Knock sensing apparatus with fail indicator for use in an internal combustion engine
First Claim
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1. Apparatus for furnishing a knock signal indicative of knocking in an internal combustion engine comprisingsensing means (1;
- 43, 44, 45,
38) for sensing mechanical oscillations in the internal combustion engine and furnishing sensing output signals corresponding thereto, said sensing output signals constituting said knock signal in the presence of engine knocking;
control circuit means (12) for generatinga first gating signal defining a measuring phase (22) during which the sensing output signals are measured for presence of said knock signal, anda second gating signal defining a test phase (23) during which the sensing output signals are measured to determine proper operation of the sensing means and generating "fail" signals if said measurement determines improper operation of the sensing means,includingcomparator means (4,
9) for comparing, during said test phase, said sensing output signals to(a) a first reference signal indicative of a predetermined minimum level, and(b) to a second reference signal indicative of a predetermined maximum level, andswitch means (3,
5) controlled by said gating signals and connecting, during said test phase, the sensing output signals to the comparator means.
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Abstract
The knock sensing equipment has a control circuit which generates gating signals for dividing the operation into a measuring phase and a test phase. In the latter, the possible malfunction of the sensor is determined. During the test phase, the sensor responds either to background noise or to a test voltage and the sensing output signals are compared to a predetermined minimum and/or maximum level. Malfunction is indicated if the signals furnished by the sensor are outside of the indicated range.
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11 Claims
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1. Apparatus for furnishing a knock signal indicative of knocking in an internal combustion engine comprising
sensing means (1; - 43, 44, 45,
38) for sensing mechanical oscillations in the internal combustion engine and furnishing sensing output signals corresponding thereto, said sensing output signals constituting said knock signal in the presence of engine knocking;control circuit means (12) for generating a first gating signal defining a measuring phase (22) during which the sensing output signals are measured for presence of said knock signal, and a second gating signal defining a test phase (23) during which the sensing output signals are measured to determine proper operation of the sensing means and generating "fail" signals if said measurement determines improper operation of the sensing means, including comparator means (4,
9) for comparing, during said test phase, said sensing output signals to(a) a first reference signal indicative of a predetermined minimum level, and (b) to a second reference signal indicative of a predetermined maximum level, and switch means (3,
5) controlled by said gating signals and connecting, during said test phase, the sensing output signals to the comparator means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
- 43, 44, 45,
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9. Apparatus for furnishing a knock signal indicative of knocking in an internal combustion engine comprising
sensing means (1; - 43, 44, 45,
38) for sensing mechanical oscillations in the internal combustion engine and furnishing sensing output signals corresponding thereto, said sensing output signals constituting said knock signals in the presence of engine knocking;control circuit means (12) for generating a first gating signal defining a measuring phase (22) during which the sensing output signals are measured for presence of said knock signal, and a second gating signal defining a test phase (23) subsequent to said measuring phase during which the sensing output signals are measured to determine proper operation of the sensing means and generating "fail" signals if said measurement determines improper operation of the sensing means, said second gating signal occuring during a portion of the engine operating cycle when no knocking signals occur; means (40) for applying a test voltage to said sensing means during said test phase; and means (27, 39;
) for evaluating the sensing output signals to determine if(a) said output signals corresponds to a first criterion indicative of malfunction of the sensor;
or(b) the output signals correspond to a second criterion indicative of proper operation of the sensor; and switch means (41, 42;
46,
47) controlled by said gating signals and connecting, during said test phase, the sensing output signals to the evaluation means. - View Dependent Claims (10, 11)
- 43, 44, 45,
Specification