Planetary friction gear for an exhaust gas turbocharger of a motor vehicle and exhaust gas turbocharger

Abstract

Planetary friction wheel transmission for an exhaust gas turbocharger (10) of a motor vehicle, comprising a sun friction wheel (22), a hollow friction wheel (26) which is flexibly designed, at least one planetary friction wheel (241, 242, 243) which is arranged between the sun friction wheel (22) and the hollow friction wheel (26), and a connecting wheel (28) for connecting the planetary friction wheel transmission (20) to another component, wherein the connecting wheel (28) is rigidly designed, is arranged on an outside of the hollow friction wheel (26) and is connected to the hollow friction wheel (26) in a torque-transmitting manner, wherein an elastic compensating element (30) is arranged radially between the hollow friction wheel (26) and the connecting wheel (28).

Description

[0001] The invention relates to a planetary friction wheel transmission for an exhaust gas turbocharger of a motor vehicle, comprising a sun friction wheel, a hollow friction wheel which is flexibly designed, at least one planetary friction wheel which is arranged between the sun friction wheel and the hollow friction wheel, wherein the hollow friction wheel radially preloads the planetary friction wheel, and a connecting wheel for connecting the planetary friction wheel transmission to another component, wherein the connecting wheel is rigidly designed, is arranged on an outside of the hollow friction wheel and is connected to the hollow friction wheel in a torque-transmitting manner.

[0002] Such planetary friction wheel transmissions are generally known from the prior art and have the advantage that high transmission ratios can be achieved in a small installation space. One such planetary friction wheel transmission is disclosed, for example, in DE 10 2006 040 020 A1. In contrast to a planetary gear transmission with gears, in which the ring gear, the sun gear, and the planet gears are each connected to one another via toothed connections, in a planetary friction wheel transmission the ring gear, the planetary friction gears, and the sun gear each have a smooth circumferential surface. The planetary friction gears bear against the smooth circumferential surfaces of the ring gear and the sun gear via their smooth circumferential surfaces, with power transmission occurring through friction between the circumferential surfaces of the planetary friction gears and the ring gear or the sun gear.The frictional force between the circumferential surfaces depends on the coefficient of friction and the normal force, i.e., the force with which the two components are pressed against each other. In the present planetary friction wheel drive, the normal force between the hollow friction wheel and the planet gears, as well as between the sun wheel and the planet gears, is generated by the flexible hollow friction wheel. During assembly, the hollow friction wheel is deformed in such a way that a surface pressure exists between the planet gears and the hollow friction wheel itself, and between the planet gears and the sun wheel. The hollow friction wheel must remain permanently flexible to ensure sufficient surface pressure and thus a corresponding frictional force at all times, even with manufacturing tolerances and / or component wear.The hollow friction wheel is connected via its outer circumferential surface to a rigid connecting wheel for coupling with another component in a torque-transmitting manner, whereby the connecting wheel can serve as a drive or as a driven element.

[0003] The problem here is the coupling between the rigid connecting wheel and the hollow friction wheel, whereby the hollow friction wheel should permanently be in a flexible state, while the connecting wheel arranged on the outer circumferential surface of the hollow friction wheel is rigid and influences the flexible state of the hollow friction wheel.

[0004] A planetary friction wheel transmission for an exhaust gas turbocharger of a motor vehicle is also known from DE 10 2022 106 231 A1. The planetary friction wheel transmission comprises a hollow friction wheel and a rigid connecting wheel connected to the hollow friction wheel, wherein the hollow friction wheel is mounted and loaded by a preload element in such a way that a preload is caused in the planetary friction wheel transmission.

[0005] Furthermore, DE 11 2011 104 534 T5 discloses a planetary friction wheel transmission for an exhaust gas turbocharger of a motor vehicle, wherein a special clamping system is provided for clamping the planetary friction wheel transmission.

[0006] The object of the invention is to provide a planetary friction wheel transmission in which the rigid connecting wheel and the flexible hollow friction wheel can be connected to each other in a simple and cost-effective manner to transmit torque, and the functioning of the planetary friction wheel transmission is not adversely affected by the connection between the flexible hollow friction wheel and the connecting wheel.

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

[0008] According to the invention, an elastic compensating element is arranged radially between the hollow friction wheel and the connecting wheel, which is preferably a belt pulley, a gear, or a sprocket. The elastic compensating element is annular and fills a circumferential gap between an inner circumferential surface of the connecting wheel and the outer circumferential surface of the hollow friction wheel. The elastic compensating element connects the hollow friction wheel and the connecting wheel, and its elastic deformability allows the flexible hollow friction wheel to deform despite the rigid connecting wheel. The elastic compensating element is connected to the hollow friction wheel and the connecting wheel by frictional, positive, and / or material bonding, thereby transmitting torque from the hollow friction wheel to the connecting wheel via the elastic compensating element.

