Patent Publication Number: US-2022235725-A1

Title: Cylinder head with integrated catalyst

Description:
FIELD 
     The present application relates generally to internal combustion engine aftertreatment systems and, more particularly, to an internal combustion engine having a cylinder head with an integrated catalyst. 
     BACKGROUND 
     In conventional internal combustion aftertreatment systems it is difficult to achieve low tailpipe emissions in the time immediately following a cold engine start due to low catalyst conversion efficiency of cold catalysts. In order to achieve acceptable conversion efficiency, the catalyst must surpass a predetermined light-off temperature. In some systems, faster light-off temperatures may be achieved, but often at the cost of high exhaust system backpressure, durability, longevity, cost, and/or complexity. While such conventional 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, a cylinder head assembly for an internal combustion engine is provided. In one example implementation, the cylinder head assembly includes a cylinder head, a bypass passage formed within the cylinder head and defining a catalyst cavity, and a bypass catalytic converter disposed within the catalyst cavity. 
     In addition to the foregoing, the described cylinder head assembly may include one or more of the following features: wherein the bypass passage is integrally cast within the cylinder head; an integrated exhaust manifold formed in the cylinder head and including a main exhaust passage and an outlet, the integrated exhaust manifold configured to receive exhaust gas from exhaust ports of the internal combustion engine; wherein the bypass passage includes an inlet and an outlet, the bypass passage inlet fluidly coupled to the main exhaust passage; and a valve disposed within the bypass passage and configured to selectively allow exhaust gas flow through the bypass passage and thus the bypass catalytic converter. 
     In addition to the foregoing, the described cylinder head assembly may include one or more of the following features: a valve disposed within the main exhaust passage and configured to selectively allow exhaust gas flow through the main exhaust passage outlet to a main catalytic converter; a second valve disposed within the bypass passage and configured to selectively allow exhaust gas flow through the bypass passage and thus the bypass catalytic converter; a water jacket formed in the cylinder head proximate the catalyst cavity and configured to circulate a coolant to provide cooling to the bypass catalytic converter; and a service port formed in the cylinder head and configured to removably receive a cap, wherein the cap is removable to enable insertion or removal of the bypass catalytic converter through the service port. 
     In accordance with another example aspect of the invention, an internal combustion engine system is provided. In one example implementation, the system includes a cylinder head, an integrated exhaust manifold formed in the cylinder head and including a main exhaust passage having an outlet, and a bypass passage formed within the cylinder head and defining a catalyst cavity. An exhaust aftertreatment system includes a main exhaust conduit with a main catalytic converter, wherein the main exhaust conduit is fluidly coupled to both the main exhaust passage outlet and the bypass passage. A bypass catalytic converter is disposed within the catalyst cavity and configured to provide emissions reduction during cold start, long idle, and/or low main catalyst temperature conditions. 
     In addition to the foregoing, the described system may include one or more of the following features: a water jacket formed in the cylinder head proximate the catalyst cavity and configured to circulate a coolant to provide cooling to the bypass catalytic converter; wherein the bypass passage is fluidly coupled to the main exhaust conduit at a location upstream of the main catalytic converter; and a valve disposed within the bypass passage and configured to selectively allow exhaust gas flow through the bypass passage and thus the bypass catalytic converter. 
     In addition to the foregoing, the described system may include one or more of the following features: a valve disposed within the main exhaust passage and configured to selectively allow exhaust gas flow through the main exhaust passage outlet to a main catalytic converter; a second valve disposed within the bypass passage and configured to selectively allow exhaust gas flow through the bypass passage and thus the bypass catalytic converter; and a service port formed in the cylinder head and configured to removably receive a cap, wherein the cap is removable to enable insertion or removal of the bypass catalytic converter through the service port. 
     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 sectional view of an example cylinder head casting with an integrated auxiliary catalyst, in accordance with the principles of the present application; and 
         FIG. 2  is a sectional view of another example cylinder head casting with an integrated auxiliary catalyst, in accordance with the principles of the present application. 
