TECHNICAL FIELD

The present invention relates to an inlet metering valve assembly intended to be installed in an engine fuel pump of a fuel injection system, in particular of a gasoline direct-injection (GDI) system.

BACKGROUND OF THE INVENTION

It is known that in a fuel injection system, a solenoid actuated spill valve is provided in the fuel pump in order to regulate the amount of fuel flowing from the fuel pump to the fuel injectors.

Commonly, the solenoid actuated spill valve controls the opening of an inlet check valve by using an armature fixed to a rod. The armature is connected to an end of a pole piece by means of a coil spring that is contracted or relaxed depending on a magnetic field created by the solenoid.

In particular, when the solenoid creates the magnetic field, the coil spring is contracted, the armature with the rod being pulled away from the inlet check valve towards the end of the pole piece. The inlet check valve is then closed and fuel is released from the fuel pump.

On the contrary, when the solenoid does not create the magnetic field, the coil spring is relaxed, the armature with the rod being pushed towards the inlet check valve. The inlet check valve is then open and fuel is pushed back in the fuel pump.

Nevertheless, in this configuration, acoustic noise is generated because of collisions between the armature and the end of the pole piece, and because of collisions between the armature and the inlet check valve. These collisions are produced because of fluctuations of a magnetic force that the armature experiments during its movement.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to resolve the above- mentioned problem in providing an inlet metering valve (IMV) assembly for an engine fuel pump of a gasoline direct-injection (GDI) system, comprising an IMV cartridge assembly and a solenoid assembly, the solenoid assembly being configured to be assembled surrounding the IMV cartridge assembly and comprising at least one coil, the IMV cartridge assembly comprising an IMV valve body and a pole piece, the pole piece comprising a peripheral wall and a longitudinal cavity delimited by said peripheral wall, the longitudinal cavity containing a guide, an armature and a metering pin, the metering pin being fixed to the armature, the at least one coil being able to create a magnetic field inducing a sliding of the armature with the metering pin inside the longitudinal cavity of the pole piece, wherein the peripheral wall of the pole piece comprises a groove comprising a first slope-shaped portion, a second slope-shaped portion and a narrowed portion, the narrowed portion forming an intersection connecting the first slope-shaped portion to the second slope-shaped portion.

Thanks to the claimed IMV assembly, at the level of the first slope-shaped portion, the magnetic field that goes through the wall of the pole piece is progressively attenuated, such that the magnetic force on the armature is substantially constant while the armature slides inside the pole piece. Then, abrupt collisions between the armature and other elements are limited.

Additionally, this effect is obtained by using a single pole piece, making manufacturing easier and avoiding relevant magnetic force penalties caused by the use of a pole piece formed by several assembled parts.

In an embodiment of the IMV assembly, a coil spring is arranged to connect the guide to the armature, the coil spring being able to shift between an extended position and a compressed position when the magnetic field is created by the at least one coil.

In an embodiment of the IMV assembly, the peripheral wall is made of a magnetic material.

In an embodiment of the IMV assembly, a thickness of the narrowed portion is thinner than a thickness of a rest of the peripheral wall of the pole piece. In an embodiment of the IMV assembly, a thickness of the narrowed portion is in a range from 0.30 mm to 0.60 mm, preferably between 0.40 mm and 0.50 mm.

In an embodiment of the IMV assembly, an angle of the first slope-shaped portion is in a range from 2° to 60°, preferably between 5° and 20°.

In an embodiment of the IMV assembly, the IMV valve body comprises a fuel inlet passage extending in a radial direction, the metering pin being arranged such that a first end of the metering pin obstructs the fuel inlet passage of the IMV valve body when the magnetic field is created by the at least one coil.

In an embodiment of the IMV assembly, the IMV valve body comprises a fuel inlet passage extending in a radial direction, the metering pin being arranged such that a first end of the metering pin uncovers the fuel inlet passage of the IMV valve body when the magnetic field is created by the at least one coil.

