Transmission for E-Axle

Abstract

An electric transmission (16) for a motor vehicle drive train (12) includes a transmission input shaft (24) for operatively connecting the electric transmission to an electric prime mover (14), a reduction gear (26) for reducing a rotational speed of the electric prime mover, a transmission (28) for establishing gear steps, including a first planetary gear set (RS1) and a second planetary gear set (RS2), a first output shaft (34) and a second output shaft (36) for transmitting drive power from the electric transmission, and a plurality of shift elements (B, C, D) for engaging the gear steps. A planet carrier of the first planetary gear set is drivingly connected to a planet carrier of the second planetary gear set, and a sun gear of the first planetary gear set is drivingly connected to a ring gear of the second planetary gear set.

Claims

1-15. (canceled)

16. An electric transmission (16) for a motor vehicle drive train (12) of a motor vehicle (10), comprising: a transmission input shaft (24) configured for operatively connecting the electric transmission to an electric prime mover (14) of the motor vehicle; a reduction gear (26) configured for reducing a rotational speed of the electric prime mover; a transmission (28) configured for establishing gear steps, the transmission (28) comprising a first planetary gear set (RS1) and a second planetary gear set (RS2); a first output shaft (34) and a second output shaft (36) configured for transmitting drive power from the electric transmission; and a plurality of shift elements (B, C, D) configured for engaging the gear steps, wherein a planet carrier of the first planetary gear set is drivingly connected to a planet carrier of the second planetary gear set, and wherein a sun gear of the first planetary gear set is drivingly connected to a ring gear of the second planetary gear set.

17. The electric transmission (16) of claim 16, wherein: the shift elements (B, C, D) comprise a first brake (C), a second brake (D), and a clutch (B), an uncoupled sun gear of the transmission (28) connectable to the input shaft by the clutch (B) and rotationally fixable by the first brake (C), an uncoupled ring gear of the transmission (28) rotationally fixable by the second brake (D); or the shift elements (B, C, D) comprise a first clutch (C), a brake (D), and a second clutch (B), a free shaft (40) connectable to the uncoupled ring gear of the transmission (28) by the first clutch (C), the free shaft connectable to the uncoupled sun gear of the transmission (28) by the second clutch (B), the free shaft rotationally fixable by the brake (D); or the shift elements (B, C, D) comprise a first brake (C) and a second brake (D), the uncoupled ring gear rotationally fixable by the first brake (C), the uncoupled sun gear rotationally fixable by the second brake (B).

18. The electric transmission (16) of claim 16, wherein two reduction gears and one direct gear are establishable with the electric transmission.

19. The electric transmission (16) of claim 16, wherein: the first planetary gear set (RS1) and the second planetary gear set (RS) are radially nested; and a planet carrier of the first planetary gear set and a planet carrier of the second planetary gear set are formed as one piece.

20. The electric transmission (16) of claim 16, wherein the shift elements (B, C, D) are constant-mesh shift elements.

21. The electric transmission (16) of claim 16, wherein the shift elements (B, C, D) include exactly three shift elements (B, C, D).

22. The electric transmission (16) of claim 16, further comprising: a ball or spur gear differential (32) at an output end of the electric transmission (16); or an axially parallel or coaxial reduction gear in the form of a 2-carrier 5-shaft transmission with an integrated differential (32).

23. The electric transmission (16) of claim 22, further comprising a differential lock (S).

24. The electric transmission (16) of claim 16, wherein the electric transmission has an overall gear ratio of greater than two.

25. The electric transmission (16) of claim 16, wherein a ratio step between two adjacent gear steps is less than two.

26. A motor vehicle drive train (12) for a motor vehicle (10), comprising: the electric transmission (16) of claim 16; and an electric prime mover (14) drivingly connected to the transmission input shaft (24).

27. The motor vehicle drive train (12) of claim 26, wherein the electric prime mover is actuatable as a synchronizer during a gear shift in the electric transmission.

28. The motor vehicle drive train (12) of claim 26, wherein: the electric transmission (16) is drivingly connectable to a first motor vehicle axle; a second motor vehicle axle is connectable to a further hybrid drive (18); and the electric prime mover (14) is one or both of suppliable with power by the further hybrid drive operated as a generator in order to establish a serial driving mode, and actuatable as a supporting force mechanism in order to maintain a supporting force during gear shifts in the further hybrid drive.

29. A method for operating the motor vehicle drive train (12) of claim 26, the method comprising one or more of: actuating the electric prime mover as a synchronizer during a gear shift in the electric transmission; supplying the electric prime mover (14) with power by a further hybrid drive operated as a generator in order to establish a serial driving mode; and actuating the electric prime mover (14) as a supporting force mechanism in order to maintain a supporting force during gear shifts in the further hybrid drive.

