CN105393115B

CN105393115B - The SOx concentration detection devices of internal combustion engine

Info

Publication number: CN105393115B
Application number: CN201480039676.XA
Authority: CN
Inventors: 水谷圭吾; 寺西真哉; 青木圭一郎; 若尾和弘; 金子丰治; 桥田达弘
Original assignee: Toyota Motor Corp
Current assignee: Toyota Motor Corp
Priority date: 2013-07-12
Filing date: 2014-06-13
Publication date: 2018-08-31
Anticipated expiration: 2034-06-13

Abstract

The purpose of the present invention is the concentration for being contained in the SOx in the exhaust gas of internal combustion engine is easily and accurately detected by limiting-current sensor.The present invention relates to the SOx concentration detection devices of the engine with limiting-current sensor 10,30.The equipment of the present invention comprises mean for detecting the detection part for the concentration for being contained in the SOx in exhaust gas using the output current of sensor when making the voltage for being applied to sensor from predetermined voltage decline.

Description

The SOx concentration detection devices of internal combustion engine

Technical field

The present invention relates to the SOx concentration detection devices of internal combustion engine.

Background technology

It describes in uncensored Japanese Patent Publication No.2-122255 and is contained in admixture of gas for measuring Oxygen-containing gas relative quantity sensor.There are two pump units for sensor tool.These pump units are by provided in series.This In sensor, it is contained in a part (particularly, the O of the oxygen-containing gas in admixture of gas₂) by being applied to upstream side pump unit Remaining oxygen-containing gas (particularly, the H for adding lower voltage to remove, and being contained in admixture of gas₂O and CO₂) it is opposite Amount is measured by applying high voltage to downstream side pump unit.

Invention content

Limiting-current sensor is known.In this sensor, usually, a certain constant voltage, which is applied in, to be used for It is contained in the detection of the concentration of the oxygen in the exhaust gas (exhaust gas) of internal combustion engine discharge.But according to for applying electricity This technology of pressure, the concentration for the SOx being contained in exhaust gas can not be detected easily and accurately.

In this respect, according to the research of present inventor, present inventors have realized that, it is being modified to When applying alive technology to limiting-current sensor, the concentration for the SOx being contained in exhaust gas can pass through limit-current type Sensor accurately detects.

Based on present inventor this understanding, the purpose of the present invention is by limiting-current sensor come accurately Detection is contained in the concentration of the SOx in exhaust gas.

The invention of the application is related to having the SOx Concentration Testings of the internal combustion engine of limiting-current sensor to set It is standby.The present invention equipment include：Detection part, for make the voltage for being applied to sensor (hereinafter, the voltage will be simply referred to as " applied voltage ") while decline from predetermined voltage by using the output current of sensor (hereinafter, the output current will be simple Referred to as " output current ") detect the concentration of the SOx in the exhaust gas for being contained in and being discharged by engine (hereinafter, this concentration of SOx It is referred to as " SOx concentration ").

According to this point, SOx concentration can be detected.Particularly, even if when applied voltage is maintained as constant voltage It occupies the influence of the SOx of output current or occupies the influence of the SOx of output current when applied voltage is enhanced less than accounting for In the case of influence with other components of output current, if occupying output when applied voltage declines from predetermined voltage device The influence of the SOx of electric current is more than the influence for other components for occupying output current, then SOx concentration also can be detected accurately Go out.

Further it is preferred that detection part while so that applied voltage is declined from predetermined voltage by output current Peak value is used as the output current of the detection for SOx concentration.Peak value be output current during applied alive decline most Small output current (or maximum output current).Therefore, peak value is and the accurate corresponding output current of SOx concentration.Thus, SOx is dense Degree can accurately be detected by peak value to be used as to the output current for the detection of SOx concentration.

Moreover, detection part can make applied voltage after predetermined voltage decline by using than predetermined voltage Output current when low voltage is applied in sensor detects the concentration for being contained in the oxygen in exhaust gas.According to this point, including The concentration and SOx concentration of oxygen in exhaust gas can be detected by single sensor.

Moreover, detection part can make applied voltage after the voltage lower than predetermined voltage rises to predetermined voltage Output current when making applied voltage decline from predetermined voltage is used as to the output current of the detection for SOx concentration. In this case, the voltage for sensor being applied to before applied alive decline starts is less than predetermined voltage.Thus, with It applies the alive voltage for starting to be applied to sensor before that declines to compare equal to the situation of predetermined voltage, is SOx concentration The consumed electric power of detection can be reduced.

Detection part can compare predetermined voltage before so that applied voltage is risen to predetermined voltage by using in application Output current when low voltage detects the concentration for being contained in the oxygen in exhaust gas.According to this point, it is contained in the oxygen in exhaust gas Concentration and SOx concentration can be detected by single sensor.

Further it is preferred that predetermined voltage is greater than or equal to 0.8V.According to this point, it is accurately right with SOx concentration to obtain The output current answered, and therefore can accurately detect SOx concentration.

Further it is preferred that applied voltage at the end of decline of the applied voltage from predetermined voltage be less than or Voltage equal to 0.7V.According to this point, can obtain with the accurate corresponding output current of SOx concentration, and therefore can be accurate Ground detects SOx concentration.

Moreover, detection part can make applied voltage according to the pace of change than the voltage with 100Hz it is small or and its Equal speed declines from predetermined voltage.According to this point, it can be ensured that can obtain with the accurate corresponding output current of SOx concentration, And it therefore can accurately detect SOx concentration.

Moreover, detection part can be such that applied voltage from the voltage lower than predetermined voltage rises, and then make to be applied Making alive declines according to the small or equal thereto speed of the pace of change than the voltage with 100Hz from predetermined voltage.According to this Point, it can be ensured that can obtain with the accurate corresponding output current of SOx concentration, and therefore can accurately detect SOx concentration.

Moreover, engine is such as petrol engine.Petrol engine is according in the major part of engine workspace Atmospheric fuel stoichiometric ratio operate.Therefore, the concentration for the oxygen being contained in exhaust gas is low.Thus, SOx concentration can It is detected easily out.

Moreover, SOx concentration detection devices can also include：Control section, for make applied voltage from predetermined voltage The absolute value of output current when decline executes the sulfur poisoning for making sensor in the case of being greater than or equal to first predetermined value Regenerated sulfur poisoning recovery control.According to this point, until the detection of the sensor caused by sulfur poisoning accuracy decline not It can occur, SOx concentration is just detected.Thus, SOx concentration can be detected more accurately.

Moreover, SOx concentration detection devices can also include for defeated when making applied voltage decline from predetermined voltage Go out performance fault of the absolute value of electric current more than alarm in the case of second predetermined value to the fuel of the combustion chamber supply of engine Control section.According to this point, in the case where fuel performance failure may occur, the user of SOx concentration detection devices can , it is realized that the performance fault of fuel may occur.

Another invention of the application is related to being contained in from the internal-combustion engine with limiting-current sensor for detecting The method of the concentration of SOx in the exhaust gas of machine discharge.This method includes：For making to be applied to the voltage of sensor from predetermined voltage The voltage of decline declines step, and step is obtained for obtaining the output current of output current of sensor during dropping step under voltage Suddenly, and for detecting the SOx's being contained in exhaust gas by using the output current obtained by output current obtaining step The SOx concentration detecting steps of concentration.

According to this point, it is capable of detecting when SOx concentration.Particularly, even if when applied voltage is maintained as constant voltage It occupies the influence of the SOx of output current or occupies the influence of the SOx of output current when applied voltage is enhanced less than accounting for In the case of influence with other components of output current, if occupying output electricity when applied voltage declines from predetermined voltage The influence of the SOx of stream is more than the influence for other components for occupying output current, then SOx concentration can be detected accurately.

Moreover, this method can also include：It is lower than predetermined voltage to sensor application later for dropping step under voltage Voltage decline after voltage apply step, and for after decline voltage apply step during by using the defeated of sensor Go out electric current to detect the oxygen concentration detecting step for the concentration for being contained in the oxygen in exhaust gas.According to this point, the oxygen being contained in exhaust gas Concentration and SOx concentration can be detected by single sensor.

Moreover, this method can also include lower than predetermined voltage for applying to sensor before dropping step under voltage Voltage applies step before the decline of voltage, applies step later for voltage before decreasing and makes to apply before drop step under voltage The voltage for being added on sensor rises to the voltage ascending step of predetermined voltage, and for during the application step of voltage before decreasing The oxygen concentration detecting step for the concentration for being contained in the oxygen in exhaust gas is detected by using the output current of sensor.According to this Point, the concentration and SOx concentration of the oxygen being contained in exhaust gas can be detected by single sensor.

