EP3387248A1

EP3387248A1 - Fuel injector

Info

Publication number: EP3387248A1
Application number: EP16806118.2A
Authority: EP
Inventors: Quentin ROUSSOT; Nicolas Rodier
Original assignee: Delphi Technologies IP Ltd
Current assignee: Delphi Technologies IP Ltd
Priority date: 2015-12-11
Filing date: 2016-12-06
Publication date: 2018-10-17
Also published as: CN108474339B; JP6888878B2; FR3045109B1; FR3045109A1; JP2019502053A; CN108474339A; WO2017097777A1

Abstract

A fuel injector (10) comprises a solenoid (24) and a nozzle in the body (30) of which a movable member (32) is slidingly guided along a longitudinal axis (X), the movable member (32) extending between a bottom end and a top end provided with a magnetic core capable of cooperating with the solenoid (24). When the solenoid (24) is powered, the movable member (32) moves towards an open position and, when the solenoid (24) is not powered, the movable member (32) is pushed back towards a closed position. The injector (10) is moreover provided with a control chamber defining a damper capable of slowing, during use, the movement of the movable member (32) towards the open position.

Description

FUEL INJECTOR TECHNICAL FIELD

The present invention relates to a fuel injector more particularly adapted to a "common rail" type injection equipment, the injector itself being provided with a nozzle whose needle is directly opened or closed by a solenoid electromagnetic actuator. .

BACKGROUND OF THE INVENTION

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

The valve member thus solicited moves in a frank and brutal manner and, a too rapid movement of the needle, especially at the opening, hinders easy control and accuracy of the injection.

SUMMARY OF THE INVENTION

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

For this purpose, the invention proposes a fuel injector comprising a pressurized fuel circuit extending from an inlet mouth in the injector to injection holes, via a valve seat controlling the opening or the closing said injection holes. The injector further comprises an electromagnet actuator provided with a fixed solenoid generating a magnetic field when it is electrically powered, and a nozzle in the body of which a movable member is guided sliding along a longitudinal axis, the movable member. extending between a low end defining the valve seat and a high end.

Advantageously, the upper end of the mobile member defines a magnetic core adapted to cooperate with the solenoid so that when the solenoid is energized, the magnetic field attracts and moves the movable member to an open position in which the valve seat opens a passage fuel injection and, when the solenoid is not powered, the limb mobile is pushed by a needle spring to a closed position in which said passage is closed prohibiting fuel injection.

In addition, the injector is provided with a control chamber defining a damper able to slow down in use the movement of the movable member to the open position.

The control chamber is defined within the movable member, said chamber being in fluid communication with the valve seat.

The damper includes an inlet valve controlling said fluid communication, the valve being movable between a first position in which the fluid communication is restricted and a second position in which the fluid communication is widely open.

The damper further comprises a valve spring continuously biasing said intake valve to the first position.

More particularly, the opening force generated by the magnetic field is greater than the sum of the closing forces exerted on the mobile member according to the general formula:

FM> F + F + FH in which FM is the opening force of the magnetic field;

F is the force of the needle spring;

F is the force of the valve spring;

FH is the force due to the hydraulic imbalance of the moving limb. In use, the valve moves to the second position when the movable member moves to the closed position.

In particular, the valve comprises a tubular body partially arranged in the control chamber, said tubular body being permanently pressed against a face of the actuator, the valve needle spring being compressed between said tubular body and a face of the Control Chamber.

The valve comprises a movable member arranged in the tubular body. The tubular body comprises a peripheral wall extending axially from a first end arranged in the control chamber to a second end bearing against one face of the actuator. The tubular body is further provided with a radial face open at its center forming an inner shoulder, the movable member of the valve in the first position being in abutment against said radial face.

BRIEF DESCRIPTION OF THE DRAWINGS

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

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

FIG. 2 is a diagram in longitudinal section of the nozzle of

Γ injector of Figure 1.

- Figure 3 is a bottom view of the pole piece adapted to the injector of Figures 1 and 2, this view showing a passage arranged for the fuel.

FIG. 4 is a construction alternative to FIG.

