Exhaust gas recirculation circuit for improved particulate filter regeneration

Abstract

Exhaust gas recirculation circuit for improved particulate filter regeneration. The technology disclosed herein relates to an EGR circuit (10) of an internal combustion engine (11) comprising an intake manifold (12) and an exhaust manifold (13) for collecting exhaust gases, the EGR circuit being configured to switch between a flow configuration, in which exhaust gas is allowed to flow through the EGR circuit, and a closed configuration, in which exhaust gas flow through the EGR circuit is prevented, and comprising: - an EGR mixer (20) fluidically connected to the intake manifold and configured to mix exhaust gases and air; - an EGR cooler (30); - an exhaust pipe (31) fluidically connecting the exhaust manifold (13) to the EGR cooler; - an intermediate pipe (32) fluidically connecting the EGR cooler to the EGR mixer; - a first EGR valve (33) mounted in the exhaust pipe to regulate and / or prevent exhaust gas flow.

Description

Technical Field

[0001] This disclosure generally relates to exhaust gas recirculation (EGR) circuits for engines in vehicles, such as (but not limited to) vehicles. This disclosure relates to an EGR circuit capable of reducing NOx emissions from an internal combustion engine (ICE) of a vehicle, while simultaneously reducing NOx emissions when necessary by ensuring sufficient exhaust gas recirculation (EGR) flow into the ICE intake manifold or by temporarily stopping the EGR flow for particulate filter (PF) regeneration. In a particular aspect, this disclosure relates to an EGR circuit for improved particulate filter regeneration. This disclosure can be applied to heavy-duty vehicles, such as trucks, buses, and construction equipment, as well as other vehicle types. Although this disclosure may be described with reference to a particular vehicle, it is not limited to any particular vehicle. Background Technology

[0002] During combustion within the cylinders of an internal combustion engine (ICE), fuel and air are injected into the ICE cylinders, and the combustion within the cylinders enables the generation of mechanical power, which is intended to be transmitted from the ICE's output shaft to the wheels via the drivetrain to ensure vehicle propulsion. This combustion involves the chemical reaction of fuel and oxygen from the air within the cylinders, resulting in major byproducts such as water and carbon dioxide, as well as undesirable pollutants such as soot and nitrogen oxides (NOx).

[0003] Because nitrogen is present in the air, NOx is formed during combustion. In fact, when the temperature reaches about 1300°C (this is the situation inside the cylinder), the nitrogen in the air recombines with oxygen to form chemical substances such as NO and NO2, collectively known as NOx emissions.

[0004] Soot is a carbon-rich aggregate that forms during partial combustion. Fuels used in ICE (Express Energies and Intakes) typically consist of a variety of hydrocarbons, many of which have long carbon chains. Because combustion is rarely complete, these long carbon chains recombine with each other according to complex reaction schemes. This leads to the formation of soot.

[0005] Emission standards have been introduced to limit pollutant emissions into the atmosphere. In Europe, these standards are known as European regulations. The technologies disclosed herein are designed to comply with European emission requirements EU7 and US requirements EPA27 and CARB27. These standards set maximum pollutant emission limits for new vehicles. Depending on the type of vehicle, several standards exist. These standards change over time and become increasingly stringent. Their aim is to reduce air pollution from road transport.

[0006] In order to reduce ICE emissions, several measures have been taken and various systems have been developed to limit soot and NOx emissions.

[0007] On the one hand, to reduce NOx emissions, a cooled exhaust gas recirculation (EGR) circuit was introduced. EGR works by diverting a portion of the exhaust gas from the internal combustion engine's exhaust manifold back into the intake manifold via a liquid-cooled EGR cooler to reduce NOx emissions. This diversion of exhaust gas leads to a decrease in combustion temperature within the cylinder due to the reduced oxygen ratio. The EGR flow rate is controlled by an EGR valve, which is controlled by the ICE's control unit based on the ICE's load and speed. Thanks to EGR, NOx formation is reduced. However, EGR often means soot formation because this recirculation results in a lower air-fuel ratio.

[0008] On the other hand, depending on the type of ICE, a particulate filter (whether diesel or gasoline) is added to the exhaust aftertreatment system to limit soot emissions. This particulate filter is typically installed downstream of the turbocharger outlet on the engine's exhaust line and, due to its honeycomb structure, captures soot particles exiting the exhaust manifold and being directed towards the exhaust line. Sometimes, when the particulate filter is loaded with a predetermined level of soot particles, it is necessary to trigger particulate filter regeneration. During regeneration, the soot particles burn within the ceramic layer inside the filter due to the heat generated in the exhaust line.

[0009] It should be noted that because the exhaust temperature of a gasoline ICE rises faster than that of a diesel ICE, the gasoline particulate filter typically does not require active regeneration for cleaning. In fact, particulate matter is more easily, continuously, and almost in real time processed. For example, when decelerating or under full load, the gasoline particulate filter cleans itself without the driver noticing.

[0010] However, the principles of the technology disclosed herein, as described below, can be applied within the framework of any ICE exhaust aftertreatment system that may produce soot and NOx.

[0011] To control the EGR flow rate to meet the target value of the EGR flow rate in the line from the ICE's exhaust manifold to the intake manifold, a cooled EGR valve is placed therein. The cooled EGR valve is designed to divert a portion of the exhaust gas (e.g., (but not limited to) 10% to 20%) from the exhaust manifold to the intake manifold. When the cooled EGR valve is fully open, this portion of the exhaust gas flows from the exhaust manifold through the line to the intake manifold. When the cooled EGR valve is fully closed, no exhaust gas flows through the line. Positioning the cooled EGR valve between fully open and fully closed allows for control of the EGR flow rate in the line. In the prior art, the cooled EGR valve is installed in the line between the exhaust manifold and the intake manifold at a sufficient distance from the exhaust manifold. This means that the cooled EGR valve is typically installed closer to the intake manifold than the exhaust manifold. This position ensures that the cooled EGR valve is exposed to exhaust gas at a lower temperature than it would be near the exhaust manifold, thereby preventing the valve plate of the cooled EGR valve from adhering to the housing of the cooled EGR valve, which is actuated within the housing to control exhaust flow.

