EP3253961B1 - Control valve for fuel injector - Google Patents

Description

TECHNICAL AREA

The present invention generally relates to the field of fuel injection in internal combustion engines. The invention relates more particularly to a control valve for a fuel injector, in particular for a common rail type injection system.

STATE OF THE ART

As is known, a fuel injector generally comprises an injector body, an injection nozzle portion and a movably mounted injector needle. The injection nozzle has at least one spray orifice for injecting fuel directly into a combustion chamber of the engine, the opening and closing of the orifice (s) being controlled by the movement of the needle. .

The actuation of the needle is done selectively by means of a control chamber associated with a control valve, itself operated by an actuator, typically solenoid. The control chamber is supplied with high pressure fuel, which allows to exert (directly or indirectly) a closing force on the needle. A channel connects the control chamber to the control valve, which allows, in the open position, to put the control chamber in communication with a low pressure section in order to reduce the pressure in the control chamber, and thus cause the needle to move to open the injector.

A control valve generally comprises a closure member which cooperates with a seat arranged in a fuel passage connecting the high pressure to the low pressure.

In the common-rail system, the fuel pressures are very high (above 2000 bar) and the injectors are therefore subjected to significant hydraulic pressures which cause stresses and deformations of the pieces. At the control valve, the pressure forces tend to deform the fuel passage with the seat and the closure member.

To overcome this problem, the EP 2 620 632 A1 describes a fuel injector whose control valve comprises a compensation chamber. A cylindrical insert is mounted in a bore of the valve body and includes a central passage for the fuel provided with a sealing seat. The closure member has an axially movable stem shape in the central passage of the insert, the member being manipulated by a solenoid or piezoelectric actuator connected to a first axial end of the closure member, the opposite second end serving as a guide in the insert. The closure member has, on the side of the first end, a seat which cooperates with the sealing seat in the central passage to open and close the valve. When the shutter member is spaced from the seat, the fuel can flow and opens the insert on the side of the first end of the closure member. The compensation chamber surrounds the insert and is in communication with the control chamber, while the pressurized fuel enters the insert through a side port therein.

The design of the control valve as described in EP 2 620 632 A1 is advantageous in that it allows a balancing of the pressures at the functional organs of the valve. In practice, however, it has been observed that under certain conditions, when opening the seat of the control valve, dynamic leakage by the seat (important) disrupts the dynamics of the control valve, for example by an effort against the movable armature of the solenoid, which is fixed to the shutter member near the seat. Thus disturbances arise under and around the armature, generating pressure oscillations influencing the movements of the shutter member.

OBJECT OF THE INVENTION

The object of the present invention is to provide a valve of improved design control, not having the disadvantages mentioned above.

GENERAL DESCRIPTION OF THE INVENTION

With this objective in mind, the present invention provides a control valve for a control chamber of a fuel injector for an internal combustion engine. The valve comprises a body provided with a bore in which a fuel supply channel opens (in communication with the control chamber). In the bore of the body is placed a generally cylindrical liner which includes an axial passage having a section defining an internal fuel passage. A side port is provided in the liner wall through which the fuel enters the internal fuel passage. A sealing seat is provided in the passage.

A sealing rod slides axially in the liner and is configured to, in a closed position, rest on the sealing seat and seal the passage, and in an open position, spaced from the sealing seat, allow fuel flow. The shutter rod includes an actuating end for connection to an actuator out of the jacket.

The control valve further comprises an annular compensation chamber surrounding the liner, defined between an outer wall of the liner and the bore. The feed channel and the lateral orifice of the liner each open into the compensation chamber, whereby the internal fuel passage can be in communication with the high pressure fuel in the control chamber of the injector.

It will be appreciated that the internal fuel passage has an outlet located downstream of the sealing seat in the jacket portion opposite the actuating end of the sealing rod. Thus, the fuel outlet is on the side of the sleeve opposite to that by which the rod is connected to the actuator, thus avoiding the high-pressure jets towards the actuator when the valve is open, and the dynamic disturbances. who as a result.

