JP7577584B2 - Classifying rotor and centrifugal air classifier - Google Patents

Description

This disclosure relates to a blade pin for a classification rotor, a classification rotor, and a centrifugal air classifier.

Conventionally, face-to-face collision type high-pressure airflow grinders with pulverization and classification functions have been used to pulverize ceramic powder and reduce variation in powder size.

However, this type of high-pressure airflow mill breaks down the powder particles into small particles by colliding them with a high-pressure airflow, which causes severe wear on the various parts inside the mill, especially on the blade pins (rod-shaped bodies) that classify the crushed powder.

In order to solve these problems, Patent Document 1 proposes a blade pin for a classifying rotor that has a hollow cylindrical portion made of urethane resin and a core material that is inserted into the hollow cylindrical portion and has both ends connected to an upper plate and a lower plate, with both ends of the core material positioned outside the hollow cylindrical portion in the axial direction and with screw holes formed at both ends.

Patent No. 4832829

The blade parts for the classification rotor made of urethane resin proposed in Patent Document 1 were unable to solve the problem of severe wear when classifying hard ceramic powders such as silicon carbide and boron carbide.

The objective of this disclosure is to provide a blade pin for a classification rotor, a classification rotor, and a centrifugal air classifier that are highly wear-resistant.

The blade pin for a classification rotor according to the present disclosure is made of a ceramic column that is made up of multiple pieces of a circular lower plate having a through hole in the thickness direction and a circular upper plate having an axial hole on the same axis as the through hole, which are joined together along the circumference.

The above-mentioned blade pin for the classification rotor may have a ceramic column having a straight body portion and a fastening portion located at at least one of both ends of the body portion and having an outer diameter smaller than that of the body portion. The classification rotor according to the present disclosure is formed by joining the step surface between the body portion and the fastening portion of the blade pin for the classification rotor to at least one of a first opposing surface facing the ceramic column of the lower plate and a second opposing surface facing the ceramic column of the upper plate via a layer made of ceramic.

The centrifugal air classifier disclosed herein uses the above-mentioned classifying rotor.

The blade pin for the classification rotor, the classification rotor, and the centrifugal air classifier disclosed herein are highly wear-resistant.

FIG. 2 is a perspective view of a vane pin for a classifying rotor according to a non-limiting embodiment of the present disclosure; FIG. 2 is a perspective view of a vane pin for a classifying rotor and a classifying rotor according to a non-limiting embodiment of the present disclosure. 3 is a cross-sectional view of the classifying rotor shown in FIG. 2 taken along an axis. FIG. 4 is an enlarged view of the periphery of a layer made of ceramics in the classifying rotor shown in FIG. 3 . FIG. 2 is a perspective view of a vane pin for a classifying rotor according to a non-limiting embodiment of the present disclosure; FIG. 1 is a schematic diagram illustrating a centrifugal air classifier according to a non-limiting embodiment of the present disclosure.

<Classifying rotor blade pin>
Hereinafter, a blade pin for a classifying rotor according to a non-limiting embodiment of the present disclosure will be described in detail with reference to the drawings. However, in each of the drawings referred to below, for the sake of convenience, only the main components necessary for explaining the embodiment are shown in a simplified form. Therefore, the blade pin for a classifying rotor may include any component not shown in each of the drawings referred to. Furthermore, the dimensions of the components in each drawing do not faithfully represent the dimensions of the actual components and the dimensional ratios of each component. These points are also true of the classifying rotor and centrifugal air classifier described below.

As shown in the example in Figures 1 to 4, the blade pin 1 for the classification rotor (hereinafter sometimes referred to as "blade pin 1") is made of a ceramic column 2 that is made up of a circular lower plate 11 having a through hole 111 in the thickness direction and a circular upper plate 12 having an axial hole 121 on the same axis S as the through hole 111, which are joined together in multiple pieces along the circumference.

That is, the blade pin 1 is made of ceramic material and is composed of a ceramic columnar body 2 that is columnar in shape. With this configuration, the blade pin 1 has high wear resistance, so that mixing of wear powder into the powder during classification of hard powder is suppressed. The powder may be, for example, a hard powder such as ceramic powder.

