Thermal exhaust gas management

Abstract

A method (200) for controlling the temperature of recirculated exhaust gas in an internal combustion engine, comprising: Operating (202) the internal combustion engine (10) in a baseline mode; Receiving (204) a signal indicating the operating temperature of a motor; (206) comparing the engine operating temperature with a predetermined IEGR threshold; if the engine operating temperature is lower than the predetermined IEGR threshold, (210) activating an IEGR mode in which internal exhaust gas recirculation is present, and activating an EEVO mode, which is an operating mode of the internal combustion engine in which exhaust valve timing is changed compared to an initial operating mode; and If the engine operating temperature is higher than the first preset IEGR threshold, the IEGR mode is deactivated and the EEVO mode is deactivated. wherein the baseline mode includes activating a primary exhaust valve opening during an exhaust event of the associated cylinder of the exhaust valve, wherein the IEGR modes include activating a secondary exhaust valve opening during an intake event of the associated cylinder of the exhaust valve and partially holding the exhaust valve (64) open between the primary exhaust valve opening and the secondary exhaust valve opening, wherein the exhaust valve (64) is fully open during the primary exhaust valve opening and the exhaust valve has less than 40% of its full opening during the secondary exhaust valve opening, including the EEVO modes: Activating the primary exhaust valve opening prior to the primary exhaust valve opening of the baseline; holding the exhaust valve fully open (64); and Closing the outlet valve (64) according to the baseline mode.

Description

INTRODUCTION

[0001] The present disclosure relates to a method for controlling the temperature of recirculated exhaust gas in an internal combustion engine.

[0002] Exhaust gas recirculation (EGR) is used in internal combustion engines to reduce throttling losses at low loads, improve knock tolerance, and lower the nitrogen oxide (NOx) content in the exhaust gas. EGR is particularly important as an emission reducer in combustion engines that run stoichiometrically lean and are therefore prone to higher NOx emissions.

[0003] Internal combustion engines that incorporate exhaust gas recirculation (EGR) systems can rely on internal EGR (IEGR), external EGR (EEGR), or a combination of both. With EEGR, EGR is introduced into the combustion chamber of an engine via an intake valve after it has passed through an external line from the exhaust system. IEGR involves introducing EGR into the combustion chamber of an engine through an exhaust valve or an intake valve without using an external line. To deliver an exhaust gas flow into the combustion chambers when using EEGR, a pressure differential is required between the engine's exhaust flow path and the point in the intake system where the exhaust gas is re-injected. In IEGR, an intake event (i.e., a volume expansion within the combustion chamber, such as during the intake stroke of a piston in an internal combustion engine) typically provides a suitable pressure differential.

[0004] An IEGR system can take advantage of this pressure differential by opening one or more exhaust valves during the intake event of the valve's corresponding cylinder. A camshaft can be configured to facilitate the selective activation and deactivation of valve control systems, allowing IEGR to be selectively enabled and / or disabled. Duration, timing, and valve lift (i.e., flow rate) are influenced by the camshaft geometry in conjunction with the valve train components. Switchable rocker arms can facilitate switching between sets of lobes on a modified camshaft to enable switching between EGR modes. For example, a variable rocker arm assembly can be actuated or switched based on oil pressure, which can be modulated by an oil control valve.When different modes are activated, different cam lobes become active, which leads to control of the timing of the valve actuation and thus to control of the IEGR.

[0005] In the initial phases of engine operation after a cold start (i.e., approximately 200 seconds), before the engine reaches normal operating temperatures (e.g., coolant temperatures above approximately 90°C), exhaust emissions may tend to exceed desirable or permissible levels. At relatively low exhaust temperatures, such as during engine warm-up, EEGR can negatively affect combustion stability and also cause increased hydrocarbon (HC) emissions. IEGR is useful in a DOC warm-up strategy.

[0006] While current IEGR modes achieve their intended purpose of increasing the exhaust gas temperature, there is a need for a new and improved method for controlling the temperature of the recirculated exhaust gas in an internal combustion engine, which allows for improved heating of the recirculated exhaust gas compared to the use of IEGR alone.

