JP2017207444A - Sensor controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sensor controller which can suppress a reduction in accuracy of gas detection in a case where control of a gas sensor element is resumed after an abnormal voltage is detected.SOLUTION: A sensor controller determines whether a gas sensor element needs to be adjusted (S190) based on history information of electromotive force Vs after a voltage value (electromotive force Vs) between a pair of first electrodes is determined to be lower than an abnormal voltage determination value Vth (S120). When determination that the gas sensor element needs to be adjusted is made, adjusting processing (S210) is executed before electric conduction of the gas sensor element is resumed. Execution of the adjusting processing by the sensor controller can make a state of the gas sensor element closer to a state in which a specific component can be detected, and a reduction in gas detection accuracy after the electric conduction is resumed can be suppressed.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a sensor control device that controls a gas sensor for detecting a specific component in a gas to be detected.

2. Description of the Related Art Conventionally, as a gas sensor, a gas sensor having a characteristic in which a current changes according to the concentration of a specific component in a detection gas is known.
For example, an oxygen sensor that is attached to an exhaust passage of an internal combustion engine such as an automobile engine and detects an oxygen concentration in exhaust gas is known as one of gas sensors used in automobiles. This oxygen sensor detects the oxygen concentration and thus detects the air-fuel ratio of the exhaust gas by utilizing the fact that the magnitude of the current flowing through the cell changes according to the oxygen concentration in the exhaust gas. The cell is configured to have, for example, a solid electrolyte body and a pair of electrodes.

  A sensor control device that controls the driving of such a gas sensor (such as an oxygen sensor) controls the energization of the gas sensor (specifically, a cell), converts the current flowing through the gas sensor into a voltage, and outputs the voltage to an electronic control unit (ECU). It has a function to do. The ECU can calculate the oxygen concentration and the air-fuel ratio of the exhaust gas using the output from the sensor control device. The ECU can use the obtained oxygen concentration and air-fuel ratio of the exhaust gas for air-fuel ratio feedback control such as adjustment of the fuel injection amount.

  Some oxygen sensors include an oxygen concentration detection cell (electromotive force cell) having a solid electrolyte body having a pair of first electrodes and a pump cell having a solid electrolyte body having a pair of second electrodes. . Such a sensor control device that controls the driving of the oxygen sensor is configured to reduce the current flowing between the pair of second electrodes of the pump cell so that the voltage generated between the pair of first electrodes of the oxygen concentration detection cell becomes the control target voltage. Control.

  If an abnormal voltage is applied to the oxygen concentration detection cell and the pump cell due to a short-circuit abnormality in the energization path to the gas sensor, the gas sensor may break down or be damaged by the application of the abnormal voltage. For example, when an abnormal voltage is applied, oxygen in the solid electrolyte body of the pump cell may be extracted as a current and blackening may occur. This blackening is a phenomenon in which a metal oxide contained in the solid electrolyte body is reduced to generate a metal. When blackening occurs, the characteristics (particularly ion conductivity) of the solid electrolyte body deteriorate.

  On the other hand, the sensor control device determines whether or not an abnormal voltage is applied to at least one of the oxygen concentration detection cell and the pump cell, and when detecting the abnormal voltage, the oxygen concentration detection cell and the pump cell. Each terminal connected to HI is set to HI impedance to stop voltage application and current application to each cell. Thereby, it can suppress that a gas sensor fails or is damaged by application of abnormal voltage.

JP 2006-275911 A

  However, the sensor control device described above detects the application of an abnormal voltage to at least one of the oxygen concentration detection cell and the pump cell, and when the control of the gas sensor is resumed after stopping the voltage application and the current application to the gas sensor, Since normal control is immediately executed, gas detection accuracy may be reduced.

  That is, when the state of the gas sensor (specifically, cell) is not normal due to the influence of the abnormal voltage, the state of the gas sensor (specifically, cell) for a certain period from the start of the normal control of the gas sensor by the sensor control device. Is not normal, normal gas detection cannot be performed, and gas detection accuracy may be reduced.

  Therefore, an object of the present invention is to provide a sensor control device that can suppress a decrease in gas detection accuracy when the control of the gas sensor is resumed after the voltage application and the current application are stopped by detecting the abnormal voltage.

  One aspect of the present invention is a sensor control device that controls a gas sensor that detects a specific component in a gas to be detected, and includes an abnormality determination unit, a history information storage unit, an adjustment process necessity determination unit, and an adjustment process. An execution unit.

  The gas sensor has an electromotive force cell and a pump cell. The electromotive force cell has a first solid electrolyte body and a pair of first electrodes formed on the first solid electrolyte body, and generates an electromotive force between the pair of first electrodes according to a concentration difference of a specific component. It is configured. The pump cell has a second solid electrolyte body and a pair of second electrodes formed on the second solid electrolyte body, and pumps oxygen between the pair of second electrodes according to an applied voltage from the sensor control device. It is configured.

  The abnormality determination unit determines whether or not a first electrode voltage value that is a voltage value between the pair of first electrodes of the electromotive force cell is a predetermined abnormal voltage value. The history information storage unit stores history information regarding the first electrode voltage value.

  The adjustment processing necessity determination unit is configured to bring the state of the gas sensor close to a state where the specific component can be detected based on the history information after the abnormality determination unit determines that the first electrode voltage value is the abnormal voltage value. The necessity of the adjustment process is determined. The adjustment process execution unit executes the adjustment process before resuming energization of the gas sensor when the adjustment process necessity determination unit determines that the adjustment process is necessary.

  Such a sensor control device determines whether or not the gas sensor adjustment process is necessary based on the history information of the voltage value after the voltage value between the pair of first electrodes is determined to be abnormal, and the adjustment process is necessary. Is determined, the adjustment process is executed before resuming energization of the gas sensor. By executing the adjustment process, the state of the gas sensor can be brought close to a state where a specific component can be detected, and a decrease in gas detection accuracy after energization restart can be suppressed.

