METHOD FOR THE QUALITY IMPROVEMENT OF A GAS-PERMEABLE OBJECT REMOVED FROM AN EXHAUST GAS SYSTEM OF AN INTERNAL COMBUSTION ENGINE AND AN APPARATUS THEREFOR

Abstract

The invention relates to a method for the quality improvement of a gas-permeable object, such as a filter or catalyst, removed from an exhaust gas system of an internal combustion engine. To attain a cost-effectively realizable method, it is provided according to the invention that, in an automated process, a condition of the object is measured, after which a quality improvement is carried out, after which a condition of the object is measured again.

Furthermore, the invention relates to an apparatus for the diagnosing and quality improvement of a gas-permeable object, such as a filter or a catalyst, removed from an exhaust gas system of an internal combustion engine.

Claims

1. A method for the quality improvement of a gas-permeable object, such as a filter (15) or catalyst, removed from an exhaust gas system of an internal combustion engine, characterized in that in an automated process, a condition of the object is measured, after which a quality improvement is carried out, after which a condition of the object is measured again.

2. The method according to claim 1, characterized in that the object is transported during the process with a workpiece carrier (3) that is gas-permeable and, in particular, comprises a diffuser.

3. The method according to claim 1, characterized in that the object is cleaned with a hot gas that is applied through an axially and/or radially adjustable variable diffuser (11) which is adapted to a geometry of the object before application of the hot gas.

4. The method according to claim 1, characterized in that a hot gas is applied to two opposing faces of the object from different directions.

5. The method according to claim 1, characterized in that a cleaning takes place with a pressurized gas, preferably air, which is applied at a velocity of 1.0 to 3 times the speed of sound.

6. The method according to claim 5, characterized in that the gas is applied through a nozzle (19), wherein a spray angle is 1 to 45, preferably 10 to 15.

7. The method according to claim 1, characterized in that, for the cleaning, a gas is applied alternatingly to a face of the object through multiple, in particular two to five, nozzles (19).

8. The method according to claim 5, characterized in that the gas is applied with time-variable pressure or in pulses, preferably at a frequency of 0.1 Hz to 100 Hz, in particular 1 Hz to 10 Hz, wherein preferably multiple, in particular two to live, nozzles (19) are used and pressure pulses (20) are applied through the individual nozzles (19) in a time-staggered manner.

9. The method according to claim 8, characterized in that a pulse frequency is selected depending on a geometry of the object such that the gas applied at alternating pressure forms a pressure wave in the object, which pressure wave is reflected at an end of the object, wherein preferably the pulse frequency is selected such that the reflected pressure wave is superposed with an advancing pressure wave in the object at a predefined position in order to attain an improved cleaning effect at the predefined position.

10. An apparatus (1) for the diagnosing and quality improvement of a gas-permeable object, such as a filter (15) or a catalyst, removed from an exhaust gas system of an internal combustion engine, in particular for performing a method according to claim 1, characterized in that a device for improving a quality of the object and a diagnostic device for measuring a condition of the object as well as a data processing device connected to the diagnostic device are provided, wherein the device for improving a quality of the object can be controlled using the data processing device so that a condition of the object can be determined and a quality improvement carried out in a fully automated process.

11. The apparatus (1) according to claim 10, characterized in that the apparatus (1) comprises a transport system for a transport of the objects that are to be cleaned with workpiece carriers (3), wherein the workpiece carriers (3) are gas-permeable, wherein preferably the workpiece carrier (3) comprises a diffuser insert (14) in order to apply a gas from below over the full area via the supply line to an object positioned on the workpiece carrier (3), wherein the diffuser insert (14) is preferably detachably connected to the workpiece carrier (3).

12. The apparatus (1) according to claim 10, characterized in that the apparatus (1) comprises a hot cleaning cell (7) for a thermal cleaning of the object, wherein a radially and/or axially adjustable variable diffuser (11) is positioned in the hot cleaning cell (7) to enable a full-area and uniform application of a hot gas to objects with different diameters.

13. The apparatus (1) according to claim 10, characterized in that the apparatus (1) comprises a cold cell (6), and that in the cold cell (6), a mechanical cleaning device (5) is provided for cleaning the object with a gas at a pulsating alternating pressure of preferably 0.1 Hz to 100 Hz, in particular 1 Hz to 10 Hz, wherein the device comprises multiple, in particular two to five, nozzles (19).

