Abstract: A gas sensor apparatus 3 in an air-fuel ratio detection system 1 includes a gas sensor element 4 which outputs a detection signal corresponding to air-fuel ratio, and a gas sensor control circuit 2 which includes a detection section 20 for outputting a first output signal VIP1, a second output signal VIP2, and a third output signal VIP3 in accordance with the detection signal. This detection section 20 outputs the first output signal VIP1 which changes in accordance with the air-fuel ratio at least within a wide first air-fuel ratio zone, the second output signal VIP2 which changes in accordance with the air-fuel ratio within a narrow zone in the vicinity of the stoichiometric ratio, and the third output signal VIP3 which changes in accordance with the air-fuel ratio within a narrow zone in the lean region.

Abstract: A gas sensor apparatus 3 in an air-fuel ratio detection system 1 includes a gas sensor element 4 which outputs a detection signal corresponding to air-fuel ratio, and a gas sensor control circuit 2 which includes a detection section 20 for outputting a first output signal VIP1, a second output signal VIP2, and a third output signal VIP3 in accordance with the detection signal. This detection section 20 outputs the first output signal VIP1 which changes in accordance with the air-fuel ratio at least within a wide first air-fuel ratio zone, the second output signal VIP2 which changes in accordance with the air-fuel ratio within a narrow zone in the vicinity of the stoichiometric ratio, and the third output signal VIP3 which changes in accordance with the air-fuel ratio within a narrow zone in the lean region.

Abstract: An abnormality diagnosis method for a gas concentration measuring device, includes electrically shutting off measurement means from an oxygen concentration detecting cell and an oxygen pump cell of a gas sensor when a voltage at one of electrical connection points through which the measurement means is electrically connected to the oxygen concentration detecting cell and the oxygen pump cell becomes equal to a predetermined abnormal voltage value, and thereafter, electrically connecting the measurement means to the oxygen concentration detecting cell and the oxygen pump cell of the gas sensor to perform an abnormality diagnosis of the gas sensor. An abnormality diagnosis apparatus for a gas concentration measuring device is also provided.

Abstract: A gas sensor (10) including a measurement chamber (28) into which a gas GS is flown and a detection element main body (40) facing the measurement chamber (28). The detection element main body (40) includes an element case 42, and a protective film (48) is adhered to a bottom surface thereof. An acoustic matching plate (50) and a piezoelectric element (51) of a substantially columnar shape and a tube body (52) provided in a position surrounding the acoustic matching plate 50 and the piezoelectric element 51 are housed in the element case (42). A filler is then introduced into the element case (42), whereby the acoustic matching plate (50), the piezoelectric element (51), and the tube body (52) are sealed by a filled layer (99).

Abstract: A detecting-element assembly (40) is configured such that a piezoelectric element (51) is housed in a casing body portion (43) of a casing (42), and is attached to a housing portion (22) of a flow path formation member (20) via a flange portion (41). Therefore, the path between the piezoelectric element (51) and the position of attachment of the detecting-element assembly (40) is elongated, whereby ultrasonic waves which leak into the interior of the detecting-element assembly (40) from the piezoelectric element (51) become unlikely to reflectively return from a joint. Thus, the influence of, for example, noise stemming from reflected waves is reduced, thereby enhancing the accuracy of detection. An average clearance of 1 millimeter or more is provided along the outer circumferential surface of the casing body portion (43) of the detecting-element assembly (40), whereby a problem of collected foreign matter is unlikely to occur.

Abstract: An abnormality diagnosis method for a gas concentration measuring device, includes electrically shutting off measurement means from an oxygen concentration detecting cell and an oxygen pump cell of a gas sensor when a voltage at one of electrical connection points through which the measurement means is electrically connected to the oxygen concentration detecting cell and the oxygen pump cell becomes equal to a predetermined abnormal voltage value, and thereafter, electrically connecting the measurement means to the oxygen concentration detecting cell and the oxygen pump cell of the gas sensor to perform an abnormality diagnosis of the gas sensor. An abnormality diagnosis apparatus for a gas concentration measuring device is also provided.

Abstract: A gas concentration sensor includes a measurement chamber for measuring a concentration of a specific gas component in a gas under measurement; an inflow path for allowing inflow of the gas under measurement thereinto and an outflow path for allowing outflow of the gas under measurement therefrom; a reflection wall for reflecting an acoustic wave; and an acoustic wave transmitting-receiving element having a transmitting-receiving surface adapted to transmit an acoustic wave toward the reflection wall and receive an acoustic wave reflected from the reflection wall. The concentration of the specific gas in the gas under measurement is detected on the basis of a propagation time between transmission of the acoustic wave and reception of the reflected acoustic wave. When a predetermined member having the sensor attached thereto is placed in a horizontal plane, the transmitting-receiving surface faces downward. A recess is formed in a peripheral portion of the reflection wall.

