EP3545186B1 - Fuel injector - Google Patents

Description

TECHNICAL AREA

The present invention relates to a fuel injector more particularly suitable for injection equipment of the "common rail" type, the injector itself being provided with a nozzle, the needle of which is directly opened or closed by an electromagnetic actuator. coil.

TECHNOLOGICAL BACKGROUND OF THE INVENTION

A fuel injector of the prior art comprises a coil actuator and a magnetic armature acting directly on a valve member also called a needle so as to open or close fuel injection holes, for example documents EP 2246554 A and WO91 / 05951A .

Such an injector imposes a hydraulically balanced, or almost balanced, needle so that the relatively small force exerted by the solenoid actuator is sufficient to move said needle. The needle is slid within a bore of an injector nozzle body, wherein one end of the needle is sealingly fitted with a nozzle seat provided on an inner surface of the bore. nozzle body, in order to control the fuel supply through injection holes located through the wall of the nozzle body. The fuel is at high pressure and flows through the injector from the inlet channel to the injection holes. The pressure exerted on the nozzle seat creates deformations which generate variations in the distribution of fuel pressure in the injection holes and in addition the opening pressure of the needle in the control chamber varies at a given pressure. Direct-acting technology aims to reduce early drift, but it does not completely eliminate it. The object of the present invention is to provide a solution which overcomes these drawbacks.

SUMMARY OF THE INVENTION

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

To this end, the invention provides a fuel injector arranged to deliver high pressure fuel to an internal combustion engine via injection holes. The injector comprises an injector body extending in a longitudinal axis a bore and a high pressure chamber and a needle slidably arranged in the bore between a top guide and a bottom guide. The needle extends between a first end provided with a valve stopper and a second end provided with a through bore. In addition, the needle can move between an open position and a closed position. The injector further comprises a piston comprising a magnetic frame and a shaft extending along the longitudinal axis between a first end and a remote second end fixed to the magnetic frame. In addition, the injector comprises an actuator comprising a fixed solenoid and generating when it is electrically supplied an opening force on the magnetic armature and a return spring generating a closing force on the piston when the solenoid is not. powered. The injector further comprises a high pressure channel extending between an inlet mouth of the injector and the injection holes, the high pressure channel comprising a first section extending into the needle, a second section s 'extending into the shaft and a third section extending into the frame. The injector further comprises the first end of the shaft being guided in the bore of the needle. In addition, the injector comprises a force amplifier arranged between the shaft and the needle, the piston moving under the action of an electromagnetic force generated by the solenoid as well as under the action of a force generated by the return spring so that the resultant of the two forces applied to the piston is transmitted and amplified to the needle.

In a first embodiment, the force amplifier comprises a hydraulic amplification chamber defined in part by an annular shoulder of the piston shaft and by a thrust face of the second end of the needle, said face thrust having an area greater than the area of the shoulder. The shaft further comprises a first damper arranged in the second section of the HP channel so that the first damper slows down a pressure wave generated by the armature and allows the excess pressure to be evacuated to the first high pressure chamber. The first damper defines at least one calibrated hole forming a restriction between the high pressure channel and the first high pressure chamber. The shaft further comprises a second damper arranged in the second section of the HP channel, between the first high pressure chamber and a second high pressure chamber so that the second shock absorber slows down the movement of the reinforcement. The second damper defines an annular space between a guide bore of the spring stopper and an outer face of the shaft. In the first embodiment, the high pressure channel is longitudinal, centered and crossing the frame right through, crossing the shaft right through and crossing the needle, the HP channel being aligned between the frame, the shaft and needle bore so that fuel flows between an inlet of the injector and injection holes of the injector body. The blind bore of the needle opens into through and through holes in the bore of the nozzle body, the holes being remote from the shutter.

In a second embodiment, the third section of the HP channel is traversing and inclined in the frame, the third section opening into the second high pressure chamber. The HP channel extends over the second section of the shaft, the HP channel axially passing through the first section of the needle. The HP channel opens into the holes arranged close to the shutter.

In a third embodiment, the third section of the HP channel is traversing and inclined in the frame, the third section opening into the second high pressure chamber. The needle defines a length less than a length of the shaft and in which the top guide is arranged close to the bottom guide. The amplification chamber is arranged close to the shutter. The HP channel extends over the second section of the shaft and axially passes through the needle opening into the through holes and arranged close to the shutter.

