Abstract:
A secondary air system comprising a variable speed air pump and a gated check valve connected between the variable speed air pump and an IC engine. The gated check valve has two ports, and generally, a first of the two ports is connected to a first bank of engine cylinders, and a second of the two ports is connected to a second bank of engine cylinders. The system further comprises a controller for controlling the speed of the variable speed air pump, and the positioning of the gated check valve. The gated check valve is operable to fully close air flow to both ports, fully open air flow to one of the two ports, or variably split air flow between the two ports.

Description:
FIELD 
       [0001]    The present disclosure relates to secondary air systems used in partial zero emissions vehicles (PZEVs) 
       BACKGROUND 
       [0002]    Secondary air systems are common in many vehicles and are used to add oxygen to exhaust gases, aiding in final burn off of any undesirable emissions. Generally, secondary air systems operate by pumping fresh air into the exhaust by a simple electrical/mechanical air pump or a special one-way reed valve that utilizes the pulsing of the exhaust from the piston firings to draw the fresh air in. The secondary air, now mixed with exhaust, is injected into the exhaust manifolds, catalytic converters, or both. 
         [0003]    In smaller engines, the secondary air system is generally used only at startup to help burn the rich air-to-fuel mixture needed to run a cold engine. Once the catalytic converter is at operational temperature, the secondary air system is shut down as it is no longer needed. 
       SUMMARY 
       [0004]    In one form, the present disclosure provides a secondary air system for an internal combustion engine comprising a variable speed air pump and a gated check valve connected between the variable speed air pump and the IC engine. The gated check valve generally has two ports. A first of the two ports is generally connected to a first bank of engine cylinders, and a second of the two ports is generally connected to a second bank of engine cylinders. However, one of the two ports can be capped, and the system used to drive a single bank of engine cylinders as well. The gated check valve is operable to fully close air flow to both ports or fully open air flow to one of the two ports, or variably split air flow between the two ports. 
         [0005]    The secondary air system also generally comprises a controller for controlling the speed of the variable speed air pump, and the positioning of the gated check valve, and at least one delta pressure feedback sensor positioned between a junction point where the variable speed air pump and gated check valve are connected, and one of the output ports of the gated check valve. The speed of the variable speed air pump is determined by comparing a measured air pressure from the delta pressure feedback sensor and comparing the measured air pressure to a desired air pressure, and can be adjusted based on the determination. 
         [0006]    The present disclosure also provides an air pump for a secondary air system comprising a fan motor contained within housing and being operable to be driven by a controller at a variable speed to draw air in from an input port and direct it towards an output port. The speed of the fan motor is adjustable. 
         [0007]    The present disclosure further provides a multi-position gated check valve for a secondary air system, the check valve comprising a housing having an input port and two output ports, and a plug mounted on a motor within the housing, the plug being operable by a controller to direct air flow from the input port to the output ports. The plug is operable to be positioned to fully close air flow to both output ports or fully open air flow to one of the two output ports, or to variably split air flow between the two ports. The check valve can also include at least one delta pressure feedback sensor positioned between the input port and one of the output ports. 
         [0008]    Further areas of applicability of the present disclosure will become apparent from the detailed description, claims and drawings provided hereinafter. It should be understood that the detailed description, including disclosed embodiments and drawings, are merely exemplary in nature, intended for purposes of illustration only, and are not intended to limit the scope of the invention, its application, or use. Thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a schematic of a conventional secondary air system; 
           [0010]      FIG. 2  is a schematic of a secondary air system with variable speed air pump and gated check valve, in accordance with a disclosed embodiment; 
           [0011]      FIG. 3  is a schematic of a variable speed air pump; 
           [0012]      FIG. 4  is a schematic of a gated check valve; 
           [0013]      FIGS. 5A-5F  are schematics showing operation of the gated check valve of  FIG. 4 ; 
           [0014]      FIG. 6  is a schematic of a gated check valve with delta pressure feedback sensors; 
           [0015]      FIGS. 7A and 7B  are graphs showing closed loop calibration of a secondary air system with variable speed air pump; and 
           [0016]      FIGS. 8A and 8B  are graphs showing calibration of an input voltage to a variable speed air pump operating on an accessory power module voltage. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    In one form, the present disclosure provides a secondary air system combining a variable speed air pump and multi-positioned gated check valve. The gated check valve can have delta pressure feedback sensors at its input and output ports. The air pump is controlled using a pulse-width-modulated (PWM) signal. As air is drawn in by the variable speed air pump, it is directed to the desired engine bank by the gated check valve. In a dual bank engine, the check valve can be fully closed, open to only bank  1 , open to only bank  2 , or variably split. In a single bank engine, the check valve can be fully closed or open, but also partially open. 
