JP2003184788A - Centrifugal blower and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem of low reliability at the time of high speed rotation due to deformation at a fixed part of a main plate and a blade with a relatively low load when an axial force acts on the main plate fixed on a rotation shaft in a centrifugal blower using the blade manufactured by extruding a metallic lump. <P>SOLUTION: The blade is inserted and fixed inside a groove to a position where the tip of the blade contacts the tip of the groove for engaging the blade formed on the main plate for fixing the blade not only in the side surface directions but also at the tip of the blade. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a centrifugal blower.

[0002]

2. Description of the Related Art Centrifugal blowers include, for example, Japanese Unexamined Patent Publication No. 2001.
Some have the structure shown in Japanese Patent Laid-Open No. 193689. FIG. 12 shows the structure at a stage in the middle of the manufacturing process of this centrifugal blower. By extruding a cylindrical metal block of aluminum using a mold, the hollow portion inside the cylinder and the outer circumference of the cylinder are obtained. The wing portion 102 is formed in the annular portion sandwiched between the extrusion ring portion 101 and

In FIG. 13, the extrusion ring 101 is further cut from the stage where the blade portion 102 is produced by the extrusion molding as described above. At this time, cutting is performed until the wing portion 102 is exposed so that both ends of the cylindrical shape are left, so that the cutting margin is reinforced by the reinforcing ring 103 that reinforces both ends of the cylindrical shape.
I am trying.

FIG. 14 is a front view and a cross-sectional view of a centrifugal blower in which a main plate 104 is fitted in the inner space of the cylindrical shape produced as described above. This is a single suction blade type in which the main plate 104 is installed at one end of the cylinder.

Further, FIG. 15 is a front view and a sectional view of the centrifugal blower in a state where the main plate 104 is fitted in the inner space of the same cylindrical shape. This is a double suction blade type in which the main plate 104 is installed near the center of the cylinder.

As described above, one-sided suction or both-sided suction can be selected depending on the position of the main plate 104, which is effective in that parts can be shared.

On the other hand, FIG. 16 is an enlarged view of the blade portion 102 and the groove portion 105 provided for fitting the blade portion 102 into the main plate 104 and the fitting portion in such a centrifugal blower. As shown in this figure, most of the groove portion 105 is the wing portion 102.
The wing portion 102 is narrower than the wing portion 10, and the wing portion 102 is fitted into the gap formed by bending and widening the main plate 104 facing the slit, and the bent portion is bent in the opposite direction and returned to the original shape.
2 is crimped and fixed. At this time, the groove 105
In order to accommodate bending of the main plate 104, a punch hole portion 106 having a width wider than the slit is provided at the tip of the.

[0008]

However, in the centrifugal fan having such a structure, when an axial force is applied to the main plate 104, the portion where the blade 102 and the main plate 104 are connected is likely to be deformed. There was a problem.

The present invention has been made in order to solve such a problem, and prevents deformation of the connecting portion between the wing portion 102 and the main plate 104, and has a highly reliable centrifuge even when operating at high speed. Aim to get a blower.

[0010]

The tip of the wing is in contact with the inner wall of the groove.

The distance between the tip of the blade and the inner wall of the groove is 0.
It is 5 mm or less.

The wing and the main plate are fixed at the position where the reinforcing ring is provided.

The length of the groove is more than half the length of the blade.

Further, the tip of the groove is wider than the width of the groove, and the blade is fixed by bending the main plate from the tip of the groove.

Furthermore, at the tip of the groove, only the side surface where the main plate is bent is formed wider than the groove.

Furthermore, the groove portion has a substantially arc shape, and the blade is fixed by bending the main plate in the direction opposite to the center point of the substantially arc shape.

A step of covering an end portion of a main plate bent substantially at a right angle with an end portion of a reinforcing ring, which is on the outer side of the wing portion toward the centrifugal direction of the rotating shaft and forms an acute angle with the centrifugal direction, and a taper on a pressing surface. Pressing the caulking jig having the crimping jig against the end of the main plate.