[0007] DE 10 2017 200 739 A1 discloses a turbocharged internal combustion engine with at least one cylinder, in which each cylinder has at least two exhaust ports. These are each equipped with a valve train that moves a valve along a longitudinal axis between a closed and an open position with a maximum stroke Δh_max,exhaust. At least one exhaust port has a variable valve train in which the opening time of the exhaust valve can be advanced.

[0008] DE 10 2005 015 853 A1 describes a method for operating a reciprocating internal combustion engine with internal and external exhaust gas recirculation, wherein the reciprocating internal combustion engine has variably controllable gas exchange valves and exhaust gas aftertreatment such as a particulate filter, a NOₓ filter, and a catalytic converter. x -Adsorber catalyst, an SCR catalyst and / or an oxidation catalyst, to which exhaust gases heated above normal exhaust gas temperatures are fed during a regeneration operation.

[0009] DE 10 2012 023 524 A1 relates to a diesel engine with an engine block comprising a cylinder, a fuel injection valve for supplying fuel to the cylinder, and a control module for controlling the opening and closing times of the intake or exhaust valves. For exhaust aftertreatment, an oxidation catalyst is provided, which is arranged in the exhaust port for the reduction of hydrocarbons (HC), as well as a diesel particulate filter (DPF), which is arranged downstream of the oxidation catalyst for separating soot particles from the exhaust stream.

[0010] AT 515 613 A1 relates to a method for heating exhaust gas components in the exhaust system of a combustion engine, particularly a self-igniting engine. To enable a simple and effective rapid increase in the temperature of exhaust gas components, it is provided that, at least in a partial load operating range with low engine load, the temperature of the exhaust gas and / or an exhaust aftertreatment device arranged in the exhaust system is measured. DESCRIPTION

[0011] The object of the invention is to improve exhaust gas recirculation control by means of baseline operation with primary exhaust port, IEGR mode with additional partially opened secondary exhaust port during the intake stroke and EEVO mode with advanced primary port opening and full opening of the exhaust valve.

[0012] This problem is solved by the subject matter according to claim 1. Further developments can be found in the dependent claims.

[0013] According to several aspects of the present disclosure, a method for controlling the temperature of recirculated exhaust gas in an internal combustion engine comprises operating the internal combustion engine in a baseline mode, receiving a signal indicating an engine operating temperature, comparing the engine operating temperature with a predetermined IEGR threshold, and, if the engine operating temperature is lower than the predetermined IEGR threshold, activating an IEGR mode and an EEVO mode, and, if the engine operating temperature is higher than the first predetermined IEGR threshold, deactivating the IEGR mode and the EEVO mode.

[0014] From another perspective, the engine's operating temperature is a coolant temperature.

[0015] From another perspective, the engine's operating temperature is an exhaust gas temperature.

[0016] From another perspective, the engine's operating temperature is an oil temperature.

[0017] From another perspective, the baseline mode includes the activation of a primary exhaust valve opening during an exhaust event of the associated cylinder of the exhaust valve.

[0018] From another perspective, the IEGR mode involves activating a secondary exhaust valve opening during an intake event of the cylinder associated with the exhaust valve and partially keeping the exhaust valve open between the opening of the primary exhaust valve and the opening of the secondary exhaust valve.

[0019] According to another aspect, the exhaust valve is fully open during the opening of the primary exhaust valve, and the exhaust valve is less than 40% fully open during the opening of the secondary exhaust valve.

[0020] From another perspective, the EEVO mode includes activating the opening of the primary exhaust valve prior to the opening of the primary exhaust valve in the baseline mode, keeping the exhaust valve fully open, and closing the exhaust valve in accordance with the baseline mode.

[0021] According to several aspects of the present disclosure, a method for controlling the temperature of recirculated exhaust gas in an internal combustion engine comprises operating the internal combustion engine in a baseline mode, receiving a signal indicating an engine operating temperature, wherein the engine operating temperature is one of coolant temperature, exhaust gas temperature and oil temperature, comparing the engine operating temperature with a predetermined IEGR threshold, activating an IEGR mode and activating an EEVO mode if the engine operating temperature is below the predetermined IEGR threshold, and deactivating the IEGR mode and EEVO mode if the engine operating temperature is above the first predetermined IEGR threshold.

