Internal combustion engine that can be operated in a 4-stroke mode and in a 2-stroke mode, and vehicle equipped with the internal combustion engine

Abstract

Internal combustion engine (3) which can be operated in a 4-stroke operating mode (4TBM) and in a 2-stroke operating mode (2TBM), - with an engine block (5) containing at least one cylinder (6) in which a piston (9) is arranged to be axially adjustable between a bottom dead center (BDC) and a top dead center (TDC), and which has at least one side opening (20) open to the cylinder (6) for the respective cylinder (6), - with a cylinder head (7) covering the respective cylinder (6) and having for the respective cylinder (6) an intake chamber (14), an exhaust chamber (15), at least one intake valve (22) for controlling an intake opening (23) connecting the intake chamber (14) to the cylinder (6) and at least one exhaust valve (24) for controlling an exhaust opening (25) connecting the exhaust chamber (15) to the cylinder (6), - with an inlet channel (21) connecting the inlet chamber (14) to the respective side opening (20), characterized in that - that the internal combustion engine (3) has a piston stroke adjustment (26) for changing an axial position of the bottom dead center (BDC) in the respective cylinder (6) which is configured such that the piston (9) locks the respective side opening (20) at bottom dead center (BDC) when the internal combustion engine (3) is operated in 4-stroke mode (4TBM), and opens the respective side opening (20) at bottom dead center (BDC) when the internal combustion engine (3) is operated in 2-stroke mode (2TBM).

Description

[0001] The present invention relates to an internal combustion engine according to the preamble of claim 1. The invention also relates to a vehicle equipped with such an internal combustion engine.

[0002] For smaller motorized devices and vehicles, two-stroke combustion engines are relatively popular due to their high power density. However, a potential drawback of two-stroke engines is their comparatively high emissions compared to four-stroke engines, particularly at low loads and / or low engine speeds.

[0003] In this respect, internal combustion engines of the same type can provide a solution, as they can be operated in both a 4-stroke and a 2-stroke mode. Such engines can, for example, operate in 4-stroke mode at low speeds and / or low loads, resulting in relatively low emissions and fuel consumption. At high speeds and / or high loads, these engines can, conversely, operate in 2-stroke mode, which is characterized, for example, by very high acceleration and high engine speeds.

[0004] A generic internal combustion engine is known, for example, from JP H06 10694 A and can be operated in a 4-stroke mode as well as in a 2-stroke mode, wherein the internal combustion engine has an engine block and a cylinder head attached to the engine block. The engine block contains at least one cylinder in which a piston is arranged to be axially adjustable between a bottom dead center and a top dead center, and which has at least one side opening open to the cylinder for the respective cylinder. The cylinder head covers the respective cylinder and has, for the respective cylinder, an intake chamber, an exhaust chamber, at least one intake valve for controlling an intake port connecting the intake chamber to the cylinder, and at least one exhaust valve for controlling an exhaust port connecting the exhaust chamber to the cylinder.Furthermore, the internal combustion engine has an intake port that connects the intake chamber to the respective side opening. In two-stroke operation, fresh air can enter the cylinder from the intake chamber through the respective side opening to effect the gas exchange required for two-stroke operation.

[0005] Another such internal combustion engine is known from WO 2018 / 161 070 A1, which has an additional gas exchange valve for controlling the side opening.

[0006] Other internal combustion engines that can be operated in a 4-stroke operating mode and in a 2-stroke operating mode are known from DE 102 03 185 A1, from CN 211 666 812 U, from JP S58 152 139 A, from WO 2013 / 097 269 A1, from JP H04 314 927 A, from US 4 392 459 A, from US 2011 / 0 253 073 A1, from JP H11 62 616 A, from DE 690 11 181 T2 and from DE 100 04 528 A1.

[0007] The present invention addresses the problem of providing an improved or at least a different embodiment for such an internal combustion engine and for a vehicle equipped therewith, which is characterized in particular by improved functionality and preferably by high performance with comparatively low pollutant emissions and comparatively low fuel consumption.

[0008] This problem is solved according to the invention by the subject matter of the independent claim. Advantageous embodiments are the subject matter of the dependent claims.

[0009] The invention is based on the general concept of equipping the internal combustion engine with a piston stroke adjustment mechanism that allows the axial position of the piston's bottom dead center in the respective cylinder to be changed. According to the invention, the piston stroke adjustment mechanism is configured such that the piston closes the respective side port, which connects the respective cylinder to the intake chamber via the intake port, at bottom dead center when the internal combustion engine is operated in 4-stroke mode, and opens the respective side port at bottom dead center when the internal combustion engine is operated in 2-stroke mode. In other words, the respective side port is positioned on the cylinder such that it lies above the piston at bottom dead center and is not covered by it when the internal combustion engine is operated in 2-stroke mode.However, as the piston moves within the cylinder from bottom dead center towards top dead center, it covers the respective side port until it has moved sufficiently close to bottom dead center again. Thus, the piston controls the respective side port according to the 2-stroke operating mode. In contrast, the respective side port is always covered by the piston when the internal combustion engine is operating in 4-stroke mode. Adjusting the piston's axial position relative to its bottom dead center is relatively simple for setting the 4-stroke and 2-stroke operating modes and is, for example, independent of the engine speed.Unlike, for example, a valve system that requires opening and closing the respective intake port for the two-stroke operating mode to enable gas exchange, this results in significantly reduced complexity, since such a valve system, at least in two-stroke mode, depends on the engine speed, which can be relatively high. Piston stroke adjustment can also be referred to as a piston stroke adjustment device.

