JP5746991B2 - 煤 Detection device - Google Patents

Description

  The present invention relates to a soot detection device that is used in an exhaust system of an internal combustion engine for automobiles and that detects particulate matter (PM) mainly composed of soot made of carbon contained in a gas to be measured.

In order to collect environmental pollutants contained in combustion exhaust, particularly particulate matter (PM) mainly composed of soot particles and soluble organic components (SOF) in automobile diesel engines, etc. A diesel particulate filter (DPF) is installed in the passage. The DPF is made of porous ceramics having excellent heat resistance, and captures particulate matter by passing combustion exhaust gas through a partition wall having a large number of pores.
If the amount of collected particulate matter exceeds the permissible amount, DPF may cause clogging and increase pressure loss or increase the slipping of particulate matter. The collection ability is restored.
The regeneration timing of the DPF generally uses the fact that the differential pressure before and after the DPF increases due to an increase in the amount of collected particulate matter. For this reason, the difference in detecting the pressure difference between the upstream and downstream of the DPF is used. A pressure sensor is installed.
The regeneration process of the DPF is performed by burning and removing particulate matter by introducing high-temperature combustion exhaust gas into the DPF by heater heating or post injection.

  On the other hand, as a sensor capable of directly detecting particulate matter in combustion exhaust gas, for example, in Patent Document 1, the first detection electrode and the soot trapping layer of the first oxygen concentration measurement unit are configured to allow soot to enter. In addition, the temperature of the first oxygen concentration measurement unit remains at the temperature of the first oxygen concentration measurement unit using a soot detection sensor provided with a soot restriction layer that prevents intrusion of soot on the surface of the second detection electrode of the second oxygen concentration measurement unit. In addition, the temperature is controlled so that soot can be combusted by oxygen generated by pumping. In this state, a voltage is applied between both electrodes of the first oxygen concentration measuring unit to pump oxygen, and the pumped oxygen is reduced. The soot is burned at the temperature using the difference between the current value I1 between the electrodes of the first oxygen concentration measurement unit and the current value I2 between the electrodes of the second oxygen concentration measurement unit (ΔI = I1−I2), It describes that the total amount of soot can be calculated.

  In addition, when this sensor is installed downstream of the DPF, the particulate matter passing through the DPF is measured, and the on-board diagnosis (OBD) monitoring of the operating state of the DPF, for example, cracking or It can be used to detect abnormalities such as breakage. Alternatively, it has been studied to install upstream of the DPF, measure the amount of particulate matter flowing into the DPF, and use it to determine the regeneration timing instead of the differential pressure sensor.

  However, as disclosed in Patent Document 1, the difference ΔI = I1−I2 between the current value I1 between the electrodes of the first oxygen concentration measurement unit and the current value I2 between the electrodes of the first oxygen concentration measurement unit is , The current value I1 between the electrodes of the first oxygen concentration measuring unit includes not only the soot combustion but also the current for simple oxygen pumping in addition to the soot combustion. Therefore, the difference in oxygen concentration between the first oxygen concentration detector and the intermediate chamber is detected in a superimposed manner, and there is a possibility that the detection error increases.

  Accordingly, in view of such circumstances, the present invention provides a soot detection device capable of detecting the soot amount deposited on the sensing electrode with high accuracy by controlling the voltage between the sensing electrode and the reference electrode to a predetermined value. The purpose is to provide.

In the first aspect of the invention (1, 1a, 1b, 1c, 1d, 1e, 1f, 1g), at least the surface of the oxygen ion conductive solid electrolyte body (4) is in the measured gas space (11). A first detection electrode (22, 22b, 22f) that exists and faces the measurement gas including soot, and a reference gas space (51, 51a, 51c , 51g) separately from the measurement gas space (11) ) Or in a reference gas space (51f) that is the same space as the measured gas space (11) and faces the reference gas that does not contain soot (21, 21b, 21f) and a pair of electrodes (21, 22, 21b, 22b, 21f , 22f ), and energization between these pair of electrodes (21, 22, 21b, 22b, 21f , 22f ) The first reference electrode (21, 2 1b, 21f) supplies oxygen for oxidizing the soot deposited on the surface of the first detection electrode (22, 22b, 22f) toward the first detection electrode (22, 22b, 22f). A soot detecting element (10, 10a, 10b, 10c, 10d, 10e) comprising a first electrochemical cell (2, 2b, 2f) and a heating means (9) for heating the solid electrolyte body (4), 10f, 10g) is disposed in the gas to be measured, and an electrochemical change when the soot deposited on the surface of the first sensing electrode (22, 22b, 22f) is oxidized is detected, A soot detecting device for detecting soot existing in a gas space (11) to be measured, the first sensing electrode (22, 22b, 22f) and the first reference electrode (21, 21b, 21f ), The detection voltage (V _D ) applied between By controlling the voltage so as to be equal to the voltage threshold value (V _REF ) in the non-connected state, the first reference electrode (21, 21b, 21f) is changed to the first detection electrode (22, 22b, 22f). by supplying oxygen for the oxidation of soot, the first sensing electrode (22, 22b, 22f) when to oxidize the soot deposited on the surface of said first electrochemical cell (2 and 2b 2f), a means for detecting the amount of soot deposited on the surface of the first sensing electrode (22, 22b, 22f) from the oxygen ion current signal (I _PM ) flowing through

In the invention of claim 2 (1, 1a, 1b, 1c, 1d, 1e, 1f, 1g), the means is an oxygen ion current signal (I) flowing through the first electrochemical cell (2, 2b, 2f). and detecting the deposited soot amount on the surface of the first sensing electrode from the integrated value _{(I SUM) (22,22b)} of _PM).