A step of extruding the inside of a cylindrical metal mass with a mold having a structure in which one end of the blade shape is a cutout portion, and cutting the outer periphery of the cylindrical shape until the cutout portion is reached to produce a blade portion. And a step of fixing the wing portion to a main plate having a rotation axis.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1. 1 is a configuration diagram of a one-side suction centrifugal blower according to Embodiment 1 of the present invention, and FIG. 1 (a) is a front view and a cross-sectional view of the one-side suction centrifugal blower, and the front view shows a centrifugal blower end portion. The shape of the main plate provided in FIG. In the figure, a blade portion 3a provided in a cylindrical annular portion of a centrifugal blower is provided in a groove portion 2a provided along the outer periphery of a circular main plate 1a having a rotation shaft hole for fitting a rotation shaft in the center. Are fitted together. In this case, since it is a single suction blade type, the main plate 1a is provided at the cylindrical end of the centrifugal blower.

FIG. 1 (b) shows the groove 2 of the main plate 1a.
It is an enlarged view of the fitting part of a and the wing part 3a. In the figure, the blade tip 4a, which is the tip of the blade 3a, has a groove 2 when fitted.
The blade portion 3a is provided at a position where it comes into contact with the inner wall of a.
It is crimped at the crimped portion 5a of a. This caulking is
Bend at the position indicated by the dotted line on the main plate 1a to form the wings 3
The groove 2a is made wider than the groove a, the wing 3a is inserted, and this time, the bent part is bent again in the direction of returning it. The diameter of the main plate 1a is set so that the outer circumference of the main plate 1a is approximately in the middle from the reinforcing ring 6a, which is the base of the blade 3a, to the blade tip 4a.

That is, the main plate 1a has a caulking portion 5a provided in the groove portion 2a and a groove portion 2a facing the caulking portion.
And the inner wall of the groove tip portion 7a which is a part of the groove portion 2a in contact with the blade tip portion 4a are fixed to the blade portion 3a.

On the other hand, FIG. 2 is an enlarged view showing the structure of the above-mentioned fitting portion between the main plate and the wing portion, and in this structure, it is fitted in the groove portion 2b provided in the main plate 1b. The blade tip 4b of the blade 3b is separated from the inner wall of the groove tip 7b of the groove 2b.

Regarding the centrifugal blower having these two structures,
When a force is applied in the axial direction of the rotary shaft of the centrifugal blower (direction of the arrow in Fig. 1), how much force is applied to the main plate, the caulking part is deformed and the position where the main plate and the blade are fixed Comparing the deviations from the experiments, the force required to shift the main plate 1a is about three times that of the main plate 1b, and the strength against the force acting in the axial direction is improved. It is considered that this is because the applied force is dispersed due to the increase in the contact portion such as the blade tip portion 4a.

In addition, it is difficult to actually completely contact all the blade tips 4a with the groove tips 7a. That is, when all the blade tips 4a and the groove tips 7a are designed and processed so as to come into contact with each other, the blades 3a are attached along the outer circumference of the main plate 1a, so that there is no play at all, and attachment is difficult. Will be. Therefore, it is necessary to provide a distance between the blade tip portion 4a and the groove tip portion 7a in order to have a slight amount of play. As a result, the wing tip 4
There is a place where a and the tip portion 7a of the groove are completely in contact with each other, and there is a place where a slight gap is formed, so that the blade portion 3a can be smoothly attached to the main plate 1a.

The distance of such a gap is set to 0.5.
If it is less than or equal to mm, the distance is such that when the main plate is deformed when the axial force is applied to the main plate, it disappears.
When an actual load is applied, the same strength as that in which the blade tip portion 4a and the groove tip portion 7a are completely in contact with each other in advance is obtained.

Further, in this way, the blade tip portion 4a has the groove portion 2a.
Since the play that occurs in the blade tip portion 4a when the main plate 1a is fitted is reduced as compared with the conventional one, the central axis of the main plate 1a and the central axis of the blade portion 3a are aligned with each other. Is easy.

