CN101514974B - Gas sensor control device - Google Patents

Gas sensor control device Download PDF

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Publication number
CN101514974B
CN101514974B CN200910008212.3A CN200910008212A CN101514974B CN 101514974 B CN101514974 B CN 101514974B CN 200910008212 A CN200910008212 A CN 200910008212A CN 101514974 B CN101514974 B CN 101514974B
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voltage
current
gas
sensor
circuit
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CN101514974A (en
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羽田聪
秋元克英
延命昭一郎
水谷圭吾
寺西真哉
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Denso Corp
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Denso Corp
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Abstract

The invention discloses a gas sensor control device including a sensor cell having a negative terminal, to which a current-voltage converter is connected, and a differential amplifier is connected to the current-voltage converter to provide a current measured result applied to a microcomputer. The current-voltage converter has an opposite-to-sensor terminal to which another differential amplifier is connected. A sensor-side terminal of the current-voltage converter and another differential amplifier is electrically connected to each other via an electric pathway having a sensor-current flow disabling pathway in which a switch circuit is provided. Closing the switch circuit allows a potential difference between both terminals of the current-voltage converter is zeroed. With the switch circuit closed, the microcomputer calculates an element current correcting value, while detecting an electromotive force of the sensor cell based on which a failure is determined.

Description

Gas sensor control device
Technical field
The present invention relates to gas sensor controller, and relate more specifically to be connected to the gas sensor control device such as the gas sensor of NOx sensor, for the output based on this gas sensor, detect the concentration of special component.
Background technology
In recent years, to more strictly controlling of toxic emission and fuel efficiency demand, be a kind of development trend always.Thereby, the technology relevant to the NOx Reducing exhaust emission of for example diesel engine and another technology relevant with the fault detect of NOx cleaning equipment need to be provided.Further, even petrol engine has the application of expansion, this application need to be in lean burn region combustion air/fuel mixture be attended by the NOx discharge of increase.Thereby, the technology relevant to NOx emission control and another technology relevant with the fault detect of NOx cleaning equipment need to be provided.Due to these situations, the demand of NOx sensor is constantly increased.And this NOx sensor can preferably include the sensing element of the multiple-unit type of utilizing zirconia solid state electrolysis plastid.
Utilization relates to the gas sensor of above-mentioned NOx sensor, due to the intrinsic error factor of sensor in practical application itself and be present in another error factor in the testing circuit that is connected to this gas sensor, on sensor current measured value, there is output error.The example of gas sensor error factor can comprise individual difference and in time deteriorated etc.The example of the error factor of testing circuit comprises the precision of circuit component and temperature characterisitic etc.Particularly, utilize NOx sensor, weak sensor current depends on NOx concentration and flows, cause due to error factor cause the risk of the further increase that declines of accuracy of detection.Utilization is configured to detect the oxygen sensor (A/F sensor) of oxygen concentration, and sensor current exists with mA level.Comparatively speaking, NOx sensor generates the sensor current of nA level, and the current level of itself and above-mentioned oxygen sensor differs 4-5 the order of magnitude.
Utilize prior art to address this is that, attempted to provide the testing circuit with the switch on the current path that the sensor current of being arranged on flows through.Temporarily open this switch to cut off the sensor current of this testing circuit of flowing through, and for example obtain in this state sensor current measured value, to calculate the output error (Japanese patent application that is, 2005-326388 referring to publication number) of this testing circuit.
Yet, utilize the testing circuit of this structure with the switch on the current path that the sensor current of being arranged on flows through, should consider the negative effect that sensor current is detected being caused by this switch.In the situation that use comprises for example switch of thyristor, can in on-off element, there is the leakage current (leakage current) of the tens nA orders of magnitude.Thus, when measuring weak current, such as the stage detecting NOx concentration, can worry to occur measuring error, and there is the space of improvement.
, utilize while relating to the gas sensor of above-mentioned NOx sensor, the function that need to detect gas sensor is that the example of normal and test item comprises for the disconnection of sensing element and determining meanwhile.When utilizing automobile exhaust gas gas sensor, under the regulation of law and standard, specify to disconnect possibly and determine.For detection of the technology example of the fault in gas sensor, can comprise based on for example element impedance of A/F sensor and come detecting sensor to disconnect.More specifically, when detecting impedance, in the voltage arranging, occur scan variations (sweep variation) with obtain curent change amplitude or can be during this scan variations computing impedance value.Therefore, based on curent change amplitude or resistance value, carry out fault detect.By carrying out fault detect based on element impedance, even if sensor output is " 0 ", so also may make, close normal running or the inquiry of failed operation.That is, utilize and take air/fuel that theoretical air-fuel ratio (stoichiometric proportion) be target than FEEDBACK CONTROL, sensor is exported being approximately that " 0 " is located to remain unchanged, even in this case, still can detect the fault such as disconnection etc.
Yet, utilize the circuit be configured to the test example weak current that NOx detection signal is example as take, can on omnibus circuit, realize weak current and detect and impedance detection, cause the deteriorated risk of NOx accuracy of detection.That is by the resulting current level of impedance detection, be, mA level.On the contrary, the current level of NOx detection signal is in nA level, and current level differs 4-5 magnitude each other.Therefore, be difficult to precision to increase and carry out NOx and detect and impedance detection, this causes detecting precision deteriorated of NOx concentration.
Further, provide a kind of technology, wherein testing circuit has and is arranged on NOx and detects the switch (Japanese patent application that is for example, 2005-3263880 referring to publication number) on the current path that electric current flows through.By using this technology, can suitably switch NOx testing circuit and impedance detection circuit, thereby likely extract as required the signal of current level.
Yet, utilize this structure, in the current path of wherein flowing through at NOx detection electric current, be provided with switch in testing circuit, need to consider that this switch can adversely affect NOx current detecting.That is, utilize and comprise for example switch of thyristor, can in on-off element, occur the leakage current (leakage current) of tens nA levels.Therefore,, when measuring weak current, in the stage such as detecting NOx concentration etc., there is the risk of measuring error, and there is the space of improvement.
Summary of the invention
Therefore, the object of this invention is to provide a kind of gas sensor control device, the current correction value of wherein suitably calculating for correcting element electric current detects the specific component concentration such as NOx concentration with the higher precision of utilization.
Another object of the present invention is to provide gas sensor control device, wherein can determine suitably the fault such as activity deficiency or disconnecting, and suppresses detecting the adverse effect of the precision of gas concentration simultaneously.
Structure for addressing the above problem and favourable effect are described below.
According to the present invention, gas sensor control device is connected to gas sensor, this gas sensor control device comprises the pair of electrodes of solid state electrolysis plastid to form on this solid state electrolysis plastid, wherein, when receiving voltage electrode being applied through this, according to the specific component concentration in measurement gas, generate element current.Utilize this gas sensor control device, utilize voltage-current converter measuring sensor electric current and will utilize the measurement result of the measured element current of this voltage-current converter from output circuit output as element current measured value.Further, in the situation that there is the voltage applying from applying voltage-setting circuitry, the element current measured value based on from output circuit output calculates the concentration (oxygen concentration and NOx concentration etc.) of special component.
Utilize one embodiment of the present of invention, switchgear (on-off circuit 71 as shown in Figure 4) is arranged on not to be had in element current flow disabled path that element current flows through.When this switchgear cuts out, regulate apply voltage-setting circuitry voltage (voltage applying) is set so that the potential difference (PD) between two terminals of voltage-current converter is in predetermined particular value.By calculating the current correction value for correcting element electric current by the output valve of output circuit under this state.Also, when detecting gas concentration based on element current measured value, temporary transient Closing Switch device is to calculate current correction value.
Utilize this structure, make switchgear enter closure state and allow to set up two stages.
In a stage, the sensor side terminal voltage of voltage-current converter is imported into and applies voltage-setting circuitry in backfeed loop.
In another stage, feed back input is made response and regulated and to apply the voltage that voltage-setting circuitry applies, so that the potential difference (PD) between two terminals of voltage-current converter is in predetermined particular value.
When operation, utilize this stage, may suitably obtain for proofreading and correct the current correction value for correcting element electric current of the change component that equals instant gas sensor control device characteristic.; the element current measured value (utilizing the element current value of circuit institute actual measurement) occurring when the potential difference (PD) between two terminals when voltage-current converter is configured to particular value with treat that the output valve (design load etc.) of original output compares, and can calculate the current correction value for correcting element electric current according to the difference of these factors.
Utilize current embodiment of the present invention, switchgear is arranged on element current flow disabled path, does not have element current to flow in this element current flow disabled path.This can be avoided causing due at switchgear, the inconvenience of the error of the element current measured value that the leakage current of responding on the semiconductor switching device such as resistor etc. causes.Especially, when measuring weak element current, owing to there being switchgear, so occur that in current measurement value error is possible.This error causes strengthening detecting the adverse effect of gas concentration result.Yet, provide this switchgear can avoid occurring this inconvenience.
Utilize the current embodiment of the invention described above, in addition, can suitably utilize the synthesis capability that improves the precision that detects gas concentration to calculate the current correction value for correcting element electric current.
Utilize current embodiment of the present invention, the potential difference (PD) between two terminals of Closing Switch device permission voltage-current converter is returned to zero.This allows can access the output valve of output circuit in the situation that potential difference (PD) remains zero.In this case, because the potential difference (PD) between two terminals of voltage-current converter is returned to zero, may set up a kind of state, wherein do not have element current to flow, that is, the state of element current ≈ 0nA, and under the state of element current ≈ 0nA, obtain current correction value.
Further, as used herein, the state of " potential difference (PD) between two terminals of voltage-current converter is returned to zero " is the state of 0nA or about 0nA corresponding to the electric current of the sensing element of flowing through.In this case, actual circuit structure comprises many circuit components and owing to there being sort circuit element, the insignificant electric current actual circuit structure of flowing through.Strictly say, although there is no the state of a kind of situation representative " element current ≈ 0nA ", suppose that the state that the existence of this insignificant current flowing that causes due to sort circuit structure and the potential difference (PD) between two terminals of voltage-current converter returned to zero is corresponding.
The state that potential difference (PD) between two terminals of voltage-current converter is returned to zero (that is, the state of element current ≈ 0nA) represents specific component concentration=0% (or 0ppm) and element current ≈ 0nA.In this case, the element current measured value under the state being returned to zero in the potential difference (PD) between two terminals of voltage-current converter (that is, the state of element current ≈ 0nA) is corresponding with offset error.Therefore,, under the state being returned to zero in the potential difference (PD) between two terminals of voltage-current converter, can preferably offset correction values be calculated as to current correction value.
Utilize current embodiment of the present invention, via the first feedback network (the feedback network L1 in Fig. 4), the output of output circuit is input to and is applied voltage-setting circuitry with feedback form, and via the second feedback network (the feedback network L2 in Fig. 4), the voltage at the sensor side terminal place of voltage-current converter is input to and is applied voltage-setting circuitry with feedback form.Switchgear is arranged in the second feedback network of two feedback networks.In normal concentration, detect operating period, the first feedback network in two feedback networks enters into conducting state, to allow to apply voltage-setting circuitry, described in arranging via the output of the described output circuit of the first feedback network input with feedback form, applies voltage.In the operating period of calculating for the current correction value of correcting element electric current, only the second feedback network in two feedback networks enters into conducting state, to apply voltage-setting circuitry described in allowing, described in arranging via the sensor side terminal voltage of the voltage-current converter of the second feedback network input with feedback form, applies voltage.
Utilize this structure, the step of choosing suitably the feedback network that applies voltage-setting circuitry can be interrupted gas concentration detection operation temporarily, now, can calculate current correction value.
Utilize current embodiment of the present invention, at least one in voltage follower and in-phase amplifier circuit is arranged on to electric pathway, by this electric pathway, the sensor side terminal of voltage-current converter and apply voltage-setting circuitry and be electrically connected to each other.Switchgear is arranged at least one in voltage follower and in-phase amplifier circuit and applies in the path between voltage-setting circuitry.Utilize this structure, at least one and the outgoing side that applies voltage-setting circuitry of not having element current to flow through in voltage follower and in-phase amplifier circuit.This makes it possible to set up path at the sensor side terminal of voltage-current converter with in applying the electric pathway between voltage-setting circuitry, in this path, does not have element current to flow through.Utilization is arranged on the switchgear on this path, can prevent that this switchgear from adversely affecting element current.
Utilize current embodiment of the present invention, apply voltage-setting circuitry and comprise the operational amplifier with negative feedback part, and voltage-current converter is connected to the outgoing side of operational amplifier in the position in negative feedback part outside.Utilize this structure, the step of measuring the voltage at least sensor opposite side terminal place that is positioned at voltage-current converter allows measuring sensor electric current.In addition, lead-out terminal voltage that can control algorithm amplifier, i.e. the voltage at the sensor opposite side terminal place of voltage-current converter, thus the voltage that can make sensor opposite side terminal place increases or reduces with respect to the voltage at sensor side terminal place.In other words, can control the potential difference (PD) between two terminals of voltage-current converter.Therefore, this can allow the potential difference (PD) between two terminals of voltage-current converter returned to zero or be controlled to other different value.
Utilize current embodiment of the present invention, project organization, so that switchgear remains closed, is set to have the voltage of given potential difference (PD) (≠ 0) by the voltage that applies that applies voltage-setting circuitry with respect to the sensor side terminal voltage of voltage-current converter.Utilize this structure, the step that makes the potential difference (PD) of two terminal supports of voltage-current converter be arranged to the set-point except zeroing value can be set up the mobile state of given element current.That is, a kind of situation representative has the state of " element current=set-point (≠ 0) ".This causes under the state of " element current=set-point ", obtaining current correction value.
When the characteristic due to instant sensor control device changes while there is gain error, potential difference (PD) between two terminals of voltage-current converter is adjusted to at least two different magnitudes of voltage, to allow exporting calculated gains corrected value according to the circuit now existing.In this case, calculated gains corrected value in the following manner.
Utilize current embodiment of the present invention, when switchgear enters into closure state, the voltage that applies that applies voltage-setting circuitry is adjusted into the voltage that induces a plurality of potential difference (PD) with respect to the sensor side terminal voltage of voltage-current converter, thereby from output circuit, obtains output valve under voltage a plurality of states to be adjusted.Output valve to the output circuit obtaining under a plurality of states is made response, and correction value calculation device is calculated as current correction value by gain calibration value.
Utilize current embodiment of the present invention, when switchgear enters into closure state, under the first state, the voltage that applies that applies voltage-setting circuitry is adjusted into for inducing isoelectric the first voltage of tune with respect to the sensor side terminal voltage of voltage-current converter, and under the second state, the voltage that applies that applies voltage-setting circuitry is adjusted into for inducing the second voltage with respect to the given potential difference (PD) (≠ 0) of the sensor side terminal voltage of voltage-current converter.Output valve to the output circuit obtaining under the first and second states is made response, and correction value calculation device is calculated as current correction value by gain calibration value.
Utilize this structure, when having given potential difference (PD) between two terminals that make voltage-current converter, voltage generating portion allows the voltage that equals the potential difference (PD) between two terminals of voltage-current converter to be input to and to apply voltage-setting circuitry.Under the closure state of switchgear, allow that the voltage that equals the potential difference (PD) between two terminals of voltage-current converter is input to the step that applies voltage-setting circuitry and cause the appearance with respect to the given potential difference (PD) (≠ 0) of the sensor side terminal voltage of voltage-current converter.
In brief, utilize above-mentioned the present invention, voltage generating portion is connected to the input that applies voltage-setting circuitry as the structure that makes to produce between two terminals of voltage-current converter potential difference (PD).In this case, according to the output voltage of voltage generating portion, between two terminals of voltage-current converter, appearance potential is poor, and this makes it possible to two potential difference (PD) between terminal and is set to any rank.
Further, can be by the concentration adjustment of special component in measurement gas for example, to two or more benchmark concentrations (that is,, for detection of oxygen concentration stoichiometry state and the atmospheric condition in waste gas).In this case, after being adjusted to this benchmark concentration, the step of measuring sensor electric current makes it possible to utilize measured value separately to obtain gain error.The concentration adjustment of special component in measurement gas can not be arrived in another situation of two or more benchmark concentrations, effective way is to provide voltage generating portion and with permission, the voltage that equals two potential difference (PD) between terminal is input to and applies voltage-setting circuitry.That is, this method is very effective for the gas sensor control device of the NOx concentration for detection of in waste gas for example.
Utilize current embodiment of the present invention, in addition, correction value calculation device can preferably calculate current correction value when sensing element remains under state of activation.There is burning voltage in the portion of terminal office that is connected to this sensing element in this permission, so that can obtain the current correction value with larger precision.
Can suitably the gas sensor of following type will be applied to for realizing gas sensor control device of the present invention.That is, gas sensor can preferably include the sensing element consisting of solid state electrolysis plastid and the Unit first and second (pump unit and sensor unit) that are exposed to gas chamber.Each in Unit first and second consists of the pair of electrodes being formed on solid state electrolysis plastid.It is other that this first module is adjusted to given concentration scale by the amount of oxygen that enters into the measurement gas of measurement gas chamber, and second unit detects the special component of the measurement gas with the amount of oxygen after this first module is adjusted.Utilize gas sensor control device, the second unit electric current that voltage-current converter measurement produces in this second unit, so that second unit current measurement value to be provided, based on this second unit current measurement value, can calculate the concentration of special component.In this case, utilize the example of the concentration of the measured special component of this second unit to comprise the concentration of NOx except oxygen and HC etc.In this case, very weak for detection of the element current of related concentrations.For example, the element current for detection of the operation of NOx concentration is in nA (nanoampere) order of magnitude.At this on the one hand, utilize this structure with above-mentioned each feature, even if element current is very weak, also can suitably detect gas concentration.
