WO2011045908A1 - センサ制御装置およびセンサ制御方法 - Google Patents
センサ制御装置およびセンサ制御方法 Download PDFInfo
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- WO2011045908A1 WO2011045908A1 PCT/JP2010/005993 JP2010005993W WO2011045908A1 WO 2011045908 A1 WO2011045908 A1 WO 2011045908A1 JP 2010005993 W JP2010005993 W JP 2010005993W WO 2011045908 A1 WO2011045908 A1 WO 2011045908A1
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- amplification
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- 238000000034 method Methods 0.000 title claims description 41
- 230000005856 abnormality Effects 0.000 claims abstract description 89
- 230000003321 amplification Effects 0.000 claims abstract description 78
- 238000003199 nucleic acid amplification method Methods 0.000 claims abstract description 78
- 238000003745 diagnosis Methods 0.000 claims abstract description 73
- 238000001514 detection method Methods 0.000 claims description 66
- 238000006243 chemical reaction Methods 0.000 claims description 57
- 238000005259 measurement Methods 0.000 claims description 52
- 238000004364 calculation method Methods 0.000 claims description 11
- 239000000126 substance Substances 0.000 claims description 11
- 230000002159 abnormal effect Effects 0.000 abstract description 15
- 238000009825 accumulation Methods 0.000 abstract description 14
- 239000007789 gas Substances 0.000 description 48
- 239000007784 solid electrolyte Substances 0.000 description 40
- 239000001301 oxygen Substances 0.000 description 37
- 229910052760 oxygen Inorganic materials 0.000 description 37
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 33
- 238000012986 modification Methods 0.000 description 9
- 230000004048 modification Effects 0.000 description 9
- 239000012212 insulator Substances 0.000 description 8
- 238000009792 diffusion process Methods 0.000 description 7
- 238000010586 diagram Methods 0.000 description 6
- 239000000919 ceramic Substances 0.000 description 5
- 238000002485 combustion reaction Methods 0.000 description 4
- 238000004590 computer program Methods 0.000 description 4
- -1 oxygen ion Chemical class 0.000 description 4
- 238000012545 processing Methods 0.000 description 4
- MWUXSHHQAYIFBG-UHFFFAOYSA-N Nitric oxide Chemical compound O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 3
- 229910001260 Pt alloy Inorganic materials 0.000 description 3
- 239000011195 cermet Substances 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000010410 layer Substances 0.000 description 3
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 2
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 2
- 239000000470 constituent Substances 0.000 description 2
- 238000005192 partition Methods 0.000 description 2
- 239000011241 protective layer Substances 0.000 description 2
- 238000005086 pumping Methods 0.000 description 2
- 230000032683 aging Effects 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 239000002341 toxic gas Substances 0.000 description 1
Images
Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/0004—Gaseous mixtures, e.g. polluted air
- G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
- G01N33/0027—General constructional details of gas analysers, e.g. portable test equipment concerning the detector
- G01N33/0036—General constructional details of gas analysers, e.g. portable test equipment concerning the detector specially adapted to detect a particular component
- G01N33/0037—NOx
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/416—Systems
- G01N27/417—Systems using cells, i.e. more than one cell and probes with solid electrolytes
- G01N27/419—Measuring voltages or currents with a combination of oxygen pumping cells and oxygen concentration cells
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/0004—Gaseous mixtures, e.g. polluted air
- G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
- G01N33/007—Arrangements to check the analyser
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/28—Testing of electronic circuits, e.g. by signal tracer
- G01R31/282—Testing of electronic circuits specially adapted for particular applications not provided for elsewhere
- G01R31/2829—Testing of circuits in sensor or actuator systems
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
- Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
Definitions
- the present invention relates to a sensor control device and a sensor control method for controlling a sensor.
- sensors that detect the concentration of nitrogen oxide (hereinafter simply referred to as “NOx”) as a specific gas in the exhaust gas of an internal combustion engine are known.
- NOx nitrogen oxide
- each input signal from the two amplifier circuits to the control unit for example, a microcomputer
- the control unit for example, a microcomputer
- GND short circuit ground fault
- a drive voltage power supply voltage
- an intermediate region between GND and Vcc is simply referred to as “intermediate region”.
- the purpose is to do.
- the present invention can be realized as the following forms or application examples in order to solve at least a part of the above-described problems.
- a sensor unit that outputs an electric signal value corresponding to a physical / chemical characteristic of a measurement target, an electric signal value output from the sensor unit, and a first detection range of the characteristic
- a first amplifying unit that amplifies the electric signal value at an amplification factor of 1, and an electric signal value output from the sensor unit; and a second that at least partially overlaps the first detection range for the characteristic
- a value indicating the characteristic is obtained based on a second amplifying unit that amplifies the electric signal value at a second amplification factor for the detection range, an output from the first amplifying unit, and an output from the second amplifying unit.
- the sensor control device including a control unit that outputs the value as a sensor detection value, a first characteristic conversion value based on an output from the first amplification unit and a second based on an output from the second amplification unit Get characteristic conversion value of A conversion value acquisition unit, and a predetermined range included in an overlap portion of the first detection range and the second detection range is set as an abnormality diagnosis range, and at least one of the first and second characteristic conversion values is A conversion value determination unit that determines whether or not the abnormality diagnosis range is included, and when the conversion value determination unit determines that the abnormality diagnosis range includes the first characteristic conversion value and the second characteristic conversion value Comparing with the characteristic conversion value, an abnormality diagnosing unit for determining whether an abnormality has occurred in at least one of the signal system including the first amplifying unit and the signal system including the second amplifying unit is provided.
- the sensor control apparatus characterized by the above-mentioned.
- the abnormality diagnosis unit includes a difference calculation unit that calculates a difference between the first characteristic conversion value and a second characteristic conversion value;
- a sensor control device comprising: an abnormality determination unit that determines the abnormality based on the calculated difference.
- the difference calculation unit includes an integrated value calculation unit that calculates an integrated value of the difference in a predetermined period
- the abnormality determination unit includes the integration
- a sensor control device configured to determine that the abnormality is present when a value becomes equal to or greater than a predetermined value.
- the converted value acquisition unit may calculate the first characteristic converted value and the first value every predetermined time set to a time shorter than the predetermined period.
- the difference calculation unit obtains the difference based on the first and second characteristic conversion values acquired by the conversion value acquisition unit every predetermined time.
- the integrated value is configured to be calculated over a plurality of times going back to the past from the present, and the abnormality determination unit, when the integrated value calculated by the difference calculation unit is equal to or greater than a predetermined value for each predetermined time, A sensor control device that is configured to determine that the abnormality is present.
- the second detection range is narrower than the first detection range
- the second amplification factor is A sensor control device that is higher than the first amplification factor
- the sensor control device includes a plurality of amplifier circuits that receive electrical signal values output from the sensor unit, and one of the amplifier circuits is A first amplifying unit for amplifying the electric signal value with a first amplification factor is configured, and another of the amplifying circuits forms a second amplifying unit for amplifying the electric signal value with the second amplification factor.
- Sensor control device includes a plurality of amplifier circuits that receive electrical signal values output from the sensor unit, and one of the amplifier circuits is A first amplifying unit for amplifying the electric signal value with a first amplification factor is configured, and another of the amplifying circuits forms a second amplifying unit for amplifying the electric signal value with the second amplification factor.
- the sensor control device according to any one of Application Examples 1 to 5, further including an amplification circuit that receives an electric signal value output from the sensor unit, wherein the amplification circuit has a gain of its own.
- the first amplification factor and the second amplification factor can be selected by switching, and the first amplification unit is configured when the amplification circuit is set to the first amplification factor.