[0010] According to an advantageous embodiment, the internal combustion engine can be configured such that the respective intake valve can be activated and deactivated. The internal combustion engine can also be configured such that the respective intake valve is activated and opens and closes the respective intake port according to the 4-stroke operating mode when the engine is operated in 4-stroke mode. Furthermore, the internal combustion engine can be configured such that the respective intake valve is deactivated and permanently closes the respective intake port when the engine is operated in 2-stroke mode. In other words, for 4-stroke operation, the respective intake valve is actuated to open and close the respective intake port according to the power strokes of the 4-stroke principle. For 2-stroke operation, however, the respective intake valve remains unactuated in its closed position to close the respective intake port.

[0011] According to an advantageous embodiment, the internal combustion engine can have an adjustable intake camshaft for actuating the respective intake valve, which is adjustable to a first intake camshaft position for the 4-stroke operating mode and to a second intake camshaft position for the 2-stroke operating mode. The intake camshaft has a cam for each intake valve, which, in the first intake camshaft position, interacts with the respective intake valve and actuates it according to the 4-stroke operating mode, while, in the second intake camshaft position, this cam does not interact with the respective intake valve and does not actuate it to open the intake port, which corresponds to the 2-stroke operating mode.The different actuations of the intake valve intended for the different operating modes are realized here by means of an adjustable intake camshaft, which in the 4-stroke operating mode actuates the intake valve with a conventional single cam that only has a radial protrusion, while in the 2-stroke operating mode it has no cam to actuate the respective intake valve or a zero cam that has no radial protrusion and therefore cannot actuate the intake valve to open the intake port.

[0012] In an alternative design, it is conceivable that a valve train, which couples the intake camshaft to the respective intake valve, could be activated and deactivated. For example, such a valve train could incorporate a hydraulic element, typically used for valve clearance adjustment and / or valve lift control, which could now be configured to interrupt the operative connection between the intake camshaft and the respective intake valve. For instance, a pushrod that couples the cam to a rocker arm actuating the intake valve could be decoupled from the cam or the rocker arm via the hydraulic element.

[0013] In another embodiment, the internal combustion engine can have a crankshaft for driving the respective piston, which is rotatably mounted on the engine block about an axis of rotation via several crankshaft bearings. These crankshaft bearings can then form components of the piston stroke adjustment mechanism and be arranged in the engine block in a position adjustable transversely to the axis of rotation of the crankshaft with respect to the respective cylinder. The crankshaft bearings can thus be adjusted at least between a first position, in which the respective piston at bottom dead center blocks the respective side opening, and a second position, in which the respective piston at bottom dead center opens or releases the respective side opening. The piston stroke adjustment mechanism can then include an adjusting device for each crankshaft bearing, which interacts with the crankshaft bearing to adjust it between the first and second positions.In other words, for the axial adjustment of the bottom dead center in each cylinder, the crankshaft bearings are moved transversely to the crankshaft's axis of rotation, resulting in a corresponding adjustment movement of the crankshaft. Through the drive coupling of the crankshaft to the respective piston, particularly in conjunction with a connecting rod, this results in an axial adjustment of the respective piston in the associated cylinder, leading to an axial adjustment of the piston's bottom dead center. Especially in a multi-cylinder internal combustion engine, adjusting the crankshaft bearings allows for synchronous axial adjustment of all connected pistons. This reduces the complexity of piston stroke adjustment in a multi-cylinder internal combustion engine. By relocating the crankshaft, or...However, the crankshaft bearings not only change the axial position of the piston's bottom dead center (BDC), but also its top dead center (TDC). In other words, repositioning the crankshaft bearings can also alter the maximum compression achievable at the piston's TDC of the ignitable mixture in the cylinder. Specifically, for two-stroke operation, the TDC can be shifted towards the bottom dead center, thus reducing the maximum compression. This can be advantageous, particularly at higher engine speeds, in terms of wear and exhaust emissions. Conversely, for four-stroke operation, this results in a higher maximum compression at the piston's TDC, improving efficiency and thus reducing fuel consumption.

[0014] An advantageous embodiment is one in which the piston stroke adjustment is configured such that the respective crankshaft bearing is adjustable between the first and second positions, transversely to the axis of rotation of the crankshaft and transversely to the axial direction of the respective cylinder. This lateral adjustment of the crankshaft transversely to the axial direction of the respective cylinder keeps the load on the crankshaft bearings parallel to the axial direction of the cylinders essentially constant and is therefore essentially independent of the current position of the crankshaft or the crankshaft bearings within the respective adjustment range. In particular, the piston stroke adjustment or the respective adjusting device does not have to work against the forces introduced into the crankshaft in the axial direction by the pistons via the connecting rods during operation of the internal combustion engine. This simplifies the overall design of the piston stroke adjustment.

