METHOD AND CONTROL APPARATUS FOR OPERATING A MOTOR VEHICLE

Abstract

A motor vehicle transmission is connected between a drive aggregate and a drive output, and includes a powershiftable main transmission group with a plurality of forward gears and at least one reversing gear. A hydrodynamic starting element is connected between the drive aggregate and the transmission. The main transmission has frictional shifting elements of which, in each gear, a first number are closed and a second number are open. The main transmission has a parking lock that, when engaged, immobilizes an output shaft of the main transmission group. A downstream range group includes at least one interlocking shifting element and can be shifted between a first range and a second range. When the motor vehicle is stationary with the drive aggregate running, to shift the downstream range group the parking lock is first engaged, and then the downstream range group is shifted into neutral from a range to be disengaged.

Claims

1-9. (canceled)

10. A method for operating a motor vehicle having a drive aggregate (1), with a transmission (2) connected between the drive aggregate (1) and a drive output (14), and having a hydrodynamic starting element (15, 18) connected between the drive aggregate (1) and the transmission (2), the method comprising: providing the transmission (2) comprising: a powershiftable main transmission group (2a) comprising: a plurality of forward gears, at least one reversing gear, a plurality of frictional shifting elements (9, 10, 11, 12, 13), of which in each gear a first number of the frictional shifting elements is closed and a second number of the frictional shifting elements is open, and a parking lock (28) configured such that when the parking lock (28) is engaged an output shaft (8) of the main transmission group (2a) is immobilized, and a downstream range group (2b) connected downstream from the main transmission group (2a), the downstream range group (2b) comprising at least one interlocking shifting element (24, 27) and which can be shifted between a first range and a second range; running the drive aggregate when the motor vehicle is stationary; engaging the parking lock (28) of the main transmission group to enable shifting the downstream range group (2b) and to immobilize the output shaft (8) of the main transmission (2a); and shifting the downstream range group (2b) into neutral from a range to be disengaged.

11. The method according to claim 10, comprising: engaging a gear in the main transmission group (2a); then, before engaging the parking lock (28) of the main transmission group, shifting the main transmission group (2a) to neutral; disengaging the parking lock (28); actuating the downstream range group (2b) shifting the downstream range group (2b) from neutral into a range to be engaged.

12. The method according to claim 1, wherein after shifting the downstream range group (2b) to neutral, shifting the downstream range group (2b) from neutral into a range to be engaged includes: shifting the main transmission group (2a) to neutral; disengaging the parking lock (28); and actuating the downstream range group (2b) so as to engage the range to be engaged.

13. The method according to claim 12, wherein disengaging the parking lock (28) takes place simultaneously with actuating the downstream range group (2b) in order to engage the range to be engaged.

14. The method according to claim 10, wherein: when a gear is engaged in the main transmission group (2a), then before and during the engagement of the parking lock (28) the main transmission group (2a) remains in the gear; and when the downstream range group (2b) has been shifted into neutral, then in order to shift the downstream range group (2b) from neutral into a range to be engaged the downstream range group (2b) is actuated in order to engage the range to be engaged while the gear in the main transmission group (2a) and the parking lock (28) remain engaged, and during this it is checked whether a tooth-on-tooth position has formed at the interlocking shifting element (24, 27) to be closed in the downstream range group (2b).

15. The method according to claim 14, comprising: determining whether a tooth-on-tooth position has formed at the interlocking shifting element (24, 27) to be closed in the downstream range group (2b); and shifting the main transmission group (2a) to neutral and then disengaging the parking lock (28), if it is found that the tooth-on-tooth position has formed.

16. The method according to claim 15, comprising disengaging the parking lock (28) if it is found that a tooth-on-tooth position has not formed at the interlocking shifting element (24, 27) to be closed in the downstream range group (2b), wherein the gear of the main transmission group (2a) remains engaged.

