Combustion engine with internal flow control of exhaust gas recirculation and variable exhaust gas rebreathing

Abstract

Internal combustion engine (12), comprising: an engine structure defining a combustion chamber (24) and intake and exhaust ports (28, 40) in communication with the combustion chamber (24); an intake system connected to the intake duct (28); an exhaust system connected to the exhaust duct (40); a valve train assembly comprising an intake valve (36a) disposed in the intake port (28), an intake valve lift mechanism engaged with the intake valve (36a), an intake cam engaged with the intake valve lift mechanism and defining an intake lift region configured to open the intake valve (36a); an exhaust valve (36b) arranged in the exhaust passage (40), an exhaust valve lift mechanism engaged with the exhaust valve (36b) and operable to open the exhaust valve (36b) at different lift heights, phases, and durations during an intake stroke, wherein the intake valve (36a) and the exhaust valve (36b) are operable by at least one camshaft (38); and a control unit (80) for controlling the exhaust valve lift mechanism to change the lift, phase and duration of the exhaust valve (36b) during an intake stroke depending on the operating conditions of the engine (12); characterized in that the internal combustion engine (12) further comprises a cam shifting system (110) having a thrust unit (112) which is rotatably and axially movable along a rotational axis (R) of the camshaft (38) attached to the camshaft (38); wherein the thrust unit (112) comprises at least two cams (116, 118, 120) for a rocker arm (44), wherein the at least two cams (116, 118, 120) each comprise a base circle (116a, 118a, 120a), an exhaust cam nose (116b, 118b, 120b) extending from the base circle (116a, 118a, 120a), and an EGR cam nose (116c, 118c, 120c) extending from the base circle (116a, 118a, 120a); wherein the cam displacement system (110) is configured such that a coupling between the cams (116, 118, 120) and the rocker arm (44) converts a rotational movement of the camshaft (38) into a pendulum movement of the exhaust valve (36b), so that the exhaust valve (36b) remains in a closed position when the rocker arm (44) contacts the base circle (116a, 118a, 120a) of a cam (116, 118, 120), and so that the exhaust valve (36b) experiences a lift and opens when the rocker arm (44) makes contact with a cam nose (116b, 118b, 120b, 116c, 118c, 120c); and wherein respective flank parts (126) of the EGR cam noses (116c, 118c, 120c) of two different cams (116, 118, 120) are arranged at the same distance from the axis of rotation (R) of the camshaft (38), so that an equal stroke is available for the rocker arm (44) and for the exhaust valve (36b).

Description

TECHNICAL FIELD

[0001] The present disclosure relates to internal combustion engines and more particularly to an internal combustion engine having internal exhaust gas recirculation. BACKGROUND

[0002] The following section provides background information to the present disclosure, which is not necessarily prior art.

[0003] In today's common combustion engines, it is common to recycle a portion of the exhaust gases to improve engine performance or reduce combustion emissions. A typical benefit of using exhaust gas recirculation (EGR) is the reduction of peak combustion temperatures, thereby reducing pollutants such as NOx, as well as reducing the necessary throttle response in gasoline engines. Recirculation is typically accomplished via external pipes that redirect a portion of the exhaust gases back into the intake manifold.

[0004] In recent years, improved internal exhaust gas recirculation (internal EGR) has been used to reduce the energy wasted (heat from the pipe run, dynamic flow losses along the pipe) by such a system and achieve additional benefits such as more stable combustion in cold conditions, reduced pollutants, and improved fuel efficiency. Internal EGR technology involves opening the exhaust valve during the intake phase, causing a so-called rebreathing stroke. Controlling the amount of internal EGR is achieved by utilizing a longer or shorter exhaust valve lift during the cylinder's intake stroke, where the pressure difference between the exhaust manifold and the combustion chamber assists in filling the combustion chamber with exhaust gases.

[0005] Controlling the amount of internal EGR solely through a higher or lower rebreathing stroke quickly reaches its limits; a small change in stroke causes a significant change in the amount of recirculated gas. This situation limits the use of internal EGR technology to a restricted area of ​​the engine's operating map.

[0006] DE 10 2009 014 087 A1 discloses an internal combustion engine with multiple cylinders, each of which is assigned an intake valve, an exhaust valve, and an intake camshaft and an exhaust camshaft. Several cams are provided to actuate the exhaust valve, with one exhaust cam having multiple cam lobes for adjusting multiple exhaust opening phases. SUMMARY

[0007] The object of the present invention is to improve the responsiveness of the variable valve train system and the extent of control of the internal EGR technique. This object is achieved by the subject matter of the independent patent claim. To this end, the present disclosure adjusts the lift compared to the conventionally used EGR phases with a view to better timing and positioning. In particular, the present invention uses a combined variation of lift, phase, and duration to improve the controllability and stability of the desired amount of EGR. The present system achieves high internal EGR performance at low loads and lower backpressure. The system also achieves improved controllability of the internal EGR at high loads without requiring ultra-low lifts.The system also allows faster warm-up of the exhaust aftertreatment system for higher conversion efficiency, reduced HC and NOx engine emissions and improved combustion stability.

