JP3074882B2 - Method for manufacturing nitrogen oxide sensor element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is provided in an exhaust gas flow path of an internal combustion engine such as a diesel engine, and is provided with N in the exhaust gas.
The present invention relates to a nitrogen oxide sensor element for detecting _OX (nitrogen oxide) concentration.

[0002]

2. Description of the Related Art Conventionally, zirconia (ZrO ₂ ) has been used as a nitrogen oxide sensor for detecting NO _x (nitrogen oxide) concentration in exhaust gas of an internal combustion engine such as a diesel engine.
A solid-electrolyte oxygen sensor using the same is used. As a general solid electrolytic oxygen sensor, zirconia (Z
An element made of stable zirconia obtained by sintering a material such as an alkaline earth metal or a rare earth element into rO ₂ ), which becomes an oxygen ion conductor at a high temperature, and is a sintered body called a solid electrolyte. . Then, the concentration difference between oxygen in the exhaust gas and the standard air is detected as an electromotive force, and the oxygen concentration in the exhaust gas is detected.

[0003]

[SUMMARY OF THE INVENTION Incidentally, although the solid electrolyte type oxygen sensor described above is optimal for detection of the exhaust gas of a gasoline engine, when using this diesel engine, NO _X in (nitrogen oxides) The detection sensitivity is low,
In addition, there is a disadvantage that the recovery time becomes longer. Therefore, recently, a nitrogen oxide sensor element using metal phthalocyanine, which is a kind of P-type semiconductor, has been proposed. However, the sensitivity and recovery time are very different depending on the stability of the crystal structure state, and the reproduction is difficult. There are problems to be solved, such as difficulty in obtaining the properties, and it has not yet been put to practical use.

Accordingly, the present invention has been devised in order to effectively solve the above-mentioned problems, and an object of the present invention is to use the above-mentioned metal phthalocyanine of a P-type semiconductor to obtain NO _X
An object of the present invention is to provide a method for manufacturing a nitrogen oxide sensor element capable of measuring a concentration accurately and with good reproducibility.

[0005]

To accomplish the above object In order to achieve the above, provided in the exhaust gas passage of an internal combustion engine such as a diesel engine, detecting the NO _X (nitrogen oxides) concentration in the exhaust gas in NO _X sensor element for,
And phthalocyanine was deposited on the surface of the insulating plane heater to form a phthalocyanine thin film, wavy of the NO _X adsorbing layer stabilized by irradiating wave line shape laser beam having a wavelength of 650~700nm to the phthalocyanine thin film it is formed and then, to the NO _X adsorbing layer, and is formed by connecting a detector for detecting the electrical resistance.

[0006]

[Action] For the present invention the above-described structure, the NO _X adsorbing layer, the NO _X gas molecules in the exhaust gas contacts, which results in the electric conductivity is doped is changed,
By detecting the electrical conductivity, it is possible to measure the NO _X gas concentration in the exhaust gas. Further, while phthalocyanine improved detection accuracy of the NO _X gas concentration with enhanced adsorption rate of the NO _X because the regulation, the better the reproducibility recovery time is shortened, always good condition sensitive nitrogen Oxide sensor element can be obtained

[0007]

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

FIG. 1B shows an embodiment of the nitrogen oxide sensor element 1 according to the present invention. As shown in the figure, the nitrogen oxide sensor element 1 has a wavy NO _X gas adsorption layer 3 made of phthalocyanine stabilized by irradiating a laser beam onto the upper surface of a planar heater 2 to which a heater power supply 5 is connected. it is formed, which are connected a detection unit 4 for measuring the electrical resistance across the NO _X gas adsorption layer 3.