Embodiment 2. 3 is a configuration diagram of a single-suction centrifugal fan according to Embodiment 2 of the present invention.
(A) is a front view and a cross-sectional view of a single suction centrifugal blower,
The front view shows the shape of the main plate provided at the end of the centrifugal blower. In the figure, a blade portion 3c provided in a cylindrical annular portion of a centrifugal blower is provided in a groove portion 2c provided along the outer periphery of a circular main plate 1c having a rotation shaft hole for fitting a rotation shaft in the center. Are fitted together. In this case, since it is a single suction blade type, the main plate 1c is provided at the cylindrical end of the centrifugal blower.

Further, FIG. 3B shows the groove portion 2 of the main plate 1c.
It is an enlarged view of the fitting part of c and the wing part 3c. In the figure, the blade tip 4c, which is the tip of the blade 3c, is engaged with the groove 2 when fitted.
The blade portion 3c is provided at a position where it contacts the inner wall of c.
The caulking portion 5c of c is fixed to the main plate 1c by being bent at the dotted line portion shown in the drawing in the same manner as in the first embodiment. The diameter of the main plate 1c is set so that the outer circumference of the main plate 1c is slightly smaller than that of the reinforcing ring 6c which is the base of the blade portion 3c.

That is, as in FIG. 1, the main plate 1c has a caulking portion 5c, an inner wall of the groove portion 2c facing the caulking portion, and a groove tip portion 7c which is a part of the groove portion 2c in contact with the blade tip portion 4c. It is fixed to the wing portion 3c by the inner wall of the main plate 1c, and the diameter of the main plate 1c is set to be larger than that of the main plate 1a.

When the diameter of the main plate 1c is larger than that of the main plate 1a in this way, the material cost increases due to the increase of the main plate area, but the blowing characteristics during operation change.

FIG. 4 shows the relationship between the air volume and the fan efficiency of the one-side suction centrifugal blower using the main plate 1a and the one-side suction centrifugal blower using the main plate 1c. In the area where the air volume is large in the figure, compared to a single-suction centrifugal fan using the main plate 1a, the main plate 1c
It can be seen that the single-suction centrifugal blower using is higher in static pressure and fan efficiency.

This is because the gap between the main plate and the reinforcing ring is smaller in the one-sided centrifugal blower using the main plate 1c than in the one-sided suction centrifugal blower using the main plate 1a. It is considered that the loss due to the air leakage in the above will be reduced.

By making the diameter of the main plate slightly smaller than that of the reinforcing ring, the static pressure and the fan efficiency can be improved.

Embodiment 3. In this embodiment, the relationship between the shape of the groove provided on the main plate and the performance of the centrifugal blower is investigated. Fig. 5 is a configuration diagram of a single-suction centrifugal fan, Fig. 5 (a) is a front view and a cross-sectional view of the single-suction centrifugal fan, and Fig. 5 (b) is an enlarged view of a fitting portion between a groove portion and a blade portion of a main plate. It is a figure.

The shape of the groove 2d of the main plate 1d of the centrifugal blower in FIG. 5 corresponds to the conventional shape, and the performance comparison with the main plate 1a of the present invention already shown in FIG. 1 will be made. First, structural differences between the main plate 1d and the main plate 1a will be described. The groove portion 2d of the main plate 1d in FIG. 5 is a caulking portion 5d for fixing the blade portion 3d to the main plate 1d.
And a substantially circular groove tip portion 7d that accommodates the blade tip portion 4d but does not contribute to caulking. On the other hand, the groove portion 2a of the main plate 1a in FIG. 1 includes a caulking portion 5a for fixing the blade portion 3a to the main plate 1a and a substantially semicircular groove tip portion 7a for accommodating the blade tip portion 4a which does not contribute to the caulking. Consists of.

FIG. 6 shows these groove tip portions 7d and groove tip portions 7d.
It is the result of examining the influence of the difference in the opening area of a on the performance of the centrifugal blower. In this figure, the horizontal axis is the air volume, and the vertical axis is the noise level and the specific noise level. From this, the main plate 1d
It can be seen that the noise level of the main plate 1a having a smaller opening area at the groove tip tends to be lower than that of the above noise level.

By thus reducing the groove tip of the groove provided on the main plate, noise generation during operation can be suppressed. In particular, metal centrifugal blowers are often used for high speed rotation by taking advantage of their high strength, so noise suppression technology is important.

