METHOD FOR OPERATING A DRIVETRAIN

• US 20120238404A1
• Filed: 11/22/2010
• Published: 09/20/2012
• Est. Priority Date: 12/10/2009
• Status: Active Grant

• Current Assignee: ZF Friedrichshafen AG (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Original Assignee: ZF Friedrichshafen AG (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Inventors: Schiele, Peter, Sohler, Michael, Platzer, Falko
• Granted Patent: US 8,858,390 B2
• Time in Patent Office: Days
• US Class Current: 477/5
• CPC Class Codes: B60K 6/48 Parallel type
• CPC Class Codes: B60W 10/02 including control of driveline clutches
• CPC Class Codes: B60W 10/026 of lock-up clutches
• 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 20/40 Controlling the engagement or disengagement of prime movers, e.g. for transition between prime movers power-up or power-down of the driveline B60W30/192
• CPC Class Codes: B60W 2510/0225 Clutch actuator position
• CPC Class Codes: B60W 2710/022 Clutch actuator position
• CPC Class Codes: B60W 2710/025 Clutch slip, i.e. difference between input and output speeds
• CPC Class Codes: B60W 30/18027 Drive off, accelerating from standstill
• CPC Class Codes: B60W 30/18063 Creeping
• CPC Class Codes: F16D 2500/1066 Hybrid
• CPC Class Codes: F16D 2500/50215 Brake pedal
• CPC Class Codes: F16D 2500/70426 Clutch slip
• CPC Class Codes: F16D 48/06 Control by electric or electronic means, e.g. of fluid pressure
• CPC Class Codes: Y02T 10/62 Hybrid vehicles

Abstract

A method of operating a drive train having a hybrid drive including a combustion engine and electric motor, a clutch located between the engine and the motor, a transmission, a starting element and a brake pedal. For electric crawling from a state in which the clutch is disengaged, the brake pedal is activated and the combustion engine is turned off, initially the starting element is brought to or maintained at a filling pressure. Next, the rotational speed of the electric motor is adjusted to be higher, by a defined slippage rotational speed, than a transmission side rotational speed. When this slippage is reached, the starting element is further engaged to create a crawl torque at the output. The electric motor continues at rotational speed control so that the slippage is maintained.

Claims

1-10. -10. (canceled)

11. A method of operating a drive train of a motor vehicle for a crawling start of the motor vehicle in which the drive train comprises a hybrid drive with a combustion engine (2) and an electric motor (3);

a clutch (4) is positioned between the combustion engine (2) and the electric motor (3);

a transmission (5) is positioned between the hybrid drive and an output (6);

the drive includes either a transmission internal starting element (9) or a transmission external starting element (7) along with a brake pedal (11) and an accelerator pedal (10), the method comprising the steps of;

initiating the crawling start of the motor vehicle, with the drive train being in a starting condition in which the clutch (4), which is positioned between the combustion engine (2) and the electric motor (3), is disengaged, and the brake pedal (11) is activated and the accelerator pedal (10) is unactivated, and the combustion engine (2) of the hybrid drive is turned off;

either bringing the starting element (7, 9) to filling pressure or maintaining the filling pressure of the starting element (7, 9) either by deactivation or after deactivation of the brake pedal (11);

immediately thereafter bringing the electric motor (3) of the hybrid drive, which is operated in a rotational speed controlled mode, to a rotational speed that is higher by a defined slippage rotational speed than a transmission side rotational speed of the transmission (5);

further engaging the starting element (7, 9) to create torque at the output (6) for the crawling start, when the slippage is reached; and

continually operating the electric motor (3) in the rotation speed controlled mode to maintain the slippage for the crawl starting.

12. The method according to claim 11, further comprising the step of ensuring that the starting element (7, 9), at an initial state, is already filled at the filling pressure such that the starting element (7, 9) is maintained, either during the disengagement or after the disengagement of the brake pedal (11), at the filling pressure.

13. The method according to claim 11, further comprising the step of ensuring that the starting element (7, 9), at an initial state, is filled more than the filling pressure such that the starting element (7, 9) is drained, either during the disengagement or after the disengagement of the brake pedal (11), to the filling pressure.

14. The method according to claim 11, further comprising the step of, immediately after the filling pressure is present at the starting element (7, 9), bringing the electric motor to a rotational speed that is higher by a defined slippage rotational speed than a transmission input rotation speed of the transmission (5).

15. The method according to claim 11, further comprising the step of bringing the electric motor to a rotational speed that is higher by a defined slippage rotational speed than a transmission output rotation speed of the transmission (5) which is multiplied by an actual transmission gear ratio.

16. The method according to claim 11, further comprising the step of limiting the crawl torque, which is provided at the output during an entire electric crawling start, to a maximum permissible crawl torque, and the maximum permissible crawl torque depends upon an applicable torque of the electric motor (3) of the hybrid drive.

17. The method according to claim 11, further comprising the step of executing a speed control to guarantee a constant crawl speed when a maximum permissible crawl speed is reached, during the crawling start.

18. The method according to claim 11, further comprising the step of, during the entire electric crawl starting, limiting the rotational speed of the electric motor (3) to a maximum permissible idle rotation speed.

19. The method according to claim 11, further comprising the step of either bringing or maintaining the starting element (7, 9) to filling pressure for the electric crawling start by means of an electrically operated auxiliary hydraulic pump.

20. The method according to claim 11, further comprising the step of monitoring the activation of the accelerator pedal (10), during an entire electric crawl starting, such that when the accelerator pedal (10) is deactivated the crawling start is continued, and when the accelerator pedal (10) is activated, the crawling start is interrupted and a starting is executed, the electric motor (3) is operated for the starting in a torque controlled mode and the starting element (7, 9) is operated in a rotational speed controlled mode.