Turbocharged internal combustion engine

Abstract

An engine system includes an internal combustion engine, at least one turbocharger, and a catalytic treatment device. The engine includes an exhaust manifold system having a main exhaust manifold and a bypass exhaust manifold. A partial engine bypass valve system is positioned between the engine and the exhaust manifold system. The bypass valve system directs all engine exhaust to the turbine wheel of the turbocharger when placed in a non-bypass position, and after passing through the turbine wheel, the gas continues to the catalytic device. In the bypass position of the bypass valve system, a bypass portion of the total exhaust gas bypasses the turbine wheel and continues to the catalytic device, while the remainder first passes through the turbine wheel before going to the catalytic device.

Description

Technical Field

[0001] The present application generally relates to turbocharged internal combustion engine systems. The present application more particularly relates to such engine systems employing a catalytic treatment device in the exhaust system. Background Art

[0002] Turbochargers are employed with some internal combustion engines in order to improve the performance of the engine. Exhaust gas discharged from the cylinders of the engine is collected in an exhaust manifold and supplied to the turbine of the turbocharger to drive the turbine wheel, which in turn drives the compressor wheel of the turbocharger. The compressor pressurizes the air and supplies it to the intake manifold of the engine. The overall pressure ratio across the internal combustion engine is thereby increased, allowing the engine to produce increased torque and power output.

[0003] Because of government regulations aimed at reducing harmful exhaust emissions from internal combustion engines, internal combustion engine systems almost always include a catalytic treatment device (commonly referred to as a catalytic converter) in the exhaust system. Within the catalytic treatment device, the exhaust flows through a dense honeycomb structure made of ceramic that is coated with a catalyst, such as platinum and palladium. Typically, there are two or more different catalysts, such as one catalyst that catalyzes a reduction process to convert nitrogen oxides into nitrogen and oxygen, and another catalyst that catalyzes an oxidation process to convert carbon monoxide into carbon dioxide.

[0004] There is a minimum temperature (called the "light-off temperature") to which the catalyst must heat before it becomes effective in converting NOx and CO in the exhaust gas into harmless substances. Thus, during a "cold start" of an engine (e.g., after a vehicle has been parked overnight and started in the morning), there is a period of time before the catalyst reaches its light-off temperature during which the catalytic treatment device is ineffective. This is an important issue because it is estimated that as much as 80% of total vehicle engine emissions are caused by engine operation during the cold start phase when the catalytic device is ineffective. It is desirable to minimize this period of time as much as possible.

[0005] The present application describes embodiments of a turbocharged internal combustion engine system that employs an advantageous method for achieving rapid light-off of a catalytic treatment device. Summary of the invention

[0006] In summary, the present application discloses an engine system comprising an internal combustion engine, at least one turbocharger and a catalytic treatment device. The engine comprises an exhaust manifold system having a main exhaust manifold and a bypass exhaust manifold. A partial engine bypass valve system is positioned between the engine and the turbocharger and the catalytic treatment device. The bypass valve system directs all engine exhaust to the turbine wheel of the turbocharger when placed in a non-bypass position, and after passing through the turbine wheel, the gas continues to travel to the catalytic device. In the bypass position of the bypass valve system, a bypass portion of the total exhaust gas bypasses the turbine wheel and continues to travel to the catalytic device, while the remainder first passes through the turbine wheel before going to the catalytic device.

[0007] According to one embodiment of the present invention, an engine system includes:

[0008] an internal combustion engine having a plurality of cylinders;

[0009] an exhaust manifold system including a main exhaust manifold receiving exhaust gas from at least some of the cylinders and a bypass exhaust manifold receiving exhaust gas from at least one of the cylinders;

[0010] a bypass line coupled to the bypass exhaust manifold to receive exhaust gas therefrom;

[0011] an exhaust feed conduit coupled to the primary exhaust manifold to receive exhaust gas therefrom;

[0012] a first turbocharger including a first compressor and a first turbine, the first turbine including an exhaust inlet coupled to the exhaust feed conduit to receive exhaust gas therefrom, and including an exhaust gas discharge conduit for discharging exhaust gas having passed through the first turbine, the downstream end of the bypass line being coupled to the exhaust gas discharge conduit; and

[0013] a partial engine bypass valve system disposed between the engine cylinders and the turbocharger, the partial engine bypass valve system being adjustable to a non-bypass position to allow exhaust gas from at least some of the cylinders to flow into the main exhaust manifold for supply to the first turbine while preventing exhaust gas from any of the engine cylinders from flowing to the bypass exhaust manifold,

[0014] the partial engine bypass valve system being alternatively adjustable to a bypass position to allow exhaust gas from at least some of the cylinders to flow into the main exhaust manifold to be supplied to the first turbine and to allow exhaust gas from at least one of the cylinders to flow into the bypass exhaust manifold to bypass the first turbine;

[0015] wherein the portion of the engine bypass valve system in the bypass position fluidly isolates the main exhaust manifold and the bypass exhaust manifold from each other.