     
    
    
     DESCRIPTION 
     Described herein are systems and methods for an emissions aftertreatment system of an internal combustion engine. An auxiliary catalyst is integrated into a bypass passage in the cylinder head and utilizes the cylinder head water jacket for liquid cooling thereof. During a cold start, long idle, and/or low main catalyst temperatures, exhaust gas is selectively bypassed into the auxiliary catalyst. The close proximity of the auxiliary catalyst to the exhaust gas in the cylinder head enables rapid heating to hasten the conversion rate of harmful exhaust constituents. Additionally, due to the liquid cooling, degradation of system catalytic conversion devices is reduced compared to conventional systems. 
     Some conventional aftertreatment systems have limited or no capacity to get the catalyst to a light-off temperature for efficient conversion of harmful exhaust constituents before approximately fifteen seconds post cold start in a turbocharged system. Every second the engine is running and the catalyst is not at or above light-off temperature, CO HC, and NOx are not being converted efficiently. The short time preceding the catalyst light-off is responsible for a very large portion of the CO, HC, and NOx breakthrough for on and off cycle starts and long idles. In conventional systems, one or more catalysts are traditionally located some distance downstream of the exhaust outlet of the heat and/or turbocharger outlet and are typically in the main exhaust flow for the entire useful life of the vehicle. 
     As the distance, wetted surface area, and thermal mass located between the exhaust ports and catalyst face increases, it becomes increasingly difficult to have the catalyst light-off in a timely manner. Common hardware designs to decrease time to light-off (e.g., decreasing distance), however, often come at the expense of the life of the catalyst because of higher temperature, gas velocities, and thermal gradients. Common calibration methods used to decrease light-off time include high RPM flare/start, very late ignition timing, and special injection strategies. However, such methods can potentially generate high temperature and high flow exhaust gases, which are good for light-off but can potentially cause undesirable NVH and aging characteristics along with increased fuel consumption. 
     Further, as a catalyst is subjected to exhaust flow, high temperatures, and/or unwanted chemicals, it slowly loses capacity for efficient conversion (catalyst aging). Conventional systems typically account for this catalyst aging by increasing precious metal loading, catalyst volume, and catalyst surface area, which can potentially be a resource burden increase complexity of the systems. 
     With reference to  FIG. 1 , an example cylinder head for an internal combustion engine is shown and indicated at reference numeral  10 . In the example embodiment, the cylinder head  10  is configured to selectively supply exhaust gas to a main exhaust aftertreatment system  12  and a light-off catalyst bypass system  14 . As described herein in more detail, the light-off catalyst bypass system  14  is selectively utilized during cold start, long idle, and/or cold catalyst conditions to rapidly heat to light-off temperatures to quickly achieve low tailpipe emissions. 
     As shown in  FIG. 1 , the cylinder head  10  generally defines an integrated exhaust manifold  20 , a bypass passage  22 , and a water jacket  24 . The integrated exhaust manifold  20  includes a plurality of cylinder exhaust passages  26  that merge together to form a main exhaust passage  28  having an outlet  30 . The bypass passage  22  includes an inlet  32 , an outlet  34 , and defines a catalyst cavity  36 , which is configured to removably receive a bypass catalytic converter or catalyst  38 , as described herein in more detail. Further, in the illustrated example, the catalyst cavity  36  includes a service port  40  configured to receive a removable cap or plug (not shown) to enable insertion/removal of the bypass catalyst  38 , for example, for replacement thereof. 
