Supercharged internal combustion engine with grouped exhaust pipes

Abstract

Supercharged internal combustion engine (10) with at least two cylinders (1), in which - each cylinder (1) has at least one inlet opening (2a, 2b) for supplying charge air via the intake system (3) and at least two outlet openings (4a, 4b) for discharging exhaust gas via the exhaust gas removal system (5), each outlet opening (4a, 4b) being connected to an exhaust line (5a, 5b), - at least one exhaust gas turbocharger (8) is provided, which comprises a turbine (8a) arranged in the exhaust gas discharge system (5) and a compressor (8b) arranged in the intake system (3), - the exhaust pipes (5a, 5b) are configured in such a way that they form two groups, each group comprising at least one exhaust pipe (5a, 5b) from each cylinder (1) and the exhaust pipes (5a, 5b) of each group each merging to form an exhaust manifold into a total exhaust pipe (6a, 6b), - the first exhaust line (6a) of a first group opens into the turbine (8a) of the at least one exhaust gas turbocharger (8), - the second exhaust line (6b) of a second group opens into the intake system (3) upstream of the compressor (8b) of the at least one exhaust gas turbocharger (8), and - the outlet openings (4b) belonging to the exhaust pipes (5b) of the second group are each equipped with an at least partially variably actuated outlet valve, wherein this outlet valve of the second group can be moved between an open position and a closed position, forming a maximum valve lift Δh 2ndexhaust oscillates and thereby closes the corresponding outlet opening (4b) during an opening process for the opening duration Δt 2ndexhaust releases, characterized in that - a blow-off line (7) is provided, in which a shut-off element (7a) is arranged and which branches off from the exhaust manifold of the second group to form a first node (7b) and opens into the exhaust gas discharge system (5) downstream of the turbine (8a) of the at least one exhaust gas turbocharger (8) to form a second node (7c), wherein the blow-off line (7) opens into the exhaust gas discharge system (5) upstream of an exhaust gas aftertreatment system (11) provided in the exhaust gas discharge system (5) to form the second node (7c).

Description

[0001] The invention relates to a supercharged internal combustion engine with at least two cylinders, in which - each cylinder has at least one inlet opening for supplying charge air via the intake system and at least two outlet openings for discharging exhaust gas via the exhaust gas removal system, with an exhaust pipe connected to each outlet opening, - at least one exhaust gas turbocharger is provided, which comprises a turbine arranged in the exhaust gas discharge system and a compressor arranged in the intake system, - the exhaust pipes are configured in such a way that they form two groups, each group comprising at least one exhaust pipe from each cylinder and the exhaust pipes of each group merging into a single exhaust pipe to form an exhaust manifold, - the first exhaust line of a first group opens into the turbine of at least one exhaust gas turbocharger, - the second exhaust line of a second group opens into the intake system upstream of the compressor of the at least one exhaust gas turbocharger, and - the outlet openings (4b) belonging to the exhaust pipes (5b) of the second group are each equipped with an at least partially variably actuated outlet valve, wherein this outlet valve of the second group can be moved between an open position and a closed position, forming a maximum valve lift Δh 2ndexhaust oscillates and thereby closes the corresponding outlet opening (4b) during an opening process for the opening duration Δt 2ndexhaust releases.

[0002] Such a generic internal combustion engine is known from US 8495992 B2.

[0003] EP 0 596 855 A1 describes an internal combustion engine with exhaust gas recirculation, in which a cooler has a bypass line in the line for the exhaust gas recirculation.

[0004] DE 10 2015 112 429 A1 discloses an internal combustion engine in which a second exhaust line of a second group opens into the intake system upstream of the compressor of an exhaust gas turbocharger.

[0005] An internal combustion engine of the aforementioned type is used as a motor vehicle drive. Within the scope of the present invention, the term "internal combustion engine" encompasses gasoline engines, but also hybrid internal combustion engines that utilize a hybrid combustion process with spark ignition, as well as hybrid drives that, in addition to a spark-ignition internal combustion engine, comprise an electric motor that can be connected to the internal combustion engine for driving purposes, which absorbs power from the internal combustion engine or delivers additional power as a switchable auxiliary drive.

[0006] Internal combustion engines have a cylinder block and at least one cylinder head, which are connected to form the cylinders and their combustion chambers. The cylinder block typically serves as the upper half of the crankcase, supporting the crankshaft and accommodating the piston or cylinder liner of each cylinder.

[0007] The crankshaft, mounted in the crankcase, absorbs the connecting rod forces and transforms the oscillating stroke of the pistons into a rotating rotation of the crankshaft. The upper crankcase half, formed by the cylinder block, is usually complemented by the oil pan, which can be mounted on the cylinder block and serves as the lower crankcase half.

[0008] The cylinder head typically houses the valve trains required for gas exchange. During gas exchange, combustion gases are removed via the exhaust system through the exhaust ports, and charge air is supplied via the intake system through the intake ports of at least two cylinders. According to the current state of the art, lift valves are used almost exclusively to control gas exchange in four-stroke engines.

[0009] Each lift valve moves between an open and a closed position, i.e., completing a maximum valve lift, thereby releasing the valve's associated opening for a certain opening duration during the opening process. The valve actuation mechanism required for the movement of a valve, including the valve itself, is called the valve train.

[0010] The task of a valve train is to open or close the intake or exhaust ports in a timely manner. Typically, rapid opening of the largest possible flow cross-section is the goal to minimize throttling losses in the incoming and outgoing gases and ensure the best possible cylinder filling and effective exhaust gas removal. Therefore, according to the current state of the art, cylinders are often equipped with two or more intake or exhaust ports.

