Internal combustion engine for a motor vehicle

Abstract

Internal combustion engine for a motor vehicle, with at least one cylinder (11), a crankshaft (12) to which at least one connecting rod (14) associated with the cylinder (11) is connected, wherein a piston (16) associated with the cylinder (11) is arranged at the end of the connecting rod (14) facing away from the crankshaft (12), an exhaust gas turbocharger (20) which has a turbocharger shaft (28) on which a compressor wheel (24) and a turbine wheel (26) are arranged non-rotatably, wherein a planetary gear (40) is interposed between the crankshaft (12) and the turbocharger shaft (28), wherein the planetary gear (40) has a ring gear (42), a sun gear (44) and several planet gears (48) rotatably mounted on a planet carrier (46), and wherein the turbocharger shaft (28) is connected to the sun gear (44), characterized by the fact that the crankshaft is connected to the ring gear (42) and the planet carrier (46) is connected to an electric motor (60).

Description

[0001] The invention relates to an internal combustion engine for a motor vehicle, comprising at least one cylinder, a crankshaft to which at least one connecting rod associated with the cylinder is connected, wherein a piston associated with the cylinder is arranged at the end of the connecting rod facing away from the crankshaft, and an exhaust gas turbocharger which has a turbocharger shaft on which a compressor wheel and a turbine wheel are arranged in a rotationally fixed manner.

[0002] Such internal combustion engines are generally known from the prior art, typically comprising several cylinders and several pistons oscillating within each cylinder, with the pistons connected to a crankshaft via connecting rods. Turbocharged internal combustion engines typically include an exhaust gas turbocharger, which comprises a turbocharger shaft, a compressor wheel attached to the turbocharger shaft, and a turbine wheel attached to the turbocharger shaft. During operation, the exhaust gas flows from the cylinders through the exhaust gas turbocharger, driving the turbine wheel. Because the compressor wheel and the turbine wheel are attached to the turbocharger shaft, the compressor wheel rotates together with the turbine wheel, compressing the air supplied to the cylinder(s).

[0003] Typically, the required boost pressure provided by the compressor wheel does not correspond to the drive power supplied by the exhaust gas mass flow around the turbine wheel. To precisely control the boost pressure, so-called exhaust gas turbochargers with a wastegate valve are used. The wastegate valve allows a portion of the exhaust gas to be selectively diverted around the turbine wheel, thereby regulating the exhaust gas mass flow around the turbine wheel and, consequently, the drive power delivered to the turbocharger shaft. A disadvantage of this is that with an open wastegate valve and a high volume of exhaust gas diverted around the turbine wheel, the temperature of the exhaust gas flowing through a catalytic converter is relatively high, which can negatively impact the catalytic converter's exhaust aftertreatment.

[0004] Alternatively, an electric motor can be mounted on the turbocharger shaft. This electric motor, connected to the turbocharger shaft, allows the shaft to be decelerated in generator mode and accelerated in driving mode. The disadvantage of this is that it requires a high-voltage system and complex control technology, which increases the weight and manufacturing and assembly costs of the combustion engine.

[0005] From WO 2009 / 014 488 A2, an internal combustion engine for a motor vehicle is known, comprising several cylinders, a crankshaft to which several connecting rods, each assigned to a cylinder, are connected, with a piston assigned to the respective cylinder being arranged at the end of the connecting rods furthest from the crankshaft. The internal combustion engine further comprises an exhaust gas turbocharger, which has a turbocharger shaft on which a compressor wheel and a turbine wheel are fixedly mounted. A planetary gear set is interposed between the crankshaft and the turbocharger shaft, the planetary gear set comprising a ring gear, a sun gear, and several planet gears rotatably mounted on a planet carrier. The turbocharger shaft is connected to the sun gear, and the crankshaft is connected to the ring gear.Furthermore, a planetary gear set is known from US 2020 / 0 182 137 A1, from US 2010 / 0 186 725 A1 and from US 5 133 188 A, which is interposed between the crankshaft and the turbocharger shaft.

[0006] The object of the invention is to provide an internal combustion engine for a motor vehicle in which the boost pressure can be adjusted in a simple, space-saving and weight-saving manner.

[0007] The problem is solved by the features of claim 1.

[0008] By interposing a planetary gear set between the crankshaft and the turbocharger shaft, wherein the planetary gear set comprises a ring gear, a sun gear, and several planet gears rotatably mounted on a planet carrier, and wherein the turbocharger shaft is connected to the sun gear, the crankshaft is connected to the ring gear, and the planet carrier is connected to an electric motor, preferably via a spur gear stage, a desired boost pressure can be set in a simple, space-saving, and weight-saving manner, and negative effects on the exhaust aftertreatment system due to the boost pressure setting can be reliably avoided. The electric motor is controlled in such a way that the speed of the turbocharger shaft can be varied depending on the speed of the electric motor.Crucially, the electric motor is not directly connected to the turbocharger shaft, but rather to the planet carrier and serves only to change the gear ratio of the planetary gear.

[0009] The gear ratio of the planetary gear can be changed by the electric motor in such a way that the turbocharger shaft is accelerated or decelerated. For this purpose, the electric motor can be operated at different speeds and in different directions of rotation.