[0008] Further areas of applicability will become apparent from the description presented herein. The description and specific examples in this summary are for illustrative purposes only and are in no way intended to limit the scope of the present disclosure. DRAWINGS

[0009] The drawings described herein are for illustrative purposes only and do not represent all possible implementations and are not intended to limit the scope of the present disclosure. Fig. 1 shows a possible embodiment of an automotive system with an internal combustion engine; Fig. 2 shows a cross-section of the combustion engine from Fig. 1; Fig. 3 is a detailed view of one possible embodiment of a cam shifting system in an internal combustion engine according to the principles of the present disclosure, showing two rocker arms; Fig. 4 is a schematic view of a rocker arm during engagement of a cam with the thrust unit, the sliding part of the groove and the driving pin; Fig. 5 is a perspective view of a possible embodiment of the thrust unit according to the present disclosure; Fig. 6 is a planar schematic view of a possible embodiment of the thrust unit according to the present disclosure; Fig. 7 is a graphical representation of the cams of a possible embodiment of the cam shifting system in an internal combustion engine according to the present disclosure; and Fig. Figure 8 is a graphical representation of the timing of the internal EGR cam lobes according to the principles of the present disclosure.

[0010] Similar reference symbols indicate similar construction phases in the various views of the drawings. DETAILED DESCRIPTION

[0011] Exemplary embodiments will now be described in more detail with reference to the accompanying drawings.

[0012] Example embodiments are provided so that this disclosure will be thorough and will fully convey the scope thereof to those skilled in the art. Numerous specific details are set forth, such as examples of specific components, devices, and methods, in order to provide a thorough understanding of embodiments of the present disclosure. Those skilled in the art will recognize that specific details may not be required, that example embodiments may be embodied in many different forms, and that no embodiment should be construed to limit the scope of the disclosure. In some example embodiments, well-known methods, well-known device structures, and well-known techniques are not described in detail.

[0013] The terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to be limiting in any way. As used herein, the singular forms "a," "an," and "the" include the plural forms, where appropriate, unless the context clearly precludes them. The terms "comprises," "comprising," "include," and "having" are inclusive and therefore indicate the presence of the specified 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. The method steps, processes, and acts described herein should not be construed to require the described or illustrated order unless specifically stated as the order of performance.It should also be noted that additional or alternative steps may be applied.

[0014] When an element or layer is described as being "on / upon," "engaging with," "connected to," or "coupled to" another element or layer, it may either be directly on / upon, engaged with, connected to, or coupled to the other element or layer, or there may be intervening elements or layers. Conversely, when an element is described as being "directly on / upon," "directly engaging with," "directly connected to," or "directly coupled to" another element or layer, there may be no intervening elements or layers. Other words used to describe the relationship between elements should be understood in the same way (e.g., "between" and "directly between," "adjacent" and "directly adjacent," etc.).As used herein, the term “and / or” includes all combinations of one or more of the related listed elements.

[0015] Although the terms first, second, third, etc., may be used herein to describe various elements, components, regions, layers, and / or sections, these elements, components, regions, layers, and / or sections are not intended to be limited by these terms. These terms may only be used to distinguish one element, component, region, layer, or section from another region, layer, or section. Terms such as "first," "second," and other numerical terms, when used herein, do not imply a sequence or order unless clearly indicated by context. Thus, a first element, component, region, layer, or section discussed below could be referred to as a second element, component, region, layer, or section without departing from the teachings of the exemplary embodiments.

[0016] Spatially relative terms such as "inner", "outer", "beneath", "under", "lower", "above", "upper", and the like may be used herein to better describe the relationship of one element or feature to other element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation besides the orientation illustrated in the figures. For example, if the device is turned over in the figures, elements described as being "below" or "under" other elements or features are then oriented "above" other elements or features. Therefore, the example term "below" can include both an above and below orientation.The device may be oriented differently (rotated by 90° or to other orientations) and the spatially relative descriptors used herein may be interpreted accordingly.

