Abstract:
A dosing module for an emissions abatement system, the dosing module including an armature, means for moving the armature and a valve body having an outlet; the dosing module having an unblocked condition, in which the armature is moveable between a first position, in which the outlet is closed by the armature, and a second position, in which the armature is spaced apart from the outlet, and wherein, in use, application of electricity to the means for moving the armature at a first level of energy causes the armature to move from the first position to the second position; the dosing module further having a blocked condition, in which flow of a liquid through the outlet is prevented, wherein, in use, application of electricity to the means for moving the armature at a second level of energy causes the dosing module to change to the unblocked condition.

Description:
FIELD OF THE INVENTION 
     Technical Field 
       [0001]    The present invention relates to a dosing module. More particularly, the present invention relates to a dosing module for use in an emission abatement system. The present invention also relates to a method of operating a dosing module. 
       BACKGROUND OF THE INVENTION 
       [0002]    In order to reduce atmospheric pollution caused by the emission of potentially harmful substances from engines, legislation has been introduced in the United States of America (USA) and the European Union (EU) to progressively lower legally binding limits for certain emissions, including oxides of nitrogen (NOx). 
         [0003]    Under US legislation, known as the “Tier 4 Final” standard, and the EU Stage IV legislation, emissions of NOx are limited to 0.40 g/kWh for engines with power outputs in the range of 56 to 560 kW. 
         [0004]    Various emission abatements technologies are known for reducing the output of NOx from diesel engines, including exhaust gas recirculation (EGR) systems, which inhibit NOx production by lowering the combustion temperature, lean NOx traps (LNT) or NOx adsorber catalysts (NAC) which act to ‘hold’ NOx, and selective catalytic reduction (SCR) which converts NO and NO2 to nitrogen and water. 
         [0005]    SCR combines the use of a catalyst such as vanadium, tungsten, copper zeolite (Cu-Zeolite) or iron zeolite (Fe-Zeolite) with a reductant such as anhydrous ammonia, aqueous ammonia or, more typically, urea, to convert NO and NO2 into nitrogen and water. Urea is typically used as the reductant, but has to be injected into the exhaust upstream of the SCR catalyst in order to thermally decompose into ammonia by the point at which it enters the SCR catalyst. Urea is preferred over ammonia, as it is substantially safer to store and transport. In the USA, commercially available urea for use with SCRs is referred to as Diesel Exhaust Fluid (DEF), whereas in Europe it is referred to as AdBlue®. For SCRs to function effectively at the lower end of the temperature spectrum it has hitherto been desirable for there to be a 50:50 split of NO and NO2, although Cu-Zeolite catalysts have been found to improve performance at temperatures of less than 300° C. when there is little NO2 available. An advantage of SCR is that is has minimal impact on specific fuel consumption. Disadvantages include the need to additionally replenish the reductant on a periodic basis and to provide space on a vehicle to package a reservoir of reductant. Typically, reductant usage is 1-7% that of diesel consumption. 
         [0006]    The urea solution is injected into the exhaust passage using a dosing module, also known as a DEF or AdBlue® injector or a dosing valve. The formation of crystals of urea within a dosing module adversely affects the supply of urea to the exhaust passage, for example the formation of urea crystals at the dosing module tip (orifice crystallization) may prevent the injection of urea out of the dosing module and the formation of urea crystals within the body of the dosing module (in-valve crystallization) may prevent movement of the valve and thus prevent the supply of urea. 
         [0007]    A known method for unblocking dosing modules is to increase the temperature of the dosing module and melt the urea crystals using exhaust gases. This requires the temperature of the dosing module to be heated to over 100° C. This is difficult to achieve since only the tip of the dosing module is located close to the exhaust gases and the body of the dosing module is surrounded by a coolant jacket. Furthermore, on a low level duty cycle, the exhaust gas temperature is not high enough raise the temperature of the dosing module to a level sufficient to melt urea crystals. 
       SUMMARY OF THE INVENTION 
       [0008]    Systems have been developed that increase the temperature of the exhaust gas in order to heat the dosing module sufficiently to melt the urea crystals; however these systems also suffer the aforementioned disadvantages, namely that only the tip of the dosing module is exposed to the exhaust gases and the cooling jacket that is present around the dosing module makes the transfer of heat at a temperature high enough to melt urea crystals from the dosing module tip to the dosing module body difficult. 