The present invention therefore proposes a control valve of improved design, incorporating a pressure compensation chamber for compensating the pressure plays, and having an improved dynamic behavior since the actuating side is not disturbed by the fuel jets. when the valve is open.

Another advantage of the invention is the simplicity of implementation.

According to a preferred variant, the outlet orifice of the internal passage is located in the end portion of the axial sleeve passage opposite the end located on the actuating side.

The shutter rod may comprise, for example, a shutter member portion cooperating with the sealing seat in the passage and a guide portion terminating in the actuating end, axially opposite to the body member portion. shutter. The shutter member portion comprises at the free end of the rod, opposite the actuating end, an annular bearing surface which cooperates with the sealing seat of the passage. The seal between the seat of the liner and the bearing surface of the shank is generally of the metal / metal type. Different forms are conceivable for sealing between the seat and the bearing surface: for example conical surfaces or plane / plane, line interface / conical surface etc. The seat contact can also be offset relative to the guide.

Preferably, the axial passage in the liner comprises: a guide section configured to slidably slide the guide portion of the closure rod; and a valve section surrounding the shutter member portion of the shutter rod, into which the side port opens and includes the sealing seat.

In order to form a valve chamber, the valve section may have a diameter greater than the diameter of the guide section. Alternatively or cumulatively, the shutter member portion of the rod could have a reduced section.

The jacket is preferably fitted into the bore and advantageously comprises two annular bearings bearing on the wall of the bore. The bearings axially delimit the compensation chamber; the sealing can be achieved by the surface contact between the bearing and the bore, but annular seals can also be used. Alternatively, the bearings could be on the shirt.

One of the bearings is advantageously located at the level of the sealing seat of the internal fuel passage, which improves the resistance to mechanical stresses and robustness at the seat.

In practice, the control valve controls the communication with a low pressure section of the injector. The output of the internal passage therefore generally opens into a chamber or section in communication with an intermediate low-pressure channel, itself in communication with a low-pressure return channel.

According to a variant, there is an operational clearance between the guide portion of the shutter rod and the guiding section of the liner allowing a fuel leakage flow rate and the leakage flow flows into an auxiliary chamber in the continuity axial of the bore, the actuation side (the auxiliary chamber is also in communication with the low pressure return channel).

The fuel return paths from the guiding leak and the seat leak are preferably isolated. For this purpose, a controlled section orifice is advantageously provided between the low-pressure return channel and the auxiliary chamber, so as to avoid the flow of fuel from the chamber (and thus from the seat leak) towards the auxiliary chamber.

According to another aspect, the present invention also relates to an injector comprising an injection nozzle fed with high-pressure fuel and a control chamber, whose pressure makes it possible to control the movement of a needle, and a control valve such as defined above, which, selectively by means of an actuator, opens or closes the communication between the control chamber and a low pressure side.

DETAILED DESCRIPTION USING THE FIGURES

• Fig. 1 : une vue en coupe longitudinale d'un injecteur équipé avec la présente vanne de commande, selon une première variante ;
• Fig. 2 : une vue de détail de la vanne de commande présentée en Fig.1 ;
• Fig. 3 : une vue en coupe de la vanne de commande de la Fig.2, le plan de coupe étant décalé angulairement par rapport à celui de la Fig.2, mais passant également par l'axe de la tige d'obturation.

Other features and characteristics of the invention will become apparent from the detailed description of some advantageous embodiments presented below, by way of illustration, with reference to the accompanying drawings. These show:

• Fig. 1 : a longitudinal sectional view of an injector equipped with the present control valve, according to a first variant;
• Fig. 2 : a detailed view of the control valve presented in Fig.1 ;
• Fig. 3 : a sectional view of the control valve of the Fig.2 , the cutting plane being angularly offset from that of the Fig.2 but also passing through the axis of the shutter rod.

