Control method for transitions between open and closed loop operation in electronic VCT controls

• US 6,807,931 B2
• Filed: 04/07/2003
• Issued: 10/26/2004
• Est. Priority Date: 06/17/2002
• Status: Active Grant

• Current Assignee: BorgWarner Incorporated
• Original Assignee: BorgWarner Incorporated
• Inventors: Taylor, Danny R., Ekdahl, Earl, Quinn, Stanley B. Jr.
• Primary Examiner(s): Denion, Thomas
• Assistant Examiner(s): Riddle, Kyle M.
• Application Number:
  US10/408,400
• Publication Number:
  US 20030230265A1
• Time in Patent Office: 568 Days
• Field of Search: 123/90.17, 123/12, 123/90-1-, 123/90.27, 123/90.31
• US Class Current: 123/90.17
• CPC Class Codes: F01L 1/34 characterised by the provision of means for changing the timing of the valves without changing the duration of opening and without affecting the magnitude of the valve lift
• CPC Class Codes: F01L 1/344 changing the angular relationship between crankshaft and camshaft, e.g. using helicoidal gear
• CPC Class Codes: F01L 1/34409 by torque-responsive means
• CPC Class Codes: F01L 1/3442 using hydraulic chambers with variable volume to transmit the rotating force
• CPC Class Codes: F02D 41/1488 Inhibiting the regulation

Abstract

In a Variable Cam Timing (VCT) control system, there are conditions when the system must operate in an open-loop mode, and other situations where closed-loop operation is desired. A number of operating states is provided for VCT control system to switch between the states. A control methodology for switching between these two modes of operation, with minimal disturbances, is described. Further, during switching from open loop to closed loop, a scheme that impedes the impact upon the VCT system is provided.

Claims

1. In a variable cam timing (VCT) system including a plurality of states indicating a set of two operational modes of the VCT system, wherein a plurality of states is provided including a first state disposed to be transferred to a second state based upon a set of conditions, the two operational modes of the VCT system consisting of open loop mode and closed loop mode, a method comprising the steps of:

providing at least one phaser having a rotor and a housing, wherein the rotor is disposed to rotate within the housing;

providing a closed feedback control loop for the VCT system to operate under the closed loop mode;

during transferring from the first state to the second state, switching from a closed loop mode to an open loop mode, wherein the closed feedback control loop is not used; and

during transferring from the second state to the first state, switching from the open loop mode to the closed loop mode, wherein the closed feedback control loop is used.

2. The method of claim 1 further comprising the step of maintaining the open loop mode while transferring between states.

3. The method of claim 1, wherein the closed feedback control loop is used when a VCT controller measures a crankshaft speed greater than a predetermined rpm.

4. The method of claim 1, wherein the closed feedback control loop is used when a VCT controller determines the system is operating within a range of temperature.

5. The method of claim 1, wherein during switching from the open loop mode to the closed loop mode, a set point adjustment occurs;

a filter is applied on the set point adjustment thereby impeding an impact upon the VCT system.

6. The method of claim 1, wherein during switching from the open loop mode to the closed loop mode, a set point adjustment occurs;

a rate control scheme is applied on the set point adjustment thereby impeding an impact upon the VCT system.

7. The method of claim 1, wherein during switching from the open loop mode to the closed loop mode, a set point adjustment occurs;

a scheme using a combination of a filter and rate control is applied on the set point adjustment thereby impeding an impact upon the VCT system.

8. The method of claim 1, is controlled by a controller.

9. The method of claim 8, wherein the controller includes an engine control unit.

10. The method of claim 1, wherein the variable cam timing (VCT) system includes a cam torque actuated (CTA) or an oil pressure actuated (OPA) systems.

11. The method of claim 1, wherein the phaser is a vane phaser.

12. In a variable cam timing (VCT) system including at least one phaser having a plurality of states indicating a set of two operational modes of the VCT system, wherein a plurality of states is provided including a first state disposed to be transferred to a second state based upon a set of conditions, the two operational modes of the VCT system consisting of open loop mode and closed loop mode, a method comprising the steps of:

providing a closed feedback control loop for the VCT system to operate under the closed loop mode;

during transferring from the first state to the second state, switching from a closed loop mode to an open loop mode, wherein the closed feedback control loop is not used; and

during transferring from the second state to the first state, switching from the open loop mode to the closed loop mode, wherein the closed feedback control loop is used;

wherein the closed feedback control loop is used when a VCT controller determines the system is operating within a range of temperature.

13. In a variable cam timing (VCT) system including at least one phaser having a plurality of states indicating a set of two operational modes of the VCT system, wherein a plurality of states is provided including a first state disposed to be transferred to a second state based upon a set of conditions, the two operational modes of the VCT system consisting of open loop mode and closed loop mode, a method comprising the steps of:

providing a closed feedback control loop for the VCT system to operate under the closed loop mode;

during transferring from the first state to the second state, switching from a closed loop mode to an open loop mode, wherein the closed feedback control loop is not used; and

during transferring from the second state to the first state, switching from the open loop mode to the closed loop mode, wherein the closed feedback control loop is used;

wherein during switching from the open loop mode to the closed loop mode, a set point adjustment occurs;

a filter is applied on the set point adjustment thereby impeding an impact upon the VCT system.

14. In a variable cam timing (VCT) system including at least one phaser having a plurality of states indicating a set of two operational modes of the VCT system, wherein a plurality of states is provided including a first state disposed to be transferred to a second state based upon a set of conditions, the two operational modes of the VCT system consisting of open loop mode and closed loop mode, a method comprising the steps of:

providing a closed feedback control loop for the VCT system to operate under the closed loop mode;

during transferring from the first state to the second state, switching from a closed loop mode to an open loop mode, wherein the closed feedback control loop is not used; and

during transferring from the second state to the first state, switching from the open loop mode to the closed loop mode, wherein the closed feedback control loop is used;

wherein during switching from the open loop mode to the closed loop mode, a set point adjustment occurs;

a rate control scheme is applied on the set point adjustment thereby impeding an impact upon the VCT system.

15. In a variable cam timing (VCT) system including at least one phaser having a plurality of states indicating a set of two operational modes of the VCT system, wherein a plurality of states is provided including a first state disposed to be transferred to a second state based upon a set of conditions, the two operational modes of the VCT system consisting of open loop mode and closed loop mode, a method comprising the steps of:

providing a closed feedback control loop for the VCT system to operate under the closed loop mode;

during transferring from the first state to the second state, switching from a closed loop mode to an open loop mode, wherein the closed feedback control loop is not used; and

during transferring from the second state to the first state, switching from the open loop mode to the closed loop mode, wherein the closed feedback control loop is used;

wherein during switching from the open loop mode to the closed loop mode, a set point adjustment occurs;

a scheme using a combination of a filter and rate control is applied on the set point adjustment thereby impeding an impact upon the VCT system.