Another invention of the application is related to limiting-current sensor.The limiting-current sensor of the present invention is used to Internal combustion is contained in detect by using the output current of sensor when the voltage for being applied to sensor declines from predetermined voltage The concentration of SOx in the exhaust gas of engine discharge.

According to this point, it is capable of providing the limiting-current sensor for detecting SOx concentration.Particularly, even if being applied The influence of the SOx of output current is occupied when making alive is maintained as constant voltage or is occupied when applied voltage is enhanced defeated Go out the SOx of electric current influence be less than occupy output current other components influence in the case of, if applied voltage from The influence that the SOx of output current is occupied when predetermined voltage declines is more than the influence for other components for occupying output current, then can Limiting-current sensor for accurately detecting SOx concentration is provided.

Moreover, sensor can be used to the voltage for being applied to sensor from predetermined voltage decline after by using The output current of sensor when the voltage lower than predetermined voltage is applied in sensor detects the oxygen being contained in exhaust gas Concentration.According to this point, the concentration and SOx concentration of the oxygen being contained in exhaust gas can be detected by single sensor.

Moreover, sensor can be used to before predetermined voltage is applied in sensor by using than predetermined voltage The output current of sensor when low voltage is applied in sensor is contained in the concentration of the oxygen in exhaust gas to detect.According to this Point, the concentration and SOx concentration of the oxygen being contained in exhaust gas can be detected by single sensor.

Description of the drawings

Fig. 1 shows a kind of embodiment (two haplotype limit-current types sensing of the limiting-current sensor of the present invention Device).

Fig. 2 shows the output characteristics of limiting-current sensor shown in FIG. 1.

Fig. 3 shows the output characteristics of limiting-current sensor shown in FIG. 1.

Fig. 4 shows the relationship between SOx concentration and the peak value of output current.

Fig. 5 shows another embodiment (the single unit type limit-current type of the limiting-current sensor of the present invention Sensor).

Fig. 6 shows the output characteristics of limiting-current sensor shown in fig. 5.

Fig. 7 is shown comprising the internal combustion with the SOx concentration detection devices of limiting-current sensor shown in Fig. 1 or 5 Engine.

Fig. 8 shows the time for showing output current corresponding with applied alive variation according to first embodiment Figure.

Fig. 9 A show a kind of mode of applied alive raising and lowering.

Fig. 9 B show the another way of applied alive raising and lowering.

Figure 10 A show an example of the circuit used in limiting-current sensor shown in Fig. 1.

Figure 10 B show an example of the circuit used in limiting-current sensor shown in Fig. 4.

Figure 11 shows an example of the embodiment of SOx Concentration Testings flow according to first embodiment.

Figure 12 shows an example of SOx Concentration Testings flow according to second embodiment.

Figure 13 shows an example of SOx Concentration Testings flow according to third embodiment.

Figure 14 shows an example of SOx concentration/air-fuel ratio testing process according to fourth embodiment.

Specific implementation mode

The SOx of the limiting-current sensor of the present invention and the internal combustion engine comprising the limiting-current sensor is dense The embodiment of degree detection device will be described with reference to the accompanying drawings.

Fig. 1 shows the limiting-current sensor of first embodiment according to the present invention.Sensor shown in FIG. 1 is two Haplotype limiting-current sensor.In Fig. 1,10 indicate that limiting-current sensor, 11A indicate the first solid electrolyte Layer, 11B indicate that the second solid electrolyte layer, 12A indicate that the first alumina layer, 12B indicate that the second alumina layer, 12C indicate the Alchlor layer, 12D indicate that the 4th alumina layer, 12E indicate that five aluminium oxide layer, 12F indicate the 6th alumina layer, and 13 indicate Limiting layer is spread, 14 indicate heater, and 15 indicate that pump unit, 15A indicate that the first pump electrode, 15B indicate the second pump electrode, 15C Indicate the voltage source of pump unit, 16 indicate that sensor unit, 16A indicate that first sensor electrode, 16B indicate second sensor electricity Pole, 16C indicate that the voltage source of sensor unit, 17A indicate that the first air introduction passage, 17B indicate the second air introduction passage, And 18 indicate inner space.

Solid electrolyte layer 11A and 11B be by the layer of the formation such as zirconium oxide, and have oxygen ion conduction property.Oxidation Aluminium layer 12A to 12F is the layer formed by aluminium oxide.It is that exhaust gas can be allowed to pass through porous layer therein to spread limiting layer 13.It is passing In sensor 10, these layer of tegillum is altogether so that the 6th alumina layer 12F, five aluminium oxide layer 12E, the 4th alumina layer 12D, the second solid electrolyte layer 11B, diffusion limiting layer 13, third alumina layer 12C, the first solid electrolyte layer 11A, second Alumina layer 12B and the first alumina layer 12A are positioned in order from the downside of Fig. 1.Heater 14 is located in the 5th And the 6th between alumina layer 12E and 12F.

First air introduction passage 17A is by first and second alumina layer 12A and 12B and the first solid electrolyte layer The space that 11A is formed, a part of the first air introduction passage 17A is to atmosphere opening.Second air introduction passage 17B is by The space that two solid electrolyte layer 11B and the 4th and five aluminium oxide layer 12D and 12E are formed, the second air introduction passage 17B A part to atmosphere opening.Inner space 18 is by first and second solid electrolyte layer 11A and 11B, diffusion limiting layer 13 And the space that third alumina layer 12C is formed, and a part for inner space 18 is via diffusion limiting layer 13 and sensor PERCOM peripheral communication.

Pump electrode 15A and 15B are the electrodes formed by platinum family element (for example, platinum and rhodium or their alloy).Electrode 15A is located in the wall surface of the side of solid electrolyte layer 11B (it is, being used to form the wall of the layer 11B of inner space 18 Face) on, and electrode 15B is located in the wall surface of the other side of solid electrolyte layer 11B (it is, being used to form second largest The wall surface of the layer 11B of gas introduction passage 17B) on.Electrode 15A and 15B and layer 11B are configured with pump unit 15.10 quilt of sensor Be configured to by the voltage of the voltage source 15C from pump unit be applied to pump unit 15 (particularly, electrode 15A and 15B it Between).It should be noted that electrode 15A is cathode side electrode, and electrode 15B is anode side electrode.

When voltage is applied in pump unit 15 and the oxygen in inner space 18 contacts pump electrode 15A, which becomes Oxonium ion on electrode 15A, and then the oxonium ion shifts to pump electrode 15B across the inside of solid electrolyte layer 11B. At this point, generate and have moved through between electrode 15A and 15B the oxonium ion amount of the inside of solid electrolyte layer 11B at than The electric current of example.Then, when oxonium ion reaches electrode 15B, oxonium ion becomes oxygen on electrode 15B, and is then discharged To the second air introduction passage 17B.It is, pump unit 15 can be included in the oxygen in exhaust gas from exhaust gas by pump action In be discharged into air, and thus, it is possible to reduce the concentration for being contained in the oxygen in exhaust gas.The energy of the pump action of pump unit 15 Power is as the voltage for being applied to pump unit 15 by the voltage source 15C of pump unit increases and increases.

Sensor electrode 16A and 16B are the electrodes formed by platinum family element (for example, platinum and rhodium or their alloy). Electrode 16A is located in the wall surface of the side of solid electrolyte layer 11A (it is, being used to form the layer 11A of inner space 18 Wall surface) on, and electrode 16B is located in the wall surface of the other side of solid electrolyte layer 11A (it is, being used to form first The wall surface of the layer 11A of air introduction passage 17A) on.Electrode 16A and 16B and layer 11A are configured with sensor unit 16.Sensing Device 10, which is configured to the voltage of the voltage source 16C from sensor unit being applied to sensor unit 16, (particularly, to be applied It is added between electrode 16A and 16B).It should be noted that electrode 16A is cathode side electrode, and electrode 16B is anode side electrode.

When voltage is applied in sensor unit 16 and SOx contact sensor electrode 16A in inner space 18, The SOx is dissolved on electrode 16A, and the oxygen of SOx becomes oxonium ion, and then the oxonium ion passes through solid electrolyte layer 11A Inside shift to sensor electrode 16B.At this moment, it generates and has moved through in layer 11A between electrode 16A and 16B The proportional electric current of the oxonium ion amount in portion.Then, when oxonium ion reaches electrode 16B, oxonium ion becomes oxygen on electrode 16B Gas, and it is then expelled to the first air introduction passage 17A.

