Internal combustion engine device with internal exhaust gas recirculation

Abstract

Internal combustion engine device with a valve train device (10) comprising a valve lift switching unit (11) and having at least one cam track (12, 13) designed to open at least one exhaust valve at least temporarily during an intake phase (14), with a throttle device (15) designed to adjust an intake cross-section, and with a control and / or regulating unit (16) for adjusting the throttle device (15), where the control and / or regulating unit (16) is designed to adjust the throttle device (15) to set internal exhaust gas recirculation, and the throttle device (15) is arranged in an intake tract (17), and the control and / or regulating unit (16) is designed to adjust a throttle device position depending on an internal combustion engine temperature, and wherein the control and / or regulating unit (16) has a first operating mode designed for operation without internal exhaust gas recirculation and a second operating mode designed for operation with internal exhaust gas recirculation, and upon switching from the first to the second operating mode, the control and / or regulating unit (16) triggers a switching of the exhaust valves, wherein the valve lift switching unit (11) is designed to change a valve lift of the exhaust valves in discrete steps, and wherein the valve train device (10) comprises a plurality of exhaust cams (21) which at least partially each have partial cams (22, 23) arranged directly next to each other, which are provided for switching the valve lift of the exhaust valves.

Description

[0001] The invention relates to an internal combustion engine device with a valve train device according to claim 1.

[0002] From JP 2001-214 812 A, a cylinder direct injection engine is known which is equipped with a compressor to increase performance and in which an internal EGR is implemented by changing the valve timing of the intake and exhaust valves.

[0003] In DE 199 14 909 A1, a camshaft for a four-stroke internal combustion engine, in particular equipped with a variable valve train, is disclosed, the cams of which actuate the intake valves (or the exhaust valves) of the internal combustion engine combustion chambers are designed in such a way that the intake valves (or the exhaust valves) can be opened not only in the respective intake stroke.

[0004] From DE 10 2005 015 852 A1, an internal combustion engine device with a valve train device comprising a valve lift switching unit and having at least one cam track intended to temporarily open at least one exhaust valve during an intake phase, with a throttle device intended to adjust an intake cross-section, is already known.

[0005] Furthermore, DE 25 03 806 discloses an internal combustion engine device with a valve train device comprising a valve lift switching unit and featuring a cam track. The cam track is designed to keep at least one exhaust valve open, at least temporarily, during an intake phase. A throttle device is provided for adjusting the intake cross-section. The throttle device is designed for adjusting internal exhaust gas recirculation and is adjusted by a control unit.

[0006] The invention is based in particular on the objective of improving a combustion process in an internal combustion engine. This objective is achieved according to the invention by the features of the independent claims. Further embodiments are described in the dependent claims.

[0007] The invention relates to an internal combustion engine device with a valve train device comprising a valve lift switching unit and having at least one cam track designed to open at least one exhaust valve at least temporarily during an intake phase, with a throttle device designed to adjust an intake cross-section, and with a control and / or regulating unit for adjusting the throttle device.

[0008] It is proposed that the throttle device be located in the intake manifold and that the control unit be designed to adjust the throttle device to regulate internal exhaust gas recirculation. This allows the amount of exhaust gas recirculated to a cylinder for subsequent combustion to be continuously adjusted, at least in certain ranges, without requiring a fully variable valve train for the exhaust side. Particularly due to the high temperature of the recirculated exhaust gases, this can lead to improvements in carbon monoxide and hydrocarbon emissions. Furthermore, the exhaust gas temperature can be increased, which can be especially beneficial during the warm-up phase.An embodiment according to the invention thus enables the optimization of the combustion process in an internal combustion engine, while keeping the costs and complexity of the valve train low. A "valve lift switching unit" is understood to be, in particular, a unit designed to switch a valve actuation characteristic for the at least one exhaust valve in discrete steps, such as, in particular, a unit designed to bring the exhaust valve into effective contact with one of at least two cam tracks. A "cam track" is understood to be, in particular, a portion of an exhaust cam that is provided for the direct actuation of the exhaust valve and / or for use by means of a cam follower to actuate the exhaust valve. Preferably, the at least one exhaust cam has at least two cam tracks.The term "intake phase" refers in particular to a phase during a working cycle in which at least one intake valve, assigned to the same cylinder as the at least one exhaust valve, is open to supply the cylinder with an air-exhaust mixture suitable for combustion. The term "intake cross-section" refers in particular to a cross-section of an intake tract that is effective during the intake phase. Internal "exhaust gas recirculation" refers in particular to exhaust gas recirculation in which exhaust gas from the exhaust tract is directly fed back into the cylinder. The term "control and / or regulation unit" refers in particular to a unit comprising at least one control unit. The term "control unit" refers in particular to a unit comprising a processor unit, a memory unit, and an operating program stored in the memory unit.In principle, the control unit can comprise several interconnected control units, which are preferably designed to communicate with each other via a bus system, such as a CAN bus system. "Designed" here refers specifically to being programmed, equipped, and / or configured for this purpose.