[0017] With reference to the Fig. 1 and Fig. 2, an automotive system 10 is shown having an internal combustion engine (ICE) 12, which has an engine block 14 with at least one cylinder 16 with at least one piston 18 for driving a crankshaft 20. A cylinder head 22, together with the piston 18, forms a combustion chamber 24. A fuel / air mixture (not shown) is introduced into the combustion chamber 24 and ignited, resulting in reciprocal movement of the piston 18 by the expanding hot exhaust gases. The fuel is provided by at least one fuel injector 26 and the air by at least one intake port 28. The fuel is supplied under high pressure from the fuel tank 34 to the fuel injector 26 via a fuel rail 30, which is connected to a fuel pump 32 for pressure increase.Each of the cylinders 16 has at least two valves 36a, 36b, which are actuated by one or more camshafts 38 that rotate in synchronization with the crankshaft 20. The intake valves 36a selectively allow air from the passage 28 into the combustion chamber 24, and alternatively, the exhaust valves 36b allow exhaust gases to escape through the passage 40, as is known to those skilled in the art. A cam phaser 42 serves to selectively change the timing between at least one of the camshafts 38 and the crankshaft 20.

[0018] In the detailed view of an embodiment in Fig. In Figure 3, two exhaust valves 36b, 36b are partially visible and have rocker arms 44, 44a. The rocker arms 44, 44a may be provided with follower rollers 46, 46a that establish contact with the cams of the camshaft 38; this will be explained in more detail below. It should be noted that different types of rocker arms 44, 44a may be used, for example, those with rocker arms.

[0019] In the Fig. 1, Fig. 2 and Fig. 3, the internal combustion engine 12 has at least two exhaust valves 36b, 36b per cylinder, for example, two exhaust valves, but the present invention can also be used for internal combustion engines that have one or more exhaust valves per cylinder. The air can be transported through an intake manifold 48 to the intake duct(s) 28. An intake duct 50 can direct ambient air to the intake manifold 48. In other embodiments, a butterfly valve 52 can be installed to control the airflow to the intake manifold 48. In still other embodiments, other blower systems can be used, for example, a turbocharger 54 with a compressor 56 that is rotatingly connected to a turbine 58. The rotation of the compressor 56 increases the pressure and temperature of the air in the intake duct 50 and intake manifold 48. A charge air cooler 60 in the intake duct 50 can reduce the temperature of the air.Turbine 58 rotates due to incoming exhaust gases from exhaust manifold 62, which directs exhaust gases from exhaust port 40 through a series of blades of turbine 58 prior to expansion. The exhaust gases exit turbine 58 and are directed into an exhaust system 64.

[0020] The exhaust system 64 may have an exhaust pipe 66 with one or more exhaust aftertreatment devices 68. The aftertreatment devices 68 may be any device that, due to its design, can change the composition of the exhaust gases. Examples of aftertreatment devices 68 include, without limitation, catalytic converters (two- and three-way), oxidation catalysts, NO xStorage catalysts, hydrocarbon adsorbers, SCR systems, and particulate filters. Other embodiments may include an exhaust gas recirculation (EGR) system 70 installed between the exhaust manifold 62 and the intake manifold 48. The EGR system 70 may include an EGR cooler 72 for lowering exhaust gas temperatures in the EGR system 70. An EGR valve 74 controls the exhaust gas flow in the EGR system 70.

[0021] The automotive system 10 may further include an electronic control unit (ECU) 80 in communication with one or more sensors and / or devices associated with the internal combustion engine 12. The ECU 80 may receive input signals from various sensors configured to generate signals related to various physical parameters related to the internal combustion engine 12. These sensors include, without limitation, a mass air flow and temperature sensor 84, a manifold pressure and temperature sensor 86, a combustion chamber pressure sensor 88, a coolant and oil level and temperature sensor 90, a fuel rail pressure sensor 92, a camshaft position sensor 94, a crankshaft position sensor 96, an exhaust pressure and temperature sensor 98, an EGR temperature sensor 100, and an accelerator pedal position sensor 102.In addition, the ECU 80 may generate output signals for various control devices whose task is to control the operation of the ICE 12, including without limitation the fuel injectors 26, the valve body 52, the EGR valve 74, and the camshaft phaser 42. Communication between the ECU 80 and the various sensors and devices is represented by dashed lines, but some are suppressed for clarity.

[0022] Now, considering the ECU 80, this device may have a digital central processing unit (CPU) connected to a memory system, or storage device, and an interface bus. The CPU is designed to execute the instructions stored as a program in the memory system and to send and receive signals via the interface bus. The memory system may have various types of memory, including optical memory, magnetic memory, solid-state memory, and other non-volatile memory. The interface bus may be designed to modulate analog and / or digital signals and send them to or receive them from the various sensors and control units.

[0023] With reference to the Fig. 3-7 and in accordance with one possible embodiment, the internal combustion engine 12 has a cam shifting system 110 with a thrust unit 112. According to one possible embodiment, in the example shown in the figures, the thrust unit 112 is a hollow member and preferably of cylindrical shape. The thrust unit 112 is rotatably attached to the camshaft 38. In other words, when the camshaft 38 rotates about a camshaft axis R, the thrust unit 112 rotates together with the camshaft 38. Furthermore, the thrust unit 112 is movable with respect to the camshaft 38, preferably axially along the camshaft's rotational axis R. As mentioned, this axial movement is known as the "shifting movement" of the thrust unit 112.

