FR2971545A1 - DEVICE AND METHOD FOR DETERMINING A LIQUID IN THE EXHAUST GAS PIPING OF AN INTERNAL COMBUSTION ENGINE - Google Patents

Abstract

Device for dosing a liquid (12), in particular a liquid (12) promoting the aftertreatment of the exhaust gases in an exhaust gas pipe (8) of an internal combustion engine (5) in which * the liquid (12) is dosed by a nozzle device (30) in the exhaust gas line (8) of the internal combustion engine (5), * the nozzle device comprises a valve (31) and the dosing of the liquid (12) for the nozzle device (30) is controlled or regulated by a metering pump (20). The valve (31) opens and closes periodically by a control of the pump. dosing (20) in snore mode.

Description

FIELD OF THE INVENTION The present invention relates to a device for dosing a liquid, in particular a liquid promoting the aftertreatment of the exhaust gases in an exhaust gas duct of an engine. internal combustion engine, in which * the liquid is dosed by a nozzle device in the exhaust pipe of the internal combustion engine, * the nozzle device comprises a valve, and * the liquid dosage for the Nozzle is controlled or regulated by a metering pump. The invention also relates to a method for dosing a liquid in the exhaust gas duct of an internal combustion engine. STATE OF THE ART As the regulations on exhaust emissions become stricter and stricter, it is practically impossible at present to reach the limit values for pollutant emissions in the exhaust gases of a vehicle. internal combustion engine with only means specific to the engine. This is why, particularly in the case of internal combustion engines of vehicles, exhaust gas aftertreatment installations mounted in the exhaust duct of internal combustion engines are already used, for example catalysts and filters. In particular, uncontrolled combustion engines increasingly use exhaust gas aftertreatment installations in which an exhaust gas aftertreatment liquid is metered into the gas line. engine exhaust. As an example, mention may be made of the fuel metering for re-generating a particulate filter or the determination of an aqueous solution of urea for catalysts for the selective reduction of nitrogen oxides. For the thermal regeneration of particulate filters, the temperature of the exhaust gases emitted by the internal combustion engines is raised so that the carbon black contained in the particulate filter can burn in a controlled manner. If it is not possible to record the temperature of the exhaust gas by means applied to the

2, fuel is injected with an additional injector into the exhaust gas; this fuel reacts in the oxidation catalyst, catalytically releasing the heat necessary for the temperature rise.

DE 10 2007 016 004 discloses a metering device in which a metering pump introduces an aftertreatment agent for the exhaust gases into the exhaust gas plant of an internal combustion engine. DE 10 2006 057 425 discloses a device for metered injecting a liquid in the exhaust gas duct of an internal combustion engine in which an injection valve operating in the snore mode doses the liquid in the exhaust gas duct of the internal combustion engine.

DESCRIPTION AND ADVANTAGES OF THE INVENTION The present invention relates to a device of the type defined above characterized in that the valve opens and closes periodically by a control of the dosing pump in humming mode.

