FR3096415A1 - Motor vehicle engine injector valve - Google Patents

Abstract

The invention relates to a valve of a fuel injector (3) comprising: - a rod (10) delimited by a valve seat (11) and shaped to be controlled by a coil (14), the rod (10) being shaped to slide along a longitudinal axis between a closed position and an open position, a longitudinal section (16) of the valve seat (11) comprising: - a first outer surface (21) extending between a point of contact (PC) and an end point (PI), and forming a non-zero angle (α1) with a direction (D) orthogonal to the longitudinal axis, called the first rear angle (α1), - a second surface external (22) extending between the end point (PI) and a longitudinal edge (17) and forming a non-zero angle (α2) with said direction (D), called the second rear angle (α2), the second angle rear (α2) being different from the first rear angle (α1). Abstract figure: Figure 2

Description

Description Title of the invention: Valve for an injector of a motor vehicle engine Technical field

The invention relates to a valve optimized for electromagnetic control of a fuel injector, such as diesel, for a combustion engine, in particular a motor vehicle.

Prior technique

In known manner, an injector comprises a needle disposed in a chamber filled with fuel and in which it slides between an open position of the chamber and a closed position of the chamber.

To do this, the needle is provided with a first end shaped to seal the chamber in the closed position, as well as a second end fluidly connected to a control valve.

[0003] Generally, such a valve comprises a valve body and an associated stem.

The rod is provided with a seat intended to cooperate with a guide element of the needle and a head, opposite the seat, driven by a coil.

Depending on whether or not the coil is supplied with electric current, the stem occupies a low position, in which the seat rests in a sealed manner on the guide element of the needle, or a low position, in which the seat is at a distance of the guide element Thus, the movement of the rod between the low position and the high position causes the needle to slide in the chamber.

[0004] However, as it is used, the injector wears out and the quantity of fuel released increases progressively, in particular in a so-called ballistic zone between the closed position and the open position of the chamber. .

We talk about injector drift Summary

The object of the present invention is to reduce this drift of the injector.

[0006] To this end, the subject of the invention is a valve for an electromagnetic control of a fuel injector of a combustion engine, in particular of a motor vehicle, the injector comprising a needle guided along an axis longitudinal in a nozzle body between a bottom guide and a top guide and, the valve comprising a valve body, a stem delimited between a valve seat and an end, called the top, opposite the valve seat, the stem being shaped to be driven by a coil, the stem being shaped to slide along a longitudinal axis in the valve body between an open position in which the valve seat is at a distance from a top face of the upper guide and a closed position of an evacuation channel opening into said upper face, position in which the valve seat is in contact with said upper face of the upper guide and, along a circle, called contact circle, surrounding the opening of said discharge channel, a surface of the valve seat comprising a central convex surface, an internal surface extending between the central convex surface and the contact circle, a first external surface extending between the contact circle and one end, called intermediate and forming a non-zero angle with a direction orthogonal to the longitudinal axis, called first rear angle, a projection of the intermediate end in a longitudinal plane being spaced from a straight line delimited by a projection of the circle of contact in the said longitudinal plane and one end of the longitudinal edge in the said longitudinal plane, a junction surface between the first external surface and the said longitudinal edge, called the second external surface, and forming a non-zero angle with the said direction orthogonal to the axis longitudinal, called second rear angle, the second rear angle being greater than the first rear angle.

Thanks to the two different inclination slopes of the seat of the valve according to the present invention, the contact pressure between the seat and the guide element in the closed position is drastically reduced, which makes it possible to minimize the drift of the injector over time while ensuring sufficient speed of movement of the rod between the closed position and the open position.

According to another characteristic of the invention, the first rear angle is between 0.5° and 5°.

According to another characteristic of the invention, the first rear angle is between 1.5° and 2°.

[0010] According to another characteristic of the invention, in a longitudinal section, a length of the first external surface is between 5 μm and 100 μm.

According to another characteristic of the invention, the second rear angle is between 15° and 60°.

According to another characteristic of the invention, the second rear angle is between 40° and 50°.

[0013] According to another characteristic of the invention, in a longitudinal section, a length of the second outer surface is between 5 μm and 100 μm.