[0010] Preferably, an externally toothed gear is formed on the planet carrier, which is operatively connected to an externally toothed gear driven by the electric motor. By forming an external tooth on the planet carrier, the spur gear stage between the electric motor and the planet carrier can be designed in a space-saving manner.

[0011] In a preferred embodiment, the electric motor is an NV electric motor, i.e., a low-voltage electric motor, which makes the electric motor small and cost-effective.

[0012] The problem is also solved by the features of claim 5.

[0013] By interposing a planetary gear set between the crankshaft and the turbocharger shaft, wherein the planetary gear set comprises a ring gear, a sun gear, and several planet gears rotatably mounted on a planet carrier, and wherein the turbocharger shaft is connected to the sun gear, the crankshaft is connected to the ring gear, and the planet carrier can be connected to the crankshaft either via a switchable clutch, for example, a multi-plate clutch, or to a switchable brake, for example, a multi-plate brake, a desired boost pressure can be set in a simple, space-saving, and weight-saving manner, and negative effects on exhaust aftertreatment due to the boost pressure setting can be reliably avoided. The rotational speed of the turbocharger shaft can be varied depending on whether the clutch or the brake is active.With the clutch engaged and the brake released, the ring gear and the planet carrier are connected to the crankshaft, transmitting torque. By strategically designing a gearbox between the clutch and the planet carrier, the direction of rotation and the gear ratio between the crankshaft and the planet carrier can be adjusted. With the brake applied and the clutch disengaged, the planet carrier is stationary.

[0014] Preferably, a gearbox is interposed between the crankshaft and the ring gear. This provides the necessary overall gear ratio between the crankshaft and the turbocharger shaft, since the turbocharger shaft rotates at a speed many times that of the crankshaft during operation. For example, the turbocharger shaft rotates at 12 times the speed of the crankshaft.

[0015] Preferably, an additional gearbox is interposed between the gearbox and the planet carrier. This allows the rotational speed of the planet carrier to be shifted within a desired speed range. Preferably, two gearbox stages are provided, which, in addition to shifting the rotational speed of the planet carrier within a desired speed range, also changes the direction of rotation of the planet carrier relative to the ring gear; that is, the planet carrier and the ring gear rotate in opposite directions during operation.

[0016] Two embodiments of the invention are explained in more detail with reference to the drawings. Fig. Figure 1 schematically shows a first design of an internal combustion engine, and Fig. Figure 2 shows a second version of an internal combustion engine.

[0017] The Fig. Figure 1 shows a first embodiment of an internal combustion engine 10, which comprises at least one cylinder 11 in which a piston 14 moves back and forth. The piston 16 is connected to a crankshaft 12 via a connecting rod 14.

[0018] The internal combustion engine 10 also includes an exhaust gas turbocharger 20. The exhaust gas turbocharger 20 comprises a housing 22 with an interior 221, a compressor wheel 24, a turbine wheel 26, and a turbocharger shaft 28. The turbocharger shaft 28 extends through the interior 221 and is rotatably mounted on the housing 22. At the two opposite ends of the turbocharger shaft 28, which protrude from the housing 22, the compressor wheel 24 and the turbine wheel 26 are fixedly attached to the turbocharger shaft 28. A flow housing (not shown) is arranged in the area of ​​the compressor wheel 24 and the turbine wheel 26, respectively. During operation of the internal combustion engine 10, the turbine wheel 26 is driven by an exhaust gas mass flow exiting the cylinder 11 and flowing through the flow housing.By coupling the turbine wheel 26 with the compressor wheel 24 via the turbocharger shaft 28, the compressor wheel 24 rotates, thereby generating a boost pressure with which the air flows into the cylinder 11.

[0019] The turbocharger shaft 28 is connected to the crankshaft 12 via a planetary gear set 40. The planetary gear set 40 comprises a ring gear 42, a sun gear 44, and several planet gears 48 rotatably mounted on a planet carrier 46. The sun gear 44 is fixedly mounted to the turbocharger shaft 28 by means of an inner circumferential surface, with an external toothing of the sun gear 44 operatively connected to the external toothing of the planet gears 48. The external toothing of the planet gears 48 is also operatively connected to an internal toothing of the ring gear 42. The planet carrier 46 is rotatably mounted on the housing 20 on both sides via two bearing elements.

[0020] The ring gear 42 also has external teeth which are operatively connected to an externally toothed gear 36. The gear 36 is rotationally fixed to an externally toothed gear 322 via a shaft projecting from the interior of the housing 221 and rotatably mounted on the housing 22. The externally toothed gear 322 is operatively connected to another externally toothed gear 321. The gear 321 is rotationally fixed to the crankshaft 12. The two gears 321 and 322 form a first spur gear stage 32, and the gear 36 and the ring gear 42 form a second spur gear stage 34.

