JP2582720Y2 - NOx sensor - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a NOx sensor for detecting NOx (nitrogen oxide) concentration in exhaust gas of an internal combustion engine such as a diesel engine.

[0002]

2. Description of the Related Art In exhaust gas of an internal combustion engine such as a diesel engine, NO which induces environmental pollution such as photochemical smog is included.
Since x (nitrogen oxide) is contained, a NOx sensor that accurately detects this and controls NOx in exhaust gas online is desired.

[0003] Conventionally, the basic structure of a NOx sensor proposed in literatures or the like is, as shown in FIG. 10 , an adsorbent made of copper phthalocyanine for adsorbing NOx on a ceramic substrate a provided in a flow path of exhaust gas. A layer b is provided, and further, gold-deposited electrodes c are provided at both ends of the adsorption layer b. That is, when NOx molecules in the exhaust gas adhere to the adsorbing layer b, electrons are exchanged between the NOx molecules and the adsorbing layer b made of copper phthalocyanine or the like, and the electron concentration changes. Since the electrical resistance of b changes,
By detecting this with the detector d , the N in the exhaust gas is reduced .
Ox concentration is to be measured .

[0004]

However, once the adsorbing layer b of the above-mentioned NOx sensor has adsorbed NOx molecules, it is difficult to remove NOx, so that measurement after the second time is impossible. Further, as described above, this NOx sensor is provided in a limited space such as in the flow path of the exhaust gas. However, since the adsorbing layer b has a flat surface, its reaction contact area is small. Was a thing,
Therefore, the NOx adsorption rate is low, the output is small, and the accuracy is poor. Therefore, there is a problem in actual use.

Accordingly, the present invention has been devised in order to effectively solve the above-mentioned problems, and the object of the present invention is to provide NOx.
Improve NOx concentration measurement accuracy by improving molecule adsorption rate
And a novel NOx sensor that can be reused repeatedly .

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, a first invention is provided in a flow path of exhaust gas of a diesel engine to detect the concentration of NOx (nitrogen oxide) in the exhaust gas. in NOx sensor, so as to form a plane heater with embedded heating wire, the said surface shaped heater surface, a plurality of irregularities or a plurality of insulating substrates or porous substrate hole portion is formed, the insulating substrate or A porous substrate surface is coated with copper phthalocyanine or nickel phthalocyanine for adsorbing NOx in the exhaust gas to form an adsorption layer, and the second invention is a diesel engine . NOx for detecting NOx (nitrogen oxide) concentration in the exhaust gas, which is provided in the exhaust gas flow path
In the sensor, a copper phthalocyanine for adsorbing NOx in the exhaust gas is formed on a surface of the rod-shaped heater having a star-shaped cross section in which a heater wire is embedded.
Alternatively, an adsorption layer is formed by coating nickel phthalocyanine .

[0007]

Since the present invention is constructed as described above, the surface area of the adsorption layer for adsorbing NOx in the exhaust gas is increased , so that the reaction contact area is increased and the NOx is reduced.
The x adsorption rate is improved. Also, this adsorption layer
Is on a planar heater via an insulating substrate or a porous substrate,
Or it is provided on the surface of a rod-shaped heater with a star-shaped cross section.
Therefore, if heated by these heaters,
NOx molecules are effectively removed, resulting in NOx
The measurement can be repeated many times.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

FIGS. 1 and 2 show a first embodiment of the NOx sensor 1 according to the first invention. This NOx
The sensor 1 is provided in a flow path of exhaust gas of an internal combustion engine such as a diesel engine and detects the concentration of NOx (nitrogen oxide) in the exhaust gas. As shown in FIG. An insulating substrate 3 is provided on one or both sides of a planar heater 2 made of ceramics, and a porous substrate 4 having a plurality of holes 5 is provided on the surface of the insulating substrate 3. Has an adsorption layer 6 formed on the surface thereof.

This adsorbing layer 6 is for adsorbing NOx in the exhaust gas, and a material such as copper phthalocyanine or nickel phthalocyanine, which adsorbs NOx in the exhaust gas, is deposited on the surface of the porous substrate 4 by a vapor deposition method or the like. It is coated. The surface area is larger than the size of the porous substrate 4. As shown in FIG. 2, electrodes 7 are connected to both ends of the adsorbing layer 6, and the electric resistance of the adsorbing layer 6 is measured by the detecting unit 8 to detect the NOx concentration in the exhaust gas. ing.

