JP2003313073A - Bottomed cylindrical body, production method thereof and sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bottomed cylindrical body in which joining strength between a cylindrical tube and a sealing body can easily be improved, to provide a production method thereof, and to provide a sensor. <P>SOLUTION: The bottomed cylindrical body is obtained by providing the inside of one end part of a cylindrical body 1 made of a ceramic with a sealing body 3 made of a ceramic, and sealing one end part of the cylindrical body 1. The cylindrical body 1 and the sealing body 3 contain ZrO<SB>2</SB>as the main crystal grains, and the cylindrical body 1 and the sealing body 3 are cofired. Both the cylindrical body 1 and the sealing body 3 contain Al<SB>2</SB>O<SB>3</SB>. Also, the Al<SB>2</SB>O<SB>3</SB>content in the sealing body 3 is higher than that in the cylindrical body 1. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bottomed tubular body, a method for manufacturing the same, and a sensor, and more particularly, a tubular body made of a solid electrolyte ceramic having oxygen ion conductivity and a sealing body are co-fired and integrated. The present invention relates to a closed bottomed cylindrical body, a manufacturing method thereof, and a sensor.

[0002]

2. Description of the Related Art Conventionally, as a method for sealing one end of a tubular body, for example, as disclosed in Japanese Patent Laid-Open No. 5-84732, an organic porous body such as a filter paper is fixed in the tubular body,
A method is known in which a ceramic slurry is poured into a cylindrical body to be deposited on the organic porous body and the organic porous body disappears during firing.

[0003]

However, in the sealing method as described above, the firing shrinkage ratios are almost the same even when the ceramic slurries forming the cylindrical body and the sealing body are the same or different. Therefore, there is a problem that the joint strength between the tubular body and the sealing body formed by filling the inside thereof is low. As a result, the interface between the tubular body and the sealing body deteriorates over time, and there is a problem that a gap or a crack is likely to occur.

When such a bottomed tubular body is used as a sensor (air-fuel ratio sensor) for detecting the oxygen concentration in the exhaust gas of an internal combustion engine of an automobile, for example, the tubular body is subject to thermal shock due to rapid temperature rise. There is a problem that the interface between the body and the sealing body deteriorates with time, and a gap or a crack is generated at the bonding interface, which destroys the sensor or adversely affects the sensor characteristics.

An object of the present invention is to provide a bottomed tubular body, a method of manufacturing the same, and a sensor which can easily improve the bonding strength between the tubular body and the sealing body.

[0006]

The bottomed tubular body of the present invention comprises:
A ceramic sealing body is provided inside one end of the ceramic cylindrical body to seal one end of the cylindrical body, and the cylindrical body and the sealing body mainly crystallize ZrO _2. In addition to containing as particles, the tubular body and the sealed body are simultaneously fired bottomed tubular body, both the tubular body and the sealed body contains Al ₂ O ₃ , and, Al ₂ in the sealed body
O ₃ content, characterized in that more than Al ₂ O ₃ content of the tubular body in.

In such a bottomed cylindrical body, a sealing ceramic molded body is provided inside one end of the cylindrical ceramic molded body, and after sealing the one end of the cylindrical ceramic molded body,
A method for manufacturing a bottomed tubular body, in which the tubular ceramic compact and the sealing ceramic compact are simultaneously fired, wherein the tubular ceramic compact and the sealing ceramic compact are ZrO ₂ main crystals. with a powder, the containing Al ₂ O _3, and has a content of Al ₂ O ₃ of the sealing ceramic molded body for locking and more than the content of Al ₂ O ₃ in the tubular ceramic molded body production method It can be obtained by using.

According to such a manufacturing method, the cylindrical ceramic molded body and the sealing ceramic molded body contain ZrO ₂ as the main crystal powder and the Al ₂ O ₃ content of the sealing ceramic molded body. Than cylindrical ceramic compacts
_{Since the 2} O ₃ content is increased, the sintering temperature T1 of the encapsulating ceramic compact containing a large amount of Al ₂ O ₃ , which is a sintering aid that promotes grain growth during firing, is set to a cylindrical ceramic compact. When the cylindrical ceramic molded body and the sealing ceramic molded body are fired at the same time, the shrinkage of the sealed body ends earlier than the shrinkage of the tubular body, and the tubular body is sealed. Is strongly tightened, the sealing body is firmly bonded to the inside of the tubular body, deterioration over time can be prevented, and strong bonding can be maintained for a long time.

