Oil deterioration sensor
First Claim
1. An oil deterioration detection apparatus comprising a sensing capacitor formed of paired electrodes dipped into oil whose deterioration is to be detected, the oil deterioration detection apparatus detecting deterioration of the oil on the basis of a change in electrostatic capacitance of the sensing capacitor, the apparatus comprising:
- a measurement signal generation circuit for generating a measurement signal to be supplied to the sensing capacitor in order to measure the electrostatic capacitance of the sensing capacitor;
a detection signal output circuit for outputting a detection signal on the basis of a response wave signal produced from the sensing capacitor in response to supply of the measurement signal thereto, the detection signal reflecting the electrostatic capacitance of the sensing capacitor; and
an output compensation mechanism for compensating the detection signal for an output level change stemming from a temperature characteristic and/or a time-course deterioration of the detection signal output circuit;
wherein the output compensation mechanism comprises a reference element whose impedance temperature coefficient is smaller than that of the sensing capacitor; and
an output compensation processing circuit for performing output compensation for the detection signal on the basis of a measured impedance of the reference element;
wherein the reference element is a reference capacitor; and
the output compensation processing circuit measures electrostatic capacitance of the reference capacitor through measurement of impedance of the reference capacitor; and
wherein the reference capacitor has an electrostatic capacitance temperature coefficient of +1% or less within a temperature range of −
30°
C. to 120°
C., wherein an electrostatic capacitance at 20°
C. is used as a reference.
1 Assignment
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Accused Products
Abstract
An engine oil deterioration detection apparatus includes a sensing capacitor CS formed of paired electrodes dipped into engine oil whose deterioration is to be detected, the engine oil deterioration detection apparatus detecting deterioration of the engine oil on the basis of a change in electrostatic capacitance of the sensing capacitor CS. A measurement signal generation circuit generates a measurement signal to be supplied to the sensing capacitor CS. A detection signal output circuit outputs a detection signal on the basis of a response wave signal produced from the sensing capacitor CS in response to supply of the measurement signal thereto, the detection signal reflecting the electrostatic capacitance of the sensing capacitor CS. A temperature compensation mechanism is provided to compensate for a level change of the detection signal stemming from a temperature characteristic and/or a time-course deterioration of the detection signal output circuit.
32 Citations
15 Claims
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1. An oil deterioration detection apparatus comprising a sensing capacitor formed of paired electrodes dipped into oil whose deterioration is to be detected, the oil deterioration detection apparatus detecting deterioration of the oil on the basis of a change in electrostatic capacitance of the sensing capacitor, the apparatus comprising:
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a measurement signal generation circuit for generating a measurement signal to be supplied to the sensing capacitor in order to measure the electrostatic capacitance of the sensing capacitor; a detection signal output circuit for outputting a detection signal on the basis of a response wave signal produced from the sensing capacitor in response to supply of the measurement signal thereto, the detection signal reflecting the electrostatic capacitance of the sensing capacitor; and an output compensation mechanism for compensating the detection signal for an output level change stemming from a temperature characteristic and/or a time-course deterioration of the detection signal output circuit; wherein the output compensation mechanism comprises a reference element whose impedance temperature coefficient is smaller than that of the sensing capacitor; and
an output compensation processing circuit for performing output compensation for the detection signal on the basis of a measured impedance of the reference element;wherein the reference element is a reference capacitor; and
the output compensation processing circuit measures electrostatic capacitance of the reference capacitor through measurement of impedance of the reference capacitor; andwherein the reference capacitor has an electrostatic capacitance temperature coefficient of +1% or less within a temperature range of −
30°
C. to 120°
C., wherein an electrostatic capacitance at 20°
C. is used as a reference. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An oil deterioration detection apparatus comprising a sensing capacitor formed of paired electrodes dipped into oil whose deterioration is to be detected, the oil deterioration detection apparatus detecting deterioration of the oil on the basis of a change in electrostatic capacitance of the sensing capacitor, the apparatus comprising:
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a measurement signal generation circuit for generating a measurement signal to be supplied to the sensing capacitor in order to measure the electrostatic capacitance of the sensing capacitor; a detection signal output circuit for outputting a detection signal on the basis of a response wave signal produced from the sensing capacitor in response to supply of the measurement signal thereto, the detection signal reflecting the electrostatic capacitance of the sensing capacitor; and an output compensation mechanism for compensating the detection signal for an output level change stemming from a temperature characteristic and/or a time-course deterioration of the detection signal output circuit, wherein the measurement signal generation circuit comprises; a voltage output section for selecting and outputting one of a plurality of analog set voltages; and a voltage output control section for controlling the voltage output of the voltage output section in such a manner that the plurality of analog set voltages are selected in a predetermined sequence and at predetermined intervals in order to produce a stepped voltage output. - View Dependent Claims (11, 12, 13, 14)
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15. An oil deterioration detection apparatus comprising:
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a sensing capacitor formed of paired electrodes to be dipped into oil; and a reference element having a smaller impedance temperature coefficient than that of said sensing capacitor, wherein said oil deterioration detection apparatus detects deterioration of the oil on the basis of comparison between a corrected relative capacitance value and a relative limit value thereof; and wherein said corrected relative capacitance value is obtained by multiplying a relative capacitance value with an electrostatic capacitance correction coefficient, and wherein said relative capacitance value is a ratio of sensor impedance measurement information reflecting the impedance of the sensing capacitor to reference element impedance measurement information reflecting the impedance of said reference element.
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Specification