- the unit is a sensor control device configured when the amplification circuit is set to the second amplification factor.
- Application Example 8 The sensor control device according to any one of Application Examples 1 to 7, wherein the characteristic is a concentration of a specific gas included in the measurement target.
- Application Example 9 A sensor unit that outputs an electric signal value corresponding to a physical characteristic or chemical characteristic of a measurement target, an electric signal value output from the sensor unit, and a first detection range of the characteristic
- Get characteristic conversion value of Conversion value acquisition step and a predetermined range included in an overlapping portion of the first detection range and the second detection range is an abnormality diagnosis range, and at least one of the first and second characteristic conversion values Is determined to be included in the abnormality diagnosis range, and when it is determined by the determination step to be included in the abnormality diagnosis range, the first characteristic conversion value and the second characteristic conversion value And an abnormality diagnosis step of determining whether or not an abnormality has occurred in at least one of the signal system including the first amplification unit and the signal system including the second amplification unit. Sensor control method.
- the present invention can be realized in the form of a computer program that realizes each step of the sensor control method according to Application Example 9 as each step of the computer program. Further, the present invention can be realized in the form of a recording medium that records the computer program, a data signal that includes the computer program and is embodied in a carrier wave, and the like.
- a value indicating the physical characteristic or chemical characteristic of the measurement target is obtained based on the output from the first amplification unit and the output from the second amplification unit.
- a “physical property or chemical property” is a physical quantity or a chemical quantity.
- the first characteristic conversion value based on the output from the first amplifying unit is compared with the second characteristic conversion value based on the output from the second amplifying unit, so that at least one of the two characteristic conversion values is obtained. Therefore, it is possible to determine whether an abnormality has occurred in at least one of the signal system including the first amplifying unit and the signal system including the second amplifying unit. it can. Therefore, a failure in which the input signal from the amplification unit becomes an abnormal value in the intermediate range can be diagnosed with high accuracy.
- the accuracy of failure diagnosis can be further improved by using the difference between the first characteristic conversion value and the second characteristic conversion value.
- the accuracy of failure diagnosis can be further improved by using the integrated value of the difference in a predetermined period.
- the input from the amplification unit since the integrated value of the difference for a plurality of times going back from the present to the past is updated every predetermined time, the input from the amplification unit has a periodicity. It is also possible to reliably determine abnormality.
- the input signal from the first amplifying unit has a relatively wide range with a low gain, and the input signal from the second amplifying unit has a relatively high gain.
- the low range For this reason, when the control unit wants to detect characteristics over a wide range, it can detect the approximate resolution by adopting the input signal from the first amplifying unit, while detecting the characteristics pinpoint. In order to achieve this, it is possible to detect with high resolution by adopting the input signal from the second amplifying unit.
- the signal system including the first amplifier unit and the second amplifier unit are included. Whether or not an abnormality has occurred in at least one of the signal systems can be diagnosed with high accuracy.
- the specific configuration of the first amplifying unit and the second amplifying unit is different from that of the above application example 6, an amplifying circuit that configures the first amplifying unit or the second amplifying unit by switching its amplification factor is provided.
- an amplifying circuit that configures the first amplifying unit or the second amplifying unit by switching its amplification factor is provided.
- the sensor control method according to Application Example 9 can obtain the same operational effects as the sensor control device according to Application Example 1.
- FIG. 5 is a flowchart showing an abnormality diagnosis process executed by a microcomputer 60. It is a graph which shows the 1st and 2nd NOx density
- FIG. 1 is a schematic configuration diagram showing a sensor control device 5 and its periphery as a first embodiment of the present invention.
- 1 is a gas sensor
- the sensor control device 5 is connected to the gas sensor 1.
- the gas sensor 1 includes a sensor element 10.
- the sensor element 10 is illustrated with a cross-sectional view showing the internal structure at the tip side portion, and the left side in the figure is the tip side of the sensor element 10.
- the gas sensor 1 is disposed in an exhaust path (not shown) through which exhaust gas from the internal combustion engine is exhausted.
- the gas sensor 1 is used to detect exhaust gas from an internal combustion engine as a measurement target and detect NOx concentration as a chemical amount of the measurement target.
- the gas sensor 1 includes a sensor element 10 having an elongated and long plate-like shape, and a housing (not shown) for attaching the gas sensor 1 to a discharge path.
- the sensor element 10 is held in the housing.
- a signal line for extracting a signal output from the sensor element 10 is drawn out from the gas sensor 1 and is electrically connected to a sensor control device 5 attached at a position away from the gas sensor 1.
- the sensor element 10 has a structure in which three plate-shaped solid electrolyte bodies 111, 121, 131 are formed in layers with insulators 140, 145 made of alumina or the like interposed therebetween.
- insulators 140, 145 made of alumina or the like interposed therebetween.
- sheet-like insulating layers 162 and 163 mainly composed of alumina are laminated, and a heater element 161 in which a heater pattern 164 mainly composed of Pt is embedded therebetween. Is provided.
- the solid electrolyte bodies 111, 121, 131 are made of zirconia, which is a solid electrolyte, and have oxygen ion conductivity.
- Porous electrodes 112 and 113 are provided on both surfaces of the solid electrolyte body 111 in the stacking direction of the sensor element 10 so as to sandwich the solid electrolyte body 111, respectively.
- the electrodes 112 and 113 are made of Pt, a Pt alloy, or cermet containing Pt and ceramics.
- a porous protective layer 114 made of ceramics is provided on the surfaces of the electrodes 112 and 113. The protective layer 114 protects the electrodes 112 and 113 from being deteriorated by being exposed to a toxic gas (reducing atmosphere) contained in the exhaust gas.
- solid electrolyte body 111 In the solid electrolyte body 111, an electric current is passed between the electrodes 112 and 113, whereby the atmosphere in contact with the electrode 112 (atmosphere outside the sensor element 10) and the atmosphere in contact with the electrode 113 (atmosphere in the first measurement chamber 150 to be described later). ) Can be pumped out and pumped in (so-called oxygen pumping).
- solid electrolyte body 111 and electrodes 112 and 113 are referred to as Ip1 cell 110.
- the solid electrolyte body 121 is disposed so as to face the solid electrolyte body 111 with the insulator 140 interposed therebetween. Similar to the solid electrolyte body 111, porous electrodes 122 and 123 are provided on both surfaces of the solid electrolyte body 121 in the stacking direction of the sensor element 10 so as to sandwich the solid electrolyte body 121.
- the electrodes 122 and 123 are provided on the inner side and the outer side of the first measurement chamber 150 on the solid electrolyte body 121 side of the first measurement chamber 150.
- the electrodes 122 and 123 are made of Pt, a Pt alloy, cermet containing Pt and ceramics, or the like.
- the electrode 122 is formed on the surface facing the solid electrolyte body 111.
- a first measurement chamber 150 as a small space is formed between the solid electrolyte body 111 and the solid electrolyte body 121.
- the first measurement chamber 150 is a small space in which exhaust gas flowing through the exhaust path is first introduced into the sensor element 10.
- the above-mentioned electrode 113 on the solid electrolyte body 111 side and the electrode 122 on the solid electrolyte body 121 side are arranged.
- a porous property that limits the flow rate of exhaust gas per unit time into the first measurement chamber 150.
- the first diffusion resistance portion 151 is provided on the tip side of the sensor element 10 of the first measurement chamber 150.
- exhaust gas per unit time flows as a partition between the opening 141 connected to the second measurement chamber 160 described later and the first measurement chamber 150.
- a second diffusion resistor 152 for limiting the amount is provided.
- Both electrodes 122 and 123 are mainly oxygen between atmospheres separated by solid electrolyte body 121 (atmosphere in first measurement chamber 150 in contact with electrode 122 and atmosphere in reference oxygen chamber 170 to be described later in contact with electrode 123).