[0014] According to another characteristic of the invention, in a longitudinal section, a length of the internal surface is between 15 μm and 100 μm.

[0015] According to another characteristic of the invention, the seat angle is between 0.1° and 2.5°.

According to another characteristic of the invention, a diameter of the valve seat is between 1.7 mm and 2 mm.

3 100171 The invention also relates to a fuel injector, in particular diesel, for a combustion engine of a motor vehicle, comprising a valve as described previously.

Brief description of the drawings

[0018] Other characteristics, details and advantages will appear on reading the detailed description below, and on analyzing the appended drawings, in which: FIG. 1

illustrates a partial longitudinal sectional view of an injector comprising a valve according to the present invention.

Fig. 2

[0020] [fig.2] illustrates a detail view of the valve seat of Figure 2.

Fig. 3

[0021] [fig.3] illustrates a detail view of the seat of FIG. 2 according to a first embodiment of the invention.

Fig. 4

[0022] [fig.4] illustrates a detail view of the seat of Figure 3.

Fig. 5

illustrates a detail view of the seat of Figure 2 according to a second embodiment of the invention.

Fig. 6

[0024] [fig.6] illustrates a detail view of the seat of Figure 5.

Fig.

7 100251 Ifig.71 illustrates a distribution of pressure exerted on the seat of figure 3.

Description of embodiments

[0026] The drawings and the description below contain, for the most part, elements of certain character.

They may therefore not only serve to better understand this disclosure, but also contribute to its definition, where applicable.

The invention relates to a valve 1 for an electromagnetic control 2 of a fuel injector 3 for a combustion engine, in particular a motor vehicle, as well as the associated injector 3.

The fuel is preferably diesel.

As shown in Figure 1, the injector 3 comprises a needle 4 and a body 5.

The body 5 comprises a recess forming a fuel circulation chamber 6.

The needle 4 extends along a longitudinal axis X between a lower end (not shown) shaped to close an outlet of the chamber and an upper end 7 shaped to be controlled by the valve 1.

100311 The needle 4 is adapted to translate along the X axis in the body 6 of the injector 3 between a closed position and an open position.

In the closed position, the lower end seals off the chamber outlet, preventing fuel from flowing out of the chamber.

In the open position, the lower end is held away from the outlet and fuel flows out of the chamber; then, the injector 3 supplies the engine with fuel.

[0032] The injector 3 also includes a spring 8 to return the needle 4 to the open position, as will be explained.

The sliding of the needle 4 in the body 5 is controlled by the valve 1, which will now be detailed, via a control chamber 9.

As seen in Figure 1, the valve 1 comprises a valve body 10 and a stem 11.

[0035] The stem 11 extends along an axis X' parallel to the axis X between a valve seat 12 forming the lower end of the stem 1 and an end 13, called the upper end, opposite the valve seat 12 .

It is noted that the axis X' is an axis of revolution of the rod 11.

The valve seat 11 will be described in detail later.

The stem 11 is shaped to slide along the axis X' in the valve body 10 between a closed position of the valve 1 in which the valve seat 12 rests in a sealed manner on a guide 14 of the needle 4 of the injector 3 and an open position of the valve 1 in which the valve seat 11 is at a distance from the guide 14.

Note that the valve is shaped so that the valve seat 12 is in contact with the top guide 14 in the closed position by defining a circle of contact between the valve seat 12 and the top guide.

[0039] The sliding of the rod 11 in the body 10 is controlled by the electromagnetic control 2, which comprises, as illustrated in figure 1, a coil 15 as well as a spring 16.

In operation, when the coil 15 is not supplied with electric current, the rod 11, under the effect of the spring 16, rests on the guide 14 in a sealed manner.

Valve 1 is then in the closed position.

The pressure exerted by the fuel in the pilot chamber 9 pushes the needle 4 into the closed position of the injector 3.

[0041] When the coil 15 is supplied with electric current, an electromagnetic force causes the stem 11 to rise which moves from the closed position to the open position, creating a fuel leak path around the valve seat 12.

Under the effect of the ratio force of the spring 8, the needle 4 rises to the opening position of the injector 3.