         [0018]    This system allows for maximum control and can improve OBD (On-Board Diagnostics) and end of line diagnostics, and permits the removal of mass air flow (MAF) sensors found in conventional secondary air systems since air flow can be determined via the delta pressure sensors. It also eliminates the need for multiple check valves, as well as several hose and joint connections, which are common sources of air leakage. 
         [0019]    The variable speed air pump disclosed herein can be used in conventional secondary air systems, i.e., those that use pressure operated; vacuum actuated, or electrically controlled check valves. For instance, end of line diagnostics must check the integrity of the entire secondary air system. Having the ability to vary the airflow and head pressure, an end of line diagnostic can better control a pressure operated check valve. At lower controlled air flow, the check valve would remain closed, thus allowing hoses and junctions in front of the check valve to be checked. At higher speeds, the pressure controlled check valve will open and allow air to flow. The variability of airflow allows vehicles to achieve desirable emissions and testing requirements. 
         [0020]    Because the air pump is electronically controlled, it can be tuned for specific engine applications and different ambient conditions. It can also be adjusted as the air pump degrades, i.e., over the vehicle life cycle. A calibrator can target a specific or programmable amount of air to optimize an oxidation reaction. As a result, because the air is held constant, the fuel is also held constant, resulting in more consistent air injection and fuel control and a more stable cold start calibration catalyst light off technique. The vehicle can also perform this function automatically by measuring actual air flow against desired air flow using MAF or delta pressure feedback sensors, and adjusting an input voltage appropriately. The input voltage can be a PWM signal input from a controller, or, as an illustrative example, the accessory power module voltage in a hybrid vehicle. Closed-loop feedback is provided by the air flow level, because air flow will increase or decrease with voltage adjustment, whether by change in pulse width ( FIGS. 7A-7B ) or increasing/decreasing the voltage directly ( FIGS. 8A-8B ). This removes variability from air pump to air pump, since all pumps can be so calibrated. 
         [0021]    Additionally, like the variable speed air pump, the gated check valve disclosed herein can be used in conventional secondary air systems, i.e., those that use simple air pumps. In a dual bank engine, the gated check value permits maximum flow control capability and the ability to account for imbalances in air flow from bank to bank. In addition, only one check valve is needed, as opposed to two in other systems. As noted above, the gated check valve can also have delta pressure feedback sensors, which allows for the removal of MAF sensors. 
         [0022]    A conventional secondary air system  1  for a dual cylinder bank, V-6 internal combustion engine  10  is shown in  FIG. 1 . System  1  comprises an air pump  2  connected, via respective hoses  3   a  and  3   b , to a pair of check valves  4   a  and  4   b . The check valves  4   a ,  4   b  can be, e.g., pressure operated, vacuum actuated (in such case, a vacuum solenoid, not pictured, is included), or electrically controlled. A second set of hoses  5   a  and  5   b  connect airflow to points of injection  6   a  and  6   b  for each bank  11   a ,  11   b . Mass air flow (MAF) sensors  7   a  and  7   b  are respectively connected to hoses  3   a  and  3   b . Such conventional secondary air systems  1  are quite simple. Controller  30  is operable to turn air pump  2  either on or off, and open or close check valves  4   a  and  4   b  (if vacuum actuated, by activating the vacuum solenoid). As a result, there is no ability to tune such a conventional system  1 . 
