FR2861802A1 - Electronic device for controlling operation of electrostatic filter, has unit for regulating current intensity based on flow rate and temperature of exhaust gas, and generator maintaining electric discharges without change in its operation - Google Patents

Abstract

The device has a monitoring circuit (20) for powering down a high voltage generator, in case of detection of fault of electrostatic filter operation. A voltage and current measuring circuit detects decrease in voltage due to sooting of a filtering cell (7). A regulating unit regulates current intensity based on flow rate and temperature of exhaust gas. The generator maintains electric discharges without change in its operation. The generator generates high voltage between 1 to 20 kilo Volts and current intensity between 1 to 50 milliamperes.

Description

The present invention relates to an electronic device for controlling

  the operation of an electrostatic filter disposed in the exhaust line of a motor vehicle.

  Such an electrostatic filter is described in the French patent application 02 06304. FIG. 1 of the accompanying drawings shows schematically the electrostatic filter described in the aforementioned patent application.

  This filter comprises a cylindrical chamber 1 having at one of its ends an inlet 2 of the exhaust gas and at the other end an outlet 3 of these exhaust gases. A metal filament 4 held by centering and isolating blocks 5, 6 extends axially between the two ends 2, 3 of the enclosure 1. The block 6 is partially made of ceramic to support the filament 4 and isolate it another part of the block which is metallic (necessary for heating by Joule effect of the filter 7). The filament 4 is surrounded by a filter cell 7 constituted by a network of wires or metal fibers defining a multitude of radial passage orifices for the exhaust gases. In addition, the filament 4 is connected to a high voltage generator 8 capable of creating between the filament 4 and the cell 7 which is connected to the ground 9, an electrostatic field.

  The exhaust gases that pass radially through the cell 7 are ionized beforehand in the vicinity of the filament 4. This ionization generates the presence of electrons and positive and negative ions which, by attaching to the soot particles of the flow will promote their capture on the fibers of cell 7.

  The state of the art provides no solution to the following problems: detecting fouling of the filter cell caused by the deposit of soot on the insulation elements of this cell, - unclog the filter cell, de-energize the high-voltage generator in the event of detection of a malfunction of the filter, - regulating the power supply of the filter in order to ensure efficient filtering with less energy, whatever the flow of the exhaust gases.

  The object of the present invention is to provide solutions to the problems mentioned above.

  The invention thus aims at an electronic device for controlling the operation of an electrostatic filter arranged in the exhaust line of a motor vehicle, this filter comprising an enclosure having at one of its ends an exhaust gas inlet. and at the other end an outlet of these exhaust gases, a metal filament extending axially between the two ends of the filter, this filament being surrounded by a filter cell constituted by a network of wires or metal fibers defining a multitude of radial passage openings for the exhaust gas, the filament being connected to a high voltage generator capable of generating a corona discharge for the ionization of the gases, the electric charging of the particles and their attachment to the fibers of the cell.

  According to the invention, this device is characterized in that said high voltage generator is adapted to generate a voltage of between 1 kV and 20 kV and a current of intensity of between 1 mA and 50 mA and that the device comprises a circuit for measuring the voltage and the current adapted to detect a voltage drop due to fouling of the filtering cell and means for generating electric discharges to unclog said filtering cell.

  According to a preferred version of the invention, the device comprises a supervisory electronic circuit adapted to de-energize the high-voltage generator if a malfunction of the filter is detected, such as a short-circuit maintained or a circuit open.

  Preferably, the electronic supervision circuit is further adapted to inform an electronic system and / or the driver of the vehicle of the occurrence of the malfunction of a filter.

  Also preferably, the device according to the invention comprises means for regulating the intensity of the current generated in the filter as a function of the flow rate and the temperature of the exhaust gases, so as to obtain efficient filtering under all circumstances. , by just consuming the necessary energy.

  Other features and advantages of the invention will become apparent throughout the description.

  In the accompanying drawings given by way of nonlimiting examples: FIG. 2 is a block diagram of the device according to the invention, FIG. 3 is a chronogram showing, in continuous mode, different operating phases of the device according to the invention, FIG. 4 is an electrical diagram of an example of the high-voltage generator used in the device according to the invention; FIG. 5 is a diagram of the circuit which makes it possible to differentiate between a functional defect of the filter and fouling of the filter, - Figure 6 is a diagram of the current regulation circuit of the high voltage.

  Figure 2 shows the block diagram of the device to ensure the different filtering features.

  These functionalities are as follows: to generate, by a generator 8, a high inter-electrode voltage of the order of 1 kV at 20 kV and to supply the supply of 1 mA at 50 mA in nominal operation, to detect by a circuit 10 fouling of the filter (soot deposition on insulation elements of the filter cells 7) resulting in a short-circuit current and therefore a voltage drop, ^ maintain and withstand regular discharges without altering the functionality of the electronics to clean the filter 7, ^ de-energize the high-voltage electronics 8 and inform an electronic circuit 11 or the conductor of a malfunction of the filter (short circuit maintained or open circuit due to a filter fault), ^ regulate by feeding the power supply of the filter 7 to ensure efficient filtering at lower energy as a function of the flow rate and the exhaust temperature of the gases.

  The diagram of Figure 3 shows that during normal operation, the high voltage may have small voltage drops due to slight clogging of the filter.

