FR3007451A1 - METHOD FOR FREEZING THE GRIPPING OF A DOSING VALVE AND DEVICE FOR IMPLEMENTING IT - Google Patents

Abstract

Method for releasing seizing of an electromagnetic metering valve (14) from a metering system for metering an aqueous urea solution for an SCR catalyst (16) into the exhaust gas channel (12) a heat engine (10). Heat is supplied to the metering valve (14) by feeding its electromagnetic coil (30). In the case of a dosing valve (14) cooled by water (20), the temperature of the cooling water (temp_W) is first determined, a temperature threshold of the cooling water is predefined. cooling (temp_W_Lim) and the supply of the coil (30) is released to release seizing only if the temperature of the cooling water (temp_W) exceeds the temperature threshold of the cooling water (temp_W_Lim).

Description

FIELD OF THE INVENTION The present invention relates to a method for releasing an electromagnetic metering valve from a metering system for metering an aqueous urea solution for an SCR catalyst into the channel. an exhaust gas of a heat engine, according to which heat is supplied to the metering valve by feeding an electromagnetic coil of the metering valve. The present invention also relates to a device for implementing such a method.

The invention also relates to an apparatus control program and an appliance control program product. State of the art DE 10 2011 004 150 A1 discloses a method for releasing the seizing of a metering valve of a metering system for metering an aqueous urea solution for a SCR catalyst of a heat engine consisting of to release the seizing of the metering valve by a heat input. The heat input, that is to say the increase of the temperature is done by feeding the electromagnetic coil of the electromagnetically controlled metering valve. DE 10 2007 017 459 A1 discloses a method for thawing a dosing valve if appropriate frozen; this method makes it possible to set the dosage rate of the aqueous urea solution in the exhaust gas channel of a heat engine. The frozen state of the electromagnetically controlled metering valve is detected by taking advantage of the rise in current when the electromagnetic coil of the metering valve is energized. The rising edge of the intensity of the current is monitored to detect the existence of a characteristic change in intensity and which is generated by the movement of the needle of the metering valve. Crystallization of urea can be achieved in an aqueous solution of urea. Urea crystallization occurs if, for example, the temperature in the dosing system is higher than 100 ° C. and after the SCR system has been turned off for some time. For example, already after a cooling time of 0.5 hours, depending on the position of the dosing system can be formed urea crystals. These urea crystals may especially clog or seize the metering valve. The movable valve needle of the metering valve can seize in the open position or in the closed position or in an intermediate position which makes it impossible to ensure the correct dosage. In this case, we will have a wrong dosage in the context of the on-board diagnosis, resulting in a fault recording.

OBJECT OF THE INVENTION The object of the present invention is to develop a method for releasing seizing of a metering valve and a device for carrying out this method. DESCRIPTION AND ADVANTAGES OF THE INVENTION To this end, the subject of the invention is a process for the release of an electromagnetically controlled metering valve from a system for the determination of an aqueous solution of urea for SCR catalyst in the exhaust gas channel of a heat engine according to the invention, characterized in that in the case of a cooling water-cooled dosing valve, the cooling water temperature (temp W), a cooling water temperature threshold is set (temp W Lim) and the supply of the electromagnetic coil of the metering valve is released to release the seizure, only if the cooling water temperature (temp W) exceeds the temperature threshold of the cooling water (temp W Lim). In other words, the process according to the invention is characterized in that in the case of a metering valve cooled by the cooling water, in particular that of the heat engine, at least one temperature measurement is provided. cooling water, for example by modeled measurements or by substitution values and the threshold of the cooling water temperature is predefined and the electric supply of the electromagnetic coil of the metering valve is not released to release seizing only if the temperature of the cooling water exceeds a temperature threshold of the cooling water. The method according to the invention makes it possible to eliminate any seizure of an electromagnetically controlled metering valve by using as little energy as possible. In particular, the thermal bias of the power stage of the electromagnetic coil control apparatus of the electromagnetically controlled metering valve is reduced to a minimum. The means according to the invention used in the case of an electromagnetically controlled metering valve cooled by the cooling water, if appropriate that of the heat engine, connects the temperature of the cooling water of the thermal management not only to cooling but also to release seizing of the metering valve. On a pure principle, the method according to the invention can be applied regardless of whether the metering valve is effectively seized or that it operates correctly. To further minimize energy consumption, a check is advantageously made to determine if the dosing valve is seized, which is indicated by a small signal. The supply of the electromagnetic coil of the electromagnetic dosing valve will only be released if there is a seizure signal. According to one development, the chronogram of the intensity of the electric current controlling the electromagnetic coil is recorded and used to detect seizing of the metering valve. This means makes it possible to simply recognize the jamming of the dosing valve without requiring additional means because the current in the electromagnetic coil of the electromagnetically controlled metering valve can be measured simply when the solenoid is being controlled, for example by detecting the voltage drop on the semiconductor path in the control device which renders any separate current sensor useless. According to another development, a measurement of the temperature of the metering valve is determined and a threshold value of the temperature of the metering valve is predefined and the electromagnetic coil of the metering valve is fed to release the temperature. seizing only if the temperature of the metering valve is below the temperature threshold of the metering valve. Under these conditions, all thermal overload of the metering valve is avoided. In another development, controlling the temperature of the dosing valve to a set value also prevents thermal overload. According to a development, the electrical resistance of the electromagnetic coil is determined and used for the dosing temperature, which makes it possible to avoid any additional temperature sensor. According to a particularly advantageous development, when stopping the heat engine, at the end of the rolling cycle, the aqueous urea solution is re-aspirated in the reagent reservoir. This means reduces the thermal capacity of the metering valve before the next start-up, which minimizes the energy consumption required for loosening or releasing seizure. According to another particularly advantageous development of the process of the invention, the metering system is emptied so that the metering valve is no longer stressed by the aqueous urea solution.