Fig. 2 shows the application voltages of the pump unit in two haplotypes carrying current sensor according to first embodiment Relationship between the output current of pump unit.The application voltage of pump unit is to be applied to pump list by the voltage source 15C of pump unit The voltage of member 15, and the output current of pump unit is the electric current flowed through between pump electrode 15A and 15B.Moreover, in fig. 2, by The line of A/F=12 instructions is shown applies alive variation in the case where the air-fuel ratio of exhaust gas is by 12 relative to pump unit Output current variation, and similarly, the line indicated by A/F=13 to A/F=18 respectively illustrates the air-fuel in exhaust gas Than by the variation relative to the output current for applying alive variation of pump unit in the case of 13 to 18.

As shown in Fig. 2, for example, the air-fuel ratio in exhaust gas is in by the application voltage of 18 and pump unit less than particular value In the case of in the range of Vth, when the output current of pump unit is negative value, the absolute value of the output current of pump unit is single with pump Member applied voltage increase and reduce, and when the output current of pump unit for positive value when, the output current of pump unit it is exhausted Increase being worth the applied voltage increase with pump unit.Moreover, the applied voltage in pump unit is in greater than or equal to spy In the case of in the constant range of definite value Vth, the output current of pump unit is steady state value, applies electricity independently of pump unit Pressure.

Similarly, sky of this relationship between the applied voltage of pump unit and the output current of pump unit in exhaust gas Combustion ratio is also set up in the case of being 12 to 17.In this respect, as understood according to fig. 2, in all air-fuel ratios to be detected In, when in the case where the output current of pump unit is by constant (independently of the application voltage of pump unit) to pump unit 15 apply When voltage, the air-fuel ratio of exhaust gas can be detected based on the output current of detected pump unit.It is, real according to first The air-fuel ratio of detection exhaust gas can be used to by applying two haplotype limiting-current sensors 10 of example.It should be noted that the sky of exhaust gas Combustion is than being with the concentration for the oxygen being contained in exhaust gas with associated parameter, and therefore, in principle, according to first embodiment Two haplotype limiting-current sensors be capable of detecting when the concentration of the oxygen being contained in exhaust gas.

Moreover, sensor unit in two haplotypes limiting-current sensor according to first embodiment is applied Relationship between voltage and the output current of sensor unit is identical as relationship shown in Fig. 2.Therefore, being applied in pump unit Under conditions of voltage is zero (it is, pump unit 15 does not work), in all air-fuel ratios to be detected, when in sensor list The output current of member to sensor unit 16 in the case of constant (independently of the application voltage of sensor unit) by applying electricity When pressure, the air-fuel ratio of exhaust gas can be detected based on the output current of detected sensor unit.It is, according to first Two haplotype limiting-current sensors 10 of embodiment can be used to the air-fuel ratio of detection exhaust gas.It should be noted that sensor The applied voltage of unit is that the voltage of sensor unit 16 is applied to by the voltage source 16C of sensor unit, and sensor The output current of unit is the electric current flowed through between sensor electrode 16A and 16B.

According to the research of present inventor, present inventor is newly, it is realized that with being contained in exhaust gas The corresponding electric current of concentration of SOx can be by making the voltage for being applied to two haplotype limiting-current sensors (particularly, by passing The voltage source 16C of sensor cell is applied to the voltage of sensor unit 16) decline from predetermined voltage and is sensed from limit-current type It is obtained in device.Next, this will be described.It should be noted that in the description that follows, output current is defeated from sensor unit 16 The electric current gone out.

It is shown in FIG. 3 and gradually rises up to 1.0V from 0.1V in applied voltage and then make applied voltage from 1.0V The variation of output current when gradually decreasing down 0.1V.The axis of abscissas instruction of Fig. 3 applies voltage, and the axis of ordinates of Fig. 3 refers to Show output current.It should be noted that (or big for making the concentration of the oxygen in the exhaust gas being contained in inner space 18 drop to zero On body pump unit 15 is applied in while changing application voltage by voltage zero).

In figure 3, solid line LU0 instructions do not contain SOx (it is, the SOx's being contained in exhaust gas is a concentration of in the offgas Zero) variation of output current when applied voltage being made to rise to 1.0V from 0.1V in the case of, and solid line LD0 instructions are in exhaust gas The variation of output current when applied voltage being made to drop to 0.1V from 1.0V in the case of without containing SOx.In figure 3, click and sweep The variation of output current when line LU1 instructions make applied voltage rise to 1.0V from 0.1V in the case where exhaust gas contains SOx, And output current of chain-dotted line LD1 instruction when applied voltage being made to drop to 0.1V from 1.0V in the case where exhaust gas contains SOx Variation.

In the case where exhaust gas does not contain SOx, when applied voltage is improved from 0.1V to 0.2V, such as the reality in Fig. 3 Shown in line LU0, output current rapidly increases to about 4 microamperes.Then, it is improved from about 0.2V to about in applied voltage When 0.85V, output current is less constant in about 4 microamperes.Then, when applied voltage is more than about 0.85V, output electricity Stream starts to increase.Then, it is improved from about 0.85V to 1.0V with applied voltage, output current gradually increases, and works as institute When application voltage reaches 1.0V, output current reaches about 7 microamperes.

Thereafter, when applied voltage gradually decreases down 0.4V from 1.0V, as shown in the realization LD0 in Fig. 3, output current Gradually reduce from about 7 microamperes, and when applied voltage falls to approximately 0.85V or less and then reaches 0.4V, it is defeated It is less constant in about 3.5 microamperes to go out electric current.

On the other hand, in the case where exhaust gas contains SOx, when applied voltage is improved from 0.1V to 0.2V, in Fig. 3 Chain-dotted line LU1 shown in, output current rapidly increases to about 4 microamperes.Then, when applied voltage is improved from about 0.2V When to about 0.6V, output current is less constant in about 4 microamperes.Then, defeated when applied voltage is more than about 0.6V Go out electric current to start to increase.Then, it being improved from about 0.6V to 1.0V with applied voltage, output current gradually increases, and When applied voltage reaches 1.0V, output current reaches about 7 microamperes.

Thereafter, when applied voltage gradually decreases down 0.4V from 1.0V, as shown in the chain-dotted line LD1 in Fig. 3, output electricity Stream gradually reduces from about 7 microamperes, and falls to approximately 0.8V or less in applied voltage and then reach about 0.7V When, output current quickly reduces, the flow direction reversion of output current, and then output current reaches about -5 microamperes.So Afterwards, in applied voltage further from when about 0.7V drops to 0.4V, output current quickly increases, and the stream of output current Dynamic direction returns to inceptive direction, and when applied voltage reaches 0.4V, output current becomes about 3.5 microamperes.

Therefore, it in the case where exhaust gas contains SOx, is improved from 0.4V to 0.8V in applied voltage and and then applies electricity When pressure drops to 0.4V from 0.8V, output current quickly reduces, and then quickly increases when applied voltage is lowered. It is exactly that, when applied voltage drops to 0.4V from 0.8V, output current changes, so that having minimum value (it is, peak value). In this respect, when applied voltage reaches about 0.7V, output current becomes peak value.

It should be noted that being more than about 0.6V in applied voltage in the case where exhaust gas contains SOx and then reaching 1.0V When output current be more than exhaust gas do not contain SOx in the case of applied voltage be more than about 0.6V simultaneously then reach 1.0V When output current.

According to the research of present inventor, present inventor is it has been realized that in two haplotype carrying currents In type sensor, relationship shown in Fig. 4 when making applied voltage drop to 0.4V from 0.8V as described above It is present between the peak value of output current and SOx concentration.It is, present inventor is it has been realized that be contained in exhaust gas In SOx concentration with reference current (it is, output current when applied voltage reaches 0.8V) and peak value difference Increase and increases.It is contained in moreover, two haplotypes limiting-current sensor according to first embodiment can be used to detection The concentration of oxygen in exhaust gas (to detect the air-fuel ratio of exhaust gas).Therefore, by using it is according to first embodiment can by with Detect two haplotype limiting-current sensors of the concentration for being contained in the oxygen in exhaust gas, SOx concentration can based on peak value come It calculates (detection).

The limiting-current sensor of first embodiment according to the present invention is shown in FIG. 5.Limit electricity shown in fig. 5 Flow pattern sensor is single unit type limiting-current sensor.In Figure 5,30 limiting-current sensor is indicated, 31 indicate Solid electrolyte layer, 32A indicate that the first alumina layer, 32B indicate that the second alumina layer, 32C indicate third alumina layer, 32D Indicate that the 4th alumina layer, 32E indicate five aluminium oxide layer, 33 indicate diffusion limiting layer, and 34 indicate heater, and 35 indicate sensing Device unit, 35A indicate that first sensor electrode, 35B indicate that second sensor electrode, 35C indicate the voltage source of sensor unit, 36 indicate air introduction passage and 37 expression inner spaces.

