JP4885804B2 - Gas sensor abnormality diagnosis method and gas sensor control device - Google Patents

Description

  The present invention relates to a gas sensor abnormality diagnosis method and a gas sensor control device for diagnosing whether or not a gas sensor installed in an exhaust pipe through which exhaust gas discharged from an internal combustion engine is in an abnormal state.

  Conventionally, an internal combustion engine such as an automobile uses a three-way catalyst to purify CO, HC and NOx contained in exhaust gas. In order to perform purification efficiently, the oxygen concentration in the exhaust gas is detected by a gas sensor attached to the exhaust pipe, and the fuel injection amount is adjusted based on the detected value, thereby mixing the fuel and air. Air-fuel ratio feedback control is performed so that (hereinafter simply referred to as “air-fuel ratio”) approaches a theoretical value. In recent years, for the purpose of performing more precise air-fuel ratio feedback control, etc., a full-range air-fuel ratio sensor as a gas sensor whose sensor output value changes linearly according to the oxygen concentration in the exhaust gas is attached to the exhaust pipe. It is getting to be.

  Here, since the sensor element of the gas sensor attached to the exhaust pipe is directly exposed to the exhaust gas, the porous portion in which poisonous components such as phosphorus contained in the exhaust gas guide the exhaust gas into the sensor element If a large amount adheres to the gas sensor, the detection sensitivity (gain of the sensor output value) of the gas sensor with respect to the concentration change of the specific gas component may be reduced. In addition, if a crack or the like may occur in the sensor element, the detection sensitivity of the gas sensor (the gain of the sensor output value) with respect to a change in the concentration of the specific gas component may increase excessively compared to when it is normal. On the other hand, since air-fuel ratio feedback control is performed based on the sensor output value of the gas sensor, if the detection sensitivity of the gas sensor is abnormal, normal control cannot be performed, and exhaust gas purification is sufficiently performed. There is a risk of being lost. Accordingly, various types of gas sensor deterioration diagnosis have been proposed.

For example, since the atmosphere is supplied to the gas sensor during the period when the fuel supply to the internal combustion engine is interrupted, the sensor output value can be predicted. A feedback-type air-fuel ratio of an internal combustion engine that diagnoses the presence or absence of a failure of the air-fuel ratio control device including the gas sensor by comparing the output value of the sensor element of the gas sensor (oxygen sensor) with a predetermined reference value after a lapse of time Diagnosis methods for control devices have been proposed (see Patent Documents 1 and 2). According to this air-fuel ratio control device, the operation of the control circuit of the air-fuel ratio control device itself determines whether or not the air-fuel ratio control device including the oxygen sensor has failed, and the air-fuel ratio is not required without requiring a special detector. There is an advantage that the presence or absence of a failure of the control device can be diagnosed.
JP-A-60-233343 JP-A-60-192847

  By the way, in the above-described conventional diagnostic method, the gas sensor is in an abnormal state depending on whether or not the sensor output value itself from the sensor element of the oxygen sensor exceeds the reference value even once after a predetermined time has elapsed since the start of fuel supply interruption. It is the structure which diagnoses whether or not. However, the change over time during the interruption of fuel supply of the output value of a gas sensor that detects a specific gas, such as an oxygen sensor, generally shows a waveform in which a plurality of extreme values appear. In addition, the sensor output value of the gas sensor may include a unique value such as noise. For this reason, in the conventional gas sensor abnormality diagnosis method, it is determined that an abnormality has occurred by mistake even if the gas sensor is still in a normal state, depending on the waveform state of the sensor output value and the influence of noise and other factors. There is a possibility that it cannot be accurately diagnosed whether or not the gas sensor is in an abnormal state.

  The present invention has been made to solve the above problems, and an object thereof is to provide a gas sensor abnormality diagnosis method and a gas sensor control device capable of accurately diagnosing whether or not a gas sensor is in an abnormal state. To do.

  In order to solve the above-described problem, the abnormality diagnosis method for a gas sensor according to the first aspect of the present invention provides a gas sensor that outputs a sensor output value corresponding to the concentration of a specific gas component in exhaust gas discharged from an internal combustion engine. An abnormality diagnosis method for a gas sensor for diagnosing whether or not the engine is in a sensor output value obtaining step for obtaining sensor output values of the gas sensor at predetermined intervals, and interruption detection for detecting interruption of fuel supply to the internal combustion engine And at least one of a maximum value and a minimum value among the sensor output values continuously acquired in the sensor output value acquisition step during a period in which the interruption of fuel supply is detected in the interruption detection step. An extreme value acquisition step of acquiring as an extreme value; an extreme value comparison step of comparing the extreme value acquired in the extreme value acquisition step with a predetermined first threshold; When the first predetermined number of extreme values is acquired in the extreme value acquisition step, whether or not the gas sensor is in an abnormal state is diagnosed based on a comparison result in the extreme value comparison step for the first predetermined number. And an abnormality diagnosis process. In the present invention, the “local maximum value” means a local maximum value of sensor output values obtained continuously, and is convex upward in a graph showing a change over time of the sensor output value. It ’s a mountain. Similarly, “local minimum value” refers to a local minimum value of sensor output values that are continuously acquired, and has a downwardly convex valley in a graph showing changes in sensor output values over time. Value. That is, an extreme value consisting of at least one of a local maximum value and a local minimum value is a local concept, so that the sensor output value acquired as an extreme value at a certain point in time is the entire range of sensor output values acquired continuously. The maximum or minimum value is not necessarily taken.

  Further, the abnormality diagnosis method for a gas sensor according to a second aspect of the invention includes the configuration according to the first aspect, wherein the extreme value acquisition step is performed after the interruption of fuel supply is detected in the interruption detection step. The acquisition of the extreme value is started after the elapse of a predetermined time set to a time longer than the predetermined interval.

  In addition to the configuration of the invention according to claim 1 or 2, the abnormality diagnosis method for a gas sensor according to a third aspect of the invention includes, in the extreme value acquisition step, the acquisition order acquired in the sensor output value acquisition step. Based on the three consecutive sensor output values, it is determined whether the second sensor output value in the acquisition order of the three sensor output values is the extreme value, and is determined to be the extreme value. The obtained sensor output value is acquired as the extreme value.

  The abnormality diagnosis method for a gas sensor according to a fourth aspect of the invention includes the configuration obtained in the extreme value acquisition step in the extreme value comparison step in addition to the configuration of the invention according to any one of the first to third aspects. The number of extreme values that are determined to be larger than the upper limit value set as the first threshold value is calculated. In the abnormality diagnosis step, the gas sensor is in an abnormal state based on the number of extreme values. It is characterized by diagnosing whether or not there is.

In addition to the configuration of the invention according to any one of claims 1 to 3 , the abnormality diagnosis method for a gas sensor according to a fifth aspect of the present invention is the extremal value comparison step, wherein the extreme value acquisition step acquires the The number of the extreme values determined to be less than the lower limit value set as the first threshold value is calculated, and the gas sensor is in an abnormal state based on the number of extreme values in the abnormality diagnosis step. It is characterized by diagnosing whether or not.

  In addition to the configuration of the invention according to any one of claims 1 to 5, the abnormality diagnosis method for a gas sensor according to a sixth aspect of the present invention is the abnormality diagnosis step, wherein the abnormality is obtained in the sensor output value acquisition step. Among the sensor output values, when the number of the sensor output values not acquired as the extreme value in the extreme value acquisition step reaches a second predetermined number, 1 acquired after the second predetermined number is reached Alternatively, a plurality of sensor output values are compared with a predetermined second threshold value to diagnose whether or not the gas sensor is in an abnormal state.

According to a seventh aspect of the present invention, there is provided a gas sensor abnormality diagnosis method according to any one of the first to fifth aspects, wherein, in the abnormality diagnosis step, the sensor output value acquisition step acquires the sensor output value acquisition step. Among the sensor output values, when the number of the sensor output values not acquired as the extreme value in the extreme value acquisition step reaches a second predetermined number, the sensor output after the second predetermined number is reached A third predetermined number of values is acquired, and a value obtained by averaging the third predetermined number of sensor output values is compared with a predetermined third threshold value to determine whether or not the gas sensor is in an abnormal state. It is characterized by making a diagnosis.

In addition to the configuration of the invention according to any one of claims 1 to 5 , the abnormality diagnosis method for a gas sensor according to an eighth aspect of the invention includes, in the abnormality diagnosis step, the sensor output value acquisition step. Among sensor output values, when the number of sensor output values not acquired as the extreme value in the extreme value acquisition step reaches a second predetermined number, the extreme values acquired in the extreme value acquisition step are averaged. It is characterized in that the gas sensor is compared with a predetermined fourth threshold value to diagnose whether or not the gas sensor is in an abnormal state.

  According to a ninth aspect of the present invention, there is provided a gas sensor control device for diagnosing whether or not a gas sensor that outputs a sensor output value corresponding to a concentration of a specific gas component in exhaust gas discharged from an internal combustion engine is in an abnormal state. A sensor output value acquisition means for acquiring sensor output values of the gas sensor at predetermined intervals; an interruption detection means for detecting interruption of fuel supply to the internal combustion engine; and a fuel detected by the interruption detection means. Extreme value acquisition means for acquiring, as an extreme value, at least one of a maximum value and a minimum value among sensor output values continuously acquired by the sensor output value acquisition means within a period during which supply interruption is detected. And an extreme value comparison means for comparing the extreme value acquired by the extreme value acquisition means with a predetermined first threshold value, and the extreme value is acquired by the extreme value acquisition means. When the number acquired, and a diagnosis means based on the comparison result of the extreme comparison means of said first predetermined number, to diagnose whether the gas sensor is in an abnormal state.

  According to a tenth aspect of the present invention, in addition to the configuration of the ninth aspect of the invention, the extremum acquisition unit is configured to perform the predetermined interval after the interruption of the fuel supply is detected by the interruption detection unit. After the elapse of a predetermined time set to a longer time, the acquisition of the extreme value is started.

  Further, in the gas sensor control device according to an eleventh aspect of the invention, in addition to the configuration of the invention according to the ninth or tenth aspect, the extreme value acquisition means has a continuous acquisition order acquired by the sensor output value acquisition means. Based on the three sensor output values, it is determined whether or not the second sensor output value in the acquisition order of the three sensor output values is the extreme value, and is determined to be the extreme value. The sensor output value is acquired as the extreme value.

  According to a twelfth aspect of the present invention, in addition to the configuration of the invention according to any one of the ninth to eleventh aspects, the extreme value comparison means includes the extreme value acquired by the extreme value acquisition means. Calculates the number of extreme values determined to be larger than the upper limit value set as the first threshold, and the abnormality diagnosis means determines whether the gas sensor is in an abnormal state based on the number of extreme values. It is characterized by diagnosing whether or not.

According to a thirteenth aspect of the present invention, in addition to the configuration of the invention according to any one of the ninth to eleventh aspects, the extreme value comparison means includes the extreme value acquisition means. The number of extreme values determined to be less than the lower limit value set as the first threshold value is calculated, and the abnormality diagnosis means determines whether the gas sensor is in an abnormal state based on the number of extreme values. It is characterized by diagnosing whether or not.

  According to a fourteenth aspect of the present invention, in addition to the configuration of the invention according to any one of the ninth to thirteenth aspects, the abnormality diagnosis unit is configured to output the sensor output acquired by the sensor output value acquisition unit. Among the values, when the number of sensor output values not acquired as extreme values by the extreme value acquisition means reaches a second predetermined number, one or more acquired after the second predetermined number is reached The sensor output value is compared with a predetermined second threshold value to diagnose whether or not the gas sensor is in an abnormal state.

Further, the gas sensor control apparatus of the invention according to claim 15, in addition to the configuration of the invention according to any one of claims 9 to 1 3, wherein the abnormality diagnosis means, said sensor obtained by the sensor output value acquisition means Among the output values, when the number of sensor output values not acquired as extreme values by the extreme value acquisition means reaches a second predetermined number, the sensor output values after the second predetermined number is reached A third predetermined number is acquired, and a value obtained by averaging the third predetermined number of sensor output values is compared with a predetermined third threshold value to diagnose whether the gas sensor is in an abnormal state. It is characterized by that.