In this case, first check whether there is seizure of the metering valve. If so, the electromagnetic coil of the metering valve is energized to release seizure in the case of an otherwise empty metering system. Filling the dosing system is only done after the successful release of the metering valve seizure. If it is found that seizure could not be eliminated, there is, if necessary, a fault signal. The device according to the invention for the implementation of the method concerns first of all a control apparatus specially designed and which comprises means for implementing the method.

The control apparatus preferably comprises at least one electrical memory which contains the recording of the process steps in the form of a control unit program. The control device program according to the invention performs all the steps of the method of the invention when the program is applied by a control apparatus.

The control device program product according to the invention with a program code recorded on a machine-readable medium makes it possible to execute the method of the invention when the program is run on a control device.

The present invention will be described in more detail below with the aid of a method of releasing the seizing of an electromagnetic metering valve of a system for assaying an aqueous solution of urea for an SCR catalyst. shown in the accompanying drawing in which the single figure shows the technical application environment of the method of the invention. DETAILED DESCRIPTION OF THE EMBODIMENT OF THE INVENTION The figure shows a heat engine 10 whose exhaust gas channel 12 is equipped with a metering valve 14 and downstream thereof, an SCR catalyst 16 is provided. cooling water circuit 18 in which the cooling water 20 has a cooling water temperature (temp W) measured by a cooling water temperature sensor 22 which supplies to a control apparatus 24 the measured value of the cooling water temperature (temp W Mess). The cooling water circuit 18 is for example the cooling circuit of the heat engine 10 or a separate cooling circuit. The metering valve 14 integrated in the cooling water circuit 18 is thus cooled by the water 20. This metering valve comprises a valve needle 26 actuated by an electromagnet 28. The electromagnetic coil 30 of the The electromagnet 28 is electrically connected to the control unit 24. The metering valve 14 can be installed on the exhaust gas channel 12 as shown in the figure. Alternatively, the metering valve 14 can also be installed in a separate metering module remote from the exhaust gas channel 12. The metering valve 14 doses an aqueous solution of urea into the exhaust gas channel 12 of the heat engine 10; this aqueous urea solution has, as precursor, the ammonia reactive agent required for the SCR 16 catalyst to reduce the crude emissions of nitrogen oxides NO ,, from the heat engine 10. The aqueous urea solution is stored in a storage tank. reactive agent 32 to be brought to the operating pressure or working pressure, by a pump 34. The pump 34 is controlled by a pump control 36 which receives a PST and an SR providing a preferably width-modulated SP During the dosing operation, the crystallization of the urea and of the aqueous urea solution in the metering valve 14 can not be ruled out. The crystals cause the needle 26 to become blocked. the metering valve 14 and the seizure or jamming can occur in the open position, in the closed position or in an intermediate position of the valve needle 26 of the metering valve 14.