[0024] The thrust unit 112 is rotatably and axially movably mounted on the camshaft 38 by means known to those skilled in the art. In the embodiments shown, the thrust unit 112 has an internal toothing 114 that engages the external toothing 114' of the camshaft 38. Thanks to the toothed connection 114, 114', the rotational movement of the camshaft 38 is transmitted to the thrust unit 112; moreover, the thrust unit 112 can slide on the camshaft 38 along the rotational axis R of the camshaft. The thrust unit 112 is provided with two or more cams 116, 118, 120 for a rocker arm 44, 44a.

[0025] According to one possible embodiment, the thrust unit 112 includes a first cam 116 having a first base circle 116a with an exhaust cam lobe 116b and an EGR cam lobe 116c extending from the base circle 116a, a second cam 118 having a second base circle 118a with an exhaust cam lobe 118b and an EGR cam lobe 118c extending from the base circle 118a, and a third cam 120 having a third base circle 120a with an exhaust cam lobe 120b and an EGR cam lobe 120c extending from the base circle 120a. The thrust unit 112 may also have additional cams.According to one possible embodiment, the additional cams, exhaust cam lobes and EGR cam lobes, may have different heights and / or circumferences than the first to third cams 116, 118, 120, or they may be provided with only one base circle to form deactivation cams for the thrust unit 112, or they may have one base circle, one exhaust cam lobe, and no EGR cam lobe to allow the internal EGR to be deactivated.

[0026] The shapes of the EGR cam lobes 116c, 118c, 120c and the exhaust cam lobes 116b, 118b, 120b are shown in Fig. 7, a graphic illustration showing the shapes of the cams along their distribution around the rotational axis R of the camshaft. In detail, Fig. 7 shows the lift provided by the cams 116, 118, and 120 (on the Y-axis (ordinate)) and the distribution over 360 degrees around the camshaft's rotational axis R (on the X-axis (abscissa)). The rocker arms 44, 44a are part of the relevant valves 36b, 36b. As is known, the coupling between the cams 116, 118, 120 and the rocker arms 44, 44a converts the rotational movement of the camshaft into a reciprocating movement of the cylinder's valves 36b, 36b. The cams 116, 118, 120 are arranged one next to the other. In the embodiments shown, cam 116 is located next to cam 118 and cam 120 is located next to cam 118. It should be noted that the cams intended to be connected to the rocker arms 44, 44a are shown in the attached figures with the same reference numerals 116, 118 and 120.

[0027] It should be noted that in the following, reference is made only to one rocker arm 44 of the valve 36b, which is intended to have contact with the cams 116, 118, 120 of the thrust unit 112. What is disclosed with respect to the rocker arm 44 can be transferred to the other rocker arms of the engine, such as the rocker arm 44a in Fig. 3.

[0028] According to a possible embodiment such as in Fig. 3, the same thrust unit 112 can be provided with two or more cams 116, 118, 120 for two or more rocker arms. Thus, in the embodiment in Fig. 3, for example, a single thrust unit 112 with two or more cams for the two rocker arms 44, 44a is provided. However, according to various possible embodiments, two thrust units with two or more cams 116, 118, 120 may also be provided to interact with the rocker arm 44 and 44a, respectively. The cams 116 and 118 may be in contact with the valve 36b of the cylinder and in particular with the rocker arm 44. As previously mentioned, the following description also applies to the cams 116, 118, and 120 in contact with the rocker arm 44a of the valve 36b.

[0029] Cams 116, 118, and 120 each have a base circle 116a, 118a, and 120a, respectively. Additionally, cams 116 and 118 also have exhaust cam lobes 116b, 118b, and 120b, and EGR cam lobes 116c, 118c, and 120c, each extending from base circle 116a, 118a, and 120a. As previously mentioned, an additional cam can serve as a deactivation cam, meaning it does not cause any cylinder valve lift and therefore only has the base circle.

