DE102021203417A1 - Transmission for a vehicle - Google Patents

Abstract

The invention relates to a transmission (10) for a vehicle, comprising an input shaft (11), an output shaft (12), a stepped planetary wheel set (20) mounted on a planet carrier (22) and two shifting elements (2, 3), the input shaft ( 11) is non-rotatably connected to a sun gear (21) of the stepped planetary gear set (20), the output shaft (12) is non-rotatably connected to the planetary carrier (22) of the stepped planetary gear set (20), planetary gears mounted on the planetary carrier (22) have effective diameters of different sizes, wherein planetary gears with a larger effective diameter (24a) mesh with both the sun gear (21) and with a first ring gear (23a), and wherein planetary gears with a smaller effective diameter (24b) mesh with a second ring gear (23b), a first Switching element (2) is designed to set the first ring gear (23a) on a non-rotatable component (0), and a second switching element (3) is designed to the second Ho hlrad (23b) fixed to a non-rotatable component. The invention also relates to an electric drive and a vehicle.

Description

The invention relates to a transmission comprising an input shaft, an output shaft, a stepped planetary gear set mounted on a planet carrier and arranged coaxially to the input shaft, and two shifting elements. The invention also relates to an electric drive and a vehicle with such a transmission or such an electric drive.

The object of the present invention is to provide an alternative transmission for a vehicle, an electric drive with such a transmission and a vehicle with such a transmission or electric drive. In particular, a multi-gear transmission is to be provided that enables the connection of a high-speed electric machine and at the same time is axially compact.

The invention is based on a transmission of the type mentioned. The transmission is characterized in that
the input shaft is non-rotatably connected to a sun gear of the stepped planetary gear set,
the output shaft is non-rotatably connected to the planet carrier of the stepped planetary gear set,
planetary gears mounted on the planet carrier have effective diameters of different sizes, planetary gears with a larger effective diameter meshing with both the sun gear and a first ring gear, and planetary gears with a smaller effective diameter meshing with a second ring gear,
a first switching element is designed to fix the first ring gear on a non-rotatable component, and
a second switching element is designed to fix the second ring gear on a non-rotatable component.

Two gears can be represented by means of the transmission. To represent a first gear, the first switching element is closed, while the second switching element is open. To represent a second gear, the first switching element is open, while the second switching element is closed.

The transmission described above advantageously has only one sun gear and one planet carrier. In particular, it is possible to mount the planetary carrier using only a single bearing. Such a transmission considerably reduces the variety of parts and is therefore lighter and cheaper than previously known transmissions. Such a gear also has good gearing efficiency.

In addition, the transmission according to the invention is extremely robust in terms of speed. On the one hand, very low ring gear and planetary gear speeds can be made possible, while the sun gears can have very high speeds. Low ring gear speeds reduce drag torque and wobbling. Low planetary gear speeds reduce bearing losses and have a positive effect on the acoustics.

A “shaft” in the context of the invention is understood to mean a rotatable component of the transmission, via which associated components of the transmission are connected to one another in a torque-proof manner or via which such a connection is established when a corresponding shifting element is actuated. The respective shaft can connect the components to one another axially or radially or both axially and radially. The respective shaft can also be present as an intermediate piece, via which a respective component is connected radially, for example. The term "shaft" does not exclude the possibility that the components to be connected can be made in one piece. In the case of components of the transmission which are connected to one another in a rotationally fixed manner only by actuation of a respective shifting element, a connection is also preferably implemented via one or more intermediate shafts.

In the context of the invention, “axial” means an orientation in the direction of a longitudinal central axis, along which the planetary gear sets are arranged lying coaxially to one another. “Radial” is then to be understood as meaning an orientation in the diameter direction of a shaft that lies on this longitudinal central axis.

The non-rotatable component of the transmission can preferably be a permanently stationary component, preferably a housing of the transmission, a part of such a housing or a component non-rotatably connected thereto. If an element of a transmission component, such as an element of a planetary gearset, is fixed permanently or temporarily by means of a shifting element to a non-rotatable component, it is permanently or temporarily prevented from rotating.