Of course, the invention is not limited to the piloting described above.

The valve seat 12 is now detailed.

As shown in Figures 2 to 8, a longitudinal section 17 of the valve seat 12 comprises a first longitudinal edge 18 and a second longitudinal edge (not shown) opposed and a bottom 20 between the longitudinal edges.

The bottom 20 includes a point, referenced PC (for contact point), corresponding to the contact between the valve seat 12 and the guide 14 of the needle 4.

The contact point is a projection in the longitudinal section 17 of the contact circle.

Between the PC contact point and the first longitudinal edge 18, the bottom 20 comprises a first segment 21 extending between the PC contact point and an end point, called intermediate point, referenced PI.

The bottom 20 also includes a second segment 22 extending between the intermediate end point PI and the longitudinal edge 18.

The first segment 21 corresponds to a projection in the longitudinal section 17 of a conical surface, called the first outer surface.

[0050] Similarly, the second segment 22 corresponds to a projection in the longitudinal section 17 of a surface forming a junction between the first external surface and the longitudinal edge.

As also visible in the figures, between the contact point PC and the second longitudinal edge, the bottom 20 comprises a third segment 23 extending between the point PC and a second end point, called intermediate point PII and forming an angle, called seat angle fi, with the direction D.

The bottom 20 also includes a fourth segment 24 extending from the intermediate point Pli.

[0052] Note that the valve seat is also determined by its diameter, which is equal to twice the distance between the axis X' and the contact point PC.

As clearly visible in the figures, the first segment 21 forms a non-zero angle al with a direction D orthogonal to the longitudinal axis X, called the first rear angle al.

Similarly, the second segment 22 forms a non-zero angle a2 with the direction D, called the second rear angle a2, the second rear angle a2 being different from the first rear angle a1.

The configuration of the two rear angles al and a2 allows a drastic reduction in the contact pressure exerted on the valve seat by the guide element.

Advantageously, the following ranges ensure reduced contact pressure as well as sufficient valve sliding speed: - the first rear angle al is between 0.5° and 5°, preferably between 1.5° and 2 - the second rear angle a2 is between 15° and 60°, in particular between 40° and 50°, preferably of the order of 45°, - the length of the first segment 20 is between .5!_trn and 100 μm, preferably between 20 μm and 100 μm, - the length of the second segment 21 is between 5 μm and 100 μm, preferably between 25 μm and 40 μm, - the seat angle is between 0, 1' and 2.5', preferably between 0.75' and 1', - the length of the third segment 22 is between 15 μm and 100 μm, preferably between 45 μm and 100 μm, - the diameter of the seat of valve is between 1.7 mm and 2 mm, preferably between 1.79 mm and 1.94 mm.

According to the variant of Figures 4 and 5, the valve 1 has the following characteristics: - the first rear angle al is 1.5' - the second rear angle a2 is 45', - the length of the first segment 20 is 20 µm, - the length of the second segment 21 is 25 µm, - the seat angle is 0.75', - the length of the third segment 22 is 45 µm, - the diameter of the valve seat is 1.983 mm.

According to the variant of Figures 6 and 7, which corresponds to the preferred embodiment, the valve 1 has the following characteristics: - the first rear angle al is 2 - the second rear angle a2 is 45 ', - the length of the first segment 20 is 100 μm, - the length of the second segment 21 is 40 μm, - the seat angle is 1°, - the length of the third segment 22 is 100 μm, - the diameter of the valve seat is 1.793 mm.

The reduction in the diameter of the seat between the variant of Figures 6 and 7 compared to the variant of Figures 4 and 5 makes it possible to further increase the hydraulic force on the first and second segments 21, 22, which increases the speed of movement of the valve I.

In particular, simulations have shown that the first variant induces a hydraulic force of the order of 41N and a contact force of 1600 MPa against respective values of the order of 60N and 3700 MPa for a valve of the prior art: thus, the first variant indeed allows a strong reduction in the contact pressure while ensuring a hydraulic force of the same order of magnitude, involving equivalent sliding speeds.

As illustrated in Figure 8, a high pressure is exerted on the first and second segments 21,22, which increases the hydraulic force.

