Dustproof sealing structure

Abstract

To provide a dustproof seal structure which makes dust or foreign objects less likely to enter a bearing gap of an air bearing and can maintain rotation performance of a rotary table over a long time.SOLUTION: A dustproof seal structure includes a stator assembly 20 rotatably supporting a rotor assembly 10, having a thrust plate 11 and a rotor 12, and forming a horizontal thrust air bearing S1 between a lower surface 11b of the thrust plate 11 and an upper surface of the stator assembly 20 by compressed air being supplied to a space between the lower surface 11b of the thrust plate 11 and the upper surface of the stator assembly 20. The thrust plate 11 and the stator assembly 20 form a sealing portion 15 through which the compressed air flows. The sealing portion 15 includes an inclined passage whose height increases from an outer peripheral surface of the thrust plate 11 toward the inside in a radial direction.SELECTED DRAWING: Figure 2

Description

Technical Field

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[0001] The present invention relates to a dustproof seal structure.

Background Art

[0002] Conventionally, in a three-dimensional measuring machine in which a measurement space is configured by three-axis orthogonal coordinates, especially when measuring a measurement object having a rotating shaft such as a roller or a gear with high precision, a rotating table is used as the fourth axis. In order to achieve high rotational accuracy, an air bearing, which is a hydrostatic air film, is adopted for the rotating table (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The fact that the rotating table is provided with an air bearing is advantageous for obtaining high rotational accuracy. However, if dust or foreign matter enters the bearing clearance of the air bearing from the outside, the rotational performance of the rotating table will deteriorate, and in some cases, the bearing guide surface may be damaged.

[0005] Therefore, the present invention has been made in view of these points, and an object thereof is to provide a dustproof seal structure in which dust and foreign matter hardly enter the bearing clearance of the air bearing, and the rotational performance of the rotating table can be maintained over a long period of time.

Means for Solving the Problems

[0006] The dustproof sealing structure of the present invention comprises a rotor assembly having a disc-shaped thrust plate and a cylindrical rotor provided on the lower surface of the thrust plate, and a stator assembly that rotatably supports the rotor assembly, wherein compressed air is supplied between the lower surface of the thrust plate and the upper surface of the stator assembly to form a horizontal thrust air bearing between the lower surface of the thrust plate and the upper surface of the stator assembly, wherein the thrust plate and the stator assembly form a sealing portion through which compressed air flows at a position radially outward from the thrust air bearing, and the sealing portion includes an inclined flow path in which the height of the flow path increases as it moves radially inward from the outer circumferential surface of the thrust plate.

[0007] The thrust plate and the stator assembly have a cavity in the position between the thrust air bearing and the seal portion that communicates with the seal portion, and the lower surface of the cavity may be lower than the upper surface of the stator assembly that forms the thrust air bearing.

[0008] The outer circumferential surface of the thrust plate may be located radially outward from the inclined flow channel.

[0009] The thrust plate and the stator assembly may be arranged so that the compressed air discharged from the thrust air bearing flows into the seal portion.

[0010] The stator assembly comprises a stator that forms a recess for receiving the rotor, and a sleeve disposed on the outside of the stator, wherein the seal portion may be formed between the upper surface of the sleeve and the lower surface of the thrust plate.

[0011] The sealing portion has a curved channel in a vertical cross-sectional view, in which the flow path includes at least one mountain-shaped portion, and the inclined channel may be formed in a part of the curved channel.

[0012] Multiple protrusions are formed on the upper surface of the sleeve, and multiple recesses having a cross-sectional shape complementary to the protrusions are formed on the lower surface of the thrust plate, and the multiple protrusions and multiple recesses may form multiple mountain-shaped portions in the flow path.

[0013] A water-repellent coating layer may be formed on at least a portion of the thrust plate facing the seal portion, or on at least a portion of the stator assembly facing the seal portion. [Effects of the Invention]

[0014] The present invention provides a dustproof sealing structure that prevents dust and foreign matter from easily entering the bearing gap of an air bearing, thereby maintaining the rotational performance of the rotary table over a long period of time. [Brief explanation of the drawing]

[0015] [Figure 1] This is a cross-sectional view showing a rotary table in one embodiment of the present invention. [Figure 2] This is a magnified view of a portion of Figure 1. [Figure 3] This figure shows a magnified portion of Figure 2. [Figure 4] This is a cross-sectional view showing a rotary table of a comparative example. [Figure 5] This is a cross-sectional view showing the configuration of the second embodiment. [Figure 6] This is a cross-sectional view showing the configuration of the third embodiment. [Figure 7] This is a cross-sectional view showing the configuration of a rotary table in a modified example. [Modes for carrying out the invention]

[0016] [First Embodiment] Embodiments of the present invention will be described with reference to the drawings. Hereinafter, the first to third embodiments will be described. In each embodiment, structural parts having the same function are denoted by the same or corresponding reference numerals. FIG. 1 is a cross-sectional view showing a rotating table according to an embodiment of the present invention. FIG. 2 is a view showing an enlarged part of FIG. 1. Although various dust and foreign matters that enter the air bearing portion of the rotating table are assumed, hereinafter, mainly, the sealing ability against oil flowing down from the upper surface of the rotating table and oil mist floating in the air will be exemplified.