The ceramics that are the material of the ceramic column 2 may be mainly composed of aluminum oxide, silicon nitride, or sialon. The main component may mean the component that is the most abundant out of a total of 100 mass% of all components that make up the ceramics. The main component may be, for example, 80 mass% or more. When the main component of the ceramics is aluminum oxide, it may contain at least one of silicon, magnesium, and calcium as an oxide. When the main component of the ceramics is silicon nitride or sialon, it may contain calcium, aluminum, and rare earth elements such as yttrium as an oxide. The above points are also true when the material of the other members is ceramic.

The components that make up the ceramics can be identified using an X-ray diffraction device (XRD) using CuKα radiation, and then the elemental content can be determined using an X-ray fluorescence analyzer (XRF) or an inductively coupled plasma (ICP) emission spectrometer (ICP) and converted into the content of the identified components.

The shape of the ceramic columnar body 2 may be cylindrical, as shown in the example of FIG. 1. However, the shape of the ceramic columnar body 2 is not limited to a cylindrical shape. The shape of the ceramic columnar body 2 may be, for example, a rectangular column shape.

The ceramic column 2 may have a straight-barreled main body 21 and a fastening portion 22 located at at least one of both ends of the main body 21 and having an outer diameter smaller than that of the main body 21. In this case, if the lower plate 11 and the upper plate 12 are provided with an engagement portion 13 such as a recess or mounting hole into which the fastening portion 22 is inserted, the fastening portion 22 can be inserted and fixed, improving reliability.

For example, as shown in the example in FIG. 1, the fastening portion 22 may be located at both ends of the main body portion 21. The fastening portion 22 may also be convex. The ends of the fastening portion 22 may be flat.

The ceramic column 2 may have a step surface 23 located between the main body portion 21 and the fastening portion 22. The step surface 23 may be a flat surface.

The feather pin 1 is not limited to a specific size. For example, the maximum length of the feather pin 1 in the direction along the axis S may be set to approximately 100 mm or more and 180 mm or less. The outermost diameter of the feather pin 1 in the direction perpendicular to the axis S may be set to approximately 10 mm or more and 50 mm or less.

Next, a non-limiting embodiment of a blade pin 1A for a classification rotor (hereinafter, sometimes referred to as "blade pin 1A") of the present disclosure will be described with reference to the drawings. Below, differences between blade pin 1A and blade pin 1 will be mainly described, and detailed descriptions of the same configuration as blade pin 1 may be omitted.

The blade pin 1A is made of a ceramic column 2 having a straight body 21, as shown in the example in FIG. 5. In other words, the ceramic column 2 in the blade pin 1A does not have a fastening portion 22. The blade pin 1A is easy to manufacture because it has a relatively simple shape.

<Classification rotor>
Next, a non-limiting embodiment of the classifying rotor of the present disclosure will be described with reference to the drawings, taking as an example a case in which the classifying rotor is provided with the above-mentioned blade pin 1.

As shown in the example of Fig. 2 to Fig. 4, the classification rotor 10 comprises a disk-shaped lower plate 11 having a through hole 111 in the thickness direction, a disk-shaped upper plate 12 having an axial hole 121 on the same axis S as the through hole 111, and a plurality of blade pins 1 made of ceramic columns 2 that connect the lower plate 11 and the upper plate 12 along the circumference. The classification rotor 10 is capable of stable classification over a long period of time because it is equipped with blade pins 1 that are highly resistant to wear.

The through hole 111 can function as an extraction hole for removing fine powder classified from the powder to the outside of the classifying rotor 10. The shaft hole 121 can also function as an attachment hole for a motor that rotates the classifying rotor 10. The shaft hole 121 may be a hole in a cylinder 122 that protrudes upward.

The axis S may also be referred to as the axis of rotation. The classification rotor 10 can rotate around the axis S. The classification rotor 10 may also be shaped to extend along the axis S.

Materials for the lower plate 11 and the upper plate 12 may include, for example, ceramics, quartz, stainless steel, cemented carbide, etc. When the lower plate 11 and the upper plate 12 are made of ceramics, the wear resistance of the classification rotor 10 is increased, and mixing of wear powder into the powder during classification of hard powder is suppressed. In addition, the entire classification rotor 10 is lighter, so the load on the motor for rotating the classification rotor 10 is reduced, and it can be used for a long period of time.

