JPH0650101A - Ceramic rotor - Google Patents

Abstract

PURPOSE:To provide a ceramic rotor wherein drilling work can be applied to a brittle ceramic mold body without application of a special pretreatment, or a center hole can be integrally formed at the time of molding, and without fear of an accident such as destruction of the mold body or a sintered body due to grinding and polishing work in a succeeding process and before and after baking, and breakdown from a center hole at the time of high speed rotation. CONSTITUTION:Each of relief holes 6 of center holes 4, 5 drilled in both end faces 2, 3 on the axis is provided with a clearance angle 7 of 2--20 deg.C at a tip curved surface 8 thereof, and a ratio d/D of each outer diameter D of shaft parts 9, 10 of a rotor 1, having the center holes 4, 5, with respect to each diameter (d) of inlets of the relief holes 6 of the center holes 4, 5 is determined 0.2-0.3. Further, a ratio l/D of each shaft outer diameter D at the center hole 4, 5 parts with respect to each depth (l) from shaft end faces 2, 3 to bottoms of the relief holes 6 is determined 0.3-0.5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic rotary body having center holes on both end surfaces on the axial center line.

[0002]

2. Description of the Related Art In recent years, ultra-precision rotating bodies in various industrial machines and rotating bodies used in high temperature atmosphere have small thermal expansion and excellent mechanical strength, heat resistance and wear resistance.
In addition, by utilizing the characteristics of ceramics that can realize weight reduction due to its small specific gravity, alumina (Al ₂ O ₃ ), zirconia (ZrO ₂ ), silicon nitride (Si ₃ N ₄ ), sialon, silicon carbide (SiC), etc. Various ceramic rotating bodies using the ceramic sintered body have been studied and proposed.

Generally, this type of ceramic rotating body, for example, a high-speed rotating body represented by a ceramic rotor or an air spindle used in a turbocharger, a gas turbine or the like, reaches tens of thousands to hundreds of thousands of revolutions per minute. Since it rotates at high speed, good dynamic balance is required.

However, since the ceramic molded body is deformed and its size varies due to firing shrinkage, it has been necessary to perform strict balance adjustment before and after firing to minimize the unbalance amount.

Therefore, in the conventional ceramic rotating body, another member such as metal is adhered to both end surfaces of the rotating shaft of the ceramic rotating body after firing, and a hole is formed in the other member substantially on the axis center line. It has been practiced to perform grinding or polishing using a diamond grindstone while rotating around a line connecting the holes, and to reduce the unbalance amount as much as possible before the final balance adjustment is performed.

However, in the above-mentioned ceramic rotating body, it is necessary to remove another member that has been adhered or grind and remove it before the final balance adjustment, so that the unbalance amount increases and the balance adjustment occurs. In addition to the case where it is not possible, there are major problems in manufacturing such as high cost because grinding or polishing using a diamond grindstone takes a long time.

Therefore, in order to solve the above problem, large and small 2 having different diameters are provided on both end faces on the axial center line of the ceramic molded body.
It has been proposed that a hole of various kinds be formed coaxially, the shaft center be fixed by the hole, and the ceramic molded body be rotated while being polished (see Japanese Patent Laid-Open No. 60-201003).

[0008]

However, when a very brittle ceramic molded body is formed by drilling and both ends on the axis center line thereof are coaxially provided with holes of two kinds, large and small, the above-mentioned problems are caused. When a small-diameter hole is drilled, minute cracks starting from the small-diameter hole are introduced, and progresses to a large crack by firing, or the ceramic rotating body is broken from the hole during grinding or polishing of the fired body, During high-speed rotation of the ceramic rotating body, there is a possibility that the ceramic rotating body itself may be destroyed from the remaining minute cracks and cracks, which may lead to a serious accident. There was a problem in that extremely complicated and large-scale pretreatment of improving the quality had to be performed.

[0009]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to make a center hole in an extremely brittle ceramic compact without special pretreatment. Sometimes there are no small cracks starting from the center hole, and even if the center hole is integrally formed during molding in advance, cracks will not be generated in the post-process such as drying, calcination, or firing. There is no risk that the ceramic molded body or ceramic sintered body will break during the progress or grinding or polishing before and after firing, and even during high-speed rotation, it may lead to a major accident such as breakage starting from the center hole. No ceramic rotating body is provided.

[0010]

In the ceramic rotating body of the present invention, the relief holes have relief hole angles of 2 to 20 ° on both end surfaces on the axial center line, and the tip thereof has a center hole having a curved surface. The ratio d / D of the outer diameter D of the shaft portion having the center hole of the ceramic rotating body to the diameter d of the relief hole inlet of the center hole is 0.2 to 0.3. Desirably, further, the depth l from the end face to the bottom of the escape hole
It is desirable that the ratio 1 / D of the outer diameter D of the shaft portion having the center hole of the ceramic rotating body to 0.3 is 0.5 to 0.5.

