Abstract:
A system for purging a device for injecting fuel into an exhaust system of an engine comprising a device having an input and an output coupled to an exhaust system, at least one air valve and at least one fuel valve. The air valve has an input an input coupled to an air supply and an output coupled to the device through a check valve. The fuel valve has an input coupled to a fuel supply and an output coupled to the device through a check valve. When the air valve is open and the fuel valve is closed, air flows from the air supply to the device and is injected into the exhaust system of the engine. When the air valve is closed and the fuel valve is open, fuel flows from the fuel supply to the device and is injected into the exhaust system of the engine.

Description:
REFERENCE TO RELATED APPLICATIONS 
     This application claims one or more inventions which were disclosed in Provisional Application No. 61/045,032, filed Apr. 15, 2008, entitled “DOSER AIR PURGE”. The benefit under 35 USC §119(e) of the United States provisional application is hereby claimed, and the aforementioned application is hereby incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention pertains to the field of exhaust systems. More particularly, the invention pertains to an exhaust system with air purging. 
     2. Description of Related Art 
     Doser valves are used to inject fuel into the exhaust system of diesel engines to burn particulate matter in a filter and thus clean them out. Therefore, they are mounted on the “hot” side of the engine in the exhaust system. Due to the very high temperatures within the exhaust system on the “hot” side of the engine, the PWM operating mode, and the necessary valve seat materials used, minute leakage of the doser valve occurs. This leakage may promote fuel to coke and clog the spray orifice of the doser valve compromising specific spray patterns, decreasing the efficiency of the filter cleaning process and of the engine. 
     SUMMARY 
     A system for purging a device for injecting fuel into an exhaust system of an engine comprising a device having an input and an output coupled to an exhaust system, at least one air valve and at least one fuel valve. The air valve has an input an input coupled to an air supply and an output coupled to the device through a check valve. The fuel valve has an input coupled to a fuel supply and an output coupled to the device through a check valve. When the air valve is open and the fuel valve is closed, air flows from the air supply to the device and is injected into the exhaust system of the engine. When the air valve is closed and the fuel valve is open, fuel flows from the fuel supply to the device and is injected into the exhaust system of the engine. 
     In an alternate embodiment, the fuel valve and air valve are combined into a single two position valve. When the single two position valve is in a first position, the air valve portion of the single two position valve is open and the fuel valve portion is closed, air flows from the air supply to the device and is injected into the exhaust system of the engine. When the single two position valve is in a second position, the air valve portion of the valve is closed and the fuel valve portion of the valve is open, fuel flows from the fuel supply to the device and is injected into the exhaust system of the engine. The single two position valve also has a transitional position in which the air valve portion and the fuel valve portion are closed and neither fuel or air flows to the device (closed cross over). 
     In another embodiment, the air valve is comprised of a first air valve and second air valve whose positions are controlled by a pilot air control valve. The output of the first air valve is the input of the second air valve and volume is coupled to the output of the first air valve and the input of the second air valve. The pilot air control valve has an input coupled to the air supply and an output coupled to the fuel valve, the first air valve, and the second air valve. When the pilot air control valve is open, the air flows to and actuates the first air valve, second air valve, and fuel valve. 
     When the pilot air control valve is closed, the first air valve is closed, the second air valve is open and the fuel valve is closed, air from the volume flows to the device and is injected into the exhaust system of the engine. 
     When the pilot air control valve is open, the first air valve is open, the second air valve is closed, and the fuel valve is open, air from the air supply flows into the volume, and fuel flows from the fuel supply to the device and is injected into the exhaust system of the engine. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1  shows a schematic of an exhaust after-treatment dosing system of the first embodiment of the present invention. 
         FIG. 2   a  shows a schematic of an exhaust after-treatment dosing system of the second embodiment of the present invention with air purging the doser valve. 
         FIG. 2   b  shows a schematic of an exhaust after-treatment dosing system of the second embodiment of the present invention with fuel entering doser valve. 
         FIG. 3  shows a schematic of an exhaust after-treatment dosing system of the third embodiment of the present invention. 
