Abstract:
An engine braking system includes a turbocharger having a turbine and a compressor. An exhaust manifold includes a first pipe for channeling a first portion of the engine exhaust and a second pipe for channeling a second portion of the engine exhaust. The first and second pipes are connected to an inlet of the turbine. A cross pipe, as part of an exhaust gas recirculation (EGR) conduit, is open between the first and second pipes and at one end to the remaining portion of the EGR conduit. A valve can be arranged within the cross pipe and ca be operable in a first mode of operation to block flow between the first and second pipes and allow flow between the first pipe and the remaining portion of the EGR conduit and to allow flow between the first and second pipes and the inlet of the turbine. The valve is operable in a second mode of operation to allow flow between the first and second pipes, and to reduce or block flow between the second pipe and the turbine inlet.

Description:
REFERENCE TO RELATED APPLICATION AND PRIORITY CLAIM 
       [0001]    This application claims the priority of Provisional Patent Application No. 61/088,634, filed on 13 Aug. 2008, the entire content of which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to internal combustion engines, including but not limited to control and operation of a turbocharger, EGR system and engine braking for an internal combustion engine. 
       BACKGROUND OF THE INVENTION 
       [0003]    Adequate and reliable braking for vehicles, particularly large tractor-trailer vehicles is desirable. While drum or disc wheel brakes are capable of absorbing a large amount of energy over a short period of time, the absorbed energy is transformed into heat in the braking mechanism. 
         [0004]    Multi-cylinder internal combustion engines, particularly diesel engines for large tractor-trailer trucks, may include an exhaust-gas turbocharger. The turbocharger includes a turbine that drives a compressor via a shaft, which generates an increased intake air pressure in the intake duct during normal operation. 
         [0005]    Braking systems are known which include exhaust brakes which inhibit the flow of exhaust gases through the exhaust system, and compression release systems wherein the energy required to compress the intake air during the compression stroke of the engine is dissipated by exhausting the compressed air through the exhaust system. 
         [0006]    In order to achieve a high engine-braking action a brake valve in the exhaust line may be closed during braking, and excess pressure is built up in the exhaust line upstream of the brake valve. The built-up exhaust gas flows at high velocity into the turbine and acts on the turbine rotor, whereupon the driven compressor increases pressure in the air intake duct. The cylinders are subjected to an increased charging pressure. In the exhaust system, an excess pressure develops between the cylinder outlet and the brake valve and counteracts the discharge of the air compressed in the cylinder into the exhaust tract via the exhaust valves. During braking, the piston performs compression work against the high excess pressure in the exhaust tract, with the result that a strong braking action is achieved. 
         [0007]    Another method disclosed in U.S. Pat. No. 4,395,884 includes employing a turbocharged engine equipped with a double entry turbine and a compression release engine retarder in combination with a diverter valve. During engine braking, the diverter valve directs the flow of air through one scroll of the divided volute of the turbine. When engine braking is employed, the turbine speed is maximized, and the inlet manifold pressure is also maximized, thereby maximizing braking horsepower developed by the engine. 
         [0008]    Other methods employ a variable geometry turbocharger (VGT). When engine braking is commanded, the variable geometry turbocharger is “clamped down” which means the turbine vanes are closed and used to generate both high exhaust manifold pressure and high turbine speeds and high turbocharger speeds. Increasing the turbocharger speed in turn increases the engine airflow and available engine brake power. The method disclosed in U.S. Pat. No. 6,594,996 includes controlling the geometry of the turbocharger for engine braking as a function of engine speed and pressure (exhaust or intake, preferably exhaust). U.S. Pat. No. 6,148,793 describes a brake control for an engine having a variable geometry turbocharger which is controllable to vary intake manifold pressure. The engine is operable in a braking mode using a turbocharger geometry actuator for varying turbocharger geometry, and using an exhaust valve actuator for opening an exhaust valve of the engine. 
         [0009]    Other methods of using turbochargers for engine braking are disclosed in U.S. Pat. Nos. 6,223,534 and 4,474,006. 
         [0010]    Controlled engine exhaust gas recirculation is a known technique for reducing oxides of nitrogen in products of combustion that are exhausted from an internal combustion engine to atmosphere. A typical EGR system comprises an EGR valve that is controlled in accordance with engine operating conditions to regulate the amount of engine exhaust gas that is re-circulated from the engine exhaust system to the air intake system so as to limit the combustion temperature and hence reduce the formation of oxides of nitrogen during combustion. Such a system is described for example in U.S. Pat. No. 7,363,761. 
