EP1751421B1 - Pump injector - Google Patents

Abstract

The invention concerns a pump injector (1) for compressing fuel, then injecting same into the combustion chamber of an internal combustion engine cylinder during a main injecting phase, said pump injector (1) comprising a needle (7) the displacement of which is monitored by a first electromagnetic valve (6) so as to enable fuel contained in the inner volume (3) of the pump injector (1) to be injected. The invention is characterized in that it comprises: a capacity (11) for storing a volume of pressurized fuel; a second electromagnetic valve (2) for communicating said capacity (11) with the inner volume (3) of the injector (1) and for enabling a secondary injection phase, said second electromagnetic valve (2) being activated simultaneously with the first electromagnetic valve (6) during said main and secondary injection phases.

Description

Technical area

The invention relates to a fuel injection system for an internal combustion engine. With this type of system, the fuel is directly sprayed inside the combustion chamber of the engine of the gasoline or diesel type in particular. It is therefore within this combustion chamber that the mixture between the fuel and the air, which plays the role of oxidizer, is effected.

It is more particularly an injector, commonly called "pump injector", thus having a piston for compressing the fuel within its internal volume. This piston is moved by means of a camshaft driven via the crankshaft of the engine either directly or indirectly.

Thus, it is necessary to differentiate this type of injector common rail devices in which the fuel is compressed upstream of several injectors themselves, which are then no longer actuated by a camshaft.

Prior art

In general, the pump injectors can inject fuel only during a main phase of injection, corresponding to the injection before the explosion in the combustion chamber. This injection is achieved through a cam profile that moves a piston inside the injector so as to compress the fuel just before the main injection. The compressed fuel is then injected into the combustion chamber.

Thus, given the profile of the cam used, this type of injection system does not allow to inject fuel outside an active zone of the cam. However, for certain applications, it may be advantageous to inject fuel at a time close to the main injection to reduce emissions and especially soot or during one or more secondary phases relatively far from the main injection phase . In particular, it is possible to refer to post-combustion injections for the regeneration of the aftertreatment systems of the exhaust gases. Indeed, with this type of secondary injections, it is possible to send unburned fuel to the level of a particulate filter in the exhaust line, which has the effect of cleaning and regenerating it. .

However, this type of injectors allowing a second injection phase currently requires complex injection systems common rail and equipped with an internal capacity to allow for pilot injections, such as in particular described in the document U.S. 4,913,113 . In this type of injector, fuel compression is not performed, and their function is limited to the injection of fuel within the combustion chamber. Thus, a common rail system allows great flexibility in multiple injection. However, it does not make it possible to achieve the forms of instantaneous injection flow, and to reach the level of the injection pressures that can be obtained with a conventional pump injector system.

In addition, it is necessary to connect each injector to a high pressure ramp which thus comprises a large number of connections which are as many potential leak areas.

To overcome these problems, it has been designed injector systems pumps injected by cams whose active area comprises a succession of hollows and bumps. It is then possible to inject at different times fuel for post-processing needs or new combustion concepts, such as HCCI meaning "Homogeneous Charge Compression Ignition". However, the requirements related to the mechanical strength and the manufacturing constraints of the cam limit the characteristics of the main active zone of the cam. They also affect the filling of the injector because of an increase in the recoil speed of the injector plunger. In addition, the position of the secondary injection is dependent on the design of the cam, which limits the flexibility and allows to vary the injection phases independently. An injector of this type is described in the document WO01 / 14712 .

To improve this flexibility, hybrid systems have also been developed that combine both pump injectors and common rail. Such a device is described in the document US-6,439,202 wherein a common rail conveying pressurized fuel is connected to the supply of the pump injectors. However, this type of system is very complex and expensive, and it requires an important qualification to perform its repair when a failure is detected at the injection system. Thus, it does not provide a satisfactory solution to achieve low cost and with great reliability secondary injection phases. Indeed, such an installation is subject to the same drawbacks of reliability as the standard common rail system because of the large number of connections present on the high pressure circuit.

Thus, the object of the invention is to provide an adaptive system for current injection systems and which is otherwise reliable and flexible. Such a system must also allow to inject fuel under pressure inside an engine, regardless of the position of the piston without limitation in the amount injected, and with very high fuel pressures.

