Supercharged four-cylinder in-line engine with parallel turbines and method for operating such a four-cylinder in-line engine

Abstract

The invention relates to a supercharged four-cylinder in-line engine with parallel turbines (17a) and a method for operating such a four-cylinder in-line engine. The four cylinders (1, 2, 3, 4) are configured to form two groups of two cylinders (1, 2, 3, 4) each. The exhaust lines (5) of the cylinders (1, 2, 3, 4) of each cylinder group merge to form an exhaust manifold (7), with at least one turbine (17a) of an exhaust gas turbocharger (17) being arranged in each exhaust line (8). The operating behavior should be improved, particularly with regard to torque characteristics, fuel consumption and / or efficiency. This is achieved in that the four cylinders (1, 2, 3, 4) are configured in such a way that in each case an outer cylinder (1, 4) and the adjacent inner cylinder (2, 3) form a group, wherein the cylinders (3, 4) of a first group are continuously operated cylinders (3, 4) when the internal combustion engine is in operation and the cylinders (1, 2) of a second group are designed as load-dependent switchable cylinders (1', 2') which can be switched off as part of a partial switch-off when the load falls below a predeterminable load.

Description

[0001] The invention relates to a supercharged internal combustion engine with a cylinder head and four cylinders arranged in series along the longitudinal axis of the cylinder head, each cylinder having at least one outlet opening for discharging the exhaust gases from the cylinder via an exhaust gas discharge system, and each outlet opening being connected to an exhaust line, in which - the four cylinders are configured in such a way that they form two groups of two cylinders each, - combine the exhaust pipes of the cylinders of each cylinder group to form an exhaust manifold, and - at least one turbine of an exhaust gas turbocharger is arranged in each exhaust line.

[0002] Furthermore, the invention relates to a method for operating such an internal combustion engine.

[0003] In the context of the present invention, the term internal combustion engine includes in particular gasoline engines, but also diesel engines and hybrid internal combustion engines, ie internal combustion engines that are operated using a hybrid combustion process.

[0004] An internal combustion engine of the type mentioned at the outset is described, for example, in German Offenlegungsschrift DE 10 2012 220 375 A1, according to which the four cylinders are configured in such a way that an outer cylinder and the adjacent inner cylinder form a group, wherein the cylinders of a first group are continuously operated cylinders when the internal combustion engine is in operation and the cylinders of a second group are designed as load-dependent switchable cylinders which can be switched off as part of a partial switch-off when the load falls below a predeterminable load.

[0005] An internal combustion engine of the type mentioned above, in which the four cylinders are configured such that an outer cylinder and the adjacent inner cylinder form a group, is also described in German Offenlegungsschrift DE 10 2004 035 323 A1. The exhaust manifolds of the two cylinder groups can be connected to one another upstream of the turbines via a connecting line in which a shut-off element is arranged. DE 10 2004 035 323 A1 also discloses a method for operating the described supercharged internal combustion engine, in particular at partial load, i.e., with individual cylinders deactivated. In this context, JP 2001-329 873 A describes the initiation of combustion in the cylinders spaced 180° apart from each other.

[0006] German patent application DE 10 2005 054 249 A1 also relates to an internal combustion engine turbocharged by exhaust gas turbocharging, which has two cylinder banks, each associated with an exhaust gas turbocharger. The exhaust gas turbochargers are connected to one another by a turbine-side exhaust gas connecting line upstream of the turbines, with a throttle arranged in the exhaust gas connecting line. In this way, even when one cylinder bank is partially shut down, i.e., deactivated, the exhaust gas from the other cylinder bank is fed to both exhaust gas turbochargers, i.e., their turbines.

[0007] DE 696 05 049 T2 also deals with the deactivation of individual cylinders under partial load, whereby it is described as advantageous to deactivate entire cylinder groups or to continue operating them permanently. Separate intake manifolds are provided for the cylinder groups on the intake side.

[0008] German patent application DE 10 2010 032 363 A1 describes a turbocharged internal combustion engine with two cylinder banks, each with an exhaust gas turbocharger assigned to each cylinder bank. Each cylinder bank has a separate intake manifold and a separate exhaust manifold. The exhaust side upstream of the turbines is connected to the intake side downstream of the compressors via an exhaust gas recirculation (EGR) line. An EGR valve is provided.

[0009] Internal combustion engines have a cylinder block and a cylinder head which are connected to form the cylinders. The cylinder head usually serves to house the valve train. In order to control the gas exchange, an internal combustion engine requires control elements and actuating devices to operate these control elements. To control the gas exchange, four-stroke engines almost exclusively use lift valves as control elements. These valves perform an oscillating lifting movement during operation of the internal combustion engine and in this way open and close the intake and exhaust ports. During the gas exchange, the combustion gases are expelled through the exhaust ports of the four cylinders and the combustion chambers are filled, i.e. the fresh mixture or charge air is sucked in through the intake ports.The valve operating mechanism required to move the valves, including the valves themselves, is called the valve train.

[0010] 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 generally combined into a common exhaust line or, in groups, into two or more exhaust lines. The combination of exhaust lines into a single exhaust line is generally referred to as an exhaust manifold, and in the context of the present invention.