  Therefore, according to this sensor control device, after the voltage value between the pair of first electrodes is determined to be abnormal, it is possible to suppress the forced gas detection using the gas sensor in a state where the specific component cannot be detected. It is possible to suppress a decrease in gas detection accuracy after resuming energization.

  The sensor control device may be configured to protect the gas sensor by stopping the voltage application and the current application to the gas sensor when the voltage value between the pair of first electrodes is determined to be abnormal. . Thereby, it is possible to prevent the gas sensor from being damaged due to the abnormal voltage value between the pair of first electrodes. Then, by performing the adjustment process from the time when the voltage application and the current energization are stopped to the time when the energization is resumed, it is possible to suppress a decrease in gas detection accuracy after the energization is resumed.

  When the gas sensor detects oxygen as a specific component and has an oxygen reference part (oxygen reference chamber, oxygen reference electrode, etc.), the oxygen concentration in the oxygen reference part of the gas sensor is used as an adjustment process. By performing the process of returning the value to an appropriate value, it is possible to suppress a decrease in gas detection accuracy after the energization is resumed.

  Next, in the above-described sensor control device, the adjustment process necessity determination unit calculates an abnormality continuation time that is a time during which the first electrode voltage value falls below a predetermined voltage reference value using the history information, When the duration is smaller than a predetermined time reference value, it is determined that adjustment processing is unnecessary, and when the abnormal duration is equal to or greater than the time reference value, it is determined that adjustment processing is necessary. Also good.

  That is, since the state of the gas sensor changes according to the length of the abnormal continuation time, it is determined according to the state of the gas sensor by determining whether adjustment processing is necessary based on the comparison result between the abnormal continuation time and the time reference value. Appropriate judgment is possible.

  For example, in the case of a gas sensor that detects oxygen, since the oxygen concentration (self-reference oxygen concentration) of the oxygen reference portion in the electromotive force cell changes according to the length of the abnormal duration, the abnormal duration and time reference value By determining whether or not the adjustment process is necessary based on the comparison result, it is possible to make an appropriate determination according to the state of the electromotive force cell.

  In addition, for example, when the abnormal continuation time becomes long and the oxygen concentration of the oxygen reference part in the electromotive force cell deviates from the appropriate value, the oxygen concentration can be brought close to the appropriate value by performing the adjustment process, and the specific component It is possible to create a state suitable for detection. When the abnormal duration is short, it is unlikely that the oxygen concentration of the oxygen reference portion in the electromotive force cell deviates from an appropriate value, so that the detection of the specific component may be resumed without performing adjustment processing.

  Next, in the above-described sensor control device, the adjustment processing necessity determination unit uses the history information to calculate an integral value of the first electrode voltage value when the first electrode voltage value falls below a predetermined voltage reference value. When the integrated value is smaller than a predetermined integration reference value, it is determined that adjustment processing is unnecessary, and when the integration value is equal to or greater than the integration reference value, it is determined that adjustment processing is required. There may be.

  In other words, since the state of the gas sensor changes according to the magnitude of the integral value, it is determined whether or not adjustment processing is necessary based on the comparison result between the integral value and the integral reference value. Judgment is possible.

  For example, in the case of a gas sensor that detects oxygen, the oxygen concentration of the oxygen reference portion (self-reference oxygen concentration) in the electromotive force cell changes according to the magnitude of the integrated value, so comparison between the integrated value and the integrated reference value By determining whether adjustment processing is necessary based on the result, it is possible to make an appropriate determination according to the state of the electromotive force cell.

  Further, for example, when the integrated value becomes large and the oxygen concentration of the oxygen reference portion in the electromotive force cell deviates from the appropriate value, the oxygen concentration can be brought close to the appropriate value by performing the adjustment process. A state suitable for detection can be created. When the integrated value is small, it is unlikely that the oxygen concentration of the oxygen reference portion in the electromotive force cell deviates from the appropriate value, so that the detection of the specific component may be resumed without performing adjustment processing.

Next, in the above-described sensor control device, the adjustment process execution unit may be configured to change the content of the adjustment process based on history information.
Instead of always executing the same processing as the adjustment processing, it is possible to execute appropriate adjustment processing according to the state of the gas sensor by changing the content of the adjustment processing according to the state of the gas sensor. Therefore, by adopting a configuration in which the adjustment process execution unit changes the content of the adjustment process based on the history information, it is possible to execute an appropriate adjustment process according to the state of the gas sensor.

  For example, when energizing the gas sensor as the adjustment process, the energization time may be changed based on the history information. Thereby, an appropriate adjustment process can be executed according to the state of the gas sensor.

  In the sensor control device of the present invention, forcibly performing gas detection using a gas sensor in a state where a specific component cannot be detected after the voltage value between the pair of first electrodes is determined to be abnormal can be suppressed. And the fall of the gas detection accuracy after energization resumption can be controlled.

It is a figure which shows the schematic system configuration | structure of the internal combustion engine to which a sensor control apparatus is attached. It is a figure which shows the schematic structure of a full range air-fuel ratio sensor. It is a figure showing the schematic structure of a gas sensor element, the schematic structure of a sensor control apparatus, and the electrical connection structure of a gas sensor element and a sensor control apparatus. It is a flowchart of the control processing performed with a sensor control apparatus. It is a figure which shows an example of the waveform showing the log | history information of the voltage value (electromotive force Vs) between a pair of 1st electrodes in an electromotive force cell.

Embodiments of a sensor control device embodying the present invention will be described below with reference to the drawings.
Hereinafter, as an example of the sensor control device according to the present invention, a sensor control device capable of detecting the oxygen concentration in the gas to be detected based on the detection signal output from the gas sensor element will be described as an example. Further, as a gas sensor provided with a gas sensor element, a full-range air-fuel ratio sensor (oxygen sensor) in which the sensor current changes linearly according to the oxygen concentration will be described as an example.

