Patent Publication Number: US-11391249-B2

Title: Engine secondary air and EGR system and method

Description:
FIELD 
     The present application relates generally to secondary air and exhaust gas recirculation (EGR) systems for internal combustion engines and, more particularly, to an internal combustion engine having a single pump and valve system to drive secondary air, EGR, and boost air to improve engine transient acceleration. 
     BACKGROUND 
     Secondary air systems are typically utilized in vehicles during engine cold start operations to add oxygen to exhaust gases. Because the engine is cold, exhaust emissions tend to be high. To reduce warm up time, the engine is operated with a richer air-to-fuel ratio and mixed with the secondary air. Once the exhaust system is at operational temperature, the secondary air system is shut down. 
     Additionally, vehicles typically include an exhaust gas recirculation (EGR) system, which recirculates a portion of engine exhaust gas back to the air intake to reduce emissions. The EGR is driven by the pressure difference between the exhaust system point of EGR extraction and the intake system point of EGR insertion. Typically, the insertion point is immediately after the throttle to take advantage of the lower pressure created when the throttle is partially open. However, the greater the opening of the throttle, the less lower pressure is created after the throttle thus potentially resulting in lowered EGR driving capability. Therefore, while such systems work well for their intended purpose, it is desirable to provide continuous improvement in the relevant art. 
     SUMMARY 
     In accordance with one example aspect of the invention, an internal combustion engine system is provided. In one example implementation, the system includes an engine, an air intake system configured to provide intake air to the engine, and an exhaust system configured to receive exhaust gas from the engine. The engine system further includes a secondary air system including a pump, an exhaust gas recirculation (EGR) system, and a valve system operably associated with the secondary air system and the EGR system. The valve system is configured to operate in a secondary air mode where the pump is utilized to supply secondary air to the exhaust system, and an EGR mode where the pump is utilized to supply EGR to the air intake system. 
     In addition to the foregoing, the described engine system may include one or more of the following features: wherein in the secondary air mode, the pump is utilized to supply secondary air to the exhaust system while EGR is prevented from being supplied to the air intake system; wherein in the EGR mode, the pump is utilized to supply EGR to the air intake system while secondary air is prevented from being supplied to the exhaust system; wherein in the EGR mode, the pump is utilized to supply EGR to the air intake system without relying on a lower pressure behind a throttle of the intake air system; and wherein in the EGR mode, the pump is utilized to supply EGR to the air intake system when a throttle of the intake air system is substantially closed. 
     In addition to the foregoing, the described engine system may include one or more of the following features: wherein the valve system is configured to further operate in a boost mode where the pump is utilized to provide boost air to the air intake system through both a portion of the secondary air system and a portion of the EGR system; wherein the valve system includes a first three-way valve; wherein the valve system further includes a second three-way valve; and wherein the secondary air system further includes a secondary air intake conduit coupled between the air intake system and the valve system, and a secondary air supply conduit coupled between the valve system and the exhaust system. 
     In addition to the foregoing, the described engine system may include one or more of the following features: wherein the EGR system includes an EGR intake conduit coupled between the exhaust system and the valve system, and an EGR supply conduit coupled between the valve system and the intake air system; a turbocharger assembly having a compressor and a turbine; and wherein the valve system includes a first three-way valve and a second three-way valve, wherein the secondary air system further includes a secondary air intake conduit coupled between the air intake system and the second three-way valve, and a secondary air supply conduit coupled between the first three-way valve and the exhaust system, and wherein the EGR system includes an EGR intake conduit coupled between the exhaust system and the second three-way valve, and an EGR supply conduit coupled between the first three-way valve and the intake air system. 
     In addition to the foregoing, the described engine system may include one or more of the following features: a connecting conduit coupled between the first and second three-way valves; wherein the pump is disposed on the connecting conduit between the first and second three-way valves and configured to selectively draw secondary air through the secondary air intake conduit or the EGR intake conduit; and wherein in the secondary air mode, the pump is utilized to supply secondary air to the exhaust system while EGR is prevented from being supplied to the air intake system, and wherein in the EGR mode, the pump is utilized to supply EGR to the air intake system while secondary air is prevented from being supplied to the exhaust system. 