Solid electrolyte layer 31 be by the layer of the formation such as zirconium oxide, and have oxygen ion conduction performance.Alumina layer 32A It is the layer formed by aluminium oxide to 32E.It is that exhaust gas can be allowed to pass through porous layer therein to spread limiting layer 33.In sensor 30 In, these layer of tegillum is altogether so that five aluminium oxide layer 32E, the 4th alumina layer 32D, third alumina layer 32C, solid Electrolyte layer 31, diffusion limiting layer 33 and the second alumina layer 32B and the first alumina layer 32A are from the downside of Fig. 5 by suitable Sequence positions.Heater 34 is located between the 4th and five aluminium oxide layer 32D and 32E.

Air introduction passage 36 is formed by solid electrolyte layer 31 and third and the 4th alumina layer 32C and 32D Space, and a part for air introduction passage 36 is to atmosphere opening.Inner space 37 is by the first alumina layer 32A, solid The space that electrolyte layer 31, diffusion limiting layer 33 and the second alumina layer 32B are formed, and a part for inner space 37 via Spread the PERCOM peripheral communication of limiting layer 33 and sensor.

Sensor electrode 35A and 35B are the electrodes formed by platinum family element (for example, platinum and rhodium or their alloy). Electrode 35A is located in the wall surface (it is, forming the wall surface of the layer 31 of inner space 37) of the side of solid electrolyte layer 31 On, and electrode 35B is located in the wall surface of the other side of solid electrolyte layer 31 (it is, forming air introduction passage 36 Layer 31 wall surface) on.Electrode 35A and 35B and layer 31 are configured with sensor unit 35.Sensor 30 be configured to by The voltage of voltage source 35C from sensor unit is applied to sensor unit 35 (particularly, between electrode 35A and 35B). It should be noted that electrode 35A is cathode side electrode, and electrode 35B is anode side electrode.

When voltage is applied in sensor unit 35 and SOx contact sensor electrode 35A in inner space 37, The Sox is decomposed on electrode 35A, and the oxygen of SOx becomes oxonium ion, and then the oxonium ion passes through the inside of layer 31 to shift to electrode 35B.At this moment, the electric current proportional to the amount of the oxonium ion for the inside for having moved through layer 31 results from electrode 35A and 35B Between.Then, when oxonium ion reaches electrode 35B, oxonium ion becomes oxygen on electrode 35B, and is then expelled to big Gas introduction passage 36.

Sensor unit in single unit type limiting-current sensor according to first embodiment applies electricity Relationship between pressure and the output current of sensor unit is identical as relationship shown in Fig. 2.Therefore, in all air-fuels to be detected Than in, when will be electric in the case where the output current of sensor unit is by constant (independently of the application voltage of sensor unit) When pressure is applied to sensor unit 35, the air-fuel ratio of exhaust gas can be examined based on the output current of detected sensor unit It surveys.It is, single unit type limiting-current sensor 30 according to first embodiment can be used to the sky of detection exhaust gas Combustion ratio.It should be noted that the air-fuel ratio of exhaust gas is that have associated parameter with the concentration for the oxygen being contained in exhaust gas, and therefore exist In principle, single unit type limiting-current sensor according to first embodiment is capable of detecting when the oxygen being contained in exhaust gas Concentration.Moreover, the applied voltage of sensor unit is to be applied to sensor unit 35 by the voltage source 35C of sensor unit Voltage, and the output current of sensor unit is the electric current flowed through between sensor electrode 35A and 35B.

According to the research of present inventor, present inventor is it has been realized that be similar to the two haplotype limit Amperometric sensor, electric current corresponding with the concentration for the SOx being contained in exhaust gas can be by making to be applied to single unit type pole The voltage (voltage that sensor unit 35 particularly, is applied to by the voltage source 35C of sensor unit) of flow pattern of rationing the power supply sensor Decline from predetermined voltage and is obtained from limiting-current sensor.Next, this will be described.It should be noted that being retouched in subsequent In stating, output current is the electric current exported by sensor unit 35, and the constant concentration for the oxygen being contained in exhaust gas is in 1%.

It is shown in FIG. 6 and gradually rises up to 1.0V from 0.1V in applied voltage and then make applied voltage from 1.0V The variation of output current when gradually decreasing down 0.1V.The axis of abscissas of Fig. 6 indicates applied voltage, and the ordinate of Fig. 6 Axis indicates output current.

In figure 6, chain-dotted line LU1 instructions make applied voltage be risen to from 0.1V in the case where exhaust gas contains SOx The variation of output current when 1.0V, and chain-dotted line LD1 instruction make in the case where exhaust gas contains SOx applied voltage from The variation of output current when 1.0V drops to 0.1V.

In the case where exhaust gas contains SOx, when applied voltage is improved from 0.1V to 0.2V, such as the click and sweep in Fig. 6 Shown in line LU1, output current quickly increases to about 100 microamperes.Then, when applied voltage is improved from about 0.2V to about When 0.6V, output current is less constant in about 100 microamperes.Then, when applied voltage is more than about 0.6V, output electricity Stream starts to increase.Then, it being improved from about 0.6V to 1.0V with applied voltage, output current slightly gradually increases, and When applied voltage reaches 1.0V, output current reaches about 105 microamperes.

Thereafter, when applied voltage gradually decreases down 0.4V from 1.0V, as shown in the chain-dotted line LD1 in Fig. 6, output electricity Stream is gradually reduced from about 105 microamperes, and is fallen to approximately 0.8V or less in applied voltage and then reached about When 0.7V, output current quickly reduces, and then output current reaches about 80 microamperes.Then, in applied voltage from about When 0.7V drops to 0.4V, output current quickly increases, and when applied voltage reaches 0.4V, output current becomes about 100 microamperes.

Therefore, it in the case where exhaust gas contains SOx, is improved from 0.4V to 0.8V in applied voltage and and then applies electricity When pressure drops to 0.4V from 0.8V, output current quickly reduces, and then quickly increases when applied voltage declines.Also It is that, when applied voltage drops to 0.4V from 0.8V, output current changes, so that having minimum value (it is, peak value). This respect, when applied voltage reaches about 0.7V, output current becomes peak value.

According to the research of present inventor, present inventor is it has been realized that in single unit type limit electricity In flow pattern sensor, relationship as relation object as shown in fig. 4 as described above make applied voltage from 0.8V is present in when dropping to 0.4V between the peak value of output current and SOx concentration.It is, present inventor is careful Know, the concentration of the SOx being contained in exhaust gas is with reference current (it is, the output electricity when applied voltage reaches 0.8V Stream) with the increase of the difference of peak value and increase.Moreover, single unit type limiting-current sensor according to first embodiment can be by For detecting the concentration for being contained in the oxygen in exhaust gas (to detect the air-fuel ratio of exhaust gas).Therefore, by using real according to first Apply the single unit type limiting-current sensor that can be used for detecting the concentration for being contained in the oxygen in exhaust gas of example, SOx concentration It can be calculated (detection) based on peak value.

It is shown in FIG. 7 comprising the SOx Concentration Testings with limiting-current sensor 10 or 30 shown in Fig. 1 or 5 The internal combustion engine of equipment.Engine shown in Fig. 7 is spark ignition type internal combustion engine (so-called petrol engine).But It is that the present invention can be applied to charge compression self-ignition type internal combustion engine (so-called diesel engine).Moreover, hair shown in Fig. 7 Motivation is grasped according to the air fuel stoichiometric ratio (stoichiometry) in main (substantial) engine workspace Make.

In the figure 7, limiting-current sensor shown in 10 or 30 expression Fig. 1 or 5, the main body of 50 expression engines, 51 Indicate cylinder cap, 52 indicate cylinder body, and 53 indicate combustion chamber, and 54 indicate fuel injector, and 55 indicate spark plug, and 56 indicate fuel pump, 57 tables Show fuel feed pump, 60 indicate piston, and 61 indicate connecting rod, and 62 indicate bent axle, and 63 indicate crank angle sensor, and 70 indicate inlet valve, 71 indicate air intake ducts, 72 indicate inlet manifold, 73 indicate ventilation fuel tanks (surge tank), 74 indicate throttle valves, 75 indicate into Tracheae, 76 indicate air flow meter, and 77 indicate air cleaner, and 80 indicate exhaust valve, and 81 indicate exhaust duct, and 82 indicate exhaust discrimination Pipe, 83 indicate exhaust pipe, and 90 indicate electronic control unit (ECU), and 91 indicate accelerator pedal and 92 expression gas pedal depressions Quantity sensor.