In the invention of claim 3 (1a, 1b, 1c, 1e, 1f, 1g), the reference gas space (51a , 51c, 51g ) and the measured gas space (11) communicate with each other, or the reference gas. The space (51 f) and the measured gas space (11) are the same space, and the soot existing in the measured gas does not pass through the measured gas in the measured gas space (11). Gas is transmitted through the porous ceramic layers (100a , 100c, 100f ), and the first reference electrode (21, 21b) is in contact as the reference gas containing no soot. .

In the invention (1, 1a, 1d) of claim 4, the gas to be measured is measured on the surface of the solid electrolyte body (4) with respect to the gas space (11) to be measured which is the same as the first sensing electrode (22). Same as second sensing electrode (32) and first reference electrode (21) facing through a porous ceramic layer (100) that does not permeate soot and does not allow gas permeation, the reference It has a pair of electrodes (31, 32) composed of a second reference electrode (31) provided facing the gas space (51 , 51a ), and an electromotive force between the pair of electrodes (31, 32) A second electrochemical cell (3) to be measured is provided, and the voltage between the electrodes (31, 32) of the second electrochemical cell (3) is _defined as the voltage threshold value (V _REF ). wherein said applying sense voltage _{(V D)} between the electrodes (21, 22) of the cell (2) To.

In the invention of claim 5 (1b, 1c, 1e, 1f, 1g), the first reference electrode (21b, 21f) is a porous ceramic layer ( 100a ) that does not transmit soot in the gas to be measured but does not transmit gas. , 100c , 100f), the reference gas space (51a, 51c) in which the same gas as the gas to be measured exists in the gas space to be measured (11) facing the first detection electrodes (22b, 22f ). , 51f) and short-circuiting between the pair of electrodes (21b, 22b , 21f, 22f ) of the first electrochemical cell (2b , 2f ), the voltage threshold (V _REF ), that is, the The detection voltage (V _D ) is set to 0.

The invention (1d, 1e, 1g) of claim 6 has an electrostatic field applying electrode (15) provided via an insulator (14) opposite to the first sensing electrode (22 , 22b , 22f ). Then , a voltage (V _ST ) is applied between the first detection electrode (22 , 22b , 22f ) and the electrostatic field application electrode (15) to form an electrostatic field, thereby forming the first detection electrode. It is characterized by collecting cocoons on the surface of the.

According to the present invention, the reference electrode (21, 21b, 21f) and the detection electrode (22) even if the oxygen concentration and the soot amount of the gas existing in the detection gas space (11) change in a superimposed manner. , 22b, 22f) by controlling the voltage (V _D ) to a predetermined voltage (V _REF ), offsetting the influence of the change in the oxygen concentration in the detected gas space (11), and oxygen pumping Oxidation of soot on the surface of the detection electrode (22, 22b, 22f) from the reference electrode (21, 21b, 21f) to the detection electrode (22, 22b, 22f) without being affected by the current due to Only oxygen ions used in the pump are pumped, and by measuring this oxygen ion current, the amount of soot deposited on the surface of the sensing electrodes (22, 22b, 22f) can be detected with high accuracy. High wrinkle detection equipment (1, 1a, 1b, 1c, 1d, 1e, 1f, 1g) can be realized.

The typical sectional view showing the outline of the eyelid detection device in a 1st embodiment of the present invention. The expansion | deployment perspective view of the wrinkle detection element used for the wrinkle detection apparatus of FIG. In the soot detection device 1 of FIG. 1, the relationship between the cell current and the cell voltage when soot is intentionally deposited on the detector in a state where there is no difference in oxygen concentration between the measured gas space and the reference gas space. FIG. In the soot detection apparatus 1 of FIG. 1, the relationship between the cell current and the cell voltage when soot is intentionally deposited on the detector in a state where there is a difference in oxygen concentration between the gas space to be measured and the reference gas space. FIG. The characteristic view which shows the effect of this invention with respect to the case where the amount of soot deposited on the surface of a detection electrode, and the oxygen concentration in to-be-measured gas change in a superimposed manner. The typical sectional view showing the outline of the eyelid detection device in a 2nd embodiment of the present invention. The expansion | deployment perspective view of the wrinkle detection element used for the wrinkle detection apparatus of FIG. The typical sectional view showing the outline of the eyelid detection device in a 3rd embodiment of the present invention. Typical sectional drawing which shows the outline | summary of the wrinkle detection apparatus in the 4th Embodiment of this invention. Typical sectional drawing which shows the outline | summary of the wrinkle detection apparatus in the 5th Embodiment of this invention. Typical sectional drawing which shows the outline | summary of the wrinkle detection apparatus in the 6th Embodiment of this invention. The typical sectional view showing the outline of the eyelid detection device in a 7th embodiment of the present invention. The typical sectional view showing the outline of the eyelid detection device in the 8th embodiment of the present invention.