30. A motor vehicle, comprising: the motor vehicle drive train (12) of claim 26; and an energy accumulator (20) configured for storing energy for supplying the electric prime mover (14).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Example aspects of the invention are described and explained in greater detail in the following with reference to a few selected exemplary embodiments in conjunction with the attached drawings, in which:

[0046] FIG. 1 shows a schematic top view of a motor vehicle that includes a motor vehicle drive train according to example aspects of the invention;

[0047] FIG. 2 shows a schematic view of the electric transmission according to example aspects of the invention;

[0048] FIG. 3 shows another variant of an electric transmission according to the invention;

[0049] FIG. 4 shows another variant of an electric transmission according to example aspects of the invention;

[0050] FIG. 5 shows a detailed view of the electric transmission according to example aspects of the invention, according to FIG. 4;

[0051] FIG. 6 schematically shows the engagement conditions of the example electric transmission according to FIGS. 2 through 5;

[0052] FIG. 7 shows another variant of an electric transmission according to example aspects of the invention;

[0053] FIG. 8 shows another variant of an electric transmission according to example aspects of the invention;

[0054] FIG. 9 shows a detailed view of the electric transmission according to example aspects of the invention, according to FIG. 8; and

[0055] FIG. 10 schematically shows the engagement conditions of the example electric transmission according to FIGS. 7 through 9.

DETAILED DESCRIPTION

[0056] Reference will now be made to embodiments of the invention, one or more examples of which are shown in the drawings. Each embodiment is provided by way of explanation of the invention, and not as a limitation of the invention. For example, features illustrated or described as part of one embodiment can be combined with another embodiment to yield still another embodiment. It is intended that the present invention include these and other modifications and variations to the embodiments described herein.

[0057] FIG. 1 schematically shows a motor vehicle that includes a motor vehicle drive train 12. The motor vehicle drive train 12 includes an electric prime mover 14 and an electric transmission 16. The electric transmission 16 and the electric prime mover 14 form an electric axle, which is connected to a rear axle of the motor vehicle 10 in the example shown. A further pure combustion or hybrid drive 18 is operatively connected to the front axle of the motor vehicle 10. It is understood that a reversed connection can also be implemented, such that the electric axle is connected to the front axle of the motor vehicle 10 and the rear axle of the motor vehicle 10 includes the further hybrid drive 18. Drive power of the electric prime mover 14 is supplied to the wheels of the motor vehicle 10 by the motor vehicle drive train 12. The motor vehicle 10 also includes an energy accumulator 20 in order to store energy, which is utilized for supplying the electric prime mover 14.

[0058] FIG. 2 schematically shows an example variant of an electric transmission 16 in a motor vehicle drive train 12.

[0059] The motor vehicle drive train 12 includes the electric transmission 16 and the electric prime mover 14, the rotor 22 of which is connected to a transmission input shaft 24. This transmission input shaft 24 is drivingly connected to a reduction gear 26. In the example shown, the reduction gear 26 includes a planetary gear set, the ring gear of which is rotationally fixed, the sun gear of which is connected to the transmission input shaft 24, and the planet carrier of which is drivingly connected to a transmission 28.

[0060] In the example shown, the transmission 28 has a first planetary gear set RS1 and a second planetary gear set RS2, which are radially nested inside each other.

[0061] The sun gear of the first planetary gear set RS1 is drivingly connected to a ring gear of the second planetary gear set RS2, wherein the two planetary gear sets RS1, RS2 are arranged in one gear set plane. In other words, the second planetary gear set RS2 is arranged radially within the first planetary gear set RS1.

[0062] In the transmission 28, the two planet carriers of the first planetary gear set RS1 and of the second planetary gear set RS2 are drivingly connected by a carrier shaft 30. The carrier shaft 30 can be designed, in particular, as one piece.

[0063] The carrier shaft 30 is also connected to a differential 32 designed as a ball differential, which transmits drive power from the electric transmission 16 onto a first output shaft 34 and a second output shaft 36, which are preferably each connected to wheels of the motor vehicle 10.

[0064] Moreover, the electric transmission 16 has a first shift element B, a second shift element C, and a third shift element D.

[0065] The first shift element B is designed as a clutch, wherein the second shift element C and the third shift element D are each designed as a brake.

[0066] The first shift element B is designed for connecting an uncoupled sun gear, i.e., the sun gear of the second planetary gear set RS2, to the transmission input shaft 24. It is understood that a pre-ratio is established by the reduction gear 26 in this connection.

[0067] The second shift element C, which is designed as a brake, is designed for rotationally fixing the sun gear of the second planetary gear set RS2, i.e., connecting the sun gear of the second planetary gear set RS2 to a housing-affixed component in a rotationally fixed manner.

