KNOCK SENSOR DIAGNOSTIC SYSTEM AND METHOD

• US 20090064762A1
• Filed: 09/11/2007
• Published: 03/12/2009
• Est. Priority Date: 09/11/2007
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations Incorporated (Motors Liquidation Co. GUC Trust)
• Inventors: Kindermann, Marilyn L., Nelson, Brian Carl, Szpakowski, Thomas A., Kiebel, Karl T., Marks, Anthony L., Horner, Robert J., Sawdon, Craig M.
• Granted Patent: US 7,562,558 B2
• Time in Patent Office: Days
• US Class Current: 73/35.50
• CPC Class Codes: F02D 2041/1432 the system including a filter, e.g. a low pass or high pass filter
• CPC Class Codes: F02D 2041/288 for performing a transformation into the frequency domain, e.g. Fourier transformation
• CPC Class Codes: F02D 35/027 using knock sensors
• CPC Class Codes: F02D 41/222 relating to the failure of sensors or parameter detection devices
• CPC Class Codes: G01L 23/225 circuit arrangements therefor
• CPC Class Codes: G01L 27/007 Malfunction diagnosis, i.e. diagnosing a sensor defect
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

A knock sensor diagnostic system may include a knock sensor. A bias circuit applies a bias voltage to the knock sensor. An input circuit receives an input signal based on the bias voltage. A control module indicates a short circuit associated with the knock sensor based on the input signal. A knock sensor diagnostic system may also or alternatively include a signal generator that generates and applies a test signal with a predetermined frequency to the knock sensor. Another input circuit receives another input signal that is based on the test signal. A control module indicates an open circuit associated with the knock sensor based on the other input signal.

Claims

1. A knock sensor diagnostic system comprising:

a knock sensor;

a bias circuit that applies a bias voltage to said knock sensor;

a first input circuit that receives a first input signal based on said bias voltage;

a control module that indicates a short circuit associated with said knock sensor based on said first input signal;

a signal generator that generates and applies a test signal with a predetermined frequency to said knock sensor; and

a second input circuit that receives a second input signal based on said test signal,

wherein said control module detects an amplitude of said test signal based on an engine speed and indicates an open circuit associated with said knock sensor based on said second input signal.

2. The knock sensor diagnostic system of claim 1 wherein said first input circuit comprises a low pass filter that filters an output of said knock sensor to generate said first input signal.

3. The knock sensor diagnostic system of claim 2 wherein said low pass filter comprises:

a resistance that is coupled between said knock sensor and said control module; and

a capacitance that is coupled between said resistance and a reference ground.

4. The knock sensor diagnostic system of claim 1 wherein said first input circuit is coupled to a low-side of said knock sensor.

11. The knock sensor diagnostic system of claim 1 wherein said bias circuit comprises:

a first resistance that is coupled between a voltage supply and a first terminal of said knock sensor;

a second resistance that is coupled across said knock sensor; and

a third resistance that is coupled between a second terminal of said knock sensor and a ground reference terminal.

22. The knock sensor diagnostic system of claim 1 wherein said test signal has a frequency level that is outside a frequency range associated with at least one of knock detection and engine background noise.

23. The knock sensor diagnostic system of claim 1 wherein said control module detects amplitude of said test signal when an engine speed is less than or equal to a predetermined speed.

24. The knock sensor diagnostic system of claim 1 wherein said control module detects background noise when an engine speed is greater than a predetermined speed, and

wherein said control module indicates an open circuit associated with said knock sensor based on said background noise.

25. The knock sensor diagnostic system of claim 1 wherein said control module detects an amplitude of said test signal over an operating speed range of an engine.

5. (canceled)

6. The knock sensor diagnostic system of claim 5 wherein said signal generator is coupled to a high-side of said knock sensor.

7. The knock sensor diagnostic system of claim 5 wherein said bias voltage is a direct current (DC) bias voltage.

8. The knock sensor diagnostic system of claim 5 wherein said second input circuit comprises an alternating current coupling circuit that removes said bias voltage from a knock sensor output signal from said knock sensor.

9. The knock sensor diagnostic system of claim 8 wherein said alternating current coupling circuit comprises:

a first capacitance coupled to a high-side of said knock sensor; and

a second capacitance that is coupled to a low-side of said knock sensor.

10. The knock sensor diagnostic system of claim 5 further comprising:

a filter that generates a filtered signal based on said second input signal;

a Fast Fourier Transform device that generates a frequency domain signal based on said second input signal; and

a signal processor that generates an engine knock signal based on said frequency domain signal.

12-21. -21. (canceled)

26. A knock sensor diagnostic system comprising:

a knock sensor;

a bias circuit that applies a bias voltage to said knock sensor;

a signal generator that generates and applies a test signal with a predetermined frequency to said knock sensor;

an input circuit that receives an input signal based on said test signal; and

a control module that detects an amplitude of said test signal based on an engine speed and indicates an open circuit associated with said knock sensor based on said input signal.

27. A knock sensor diagnostic system comprising:

a knock sensor;

a bias circuit that applies a bias voltage to said knock sensor;

a first input circuit that receives a first input signal based on said bias voltage;

a control module that indicates a short circuit associated with said knock sensor based on said first input signal;

a signal generator that generates and applies a test signal with a predetermined frequency to said knock sensor; and

a second input circuit that receives a second input signal based on said test signal,

wherein said control module indicates an open circuit associated with said knock sensor based on said second input signal, and

wherein said test signal has a frequency level that is outside a frequency range associated with at least one of knock detection and engine background noise.