Combustion engine system

Abstract

An internal combustion engine system includes an internal combustion engine with a combustion chamber, an intake passage through which outside air flows, and an exhaust passage through which exhaust gas flows. A compressor is arranged in the intake passage and rotated by a turbine to compress outside air. A first return passage branches off from the exhaust passage and merges with the intake passage. An EGR cooler cools exhaust gas flowing through the first return passage. A second return passage branches off from the first return passage. A bypass passage branches off from the first return passage between an electric supercharger and the EGR cooler. A three-way valve is arranged where the bypass passage and the first return passage are connected. An intake valve is arranged in the intake passage between the point where the first return passage and the intake valve are connected and the point where the bypass passage and the intake valve are connected.

Description

BACKGROUND(a) Field of the invention

[0001] The present invention relates to an internal combustion engine system, and more particularly to an internal combustion engine system that recirculates exhaust gas in all driving ranges and maintains engine torque without using a rich air-fuel ratio in a high-speed, high-load range. (b) Description of the related art

[0002] An internal combustion engine mixes air and fuel properly and generates power by combusting the gas mixture. To achieve the required output power and combustion efficiency, sufficient air must be supplied to the internal combustion engine. Accordingly, a turbocharger is used to increase combustion efficiency and supply sufficient air to the internal combustion engine. On the other hand, an exhaust gas recirculation (EGR) system is installed on an internal combustion engine to reduce harmful exhaust gases and improve fuel efficiency.

[0003] The EGR system injects a portion of the exhaust gas from the internal combustion engine (e.g., approximately 5-20%) into the combustion chamber along with fresh air, resulting in higher pressure than if only fresh air were supplied to the combustion chamber. Pumping loss can thus be reduced. Furthermore, it may be possible to reduce the occurrence of knocking, which impairs the efficiency and performance of the gasoline internal combustion engine, by reducing the reactivity of the air-fuel mixture.

[0004] A low-pressure EGR (LP EGR) device can be used to apply the EGR system to an internal combustion engine equipped with a turbocharger. The LP EGR device includes exhaust gas passing through a turbocharger turbine and a three-way catalyst to an intake passage upstream of the turbocharger's compressor. Therefore, the flow of exhaust gas recirculated in the LP EGR device is generated using the difference between the exhaust pressure on a downstream side of the catalyst and the air pressure on an upstream side of the compressor.

[0005] However, in a low-load range of the internal combustion engine, where the exhaust gas pressure downstream of the catalyst is similar to atmospheric pressure, the pressure difference between an upstream side of an EGR valve and a downstream side of the EGR valve is minimal. Therefore, when the internal combustion engine operates in a low-load range, it may be difficult to supply the exhaust gas to the internal combustion engine. Meanwhile, if the fuel quantity is increased beyond a theoretical air-fuel ratio, the air utilization may increase and the reactivity of the air-fuel mixture may decrease. Therefore, engine knocking is reduced and engine torque may be increased.

[0006] To increase the maximum torque of an internal combustion engine under full load conditions, a strategy of combustion at a richer air-fuel ratio than the theoretical air-fuel ratio has recently been applied to a gasoline engine. Furthermore, with combustion at a rich air-fuel ratio, the adiabatic flame temperature is reduced, and thus the exhaust gas temperature can be reduced while maintaining the engine torque. Therefore, the strategy of combustion at a richer air-fuel ratio than the theoretical air-fuel ratio is used to lower the exhaust gas temperature to prevent damage to the catalyst, turbine, intake manifold, and exhaust manifold due to excessively hot exhaust gas in the high-speed and high-load range.

[0007] However, if fuel is burned at a rich air-fuel ratio, fuel efficiency may deteriorate and the emission of incomplete combustion products, such as unburned hydrocarbons and carbon monoxide, may increase. Therefore, regulations for rich air-fuel combustion are being developed to reduce air pollution caused by exhaust gases. If combustion at the theoretical air-fuel ratio is applied in all driving ranges without using rich air-fuel combustion under the preceding conditions, engine power and torque losses may occur.

[0008] The foregoing information disclosed in this section is provided solely for the purpose of facilitating an understanding of the background of the invention and may therefore contain information that does not constitute prior art already known to a person of ordinary skill in the art in this country.

[0009] JP 2018 - 184 873 A describes a control device for an internal combustion engine with a turbocharger, an exhaust gas recirculation system and an exhaust gas recirculation compressor, which is intended to suppress a response delay in the control of the amount of exhaust gas recirculated into the intake air.

