Differential transmission for motor vehicles

Abstract

The present invention relates to a differential transmission mechanism (10), which comprises a rotatably supported differential housing (12) and an axle drive gear (14) which cannot rotate relative to the differential housing (12). The present invention is characterized in that the differential housing (12) has two mating surfaces on its outer peripheral surface, and the axle drive gear (14) has two radially opposite mating surfaces on its inner peripheral surface, and the mating surfaces formed on the outer peripheral surface of the differential housing (12) and the mating surfaces formed on the inner peripheral surface of the axle drive gear (14) are respectively designed as mating surfaces separated in an axial direction (a) and spaced apart from each other by a distance (A) in terms of geometric structure, and the axle drive gear (14) is pressed onto the differential housing (12), so that the axle drive gear (14) and the differential housing (12) are connected to each other by means of a first press-fit portion (22-1) and a second press-fit portion (22-2) separated from the first press-fit portion and spaced apart by a distance (A) in the axial direction.

Description

Technical Field

[0001] The invention relates to a differential transmission for a motor vehicle of the type specified in the preamble of claim 1 . Background Art

[0002] Differential transmissions and different solutions for supporting the axle drive gear on the differential housing are well known from the prior art. See, for example, EP 2 740 562 B1, DE 10 2017 006 417 A1 and DE 102016 218 087 A1. In particular, axial forces introduced via the toothing of the axle drive gear can lead to "tipping" and thus to a change in position of the toothing, which in turn leads to a more unfavorable tooth contact and thus to an uneven transmission of motion (speed, torque). The uneven transmission of motion leads to abnormal sounds, which in turn can cause vehicle defects. In particular, in the case of new vehicle concepts with electric drives, the impact of these acoustic defects is increasing. Summary of the invention

[0003] The object of the present invention is to improve a differential gear of the type specified in the preamble of claim 1 in order to prevent undesired changes in the tooth position and thus reduce the risk of acoustic disturbances occurring during operation.

[0004] This object is achieved by the characterizing features of claim 1 in combination with the features of its preamble.

[0005] The dependent claims form advantageous developments of the invention.

[0006] In a known manner, the differential gear comprises a rotatably mounted differential housing and an axle gear with external toothing, which is mounted in a rotationally fixed manner on the differential housing and which in turn meshes with an associated drive shaft via its external toothing and is driven.

[0007] According to the invention, the differential housing has two mating surfaces on its outer circumference, and the axle drive gear has two corresponding mating surfaces on its inner circumference, which are diametrically opposed (to the mating surfaces of the differential housing). It should be pointed out only for the sake of completeness that the mating surfaces formed on the differential housing and on the axle drive gear are designed as circumferential mating surfaces. Furthermore, according to the invention, it is provided that the mating surfaces formed on the outer circumference of the differential housing and the mating surfaces formed on the inner circumference of the axle drive gear are designed as mating surfaces separated in the axial direction and spaced apart from each other by a distance A in terms of geometric construction, and the axle drive gear is pressed onto the differential housing, so that the axle drive gear and the differential housing are connected to each other by means of a first press fit and a second press fit separated from the first press fit and spaced apart in the axial direction by a distance A.

[0008] The design according to the invention has the effect that a support having a very strong anti-tilting effect is provided due to two separate press fits that are axially spaced apart by a distance A. This advantageously ensures that all forces caused by the toothing can be absorbed by means of the anti-tilting support according to the invention. The tilting gradient is thus significantly reduced, as a result of which an optimal tooth contact and thus a uniform transmission of motion that does not cause undesirable interfering noises is ensured.

[0009] Preferably, in the axial direction, the mating surfaces formed on the outer circumference of the differential housing and the mating surfaces formed on the inner circumference of the axle drive gear are each separated from one another by a circumferential groove machined into the respective circumference, wherein the grooves each have a length in the axial direction that is equal to the distance A. The grooves ensure an effective geometric separation of the mating surfaces and thus of the press fit that can be easily produced. A further advantage is that the material removal caused by the grooves has a favorable effect on the weight of the component, so that a particularly weight-optimized design can be achieved. By appropriately dimensioning the groove depth, the material removal and thus the weight saving can be influenced in a simple manner.

[0010] In this case, the groove preferably has a rectangular, triangular or semicircular basic shape.

[0011] In order to ensure sufficient support to prevent tilting, the distance A between the mating surfaces should be as large as possible. First attempts have shown that the desired effect, namely the support to prevent tilting, is ensured in the following cases:

[0012] 0.5≤A / L≤0.7

[0013] Wherein, L represents the axial length of the inner peripheral surface of the axle transmission gear in the axial direction.