[0015] According to another advantageous embodiment, the piston stroke adjustment for the respective crankshaft bearing can include a return mechanism that counteracts the adjusting mechanism and interacts with it to adjust the crankshaft bearing between the first and second positions. The adjusting mechanism and the return mechanism can be configured such that the adjusting mechanism allows the respective crankshaft bearing to be adjusted from an initial position, formed by the first and second positions, to an end position, formed by the first and second positions. In contrast, the return mechanism allows the respective crankshaft bearing to be adjusted back from the end position to the initial position.In this design, the piston stroke adjustment, using the respective actuating device, only needs to effect the adjustment from the initial position to the final position, as the return from the final position to the initial position is achieved using the return mechanism. This simplifies the design of the piston stroke adjustment.

[0016] According to an advantageous embodiment, the respective actuating device can be designed as a hydraulic device that uses pressurized hydraulic fluid to drive the respective crankshaft bearing from its initial position to its final position. Additionally, the respective return mechanism can be designed as a spring mechanism that is tensioned when the crankshaft bearing is moved from its initial position to its final position, and whose return force drives the crankshaft bearing from its final position back to its initial position. Thus, when the pressure in the hydraulic fluid is reduced, the respective return mechanism can, by means of its return force, move the crankshaft bearing from its final position back to its initial position.For example, the piston stroke adjustment can be configured as a piston-cylinder assembly, in which a bearing housing forms a cylinder. Bearing shells within this cylinder, in which the crankshaft is rotatably mounted about the axis of rotation, form a bearing piston that is adjustable between its initial and final positions within this bearing housing. The bearing shells separate two chambers within the bearing housing. One chamber can be pressurized with the hydraulic fluid, while the other chamber contains the return mechanism.

[0017] According to another embodiment, the internal combustion engine can have an adjustable exhaust camshaft for actuating the respective exhaust valve, which is adjustable to a first exhaust camshaft position for the 4-stroke operating mode and to a second exhaust camshaft position for the 2-stroke operating mode. The exhaust camshaft can have a first cam for each exhaust valve, which interacts with the respective exhaust valve in the first exhaust camshaft position and actuates it according to the 4-stroke operating mode, and a second cam, which interacts with the respective exhaust valve in the second exhaust camshaft position and actuates it according to the 2-stroke operating mode. For example, the respective first cam can be designed as a single cam with only a radial projection along its circumference.In contrast, the respective second cam can be designed as a double cam, which has two diametrically opposed radial protrusions.

[0018] According to another advantageous embodiment, the internal combustion engine can have an exhaust gas turbocharger connected to the cylinder head to supply charged fresh air to the respective intake chamber. The use of an exhaust gas turbocharger facilitates operation in two-stroke mode when the cylinder is filled with charged fresh air via the respective side port. Unlike a conventional two-stroke engine, where fresh air is supplied to the cylinder through a crankcase and thus quasi-axially, no lubricating oil is carried away from the crankcase when fresh air is supplied via such side ports. Consequently, the internal combustion engine presented here is characterized by comparatively low oil consumption even in two-stroke mode. The use of an exhaust gas turbocharger supports the supply of fresh air to the cylinder during the gas exchange process.

[0019] According to another embodiment, the internal combustion engine can have a fuel injector for each cylinder, which is mounted on the cylinder head for injecting fuel into the cylinder. This achieves direct fuel injection into the respective cylinder. Such direct injection leads to significantly improved pollutant emissions and significantly reduced fuel consumption, both in 4-stroke and 2-stroke operating modes.

[0020] The combustion engine presented here can optionally be equipped with an ignition device for each cylinder, mounted on the cylinder head to ignite a combustible mixture in the cylinder. With such an ignition device, the combustion engine is configured as a spark-ignition engine, allowing its operation to be optimized with regard to emissions, fuel consumption, and performance by selecting the ignition timing. This is particularly advantageous for a high-speed combustion engine.

[0021] A vehicle according to the invention comprises a chassis and an internal combustion engine of the type described above, which serves to propel the vehicle and is arranged on or in the chassis for this purpose. The vehicle can be, in particular, a snowmobile, also known as a snow sled, or a personal watercraft, which corresponds to a motorized watercraft without side walls, in which the rider can sit and / or stand. The vehicle can also be a smaller road motorcycle, in particular a moped or moped-style motorcycle. Likewise, the internal combustion engine can be used in smaller machines in which idling phases and power phases alternate.

[0022] Further important features and advantages of the invention will become apparent from the dependent claims, the drawings and the associated description of the figures based on the drawings.

[0023] The components of a higher-level unit, such as a facility, device or arrangement, mentioned above and to be mentioned below, which are designated separately, may form separate parts or components of this unit or be integral areas or sections of this unit, even if this is shown differently in the drawings.

[0024] Preferred embodiments of the invention are shown in the drawings and are explained in more detail in the following description, wherein identical reference numerals refer to identical or similar or functionally identical components.