17. A control unit of a motor vehicle, the motor vehicle comprising: a drive aggregate (1), a transmission (2) connected between the drive aggregate (1) and a drive output (14) and a hydrodynamic starting element connected between the drive aggregate (1) and the transmission (2); wherein the hydrodynamic starter element comprises a converter (15) and a converter bridging clutch (18); wherein the transmission (2) comprises a powershiftable main transmission group (2a) and a downstream range group (2b) connected downstream from the main transmission group (2a); wherein, when a gear is engaged in the main transmission group (2a), the control unit is configured to actuate a first number of frictional shifting elements (9, 10, 11, 12, 13) of the main transmission group (2a) to close the shifting elements and configured to a second number of frictional shifting elements (9, 10, 11, 12, 13) to open the shifting elements; wherein, when the motor vehicle is stationary with its drive aggregate (1) running, then to shift the downstream range group (2b) the control unit is configured to actuate a parking lock (28) of the main transmission group (2a) in order to immobilize an output shaft (8) of the main transmission group (2a), and configured to actuate an interlocking shifting element (24, 27) of the downstream range group (2b) in order to shift the downstream range group (2b) from a range to be disengaged into neutral.

18. The control unit according to claim 17, wherein the control unit is configured to carry out the method according to claim 10 automatically.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Preferred further developments emerge from the subordinate claims and the description given below. Example embodiments of the invention, to which it is not limited, are explained in greater detail with reference to the drawings, which show:

[0019] FIG. 1: An example of a drive-train diagram of a motor vehicle with an example of a transmission comprising a main transmission group and a downstream range group:

[0020] FIG. 2: A shifting matrix of the main transmission group in FIG. 1:

[0021] FIG. 3: A possible design of the downstream range group in FIG. 1;

[0022] FIG. 4: An alternative configuration of the downstream range group in FIG. 1.

DETAILED DESCRIPTION

[0023] FIG. 1 shows schematically an example of a drive-train diagram of a motor vehicle. The drive-train in FIG. 1 comprises a transmission 2 and a drive output 14, wherein the transmission 2 is connected between the drive aggregate 1 and the drive output 14.

[0024] The transmission 2 comprises a main transmission group 2a which provides a plurality of forward gears and at least one reversing gear, and a downstream range group 2b connected on its drive input side downstream from the main transmission group 2a, which provides a first driving range and a second driving range. The first driving range can be a slow-drive range and the second driving range a fast-drive range. The first driving range can also be an all-wheel driving range and the second driving range can be a non-all-wheel driving range.

[0025] Between the drive aggregate 1 and the transmission 2, namely in the example embodiment shown between the drive aggregate 1 and the main transmission group 2a, is connected a hydrodynamic starting element with a converter 15 and a converter bridging clutch 18. A converter 15 comprises a turbine 16, and in the example embodiment shown, the turbine 16 is coupled in a rotationally fixed manner to an input shaft 7 of the main transmission group 2a. In addition, a converter 15 has a pump 17. The pump 17 is coupled rotationally fixed to the drive aggregate 1. The structure of such a converter 15 is familiar to a person with knowledge of the field.

[0026] The downstream range group 2b of the transmission 2 is connected between the main transmission group 2a of the transmission 2 and the drive output 14, and the downstream range group 2b is coupled to an output shaft 8 of the main transmission group 2a. Sometimes an upstream splitter group can be connected upstream from the main transmission group 2a, this then being located between the hydrodynamic starting element and the main transmission group 2a.

[0027] In the example embodiment shown, the main transmission group 2a of the transmission 2 comprises a plurality of gearsets 3, 4 5, and 6 and a plurality of frictional shifting elements 9, 10, 11, 12, and 13 that co-operate with the said gearsets, the two shifting elements 9 and 10 also being denoted shifting elements A and B. and the shifting elements 11, 12, and 13 also being denoted shifting elements C, D, and E. The shifting elements A and B and the shifting elements C, D, and E are in each case frictional shifting elements, namely the shifting elements A and B being brakes and the shifting elements C. D, and E being clutches.

[0028] FIG. 2 shows a shifting matrix of the main transmission group 2a of the transmission 2 in FIG. 1. It can be seen from FIG. 2 that in the case of the main transmission group 2a of the transmission 2 in FIG. 1, a total of eight frictional and thus traction-force-transmitting forward gears D1 to D8, and one frictional and thus traction-force-transmitting reversing gear R, can be provided. In each of these traction-force-transmitting gears D1 to D8 and R, a defined first number of shifting elements, namely three shifting elements of the main transmission group 2a, are closed, while in contrast a defined number of shifting elements, namely two shifting elements of the main transmission group 2a are open in each traction-force-transmitting and thus frictional gear.