Utilize gas sensor control device of the present invention, the gas sensor (sensing element) with above-mentioned Unit first and second can further preferably comprise the Unit the 3rd (watch-dog unit) for detection of the remaining oxygen concentration of measurement gas in measurement gas chamber.Utilize this gas sensor, Unit the second and the 3rd has the electrode forming with public electrode, from common driver circuit part, to this public electrode, applies voltage.In this case, this gas sensor control device comprises for measuring the second unit current detection circuit of the second unit electric current producing at second unit and for measuring the 3rd cell current testing circuit of the 3rd cell current producing in Unit the 3rd, and Unit the second and the 3rd is combined with switchgear.The output valve of the output circuit based on obtaining in the situation that utilizing switchgear by the second and the 3rd cell current testing circuit closure, second unit current detection circuit and the 3rd cell current testing circuit can calculate for proofreading and correct the current correction value of second unit electric current and for proofreading and correct the current correction value of the 3rd cell current.
Utilize this structure, disconnect separately or closed laying respectively at for second and the switchgear of the current detection circuit of Unit the 3rd, thereby make it possible to calculate separately the characteristic variations of current detection circuit (circuit error) separately.With switchgear is arranged on for second with the drive circuit part of the 3rd units shared in structure compare, this structure makes it possible to higher accuracy computation current correction value.
Further, can preferably provide failure determination device, for the current correction value for correcting element electric current based on from correction value calculation device, determine at least one fault occurring at sensing element and sensor circuit.That is, during breaking down, have risk at least one of sensing element and sensor circuit, this is because the current correction value of calculating in the manner described above has impossible value (utilize and proofread and correct indeterminable value).Therefore, can determine by carry out fault by current correction value.
Further, can preferably provide voltage to apply interrupting device, while there is fault for determining at failure determination device, interrupt being applied to the voltage of sensing element.This has suppressed, when fault occurs, sensing element is applied to the adverse effect to sensing element that voltage causes continuously, thereby protects this sensing element.
Utilize another embodiment of the present invention, the gas sensor that is connected to gas sensor control device comprises sensing element, this sensing element consists of solid state electrolysis plastid and the pair of electrodes being formed on this solid state electrolysis plastid, wherein when receiving the voltage being applied in this pair of electrodes, according to the concentration of special component in measurement gas and producing component electric current.Utilize this gas sensor control device, utilize voltage-current converter measuring sensor electric current and will utilize the measurement result output of the measured element current of this voltage-current converter as the element current measured value from output circuit.Further, in the situation that exist from the voltage that applies that applies voltage-setting circuitry, the element current measured value based on from output circuit output calculates the concentration (oxygen concentration and NOx concentration etc.) of special component.
Utilize the present embodiment, switchgear (on-off circuit 71 as shown in Figure 4) is connected to and in electric pathway, there is no the mobile path of element current, by this electric pathway, the sensor side terminal of voltage-current converter with apply voltage-setting circuitry and be electrically connected to each other.When switchgear cuts out, the potential difference (PD) between two terminals of voltage-current converter is returned to zero, and detects in this case the electromotive force of sensing element.Then executable operations is to determine the fault at least one of sensing element and sensor circuit based on detected electromotive force.In addition, when detecting gas concentration based on element current measured value, can instantaneous Closing Switch device to detect electromotive force.
Utilize this structure, by the potential difference (PD) between two terminals of voltage-current converter is returned to zero, can set up a kind of mobile state of element current that do not have, that is, and the state of element current ≈ 0nA, and can suitably detect the electromotive force of sensing element.Now, if sensing element runs into fault, such as infringement or activity is not enough etc. or such as other faults such as sensor circuit disconnections, can not obtain suitable sensor electrical kinetic potential value.This makes it possible to carry out fault based on sensor electrical kinetic potential and determines.
Utilize the present embodiment, switchgear is arranged on and is not had on the mobile path of element current.This can be avoided causing due at switchgear, such as the semiconductor switching device of resistor etc., on the inconvenience of error of the element current measured value that causes of the leakage current responded to.Especially, when measuring similar NOx and detect the weak element current of electric current, due to the existence of switchgear, in current measurement value, occur that error is possible.This error causes strengthening detecting the adverse effect of gas concentration result.Yet, can avoid this inconvenience.
Utilize above-mentioned the present embodiment, can correctly determine the fault the disconnection producing in sensor, make to minimize detecting the adverse effect of the precision of gas concentration simultaneously.
Further, the state of the potential difference (PD) " by returning to zero " between two of voltage-current converter terminals is that 0nA or the state that approaches 0nA are corresponding with the electric current of the sensing element of flowing through.In this case, actual circuit structure is comprised of many circuit components and owing to there being such circuit component, the insignificant electric current actual circuit structure of flowing through.Strictly say, although there is no the state of a kind of situation representative " element current ≈ 0nA ", suppose that the state of the existence of this insignificant current flowing that causes due to sort circuit structure and the potential difference (PD) " by returning to zero " between two terminals of voltage-current converter is corresponding.
Can be by using this following structure that the potential difference (PD) between two terminals of voltage-current converter is returned to zero.; gas sensor control device preferably can be arranged in this structure; so that when switchgear is closed; in backfeed loop, the sensor side terminal voltage of voltage-current converter is input to and applies voltage-setting circuitry, to allow applying the determined voltage that arranges of voltage-setting circuitry by this, equal sensor side terminal voltage.
As the method for detecting sensor electromotive force, can when switchgear is closed, with the sensor side terminal voltage of voltage-current converter, preferably detect the electromotive force of sensing element.Alternately, when switchgear is closed, measure voltage and the executable operations on the plus end of sensing element and negative terminal, located and with the difference based between measuring voltage value, detect the electromotive force of sensing element.
Utilize any of above-mentioned this structure, can suitably detect electromotive force.Yet, use the step of the difference between the plus end of sensing element and the measuring voltage value of negative terminal to make it possible to detect reliably electromotive force with higher precision.
Utilize the present embodiment, can preferably the sensor side terminal of voltage-current converter be connected to reference potential part (for example take ground connection as example) via bias resistor.In brief, when the fault such as disconnecting etc. occurs, do not generate sensor electrical kinetic potential, cause uncertain circuit output.Utilize this result, even if sensor electrical kinetic potential does not exist, bias resistor also allows the sensor side terminal voltage of voltage-current converter to be maintained at given voltage.Therefore, even if electromotive force does not exist, also can make circuit stable output, using and sensor electrical kinetic potential can be detected as fault value.
Utilize the present embodiment, the first feedback network (as the feed back input electric pathway L1 in Fig. 4) and the second feedback network (as the feed back input electric pathway L2 in Fig. 4) can be preferably provided, wherein, this first feedback network causes the output of output circuit to be imported in backfeed loop applying voltage-setting circuitry and this second feedback network to cause the sensor side terminal voltage of voltage-current converter to be output in backfeed loop applying voltage-setting circuitry.In these two kinds of feedback networks, the second feedback network comprises switchgear.In normal concentration, detect operating period, only the first feedback network of these two feedback networks enters into conducting state and according to the output setting of the output circuit of inputting via this first feedback network at backfeed loop, applies voltage to allow applying voltage-setting circuitry.Further, in the operating period of detecting electromotive force, only the second feedback network in two feedback networks enters into conducting state to allow to apply voltage-setting circuitry according to arranging and apply voltage via the sensor side terminal voltage of the voltage-current converter of the second feedback network input at backfeed loop.In this case, the potential difference (PD) between two of voltage-current converter terminals is returned to zero.
Utilize this structure, suitably make feedback network be switched to apply the step of voltage-setting circuitry that gas concentration is detected and interrupted temporarily, thus the electromotive force of detecting sensor.
Utilize the present embodiment, at least one in voltage follower and in-phase amplifier circuit is arranged in electric electric pathway, by this electric pathway, and the sensor side terminal of voltage-current converter and apply voltage-setting circuitry and be electrically connected to each other.Switchgear is arranged at least one in voltage follower and in-phase amplifier circuit and applies in the path between voltage-setting circuitry.Utilize this structure, there is no element current flows through in voltage follower or in-phase amplifier circuit at least one.This makes it possible to provide and there is no element current flow passage at the sensor side terminal of voltage-current converter and in applying the electric pathway between voltage-setting circuitry.In addition, in this path, provide switchgear to prevent that this switchgear from adversely affecting element current.
Utilize the present embodiment, apply voltage-setting circuitry and can preferably include and there is the operational amplifier of negative feedback part and voltage-current converter be preferably connected to the outgoing side of operational amplifier at the outer fix place of negative feedback part.Utilize this structure, the step of the voltage of the relative terminal of at least sensor of measuring voltage-current converter can be detected element current.In addition lead-out terminal voltage that can control algorithm amplifier, the i.e. voltage at the relative terminal of the sensor of voltage-current converter place.For sensor side terminal voltage, this can increase or reduce sensor opposite side terminal voltage.In other words, can control the potential difference (PD) between two terminals of voltage-current converter.Therefore, this can make the potential difference (PD) between two terminals of voltage-current converter be returned to zero.
Utilize the present embodiment, terminal voltage measuring apparatus can be preferably provided, for measuring the voltage of the portion of terminal office of each self-electrode that is connected to sensing element.Further, not only can based on electromotive force preferably do be out of order definite, and can based in sensing element and sensor circuit at least one and based on terminal voltage separately and preferably do be out of order definite.This causes detecting such as puncturing, the fault of activity deficiency and disconnection etc. and can detect other fault such as the electrode grounding short circuit of power shortage and sensing element.
Utilize the present embodiment, can preferably provide voltage to apply interrupting device, for when make exist fault really Interruption to sensing apparatus applying of voltage be set.This eliminates because continuous first sensing element when breaking down applies the adverse effect to this sensing element that voltage causes, thereby this sensing element is advantageously protected.
Utilize the present embodiment, can preferably in the situation that sensing element is in activity state, carry out electromotive force and detect.That is, at for example gas sensor, between the starting period, this sensing element is risen to given activity temperature to be in the state of complete activity, subsequently detecting sensor electromotive force suitably.Utilize the present invention, can make the defect of the detection electromotive force that the inactivity (that is, at lower temperature) by sensing element causes minimize.This makes it possible to carry out fault detect with larger precision.
Utilize the present embodiment, can preferably gas sensor control device be applied in above-mentioned gas sensor.That is, gas sensor comprises the sensing element with the Unit first and second that are exposed to gas chamber.Each in Unit first and second consists of the pair of electrodes being formed on solid state electrolysis plastid.This first module is adjusted to given concentration rank by the amount of oxygen that enters into the measurement gas of measurement gas chamber, and second unit detects the special component (NOx concentration) of the measurement gas with the amount of oxygen after this first module is adjusted.Utilize gas sensor control device, voltage-current converter is measured the element current in present second unit.In this case, utilize the measured special component of this second unit to comprise the concentration of NOx except oxygen and HC etc., and very weak for detection of the element current of this concentration.For example, element current while, detecting NOx concentration is in nA (nanoampere) order of magnitude.Utilize each above-mentioned property feature, even if element current is very weak, still can suitably detect gas concentration.
Utilize the present embodiment, preferably the oxygen concentration in measurement gas chamber is in and represents given concentration level other detects compared with carrying out electromotive force in other situation of low oxygen level.That is, at gas sensor for example between the starting period, when making first module suitably discharge too much oxygen from measurement gas chamber, detecting sensor electromotive force suitably.Therefore, can eliminate the defect in the caused detection electromotive force of excessive oxygen (oxygen is excessive) being present in measurement gas chamber.This makes it possible to carry out fault detect with larger precision.
Can recognize, the remaining oxygen concentration in measurement gas chamber incrementally changes so that the electromotive force of second unit changes according to remaining oxygen concentration.Utilize the present embodiment, therefore, can preferably detect be present in measurement gas chamber remaining oxygen concentration and according to being present in the detected remaining oxygen concentration in measurement gas chamber, fault determined value is set to variable rank.Then, based on fault determined value and detected electromotive force, carry out about at least one the fault in sensing element and sensor circuit and determine.Therefore,, even if the remaining oxygen concentration in measurement gas chamber incrementally changes, also can realize with higher precision fault and determine.
Accompanying drawing explanation
These and other feature of the present invention and advantage will become apparent by the illustrated following description of accompanying drawing, wherein:
Fig. 1 means according to the sectional view of the gas sensor control device of the embodiment of the present invention, this gas sensor control device is applied in the gas sensor that comprises NOx sensor and NOx sensor circuit, and the element internal structure of NOx sensor has been described simultaneously;
Fig. 2 means the block scheme of the profile of the NOx sensor circuit shown in Fig. 1;
Fig. 3 means the circuit structure diagram of the sensor-unit/watch-dog shown in Fig. 2-unit drive circuit part;
Fig. 4 means the circuit structure diagram of the Is testing circuit part shown in Fig. 2;
Fig. 5 means the circuit structure diagram of the sensor-unit/watch-dog shown in Fig. 2-cell protection circuit part;
Fig. 6 means the process flow diagram of the calculation routine for sensor output calibration value that will be carried out by the microcomputer shown in Fig. 1;
Fig. 7 A means the figure of relation between sensor current Is and NOx concentration;
Fig. 7 B means the figure of relation between watch-dog cell current Im and NOx concentration;
Fig. 7 C means the figure of relation between offset error (Is-Im) and NOx concentration;
Fig. 8 means the process flow diagram of the fault detect routine that will be carried out by the microcomputer shown in Fig. 1;
Fig. 9 A is the circuit structure diagram of the Is testing circuit part of gas sensor control device according to another embodiment of the present invention;
Fig. 9 B means the frequency dependent result to the impedance of sensor unit when applying alternating voltage with change frequency;
Fig. 9 C means the oscillogram of the mode of operation of sensor unit;
Figure 10 means the process flow diagram of the calculation routine for sensor output calibration value that will partly be carried out by the Is testing circuit of the second embodiment shown in Fig. 9;
Figure 11 A means the graph of a relation between sensor unit electric current I s and NOx concentration, and shows gain error;
Figure 11 B means the graph of a relation between watch-dog cell current Im and NOx concentration, and shows gain error;
Figure 11 C means the graph of a relation between offset error (Is-Im) and NOx concentration, and shows gain error;
Figure 12 is the circuit structure diagram of the Is testing circuit part of gas sensor control device according to another embodiment of the present invention;
Figure 13 means the sectional view of gas sensing element of the first modification of the gas sensing element shown in Fig. 1;
Figure 14 is the sectional view along the gas sensing element of the A-A line drawing in Figure 13;
Figure 15 is the sectional view along the gas sensing element of the B-B line drawing in Figure 13 and Figure 14;
Figure 16 means the sectional view of the gas sensing element of the first modification that is connected to NOx sensor circuit, and wherein this NOx sensor circuit comprises sensor circuit, pump circuit and monitor circuit;
Figure 17 means the sectional view of gas sensing element of the second modification of the gas sensing element shown in Fig. 1;
Figure 18 is the sectional view along the gas sensing element of the C-C line drawing in Figure 17;
Figure 19 is the sectional view along the gas sensing element of the D-D line drawing in Figure 17 and Figure 18;
Figure 20 means the sectional view of gas sensing element of the 3rd modification of the gas sensing element shown in Fig. 1;
Figure 21 is the sectional view along the gas sensing element of the E-E line drawing in Figure 20;
Figure 22 is the sectional view along the gas sensing element of the F-F line drawing in Figure 20 and 21;
Figure 23 means the sectional view of gas sensing element of the 4th modification of the gas sensing element shown in Fig. 1;
Figure 24 is the sectional view along the gas sensing element of the G-G line drawing in Figure 23;
Figure 25 is the sectional view along the gas sensing element of the H-H line drawing in Figure 23 and Figure 24;
Figure 26 means the sectional view of gas sensing element of the 5th modification of the gas sensing element shown in Fig. 1;
Figure 27 is the sectional view along the gas sensing element of the I-I line drawing in Figure 26;
Figure 28 is the sectional view along the gas sensing element of the J-J line drawing in Figure 26 and Figure 27;
Figure 29 means the sectional view of gas sensing element of the 6th modification of the gas sensing element shown in Fig. 1;
Figure 30 is the sectional view along the gas sensing element of the K-K line drawing in Figure 29;
Figure 31 is the sectional view along the gas sensing element of the L-L line drawing in Figure 29 and Figure 30;
Figure 32 means the sectional view of gas sensing element of the 7th modification of the gas sensing element shown in Fig. 1;
Figure 33 is the sectional view along the gas sensing element of the M-M line drawing in Figure 32;
Figure 34 is the sectional view along the gas sensing element of the N-N line drawing in Figure 32 and Figure 33;
Figure 35 means the sectional view of gas sensing element of the 8th modification of the gas sensing element shown in Fig. 1;
Figure 36 is the sectional view along the gas sensing element of the P-P line drawing in Figure 35; And
Figure 37 is the sectional view along the gas sensing element of the Q-Q line drawing in Figure 35 and Figure 36.
Embodiment
Now, describe below with reference to the accompanying drawings the gas sensor control device of each embodiment according to the present invention in detail.Yet, by the present invention be understood to these embodiment of being not limited to the following describes and also can in conjunction with other known technology or with described known technology have equivalent function other technology realize technological concept of the present invention.
In the following description, should be appreciated that, such as " right side ", " left side ", " cardinal extremity part ", " fore-end ", " top ", " bottom ", " above ", the term of " below ", " above ", " below ", " sensor side terminal ", " the opposite side terminal of sensor ", " sensor side terminal voltage ", " the opposite side terminal voltage of sensor " etc. is facilitate word and should not be understood to restricted term.
As used herein, term " sensor side terminal " refers to a terminal of the current-voltage converter of a position that is arranged on close sensor unit, and term " the opposite side terminal of sensor " refers to the another terminal of this current-voltage converter, that is, be arranged on the terminal of the another position relative with sensor unit.Similarly, term " sensor side terminal voltage " refers to the terminal voltage at a terminal place that appears at current-voltage converter, and term " the opposite side terminal voltage of sensor " refers to the terminal voltage at the another terminal place of current-voltage converter.
Now, with reference to accompanying drawing, describe gas sensor controller according to an embodiment of the invention in detail.
