STARTING DEVICE FOR A TRANSMISSION

Abstract

Disclosed is a starting device for a transmission. The starting device includes a drive input shaft provided for coupling the starting device to a drive engine connected upstream from the transmission. An output shaft is configured to connect the starting device to a gearset of the transmission. The drive input shaft and the output shaft can be connected rotationally fixed to one another by means of a first shifting element. An electric machine is provided whose rotor is connected to an intermediate shaft. The intermediate shaft is coupled to the output shaft by way of at least one gear step. In order to realize integration of the upstream drive engine and the electric machine, a second shifting element is also provided which, when actuated, forms a rotationally fixed connection between the intermediate shaft and the drive input shaft.

Claims

1-12. (canceled)

13. A starting device (11) for a transmission (4) having a drive engine, the starting device comprising: a drive input shaft (12) configured to couple the starting device (11) to a drive engine connected upstream from a transmission (4); an output shaft (15) configured to connect the starting device (11) to a gearset (8) of the transmission (4); a first shifting element (26) configured to connect rotationally fixed the drive input shaft (12) and the output shaft (15); an electric machine (17) with a rotor (19) connected to an intermediate shaft (16); at least one gear step coupling the intermediate shaft (16) to the output shaft (15); and a second shifting element (25), which when actuated, connects rotationally fixed the intermediate shaft (16) and the drive input shaft (12).

14. The starting device (11) according to claim 13, further comprising a planetary stage (20) coupling the intermediate shaft (16) and the output shaft (15), the planetary stage (20) including a first element, a second element, and a third element, respectively, in the form of a sun gear (21), a planetary web (22), and a ring gear (23), wherein the first element is connected rotationally fixed to the intermediate shaft (16), the second element is connected rotationally fixed to the output shaft (15), and the third element of the planetary stage (20) is permanently fixed.

15. The starting device (11) according to claim 14, wherein the first element of the planetary stage (20) is the sun gear (21), the second element of the planetary stage (20) is the planetary web (22), and the third element of the planetary stage (20) is the ring gear (23), and at least one planetary gearwheel (24) is mounted to rotate on the planetary web (22) so that the at least one planetary gearwheel meshes both with the sun gear (21) and with the ring gear (23).

16. The starting device (11) according to claim 12, wherein, the first shifting element (26) is in the form of an interlocking shifting element.

17. The starting device (11) according to claim 16, wherein the first shifting element is in the form of a claw-type shifting element.

18. The starting device (11) according to claim 13, wherein the second shifting element (25) is in the form of a frictional shifting element.

19. The starting device (11) according to claim 18, wherein the second shifting element (25) is in the form of a disk-type shifting element.

20. The starting device (11) according to claim 18, wherein the second shifting element (25) is a shifting element which is open when in the non-actuated condition of an associated actuating device.

21. The starting device (11) according to claim 13, wherein the drive input shaft (12) includes a first shaft section (13) connected to the second shifting element (25), and the drive input shaft includes a second shaft section (14) radially inside the first shaft section (13), wherein the second shaft section (14) connects the drive input shaft (12) to the first shifting element (26) such that the first shifting element (26) can be actuated via a shaft access (28) by way of the first shaft section (13).

22. A transmission (4) for a motor vehicle, the transmission, comprising a starting device (11) according to claim 13.

23. The transmission (4) according to claim 22, wherein the output shaft (15) of the starting device (11) is connected rotationally fixed to an input shaft (10) by way of which the output shaft (15) of the starting device (11) is connected to a gearset (8) of the transmission (4).

24. A method for operating a transmission (4) according to claim 22 having a starting device (11) according to claim 19, the method comprising: changing from a coupling of the drive input shaft (12) with the output shaft (15) by means of the second shifting element (25), to a coupling of drive input shaft (12) with the output shaft (15) by means of the first shifting element (26), wherein changing the coupling includes: first opening the second shifting element (25); then, increasing a rotation speed of the output shaft (15) by carrying out a gearshift in a gearset (8) of the transmission (4); and then closing the first shifting element (26) as soon as essentially synchronous rotation speeds are reached in the first shifting element (26).