[0011] The specific configuration of the exhaust gas removal system, namely the manner in which the exhaust pipes of the four cylinders are brought together in each individual case, depends on the respective objective, in particular on the operating ranges with regard to which the operating behavior of the internal combustion engine is to be optimized, and in particular on whether the internal combustion engine is supercharged by means of exhaust gas turbocharging.

[0012] Modern internal combustion engines are increasingly being equipped with turbocharging. Typically, turbocharging is achieved by means of an exhaust gas turbocharger, in which a compressor and a turbine are arranged on the same shaft. The hot exhaust gas flow is fed to the turbine, expands, releasing energy in the turbine, and thereby causes the turbocharger shaft to rotate. The energy transferred from the exhaust flow to the turbine and ultimately to the shaft drives the compressor, which is also arranged on the shaft. This compressor delivers and compresses the charge air supplied to it, thereby supercharging the cylinders and the internal combustion engine.

[0013] The advantages of the exhaust gas turbocharger compared to mechanical superchargers, for example, are that there is no mechanical connection between the charger and the internal combustion engine for power transmission, or no connection is required. While a mechanical supercharger draws all of the energy it needs for its drive from the internal combustion engine, thus reducing the power delivered and adversely affecting efficiency, the exhaust gas turbocharger utilizes the exhaust energy from the hot exhaust gases.

[0014] Turbocharging primarily serves to increase the performance of the 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 allows the fuel mass and thus the mean effective pressure to be increased. Turbocharging is a suitable means of increasing the power of an internal combustion engine while maintaining the same displacement, or of reducing the displacement while maintaining the same power. In either case, turbocharging leads to an increase in package power and a more favorable power-to-mass ratio. Under the same vehicle conditions, the load spectrum can thus be shifted toward higher loads, where specific fuel consumption is lower.

[0015] Turbocharging therefore supports the ongoing efforts in the development of internal combustion engines to minimize fuel consumption, i.e., to improve the efficiency of the internal combustion engine. Another fundamental goal is to reduce pollutant emissions. Turbocharging of the internal combustion engine can also be effective in solving this problem. With a targeted design of the turbocharging system, advantages can be achieved both in efficiency and in exhaust emissions.

[0016] The design of exhaust gas turbocharging presents difficulties, although the goal is generally to achieve a noticeable increase in power across all engine speed ranges. When using a single exhaust gas turbocharger, a drop in torque is observed below a certain engine speed. This drop in torque becomes understandable when one considers that the boost pressure ratio depends on the turbine pressure ratio. Reducing the engine speed leads to a lower exhaust gas mass flow and thus to a lower turbine pressure ratio. As a result, the boost pressure ratio also decreases at lower engine speeds, which equates to a drop in torque.

[0017] In principle, the drop in boost pressure can be counteracted by reducing the turbine cross-section and the associated increase in the turbine pressure ratio. Ultimately, this only counteracts the torque drop to a limited extent, shifting the torque drop further to lower engine speeds. Furthermore, this approach—i.e., reducing the turbine cross-section—has its limitations, since the desired boosting and power increase must be possible without restriction and to the desired extent even at high engine speeds. Various measures are used to improve the torque characteristics of a turbocharged internal combustion engine.

[0018] For example, by designing a small turbine cross-section and simultaneously blowing off exhaust gases, whereby the exhaust gas blowoff can be controlled by boost pressure or exhaust pressure. This type of turbine is also known as a wastegate turbine. If the exhaust gas mass flow exceeds a critical value, a portion of the exhaust gas flow is diverted past the turbine via a bypass line as part of the so-called exhaust gas blowoff. However, this approach has the disadvantage that the boosting behavior is inadequate at higher engine speeds.

[0019] In principle, a small design of the turbine cross-section together with a charge air blow-off is also possible, although this variant is rarely used due to the energetic disadvantages of the charge air blow-off, namely the deterioration of the effective efficiency, and the existing compressors can reach their delivery limit and thus the desired performance can no longer be achieved.

[0020] The exhaust turbocharger can also be designed for high engine speeds with a large turbine cross-section. In this case, the intake system is configured to achieve dynamic turbocharging through wave action at low engine speeds. The disadvantages of this approach are the high construction complexity and the sluggish response during engine speed changes.

[0021] A turbine with variable turbine geometry allows the turbine geometry or the effective turbine cross-section to be adapted to the respective operating point of the internal combustion engine within a certain range, so that the turbine geometry can be controlled with regard to low and high speeds as well as for low and high loads.

[0022] The torque characteristics of a supercharged internal combustion engine can also be advantageously influenced by several exhaust gas turbochargers arranged in series.

[0023] Finally, the torque characteristics can also be improved by using several turbochargers arranged in parallel with correspondingly small turbine cross-sections, as is the case with the internal combustion engine that is the subject of the present invention and which has two turbines arranged in parallel. With regard to the configuration of the exhaust gas removal system, two different concepts must be distinguished.

[0024] According to a first approach, at low engine speeds or in the lower load range, i.e., with smaller exhaust gas quantities, the entire exhaust gas is directed through only one of the two turbines, while the other turbine is blocked, i.e., shut off, by a shut-off element. This allows a sufficiently high turbine pressure ratio to be generated even in the lower engine speed range. As the exhaust gas quantity increases, the second turbine is then switched on by opening the shut-off element.

