ELECTRIC DRIVE UNIT

Description

Technical field

[0001] The invention relates to an electric drive device comprising an electric motor part and a transmission part, wherein a rotor shaft is coupled to a transmission input shaft within a connection area for torque transmission. Furthermore, the invention relates to the use of the electric drive device in an electrically powered vehicle, in particular an electrically powered passenger car or an electrically powered light commercial vehicle. State of the art

[0002] DE 10 2012 210 682 A1 discloses an electric machine with a rotor shaft which has a pinion for transmitting torques to a planetary gear set. The rotor shaft of the electric machine is supported at both ends, with the rotor and pinion arranged between the two bearings. The bearing at one end of the rotor shaft is in the machine housing, the bearing at the other end of the rotor shaft is in a blind hole of an output shaft.

[0003] DE 10 2012 203 809 A1 discloses an electric machine with a rotor shaft in which all components arranged on the rotor shaft are located between two bearings. In addition to the rotor and a pinion which engages with the planet carrier of a planetary gear, a device for axial movement or axial fixing of the rotor shaft between its two bearings is arranged on the disclosed rotor shaft.

[0004] In designs of electric drive systems with a rotor shaft, vibrations can occur due to the torque-transmitting connection between a gearbox input shaft and the rotor shaft. These vibrations originate from this connection. Vibrations can occur both when the electric machine is rotating in forward and reverse directions.

[0005] Further electric drive devices are known from DE 10 2011 010204 A1, EP 2 120 315 A1, DE 10 2018 104685 A1 and US 6 074 165 A. Document DE 10 2011 010204 A1 discloses an electric drive device with an electric machine part and a transmission part, wherein a rotor shaft is coupled to a transmission input shaft within a connection area such that torque transmission takes place, wherein an axial connection is formed between the rotor shaft and the transmission input shaft in the connection area, wherein the axial connection has a retaining ring which is received on the rotor shaft and supports a disk-shaped element. Description of the invention

[0006] According to the invention, an electric drive device is proposed which comprises an electric machine part and a gearbox part, wherein a rotor shaft is coupled to a gearbox input shaft in such a way that torque transmission takes place within a connection area and an axial connection is provided in the connection area between the rotor shaft and the gearbox input shaft.

[0007] The axial connection between the rotor shaft of the electric machine on the one hand and the input shaft of the gearbox on the other effectively dissipates axial forces, which can lead to vibrations, into the rolling bearings, which in particular provide rotatable support for the gearbox input shaft, and into a housing that supports the rolling bearings. This applies to both directions of rotation of the electric machine, i.e., for reverse and forward travel of an electrically powered vehicle.

[0008] According to the invention, the transmission input shaft is designed as a hollow shaft, the inner surface of which encloses the pinion shaft in the connection area. This results in a compact design of the connection area, within which, for example, a cylindrical surface of the rotor shaft, which is provided with a splined connection or the like, interacts with a complementary geometry on the inner cylindrical surface of the hollow shaft. This allows the transmission of even the highest torques without the material stress reaching unacceptably high levels at any point.

[0009] According to the invention, the axial connection has a retaining ring which is mounted on the rotor shaft and supports a disc-like element. The retaining ring can, for example, be mounted in a groove on the circumference of the rotor shaft, or be designed as a snap ring, while the disc-like element can, for example, be designed as a disc spring.

[0010] According to the invention, the disc-shaped element rests against a circumferential shoulder of the inner shell of the transmission input shaft and is designed as a disc spring.

[0011] In further developments of the electric drive unit, the retaining ring can be designed as a flat ring, a circumferentially corrugated ring, or a conical ring. This variation in the retaining ring's geometry allows for simple adaptation to different operating conditions and the axial forces to be transmitted.

[0012] In a further embodiment of the electric drive device, the axial connection can be designed in such a way that it has a lock nut which interacts with a snap ring.

[0013] In another possible embodiment of the electrical drive device proposed according to the invention, the axial connection is designed such that it comprises a disc spring which is attached to an end face of the rotor shaft by means of a screw connection.

[0014] In a further advantageous embodiment of the electric drive device according to the invention, the circumferential shoulder on the inner surface of the transmission input shaft is designed as a diameter reduction. Depending on the requirements for the geometry of the circumferential shoulder and the axial forces to be transmitted, forward and reverse travel, the circumferential shoulder can be adapted to the axial forces occurring and can be manufactured in a particularly simple manner during the production and adaptation of the hollow shaft as the transmission input shaft.

[0015] In a further advantageous embodiment of the electrical drive device proposed according to the invention, a force flow through the second bearing into a housing is effected by the axial connection between the rotor shaft and the gearbox input shaft.