As is clear from FIG. 1 and the like, since the main plate is fixed to the wing portion by crimping, the groove tip portion is required as a bending margin for bending the crimped portion of the main plate. Therefore, instead of the circular shape as shown in FIG. 1, a slit that can further reduce the opening area and extends in a direction substantially perpendicular to the groove may be used.

Further, in the case of manufacturing the centrifugal blower having the structure of FIG. 5, in order to fix the main plate 1d and the blade portion 3d, the side on which the blade portion 3d is applied with pressure when the centrifugal blower rotates in advance ( A part of the main plate 1d located on the pressure surface side) is bent along the dotted line in the figure, and the blade portion 3 is formed in the groove 2d of the main plate 1d.
After inserting d, the bent portion is stretched again so as to be flat at a position to be fixed, thereby performing the caulking process. In this case, the productivity is improved because it suffices to bend the main plate 1d that contacts one side of the groove 2d.

At this time, the pressure surface of the wing 3d is
Since it is located in the inner diameter direction of the warp provided on the main plate 1d
If a large amount of bending is not taken when the part is bent along the dotted line, the main plate 1d and the wing part 3d interfere with each other.

On the other hand, for example, in the case of manufacturing a centrifugal blower having the structure of FIG. 1, in order to fix the main plate 1a and the blade portion 3a, the side on which the blade portion 3a is prestressed when the centrifugal blower rotates. Bend a part of the main plate 1a on the opposite side (negative pressure surface side) along the dotted line in the figure, insert the wing 3a into the groove 2a of the main plate 1a, and then flatten the bent part again at the position to be fixed. It is caulked by stretching so that it becomes.

When the bent portion of the main plate is changed from the pressure-applied side to the opposite side for caulking as described above,
Since the suction surface of the wing portion 3a is located in the outer diameter direction of the warp provided in the wing portion 3a, when the main plate 1a is bent along the dotted line, the main plate 1a and the wing portion 3a can be bent with a large bending amount. Since it is possible to avoid the interference, the caulking process between the blade portion and the main plate is facilitated and the productivity is improved.

Fourth Embodiment FIG. 7 is a partially enlarged view of a cross section of the single-suction centrifugal blower. In this figure, the main plate 1e has, for example, the same shape as the main plate 1a shown in FIG. 1, and the position where the main plate 1e and the wing portion 3e are fixed is optimized. Basically, the main plate 1e can be fixed at any position with respect to the axial direction of the cylindrical shape of the centrifugal blower, since the blade 3e is basically only caulked by the caulking portion 5e. However, since the range indicated by A in the figure is the same as the width of the reinforcing ring 6e, it is a position that is unlikely to be affected by the deflection of the blade portion 3e due to high-speed rotation.

Therefore, by selecting the fixing position with the main plate 1e within the width (range A) of the reinforcing ring 6e, the durability at high speed rotation is enhanced. In FIG. 7, a single suction centrifugal blower is taken as an example, but the reinforcing ring uses the extrusion to form the blade portion and then cuts the outer periphery of the cylindrical shape, and the uncut portion of the cutting is used as the reinforcing ring. Therefore, it is possible to provide not only the cylindrical end portion as shown in this figure but also the reinforcing ring at the central portion. By doing so, even in the double suction centrifugal blower, it is possible to improve the strength of the fixed portion between the main plate and the blade portion in the same manner as this embodiment.

Embodiment 5. FIG. 8 shows the first to fourth embodiments.
Different from the above, the flow of a general manufacturing method of a single-suction centrifugal blower that does not adopt a method of fixing a blade portion by providing a groove portion on a main plate is shown. As shown in FIG. 8A, the wing portion 3f
When a single-suction centrifugal blower is manufactured by fixing the cylindrical end portion of the centrifugal blower having a cross-sectional shape substantially perpendicular to the main plate 1f, as shown in FIG. 9
It is bent at 0 ° and is brought into close contact with the reinforcing ring 6f which is the end of the cylindrical portion. Next, as shown in FIG. 8C, the end portion of the main plate 1f is bent so as to cover the reinforcing ring 6f by the first caulking jig 8 whose contact surface has a taper angle of about 45 degrees downward. Thereafter, as shown in FIG. 8 (d), the main plate 1f is bent by a second caulking jig 9 whose contact surface is substantially vertical so that the end portion of the main plate 1f has a substantially U shape.
The main plate 1f and the reinforcing ring 6f are fixed.