[0025] However, the shut-off element is subject to high thermal stress, which is why nickel-containing materials often have to be used in its production, which are comparatively expensive, especially compared to the material used for the cylinder head, such as aluminum. In addition to packaging, sealing and durability, i.e., durability, pose problems.

[0026] A shut-off element is unnecessary if the exhaust gas removal system is configured according to the internal combustion engine according to the invention. The four cylinders are configured such that they form two groups of two cylinders each. The exhaust lines of each cylinder group lead together to form a separate exhaust manifold, with a turbine of an exhaust gas turbocharger being arranged in each of the two exhaust lines. As a result of the grouping, the exhaust gas volume upstream of each turbine is smaller, which improves the response of the turbines and thus the turbocharger and the torque characteristics overall. Furthermore, grouping generally leads to a shortening of the overall path of all exhaust lines and also to a reduction in the mass of the exhaust gas removal system upstream of the turbines.By reducing the mass, the thermal inertia of the relevant section is reduced and the exhaust gas enthalpy, which is largely determined by pressure and temperature, can be better utilized on the turbine side.

[0027] A further advantage of the cylinder grouping according to the invention is that at low loads or engine speeds, i.e., with low exhaust gas quantities, the pre-exhaust surge can be advantageously used for pulse-charging. Pulse-charging allows high turbine pressure ratios to be achieved even at low turbine speeds. In this way, high boost pressure ratios, i.e., high boost pressures, can be generated with only low exhaust gas quantities.

[0028] In order to utilize the dynamic wave processes occurring in the exhaust gas removal system, especially the pre-exhaust surges, for turbocharging and to improve the operating behavior of the internal combustion engine, the pressure peaks or pre-exhaust surges in the exhaust system must be preserved. It is particularly advantageous if the pressure fluctuations in the exhaust lines amplify each other, or at least do not weaken or cancel each other out.

[0029] It is advantageous to group the exhaust pipes or cylinders in such a way that the high pressures, especially the pre-exhaust surges of the individual cylinders, are retained in the exhaust gas removal system. In a cylinder head with four cylinders arranged in line, it is advantageous to combine two cylinders, each with a firing interval of 360°, into a cylinder group.

[0030] Pulse charging proves particularly advantageous for accelerating the turbine impeller, i.e., for increasing the turbine speed, which can drop noticeably when the engine is idling or at low load and often needs to be increased again as quickly as possible using the exhaust gas flow when the load demands increase. The inertia of the impeller and the friction in the shaft bearings generally delay the acceleration of the impeller to higher speeds and thus an immediate increase in boost pressure.

[0031] Against the background of the above, it is an object of the present invention to provide a supercharged internal combustion engine according to the preamble of claim 1, which is improved with regard to operating behavior, in particular with regard to torque characteristics, fuel consumption and / or efficiency.

[0032] A further sub-object of the present invention is to provide a method for operating such an internal combustion engine.

[0033] The first sub-task is solved by a supercharged internal combustion engine with a cylinder head and four cylinders arranged in series along the longitudinal axis of the cylinder head, each cylinder having at least one exhaust opening for discharging the exhaust gases from the cylinder via an exhaust gas removal system, and each exhaust opening being connected to an exhaust line, in which - the four cylinders are configured in such a way that they form two groups of two cylinders each, - combine the exhaust pipes of the cylinders of each cylinder group to form an exhaust manifold, and - at least one turbine of an exhaust gas turbocharger is arranged in each exhaust line, and which is characterized in that - the four cylinders are configured in such a way that an outer cylinder and the adjacent inner cylinder form a group, the cylinders of a first group being continuously operated cylinders when the internal combustion engine is in operation and the cylinders of a second group being designed as load-dependent switchable cylinders which can be switched off as part of a partial switch-off when the load falls below a predeterminable load, - the exhaust manifolds of the two cylinder groups upstream of the turbines can be connected to each other via a connecting line, wherein a shut-off element is arranged in the connecting line, - each cylinder has at least one intake port for supplying charge air via the intake system, with each intake port being connected to an intake line, - combine the intake lines of the cylinders of each cylinder group to form an intake manifold, and - at least one compressor of an exhaust gas turbocharger is arranged in each total intake line.

[0034] In the internal combustion engine according to the invention, the cylinders of a cylinder group are designed as load-dependent cylinders. For the purpose of differentiation, this group is referred to below as the second group, whereas the cylinder group that is continuously operated—when the internal combustion engine is in operation—is referred to as the first group.

[0035] Cylinder deactivation, i.e. the deactivation of individual cylinders in certain load ranges, is a method for dethrottled gasoline engines. The efficiency of gasoline engines in the part-load range can be improved, i.e. increased, in this way. This is because deactivating one cylinder in a multi-cylinder internal combustion engine increases the load on the other cylinders still in operation at constant engine power. This means that the throttle valve can or must be opened further to introduce a larger air mass into these cylinders. This overall dethrottles the internal combustion engine. The cylinders that are constantly in operation then also operate in part-load mode of the gasoline engine in ranges where the specific fuel consumption is lower. The load spectrum is shifted towards higher loads.