         FIG. 4  shows a schematic of an exhaust after-treatment dosing system of the fourth embodiment of the present invention. 
         FIG. 5  shows a schematic of exhaust after-treatment dosing system with dual lines. 
         FIG. 6  shows a schematic of exhaust after-treatment dosing system mounted on the exhaust tube. 
         FIG. 7  shows a schematic of a cross-section of  FIG. 6 . 
         FIG. 8  shows a cross-section of the shut off valves of  FIGS. 5 and 6 . 
         FIG. 9  shows a cross-section of the check valve assembly interface with the doser valve of  FIGS. 5 and 6 . 
         FIG. 10   a - 10   c  show schematics of an exhaust after-treatment dosing system integrated into an injector or remotely mounted in the engine with the use of a line between the valve and an injector nozzle 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows an exhaust after-treatment dosing system of a first embodiment. The exhaust after-treatment dosing systems include a valve assembly  2 , a check valve assembly  13 , and a device for injecting fuel into an exhaust system, for example a doser valve  17 . The check valve assembly  13  is preferably installed as close to the inlet of the doser valve  17  as possible. An advantage of having the check valve assembly  13  near the doser valve  17  is that the line  18  to the doser valve  17  is short and only a minimum amount of fuel needs to be purged from the line. The air and fuel valve assembly  2  is located upstream of the check valve  13  assembly. Dual lines  7 ,  12  are used between the valve assembly  2  and the check valve assembly  13  as shown in  FIGS. 5-9 . It should be noted that while only two valves (one for air and one for fuel) are shown in  FIGS. 5-9 , multiple valves may be present. 
     A supply of air  3  is provided to a solenoid controlled on/off air valve  5  within the valve assembly through line  4 . When the solenoid controlled air valve  5  is turned on, or the solenoid is energized, the air valve  5  is moved to a position such that air may pass through the air valve  5  to line  7  leading to the check valve assembly  13  and the doser valve  17 . When the solenoid is de-energized, a spring  6  biases the air valve  5  to a position where the air from line  4  is blocked and prevented from entering line  7  leading to the check valve assembly  13 . The pressure of the air supply may be regulated. 
     Regulated fuel  8  is supplied to a solenoid controlled on/off fuel valve  10  within the valve assembly through line  9 . When the solenoid controlled fuel valve  10  is turned on, or the solenoid is energized, the fuel valve  10  is moved to a position such that fuel may pass through the fuel valve  10  to line  12  leading to the check valve assembly  13  and the doser valve  17 . When the solenoid is de-energized, a spring  11  biases the fuel valve  10  to a position where the regulated fuel from line  9  is blocked and prevented from entering line  12  leading to the check valve assembly  13 . 
     The check valve assembly  13  includes a first check valve  14  and a second check valve  15  each leading to line  16  leading and the doser valve  17 . The check valves  14  and  15  prevent air from moving into fuel line  12  and fuel from moving into air line  7 . The check valve assembly  13  may be present close to the doser valve or in the valve assembly. 
     The air valve  5  and fuel valve  10  are controlled by the ECU and both valves preferably have low internal leakage. 
     The doser valve  17  is any prior art doser valve. 
       FIGS. 2   a  and  2   b  show exhaust after-treatment dosing system of a second embodiment. The exhaust after-treatment dosing system includes a valve assembly  20 , a check valve assembly  13 , and a device for injecting fuel into an exhaust system, preferably a doser valve  17 . The valve assembly  20  is located upstream of the check valve  13  assembly. The check valve assembly  13  is preferably installed as close to the inlet of the doser valve as possible. An advantage of having the check valve assembly  13  near the doser valve  17  is that the line  18  leading to the doser valve is short and only a minimum amount of fuel needs to be purged from the line. Dual lines  7 ,  12  are used between the valve assembly  20  and the check valve assembly  13  as shown in  FIGS. 5-9 . It should be noted that while only two valves (one for air and one for fuel) are shown in  FIGS. 5-9 , multiple valves may be present as shown in  FIGS. 2   a  and  2   b.    