In an embodiment of the IMV assembly, the IMV valve body comprises a longitudinal cavity and the guide comprises a longitudinal cavity, the longitudinal cavity of the IMV valve body and the longitudinal cavity of the guide being concentric, the metering pin being arranged to move along said longitudinal cavities when the magnetic field is created by the at least one coil.

In an embodiment of the IMV assembly, the guide is made of a non magnetic material.

The invention further extends to an engine fuel pump for a gasoline direct- injection (GDI) system, comprising an IMV assembly as previously described.

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 shows a schematic front view of a fuel pump of a GDI system.

Figure 2 shows a perspective view of the fuel pump of figure 1, and of an IMV cartridge assembly and a solenoid assembly as per the present invention.

Figure 3 shows a perspective view of a section of an IMV assembly as per the present invention.

Figure 4 shows a perspective view of the IMV cartridge assembly of figure

2 Figure 5 shows a detail of the IMV assembly of figure 3 as per a first embodiment in a first position.

Figure 6 shows a detail of the IMV assembly of figure 3 as per a second embodiment. Figure 7 shows a detail of the IMV assembly of figure 3 as per the embodiment of figure 5 in a second position.

Figure 8 shows a diagram of magnetic flux lines of a magnetic field going through the IMV cartridge assembly of figure 2 at a current of 1 A. DESCRIPTION OF THE PREFERRED EMBODIMENTS

Figure 1 shows a fuel pump 10 of a gasoline direct-injection (GDI) system. The fuel pump 10 comprises a plunger 12, a plunger chamber 14, a fuel inlet 16 and a fuel outlet 18.

The fuel inlet 16 allows an entry of fuel in the fuel pump 10. The fuel outlet 18 allows fuel to exit from the fuel pump 10 towards the fuel injectors (not shown).

The plunger chamber 14 has preferably a substantially cylindrical shape extending along a longitudinal direction A. The plunger chamber 14 comprises a lateral wall 15.

The plunger 12 is configured to operate a back and forth movement inside the plunger chamber 14. The back and forth movement is operated along the longitudinal direction A.

Fuel entering in the fuel pump 10 is intended to reach the plunger chamber 14. The fuel inside the plunger chamber 14 is pressurized due to the back and forth movement of the plunger 12. The pressurization of fuel induces the exit of fuel from the plunger chamber 14 via the fuel outlet 18.

As clearly shown in figure 2, the lateral wall 15 of the plunger chamber 14 comprises a hole 20. The hole 20 contains an inlet check valve 22 configured to switch between an open position and a closed position. In the closed position, fuel in the plunger chamber 14 is pushed to the fuel outlet 18, a reverse flow of fuel that has entered in the plunger chamber 14 being prevented. In the open position, fuel flows back towards the fuel inlet 16.

The fuel pump 10 further comprises an inlet metering valve (IMV) assembly 24 installed in the hole 20. The IMV assembly 24 is positioned against the check valve 22. Preferably, the IMV assembly 24 is welded to the fuel pump 10

The IMV assembly 24 comprises an IMV cartridge assembly 26 and a solenoid assembly 28. The IMV cartridge assembly 26 and the solenoid assembly 28 are configured to be assembled between them. As it will be described later, the solenoid assembly 28 is assembled surrounding the IMV cartridge assembly 26.

The solenoid assembly 28 comprises a substantially cylindrical portion 30. As shown in figure 3, the substantially cylindrical portion 30 comprises a front face 32, a rear face 34 and a lateral wall 35.

A flux ring 40 is provided on the front face 32. Advantageously, the flux ring 40 is welded to the front face 32. The flux ring 40 is shaped to be inserted into the hole 20 when the IMV assembly 24 is installed therein, the rest of the solenoid assembly 28 remaining outside said hole 20. Preferably, the flux ring 40 is slide- fitted in the hole 20 and welded to the lateral wall 15 of the fuel pump 10.

A longitudinal cavity 36 goes through the cylindrical portion 30 and the flux ring 40. The longitudinal cavity 36 extends along a longitudinal direction B of the cylindrical portion 30 and of the flux ring 40. The longitudinal direction B is substantially perpendicular to the longitudinal direction A when the IMV assembly 24 is installed in the hole 20. The longitudinal cavity 36 is substantially centred in the cylindrical portion 30 and in the flux ring 40.