The invention also relates to a method of the type described above characterized in that the dosing of the liquid is controlled or regulated by a metering pump. The device according to the invention as defined above offers the advantage vis-à-vis the state of the art that the dosage of the liquid is controlled or regulated by a dosing pump so that the pressure and dosage fluid is generated at a location where the injection valve delivers the liquid in the exhaust gas in a humming mode, which allows dosing of small amounts of liquid into the exhaust line and allows very fine spray. The dosage is not disturbed or is only very slightly affected by the pressure variations, for example those generated by a feed installation mounted downstream of the metering pump, in particular in the low-pressure circuit of the injection system. fuel injection. This results in a simplification of the system concept with simplified hydraulic behavior, an extended operating range in metered quantity and higher metering accuracy. The cost is for example reduced because of the elimination of a dosing unit and the application costs for the internal combustion engine are lower due to the simple hydraulic behavior; For example, in this case, it is not necessary to take into account the pressure variations with two or more valves limiting the flow with a complex hydraulic behavior in this application. In another advantageous embodiment, the nozzle device comprises a pressure-controlled valve which, when an opening pressure is reached or exceeded, releases the liquid dosage into the exhaust gas line of the internal combustion engine. dull. A pressure-controlled valve can be made without electrical control, which makes it particularly simple and economical. Advantageously, the opening pressure of the sub-valve is greater than the pressure prevailing in a tank mounted upstream of the metering pump or higher than a pressure in a low pressure circuit located upstream of the metering pump, for example in the low pressure circuit of a fuel injection system. The valve will open under these conditions only if the pressure in the supply tank or the low-pressure circuit is raised by the metering pump. Under these conditions, undesired malfunctions and dosages are avoided by the valve. According to another advantageous development of the device, in case of disturbance of the operation, especially if the power supply is permanent or if there is an electrical short circuit, the metering pump does not deliver any liquid. This makes it possible to avoid that, in the event of a fault or a disturbance in operation, the liquid passes into the exhaust pipe and from there pollutes the environment. If, in the event of a disturbance in operation, the metering pump no longer provides liquid, the injection valve remains closed, which avoids the unwanted dosing of liquid in the exhaust gas line. This also makes it possible to simply have a safety function of the device so that in the event of failure of the metering pump, there is no liquid dosing in the exhaust gas line of the device. internal combustion engine. To increase the dosing accuracy, it is advantageous if the quantity of liquid delivered by the pump is independent of the back pressure in the exhaust gas line or the quantity of liquid dosed depends exclusively on the control of the pump. pump. Thanks to the use of an adjustable piston pump as a dosing pump, the measurement and the dosing can advantageously be carried out in a single unit so that the quantity of dosed liquid then depends exclusively on the duration of the dosing. control of the dosing pump. Advantageously, a pulsation damper is installed between the reservoir and the nozzle device, in particular between the dosing pump and the valve. The damping of the pressure oscillations between the tank or a low pressure circuit of the fuel injection system and the metering pump makes it possible to further increase the accuracy of the metering pump dosing. The damping of the pressure oscillations between the metering pump 20 and the valve is particularly advantageous because the mode of snoring of the valve can be disturbed by pressure variations. It is particularly advantageous for the dosing pump to pressurize the liquid at a frequency of 1 to 10 Hz and / or for the dosing valve to open and close periodically at a frequency in the range of 1 to 10 Hz. 1 000 Hz. A control frequency of the dosing pump within this frequency range ensures that the dosing pump transfers the characteristic quantities required for the aftertreatment of the constant pressure liquid exhaust gas to the injection valve. . In the humming mode of the injection valve at a frequency of about 1000 Hz, the amount of liquid supplied by the metering pump is metered in the form of small and small portions into the gas line. exhaust and can thus be evenly distributed in the vein of the exhaust gas without causing deposition on the injection valve or in the exhaust pipe.

Drawings The present invention will be described in more detail below with the aid of exemplary embodiments of a device for metering a liquid, in particular a liquid to assist the aftertreatment of the exhaust gases represented. in the accompanying drawings in which: - Figure 1 is a diagram of a device according to the invention for dosing liquid in the exhaust gas duct of an internal combustion engine, - Figure 2 shows an alternative embodiment of the device according to the invention for dosing a liquid in the exhaust gas duct of an internal combustion engine, - Figure 3 shows a diagram showing the quantity of liquid supplied by the dosing pump according to of the exhaust gas antagonist pressure; FIG. 4 shows the variations of the liquid pressure at the outlet of the metering pump as a function of the control of the metering pump; FIG. the pr an injector depending on the control of the metering pump when the injector opens and closes periodically in humming mode. DESCRIPTION OF EMBODIMENTS In FIGS. 1 and 2, the same references will be used to designate the same elements or elements of the same function.

Figure 1 shows a first embodiment of the device according to the invention. A feed tank 10 containing a liquid 12 is connected by a connecting line 41 to a filter 13. The filter 13 is connected by a second connecting line 45 to a do-wise pump 20; the connecting pipe 45 is equipped with a pressure sensor 24. The outlet 21 of the metering pump 20 is connected by another conduit 46 to a nozzle device 30, for example an injection valve 31; the connecting line 46 comprises a pulsation damping 22 and a pressure sensor 26. The injection valve 31 is mounted on the exhaust gas duct 8 of an internal combustion engine 5.

