Patent Application
20190145499
The invention relates generally to a transmission for a motor vehicle, and to a motor vehicle drive train having such a transmission.
DE 10 2013 002 586 A1 describes a transmission for a motor vehicle, in which two planetary gear sets are provided between an input shaft and an output shaft, each of which is composed of one sun gear, one ring gear, and one planet carrier. Furthermore, multiple shift elements are provided, via the selective actuation of which the planetary gear sets are able to be coupled to each other in order to define different gears between the input shaft and the output shaft. In all, four forward gears are selectable between the input shaft and the output shaft in this case.
In the present case, a transmission refers to a multi-stage transmission, i.e., multiple different transmission ratios are selectable, as gears, between an input end and an output end of the transmission by actuating appropriate shift elements, wherein this is preferably automatically carried out. Depending on the arrangement of the shift elements, the shift elements are clutches or even brakes. These types of transmissions are utilized preponderantly in motor vehicles in order to implement an available tractive force of a drive machine of the particular motor vehicle in a manner which is suitable with respect to various criteria.
An example problem addressed by the present invention is that of providing an alternative embodiment of the transmission known in the prior art, which has four forward gears between an input shaft and an output shaft.
According to example aspects of the invention, a transmission includes an input shaft and an output shaft, as well as a first planetary gear set and a second planetary gear set. The first and second planetary gear sets each include a first element, a second element, and a third element in the form of a sun gear, a ring gear, and a planet carrier, wherein the first and second planetary gear sets guide a power flow from the input shaft to the output shaft. For this purpose, a first shift element, a second shift element, a third shift element, a fourth shift element, and a fifth shift element are provided, the selective actuation of the first, second, third, fourth, and fifth shift elements couple the first and second planetary gear sets to each other while selecting different gears between the input shaft and the output shaft.
In this case, the input shaft is rotationally fixable to the first element of the first planetary gear set via the first shift element and to the third element of the second planetary gear set via the second shift element, wherein the first element of the first planetary gear set is also rotationally fixable to a rotationally fixed component of the transmission via the third shift element. The third element of the second planetary gear set is rotationally fixable to this rotationally fixed component via the fourth shift element. Moreover, the second element of the first planetary gear set and the second element of the second planetary gear set are jointly rotationally fixed to the output shaft. Finally, the third element of the first planetary gear set is rotationally fixed to the first element of the second planetary gear set and, jointly therewith, is rotationally fixable to the rotationally fixed component via the fifth shift element.
In other words, the second element of the first planetary gear set and the second element of the second planetary gear set are therefore permanently rotationally fixed to each other and are jointly connected to the output shaft. In addition, the third element of the first planetary gear set and the first element of the second planetary gear set are rotationally fixed to each other.
By engaging the first shift element, the input shaft of the transmission is rotationally fixed to the first element of the first planetary gear set, whereas an actuation of the second shift element results in a rotationally fixed connection of the input shaft to the third element of the second planetary gear set. Moreover, an engagement of the third shift element results in a fixation of the first element of the first planetary gear set to the rotationally fixed component, whereby the third element of the second planetary gear set is coupled upon actuation of the fourth shift element. Finally, the third element of the first planetary gear set and the first element of the second planetary gear set are jointly rotationally fixed to the rotationally fixed component by engaging the fifth shift element.
Therefore, each of the first and the second shift elements is a clutch, which, upon actuation, synchronizes rotatable components of the transmission in terms of their turning motions, while each of the third, the fourth, and the fifth shift elements is a brake which, upon actuation, decelerates the respective rotatable component of the transmission to a standstill and rotationally fixes it to the rotationally fixed component.
A transmission according to the invention is distinguished by a compact design, low component loads, and good gearing efficiency.
In the transmission according to the invention, four forward gears and one reverse gear are implementable. In doing so, a first forward gear is selected by actuating the first and the fifth shift elements, while a second forward gear is selected by engaging the second and the fifth shift elements. Moreover, a third forward gear is selected by actuating the first and the second shift elements, while a fourth forward gear is selected by actuating the second and the third shift elements. On the other hand, the reverse gear is selected by actuating the first and the fourth shift elements.
With the aid of a suitable selection of stationary transmission ratios of the planetary gear sets, a transmission ratio range which is suitable for the application in the case of a motor vehicle is implemented as a result. The condition of two shift elements in each case is always to be varied in order to successively select the forward gears in sequence, by disengaging one of the shift elements contributing to the preceding forward gear and engaging another shift element in order to implement the subsequent forward gear. As a further consequence thereof, a shift between the gears occurs very rapidly.