[0011] The at least two cylinders of the internal combustion engine which is the subject of the present invention are equipped with at least one inlet opening and at least two outlet openings.

[0012] According to the prior art, the intake lines leading to the intake ports and the exhaust lines connecting to the exhaust ports are at least partially integrated into the cylinder head. The exhaust lines of the cylinders are often combined into a common exhaust line or—as in the internal combustion engine according to the invention—in groups to form two exhaust lines. The combination of exhaust lines into a single exhaust line is referred to as an exhaust manifold, whereby, for the purposes of the present invention, the exhaust line is considered to be part of the exhaust manifold.

[0013] Downstream of the manifold, the exhaust gases are fed to at least one exhaust gas turbocharger and / or one or more exhaust gas aftertreatment systems to boost the turbine. In some cases, exhaust gas is recirculated to the intake system.

[0014] In the internal combustion engine that is the subject of the present invention, exhaust gas originating from the cylinders is fed to the turbine of at least one exhaust gas turbocharger via a first exhaust line for the purpose of charging. A second exhaust line connects the cylinders on the exhaust side to the intake system upstream of the compressor of the at least one exhaust gas turbocharger. The exhaust lines of the cylinders are configured such that they form two groups, each group comprising at least one exhaust line from each cylinder, and the exhaust lines of each group each merge into a single exhaust line, forming an exhaust manifold.

[0015] Internal combustion engines of this type and methods for operating such internal combustion engines are described, for example, in German Offenlegungsschrift DE 10 2016 111 686 A1. According to a variant of DE 10 2016 111 686 A1, for example, the exhaust gas from a first group of exhaust pipes can be introduced into the intake system downstream or upstream of a compressor of an exhaust gas turbocharger and / or fed to a turbine of the exhaust gas turbocharger, whereas the exhaust gas from a second group of exhaust pipes can be introduced upstream of the compressor and / or fed to the turbine. The aim is to achieve improved knock control and / or improved blowing or scavenging of the cylinders with fresh air, while maintaining a stoichiometric air ratio during exhaust gas aftertreatment, if necessary. The latter is of particular interest with regard to exhaust gas aftertreatment using a three-way catalytic converter.Accelerating the exhaust turbocharger can also be achieved by increasing the gas flow through the cylinders. Purging the cylinders with fresh air is used primarily for cooling; for improved knock control or a reduction in the tendency to knock.

[0016] The advantage of an exhaust gas turbocharger over a charger driven by an auxiliary drive is that an exhaust gas turbocharger uses the exhaust energy of the hot exhaust gases, whereas a charger draws the energy required for its drive directly or indirectly from the internal combustion engine and thus, at least as long as the drive energy does not originate from energy recovery, adversely affects, i.e. reduces, efficiency. Unless the charger is driven by an electric motor, i.e., is electrically driven, a mechanical or kinematic connection is usually required to transmit power between the charger and the internal combustion engine, which also adversely affects or determines the packaging in the engine compartment.

[0017] An exhaust gas turbocharger comprises a compressor and a turbine arranged on the same shaft. The hot exhaust gas flow is fed to the turbine and expands, releasing energy in the turbine, which causes the shaft to rotate. The energy transferred from the exhaust flow to the turbine and finally to the shaft is used to drive the compressor, which is also arranged on the shaft. The compressor conveys and compresses the charge air fed to it, thereby supercharging at least two cylinders. If necessary, charge air cooling is provided to cool the compressed charge air before it enters the cylinders.

[0018] The primary purpose of turbocharging is to increase the performance of an internal combustion engine. The air required for the combustion process is compressed, allowing a larger air mass to be supplied to each cylinder per combustion cycle. This increases the fuel mass and thus the mean effective pressure. Turbocharging is a suitable means of increasing the power of an internal combustion engine without changing the displacement or reducing the displacement without changing the power. In either case, turbocharging increases the package power and results in a more favorable power-to-weight ratio. If the displacement is reduced, the load spectrum can be shifted towards higher loads, where specific fuel consumption is lower, provided the vehicle conditions remain the same.

[0019] Turbocharging therefore supports efforts to minimize the fuel consumption of an internal combustion engine, i.e. to improve the efficiency of the internal combustion engine.

[0020] With a suitable transmission design, so-called downspeeding can also be achieved, which also results in lower specific fuel consumption. Downspeeding takes advantage of the fact that specific fuel consumption is generally lower at low engine speeds, especially at higher loads.

[0021] Carbon dioxide emissions, which are directly correlated with fuel consumption, decrease with decreasing fuel consumption anyway. To comply with pollutant emission limits, various exhaust gas aftertreatment systems are regularly used to convert pollutants.

[0022] In order to further reduce the fuel consumption of an internal combustion engine, additional measures are required in addition to turbocharging.

[0023] Fuel consumption and therefore efficiency are particularly problematic in gasoline engines, i.e. spark-ignition internal combustion engines. The reason for this lies in the basic working principle of the gasoline engine. Load control is generally achieved by means of a throttle valve in the intake system. By adjusting the throttle valve, the pressure of the intake air behind the throttle valve can be reduced more or less. The further the throttle valve is closed, i.e. the more it blocks the intake system, the greater the pressure loss of the intake air across the throttle valve and the lower the pressure of the intake air downstream of the throttle valve and before it enters at least one cylinder, i.e. the combustion chamber. With a constant combustion chamber volume, the air mass, i.e. the quantity, can be adjusted in this way via the pressure of the intake air.This also explains why quantity control proves to be disadvantageous, especially in partial load operation, because low loads require high throttling and pressure reduction in the intake system, which means that the gas exchange losses increase with decreasing load and increasing throttling.