Presentation of the invention

The invention therefore relates to a pump injector according to claim 1.

In other words, each injector comprises an area where pressurized fuel can be stored and then evacuated to allow a secondary injection phase that can occur early, or late compared to the main injection phase to n ' any moment of the cycle. This capacitance is placed in communication with the internal volume of the injector by means of a second solenoid valve which, when it is simultaneously activated with the first solenoid valve, makes it possible to carry out several injections and in particular a main injection phase and a secondary phase.

In practice, the pump injector comprises, at a filling pipe intended to allow the filling of the fuel capacity under pressure, a non-return filling means adapted to allow the flow of fuel in one direction, from the internal volume to the capacity.

In other words, the capacity is connected to the internal volume of the injector by means of a filling pipe in which the fuel under pressure circulates in only one direction. Indeed, a non-return means, such as a valve, is reported inside this pipe to allow the flow of fuel in the direction of the internal volume to the capacity. The circulation of fuel inside this pipe does not occur until the main injection phase is over. This is achieved by disabling the first solenoid valve while keeping the second one active.

In practice, the non-return filling means may comprise a member for allowing the flow of fuel when the pressure difference between the internal volume and the capacity exceeds a predetermined threshold value.

In other words, it is possible to fill the capacity only when the pressure difference between the two orifices of the non-return means is greater than a predetermined threshold value. This can in particular be achieved by means of a member which comprises an elastic means such as a spring whose calibration is adapted according to the predetermined threshold.

More specifically, this elastic means can be calibrated at a pressure which is greater than that present in the injector during the main injection phase. In this case, the dead volume internal to the injector is not increased compared to a standard injector and the yield is identical.

In a particular embodiment and in particular during a post injection at a time very close to the main injection, the elastic means acts as a pressure limiter. This situation occurs mainly when the duration is long, the engine speed is high and that a post injection is performed at a very close time to the end of the main injection, without having to operate the second solenoid valve.

In practice, the injector comprises, at the level of an injection pipe intended to make the capacity communicate with the internal volume, a non-return injection means capable of allowing the flow of the fuel in one direction only, the capacity towards the internal volume.

Thus, the fuel under pressure is evacuated from the capacity when an injection must be made, at a specific injection line, which allows the fuel to circulate in one direction only, and more specifically in the sense of capacity towards the internal volume of the injector. This circulation is performed once the capacity filled and the second solenoid valve activated since it then allows the capacity to communicate with the internal volume of the injector.

Brief description of the figures

• la figure 1 est un schéma de principe de l'injecteur pompe, conforme à l'invention ;
• les figures 2a à 2f sont des schémas de principe représentant les différentes étapes du fonctionnement de l'injecteur pompe, conformément à l'invention ;
• la figure 3 est une coupe longitudinale de l'injecteur, conforme à l'invention ;
• la figure 4 est un chronogramme permettant de montrer les différents états des électrovannes et les variables relatives à l'injection de carburant dans le moteur.

The manner of carrying out the invention as well as the advantages which derive from it will emerge clearly from the description of the embodiment which follows, given by way of indication and not by way of limitation, in support of the appended figures in which:

• the figure 1 is a block diagram of the pump injector according to the invention;
• the Figures 2a to 2f are schematic diagrams representing the different stages of the operation of the pump injector according to the invention;
• the figure 3 is a longitudinal section of the injector according to the invention;
• the figure 4 is a chronogram to show the different states of the solenoid valves and the variables relating to the injection of fuel into the engine.

Way of describing the invention

As already mentioned, the invention relates to a pump injector for compressing and then injecting fuel into the combustion chamber of an engine.

As shown schematically in the figure 1 , the pump injector (1) compresses fuel that is initially at a low pressure in a supply circuit (16). This compression is obtained by means of a cam (4) driven in rotation by the movement of the crankshaft motor directly or indirectly. This cam (4) then moves a piston (5) capable of compressing the fuel. A solenoid valve (2) then makes it possible to close or open the internal volume (3) of the injector (1), so as to allow the increase of the pressure inside its internal volume (3), or the admission of fuel to be compressed.

A second solenoid valve (6) makes it possible to lock the displacement of a needle (7) whose displacement makes it possible to release an orifice (9) allowing injection.

