CN108368933B - Transmission and drive unit with transmission - Google Patents

Abstract

The invention relates to a transmission (2) having at least one housing (7) and a planetary transmission (8), wherein the planetary transmission (8) is formed at least by a central axis (3) around the transmission (2) ) a planet carrier ( 10 ) rotatably mounted in the housing ( 7 ) and a sun gear ( 6 ) rotatable about an axially oriented central axis ( 3 ) in tooth engagement with the planet gear ( 9 ) and wherein the sun gear ( 6 ) is axially supported on a component ( 34 ) of the transmission ( 2 ) by means of an axial bearing ( 11 ) in the same direction as the central axis ( 3 ).

Description

Transmission and drive unit with transmission

technical field

A transmission with at least one housing and a planetary gear, wherein the planetary gear is at least supported by a planet carrier rotatably supported in the housing about a central axis of the transmission and by a rotatable about the axial central axis 2. The sun gear is formed in a tooth-fitted state with the planet gear, and wherein the sun gear is axially supported on the components of the transmission device in the same direction as the central axis by means of an axial bearing. The invention also relates to a drive unit with an electric drive and such a transmission, in which the sun gear is connected to the rotor shaft of the electric drive.

Background technique

Such a transmission is disclosed in JP2011208758A2. The transmission is a hybrid drive train with an internal combustion engine and two electric motors. The electric motor can optionally be used as a drive or as a generator. The rotor shaft of one of the drives is supported, as is common in electric motors, in the housing of the drive unit by means of ball bearings and is operatively connected to the planetary gear via a slip clutch of the multi-plate clutch type. A planetary transmission has a planet carrier, a planetary set, a ring gear and a sun gear. The multi-plate clutch consists of an outer lamination carrier and an inner lamination carrier. The hub of the outer lamination carrier is provided with splines which are in a form-locking connection with the splines of the rotor shaft. On the outer lamination carrier, on the inside, as usual, axially displaceable outer laminations are placed, which alternate with the inner laminations of the multi-plate clutch. The inner laminations are placed from the outside on the inner lamination carrier, whose hub is the sun gear of the planetary gear. The uprights of the sun gear and the inner lamination carrier are fixedly connected to each other. The sun gear is supported radially on the rotor shaft at one bearing point by means of a sliding bearing and axially on the planet carrier at the other bearing point by means of an axial bearing. The planet carrier is supported radially on the shaft via needle bearings, and this shaft is supported radially via ball bearings on the housing of the drive unit.

The sun gear must be able to center itself radially relative to the central axis of the planetary gear freely and unhindered on the planet gears, so that the power is transmitted uniformly to all planet gears in toothed engagement with the sun gear. The sun gear with helical gearing is supported here axially on the planet carrier via an axial bearing.

The disadvantage of this arrangement is that self-centering is hindered by form-fitting connections and intermediate misalignments of the rotating structural elements or their bearings. As a result, undesired forcing forces are generated in the toothing and the bearing, which can lead to premature failure of the drive unit. The individual components and their fit must therefore be produced very precisely with corresponding effort and expense. To overcome this, form-fitting connections with significantly larger play are often produced to compensate for these disadvantages. However, this relatively large play leads to relative movements in the connection precisely in the case of connections with undesired misalignments. These relative movements can lead to noise and can also lead to unwanted wear.

In addition, the axial clamping forces in this arrangement can lead to axial forces acting on the bearing points, whose ball bearings are not designed or suitable for bearing high axial forces. In order to cope with this situation, the axial loads are "transferred" to axial needle or roller bearings, which have to be designed correspondingly large for high loads and therefore require a lot of installation space.

SUMMARY OF THE INVENTION

The object of the present invention is therefore to create a transmission and in particular an electric drive transmission of a drive unit with an electric drive, in which clamping forces between the structural elements are avoided and the sun gear can move unhindered in the It is centered and requires little installation space.

The invention provides that the axial bearing of the sun gear used in the transmission is a ball bearing. Furthermore, the invention also provides for a drive unit with such a transmission.