With reference to FIG. 1, FIG. 2, the wrinkle detection apparatus 1 in the 1st Embodiment of this invention is demonstrated.
The soot detection device 1 includes at least a surface of the oxygen ion conductive solid electrolyte body 4, a first detection electrode 22 facing the measurement gas space 11 through which the measurement gas flows, and a surface of the first detection electrode 22. A pair of electrodes 21 and 22 including a first reference electrode 21 facing a reference gas space 51 that is partitioned separately from the measured gas space 11, and energization between the pair of electrodes 21 and 22. A first electrochemical cell 2 for supplying oxygen for oxidizing soot deposited on the surface of the first sensing electrode 22 from the first reference electrode 21 toward the first sensing electrode 22, and a solid electrolyte Electrochemical change when the soot detecting element 10 provided with the heating means 9 for heating the body 4 is disposed in the gas to be measured and the soot deposited on the surface of the first sensing electrode 22 is oxidized. Is detected and is present in the measured gas space 11 A soot detecting apparatus 1 for detecting that soot, the first sensing electrode 22 and the detection voltage V _D applied between the first reference electrode 21, voltage threshold V _REF in a state in which soot is not deposited By controlling the voltage so as to be equal to each other, oxygen for oxidizing soot is supplied from the first reference electrode 21 to the first detection electrode 22 and deposited on the surface of the first detection electrode 22. The soot is oxidized, and the amount of soot deposited on the surface of the first sensing electrode 22 is detected from the oxygen ion current signal I flowing in the first electrochemical cell 2 at this time.

In addition, in the present embodiment, the soot existing in the measurement gas does not permeate the gas to be measured on the surface of the solid electrolyte body 4 with respect to the measurement gas space 11 that is the same as the first detection electrode 22. A pair of electrodes composed of a second detection electrode 32 facing through the porous ceramic layer 100 and a second reference electrode 31 provided facing the reference gas space 51, the same as the first reference electrode 21. And a second electrochemical cell 3 for measuring an electromotive force between the pair of electrodes 31 and 32, and a voltage V _REF between the electrodes 31 and 32 of the second electrochemical cell 3 is A detection voltage V _D is applied between the electrodes 21 and 22 of the first electrochemical cell 2 as the voltage threshold V _REF .

In the second electrochemical cell 3, the second sensing electrode 32 is formed with the porous ceramic layer 100 that allows the gas flowing in the gas space 11 to be measured to pass but does not allow soot to pass, so that soot is deposited. In this state, the voltage V _REF based on the electromotive force generated by the difference in oxygen concentration between the measured gas space 11 and the reference gas space 51 is detected, and the detection voltage V _D applied to the first electrochemical cell 2 is Feedback control (F / B) is performed so that the voltage threshold V _{REF in a} state where no soot is deposited is equal to the voltage V _REF detected by the second electrochemical cell 3.
Note that, even when the oxygen concentration present in the gas to be measured is changed by a test using the soot detection device of the present invention, which will be described later, a known amount of soot deposited on the surface of the first detection electrode 22 is detected. It is confirmed that the integrated current I _SUM detected in this way shows a correlation with extremely high accuracy. In the present invention, the integrated value I obtained by integrating the oxygen ion current signal flowing through the first electrochemical cell 2 for a predetermined time is obtained. It has been found that it is desirable to detect the amount of soot deposited on the surface of the first sensing electrode 22 from the _SUM .
When the soot detection device of the present invention is provided in the combustion exhaust flow path of an internal combustion engine and used on a so-called onboard, the amount of soot contained in the combustion exhaust as the gas to be measured is unknown, and the first detection The soot deposited on the surface of the electrode 22 is continuously oxidized.
Therefore, in the actual detection control, for example, the oxygen ion current signal detected by the first electrochemical cell 2 is integrated for a certain time of about 1 s to 10 s, and the amount of soot deposited / oxidized per that time is calculated. It will be detected.

In the soot detecting device 1, a sheet-like solid electrolyte body 4 for constituting the first electrochemical cell 2 and the second electrochemical cell 3 and a sheet-like spacer 5 for forming the reference gas space 51. And the heater 9 which heats these is laminated | stacked one by one, and the wrinkle detection element 10 is comprised. A more specific configuration of the wrinkle detection element 10 will be described later with reference to FIG.
In this embodiment, a current detecting means A for detecting a current I _PM flowing in the first electric cell 2, a voltage detector V for detecting the voltage V _REF between the second electric cell 3 of the electrode 31, 32 The detection voltage V _D of the current detection means A is equal to the voltage V _REF generated by the difference between the oxygen concentration in the measured gas space 11 detected by the voltage detection means V and the oxygen concentration in the reference gas space 51. By controlling the detection error of the first electric cell 2 due to the difference in oxygen concentration, and only the oxygen ion current that flows when the soot deposited on the surface of the first sensing electrode 22 is oxidized. The current detection means A can be detected with high accuracy.
The voltage detection means V may include voltage application means for applying an arbitrary voltage between the second reference electrode 31 and the second detection electrode 32 of the second electric cell.