[0036] The cylinders that continue to operate during partial shutdown also have improved mixture formation due to the larger air mass supplied and tolerate higher exhaust gas recirculation rates.

[0037] Further efficiency advantages arise from the fact that a deactivated cylinder, due to the lack of combustion, does not generate any wall heat losses as a result of heat transfer from the combustion gases to the combustion chamber walls.

[0038] Partial deactivation, in conjunction with exhaust gas turbocharging, offers further advantages when the cylinders are configured as described in the invention, i.e., two cylinder groups, each with two cylinders, are formed, and the exhaust lines of each cylinder group are combined into a separate exhaust line, separate from the exhaust lines of the other cylinder group, forming a separate exhaust manifold. The advantages realized thereby extend far beyond those of partial deactivation alone. Synergies arise when partial deactivation is applied to the internal combustion engine turbocharged according to the invention.

[0039] If the second cylinder group is deactivated during partial load operation of the internal combustion engine when the load falls below a predefined level, the charge air mass supplied to the first cylinder group increases, and thus the amount of exhaust gas removed from this cylinder group during the charge cycle. Therefore, more exhaust gas is supplied, i.e., provided, to the first turbine, which is assigned to the first cylinder group and is supplied with exhaust gas from it, during partial load operation of the internal combustion engine than in prior art designs. This improves the operating behavior of the charger and thus the operating behavior of the internal combustion engine.

[0040] Although diesel engines, i.e., compression-ignition internal combustion engines, have a higher efficiency, i.e., lower fuel consumption, than gasoline engines due to the applied quality control, in which the load is adjusted by quantity control via the filling of the cylinders with fresh mixture, fuel consumption in diesel engines can also be reduced by partial shutdown, i.e., by shutting down individual cylinders in certain load ranges. The statements made in connection with gasoline engines also apply analogously to diesel engines.

[0041] This achieves the first object underlying the invention, namely providing a supercharged internal combustion engine which is improved in terms of operating behavior, in particular in terms of torque characteristics, fuel consumption and / or efficiency.

[0042] The grouping of the four cylinders according to the invention, in which an outer cylinder and the adjacent inner cylinder form a group, has the significant advantage over the conventional cylinder grouping of a four-cylinder in-line engine that the two exhaust manifolds are arranged next to one another in the cylinder head, i.e. adjacent to one another along the longitudinal axis of the cylinder head, wherein the two exhaust manifolds can exit the cylinder head at an equal distance from the mounting face of the cylinder head, i.e. at the same height, whereby a cylinder head with a low overall height can be realized, which is advantageous in terms of packaging in the engine compartment. The connection and arrangement of the exhaust gas turbochargers is also simplified. The turbines can be arranged as close to the engine as possible without any problems.

[0043] In contrast, in a conventional state-of-the-art cylinder grouping, in which the inner cylinders form a cylinder group and the outer cylinders form a cylinder group, the two exhaust manifolds are arranged at least partially above one another in the cylinder head, which is why the cylinder head has a correspondingly high overall height. The two exhaust manifolds exit the cylinder head at different distances from the mounting face of the cylinder head, i.e., not at the same height. Connecting and arranging the exhaust turbochargers is considerably more difficult due to the generally small distance between the manifolds.

[0044] According to the invention, the exhaust manifolds of the two cylinder groups upstream of the turbines can be connected to one another via a connecting line, wherein a shut-off element is arranged in the connecting line.

[0045] The exhaust gas volume upstream of a turbine can then be varied, i.e. adapted to different operating conditions of the internal combustion engine, in particular to different exhaust gas quantities. For pulse charging with small exhaust gas quantities, it is advantageous to group the cylinders in such a way that the pre-exhaust pulses of the individual cylinders are retained in the exhaust gas removal system. In a cylinder head with four cylinders arranged in series, it is advantageous in this regard to combine two cylinders, each with a firing interval of 360° CA, into a cylinder group and to keep the two exhaust manifolds separate from one another by closing the shut-off element in the connecting line.

[0046] In order to be able to operate a turbine provided downstream of the cylinders in the exhaust system optimally with large exhaust gas quantities, the turbine should be subjected to an exhaust gas flow that is as constant as possible, which is why a little-changing pressure upstream of the turbine is preferred under these operating conditions in order to achieve so-called back-up charging.

[0047] A sufficiently large exhaust gas volume upstream of the turbine can smooth out pressure pulsations in the exhaust lines. Therefore, connecting the exhaust manifolds of the two cylinder groups upstream of the turbines via a connecting line can prove advantageous for larger exhaust gas volumes.

[0048] According to the invention, each cylinder has at least one intake port for supplying charge air via the intake system, with an intake line connected to each intake port. The intake lines of the cylinders of each cylinder group merge to form an intake manifold, and at least one compressor of an exhaust gas turbocharger is arranged in each intake line.

[0049] If the cylinders are grouped in the manner according to the invention and the exhaust manifolds of the two groups are configured in the manner according to the invention, it is advantageous to design the intake system in a corresponding manner, namely as described above. Then, the advantages realized on the exhaust side can be optimally utilized in generating a sufficiently high turbine pressure ratio on the intake side to generate a satisfactory boost pressure by means of the two compressors.