[0010] EP 2 808 518 A1 describes an exhaust gas recirculation device for an internal combustion engine which is intended to extend an operating range in which homogeneous lean combustion is possible. PRESENTATION OF THE INVENTION

[0011] The present invention provides an internal combustion engine system that recirculates exhaust gas in all drive ranges and maintains engine torque without using a rich air-fuel ratio in a high speed and high load range.

[0012] An internal combustion engine system according to an exemplary embodiment of the present invention may include: an internal combustion engine having at least one combustion chamber that generates drive torque by burning an air-fuel mixture; an intake passage through which outside air supplied to the combustion chamber flows; an exhaust passage through which exhaust gas discharged from the combustion chamber of the internal combustion engine flows; a turbocharger having a turbine arranged in the exhaust passage and a compressor in the intake passage that rotates with the turbine to compress outside air; a first recirculation passage branching off from the exhaust passage at a downstream portion of the turbine and merging with the intake passage; and an EGR cooler arranged in the first recirculation passage and configured to cool exhaust gas flowing through the first recirculation passage.

[0013] Furthermore, the internal combustion engine system may include: an electric supercharger disposed in the first return line at a downstream portion of the EGR cooler; a second return line branching from the first return line between the EGR cooler and the electric supercharger and joining the first return line at an upstream portion of the electric supercharger; a bypass line branching from the first return line between the electric supercharger and the EGR cooler and joining the intake line; a three-way valve disposed in a portion where the bypass line and the first return line are connected; and an intake valve disposed in the intake line between a portion where the first return line and the intake valve are connected and a portion where the bypass line and the intake valve are connected.

[0014] The internal combustion engine system may further include a controller configured to operate the intake valve, the EGR valve, the three-way valve, and the electric supercharger based on an engine speed and an engine load. In a low-speed, high-load range, the controller may be configured to close the intake valve, open the EGR valve, operate the three-way valve to connect the first return line between a portion where the intake line and the first return line are connected, and provide fluid communication between a portion where the first return line and the bypass line are connected and the bypass line, and operate the electric supercharger in a forward direction.

[0015] A recirculation gas flowing through the second recirculation line and the outside air flowing from the intake line into the first recirculation line can be compressed by the electric supercharger and supplied to the combustion chamber, passing through the bypass line into the intake line. In a low-speed, medium-load range, the controller can be configured to open the intake valve, open the EGR valve, operate the three-way valve to prevent fluid communication between the first recirculation line and the bypass line, and stop the operation of the electric supercharger.

[0016] The outside air flowing through the intake passage and the recirculation gas flowing through the first return passage and the second return passage can be compressed by the compressor and supplied to the combustion chamber. In a low-speed, low-load range, the controller can be configured to open the intake valve, close the EGR valve, operate the three-way valve to provide fluid communication between the first return passage, between a portion where the exhaust passage and the first return passage are connected, and a portion where the intake passage and the first return passage are connected, and prevent fluid communication between the first return passage and the bypass passage, and operate the electric supercharger in a reverse direction.The outside air flowing through the intake line and the return gas flowing through the first return line can be fed to the combustion chamber by the compressor.

[0017] An internal combustion engine system according to another exemplary embodiment of the present invention may include: an internal combustion engine having at least one combustion chamber that generates drive torque by burning an air-fuel mixture; an intake passage through which outside air supplied to the combustion chamber flows; an exhaust passage through which exhaust gas discharged from the combustion chamber of the internal combustion engine flows; a turbocharger having a turbine arranged in the exhaust passage and a compressor arranged in the intake passage, which is rotated with the turbine to compress outside air; a warm-up catalytic converter (WCC) arranged in the exhaust passage at a downstream portion of the turbine; an under-floor catalytic converter (UCC) arranged in the exhaust passage at a downstream portion of the WCC;and a first return line branching off from the exhaust line between the WCC and the UCC and merging with the intake line;

[0018] The internal combustion engine system may further comprise: an EGR cooler arranged in the first return line and configured to cool exhaust gas flowing through the first return line; an electric supercharger arranged in the first return line at a downstream portion of the EGR cooler and configured to compress recirculation gas flowing through the first return line or outside air flowing through the first return line; a second return line branching off from the first return line between the EGR cooler and the electric supercharger and merging with the first return line at an upstream portion of the electric supercharger; a bypass line branching off from the first return line between the electric supercharger and the EGR cooler and merging with the intake line;a three-way valve disposed in a portion where the bypass line and the first return line are connected; and a suction valve disposed in the suction line between a portion where the first return line and the suction valve are connected and a portion where the bypass line and the suction valve are connected.