       SUMMARY OF THE INVENTION 
       [0011]    The exemplary embodiments of the invention provide an engine braking system including a turbocharger having a turbine and a compressor. An exhaust manifold includes a first pipe for channeling a first portion of the engine exhaust and a second pipe for channeling a second portion of the engine exhaust. The first and second pipes are connected to an inlet of the turbine. A cross pipe, as part of an exhaust gas recirculation (EGR) conduit, is open between the first and second pipes and at one end to the remaining portion of the EGR conduit. A valve can be arranged within the cross pipe and is operable in a first mode of operation to block flow between the first and second pipes and allow flow between the first pipe and the remaining portion of the EGR conduit and to allow flow between the first and second pipes and the inlet of the turbine. The valve is operable in a second mode of operation to allow flow between the first and second pipes, and to block flow between the second pipe and the turbine inlet. Thus, a substantially reduced flow occurs between the second pipe and the turbine inlet and a substantially increased flow occurs between the first pipe and the turbine inlet. One example of the second mode of operation is that no flow occurs between the second pipe and the turbine inlet, no flow occurs through the remaining portion of the EGR conduit, the second portion of the exhaust gas flows through the cross pipe, and substantially the first and second portions of the total exhaust flow is channeled through the first pipe and into the turbine inlet. 
         [0012]    According to the exemplary embodiment, during operation in the second mode a control positions the valve and closes an EGR valve that is within the EGR conduit. In the first mode of operation, the EGR valve is controlled by the engine control module and software therein to reduce emissions. 
         [0013]    The turbine may comprise a variable geometry turbine and/or a divided volute turbine. 
         [0014]    According to the exemplary embodiment, the valve comprises a flapper valve rotatable between two positions corresponding to the first and second modes. 
         [0015]    The exemplary embodiment of the invention provides an exhaust and air intake system for an engine. The system includes a first exhaust pipe means for channeling a first portion of exhaust gas generated by the engine, and a second exhaust pipe means for channeling a second portion of the exhaust gas generated by the engine. An air intake system includes an air compressor, an air inlet to the air compressor, and a compressed air intake manifold. A turbine drives the air compressor; the turbine having a turbine inlet for flow-connecting the first and second exhaust pipe means. An exhaust gas recirculation (EGR) means selectively connects the first pipe means, the second pipe means and the air intake system and selectively delivers exhaust gas to the air intake system. The EGR system can also selectively channel exhaust gas flow, in a reverse direction, between the first and second pipe means. A valve means, in a first mode of operation, opens exhaust gas flow between the second pipe means and the turbine inlet and closes exhaust gas flow between the second pipe means and the exhaust gas recirculation means. Accordingly, an amount of exhaust gas from the first portion of exhaust gas flows through the first pipe means into the exhaust gas recirculation means and a remaining amount of the first portion of exhaust gas flows from the first pipe means to the turbine inlet. The second portion of exhaust gas flows through the second pipe means into the turbine inlet. The valve means, in a second mode of operation, closes exhaust gas flow between the second pipe means and the turbine inlet and opens exhaust gas flow between the second pipe means and the exhaust gas recirculation means. 
         [0016]    The valve means can include a flapper or butterfly plate valve located between the exhaust gas recirculation means and the second pipe means, and an EGR valve located in the exhaust gas recirculation means. In the second mode of operation, the EGR valve can be substantially closed or made more restrictive to flow, and in the first mode of operation the EGR valve is controlled to reduce engine emissions. 
         [0017]    Numerous other advantages and features of the present invention will be become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  is a block diagram of an engine system that includes a turbocharger and an exhaust gas control valve in accordance with an exemplary embodiment of the invention; 
           [0019]      FIG. 2  is fragmentary sectional view of a portion of the exhaust system and turbocharger shown in  FIG. 1  in a normal operating mode; 
           [0020]      FIG. 3  is a fragmentary sectional view of the exhaust system and turbocharger shown in  FIG. 2  in an engine braking mode of operation; 
           [0021]      FIG. 4  is a fragmentary sectional view of a portion of a prior art exhaust system and turbocharger in a normal operating mode; 
           [0022]      FIG. 5  is a fragmentary sectional view of an alternate exemplary embodiment exhaust system and turbocharger in accordance with the invention shown in a normal mode of operation; 
           [0023]      FIG. 6  is a perspective view of a portion of the exhaust system shown in  FIG. 5 ; 
           [0024]      FIG. 7  is a fragmentary sectional view of the exhaust system shown in  FIG. 5  in an engine braking mode of operation 
           [0025]      FIG. 8  is a fragmentary sectional view of a further alternate exemplary embodiment exhaust system and turbocharger in accordance with the invention shown in a normal mode of operation; 
           [0026]      FIG. 9  is an exploded perspective view of a portion of the exhaust system shown in  FIG. 8 ; 
           [0027]      FIG. 10  is a reduced perspective view of the portion of the exhaust system shown in  FIG. 9  as assembled; and 
           [0028]      FIG. 11  is a fragmentary sectional view of the exhaust system shown in  FIG. 8  in an engine braking mode of operation. 