If, in order to promote the aftertreatment of the exhaust gases, it is desired to introduce, by metering, the liquid 12 into the exhaust gas duct 8 of the internal combustion engine 5, the metering pump 20 draws the liquid 12 from the reservoir 10 through the link line 41; the liquid 12 is for example an aqueous solution of urea or fuel; this liquid is cleaned in the filter 13 and arrives at the metering pump 20 through the connecting line 45. The metering pump 20 puts the liquid 12 under a pressure (p); the curve representing the variations of the pressure generated as a function of time (t) by the metering pump 20 at its outlet 21 has a "substantially rectangular" shape as shown in FIG. 4; this means that the control of the metering pump 20 produces a rapid rise in pressure to a maximum pressure level (pp) of the metering pump 20; this level of maximum pressure (pp) is substantially maintained until the end of the control of the metering pump 20. Then the pressure (p) drops again sharply. In addition to establishing the pressure, the dosing pump 20 also has the function of measuring the quantity of liquid 12 to be dosed in the exhaust gas pipe 8. This measurement is done over time The maximum pressure level (pp) generated by the metering pump 20 exerts a hydraulic force on the injection valve 31; this force is greater than the holding force applied to the closing member 32 of the injection valve 31. Exceeding the holding force of the closure member 32 of the injection valve 31, the opening pressure (ps) in the injection valve 31 which opens and ensures the injection of the liquid 12 and the preparation of the spraying of the liquid 12 during the metered injection into the exhaust pipe. The opening of the injection valve 31 makes a short, slightly lower pressure (p) at the injection valve 31, up to the closing pressure (ps) at which the closure member 32 again closes the injection valve 31. The closing of the closure member 32 causes the pressure (p) to rise again, generating a periodic opening and closing characteristic of the injection valve 31, a movement which is called snore mode. The curve of the variations of the pressure as a function of time (t) for such a mode of humming according to the control of the do-wise pump 20 is shown in FIG. 5. The rapid opening and periodic closing of the injector 31 each time the injection dosed finely small amounts of liquid 12 in the exhaust pipe 8 of the internal combustion engine 5. In addition, typically for the dosing pump 20, the quantity (Q ') The flow rate of liquid 12 is as shown in FIG. 3 independent of the back pressure (4p) in the exhaust gas duct 8. The quantitative control of the metering pump 20 can be done by modulating the width of the pump. pulse and frequency modulation. In the absence of control of the metering pump 20, no pressure is established so that the injection valve 31 is closed when the metering pump 20 is not controlled. A pulsation damper 22 equips the connecting line 46 connecting the metering pump 20 to the injection valve 31; this pulsation damper dampens the pressure oscillations generated by the pressure supplied by the metering pump 20 and / or by the dosing of the liquid 12 by the valve 31. The injection valve 31 is made as a plateau valve, spring loaded opening outwards. Insofar as the closure member 32 of the injection valve 31 is positioned by a valve spring and is centered by the liquid passage 12 through the injection valve 31, guiding can be avoided. Mechanical closure member 32. The various parts of the injection valve 31 are metal. Since a reliable humming mode of the injection valve 31 is only possible within a relatively narrow pressure range, the pulsation damper 22 avoids exiting from this narrow pressure range.

The pulsation damper 22 is a diaphragm, pneumatic or hydraulic volume damper. The pulsation damper is preferably installed in the immediate vicinity of the outlet 21 of the metering pump 20. In a variant, the pulsation damper 22 can also be integrated in the metering pump 20.

In addition, the pressure (p) in line 45 is measured by a pressure sensor 24 installed in line 45 and in line 46 by a pressure sensor 26 installed in line 46. Pressure sensors 24, 26 The pressure sensor 26 can further detect any disturbance or failure of the injection valve 31. The injection valve 31 can be cooled. by air or water. Alternatively, in the case of a simplified embodiment of the device, the pulsation damper 22 and at least one of the pressure sensors 24, 26 can be omitted. In particular, if one removes 22, it is advantageous for the length of the pipe 46 between the metering pump 20 and the injection valve 31 to be as short as possible so that the pressure waves and the pressure variations they result in being as small as possible. As a variant of the embodiment shown in FIG. 1, the filter 13 between the metering pump 20 and the feed tank 10 can also be omitted, the liquid 12 then being drawn directly by the metering pump 20. The metering pump 20 is preferably an adjustable piston pump, for example an electromagnetically controlled oscillating piston pump. However, alternatively, it is also possible to use pumps operating according to other delivery principles, in particular pumps which can have the pressure curve of FIG. 4. Alternatively, the injector 31 can be made in the form a tray valve opening inwards or in other embodiments. The various components of the injection valve 31 may also be made of non-metallic materials, particularly in suitable ceramics, polymers or composite materials.

In particularly simple embodiments of the device, an uncooled injection valve 31 may also be used. Figure 2 shows an alternative embodiment of the device of the invention. The low pressure circuit 15 of the injection system comprises a reservoir 10 containing a liquid 12 and an upstream pre-feed pump 14. The reservoir is connected by a filter connection line 41 to the filter 13. Another connection line 42 connects the filter 13 to the upstream pump 14 of the low pressure circuit 15 of the fuel injection system. The upstream pump 14 is connected by a line 43 to a bypass point 52. A connecting line 45 connects the point of departure 52 to the metering pump 20; the connecting line 45 is equipped with a pressure sensor 24. A line 44 connects the bypass point 52 to a high pressure zone 18 of the fuel injection system; the high-pressure zone 18 comprises, in known manner, a high pressure pump, a pressure accumulator and at least one fuel injector. The high pressure zone 18 is connected by a return line 49 to the reservoir 10. Another connecting line 46 connects the outlet 21 of the metering pump 20 to the injection valve 31; a pulsation damper 22 and a pressure sensor 26 equip the connecting pipe 46. The injection valve 31 is mounted on the exhaust gas line 8 of the internal combustion engine 5. The liquid 12, in particular the fuel, is sucked by the upstream pump 14 into the supply tank 10 to pass through the connecting pipe 41 in the filter 13 which retains the particles and impurities of the liquid 12. From there, the liquid 12 passes through the pipe of Link 42 in the upstream pump 14 which compresses the liquid and delivers it through line 43 to the diversion point 52. From the diversion point 52, a first partial vein of liquid passes through the connecting connection 44 in the high pressure zone 18 of the fuel injection system while a second partial vein passes through the connecting pipe 45 to feed the metering pump 20. The connecting pipe 45 is equipped with a pressure sensor 24 who me-su re the pressure of the liquid 12 in the connecting pipe 45. The generation of the pressure by the metering pump 20 is similar to the first embodiment according to FIG.