A fuel injector 10 for a common rail injection system, equipped with a variant of the present control valve, will now be described with reference to the Figures 1 to 3 . The general operating principle of such an injector 10 is conventional, similar to that of the injector of the state of the art mentioned in the introduction.

The injector 10 generally comprises an injector body with, in the lower part on the Fig.1 , an injection nozzle section 14 accommodating an injector needle 16 movably mounted in the nozzle 14 so as to slide axially. The nozzle 14 has an injection end 18 with at least one injection port 20, the injector 10 being mounted in the engine so that the injection end 18 protrudes into the combustion chamber (not shown), allowing the injection of high pressure fuel in the form of a spray. In the injector 10, the fuel circulates in a high-pressure channel 22 and accumulates in the injector body, around the needle 14. In the Figure 1 the injector is in the closed position: the front end 23 of the needle rests on a seat in the injection end 18 of the nozzle 14 and prevents the passage of fuel towards the injection orifices 20.

The actuation of the needle 16 is made selectively by means of a control chamber 24 associated with a valve of control 26, itself operated by an actuator 28, typically solenoid, which thus allows to control the opening and closing of the injection port (s) 20. The solenoid actuator comprises, in a known manner in itself, a fixed portion 28 ₁ with a coil which cooperates with a movable portion 28 ₂ also called "armature" whose displacement is generated by the magnetic field created by the coil 28 ₁ when it is supplied with current. Such an actuator is well known in the state of the art and does not require further explanation.

The control chamber 24 receives the rear end 17 of the needle 16 (opposite to the front end 23) and is supplied with high pressure fuel via an inlet port 19, which allows to exercise (here so direct) a closing force on the needle 16. A spring 29 is arranged in the chamber 24 to exert permanently on the needle 16 a force in the closing direction. An outlet orifice 30 connects, through a supply channel 32, the control chamber 24 to the control valve 26, which allows, in the open position of the valve 26, to put in fluid communication the chamber of 24 control with a low pressure section, to reduce the pressure in the control chamber 24, and thus cause the displacement of the needle 14 which moves back into the chamber 24 and disengages from its seat, letting the fuel to the injection ports.

The control valve 26 is illustrated in more detail on the Figure 2 . It comprises a body 34 with a bore 36 (not through) forming a cylindrical housing. The reference sign 38 designates a jacket constituted by a cylindrical insert fixed in the bore 36, preferably by fitting. The liner 38 has a central axial passage 40, in which slides axially a shutter rod 42. The central passage 40 defines, over a portion of its length, a fuel passage 44 which extends between an inlet port 46 (or piercing) in the wall of the liner 38 and an outlet port 48. A sealing seat 50 is provided in the fuel passage 44, with which the shutter rod 42 which is connected to the actuator cooperates with. 28.

In fact, the shutter rod 42 includes an organ portion shutter 45 and a guide portion 47 terminating in the actuating end 49, out of the sleeve 38, by which it is connected to the armature 28 ₂ of the actuator. In the variant, the connecting end 48 and the armature 28 ₂ are in an auxiliary chamber 51 of the valve body 34, in which the armature can move with the closure member.

An annular compensation chamber 52 is defined between a portion 54 of the outer peripheral wall of the liner and the bore 36, so that it surrounds the liner 38. In practice, an annular recess is preferably provided on a section of the bore to give volume to the clearing chamber. It will be noted that the supply channel 32 opens into the compensation chamber 52, as well as the lateral orifice 46 of the jacket, which puts the internal fuel passage 44 in communication with the control chamber 24.

It will be appreciated that the sealing seat 50 of the fuel passage and the outlet 48 are located in a portion of the liner 38 remote from the region of actuation of the sealing rod 42. With respect to the orientation of the figure 1 , the liner 38 has an upper portion facing the actuator 28 and through which the shutter rod 42 is connected thereto, and a lower portion, which carries the seat 50 and the outlet 48. Thus, In the open position of the shutter rod 42 (away from the seat 50), there is a gap between the opening rod 42 and the seat 50 through which the fuel flows from the fuel passage downward (also called dynamic leakage or control) in a leakage chamber 60 in communication with a channel 62 connected to the low pressure.