In a fourth embodiment, the third section of the HP channel is transverse and inclined in the frame, the third section opening into the second high pressure chamber. The HP channel extends over the second section of the shaft and axially passes through the needle in the bore opening into the holes, the holes being open into the bore of the nozzle body.

BRIEF DESCRIPTION OF THE DRAWINGS

• La figure 1 est une vue en coupe partielle d'un injecteur selon un premier mode de réalisation
• La figure 2 est une vue en coupe agrandie de la chambre d'amplification
• La figure 3 est une vue en coupe partielle d'un injecteur selon un deuxième mode de réalisation.
• La figure 4 est une vue en coupe partielle d'un injecteur selon un troisième mode de réalisation.
• La figure 5 est une vue en coupe partielle d'un injecteur selon un quatrième mode de réalisation.

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

• The figure 1 is a partial sectional view of an injector according to a first embodiment
• The figure 2 is an enlarged sectional view of the amplification chamber
• The figure 3 is a partial sectional view of an injector according to a second embodiment.
• The figure 4 is a partial sectional view of an injector according to a third embodiment.
• The figure 5 is a partial sectional view of an injector according to a fourth embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention is now described with reference to the figures and for the sake of clarity and conciseness of the description, an orientation from top to bottom according to the direction of the figures will be used without any limiting intention as to the extent of the protection, in particular the look at the different installations of an injector in a vehicle. Words such as “up, down, below, above, vertical, up, down…” will be used without limiting intention. In addition, the term near will be used in the sense of little distant, neighbor as mentioned in the Larousse dictionary.

A fuel injector 10 shown in figure 1 is briefly described so as to identify the main components. The injector 10 extends along a longitudinal main axis X, and comprises from bottom to top, in the conventional and non-limiting sense of the figures, a nozzle assembly 12 comprising a valve member 14 or commonly called needle 14 and a body nozzle 16, an actuator 18, a top guide 20, a piston 22 slidably arranged in the top guide 20 and a high pressure channel 24 also called HP channel 24.

As described in the figure 1 , the injector body 16 is provided with a bore 26 extending along a longitudinal axis X, between a first end 28 provided with a seat 31, a bag 30 provided with a plurality of injection holes 32 and a second end 34 from which the bore 26 opens.

Needle 14 is slidably arranged in nozzle body 16 between an open position and a closed position. The needle 14 extends along the X axis between a first end 36 provided with a valve obturator 38 commonly called obturator 38 and a second end 40 provided with a longitudinal blind bore 42 opening out.

The actuator 18 comprises a solenoid 44 fixed in the injector body 16, a non-magnetic spacer 46 in order to magnetically isolate and align the injector body 16 with an injector holder body (not shown) comprising a high pressure connection. (not shown) and a connector support (not shown).

According to figure 1 , the top guide 20 is arranged in the injector body 16. The top guide 20 cooperates with the piston 22 and the needle 14.

As described in figures 1 and 2 , the piston 22 comprises a magnetic armature 48 and a shaft 50 extending along the longitudinal axis X. The magnetic armature 48 is movable between a first position and a second position defined by the movement of the piston 22, the magnetic armature 48 cooperating with the solenoid 44. The shaft 50 comprises a first end 52 arranged in the bore 42 of the needle and a second end 54 fixed to the magnetic armature 48. The piston 22 further comprises a spring seat 55. fixed on the shaft 50 in order to serve as a support for a return spring 58. The shaft 50 is guided both by the top guide 20 and by a spring stop 61 open at its center. The return spring 58 is arranged in a first high pressure chamber 59 included between the seat 55 and the spring stopper 61. The spring stopper 61 is between the first high pressure chamber 59 and a second high pressure chamber 67.

The high pressure channel 24 is arranged between an inlet of the injector (not shown) and injection holes 32 so that the fuel circulates in the injector 10 in order to deliver high pressure fuel to a internal combustion engine. The high pressure channel 24 comprises a first section arranged 74 in the bore 42 of the needle, a second section 76 arranged in the shaft 50 and a third section 78 arranged in the frame 48.

dans lequel les caractéristiques suivantes représentent :

• Dn est le diamètre extérieur de l'aiguille 14,
• Dl est le diamètre de guidage intérieur de l'arbre 50 mesuré à la première extrémité de l'arbre 50 en contact avec l'alésage 42 axial borgne de l'aiguille.
• Du est le diamètre extérieur de l'arbre 50.

