Gear mechanism

Abstract

[Gear device with a gear ring (1) and a differential cage (2), wherein the gear ring has an external toothing (4) for power transmission and a gear ring connecting region (5), and wherein the differential carrier (2), which is adapted to receive differential gears, has a differential carrier connection area, 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 connection area has a, at least partially, cylindrical, differential carrier centering surface and a differential carrier welding area, 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 cage welding area by means of a welded joint (13), wherein the gear ring (1) and the differential cage (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 joint (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 cutting plane by a relief cavity cross-section, and wherein the weld joint (13) enters the relief cavity cross-section at the weld root point (14).

Description

The prior art discloses a power transmission device having an annular gearwheel and a hub component, wherein the gearwheel is applied to this hub component and is connected thereto by means of a weld seam, in particular US 2022 / 0235857 A1 shows such a device, wherein the gearwheel is designed as a so-called final drive gearwheel in a motor vehicle drive train and the hub component is designed as a differential cage.The invention is explained below with reference to a drive transmission device; this is not to be understood as a restriction of the invention to such an application. In the power transmission of drive power, high loads occur in a motor vehicle, and the regions of a gearwheel which are directly involved in this power transmission, such as the toothing, are usually manufactured from a steel material. In the case of an axle transmission, this gear wheel consisting of steel material is to be connected to a differential cage, which usually consists of a cast material. A centering seat is provided for centering the gearwheel with respect to the differential cage, and a welded seam is provided for the materially bonded connection. When forming a weld seam, stresses may occur which may have a negative influence on the service life of the drive transmission device.It is an object of the invention to specify a gearwheel device having improved operating characteristics, this object being achieved by a gearwheel device according to patent claim 1, preferred developments of the invention being the subject matter of the dependent claims.Within the meaning of the invention, a gear mechanism is understood to mean a mechanism for transmitting drive power in the form of rotational speed and torque. For this power transmission, the gear device has a gear ring with a toothing which is configured to be in engagement with at least one further toothing of a further gear and to transmit the drive power with it in a rolling movement. Furthermore, the gear device has a differential cage which is designed as a hub body for this gear ring.As stated, the gear ring has external teeth for power transmission and further a gear ring connection region. The differential carrier is configured to receive differential gears, in particular a conical differential gearset, and further has a differential carrier connecting region. The gear ring is connected by means of the gear ring connecting region to the differential cage in the differential cage 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; preferably this welding region is also, at least substantially, of hollow cylindrical configuration. The differential cage connecting region has a cylindrical differential cage centring surface, at least in sections, which is preferably designed to be complementary to the toothed wheel ring centring surface. Furthermore, the differential cage connecting region has a preferably at least sectionally cylindrical differential cage welding region. To form the welded connection to the gear ring, this differential cage welded region is welded to this gear ring welded region.The gear ring is accommodated on the differential carrier in such a way that the gear ring centering surface contacts the differential carrier connecting surface and the position of the gear ring relative to the differential carrier is thus fixed with respect to a gear rotation axis. For the purposes of the invention, this gear wheel axis of rotation is to be understood as meaning the axis about which the gear wheel device rotates in the planned operation. Furthermore, this gear ring is arranged at least substantially concentrically to this gear rotation axis.The differential cage and the gear ring are connected to one another by means of the welded connection in a materially integral manner (gear ring welded region welded to differential cage welded region). The gearwheel device has in the interior a cavity which is partly bounded by the gearwheel ring and partly by the differential cage, known as the relief cavity. This relief cavity is thus enclosed by the toothed ring and the differential cage. Furthermore, the relief cavity is arranged concentrically to the gear wheel axis of rotation and has an annular geometry encircling this gear wheel axis of rotation. The welded connection, by means of which the gear ring and the differential cage are connected to one another, extends into this relief cavity.Geometrically, the profile of the relief cavity can be described in a sectional plane, so-called relief cavity sectional plane. The relief cavity cutting plane passes through the gear axis of rotation. Furthermore, the relief cavity sectional plane intersects the gear ring and the differential carrier, so that the relief cavity in this relief cavity sectional plane is depicted by a relief cavity cross section. As explained, the welded connection for connecting the gear ring to the differential cage extends into the relief cavity or opens into the relief cavity, in particular in the cavity sectional plane in which the profile of the relief cavity can be seen, the welded connection opens at an imaginary point, so-called weld seam root point, in the relief cavity cross section.It is proposed that a maximum longitudinal extent of the relief cavity cross section, i.e. its maximum extent parallel to the gearwheel axis of rotation, is greater than a maximum height extent of the relief cavity cross section, i.e. its extent orthogonal to the gearwheel axis of rotation. This height extension accordingly represents the maximum extension of the relief cavity cross section in the radial direction, i.e. orthogonally to the gear wheel axis of rotation. Further preferably, this maximum longitudinal extension is selected from a range which is greater than 1.05 times this maximum height extension and further preferably greater than 1.2 times and preferably greater than 1.5 times and further preferably this maximum longitudinal extension is less than 4 times this maximum height extension and preferably less than 2.5 times and preferably less than 2 times. In particular by means of such a configuration of the relief cavity cross section, low internal stresses occur as a result of the connection of the gearwheel ring to the differential cage, in particular as a result of the welded connection.In a preferred embodiment, the relief cavity in the relief cavity sectional plane delimits a line, 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 seam root point, the relief cavity contour or a tangent to the relief cavity contour runs initially, at least substantially, orthogonally to the gear wheel axis of rotation. For the purposes of the invention, at least substantially means a range of the inclination of the relief cavity contour with respect to the orthogonal to the gear rotation