[0021] The planet carrier 46 has external teeth which are operatively connected to an externally toothed gear 53 rotatably mounted on the housing 22. The externally toothed gear 53 is also operatively connected to another externally toothed gear 52. The planet carrier 46 and the two gears 53 and 52 form a two-stage auxiliary transmission 50. The gear 52 can be coupled to the gear 36 via a switchable clutch 54. For this purpose, the clutch 54 has a first clutch element 541, which is rotationally fixed to the gear 52, and a second clutch element 542, which is rotationally fixed to the gear 36. The clutch elements 541 and 542 are separated from each other in a disengaged state and connected to each other and rotate together in an engaged state.In the uncoupled state of the clutch 54, the planet carrier 46 is held by a switchable brake 55, the brake 55 comprising a first brake element 551 attached to the housing 22 and a brake element 552 firmly connected to the planet carrier 46.

[0022] Fig. Figure 2 shows a second version of the internal combustion engine 10. The crucial difference to the first version according to Fig. The difference is that, instead of coupling the planet carrier 46 to the crankshaft 12, an electric motor 60 is connected to the planet carrier 46, and thus the planet carrier 46 can be driven by the electric motor 60. The brake 55 is also omitted in the second embodiment according to Fig. 2. The electric motor 60 is connected to the planet carrier 46 via a gear stage 62, wherein the gear stage 62 is driven by an externally toothed gear 64 and the planet carrier 46, which is as in the first embodiment according to Fig. 1. It has an external toothing. All other components of the second version correspond to the first version.

[0023] Both designs allow for the targeted alteration of the rotational speed of the turbocharger shaft 28, thereby adjusting the boost pressure, which depends on the rotational speed of the compressor wheel 24 and thus on the rotational speed of the turbocharger shaft 28. To selectively change the rotational speed of the turbocharger shaft 28, the gear ratio of the planetary gear set 40 is altered by selectively changing the rotational speed of the planet carrier 46.

[0024] According to the first version after Fig. 1. A first gear ratio of the planetary gear 40 is present when the brake 55 is closed and the clutch 54 is open. In this state, the rotational speed of the planet carrier 46 is zero. When the brake 55 is opened and the clutch 54 is engaged, the planet carrier 46 is driven by the crankshaft 12. In this case, the planet carrier 46 rotates in the opposite direction to the ring gear 42, thereby increasing the rotational speed of the turbocharger shaft 28 compared to the state in which the planet carrier 46 is stationary due to the closed brake 55.

[0025] According to the second version after Fig. 2. The gear ratio of the planetary gear 40 can be adjusted almost arbitrarily by controlling the electric motor 60 accordingly. In this way, the electric motor 60 can be operated at different speeds and in different directions of rotation, thereby enabling the turbocharger shaft 28 to be accelerated or decelerated in a controlled manner.

Claims

[1] Internal combustion engine for a motor vehicle, with at least one cylinder (11), a crankshaft (12) to which at least one connecting rod (14) associated with the cylinder (11) is connected, wherein a piston (16) associated with the cylinder (11) is arranged at the end of the connecting rod (14) facing away from the crankshaft (12), an exhaust gas turbocharger (20) which has a turbocharger shaft (28) on which a compressor wheel (24) and a turbine wheel (26) are arranged non-rotatably, wherein a planetary gear (40) is interposed between the crankshaft (12) and the turbocharger shaft (28), wherein the planetary gear (40) has a ring gear (42), a sun gear (44) and several planet gears (48) rotatably mounted on a planet carrier (46), and wherein the turbocharger shaft (28) is connected to the sun gear (44), characterized by , that the crankshaft is connected to the ring gear (42) and the planet carrier (46) is connected to an electric motor (60). [2] Internal combustion engine according to claim 1, characterized by , that a spur gear stage (62) is interposed between the electric motor (60) and the planetary gear (40). [3] Internal combustion engine according to claim 2, characterized by , that an externally toothed gear is formed on the planet carrier (46), which is operatively connected to an externally toothed gear (64) driven by the electric motor (60). [4] Internal combustion engine according to any one of the preceding claims, characterized by , that the electric motor (60) is a low-voltage electric motor. [5] Internal combustion engine for a motor vehicle, with at least one cylinder (11), a crankshaft (12) to which at least one connecting rod (14) associated with the cylinder (11) is connected, wherein a piston (16) associated with the cylinder (11) is arranged at the end of the connecting rod (14) facing away from the crankshaft (12), an exhaust gas turbocharger (40) which has a turbocharger shaft (28) on which a compressor wheel (24) and a turbine wheel (26) are arranged non-rotatably, wherein a planetary gear (40) is interposed between the crankshaft (12) and the turbocharger shaft (28), wherein the planetary gear (40) has a ring gear (42), a sun gear (44) and several planet gears (48) rotatably mounted on a planet carrier (46), and wherein the turbocharger shaft (28) is connected to the sun gear (44), and the crankshaft (12) is connected to the ring gear (42), characterized by , that the planet carrier (46) can be connected either to the crankshaft (12) via a switchable clutch (54) or to a switchable brake (55). [6] Internal combustion engine according to any one of the preceding claims, characterized by , that a gearbox (30) is interposed between the crankshaft (12) and the ring gear (42). [7] Internal combustion engine according to claims 5 and 6, characterized by , that an additional gearbox (50) is interposed between the gearbox (30) and the planet carrier (46).

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