Method and system for variable cam timing device

Patent metadata

Field	Value
Publication number	US-10267187-B2
Application number	US-201715464158-A
Country	US
Kind code	B2
Filing date	Mar 20, 2017
Priority date	Oct 21, 2014
Publication date	Apr 23, 2019
Grant date	Apr 23, 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:
in response to a command for phasing a cam torque actuated variable cam timing phaser from a locked position,
jumping a spool valve from a detent region to outside a null region; and
ramping the spool valve through the null region; and

in response to system oil pressure falling below a threshold, adjusting spool valve position to reduce the system oil pressure applied to a locking circuit of the phaser.

2. The method of claim 1 , further comprising moving cam timing via cam torque actuated hydraulic pressure separate from engine generated oil pressure via the spool valve.

3. The method of claim 2 , wherein the ramping is performed while monitoring for cam timing movement away from the locked position.

4. The method of claim 3 , wherein moving the cam timing via the spool valve includes moving the spool valve to an advance region to use the cam torque actuated hydraulic pressure to advance a cam timing phaser position, moving the spool valve to a retard region to use the cam torque actuated hydraulic pressure to retard the phaser position, and moving the spool valve to the null region to use the cam torque actuated hydraulic pressure to hold the phaser position.

5. The method of claim 4 , wherein using the cam torque actuated hydraulic pressure to advance the cam timing phaser position includes flowing hydraulic fluid from a retard chamber of the phaser to an advance chamber through a phasing circuit using the cam torque actuated hydraulic pressure, and wherein using the cam torque actuated hydraulic pressure to retard the cam timing phaser position includes flowing hydraulic fluid from the advance chamber to the retard chamber through the phasing circuit using the cam torque actuated hydraulic pressure, and wherein using the cam torque actuated hydraulic pressure to hold the cam timing phaser position includes disabling flow of the hydraulic fluid through the phasing circuit between the retard and advance chamber.

6. The method of claim 5 , wherein using the cam torque actuated hydraulic pressure to advance the cam timing phaser position includes using advanced cam torsions and wherein using the cam torque actuated hydraulic pressure to retard the cam timing phaser position includes using retarded cam torsions.

7. The method of claim 6 , wherein adjusting the position of the spool valve in response to system oil pressure includes moving the spool valve to a detent region.

8. The method of claim 1 , wherein system oil pressure is not used to move the cam timing.

9. The method of claim 8 , further comprising, raising an engine idle speed to raise the system oil pressure above the threshold.

10. The method of claim 9 , wherein the engine idle speed is raised after a threshold duration has elapsed since the engagement of the locking pin with no rise in system oil pressure.

11. The method of claim 2 , further comprising, in response to the system oil pressure rising above the threshold, moving the spool valve out of the detent region.

12. The method of claim 1 , wherein phasing the cam torque actuated phaser from the locked position includes moving the phaser to an unlocked position, the unlocked position advanced or retarded of the locked position.

13. The method of claim 12 , wherein jumping the spool valve to outside the null region is based on a direction of the command for phasing.

14. The method of claim 13 , wherein the jumping includes jumping to a retard region outside the null region when the command for phasing is to an unlocked advance position, and wherein the jumping includes jumping to an advance region outside the null region when the command for phasing is to an unlocked retard position.

15. The method of claim 14 , wherein the advance region outside the null region is on a first side of the null region and wherein the retard region outside the null region is on a second, opposite side of the null region.

16. The method of claim 15 , wherein the jumping to a retard region is based on the unlocked advance position, the spool valve jumped further into the retard region as a degree of advance of the unlocked advance position increases; and wherein the jumping to an advance region is based on the unlocked retard position, the spool valve jumped further into the advance region as a degree of retard of the unlocked retard position increases.

17. The method of claim 13 , wherein a direction of the ramping through the null region is based on the direction of the command for phasing.

18. The method of claim 17 , wherein the ramping includes ramping from a retard region outside the null region, through the null region, to an advance region immediately outside the null region when the command for phasing is to an unlocked advance position, and ramping from the advance region outside the null region, through the null region, to the retard region immediately outside the null region when the command for phasing is to an unlocked retard position.

19. The method of claim 18 , wherein a rate of the ramping is based on one or more of engine speed, engine oil pressure, and engine oil temperature.

20. A method for a cam torque actuated variable cam timing phaser, comprising:
in response to an unlocking advance phasing command, jumping a spool valve from a detent region to a retard region outside a null region before ramping the spool valve through the null region towards an advance region;
in response to an unlocking retard phasing command, jumping the spool valve from the detent region to the advance region outside the null region before ramping the spool valve through the null region towards the retard region; and
in response to engine speed generated hydraulic pressure applied on a locking circuit of the phaser being lower than a threshold, moving a spool valve of the phaser to the detent region to move and hold the phaser at a locking position with a locking pin engaged.

Assignees

• Ford Global Tech Llc

Inventors

• Pietrzyk Paul A
• Badillo Ed
• Rollinger John Eric

Classifications

• F01L1/344

  changing the angular relationship between crankshaft and camshaft, e.g. using helicoidal gear · CPC title

• F01L1/3442 Primary

  using hydraulic chambers with variable volume to transmit the rotating force · CPC title

• F01L1/047

  Camshafts · CPC title

• F01L2001/34463

  Locking position intermediate between most retarded and most advanced positions · CPC title

• F01L1/34409

  by torque-responsive means · CPC title