[0022] From another perspective, the baseline mode involves activating a primary exhaust valve opening during an exhaust event of the associated cylinder of the exhaust valve, with the exhaust valve being fully opened during the primary exhaust valve opening.

[0023] According to another aspect, the IEGR mode involves the activation of a secondary exhaust valve opening during an intake event of the cylinder associated with the exhaust valve, wherein the exhaust valve is less than 40% fully open during the secondary exhaust valve opening and the exhaust valve is held partially open between the primary exhaust valve opening and the secondary exhaust valve opening.

[0024] From another perspective, the EEVO mode includes activating the opening of the primary exhaust valve prior to the opening of the primary exhaust valve in the baseline mode, keeping the exhaust valve fully open, and closing the exhaust valve in accordance with the baseline mode.

[0025] According to several aspects of the present disclosure, an internal combustion engine comprises at least one combustion cylinder, at least one exhaust valve designed to allow combustion gases to be expelled from the combustion cylinder, and a camshaft with cams designed to control the at least one exhaust valve, the camshaft further being designed to selectively actuate the at least one exhaust valve in at least one of a baseline mode, an IEGR mode, and an EEVO mode.

[0026] According to another aspect, the internal combustion engine further comprises a control module, wherein the control module is designed to receive a signal indicating an engine operating temperature and to operate the internal combustion engine in baseline mode when the engine temperature exceeds a predetermined IEGR threshold, and to operate the internal combustion engine in both IEGR mode and EEVO mode when the engine temperature is below the predetermined IEGR threshold.

[0027] From another perspective, the engine's operating temperature is a coolant temperature.

[0028] From another perspective, the engine's operating temperature is an exhaust gas temperature.

[0029] From another perspective, the engine's operating temperature is an oil temperature.

[0030] According to another aspect, when operating in baseline mode, the camshaft is adapted to actuate a primary exhaust valve opening by fully opening the exhaust valve during an exhaust event of the associated cylinder of the exhaust valve.

[0031] According to another aspect, when operating in IEGR mode, the camshaft is adapted to actuate a secondary exhaust valve opening by opening the exhaust valve to less than 40% of its full opening during an intake event of the cylinder to which the exhaust valve belongs, and by keeping the exhaust valve partially open between the opening of the primary exhaust valve and the opening of the secondary exhaust valve.

[0032] Another aspect is that when operating in EEVO mode, the camshaft is adapted to actuate the opening of the primary exhaust valve before the opening of the baseline primary exhaust valve, keeping the exhaust valve fully open and closing the exhaust valve according to the baseline mode.

[0033] Further areas of application will become apparent from the description given here. It should be understood that the description and the specific examples serve only for illustration and are not intended to limit the scope of this disclosure. BRIEF DESCRIPTION OF THE FIGURES

[0034] The figures described here serve only for illustration and are not intended to limit the scope of the present revelation in any way. Fig. Figure 1 is a schematic representation of an internal combustion engine in accordance with an exemplary embodiment of the present disclosure; Fig. 2 is a side section of a cylinder of the in Fig. 1 internal combustion engine shown; Fig. Figure 3 is a schematic flowchart of a process according to an exemplary embodiment; Fig. Figure 4 is a graphical representation of a baseline mode according to an exemplary embodiment; and Fig. Figure 5 is a graphical representation of an EEVO and IEGR operating mode according to an exemplary embodiment. DETAILED DESCRIPTION

[0035] The following description is merely exemplary and is not intended to limit the present disclosure, application or use.

[0036] With reference to Fig. 1 and Fig. 2 comprises an internal combustion engine assembly 10 in an exemplary embodiment, an engine structure 12, an intake system 14, an exhaust system 16, a valve train assembly 18, and an exhaust gas recirculation (EGR) assembly 20. The engine structure 12 comprises an engine block 24 coupled to a cylinder head 26 to define the cylinders 22, which form combustion chambers. The cylinder head 26 defines intake ports 28 and exhaust ports 30, which communicate with the combustion chambers.

