FR2925581A1 - Pressurized fuel injecting system for use in exhaust line of oil engine, has resistive and capacitive hydraulic elements arranged between supply pump and injector, where capacitive element is mounted in downstream of resistive element - Google Patents

Abstract

The system (33) has an injector (2) connected to a supply pump by a supply pipe. A resistive hydraulic element (34) and a capacitive hydraulic element (35) are arranged between the pump and the injector. The capacitive hydraulic element is mounted in downstream of the resistive hydraulic element. The resistive hydraulic element has a restrictor placed in the supply pipe. The capacitive hydraulic element has an additional volume that contains volume of fuel. A fuel flow limiting device is mounted in the supply pipe. An independent claim is also included for a method for injecting fuel in an exhaust system of an internal combustion engine.

Description

PATENT APPLICATION B07-3466 - AxC / EVH

Simplified joint stock company known as: RENAULT sas System and method of injecting fuel into the exhaust system of an internal combustion engine Invention of: CARRE Bertrand GUILLAT Samuel Van DEN BERGHE Véran VIOLO Gino System and method of fuel injection in the exhaust system of an internal combustion engine

The present invention is in the field of internal combustion engines and in particular diesel type engines equipped with a particulate filter mounted in the exhaust line of the engine. The invention relates more particularly to the regeneration system of such a particulate filter, that is to say the system which allows to remove the soot particles that have been trapped in the filter as and when the passage exhaust gases through the filter. To remove the soot particles thus trapped by such a particulate filter, it is possible to proceed by injecting fuel into the exhaust pipe of the engine, upstream of a catalytic device. It is thus possible to obtain a significant increase in temperature, by oxidizing the vaporized fuel in the flow of the exhaust gas and passing through the oxidation device. Such an oxidation reaction is in fact highly exothermic, which results in an increase in the temperature of the exhaust gas at the outlet of the catalytic device to a temperature level sufficiently high to be able to burn off the soot particles which have was stored in the particulate filter mounted downstream of the catalytic device in the exhaust line.

The fuel injection can be carried out directly in the exhaust line near the catalytic oxidation device. It can also be performed upstream of a turbine when the engine is equipped with a turbocharger, the exhaust gas passing through the turbine so as to transfer part of their energy and thereby rotate the compressor for raise the pressure of the gases admitted to the engine. It should be noted that the catalytic device which makes it possible to increase the temperature as a result of the injection of fuel into the exhaust line can be arranged in the immediate vicinity of the particulate filter or, on the contrary, be separated therefrom. of the exhaust line. The fuel injector is an electromechanical system which, subjected to a difference in pressure between the upstream and the downstream, makes it possible to dose a determined quantity of fuel from an electric control. To ensure good control of the injected fuel volume for a given electrical control, it is necessary to ensure good stability of the instantaneous pressure difference across an injector.

The evolution of the instantaneous pressure depends on the characteristics of the engine (displacement, geometry of the exhaust ducts, characteristics of the turbine, etc.) and the operating point (rotation speed, load, etc.). In addition, the evolution of the instantaneous pressure also depends on the characteristics of the fuel supply circuit of the injector. In general, the injection system comprises a hydraulic pump, associated with a pressure-limiting device, whose purpose is to guarantee a fixed set pressure whatever the flow rate consumed by the injection device, as well as by other possible applications and in particular the injection of fuel into the engine cylinders. European Patent Application 1,211,396 (Toyota) describes a fuel supply system for an injector mounted upstream of the turbine of the turbocharger, in a supercharged internal combustion engine. The feed system includes a control valve that can be opened during the regeneration phases of a particulate filter. In addition, a safety shut-off valve is placed downstream of the feed pump in order to cut off the feed if a fuel loss is detected, thus indicating a malfunction of the injector likely to damage the catalytic device and the particulate filter by too much temperature rise.

The object of the present invention is to improve the stability of the instantaneous supply pressure of the fuel injector during the injection. The invention also aims to maintain the supply pressure of the injector regardless of the injection rate demand. The invention also aims to prevent the fuel injection in the exhaust line disturbing the fuel supply of the internal combustion engine itself, for example by amplifying in some modes, the pressure oscillations . Finally, the object of the invention is also to preserve the after-treatment devices such as oxidation catalyst and particulate filter, mounted in the exhaust line while avoiding that a too high fuel flow will result in an increase exaggerated temperature that could deteriorate these organs in case of failure of the injector. In one embodiment, a fuel injection system in the exhaust circuit of an internal combustion engine, for a temperature rise in a catalytic exhaust gas treatment device, comprises a pump supply and an injector connected to the pump via a supply line. The system comprises, between the pump and the injector, at least one resistive hydraulic element and at least one capacitive hydraulic element, mounted downstream of the resistive element.