         [0009]    According to a first aspect of the invention there is provided a dosing module for an emissions abatement system, the dosing module including an armature, means for moving the armature and a valve body having an outlet; the dosing module having an unblocked condition, in which the armature is moveable between a first position, in which the outlet is closed by the armature, and a second position, in which the armature is spaced apart from the outlet, and wherein, in use, application of electricity to the means for moving the armature at a first level of energy causes the armature to move from the first position to the second position; the dosing module further having a blocked condition, in which flow of a liquid through the outlet is prevented, wherein, in use, application of electricity to the means for moving the armature at a second level of energy causes the dosing module to change to the unblocked condition. 
         [0010]    When the dosing module is in the blocked condition, movement of the armature may be prevented. 
         [0011]    The second level of energy may be greater than the first level of energy. 
         [0012]    The first level of energy may be defined by a first power, preferably a first electrical current and/or the second level of energy may be defined by a second power, preferably a second electrical current. 
         [0013]    The second electrical current may be at least 400 milliamps, preferably at least 500 milliamps. 
         [0014]    The dosing module may have a first temperature and application of electricity to the means for moving the armature at the second level of energy may cause the temperature of the dosing module to be increased to a second temperature. 
         [0015]    The second temperature may be at least 100° C. 
         [0016]    The dosing module may further include a spring to bias the armature towards the outlet in the first position. The means for moving the armature may be a coil device. The coil device may include a coil. 
         [0017]    Application of electricity to the coil at the first level of energy may cause the armature to move from the first position to the second position. 
         [0018]    Application of electricity to the coil at the second level of energy may cause the dosing module to change to the unblocked condition. 
         [0019]    The coil may be a first coil and the coil device may further include a second coil. 
         [0020]    Application of electricity to the first coil at the first level of energy may cause the armature to move from the first position to the second position and/or application of electricity to the second coil at the second level of energy may cause the dosing module to change to the unblocked condition. 
         [0021]    When the armature is in the second position, a liquid may flow through the outlet. The liquid may include a reductant. The liquid may include urea. The liquid may include Diesel Exhaust Fluid or AdBlue®. 
         [0022]    When the dosing module is in the blocked condition, flow of a liquid through the outlet may be prevented by crystals of the liquid. 
         [0023]    The dosing module may further include a coolant, for example a cooling jacket or cooling fins. 
         [0024]    The dosing module may be an engine after-treatment dosing module. 
         [0025]    According to a second aspect of the invention there is provided a vehicle including an engine and an exhaust system, the exhaust system including an emissions abatement system having a dosing module according to the first aspect of the invention. The vehicle may be a working machine, for example a loadall or a backhoe or a loading shovel or an excavator. 
         [0026]    According to a third aspect of the invention there is provided a method of operating a dosing module for an emissions abatement system, the method including the steps: 
         [0027]    (a) determining that the dosing module is in a blocked condition; 
         [0028]    (b) increasing the temperature of the dosing module by applying electricity to the dosing module; and 
         [0029]    (c) heating the dosing module until the dosing module is in an unblocked condition, in which liquid can flow through the dosing module. 
         [0030]    The method may further include the step: 
         [0031]    (d) operating the dosing module to pass liquid through the dosing module. 
         [0032]    The step of determining that the dosing module is in a blocked condition may include determining that flow of a liquid through the dosing module is prevented. 
         [0033]    The step of determining that the dosing module is in a blocked condition may include: 
         [0034]    (i) determining a first pressure of a liquid to be supplied by the dosing module prior to actuation of the dosing module; 
         [0035]    (ii) determining a second pressure of a liquid to be supplied by the dosing module during actuation of the dosing module; and 
         [0036]    (iii) comparing the first pressure and the second pressure. 
         [0037]    The second pressure may be greater than the first pressure. 
         [0038]    The step of increasing the temperature of the dosing module by applying electricity to the dosing module may include increasing the temperature to at least 100° C. 
         [0039]    The step of increasing the temperature of the dosing module by applying electricity to the dosing module may include holding the increased temperature for less than 400 seconds, preferably less than 200 seconds. 
         [0040]    The step of increasing the temperature of the dosing module by applying electricity to the dosing module may include applying an electrical current to the dosing module. The electrical current may be at least 400 milliamps, preferably at least 500 milliamps. 
         [0041]    The liquid may include a reductant. The liquid may include urea. The liquid may include Diesel Exhaust Fluid or AdBlue®. 