Further, the gas sensor control apparatus of the invention according to claim 16, in addition to the configuration of the invention according to any one of claims 9 to 1 3, wherein the abnormality diagnosis means, said sensor obtained by the sensor output value acquisition means Among the output values, when the number of sensor output values not acquired as extreme values by the extreme value acquisition means reaches a second predetermined number, the extreme values acquired by the extreme value acquisition means are averaged. The measured value is compared with a predetermined fourth threshold value to diagnose whether or not the gas sensor is in an abnormal state.

  According to the gas sensor abnormality diagnosis method of the first aspect of the present invention, the sensor output value used for abnormality diagnosis is a sensor output value obtained continuously during a period in which interruption of fuel supply to the internal combustion engine is detected. Among these, at least one of the maximum value and the minimum value (extreme value) is used. Then, the first predetermined number of extreme values acquired are compared with a predetermined first threshold value, and whether or not the gas sensor is in an abnormal state is diagnosed based on the first predetermined number of comparison results. I am doing so. For this reason, even if a specific sensor output value such as noise is accidentally acquired within a period in which interruption of fuel supply to the internal combustion engine is detected, it is determined whether or not the gas sensor is in an abnormal state. Well, it can be judged accurately. Further, according to the gas sensor abnormality diagnosis method of the present invention, it is possible to diagnose whether or not the gas sensor is in an abnormal state at the time when the first predetermined number of extreme values are acquired. Without waiting for this, it is possible to accurately diagnose the abnormality of the gas sensor at an early stage.

  Further, according to the abnormality diagnosis method for a gas sensor of the invention according to claim 2, in addition to the effect of the invention of claim 1, exhaust gas existing around the gas sensor from the start of interruption of fuel supply to the internal combustion engine An extreme value of the sensor output value used in the abnormality diagnosis process is acquired after a predetermined time appropriately determined based on the time necessary for switching to a gas having a known concentration. For this reason, it is possible to acquire an extreme value in a state where the waveform of the sensor output value is relatively stable, and it is possible to more accurately determine whether or not the gas sensor is in an abnormal state.

  According to the gas sensor abnormality diagnosis method of the invention of claim 3, in addition to the effect of the invention of claim 1 or 2, the three sensors in which the acquisition order acquired in the sensor output value acquisition step is continuous. Based on the output value, the acquisition order of these three sensor output values is determined to determine whether the second sensor output value is an extreme value or not. The extreme value can be reliably acquired from the sensor output values acquired continuously.

  According to the gas sensor abnormality diagnosis method of the invention of claim 4, in addition to the effect of the invention of any of claims 1 to 3, the acquired extreme value is set as a first threshold value. By performing abnormality diagnosis of the gas sensor based on the number determined to be larger than the upper limit value, it is possible to accurately diagnose whether or not the detection sensitivity of the gas sensor is “high gain abnormality”.

According to the gas sensor abnormality diagnosis method of the invention of claim 5, in addition to the effect of the invention of any one of claims 1 to 3 , the acquired extreme value is set as the first threshold value. By performing abnormality diagnosis of the gas sensor based on the number determined to be less than the lower limit value, it is possible to accurately diagnose whether or not the detection sensitivity of the gas sensor is “low gain abnormality”.

  According to the gas sensor abnormality diagnosis method of the invention of claim 6, in addition to the effect of the invention of any of claims 1 to 5, it is not acquired as an extreme value among the acquired sensor output values. When the sensor output value reaches the second predetermined number, the gas sensor compares the one or more sensor output values acquired after reaching the second predetermined number with a predetermined second threshold value. Diagnose whether there is an abnormal condition. For this reason, the gas sensor is in an abnormal state even when the extreme predetermined value of the sensor output value cannot be obtained due to the operating state of the internal combustion engine before the interruption of fuel supply is detected. Whether or not can be complementarily diagnosed. Furthermore, since it is possible to diagnose whether or not the gas sensor is in an abnormal state when the number of sensor output values not acquired as extreme values reaches the second predetermined number, the extreme value of the sensor output value is Even if the first predetermined number cannot be obtained, it is possible to accurately diagnose abnormality of the gas sensor at an early stage without waiting for cancellation of interruption of fuel supply.

According to the gas sensor abnormality diagnosis method of the invention of claim 7, in addition to the effect of the invention of any of claims 1 to 5 , it is not acquired as an extreme value among the acquired sensor output values. When the sensor output value reaches the second predetermined number, a value obtained by averaging the third predetermined number of sensor output values acquired after the second predetermined number is reached, and a predetermined third threshold value are obtained. In comparison, it is diagnosed whether or not the gas sensor is in an abnormal state. By diagnosing using a value obtained by averaging the third predetermined number of sensor output values, noise or the like can be compared to diagnosing whether or not the gas sensor is in an abnormal state using one sensor output value. The influence when a unique sensor output value is accidentally acquired can be reduced. For this reason, the gas sensor is in an abnormal state even when the extreme predetermined value of the sensor output value cannot be obtained due to the operating state of the internal combustion engine before the interruption of fuel supply is detected. Whether or not can be determined in a complementary and accurate manner. The sensor output value averaging process includes a third predetermined number of sensors in addition to a simple averaging process in which sensor output values for a third predetermined number are accumulated (integrated) and divided by the third predetermined number. For example, a process of performing a weighted average of output values.

According to the gas sensor abnormality diagnosis method of the invention of claim 8, in addition to the effect of the invention of any of claims 1 to 5 , it is not acquired as an extreme value among the acquired sensor output values. When the sensor output value reaches the second predetermined number, the value obtained by averaging the extreme values acquired so far is compared with a predetermined fourth threshold value to determine whether or not the gas sensor is in an abnormal state. I'm diagnosing. For this reason, the gas sensor is in an abnormal state even when the extreme predetermined value of the sensor output value cannot be obtained due to the operating state of the internal combustion engine before the interruption of fuel supply is detected. Whether or not can be determined in a complementary and accurate manner. In addition, as the averaging process of the extreme values of the sensor output values, in addition to the simple averaging process of accumulating (accumulating) the number of acquired extreme values and dividing by the acquired number, the weighted average of the extreme values The process to perform etc. are mentioned.

  According to the gas sensor control device of the invention according to claim 9, as the sensor output value used for abnormality diagnosis, the sensor output value obtained continuously during the period in which interruption of fuel supply to the internal combustion engine is detected Among these, at least one of the maximum value and the minimum value (extreme value) is used. Then, the first predetermined number of extreme values acquired are compared with a predetermined first threshold value, and whether or not the gas sensor is in an abnormal state is diagnosed based on the first predetermined number of comparison results. I am doing so. For this reason, even if a specific sensor output value such as noise is accidentally acquired within a period in which interruption of fuel supply to the internal combustion engine is detected, it is determined whether or not the gas sensor is in an abnormal state. Well, it can be judged accurately. Furthermore, according to the gas sensor control device of the present invention, it is possible to diagnose whether or not the gas sensor is in an abnormal state when the first predetermined number of extreme values are acquired. Therefore, it is possible to diagnose the abnormality of the gas sensor accurately at an early stage.

  According to the gas sensor control device of the invention of claim 10, in addition to the effect of the invention of claim 9, the exhaust gas existing around the gas sensor is known from the start of interruption of fuel supply to the internal combustion engine. An extreme value of the sensor output value used for the abnormality diagnosis process is acquired after a predetermined time appropriately determined based on the time required for switching to a concentration gas (such as the atmosphere). For this reason, it is possible to acquire an extreme value in a state where the waveform of the sensor output value is relatively stable, and it is possible to more accurately determine whether or not the gas sensor is in an abnormal state.

  Moreover, according to the gas sensor control apparatus of the invention which concerns on Claim 11, in addition to the effect of the invention of Claim 9 or 10, three said sensor output values with which the acquisition order acquired in the sensor output value acquisition process continues The acquisition order of these three sensor output values is determined to determine whether or not the second sensor output value is an extreme value, and the extreme value is acquired. The extreme value can be reliably acquired from the sensor output value acquired

  According to the gas sensor control device of the invention of claim 12, in addition to the effect of the invention of any of claims 9 to 11, an upper limit value set as the first threshold value among the acquired extreme values By diagnosing the abnormality of the gas sensor based on the number determined to be larger than that, it is possible to accurately diagnose whether or not the detection sensitivity of the gas sensor is “large gain abnormality”.

Further, according to the gas sensor control device of the invention according to claim 13, in addition to the effect of the invention according to any one of claims 9 to 1 1, of the obtained extreme lower limit is set as the first threshold value By performing abnormality diagnosis of the gas sensor based on the number determined to be less than the value, it is possible to accurately diagnose whether or not the detection sensitivity of the gas sensor is “low gain abnormality”.

  According to the gas sensor control device of the invention of claim 14, in addition to the effect of the invention of any of claims 9 to 13, a sensor that has not been acquired as an extreme value among the acquired sensor output values. When the output value reaches the second predetermined number, the gas sensor is in an abnormal state by comparing one or more sensor output values acquired after the second predetermined number is reached with a predetermined second threshold value. Is diagnosed. For this reason, the gas sensor is in an abnormal state even when the extreme predetermined value of the sensor output value cannot be obtained due to the operating state of the internal combustion engine before the interruption of fuel supply is detected. Whether or not can be complementarily diagnosed. Furthermore, since it is possible to diagnose whether or not the gas sensor is in an abnormal state when the number of sensor output values not acquired as extreme values reaches the second predetermined number, the extreme value of the sensor output value is Even if the first predetermined number cannot be obtained, it is possible to accurately diagnose abnormality of the gas sensor at an early stage without waiting for cancellation of interruption of fuel supply.

Further, according to the gas sensor control device of the invention according to claim 15, in addition to the effect of the invention according to any one of claims 9 to 1 3, out of the acquired sensor output value has not been acquired as extreme When the sensor output value reaches the second predetermined number, a value obtained by averaging the third predetermined number of sensor output values acquired after reaching the second predetermined number is compared with a predetermined third threshold value. Thus, it is diagnosed whether or not the gas sensor is in an abnormal state. By diagnosing using a value obtained by averaging the third predetermined number of sensor output values, noise or the like can be compared to diagnosing whether or not the gas sensor is in an abnormal state using one sensor output value. The influence when a unique sensor output value is accidentally acquired can be reduced. For this reason, the gas sensor is in an abnormal state even when the extreme predetermined value of the sensor output value cannot be obtained due to the operating state of the internal combustion engine before the interruption of fuel supply is detected. Whether or not can be determined in a complementary and accurate manner.

Further, according to the gas sensor control device of the invention according to claim 16, in addition to the effect of the invention according to any one of claims 9 to 1 3, out of the acquired sensor output value has not been acquired as extreme When the sensor output value reaches the second predetermined number, a value obtained by averaging the extreme values acquired so far is compared with a predetermined fourth threshold value to determine whether or not the gas sensor is in an abnormal state. I'm diagnosing. For this reason, the gas sensor is in an abnormal state even when the extreme predetermined value of the sensor output value cannot be obtained due to the operating state of the internal combustion engine before the interruption of fuel supply is detected. Whether or not can be determined in a complementary and accurate manner.

  Hereinafter, an embodiment of a gas sensor abnormality diagnosis method and a gas sensor control device embodying the present invention will be described with reference to the drawings. As an example, a full-range air-fuel ratio sensor element 10 (hereinafter simply referred to as “sensor element 10”) capable of detecting the oxygen concentration corresponding to the theoretical air-fuel ratio point and the total air-fuel ratio from the rich region to the lean region. And the concentration of oxygen contained in the exhaust gas of the internal combustion engine such as an automobile is detected from the sensor output value output from the gas sensor unit 3, and the detection result of the oxygen concentration is used to control the air-fuel ratio of the internal combustion engine. A case where the present invention is applied to the gas sensor control device 1 of the first embodiment will be described.