[0012] When particulate filter regeneration is triggered, the ICE needs to be operated with a fully closed EGR valve. In fact, in order to burn off soot particles during particulate filter regeneration, the ICE must supply exhaust gas to the Exhaust Aftertreatment System (EATS) line that simultaneously meets sufficiently high exhaust temperatures, mass flow rates, and NOx emission conditions. If any of these parameters falls below a threshold, particulate filter regeneration may not occur at all, or it may occur for a significantly increased duration (i.e., several hours of engine running time), which is unacceptable.

[0013] Therefore, during particulate filter regeneration, the EGR flow rate is set to zero, meaning the cooled EGR valve should be completely closed. However, in reality, even when the cooled EGR valve is in its fully closed position, EGR flow still passes through it. This is due to the fact that within the housing of the cooled EGR valve, there is a gap between the valve plate and the housing to prevent the valve plate from adhering to the housing when hot exhaust gas flows through the valve. This results in internal EGR leakage flow through the cooled EGR valve even when it is intended to be in its fully closed position.

[0014] Single or double lift EGR valves exist, and they are known to have less internal leakage compared to the commonly used single butterfly EGR valve. Unfortunately, these valves have the disadvantages of resulting in high pressure drops and requiring high control forces. Furthermore, at the small opening position corresponding to the EGR valve, single or double lift valves are more difficult to control compared to single butterfly valves.

[0015] The technology disclosed in this paper falls within this background scope and proposes an EGR loop that allows particulate filters to regenerate by providing the required conditions in terms of exhaust temperature, flow rate, and NOx content.

[0016] Another objective of the technology disclosed herein is to reduce internal leakage of the EGR when the cooled EGR valve is fully closed, thereby increasing the NOx content to a level above the minimum threshold. Summary of the Invention

[0017] According to a first aspect of this disclosure, an exhaust gas recirculation circuit for an internal combustion engine includes an intake manifold and an exhaust manifold, the exhaust manifold being used to collect exhaust gas produced from combustion in the internal combustion engine, the exhaust gas recirculation circuit being configured to switch between a flow configuration and a closed configuration, or vice versa, in the flow configuration allowing exhaust gas to flow through the exhaust gas recirculation circuit, and in the closed configuration blocking exhaust gas flow through the exhaust gas recirculation circuit, the exhaust gas recirculation circuit comprising: - An EGR mixer, which is designed to be fluidly connected to the intake manifold and configured to supply exhaust gas and air and mix them. - An EGR cooler, which is designed to supply exhaust gas at the exhaust temperature from the exhaust manifold and deliver exhaust gas at a target intake temperature. - Exhaust pipe, which is designed to fluidly connect the exhaust manifold to the EGR cooler. - An intermediate pipe that fluidly connects the EGR cooler to the EGR mixer. - A first EGR valve, configured to regulate the exhaust flow from the exhaust manifold to the EGR mixer in the flow configuration and to block the exhaust flow to the EGR mixer in the closed configuration, the first EGR valve being installed in the exhaust pipe.

[0018] Due to these characteristics, the exhaust gas recirculation (EGR) loop of the technology disclosed herein provides a more responsive response to the internal combustion engine during a transient phase when the engine changes its operating mode. This transient phase is the transition from when the internal combustion engine is running and the EGR is in operation to when the EGR needs to be stopped or at least significantly reduced to increase the exhaust gas temperature, mass flow rate, and NOx content toward the exhaust aftertreatment system. The specific positioning of the first EGR valve upstream of the EGR cooler reduces the dead volume toward the exhaust manifold volume. This means that the volume that exhaust gas may occupy in the exhaust pipe is minimized. This results in an improved response of the internal combustion engine to the aforementioned transition.

[0019] Optionally, in some examples, including at least one preferred example, the first EGR valve is mounted on the exhaust manifold. The first EGR valve forms a port directly on the wall of the exhaust manifold to direct exhaust gas toward the EGR cooler into the exhaust pipe when needed. This positioning provides the advantage of no dead volume in the exhaust pipe, thereby avoiding negative impacts on the transient response of the internal combustion engine.

[0020] Optionally, in some examples, including at least one preferred example, the exhaust gas recirculation loop includes a second EGR valve mounted in the intermediate pipe, the second EGR valve being configured to switch from an open position to a closed position to block exhaust gas flow from the exhaust manifold to the EGR mixer in the closed configuration.

[0021] Optionally, in some examples, including at least one preferred example, the first EGR valve is a butterfly valve.

[0022] Optionally, in some examples, including at least one preferred example, the second EGR valve is a butterfly valve.

[0023] Compared to lift valves, butterfly valves have the advantage of not causing a high pressure drop. Furthermore, butterfly valves are easier to control because they do not require high actuation force.

[0024] The second EGR valve is located downstream of the EGR cooler. When the exhaust gas recirculation loop is in the flow position, this means that exhaust gas recirculation from the exhaust manifold to the intake manifold is permitted. The first EGR valve is open and the second EGR valve is in its open position. The exhaust flow rate is controlled by the percentage opening of the first and second EGR valves. It should be noted that the second EGR valve can be in its open position (i.e., fully open) or its closed position (i.e., fully closed) without any other intermediate position, or it can switch between its open and closed positions at multiple other percentage openings, thereby also controlling the exhaust flow rate. When the second EGR valve is only in the open or closed position, the exhaust flow rate is controlled by the first EGR valve.