         [0042]    When the dosing module is in the blocked condition, flow of a liquid through the outlet may be prevented by crystals of the liquid. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0043]    Embodiments of the invention will now be described with reference to the accompanying drawings in which: 
           [0044]      FIG. 1  is a schematic representation of an exhaust system for a working machine; 
           [0045]      FIG. 2  is a cross section view of a dosing module according to a first embodiment in the closed position; 
           [0046]      FIG. 3  is a cross section view of the dosing module of  FIG. 2  in the open position; 
           [0047]      FIG. 4  is a flow diagram showing operation of a dosing module according to the present invention; and 
           [0048]      FIG. 5  is a cross section view of a dosing module according to an alternative embodiment in the closed position. 
       
    
    
     DETAILED DESCRIPTION 
       [0049]    Referring now to  FIG. 1  there is shown an exhaust system  10 . The exhaust system  10  is connected to an internal combustion engine  12 , a supply module  14  and a dosing control unit  16 . The supply module  14  is connected to a tank  18 , which has a solution of urea  20  contained within it. 
         [0050]    The exhaust system  10  includes an exhaust mixer  22 , a dosing module  24  and a selective catalytic reducer  26 . 
         [0051]    The internal combustion engine  12  is connected to the exhaust mixer  22  by passageway  28  and the exhaust mixer  22  is connected to the selective catalytic reducer  26  by passageway  30 . In this way, exhaust gas can pass from the internal combustion engine  12  to the selective catalytic reducer  26 . 
         [0052]    The tank  18  is connected to the supply module  14  by passageway  32  and the supply module is connected to the dosing module by passageway  34 . In this way, urea solution  20  can pass from the urea tank  18  through the supply module  14  to the dosing module  24 . 
         [0053]    The dosing module  24  is connected to the exhaust mixer  22  by the passageway  35 . In this way, urea solution  20  can be transferred from the dosing module  24  to the exhaust mixer  22  when required. 
         [0054]    The dosing control unit  16  is connected to the dosing module  24  by connection  36  and the dosing control unit  16  is connected to the supply module  14  by connection  38 . In this way, the dosing control unit  16  is able to detect the condition of the dosing module  24  and ensure that urea solution  20  is supplied to the dosing module by the supply module  14  and/or to the exhaust mixer  22  by the dosing module  24  when required. 
         [0055]    The exhaust system  10  further includes an exhaust  40  by which treated exhaust gas is released to the atmosphere. 
         [0056]    The dosing module  24  will now be described with particular reference to  FIGS. 2 and 3 . 
         [0057]    The dosing module  24  includes a housing or body  42 , an injector  44 , armature  46 , a spring  48 , a solenoid coil  50  and a coolant jacket  54 . 
         [0058]    The housing or body  42  includes an electrical connector  52  and a central passageway  60  having a first end or inlet  62  and a second end  64 . 
         [0059]    The injector  44  is a generally cylindrical, hollow body having a central bore  66 . The injector  44  has a first end  69  and a second end or outlet  71 . 
         [0060]    The armature  46  is a generally cylindrical body having a first end  68  and a second end  70 . The armature  46  has a T-shaped portion  72  adjacent to the first end  68 . The T-shaped portion  72  has a shoulder  73 . The armature  46  includes a flared portion  74  at the second end  70 . 
         [0061]    The spring  48  has a first end  76  and a second end  78 . 
         [0062]    The coolant jacket  54  includes an inlet  56  and a coolant channel  58  by which coolant is supplied to and is circulated around the housing  42 . 
         [0063]    The dosing module  24  is constructed as follows. 
         [0064]    The solenoid coil  50  is inserted in the second end  64  of the housing  42 . The injector  44  is inserted in the central passageway  60  of the housing  42  such that the central bore  66  of the injector  44  extends the length of the dosing module  24  from the first end  62  of the housing  42  to the outlet  71  of the injector  44 . 
         [0065]    The first end  76  of the spring  48  is mounted to the shoulder  73  of the T-shaped portion  72  of the armature  46  and the second end  78  of the spring  48  is mounted adjacent to the second end  64  of the housing  42 . 
         [0066]    The armature  46  and spring  48  are mounted in the central bore  66  of the injector  44  such that the spring  48  biases the second end  70  of the armature towards the outlet  71  of the injector  44  (as shown in  FIG. 2 ). The outlet  71  of the injector  44  is closed by the flared portion  74  of the armature  46 . 
         [0067]    The first end  62  of the housing  42  is connected to the supply module  14  by passageway  34  and the outlet  71  of the injector  44  is connected to the exhaust mixer  22  by the passageway  35 . 
