Method for operating a vehicle drive train with a drive motor, an output and a transmission which is arranged between the drive motor and the output

Patent metadata

Field	Value
Publication number	US-10539227-B2
Application number	US-201715598436-A
Country	US
Kind code	B2
Filing date	May 18, 2017
Priority date	May 20, 2016
Publication date	Jan 21, 2020
Grant date	Jan 21, 2020

Abstract

A method for operating a vehicle drivetrain (1) includes proceeding, in the presence of the demand for activation of the engine start-stop function of the vehicle drivetrain (1) and a simultaneously shut-down drive machine (2), from an operating state of the vehicle drivetrain (1) during which a sailing operating function of the vehicle drivetrain (1) is active, during which the drive machine (2) is decoupled from the drive output (3), during which the positively engaging shift element (F) is open and during which a rotational speed (n_ab) of the drive output (3) is higher than a defined rotational speed at which a rotational speed difference between shift element halves of the positively engaging shift element (F) lies within a rotational speed range within which the positively engaging shift element (F) is transferrable into the closed operating state, and actuating the positively engaging shift element (F) in a closing direction no later than when the defined rotational speed is reached.

First claim

The invention claimed is:

1. A method for operating a vehicle drivetrain ( 1 ), the vehicle drivetrain ( 1 ) having a drive machine ( 2 ), a drive output ( 3 ) and a gearbox ( 4 ), the gearbox ( 4 ) arranged in power flow between the drive machine ( 2 ) and the drive output ( 3 ), the gearbox ( 4 ) having at least one positively engaging shift element (A, F) and a plurality of frictionally engaging shift elements (B, C, D, E), the at least one positively engaging shift element (A, F) and the plurality of frictionally engaging shift elements (B, C, D, E) selectively closable in order to engage different transmission ratios (“1” to “R”) of the gearbox ( 4 ), only some of the transmission ratios (“1” to “R”) engageable with the at least one positively engaging shift element (A, F), the vehicle drivetrain ( 1 ) configured such that, during a demand for activation of an engine start-stop function of the vehicle drivetrain ( 1 ), the drive machine ( 2 ) is decoupled from the drive output ( 3 ), the drive machine ( 2 ) is shut down, and the at least one positively engaging shift element (A, F) is transferred into or kept in a closed operating state of the at least one positively engaging shift element (A, F), the method comprising:
when there is the demand for activation of the engine start-stop function of the vehicle drivetrain ( 1 ) and a simultaneously shut-down drive machine ( 2 ), operating the vehicle drivetrain ( 1 ) with a sailing operating function of the vehicle drivetrain ( 1 ) active, with the drive machine ( 2 ) decoupled from the drive output ( 3 ), with the positively engaging shift element (F) open, and with a rotational speed (n_ab) of the drive output ( 3 ) greater than a defined rotational speed at which a rotational speed difference between shift element halves of the positively engaging shift element (F) lies within a rotational speed range within which the positively engaging shift element (F) is transferrable into the closed operating state; and
actuating the positively engaging shift element (F) in a closing direction no later than when the defined rotational speed is reached.

2. The method of claim 1 , further comprising ending actuation of the positively engaging shift element (F) in the closing direction when, in a standstill state of the vehicle, an open operating state of the positively engaging shift element (F) is identified.

3. The method of claim 1 , further comprising:
identifying, when the sailing operating function is active, a present operating state of the vehicle drivetrain ( 1 ) and the transmission ratio (“1” to “9”) that has to be engaged in the gearbox ( 4 ) during a restart of the drive machine ( 2 ) as a result of activation of the engine start-stop function; and
holding at least those shift elements (B, C, D) of the plurality of frictionally engaging shift elements (B, C, D, E) which have to be closed in order to engage the transmission ratio (“1” to “9”) that has to be engaged in the gearbox ( 4 ) for a departure from the sailing operating function in an operating state prepared for an activation of the shift elements (B, C, D) of the plurality of frictionally engaging shift elements (B, C, D, E).