Thus a first-order filtration is applied between the pressure oscillations at the inlet of the system and the pressure oscillations upstream of the injector. Preferably, a resistive element is constituted by a restriction placed in the feed pipe upstream of any other resistive or capacitive element. In one embodiment, a capacitive element is constituted by an additional volume capable of containing a volume of fuel, placed in the supply line.

In one embodiment, a capacitive element is constituted by a pneumatic or mechanical accumulator. Another capacitive element may consist of a mechanically controlled pressure regulator.

Another capacitive element may be constituted by a flow controller mechanically controlled pressure. The different resistive and capacitive elements are preferably mounted in series on the supply line. In an advantageous embodiment, the injection system further comprises a flow restrictor device mounted in the supply line so as to prevent a failure of the injector, leading to too much injected fuel flow, does not lead to deterioration of the catalytic exhaust gas treatment device downstream of the injector.

In another aspect, there is provided a method of injecting fuel into the exhaust circuit of an internal combustion engine, for the purpose of raising the temperature in a catalytic exhaust gas treatment device, in a which uses a fuel supply system for an injector and first-order filtration is applied to a control system having, as inputs, the pressure upstream of the feed system and the injected fuel flow and as outputs, the fuel flow feeding the fuel system and the supply pressure of the injector. For example, it is possible to use at least one resistive hydraulic element and at least one capacitive hydraulic element, mounted downstream of the resistive element. The dimensions of the resistive and capacitive elements are chosen so as to obtain the desired level of filtration and to reduce the local variations in pressure during the injection. The invention will be better understood by studying a particular embodiment described by way of non-limiting example and illustrated by the appended drawings, in which: FIG. 1 schematically illustrates an embodiment of an architecture for a system according to the invention; and FIG. 2 illustrates the principle of the mode of action of the system according to the invention. As illustrated in Figure 1, very schematically, a fuel injection system comprises a feed pump 1 and an injector 2 connected to the pump 1 by a supply line 3. The feed pump 1 also serves to supply fuel, the injection device associated with the cylinders of the combustion engine not shown in the figure, by a supply line 4. The pump 1 draws fuel through a pipe 5 from a reservoir 6. The drive of the feed pump 1 can be any. The pump may be a pump dedicated exclusively to the supply of the injector 2 or, on the contrary, serve both as illustrated in FIG. 1, to supply the injectors of the combustion engine via the line 4 and the injector 2. by the pipe 3. A pressure relief device 7 is mounted on the outlet pipe 8 of the feed pump 1 so as to maintain substantially constant the pressure at the outlet of the feed pump 1. In the illustrated example in Figure 1, the pressure relief device 7 comprises a movable member 9 under the action of a spring 10, a fuel leakage flow can return to the tank 6 by a return duct 11. The injector 2 is capable injecting pressurized fuel in vaporized form into the exhaust duct 12 upstream of a catalytic oxidation device 13 itself disposed upstream of a particulate filter 14. The exhaust gases from the engine internal combustion in the exhaust pipe 12, the soot particles contained in these exhaust gases being retained by the particle filter 14. In the example illustrated, the particle filter 14 is placed in the same housing 15 as the device Of catalytic oxidation 13. It would of course be conceivable to have two separate devices at a certain distance in the exhaust line 12.

In normal operation, the injector 2 is not supplied with fuel, a control valve 16 controlled by means of an electrical signal coming from a connection 17 is in the closed position, thus isolating the supply pipe 3 of the feed pump 1. When a regeneration of the particulate filter 14 is required, the valve 16 is controlled in the opening direction to supply the injector 2 with pressurized fuel. In the embodiment illustrated in Figure 1, the supply pipe 3 comprises a restriction 18 or a nozzle, placed at the inlet of the supply pipe 3, and constituting a resistive hydraulic element. By hydraulic resistive element is meant an element governed by a law of the form Q = f (AP), where Q is the flow rate that passes through said element and AP is the differential pressure between the upstream and the downstream of the element.