     A supply of air  3  is supplied to a solenoid controlled three way air control valve V 1  through line  4 . The three way air control valve V 1  controls the air pressure to a fuel valve V 2 , as well as to two other air valves V 3 , V 4 . 
     The first air valve V 3  and the second air valve V 4  have two positions. In a first or default position of the first air valve V 3 , air from line  24 , which is connected to line  4  and the air supply  3 , is blocked from moving through the first air valve V 3 . In a second position of the first air valve V 3 , air from line  24  may pass through the air valve V 3  and into a finite volume VOL. 
     In a first or default position of the second air valve V 4 , air from finite volume VOL may move through the second air valve V 4  to line  7  leading to the check valve assembly  13  and the doser valve  17 . In a second position, air from the finite volume VOL is blocked from moving into line  7  leading to the check valve assembly  13  and the doser valve  17 . 
     A supply of fuel  8  is supplied to a fuel valve  32  or V 2  through line  9 . The fuel valve V 2  is moved from a first position to a second position by air pressure in line  36 . When air pressure is not present, spring  33  moves the fuel valve V 2  to a first or default position where fuel is blocked from enter line  12  leading to the check valve assembly  13  and the doser valve  17 . When air pressure is present, the fuel valve V 2  is moved to a second position where fuel moves from line  9 , through the valve to line  12  leading to the check valve assembly  13  and the doser valve  17 . 
     If the three way air control valve V 1  is in a position where air is blocked from line  4  from entering line  34  and  36 , connecting the air valves V 3 , V 4  and the fuel valve V 2  together, then all of the valves are biased by springs  27 ,  29 ,  33  to their first position or default position and any air in lines  34  and  36  is vented to atmosphere. 
     Referring to  FIG. 2   a , at the end of a dosing cycle, the solenoid controlled three way air control valve V 1  is de-energized, and the spring  23  biases the air control valve V 1  to a position where regulated air in line  4  is blocked from entering lines  34  and  36  leading to the fuel valve V 2 , the first air valve V 3  and the second air valve V 4 , and lines  34  and  36  are vented to atmosphere. Without the air pressure, the first air valve V 3  is spring  27  biased to the first or default position blocking the air from line  24 . The second air valve V 4  is moved to the first or default position allowing air present in the finite volume VOL to discharge its air through the second air valve V 4  and into line  7  leading to the check valve assembly  13  and the doser valve  17 . Air from the finite volume VOL will continue to dispense into line  7  through the check valve assembly  13  and into the doser valve  17  until the finite volume VOL is empty or the doser valve  17  is de-energized. 
     When the solenoid controlled three way air control valve V 1  is energized, the valve V 1  is moved to a position where air is provided to the fuel valve V 2  and the first and second air valves V 3 , V 4  as shown in  FIG. 2   b . The force of the air is greater than the spring force of springs  27 ,  29  on the first and second air valves V 3 , V 4  and move the first and second air valves V 3 , V 4  to their second positions. With the air valves in their second positions, air from line  24  may pass through the first air valve V 3  to line  37 , pressurizing the finite volume VOL, but is blocked by the second air valve V 4  from entering the check valve assembly  13  and the doser valve  17 . At the same time, the fuel from line  9  may pass through the fuel valve V 2  leading to line  12  and the check valve assembly  13  and doser valve  17 . 
     The check valve assembly  13  includes a first check valve  14  and a line  16  leading to the doser valve  17  and a second check valve  15  and a line  16  leading to the doser valve  17 . The check valves  14  and  15  prevent air from moving into fuel line  12  and fuel from moving into air line  7 , respectively. The check valve assembly  13  may be present close to the doser valve  17  as shown on the “hot” side of the engine or in the valve block on the “cold” side of the engine that houses the valves  5 ,  10 . 
     The three way air control valve V 1  is controlled by the ECU, the only electrical interface being used with this system to dispense a controlled volume of air for purging fuel from the inlet line to the doser valve. These features simplify installation and conserve air. 