Preferably, the longitudinal cavity 36 is cylindrically- shaped with a diameter D1 and a length LI.

As also shown in figure 3, at least one coil 38 is installed in the lateral wall 35. The coil 38 surrounds the longitudinal cavity 36 over a length L2. The length L2 is shorter than the length LI of the longitudinal cavity 36. Preferably, the length L2 is also shorter than a distance L3 between the front face 32 and the rear face 34. The distance L3 is smaller than the length LI.

The coil 38 is, for example, a wire coil comprising a number of wire turns included in a range from 300 to 700 wire turns, preferably between 450 and 550 wire turns. The coil 38 is configured to create a magnetic field by means of a current going through the coil 38. Preferably, the current on the coil 38 is equal to or smaller than 2 A. As best seen from figure 2, the IMV cartridge assembly 26 is shaped to be partially inserted in the longitudinal cavity 36. The IMV cartridge assembly 26 is further assembled in the hole 20 of the fuel pump 10 against the check valve 22, and welded to the fuel pump 10.

As shown in figure 4, the IMV cartridge assembly 26 comprises an IMV valve body 42 and a pole piece 44.

The IMV valve body 42 comprises a first portion 43 and a second portion 45. The second portion 45 is shaped to be inserted into the pole piece 44 as it will be detailed later. The first portion 43 and the second portion 45 are substantially cylindrically-shaped. A diameter D2 of the first portion 43 is larger than a diameter D3 of the second portion 45. The first portion 43 and the second portion 45 extend along a longitudinal direction C of the IMV cartridge assembly 26.

A fuel inlet passage 52 is provided in the first portion 43. The fuel inlet passage 52 extends along a radial direction of the IMV cartridge 26, said radial direction being substantially perpendicular to the longitudinal direction C. As shown in figures 5 to 7, when the IMV assembly 24 is installed in the hole 20 of the fuel pump 10, the fuel inlet passage 52 lies is front of a bore 54 of the fuel pump 10. The bore 54 connects the IMV assembly 24 to the fuel inlet 16, such that fuel arrives into the IMV assembly 24 via the fuel inlet passage 52. A diameter of the fuel inlet passage 52 is comprised in a range from 1 mm to 4 mm, preferably between 1.5 mm and 2 mm.

The IMV valve body 42 further comprises a longitudinal cavity 56. The longitudinal cavity 56 extends along the longitudinal direction C through the first portion 43 and the second portion 45. Preferably, the longitudinal cavity 56 is cylindrically-shaped with a diameter D4.

Advantageously, the IMV valve body 42 is made of a non-magnetic material.

As shown in figures 4 to 6, the pole piece 44 is formed by a peripheral wall 47 comprising an external face 49, an internal face 51 and a closed end 58. The wall 47 is made of a magnetic material. A thickness of the wall 47 is not constant along the pole piece 44. In particular, the wall 47 comprises at the external face 49 a groove. The groove has a substantially triangular longitudinal section. The groove is formed by a first slope-shaped portion 70, a narrowed portion 72 and a second slope-shaped portion 71 that will be later described.

The pole piece 44 comprises a first portion 46 and a second portion 48. The first portion 46 and the second portion 48 are substantially cylindrical-shaped. A diameter D5 of the first portion 46 is longer than a diameter D6 of the second portion 48. Advantageously, the diameter D6 is substantially equal to the diameter D1 of the longitudinal cavity 36, such that the second portion 48 of the IMV cartridge assembly 26 can be fitted in the longitudinal cavity 36 of the solenoid assembly 28.

The first portion 46 and the second portion 48 extend along the longitudinal direction C of the IMV cartridge assembly 26. A length L4 of the second portion 48 is substantially equal to the length LI of the longitudinal cavity 36.

Advantageously, when the IMV cartridge assembly 26 is installed in the longitudinal cavity 36 of the solenoid assembly 26, the longitudinal direction B and the longitudinal direction C coincide.