- Figures 5 and 6 are diagrams in section according to two embodiments of a valve seat of an injector nozzle adapted to the injector of Figures 1 and 2.

- Figures 7 and 8 similar to Figure 2 illustrate two phases of operation of the injector nozzle.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A fuel injector 10 shown in FIG. 1 has an elongate body extending along a longitudinal axis X and comprises an actuator portion 12, shown at the top of the figure, and a hydraulic portion 14 shown at the bottom of the figure. The boundary between the two parts 12, 14, being symbolized by a solid line. In the injector 10, a pressurized fuel supply circuit 16 extends from an inlet mouth 18, generally arranged at the top of the injector, to injection holes 20 located at the bottom of the nozzle. hydraulic portion 14 and for vaporizing fuel pressurized in a combustion chamber of an internal combustion engine. Throughout this description, relative terms such as "up, down, above, below ..." will be used for purposes of clarity and simplification, with reference to the arbitrary meaning of the figures and without limiting intent. of the scope of the invention.

In addition, in the lower part of the body 22 of the actuator portion 12 is arranged a solenoid 24 of toroidal shape electrically connected by connecting son extending upwardly to a connector 26 adapted to receive the complementary connector of a control unit. In the central space of the toroidal solenoid 24 is arranged a polar piece 28 magnetic X axis pierced to arrange a portion of the high pressure circuit 16.

In the body 30 of the hydraulic portion 14 is slidably arranged along the longitudinal axis X a movable valve member 32 extending between a high end and a thin and pointed low end which has helped to generalize the known name of needle . A magnetic core 34 is integral with the upper end and the lower end cooperates with an inner face of the hydraulic portion body 30 to form a valve seat 36, said seat 36 extending in a circular line of diameter D36. The valve member 32 is movable between a fully open position PO in which the valve seat 36 is open, the pointed end being remote from the inner face of the body leaving the pressurized fuel an open passage to the injection holes. and, a closed position PF where said passage is closed, the pointed end being in sealing contact against the inner face of the body 30 thus retaining the fuel upstream of the valve seat 36 closed.

The actuator 12 and hydraulic 14 parts are firmly held together by means of an injector nut 38 which on the one hand rests against a radial shoulder of the body of the hydraulic part and, on the other hand is screwed to the body 22 of the actuator part.

The movements of the mobile member 32 are directly controlled by the actuator. Thus, when the solenoid 24 is electrically powered, it generates a magnetic field M which loops around the solenoid ring, passes through the pole piece 28 and the magnetic core 34 attracting to the open position PO the movable valve member 32. The diagram of Figure 2 allows to clarify the first description of Figure 1 and focusing on the lower part of the injector and detailing in particular an embodiment.

The body 22 of the actuator portion extends downwardly to a transverse radial face 40 in which opens a cylindrical housing for the arrangement of the solenoid 24 and the pole piece 28. In addition the high pressure circuit 16 , which extends axially X in the body 22, passes to the center of the pole piece 28 and opens at the center of said transverse face 40.

The pole piece 28 arranged in the central space of the toroidal solenoid is a part of revolution along the longitudinal axis X and which extends axially upwardly from a circular lower face 42 and then along a cylindrical base, then a central portion conical pyramidal up to a cylindrical top again of small section. From the center of the summit to the center of the lower face 42 extends axially X a central channel 44 integral with the high pressure circuit 16. In the center of the lower face 42, the pole piece is provided with a star passage 46 creating a communication of fluid between the high pressure circuit 16 and the hydraulic part 14 and, a bearing surface extending from the lower face 42.

FIG. 3 represents an example of the pole piece 28, seen from below, the star passage 46 being in cross with four branches. Alternatively to this cross, the skilled person will realize fluid communications to one or two branches, there is the limit to continue to speak of star, or three branches or more. Similarly, the diagram of Figure 3 symbolizes four rectangular branches of other shapes that can also be adopted. The body 30 of the hydraulic part has a peripheral wall 48 defining a continuous interior space comprising an upstream space 50 of large section and a narrower downstream space 52. The magnetic core 34 is slidably fitted along the longitudinal axis X in the upstream space 50 and the narrow portion 54 of the mobile member is guided in the downstream space 52 by a low guide 56 fitted axially sliding against the inner wall of the downstream space 52. Passages 58 formed in the core 34 allow the passage of fuel from the upstream space 50 to the downstream space 52. In the diagram of Figure 2 these passages 58 are vertical holes arranged on the periphery of the nucleus and, the person skilled in the art will be able to arrange all kinds of passages 58, are in full material, either as straight or helical peripheral notches but, whatever they are, these passages allow a free circulation of the pressurized fuel.