[0014] The first embodiment of the differential gear according to the invention is characterized in that the two press fits have a small radial interference / radial overlap of 10 μm to 50 μm, and an additional material-locked connection or a form-locked connection is provided between the axle drive gear and the differential housing. In this embodiment, it is advantageous that the two components can be joined simply due to the relatively small radial interference and that—due to the additional material-locked or form-locked connection—a high torque transmission is ensured.

[0015] According to a first embodiment, the additional connection is designed as a welded connection. In addition to rapid, simple and therefore cost-effective production, it is ensured that no further axial fastening is required.

[0016] In order to additionally save component weight, the welded connection is preferably designed as a one-sided circumferential weld seam which is arranged only in the region of the first press fit or only in the region of the second press fit.

[0017] Preferably, the welded connection is produced by means of electro-welding or laser welding.

[0018] According to a second design of the first embodiment, the additional connection is designed in the form of a polygonal tooth structure or a key joint (spline connection or flat key connection), wherein a fixing element is arranged between the axle drive gear and the differential housing to prevent relative movement in the axial direction. The advantage of the second design is that due to the form-locking connection, the second design has a lower component weight than the first design.

[0019] In this case, the fixing element is preferably designed in the form of a fixing ring, in particular in the form of a wedge-shaped fixing ring.

[0020] The second alternative embodiment of the tooth support according to the invention is characterized in that the two press fits have a radial interference fit of more than 200 μm and the axle drive gear is connected to the differential housing in a rotationally fixed and axially fixed manner solely via the force-locking connection produced by the two press fits. This advantageously provides a particularly weight-optimized design.

[0021] Preferably, the differential housing is made of cast iron and the axle drive gears are made of a hardenable material. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Further advantages and application possibilities of the invention emerge from the following description in conjunction with the exemplary embodiments shown in the drawings.

[0023] The figure shows:

[0024] Figure 1 A cross-sectional view showing a first embodiment of a differential transmission mechanism according to the present invention;

[0025] Figure 2 Shown in top view Figure 1 The differential transmission mechanism in the

[0026] Figure 3 A second embodiment of the differential transmission mechanism is shown in cross section;

[0027] Figure 4 Shown in top view Figure 3 The differential transmission mechanism in the

[0028] Figure 5 A cross-sectional view showing a third embodiment of the differential transmission mechanism according to the present invention;

[0029] Figure 6 Shown in top view Figure 5 Differential transmission mechanism. DETAILED DESCRIPTION

[0030] In the following description and drawings, in order to avoid repetition, identical components and parts are denoted by the same reference numerals, as long as no further distinction is necessary or as long as it is reasonable.

[0031] Figure 1 and Figure 2 A first specific embodiment of a differential gear of a motor vehicle is shown, which is designated as a whole by the reference numeral 10 .

[0032] The differential gear 10 comprises a differential housing 12 and an axle gear 14 which is connected in a rotationally fixed manner to the differential housing 12. The axle gear 14 is operatively connected via its external toothing 14-1 to a drive shaft which is not shown here for the sake of clarity.

[0033] The differential housing 12 drives four planetary gears 18 via a cross-shaft 16 , which in turn mesh with two driven wheels 20 , which can be connected in a rotationally fixed manner to half shafts (not shown here for the sake of clarity).

[0034] like Figure 1 and Figure 2 As shown, the differential housing 12 has two mating surfaces on its outer circumference, and the axle drive gear 14 has two mating surfaces (diametrically opposed to the above-mentioned mating surfaces) on its inner circumference, and the mating surfaces are respectively constructed as mating surfaces separated in the axial direction a and spaced apart from each other by a distance A in terms of geometric structure, so that the axle drive gear 14 pressed onto the differential housing 12 is connected to each other by means of a first press-fit portion 22-1 and a second press-fit portion 22-2 separated from the first press-fit portion and spaced apart by a distance A in the axial direction.

[0035] In order to ensure sufficient spacing between the press-fit portions 22-1 and 22-2 for supporting against tilting, the distance A should be selected such that:

[0036] 0.5≤A / L≤0.7

[0037] Here, the axial length of the inner circumference of the axle drive gear 14 in the axial direction a is denoted by L.

[0038] In order to separate the mating surface, and then the first press-fit portion 22-1 and the second press-fit portion 22-2 in terms of geometric structure, as shown in FIG. Figure 1It can further be seen that a groove 24 is respectively milled into the circumference of the differential housing 12 and into the circumference of the axle gear 14. In addition to the geometric separation, the grooves 24 also bring about a weight reduction in a particularly advantageous manner.