In the reference gas space 51 in the present embodiment, the atmosphere as a reference oxygen concentration gas having a constant oxygen concentration is introduced.
As shown in FIG. 2, the reference gas space 51 is formed by a punched hole 51 provided in the spacer 5 stacked below the solid electrolyte 4. Further, the punched hole 51 has a passage portion 52 as a groove extending in the longitudinal direction of the soot detection device 1, and the atmosphere is introduced through the passage portion 52. The spacer 5 is made of a known insulating material such as alumina.
The solid electrolyte body 4 for constituting the first electrochemical cell 2 and the second electrochemical cell 3 is made of an electrolyte material having oxygen ion conductivity such as known zirconia and ceria.
The first electrochemical cell 2 is composed of a solid electrolyte body 4, a pair of first detection electrodes 22 and a first reference electrode 21 which are disposed so as to sandwich the solid electrolyte body 4.
Of the pair of electrodes 21, 22, one first detection electrode 22 is provided on the surface of the solid electrolyte body 4 on the side facing the measured gas space 11, and the other first reference electrode 21 is a reference. It is provided on the surface of the solid electrolyte body 4 on the side facing the gas space 51.

The second electrochemical cell 3 includes a solid electrolyte body 4, and a pair of second detection electrodes 32 and a second reference electrode 31 disposed so as to sandwich the solid electrolyte body 4.
Of the pair of electrodes 31, 32, one second detection electrode 32 is provided on the surface of the solid electrolyte body 4 on the side facing the measured gas space 11, and the other second reference electrode 31 is a reference. It is provided on the surface of the solid electrolyte body 4 on the side facing the gas space 51.
Further, the detection electrode 32 is covered with a porous ceramic layer 100 provided as a soot filter layer which prevents soot from entering and allows gas to pass therethrough.
The porous ceramic layer 100 is made of an insulating material such as alumina, and is a porous body having pores that can pass gas flowing through the gas space 11 to be measured but cannot pass soot.
Note that the pores of the porous ceramic layer 100 in the present embodiment do not prevent free gas movement, and do not serve as oxygen diffusion resistance.
Specifically, the porosity of the porous ceramic layer 100 is preferably 5 to 30%, more preferably about 10 to 20%.
For each of the electrodes 21, 22, 31, and 32 constituting the first electrochemical cell 2 and the second electrochemical cell 3, for example, a known porous cermet electrode such as Pt or Au is preferably used.

Further, as shown in FIG. 2, the electrodes 21, 22, 31, and 32 are integrally formed with leads 210, 220, 310, and 320 for taking out electrical signals therefrom.
Each of the electrodes 21, 22, 31, 32 and the leads 210, 220, 310, 320 is made of a cermet material mainly composed of a noble metal such as Pt and a ceramic such as zirconia.
Here, the portions other than the electrodes 21, 22, 31, 32 formed on the surface of the solid electrolyte body 4, particularly the portions where the leads 210, 220, 310, 320 are formed, include the solid electrolyte body 4 and the leads 210, 220, An insulating layer such as alumina (not shown) is preferably formed between 310 and 320.

The heater 9 provided as a heating means is formed by patterning a heater electrode 8 that generates heat on the upper surface of an insulating layer 7 made of alumina or the like, and is made of alumina or the like on the upper surface (surface on the spacer 5 side) of the heater electrode 8. An insulating layer 6 is formed.
As the heater electrode 8, cermet of Pt and ceramics such as alumina is usually used.
The heater 9 generates heat by power supply from a heater energization control device (not shown) provided with a heater electrode 8 outside, and does not oxidize soot, but heats the cells 2 and 3 to a temperature at which they can be activated.
Further, by raising the temperature of the soot detection device 1 to be equal to or higher than the soot combustion temperature, the soot detection unit 22 exposed in the gas space 11 to be measured of the soot detection element 10, the surface of the porous ceramic layer 100, the lead 220, The soot accumulated excessively on the insulating layer covering 320 is burned and removed.

Further, as shown in FIG. 2, the cells 2, 3 and the heater electrode 8 are connected to the terminal P of the sensor base through a through hole SH formed in the insulating layer 7 or the like.
Then, a lead wire is connected to the terminal P through a connector by crimping, brazing, or the like, and the current detecting means A, the first electrochemical cell 2, the voltage detecting means V, and the second provided outside. It is possible to exchange electrical signals between the electrochemical cell 3, a heater energization control device (not shown), and the heater 9.