Advantageously, in the transmission according to the invention, one reverse gear for a power train is implementable via the drive machine connected upstream from the transmission. This reverse gear is implementable, in this case, as an alternative or in addition to an arrangement of an electric machine in the transmission, in order to still be capable of enabling the motor vehicle to travel in reverse in the case of a failure of the electric machine.
According to one embodiment of the invention, the first planetary gear set and the second planetary gear set are jointly arranged in a gear plane. This is possible in the present case since the third element of the first planetary gear set and the first element of the second planetary gear set are rotationally fixed to each other. An arrangement in a gear plane means, in this case, that the first and the second gear sets are installed in the transmission essentially at an axial height. In particular, the first planetary gear set is arranged radially inside the second planetary gear set in this case. The third element of the first planetary gear set and the first element of the second planetary gear set are a single piece in this case, in that, for example, a ring gear of the internal planetary gear set is provided on an outer circumference with a gearing which defines a sun gear of the external planetary gear set. Alternatively, the third element of the first planetary gear set and the first element of the second planetary gear set are separate components, however, which are rotationally fixed to each other.
According to yet another embodiment of the invention, the respective planetary gear set is present as a minus planetary gear set, wherein the respective first element of the respective planetary gear set is a respective sun gear, the respective second element of the respective planetary gear set is a respective planet carrier, and the respective third element of the respective planetary gear set is a respective ring gear. A minus planetary gear set is composed, in a way known, in principle, to a person skilled in the art, of the elements sun gear, planet carrier, and ring gear, wherein the planet carrier guides at least one planetary gear, although preferably multiple planetary gears which each individually intermesh with the sun gear as well as with the surrounding ring gear. Of the first and the second planetary gear sets, one or even both planetary gear sets are then configured as such minus planetary gear sets. It is particularly preferred when the two planetary gear sets are present as minus planetary gear sets, whereby a particularly compact design can be implemented.
Alternatively or additionally thereto, at least one of the first and second planetary gear sets is a plus planetary gear set, wherein the first element of the respective planetary gear set is a sun gear, the second element of the respective planetary gear set is a ring gear, and the third element of the respective planetary gear set is a planet carrier. In a plus planetary gear set, the sun gear, ring gear, and planet carrier are present, wherein the planetary carrier guides at least one pair of planet gears, in which the one planet gear of each pair of the at least one pair of planet gears is meshed with the internal sun gear and the other planet gear of each pair of the at least one pair of planet is meshed with the surrounding ring gear, and the planet gears in each pair of the at least one pair of planet are intermeshed with each other. In the transmission according to the invention, one or even both planetary gear sets are such plus planetary gear sets.
Where possible, a minus planetary gear set is replaceable by a plus planetary gear set, wherein, as compared to the minus planetary gear set, the ring gear connection and the planet carrier connection are to be interchanged, and a respective stationary transmission ratio is to be increased by one. As mentioned above, it is preferred, however, when both planetary gear sets are minus planetary gear sets.
In one refinement of the invention, one or multiple shift elements are each implemented as a friction-locking shift element. Friction-locking shift elements have the advantage that they are also shiftable under load, and therefore a changeover between the gears is carried out without an interruption of tractive force. It is particularly preferred, however, when the fourth shift element and/or the fifth shift element are each a form-fit shift element, such as a dog clutch or a lock-synchronizer mechanism. This is the case because the fifth shift element contributes to the first two forward gears, and therefore, when the gears are upshifted in succession, all that is necessary in this case is to disengage the fifth shift element. The fourth shift element contributes only to the engagement of the reverse gear. A form-fit shift element has the advantage over a friction-locking shift element that only low drag torques occur in the disengaged condition, and therefore high efficiency is achievable. In addition, a version as a steel-steel element or a band brake is also an option here.
According to one design option of the invention, the first and/or the third shift elements are/is arranged on a side of the first planetary gear set facing a mounting interface of the input shaft. The two shift elements therefore lie on an input side of the transmission and are easily accessed. Alternatively or additionally, the second shift element is arranged on a side of the second planetary gear set facing away from a mounting interface of the input shaft. Consequently, the second shift element is also easily accessed from an axial side of the transmission. The fourth and the fifth shift elements preferably each radially surround the respective planetary gear set and lie essentially axially at the level thereof, i.e., the fourth shift element surrounds the second planetary gear set and the fifth shift element surrounds the first planetary gear set.