[0039] In this case, the machined grooves 24 each have a substantially rectangular basic shape (cross-section).

[0040] Since the two press fits 22-1, 22-2 are arranged at intervals in the axial direction a, an extremely tilt-resistant support is provided which can absorb all axial forces caused by the meshing of the external toothing 14-1 of the axle drive gear 14 with the drive shaft (not shown here), thereby ensuring optimal tooth contact and thus a uniform transmission of movement without causing undesirable interfering noise.

[0041] According to Figure 1 and Figure 2 In the embodiment shown in , the two press fits 22 - 1 and 22 - 2 have a radial interference of 10 μm to 50 μm. In addition, in order to ensure the torque transmission, an additional form-locking connection is designed in the area of ​​the first press fit 22 - 1 between the axle drive gear 14 and the differential housing 12. Axial stability is ensured by a fixing ring 26.

[0042] If especially by Figure 2 It can be seen that the positive connection is designed in the present case in the form of a polygonal toothing 28 .

[0043] exist Figure 3 and Figure 4 The second embodiment shown in FIG. 1 corresponds essentially to the embodiment shown in FIG. Figure 1 and Figure 2 The second embodiment differs from the first embodiment in that the additional connection for transmitting torque is designed in the form of a welded connection 30 between the axle drive gear 14 and the differential housing 12. Figure 3 and Figure 4 As shown, the welded connection 30 is designed as a one-sided, circumferential weld seam which is arranged only in the region of the first press fit 22 - 1 . In addition to the torque transmission, the weld seam also ensures axial securing.

[0044] The differential case according to the present invention is Figure 5 and Figure 6The third embodiment shown in the figure is distinguished by the fact that, in order to transmit torque, no form-locking or material-locking connection is provided, but only a force-locking connection is provided. In order to ensure sufficient torque transmission, the two press fits 22-1, 22-2 have a radial interference greater than 200 μm.

Claims

1. A differential transmission mechanism (10), comprising a rotatably supported differential housing (12) and an axle drive gear (14) which is non-rotatable relative to the differential housing (12), It is characterized in that The differential case (12) has two mating surfaces on its outer circumference, and the axle drive gear (14) has two radially opposite mating surfaces on its inner circumference, wherein the mating surfaces formed on the outer circumference of the differential case (12) and the mating surfaces formed on the inner circumference of the axle drive gear (14) are respectively designed as mating surfaces separated from each other by a distance (A) in an axial direction (a), and the axle drive gear (14) is pressed onto the differential case (12), so that the axle drive gear (14) and the differential case (12) are connected to each other by means of a first press-fit portion (22-1) and a second press-fit portion (22-2) separated from the first press-fit portion and spaced apart by a distance (A) in the axial direction. The mating surface formed on the outer circumference of the differential housing (12) and the mating surface formed on the inner circumference of the axle transmission gear (14) are separated from each other in the axial direction (a) by circumferential grooves (24) machined in the corresponding circumferences, wherein the grooves (24) have a length in the axial direction (a) that is equal to the distance (A). The two press-fit parts (22-1, 22-2) have a radial interference fit of 10 μm to 50 μm, and an additional material-locked connection part or a form-locked connection part is designed between the axle drive gear (14) and the differential housing (12). The additional connection is designed in the form of a polygonal tooth structure or a key joint (28), and a fixing element (26) is arranged between the axle drive gear (14) and the differential housing (12) to prevent relative movement in the axial direction (a).

2. The differential transmission mechanism (10) according to claim 1, It is characterized in that The groove (24) has a rectangular, triangular or semicircular basic shape.

3. The differential transmission mechanism (10) according to claim 1 or 2, It is characterized in that In the axial direction (a), the inner circumference of the axle transmission gear (14) has a length (L), and the distance (A) between the mating surfaces relative to the length (L) of the inner circumference satisfies: 0.5≤A / L≤0.

7.

4. The differential transmission mechanism (10) according to claim 1, It is characterized in that The additional connection is designed in the form of a welded connection (30).

5. The differential transmission mechanism (10) according to claim 4, It is characterized in that The welded connection (30) is designed as a one-sided weld seam which is arranged only in the region of the first press fit (22-1) or only in the region of the second press fit (22-2).

6. The differential transmission mechanism (10) according to claim 4 or 5, It is characterized in that The welded connection (30) is produced by means of electron welding or laser welding.

7. The differential transmission mechanism (10) according to claim 1, It is characterized in that The fixing element (26) is designed in the form of a fixing ring.

8. The differential transmission mechanism (10) according to claim 1 or 2, It is characterized in that The differential housing (12) is made of cast iron and the axle drive gear (14) is made of a hardenable material.

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