[0029] The shifting elements of the main transmission group 2a, which are closed in the respective frictional and hence traction-force-transmitting gears, are indicated in FIG. 2 by a dot. For example, in forward gear D1 of the main transmission group 2a the shifting elements A, B. and C, and in forward gear D2 of the main transmission group 2a, the shifting elements A, B. and E are closed. In the reversing gear R of the main transmission group 2a, the shifting elements A, B, and D are closed. The shifting elements closed in forward gears D3, D4, D5, D6, D7, and D8 of the main transmission group 2a can also be seen from the shifting matrix in FIG. 2.

[0030] The main transmission group 2a also has a parking lock 28, such that when the parking lock 28 is engaged the output shaft 8 of the main transmission 2a is immobilized.

[0031] As already mentioned, the downstream range group 2b is connected between the output shaft 8 of the main transmission group 2a and the drive output 14. In this case the said downstream range group 2b can be designed as shown as an example in FIG. 3, wherein in FIG. 3 the downstream range group 2b comprises a planetary gear system 20 and a shifting element 24. The output shaft 8 of the main transmission group 2a is coupled to a sun gear 21 of the planetary gear system 20. The drive output 14 is coupled by way of an output shaft 19 of the downstream range group 2b to a web 23 of the planetary gear system 20. Depending on the shift position of the shifting element 24, a ring gear 22 of the planetary gear system 20 is either fixed to the housing in the slow-drive range L or is coupled to the web 23 in the fast-drive range S.

[0032] FIG. 4 shows an alternative configuration of the downstream range group 2b, which otherwise than in FIG. 3, is not of planetary design, but rather, in the form of a spur gear structure. Thus, the downstream range group in FIG. 4 has two spur gear stages 25 and 26 and a shifting element 27. Depending on the shift position of the shifting element 27, the output shaft 8 of the main transmission group 2a is coupled to the downstream range group 2b either via the spur gear stage 25 or via the spur gear stage 26.

[0033] The invention now relates to a method for shifting the downstream range group 2b of the transmission 2, which in its powershiftable main transmission group 2a comprises frictional shifting elements 9, 10, 11, 12, and 13, in a safe and reliable manner, specifically when the motor vehicle is at rest with its drive aggregate 1 running.

[0034] When the motor vehicle is at rest with its drive aggregate 1 running, to shift the downstream range group 2b the parking lock 28 of the main transmission group 2a is first engaged in order to immobilize the output shaft 8 of the main transmission group 2a. Then, the downstream range group 2b is shifted out of a range to be disengaged into neutral. The downstream range group 2b can remain in this neutral position for an arbitrarily long time without any risk that owing to drag losses in the main transmission group 2a the output shaft 8 of the main transmission group 2a will accelerate too much so that thereafter, the range to be engaged in the downstream range group 2b can no longer be engaged reliably.

[0035] When the motor vehicle is at rest with its drive aggregate 1 running and with a gear engaged in the main transmission group 2a, in a first variant of the invention, the main transmission group 2a is shifted into neutral before the parking lock 28 is engaged. Only after that, once the main transmission group 2a has been shifted to neutral, is the parking lock 28 of the main transmission 2a engaged and the downstream range group 2b then shifted to neutral. To shift the downstream range group 2b from neutral into a range to be engaged, the parking lock 28 is then disengaged and the downstream range group 2b is then actuated in order to engage the range to be engaged. In that way the range to be engaged can always be engaged reliably in the downstream range group 2b.

[0036] As a result of the drag torques in the main transmission group 2a, when the downstream range group 2b is shifted into the range to be engaged, the output shaft 8 of the main transmission group 2a is slightly accelerated, so that even a tooth-on-tooth position sometimes formed at the interlocking shifting element 24, 27 of the downstream range group 2b can be resolved.

[0037] When the motor vehicle is stationary with the drive aggregate 1 running and a gear is engaged in the main transmission group 2a, according to a second variant of the invention, it is provided that before and during the engagement of the parking lock 28 in the main transmission group 2a the main transmission group 2a remains in the gear concerned. After engaging the parking lock 28, the downstream range group 2b is then shifted to neutral. For the subsequent shifting of the downstream range group 2b from neutral into a range to be engaged, the main transmission group 2a is then first shifted to neutral and then the parking lock 28 is disengaged and the downstream range group 2b is actuated for engaging the range to be engaged. In this way, too, the range to be engaged in the downstream range group 2b can be engaged safely and reliably, if need be, with automatic resolution of a tooth-on-tooth position at the interlocking shifting element 24, 27 of the downstream range group 2b to be shifted.