The lower plate 11 and the upper plate 12 may have an engagement portion 13 into which the fastening portion 22 of the vane pin 1 is inserted. The number of vane pins 1 may be 24 or more and 120 or less. The vane pins 1 may be positioned at equal intervals along the circumference. The vane pins 1 may extend along the axis S.

The classification rotor 10 may be configured such that the step surface 23 between the main body 21 and the fastening portion 22 of the blade pin 1 and at least one of the first opposing surface 112 facing the ceramic column 2 of the lower plate 11 and the second opposing surface 123 facing the ceramic column 2 of the upper plate 12 are joined via a layer 14 made of ceramic. For example, as shown in the example in FIG. 4, the step surface 23 and the first opposing surface 112, and the step surface 23 and the second opposing surface 123 may each be joined via a layer 14.

When the step surface 23 and at least one of the first opposing surface 112 and the second opposing surface 123 are bonded via the layer 14, powder is less likely to become trapped between the step surface 23 and at least one of the first opposing surface 112 and the step surface 23 and the second opposing surface 123 during classification, and each surface is less likely to be damaged.

When the lower plate 11 and the upper plate 12 are made of ceramics, the ceramics in the ceramic column 2, the lower plate 11, the upper plate 12, and the layer 14 may be the same or different. For example, the layer 14 joining the step surface 23 and the first opposing surface 112 may be made of ceramics having the same main component as the ceramics in the ceramic column 2 and the lower plate 11. In this case, the step surface 23 and the first opposing surface 112 can be firmly joined. In addition, the layer 14 joining the step surface 23 and the second opposing surface 123 may be made of ceramics having the same main component as the ceramics in the ceramic column 2 and the upper plate 12. In this case, the step surface 23 and the second opposing surface 123 can be firmly joined. The thickness of the layer 14 may be set to, for example, about 40 μm or more and 60 μm or less.

The layer 14 may have a first protrusion 141 connected to the layer 14 on the inner circumferential side. The presence of the first protrusion 141 makes it difficult for powder to be sandwiched between the layer 14 and the lower plate 11 and between the layer 14 and the upper plate 12 on the inner circumferential side, reducing the risk of the sandwiched powder being mixed in as a foreign object even when different powders are classified in the front and rear.

The average diameter of the closed pores present in the first convex portion 141 may be 1.5 times or less the average diameter of the closed pores present in the vicinity of the first convex portion 141 of at least one of the lower plate 11 and the upper plate 12. In this case, since the closed pores present in the first convex portion 141 are small, the occurrence of microcracks originating from the closed pores of the first convex portion 141 and the progression of the microcracks to the layer 14 and the feather pin 1 can be suppressed.

The average diameter of the closed pores present in the first convex portion 141 may be 0.8 times or more the average diameter of the closed pores present in the vicinity of the first convex portion 141 of at least one of the lower plate 11 and the upper plate 12. In addition, the average diameter of the closed pores present in the first convex portion 141 may be smaller than the average diameter of the closed pores present in the vicinity of the first convex portion 141 of at least one of the lower plate 11 and the upper plate 12.

The average diameter of the closed pores is not limited to a specific value. For example, the average diameter of the closed pores present in the first convex portion 141 may be set to approximately 0.8 μm or more and 1.7 μm or less. In addition, the average diameter of the closed pores present in the vicinity of the first convex portion 141 of at least one of the lower plate 11 and the upper plate 12 may be set to approximately 1 μm or more and 2.1 μm or less.

The average diameter of the closed pores present in the vicinity of the first convex portion 141 and at least one of the lower plate 11 and the upper plate 12 (hereinafter, at least one of the lower plate 11 and the upper plate 12 is also referred to as the annular plate) may be measured, for example, by cross-sectional observation using a scanning electron microscope. A sample including a part of the annular plate to be measured and the first convex portion 141 in contact with the annular plate is cut out and embedded in a polyester-based resin to form a cylindrical sample. Here, the cross section of the sample may be mirror-finished using diamond abrasive grains. The magnification may be set to, for example, 500 times. The observation range for observing the cross section of the sample may be set to, for example, a horizontal length of 256 μm and a vertical length of 192 μm, and the lower plate 11 and the first convex portion 141 may be divided, and the upper plate 12 and the first convex portion 141 may also be divided.

