Abstract:
A control circuit for a vehicle powertrain includes a switch that selectivity interrupts current flow between a first terminal and a second terminal. A first power source provides power to the first terminal and a second power source provides power to the second terminal and to a heater of a heated diesel particulate filter (DPF). The switch is opened during a DPF regeneration cycle to prevent the first power source from being loaded by the heater while the heater is energized.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/955,213, filed on Aug. 10, 2007. The disclosure of the above application is incorporated herein by reference. 
     
    
     STATEMENT OF GOVERNMENT RIGHTS 
       [0002]    This invention was produced pursuant to U.S. Government Contract No. DE-FC-04-03 AL67635 with the Department of Energy (DoE). The U.S. Government has certain rights in this invention. 
     
    
     FIELD 
       [0003]    The present disclosure relates to power control circuits for electrically heated diesel particulate filters. 
       BACKGROUND 
       [0004]    The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. 
         [0005]    An electrically heated diesel particulate filter (DPF) filters particulates or soot from the exhaust stream of a diesel internal combustion engine. When the DPF is full of soot it is regenerated by passing an electrical current through a heating element that is proximate to the DPF. The heater heats a portion the accumulated soot to its combustion temperature. The heated soot ignites, turns to gas, and passes through the DPF, thereby clearing it for another filtering cycle. The soot that is ignited by the heater also begins a flame or ember front that propagates through the remaining soot to also clear it from the DPF during the regeneration cycle. 
         [0006]    An electrical system of the vehicle provides power for the heater. Since the exhaust gas carries heat away from the heater and reduces its temperature, the amount of power necessary to ignite the soot is based in part on the exhaust flow rate through the DPF. At high exhaust flow rates the power from the electrical system may be insufficient to heat the heater to a temperature that will ignite the soot during the regeneration cycle. 
       SUMMARY 
       [0007]    A control circuit for a vehicle powertrain includes a switch that selectivity interrupts current flow between a first terminal and a second terminal. A first power source provides power to the first terminal and a second power source provides power to the second terminal and to a heater of a heated diesel particulate filter (DPF). The switch is opened during a DPF regeneration cycle to prevent the first power source from being loaded by the heater while the heater is energized. 
         [0008]    In some features the first power source is a battery. The second power source is a generator. The switch is a relay switch. The control circuit further includes a powertrain control module that estimates a quantity of soot in the DPF and that opens the relay switch after the estimated quantity exceeds a predetermined quantity. The control circuit also includes a plurality of switches that selectively communicate the power from the second power source to respective heater zones of the heater. The switches are transistor switches. A current sense circuit generates a first signal indicative of an amount of current flowing to the heater. The current sense circuit includes a sense resistor in series with the current and an amplifier that generates the first signal based on a voltage drop across the sense resistor. An amplifier generates a second signal based on a voltage of the second power source. 
         [0009]    A control circuit for a vehicle powertrain includes a first switch that selectivity interrupts current flow between a first terminal and a second terminal, a battery that provides power to the first terminal, a generator that provides power to the second terminal and to a heater of a heated diesel particulate filter (DPF), a second switch that selectively communicates the power from the second power source to the heater, and a powertrain control module that controls the first and second switches and that estimates a quantity of soot in the DPF. The powertrain control module opens the first switch and closes the second switch after the estimated quantity of soot exceeds a predetermined quantity of soot, thereby powering the heater with the generator and preventing the heater from loading the battery. 
         [0010]    In other features the first switch is a relay. The heated DPF includes a plurality of resistive heaters and the second switch comprises a plurality of transistor switches that selectively communicate the power from the second power source to a respective one of the resistive heaters. A current sense circuit generates a first signal indicative of an amount of current flowing to the heater. The current sense circuit includes a sense resistor in series with the current and an amplifier that generates the first signal based on a voltage drop across the sense resistor. An amplifier generates a second signal based on a voltage of the second power source. 
