FR2924175A3 - Fuel injecting device for combustion engine, has sliding needle comprising portion introduced in control chamber, and closing unit adopting intermediate stable configuration in which fuel leakage opening is partially closed - Google Patents

Abstract

The device (1) has a fuel injector (2) comprising a control chamber (3) with a fuel leakage opening (4), and an injection chamber (5) comprising a fuel injection outlet (6). A fuel input conduit (7) leads to each of the chambers, and a sliding needle (8) has a portion (10) introduced in the control chamber. A selective leakage opening closing unit (11) with a stopper is moved between stable closing and releasing configurations of the opening for selectively closing the opening. The closing unit adopts an intermediate stable configuration in which the opening is partially closed.

Description

FIELD OF THE INVENTION The present invention relates generally to the field of fuel injection for combustion engines. More particularly, the invention relates to a fuel injection device comprising a fuel injector provided with: a control chamber provided with a fuel leakage opening; an injection chamber comprising a fuel injection outlet; a fuel supply pipe opening into each of said chambers; A sliding needle vis-à-vis said chambers and having a first portion introduced into the control chamber and a second portion distinct from the first portion introduced into the injection chamber, the needle being adapted to adopt a sliding position in which it closes said injection outlet and a sliding position in which it releases this injection outlet; the device comprising means for selectively closing the movable leak aperture between stable configurations of sealing and releasing the fuel leakage aperture. It has been found that there is a need to control the evolution of the flow of fuel passing through the injection outlet.

In this context, the present invention aims to provide a fuel injection device allowing some control of this fuel flow. For this purpose, the fuel injection device of the invention, moreover, conforming to the generic definition given in the preamble defined above, is essentially characterized in that the closure means are adapted to adopt a stable configuration. intermediate in which the fuel leak opening is partially closed. Thanks to the invention the device has a total fuel leakage section passing through the opening of the control chamber which is variable between three stable values of total leakage section.

It should be noted that a total leakage section is the sum of the sections limiting the leakage of fuel via the leakage opening of the control chamber. In this case when the sealing means are in a stable shutter configuration, the total leakage section via the opening is zero, when the sealing means are in a stable release configuration, the total leakage section via the aperture expressed in section area unit then takes a constant positive value. Finally, when the sealing means are in an intermediate stable configuration, the total leakage section has a value expressed in leakage section area unit which is stable and between zero and the positive constant value reached in the release configuration. The term stable configuration implies that the sealing means are adapted to maintain fuel passage section values expressed in unit area for each respective stable configuration, each of these stable values being predefined.

It has been found that by controlling the speed of fuel leakage through the leakage opening, it is then possible to control the speed of movement of the sliding needle, which correlatively makes it possible to better control the evolution over time of the flow of fuel passing through the injection outlet also called introduction rate. Thanks to the invention, if the closure means are in stable configuration of release of the opening then there is a maximum total leakage section and the flow of fuel passing through the leakage opening of the control chamber is then maximum. This results in a rapid drop in the pressure prevailing inside the control chamber and correspondingly a rapid rise of the needle which causes a rapid increase in the fuel injection rate via the fuel injection outlet of the injection chamber. Finally, when the sealing means are in an intermediate stable configuration, the total fuel leakage section is stable and less than the maximum stable leakage section obtained when the sealing means are in the release configuration. As a result, the pressure in the control chamber decreases due to leakage but with a lower rate of decrease than when the total leakage section is maximum. The needle up rate and correspondingly the rate of increase of the fuel injection rate via the fuel injection output of the injection chamber are reduced compared to what they are with a leakage section. maximum total. The invention thus makes it possible to control the rate of rise of the needle of the injector and the evolution over time of the injection rate. It can be made that the closure means comprise a first part forming a fuel transfer line passing through the opening of the control chamber and a second part movable relative to the first part, the first part being movable by relative to said opening of the control chamber, these first and second parts being adapted - so that when the closure means are in stable shutter configuration, said first piece is in sealing contact against said opening of the control chamber, the second piece then closing the fuel transfer line of the first piece; - So that when the sealing means are in intermediate stable configuration, said first part is then in sealing contact against said opening of the control chamber, the second part then allowing the transfer of fuel through the fuel transfer pipe the first piece; and so that when the closure means are in the closed configuration, said first part is then moved away from said leakage aperture of the control chamber thus allowing a fuel leakage between said first part and said leakage opening of said control room. The fact of having first and second moving parts relative to each other and with respect to the leakage opening makes it possible to obtain simply (by simple displacement of these two parts) and with a reduced number of parts the three stable configurations of the shutter means of the opening. It can also be ensured that the first piece is a tube comprising at least one fuel passage perforation coming from said control chamber and in which the second piece slides, the second piece being adapted to seal said at least one perforation of said first piece when the sealing means are in stable shutter configuration and to release said perforation when the closure means are in intermediate stable configuration. This embodiment makes it possible to simply produce the first and second parts by a simple perforated tube and a shaft sliding in the tube to selectively seal or discover the perforations of the tube and thus allow leakage via the calibrated perforation section.

