Control method for electro-hydraulic control valves over temperature range

• US 20040003788A1
• Filed: 04/04/2003
• Published: 01/08/2004
• Est. Priority Date: 06/17/2002
• Status: Active Grant

• Current Assignee: BorgWarner Incorporated
• Original Assignee: BorgWarner Incorporated
• Inventors: Taylor, Danny R., Quinn, Stanley B. Jr.
• Granted Patent: US 6,938,592 B2
• Time in Patent Office: Days
• US Class Current: 123/90.15
• CPC Class Codes: F01L 1/022 Chain drive
• CPC Class Codes: F01L 1/024 Belt drive
• 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: F01L 2001/34426 Oil control valves
• CPC Class Codes: F01L 2001/34453 Locking means between driving and driven members
• CPC Class Codes: F01L 2800/00 Methods of operation using a variable valve timing mechanism

Abstract

In a variable cam timing (VCT) system (10a) which has a feedback control loop wherein an error signal (36) relating to at least one sensed position signal of either a crank shaft position (24a) or at least one cam shaft position (22a) is fed back for correcting a predetermined command signal (12). The system further includes a valve (14) for controlling a relative angular relationship of a phaser (42); and includes a variable force solenoid (20) for controlling a translational movement of the valve (14). An improved control method comprising the steps of: providing a dither signal (38) sufficiently smaller than the error signal (36); as temperature varies, changing at least one parameter relating to the dither signal (38); and applying the dither signal (38) upon the variable force solenoid (20), thereby using the dither signal (38) for overcoming a system hysteresis without causing excessive movement of valve (14).

Claims

1. In a variable cam timing (VCT) system (10a) having a feedback control loop wherein an error signal (36) relating to at least one sensed position signal of either a crank shaft position (24a) or at least one cam shaft position (22a) is fed back for correcting a predetermined command signal (12), the system further having a valve (14) for controlling a relative angular relationship of a phaser (42) and having a variable force solenoid (20) for controlling a translational movement of the valve (14), an improved control method comprising the steps of:

providing a dither signal (38) sufficiently smaller than the error signal (36);

as temperature varies, changing at least one parameter relating to the dither signal (38); and

applying the dither signal (38) upon the variable force solenoid (20), thereby using the dither signal (38) for overcoming a system hysteresis without causing excessive movement of valve (14).

2. The method of claim 1, wherein said at least one parameter is dither signal amplitude.

3. The method of claim 1, wherein said at least one parameter is dither signal frequency.

4. The method of claim 1, wherein said at least one parameter is a combination of dither signal amplitude and frequency.

5. In a variable cam timing (VCT) system (10a) having a feedback control loop wherein an error signal (36) relating to at least one sensed position signal of either a crank shaft position (24a) or at least one cam shaft position (22a) is fed back for correcting a predetermined command signal (12), the system further having a valve (14) for controlling a relative angular relationship of a phaser (42) and having a variable force solenoid (20) for controlling a translational movement of the valve (14), an improved control method comprising the steps of:

providing a pulse width modulation (PWM) signal disposed to generate a set of frequencies, wherein each frequency inherently includes a dither signal for overcoming system hysteresis at a predetermined temperature range; and

as temperature varies, changing the frequency, thereby using the set of frequencies for overcoming a system hysteresis within a temperature range without causing excessive movement of valve (14).