In the method of manufacturing the nitrogen oxide sensor element 1, first, as shown in FIG. 1A, a ceramic insulating material is powdered and plasma sintered so as to surround the wavy heater wire 6. Then, the sheet heater 2 is manufactured by sintering by hot pressing. Next, this planar heater 2
Phthalocyanine (C ₃₂ H) which is a p-type semiconductor
After vapor deposition of ₁₆ N ₈ ) or another metal phthalocyanine thin film 7, as shown in FIG. 1B, the phthalocyanine thin film 7 is irradiated with a laser beam having a wavelength of 650 to 700 nm in a wavy manner to form the phthalocyanine thin film 7. After stabilization, the phthalocyanine thin film 7 not irradiated with the laser beam is removed to form a wavy NO _X gas adsorption layer 3. Note that the NO _X gas adsorption layer 3 in consideration of the thermal conductivity, is formed along the heater wire 6 embedded in advance in the planar heater 2. The stabilization of phthalocyanine utilizes the photochemical burning (PHB) phenomenon. This photochemical burning phenomenon is a photochemical or photophysical process in which a hole of the same wavelength as the irradiation light is generated in the absorption spectrum of a material, and this hole is retained for a long time as long as the system is kept at a low temperature. It is a phenomenon. The absorption spectrum of phthalocyanine has a stable state of about 680 nm and a metastable state of about 650 nm. When a laser beam of this wavelength is irradiated, hydrogen atom pairs in the molecular structure are rotated by 90 ° as shown in FIG. Then, it is shifted to a stabilized state. That is, the columnar structure in which the hydrogen atom pairs in the molecular structure are rotated by 90 ° has better dispersion of NO ₂ gas and higher sensitivity. Further, as a laser oscillator that oscillates a laser beam having a wavelength of 650 to 700 nm, for example, GAP · Z
By using an oscillator material of nO / GAP. This G
The oscillator material of AP-ZnO / GAP is GAP-ZnO
(A mixture of gallium phosphide and zinc oxide) and GAP (gallium phosphide), in which a laser having a high wavelength of 700 nm is generated. That is, 68
In this embodiment, GAP · ZnO / GAP is used because an oscillator material that emits a laser beam having a wavelength of 0 nm cannot be clearly found.
The laser light of a high wavelength of 700 nm oscillated from the above oscillator material is used.

Then, as shown in FIG. 2, the nitrogen oxide sensor element 1 formed as described above is fixed to a holding table 7 and provided in an exhaust gas flow path 8 to form a large number of exhaust gas vent holes 9. Will be installed and used in the protective cover 10 on which is formed.

[0011] Nitrogen oxide sensor element 1 formed as above is in the NO _X adsorbing layer, the NO _X gas molecules in the exhaust gas contacts, which will be doped electrical conductivity changes, the by detecting the electrical conductivity, it will measure the NO _X gas concentration in the exhaust gas. Then, after the measurement, the adsorbed NO _X is heated by the heater 5 to remove NO _X and can be regenerated.
Further, since the phthalocyanine constituting the NO _X adsorption layer 3 is stabilized, a stable state is not maintained for a long time, so that the detection sensitivity to the NO _X gas concentration is improved and the recovery time is shortened. Reproducibility is improved, and a state of good sensitivity can be always maintained.

[0012]

According to the above summary the present invention, since the phthalocyanine constituting the NO _X adsorbing layer is stabilized, thereby improving the detection sensitivity for NO _X gas concentration, reproducible recovery time is shortened It has excellent effects such as maintaining good sensitivity over a long period of time.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing one embodiment of the present invention.

FIG. 2 is a sectional view showing an attached state of a NO _X sensor.

FIG. 3 is a structural diagram showing a structural formula of phthalocyanine and oxygen atom pairs.

[Explanation of symbols]

1 nitrogen oxide sensor element 2 planar heater 3 NO _X adsorbing layer 4 detector 7 phthalocyanine thin film 8 exhaust gas channel G exhaust gas

────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Yuichiro Hara 8 Tsurana, Fujisawa City, Kanagawa Prefecture Isuzu Central Research Laboratory Co., Ltd. (56) References JP-A-53-113596 (JP, A) JP-A-56- 122943 (JP, A) JP-A-59-142581 (JP, A) JP-A-4-216449 (JP, A) JP-A-58-141246 (JP, A) JP-A-5-45316 (JP, A) JP-A-5-45317 (JP, A) JP-T-62-502987 (JP, A) JP-T-Hei 4-501461 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 27/12 CA (STN)

Claims (1)

(57) [Claims] 1. A nitrogen oxide sensor element provided in an exhaust gas passage of an internal combustion engine such as a diesel engine for detecting the concentration of NO _x (nitrogen oxide) in the exhaust gas. by depositing phthalocyanine on the surface of the heater to form a phthalocyanine thin film, forming a wavy of the NO _x adsorbing layer the laser beam was stabilized by irradiating the wavy wavelength of 650~700nm to the phthalocyanine thin film, then , wherein the NO _X adsorbent layer, the manufacturing method of the nitrogen oxide sensor element, characterized in that formed by connecting a detector for detecting the electrical resistance.