     In the example embodiment, the main exhaust aftertreatment system  12  generally includes a main exhaust conduit  50  having one or more main catalytic converters  52  to reduce or convert a desired exhaust gas constituent such as, for example, carbon monoxide (CO), hydrocarbon (HC), and/or nitrogen oxides (NOx). The main exhaust conduit  50  is fluidly coupled to the integrated exhaust manifold main outlet  30  (optionally via a turbocharger turbine  42 , shown in phantom) and configured to receive exhaust gas from the vehicle engine and supply the exhaust gas to the main catalytic converter  52 . In order to efficiently reduce or convert CO, HC, and NOx, the catalytic converter  52  must reach a predetermined light-off temperature. However, during some vehicle operations such as, for example, cold starts, long idle, and cold catalyst conditions, the catalytic converter  52  is below light-off temperature and therefore has a low catalyst conversion efficiency. 
     In order efficiently reduce or convert the unwanted exhaust gas constituents while the catalytic converter  52  is below the light-off temperature, the vehicle utilizes the light-off catalyst bypass system  14  to redirect at least a portion of the exhaust gas from the integrated exhaust manifold  20 , into the bypass passage  22 , and through the bypass catalyst  38 . Because the bypass catalyst  38  is integrated into the cylinder head  10 , it is in close proximity to the engine combustion chambers and receives the exhaust gas quicker and at a higher temperature than the main catalytic converter  52  would. Thus, the bypass catalyst  38  is rapidly heated to its predetermined light-off temperature to achieve high catalyst conversion efficiency before the main catalytic converter  52  alone. 
     In the example embodiment, the light-off catalyst bypass system  14  generally includes the bypass catalyst  38 , a first valve  60 , and a second valve  62 . The bypass catalyst  38  is disposed within the bypass passage  22 , which is fluidly connected to the main exhaust conduit  50  upstream of the main catalytic converter  52  by a bypass conduit  44  coupled to the bypass passage outlet  34 . The first valve  60  is located within the main exhaust passage  28  and is configured to move to any desired position between a fully open position  64  (in phantom) and a fully closed position  66  (in solid). The second valve  62  is located within the bypass passage  22  and is configured to move to any desired position between a fully open position  68  (in solid) and a fully closed position  70  (in phantom). Although illustrated in the example implementation as butterfly valves, it will be appreciated that valves  60 ,  62  may be any suitable valve that enables light-off catalyst bypass system  14  to operate as described herein. 
     A controller  72  (e.g., engine control unit) is in signal communication with the first valve  60  and the second valve  62  and is configured to move the first and second valves  60 ,  62  to any position between their respective fully open and fully closed positions. As used herein, the term controller 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. 
     In one example, the bypass catalyst  38  is a three-way catalyst configured to remove CO, HC, and NOx from the exhaust gas passing therethrough, as described herein in more detail. However, it will be appreciated that bypass catalyst  38  may be any suitable catalyst that enables light-off catalyst bypass system  14  to remove any desired pollutant or compound such as, for example, a hydrocarbon trap or a four-way catalyst. In another example, bypass catalyst  38  has a cell density of between approximately 800 and approximately 1200 cells per square inch, or between 800 and 1200 cells per square inch. 
     In the example embodiment, cylinder head  10  also includes a water jacket  24 . Advantageously, the water jacket  24  includes flow channels  74  extended to and disposed about the bypass passage  22  and the bypass catalyst  38 . In this way, the cylinder head coolant loop extends around the bypass catalyst  38  and is configured to supply coolant (e.g., water) around the bypass catalyst  38 . By keeping the bypass catalyst  38  at a lower temperature, particularly when exhaust gas is not passing therethrough (e.g., during normal operation), the life and durability of the catalyst  38  is extended. 
     In the example embodiment, the light-off catalyst bypass system  14  is configured to selectively operate in (i) a normal or warm catalyst mode, (ii) a cold catalyst mode, and (iii) a mixed flow mode. In the warm catalyst mode, controller  72  determines the main catalytic converter  52  has reached the predetermined light-off temperature (e.g., via temperature sensor, modeled, etc.) and moves the first valve  60  to the fully open position  64  and the second valve  62  to the fully closed position  70 . In this mode, the fully closed second valve  62  facilitates preventing the exhaust gas in the integrated exhaust manifold  20  from entering the bypass passage  22  and thus bypass catalyst  38 . Instead, the exhaust gas is directed through main exhaust passage  28 , into the main exhaust conduit  50 , and through the main catalytic converter  52  before being exhausted to the atmosphere. 