Further, in the method for producing a bottomed tubular body of the present invention, the content of Al ₂ O _{3 is} 100 (mole part) with respect to 100 mole parts of the main crystal powder in the tubular ceramic molded body, and the ceramic molding for sealing is formed. Al ₂ O _{3 with} respect to 100 parts by mole of the main crystal powder in the body
When the content is n (molar part), 0.3 ≦ (nm) is satisfied. In such a method of manufacturing a bottomed tubular body, the sintering temperature T1 of the sealing ceramic molded body is certainly lower than the sintering temperature T2 of the tubular ceramic molded body, and the tubular body forms the sealed body. It is possible to sinter in a more tightly clamped state and maintain a strong bond for a long time.

Further, in the method for producing a bottomed tubular body of the present invention,
The sintering temperature T1 of the sealing ceramic compact is lower than the sintering temperature T2 of the tubular ceramic compact, and is kept at a temperature higher than the sintering temperature T1 and lower than the sintering temperature T2. It is characterized in that after the stop ceramic molded body is sintered, it is kept at a temperature higher than the sintering temperature T2 to sinter the tubular ceramic molded body.

According to such a manufacturing method, after the sealing body is completely sintered at a temperature higher than the sintering temperature T1 and lower than the sintering temperature T2, the temperature is higher than the sintering temperature T1 of the sealing body. By firing at a high temperature and higher than the sintering temperature T2,
Tightening by the tubular body with respect to the sealing body occurs more efficiently, and a sintered body with no gaps in the joint surface can be obtained.

In the method for manufacturing a bottomed tubular body of the present invention, the rare earth element oxide is contained in the tubular ceramic molded body and the sealing ceramic molded body, and the rare earth element oxide in the tubular ceramic molded body is included. Content x is 4 to 7 mol%, the rare earth element oxide content y in the sealing ceramic molded body is 4.4 to 8 mol%, and 0.4 ≦ (y−x)
It is desirable to satisfy.

As a result, for example, the content of the rare earth element oxide (RE ₂ O ₃ : RE is a rare earth element) in the cylindrical body containing ZrO ₂ as a main component, which is often used as a solid electrolyte, and the sealed body is made different. As a result, the mutual diffusion of Zr and RE across the interface between the tubular body and the sealing body is promoted, and Z between the tubular body and the sealing body is promoted.
The bonding force between rO ₂ is increased, the sealing body is firmly bonded to the inner surface of the tubular body, and the bonding strength between the tubular body and the sealing body can be improved.

In the method for manufacturing a bottomed tubular body of the present invention, the one end of the tubular ceramic molded body is sealed by the sealing ceramic molded body in the slurry forming the sealing ceramic molded body. The one end of the cylindrical ceramic molded body is soaked and then dried by hanging, or one end of the cylindrical ceramic molded body is sealed with a sealing member, and then the ceramic molded body for sealing is formed. It is preferable that the slurry is dropped into the cylindrical ceramic molded body and dried.

According to such a manufacturing method, the ceramic slurry forming the sealing ceramic molded body can be easily supplied into the cylindrical ceramic molded body, and furthermore, the sealing ceramic can be provided inside one end of the cylindrical ceramic molded body. A molded body can be easily formed and mass productivity can be expected.

The sensor of the present invention comprises a cylindrical body with a bottom according to claim 1, which is made of solid electrolyte ceramics, and electrodes are formed on the inner and outer surfaces of the cylindrical body with the bottom, which face each other. In such a sensor, for example, a sensor for detecting the oxygen concentration in the exhaust gas of an internal combustion engine of an automobile or the like by utilizing the oxygen ion conductivity of solid electrolyte ceramics ( It can be used as an air-fuel ratio sensor) and can firmly bond the tubular body and the sealing body and maintain high bonding strength for a long period of time. It can withstand thermal shock sufficiently, and can significantly extend the sensor life.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The bottomed tubular body of the present invention is, as shown in FIG. 1, provided with a ceramic sealing body 3 inside one end of a ceramic tubular body 1 to thereby form a tubular body. One end of the body 1 is sealed. The main crystal grains of the cylindrical body 1 and the sealing body 3 are ZrO ₂ , and the cylindrical body 1 and the sealing body 3 are co-fired and integrated.

