JPH095291A - Manufacture of limiting current type ceramic oxygen sensor - Google Patents

Abstract

PURPOSE: To provide a manufacturing method for a limiting current type ceramic oxygen sensor wherein clogging in the narrow through hole of a cap is removed for improvement in yield of the oxygen sensor. CONSTITUTION: A narrow through hole 12 formed in a ceramic cap 11 is soaked in ER fluid 13, and electrodes 14 and 15 are assigned at the upper and lower parts of the ER fluid 13 for applying an electric field, and at the same time, an vibration exciter 18 applies vibration between the ER fluid 13 and the ceramic cap 11. In the narrow through hole 12 of the ceramic cap 11, a cluster of fine particles in the ER fluid 13 is farmed in parallel to the narrow through hole 12, and the cluster acts as a lapping rod so that grinding particles in the narrow through hole 12 are removed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a limiting current type ceramic oxygen sensor, and more particularly to a method for removing clogging in a through-hole of a cap having the through-hole.

[0002]

2. Description of the Related Art Generally, mechanical polishing using a fine grain abrasive is used for finish polishing of various machined parts. However, depending on the part, the shape and position of the surface to be polished may
It is impossible or extremely difficult to apply mechanical pressure. A magnetic polishing method that uses a magnetic abrasive to generate a polishing pressure by the action of a magnetic field is known as an effective polishing method for the surface finish of a curved surface or an inner surface of a cylinder, but there are precision parts that are difficult to apply even with this method. .

As one of such parts, there is a ceramic cap 64 of a limiting current type ceramic oxygen sensor 60 shown in FIG. The ceramic oxygen sensor 60 is composed of a ceramic ion conductor 61 having pumping electrodes 62 and 63 formed on both surfaces thereof, and a ceramic cap 64 having a through hole 65 provided on one surface thereof. A heater 66 is formed on the ceramic cap 64. The through-pores 65 formed in the ceramic cap 64 are for supplying oxygen to the ceramic ion conductor 61 by diffusion rate control, whereby so-called limiting current characteristics are obtained.

In a small-sized limiting current type ceramic oxygen sensor, the through pores 65 have a diameter of 10 μm or less and a depth of about 0.8 mm. When mechanical polishing is performed on the ceramic cap 64 in which such through-holes 65 are formed in advance, the through-holes 65 are clogged with abrasive grains. Since the diameter of the through pores 65 is small and deep, even if ultrasonic cleaning is performed thereafter, about 30% of the polishing abrasive grains remain without being removed and do not sufficiently function as diffusion-controlled pores, resulting in a defective product.

[0005]

As described above, in the cap of the limiting current type oxygen sensor, it is difficult to remove the clogging of the penetrating pores by ultrasonic cleaning after polishing, which is a major cause of the decrease in product yield. Was becoming. The present invention has been made in view of the above points, and provides a method of manufacturing a limiting current type ceramic oxygen sensor capable of reliably removing the clogging of the through pores of the cap and improving the yield of the oxygen sensor. Has an aim.

[0006]

According to the present invention, a ceramic ion conductor having electrodes formed on both sides thereof is joined to one surface side thereof with a cap having through pores for supplying oxygen by diffusion control. In the method for manufacturing a limiting current type ceramic oxygen sensor, after mechanically polishing the cap, at least a portion of the cap where the through pores are formed is placed in an electrorheological fluid in which dielectric fine particles are dispersed in an insulating solvent. Immersion, applying an electric field to the electrorheological fluid, giving vibration that causes a frictional force between the electrorheological fluid and the inner surface of the through-hole, and performing a finishing treatment on the inner surface of the through-hole. It has a feature.

In the present invention, preferably, the electric field applied to the electrorheological fluid is in a direction parallel to the through pores. Further, the vibration that causes a frictional force between the electrorheological body and the inner surface of the through-hole of the cap mechanically vibrates the cap from the outside, or mechanically externally applies an electrode for applying an electric field to the electrorheological fluid. Just vibrate. Alternatively, instead of such mechanical vibration, a method of vibrating the dielectric fine particles in the electro-viscous body with an electric force by using an electric field applied to the electro-viscous body as a low-frequency AC electric field may be used.

[0008]

[Operation] Electro-Rheorogical Fluid,
The ER fluid) is a kind of colloidal solution in which dielectric particles are uniformly dispersed in an insulating solvent. When an electric field is applied, the dispersed particles cause dielectric polarization to form clusters, and an apparent viscosity. Is known to change. The ER fluid has been attempted to be applied to, for example, a vehicle shock absorber, a clutch, an engine mount, etc. by utilizing its viscosity change.

The present invention utilizes a cluster of dispersed fine particles connected in a chain, which is a source of viscosity increase (so-called ER effect) when an electric field is applied to an ER fluid, as an abrasive. That is, when an electric field is applied to the ER fluid to form clusters and relative vibration that causes a frictional force due to the clusters between the ER fluid and the surface to be treated is applied,
Surface finish processing becomes possible.