[0009] This allows for a certain degree of deformation of the flexible hollow friction wheel in a simple and cost-effective manner, despite the connection between the flexible hollow friction wheel and the rigid connecting wheel, thus ensuring the functionality of the planetary friction wheel drive.

[0010] Preferably, the flexible hollow friction wheel is made from a metal sheet, in particular a steel sheet. This allows the flexible hollow friction wheel to be manufactured simply and cost-effectively.

[0011] In a preferred embodiment, the connecting gear is axially force-balanced. In other words, no net axial forces result from the coupling of the connecting gear with an associated component, particularly a gear, which must be supported by the planetary friction wheel drive and transmitted through the connection between the connecting gear and the hollow friction wheel. On the one hand, the teeth of a connecting gear designed as a gear or pulley can be straight-cut, thus eliminating axial forces. On the other hand, the connecting gear can be helical-cut. In this case, the teeth are designed such that the axial forces generated by the helical gearing are balanced. An example of this is a so-called herringbone gear.Because the connecting wheel is axially force-balanced, the transmission of axial forces via the compensating element is prevented. This prevents the deformation of the flexible hollow friction wheel, enabled by the compensating element, from being negatively affected.

[0012] Preferably, the elastic compensating element is made of plastic, in particular of an elastomer, which makes the compensating element easy and inexpensive to manufacture.

[0013] In a preferred embodiment, the elastic compensating element is bonded to the hollow friction wheel and / or the connecting wheel. This ensures a reliable connection between the compensating element and the hollow friction wheel and / or connecting wheel. Furthermore, no additional measures are required to axially fix the compensating element between the hollow friction wheel and the connecting wheel. Preferably, the elastic compensating element is vulcanized to the hollow friction wheel and / or the connecting wheel. Alternatively, the compensating element could be bonded to the hollow friction wheel and / or the connecting wheel.

[0014] The invention is further solved by an exhaust gas turbocharger comprising a turbine wheel, a compressor wheel (the turbine wheel and the compressor wheel being fixedly arranged on a turbocharger shaft), and a planetary friction drive according to any one of claims 1 to 7 (the planetary friction drive being torque-transmitting to the turbocharger shaft). Typically, a housing is provided in which the turbocharger shaft is rotatably mounted and which defines an air space in which the compressor wheel is arranged and an exhaust gas space in which the turbine wheel is arranged. For the advantages, reference is made to the preceding paragraphs.

[0015] An embodiment of the invention is explained in more detail with reference to the drawing. Fig. Figure 1 shows an exhaust gas turbocharger with a planetary friction drive in a perspective view, and Fig. 2 shows the planetary friction wheel gear from Fig. 1 in cross-section.

[0016] The Fig. Figure 1 shows an exhaust gas turbocharger 10, which is used together with an internal combustion engine in a motor vehicle.

[0017] The exhaust gas turbocharger 10 comprises a turbine wheel 12 and a compressor wheel 14, which are arranged non-rotatably on a turbocharger shaft 16. The exhaust gas turbocharger 10 also typically includes a housing, which is located in the Fig.Figure 1 (not shown) shows the housing in which the turbine wheel 12 and the compressor wheel 14 are arranged, with the turbocharger shaft 16 rotatably mounted on the housing. During operation of the exhaust gas turbocharger 10, and thus during operation of the internal combustion engine, the exhaust gas flows from the combustion chambers of the internal combustion engine to the exhaust gas turbocharger 10 and flows around the turbine wheel 12. The flow around the turbine wheel 12 drives the turbine wheel 12, causing the turbocharger shaft 16 to rotate together with the turbine wheel 12. Because the compressor wheel 14 is fixed to the turbocharger shaft 16, it rotates with the turbocharger shaft 16 and the turbine wheel 12. Through its rotation, the compressor wheel 14 compresses the air flowing into the combustion chambers of the internal combustion engine, which is required for the combustion process in the combustion chambers.

[0018] The exhaust gas turbocharger 10 also has a planetary friction wheel transmission 20, via which the turbocharger shaft 16 is connected to another component of the motor vehicle, for example a crankshaft of the internal combustion engine.