The solid electrolyte body 4, the spacer 5, and the insulating layers 6 and 7 can be formed into a sheet shape by a known manufacturing method such as a doctor blade method or an extrusion molding method.
Further, each of the electrodes 21, the leads 210, and the terminals P can be formed by screen printing or the like.
And each sheet | seat is integrated by laminating | stacking and baking.

Next, the principle of operation of the gas sensor element having the above configuration will be described. In FIG. 1, soot existing in a measurement gas such as combustion exhaust flowing in the measurement gas space 11 is deposited on the surface of the first detection electrode 22 provided in the first electrochemical cell 2.
On the other hand, since the second detection electrode 32 provided in the second electrochemical cell 3 is covered with the soot filter layer 100, soot is deposited on the surface of the soot filter layer 100. The gas to be measured reaches, but the soot does not.
The first reference electrode 21 and the second reference electrode 31 are in contact with the atmosphere as the reference oxygen concentration gas, and the respective electrode potentials are kept constant.
An electromotive force is generated between the electrodes 31 and 32 of the second electrochemical cell 3 based on the oxygen concentration difference between the two electrodes.

On the other hand, between the electrodes 21 and 22 of the first electrochemical cell 2, in addition to the electromotive force based on the difference in oxygen concentration between the two electrodes, the electromotive force caused by deposition of soot on the surface of the first detection electrode 22. Will occur.
The electromotive force due to soot deposition is presumed to be due to a mixed potential mechanism that balances the following reactions on the surface of the first sensing electrode 22.
C (煤) + 2O ²⁻ → CO ₂ + 4e ⁻ Formula 1
O ₂ + 4e ⁻ → 2O ² ... 2

FIG. 3 shows a relationship between the cell current I and the cell voltage V when the soot is intentionally deposited on the detection unit of the soot detecting element 10 in the soot detecting device 1 of FIG.
The gas space 11 to be measured at this time is the atmosphere (oxygen concentration of about 21%), the element temperature (the temperature of the first electrochemical cell 2 and the second electrochemical cell 3) is 400 ° C., A sufficient amount of soot (about 0.1 g) is deposited on the surfaces of one electrochemical cell 2 and the second electrochemical cell 3.
In addition, since the second detection electrode 32 of the second electrochemical cell 3 is covered with the soot filter layer 100, only the gas contacts the second detection electrode 32 of the second electrochemical cell 3. ing.
Since each of the first detection electrode 22, the first reference electrode 21, the second detection electrode 32, and the second reference electrode 31 is an air atmosphere, an electromotive force due to an oxygen concentration difference is generated in each cell 2, 3. Does not occur.

When a voltage V is applied to the pair of electrodes 31 and 32 of the second electrochemical cell 3 so that the second detection electrode 32 becomes a positive electrode, oxygen is reduced on the surface of the second reference electrode 31. It becomes oxygen ions and is discharged to the second detection electrode 32 side by the pumping action.
On the contrary, when the voltage V is applied so that the second reference electrode 31 becomes a positive pole, oxygen is reduced on the surface of the second detection electrode 32 to become oxygen ions, and the second action is caused by the pumping action. It is discharged to the reference electrode 31 side.

On the other hand, since the second first detection electrode 22 of the first electrochemical cell is directly exposed to the gas space 11 to be measured, not only the gas to be measured (atmosphere) but also soot contacts with it, and the electromotive force associated therewith Will occur.
Although the mechanism at this time is not necessarily clarified, a current due to the reaction shown in the above-described equation 1 tends to flow on the surface of the first detection electrode 22, so that the above-described current is canceled out. It is considered that the reaction of Formula 2 in FIG.
Therefore, as shown in FIG. 3, the current-voltage curve (solid line) of the first electrochemical cell 2 is higher than the current-voltage curve of the second electrochemical cell 3 (single-dotted line). The curve is shifted upward by the minute.

FIG. 4 shows the result of a similar experiment conducted with the oxygen concentration in the gas space 11 to be measured being 1%.
The current-voltage curve is shifted to the left by the electromotive force of the oxygen concentration cell due to the difference in oxygen concentration from the reference gas space 51 into which the atmosphere is introduced.
In principle, the voltage between the first reference electrode 21 and the first sensing electrode 22 of the first electrochemical cell 2 is set to the second reference electrode 31 and the second reference voltage of the second electrochemical cell 3. Voltage is controlled to be equal to the voltage between the first and second sensing electrodes 32, and the difference ΔI between the current value I1 of the first electrochemical cell 2 and the current value I2 of the second electrochemical cell 3 is measured. It is considered that the soot electrochemical oxidation current can be detected according to Equation 1 and the soot accumulation amount can be obtained by integrating the current.

