Method for controlling a hybrid drivetrain

• US 8,062,173 B2
• Filed: 06/03/2009
• Issued: 11/22/2011
• Est. Priority Date: 06/12/2008
• Status: Active Grant

• Current Assignee: ZF Friedrichshafen AG (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Original Assignee: ZF Friedrichshafen AG (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Inventors: Lemp, Thomas, Tenbrock, Friedrich, Allgaier, Bernd, Gromus, Michael
• Primary Examiner(s): PHAN, HAU VAN
• Application Number:
  US12/477,191
• Publication Number:
  US 20090312143A1
• Time in Patent Office: 902 Days
• Field of Search: 477/2, 477/5, 477/6, 477/14, 477/15, 180/65.21, 180/65.265, 180/65.25, 180/65.26, 180/65.27, 180/65.28, 180/65.285, 903/903, 903/913, 903/914, 903/918
• US Class Current: 477/5
• CPC Class Codes: B60K 6/365 with the gears having orbital motion
• CPC Class Codes: B60K 6/387 Actuated clutches, i.e. clutches engaged or disengaged by electric, hydraulic or mechanical actuating means
• CPC Class Codes: B60K 6/48 Parallel type
• CPC Class Codes: B60K 6/543 the transmission being a continuously variable transmission
• CPC Class Codes: B60K 6/547 the transmission being a stepped gearing
• CPC Class Codes: B60L 2240/423 Torque
• CPC Class Codes: B60W 10/02 including control of driveline clutches
• CPC Class Codes: B60W 10/06 including control of combustion engines
• CPC Class Codes: B60W 10/08 including control of electric propulsion units, e.g. motors or generators
• CPC Class Codes: B60W 20/00 Control systems specially adapted for hybrid vehicles hybrid vehicle design, B60K6/00; electric vehicles B60L
• CPC Class Codes: B60W 2710/027 Clutch torque
• CPC Class Codes: B60W 2710/0666 Engine torque
• CPC Class Codes: B60W 2710/083 Torque
• CPC Class Codes: B60W 30/18072 Coasting
• CPC Class Codes: B60W 30/18109 Braking
• CPC Class Codes: B60W 30/192 Mitigating problems related to power-up or power-down of the driveline, e.g. start-up of a cold engine
• CPC Class Codes: B60Y 2400/428 Double clutch arrangements; Dual clutches
• CPC Class Codes: Y02T 10/62 Hybrid vehicles
• CPC Class Codes: Y02T 10/64 Electric machine technologies in electromobility

Abstract

A method for controlling a hybrid drivetrain of a motor vehicle such that, during a thrust operation of the vehicle, a change takes place from a combustion-powered driving mode, in which the combustion engine is in a thrust operation, the separator clutch is engaged and the electric machine contributes no force, or from a combined driving mode in which the engine is in a thrust operation, the clutch is engaged and the electric machine operates as a generator, to an electric driving mode in which the engine is switched off, the clutch is disengaged and the electric machine operates as a generator. To efficiently change driving modes, the clutch is partially disengaged to a slip limit; the clutch is then completely disengaged; and when the clutch reaches the slip limit, the generator torque of the electric machine is increased inversely to the torque that can be transmitted by the clutch.

Claims

1. A method of controlling a hybrid drivetrain of a motor vehicle, in which the motor vehicle has, arranged in series, a combustion engine (VM), a separator clutch (K), an electric machine (EM) that is operable as a motor and a generator, and a drive transmission which is drivingly connected, on an output side thereof, with a drive axle of the motor vehicle such that, during a thrust operation of the motor vehicle, a change takes place either from a combustion-powered driving mode in which the combustion engine (VM) is in a thrust operation, the separator clutch (K) is engaged and the electric machine (EM) does not contribute any driving no force, or from a combined driving mode in which the combustion engine (VM) is in the thrust operation, the separator clutch (K) is engaged and the electric machine (EM) operates as a generator, to an electric driving mode in which the combustion engine (VM) is turned off, the separator clutch (K) is disengaged and the electric machine (EM) operates as a generator, the change to the electric driving mode, during the thrust operation of the motor vehicle, is carried out by the method comprising the steps of:

commencing disengagement of the separator clutch (K) up to a slip limit;

disengaging the separator clutch (K) from the slip limit until the separator clutch (K) is completely disengaged; and

from the slip limit until the separator clutch (K) is completely disengaged, increasing generator torque (M_EM) by a same amount as the reduction of torque (M_K) that is transmitted by the separator clutch (K) when the separator clutch (K) is being disengaged.

2. The method according to claim 1, further comprising the step of disengaging the separator clutch (K) is in accordance with a predetermined torque variation (M_K(t)).

3. The method according to claim 2, further comprising the step of defining the predetermined torque variation (M_K(t)) of the separator clutch (K) as a ramp-shaped torque decrease with a constant torque gradient (dM_K/dt =C).

4. The method according to claim 1, further comprising the step of disengaging the separator clutch (K), during a first phase (t0 to t1), until the separator clutch (K) reaches the slip limit (t1), more rapidly than disengaging the separator clutch (K) in a subsequent, second phase (t1 to t2) until the separator clutch (K) is fully disengaged (t2).

5. The method according to claim 1, wherein the motor vehicle has a starting friction clutch which is positioned either immediately upstream from or integrated in the drive transmission and the method further comprising the step of maintaining disengagement of the starting friction clutch as far as a slip limit during the change of the hybrid driving mode to damp torque peaks.

6. The method according to claim 1, wherein the drive transmission is a dual-clutch transmission with two shifting clutches and the method further comprising the step of maintaining disengagement of one of the load-transmitting shifting clutches as far as a slip limit during the change of the hybrid driving mode to damp torque peaks.

7. The method according to claim 1, wherein the drive transmission is an automatic planetary transmission provided with frictional shift elements and the method further comprising the step of maintaining disengagement of at least one load-transmitting frictional shift element as far as a slip limit during the change of the hybrid driving mode to damp torque peaks.

8. The method according to claim 1, wherein a hydraulic torque converter is provided with a bridging clutch which are positioned immediately upstream from the drive transmission and the method further comprising the step of maintaining disengagement of the bridging clutch during the change of the hybrid driving mode to damp torque peaks.

9. The method according to claim 1, further comprising the step of carrying out a gearshift operation at a time close to that of the hybrid driving mode change in co-ordination with the hybrid driving mode change.

10. The method according to claim 9, wherein the drive transmission is a change-speed transmission in which gearshifts are accompanied by the traction force interruption and the method further comprising the step of disengaging the separator clutch (K) at an accelerated rate during a gearshift-related thrust traction force interruption.