The vicinity of the first convex portion 141 of the annular disc refers to the remainder of the annular disc when the cross-sectional area of the first convex portion 41 in the observation range is 25% to 50%, assuming that the observation range including a part of the annular disc and a part of the first convex portion 141 in contact with the annular disc is 100%.

Each of these divided observation areas can be analyzed, and the average diameter of the closed pores can be determined by applying a particle analysis technique using the image analysis software "Azokun (Ver. 2.52)" (registered trademark, manufactured by Asahi Kasei Engineering Co., Ltd.). The average diameter of the closed pores can be the average value of the equivalent circle diameters.

In the analysis, the particle analysis setting conditions are: particle brightness is dark, binarization method is manual, threshold is 70 to 100, small figure removal area is 0.3 μm ^{2 ,} and a noise removal filter is used.

In the above measurements, the threshold value was set to 70 to 100, but the threshold value can be adjusted according to the brightness of the image, which is the observation range. The particle brightness is set to dark, the binarization method is set to manual, the small figure removal area is set to 0.3 ^μm2 , and a noise removal filter is used. The threshold value can then be adjusted so that the markers appearing in the image match the shapes of closed pores.

The layer 14 may have a second protrusion 142 connected to the layer 14 on the outer circumferential side. In this case, even when used in a highly corrosive environment, the layer 14 is less susceptible to corrosion, reducing the risk of separation between the lower plate 11 and/or the upper plate 12 and the feather pin 1, and allowing use over a long period of time.

The average diameter of the closed pores present in the second convex portion 142 may be 1.5 times or less the average diameter of the closed pores present in the vicinity of the second convex portion 142 of at least one of the lower plate 11 and the upper plate 12. In this case, since the closed pores present in the second convex portion 142 are small, the occurrence of microcracks originating from the closed pores of the second convex portion 142 and the progression of the microcracks to the layer 14 and the feather pin 1 can be suppressed.

The average diameter of the closed pores present in the second convex portion 142 may be 0.8 times or more the average diameter of the closed pores present in the vicinity of the second convex portion 142 of at least one of the lower plate 11 and the upper plate 12. In addition, the average diameter of the closed pores present in the second convex portion 142 may be smaller than the average diameter of the closed pores present in the vicinity of the second convex portion 142 of at least one of the lower plate 11 and the upper plate 12.

For example, the average diameter of the closed pores present in the second convex portion 142 may be set to approximately 0.8 μm or more and 1.7 μm or less. In addition, the average diameter of the closed pores present in the vicinity of the second convex portion 142 of at least one of the lower plate 11 and the upper plate 12 may be set to approximately 1 μm or more and 2.1 μm or less.

The average diameter of the closed pores present in the second convex portion 142 and in the vicinity of the second convex portion 142 of the annular disk may be measured, for example, by cross-sectional observation using a scanning electron microscope. A sample including a part of the annular disk to be measured and the second convex portion 142 in contact with the annular disk is cut out and embedded in a polyester-based resin to form a cylindrical sample. Here, the cross section of the sample may be mirror-finished using diamond abrasive grains. The magnification may be set to, for example, 500 times. The observation range for observing the cross section of the sample may be set to, for example, a horizontal length of 256 μm and a vertical length of 192 μm, and the lower plate 11 and the second convex portion 142 may be divided, and the upper plate 12 and the second convex portion 142 may also be divided.

The vicinity of the second convex portion 142 of the annular disc refers to the remainder of the annular disc when the observation range including a part of the annular disc and a part of the second convex portion 142 in contact with the annular disc is taken as 100%, and the cross-sectional area of the second convex portion 142 is between 25% and 50%.