[0062]Simulations have also made it possible to show that the second variant induces a hydraulic force of the order of 60N and a contact force of 1600 MPa.

The sliding speed of the second variant is therefore further improved.

The illustrated segment 22 is straight.

Nevertheless, the second outer surface is not limited to this shape, and any type of junction between the first outer surface and the longitudinal edge could be envisaged, provided that appropriate values are obtained for the hydraulic force and the sliding speed.

For example, surface 22 could be concave or conversely convex.

The surface 22 could also have a step shape in the longitudinal section 17.

[0064] X longitudinal axis of the injector X' longitudinal axis of the valve D direction orthogonal to X' PC point of contact PI intermediate point PH second intermediate point al first rear angle a2 second rear angle ri seat angle 1 Valve 2 Control electromagnetic 3 Injector 4 Needle 5 Injector body 6 Upper end of the needle 7 Circulation chamber 8 Spring 9 Pilot chamber Valve body 11 Stem 12 Valve seat 13 Upper end 14 Needle guide Coil 16 Spring 17 Section longitudinal 18 Longitudinal edge Bottom 21 First segment 22 Second segment 23 Inner surface Third segment 24 Fourth segment.

8 9 [Claim 1] [Claim 2]

Claims (1)

CLAIMS Valve for an electromagnetic control (2) of a fuel injector (3) of a combustion engine, in particular of a motor vehicle, the injector comprising a needle (4) guided along a longitudinal axis (X) in a nozzle body between a bottom guide and a top guide (14) and, the valve comprising: - a valve body (10), - a stem (11) delimited between a valve seat (12) and an end ( 13), called high, opposite the valve seat (12), the stem being shaped to be driven by a coil (15) (2), the stem (11) being shaped to slide along a longitudinal axis (X ') in the valve body between an open position in which the valve seat (12) is at a distance from an upper face of the upper guide (14) and a closed position of an evacuation channel opening into said upper face, position in which the valve seat (12) is in contact with said upper face of the upper guide (14) and, along a circle, called circle of contact, surrounding the opening of said evacuation channel , a surface (17) of the valve seat (12) comprising: - a central convex surface (24), - an internal surface (23) extending between the central convex surface (24) and the contact circle (PC) , - a first outer surface (21) extending between the contact circle (PC) and one end, called intermediate (PI) and forming a non-zero angle (al) with a direction (D) orthogonal to the longitudinal axis (X'), called first rear angle (al), - a projection of the intermediate end in a longitudinal plane being spaced from a straight line delimited by a projection of the contact circle (PC) in said longitudinal plane and one end of the longitudinal edge (18) in said longitudinal plane, - a junction surface between the first outer surface (21) and said longitudinal edge (18) of the valve seat, called second outer surface (22), and forming a non-zero angle ( a2) with said direction (D) orthogonal to the longitudinal axis (X), called the second rear angle (a2), the second rear angle (a2) being greater than the first rear angle (al). Valve according to the preceding claim, in which the first angle 10 [Claim 3] [Claim 4] [Claim 5] [Claim 6] [Claim 7] [Claim 8] [Claim 9] [Claim 10] [Claim 11] back ( a1) is between 0.50 and 5'. Valve according to the preceding claim, in which the first rear angle (a1) is between 1.50 and 2'. Valve according to one of the preceding claims, in which, in a longitudinal section (17), a length of the first outer surface (21) is between 5 pm and 100 pm. Valve according to one of the preceding claims, in which the second rear angle (a2) is between 150 and 60°. Valve according to the preceding claim, in which the second rear angle (a2) is between 40' and 50'. Valve according to one of the preceding claims, in which, in a longitudinal section (17), a length of the second outer surface (22) is between 5 µm and 100 µm. Valve according to one of the preceding claims, in which, in a longitudinal section, a length of the internal surface (23) is between 15 µm and 100 µm. Valve according to one of the preceding claims, in which an angle of the internal surface, called seat surface (Ji), is between 0.10 and 2.5°. Valve according to one of the preceding claims, in which a diameter of the valve seat (11) is between 1.7 min and 2 mm. Fuel, in particular diesel, injector for a motor vehicle combustion engine, comprising a valve according to one of the preceding claims.