[0025] Because the first EGR valve is mounted upstream of the EGR cooler, between the exhaust manifold and the EGR cooler, and possibly on the exhaust manifold, this means that the first EGR valve is exposed to exhaust gas with high temperatures. To avoid potential failure of the first EGR valve due to these high temperatures, a gap between the valve housing and the valve plate is necessary. This gap prevents the valve plate from adhering to the valve housing. This also means that in the fully closed position of the first EGR valve, a low exhaust flow rate is allowed through it. Under most operating conditions of an internal combustion engine, this has no effect because the key parameters such as exhaust temperature, flow rate, and NOx content will not fall below the threshold limits that allow particulate filter regeneration. However, under some other operating conditions, especially under low loads on the internal combustion engine, NOx content should be increased, and therefore exhaust temperature should be increased to reach the required threshold limits. The low exhaust flow rate through the first EGR valve (also known as internal leakage) can make it difficult or even impossible to achieve the conditions required for particulate filter regeneration.

[0026] The second EGR valve overcomes this problem because it can switch to its off position when the exhaust gas recirculation circuit should be in its closed configuration. Since the second EGR valve is located downstream of the EGR cooler, it is exposed to lower exhaust gas temperatures. Therefore, the risk of the valve plate adhering to the valve housing is significantly reduced compared to the first EGR valve. Consequently, the second EGR valve can be designed with a very small gap between the valve plate and the valve housing. This design results in almost no exhaust gas flowing through the second EGR valve in its off position.

[0027] The second EGR valve allows for the reduction or even elimination of EGR leakage flow using the exhaust gas recirculation loop. It ensures that the NOx content in the exhaust gas increases to a level exceeding the threshold limit required for regenerating the particulate filter in the exhaust line.

[0028] Positioning the second EGR valve downstream of the EGR cooler results in two technical characteristics: First, and as described above, the second EGR valve faces the exhaust gas with a lower temperature (compared to when positioned upstream of the EGR cooler), thus allowing the use of a second EGR valve with a small gap between the valve plate and the valve body. Second, the volumetric flow rate downstream of the EGR cooler is lower than the EGR flow rate upstream of the EGR cooler. This results in an intermediate pipe with a smaller diameter than the exhaust pipe (i.e., the pipe upstream of the EGR cooler) and a second EGR valve with a smaller diameter. These characteristics have a synergistic effect of significantly reducing EGR leakage flow.

[0029] Optionally, in some examples, including at least one preferred example, the exhaust gas recirculation loop further includes an actuator connected to a second EGR valve, the actuator being configured to actuate the second EGR valve to its closed position when the exhaust gas recirculation loop transitions from a flow configuration to a closed configuration.

[0030] Each of the first and second EGR valves is associated with an actuator. As will be described in detail below, the internal combustion engine includes a control unit configured to control various parameters of the internal combustion engine. That is, the control unit is configured to receive signals indicating the state of the internal combustion engine and to send commands, at least to the actuators of the EGR valves, to cause the internal combustion engine to operate according to instructions that may be stored on the control unit or stored in a remote memory in communication with the control unit.

[0031] Optionally, in some examples, including at least one preferred example, the actuator is a pneumatic actuator.

[0032] Optionally, in some examples, including at least one preferred example, the actuator is an electric actuator.

[0033] According to a second aspect of this disclosure, an internal combustion engine includes an intake manifold, an exhaust manifold, and an exhaust system, the exhaust manifold being used to collect exhaust gas produced from combustion in the internal combustion engine, and the exhaust system comprising: - As described in this article, exhaust gas recirculation loop, - An exhaust aftertreatment system designed to treat contaminants contained in the exhaust gas. - An exhaust line that fluidly connects the exhaust manifold to the exhaust aftertreatment system. - A control unit configured to send a switching signal to the exhaust gas recirculation loop to switch from the flow configuration to the closed configuration or vice versa.

[0034] Optionally, in some examples, including at least one preferred example, the internal combustion engine further includes a throttle valve and a throttle valve actuator, the throttle valve being mounted in the exhaust line, and the throttle valve actuator being connected to the throttle valve and configured to actuate the throttle valve to maintain a target pressure value within the exhaust manifold.

[0035] Control of the throttle valve ensures that the target pressure is reached within the exhaust manifold, allowing the internal combustion engine to operate as needed. The throttle valve needs to be actuated when the threshold limit for initiating particulate filter regeneration is not met. In addition to the throttle valve actuation causing a temporary, at least partially, cessation of exhaust flow in the exhaust line, the exhaust temperature increases and the NOx content exceeds the threshold limit. Particulate filter regeneration is permitted as the exhaust recirculation loop transitions from its flow configuration to its closed configuration.

[0036] Optionally, in some examples, including at least one preferred example, the throttle actuator is an electric actuator.

[0037] Optionally, in some examples, including at least one preferred example, the internal combustion engine further includes a compressed air unit and a main air supply pipe, the main air supply pipe fluidly connecting the compressed air unit to the throttle actuator, the throttle actuator being a pneumatically driven actuator, the compressed air unit being configured to supply compressed air to the throttle actuator.

[0038] Optionally, in some examples, including at least one preferred example, the internal combustion engine further includes an auxiliary air supply pipe that fluidly connects the main air supply pipe to the pneumatic actuator, the pneumatic actuator and the throttle actuator being configured to be supplied with compressed air simultaneously.

[0039] When the actuator is pneumatic, the capacity of the compressed air unit can be shared to direct compressed air to where it is needed in the exhaust gas recirculation loop. This results in efficient operation of the internal combustion engine.

[0040] Optionally, in some examples, including at least one preferred example, the pneumatic actuator is connected to the exhaust manifold.

[0041] The internal combustion engine according to the technology disclosed herein, as described above, also exhibits advantages similar to those of the exhaust gas recirculation circuit according to the technology disclosed herein. Other technical effects and advantages will be detailed in the specific embodiments.

[0042] According to a third aspect of this disclosure, a vehicle includes such an internal combustion engine.

[0043] The aspects, examples (including any preferred examples) and / or appended claims disclosed herein may be suitably combined with each other, as will be apparent to those skilled in the art. Additional features and advantages are disclosed in the following description, claims and drawings, and are in part apparent to those skilled in the art, or may be recognized by practice of the disclosure as set forth herein. Attached Figure Description

[0044] The example will be described in more detail below with reference to the accompanying drawings.