As described above, when the caulking process is performed using the two types of caulking jigs, the caulking is performed in two steps.

On the other hand, FIG. 9 shows a flow of a method of manufacturing a single-suction centrifugal blower which does not adopt a method of fixing a blade portion by providing a groove portion on a main plate. As shown in FIG. 9 (a), when the cylindrical end portion of the centrifugal blower having an acute-angled cross-section with respect to the blade portion 3g is fixed to the main plate 1g to manufacture a single-suction centrifugal blower, FIG. 9 (b) As described above, the end portion of the main plate 1g is previously bent at about 90 degrees, and the end portion of the cylindrical portion is tightly attached to the reinforcing ring 6g. Next, as shown in FIG.
The end portion of the main plate 1g is bent to cover the reinforcing ring 6g by the first caulking jig 8 whose contact surface has a taper angle of about 45 degrees downward, and the main plate 1g and the reinforcing ring 6g are fixed. .

As described above, by providing the reinforcing ring with the taper, it is possible to perform the caulking process using one kind of caulking jig, and the caulking is completed in one step.

Sixth Embodiment FIG. 10 is a schematic view of a wing portion formed by extrusion molding, and FIG.
In the state immediately after the extrusion molding process, as is clear from the II cross-sectional view, a cylindrical metal block of aluminum remains around the blade portion 3h. Next, as shown in FIG. 10B, after the extrusion molding, the outer circumference of the cylinder is changed to the reinforcing ring 6h at the end.
The blade is cut to leave the blade 3h exposed.
In the II-II sectional view at this time, it can be seen that a part of the wing portion 3h has an edge shape with an acute angle due to cutting.

Since such an acute-angled edge is not preferable in terms of safety, after the extrusion molding process, deburring is performed at the same time as deburring, but the edge is rounded. However, it is difficult to effectively round the edge of a metal that is relatively soft such as aluminum.

Therefore, the shape of the die used for the extrusion molding process is reviewed, and a die is manufactured by extruding the edge portion after cutting the outer periphery of the cylinder by extrusion, and the extrusion molding process is performed using this. . Figure 11
FIG. 10A shows a shape obtained by extruding using a metal mold having a shape in which a portion having an acute angle is cut out after cutting the outer periphery of a cylindrical shape, and the cutout shape portion 10 becomes an edge in FIG. 10B. The part has been removed by extrusion beforehand.

By cutting the outer peripheral portion of such a cylindrical portion until the blade portion 3i is exposed, as shown in FIG. 11B, a blade portion 3i having no sharp edge portion in advance is obtained,
Eliminating the edge removal process improves productivity and
At the same time, the edges can be reliably removed from the product, improving safety.

The same applies when a magnesium alloy or the like is used instead of the aluminum alloy.

[0054]

EFFECTS OF THE INVENTION By fixing the main plate and the blade portion having such a shape by caulking, the fixing strength between the blade and the main plate of the centrifugal blower made of metal is improved.

Further, by reducing the area of the groove tip portion of the main plate, the blowing and noise characteristics are improved.

Furthermore, by forming the notch at one end of the blade, the edge is surely removed and the productivity is improved without removing the edge portion.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a single-suction centrifugal fan according to a first embodiment of the present invention.

FIG. 2 is an enlarged view showing a configuration of a fitting portion between a main plate and a wing portion according to the first embodiment of the present invention.

FIG. 3 is a configuration diagram of a single-suction centrifugal fan according to a second embodiment of the present invention.

FIG. 4 is a single suction centrifugal fan using the main plate 1a and the main plate 1.
It is a relationship between the air volume and the fan efficiency of a single-suction centrifugal fan using c.

FIG. 5 is a configuration diagram of a single-suction centrifugal fan according to a third embodiment of the present invention.

FIG. 6 is a result of examining the influence of the difference in the opening area of the groove tip portion 7d and the groove tip portion 7a on the performance of the centrifugal blower.