According to yet another embodiment of the invention, mounting interfaces of the input shaft and of the output shaft are situated coaxially to each other. In this case, the mounting interface of the input shaft is preferably provided at one axial end of the transmission, while the mounting interface of the output shaft is axially between the first and the second planetary gear sets. In an arrangement of the planetary gear sets in a gear plane, the mounting interface of the output shaft can also lie in the area of the same axial end as the mounting interface of the input shaft. In particular, the external interface of the output shaft includes a tooth system in this case, which intermeshes with a tooth system of a shaft arranged axially parallel to the input shaft axis of the transmission. It is particularly preferred that the axle differential of a drive axle is then arranged on this shaft. This type of arrangement is particularly suitable for the application in a motor vehicle including a drive train aligned transversely to the direction of travel of the motor vehicle.
In one refinement of the invention, an electric machine is provided, a rotor of the electric machine is coupled in a rotationally fixed manner to one of the rotatable components of the transmission. Preferably, a stator of the electric machine is then rotationally fixed to the rotationally fixed component of the transmission, wherein the electric machine is operable as an electric motor and/or as a generator in this case in order to implement different functions. In particular, purely electric driving, boosting via the electric machine, deceleration and recuperation, and/or synchronization in the transmission are implementable via the electric machine. The rotor of the electric machine can lie coaxial to the respective component or axially offset with respect thereto in this case, wherein, in the latter case, a coupling via an intermediate spur gear stage or even a flexible traction drive mechanism is then implementable.
Preferably, the rotor of the electric machine is coupled in a rotationally fixed manner to the input shaft in this case, wherein, as a result, purely electric travel of the motor vehicle is implemented in a suitable way. For this purpose, one of the gears in the transmission is selected, wherein, in the forward gears, one reverse gear of the motor vehicle is implementable in this case, by initiating a turning motion in the opposite direction via the electric machine, whereby the reverse operation of the motor vehicle takes place in the transmission ratio of the respective forward gear. Consequently, the transmission ratios of the forward gears are usable for electric forward travel as well as for electric travel in reverse. The rotor of the electric machine, apart from the input shaft, is also connectable to one of the remaining rotatable components of the transmission, however.
According to yet another design option of the invention, which is implemented, in particular, in combination with the aforementioned arrangement of an electric machine, a separating clutch is also provided, via which the input shaft is rotationally fixable to a connecting shaft. The connecting shaft is utilized within a motor vehicle drive train as the connection to the drive machine. Providing the separating clutch has the advantage, in this case, that a connection to the driving machine is interruptible during the purely electric driving, whereby the drive machine is not entrained. The separating clutch is preferably, in this case, a friction-locking shift element, such as a multi-disk clutch, or a form-fit shift element, such as a dog clutch or a lock-synchronizer mechanism.
In general, a starting component is connectable upstream from the transmission, for example a hydrodynamic torque converter or a friction clutch. This starting component is then also an integral part of the transmission and acts to configure a starting process, in that the starting component enables a slip speed between the internal combustion engine and the input shaft of the transmission. In this case, one of the shift elements of the transmission or the separating clutch, which may be present, is also such a starting component, in that it is a frictional shift element. In addition, a one-way clutch with respect to the transmission housing or to another shaft is disposable on each shaft of the transmission, in principle.
The transmission according to the invention is, in particular, part of a motor vehicle drive train and is then arranged between a drive machine of the motor vehicle, which is, in particular, an internal combustion engine, and further components of the drive train, which follow in the direction of power flow to driving wheels of the motor vehicle. In this case, the input shaft of the transmission is either permanently coupled to a crankshaft of the internal combustion engine in a rotationally fixed manner or is connectable thereto via an intermediate separating clutch or a starting component, wherein a torsional vibration damper is also providable between the internal combustion engine and the transmission. On the output end, the transmission is then preferably coupled, within the motor vehicle drive train, to an axle transmission of a drive axle of the motor vehicle, wherein a connection to an interaxle differential can also be present in this case, however, via which a distribution to multiple driven axles of the motor vehicle takes place.
In the sense of the invention, the expression that two components of the transmission are “connected” or “coupled” to each other means that these components are permanently connected, and therefore these components rotate at one and the same rotational speed. In that respect, no shift element is provided between these components, which can be elements of the planetary gear sets or even shafts or a rotationally fixed component of the transmission. Instead, the corresponding components are rigidly connected to each other.