         [0068]    With the dosing module  24  in the configuration shown in  FIG. 2 , urea solution  20  cannot pass from the inlet  62  of the housing  42  to the outlet  71  of the injector  44  and thus urea solution  20  is not supplied to the exhaust mixer  22 . 
         [0069]    Operation of the dosing module  24  to supply urea solution  20  to the exhaust mixer  22  will now be described. 
         [0070]    As shown in  FIG. 2 , the outlet  71  of the injector  44  is closed by the flared end  74  of the armature  46 . 
         [0071]    The supply of electricity via the electrical connector  52  to the dosing module  24  causes the solenoid coil  50  to be charged and the armature  46  to move towards the first end  62  of the housing  42  against the bias of the spring  48 . This results in the flared end  74  of the armature  46  moving away from the outlet  71  of the injector  44  and the dosing module to be in the open position (as shown in  FIG. 3 ). 
         [0072]    With the dosing module  24  in the position shown in  FIG. 3 , urea solution  20  is able to flow from the first end  62  of the housing  42  to the outlet  71  of the injector  44  and thus urea solution  20  can be supplied to the exhaust mixer  22 . 
         [0073]    As described above, the formation of crystals of urea within known dosing module adversely affects the supply of urea to the exhaust mixer, for example by blocking the passage through which the urea solution passes when the dosing module is activated and/or by preventing movement of the armature within the dosing module. 
         [0074]    Operation of the dosing module  24  of the present invention will now be described with particular reference to  FIG. 4 . 
         [0075]    When the engine (not shown) of a working machine (not shown) on which the dosing module  24  is installed is started  80 , the dosing module control unit  16  runs a dosing module diagnostic check  82  to determine if urea solution  20  is able to pass through the dosing module  24  to the exhaust mixer  22 , for example by determining the pressure of urea solution  20  at the inlet  62  of the housing  42  and comparing the determined pressure with the pre-determined pressure of urea solution  20  at the inlet  62  of the housing  42  when the dosing module  24  is in each of the configurations shown in  FIGS. 2 and 3  (i.e. in the open and closed positions). 
         [0076]    In the event that the dosing module  24  passes the dosing module diagnostic check  82 , normal operation continues  84  as described above. 
         [0077]    In the event that the dosing module  24  does not pass the dosing module diagnostic check  82 , the dosing module  24  is detected to be blocked  86 . The detection of a blocked dosing module  86  causes the dosing module control unit  16  to trigger heat up mode  88 . With the dosing module  24  in heat up mode  88 , electricity is supplied to the solenoid coil  50  at a greater power than is used to operate the dosing module under normal conditions, for example use of a current of at least 400 milliamps. This causes the temperature of the dosing module  24  to be increased, for example to 100° C. The temperature is held for a period of time  90 , for example 360 seconds. 
         [0078]    The dosing module control unit  16  undertakes a diagnostic check  92  to determine if the crystals of urea have melted and therefore if the dosing module  24  is unblocked. 
         [0079]    In the event that the dosing module  24  is determined to be unblocked, normal operation continues  84  as described above. 
         [0080]    In the event that the dosing module  24  is determined to still be blocked, the dosing module control unit  16  repeats heat up mode  88 . As described above, with the dosing module  24  in heat up mode  88 , electricity is supplied to the solenoid coil  50  at a greater power than is used to operate the dosing module under normal conditions, for example use of a current of at least 400 milliamps. This causes the temperature of the dosing module  24  to be increased, for example to 100° C. The temperature is held for a period of time  90 , for example 360 seconds. 
         [0081]    The dosing module control unit  16  undertakes a diagnostic check  92  to determine if the crystals of urea have melted and therefore if the dosing module  24  is unblocked. 
         [0082]    In the event that the dosing module  24  is determined to be unblocked, normal operation continues  84  as described above. 
         [0083]    In the event that the dosing module  24  is determined to still be blocked, the dosing module control unit  16  triggers an alert that there is a fault  96  with the dosing module  24 . 
         [0084]    The present invention advantageously enables the dosing module  24  to be heated to a temperature that enables urea crystals within the dosing module  24  to be melted even in the presence of a cooling jacket  54  around the outside of the dosing module  24 . 
         [0085]    Referring now to  FIG. 5  there is shown a dosing module  124  according to a second embodiment of the present invention. 
         [0086]    The dosing module  124  includes a first housing or body  142 , an injector  144 , an armature  146 , a spring  148 , a first solenoid coil  150  and a second housing  143  in which a second solenoid coil (not shown) is housed. 