The first portion 46 and the second portion 48 are substantially hollow, forming a longitudinal cavity 50 of the IMV cartridge assembly 26. The longitudinal cavity 50 extends along the longitudinal direction C, from the first portion 46 to the closed end 58. The longitudinal cavity is delimited by the internal face 51 of the peripheral wall 47. Advantageously, the longitudinal cavity 50 is substantially cylindrical.

A diameter of the longitudinal cavity 50 in the first portion 46 is substantially equal to the diameter D3 of the second portion 45 of the IMV valve body 42. Then, the second portion 45 of the IMV valve body 42 can be inserted in the longitudinal cavity 50, such that the IMV valve body 42 is fitted in the IMV cartridge assembly 26.

The longitudinal cavity 50 comprises an armature 60, a guide 62 and a coil spring 64. The coil spring 64 is arranged to connect the armature 60 to the guide 62. The coil spring 64 is able to shift between an extended position (shown in figures 4 to 6) and a compressed position (shown in figure 7) depending on the magnetic field created by the coil 38. The coil spring 64 is made of a magnetic or of a non-magnetic material. The guide 62 has a shape and dimensions chosen such that the guide 62 can be fitted in the cavity 50. For example, the guide has a substantially frustoconical shape. The guide 62 is crossed by a longitudinal cavity 66. The longitudinal cavity 66 extends along the longitudinal direction C.

Advantageously, the guide 62 is made of a non-magnetic material.

The armature 60 has a shape and dimensions chosen such that the armature 60 is sliding-mounted in the cavity 50. The armature 60 is crossed by a longitudinal cavity 76 extending along the longitudinal direction C. Advantageously, the longitudinal cavity 76 is substantially cylindrical, a diameter D7 of the longitudinal cavity 76 being slightly smaller than the diameter D4 of the longitudinal cavity 56.

Advantageously, the longitudinal cavities 66, 76 are concentric. Moreover, when the IMV valve body 42 is fitted in the pole piece 44, the longitudinal cavities 56, 66 and 76 are concentric.

A metering pin 68 is fixed to the armature 60. In particular, the metering pin 68 is provided in the longitudinal cavity 76. The metering pin 68 has a shape and dimensions chosen such that the metering pin 68 is partially press-fitted in the longitudinal cavity 66 of the armature 60. In particular, an intermediate portion of the metering pin is press-fitted in the longitudinal cavity 66, a first end and a second end of the metering pin 68 extending outside the longitudinal cavity 66. Alternatively, the intermediate portion of the metering pin 68 can be welded to the longitudinal cavity 66.

The first end of the metering pin 68 is intended to be inserted in the longitudinal cavity 56 of the IMV valve body 42. The second end of the metering pin 68 is intended to be inserted in the longitudinal cavity 66 of the guide 62.

The shape and dimensions of the metering pin 68 allows the metering pin 68 to slide in the longitudinal cavities 56, 66. Then, the IMV valve body 42 and the guide 62 have a role of guiding a movement of the metering pin 68 along the longitudinal direction C.

Advantageously, a diameter of the metering pin is comprised in a range from 1 mm to 5 mm, preferably between 2.5 mm and 3.5 mm. A length of the metering pin 68 is comprised in a range from 20 mm to 40 mm, preferably from 25 mm to 35 mm. Advantageously, the armature 60 is made of a magnetic material. Then, when the pole piece 44 of the IMV cartridge assembly 26 is inserted in the longitudinal cavity 36 of the solenoid assembly 28, and the coil 38 is creating the magnetic field, the armature 60 experiments a magnetic force. As shown in figure 7, the magnetic force induces a displacement of the armature 60 along the longitudinal direction C towards the guide 62, causing a compression of the coil spring 64. When the coil 38 stops creating the magnetic field, the magnetic force on the armature 60 ceases and the armature 60 slides in an opposite direction along the longitudinal direction C. The coil spring 64 is then extended, as shown in figures 4 to 6.