According to the present invention, the angle of the relief holes formed on both end surfaces on the axis center line is specified to be 2 to 20 °, because when the relief hole angle is less than 2 °, the center hole drill is used during the drilling process. When the stress that spreads the hole acts on the shaft of the ceramic molded body to cause cracks in the shaft, and when the center hole is integrally formed in advance during molding, when the mold for the center hole is released, It is not preferable because minute cracks are easily generated and cracks are generated from the center hole in the various post-processes.

On the other hand, when the clearance hole angle exceeds 20 °,
This is not preferable because the axial position stability of the ceramic molded body by the center hole drill during drilling processing deteriorates.

Next, if the tip of the relief hole is formed into a conventional conical shape, a minute crack is likely to be generated at the tip of the cone when drilling or separating the center hole forming die from the molded body, so that a curved surface is formed. Desirably, it is more desirable that the curved surface continues smoothly from the clearance hole wall surface.

Further, the outer diameter D of the shaft portion having the center hole of the ceramic rotating body with respect to the diameter d of the relief hole inlet of the center hole
The ratio d / D of is preferably 0.2 to 0.3,
When the ratio d / D is less than 0.2, it becomes difficult to remove foreign matters such as ceramic scraps and the like adhering to the inside of the center hole in various subsequent manufacturing steps, while the ratio d / D is 0.3. If it exceeds, the large cracks easily reach from the inner wall of the escape hole to the outer surface of the shaft portion during the drilling process or when the center hole forming die is separated from the formed body.

Further, the ratio 1 / D of the shaft outer diameter D of the center hole to the depth 1 from the end face of the shaft of the ceramic rotating body to the bottom of the escape hole is preferably 0.3 to 0.5, If the ratio 1 / D is less than 0.3, the tapered surface for receiving the center tool cannot be sufficiently formed, or the tip of the center tool comes into contact with the lower portion of the clearance hole to easily cause a deviation from the axis center.
Further, when the ratio 1 / D exceeds 0.5, cracks are likely to occur in the clearance hole portion during drilling processing or when the center hole molding die is separated from the molded body.

[0016]

In the ceramic rotating body of the present invention, the clearance holes of the center holes formed on both end surfaces on the shaft center line are provided with an angle, and the tips of the clearance holes are formed into a curved surface. Ratio d / D of the outer diameter D of the shaft portion having the center hole of the ceramic rotating body to the inlet diameter d, and the shaft outer diameter of the center hole portion with respect to the depth 1 from the end surface of the ceramic rotating body to the escape hole bottom. By specifying the ratio D / D of D, the center hole molding die can be released from the center hole molding die without unnecessary stress being concentrated on the shaft part, the center hole tip and the inner wall during drilling and center hole molding. It works to make it easier.

[0017]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a sectional view in which the ceramic rotating body of the present invention is applied to a ceramic radial turbine rotor, and FIG. 2 is a partially cutaway view showing an enlarged main part of the ceramic rotating body of the present invention.

In FIG. 1, reference numeral 1 is a cone-shaped hub portion 1.
1 has a wing portion 12 made of a silicon nitride sintered body,
This is a ceramic rotating body that forms a ceramic radial turbine rotor having center holes 4 and 5 on both end surfaces 2 and 3 on the axial center lines of the shaft portions 9 and 10.

The molded body of the ceramic rotary body 1 forming the above-mentioned ceramic radial turbine rotor can be molded by a well-known molding method such as a slurry casting molding method, an injection molding method or a powder pressure molding method. The densities are different and uneven in each part.

Therefore, in the present invention, the relief holes of the center holes provided on both end surfaces on the axial center line of the molded body are provided with an angle, and the tip of the relief hole is formed into a curved surface. Ratio d / D of the outer diameter D of the shaft portion having the center hole of the ceramic rotating body to the inlet diameter d, and the shaft outer diameter of the center hole portion with respect to the depth 1 from the end surface of the ceramic rotating body to the escape hole bottom. By specifying the ratio 1 / D of D, a defect-free center hole can be formed.

By fixing the shaft center with the two center holes thus formed and rotating the molded body, it is possible to easily grind and polish not only the diamond grindstone but also the general green corundum grindstone, thereby reducing the processing time. In addition to being able to achieve shortening and low cost, a ceramic rotary body with a very good dynamic balance can be obtained even after firing the molded body after grinding and polishing.

Next, a ceramic rotating body made of a silicon nitride sintered body integrally formed with a center hole by a slurry casting method is used as an evaluation sample, and the shape of the center hole will be described in detail with reference to FIG. .