On the other hand, if a shift element is provided between two components of the transmission, these components are not permanently coupled to each other in a rotationally fixed manner. Instead, a rotationally fixed coupling is first carried out via the intermediate shift element, and the components are “connectable” or “fixable” to each other. In this case, an actuation of the shift element means, in the sense of the invention, that the respective shift element is transferred into an engaged condition and, consequently, equalizes the components coupled thereto in terms of their turning motions. In the case of an embodiment of the respective shift element as a form-fit shift element, the components rotationally fixed to each other via the shift element rotate at the same rotational speed, while, in the case of a friction-locking shift element, speed differences can exist between the components even after an actuation of said shift element. This intentional or even unintentional condition is nevertheless referred to, within the scope of the invention, as a rotationally fixed connection of the respective components via the shift element.
Advantageous embodiments of the invention, which are explained in the following, are represented in the drawings. In the drawings, the following is shown:
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.
The first and second planetary gear sets P1 and P2 are therefore each a minus planetary gear set in this case, in which the respective planet carrier guides one planetary gear, although preferably multiple planetary gears, in a rotatably mounted manner, each of the planetary gears individually intermeshing with the radially internal sun gear and also with the surrounding ring gear. At a point which would be permissible by the connection, however, individual or even both of the first and second planetary gear sets P1, P2 could also be so-called plus planetary gear sets, in which a respective planet carrier supports at least one pair of planet gears, one planet gear of each pair of the at least one pair of planet gears being meshed with a radially internal sun gear and another planet gear of each pair of the at least one pair of planet gears being meshed with a radially surrounding ring gear, and the planet gears of the pair of gears intermesh with each other. As compared to a minus planetary gear set, the second element E21, E22 of each of the first and second planetary gear sets P1, P2 would then need to be a ring gear and the third element E31, E32 of each of the first and second planetary gear sets P1, P2 would need to be a planet carrier and, in addition, a stationary transmission ratio would need to be increased by one.
As is apparent in
An input shaft GW1 of the transmission G is connectable, on the one hand, to the first element E11 of the first planetary gear set P1 via the first shift element K1 and, on the other hand, to the third element E32 of the second planetary gear set P2 via the second shift element K2. The first element E11 of the first planetary gear set P1, in turn, is rotationally fixable via the third shift element B1 to a rotationally fixed component GG which is preferably a transmission housing of the transmission G or a part of such a transmission housing. The third element E32 of the second planetary gear set P2 is also rotationally fixable to the rotationally fixed component GG by actuating the fourth shift element B2.
As is also apparent in
The first and second planetary gear sets P1, P2 are axially arranged in the sequence first planetary gear set P1 and second planetary gear set P2, wherein the first shift element K1 and the third shift element B1 are located axially on a side of the first planetary gear set P1 facing away from the second planetary gear set P2, on which side a mounting interface GW1-A of the input shaft GW1 also lies. On the other hand, the second shift element K2 is arranged on an axial end of the transmission G lying opposite thereto and, therefore, lies on a side of the second planetary gear set P2 facing away from the first planetary gear set P1. The fourth shift element B2 is located axially at the level of the second planetary gear set P2, radially surrounding same, while the fifth shift element B3 is provided axially at the level of and radially surrounding the first planetary gear set P1. In this case, a supply of the first shift element K1 and of the third shift element B1 via a common line is possible.
In addition, a mounting interface GW2-A of the output shaft GW2, which lies axially between the first planetary gear set P1 and the second planetary gear set P2 in this case, is coaxial to the mounting interface GW1-A of the input shaft GW1. The mounting interface GW1-A of the input shaft GW1 is utilized, in the motor vehicle drive train from
In the case of the embodiment according to
Purely electric driving is implementable via the electric machine EM, wherein, in this case, the separating clutch K0 is disengaged in order to decouple the input shaft GW1 from the connecting shaft AN and to not entrain the internal combustion engine VKM. For the rest, the embodiment according to
As is apparent in
The reverse gear R1, in which a reverse operation of the motor vehicle is implementable even during driving with the aid of the internal combustion engine VKM, is selected, on the other hand, by engaging the first shift element K1 and the fourth shift element B2.
As represented in
The arrangement of an electric machine EM shown in
With the aid of the embodiments according to the invention, a transmission having a compact design and good efficiency is implementable.
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2016 207 481.4 | May 2016 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2017/057146 | 3/27/2017 | WO | 00 |