[0016] Furthermore, it should be emphasized that in the electric drive device according to the invention, the axial connection between the rotor shaft and the gearbox input shaft causes a force flow through the second bearing, corresponding to the respective direction of rotation of the rotor shaft. This allows the axial force to be transferred via the rolling bearing into the housing for both directions of rotation of the electric machine, i.e., for reverse and forward travel, thus preventing vibration effects.

[0017] Furthermore, the invention relates to the use of the electric drive device in an electrically powered vehicle, in particular an electrically powered passenger car or an electrically powered light commercial vehicle. Advantages of the invention

[0018] The solution proposed according to the invention makes it possible to connect the rotor shaft of the electric machine to the input shaft of the gearbox. This avoids the disadvantages, particularly the occurrence of vibrations, associated with an angled bearing arrangement, especially an X-bearing configuration, and ensures a well-defined axial position of the rotor shaft. The axial connection proposed according to the invention also eliminates the need to subject another of the rolling bearings supporting the rotor shaft to a preload force. Furthermore, the application of the concept proposed according to the invention allows for a smaller size of this rolling bearing, since, according to the solution proposed according to the invention, this bearing does not have to absorb any axial forces.In a three-point bearing arrangement for the rotor shaft and gearbox input shaft, the axial forces are absorbed and transferred to the housing only by the middle, i.e., the second, bearing. The solution proposed according to the invention particularly eliminates rotor shaft vibration, as axial displacement of the rotor shaft is ensured by the axial connection that maintains its defined position. The defined axial position of the rotor shaft and the associated gearbox input shaft, via the axial connection proposed according to the invention, allows for vibration-free operation, both in the forward and reverse directions of rotation of the electric machine.

[0019] Furthermore, a variety of rolling bearing types can be used. Instead of the preloaded X-bearing concept, the axial connection proposed according to the invention between the gearbox input shaft and the rotor shaft connected to it can hold the rotor shaft in an axial position. This allows a fixed-floating bearing principle to be implemented instead of a preloaded X-bearing, where the occurrence of vibrations acting in the axial direction cannot be completely ruled out. The solution proposed according to the invention effectively counteracts this disadvantage. Brief description of the drawings

[0020] The invention is described in more detail below with reference to the drawings.

[0021] They show: Figure 1 shows an angled X-bearing of a rotor shaft / gearbox input shaft combination of an electric drive unit; Figure 2 shows a detail fromFigure 1 , representing the connection area between the transmission input shaft and the rotor shaft, Figure 3 shows a possible embodiment of the axial connection proposed according to the invention between the transmission input shaft and the rotor shaft, and Figure 4 shows a force curve that develops in connection with the axial connection between the transmission input shaft on the one hand and the rotor shaft on the other.

[0022] Figure 1Figure 1 shows an electric drive unit 10 comprising an electric motor unit 12 and a gearbox unit 14. A rotor shaft 16 runs within the electric motor unit 12 of the electric drive unit 10 and is coupled to a gearbox input shaft 18 for torque transmission 44. A toothed gear 20 or a pinion is located on the circumference of the gearbox input shaft 18. The assembly consisting of the rotor shaft 16 and the gearbox input shaft 18 is rotatably mounted in a housing of the electric drive unit 10 (not shown) in a first bearing 22, a second bearing 24, and a third bearing 26. The rotor shaft 16 is driven by the electric drive unit 10, which is not shown in detail here.

[0023] From the representation according to Figure 1It is further evident that the electric motor section 12 is separated from the gearbox section 14 by a radial shaft seal 28. The first bearing 22 and the second bearing 24 are configured in a preloaded X-position 30; a seat for a rotor (not shown) of the electric drive unit 10 on the outer surface 34 of the rotor shaft 16 is designated by position 32. Due to the preloaded X-position 30 of the first bearing 22 relative to the second bearing 24, an axial load 36 is established from the gear teeth 20, depending on the direction of rotation of the rotor shaft 16, i.e., during forward or reverse travel, which is distributed in the two directions of action 38 according to the Figure 1 The registered double arrow should be effective.

[0024] In the area of ​​the second bearing 24, there is a contact ring 40, which marks the contact area between the gearbox input shaft 18 and the rotor shaft 16. In this area, when the preloaded X-position 30 is formed as shown in the illustration, Figure 1 to the occurrence of vibrations (hammer effect).

[0025] From the representation according to Figure 1 It can also be seen that within a connection area 42 on the outer surface 34 of the rotor shaft 16 a multi-spline connection 46 is formed, which interacts with a corresponding geometry on the inside of the gearbox input shaft 18.

[0026] A preload force acting on the first bearing 22 of the preloaded X-position 30 in the axial direction is designated by position 78; this also acts on the third bearing 26, in which the rotor shaft 16 is rotatably mounted.

