Modulated voltage for a solenoid valve

• US 6,493,204 B1
• Filed: 08/30/1999
• Issued: 12/10/2002
• Est. Priority Date: 07/09/1999
• Status: Expired due to Term

• Current Assignee: Kelsey-Hayes Co. (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Original Assignee: Kelsey-Hayes Co. (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Inventors: Moore, Daniel D., Glidden, David J., Whelan, Gary P.
• Primary Examiner(s): FLEMING, FRITZ M
• Application Number:
  US09/385,997
• Time in Patent Office: 1,198 Days
• Field of Search: 361/152-156, 361/160, 361/187, 340/644, 324/415, 324/418
• US Class Current: 361/187
• CPC Class Codes: B60T 8/36 including a pilot valve responding to an electromagnetic force
• CPC Class Codes: B60T 8/366 Valve details
• CPC Class Codes: B60T 8/88 with failure responsive means, i.e. means for detecting and indicating faulty operation of the speed responsive control means
• CPC Class Codes: H01F 7/1844 Monitoring or fail-safe circuits for relays H01H47/002
• CPC Class Codes: H01H 47/325 by switching regulator

Abstract

A circuit for actuating an ABS solenoid valve coil with a pulse width modulated voltage having a constant frequency and variable duty cycle. The coil current is a function of the duty cycle of the pulse width modulated voltage. By controlling the duty cycle, current saturation of the coil can be avoided to provide for a faster response upon deactuation of the coil. Feedback is included in the circuit to verify correct functioning of electrical components.

Claims

1. A control unit for a solenoid valve comprising:

a power supply;

a solenoid valve coil have a first end and a second end, said first end of said solenoid valve coil being connected to said power supply;

an electronic switch having a first terminal connected to said second end of solenoid valve coil, said electronic switch also having a second terminal connected to ground, said electronic switch operable for controlling the flow of an electric current through said solenoid valve coil, said switch further having a control port and being responsive to a control signal applied to said control port to transition between conducting and non-conducting stages;

a signal generator included within a microprocessor, said microprocessor having an output control port connected to said control port of said electronic switch, said signal generator operative to generate a control signal at said microprocessor output control port, said control signal being a pulse width modulated signal having a variable duty cycle and a constant frequency and said signal generator being operable to generate a first control signal with a predetermined first constant duty cycle sufficient to begin to move an armature of an associated solenoid valve and then to generate a second control signal with a second predetermined constant duty cycle that is less than said first duty cycle and is sufficient to maintain the associated solenoid valve armature in a desired position within the valve; and

a single voltage divider connected across said electronic switch, said voltage divider including a center tap connected to a feedback port of said microprocessor, said microprocessor being responsive to a voltage appearing at said center tap to confirm the operation of said electronic switch.

2. The control unit according to claim 1 further including a diode having an anode connected to the junction of said solenoid coil supply and said electronic switch and further including a Zener diode having a cathode connected to an cathode of said diode, said Zener diode also having an anode connected to said control port of said electronic switch, said diode and Zener diode being operative to provide a discharge path through said electronic switch for the coil current when said switch changes from a conducting to a non-conducting state.

3. The control unit according to claim 2 wherein said electronic switch is a field effect transistor having a gate coupled to said microprocessor control port.

4. The control unit according to claim 1 further including a diode having a cathode connected to the end of said solenoid coil connected to said power supply and further including a Zener diode having an anode connected to an anode of said diode, said Zener diode also having a cathode connected to the junction of said solenoid coil supply and said electronic switch, said diode and Zener diode being operative to provide a discharge path for the coil current when said switch changes from a conducting to a non-conducting state.

5. The control unit according to claim 4 further including a feedback resistor connected between the junction of said diode and said Zener diode and said center tap of said voltage divider, said microprocessor being responsive to the voltage appearing at said voltage divider center tap to confirm the operation of said solenoid coil.

6. The control unit according to claim 5 wherein said electronic switch is a field effect transistor having a gate coupled to said microprocessor control port.

7. The control unit according to claim 6 wherein the control unit is included in an anti-lock brake system.

8. The control unit according to claim 7 wherein the control unit is included in a traction control system.

9. The control unit according to claim 4 further including a feedback resistor connected between the junction of said diode and said Zener diode and said center tap of said voltage divider, said microprocessor being responsive to the voltage appearing at said voltage divider center tap to confirm the operation of said diode.

10. The control unit according to claim 4 further including a feedback resistor connected between the junction of said diode and said Zener diode and said center tap of said voltage divider, said microprocessor being responsive to the voltage appearing at said voltage divider center tap to confirm the operation of said Zener diode.

11. A method for controlling the current flowing through a solenoid valve coil comprising the steps of:

(a) providing an electronic switch connected to the valve coil, the switch having a control port and being responsive to a control voltage applied to the control port to change between conducting and non-conducting states;

(b) applying a pulse width modulated control voltage having a constant frequency and variable duty cycle to the control port of the switch, the voltage having an initial duty cycle having a first predetermined value, the initial duty cycle being sufficient to cause the valve armature to begin to move within the valve from a deactuated position to an actuated position;

(c) reducing the duty cycle to a second predetermined value upon the valve armature reaching a desired position within the solenoid valve, the second predetermined value being less than the first predetermined value, the second predetermined value being sufficient to provide a coil current which will hold the valve armature in the desired position; and

(d) subsequent to step (c), further reducing the duty cycle to a third predetermined value that is less than the second predetermined value and greater than zero to cause the valve armature to begin to move back toward the deactuated position.

12. The method according to claim 11 further including providing a device for periodically sampling the voltage across the electronic switch when the electronic switch is a conducting state and comparing the sampled voltage to a first threshold voltage, the device being operative to actuate a warning device if the sampled voltage is greater than the first threshold voltage.

13. The method according to claim 12 wherein the device for periodically sampling the voltage across the electronic switch also samples the voltage across the electronic switch when the electronic switch is in a non-conducting state and compares the sampled voltage to a second threshold voltage, the device being operative to actuate the warning device if the sampled voltage is less than the second threshold voltage.

14. The method according to claim 13 wherein the voltage sampled while the electronic switch is in a non-conducting state is compared to a third threshold voltage and the device actuates the warning device if the sampled voltage is greater than the third threshold voltage.

15. The method according to claim 13 wherein the third threshold voltage is greater than the second threshold voltage.

16. The method according to claim 11 also including increasing the duty cycle to a fourth predetermined value which is between the second and third predetermined values for the duty cycle as the valve armature approaches the deactuated position to slow the return of the armature to the deactuated position.

17. The method according to claim 11 wherein the solenoid valve is a proportional valve.