However, actually, the current I1 of the first electrochemical cell 2 and the current I2 of the second electrochemical cell 3 are other than the voltage at which the current of the second electrochemical cell 3 becomes 0. In addition to the soot electrochemical oxidation current according to Equation 1, an oxygen pumping current flows, and the difference between the current value I1 of the first electrochemical cell 2 and the current value I2 of the second electrochemical cell 3 (ΔI = Even if I1-I2) is taken, since there is a measurement variation, the electromotive force generated by the density cell cannot be completely cancelled, which causes a detection error.
On the other hand, in the present invention, as shown in FIG. 1, the voltage V _REF between the electrodes 31 and 32 of the second electrochemical cell 3 (that is, the voltage at which the current of the second electrochemical cell 3 becomes 0) is measured. Then, the detection voltage V _D between the electrodes 21 and 22 of the second electrochemical cell 2 is controlled so as to be the same as this voltage.
At this time, the current I flowing through the first electrochemical cell 2 is only the soot electrochemical oxidation current I _PM according to the formula 1.
By measuring and accumulating this current, the amount of soot can be accurately measured without being affected by the oxygen concentration of the gas space 11 to be measured.

Figure 5 is for the soot detecting apparatus of FIG. 1 in the present invention showing the relationship of the integrated current I _SUM soot deposition amount Q, also accurately soot deposition vary the oxygen concentration in the measurement gas space 11 It can be seen that the quantity can be detected.
This figure shows the voltage-current characteristics detected by the first electrochemical cell 2 at the different oxygen concentrations shown in FIGS. 3 and 4, and is accurate regardless of the oxygen concentration in the gas to be measured. It can be seen that the amount of particulate matter deposited can be detected.

6, 7 and 8 are diagrams showing another embodiment of the present invention.
In the following description of the embodiments, the same components as those in the above embodiments are denoted by the same reference numerals, and similar components are distinguished by adding alphabetical branch numbers. Description will be made centering on characteristic features of the embodiment and differences from the other embodiments. The same applies to other embodiments.
In the soot detecting device 1a in the second embodiment of the present invention shown in FIG. 6, as shown in FIG. 7, the reference gas space 51a of the spacer 5a made of an insulating material such as alumina constituting the soot detecting element 10a is provided. At least a part of the partitioning insulator wall surface is a porous ceramic layer 100a.
Here, the porous ceramic layer 100a of the spacer 5a has pores that can pass the gas in the measured gas space 11 but cannot pass soot, like the porous ceramic layer 100 described above.
Therefore, the gas component in the reference gas space 51a is substantially equal to the gas component in the measured gas space 11.

That is, in Example 1a of FIG. 6, a gas having the same gas component as the gas in the measured gas space 11 excluding soot is used as the reference gas. For this reason, in this embodiment, since it is not necessary to introduce the atmosphere into the reference gas space 51a, it is not necessary to provide the passage portion 52 in the spacer 5a.
In principle, since the oxygen concentration in the measured gas space 11 and the oxygen concentration in the reference gas space 51a are the same at this time, no electromotive force is generated in the second electrochemical cell 3 (between the electrodes 31, 32). the voltage _{V REF} becomes 0) for the voltage _{V D} applied to the first electrochemical cell 2 becomes in the same state as that shorted for 0, electrodes 21 and 22.

On the other hand, as commonly used in general gas sensors such as oxygen sensors, in the soot detection device 1, when air is used as a reference gas, soot detection element 10 is held in a substantially cylindrical housing, and various signals are used. A structure that seals the base end side while drawing a wire is provided, a vent hole for introducing air into the sealed portion is provided, and a water repellent filter made of porous fluororesin or the like is further provided in the vent hole It is necessary to prevent moisture from entering from the air holes, and the structure as a sensor is complicated.
According to the present embodiment, as in the above-described embodiment, the amount of soot accumulated on the surface of the first detection electrode 22 can be accurately detected regardless of the oxygen concentration in the gas to be measured. In addition, since it is not necessary to provide a configuration for introducing the atmosphere as a reference gas, a complicated structure for introducing the atmosphere into the sensor while preventing moisture from entering as in the past is adopted. It is not necessary and not only has a very simple structure, but also has no ventilation hole, so it is possible to completely block water from the base end side and further improve the reliability and durability of the soot detection device 1a. It becomes.

Further, if the gas component concentration in the gas space to be measured 11 and the reference gas space 51a are the same, the voltage between the electrodes 21 and 22 of the first electrochemical cell 2 is controlled to 0, so that FIG. It is possible to use the soot detecting element 10b having a structure in which the second electrochemical cell 3 is omitted, such as the soot detecting device 1b in the third embodiment of the present invention shown in FIG.
In the soot detection device 1b according to the third embodiment, the soot detection with high accuracy is possible and the structure for introducing the atmosphere as the reference gas is omitted as in the soot detection device 1a according to the second embodiment. In addition to exhibiting the effect that can be achieved, the structure of the wrinkle detecting element 10b is extremely simple, and the manufacturing cost can be reduced.

Further, as in the soot detecting device 1c in the fourth embodiment shown in FIG. 9, a communication hole 12 is formed in the spacer 5c so as to communicate with the gas space 11 to be measured and through which soot and gas can pass. The same effect can be obtained even when the soot detecting element 10c having the porous ceramic layer 100c having pores that can permeate gas but cannot permeate so as to cover 21b.