With this configuration, it avoids the fuel outlet by the upper part of the sleeve 38, and therefore the jet effects towards the frame 28 ₂ of the actuator. This imparts greater dynamic stability to the valve.

Some constructive provisions of this variant can be noted.

The liner 38 includes a guide section 64 configured to slidably slide the guide portion 47 of the closure rod 42. The diameters are preferably adjusted for operational clearance that allows for low fuel functional leakage. which escapes from the jacket 38 of the actuating side into the auxiliary chamber 51.

The liner 38 also includes a valve section 66 defining the internal fuel passage and surrounding the shutter member portion 45 of the sealing rod 42, into which the side port 46 opens and includes the sealing seat 50 The valve section 66 has a diameter greater than the diameter of the guide section 64, forming a chamber 68. The sealing seat 50 is, seen in the direction of flow of the fuel, at the outlet of the chamber. valve 68.

In fact, the sealing seat 50 is formed as an annular surface provided on an annular projection 70 in the central passage 40, this projection 70 to reduce the section of the passage near the lower end of the sleeve 38 (therefore opposite to the actuating end).

The present configuration makes it possible to offer a solid and robust sealing seat, notably because of the direction of flow and the fact that the edge between the sealing surface of the seat contact and the discharge diameter 48 can be moved away from the seat, without changing the balance of the valve.

The shutter member portion 45 of the shutter rod 42 carries at its free end a chamfer 72 acting as a bearing surface cooperating with the seat 50. In the closed position, a line or ring of the surface of the The support is in contact with the seat 50 to form the seal of the valve. The seal is generally of the metal / metal type; there may be an offset at the seat. The outlet orifice 48 of the fuel passage, respectively of the jacket 38, coincides with the narrowed passage section formed by the projection 70.

As will be understood, in the figure 1 the control valve 26 is closed: the closure member 42 rests on the seat 50. feeding the winding of the actuator 28 is created a magnetic field that attracts the armature (here upwards) and releases the shutter rod 42 from its rest position. It then creates an annular passage between the seat 50 and the sealing surface 72 which allows a seat leak: the valve is open and the fuel flows to the low pressure.

Preferably, the mounting of the cylindrical insert forming the liner 38 is by fitting and sealing manner. For this purpose there are provided two bearing regions 90 formed on the outer surface of the liner 38, although this is not imperative. These two bearings 90 also sealingly close the compensation chamber at its two axial ends. Seals can also be used.

It will be appreciated that one of the bearings 90 is positioned at the height of the sealing seat 50 of the internal fuel passage, which further improves the resistance to mechanical stresses and robustness at the seat.

• fuite de siège : écoulement principal de carburant à travers la vanne, existe uniquement en position d'ouverture de la tige d'obturation. Le carburant traverse le passage de carburant 66 et s'écoule par la sortie 48 dans la chambre 60.
• fuite guide : faible écoulement de carburant au niveau du jeu opérationnel entre la portion de guidage 47 de la tige d'obturation 42 et la section de guidage 64 de la chemise 38.

The figure 3 is a view of the valve 26 in a cutting plane different from that of the figure 2 which shows better the flow of the fuel return. As explained above, there are two sources of flow of the valve 26:

• Seat leakage: Main fuel flow through the valve, exists only in the open position of the shutter rod. The fuel passes through the fuel passage 66 and flows through the outlet 48 into the chamber 60.
• guide leakage: low fuel flow at the operational clearance between the guide portion 47 of the sealing rod 42 and the guide section 64 of the sleeve 38.