Below with reference to NOx concentration detection system, the present embodiment is described, the NOx sensor on the gas outlet of engine is onboard installed in this NOx concentration detection system utilization, this NOx sensor is set and so that the output transmitting from this NOx sensor is made to response, detects the NOx concentration of waste gas.Further, on car, engine can comprise for example diesel engine.This diesel engine has gas outlet, on this gas outlet, carries off-gas cleaning equipment, and this off-gas cleaning equipment comprises NOx cleaning catalyst (catalyzer and selectivity that NOx blocks minimizing type reduce catalyzer etc.).The fault diagnosis of off-gas cleaning equipment is carried out in output based on NOx sensor.This NOx sensor is installed to transmit this output on the gas outlet in the downstream area of NOx cleaning catalyst.To making response from the output of NOx sensor to calculate the NOx concentration (NOx purifying rate) of NOx cleaning catalyst.If find that resulting concentration surpasses given fault determined value, makes the failed diagnosis of NOx cleaning catalyst.
First, below with reference to the Fig. 1 in accompanying drawing, describe the gas sensing element 10 that forms NOx sensor in detail.
As shown in Figure 1, sensing element 10 adopts the structure of so-called lamination (stack) type with inner structure as shown in Figure 1.Should be appreciated that horizontal direction in Fig. 1 represents the longitudinal direction of sensing element 10.Sensing element 10 has the representation element cardinal extremity part right side of (being suitable for being installed on gas outlet) and the right side of representation element fore-end.
Sensing element 10 has three cellular constructions that comprise pump unit, sensor unit and watch-dog unit.Press stacking these unit of structure to form assembly.In addition, with pump unit class seemingly, watch-dog unit has from the function of measurement gas discharge oxygen, and thereby, this watch-dog unit is commonly called auxiliary pump unit or the second pump unit.
Utilize sensing element 10, the first and second electrolyte bodies 11 and 12 by make and form the structure of similar thin slice such as the oxygen ion conduction material of zirconia etc.The first and second electrolyte bodies 11 and 12 are through dividing plate 13 and stacking to be spaced apart from each other to set a distance each other, and this dividing plate 13 is by making such as the insulating material of aluminium oxide etc.Wherein, the first electrolyte body 11 being arranged in upper area has the fore-end that is formed with waste gas inlet entrance 11a, via this waste gas inlet entrance 11a, the waste gas filling the air in the fore-end peripheral region of gas sensing element 10 is directed into the first chamber 14 limiting between the first and second electrolyte bodies 11 and 12.This first chamber 14 is communicated with the second chamber 16 via valve portion 15, and wherein this second chamber 16 is limited between the first and second electrolyte bodies 11 and 12, and valve portion 15 is between the first and second chambers 14 and 16.The first electrolyte body 11 has top surface, this top surface comprise be provided with for waste gas is extracted the first chamber 14 and from the porous diffusion layer 17 of these the first chamber 14 discharging waste gas half and be provided with second half of insulation course 19 with sunk part 19a, this sunk part 19a is for limiting the plasmas channel 18 as reference gas compartment.
Further, the second solid state electrolysis plastid 12 has basal surface, is provided with the insulation course 21 with sunk part 21a on it, and this sunk part 21a is used for limiting plasmas channel 22.Well heater (calandria) 23 is embedded in insulation course 21 for heating whole sensing element 10.Utilize this structure, well heater 23 heat pump unit 31, watch-dog unit 34 and sensor unit 35.This contributes to activate these unit 31,34 and 35.From external power source (not shown) to well heater 23, provide electric power to generate heat energy.
The the second solid state electrolysis plastid 12 being arranged in lower region has the pump unit 31 arranging towards the first chamber 14.This pump unit 31 is for the oxygen of waste gas being directed in this first chamber 14 or discharging this oxygen, so that remaining oxygen concentration is adjusted to given concentration in this first chamber 14.This pump unit 31 comprises that a pair of top electrode 32 and bottom electrode 33, the second solid state electrolysis plastids 12 are arranged between these two electrodes.Top electrode 32 towards the first chamber 14 is used as the nonactive electrode of NOx (electrode that is difficult to decomposing N Ox).31 pairs of this pump unit voltage applying through electrode 32 and 33 is made response and is worked so that the oxygen being present in this first chamber 14 is decomposed and is discharged into plasmas channel 22 by electrode 33.
Further, the first solid state electrolysis plastid 11 being arranged on upside has cardinal extremity part, and this base end part divides and is formed with watch-dog unit 34 and sensor unit 35.After pump unit 31 discharge remaining oxygens, this watch-dog unit 34 produces and depends on the electromotive force of remaining oxygen concentration or make response and generate electric current output applying voltage in the second chamber 16.The gas of sensor unit 35 based on being present in this second chamber 16 detects NOx concentration.
Be arranged on and column position watch-dog unit 34 close to each other and sensor unit 35 comprise the electrode 36 that arranges in the face of the second chamber 16 and 37 and the public electrode 38 that arranges in the face of plasmas channel 18.That is, the version of the first electrolyte body 11 and electrode 36 and public electrode 38 is taked to comprise in watch-dog unit 34, and wherein electrode 36 and public electrode 38 are arranged in relative position and middle intervention has the first electrolyte body 11.Equally, sensor unit 35 takes to comprise the version of the first electrolyte body 11 and electrode 37 public electrodes 38, and wherein electrode 37 and public electrode 38 are arranged in relative position and middle intervention has the first electrolyte body 11.The electrode 36 of watch-dog unit 34 (being arranged on towards the position of the second chamber 16) is by do not have activated noble metal such as Au-Pt to make to NOx.The electrode 37 of sensor unit 35 (being arranged on towards the position of the second chamber 16) is by the activated noble metal such as platinum Pt and rhodium Rh etc. of NOx is made.Although for convenience's sake, Fig. 1 show be arranged on respect to waste gas streams to the place ahead and rear the watch-dog unit 34 and the sensor unit 35 that with structure side by side, arrange, but should be appreciated that, in fact, watch-dog unit 34 and sensor unit 35 can be arranged in be equal to waste gas streams to position.
Here, sensing element 10 longitudinally on pump placed side by side unit 31, watch-dog unit 34 and sensor unit 35.Therefore, this pump unit 31 is positioned at the leading section office of sensing element 10, and this watch-dog unit 34 and sensor unit 35 are positioned at the cardinal extremity part (being suitable for being installed on gas outlet) of sensing element 10 and locate.
Utilize the sensing element 10 of above-mentioned this structure, through porous diffusion layer 17 and waste gas inlet entrance 11a, waste gas is directed to the first chamber 14.When waste gas is neighbouring by pump unit 31, pump unit is applied to voltage V pbe applied to the two ends of pump cell electrode 32 and 33.During applying this voltage, there is decomposition reaction so that pump unit 31 extracts or discharge oxygen according to the oxygen concentration in the first chamber 14.When this occurs, towards the first pump cell electrode 32 of the first chamber 14, by the nonactive electrode of NOx, formed.Therefore, the NOx of pump unit 31 in can not waste gas decomposition, and only allow oxygen to be decomposed and be discharged into plasmas channel 22 from electrode 33.Utilize this function of pump unit 31, the first chamber 14 is maintained in the situation with given low oxygen concentration.
By near the gas (oxygen concentration is conditioned) pump unit 31, flow into the second chamber 16, make watch-dog unit 34 generate output according to remaining oxygen concentration in gas.From watch-dog unit power supply V mwhen applying given watch-dog unit to the two ends of watch- dog cell electrode 36 and 38 and applying voltage, using the output detections of watch-dog unit 34 as watch-dog cell current I m.Further, from sensor unit power supply V sto sensor unit electrode 37 and 38, apply given sensor unit voltage and allow the NOx in gas be decomposed and reduce, resulting oxygen is discharged into plasmas channel 18 via electrode 38.When this occurs, electric current (sensor unit electric current I s) sensor unit 35 of flowing through, thereby detect the NOx concentration in waste gas.
For this reason, sensing element 10 is connected to NOx sensor circuit 40.This NOx sensor circuit 40 comprises as microcomputer 41 and the control circuit part (will be described with reference to figure 2 below) of carrying out sensor control subject.This microcomputer 41 and control circuit are partly controlled each voltage, comprising: be applied to the electrode 32 of pump unit 31 and the pump cell voltage V at 33 two ends p; Be applied to the electrode 36 of watch-dog unit 34 and the watch-dog cell voltage V at 38 two ends mand be applied to the electrode 37 of sensor unit 35 and the sensor unit voltage V at 38 two ends s.Microcomputer 41 is sequentially applied with the various measured values about pump cell current Ip, watch-dog cell current Im and sensor unit electric current I s, and according to the measured value of these parameters, this microcomputer 41 calculates oxygen concentration and NOx concentration.
Fig. 2 means the block scheme of the profile of NOx sensor circuit 40.NOx sensor circuit 40 not only comprises the various circuit shown in figure, and comprises for brief description unshowned heater driver circuit in Fig. 2.
As shown in Figure 2, NOx sensor circuit 40 have be connected to pump unit 31 electrode 32 and 33 plus end PS+ and negative terminal PS-, be connected to watch-dog unit 34 and sensor unit 35 public electrode 38 public terminal COM+ and be connected to watch-dog unit 34 and negative terminal MS-and the SS-of the electrode 36 of sensor unit 35 and 37.
The plus end PS+ that pump unit drive circuit part 42 is connected to pump unit 31 will be applied to pump unit 31 pump unit to arrange changeably applies voltage.Ip testing circuit part 43 is connected to the negative terminal PS-of pump unit 31, for detection of pump cell current Ip.Pump unit drive circuit part 42 comes control pump unit to apply voltage according to the pump cell current Ip that utilizes Ip testing circuit part 43 to detect.The pump cell current Ip that utilizes Ip testing circuit part 43 to detect is sequentially input to microcomputer 41.
Further, the public terminal COM+ of positive potential side that sensor-unit/watch-dog-unit drive circuit part 44 is connected to sensor unit 35 and watch-dog unit 34 is to apply common electric voltage to it.The negative terminal SS-and the MS-that Is testing circuit part 45 and Im testing circuit part 46 are connected to sensor unit 35 and watch-dog unit 34, be respectively used to detection sensor unit electric current I m and watch-dog cell current Im.Is testing circuit part 45 and Im testing circuit part 46 are connected to microcomputer 41.Is testing circuit part 45 and Im testing circuit part 46 are calculated according to sensor unit electric current I s and measured current measurement value VS1 and the VM1 of monitoring unit electric current I m, and this current measurement value VS1 and VM1 are sequentially input to microcomputer 41.In addition, Is testing circuit part 45 and Im testing circuit part 46 are at terminal COM+, SS-and MS-place measurement terminal voltage separately, and this terminal voltage is sequentially applied to microcomputer 41.
Sensor-unit/watch-dog-cell protection circuit part 48 is connected to sensor-unit/watch-dog-unit drive circuit part 44, for interrupting, to the voltage of watch-dog unit 34 and sensor unit 35, applies during breaking down etc., to protect this watch-dog unit 34 and this sensor unit 35.
Each circuit part that forms NOx sensor circuit 40 parts will be described in detail below.Yet, utilizing the present embodiment, pump unit 31 has circuit structure same as the prior art, therefore, has omitted the details of pump unit drive circuit part 42 and Ip testing circuit part here.
Fig. 3 is the circuit structure diagram of sensor-unit/watch-dog-unit drive circuit part 44.In Fig. 3, the voltage divider resistance circuit 51 that comprises two resistors is connected to constant pressure source (being in constant voltage Vcc) and dividing potential drop VX1 is applied to "+" input terminal of operational amplifier 52.This operational amplifier 52 has lead-out terminal, and public terminal COM+ is connected to this lead-out terminal via on-off circuit 53 and protective resistor 54.This operational amplifier 52 has negative feedback part, wherein provides protective resistor 55.Capacitor 56 is connected to public terminal COM+, for solving ESD (static discharge) problem.
Further, voltage follower 58 is connected to the node A1 in identical voltage with public terminal COM+ via protective resistor 57.Utilize sensor-unit/watch-dog-unit drive circuit part 44, using the Voltage-output at public terminal COM+ place as public terminal voltage Vcom.
On-off circuit 53 is taked such version: the voltage from sensor-unit/watch-dog-cell protection circuit part 48 input is applied to look-at-me SG1 and make response and switch on and off (closed or open), this will be described in detail hereinafter.Voltage is applied to look-at-me SG1 and via negative circuit 59, be applied to on-off circuit 53.Utilize the circuit of this structure, if SG1=" low " (in the situation that allowing voltage to apply), Closing Switch circuit 53 is to allow voltage divider resistance circuit 51 to apply dividing potential drop VX1 to public terminal COM+.In addition, if SG1=" height " (in the situation that interrupt voltage applies) opens this on-off circuit 53 to interrupt dividing potential drop VX1 applying to public terminal COM+.
Next the structure of Is testing circuit 45 is described with reference to Fig. 4.In Fig. 4, the negative terminal SS-of sensor unit 35 is connected to current-voltage converter 61 and the differential amplifier circuit 62 being connected in series.In this case, especially, current-voltage converter 61 is connected to for representing the outside (outside of feedback system) of negative feedback part of the output of the operational amplifier that forms differential amplifier circuit 62.This differential amplifier circuit 62 has "-" input terminal that is connected to "+" input terminal of resistor bleeder circuit 63 and is connected with negative feedback input electric pathway L1, and this resistor bleeder circuit 63 is suitable for utilizing two resistors to carry out dividing potential drop to constant voltage Vcc.
Further; in two terminals (node B1 and B2) of current-voltage converter 61; the node B 1 (being hereinafter referred to as " the sensor side terminal of current-voltage converter 61 ") that is connected to negative terminal SS-is connected to voltage follower 65 via protective resistor 64, and the lead-out terminal of this voltage follower 65 is connected to "+" input terminal of differential amplifier circuit 66.In addition, node B2 (being hereinafter referred to as " the sensor opposite side terminal of current-voltage converter 61 ") is connected to "-" input terminal of this differential amplifier circuit 66.Therefore, the current-voltage converter 61 if sensor unit electric current I s flows through, depends on sensor unit electric current I s, between two terminals of current-voltage converter 61 (that is, two node B1 and B2), has potential difference (PD).Utilize differential amplifier circuit 66 with given enlargement factor, this potential difference (PD) to be amplified, and subsequently using this potential difference (PD) output as sensor-cell current measured value VS1.
By for representing that sensor-cell current measured value VS of the output of differential amplifier circuit 66 is input to "-" input terminal of differential amplifier circuit 62 via negative feedback input electric pathway L1.In order more specifically to describe, this differential amplifier circuit 66 is as " " and differential amplifier circuit 62 is as " applying voltage-setting circuitry " for output circuit.The lead-out terminal of differential amplifier circuit 66 and differential amplifier circuit 62 "-" input terminal is connected to each other via negative feedback input electric pathway L1.On-off circuit 67 is arranged in negative feedback input electric pathway L1 to connect or disconnects (closed or open) electric pathway L1, this on-off circuit 67 be also connected with comprise resistor and capacitor for eliminating the LPF (low-pass filter) 68 of noise.Normal, detect in operation, on-off circuit 67 remains closed, thereby allows to represent that sensor-cell current measured value VS1 of the output of this differential amplifier circuit 66 is input to differential amplifier circuit 62 with feedback form.In addition, this on-off circuit 67 comprises such as take the semiconductor switch that transistor etc. is example (adopting identical structure with each in following each on-off circuit).
Voltage follower 65 generates the output voltage of the voltage (that is, the voltage on the negative terminal SS-of sensor unit 35) that is equal to node B1 place, and this output voltage is exported as sensor-unit terminal voltage VS2.
In addition, the lead-out terminal of voltage follower 65 and differential amplifier circuit 62 "+" input terminal is connected to each other via negative feedback input electric pathway L2, this negative feedback input electric pathway L2 is connected to on-off circuit 71, for connecting or disconnecting (closed or open) this negative feedback input electric pathway L2.In normal running, this on-off circuit 71 stays open, thereby allows to represent that sensor-cell current measured value VS2 of the output of this voltage follower 65 is imported into differential amplifier circuit 62 with feedback form.Here, this voltage follower 65 has the input impedance of increase and does not have element current to flow to this voltage according to the output of device 65.Therefore, negative feedback can be inputted to electric pathway L2 is appointed as and does not have the mobile element-current flowing of element current to forbid path.This on-off circuit 71 is arranged on element-current flowing to be forbidden in path L2.
The on- off circuit 67 and 71 that is connected to negative feedback input electric pathway L1 and L2 has such structure: the circuit switching signal SG2 with high or low level of slave microcomputer 41 transmission is made response and is switched on or switched off (closed or open).This circuit switching signal SG2 by former state be input to on-off circuit 67 and be input to on-off circuit 71 through negative circuit 72.Utilize the present embodiment, if SG2=" height ", Closing Switch circuit 67 and cut-off switch 71.Now, the negative feedback input electric pathway L1 that only negative feedback is inputted in electric pathway L1 and L2 enters into on-state.On the contrary, if SG2=" low ", cut-off switch circuit 67 and Closing Switch 71.Now, the negative feedback input electric pathway L2 that only negative feedback is inputted in electric pathway L1 and L2 enters into on-state.Make to disconnect disconnection and Closing Switch circuit 67 and 71 under the pattern contrary with closed sequential, thereby making one in only negative feedback input electric pathway L1 and L2 to enter into on-state.
When detecting in the normal operation period NOx concentration, when measuring according to the NOx concentration of waste gas during mobile sensor current Is, the microcomputer 41 circuit switching signal SG2s of output in high level.In this case, the output VS1 of differential amplifier circuit 66 is imported into "-" input terminal of differential amplifier circuit 62 via negative feedback input electric pathway L1.Then, according to the output VS1 of differential amplifier circuit 66, amplify the output of differential amplifier circuit 62.Now, s is larger for sensor unit electric current I, and VS1 is also larger in output, and the output that is simultaneously attended by differential amplifier circuit 62 reduces.