Fuel injector 54, spark plug 55, throttle valve 74, crank angle sensor 63, air flow meter 76, gas pedal depression Quantity sensor 92 and limiting-current sensor 10 or 30 are electrically connected with ECU 90.ECU 90 is to fuel injector 54, spark plug 55 The signal for operating them is sent with throttle valve 74.Moreover, ECU 90 is received from crank angle sensor 63, air mass flow The signal of meter 76 and accelerator pedal sensor 92.Signal corresponding with the rotating speed of bent axle 62 is by crank angle sensor 63 Output.ECU 90 calculates engine speed based on the signal received from crank angle sensor 63.With pass through air flow meter Flow (it is, flow of the air in sucking combustion chamber 53) corresponding signal of air exported by air flow meter 76. ECU 90 calculates inhaled air volume based on the signal received from air flow meter 76.It is corresponding with the volume under pressure of accelerator pedal 91 Signal is exported by accelerator pedal sensor 92.ECU 90 is based on the signal received from accelerator pedal sensor 92 To calculate engine load.

<Limiting-current sensor>

Limiting-current sensor 10 or 30 is installed on exhaust pipe 83.Therefore, as will be sensed by limit-current type The gas (it is, gas to be detected) for the object that device 10 or 30 detects is the exhaust gas being discharged from combustion chamber 53.Be contained in The corresponding electric current of concentration of the Sox to reach capacity in the exhaust gas of amperometric sensor is defeated by limiting-current sensor 10 or 30 Go out.ECU 90 calculates the SOx concentration (details of the computational methods based on the electric current received from limiting-current sensor 10 or 30 It will be described later).

SOx Concentration Testings according to first embodiment will be described with reference to Fig. 8.According to first embodiment, applied voltage Consistently it is held in 0.4V (referring to the period shown in Fig. 8 before time T0).It is, the voltage of 0.4V is constant Ground is applied to sensor.Then, in SOx Concentration Testings according to first embodiment, applied voltage from 0.4V improve to 0.8V (is referred to shown in Fig. 8 from time T0 to the period of time T1), and then, applied voltage is dropped to from 0.8V 0.4V (is referred to shown in Fig. 8 from time T1 to the period of time T2).At this moment, ECU by applied voltage from 0.8V (it is, detection) SOx to be calculated using reference current and the peak value for the output current for being input to ECU dense when dropping to 0.4V Degree.At this moment, the counted SOx concentration of institute increases with the difference of reference current and peak value and is increased.

It should be noted that in SOx concentration by using the difference of peak value and reference current (hereinafter, the difference is referred to as " electric current Difference ") come the feelings that calculate and (obtained for example, SOx concentration corresponding with current difference first passes through each current difference experiment etc. in advance) Under condition, these SOx concentration obtained are stored in the form of the mapping as the function of current difference in ECU, and SOx concentration is logical Cross read from mapping with during the detection of SOx concentration the corresponding SOx concentration of calculated current difference calculate.

The limiting-current sensor of SOx concentration detection devices according to first embodiment can be used to detection and be contained in The concentration of oxygen in exhaust gas (to detect the air-fuel ratio of exhaust gas).Therefore, it is set according to SOx Concentration Testings according to first embodiment Standby, the concentration for the SOx being contained in exhaust gas can be by using the biography that can be used for detecting the concentration for being contained in the oxygen in exhaust gas Sensor detects.It is, present inventor it has been realized that applied voltage be maintained as constant voltage (for example, The influence of the SOx of output current is occupied when 0.4V) or the influence of the SOx of output current is occupied when applied voltage is enhanced Less than occupy output current other components (for example, O₂And NOx) influence, and on the other hand, in applied voltage from pre- The influence that constant voltage (for example, 0.8V) acts the SOx that output current is occupied when declining is more than other components for occupying output current It influences, and thus, according to SOx concentration detection devices according to first embodiment, SOx concentration can be by using can be used for The sensor of the concentration for the oxygen being contained in exhaust gas is detected accurately to detect.

Moreover, peak value be as the output current during applied alive decline and with the feelings in SOx a concentration of zero The most dramatically different output current of output current under condition.Therefore, peak value is and the accurate corresponding output current of SOx concentration.Cause And SOx concentration can more accurately be detected by the way that peak value is used as the output current for SOx Concentration Testings.

Moreover, according to first embodiment, the voltage that sensor is applied to before applied voltage is begun to decline is 0.4V. Therefore, which is less than the 0.8V applied when applied alive decline starts.Thus, according to first embodiment, in institute Application voltage is applied to sensor situation of the voltage equal to 0.8V before beginning to decline is compared, and is consumed by SOx Concentration Testings Electric power can be reduced.

It should be noted that in SOx Concentration Testings according to first embodiment, the application when applied voltage is begun to ramp up Voltage (it is, being consistently applied to the voltage of sensor) is not limited to 0.4V, and can apply electricity in raising Pressure after decline applied voltage when for generate have peak value output current variation free voltage, for example, be less than or Voltage equal to 0.6V, it is preferable that the voltage equal with 0.4V.

Moreover, application voltage at the end of applied alive rising is not limited to 0.8V, and can carry The free voltage of variation when declining applied voltage after high applied voltage for generating the output current with peak value, or Person greater than or equal to output voltage stabilized range (it is, SOx it is a concentration of zero in the case of output current it is less constant (with institute Apply voltage it is unrelated) range, for example, 0.2V~0.8V) maximum voltage free voltage, for example, higher than 0.8V voltage.

Moreover, application voltage at the end of applied alive decline is not limited to 0.4V, and can be less than Or the free voltage of voltage corresponding equal to peak value, for example, the voltage less than or equal to 0.7V, it is preferable that equal with 0.4V Voltage.Therefore, it is applied it is alive rise start when application voltage can at the end of applied alive decline Voltage it is identical or different.

Moreover, in SOx Concentration Testings according to first embodiment, peak value has been used, still, the generation as the peak value It replaces, it is defeated in the range of can using the output current being quickly decreased or increased when applied voltage drops to 0.4V from 0.8V Go out electric current.

It should be noted that the concentration for the oxygen being contained in the exhaust gas in the inner space of flow sensor applies electricity in decline It can change during pressure.In this case, the output current instruction when applied voltage is by 0.8V applies voltage change Oxygen concentration before, and the output current when applied voltage is by 0.4V indicates that the oxygen after applying voltage change is dense Degree.Therefore, compared with the output current when applied voltage is 0.8V, the output current when applied voltage is 0.4V is more Accurately reflect the concentration of the oxygen in the exhaust gas being contained in the inner space of sensor when peak value is exported.Therefore, exist In SOx Concentration Testings according to first embodiment, in the case where applied voltage drops to 0.4V from 0.8V, as with reference to electricity The replacement of stream, the output current when applied voltage reaches 0.4V from the time (or when have passed through scheduled Between after output current) be used as reference current.According to this point, even if the concentration of the oxygen in being contained in exhaust gas is in institute When changing during applying alive decline, SOx concentration also can be detected accurately.

Moreover, in the first embodiment, calculating the replacement of SOx concentration as peak value and reference current is used, can making SOx concentration is calculated with peak value and conversion coefficient.In this respect, the counted SOx concentration of institute increases as peak value increases towards negative value Greatly.It is, when peak value is negative, the counted SOx concentration of institute increases with the absolute value of peak value and is increased, and when peak value is just When, counted SOx concentration with peak value absolute value reduce and increase.It should be noted that conversion coefficient is for according to shown in Fig. 4 Relationship peak value is converted to the coefficient of SOx concentration.Certainly, in the case where peak value occurs as positive value, the counted SOx of institute Concentration increases towards positive value with peak value and is increased.

In SOx Concentration Testings according to first embodiment, if speed (the scanning speed that applied voltage rises or falls Degree) it is excessively high, then can there is no peak value to be exported, or can not export when applied voltage is lowered abundant with SOx concentration Corresponding peak value.Therefore, in SOx Concentration Testings according to first embodiment, it is preferred that wherein fully right with SOx concentration The peak value answered is selected when applied voltage is lowered by the speed for applying voltage raising and lowering of output.

Particularly, as shown in Figure 9 A, it is preferred that applied voltage is enhanced so that apply the alive rate of climb It is gradually reduced, and then applied voltage is lowered so that apply alive decrease speed and gradually increase.Otherwise, as schemed Shown in 9B, it is preferred that applied voltage is enhanced so that it applies the alive rate of climb and is held in constant speed, and And then applied voltage is lowered so that is applied alive decrease speed and is held in constant speed.