Similarly, passages not shown allow the flow of fuel on either side of the bottom guide 56, said passages not shown being often helical grooves made at the periphery of the bottom guide 56.

According to an embodiment shown diagrammatically in FIG. 2, the core 34 and the narrow portion 54 of the movable member are two distinct pieces.

complementarily arranged. The core 34 is provided with a blind axial bore 60 forming a control chamber 60, which is cylindrical and open in the center of the upstream face 62 of the core, said control chamber 60 being closed downstream by the narrow portion 54 the movable member which is inserted into the bore and permanently fixed to the core so as to form a bottom 64 to the control chamber 60. According to the diagram of Figure 2, said bottom formed by the upper end of the narrow portion 54 the movable member comprises a peripheral annular face 66 and a central cylindrical protrusion whose vertex face 68 is circular and transverse.

In the control chamber 60 is arranged a valve 70 comprising a hollow valve body 72 in which is arranged a movable member 74.

According to the embodiment of FIG. 2, the valve body 72 is a cylindrical and tubular piece of which a peripheral wall 76 is partially closed at one end by a transverse shoulder 78 provided with an axial opening 80.

The peripheral wall 76 extends axially X from a lower annular face 82 arranged facing the bottom of the chamber 60 to an upper annular face 84 which is also the upper face of the shoulder 78.

The peripheral wall 76 and the shoulder 78 define a cylindrical internal space limited by the internal cylindrical face 86 of the peripheral wall 76 and by the lower face 88 of the shoulder, in which space is arranged axially sliding the mobile member 74.

The outer face 90 of said peripheral wall 76 is cylindrical and is slidably fitted against the inner wall in the bore 60. most of it is guided in the control chamber 60 emerges partially from it, the upper face 84 of the shoulder, transverse annular face, bearing against the lower face 42 of the pole piece. More precisely, said upper face 84 bears only against the portions of the lower face 42 of the pole piece which are between the branches of the star passage 46.

In a construction alternative illustrated in FIG. 4, the lower face 42 of the pole piece is a plane and smooth disk, only the central channel 44 opening at the center of this face 42 and the upper face 84 of the valve body is provided with radial passages forming the star passage 46, radial passages through which the fuel can flow from the central channel 44 into the upstream space 50. In Figure 4, four radial radial passages are shown but the skilled person will know to make other alternatives with different passages in number.

Said mobile valve member 74 is a cylinder extending axially between a lower transverse face 92, arranged facing the bottom of the chamber 60 and a transverse upper face 94 arranged facing the lower face 88 of the shoulder. The mobile member 74 is further provided with an axial channel 96 passing through and opening in the center of the lower face 92 and the center of the upper face 94. Said channel 96 is provided with a restriction 98 of small section, said restriction 98 being, according to the construction mode of the diagram of Figure 2, arranged close to the upper face 94, but can also be arranged in the center of the axial channel 96 or near the bottom face 92 of the movable member. In addition, on the upper face 94 is arranged a circular protrusion forming a sealing lip 100 of diameter D100 adapted to be in sealing contact against the lower face 88 of the shoulder.

In the control chamber 60 are arranged a needle spring 102 compressed between the peripheral annular surface 66 of the bottom of the chamber and the lower face 82 of the wall of the body and a valve spring 104 compressed between the circular face 68 of top of the protrusion of the bottom of the chamber and the lower face 92 of the movable member. The valve spring 104 generates an axial force F 104 and, said valve spring 104 is calculated as a function of the diameter D 100 of the sealing lip, so that the force F 104 generated is of the order of magnitude of the force generated by the pressurized fuel on the movable member 74 of the valve during the closing phase of the needle which is detailed below in the description. The needle spring 102 continuously urges the upper face 84 of the valve body toward a bearing against the portions of the lower face 42 of the pole piece extending between the branches of the star passage and the valve spring 104 urges permanently the sealing lip 100 towards a bearing against the underside of the shoulder.