On the contrary, if the potential difference (PD) between two terminals of current-voltage converter 61 is returned to zero and flows through, the electric current of this current-voltage converter 61 is 0nA, and microcomputer 41 output low signals are as circuit switching signal SG2.This makes the output VS2 of voltage follower via negative feedback input electric pathway L2, be imported into "+" input terminal of differential amplifier circuit 62.Now, the voltage that this differential amplifier circuit 62 is located the terminal being oppositely arranged with sensor of current-voltage converter 61 (node B2) is adjusted to the identical voltage of voltage of the current-voltage converter 61 of locating with the terminal (node B1) of more close this sensor.This is returned to zero potential difference (PD) between two terminals of current-voltage converter 61 and has there is no the flow through resulting state (that is, being expressed as the state of electric current=0nA) of this current-voltage converter 61 of electric current.In this case, do not have the flow through state of current-voltage converter 61 of electric current to represent the state of NOx concentration=0ppm.If there is offset error, in output valve, there is take the deviation that this error is value.Therefore, may obtain offset error based on this output.
Further, from the existence of the low signal as the circuit switching signal SG2 output of microcomputer 41, cause not having the electric current state of current-voltage converter 61 of flowing through.Now, at the negative terminal SS-place of sensor unit 35, occur that its level depends on the voltage of sensor electrical kinetic potential, and measure this voltage as sensor-unit terminal voltage VS2.
In two terminals (node B1 and B2) of current-voltage converter 61, node B1 is connected to bias current resistor 75 and ESD (static discharge) protective condenser 76.That is other terminal that, bias current resistor 75 and esd protection capacitor 76 have the terminal of the sensor side terminal (B1) that is connected to current-voltage converter 61 and be connected to ground.Bias current resistor 75 has for example 1M Ω or larger resistance value.
Here, utilization is connected to the bias current resistor 75 of node B1 (the sensor side terminal of current-voltage converter 61), when in the situation that such as disconnect or element fracture fault exist while measuring electromotive force in the above described manner, can be set to fixed voltage by sensor-cell current measured value VS2.In other words, can obtain a value, for solving the fault of the electromotive force of representative sensor-cell current measured value VS2.That is, in the situation that such as disconnect or element fracture fault occur not having electromotive force to appear in sensor unit 35 and sensor-cell current measured value VS2 (voltage at node B1 place in accompanying drawing) is uncertain.Yet, utilization has the Is testing circuit part 45 of this structure that comprises bias current resistor 75, even in the non-existent situation of sensor electrical kinetic potential, still sensor-cell current measured value VS2 can be remained on to given voltage (this voltage depends on the resistance value of bias current resistor 75).Therefore, even if electromotive force does not exist, sensor-cell current measured value VS2 is also stable, and this can be with the form detecting sensor electromotive force of exceptional value.
Utilize current embodiment, further, bias current resistor 75 has the low potential side that is connected to ground.The present invention is not limited to such circuit and connects and can take a kind of structure, so that the low potential side of bias current resistor 75 is connected to the reference potential that is maintained at fixed voltage electromotive force.For example, other optional structure can comprise that bias current resistor 75 has the structure of the one end that is connected to power circuit and one section of structure that is connected to the circuit part of the given voltage of output of bias current resistor 75, and wherein the scope of this given voltage is between ground voltage and supply voltage.
Utilize the bias current resistor 75 provide according to this configuration, flow through bias current resistor 75 be attended by the magnitude of current being caused by the current-voltage converter 61 of flowing through and reduce of electric current.Therefore, Is testing circuit part 45 can be arranged in circuit structure, reason is that the flow through magnitude of current of current-voltage converter 61 of initial measurement allows the component of compensating measure electric current.
Im testing circuit part 46 has identical circuit structure with Is testing circuit part 45, redundant description and the description of therefore having omitted same section.That is, circuit as shown in Figure 4 also can be intactly as Im testing circuit part 46.As shown in Figure 2, microcomputer 41 outputs are for the circuit switching signal SG3 that is applied to Im testing circuit part 46 of watch-dog unit.When receiving circuit switching signal SG3, Im testing circuit part 46 is switched to select a kind of state from following two states:, from normal running, detect potential difference (PD) between the state of remaining oxygen concentration and two terminals of current-voltage converter returned to zero (according to circuit is cut to signal SG2 and is made response and the same way of executable operations) state (state of electric current=0nA).In addition, as shown in Figure 4, Im testing circuit part 46 is set and with output, replaces watch-dog-cell current measured value VM1 of sensor-cell current measured value VS1, output simultaneously replaces the watch-dog unit terminal voltage VM2 of sensor-unit terminal voltage VS2.In the situation that the potential difference (PD) between two terminals of current-voltage converter is returned to zero, can measure watch-dog unit electromotive force based on watch-dog unit terminal voltage VM2.
As shown in Figure 2, microcomputer 41 is applied with the sensor-cell current measured value VS2 exporting from Is testing circuit part 45 and the watch-dog-cell current measured value VS1 exporting from Im testing circuit part 46, based on above-mentioned value, microcomputer 41 calculates (Is-Im) value.Then, based on (Is-Im) value, microcomputer 41 further calculates the NOx concentration in waste gas.
Next, below with reference to Fig. 5, describe the structure of sensor-unit/watch-dog-cell protection circuit part 48 in detail.Sensor-unit/watch-dog-cell protection circuit part 48 detects power shortage or fault and ground short circuit or the fault of the positive potential side of present sensor unit 35 and watch-dog unit 34 and the circuit part (being connected to the circuit region of positive potential public terminal COM+ and negative terminal SS-and MS-) of this sensor unit 35 of negative potential side place and watch-dog unit 34.Utilize the present embodiment, sensor-unit/watch-dog-cell protection circuit part 48 is corresponding to " voltage applies interrupting device ".
In Fig. 5; sensor-unit/watch-dog-cell protection circuit part 48 is applied with from the public terminal voltage Vcom of sensor-unit/watch-dog-unit drive circuit part 44 outputs, from sensor-unit terminal voltage VS2 of Is testing circuit part 45 outputs and the watch-dog-unit terminal voltage VM2 exporting from Im testing circuit part 46.In addition the fault that, holding circuit part 48 is applied with slave microcomputer 41 transmission is determined signal SG4.Although will be described in detail belows, fault determines signal SG4; but in brief; fault determines that signal SG4 takes binary signal form; SG4=" height " for normal running and SG4=" low " when breaking down; further; to being applied to each input signal of sensor-unit/watch-dog-unit drive circuit part 44, make response, sensor-unit/watch-dog-cell protection circuit part 48 formation voltages apply stop signal SG1.This details will be described below.
Sensor-unit/watch-dog-cell protection circuit part 48 comprises 5 comparator circuit 81-85, and it operates in the following manner.
The first 81 pairs of comparator circuits public terminal voltage Vcom (being 4.4V in the normal operation period) and reference voltage V ref1 (for example, 4.6V) compare.In this case, in the normal operation period, Vcom < Vref1 and this first comparator circuit 81 provide " low " output.On the contrary, during breaking down, Vcom > Vref1 and this first comparator circuit 81 provide another " height " output.For example, if there is power shortage in the region that is connected to public terminal COM+, this first comparator circuit 81 generates " height " output.
Second 82 pairs of comparator circuits sensor-unit terminal voltage VS2 (being 4.0V in the normal operation period) and reference voltage V ref2 (for example, 3.8V) compare.In this case, in the normal operation period, a kind of situation represents that VS2 > Vref2 and this second comparator circuit 82 provide " low " output.On the contrary, during breaking down, another situation represents that VS2 < Vref2 and this second comparator circuit 82 provide another " height " output.For example, if there is ground short circuit in the region that is connected to negative terminal SS-, the second comparator circuit 82 generates " height " output.
The 3rd 83 pairs of comparator circuits watch-dog-unit terminal voltage VM2 (being 4.0V in the normal operation period) and reference voltage V ref3 (for example, 3.8V) compare.In this case, in the normal operation period, a kind of situation represents that VM2 > Vref3 and the 3rd comparator circuit 83 provide " low " output.On the contrary, during breaking down, another situation represents that VM2 < Vref3 and the 3rd comparator circuit 82 provide another " height " output.For example, if there is ground short circuit in the region that is connected to negative terminal MS-, the 3rd comparator circuit 83 generates " height " output.
The 4th 84 pairs of comparator circuits public terminal voltage Vcom and sensor-unit terminal voltage VS2 compare.In this case, in the normal operation period, Vcom > VS2 and the 4th comparator circuit 84 provide " low " output.On the contrary, during breaking down, Vcom < VS2 and the 4th comparator circuit 84 provide another " height " output.For example, if occur ground short circuit in the region that is connected to public terminal COM+ or occur power shortage at negative terminal SS-place, the 4th comparator circuit 84 generates " height " output.
The 5th 85 pairs of comparator circuits public terminal voltage Vcom and watch-dog unit terminal voltage VM2 compare.In this case, in the normal operation period, Vcom > VM2 and the 5th comparator circuit 85 provide " low " output.On the contrary, during breaking down, Vcom < VM2 and the 5th comparator circuit 85 provide another " height " output.For example, if occur ground short circuit in the region that is connected to public terminal COM+ or occur power shortage at negative terminal MS-place, the 5th comparator circuit 85 generates " height " output.
Although not shown in the accompanying drawings, the resistor voltage divider circuit consisting of two resistors is reference voltage V ref1 to each of Vref3 by constant voltage Vcc dividing potential drop.
The fault of the output of five comparator circuit 81-85 and slave microcomputer 41 outputs is determined to signal SG4 is input to OR circuit 86.In this case, if be applied to any in a plurality of input signals of OR circuit 86 in high level, this OR circuit 86 generates " height " signals and applies stop signal SG1 as voltage.If SG1=" height ", disconnect as mentioned above the commutation circuit 53 of sensor-unit/watch-dog-unit drive circuit 44, thereby interrupt voltage is to apply (referring to Fig. 3) of public terminal COM+.That is, the fault that probably sensor unit 35 and watch-dog unit 34 occur such as power shortage or ground short circuit, or alternatively, microcomputer 41 output faults are determined signal SG4.In this case, interrupt applying to the voltage of sensor unit 35 and watch-dog unit 34, thereby realize the effect of protecting these unit.More specifically, this has stoped excessive electric current flow through sensor unit 35 and watch-dog unit 34, thereby can suppress the infringement to sensing element.
The first operation of calculating sensor output offset and the second operation of detection failure by microcomputer 41, carried out are described now.Calculating operation about sensor output offset is the operation of carrying out during NOx concentration detecting, at the circuit based under this state, export to carry out the operating period of calculating output offset (the particularly offset correction values of the present embodiment), executable operations is to return to zero the potential difference (PD) between two terminals of the current-voltage converter in Is testing circuit part 45 and Im testing circuit part 46 temporarily.Further, the electromotive force of resulting sensor unit 35 or watch-dog unit 36 during terminal potential difference (PD) based at above-mentioned interim zeroing current-voltage converter, failure detection operations is for detection of the existence of the fault such as disconnection or element fracture and element activity deficiency etc. or do not exist.
First, below with reference to the process flow diagram shown in Fig. 6, describe the procedure routine for calculating sensor output offset in detail.And microcomputer 41 repeats the procedure routine shown in Fig. 6 with the given time cycle.Here described for calculating the sequence of offset correction values of the output valve (VS1) of Is testing circuit part 45.
In Fig. 6, at step S11, to whether making inquiry to calculate offset correction values in current sequential executable operations.Utilize the present embodiment, for section computing time of the offset correction values that will obtain, be set to 10 seconds and each 10 seconds of time lapse, to step S11, answer is "yes".Can preferably according to the speed that for example circuit temperature changes, be identified for the computation period of offset correction values.If the calculating sequential for offset correction values exists, operation proceeds to step S12, wherein whether the temperature of sensor unit 35 is risen to given activationary temperature (for example, 750 ℃) and makes inquiry.More specifically, time, the electric power amplitude that is applied to well heater or the impedance detection value relevant to this sensor unit 35 based on start passage from engine start determined the temperature propradation of sensor unit 35.
If the temperature of sensor unit 35 rises to given activationary temperature, operation proceeds to step S13, and wherein executable operations is to be switched to low level by the level of circuit switching signal SG2 from high level.This allows 45 pairs of conducting states (in the sequence L1 → L2 of the present embodiment) that are connected to feed back input electric pathway L1 and the L2 of differential amplifier circuit 62 of Is testing circuit part to switch.The electric current of this current-voltage converter 61 that makes to flow through is set to 0nA wittingly.At follow-up step S14, after circuit switching signal SG2 is switched to " low " level from " height ", carry out standby operation until realize stable output.
After standby operation carries out given interval, at step S15, executable operations is to read output VS1 and to calculate offset correction values Foff based on this VS1 value from differential amplifier circuit 66.In the present embodiment, VS1 value is converted into electric current so that offset correction values Foff to be provided in the given time.By offset correction values Foff be stored in alternate device (for example take EEPROM or backup RAM be example) in.In other words, offset correction values Foff be stored as to learning value in alternate device and suitably upgrade.
Afterwards, at step S16, circuit switching signal SG2 is switched to " high " state from " low " state.This permission is connected to differential amplifier circuit 62 by feed back input electric pathway L1, and is attended by the result that Is testing circuit part 45 is turned back to normal NOx concentration detected state.At subsequent step S17, by circuit switching signal SG2 after " low " state is switched to " high " state, carry out standby operation so that the stable output of Is testing circuit part 45.Then, after standby operation carries out given interval, restart normal NOx concentration and detect operation (at step S18).
By the offset correction values Foff calculating in the manner described above suitably for correcting sensor cell current Is (in the current conversion value of VS1), operating period this electric current by proceeding measurement to detect NOx concentration.That is, from the sensor unit electric current I s at NOx concentration operating period measurement gained, deduct offset correction values Foff, thus the sensor unit electric current after calculation correction (the sensor unit electric current=Is-Foff after correction).Then, the sensor unit electric current based on after proofreading and correct calculates NOx concentration.
In fact, executable operations to be to calculate offset correction values, and it is not only for Is testing circuit part 45 but also for Im testing circuit part 46, and by calculating NOx concentration by the offset correction values of these two testing circuit parts 45 and 46.In this case, from sensor unit electric current I s (measured value), deduct offset correction values for the sensor unit sensor unit electric current with calculation correction, and deduct offset correction values for the monitoring unit sensor unit electric current with calculation correction from watch-dog cell current Im (measured value).Then poor (the watch-dog cell current after the sensor unit electric current-correction after=correction) of the sensor unit electric current based on after proofreading and correct and the watch-dog cell current after correction calculates NOx concentration.
As shown in Figure 7 A, there is respectively offset error in the sensor unit electric current I s in NOx sensor circuit 40 and watch-dog cell current Im.In Fig. 7 A, term " sensor output " refers to that actual current value and the term " electric circuit inspection value " appearing on sensor element 10 refers to the measured value that utilizes the measured real sensor output of NOx sensor circuit (comprising Is testing circuit part 45 and Im testing circuit part 46).
In Fig. 7 A, electric circuit inspection value and sensor output increase linearly with the increase of NOx concentration.Between electric circuit inspection value and sensor output, there is offset error.
In Fig. 7 B, electric circuit inspection value is in the first watch-dog cell current Im and sensor output at the second watch-dog control cell current Im, and offset error is between these two current values.
In Fig. 7 C, electric circuit inspection value and sensor output increase linearly with the increase of offset error.Between electric circuit inspection value and sensor output, there is offset error.
In this case, executable operations is usingd to obtain to sensor and is exported relevant offset error as offset correction values, and it is used to correcting sensor cell current Is and watch-dog cell current Im respectively subsequently.This can suppress the precise decreasing that NOx concentration that the offset error about electric circuit inspection value causes is calculated.
Fig. 8 means to sensor unit electromotive force is made response and carried out the process flow diagram of the procedure routine of failure detection operations.Preferably, by microcomputer 41, with cycle preset time, repeat this procedure routine.
In Fig. 8, at step S21, to whether existing fault detect sequential to make inquiry.In the present embodiment, the fault detect cycle was set to for 0.5 second, and passed for 0.5 second at every turn, and the answer of step S21 is yes.If fault detect sequential exists, operation proceeds to step S22, wherein with the performed same way of step S12 to whether the temperature increase of sensor unit 35 for example, being made to inquiry to given activationary temperature (, 750 ℃).Further, at step S23, whether oxygen after the engine start is discharged by the chamber 14 and 16 from sensor element 10 and whether remaining oxygen concentration is in given low oxygen concentration and makes inquiry fully.Time based on for example passing from engine start is determined the emissions status of remaining oxygen.
If the answer of step S22 and S23 is yes, operation proceeds to step S24, wherein the circuit switching signal SG2 that outputs to Is testing circuit part 45 is switched to " low " level from " height ".This makes feed back input electric pathway L1 and L2 be switched (in the present embodiment, according to the order of L1 → L2) for differential amplifier circuit 62.The electric current of this current-voltage converter 61 that allows to flow through is set to 0mA wittingly.In subsequent step S25, after circuit switching signal SG2 is switched to " low " level from " height ", carry out standby operation until stable output.
After standby operation executed given interval, at step S26, executable operations to be to read public terminal voltage Vcom and sensor-unit terminal voltage VS2, based on these voltage, and the electromotive force of detection sensor unit 35.More specifically, from public terminal voltage Vcom (, measured electromotive force on the plus end of sensor unit) step that deducts sensor-unit terminal voltage VS2 (that is, on the negative terminal of sensor unit measured electromotive force) allows the electromotive force value 35 of calculating sensor unit 35.In addition, now, by the electromotive force value of sensor unit 35 be stored in alternate device (for example take EEPROM or backup RAM be example) in.