- An electromotive force is generated according to the partial pressure difference.
- solid electrolyte body 121 and both electrodes 122 and 123 are referred to as oxygen concentration detection cell (hereinafter simply referred to as “Vs cell”) 120. That is, the Vs cell 120 includes electrodes 122 and 123 provided on the inner side and the outer side of the first measurement chamber 150.
- the solid electrolyte body 131 is disposed so as to face the solid electrolyte body 121 with the insulator 145 interposed therebetween.
- Porous electrodes 132 and 133 are provided separately on the surface of the solid electrolyte body 131 facing the solid electrolyte body 121 side.
- the porous electrodes 132 and 133 are made of Pt, a Pt alloy, cermet containing Pt and ceramics, or the like.
- the insulator 145 is not disposed between the solid electrolyte body 131 and the solid electrolyte body 121, and a reference oxygen chamber 170 is formed as an independent small space.
- the electrode 132 and the electrode 123 of the Vs cell 120 are disposed.
- the space of the reference oxygen chamber 170 sandwiched between the electrodes 132 and 120 is filled with a ceramic porous body.
- the insulator 145 is not disposed between the solid electrolyte body 131 and the solid electrolyte body 111, and a second measurement chamber 160 is formed as an independent small space.
- the second measurement chamber 160 is separated from the reference oxygen chamber 170 by an insulator 145.
- the solid electrolyte member 121 and the insulator 140 are provided with openings 125 and 141 so as to communicate with the second measurement chamber 160.
- the first measurement chamber 150 and the opening 141 are connected with the second diffusion resistance portion 152 interposed therebetween.
- the solid electrolyte body 131 and the electrodes 132 and 133 are separated from each other by the insulator 145 (the atmosphere in the reference oxygen chamber 170 in contact with the electrode 132 and the second measurement in contact with the electrode 133).
- Oxygen can be pumped out between the atmosphere in the chamber 160 and is referred to as an Ip2 cell 130 in this embodiment.
- the electrode 113 on the first measurement chamber 150 side of the Ip1 cell 110, the electrode 122 on the first measurement chamber 150 side of the Vs cell 120, and the electrode 133 on the second measurement chamber 160 side of the Ip2 cell 130 are connected to a reference potential. .
- the sensor control device 5 is electrically connected to the sensor element 10 of the gas sensor 1.
- the sensor control device 5 includes a microcomputer 60 and an electric circuit unit 58 as constituent entities.
- the microcomputer 60 includes a CPU 61, a RAM 62, a ROM 63, a signal input / output unit 64, an A / D converter 65, and a timer clock (not shown) having a known configuration.
- the CPU 61 communicates with the RAM 62 and the ROM 63, communicates with the ECU 90 through the signal input / output unit 64, and communicates with the electric circuit unit 58 through the signal input / output unit 64 and the A / D converter 65.
- information related to fuel supply to the internal combustion engine is input from the ECU 90 to the microcomputer 60.
- the electric circuit unit 58 includes a reference voltage comparison circuit 51, an Ip1 drive circuit 52, a Vs detection circuit 53, an Icp supply circuit 54, an Ip2 detection circuit 55, a Vp2 application circuit 56, and a heater drive circuit 57. Under the control of the microcomputer 60, the electric circuit unit 58 detects the NOx concentration in the exhaust gas using the sensor element 10 of the gas sensor 1.
- the Icp supply circuit 54 supplies a current Icp between the electrodes 122 and 123 of the Vs cell 120 and pumps oxygen from the first measurement chamber 150 into the reference oxygen chamber 170.
- the Vs detection circuit 53 is a circuit for detecting the voltage Vs between the electrodes 122 and 123, and outputs the detection result to the reference voltage comparison circuit 51.
- the reference voltage comparison circuit 51 is a circuit for comparing the voltage Vs detected by the Vs detection circuit 53 with a reference voltage (for example, 425 mV) as a reference, and outputs the comparison result to the Ip1 drive circuit 52. Yes.
- the Ip1 drive circuit 52 is a circuit for supplying an Ip1 current between the electrodes 112 and 113 of the Ip1 cell 110. Based on the comparison result of the voltage Vs between the electrodes 122 and 123 of the Vs cell 120 by the reference voltage comparison circuit 51, the Ip1 drive circuit 52 generates the Ip1 current so that the voltage Vs substantially matches the preset reference voltage. Adjust the size and orientation. As a result, in the Ip1 cell 110, oxygen is pumped from the first measurement chamber 150 to the outside of the sensor element 10, or oxygen is pumped from the sensor element 10 to the first measurement chamber 150.
- the first measurement chamber 150 is maintained such that the voltage between the electrodes 122 and 123 of the Vs cell 120 is maintained at a constant value (reference voltage value).
- the oxygen concentration in the inside is adjusted.
- the Vp2 application circuit 56 is a circuit for applying a voltage Vp2 (for example, 450 mV) between the electrodes 132 and 133 of the Ip2 cell 130, and controls the pumping of oxygen from the second measurement chamber 160 to the reference oxygen chamber 170.
- the Ip2 detection circuit 55 is a circuit that detects the value of the current Ip2 flowing from the electrode 133 of the Ip2 cell 130 to the electrode 132.
- the heater drive circuit 57 is a circuit for keeping the temperature of the solid electrolyte bodies 111, 121, 131 at a predetermined temperature.
- the heater drive circuit 57 is controlled by the CPU 61 to flow current to the heater pattern 164 of the heater element 161 to heat the solid electrolyte bodies 111, 121, 131 (in other words, the Ip1 cell 110, the Vs cell 120, and the Ip2 cell 130).
- the heater pattern 164 is a single electrode pattern connected within the heater element 161, and one end is grounded and the other end is connected to the heater drive circuit 57.
- the heater drive circuit 57 controls the heater pattern 164 to be PWM energized so that a current flows through the heater pattern 164 so that the solid electrolyte bodies 111, 121, 131 have a target temperature.
- the sensor control device 5 configured as described above detects the NOx concentration in the exhaust gas using the sensor element 10 of the gas sensor 1. Next, the operation at the time of detecting the NOx concentration using the gas sensor 1 will be described.
- the solid electrolyte bodies 111, 121, and 131 that constitute the sensor element 10 of the gas sensor 1 are heated and activated as the heater pattern 164 to which a drive current flows from the heater drive circuit 57 is heated.
- the Ip1 cell 110, the Vs cell 120, and the Ip2 cell 130 that have reached a target temperature by heating are in a state of operating as follows.
- the exhaust gas flowing through the exhaust path (not shown) is introduced into the first measurement chamber 150 while being restricted by the first diffusion resistance unit 151.
- a weak current Icp flows through the Vs cell 120 from the electrode 123 side to the electrode 122 side by the Icp supply circuit 54.
- oxygen in the exhaust gas can receive electrons from the electrode 122 in the first measurement chamber 150 on the negative electrode side, and the oxygen that has received the electrons flows into the solid electrolyte body 121 as oxygen ions. It moves into the oxygen chamber 170. That is, when the current Icp flows between the electrodes 122 and 123, oxygen in the first measurement chamber 150 is sent into the reference oxygen chamber 170.
- the Vs detection circuit 53 detects the voltage Vs between the electrodes 122 and 123.
- the detected voltage Vs is compared with a reference voltage (for example, 425 mV) by the reference voltage comparison circuit 51, and the comparison result is output to the Ip1 drive circuit 52.
- a reference voltage for example, 425 mV
- the oxygen concentration in the exhaust gas in the first measurement chamber 150 is It approaches a predetermined value (for example, 10 ⁇ 8 to 10 ⁇ 9 atm).