The sun gear is supported axially by means of ball bearings in a supported manner on the component. The component can be, for example, a drive shaft, an adjacent planet carrier or a housing. One embodiment of the invention provides that the component is a planet carrier of the transmission. The ball bearing is a radial bearing in type and is equipped with at least a first rolling raceway, which is associated with the sun gear in a rotationally fixed manner, and at least one second rolling raceway, which is formed on the outer ring, and is provided with a radially arranged rolling raceway. Balls between tracks. The second rolling raceway on the outer ring concentrically surrounds the first rolling raceway at the sun gear on the peripheral side. Alternatively or preferably, the inner rolling raceway is formed on the inner ring resting on the sun gear. The particularity of the invention is that the outer ring of the ball bearing is freely movable in the radial direction relative to the component, so that the ball bearing, contrary to its original design, serves only as an axial bearing. The central axis of the transmission is oriented axially. Therefore, the radial direction is transverse to the central axis.

The outer ring of the ball bearing is preferably axially locked on both sides on the component, so that the sun gear is advantageously supported axially in both axial directions. This has several advantages over conventional bearings with axial needle bearings. A conventional axial bearing, which acts in opposite axial directions, consists in a gear mechanism of two axial needle or roller bearings which are arranged on the left and right of the component to be supported. Correspondingly, costs are incurred for the manufacture and installation of the two bearings into the transmission. Construction space must be provided for both bearings. In the transmission according to the invention, however, only the installation space for one bearing is required. The cost for manufacturing and assembling the transmission is greatly reduced because only one bearing is used. The internal friction of ball bearings is smaller than that of axial bearings. The outlay for lubrication and cooling in the transmission can be reduced by the use of ball bearings.

The ball bearing can advantageously be a catalog part supplied as a series product. They are very suitable for use at high revs. Because the outer ring is free to set, the ball bearing cannot withstand radial forces, but the axial forces are distributed evenly to all the balls. Despite the use of radial bearings, the sun gear can be freely centered, since the outer ring is free relative to the components. The permissible rated speeds of ball bearings are significantly higher than those of axial needle roller bearings.

Axial bearings usually used for axial support are of the type of axial needle roller bearings, which consist of two axial discs and a needle roller crown. The rolling bodies of the needle roller crowns are known as needle rollers guided in an axial cage. The rolling contact is correspondingly configured as a line contact. These bearings therefore have a relatively high axial load carrying capacity. The internal friction of the axial bearing is correspondingly high. Furthermore, a limit is placed on the rotational speed of the axial needle or roller bearing due to the difference in rotational speed between the radially inner side of the axial raceway and the radially outer side of the axial raceway. In the case of an electric motor drive unit, the power associated with the high drive rotational speed of the electric motor is reduced by means of a planetary gear to lower rotational speeds and higher torques. In this case, the input shaft of the planetary gear, which is coupled to the rotor shaft, is subjected to the drive rotational speed of the electric motor 1:1. Since the input shaft in this case is the sun gear, according to the prior art, correspondingly, an axial needle bearing must be provided for high rotational speeds. This can sometimes be very difficult for the reasons mentioned above. The axial bearing is thus very fragile, since its load limit itself is exhausted by the speed limit. Axial loads due to tooth forces, which can also become higher due to axial forces or stresses due to misalignment, can therefore inevitably lead to premature failure of bearings such as axial needle roller bearings.

The ball bearing used in the transmission device according to the invention preferably has one row or can also have several rows of balls which are adjacent on the circumferential side. The ball center points of a row of balls lie in the center point radial plane with the same radial spacing with respect to the rotation axis of the ball bearing, said center point radial plane being perpendicular to the rotation axis of the ball bearing and the center axis of the drive shaft pass through.