axis of + / - 10 degrees with respect thereto, preferably a range of + / - 5 degrees and preferably a range of + / - 2 degrees. In particular, by virtue of such a configuration of the relief cavity contour, particularly low internal stresses result from the connection of the gearwheel ring to the differential main body by the welded connection. Further preferably, the weld root point is to be understood as a planar region of the relief cavity contour.In a preferred embodiment of the invention, the differential cage has, at least as one component, a casting material and the differential cage preferably consists of this casting material. Preferably, such a casting material is configured as a spheroidal graphite casting, preferably as a lamellar graphite casting or the like. Further preferably, the gear ring comprises, at least as one component, a steel material, preferably the gear ring consists of such a steel material. Such a steel material is preferably to be understood as a case-hardened steel, preferably a tempered steel and further preferably a nitrided steel. In particular in the case of a material combination of the gearwheel ring with the differential carrier, as is proposed, the proposed embodiment leads to low stresses during cooling after the connection of the gearwheel ring with the differential carrier and is therefore particularly advantageous.In a preferred embodiment, the welded connection between the gear ring and the differential cage is designed as a laser welded connection. In particular by means of a laser weld connection, when this little heat is generated, it is introduced both into the differential cage and into the gearwheel ring and this leads, in conjunction with the proposed configuration of the relief cavity, to low internal stresses of the gearwheel device and thus to increased operating reliability.In a preferred embodiment, the relief cavity is connected in a fluid-conducting manner to the environment surrounding the gearwheel device by at least one circulation recess. Preferably, at least one, preferably a plurality, of such circulation recesses extends radially inward, i.e. in particular in the direction of the gear wheel axis of rotation, starting from the relief cavity. Such a circulation recess enables air to be exchanged between the environment surrounding the gear device and the relief cavity. In particular when producing the welded connection between the toothed wheel ring and the differential cage, such a circulation recess is advantageous, in particular for the gas discharge from the relief cavity.Individual features and embodiments of the invention are explained in more detail below with reference to the at least partially schematic figures, wherein combinations of features other than those shown are also possible and advantageous, and it shows: FIG. 1 is a half section of the gear device, FIG. 2 : a detailed sectional illustration of the connection of the toothed wheel ring to the differential cage.FIG. 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 is engaged with a motor pinion (not shown) of an electric traction machine for transmitting drive power. The toothed ring 1 is accommodated on a hub component which is designed as a differential cage 2. In the differential carrier 2, a bevel gear differential gearset 3 is installed for distributing the driving power to left and right driving wheels (not shown).The toothed ring 1 has an external toothing 4 designed as helical toothing for power transmission with this motor pinion. The ring gear connecting portion 5 has a ring gear welding portion 6 and a ring gear centering surface 7. The toothed ring centering surface 7 is designed as a hollow cylindrical centering surface.Furthermore, the differential cage 2 has a differential cage connecting region 8 with the cylindrical differential cage centring surface 9. Furthermore, the differential cage connecting region 8 also has the differential cage welding region 10. The gear ring centering surface 7 contacts the differential carrier connecting surface 9, and thus the position of the gear ring 1 relative to the differential carrier 2 is fixed with respect to the gear rotation axis 11. The gear ring welding region 6 is connected to the differential cage welding region in a materially integral manner by means of a welded connection 13.The gear ring 1 and the differential cage 2 enclose the relief cavity, wherein the relief cavity is arranged concentrically to the gear rotation axis 11 and has an annular geometry which extends around the gear rotation axis 11 and is described by the relief cavity cross section 12. The welded connection 13 extends into this relief cavity; this can be seen at the root point 14 in the relief cavity cross section 12. In the view shown, the relief cavity sectional plane coincides with the representation plane and thus extends through the gearwheel rotational axis 11 or the gearwheel rotational axis 11 is a component of the relief cavity sectional plane and thus also intersects the gearwheel ring 1 and the differential cage 2.The maximum longitudinal extension L of the relief cavity cross section 12, i.e. its extension parallel to the gear wheel axis of rotation 11, is greater than the maximum height extension H of the relief cavity cross section 12, i.e. its extension orthogonal to the gear wheel axis of rotation 11.The line delimiting the relief cavity cross section 12 in the relief cavity cutting plane, so-called relief cavity contour 15, starting from the weld seam root point 14, initially has a course orthogonal to the gear wheel axis of rotation 11. In particular, due to this configuration, low internal stresses occur as a result of the cooling of the welded connection 13 during the production thereof.The differential cage 2 shown in FIG. 1 consists of a cast material, whereas the toothed wheel ring 1 consists of a steel material, and a material selection appropriate for production and loading is thus achieved. The welded connection 13 between the toothed wheel ring 1 and the differential cage 2 is produced by a laser beam method, i.e. by laser welding, and it is thus possible to produce a welded connection which runs around the toothed wheel rotational axis 11 and has a low heat input and a high strength.As can be seen in particular in FIG. 2, the relief cavity is connected in a fluid-conducting manner to the environment surrounding the gearwheel device by a plurality of circulation recesses 16, one of which is illustrated. Furthermore, in this illustration, the course of the relief cavity contour 15 which is orthogonal to the gear wheel axis of rotation 11 starting from the weld seam root point 14 can be clearly seen. The welded connection 13 is designed to be encircling about the gearwheel axis of rotation 11, so that a likewise encircling weld seam root is produced, which is illustrated in the illustration plane as a weld seam root point 14. The circulation recess 16 allows air circulation of the relief cavity 12 with the environment surrounding the gear device, in particular when establishing the welded connection 13.List of reference numbers:1 Gear ring 2 Differential cage 3 Bevel gear differential gearset 4 External toothing 5 Gear ring connecting region 6 Gear ring welding region 7 Gear ring centering surface 8 Differential cage connecting region 9 Differential cage centering surface 10 Differential cage welding region 11 Gear rotation axis 12 Relief cavity 13 Welding connection between 1 and 2 14 Weld seam root point 15 Relief cavity contour 16 Circulation recess L Maximum extension of 12 in the direction of 11 H Maximum extension of 12 in the orthogonal direction of 11References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedUS 2022 / 0235857 A1