The switching elements can each be in the form of a clutch, a brake or a switchable freewheel. They can also each be formed either frictionally or positively. In addition, respective combinations may exist.

In a preferred embodiment, both the first and the second switching element are each designed as a brake. The brakes can be executed positively or frictionally. The particular advantage of two brakes is that, unlike hydraulically actuated clutches, there is no need for rotary feedthroughs.

In a preferred embodiment, the first shifting element is designed with a form fit and the second shifting element is designed with a friction fit. Such a selection allows for a seamless pull upshift from first to second gear. In addition, an open brake causes less drag torque than an open clutch. However, the use of a clutch makes release bearings necessary, so that the clutch cannot be arranged radially between the ring gear and the non-rotating component. This preferred embodiment is therefore less axially compact than the previously described embodiment with two radially nested brakes.

The transmission described above, which can also be referred to as a 2-carrier 4-shaft transmission, enables two forward gears, with a first gear being obtained by engaging the first shifting element and a second gear being obtained by engaging the second shifting element.

However, a transmission with more than two gears, in particular three gears, can also be provided. It is therefore preferred if a third planetary gear set and a third shifting element are provided, with a third sun gear of the third planetary gear set being connected to the input shaft in a rotationally fixed manner, the third shifting element being designed to fix a third ring gear on the rotationally fixed component, and the third planetary carrier has at least one third planetary gear that has the same axis of rotation as the first and second planetary gears, and the fastening element is also designed to support the third planetary gear. A third gear can be generated by closing the third shift element.

In other words, a third planetary gear set is arranged in a manner analogous to the first two planetary gear sets. The third planetary gear set is preferably designed as a minus planetary gear set.

In a further embodiment of the invention, a differential device connected to the output shaft is provided. It is common practice to reduce the speed of the output shaft before it is introduced into the differential assembly. For the pre-translation, it is expedient to provide a transmission gear, for example in the form of a spur gear or a planetary gear. At this point it is pointed out that the differential device can be used with both a 2-speed variant and a 3-speed variant of the transmission.

The output shaft of the transmission preferably has teeth, via which the output shaft is then in operative connection in the motor vehicle drive train with a differential device arranged axially parallel to the output shaft. In this case, the operative connection can be provided by means of a spur gear stage, with a first spur gear forming the toothing of the output shaft or being connected to the output shaft in a rotationally fixed manner, while a second spur gear of the spur gear stage, preferably an input element of the differential device, is correspondingly in toothed engagement with the output shaft.

As an alternative to this, provision can be made to provide an additional planetary gear set instead of a spur gear stage. It is therefore preferred if at least a second planetary gear set is provided with a fourth sun gear, a fourth planet carrier and a fourth ring gear. A first element from the group consisting of the second sun gear, the second planet carrier and the second ring gear is connected to the output shaft in a rotationally fixed manner. A second element from the group consisting of the second sun gear, the second planet carrier and the second ring gear is connected in a rotationally fixed manner to an input element of the differential device. A third element from the group consisting of the second sun gear, the second planet carrier and the second ring gear is permanently fixed to the non-rotatable component.

There are three advantageous connections of the at least fourth planetary gear set to the differential device: the first element can be the sun gear, the second element can be the planet carrier and the third element can be the ring gear. In an alternative connection, the first element can be the ring gear, the second element can be the planet carrier and the third element can be the sun gear. In an alternative connection to this, the first element can be the sun gear, the second element is the ring gear and the third element can be the planet carrier. Each of the three solutions provides a different pre-ratio for the vehicle's output shafts.

The spur gear solution offers the advantage of providing a transmission with a differential device that is particularly compact axially. In contrast, the planetary gear set solution offers the advantage of providing a transmission with a differential device that is particularly compact radially.

If at least a second planetary gear set is provided as a transmission gear, it is also preferred if one of the two output shafts of the Differential device is passed through the hollow-shaped sun gears of the first and second planetary gear sets and through the hollow-shaped input shaft.