[0037] As in Fig. As shown schematically in Figure 1, the engine assembly 10 defines four cylinders 22-1, 22-2, 22-3, 22-4. For the sake of simplicity, only a single representative cylinder 22 is shown in the Fig. 2 shown in the sectional view; the features and aspects relating to the in Fig. The points discussed for cylinders 22 shown are relevant to the other cylinders 22, but are equally applicable to the remaining cylinders 22. Furthermore, it is assumed that the present teachings apply to any number of piston-cylinder arrangements and a variety of reciprocating engine configurations, including but not limited to V-engines, inline engines, and horizontally opposed engines, as well as both overhead cam and cam-block configurations.

[0038] The intake system 14, in an exemplary embodiment, consists of an intake duct 32, an intake manifold 36 coupled to the cylinder head 26 and in fluid communication with the intake duct 32, and an intake throttle valve 38 located in the intake duct 32. The intake throttle valve 38 can be configured for one or more purposes: (a) airflow control, (b) pressure differential across a short-path EGR cooler, (c) soft engine shutdown, (d) control of the EGR flow rate, and / or (e) control of the flow rate of intake air to the intake ducts 28 through the intake manifold 36. The intake system 14 also includes a turbocharger 40, including an intake side 42 (compressor), located in the intake duct 32, and an air filter 44, also located in the intake duct 32.The inlet channel 32 can define an air inlet into the intake system 14, and the turbocharger 40 can be connected to the inlet openings 28 via the intake manifold 36. Although a single turbocharger 40 is shown, it is assumed that the present disclosure applies equally to arrangements with multiple turbochargers.

[0039] The exhaust system 16 can comprise an exhaust pipe 48, an exhaust manifold 52 coupled to the cylinder head 26 and connected to the exhaust pipe 48, a diesel particulate filter (DPF) 54, and a catalyst 56 for selective catalytic reduction (SCR) arranged in the exhaust pipe 48. Although it is shown that a single DPF 54 and a single SCR catalyst 56 are included, it is understood that the present disclosure is not limited to such arrangements. The DPF 54 can alternatively be incorporated into a combined DPF / SCR catalyst. Furthermore, the SCR catalyst 56 can alternatively be arranged upstream of the DPF 54, or an additional SCR catalyst (not shown) can be arranged upstream of the DPF 54.An exhaust side 58 (turbine) of the turbocharger 40 can be arranged in the exhaust line 48 and can contain a turbine wheel that is connected to and driven by the exhaust gas flowing through the exhaust line 48. The exhaust side 58 of the turbocharger 40 can include a variable exhaust outlet 60 that controls the limitation of the exhaust gas flow through the turbocharger 40. The variable exhaust outlet 60 can have the form of a variable nozzle.

[0040] As in Fig. As shown in Figure 2, the valve train assembly 18 can comprise intake valves 62 in the intake ports 28, exhaust valves 64 in the exhaust ports 30, intake valve lift mechanisms 66 mounted on the cylinder head 26 and engaging with the intake valves 62, exhaust valve lift mechanisms 68 mounted on the cylinder head 26 and engaging with the exhaust valves 64, an intake camshaft 70 rotatably mounted on the cylinder head 26 and engaging with the intake valve lift mechanisms 66, and an exhaust camshaft 72 rotatably mounted on the cylinder head 26 and engaging with the exhaust valve lift mechanisms 68. The intake camshaft 70 can have intake cams 74 that engage with each of the intake valve lift mechanisms 66.The intake camshaft 70 may include an intake camshaft adjuster (not shown), and the intake valve lift mechanisms 66 may take a variety of forms, including but not limited to conventional or variable valve lift mechanisms.

[0041] The exhaust valve lift mechanisms 68 can form hydraulically actuated, disabling valve lift mechanisms that can be operated in a variety of modes, such as a baseline mode, an IEGR mode, and an EEVO mode. In the present non-limiting example, the exhaust valve lift mechanisms 68 can have the form of a rocker arm with a pair of outer arms 78, an inner arm with a roller 82, and a locking mechanism that selectively couples the outer arms 78 to the inner arm. The locking mechanism can be switched between locked and unlocked positions by a pressure fluid supply. The locking mechanism can secure the outer arms 78 for displacement with the inner arm during a particular mode and can allow relative displacement between the outer arms 78 and the inner arm during another mode.