The rolling tracks of a ball bearing are grooves extending around the axis of rotation, which are formed axially between two edges extending annularly around the axis of rotation. The groove is formed as a curve longitudinally along the axis of rotation of the ball bearing in any longitudinal section. The curve is concavely curved in the direction of the axis of rotation/shaft, viewed from the ball center on the shaft side at the inner rolling track, or concavely curved towards the housing when viewed from the ball centre on the housing side at the outer rolling track direction is concavely curved. Curves are described in the simplest case by radii, respectively. This radius is larger than the ball radius. The ratio between the radius and the ball radius is called the closeness. Viewed in such a longitudinal section, however, the grooves can be described not only by a single radius, but by any desired curvature, for example by a plurality of interconnected curved sections with different radii. These curves each have vertices. A vertex is to be understood as a point on the curve in the load direction in the nominal state, at which point the curve changes direction in its course.

The type of ball bearing can be described in terms of the orientation set at rated load and in terms of the number of its contacts in operation and thus the direction of the load. Here, a distinction is made between the rated state when the ball bearing is unloaded and the loaded state when the ball bearing is loaded.

Ball bearings are characterized by the point contact of the balls with the rolling raceways. In this case, when the ball bearing is in the rated state, the convexly curved surfaces of the balls are each supported at at least one contact point in corresponding concave grooves of the inner and outer rolling raceways. Here, the contact points of the two rolling raceways are opposed to each other with reference to the ball center point, and can be connected by an imaginary pressure line. The pressure line here extends through the ball center point. The angle formed between the corresponding pressure line and the radial plane of the center point when the ball bearing is in the rated state is called the rated pressure angle. The complementary angle between the center point radial planes with respect to the 90° angle is correspondingly the angle between the pressure line and the center axis.

When the ball bearing is loaded, observe the resulting bearing load (force) due to the radial and axial components, which extends along the pressure line under load. Here, one of the components can also be zero.

Under load, the point contact becomes a surface contact, which is ideally described as a pressure ellipse. The extension of the pressure ellipse is also related to the size of the load, the size of the balls and the geometry of the rolling raceway. The corresponding pressure line extends under load through the center of gravity of the ellipses of the two pressure ellipses and through the ball center point. The pressure line is inclined relative to the center point radial plane by an operating pressure angle, which can be different from the nominal pressure angle. The difference between the operating pressure angle and the rated pressure angle depends on criteria such as the direction of action of the resultant, the running clearance of the bearing, elastic deformation, the direction change of the load and the type of ball bearing.

In the transmission, at least two types of radial ball bearings are optionally provided according to the invention, however they are used for the axial support of the sun gear on the planet carrier.

The invention provides that at least one radial ball bearing is used, which can be a ball bearing with two-point contact and which is also widely known as radial deep groove ball bearing or radial ball bearing. In radial ball bearings in two-point contact, the pressure line is first oriented radially towards the axis of rotation in the nominal state and intersects the axis of rotation at a common point. The inner rolling track and the outer rolling track are arranged concentrically to each other such that the apexes of the concave curves of the two rolling tracks are radially in the center point radial plane with respect to each other in the rated state of the ball bearing. Opposite, the ball center is also located in the radial plane of the center point. The contacts lie on the vertices of the curve of the rolling raceway in the radial plane. The rated pressure angle is 0°.

With only radial bearing loads, the resultant of the bearing loads in radial ball bearings is directed perpendicular to the axis of rotation by means of two-point contact. In radial ball bearings, the bearing load is partially distributed over only a few of the balls of the ball bearing which are adjacent to each other on the circumferential side, while the others remain almost unloaded. The pressure lines in the loaded balls are here also oriented radially perpendicular to the axis of rotation and all extend in a radial plane. The corresponding operating pressure angle formed between the corresponding pressure line and the radial plane corresponds to the nominal pressure angle and is equal to 0°.