In FIG. 2, there is shown a cross section of a center hole 4 having a depth 1 formed in the end surface 2 of the shaft portion 9 of which one diameter of the ceramic rotating body is indicated by D. The center hole 4 is a clearance hole 6 and a clearance hole 6 is a clearance hole. It has a corner 7, the entrance of the escape hole 6 has a diameter d, and its tip forms a curved surface 8.

An evaluation sample contains silicon nitride (Si ₃ N ₄ ) as a main component, yttria (Y ₂ O ₃ ) and tungsten oxide (WO ₃ ) as a sintering aid, and an organic binder, a dispersant and a solvent. 2 is cast into a rod-shaped molding die having an outer diameter of 15 mm and a length of 50 mm, which has center hole-shaped protrusions having the dimensions shown in FIG. After calcination and after firing,
The center hole was visually inspected with a stereoscopic microscope, and the evaluation sample after the calcination and after the calcination was also inspected for the presence of defects such as cracks by the fluorescent penetrant inspection method. A comparative example was formed by forming only the shape of the tip of the escape hole into a conical shape of about 120 °. The results are shown in Table 1.

[0026]

[Table 1]

FIG. 3 is a sectional view of a ceramic rotating body of the present invention applied to a ceramic axial flow type rotor as another embodiment, which is composed of a silicon nitride sintered body around a disk-shaped hub portion 13. The wing portion 14 is provided, and the center holes 4 having the dimension and shape of the present invention are formed on both end surfaces 2 and 3 on the axial center lines of the shaft portions 9 and 10.
5 is a ceramic axial flow type rotor forming the ceramic rotating body 1 in which No. 5 was formed, and no abnormality was found in the center hole both after calcination and after calcination.

FIG. 4 is a cross-sectional view in which the ceramic rotating body of the present invention is applied to an air spindle as another embodiment. The shaft portions 9 and 10 made of an alumina sintered body or a silicon carbide sintered body are shown. It is an air spindle which is a ceramic rotating body 1 having center holes 4 and 5 of the present invention on both end faces 2 and 3 on the axis center line of the center hole, both after calcination and after calcination. No abnormalities were observed.

[0029]

As described in detail above, the ceramic rotating body of the present invention has relief holes at both end surfaces on the axial center line, each having a relief hole angle of 2 to 20 °, and its tip having a center hole having a curved surface. Then, the ratio d / D of the outer diameter D of the shaft portion having the center hole of the ceramic rotating body to the diameter d of the clearance hole inlet of the center hole is
In the range of 0.2 to 0.3, the ratio 1 / D of the outer diameter D of the shaft portion having the center hole of the ceramic rotating body to the depth 1 from the end face to the bottom of the escape hole is 0.3 to 0.5. Since it was set to the range, it is possible to perform drilling processing without giving a microcrack starting from the center hole to the extremely brittle ceramic molded body without special pretreatment.
Even if the center hole is integrally formed at the time of molding in advance, cracks may develop in the post-process such as drying, calcination, or firing, or ceramic molding or ceramic sintering may be performed during grinding or polishing before or after firing. It is possible to obtain a highly reliable ceramic rotating body that does not have a possibility of being broken and does not lead to a large accident such as breakage starting from the center hole even at high speed rotation.

[Brief description of drawings]

FIG. 1 is a cross-sectional view in which a ceramic rotating body of the present invention is applied to a ceramic radial turbine rotor.

FIG. 2 is an enlarged partial cutaway view of an essential part of the ceramic rotating body of the present invention.

FIG. 3 is a cross-sectional view in which the ceramic rotating body of the present invention is applied to a ceramic axial flow type rotor.

FIG. 4 is a sectional view in which the ceramic rotating body of the present invention is applied to an air spindle.

[Explanation of symbols]

 1 Ceramic Rotating Body 2, 3 End Face 4, 5 Center Hole 6 Clearance Hole 7 Clearance Hole Angle 8 Curved Surface 9, 10 Shaft

Claims (3)

[Claims] 1. A ceramic rotating body having center holes on both end surfaces on a shaft center line, wherein the escape holes of the center holes are 2 to 3.
A ceramic rotating body having an escape hole angle of 20 °, wherein a tip of the escape hole forms a curved surface. 2. The ratio d / D of the outer diameter D of the shaft portion having the center hole of the ceramic rotating body to the diameter d of the relief hole inlet of the center hole is 0.2 to 0.3. The ceramic rotating body according to claim 1. 3. The outer diameter D of the shaft portion having the center hole of the ceramic rotating body with respect to the depth 1 from the end face to the bottom of the escape hole.
2. The ceramic rotating body according to claim 1, wherein the ratio 1 / D is 0.3 to 0.5.