     In the cold catalyst mode, controller  72  determines the main catalytic converter  52  is below the predetermined light-off temperature or that another vehicle condition exists such as, for example, a cold start or long idle condition. The controller  72  moves the first valve  60  to the fully closed position  66  and the second valve  62  to the fully open position  68 . In this mode, the fully closed first valve  60  facilitates preventing the exhaust gas in the integrated exhaust manifold  20  from entering the main exhaust conduit  50 . Instead, the exhaust gas is directed through bypass passage  22  and bypass catalyst  38  before being directed to the main exhaust conduit  50  and atmosphere. Once the main catalytic converter  52  has reached the light-off temperature, the controller  72  may then switch the light-off catalyst bypass system  14  to the normal mode. 
     In the mixed flow mode, controller  72  moves the first valve  60  to a partially open/closed condition and moves the second valve  62  to a partially open/closed position. In this mode, depending on the opening amount of the first and second valves  60 ,  62 , a first portion of the exhaust gas in the integrated exhaust manifold  20  is directed through the main exhaust passage  28  and into the main exhaust conduit  50 . At the same time, a second portion of the exhaust gas in the integrated exhaust manifold  20  is directed through bypass passage  22  and bypass catalyst  38 . The two portions of exhaust gas recombine in the main exhaust conduit  50  and are subsequently passed through the main catalytic converter  52  and exhausted to atmosphere. It will be appreciated that controller  72  can make real time adjustments to the opening percentage of each of the first and second valves  60 ,  62  to control various conditions of the vehicle and its exhaust system. 
     Accordingly, cylinder head  10  provides a liquid cooled, integrated auxiliary catalyst  38  that can allow exhaust gas to bypass the main exhaust path, for example, during cold start, long ide, and low main catalyst  52  temperature conditions. The cylinder head  10  also includes an integrated valve system with valves  60 ,  62 , which are also liquid cooled by water jacket  24 . In this way, cylinder head  10  enables increased emissions system efficacy with decreased degradation due to aging. 
       FIG. 2  illustrates an alternative embodiment of the cylinder head at  100 . Cylinder head  100  is similar to cylinder head  10  except a bypass passage  122  includes an inlet  132  located on a cylinder exhaust passage  126 , as well as arranges the bypass catalyst  138  substantially perpendicular to a main exhaust passage  128 , as opposed to substantially perpendicular in cylinder head  10 . Additionally, a first valve  160  is disposed with a rotational axis horizontally across the main exhaust passage  128  rather than disposed vertically as in cylinder head  10 . 
     In the example embodiment, the cylinder head  100  generally defines an integrated exhaust manifold  120 , bypass passage  122 , and a water jacket  124 . The integrated exhaust manifold  120  includes a plurality of cylinder exhaust passages  126  that merge together to form main exhaust passage  128  having an outlet  130 . The bypass passage  122  includes inlet  132 , an outlet  134  and defines a catalyst cavity  136 , which is configured to removably receive a bypass catalyst  138 , which is described herein in more detail. 
     In the example embodiment, a main exhaust aftertreatment system  112  generally includes a main exhaust conduit  150  having one or more main catalytic converters  152  to reduce or convert a desired exhaust gas constituent such as, for example, carbon monoxide (CO), hydrocarbon (HC), and/or nitrogen oxides (NOx). The main exhaust conduit  150  is fluidly coupled to the integrated exhaust manifold main outlet  130  (optionally via a turbocharger turbine  142 , shown in phantom) and configured to receive exhaust gas from the vehicle engine and supply the exhaust gas to the main catalytic converter  152 . In order to efficiently reduce or convert CO, HC, and NOx, the catalytic converter  152  must reach a predetermined light-off temperature. However, during some vehicle operations such as, for example, cold starts, long idle, and cold catalyst conditions, the catalytic converter  152  is below light-off temperature and therefore has a low catalyst conversion efficiency. 