14. The apparatus (1) according to claim 13, characterized in that the apparatus (1) is set up for determining a pulse frequency at which a pressure wave reflected at an end of the object is superposed with an advancing pressure wave at a predefined position in the object to achieve an improved cleaning effect at the predefined position.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Additional features, benefits and effects of the invention follow from the exemplary embodiment described below. The drawings which are thereby referenced show the following:

[0051] FIG. 1 An apparatus according to the invention in a side view;

[0052] FIG. 2 A detailed illustration of an apparatus according to the invention;

[0053] FIG. 3 through 5 A workpiece carrier of an apparatus according to the invention;

[0054] FIG. 6 An additional detailed illustration of an apparatus according to the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0055] FIG. 1 shows in a side view an apparatus 1 according to the invention for the cleaning and quality improvement of an object, such as a filter 15 or catalyst, removed from an exhaust gas system of an internal combustion engine, wherein a side cover is not illustrated. The apparatus 1 according to the invention and the method according to the invention are explained below in reference to a filter 15, even though an implementation with other gas-permeable objects is also possible.

[0056] The apparatus 1 comprises a transfer region 2, a cold cell 6 and a hermetically sealed hot cleaning cell 7. To carry out the method according to the invention, a filter 15 that is to be cleaned is positioned in the transfer region 2 on a workpiece carrier 3. In a fully automatic manner, the filter 15 is then transported into the cold cell 6 for condition measurement and cleaning and subsequently into the hot gas cell and finally back to the transfer position. During an entry of the filter 15 into the cold cell 6, a filter geometry is scanned by a stationarily positioned laser scanner, so that devices in the cold cell 6 and the hot gas cell can be adapted to a filter geometry and, if necessary, any interfering contours present.

[0057] For a transport of the workpiece carrier 3 and a filter 15, a chain drive or a heavy-duty guide based on a drawer principle can be provided. Typically, the workpiece carriers 3 are connected via positive-fit connections to a conveyor system 8 and conveyed through the apparatus 1, wherein positioning aids can also be provided for a central and location-oriented position of the filters 15 and catalysts. For an automatic processing of multiple components, a workpiece buffer can also be provided in the workpiece feed, from which buffer one part after another can automatically be fed. After a cleaning, the cleaned parts can be stored in a finished part buffer.

[0058] In the cold cell 6, a device for detecting a condition of the filter 15 or a diagnostic device is provided, for example a device for testing a differential pressure of the filter 15 or a camera for optical analysis, a laser scanner or the like. Of course, devices for the condition measurement can in principle be provided both in the cold cell 6 and also in the hot cleaning cell 7. Based on a condition of the filter 15 measured with the diagnostic device, a decision is then made in an automated manner about a cleaning that is to be performed or parameters for a cold cleaning or hot cleaning. For an automated decision, empirical values from previously performed cleanings can also be used as a resource by a decision logic in a data processing system. The apparatus 1 can thus also be embodied as a self-learning apparatus 1 so that an efficiency of the method is constantly improved with an increasing number of cleanings performed. A decision is thereby made in an automated manner about a necessary cleaning depending on a measured quality or a condition of the filter 15, or a cleaning strategy is determined and implemented independently of an operator.

[0059] Furthermore, a device embodied as a mechanical cleaning device 5 for improving a quality of the object is provided in the cold cell 6 to enable a compressed air cleaning of the filter 15. This device can comprise one or more nozzles 19 with which compressed air can be applied to the filter 15 at an air discharge velocity of, for example, Mach 1.91 and with a narrow spray angle.

[0060] Typically, in the mechanical cleaning device 5, two to five nozzles 19 are provided which are simultaneously supplied with a flow or pulsated in a time-staggered manner, for example via a piston shuttle valve. In this manner, the application of pressure waves to the filter 15 is possible, which waves are reflected at a bottom end of the filter 15 or an open end. Thus, as a result of a superposition of advancing and returning waves in the filter 15, a pressure increase occurs at pre-calculable positions, so that a removal can take place in a targeted manner at defined positions. In addition, it has been shown that a superposition of advancing and returning waves in the filter 15 also causes a pressure increase or pressure pulsations perpendicular to a stream direction, that is, roughly in a horizontal direction in the exemplary embodiment. This also leads to a cleaning effect in adjacent cells of a particle filter with a honeycomb structure, even if compressed air is not directly applied to these adjacent cells.