[0024] To reduce the losses described above, various strategies for de-throttling a gasoline engine have been developed. One approach to de-throttling a gasoline engine, for example, is a gasoline engine operating process with direct injection.

[0025] Another approach to dethrottle a gasoline engine is the use of an at least partially variable valve train. In contrast to conventional valve trains, in which both the valve lift and the valve timing are fixed, these parameters, which influence the combustion process and thus fuel consumption, can be varied to a greater or lesser extent using variable valve trains. Throttle-free and thus loss-free load control is already possible if the valve train is partially variable and, for example, the closing time of an intake valve and / or the intake valve lift can be varied. The mixture mass or air mass flowing into the combustion chamber during the intake process is then controlled not by the throttle valve, but by the intake valve lift or the opening duration of the intake valve.Fully variable valve trains are very cost-intensive, which is why partially variable or switchable valve trains are often used.

[0026] In this context, it should also be noted that the efficiency η of the gasoline engine correlates at least approximately with the compression ratio ε. This means that the efficiency η increases with the compression ratio ε, is generally higher with a higher compression ratio and generally lower with a lower compression ratio.

[0027] Consequently, the cylinders of an internal combustion engine should preferably be equipped with the highest possible compression ratio for efficiency. However, the compression ratio cannot be increased indefinitely, since as the compression ratio increases, so does the tendency to knock, i.e., the tendency for self-ignition of mixture components. Modern gasoline engines therefore generally have a compression ratio of 8 to 12 at most, with a compression ratio of approximately 15 promising the best efficiency. While this limits efficiency, it also ensures the necessary protection against knocking, especially under high loads.

[0028] According to the current state of the art, the tendency to knock is also counteracted by retarding the ignition timing when necessary, for example, at higher loads, which shifts the combustion center of gravity to a later stage and reduces the combustion pressure and combustion temperature. However, this has a detrimental effect on efficiency.

[0029] At higher loads, where the operation of the internal combustion engine is increasingly limited by the fact that knocking must be reliably limited under all circumstances, the tendency to knock can also be counteracted by closing the intake of a cylinder later. By extending the intake opening duration or by late closing of at least one intake valve, the effective compression ratio ε effbe lowered, whereby a portion of the cylinder fresh charge or combustion air is expelled back into the intake system during the compression stroke while the intake is still open. A high geometric compression ratio ε geo , which is generally considered advantageous and contributes significantly to improving efficiency at lower loads, can be virtually reduced at higher loads or replaced by a lower effective compression ratio ε eff replaced and thus defused.

[0030] According to the prior art, modular, particularly two-part, intake camshafts are used for this purpose. These include a first outer intake camshaft and a second inner intake camshaft, with the inner intake camshaft being rotatably mounted in the hollow outer intake camshaft. German Offenlegungsschrift DE 10 2010 008 958 A1 describes such a camshaft.

[0031] Against the background of the above, it is the object of the present invention to provide a supercharged internal combustion engine according to the preamble of claim 1, which is further improved with regard to its operating behavior.

[0032] This problem is solved with the characterizing features of claim 1.

[0033] In the internal combustion engine according to the invention, the opening process of an exhaust valve or the associated outlet opening of the second group of exhaust pipes can be varied.

[0034] During normal operation of the warmed-up internal combustion engine, when the valves of all cylinder openings are activated and operated, the exhaust valves belonging to the exhaust openings of the second group are actuated regularly with the aim of recirculating exhaust gases or gases into the intake system upstream of the compressor. The maximum valve lift Δh of the exhaust valves of the second group is formed or completed in the compression phase or expansion phase of the corresponding cylinder near the top dead center of the gas exchange, i.e. during the transition from the compression phase to the expansion phase, possibly at the top dead center of the gas exchange.

[0035] During the warm-up phase, it may be advisable in individual cases not to discharge exhaust gas from the cylinders via the exhaust gas removal system via the first exhaust line. Suitable means must be provided for this purpose. In this case, the exhaust valves of the second group are required for an effective gas exchange and must be actuated accordingly. To achieve this, the opening process must be able to be advanced. This means that the exhaust ports of the second group are opened earlier, in such a way that the maximum valve lift Δh is achieved during the compression phase of the gas exchange of the corresponding cylinder.

[0036] When the internal combustion engine returns to normal operation, the opening process must then be retarded in the opposite direction so that the exhaust ports of the second group open later again. The maximum valve lift Δh is then again achieved during the transition from the compression phase to the expansion phase, possibly at top dead center of the gas exchange.

[0037] The fact that the outlet valves belonging to the outlet openings of the second group can be actuated at least partially variably according to the invention has further advantages.

[0038] By advancing or retarding the opening of an exhaust valve belonging to the second group, the valve overlap with an exhaust valve of the cylinder belonging to the first group can be varied and adjusted. This means that the crank angle range in which the cylinder-associated exhaust ports of both groups of exhaust lines are open can be adjusted as needed. This makes it possible, in particular, to influence the gas quantity supplied to the turbine of the at least one exhaust gas turbocharger via the first exhaust line and the gas quantity introduced into the intake system upstream of the compressor of the at least one exhaust gas turbocharger via the second exhaust line.

[0039] Furthermore, this concept can be used to influence the composition of the gas introduced into the intake system upstream of the compressor of at least one exhaust turbocharger via the second exhaust line. The earlier an exhaust valve belonging to an exhaust port of the second group is opened, the greater the proportion of exhaust gas in the gases recirculated into the intake system. A later opening, however, reduces the proportion of exhaust gas in favor of the fresh air resulting from cylinder scavenging.

[0040] The internal combustion engine according to the invention solves the first problem underlying the invention, namely to provide a supercharged internal combustion engine according to the preamble of claim 1, which is further improved with regard to its operating behavior.

