Method and system for variable cam timing device

Patent metadata

Field	Value
Publication number	US-2016108772-A1
Application number	US-201414520174-A
Country	US
Kind code	A1
Filing date	Oct 21, 2014
Priority date	Oct 21, 2014
Publication date	Apr 21, 2016
Grant date	—

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

1 . A method, comprising:
moving cam timing via cam torque actuated hydraulic pressure separate from engine generated oil pressure via a spool valve; and in response to system oil pressure falling below a threshold, adjusting a position of the spool valve to reduce the system oil pressure applied to a locking circuit of the phaser.

2 . The method of claim 1 , wherein moving the cam timing via a spool valve includes moving a 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 a null region to use the cam torque actuated hydraulic pressure to hold the phaser position.

3 . The method of claim 2 , 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.

4 . The method of claim 3 , 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.

5 . The method of claim 4 , wherein adjusting the position of the spool valve in response to system oil pressure includes moving the spool valve to a detent region.

6 . The method of claim 5 , wherein moving the cam timing via the spool valve further includes maintaining the system oil pressure applied to the locking circuit of the phaser to hold a locking pin disengaged.

7 . The method of claim 6 , wherein adjusting the position of the spool valve to reduce the system oil pressure applied to the locking circuit includes enabling engagement of the locking pin.

8 . The method of claim 7 , wherein adjusting the position of the spool valve to reduce the system oil pressure further includes disabling flow of the hydraulic fluid through the phasing circuit.

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

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

11 . The method of claim 10 , 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.

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

13 . The method of claim 12 , wherein moving the spool valve out of the detent region includes increasing the hydraulic pressure on the locking circuit of the phaser to disengage the locking pin.

14 . A method, comprising:
while cam torque generated hydraulic pressure in a phasing circuit of a cam torque actuated cam timing phaser is higher than a threshold,
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 a detent region to move and hold the phaser at a locking position with a locking pin engaged.

15 . The method of claim 14 , wherein moving the spool valve to move the phaser includes moving the phaser to the locking position by flowing hydraulic fluid through a detent circuit of the phaser and not through the phasing circuit of the phaser.

16 . The method of claim 15 , further comprising, holding the phaser at the locking position for a threshold duration, and in response to less than a threshold increase in engine speed generated hydraulic pressure during the threshold duration, increasing engine idle speed.

17 . A method, comprising:
during a first condition, when system oil pressure in a locking circuit of a variable cam phaser is lower than a threshold, holding the phaser in a mid-lock position with a locking pin engaged; and during a second condition, when system oil pressure is higher than the threshold, holding the phaser in the mid-lock position without engaging the locking pin by utilizing cam torque generated oil pressure.

18 . The method of claim 17 , wherein the mid-lock position corresponds to a position between an advance region and a retard region of the cam phaser.

19 . The method of claim 18 , wherein the variable cam phaser is a cam torque actuated phaser and wherein during the second condition, a camshaft torque pulse is used to move the spool valve to the mid-lock position, and wherein during the first condition, the camshaft torque pulse remains unused.

20 . The method of claim 19 , wherein during the first condition, a spool valve coupled to the phaser is moved to a detent region, and wherein during the second condition, the spool valve is moved to one of the advance and the retard region.

Assignees

• Ford Global Tech Llc

Inventors

• Pietrzyk Paul A
• Rollinger John Eric
• Hanshaw Jamie Charles
• Badillo Ed
• Fournelle Gilbert

Classifications

• F01L1/34409 Primary

  by torque-responsive means · CPC title

• F02D41/222

  relating to the failure of sensors or parameter detection devices · CPC title

• F02D41/22

  Safety or indicating devices for abnormal conditions {(in air/fuel ratio feedback systems F02D41/1495, in electric control linkage F02D11/107, in purge control systems F02M25/0809)} · CPC title

• F02D41/1497

  With detection of the mechanical response of the engine · CPC title

• F02D31/001

  Electric control of rotation speed · CPC title