It can be made so that said perforation of said first piece is a lateral perforation of the tube. Preferably, the device comprises means for controlling the shutter means adapted to transmit at least first and second control signals and the control means being adapted to switch to a stable release configuration upon reception of the first signal and in an intermediate stable configuration. receiving the second signal. It can be arranged that the closure means comprise at least one controlled means for generating a magnetic flux, said first part comprising at least one magnetizable zone and said second part comprising at least one magnetizable zone, the generation controlled means a magnetic flux being adapted to selectively generate and upon receipt of a control a magnetic flux causing the passage of said sealing means in at least one of their stable configurations of closure, release or intermediate. With this embodiment according to the intensity of the magnetic flux applied to each piece can be forced to move the first piece and / or the second part which are at least partially magnetizable. It can be arranged that said first and second parts are adapted to slide relative to each other along a sliding axis and that said magnetizable zones of the first and second parts extend radially with respect to this sliding axis. . It can be arranged that said magnetizable zones of the first and second parts are in the form of trays extending in planes perpendicular to said sliding axis. This embodiment allows a symmetrical distribution along the axis of sliding of the forces generated by the magnetization of the magnetizable zones. This embodiment facilitates the sliding of the first and second parts relative to each other.

It can be arranged that the device of the invention comprises a first stop limiting the mobility of the first piece vis-à-vis said opening of the control chamber and a second stop limiting the mobility of the second piece vis-à-vis -vis of said opening of the control chamber. This embodiment using stops makes it possible to simply predetermine the positions of the parts for each of the stable configurations of the closure means. It can be arranged that the device of the invention comprises a main elastic means adapted to exert a force for contacting said first piece against said opening of the control chamber. It can be arranged that the device of the invention comprises a secondary elastic means adapted to exert a stress on the second part tending to force this second part in a position opposing the transfer of fuel through the transfer line of fuel from the first piece. The advantage of each of these elastic means is to promote the return of the closure means in the closure configuration. Other characteristics and advantages of the invention will become clear from the description which is given below, by way of indication and in no way limiting, with reference to the accompanying drawings, in which: FIG. 1 shows an injection device comprising an injector and means for selectively closing the leakage opening of a control chamber of the injector; FIGS. 2a, 2b, 2c show a portion of the device of the invention in each of its respective stable shutter, intermediate and release configurations; FIGS. 3a, 3b, 3c represent, for each stable configuration of shutter means, a graph of the evolution over time of a control signal of the shutter means and a graph of the evolution over time of the shutter rate. introduction of fuel via the injection opening. The invention relates to a fuel injection device comprising a fuel injector 2 having: a control chamber 3 provided with a fuel leakage opening 4; an injection chamber 5 comprising a fuel injection outlet 6; - A fuel supply pipe 7 opening into each of said chambers 3, 5. This injector comprises a needle 8 which is slidably mounted in the body of the injector and each end of which opens respectively into the control chamber 3 and in the injection chamber 5.

This needle 8 has a section at the control chamber 3 which is greater than its section at the injection chamber 5. This needle also has an end at the injection chamber 5 which is adapted to selectively closing the injection outlet 6.