[0042] The exhaust camshaft 72 can have EGR cams 88 that engage with each of the outer arms 78, and exhaust cams 90 that are located between pairs of EGR cams 88 and engage with the inner arm. Each of the EGR cams 88 can define an EGR lift range 92 that is at least partially rotationally aligned with an intake lift range 94 defined by a corresponding intake cam 74. The exhaust cams 90 can define an exhaust lift range 96 that is rotationally offset relative to the EGR lift range 92 and the intake lift range 94.

[0043] The EGR assembly 20 can comprise an EGR line 98, an EGR cooler 100, and a cooler bypass 102 located in the EGR line 98, an EGR control valve 104, and a backpressure control valve 106. The EGR line 98 can extend from the exhaust line 48 at a point between the turbocharger 40 and an outlet of the exhaust line 48 to the intake system 14 to establish a connection between the intake system 14 and the exhaust system 16.

[0044] In the Fig. In the non-limiting example shown in Figure 1, the EGR control valve 104 can be arranged at the outlet of the EGR line 98 and control the exhaust gas recirculation flow from the EGR line 98 to the intake system 14. A backpressure control valve 106 can be arranged in the exhaust line 48 at a point between the EGR line 98 and an outlet of the exhaust line 48. In the example shown in Figure 1, the EGR control valve 104 can be arranged at the outlet of the exhaust line 98. Fig. In the non-limiting example shown, the backpressure control valve 106 is located at the outlet of the exhaust line 48. The DPF 54 can be located in the exhaust line 48 at a point between the outlet side 58 of the turbocharger 40 and the backpressure control valve 106. The arrangement discussed above provides an IEGR system in combination with a low-pressure EGR system.

[0045] The engine assembly 10 may additionally include a control module 108 in conjunction with the EGR control valve 104 and the backpressure control valve 106. The pressure fluid supply for the exhaust valve lift mechanisms 68 may include oil control valves that are connected to and controlled by the control module 108. It should be noted that the intake throttle valve 38 may also be connected to the control module 108.

[0046] The backpressure control valve 106 can be used to control the pressure differential between the intake system 14 and the exhaust system 16 for both the IEGR system and the low-pressure EGR system to adjust the exhaust gas recirculation in the engine assembly 10. The exhaust valve lift mechanisms 68 and the EGR control valve 104 can be adjusted by the control module 108 to ensure the desired exhaust gas recirculation during engine operation. The intake throttle valve 38 and the variable exhaust outlet 60 of the turbocharger 40 can also be used to control the pressure differential between the intake system 14 and the exhaust system 16 to further adjust the amount of exhaust gas recirculated in the engine assembly 10. In some arrangements, the EGR assembly 20 may additionally include a bypass channel 112 and a bypass valve 114, which is located in the bypass channel 112 and communicates with the control module 108.The bypass channel 112 can extend from the exhaust manifold 52 to a section of the intake channel 32 located between the intake throttle valve 38 and the intake manifold 36 to allow further control of the exhaust gas recirculation.

[0047] The EGR stroke area 92 of the EGR cams 88 ensures internal exhaust gas recirculation. The IEGR system can be used as a high-pressure EGR system, thus eliminating the typical high-pressure EGR lines and coolers, as well as the potential for high-pressure EGR cooler fouling.

[0048] As in Fig. As shown in Figure 2, the lift regions 92, 94, and 96 can generally be defined as regions of the cams 74, 88, and 90, including the cam tips extending from a base circle region to provide valve lift. The exhaust valve 64 can be moved to an open position when the tips of the exhaust cams 90 engage the exhaust valve lift mechanisms 68. The exhaust valve 64 can also be moved to an open position when the tips of the EGR cams 88 engage the exhaust valve lift mechanisms 68 during IEGR mode. The EGR cams 88 can provide internal exhaust gas recirculation when the exhaust valve lift mechanisms 68 are operated in IEGR mode.