[0050] The valve train is designed to open and close the cylinder intake and exhaust ports in a timely manner during the charge cycle. The goal is to achieve rapid opening of the largest possible flow cross-sections in order to minimize throttling losses in the incoming charge air flow and the outgoing exhaust gas flow, and to ensure a good filling of the combustion chamber with fresh mixture and effective, i.e., complete, evacuation of the exhaust gases.

[0051] Further advantageous embodiments of the supercharged internal combustion engine are discussed in connection with the subclaims.

[0052] Advantageous embodiments of the turbocharged internal combustion engine are those in which the exhaust lines of the two cylinder groups merge into a common exhaust line downstream of the turbines. Combining the exhaust lines reduces the overall length of the exhaust lines and also offers advantages with regard to exhaust gas aftertreatment, since the entire exhaust gas can be treated within the framework of a common exhaust gas aftertreatment system. In particular, only one exhaust gas aftertreatment system of a specific type needs to be provided.

[0053] Embodiments of the supercharged internal combustion engine in which the engine is a spark-ignition internal combustion engine are advantageous. As already explained, due to the quantity control in gasoline engines, there is a greater need for concepts to improve efficiency, which is why a spark-ignition internal combustion engine is particularly suitable for being designed according to the invention.

[0054] Embodiments of the supercharged internal combustion engine are advantageous in which the exhaust pipes of the cylinders of each cylinder group merge within the cylinder head to form a complete exhaust pipe.

[0055] Integrating the exhaust manifold as far as possible into the cylinder head, as described above, i.e. merging the exhaust pipes of the cylinder groups into a complete exhaust pipe as extensively as possible in the cylinder head, has a number of advantages.

[0056] On the one hand, the integration of the manifolds leads to a more compact design of the internal combustion engine and tighter packaging of the entire drive unit in the engine compartment. On the other hand, it results in cost advantages in manufacturing and assembly. Weight is also reduced.

[0057] The short exhaust pipes also have a beneficial effect on the arrangement and operation of an exhaust aftertreatment system, which can be provided downstream of the cylinders. The path of the hot exhaust gases to the exhaust aftertreatment systems should be as short as possible to give the exhaust gases little time to cool down and to allow the exhaust aftertreatment systems to reach their operating or light-off temperature as quickly as possible, particularly after a cold start of the internal combustion engine. In this respect, it is advantageous to minimize the thermal inertia of the section of the exhaust pipes between the exhaust port on the cylinder and the exhaust aftertreatment system. This can be achieved by reducing the mass and length of this section, i.e., by shortening the corresponding exhaust pipes by integrating the manifolds.

[0058] In internal combustion engines turbocharged by exhaust gas turbochargers, the goal is to position the turbines as close as possible to the exhaust, i.e., the cylinder exhaust ports, in order to optimally utilize the exhaust enthalpy of the hot exhaust gases, which is largely determined by the exhaust pressure and temperature, and to ensure rapid turbocharger response. Here, too, the thermal inertia and the volume of the piping system between the cylinder exhaust ports and the respective turbine should be minimized, which is why shortening the piping by integrating the exhaust manifold into the cylinder head is advantageous.

[0059] Furthermore, in liquid-cooled internal combustion engines, it can be advantageous to integrate the exhaust manifold into the cylinder head in order to benefit from the cooling provided in the cylinder head and to avoid having to manufacture the manifolds from materials with high thermal loads, which are cost-intensive.

[0060] The integration of the exhaust manifold into the cylinder head often results in the cylinders influencing each other during gas exchange. According to the invention, this can be avoided by having a group comprise only two cylinders and operating these two cylinders at a distance of 360°CA, i.e., combustion in the two cylinders of a group is initiated at a distance of 360°CA.

[0061] For the reasons stated above, embodiments of the supercharged internal combustion engine are advantageous in which each cylinder has two exhaust openings for discharging the exhaust gases from the cylinder via an exhaust gas discharge system.

[0062] For the same reasons, embodiments of the supercharged internal combustion engine are advantageous in which each cylinder has two inlet openings for supplying charge air via the intake system.

[0063] Embodiments of the supercharged internal combustion engine are advantageous in which a crankshaft belonging to a crank mechanism is provided, which has a crankshaft throw associated with each cylinder, wherein - the crankshaft throws are arranged at a distance from each other along the longitudinal axis of the crankshaft, - the two crankshaft throws of the two cylinders of each cylinder group are not offset in the circumferential direction around the longitudinal axis of the crankshaft, so that the two cylinders of a cylinder group are mechanically synchronous cylinders, and - the crankshaft throws of one cylinder group are arranged on the crankshaft rotated by 180°KW in the circumferential direction around the longitudinal axis relative to the crankshaft throws of the other cylinder group.

[0064] To ensure that the cylinders in a group do not influence or hinder each other during the charge cycle, the four cylinders are preferably operated in such a way that the cylinders in a cylinder group have the greatest possible offset in terms of their working processes. To achieve this, during normal operation of the internal combustion engine, combustion is initiated alternately in a cylinder in the first cylinder group and a cylinder in the second cylinder group - for example by means of spark ignition. Process variants in which the cylinders are ignited in the sequence 1 - 3 - 2 - 4 or in the sequence 1 - 4 - 2 - 3 can be advantageous. The numbering of the cylinders in an internal combustion engine is regulated in DIN 73021. In in-line engines, the cylinders are numbered sequentially.