     In accordance with another example aspect of the invention, a method is provided for selectively providing secondary air and exhaust gas recirculation (EGR) in an internal combustion engine system having an air intake system and an exhaust system by utilizing a single pump and a valve system operably coupled to a secondary air system and an EGR system. In one example implementation, the method includes operating in a secondary air mode by moving the valve system to a position allowing secondary airflow to the valve system and preventing EGR flow to the valve system, and operating the single pump to supply secondary air through the secondary air system to the exhaust system. The method further includes operating in an EGR mode by moving the valve system to a position allowing EGR flow to the valve system and preventing secondary air flow to the valve system, and operating the single pump to supply EGR through the EGR system to the intake air system. 
     In addition to the foregoing, the described method may include one or more of the following features: operating a boost mode by moving the valve system to a position allowing secondary airflow to the valve system and preventing EGR flow to the valve system, further moving the valve system to a position allowing the secondary airflow to flow through a portion of the EGR system to the air intake system, and operating the single pump to supply boost air through a portion of the secondary air system and the portion of the EGR system to the air intake system. 
     In addition to the foregoing, the described method may include one or more of the following features: wherein the step of moving the valve system to a position allowing secondary airflow to the valve system and preventing EGR flow to the valve system comprises moving a first three-way valve to a position allowing secondary airflow to flow to the exhaust system, and moving a second three-way valve to a position allowing secondary airflow through the second three-way valve and preventing EGR flow through the second three-way valve; and wherein the step of moving the valve system to a position allowing EGR flow to the valve system and preventing secondary air flow to the valve system comprises moving a first three-way valve to a position allowing EGR flow to flow to the intake system, and moving a second three-way valve to a position allowing EGR flow through the second three-way valve and preventing secondary airflow through the second three-way valve. 
     Further areas of applicability of the teachings of the present disclosure will become apparent from the detailed description, claims and the drawings provided hereinafter, wherein like reference numerals refer to like features throughout the several views of the drawings. It should be understood that the detailed description, including disclosed embodiments and drawings references therein, are merely exemplary in nature intended for purposes of illustration only and are not intended to limit the scope of the present disclosure, its application or uses. Thus, variations that do not depart from the gist of the present disclosure are intended to be within the scope of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustration of an example naturally aspirated engine with secondary air and EGR systems, in accordance with the principles of the present application; and 
         FIG. 2  is a schematic illustration of an example charged engine with secondary air and EGR systems, in accordance with the principles of the present application. 
     
    
    
     DESCRIPTION 
     Described herein are systems and methods utilizing a single pump to drive EGR, drive secondary air to mitigate engine out emissions, and drive boost air to improve transient acceleration of an internal combustion engine. The systems include dual three-way valves to selectively switch between driving secondary air, EGR, and boost air to improve vehicle and engine performance. When utilized for EGR, the driving capability no longer relies on the lower pressure behind the throttle, thus enabling EGR when the throttle fully open or substantially fully open. This extended EGR usage range allows for the use of EGR to reduce knock sensibility in engine operating points where the throttle is open or substantially open, thereby reducing fuel consumption by allowing the spark to be advanced. When utilized engine boost (e.g., improved acceleration), the pump increases air flow at engine intake thereby boosting the charge and allowing for more fuel to be injected and reducing the time for engine response. 
     With initial reference to  FIG. 1 , an example naturally aspirated engine system is illustrated and generally identified at reference numeral  10 . In the example embodiment, naturally aspirated engine system  10  generally includes an engine  12 , an air intake system  14 , an exhaust system  16 , a secondary air system  18 , and an exhaust gas recirculation (EGR) system  20 . As described herein in more detail, the engine system  10  further includes a valve system  24  configured to selectively drive secondary air, EGR, and boost air to improve vehicle performance and capability. 
     With continued reference to  FIG. 1 , the air intake system  14  includes an air intake conduit  30  having an air inlet  32  configured to receive fresh or recirculated air, an air filter  34 , and a throttle  36 . Air intake conduit  30  is fluidly coupled to engine  12 , and the throttle  36  is configured to selectively move between open and closed positions to regulate the amount of air and/or fuel supplied to cylinders  38  of the engine  12 . The exhaust system  16  includes an exhaust manifold  50  configured to supply an exhaust gas from the cylinders  38  to an exhaust gas conduit  52 . One or more exhaust gas aftertreatment components  54 , such as a catalytic converter, are disposed within exhaust gas conduit  52  to treat the exhaust gas. The treated exhaust gas is then directed to the EGR system  20  or exhaust to the atmosphere via exhaust gas outlet  56 . 