[0041] According to the state of the art, the exhaust pipes of three-cylinder in-line engines are rarely grouped together, since three-cylinder in-line engines are inherently difficult to access within a group, especially within a cylinder group. However, the inventive merging of the exhaust pipes allows this to be done without any problems.

[0042] Therefore, embodiments of the internal combustion engine in which three cylinders are provided, which are preferably arranged in series, are also advantageous.

[0043] Further advantageous embodiments of the internal combustion engine according to the invention are discussed in connection with the subclaims.

[0044] Embodiments of the supercharged internal combustion engine are advantageous in which the exhaust valve of the second group belonging to an exhaust port of the second group is variable in such a way that the opening process can be advanced and / or retarded. Regarding the advantages of this embodiment, reference is made to the above explanations.

[0045] Embodiments of the supercharged internal combustion engine are advantageous in which the outlet openings belonging to the exhaust lines of the first group are each equipped with an at least partially variably actuated outlet valve, wherein this outlet valve of the first group can be moved between an open position and a closed position, forming a maximum valve lift Δh 1stexhaust oscillates and thereby closes the corresponding outlet opening during an opening process for the opening duration Δt 1stexhaust releases.

[0046] In this context, embodiments of the supercharged internal combustion engine are advantageous in which the exhaust valve of the first group belonging to an exhaust opening of the first group is variable in such a way that the opening process can be shifted to an early and / or late stage.

[0047] By advancing or retarding the opening of an exhaust valve belonging to the first group, the valve overlap with an exhaust valve of the cylinder belonging to the second group can be varied and adjusted. This means that the crank angle range in which the cylinder-associated exhaust ports of both groups of exhaust pipes are open can be adjusted. As already described elsewhere in connection with the variable exhaust valves belonging to the second group, it is possible to influence the gas quantities that are discharged via the first exhaust pipe or introduced into the intake system via the second exhaust pipe.

[0048] By adjusting the timing of the exhaust valves belonging to the first group, it is also possible to influence the composition of the gas introduced into the intake system upstream of the compressor of the at least one exhaust gas turbocharger via the second exhaust line. The earlier an exhaust valve belonging to an exhaust port of the first group is opened, the more exhaust gas is fed to the turbine via the first exhaust line, and the less exhaust gas is part of the gas recirculated into the intake system. Opening it later, however, has the opposite effect.

[0049] Embodiments of the supercharged internal combustion engine are advantageous in which the inlet openings are each equipped with an at least partially variably actuated inlet valve, wherein this inlet valve can be moved between an open position and a closed position, forming a maximum valve lift Δh intakeoscillates and thereby closes the corresponding inlet opening during an opening process for the opening duration Δt intake Equipping a cylinder-associated intake port with an at least partially variably actuated intake valve may be sufficient in individual cases, depending on the objective.

[0050] The internal combustion engine can be dethrottled using at least partially variable intake valve trains. As already mentioned, throttle-free and thus loss-free load control is possible if the closing time of an intake valve and / or the intake valve lift can be varied. The intake mixture mass or air mass flowing into the combustion chamber can be controlled via the intake valve lift or the opening duration of the intake valve.

[0051] An increased tendency to knock at higher loads can be counteracted by closing a cylinder's intake later. By extending the intake opening duration or by late closing of at least one intake valve, the effective compression ratio can be lowered, with a portion of the cylinder's fresh charge or combustion air being expelled back into the intake system during the compression stroke while the intake is still open. In this way, a high geometric compression ratio is reduced as needed.

[0052] In this context, embodiments of the supercharged internal combustion engine are advantageous - also for the reasons mentioned above - in which the inlet valve belonging to an inlet opening is variable in such a way that the opening process can be shifted early and / or late.

[0053] Embodiments of the supercharged internal combustion engine are advantageous in which each cylinder has at least two inlet openings for supplying charge air via the intake system.

[0054] By providing large flow cross-sections, throttle losses in the incoming charge air can be kept to a minimum and good cylinder filling can be ensured. Therefore, it is advantageous to equip the cylinders with more than one intake port, i.e., with at least two intake ports.

[0055] For similar or analogous reasons, embodiments of the supercharged internal combustion engine are advantageous in which each cylinder has three exhaust openings for discharging exhaust gas via an exhaust gas discharge system, wherein the exhaust lines of two exhaust openings per cylinder also form the exhaust manifold of the first group.

[0056] During normal operation of the internal combustion engine, or as a rule, the cylinders are evacuated primarily via the exhaust ports or the exhaust pipes of the first group. This means that the majority of the exhaust gas is removed from the cylinders via the first exhaust pipe.

[0057] In this respect, it is advantageous that the exhaust lines of two exhaust ports per cylinder form the exhaust manifold of the first group, i.e., they open into the first exhaust line. This provides the exhaust path with a larger inlet cross-section, namely two exhaust ports, via the first exhaust line.

[0058] For the reasons stated above, embodiments of the supercharged internal combustion engine in which the outlet openings belonging to the exhaust pipes of the first group have a larger diameter than the outlet openings belonging to the exhaust pipes of the second group are also advantageous.

[0059] This embodiment of the outlet openings assigns the exhaust gas path via the first overall exhaust line with a larger diameter of the outlet opening the inlet cross-section or a larger inlet cross-section.

[0060] Embodiments of the supercharged internal combustion engine are advantageous in which each exhaust valve of the first group and each exhaust valve of the second group is equipped with an actuating device to actuate and open the exhaust valve, said actuating device comprising a cam arranged on a camshaft which, when the camshaft is rotating, can be brought into engagement with a cam follower element, whereby the associated exhaust valve can be actuated.