In an alternative not shown, the movable valve member 74 is a ball of a diameter greater than that of the opening 80 so that the valve spring 104 permanently urges the ball to a closed position of the opening 80. In addition, the valve body 72 is provided with a restricted orifice extending through the wall of the valve body from the peripheral wall 76 of the body to the control chamber. Said orifice itself forming a restriction equivalent to the restriction 98 mentioned above, the ball never blocking the restricted orifice.

Under the movable core 34 extends, in the downstream space 52, the narrow part

54 to its pointed end forming the valve seat 36. At the end of the body of the movable portion is formed a small cavity known as the bag 106, the injection holes 20 passing through the wall of the body between said bag 106 and the outer face of the body.

The operation of the injector 10 is now briefly described.

In a first phase the solenoid 24 is not powered

electrically. The pressurized fuel occupies the entire free volume in the body 30 of the hydraulic part, in particular between the lower face 42 of the pole piece and the upstream face 62 of the core, the inside of the control chamber 60, the downstream space 52 from the core to the valve seat 36. The valve body 72 is applied against the underside of the pole piece by the needle spring 102 and the lip 100 of the movable member 74 is held by the spring of valve 104 sealingly bears against the shoulder 78 of the valve body. The movable member 32 is held in the closed position PF by the first 102 and second 104 springs which exert forces on him permanently urging towards this closed position PF. In addition, the mobile member 32 is hydraulically slightly unbalanced because, in the closed position, the pressure under the seat 36 in the bag 106, is low and the sum of the surfaces of the faces of the moving member 32 subjected to the pressure of the fuel and generating on the mobile member a closing force is slightly greater than the sum of the surfaces of the faces of the movable member 32 subjected to the pressure of the fuel and generating on the movable member an opening force, the difference being the area under the seat 36 of the extreme point of the mobile member. This hydraulic imbalance is all the more important as the diameter D36 of the seat is large.

In a second phase, or phase of opening of the needle, illustrated in Figure 7, the solenoid 24 is electrically powered and generates the magnetic field M which attracts the movable core 34 to the pole piece. For the movable member 32 to move from the closed position PF to the open position PO the opening force generated by the magnetic field M must overcome the forces of the two springs 102, 104, and the hydraulic imbalance related to the seat dimension 36. If the springs generate weak forces, some Newtons, the hydraulic imbalance may generate a greater force and, in order to use a known solenoid whose attraction force remains modest, modelings and tests have been carried out by making seats in two different configurations.

Trials and modeling have been successfully conducted by choosing the following values:

Opening force FM of the magnetic field = 150N;

Force F 102 of spring needle = 25N;

Lip diameter D 100 of 2 mm;

Force F 104 of the valve spring = 5N;

Diameter D36 of the seat = 0.7 mm.

For these calculations the control chamber had a diameter of 4 mm and a volume of 20 mm ³ .

The closing force FH, expressed in Newtons, due to the hydraulic imbalance is calculated as a function of the fuel pressure P, expressed in bar, and of the seat diameter D36, expressed in mm, according to the formula:

FH = [P / 10]. [(π. D36 ² ) / 4] For a working pressure P of 2000 bar and the diameter D36 of 0.7 mm the hydraulic force FH is 77N.