[0018] In the bottomed cylindrical body of the present invention, the tubular body 1, the sealing body 3 is contained Al ₂ O _3, the Al ₂ O ₃ content of the tube in 1 m ( Molar part), Al ₂ O ₃ in the sealing body ₃
The feature is that n> m is satisfied when the content is n (molar part). This is because the tightening force of the tubular body 1 is low when n ≦ m. In particular, from the viewpoint of improving the tightening force due to the contraction of the tubular body 1 and suppressing the generation of gaps at the joint interface, it is desirable to satisfy 0.3 ≦ (nm), and further 0.5 ≦. It is desirable that it is (nm).

The bottomed tubular body is composed of a solid electrolyte having oxygen ion conductivity, and Zr containing a rare earth element oxide as a solid solution.
It is composed of O ₂ .

Therefore, the main crystal grains of the tubular body 1 and the sealing body 3 are ZrO ₂ grains in which the rare earth element oxide is solid-dissolved. By utilizing this oxygen ion conductivity,
It can be used as a sensor for detecting the oxygen concentration in the exhaust gas of an internal combustion engine such as an automobile. The rare earth element includes Y, Yb, Ce and the like.

As shown in FIG. 2, the bottomed cylindrical body having the above-described structure has a cylindrical ceramic molded body formed by forming a sealing ceramic molded body inside one end of the cylindrical ceramic molded body 11. After sealing one end of the molded body 11, the tubular ceramic molded body 11 and the sealing ceramic molded body are simultaneously fired to be formed.

Specifically, first, in order to form the cylindrical ceramic molded body 11 and the sealing ceramic molded body, ZrO ₂ powder in which a rare earth element oxide is solid-dissolved and Al ₂ O ₃ powder are prepared.

That is, ZrO in which a rare earth element oxide is formed as a solid solution
_A cylindrical ceramic molded body 11 and a sealing ceramic molded body are produced by using a slurry formed by adding an organic solvent to a mixed powder of ₂ powder and Al ₂ O ₃ powder and mixing them.

The cylindrical ceramic molded body 11 is formed by extrusion molding, and the sealing ceramic molded body is formed by a slurry dipping method or a slurry dropping method.

To form the sealing ceramic molded body by the slurry dipping method, first, one end of the cylindrical ceramic molded body 11 is immersed in the slurry contained in the container 9 for a certain period of time and then pulled up and dried. Then, the sealing ceramic molded body is filled and formed inside one end of the cylindrical ceramic molded body 11.

In the slurry dropping method, the lower end of the cylindrical ceramic molded body 11 is sealed with the sealing member 10 made of, for example, carbon, and then the above is performed from the opening of the upper end of the cylindrical ceramic molded body 11. After dropping the slurry and drying,
By removing the sealing member 10, a cylindrical ceramic molded body 11 is formed.
A ceramic molding for sealing is formed at the lower end of the.

By using these slurry dipping method and slurry dropping method, the ceramic slurry forming the sealing body can be easily enclosed in the cylindrical ceramic molded body 11, and mass productivity can be expected. Further, the simultaneous firing eliminates the need for repeated exposure to a high temperature atmosphere, can reduce the cause of deterioration of the characteristics of the sintered body, and can reduce the cost by shortening the process.

In this way, the cylindrical ceramic molded body 11
Formed by filling the ceramic molded body for sealing at one end of
This is fired at a predetermined temperature to produce the bottomed tubular body of the present invention.