Moreover, particularly, in SOx Concentration Testings according to first embodiment, when being applied to express by frequency It is excellent when applying alive variation when voltage is improved from 0.4V to 0.8V and then applied voltage drops to 0.4V from 0.8V Choosing is that frequency is less than or equal to 100Hz.In other words, to applied alive preferably since applied alive rising Decline terminate the required time be longer than or be equal to 0.01 second.

It should be noted that including that (two haplotype limit-current types sense limiting-current sensor shown in FIG. 1 in engine Device) in the case of, such as circuit shown in Figure 10 A is used as SOx detection circuits.In Figure 10 A, 10 indicate that limit-current type passes Sensor (it is, limiting-current sensor shown in FIG. 1), 14 indicate heater, and 15 indicate pump unit, and 16 indicate sensor Unit, 90 indicate ECU, and 91 indicate to apply voltage commanding section, and 92 expression parameter calculating sections, 93 indicate heater control unit Point, 94P and 94S indicate that apply voltage control circuit and 95P and 95S indicates output current detection circuit respectively respectively.

Applying voltage commanding section 91, parameter calculating portion 92 and heater control unit divides 93 to be the element of ECU 90.

Application voltage control will be sent to the relevant order of voltage for being applied to pump unit 15 by applying voltage commanding section 91 Circuit 94P processed, and application voltage control circuit will be sent to the relevant order of voltage for being applied to sensor unit 16 94S。

Parameter calculating portion 92 receives signal corresponding with the output current of pump unit from output current detection circuit 95P, The output current for calculating pump unit based on the reception signal, and the sky of exhaust gas is calculated based on this counted output current Combustion is than (or the concentration for the oxygen being contained in exhaust gas).Parameter calculating portion 92 is received and is passed from output current detection circuit 95S The corresponding signal of output current of sensor cell, the output current that sensor unit is calculated based on the reception signal, and base The concentration for being contained in the SOx in exhaust gas is calculated in this counted output current.Moreover, parameter calculating portion 92 is based on receiving The impedance of the circuit in sensor 10 is calculated from the signal of output current detection circuit 95P and 95S, and will be with this calculation The relevant information of impedance obtained is sent to heater control unit point 93.Heater control unit point 93 will be used for based on reception autoregressive parameter Calculating section 92 is sent to heater 14 with the relevant information of impedance to control the control signal of heater 14.

Apply voltage control circuit 94P based on received from apply voltage commanding section 91 order (or based on received from The order of voltage commanding section 91 and being provided by output current detection circuit 95P corresponding with pump unit output current is provided Signal) control the applied voltage of pump unit.

The output current of output current detection circuit 95P detection pump units, and the output current pair that will be measured with this The signal answered is sent to parameter calculating portion 92 and applies voltage control circuit 94P.

Apply voltage control circuit 94S based on received from applying the order of voltage commanding section 91 (or received from application The order of voltage commanding section 91 is being provided by output current detection circuit 95S corresponding with sensor unit output current Signal) control the applied voltage of sensor unit.

The output current of output current detection circuit 95S detection sensor units, and the output current that will be measured with this Corresponding signal is sent to parameter calculating portion 92 and applies voltage control circuit 94S.

Include the feelings of limiting-current sensor shown in fig. 5 (single unit type limiting-current sensor) in engine Under condition, such as circuit shown in Figure 10 B is used as SOx detection circuits.In fig. 1 ob, 30 indicate limiting-current sensors ( It is exactly limiting-current sensor shown in fig. 5), 34 indicate heater, and 35 indicate sensor unit, and 90 indicate ECU, 91 tables Show application voltage commanding section, 92 expression parameter calculating sections, 93 indicate heater control unit point, and 94 indicate to apply voltage control Circuit and 95 expression output current detection circuits.

Application electricity will be sent to the relevant order of voltage for being applied to sensor unit 35 by applying voltage commanding section 91 Press control circuit 94.

Parameter calculating portion 92 receives letter corresponding with the output current of sensor unit from output current detection circuit 95 Number, the output current that sensor unit is calculated based on the reception signal, and calculated based on this counted output current The air-fuel ratio (concentration for the oxygen being either contained in exhaust gas) of exhaust gas or the concentration for being contained in the SOx in exhaust gas.Moreover, parameter Calculating section 92 calculates the impedance of the circuit in sensor 30 based on the signal received from output current detection circuit 95, and Heater control unit point 93 will be sent to this counted relevant information of impedance.Heater control unit point 93 will be used to be based on With the relevant information of impedance received from parameter calculating portion 92 heater 34 is sent to control the control signal of heater 34.

Apply voltage control circuit 94 based on received from apply voltage commanding section 91 order (or received from apply electricity The order or being provided by output current detection circuit 95 corresponding with sensor unit output current of command portion 91 is provided Signal) control the applied voltage of sensor unit.

The output current of 95 detection sensor unit of output current detection circuit, and the output current pair that will be measured with this The signal answered is sent to parameter calculating portion 92 and applies voltage control circuit 94.

An example of the flow of aforementioned SOx Concentration Testings according to first embodiment is described below.The flow is shown in figure In 11.

When the flow shown in Figure 11 starts, applied voltage is held in 0.4V.Then, in step 10, electricity will be applied Vs is pressed to be improved from 0.4V towards 0.8V.Next, in step 11, judge whether applied voltage Vs has reached 0.8V (Vs= 0.8V).In this respect, when judging Vs=0.8V, then flow proceeds to step 12.On the other hand, when not judging Vs When=0.8V, then flow returns to step 10.Therefore, the rising of applied voltage Vs continues, and judges until in step 11 Until going out Vs=0.8V.

In step 12, applied voltage Vs is declined from 0.8V towards 0.4V, and output current Is is detected.Next, In step 13, judge whether applied voltage Vs has reached 0.4V (Vs=0.4V).In this respect, when judging Vs=0.4V When, flow proceeds to step 14.On the other hand, when not judging Vs=0.4V, then flow returns to step 12.Therefore, The decline of applied voltage Vs and the detection of output current Is continue, until judging that Vs=0.4V is in step 13 Only.

In step 14, SOx concentration Cs sox is calculated based on the peak value of the output current Is measured in step 12, and so Afterwards, which terminates.

It should be noted that in the SOx Concentration Testings according to previous embodiment, it is assumed that related to the SOx in sensor unit Reaction be the reason of electric current corresponding with SOx concentration is exported by sensor when applied voltage is lowered.It is another Aspect, the reason are substantially influenced by the temperature of sensor unit.Accordingly, it is considered to the SOx being contained in exhaust gas Extremely low concentration, it is preferred that the temperature of sensor unit remains steady temperature.Thus, in the aforementioned embodiment, heater It can be controlled to that the temperature of sensor unit is made to be held in steady temperature.According to this point, SOx concentration is more accurately detected Go out.

Moreover, in the case where being contained in the catalyst of the component in exhaust gas for purifying and being provided on exhaust pipe, packet It can be captured by catalyst contained in the SOx in exhaust gas.In this case, if limiting-current sensor is installed in catalysis On the exhaust pipe in the downstream of agent, then SOx concentration will not be detected accurately.Thus, in the aforementioned embodiment, in catalyst quilt In the case of being provided on exhaust pipe, it is preferred that limiting-current sensor is installed in the exhaust pipe of the upstream of catalyst On.

Second embodiment will be described.It should be noted that the configuration and control according to second embodiment that hereafter will not be described again System be with those configurations according to first embodiment and control it is identical, or in view of being described below and second is real It is significantly obtained from those configurations according to first embodiment and control in the case of applying the configuration of those of example correspondence and control Configuration and control.

According to second embodiment, applied voltage is consistently held in 0.4V.Then, according to second embodiment In SOx Concentration Testings, applied voltage is improved from 0.4V to 0.8V, and then, and applied voltage drops to 0.4V from 0.8V. At this moment, ECU judges the absolute value that the peak value of the output current of ECU is input to when applied voltage drops to 0.4V from 0.8V Whether first predetermined value is greater than or equal to.In this respect, in the case where the absolute value of peak value is greater than or equal to first predetermined value, ECU executes sulfur poisoning recovery control (details of the control will be described later).On the other hand, it is less than the in the absolute value of peak value In the case of one predetermined value, ECU calculates (it is, detection) SOx concentration by using peak value and reference current.