[0016] In one embodiment of the invention, the engine cylinders are divided into a first subgroup of cylinders and a second subgroup of cylinders, and the partial engine bypass valve system comprises a three-way valve having a valve inlet, a first outlet, and a second outlet, wherein the valve inlet is coupled to the bypass exhaust manifold to receive exhaust gas therefrom, the first outlet is coupled to the main exhaust manifold to supply exhaust gas thereto, and the second outlet is coupled to the upstream end of the bypass line. The three-way valve in the bypass position allows exhaust gas from the first subgroup of cylinders to bypass the first turbine and continue into the exhaust discharge conduit, while exhaust gas from the second subgroup of cylinders passes through the first turbine. The three-way valve in the non-bypass position causes exhaust gas from all engine cylinders to mix and pass through the exhaust feed conduit.

[0017] In this embodiment, the present invention is applicable to engines having various numbers of cylinders. In one embodiment, the engine has four cylinders, the first subgroup includes one cylinder, and the second subgroup includes three cylinders. In another embodiment, the engine has six cylinders, the first subgroup includes two cylinders, and the second subgroup includes four cylinders.

[0018] In some embodiments, more than one turbocharger may be employed. For example, in one embodiment, there is a second turbocharger, the second turbocharger including a second compressor and a second turbine, the engine system including a conduit system and one or more valves for selectively activating both the first and second turbochargers, or alternatively for activating the first turbocharger when the second turbocharger is inactive, and wherein the bypass line is arranged such that when the three-way valve is in the bypass position, exhaust gas bypasses both the first turbine and the second turbine.

[0019] In another embodiment of the present invention, a partial engine bypass valve system includes a main exhaust valve for each of the cylinders and a secondary exhaust valve for at least one of the cylinders. Each secondary exhaust valve is coupled to the bypass exhaust manifold to feed exhaust gas from the corresponding cylinder into the bypass exhaust manifold when the secondary exhaust valve is open, and each main exhaust valve is coupled to the main exhaust manifold to feed exhaust gas from the corresponding cylinder into the main exhaust manifold when the main exhaust valve is open. In operation, in a non-bypass position of the bypass valve system, during the exhaust phase of each engine cycle, the bypass exhaust valve remains closed while the main exhaust valve is open, and in a bypass position, during the exhaust phase of each engine cycle, the bypass exhaust valve and the main exhaust valve are open.

[0020] The present invention includes a method for operating an engine system. In one embodiment, a method for operating an engine system is provided, the engine system comprising: an internal combustion engine having a plurality of cylinders in which an air-fuel mixture is combusted to produce exhaust gas; a turbocharger having a turbine wheel for receiving the exhaust gas and a compressor wheel driven by the turbine wheel; and a catalytic treatment device that receives the exhaust gas and converts exhaust gas components into less harmful compounds. The method includes the following steps:

[0021] (a) determining whether a cold start condition exists such that the catalytic treatment device operates below a light-off temperature at which the catalytic treatment device becomes effective to convert the exhaust gas constituents into the less harmful compounds;

[0022] (b) if it is determined that a cold start condition does not exist, directing a total amount of exhaust gas from the engine through the turbine wheel before continuing to the catalytic treatment device; and

[0023] (c) if a cold start condition is determined to exist, directing a bypassed portion of the total amount of exhaust gas from the engine to bypass the turbine wheel and continue to the catalytic treatment device, and directing a remaining portion of the total amount of exhaust gas through the turbine wheel before continuing to the catalytic treatment device.

[0024] In one embodiment, the engine cylinders are divided into a first subset of one or more cylinders and a second subset of cylinders. Step (b) includes directing exhaust gas from both the first and second subsets of cylinders to the turbine wheel, and step (c) includes directing exhaust gas from the first subset of cylinders to bypass the turbine wheel and continue to the catalytic treatment device.

[0025] Alternatively, if a cold start condition is determined to exist, a cold start fuel schedule may be employed in the first subset of the cylinders and a normal fuel schedule may be employed in the second subset of the cylinders. Cold start combustion timing may also be employed in the first subset of the cylinders and a normal combustion timing may be used in the second subset of the cylinders.