When radial deep groove ball bearings are also loaded with an axial force component, that is to say also with forces acting in the same direction as the axis of rotation, the rolling raceways can move axially against each other and/or roll over with respect to each other . The ball centre points of the individual balls may be displaced from a common radial plane towards different, mutually adjacent radial planes. The resulting bearing load will fall on a pressure line that slopes toward the radial plane at an operating pressure angle greater than 0° on one side, and 0 and less than 90° on the other direction, depending on the direction of the load. The corresponding complementary angles between them are inclined towards the axis of rotation. The axial component is partially distributed over the balls of the ball bearing. Depending on the magnitude of the axial component, the radial component is distributed over only a few balls that are adjacent to each other on the circumferential side, or is distributed more or less partially to the ball bearing due to the axial prestress of the ball bearing with a sufficiently large axial component. on all balls. The apexes of the concave curve of the rolling raceway are displaced axially towards each other, depending on the bearing play, compactness and elastic deflection, in such a way that the apex of the inner rolling track is located at the corresponding apex of the outer raceway. The other is perpendicular to the radial plane passed by the axis of rotation. The pressure ellipse and its center of gravity accordingly protrude from the common radial plane and apex, and at the same time go up to the corresponding edge of the rolling raceway. When the contact of the balls with the rolling raceway moves too far to the edge of the edge, the pressure ellipse cannot be formed completely flat. And "broken" on the edges of the edges. The stresses that arise here are unevenly distributed and extend beyond the edges of the edges. As a result, impermissible edge stresses can occur at the edges of the edges and undesired stress peaks in the balls. Therefore, ball bearings with two-point contact can only carry limited axial bearing loads. Since the deep groove ball bearing can only be loaded axially in use according to the invention, these loads are advantageously distributed first over all the balls and not over a portion. Deep groove ball bearings can be used at high speeds and have only small internal friction due to two-point contact. However, deep groove ball bearings can only be used when the expected axial forces are relatively low.

A further and preferred embodiment of the invention therefore provides for the use of a four-point ball bearing. In a four-point ball bearing, the inner and outer rolling raceways are separated in any longitudinal section along the axis of rotation through the ball bearing and are described by two concave curves or two vertices, respectively . This can be on the groove of an undivided bearing ring or a "separated" groove formed by two rings of the bearing ring, respectively. This results in the contact of the corresponding balls at least in the nominal state on the four contacts. The outer rolling raceway has two of these contacts, and two of the contacts are designed on the inner rolling raceway.

The grooves are arranged radially concentric to one another in such a way that, in any longitudinal section through the ball bearing along the axis of rotation, correspondingly, one vertex of the outer rolling track is not only at the other vertex of the outer rolling track. Axially opposite, and also radially opposite a vertex on the inner rolling raceway in a plane or slightly offset in the axial direction. In this case, the apexes of the inner rolling track have the same radial distance from the axis of rotation in the nominal state and in the loaded state, but lie in different radial planes axially spaced apart from each other. The radial plane is axially adjacent to the center point radial plane. The same holds true for outer rolling raceways. Under normal circumstances, accordingly, one vertex of the inner rolling raceway and one vertex of the outer rolling raceway lie in a common radial plane, which is perpendicularly penetrated by the axis of rotation of the ball bearing. In the rated state, the vertices are contacts.

The contact geometry is designed such that, on each ball of the four-point ball bearing, a pressure line passes through the contact with the outer raceway in the first radial plane and through the second contact. In the radial plane, the contact with the inner rolling raceway extends, and there is also a pressure line through the contact with the outer rolling raceway in the second radial plane and through the first radial In-plane, extends in contact with the inner rolling raceway. Corresponding lines of pressure penetrate through corresponding ball center points in the radial plane of the center point as defined. The pressure line from one of the sides intersects the axis of rotation of the four-point ball bearing or the central axis of the transmission at a common point of intersection. Thereby, two pressure lines respectively intersect at one of the ball center points which are co-located in the radial plane of one center point. The points of intersection on the axes of rotation are axially spaced from each other and to the left and right from the radial plane in which the ball center points lie. This results in that the pressure lines are each oriented obliquely with respect to the radial plane with a desired pressure angle of greater than 0° and a corresponding complementary angle of less than 90°.

In a load state where only radial loads are present, the forces in the four-point ball bearing are distributed over only a few balls that are circumferentially adjacent to each other, so that these balls are supported on the four contacts in the ball bearing. In a load state with radial and axial loads, the contacts remain relatively firmly at the apex, or move only slightly therefrom, ie the nominal pressure angle and the operating pressure angle are the same or almost the same. This deviation can be pre-set by the turning and the closeness of the shaft within the framework of the running clearance. The rolling raceways and thus the bearing rings are held relatively firmly in their position. Thus, advantageously, changes in the orientation of the contacts relative to the corresponding edges do not have to be taken into account. Can withstand large axial loads, especially alternating loads.