  First, with reference to FIG. 1, the structure of the gas sensor control apparatus 1 and the gas sensor unit 3 is demonstrated. FIG. 1 is a system configuration diagram showing a schematic configuration of the gas sensor control device 1 and the gas sensor unit 3. The gas sensor unit 3 outputs a sensor output value corresponding to the oxygen concentration contained in the exhaust gas of the internal combustion engine, and is connected to the gas sensor 2 including the sensor element 10 and the ceramic heater 41, and the sensor element 10. A sensor drive circuit unit 4 including a heater voltage supply circuit 43 connected to the sensor control circuit 31 and the ceramic heater 41 is provided. Further, the gas sensor unit 3 includes three lead wires (pump-side lead wire 53, common lead wire 54, and detection-side lead wire 55) for electrically connecting the sensor element 10 and the sensor control circuit 31. Yes. On the other hand, the gas sensor control device 1 diagnoses whether or not the gas sensor 2 is in an abnormal state, and based on the sensor resistance value signal separately output from the sensor control circuit 31 provided in the gas sensor unit 3, the heater voltage supply circuit 43 Although equipped with an ECU 60 for controlling, although not shown, a display for notifying the diagnosis result of the abnormality diagnosis process of the present invention, a notification means such as an alarm device, and an output means such as a communication device for outputting to an external device are required. Depending on the provision.

  The heater voltage supply circuit 43, the ECU 60, and the sensor control circuit 31 each start to operate in synchronization with an activation signal input from the outside when the internal combustion engine is activated.

  Hereinafter, each structure with which the gas sensor unit 3 is provided is explained in full detail. First, the sensor element 10 provided in the gas sensor 2 will be described with reference to FIG. As shown in FIG. 1, the sensor element 10 includes a shielding layer 23, an oxygen concentration detection cell 15, a gas detection chamber 19, and an oxygen pump cell 11 stacked in this order from bottom to top. Hereafter, each structure with which the sensor element 10 is provided is explained in full detail with reference to FIG.

The oxygen pump cell 11 includes porous electrodes 13 and 14 on both plate surfaces (front side plate surface and back side plate surface) of the plate-shaped solid electrolyte body 12, and oxygen (O ₂ ) which is a specific gas detected by the gas sensor 2. Pumping is performed. The oxygen concentration detection cell 15 includes porous electrodes 17 and 18 on both plate surfaces (front plate surface and back plate surface) of a plate-shaped solid electrolyte body 16, and generates an electromotive force according to the oxygen concentration. . The gas detection chamber 19 is provided between the oxygen pump cell 11 and the oxygen concentration detection cell 15 and is a space into which the gas to be detected is introduced. The gas detection chamber 19 includes the porous electrode 14 of the oxygen pump cell 11 and the oxygen concentration detection cell 15. The porous electrode 17 is disposed so as to face the gas detection chamber 19. In addition, a gas diffusion porous layer 21 for controlling the diffusion of the detection gas introduced into the gas detection chamber 19 is disposed in the path for introducing the detection gas into the gas detection chamber 19. The solid electrolyte bodies 12 and 16 and the shielding layer 23 are mainly made of partially stabilized zirconia in which yttria is solid-solved as a stabilizer, and the porous electrodes 13, 14, 17 and 18 are mainly made of platinum. Is formed.

  Further, a shielding layer 23 is disposed on the surface of the oxygen concentration detection cell 15 opposite to the gas detection chamber 19 side with the porous electrode 18 interposed therebetween. Oxygen is accumulated in the porous gap of the porous electrode 18 sandwiched between the shielding layer 23 and the oxygen concentration detection cell 15, and the accumulated oxygen is detected in the oxygen concentration detection cell 15. It becomes the reference oxygen when detecting the oxygen concentration of the gas. For this reason, the porous electrode 18 functions as an oxygen reference electrode.

  Next, the ceramic heater 41 provided in the gas sensor 2 will be described with reference to FIG. The ceramic heater 41 is formed in a flat plate shape and is disposed to face the oxygen pump cell 11 of the sensor element 10. The ceramic heater 41 is for activating the sensor element 10, and is controlled by the electric power supplied from the heater voltage supply circuit 43 so that the temperature of the sensor element 10 becomes a predetermined temperature. On the other hand, the heater voltage supply circuit 43 supplies power to the ceramic heater 41 provided in the gas sensor 2 according to control by the ECU 60 described later.

  Next, the sensor control circuit 31 will be described with reference to FIG. The sensor control circuit 31 is electrically connected to the sensor element 10 through the three lead wires described above, and outputs a sensor output value to the ECU 60. The sensor control circuit 31 includes a pump current drive circuit 33, a voltage output circuit 35, a reference voltage comparison circuit 39, and a minute current supply circuit 40, which are known circuits.

  The minute current supply circuit 40 provided in the sensor control circuit 31 supplies a minute current Icp from the porous electrode 18 side of the oxygen concentration detection cell 15 to the porous electrode 17 side. When the minute current supply circuit 40 energizes the minute current Icp, oxygen is pumped to the porous electrode 18 side, and the porous electrode 18 functions as an oxygen reference electrode. The voltage output circuit 35 detects an electromotive force Vs generated between the porous electrodes 17 and 18 of the oxygen concentration detection cell 15. The reference voltage comparison circuit 39 holds a predetermined reference voltage (450 [mV] in the present embodiment) inside, and compares the electromotive force Vs detected by the voltage output circuit 35 with the reference voltage. The comparison result is fed back to the pump current drive circuit 33. The pump current drive circuit 33 controls the pump current Ip that flows through the oxygen pump cell 11 based on the comparison result received from the reference voltage comparison circuit 39.

  Next, the ECU 60 included in the gas sensor control device 1 will be described with reference to FIG. The ECU 60 controls the heater voltage supply circuit 43 that controls the energization of the heater, the CPU 61 that controls the main control of the gas sensor control device 1, the ROM 62 that stores programs, various setting values used in an abnormality diagnosis process described later, and the like. A random access memory (RAM) 63 is provided. In addition to the sensor output value and sensor resistance value signal output from the gas sensor 2 via the sensor drive circuit unit 4, the ECU 60 receives signals related to the fuel supply status to the internal combustion engine, and ON / OFF of the ignition switch. Other information such as a signal and a signal regarding whether or not all the operating parameter conditions indicating the operating state of the internal combustion engine are all satisfied for a predetermined time are input. The gas sensor control device 1 may be configured to include one or both of the sensor control circuit 31 and the heater voltage supply circuit 43. Similarly, the gas sensor unit 3 includes the sensor control circuit 31 and the heater voltage supply. Either or both of the circuits 43 may be omitted. For example, when the gas sensor control device 1 includes the sensor control circuit 31 and the heater voltage supply circuit 43, the sensor output value is directly input from the gas sensor 2 to the gas sensor control device 1. That is, in the present invention, the sensor output value output from the gas sensor 2 is input to the gas sensor control device 1 through various interfaces such as the sensor control circuit 31 in addition to the case of being input directly to the gas sensor control device 1. It may be. In the first embodiment, since the sensor output value output from the gas sensor 2 is input to the gas sensor control device 1 via the sensor control circuit 31, the “sensor output output from the gas sensor unit 3” is provided. The “value” corresponds to the “sensor output value of the gas sensor” of the present invention.

  A storage area of the RAM 63 provided in the ECU 60 will be described with reference to FIG. FIG. 2 is a conceptual diagram for explaining the storage area of the RAM 63. As shown in FIG. 2, the RAM 63 includes a work area 631 that stores various setting values read from the ROM 62, calculation results calculated by the CPU 61, and whether various operating parameter conditions of the internal combustion engine are satisfied for a predetermined time. And a confirmation flag storage area 632 for storing a confirmation flag indicating the above. The RAM 63 stores a sensor output value storage area 633 for storing the sensor output value output from the gas sensor unit 3, and a timer for storing a count value by which a value is added by a predetermined amount every predetermined time by a timer program (not shown). Counter storage area 634. In addition, the RAM 63 acquires a “maximum value” that is a local maximum value among sensor output values acquired at predetermined intervals, which are parameters used in the abnormality diagnosis process, and a maximum value among the acquired sensor output values. "Maximum number of acquisitions", the number of acquisitions of sensor output values that are not maximum among the acquired sensor output values, "Maximum number of unacquired times", the maximum value of the sensor output value is the upper limit A parameter storage area 635 for storing “number of times greater than a” that is determined to be greater than the value a, “number of times less than b” that is the number of times that the maximum value of the sensor output value is determined to be less than the lower limit b, and the like. It has. The RAM 63 is also input to the measurement completion flag storage area 636 for storing a measurement completion flag indicating whether or not the abnormality diagnosis process is performed, the diagnosis result storage area 637 for storing the diagnosis result in the abnormality diagnosis process, and the gas sensor control device 1. Other signals such as a signal relating to the fuel supply status to the internal combustion engine, a signal relating to the ON / OFF of the ignition switch, and a signal relating to whether or not various operating parameter conditions indicating the operating state of the internal combustion engine are all satisfied for a predetermined time. And an input information storage area 638 for storing the above information. Further, the RAM 63 includes various storage areas not shown in the drawing as required.

  Next, the control of the heater voltage supply circuit 43 by the gas sensor control device 1 will be briefly described. Although not shown in FIG. 1, the gas sensor control device 1 includes a known sensor resistance value detection circuit in the sensor control circuit 31. Specifically, this sensor resistance value detection circuit periodically supplies a constant current from a current supply circuit different from the minute current supply circuit 40 to the oxygen concentration detection cell 15, and at that time, the oxygen concentration detection cell A potential difference generated between the 15 porous electrodes 17 and 18 is detected as a sensor resistance value signal, and this signal is output to the ECU 60. The ECU 60 detects the temperature Tc of the sensor element 10 based on the sensor resistance value signal output from the gas sensor unit 3, and outputs a signal for controlling the voltage applied to the ceramic heater 41 based on the detected temperature Tc. This is output to the heater voltage supply circuit 43. More specifically, the oxygen concentration detection cell 15 is set so that the temperature Tc of the sensor element 10 becomes a normal temperature (for example, 800 [° C.]) higher than the activation temperature (for example, 600 [° C.]). The temperature control process is executed to adjust the magnitude of the voltage VH applied to the heater based on the sensor resistance value signal from the sensor control circuit 31 so that the sensor resistance value Rpvs of the sensor becomes the target resistance value Rta corresponding to this normal temperature. Is done. Note that there is a correlation between the temperature Tc in the oxygen concentration detection cell 15 of the sensor element 10 and the sensor resistance value Rpvs, and the temperature Tc of the sensor element 10 can be detected based on the sensor resistance value Rpvs. is there. As a result, the oxygen pump cell 11 and the oxygen concentration detection cell 15 are heated to the activation temperature or higher, and the sensor element 10 enters an activated state where oxygen can be detected. Note that the temperature control process executed by the ECU 60 may be executed by adopting a known method, and specifically, executed by the method disclosed in Japanese Patent Laid-Open No. 2003-185626. Therefore, further explanation is omitted.

Next, a method for the gas sensor control device 1 to detect the oxygen concentration in the exhaust gas based on the sensor output value output from the gas sensor unit 3 to detect the air-fuel ratio will be briefly described. An electromotive force Vs corresponding to the oxygen concentration in the gas detection chamber 19 is generated between the porous electrode 17 and the porous electrode 18 of the oxygen concentration detection cell 15 provided in the sensor element 10. In the sensor element 10, oxygen (O ₂ ) is pumped or pumped into the gas detection chamber 19 using the oxygen pump cell 11 so that the electromotive force Vs becomes a constant value (for example, 450 [mV]). Is called. At this time, since the current value and current direction of the pump current Ip flowing through the oxygen pump cell 11 change according to the oxygen concentration in the exhaust gas, the oxygen concentration in the exhaust gas is detected based on the detection result of the pump current Ip. it can. In the first embodiment, a voltage proportional to the amount of the pump current Ip is output as a sensor output value from the sensor control circuit 31 to the gas sensor control device 1 including the ECU 60, and the ECU 60 uses the sensor output value. Thus, the oxygen concentration of the exhaust gas is detected, and whether or not the gas sensor 2 is in an abnormal state is diagnosed. The ECU 60 detects the air-fuel ratio of the internal combustion engine by using the detected oxygen concentration because there is a correlation between the oxygen concentration in the exhaust gas and the air-fuel ratio.