[0027] Figure 2It can be seen that the toothed running 20 formed on the circumference of the transmission input shaft 18 interacts with a transmission gear 48. The torque transmission 44 from the rotor shaft 16 to the transmission input shaft 18 is effected via the splined connection 46 to a complementary geometry formed on an inner surface 66 of the transmission input shaft 18, which is designed as a hollow shaft 60. Within the connection area 42, axial guidance is provided only by the contact ring 40. Reference numeral 50 designates a first direction of action of the axial force or axial load 36, which leads to the hammer effect.

[0028] From the representation according to Figure 2It is further evident that the second bearing 24, shown here as an example, is designed as a ball bearing and comprises a spherical rolling element 58. The rolling elements 58 of the second bearing 24 are located between an inner ring 54 and an outer ring 56 of the second bearing 24. The preloaded X-position 30 is represented with respect to the second bearing 24 by the arrow extending obliquely from its inner ring 54 to its outer ring 56. Embodiments of the invention

[0029] In the following description of embodiments of the invention, identical or similar elements are designated by the same reference numerals, and repeated descriptions of these elements are omitted in individual cases. The figures represent the subject matter of the invention only schematically.

[0030] From the representation according to Figure 3 It is evident that of the rotor shaft 16, which is located in Figure 3 The electric drive unit 10 (not shown) is driven by a torque transmission 44 within the connection area 42 to the gearbox input shaft 18, which is designed as a hollow shaft 60. This is achieved by a multi-spline connection 46 formed on the outer surface 34 of the rotor shaft 16, which interacts with a torque-transmitting geometry complementary to the multi-spline connection 46 on an inner surface 66 of the gearbox input shaft 18, which is designed as a hollow shaft 60. The outer circumference of the gearbox input shaft 18 has a toothed gear 20 or, alternatively, a pinion. This meshes with a gear 48 of a gearbox (not shown) of the gearbox section 14 of the electric drive unit 10. Figure 1 .

[0031] Within the connection area 42 between the transmission input shaft 18 and the rotor shaft 16, the arrangement is supported by the second bearing 24. The second bearing 24 is shown in the illustration according to Figure 3 For example, it is designed as a ball bearing and comprises several spherically shaped rolling elements 58 located between an inner ring 54 of the second bearing 24 and its outer ring 56. The second bearing 24 is mounted in a housing 80 of the electric drive unit 10.

[0032] Within the connection area 42 is an axial connection 62. This ensures a defined axial position of the gearbox input shaft 18 relative to the rotor shaft 16 and vice versa. By providing the axial connection 62, which can be manufactured in several embodiments, the occurrence of vibrations is avoided, which are particularly problematic during operation in the Figure 1The preloaded X-position 30 of the first bearing 22 with respect to the second bearing 24 can occur. By providing the axial connection 62 proposed according to the invention within the connection area 42 between the transmission input shaft 18 on the one hand and the rotor shaft 16 on the other, axial forces can be dissipated into the housing 80 and, due to the axial connection 62 proposed according to the invention, no longer lead to the occurrence of vibrations or hammering acoustic noises in the area of ​​the contact ring 40 between the inner ring 54 and a shoulder of the outer surface 34 of the rotor shaft 16.

[0033] The connection area 42 can, for example, include a retaining ring 68. The retaining ring 68 has a first end face 72 and a second end face 74 and is, for example, recessed in a circumferential groove on the circumference of the rotor shaft 16 in the region of its end face 64. The axial connection 62 further comprises a disc-shaped element 70, for example, designed as a disc spring. The retaining ring 68 can, for example, be designed as a flat ring, a snap ring, a circumferentially corrugated ring, or a conical ring. The disc-shaped element 70 is preferably arranged in the inner shell 66 of the transmission input shaft 18, which is designed as a hollow shaft 60, such that it bears against a circumferential shoulder 84 formed on the inner shell 66 of the hollow shaft 60. The circumferential shoulder 84 can, for example, be formed by reducing the diameter of the hollow shaft 60.Its purpose is to allow the disc-shaped element 70 to be supported in the axial direction. Instead of the one in . Figure 3 In the illustrated embodiment of the axial connection 62, it can also include a lock nut that interacts with a snap ring. In a further embodiment, the retaining ring 68 can also be fastened to the end face 64 of the rotor shaft 16 by means of a screw, which may have an internal thread coinciding with its centering bore, serving to fasten the disc spring or the like. This allows for a further embodiment of the axial connection 62 proposed according to the invention.

[0034] From the representation according to Figure 3It can further be seen that the splined connection 46 is recessed on the circumference of the rotor shaft 16 by means of a relief groove 76. The splined connection 46 between the inner surface 66 of the gearbox input shaft 18, which is designed as a hollow shaft 60, serves to transmit torque 44, while the axial connection 62 transmits only the axial loads 36, as can be seen from Figure 4 is shown.