         [0023]      FIG. 2  illustrates an exemplary secondary air system  100  having a variable speed air pump  120  and two-port multi-position gated check valve  140 , each operated by controller  130 . The variable speed air pump  120  and gated check valve  140  are coupled with an output port  125  of the variable speed air pump/input port  145  of the gated check valve. As shown in  FIG. 2 , the check valve  140  is coupled with an output port  125 , but it is understood that an intermediate member could be connected between them, so long as there is fluid communication between them. The gated check valve  140  directs air pumped in by the variable speed air pump  120  to either, both or none of cylinder banks  11   a  and  11   b  of engine  10 , via hoses  150   a ,  150   b.    
         [0024]    Optional delta-pressure feedback sensors  170   a  and  170   b  can be connected to the secondary air system  100  to measure pressure differentials between a point  141  at the junction of the output port  125  of the variable speed air pump/input port  145  of the gated check valve, and points  142   a ,  142   b  at output ports  146   a ,  146   b  of the gated check valve  140 . The speed of the variable speed air pump can be determined by comparing a measured air pressure from the delta pressure feedback sensor and comparing the measured air pressure to a desired air pressure. With a result, controller  130  can adjust the speed of the pump, either by changing a duty cycle (pulse width) of a PWM control signal, or increasing or decreasing a drive voltage. 
         [0025]      FIG. 3  shows variable speed air pump  120  in more detail. Variable speed air pump  120  comprises a housing having a controllable motorized fan  123  within the pump  120 , an input port  124  and an output port  125 . Electrical connector  129  permits air pump  120  to be controlled by controller  130 . Electrical connector  129  may deliver both electrical power and ground, as well as duty cycle or control information. The fan  123  is preferably pulse-width modulation (PWM) controlled, so that the duty cycle of an input signal can control the absolute speed of the fan, e.g., from 0% to 100%. However, it should be appreciated that the fan  123  can be directly voltage controlled, e.g., via the accessory power module voltage as on a hybrid electric vehicle 
         [0026]      FIG. 4  shows a two-port multi-position gated check valve  140  in more detail. The check valve  140  comprises a series of spaced apart valve walls  148   a ,  148   b  and  148   c  mounted within a housing  140  which permit direction of airflow out of the valve ports. Two-port multi-position gated check valve  140  comprises a plug  144  mounted on a motor  143 , preferably a stepper motor, contained within a housing of the valve  140 , rotatably configured to direct or block airflow between one or more of the valve walls  148   a ,  148   b  and  148   c . The plug  144  is, for example, rubberized to ensure a tight seal when in a desired position against valve walls  148   a ,  148   b  and  148   c . Electrical connector  149  permits valve  140  to be controlled by controller  130 . Electrical connector  149  may deliver both electrical power and ground, as well as control information. Although the gated check valve  140  is optimally used with dual bank engines, i.e., engine  10  in  FIG. 2 , it can also operate on single bank engines. In such case, a cap  147  is fitted to one of output ports  146   a ,  146   b.    
         [0027]      FIGS. 5A-5F  show various operational modes of gated check valve  140 .  FIG. 5A  shows plug  144  aligned to permit 50/50 airflow to both output ports  146   a ,  146   b .  FIG. 5B  shows plug  144  aligned to fully open port  146   a , but close port  146   b .  FIG. 5C  shows the opposite, with port  146   a  being closed and port  146   b  being fully open.  FIG. 5D  shows plug  144  aligned to provide a variable split airflow (60/40 is shown, but it should be understand any split, e.g., 53/47, or 61/39, could be achieved) to ports  146   a ,  146   b .  FIG. 5E  shows plug  144  in a fully closed position, i.e., one where no airflow exits ports  146   a ,  146   b .  FIG. 5F  shows valve  140  in a single bank configuration using cap  147 . It is understood that controller  130  is programmed to reconfigure valve  140  per  FIGS. 5A-5F . 
         [0028]      FIG. 6  shows the optional delta-pressure feedback sensors  170   a  and  170   b  installed on two-port multi-position gated check valve  140 . As shown, the sensors  170   a ,  170   b  can measure a pressure differential between the input port  145  and the output ports  146   a ,  146   b  of the gated check valve  140 . The controller  130  can use this information to adjust the valve  140  if needed