[0019] The internal combustion engine system may include a controller configured to operate the intake valve, the EGR valve, the three-way valve, and the electric supercharger based on an engine speed and an engine load. In a medium-speed, high-load range and a high-speed, high-load range, the controller may be configured to open the intake valve, close the EGR valve, operate the three-way valve to provide fluid communication between the first return line between a portion where the exhaust line and the first return line are connected and a portion where the intake line and the first return line are connected, and prevent fluid communication between the first return line and the bypass line, and operate the electric supercharger in a forward direction.

[0020] A portion of the outside air flowing into the intake passage may be supplied directly to the compressor, and the remaining outside air flows backward to the first return passage and is supplied to the UCC. According to an exemplary embodiment of the present invention, it may be possible to expand a range where exhaust gas can be recirculated to a low-load range by using an electric supercharger, and engine performance and fuel consumption can be improved by supplying charged air to the internal combustion engine in a low-speed, high-load range where it is difficult to supply sufficient charged air from a turbocharger.Furthermore, in a high-speed, high-load range where a rich air-fuel ratio combustion strategy is applied, a portion of the outside air (fresh air) flowing through an intake pipe may be fed to a catalyst to purify products of incomplete combustion of the exhaust gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The objects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which: Fig. 1 shows a schematic view of an internal combustion engine system according to an exemplary embodiment of the present invention; Fig. 2 shows a block diagram of an internal combustion engine system according to an exemplary embodiment of the present invention; Fig. 3 shows a schematic view of an internal combustion engine system according to an exemplary embodiment of the present invention in a low speed, high load region; Fig. 4 shows a schematic view of an internal combustion engine system according to an exemplary embodiment of the present invention in a low speed, medium load region; Fig. 5 shows a schematic view of an internal combustion engine system according to an exemplary embodiment of the present invention in a low speed and low load region; Fig. 6 shows a schematic view of an internal combustion engine system according to an exemplary embodiment of the present invention in a medium speed, high load region and a high speed, high load region. DETAILED DESCRIPTION

[0022] It is understood that the term “vehicle” or other similar term, as used herein, includes motor vehicles in general, such as passenger cars, including sport utility vehicles (SUVs), buses, trucks, various commercial vehicles, watercraft, including various boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles, and other alternative fuel vehicles (e.g., fuels derived from feedstocks other than petroleum).

[0023] As mentioned herein, a hybrid vehicle is a vehicle that has two or more power sources, for example, vehicles with both gasoline and electric power.

[0024] The terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the present invention.

[0025] As used herein, the singular forms "a" and "a," "an" and "the" are intended to include the plural forms unless the context clearly precludes it. It is further understood that the terms "comprises" and / or "comprising," when used in this specification, indicate the presence of recited features, integers, steps, acts, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, acts, elements, components, and / or groups thereof. As used herein, the term "and / or" includes any and all combinations of one or more of the corresponding recited items. The term "connected" refers to a physical relationship between two components, where the components are either directly connected or indirectly connected via one or more intermediate components.

[0026] Although the exemplary embodiment is described as using a plurality of units to perform the exemplary process, it should be understood that the exemplary processes may also be performed by one or a plurality of modules. Furthermore, it should be understood that one or more of the following methods or aspects thereof may be performed by at least one controller. The term "controller" or "controller" may refer to a hardware device that includes a memory and a processor. The memory is configured to execute program instructions, and the processor is specifically programmed to execute the program instructions to perform one or more of the processes further described below. Furthermore, it should be understood that the following methods may be performed by a system that includes the controller, as described in more detail below.

[0027] Furthermore, the controller of the present invention may be embodied as a non-transitory computer-readable medium containing executable program instructions executed by a processor or the like. Examples of computer-readable media include, but are not limited to, ROM, RAM, compact disc (CD)-ROMs, magnetic tapes, floppy disks, USB flash drives, smart cards, and optical data storage devices. The computer-readable recording medium may also be distributed in a computer network so that the program instructions are stored and executed in a distributed manner, e.g., by a telematics server or a controller area network (CAN).

[0028] Hereinafter, an internal combustion engine system according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings. Fig. 1 shows a schematic view of an internal combustion engine system according to an exemplary embodiment of the present invention. As in Fig. 1, an internal combustion engine system according to an exemplary embodiment of the present invention may include an internal combustion engine 10, an intake passage 20, an exhaust passage 30, and an exhaust gas recirculation (EGR) device.