[1. First Embodiment]
[1-1. overall structure]
First, a schematic system configuration of an internal combustion engine 3 to which the sensor control device 1 of the first embodiment is attached will be described with reference to FIG.

  The internal combustion engine 3 has an engine body 5 and an exhaust pipe 7 and is mounted on an automobile. The engine body 5 generates power for driving the automobile. The exhaust pipe 7 is connected to the engine body 5 and discharges exhaust gas discharged from the engine body 5 to the outside of the vehicle.

  A full-range air-fuel ratio sensor 9 is disposed on the path of the exhaust pipe 7. More specifically, the full-range air-fuel ratio sensor 9 is a gas sensor that detects a gas concentration (oxygen concentration) of a specific component (oxygen in the first embodiment) in the exhaust gas flowing through the exhaust passage of the exhaust pipe 7. The full-range air-fuel ratio sensor 9 is electrically connected to the sensor control device 1 disposed at a position distant from itself through a harness 11 and is energized by the sensor control device 1 to detect the oxygen concentration. To do.

  The sensor control device 1 is driven by receiving power from the battery 15 and outputs an oxygen concentration detection signal detected by using the full-range air-fuel ratio sensor 9 to an engine control device 17 (hereinafter also referred to as ECU 17). The ECU 17 executes air-fuel ratio feedback control of the engine body 5 based on the detection signal output from the sensor control device 1.

  In addition, the arrangement | positioning aspect of the sensor control apparatus 1 can be changed suitably, for example, the sensor control apparatus 1 is incorporated in ECU17, and the sensor control apparatus 1 incorporated in ECU17 controls the whole area air-fuel ratio sensor 9. Good.

  In the first embodiment, when the fuel is supplied to the engine body 5, the exhaust gas becomes the detection target of the entire region air-fuel ratio sensor 9 as described above. On the other hand, in a state where the fuel supply to the engine body 5 is stopped (fuel cut period), the atmosphere flows through the exhaust pipe 7, and therefore the atmosphere flowing through the exhaust pipe 7 is detected by the entire-range air-fuel ratio sensor 9. It becomes. In the following description, it is assumed that the “detected gas” to be detected by the full-range air-fuel ratio sensor 9 includes both exhaust gas and air.

[1-2. Full range air-fuel ratio sensor]
Next, the full-range air-fuel ratio sensor 9 will be briefly described with reference to FIG.
The full-range air-fuel ratio sensor 9 includes a cylindrical metal shell 23, a plate-shaped gas sensor element 25 extending in the direction of the axis O (the vertical direction in FIG. 2), and a cylindrical ceramic sleeve 27 surrounding the gas sensor element 25. A cylindrical first separator 31 surrounding the periphery of the rear end (upper side in FIG. 2) of the gas sensor element 25, and a plurality of connection terminals 33 disposed between the gas sensor element 25 and the first separator 31. It is equipped with.

  The gas sensor element 25 includes a detection unit 35 that detects the concentration of oxygen contained in the exhaust gas on the front end side, and a plurality of main surfaces that are in a positional relationship between the front and back sides of the outer surface on the rear end side have a plurality of An electrode pad 37 is formed.

  The plurality of connection terminals 33 are electrically connected to the electrode pads 37 of the gas sensor element 25, respectively, and are also electrically connected to the plurality of lead wires 39 disposed inside the entire region air-fuel ratio sensor 9 from the outside. Has been. In addition, the some lead wire 39 comprises at least one part of the harness 11 (refer FIG. 1).

  The metal shell 23 is configured to hold the gas sensor element 25 inserted through the through hole 41. That is, the ceramic holder 43, the talc rings 45 and 47, and the ceramic sleeve 27 are laminated in the through hole 41 of the metal shell 23 so as to surround the periphery of the gas sensor element 25. A protector 49 having a ventilation hole is attached to the front end side of the metal shell 23.

  On the other hand, an outer cylinder 51 is fixed to the outer periphery of the rear end side of the metal shell 23, and a grommet 53 is disposed on the rear end side of the outer cylinder 51. Two separators 55 are arranged.

[1-3. Gas sensor element]
Next, the structure of the gas sensor element 25 will be described with reference to FIG.
The gas sensor element 25 includes a first solid electrolyte body 61 and a second solid electrolyte body 63 mainly composed of zirconia, a first insulating base 65, a second insulating base 67, a third insulating base 69 and a fourth base mainly composed of alumina. And an insulating base 71.

  In the gas sensor element 25, the first insulating base 65, the second insulating base 67, the first solid electrolyte body 61, the third insulating base 69, the second solid electrolyte body 63, and the fourth insulating base 71 are shown from below in FIG. Are stacked in this order.

  A pair of first electrodes 73 and 75 mainly composed of platinum are formed on both surfaces (vertical direction in FIG. 3) of the first solid electrolyte body 61, respectively. Of these, the first electrode 73 is embedded between the first solid electrolyte body 61 and the second insulating base 67. A pair of second electrodes 77 and 79 are formed on both surfaces of the second solid electrolyte body 63, respectively.

  The first solid electrolyte body 61, the second solid electrolyte body 63, the first insulating base 65, the second insulating base 67, the third insulating base 69, and the fourth insulating base 71 are all perpendicular to the paper surface of FIG. FIG. 3 shows a cross section orthogonal to the longitudinal direction (that is, a cross section of the detection unit 35).

  A hollow detection chamber 81 into which exhaust gas can be introduced while using the first solid electrolyte body 61 and the second solid electrolyte body 63 as wall surfaces at one end side in the longitudinal direction of the third insulating substrate 69 (that is, the detection unit 35). Is formed. At both ends of the detection chamber 81 in the width direction (left-right direction in FIG. 3), a porous diffusion rate controlling portion 83 is provided for regulating the amount of inflow when the exhaust gas is introduced into the detection chamber 81 from the outside. ing.