     In the example embodiment, the secondary air system  18  generally includes a secondary air intake conduit  60 , a secondary air supply conduit  62 , and a secondary air pump  64 . The secondary air pump  64  is configured to supply secondary air via the secondary air supply conduit  62  to a location in the exhaust gas conduit  52  upstream of the aftertreatment component(s)  54 . 
     In the illustrated example, the EGR system  20  generally includes an EGR intake conduit  70 , an EGR supply conduit  72 , and an EGR cooler  74 . An optional EGR valve  76  is configured to control the flow of exhaust gas into the EGR intake conduit  70  where the EGR flow is subsequently cooled within the EGR cooler  74 . The cooled EGR flow is then directed via the EGR supply conduit  72  to a location on the air intake conduit  30  upstream of the engine  12  for supplying the EGR flow thereto. In the illustrated example, the EGR supply conduit  72  is fluidly coupled to the air intake conduit  30  at a location downstream of the throttle  36  and upstream of the engine  12 . However, it will be appreciated that EGR supply conduit  72  may be coupled to the air intake conduit  30  in various locations such as, for example, upstream of the throttle  36  and downstream of the air filter  34 . 
     In the example embodiment, the valve system  24  generally includes a first three-way valve  80  and a second three-way valve  82  in signal communication with a controller  84 , which may also be in signal communication with throttle  36 , pump  64 , and/or EGR valve  76 . The first three-way valve  80  includes a rotatable flapper  86  configured to selectively seal air flow through one of the secondary air supply conduit  62  and the EGR supply conduit  72 . The second three-way valve  82  includes a rotatable flapper  88  configured to selectively seal flow from one of the secondary air intake conduits  60  and the EGR intake conduit  70 . As shown in  FIG. 1 , a connecting conduit  90  is fluidly coupled between an outlet of the second valve  82  and an inlet of the first valve  80 . In the illustrated example, the pump  64  is disposed on the connecting conduit  90  between the first and second valves  80 ,  82 . Although described as flapper-type valves, it will be appreciated that valves  80  and  82  may be any suitable type of valve that enables system  10  to function as described herein. 
     In one example operation, controller  84  is configured to operate naturally aspirated engine system  10  in (i) a normal mode, (ii) a secondary air mode, (iii) an EGR mode, and (iv) a boost mode. As shown in  FIG. 1 , operation in (i) normal mode produces an air/exhaust flow shown by line  92 , operation in (ii) secondary air mode produces an air/exhaust flow shown by line  94 , operation in (iii) EGR mode produces an air/exhaust flow shown by line  96 , and operation in (iv) boost mode produces an air/exhaust flow shown by line  98 . 
     In the example (i) normal mode operation, controller  84  is programmed to turn secondary air pump  64  off and valve  80  to close path  72  and valve  88  to close path  70 . In this configuration, shown by line  92 , air enters air intake conduit  30  via air inlet  32  and is directed to the engine  12  where it is mixed with fuel and combusted in cylinders  38 . The resulting exhaust gas is directed through the exhaust manifold  50  and exhaust gas conduit  52  to the exhaust gas outlet  56 . 
     In the example (ii) secondary air mode operation, for example during a cold start, controller  84  is programmed to operate first valve  80  to move flapper  86  to prevent flow into EGR supply conduit  72 , and operate second valve  82  to move flapper  88  to prevent flow from EGR intake conduit  70 . Controller  84  then turns on pump  64 , which as shown by line  94 , draws additional airflow into secondary air intake conduit  60 , through pump  64 , and subsequently through secondary air supply conduit  62 . In this way, secondary air is supplied to the exhaust system  16 . 
     In the example (iii) EGR mode operation, controller  84  is programmed to operate first valve  80  to move flapper  86  to prevent flow into secondary air supply conduit  62 , and operate second valve  82  to move flapper  88  to prevent flow from secondary air supply conduit  62 . Controller  84  then turns on pump  64 , which as shown by line  96 , draws EGR into the EGR intake conduit  70 , through pump  64 , and subsequently through EGR supply conduit  72 . Additionally, controller  84  may control the opening of EGR valve  76  to further vary the EGR flow into the EGR intake conduit  70 . In this way, EGR is supplied to the intake air system  14  for subsequent re-combustion in cylinders  38 . 