[0025] They show, schematically, Fig. 1 a highly simplified side view of a vehicle with an internal combustion engine, Fig. 2 a highly simplified schematic representation of the internal combustion engine, Fig. 3 a further simplified representation of the internal combustion engine with one piston at bottom dead center during a 4-stroke operating mode, Fig. 4 a view like in Fig. 3, however with the piston at top dead center during the 4-stroke operating mode, Fig. 5 a view like in the Fig. 3 and Fig. 4, however with the piston at bottom dead center during a 2-stroke operating mode, Fig. 6 a view like in the Fig. 3 to 5, however with the piston at top dead center during 2-stroke operating mode, Fig. 7 A highly simplified sectional view of a crankshaft bearing.

[0026] Accordingly Fig. 1 comprises a vehicle 1, which in the example is the Fig. The vehicle 1 consists of a snowmobile or a snow sled, a chassis 2, and an internal combustion engine 3, which is arranged on or in the chassis 2 and serves to propel the vehicle 1. For example, the internal combustion engine 3 can drive a snow chain 4 of the vehicle 1. The configuration of the vehicle 1 as a snowmobile is shown here only as an example. The vehicle 1 can also be configured as a personal watercraft or a road motorcycle.

[0027] The internal combustion engine 3 is configured to operate selectively in either a 4-stroke operating mode (4TBM) or a 2-stroke operating mode (2TBM). In particular, an engine control unit 27 can be provided for this purpose, which is appropriately coupled to the internal combustion engine 3. The engine control unit 27 can, for example, switch between the 4-stroke operating mode (4TBM) and the 2-stroke operating mode (2TBM) depending on the current speed of the internal combustion engine 3 and / or depending on the current load or load requirement of the internal combustion engine 3. Possible are a limit speed, above which the motor control 27 switches from the 4-stroke operating mode 4TBM to the 2-stroke operating mode 2TBM and / or a limit load, above which the motor control 27 switches the internal combustion engine 3 from the 4-stroke operating mode 4TBM to the 2-stroke operating mode 2TBM.

[0028] Accordingly Fig. 1. The internal combustion engine 3 has an engine block 5 in which at least one cylinder 6 is formed. According to [reference to relevant section], the engine block 5 is connected to... Fig. 2 upwards a cylinder head 7, which is usually attached to the engine block 5 and which covers the respective cylinder 6. According to Fig. 2 typically connects a crankcase 8 to the bottom of the engine block 5, into which the respective cylinder 6 opens. A piston 9 is axially adjustable within each cylinder 6. The piston 9 is driven via a connecting rod 10 by a crankshaft 11, which is rotatably mounted on the engine block 5 about an axis of rotation 13 in at least two crankshaft bearings 12. The cylinder head 7 also contains a channel-shaped intake chamber 14 for supplying fresh air to the respective cylinder 6 and a channel-shaped exhaust chamber 15 for removing exhaust gas from the respective cylinder 6.

[0029] In the example of the Fig. 2. The combustion engine 3 is also equipped with an exhaust gas turbocharger 16, which in the usual manner comprises a turbine 17 and a compressor 18. Fresh air drawn in from the environment 19 is compressed into charge air by means of the compressor 18, so that charged fresh air or charge air is supplied to the respective intake chamber 14. The exhaust gas is discharged from the respective exhaust chamber 15 and expanded in the turbine 17 and then returned to the environment 19 via an exhaust aftertreatment system (not shown here).

[0030] According to the Fig. 3 to 6, the respective piston 9 in the associated cylinder 6 is axially positioned between one in the Fig. 3 and Fig. 5 shown bottom dead center UT and one in the Fig. 4 and Fig. The top dead center (TDC) shown in Figure 6 is adjustable by stroke. Furthermore, at least one side opening 20, open to cylinder 6, is formed in the engine block 5 and is fluidically connected to the intake chamber 14 via a connecting channel 21. Depending on the dividing line between engine block 5 and cylinder head 7, this intake channel 21 is formed at least partially in engine block 5 and / or at least partially in cylinder head 7. In the illustrations of the Fig. Figures 3 to 6 show only a single such side opening 20. It is clear that, in principle, two or more such side openings 20 can also be present, distributed in the circumferential direction and connected to the inlet chamber 14 via a common inlet channel 21 or via several separate inlet channels 21.

[0031] The cylinder head 7 also has at least one intake valve 22 for controlling an intake port 23, which connects the respective cylinder 6 to the intake chamber 14. Furthermore, the cylinder head 7 has at least one exhaust valve 24, which serves to control an exhaust port 25, which connects the cylinder 6 to the exhaust chamber 15.

[0032] The combustion engine 3 presented here is configured to operate in a 4-stroke mode (4TBM) and a 2-stroke mode (2TBM), depending on speed and / or load. For this purpose, the combustion engine 3 is also equipped with a Fig. The cylinder 6 is equipped with a piston stroke adjustment 26, shown as an example, which allows the axial position of the bottom dead center (BDC) of the respective piston 9 within the respective cylinder 6 to be changed. This piston stroke adjustment 26 is configured such that the piston 9 opens the respective side opening 20 at bottom dead center (BDC) according to Fig. 3 is locked when the internal combustion engine 3 is operated in 4-stroke mode (4TBM). In contrast, the piston 9 releases or opens the respective side opening 20 at bottom dead center (BDC) when the internal combustion engine 3 is operated in 2-stroke mode (2TBM).