In addition, when the second convex portion 142 is not in contact with at least one of the upper surface of the lower plate 11 and the lower surface of the upper plate 12 (i.e., a part of the outer circumferential surface of the main body 21 is flush with at least one of the upper surface of the lower plate 11 and the lower surface of the upper plate 12), the vicinity of the second convex portion 142 of the annular disk refers to the remainder of the annular disk when the cross-sectional area of the second convex portion 142 in the observation range is set to be 25% to 50%, assuming that the observation range including the corner formed by the outer circumferential surface of the lid body 2 and the lower surface of the lid body 2 and a part of the second convex portion 142 is 100%. In either case, the cross-sectional area of the remainder of the annular disk is set to be 25% to 50%.
After this, the average diameter of the closed pores can be obtained using the same method as described above.

The average diameter of the closed pores present in the inward portion 124 including the second opposing surface 123 of the upper plate 12 may be smaller than the average diameter of the closed pores present in the outward portion 126 including the upper surface 125 of the upper plate 12. In this case, the hardness of the second opposing surface 123 is higher than that of the upper surface 125, so the wear resistance of the second opposing surface 123 is improved. On the other hand, the upper surface 125 is more likely to vibrate due to the rotation of the motor than the second opposing surface 123, but this vibration can be reduced.

The inward portion 124 may be located closer to the second opposing surface 123 than the center 12a in the thickness direction of the upper plate 12. The outward portion 126 may be located closer to the upper surface 125 than the center 12a in the thickness direction of the upper plate 12. The thickness of the upper plate 12 described above may be the thickness of the upper plate 12 excluding the axial hole 121. The thickness of the upper plate 12 excluding the axial hole 121 may be set to approximately 15 mm or more and 30 mm or less. In addition, the average diameter of the closed pores present in the inward portion 124 may be set to approximately 2 μm or more and 7 μm or less. The average diameter of the closed pores present in the outward portion 126 may be set to approximately 3 μm or more and 8 μm or less.

The average diameter of the closed pores present in the inward portion 124 and the outward portion 126 may be measured by, for example, cross-sectional observation using a scanning electron microscope. Samples including the inward portion 124 and the outward portion 126 to be measured may be cut out, and the cross-section of the sample may be mirror-finished using diamond abrasive grains. The magnification may be set to, for example, 500 times. The observation range for observing the cross-section of the sample may be set to, for example, a horizontal length of 256 μm and a vertical length of 192 μm.
After this, the average diameter of the closed pores can be obtained using the same method as described above.

The outer peripheral surface 211 of the main body 21 of the ceramic column 2, the outer peripheral surface 221 of the fastening portion 22, the first opposing surface 112 of the lower plate 11, and the second opposing surface 123 of the upper plate 12 may be as-fired surfaces. If they are as-fired surfaces, there is no crushed layer on the as-fired surfaces, so that shedding from the as-fired surfaces is suppressed.

The classifying rotor 10 is not limited to a specific size. For example, the maximum length of the classifying rotor 10 in the direction along the axis S may be set to approximately 150 mm or more and 220 mm or less. The outermost diameter of the classifying rotor 10 in the direction perpendicular to the axis S may be set to approximately 280 mm or more and 350 mm or less.

In the example shown in FIG. 2, the classifying rotor 10 includes a blade pin 1, but is not limited to this form. For example, the classifying rotor 10 may include a blade pin 1A. In this case, the classifying rotor 10 may include at least one of the two ends of the main body 21 and at least one of the first opposing surface 112 and the second opposing surface 123 joined via a layer 14.

Next, the manufacturing method of the classification rotor of the present disclosure will be described using as an example the case of manufacturing a classification rotor 10 in which the lower plate 11 and the upper plate 12 are made of ceramics, and the step surface 23 and the first opposing surface 112, and the step surface 23 and the second opposing surface 123 are bonded via a layer 14, respectively.

First, a powder mixture is weighed out so that the magnesium hydroxide is 0.3% to 0.42% by mass when converted to oxide (MgO), silicon oxide is 0.03% to 0.05% by mass, calcium carbonate is 0.01% to 0.02% by mass when converted to oxide (CaO), and the remainder is aluminum oxide. The powder mixture is then placed in a rotary mill together with a solvent such as water and mixed with ceramic balls made of aluminum oxide with a purity of 99.5% to 99.99%.

