Method and system for variable cam timing device

Patent metadata

Field	Value
Publication number	US-10337361-B2
Application number	US-201715479202-A
Country	US
Kind code	B2
Filing date	Apr 4, 2017
Priority date	Oct 21, 2014
Publication date	Jul 2, 2019
Grant date	Jul 2, 2019

Abstract

Methods and systems are described for an engine with a cam torque actuated variable cam timing phaser. Phaser positioning control is improved by reducing inaccuracies resulting from inadvertent spool valve and/or phaser movement when the spool valve is commanded between regions. In addition, improved spool valve mapping is used to render phaser commands more consistent and robust.

First claim

The invention claimed is:

1. A method, comprising:
moving a spool valve of a cam torque-actuated variable cam timing phaser to a detent region after occurrence of a first torsional pulse of a camshaft but before occurrence of a second torsional pulse of the camshaft occurring immediately after the first torsional pulse;
moving the spool valve to adjust the cam torque actuated variable cam timing phaser to a locking position;
holding the phaser at the locking position without engaging a locking pin for a duration; and
after the duration, further moving the spool valve to engage the locking pin.

2. The method of claim 1 , wherein the spool valve is moved to the detent region from a position away from the detent region.

3. The method of claim 2 , wherein the position away from the detent region includes one of a position in a null region, an advance region, and a retard region of the spool valve.

4. The method of claim 1 , wherein the spool valve is moved to the detent region after occurrence of the first torsional pulse but before occurrence of the second torsional pulse while the cam timing phaser is held in the locking position without engaging a locking pin.

5. The method of claim 4 , further comprising, before moving the spool valve, using cam torque to move the cam timing phaser to the locking position.

6. The method of claim 5 , wherein using cam torque to move the cam timing phaser to the locking position includes, when the cam timing phaser is located retarded of the locking position, moving the spool valve to the advance region until the phaser is in the locking position;
then moving the spool valve to the null region before a torsional pulse;
holding the spool valve in the null region until the torsional pulse has elapsed; and
after the torsional pulse has elapsed and before a next torsional pulse starts, moving the spool valve to the detent region.

7. The method of claim 6 , wherein using cam torque to move the cam timing phaser to the locking position further includes, when the cam timing phaser is located advanced of the locking position,
moving the spool valve to the retard region until the phaser is in the locking position;
then moving the spool valve to the null region before a torsional pulse;
holding the spool valve in the null region until the torsional pulse has elapsed; and
after the torsional pulse has elapsed and before a next torsional pulse starts, moving the spool valve to the detent region.

8. The method of claim 7 , further comprising, after moving the spool valve to the detent region, holding the phaser in the locking position by engaging the locking pin.

9. The method of claim 1 , wherein the torsional pulses are retard torsional pulses.

10. The method of claim 1 , further comprising, estimating a timing of the torsional pulses based on camshaft position relative to crankshaft position.

11. A method, comprising:
moving a cam torque actuated variable cam timing phaser from advanced of a locking position to the locking position by moving a spool valve through a retard region of the spool valve in between torsional pulses of a camshaft; and
during selected conditions,
ramping the spool valve from a detent region to a retard region; and
mapping a transitional region between the detent and retard regions based on phaser movement away from a locked position, the phaser movement responsive to the ramping.

12. The method of claim 11 , wherein the torsional pulses are retard torsional pulses.

13. The method of claim 12 , wherein moving through the retard region in between torsional pulses includes holding a position of the spool valve during torsional pulses.

14. The method of claim 11 , wherein moving the cam torque actuated phaser by moving the spool valve includes:
first moving the spool valve to the retard region and holding the spool valve in the retard region until the phaser reaches the locking position;
then, while holding the phaser in the locking position without engaging a locking pin, moving the spool valve to a null region before a torsional pulse;
then, holding the spool valve in the null region while the torsional pulse occurs; and
after the torsional pulse has passed, moving the spool valve from the null region to a detent region.

15. The method of claim 14 , further comprising, after moving the spool valve to the detent region, engaging the locking pin to lock the phaser in the locking position.

16. The method of claim 11 , further comprising, moving the cam torque actuated variable cam timing phaser from retarded of the locking position to the locking position by moving the spool valve to an advance region, and then moving the spool valve to the detent region through the retard region of the spool valve in between torsional pulses of the camshaft.

17. The method of claim 11 , wherein the selected conditions include a green engine condition.

18. The method of claim 11 , wherein the selected conditions include a threshold distance elapsed since a last mapping or a threshold duration elapsed since a last mapping.

19. The method of claim 11 , wherein the selected conditions include a DFSO condition.

20. The method of claim 11 , wherein the selected conditions include phaser position error being higher than a threshold.

Assignees

• Ford Global Tech Llc

Inventors

• Rollinger John Eric
• Pietrzyk Paul A
• Badillo Edward

Classifications

• F01L1/34409 Primary

  by torque-responsive means · CPC title

• F01L1/047

  Camshafts · CPC title

• F01L1/08

  Shape of cams · CPC title

• F01L2001/3443

  Solenoid driven oil control valves · CPC title

• F02D13/0219

  by shifting the phase, i.e. the opening periods of the valves are constant · CPC title