It should be noted that the setting for example, first predetermined value according to second embodiment is such as got off.The SOx being contained in exhaust gas Sulphur ingredient can be adhered to first sensor electrode.According to the research of present inventor, present inventor is , it is realized that the adherency sulfur content (it is, being adhered to the amount of the sulphur of first sensor electrode) increases, the absolute value of peak value increases. Then, sizable in the adherency sulfur content, accuracy of detection (particularly, the inspection of SOx concentration of limiting-current sensor Survey precision) it can decline.Therefore, in the case where it is big to adhere to sulfur content, preferably removal is adhered to first sensor electrode Sulphur (it is, executing sulfur poisoning recovery control).Thus, for example, the peak value that wherein sulfur poisoning recovery control should be performed Absolute value is (it is, be input to the absolute of the peak value of the output current of ECU when applied voltage drops to 0.4V from 0.8V Value) it is set to first predetermined value according to second embodiment.

It should be noted that known control, for example, for improving applied voltage to relatively high voltage (for example, being higher than Or the voltage equal to 0.8V and is particularly equal to the voltage of 1.0V) control can be used as sulfur poisoning recovery control.

According to SOx concentration detection devices according to second embodiment, sensor accuracy of detection can due to sulfur poisoning ( It is exactly sulphur to the adherency to first sensor electrode) and in the case of decline, sulfur poisoning recovery control is performed.In other words, directly To the possibility of the accuracy of detection for not having the sensor caused by sulfur poisoning declined, the detection of SOx concentration is just performed.Cause And according to SOx concentration detection devices according to second embodiment, SOx concentration can be detected more accurately.

One example of SOx Concentration Testings flow according to second embodiment will be described.The flow is shown in Figure 12.

When the flow shown in Figure 12 starts, applied voltage is held in 0.4V.Then, in step 20, applied voltage Vs is improved from 0.4V towards 0.8V.Next, in step 21, judge whether applied voltage Vs has reached 0.8V (Vs=0.8V). In this respect, when judging Vs=0.8V, flow proceeds to step 22.On the other hand, when not judging Vs=0.8V, The flow returns to step 20.Therefore, the raising of applied voltage Vs continues, until judging Vs=0.8V in step 21 Until.

In step 22, applied voltage Vs is set to decline from 0.8V towards 0.4V, and detect output current Is.Next, Step 23, judge whether applied voltage Vs has reached 0.4V (Vs=0.4V).In this respect, when judging Vs=0.4V, Flow proceeds to step 24.On the other hand, when not judging Vs=0.4V, which returns to step 22.Therefore, it is applied The decline of making alive Vs and the detection of output current Is continue, until until step 23 judges Vs=0.4V.

In step 24, the absolute value of the peak value of the output current Is detected in step 22 is judged | Is | whether it is more than first Predetermined value Isth1 (| Is |>Isth1).In this respect, when judging | Is |>When Isth1, flow proceeds to step 25, in the step Sulfur poisoning recovery control is performed in rapid, and then the flow terminates.On the other hand, when not judging | Is |>When Isth1, Flow proceeds to step 26, calculates SOx concentration based on the peak value of the output current Is detected in step 22 in this step Csox, and then the flow terminates.

<3rd embodiment>

3rd embodiment explained below.It should be noted that the configuration according to third embodiment that hereafter will not be described again and Control be with configure and control according to those of previous embodiment it is identical, or in view of according to the be described below Those of three embodiments configure and control in the case of significantly obtain from being configured and controlled according to those of previous embodiment Configuration and control.

According to third embodiment, applied voltage is consistently held in 0.4V.Then, according to third embodiment In SOx Concentration Testings, applied voltage is improved from 0.4V to 0.8V, and then, and applied voltage drops to 0.4V from 0.8V. At this moment, ECU judges the absolute value that the peak value of the output current of ECU is input to when applied voltage drops to 0.4V from 0.8V Whether second predetermined value is greater than or equal to.In this respect, in the case where the absolute value of peak value is greater than or equal to second predetermined value, ECU alarms to the performance fault of fuel.On the other hand, in the case where the absolute value of peak value is less than second predetermined value, ECU (it is, detection) SOx concentration is calculated by using peak value and reference current.

It should be noted that for example, second predetermined value according to third embodiment be set it is as follows.As described above, The sulphur ingredient for the SOx being contained in exhaust gas can be adhered to first sensor electrode, and grinding according to present inventor Study carefully, it has been realized that adherency sulfur content increases, the absolute value of peak value increases present inventor.Then, in the adherency sulfur content phase In the case of big, the accuracy of detection (particularly, the accuracy of detection of SOx concentration) of limiting-current sensor can decline.At this One of the reason of aspect, the high concentration for the SOx being contained in exhaust gas is adherency sulfur content increase.Then, with being contained in fuel Sulphur ingredient concentration increase, be contained in the SOx in exhaust gas concentration increase.Therefore, sulphur ingredient in being contained in fuel In the case that concentration height may occur to unacceptable and therefore fuel performance fault, preferably the failure is carried out Alarm.

Thus, for example, (particularly, being contained in the case where the performance of fuel is not in acceptable performance range The concentration of sulphur in fuel be higher than acceptable concentration in the case of) from the absolute value more than or equal to peak value (it is, in institute Apply voltage be input to when dropping to 0.4V from 0.8V ECU output current peak value absolute value) minimum value value in fit When the value selected is set to second predetermined value according to third embodiment.

It should be noted that second predetermined value according to third embodiment can be with first predetermined value phase according to second embodiment It is same or different.

It is right in the case where fuel performance failure may occur according to SOx concentration detection devices according to third embodiment Failure is alarmed, and therefore, and the user of SOx concentration detection devices can appreciate that the performance fault of fuel may be sent out It is raw.

One example of SOx Concentration Testings flow according to third embodiment will be described.The flow is shown in Figure 13.

When the flow shown in Figure 13 starts, applied voltage is held in 0.4V.Then, in step 30, applied voltage Vs is improved from 0.4V to 0.8V.Next, in step 31, judge whether applied voltage Vs has reached 0.8V (Vs=0.8V). In this respect, when judging Vs=0.8V, flow proceeds to step 32.On the other hand, when not judging Vs=0.8V, Flow returns to step 30.Therefore, the rising of applied voltage Vs continues, until judging that Vs=0.8V is in step 31 Only.

In step 32, so that applied voltage Vs is declined from 0.8V towards 0.4V and detect output current Is.Next, in step 33, judge whether applied voltage Vs has reached 0.4V (Vs=0.4V).In this respect, when judging Vs=0.4V, flow Proceed to step 34.On the other hand, when not judging Vs=0.4V, flow returns to step 32.Therefore, applied voltage The decline of Vs and the detection of output current Is continue, until until step 33 judges Vs=0.4V.

In step 34, the absolute value of the peak value of the output current Is detected in step 32 is judged | Is | whether it is more than second Predetermined value Isth2 (| Is |>Isth2).In this respect, when judging | Is |>When Isth2, flow proceeds to step 35, in the step The performance fault of fuel is alarmed in rapid, and then the flow terminates.On the other hand, when not judging | Is |>Isth2 When, flow proceeds to step 36, and it is dense to calculate SOx based on the peak value of the output current Is detected in step 32 in this step Csox is spent, and then, which terminates.

Fourth embodiment will be described.It should be noted that the configuration and control according to fourth embodiment that hereafter will not be described again System be with configure and control according to those of previous embodiment it is identical, or in view of according to will be described below the Those of four embodiments configure and control in the case of significantly obtain from being configured and controlled according to those of previous embodiment Configuration and control.

According to fourth embodiment, applied voltage is consistently held in 0.4V.It is, the voltage of 0.4V is by consistently It is applied to sensor unit.In this respect, the voltage of 0.4V is greater than or equal to voltage Vth shown in Fig. 2, and is wherein useless The air-fuel ratio of gas is constant (independently of the application electricity of sensor unit by the output current of sensor unit in the case of constant Pressure) voltage.

Then, according in the SOx of fourth embodiment concentration/air-fuel ratio detection, ECU is constant based on the voltage in 0.4V The output current of sensor unit when ground is applied to sensor unit calculated from relationship shown in Fig. 2 (it is, detection Go out) air-fuel ratio.

On the other hand, in the case where needing to carry out the detection of SOx concentration, the applied voltage of sensor unit is from 0.4V It improves to 0.8V, and then, the applied voltage of sensor unit drops to 0.4V from 0.8V.At this moment, ECU is in sensor By using the peak value and reference current of the output current for being input to ECU when the applied voltage of unit drops to 0.4V from 0.8V To calculate (detection) SOx concentration.

Moreover, sensor unit applied voltage after 0.8V drops to 0.4V, ECU is based on sensor unit Output current calculates (it is, detecting) air-fuel ratio from relationship shown in Fig. 2.Certainly, at this moment, sensor unit Applied voltage be held in 0.4V.