  Next, a process for diagnosing whether or not the gas sensor 2 is in an abnormal state based on the sensor output value of the gas sensor 2 will be described with reference to FIGS. FIG. 3 is a graph showing an example of a sensor signal indicating a change over time in the sensor output value output from the gas sensor unit 3 after the start of interruption of fuel supply to the internal combustion engine, and FIG. 4 is surrounded by a dotted line in FIG. It is the graph which expanded the part 130. FIG. 5 is a flowchart showing a flow of main processing of abnormality diagnosis processing for diagnosing whether or not the gas sensor 2 is in an abnormal state. FIG. 6 is an abnormality diagnosis processing executed in the main processing shown in FIG. It is a flowchart which shows the flow. The programs for executing the processes shown in FIGS. 5 and 6 are stored in the ROM 62 and executed by the CPU 61 shown in FIG. 1 like other programs executed in the ECU 60.

  First, an example of a sensor signal indicating a change over time of a sensor output value used in an abnormality diagnosis process for diagnosing whether or not the gas sensor 2 is in an abnormal state will be briefly described with reference to FIGS. 3 and 4. A graph 100 shown in FIG. 3 shows sensor signals 101 to 104 as an example of the waveform of the sensor signal after the start of interruption of fuel supply to the internal combustion engine (hereinafter referred to as “F / C”). An example in which the sensor signal 101 is diagnosed as “gain large abnormality” in which the sensor output value with respect to the oxygen concentration in the exhaust gas is too large (in other words, the detection sensitivity of the gas sensor 2 is too large) by an abnormality diagnosis process described later. The sensor signal 102 shows a waveform whose period is substantially constant and whose amplitude varies periodically, and is an example of being diagnosed as “gain large abnormality” by an abnormality diagnosis process described later. Further, the sensor signal 103 shows a waveform whose period is substantially constant and the amplitude periodically varies, and is an example of being diagnosed as normal by an abnormality diagnosis process described later. The sensor signal 104 has a substantially constant period. A waveform whose amplitude periodically varies, and a sensor output value with respect to the oxygen concentration in the exhaust gas is too small (in other words, the detection sensitivity of the gas sensor 2 is too small) by an abnormality diagnosis process described later. It is an example diagnosed as being. FIG. 4 shows the sensor output values 201 to 206 after a predetermined period X1 has elapsed from the start of the F / C indicated by the arrow 111 by enlarging the portion 130 surrounded by the dotted line in FIG. ing.

  Next, the outline of the abnormality diagnosis process of the first embodiment will be briefly described. Since the atmosphere is supplied to the gas sensor 2 during F / C, the sensor output value of the gas sensor 2 output from the gas sensor unit 3 depends on the oxygen concentration in the atmosphere after a predetermined time has elapsed since the start of the F / C. The predetermined value is displayed. The poisoning component such as phosphorus contained in the exhaust gas adheres to the porous portion (specifically, the gas diffusion porous layer 21) of the gas sensor 2 in large quantities, or the sensor element 10 is cracked. When the deterioration of the gas sensor 2 occurs, the detection sensitivity of the gas sensor 2 with respect to a change in the oxygen concentration becomes excessively small or excessively large, which is different from the sensor output value in a predicted range according to the oxygen concentration in the atmosphere. The value comes to show.

  Therefore, an upper limit value or a lower limit value that defines a range of a sensor output value at which the gas sensor 2 is determined to be in a normal state after a predetermined time has elapsed from the start of F / C, and a sensor output value output from the gas sensor unit 3 By using it, it can be diagnosed whether the gas sensor 2 is in an abnormal state. However, in general, the graph plotting the change over time of the sensor output value of the gas sensor 2 shows a waveform in which a plurality of extreme values appear like the sensor signals 102 to 104 of the graph 100 shown in FIG. If the sensor output value exceeds the upper limit value or falls below the lower limit value even once, it is judged that an abnormality has occurred in the gas sensor. I can't. Further, since a unique sensor output value such as noise may appear, such as the sensor output value 210 of the sensor signal 104, the sensor output value is directly compared with the upper limit value or the lower limit value, and the sensor output value is If it is determined that an abnormality has occurred in the gas sensor when the upper limit is exceeded or falls below the lower limit, an accurate abnormality diagnosis cannot be performed. On the other hand, in the gas sensor abnormality diagnosis method of the present invention, among the sensor output values continuously acquired at predetermined intervals, the maximum value appearing on the larger value side is sequentially acquired and obtained for the first predetermined number. The maximum value is compared with an upper limit value or a lower limit value which is a first threshold value at which the gas sensor 2 is determined to be abnormal. Then, when comparing the first predetermined number of individual maximum values with the upper limit value, whether or not the gas sensor 2 is in an abnormal state is diagnosed based on the number of maximum values determined to be larger than the upper limit value. Like to do. For this reason, the present invention is also applicable to a case where the sensor output value shows a waveform in which a plurality of extreme values appear like the sensor signals 102 to 104 of the graph 100 shown in FIG. 3, or when noise is superimposed on the sensor output value. According to this gas sensor abnormality diagnosis method, it is possible to accurately diagnose abnormality of the gas sensor.

  Next, the main process of the abnormality diagnosis process for diagnosing whether or not the gas sensor 2 corresponding to the gas sensor of the present invention is in an abnormal state will be described with reference to the flowchart shown in FIG. As shown in the flowchart of FIG. 5, in the main process, first, various data, flags, and the like are initialized (S5). In this process, for example, a measurement completion flag indicating whether or not the abnormality diagnosis process is performed is set to 0 indicating that the abnormality diagnosis process has not been performed, stored in the measurement completion flag storage area 636 of the RAM 63, and stored in the sensor output value storage area 633. The sensor output value and its acquisition order n are cleared (S5). Subsequently, it is determined whether or not the sensor element 10 is activated (S10). This process is a process for determining whether or not the sensor element 10 is heated to reach a temperature at which the mobility of oxygen ions in the gas sensor 2 becomes high and is in a detectable state. As described above, since there is a correlation between the temperature Tc in the oxygen concentration detection cell 15 of the sensor element 10 and the sensor resistance value Rpvs, this processing is based on the sensor resistance value Rpvs of the oxygen concentration detection cell 15. It is then determined whether the sensor element 10 is activated.

  When it is determined that the sensor element 10 is not activated (S10: No), the process waits until it is determined that the sensor element 10 is activated. On the other hand, when it is determined that the sensor element 10 is activated (S10: Yes), a timer for acquiring the sensor output value of the gas sensor 2 output from the gas sensor unit 3 at a predetermined interval is started. (S15). By this processing, the count value stored in the timer counter storage area 634 is automatically updated every predetermined time by another program executed separately. Subsequently, the count value of the timer is reset and stored in the timer counter storage area 634 (S20). In this process, the timer may be reset so that the elapsed time from when the timer is reset to when the process of S45 described later is executed can be known. When it is determined that the sensor element 10 is activated (S10: Yes), drive control of the sensor element 10 using the sensor control circuit 31 is also started.

  Subsequently, the confirmation flag storage area 632 of the RAM 63 is referred to, and it is determined whether or not various operation parameter conditions indicating the operation state of the internal combustion engine are all satisfied for a predetermined time (S25). This process is a process for determining whether or not a condition for performing the abnormality diagnosis process is satisfied. In the gas sensor control device 1 of the first embodiment, when various operating parameters are monitored by another program that is separately executed, and it is confirmed that all the operating parameter conditions are continuously established for a predetermined time. In the confirmation flag storage area 632 of the RAM 63, 1 indicating that the condition is satisfied is stored. The operating parameter condition can be appropriately determined according to the configuration, characteristics, etc. of the internal combustion engine. In the first embodiment, the engine speed is 2000 rpm or more and 5000 rpm or less, and the engine cooling water is used. The water temperature of 50 ° C. or more and 300 ° C. or less is set as the operating parameter condition.

  In S25, when the confirmation flag storage area 632 of the RAM 63 is referred to and 0 indicating that the condition is not satisfied is stored in the confirmation flag (S25: No), subsequently, a maximum value that is a parameter used in the abnormality diagnosis processing 0 is set for each of the maximum value acquisition count, maximum value unobtained count, greater than a count, and less than b count, and is stored in the parameter storage area 635 of the RAM 63 (S35). Subsequently, the sensor output value of the gas sensor 2 is acquired and stored in the sensor output value storage area 633 (S40). On the other hand, when 1 indicating that the condition is satisfied is stored in S25 (S25: Yes), an abnormality diagnosis process for diagnosing whether or not the gas sensor 2 is in an abnormal state is performed (S30). . This abnormality diagnosis process will be described later with reference to the flowchart shown in FIG.

  Subsequent to S30 or S40, the timer counter storage area 634 is referred to, and it is determined whether 10 [msec] has elapsed after the timer reset in S20 (S45). This process is a process for acquiring sensor output values at predetermined intervals (10 [msec] in the first embodiment). Note that the predetermined interval may be determined as appropriate according to the characteristics and application of the gas sensor unit 3 (gas sensor 2), and is not limited to 10 [msec] in the first embodiment. If it is determined in S45 that 10 [msec] has not elapsed (S45: No), the process waits until it is determined that 10 [msec] has elapsed. On the other hand, when it is determined that 10 [msec] has elapsed (S45: Yes), the process returns to S20 and is repeated.

  As described in detail above, the main process of the gas sensor control device 1 is executed. Next, the abnormality diagnosis process executed in the main process shown in FIG. 5 will be described with reference to the flowchart shown in FIG. As shown in the flowchart of FIG. 6, in the abnormality diagnosis process, first, the measurement completion flag storage area 636 and the input information storage area 638 are referred to, and after the ignition switch (IG SW) is turned on, the abnormality diagnosis process is performed once. It is determined whether it is not (S305).

  When 0 indicating that the abnormality diagnosis process has not been performed is stored in the measurement completion flag storage area 636 (S305: Yes), subsequently, an input storing a signal related to the fuel supply status to the internal combustion engine The information storage area 638 is referred to, and it is determined whether or not F / C is being performed (S310). This process corresponds to the interruption detection step of the present invention, and is a process for diagnosing whether or not the gas sensor 2 is in an abnormal state by detecting whether or not F / C is being performed. For this reason, the process of S310 should just be able to detect whether it is in F / C, and is not limited to the processing method of 1st Embodiment. If it is determined that the F / C is being performed (S310: Yes), it is then determined whether or not a predetermined time X1 has elapsed since the start of the F / C (S315). This predetermined time X1 is a time longer than the predetermined interval of S45 that is appropriately determined based on the time required for the exhaust gas in the exhaust pipe to be replaced with the atmosphere after the start of F / C. The specific example shown in FIG. Then, it is between 3.0 [sec] indicated by an arrow 111.

  If it is determined in S315 that the predetermined time X1 has elapsed since the start of F / C (S315: Yes), it is determined that the sensor output value corresponding to the oxygen concentration contained in the atmosphere can be acquired. Thus, the sensor output value output from the gas sensor unit 3 is acquired and stored in the sensor output value storage area 633 together with the sensor output value acquisition sequence n (S320). This process is a process corresponding to the sensor output value acquisition step of the present invention, and sensor output values are acquired at predetermined intervals (10 [msec] in the first embodiment).

