Abstract:
A particulate filter is provided. The particulate filter includes: a plurality of sensors located in the filter; and a controller operatively connected to the sensors to determine a relative flow velocity over the sensors. A method for detecting obstructions in a filter may also be provided. The method may include: locating a sensor in a zone within a filter; connecting the sensor to a controller; monitoring the sensor with the controller; and determining whether the zone is obstructed based on data received from the sensor.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to diesel particulate filters. More particularly, the present invention relates to a system and method for detecting clogs in specific areas in zones of a diesel particulate filter. 
       BACKGROUND OF THE INVENTION 
       [0002]    Exhaust from engines such has diesel engines are filtered for particulate matter. A clogged filter can reduce the performance of the engine. Filters are often changed or cleaned based on a time frame measured in engine running time, miles driven or time as measured by the calendar. Such time intervals can result in clean filters being changed or cleaned and dirty as clogged filters remaining in service until the next time interval. 
         [0003]    Accordingly, it is desirable to provide a method and apparatus that determines the actual condition of the filter. 
       SUMMARY OF THE INVENTION 
       [0004]    The foregoing needs are met, to a great extent, by the present invention, wherein in one aspect an apparatus is provided that in some embodiments provides a method and apparatus for detecting whether a portion of a diesel particulate filter is clogged. In some embodiments, the system and apparatus can also detect which portions of a particulate filter are clogged. Further, in other embodiments the system and an apparatus can detect how badly various portions of the filter may be clogged. 
         [0005]    In accordance with one embodiment of the present invention, a particulate filter is provided. The particulate filter includes: a plurality of sensors located in the filter; and a controller operatively connected to the sensors to determine a relative flow velocity over the sensors. 
         [0006]    In accordance with another embodiment of the present invention, a method for detecting obstructions in a filter may also be provided. The method may include: locating a sensor in a zone within a filter; connecting the sensor to a controller; monitoring the sensor with the controller; and determining whether the zone is obstructed based on data received from the sensor. 
         [0007]    In accordance with yet another embodiment of the present invention, a particulate filter may be provided. The particulate filter may include: a means for detecting a temperature at a plurality of locations in the filter; and a means for monitoring and controlling the means for detecting a temperature at a plurality of locations connected to the means for detecting a temperature at a plurality of locations to determine a relative flow velocity over the means for detecting a temperature at a plurality of locations. 
         [0008]    There has thus been outlined, rather broadly, certain embodiments of the invention in order that the detailed description thereof herein may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional embodiments of the invention that will be described below and which will form the subject matter of the claims appended hereto. 
         [0009]    In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of embodiments in addition to those described and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, are for the purpose of description and should not be regarded as limiting. 
         [0010]    As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a schematic diagram of a diesel particulate filter and a controller in accordance with an embodiment of the invention. 
           [0012]      FIG. 2  is a partial side view of a portion of a particulate filter in accordance with an embodiment of the invention. 
           [0013]      FIG. 3  is a partial side view of a portion of the filter in accordance with an embodiment of the filter. 
           [0014]      FIG. 4  is a cross-sectional view of a filter in accordance with an embodiment of the invention. 
           [0015]      FIG. 5  is a cross-sectional view of a filter in accordance with an embodiment of the invention. 
           [0016]      FIG. 6  is a table showing the status of various zones of the filter as shown in  FIG. 5 . 
           [0017]      FIG. 7  is a table showing the status of various zones of the filter shown in  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    The invention will now be described with reference to the drawing figures, in which like reference numerals refer to like parts throughout. An embodiment in accordance with the present invention provides a method and apparatus for detecting whether portions of a particular filter are clogged. Throughout this document the terms diesel particulate filter (DPF) and particulate filter are all used. It is intended that the principles discussed regarding the filter are not limited only to diesel particulate filters but can be applied to filters in general. Thus, the term diesel particulate filter or DPF is meant to be exemplarily rather than limiting. 
         [0019]      FIG. 1  shows a filter assembly  110  in accordance with an embodiment of the invention. The filter assembly  110  is shown in schematic form and is not to scale. Several of the features may be enlarged for purposes of clarity. The filter assembly  110  includes a housing  112 . On the left hand side of the filter assembly  110  is an inlet  114 . As shown by arrow A, a fluid such as a gas to be filtered flows into the filter assembly  110  through the inlet  114  in the direction shown by arrow A. In some embodiments of the invention, the fluid may be exhaust gases from a diesel engine. However, other fluids may also flow into the filter in other applications. 