- the Ip1 drive circuit 52 when the oxygen concentration of the exhaust gas introduced into the first measurement chamber 150 is lower than a predetermined value, an Ip1 current is passed through the Ip1 cell 110 so that the electrode 112 side becomes a negative electrode. As a result, in the Ip1 cell 110, oxygen is pumped from the outside of the sensor element 10 into the first measurement chamber 150. On the other hand, when the oxygen concentration of the exhaust gas introduced into the first measurement chamber 150 is higher than a predetermined value, the Ip1 drive circuit 52 supplies an Ip1 current to the Ip1 cell 110 so that the electrode 113 side becomes a negative electrode. As a result, in the Ip1 cell 110, oxygen is pumped from the first measurement chamber 150 to the outside of the sensor element 10. The oxygen concentration in the exhaust gas can be detected based on the magnitude of the Ip1 current at this time and the flowing direction.
- the exhaust gas whose oxygen concentration is adjusted in the first measurement chamber 150 is introduced into the second measurement chamber 160 via the second diffusion resistance unit 152.
- NOx in the exhaust gas in contact with the electrode 133 in the second measurement chamber 160 is decomposed (reduced) into N2 and O2 using the electrode 133 as a catalyst.
- the decomposed oxygen receives electrons from the electrode 133, becomes oxygen ions (dissociates), flows through the solid electrolyte body 131, and moves into the electrode 123 (reference oxygen chamber 170).
- the NOx concentration can be detected based on this Ip2 current.
- the Ip2 detection circuit 55 is a circuit that detects the value of the current Ip2 that flows from the electrode 133 to the electrode 132 of the Ip2 cell 130.
- the value of the current Ip2 has two values. Detected by value. Next, the detailed circuit configuration of the Ip2 detection circuit 55 will be described.
- FIG. 2 is a diagram showing a circuit configuration of the Ip2 detection circuit 55. As shown in FIG. As shown in the drawing, the above-described Vp2 application circuit 56 is connected to the electrode 132 which is the positive terminal of the sensor element 10 via the buffer 201 and the current detection resistor 202.
- a first differential amplifier circuit 210 and a second differential amplifier circuit 220 are connected to points A and B at both ends of the current detection resistor 202, and the first and second differential amplifier circuits are connected. Outputs OP 1 and OP 2 of 210 and 220 are input to the microcomputer 60.
- the sensor element 10 and the current detection resistor 202 correspond to the “sensor unit” in Application Example 1.
- the first and second differential amplifier circuits 210 and 220 have a parallel relationship, and each of the first and second differential amplifier circuits 210 and 220 includes operational amplifiers 211 and 221 and four resistors 212 to 220. 215 and 222-225. Note that a voltage of 1.389 V is applied to the + input pin of the operational amplifier 221 on the second differential amplifier circuit 220 side via the resistor 225 and the buffer 226.
- the operational amplifiers 211 and 221 are driven with a constant driving voltage (for example, 5 V) obtained by stepping down the battery power supply.
- the first differential amplifier circuit 210 has an amplification factor (Gain) of 10 times and an offset (Offset) of 0V.
- the second differential amplifier circuit 220 has an amplification factor of 24 and an offset of 1.389V.
- Outputs OP1 and OP2 of the first and second differential amplifier circuits 210 and 220 are input to the A / D converter 65 of the microcomputer 60.
- the output OP1 of the first differential amplifier circuit 210 is within the operating voltage range (for example, 0 to 5 V) of the A / D converter 65 within a predetermined wide range (for example, 0 to 700 [ppm]) of the NOx concentration.
- the first differential amplifier circuit 210 can realize an appropriate signal output in a wide range.
- the output OP2 of the second differential amplifier circuit 220 falls within the operating voltage range of the A / D converter 65 within a predetermined narrow range of NOx concentration (for example, ⁇ 100 to 200 [ppm]).
- the second differential amplifier circuit 220 can realize an appropriate signal output in a narrow range.
- the “wide range” corresponds to the “first detection range” in Application Example 1
- the first differential amplifier circuit 210 corresponds to the “first amplification unit” in Application Example 1.
- the “narrow range” corresponds to the “second detection range” in Application Example 1
- the second differential amplifier circuit 220 corresponds to the “second amplification unit” in Application Example 1.
- the CPU 61 provided in the microcomputer 60 outputs the first and second digital signals output from the A / D converter 65, that is, the outputs of the first and second differential amplifier circuits 210 and 220.
- the A / D conversion values of OP1 and OP2 are taken in, and the NOx concentration (NOx concentration conversion value) is calculated based on the A / D conversion value selected alternatively from the two A / D conversion values.
- the first NOx concentration (converted to NOx concentration) is obtained by multiplying the A / D conversion value of the output OP1 of the first differential amplifier circuit 210 by a predetermined value (a constant predetermined according to the sensor element 10).
- the first NOx concentration is output as a final sensor detection value of the NOx concentration.
- the A / D conversion value of the output OP2 of the second differential amplifier circuit 220 is multiplied by the predetermined value to multiply the second NOx concentration (NOx concentration). (Converted value) is obtained, and the second NOx concentration is output as the final sensor detection value of the NOx concentration.
- the output of the second differential amplifier circuit 220 is output.
- detection with high resolution becomes possible.
- the microcomputer 60 and the NOx concentration calculation process executed by the CPU 61 of the microcomputer 60 correspond to the “control unit” in the first application example.
- Abnormal diagnosis The microcomputer 60 provided in the sensor control device 5 having the above configuration further performs abnormality diagnosis of the sensor control device 5. This abnormality diagnosis will be described in detail below.
- FIG. 3 is a flowchart showing an abnormality diagnosis process executed by the CPU 61 of the microcomputer 60.
- This abnormality diagnosis process is repeatedly executed every predetermined time.
- the CPU 61 first determines whether or not the sensor element 10 is in a sensing enabled state (step S110). Specifically, whether or not all the conditions such as the temperature of the solid electrolyte bodies 111, 121, 131 provided in the sensor element 10 being equal to or higher than a predetermined value and the power supply voltage of the sensor element 10 being higher than a predetermined value are satisfied. Therefore, it is determined whether or not the sensor element 10 is in a sensing enabled state.
- step S110 If it is determined in step S110 that the sensor element 10 is not in a sensing enabled state, the CPU 61 clears the differential accumulation buffer prepared in advance (step S120), and then returns to “return” to indicate this abnormality. The diagnosis process is temporarily terminated.
- the difference accumulation buffer will be described later.
- the CPU 61 outputs the first and second digital signals output from the A / D converter 65, that is, the first and second digital signals.
- the A / D conversion values of the outputs OP1 and OP2 of the differential amplifier circuits 210 and 220 are taken, the A / D conversion value of the output OP1 is multiplied by a predetermined value, and the A / D conversion value of the output OP2 is multiplied by the predetermined value
- the first and second NOx concentrations (NOx concentration converted values) Ip2W and Ip2N are obtained (step S130).
- the predetermined value is a constant determined in advance according to the sensor element 10.
- FIG. 4 is a graph showing the first and second NOx concentrations Ip2W and Ip2N with respect to the A / D conversion value.
- the vertical axis of the graph represents the A / D conversion values of the outputs OP1 and OP2 of the first and second differential amplifier circuits 210 and 220, and the horizontal axis of the graph represents the NOx concentration.
- the solid line in the graph indicates the first NOx concentration Ip2W, and the alternate long and short dash line indicates the second NOx concentration Ip2N.
- the first NOx concentration Ip2W has an amplification factor of 10 times over a wide range and an offset of 0 V
- the second NOx concentration Ip2N has an amplification factor of 24 times over a narrow range and an offset of 1 .389V.
