Planetary gears for a motor vehicle drivetrain

Abstract

Planetary gear set (10) for a motor vehicle drive train, comprising an input shaft (12) non-rotatably connected to a sun gear (14) of the planetary gear set (10), a planet carrier (16) on which a first set of first planet gears (18) is mounted, wherein the first planet gears (18) each have a first planet gear toothing with a first pitch circle diameter, a second set of second planet gears (20) on which a second set of second planet gears (20) is mounted, wherein the second planet gears (20) each have a second planet gear toothing (20a) with a second pitch circle diameter, the second pitch circle diameter being smaller than the first pitch circle diameter, and wherein a first planet gear (18) of the first set is arranged axially next to a second planet gear (20) of the second set, forming a planet gear pair and being non-rotatably connected to each other, and a first ring gear (22).which meshes with the first planet gears (18) and a second ring gear (24) which meshes with the second planet gears (20), wherein two braking devices (26, 28) are provided by means of which the first and the second ring gear (22, 24) can each be braked to a gearbox housing (32), and wherein an output shaft (30) can be driven by means of the planet carrier (16), wherein the planet gears (18, 20) are each mounted on the planet carrier (16) via external bearings (34, 36), and wherein the first and second planet gear (18, 20) of a planet gear pair are designed as separate components, wherein the planet gears (18, 20) are connected non-rotatably by means of a positive locking connection, and the positive locking connection is designed as a splined connection (38) with an external toothing (38a) on the second planet gear (20),wherein the external toothing (38a) is arranged adjacent to or at most slightly spaced apart from the second planet gear (20) in the axial direction of the second planet gear (20) and wherein the tip circle diameter (38b) of the external toothing (38a) is at least minimally smaller than the root circle diameter (20b) of the second planet gear (20a).

Description

[0001] The invention relates to a planetary gear for a drive train of a motor vehicle with the features of the preamble of claim 1.

[0002] From DE102013225519 A1 a planetary gear for motor vehicles is known with an input shaft forming a sun gear, with a planet carrier which carries a first set of planet gears, with a second set of planet gears and with two ring gears.

[0003] The invention is based on the objective of providing a compact planetary gearbox with high torque capacity.

[0004] According to the invention, the problem is solved by a planetary gear unit with the features of claim 1.

[0005] The invention relates to a planetary gear for a motor vehicle drive train, comprising an input shaft non-rotatably connected to a sun gear of the planetary gear, a planet carrier on which a first set of first planet gears is mounted, wherein the first planet gears each have a first planet gear toothing with a first pitch circle diameter, on which a second set of second planet gears is mounted, wherein the second planet gears each have a second planet gear toothing with a second pitch circle diameter, the second pitch circle diameter being smaller than the first pitch circle diameter, and wherein a first planet gear of the first set forms a planet gear pair with a second planet gear of the second set and is non-rotatably connected to each other, a first ring gear meshing with the first planet gears, and a second ring gear meshing with the second planet gears. 20) combs, wherein two braking devices are provided, by means of which the first and the second ring gear can each be braked to a gearbox housing, and wherein an output shaft can be driven by means of the planet carrier.

[0006] According to the invention, the planet gears are each mounted on the planet carrier via external bearings. Advantageously, this allows the second planet gears to have a smaller pitch circle diameter compared to planet gears mounted internally using bolts and needle bearings in prior art. Consequently, while maintaining the same diameter ratios and thus the same gear ratios of the planetary gear set, the other gears, especially the ring gears, can be made significantly smaller. This advantageously provides sufficient space in the radial direction of the planetary gear set to integrate the multi-disc brake and the positive-locking switching element radially outside and axially within a certain axial area of ​​the planetary gear set, without affecting the overall length.Within the scope of the invention, the external bearings are designed, in particular, as tapered roller bearings, angular contact ball bearings, or deep groove ball bearings, and advantageously enable good axial support within the planet carrier. This allows for an unbalanced design of the axial tooth forces in the gear design of the gears of the two gear planes, formed by the second ring gear and the second planet gears, so that the gear teeth can be designed more favorably with few compromises regarding tooth width and acoustics. The external support of the planet gears according to the invention, via external bearings with a larger diameter compared to a bearing diameter of an internal bearing on a bolt, advantageously offers a more stable base and greater robustness over the service life of the planetary gear set, and in particular greater bending stiffness against high tilting moments.A design of a generic planetary gear with an internal bearing for each planet gear pair is comparatively less stable than the planetary gear according to the invention, since the bolts for the internal bearing must be comparatively long and thin to ensure sufficiently robust support across twice the tooth width of the planet gear pair. Advantageously, the planetary gear according to the invention with external bearings for the planet gears has a higher torque capacity than a generic planetary gear with internally mounted planet gears, since the external bearings have a larger diameter and thus a greater load-bearing capacity.

[0007] In one embodiment of the invention, a common external bearing with a first bearing point and a second bearing point is provided for each pair of planetary gears.

[0008] In one embodiment of the invention, the first and second brake devices are arranged radially outside the first and second ring gears.