[0065] The cylinders are fired at intervals of 180°CA, so that, starting from the first cylinder, the ignition timings measured in °CA are as follows: 0 - 180 - 360 - 540. Consequently, the cylinders in a cylinder group exhibit a thermodynamic offset of 360°CA. Considering that the exhaust valves generally open between 220°CA and 260°CA, it becomes clear that, with the selected ignition sequence, the cylinders in a group cannot influence each other during the gas exchange, regardless of how quickly the exhaust pipes merge downstream of the exhaust ports into a single exhaust pipe.

[0066] A firing order that deviates from the conventional firing order 1 - 3 - 4 - 2 also requires a crankshaft that deviates from the conventional crankshaft, ie a crankshaft throw that deviates from the conventional crankshaft throw.

[0067] According to the embodiment in question, a crankshaft is used with which the cylinders of a cylinder group run mechanically synchronously, i.e., they pass through top and bottom dead center at the same time. To achieve this, the corresponding crankshaft throws of the two cylinders must not exhibit any offset in the circumferential direction around the longitudinal axis of the crankshaft. The thermodynamic offset of 360°CA is then realized by the firing order.

[0068] In order to achieve an ignition interval of 180°CA for all four cylinders, the crankshaft throws of one cylinder group are arranged on the crankshaft rotated by 180°CA in the circumferential direction relative to the crankshaft throws of the other cylinder group.

[0069] The turbines used can generally be equipped with a variable turbine geometry, which can be adjusted to suit the respective operating point of the internal combustion engine. A wastegate design may also be advantageous in individual cases.

[0070] Embodiments in which the supercharged internal combustion engine is equipped with liquid cooling are advantageous.

[0071] Embodiments in which the cylinder head is equipped with at least one integrated coolant jacket to form the liquid cooling system are advantageous.

[0072] Turbocharged internal combustion engines, in particular, are subject to high thermal stress, which places greater demands on their cooling system. Liquid cooling can dissipate large amounts of heat, which is why it is advantageous to equip the internal combustion engine with liquid cooling.

[0073] Liquid cooling requires the internal combustion engine, i.e., the cylinder head or cylinder block, to be equipped with an integrated coolant jacket, i.e., the arrangement of coolant channels carrying the coolant through the cylinder head or cylinder block. The heat is transferred to the coolant already inside the component. The coolant is pumped by a pump located in the cooling circuit, causing it to circulate in the coolant jacket. The heat transferred to the coolant is thus dissipated from the interior of the head or block and extracted from the coolant again in a heat exchanger.

[0074] The second sub-task underlying the invention, namely to demonstrate a method for operating a supercharged internal combustion engine according to a previously described type, is achieved by a method which is characterized in that the combustion is initiated in the cylinders at a distance of 180 °CA.

[0075] The initiation, i.e., the start of combustion, can be achieved by external ignition, for example, using a spark plug, or by self-ignition or compression ignition. This process can therefore be applied to gasoline engines, as well as diesel engines and hybrid internal combustion engines.

[0076] What has been said in connection with the internal combustion engine according to the invention also applies to the method according to the invention.

[0077] Process variants can be advantageous which are characterized in that the combustion is initiated in the cylinders in the order 1 - 3 - 2 - 4 and at intervals of 180 °CA, whereby the cylinders are counted and numbered in sequence along the longitudinal axis of the cylinder head, starting with an outer cylinder.

[0078] However, process variants can also be advantageous which are characterized in that the combustion is initiated in the cylinders in the order 1 - 4 - 2 - 3 and at intervals of 180 °CA, wherein the cylinders, starting with an outer cylinder, are counted and numbered in sequence along the longitudinal axis of at least one cylinder head.

[0079] In internal combustion engines whose cylinders are equipped with ignition devices to initiate spark ignition, process variants are advantageous in which the cylinders are ignited by spark ignition at intervals of 180°CA.

[0080] For internal combustion engines whose cylinders are operated by self-ignition, process variants are advantageous in which the self-ignition of the cylinders is initiated at intervals of 180 °CA.

[0081] Advantageous are process variants in which the two cylinders of the second group - when the load falls below a specified load T down be switched off, and - when a specified load T is exceeded up be switched on.

[0082] Process variants in which the preset load T down and / or T up depends on the speed n of the internal combustion engine.

[0083] Process variants in which the fuel supply to a deactivated cylinder and / or the spark ignition of a deactivated cylinder are deactivated are advantageous.

[0084] In a non-turbocharged internal combustion engine, the exhaust gas quantity corresponds approximately to the engine speed and / or load, depending on the load control used in the specific case. In a traditional gasoline engine with quantity control, the exhaust gas quantity increases with increasing load, even at a constant engine speed. In contrast, in traditional diesel engines with quality control, the exhaust gas quantity is only dependent on engine speed because the mixture composition, but not the mixture quantity, varies with load changes and at a constant engine speed.

[0085] In an internal combustion engine turbocharged by exhaust gas turbocharging, it must be considered that the boost pressure on the intake side can change with load and / or engine speed and influences the exhaust gas volume. The relationships between exhaust gas volume and load or engine speed presented in simplified form above therefore do not apply in this general form.