To supply the electromagnetic coil 30 of the electromagnetic dosing valve 14, there is provided a metering valve control 38 which receives a dosing signal s D and a release signal s L and preferably gives an operating voltage U for the electromagnetic coil 30. For transient phases such as switching on and off the function voltage U, there is a current curve which depends in particular on the inductance of the magnetic circuit in the metering valve 14. stationary states, the maximum intensity depends on the electrical resistance itself dependent on the temperature of the electromagnetic coil 30. It will no longer be possible to distinguish the temperature of the electromagnetic coil 30 from the temperature of the metering valve ( DV temp). The temperature is generally referred to as the dosing valve temperature (DV temp). In order to determine at least one measurement of the temperature of the dosing valve (DV temp), there is provided a temperature determining means 40 which from the operating voltage across the electromagnetic coil 30 and the intensity I of the current passing through the electromagnetic coil 30, provides a measurement of the temperature of the metering valve (DV temp). The intensity I of the current is measured by an intensity sensor I S. In practice, it is possible to eliminate such a current sensor or instead to determine the current I corresponding to the voltage drop across a semiconductor stage. of the metering valve control 38 as a measure of the intensity I.

Seizure determination means 42 determines the seizure of the metering valve 14 from the upstream or downstream sidewall flowing through the electromagnetic coil 30 which is detected at the branch when applying the operating voltage U or when the voltage of the electromagnetic coil 30 is cut off. Due to the inductance of the electromagnetic coil 30 and the magnetic components of the metering valve 14, crossed by the magnetic lines, the sides of the intensity have a characteristic shape making it possible in particular to deduce the movement of the valve needle 26. To determine the movement or the position of the valve needle 26 from the current I passing through the electromagnetic coil 30, reference can be made to known techniques. If the seizure determination means 42 does not recognize the characteristic variation of the intensity related to the movement of the valve needle 26, this means 42 provides a seizing signal S K1 which signals seizing of the metering valve 14. A release signal setting means 44 provides, as a function of the seizing signal S K1, a release signal SL which can urge the control 38 of the metering valve to supply the electromagnetic coil 30 to supply heat to the gate valve. assay 14 and increase its temperature to melt the urea crystals. The metering valve control 38 may, for example, supply the usual operating voltage U of the electromagnetic coil 30 then traversed by the maximum current I. But to protect the electromagnetic coil 30 against overloads during the supply to release the seizure, the operating voltage can be reduced to a level lower than the usual operating voltage U during the dosing mode so that even the maximum possible current is reduced to a value corresponding, for example, to the holding current of the metering valve. 14 which maintains just the current position of the valve needle 26. For this, it must be taken into account that the power supply to release seizure lasts much longer, for example several seconds, up to a few minutes by comparison pulse width modulated mode used for the assay.

For a power supply as energy efficient as possible, to release the seizing of the metering valve 14, it is provided that for a metering valve 14 cooled by cooling water 20, the signal fixing means Release 44 provides this release signal SL only if the measured value of the temperature of the cooling water (temp. WMt) supplied by the temperature sensor 22 exceeds a water temperature threshold. cooling (temp W Lim). The temperature sensor 22 may also be removed and in this case a modeled value / evaluated value or a substitution value of the cooling water temperature (temp. W) is used. The comparison is made by a cooling water temperature comparator 46 which compares, for example, the temperature of the cooling water (temp W) for example the measured value of the temperature of the cooling water (temp. W Mess) or the temperature threshold of the dosing valve (temp DV Lim). The cooling water temperature comparator 46 provides a first release signal FG1 for the release signal setting means 44 if the measurement value of the cooling water temperature (temp WMt) exceeds the temperature threshold of the cooling water (temp W Lim). The release signal setting means 44 provides the release signal S L only if there is the first clear signal FG1. The temperature threshold of the cooling water (temp W Lim) can be, for example, in a range between 50 ° C. and 80 ° C. The solenoid valve 14 is protected against any over-temperature if the supply of the electromagnetic valve 14 to release seizing is only done if the measurement of the temperature of the metering valve (DV temp) is below a temperature threshold of the dosing valve (temp DV Lim). In order to compare, there is provided a temperature controller of the metering valve 48 which provides the measurement of the metering valve temperature (DV temp) given by the metering valve temperature determination means 48 to compare this value at the temperature threshold of the dosing valve (temp. DV Lim) and generate a second release signal FG2 only if the measurement of the temperature of the dosing valve (temp. DV) is below the temperature threshold of the dosing valve (temp DV Lim). Preferably there is a regulation at a threshold of the temperature of the electromagnetic coil 30 of the metering valve 14. For this, at least one measurement of the temperature of the electromagnetic coil 30 is obtained for example by using the internal resistance of the electromagnetic coil 30. This also ensures protection against thermal overload of the metering valve 14. In an advantageous development, the electromagnetic valve 14 is energized to release the seizure only if there is at least one aqueous solution of urea in the metering valve 14. With the proviso that there is still an aqueous solution of urea in the metering valve 14, this solution is first sucked back with the pump 34 into the the reagent reservoir 32. A means for attaching the re-aspiration 50 provides for this purpose a re-aspiration signal SR and a third release signal FG3. The means for fixing the suction 50 determines these signals for example according to the operating state of the heat engine 10. A re-suction is provided if the heat engine 10 has been stopped but if the control unit 24 is operating. still in post-operation providing the power supply of the control device 24 as long as the means provided for the post-operation such as for example the re-aspiration have not been treated. The re-suction signal SR is supplied to the pump control 36 which then fixes the pump control signal SP to reverse the direction of rotation of the pump 34 and thereby aspirate the aqueous solution of urea from the metering valve 14 in order to pump this solution to the reagent reservoir 32. In a variant, a special re-suction pump is also provided.