- the CPU 61 determines whether or not at least one of the first and second NOx concentrations Ip2W and Ip2N is included in the abnormality diagnosis range ZN (step S140).
- the abnormality diagnosis range ZN is included in an overlapping portion between a wide range based on the output OP1 of the first differential amplifier circuit 210 and a narrow range based on the output OP2 of the second differential amplifier circuit 220.
- the predetermined range is, for example, 50 to 100 [ppm]. If it is determined in step S140 that at least one of the first and second NOx concentrations Ip2W and Ip2N is not included in the abnormality diagnosis range ZN, the process returns to “Return” and the process is temporarily terminated.
- step S140 when it is determined in step S140 that at least one of the first and second NOx concentrations Ip2W and Ip2N is included in the abnormality diagnosis range ZN, the CPU 61 determines from the second NOx concentration Ip2N to the first NOx concentration Ip2W. Is subtracted to calculate the difference D (step S150).
- the difference D is obtained by subtracting the second NOx concentration Ip2N from the first NOx concentration Ip2W. May be calculated.
- the CPU 61 stores the difference D calculated in step S150 in the difference accumulation buffer (step S160).
- the difference accumulation buffer is prepared in the RAM 62 (FIG. 1), and the details are as follows.
- FIG. 5 is an explanatory diagram showing the difference accumulation buffer BF.
- the difference accumulation buffer BF includes 16 fields FD1 to FD16 and can accumulate the difference D for 16 times.
- the latest difference D (0) is stored in the leftmost field FD1 in the figure, and the differences D (-1), D (-2),... , D ( ⁇ 14) are stored, and the difference D ( ⁇ 15) before the fifteenth generation is stored in the rightmost field FD16 in the drawing.
- step S160 in FIG. 3 each time step S160 in FIG. 3 is executed, each content stored in the fields FD1 to FD15 is shifted to the right by one field, and the difference D calculated in step S150 is stored in the leftmost field FD1 in the drawing.
- the difference D for the past 16 times (samples) is always updated and stored.
- the CPU 61 adds the difference D of each generation stored in the difference accumulation buffer BF, that is, adds (accumulates) D (0) to D ( ⁇ 15), thereby obtaining the difference accumulated value Dint. Calculate (step S170). Thereafter, the CPU 61 determines whether or not the difference integrated value Dint is equal to or greater than a predetermined value Di0 (step S180).
- the predetermined value Di0 is a constant determined in consideration of noise and circuit variation, and is, for example, 200 [ppm].
- step S190 determines that the diagnosis result is “abnormal” (step S190).
- the diagnosis result is notified to the outside by, for example, transmitting it to the ECU 90.
- step S190 the process returns to “return” to end the abnormality diagnosis process.
- step S180 determines that the difference integrated value Dint is less than the predetermined value Di0.
- the CPU 61 and the process of step S130 executed by the CPU 61 correspond to the “converted value acquisition unit” in application example 1. Further, the CPU 61 and the process of step S140 executed by the CPU 61 correspond to the “converted value determination unit” in application example 1. The CPU 61 and the processing of steps S150 to S190 executed by the CPU 61 correspond to the “abnormality diagnosis unit” in application example 1.
- the first NOx concentration Ip2W based on the output OP1 of the first differential amplifier circuit 210 and the output of the second differential amplifier circuit 220 are used.
- the difference D between the first NOx concentration Ip2W and the second NOx concentration Ip2N (Second NOx concentration Ip2N ⁇ first NOx concentration Ip2W) is obtained, 16 samples retroactive from the present of the difference D are stored in the difference accumulation buffer BF, and an integrated value (difference integrated value) of these differences D is stored.
- the diagnosis result is determined to be “abnormal”.
- an abnormality failure
- the signal system including the first differential amplifier circuit 210 and the signal system including the second differential amplifier circuit 220 the first NOx concentration Ip2W and the second Since the difference D from the NOx concentration Ip2N increases and the difference integrated value Dint increases, as described above, by determining whether the difference integrated value Dint is equal to or greater than the predetermined value Di0, the differential amplifier circuit 210, A failure in which the input signal from 220 becomes an abnormal value in the intermediate range can be diagnosed with high accuracy.
- FIG. 6 is a flowchart showing an abnormality diagnosis process executed in the sensor control apparatus of the second embodiment of the present invention.
- the sensor control device of the second embodiment is different from the sensor control device 5 of the first embodiment only in the content of the abnormality diagnosis process, and the other software configuration and hardware configuration are the same.
- This abnormality diagnosis process corresponds to FIG. 3 of the first embodiment.
- the CPU of the microcomputer performs the same steps S110, S130, S140, and S150 as in the first embodiment. Execute.
- the CPU determines whether or not the difference D is greater than or equal to a predetermined value D0 (step S260).
- the predetermined value D0 is a constant determined in consideration of noise and circuit variations, and is, for example, 20 [ppm]. If it is determined in step S260 that the difference D is greater than or equal to the predetermined value D0, the CPU increments the counter value CNT by the value 1 (step S270). The counter value CNT is used to count the number of times that the difference D is equal to or greater than the predetermined value D0, and is cleared when it is determined in step S260 that the difference D is less than the predetermined value D0 (step S220). .
- step S280 After incrementing the counter value CNT in step S270, the CPU determines whether or not the counter value CNT is 10 or more (step S280), and if it is determined that the value is 10 or more, the CPU The result is determined to be “abnormal” (step S190).
- the processing in step S190 is the same as that in the first embodiment. Thereafter, the process returns to “RETURN”, and the abnormality diagnosis process is temporarily terminated.
- step S280 if it is determined in step S280 that the counter value CNT is less than the value 10, the CPU returns to “RETURN” without executing step S190, and once ends this abnormality diagnosis processing.
- step S110 If it is determined in step S110 that the sensor element 10 is not in a sensing enabled state, the CPU exits to “return” and once ends the abnormality diagnosis process.
- the input signal from the differential amplifier circuit is in the intermediate range as in the first embodiment. It is possible to diagnose a failure having an abnormal value with high accuracy.
- FIG. 7 is a diagram showing a circuit configuration of the Ip2 detection circuit 355 of the third embodiment.
- the Ip2 detection circuit 355 includes a single differential amplifier circuit (third differential amplifier circuit) 320, and this third differential amplifier circuit.
- 320 differs from the sensor control device 5 of the first embodiment in that 320 is configured to be able to switch its amplification degree. 7, the elements common to FIG. 1 (specifically, the sensor element 10, the Vp2 application circuit 56, the buffer 201, the current detection resistor 202, the microcomputer 60, and the A / D converter 65) are the same. The number is indicated.
- the third differential amplifier circuit 320 is connected to the points A and B at both ends of the current detection resistor 202.
- the output OP3 is input to the A / D converter 65 of the microcomputer 60.
- the non-inverting input terminal (+ input pin) of the operational amplifier 321 has a potential at the point A via a resistor 324 and 1.389V or 0V via a switch SW2. Is added as an offset voltage (offset). That is, when the switch SW2 is connected to the resistor 325, 1.389V is applied to the + input pin of the operational amplifier 321 via the resistor 325 and the buffer 326, while the switch SW2 is connected to the resistor 315. In some cases, 0V is applied to the + input pin of operational amplifier 321 through resistor 315.
- the potential at the point B is connected to the inverting input terminal ( ⁇ input pin) of the operational amplifier 321 via the resistor 322, and the operational amplifier 321 itself is further connected via the resistor 323. Output has been added.