         [0011]    A method of providing power to a heater of a heated diesel particulate filter (DPF) includes electrically connecting first and second power sources to each other, deciding to energize the heater, electrically disconnecting the first and second power sources from each other, and powering the heater from the second power source. 
         [0012]    In other features the method includes diagnosing the heater based on monitoring at least one of a voltage and current to the heater. The heater includes a plurality of heater zones and the powering step includes sequencing the power to each of the heater zones individually. The method includes managing at least one load that is powered by the first power source during the powering step. The method includes increasing an output voltage of the second power source while the first and second power sources are electrically disconnected. 
         [0013]    In still other features, the systems and methods described above are implemented by a computer program executed by one or more processors. The computer program can reside on a computer readable medium such as but not limited to memory, non-volatile data storage and/or other suitable tangible storage mediums. 
         [0014]    Further areas of applicability of the present disclosure will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the disclosure, are intended for purposes of illustration only and are not intended to limit the scope of the disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: 
           [0016]      FIG. 1  is a functional block diagram of a heater control circuit for a heated DPF; and 
           [0017]      FIG. 2  is a cross-sectional view of heater zones of the heated DPF of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    The following description is merely exemplary in nature and is in no way intended to limit the disclosure, its application, or uses. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A or B or C), using a non-exclusive logical or. It should be understood that steps within a method may be executed in different order without altering the principles of the present disclosure. 
         [0019]    As used herein, the term module refers to an Application Specific Integrated Circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that execute one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality. 
         [0020]    Referring now to  FIG. 1 , a functional block diagram is shown of a vehicle powertrain that includes a diesel engine  10 , a heated diesel particulate filter (DPF)  12 , and control circuitry that provides power to one or more heaters of heated DPF  12 . Exhaust from diesel engine  10  includes soot or particulate matter that heated DPF  12  traps. From time to time the control circuitry energizes heated DPF  12  to burn off the trapped soot and thereby empty or regenerate heated DPF  12 . While the control circuitry energizes heated DPF  12  it also opens a relay  18 . When relay  18  is open it electrically isolates the power (B+) from a generator  14  from the power from a battery  16 . It should be appreciated that generator  14  may also be implemented with an alternator and rectifier as is known in the art. 
         [0021]    During the regeneration cycle the control circuitry powers heated DPF  12  exclusively from generator  14  and powers other vehicle loads  19  exclusively from battery  16 . The control circuitry thereby prevents the electrical load presented by heated DPF  12  from reducing the voltage available to other vehicle loads  19 . As a result, vehicle loads  19  receive adequate power during the regeneration cycle and are free of undesirable effects such as drooping fan speeds, dimming headlamps, and other such effects while heated DPF  12  is energized. In some embodiments the vehicle loads  19  can be load managed by a control module to prevent them from reducing the output voltage of battery  16  to less than a predetermined voltage. The load management may also be as simple as inhibiting significant loads, such as a highest climate control fan speed, a heated back light, and the like, while relay  18  is open. Opening relay  18  also allows the output voltage of generator  14  to be regulated at a higher voltage than the voltage of battery  16  without damaging vehicle loads  19 . While generator  14  is operating with an increased output voltage it can generate more power than when its output voltage is regulated to the voltage of battery  16 . The increased power improves the heat output of the heater when compared to the heat output of the heater when it operates at the voltage of battery  16 . 
         [0022]    The control circuitry will now be described in more detail. Heated DPF  12  can include one or more zones or regions that may be individually energized and heated. For example, each zone may be formed by an associated resistive heating element. Referring briefly to  FIG. 2 , a cross section view A-A of heated DPF  12  shows five heater zones. The five zones are identified by numerals  1 - 5 . Zones  1 ,  2 ,  4  and  5  each have a quarter-semicircle shape and are arranged to form a circle. Zone  3  has a circular shape and is positioned at the center of the circle formed by zones  1 ,  2 ,  4  and  5 . It should be appreciated that a different quantity and/or arrangement of zones may be used based on the cross-sectional area of heated DPF  12 , power available from the control circuit, anticipated exhaust flow rates through heated DPF  12 , and other factors that affect the ability of the heater to ignite soot in heated DPF  12 . 