To ensure proper operation of the injector, the actuator must be able to lift the movable member according to the general formula:

FM> F102 + F104 + FH or:

FM> F102 + F104 + [P / 10]. [(π. D36 ² ) / 4]

The values above are a possible example of choice:

150> 25 + 5 + 77

Other values respecting the general formula above stated can be selected for example by choosing them in the following boxes:

100N <FM force of the magnetic field <180N

15N <Force F 102 of spring 1 'needle <5 ON

IN <Force F 104 of valve spring <10N

0.5 mm <seat diameter D36 <1 mm

A second configuration illustrated in FIG. 6 is a double-contact seat 36. The bag 106 is of the order of 1.5 mm in diameter and the mobile member 32 is provided at its pointed end with an axial extension penetrating to the bottom of the bag 106, so that in the closed position PF the movable member 32 contacts the body in a first circular line 110 of first diameter Dl 10 at the top of the bag and a second circular line 112 of second diameter Dl 12 at the bottom of the bag. In addition, the movable member 32 is provided with an internal channel 114 creating a fluid communication between the upstream internal downstream space 52 to the first circular line 110 and the end of said downstream extension 108 to the second circular line 112. The injection holes 20 open in an annular space 116 between the circular lines 110, 112, and the internal channel 114 allows the pressurized fuel to reach a small space under said extension 108. According to this second configuration the imbalance in the closed position PF is limited to the annular area between the first diameter D1 and the second diameter D1 12, and an embodiment in which said diameters DUO, D112 are very close to each other minimizes the hydraulic imbalance. This dual contact configuration requires that the two contacts are sealed so that the extension 108 is slightly flexible and deformable at the second circular line 112 of contact.

According to this second configuration of the seat, the general formula above stated becomes:

FM> F102 + F104 + [P / 10]. [(π. (| DUO ² - Dl 12 ² |) / 4] An interest of this second configuration appears immediately since the seat diameters D 1, D 1, D 12 can be chosen larger than in the first configuration, only the difference between these diameters matters.

During this second phase of operation during which the mobile member 32 moves in open position PO, the pressurized fuel flows into the bag 106, or the annular space 116, where the pressure increases which contributes to the effort of opening of the mobile member. Returning to the open position PO, the volume of the control chamber 60 decreases and the pressurized fuel which was in the control chamber 60 contributes to keeping the movable member 74 of the valve in sealing engagement against the body 72 of the valve, the fuel that leaves the control chamber through the axial channel 96 and its restriction 98. This passage restricts the flow of fuel and therefore, the pressure in the control chamber 60 increases and generates a force opposing the lifting of the mobile member 32 and slowing down the opening movement.

In a third phase of operation, illustrated in FIG. 8, or the closing phase of the needle, the power supply of the solenoid is interrupted. The mobile member 32 is then subjected to the forces of the two springs 102, 104 only, the mobile member in the open position PO being

hydraulically almost balanced. A slight imbalance can be created by a pressure drop between the upstream seat 36 and the bag 106. Indeed, the lifting of the movable member 32 opens at the seat 36 a restricted fluid passage to the injection holes 20 The moving member 32 begins to move to the closed position PF and the volume of the control chamber 60 increases and thus the pressure in the control chamber 60 decreases. In doing so, the fuel under pressure that arrives via the central channel 44 of the pole piece bears on the movable member 74 of the valve which moves in the body 72 and a little more compresses the valve spring 104. The sealing lip 100 then leaves the contact with the body and opens a wide passage to the fuel which can unrestrictedly enter the control chamber 60, which contributes to a rapid closure of the movable member 32.

In the alternative in which the movable valve member is a ball, when the solenoid is not energized the ball closes the opening 80 and, when the solenoid is energized, the needle begins to rise, the ball remains plated against the opening 80 and the compressed fuel in the control chamber escapes through the restricted orifice extending through the wall of the valve body. When the supply is cut off and the needle is in the open position, the two springs 102, 104 push back the needle and, during the closing movement of the needle, the pressure in the control chamber decreases and the Pressurized fuel can push the ball back and open the opening 80 so that the pressure in the control chamber increases.