In a first embodiment and according to figures 1 and 2 , the high pressure channel 24 extends through the frame 48, the shaft 50 and into the needle 14. The injector 10 further comprises a force amplifier 56 arranged between the shaft 50 and the needle 14. The shaft 50 is arranged to slide in the bore 42 of the needle under the action of an electromagnetic force F1 (not shown) generated by the solenoid 44 as well as under the action of a force F2 ( not shown) generated by the return spring 58. The force exerted on the piston 22 is a resultant Fr (not shown) of the forces F1, F2 (not shown) which is fully transmitted to the needle 14. The resulting force Fr is the vector sum of the electromagnetic force F1 and the force F2 generated by the return spring 58 which the piston undergoes 22. The force amplifier 56 comprises a hydraulic amplification chamber 56 defined in part by an annular shoulder 60 of the 'shaft 50 of the piston, by a thrust face 62 of the second end 40 of the needle and by faces 63 of the top guide 20. The thrust face 62 has an area A62 greater than an area A60 of the shoulder 60. The amplification chamber 56 amplifies the resulting force Fr (not shown) of the electromagnetic force F1 (not shown) and the force F2 (not shown) generated by the return spring and this in a ratio which corresponds to the following ratio: $$\mathrm{Ratio}=\left({\mathrm{Dn}}^2-{\mathrm{<figure-callout\; id="2"\; label="Dl"\; filenames="imgf0001.png"\; state="\{\{state\}\}">Dl</figure-callout>}}^2\right)/\left({\mathrm{Of}}^2-{\mathrm{<figure-callout\; id="2"\; label="Dl"\; filenames="imgf0001.png"\; state="\{\{state\}\}">Dl</figure-callout>}}^2\right)>1$$

in which the following characteristics represent:

• Dn is the outer diameter of needle 14,
• D1 is the inner guide diameter of shaft 50 measured at the first end of shaft 50 in contact with the blind axial bore 42 of the needle.
• Du is the outside diameter of shaft 50.

As described in figures 1 and 2 , the shaft 50 further comprises a first damper 64 arranged in the second section 76 of the HP channel 24 so that the first damper 64 slows down a pressure wave generated by the armature 48 and then makes it possible to release the overpressure in the first high pressure chamber 59. According to figure 1 , the damper 64 is a restriction 64 which is arranged close to the first end 52 of the piston shaft. The restriction 64 is defined by at least one hole 64. In this embodiment, the section (not shown) of the hole 64 being small, a single hole 64 is sufficient. The section (no shown) of the hole 64 by a plane orthogonal to a longitudinal axis (not shown) of the hole 64 is a circle whose center is located on the longitudinal axis (not shown) of the hole 64. The hole 64 has a diameter between 0 , 2 mm and 1 mm. In an alternative to this embodiment the restriction 64 may be a plurality of holes 64. The section of the holes 64 is in this case larger than for a single hole. The diameter of the holes 64 is then between approximately 1.5 mm to 3 mm. As described in figure 1 , the shaft 50 further comprises a second damper 66 arranged close to the second end 54 of the shaft. The second damper 66 is arranged in the second section 76 of the HP channel 24. The second damper 66 is between the first high pressure chamber 59 and the second high pressure chamber 67. As described in figure 1 , the second damper 66 defines an annular space between a guide bore 82 of the spring stopper 61 and an outer face 69 of the shaft. The second damper 66 is located between the movable magnetic armature 48 and the return spring 58 so that the second damper 66 forming a second restriction 66 slows down the movement of the armature 48. The high pressure channel 24 is longitudinal, centered and crossing on either side of the frame 48, of the shaft 50 and of the needle 14. The HP channel 24 is aligned between the frame 48, the shaft 50 and the bore of the needle 42 so that the fuel circulates between an inlet mouth of the injector (not shown) and injection holes 32 of the injector body. The needle 14 includes a longitudinal recess 70 arranged on an outer surface 72 of the needle. The bottom guide 21 is a guide face arranged in a bottom part of the bore 26 of the nozzle body in order to guide the shutter 38 as closely as possible on the seat 31 of the nozzle. The top guide 20 is arranged in the nozzle body 16. The bottom guide 20 is fixed and serves to guide the shaft 50 in the body 16.