10 and 11 are diagrams showing another embodiment of the present invention.
The wrinkle detection device 1d according to the fifth embodiment of the present invention shown in FIG. 10 is the side on which the first detection electrode 22 and the second detection electrode 32 of the wrinkle detection device 1 of the example of FIG. 1 are formed. A wrinkle detecting element 10d having a spacer 14 made of an insulating material such as alumina and a shielding plate 13 formed on the surface is used.
Furthermore, the soot collection space 16 is partitioned by the surface of the solid electrolyte body 4, the spacer 14, and the shielding plate 13, and the soot collection space 16 and the measured gas space 11 are formed by the notch formed in the spacer 14. Has come to communicate.
An electrostatic field application electrode 15 for applying an electrostatic field is formed on the side of the shielding plate 13 facing the soot collection space 16 so as to face the first detection electrode 22 and the second detection electrode 32. ing.

In general, the soot particles contained in the combustion exhaust gas of the internal combustion engine are charged positively, so that a voltage is applied so that the first detection electrode 22 becomes a negative electrode between the electrostatic field application electrode 15 and the first detection electrode 22. Is applied, an electrostatic field is formed in the space between the electrostatic field application electrode 15 and the first detection electrode 22, and the positively charged soot particles are affected by the electrostatic field and are subjected to the first detection as a negative electrode. It is collected on the surface of the electrode 22.
Thereby, it becomes possible to collect the soot floating in the gas space 11 to be measured more effectively, and the detection sensitivity of the soot detecting device 1d is improved.
Furthermore, the soot detecting device 1e according to the sixth embodiment of the present invention shown in FIG. 11 is the soot detecting element provided with the soot collecting space 16 and the electrostatic field applying electrode 15 in the soot detecting device 1b in the example of FIG. 10e is used and has the same effect as the embodiment of FIG.

With reference to FIG. 12, a wrinkle detection device 1f according to a seventh embodiment of the present invention will be described.
In the said embodiment, the 1st reference electrodes 21 and 21f and the 1st detection electrodes 22 and 22b are provided in the surface which the solid electrolyte body 4 opposes, respectively, and the 1st reference electrodes 21 and 21b are measured gas space. The first electrochemical cells 2, 2 b are made to face the reference gas spaces 51, 51 a, 51 c for introducing the reference gas separately from 11 and the first detection electrodes 22, 22 b to face the gas space to be measured. In the present embodiment, the solid electrolyte body 4 is formed so as to sandwich the solid electrolyte body 4. However, in the present embodiment, the same space as the measured gas space 11 is used as the reference gas space 51 f and the solid facing the measured gas space 11 is used. Both the first reference electrode 21f and the first detection electrode 22f are formed only on one surface of the electrolyte body 4, and the surface of the first reference electrode 21f is present in the gas to be measured. Is not transparent, The first electrochemical cell 2f is covered with a porous ceramic layer 100f that transmits only the body, and the first reference electrode 21f and the first detection electrode 22f are short-circuited and applied to the first electrochemical cell 2f. The difference is that the oxygen ion current flowing through the first electrochemical cell 2f is detected by setting the voltage to 0.
In the present embodiment, in addition to the same effects as those of the third embodiment of the present invention shown in FIG. 8, there is no need to divide the reference gas space 51 different from the measured gas space 11, and the reference gas space 51f. Therefore, the soot detection element 10f can be further simplified.

In the wrinkle detection device 1g according to the eighth embodiment of the present invention shown in FIG. 13, the first reference electrode 21f and the first detection electrode 22f are attached to the solid electrolyte body 4 as in the eighth embodiment. The first reference electrode 21f is formed on the surface facing the measurement gas space 11, and is covered with the porous ceramic layer 100f.
Further, a spacer 14g made of an insulating material such as alumina and a shielding plate 13 are formed on the surface on which these electrodes 21f and 22f are formed. The spacer 14g and the shielding plate 13 form a soot collection space. 16 is also used as a reference gas space 51g, and the soot collection space 16 and the gas space to be measured 11 are communicated with each other by a notch formed in the spacer 14g.
On the side of the shielding plate 13 facing the soot collection space 16, an electrostatic field application electrode 15 for applying an electrostatic field is formed so as to face the first reference electrode 21f and the first detection electrode 22f. The wrinkle detecting element 10g is configured.
Also in the present embodiment, in addition to being able to detect wrinkles with high accuracy, in the same manner as in the above embodiment, a wrinkle is formed between the first detection electrode 22f and the electrostatic field applying electrode 15 by the electrostatic field applying electrode 15. The electrostatic field to be collected can be applied, so that the soot floating in the measured gas space 11 can be collected more effectively, and the detection sensitivity of the soot detecting device 1g can be improved.