[0029] The internal combustion engine 10 combusts an air-fuel mixture in which fuel and air are mixed to convert chemical energy into mechanical energy. The internal combustion engine 10 may include a plurality of combustion chambers 11, an intake manifold 13, a throttle valve 15, and an exhaust manifold 17. The combustion chambers 11 generate drive torque by burning fuel. Although the drawings show that the internal combustion engine 10 has four combustion chambers 21, the number of combustion chambers 21 is not limited thereto. The intake manifold 13 distributes air into the combustion chambers 11. The throttle valve 15 is disposed in the intake manifold 13. The amount of air supplied to the intake manifold 13 is adjusted by the throttle valve 15.

[0030] In particular, the exhaust manifold 17 may be connected to the combustion chamber 11. Exhaust gas discharged from the combustion chamber 11 may be discharged through the exhaust manifold 17. The internal combustion engine 10 may be, but is not limited to, a direct-injection gasoline engine that injects fuel directly into the gasoline engine. The intake manifold 20 may be connected to the intake manifold 13 and the exhaust gas recirculation device 50. An air cleaner 21, an intake valve 27, a compressor 22 of a turbocharger 23, and a charge air cooler 25 may be arranged in series in the intake line 20. The air cleaner 21 may be configured to filter outside air flowing into the intake line 20.

[0031] The compressor 22 of the turbocharger 23 may be arranged in the intake line 20 at a downstream portion of the air cleaner 21. The compressor 22 may be rotated in cooperation with a turbine 24 and may be configured to compress outside air flowing through the intake line 20 and / or recirculation gas flowing through the intake line 20. The charge air cooler 25 may be arranged in the intake line 20 at a downstream portion of the compressor 22. The charge air cooler 25 may be configured to cool outside air flowing through the intake line 20 and / or recirculation gas flowing through the intake line 20.

[0032] The intake valve 27 can be arranged in the intake line 20 between the compressor 22 and the air cleaner 21. The flow of outside air and / or recirculation gas through the intake line 20 can be adjusted with the intake valve 27. The turbine 24 of the turbocharger 23 and a catalyst 40 can be arranged in the exhaust line 30. The turbine 24 can be rotated by exhaust gas discharged from the combustion chamber 11.

[0033] Furthermore, the catalyst 40 may be arranged in the exhaust conduit 30 at a downstream portion of the turbine 24. The catalyst 40 may include a warm-up catalyst (WCC) 41 and an underbody catalyst (UCC) 43. The catalyst 40 may be configured to purify harmful material contained in the exhaust gas discharged from the combustion chamber 11. Exhaust gas flowing through the exhaust conduit 30 may be purified by the WCC 41 and supplied to the UCC 43. The UCC 43 may be arranged in the exhaust conduit 30 at a downstream portion of the WCC 41.

[0034] Furthermore, the exhaust gas recirculation device 60 may include a first recirculation line 61, a second recirculation line 63, a bypass line 74, a three-way valve 75, an electric supercharger 76, an EGR cooler 65, and an EGR valve 67. The exhaust gas recirculation device 60 may be, but is not limited to, a low-pressure EGR (LP EGR) device. The exhaust gas recirculation device 60 and the electric supercharger 76 will be described in detail. The first recirculation line 61 may branch off from the exhaust line 30 at a downstream portion of the turbine 24 and merge with the intake line 20 at a downstream portion of the air cleaner 21. Preferably, the first recirculation line 61 may branch off from the exhaust line 20 between the WCC 41 and the UCC 43.

[0035] A portion of the exhaust gas flowing through the exhaust line 30 may flow into the first recirculation line 61. Hereinafter, exhaust gas flowing into the first recirculation line 61 is referred to as recirculation gas (or EGR gas). The recirculation gas may flow through the first recirculation line 61 into the second recirculation line 63. Furthermore, a portion of the outside air flowing through the first recirculation line 61 may be supplied to the UCC by flowing backward through the first recirculation line 61. The EGR cooler 65 may be configured to cool recirculation gas or outside air flowing into the first recirculation line 61.

[0036] The electric charger 76 may be arranged in the first return line at a downstream portion of the EGR cooler 65. The electric charger 76 may be configured to compress recirculation gas and / or outside air flowing through the first return line. The electric charger 76 may include a motor and an electric compressor. The second return line 63 may branch off from the first return line at a downstream portion of the EGR cooler 65 and merge with the first return line at an upstream portion of the electric charger 76. The EGR valve 67 may be arranged in the second return line 63, and the amount of recirculation gas may be adjusted by the EGR valve 67.

[0037] The bypass line 74 may branch off from the first return line 61 between the EGR cooler 65 and the electric charger 76 and merge with the intake line 20 between the intake valve 27 and the compressor 22. The three-way valve 75 may be arranged at a portion where the first return line 61 and the bypass line 74 are connected.