[0068] The third shift element D, i.e., the second brake, is designed for rotationally fixing an uncoupled ring gear, i.e., in particular, the ring gear of the first planetary gear set RS1.

[0069] Due to this advantageous arrangement of the shift elements and the transmission components, two reduction gears and one direct gear having a very high efficiency can be created with the electric transmission 16. The stationary transmission ratios of the two planetary gear sets RS1, RS2 are in a structurally favorable range with a value less than (<) 2.2.

[0070] It is understood that the shift elements can be at least partially designed as constant-mesh shift elements. In particular, all shift elements can also be designed as frictional shift elements.

[0071] In the example shown in FIG. 2, the reduction gear is connected upstream from the transmission 28 as viewed from the electric prime mover 14. As a result, a high rotational speed of the electric prime mover 14 can be reduced already before entering the transmission 28.

[0072] The planetary gear sets RS1, RS2 arranged in the transmission 28 are designed as a nested CC-SR gear set, wherein CC is to be understood to stand for a connection of the two planet carriers (“C” for “carrier”) and SR for a connection of a sun gear to a ring gear (“S” for “sun”, “R” for “ring”).

[0073] Another example variant of an electric transmission 16 according to aspects of the invention is shown in FIG. 3. In contrast to the example embodiment shown in FIG. 2, the transmission input shaft 24 is initially connected to the transmission 28 and then to the reduction gear 26. Otherwise, the connections and the mode of operation are identical to the example embodiment shown in FIG. 2. Due to the downstream reduction gear set, i.e., the reduction gear 26 arranged downstream from the transmission 28 in the power flow, high torques first arise upstream from the differential 32.

[0074] FIG. 4 shows another example variant of an electric transmission 16 according to aspects of the invention. In contrast to the example embodiment shown in FIG. 3, the differential 32 and the reduction gear 26 are combined to form a two-carrier five-shaft transmission. As a result, the functionality of the differential 32 and a reduction, as with a reduction gear 26, can be achieved. In other words, in the example embodiment shown in FIG. 4, the reduction gear 26 also has a differential. This is achieved by two planetary gear sets, which are also radially nested.

[0075] FIG. 5 shows the example electric transmission 16 according to FIG. 4 in greater detail and fully constructed.

[0076] The shift elements B, C, D are each designed as a frictional shift element. The individual transmission components are labeled similarly to the schematic view according to FIG. 4.

[0077] In FIG. 6, the engagement conditions of the individual shift elements for engaging the individual gear steps are schematically shown in a gear shift matrix 38, wherein an “X” indicates that the particular shift element is engaged, i.e., drivingly connects the transmission components associated with the shift element to one another. If an entry is not present in the gear shift matrix 38, it is to be assumed that the particular shift element is disengaged, i.e., does not transmit drive power.

[0078] The third shift element D is to be engaged for engaging the first step 1G.

[0079] The second gear step 2G can be established by engaging the second shift element C.

[0080] An engagement of the first shift element B establishes the third gear step 3G.

[0081] It is understood that a two-speed design can also be created, wherein one shift element is omitted. It is also understood that the gear step that is engageable with this shift element is no longer available in the two-speed variant.

[0082] FIG. 7 shows another example variant of an electric transmission 16 according to aspects of the invention. In contrast to the example embodiment shown in FIG. 2, the CC-SR gear set is no longer radially nested, but rather shown in an example embodiment situated next to one another. Moreover, the electric transmission 16 includes a free shaft 40, which is displaceable in its axial position by a selector fork 42 and, in this way, engages each of the individual shift elements B, C, D. In other words, each engagement condition necessary for engaging three gear steps can be established by displacing the free shaft 40 in the axial direction.

[0083] The rotor 22 of the electric prime mover 14 is connected to the transmission input shaft 24, wherein the transmission input shaft 24 is connected to the sun gear of the first planetary gear set RS1 and to the ring gear of the second planetary gear set RS2. The two planetary gear sets RS1, RS2 are drivingly connected to each other at their planet carriers with the carrier shaft 30, wherein the carrier shaft 30 is also drivingly operatively connected to a 2-carrier 5-shaft transmission arranged axially parallel at the first planetary gear set RS1 and the second planetary gear set RS2. As in the example embodiment shown in FIG. 4, this 2-carrier 5-shaft transmission has a reduction function as well as a differential function and distributes drive power onto the first output shaft 34 and the second output shaft 36 of the electric transmission 16.

