Method for actuating a vehicle powertrain

Patent metadata

Field	Value
Publication number	US-9925982-B2
Application number	US-201615342616-A
Country	US
Kind code	B2
Filing date	Nov 3, 2016
Priority date	Nov 3, 2015
Publication date	Mar 27, 2018
Grant date	Mar 27, 2018

Abstract

A method for operating a vehicle drive train includes operating the vehicle drive train with a drive unit switched on, with the drive unit connected to an output by a transmission, and with a positive-locking shifting element open. In response to a coasting operating state request for the vehicle drive train and a rotational speed of a transmission output being greater than a threshold, the drive unit is switched off and power flow between the drive unit and the output is interrupted by opening at least one of a plurality of frictional-locking shifting elements. The method also includes closing the positive-locking shifting element during the coasting operating state and no later than a leave coasting operating state request.

First claim

The invention claimed is:

1. A method for operating a vehicle drive train, the vehicle drive train having a drive unit, an output and a transmission for power flow between the drive unit and the output, the transmission having at least one positive-locking shifting element and a plurality of frictional-locking shifting elements operable for presentation of transmission ratios of the transmission, a portion of the transmission ratios presentable through the positive-locking shifting element, the method comprising:
operating the vehicle drive train with the drive unit switched on, with the drive unit connected to the output by the transmission, and with the positive-locking shifting element open;
in response to a coasting operating state request for the vehicle drive train and a rotational speed of a transmission output being greater than a threshold, switching off the drive unit and interrupting the power flow between the drive unit and the output by opening at least one of the plurality of frictional-locking shifting elements; and
closing the positive-locking shifting element during the coasting operating state and no later than a leave coasting operating state request,
wherein the vehicle drive train is operable with the drive unit switched on, with the drive unit connected to the output by the transmission at one of the transmission ratios presentable through the positive-locking shifting element after closing the positive-locking shifting element.

2. The method of claim 1 , wherein closing the positive-locking shifting element comprises closing the positive-locking shifting element in response to the coasting operating state request before or after switching off the drive unit.

3. The method of claim 1 , further comprising, prior to closing the positive-locking shifting element, transferring a gear set of the transmission into an at least partially blocked operating state by actuating of at least two of the plurality of frictional-locking shifting elements, a transmission input shaft held in a torque-proof manner and a transmission output shaft connected to the output rotatable in the at least partially blocked operating state of the gear set.

4. The method of claim 3 , wherein the gear set of the transmission is held in the at least partially blocked operating state at least until a rotational speed of the drive unit is less than a threshold value.

5. The method of claim 4 , further comprising varying a transfer capacity of the at least two of the plurality of frictional-locking shifting elements in order to generate a differential rotational speed between shifting element halves of the positive-locking shifting element prior to closing the positive-locking shifting element.

6. The method of claim 3 , further comprising closing the plurality of frictional-locking shifting elements when the power flow between the drive unit and the output is interrupted at the transmission, the closed frictional-locking shifting elements permitting rotation of the transmission output shaft.

7. The method of claim 3 , further comprising, with an activated coasting operating state of the vehicle drive train, reducing actuating forces of the plurality of frictional-locking shifting elements to a level at which the plurality of frictional-locking shifting elements have a slip-free operating state and from which the plurality of frictional-locking shifting elements are switchable on or off within short operating times.

8. The method of claim 1 , further comprising closing a converter lock-up clutch provided between the transmission and the drive unit for bridging a hydrodynamic torque converter during the coasting operating state when the drive unit is switched off.

9. The method of claim 1 , further comprising opening the positive-locking shifting element or keeping the positive-locking shifting element open in response to a deactivate coasting operating state request,
wherein the vehicle drive train is operable with the drive unit switched on, with the drive unit connected to the output by the transmission, and with the positive-locking shifting element open during the deactivated coasting operating state.

10. The method of claim 1 , further comprising raising actuating forces of the frictional-locking shifting elements to be closed after leaving of the coasting operating state of the vehicle drive train while the other frictional-locking shifting elements are open.

11. The method of claim 1 , further comprising detecting an interruption of the power flow between the drive unit and the output at the transmission when a deviation between a rotational speed of a transmission input shaft and a product arising from a rotational speed of a transmission output shaft and the transmission ratio engaged in the transmission is greater than a limit value.

12. The method of claim 1 , further comprising:
determining the current operating state of the vehicle drive train and the transmission ratio to be engaged upon leaving the coasting operating state; and
holding at least the frictional-locking shifting elements that are to be switched on to present the transmission ratio to be engaged upon leaving the coasting operating state in an operating state prepared for switching on the frictional-locking shifting elements.

13. The method of claim 1 , further comprising:
engaging a synchronization transmission ratio in the transmission, the positive-locking shifting element being closed and at least one additional positive-locking shifting element being open at the synchronization transmission ratio; and
in response to a deactivate coasting operating state request, shifting the transmission from the synchronization transmission ratio to a requested transmission ratio, the positive-locking shifting element being closed and the at least one additional positive-locking shifting element being closed in the requested transmission ratio,
wherein shifting the transmission from the synchronization transmission ratio to the requested transmission ratio comprises switched off one of the plurality of frictional-locking shifting elements and closing the at least one additional positive-locking shifting element.

14. The method of claim 1 , wherein the one of the plurality of frictional-locking shifting elements opened for interrupting the power flow between the drive unit and the output is only closed when a blocking state of a gear set of the transmission is canceled.

15. The method of claim 1 , further comprising:
in response to a deactivate coasting operating state request, checking whether a transmission ratio engaged during the activated coasting operating state corresponds to a requested transmission ratio to be engaged as a function of the event requesting deactivation of the coasting operating state; and
in response to determination of a deviation, engaging the requested transmission ratio.

16. The method of claim 1 , further comprising restarting the drive unit upon leaving the coasting operating state and with a rotational speed on the side of the transmission under a specified speed,
wherein the power flow between the drive unit and the output through the transmission is only established when a rotational speed of the drive unit exceeds the synchronous rotational speed of the transmission input shaft corresponding to the rotational speed of the transmission output shaft, the rotational speed of the transmission output shaft adjusted when the requested transmission ratio is engaged in the transmission.

Assignees

• Zahnradfabrik Friedrichshafen

Inventors

• Schiele Peter

Classifications

• F16H2200/2046

  with six engaging means · CPC title

• B60W10/06

  including control of combustion engines · CPC title

• B60W10/115

  with planetary gears · CPC title

• F16H2200/0065

  the gear ratios comprising nine forward speeds · CPC title

• F16H2200/2012

  with four sets of orbital gears · CPC title