     In the example (iv) boost mode operation, controller  84  is programmed to operate first valve  80  to move flapper  86  to prevent flow into secondary air supply conduit  62 , and operate second valve  82  to move flapper  88  to prevent flow from EGR intake conduit  70 . Controller  84  then turns on pump  64 , which as shown by line  98 , draws air into the secondary air intake conduit  60 , through pump  64 , and subsequently through EGR supply conduit  72 . In this way, boost air is supplied to the intake air system  14  to increase air flow at engine intake, thereby boosting the charge and allowing for more fuel to be injected and reducing the time for engine response. 
     With reference now to  FIG. 2 , an example turbocharged engine system is illustrated and generally identified at reference numeral  110 . In the example embodiment, turbocharged engine system  110  generally includes an engine  112 , an air intake system  114 , an exhaust system  116 , a secondary air system  118 , an EGR system  120 , and a turbocharger assembly  122 . 
     As illustrated, turbocharger assembly  122  generally includes a compressor  126 , which is rotatably coupled to a turbine  128  via a shaft (not shown). The compressor  126  is configured to compress intake air and includes an inlet configured to receive ambient air, and an outlet in fluid communication with the vehicle engine  112 . The turbine  128  is configured to utilize exhaust gas to rotate the compressor  126  and includes an exhaust inlet configured to receive exhaust gas from the engine  112 , and an exhaust outlet fluidly coupled to the exhaust system  116 . 
     Similar to engine system  10 , the turbocharged engine system  110  includes a valve system  124  configured to selectively drive secondary air, EGR, and boost air to improve vehicle performance and capability. It will be appreciated, however, that the described secondary air systems, EGR systems, and valve systems may be utilized with other types of engine systems such as, for example, a supercharged engine system. 
     With continued reference to  FIG. 2 , the air intake system  114  generally includes an air intake conduit  130  having an air inlet  132  configured to receive fresh or recirculated air, an air filter  134 , and a throttle  136 . Air intake conduit  130  is fluidly coupled to engine  112  via the compressor  126 , and the throttle  136  is configured to selectively move between open and closed positions to regulate the amount of air and/or fuel supplied to engine cylinders  138 . The exhaust system  116  includes an exhaust manifold  150  configured to supply an exhaust gas from the cylinders  138  to the turbine  128  and subsequently to an exhaust gas conduit  152 . One or more exhaust gas aftertreatment components  154  are disposed within exhaust gas conduit  152  to treat the exhaust gas. The treated exhaust gas is then directed to the EGR system  120  or exhausted to the atmosphere via exhaust gas outlet  156 . 
     In the example embodiment, the secondary air system  118  generally includes a secondary air intake conduit  160 , a secondary air supply conduit  162 , and a secondary air pump  164 . The secondary air pump  164  is configured to supply secondary air via the secondary air supply conduit  162  to a location in the exhaust gas conduit  152  upstream of the aftertreatment component(s)  154  and downstream of the turbine  128 . 
     In the illustrated example, the EGR system  120  generally includes an EGR intake conduit  170 , an EGR supply conduit  172 , and an EGR cooler  174 . An optional EGR valve  176  is configured to control the flow of exhaust gas into the EGR intake conduit  170  where the EGR flow is subsequently cooled within the EGR cooler  174 . The cooled EGR flow is then directed via the EGR supply conduit  172  to a location on the air intake conduit  130  upstream of the engine  112  for supplying the EGR flow thereto. In the illustrated example, the EGR supply conduit  172  is fluidly coupled to the air intake conduit  130  at a location upstream of the compressor  126 . However, it will be appreciated that EGR supply conduit  172  may be coupled to the air intake conduit  130  in various locations. 
     In the example embodiment, the valve system  124  generally includes a first three-way valve  180  and a second three-way valve  182  in signal communication with a controller  184 , which may also be in signal communication with throttle  136 , pump  164 , and/or EGR valve  176 . The first three-way valve  180  includes a rotatable flapper  186  configured to selectively seal air flow through one of the secondary air supply conduits  162  and the EGR supply conduit  172 . The second three-way valve  182  includes a rotatable flapper  188  configured to selectively enable flow from one of the secondary air intake conduits  160  and the EGR intake conduit  170  by sealing off the other of the two. A connecting conduit  190  is fluidly coupled between an outlet of the second valve  182  and an inlet of the first valve  180 . In the illustrated example, the pump  164  is disposed on the connecting conduit  190  between the first and second valves  180 ,  182 . Although described as flapper-type valves, it will be appreciated that valves  180  and  182  may be any suitable type of valve that enables system  10  to function as described herein. 