Furthermore, a fourth switching element can be provided, which is designed to connect an input element of the differential device to an output element of the differential device in a torque-proof manner. The fourth switching element, which is preferably present as a clutch, acts as a differential lock.

According to a second aspect, an electric drive is provided. The electric drive includes a transmission as described above and an electric machine which is connected to the input shaft of the transmission. The rotor of the electric machine can be connected in a torque-proof manner to the input shaft or to the input shaft via a transmission gear. The electric machine is arranged coaxially or axially parallel to the input shaft.

According to a third aspect of the invention, a vehicle is provided with a transmission as described above or an electric drive as described above.

The fact that two components of the transmission are "connected" or "coupled" in a rotationally fixed manner or "are connected to one another" means, in the context of the invention, a permanent coupling of these components so that they cannot rotate independently of one another. In particular, no switching element is provided between these components, which can be elements of the planetary gear sets and/or shafts and/or a non-rotatable component of the transmission, but the corresponding components are firmly coupled to one another. A torsionally flexible connection between two components is also understood to be fixed or non-rotatable. In particular, a non-rotatable connection can also contain joints, e.g. to enable a steering movement or a deflection of a wheel.

• 1 eine schematische Ansicht eines Kraftfahrzeugantriebsstranges entsprechend einer ersten Ausführungsform;
• 2 einen Elektroantrieb mit einem Getriebe in einer bevorzugten Ausführungsform in einer schematischen Ansicht;
• 3 den Elektroantrieb aus 2 in einer weiteren bevorzugten Ausführungsform in einer schematischen Ansicht;
• 4 einen weiteren Elektroantrieb in einer bevorzugten Ausführungsform in einer schematischen Ansicht; und
• 5 verschiedene Anbindungsmöglichkeiten einer Abtriebskonstante in einer schematischen Ansicht.

Advantageous embodiments of the invention, which are explained below, are shown in the drawings. It shows:

• 1 a schematic view of a motor vehicle drive train according to a first embodiment;
• 2 an electric drive with a transmission in a preferred embodiment in a schematic view;
• 3 off the electric drive 2 in a further preferred embodiment in a schematic view;
• 4 another electric drive in a preferred embodiment in a schematic view; and
• 5 Various connection options for an output constant in a schematic view.

1 shows a schematic view of a motor vehicle drive train of a vehicle 100 according to a first embodiment, wherein an electric machine 7 is connected to a transmission 10 in the motor vehicle drive train. Transmission 10 and electric machine 7 form an electric drive 1. A differential device 60 is connected downstream of transmission 10 on the output side, via which drive power is distributed to drive wheels 105 of a drive axle B of the vehicle, with a planetary gear set being arranged between transmission 10 and differential 60 for pre-translating the output speed . The transmission 10 and the electric machine 7 are arranged in a common housing 0 of the electric drive 1 . As also in 1 As can be seen, the electric machine 7, the transmission 10 and also the differential device 60 are aligned transversely to a direction of travel of the vehicle 100.

2 shows an electric drive 1, as in a vehicle 1 can be used, comprising a gear 10 in a preferred embodiment and an electric machine connected to the gear 7. The electric machine has a rotor 7.1 and a fixed to a non-rotatable component 0 stator 7.2. The transmission 10 comprises an input shaft 11 connected to the rotor 7.1, an output shaft 12, a stepped planetary gear set 20 mounted on a planet carrier 22 and arranged coaxially to the input shaft, and two shifting elements 2, 3 designed as brakes.

The input shaft 11 is non-rotatably connected to a sun gear 21 of the stepped planetary gear set (20). The output shaft 12 is non-rotatably connected to the planetary carrier 22 of the stepped planetary gearset 20 . The transmission has planetary gears mounted on planet carrier 22 with effective diameters of different sizes, planetary gears with a larger effective diameter 24a meshing both with sun gear 21 and with a first ring gear 23a, and planetary gears with a smaller effective diameter 24b with a second ring gear 23b in meshing. The first switching element 2 is designed to fix the first ring gear 23a to a non-rotatable component 0 and a second switching element 3 is designed to fix the second ring gear 23b to a non-rotating component.

