Gearwheel device

Abstract

Proposed is a gearwheel device having a gearwheel ring (1) and a differential cage (2), wherein: the gearwheel ring has an external toothing (4) for transmitting power and has a gearwheel ring connecting region (5); the differential cage (2), which is designed to hold differential gearwheels, has a differential cage connecting region; the gearwheel ring connecting region has a gearwheel ring centring surface, which is hollow-cylindrical at least in portions, and a gearwheel ring welding region; the differential cage connecting region has a differential cage centring surface, which is cylindrical at least in portions, and a differential cage welding region; the gearwheel ring centring surface makes contact with the differential cage centring surface and thus defines the position of the gearwheel ring relative to the differential cage with respect to a gearwheel axis of rotation (11); the gearwheel ring welding region is connected by means of a welded connection (13) to the differential cage welding region; the gearwheel ring (1) and the differential cage (2) surround a relief cavity (12); the relief cavity (12) is concentric with respect to the gearwheel axis of rotation (11) and has an annular geometry encircling said gearwheel axis of rotation (11); said welded connection (13) extends into said relief cavity (12); a relief cavity section plane extending through the gearwheel axis of rotation (11) intersects the relief cavity (12), the gearwheel ring (1) and the differential cage (2); the relief cavity (12) is represented in said relief cavity section plane by a relief cavity cross section; and the welded connection (13) enters the relief cavity cross section at the weld seam root (14). (Fig. 1) 35

Description

[0001] Gear device

[0002] From the prior art, a power transmission device with an annular gear and a hub component is known, wherein the gear is applied to this hub component and connected to it by means of a weld seam, in particular US 2022 / 0235857 A1 shows such a device, wherein the gear is designed as a so-called final drive gear in a motor vehicle drive train and the hub component as a differential carrier.

[0003] The invention is explained below using a drive gear device; this is not to be understood as a restriction of the invention to such an application. During the transmission of drive power in a motor vehicle, high loads occur; the areas of a gear that are directly involved in this power transmission, such as the toothing, are usually made of a steel material. In the case of an axle drive, this gear made of steel material is to be connected to a differential carrier, which is usually made of a cast material. A centering seat is provided to center the gear relative to the differential carrier, and a weld seam is provided for a material-to-material connection. When a weld seam is formed, stresses can arise that can have a negative impact on the service life of the drive gear device.

[0004] It is an object of the invention to provide a gear device with improved operating characteristics, this object is achieved by a gear device according to claim 1, preferred developments of the invention are the subject of the dependent claims.

[0005] For the purposes of the invention, a gear device is understood to be a device for transmitting drive power in the form of speed and torque. For this power transmission, the gear device has a gear ring with teeth that are designed to engage with at least one further toothing of another gear and to transmit the drive power with this toothing in a rolling motion. The gear device also has a differential carrier, which is designed as a hub body for this gear ring. As explained, the gear ring has external teeth for power transmission and a gear ring connecting region. The differential carrier is designed to accommodate differential gears, in particular a bevel gear differential gear set, and also has a differential carrier connecting region.The gear ring is connected to the differential carrier in the differential carrier connecting region by means of the gear ring connecting region. The gear ring connecting region has a hollow-cylindrical gear ring centering surface, at least in sections, and furthermore it also has a gear ring welding region; this welding region is preferably also designed, at least substantially, as a hollow cylinder. The differential carrier connecting region has a cylindrical differential carrier centering surface, at least in sections, which is preferably designed complementary to the gear ring centering surface. Furthermore, the differential carrier connecting region has a cylindrical differential carrier welding region, preferably at least in sections. To form the welded connection with the gear ring, this differential carrier welding region is welded to this gear ring welding region.

[0006] The gear ring is mounted on the differential carrier in such a way that the gear ring centering surface contacts the differential carrier connecting surface, thus determining the position of the gear ring relative to the differential carrier with respect to a gear rotation axis. For the purposes of the invention, this gear rotation axis is understood to be the axis around which the gear assembly rotates during normal operation. Furthermore, the gear ring is arranged at least substantially concentrically with this gear rotation axis.

[0007] The differential carrier and the gear ring are integrally connected to one another by means of a weld (gear ring weld area welded to the differential carrier weld area). The gear assembly has a cavity inside, which is partially defined by the gear ring and partially by the differential carrier, the so-called relief cavity. The gear ring and the differential carrier enclose this relief cavity. Furthermore, the relief cavity is arranged concentrically to the gear rotation axis and has an annular geometry encircling this gear rotation axis. The weld connecting the gear ring and the differential carrier extends into this relief cavity. Geometrically, the profile of the relief cavity can be described in a sectional plane, the so-called relief cavity sectional plane.The relief cavity section plane runs through the gear's rotational axis. Furthermore, the relief cavity section plane intersects the gear ring and the differential carrier, so that the relief cavity is represented by a relief cavity cross-section in this relief cavity section plane. The welded joint connecting the gear ring to the differential carrier extends, as explained, into the relief cavity, or rather, it opens into the relief cavity. In particular, in the cavity section plane where the profile of the relief cavity is visible, the welded joint opens at an imaginary point, the so-called weld root point, in the relief cavity cross-section.