According to one variant, the dosing system is already emptied of the aqueous solution of urea. In this case, it must first be checked whether the metering valve 14 is seized. If so, it feeds the electromagnetic coil 30 of the metering valve 14 to release seizure in the otherwise empty metering system. Filling of the metering system will be done once the seizing of the metering valve 14 released. If, however, it is found that seizure can not be eliminated, a fault signal may be issued.10 NOMENCLATURE OF THE MAIN ELEMENTS 10 Engine 12 Exhaust gas channel 14 Dosing valve 16 Catalyst SCR 18 Cooling water circuit 20 Cooling water 22 Cooling water temperature sensor 24 Control unit 26 Valve needle 28 Solenoid 20 Electromagnet coil 24 Control unit 30 Solenoid coil 32 Reservoir of reagent 34 Pump 36 Pump control 38 Dosing valve control 40 Temperature determination medium 42 Seizure determination means 44 Release signal setting method 46 Cooling water temperature comparator 48 Temperature comparator of the dosing valve 50 Re-suction fixation means

Claims (8)

CLAIMS 1 °) Method for releasing the seizure of an electromagnetic metering valve (14) of a metering system for dosing an aqueous solution of urea for an SCR catalyst (16) in the exhaust gas channel (12) ) of a heat engine (10), a method according to which heat is supplied to the metering valve (14) by supplying the electromagnetic coil (30) of the metering valve (14), characterized in that in the In the case of a dosing valve (14) cooled by cooling water (20), the temperature of the cooling water (temp. W) is first determined, - a temperature threshold is predefined. cooling water (temp W Lim), and - the supply of the electromagnetic coil (30) of the metering valve (14) is released to release seizing only if the temperature of the cooling water ( temp W) exceeds the temperature threshold of the cooling water (temp W Lim). 2) Method according to claim 1, characterized by a control to determine whether there is seizure of the metering valve (14) and report seizure by a seizure signal S Kl. Method according to Claim 2, characterized in that the intensity timing diagram is detected during the electrical control of the electromagnetic coil (30) and operated for detecting seizing of the metering valve (14). . 4) Method according to claim 1, characterized in that - it is determined a measurement of the temperature of the metering valve (DV temp), - the temperature threshold of the metering valve (temp DV Lim) is predefined, and - the electromagnetic coil (30) of the metering valve (14) is supplied to release the seizure only if the temperature of the metering valve (DV temp) is below the temperature threshold of the metering valve (temp. ). Process according to Claim 1, characterized in that a measurement of the temperature of the electromagnetic coil (30) of the metering valve (14) is determined and the temperature of the electromagnetic coil (30) is regulated. on a set value. Process according to Claim 4, characterized in that the electrical resistance of the electromagnetic coil (30) is determined and used as a measure of the temperature of the dosing valve (DV temp). Method according to claim 1, characterized in that before supplying the electromagnetic coil (30) of the electromagnetic valve (14) to release seizure, the aqueous urea solution is re-aspirated to the reservoir of the electromagnetic valve (14). reactive agent (32). Process according to Claim 2, characterized in that, starting from an empty dosing system whose metering valve (14) is no longer in contact with an aqueous solution of urea, it is firstly checked whether the metering valve (14) is scratched and in the case where a grip has been detected, the electromagnetic coil (30) of the metering valve (14) is fed to release the seizure in the case of a control system. empty dosage and it is only after releasing the seizing that the dosing system is filled. 359 °) Device for releasing the seizure of an electromagnetic dosage vane, characterized in that it comprises a device for control (24) for carrying out the method according to one of claims 1 to 8. 10 °) control program which performs all the steps of the method according to any one of claims 1 to 8 when the program is applied by a control apparatus (24). 11 °) Control program product with a program code recorded on a machine readable medium for carrying out the method according to one of claims 1 to 8 when the program is applied by a control device. 15