Method for operating a drive train of a vehicle

Abstract

A method for operating a drive train of a vehicle with a hydrodynamic torque converter, one transmission device and one prime mover during a gearshift starting from an actual ratio to a target ratio. A nominal standard of the control pressure of the shifting element to be disengaged is adjusted according to a nominal standard of the control pressure of the shifting element to be engaged. The rotational speed of a turbine of the torque converter is passed during the gearshift, starting from a synchronous rotational speed of the turbine of the actual ratio, in direction of a synchronous rotational speed of the turbine of the target ratio, the nominal standard of the control pressure of the shifting element to be disengaged.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described, by way of example, with reference to the accompanying drawings in which:

FIG. 1 is an extensively schematized representation of a drive train of a vehicle;

FIG. 2 is several curves corresponding with each other of operation parameters of different parts of the drive train, according to FIG. 1, during a simple push upshift;

FIG. 3 is a curve of a nominal standard of the rotational speed of a turbine of a hydrodynamic torque converter and a curve diverging therefrom of the actual rotational value of the turbine, and curves corresponding therewith of the control pressure of the shifting element to be disengaged and of the shifting element to be engaged, and

FIG. 4 is a representation essentially corresponding to FIG. 3 of curves of the turbine rotational speed and of the control pressure of the shifting element to be disengaged during a push upshift upon an occurrence of flare.

Claims

1-20. (canceled)

21. A method for operating a drive train of a vehicle during a gearshift from an actual transmission ratio (i_ist) to a target transmission ratio (i_ziel), the drive train having a hydrodynamic torque converter (3), a transmission device (4) and a prime mover (2), the method comprising the steps of: transmitting a shifting signal to the transmission device (4);initiating a transmission ratio change by reducing a transmitting capacity of a shifting element engaged in a power flow of the automatic transmission (actual ratio (i_ist)) and simultaneously preparing a shifting element to be engaged in the power flow of the transmission device (target ratio (i_ziel));adjusting a nominal standard of a control pressure (p_kab) of the shifting element to be disengaged, with respect to a nominal standard of the control pressure (p_kzu) of the shifting element to be engaged, such that an actual rotational speed (n_t_ist) of a turbine of the torque converter is altered, during the gearshift, from a synchronous rotational speed (n_t(“i_ist”)) of the turbine of the ratio (i_ist) to a synchronous rotational speed (n_t(“i_ziel”)) of the turbine of the target ratio (i_ziel); andadjusting the nominal standard of the control pressure (p_kab) of the shifting element to be disengaged, until a divergence of the actual rotational speed (n_t_ist) from a predefined nominal standard (n_t) of the rotational speed of the turbine is less than a threshold value, when the divergence of the actual rotational speed (n_t_ist) from a predefined nominal standard (n_t) of the rotational speed of the turbine is higher than the threshold value.

22. The method according to claim 21, further comprising the step of compensating for dispersions, produced by at least one of tolerance and wear, in control behavior of the shifting element to be engaged by adaptation routines.

23. The method according to claim 21, further comprising the step of changing the control pressures (p_kab) of the shifting element to be disengaged, the control pressures (p_kzu) of the shifting element to be engaged and transition moments at which a curve of the actual rotational speed (n_t_ist) of the turbine depending on operation parameters that characterize operation points of the shifting element to be disengaged and operation points of the shifting element to be engaged.

24. The method according to claim 21, further comprising the step of lowering the control pressure (p_kab) of the shifting element to be disengaged, in the presence of a shifting need, from a pressure value (p_sys) at which the shifting element to be disengaged is completely closed to a holding pressure value (p_kab_h) at which the shifting element to be disengaged is still closed and while another pressure reduction of the control pressure (p_kab) of the shifting element to be disengaged passes to a slip operation.

25. The method according to claim 24, further comprising the step of pre-filling the shifting element to be engaged, in the presence of a shifting need during a quick filling phase and next a filling compensation phase, such that the shifting element to be engaged has a pressure value (p_kzu_fa) at which a transmitting capacity of the shifting element to be engaged is approximately zero and an increase of a control pressure (p_kzu) of the a shifting element to be engaged produces an increase of the transmitting capacity of the a shifting element to be engaged.

26. The method according to claim 21, further comprising the step of maintaining the control pressure (p_kab) of the shifting element to be disengaged during a variable time period at a pressure level of a holding pressure value (p_kab_h), the variable time period correcting itself, essentially up to an end of the filling compensation phase of the shifting element to be engaged, to extend a varying time value, depending on at least one of a transmission input torque and a temperature of hydraulic fluid of the transmission.