         [0023]    Each zone is energized exclusive of the other zones. The energized zone heats a portion of the accumulated soot to its combustion temperature. Once the soot ignites then the zone can be turned off. The ignited soot propagates a flame or ember front through the remaining soot to regenerate a respective portion of the filter. The zone is turned on for less than the duration of the regeneration cycle of the respective zone. Since a portion of the regeneration is fueled by the burning soot itself, the zone-heated DPF can use less electrical energy and provide improved fuel economy over other types of heated DPFs  12 . An example of a zone-heated DPF  12  is described in U.S. patent application Ser. No. 11/561,100, which is hereby incorporated by reference in its entirety. 
         [0024]    Returning now to  FIG. 1 , a positive terminal of battery  16  communicates with vehicle loads  19 . Examples of vehicle loads  19  include headlamps, fan motors, and the like. The positive terminal of battery  16  also communicates with a first terminal F of a relay  18 . A common terminal C of relay  18  communicates with an output of generator  14 . Relay  18  may be implemented with an electromechanical relay, a solid state relay, a transistor switch, or other suitable switching device. A diode  20  may be connected across the contacts of relay  18  to bias a field of generator  14  even when relay  18  is open. 
         [0025]    The output of generator  14  also provides power to drains of transistors Q 1 -Q 5 . Sources of transistors Q 1 -Q 5  selectively provide power to respective heater zones  1 - 5  of heated DPF  12  (shown in  FIG. 2 ). Gates of transistors Q 1 -Q 5  are driven by respective outputs of a driver control module  22 . Driver control module  22  turns on one or more transistors Q 1 -Q 5  to turn on respective ones of the heater zones. Driver control module  22  communicates with a powertrain control module (PCM)  24  to determine which of transistors Q 1 -Q 5  to turn on. In some embodiments the transistors Q 1 -Q 5  are turned on sequentially and one at a time so that each corresponding heater zone receives the full power from generator  14  for a limited time. 
         [0026]    In some embodiments the current to drains of transistors Q 1 -Q 5  may pass through a sense resistor  28 . An amplifier  30  amplifies the signal across sense resistor  28 . The amplified signal is communicated to PCM  24  and represents the amount of current that is flowing to transistors Q 1 -Q 5  and consequently to the heater of heated DPF  12 . A resistor  32  can be used to present some minimum load to the output of generator  14 . The minimum load prevents the output voltage of generator  14  from becoming excessive and potentially damaging transistors Q 1 -Q 5 . An amplifier  34  may be employed to amplify or buffer the voltage applied to the drains of transistors Q 1 -Q 5 . The signal from amplifier  34  is communicated to PCM  24  and represents the amount of voltage that is applied to transistors Q 1 -Q 5  and consequently the activated heater zone(s) of heated DPF  12 . PCM  24  can employ the signals from amplifiers  30  and/or  34  to diagnose transistors Q 1 -Q 5  and/or their corresponding heater zones. PCM  24  estimates a quantity of soot in heated DPF  12 . When the estimated quantity of soot exceeds a predetermined quantity of soot then PCM  24  opens relay  18 , commands for one of transistors Q 1 -Q 5  to be turned on, and increases the output voltage of generator  14 . 
         [0027]    PCM  24  may receive power from battery  16  via an ignition switch  40 . PCM  24  may also receive power directly from battery  16 . In such a configuration, PCM  24  can receive the signal from ignition switch  36  to indicate that engine  10  may be running. 
         [0028]    PCM  24  can also communicate a generator field signal  42  to generator  14 . PCM  24  can vary a duty cycle of generator field signal  42  to control the output voltage of power of generator  14 . PCM  24  can also receive a generator field diagnostic signal  44  that indicates whether the generator field is turned on or off at any moment. PCM  24  can then diagnose the generator field based on the generator field signal  42  and the generator field diagnostic signal  44 . 
         [0029]    Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, the specification, and the following claims.