The internal friction of a four-point ball bearing is relatively high under normal conditions, ie under radial load or combined radial-axial load, due to the four-point contact. However, in the case of a four-point ball bearing with only an axial load, due to the running play, a two-point contact according to the type of angular contact ball bearing is formed, so that this disadvantage can be eliminated by the use of the four-point ball bearing according to the invention. This unifies the advantages of allowing high rated speeds, low internal friction of the two-point contact of the deep groove ball bearing, and high strength of the four-point radial bearing.

Description of drawings

The invention will be explained in more detail below by means of an exemplary embodiment of a drive unit 1 with a transmission 2 .

FIG. 1 shows the drive unit 1 in a schematic and simplified longitudinal section along the central axis 3 of the transmission 2 .

FIG. 2 shows a detail Z from the transmission 2 shown in FIG. 1 on an enlarged scale not to true scale.

Detailed ways

FIG. 1 : The drive unit 1 has an electric motor drive 4 , the rotor shaft 5 of which is operatively connected to the sun gear 6 of the transmission 2 via a form-locking connection. The form-locking connection is produced, for example, by splines, so that the sun gear 6 can be displaced axially relative to the rotor shaft 5 in a limited manner. This ensures that the bearing 28 of the rotor shaft 5 cannot exert an axial force of the sun gear 6 . The transmission 2 is not shown completely. Parts of the housing 7 and the planetary gear 8 can be seen. The planetary transmission 8 is composed of at least a planet carrier 10 , a sun gear 6 and a set of planet gears 9 . The planet carrier 10 has two carrier plates 10a and 10b on which the planet pins 9a are carried. The planetary wheel 9 is mounted on the planetary pin 9a. The axes of rotation of the sun gear 6 and of the planet carrier 10 are respectively the central axis 3 . The sun gear 6 is axially supported or supported on a component 34 of the transmission 2 by means of the axial bearing 11 in the same direction as the central axis 3 . The axial bearing 11 is mounted on the shaft end of the sun gear 6 which is axially remote from the rotor shaft 5 and is mounted in the component 34 . The member 34 is the planet carrier 10 in this embodiment.

FIG. 2 : The planet carrier 10 has housing holes 18 in the carrier plate 9 b which are drilled, punched or otherwise introduced into the material of the planet carrier 10 . An inner cylindrical surface 18a is formed in the interior of the housing bore 18 .

The axial bearing 11 is a ball bearing 12 . The ball bearing 12 has an inner rolling raceway 13 on the inner ring 14 . The inner ring 14 is separate and fixedly mounted on the shaft head 6a of the sun gear 6 . A separate inner rolling raceway 13 is formed on the inner ring 14 . As an alternative, it is conceivable that the inner rolling raceway is introduced directly into the surface of the shaft head 6a. Furthermore, the ball bearing 12 is provided with an outer ring 15 on which an outer rolling raceway 16 is formed. The outer ring 15 surrounds the inner ring 14 on the peripheral side around the central axis 3 . Thereby, the rolling races 13 and 16 are arranged concentrically with each other. In the radial direction, between the outer ring 15 and the inner ring 14 , the balls 17 are arranged in a row on the rolling raceways 13 and 16 on the circumferential side around the central axis 3 . The rotation axis of the ball bearing 12 and the central axis 3 coincide with each other. The outer ring 15 is freely movable in the radial direction relative to the component 34 and, in the radial gap S, is movable in the radial direction relative to the inner cylindrical surface 18 a and in the axial direction towards the central axis 3 are fixed axially between the safety ring 19 and the housing shoulder 18b in both directions. The radial gap S is formed according to FIG. 2 by the gap dimensions S1 and S2 of the annular gap 20 , each of which is ideally half the radial gap S. Ideally, the sun gear 6 is centered on the planet gears 9 such that its axis of rotation corresponds exactly concentrically with the central axis 3 . The sun gear 6 is supported on only one bearing point of the transmission 2 , which has a ball bearing 12 as the sole bearing. The advantage is that the sun gear 6 can thus be centered unhindered by pivoting and/or parallel movement relative to the central axis 3 within the framework of the gap.