Downstream of the restriction 18 is mounted an additional volume 19 which is connected to the supply line 3 by a specific branch 20 or which is in direct communication with said supply line 3. The additional volume 19 is capable of contain a certain volume of fuel, and therefore constitutes a hydraulic capacitive element. By hydraulic capacitive element is meant an element governed by a law of the form dP / dt = f (Q), where P is the pressure and Q is the flow rate of the hydraulic fluid. In the example illustrated in Figure 1, downstream of the additional volume 19, is mounted in the pipe 3 a mechanical accumulator 21. Such a mechanical accumulator is an element capable, when subjected to hydraulic pressure, to absorb some of the energy. In the example illustrated in Figure 1, a movable piston 22 is subjected to the action of a spring 23. It could, of course, replace such a mechanical accumulator by a pneumatic accumulator comprising a membrane defining a portion of a closed chamber, filled with a compressible gas. The membrane is then likely to deform to absorb a portion of the energy in case of pressure increase. The deformation of the membrane or the displacement of the movable piston 22 generate an increase in volume of the chamber of the accumulator 21 which has the effect of reducing the pressure to which it is subjected. The accumulator 21 is also able to restore this energy when the pressure to which it is subjected decreases. Such a component is comparable to a pure stiffness, and therefore constitutes a hydraulic capacitive element as defined above. Downstream of the hydraulic accumulator 21, is mounted in the example of Figure 1, a mechanically controlled pressure regulator referenced 24. This element comprises a movable piston 25, subjected to the action of a return spring 26 and capable of closing or disengaging an orifice 27 connected to a discharge line 28 capable of reducing a portion of the fuel flow to the reservoir 6. The pressure regulator 24, connected directly to the supply line 3, is therefore capable of discharging a control volume when the pressure rises above a set value defined by the calibration of the spring 26 thus releasing a certain flow of fuel to the reservoir. When the pressure is below the setpoint, any leakage flow is interrupted. The pressure regulator 24 controlled mechanically is equivalent to a pressure limiter. This element plays the role of a hydraulic capacitive element as defined above. Downstream of the pressure regulator 24 is mounted in the supply line 3 a flow regulator 29, controlled mechanically under pressure. This regulator 29 comprises a movable member 30 subjected to the action of a return spring 31 and capable of closing more or less a passage 32 to the injector 2. The flow regulator 29 is thus able to pass a flow to the injector 2 when the pressure upstream of the flow regulator 29 is lower than a set pressure which corresponds to the calibration of the spring 31. When the pressure upstream of the regulating device 29 is greater than the set value, the movable member 30 closes the passage 32 against the force of the spring 31, thus reducing the flow to the injector 2. Unlike what was the case of the pressure regulator 24, which was mounted in parallel on the supply line 3, the flow regulator 29 is connected in series directly in the supply line 3. No fuel return to the tank of the hydraulic system exists for the flow regulator 29.

The restriction 18 constitutes, as has been said previously, a purely hydraulic resistive element. The supply line 3, which allows the transfer of fuel to the injector 2 as well as the transfer of fuel between the various elements of the supply circuit, also constitutes a resistive element due to the regular pressure drop along the the driving. The supply line 3 is also a capacitive element because of its internal hydraulic volume. The other elements disposed downstream of the restriction 18, directly in series along the feed pipe 3 or in derivation relative thereto, such as the additional volume 19, the accumulator 21, the pressure regulator 24 and the flow regulator 29, constitute hydraulic capacitive elements as defined above. To prevent a failure of the injector resulting in too much injected fuel flow may destroy the post-treatment organs that constitute the oxidation catalyst 13 and the particulate filter 14 by an exaggerated increase in temperature, has in the feed duct 3, for example immediately upstream of the injector 2, a member capable of avoiding any excessive flow of fuel. Such a member may be constituted for example by a cutoff solenoid valve 32a, which is an electromechanical device allowing or not allowing the passage of fuel according to an electric control. It is also possible to use, in association with such a cutoff solenoid valve or in place thereof, a flow-limiting device and which is a mechanical system making it possible to pass a pulsating flowrate but not allowing the passage of a continuous flow rate greater than a threshold value defined by the calibration of a return spring of a movable member.