Next, a molding binder such as polyvinyl alcohol, polyethylene glycol, or acrylic resin is added and mixed to obtain a slurry. Here, the amount of molding binder added is 2 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the mixed powder.

Next, the slurry is spray-dried using a spray drying device to obtain granules. The granules are molded by a CIP (Cold Isostatic Pressing) method, for example, at a pressure of 80 MPa to 100 MPa, to obtain a cylindrical molded body. This molded body is then subjected to cutting or other processing to obtain precursor A for the lower plate 11, precursor B for the upper plate 12, and precursor C for the vane pin 1.

Here, a paste containing aluminum oxide powder, cellulose polysaccharides, and a solvent is prepared.

Specifically, a solvent such as water or ethanol is added to the mixed powder so that the volume ratio of mixed powder to solvent is 55-60:40-45, and the total of this solvent and mixed powder is 100 parts by mass. To this 100 parts by mass, 8 parts by mass to 20 parts by mass of cellulose polysaccharide is added, and these are placed in a storage container in a stirring device and mixed and stirred to obtain a paste.

Here, the cellulose polysaccharide is, for example, at least one of methyl cellulose, ethyl cellulose, ethyl methyl cellulose, hydroxymethyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl methyl cellulose, carboxymethyl cellulose, carboxymethyl ethyl cellulose, and carboxyethyl cellulose.

The average diameter of the closed pores may be adjusted, for example, by the conditions when stirring the paste. For example, if the average diameter of the closed pores in the first convex portion 141 is to be 1.5 times or less than the average diameter of the closed pores in the vicinity of the first convex portion 141 of the lower plate 11 and the upper plate 12, the rotation speed of the stirring device may be set to 1200 rpm or more and 1600 rpm or less, and the rotation time may be set to 5 minutes or more and 15 minutes or less. Also, if the average diameter of the closed pores in the first convex portion 141 is to be smaller than the average diameter of the closed pores in the vicinity of the first convex portion 141 of the lower plate 11 and the upper plate 12, the rotation speed may be increased to 1400 rpm or more and 1600 rpm or less, and the rotation time may be set to 5 minutes or more and 15 minutes or less.

By stirring the paste within this range of stirring conditions, it is possible to adjust the average diameter of the closed pores to the above-mentioned relationship. The above points can also be applied to adjusting the average diameter of the closed pores present in the second convex portion 142.

After the paste is applied to the opposing surfaces of at least one of precursors A and C, and at least one of precursors B and C, the opposing surfaces are placed facing each other and precursors A and B are pressurized, for example, at a pressure of 20 kPa to 40 kPa. At this time, the paste may be allowed to overflow from the opposing surfaces on the inner and outer circumferential sides. Then, a precursor in which precursors A, B, and C are connected is obtained by the above pressurization.

Next, the paste is dried by holding it at room temperature for 12 to 48 hours while adjusting the humidity. The precursor is then fired in an air atmosphere at a temperature of 1500°C to 1700°C for 5 to 8 hours to obtain the classification rotor 10.

To obtain a classification rotor in which the average diameter of the closed pores in the inward-facing portion, including the second opposing surface of the upper plate, is smaller than the average diameter of the closed pores in the outward-facing portion, including the upper surface of the upper plate, precursor B is made thick in advance (for example, at least twice the thickness of the upper plate), and after firing, the upper layer side and the lower layer side are ground so that the grinding allowance is greater on the outward-facing side than on the inward-facing side.

Note that the above manufacturing method is one example of a method for manufacturing the classification rotor 10. Therefore, it goes without saying that the classification rotor 10 is not limited to being manufactured by the above manufacturing method.

<Centrifugal air classifier>
Next, a centrifugal air classifier according to a non-limiting embodiment of the present disclosure will be described with reference to the drawings, taking as an example a case in which the above-described classifying rotor 10 is used.

As shown in the example in FIG. 6, a centrifugal air classifier 100 (hereinafter sometimes referred to as "classifier 100") is configured using a classification rotor 10. The classifier 100 is configured using a classification rotor 10 equipped with a blade pin 1 that is highly resistant to wear, and therefore is capable of stable classification over a long period of time.