[0086] Therefore, it may be advantageous to base the partial shutdown on the exhaust gas volume rather than the load. If the exhaust gas volume falls below a predefined exhaust gas volume, a partial shutdown occurs.

[0087] In this respect, process variants can be advantageous in which the two cylinders of the second group - be switched off when a specified exhaust gas quantity is not reached, and - be switched on when a predefined exhaust gas quantity is exceeded.

[0088] In the following, the state of the art is described using an embodiment according to the Fig. 1 to 3 are described in more detail. Here: Fig. 1 schematically shows the fragment of an internal combustion engine according to the prior art, Fig. 2 schematically shows the exhaust manifolds integrated into the cylinder head of the Fig. 1 shown internal combustion engine in plan view, and Fig. 3 a design of the crankshaft of the internal combustion engine as a schematic diagram.

[0089] Fig. Figure 1 schematically shows a fragment of a four-cylinder in-line engine. Cylinders 1, 2, 3, and 4 are arranged along the longitudinal axis of the cylinder head 10. Each cylinder 1, 2, 3, and 4 is equipped with an exhaust port 5a, to which an exhaust line 5 is connected for discharging the exhaust gases from cylinders 1, 2, 3, and 4 via an exhaust gas removal system 6.

[0090] The four cylinders 1, 2, 3, 4 form two groups, each with two cylinders 1, 2, 3, 4, whereby an outer cylinder 1, 4 and the adjacent inner cylinder 2, 3 form a group. The exhaust pipes 5 of the cylinders 1, 2, 3, 4 of each cylinder group each merge to form a separate exhaust manifold 7 into a single exhaust pipe 8. The turbine 17a of an exhaust gas turbocharger 17 is arranged in each single exhaust pipe 8, which drives an associated compressor 17b arranged in the intake system. Fig. 1, the two exhaust manifolds 7 are integrated into the cylinder head 10, ie the exhaust pipes 5 of each group merge within the cylinder head 10 to form a total exhaust pipe 8.

[0091] When the internal combustion engine is in operation, the cylinders 3, 4 of a first group represent permanently operated cylinders 3, 4 of the internal combustion engine, whereas the cylinders 1, 2 of a second group are designed as load-dependent switchable cylinders 1', 2', which are switched off as part of a partial switch-off when the load falls below a predeterminable load.

[0092] Fig. 2 shows schematically the two exhaust manifolds 7 integrated into the cylinder head 10 of the Fig. 1 shown internal combustion engine in plan view. It is intended only as a supplement to Fig. 1, which is why reference is made to Fig. 1 and the corresponding description. The same reference numerals were used for the same components.

[0093] The exhaust pipes 5 of the two cylinder groups merge separately from one another to form two integrated exhaust manifolds 7 within the cylinder head to form complete exhaust pipes 8.

[0094] Fig. 3 shows an embodiment of the crankshaft 15 of the internal combustion engine as a schematic diagram.

[0095] The crankshaft 15 shown has five bearings 16 and, for each cylinder, has a crankshaft throw 11, 12, 13, 14 associated with the cylinder. The crankshaft throws 11, 12, 13, 14 are arranged at a distance from one another along the longitudinal axis 15a of the crankshaft 15, wherein the two crankshaft throws 11, 12, 13, 14 of the two cylinders of each cylinder group have no offset in the circumferential direction around the longitudinal axis 15a of the crankshaft 15, so that the cylinders of each cylinder group are mechanically synchronous cylinders. The crankshaft throws 11, 12 of the first two cylinders, i.e., the first cylinder group, are arranged on the crankshaft 15 offset by 180° in the circumferential direction from the crankshaft throws 13, 14 of the third and fourth cylinders, i.e., the second cylinder group. The mass moment M resulting from the inertia forces should preferably be compensated by means of mass balancing (not shown). Reference symbol 1 first cylinder, external cylinder 1' switchable cylinder of the second cylinder group 2 second cylinder, internal cylinder 2' switchable cylinder of the second cylinder group 3 third cylinder, internal cylinder 4 fourth cylinder, external cylinder 5 exhaust pipe 5a Outlet opening 6 Exhaust gas removal system 7 exhaust manifold 8 Complete exhaust pipe 9 Intake line 9a Inlet opening 10 cylinder head 11 Crankshaft throw of the first cylinder 12 Crankshaft throw of the second cylinder 13 Crankshaft throw of the third cylinder 14 Crankshaft throw of the fourth cylinder 15 Crankshaft 15a Longitudinal axis of the crankshaft 16 crankshaft bearings, bearings 17 exhaust gas turbocharger 17a Turbine 17b Compressor °CA degrees crank angle