  On the other hand, when 1 indicating that the abnormality diagnosis process is being performed is stored in the measurement completion flag storage area 636 in S305 (S305: No), it is determined that the F / C is not being performed in S310 (S310). : No), or when it is determined in S315 that the predetermined time X1 has not elapsed since the start of the F / C (S315: No), there is a condition for performing a diagnosis as to whether or not the gas sensor 2 is in an abnormal state. Since it is determined that they are not in order, the maximum value of the sensor output value, which is a parameter used in the abnormality diagnosis process, the maximum value acquisition count, the maximum unacquired count, the number greater than a, and the number less than b are each set to 0. Is set and stored in the parameter storage area 635 of the RAM 63 (S450). This process is a process for resetting parameters used in the abnormality diagnosis process, and the gas sensor 2 is brought into an abnormal state only when it is determined by this process that conditions for continuously performing the abnormality diagnosis are satisfied. It can be diagnosed whether or not there is. Subsequently, the abnormality diagnosis process is terminated, and the process returns to the main process of FIG.

  Subsequent to S320, the sensor output value storage area 633 is referred to, and the three most recent sensor output values in which the acquisition order is continuous, that is, the acquisition order is the (n-2) th, (n-1) th, and nth sensor outputs. Whether or not a value is acquired, the (n-2) th sensor output value is less than or equal to the (n-1) th sensor output value, and the (n-1) th sensor output value satisfies a condition greater than the nth sensor output value. Determination is made (S325). This process and S330 to be described later are processes corresponding to the extreme value acquisition process of the present invention. Based on three sensor output values in which the acquisition order is continuous, the acquisition order in the three sensor output values is the second. This is a process for determining whether or not the sensor output value is a local maximum value and is a local maximum value that becomes a convex peak in the graph shown in FIG. In the case immediately after the lapse of the predetermined time X1 from the start of F / C, and n is 1 or 2, since the three most recent sensor output values are not stored, this processing may be omitted. Good. In addition, when storing the sensor output value continuously output from the start of F / C before the elapse of the predetermined time X1 together with the acquisition order n, for example, it is output from the gas sensor unit 3 immediately before or after the above-described S450. When the sensor output value is acquired and stored in the sensor output value storage area 633 together with the sensor output value acquisition order n, the acquisition order acquired before the elapse of the predetermined time X1 from the start of F / C is n−. Using the second sensor output value and the (n−1) th and nth sensor output values acquired after a predetermined time X1 has elapsed from the start of F / C, it is determined whether or not the above condition is satisfied. May be. In such a case, even when the sensor output value acquired immediately after the lapse of the predetermined time X1 from the start of F / C is the maximum value, the sensor output value can be acquired as the maximum value (S325: Yes, S330).

  As in the case where the three sensor output values in the acquisition order are the sensor output values 204 to 206 of the sensor signal 102 shown in FIG. 4, the above condition is satisfied, and the (n−1) th sensor output value is the maximum value ( In the specific example shown in FIG. 4, if it is determined that the sensor output value is indicated by a black circle (S325: Yes), then the n−1th sensor whose acquisition order is the second sensor output value. The output value, the sensor output value 205 indicated by a black circle in the above-described specific example, is stored as a maximum value in the parameter storage area 635 (S330). On the other hand, the process when it is determined that the above condition is not satisfied and the (n−1) th sensor output value is not the maximum value (S325: No) will be described later.

  Subsequent to S330, the local maximum value in the parameter storage area 635 is referred to, and whether or not the local maximum value is larger than the upper limit value a that defines the range of the sensor output value that is determined to be in the normal state of the gas sensor 2. Determination is made (S335). This process is a process corresponding to the extreme value comparison step of the present invention. The upper limit value a is determined based on a range in which the gas sensor 2 is determined to normally output a sensor output value corresponding to the oxygen concentration contained in the atmosphere, and is indicated by a dotted line 112 in the specific example shown in FIG. 5 [V]. In the above-described specific example, as shown in FIG. 4, it is determined that the sensor output value 205 is larger than 4.5 [V] indicated by the dotted line 112 (S335: Yes), and then the gas sensor 2 is in a normal state. Since it is determined that the sensor output value is not within the determined range, the number of times greater than a is incremented by 1 (incremented) and stored in the parameter storage area 635 (S345). This process is a process corresponding to the extreme value comparison step together with S335, and is a process for calculating the number of maximum values determined that the acquired maximum value is larger than the upper limit value a.

  On the other hand, when it is determined that the maximum value is equal to or less than the upper limit value a (S335: No), subsequently, the maximum value in the parameter storage area 635 is referred to and it is determined that the gas sensor 2 is in a normal state. It is determined whether or not it is less than a lower limit b that defines the range of the sensor output value (S340). This process is a process corresponding to the extreme value comparison step of the present invention, as in S335, and the lower limit b is that the gas sensor 2 normally outputs a sensor output value corresponding to the oxygen concentration contained in the atmosphere. It is determined based on the determined range, and is 3.0 [V] indicated by the dotted line 113 in the specific example shown in FIG.

  In S340, when it is determined that the maximum value is less than the lower limit value b (S340: Yes), it is determined that the gas sensor 2 is not within the range of the sensor output value that is determined to be in a normal state. Therefore, the number of times less than b is incremented by 1 (incremented) and stored in the parameter storage area 635 (S350). This process is a process corresponding to the extreme value comparison step together with S340, and is a process for calculating the number of maximum values determined that the acquired maximum value is less than the lower limit value b. On the other hand, when it is determined that the maximum value is greater than or equal to the lower limit value b (S340: No), it is determined that the maximum value is within the normal range. Subsequent to S345, S350, or S340, the maximum value acquisition count is incremented by 1 (incremented) and stored in the parameter storage area 635 (S355). This process is a process for integrating the number of sensor output values acquired as maximum values in S330.

  Subsequently, the maximum value acquisition count in the parameter storage area 635 is referred to, and it is determined whether or not the maximum value is acquired by a predetermined number A or more (S360). This process is a process for making a comparison between the maximum value and the upper limit value a for the first predetermined number A and diagnosing whether or not the gas sensor 2 is in an abnormal state based on the comparison result. This predetermined number A is a number corresponding to the first predetermined number of the present invention, and is appropriately determined according to the characteristics and application of the gas sensor 2, a predetermined interval at which the sensor output value is acquired, and the like in the first embodiment. It is determined. When it is determined that the maximum value is not acquired over the predetermined number A (S360: No), a sufficient number of comparison results for diagnosing whether or not the gas sensor 2 is in an abnormal state has not been obtained. Therefore, the abnormality diagnosis process is terminated and the process returns to the main process shown in FIG.

  On the other hand, when it is determined that the maximum value is acquired by the predetermined number A or more (S360: Yes), it is determined that a sufficient number of comparison results are obtained for diagnosing whether or not the gas sensor 2 is in an abnormal state. Therefore, the number of times larger than a in the parameter storage area 635 is subsequently referred to, and it is determined whether or not the number of times larger than a is equal to or greater than the predetermined number B (S365). The predetermined number B is appropriately determined according to the characteristics of the gas sensor 2, the accuracy of abnormality diagnosis, and the like, and is determined to be 10 in the first embodiment. When it is determined that the number of times greater than a is equal to or greater than the predetermined number B (S365: Yes), it is diagnosed that the detection sensitivity of the gas sensor 2 is too high, “gain large abnormality”, and the diagnosis result is stored as a diagnosis result. It is stored in the area 637 (S375). On the other hand, if it is determined in S365 that the number of times greater than a is less than the predetermined number B (S365: No), then the number of times less than b in the parameter storage area 635 is referred to, and the number of times less than b is the predetermined number B. It is determined whether or not this is the case (S370). When it is determined that the number of times less than b is equal to or greater than the predetermined number B (S370: Yes), it is diagnosed that the detection sensitivity of the gas sensor 2 is too small, “Gain small abnormality”, and the diagnosis result is stored in the diagnosis result storage area. 637 (S380). On the other hand, when it is determined that the number of times less than b is less than the predetermined number B (S370: No), the gas sensor 2 is diagnosed as normal, and the diagnosis result is stored in the diagnosis result storage area 637 (S385). ).

  Thus, when the maximum value acquisition count has reached the predetermined number A (S360: Yes), based on the comparison result between the maximum value of the sensor output value for the predetermined number A and the upper limit value a or the lower limit value b ( S365, S370), whether or not the gas sensor 2 is in an abnormal state is diagnosed (S375, S380 and S385). S365, S370, S375, S380 and S385 are processes corresponding to the abnormality diagnosis step of the present invention. As described above, since the gas sensor 2 is diagnosed using the comparison result for the predetermined number A, whether or not a specific sensor output value such as noise is accidentally acquired, It is possible to accurately and accurately determine whether or not the gas sensor is in an abnormal state. Although the same predetermined number B is used in S365 and S370, different values may be used for this predetermined number in S365 and S370.

  Subsequent to S375, S380, or S385, 1 indicating that the abnormality diagnosis process has been performed is set in the measurement completion flag and stored in the measurement completion flag storage area 636 (S390). This process is a process for performing the abnormality diagnosis process only once every time the ignition switch is turned on. In the abnormality diagnosis process executed after the next time, the abnormality diagnosis process has already been performed in S305. It will be judged (S305: No). Subsequently, the abnormality diagnosis process is terminated, and the process returns to the main process shown in FIG.

  In S325, the n-2th sensor output value is greater than or equal to the (n-1) th sensor output as the three sensor output values having the consecutive acquisition orders are the sensor output values 201 to 203 shown in FIG. The first sensor output value does not satisfy the condition larger than the nth sensor output value, and it is determined that the (n−1) th sensor output value (the sensor output value 202 indicated by a white circle in the above specific example) is not the maximum value. (S325: No), the maximum value unacquired number is incremented by 1 (incremented) and stored in the parameter storage area 635 (S405). This process is a process for integrating the number of sensor output values (sensor output values indicated by white circles in the specific example of FIG. 4) not acquired as the maximum value as the maximum value unobtained count. Subsequently, the maximum value unobtained number of times in the parameter storage area 635 is referred to, and it is determined whether or not the maximum value unobtained number is equal to or greater than a predetermined number C (S410). This process is a process for complementarily diagnosing whether or not the gas sensor 2 is in an abnormal state even when the sensor output value does not show a maximum value. The predetermined number C is a number corresponding to the second predetermined number of the present invention, and can be appropriately determined according to a predetermined number A that defines the frequency of acquiring the maximum value or the number of times of acquiring the maximum value, In the first embodiment, it is set to 100.

  If it is determined that the maximum value unacquired number is less than the predetermined number C (S410: No), the abnormality diagnosis process is terminated, and the process returns to the main process shown in FIG. On the other hand, when it is determined that the maximum value unacquired number is greater than or equal to the predetermined number C (S410: Yes), the sensor output value storage area 633 is subsequently referred to, and the nth sensor output value is equal to the upper limit described above. It is determined whether or not the value is larger than the value a (S415). This upper limit value a corresponds to the second threshold value, and may be the same value as the upper limit value (first threshold value) used in S335, or may be a different value. When it is determined that the n-th sensor output value is larger than the above-described upper limit value a (S415: Yes), the gas sensor 2 is diagnosed as having a large gain abnormality, and the diagnosis result is a diagnosis result storage area 637. (S420). On the other hand, when it is determined that the n-th sensor output value is equal to or less than the above-described upper limit value a (S415: No), the gas sensor 2 is diagnosed as normal, and the diagnosis result is stored in the diagnosis result storage area 637. Stored (S425). Thus, when the maximum value unobtained count, which is the number of sensor output values not acquired as the maximum value, reaches the predetermined number C (S410: Yes), the acquisition order nth when the predetermined number is reached. The sensor output value is compared with an upper limit value a which is a predetermined second threshold value (S415) to diagnose whether the gas sensor 2 is in an abnormal state (S420, S425), S410, S415, S420. And the process of S425 is a process corresponded to the abnormality diagnosis process of this invention.

  Subsequent to S420 or S425, 1 indicating that the abnormality diagnosis process has been performed is set in the measurement completion flag and stored in the measurement completion flag storage area 636 (S430). This process is the same as S390. Subsequently, the abnormality diagnosis process is terminated, and the process returns to the main process shown in FIG.