[0009] In one embodiment of the invention, a first planet gear of a planet gear pair is connected to a second planet gear of the same pair in a rotationally fixed manner via a positive-locking connection. In this embodiment, the first and second planet gears of a planet gear pair are designed as separate components. A conventional manufacturing-related runout of running gears such as planet gears requires a certain amount of free space in the axial direction that is not usable for the tooth widths. Advantageously, this requirement can be circumvented with this embodiment of the invention, so that the planetary gear set of this embodiment can be advantageously designed to be axially shorter.

[0010] In one embodiment of the invention, the positive-locking connection is designed as a splined connection with external teeth on the second planet gear, wherein the external teeth are arranged adjacent to or at most slightly spaced apart from the second planet gear teeth in the axial direction of the second planet gear, and wherein the tip diameter of the external teeth is at least minimally smaller than the root diameter of the second planet gear teeth. Thus, the runout of the running teeth will advantageously not affect the splined connection.

[0011] In a further embodiment of the invention, individual teeth of the splined connection are not continuous. This embodiment of the invention can advantageously serve as an assembly aid for precise angular alignment of the first and second planetary gears relative to each other.

[0012] Precise radial centering of the first and second planet gears relative to each other can advantageously be achieved either via flank centering of the splined connection, indirectly via the external bearing, or via an additional functional diameter next to the splined connection.

[0013] In one embodiment of the invention, the first planet gear and the second planet gear of a planet gear pair are designed as a single component. In other words, the first planet gear and the second planet gear of a planet gear pair are designed as a single stepped planet gear.

[0014] In one embodiment of the invention, the first bearing point of each planetary gear pair is arranged radially within the first planetary gear toothing.

[0015] In one embodiment of the invention, the first bearing point is arranged essentially axially within the first planet gear toothing. Advantageously, a planetary gear of this embodiment is not, or only slightly, longer in the axial direction compared to an internal bearing arrangement, since at least one of the two bearings can be nested axially within the larger first planet gear, provided this planet gear is sufficiently large.

[0016] In one embodiment of the invention, the second ring gear has a ring gear carrier which is made in at least two parts, wherein one carrier cup has an inner diameter that is larger than the outer diameter of the planet carrier. This embodiment of the invention advantageously allows the planetary gear to be mounted for planetary gear dimensions in which the smaller second ring gear has a smaller inner diameter than the outer diameter of the planet carrier and therefore cannot be slid over the planet carrier during assembly. In order to nevertheless enable assembly in this case, this embodiment of the invention provides for the ring gear carrier to be made in two parts.

[0017] In one embodiment of the invention, the input shaft is coupled to a rotor of an electric machine, in particular in a rotationally fixed manner. In particular, the planetary gear according to the invention can be arranged together with the electric machine in the area of ​​the rear axle or the front axle and used for driving an electric vehicle.

[0018] Further details of the invention are described in the figures with reference to schematically illustrated embodiments. List of characters Fig. 1 a schematic representation of a possible embodiment of the planetary gear according to the invention

[0019] Fig. Figure 1 shows a planetary gear 10 For the powertrain of a motor vehicle, especially an electric vehicle. The planetary gear. 10 a sun wheel 14 on, which has an input wave 12is connected in a rotationally fixed manner. The planetary gear 10 also features a planetary carrier 16 on which a set of first planetary gears 18 is mounted, with the first planetary gears 18 Each planetary gear has a first planetary gear toothing with a first pitch circle diameter. On the planet carrier 16 is further a second set of second planetary gears 20 mounted, with the second planetary gears 20 Each has a second planetary gear toothing. 20a with a second pitch circle diameter. The second pitch circle diameter of the second planet gears 20 is smaller than the first pitch circle diameter of the first planet gears 18 The second pitch circle diameter of the second planet gear teeth of the second planet gears 20 is smaller than the first pitch circle diameter of the first planet gear teeth of the first planet gears 18. Each a first planetary gear 18 of the first set of first planetary gears 18 is equipped with a second planetary gear 20 of the second set of second planetary gears 20 They are arranged axially side by side, connected to each other in a rotationally fixed manner, and form a planetary gear pair. The first planetary gears 18 combing with a first ring gear 22 The second planet gears mesh with a second ring gear. 24 The diameter of the second ring gear 24 is smaller than the diameter of the first ring gear 22 The first ring gear 22 is via a multi-disc brake system on the gearbox housing 32 lockable. The second hollow gear 24 is via a claw switching element 28 on the gearbox housing 32 Lockable. The multi-disc brake system 22 is radially outside the first ring gear 22arranged. The inner plate carrier of the multi-plate brake assembly is integral with the first ring gear. 22 trained. The hollow gear 24 features a hollow gear carrier 24a on, which is designed in two parts, and a support pot 24b with an inner diameter 24c The claw switching element features... 28 is radially outside the carrier pot 24b arranged. The planetary carrier 16 driven via a differential 29 an output shaft 30 on, which is not driven by a drive in Fig. The planetary gear is used in the motor vehicle wheel shown in section 1. 10 is via the input wave 12 with a not in Fig. The rotor of an electric motor for driving an electric or hybrid vehicle is connected to the electric motor, the 2-speed planetary gearbox 12, and the differential. 29 are advantageously combined in the gearbox housing 32arranged and form a particularly compact electric axle drive with high torque capacity.