[0008] It is proposed that a maximum longitudinal extent of the relief cavity cross-section, i.e. its maximum extent parallel to the gear rotation axis, is greater than a maximum vertical extent of the relief cavity cross-section, i.e. its extent orthogonal to the gear rotation axis. This vertical extent therefore represents the maximum extent of the relief cavity cross-section in the radial direction, i.e. orthogonal to the gear rotation axis. Further preferably, this maximum longitudinal extent is selected from a range which is greater than 1.05 times this maximum vertical extent and further preferably greater than 1.2 times and preferably greater than 1.5 times and further preferably this maximum longitudinal extent is less than 4 times this maximum vertical extent and preferably less than 2.5 times and preferably less than 2 times.In particular, by means of such a design of the relief cavity cross-section, low residual stresses occur due to the connection of the gear ring with the differential carrier, in particular due to the welded connection.

[0009] In a preferred embodiment, the relief cavity in the relief cavity sectional plane is defined by a line, the so-called relief cavity contour. Figuratively, the relief cavity contour in the relief cavity sectional plane encloses the relief cavity or the relief cavity cross-section, and starting from the weld root point, the relief cavity contour, or a tangent to the relief cavity contour, initially runs at least substantially orthogonal to the gear rotation axis. For the purposes of the invention, "at least substantially" means a range of inclination of the relief cavity contour relative to the orthogonal to the gear rotation axis of + / - 10 degrees to the latter, preferably a range of + / - 5 degrees, and more preferably a range of + / - 2 degrees.In particular, such a design of the relief cavity contour results in particularly low residual stresses due to the welded connection of the gear ring to the differential base body. Furthermore, the weld root point is preferably understood as a flat area of ​​the relief cavity contour.

[0010] In a preferred embodiment of the invention, the differential carrier comprises, at least as one component, a cast material, and preferably the differential carrier is made of this cast material. Such a cast material is preferably designed as spheroidal graphite cast iron, preferably as lamellar graphite cast iron or the like. Further preferably, the gear ring comprises, at least as one component, a steel material, and preferably the gear ring is made of such a steel material. Such a steel material is preferably understood to be a case-hardened steel, preferably a heat-treated steel, and more preferably a nitrided steel. In particular, with a material combination of the gear ring and the differential carrier as proposed, the proposed embodiment leads to low stresses during cooling after the gear ring has been connected to the differential carrier and is therefore particularly advantageous.

[0011] In a preferred embodiment, the welded joint between the gear ring and the differential carrier is formed as a laser welded joint. In particular, a laser welded joint generates little heat during the generation of this joint, both in the differential carrier and in the gear ring. In conjunction with the proposed design of the relief cavity, this leads to low residual stresses in the gear assembly and thus to increased operational reliability.

[0012] In a preferred embodiment, the relief cavity is fluidically connected to the environment surrounding the gear assembly by at least one circulation recess. Preferably, at least one, and preferably a plurality of, such circulation recesses extend radially inward from the relief cavity, i.e., in particular, toward the gear rotation axis. Such a circulation recess enables air exchange between the environment surrounding the gear assembly and the relief cavity. Such a circulation recess is particularly advantageous when creating the welded joint between the gear ring and the differential carrier, especially for gas removal from the relief cavity.

[0013] In the following, individual features and embodiments of the invention are explained in more detail with reference to the at least partially schematic figures, in which combinations of features other than those shown are also possible and advantageous, it shows: Fig.1: a half section of the gear device is shown,

[0014] Fig.2: a detailed sectional view of the connection of the gear ring with the differential carrier.

[0015] Figure 1 shows a half-section through a drive differential. The drive differential has a final drive gear, which is designed as a gear ring 1. This gear ring 1 engages with a motor pinion (not shown) of an electric traction machine to transmit drive power. The gear ring 1 is mounted on a hub component, which is designed as a differential carrier 2. A bevel gear differential gear set 3 is arranged in the differential carrier 2 to distribute the drive power to a left and a right drive wheel (not shown).

[0016] The gear ring 1 has external teeth 4 designed as helical gearing for power transmission with this motor pinion. The gear ring connection area 5 has a gear ring welding area 6 and a gear ring centering surface 7. The gear ring centering surface 7 is designed as a hollow cylindrical centering surface.