     In one example operation, controller  184  is configured to operate turbocharged engine system  110  in (i) a normal mode, (ii) a secondary air mode, (iii) an EGR mode, and (iv) a boost mode. As shown in  FIG. 2 , operation in (i) normal mode produces an air/exhaust flow shown by line  192 , operation in (ii) secondary air mode produces an air/exhaust flow shown by line  194 , operation in (iii) EGR mode produces an air/exhaust flow shown by line  196 , and operation in (iv) boost mode produces an air/exhaust flow shown by line  198 . 
     In the example (i) normal mode operation, controller  184  is programmed to turn secondary air pump  164  off and valve  80  to close path  72  and valve  88  to close path  70 . In this configuration, as shown by line  192 , air enters air intake conduit  130  via air inlet  132  and is directed to the compressor  126  where the air is compressed (charged). The compressed air is subsequently directed to the engine  112  where it is mixed with fuel and combusted in cylinders  138 . The resulting exhaust gas is directed through the exhaust manifold  150  to the turbine  128  where it is utilized to transfer rotatable motion to the compressor  126  for compressing intake air. The exhaust gas is then directed via exhaust gas conduit  152  to the exhaust gas outlet  156  and atmosphere. 
     In the example (ii) secondary air mode operation, for example during a cold start, controller  184  is programmed to operate first valve  180  to move flapper  186  to prevent flow into EGR supply conduit  172 , and operate second valve  182  to move flapper  188  to prevent flow from EGR intake conduit  170 . Controller  184  then turns on pump  164 , which as shown by line  194 , draws additional airflow into secondary air intake conduit  160 , through pump  164 , and subsequently through secondary air supply conduit  162 . In this way, secondary air is supplied to the exhaust system  116 , for example, in a location downstream of the turbine  128 . 
     In the example (iii) EGR mode operation, controller  184  is programmed to operate first valve  180  to move flapper  186  to prevent flow into secondary air supply conduit  162 , and operate second valve  182  to move flapper  188  to prevent flow from secondary air supply conduit  162 . Controller  184  then turns on pump  164 , which as shown by line  196 , draws EGR into the EGR intake conduit  170 , through pump  164 , and subsequently through EGR supply conduit  172 . Additionally, controller  184  may control the opening of EGR valve  176  to further vary the EGR flow into the EGR intake conduit  170 . In this way, EGR is supplied to the intake air system  114  to a location upstream of compressor  126  for subsequent re-compression and re-combustion in cylinders  138 . 
     In the example (iv) boost mode operation, controller  184  is programmed to operate first valve  180  to move flapper  186  to prevent flow into secondary air supply conduit  162 , and operate second valve  182  to move flapper  188  to prevent flow from EGR intake conduit  170 . Controller  184  then turns on pump  164 , which as shown by line  198 , draws air into the secondary air intake conduit  160 , through pump  164 , and subsequently through EGR supply conduit  172  to a location upstream of compressor  126 . In this way, boost air is supplied to the intake air system  114  to increase air flow at engine intake, thereby boosting the charge and allowing for more fuel to be injected and reducing the time for engine response. 
     Described herein are systems and methods utilizing a single pump to drive EGR, drive secondary air to mitigate engine out emissions, and drive boost air to improve transient acceleration of an internal combustion engine. The systems include dual three-way valves to selectively the drive secondary air and EGR to improve vehicle and engine performance. Advantageously, the EGR driving capability is decoupled from the pressure difference created by the throttle movement. Thus, utilizing the pump, EGR can be used independently of the pressure difference and the EGR usage range can be extended outside of typical boundaries, thereby reducing fuel consumption by reducing knock tendency and advancing spark timing. 
     As used herein, the term controller or module refers to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that executes one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality. 
     It will be understood that the mixing and matching of features, elements, methodologies, systems and/or functions between various examples may be expressly contemplated herein so that one skilled in the art will appreciate from the present teachings that features, elements, systems and/or functions of one example may be incorporated into another example as appropriate, unless described otherwise above. It will also be understood that the description, including disclosed examples and drawings, is merely exemplary in nature intended for purposes of illustration only and is not intended to limit the scope of the present disclosure, its application or uses. Thus, variations that do not depart from the gist of the present disclosure are intended to be within the scope of the present disclosure.