[0045] Figure 1 This is a perspective view of an example vehicle equipped with an internal combustion engine and an exhaust gas recirculation circuit, based on an example example.

[0046] Figure 2 This is a schematic diagram illustrating an exemplary exhaust gas recirculation loop according to an example.

[0047] Figure 3 This is a schematic diagram illustrating an exemplary exhaust gas recirculation loop according to an example.

[0048] Figure 4 This is a schematic diagram illustrating an exemplary exhaust gas recirculation loop according to an example.

[0049] Figure 5 This is a schematic diagram illustrating an exemplary exhaust gas recirculation loop according to an example. Detailed Implementation

[0050] The detailed description set forth below provides information and examples of the techniques disclosed herein with sufficient detail to enable those skilled in the art to practice this disclosure.

[0051] The features, variations, and various embodiments of the technologies disclosed herein, as they have been described or as they will be presented in the detailed description below, can be associated with each other in various combinations to the extent that they are compatible with or non-exclusive of each other. In particular, if the selection of such features is sufficient to give a technological advantage and / or distinguish the technologies disclosed herein from the prior art, it may be conceivable that variations of the technologies disclosed herein may include only the features subsequently described, selected separately from the other features described.

[0052] For clarity, the same elements are represented by the same reference numerals in different figures.

[0053] Figure 1 This is a perspective view of an example vehicle equipped with an internal combustion engine 11 and an exhaust gas recirculation circuit 10 according to an example. As shown, vehicle 1 is a truck. However, the method of the technology disclosed herein can be applied to any internal combustion engine and exhaust gas recirculation circuit, and the vehicle can be any vehicle, such as a bus or a sedan.

[0054] Figure 2 This is a schematic diagram illustrating an exemplary exhaust gas recirculation loop 10 according to one example. Figure 2The diagram schematically illustrates an internal combustion engine 11. The internal combustion engine 11 includes multiple cylinders. As an example, the internal combustion engine is a 6-cylinder inline engine. This arrangement is an example of an engine to which the techniques disclosed herein can be applied. However, the scope of the techniques disclosed herein is not limited to this type of engine, but can be applied to any other type of internal combustion engine, regardless of the number of cylinders and their arrangement relative to each other.

[0055] The internal combustion engine 11 includes an intake manifold 12 and an exhaust manifold 13. The intake manifold is configured to receive air to be supplied to the cylinders of the internal combustion engine 11. During operation, the internal combustion engine 11 receives air from the intake manifold 12, and fuel is injected into the cylinders. Combustion occurs within the cylinders, thereby generating mechanical power intended to be transmitted from the output shaft of the internal combustion engine through the drivetrain to the wheels to ensure vehicle propulsion. Combustion involves a chemical reaction between fuel and oxygen from the air within the cylinders, resulting in major byproducts such as water and carbon dioxide, as well as undesirable pollutants such as soot and nitrogen oxides (NOx).

[0056] The exhaust manifold 13 collects exhaust gas produced by combustion in the cylinders of the internal combustion engine 11.

[0057] The internal combustion engine 11 also includes an exhaust system 100, which includes an exhaust gas recirculation loop 10, which will be described in detail below. The exhaust system 100 also includes: an exhaust aftertreatment system 110 designed to treat contaminants contained in the exhaust gas; an exhaust line 111 fluidly connecting the exhaust manifold 13 to the exhaust aftertreatment system 110; and a control unit 120 configured to send signals to the exhaust gas recirculation loop 10 in accordance with the operation of the internal combustion engine 11.

[0058] The exhaust aftertreatment system 110 will not be described in detail because it includes aftertreatment elements known in the art, such as a particulate filter, to physically capture soot particles emitted by the internal combustion engine 11 during the combustion process in which combustion does not occur as complete combustion, and optionally includes an SCR system (selective catalytic reduction) to convert residual NOx in the exhaust flowing in the exhaust line 111 into N2 and H2O.

[0059] The exhaust gas recirculation loop 10 of the technology disclosed herein will now be described in detail. The exhaust gas recirculation loop 10 is configured to switch between a flow configuration and a closed configuration, or vice versa, in which the flow configuration allows exhaust gas to flow through the exhaust gas recirculation loop 10, and in which the closed configuration blocks the flow of exhaust gas through the exhaust gas recirculation loop 10. In other words, in the flow configuration, exhaust gas can flow through the exhaust gas recirculation loop 10, while in the closed configuration, exhaust gas cannot flow through the exhaust gas recirculation loop 10. The exhaust gas recirculation loop 10 can switch from a flow configuration to a closed configuration, and it can also switch from a closed configuration to a flow configuration.

[0060] The exhaust gas recirculation circuit 10 includes an EGR mixer 20, which is designed to be fluidly connected to the intake manifold 12 and configured to supply exhaust gas and air and mix them. The internal combustion engine 11 includes an air inlet 200 to supply air to the cylinders. Air from this air inlet passes through a compressor 201 before entering a boost air cooler 202. The outlet of the boost air cooler 202 is fluidly connected to the EGR mixer 20. This constitutes an air supply line.

[0061] The exhaust gas recirculation loop 10 includes an EGR cooler 30 designed to supply exhaust gas from the exhaust manifold 13 at an exhaust temperature of Tex and deliver exhaust gas at a target intake temperature of Tin. In other words, the EGR cooler 30 functions to reduce the exhaust gas temperature from Tex to Tin. The exhaust gas recirculation loop 10 includes an intermediate pipe 32 fluidly connecting the EGR cooler 30 to an EGR mixer 20. It should be understood that the intermediate pipe 32 extends from the outlet of the EGR cooler 30 to the inlet of the EGR mixer 20. As a result, the exhaust gas flowing through the EGR cooler 30 is mixed with the air flowing through the air supply line in the EGR mixer 20 to form an air-to-exhaust mixture. The EGR mixer 20 can have any form capable of achieving an air-to-exhaust mixture. It can be a simple pipe fluidly connected to the intermediate pipe 32 and the air supply line, or it can be a mixer with a dedicated volume to allow the air and exhaust gas to mix before entering the pipe fluidly connected to the intake manifold 12.