Note that the first electrode 75 formed on the first solid electrolyte body 61 and the second electrode 77 formed on the second solid electrolyte body 63 are respectively exposed inside the detection chamber 81. .
A heating resistor 85 mainly composed of platinum is embedded between the first insulating base 65 and the second insulating base 67. The first insulating substrate 65, the second insulating substrate 67, and the heating resistor 85 function as a heater for heating and activating the first solid electrolyte body 61 and the second solid electrolyte body 63.

  The surface of the second electrode 79 formed on the second solid electrolyte body 63 is covered with a porous protective layer 87 made of ceramics (for example, alumina). That is, the second electrode 79 is protected by the protective layer 87 so as not to be deteriorated by poisoning components such as silicon contained in the exhaust gas. The fourth insulating base 71 laminated on the second solid electrolyte body 63 is provided with an opening 89 so as not to cover the second electrode 79, and the protective layer 87 is disposed inside the opening 89. ing.

  In the gas sensor element 25 configured as described above, the first solid electrolyte body 61 and the pair of first electrodes 73 and 75 provided on both surfaces thereof are in accordance with the difference in oxygen concentration between the first electrodes 73 and 75. It functions as an oxygen concentration detection cell 91 that generates electromotive force (that is, electromotive force cell 91: hereinafter also referred to as “Vs cell 91”). One first electrode 73 functions as an oxygen reference electrode that maintains an oxygen concentration that serves as a reference for detecting the oxygen concentration inside the detection chamber 81.

  Similarly, the second solid electrolyte body 63 and a pair of second electrodes 77 and 79 provided on both surfaces of the second solid electrolyte body 63 pump oxygen into the detection chamber 81 from the outside, or pump oxygen from the detection chamber 81 to the outside. It functions as a pump cell 93 (hereinafter also referred to as “Ip cell 93”).

[1-4. Sensor control device]
Next, the configuration of the sensor control device 1 will be described with reference to FIG.
The sensor control device 1 includes a microcomputer 101 and an electric circuit unit 103.

  The microcomputer 101 can be realized using, for example, a microcomputer chip on which a CPU 101a, a ROM 101b, a RAM 101c, a nonvolatile memory (not shown), and the like having a known configuration are mounted. The ROM 101b stores a control program for causing the CPU 101a to execute each process, and various information (for example, mathematical formulas, map information, information conversion tables) used by the control program.

  The electric circuit unit 103 includes a heater voltage supply circuit 105, a minute current supply circuit 109, a voltage detection circuit 111, a reference voltage comparison circuit 113, a pump current drive circuit 115, and a pump current detection circuit 117.

The heater voltage supply circuit 105 performs PWM control on the voltage Vh supplied to both ends of the heating resistor 85 to cause the heating resistor 85 to generate heat, and heats the Ip cell 93 and the Vs cell 91.
The minute current supply circuit 109 causes a minute current Icp to flow from one first electrode 73 of the Vs cell 91 to the other first electrode 75 side, moves oxygen ions to the first electrode 73 side, and serves as a reference for gas detection. An oxygen concentration atmosphere is generated in the first electrode 73. Thereby, the 1st electrode 73 functions as an oxygen reference electrode used as a standard for detecting oxygen concentration in gas to be detected.

  The voltage detection circuit 111 detects an electromotive force Vs generated between the pair of first electrodes 73 and 75 of the Vs cell 91 when detecting the oxygen concentration. The detection result is output to the reference voltage comparison circuit 113.

  The reference voltage comparison circuit 113 compares the predetermined reference voltage Va with the electromotive force Vs detected by the voltage detection circuit 111 and feeds back the comparison result to the pump current drive circuit 115.

  The pump current drive circuit 115 controls the magnitude and direction of the pump current Ip that flows between the pair of second electrodes 77 and 79 of the Ip cell 93 based on the comparison result obtained from the reference voltage comparison circuit 113. As a result, oxygen is pumped into the detection chamber 81 and oxygen is pumped out of the detection chamber 81 by the Ip cell 93.

  The pump current detection circuit 117 detects the pump current Ip flowing between the pair of second electrodes 77 and 79 of the Ip cell 93, converts the voltage, and outputs it as a detection signal to the microcomputer 101.

In the first embodiment, the reference voltage Va to be compared with the electromotive force Vs by the reference voltage comparison circuit 113 when detecting the oxygen concentration is predetermined.
That is, when detecting the oxygen concentration, the operation of the pump current drive circuit 115 is controlled so that the electromotive force Vs approaches the reference voltage Va. Thereby, the oxygen concentration in the exhaust gas can be calculated based on the pump current Ip controlled by the pump current drive circuit 115. The reference voltage Va is set to a voltage value (for example, 450 mV) such that moisture (H ₂ O) in the exhaust gas introduced into the detection chamber 81 is not substantially dissociated.

[1-5. Engine control unit (ECU)]
Next, the configuration of the engine control device 17 (ECU 17) will be described.
The ECU 17 is a device for electronically controlling driving of the engine body 5 of the automobile. The ECU 17 can be configured using a microcomputer chip on which a CPU, a ROM, a RAM, and the like having a known configuration are mounted. The ECU 17 executes various control processes (control of fuel injection timing, control of ignition timing, etc.) according to the execution of the control program.

  As information for performing such control, an output (detection signal) corresponding to the oxygen concentration in the exhaust gas is transmitted from the sensor control device 1 to the ECU 17. Further, as other information, signals from other sensors (for example, information such as a crank angle at which the piston position and the rotation speed of the engine body 5 can be detected, a coolant temperature, a combustion pressure, etc.) are also transmitted to the ECU 17. The

[1-6. Oxygen concentration detection]
Next, an oxygen concentration detection method performed by the sensor control device 1 will be described.
An operation for detecting the oxygen concentration of the exhaust gas (and hence the air-fuel ratio of the exhaust gas) using the full-range air-fuel ratio sensor 9 will be described.