[0026] In one embodiment, each of the engine cylinders has a main exhaust valve, and one or more of the cylinders has an additional bypass exhaust valve. Then, step (b) comprises opening both the bypass exhaust valve and the main exhaust valve during the exhaust phase of each engine cycle, so that the bypass portion of the total exhaust volume is discharged through the bypass exhaust valve and fed through a bypass line bypassing the turbine impeller, and the remaining portion of the total exhaust volume is discharged through the main exhaust valve and fed to the turbine impeller. Step (c) comprises keeping the bypass exhaust valve closed and opening the main exhaust valve during the exhaust phase of each engine cycle, so that the total exhaust volume is discharged through the main exhaust valve and fed to the turbine impeller. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Having generally described the present disclosure, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and in which:

[0028] Figure 1 is a schematic illustration of a turbocharged engine system according to the prior art;

[0029] Figure 2 is a schematic illustration of a turbocharged engine system according to a first embodiment of the present invention, wherein the three-way valve is in a non-bypass position;

[0030] Figure 3 The engine system of the first embodiment is shown with the three-way valve in the bypass position;

[0031] Figure 4 is a schematic illustration of a turbocharged engine system according to a second embodiment of the present invention, showing a three-way valve in a bypass position;

[0032] Figure 4A According to the second embodiment of the present invention, but relative to Figure 4 A schematic illustration of a slightly modified version of a turbocharged engine system showing a three-way valve in a bypass position;

[0033] Figure 5 is a schematic illustration of a turbocharged engine system according to a third embodiment of the present invention, showing a three-way valve in a bypass position;

[0034] Figure 6 is a cross-sectional view of a three-way valve according to one embodiment for practicing the present invention;

[0035] Figure 7 It is along Figure 6 A cross-sectional view of line 7-7 in FIG. 1 , wherein the valve is in a non-bypass position;

[0036] Figure 8 Similar to Figure 7 , which shows the valve in a bypass position;

[0037] Fig. 9 is a schematic diagram of a turbocharged engine system according to a fourth embodiment of the present invention;

[0038] Fig.10 is a flow chart of a method according to an embodiment of the present invention;

[0039] Fig.11 is a schematic illustration of a turbocharged engine system according to a fifth embodiment of the present invention showing a portion of an engine bypass valve system in a non-bypass position; and

[0040] Fig.12 Similar to Fig.11 , which shows a portion of the engine bypass valve system in the bypass position. DETAILED DESCRIPTION

[0041] The present disclosure will now be described in more detail with reference to the above-mentioned drawings, which depict some, but not all, embodiments of the inventions to which the present disclosure pertains. These inventions may be implemented in various forms (including forms not expressly described herein) and should not be construed as being limited to the specific exemplary embodiments described herein. In the following description, similar reference numerals refer to similar elements throughout.

[0042] Figure 1A turbocharged engine system arranged in accordance with the prior art is shown. The engine system includes an internal combustion engine 20 having a plurality (in the illustrated embodiment, four) of cylinders 22. The engine cylinders receive air from an intake manifold 24. A fuel system (not shown) also delivers fuel for introduction into the cylinders. The fuel-air mixture is combusted in the cylinders, and the resulting exhaust gas is discharged from the cylinders into an exhaust manifold 26. The engine system includes a turbocharger 30 for increasing the pressure of the air supplied to the intake manifold 24. The turbocharger includes a compressor having a compressor wheel 40 mounted on one end of a rotatable shaft 32, and a turbine having a turbine wheel 50 mounted on the other end of the shaft. The compressor wheel 40 is housed in a compressor housing (not shown), which defines an air inlet for directing air into the compressor wheel, and further defines a volute for receiving air that has been pressurized by the compressor wheel. The air is discharged from the volute to the intake manifold 24 of the engine through a suitable ductwork 42. The turbine wheel 50 is housed within a turbine housing (not shown) that defines an annular scroll or volute for receiving exhaust gas from the exhaust manifold 26 via an exhaust feed conduit 52 coupled between the exhaust manifold and an inlet of the turbine housing. Exhaust gas in the scroll is directed through a nozzle into the turbine wheel 50 and expands as it passes through the turbine wheel, thereby rotatably driving the turbine wheel, which in turn drives the compressor wheel 40.

[0043] The prior art engine system includes an exhaust gas discharge conduit 54 that receives exhaust gas that has passed through a turbine wheel 50. A catalytic treatment device 60 is connected to the exhaust gas discharge conduit. The exhaust gas passes through the catalytic treatment device where NOx and CO components are converted into nitrogen, oxygen and carbon dioxide for discharge into the atmosphere.

[0044] In some prior art engine systems (e.g. Figure 1 In the engine system shown in ), the problem of excessive emissions during cold starts (due to the time required for the exhaust gas to reach ignition temperature) is solved by providing a wastegate 56. When closed, the wastegate constrains all of the exhaust gas delivered by the exhaust feed conduit 52 to pass through the turbine impeller 50. However, when the wastegate is open, a portion of the exhaust gas can pass through the wastegate, thereby bypassing the turbine impeller, and enter the exhaust discharge conduit 54 downstream of the turbine impeller. Some wastegates can be adjusted to various degrees of opening to adjust the fractional portion of the total exhaust gas flow that is bypassed around the turbine impeller. In any case, the fact that some fractional portion of the exhaust gas does not pass through the turbine impeller means that the temperature of those gases entering the catalytic treatment device 60 is significantly higher than the temperature of the gases that must first pass through the turbine impeller. This higher temperature helps to accelerate the catalyst ignition process.