As can be seen clearly, the first brake 2 is axially on a level with the sun gear 21, the planet gear with the larger effective radius 24a and the ring gear 23a. For this purpose, the brake 3 is spaced apart axially and is placed axially on one level with the planet gear with the smaller effective radius 24b and the ring gear 23b.

By selectively actuating the brakes 2, 3, two forward gears can be achieved, with one of the two shifting elements having to be actuated to form the gears while the other one is open. A first gear can be achieved by actuating the first brake 2 and a second gear can be achieved by actuating the second brake 3 .

The output shaft 12 of the transmission 10 also has teeth, via which the output shaft 12 is operatively connected to a differential device 60 which is arranged axially parallel to the output shaft 12 and is designed as a bevel gear differential. According to this example, the operative connection is provided by means of a spur gear stage, with a first spur gear 64 forming the toothing of the output shaft 12 , while a second spur gear 61 of the spur gear stage meshes with the output shaft 12 . The second spur gear 61 also forms the input element of the differential

The bevel gear differential 60 also has, in a manner known per se, two output elements 62, 63 which in turn are each connected to a drive shaft of the vehicle. Furthermore, in 2 a parking lock gear 8 is shown, which is assigned to the output shaft 12 and is arranged axially between the teeth 64 and the planetary gear set 20 .

the inside 2 The electric drive shown is a 2-speed drive with a paraxial design. This drive is very compact, in particular axially compact, and enables closed hydraulics, among other things.

3 shows the electric drive 1 2 , In contrast to the embodiment gem. 2 a differential lock 9 is provided in the form of a clutch. In the actuated state, the clutch 9 connects the input element 61 to the second output element 63 of the differential 60 in a rotationally fixed manner.

4 shows the gearbox 2 , In contrast to the embodiment gem. 2 the translation of the speed of the output shaft 12 is effected with a second planetary gear set 70 instead of with a spur gear stage.

The second planetary gear set 70 includes a second sun gear 71, a second planet carrier 72 and a third ring gear 73. A first element from the group consisting of the second sun gear, second planet carrier and third ring gear, in this case the sun gear 71, is connected to the output shaft 12 in a torque-proof manner. A second element from the group consisting of the second sun gear, second planetary carrier and third ring gear, in this case the planetary carrier 72, is connected to an input element 61 of the differential device 60 in a torque-proof manner. A third element from the group consisting of the second sun gear, the second planet carrier and the third ring gear, in this case the ring gear 73, is permanently fixed to the non-rotatable component 0. The first output element 62 of the differential 60 is passed through the input shaft designed as a hollow shaft.

the inside 4 The electric drive shown is a 2-speed coaxial drive. This drive is very compact, particularly radially compact, and allows, among other things, closed hydraulics. According to this embodiment, the sun gear 71 is connected to the output shaft 12 and the planetary carrier 72 to the differential 60, while the ring gear 73 is fixed. However, the so-called output constant can also be connected to the transmission 10 in a different way, as in 5 is shown.

5 shows on the left the second planetary gear set 70 in the first connection variant described above.

A second connection variant of the second planetary gear set 70 is shown in the middle, in which case, in contrast to the first variant, the connection of the sun gear and ring gear are reversed. Accordingly, a first element from the group consisting of the second sun gear, the second planet carrier and the third ring gear, in this case the ring gear 73, is connected to the output shaft 12 in a rotationally fixed manner. A second element from the group consisting of the second sun gear, second planetary carrier and third ring gear, in this case the planetary carrier 72, is connected to an input element 61 of the differential device 60 in a torque-proof manner. A third element from the group consisting of the second sun gear, the second planet carrier and the third ring gear, in this case the sun gear 71, is permanently fixed to the non-rotatable component 0.