[0062] The exhaust gas recirculation loop 10 includes an exhaust pipe 31 designed to fluidly connect the exhaust manifold 13 to the EGR cooler 30. As described above, exhaust gases are generated during combustion and collected in the exhaust manifold 13. Their temperature is TeX. The majority of the exhaust gases flow toward the exhaust line 111, typically passing through the turbine to the exhaust aftertreatment system 110, where they are treated to remove NOx and soot. A portion of the exhaust gases in the exhaust manifold 13 is directed through the exhaust gas recirculation loop 10. This portion of the exhaust flows through the exhaust pipe 31 into the EGR cooler 30, where the exhaust temperature is reduced from TeX to Tin. The exhaust leaves the EGR cooler and flows through the intermediate pipe 32 toward the EGR mixer 20, where it is mixed with fresh air from the air inlet. The mixture of fresh air and exhaust gases is directed to the intake manifold 12. Therefore, this portion of exhaust gas recirculated toward the intake manifold is cooled in the EGR cooler 30 (e.g., a liquid-cooled EGR cooler). This recirculation of cooled exhaust gas results in a reduced proportion of oxygen entering the cylinders, leading to lower combustion temperatures. Lower NOx levels are emitted during this combustion period.

[0063] In order to enable the recirculation of a portion of the exhaust gas, the exhaust gas recirculation loop 10 includes a first EGR valve 33, which is configured to regulate the exhaust gas flow from the exhaust manifold 13 to the EGR mixer 20 in the flow configuration and to block the exhaust gas flow to the EGR mixer 20 in the closed configuration.

[0064] According to the technology disclosed herein, a first EGR valve 33 is installed in the exhaust pipe 31. In the direction of exhaust flow from the exhaust manifold to the intake manifold, the first EGR valve 33 is installed upstream of the EGR cooler 30.

[0065] Therefore, the EGR flow is controlled by a first EGR valve, which is controlled by the internal combustion engine's control unit based on the engine's load and speed. As mentioned earlier, the recirculation of a portion of the exhaust gas enables a reduction in NOx formation.

[0066] The opening degree of the first EGR valve 33 determines the EGR flow rate through the exhaust gas recirculation loop 10. For this purpose, the first EGR valve 33 can be fully open, meaning the maximum flow rate of exhaust gas recirculated through the exhaust gas recirculation loop 10. The first EGR valve 33 can also be partially open. In this configuration, the percentage of its opening determines the lower EGR flow rate. The percentage of the opening of the first EGR valve 33 is primarily driven by the load of the internal combustion engine and the NOx level in the exhaust manifold 13. As an example, the maximum percentage of exhaust gas measured in the intake manifold is approximately 15%.

[0067] Positioning the first EGR valve 33 upstream of the EGR cooler 30 means that the first EGR valve 33 is installed near the exhaust manifold, where the exhaust is hottest. This positioning is counterintuitive, as it is preferable to place it downstream of the EGR cooler, exposing it to the cooled exhaust.

[0068] Compared to a position downstream of the EGR cooler, the specific positioning of the first EGR valve 33 upstream of the EGR cooler reduces the dead volume toward the exhaust manifold volume. Such dead volume negatively impacts the transient response of the internal combustion engine. As a result, the technology disclosed herein improves the responsiveness of the internal combustion engine in terms of speed.

[0069] Optionally, in some examples, including at least one preferred example, the first EGR valve 33 is directly mounted on the exhaust manifold 13. This means that the first EGR valve 33 forms the outlet port of the exhaust manifold 13. When the first EGR valve 33 is at least partially open, exhaust gas can flow through the first EGR valve 33, which causes exhaust gas to flow through the exhaust gas recirculation loop 10. Therefore, there is no dead volume toward the exhaust manifold volume.

[0070] like Figure 2 The internal combustion engine 11 depicted also includes a throttle valve 112 mounted in an exhaust line 111. As a reminder, the exhaust line 111 is a line fluidly connected to the exhaust manifold 13 on one side and fluidly connected to the exhaust aftertreatment system 110 on the other side. Therefore, the exhaust line 111 is the line through which exhaust gas flows from the exhaust manifold to the aftertreatment system.

[0071] The internal combustion engine 11 also includes a throttle actuator 113 connected to the throttle valve 112. This throttle actuator is configured to actuate the throttle valve 112. The throttle valve 112 can be in various positions. Depending on the position of the throttle valve 112, it results in a corresponding pressure value in the exhaust manifold 13. Actuation of the throttle valve 112 allows the maintenance of a target pressure value within the exhaust manifold 13.

[0072] As a non-limiting example, the throttle actuator 113 may be an electric actuator.

[0073] As another example, the throttle actuator 113 can be a pneumatically driven actuator. In this case, the internal combustion engine 11 also includes a compressed air unit 130 and a main air supply line 131 that fluidly connects the compressed air unit 130 to the throttle actuator 113. The compressed air unit 130 is configured to supply compressed air to the throttle actuator 113. Figure 2As depicted, control unit 120 is operatively connected to compressed air unit 130. This means that control unit 120 sends commands to compressed air unit 130 to operate according to instructions that can be stored in control unit. Based on the pressure level within exhaust manifold 13, control unit 120 triggers compressed air unit 130 to supply compressed air to throttle actuator 113 to activate throttle valve 112.