The complete assembly of the injector 10 consists in assembling together the actuator 18, the nozzle assembly 12, the top guide 20, the piston 22 and the injector holder body (not shown) using a nut 15. As described in figure 1 , the nut 15 is screwed onto the injector holder body (not shown).

In a second embodiment and as described in figure 3 , the third section 78 of the HP channel passes through between a first face 84 and a second face 86. The third section 78 of the HP channel is inclined in the frame 48. The angle of inclination between the longitudinal axis X and the third section 78 is between 10 and 45 degrees. The third section 78 of the HP channel opens into the second high pressure chamber 67. The second section 76 of the HP channel extends over a portion of the shaft 50 between at least one hole 64 and the first section 74 of the HP channel. According to figure 3 , the first restriction 64 is at least one hole 64 arranged in the shaft 50. The hole 64 opens out on one side into the first high pressure chamber 59 and on the other side into the second section 76. The first section 74 of the HP channel extends axially inside the needle 14 and opens into a plurality of holes 80 arranged close to the shutter 38 of the needle. In an alternative to the second embodiment, the first restriction 64 can be a plurality of holes 64.

In a third embodiment and as described in figure 4 , the third section 78 of the HP channel passes through between a first face 84 and a second face 86. The third section 78 of the HP cala is inclined in the frame 48. The angle of inclination between the longitudinal axis X and the third section 78 is between 10 and 45 degrees. The second section 76 of the HP channel extends over a portion of the shaft 50 between at least one hole 64 and the first section 74 of the HP channel. The shaft 50 has the length L50 greater than the length L14 of the needle 14. The plurality of holes 80 is arranged in a lower part of the shaft 50 and close to both the first end 52 and the shutter. 38 of the needle. The top guide 20 is arranged close to the bottom guide 21.

In a fourth embodiment and as described in figure 5 , the third section 78 of the HP channel passes through between the first face 84 and the second face 86. The third section 78 of the HP channel is inclined in the frame 48. The angle of inclination between the longitudinal axis X and the third section 78 is between 10 and 45 degrees. The difference with the first embodiment is that the third section 78 opens into the second high pressure chamber 67. The first and the second damper 64, 66 are arranged identically in the four embodiments.

The operation of the injector 10 is now briefly presented with reference to the figures 1 to 4 .

The injector 10 is arranged within a fuel injection equipment of the common rail type (not shown) supplying several injectors with fuel under pressure. Through the inlet of the injector (not shown) therefore enters pressurized fuel and, in diesel injection equipment, the pressurization of the diesel fuel can reach 2000 or 3000 bars. To illustrate this operation, it is arbitrarily chosen that the fuel pressure at the inlet of the injector is 2500 bars.

When the solenoid is energized, fuel enters through the HP channel 24, The magnetic force creates the electromotive force which draws the armature 48 upward as opposed to the return spring 58 which pushes the piston 22 downward. opposite of solenoid 44. The resultant Fr of the 2 electromotive force F1 and the force generated F2 by the return spring 58 will move the piston 22 upwards and consequently the shutter 38 of the needle is itself moved away from the seat 31 of the body of nozzle in open position. The forces Fr, F1, F2 are not shown. Thus the fuel will circulate through the HP channel 24 then passing through the bore 26 of the nozzle body, then the fuel will reach the injection holes 32 through which the fuel will arrive in the combustion chamber (not shown).

When the solenoid 44 is not supplied, the electromagnetic force F1 (not shown) is interrupted and the force generated F2 by the return spring 58 will move the piston 22 downwards and consequently the shutter 38 will come. in contact with the seat 31 in order to close the injection holes 32 of the nozzle body.