4. The method of claim 1 , further comprising transferring, when the sailing operating function is active, a gear set ( 5 ) of the gearbox ( 4 ) into an at least partially blocked operating state by actuation of multiple frictionally engaging shift elements (B, C, D) of the plurality of frictionally engaging shift elements (B, C, D, E), a gearbox input shaft ( 6 ) held rotationally fixed and a gearbox output shaft ( 9 ) connected to the drive output ( 3 ) being rotatable in the at least partially blocked operating state.

5. The method of claim 4 , further comprising selecting, depending on the present operating state profile of the vehicle drivetrain ( 1 ), a sequence of the shift elements (B, C, D) of the plurality of frictionally engaging shift elements (B, C, D, E) that have to be actuated in succession for the partial blocking of the gear set ( 5 ).

6. The method of claim 4 , further comprising lowering, when the sailing operating state of the vehicle drivetrain ( 1 ) is active, actuation forces of the frictionally engaging shift elements (B, C, D) of the plurality of frictionally engaging shift elements (B, C, D, E) to a level at which the frictionally engaging shift elements (B, C, D) of the plurality of frictionally engaging shift elements (B, C, D, E) are still in a slippage-free operating state and proceeding from which the shift elements (B, C, D) of the plurality of frictionally engaging shift elements (B, C, D, E) are activatable or deactivatable within short operating times.

7. The method of claim 6 , further comprising:
activating the engine start-stop function to depart from the sailing operating function of the vehicle drivetrain ( 1 );
raising the actuation forces of the shift elements (B, C, D, E) of the plurality of frictionally engaging shift elements (B, C, D, E) that have to be held in or transferred into the closed operating state in order to depart from the sailing operating function of the vehicle drivetrain ( 1 ); and
opening the shift elements (B, C, D, E) of the plurality of frictionally engaging shift elements (B, C, D, E) that are not required to depart from the sailing operating function of the vehicle drivetrain ( 1 ).

8. The method of claim 7 , further comprising varying a torque transfer capacity of at least one of the shift elements (B, C, D) of the plurality of frictionally engaging shift elements (B, C, D, E) that is actuated for the at least partial blocking of the gear set ( 5 ) so that a rotational speed difference required for the closure of a further positively engaging shift element (A) is generated between shift element halves of the further positively engaging shift element (A) in the open operating state of the further positively engaging shift element (A).

9. The method of claim 1 , further comprising, during the demand for activation of the engine start-stop function and an associated demand for engaging a transmission ratio (“1” to “3”) engageable in the gearbox ( 4 ) by closing of the positively engaging shift element (F) and in response to identification of the open operating state of the positively engaging shift element (F) in a vehicle standstill state:
engaging a synchronization transmission ratio (“5” to “7”) in the gearbox ( 4 ), the positively engaging shift element (F) being in the open operating state in the synchronization transmission ratio (“5” to “7”); and
then deactivating a frictionally engaging shift element (B, C or E) of the plurality of frictionally engaging shift elements (B, C, D, E) and closing the positively engaging shift element (F) in order to implement a subsequent change in transmission ratio proceeding from the synchronization transmission ratio (“5” to “7”) in the direction of the demanded transmission ratio (“1” to “3”).

10. The method of claim 1 , further comprising triggering, when the engine start-stop function is active, a demand for activation of the sailing operating function in response to an exceedance of a defined threshold value of the rotational speed (n_ab) of the drive output ( 3 ).

11. The method of claim 1 , further comprising triggering, when the engine start-stop function is active, a demand for activation of the sailing operating function in response to an exceedance of a defined threshold value of the rotational speed (n_ab) of the drive output ( 3 ) for longer than a predefined time period or after a driving distance longer than a defined driving distance has been traveled.

12. The method of claim 1 , further comprising:
transferring the positively eng

Assignees

• Zahnradfabrik Friedrichshafen

Inventors

• Schiele Peter
• Brockmann Johannes

Classifications

• F16H2200/2094

  using positive clutches, e.g. dog clutches · CPC title

• F16H61/0204 Primary

  for gearshift control, e.g. control functions for performing shifting or generation of shift signal · CPC title

• F16H2200/2079

  using freewheel type mechanisms, e.g. freewheel clutches · CPC title

• F16H2061/0474

  by smoothing engagement or release of positive clutches; Methods or means for shock free engagement of dog clutches · CPC title

• F16H2200/0065

  the gear ratios comprising nine forward speeds · CPC title