[0045] However, a disadvantage of this approach is that the pressure ratio across the turbine immediately drops significantly when the wastegate 56 opens. Therefore, for those exhaust gases that pass through the turbine wheel, the amount of work that can be produced in the turbine wheel is significantly reduced. Therefore, as long as the wastegate remains open, turbocharger performance (and therefore engine system performance) is reduced.

[0046] The present invention is directed to solving the light-off problem without as much of a compromise in turbocharger performance as occurs in some prior art engine systems. Figure 2 , showing a first embodiment of the present invention. The engine 20 has four cylinders 22 fed with air from an intake manifold 24 and includes a turbocharger 30 whose compressor wheel 40 pressurizes the air delivered to the intake manifold, as in Figure 1 The turbine wheel 50 of the turbocharger receives exhaust gas via an exhaust gas feed conduit 52 and discharges exhaust gas via an exhaust gas discharge conduit 54, as in the existing system. However, unlike the existing system, the engine 20 in the system according to the first embodiment of the present invention has its cylinders 22 divided into two subgroups. The first subgroup (in this embodiment, having a single cylinder 22a) discharges exhaust gas into a bypass exhaust manifold 26a, and the second subgroup (in this embodiment, having three cylinders 22b) discharges its exhaust gas into a separate main exhaust manifold 26b. The system further includes a bypass line 80 for allowing the exhaust gas to bypass the turbine impeller.

[0047] The system according to the present invention includes a partial engine bypass valve system operable to cause a portion of the total engine exhaust gas to bypass the turbine wheel during cold start conditions. Figure 2 and Figure 3 In the embodiment of the present invention, the partial engine bypass valve system includes a three-way valve 70 having a valve inlet 72, a first outlet 74, and a second outlet 76. The valve inlet 72 is coupled to the bypass exhaust manifold 26a to receive exhaust gas therefrom, the first outlet 74 is coupled to the main exhaust manifold 26b to supply exhaust gas thereto, and the second outlet 76 is coupled to the upstream end of the bypass line 80.

[0048] The three-way valve 70 can be adjusted to a non-bypass position ( Figure 2 ), wherein the flow path leads from the valve inlet 72 to the first outlet 74, while the second outlet 76 is closed. In this non-bypass position, the three-way valve establishes fluid communication between the two exhaust manifolds 26a and 26b so that they essentially act as a single manifold, similar to a typical exhaust manifold. The three-way valve in the non-bypass position causes exhaust gas from all engine cylinders 22a and 22b to mix and reach the turbine impeller through the exhaust gas feed conduit 52.

[0049] Alternatively, the three-way valve 70 may be placed in the bypass position ( Figure 3 ), in which the flow path leads from the valve inlet 72 to the second outlet 76, while the first outlet 74 is closed. In this bypass position, the valve 70 provides a fluid isolation between the two exhaust manifolds 26a and 26b, and the exhaust gas from the first subgroup including the cylinders 22a is fed through the bypass line 80, while the exhaust gas from the second subgroup of cylinders 22b is fed to the turbine wheel 50 through the exhaust gas feed conduit 52.

[0050] The downstream end of the bypass line 80 is coupled to the exhaust gas discharge conduit 54 at a position downstream of the turbine impeller 50 and upstream of the catalytic treatment device 60. Thus, when the three-way valve is in the bypass position, the exhaust gas from the first subset of engine cylinders bypasses the turbine impeller and continues directly into the exhaust gas discharge conduit and then into the catalytic treatment device. In this way, the present invention achieves improved turbine performance relative to a turbocharger with a wastegate, because the exhaust gas driving the turbine impeller does not experience the pressure drop caused by the open wastegate. In this regard, a key aspect of the system according to an embodiment of the present invention is that the three-way valve fluidly isolates two exhaust gas flows from two engine cylinder subsets, respectively. Thus, the path with lower resistance (i.e., the flow path from the bypass exhaust manifold 26a through the valve inlet 72 to the second outlet 76 and into the bypass line 80) is fluidly isolated from the path with higher resistance (i.e., the flow path from the main exhaust manifold 26b through the exhaust gas feed conduit 52 and through the turbine impeller 50). This is in contrast to a wastegate, which opens the second path (bypassing the turbine wheel) while still placing the first path (through the turbine wheel) in fluid communication with the second path. The turbine performance penalty caused by a wastegate is therefore something the present invention aims to substantially mitigate or completely eliminate.