As a variant, in the low pressure circuit 15, the upstream pump 14 can also be located between the supply tank 10 and the filter 13. It is also possible to equip the upstream pump 14 with a filter 13, in particular the suction side. As another alternative, the upstream pump 14 may also have two outlets, one output of the upstream pump 14 passing through a connecting line 45 to be connected to the metering pump 20 and the other outlet of the upstream pump 14. being connected by the connecting line 44 to the high pressure zone 18 of the fuel injection system, in particular to a high pressure pump. Alternatively, the connecting line 45 may also be connected to the low pressure outlet of a high pressure pump forming part of the high pressure zone 18; in this case, a complementary pulsation damper can be connected to the connecting pipe 45 to damp the pressure oscillations generated by the high pressure pump. io ii NOMENCLATURE Internal combustion engine 8 Exhaust gas line 5 10 Tank 12 Liquid 13 Filter 14 Upstream pump 15 Low pressure circuit io 18 High pressure range 20 Dosing pump 21 Dosing pump outlet 22 Pressure damper 24 Sensor Pressure sensor 15 26 Pressure sensor 30 Nozzle device 31 Injection valve 32 Closing device 41 Connection line 20 42 Pulsation damper 44 Connecting line 45 Connecting line 46 Connecting line 52 By-pass 25 P Pressure in the line pipe 45 Po Opening pressure ps Closing pressure T Time 30

Claims (1)

CLAIMS1 »Device for dosing a liquid (12), especially a liquid (12) promoting the aftertreatment of the exhaust gases in an exhaust gas pipe (8) of an internal combustion engine ( 5), wherein * the liquid (12) is dosed by a nozzle device (30) into the exhaust gas duct (8) of the internal combustion engine (5), * the nozzle device comprises a valve (31), and - the dosing of the liquid (12) for the nozzle device (30) is controlled or regulated by a dosing pump (20), characterized in that the valve (31) opens and periodically closes by a control of the dosing pump (20) in humming mode. 2 »Device according to claim 1, characterized in that the nozzle device (30) comprises a pressure-controlled valve (31) which, when an opening pressure (ps) is reached or exceeded, releases the dosage of the liquid (12) in the exhaust gas duct (8) of the internal combustion engine (5). 3 »Device according to claim 2, characterized in that the opening pressure (ps) of the valve (31) is greater than the pressure in a reservoir (10) mounted upstream of the do-wise pump (20). ) or higher than a pressure in a low pressure circuit (15) upstream of the metering pump (20), for example in the low pressure circuit of a fuel injection system. 4 »Device according to claim 1, characterized in that in case of malfunction, especially in case of permanent power supply or short-circuit, the metering pump (20) delivers no liquid (12). The device according to claim 1, characterized in that the quantity of liquid (12) transferred by the metering pump (20) is independent of the back pressure in the exhaust gas duct (8) or the amount of liquid (12) dosed depends exclusively on the control of the dosing pump (20). 6 »Device according to claim 1, characterized by a control of the flow rate of the metering pump (20) by pulse width modulation or frequency modulation. 7 »Device according to claim 1, characterized by a pulsation damper (22) installed between the metering pump (20) and the nozzle device (30). 8 »Device according to claim 1, characterized by pressure sensors (24), including pressure sensors (24) for controlling or regulating the metering pump (20) which serve to regulate or diagnose the metering pump. 9 »Method for dosing a liquid (12), in particular a liquid (12) promoting the aftertreatment of the exhaust gases in an exhaust gas pipe (8) of an internal combustion engine ( 5) and which dose liquid (12) in the exhaust gas duct (8) of the internal combustion engine (5) with a nozzle device (30), characterized in that the dosage liquid (12) is controlled or regulated by a do-wise pump (20).