  As described above in detail, the abnormality diagnosis process of the first embodiment is executed. The diagnosis result in the abnormality diagnosis process is obtained by a program separately executed in the ECU 60 by a display means such as a display (not shown) provided in the gas sensor control device 1, a voice notification means such as an alarm device or a speaker, a warning lamp, or the like. May be output to an external device from a dedicated output terminal, or may be output to an external device by serial communication.

  In the first embodiment, the CPU 61 shown in FIG. 1 that detects interruption of fuel supply to the internal combustion engine with reference to the input information storage area 638 of the RAM 63 in S310 shown in FIG. Functions as interruption detection means. Also, the sensor output value of the gas sensor 2 is acquired at a predetermined interval (S320), and the CPU 61 shown in FIG. 1 functions as the sensor output value acquisition means of the present invention. Further, after the interruption of the fuel supply to the internal combustion engine is detected, after the elapse of a predetermined time X1 set to a time longer than the predetermined interval for acquiring the sensor output value (S315: Yes), the acquisition order continues to three Based on the sensor output value, it is determined whether or not the sensor output value having the second acquisition order among the three sensor output values is a maximum value (S325), and the sensor output determined to be the maximum value. 1 is acquired as a maximum value (S325: Yes, S330), the CPU 61 shown in FIG. 1 functions as an extreme value acquisition unit of the present invention.

  Further, in S335 of the flowchart shown in FIG. 6, the maximum value of the sensor output value acquired in S330 is compared with an upper limit value a which is a predetermined first threshold value, and is determined to be larger than the upper limit value a. The CPU 61 shown in FIG. 1, which calculates the number of maximum values (S335: Yes, S345), functions as an extreme value comparison unit of the present invention. Similar to S335, in S340 of the flowchart shown in FIG. 6, the acquired maximum value is compared with a lower limit value b which is a predetermined first threshold value (S340), and is determined to be less than the lower limit value b. The CPU 61 shown in FIG. 1 calculates the number of maximum values (S340: Yes, S350), and functions as an extreme value comparison unit of the present invention. When a predetermined number of local maximum values is acquired (S360: Yes), based on the comparison results in S335 and S340 for the predetermined number (S365 and S370), it is diagnosed whether or not the gas sensor 2 is in an abnormal state. (S375, S380, S385), the CPU 61 shown in FIG. 1 functions as an abnormality diagnosis means of the present invention. Moreover, when the sensor output value not acquired as the maximum value among the sensor output values acquired in S320 of the flowchart shown in FIG. 6 has reached the predetermined number C (S410: Yes), the predetermined number C has been reached. 1 is compared with an upper limit value a which is a predetermined second threshold value (S415) to diagnose whether the gas sensor 2 is in an abnormal state (S420, S425). The CPU 61 shown functions as abnormality diagnosis means of the present invention.

  According to the gas sensor abnormality diagnosis method and the gas sensor control device 1 of the first embodiment described in detail above, the sensor output value obtained continuously during the period in which interruption of fuel supply to the internal combustion engine is detected. 3 is a local maximum value, and in the graph shown in FIG. 3, a maximum value that is a convex peak is acquired, and the acquired maximum value and a predetermined first threshold value, upper limit value a and lower limit value b. Are sequentially diagnosed, and based on the comparison result between the maximum value for the predetermined number A and the first threshold value, the gas sensor is diagnosed as to whether or not it is in an abnormal state. Even when the value is accidentally acquired, it can be accurately and accurately determined whether or not the gas sensor is in an abnormal state. Further, when a predetermined number A of extreme values corresponding to the first predetermined number of the present invention is acquired, or a sensor output value not acquired as an extreme value is a predetermined number corresponding to the second predetermined number of the present invention. When it becomes C, it can be diagnosed whether or not the gas sensor 2 is in an abnormal state. Therefore, an accurate gas sensor abnormality diagnosis can be performed at an early stage without waiting for the cancellation of fuel supply interruption.

  Also, a sensor used for abnormality diagnosis processing after a predetermined time X1 has elapsed from the start of F / C, after a predetermined time X1 determined based on the time required for the exhaust gas existing around the gas sensor 2 to be replaced with the atmosphere having a known concentration. Since the extreme value of the output value is acquired, the extreme value can be acquired in a state in which the waveform of the sensor output value is relatively stable compared to that during the predetermined time X1, and an abnormal state of the gas sensor can be obtained. It can be judged more accurately whether or not there is. As described above, according to the gas sensor abnormality diagnosis method and the gas sensor control apparatus 1 of the first embodiment, it is possible to detect that the gas sensor 2 is in an abnormal state with higher accuracy. A secondary effect that an increase in harmful components in the exhaust gas can be prevented is obtained.

  Next, the abnormality diagnosis process of the second embodiment will be described with reference to the flowcharts shown in FIGS. The abnormality diagnosis process executed in the gas sensor control device 1 of the second embodiment is the above process shown in the flowchart of FIG. 6 when the number of sensor output values that have not been acquired as the maximum value reaches a predetermined number C. This is different from the abnormality diagnosis process of the first embodiment.

  Since the physical configuration of the gas sensor control device 1 of the second embodiment is the same as that of the first embodiment, description thereof is omitted. The electrical configuration of the gas sensor control device 1 of the second embodiment is the same as that of the first embodiment except for the configuration of the RAM 63. In the RAM 63 of the second embodiment, in addition to the storage area provided in the RAM 63 of the first embodiment, a diagnosis switching flag for storing a diagnosis switching flag for switching a diagnosis method when the maximum value unacquired count is a predetermined number C or more is stored. A storage area (not shown) is provided. Further, in the parameter storage area 635 of the RAM 63 of the second embodiment, in addition to the items stored in the first embodiment, the gas sensor 2 is in an abnormal state when the maximum value unobtained count is a predetermined number C or more. The parameter used for the process which complementarily diagnoses whether it exists in is stored. That is, in the parameter storage area 635 of the RAM 63 of the second embodiment, the “maximum value integration” for integrating the maximum values, the “maximum average value” obtained by dividing the maximum value integration by the number of maximum value acquisitions, and When the diagnosis switching flag is 1, “sensor output value integration” for integrating the sensor output values is stored. In the parameter storage area 635 of the RAM 63 of the second embodiment, an “average value counter” that accumulates the number of sensor output values accumulated in the sensor output value integration, and the sensor output value integration is divided by the average value counter. The “sensor output average value” obtained in this manner is stored.

  The main process of the abnormality diagnosis process executed in the gas sensor control device 1 of the second embodiment is the same as that of the first embodiment except for S5, S30, and S35 in the flowchart shown in FIG. A description of processing that is the same as in the first embodiment will be omitted, and processing that is different from the main processing in the first embodiment will be described below. In S5 and S35 of the second embodiment, in addition to the processing executed in the first embodiment, the items unique to the second embodiment stored in the parameter storage area 635 are initialized. That is, in S5 and S35 of the second embodiment, the maximum value, the maximum value acquisition count, the maximum value unobtained count, the greater than a count, the less than b count, and the maximum value integration, which are parameters used for abnormality diagnosis processing , Diagnosis switching flag, sensor output value integration, average value counter, sensor output average value, maximum value average value are each set to 0, and stored in a diagnostic switching flag storage area (not shown) or parameter storage area 635 of RAM 63. Processing is executed.

  Next, the abnormality diagnosis process (S30) of the second embodiment executed in the main process shown in FIG. 5 will be described with reference to the flowcharts of FIGS. 7 and 8 are flowcharts showing the flow of the abnormality diagnosis process according to the second embodiment executed in the main process shown in FIG. 7 and FIG. 8 is stored in the ROM 62, and is executed by the CPU 61 shown in FIG. 1 like other programs executed in the ECU 60. In the flowcharts of FIGS. 7 and 8, the same step numbers are assigned when the same process as the abnormality diagnosis process of the first embodiment shown in the flowchart of FIG. 6 is executed. A description of processing similar to that of the first embodiment is omitted or simplified, and processing different from the abnormality diagnosis processing of the first embodiment will be described in detail below.

  In the flowchart of FIG. 7, the processing of S305, S310, and S315 is the same as that of the first embodiment shown in the flowchart of FIG. When it is determined that the conditions of S305, S310, or S315 are not satisfied (S305: No, S310: No or S315: No), the maximum value of the sensor output value, which is a parameter used in the abnormality diagnosis process, 0 is set for each of the maximum value acquisition count, maximum value unobtained count, greater than a count, and less than b count, and is stored in the parameter storage area 635 of the RAM 63 (S451). Furthermore, in the second embodiment, when the maximum value unacquired number is equal to or greater than the predetermined number C, the maximum value integration, which is a parameter used for the process of supplementarily diagnosing whether or not the gas sensor 2 is in an abnormal state, The diagnosis switching flag, sensor output value integration, average value counter, sensor output average value, and maximum value average value are each set to 0, and stored in the diagnosis switching flag storage area (not shown) or parameter storage area 635 of the RAM 63. (S451). Subsequently, the abnormality diagnosis process is terminated, and the process returns to the main process of FIG.

  If it is determined in S315 that the predetermined time X1 has elapsed since the start of F / C (S315: Yes), the sensor output value is subsequently acquired (S320). Since this process is the same as that of the first embodiment, a description thereof will be omitted. Subsequent to S320, a diagnosis switching flag storage area (not shown) in the RAM 63 is referred to, and it is determined whether or not 0 is set in the diagnosis switching flag (S323). The process when it is determined that the diagnosis switching flag is not 0 (S323: No) will be described later. On the other hand, when it is determined that the diagnosis switching flag is 0 (S323: Yes), the process of S325 is subsequently executed as shown in the flowchart of FIG. Since the process of S325 is the same as that of the first embodiment, a description thereof will be omitted.

  When it is determined in S325 that the (n-2) th sensor output value is equal to or smaller than the (n-1) th sensor output value and the (n-1) th sensor output value satisfies the condition larger than the nth sensor output value. (S325: Yes) Subsequently, the process of S330 similar to that of the first embodiment shown in the flowchart of FIG. 6 is executed. Subsequently, the maximum value acquired in S330 is integrated into the maximum value integration and stored in the parameter storage area 635 (S333). Subsequently, a local maximum value acquisition process is executed (S700). In this processing, processing similar to S335 to S390 of the first embodiment shown in the flowchart of FIG. 6 is executed.

  On the other hand, in S325, it is determined that the (n-2) th sensor output value is equal to or smaller than the (n-1) th sensor output value and that the (n-1) th sensor output value does not satisfy the condition greater than the nth sensor output value. If it is to be performed (S325: No), then the same processes of S405 and S410 as in the first embodiment are executed in order. When it is determined in S410 that the maximum value unacquired number is less than the predetermined number C (S410: No), the abnormality diagnosis process is terminated, and the process returns to the main process shown in FIG. On the other hand, when it is determined that the maximum value unacquired number is greater than or equal to the predetermined number C (S410: Yes), subsequently, the maximum value acquisition number in the parameter storage area 635 is referred to, and the maximum value acquisition number is It is determined whether it is larger than the number D and less than the predetermined number A (S605). This processing is performed when the sensor output value that has not been acquired as the extreme value reaches the second predetermined number in accordance with the maximum value acquisition count at the time when it is determined that the maximum value unacquired count is less than the predetermined number C. This is a process for determining the process to be executed. The predetermined number A and the predetermined number D are appropriately determined according to the characteristics and application of the gas sensor 2, the predetermined interval at which the sensor output value is acquired, and the like. In the second embodiment, the predetermined number A is the same as S360 of the first embodiment shown in the flowchart of FIG. 6 and is set to 15, and the predetermined number D is set to 5.