In the present variant, there is an annular clearance between the valve body 34 (generally cylindrical, and the outer casing 81 of the injector.) This annular clearance forms an annular collection chamber 76 in communication with a return channel. low pressure 78. The trailing chamber 60 is in communication with the collection chamber 76 via the channel 62. The auxiliary chamber 51 (accommodating the frame 28 ₂ ) is also in communication with the collection chamber 76 via a radial channel 80 (or more). The diameter of the channel 80 is determined so that the flow of fuel from the seat leak can not pass from the annular chamber 76 towards the chamber 51. Thus, the return circuits of the seat leak and the guide leakage (represented respectively by lines 82 and 84) are insulated in the valve body 34, and combine only at the inlet of the return channel 78.

Claims (11)

1. Control valve for a control chamber of a fuel injector for an internal combustion engine, the said control valve comprising:

   a body (34) provided with a bore (36) into which a fuel supply duct (32) opens;

   a jacket (38) of cylindrical general shape inserted into the bore (36) and comprising an axial passage (40) of which a cross section defines an inner fuel passage (44), into which the fuel enters via a lateral orifice (46), a sealing seat (50) being provided in the passage (44);

   a shut-off rod (42) sliding axially in the jacket (38) and configured, in a closure position, to rest on the sealing seat (50) and shut off the passage and, in an opening position, away from the sealing seat (50), to allow the flow of fuel, the shut-off rod (42) comprising an actuating end (49) for connection to an actuating device (28) outside the jacket;

   an annular compensation chamber (52) surrounding the jacket (38), defined between an outer wall of the jacket (38) and the bore (36), the supply duct (32) and the lateral orifice (42) of the jacket each opening into the compensation chamber (52);
   characterized in that

   the inner fuel passage (44) has an outlet orifice (48) situated downstream of the sealing seat (50) in the jacket part opposite to the actuating end (49) of the shut-off rod (42).
2. Control valve according to Claim 1, in which the outlet orifice (48) of the inner passage (44) is situated in the end part of the axial passage (40) of the jacket opposite to the end situated on the actuating side.
3. Control valve according to Claim 1 or 2, in which the shut-off rod (42) comprises a part forming a shut-off member (45) cooperating with the sealing seat (50) in the passage (44) and a guide part (47) terminating in the actuating end (49), axially opposite to the part forming the shut-off member (45).
4. Control valve according to Claim 3, in which the axial passage (40) in the jacket (38) comprises:

   a guide section (64) configured to provide a sliding fit of the guide part (47) of the shut-off rod; and

   a valve section (66) surrounding the part forming the shut-off member (45) of the shut-off rod, into which the lateral orifice (46) opens and comprising the sealing seat (50).
5. Control valve according to Claim 4, in which the valve section (66) has a diameter greater than the diameter of the guide section (64).
6. Control valve according to any one of the preceding claims, in which the jacket (38) is fitted into the bore (36) and preferably comprises two annular bearings (90) bearing on the wall of the bore.
7. Valve according to Claim 6, in which one of the bearings is situated at the height of the sealing seat of the inner fuel passage.
8. Control valve according to any one of the preceding claims, in which there is an operational clearance between the guide part of the shut-off rod and the guide section of the jacket allowing a fuel leakage flow; and
   the leakage flow flows into an auxiliary chamber in the axial continuity of the bore, on the actuating side.
9. Control valve according to any one of the preceding claims, in which the outlet orifice (48) of the inner passage (44) opens into a chamber (60) in communication with an intermediate low-pressure duct (62).
10. Control valve according to Claim 9 when dependent on Claim 8, in which the intermediate low-pressure duct (62) and the auxiliary chamber (51) are in fluid communication with a low-pressure return duct (78), a controlled orifice (80) being advantageously provided between the low-pressure return duct and the auxiliary chamber to avoid the flow of fuel from the chamber (60) to the auxiliary chamber (51).
11. Injector comprising an injection nozzle supplied with fuel and a control chamber of which the pressure makes it possible to control the movement of a needle, and a control valve according to any one of the preceding claims, which, selectively by means of an actuator, opens or closes the communication between the control chamber and a low-pressure side.

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