     In order efficiently reduce or convert the unwanted exhaust gas constituents while the catalytic converter  152  is below the light-off temperature, the vehicle utilizes a light-off catalyst bypass system  114  to redirect at least a portion of the exhaust gas from the integrated exhaust manifold  120 , into the bypass passage  122 , and through the bypass catalyst  138 . Because the bypass catalyst  138  is integrated into the cylinder head  100 , it is in close proximity to the engine combustion chambers and receives the exhaust gas quicker and at a higher temperature than the main catalytic converter  152  would. Thus, the bypass catalyst  138  is rapidly heated to its predetermined light-off temperature to achieve high catalyst conversion efficiency before the main catalytic converter  152  alone. 
     In the example embodiment, the light-off catalyst bypass system  114  generally includes the bypass catalyst  138 , first valve  160 , and a second valve  162 . The bypass catalyst  138  is disposed within the bypass passage  122 , which is fluidly connected to the main exhaust conduit  150  upstream of the main catalytic converter  152  by a bypass conduit  144  coupled to the bypass passage outlet  134 . The first valve  160  is located within the main exhaust passage  128  and is configured to move to any desired position between a fully open position  164  (not shown) and a fully closed position  166 . The second valve  162  is located within the bypass passage  122  and is configured to move to any desired position between a fully open position  168  (in solid) and a fully closed position  170  (in phantom). Although illustrated in the example implementation as butterfly valves, it will be appreciated that valves  160 ,  162  may be any suitable valve that enables light-off catalyst bypass system  114  to operate as described herein. 
     A controller  172  (e.g., engine control unit) is in signal communication with the first valve  160  and the second valve  162  and is configured to move the first and second valves  160 ,  162  to any position between their respective fully open and fully closed positions. 
     In one example, the bypass catalyst  138  is a three-way catalyst configured to remove CO, HC, and NOx from the exhaust gas passing therethrough, as described herein in more detail. However, it will be appreciated that bypass catalyst  138  may be any suitable catalyst. In another example, bypass catalyst  138  has a cell density of between approximately 800 and approximately 1200 cells per square inch, or between 800 and 1200 cells per square inch. 
     In the example embodiment, cylinder head  100  also includes a water jacket  124 . Advantageously, the water jacket  124  includes flow channels  174  extended to and disposed about the bypass passage  122  and the bypass catalyst  138 . In this way, the cylinder head coolant loop extends around the bypass catalyst  138  and is configured to supply coolant around the bypass catalyst  138 . By keeping the bypass catalyst  138  at a lower temperature, particularly when exhaust gas is not passing therethrough, the life and durability of the catalyst  138  is extended. 
     Described herein are systems and methods for improving vehicle emissions systems efficiency, particularly during cold start, long idle, and low main catalyst temperature conditions. The system includes a small bypass catalyst system located very close to the exhaust port(s) inside the cylinder head. The small catalyst system can receive exhaust flow during light-of (start-up), extended idle, some low load conditions, or other conditions. The small catalyst utilizes the relatively low temperature of the water jacketed cylinder head for cooling to minimize aging, and the system includes at least one valve located between the exhaust ports and the turbocharger or exhaust manifold. The valve selectively blocks flow to the small catalyst, for example, depending on pressure differentials forced by the specific design the system is being adapted for. 
     When the valve is in a light-off position, exhaust gases from the exhaust ports are directed through the small bypass catalyst. When the valve is in normal operating condition, the exhaust flow is directed through the manifold and optional turbocharger. The valve actuator can have continuous control over the flow split between the light-off and normal valve positions, for example, to allow for increased water cooling of the assembly to prolong life of the small bypass catalyst. 
     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.