[0074] Since it is not central to the technology disclosed herein, and unless otherwise stated, it may be mentioned that communication between control unit 120 and other components of exhaust gas recirculation loop 10 and internal combustion engine 11 is achieved through sensor signals and actuator commands. The transmission of signals and commands to and from control unit 120 is performed using known communication means, such as wired connections, wireless connections, local area network buses, serial peripheral interface buses, etc. For these purposes, control unit 120 may include at least one processor. Under the term "processor," it should be understood as at least one of a processor, microprocessor, application-specific integrated circuit (also referred to by its abbreviation ASIC), electronic circuit, and central processing unit. Control unit 120 may include at least one memory component (read-only, programmable read-only, random access, hard disk drive, etc.) capable of storing machine-readable instructions accessible by the processor to provide the desired functionality.

[0075] Figure 3 This is a schematic diagram showing an exemplary exhaust gas recirculation loop 10 according to an example. Figure 3 The exhaust gas recirculation loop 10, as shown in the figure, is... Figure 2 The exhaust gas recirculation loops shown in the diagram are the same.

[0076] Figure 3 The exhaust gas recirculation loop 10 shown also includes a second EGR valve 40 installed in the intermediate pipe 32. Therefore, the second EGR valve 40 is located downstream of the EGR cooler 30. The second EGR valve 40 is configured to switch from an open position to a closed position to block exhaust gas flow from the exhaust manifold 13 to the EGR mixer 20 in a closed configuration, or to switch from a closed position to an open position. This means that the second EGR valve 40 is in the open position to allow exhaust gas to flow through the exhaust gas recirculation loop 10, as described above. Furthermore, when it is desired that no exhaust gas flows through the exhaust gas recirculation loop 10, the second EGR valve 40 is in a fully closed position (closed position) to prevent exhaust gas from passing through the exhaust gas recirculation loop 10. Conversely, when the second EGR valve 40 is in its closed position, it can change its configuration and switch back to its open position according to the requirements of the internal combustion engine.

[0077] exist Figure 3On the left side, a cross-sectional view of the exhaust pipe 31 is depicted. Within the exhaust pipe 31, a first EGR valve 33 is shown. The first EGR valve 33 is a butterfly valve and is shown in its closed configuration. The first EGR valve 33 includes a valve plate 331 that rotates within a valve housing 332. It can be seen that in this fully closed configuration, there is a gap between the valve plate 331 and the valve housing 332. This gap is forced when the exhaust temperature is at a high level (approximately 700°C) at the exhaust manifold outlet to prevent adhesion between the valve plate and the housing. These gaps, even if small, form passages for the exhaust gas. This means that even in the fully closed configuration of the first EGR valve 33, some exhaust gas can still flow through the exhaust gas recirculation loop 10.

[0078] As previously mentioned, there are situations during the operation of an internal combustion engine where exhaust gas recirculation should not occur. One of these situations is the regeneration of a particulate filter. During the particulate filter regeneration process, the soot particles captured by the filter are burned off. The conditions for successful particulate filter regeneration are the simultaneous presence of high exhaust temperature, high exhaust mass flow rate, and NOx emissions in the exhaust line. Non-limiting examples of the values ​​required for parking regeneration of a truck at idle are an exhaust temperature above 250°C, an exhaust mass flow rate above 0.07 kg / s, and a NOx concentration of at least 1000 ppm in the exhaust. Other thresholds may be applied depending on the vehicle's speed and load.

[0079] During the soot regeneration step, the exhaust manifold pressure is closed-loop controlled by a control unit 120 acting on the compressed air unit 130 and an actuator 113 for actuating the throttle valve 112 to achieve a target pressure within the exhaust manifold. When the exhaust manifold pressure is at the target pressure, the passage formed in the first EGR valve 33 results in high leakage flow in the exhaust recirculation loop 10 (while no exhaust flow is expected through the exhaust recirculation loop 10), and the NOx level in the exhaust manifold drops below the desired threshold. Therefore, under these conditions, performing particulate filter regeneration becomes difficult or even impossible.

[0080] The second EGR valve 40 reduces exhaust leakage flow. When the particulate filter regeneration step is triggered, the control unit sends commands to the first EGR valve 33 and the second EGR valve 40 to switch them to their fully closed positions. As explained above, even in their fully closed positions, a small flow of exhaust gas may circulate through the first EGR valve 33. By adding the second EGR valve 40, which is switched to its closed position, exhaust leakage flow in the exhaust recirculation loop 10 is reduced. Therefore, in the closed configuration of loop 10 (that is, when the second EGR valve 40 is closed), the second EGR valve 40 blocks exhaust flow from the exhaust manifold 13 to the EGR mixer 20. When the exhaust leakage flow is reduced to an acceptable level, it leads to an increase in NOx emissions in the exhaust gas within the exhaust manifold until the desired NOx level is reached, thereby ensuring that particulate filter regeneration can occur properly.

[0081] The second EGR valve 40 can be a single butterfly valve, or it can be a single lift valve. As mentioned earlier, a single lift valve has the advantage of a complete seal when closed, but at the cost of an increased pressure drop, resulting in increased pumping losses and fuel consumption losses.

[0082] Optionally, in some examples, including at least one preferred example, the second EGR valve 40 is a single butterfly valve. When the second EGR valve 40 is installed in the intermediate pipe 32 (that is, downstream of the EGR cooler 30), the exhaust temperature exposed to the second EGR valve 40 is approximately 150°C. Compared to the first EGR valve 33, this allows for a smaller clearance (the distance between the valve plate and the valve housing) because the risk of valve adhesion is reduced. This results in reduced internal leakage through the second EGR valve 40.

[0083] Optionally, in some examples, including at least one preferred example, the second EGR valve 40 may include a sealing device, such as an O-ring integrated into the second EGR valve, thereby significantly reducing internal leakage.

[0084] Because of the second EGR valve 40, the required flow rate of exhaust gas is ensured through the exhaust gas recirculation loop 10 in the flow configuration (with the second EGR valve 40 in its open position), while in the closed configuration, little or no exhaust gas flow passes through the exhaust gas recirculation loop 10.