[0019] The planetary friction drive 20 comprises a sun wheel 22, several planetary friction wheels 241, 242, 243, a planet carrier 25 supporting the planetary friction wheels 241, 242, 243, and a hollow friction wheel 26. The sun wheel 22 is rotationally fixed to the turbocharger shaft 16 or is formed by the turbocharger shaft 16. The planetary friction wheels 241, 242, 243 are rotatably mounted on the planet carrier 25, which is rotatably mounted on the housing, allowing the rotational speed of the planet carrier 25 to be changed and thereby the gear ratio of the planetary friction drive 20 to be changed. For example, the planet carrier 25 can be coupled to an electric motor (not shown), allowing the gear ratio of the planetary friction drive 20 to be adjusted depending on the rotational speed of the electric motor.The hollow friction wheel 26 has an inner circumferential surface against which the planetary friction wheels 241, 242, 243 bear, the planetary friction wheels 241, 242, 243 also bearing against the sun friction wheel 22. The sun friction wheel 22, the planetary friction wheels 241, 242, 243 and the inner circumferential surface of the hollow friction wheel 26 each have a cylindrical friction surface, so that the torque transmission between the planetary friction wheels 241, 242, 243 and the sun friction wheel 22 as well as the hollow friction wheel 26 is force-fit and thus occurs by friction.

[0020] To provide sufficient normal forces for friction between the planetary friction wheels 241, 242, 243 and the sun friction wheel 22, as well as the hollow friction wheel 26, the hollow friction wheel 26 is flexible, in particular made of a metal sheet, and is pre-tensioned in the assembled state. This causes the hollow friction wheel 26 to press against the planetary friction wheels 241, 242, 243 in such a way that a pressure is exerted between the hollow friction wheel 26 and the planetary friction wheels 241, 242, 243, as well as between the planetary friction wheels 241, 242, 243 and the sun friction wheel 22.

[0021] A connecting gear 28 is arranged on the outside of the hollow friction wheel 26. This connecting gear is rigidly mounted and torque-transmitting to the hollow friction wheel 26. The connecting gear 28 has an arrow-shaped toothing 29, through which it is operatively connected to another driving component, for example, the crankshaft of the internal combustion engine. The arrow-shaped toothing 29 provides axial force balancing for the connecting gear. Alternatively, the connecting gear 28 could be designed as a belt pulley or a sprocket.

[0022] An elastic compensating element 30, made of plastic, is arranged between the hollow friction wheel 26 and the connecting wheel 28. This compensating element is bonded to the outer surface of the hollow friction wheel 26, in particular by vulcanization. The connecting wheel 28 is force-fitted to the compensating element 30, thereby transmitting torque.

[0023] The elastic compensating element 30 arranged between the hollow friction wheel 26 and the connecting wheel 28 allows a certain degree of deformability of the flexible hollow friction wheel 26 in a simple and cost-effective manner, despite the connection between the hollow friction wheel 26 and the connecting wheel 28, thereby ensuring the proper functioning of the planetary friction wheel drive 20.

Claims

[1] Planetary friction wheel drive for an exhaust gas turbocharger (10) of a motor vehicle, with a solar friction wheel (22), a hollow friction wheel (26) which is flexibly designed, at least one planetary friction wheel (241, 242, 243) which is arranged between the solar friction wheel (22) and the hollow friction wheel (26), and a connecting wheel (28) for connecting the planetary friction wheel drive (20) to another component, wherein the connecting wheel (28) is rigidly designed, is arranged on an outside of the hollow friction wheel (26) and is connected to the hollow friction wheel (26) in a torque-transmitting manner, characterized by , that The hollow friction wheel (26) is deformed during assembly in such a way that a surface pressure exists between the planetary friction wheel (241, 242, 243) and the hollow friction wheel (26) itself and between the planetary friction wheels (241, 242, 243) and the sun friction wheel (22), wherein an elastic compensating element (30) is arranged radially between the hollow friction wheel (26) and the connecting wheel (28). [2] Planetary friction wheel gear according to claim 1, characterized by , that the flexible hollow friction wheel (26) is made of a metal sheet. [3] Planetary friction wheel drive according to claim 1 or 2, characterized by , that the connecting wheel (28) is a belt pulley, a gear or a sprocket. [4] Planetary friction wheel gear according to claim 3, characterized by , that the connecting wheel (28) is designed to be force-balanced in the axial direction. [5] Planetary friction wheel gear according to any one of the preceding claims, characterized by, that the elastic compensating element (30) is made of plastic. [6] Planetary friction wheel gear according to any one of the preceding claims, characterized by , that the elastic compensating element (30) is materially bonded to the hollow friction wheel (26) and / or to the connecting wheel (28). [7] Planetary friction wheel gear according to claim 6, characterized by , that the elastic compensating element (30) is vulcanized to the hollow friction wheel (26) and / or the connecting wheel (28). [8] Exhaust gas turbocharger with a turbine wheel (12), a compressor wheel (14), wherein the turbine wheel (12) and the compressor wheel (14) are fixedly arranged on a turbocharger shaft (16), and a planetary friction wheel transmission (20) according to one of claims 1 to 7, wherein the planetary friction wheel transmission (20) is connected to the turbocharger shaft (16) in a torque-transmitting manner.

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