25. A method for operating a transmission (4) according to claim 22 with a starting device (11) according to claim 19, the method comprising: changing a coupling of the drive input shaft (12) to the output shaft (15) by means of the second shifting element (25), to a coupling of the drive input shaft (12) to the output shaft (15) by means of the first shifting element (26), wherein changing the coupling includes: first opening the second shifting element (25); shifting a gearset (8) of the transmission (4) to neutral; then bringing the output shaft (15) to a rotation speed by the electric machine (17) such that a rotation speed at the first shifting element (26) and the rotation speed of the output shaft (15) are essentially synchronous; and then closing the first shifting element (26).

26. A method for operating a transmission (4) according to claim 22 with a starting device (11) according to claim 19, the method comprising: changing a coupling of the drive input shaft (12) to the output shaft (15) by means of the second shifting element (25), to a coupling of the drive input shaft (12) to the output shaft (15) by means of the first shifting element (26), wherein changing the coupling includes: progressively closing with slip the second shifting element while the first shifting element (26) is in a closed condition; opening the first shifting element (26) upon reaching a load-free condition of the first shifting element (26), the load-free condition by virtue of a power flow route via the second shifting element (25); and fully closing the second shifting element (25).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] An advantageous embodiment of the invention, which is explained in greater detail below, is illustrated in the drawings, which show:

[0035] FIG. 1: A schematic representation of a motor vehicle drivetrain; and

[0036] FIG. 2: A schematic representation of a transmission of the motor vehicle drivetrain in FIG. 1, which corresponds to a preferred embodiment of the invention.

DETAILED DESCRIPTION

[0037] FIG. 1 shows a schematic representation of a motor vehicle drivetrain 1 of a hybrid vehicle, in particular a passenger car. In this case the motor vehicle drivetrain comprises an internal combustion engine 2 which is connected to a transmission 4 via an intermediate torsion fluctuation damper 3. Downstream on the output side of the transmission 4 is connected a differential gear system 5, by means of which drive power is distributed to drive wheels 6 and 7 of a drive axle of the hybrid vehicle.

[0038] The transmission 4 and the torsion fluctuation damper 3 are arranged in a common housing of the transmission 4, in which the differential gear system 5 can also be integrated. As can also be seen in FIG. 1, the internal combustion engine 2, the torsion fluctuation damper 3, the transmission 4 and also the differential gear system 5 are aligned in the travel direction of the hybrid vehicle.

[0039] FIG. 2 shows a schematic representation of the transmission 4. In this case the transmission 4 is designed in accordance with a preferred embodiment of the invention and comprises a gearset 8 which is connected via a drive output shaft 9 to the downstream differential gear system 5 shown in FIG. 1 and by means of which various gears can be engaged between the drive output shaft 9 and an input shaft 10 arranged coaxially therewith. Changes between the gears of the gearset 8 can in each case be made under load. On the input shaft 10 the gearset 8 is also connected to an upstream starting device 11 of the transmission 4, so that by way of the starting device 11, in the motor vehicle drivetrain 1 in FIG. 1 a connection on the drive input side, of the input shaft 10 to the upstream internal combustion engine 2 can be made.

[0040] The starting device 11 is in this case designed in accordance with a preferred embodiment of the invention. Thus, the starting device 11 comprises a drive input shaft 12 which, in the motor vehicle drivetrain 1 of FIG. 1 is connected to the upstream torsion fluctuation damper 3 and is thus permanently coupled to the internal combustion engine 2. The drive input shaft 12 is coaxial with the input shaft 10 and on a side facing toward the gearset 8 has a first shaft section 13 in the form of a hollow shaft section and radially inside which a second shaft section 14 of the drive input shaft 12 is provided. The second shaft section 14 is in the form of a solid shaft section.

[0041] Besides the drive input shaft 12, the starting device 11 also has an output shaft 15 and an intermediate shaft 16, which are arranged coaxially with the drive input shaft 12. The output shaft 15 is in this case permanently connected rotationally fixed to the input shaft 10 of the gearset 8, so the output shaft 15 and the input shaft 10 can be made integrally, as one piece. Alternatively, however, the input shaft 10 and the output shaft 15 can be made as separate shafts which are permanently connected and rotationally fixed to one another by means of an appropriate connection, and which therefore rotate at the same rotation speed.