Figures 1 and 2: The ball bearing 12 is a four-point ball bearing in which the ball centre points 23 of the balls are located in a radial plane ME extending perpendicular to the centre point in the plane of the drawing. In the longitudinal section shown and extending along the central axis 3 (see, in particular, FIG. 2 ), the four-point ball bearing is in each case passed through two imaginary balls that intersect at the ball center point 23 and in each case pass through the ball and the The first contact 24 of the inner rolling race 13 and the contact lines 21 and 22 with the second contact 25 of the outer rolling race 16 are characterized. In each radial plane E1 or E2 there are contact points 24 and 25 . The two radial planes E1 and E2 extend on the left parallel to the center point radial plane ME. Each contact line is inclined towards the central axis at an angle of 90°>α>0°, preferably at an angle of 90°>α>55°. Starting from this contact geometry and the play in the ball bearing 12 , the sun gear 6 is supported on the inner ring by an axial force in one of the axial directions, depending on the load direction, via the shaft shoulder 26 and along the contact line 22 via The outer ring 15 and the securing ring 19 are supported in the housing bore 18 or by an axial force in the other axial direction via the securing ring 27 on the inner ring 14 and along the contact line 21 via the outer ring 15 . on the housing shoulder 18b. The selected angular range ensures that standard four-point ball bearings, such as the catalog product series, can be used as axial bearings and that the axial load capacity remains in the optimum range at high speeds.

FIG. 1 : The planet carrier 10 is rotatably supported about the central axis 3 at the first bearing point 29 and the second bearing point 30 axially spaced from the first bearing point and fixed in the opposite axial direction is supported on the housing 7. Each bearing point 29 and 30 has an angular contact ball bearing 31 and 32 . The individual angular contact ball bearings 31 and 32 are characterized in the longitudinal section according to FIG. 1 by contact lines 33 which are inclined relative to the central axis 3 at an angle of 90°>α>0°. Here, the angular contact ball bearings 31 and 32 are arranged relative to each other in such a way that the contact line 33 intersects the central axis 3 at a point of intersection 35 located axially between the two bearing points 29 and 30 in each case. The ball bearing 12 is arranged concentrically with one of the angular contact ball bearings 32 in such a way that it is surrounded by the angular contact ball bearing 32 so that the required axial installation space for the two ball bearings 12 and 32 is advantageously reduced to only one Space requirements for ball bearings.

List of reference signs

1 drive unit

2 Transmission

3 central axis

4 Electric motor drive

5 Rotor shaft

6 sun gear

6a axle head

7 Housing

8 Planetary gear

9 Planetary gear

9a Planetary pin

10 Planet carrier

10a Carrier plate

10b carrier plate

11 Axial bearing

12 Ball bearing

13 inner rolling raceway

14 inner ring

15 Outer ring

16 outer rolling raceways

17 Balls

18 Housing hole

18a Internal cylindrical surface

18b Housing shoulder

19 Safety ring

20 annular gap

21 Contact wire

22 Contact wire

23 Ball center point

24 contacts

25 contacts

26 Shaft shoulder

27 safety ring

28 Supporting part of rotor shaft

29 Support parts

30 Support parts

31 Angular contact ball bearings

32 Angular contact ball bearings

33 Contact wire

34 Components

35 intersection

Claims (10)