[0051] At the same time, the direct path of the exhaust gas from the first engine cylinder subbank to the catalytic treatment device helps to accelerate catalyst light-off, similar to the effect of a conventional wastegate.

[0052] The present invention is applicable to various engine system layouts. Figure 4 The second embodiment of the present invention is shown. The engine system of the second embodiment is similar in many respects to the first embodiment, the main difference being that instead of having a single turbocharger, Figure 4The engine system of the second embodiment has a twin turbocharger design. In particular, the engine system of the second embodiment includes a first turbocharger 30 and a second turbocharger 130 arranged in a series relationship with each other. Therefore, the first (low-pressure) compressor impeller 40 of the first turbocharger pressurizes the air and supplies it to the inlet of the second (high-pressure) compressor impeller 140 of the second turbocharger, which further pressurizes the air and delivers it to the engine intake manifold 24. On the turbine side, the second (high-pressure) turbine impeller 150 of the second turbocharger expands the exhaust gas portion and supplies it to the first (low-pressure) turbine impeller 50 of the first turbocharger, which further expands the exhaust gas and discharges it through the exhaust gas discharge conduit 52.

[0053] As is common in twin-turbocharger engine layouts, Figure 4 The engine system includes a compressor bypass valve 146, which can be opened so that most of the air from the first compressor impeller 40 will bypass the second compressor impeller 140. Correspondingly, the turbine side includes a turbine bypass valve 156, which can be opened so that most of the exhaust gas will bypass the second turbine 150 and continue directly to the first turbine impeller 50. The compressor and turbine bypass valves enable the engine system to operate in a single-stage mode or a two-stage series mode, depending on the engine operating conditions.

[0054] exist Figure 4 In the embodiment of , when the three-way valve 70 is placed in the bypass position, exhaust gas from the bypass exhaust manifold 26a' bypasses both turbines and continues directly to the catalytic treatment device 60, while exhaust gas from the main exhaust manifold 26b passes through the second turbine 150 and then through the first turbine 50 (when in two-stage series mode), or through the first turbine 50 (when in single-stage mode) before going to the catalytic treatment device. Figure 4A In the alternative embodiment shown in , the bypass line 80 is arranged to bypass only the second turbine 150. That is, the downstream end of the alternative bypass line 80 is connected to the exhaust gas discharge duct 54 after the first turbine impeller 50, and its downstream end is connected to the exhaust gas feed duct 52 between the two turbines.

[0055] Although Figure 4 and Figure 4A A twin turbo engine layout is shown in which the turbochargers are arranged in series, but it is also within the scope of the invention to arrange the turbochargers in parallel with each other.

[0056] The present invention is not limited to any particular number of engine cylinders. Figure 5 A third embodiment of the present invention is shown. Figure 5 The engine system is roughly similar to Figure 2 and Figure 3An embodiment, except that the 4-cylinder engine is replaced with Figure 5 The engine system of the third embodiment has a 6-cylinder engine. Another difference relates to how the engine cylinders are divided into subgroups. In the engine system of the third embodiment, the first subgroup has two cylinders 22a, which feed their exhaust gas into the bypass exhaust manifold 26a', and the second subgroup has four cylinders 22b, which feed their exhaust gas into the main exhaust manifold 26b'. However, the engine system of the third embodiment is substantially similar to the first embodiment described above in terms of how the three-way valve 70 operates.

[0057] Figures 6 to 8 One embodiment of a three-way valve 70 that can be used to practice the present invention is depicted. The valve includes a valve housing 70H that houses a valve member or rotor 70R having an actuator shaft 70S protruding from the housing. The valve rotor is rotatable about an axis defined by the shaft so that, alternatively, the valve rotor can be placed in a first position ( Figure 7 ) or the second position ( Figure 8 ). Exhaust gas enters valve 70 along direction or axis A0. The valve rotor and housing are configured to rotate the flow through approximately 90 degrees so that exhaust gas exits the valve along first axis A1 through first outlet 74 (when the valve rotor is in Figure 7 ), or alternatively, exits the valve along the second axis A2 through the second outlet 76 (when the valve rotor is in the first position Figure 8 As previously described, exhaust gas from the first engine cylinder subgroup enters the valve through inlet 72. When the valve rotor is in the Figure 7 When the valve rotor is in the first (non-bypass) position, gas exits from the first outlet 74 and is fed into the main exhaust manifold so that it mixes with the exhaust gas from the second subset of engine cylinders. Figure 8 In the second (bypass) position, the gas exits from the second outlet 76 and passes through the bypass line 80 (see Figures 2 to 5 Any of ) is fed directly to the catalytic treatment equipment.