LIST OF REFERENCES USED

10

injector

12

nozzle set

14

needle

15

nut

16

nozzle body

18

actuator

20

top guide

21

bottom guide

22

piston

24

HP channel

26

injector body bore

28

first end of the body

30

bag

31

seat

32

injection holes

34

second end of the body

36

first end of the needle

38

shutter

40

second end of the needle

42

needle bore

44

solenoid

46

spacer

48

frame

50

tree

52

first end of the shaft

54

second end of the shaft

55

spring seat

56

force amplifier

58

spring

59

first high pressure chamber

60

shoulder

61

spring stopper

62

thrust face

63

top guide faces

64

first restriction

66

second restriction

67

second high pressure chamber

69

outer surface of the tree

70

obviously

72

outer needle surface

74

first section

76

second section

78

third section

80

hole

82

guide bore of the spring stopper

84

First face of the framework

86

Second face of the framework

X

longitudinal axis

A60

shoulder area

A62

thrust face area

L50

shaft length

L14

Needle length

Claims (9)

1. Fuel injector (10) arranged to deliver high-pressure fuel to an internal combustion engine via injection holes (32), the injector comprising:

   an injector body (16) extending along a longitudinal axis (X) comprising a bore (26) and a high-pressure chamber (56), and

   a needle (14) arranged so as to slide in the bore (26) between an upper guide (20) and a lower guide (21), the needle (14) extending between a first end (36) provided with a valve obturator (38) and a second end (40) provided with an open bore (42), the needle (14) being able to move between an open position and a closed position,

   a piston (22) comprising a magnetic armature (48) and a shaft (50) extending along a longitudinal axis (X) between a first end (52) and a remote second end (54) secured to the magnetic armature (48),

   an actuator (18) comprising a fixed solenoid (44) and generating, when supplied with electricity, and opening force on the magnetic armature (48) and,

   a return spring (58) generating a closing force on the piston (22) when the solenoid (44) is not energized,
   characterized in that the injector (10) further comprises a high-pressure duct (24) extending between an inlet mouth of the injector (10) and the injection holes (32), the high-pressure duct (24) comprising a first segment (74) extending in the needle (14), a second segment (76) extending in the shaft (50) and a third segment (78) extending in the armature (48) and,

   in that the first end (52) of the shaft is guided in the bore (42) of the needle and,

   in that the injector (10) further comprises a force amplifier (56) arranged between the shaft (50) and the needle (14), the piston (22) moving under the action of an electromagnetic force (F1) generated by the solenoid (44) as well as under the action of a force (F2) generated by the return spring (58) such that the resultant force (Fr) acting on the piston (50) is transmitted to and amplified at the needle (14), the force amplifier (56) comprising a hydraulic amplification chamber (56) defined in part by an annular shoulder (60) of the shaft (50) of the piston and by a thrust face (62) of the second end (40) of the needle, said thrust face (62) having a surface area (A62) greater than the surface area (A60) of the shoulder.
2. Fuel injector (10) according to the preceding claim, wherein the shaft (50) further comprises a first damper (64) arranged in the second segment (76) of the HP duct such that the first damper (64) slows a pressure wave generated by the armature (48) and makes it possible to evacuate the overpressure to a first high-pressure chamber (59).
3. Fuel injector (10) according to Claim 2, wherein the first damper (64) defines at least one calibrated hole (64) forming a first restriction (64) between the high-pressure duct (24) and the first high-pressure chamber (59).
4. Fuel injector (10) according to any one of the preceding claims, wherein the shaft (50) further comprises a second damper (66) arranged in the second segment (76) of the HP duct, between the first high-pressure chamber (59) and a second high-pressure chamber (67) in such a way that the second damper (66) slows the movement of the armature (48).
5. Fuel injector (10) according to Claim 4, wherein the second damper (66) defines an annular space between a guiding bore (82) for the spring stop (61) and an outer face (69) of the shaft.
6. Fuel injector (10) according to any one of the preceding claims, wherein the high-pressure duct (24) is longitudinal, centred and passing right through the armature (48), passing right through the shaft (50) and passing through the needle (14), the HP duct (24) being aligned between the armature (48), the shaft (50) and the bore (42) of the needle in such a way that the fuel flows between an inlet mouth of the injector and injection holes (32) of the injector body.
7. Fuel injector (10) according to any one of Claims 1 to 5, wherein the third segment (78) of the HP duct passes through and is inclined in the armature (48), the third segment (78) opening into the second high-pressure chamber (67).
8. Fuel injector (10) according to Claim 7, wherein the HP duct (24) extends on the second segment (76) of the shaft, the HP duct (24) passing axially through the first segment (74) of the needle (14).
9. Fuel injector (10) according to Claim 8, wherein the HP duct (24) opens into the holes (80) arranged close to the obturator (38).

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