Subsequently, at step S27, whether detected electromotive force in step S26 is in predetermined normal range and makes inquiry.More specifically, to remain essentially in the electromotive force of thin poor state and sensor unit 35 are magnitudes of voltage of about 0.2V to the chamber of sensing element 10.Therefore, normal range is set to the scope (from the scope of 0.1V to 0.3V) at 0.2V ± 0.1V.Yet, consider that in the normal operation period it is 0.4V (=4.4-4.0V) that sensor unit applies voltage, normal range can be in the scope from 0.1V to 0.4V.
If electromotive force is in normal range, operation proceeds to step S28, if wherein such as disconnecting or the fault of element fracture etc. does not occur, make normal judgement.Further, if electromotive force, outside normal range, operates and proceeds to step S29, wherein the given number of times of the continuous appearance of the fault in electromotive force is inquired.If given number of times appears in fault in electromotive force continuously, operation proceeds to step S30, wherein when the fault of existence such as disconnection or element fracture etc., makes fault verification.
If make the judgement such as the fault appearance of disconnection or element fracture etc., with permission, the fault detection signal with " height " level outputed to sensor-unit/watch-dog-cell protection circuit part 48 in step S31 executable operations.
Subsequently, at step S32, executable operations is to be switched to " height " level by circuit switching signal SG2 from " low ".This feed back input electric pathway that is allowed for differential amplifier circuit 62 turns back to " L1 ", and is attended by the result that Is testing circuit part 45 is turned back to normal NOx concentration detected state.At subsequent step S33, after circuit switching signal SG2 is switched to " height " level from " low " in order, carry out standby operation so that stable output.After standby operation executed given interval, restart normal NOx concentration and detect operation (step S34).
Although not shown in the accompanying drawings, according to the similar sequence shown in Fig. 8 and according to mode same as described above, based on watch-dog-unit electromotive force, watch-dog unit 34 is set to carry out failure detection operations.For simplicity, make Im testing circuit part 46 enter into the state that the potential difference (PD) between two terminals of current-voltage converter is returned to zero, under this state, by usage monitoring device-unit, terminal voltage VM2 detects watch-dog cell voltage.Then, whether watch-dog unit electromotive force is in normal range to (scope from 0.1 to 0.3V or from 0.1 to 0.4V scope) and makes inquiry, based on this inquiry result, carry out fault verification.The fault that this allows watch-dog unit 34 to detect such as disconnection or element fracture etc.
In utilizing the present embodiment of this structure, gas sensor control device has each advantage of listing below.
The structure of design Is testing circuit part 45 (or Im testing circuit parts 46), to make it have the on-off circuit 71 being arranged in electric pathway, does not have cell current (sensor unit electric current or watch-dog cell current) this electric pathway of flowing through.Even if on-off circuit 71 remains closed, the output VS1 (or VM1) based on differential amplifier circuit 66, Is testing circuit part 45 is calculated offset correction values Foff.Utilize this structure, if there is offset error on NOx sensor circuit 40, can suitably obtain the offset correction values Foff that is equal to this offset error.
Especially, further, on-off circuit 71 is arranged in electric pathway (feed back input electric pathway L2), there is no element current this electric pathway (in other words, on-off circuit 71 is not arranged in the electric pathway that wherein leaves element current) of flowing through.This has been avoided in element current measured value, occurring error due to the leakage current causing in on-off circuit 71, more particularly, and due to the leakage current causing in the semiconductor switch such as resistor etc.That is,, even there is leakage current in on-off circuit 71, do not occur element current measured value adverse influence (even if adverse influence occurs, it can be ignored completely).When the weak NOx in the structure of measuring similar the present embodiment detects electric current, because the existence of on-off circuit causes the existence of error in current measurement value can cause NOx concentration to detect the adverse effect increasing, but can avoid this inconvenience.
Utilize this ability of correctly calculating offset correction values Foff and eliminating the adverse effect that the leakage current by the on-off circuit of flowing through causes, can be with larger accuracy detection NOx concentration.Further, even due to temperature characterisitic and in time deteriorated and occur output error in NOx sensor circuit 40, still can suitably solve output characteristics, can correctly detect NOx concentration.
Utilize the present embodiment, design this structure, even so that Closing Switch circuit 71 is so that the step permission of the potential difference (PD) zeroing between two terminals of current-voltage converter 16 still can be calculated offset correction values Foff by the output VS1 (or VM1) based on differential amplifier circuit 66 when potential difference (PD) remains zeroing state.This can correctly detect offset correction values Foff by the output VS1 (or VM1) based under the measuring state of NOx=0ppm.
When on-off circuit 71 remains closed, measure the terminal voltage (that is, public terminal voltage Vcom and sensor-unit terminal voltage VS2) on the positive and negative terminal of present sensor unit 35.Then, by the difference with between detected terminal voltage, detect the electromotive force (with the operation identical with watch-dog unit 34) of this sensor unit 35.This can accurately detect electromotive force.Yet, should be appreciated that, can only with sensor-unit terminal voltage VS2, detect electromotive force.
Is testing circuit part 45 (or Im testing circuit part 46) has the structure that on- off circuit 67 and 71 is separately positioned on two feed back input electric pathway L1 and L2.This allows to disconnect or Closing Switch circuit 67 and 71 according to the needs of the needs of the normal NOx concentration of detection or calculating offset correction values, thereby executable operations is suitably to change being in the feed back input electric pathway of conducting state.Utilize this structure, the step that suitably feed back input electric pathway is switched to differential amplifier circuit 62 can make NOx concentration detect by interim interruption to carry out the calculating about offset correction values.
Further, current-voltage converter 61 is connected to the outside of the negative feedback part of differential amplifier circuit 62, thereby may controls the output (voltage at the terminal place relative with sensor of this current-voltage converter 61) of this differential amplifier circuit 62.This can regulate with the degree changing the potential difference (PD) on two terminals of current-voltage converter 61.Therefore, can make the potential difference (PD) zeroing on two terminals of current-voltage converter 61.
Utilize Is testing circuit part 45, by the sensor side terminal of current-voltage converter 61 via bias current resistor 75 ground connection (being positioned at reference voltage part).Therefore, even without sensor electrical kinetic potential, exist, current-voltage converter 61 also can make due to the existence of bias current resistor 75 sensor side terminal voltage remain on given voltage.Therefore, even without electromotive force, exist, still can make circuit stable output in operation, using and sensor electrical kinetic potential can be detected as fault value.
Utilize the present embodiment, common driver circuit 44 is connected to the positive potential electrode of sensor unit 35 and watch-dog unit 34 and the negative potential electrode of sensor unit 35 and watch-dog unit 34 is connected respectively to Is testing circuit part 45 and Im testing circuit part 46, and on-off circuit 71 is also connected to Is testing circuit part 45 and Im testing circuit part 46.This allows current measurement value VS1 and VM1 based on obtaining from each testing circuit part 45 and 46 to calculate Is testing circuit part 45 and Im testing circuit part 46 offset correction values separately.This makes it possible to calculate for each unit the characteristic variations (circuit error) of each testing circuit part 45 and 46.Therefore, compare with implementation on-off circuit being arranged on when representing sensor-unit/watch-dog unit drive circuit 44 of unit 34 and 35 common driver circuit, can further increase the precision of the offset correction values that will calculate.
For calculating sensor output calibration value (referring to Fig. 6), project organization is so that the state of activity gets off to calculate offset correction values Foff in sensor unit 35 (or watch-dog unit 34) remains on temperature.This obtains offset correction values Foff with larger precision when can make circuit output remain on steady state (SS).
For calculating sensor output calibration value (referring to Fig. 6), similarly, can design to provide stand-by time interval to wait at the disconnection of on- off circuit 67 and 71 and the stable output of the transition period of closed procedure.This can obtain sensor-cell current measured value VS1 and circuit output keeps stable.Therefore, can obtain NOx concentration value and offset correction values Foff with larger precision.In addition, replace to wait for the given time, can carry out standby operation until the temporal variable quantity of VS1 (rate of change) reaches set-point or still less.
And then, Is testing circuit part 45 is taked following form: structure is set with the electromotive force (mode that detects electromotive force with Im testing circuit part 46 is identical) of detection sensor unit 35 when on-off circuit 71 is closed, carries out fault determine based on this electromotive force.This can correctly detect the fault of appearance when fault occurs with forms such as element fracture, activity defect and disconnections.
Sensor-unit/watch-dog-cell protection circuit part 48 is taked following version: wherein based on public terminal voltage Vcom; for representing that sensor-unit terminal voltage VS2 and the watch-dog unit terminal voltage VM2 of each terminal voltage of sensor unit 35 and watch-dog unit 3 carries out fault detect (that is, each terminal voltage based in reality designs this structure with output fault detection signal SG4).Can not only detect like this such as the fault of element fracture, activity defect and disconnection etc. but also can detect the fault such as power shortage and ground short circuit occurring at the electrode place of sensor unit 35 and watch-dog unit 34.
Utilize the opertaing device of the present embodiment, project organization is: if make determining of occurring such as the various faults that disconnect etc., output " height " signal determines that as fault signal SG4 will be applied to sensor unit 35 and watch-dog unit 34 voltage to allow sensor-unit/watch-dog-unit drive circuit part 44 to interrupt provides.This causes suppressing owing to applying continuously to unit the adverse effect to sensing element that voltage causes in fault between the apparition, can protect sensing element simultaneously.
When utilizing NOx sensor circuit 40, need supposition, first reason is that weak current flows, and for example, if there is various faults (, power shortage and ground short circuit, in particular at terminal place), can make excessive electric current this sensing element of flowing through.This causes damaging the adverse effect of the risk that sensing element and output characteristics change.In this respect, as mentioned above, in fault, between the apparition, interrupt applying to the voltage of unit, can protect this sensing element.
Design error failure detects routine (referring to Fig. 8) to be had the state of the activity of temperature and is starting the sensor electrical kinetic potential under the state that the oxygen in the chamber 14 and 16 of sensing element 10 after engine fully discharged to detect at sensor unit 35 (or watch-dog unit 34).This is detecting sensor electromotive force correctly, and is attended by the precision increase of detection failure operation.
Utilize this fault detect routine (with reference to Fig. 8), similarly, provide stand-by time interval to wait at on- off circuit 67 and 71 disconnections and the stable output of closed procedure transition period.This can be at detecting sensor electromotive force under steady state (SS), thereby increases the precision of detection failure.In addition, replace to wait for preset time, can carry out standby operation until the time variation amount of VS1 (rate of change) reaches set-point or still less.
(the second embodiment)
To describe the circuit structure forming according to the Is testing circuit part of the gas sensor control device of second embodiment of the invention below, and mainly concentrate on the part that is different from the first embodiment.
Utilize the gas sensor control device of the present embodiment, suppose that Is testing circuit part 45A (or Im testing circuit part 46A) has a kind of state (for convenience's sake, be referred to as " the first state ") and another kind of state is (for convenience's sake, be referred to as " the second state "), wherein in the first state, the potential difference (PD) between two of current-voltage converter terminals is returned to zero, and the potential difference (PD) between two terminals of current-voltage converter has the value that is different from the level that returns to zero in the second state.The output that the gas sensor control device of the present embodiment obtains Is testing circuit part 45A (or Im testing circuit part 46A) under this first and second states is with based on exporting calculated gains corrected value from resulting these of the first and second states, as current correction value.
Utilize the gas sensor control device of the present embodiment, Is testing circuit part 45A has circuit structure as shown in Figure 9 A.Circuit structure shown in Fig. 9 A comprises the circuit structure shown in Fig. 4, and wherein a part is revised.Therefore, similar or corresponding ingredient has identical Reference numeral.The Is testing circuit part 45A of the present embodiment and the difference of the Is testing circuit part 45 shown in Fig. 4 are the feature the following describes.That is, the Is testing circuit part 45A shown in Fig. 9 A comprises voltage follower circuit 92, "-" input terminal that it is used as " voltage generating portion " and is connected to differential amplifier circuit 62.This allows will to be input to differential amplifier circuit 62 from the voltage of voltage follower circuit 92 outputs during calculating current correction value, thereby the potential difference (PD) between two terminals of current-voltage converter 61 is set to set-point (≠ 0).
Utilize the Is testing circuit part 45A shown in Fig. 9 A, the plus end of differential amplifier circuit 62 is via capacitor C0 ground connection.This has suppressed the change in voltage of the gas sensing element 10 that causes due to the peak value occurring during cut-off switch 71 or surge voltage.
Fig. 9 B means the frequency dependent result to the impedance of the sensor unit 35 of gas sensing element 10 when applying alternating voltage with change frequency, and wherein, transverse axis represents the real part Z ' of impedance (Ω), and the longitudinal axis represents the imaginary part Z of impedance (Ω) ".
In Fig. 9 B, when sensor unit 35 being applied to R1 while thering is high-frequency alternating voltage and represent the impedance of the real part of this sensor unit 35, under this high-frequency, there is O 2-spread and occur that electronics shifts; C1 represents the curve of the impedance R2 of covering sensor unit 35, and wherein, the diffusion of the crystal boundary of O-2 occurs; C2 represents the curve of impedance R3 of the real part of covering sensor unit 35, wherein occurs absorbing with separated and occur O 2-surface diffusion; And C3 represents the impedance Z of the real part of covering sensor unit 35 ' curve, wherein there is gas diffusion and gas sensing element applied to low-frequency ac voltage.In Fig. 9 B, F1 also represents frequency range, mainly occurs comprising electrode reaction and the zirconic frequency characteristic of the sensor unit 35 of solid state electrolysis plastid 11 and electrode pair 37 and 38 in this frequency range, and F2 represents the frequency range that gas diffusion occurs.
Fig. 9 C means the oscillogram of the mode of operation of gas sensing element 110.In Fig. 9 C, W1 represent to utilize the voltage measurement sensor unit 35 apply output current measuring state or electric current is applied to sensor unit to allow terminal voltage to be in the state of set-point.Time and W1b indication that W1a indication is applied to sensor unit 35 by voltage do not apply voltage there is electromotive force between the electrode at this sensor unit 35 to sensor unit 35.Voltage and the W2a indication electromotive force of the 0.4V that W2 indication applies at electrode pair 37 and 38 supports of sensor unit 35 (referring to Fig. 1) appear in sensor unit 35, and W3 represents the flow through waveform of cell current (element current) of sensor unit 35 of indication, and W4 represents the time (ms).
During W1b, the operation that utilizes foregoing circuit is for the electric current of the electrode pair of the sensor unit 35 of flowing through return to zero (for the electromotive force that will measure).Waveform W2 and W3 indication is the variation of terminal voltage and the variation of element current (cell current) when the electric current zeroing that utilizes circuit to make to flow through sensor unit 35.When the electric current zeroing of the sensor unit 35 that makes to flow through, the terminal voltage on sensor unit 35 is owing to occurring that electromotive force causes the change in voltage on this sensor unit.
More particularly, feed back input electric pathway L1 is connected to "-" input terminal of differential amplifier circuit 62, voltage follower circuit 92 is also connected to "-" input terminal of this differential amplifier circuit 62 via on-off circuit 91.Voltage follower circuit 92 comprises resistive divider circuit, and it comprises two resistors, by this resistor, fixed voltage Vcc is carried out to dividing potential drop so that resulting voltage VX2 to be provided.On-off circuit 93 is also connected to feed back input circuit L1.
Design is arranged on on-off circuit 91 in the circuit shown in Fig. 9 A and 93 extraly with to being that the circuit switching signal SG5 with " height " and " low " binary value of slave microcomputer 41 inputs in the situation of " low " signal (that is, when disconnecting the on-off circuit 67 of feed back input electric pathway L1 and the on-off circuit 71 of closed feedback input electric pathway L2) makes response and is opened or is closed (closed or disconnection) at circuit switching signal SG2.Circuit switching signal SG5 is intactly input to an on-off circuit 93 and is input to another on-off circuit 91 through negative circuit 94.
Utilize the gas sensor control device of the present embodiment, if SG5=" H ", Closing Switch circuit 93 and cut-off switch 91.On the contrary, if SG5=" L ", cut-off switch circuit 93 and Closing Switch 91.In a word, with contrary disconnection and closure time cycle, disconnect or Closing Switch 91 and 93.
Here, in the situation based on hypothesis SG2=" L " (on-off circuit 67 is disconnected and on-off circuit 71 is closed), in the situation of SG5=" H " and SG5=" L ", get off to describe performed operation.Should be appreciated that, SG5=" H " corresponding to " the first state " and SG5=" L " corresponding to " the second state ".
If SG5=" H ", "-" input terminal of differential amplifier circuit 62 and voltage follower circuit 92 disconnect each other.In this case, the identical mode that circuit is described with the operation with reference to SG2=" L " in figure 4 occurs.That is, differential amplifier circuit 62 regulates the terminal relative with sensor (node B2) of current-voltage converter 61 to locate voltage.This is returned to zero the potential difference (PD) between two terminals of current-voltage converter 61, thereby there is no electric current this current-voltage converter 61 (being expressed as electric current=0nA) of flowing through.Therefore, this differential amplifier circuit 66 provides, and this output VS1 has NOx concentration=0[ppm] remain on the value place that equals circuit output error under the detected state of (equaling off-set value).
Further, if SG5=" L ", "-" input terminal of differential amplifier circuit 62 and voltage follower circuit 92 are connected to each other.In this case, the voltage that this differential amplifier circuit 62 regulates the terminal (node B1) of the current-voltage converter 61 of more close sensor to locate.This makes the sensor side terminal (node B1) of voltage locate at the terminal relative with sensor (node B2) of current-voltage converter 61 for to(for) current-voltage converter 61 in causing the level of given voltage potential (=corresponding to VX2 voltage).When this occurs, the potential difference (PD) between two terminals of current-voltage converter 61 represents according to the assumed value of voltage VX2.This state is corresponding with the state that detects initial definite NOx concentration (α [ppm]).Therefore, the instant output VS1 of differential amplifier circuit 66 remains on the value equating with circuit output error under detected state at NOx concentration=α [ppm].
Be equivalent to NOx concentration=0[ppm] obtain output VS1 under the first state of state, also under the second state that is equivalent to NOx concentration=α [ppm] state, obtain output VS1.Can be by using these outputs to obtain gain error.