- a circuit in which a switch SW1 and a resistor 313 are connected in series is connected in parallel with the resistor 323. For this reason, by turning ON / OFF the switch SW1, the resistance value of the feedback resistor interposed between the negative input pin of the operational amplifier 221 and the output of the operational amplifier 321 itself, the resistance value of the resistor 323, the resistor 323, It is possible to switch to one of the combined values of 313 parallel connections. By this switching, the amplification factor (gain) of the third differential amplifier circuit 320 can be switched to either the first amplification factor (10 times) or the second amplification factor (24 times).
- the third differential amplifier circuit 320 is configured such that the switch SW1 is switched in synchronization with the switch SW2 based on a command from the microcomputer 60. Specifically, the switch SW1 is turned on and the switch SW1 is turned on. When SW2 is connected to resistor 315, the amplification factor is 10 times and the offset is 0 V. When switch SW2 is turned OFF and switch SW2 is connected to resistor 325, the amplification factor is 24 times and the offset is 1. 389V.
- the output OP3 when the amplification factor of the third differential amplifier circuit 320 is switched to 10 times is within a predetermined wide range of NOx concentration within the operating voltage range of the A / D converter 65 (for example, 0 to 5 V).
- the output OP3 when the amplification degree of the third operation amplification circuit 320 is switched to 24 times falls within the operation voltage range of the A / D converter 65 within a predetermined narrow range of the NOx concentration.
- An appropriate signal output can be realized in a narrow range.
- FIG. 8 is a flowchart showing an abnormality diagnosis process executed by the CPU of the microcomputer 60.
- the abnormality diagnosis process is periodically executed by an interrupt process.
- the CPU first determines whether or not the sensor element 10 is in a sensing enabled state (step S310). Since this determination is the same as the process of step S110 shown in the first embodiment, a description thereof will be omitted.
- step S310 If it is determined in step S310 that the sensor element 10 is not in a sensing enabled state, the CPU ends the abnormality diagnosis process. On the other hand, when it is determined in step S310 that the sensor element 10 is in a sensing enabled state, the CPU sets the amplification factor of the third differential amplifier circuit 320 to 24 times (second amplification factor). The switch SW1 is turned off and the switch SW2 is instructed to be connected to the resistor 325 (step S320). As a result, the third differential amplifier circuit 320 is set to an amplification factor of 24 and an offset of 1.389V.
- step S330 the A / D conversion value of the output OP3 of the third differential amplifier circuit 320 is fetched, and the A / D conversion value of the output OP3 is multiplied by a predetermined value to obtain a second NOx concentration (NOx concentration). Conversion value) Ip2N is obtained.
- step S340 determines whether or not the second NOx concentration Ip2N is included in the abnormality diagnosis range ZN (see FIG. 4) (step S340). If it is determined in step S340 that the second NOx concentration Ip2N is not included in the abnormality diagnosis range ZN, the CPU ends the abnormality diagnosis process. On the other hand, if it is determined in step S340 that the second NOx concentration Ip2N is included in the abnormality diagnosis range ZN, the process proceeds to step S350, and the CPU increases the amplification factor of the third differential amplifier circuit 320 by 10 (first To set the switch SW1 to ON and connect the switch SW2 to the resistor 315.
- the third differential amplifier circuit 320 is set with an amplification factor of 10 and an offset of 0V.
- step S360 the A / D conversion value of the output OP3 of the third differential amplifier circuit 320 is fetched, and the A / D conversion value of the output OP3 is multiplied by a predetermined value to obtain the first NOx concentration (NOx concentration). Conversion value) Ip2W is obtained.
- step S370 the CPU calculates a difference D by subtracting the first NOx concentration Ip2W from the second NOx concentration Ip2N (step S370). Subsequently, in step S370, a process of determining whether or not the calculated difference D is equal to or greater than a predetermined value D0 (for example, 200 [ppm]) set for determining abnormality. If it is determined in step S370 that the difference D is greater than or equal to the predetermined value D0, the CPU sets the diagnosis result to “abnormal” (step S390). The diagnosis result is notified to the outside by transmitting it to the ECU, for example. On the other hand, if it is determined in step S390 that the difference value D is less than the predetermined value D0, the CPU ends the abnormality diagnosis process without executing step S390.
- a predetermined value D0 for example, 200 [ppm]
- abnormality diagnosis is performed based on the difference D between the first NOx concentration Ip2W and the second NOx concentration Ip2N. Instead, the first NOx concentration is determined.
- An abnormality diagnosis may be performed based on the ratio between the concentration Ip2W and the second NOx concentration Ip2N. For example, the ratio can be obtained, and it can be determined that the ratio is abnormal when the ratio is equal to or greater than a predetermined value for determining abnormality.
- it is not necessary to be limited to the configuration based on the difference or the ratio and any method may be used as long as the configuration compares the first NOx concentration Ip2W and the second NOx concentration Ip2N.
- Second modification when performing abnormality determination, it is determined whether or not at least one of the first and second NOx concentrations Ip2W and Ip2N is included in the abnormality diagnosis range ZN. Alternatively, it may be configured to determine whether or not the first NOx concentration Ip2W is included in the abnormality diagnosis range ZN (the second NOx concentration Ip2N is not particularly determined), or the second NOx concentration Ip2N May be included in the abnormality diagnosis range ZN (the first NOx concentration Ip2W is not particularly determined).
- abnormality diagnosis of both the signal system including the first differential amplifier circuit 210 and the signal system including the second differential amplifier circuit 220 can be performed.
- abnormality diagnosis of the signal system including the differential amplifier circuit on the NOx concentration Ip2 side determined to be included in the abnormality diagnosis range ZN can be performed.
- a wide range (0 to 700 [ppm]) as the first detection range and a narrow range ( ⁇ 100 to 200 [ppm]) as the second detection range are partly.
- a narrow range may be set to, for example, 0 to 200 [ppm], and a wide range may include the narrow range.
- the first differential amplifier circuit 210 has a gain of 10 times and an offset of 0 V
- the second differential amplifier circuit 220 has a gain of 24 times and an offset of 1.389 V.
- the third differential amplifier circuit 320 is switched between a state where the gain is 10 times and the offset is 0 V, and a state where the gain is 24 times and the offset is 1.389 V.
- these gains and offsets may have any values as long as the first detection range and the second detection range can partially overlap.
- the threshold value Di0 for the difference integrated value Dint is a value different from that of the first embodiment according to the number.
- the configuration of the gas sensor 1 controlled by the sensor control device 5 and the sensor element 10 included in the gas sensor 1 can be changed as appropriate.
- the gas sensor 1 (sensor element 10) of the present embodiment includes the Vs cell 120 on the lower side of the first measurement chamber 150 in FIG. 1, but a sensor control device that controls a gas sensor that does not include the Vs cell 120.
- the present invention may be applied.
- the configuration is applied to the gas sensor 1 capable of detecting the NOx concentration.
- the oxygen concentration, the HC concentration, or the CO concentration can be detected as the chemical amount. It is good also as a structure applied to a gas concentration sensor.
- it can be used for a gas concentration detection device other than for automobiles, or a gas other than exhaust gas can be used as a detected gas (for example, intake gas).
- the present invention is not limited to the gas concentration sensor, and may be configured to detect other chemical amounts such as the concentration of a specific component contained in the liquid to be measured.
- the present invention is not limited to the chemical amount, and may be configured to be applied to a sensor that detects a physical quantity, for example, the temperature or pressure of the measurement target gas.
- a part of the configuration realized by hardware may be replaced with software, and conversely, a part of the configuration realized by software may be replaced with hardware. May be.