         [0020]    At the opposite end of the filter assembly  110  is an outlet  116 . As shown by arrow F, fluid that has been filtered by flowing through the filter assembly  110  exits the filter assembly  110  via the outlet  116 . Between the inlets  114  and  116  is the filter media  118 . The filter media  118  is used to conduct the filtering function. The filter media  118  may be divided into multiple channels or zones  120 . The zones will be identified by reference numeral  120 , particular zones may be identified by a letter after the reference number  120 , such as,  120   a,    120   b,    120   c  in  FIG. 1 . In  FIGS. 4-6 , the various zones are identified numerically by numbers  1 - 25 . 
         [0021]    A blockage  122  or clog in the filter media  118  is shown in zone  120   a.  The blockage  122  may be ash or soot or a combination of both. Blockages or clogs within the filter media  118  may also be comprised of any substance. The blockage  122  or clog in the filter media  118  shown in zone  120   a  is meant to be representative only. Blockages  122  can occur anywhere in the filter media  118 . Furthermore, multiple blockages  122  can also exist within the same or within different zones  120  with the filter media  118 . 
         [0022]    A temperature flow grid  124  is an optional feature as shown in  FIG. 1 . Some embodiments of the invention the temperature flow grid  124  may be made of a mesh grid. The temperature flow grid  124  may be a metal grid such as wire or a screen that is used to provide support for sensors  134  (not shown in  FIG. 1 , but shown in  FIGS. 2 and 3 ) which will be discussed in more detail further below. 
         [0023]    The controller  126  may be operatively connected to the sensors  134  (as seen in  FIGS. 2 and 3 ) which may be integrated with the grid  124 . The controller  126  may be operatively connected to the optional heating element  128 . 
         [0024]    In embodiments of the invention where the heating element  128  is used, diesel exhaust fumes or other gases desired to be filtered enter into the inlet  114  as shown by arrow A. The gases may be heated to a desired temperature by the heating element  128 . Gases continue to flow as shown by arrow C into various zones  120  within the filter media  118 . The gases are free to move within the zones as shown by arrow D. For example, if the gases encounter an obstruction  122  as shown in zone  120   a,  the volume of gas will be moved through other channels  120  such as channels  120   b  and  120   c.    
         [0025]    The velocity of the gas flowing through channel A will be reduced due to the partial blockage  122 . The velocity of the gas flowing through channel or zones  120   b  and  120   c  is increased as those channels are moving the gas directed from zone  120   a  in addition to the gas normally going through their zones. This increased velocity translates into increased flow through zones  120   b  and  120   c.    
         [0026]    Stated another way, the net diffusion rate of the gas across the membrane is proportial to the difference in pressure in the area of the membrane. Zone or channel  120   a  diffusion rate is essentially cut in half in the example scenario. This decreases the flow through channel  120   a  and usually does not create a increase in pressure in zone or channel A, however, the reason why pressure is not increased in Zone A is due to the diffusion rate of the gas moving through channels  120   b  and  120   c,  which increase flow and in turn increases velocity for those channels. Thus, by measuring the air velocity for multiple sections or zones of the diesel particulate filter  110 , clogged and unclogged zones in the filter  118  may be determined. The lower the velocity in any particular zone indicates that the zone having lower velocity has an obstruction due to ash or soot and needs to be cleaned. 
         [0027]    A high velocity is indictive of a non-clogged, free flowing zone. Monitoring of the flow of air or gas through the various zones may show different velocities between the zones. The higher the sensitivity of the sensors  134 , the more accurate or better the result. 
         [0028]    Typically, sensitive air flow measurements from multiple zones of a cylinder may be taken with sensors  134  such as, for example but not limited to, hot wire anemometers. Hot wire anemometers work such that air flow over the wire cools the exposed wire. The higher the flow, the cooler the wire. Thus, a cooler wire indicates a relatively higher velocity. The wire temperature can be monitored by the controller  126 . Some drawbacks with hot wire anemometers are they may be expensive and delicate. 
         [0029]    In accordance with the invention, thermistors can also be used based on a similar principle as hot wire anemometers. The thermistor may be more sensitive to temperature changes in the gas flow the thermistor is located in. A thermistor may be very sensitive and linear over small ranges and maybe durable and relatively inexpensive. 
         [0030]      FIGS. 2 and 3  are partial views of the filter assembly  110  shown in  FIG. 1 . The various zones  120   a,    120   b  or  120   c  are shown at the left of each Figure. Gas flows through the filter media  118  into the funnel zone  30  in the direction of the arrows indicated. The gas flows over the sensor  134  which is shown in  FIGS. 2 and 3  as a thermistor, which may be part of a copper grid  124 . 