[0058] As already noted, a key aspect of the three-way valve 70 is to fluidly isolate the flow path from the inlet 72 to the first outlet 74 from the flow path from the inlet 72 to the second outlet 76, as described in accordance with Figure 7 and Figure 8 The result is that when the valve is Figure 7When the valve is in the non-bypass position, the valve establishes fluid communication between the main exhaust manifold and the bypass exhaust manifold so that they together essentially act as a single manifold. However, when the valve is in the bypass position, the two exhaust manifolds are fluidly isolated from each other, as previously described. This fluid isolation means that exhaust gas from the main exhaust manifold is delivered to the turbine of the turbocharger without experiencing a pressure drop as would occur in a system with a conventional wastegate.

[0059] Fig. 9 A fourth embodiment of the present invention is described. The engine system of the fourth embodiment is similar to Figure 5 1. The third embodiment of the present invention, the primary difference relates to how fuel control and / or combustion timing is implemented in each of the first and second subsets of cylinders 22a, 22b. Fig. 9 A fuel controller 90 (including a fuel pump and a control unit for regulating the fuel delivery of the pump) is depicted for feeding fuel through a fuel rail 92 to electronically controlled fuel injectors 94a and 94b, which spray fuel into the cylinders. (Alternatively, there may be two separate fuel rails for the two groups of fuel injectors.) According to this embodiment, the fuel delivery schedule of the first subset of cylinders 22a via the first fuel injector 94a may be different from the fuel delivery schedule of the second subset of cylinders 22b via the second fuel injector 94b. In addition, the respective combustion timings within the two subsets of cylinders may be different from each other. For example, retarding the spark in the cylinders of the first subset may provide late combustion and produce higher exhaust temperatures. In this way, the temperature and / or pressure of the exhaust gas discharged from the first subset of cylinders 22a during cold start may be controlled independently of the temperature and / or pressure of the exhaust gas discharged from the second subset of cylinders 22b.

[0060] A method according to an embodiment of the present invention is shown in the form of a flow chart. Fig.10 . Decision step 101 inquires whether a cold start condition exists. There are various ways in which a cold start condition can be detected. For example, one technique is to determine how much time has elapsed since the last operation of the engine, and if the elapsed time exceeds a predetermined amount, it is assumed that the catalytic device has cooled below its light-off temperature. At start-up of the engine, it can be assumed that the cold start condition will persist for a predetermined period of time. Alternatively, a temperature measurement can be made at a suitable location (e.g., on or within the catalytic device), and the cold start condition can be determined based on an empirical correlation between the measured temperature and the emission level from the exhaust pipe of the engine, so that as long as the measured temperature is below a predetermined limit, a cold start condition is assumed.

[0061] In any case, if a cold start condition is found to exist in query step 101, then at step 103, the three-way valve is placed (or allowed to remain) in the bypass position. Alternatively, at step 105, a modified cold start fuel schedule (and possibly a modified cold start combustion timing) may be employed for a first subset of engine cylinders whose exhaust gas will be fed directly to the catalytic treatment device, while a normal fuel schedule and normal combustion timing are used in the second subset of said cylinders. The method then returns to query step 101 for the next iteration. If at some point, query step 101 produces a "no" result, such that a cold start condition no longer exists, then at step 102, the three-way valve is placed (or allowed to remain) in the non-bypass position, and at step 104, a normal fuel schedule is employed for the first subset of cylinders.

[0062] Fig.11 and Fig.12 An engine system according to a fifth embodiment of the present invention is shown. While the previous embodiments employed a partial engine bypass valve system in the form of a three-way valve 70 positioned between the main exhaust manifold and the bypass exhaust manifold, the engine system of the fifth embodiment achieves similar results through special dual exhaust valves in one or more engine cylinders, with the two exhaust valves of each cylinder being actuated independently of each other. Thus, a four-cylinder engine is shown, with each cylinder having a main exhaust valve 70b. In addition, at least one cylinder has a bypass exhaust valve 70a. The illustrated embodiment has a single cylinder including an additional bypass exhaust valve. The variable cam system is operable to open and close the main exhaust valve 70b during the exhaust phase of each engine cycle as usual, and to open and close or keep closed the bypass exhaust valve 70a during each exhaust phase. Fig.11 Depicted is the state of the exhaust valves during the exhaust phase when it is desired that all engine exhaust be fed to the turbine wheel 50. The main exhaust valve 70b opens, but the bypass exhaust valve 70a remains closed. Thus, all engine exhaust is discharged through the main exhaust valve into the main exhaust manifold 26b'', from which it is fed to the turbine wheel. This corresponds to a non-bypass position of the partial engine bypass valve system.