  When the maximum value acquisition count is greater than the predetermined number D and not less than the predetermined number A (S605: No), it is subsequently determined whether or not the maximum value acquisition count is equal to or less than the predetermined number D. (S645). If the maximum value acquisition count is less than or equal to the predetermined number D (S645: Yes), then 1 is set in the diagnosis switching flag and stored in a diagnosis switching flag storage area (not shown) (S650). When this diagnosis switching flag is 1, as will be described later, the sensor output average value calculated from the predetermined number E of sensor output values acquired after the maximum value unobtained count reaches the predetermined number C is used. Then, processing for determining whether or not the gas sensor 2 is in an abnormal state is executed (S505 to S550). Subsequently, the abnormality diagnosis process is terminated, and the process returns to the main process of FIG. On the other hand, if the maximum value acquisition count is not less than or equal to the predetermined number D (S645: No), then the abnormality diagnosis process is terminated and the process returns to the main process in FIG.

  In S605, when the number of local maximum acquisitions is greater than the predetermined number D and less than the predetermined number A (S605: Yes), the local maximum average is obtained by dividing the local maximum integration by the number of local maximum acquisitions. A value is calculated and stored in the parameter storage area 635 (S610). This maximum average value corresponds to the “value obtained by averaging the extreme values” of the present invention. Subsequently, the local maximum average value in the parameter storage area 635 is referred to, and it is determined whether or not the local maximum average value is larger than the upper limit value a (S615). The upper limit value a in S615 is a value corresponding to the “fourth threshold value” of the present invention. When it is determined that the local maximum average value is larger than the upper limit value a (S615: Yes), it is diagnosed that the detection sensitivity of the gas sensor 2 is too large, “gain large abnormality”, and the diagnosis result is stored in the diagnosis result storage area. 637 (S625). On the other hand, in S615, when it is determined that the maximum average value is not greater than the upper limit value a (S615: No), it is subsequently determined whether the maximum value average value is less than the lower limit value b (S620). ). The lower limit value b in S620 is a value corresponding to the “fourth threshold value” of the present invention together with the upper limit value a. When it is determined that the local maximum average value is less than the lower limit value b (S620: Yes), it is diagnosed that the detection sensitivity of the gas sensor 2 is too small, “Gain small abnormality”, and the diagnosis result is stored as a diagnosis result. It is stored in the area 637 (S630). On the other hand, when it is determined that the average maximum value is not less than the lower limit value b (S620: No), the gas sensor 2 is diagnosed as normal, and the diagnosis result is stored in the diagnosis result storage area 637 ( S635).

  As described above, when the maximum value unacquired number reaches the predetermined number C (S410: Yes), the upper limit value a and the lower limit value b corresponding to the fourth threshold value are compared with the maximum value average value (S615, S615). S620) and the process of diagnosing whether or not the gas sensor 2 is in an abnormal state (S625, S630, S635) is a process corresponding to the abnormality diagnosis step of the present invention. In the second embodiment, the same value as the upper limit value a and the lower limit value b used in S335 and S340 of the first embodiment shown in the flowchart of FIG. 6 is used as the fourth threshold value. Alternatively, a value different from the lower limit value b may be used. In the second embodiment, the upper limit value a and the lower limit value b, which are two different values, are used as the fourth threshold value, but either one may be used. However, in order to perform a more accurate and accurate diagnosis, it is preferable to use two different fourth threshold values as in the second embodiment.

  Subsequent to S625, S630, or S635, 1 indicating that the abnormality diagnosis process has been performed is set in the measurement completion flag, and stored in the measurement completion flag storage area 636 (S640). This process is the same as S390 of the first embodiment shown in the flowchart of FIG. Subsequently, the abnormality diagnosis process is terminated, and the process returns to the main process shown in FIG.

  In S323, when it is determined that the diagnosis switching flag is 1 and not 0 (S323: No), the sensor output value acquired in S320 is added to the sensor output value integration, and the parameter storage area 635 is obtained. (S505). Subsequently, the average value counter is incremented (incremented) by 1 and stored in the parameter storage area 635 (S510). Subsequently, the average value counter in the parameter storage area 635 is referred to, and it is determined whether or not the average value counter is equal to or greater than a predetermined number E (S515). The predetermined number E is a number corresponding to the third predetermined number of the present invention, and is appropriately determined according to the characteristics and application of the gas sensor 2, a predetermined interval at which the sensor output value is acquired, and the like in the second embodiment. It is determined. If it is determined that the average value counter is not equal to or greater than the predetermined number E (S515: No), then the abnormality diagnosis process is terminated and the process returns to the main process shown in FIG. On the other hand, if it is determined that the average value counter is equal to or greater than the predetermined number E (S515: Yes), then the sensor output average value is obtained by dividing the sensor output value integration by the predetermined number E (average value counter). It is calculated and stored in the parameter storage area 635 (S520). This sensor output average value corresponds to “a value obtained by averaging the third predetermined number of sensor output values” of the present invention.

  Subsequently, the sensor output average value in the parameter storage area 635 is referred to, and it is determined whether or not the sensor output average value is larger than the upper limit value a (S525). The upper limit value a in S525 is a value corresponding to the “second threshold” and “third threshold” of the present invention. When it is determined that the sensor output average value is larger than the upper limit value a (S525: Yes), it is diagnosed that the detection sensitivity of the gas sensor 2 is too large, “gain large abnormality”, and the diagnosis result is stored in the diagnosis result storage area. 637 (S535). On the other hand, when it is determined in S525 that the sensor output average value is not greater than the upper limit value a (S525: No), it is subsequently determined whether the sensor output average value is less than the lower limit value b (S530). ). The lower limit b in S530 is a value corresponding to the “second threshold” and “third threshold” of the present invention together with the upper limit a. When it is determined that the sensor output average value is less than the lower limit value b (S530: Yes), it is diagnosed that the detection sensitivity of the gas sensor 2 is too small, “low gain abnormality”, and the diagnosis result is stored as a diagnosis result. It is stored in the area 637 (S540). On the other hand, when it is determined that the sensor output average value is not less than the lower limit value b (S530: No), the gas sensor 2 is diagnosed as normal and the diagnosis result is stored in the diagnosis result storage area 637 ( S545).

  Thus, when the maximum value unacquired number reaches the predetermined number C (S410: Yes), the sensor calculated from the sensor output value of the predetermined number E acquired after the maximum value unacquired number reaches the predetermined number C. A process of comparing the output average value with the upper limit value a and the lower limit value b (S525, S530) and diagnosing whether the gas sensor 2 is in an abnormal state (S535, S540, S545), This is a process corresponding to the abnormality diagnosis process. In the second embodiment, the same value as the upper limit value a and the lower limit value b used in S335 and S340 of the first embodiment shown in the flowchart of FIG. 6 is used as the third threshold value (second threshold value). However, a value different from the upper limit value a and the lower limit value b may be used. In the second embodiment, the upper limit value a and the lower limit value b, which are two different values, are used as the third threshold value (second threshold value), but either one may be used. However, in order to implement a more accurate and accurate diagnosis, it is preferable to use two different third threshold values (second threshold values) as in the second embodiment.

  Subsequent to S535, S540, or S545, 1 indicating that the abnormality diagnosis process has been performed is set in the measurement completion flag and stored in the measurement completion flag storage area 636 (S550). This process is the same as S390 of the first embodiment shown in the flowchart of FIG. Subsequently, the abnormality diagnosis process is terminated, and the process returns to the main process shown in FIG.

  As described above in detail, the abnormality diagnosis process of the second embodiment is executed. In the second embodiment, among the sensor output values acquired in S320 of the flowchart shown in FIG. 7, the number of sensor output values that have not been acquired as local maximum values (S325: No) has reached a predetermined number C. When (S410: Yes), a predetermined number E of sensor output values after reaching the predetermined number C is acquired (S320) and integrated (S505), and the sensor output which is the average value of the sensor output values of the predetermined number E The average value is compared with the upper limit value a and the lower limit value b (S525, S530) to diagnose whether the gas sensor 2 is in an abnormal state (S535, S540, S545). The CPU 61 shown in FIG. It functions as an abnormality diagnosis means of the present invention.

  Among the sensor output values acquired in S320 of the flowchart shown in FIG. 7, when the number of sensor output values that have not been acquired as maximum values (S325: No) reaches a predetermined number C (S410: Yes), the maximum value The average value is compared with the upper limit value a and the lower limit value b (S615, S620) to diagnose whether the gas sensor 2 is in an abnormal state (S625, S630, S635). The CPU 61 shown in FIG. It functions as an abnormality diagnosis means of the present invention.

  According to the abnormality diagnosis method of the second embodiment, when the sensor output value not acquired as the maximum value reaches the predetermined number C (S410: Yes), depending on the number of maximum value acquisition (S605), S610 -S640 process and S520-S550 process are switched. When the maximum value acquisition count is less than or equal to the predetermined number D (S605: No, S645: Yes), after the predetermined number C is reached, a predetermined number E of sensor output values are acquired (S320) and integrated ( S505), obtaining an average value thereof (S520), comparing the sensor output average value with the upper limit value a and the lower limit value b (S525, S530), and diagnosing whether or not the gas sensor is in an abnormal state. (S535, S540, S545). By using the average value of the third predetermined number of sensor output values to make a diagnosis, it is possible to use a single sensor output value to diagnose whether or not the gas sensor is in an abnormal state. The influence when the output value is accidentally acquired can be reduced.

  On the other hand, when the maximum value acquisition count is larger than the predetermined number D and less than the predetermined number A (S605: Yes), the maximum value average value acquired so far, the upper limit value a and the lower limit value b are In comparison (S615, S620), it is diagnosed whether the gas sensor is in an abnormal state (S625, S630, S635).

  Thus, according to the second embodiment, when the extreme predetermined value of the sensor output value cannot be obtained due to the operating state of the internal combustion engine before the interruption of the fuel supply is detected, etc. Even if it exists, it can complementarily and accurately determine whether the gas sensor is in an abnormal state. Furthermore, by switching the diagnosis method according to the maximum value acquisition count, it is possible to accurately diagnose whether or not the gas sensor is in an abnormal state by a diagnosis method suitable for the maximum value acquisition count.

  The present invention is not limited to the first and second embodiments, and various modifications may be made without departing from the scope of the present invention. For example, in the first and second embodiments, the case where the gas sensor 2 that detects oxygen as the specific gas in the exhaust gas diagnoses whether or not it is in an abnormal state has been described. As a specific gas component, the gas sensor is not limited to a gas sensor that detects an oxygen concentration, and a gas sensor that detects HC, CO, NOx, or the like as a specific gas component and detects their concentration can also be applied.

  In the first embodiment, in the abnormality diagnosis process shown in FIG. 6, a process for diagnosing whether or not there is a large gain abnormality (S365, S415), and a process for diagnosing whether or not there is a small gain abnormality (S370). However, only one of these processes may be implemented, or any two combinations may be implemented. However, in order to carry out a more accurate and accurate diagnosis, it is determined whether or not the gas sensor is in an abnormal state using the upper limit value and the lower limit value which are two different first threshold values as in the first embodiment. It is preferable to diagnose this.

  In the first and second embodiments, in S325 of the abnormality diagnosis process shown in FIG. 6, the three most recent sensor output values in which the acquisition order continues, that is, the acquisition order is n−2, n−1, And, the nth is acquired, the (n-2) th sensor output value is equal to or smaller than the (n-1) th sensor output value, and the (n-1) th sensor output value is larger than the nth sensor output value. It is determined whether or not the (n−1) th sensor output value is a maximum value (S325), but this process may be a process for acquiring an extreme value and is limited to this method. Not. Therefore, for example, when the extreme value appearance period is known in advance, after the start of acquisition of the extreme value, only the extreme value acquired first is the three sensor output values whose acquisition order is continuous as in the first embodiment. Is used to determine whether or not the second sensor output value is an extremum among the three sensor output values, and then the timing at which the first extremum acquired is acquired. The extreme value may be acquired based on the appearance frequency of the extreme value.

