Method for detecting failure of a relay

• US 6,909,285 B2
• Filed: 09/11/2002
• Issued: 06/21/2005
• Est. Priority Date: 09/11/2002
• Status: Expired due to Fees

• Current Assignee: Visteon Global Technologies Incorporated (Visteon Corporation)
• Original Assignee: Visteon Global Technologies Incorporated (Visteon Corporation)
• Inventors: Floros, John Harry, Jordan, Paul Thomas
• Primary Examiner(s): Nguyen, Vincent Q.
• Application Number:
  US10/241,101
• Publication Number:
  US 20040047097A1
• Time in Patent Office: 1,014 Days
• Field of Search: 324/418, 324/423, 324/380, 324/382, 324/503, 324/537, 318/139, 318/140, 180/404, 307/125, 307/9.1, 307/10.1
• US Class Current: 324/382
• CPC Class Codes: G01R 31/3278 of relays, solenoids or reed switches measuring contact resistance G01R27/205; high voltage magnetic switches G01R31/3271, G01R31/333; testing electric windings G01R31/72; monitoring of fail safe circuits H01H47/002
• CPC Class Codes: H01H 47/002 Monitoring or fail-safe circuits

Abstract

A method for detecting failure of a relay operating in a vehicle having an ignition switch, a power supply, a capacitor, and a pre-charge circuit to pre-charge the capacitor with the relay switching power from the power supply to the pre-charged capacitor, the method comprising the steps of: performing a capacitor pre-charge test; and performing a capacitor discharge test. Preferably, the capacitor pre-charge test is performed when the ignition is switched ON and the capacitor discharge test is performed when the ignition is switched OFF.

Claims

1. A method for detecting failure of a relay operating in a vehicle having an ignition switch, a power supply, a capacitor, and a pre-charge circuit to pre-charge the capacitor with the relay switching power from the power supply to the pre-charged capacitor, the method comprising the step of:

performing a capacitor discharge test, wherein the step of performing a capacitor discharge test includes the steps of;

opening the relay to disconnect the power supply from the capacitor;

checking the capacitor for a discharged over-voltage condition; and

delaying opening the relay to disconnect the power supply from the capacitor for a predetermined discharge time period and wherein the step of checking the capacitor for a discharged over-voltage condition is performed after the predetermined discharge time period has elapsed.

2. The method of claim 1 further including the step of storing a capacitor discharge failure error in memory when a discharged over-voltage condition is detected.

3. A method for detecting failure of a relay operating in a vehicle having an ignition switch, a power supply, a capacitor, and a pre-charge circuit to pre-charge the capacitor with the relay switching power from the power supply to the pre-charged capacitor, the method comprising the steps of:

performing a capacitor discharge test, and

performing a capacitor pre-charge test, wherein the step of performing a capacitor pre-charge test includes the steps of;

activating the pre-charge circuit to initiate pre-charging of the capacitor;

checking the capacitor for a pre-charge over-voltage condition;

checking the capacitor for a pre-charge under-voltage condition;

deactivating the pre-charge circuit;

closing the relay to provide power from the power supply to the capacitor; and

checking the capacitor for a post-charged under-voltage condition.

4. The method of claim 3 wherein the capacitor pre-charge test is performed after the ignition switch is ON.

5. The method of claim 3 further including a step of delaying for a predetermined post-charged time period before checking the capacitor for a post-charged under-voltage condition is performed.

6. The method of claim 5 wherein the step of checking the capacitor for a pre-charge under-voltage condition is performed after the predetermined pre-charging time period has elapsed.

7. The method of claim 3 wherein the step of checking the capacitor for a pre-charge over-voltage condition further includes repetitively checking the capacitor for a pre-charge over-voltage condition for a predetermined pre-charging time period.

8. A method for detecting failure of a relay operating in a vehicle having an ignition switch, a power supply, a capacitor, and a pre-charge circuit to pre-charge the capacitor with the relay switching power from the power supply to the pre-charged capacitor, the method comprising the steps of:

performing a capacitor discharge test;

activating the pre-charge circuit to initiate pre-charging of the capacitor;

deactivating the pre-charge circuit;

closing the relay to provide power from the power supply to the capacitor;

checking the capacitor for a post-charged under-voltage condition;

checking the capacitor for a pre-charge over-voltage condition; and

checking the capacitor for a pre-charge under-voltage condition,

wherein the step of checking the capacitor for a pre-charge over-voltage condition further includes repetitively checking the capacitor for a pre-charge over-voltage condition for a predetermined pre-charging time period.

9. The method according to claim 8 wherein the step of checking the capacitor for a pre-charge under-voltage condition is performed after the predetermined pre-charging time period has elapsed.