Abstract: An ultrasonic-wave propagation-time measuring method and gas concentration sensor are disclosed in which a reception wave which has been transmitted and received by an ultrasonic element 5 is subjected to full-wave rectification in order to obtain a full-wave-rectified wave, which is then integrated by an integration circuit 37 to obtain an integral value. A peak value of the integral value is held by a peak-hold circuit 39. As to detection of gas concentration, a threshold-level calculation section 21e sets a reference value on the basis of the peak value, and a point in time when the amplitude of a reception wave having undergone full-wave rectification is judged by a comparator 43 to have reached the reference value is regarded as an arrival time. Subsequently, a gas concentration is determined on the basis of a period between the emission time and the arrival time.

Abstract: A detecting-element assembly (40) is configured such that a piezoelectric element (51) is housed in a casing body portion (43) of a casing (42), and is attached to a housing portion (22) of a flow path formation member (20) via a flange portion (41). Therefore, the path between the piezoelectric element (51) and the position of attachment of the detecting-element assembly (40) is elongated, whereby ultrasonic waves which leak into the interior of the detecting-element assembly (40) from the piezoelectric element (51) become unlikely to reflectively return from a joint. Thus, the influence of, for example, noise stemming from reflected waves is reduced, thereby enhancing the accuracy of detection. An average clearance of 1 millimeter or more is provided along the outer circumferential surface of the casing body portion (43) of the detecting-element assembly (40), whereby a problem of collected foreign matter is unlikely to occur.

Abstract: A gas concentration sensor includes a measurement chamber for measuring a concentration of a specific gas component in a gas under measurement; an inflow path for allowing inflow of the gas under measurement thereinto and an outflow path for allowing outflow of the gas under measurement therefrom; a reflection wall for reflecting an acoustic wave; and an acoustic wave transmitting-receiving element having a transmitting-receiving surface adapted to transmit an acoustic wave toward the reflection wall and receive an acoustic wave reflected from the reflection wall. The concentration of the specific gas in the gas under measurement is detected on the basis of a propagation time between transmission of the acoustic wave and reception of the reflected acoustic wave. When a predetermined member having the sensor attached thereto is placed in a horizontal plane, the transmitting-receiving surface faces downward. A recess is formed in a peripheral portion of the reflection wall.

Abstract: A gas sensor (10) including a measurement chamber (28) into which a gas GS is flown and a detection element main body (40) facing the measurement chamber (28). The detection element main body (40) includes an element case 42, and a protective film (48) is adhered to a bottom surface thereof. An acoustic matching plate (50) and a piezoelectric element (51) of a substantially columnar shape and a tube body (52) provided in a position surrounding the acoustic matching plate 50 and the piezoelectric element 51 are housed in the element case (42). A filler is then introduced into the element case (42), whereby the acoustic matching plate (50), the piezoelectric element (51), and the tube body (52) are sealed by a filled layer (99).

Abstract: An ultrasonic-wave propagation time measuring method which enables determination of accurate propagation time, a gas-pressure measuring method, a gas-flow-rate measuring method, and a gas sensor. A reception wave which has been transmitted and received by an ultrasonic element 5 is shaped and integrated by an integration circuit 67 to obtain an integral value. A peak value of the integral value is held by a peak-hold circuit 39. As to detection of gas concentration, a resistance-voltage-division circuit 41 sets a reference value on the basis of the peak value, and a point in time when the integral value of the reception wave is judged by a comparator 43 to have reached the reference value is regarded as an arrival time. Subsequently, a gas concentration is detected on the basis of a period between the emission time and the arrival time.

Abstract: An ultrasonic-wave propagation-time measuring method and gas concentration sensor are disclosed in which a reception wave which has been transmitted and received by an ultrasonic element 5 is subjected to full-wave rectification in order to obtain a full-wave-rectified wave, which is then integrated by an integration circuit 37 to obtain an integral value. A peak value of the integral value is held by a peak-hold circuit 39. As to detection of gas concentration, a threshold-level calculation section 21e sets a reference value on the basis of the peak value, and a point in time when the amplitude of a reception wave having undergone full-wave rectification is judged by a comparator 43 to have reached the reference value is regarded as an arrival time. Subsequently, a gas concentration is determined on the basis of a period between the emission time and the arrival time.

Abstract: A gas concentration sensor comprises an ultrasonic element 33 opposite a reflection surface 34. A depression 34a is formed on an edge portion of a reflection surface 34 which is in contact with a side wall of a measurement chamber 32 such that a bottom surface of the depression 34a is substantially in parallel with the reflection surface 34. The distance between the ultrasonic element 33 and the edge portion of the reflection surface 34 becomes greater than the distance between the ultrasonic element 33 and a central portion of the reflection surface 34. As a result, an indirect wave, which impinges obliquely on the side wall of the measurement chamber 32 and propagates along the side wall, is reflected from the bottom surface of the depression 34a and propagates.