       FIG. 3  shows an exhaust after-treatment dosing system of a third embodiment. The exhaust after-treatment dosing system includes a valve assembly  32  with a pressure regulator  60  and a fuel valve  43 , a check valve assembly  13 , and a device for injecting fuel into the exhaust system, for example a doser valve  17 . The check valve assembly  13  may be built into the inlet of the doser valve  17 . An advantage of having the check valve assembly  13  near the doser valve  17  is that the line  18  leading to the doser valve  17  is short and only a minimum amount of fuel needs to be purged from the line. The pressure regulator  60  and fuel valve  43  are located upstream of the check valve  13  assembly. Dual lines  7 ,  12  are used between the pressure regulator  60  and fuel valve  43  and the check valve assembly  13  similar to  FIGS. 5-9 . 
     Fuel  8  is supplied to a solenoid controlled on/off fuel valve  43  through line  9 . When the solenoid is energized, the fuel valve  43  is moved to a position such that fuel may pass through the fuel valve  43  to line  12  leading to the check valve assembly  13  and the doser valve  17 . When the solenoid is de-energized, a spring  44  biases the fuel valve  43  to a position where the regulated fuel from line  9  is blocked and prevented from entering line  12  leading to the check valve assembly  13 . 
     An air pressure regulator  60  provides a low pressure preset continuous air pressure to the check valve assembly  13  and the doser valve  17 . The constant air pressure supplied to the doser valve  17  minimizes coking of the outlet orifice as shown in  FIGS. 7 and 9 . The continuous air pressure supplied by the air pressure regulator  60  is generally less than the fuel system pressure and is shown as less than 3.0 Bar, although other pressures may be used. 
     The check valve assembly  13  includes a first check valve  14  and a line  16  leading to the doser valve  17  and a second check valve  15  and a line  16  leading to the doser valve  17 . The check valves  14  and  15  prevent air from moving into fuel line  12  and fuel from moving into air line  7 . The check valve assembly  13  may be present close to the doser valve or in the valve assembly  32 . 
     When the fuel valve  43  is moved to a position such that fuel may pass through the fuel valve  43  to line  12  leading to the check valve assembly  13  and the doser valve  17 , the fuel pressure will hold check valve  14  closed, blocking air flow. Once the fuel valve  43  is de-energized, blocking the flow of fuel to the check valve assembly  13 , continuous air pressure is applied to the doser valve  17 . 
       FIG. 4  shows an exhaust after-treatment dosing system of a fourth embodiment. The exhaust after-treatment dosing systems include a valve assembly  32  with a pressure regulator  60  and a fuel valve  43 , a check valve assembly  13 , and device for injecting fuel into an exhaust system, for example, single or multiple orifices  58  of a nozzle (not shown) that creates desired spray plume and atomization of fuel. A doser valve (not shown) is also present upstream to control the fuel supply to the orifice(s) of the nozzle. The check valve assembly  13  may be located near the orifices of the nozzle. An advantage of having the check valve assembly  13  near the orifices is that the line  18  leading to the doser valve  17  is short and only a minimum amount of fuel needs to be purged from the line. The pressure regulator  60  and fuel valve  43  are located upstream of the check valve  13  assembly. Dual lines  7 ,  12  are used between the pressure regulator  60  and fuel valve  43  and the check valve assembly  13  similar to  FIGS. 5-9 . 
     Fuel  8  is supplied to a solenoid controlled on/off fuel valve  43  through line  9 . When the solenoid of the fuel valve  43  is energized, the fuel valve  43  is moved to a position such that fuel may pass through the fuel valve  43  to line  12  leading to the check valve assembly  13  and the orifice(s)  58 . When the solenoid is de-energized, a spring  44  biases the fuel valve  43  to a position where the regulated fuel from line  9  is blocked and prevented from entering line  12  leading to the check valve assembly  13 . 
     An air pressure regulator  60  provides a low pressure preset continuous air pressure to the check valve assembly and the orifice(s). The constant air pressure supplied to the orifice(s) minimizes coking of the outlet orifice (s). The continuous air pressure supplied by the air pressure regulator  60  is less than the fuel system pressure and is shown as less than 3.0 Bar, although other pressures may be used. 