1. Transmission (2) having at least one housing (7) and a planetary transmission (8), wherein the planetary transmission (8) is formed at least by a planet carrier (10) which is mounted in the housing (7) so as to be rotatable about a central axis (3) of the transmission (2) and by a sun gear (6) which is rotatable about an axially oriented central axis (3) and which is in toothed engagement with the planet gears (9), and wherein the sun gear (6) is axially supported on a component (34) of the transmission (2) by means of an axial bearing (11) in the same direction as the central axis (3), characterized in that the axial bearing (11) is a ball bearing (12), wherein the sun gear (6) is mounted on the component (34) so as to be rotatable about the central axis (3) by means of the ball bearing (12), and the ball bearing (12) is provided with at least one rolling track (C) which is assigned to the inside of the sun gear (6) in a manner such that it is resistant to relative rotation (C 13) And at least one outer rolling track (16) formed on the outer ring (15) and balls (17) arranged radially between the rolling tracks (13, 16), wherein the outer rolling track (16) concentrically surrounds the inner rolling track (13) in a peripheral manner, and the outer ring (15) is arranged radially transversely to the central axis (3) and radially movably relative to the component (34).

2. Transmission according to claim 1, characterized in that the component (34) is a planet carrier (10) and the outer ring (15) is axially fixed in the opposite direction in an inner cylindrical housing bore (18) of the planet carrier (10) which is concentric to the central axis (3), wherein a radial movement play in the housing bore (18) which is directed transversely to the axial direction is formed between the inner cylindrical housing bore (18) and the outer ring (15).

3. Transmission according to claim 2, characterized in that the radial movement gap is formed by an annular gap (20) encircling around the centre axis (3).

4. Transmission according to claim 1, characterized in that the ball bearing (12) is a four-point ball bearing, wherein the four-point ball bearing is characterized in arbitrary, imaginary and longitudinal sections extending along the central axis (3) through the ball bearing (12) by respective imaginary contact lines (21, 22) intersecting at a ball center point (23) and here passing through the ball (17) respectively a first contact point (24) with the inner rolling track (13) and a second contact point (25) with the outer rolling track (16), and wherein each contact line (21, 22) is inclined with respect to the central axis (3) by an angle of 90 ° > α > 0 °.

5. Transmission according to claim 4, characterized in that the angle is 90 ° > α > 55 °.

6. Transmission according to claim 1, 2 or 4, characterized in that the sun wheel (6) is supported in the transmission (2) on only one bearing point, wherein the bearing point has the ball bearing (12) as the only bearing.

7. Drive unit (1) having an electric motor drive (4) and having a transmission (2) according to claim 1, wherein the sun gear (6) is operatively connected to the rotor shaft (5) of the electric motor drive (4), characterized in that the ball bearings (12) are arranged on a shaft end of the sun gear (6) in the planet carrier (10) which axially faces away from the rotor shaft (5), and the outer ring (15) is axially fixed in the opposite direction in a housing bore (18) which is cylindrical on the inner side of the planet carrier (10) and concentric with the central axis (3), wherein a radial movement gap, i.e. directed transversely to the axial direction, in the housing bore (18) is formed between the planet carrier (10) and the outer ring (15).

8. Drive unit according to claim 7, characterized in that the planet carrier (10) is supported in a rotatable manner about the central axis (3) on a first bearing point (29) and a second bearing point (30) spaced apart from the first in the axial direction and is fixedly supported in the opposite axial direction on the housing (7), and wherein each bearing point (29, 30) has an angular ball bearing (31, 32), wherein the respective angular ball bearing (31, 32) is characterized in any arbitrary, imaginary and longitudinal sectional view extending along the central axis (3) through the ball bearing (12) by an imaginary angular ball bearing contact line (33) which passes through a ball center point (23) and here respectively through an inner rolling track of the ball bearing (31, 32) and an outer rolling track of the angular ball bearing (31, 32), and wherein each contact line (33) is inclined with respect to the central axis (3) at an angle of 90 ° > α > 0 °.

9. Drive unit according to claim 8, characterized in that the angular ball bearings (31, 32) are set up relative to one another in such a way that the contact line (33) of the respective angular ball bearing (31, 32) intersects the central axis (3) at an intersection point (35) which lies on the central axis (3) axially between the first and second bearing points (29, 30).

10. Drive unit according to claim 9, characterized in that the ball bearing (12) is surrounded by one of the angular contact ball bearings (31, 32) in a circumferential direction around the centre axis (3).

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