[0038] Through the operation of the three-way valve 75, the first return line 61 can be fluidly connected between a portion where the intake line 20 and the first return line 61 can be connected and a portion where the first return line 61 and the bypass line 74 can be connected, and the bypass line 74 can be fluidly connected to the first return line 61. Accordingly, when the first return line 61 and the bypass line are connected, outside air supplied from the intake line 20 can flow backward through the first return line and the bypass line 74 (see Fig. 3). Furthermore, the operation of the three-way valve 75 blocks the connection between the first return line 61 and the bypass line 74.

[0039] If the connection between the first return line 61 and the bypass line 74 is blocked, return gas and / or outside air can flow through the first return line 61 and not into the bypass line (see Fig. 4 to Fig. 5). Furthermore, by operating the three-way valve 75, the first return line 61 can be fluidly connected between a portion where the exhaust line 30 and the first return line 61 can be connected and a portion where the intake line 20 and the first return line 61 are connected, and the connection between the first return line 61 and the bypass line 74 can be blocked. The three-way valve 75 can be operated by a control signal from a controller.

[0040] The electric supercharger 76 may be configured to compress recirculation gas flowing through the first recirculation line 61 and outside air flowing backward through the first recirculation line 61, and the compressed recirculation gas and the compressed outside air may be supplied to the combustion chamber 11 of the internal combustion engine 10. The electric supercharger 76 may be operated as a pump, and air flowing backward through the first recirculation line 61 may be supplied to the UCC 43 as needed.

[0041] In the description of the present invention, an operation of the electric supercharger that compresses a fluid (e.g., recirculation gas and / or outside air) flowing from a portion where the intake passage 20 and the first return passage 61 are connected to a portion where the first return passage 61 and the bypass passage 74 are connected is referred to as a forward operation of the electric supercharger (see solid arrow in Fig. 1). Furthermore, an operation of the electric supercharger that compresses a fluid (e.g., recirculation gas and / or outside air) flowing from a portion where the exhaust passage 30 and the first recirculation passage 61 are connected to a portion where the first recirculation passage 61 and the intake passage 20 are connected is referred to as a reverse operation of the electric supercharger (see dashed arrow in Fig. 1).

[0042] With reference to Fig. 2, the internal combustion engine system according to an exemplary embodiment of the present invention may further include a travel information detector 80, a differential pressure sensor 90, and a controller 100. The travel information detector 80 may be a sensor configured to detect an engine speed and an engine load, and the detected engine speed and engine load may be transmitted to the controller 100. The differential pressure sensor 90 may be configured to detect a differential pressure between a pressure in the intake line between the air cleaner 21 and the intake valve 27 and a pressure in the first return line 61. The differential pressure detected by the differential pressure sensor 90 may be transmitted to the controller 100. The controller 100 may be configured to determine a travel range of the internal combustion engine 10 based on the engine speed and the engine load.

[0043] Specifically, the driving range can be divided into a low speed low load range, a low speed medium load range, a low speed high load range, a medium speed medium load range, a medium speed medium load range, a medium speed high load range, a high speed low load range, a high speed medium load range, and a high speed high load range.

[0044] The controller 100 may be configured to operate the intake valve 27, the EGR valve 67, the three-way valve 75, and the electric supercharger 76 based on the engine speed and the engine load. Furthermore, the controller 100 may be configured to operate the turbocharger 23. The controller 100 may be provided as at least one processor operating by means of a predetermined program, and the predetermined program executes each step of a method for operating the internal combustion engine system according to an exemplary embodiment of the present invention.

[0045] Hereinafter, an operation of the internal combustion engine system according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings. Fig. 4 shows a schematic view of an internal combustion engine system according to an exemplary embodiment of the present invention in a low speed and medium load range.

[0046] When the drive range of the internal combustion engine is a low-speed, high-load range, the controller 100 may be configured to close the intake valve 27 and open the EGR valve 67. At the same time, the controller 100 may be configured to operate the three-way valve 75 to provide fluid communication between the first return line 61 between a portion where the intake line 20 and the first return line 61 are connected and a portion where the first return line and the bypass line 74 are connected.

[0047] When the intake valve 27 is closed, no outside air and / or recirculation gas flows through the intake pipe 20 between a portion where the intake pipe 20 and the first return pipe are connected and a portion where the intake pipe 20 and the bypass pipe 29 are connected. Therefore, outside air flowing backward through the air cleaner 21 flows through the first return pipe 61 and can be compressed by forward operation of the electric supercharger 76. When the EGR valve 67 is opened, recirculation gas flowing from the exhaust pipe 30 into the first return pipe flows through the second return pipe 63 and can be compressed by forward operation of the electric supercharger 76.