The device also comprises a pump (not shown) supplying the inlet pipe 7 with pressurized fuel. The device further comprises means 5 shutter 11 selectively the leakage opening 4 of the control chamber. A force F1 is exerted by the fuel on the needle portion which plunges into the control chamber and likewise a force F2 is exerted by the fuel on the needle portion which plunges into the injection chamber. These efforts are opposite in meaning and collinear. The force F1 tends to force the needle to close off the injection outlet 6 whereas the force F2 opposes this obturation and tends to move the needle away from this outlet 6. When the needle In the shut-off configuration, the fuel pressure P1 in the control chamber 3 is equal to the pressure P2 in the injection chamber 5. Due to the superiority of the needle section immersed in the chamber the force F1 is then greater than the force F2 and the needle is forced towards the injection outlet 6 so as to seal it. as is the case in Figures 2-a and 3-a. When the closure means 11 is in the release configuration or in the intermediate configuration, the fuel pressure P1 in the control chamber 3 then becomes less than the pressure P2 in the injection chamber 5. The force F1 is then less than the force F2 and the needle is forced towards the control chamber 3 so as to deviate from the shutter outlet 6 as is the case in Figures 2-b, 2-c and 3-b , 3-c. The sealing means 11 comprise: a first piece 12 having a tube-shaped portion perforated at its end and further having lateral perforations on the walls of the tube; a second piece 13 having a rod-shaped portion, this portion being slidably mounted inside the tube-shaped portion of the first piece so as to selectively close or release (depending on the sliding position of the second piece in the first piece) or the perforations 15 of the tube of the first piece 12. When the perforation or perforations 15 are released, fuel can then pass inside the first piece 12 as is the case on Figure 2-b. Conversely, when the perforation (s) 15 of the first part are closed off by the second part (13), the fuel can not then flow through the first part (12). The first part (12) is slidably mounted relative to the leakage opening of the first part (12). fuel 4 of the control chamber 3 so that the first piece 12 can selectively come into sealing contact against this opening 4 in order to seal it at least partially as is the case in FIGS. 2-a and 2 b. Once the first piece 12 in sealed contact against the opening 4, the fuel is either prohibited to transit via the opening 4 if the second part closes the perforation or holes of the first part, or allowed to transit through this opening 4 if the second part is positioned vis-à-vis the first to release the perforations 15. The axis of sliding of the first part vis-à-vis the second is substantially parallel to the axis of sliding of the first 4. Each of the first and second parts 12, 13 comprises a clean tray-shaped portion 17, these plates 17 extend radially with respect to this sliding axis and containing a magnetizable material. . The shutter means further comprise a controlled means 16 for generating a magnetic flux which is in this case an electric coil selectively supplied by a control means.

Upon receipt of the command, the coil 16 generates a magnetic flux tending to move the first and second parts of the opening 4. The sealing means 11 further comprise a first stop 18 limiting the mobility of the first piece 12 screws with respect to said opening 4 of the control chamber 3 and a second stop 19 limiting the mobility of the second part 13 vis-à-vis said opening 4 of the control chamber. The first and second stops respectively make it possible to define stable positions of the first and second parts 12, 13, vis-à-vis the opening 4. It should be noted that it is ensured that the perforations 15 made in the first piece 12 form the total fuel passage section when these perforations are free which is less than a total passage section obtained when the first piece 12 is in a stable position away from the opening 4. The closure means 11 also comprise a main elastic means 20 in this case a spring adapted to exert a force for contacting said first piece 12 against said opening 4 of the control chamber and a secondary elastic means 21 in this case a spring adapted to exert a stress on the second part 13 tending to force this second piece 13 in a position opposing the transfer of fuel through the pipe of fuel transfer of the first piece 12. These elastic means tend to force the passage of the closure means in their closure configuration or in other words tend to oppose the force of attraction of the parts 12 , 13 by the coil 16. The closing means are adapted so that the second part 13 moves towards the coil 16 when the magnetic flux generated by this coil reaches at least a low threshold level. The sealing means are also adapted so that the first part 12 moves towards the coil 16 only when the magnetic flux generated by this coil reaches at least a high threshold level higher than the low threshold. In this way as long as the low threshold is not reached the first and second parts do not move towards the coil, as is the case in Figure 2-a since the control current of the coil is zero as the shows figure 3-a.

Then when the low threshold is reached but the high threshold is not yet reached, the first part does not move to the coil, only the second part then moves to the coil as is the case in Figure 2 -b since the control current of the coil is no longer zero as shown in Figure 3-b. The sealing means are then in stable intermediate configuration and the opening 4 of the chamber 3 is then partially released thus leaving the fuel escape in a stable flow. It then results in a gradual rise of the injector needle thus allowing an increase in the injection rate. When the high threshold of the magnetic flux is reached, the first part moves towards the coil, in the same way as the second part, as is the case in FIG. 2-c since the control current of the coil (visible on Figure 3-c) is then greater than it was to control the passage of the shutter means in intermediate configuration.

The sealing means are then in a stable release configuration since the parts 12 and 13 are in abutment and the opening 4 of the chamber 3 is then completely released, thus allowing the fuel to escape in a stable flow greater than that it was with the shutter means in intermediate configuration. It then results in a gradual rise of the injector needle thus allowing an increase in the injection rate. The needle up rate and the rate of increase of the injection rate visible in FIG. 3-c are greater when the closure means are in a stable release configuration compared to what they are when the shutter means are in stable intermediate configuration. According to the control signal applied to the coil, that is to say according to the intensity level applied to the coil, then selectively controls the passage of the closure means in a stable release configuration, a stable intermediate configuration or a stable shutter configuration and it is also possible to control the rate of ascent of the needle and therefore the rate of increase of the rate of introduction of fuel. The invention therefore makes it possible to influence the rate of introduction of fuel by simply varying the control signal of the shutter means.

