine, said injector having an elongated shape extending along a main axis (X) and comprising a body (24, 86) defining an inner space (26, 90) wherein, in use, fuel at high pressure enters via an inlet (18) and wherein, a solenoid (36) is adapted to generate sufficient forces to reciprocally move a needle valve member (98) between a closed position (CP) of a valve seat (103) preventing fuel injection and, an open position (OP) of said valve seat (103) enabling said fuel injection through spray holes (22) drilled at a bottom end of the injector body; said solenoid comprising a coil (38) fixed to said body cooperating with a magnetic armature (106) fixed to said needle (98) and, a metallic tube (60) extending in said body inner space (26) from a first end (62) connected to a return low pressure port (79) to a second end (64) defining a bore (65) wherein is slidably inserted a piston (105) integral to the head (100) of the needle valve member, the tube (60) inside channel being in fluid communication with the drain and remaining at a low pressure at all-time thus reducing the needle surface pressurised by high pressure.

2. Fuel injector (10) as claimed in the preceding claim wherein, said injector inner space (26, 90) is divided by a core member (40) in an upper chamber (26) wherein extends the tube (60) and in a nozzle chamber (90) wherein extends the needle (98), said core member (40) being provided with a through hole (46) for the second end (64) of the tube and the head (100) of the needle to be slidably engage together.

3. Fuel injector (10) as claimed in claim 2 wherein the coil (38) is positioned around said core (40).

4. Fuel injector (10) as claimed in any one of the claims 2 or 3 further comprising a fluid communication (46, 114, 116, 118) enabling fuel to flow between said upper chamber (26) and said nozzle chamber (90).

5. Fuel injector (10) as claimed in claim 4 wherein said fluid communication (46) partially extends through the core (40).

6. Fuel injector (10) as claimed in any one of the claims 4 or 5 wherein said fluid communication (114, 116, 118) partially extends through the armature (106).

7. Fuel injector (10) as claimed in claim 6 wherein the section area of the fluid communication (114, 116, 118) evolves from an open state when the needle (98) is in closed position (CP) to a restricted state when the needle is in open position (OP).

8. Fuel injector (10) as claimed in claim 7 wherein the fluid communication (114, 116, 118) comprises a first path defined by a first hole (114) and a throttle (116) having a fixed section generating, in use, a pressure difference between said upper chamber (26) and said nozzle chambers (90) and, a second path defined partially by a second hole (118), said second path having an evolving section.

9. Fuel injector (10) as claimed in claim 8 wherein the magnetic armature (106) cooperates with the core (40) to define together said second path of the fluid communication.

10. Fuel injector (10) as claimed in claim 9 wherein the opening section of said second path increases continuously from a first state when the needle (98) is in open position (OP) to a second state when the needle (98) moves to the closed position (CP).

11. Fuel injector (10) as claimed in claim 10 wherein in said first state, said second path is fully closed, the open state of the fluid communication being the fixed section of the throttle (116).

12. Fuel injector (10) as claimed in any one of the preceding claims further comprising an adjusting member (67) fixed to the injector body (24) and defining a thrust face (70) against which abuts the top end face (63) of the tube.

13. Fuel injector (10) as claimed in claim 12 wherein said adjusting member (67) is a cylinder fixed in a bore (68) extending through the body of the injector, said cylindrical adjusting member (67) comprising an upper inlet portion (74) fixed in said bore (68) and a lower portion (75) defining said thrust face (70).

14. Fuel injector (10) as claimed in claim 13 wherein said lower portion (75) is provided with an inner conduit (77) opening in said thrust face (70) and interconnecting the tube inner channel (61) to the low pressure drain port (79).

15. Fuel injector (10) as claimed in any one of the claims 13 or 14 wherein said cylindrical adjusting member (67) is press fitted in said bore (68).

16. Fuel injector (10) as claimed in any one of the claims 13 or 14 wherein said cylindrical adjusting member (67) is threaded and tightened in said bore (68).

17. Fuel injector (10) as claimed in any one of the claims 12 to 16 wherein the adjusting member (67) is provided with engagement means (78) for complementary attachment of a tool enabling a positioning adjustment of the adjusting member (67) in said bore (68).

18. Fuel injector (10) as claimed in any one of the claims 12 to 17 wherein the adjusting member (67) is further provided with a hole (70) defining the fuel inlet (18).

19. Fuel injector (10) as claimed in claim 18 wherein said hole (70) extends from an opening in its outer end to a blind bottom end (73).

20. Fuel injector (10) as claimed in any one of the claims 18 or 19 wherein the adjusting member (67) further comprises a filter (80) arranged in said hole (73).

21. Fuel injector (10) as claimed in claim 20 wherein said filter (80) comprises a plurality of micro-drillings extending from said hole (73) to said inner chamber (26).

5

22. Fuel injector (60) as claimed in any of the preceding claims wherein the needle valve member (98) is axially guided between a lower guiding means and an upper guiding means defined between an armature peripheral face (108) and a complementary face of the injector body (86).