[0038] The release of the parking lock 28 and the actuation of the downstream range group 2b to engage the range to be engaged preferably take place simultaneously, or alternatively immediately after one another, with a time overlap.

[0039] When the motor vehicle is stationary with the drive aggregate 1 running and a gear is engaged in the main transmission group 2a, in accordance with a third alternative of the invention, before and during the engagement of the parking lock 28 in the main transmission group 2a, the main transmission group 2a can remain in the gear concerned. When thereafter the downstream range group 2b is shifted to neutral, then for the subsequent shift of the downstream range group 2b from neutral into the range to be engaged the downstream range group 2b, namely its interlocking shifting element 24 or 27, is actuated in order to engage the said range to be engaged and this is done while the gear in the main transmission group 2a and the parking lock 28 remain engaged.

[0040] During this, in accordance with the third alternative of the invention, it is checked whether a tooth-on-tooth position has formed at the interlocking shifting element 24 or 27 to be closed. If it is found that a tooth-on-tooth position has formed at the interlocking shifting element 24 or 27 of the downstream range group 2b, then the main transmission group 2a is first shifted to neutral and then the parking lock 28 is disengaged in order then to resolve the tooth-on-tooth position and shift the downstream range group 2b into the range to be engaged. If there is no tooth-o-tooth position at the interlocking shifting element 24 or 27 of the downstream range group 2b, then after the shifting of the downstream range group 2b, i.e. after it has been changed to the range to be engaged, the parking lock 28 is disengaged and in that case the gear in the main transmission group 2a remains engaged throughout the process.

[0041] Accordingly, in the method according to the invention, to shift the downstream range group 2b, before the range to be disengaged in the downstream range group 2b has been disengaged the parking lock 28 in the main transmission group 2a is engaged in order to immobilize the output shaft 8 of the main transmission group 2a. In that case the main transmission group 2a can also previously be shifted to neutral, but alternatively the gear remains engaged in the main transmission group 2a. In each case the output shaft 8 of the main transmission group 2a is prevented from accelerating too much when the downstream range group 2b is in neutral. Thus, the downstream range group can subsequently be shifted reliably from neutral into the range to be engaged.

[0042] The invention also relates to a control unit which is designed to carry out the above-described method automatically. The control unit according to the invention is in particular a transmission control unit, preferably an electric or electronic transmission control unit. When the motor vehicle is at rest with the drive aggregate 1 running, in order to shift the downstream range group 2b the control unit actuates the parking lock 28 to engage it in order to immobilize the output shaft 8 of the main transmission group 2a. Thereafter, the control unit actuates an interlocking shifting element 24 or 27 of the downstream range group 2b in order to shift the downstream range group 2b from a range to be disengaged, into neutral.

[0043] As already mentioned above, the control unit according to the invention is preferably an electronic control unit which has hardware means and software means for carrying out the method according to the invention. The hardware means include data interfaces for exchanging data with the assemblies involved in carrying out the method according to the invention, for example with the parking lock 28 and the interlocking shifting element 24 or 27 of the downstream range group 2b and the shifting elements of the main transmission group 2a. The hardware means also include a processor for data processing and a memory for data storage. The software means include program modules which are implemented in the control unit according to the invention for carrying out the method according to the invention.

INDEXES

[0044] 1 Drive aggregate [0045] 2 Transmission [0046] 2a Main transmission group [0047] 2b Downstream range group [0048] 3 Gearset [0049] 4 Gearset [0050] 7 Gearset [0051] 6 Gearset [0052] 7 Input shaft of the main transmission group [0053] 8 Output shaft of the main transmission group [0054] 9 Shifting element A [0055] Shifting element B [0056] 11 Shifting element C [0057] 12 Shifting element D [0058] 13 Shifting element E [0059] 14 Drive output [0060] 15 Converter [0061] 16 Turbine [0062] 17 Pump [0063] 18 Converter bridging clutch [0064] 19 Output shaft of the downstream range group [0065] 20 Planetary gear system [0066] 21 Sun gear [0067] 22 Ring gear [0068] 23 Web [0069] 24 Shifting element [0070] 25 Spur gear stage [0071] 26 Spur gear stage [0072] 27 Shifting element [0073] 28 Parking lock