The invention can also be used to obtain a double slope of growth of the needle upward speed and correlatively of the rate of increase of the rate of introduction. For this purpose it is possible to make it possible to control, via a signal, the displacement of the first part 12, and before the needle is completely removed from the injection outlet 6, to control the displacement of the second part 13. To play on the closing speed of the injection outlet 6, and therefore on the speed of movement of the needle 8 to this outlet 6, it can be decided to control the simultaneous movement of the first and second parts 12, 13 by reducing enough power of the coil which leads to a high output shutter speed 6. Alternatively, in order for the drop curve of the introduction rate in time to be a two-slope curve, it is possible to decide to control the simultaneous displacement of the first and second parts 12, 13 and then before the needle has reached its end. closing position of the output 6 is controlled the raising of the second piece 13 to the coil 16 and finally it controls the passage in shutter configuration

Claims (10)

claims 1) Fuel injection device (1) comprising a fuel injector (2) with: - a control chamber (3) with a fuel leakage opening (4); - an injection chamber (5) having a fuel injection outlet (6); - A fuel supply pipe (7) opening into each of said chambers (3, 5); - a sliding needle (8) vis-à-vis said chambers (3, 5) and having a first portion (10) introduced into the control chamber (3) and a second portion (9) separate from the first portion introduced into the injection chamber (5), the needle (8) being adapted to adopt a sliding position in which it closes said injection outlet (6) and a sliding position in which it releases this output of injection (6); the device comprising selective closing means (11) for the leakage aperture (4) movable between stable configurations for closing and releasing the fuel leakage opening, characterized in that the shut-off means are adapted to adopt an intermediate stable configuration in which the fuel leakage opening (4) is partially closed. 2) fuel injection device according to claim 1, characterized in that the closure means (11) comprise a first part (12) forming a fuel transfer pipe passing through the opening (4) of the chamber control member (3) and a second piece (13) movable relative to the first piece (12), the first piece (12) being movable relative to said opening (4) of the control chamber (3), these first and second pieces (12, 13) being adapted. - so that when the closure means (11) are in stable shutter configuration, said first piece (12) is in sealing contact against said opening (8) of the control chamber (3), the second piece (13) ) then closing the fuel transfer line (14) of the first piece (12); - so that when the closure means (11) are in intermediate stable configuration, said first piece (12) is then in sealing contact against said opening (8) of the control chamber (3), the second piece (13) then allowing the transfer of fuel through the fuel transfer line (14) of the first piece (12); and - so that when the closing means (11) are in the closed configuration, said first piece (12) is then moved away from said leakage opening (4) of the control chamber (3) thus allowing a leak of fuel between said first piece (12) and said leakage opening (4) of said control chamber (3). 3) fuel injection device according to claim 2, characterized in that the first piece (12) is a tube comprising at least one fuel passage perforation (15) from said control chamber (3) and wherein slides the second piece (13), the second piece (13) being adapted to close said at least one perforation (15) of said first piece (12) when the closure means (11) are in a stable shutter configuration and to release said perforation (15) when the sealing means (11) are in intermediate stable configuration. 4) A fuel injection device according to claim 3, characterized in that said perforation (15) of said first piece (12) is a lateral perforation of the tube. 5) fuel injection device according to at least one of claims 2 to 4, characterized in that the closure means (11) comprise at least one controlled means (16) for generating a magnetic flux, said first piece (12) comprising at least one magnetizable zone and said second piece (13) comprising at least one magnetizable zone, the magnetic flux generating controlled means (16) being adapted to generate selectively and upon receipt of a command a magnetic flux causing the passage of said closure means (1) in at least one of their stable configurations of closure, release or intermediate. 6) fuel injection device according to claim 5, characterized in that said first and second parts (12, 13) are adapted to slide relative to each other along a sliding axis and in that said magnetizable zones (17) of the first and second parts (12, 13) extend radially with respect to this sliding axis. 7) A fuel injection device according to claim 6, characterized in that said magnetizable zones (17) of the first and second parts (12, 13) are in the form of trays extending in planes perpendicular to said sliding axis. . 8) fuel injection device according to at least one of the preceding claims combined with claim 2, characterized in that it comprises a first stop (18) limiting the mobility of the first piece (12) vis-à- screw of said opening (4) of the control chamber (3) and a second stop (19) limiting the mobility of the second piece (13) vis-à-vis said opening (4) of the control chamber. 9) Fuel injection device according to at least one of the preceding claims combined with claim 2, characterized in that it comprises a main elastic means (20) adapted to exert a contacting force of said first piece (12) against said opening (4) of the control chamber. 10) fuel injection device according to at least one of the preceding claims combined with claim 2, characterized in that it comprises a secondary elastic means (21) adapted to exert a stress on the second piece (13) having tendency to force this second piece (13) into a position opposing the transfer of fuel through the fuel transfer line of the first piece (12).