[0030] As in the Fig. 6 and Fig. 7, the cams 116, 118, and 120 may have EGR cam lobes 116c, 118c, 120c with different heights relative to the camshaft rotational axis R. Additionally, the EGR cam lobes 116c, 118c, 120c may have different circumferential lengths. The EGR cam lobes 116c, 118c, and 120c may each also have different rotational origins, such that the phases of the individual EGR cam lobes differ from one another. Consequently, each of the cam lobes 116c, 118c, 120c effects a different actuation of the valve 36, and in particular, a different valve lift height, phase, and duration for tuning internal EGR activation under different engine operating conditions.In detail, an EGR cam lobe 116c of the first cam 116 may have a trailing flank portion 126 at the same distance from the camshaft's rotational axis R as a portion 126 of the EGR cam lobe 118c of the second cam 118 and the portion 126 of the EGR cam lobe 120c of the third cam 120, in order to provide the same return travel of the rocker arm 44, 44a. These portions 126 of the cam lobes of different cams 116, 118, 120 are shown, for example, in the graphic representation in . Fig. 7, wherein the return portion 126 of the cam lobes 116c, 118c, and 120c of the cams 116, 118, 120 partially overlap, i.e., are arranged at the same distance from the rotational axis of the camshaft to provide the same lift for the rocker arm. That is, the adjacent cams 116, 118, 120 have a portion 126 of a cam lobe that is arranged at the same distance from the rotational axis R of the camshaft to provide the same lift for the rocker arm 44 upon return to the base circle.

[0031] These parts 126 of the EGR cam lobes 116c, 118c, 120c can be arranged directly adjacent to one another and are each at the same distance from the camshaft's rotational axis R. As such, these parts form a common cam surface because they provide the same lift for the valve. As explained below, during the movement of the thrust unit 112, the rocker arm 44 contacts at least a portion of the cam lobe, preferably a portion that is at the same distance from the camshaft's rotational axis as a portion of a cam lobe of another cam.

[0032] As is known, valve 36 is de-actuated (lifted) and remains in a closed position when the valve's rocker arm 44 contacts the base circle 116a, 118a, 120a of a cam. In contrast, when the rocker arm 44 contacts the cam lobe of a cam, the valve experiences a lift and opens. The height of the lobe determines the valve's lift from the closed to the open position.

[0033] As in the example in Fig. 7, the base circle 116a, 118a, 120a corresponds to the part of the lines that do not provide lift, while the cam lobes correspond to the part of the lines that provide lift of the rocker arm. According to one embodiment, the base circle 116a of cam 116 may have the same diameter as the base circle 118a of cam 118. Likewise, the base circle 120a of the remote cam 120 may have the same diameter as the other base circles of the other cams 116, 118. The term diameter is used herein to indicate that the base circles 116a, 118a, and 120a are the same distance from the rotational axis R of the camshaft. Preferably, the distance is measured along a radial line passing through the rotational axis R of the camshaft.According to one embodiment, the cams 116, 118, 120 with the exhaust cam lobes 116b, 118b, 120b all have the same shape, although the shapes (height and duration) of the exhaust cam lobes 116b, 118b, 120b may be different.

[0034] According to one embodiment, the thrust unit 112 may have at least one groove 128. In particular, the internal combustion engine 12, such as in the embodiment shown, has at least one drive pin 130 that can selectively engage and disengage from the groove 128. In the embodiments shown, for example in Fig. 3, there are two drive pins 130. At least one drive pin 130 is actuated by a suitable device, such as an actuator controlled by the ECU 80 of the internal combustion engine, to be moved from a position engaged in the groove 128 to a position disengaged from the groove 128. According to one possible embodiment, at least one drive pin 130 can be selectively extended and retracted by a body of a suitable actuator to engage or disengage from the groove 128. The groove 128 has a sliding portion 128a, and the drive pin 130 can selectively engage or disengage from the sliding portion 128a of the groove 128. The connection between the drive pin 130 and the sliding portion 128a of the groove 128 causes the movement of the thrust unit 112 along the camshaft, i.e., the translation of the thrust unit 112.

[0035] The sliding portion 128a can be spirally shaped, e.g., as a curve between two points, or arranged at different distances from each other along the camshaft's rotational axis. That is, the sliding portion 128a extends to connect points on the surface of the thrust unit that lie on different planes perpendicular to the camshaft's rotational axis R. The sliding portion can have a right or left slope, thus allowing the thrust unit 112 to be displaced during the camshaft's rotation while the drive pin engages the sliding portion 128a of the groove.

[0036] As shown in the schematic view of Fig. As can be seen in Figure 4, the thrust unit 112 is displaced along the camshaft when the drive pin 130 engages the sliding part 128a after actuation. While the thrust part 112 is displaced, the rocker arm 44 engages with at least two cams. In other words, before the thrust unit begins to move, the rocker arm 44 comes into contact with the first cam 116; at the end of the movement, the rocker arm is in contact with the other cam 118. It should be noted that the sliding part 128a is shown schematically; for clarity, the actual dimensions have been reduced. The sliding part 128a, ie the screw-like part, extends between two straight parts 128b of the groove 128, which runs over two surfaces perpendicular to the axis of rotation of the camshaft. When the driving pin 130 engages in said straight parts 128b of the groove 128, the pushing unit 112 is not displaced along the axis of rotation of the camshaft.