       
    
    
     DETAILED DESCRIPTION 
       [0029]    While this invention is susceptible of embodiment in many different forms, there are shown in the drawings, and will be described herein in detail, specific embodiments thereof with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the specific embodiments illustrated. 
         [0030]    An engine  100  is shown schematically in  FIG. 1 . The engine  100  has a block  101  that includes a plurality of cylinders. The cylinders in the block  101  are fluidly connected to an intake system  103  and to an exhaust system  105 . The exhaust system includes a first pipe  105   a  from cylinders  1 ,  2  and  3  of one bank of cylinders and a second pipe  105   b  from cylinders  4 ,  5  and  6  of an opposite bank of cylinders. A turbocharger  107  includes a turbine  109 . The turbine  109  shown has a single turbine inlet port  113  connected to the exhaust system  105 . The turbocharger  107  may additionally include a compressor  111  connected to the intake system  103  through an inlet air passage  115 . 
         [0031]    During operation of the engine  100 , air may enter the compressor  111  through an air inlet  117 . Compressed air may exit the compressor  111  through the inlet air passage  115 , and pass through an optional charge air cooler  119  and an optional inlet throttle  121  before entering an intake manifold  122  of the intake system  103 . 
         [0032]    Exhaust gas from the exhaust system  105  may be routed through an exhaust gas recirculation (EGR) conduit  124  to an exhaust gas recirculation (EGR) cooler  123  and pass through an EGR valve  125  before meeting and mixing with air from the inlet throttle  121  at a junction  127 . 
         [0033]    The inlet port  113  of the turbine  109  may be connected to the exhaust pipes  105   a,    105   b  in a manner that forms a distribution manifold  129 . Exhaust gas passing through the turbine  109  may exit the engine system  100  through a tailpipe  135 . 
         [0034]    At times when the EGR valve  125  is at least partially open, exhaust gas flows through the first pipe  105   a,  through the conduit  124 , through the EGR cooler  123 , through the EGR valve  125  and into the junction  127  where it mixes with air from the inlet throttle  121 . An amount of exhaust gas being re-circulated through the EGR valve  125  may depend on an opening percentage of the EGR valve  125 . 
         [0035]    The conduit  124  is also connected to the second pipe  105   b.  A relatively short cross pipe  124   a  of the conduit  124  is arranged between the pipes  105   a  and  105   b.  The cross pipe  124   a  facilitates exhaust gas flow in either direction depending on the operating mode. An engine brake valve  133  is positioned within the intersection of the conduit  124  and the second pipe  105   b.  During normal operation, the valve  133  closes the flow connection between the conduit  124  and the second pipe  105   b.  During normal operation, exhaust gas flows from the first pipe  105   a  to the inlet  113  of the turbine and some amount of exhaust gas flows from the first pipe  105   a  to the EGR cooler  123 . Exhaust gas flowing within the second pipe  105   b  flows through the valve  133  and into the turbine inlet  113  and generally does not flow through the valve  133  into or from the conduit  124 . 
         [0036]    During engine braking however, the valve  133  changes position and opens a flow path through the cross pipe  124   a  from the second pipe  105   b  to the first pipe  105   a  and closes the flow path from the second pipe  105   b  to the turbine inlet  113 . The valve  133  can be configured to also close the flow path from the second pipe  105   b  to the EGR cooler  123  or alternately the EGR valve  125  can be closed to close this flow path. 
         [0037]    Because the exhaust gas from both the bank of cylinders  1 ,  2  and  3  and the bank of cylinders  4 ,  5  and  6  must pass through one side of the turbine, the turbine speed is increased. For a variable geometry turbocharger the vanes can also be changed to increase turbine speed. Increased turbine speed corresponds to an increased compressor speed and increased air flow through the engine increases the capability of the engine for engine braking. A more complete description of engine braking can be found in U.S. Pat. Nos. 6,594,996; 6,223,534; 6,148,793; 4,474,006 and 4,395,884; all herein incorporated by reference. 