Claims

[1] Supercharged internal combustion engine with a cylinder head (10) and four cylinders (1, 2, 3, 4) arranged in series along the longitudinal axis of the cylinder head (10), wherein each cylinder (1, 2, 3, 4) has at least one outlet opening (5a) for discharging the exhaust gases via an exhaust gas discharge system (6) from the cylinder (1, 2, 3, 4) and an exhaust line (5) is connected to each outlet opening (5a), in which - the four cylinders (1, 2, 3, 4) are configured to form two groups of two cylinders each (1, 2, 3, 4), - the exhaust pipes (5) of the cylinders (1, 2, 3, 4) of each cylinder group are combined to form an exhaust manifold (7) into a single exhaust pipe (8), and - at least one turbine (17a) of an exhaust gas turbocharger (17) is arranged in each exhaust line (8), characterized by , that - the four cylinders (1, 2, 3, 4) are configured in such a way that in each case an outer cylinder (1, 4) and the adjacent inner cylinder (2, 3) form a group, wherein the cylinders (3, 4) of a first group are continuously operated cylinders (3, 4) when the internal combustion engine is in operation and the cylinders (1, 2) of a second group are designed as load-dependent switchable cylinders (1', 2') which can be switched off as part of a partial switch-off when the load falls below a predeterminable load, - the exhaust manifolds (7) of the two cylinder groups upstream of the turbines (17a) can be connected to one another via a connecting line, wherein a shut-off element is arranged in the connecting line, - each cylinder (1, 2, 3, 4) has at least one inlet opening (9a) for supplying charge air via the intake system, with an intake line (9) connecting to each inlet opening (9a), - the intake lines (9) of the cylinders (1, 2, 3, 4) of each cylinder group are combined to form an intake manifold, and - at least one compressor (17b) of an exhaust gas turbocharger (17) is arranged in each total intake line. [2] Supercharged internal combustion engine according to claim 1, characterized by that the exhaust pipes (8) of the two cylinder groups merge downstream of the turbines (17a) to form a common exhaust pipe. [3] Supercharged internal combustion engine according to claim 1 or 2, characterized by that the internal combustion engine is a spark-ignition internal combustion engine. [4] Supercharged internal combustion engine according to one of the preceding claims, characterized by that the exhaust pipes (5) of the cylinders (1, 2, 3, 4) of each cylinder group within the cylinder head (10) each merge to form a total exhaust pipe (8). [5] Supercharged internal combustion engine according to one of the preceding claims, characterized by that each cylinder (1, 2, 3, 4) has two outlet openings (5a) for discharging the exhaust gases from the cylinder (1, 2, 3, 4) via an exhaust gas discharge system (6). [6] Supercharged internal combustion engine according to one of the preceding claims, characterized by that each cylinder (1, 2, 3, 4) has two inlet openings (9a) for supplying charge air via the intake system. [7] Supercharged internal combustion engine according to one of the preceding claims, characterized by that a crankshaft (15) belonging to a crank mechanism is provided, which has for each cylinder (1, 2, 3, 4) a crankshaft throw (11, 12, 13, 14) belonging to the cylinder (1, 2, 3, 4), wherein - the crankshaft throws (11, 12, 13, 14) are arranged at a distance from one another along the longitudinal axis (15a) of the crankshaft (15), - the two crankshaft throws (11, 12, 13, 14) of the two cylinders (1, 2, 3, 4) of each cylinder group have no offset in the circumferential direction around the longitudinal axis (15a) of the crankshaft (15), so that the two cylinders (1, 2, 3, 4) of a cylinder group are mechanically synchronous cylinders (1, 2, 3, 4), and - the crankshaft throws (11, 12, 13, 14) of one cylinder group are arranged on the crankshaft (15) rotated by 180°KW in the circumferential direction around the longitudinal axis (15a) relative to the crankshaft throws (11, 12, 13, 14) of the other cylinder group. [8] Method for operating a supercharged internal combustion engine according to one of the preceding claims, characterized by that in cylinders (1, 2, 3, 4) combustion is initiated at intervals of 180 °CA. [9] Method according to claim 8, characterized bythat in the cylinders (1, 2, 3, 4) the combustion is initiated in the order 1 - 3 - 2 - 4 and at intervals of 180 °CA, whereby the cylinders (1, 2, 3, 4) are counted and numbered in sequence along the longitudinal axis of the cylinder head (10), starting with an outer cylinder (1, 4). [10] Method according to claim 8, characterized by that in the cylinders (1, 2, 3, 4) the combustion is initiated in the order 1 - 4 - 2 - 3 and at intervals of 180 °CA, wherein the cylinders (1, 2, 3, 4) are counted and numbered in sequence along the longitudinal axis of the at least one cylinder head (10), starting with an outer cylinder (1, 4). [11] Method according to one of claims 8 to 10, characterized by that each cylinder (1, 2, 3, 4) is equipped with an ignition device to initiate external ignition and the cylinders (1, 2, 3, 4) are ignited by means of external ignition at intervals of 180 °CA. [12] Method according to one of claims 8 to 10, characterized by that the cylinders (1, 2, 3, 4) are operated by means of self-ignition and the self-ignition of the cylinders (1, 2, 3, 4) is initiated at intervals of 180 °CA. [13] Method according to one of claims 8 to 12, characterized by that the two cylinders (1', 2') of the second group - when the load falls below a specified load T down be switched off, and - when a specified load T is exceeded up be switched on. [14] Method according to claim 13, characterized by that the specified load T down and / or T up depends on the speed n of the internal combustion engine. [15] Method according to claim 13 or 14, characterized by that the fuel supply of a deactivated cylinder (1', 2') and / or the external ignition of a deactivated cylinder (1', 2') is deactivated.

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