[0048] Since the first return line 61 is provided between a portion where the intake line 20 and the first return line 61 are connected and a portion where the first return line and the bypass line 74 are connected by the three-way valve 75, outside air and return gas compressed by the electric supercharger 76 can be simultaneously supplied to the combustion chamber 11 through the bypass line 74 and the intake line at a downstream portion of the intake valve 27.

[0049] In the low-speed, high-load ranges, the amount of exhaust gas discharged from the combustion chamber 11 is insufficient, making it difficult to compress outside air with the turbocharger 23. Accordingly, in the low-speed, high-load range, the compressed air can be supplied to the combustion chamber 11 by the forward operation of the electric supercharger, and thus sufficient engine torque can be output. Furthermore, the fuel consumption of the internal combustion engine 10 can be improved because the responsiveness of the air-fuel mixture in the combustion chamber 11 can be increased, and knocking can be suppressed by the supply of recirculation gas.

[0050] Fig. 4 shows a schematic view of an internal combustion engine system according to an exemplary embodiment of the present invention in a low-speed, medium-load range. When the driving range of the internal combustion engine 10 is a low-speed, medium-load range, the controller 100 may be configured to open the intake valve 27 and open the EGR valve 67. At the same time, the controller 100 may be configured to operate the three-way valve 75 to block the connection between the first return line 61 and the bypass line 74 and to stop the operation of the electric charger 76.

[0051] Since the intake valve 27 is open, the intake passage 20 is separated between a portion where the first return passage 61 and the intake passage 20 are connected and a portion where the bypass passage 74 and the intake passage 20 are connected, and outside air flowing from the air cleaner 21 can be directly supplied to the combustion chamber 11 through the compressor 22 of the turbocharger 23. Furthermore, since the EGR valve 67 is open and the first return passage 61 and the bypass passage 74 are not communicated with each other by the operation of the three-way valve 75, recirculation gas flowing from the exhaust passage 30 through the first return passage 61 can be supplied to the intake passage 20 through the second return passage 63.

[0052] Then, the recirculation gas can be supplied to the combustion chamber 11 after being compressed by the compressor 22 of the turbocharger 23. Since recirculation gas can be supplied to the combustion chamber in the low-speed, medium-load range, as described above, the responsiveness of the air-fuel mixture in the combustion chamber 11 can be increased and knocking can be suppressed. Therefore, the fuel consumption of the internal combustion engine 10 can be improved.

[0053] Fig. 5 shows a schematic view of an internal combustion engine system according to an exemplary embodiment of the present invention in a low-speed, low-load range. When the driving range of the internal combustion engine 10 is a low-speed, low-load range, the controller 100 may be configured to open the intake valve 27 and close the EGR valve 67. Furthermore, the controller 100 may be configured to operate the three-way valve 75 to provide communication between the first return line 61, between a portion where the exhaust line 30 and the first return line 61 are connected, and a portion where the intake line 20 and the first return line 61 are connected, and to block communication between the first return line 61 and the bypass line 74. At the same time, the controller 100 may be configured to operate the electric charger in reverse operation.

[0054] Since the intake valve 27 is opened, outside air can flow between a portion where the first return line 61 and the intake line 20 are connected and a portion where the bypass line 74 and the intake line 20 are connected.

[0055] Therefore, outside air flowing from the air cleaner 21 can be directly supplied to the combustion chamber 11 through the compressor 22 of the turbocharger 23. Furthermore, since the EGR valve 67 is closed and the first recirculation passage 61 is connected between a portion where the exhaust passage 30 and the first recirculation passage 61 are connected and a portion where the intake passage 20 and the first recirculation passage 61 are connected, recirculation gas flowing from the exhaust passage 30 can only flow through the first recirculation passage 61 and can be prevented from flowing through the second recirculation passage 63. Since the first recirculation passage 61 and the bypass passage 74 are not connected, recirculation gas is prevented from flowing through the bypass passage 74. Therefore, recirculation gas can be supplied to the intake passage 20 by the electric supercharger 76 operating as a pump.

[0056] In low-speed and low-load ranges, the pressure of the recirculation gas is lower than the pressure of the outside air flowing through the intake passage 20, and therefore, the circulation of the recirculation gas through the recirculation passage may not be uniform. Therefore, by operating the electric supercharger 76 installed in the first recirculation passage 61 in the reverse direction, the recirculation gas can be supplied more evenly to the combustion chamber 11 through the first recirculation passage 61, thereby improving the fuel consumption of the internal combustion engine.