27. The method according to claim 26, further comprising the step of reducing the control pressure (p_kab) of the shifting element to be disengaged, after expiration of the variable time period, to a second control pressure (p_kab) determined by the actual rotational speed (n_t_ist) of the turbine and an actual output torque of the turbine.

28. The method according to claim 21, further comprising the step of reducing the control pressure (p_kab) of the shifting element to be disengaged via a pressure ramp, over a time period until reaching a shifting pressure value (p_kab_s), depending on transmission input torque and a temperature of hydraulic fluid of the transmission device, and depending on a moment at which the control pressure (p_kzu) of the shifting element to be engaged is raised by the filling compensation pressure (p_kzu_fa) in direction of the shifting pressure (p_kzu_s), at which the shifting element to be engaged is with a transmitting capacity such that the rotational speed (n_t) of the turbine is transferred from a level of a synchronous rotational speed (n_t(“i_ist”)) of the turbine of the actual ratio (i_ist) in direction of the synchronous rotational speed (n_t(“i_ziel”)) of the turbine of the target ratio (i_ziel).

29. The method according to claim 28, further comprising the step of jerkily lowering the control pressure (p_kab) of the shifting element to be disengaged, from a holding pressure (p_kab_h) to the shifting pressure (p_kab_s), when a moment at which the control pressure (p_kzu) of the shifting element to be engaged is raised to the shifting pressure value (p_kzu_s) is stored from the time point of view prior to the moment at which the control pressure (p_kab) of the shifting element to be disengaged reaches the shifting pressure value (p_kab_s).

30. The method according to claim 28, further comprising the step of changing the moment at which the control pressure (p_kab) of the shifting element to be disengaged reaches the shifting pressure value (p_kab_s) by a time value when the actual rotational speed (n_t_ist) of the turbine diverges more than the threshold value from the nominal standard (n_t) of the rotational speed of the turbine.

31. The method according to claim 30, further comprising the step of cyclically adapting the time value via the operational a curve of the drive train (1) during the gearshift according to the divergence of the actual rotational speed (n_t_ist) of the turbine from the nominal standard (n_t) of the rotational speed of the turbine.

32. The method according to claim 30, further comprising the step of determining the time period according to a gradient of a curve of the actual rotational speed (n_t_ist) of the turbine.

33. The method according to claim 30, further comprising the step of determining the time value according to a difference between a gradient of a curve of the actual rotational speed (n_t_ist) of the turbine and a gradient of a curve of the nominal standard (n_t) of the rotational speed of the turbine.

34. The method according to claim 30, further comprising the step of determining the time value according to different operating state parameters of the drive train (1).

35. The method according to claim 30, further comprising the step of keeping the control pressure of the shifting element to be disengaged, upon detection of a divergence of the actual rotational speed from the nominal standard of the rotational speed of the turbine greater than the threshold value, at the actual pressure value until the divergence is less than the threshold value, the control pressure being subsequently lowered within a time period determined on the shifting pressure value.

36. The method according to claim 30, further comprising the step of raising the control pressure of the shifting element to be disengaged, upon detection of a divergence of the actual rotational speed of the turbine from the nominal standard of the rotational speed of the turbine, greater than the threshold value, to a pressure value and kept at the pressure value until the divergence is less than the threshold value, the control pressure then being lowered within the time period determined to the shifting pressure value.

37. The method according to claim 31, further comprising the step of varying the input torque (m_mot) of the prime mover (2) to minimize the divergence of the actual rotational speed (n_t_ist) of the turbine from the nominal standard of the rotational speed of the turbine.

38. The method according to claim 31, further comprising the step of raising the control pressure (p_kzu) of the shifting element to be engaged, after reaching the shifting pressure value (p_kzu_s), during a regulated powershift phase to a pressure value at which the shifting element is in a slip-free state.

39. The method according to claim 38, further comprising the step of raising the control pressure (p_kzu) of the shifting element to be engaged, in slip-free state of the shifting element to be engaged, to the holding pressure (p_kzu_h) and then to the system pressure (p_sys).

40. The method according to claim 31, further comprising the step of lowering the control pressure (p_kab) of the shifting element to be disengaged, after reaching the shifting pressure (p_kab_s) during a regulated powershift phase, to a pressure value (p_kab_o) at which the shifting element is essentially open.