[0033] The internal combustion engine 3 can also be conveniently configured so that the respective inlet valve 22 can be activated and deactivated. For the 4-stroke operating mode 4TBM, the respective inlet valve 22 is activated, while for the 2-stroke operating mode 2TBM it is deactivated. The activated inlet valve 22 opens and closes the associated inlet port 23 according to the 4-stroke operating mode 4TBM when the internal combustion engine 3 is operated in 4-stroke mode 4TBM. In 4-stroke mode 4TBM, the respective side port 20 remains permanently closed, so that it is covered and thus blocked by the piston 9 from bottom dead center (BDC) to top dead center (TDC).

[0034] In the 4-stroke operating mode 4TBM, four working strokes of the 4-stroke operating mode 4TBM occur sequentially in the usual manner, forming a continuously repeating cycle. In a first working stroke or charging stroke, cylinder 6 is filled with fresh air. The first working stroke begins at the first top dead center (TDC) of piston 9 according to... Fig. 4 and ends at a first bottom dead center (BDC) of piston 9 according to Fig. 3. During the first power stroke, the intake valve 22 is actuated to open the intake port 23, allowing the charged fresh air from the fresh air chamber 22 to flow into the cylinder 6. In a subsequent second power stroke, also known as the compression stroke, the fresh air is compressed in the cylinder 6. For this purpose, the intake valve 22 is actuated to close the intake port 23. The piston 9 then begins to move from its first bottom dead center (BDC) according to... Fig. 3 and moves to its second top dead center (TDC) according to Fig. 4. Fuel injection typically occurs during the compression stroke. At second top dead center (TDC), the compressed fuel-air mixture is ignited in cylinder 6. This is followed by a third power stroke, also known as the expansion stroke, in which the ignited mixture moves the piston 9 from second top dead center (TDC) according to... Fig. 4 to the second bottom dead center UT according to Fig. 3. Following this, a fourth working stroke, also known as the purge stroke, takes place, in which the piston 9 moves from the second bottom dead center (BDC) according to Fig. 3 back to top dead center (TDC) according to Fig. 4 is adjusted. During the fourth working stroke, the respective exhaust valve 24 is actuated to open the corresponding exhaust port 25, so that during the fourth working stroke the exhaust gas generated in cylinder 6 can be expelled from cylinder 6, whereby the exhaust gas from cylinder 6 enters the exhaust chamber 15 and flows on from there. At the end of the fourth working stroke, the piston 9 is again at top dead center (TDC) according to Fig. 4, which then corresponds to the first top dead center (TDC) of the next cycle of the 4-stroke operating mode (4TBM).

[0035] If, on the other hand, the internal combustion engine 3 is operated in 2-stroke mode 2TBM, the intake valve 22 is deactivated, so that the corresponding intake port 23 is permanently closed. During 2-stroke mode 2TBM, however, the piston 9 can control the respective side port 20 due to the piston stroke adjustment 26 and open it in the region of bottom dead center (BDC), so that fresh air can flow into the cylinder 6 through the intake port 21 and the respective side port 20. The cycles of 2-stroke mode 2TBM comprise only two power strokes. The first power stroke, which can also be referred to as the gas exchange and compression stroke, begins at bottom dead center (BDC) according to Fig. 5 and ends at top dead center TDC according to Fig. 6. During the first power stroke, the intake valve 22 is deactivated, so the corresponding intake port 23 is closed. In contrast, the respective exhaust valve 24 is actuated to open the corresponding exhaust port 25. The fresh air flowing into cylinder 6 through the side port 20 drives the exhaust gas out of cylinder 6 through the exhaust port 25. As soon as the piston 9 closes the respective side port 20 during the first power stroke, the exhaust valve 24 is also actuated to close the exhaust port 25. Subsequently, the piston 9, moving to top dead center (TDC), compresses the fresh air. During the compression process, fuel injection also occurs, and the mixture is ignited at top dead center (TDC). This is followed by the second power stroke, which also represents an expansion stroke and occurs at top dead center according to... Fig. 6 begins and at bottom dead center UT according to Fig. 5 ends. During the second power stroke, the ignited mixture expands, driving the piston 9 back towards bottom dead center (BDC). At bottom dead center (BDC), the respective exhaust valve 24 is then actuated to open the exhaust port 25. Essentially simultaneously, the piston 9 opens the respective side port 20, so that a new cycle of the 2-stroke operating mode 2TBM begins with the next first power stroke.

[0036] For the activation and deactivation of the respective intake valve 22, the internal combustion engine 3 can have an adjustable intake camshaft 28, which is adjustable to a first intake camshaft position 28' for the 4-stroke operating mode 4TBM and to a second intake camshaft position 28" for the 2-stroke operating mode 2TBM. The intake camshaft 28 can have a cam 29 for actuating the respective intake valve 22, which interacts with the respective intake valve 22 in the first intake camshaft position 28' and actuates the intake valve 22 according to the 4-stroke operating mode 4TBM. The cam 29 is configured here as a single cam, whereby the cam 29 actuates the intake valve 22 exactly once to open the intake port 23 with each complete revolution of the intake camshaft 28.This cam 29 is adjusted in the second intake camshaft position 28" relative to the intake valve 28 to such an extent that it can no longer actuate the intake valve 22, so that the intake camshaft 28 in the second intake camshaft position 28" does not actuate the intake valve 22 according to the 2-stroke operating mode 2TBM, so that the intake valve 22 keeps the intake opening 23 permanently closed during the 2-stroke operating mode 2TBM.