[0057] Fig. 6 shows a schematic view of an internal combustion engine system according to an exemplary embodiment of the present invention in a medium-speed, high-load range and a high-speed, high-load range. When the driving range of the internal combustion engine 10 is a medium-speed, high-load range and a high-speed, high-load range, reference can be made to Fig. 6 the control must be set up to open the intake valve 27 and close the EGR valve 67.

[0058] Furthermore, the controller 100 may be configured to operate the three-way valve 75 to provide communication between the first return line 61, between a portion where the exhaust line 30 and the first return line 61 are connected, and a portion where the intake line 20 and the first return line 61 are connected, and to block the connection between the first return line 61 and the bypass line 74. The controller 100 may simultaneously be configured to operate the electric charger in a forward mode.

[0059] Since the intake valve 27 is open, outside air can flow through the intake pipe 20 between a portion where the first return pipe 61 and the intake pipe 20 are connected and a portion where the bypass pipe 74 and the intake pipe 20 are connected. Therefore, outside air flowing from the air cleaner 21 can be directly supplied to the combustion chamber 11 through the compressor 22 of the turbocharger 23.

[0060] Furthermore, in this case, the EGR valve is closed, the first return passage 61 is connected between a portion where the exhaust passage 30 and the first return passage 61 are connected and a portion where the intake passage 20 and the first return passage 61 are connected, and the electric supercharger can be operated in a forward operation. Therefore, exhaust gas can be prevented from flowing into the first return passage 61 and the second return passage 53, and a portion of the outside air flowing through the air cleaner 21 can flow backward through the first return passage and be supplied to the UCC 43.

[0061] In the medium-speed, high-load range and the high-speed, high-load range, the exhaust gas discharged from the combustion chamber 11 may contain a significant amount of incomplete combustion products due to the rich air-fuel ratio. Therefore, when a portion of outside air is supplied to the UCC 43 through the first return line 61, sufficient oxygen can be supplied to oxidize the incomplete combustion products of a three-way catalyst of the UCC 43, and the incomplete combustion products can be converted into harmless components and discharged outside the vehicle. List of reference symbols 10 Combustion engine 11 Combustion chamber 13 Intake manifold 15 Throttle valve 17 exhaust manifold 20 intake line 21 air purifiers 22 compressors 23 turbochargers 24 turbines 25 intercoolers 27 Intake valve 30 exhaust pipe 40 Catalyst 41 WCC 43 UCC 60 exhaust gas recirculation device 61 first return line 63 second return line 65 EGR cooler 67 EGR valve 75 three-way valve 76 electric chargers 80 Trip information detector 90 differential pressure sensor 100 Control

[0062] Although the invention has been described in connection with what are presently considered exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. On the contrary, it is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