[0085] Optionally, in some examples, including at least one preferred example, the exhaust gas recirculation loop 10 includes an actuator 41 connected to a second EGR valve 40. The actuator 41 is configured to actuate the second EGR valve 40 to its closed position when the exhaust gas recirculation loop 10 transitions from a flow configuration to a closed configuration. A control unit 120 is operatively connected to the actuator 41 and is configured to send commands directly or indirectly to the actuator 41 when it is necessary to switch the exhaust gas recirculation loop 10 to a closed configuration.

[0086] like Figure 3 As shown, actuator 41 is a pneumatic actuator. In this configuration, control unit 120 sends a command to compressed air unit 130 to supply compressed air to actuator 41 to activate second EGR valve 40. For this purpose, internal combustion engine 11 includes an auxiliary air supply line 132 that fluidly connects main air supply line 131 to pneumatic actuator 41. Advantageously, pneumatic actuator 41 and throttle actuator 113 are configured to be supplied with compressed air simultaneously.

[0087] Figure 4 This is a schematic diagram showing an exemplary exhaust gas recirculation loop 10 according to an example. Figure 4 The exhaust gas recirculation loop 10 shown is... Figure 3 The exhaust gas recirculation loops shown are identical. The only difference between the two exhaust gas recirculation loops is the fluid connection of the pneumatic actuator 41. Although in Figure 3 In the circuit, the pneumatic actuator 41 is fluidly connected to the compressed air unit 130, but as Figure 4 In one variant, the pneumatic actuator 41 is connected to the exhaust manifold 13.

[0088] As a result, the second EGR valve 40 is directly controlled by the exhaust manifold pressure. This leads to a simplification of the piping, as this configuration requires only one pipe extending from the exhaust manifold 13 to the second EGR valve 40. Control of the second EGR valve 40 is also simplified, as it can switch between its open and closed positions based on the pressure level in the exhaust manifold. Furthermore, the fluid connection between the exhaust manifold and the second EGR valve 40 has the advantage that, in the case where the throttle actuator 113 is an electric actuator, the compressed air unit 130 can be eliminated.

[0089] Figure 5 This is a schematic diagram showing an exemplary exhaust gas recirculation loop 10 according to an example. Figure 5 The exhaust gas recirculation loop 10 shown is... Figure 4 The exhaust gas recirculation circuits shown are almost identical. The only difference is that the first EGR valve 33 and the second EGR valve 40 are each connected to an electric actuator controlled by the control unit 120. Considering that the throttle valve 112 can also be equipped with an electric actuator, the compressed air unit 130 is no longer needed.

[0090] Example 1: An exhaust gas recirculation loop 10 for an internal combustion engine 11, the internal combustion engine 11 including an intake manifold 12 and an exhaust manifold 13 for collecting exhaust gas produced from combustion in the internal combustion engine 11, the exhaust gas recirculation loop 10 being configured to switch between a flow configuration and a closed configuration, or vice versa, in which the flow configuration allows exhaust gas to flow through the exhaust gas recirculation loop 10, and in the closed configuration blocks the flow of exhaust gas through the exhaust gas recirculation loop 10, the exhaust gas recirculation loop 10 including: - EGR mixer 20, which is designed to be fluidly connected to intake manifold 12 and configured to supply exhaust gas and air and mix the exhaust gas and air. - EGR cooler 30, which is designed to supply exhaust gas at exhaust temperature Tex from exhaust manifold 13 and deliver exhaust gas at target intake temperature Tin. - Exhaust pipe 31, which is designed to fluidly connect exhaust manifold 13 to EGR cooler 30, - Intermediate pipe 32, which fluidly connects the EGR cooler 30 to the EGR mixer 20. - A first EGR valve 33 is configured to regulate the exhaust flow from the exhaust manifold 13 to the EGR mixer 20 in a flow configuration and to block the exhaust flow to the EGR mixer 20 in a closed configuration. The first EGR valve 33 is installed in the exhaust pipe 31.

[0091] Example 2: The exhaust gas recirculation loop 10 according to Example 1 further includes a second EGR valve 40 installed in the intermediate pipe 32, the second EGR valve 40 being configured to switch from an open position to a closed position to block exhaust gas flow from the exhaust manifold 13 to the EGR mixer 20 in a closed configuration.

[0092] Example 3: The exhaust gas recirculation loop 10 according to Example 1 or 2, wherein the first EGR valve 33 is a butterfly valve.

[0093] Example 4: The exhaust gas recirculation loop 10 according to Example 2 further includes an actuator 41 connected to a second EGR valve 40, the actuator 41 being configured to actuate the second EGR valve 40 to its closed position when the exhaust gas recirculation loop 10 transitions from a flow configuration to a closed configuration.

[0094] Example 5: The exhaust gas recirculation loop 10 according to Example 4, wherein the actuator 41 is a pneumatic actuator.

[0095] Example 6: The exhaust gas recirculation loop 10 according to Example 4, wherein the actuator 41 is an electric actuator.

[0096] Example 7: An internal combustion engine 11 includes an intake manifold 12, an exhaust manifold 13, and an exhaust system 100, the exhaust manifold 13 being used to collect exhaust gases produced from combustion in the internal combustion engine 11, the exhaust system including: - Exhaust gas recirculation circuit 10 according to any one of Examples 1 to 6 - Exhaust aftertreatment system 110, which is designed to treat pollutants contained in exhaust gas. - Exhaust line 111, which fluidly connects exhaust manifold 13 to exhaust aftertreatment system 110, - Control unit 120, which is configured to send a switching signal to exhaust gas recirculation loop 10 to switch from a flow configuration to a closed configuration or vice versa.

[0097] Example 8: The internal combustion engine 11 according to Example 7 further includes a throttle valve 112 and a throttle valve actuator 113, the throttle valve 112 being mounted in the exhaust line 111, and the throttle valve actuator 113 being connected to the throttle valve 112 and configured to actuate the throttle valve 112 in order to maintain a target pressure value within the exhaust manifold 13.

[0098] Example 9: The internal combustion engine 11 according to Example 8, wherein the throttle actuator 113 is an electric actuator.