In the method for producing a bottomed cylindrical body of the present invention, in particular, ZrO ₂ is used as the main crystal powder of the cylindrical ceramic molded body 11 and the sealing ceramic molded body, and the cylindrical ceramic molded body 11 and the sealed ceramic molded body are sealed. All ceramic moldings for A
Al in a ceramic molding for sealing containing l ₂ O _3
2 O ₃ content is required to be larger than the content of Al ₂ O ₃ of the cylindrical ceramic molded body 11.

[0030] Thus, the content of Al ₂ O ₃ ceramic molded body for sealing, Al ₂ cylindrical ceramic molded body 11
The sintering temperature T1 of the encapsulating ceramic compact containing a large amount of Al ₂ O ₃ , which is a sintering aid that promotes grain growth during firing by increasing the O ₃ content, is set to a tubular ceramic compact. The temperature can be lower than the sintering temperature T2 of the body 11, which allows the sealing body 3 to be joined with the tubular body 1 in a tightened state,
A strong joint strength can be obtained.

In particular, the Al ₂ O ₃ content per 100 mol parts of the main crystal powder in the cylindrical ceramic compact 11 is m (mol%), and the Al ₂ O ₃ relative to 100 mol parts of the main crystal powder in the sealing ceramic compact is _2. When the O ₃ content is n (mol%),
By satisfying 0.3 ≦ (nm), it is possible to join the sealing body 3 with the tubular body 1 in a more tightly clamped state, and to obtain stronger joining strength.

Further, in the present invention, the cylindrical ceramic molded body 11 and the sealing ceramic molded body contain a rare earth element,
The content x of the rare earth element oxide in the cylindrical ceramic molded body 11 is 4 to 7 mol%, and the content y of the rare earth element oxide in the sealing ceramic molded body is 4.4 to 8 mol%. , 0.4 ≦ (y−x) is desirable.

By having such a composition, mutual diffusion of Zr and RE sandwiching the interface between the tubular body and the sealing body is promoted, and the bonding force between ZrO _{2 of the} tubular body and the sealing body is increased. The sealing body is firmly bonded to the inner surface of the tubular body, and the bonding strength between the tubular body and the sealing body can be improved. From the viewpoint of further promoting mutual diffusion of Zr and RE across the interface between the tubular body and the sealing body, 5 ≦ x ≦ 6, 6 ≦ y ≦ 7, 1 ≦ (y−x)
It is desirable that ≦ 2.

Further, in the method for producing a bottomed cylindrical body of the present invention,
The sintering temperature T1 of the ceramic molding for sealing is kept lower than the sintering temperature T2 of the tubular ceramic molded body 11 and at a temperature higher than or equal to the sintering temperature T1 and lower than the sintering temperature T2. It is desirable to sinter the tubular ceramic compact 11 by sintering the stop ceramic compact and then keeping it at a temperature higher than the sintering temperature T2.

By temporarily holding the temperature above the sintering temperature T1 and below the sintering temperature T2, the sintering of the sealing body is completely completed, and by keeping the temperature higher than the sintering temperature T2, By advancing the sintering of the shaped body, the tightening of the cylindrical body with respect to the sealing body occurs more efficiently, and it is possible to obtain a sintered body having no gap on the joint surface.

The sensor of the present invention has a bottomed tubular body made of the above-mentioned solid electrolyte ceramics, and has a sensing portion formed by forming electrodes on the inner and outer surfaces of the tubular body which face each other. 3 shows an air-fuel ratio sensor. This air-fuel ratio sensor is, for example, a perspective view of FIG.
As shown in the sectional view taken along line X ₁ -X _{1 in} (b), ZrO ₂ is formed on the inner surface and the outer surface of the tubular body 15 whose tip is sealed by the sealing body.
A reference electrode 16 and a measurement electrode 17 each of which is a platinum electrode in which particles are dispersed are adhered and formed.

Formed on the outer surface of the cylindrical body 15 whose tip is sealed
Around the measured measuring electrode 17 ₂O₃, Al₂O₃And M
Complex oxide with gO or Al₂O₃And Y₂O₃Etc.
Ceramic insulation made of compound oxide with a thickness of 2 to 50 μm
Layer 18 has been deposited. And this ceramic
Part or all of the measuring electrode 17 is exposed on the insulating layer 18.
Predetermined opening 19 is formed so that
Is platinum or the like in the ceramic insulating layer 18 around the mouth 19?
The heating element 20 is embedded.

