VCT solenoid dither frequency control

• US 20030230266A1
• Filed: 04/04/2003
• Published: 12/18/2003
• Est. Priority Date: 06/17/2002
• Status: Active Grant

• Current Assignee: BorgWarner Incorporated
• Original Assignee: BorgWarner Incorporated
• Inventors: Taylor, Danny R., Ekdahl, Earl
• Granted Patent: US 6,736,094 B2
• Time in Patent Office: Days
• US Class Current: 123/90.15
• 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: F01L 2001/34426 Oil control valves
• CPC Class Codes: F02D 41/1408 Dithering techniques

Abstract

A method that uses a dither signal for reducing hysteresis effect in a variable cam timing system is provided. The method includes the steps of: a) providing a dither signal having at least two switchable frequencies; b) determining the frequency characteristics of an engine speed; c) determining at least one frequency beating point in relation to a neighborhood of an engine crank RPM values; and d) changing the dither signal frequency when the engine is operating within the neighborhood of the engine crank RPM values. Thereby frequency beating effect is reduced.

Claims

1. A method using a dither signal for reducing hysteresis effect in a variable cam timing system, comprising the steps of:

a) providing a dither signal having at least two switchable frequencies;

b) determining the frequency characteristics of an engine at different speeds;

c) determining at least one frequency beating point in relation to a neighborhood of an engine crank RPM values; and

d) changing the dither signal frequency when the engine is operating within the neighborhood of the engine crank RPM values, thereby reducing frequency beating effect.

2. The method of claim 1 further comprising the step of after changing the dither signal frequency and when the engine is operating outside the neighborhood, changing the dither signal frequency to a predetermined value.

3. The method of claim 2, wherein the predetermined value is the original dither frequency.

4. The method of claim 1, wherein the at least one beating point is related to primary harmonic of engine frequency.

5. The method of claim 1, wherein the at least one frequency beating point is related to secondary, or higher harmonics of engine frequencies.

6. The method of claim 1, wherein the changing of dither frequency is accomplished by varying the duty cycle of a pulse width modulation scheme

7. The method of claim 1, wherein the changing of dither frequency is accomplished by varying the electric current strength on a coil.

8. The method of claim 1, wherein the variable cam timing system is a CTA or an OPA variable cam timing system.