LIST OF REFERENCES USED

X longitudinal axis

PO open position of the valve member

PF closed position of the valve member

10 injector

12 actuator part

14 hydraulic part

16 high pressure fuel circuit

18 entrance mouth

20 injection holes

22 body of the actuator part

24 solenoid

26 connector

28 pole piece

30 bodies of the hydraulic part 32 moving valve member

34 magnetic core

36 valve seat

38 injector nut

5 40 face of the actuator part body

42 underside of the pole piece

44 central channel in the polar room

46 star passage

48 peripheral wall of the hydraulic body

10 50 upstream space internal to the hydraulic part body

52 internal downstream space at the hydraulic body

54 narrow part of the moving limb

56 guide down

58 fuel passage

15 60 bore - control chamber

62 upstream face of the nucleus

64 bottom of the control chamber

66 peripheral ring face

68 bottom face of the bottom

20 70 flapper

72 valve body

74 movable member of flapper

76 peripheral wall of the valve body

78 shoulder

25 80 axial opening in the shoulder

82 lower annular surface of the peripheral wall

84 upper annular surface of the body / shoulder

86 inner side of the valve body

88 underside of the shoulder

30 90 outer face of the valve body

92 lower face of the moving limb

94 upper side of the moving limb

96 axial channel 98 restriction

100 sealing lip

102 first spring - needle spring

104 second spring - clapper spring

106 bag

108 extension

110 first circular line

112 second circular line

114 internal channel

116 annular space

M magnetic field

D36 seat diameter

D100 diameter of the circular lip

DUO diameter of the first circular line

Dl 12 diameter of the second circular line

FM force of opening of the magnetic field

FH closing force due to hydraulic imbalance

F 102 spring force needle

F 104 spring force of valve

Claims

A fuel injector (10) comprising a pressurized fuel circuit (16) extending from an inlet port (18) to injection holes (20) via a valve seat (36) controlling the fuel opening or closing said injection holes, the injector (10) further comprising an electromagnet actuator provided with a fixed solenoid (24) generating a magnetic field (M) when electrically powered and, a nozzle in the body (30) of which a movable member (32) is slidably guided along a longitudinal axis (X), the movable member (32) extending between a low end defining the valve seat (36) and an end high,

characterized in that

the upper end of the movable member is provided with a magnetic core (34) adapted to cooperate with the solenoid (24) so that, when the solenoid (24) is energized the magnetic field (M) attracts and moves the moving member (32) to an open position (PO) in which the valve seat (36) opens a fuel injection passage and, when the solenoid (24) is not energized, the movable member (32) is pushed back by a needle spring (102) to a closed position (PF) in which said passage is closed preventing fuel injection,

the injector (10) is further provided with a control chamber (60) defining a damper adapted to slow down in use the movement of the movable member (32) to the open position (PO).

2. fuel injector (10) according to the preceding claim wherein the control chamber (60) is defined inside the movable member (32), said chamber (60) being in fluid communication with the valve seat ( 36).

The fuel injector (10) of claim 2 wherein the damper comprises an intake valve (70) controlling said

fluid communication, the valve (70) being movable between a first position in which the fluid communication is restricted and a second position in which the fluid communication is widely open.

The fuel injector (10) of claim 3 wherein the damper further comprises a valve spring (104) continuously biasing said intake valve to the first position.

The fuel injector (10) according to claim 4 wherein the opening force FM generated by the magnetic field (M) is greater than the sum of the closing forces exerted on the movable member (32) according to the general formula:

FM> F 102 + F 104 + FH in which

FM is the opening force of the magnetic field;

F 102 is the force of the needle spring;

F 104 is the force of the poppet spring;

FH is the force due to the hydraulic imbalance of the moving limb (32).

A fuel injector (10) according to any one of claims 3 to 5 wherein, in use, the valve (70) moves to the second position when the movable member (32) moves to the closed position (PF ).

7. fuel injector (10) according to any one of claims 3 to 6 wherein the valve (70) comprises a body (72) for tubular portion arranged in the control chamber, said body (72) tubular being permanently pressed against a face (42) of the actuator, the valve needle spring (102) being compressed between said tubular body (72) and a face (66) of the control chamber.

The fuel injector (10) according to claim 7, wherein the valve (70) comprises a movable member (74) arranged in the tubular body (72).

The fuel injector (10) according to claim 8 wherein the tubular body (72) comprises an axially extending peripheral wall (76) (X) of a first end (82) arranged in the control chamber up to at a second end (84) bearing against a face (42) of the actuator, the tubular body (72) being further provided with a radial face open at its center forming a inner shoulder (78), the movable member (74) of the valve in the first position bearing against said radial face.