         [0038]    A prior art arrangement of an exhaust manifold  200  and turbine  109  is shown in  FIG. 4 . The exhaust manifold  200  includes a first exhaust pipe  205   a  receiving exhaust gas from cylinders  1 ,  2  and  3  and a second exhaust pipe  205   b  receiving exhaust gas from cylinders  4 ,  5  and  6  that are flow connected to the turbine inlet  113 . An EGR conduit  210  branches off the pipe  205   a  and is located behind the pipe  205   b  but not flow connected to the pipe  205   b.  EGR flow is taken from the pipe  205   a  only and is controlled by an EGR valve (not shown) downstream and in flow communication with the EGR conduit  210 . 
         [0039]      FIGS. 2 and 3  illustrate a modification of the arrangement shown in  FIG. 4  in order to configure the exhaust system as shown in  FIG. 1 . A modified exhaust manifold  220  is provided. 
         [0040]      FIG. 2  shows the brake valve  133  in a first mode of operation. This mode generally corresponds to a normal operation (no engine braking) of the engine. A first exhaust gas portion  240  flowing through a branch pipe  105   c  from no.  1  cylinder (see  FIG. 1 ) and through the first pipe  105   a  from nos.  2  and  3  cylinders, enters the turbine inlet. A controlled amount of exhaust gas, the EGR exhaust gas  242 , passes through an opening  243  in the first pipe  105   a  and into the cross pipe  124   a  (beneath the second pipe  105   b ) and through the EGR conduit  124  to the EGR cooler  123  (shown in  FIG. 1 ). The EGR exhaust gas  242  is controlled by the EGR valve  125  (shown in  FIG. 1 ) that is downstream of the cooler  123 . The EGR valve  125  is controlled by the engine control unit or computer to limit emissions. A second exhaust gas portion  246  of exhaust gas flows through a branch pipe  105   d  from no.  4  cylinder (see  FIG. 1 ) and through the second pipe  105   b  from the nos.  5  and  6  cylinders, to the turbine inlet  113 . The valve  133  closes an opening  250  formed or cut though a wall of the second pipe  105   b  that would otherwise open the second pipe  105   b  to the cross pipe  124   a.    
         [0041]      FIG. 3  shows the brake valve  133  in a second mode of operation. This mode corresponds to an engine braking mode of operation. During engine braking,  FIG. 3  demonstrates one aspect of operation, that is, the re-routing of exhaust gas to increase the speed of the turbine and thus increase the amount of compressed air into the engine. In addition to the operation described in  FIG. 3 , one or more exhaust valves of the engine can be opened, as described in U.S. Pat. Nos. 6,594,996; 6,148,793; 6,779,506; 6,772,742 or 6,705,282, herein incorporated by reference, to maximizing braking horsepower developed by the engine. 
         [0042]    The first exhaust gas portion  240  flowing through the branch pipe  105   c  from the no.  1  cylinder (see  FIG. 1 ) and through the first pipe  105   a  from nos.  2  and  3  cylinders, enters the turbine inlet  113 . The valve  133  has been rotated to be positioned into the second pipe  105   b  to block the EGR exhaust gas  242  from entering the turbine inlet  113  directly from the second pipe  105   b.  The second exhaust gas portion  246  flowing through the branch pipe  105   d  from no.  4  cylinder (see  FIG. 1 ) and through the second pipe  105   b  from the nos.  5  and  6  cylinders, flows through the opening  250  in the wall of the second pipe  105   b,  and into the cross pipe  124   a  (beneath or behind the second pipe  105   b ) in a reverse direction compared to the flow through the cross pipe  124   a  in the first mode of operation. The second exhaust gas portion  242  must join the first exhaust gas portion  240  and flow though the first pipe  105   a  into the turbine inlet  113 . During engine braking, the EGR valve  125  can be closed or otherwise controlled to block or limit the EGR flow  246  through the conduit  124  to the cooler  123 . 