A third connection variant of the second planetary gear set 70 is shown on the right, in which case, in contrast to the first variant, the connection of the planet carrier and ring gear are reversed. Accordingly, a first element from the group consisting of the second sun wheel, the second planet carrier and the third ring wheel, in this case the sun wheel 71, is connected to the output shaft 12 in a torque-proof manner. A second element from the group second sun gear, second The planetary carrier and the third ring gear, in this case the ring gear 73, is connected in a torque-proof manner to an input element 61 of the differential device 60. A third element from the group consisting of the second sun gear, the second planet carrier and the third ring gear, in this case the planet carrier 72, is permanently fixed to the non-rotatable component 0.

Reference List

1

electric drive

2

switching element

3

switching element

7

electric machine

7.1

rotor

7.2

stator

8th

parking lock

9

Shift element, clutch, differential lock

10

transmission

11

input shaft

12

output shaft

20

first planetary gear set

21

first sun wheel

22

first planet carrier

23a

first ring gear

23b

second ring gear

24a

Planet wheel with larger effective diameter

24b

Planet wheel with smaller effective diameter

60

Differential device, bevel gear differential

61

Input element, toothing, second gear of the spur gear stage

62

output element

63

output element

64

Toothing, first gear of the spur gear stage

70

second planetary gear set

71

second sun wheel

72

second planet carrier

73

third ring gear

100

vehicle

105

drive wheels of the vehicle

A

electric drive axle

B

vehicle drive axle

Claims (11)

Transmission (10) for a vehicle, comprising an input shaft (11), an output shaft (12), a stepped planetary gear set (20) mounted on a planet carrier (22) and arranged coaxially to the input shaft (11), and two shifting elements (2, 3) , whereby the input shaft (11) is non-rotatably connected to a sun gear (21) of the stepped planetary gear set (20), the output shaft (12) is non-rotatably connected to the planet carrier (22) of the stepped planetary gear set (20), Planet gears mounted on the planet carrier (22) have effective diameters of different sizes, planet gears with a larger effective diameter (24a) meshing both with the sun gear (21) and with a first ring gear (23a), and planet gears with a smaller effective diameter (24b) mesh with a second ring gear (23b), a first switching element (2) is designed to fix the first ring gear (23a) on a non-rotatable component (0), and a second switching element (3) is designed to fix the second ring gear (23b) on a non-rotatable component. gear after claim 1 , wherein at least one of the switching elements (2, 3) is formed positively. gear after claim 1 or 2 , wherein at least one of the switching elements (2, 3) is formed frictionally. Transmission according to one of the preceding claims, wherein at least one of the shifting elements (2, 3) is designed as a brake. Transmission according to one of the preceding claims, wherein at least one of the shifting elements (2, 3) is designed as a clutch. Transmission according to one of the preceding claims, wherein a differential device (60) is provided which is connected to the output shaft (12) via a transmission gear. gear after claim 6 , wherein the transmission gear is designed as a spur gear stage, a first spur gear (64) of the spur gear stage being non-rotatably connected to the output shaft (12) and a second spur gear (61) of the spur gear stage forming the input element of the differential device (60). gear after claim 6 , wherein the transmission gear is designed as a second planetary gear set (70) with a second sun gear (71), a second planetary carrier (72) and a third ring gear (73), wherein - a first element from the group of second sun gear, second planetary carrier and third ring gear is non-rotatably connected to the output shaft (12), - a second element from the group of second sun gear, second planetary carrier and third ring gear is non-rotatably connected to an input element (61) of the differential device (60), - a third element from the group of second sun gear , second planet carrier and third ring gear is permanently fixed to the non-rotatable component (0). Transmission after one of Claims 6 until 8th , wherein a third switching element (6) is provided, which is designed to connect an input element (61) of the differential device (60) to an output element (62, 63) of the differential device (60) in a torque-proof manner. Electric drive with a gear according to one of the preceding claims, wherein the input shaft (10) is connected to a rotor (7.1) of an electric machine (7). Vehicle with a transmission according to any of Claims 1 until 9 or an electric drive claim 10 .

Images