The locking of the position of the needle (7) is obtained by realizing or not a pressure difference between the two ends of the needle (7). When the pressure is equal to these two ends, a return means (8) then makes it possible to return the needle (7) to its closed position.

According to a main characteristic of the invention, a capacitor (11) makes it possible to store fuel under pressure so as to allow injection into one or more secondary phases. In this way, it is then possible to inject at times very far from the main injection either by anticipation or with delay.

As shown, the two solenoid valves (2, 6) are of the mono-stable type because they comprise an elastic return means to allow them to return to the deactivated state once the supply has been cut off. These solenoid valves (2, 6) may in particular comprise two states and three channels. In this way, it is possible to set, by means of the solenoid valve (2), the internal volume (3) of the injector (1) either at the pressure of the supply circuit (16) or at the pressure P compressed fuel contained in the capacity (11). By means of the solenoid valve (6), either the two ends of the needle (7) are at the pressure contained in the internal volume (3) of the injector (1), or an end at the pressure contained in the internal volume (3) and the other at the pressure contained in the supply circuit (16).

A filling pipe (15) comprises a non-return means (10), so as to allow circulation in this filling pipe (15) only in one direction, namely in the direction of the internal volume (3) up to capacity (11).

A second non-return means (12) is attached to an injection pipe (14) so as to allow the circulation of the pressurized fuel only in one direction, namely the direction of the capacity (11) to the internal volume (3) of the injector (1).

As shown, the non-return means (10) comprises a member (13) which is in the form of a resilient member of the spring type. In this way, the circulation of the fuel inside this filling pipe (15) is only possible when the pressure difference between the two orifices of the non-return valve (10) exceeds a predetermined threshold value.

The operation of the pump injector takes place as the phases described in Figures 2a to 2f . Thus, as represented in figure 2a , the solenoid valve (2) being deactivated, the raising of the piston (5) causes the suction of the fuel contained in the supply circuit (16). The chamber (17) left free by the piston (5) thus fills when the profile of the cam (4) allows the raising of the piston (5).

As shown in figure 2b , corresponding to the phase beginning at time t1 of the figure 4 when the cam (4) has a hump, this causes the piston (5) to descend and, therefore, so that the fuel is not driven into the supply circuit (16), the solenoid valve (2) is activated to increase the pressure of the fuel on the one hand inside the chamber (17) and on the other hand, inside the internal volume (3) of the pump injector (1).

As shown in Figure 2c , corresponding to the phase beginning at time t2 of the figure 4 it is then possible to inject the fuel under pressure into the combustion chamber of the engine. To do this, it is then necessary to activate the solenoid valve (6) concomitantly with the solenoid valve (2). Indeed, this solenoid valve (6) makes it possible to put one of the sides of the needle (7) at the pressure of the fuel contained in the supply circuit (16), and consequently, when the pressure P of the fuel contained in the internal volume (3) is greater than the pressure exerted by the return spring (8), the needle (7) moves and allows holes (9) to inject the fuel into the combustion chamber of the corresponding cylinder.

As shown in figure 2d , corresponding to the phase beginning at time t3 of the figure 4 once the main injection is complete, it is possible to store pressurized fuel within a capacity (11). To do this, the solenoid valve (6) is deactivated, which makes it possible to put the two sides of the needle (7) at the same pressure P and consequently, this causes its descent under the effect of the return spring ( 8). Fuel contained in the internal volume (3) is then able to flow inside a filling pipe (15) of the capacity (11).

However, this pipe (15) has a non-return means (10) to circulate the fuel in one direction. In fact, the only direction of circulation inside this pipe (15) is then that going from the internal volume (3) of the injector (1) to the capacity (11). As shown schematically, this non-return means (10) may comprise an elastic member (13) to allow the flow of fuel in this pipe (15) when the fuel pressure P exceeds a predetermined threshold value.

As shown in figure 2e , corresponding to the phase beginning at time t4 of the figure 4 regardless of the direction of movement of the piston (5), it is then possible to discharge both the internal volume (3) of the injector (1) and the chamber (17), and thus to mechanically release the cam , while keeping stored the fuel under high pressure in the capacity (11).