[0061] In this context, embodiments of the supercharged internal combustion engine are advantageous in which the cams of the actuating devices of the at least two exhaust valves of each cylinder are arranged on an at least two-part camshaft which comprises at least two camshaft sections which can be rotated relative to one another, wherein the cams of the exhaust valves of the first group are arranged on a first camshaft section and the cams of the exhaust valves of the second group are arranged on a second camshaft section and the at least two-part camshaft comprises an outer hollow camshaft and an inner camshaft which is arranged rotatably in the hollow camshaft as camshaft sections.

[0062] In internal combustion engines which are equipped with an at least two-part camshaft on the exhaust side, embodiments may be advantageous in which the at least two-part camshaft comprises the outer hollow camshaft as the first camshaft section and the inner camshaft rotatably arranged in the hollow camshaft as the second camshaft section.

[0063] In the case of internal combustion engines which are equipped with an at least two-part camshaft on the exhaust side, embodiments may also be advantageous in which the at least two-part camshaft comprises the outer hollow camshaft as the second camshaft section and the inner camshaft rotatably arranged in the hollow camshaft as the first camshaft section.

[0064] In this context, embodiments of the supercharged internal combustion engine are advantageous in which a first camshaft adjuster is provided in order to rotate the inner camshaft relative to the outer hollow camshaft.

[0065] In internal combustion engines with a crankshaft which can be at least drive-connected to an at least two-part camshaft provided on the exhaust side, embodiments in which a second camshaft adjuster is provided in order to rotate the camshaft relative to the crankshaft can be advantageous.

[0066] When using an at least two-part camshaft provided on the exhaust side, embodiments of the supercharged internal combustion engine can be advantageous in which a position sensor is provided in order to measure the rotational position of the inner camshaft relative to the outer hollow camshaft.

[0067] Embodiments of the supercharged internal combustion engine are advantageous in which a blow-off line is provided in which a shut-off element is arranged and which branches off from the exhaust manifold of the second group to form a first node and opens into the exhaust gas discharge system to form a second node downstream of the turbine of the at least one exhaust gas turbocharger.

[0068] Exhaust gas from the exhaust manifold of the second group can then be led past the turbine of the exhaust turbocharger via a blow-off line.

[0069] A storage tank for unburned hydrocarbons is preferably provided in the blow-off line. This concept allows the exhaust gas to be treated close to the engine and as needed during the warm-up phase, particularly after a cold start, with unburned hydrocarbons present in the exhaust gas being collected and stored in the storage tank provided according to the invention.

[0070] The discharge of exhaust gas via the first exhaust line is prevented, i.e., suppressed, using suitable means. A shut-off element in the exhaust gas discharge system upstream or downstream of the turbine can serve as a suitable means. Alternatively, the discharge of exhaust gas via the first exhaust line can be prevented by equipping the outlet openings of the first group with switchable valves and switching these valves off. The introduction of exhaust gas into the intake system is preferably stopped, for example, by closing a shut-off element provided in the second exhaust line.

[0071] By opening the shut-off element provided in the blow-off line, the blow-off line is released for the exhaust gas originating from the second exhaust manifold and the storage tank for unburned hydrocarbons is supplied with exhaust gas.

[0072] The unburned hydrocarbons collected in the accumulator can then be released and oxidized under different operating conditions. Preferably, the unburned hydrocarbons collected in the accumulator are introduced into the exhaust gas removal system with the exhaust gas flowing through the blow-off line and oxidized using a catalyst in the exhaust gas removal system.

[0073] Since no exhaust gas is removed from the cylinders via the first exhaust line during the warm-up phase, the exhaust valves belonging to the exhaust ports of the second group must be actuated to ensure effective gas exchange. This means that the exhaust ports of the second group are preferably opened in such a way that the maximum valve lift Δh max is formed in a compression phase of the corresponding cylinder.

[0074] When the engine is warmed up and the exhaust gas is predominantly discharged from the cylinders via the first exhaust line, the exhaust valves of the second group can be opened later if required.

[0075] In this context, embodiments of the supercharged internal combustion engine are advantageous in which the blow-off line opens into the exhaust gas discharge system upstream of an exhaust gas aftertreatment system provided in the exhaust gas discharge system, forming the second junction point. The exhaust gas aftertreatment system is preferably a three-way catalytic converter.

[0076] In the case of internal combustion engines with a blow-off line, embodiments are advantageous in which a shut-off element is provided in the second exhaust line downstream of the first junction point.

[0077] The introduction of exhaust gas into the intake system is preferably adjusted by closing a shut-off element provided in the second overall exhaust line when exhaust gas originating from the cylinders is discharged via the blow-off line and the discharge of exhaust gas via the first overall exhaust line is prevented, i.e. adjusted.

[0078] The shut-off element provided in the second exhaust line can also be used to adjust the recirculation rate of an exhaust gas recirculation system.

[0079] When using a blow-off line, embodiments of the supercharged internal combustion engine in which a cooler is provided in the second overall exhaust line downstream of the first junction point are advantageous.

[0080] To support the cooling function by flushing the cylinders with fresh air and further reduce the tendency to knock, it may be advantageous to provide a cooler in the second exhaust line. The cooler is also used to reliably prevent compressor overheating, i.e., to prevent thermal overload of the compressor.

[0081] The second exhaust line can also be used for the recirculation of combustion gases, i.e., for exhaust gas recirculation. High recirculation rates require cooling of the recirculating exhaust gas, which lowers the temperature and increases the density of the exhaust gas, allowing a larger exhaust gas mass to be recirculated. Consequently, it is advantageous to equip the exhaust gas recirculation with a cooler. Condensate may form during cooling, which is then separated in the cooler.