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Abstract
Description
A-1.全体構成:
図1は、本発明の第1実施例としてのセンサ制御装置5とその周辺を示す概略構成図である。図中の1はガスセンサであり、センサ制御装置5はガスセンサ1に接続されている。ガスセンサ1はセンサ素子10を備える。センサ素子10は、先端側部分における内部構造を示す断面図をもって図示しており、図中左側がセンサ素子10の先端側となっている。
Ip2検出回路55は、前述したように、Ip2セル130の電極133から電極132に流れた電流Ip2の値の検出を行う回路であるが、本実施例では、電流Ip2の値は、2通りの値でもって検出される。Ip2検出回路55の詳細な回路構成について次に説明する。
図1に戻って、マイクロコンピュータ60に備えられるCPU61は、A/Dコンバータ65から出力される第1および第2のデジタル信号、すなわち、第1および第2の差動増幅回路210,220の出力OP1,OP2のA/D変換値を取り込み、両A/D変換値のうちから択一的に選択されたA/D変換値に基づいてNOx濃度(NOx濃度換算値)を算出する。詳しくは、第1の差動増幅回路210の出力OP1のA/D変換値に所定値(センサ素子10に応じて予め定められた定数)を乗算することにより第1のNOx濃度(NOx濃度換算値)を求め、この第1のNOx濃度が前記狭範囲に含まれないときには、前記第1のNOx濃度をNOx濃度の最終的なセンサ検出値として出力する。一方、第1のNOx濃度が前記狭範囲に含まれるときには、第2の差動増幅回路220の出力OP2のA/D変換値に前記所定値を乗算することにより第2のNOx濃度(NOx濃度換算値)を求め、その第2のNOx濃度をNOx濃度の最終的なセンサ検出値として出力する。
前記構成のセンサ制御装置5に備えられるマイクロコンピュータ60は、さらに、センサ制御装置5の異常診断を行う。この異常診断について、以下に詳述する。
に、CPU61は、診断結果を「異常」であると確定する(ステップS190)。なお、この診断結果は、例えば、ECU90に送信する等して外部に通知する。ステップS190の実行後、「リターン」に抜けて、この異常診断処理を一旦終了する。一方、ステップS180で、差分積算値Dintが所定値Di0を下回ると判定された場合には、CPU61は、ステップS190を実行することなく、すなわち、異常診断結果は「正常」である旨を維持したまま、「リターン」に抜けて、この異常診断処理を一旦終了する。
以上詳述したように第1実施例のセンサ制御装置5によれば、第1の差動増幅回路210の出力OP1に基づく第1のNOx濃度Ip2Wと、第2の差動増幅回路220の出力OP2に基づく第2のNOx濃度Ip2Nとの少なくとも一方が異常診断範囲ZNに含まれるときに、第1のNOx濃度Ip2Wと第2のNOx濃度Ip2Nとの差分D(本実施例では、差分D=第2のNOx濃度Ip2N-第1のNOx濃度Ip2W)を求め、その差分Dの現在から過去に遡る16サンプル分を差分蓄積用バッファBFに記憶し、これら差分Dの積算値(差分積算値)Dintを求め、その差分積算値Dintが所定値Di0以上となったときに、診断結果が「異常」であると確定するように構成されている。第1の差動増幅回路210を含む信号系統と第2の差動増幅回路220を含む信号系統とのうちの少なくとも一方で異常(故障)が発生すると、第1のNOx濃度Ip2Wと第2のNOx濃度Ip2Nとの差分Dが大きくなり、差分積算値Dintは大きくなることから、上述したように、差分積算値Dintが所定値Di0以上となったかを判定することで、差動増幅回路210、220からの入力信号が中間域において異常値となる故障を高精度に診断することができる。
図6は、本発明の第2実施例のセンサ制御装置において実行される異常診断処理を示すフローチャートである。第2実施例のセンサ制御装置は、第1実施例のセンサ制御装置5と比較して、異常診断処理の内容が相違するだけで、その他のソフトウェアの構成や、ハードウェアの構成は同一である。この異常診断処理は、第1実施例の図3に対応したものであり、図6に示すように、マイクロコンピュータのCPUは、第1実施例と同じステップS110、S130、S140、S150の処理を実行する。
て予め定めた定数であり、例えば20[ppm]である。ステップS260で、差分Dが所定値D0以上であると判定された場合には、CPUは、カウンタ値CNTを値1だけインクリメントする(ステップS270)。カウンタ値CNTは、差分Dが所定値D0以上となった回数をカウントするためのもので、ステップS260で、差分Dが所定値D0を下回ると判定されたときに、クリアされる(ステップS220)。
本発明の第3実施例のセンサ制御装置について、以下に説明する。第3実施例のセンサ制御装置は、第1実施例のセンサ制御装置5と比較して、Ip2検出回路の構成および異常診断処理の内容が相違するものであり、その他の構成は同一である。図7は、第3実施例のIp2検出回路355の回路構成を示す図であり、差動増幅回路(第3の差動増幅回路)320が1つからなり、この第3の差動増幅回路320が自身の増幅度を切り換え可能に構成されてなる点で第1実施例のセンサ制御装置5とは構成が異なる。なお、図7では、図1と共通する要素(具体的には、センサ素子10、Vp2印加回路56、バッファ201、電流検出抵抗器202、マイクロコンピュータ60、A/Dコンバータ65)については、同一の番号にて表記している。
・第1変形例:
前記第1~第3実施例では、第1のNOx濃度Ip2Wと、第2のNOx濃度Ip2Nとの差分Dに基づいて、異常診断を行っているが、これに換えて、前記第1のNOx濃度Ip2Wと第2のNOx濃度Ip2Nとの比率に基づいて異常診断を行う構成としてもよい。例えば、前記比率を求めて、比率が異常を判定するための所定値以上であるときに異常であると判定する構成とすることができる。さらに、前記差分や比率に基づく構成に限定される必要もなく、第1のNOx濃度Ip2Wと第2のNOx濃度Ip2Nとを対比する構成であれば、どのような手法によるものでもよい。
前記第1および第2実施例では、異常判定を行うに際し、第1および第2のNOx濃度Ip2W、Ip2Nの少なくとも一方が異常診断範囲ZNに含まれるか否かを判定していたが、これに換えて、第1のNOx濃度Ip2Wが異常診断範囲ZNに含まれるか否かを判定する(第2のNOx濃度Ip2Nについては特に判定しない)構成としてもよいし、あるいは、第2のNOx濃度Ip2Nが異常診断範囲ZNに含まれるか否かを判定する(第1のNOx濃度Ip2Wについては特に判定しない)構成としてもよい。前記第1および第2実施例では、第1の差動増幅回路210を含む信号系統と第2の差動増幅回路220を含む信号系統との双方の異常診断を行うことができ、この第2変形例では、異常診断範囲ZNに含まれると判断されたNOx濃度Ip2側の差動増幅回路を含む信号系統の異常診断を行うことができる。
前記第1~第3実施例では、第1の検出範囲としての広範囲(0~700[ppm])と、第2の検出範囲としての狭範囲(-100~200[ppm])とが一部分で重なる構成としていたが、これに換えて、狭範囲を例えば0~200[ppm]として、広範囲が狭範囲を内包する構成としてもよい。さらに、第1および第2実施例では、第1の差動増幅回路210はゲインが10倍、オフセットが0Vであり、第2の差動増幅回路220はゲインが24倍、オフセットが1.389Vである構成を採り、また、第3実施例では第3の差動増幅回路320を、ゲインが10倍、オフセットが0Vの状態と、ゲインが24倍、オフセットが1.389Vの状態とで切り替える構成を採るようにしたが、これらゲインおよびオフセットは、第1の検出範囲と第2の検出範囲とを一部分で重ならせることができれば、どのような値とすることもできる。