Since the metering pin 68 is press-fitted in the longitudinal cavity 76 of the armature 60, the displacement of the armature 60 along the longitudinal direction C entails an analogue displacement of the metering pin 68. As previously said, the metering pin 68 can freely slide along the longitudinal direction C in the longitudinal cavities 56, 66. A maximum stroke of the metering pin along the longitudinal direction C is comprised in a range from 2 mm to 4 mm, preferably from 2.5 mm to 3.5 mm.

By the displacement of the metering pin 68, the IMV assembly 24 is configured to control the amount of fuel that enters in the plunger chamber 14 from the fuel inlet 16. Since the first end of the metering pin 68 slides in the longitudinal cavity 56 of the IMV body valve 42, the fuel inlet passage 52 can be totally obstructed, partially obstructed or uncovered by the metering pin 68. Then, the amount of fuel entering via the radial cavity 56 varies according to a position of the metering pin 68 in the longitudinal cavity 56.

In the embodiment shown in figures 5 and 7, the metering pin 68 totally obstructs the fuel inlet passage 52 when the coil 38 stops creating the magnetic field. Additionally, when the coil 38 stops creating the magnetic field, the check valve 22 is in the closed position. In this embodiment, the armature 60 is positioned in an intermediate position between the IMV valve body 42 and the guide 62. As shown in figure 7, when the coil 38 is actuated, the armature 60 moves away from the IMV valve body 42 by the action of the magnetic field, the coil spring 64 being compressed. The metering pin 68 is then moved such that the fuel inlet passage 52 is gradually unblocked and fuel can enter. The check valve 22 is gradually open as the armature 60 moves away from the IMV valve body 42.

In the embodiment shown in figure 6, the fuel inlet passage 52 is uncovered when the coil 38 stops creating the magnetic field, the check valve 22 being in the open position. In this embodiment, the guide 62 is positioned in an intermediate position between the IMV valve body 42 and the armature 60. When the coil 38 is actuated, the armature 60 moves towards the guide 62 by the action of the magnetic field, the coil spring 64 being compressed. The metering pin 68 is then moved such that the fuel inlet passage 52 is gradually obstructed and the entry of fuel is blocked. The check valve 22 is gradually closed as the armature 60 moves towards the guide 62.

As previously said, the peripheral wall 47 comprises a groove formed by a first slope-shaped portion 70, a second slope-shaped portion 71 and a narrowed portion 72. The narrowed portion 72 forms a bottom of the groove.

The narrowed portion 72 constitutes an intersection connecting the first slope-shaped portion 70 to the second slope-shaped portion 71. Advantageously, the narrowed portion 72 is substantially parallel to the longitudinal direction C. Preferably, the first slope-shaped portion 70, the second slope-shaped portion 71, and the narrowed portion 72 are positioned in a substantially central portion of the pole piece 44.

The first slope-shaped portion 70 and the narrowed portion 72 allow the magnetic force on the armature 60 to be substantially constant during the sliding of the armature 60 along the longitudinal direction C. The first slope-shaped portion 70 and the narrowed portion 72 are contiguous. A thickness of the narrowed portion 72 is thinner than the thickness of the rest of the wall 47, such that the narrowed portion 72 limits the transmission through the wall 47 of the magnetic field created by the coil 38. Since the wall 47 is made of a magnetic material, the magnetic field tends to go through the thickest regions of the wall 47, as shown in figure 7. Preferably, the thickness of the narrowed portion is in a range from 0.30 mm to 0.60 mm, preferably between 0.40 mm and 0.50 mm.

The first slope-shaped portion 70 constitutes an inclined portion of the wall 47 inducing a gradual decreasing in the thickness of the wall 47. In particular, the wall 47 decreases from a first thickness to a second thickness along the first slope- shaped portion 70. Advantageously, the second thickness corresponds to the thickness of the narrowed portion 72. An angle a of the first slope-shaped portion 70 is comprised in a range from 2° to 60°, preferably between 5° and 20°. The angle a is measured between the first slope-shaped portion 70 and the internal face 51 of the wall 47.