Next, below by the operation of describing microcomputer 41 how to explain calculating sensor output calibration value.
Figure 10 means according to the process flow diagram of the routine of the operation for calculating sensor output calibration value of the present embodiment.Utilize this routine.Gain calibration value is calculated as to sensor output calibration value.And utilize microcomputer 41 repeatedly to carry out the routine shown in Figure 10 with the given time cycle.Here, the gain calibration value of how calculating for the output valve (VS1) of Is testing circuit part is described.
Step S41 in Figure 10, the calculating sequential that whether current time is belonged to gain calibration value is inquired.Utilize the present embodiment, corrected value computation period was set to for 10 seconds and passed for 10 seconds at every turn, made step S41 for correct.If current time belongs to the calculating sequential for gain calibration value, operation proceeds to step S42, wherein whether the temperature of sensor unit 35 is thus lifted to given activationary temperature (for example, 750 ℃) and inquires.More specifically, the impedance detection value based on start passed time or sensor unit 35 from engine start is determined the temperature propradation of this sensor unit 35.
If the temperature of sensor unit 35 is thus lifted to given activationary temperature, operation proceeds to step S43, wherein the circuit conversion circuit SG2 that outputs to Is testing circuit part 45 is switched to " L " from " H ".This allows Is testing circuit part 45 to switch for the feed back input electric pathway L1 of differential amplifier circuit 62 and the conducting state of L2, and the electric current that is attended by the current-voltage converter 61 of flowing through is arranged to the result of 0nA wittingly.When this occurs, input voltage switching signal SG5 remains intact " height " signal under above-mentioned " the first state ".At subsequent step S44, under conducting state, circuit conversion signal SG2 is switched to " low " afterwards from " height ", carry out standby operation to wait for stable output.In standby operation, after the passage of given time interval, in step S45, executable operations is to read the output VS1 of differential amplifier circuit 66.The output VS1 reading at step S45 equals that offset error and its can be enough to be used in based on VS1 (effect realizing in similar step S15 in Fig. 6) and the offset correction values Foff that calculates.
Subsequently, at step S46, input voltage switching signal SG5 is switched to " L " from " H ".This allows Is testing circuit part 45 to be under " the second state ", and under this " second state ", "-" input terminal and the voltage follower circuit 92 of differential amplifier circuit 62 are connected to each other.At follow-up step S47, circuit conversion circuit SG2 under conducting state by after " height " → " low " switched, carry out standby operation to wait for stable output.After the passage of time interval given under standby operation, in step S48 executable operations again to read the output VS1 of differential amplifier circuit 66.
Afterwards, at step S49, output VS1 based on reading at step S45 (, the VS1 value of reading under the first state) and the output VS1 reading at step S48 (that is the VS1 value of, reading under the second state) and calculated gains corrected value Fgain to be stored in alternate device, (for example take EPROM and backup RAM as example).In other words, gain calibration value Fgain is stored in alternate device as the learning value that will upgrade with suitable sequential.
Here, two sensor output VS 1 are illustrated in circuit output measured under the state that detects each NOx concentration, and the use of these binary values makes it possible to calculate the susceptibility (gain) for the sensor output of NOx concentration.When this occurs, the NOx concentration of supposing under the first state is 0[ppm] and the NOx concentration of supposing under the second state be α [ppm].Suppose at the first state lower sensor output VS1 and be Is1 and be Is2 in the current conversion value of the second state lower sensor output VS1, calculated gains corrected value Fgain according to the following formula:
Fgain＝(Is2-Is1)/(α-0)
＝(Is2-Is1)/α
Subsequently, at step S50 and S51, input voltage switching signal SG2 is switched to " H " and input voltage switching signal SG5 is switched to " H " from " L " from " L ".This permission is switched to L1 by the feed back input electric pathway to differential amplifier circuit 62, in this case, "-" input terminal of differential amplifier circuit 62 and voltage follower circuit 92 disconnect each other, and are attended by the result that Is testing circuit part 45 is returned to normal NOx concentration detected state.
At subsequent step S52, being switched to " H " and circuit is changed to SG5 from " L ", circuit switching signal SG2 is switched to " H " afterwards from " L ", carry out standby operation until obtain stable output.Under standby operation, after the passage of given time interval, restart normal NOx concentration and detect operation (at step S51).
The gain calibration value Fgain calculating is in the above described manner applicable to proofread and correct the sensor unit electric current I s (the current conversion value of VS1) measuring in order.That is the step that, deducts gain calibration value Fgain from sensor unit electric current I s measured when detecting NOx concentration allows the sensor unit electric current (to be expressed as the mode of the sensor unit electric current=Is-Fgain after correction) after calculation correction.Then, the sensor unit electric current based on after this correction calculates NOx concentration.
In fact, not only Is testing circuit part 45 but also Im testing circuit part 46 are all carried out the calculating of gain calibration value and by using two gain calibration values that transmit from Is testing circuit part 45 and Im testing circuit part 46 to calculate NOx concentration.In this case, the sensor unit electric current of the gain calibration value that deducts sensor unit from sensor unit electric current I s (measured value) with calculation correction.Similarly, the watch-dog cell current of the gain calibration value that deducts watch-dog unit from watch-dog cell current Im (measured value) with calculation correction.Then, poor (the watch-dog cell current after the sensor unit electric current-correction after=correction) of the sensor unit electric current based on after proofreading and correct and the watch-dog cell current after correction calculates NOx concentration.
As shown in figure 11, utilize NOx sensor circuit 40, between sensor unit electric current I s and watch-dog cell current Im, occur respectively gain error (Is-Im).In Figure 11, term " sensor output " refers to that actual current value and the term " electric circuit inspection value " appearing in sensing element 10 refers to according to real sensor output by the measured measured value of NOx sensor circuit 40 (comprising Is testing circuit part 45 and Im testing circuit part 46).
In this case, the gain error of obtaining sensor output is as gain calibration value, by come correcting sensor cell current Is and watch-dog cell current Im by this gain calibration value.This has suppressed the decline of the NOx concentration precision that the gain error by electric circuit inspection value causes.
The NOx sensor circuit of the second embodiment has following each advantage.
The structure that middle design NOx is set at circuit is obtained output VX1 to equal under the first state of NOx concentration=0 and to equal under the second state of NOx concentration=α, with based on each output calculated gains corrected value Fgain.This makes it possible to suitably obtain the gain calibration value Fgain that equals the gain error that causes in NOx sensor circuit 40.In addition similar with the first embodiment, not having on-off circuit to be arranged on wherein stream has in the electric pathway of element current (sensor unit electric current and watch-dog cell current).Therefore, can avoid the leakage current causing due to on-off circuit and in element current measured value, occur the inconvenience of error.
The adverse effect that calculated gains corrected value Fgain causes with the elimination leakage current that on-off circuit was caused in the above described manner.This causes increasing the precision that detects NOx concentration.Further, even due to temperature characterisitic and running modification and output error occurs in NOx sensor circuit 40 and change in this output error, can suitably adjust this output characteristics, and correctly carry out NOx measurement of concetration.
For the structure that causes producing given potential difference (PD) between two terminals of current-voltage converter 61, voltage follower circuit 92 is connected to "-" input terminal of differential amplifier circuit 62.This makes between two terminals of current-voltage converter 61 to occur the potential difference (PD) consistent with the output voltage of this voltage follower circuit 92, this make the potential difference (PD) between can two terminals be set to any grade.
Further, when detecting NOx concentration, only, when NOx concentration=oppm under atmospheric conditions, just may there is benchmark concentration.In this case, although only utilize current measurement value calculated gains corrected value very difficult in NOx concentration=oppm situation, the step that the first state is transformed into the second state makes NOx sensor can obtain gain calibration value.
(other is revised)
The present invention is not limited to the structure of above-mentioned each embodiment and can in following modification, realizes.
Utilize above-mentioned each embodiment, Is testing circuit part 45 takes to comprise the structure of " applying voltage-setting circuitry ", should " applying voltage-setting circuitry " comprise differential amplifier circuit 62.Alternately, apply voltage-setting circuitry and can comprise in-phase amplifier circuit.To describe the circuit structure shown in Figure 12 below, and concentrate on the place that is different from Fig. 4.Similarly appropriate section has identical Reference numeral.Utilize the circuit structure shown in Figure 12, with circuitry phase, be also used as applying voltage-setting circuitry, and input in relevant structure and can modify to voltage.
Utilize the circuit structure shown in Figure 12, in-phase amplifier circuit 101 is provided as applying voltage-setting circuitry.This in-phase amplifier circuit 101 has "-" input terminal of the sensor side terminal (node B1) that is connected to current-voltage converter 61, and the voltage of node B1 is retained as the voltage at "+" input terminal place of this in-phase amplifier circuit 101.The dividing potential drop node of resistive divider circuit 63 is connected to "+" input terminal of in-phase amplifier circuit 101 via on-off circuit 102, the lead-out terminal of voltage follower 65 is connected to "+" input terminal of in-phase amplification circuit 101 via on-off circuit 71.
In the structure that middle design on- off circuit 102 and 71 are set, so that being made, the circuit conversion signal SG2 of slave microcomputer 41 inputs responds and is switched on or turn-offs (closed or disconnection).Circuit conversion signal SG2 is intactly applied to a terminal of on-off circuit 71 and is applied to another on-off circuit 71 through negative circuit 103.
Utilize current modification, if SG2=" H ", on-off circuit 102 closures and on-off circuit 71 disconnect so that the dividing potential drop VX3 of resistive divider circuit 63 is imported into "+" input terminal of in-phase amplifier circuit 101.Further, if SG2=" L ", on-off circuit 102 disconnections and on-off circuit 71 closures are so that the output of voltage follower 65 is imported into "+" input terminal of in-phase amplifier circuit 101.In a word, utilize disconnection and the closure time cycle that pattern is contrary to disconnect and Closing Switch circuit 102 and 71, cause the reformed structure of input voltage of in-phase amplifier circuit 101.
Utilize sort circuit structure, when detecting NOx concentration in the normal moment, circuit switching signal SG2 is that " height " signal and voltage VX3 are applied to negative terminal SS-.This permission carrys out survey sensor cell current Is according to the Nox concentration in waste gas.On the contrary, when calculating offset correction values, circuit switching signal SG2 is that the output VS2 of " low " signal and voltage follower 65 is applied to "+" input terminal of in-phase amplifier circuit 101 via feed back input electric pathway L2.Thus, in the potential difference (PD) that does not have electric current to flow through can to return to zero under the state of current-voltage converter 61 (electric current=0nA) between two terminals of this current-voltage converter 61.Therefore, the sensor output VS 1 of instant appearance is made to response, can calculate offset correction values.In addition, to sensor-unit, terminal voltage VS2 makes response, can detecting sensor electromotive force.
Utilize the first embodiment, design circuit structure is to allow sensor-unit/watch-dog-unit drive circuit part 44 to interrupt applying voltage, for protect this sensor when occurring such as various faults such as disconnections.Can be with other structural change sort circuit structure.More particularly, sensor-unit/watch-dog-unit drive circuit part 44 allows protective resistor 54 to have large resistance value (with about hundreds of kilohm order of magnitude to 1 megohm) thereby makes its current limited for example, in predetermined upper limit current (take aging current as example).Alternately, the output of the electric current of operational amplifier 52 is limited.Utilize this structure, even if the maximum current of this sensor unit 35 of flowing through is restricted, still can protect sensing element when there is faults such as power shortage and ground short circuit on the negative terminal at this sensor unit 35.In this case, can preferably take unit to apply voltage is limited under aging voltage to regulate the structure of sensor characteristic.
Utilize above-mentioned each embodiment, project organization to comprise voltage follower 65 in electric pathway, wherein, the sensor side terminal of current-voltage converter 61 and differential amplifier circuit 62 are connected to each other to provide by this electric pathway and do not make the flow through structure of feed back input electric pathway L1 of Is testing circuit part of element current.Alternately, can replace voltage follower 65 with in-phase amplifier circuit.That is, in this case, it has represented the situation that on-off circuit 71 is set in the electric pathway (feedback electric pathway L2) between in-phase amplifier circuit and differential amplifier circuit 62.
Utilize above-mentioned each embodiment, as described with reference to figure 2, sensor-cell current measured value VS1 and watch-dog-cell current measured value VM1 are imported into microcomputer 41 to allow this microcomputer 41 to calculate (Is-Im) value.Can be with this structure of following structural modification.That is, provide (Is-Im) counting circuit part that for example comprises differential amplifier circuit partly be applied with from sensor-cell current measured value VS1 of Is testing circuit part 45 outputs and the watch-dog-cell current measured value VM1 exporting from Im testing circuit part 46 to allow being somebody's turn to do (Is-Im) counting circuit.This allows counting circuit partly to calculate (Is-Im) value, and this value is output to microcomputer 41 subsequently.
Utilize above-mentioned the second embodiment, circuit structure is set so that when calculated gains corrected value Fgain, be equivalent to NOx concentration=0[ppm] obtain output VS1 under the first state of state and be equivalent under the second state of NOx concentration=α [ppm] state and obtain output VS1, each output VS1 under this two states is made to response and calculated gains corrected value Fgain.Alternately, can revise sort circuit structure, therefore except this two states, can being equivalent to the state of NOx concentration=β [ppm], (β ≠ 0 obtains output VS1 under α) and makes response and calculated gains corrected value Fgain with each output VS1 under these three kinds of states.
In addition, another alternative structure can be set, so that under two states, be equivalent under the state of NOx concentration=α [ppm] and NOx concentration=β [ppm], obtain respectively output VS1, to allow that each output VS1 under this two states is made to response and calculated gains corrected value Fgain.
Utilize above-mentioned each embodiment, sensing element is set to comprise in so-called three cellular constructions of pump unit, sensor unit and watch-dog unit.Can revise this structure.For example, this sensing element can take to comprise the structure of so-called two cellular constructions, and this two cellular construction comprises pump unit and sensor unit.In addition, when usage monitoring device unit (Unit the 3rd), this watch-dog unit can be the electrodynamic element of output electromotive force.
The special component being detected can be the target except NOX.For example, can change gas detector to survey targets such as the HC in waste gas (charing hydrogen) and CO (carbonic oxide).In this case, pump unit is set to discharge unnecessary oxygen from waste gas, and sensing cell is set with decomposing H C and CO after the unnecessary oxygen of discharge, detect thus HC concentration and CO concentration.
Gas sensor control device can be by the controller of the clear and definite gas sensor as using in other type of engine such as gasoline engine except diesel engine.A kind of structure of can taking gas sensor detects the gas beyond removing exhaust gas, and can be the type for the application except automobile.
Figure 13-16 are with reference to the accompanying drawings described the gas sensing element 110 of this modification in detail.
As shown in Figure 13 and 14, gas sensing element 110 comprises that each all has the first and second solid state electrolysis bodies 151 and 152 of oxygen-ion conductive, is limited between the first and second electrolyte bodies 151 and 152 for entering the measurement gas chamber 111 of measurement gas and for measurement gas being introduced to the diffusional resistance part 120 of measurement gas chamber 111 under given diffusional resistance.
In addition, gas sensing element 110 comprises sensor unit 130, for detection of the concentration that is allowed to enter the designated gas comprising in the measurement gas of measurement gas chamber 111, oxygen pump unit 125, be used for adjusting and enter the oxygen concentration in measurement gas chamber 111, oxygen detection unit 140, for measuring the oxygen concentration of this measurement gas chamber 111.
Sensor unit 135 comprises the first solid state electrolysis plastid 151, to be formed on a lip-deep potential electrode 134 of first electrolyte body 151 and the reference electrode 132 paired with potential electrode 134 forming with the aspectant mode of measurement gas chamber 111 on another surface of the first electrolyte body 151.
Oxygen pump unit 125 comprises the second solid state electrolysis plastid 152, to be formed on a lip-deep internal pump electrode 121 of the second electrolyte body 152 and the external pump electrode 122 paired with internal pump electrode 121 forming with the aspectant mode of measurement gas chamber 111 on another surface of the second electrolyte body 152.
Oxygen watch-dog unit 140 comprises the first solid state electrolysis plastid 151, to be formed on a lip-deep internal control device electrode 131 of first electrolyte body 151 and the outer monitoring device electrode 142 paired with internal control device electrode 131 forming with the aspectant mode of measurement gas chamber 111 on another surface of the first electrolyte body 151.
Diffusional resistance part 120 is formed between the first electrolyte body 151 and the second electrolyte body 152 along the direction vertical with stacked direction.
As shown in figure 15, potential electrode 134 is placed in measurement gas chamber 111, in the inside location of the outer wall 211 of internal pump electrode 121.In addition, internal control device electrode 141 is placed in measurement gas chamber 111, in the inside location of the inside of internal pump electrode 121 end wall 212.
As shown in Figure 13 and 14, gas sensing element 110 has the interval bodies 130 that are clipped in the first and second solid state electrolysis plastids 151 and 152 centres, to limit measurement gas chamber 111.
In addition, in another surface of the first electrolyte body 151 via the stacking protective shield 140 of interval body 131, to limit the first reference gas compartment RGC1.
Further, stacking interval body 132 on a surface of the second solid state electrolysis plastid 152 relative with measurement gas chamber 111, to limit the second reference gas compartment 102.Ceramic heater 115 is stacked on the second solid state electrolysis plastid 152 via interval body 132, for heating oxygen pump unit 125, sensor unit 135 and oxygen watch-dog unit 140.
The outer monitoring device cell electrode 142 of the reference electrode 132 of sensor unit 135 and oxygen watch-dog unit 140 consists of unified public electrode, and this public electrode has the function as reference electrode 132 and outer monitoring device cell electrode 142.In addition, reference electrode 132 is upper with another surface that outer monitoring device cell electrode 142 is formed on the first solid state electrolysis plastid relative with internal control device electrode 141 with potential electrode 134, to be exposed to the first reference gas compartment RGC1.
In addition, the external pump electrode 122 of oxygen pump unit 125 is placed on 152 1 surfaces of the second solid state electrolysis plastid relative with internal pump electrode 121, to be exposed to other compartment 102 of the second benchmark.