[0009] The control unit is designed to adjust the throttle position depending on the engine temperature. This allows for the effective use of internal exhaust gas recirculation, particularly during the warm-up phase, to improve the combustion process. For example, a higher exhaust gas temperature can be achieved without increasing fuel consumption, which is particularly advantageous for bringing filters and / or catalytic converters located in the exhaust system up to operating temperature quickly without sacrificing fuel economy. Furthermore, by combining internal exhaust gas recirculation with external exhaust gas recirculation, especially low-pressure recirculation, emissions of carbon monoxide and hydrocarbons can be reduced, and a more favorable lambda value can be achieved.

[0010] Furthermore, a method for operating an internal combustion engine is proposed, comprising a valve train device including a valve lift switching unit and having at least one cam track that opens at least one exhaust valve at least temporarily during an intake phase, and a throttle device for adjusting the intake cross-section, and a control unit that adjusts the throttle device. The control unit adjusts the throttle device for internal exhaust gas recirculation. The throttle device is located in the intake tract, and its position is adjusted by the control unit depending on the internal combustion engine temperature, thereby improving the combustion process in the internal combustion engine.

[0011] Further advantages will become apparent from the following description of the drawing. The drawing illustrates an embodiment of the invention. The drawing, the description, and the claims contain numerous features in combination. A person skilled in the art will expediently consider the features individually and combine them into meaningful further combinations.

[0012] This shows: Fig. 1 schematically depicts an internal combustion engine device, Fig. 2 the internal combustion engine device in a perspective view and Fig. 3 cam curves of cam tracks of a valve train device of the internal combustion engine device.

[0013] The Fig. Figure 1 shows an internal combustion engine device for a motor vehicle according to the invention. The internal combustion engine device comprises a valve train device 10, an intake manifold 17, and an exhaust manifold 18. Furthermore, the internal combustion engine device comprises a plurality of intake valves (not shown) and a plurality of exhaust valves (not shown) for gas exchange between the intake manifold 17, cylinders 19 of the internal combustion engine device, and the exhaust manifold 18. The exhaust manifold 18 includes a diesel particulate filter 20. The internal combustion engine device is designed as a diesel engine.

[0014] The valve train device 10 comprises a valve lift switching unit 11, which is designed to change the valve lift of the exhaust valves in discrete steps. The valve train device 10 comprises a plurality of exhaust cams 21, each of which at least partially has sub-cams 22, 23 arranged directly adjacent to one another, which are provided for switching the valve lift of the exhaust valves. The sub-cams 22, 23 each have at least two cam tracks 12, 13, each of which defines the valve lift of the corresponding exhaust valve.

[0015] In a particularly advantageous embodiment, the valve lift switching unit 11 is designed to displace the exhaust cams 21, which are intended for switching, along their axis of rotation. The valve train assembly 10 comprises a cam shaft 24 and cam elements 25 that are axially displaceable on the cam shaft 24, each of which carries one or more of the exhaust cams 21 intended for switching. The valve lift switching unit 11 further comprises a switching cam 26, which is designed to convert a rotary movement of the cam elements 25 into an axial switching force. However, other embodiments of the valve lift switching unit 11, known to those skilled in the art, are also conceivable.

[0016] For internal exhaust gas recirculation, a portion of the cam tracks 12, 13 of a portion of the exhaust cams 21 are designed to open the corresponding exhaust valve during an intake phase 14 of the corresponding cylinder 19. Each cylinder 19 of the internal combustion engine comprises exactly one cam track 13 assigned to the corresponding cylinder 19, which is designed to open the corresponding exhaust valve during the intake phase 14. By opening the exhaust valve during the intake phase 14, exhaust gases from the exhaust tract 18 enter the corresponding cylinder 19. The exhaust gases are thus fed back into the cylinder 19. Simultaneously, the intake valves are open. A mixture of exhaust gases and fresh gases is thus supplied to the cylinder 19, which is combusted in the cylinder 19 during a subsequent ignition.