     The check valve assembly  13  includes a first check valve  14  and a line  16  leading to orifice(s) of a nozzle and a second check valve  15  and a line  16  leading to orifice(s) of a nozzle. The check valves  14  and  15  prevent air from moving into fuel line  12  and fuel from moving into air line  7 . The check valve assembly  13  may be present close to the nozzle or in the valve assembly  32 . 
     When the fuel valve  43  is moved to a position such that fuel may pass through the fuel valve  43  to line  12  leading to the check valve assembly  13  and the orifices of the nozzle, the fuel pressure will hold check valve  14  closed, blocking air flow. Once the fuel valve  43  is de-energized, blocking the flow of fuel to the check valve assembly, continuous air pressure is applied to the orifice(s) of the nozzle. 
       FIGS. 10   a - 10   c  show an exhaust after-treatment dosing system of a fifth embodiment. The exhaust after-treatment dosing system includes a single two position valve  70  that combines the air valve and fuel valve into a single valve and may be integrated into an injector with a nozzle  75  or remotely mounted in the engine compartment with the use of a line  73  between the valve  70  and an injector with a nozzle  75 . 
     A supply of air  3  and fuel  8  are provided to the solenoid  72  controlled two position valve  70  through lines  4  and  9  respectively. The pressure of the air supply may be regulated or unregulated air. The air source is preferably from the vehicle, for example the air may be from turbo boost air or the air brake system. The fuel source is preferably from the vehicle fuel supply and dispenses pulses of fuel to the injector&#39;s nozzle  75 . The valve  70  is connected to the injector&#39;s nozzle  75  through line  73 . From the injector&#39;s nozzle  75 , air or fuel is expelled into the engine exhaust system  76  of the engine. 
     In a first position of the two position valve  70 , as shown in  FIG. 10   a , the solenoid  72  is “off” and the spring  71  moves the two position valve  70  to a position in which the fuel from fuel supply  3  is blocked from exiting line  9  and reaching line  73  leading to the injector nozzle  75 . Air from the air supply  3  is allowed to flow from line  4  at a constant rate through the valve  70  to line  73  and the injector nozzle  75  to prevent injector coking from occurring. 
     When the solenoid  72  is turned “on” and the force of the solenoid  72  on the two position valve  70  is greater than the force of the spring  71 , the two position valve  70  moves to a second position as shown in  FIG. 10   b . In the second position, air from the air supply  3  is blocked from exiting line  4  and reaching line  73  leading to the injector nozzle  75 . Fuel from the fuel supply  8  is allowed to flow from line  9  at a constant rate through the valve  70  to line  73  and the injector nozzle  75 . 
     With the pulsing of the solenoid controlled by a pulse width modulated (PWM) signal at varying or constant duty cycle at a varying or constant frequency from the ECU, the air pulses between each fuel pulse allowed through the two position valve  70  to the injector nozzle  75 , aids in preventing injector nozzle coking and improves fuel atomization. 
     It should be noted that when the two position valve  70  moves from the first position to the second position, the supply of air  3  from line  4  to line  73  leading to the nozzle  75  is blocked prior to line  73  being open to receiving fuel from the fuel supply  8 . Similarly, when the two position valve  70  moves from the second position to the first position, the supply of fuel  8  from line  9  leading to the nozzle  75  is blocked prior to line  73  being open to receiving air from the air supply  3 . 
     The two position valve  70  also has a transitional or cross over position, as shown in  FIG. 10   c , in which the force of the solenoid  72  on one side of the valve  70  is equal to the spring force  71  on the opposite side of the valve. In this position, the supply of air  3  from line  4  and the supply of fuel  8  from line  9  are both blocked from line  73  leading to the injector nozzle  75 . Ultimately, air continues to flow when the electrical signal to the solenoid is removed. 
     Accordingly, it is to be understood that the embodiments of the invention herein described are merely illustrative of the application of the principles of the invention. Reference herein to details of the illustrated embodiments is not intended to limit the scope of the claims, which themselves recite those features regarded as essential to the invention.