  In the case of detecting the oxygen concentration, in the circuit shown in FIG. 3, a minute current Icp is first caused to flow from one first electrode 73 to the other first electrode 75 of the Vs cell 91 by the minute current supply circuit 109. By this energization, oxygen in the exhaust gas is pumped from the other first electrode 75 side to the first electrode 73 side through the first solid electrolyte body 61, and the first electrode 73 functions as an oxygen reference electrode. .

  Then, the voltage detection circuit 111 detects the electromotive force Vs generated between the first electrodes 73 and 75, and the reference voltage comparison circuit 113 compares the electromotive force Vs with the reference voltage Va. In the pump current driving circuit 115, based on the comparison result by the reference voltage comparison circuit 113, the magnitude and direction of the pump current Ip that flows between the second electrodes 77 and 79 of the Ip cell 93 so that the electromotive force Vs approaches the reference voltage Va. To control.

  When the air-fuel ratio of the exhaust gas flowing into the detection chamber 81 is richer than the stoichiometric air-fuel ratio, the oxygen concentration in the exhaust gas is thin, so that oxygen is pumped into the detection chamber 81 from the outside in the Ip cell 93. The pump current Ip flowing between the second electrodes 77 and 79 is controlled. On the other hand, when the air-fuel ratio of the exhaust gas flowing into the detection chamber 81 is leaner than the stoichiometric air-fuel ratio, a large amount of oxygen is present in the exhaust gas, so that oxygen is pumped out of the detection chamber 81 to the outside in the Ip cell 93. Thus, the pump current Ip flowing between the second electrodes 77 and 79 is controlled.

  The pump current Ip at this time is converted into a voltage by the pump current detection circuit 117 and output to the microcomputer 101 as the output (detection signal) of the full-range air-fuel ratio sensor 9. The microcomputer 101 can specify the concentration of oxygen contained in the exhaust gas and thus the air-fuel ratio of the exhaust gas based on the magnitude and direction of the pump current Ip output from the full-range air-fuel ratio sensor 9.

That is, as described above, in the first embodiment, the full-range air-fuel ratio sensor 9 and the sensor control device 1 perform the operation of detecting the oxygen concentration of the exhaust gas (the air-fuel ratio of the exhaust gas).
[1-7. Control processing]
Next, the gas concentration detection process executed in the microcomputer 101 of the sensor control apparatus 1 will be described with reference to the flowchart of FIG.

  In the microcomputer 101 of the sensor control apparatus 1, the ROM 101b described above stores a program related to the gas concentration detection process, and the CPU 101a reads the program and executes the gas concentration detection process.

  When the engine body 5 is started and the gas concentration detection process is started in the microcomputer 101, first, normal control related to gas concentration detection is executed in S110 (S represents a step). The normal control is a control process for detecting the oxygen concentration of the exhaust gas based on the above-described oxygen concentration detection method.

In next S120, it is determined whether or not an abnormality has occurred in the gas sensor element 25. If an affirmative determination is made, the process proceeds to S130, and if a negative determination is made, the process proceeds to S110 again.
That is, in the gas concentration detection process, when the gas sensor element 25 is normal, the processes of S110 and S120 are repeatedly executed to continue the detection of the oxygen concentration, and when an abnormality occurs in the gas sensor element 25, the process proceeds to S130. Migrate to

  In S120, a voltage value (in other words, electromotive force Vs) between the pair of first electrodes 73 and 75 in the electromotive force cell 91 is detected, and the electromotive force Vs and a predetermined abnormal voltage determination value Vth (here) Then, -50 mV) is compared. In S120, an affirmative determination is made when the electromotive force Vs is smaller than the abnormal voltage determination value Vth, and a negative determination is made when the electromotive force Vs is greater than or equal to the abnormal voltage determination value Vth.

  When an affirmative determination is made in S120 and the process proceeds to S130, in S130, processing for storing a voltage value (in other words, electromotive force Vs) between the pair of first electrodes 73 and 75 is started (hereinafter also referred to as voltage storage processing). To do. In this voltage storage process, the electromotive force Vs is repeatedly detected, and the detected electromotive force Vs is stored in the RAM 101c in time series, whereby the history information of the electromotive force Vs after the occurrence of abnormality is stored in the RAM 101c.

  In next S140, all terminals connected to the gas sensor element 25 among the terminals of the sensor control device 1 are set to Hi impedance. Thereby, it can suppress that the voltage application and electric current supply from the sensor control apparatus 1 with respect to the gas sensor element 25 are continued, and the gas sensor element 25 can be protected.

  In the next S150, the ECU 17 is notified that an abnormality has occurred in the gas sensor element 25, and a process of stopping the engine body 5 is executed. Specifically, an abnormality notification signal and an engine stop command are output from the sensor control device 1 to the ECU 17, and the ECU 17 stops the control process of the engine body 5.

  In next S160, it is determined whether or not the electromotive force Vs is larger than the abnormal voltage determination value Vth. If an affirmative determination is made, the process proceeds to S170, and if a negative determination is made, the same step is repeatedly executed to stand by.

  When an affirmative determination is made in S160 and the process proceeds to S170, the voltage storage process is stopped and the process of storing the voltage value (in other words, the electromotive force Vs) between the pair of first electrodes 73 and 75 is stopped in S170. .

  In next S180, the calculation of abnormality information using the history information of the electromotive force Vs is executed. Specifically, after it is determined in S120 that an abnormality has occurred, the time during which the electromotive force Vs has been smaller than the abnormal voltage determination value Vth (hereinafter also referred to as an abnormal continuation time Te) is calculated.

FIG. 5 shows an example of a waveform representing history information of a voltage value (in other words, electromotive force Vs) between the pair of first electrodes 73 and 75 in the electromotive force cell 91.
In FIG. 5, the gas sensor element 25 is in an abnormal state at time t1 (the voltage value (electromotive force Vs) between the pair of first electrodes 73 and 75 is lower than the abnormal voltage determination value Vth), and thereafter at time t2. In this example, the electric power Vs is higher than the abnormal voltage determination value Vth, and the electromotive force Vs gradually approaches 0V.