[0017] To adjust the mixture of the supplied fresh gases and the recirculated exhaust gases, the internal combustion engine device includes a throttle device 15. The throttle device 15 is arranged in the intake tract 17. The intake cross-section can be adjusted by means of the throttle device 15. The throttle device 15 includes at least one electronically controlled throttle valve, which is provided for changing the intake cross-section. For adjusting the throttle valve, the internal combustion engine device includes a control unit 16, to which the throttle device 15 is connected.

[0018] The valve train device 10 is designed for internal exhaust gas recirculation by opening at least one exhaust valve during the intake phase 14, at least in the operating state in which the corresponding cam track 12, 13 is engaged. To adjust the internal exhaust gas recirculation, the control unit 16 is designed to adjust the throttle device 15 and thus, in particular in the operating state in which at least one exhaust valve is open during the intake phase 14, to adjust the amount of exhaust gas supplied to the cylinder 19 via the exhaust valve.

[0019] By adjusting the throttle device 15, the control unit 16 changes the pressure in the intake tract 17 during the intake phase 14. The control unit 16 thus establishes a pressure differential between the intake tract 17 and the exhaust tract 18 by adjusting the throttle device 15. A pressure differential between the intake valves and the exhaust valves of a cylinder 19 depends directly on the setting of the throttle device 15.

[0020] The amount of exhaust gas that is fed back to cylinder 19 via internal exhaust gas recirculation depends directly on the pressure difference between the intake and exhaust valves. The control unit 16, by adjusting the throttle device 15, is thus designed to regulate the internal exhaust gas recirculation. The control unit 16 can continuously vary the amount of internally recirculated exhaust gas, at least in certain ranges.

[0021] The control unit 16 has a first operating mode, which is intended for operation without internal exhaust gas recirculation, and a second operating mode, which is intended for operation with internal exhaust gas recirculation. When switching from the first to the second operating mode, the control unit 16 triggers a switching of the exhaust valves. Simultaneously with the switching of the valve lift for the corresponding exhaust valves, the control unit 16 adjusts the position of the throttle device 15 to the current operating state of the internal combustion engine. The adjustment of the throttle device 15 depends on various parameters, such as, in particular, the temperature of the internal combustion engine and the temperature of the exhaust system.

[0022] The control unit 16 activates internal exhaust gas recirculation, particularly during the warm-up phase of the internal combustion engine, i.e., when the engine temperature is low. Internal exhaust gas recirculation replaces external high-pressure exhaust gas recirculation. In principle, internal exhaust gas recirculation can also be used in the Fig. Replace the high-pressure exhaust gas recirculation line shown in 1.

[0023] The internal combustion engine device further comprises an external low-pressure exhaust gas recirculation system 27, which is designed to return exhaust gas from the exhaust tract 18 to the intake tract 17. The internal combustion engine device has an exhaust gas turbocharger 28, which divides the intake tract 17 and the exhaust tract 18 into a low-pressure section and a high-pressure section, respectively. The external low-pressure exhaust gas recirculation system 27 is arranged between the low-pressure section of the exhaust tract 18 and the low-pressure section of the intake tract 17. During the warm-up phase and / or during normal operation, the control unit 16 can also establish a mixed operation, whereby a portion of the exhaust gas is supplied to the corresponding cylinder 19 via the internal exhaust gas recirculation system and a portion of the exhaust gas is supplied via the external low-pressure exhaust gas recirculation system 27.

[0024] The low-pressure exhaust gas recirculation system 27 comprises an exhaust pipe 29 arranged between the intake manifold 17 and the exhaust manifold 18. An exhaust gas recirculation cooler 30 is arranged in the exhaust pipe 29, which is designed to cool the exhaust gas before it is introduced into the intake manifold 17. An adjustable flap 31 is also arranged in the exhaust pipe 29, which is designed to change the cross-section of the exhaust pipe 29. Furthermore, the low-pressure exhaust gas recirculation system 27 has a flap 32 arranged in the exhaust manifold 18, which is designed to partially close the exhaust manifold 18. The two flaps 31 and 32 are designed to adjust the amount of exhaust gas recirculated via the low-pressure exhaust gas recirculation system 27. The throttle device 15 for adjusting the internal exhaust gas recirculation is located downstream of the point where the exhaust pipe 29 enters the intake manifold 17 and downstream of a charge air cooler 33.

[0025] In principle, any combination of the internal exhaust gas recirculation according to the invention, the external low-pressure exhaust gas recirculation 27, and the external high-pressure exhaust gas recirculation shown in dashed lines is conceivable. In particular, it is also possible to completely dispense with the external low-pressure exhaust gas recirculation 27 and / or the external high-pressure exhaust gas recirculation shown in dashed lines.

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