[0082] In this context, embodiments of the supercharged internal combustion engine in which the cooler is equipped with a bypass line are advantageous.

[0083] Advantageous embodiments of the supercharged internal combustion engine include a charge air cooler in the intake system downstream of the compressor of the at least one exhaust gas turbocharger. This cooler cools the compressed charge air before it enters the at least two cylinders. The cooler lowers the temperature and thus increases the density of the charge air, so that the cooler also contributes to better filling of the cylinders, i.e., to a larger air mass. In a sense, compression occurs through cooling.

[0084] Embodiments of the supercharged internal combustion engine are advantageous in which at least one three-way catalyst is provided in the exhaust gas discharge system downstream of the turbine of the at least one exhaust gas turbocharger for the purpose of exhaust gas aftertreatment.

[0085] To reduce pollutant emissions, the internal combustion engine can be equipped with various exhaust aftertreatment systems. Catalytic reactors utilize catalytic materials to ensure the oxidation of incompletely burned combustion products, even at low temperatures. If nitrogen oxides are also to be reduced, this can be achieved by using a three-way catalytic converter, which, however, requires stoichiometric operation (λ ≈ 1) of the internal combustion engine within narrow limits. In this case, the nitrogen oxides are reduced using the existing non-oxidized exhaust gas components, namely carbon monoxide and unburned hydrocarbons, while simultaneously oxidizing these exhaust gas components.

[0086] Embodiments of the supercharged internal combustion engine are advantageous in which the turbine of the at least one exhaust gas turbocharger is designed as a wastegate turbine, wherein upstream of this turbine a bypass line branches off from the exhaust gas discharge system and a shut-off element is provided in the bypass line.

[0087] Also advantageous are embodiments of the supercharged internal combustion engine in which the turbine of the at least one exhaust gas turbocharger has a variable turbine geometry, which allows extensive adaptation to the respective operating point by adjusting the turbine geometry or the effective turbine cross-section. Guide vanes are arranged upstream of the turbine impeller to influence the flow direction. In contrast to the rotor blades of the rotating impeller, the guide vanes do not rotate with the turbine shaft, i.e. the impeller. Although the guide vanes are arranged stationary, they are not completely immobile, but can rotate about their axis, so that the flow to the rotor blades can be influenced. If, on the other hand, the turbine has a fixed, unchanging geometry, the guide vanes are not only stationary, but also completely immobile, i.e.rigidly fixed, if a guidance device is provided at all.

[0088] In the following, the invention is described using three embodiments and in accordance with the Fig. 1, Fig. 2a, Fig. 2b and Fig. 2c is described in more detail. Here: Fig. 1 schematically shows an embodiment of the supercharged internal combustion engine, Fig. 2a the valve lift curves of the Fig. 1 shown internal combustion engine according to a first embodiment, Fig. 2b the valve lift curves of the Fig. 1 shown internal combustion engine according to a second embodiment, and Fig. 2c the valve lift curves of the Fig. 1 shown internal combustion engine according to a third embodiment.

[0089] Fig. 1 schematically shows a first embodiment of the supercharged internal combustion engine 10, which is equipped with an exhaust gas turbocharger 8. The exhaust gas turbocharger 8 comprises a turbine 8a arranged in the exhaust gas discharge system 5 and a compressor 8b arranged in the intake system 3. The hot exhaust gas expands in the turbine 8a, releasing energy, which causes the shaft of the exhaust gas turbocharger 8 to rotate. The energy released by the exhaust gas flow to the turbine 8a and finally to the shaft is used to drive the compressor 8b, which is also arranged on the shaft. The compressor 8b compresses the charge air and supplies the compressed charge air to the cylinders 1 via the intake system 3, in which an intercooler 12 and a throttle element 13 are arranged, thereby supercharging the internal combustion engine 10.

[0090] It is a three-cylinder in-line engine 10, in which the three cylinders 1 are arranged along the longitudinal axis of the cylinder head, i.e., in series. Each cylinder 1 has two intake ports 2a, 2b for supplying charge air via intake system 3 and two exhaust ports 4a, 4b, to which exhaust pipes 5a, 5b are connected for discharging the exhaust gases via exhaust gas removal system 5.

[0091] The exhaust pipes 5a, 5b are configured in such a way that they form two groups, each group comprising an exhaust pipe 5a, 5b from each cylinder 1. The exhaust pipes 5a, 5b of each group each merge to form an exhaust manifold into a complete exhaust pipe 6a, 6b, wherein the exhaust pipes 5a that connect to the first cylinder-associated exhaust openings 4a merge to form a first complete exhaust pipe 6a and the exhaust pipes 5b that connect to the second cylinder-associated exhaust openings 4b merge to form a second complete exhaust pipe 6b.

[0092] The first exhaust line 6a of the first group opens into the turbine 8a, whereas the second exhaust line 6b of the second group opens into the intake system 3 upstream of the compressor 8b.

[0093] In the exhaust gas discharge system 5 downstream of the turbine 8a, two exhaust gas aftertreatment systems 11 are provided, namely two three-way catalysts 11a arranged at a distance from one another.

[0094] A blow-off line 7 branches off from the exhaust manifold of the second group, forming a first junction point 7b, and opens into the exhaust gas discharge system 5 downstream of the turbine 8a, specifically between the two spaced-apart three-way catalysts 11a, forming a second junction point 7c. A shut-off element 7a is provided in the blow-off line 7.

[0095] The introduction of gas into the intake system 3 is controlled by closing a shut-off element 6b'' provided in the second exhaust line 6b. The shut-off element 6b'' is arranged downstream of the first junction 7b and downstream of a cooler 6b' and is used to adjust the amount of gas or exhaust gas to be recirculated. The cooler 6b' can optionally be equipped with a bypass line 6b''', which allows bypassing the cooler 6b'' (dashed line).