[0017] Furthermore, the differential carrier 2 has a differential carrier connection area 8 with the cylindrically shaped differential carrier centering surface 9. Furthermore, the differential carrier connection area 8 also has the differential carrier welding area 10. The gear ring centering surface 7 contacts the differential carrier connection surface 9, thus determining the position of the gear ring 1 relative to the differential carrier 2 with respect to the gear rotation axis 11. The gear ring welding area 6 is integrally connected to the differential carrier welding area by means of a welded joint 13.

[0018] The gear ring 1 and the differential carrier 2 enclose the relief cavity. The relief cavity is arranged concentrically to the gear rotation axis 11 and has an annular geometry surrounding the gear rotation axis 11, which is described by the relief cavity cross-section 12. The welded joint 13 extends into this relief cavity, as can be seen at the root point 14 in the relief cavity cross-section 12. In the view shown, the relief cavity cutting plane coincides with the representation plane and thus runs through the gear rotation axis 11, or the gear rotation axis 11 is part of the relief cavity cutting plane and thus also intersects the gear ring 1 and the differential carrier 2. In the representation shown in Figure 1, the relief cavity cross-section 12 can thus be seen.The maximum longitudinal extent L of the relief cavity cross-section 12, i.e. its extent parallel to the gear rotation axis 11, is greater than the maximum vertical extent H of the relief cavity cross-section 12, i.e. its extent orthogonal to the gear rotation axis 11.

[0019] The line delimiting the relief cavity cross-section 12 in the relief cavity section plane, the so-called relief cavity contour 15, initially has a course orthogonal to the gear rotation axis 11, starting from the weld root point 14. This design, in particular, results in low residual stresses due to the cooling of the weld joint 13 during its creation.

[0020] The differential carrier 2 shown in Figure 1 is made of a cast material, whereas the gear ring 1 is made of a steel material, thus achieving a material selection that is suitable for production and load-bearing capacity. The welded joint 13 between the gear ring 1 and the differential carrier 2 is created using a laser beam process, i.e., laser welding, thus making it possible to create a welded joint that runs around the gear rotation axis 11 with low heat input and high strength.

[0021] As can be seen particularly in Figure 2, the relief cavity is fluidically connected to the environment surrounding the gear device by means of several circulation recesses 16, one of which is shown. Furthermore, the course of the relief cavity contour 15, orthogonal to the gear rotation axis 11 and extending from the weld seam root point 14, is clearly visible in this illustration. The weld joint 13 is designed to extend circumferentially around the gear rotation axis 11, resulting in a weld seam root that also extends circumferentially, which is shown in the illustration plane as the weld seam root point 14. The circulation recess 16 enables air circulation between the relief cavity 12 and the environment surrounding the gear device, particularly when creating the weld joint 13. List of reference symbols:

Claims

Claims 1. A gear device comprising a gear ring (1) and a differential carrier (2), wherein the gear ring has external teeth (4) for power transmission and a gear ring connecting region (5), and wherein the differential carrier (2), which is configured to receive differential gears, has a differential carrier connecting region, wherein the gear ring connecting region has a, at least partially, hollow-cylindrical gear ring centering surface and a gear ring welding region, and wherein the differential carrier connecting region has a, at least partially, cylindrical, differential carrier centering surface and a differential carrier welding region,wherein the gear ring centering surface contacts the differential carrier centering surface and thus determines the position of the gear ring relative to the differential carrier with respect to a gear rotation axis (11), and wherein the gear ring welding area is connected to the differential carrier welding area by means of a welded connection (13), wherein the gear ring (1) and the differential carrier (2) surround a relief cavity (12), wherein the relief cavity (12) is arranged concentrically to the gear rotation axis (11) and has an annular geometry surrounding this gear rotation axis (11), and wherein this welded connection (13) extends into this relief cavity (12), wherein a relief cavity cutting plane which runs through the gear rotation axis (11),intersects the relief cavity (12) as well as the gear ring (1) and the differential carrier (2), and wherein the relief cavity (12) is depicted in this relief cavity sectional plane by a relief cavity cross-section, and wherein the welded joint (13) enters the relief cavity cross-section at the weld root point (14), characterized in that a maximum longitudinal extent (L) of the relief cavity cross-section, i.e. its extent parallel to the gear rotation axis (11), is greater than a maximum vertical extent (H) of the relief cavity cross-section, i.e. its extent orthogonal to the gear rotation axis (11).

2. Gear device according to claim 1, characterized in that a line delimiting the relief cavity (12) in the relief cavity sectional plane, starting from the weld seam root point (14), initially runs at least substantially orthogonally to the gear rotation axis (11).

3. Gear device according to one of claims 1 or 2, characterized in that the differential carrier (2), at least as one component, has a cast material and that the gear ring (1), at least as one component, has a steel material.

4. Gear device according to one of the preceding claims, characterized in that the welded joint (13) is produced by means of a laser welding process.

5. Gear device according to one of the preceding claims, characterized in that the relief cavity (12) is fluidically connected to the environment surrounding the gear device via at least one circulation recess (16).

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