It should be noted that being used for SOx concentration/air-fuel according to fourth embodiment in two haplotype limiting-current sensors In the case of than detection, when the detection of air-fuel ratio is performed, the voltage for being applied to pump unit 15 is made to become zero.

According to fourth embodiment, the concentration of the air-fuel ratio of exhaust gas and the SOx being contained in exhaust gas can be by individually passing Sensor detects.

It will be described according to an example of the SOx of fourth embodiment concentration/air-fuel ratio testing process.The flow is shown in figure In 14.

When the flow shown in Figure 14 starts, applied voltage is held in 0.4V.Then, in step 40, judge SOx concentration Whether detection label (flag) Fsox is set (Fsox=1).Sox is the SOx's be contained in exhaust gas for the flag F It is set when the detection of concentration, and is reset when the detection of the concentration of the SOx in being contained in exhaust gas is completed.In step 40, When judging Fsox=1, flow proceeds to step 41.On the other hand, when not judging Fsox=1, flow proceeds to Step 47.

In step 47, output current Is is detected.Next, in step 48, air-fuel ratio A/F is based on detecting in step 47 To output current Is calculate, and then the flow terminates.

In step 41, applied voltage Vs is improved from 0.4V towards 0.8V.Next, in step 42, applied voltage is judged Whether Vs has reached 0.8V (Vs=0.8V).In this respect, when judging Vs=0.8V, flow proceeds to step 43.It is another Aspect, when not judging Vs=0.8V, flow returns to step 41.Therefore, the rising of applied voltage Vs continues, Until until step 42 judges Vs=0.8V.

In step 43, applied voltage Vs is set to decline from 0.8V towards 0.4V, and detect output current Is.Next, Step 44, judge whether applied voltage Vs has reached 0.4V (Vs=0.4V).In this respect, when judging Vs=0.4V, Flow proceeds to step 45.On the other hand, when not judging Vs=0.4V, flow returns to step 43.Therefore, applied The decline of voltage Vs and the detection of output current Is continue, until until step 44 judges Vs=0.4V.

In step 45, SOx concentration Cs sox is calculated based on the peak value of the output current Is detected in step 43.It connects down Come, in step 46, SOx Concentration Testing flag Fs sox is reset, and then the flow terminates.

It should be noted that in the SOx Concentration Testings according to previous embodiment, apply electricity before the reduction of applied voltage Pressure is enhanced.But in the case where applied voltage reduces, even if applied voltage does not have before applied alive decline The advantages of being enhanced, also capable of at least obtaining previous embodiment.

Moreover, in the aforementioned embodiment, the concentration of oxygen and the concentration of Sox are examined by using the output current of sensor It surveys.However, it is possible to detect the only concentration of SOx by using the output current of sensor.

Claims

1. a kind of SOx concentration detection devices of the internal combustion engine with limiting-current sensor, which is characterized in that including：

Detection part, for by using the sensor when making the voltage for being applied to the sensor decline from predetermined voltage Output current, to detect the concentration being contained in from the SOx in the exhaust gas that the engine is discharged,

The influence that the SOx of the output current is wherein occupied in the decline from the predetermined voltage of applied voltage is more than occupancy The influence of other compositions in the exhaust gas of the output current, and

The wherein described detection part, which uses, makes the voltage for being applied to the sensor decline when institute from the predetermined voltage The peak value for stating the output current of sensor, the output current of the detection as the concentration for the SOx, the peak Value is minimum output current or maximum output current of the output current during applied alive decline.

2. SOx concentration detection devices according to claim 1, wherein the detection part use makes to be applied to the biography The voltage of sensor is applied to the sensor after predetermined voltage decline, by the voltage lower than the predetermined voltage The output current of Shi Suoshu sensors, to detect the concentration for the oxygen being contained in the exhaust gas.

3. SOx concentration detection devices according to claim 1, wherein the detection part use makes to be applied to the biography The voltage of sensor improves to the predetermined voltage from the voltage lower than the predetermined voltage, makes to be applied to the sensing The output current of the voltage of device sensor when declining from the predetermined voltage, as the dense of the SOx The output current of the detection of degree.

4. SOx concentration detection devices according to claim 3, wherein the detection part use makes to be applied to the biography The voltage of sensor rise to the predetermined voltage before, the voltage lower than the predetermined voltage is applied to the biography The output current of sensor when sensor, to detect the concentration for the oxygen being contained in the exhaust gas.

5. SOx concentration detection devices according to claim 1, wherein the predetermined voltage is above or the electricity equal to 0.8V Pressure.

6. SOx concentration detection devices according to claim 1, wherein the voltage for making to be applied to the sensor from The voltage that the sensor is applied at the end of the decline of the predetermined voltage is less than or the voltage equal to 0.7V.

7. SOx concentration detection devices according to claim 1, wherein the detection part according to less than or equal to The speed of the pace of change of the voltage of 100Hz makes the voltage for being applied to the sensor decline from the predetermined voltage.

8. SOx concentration detection devices according to claim 3 or 4, wherein the detection part is according to less than or equal to tool There is the speed of the pace of change of the voltage of 100Hz to make to be applied to the voltage of the sensor from lower than the predetermined voltage The voltage rises, and the voltage for being applied to the sensor is then made to decline from the predetermined voltage.

9. SOx concentration detection devices according to claim 1, wherein the engine is petrol engine.

10. SOx concentration detection devices according to claim 1, wherein the equipment further includes：Make to be applied to for working as The voltage of the sensor when declining from the predetermined voltage absolute value of the output current of the sensor be more than Or the control unit equal to the sulfur poisoning recovery control in the case of first predetermined value, executing the sulfur poisoning recovery for making the sensor Point.

11. SOx concentration detection devices according to claim 1, wherein the equipment further includes：Make to be applied to for working as The voltage of the sensor when declining from the predetermined voltage absolute value of the output current of the sensor be more than Or it equal in the case of second predetermined value, alarms the failure of the performance of the fuel of the combustion chamber supply to the engine Control section.

12. a kind of for detecting the SOx being contained in from the exhaust gas that the internal combustion engine with limiting-current sensor is discharged Concentration method, which is characterized in that including：

Voltage for making the voltage for being applied to the sensor decline from predetermined voltage declines step；

Output current obtaining step for the output current for obtaining the sensor during the voltage declines step；And

For being contained in the exhaust gas by using the output current obtained by the output current obtaining step to detect In the SOx concentration SOx concentration detecting steps,

Wherein use the output current when making the voltage for being applied to the sensor decline from the predetermined voltage Peak value, the output current of the detection as the concentration for the SOx, the peak value are that the output current is being applied Minimum output current during the decline of voltage or maximum output current.

13. according to the method for claim 12, wherein the method further includes：

Reduction for the voltage lower than the predetermined voltage to be applied to the sensor after declining step in the voltage Voltage applies step afterwards；And

For by detecting packet using the output current of the sensor during the voltage application step after the reduction The oxygen concentration detecting step of concentration contained in the oxygen in the exhaust gas.

14. method according to claim 12 or 13, wherein the method further include：

Reduction for the voltage lower than the predetermined voltage to be applied to the sensor before the voltage declines step Preceding voltage applies step；

For making to be applied to the sensing after the voltage application step before the reduction and before the voltage declines step The voltage that the voltage of device is increased to the predetermined voltage improves step；And

For by detecting packet using the output current of the sensor during the voltage application step before the reduction The oxygen concentration detecting step of concentration contained in the oxygen in the exhaust gas.

15. a kind of limiting-current sensor, which is characterized in that for by using the voltage for being applied to the sensor from The output current of the sensor is contained in detect from the SOx's in the exhaust gas that internal combustion engine is discharged when predetermined voltage decline Concentration,

Described in the wherein described sensor is used when making the voltage for being applied to the sensor decline from the predetermined voltage The peak value of the output current of sensor, the output current of the detection as the concentration for the SOx, the peak value It is minimum output current or maximum output current of the output current during applied alive decline.

16. sensor according to claim 15, wherein the sensor is used for by using being applied to the sensing The voltage of device is after predetermined voltage decline, when the voltage lower than the predetermined voltage is applied to the sensor The output current of the sensor, to detect the concentration for the oxygen being contained in the exhaust gas.

17. sensor according to claim 15 or 16, wherein the sensor is used for by using in the predetermined electricity Press sensor when being applied to the sensor before being applied in the sensor, by the voltage lower than the predetermined voltage The output current, to detect the concentration for the oxygen being contained in the exhaust gas.