[0099] Example 10: The internal combustion engine 11 according to Example 8 further includes a compressed air unit 130 and a main air supply pipe 131, the main air supply pipe 131 fluidly connecting the compressed air unit 130 to a throttle actuator 113, the throttle actuator 113 being a pneumatically driven actuator, the compressed air unit 130 being configured to supply compressed air to the throttle actuator 113.

[0100] Example 11: The internal combustion engine 11 according to Example 10 in conjunction with Example 5 further includes an auxiliary air supply pipe 132 that fluidly connects the main air supply pipe 131 to a pneumatic actuator 41, the pneumatic actuator 41 and the throttle actuator 113 being configured to be supplied with compressed air simultaneously.

[0101] Example 12: An internal combustion engine 11 according to any one of Examples 7 to 9 in conjunction with Example 5, wherein a pneumatic actuator 41 is connected to an exhaust manifold 13.

[0102] Example 13: A vehicle including an internal combustion engine 11 according to any one of Examples 7 to 12.

[0103] The terminology used herein is for descriptive purposes only and is not intended to limit this disclosure. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items. It will be further understood that, when used herein, the terms “comprises,” “comprising,” “includes,” and / or “including” specify the presence of the stated features, wholes, actions, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, wholes, actions, steps, operations, elements, components, and / or combinations thereof.

[0104] It should be understood that although the terms “first,” “second,” etc., may be used herein to describe various elements, these elements should not be limited by these terms. These terms are used only to distinguish one element from another. For example, without departing from the scope of this disclosure, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element.

[0105] Relative terms such as “below,” “above,” “upper,” “lower,” “horizontal,” or “vertical” may be used herein to describe the relationship between one element and another as shown in the figures. It should be understood that these terms, and those discussed above, are intended to cover different orientations of the device other than those depicted in the figures. It should be understood that when an element is referred to as “connected” or “linked” to another element, it may be directly connected or linked to the other element, or there may be intermediate elements. Conversely, when an element is referred to as “directly connected” or “directly linked” to another element, there are no intermediate elements.

[0106] Unless otherwise defined, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. It will be further understood that the terms used herein shall be interpreted as having the same meaning as they have in the context of this specification and the relevant field, and shall not be interpreted in an idealized or overly formal sense unless expressly defined herein.

[0107] It should be understood that this disclosure is not limited to the aspects shown above and in the accompanying drawings; rather, those skilled in the art will recognize that many modifications and variations can be made within the scope of this disclosure and the appended claims. Aspects disclosed in the drawings and specification are for illustrative purposes only and not for limiting purposes, and the scope of this disclosure is set forth in the appended claims.

Claims

1. An internal combustion engine (11) comprising an intake manifold (12), an exhaust manifold (13), and an exhaust system (100), said exhaust manifold (13) for collecting exhaust gases produced from combustion in said internal combustion engine (11), said exhaust system (100) comprising: - An exhaust gas recirculation loop (10), the exhaust gas recirculation loop (10) being configured to switch between a flow configuration and a closed configuration or vice versa, in the flow configuration allowing exhaust gas to flow through the exhaust gas recirculation loop (10), in the closed configuration blocking exhaust gas flow through the exhaust gas recirculation loop (10), the exhaust gas recirculation loop (10) comprising: An EGR mixer (20) is intended to be fluidly connected to the intake manifold (12) and configured to supply exhaust gas and air and mix the exhaust gas and air. An EGR cooler (30) is designed to be supplied with exhaust gas at exhaust temperature (Tex) from the exhaust manifold (13) and to deliver exhaust gas at a target intake temperature (Tin). An exhaust pipe (31) is provided to fluidly connect the exhaust manifold (13) to the EGR cooler (30). Intermediate pipe (32) fluidly connects the EGR cooler (30) to the EGR mixer (20). A first EGR valve (33) is configured to regulate the exhaust flow from the exhaust manifold (13) to the EGR mixer (20) in the flow configuration and to block the exhaust flow to the EGR mixer (20) in the closed configuration. The first EGR valve (33) is installed in the exhaust pipe (31). A second EGR valve (40) is installed in the intermediate pipe (32) and is configured to switch from an open position to a closed position to block exhaust flow from the exhaust manifold (13) to the EGR mixer (20) in the closed configuration. An actuator (41) is connected to the second EGR valve (40), the actuator (41) being configured to actuate the second EGR valve (40) to the closed position when the exhaust gas recirculation loop (10) transitions from the flow configuration to the closed configuration, the actuator (41) being a pneumatic actuator. - An exhaust aftertreatment system (110) designed to treat contaminants contained in the exhaust gas. - An exhaust line (111) fluidly connects the exhaust manifold (13) to the exhaust aftertreatment system (110). - A control unit (120) configured to send a switching signal to the exhaust gas recirculation loop (10) to switch from the flow configuration to the closed configuration or vice versa. The internal combustion engine (11) is characterized in that the pneumatic actuator (41) is connected to the exhaust manifold (13).

2. The internal combustion engine (11) according to claim 1, wherein, The first EGR valve (33) is a butterfly valve.

3. The internal combustion engine (11) according to claim 1 or 2 further includes a throttle valve (112) and a throttle valve actuator (113), the throttle valve (112) being mounted in the exhaust line (111), and the throttle valve actuator (113) being connected to the throttle valve (112) and configured to actuate the throttle valve (112) to maintain a target pressure value in the exhaust manifold (13).

4. The internal combustion engine (11) according to claim 3, wherein, The throttle actuator (113) is an electric actuator.

5. The internal combustion engine (11) according to claim 3, further comprising a compressed air unit (130) and a main air supply pipe (131), the main air supply pipe (131) fluidly connecting the compressed air unit (130) to the throttle actuator (113), the throttle actuator (113) being a pneumatically driven actuator, the compressed air unit (130) being configured to supply compressed air to the throttle actuator (113).

6. A vehicle comprising an internal combustion engine (11) according to any one of claims 1 to 5.

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