[0020] The planetary gear pairs each consist of a first planetary gear 18 and a second planetary gear 20 are jointly provided with an external storage facility, also referred to as a first storage site. 34 and an external warehouse also referred to as a second storage site 36 stored on the planetary carrier. The storage location 34 is radially inside and essentially axially inside the first planetary gear 18 arranged. The first planetary gear in each case 18 is via a splined connection 38 with the second planetary gear in each case 20 The planetary gear pair is connected in a rotationally fixed manner. The splined connection 38 has an external toothing 38a on the second planetary gear 20 on, whereby the external teeth 38ain the axial direction of the second planetary gear 20 to the second planetary gear toothing 20a adjacent and wherein the pitch circle diameter 38b the external gearing 38a at least slightly smaller than the base circle diameter 20b the second planetary gear toothing 20a has been executed.

[0021] The hollow gear carrier is required for mounting the planetary gear. 24a The design consists of two parts, with the support pot being 24b an inner diameter 24c has which is larger than an outer diameter 16a of the planetary carrier 16 is a connector. 24d for a representation of a fixed connection between the second ring gear 24 and the carrier pot 24b of the second ring gear 24 is secured by a retaining ring 24e in the carrier pot 24b axially secured. The support cup 24b points in a pot bottom 24fa circular central opening 24g , viewed in the axial direction, on which the second ring gear 24 opposite side. The carrier pot 24b is via axial bearing 24h , 24k axially supported, wherein the axial bearing 24 k protrudes into the central opening and the axial bearing 24h at least spatially close to the central opening 24g are arranged so that the axial bearings 24h , 24k Advantageously, they have a comparatively small bearing diameter and are therefore particularly resistant to high speeds during operation of the planetary gearbox. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 102013225519 A1

[0002]

Claims

[1] Planetary gear set (10) for a drive train of a motor vehicle, comprising an input shaft (12) non-rotatably connected to a sun gear (14) of the planetary gear set (10), comprising a planet carrier (16) on which a first set of first planet gears (18) is mounted, wherein the first planet gears (18) each have a first planet gear toothing with a first pitch circle diameter, on which a second set of second planet gears (20) is mounted, wherein the second planet gears (20) each have a second planet gear toothing (20a) with a second pitch circle diameter, wherein the second pitch circle diameter is smaller than the first pitch circle diameter, and wherein a first planet gear (18) of the first set is arranged axially next to a second planet gear (20) of the second set, forming a planet gear pair and being non-rotatably connected to each other, comprising a first ring gear,(22) which meshes with the first planet gears (18) and a second ring gear, (24) which meshes with the second planet gears (20), wherein two braking devices (26, 28) are provided, by means of which the first and the second ring gear (22, 24) can each be braked to a gearbox housing (32), and wherein an output shaft (30) can be driven by means of the planet carrier (16), , characterized by , that the planet gears (18, 20) are each mounted on the planet carrier (16) via external bearings (34, 36). [2] Planetary gear according to claim 1, characterized by , that for each pair of planetary gears a common external bearing is provided with a first bearing point (34) and a second bearing point (36). [3] Planetary gear unit according to claim 1 or 2, characterized by, that the first and second planet gear (18, 20) of a planet gear pair are designed as separate components, wherein the planet gears (18, 20) are connected in a rotationally fixed manner via a positive locking connection. [4] Planetary gear according to claim 3, characterized by , that the positive locking connection is designed as a splined connection (38) with an external toothing (38a) on the second planet gear (20), wherein the external toothing (38a) is arranged adjacent to or at most slightly spaced apart from the second planet gear toothing (20a) in the axial direction of the second planet gear (20), and wherein the tip circle diameter (38b) of the external toothing (38a) is at least minimally smaller than the root circle diameter (20b) of the second planet gear toothing (20a). [5] Planetary gear set according to any of the preceding claims, characterized by, that the first bearing point (34) of each planet gear pair is arranged radially within the first planet gear toothing. [6] Planetary gear set according to any of the preceding claims, characterized by , that the first bearing point (34) is arranged substantially axially within the first planet gear toothing. [7] Planetary gear set according to any of the preceding claims, characterized by , that the second ring gear (24) has a ring gear carrier (24a) which is designed in at least two parts, wherein a carrier pot (24b) has an inner diameter (24c) which is larger than the outer diameter (16a) of the planet carrier (16). [8] Planetary gear set according to any of the preceding claims, characterized by , that the first and second brake devices (26, 28) are arranged radially outside the first and second ring gears (22, 24). [9] Planetary gear set according to any of the preceding claims, characterized by , that the input shaft (12) is coupled to a rotor of an electric machine. [10] Planetary gear set according to any of the preceding claims, characterized by , that the planetary gear (10) is designed as a 2-speed gear unit, by means of which two forward gears can be switched.

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