[0049] The engine assembly includes first EGR cams 88 and first exhaust cams 90, which engage with the first exhaust valve lift mechanisms 68 for each of the cylinders 22-1, 22-2, 22-3, 22-4.

[0050] In an exemplary embodiment of the present revelation, in Fig. 3 A method 200 for controlling the temperature of recirculated exhaust gas in an internal combustion engine 10 is graphically represented. Starting with block 202, the method 200 includes the operation of the internal combustion engine 10 in baseline mode. With reference to Fig. Figure 4 shows, in a non-limiting example, the opening profiles for the inlet valves 62 and the exhaust valves 64 of a cylinder 22. The x-axis in Fig. 4 represents the crank angle and the Y-axis represents the valve lift.

[0051] The baseline mode includes a primary exhaust valve opening, as specified at 120. The primary exhaust valve opening 120 comprises a gradual opening followed by a gradual closing of the associated cylinder 22 exhaust valve during an exhaust event. During the primary exhaust valve opening 120, the exhaust valve 64 is fully opened. As in Fig. As shown in Figure 3, the stroke 122 of the primary exhaust valve 64 when fully open is between approximately 9 mm and 10 mm. After the exhaust event, the intake valve 62 is opened during an intake event for the associated cylinder, as shown in Figure 124.

[0052] With renewed reference to Fig. 3. Continuing to block 204, control module 108 receives a signal indicating the engine operating temperature. The engine operating temperature can be based on the engine coolant temperature, the exhaust gas temperature, or the engine oil temperature. On the way to block 206, the engine operating temperature is compared to a predefined IEGR threshold. If the engine operating temperature is higher than the predefined IEGR threshold, no action is taken when transitioning to block 208, and the baseline control mode continues. Transiting to block 210, if the engine operating temperature is below the predefined IEGR threshold, an IEGR mode is activated, and an EEVO mode is enabled.

[0053] With reference to Fig. 5. The IEGR mode includes the activation of a secondary exhaust valve opening 126 after the primary exhaust valve opening 120 during the intake event of cylinder 22 associated with exhaust valve 64. During the secondary exhaust valve opening 126, a secondary valve lift 128 of the exhaust valve 64 is opened by less than 40% of the primary valve lift 122 when the exhaust valve 64 is fully open. In the Fig. In the non-limiting example embodiment shown in Figure 5, the secondary valve lift 128 of the exhaust valve 64 during the secondary exhaust valve opening 126 is between approximately 2 mm and 3 mm. IEGR increases the ignition energy of the charge to reduce HC and CO emissions and increases the exhaust temperature. A full opening of the secondary exhaust valve 126 during IEGR mode can occur while a corresponding intake valve 62 (i.e., the intake valve for the same cylinder) is open, as illustrated by the intake valve lift event 124.

[0054] Furthermore, the exhaust valve 64 is held partially open between the primary exhaust valve opening 120 and the secondary exhaust valve opening 126, as shown in 127. Fig. 5. If the exhaust valve 64 is not located between the primary and secondary exhaust valve openings 120, 126, the stroke duration is shortened. This increases the engine's operating speed range for switching between modes and improves the engine's NVH characteristics at all speeds.

[0055] Once again on Fig. 5 Referring to this, the EEVO modes involve activating a primary exhaust valve that opens 120A before the baseline primary exhaust valve 120A opens. Exhaust valve 64 opens prematurely compared to the baseline mode and is held in the fully open position until it closes. While primary exhaust valve 120A is opening in EEVO mode, exhaust valve 64 closes according to the same profile as in the baseline mode. In the non-limiting example embodiment described in Fig. As shown in Figure 5, the opening of the primary exhaust valve 120A in EEVO mode occurs approximately 40-70 degrees earlier than the opening of the primary exhaust valve 120A in baseline mode, as shown in Figure 130. Fig. 5 is indicated.

[0056] On the way to block 212, control module 108 receives another signal indicating the engine's operating temperature. On the way to block 214, the engine's operating temperature is compared to a predefined IEGR threshold. Upon transitioning to block 216, if the engine's operating temperature exceeds the predefined IEGR threshold, the IEGR and EEVO modes are deactivated, and the baseline mode is activated. Upon transitioning to block 218, if the engine's operating temperature is below the predefined IEGR threshold, the engine continues to operate with the IEGR and EEVO modes activated.