In particular, when the direction of the electric field and the direction of vibration applied to the ER fluid are set parallel to the surface to be treated, the grinding that clogs the through pores of the cap of the limiting current type ceramic oxygen sensor, which has been difficult to remove in the past. Grains can be reliably removed. That is, when the electric field and the direction of vibration are set as described above, a large number of clusters connected in a chain form in parallel with the through pores to be processed are formed in the ER fluid, and this acts as a so-called minute lapping rod. .

The same surface treatment can be performed by using an ER fluid in which dielectric fine particles and ferromagnetic fine particles are dispersed in an insulating solvent. In this case, by applying an electric field and a magnetic field to the ER fluid and simultaneously applying vibration, the frictional force due to the dielectric fine particles and the frictional force due to the ferromagnetic fine particles can be applied to the inner surface of the through-pores. By selecting, it is possible to effectively finish the cap. In particular, the combination of electric and magnetic fields provides a variety of finishing conditions.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an apparatus configuration of an embodiment applied to remove clogging of through pores of a ceramic cap 11 used in the above-described limiting current type ceramic oxygen sensor. As described above, the ceramic cap 11 is mechanically polished in the state where the fine through pores 12 are formed in advance,
The through holes 12 are clogged with an abrasive that cannot be mechanically taken out. One end of this ceramic cap 11 is fixed by a supporting member 19.

Through-pore 12 of ceramic cap 11
Are kept immersed in the ER fluid 13. Specifically, for example, the ER fluid 13 is dropped from above the cap 11,
By sucking this from below, the inside of the through hole 12 is completely ER
It is filled with the fluid 13. The ER fluid 13 has Cu electrodes 14 and 15 for applying an electric field above and below it.
Is arranged, and electric power is supplied from the power supply 16 to this. In the embodiment, an AC power supply of 20 to 50 Hz is used as the power supply 16.

The electrodes 14 and 15 are supported by a supporting member 17, and the supporting member 17 is vibrated by a vibration exciter 18 as indicated by an arrow in the figure. That is, in FIG. 1, the surface to be treated is the inner surface of the through hole 12 of the cap 11, and the ER fluid 13 has the through hole 1 thereof.
2 is applied, and the electrodes 14 and 15 are vibrated in parallel to the through pores 12, resulting in the ER fluid 13
Relative vibration is applied between the inner wall of the through hole 12 and the through hole 12.

The ER fluid 13 is, for example, an alkylnaphthalene or silicone oil used as an insulating solvent, in which beard-like crystals (whiskers) of high hardness calcium carbonate are dispersed as dielectric fine particles. The whiskers have a length of 10 to 30 μm and a diameter of about 1 μm.

FIG. 2 shows how the particles of the ER fluid 13 are dispersed. When no electric field is applied between the electrodes 14 and 15, the whiskers 13b are uniformly dispersed in the solvent 13a in random directions, as shown in FIG. 2 (a). When an electric field is applied to this, as shown in FIG. 2B, at the same time as the individual whiskers 13b are dielectrically polarized,
These are connected to each other in a chain to form a cluster 13c. In particular, by applying an AC electric field of about 50 Hz, a high polarizability can be obtained, and individual whiskers become electric dipoles and are connected to each other to form the cluster 13c.

In the case of the embodiment shown in FIG. 1, the cluster 13c is located in the through-pore 1 of the cap 11 from the direction of the electric field application, as shown in the enlarged sectional view of FIG.
Arrange in parallel with 2. Therefore, when the electrodes 14 and 15 are vertically vibrated, as shown in the plan view of FIG. 3B, the cluster 13c causes the minute lapping bar to be formed against the abrasive grains 20 attached to the inner wall of the through hole 12. Work as. That is, a frictional force is applied to the inner surface of the through-pore 12 and the abrasive grains 20
Will be scraped out. Actually, the applied voltage is 1-2
It was confirmed that the abrasive clogged in the through-pores 12 that could not be taken out by ultrasonic cleaning could be removed cleanly by setting the kV (frequency 20 to 50 Hz) and the applied vibration to a total amplitude of 0.175 mm (frequency 20 Hz).

The dielectric fine particles to be dispersed in the ER fluid are not limited to calcium carbonate whiskers, and other fine particles that are easily polarized and have a hardness higher than a certain degree and are suitable for polishing, such as barium titanate and silica, and insulating. A coated metal or the like can be used. The shape of the fine particles is not limited to whiskers, and may be spherical.