[0063] Fig.12An engine system is shown in which part of the engine bypass valve system is in the bypass position, such as would be used during cold start conditions. During the exhaust phase of each engine cycle, for each cylinder having a bypass exhaust valve 70a, the bypass exhaust valve is opened, but the main exhaust valve 70b remains closed. For the other cylinders having only a main exhaust valve, it is opened as usual. Therefore, a portion of the total exhaust gas is discharged through the bypass exhaust valve 70a into the bypass exhaust manifold 26a'', from which it is fed through the bypass line 80 to bypass the turbine impeller. The remainder of the exhaust gas is discharged through the main exhaust valve 70b into the main exhaust manifold 26b'', from which it is fed to the turbine impeller. Therefore, the valve system of this embodiment achieves similar results to the prior art embodiments, but without the need for a separate three-way valve.

[0064] exist Fig.11 and Fig.12 In the embodiment shown in FIG. 1 , only one engine cylinder has an additional bypass exhaust valve 70 a. However, alternatively, it is within the scope of the present invention for multiple engine cylinders to have additional bypass exhaust valves.

[0065] The present invention is applicable to many different types of internal combustion engines, including diesel, gasoline, natural gas, etc. Although embodiments with one turbocharger or two turbochargers have been shown, the present invention is not so limited; the present invention can be practiced with engine systems having more than two turbochargers (either in series or in parallel arrangements).

[0066] Based on this disclosure, those skilled in the art will recognize that modifications and other embodiments of the invention described herein can be made without departing from the inventive concepts described herein. Specific terms used herein are employed for explanatory purposes, not for limiting purposes. Therefore, the present invention is not limited to the specific embodiments disclosed, and modifications and other embodiments are intended to be included within the scope of the appended claims.

Claims

1. An engine system, comprising: an internal combustion engine having a plurality of cylinders, wherein the engine cylinders are divided into a first subgroup of cylinders and a second subgroup of cylinders; an exhaust manifold system including a main exhaust manifold receiving exhaust gas from the second subset of cylinders and a bypass exhaust manifold receiving exhaust gas from the first subset of cylinders; a bypass line coupled to the bypass exhaust manifold so as to receive exhaust gas therefrom; an exhaust feed conduit coupled to the primary exhaust manifold so as to receive exhaust gas therefrom; a first turbocharger including a first compressor and a first turbine, the first turbine including an exhaust gas inlet coupled to the exhaust gas feed conduit so as to receive exhaust gas therefrom, and including an exhaust gas discharge conduit for discharging exhaust gas having passed through the first turbine, the downstream end of the bypass line being coupled to the exhaust gas discharge conduit; and a partial engine bypass valve system disposed between the engine cylinders and the turbocharger, the partial engine bypass valve system defining a non-bypass position and a bypass position and comprising a three-way valve having a valve inlet, a first outlet, and a second outlet, wherein the valve inlet is coupled to the bypass exhaust manifold for receiving exhaust gas therefrom, the first outlet is coupled to the main exhaust manifold for supplying exhaust gas thereto, and the second outlet is coupled to an upstream end of the bypass line, the three-way valve in the non-bypass position allowing exhaust gas from the first subset of cylinders to flow directly into the main exhaust manifold while preventing exhaust gas from any of the engine cylinders from flowing via the bypass exhaust manifold to the bypass line, so that the exhaust gas from all engine cylinders is mixed and passed through the exhaust gas feed conduit for supply to the first turbine, Therein, the three-way valve in the bypass position allows exhaust gas from the first subset of cylinders to bypass the first turbine and continue into the exhaust discharge conduit, while exhaust gas from the second subset of cylinders flows into the main exhaust manifold to be supplied to the first turbine.

2. The engine system of claim 1 further comprising a catalytic treatment device coupled to the exhaust gas discharge conduit to receive exhaust gas therefrom.

3. The engine system according to claim 1, wherein: The engine has four cylinders, the first subgroup includes one cylinder, and the second subgroup includes three cylinders.

4. The engine system according to claim 1, wherein: The engine has six cylinders, the first subset includes two cylinders, and the second subset includes four cylinders.

5. The engine system of claim 1 further comprising a second turbocharger, the second turbocharger comprising a second compressor and a second turbine, the engine system comprising a piping system and one or more valves for selectively activating both the first and second turbochargers, or alternatively for activating the first turbocharger when the second turbocharger is inactive, and wherein, The bypass line is arranged such that when the three-way valve is in the bypass position, exhaust gas bypasses both the first turbine and the second turbine.

6. The engine system of claim 1 further comprising a second turbocharger, the second turbocharger comprising a second compressor and a second turbine, the engine system comprising a piping system and one or more valves for selectively activating both the first and second turbochargers, or alternatively for activating the first turbocharger when the second turbocharger is inactive, and wherein, The bypass line is arranged such that exhaust gas bypasses only the second turbine when the three-way valve is in the bypass position.