[0096] Fig. 2a shows the valve lift curves A1, A2 and E of the Fig. 1 according to a first embodiment of the valve train or valve control.

[0097] Shown are the valve lift curve A1 of the exhaust valve of the first cylinder-associated exhaust port 4a, the valve lift curve A2 of the exhaust valve of the second cylinder-associated exhaust port 4b and valve lift curve E of the intake valve of a cylinder-associated intake port 2a, 2b.

[0098] During normal operation of the internal combustion engine 10, the exhaust valves of the first exhaust ports 4a open according to the valve lift curve A1 in the compression phase before the top dead center of the gas exchange LOT in order to discharge exhaust gas, and the intake ports 2a, 2b open according to the valve lift curve E in the expansion phase after the top dead center of the gas exchange LOT in order to supply fresh charge air to the cylinders 1.

[0099] The exhaust valves of the second exhaust ports 4b open according to valve lift curve A2 during the transition from the compression phase to the expansion phase of the associated cylinder 1, with the maximum valve lift Δh occurring near top dead center of the gas exchange LOT. The maximum valve lift Δh is significantly smaller in order to reliably avoid a collision or contact with the piston. Via the second exhaust ports 4b, both exhaust gas from the cylinders 1 enters the second exhaust line 6b or the second exhaust manifold, as well as fresh air or charge air, which flows from the intake system 3 via the intake ports 2a, 2b into the cylinders 1 and from there via the second exhaust ports 4b into the second exhaust line 6b as part of a scavenging process.

[0100] The exhaust valves of the second exhaust ports 4b are partially variable, in this case in such a way that the opening process can be shifted forward or retarded. This is indicated by a double arrow.

[0101] By shifting the opening process, the gas quantities supplied to the turbine 8a via the first exhaust line 6a or introduced into the intake system 3 via the second exhaust line 6b can be influenced. Furthermore, the composition of the gas introduced into the intake system 3 via the second exhaust line 6b can be influenced.

[0102] Fig. 2b shows the valve lift curves A1, A2 and E of the Fig. 1 according to a second embodiment. In addition to the Fig. 1 and Fig. 2a executed.

[0103] The intake valves of intake ports 2a, 2b are partially variable, in this case in such a way that the opening process can be advanced or retarded. This is indicated by a double arrow. It is possible to influence the knock tendency, the effective compression ratio, the valve overlap with the exhaust valves of the first exhaust ports 4a and the second exhaust ports 4b, as well as the scavenging of cylinder 1 with fresh air.

[0104] Fig. 2c shows the valve lift curves A1, A2 and E of the Fig. 1 according to a third embodiment. In addition to the Fig. 1, Fig. 2a and Fig. 2b executed.

[0105] The exhaust valves of the first exhaust ports 4a are partially variable, in this case in such a way that the opening process can be shifted forward or retarded. This is indicated by a double arrow. Reference symbol 1 cylinder 2a Inlet opening 2b Inlet opening 3 Intake system 3a Intake line 3b Intake line 4a Outlet opening of the first group 4b Outlet opening of the second group 5 Exhaust gas removal system 5a Exhaust pipe of an outlet opening of the first group 5b Exhaust pipe of an outlet opening of the second group 6a first exhaust pipe 6b second exhaust pipe 6b' cooler 6b" shut-off element 6b''' Radiator bypass line 7 Blow-off line 7a Shut-off element 7b first junction 7b second junction 8 exhaust gas turbochargers 8a Turbine 8b Compressor 9 Turbine bypass line, turbine waste gate 9a Shut-off element 10 supercharged internal combustion engine, three-cylinder in-line engine 11 Exhaust aftertreatment system 11a Three-way catalyst 12 intercoolers 13 Throttle element Δh valve lift of a valve Δh 1stexhaust maximum valve lift of an exhaust valve belonging to an exhaust port of the first group Δh 2ndexhaust maximum valve lift of an exhaust valve belonging to an exhaust port of the second group Δh intake maximum valve lift of an intake valve belonging to an intake port Δt opening time of an exhaust valve Δt 1stexhaust Opening duration of an exhaust valve belonging to an exhaust port of the first group Δt 2ndexhaust Opening duration of an exhaust valve belonging to an exhaust port of the second group Δt intake Opening duration of an intake valve belonging to an intake port °CA degrees crank angle LOT top dead center of the gas exchange A1 Valve lift curve of the exhaust valve of the first cylinder-associated exhaust port A2 Valve lift curve of the exhaust valve of the second cylinder-associated exhaust port E Valve lift curve of the intake valve of a cylinder-associated intake port