In the case shown in FIG. 5, the time from time t1 to time t2 corresponds to the abnormal continuation time Te.
In S180, when calculating the abnormality information using the history information of the electromotive force Vs, the abnormal integral value Se may be calculated instead of the abnormality duration time Te. The abnormal integral value Se is an integral value (the area of a region indicated by a hatched pattern in FIG. 5) when the waveform of the electromotive force Vs falls below the abnormal voltage determination value Vth.

  In the next S190, it is determined whether or not the adjustment processing of the gas sensor element 25 is necessary based on the abnormality information calculated in S180. If an affirmative determination is made, the process proceeds to S200, and if a negative determination is made, S220. Migrate to

  The determination process in S190 is executed based on, for example, a determination result as to whether or not the abnormality information satisfies a predetermined adjustment necessity determination condition. Specifically, the abnormality duration time Te as the abnormality information is compared with a predetermined time reference value Tth (for example, 1.0 msec), and affirmative when the abnormality duration time Te is greater than the time reference value Tth. A negative determination is made when the abnormal duration Te is less than or equal to the time reference value Tth.

  In S190, the abnormal integration value Se as the abnormality information is compared with a predetermined integration reference value Sth, and when the abnormal integration value Se is larger than the integration reference value Sth, an affirmative determination is made, and the abnormal integration value Se. The negative determination may be made when is less than or equal to the integration reference value Sth.

  When an affirmative determination is made in S190 and the process proceeds to S200, in S200, a process of determining the content of the adjustment process based on the abnormality information is executed. Specifically, the adjustment processing execution time is set longer as the abnormality duration time Te as the abnormality information becomes longer, and the adjustment processing execution time is set shorter as the abnormality duration time Te becomes shorter.

  When calculating the abnormal integral value Se as abnormal information in S180, the adjustment processing execution time is set longer as the abnormal integration value Se increases, and the adjustment processing execution time is set shorter as the abnormal integration value Se decreases. May be.

In the next S210, adjustment processing is executed based on the content determined in S200.
In this embodiment, as the adjustment process of the gas sensor element 25, a process of causing a minute current Icp to flow from one first electrode 73 of the Vs cell 91 to the other first electrode 75 side is executed. By energizing the minute current Icp in this way, oxygen ions can be moved to the first electrode 73 side, and a preparation process for causing the first electrode 73 to function as an oxygen reference electrode can be realized. In addition, since the oxygen ion of the first electrode 73 is lost more as the application time of the abnormal voltage becomes longer, for example, by setting the execution time of the adjustment process longer as the abnormality duration time Te becomes longer as described above, More oxygen ions can be moved to the 1 electrode 73 side.

  If a negative determination is made in S190 or if the process of S210 is completed and the process proceeds to S220, the ECU 17 is notified that gas detection using the gas sensor element 25 is possible in S220. Specifically, a gas detectable signal is output from the sensor control device 1 to the ECU 17.

  The ECU 17 that has received the gas detectable signal determines whether or not other engine start permission conditions (reception of a start command from the user, completion of normal state confirmation of various sensors, etc.) are satisfied, and all engine start permission is determined. When the condition is satisfied, the engine body 5 is started and various control processes are started.

  In next S230, it is determined whether or not the engine main body 5 has been started. If the determination is affirmative, the process proceeds to S110 again. If the determination is negative, the same step is repeatedly executed to stand by. That is, it waits until the engine main body 5 is started, and when the engine main body 5 is started, the normal control relating to the gas concentration detection is executed by executing S110 again.

  As described above, in the gas concentration detection process, when the gas sensor element 25 is normal (negative determination in S120), the detection of oxygen concentration (S110) is continued and an abnormality occurs in the gas sensor element 25 ( For affirmative determination in S120, the control of the gas sensor element 25 is temporarily stopped (S140).

  In this gas concentration detection process, after an abnormality occurs in the gas sensor element 25 and the control of the gas sensor element 25 is temporarily stopped, it is determined whether or not an adjustment process is necessary according to the state of the gas sensor element 25 (S190). If so, the adjustment process (S210) is executed. If it is determined that the adjustment process is unnecessary (No in S190) or if the adjustment process (S210) is executed, a gas detectable signal is transmitted to the ECU 17 (S220). Thereafter, when the engine body 5 is started again by the ECU 17 (Yes in S230), gas detection using the gas sensor element 25 (S110) is resumed.

This gas concentration detection process is continuously executed until the sensor control device 1 is stopped.
[1-8. effect]
As described above, in the sensor control device 1 of the present embodiment, the microcomputer 101 executes S120 of the gas concentration detection process, whereby the voltage value between the pair of first electrodes 73 and 75 in the electromotive force cell 91 ( It is determined whether or not the electromotive force Vs) is lower than the abnormal voltage determination value Vth, and whether or not an abnormality has occurred in the gas sensor element 25 is determined based on the determination result.

  The sensor control apparatus 1 causes the RAM 101c to store history information regarding the voltage value (electromotive force Vs) between the pair of first electrodes 73 and 75 by the microcomputer 101 executing the voltage storage process activated in S130.

  The sensor control apparatus 1 determines whether or not adjustment processing is required to bring the state of the gas sensor element close to a state where gas detection is possible based on the history information regarding the electromotive force Vs by the microcomputer 101 executing S190. . In S190, the abnormality information calculated in S180 is used as the history information regarding the electromotive force Vs.