[0061] A possible embodiment of a mechanical cleaning device 5 of this type is illustrated in FIG. 2, wherein regions with different pressures are also visualized as in a schlieren image. The mechanical cleaning device 5 is thereby embodied as a duplex nozzle 18 having two nozzles 19. The nozzles 19 are set up to apply supersonic pressure pulses 20 at a frequency of 1 Hz to 10 Hz and are typically actuated such that compressed air is applied in a pulsated manner by one nozzle 19 while the other nozzle 19 is closed. An opening and closing of the nozzles 19 is thereby possible very rapidly or with steep edges, so that pressure curves over time have a rectangular shape and a large flow velocity gradient as well as a strong impulse can be generated. This results in pressure pulses 20 advancing along a direction of flow 12 at a supersonic velocity with a very narrow spray angle. The pressure pulses 20 emitted by the respective nozzles 19 thereby move along streamlines of the nozzles 19 which, starting at each nozzle 19, extend in the direction of flow 12 and are thus also roughly parallel and typically have a distance between them of only a few centimeters, in particular a few millimeters.

[0062] In the mechanical cleaning device 5 illustrated in FIG. 2, six pressure pulses 20 each are applied or emitted by one nozzle 19, after which this nozzle 19 is closed and six pulses are applied by the respective other nozzle 19. In a region of the pressure pulses 20 or the advancing air, a static pressure on the respective streamline is significantly lower than in a region in which no pressure pulse 20 is advancing or in which the air is still. The pulsating actuation of the nozzles 19 thus causes not only a pulsating application of air in the direction of flow 12, but also correspondingly propagating pressure fluctuations in the direction of flow 12. Since the nozzles 19 are actuated alternatingly and a distance between the nozzles 19 in roughly parallel alignment is very small, this results in a strong pressure gradient perpendicular to the direction of flow 12 between a pressure pulse 20 and a region in which there is no pressure pulse 20, or between the streamlines of the two nozzles 19, so that a pulsating flow gradient transverse to the direction of flow 12 is produced. This pulsating flow gradient transverse to the direction of flow 12 causes a spatial pulsation field or spatially propagating pressure fluctuations which, together with interference effects, enable an increased cleaning effect.

[0063] In the filter 15, the pressure differences in the direction of flow 12 and perpendicular to the direction of flow 12 result in an improved removal of soot and dust from interior filter walls. Another advantage of this cleaning method is that, through the pulsating application of compressed air, less compressed air is required for cleaning than in a continuous application of compressed air. Furthermore, an application of force to the filter 15 is less than with a continuous application of pressure, as a consequence of which damage to the filter 15 is avoided.

[0064] The device for compressed air cleaning of the filter 15 is normally set up to apply compressed air to a small section of a face of the filter 15. In order to still be able to fully clean the filter 15, a Cartesian robot 4 is usually also provided for the variable positioning of the device in all spatial directions relative to the filter 15 in the cold cell 6.

[0065] Typically, a diagnostic device for the condition measurement of the filter 15 is also positioned relative to the filter 15 by the Cartesian robot 4 in order to assess a quality of individual sections of the filter 15, for example optically, with a differential pressure test, by measuring a degree of blackening, or by measuring a particle capture rate or a particle retention capacity. A particle retention capacity is typically determined in that, by means of a particle generator, a particle-containing gas is generated that is applied to the filter, after which particles transported through the filter are measured at a position located downstream. The mechanical cleaning device 5 can thereby also be embodied as a combined cleaning and diagnostic device, for example, with a diagnostic and cleaning nozzle or a combination nozzle for applying compressed air for the cleaning and for the differential pressure test and/or for the application of a reactive gas to assess a catalytic reactivity. Furthermore, a camera for the optical assessment of the filter 15 can be provided in or on the combination nozzle. In addition, a hot gas for regeneration and for cleaning can also be applied by means of the combination nozzle.

[0066] Normally, a condition of the filter 15, in particular a differential pressure, is measured at approximately 50 positions on a particle filter, so that heavily contaminated regions or regions with inadequate quality can be identified and subsequently cleaned in a targeted manner in order to improve a quality of said regions.