The classifier 100 may include a casing 101 that houses the classifying rotor 10, a motor 102 that rotates the classifying rotor 10, a supply pipe 103 that supplies raw material to the inside of the casing 101, a number of nozzles 104 that are located below the supply pipe 103 and supply compressed air to the inside of the casing 101, and an outlet pipe 105 that transports the fine powder classified by the classifying rotor 10 to the outside of the casing 101.

Although the above provides examples of embodiments of the present disclosure, it goes without saying that the present disclosure is not limited to the above embodiments and may be any embodiment without departing from the gist of the present disclosure.

For example, in the above embodiment, the lower plate 11 has a through hole 111, and the upper plate 12 has an axial hole 121. However, the configurations of the lower plate 11 and the upper plate 12 may be reversed. That is, the upper plate 12 may have the through hole 111, and the lower plate 11 may have the axial hole 121.

In addition, in the above embodiment, the fastening portion 22 is convex, but the fastening portion 22 may be concave. In this case, the lower plate 11 and the upper plate 12 may have an engagement portion 13 such as a convex portion that is inserted into the concave fastening portion 22. Note that when the fastening portion 22 is located at both ends of the main body portion 21, one fastening portion 22 may be convex and the other fastening portion 22 may be concave.

In the above embodiment, the ceramic layer 14 is used to bond the step surface 23 to at least one of the first opposing surface 112 and the second opposing surface 123, but a layer made of another material may be used instead. Examples of layers made of another material include a layer made of a synthetic resin such as an epoxy resin, a layer made of glass, etc.

LIST OF SYMBOLS 1: Classifying rotor blade pin 2: Ceramic column 21: Main body 211: Outer surface 22: Fastening portion 221: Outer surface 23: Step surface 10: Classifying rotor 11: Lower plate 111: Through hole 112: First opposing surface 12: Upper plate 121: Shaft hole 122: Cylinder 123: Second opposing surface 124: Inward portion 125: Upper surface 126: Outward portion 12a: Center 13: Engagement portion 14: Layer 141: First convex portion 142: Second convex portion 100: Centrifugal air classifier 101: Casing 102: Motor 103: Supply pipe 104: Nozzle 105: Discharge pipe S: Shaft

Claims (8)

The classification rotor blade comprises a disk-shaped lower plate having a through hole in the thickness direction, a disk-shaped upper plate having an axial hole on the same axis as the through hole, and a plurality of ceramic columnar blade pins that connect the lower plate and the upper plate along the circumference ,
the ceramic columnar body has a straight-barreled main body portion and a fastening portion located at least at either one of both ends of the main body portion and having an outer diameter smaller than that of the main body portion;
A classification rotor, in which a step surface between the main body portion and the fastening portion of the blade pin for the classification rotor and at least one of a first opposing surface facing the ceramic column of the lower plate and a second opposing surface facing the ceramic column of the upper plate are joined via a layer made of ceramic. The classifying rotor according to claim 1 , wherein the layer has a first protrusion connected to the layer on an inner peripheral side of the circumference. 3. The classification rotor according to claim 2, wherein an average diameter of closed pores present in the first convex portions is 1.5 times or less an average diameter of closed pores present in the vicinity of the first convex portions of at least one of the lower plate and the upper plate. The classifying rotor according to any one of claims 1 to 3 , wherein the layer has a second protrusion connected to the layer on an outer circumferential side of the circumference. The classification rotor according to claim 4 , wherein an average diameter of closed pores present in the second convex portions is 1.5 times or less an average diameter of closed pores present in the vicinity of the second convex portions of at least one of the lower plate and the upper plate. A classification rotor according to any one of claims 1 to 5 , wherein the average diameter of closed pores present in an inward portion including the second opposing surface of the upper plate is smaller than the average diameter of closed pores present in an outward portion including the upper surface of the upper plate. A classification rotor as described in any one of claims 1 to 6 , wherein the outer surface of the main body portion of the ceramic column, the outer surface of the fastening portion, the first opposing surface of the lower plate, and the second opposing surface of the upper plate are as-fired surfaces. A centrifugal air classifier using the classification rotor according to any one of claims 1 to 7 .

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