If it is determined in S190 that the adjustment process is necessary, the sensor control device 1 executes the adjustment process before resuming energization of the gas sensor element 25 by executing S210.
Such a sensor control device 1 is based on the history information of the electromotive force Vs after it is determined that the voltage value (electromotive force Vs) between the pair of first electrodes 73 and 75 is lower than the abnormal voltage determination value Vth. Then, the necessity of the adjustment process of the gas sensor element 25 is determined. When it is determined that the adjustment process is necessary, the sensor control device 1 executes the adjustment process before resuming energization of the gas sensor element 25. By executing the adjustment process, the sensor control device 1 can bring the state of the gas sensor element 25 close to a state where gas can be detected, and can suppress a decrease in gas detection accuracy after energization is resumed.

  Therefore, according to this sensor control device 1, after it is determined that the voltage value (electromotive force Vs) between the pair of first electrodes 73 and 75 is abnormal, the gas sensor element 25 in a state where gas detection is impossible is used. Therefore, it is possible to suppress the forced gas detection, and it is possible to suppress a decrease in gas detection accuracy after the energization is resumed.

  The sensor control device 1 sets all terminals connected to the gas sensor element 25 to Hi impedance when it is determined that the voltage value (electromotive force Vs) between the pair of first electrodes 73 and 75 is abnormal. (S140). Thereby, it can suppress that the voltage application and electric current supply from the sensor control apparatus 1 with respect to the gas sensor element 25 are continued, and the gas sensor element 25 can be protected. And the sensor control apparatus 1 can suppress the fall of the gas detection accuracy after energization resumption by performing adjustment processing (S210) from the time of stopping voltage application and electric current energization to energization resumption.

  The gas sensor element 25 detects oxygen as a specific component, and includes a first electrode 73 (oxygen reference electrode) as an oxygen reference portion. For this reason, the sensor control apparatus 1 performs the process which returns the oxygen concentration in the 1st electrode 73 of the gas sensor element 25 to an appropriate value as an adjustment process, and brings the state of the gas sensor element 25 close to the state which can detect gas. Therefore, it is possible to suppress a decrease in gas detection accuracy after resuming energization.

  Next, the sensor control apparatus 1 calculates the abnormal duration Te using the history information of the electromotive force Vs by the microcomputer 101 executing S180. Then, the sensor control device 1 determines that adjustment processing is necessary when the abnormal continuation time Te is greater than the time reference value Tth (positive determination in S190), and when the abnormal continuation time Te is equal to or less than the time reference value Tth. It is determined that the adjustment process is unnecessary (No determination in S190).

  That is, since the state of the gas sensor element 25 changes according to the length of the abnormal duration Te, the gas sensor is determined by determining whether adjustment processing is necessary based on the comparison result between the abnormal duration Te and the time reference value Tth. Appropriate determination according to the state of the element 25 is possible.

  For example, in the case of the gas sensor element 25 that detects oxygen, since the oxygen concentration (self-reference oxygen concentration) in the first electrode 73 of the electromotive force cell 91 changes according to the length of the abnormal duration Te, the abnormal duration time. By determining whether or not the adjustment process is necessary based on the comparison result between Te and the time reference value Tth, it is possible to make an appropriate determination according to the state of the electromotive force cell 91.

  Further, for example, when the abnormal continuation time Te becomes long and the oxygen concentration in the electromotive force cell 91 deviates from the appropriate value, the oxygen concentration can be brought close to the appropriate value by performing the adjustment process. The state can be brought close to a state suitable for gas detection. Note that when the abnormal duration Te is short, the oxygen concentration in the electromotive force cell 91 is unlikely to deviate from an appropriate value, and therefore gas detection using the gas sensor element 25 may be resumed without performing adjustment processing. .

  Next, when the microcomputer 101 executes S180, the sensor control device 1 can adopt a configuration that calculates the abnormal integral value Se using the history information of the electromotive force Vs. The sensor control device 1 having such a configuration determines that adjustment processing is necessary when the abnormal integral value Se is larger than the integral reference value Sth (positive determination in S190), and the abnormal integral value Se is equal to or less than the integral reference value Sth. In some cases, it is possible to adopt a configuration in which it is determined that the adjustment process is unnecessary (No determination in S190).

  That is, since the state of the gas sensor element 25 changes according to the magnitude of the abnormal integral value Se, the gas sensor is determined by determining whether adjustment processing is necessary based on the comparison result between the abnormal integral value Se and the integral reference value Sth. Appropriate determination according to the state of the element 25 is possible.

  For example, in the case of the gas sensor element 25 that detects oxygen, the oxygen concentration (self-reference oxygen concentration) in the first electrode 73 of the electromotive force cell 91 changes according to the magnitude of the abnormal integral value Se. By determining whether or not adjustment processing is necessary based on the comparison result between Se and the integration reference value Sth, it is possible to make an appropriate determination according to the state of the electromotive force cell 91.

  For example, when the abnormal integral value Se increases and the oxygen concentration in the electromotive force cell 91 deviates from the appropriate value, the oxygen concentration can be brought close to the appropriate value by performing the adjustment process. The state can be brought close to a state suitable for gas detection. Note that when the abnormal integral value Se is small, the oxygen concentration in the electromotive force cell 91 is unlikely to deviate from the appropriate value, and therefore gas detection using the gas sensor element 25 may be resumed without performing adjustment processing. .

  Next, the sensor control device 1 executes history information of the voltage value (electromotive force Vs) between the pair of first electrodes 73 and 75 (specifically, the calculation is performed in S180) by the microcomputer 101 executing S200. The content of the adjustment process is determined based on the abnormal information). Specifically, the adjustment processing execution time is set longer as the abnormality duration time Te as the abnormality information becomes longer, and the adjustment processing execution time is set shorter as the abnormality duration time Te becomes shorter.

  As described above, the adjustment process is not always performed with the same contents, but the adjustment process is performed according to the state of the gas sensor element 25, so that the appropriate adjustment process according to the state of the gas sensor element 25 is performed. Can be executed.

  When calculating the abnormal integral value Se as abnormal information in S180, the adjustment processing execution time is set longer as the abnormal integration value Se increases, and the adjustment processing execution time is set shorter as the abnormal integration value Se decreases. May be.