[0057] Control over baseline, IEGR, and EEVO modes is achieved through the use of engine valve hardware, which causes an exhaust valve 64 to open during an intake stroke of the engine 10. Duration, timing, and flow rate can all be controlled by the valve train. A variable geometry valve train is capable of switching between baseline, IEGR, and EEVO modes. For example, a variable rocker arm assembly can be actuated based on oil pressure, which can be modulated by an oil control valve. When different modes are activated, different cams become active, resulting in different valve timings.In one exemplary embodiment, the hardware described above can be used to provide an IEGR / EEVO control mode strategy that includes switching between valve profiles, variable intake flow throttling, exhaust backpressure control, and timed events in the injection system. Combined, this can create a strategy to improve the rate at which the exhaust gas temperature reaches a desired operating temperature, as well as the conversion efficiency of the aftertreatment system.

[0058] Operating in IEGR or EEVO mode alone offers improvements in cold-start emissions, aftertreatment effectiveness, and drivability when the engine is cold. Further benefits can include improved fuel economy combined with reduced reliance on injecting raw fuel into the exhaust to heat NOx aftertreatment systems. IEGR significantly increases the effectiveness of warm-up modes, which in turn leads to considerably improved warm-up emissions. Therefore, IEGR must only be used for warm-up, enabling diesel engines to achieve lower emissions. Under high load, however, IEGR can be deactivated, thus facilitating smoke reduction through EEGR.

[0059] The use of IEGR and EEVO in conjunction increases exhaust gas temperature and provides HC and NOx control, improving the performance of the engine / aftertreatment system compared to IEGR or EEVO alone. Synergistic effects of using EEVO and IEGR together include: 1) increased exhaust gas temperature, 2) improved IEGR by increasing the temperature of the recirculation gas due to EEVO, and 3) improved EEVO capability by increasing the cylinder internal temperature at intake valve closure due to IEGR.

[0060] The advantages of using EEVO and IEGR together allow diesel engines to achieve extremely low emissions without the need for very expensive aftertreatment systems such as LNT, PNA catalysts, etc., and alternative methods for rapid warm-up such as eDOC, exhaust gas burners, etc.

[0061] The description of the present revelation is merely exemplary, and variations that do not deviate from the core of the present revelation are to be considered within its scope. Such variations are not to be regarded as a departure from the spirit and scope of the present revelation.

Claims

[1] A method (200) for controlling the temperature of recirculated exhaust gas in an internal combustion engine, comprising: Operating (202) the internal combustion engine (10) in a baseline mode; Receiving (204) a signal indicating the operating temperature of a motor; (206) comparing the engine operating temperature with a predetermined IEGR threshold; if the engine operating temperature is lower than the predetermined IEGR threshold, (210) activating an IEGR mode in which internal exhaust gas recirculation is present, and activating an EEVO mode, which is an operating mode of the internal combustion engine in which exhaust valve timing is changed compared to an initial operating mode; and If the engine operating temperature is higher than the first preset IEGR threshold, the IEGR mode is deactivated and the EEVO mode is deactivated. wherein the baseline mode includes activating a primary exhaust valve opening during an exhaust event of the associated cylinder of the exhaust valve, wherein the IEGR modes include activating a secondary exhaust valve opening during an intake event of the associated cylinder of the exhaust valve and partially holding the exhaust valve (64) open between the primary exhaust valve opening and the secondary exhaust valve opening, wherein the exhaust valve (64) is fully open during the primary exhaust valve opening and the exhaust valve has less than 40% of its full opening during the secondary exhaust valve opening, including the EEVO modes: Activating the primary exhaust valve opening prior to the primary exhaust valve opening of the baseline; holding the exhaust valve fully open (64); and Closing the outlet valve (64) according to the baseline mode. [2] The method (200) according to claim 1, wherein the engine operating temperature is a coolant temperature. [3] The method (200) according to claim 1, wherein the engine operating temperature is an exhaust gas temperature. [4] The method (200) according to claim 1, wherein the engine operating temperature is an oil temperature.

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