Claims

[1] Supercharged internal combustion engine (10) with at least two cylinders (1), in which - each cylinder (1) has at least one inlet opening (2a, 2b) for supplying charge air via the intake system (3) and at least two outlet openings (4a, 4b) for discharging exhaust gas via the exhaust gas removal system (5), wherein an exhaust line (5a, 5b) is connected to each outlet opening (4a, 4b), - at least one exhaust gas turbocharger (8) is provided, which comprises a turbine (8a) arranged in the exhaust gas discharge system (5) and a compressor (8b) arranged in the intake system (3), - the exhaust pipes (5a, 5b) are configured in such a way that they form two groups, each group comprising at least one exhaust pipe (5a, 5b) from each cylinder (1) and the exhaust pipes (5a, 5b) of each group each merging to form an exhaust manifold into a total exhaust pipe (6a, 6b), - the first exhaust line (6a) of a first group opens into the turbine (8a) of the at least one exhaust gas turbocharger (8), - the second exhaust line (6b) of a second group opens into the intake system (3) upstream of the compressor (8b) of the at least one exhaust gas turbocharger (8), and - the outlet openings (4b) belonging to the exhaust lines (5b) of the second group are each equipped with an at least partially variably actuated outlet valve, wherein this outlet valve of the second group can be moved between an open position and a closed position, forming a maximum valve lift Δh 2ndexhaust oscillates and thereby the associated outlet opening (4b) during an opening process for the opening duration Δt 2ndexhaust releases, characterized by , that - a blow-off line (7) is provided, in which a shut-off element (7a) is arranged and which branches off from the exhaust manifold of the second group to form a first node (7b) and opens into the exhaust gas discharge system (5) downstream of the turbine (8a) of the at least one exhaust gas turbocharger (8) to form a second node (7c), wherein the blow-off line (7) opens into the exhaust gas discharge system (5) upstream of an exhaust gas aftertreatment system (11) provided in the exhaust gas discharge system (5) to form the second node (7c). [2] Supercharged internal combustion engine (10) according to claim 1, characterized by that the outlet valve of the second group belonging to an outlet opening (4b) of the second group is variable in such a way that the opening process can be shifted early and / or late. [3] Supercharged internal combustion engine (10) according to claim 1 or 2, characterized bythat the outlet openings (4a) belonging to the exhaust pipes (5a) of the first group are each equipped with an at least partially variably actuated outlet valve, wherein this outlet valve of the first group can be moved between an open position and a closed position, forming a maximum valve lift Δh 1stexhaust oscillates and thereby the associated outlet opening (4a) during an opening process for the opening duration Δt 1stexhaust releases. [4] Supercharged internal combustion engine (10) according to claim 3, characterized by that the outlet valve of the first group belonging to an outlet opening (4a) of the first group is variable in such a way that the opening process can be shifted early and / or late. [5] Supercharged internal combustion engine (10) according to one of the preceding claims, characterized bythat the inlet openings (2a, 2b) are each equipped with an at least partially variably actuated inlet valve, wherein this inlet valve can be moved between an open position and a closed position, forming a maximum valve lift Δh intake oscillates and thereby the associated inlet opening (2a, 2b) during an opening process for the opening duration Δt intake releases. [6] Supercharged internal combustion engine (10) according to claim 5, characterized by that the inlet valve belonging to an inlet opening (2a, 2b) is variable in such a way that the opening process can be shifted early and / or late. [7] Supercharged internal combustion engine (10) according to one of the preceding claims, characterized by that each cylinder (1) has at least two inlet openings (2a, 2b) for supplying charge air via the intake system (3). [8] Supercharged internal combustion engine (10) according to one of the preceding claims, characterized bythat each cylinder (1) has three exhaust openings (4a, 4b) for discharging exhaust gas via an exhaust gas removal system (5), wherein the exhaust lines (5a, 5b) of two exhaust openings (4a, 4b) per cylinder (1) also form the exhaust manifold of the first group. [9] Supercharged internal combustion engine (10) according to one of the preceding claims, characterized by that the outlet openings (4a) belonging to the exhaust pipes (5a) of the first group have a larger diameter than the outlet openings (4b) belonging to the exhaust pipes (5b) of the second group. [10] Supercharged internal combustion engine (10) according to one of the preceding claims, characterized bythat each exhaust valve of the first group and each exhaust valve of the second group is equipped with an actuating device for actuating and opening the exhaust valve, this actuating device comprising a cam arranged on a camshaft which, when the camshaft is rotating, can be brought into engagement with a cam follower element, whereby the associated exhaust valve can be actuated. [11] Supercharged internal combustion engine (10) according to claim 10, characterized bythat the cams of the actuating devices of the at least two exhaust valves of each cylinder are arranged on an at least two-part camshaft which comprises at least two camshaft sections which can be rotated relative to one another, wherein the cams of the exhaust valves of the first group are arranged on a first camshaft section and the cams of the exhaust valves of the second group are arranged on a second camshaft section and the at least two-part camshaft comprises an outer hollow camshaft and an inner camshaft which is arranged rotatably in the hollow camshaft as camshaft sections. [12] Supercharged internal combustion engine (10) according to claim 11, characterized by that the at least two-part camshaft comprises the outer hollow camshaft as the first camshaft section and the inner camshaft rotatably arranged in the hollow camshaft as the second camshaft section. [13] Supercharged internal combustion engine (10) according to claim 11, characterized by that the at least two-part camshaft comprises the outer hollow camshaft as the second camshaft section and the inner camshaft rotatably arranged in the hollow camshaft as the first camshaft section. [14] Supercharged internal combustion engine (10) according to one of claims 11 to 13, characterized by that a first camshaft adjuster is provided to rotate the inner camshaft relative to the outer hollow camshaft. [15] Supercharged internal combustion engine (10) according to one of claims 11 to 14 with a crankshaft which is at least drive-connectable to the at least two-part camshaft, characterized by that a second camshaft adjuster is provided to rotate the camshaft relative to the crankshaft. [16] Supercharged internal combustion engine (10) according to one of claims 11 to 15, characterized bythat a position sensor is provided to measure the rotational position of the inner camshaft relative to the outer hollow camshaft. [17] Supercharged internal combustion engine (10) according to one of the preceding claims, characterized by that a shut-off element (6b'') is provided in the second overall exhaust line (6b) downstream of the first junction point (7b). [18] Supercharged internal combustion engine (10) according to one of the preceding claims, characterized by that a cooler (6b') is provided in the second exhaust line (6b) downstream of the first junction point (7b). [19] Supercharged internal combustion engine (10) according to claim 18, characterized by that the cooler (6b') is equipped with a bypass line (6b''').

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