         [0087]    The first housing  142  includes a first electrical connector  152  and a central passageway  160  having a first end or inlet  162  and a second end  164 . 
         [0088]    The injector  144  is a generally cylindrical, hollow body having a central bore  166 . The injector  144  has a first end  169  and a second end or outlet  171 . 
         [0089]    The armature  146  is a generally cylindrical body having a first end  168  and a second end  170 . The armature  146  has a T-shaped portion  172  adjacent to the first end  168 . The T-shaped portion  172  has a shoulder  173 . The armature  146  includes a flared portion  174  at the second end  170 . 
         [0090]    The spring  148  has a first end  176  and a second end  178 . 
         [0091]    The second housing  143  includes a second electrical connector  155  and a central passageway  163 . 
         [0092]    The dosing module  124  is constructed as follows. 
         [0093]    The solenoid coil  150  is inserted in the central passageway  163  of the second housing  143 . The injector  144  is inserted in the central passageway  160  of the housing  142  and the central passageway  163  of the second housing  143  such that the central bore  166  of the injector  144  extends the length of the dosing module  124  from the first end  162  of the first housing  142  to the outlet  171  of the injector  144 . 
         [0094]    The first end  176  of the spring  148  is mounted to the shoulder  173  of the T-shaped portion  172  of the armature  146  and the second end  178  of the spring  148  is mounted adjacent to opening  167  in the second housing  143 . 
         [0095]    The armature  146  and spring  148  are mounted in the central bore  166  of the injector  144  such that the spring  148  biases the second end  170  of the armature  146  towards the outlet  171  of the injector  144  (as shown in  FIG. 5 ). The outlet  171  of the injector  144  is closed by the flared portion  174  of the armature  146 . 
         [0096]    The first end  162  of the first housing  142  is connected to the supply module  14  by passageway  34  and the outlet  171  of the injector  144  is connected to the exhaust mixer  22  by the passageway  35 . 
         [0097]    With the dosing module  24  in the configuration shown in  FIG. 5 , urea solution  20  cannot pass from the inlet  162  of the first housing  142  to the outlet  171  of the injector  144  and thus urea solution  20  is not supplied to the exhaust mixer  22 . 
         [0098]    Operation of the dosing module  124  is as described in connection with the first embodiment of the invention, with the exception that supply of electricity from the first electrical connector  152  to the dosing module  124  causes the solenoid coil  150  to be charged and the armature  146  to move towards the first end  162  of the first housing  142  against the bias of the spring  148 . This results in the flared end  174  of the armature  146  moving away from the outlet  171  of the injector  144  and the dosing module to be in the open position (as shown in  FIG. 3  in relation to the first embodiment of the invention). 
         [0099]    In the event that the dosing module  124  does not pass the dosing module diagnostic check  82 , the detection of a blocked dosing module  86  causes the dosing module control unit  16  to trigger heat up mode  88 . With the dosing module  124  in heat up mode  88 , electricity from the second electrical connector  155  is supplied to the second solenoid coil (not shown) at a greater power than is used to operate the dosing module  124  under normal conditions, for example use of a current at least 400 milliamps. This causes the temperature of the dosing module  24  to be increased, for example to 100° C. The temperature is held for a period of time  90 , for example 360 seconds. 
         [0100]    As described in relation to the first embodiment of the invention, the dosing module  24  includes a cooling jacket  54 . It will be understood that the dosing module  24  may include alternative means to cool the dosing module, for example cooling fins. 
         [0101]    As shown in  FIG. 5 , the dosing module  124  does not include a cooling jacket. It will be understood that the dosing module  124  may include a cooling jacket, for example as shown in  FIGS. 2 and 3 , or cooling fins. 
         [0102]    As described in relation to the second embodiment of the invention, the first electrical connector supplies electricity to the first solenoid coil for moving the armature and the second electrical connector supplies electricity to the second solenoid coil for heating the dosing module and melting urea crystals. It will be understood that either or both of the first and second electrical connectors may supply electricity to the first solenoid coil for moving the armature and/or either or both of the first or second electrical connectors may supply electricity to the second solenoid coil for heating the dosing module and melting urea crystals. 
         [0103]    In the embodiments described above, the temperature of the dosing module  24 ,  124  is increased by supplying electricity at a greater power than is used to operate the dosing module under normal conditions. It will be understood that in alternative embodiments, the temperature of the dosing module may be increased by supplying electricity at the same power as is used to operate the dosing module under normal conditions, but for a longer period of time.