[0042] Whereas the output shaft 15 is made essentially as a solid shaft, the intermediate shaft 16 is a hollow shaft. Coaxially with the drive input shaft 12, the output shaft 15 and the intermediate shaft 16, an electric machine 17 is also installed, which machine consists of a stator 18 and a rotor 19 and can be operated on the one hand as a generator and on the other hand as an electric motor. The rotor 19 of the electric machine 17 is in this case connected permanently and in a rotationally fixed manner to the intermediate shaft 16, this connection being a solid connection between the rotor 19 and the intermediate shaft 16.

[0043] As can also be seen in FIG. 2, the intermediate shaft 16 and the output shaft 15, and therefore also the input shaft 10 of the gearset 8, are permanently coupled by way of a gear step in the form of a planetary stage 20. The planetary stage 20 consists of a sun gear 21, a planetary web 22 and a ring gear 23, wherein the planetary web 22 carries at least one planetary gearwheel 24 mounted to rotate on it, this gearwheel meshing with both the sun gear 21 and the ring gear 23.

[0044] In the present case the sun gear 21 is permanently connected rotationally fixed to the intermediate shaft 16, whereas in contrast the planetary web 22 is permanently connected to the output shaft 15 and therefore also to the input shaft 10. On the other hand, the ring gear 23 is permanently fixed and thus permanently prevented from rotating, this preferably being done by connecting the ring gear 23 rotationally fixed to a transmission housing of the transmission 4 or to a component attached to the transmission housing in a rotationally fixed manner. By virtue of the planetary stage 20 a rotation movement of the intermediate shaft 16 is geared down to the slow range on the output shaft 15, so the electric machine 17 can be made as a compact and fast-running machine.

[0045] The drive input shaft 12 can on the one hand be connected by its first shaft section 13, by means of a shifting element 25, rotationally fixed to the intermediate shaft 16 whereby, as a result, a rotation movement of the drive input shaft 12 is transmitted to the output shaft 15 with the gear ratio of the planetary stage 20. On the other hand, the drive input shaft 12 can also be connected by its second shaft section 14, directly rotationally fixed by means of a shifting element 26, to the output shaft 15, so that in this way the drive input shaft 12 and the output shaft 15, and therefore also the input shaft 10, all rotate with the same rotation speed.

[0046] In the present case the shifting element 25 is in the form of a frictional shifting element and is specifically a disk clutch, by means of which the rotationally fixed connection between the first shaft section 13 of the drive input shaft 12 and the intermediate shaft 16 can be formed under load. In this case, if a control element associated with the shifting element 25—not illustrated further here—is not actuated, the shifting element 25 is in an open condition (“normally open”). On the other hand, the shifting element 26 is in the form of an interlocking shifting element, such that the shifting element 26 is an unsynchronized claw clutch. The shifting element 26 is actuated by a control element 27 by means of a shaft access via the first shaft section 13.

[0047] During the operation of the motor vehicle drivetrain 1 in FIG. 1, in a starting process of the hybrid vehicle a starting gear is selected in the gearset 8 of the transmission 4 and the shifting element 25 is used as the starting element. For that purpose, the internal combustion engine 2 is adjusted to a desired starting rotation speed and, in addition, the shifting element 25 is progressively closed with slip, whereby rotation speed equality is progressively produced between the drive input shaft 12 and the intermediate shaft 16. During this the rotation movement of the intermediate shaft 16 is geared via the planetary stage 20 to the output shaft 15 and hence also the input shaft 10. The gear ratio of the planetary stage 20 then acts to relieve the load on the shifting element 25 owing to the thereby lesser effect of the torque on the shifting element 25. If the shifting element 25 is then fully closed and a motor rotation speed of the internal combustion engine 2 is high enough, or a gearshift is the transmission 4 is attempted, then a shift to a higher gear takes place in the gearset 8 of the transmission 4.

[0048] Thereafter, driving first continues with the shifting element 25 closed until with a randomly occurring pull-push change a shift takes place in the starting device 11 by changing from the shifting element 25 to the shifting element 26. The background here is that when the shifting element 26 is closed, driving can be done with greater efficiency since with the same gear in the gearset 8, a lower rotation speed is set in the internal combustion engine 2 and in addition, for the shifting element 26 no permanent energy supply has to be supplied to the actuating device 27.