[0037] It should be noted that the thrust unit 112 can be moved by the sliding part 128a and the groove 128 along the camshaft between at least two positions which correspond to the positions in which the rocker arm 44, 44a comes into contact with two different cams 116, 118, 120 of the thrust unit 112.

[0038] It should be noted that the cam shifting system 110 of the internal combustion engine may have two or more drive pins 130, as shown in Fig. 3, so that upon engagement of different driver pins 130 in the sliding part 128a, a different movement of the thrust unit 112 along the axis of rotation of the camshaft can be achieved, which corresponds to different positions in which the rocker arm 44 has contact with different cams 116, 118, 120. During the movement of the thrust unit along the axis of rotation of the camshaft, ie during the movement caused by the engagement of the driver pin 130 in the sliding part 128a, the rocker arm 44 and in particular the scanning roller 46 makes contact with at least two cams 116, 118, 120.

[0039] The cam displacement system 110 according to the present disclosure, and in particular the sliding part 128a, are designed such that during the displacement of the thrust unit 112 along said rotational axis R of the camshaft, the rocker arm 44 is in contact with at least a part of at least one cam nose 116b, 118b. In other words, in the known cam displacement system, the rocker arm is in contact with the cam nose of the cam as well as with the base circle when the thrust unit moves along the camshaft to provide contact of the rocker arm from a first cam to at least one further cam 116, 118, 120. More specifically, the sliding part 128a of the groove 128 extends over an arc A of the external surface of the thrust unit 112 and a thrust path of the rocker arm FSP (an example in Fig. 7) between at least two cams 116, 118, 120, and the thrust path of the rocker arm includes at least a portion of at least one cam lobe 116b, 118b. In other words, when the thrust unit moves along the camshaft, the rocker arm 44 is moved between at least two cams 116, 118, 120, for example, from a position in contact with the first cam 116 to a position in contact with another cam 118.

[0040] According to a possible embodiment, such as in Fig. As shown in Figure 4, the sliding portion 128a of the groove 128 extends over an arc A that is greater than the arc B over which the base circle 116a, 118a, 120a extends. The arcs A and B cover the angles measured from the rotational axis R of the camshaft. The sliding portion 128a extends over the surface of the thrust unit and thus corresponds to an arc of revolution of the camshaft that is greater than the extension of the base circle of a cam of the thrust unit. Consequently, the rocker arm is in contact with the base circle and also with at least part of the cam nose 116b, 118b, 120b when the thrust unit moves along the camshaft, since the drive pin engages the sliding portion 128a. According to a possible embodiment, the arc B over which the base circle 116a, 118a, 120a extends is determined by the longest base circle 116a, 118a, 120a of said at least two cams 116, 118, 120.

[0041] The thrust path of the rocker arm FSP, also called the thrust window of the rocker arm, ie the part of the cams 116, 118, 120 that is in contact with the rocker arm 44 when the thrust unit moves along the axis of rotation R of the camshaft while rotating together with the camshaft, comprises the cam noses 116b, 118b, 120b as well as the base circles 116a, 118a, 120a (see for example Fig. 7). In other words, the rocker arm thrust path represents the surface of the cams that are in contact with the rocker arm during the rotation of the camshaft and the movement of the thrust unit along the camshaft due to the engagement of the drive pin 130 with the sliding part 128a of the groove 128. The rocker arm thrust path FSP can also be viewed as the arc of the cams that are in contact with the rocker arm during the rotation of the camshaft and the movement of the thrust unit along the camshaft.

[0042] As already mentioned above, the contact of the rocker arm 44 with a cam nose of the cam can advantageously extend the thrust path of the rocker arm FSP, so that the displacement of the thrust unit can be carried out at an increased rotation angle of the camshaft, thereby providing more time for the displacement and reducing the affected accelerations. Advantageously, according to one possible embodiment, the rocker arm 44 can make contact with at least a portion of the base circle 116a of the first cam 116, as well as a portion of the cam nose 118b of the second cam 118, while the thrust unit 112 moves along the camshaft 38. According to one possible embodiment, the rocker arm 44 makes contact with two cam noses of at least two different cams during the movement of the thrust unit 112.

[0043] According to one possible embodiment, a portion 126 of a cam lobe 116b of one cam 116 is arranged at the same distance from the rotational axis R of the camshaft as a portion 126 of a cam lobe 118b of another cam 118 in order to provide the same lift of the rocker arm 44. In other words, the portions 126 of the cam lobes 116b, 118b of the two different cams 116, 118, which are preferably adjacent, are arranged at the same distance from the rotational axis R of the camshaft. In detail, the cams 116, 118 have a common surface on a portion of their cam lobes, which are arranged at the same distance from the rotational axis R of the camshaft, so that the same lift is available for the rocker arm and thus also for the cylinder valve 36 of the cylinder.