[0037] In the Fig. 3 and Fig. 4 The section plane is located in the area of ​​the cam 29 to show the interaction of the cam 29 with the intake valve 22 in the first intake camshaft position 28' during the 4-stroke operating mode 4TBM. In contrast, in the Fig. 5 and Fig. 6 the cutting plane outside this cam 29, so that the cam 29 in the Fig. 5 and Fig. 6 is not recognizable. This shows the lack of interaction between the cam 29 and the intake valve 22, so that the intake valve 22 remains unactuated and is therefore deactivated for the 2-stroke operating mode 2TBM.

[0038] The internal combustion engine 3 can also have an adjustable exhaust camshaft 30 configured to actuate the respective exhaust valve 24. The exhaust camshaft 30 is adjustable to a first exhaust camshaft position 30' for the 4-stroke operating mode 4TBM and to a second exhaust camshaft position 30" for the 2-stroke operating mode 2TBM. The exhaust camshaft 30 is equipped with a first cam 31, which is active in the first exhaust camshaft position 30' and interacts with the exhaust valve 24, and with a second cam 32, which is active in the second exhaust camshaft position 30" and interacts with the exhaust valve 24. During the 4-stroke operating mode 4TBM, the exhaust camshaft 30 is adjusted to the first exhaust camshaft position 30', so that the first cam 31 to actuate the exhaust valve 24 works together with the exhaust valve 24 and actuates it according to the 4-stroke operating mode 4TBM.The first cam 31 is again designed as a single cam, so that the exhaust valve 24 is actuated exactly once to open the exhaust port 25 during one revolution of the exhaust camshaft 30.

[0039] During the 2-stroke operating mode 2TBM, the exhaust camshaft 30 is in its second exhaust camshaft position 30", in which the second cam 32 interacts with the exhaust valve 24 to actuate the exhaust valve 24 according to the 2-stroke operating mode 2TBM. For this purpose, the second cam 32 can be configured as a double cam, characterized by the fact that the exhaust valve 24 is actuated twice during one revolution of the exhaust camshaft 30 by means of the second cam 32 to open the exhaust port 25.

[0040] In the Fig. 3 and Fig. 4 The section plane is located in the area of ​​the first cam 31 to show the interaction of the first cam 31 with the exhaust valve 24 in the first exhaust camshaft position 30' during the 4-stroke operating mode 4TBM. In contrast, in the Fig. 5 and Fig. 6 the section plane in the area of ​​the second cam 32 to show the interaction of the second cam 32 with the exhaust valve 24 in the second exhaust camshaft position 30" during the 2-stroke operating mode 2TBM.

[0041] As mentioned above with reference to Fig. As explained in section 2, the internal combustion engine 3 has a crankshaft 11 connected to the respective piston 9, which is rotatably mounted on the engine block 5 about the axis of rotation 13 via several crankshaft bearings 12. Fig. Figure 7 schematically shows one of these crankshaft bearings 12. According to an advantageous embodiment, the crankshaft bearings 12 can each form a component of the piston stroke adjustment 26. For this purpose, the respective crankshaft bearing 12 is adjustably arranged on the engine block 5 or relative to the engine block 5 transversely to the axis of rotation 13. Fig. Figure 7 indicates the bidirectional adjustability of the crankshaft bearing 12 relative to the engine block 5 with a double arrow and is labelled 33. The crankshaft bearing 12 is adjustable between a first position and a different second position. The first position corresponds to the 4-stroke operating mode 4TBM and, via the drive coupling between the crankshaft 11 and the piston 9, causes the piston 9 to move the Fig. The piston 9 has the bottom dead center (BDC) shown in Figure 3, in which it closes the respective side opening 20. The second position of the crankshaft bearing 12 is assigned to the 2-stroke operating mode 2TBM and, via the drive coupling between the crankshaft 11 and the piston 9, causes the bottom dead center (BDC) of the piston 9 to be lowered to such an extent that the piston 9, according to Figure 3, has the bottom dead center (BDC) of the crankshaft 11. Fig. 5 at bottom dead center (BDC) releases the respective side opening 20. Since the kinematic drive coupling of the crankshaft 11 via the respective connecting rod 10 to the piston 9 does not change due to the adjustment of the crankshaft bearing 12, the overall piston stroke remains essentially the same, so that the axial adjustment of bottom dead center (BDC) is accompanied by an essentially equal axial adjustment of top dead center (TDC). This results in the piston 9 at top dead center (TDC) during the 2-stroke operating mode 2TBM according to Fig. 6 of the gas exchange valves 22 and 24 has a greater distance than at top dead center (TDC) during the 4-stroke operating mode 4TBM according to Fig. 4. Accordingly, for the 2-stroke operating mode 2TBM, a reduction in the compression ratio is achieved, which is advantageous for the operation of the internal combustion engine 3 at relatively high speeds, which are intended for the 2-stroke operating mode 2TBM.