[0001]

Claims

Gear device with a gear ring (1) and a differential cage (2), wherein the gear ring has an external toothing (4) for power transmission and a gear ring connecting region (5), and wherein the differential cage (2), which is configured to accommodate differential gears, has a differential cage connecting region, wherein the gear ring connecting region has a hollow cylindrical gear ring centring surface, at least in sections, and a gear ring welding region, and wherein the differential cage connecting region has a cylindrical differential cage centring surface, at least in sections, and a differential cage welding region, wherein said ring gear centering surface contacts the differential cage centering surface and thus fixes the position of the ring gear relative to the differential cage with respect to a gear wheel axis of rotation (11), and wherein the ring gear welding region is connected to the differential cage welding region by means of a welded connection (13), wherein the ring gear (1) and the differential cage (2) surround a relief cavity (12), wherein the relief cavity (12) is arranged concentrically with respect to the gear wheel axis of rotation (11) and has an annular geometry encircling said gear wheel axis of rotation (11), and wherein said welded connection (13) extends as far as into said relief cavity (12), wherein a relief cavity cutting plane which extends through the gear wheel axis of rotation (11), Cutting through the relief cavity (12) and the toothed ring (1) and the differential cage (2), and wherein the relief cavity (12) is depicted in this relief cavity cutting plane by a relief cavity cross section, and wherein the welded connection (13) enters the relief cavity cross section at the welded seam root point (14), characterized in that a maximum longitudinal extent (L) of the relief cavity cross section, i.e. its extent parallel to the toothed wheel rotation axis (11), is greater than a maximum vertical extent (H) of the relief cavity cross section, i.e. its extent orthogonal to the toothed wheel rotation axis (11).Gear device according to Claim 1, characterized in that a line delimiting the relief cavity (12) in the relief cavity section plane, starting from the weld seam root point (14), initially runs at least substantially orthogonally to the gear wheel axis of rotation (11).Gear device according to one of Claims 1 or 2, characterized in that the differential cage (2) has, at least as one constituent, a casting material, and in that the gear ring (1), at least as one constituent, has a steel material.Gear device according to one of the preceding claims, characterized in that the welded connection (13) is produced by means of a laser welding method.Gear device according to one of the preceding claims, characterized in that the relief cavity (12) is connected in a fluid-conducting manner to the environment surrounding the gear device by at least one circulation recess (16).

Images