[0035] Figure 4 Figure 82 shows a force flow 82 originating from the rotor shaft 16 as soon as it is driven in one of its directions of rotation for torque transmission 44. The axial force acting in one of the two directions 50, 52 is transmitted to the second bearing 24 via the axial connection 62 between the rotor shaft 16 on the one hand and the gearbox input shaft 18 on the other, thereby causing the Figure 4 The force flow into the housing 80, as shown with reference numeral 82, is established. In the

[0036] Representation according to Figure 4 The second bearing 24 is also designed as a rolling bearing – here as a ball bearing – with a spherical rolling element 58 that runs between an inner ring 54 and an outer ring 56, which is received in the housing 80. In the embodiment according to Figure 4 The axial connection 62 comprises, in addition to the retaining ring 68, the disc-shaped element 70, which is supported on the circumferential shoulder 84 of the inner surface 66 of the hollow shaft 60. The axial connection 62 fixes the positions of the two shafts, i.e., the transmission input shaft 18 on the one hand and the rotor shaft 16 on the other, relative to each other. This allows for a defined force transmission into the second bearing 24. With regard to the Figure 4The force flow 82 shown, which coincides with one of the directions of rotation of the electric drive unit 10, is exactly the opposite when the electric drive unit 10 is driven in the opposite direction. In this case, the forces shown in Figure 4 to reverse the arrows shown so that they point in the opposite direction.

[0037] Also with regard to the representation according to Figure 4 It should be noted that the axial connection 62 can be manufactured in various ways. Besides the one described in Figure 4In the illustrated embodiment of the axial connection 62 with retaining ring 68 and disc-shaped element 70, for example a Belleville spring, the retaining ring 68 can also be fastened to the end face 64 of the rotor shaft 16 by means of a screw. For this purpose, an internal thread must be cut into the end face 64 concentrically to the axis of rotation of the rotor shaft 16. Furthermore, a snap ring can also be arranged on the rotor shaft 16 by means of a lock nut.

[0038] Notwithstanding the embodiment of the axial connection 62, a defined position of the rotor shaft 16 relative to the transmission input shaft 18 can be achieved by means of this connection, so that instead of the more vibration-prone preloaded X-position 30 of the first bearing 22 relative to the second bearing 24, a fixed-floating bearing arrangement can be implemented. This arrangement is significantly more robust with regard to the dissipation of axial forces into the housing 80 and, due to the axial connection 62 proposed according to the invention, is suitable for dissipating these forces into the housing 80. This considerably improves the driving comfort when reversing and driving forward with the electric drive unit 10 of an electrically powered vehicle.

[0039] The invention is not limited to the embodiments described here and the aspects highlighted therein. Rather, within the scope specified by the claims, a multitude of modifications are possible that fall within the bounds of what is considered skilled in the art.

Claims

1. Electrical drive device (10) comprising an electric machine part (12) and a gearbox part (14), wherein a rotor shaft (16) is coupled to a gearbox input shaft (18) within a connecting region (42) in such a way that torque transmission (44) occurs, wherein an axial connection (62) is formed between the rotor shaft (16) and the gearbox input shaft (18) in the connecting region (42), wherein the gearbox input shaft (18) is designed as a hollow shaft (60), the inner lateral surface (66) of which surrounds the rotor shaft (16) in the connecting region (42), wherein the axial connection (62) has a retaining ring (68) which is mounted on the rotor shaft (16) and supports a disc-shaped element (70), wherein the disc-shaped element (70) rests against a circumferential shoulder (84) of the inner lateral surface (66) of the gearbox input shaft (18) and is designed as a plate spring.

2. Electrical drive device (10) according to Claim 1, characterized in that the retaining ring (68) is designed as a flat ring, as a ring with a corrugation in the circumferential direction or as a conical ring.

3. Electrical drive device (10) according to Claims 1 and 2, characterized in that the axial connection (62) comprises a locknut with snap ring.

4. Electrical drive device (10) according to Claim 1, characterized in that the plate spring is fastened to an end side (64) of the rotor shaft (16) by means of a screw connection.

5. Electrical drive device (10) according to Claim 1, characterized in that the circumferential shoulder (84) on the inner lateral surface (66) of the gearbox input shaft (18) is designed as a portion of reduced diameter.

6. Electrical drive device (10) according to Claims 1 to 5, characterized in that a force flow (82) occurs through a second bearing (24) into a housing (80) owing to the axial connection (62) between the rotor shaft (16) and the gearbox input shaft (18).

7. Electrical drive device (10) according to Claim 6, characterized in that a force flow (82) occurs through the second bearing (24) in accordance with a direction of rotation of the rotor shaft (16) owing to the axial connection (62) between the rotor shaft (16) and the gearbox input shaft (18).

8. Use of the electrical drive device (10) according to any of Claims 1 to 7 in an electrically driven vehicle, in particular an electrically driven passenger car or an electrically driven light commercial vehicle.