[0044] Advantageously, according to one embodiment of the invention, during the movement of the thrust unit 112 along the rotational axis R of the camshaft, the rocker arm 44 makes contact with a part 126 of the cam nose, which is arranged at the same distance from the rotational axis of the camshaft as a part 126 of the cam nose of another cam. According to one possible embodiment, during the movement of the thrust unit 112 along the rotational axis R of the camshaft, the rocker arm 44 makes contact with the parts 126 of two cam noses, which are arranged at the same distance from the rotational axis of the camshaft.

[0045] According to one possible embodiment, the part 126, which is arranged at the same distance from the rotational axis R of the camshaft in order to provide the same stroke of the rocker arm, contains at least a portion of the opening flank of the EGR cam lobes 116c, 118c, 120c. In other words, according to one possible embodiment of the invention, during the movement of the thrust unit along the camshaft, contact is made by the rocker arm 44 with at least a portion of an opening flank 126 of at least one cam lobe 116c, 118c, 120c.

[0046] According to a possible embodiment, such as in the Fig. As can be seen in Figure 3, the thrust unit 112 can be provided with two or more cams 116, 118, 120 for each rocker arm and a single groove 128. However, other possible embodiments are also possible, e.g., a single thrust unit with two or more cams, a groove, and a relative drive pin for controlling the movement of the thrust unit for a single rocker arm of the internal combustion engine.

[0047] The present invention also relates to a method for controlling valve actuation in an internal combustion engine 12 having a cam shifting system 110 according to the invention. What was previously disclosed for the internal combustion engine can also be applied to the method, and vice versa. The method comprises the steps of operating the internal combustion engine to rotate the camshaft 38 with the aim of actuating at least one exhaust valve 36b of the cylinder. The method further includes the step of actuating the drive pin 130 to engage the sliding part 128a of the groove 128 so that the thrust unit 112 can be moved relative to the camshaft 38 along the camshaft's rotational axis R.As already mentioned, during the movement of the thrust unit 112 along the rotational axis R of the camshaft, the rocker arm 44, 44a makes contact with a part 126 of an EGR cam nose 116c, 118c, 120c of a first cam 116, 118, 120, which is installed at the same distance from the rotational axis R of the camshaft as a part 126 of an EGR cam nose 116c, 118c, 120c of another cam 116, 118, 120, in order to provide the same stroke of the rocker arm 44, 44a.

[0048] It should be noted that the movement of the thrust unit 112 can be performed to achieve the desired actuation (lift) of at least one valve of the cylinder. Consequently, engagement / retraction of the drive pin 130 into / from the sliding portion 128a of the groove 128 of the thrust unit 112 can be performed according to the present method to enable contact of at least one rocker arm 44, 44a with the desired cam 116, 118, 120 having the desired profile for the desired valve lift. The movement of the thrust unit can be performed via the ECU 80 of the internal combustion engine, which controls the engagement / retraction of the drive pin 130 into / from the sliding portion 128a.

[0049] According to one embodiment, the method includes a step of monitoring at least one value of at least one operating parameter of the internal combustion engine 12 during operation. This one operating parameter can be an engine load parameter measured and / or evaluated by at least one sensor (not shown), possibly in conjunction with stored data. The method step of actuating the driver pin 130 with the aim of engaging the sliding part 128a of the groove 128 in order to displace the thrust unit 112 relative to the camshaft 38 is carried out as a function of the monitored value of at least one operating parameter.

[0050] According to one possible embodiment, the contact of the rocker arm with at least two cams of the thrust unit is established by making contact with a part of at least two cam noses of two cams, which are installed at the same distance from the rotational axis of the camshaft in order to provide the same lift of the valve. During the movement of the thrust unit 112 along the rotational axis R of the camshaft, the rocker arm 44, 44a makes contact with a part 126 of a cam nose 116b, 118b of a first cam 116, 118, 120, which is installed at the same distance from the rotational axis R of the camshaft as a part 126 of a cam nose of another cam, in order to provide the same lift of the rocker arm 44, 44a.

[0051] As previously discussed in connection with the internal combustion engine, the rocker arm can make contact with at least part of the opening flank 126 of the cam nose during the movement of the thrust unit.

[0052] The system of the present disclosure provides a second valve opening event where the angle, lift, and duration are variable for internal EGR quantity control from light to high engine load. Specifically, the system provides high internal EGR capability at low loads and controllability of internal EGR at high loads without requiring ultra-low lift. This also allows for faster warm-up of the exhaust aftertreatment system for higher conversion efficiency, reduced HC and NOx engine emissions, and improved combustion stability.