[0067] Furthermore, a device for moving the workpiece carrier 3 in the cold cell 6 can be provided to reach a desired position of the diagnostic device or cleaning nozzle relative to the filter 15. For example, a diagnostic or cleaning nozzle can be translationally movable in three spatial directions and the workpiece carrier 3 rotationally movable in one or more spatial directions, in order to achieve a suitable relative positionability of the filter 15 and combination nozzle with a constructionally simple design, and thus to achieve a suitable cleaning effect.

[0068] Furthermore, a measurement of a catalytic reactivity can occur in sections, for example in that an NO/NO2 conversion is detected by means of an application of nitrogen monoxide to the filter 15 and a subsequent measurement of nitrogen dioxide at a position located downstream below the filter 15. In addition, a measurement of a CO/CO2 conversion, a conversion of HC gas into CO and CO2 and H2O and the like can of course also be provided for the quality measurement. Furthermore, a formation of ammonia gas in SCR catalysts and a conversion of ammonia and nitrogen oxides into nitrogen and CO2 and the like can also be detected, preferably also in sections.

[0069] At a position below a conveyor system 8 for the workpiece carrier 3, an extraction line 9 is arranged in the cold cell 6 to collect, remove and dispose of soot cleaned off of the filter 15. For this purpose, a dust separator, in particular a cyclone separator, can be provided.

[0070] Based on a measured quality of the filter 15, parameters for a necessary cleaning, for example a duration of a mechanical cleaning or a temperature of a thermal cleaning in the hot gas cell, are then selected in an automated manner, after which a possibly necessary mechanical cleaning is performed in the cold cell 6. Based on measured data, a comparison with a reference component can also be carried out, and the filter can be evaluated as being good or bad based on the comparison.

[0071] Adjoining the cold cell 6 is the hot cleaning cell 7 for improving a quality of the filter through a thermal cleaning in the apparatus 1, which hot cleaning cell 7 is separated from the cold cell 6 by an automatic and sealing door. In this manner, a hermetic separation of an interior of the hot cleaning cell 7 from the cold cell 6 and a surrounding environment is achieved, so that an escape of hot air during a hot cleaning is prevented and, if necessary, an inflow of oxygen can be interrupted in the event of an undesired thermal reaction. Furthermore, a variable diffuser 11 with a variable geometry in radial and axial directions is provided at the head end in the hot cleaning cell 7. The variable diffuser 11 can thus be adapted to filters 15 with different diameters in a simple and automated manner. For example, the illustrated apparatus 1 is suitable for filters 15 with substrate sizes of 4 inches to 15 inches. The variable diffuser 11, which can be adapted both to round and also to rectangular faces of filters, is connected to a hot gas supply line 10, so that a hot gas such as air can be applied to the filter 15 for cleaning through the variable diffuser 11. Furthermore, the hot gas supply line 10 also opens into a region below a conveyor system 8 for the workpiece carrier 3 so that, in the hot cleaning cell 7, an application to the filter 15 is possible both from above through variable diffuser 11 having a variable geometry and also from below through a gas-permeable workpiece carrier 3 having a diffuser insert 14. A hot gas can be created centrally using a heater. Alternatively, one heater each, for example an electrically powered heater, can be provided at the bottom end and head end in the hot gas cell.

[0072] An exhaust air from the hot gas cell is conducted via a heat exchanger that is not illustrated, in order to recover an energy from the hot gas after the cleaning, for example to preheat a hot gas before cleaning. A residual heat or an exergy present can be removed from the cold cell with the exhaust air and from the system with a scavenging air.

[0073] FIG. 3 shows a workpiece carrier 3 with a diffuser insert 14 in an exploded view. As can be seen, the workpiece carrier 3 comprises a central opening 13 in which a diffuser insert 14 is arranged. This also enables a full-area and uniform application of gas to a bottom face of the filter 15, which face is connected to the workpiece carrier 3.

[0074] FIGS. 4 and 5 show sections through workpiece carriers 3 of apparatuses 1 according to the invention, in which carriers different diffuser inserts 14 are arranged with filters 15 of a different size. As can be seen, because of the detachable connection of diffuser inserts 14 of a different size to workpiece carriers 3, the same workpiece carrier 3 can be easily adapted for a wide range of different filter geometries or diameters through an exchange of corresponding diffuser inserts 14. It is thus ensured that, even with filters 15 of a different size, an entire volumetric flow of a hot gas is conducted into the filter 15 during a hot gas cleaning, so that a high energy efficiency is achieved, which particularly for a use of the apparatus 1 in small motor vehicle repair shops is advantageous.