         [0043]      FIG. 5  illustrates a further embodiment of the invention wherein a modified exhaust manifold  300  and turbine  109  shown in  FIG. 4  has been modified with a central valve  302 .  FIG. 5  shows a first mode of operation. This mode generally corresponds to a normal operation (no engine braking) of the engine. The valve  302  includes a base  304  with a valve seat  306  (shown in  FIG. 6 ). A rotatable butterfly-type valve element  310  is mounted on an axle or spindle  314 . In the first mode of operation shown in  FIG. 5 , the valve allows the first exhaust gas portion  240  from the branch pipe  105   c  and the first pipe  105   a  to flow into the turbine inlet. The EGR exhaust gas  242  flows through the opening  243  in the wall of the first pipe  105   a,  through the EGR conduit  124  behind or beneath the second pipe  105   b,  and to the EGR cooler and EGR valve as shown in  FIG. 1 . There is no opening  250  in the embodiment shown in  FIGS. 5 and 7 . The second exhaust gas portion  246  from the branch pipe  105   d  and the second pipe  105   b  flows into the turbine inlet  113 . 
         [0044]      FIG. 7  shows a second mode of operation. This mode corresponds to an engine braking mode of operation. During engine braking,  FIG. 7  demonstrates one aspect of operation, that is, the re-routing of exhaust gas to increase the speed of the turbine and thus increase the amount of compressed air into the engine. In addition to the operation described in  FIG. 7 , one or more exhaust valves of the engine can be opened, as described in U.S. Pat. Nos. 6,594,996; 6,148,793; 6,779,506; 6,772,742 or 6,705,282, herein incorporated by reference, to maximizing braking horsepower developed by the engine. 
         [0045]    The valve element  310  has been pivoted about the axle or spindle  314  by an external actuator (not shown) to be in a position wherein the first exhaust gas portion  240  from the branch pipe  105   c  and the first pipe  105   a  cannot enter the turbine inlet  113  directly but must pass over the valve element  310  to enter the second pipe  105   b  to flow with the second exhaust gas portion  246  into the inlet  113 . The EGR valve  125  (shown in  FIG. 1 ) can be closed or otherwise controlled to block or limit the EGR exhaust gas  242  though the opening  243  and the EGR conduit  124  to the cooler  123  (shown in  FIG. 1 ). 
         [0046]      FIG. 8  illustrates a still further embodiment of the invention wherein a modified exhaust manifold  400  and turbine  109  shown in  FIG. 4  has been modified with a central valve  402 .  FIG. 8  shows a first mode of operation. This mode generally corresponds to a normal operation (no engine braking) of the engine. The valve  402  includes a cover  404  with a bushing  406  that journals and seals a spindle  414  (shown in  FIG. 9 ). A rotatable butterfly-type valve element  410  is mounted on the spindle  414 . 
         [0047]    In the first mode of operation shown in  FIG. 8 , the valve  402  allows the first exhaust gas portion  240  from the branch pipe  105   c  and the first pipe  105   a  to flow into the turbine inlet. The EGR exhaust gas  242  flows through the opening  243  in the wall of the first pipe  105   a,  through the EGR conduit  124  behind or beneath the second pipe  105   b,  and to the EGR cooler and EGR valve as shown in  FIG. 1 . There is no opening  250  in the embodiment shown in  FIGS. 8 and 11 . The second exhaust gas portion  246  from the branch pipe  105   d  and the second pipe  105   b  flows into the turbine inlet  113 . 
         [0048]    A flat stop surface  426  of the manifold  400  is provided to support the butterfly element  410 . 
         [0049]      FIG. 11  shows a second mode of operation. This mode corresponds to an engine braking mode of operation. During engine braking,  FIG. 11  demonstrates one aspect of operation, that is, the re-routing of exhaust gas to increase the speed of the turbine and thus increase the amount of compressed air into the engine. In addition to the operation described in  FIG. 11 , one or more exhaust valves of the engine can be opened, as described in U.S. Pat. Nos. 6,594,996; 6,148,793; 6,779,506; 6,772,742 or 6,705,282, herein incorporated by reference, to maximizing braking horsepower developed by the engine. 
         [0050]    The valve element  410  has been pivoted about the spindle  414  by an external actuator (not shown) to be in a position wherein the second exhaust gas portion  246  from the branch pipes  105   b  and  105   d  cannot enter the turbine inlet  113  directly but must pass over the valve element  410  and through the opening  243  to enter the first pipe  105   a  to flow with the first exhaust gas portion  240  into the inlet  113 . The EGR valve  125  (shown in  FIG. 1 ) can be closed or otherwise controlled to block or limit the EGR exhaust gas  242  though the opening  243  and the EGR conduit  124  to the cooler  123  (shown in  FIG. 1 ). 
         [0051]    A flat stop surface  446  of the manifold  400  is provided to support the butterfly element  410 . 
         [0052]    From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope of the invention. It is to be understood that no limitation with respect to the specific apparatus illustrated herein is intended or should be inferred.