[0084] In the engagement condition shown in FIG. 7, the first shift element B and the third shift element D are engaged. The connections necessary for engaging the gear steps can be established by the shift elements B, C, D arranged at the free shaft 40 by moving the free shaft 40 in the axial direction further away from the electric prime mover 14. The first shift element B is designed for drivingly connecting the sun gear of the second planetary gear set RS2 to the free shaft 40. The second shift element C is designed for drivingly connecting the ring gear of the first planetary gear set RS1 to the free shaft 40. The third shift element D is designed for rotationally fixing the free shaft 40.

[0085] FIG. 8 shows another example variant of an electric transmission 16 according to aspects of the invention. In contrast to the example embodiment shown in FIG. 7, the 2-carrier 5-shaft transmission is arranged coaxially to the first planetary gear set RS1 and the second planetary gear set RS2, although axially offset with respect to the first planetary gear set RS1 and the second planetary gear set RS2. The 2-carrier 5-shaft transmission is arranged at a side opposite the electric prime mover 14 with respect to the first planetary gear set RS1 and the second planetary gear set RS2. The connections at the free shaft 40 and the remaining connections in the electric transmission 16 are similar to the example embodiment shown in FIG. 7. In the condition shown in FIG. 8, therefore, the second shift element C and the third shift element D are engaged. Accordingly, the free shaft 40 is connected to the ring gear of the first planetary gear set RS1 in a rotationally fixed and driving manner.

[0086] FIG. 9 shows the example electric transmission 16 according to FIG. 8 in greater detail and fully constructed. Identical reference characters refer to identical features and are not explained once more. In contrast to the schematic view of an example embodiment shown in FIG. 8, the example embodiment shown in FIG. 9 includes a differential lock S, which is designed for drivingly connecting the two output shafts 34, 36 to each other. In the example shown, this is achieved due to the fact that axially engaging the differential lock S to the right in the example embodiment shown effectuates a form-locking connection.

[0087] FIG. 10 shows, in a gear shift matrix 44 similar to the gear shift matrix 38 according to FIG. 6, the engagement conditions for engaging the gear steps 1G, 2G, 3G of the electric transmission 16 according to FIGS. 7 through 9.

[0088] The second shift element C and the third shift element D are to be engaged for engaging the first gear step 1G.

[0089] The second gear step 2G is established by engaging the first shift element B and the third shift element D.

[0090] The third gear step 3G is established by engaging the first shift element B and the second shift element C.

[0091] The invention has been comprehensively described and explained with reference to the drawings and the description. The description and the explanation are to be understood as an example and are not to be understood as limiting. The invention is not limited to the disclosed embodiments. Other embodiments or variations result for a person skilled in the art within the scope of the utilization of the present invention and within the scope of a precise analysis of the drawings, the disclosure, and the following claims.

[0092] In the claims, the words “comprise” and “comprising” do not rule out the presence of further elements or steps. The indefinite article “a” does not rule out the presence of a plurality. A single element or a single unit can carry out the functions of several of the units mentioned in the claims. The mere mention of a few measures in multiple various dependent claims is not to be understood to mean that a combination of these measures cannot also be advantageously utilized. Reference characters in the patent claims are not to be understood as limiting. A method for operating a motor vehicle drive train 12 can be implemented, for example, in the form of a computer program that is run on a control unit for the motor vehicle drive train 12. A computer program can be stored/distributed on a non-volatile data carrier, for example, on an optical memory or on a solid state drive (SSD). A computer program can be distributed together with hardware and/or as part of a piece of hardware, for example, by the Internet or by hard-wired or wireless communication systems.

[0093] Modifications and variations can be made to the embodiments illustrated or described herein without departing from the scope and spirit of the invention as set forth in the appended claims. In the claims, reference characters corresponding to elements recited in the detailed description and the drawings may be recited. Such reference characters are enclosed within parentheses and are provided as an aid for reference to example embodiments described in the detailed description and the drawings. Such reference characters are provided for convenience only and have no effect on the scope of the claims. In particular, such reference characters are not intended to limit the claims to the particular example embodiments described in the detailed description and the drawings.

REFERENCE CHARACTERS

[0094] 10 motor vehicle [0095] 12 motor vehicle drive train [0096] 14 electric prime mover [0097] 16 electric transmission [0098] 18 hybrid drive [0099] 20 energy accumulator [0100] 22 rotor [0101] 24 transmission input shaft [0102] 26 reduction gear [0103] 28 transmission [0104] 30 carrier shaft [0105] 32 differential [0106] 34 first output shaft [0107] 36 second output shaft [0108] 38 gear shift matrix [0109] 40 free shaft [0110] 42 selector fork [0111] 44 gear shift matrix [0112] B-D shift elements [0113] RS1 first planetary gear set [0114] RS2 second planetary gear set [0115] S differential lock