Potential electrode 134 and internal control device electrode 141 are positioned on a surface of the first solid state electrolysis plastid, and this region is along the longitudinal direction Y given distance separated from one another of gas sensing element 110.As shown in figure 15, in addition, internal pump electrode 121 is formed in the region with whole girth with around potential electrode 134 and watch-dog electrode 141.
As shown in figure 14, diffusional resistance part 120 and internal pump electrode 121 close on placement each other along stacking direction Z.Diffusional resistance part 120 is formed on the two ends of measurement gas chamber 111 in couples along the Width X vertical with longitudinal direction Y with stacking direction Z.Utilize the present embodiment, each diffusional resistance part 120 is by comprising that ceramic permeable mass forms, such as aluminium oxide etc.Diffusional resistance part 120 is clipped between internal pump electrode 121 and the first solid state electrolysis plastid 151, and partly overlaps with the internal pump electrode 121 along stacking direction Z.
The outside end wall of diffusional resistance part 120 and the bee-line S between potential electrode 134 are probably in the scope of 1-3mm.
The first and second solid state electrolysis plastids 151 and 152 have principal ingredient, for example the material of zirconia and ceria and so on.In addition, interval body 130,131 and 132 is principal ingredients of aluminium oxide.
As shown in figure 16, further, the potential electrode 134 of sensor unit 135 and reference electrode 132 are connected to NOx sensor circuit 40 via IS detection circuit part 45 and sensor unit power supply Vs.
In addition, potential electrode 134 and reference electrode 132 consist of the metallic ceramics composite material that comprises metal ingredient and ceramic component, and wherein metal ingredient has the principal ingredient of Pt, and ceramic component comprises zirconic principal ingredient.Can determine that ceramic component content is the value in the scope for example from 10 to 20wt% with respect to the general assembly (TW) of metal ingredient and ceramic component.
In addition, potential electrode 134 is included in the activated Pt-Rh electrode of antagonism nitrogen oxide NOx aspect tool.Pt-Rh electrode contains Rh, this Rh content with respect to the general assembly (TW) of metal ingredient for example between 10-50wt%.
In addition, similar with potential electrode 134 and the reference electrode 132 of sensor unit 135, internal pump electrode 121 and external pump electrode 122 be by cermet material, and this cermet material comprises to have the major metal of Pt and comprise take the ceramic component that zirconia is principal ingredient.Can determine that ceramic component content is the value in the scope for example from 10 to 20wt% with respect to the general assembly (TW) of old minute of metal and ceramic component.
In addition, internal pump electrode 121 is comprised of Pt-Au electrode, and this Pt-Au electrode does not have activity aspect antagonism NOx.Au content is the value between 1-10wt% for example with respect to the general assembly (TW) of metal ingredient.
As shown in figure 16, the internal control device electrode 141 of oxygen watch-dog unit 140 is connected with NOx sensor circuit 40 with Im testing circuit part 46 via watch-dog unit power supply Vm with outer monitoring device electrode 142.
Similar with potential electrode 134 and the reference electrode 132 of sensor unit 135, internal control device electrode 141 and outer monitoring device electrode 142 consist of the metallic ceramics composite material that comprises metal ingredient and ceramic component, wherein metal ingredient has the principal ingredient of Pt, and ceramic component comprises zirconic principal ingredient.Can determine that ceramic component content is the value in the scope for example from 10 to 20wt% with respect to the general assembly (TW) of metal ingredient and ceramic component.
In addition, internal pump electrode 121 consists of Pt-Au electrode, should aspect Pt-Au electrode antagonism NOx, not have activity.Au content is the value between 1 to 10% for example with respect to the general assembly (TW) of metal ingredient.
Oxygen watch-dog unit 140 comprises feedback circuit 750, and it allows the current value of being measured by Im testing circuit part 46 to feed back to oxygen pump unit 125, so that can control in operation oxygen pump unit 125.That is to say, for example, if carried out, control so that the current value of being measured by Im testing circuit part 46 surpasses set-point, increase the voltage that is applied to oxygen pump unit 125 from pump unit power supply Vp, to increase the ability that the oxygen from 111 transmission of measurement gas chamber is pumped into the second reference gas compartment 102.
In addition, potential electrode 31, reference electrode 132 (outer monitoring device electrode 142), internal control device electrode 141, internal pump electrode 121 and external pump electrode 122 are all electrically connected to outside terminal through the lead portion of electricity conduction and through hole.
As shown in Figure 13 and 14, the heating element 150 that metallic ceramics well heater 115 comprises well heater substrate 115a, is stacked on the insulation course 115b on well heater substrate 115a and is clipped in well heater substrate 115a and insulation course 115b is middle.
Utilize this metallic ceramics well heater 115, closer, for heating element 150 and the lead portion 153 heating, by composition, be formed on the thin slice of being made by aluminum when connecting, and insulation course 115b is placed on heating element 150.Heating element 150 is made by containing ceramic metallic ceramics composite material, such as Pt and aluminium etc.
Ceramic heater 115 produces heat for allowing when heating element 150 is applied with the electric power from outside, for oxygen pump unit 125, sensor unit 135 and oxygen watch-dog unit 140 being heated to the temperature of activity.
Heating element 150 is via the lead portion 130, through hole (not shown) and the terminal part (not shown) that are integrally formed with heating element 150 and be applied with electric power.
In addition, the first and second solid state electrolysis plastids 151 and 152, interval body 130,131 and 132, insulation course 115b and heating substrate 115a can form by knife coating or injection moulding etc. the parts of similar thin slice.
Further, can be by formation potential electrode 134, reference electrode 132, internal control device electrode 141, outer monitoring device electrode 142, internal pump electrode 121 and external pump electrodes 122 such as method for printing screen.
In addition, the porous body of formation diffusional resistance part 120 can be formed by methods such as serigraphys.
In addition, gas sensing element 110 can form by stacking ceramic sheet, is suitably formed with above-mentioned various electrode, to form duplexer and to fire this duplexer with unified structure.
Next will the principle of operation of gas sensing element 110 be described.
First, under given diffusional resistance, measurement gas by diffusional resistance part 120 to be introduced in measurement gas chamber 111.According to the diffusional resistance of diffusional resistance part 120, determine the measurement gas amount of introducing.Between the surperficial transmission period in measurement gas by the internal pump electrode 121 of oxygen pump unit 125, the oxygen concentration of measurement gas utilizes oxygen pump unit 125 to regulate.
That is to say, between the pair of electrodes of oxygen pump unit 125, apply voltage and using permission external pump electrode 122 as positive electrode, this is reduced to form oxonium ion by the oxygen that causes being included in measurement gas on internal pump electrode 121.Due to pump action, oxonium ion is discharged into the external pump electrode 122 that is exposed to reference gas compartment 102.On the contrary, if apply voltage to allow internal pump electrode 121 to become positive electrode, externally oxygen occurs on pump electrode 122 and reduce to form oxonium ion, this oxonium ion will be discharged into the internal pump electrode 121 that is exposed to measurement gas chamber 111 due to pump action.That is to say, the structure of design oxygen pump unit 125 is so that when being applied to voltage employing paired electrode, and oxygen pump unit 125 allows oxygen to flow into or flows out measurement gas chamber 125 to adjust the oxygen concentration in measurement gas chamber 111.
Especially, when measurement gas is flowed through diffusional resistance part 120, measurement gas may be easy to contact with internal pump electrode 121, causes oxygen concentration to be easy to be reconciled.
Next, measurement gas arrives the potential electrode 134 of sensor unit 135 and the internal control device electrode of oxygen watch-dog unit 140 through internal pump electrode 121.
For example, on the paired electrode that given voltage (0.4 volt) is applied to oxygen watch-dog unit 140 so that when being exposed to the outer monitoring device electrode 142 of the first reference gas compartment RGC1 and becoming positive electrode, on the internal control device electrode 141 that is exposed to the first reference gas compartment RGC1, there is measurement gas in the minimizing of oxygen.This has also caused the formation of oxonium ion, and this oxonium ion is exposed to the internal control device electrode 141 of measurement gas chamber 111 because pump action is discharged into, thereby oxonium ion is flowed.
Here, because internal control device electrode 141 is comprised of the electrode that comprises the metallic ceramics class of Pt-Au alloy, this Pt-Au alloy does not have activity aspect decomposing N Ox, the oxygen ion current of the oxygen watch-dog unit 140 of therefore flowing through depends on the amount that is included in the amount of oxygen in measurement gas and does not depend on oxides of nitrogen.This allows to detect the current value of oxygen watch-dog unit 140 of flowing through, thereby can detect the oxygen concentration in measurement gas chamber 111.
Further, the structure of the gas sensing element 110 of design the present embodiment, so that can, according to flowing through the current detection value of oxygen watch-dog unit 140 and control oxygen pump unit 125 via feedback circuit 750, there is the oxygen concentration in given fixed value to allow measuring other chamber 111.; to the output signal of air element 140 being made to response from oxygen; control is for example applied to the voltage of oxygen pump unit 130, to allow oxygen watch-dog unit 140 that the current value of the fixed value (0.2 μ m) of its value in expectation is provided, and this will make the oxygen concentration of measuring other chamber 111 be controlled at fixed value.In addition, given voltage (for example, 0.4V) is applied to sensor unit 135 and becomes positive pole so that be exposed to the reference electrode 132 of the first reference gas compartment RGC1.As mentioned above, because potential electrode 134 comprises by the cermet electrodes of making at the Pt-Rh alloy aspect decomposing nitrogen oxide with activity, so be included in the phenomenon that oxygen in the measurement gas entering in measurement gas chamber 111 and oxides of nitrogen reduce in potential electrode 134, to form oxonium ion.Due to pump action, oxonium ion is discharged into the reference electrode 132 that is exposed to the first reference gas compartment RGC1, thereby makes flux of oxygen ions flow through potential electrode 134 and reference electrode 132.This electric current represents the electric current of deriving from being included in NOx measurement gas and oxygen concentration.
Meanwhile, as mentioned above, the electric current of the oxygen concentration in measurement gas chamber 111 is depended in the representative of the electric current of the oxygen watch-dog unit 140 of flowing through.Therefore, can detect NOx concentration with the difference of the current value of the oxygen watch-dog unit 140 of flowing through by the current value based on the sensor unit 135 of flowing through.
Gas sensing element 110 operates in the following manner.
On the first solid state electrolysis plastid 151, form diffusional resistance part 120 to extend from measurement gas chamber 111 along the direction vertical with stacked direction between the first and second solid state electrolysis plastids 151 and 152.This has shortened the outer wall 120a of diffusional resistance part 120, i.e. distance between the inlet port of measurement gas, and potential electrode 134, thus the response of gas sensing element 110 is strengthened.
Utilize the gas sensing element 110 of the present embodiment, in the region of extending at the vertical Width X of the longitudinal direction Y along with gas sensing element 110, on the first solid state electrolysis plastid 151, form diffusional resistance part 120.This is easy to produce the outer wall of each diffusional resistance part 120, i.e. the effect that distance between measurement gas inlet port, and potential electrode 134 reduces.Therefore, gas sensing element 110 can have the response of further enhancing.
In addition, in the outer wall 211 of internal pump electrode 121, in inner region, on the first solid state electrolysis plastid 151, form potential electrode 134.This allows oxygen pump unit 125 to regulate the oxygen concentration in this measurement gas before measurement gas arrives potential electrode 134.Therefore, gas sensing element 110 can have higher measuring accuracy.
Utilize the gas sensing element 110 of the present embodiment, especially, in the outer wall 212 of internal pump electrode 121, in inner region, on the first solid state electrolysis plastid 151, form potential electrode 134.This allows to utilize oxygen pump unit 125 suitably to regulate oxygen concentration, and provides the measurement gas after oxygen concentration regulates with backward potential electrode 134.Therefore, gas sensing element 110 has higher precision aspect the specific gas concentration of measurement.
Further, along stacked direction, diffusional resistance part 12 and internal pump electrode 121 are arranged close to each other.Therefore, in measurement gas, by diffusional resistance part 120, be directed into and can make measurement gas suitably remain with internal pump electrode 121 during stage of measurement gas chamber 111 to contact.In this stage, therefore, oxygen pump unit 125 is pumping oxygen suitably, thereby can suitably regulate the oxygen concentration in measurement gas.
In addition, utilize the gas sensing element 110 be provided with oxygen watch-dog unit 140, can accurately obtain oxygen concentration in measurement gas chamber 111 to obtain measurement result.This measurement result is used for to FEEDBACK CONTROL, to control oxygen pump unit 125 measured value for correcting sensor unit 135 by this measurement result simultaneously, to improve measuring accuracy.In addition, internal control device electrode 141 is arranged on internal pump electrode 121 outer wall 211 in inner region.This can make oxygen watch-dog unit 120 accurately measure oxygen concentration, wherein utilizes oxygen pump unit 125 to regulate the oxygen concentration of this measurement gas.
Especially, if attempt to reduce outer wall 120a and the response of the distance S between potential electrode 134 to be improved of diffusional resistance part 120, in suitably guaranteeing oxygen pumpability process, there will be difficult risk.Therefore, provide the step of oxygen watch-dog unit 140 cause minimizing the oxygen concentration fluctuation in measurement gas chamber 111 and proofread and correct this measured value.Therefore, can guarantee to detect the precision of specific gas concentration (NOx concentration).
Utilize the gas sensing element 110 of the present embodiment, in addition, internal control device electrode 141 be arranged on internal pump electrode 121 inside end wall 212 in inner region.This makes it possible to provide and have the measurement gas of utilizing the oxygen concentration that oxygen pump unit 125 regulated to inner watch-dog electrode 141, thereby improves the precision of measuring oxygen concentration.
In addition, the structure of the gas sensing element 110 of design the present embodiment is made response and is controlled the voltage that is applied to oxygen pump unit 125 with the detection signal of the oxygen concentration to about in oxygen watch-dog unit 140.This allows the oxygen concentration in measurement gas chamber 111 to remain on fixed value.Especially, if attempt to reduce outer wall 120a and the response of the distance S between potential electrode 134 to be improved of diffusional resistance part 120, internal pump electrode 121 tends to have the width W reducing, and causes the difficult risk in suitably guaranteeing oxygen pumpability.Therefore, allow the oxygen concentration in oxygen watch-dog unit 140 control measurement gas chamber 111, in backfeed loop, to oxygen pump unit 125, provide resulting detection signal, to regulate at an easy rate oxygen concentration simultaneously.
In addition, the structure of design oxygen watch-dog unit 140, so that when applying given voltage between internal control device electrode 141 and outer monitoring device electrode 142, causes depending on the current flowing of the oxygen concentration in measurement gas.In addition, make another design to detect specific gas concentration (NOx concentration) according to the flow through electric current of sensor unit 135 and the difference between currents of the oxygen watch-dog unit 140 of flowing through.This makes it possible in correcting sensor unit 135, about the measured value of specific gas concentration (NOx concentration), can obtain accurate measured value.
Further, because diffusional resistance part 12 consists of porous body, so can easily regulate diffusional resistance.
In addition, the bee-line S between the outer wall 120a of diffusional resistance part 120 and potential electrode 134 is set to the value within the scope of 1 to 3mm.This causes obtaining having the gas sensing element 110 of suitable improvement response, guarantees the measuring accuracy suitably improving simultaneously.
As mentioned above, utilize above-described embodiment, can provide and there is fabulous response and the gas sensing element of high measurement accuracy more.
Below with reference to Figure 17-19, describe the gas sensing element 110A of the second modification in detail, wherein similarly those of components and gas sensing element in the first modification shown in Figure 13-16 have identical reference marker.
The difference of the gas sensing element 110A of the second modification and the gas sensing element 110 of the first modification is the structure of gas diffusion resistance part 120A.; utilize the gas sensing element 110A of the second modification; gas diffusion resistance part 120A is not that the porous body by the gas diffusion resistance part 120 of the gas sensing element 110 for the first modification forms, but is formed by the slit with minimum clearance.By suitably regulating thickness along stacked direction Z, in structure, form slit to obtain the diffusional resistance of expectation.Can be set to for example 5-50 μ m by this thickness.
The gas sensing element 110A of the second modification has other identical structure with the gas sensing element 110 of the first modification.
Utilize the gas sensing element 110A of the present embodiment, do not need to carry out the step that forms porous body, thereby realize the minimizing of manufacturing cost.
In addition, thus the gas sensing element of the gas sensing element 110A in the present embodiment and the first modification 110 carry out identical operation and, omitted identical detailed description here.
Below with reference to Figure 20-22, describe the gas sensing element 110B of the 3rd modification in detail, wherein similarly those of the gas sensing element of components and the first modification shown in Figure 13-16 have identical Reference numeral.
The difference of the gas sensing element 110B of the 3rd modification and the gas sensing element 110 of the first modification is that gas diffusion resistance part 120B is arranged between potential electrode 134 and internal pump electrode 122, for providing diffusional resistance to measurement gas.
Gas diffusion resistance part 120B comprises by the porous body of making such as the pottery of aluminium oxide etc., thereby it forms and covers potential electrode 134 and oxygen watch-dog electrode on the first solid state electrolysis plastid 151.In addition, gas diffusion resistance part 120B be arranged in internal pump electrode 121 inside end wall 212 to inner region.
The gas sensing element 110B of the 3rd modification has other identical structure with the gas sensing element 110 of the first modification.
Utilize the gas sensing element 110B of current modification, can provide the measurement gas of first utilizing oxygen pump unit 125 to be adjusted to suitable oxygen concentration to potential electrode 134, make it possible to improved accuracy detection specific gas concentration.
The operation that gas sensing element 110B execution in current modification is identical with the gas sensing element 110 in the first modification, therefore, has saved the detailed description of same section here.
Below with reference to Figure 23-25, describe the gas sensing element 110C of the 4th modification in detail, wherein similarly those of the gas sensing element of components and the first modification shown in Figure 13-16 have identical Reference numeral.