The second slope-shaped portion 71 also constitutes an inclined portion of the wall 47 inducing a gradual decreasing in the thickness of the wall 47. A minimal thickness of the second slope-shaped portion 71 corresponds to the thickness of the narrowed portion 72. An angle between the second slope-shaped portion 71 and the internal face 51 is greater that the angle a. Preferably, the second slope-shaped portion 71 is shorter that the first slope-shaped portion 70.

The gradual decreasing in thickness of the first slope-shaped portion 70 allows obtaining a gradual attenuation of the magnetic force along the full stroke of the metering ping 68. In addition, since the IMV valve body 42 and the guide 62 are made of a non-magnetic material, abrupt changes of the magnetic force near the IMV valve body 42 and the guide 62 are avoided.

As shown in the embodiments of figures 5 and 6, when the coil spring 64 is in the extended position, the first slope-shaped portion 70 lies in front of the coil spring 64, the narrowed portion 72 lying in front of the armature 60. Advantageously, an end of the first slope-shaped portion 70 adjacent to the narrowed portion 72 is substantially in a same longitudinal position of the pole piece than an end of the armature 60 when the coil spring 64 is in the extended position.

It must be noted that in the IMV assembly 24 as per the present invention, the coil 38 is configured to receive current during the full stroke of the metering pin 68. The current varies during the full stroke of the metering pin 68, the magnetic field created by the coil 38 varying because of the current variation. The magnetic force on the armature 60 is nevertheless constant during the full stroke of the metering pin 68 thanks to first slope-shaped portion 70 and the narrowed portion 72. For example, the IMV assembly 24 is configured to induce a constant magnetic force on the armature when the current going through the coil 38 varies between 0.8 A and 1.6 A.

The IMV valve body 42, the armature and the guide can contain axial bores 80, as shown in figure 4. The axial bores 80 serve for pressure balancing and thermal cooling of the IMV valve body 42. Pressure balancing is particularly useful in order to avoid undesired forces that modify the armature position during actuation. Preferably, at least one between the IMV valve body 42, the armature or the guide comprises axial bores 80. Please note that the invention is not limited to the illustrated embodiments.

In particular, the groove comprising the first slope-shaped portion 70, the second slope-shaped portion 71 and the narrowed portion 72 could be formed on the internal face 51 of the peripheral wall 47, instead of on the external face 49 of the peripheral wall 47.

LIST OF REFERENCES

A longitudinal direction of the plunger chamber B longitudinal direction of the cylindrical portion of the solenoid assembly and of the flux ring

C longitudinal direction of the IMV cartridge assembly LI length of the of the longitudinal cavity of the cylindrical portion L2 length of the coil

L3 distance between the front and the rear faces of the cylindrical portion

L4 length of the second portion of the pole piece D1 diameter of the longitudinal cavity of the solenoid assembly D2 diameter of the first portion of the IMV valve body D3 diameter of the second portion of the IMV valve body D4 diameter of the longitudinal cavity of the IMV valve body D5 diameter of the first portion of the pole piece D6 diameter of the second portion of the pole piece D7 diameter of the longitudinal cavity of the armature a angle of the first slope-shaped portion

10 fuel pump

12 plunger

14 plunger chamber

15 lateral wall of the plunger chamber

16 fuel inlet

18 fuel outlet

20 hole

22 check valve

24 inlet metering valve (IMV) assembly

26 IMV cartridge assembly

28 solenoid assembly cylindrical portion of the solenoid assembly front face of the cylindrical portion of the solenoid assembly rear face of the cylindrical portion of the solenoid assembly lateral wall of the cylindrical portion of the solenoid assembly longitudinal cavity of the solenoid assembly coil flux ring IMV valve body first portion of the IMV valve body pole piece second portion of the IMV valve body first portion of the pole piece peripheral wall of the pole piece second portion of the pole piece external face of the peripheral wall of the pole piece longitudinal cavity of the IMV cartridge assembly internal face of the peripheral wall of the pole piece fuel inlet passage of the IMV valve body bore longitudinal cavity of the IMV valve body closed end of the peripheral wall of the pole piece armature guide coil spring longitudinal cavity of the guide metering pin first slope-shaped portion second slope-shaped portion narrowed portion76 longitudinal cavity of the armature axial bore