DESCRIPTION OF SYMBOLS 1 Soot detection apparatus 2 1st electrochemical cell 3 2nd electrochemical cell 4 Solid electrolyte body 5, 14 Spacer 51 Reference gas space 9 Heating means (heater)
DESCRIPTION OF SYMBOLS 100 Porous ceramic layer 12 Slit 13 Shielding layer 16 Soot collection space 11 Gas space to be measured 15, 21, 22, 31, 32 Electrode

JP 2009-281974 A

Claims (6)

First detection electrodes (22, 22b, 22f) that are present in the measured gas space (11) and face the measured gas including soot at least on the surface of the oxygen ion conductive solid electrolyte body (4). When the reference gas space and the measurement gas space (11) which is partitioned separately (51, 51a, 51c, 51 g) present in, or reference gas with the same space as the measurement gas space (11) A pair of electrodes (21, 22, 21b, 22b, 21f, 22f) comprising a first reference electrode (21, 21b, 21f) that exists in the space (51f) and faces the reference gas that does not contain soot. And the first reference electrode (21, 21b, 21f) to the first detection electrode (22, 22b) by energization between the pair of electrodes (21, 22, 21b, 22b, 21f , 22f ). , 22f) A first electrochemical cell (2, 2b, 2f) for supplying oxygen for oxidizing soot deposited on the surface of the first sensing electrode (22, 22b, 22f), and the solid electrolyte body ( 4) A soot detecting element (10, 10a, 10b, 10c, 10d, 10e, 10f, 10g) provided with a heating means (9) for heating the gas is measured in the gas to be measured, and the first detection It is a soot detection device that detects soot existing in the gas space to be measured (11) by detecting an electrochemical change when soot deposited on the surface of the electrodes (22, 22b, 22f) is oxidized. And
The detection voltage (V _D ) applied between the first detection electrode (22, 22b, 22f) and the first reference electrode (21, 21b, 21f ), and the voltage when no soot is deposited By controlling the voltage so that the threshold value (V _REF ) is equal,
Oxygen for oxidizing soot is supplied from the first reference electrode (21, 21b, 21f) to the first detection electrode (22, 22b, 22f), and the first detection electrode (22, 22b) is supplied. , when to oxidize the soot deposited on the surface of 22f), said first electrochemical cell (2 and 2b, the first sensing electrode of an oxygen ion current signal flowing through 2f) _{(I PM) (22} , 22b, 22f), a soot detecting device (1, 1a, 1b, 1c, 1d, 1e, 1f, 1g) having means for detecting the soot amount accumulated on the surface of the soot. Said means, said first electrochemical cell (2 and 2b, 2f) on the surface of the oxygen ion current signal flowing through the integrated value of _{(I PM)} the first sensing electrode from _{(I SUM) (22,22b)} The soot detecting device (1, 1a, 1b, 1c, 1d, 1e, 1f, 1g) according to claim 1, wherein the amount of soot accumulated is detected. The reference gas space (51a , 51c, 51g ) and the measured gas space (11) communicate with each other, or the reference gas space ( 51f) and the measured gas space (11) are the same space. In addition, the soot existing in the gas to be measured does not pass through the gas to be measured in the gas space to be measured (11), and the gas passes through the porous ceramic layers ( 100a, 100c, 100f ). The soot detection device (1a, 1b, 1c) according to claim 1 or 2, wherein the first reference electrode (21, 21b) is in contact with the reference gas not containing soot. 1e, 1f, 1g). On the surface of the solid electrolyte body (4), a porous material that does not permeate the soot existing in the measurement gas but permeates the gas to the measurement gas space (11) that is the same as the first detection electrode (22). A second sensing electrode (32) facing through the porous ceramic layer (100);
A pair of electrodes (31, 32) consisting of a second reference electrode (31) provided facing the reference gas space (51 , 51a ), the same as the first reference electrode (21);
A second electrochemical cell (3) for measuring the electromotive force between the pair of electrodes (31, 32) is provided, and the voltage between the electrodes (31, 32) of the second electrochemical cell (3) is The detection voltage (V _D ) is applied between the electrodes (21, 22) of the first electrochemical cell (2) as the voltage threshold (V _REF ). The wrinkle detection device according to claim 1 (1, 1a, 1d). The first reference electrodes (21b, 21f) pass through the first sensing electrodes (22b, 21f) via the porous ceramic layers ( 100a, 100c , 100f) that do not transmit soot in the gas to be measured but transmit gas. 22f ) faces the reference gas space (51a, 51c, 51f) where the same gas as the gas to be measured exists in the gas space to be measured (11) facing
The pair of electrodes (21b, 22b , 21f, 22f ) of the first electrochemical cell (2b , 2f ) is short-circuited, and the voltage threshold (V _REF ), that is, the detection voltage (V _D ) is set to 0. The wrinkle detection device (1b, 1c, 1e, 1f, 1g) according to any one of claims 1 to 3. An electrostatic field application electrode (15) provided via an insulator (14) facing the first detection electrode (22 , 22b , 22f );
The surface of the first sensing electrode is formed by applying a voltage (V _ST ) between the first sensing electrode (22 , 22b , 22f ) and the electrostatic field applying electrode (15) to form an electrostatic field. The soot detecting device (1d, 1e, 1g) according to any one of claims 1 to 5, wherein soot is collected on the top.

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