When activating the solenoid valve (2), corresponding to the phase starting at time t5 of the figure 4 , the pressurized fuel contained in the capacity (11) then fills the internal volume (3) of the injector (1) through an injection pipe (14) which has a non-return means (12). Therefore, within this pipe (14), the fuel can flow in one direction, that of the capacity (11) to the internal volume (3).

As shown in figure 2f , corresponding to the beginner phases at instants t6 and t8 of the figure 4 if it is desired to perform an injection during a secondary phase, it is then necessary to activate concomitantly the solenoid valve (2) with the solenoid valve (6), which makes it possible to release the needle (7) by putting one its ends at the pressure of the fuel contained in the supply circuit (16), while the other end is at the pressure P of the fuel initially compressed and stored in the capacity (11), with the pressure losses close.

This technique therefore makes it possible to inject fuel at times very far from the main injection phase, corresponding substantially to the top dead center of the piston inside the cylinder in question.

To stop the secondary injection phase, and as shown in FIG. figure 4 in the beginners phases at times t7 and t9, it is necessary to simultaneously deactivate the two solenoid valves (2, 6).

As shown in figure 3 , the pump injector can be assembled from a number of sections (20, 21, 22, 23, 24, 25), in order to facilitate its design and the realization of the various pipes present inside its volume internal (3). Thus, the capacity (11) can for example be straddling between several sections (24, 25) and be made by a recess opening in several sections. The anti-return means (10, 12) are obtained by means of balls, able to move inside a housing. The displacement of these balls makes it possible to obstruct or not an orifice and then prohibits the flow of fuel inside this pipe.

As shown in figure 4 the displacement of the plunger (5), driven by the cam (4), is represented by the curve D5. The piloting of the two solenoid valves (2, 6), represented in the curves E2 and E6, thus makes it possible to inject fuel under pressure, and this during a cycle of raising of the piston (5).

The fuel injection is represented by the curve D9, corresponding to the flow of fuel flowing through the orifices (9).

The curves P3 and P11 respectively correspond to the fuel pressure inside the internal volume (3) of the injector (1) and inside the capacity (11).

Obviously during the secondary injection phase and especially at times t6 and t8, the pressures P3 and P6 decrease when the flow D9 appears.

• il permet d'injecter du carburant en dehors de la phase d'injection principale à n'importe quel moment du cycle;
• il permet d'injecter du carburant à très haute pression, et ce au moyen d'une solution à haute fiabilité ;
• il ne nécessite pas de modification d'architecture du moteur et peut directement remplacer les dispositifs existants, ce qui est non négligeable en termes de coût.

It follows from the foregoing that a pump injector according to the invention has many advantages, in particular:

• it makes it possible to inject fuel outside the main injection phase at any moment of the cycle;
• it can inject fuel at very high pressure, using a highly reliable solution;
• it does not require engine architecture modification and can directly replace existing devices, which is not insignificant in terms of cost.

Claims (2)

1. Pump injector (1) for compressing fuel, and then injecting it inside the combustion chamber (18) of a heat engine cylinder during a main injection phase, said pump injector (1) comprising:

   ■ a needle (7) with the movement thereof being controlled by a first electronically-controlled valve (6) to allow the fuel contained in the internal volume (3) of the pump injector (1) to be injected;

   ■ a capacity (11), for storing a volume of pressurized fuel; characterized in that it also comprises:

   ■ a second electronically-controlled valve (2) suitable for bringing said capacity (11) into communication with the internal volume (3) of the injector (1) to allow a secondary injection phase, said second electronically-controlled valve (2) being activated concomitantly with the first electronically-controlled valve (6) during said main and secondary injection phases;

   a non-return filling means (10) provided in a filling pipe (15) for allowing the capacity (11) to be filled with pressurized fuel, said non-return means (10) being suitable for allowing the flow of fuel in only one direction, from the internal volume (3) to the capacity (11), and comprising a component (13) for allowing the fuel to flow when the pressure difference between the internal volume (3) and the capacity (11) exceeds a pre-set threshold value greater than the pressure inside the injector, during the main injection phase
2. Pump injector as claimed in claim 1, characterized in that it comprises, in an injection pipe (14) for bringing the capacity (11) into communication with the internal volume (3), a non-return injection means (12) suitable for allowing the fuel to flow in only one direction, from the capacity (11) to the internal volume (3).

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