         [0031]      FIG. 2  shows flow through zones  120   b  and  120   c  which are not obstructed and thus have normal air velocity, air flow, air volume and normal resistive of change in the thermistor over time. An increase in the air velocity, air flow, air volume and normal resistive change in the thermistor over time would indicate that some other zone  120  filter assembly  110  may be blocked. 
         [0032]      FIG. 3  shows the funnel zone  130  of the partially blocked zone  120   a.  Due to the partial blockage, there is lower air velocity, less volume, and less air flow and a small resistive change over time. 
         [0033]      FIG. 4  is a cross-sectional view of the filter assembly  110 .  FIG. 4  is not intended to be to scale but shows zones having round cross sections and cross sections of other shapes. The zones in  FIG. 4  are numbered  1 - 25 . In some embodiments in accordance with the invention, the zones are of approximately equal cross-sectional area. In some embodiments the filter assembly has a thickness of approximately two inches. 
         [0034]    The round areas shown in  FIG. 4  are the funnel zones  130 . A sensor  134  is associated with each of the zones  1 - 25 . While not shown in  FIG. 4 , the sensors  134  may be connected or connected to a wire mesh grid  124 . The mesh grid  124  may help transfer heat to the sensor  134  and help secure the sensor  134  in the center of the zone  120 . 
         [0035]    In some embodiments of the invention, the heater  128  is controlled by the controller  126  and is used to heat the air or gas entering the filter assembly  110 . After an amount of time, the system will enter a steady state. In some embodiments of the invention a honeycomb air straightener, high beta or similar device may be placed up stream. The grid  124  of sensors  130  may be placed directly on the filter media  128  near the outlet  116  of the filter assembly  110 . The controller  126  may monitor the temperature of each sensor  134  over time. A zone  120  that has a reduced flow due to a clog  122  blockage will show a slower rise in temperature over time and an ultimately lower temperature at the end of a test period. 
         [0036]    In some embodiments of the invention, the baseline temperature could be room temperature. In some embodiments of the invention, other useful information may also be collected from the sensors  134  and the controller  126 . For example, if it is assumed that soot absorbs more heat than ash, then zones or channels  120  of the filter media  118  that contains soot residue as opposed to ash residue may have a longer delay before a temperature rise begins and or a slower additional rise time if the temperature is monitored or graphed over time. 
         [0037]    In other embodiments of the invention, the optional heating element  128  may not be used. In such embodiments, flow of air over the thermistor or sensor  134  would cause a negative temperature change due to heat dissipation. Thus, depending on the sensitivity of the result, no heat necessarily needs to be added to the system in order to determine the flow rate for each of the zones  120 . 
         [0038]      FIG. 5  is an illustration similar to that shown in  FIG. 4  having multiple zones or channels  120  in the filter media  118 . The multiple zones or channels  120  are numbered  1 - 25 . Different hatching schemes are associated with the various channels  120  and can be compared to the hatching scheme shown in the chart shown in  FIG. 6 . The chart in  FIG. 6  shows an associated detected condition of its channel  120 . The numbers on the left column correspond to the zone or channel  120  numbers  1 - 25 . 
         [0039]      FIG. 7  is also a chart that is associated with the filter media  118  shown in  FIG. 5 . Various zones  1 - 25  have been monitored for sixty seconds and various data has been collected. In the example test illustrated and shown in  FIGS. 5-7  a point system has been assigned with weighted results depending on the results of the test. In the example test, the overall average flow of the filter assembly  110  was normal. Taking into account the clean zones which increased airflow and the failed zones which largely diminished airflow, the overall airflow balance out. The failed and ash zones where taken into account via a separate point total. 
         [0040]      FIG. 7  illustrates the various points assigned to the different zones resulting in the point total. The conclusion of the example test shows that the overall flow of the filter was acceptable and that the ash and soot content in the filter media  118  is taken into account to determine that the filter media is only 73% clean. This result could be calculated by the controller  126  in some embodiments of the invention or by user in other embodiments. One of ordinary skill in the art would appreciate the various percentages of blockages could be considered acceptable, not acceptable for various situations. The percentages which would place the filter into the acceptable, non-acceptable or imminent range may be determined on an individual basis. 
         [0041]    The many features and advantages of the invention are apparent from the detailed specification, and thus, it is intended by the appended claims to cover all such features and advantages of the invention which fall within the true spirit and scope of the invention. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.