[0042] To adjust the crankshaft bearing 12, the piston stroke adjustment 26 is equipped with an adjusting device 34, which interacts with the crankshaft bearing 12 to adjust it between the first and second positions. A preferred configuration for the piston stroke adjustment 26 is such that the adjustability 33 of the crankshaft bearing 12 is oriented transversely to the axis of rotation 13 and also transversely to the axial direction X of the respective cylinder 6. The axial direction X is defined by the longitudinal center axis of the respective cylinder 6, which is located in the Fig. 3 to 6 is indicated and labelled 35. The axial direction X runs parallel to the longitudinal center axis 35 of the respective cylinder 6. The axial direction X also runs parallel to the stroke direction of the respective piston 9, which is indicated in the Fig. 3 to 6, indicated by a double arrow and labelled 36. This allows the adjustment of the crankshaft bearing 12 transversely to the stroke direction 36 of the respective piston 9 and transversely to the axis of rotation 13 of the crankshaft 11.

[0043] According to Fig. 7. The piston stroke adjustment 26 can also include a return mechanism 37, which interacts with the crankshaft bearing 12 to adjust it between the first and second positions. The adjusting mechanism 34 and the return mechanism 37 are coordinated and configured to operate in opposite directions. Consequently, the respective crankshaft bearing 12 can be adjusted from an initial position to an end position using the adjusting mechanism 34. The initial position is defined by the first and second positions, while the end position is defined by the corresponding second position. For example, the initial position can be defined by the first position and thus be present during the 4-stroke operating mode (4TBM), while the end position is defined by the second position, which is present during the 2-stroke operating mode (2TBM).The reset mechanism 37 then causes the crankshaft bearing 12 to return from its end position to its initial position. In the example of the... Fig. In Figure 7, the actuating device 34 is configured as a hydraulic device 38, such that it uses pressurized hydraulic fluid to drive the respective crankshaft bearing 12 from its initial position to its final position. For this purpose, the hydraulic device 38 can include a hydraulic pump 39, a metering valve 40, and a reservoir (not shown). The return device 37 can be configured as a spring device 41, such that the spring device 41 is tensioned when the crankshaft bearing 12 is moved from its initial position to its final position. The return force of the spring device 41 then drives the crankshaft bearing 12 from its final position to its initial position.

[0044] In the example of the Fig. 7 The piston stroke adjustment 26, together with the respective crankshaft bearing 12, forms a piston-cylinder assembly 42, which has a cylindrical bearing housing 43 in which the crankshaft bearing 12 forms a bearing piston 48. The crankshaft bearing 12 can have two bearing shells 44, 45 in which the crankshaft 11 is supported. The bearing piston 48 is adjustable in the bearing housing 43 in the direction of adjustability 33 and thereby separates a first chamber 46 from a second chamber 47 in the bearing housing 43. The spring assembly 41 is arranged in the second chamber 47. The first chamber 46 can be supplied with hydraulic pressure, i.e., pressurized hydraulic fluid, by means of the hydraulic assembly 38. The pressure build-up in the first chamber 46 pushes the bearing piston 48 with the crankshaft 11 supported therein into Fig. 7 from left to right, whereby the spring assembly 41 is tensioned in the second chamber 47. If, on the other hand, the pressure in the first chamber 46 is reduced, the restoring force of the spring assembly 41 causes the bearing piston 48 to return to its original position. Fig. 7 is shifted from right to left.

[0045] According to the Fig. 3 to 6, the internal combustion engine 3 can have a fuel injector 49 for the respective cylinder 6, which is attached to the cylinder head 7 and serves to inject fuel into the cylinder 6. Additionally or alternatively, the internal combustion engine 3 can have an ignition device 50 for the respective cylinder 6, which is attached to the cylinder head 7 and serves to ignite an ignitable mixture in the cylinder 6.