前記第1実施例では、差分蓄積用バッファBFに16個のフィールドFD1~FD16を設け、現在から過去に遡る16サンプル分の差分を積算する構成としたが、これに換えて、他の数のサンプル分を積算する構成としてもよい。なお、この場合には、差分積算値Dintについての閾値Di0は、その数に応じた、第1実施例とは異なった値となる。
センサ制御装置5が制御するガスセンサ1、およびガスセンサ1が備えるセンサ素子10の構成は適宜変更可能である。例えば、本実施形態のガスセンサ1(センサ素子10)は、図1において、第1測定室150の下側にVsセル120を備えていたが、Vsセル120を備えないガスセンサを制御するセンサ制御装置に、本発明を適用してもよい。
前記第1~第3実施例では、NOx濃度を検出可能なガスセンサ1に適用する構成であったが、これに換えて、化学量として酸素濃度、あるいは、HC濃度やCO濃度を検出可能とするガス濃度センサに適用する構成としてもよい。さらに、自動車用以外のガス濃度検出装置に用いることや、排ガス以外のガスを被検出ガス(例えば、吸気ガス)とすることも可能である。また、ガス濃度センサに限る必要もなく、例えば、被測定対象液体中に含まれる特定成分の濃度等の他の化学量を検出する構成としてもよい。さらに、化学量に限る必要もなく、物理量、例えば、被測定対象ガスの温度や圧力を検出するセンサに適用する構成とすることもできる。
5…センサ制御装置
10…センサ素子
51…基準電圧比較回路
52…Ip1ドライブ
53…Vs検出回路
54…Icp供給回路
55,355…Ip2検出回路
56…Vp2印加回路
57…ヒータ駆動回路
58…電気回路部
60…マイクロコンピュータ
61…CPU
62…RAM
63…ROM
64…信号入出力部
65…A/Dコンバータ
90…ECU
111、131…固体電解質体
112、113、132、133…電極
130…Ip2セル
150…第1測定室
151…第1拡散抵抗部
152…第2拡散抵抗部
160…第2測定室
201…バッファ
202…電流検出抵抗器
210…第1の差動増幅回路
211…オペアンプ
220…第2の差動増幅回路
221…オペアンプ
226…バッファ
320…第3の差動増幅回路
321…オペアンプ
Ip2W…第1のNOx濃度
Ip2N…第2のNOx濃度
D…差分
Dint…差分積算値
BF…差分蓄積用バッファ
ZN…異常診断範囲
SW1,SW2…スイッチ
Claims (9)
- 被測定対象の物理的特性または化学的特性に対応した電気信号値を出力するセンサ部と、
前記センサ部から出力される電気信号値を受け取り、前記特性の第1の検出範囲について第1の増幅率で前記電気信号値を増幅する第1増幅部と、
前記センサ部から出力される電気信号値を受け取り、前記特性についての前記第1の検出範囲と少なくとも一部が重なる第2の検出範囲について第2の増幅率で前記電気信号値を増幅する第2増幅部と、
前記第1増幅部からの出力と前記第2増幅部からの出力とに基づいて前記特性を示す値を求め、該値をセンサ検出値として出力する制御部と
を備えるセンサ制御装置において、
前記第1増幅部からの出力に基づく第1の特性換算値と、前記第2増幅部からの出力に基づく第2の特性換算値とを取得する換算値取得部と、
前記第1の検出範囲と第2の検出範囲との重複部分に含まれる所定の範囲を異常診断範囲とし、前記第1および第2の特性換算値のうちの少なくとも一方が前記異常診断範囲に含まれるか否かを判定する換算値判定部と、
前記換算値判定部により前記異常診断範囲に含まれると判定されたときに、前記第1の特性換算値と第2の特性換算値とを対比して、前記第1増幅部を含む信号系統と第2増幅部を含む信号系統とのうちの少なくとも一方で異常が発生したか否かを判定する異常診断部と
を備えることを特徴とするセンサ制御装置。 - 請求項1に記載のセンサ制御装置であって、
前記異常診断部は、
前記第1の特性換算値と第2の特性換算値との差分を算出する差分算出部と、
前記算出された差分に基づいて、前記異常の判定を行う異常判定部と
を備えるセンサ制御装置。 - 請求項2に記載のセンサ制御装置であって、
前記差分算出部は、
前記差分についての所定期間における積算値を求める積算値算出部を備え、
前記異常判定部は、
前記積算値が所定値以上となったときに、前記異常である旨の判定を行う構成である、
センサ制御装置。 - 請求項3に記載のセンサ制御装置であって、
前記換算値取得部は、
前記所定期間よりも短い時間に設定された所定時間毎に、前記第1の特性換算値と第2の特性換算値との取得を行う構成であり、
前記差分算出部は、
前記所定時間毎に、前記換算値取得部により取得された前記第1および第2の特性換算値に基づく前記差分の積算値を、現在から過去に遡る複数回分にわたって算出する構成であり、
前記異常判定部は、
前記所定時間毎に、前記差分算出部により算出された積算値が所定値以上となったときに、前記異常である旨の判定を行う構成である、センサ制御装置。 - 請求項1ないし4のいずれかに記載のセンサ制御装置であって、
前記第2の検出範囲は、前記第1の検出範囲よりも狭く、
前記第2の増幅率は、前記第1の増幅率よりも高い、センサ制御装置。 - 請求項1ないし5のいずれかに記載のセンサ制御装置であって、
前記センサ部から出力される電気信号値を受け取る複数の増幅回路を備え、
前記増幅回路の1つが、前記第1の増幅率で前記電気信号値を増幅する第1増幅部を構成し、前記増幅回路のもう1つが、前記第2の増幅率で前記電気信号値を増幅する第2増幅部を構成する、センサ制御装置。 - 請求項1ないし5のいずれかに記載のセンサ制御装置であって、
前記センサ部から出力される電気信号値を受け取る増幅回路を備え、前記増幅回路は、自身の増幅率の切り換えにより前記第1の増幅率と前記第2の増幅率を選択可能とされ、前記第1増幅部は、前記増幅回路を前記第1の増幅率に設定したときに構成され、前記第2増幅部は、前記増幅回路を前記第2の増幅率に設定したときに構成される、センサ制御装置。 - 請求項1ないし7のいずれかに記載のセンサ制御装置であって、
前記特性は、前記被測定対象に含まれる特定ガス濃度である、センサ制御装置。 - 被測定対象の物理的特性または化学的特性に対応した電気信号値を出力するセンサ部と、前記センサ部から出力される電気信号値を受け取り、前記特性の第1の検出範囲について第1の増幅率で前記電気信号値を増幅する第1増幅部と、前記センサ部から出力される電気信号値を受け取り、前記特性についての前記第1の検出範囲と少なくとも一部が重なる第2の検出範囲について第2の増幅率で前記電気信号値を増幅する第2増幅部とを用いて、前記第1増幅部からの出力と前記第2増幅部からの出力とに基づいて前記特性を示す値を求め、該値をセンサ検出値として出力するセンサ制御方法において、
前記第1増幅部からの出力に基づく第1の特性換算値と、前記第2増幅部からの出力に基づく第2の特性換算値とを取得する換算値取得工程と、
前記第1の検出範囲と第2の検出範囲との重複部分に含まれる所定の範囲を異常診断範囲とし、前記第1および第2の特性換算値のうちの少なくとも一方が前記異常診断範囲に含まれるか否かを判定する判定工程と、
前記判定工程により前記異常診断範囲に含まれると判定されたときに、前記第1の特性換算値と第2の特性換算値とを対比して、前記第1増幅部を含む信号系統と第2増幅部を含む信号系統とのうちの少なくとも一方で異常が発生したか否かを判定する異常診断工程と
を備えることを特徴とするセンサ制御方法。
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