[1-9. Correspondence of wording]
Here, the correspondence of words in the present embodiment will be described.
The sensor control device 1 corresponds to an example of a sensor control device, the full-range air-fuel ratio sensor 9 corresponds to an example of a gas sensor, and the oxygen concentration detection cell 91 (electromotive force cell 91, Vs cell 91) corresponds to an example of an electromotive force cell. The pair of first electrodes 73 and 75 corresponds to an example of a pair of first electrodes, the oxygen pump cell 93 (Ip cell 93) corresponds to an example of a pump cell, and the pair of second electrodes 77 and 79 includes a pair of This corresponds to an example of the second electrode.

  The microcomputer 101 that executes S120 corresponds to an example of an abnormality determination unit, and the voltage value (electromotive force Vs) between the pair of first electrodes 73 and 75 corresponds to an example of a first electrode voltage value. The “voltage value smaller than the value Vth” corresponds to an example of an abnormal voltage value.

The microcomputer 101 that executes the voltage storage process corresponds to an example of a history information storage unit, and the history information of the electromotive force Vs corresponds to an example of history information related to the first electrode voltage value.
The microcomputer 101 that executes S190 corresponds to an example of an adjustment processing necessity determination unit, the abnormal duration Te corresponds to an example of an abnormal duration, the time reference value Tth corresponds to an example of a time reference value, and abnormal integration The value Se corresponds to an example of an integral value of the first electrode voltage value, and the integration reference value Sth corresponds to an example of an integration reference value.

The microcomputer 101 that executes S200 and S210 corresponds to an example of an adjustment processing execution unit.
[2. Other Embodiments]
As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, In the range which does not deviate from the summary of this invention, it is possible to implement in various aspects.

  For example, in the above embodiment, the configuration for executing the process (S200) for determining the execution time of the adjustment process based on the history information of the electromotive force Vs has been described, but this process is not necessarily a necessary process. That is, the process of S200 may be omitted by setting the execution time of the adjustment process to a predetermined fixed value. Thereby, reduction of the processing load of the sensor control apparatus 1 at the time of performing a gas concentration detection process can be aimed at.

  In addition, the numerical values in the abnormal voltage determination value Vth, the time reference value Tth, etc. are not limited to the above numerical values, and are appropriate values according to various conditions such as the specifications and applications of the sensor control device and the gas sensor element. May be set respectively.

  Next, in the above embodiment, as the gas sensor for detecting a specific component in the gas to be detected, the all-region air-fuel ratio sensor for detecting the oxygen concentration in the gas to be detected has been described, but the control target of the sensor control device of the present invention The gas sensor is not limited to the full-range air-fuel ratio sensor. The gas sensor to be controlled by the sensor control device of the present invention may be a gas sensor having an electromotive force cell and a pump cell, and examples thereof include a NOx sensor.

  DESCRIPTION OF SYMBOLS 1 ... Sensor control apparatus, 3 ... Internal combustion engine, 5 ... Engine main body, 7 ... Exhaust pipe, 9 ... Entire area air-fuel ratio sensor, 17 ... Engine control apparatus (ECU), 25 ... Gas sensor element, 61 ... 1st solid electrolyte body , 63 ... the second solid electrolyte body, 65 ... the first insulating base, 67 ... the second insulating base, 69 ... the third insulating base, 71 ... the fourth insulating base, 73 ... the first electrode, 75 ... the first electrode, 77 ... Second electrode, 79 ... Second electrode, 91 ... Oxygen concentration detection cell (electromotive force cell), 93 ... Oxygen pump cell, 101 ... Microcomputer, 101a ... CPU, 101b ... ROM, 101c ... RAM, 103 ... Electric circuit section .

Claims (4)

A sensor control device for controlling a gas sensor for detecting a specific component in a gas to be detected,
The gas sensor includes an electromotive force cell and a pump cell. The electromotive force cell includes a first solid electrolyte body and a pair of first electrodes formed on the first solid electrolyte body. The pump cell is configured to generate an electromotive force between the pair of first electrodes according to a concentration difference, and the pump cell includes a second solid electrolyte body and a pair of second electrodes formed on the second solid electrolyte body. And configured to pump oxygen between the pair of second electrodes in accordance with an applied voltage from the sensor control device,
An abnormality determining unit that determines whether or not a first electrode voltage value that is a voltage value between the pair of first electrodes of the electromotive force cell is a predetermined abnormal voltage value;
A history information storage unit for storing history information related to the first electrode voltage value;
Adjustment processing for bringing the state of the gas sensor close to a state where the specific component can be detected based on the history information after the abnormality determination unit determines that the first electrode voltage value is the abnormal voltage value. An adjustment processing necessity determination unit for determining whether or not
An adjustment process execution unit that executes the adjustment process before resuming energization of the gas sensor when the adjustment process is determined to be necessary by the adjustment process necessity determination unit;
A sensor control device comprising: The adjustment processing necessity determination unit calculates an abnormal duration that is a time during which the first electrode voltage value falls below a predetermined voltage reference value using the history information, and the abnormal duration is predetermined. If it is smaller than the time reference value, it is determined that the adjustment process is unnecessary, and if the abnormal duration is equal to or greater than the time reference value, it is determined that the adjustment process is necessary.
The sensor control device according to claim 1. The adjustment process necessity determination unit calculates an integral value of the first electrode voltage value when the first electrode voltage value falls below a predetermined voltage reference value using the history information, and the integral value is When the integral reference value is smaller than a predetermined integral reference value, it is determined that the adjustment process is unnecessary, and when the integral value is equal to or greater than the integral reference value, it is determined that the adjustment process is necessary.
The sensor control device according to claim 1. The adjustment process execution unit changes the content of the adjustment process based on the history information.
The sensor control apparatus as described in any one of Claims 1-3.

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