[1] Internal combustion engine system, comprising: an internal combustion engine (10) having at least one combustion chamber (11) which generates drive torque by burning an air-fuel mixture; an intake line (20) in which outside air supplied to the combustion chamber (11) flows; an air purifier (21); an exhaust pipe (30) in which exhaust gas discharged from the combustion chamber (11) of the internal combustion engine (10) flows; a turbocharger (23) having a turbine (24) arranged in the exhaust line (30) and a compressor (22) arranged in the intake line (20) which is rotated with the turbine (24) to compress outside air; a first return line (61) branching off from the exhaust line (30) at a downstream portion of the turbine (24) and merging with the intake line (20); an exhaust gas recirculation (EGR) cooler (65) arranged in the first recirculation line (61) and configured to cool exhaust gas flowing through the first recirculation line (61); an electric charger (76) arranged in the first return line (61) at a downstream portion of the EGR cooler (65); a second return line (63) branching off from the first return line (61) between the EGR cooler (65) and the electric charger (76) and merging with the first return line (61) at an upstream portion of the electric charger (76); a bypass line (74) which branches off from the first return line (61) between the electric charger (76) and the EGR cooler (65) and is joined to the intake line (20); a three-way valve (75) arranged in a portion where the bypass line (74) and the first return line (61) are connected; and a suction valve (27) arranged in the suction line (20) between a portion where the first return line (61) and the suction valve (27) are connected and a portion where the bypass line (74) and the suction valve (27) are connected; wherein the intake valve (27) is arranged in the intake line (20) between the compressor (22) and the air cleaner (27). [2] The internal combustion engine system of claim 1, further comprising: a controller (100) configured to operate the intake valve (27), an EGR valve (67), the three-way valve (75), and the electric charger (76) based on an engine speed and an engine load. [3] Internal combustion engine system according to claim 2, wherein in a low speed and high load range, the controller (100) is arranged: to close the intake valve (27); to open the EGR valve (67); to operate the three-way valve (75) to provide fluid communication between the first return line (61), between a portion where the suction line (20) and the first return line (61) are connected, and a portion where the first return line (61) and the bypass line (74) are connected, and the bypass line (74); and to operate the electric charger (76) in a forward direction. [4] An internal combustion engine system according to claim 3, wherein a recirculation gas flowing through the second recirculation line (63) and the outside air flowing from the intake line (20) into the first recirculation line (61) are compressed by the electric charger (76) and supplied to the combustion chamber (11), passing through the bypass line (74) to the intake line (20). [5] Internal combustion engine system according to claim 2, wherein in a low speed and medium load range, the controller (100) is arranged: to open the intake valve (27); to open the EGR valve (67); to operate the three-way valve (75) to block the connection between the first return line (61) and the bypass line (74); and to stop the operation of the electric charger (76). [6] Internal combustion engine system according to claim 5, wherein the outside air flowing through the intake line (20) and the return gas flowing through the first return line (61) and the second return line (63) are supplied to the combustion chamber (11) in a compressed manner by the compressor (22). [7] Internal combustion engine system according to claim 2, wherein in a low speed and low load range, the controller (100) is arranged: to open the intake valve (27); to close the EGR valve (67); to operate the three-way valve (75) to provide fluid communication between the first return line (61) between a portion where the exhaust line (30) and the first return line (61) are connected and a portion where the intake line (20) and the first return line (61) are connected, and to block the communication between the first return line (61) and the bypass line (74); and to operate the electric charger (76) in a reverse direction. [8] An internal combustion engine system according to claim 7, wherein the outside air flowing through the intake line (20) and the recirculation gas flowing through the first return line (61) are supplied to the combustion chamber (11) by the compressor (22). [9] Internal combustion engine system, comprising: an internal combustion engine (10) having at least one combustion chamber (11) which generates drive torque by burning an air-fuel mixture; an intake line (20) in which outside air supplied to the combustion chamber (11) flows; an air purifier (21); an exhaust pipe (30) in which exhaust gas discharged from the combustion chamber (11) of the internal combustion engine (10) flows; a turbocharger (23) having a turbine (24) arranged in the exhaust line (30) and a compressor (22) arranged in the intake line (20) which is rotated with the turbine (24) to compress outside air; a warm-up catalyst (WCC) disposed in the exhaust line (30) at a downstream portion of the turbine (24); an underbody catalyst (UCC) arranged in the exhaust line (30) at a downstream portion of the WCC; a first return line (61) branching off from the exhaust line (30) between the WCC and the UCC and merging with the intake line (20); an exhaust gas recirculation (EGR) cooler (65) arranged in the first recirculation line (61) and configured to cool exhaust gas flowing through the first recirculation line (61); an electric charger (76) arranged in the first return line (61) at a downstream portion of the EGR cooler (65) and configured to compress return gas or outside air flowing through the first return line (61); a second return line (63) branching off from the first return line (61) between the EGR cooler (65) and the electric charger (76) and merging with the first return line (61) at an upstream portion of the electric charger (76); a bypass line (74) which branches off from the first return line (61) between the electric charger (76) and the EGR cooler (65) and is joined to the intake line (20); a three-way valve (75) arranged in a portion where the bypass line (74) and the first return line (61) are connected; and a suction valve (27) arranged in the suction line (20) between a portion where the first return line (61) and the suction valve (27) are connected and a portion where the bypass line (74) and the suction valve (27) are connected; wherein the intake valve (27) is arranged in the intake line (20) between the compressor (22) and the air cleaner (27). [10] Internal combustion engine system according to claim 9, comprising: a controller (100) configured to operate the intake valve (27), the EGR valve (67), the three-way valve (75), and the electric charger (76) based on an engine speed and an engine load. [11] An internal combustion engine system according to claim 10, wherein in a medium speed and high load range and a high speed and high load range, the controller (100) is arranged: to open the intake valve (27); to close the EGR valve (67); to operate the three-way valve (75) to provide fluid communication between the first return line (61), between a portion where the exhaust line (30) and the first return line (61) are connected, and a portion where the intake line (20) and the first return line (61) are connected, and to block the communication between the first return line (61) and the bypass line (74); and to operate the electric charger (76) in a forward direction. [12] An internal combustion engine system according to claim 11, wherein a portion of the outside air flowing into the intake passage (20) is directly supplied to the compressor (22) and a remaining amount of outside air flows backward to the first return passage (61) and is supplied to the UCC.

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