Further, the heating element 20 has a lead electrode 21.
Is connected to the terminal electrode 22 through the above, and by applying a current to the heating element 20 through these, the heating element 2
0 is heated so that the sensing unit including the measuring electrode 17, the tubular body 15 and the reference electrode 16 can be rapidly heated to a predetermined temperature. Further, a ceramic heat insulating layer 23 is formed on the surface of the ceramic insulating layer 18 in order to prevent heat from being dissipated from the heating element 20.

On the surface of the measuring electrode 17, in order to prevent the electrode from being poisoned, a porous layer made of ZrO ₂ (containing rare earth element oxide such as Y ₂ O ₃ ), Al ₂ O ₃ , MgAl ₂ O ₄ or the like. A quality ceramic protective layer 24 is formed. Alternatively, ZrO ₂ (Y ₂ O having fine pores on the surface of the measurement electrode 17 is used.
Rare earth element oxides such as ₃ ), Al ₂ O ₃ , MgAl ₂ O
₄ , a gas diffusion rate controlling layer using MgO, γ-Al ₂ O ₃ or the like may be formed.

In the sensor as described above, the bottomed tubular body of the present invention is used as a sensor (air-fuel ratio sensor) for detecting the oxygen concentration in the exhaust gas of an internal combustion engine of an automobile or the like, whereby a rapid temperature rise, etc. It can sufficiently withstand the thermal shock caused by, and can enhance the reliability during long-term operation.

[0041]

EXAMPLE A commercially available Al ₂ O ₃ powder having an average particle size of 0.3 μm and a main crystal powder were prepared by a coprecipitation method.
1 to 6.2 mol% Y ₂ O ₃ -containing ZrO ₂ powder and 5 to 7.2 mol% as a main crystal powder produced by a coprecipitation method
ZrO ₂ powder containing Y ₂ O ₃ was prepared.

Next, the ZrO ₂ powder containing 4.1 to 6.2 mol% Y ₂ O _{3 was} added to 100 parts by mol of the ZrO ₂ powder.
After adding and mixing the Al ₂ O ₃ powder in the proportions shown in Table 1,
A kneaded clay was prepared by adding a polyvinyl alcohol solution as an organic binder and pure water as a solvent, and a cylindrical ceramic molded body having an outer diameter of 5 mm and an inner diameter of 3 mm was manufactured by extrusion molding.

On the other hand, Zr containing 5 to 7.2 mol% Y ₂ O ₃
O ₂ powder, Table 1 to 100 parts by mole of the ZrO ₂ powder
After adding and mixing the Al ₂ O ₃ powder in the ratio shown in, a predetermined amount of mineroll was added as a solvent to prepare a slurry for a ceramic molded body for sealing.

Thereafter, the cylindrical ceramic molded body was dipped in the above slurry, lifted and dried to produce a molded body in which the inside of one end of the cylindrical ceramic molded body was sealed with a sealing ceramic molded body. .

Thereafter, this molded body was subjected to 1400 in the atmosphere.
It was kept at 1 ° C. for 1 hour and at 1550 ° C. for 1 hour, and integrally baked in a two-step pattern to produce a bottomed tubular body. still,
The sintering temperature T1 of the molded ceramic body for sealing is 1350.
˜1400 ° C., and the sintering temperature T2 of the cylindrical ceramic molded body was 1500 to 1550 ° C.

For each of the 20 bottomed cylindrical bodies obtained, the temperature cycle of raising the temperature from room temperature to 700 ° C. in 30 seconds and then air-cooling to room temperature was defined as one cycle,
Table 1 shows the ratio of the samples in which cracks were generated at the joint between the tubular body and the sealing body after the test was carried out 0,000 times (thermal cycle test) as the crack ratio. In addition, regarding the sample bonded under the same conditions, the cross-section was cut after the thermal cycle test to confirm the presence or absence of a gap between the cylindrical body and the sealing body with a metallurgical microscope (150 times). It was These results are shown in Table 1.
Described in.