Claims

[1] Internal combustion engine (3) which can be operated in a 4-stroke operating mode (4TBM) and in a 2-stroke operating mode (2TBM), - with an engine block (5) containing at least one cylinder (6) in which a piston (9) is arranged to be axially adjustable between a bottom dead center (BDC) and a top dead center (TDC), and which has at least one side opening (20) open to the cylinder (6) for the respective cylinder (6), - with a cylinder head (7) covering the respective cylinder (6) and having for the respective cylinder (6) an intake chamber (14), an exhaust chamber (15), at least one intake valve (22) for controlling an intake opening (23) connecting the intake chamber (14) to the cylinder (6) and at least one exhaust valve (24) for controlling an exhaust opening (25) connecting the exhaust chamber (15) to the cylinder (6), - with an inlet channel (21) that connects the inlet chamber (14) to the respective side opening (20), characterized by , - that the internal combustion engine (3) has a piston stroke adjustment (26) for changing an axial position of the bottom dead center (BDC) in the respective cylinder (6) which is configured such that the piston (9) locks the respective side opening (20) at bottom dead center (BDC) when the internal combustion engine (3) is operated in 4-stroke mode (4TBM), and opens the respective side opening (20) at bottom dead center (BDC) when the internal combustion engine (3) is operated in 2-stroke mode (2TBM). [2] Internal combustion engine (3) according to claim 1, characterized by , - that the internal combustion engine (3) is configured such that the respective inlet valve (22) can be activated and deactivated, - that the internal combustion engine (3) is configured such that the respective inlet valve (22) is activated and the respective inlet opening (23) opens and closes according to the 4-stroke operating mode (4TBM) when the internal combustion engine (3) is operated in 4-stroke operating mode (4TBM), - that the internal combustion engine (3) is configured such that the respective inlet valve (22) is deactivated and the respective inlet opening (23) is permanently blocked when the internal combustion engine (3) is operated in 2-stroke mode (2TBM). [3] Internal combustion engine (3) according to claim 1 or 2, characterized by , - that the internal combustion engine (3) has an adjustable intake camshaft (28) for actuating the respective intake valve (22), which is adjustable to a first intake camshaft position (28') for the 4-stroke operating mode (4TBM) and to a second intake camshaft position (28") for the 2-stroke operating mode (2TBM), - that the intake camshaft (28) has a cam (29) for the respective intake valve (22) which in the first intake camshaft position (28') interacts with the respective intake valve (22) and actuates it in accordance with the 4-stroke operating mode (4TBM) and which in the second intake camshaft position (28") does not interact with the respective intake valve (22) and does not actuate it in accordance with the 2-stroke operating mode (2TBM). [4] Internal combustion engine (3) according to any one of the preceding claims, characterized by , - that the internal combustion engine (3) has a crankshaft (11) connected to the respective piston (9) for drive, which is rotatably mounted on the engine block (5) about an axis of rotation (13) via crankshaft bearings (12), - that the crankshaft bearings (12) form components of the piston stroke adjustment (26) and are arranged in the engine block (5) in a manner adjustable transversely to the axis of rotation (13) with respect to the respective cylinder (6) and are adjustable at least between a first position in which the respective piston (9) at bottom dead center (BDC) blocks the respective side opening (20) and a second position in which the respective piston (9) at bottom dead center (BDC) opens the respective side opening (20), - that the piston stroke adjustment (26) for the respective crankshaft bearing (12) has an adjusting device (34) which interacts with the crankshaft bearing (12) to adjust it between the first position and the second position. [5] Internal combustion engine (3) according to claim 4, characterized by , - that the piston stroke adjustment (26) is configured such that the respective crankshaft bearing (12) is adjustable transversely to the axis of rotation (13) of the crankshaft (11) and transversely to the axial direction (X) of the respective cylinder (6) between the first position and the second position. [6] Internal combustion engine (3) according to claim 4 or 5, characterized by , - that the piston stroke adjustment (26) for the respective crankshaft bearing (12) has a return mechanism (37) that counteracts the adjusting device (34) and that works together with the crankshaft bearing (12) to adjust it between the first position and the second position, - that the actuating device (34) and the resetting device (37) are configured such that the actuating device (34) can adjust the respective crankshaft bearing (12) from an initial position formed by one of the first position and second position to an end position formed by the other of the first position and second position, while the resetting device (37) can adjust the respective crankshaft bearing (12) back from the end position to the initial position. [7] Internal combustion engine (3) according to claim 6, characterized by , - that the respective actuating device (34) is designed as a hydraulic device (38) which uses a pressurized hydraulic fluid to drive the respective crankshaft bearing (12) to adjust it from the initial position to the final position, - that the respective return device (37) is designed as a spring device (41) which is tensioned when the crankshaft bearing (12) is adjusted from the initial position to the final position and whose return force drives the crankshaft bearing (12) from the final position to the initial position. [8] Internal combustion engine (3) according to any one of the preceding claims, characterized by , - that the internal combustion engine (3) has an adjustable exhaust camshaft (30) for actuating the respective exhaust valve (24), which is adjustable to a first exhaust camshaft position (30') for the 4-stroke operating mode (4TBM) and to a second exhaust camshaft position (30") for the 2-stroke operating mode (2TBM), - that the exhaust camshaft (30) has for the respective exhaust valve (24) a first cam (31) which in the first exhaust camshaft position (30') interacts with the respective exhaust valve (24) and actuates it in accordance with the 4-stroke operating mode (4TBM), and a second cam (32) which in the second exhaust camshaft position (30") interacts with the respective exhaust valve (24) and actuates it in accordance with the 2-stroke operating mode (2TBM). [9] Internal combustion engine (3) according to any one of the preceding claims, characterized by , - that the internal combustion engine (3) has an exhaust gas turbocharger (16) which is connected to the cylinder head (7) for supplying charged fresh air to the respective intake chamber (14), and / or - that the internal combustion engine (3) has a fuel injector (49) for the respective cylinder (6) which is attached to the cylinder head (7) for injecting fuel into the cylinder (6), and / or - that the internal combustion engine (3) has an ignition device (50) for the respective cylinder (6) which is attached to the cylinder head (7) for igniting an ignitable mixture in the cylinder (6). [10] Vehicle (1), - with a chassis (2) and - with an internal combustion engine (3) according to one of the preceding claims for driving the vehicle (1), which is arranged on or in the chassis (2).

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