A heater power supply 9 is connected to the heater wire 9a of the planar heater 2, and heats the insulating substrate 3 and the porous substrate 4 to 400 ° C. or higher to apply the heat to the adsorbing layer 6 of the porous substrate 4. The adsorbed NOx is removed and regenerated.

In the above, when NOx molecules in the exhaust gas adhere to the adsorption layer 6, electrons are exchanged between the NOx molecules and the adsorption layer 6 made of copper phthalocyanine or the like.
When the electron concentration changes, the electric resistance of the adsorption layer 6 changes. This is detected by the detection unit 8, and the NOx concentration in the exhaust gas is measured. Then, when the measurement is completed, the planar heater 2 is heated by the heater wire 9a energized from the heater power supply 9, whereby the insulating substrate 3 and the porous substrate 4 are heated.
Is heated to 400 ° C. or higher, NOx adsorbed on the adsorption layer 6 of the porous substrate 4 is removed, and the adsorption layer 6 is regenerated.

That is, in this embodiment, since the adsorption layer 6 is formed on the porous substrate 4 in which many holes 5 are formed, the surface area of the adsorption layer 6 is smaller than the size of the porous substrate 4. Can be made extremely large, so that the reaction contact area between NOx and the adsorption layer 6 increases, and NO
The x adsorption rate is improved, and accurate NOx concentration measurement is possible. Further, the adsorption layer 6 is regenerated by heating the planar heater 2.
Therefore, it can be reused repeatedly.

In this embodiment, a flat insulating substrate 3 is used.
In the case where the adsorption layer 6 is formed on the surface of the porous substrate 4 through the
As described above, the insulating substrate 3 itself has a plurality of irregularities or a plurality of irregularities.
If the surface area is increased by having a hole of
The adsorption layer 6 is formed directly on the surface of the substrate 3 or as shown in FIG.
As shown, the structure may be such that the insulating substrate 3 is omitted .

FIG. 4 shows a second embodiment of the present invention. As shown, the NOx sensor 1a
Is provided on one or both sides of the planar heater 2 in which the heater wire 9a is embedded, an insulating substrate 3a having a corrugated surface, and the surface of the insulating substrate 3a is coated with copper phthalocyanine, nickel phthalocyanine, or the like. Adsorption layer 6a
Is formed. An electrode 7 is connected to the adsorbing layer 6a in the same manner as in the above embodiment.
Of the NOx in the exhaust gas
The concentration has been detected. Also, the heater wire 9 of the planar heater 2
Similarly, a heater power supply 9 is connected to a, and the insulating substrate 3a is heated to 400 ° C. or higher to remove NOx adsorbed on the adsorbing layer 6 of the insulating substrate 3a, and is regenerated.

That is, in the present embodiment, the surface of the insulating substrate 3a is formed into a corrugated shape, so that the surface area of the adsorption layer 6 is increased and the reaction area per unit element area is increased as in the above embodiment. Thus, the adsorption rate of NOx to the adsorption layer 6 is improved. Next, FIG. 5 shows a third embodiment of the NOx sensor 1b according to the first invention. As shown in the figure, the NOx sensor 1b has a plurality of convex portions 10 formed on one or both surfaces of a planar heater 2 in which a heater wire 9a is embedded. A substance that adsorbs NOx is coated by a vapor deposition method or the like to form an adsorption layer 6b. As in the above embodiment, the heater power supply 9 is connected to the heater wire 9a of the planar heater 2, and the detectors 8 are connected to both ends of the adsorption layer 6b.

In this embodiment, the plurality of projections 10 increase the surface area of the adsorbing layer 6b, so that the reaction area per unit element area can be increased similarly to the above embodiment. In addition, the adsorption rate of NOx to the adsorption layer 6b can be improved.

Next, FIG. 6 shows an embodiment of the NOx sensor 1c according to the second invention. As shown in the figure, the NOx sensor 1c is formed by coating the surface of a bar-shaped heater 2a having a star-shaped cross section in which a heater wire 9a is embedded with copper phthalocyanine or nickel phthalocyanine for adsorbing NOx in the exhaust gas. 6c. As in the above embodiment, the heater power supply 9 is connected to the heater wire 9a of the rod-shaped heater 2a, and the detection units 8 are connected to both ends of the adsorption layer 6b.