Referring to FIG. 2, which schematically illustrates the general architecture of the system of the present invention referenced 33 as a whole, it can be seen that it uses at least one resistive input element denoted R and referenced 34 in FIG. 2, and at least one capacitive element denoted C and referenced 35 in FIG. 2, placed downstream of the resistive element 34. The two inputs of the system 33 are the upstream pressure Pamont, that is to say the pressure supplied at the output of the feed pump 1, and the flow through the feed system noted Qsyst. The two responses of the system are the supply pressure of the injector denoted by Pal; m and the injected flow rate Q i, i which is the flow of fuel injected by the injector 2 The choice of the characteristic dimensions of the resistive and capacitive elements allows to determine the cutoff frequency for upstream pressure oscillations, that is to say the pressure supplied by the pump 1. The cutoff frequency Cutoff is indeed defined by: F cut 1 where RC is the constant of time of the transfer function connecting the pressure Pamont to the inlet of the fuel supply circuit 33 and the supply pressure Pal; m of the injector 2. This time constant makes it possible to obtain the filtration level of the desired oscillations. The choice of the dimensions of the capacitive elements makes it possible to play on the variation of geometric volume of the supply system, and to maintain at any time a compromise between the variation of geometrical volume and the flow of fuel Q, which is the flow injected by the injector 2. The choice of the dimensions of the various capacitive elements also makes it possible to play on the profile of evolution of the supply pressure of the injector 2, while the dimensions and the characteristics of the resistive elements and in particular the 18 restriction, play on Qmot flow supplying the injection device associated with the engine cylinders. It is thus possible to obtain the best dynamic compromise for the Qsyst flow rate in order to avoid that this dynamic flow rate significantly modifies the fuel pressure supplying the injectors of the combustion engine via line 4.

The present invention thus makes it possible to overcome the drawbacks resulting from the pressure variations at the outlet of the feed pump 1. Thanks to the present invention, the instantaneous supply pressure of the injector 2 oscillates around a value average. Thanks to the filtering performed by the presence of the resistive and capacitive elements, it is indeed possible to extract from the instantaneous pressure signal the mean value that is as stable as possible. The invention also makes it possible to maintain the supply pressure of the injector during the injection, while ensuring that the pressure upstream of the injector does not collapse during the injection, because the demand for fuel flow required by the injector. Finally, thanks to the invention, it avoids any interaction of the feed circuit of the injector 2 on the other members of the combustion engine, interactions that could degrade the operation of the latter.

Claims (10)

1. Fuel injection system in the exhaust circuit of an internal combustion engine, for the purpose of raising the temperature in a catalytic exhaust gas treatment device, comprising a fuel pump (1 ) and an injector (2) connected to the pump by a supply line (3), characterized in that the system comprises, between the pump and the injector, at least one resistive hydraulic element and at least one hydraulic element capacitive, mounted downstream of the resistive element. 2. Injection system according to claim 1 wherein a resistive element is constituted by a restriction (18) placed in the supply line upstream of any other resistive or capacitive element. 3. injection system according to one of the preceding claims wherein a capacitive element is constituted by an additional volume (19) capable of containing a volume of fuel, placed in the supply line. 4. Injection system according to one of the preceding claims wherein a capacitive element is constituted by a pneumatic or mechanical accumulator (21). 5. injection system according to one of the preceding claims wherein a capacitive element is constituted by a pressure regulator (24) controlled mechanically. 6. Injection system according to one of the preceding claims wherein a capacitive element is constituted by a flow regulator (29) controlled mechanically under pressure. 7. Injection system according to one of the preceding claims wherein the different resistive and capacitive elements are connected in series on the supply line. 8. Injection system according to one of the preceding claims further comprising a flow limiter device (32a) mounted in the supply line. 9. A method of injecting fuel into the exhaust circuit of an internal combustion engine for the purpose of raising the temperature in a catalytic exhaust gas treatment device, characterized by the fact that a fuel supply system for an injector and first-order filtration is applied to a control system having, as inputs, the upstream pressure of the fuel system and the injected fuel flow and as outputs, the flow of fuel supplying the fuel system and the supply pressure of the injector. 10. The method of claim 9 wherein there is used at least one resistive hydraulic element and at least one capacitive hydraulic element, mounted downstream of the resistive element and the dimensions of the resistive and capacitive elements are chosen so as to obtain the level of resistance. filtration and reduce local pressure variations during injection.