[0047]

[Table 1]

From the results shown in Table 1, the sample No. in which the difference in the Al ₂ O ₃ content between the cylindrical ceramic molded body and the sealing ceramic molded body deviates from the range of the present invention. 1-3, No. In No. 7, many samples were peeled or cracked after the thermal cycle test.

In contrast to these comparative examples, in the samples of the present invention, the rate of occurrence of gaps after the heat cycle test was suppressed to 10% or less, and the rate of crack generation after the heat cycle test was also 5% or less. Therefore, it can be seen that even when used as an air-fuel ratio sensor, it has high reliability.

[0050]

As described above in detail, a bottomed cylindrical body of the present invention, Al ₂ O ₃ of the tubular body in the content of Al ₂ O ₃ in the sealing body
Since the content is higher than the content, the shrinkage during firing of the tubular body and the sealed body is controlled, and the tubular body is sintered after the completion of the sintering of the sealed body, resulting in a high tubular body and a sealed body. Bonding strength can be maintained for a long time. As a result, when such a bottomed tubular body is used as an air-fuel ratio sensor that detects the oxygen concentration in the exhaust gas of an internal combustion engine such as an automobile, thermal shock resistance due to rapid temperature rise can be improved.

[Brief description of drawings]

1A and 1B show a bottomed tubular body of the present invention, wherein FIG. 1A is a perspective view and FIG. 1B is a sectional view.

FIG. 2 is a process drawing for explaining a method for producing a bottomed tubular body of the present invention.

3A and 3B show an air-fuel ratio sensor of the present invention, wherein FIG. 3A is a perspective view and FIG. 3B is a sectional view taken along line X ₁ -X _{1 of} FIG.

[Explanation of symbols]

1 ... Cylindrical body 3 ... Sealing body 11 ... Cylindrical ceramic molded body 16 ... Reference electrode 17 ... Measuring electrode

Claims (5)

[Claims] 1. A ceramic sealing body is provided inside one end of a ceramic cylindrical body to seal one end of the cylindrical body, and the cylindrical body and the sealing body are separated from each other. A bottomed tubular body containing ZrO ₂ as main crystal grains, and the tubular body and the sealing body being co-fired, wherein both the tubular body and the sealing body are Al ₂ O ₃ And a bottomed tubular body characterized in that the Al ₂ O ₃ content in the sealed body is higher than the Al ₂ O ₃ content in the tubular body. 2. A sealing ceramic molded body is provided inside one end of the cylindrical ceramic molded body to seal one end of the cylindrical ceramic molded body, and then the cylindrical ceramic molded body and the sealing body are sealed. A method for producing a bottomed cylindrical body by co-firing a stop ceramic molded body, wherein the cylindrical ceramic molded body and the sealing ceramic molded body have ZrO ₂ as a main crystal powder and Al ₂ O ₃ And a content of Al ₂ O ₃ in the sealing ceramic molded body is higher than the content of Al ₂ O ₃ in the cylindrical ceramic molded body. . 3. Main crystal powder 10 in a cylindrical ceramic compact.
Al for 0 mol part ₂O₃The content is m (mole part),
In 100 parts by mole of the main crystal powder in the ceramic molding for sealing
To Al₂O₃When the content is n (molar part), 0.3
3. ≦ (n−m) is satisfied.
The manufacturing method of the bottomed cylindrical body. 4. A sintering temperature T1 of a ceramic molding for sealing.
Is lower than the sintering temperature T2 of the cylindrical ceramic molded body,
Further, after being kept at a temperature higher than or equal to the sintering temperature T1 and lower than the sintering temperature T2 to sinter the sealing ceramic molded body, the temperature is kept higher than the sintering temperature T2, and the tubular shape is obtained. The method for producing a bottomed tubular body according to claim 2 or 3, wherein the ceramic molded body is sintered. 5. The solid electrolyte ceramics according to claim 1.
A sensor, comprising: the bottomed tubular body described above; and a sensing section provided with electrodes formed on inner and outer surfaces of the bottomed tubular body facing each other.