  In the first embodiment, the maximum value is used as the extreme value of the present invention in the abnormality diagnosis process shown in FIG. 6 and in the second embodiment in the abnormality diagnosis process shown in FIGS. However, the present invention is not limited to this, and a minimum value may be used as an extreme value, or both a maximum value and a minimum value may be used. Furthermore, in the first and second embodiments, the gas sensor abnormality diagnosis process is performed only once each time the ignition switch is turned on. However, the present invention is not limited to this, and the ignition switch is turned on and turned off. The gas sensor abnormality diagnosis process may be performed a plurality of times in the meantime.

  In the first embodiment, in S335 of the abnormality diagnosis process shown in FIG. 6, the number of maximum values determined to have a maximum value greater than the upper limit value a is calculated as a number greater than a, and in S365 from a. When the large number is greater than or equal to the predetermined number B (S365: Yes), the gas sensor 2 has determined that the gain is abnormally abnormal (S375), but the present invention is not limited to this. For example, in S335, the number of maximum values for which the maximum value is determined to be less than or equal to the upper limit value is calculated as the number of upper limit values a or less. If it is determined that the number of times equal to or less than the upper limit value a is less than the predetermined number B, the gas sensor 2 may determine that the gain is abnormal. The same applies to the processing in S340 and S370 of the abnormality diagnosis processing of the first embodiment shown in FIG. 6 and the processing in S700 of the abnormality diagnosis processing of the second embodiment shown in FIGS. 7 and 8.

  In the first embodiment, whether or not the gas sensor 2 is in an abnormal state is determined by comparing the nth sensor output value, which is the latest sensor output value, with the upper limit value a in S415 of the abnormality diagnosis process shown in FIG. Similarly, when the nth sensor output value is smaller than the lower limit value b, the nth sensor output value, which is the latest sensor output value, is compared with the lower limit value b. If it is “low gain abnormality” and the n-th sensor output value is equal to or greater than the lower limit value b, it may be determined that the state is normal. Further, in S415 of the abnormality diagnosis process shown in FIG. 6, whether or not the gas sensor 2 is in an abnormal state by comparing one or more sensor output values acquired after reaching the predetermined number C with the upper limit value a. You may make it diagnose.

  In the second embodiment, when the number of sensor output values that have not been acquired as maximum values (S325: No) among the sensor output values acquired in S320 of the flowchart shown in FIG. 7 has reached a predetermined number C. As the processing of (S410: Yes), the processing of S610 to S640 shown in the flowchart of FIG. 8 and the processing of S520 to S550 shown in the flowchart of FIG. 7 are switched according to the number of local maximum acquisition times (S605). However, it is not limited to this. For example, regardless of the maximum value acquisition count, either the processing of S610 to S640 or the processing of S520 to S550 may be executed, or the processing of S610 to S640 and S520 to S520 depending on the maximum value acquisition count. You may make it switch either of the process of S550 and S415-S430 of 1st Embodiment shown in the flowchart of FIG. However, since the processes of S610 to S640 cannot be performed unless the number of extreme values is acquired when the number of sensor output values reaches the predetermined number C, the gas sensor 2 is abnormal as in the second embodiment. It is preferable that another process capable of diagnosing whether or not it is in a state can be separately implemented.

  In the second embodiment, whether or not the gas sensor 2 is in an abnormal state by comparing one or more sensor output values acquired after the predetermined number C is reached with the upper limit value a (lower limit value b). Is not limited to the processing of S520 to S550 shown in the flowchart of FIG. For example, the integrated value of a plurality of sensor output values acquired after reaching the predetermined number C may be compared with the second threshold value.

  Moreover, although the 3rd threshold value (2nd threshold value) and 4th threshold value of 2nd Embodiment set the value similar to a 1st threshold value, it is not limited to this, It seems to set another value, respectively. It may be.

  The present invention can be applied to a gas sensor control device that controls a gas sensor.

2 is a system configuration diagram showing a schematic configuration of a gas sensor control device 1 and a gas sensor unit 3. FIG. 3 is a conceptual diagram for explaining a storage area of a RAM 63. FIG. It is a graph which shows an example of the sensor signal which shows a time-dependent change of the sensor output value output from the gas sensor unit 3 after the start of interruption of fuel supply to an internal combustion engine. It is the graph which expanded the part 130 enclosed with the dotted line of FIG. It is a flowchart which shows the flow of the main process of the abnormality diagnosis process which diagnoses whether the gas sensor 2 is in an abnormal state. It is a flowchart which shows the flow of the abnormality diagnosis process performed in the main process shown in FIG. It is a flowchart which shows the flow of the abnormality diagnosis process of 2nd Embodiment performed in the main process shown in FIG. It is a flowchart which shows the flow of the abnormality diagnosis process of 2nd Embodiment performed in the main process shown in FIG.

DESCRIPTION OF SYMBOLS 1 Gas sensor control apparatus 2 Gas sensor 3 Gas sensor unit 31 Sensor control circuit 33 Pump current drive circuit 35 Voltage output circuit 39 Reference voltage comparison circuit 40 Micro current supply circuit 41 Ceramic heater 43 Heater voltage supply circuit 60 ECU
61 CPU
62 ROM
63 RAM
201-206,210 Sensor output value

Claims (16)

A gas sensor abnormality diagnosis method for diagnosing whether or not a gas sensor that outputs a sensor output value corresponding to a concentration of a specific gas component in exhaust gas discharged from an internal combustion engine is in an abnormal state,
A sensor output value acquisition step of acquiring sensor output values of the gas sensor at predetermined intervals;
An interruption detecting step for detecting interruption of fuel supply to the internal combustion engine;
During the period in which the interruption of fuel supply is detected in the interruption detection step, at least one of the maximum value and the minimum value among the sensor output values continuously acquired in the sensor output value acquisition step is set as an extreme value. An extreme value acquisition process to be acquired;
An extreme value comparison step of comparing the extreme value acquired in the extreme value acquisition step with a predetermined first threshold;
When the first predetermined number of extreme values is acquired in the extreme value acquisition step, whether or not the gas sensor is in an abnormal state is diagnosed based on a comparison result in the extreme value comparison step for the first predetermined number. An abnormality diagnosis method for a gas sensor, comprising:   The extremum acquisition step starts acquiring the extremum after a lapse of a predetermined time set to a time longer than the predetermined interval after the interruption of fuel supply is detected in the interruption detection step. The abnormality diagnosis method for a gas sensor according to claim 1.   In the extreme value acquisition step, the sensor output value having the second acquisition order among the three sensor output values based on the three sensor output values acquired in the sensor output value acquisition step. 3. The gas sensor abnormality diagnosis according to claim 1, wherein the sensor output value determined as the extreme value is acquired as the extreme value. Method. In the extreme value comparison step, the extreme value acquired in the extreme value acquisition step is calculated as the number of the extreme values determined to be larger than the upper limit value set as the first threshold,
4. The abnormality diagnosis method for a gas sensor according to claim 1, wherein in the abnormality diagnosis step, it is diagnosed whether or not the gas sensor is in an abnormal state based on the number of extreme values. In the extreme value comparison step, the number of the extreme values determined to be less than the lower limit value set as the first threshold value is calculated as the extreme value acquired in the extreme value acquisition step;
And in the diagnosis process, based on the number of the extreme values, the gas sensor abnormality diagnostic method according to any one of claims 1 to 3, characterized in that diagnoses whether the gas sensor is in an abnormal state.   In the abnormality diagnosis step, among the sensor output values acquired in the sensor output value acquisition step, the number of sensor output values not acquired as the extreme value in the extreme value acquisition step reaches a second predetermined number. When the second predetermined number is reached, one or more sensor output values acquired after the second predetermined number is compared with a predetermined second threshold value to determine whether or not the gas sensor is in an abnormal state. 6. The abnormality diagnosis method for a gas sensor according to claim 1, wherein diagnosis is performed. In the abnormality diagnosis step, among the sensor output values acquired in the sensor output value acquisition step, the number of sensor output values not acquired as the extreme value in the extreme value acquisition step reaches a second predetermined number. When the second predetermined number is reached, a third predetermined number of sensor output values after the second predetermined number is acquired, a value obtained by averaging the third predetermined number of sensor output values, and a predetermined third threshold value are obtained. preparative by comparing the gas sensor abnormality diagnostic method according to any one of claims 1 to 5, characterized in that diagnoses whether the gas sensor is in an abnormal state. In the abnormality diagnosis step, among the sensor output values acquired in the sensor output value acquisition step, the number of sensor output values not acquired as the extreme value in the extreme value acquisition step reaches a second predetermined number. And comparing the value obtained by averaging the extreme values acquired in the extreme value acquisition step with a predetermined fourth threshold value to diagnose whether or not the gas sensor is in an abnormal state. The method for diagnosing abnormality of a gas sensor according to any one of claims 1 to 5 . A gas sensor control device that diagnoses whether or not a gas sensor that outputs a sensor output value corresponding to the concentration of a specific gas component in exhaust gas discharged from an internal combustion engine is in an abnormal state,
Sensor output value acquisition means for acquiring sensor output values of the gas sensor at predetermined intervals;
Interruption detecting means for detecting interruption of fuel supply to the internal combustion engine;
Of the sensor output values continuously acquired by the sensor output value acquisition means during the period in which the interruption of fuel supply is detected by the interruption detection means, at least one of a maximum value and a minimum value is set as an extreme value. Extreme value acquisition means for acquiring;
Extreme value comparison means for comparing the extreme value acquired by the extreme value acquisition means with a predetermined first threshold;
When the first predetermined number of extreme values is acquired by the extreme value acquisition means, it is diagnosed whether or not the gas sensor is in an abnormal state based on the first predetermined number of comparison results by the extreme value comparison means. And a gas sensor control device comprising:   The extreme value acquisition means starts acquisition of the extreme value after a lapse of a predetermined time set to a time longer than the predetermined interval after interruption of fuel supply is detected by the interruption detection means. The gas sensor control device according to claim 9.   The extreme value acquisition means is based on the three sensor output values acquired in succession by the sensor output value acquisition means, and the sensor output value having the second acquisition order among the three sensor output values. The gas sensor control device according to claim 9, wherein the sensor output value determined to be the extreme value is acquired as the extreme value. The extreme value comparison means calculates the number of extreme values determined that the extreme value acquired by the extreme value acquisition means is larger than an upper limit value set as the first threshold value,
The gas sensor control device according to claim 9, wherein the abnormality diagnosis unit diagnoses whether or not the gas sensor is in an abnormal state based on the number of extreme values. The extreme value comparing means calculates the number of extreme values determined to be less than a lower limit value set as the first threshold value by the extreme value acquired by the extreme value acquisition means,
The abnormality diagnosis means based on the number of the extreme values, the gas sensor control device according to any one of claims 9 to 1 1, characterized in that diagnoses whether the gas sensor is in an abnormal state.   The abnormality diagnosis unit has reached a second predetermined number of sensor output values not acquired as extreme values by the extreme value acquisition unit among the sensor output values acquired by the sensor output value acquisition unit. When the second predetermined number is reached, one or more sensor output values acquired after the second predetermined number are compared with a predetermined second threshold value to determine whether or not the gas sensor is in an abnormal state. The gas sensor control device according to claim 9, wherein the gas sensor control device is a gas sensor control device. The abnormality diagnosis unit has reached a second predetermined number of sensor output values not acquired as extreme values by the extreme value acquisition unit among the sensor output values acquired by the sensor output value acquisition unit. A third predetermined number of sensor output values after reaching the second predetermined number, a value obtained by averaging the third predetermined number of sensor output values, a predetermined third threshold value, and comparing the gas sensor control unit according to any one of claims 9 to 1 3, characterized in that diagnoses whether the gas sensor is in an abnormal state. The abnormality diagnosis unit has reached a second predetermined number of sensor output values not acquired as extreme values by the extreme value acquisition unit among the sensor output values acquired by the sensor output value acquisition unit. And comparing the value obtained by averaging the extreme values acquired by the extreme value acquisition means with a predetermined fourth threshold value to diagnose whether or not the gas sensor is in an abnormal state. the gas sensor control device according to any one of claims 9 to 1 3, characterized.

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