FIG. 7 is a partially enlarged view of a cross section of a single-suction centrifugal fan according to a fourth embodiment of the present invention.

FIG. 8 is a flowchart of a general method for manufacturing a single-suction centrifugal blower.

FIG. 9 is a flowchart of a method for manufacturing a single-suction centrifugal fan according to the fifth embodiment of the present invention.

FIG. 10 is a schematic view of a wing made by extrusion molding.

FIG. 11 is a schematic view of a wing portion formed by extrusion molding processing according to a sixth embodiment of the present invention.

FIG. 12 shows a state in which a conventional centrifugal blower is being manufactured.

FIG. 13 is a state in the process of manufacturing a conventional centrifugal blower.

FIG. 14 is a front view and a cross-sectional view of a conventional centrifugal blower.

FIG. 15 is a front view and a cross-sectional view of a conventional centrifugal blower.

FIG. 16 is an enlarged view of a fitting portion between a main plate and a groove portion of a conventional centrifugal blower.

[Explanation of symbols]

1a-1g Main plate, 2a-2d Groove part, 3a-3i
Blade portion, 4a to 4d Blade tip portion, 5a to 5d Caulking portion, 6a to 6h Reinforcing ring, 7a to 7d, Groove tip portion, 8 First caulking jig, 9 Second caulking jig, 10 Notch shape portion .

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yasuhiro Ikeda             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. (72) Inventor Takeshi Tsubouchi             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. (72) Inventor Hitoshi Kikuchi             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. (72) Inventor Yasunari Takada             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. (72) Inventor, Yasuyuki Yokote             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. (72) Inventor Naoko Yokoya             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. F term (reference) 3H033 AA02 BB02 BB06 BB19 CC01                       DD04 DD12 DD17 DD25 DD26                       EE06 EE11

Claims (9)

[Claims] 1. A rotary shaft, a main plate fixed to the rotary shaft, a groove portion provided from an end portion of the main plate toward the center of the main plate, and a wing portion inserted into and fixed to the groove portion. And a tip portion of the blade portion is in contact with an inner wall of the groove portion. 2. A rotary shaft, a main plate fixed to the rotary shaft, a groove portion provided from an end portion of the main plate toward the center of the main plate, and a blade portion inserted and fixed in the groove portion. And a distance between the tip of the blade and the inner wall of the groove is 0.5 mm or less. 3. A rotary shaft, a main plate fixed to the rotary shaft, a groove portion provided from an end portion of the main plate toward the center of the main plate, and a wing portion inserted into and fixed to the groove portion. ,
A centrifugal blower, comprising: a reinforcing ring that reinforces one end of the blade portion extending in the direction of the rotation axis, and fixing the blade portion and the main plate at a position where the reinforcing ring is provided. 4. The centrifugal blower according to claim 1, wherein the length of the groove is not less than half the length of the blade. 5. The tip of the groove is wider than the width of the groove, and the blade is fixed by bending the main plate from the tip of the groove. Or the described centrifugal blower. 6. The centrifugal blower according to claim 5, wherein the tip of the groove is wider than the groove only in the side surface where the main plate is bent. 7. The groove portion has a substantially arc shape, and the blade is fixed by bending a main plate in a direction opposite to the center point of the substantially arc shape. Centrifugal blower. 8. A main plate fixed to a rotary shaft, a wing portion provided with a reinforcing ring at an end thereof, and an end portion of the main plate fixed to the reinforcing ring to fix the main plate and the wing portion. In the method for manufacturing a centrifugal blower, which is outside the blade portion in a centrifugal direction of the rotating shaft, of the main plate bent substantially at an end of the reinforcing ring forming an acute angle with the centrifugal direction. A method of manufacturing a centrifugal blower, comprising: a step of covering an end portion; and a step of pressing a caulking jig having a pressing surface with a taper to an end portion of the main plate. 9. A step of extruding the inside of a cylindrical metal ingot by a die having a structure in which one end of a blade shape has a cutout portion, and cutting the outer periphery of the cylindrical shape until the cutout portion is reached. And a step of fixing the blade to a main plate having a rotation axis.