[0075] FIG. 6 shows in detail the variable diffuser 11 of the hot gas cell of the apparatus 1 according to the invention. The variable geometry of the variable diffuser 11 is thereby achieved by flat or plate-shaped elements 17 that can be slid into one another, in this case thin, approximately tapered and/or flexible metal plates, which are arranged along a circular contour 16 at an upper end such that they can be moved or pivoted about an axis tangential to the circular contour 16. During a cleaning, a center point of a circle of the contour 16 is positioned roughly on an imaginary longitudinal axis of a filter 15 located in the hot gas cell. A plane of the circle lies roughly perpendicular to the imaginary longitudinal axis and perpendicular to an image plane in FIG. 6.

[0076] By means of the correspondingly movable arrangement of plate-shaped, preferably heat-resistant, elements 17, a sliding-into-one-another of the metal plates, and thus a variation of an effective diameter, is possible at a lower end of the variable diffuser 11, similar to an afterburner jet on a supersonic aircraft. A hot gas supply line 10 is connected to the variable diffuser 11, so that a filter 15 positioned on a workpiece carrier 3 in the hot gas cell can be cleaned both from above and also from below with a hot gas at a temperature of typically 200 C. to 900 C. This results in a particularly efficient cleaning, as an energy necessary for the cleaning can be reduced by the dual-sided application of a hot gas. In order to be able to operate the system with a low connected load, a cleaning from above normally takes place alternatingly with a cleaning from below, even though a simultaneous cleaning from above and below is also possible in principle.

[0077] Typically, a condition of the filter 15 after a cleaning with compressed air and a cleaning with a hot gas is measured again in an automated manner to determine a cleanliness condition. A decision can then be made in a data processing device in an automated manner about whether a new and, if necessary, which cleaning is required, or whether a cleaning is complete. If the cleaning is complete, the filter 15 is transported to the transfer position with the workpiece carrier 3 by means of the conveyor system 8, at which position the filter 15 can be removed. Finally, a paper printout regarding a completed cleaning and an attained cleanliness condition can also be created to document a completed cleaning. Based on the cleanliness condition attained, an expected remaining service life can thereby be calculated and outputted.

[0078] All method steps between the delivery of the filter 15 at the transfer position and the removal of the filter 15 take place in an automated manner, so that no manual intervention is required. Although only one filter 15 is illustrated in the apparatus 1 in the exemplary embodiment, an embodiment of the apparatus 1 with an integrated buffer storage for additional filters 15 is also possible, so that multiple filters 15 can be delivered simultaneously and can be measured and cleaned or reprocessed in the apparatus 1.

[0079] With an apparatus 1 according to the invention and a corresponding method, a fully automated cleaning of a soiled object such as a filter 15 or catalyst is possible in a particularly energy-efficient manner. The corresponding apparatus 1 can be operated at low electric power and, at the same time, can be produced in a very compact and cost-effective manner. For example, through a sequential measurement and cleaning in the cold cell 6 on the one hand and subsequently in the hot gas cell on the other hand, a connected load of the apparatus 1 of only 13 kW can be achieved, even though a total of the wattage ratings of energy consumers in the apparatus 1 can be 20 kW and higher. Furthermore, the apparatus 1 from the exemplary embodiment is set up for the exclusive dry cleaning of the filter 15, so that no liquids need to be stocked, cleaned or disposed of. The apparatus 1 can thus be embodied to have a small installation space and to be very compact, as a result of which the apparatus can be transported through typical repair shop doors with a width of 0.8 m and a height of 1.8 m and can be operated with little effort. Typically, all process materials, temperatures, pressures, movements and the like necessary for the method are supplied by the apparatus, so that only a power connection is required to operate the apparatus.

[0080] The apparatus 1 is therefore well suited for a decentralized use, for example in motor vehicle repair shops. A compressor necessary for the supply of compressed air in the apparatus 1 can thereby also be used to supply compressed air in the motor vehicle repair shop. In addition, a waste heat from the hot gas cell can also be reused to further reduce an energy requirement.