[0049] In a first variant of the invention the changeover from a power flow route via the shifting element 25 to a power flow route via the shifting element 26 takes place by first opening the shifting element 25. Thereafter, in the gearset 8 of the transmission 4 a downshift to a lower gear is initiated if possible and thereby the rotation speed of the input shaft 10 and hence also that of the output shaft 15 of the starting device 11 is increased. When that has taken place a slight correction of the motor rotation speed of the internal combustion engine 2 is made in order to obtain a synchronous rotation speed at the shifting element 26. When that has been done, the shifting element 26 is closed and after that, if necessary, a gearshift in the gearset 8 of the transmission 4 to a desired gear is carried out.

[0050] Alternatively, the changeover from the shifting element 25 to the shifting element 26 can also be carried out by first opening the shifting element 25 and also carrying out a shift to neutral in the gearset 8 of the transmission 4, after which the input shaft 10 of the gearset 8 is decoupled from the drive output shaft 9. Thereafter, by means of the electric machine 17 with the help of the intermediate shaft 16 the output shaft 15 of the starting device 11 is brought to a rotation speed such that the rotation speeds at the shifting element 26 are essentially synchronous. Since the output shaft 15 is coupled permanently to the intermediate shaft 16 and hence also to the rotor 19 of the electric machine by way of the planetary stage 20, the electric machine can be used to produce the synchronous rotation speed. When the rotation speed speeds at the shifting element 26 are essentially synchronous, the shifting element 26 is closed. After that, a powershift can be carried out to a desired gear in the gearset 8.

[0051] The starting device 11 of the transmission 4 can also be used while the hybrid vehicle is driving to change to a crawling mode, in which the hybrid vehicle can be driven up a steep incline more easily since the gear ratio of the planetary stage 20 is also being used. In an initial situation a gear is selected in the gearset 8 of the transmission 4 and the shifting element 26 is closed in the starting device 11, while the shifting element 25 is open. If the need for a high torque at low driving speed is now recognized, for example due to a steep inclination of the road, then a shift from a power flow route via the shifting element 26 to a power flow route via the shifting element 25 is initiated. For this the shifting element 25 is progressively closed with slip, so that the power flow route via the shifting element 25 increases. From a condition in which the shifting element 26 is essentially free from load, the shifting element 26 is then opened. After that the shifting element 25 is then fully closed so that the gear ratio of the planetary stage 20 can be used for driving.

[0052] In the motor vehicle drivetrain 1 of FIG. 1, purely electric driving can also take place in that, in the starting device 11, the shifting elements 25 and 26 are both open and a drive power is supplied by the electric machine 17 operating as an electric motor. In this case a drive input movement of the electric machine 17 is transmitted by way of the planetary stage 20 to the output shaft 15 of the starting device 11 and hence also to the input shaft 10 of the gearset 8.

[0053] Furthermore, in the closed condition of the shifting element 26 of the starting device 11, the drive powers of the internal combustion engine 2 and the electric machine 17 can be summed, so that in such a case the planetary stage 20 functions as a summation stage.

[0054] By virtue of the design of a starting device according to the invention, a suitable integration of an electric machine and an upstream internal combustion engine can be realized.

INDEXES

[0055] 1 Motor vehicle drivetrain [0056] 2 Internal combustion engine [0057] 3 Torsion fluctuation damper [0058] 4 Transmission [0059] 5 Differential gear system [0060] 6 Drive wheel [0061] 7 Drive wheel [0062] 8 Gearset [0063] 9 Drive output shaft [0064] 10 Input shaft [0065] 11 Starting device [0066] 12 Drive input shaft [0067] 13 First shaft section [0068] 14 Second shaft section [0069] 15 Output shaft [0070] 16 Intermediate shaft [0071] 17 Electric machine [0072] 18 Stator [0073] 19 Rotor [0074] 20 Planetary stage [0075] 21 Sun gear [0076] 22 Planetary web [0077] 23 Ring gear [0078] 24 Planetary gearwheel [0079] 25 Shifting element [0080] 26 Shifting element [0081] 27 Actuating device [0082] 28 Shaft access