The actual finishing process of the ceramic cap 13 can be performed, for example, as shown in FIG.
Mechanically polished cap 11 having through holes 12 formed therein
While being carried by a carrying means such as a belt conveyor (not shown), the ER fluid 13 is dropped as shown in (a) to fill the through pores 12 with the ER fluid 13 as described above. Next, as shown in (b), the electrodes 14 and 15 are brought into contact with the ER fluid 13 from above and below to apply an electric field, and at the same time, relative vibration is applied between the electrodes 14 and 15 and the cap 11 in the same direction as the electric field. Finally, as shown in (c), the ER fluid 13 is washed away.

Alternatively, batch processing as shown in FIG. 5 is also possible. As shown in the figure, the ER fluid 53 is put in the container 51, and a plurality of mechanically polished ceramic caps 11 are erected and held therein by the support tray 52. Tray 5
2 is vibrated in the arrow direction by a rod 54 that penetrates the container 51 in a liquid-tight manner. Further, parallel electrodes 55 and 56 are arranged in the ER fluid 53, and these are connected to an AC power source 57. Then, while applying the electric field to the ER fluid 53, the cap 11 is vibrated in parallel with the electric field,
Perform finishing process.

In the above embodiments, the ER fluid is mechanically vibrated at the same time as the AC electric field, but it is also possible to vibrate the fine particles in the ER fluid only by the AC electric field without applying mechanical vibration. In particular, when the AC electric field to be applied is a low-frequency electric field of about 10 Hz, there is a delay in the polarization of the dielectric particles in the ER fluid, that is, a delay with respect to the electric field change of the electric dipole formation. The difference causes the electric force to act between the particles, and FIG.
Vibration can be generated due to a slight state transition between the state of (a) and the state of (b) of FIG.

In the embodiment, the ER fluid in which only the dielectric fine particles are dispersed is used. However, the ER fluid in which the ferromagnetic fine particles such as magnetite are dispersed is used at the same time as the dielectric fine particles. At the same time, a magnetic field can be applied to perform the same finishing treatment. In this case, if vibration is applied and the applied magnetic field is rotated at an appropriate cycle,
The frictional force of the dielectric fine particles and the frictional force of the ferromagnetic fine particles work to enable effective surface treatment. This method is a combination of a method of polishing using the ER effect and a method of magnetic polishing, and since a magnetic field enters as a parameter in addition to the electric field, the surface finishing processing conditions are highly diverse.

[0023]

As described above, according to the present invention, E
By using a cluster in which dispersed fine particles are connected in a chain shape when an electric field is applied to the R fluid as an abrasive, vibration causing a frictional force between the ER fluid and the inner surface of the through hole of the ceramic cap is applied, Conventionally, it is possible to remove clogging of the through pores, and it is possible to improve the yield of the limiting current type ceramic oxygen sensor.

[Brief description of drawings]

FIG. 1 shows a processing method according to an embodiment of the present invention.

FIG. 2 shows a state of medium dispersion of an ER fluid in the same example.

FIG. 3 is an enlarged view showing a state of through-pore treatment in the same example.

FIG. 4 shows a processing method of another embodiment of the present invention.

FIG. 5 shows a processing method according to still another embodiment of the present invention.

FIG. 6 shows a limiting current type ceramic oxygen sensor.

[Explanation of symbols]

11 ... Ceramic cap, 12 ... Through pores, 13 ... E
R fluid, 14, 15 ... Electrode, 16 ... Power supply, 17 ... Electrode support member, 18 ... Vibrator, 13a ... Insulating solvent, 13b ...
Whiskers (dielectric fine particles), 13c ... Cluster, 51
... Container, 52 ... Support tray, 53 ... ER fluid, 54 ... Rod, 55, 56 ... Electrode, 37 ... Power supply, 60 ... Limiting current type ceramic oxygen sensor, 61 ... Ceramic ion conductor, 62, 63 ... Electrode, 64 … Ceramic cap, 6
5 ... Through pores, 66 ... Heater.

Claims (3)

[Claims] 1. A limiting current type ceramic oxygen sensor comprising: a ceramic ion conductor having electrodes formed on both sides thereof; and a cap having through pores for supplying oxygen by diffusion control formed on one side of the ceramic ion conductor. In the manufacturing method, after mechanically polishing the cap, at least a portion of the cap in which the through pores are formed is immersed in an electrorheological fluid in which dielectric particles are dispersed in an insulating solvent, and the electrorheological fluid is subjected to an electric field. Is applied to give a vibration that causes a frictional force between the electrorheological fluid and the inner surface of the through-hole, and the finishing process of the inner surface of the through-hole is performed. Sensor manufacturing method. 2. The method of manufacturing a limiting current type ceramic oxygen sensor according to claim 1, wherein the electric field applied to the electrorheological fluid is in a direction parallel to the through pores. 3. The method for manufacturing a limiting current type ceramic oxygen sensor according to claim 1, wherein the vibration is externally applied as mechanical vibration between the electrorheological fluid and the cap.