[0053] In particular, with reference to Fig. 8, at light engine load, a higher lift and a longer duration can be selected for the EGR cam nose 120c, where the cam nose is set to position “A” towards the intake port, as in Fig. 8, while at high engine load a smaller lift and a shorter duration of the EGR cam lobe 116c are selected, in which the cam lobe is set, for example, to position “B” towards the intake opening, as in Fig. 8. At medium load, or during the load change from high to low, it may be desirable to have an EGR cam lobe 118c with a mid-range position C for a mid-range of lift and duration, as shown in Fig.8. The relative angular adjustment of the EGR cam lobes 120c, 118c, 116c may be implemented based on the optimal angular position for the engine operating conditions for each cam lobe. Alternatively, the ECU 80 may control the operation of the cam phaser 42 and the boost unit 112 depending on the engine load according to a predetermined schedule to enable improved control of the internal EGR requirements at low and high engine loads. The internal EGR may provide faster control response to charge loss during transient operation; efficient heating of the in-cylinder charge using recycled energy and loading of residuals from the previous cycle into the intake; increasing engine cold-start preheating by partially replacing fuel-assisted preheating strategies; and higher aftertreatment efficiency with reduced emissions during warm-up in diesel engines.

[0054] Switching from internal EGR to low-pressure EGR reduces peak emissions and expands the application area for low-pressure EGR.

[0055] The foregoing description of the embodiments is for purposes of illustration and description only. It is not exhaustive and is not intended to limit the disclosure in any way. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but may be interchangeable and usable in a selected embodiment, even if not separately shown or described. Various variations are also conceivable. Such variations do not constitute a departure from the disclosure, and all such modifications are to be considered part of and within the scope of the disclosure.

Claims

[1] Internal combustion engine (12), comprising: an engine structure defining a combustion chamber (24) and intake and exhaust ports (28, 40) in communication with the combustion chamber (24); an intake system connected to the intake duct (28); an exhaust system connected to the exhaust duct (40); a valve train assembly comprising an intake valve (36a) disposed in the intake port (28), an intake valve lift mechanism engaged with the intake valve (36a), an intake cam engaged with the intake valve lift mechanism and defining an intake lift region configured to open the intake valve (36a); an exhaust valve (36b) arranged in the exhaust passage (40), an exhaust valve lift mechanism engaged with the exhaust valve (36b) and operable to open the exhaust valve (36b) at different lift heights, phases, and durations during an intake stroke, wherein the intake valve (36a) and the exhaust valve (36b) are operable by at least one camshaft (38); and a control unit (80) for controlling the exhaust valve lift mechanism to change the lift, phase and duration of the exhaust valve (36b) during an intake stroke depending on the operating conditions of the engine (12); characterized by , that the internal combustion engine (12) further comprises a cam shifting system (110) having a thrust unit (112) which is rotatably and axially movable along a rotational axis (R) of the camshaft (38) attached to the camshaft (38); wherein the thrust unit (112) comprises at least two cams (116, 118, 120) for a rocker arm (44), wherein the at least two cams (116, 118, 120) each comprise a base circle (116a, 118a, 120a), an exhaust cam nose (116b, 118b, 120b) extending from the base circle (116a, 118a, 120a), and an EGR cam nose (116c, 118c, 120c) extending from the base circle (116a, 118a, 120a); wherein the cam displacement system (110) is configured such that a coupling between the cams (116, 118, 120) and the rocker arm (44) converts a rotational movement of the camshaft (38) into a pendulum movement of the exhaust valve (36b), so that the exhaust valve (36b) remains in a closed position when the rocker arm (44) contacts the base circle (116a, 118a, 120a) of a cam (116, 118, 120), and so that the exhaust valve (36b) experiences a lift and opens when the rocker arm (44) makes contact with a cam nose (116b, 118b, 120b, 116c, 118c, 120c); and wherein respective flank parts (126) of the EGR cam noses (116c, 118c, 120c) of two different cams (116, 118, 120) are arranged at the same distance from the axis of rotation (R) of the camshaft (38), so that an equal stroke is available for the rocker arm (44) and for the exhaust valve (36b). [2] Internal combustion engine (12) according to claim 1, wherein the EGR cam noses (116c, 118c, 120c) of the at least two cams (116, 118, 120) have different heights relative to the rotational axis (R) of the camshaft (38); and / or wherein the EGR cam noses (116c, 118c, 120c) of the at least two cams (116, 118, 120) have different circumferential lengths; and / or wherein the EGR cam lobes (116c, 118c, 120c) of the at least two cams (116, 118, 120) each have different rotational starting points, so that respective phases of the individual EGR cam lobes (116c, 118c, 120c) differ from one another.

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