  When a heavy fouling is detected, larger voltage drops are detected by the circuit 10 and the device then controls an increase of the current beyond the setpoint to generate energy discharges (in limit of arc speed). ), to clean the filter.

  The timing diagram of Figure 3 also shows the voltage and current drops resulting from a short circuit due to a filter fault.

  The topology of the high voltage generator 8 is shown in FIG. 4.

  In this figure, the reference 12 designates the low-voltage network which supplies the generator, 13 denotes a resonant capacitance, 14 denotes a resonant inductor, 15 a transformer, 16 a switch for example mosfet, 17 a capacitive multiplier and 18 a resistor which model the impedance of the filter. The low voltage network may be that of the vehicle or that of an intermediate power supply to the inverter and the high voltage rectifier circuit.

  Thus, the device may comprise a power electronics comprising a generator HT consisting of: a converter 12 which may be the on-board power supply network or a DCIDC converter; - an inverter for generating a sinusoidal current to power a transformer and a capacitive multiplier; a transformer assembly, a capacitive multiplier for generating the high voltage.

  This topology responds adequately to provide the high voltage generation functions, to deliver the current required for the application and to maintain the short circuits (short-circuit with the primary impedance capacity 13 and the self 14).

  This topology makes it possible to reduce the size of the transformer 15 by means of a capacitive multiplier 17 and thus the cost of the power electronics.

  It also makes it possible to directly transform the input voltage into a high voltage without the need for an intermediate DC voltage converter. One could of course use any other high voltage generator according to the state of the art.

  The detection of fouling (see block 10 figure 2) as well as a functional defect of the filter must be differentiated.

  Functional faults in the filter may be due to filter wear, manufacturing or assembly failure. Clogging of the filter can be weak or strong: the generator 8 can ensure its cleaning by energy discharge.

  1 st case: dirty filter Faulty case The generator being sized for a certain peak power, if the short circuit is due to a specific fouling, the high voltage drops punctually and returns to its previous level.

  Case of heavy clogging The generator being sized for a certain peak power, if the short circuit is due to a heavy clogging, the high voltage drops repeatedly and may not return to its previous level.

  The generator electronics are sized and driven to generate a current boost (see Figure 3) to clean the filter. A low threshold detection and a low threshold occurrence frequency makes it possible to differentiate a heavy fouling from a low fouling.

  2nd case: filter in functional short-circuit fault A short circuit maintained and prolonged drops the high voltage to 0V. A short circuit detection makes it possible to differentiate a short circuit from a heavy fouling of the filter.

  A method of implementation is for example the following (see Figure 5). The measurement of the high voltage is compared with detection thresholds in order to be able to differentiate between a functional defect of the filter and a filter fouling.

  Open filament detection is by the same method using a high threshold comparator.

  In the event of a short circuit detected due to a functional filter fault or open circuit detection, the supervisor 20 will instruct the stop generator to operate.

  An electronics 11 can then inform the driver of the lack of filtering.

  Other detection methods may be used according to the state of the art (measurement of the primary current, measurement of the secondary current ...).

  Another aspect of the invention relates to the mode of controlling the high voltage to generate in the inter-electrode space enough ions to bond the soot particles to the filtering cells 7.

  The adequate control mode to ensure effective filtering is to regulate the generator 8 current.

  A device for implementing such a regulation may be that represented in the diagram of FIG. 6.

  In this example, the measurement of the current is made by a shunt of which one of the potentials is located on a low voltage side of the power supply.

Claims (5)

  An electronic device for controlling the operation of an electrostatic filter arranged in the exhaust line of a motor vehicle, this filter comprising an enclosure (1) comprising at one of its ends an inlet (2) for the exhaust gases. exhaust and at the other end an outlet (3) of these exhaust gases, a metal filament (4) extending axially between the two ends of the filter, this filament (4) being surrounded by a filter cell ( 7) constituted by a network of wires or metal fibers defining a multitude of radial passage openings for the exhaust gas, the filament (4) being connected to a high voltage generator (8) capable of generating a corona discharge allowing ionization of the gases, the electric charging of the particles and their attachment to the fibers of the cell, characterized in that said high voltage generator (8) is adapted to generate a voltage of between 1 kV and 20 kV and a current of intensity between 1 mA and 50 mA and in that the device comprises a circuit (10) for measuring the voltage and the current adapted to detect a voltage drop due to fouling of the filter cell (7). ) and means for generating electric discharges for cleaning said filter cell (7).   2. Device according to claim 1, characterized in that it comprises an electronic supervisory circuit (20) adapted to de-energize the high voltage generator (8) in case of detection of a malfunction of the filter, such as 'a short circuit maintained or an open circuit.   3. Device according to claim 2, characterized in that the electronic supervision circuit (20) is further adapted to inform an electronic system (11) and / or the driver of the vehicle of the appearance of the malfunction of the filter.   4. Device according to one of claims 1 to 3, characterized in that it comprises means for regulating the intensity of the current generated in the filter as a function of the flow rate and the temperature of the exhaust gas.   5. Device according to one of claims 1 to 4, characterized in that it comprises a power electronics which comprises a generator HT consisting of: a converter (12) which can be the edge supply network 5 of the vehicle or a DCIDC converter - an inverter for generating a sinusoidal current for supplying a transformer and a capacitive multiplier - a transformer assembly, a capacitive multiplier for generating the high voltage.