7. An engine system comprising An internal combustion engine having a plurality of cylinders, wherein The engine cylinders are divided into a first sub-group of cylinders and a second sub-group of cylinders; each cylinder in both the first and second sub-groups of cylinders has a main exhaust valve for discharging exhaust gas from the cylinder; an exhaust manifold system including a main exhaust manifold receiving exhaust gas from the second subset of cylinders and a bypass exhaust manifold receiving exhaust gas from the first subset of cylinders; a bypass line coupled to the bypass exhaust manifold so as to receive exhaust gas therefrom; an exhaust feed conduit coupled to the primary exhaust manifold so as to receive exhaust gas therefrom; a first turbocharger including a first compressor and a first turbine, the first turbine including an exhaust gas inlet coupled to the exhaust gas feed conduit so as to receive exhaust gas therefrom, and including an exhaust gas discharge conduit for discharging exhaust gas having passed through the first turbine, the downstream end of the bypass line being coupled to the exhaust gas discharge conduit; and a partial engine bypass valve system disposed between the engine cylinder and the turbocharger, the partial engine bypass valve system defining a non-bypass position and a bypass position, wherein the partial engine bypass valve system comprises a bypass exhaust valve for each cylinder of the first subset of cylinders, each bypass exhaust valve being coupled to the bypass exhaust manifold so as to feed exhaust gas from the first subset of cylinders into the bypass exhaust manifold when the bypass exhaust valve is open, and each main exhaust valve being coupled to the main exhaust manifold so as to feed exhaust gas from all cylinders into the main exhaust manifold when the main exhaust valve is open, wherein, in the non-bypass position, during the exhaust phase of each engine cycle, the bypass exhaust valve remains closed and the main exhaust valve opens, such that exhaust gas from the first subset of cylinders flows directly into the main exhaust manifold and exhaust gas from the second subset of cylinders flows directly into the main exhaust manifold for supply to the first turbine, while exhaust gas is prevented from flowing from any of the engine cylinders to the bypass exhaust manifold, Wherein, in the bypass position, during the exhaust phase of each engine cycle, the bypass exhaust valve of the first sub-group cylinders and the main exhaust valve of the second sub-group cylinders are opened, while the main exhaust valve of the first sub-group cylinders is closed, so that exhaust gas from the first sub-group cylinders flows into the bypass exhaust manifold and thereby bypasses the first turbine, and exhaust gas from the second sub-group cylinders flows into the main exhaust manifold so as to be supplied to the first turbine.

8. A method for operating an engine system, the engine system comprising: an internal combustion engine having a plurality of cylinders in which an air-fuel mixture is combusted to produce exhaust gas; a turbocharger having a turbine wheel for receiving the exhaust gas and a compressor wheel driven by the turbine wheel; and a catalytic treatment device that receives the exhaust gas and converts exhaust gas components into less harmful compounds, the method comprising the steps of: (a) determining whether a cold start condition exists such that the catalytic treatment device operates below a light-off temperature at which the catalytic treatment device becomes effective to convert the exhaust gas constituents into the less harmful compounds; (b) if it is determined that a cold start condition does not exist, directing a total amount of exhaust gas from the engine through the turbine wheel before continuing to the catalytic treatment device; and (c) if a cold start condition is determined to exist, directing a bypassed portion of the total amount of exhaust gas from the engine to bypass the turbine wheel and continue to the catalytic treatment device, and directing a remaining portion of the total amount of exhaust gas through the turbine wheel before continuing to the catalytic treatment device.

9. The method according to claim 8, wherein: The engine cylinders are divided into one or more cylinders of a first subset and cylinders of a second subset, and wherein step (b) includes directing exhaust gas from both the first and second subsets of cylinders to the turbine impeller, and step (c) includes directing exhaust gas from the first subset of cylinders to bypass the turbine impeller and continue to the catalytic treatment device.

10. The method according to claim 9, further comprising the steps of: If it is determined that cold-start conditions exist, a cold-start fuel schedule is employed in the first subset of the cylinders and a normal fuel schedule is employed in the second subset of the cylinders.

11. The method according to claim 10, further comprising the steps of: If it is determined that cold-start conditions exist, cold-start combustion timing is employed in the first subset of the cylinders and normal combustion timing is employed in the second subset of the cylinders.

12. The method according to claim 8, wherein: Each of the engine cylinders has a main exhaust valve, and one or more of the cylinders has an additional bypass exhaust valve, wherein step (c) includes opening the bypass exhaust valve and the main exhaust valve during the exhaust phase of each engine cycle, so that the bypass portion of the total exhaust gas is discharged through the bypass exhaust valve and fed through a bypass line bypassing the turbine impeller, and the remaining portion of the total exhaust gas is discharged through the main exhaust valve and fed to the turbine impeller, and wherein step (b) includes keeping the bypass exhaust valve closed and opening the main exhaust valve during the exhaust phase of each engine cycle, so that the total exhaust gas is discharged through the main exhaust valve and fed to the turbine impeller.

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