The difference of the gas sensing element 110C of the 4th modification and the gas sensing element 110 of the first modification is that oxygen pump unit 125C has the internal pump electrode 121C and the gas diffusion resistance part 120C that in the whole surf zone towards measurement gas chamber 111, on the second solid state electrolysis plastid 152, form and is formed in whole measurement gas chamber 111 to cover potential electrode 134 and internal control device electrode 141, for being provided for the diffusional resistance of measurement gas.
The gas sensing element 110C of current modification has other identical structures with the gas sensing element 110 of the first modification.
The gas sensing element 110C that utilizes current modification, oxygen pump unit 125C can regulate the oxygen concentration in measurement gas chamber 111 at an easy rate.
The gas sensing element 110C of current modification has other identical structures with the gas sensing element 110 of the first modification, therefore, has saved the detailed description of same section here.
Below with reference to Figure 26-28, describe the gas sensing element 110D of the 5th modification in detail, wherein similarly those of the gas sensing element 110C of components and the 4th modification have identical Reference numeral.
The gas sensing element 110D of the 5th modification is that with the difference of the gas sensing element 110C of the 4th modification measurement gas chamber 111D comprises the first measurement gas chamber 211D and the second measurement gas chamber 311D communicating via restricted part 213 each other, and internal pump electrode 121C towards the first measurement gas chamber 211D, measure 134 and internal control device electrode 141 towards the second measurement gas chamber 311D.In addition, at the whole surf zone being arranged in towards the position of the first measurement gas chamber 211D, on the second solid state electrolysis plastid 152, form internal pump electrode 121C.
Interval body 130 is arranged between the first and second electrolyte bodies 151 and 152 and comprises ceramic layer 130a, 130b and the 130c of three layers of form, and these three layers have the cut out portion forming at diverse location.Ceramic layer 130a has the first cut out portion, by it, defines restricted part 213, and ceramic layer 130c have three cuts part, by it, defines the second measurement gas chamber 311D.
The gas sensing element 110C of current modification has other identical structures with the gas sensing element 110 of the first modification.
The gas sensing element 110D that utilizes current modification, measurement gas is directed into the first measurement gas chamber 211D through diffusional resistance part 120, and in this first measurement gas chamber 211D, oxygen pump unit 125C regulates oxygen concentration.Subsequently, measurement gas is by restricted part 213 to flow into the second measurement gas chamber 311D, and in this second measurement gas chamber 311D, sensor unit 135 detects specific gas concentration and oxygen watch-dog unit 140 detection oxygen concentrations.
Therefore, can obtain having the more gas sensing element 110D of high measurement accuracy.
The operation that the gas sensing element 110D execution of current modification is identical with the gas sensing element 110C in the 4th modification, therefore, has saved identical detailed description here.
Below with reference to Figure 29-31, describe the gas sensing element 110E of the 6th modification in detail, wherein similarly those of the gas sensing element 110 to 110D of components and above-mentioned first to fourth modification have identical Reference numeral.
The difference of the gas sensing element 110E of the 6th modification and the gas sensing element of first to fourth modification 110 to 110D is not have watch-dog unit 140.
Utilize this structure, oxygen pump unit 125 fully discharges for the oxygen to from measurement gas chamber 111, oxygen concentration is reduced to 135 pairs of sensor units, detects the degree that specific gas concentration (NOx concentration) does not have adverse effect.
The gas sensing element 110E of current modification has other identical structures with the gas sensing element 110 of the first modification.
Utilize current modification, can manufacture at an easy rate gas sensing element 110E and simple in structure, cost is low.
The operation that the gas sensing element 110E execution of current modification is identical with the gas sensing element 110 in the first modification, therefore, has saved identical detailed description here.
Below with reference to Figure 32-34, describe the gas sensing element 110F of the 7th modification in detail, wherein similarly those of the gas sensing element 110 of components and above-mentioned the first modification have identical Reference numeral.
The difference of the gas sensing element 110F of the 7th modification and the gas sensing element 110 of the first modification is that this gas sensing element 110F has the far-end that is formed with diffusional resistance part 120F.
From Figure 33 and 34, it is evident that, the internal control device electrode 141 of the potential electrode 134 of sensor unit 135 and oxygen watch-dog unit 140 is formed on the first solid state electrolysis plastid 151, and is spaced apart from each other along Width X in mode parallel to each other.
The gas sensing element 110F of current modification has other identical structures with the gas sensing element 110 of the first modification.
In normal use, near the region of sensor unit 135 this far-end, be arranged on gas sensing element 110F.Therefore, the step that Y provides diffusional resistance part 120F on the far-end of gas sensing element 110F is in a longitudinal direction the outer wall of minimizes diffusion resistance part 120F suitably, i.e. distance S between the inlet port of measurement gas, and potential electrode 134.
As mentioned above, the step of further, placing potential electrode 134 and internal control device electrode 141 along Width X in mode parallel to each other equates the interval between the outer wall 120a of potential electrode 134 and internal control device electrode 141 and diffusional resistance part 120F.Thereby, use the oxygen concentration of oxygen watch-dog unit 140 detections and the oxygen concentration in the actual measurement gas remaining in potential electrode 134 to be equal to each other.This causes can be with the specific gas concentration in higher accuracy detection measurement gas (NOx concentration).
The gas sensing element 110F of current modification has other identical structures with the gas sensing element 110 of the first modification.
Below with reference to Figure 35-37, describe the gas sensing element 110G of the 8th modification in detail, wherein similarly those of the gas sensing element 110 of components and above-mentioned the first modification have identical Reference numeral.
The difference of the gas sensing element 110G of current modification and the gas sensing element 110 of the first modification be by internal pump electrode 121 be arranged on diffusional resistance part 120 in inner region.
That is,, on stacked direction Z, diffusional resistance part 120 is not overlapping with internal pump electrode 121.In addition,, on Width X, the inside end wall 122 of diffusional resistance part 120 remains on state located adjacent one another with the outer wall 211 of internal pump electrode 121.
The gas sensing element 110G of current modification has other identical structures with the gas sensing element 110 of the first modification.
Utilize the gas sensing element 110G of current modification, the measurement gas by diffusional resistance part 120 can contact with internal pump electrode 121 reliably, thereby makes oxygen pump unit 125 realize the control to oxygen pumpability in more reliable mode.
Therefore, can obtain having the more gas sensing element 110G of high measurement accuracy.
The gas sensing element 110G of current modification carries out the operation identical with the gas sensing element 110 of the first modification, therefore, has saved the detailed description of same section here.
When describing specific embodiments of the invention in detail, will be understood by those skilled in the art that and can make the various modifications of these details and substitute according to general teachings of the present disclosure.Therefore, disclosed concrete structure does not just schematically limit the scope of the invention, and scope of the present invention is provided by the complete range of described claim and equivalent thereof.

Claims (14)

1. a gas sensor control device that is connected to gas sensor, described gas sensor comprises by solid state electrolysis plastid and is formed on the gas sensing element that the pair of electrodes on described solid state electrolysis plastid forms, wherein when receiving the voltage that is applied to described pair of electrodes two ends, according to the concentration of special component in measurement gas and producing component electric current, described gas sensor control device comprises:
Current-voltage converter, has a terminal of the electrode being connected in described pair of electrodes, for measuring the described element current of the described current-voltage converter of flowing through;
Output circuit, for to utilizing the measured described element current of described current-voltage converter to make response, exports measured result as element current measured value;
Apply voltage-setting circuitry, the another terminal that is connected to described current-voltage converter with arrange to be applied to described gas sensing element described pair of electrodes two ends apply voltage;
The first electric pathway, be connected to described output circuit and described in apply between voltage-setting circuitry apply voltage-setting circuitry described in described element current measured value be applied to;
The second electric pathway, be connected to described current-voltage converter a described terminal and described in apply between voltage-setting circuitry, in described the second electric pathway, do not have element current to flow;
Switchgear, is arranged in described the second electric pathway, for disconnecting selectively and closed described the second electric pathway; And
Calculation element, for from described when applying described voltage that voltage-setting circuitry applies and existing, the described element current measured value based on from described output circuit output calculates the concentration of described special component;
Wherein, the rank after driving the step of described switchgear to apply that voltage-setting circuitry is described described in allowing to apply voltage and be set to regulate, so that the potential difference (PD) between two terminals of described current-voltage converter is in predetermined particular value.
2. gas sensor control device as claimed in claim 1, wherein:
Output acquisition device allows described switchgear closure so that the described potential difference (PD) between described two terminals of described current-voltage converter is returned to zero, to obtain the output valve of described output circuit in the situation that described potential difference (PD) remains on zeroing.
3. gas sensor control device as claimed in claim 2, wherein:
Described the first electric pathway comprises the first feedback network, described output by output circuit described in described the first feedback network applies voltage-setting circuitry described in being input to feedback form, and described the second electric pathway comprises the second feedback network, the voltage that appears at a described terminal place of described current-voltage converter by described the second feedback network applies voltage-setting circuitry described in being input to feedback form;
Wherein, described switchgear is arranged in described the second feedback network;
Thereby in normal concentration, detect operating period, described the first feedback network enters into conducting state and described in arranging via the described output of the described output circuit of described the first feedback network input with feedback form, applies voltage to apply voltage-setting circuitry described in allowing;
And calculating for proofreading and correct the operating period of the current correction value of described element current, only described the second feedback network enters into conducting state and described in arranging via the described voltage of a described terminal of the described current-voltage converter of described the second feedback network input with feedback form, applies voltage to apply voltage-setting circuitry described in allowing.
4. gas sensor control device as claimed in claim 2, also comprises:
One device, for apply described in making when described switchgear enters into closure state voltage-setting circuitry described in apply voltage and be adjusted to the voltage that goes out a plurality of potential difference (PD) with respect to the voltage induced of the described terminal of described current-voltage converter, to obtain output valve from described output circuit under a plurality of states that are conditioned at voltage;
Wherein, correction value calculation device to the described output valve of the described output circuit obtaining under described a plurality of states make response and calculated gains corrected value as current correction value.
5. gas sensor control device as claimed in claim 2, wherein:
The described gas sensing element of described gas sensor comprises described solid state electrolysis plastid and the first module and the second unit that are exposed to measurement gas chamber, each in described first module and described second unit consists of the pair of electrodes being formed on described solid state electrolysis plastid, described first module is adjusted to given concentration rank by the amount of oxygen that enters into the measurement gas of described measurement gas chamber, and described second unit detects the special component with the described measurement gas of utilizing the described amount of oxygen after described first module regulates; And
The second unit electric current that described current-voltage converter measurement produces in described second unit, so that second unit current measurement value to be provided, calculates the concentration of described special component based on described second unit current measurement value.
6. gas sensor control device as claimed in claim 2, also comprises:
Failure determination device, for determining at least one fault occurring at described gas sensing element and sensor circuit based on what produced by correction value calculation device for proofreading and correct the current correction value of described element current.
7. gas sensor control device as claimed in claim 1, also comprises:
Electromotive force pick-up unit, for making described switchgear closure to allow potential difference (PD) between two terminals of described current-voltage converter in zeroing state, for detection of appear at the electromotive force in described gas sensing element under described zeroing state; And
Failure determination device, for determining described gas sensing element and at least one the fault that is connected to the sensor circuit of described gas sensing element based on utilizing the detected described electromotive force of described electromotive force pick-up unit to carry out.
8. gas sensor control device as claimed in claim 7, wherein:
Described in the voltage of a described terminal of described current-voltage converter being input in backfeed loop, apply voltage-setting circuitry so that by described apply voltage-setting circuitry set described in apply the described voltage that voltage equals a described terminal of described current-voltage converter;
Thereby the described potential difference (PD) between described two terminals of described current-voltage converter is returned to zero.
9. gas sensor control device as claimed in claim 7, wherein:
Described the first electric pathway is included in the first feedback network that makes the described output of described output circuit apply voltage-setting circuitry described in being input in backfeed loop, and described the second electric pathway voltage of being included in a described terminal place that makes to be positioned at described current-voltage converter in backfeed loop applies the second feedback network of voltage-setting circuitry described in being input to;
Wherein, described switchgear is arranged in described the second feedback network;
Wherein, in normal concentration, detect operating period, only described the first feedback network enters into conducting state, to apply voltage-setting circuitry described in allowing, described in arranging to the described described output that applies the described output circuit of voltage-setting circuitry input via described the first feedback network, applies voltage in backfeed loop; And
And in the operating period of detecting described electromotive force, only described the second feedback network enters into conducting state and described in arranging via the described voltage of a described terminal of the described current-voltage converter of described the second feedback network input at backfeed loop, applies voltage to apply voltage-setting circuitry described in allowing, so that the described potential difference (PD) between described two terminals of described current-voltage converter is returned to zero.
10. gas sensor control device as claimed in claim 7, also comprises:
Voltage applies interrupting device, for applying voltage described in interruption when described failure determination device determines that fault exists, described in described gas sensing element, applies.
11. gas sensor control devices as claimed in claim 7, wherein:
The described gas sensing element of described gas sensor comprises described solid state electrolysis plastid and the first module and the second unit that are exposed to measurement gas chamber, each in described first module and described second unit consists of the pair of electrodes being formed on described solid state electrolysis plastid, described first module is adjusted to given concentration rank by the amount of oxygen that enters into the measurement gas of described measurement gas chamber, and described second unit detects the special component with the described measurement gas of utilizing the described amount of oxygen after described first module regulates; And
Wherein, described current-voltage converter is measured the described element current in present described second unit.
12. gas sensor control devices as claimed in claim 11, wherein:
The oxygen concentration of described electromotive force pick-up unit in described measurement gas chamber is in representing that carrying out described electromotive force in other other situation of low oxygen level of described given concentration level detects.
13. gas sensor control devices as claimed in claim 3, wherein:
Described gas sensing element has gas range of scatter frequency, and on described gas range of scatter frequency, described gas sensing element has gas diffusivity so that described measurement gas enters into the inner side of described gas sensing element; And
During the time interval that is less than gas diffusion enables frequency scope, described element current is returned to zero.
14. gas sensor control devices as claimed in claim 3, wherein:
Described element current is in 4nA/ppm or less value.
CN200910008212.3A 2008-02-19 2009-02-19 Gas sensor control device Expired - Fee Related CN101514974B (en)

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Families Citing this family (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9568395B2 (en) 2012-02-15 2017-02-14 Toyota Jidosha Kabushiki Kaisha NOx sensor control device
CN102706931B (en) * 2012-05-31 2014-07-09 成都安可信电子股份有限公司 Biasing and non-biasing operating circuit of electrochemical gas sensor and biasing configuration circuit
DE102013206637A1 (en) * 2013-04-15 2014-10-16 Robert Bosch Gmbh Method for analyzing a gas
CN103323106B (en) * 2013-06-09 2015-11-18 国家电网公司 A kind of luminous power test macro
JP6101669B2 (en) * 2013-12-16 2017-03-22 株式会社日本自動車部品総合研究所 Gas sensor
JP6476654B2 (en) * 2014-08-26 2019-03-06 株式会社デンソー Micro current detector
JP6500547B2 (en) * 2015-03-25 2019-04-17 株式会社デンソー Gas sensor
JP6769909B2 (en) * 2017-03-31 2020-10-14 日本碍子株式会社 Gas sensor
DE102019107736B4 (en) * 2019-03-26 2024-07-04 Energybox Ltd. Measuring equipment and measuring method
CN110672331B (en) * 2019-07-02 2021-09-10 成都恩吉威汽车技术有限公司 Wide-range oxygen sensor signal acquisition and signal simulation control unit
CN110208686B (en) * 2019-07-19 2024-05-03 深圳市无眼界科技有限公司 Electrochemical sensor simulation device
CN111397653B (en) * 2020-04-01 2021-11-19 中煤科工集团重庆研究院有限公司 Fault diagnosis system and method for sensor for coal mine
CN112763552B (en) * 2020-12-24 2023-01-06 潍柴动力股份有限公司 Detection method and device of nitrogen-oxygen sensor

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1480039A1 (en) * 2003-05-09 2004-11-24 Denso Corporation Fault detecting apparatus of different types of faults of solid electrolyte gas sensors
EP1586889A2 (en) * 2004-04-16 2005-10-19 Denso Corporation Gas concentration measuring apparatus designed to compensate for output error
CN1715900A (en) * 2004-06-28 2006-01-04 株式会社电装 Gas concentration measuring apparatus designed to compensate for output error

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP4098944B2 (en) * 2000-03-29 2008-06-11 日本特殊陶業株式会社 Control method of gas sensor
JP4016790B2 (en) * 2002-10-10 2007-12-05 株式会社デンソー Gas concentration detector
JP4872198B2 (en) * 2004-04-16 2012-02-08 株式会社デンソー Gas concentration detector
JP2006300625A (en) * 2005-04-19 2006-11-02 Toyota Motor Corp Abnormality detection device of oxygen sensor
JP2007132798A (en) * 2005-11-10 2007-05-31 Ngk Spark Plug Co Ltd Nox detector
JP2008309640A (en) * 2007-06-14 2008-12-25 Denso Corp Gas concentration detector
JP4680276B2 (en) * 2008-03-17 2011-05-11 株式会社デンソー Gas sensor element
JP5091055B2 (en) * 2008-08-27 2012-12-05 日本特殊陶業株式会社 Gas concentration detection device, gas concentration detection system

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1480039A1 (en) * 2003-05-09 2004-11-24 Denso Corporation Fault detecting apparatus of different types of faults of solid electrolyte gas sensors
EP1586889A2 (en) * 2004-04-16 2005-10-19 Denso Corporation Gas concentration measuring apparatus designed to compensate for output error
CN1715900A (en) * 2004-06-28 2006-01-04 株式会社电装 Gas concentration measuring apparatus designed to compensate for output error

Non-Patent Citations (4)

* Cited by examiner, † Cited by third party
Title
JP特开2002-372514A 2002.12.26
JP特开2005-326388A 2005.11.24
JP特开2006-71429A 2006.03.16
JP特开平11-6815A 1999.01.12

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