As described above, in this embodiment, by forming the heater portion in a bar shape having a star-shaped cross section, it is possible to increase the surface area of the adsorption layer 6c, and the same effect as that of the above embodiment can be obtained. Furthermore, a new effect of reducing the pressure loss of the exhaust gas flowing through the exhaust passage (not shown) can be obtained. In order to improve the detection accuracy of the NOx sensor 1c, as shown in FIG. 7, a plurality of these rod-shaped NOx sensors 1c are arranged in parallel, and electrodes 7a are provided at both ends thereof so as to bridge them. The heater 7 may be connected to the electrode 7a, and the detectors 8 may be connected to both ends of the adsorption layer 6b.

In this embodiment, the heater portion is a bar having a star-shaped cross section. However, the present invention is not limited to this. A plurality of concave and convex portions such as the above-described NOx sensors 1 to 1b are provided on the side of the bar. The same effect as described above can be obtained by forming or forming a wave shape to increase the surface area.

[0021]

[0022]

[0023]

FIGS. 8 and 9 show one embodiment of a method of manufacturing the sheet heater and the bar heater 2a used in each of the above embodiments. First, according to the manufacturing method shown in FIG. 8, an insulating material such as ceramic constituting the planar heater 2 and the rod-shaped heater 2a is powdered, and the insulating powder 12 is arranged so as to surround the heater wire 9a. It is obtained by sintering by a sintering method, a hot pressing method, or the like, and solidifying and forming into a predetermined shape. On the other hand, the manufacturing method shown in FIG. 9 powders a substance such as Ni—Cr or W that forms the heater wire 9a, continuously arranges the heater powder 13, and surrounds the sheet heater 2 and the After arranging it so as to surround the insulating powder 12 made of an insulating material constituting the rod-shaped heater 2a, it is sintered by a plasma sintering method or a hot press method and solidified into a predetermined shape as described above. A heater wire 9a and a heater power supply 9 are connected to both ends of the heater 2c.

As described above, the insulating material constituting the sheet heater 2 and the rod-shaped heater 2a and the material constituting the heater are powdered, whereby a heater having a desired shape can be easily manufactured. be able to.

[0026]

[Effects of the Invention] In short , according to the present invention, the adsorption layer
By increasing the reaction contact area per unit area,
NOx adsorption rate is improved, so NOx concentration detection accuracy
And the adsorption layer is effective by heating the heater.
That can be reused repeatedly.
It has excellent effects such as becoming.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of the first invention.

FIG. 2 is a sectional view showing an embodiment of the first invention.

FIG. 3 is a sectional view showing a modified embodiment of the first invention.

FIG. 4 is a perspective view showing a second embodiment of the first invention.

FIG. 5 is a perspective view showing a third embodiment of the first invention.

FIG. 6 is a perspective view showing an embodiment of the second invention.

FIG. 7 is a perspective view showing another embodiment of the second invention.

FIG. 8 is an explanatory view showing one embodiment of a method for manufacturing a heater.
You.

FIG. 9 is an explanatory view showing another embodiment of the method for manufacturing a heater.
It is.

FIG. 10 is a schematic diagram showing a basic structure of a conventional NOx sensor.
It is.

[Description of Symbols] 1, 1a, 1b, 1c, 1d NOx sensor 2 Planar heater 2a Bar heater 3, 3a Insulating substrate 5 Hole 6, 6, 6a, 6b, 6c, 6d Adsorption layer 9a Heater wire 10 Convex portion 11 Adsorption powder

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-193051 (JP, A) JP-A-1-148953 (JP, A) JP-A-1-206252 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) G01N 27/12

Claims (2)

(57) [Scope of request for utility model registration] 1. A NOx sensor provided in a flow path of an exhaust gas of a diesel engine for detecting a NOx (nitrogen oxide) concentration in the exhaust gas, wherein a planar heater having a heater wire embedded therein is formed. An insulating substrate having a plurality of irregularities or a plurality of holes formed on the surface of the planar heater
Alternatively , a NOx sensor comprising a porous substrate , and an adsorption layer formed by coating copper phthalocyanine or nickel phthalocyanine for adsorbing NOx in the exhaust gas on the surface of the insulating substrate or the porous substrate. . 2. A NOx sensor provided in a flow path of an exhaust gas of a diesel engine and detecting a NOx (nitrogen oxide) concentration in the exhaust gas. NOx formed by coating the surface of the rod-shaped heater with copper phthalocyanine or nickel phthalocyanine for adsorbing NOx in the exhaust gas.
Sensor.