[0017] [Outline of the Rotating Table of the Present Embodiment] As shown in FIG. 1, the rotating table S100 of the present embodiment includes a rotor assembly 10, a stator assembly 20, a rotation drive mechanism 51, an air supply source 52, and a control device 53. A thrust air bearing S1 and a radial air bearing S2 are formed between the rotor assembly 10 and the stator assembly 20, and the rotor assembly 10 is configured to rotate about a rotation axis C.

[0018] In this type of rotating table, for example, oil may flow down from the upper surface of the rotor assembly 10 and enter the thrust air bearing S1 between the rotor assembly 10 and the stator assembly 20. In the rotating table S100 of the present embodiment, an annular seal portion 15 is formed at a position radially outside the thrust air bearing S1, and this seal portion 15 functions as a dust-proof seal structure. By providing such a seal portion 15, the oil is prevented from entering up to the thrust air bearing S1.

[0019] [Configuration of Each Part] The rotor assembly 10 has a disk-shaped thrust plate 11 and a rotor 12. The rotor assembly 10 rotates about a rotation axis C extending in the vertical direction.

[0020] As shown in Figure 2, the thrust plate 11 has an upper surface 11a, a lower surface 11b, and an outer peripheral surface 11c. The upper surface 11a is a horizontal mounting surface on which a predetermined object is placed. The lower surface 11b is, for example, a horizontal plane, and a cylindrical rotor 12 is fixed to the center of the lower surface 11b. The outer peripheral surface 11c extends vertically, for example.

[0021] The stator assembly 20 includes a stator 21, a sleeve 25, and an O-ring 28. The stator assembly 20 is fixed on a base 50.

[0022] The stator 21 is an annular member that forms a circular recess 20h in which the rotor 12 is positioned. The stator 21 has an upper surface 21a, an inner circumferential surface 21b, and an outer circumferential surface 21c. The upper surface 21a is a horizontal surface facing the lower surface 11b. The inner circumferential surface 21b is the surface facing the outer circumferential surface of the rotor 12, and the outer circumferential surface 21c is the surface facing the inner circumferential surface of the sleeve 25.

[0023] An air passage 30 is formed inside the stator 21 to supply compressed air to the thrust air bearing S1 and the radial air bearing S2. In this embodiment, the air passage 30 has a first passage 31, a second passage 32, a third passage 33, and a fourth passage 34.

[0024] The first passage 31 is a passage for supplying compressed air from the air supply source 52 (Figure 1) to the second passage 32. An outer peripheral air supply groove 32a is formed on the radially outer side of the second passage 32. O-rings 28 are positioned above and below this outer peripheral air supply groove 32a. The O-rings 28 have a ring shape that surrounds the stator 21 and seal the space between the outer peripheral surface 21c of the stator 21 and the inner peripheral surface of the sleeve 25.

[0025] The third passage 33 supplies compressed air from the second passage 32 to the upper surface 21a of the stator 21. The fourth passage 34 supplies compressed air from the second passage 32 to the inner circumferential surface 21b of the stator 21. As illustrated in Figure 2, an air intake throttle 22a that opens to the upper surface 21a of the stator 21 and adjusts the amount of air supplied from the third passage 33 may be located in the third passage 33. Similarly, an air intake throttle 22b that opens to the inner circumferential surface 21b of the stator 21 and adjusts the amount of air supplied from the fourth passage 34 may be located in the fourth passage 34. This air intake throttle 22b may be formed to extend radially around, for example, the rotation axis C (Figure 1).

[0026] The sleeve 25 is an annular member positioned radially outward from the stator 21. For example, the sleeve 25 is approximately the same height as the stator 21, or slightly higher. The upper surface of the sleeve 25 cooperates with the lower surface 11b of the thrust plate 11 to form a seal portion 15.

[0027] In this embodiment, the stator 21 and sleeve 25 constitute the stator assembly 20 as described above, but the stator assembly 20 may be a single component. For example, instead of using the upper surface of the sleeve 25 to form the flow path of the seal portion 15, a structural component for forming the flow path may be provided near the outer circumference of the stator. Specifically, an annular, mountain-shaped member may be provided on the bottom surface of the cavity or radially outward from the cavity.

[0028] The air supply source 52 (Figure 1) is, for example, a compressor, which supplies compressed air to the air passage 30. The operation of the air supply source 52 is controlled by a control device 53, for example.

[0029] The rotary drive mechanism 51 is a mechanism for rotating the rotor assembly 10. Although not shown in the figures, the rotary drive mechanism 51 includes a drive source such as a motor and a transmission mechanism that transmits the output from the motor. The operation of the rotary drive mechanism 51 is controlled by a control device 53, for example.

[0030] (Operation of the air bearing and rotation of the rotor assembly 10) In the rotary table S100 configured as described above, compressed air is supplied from the air supply source 52 through the air passage 30 between the rotor assembly 10 and the stator assembly 20, thereby forming the thrust air bearing S1 and the radial air bearing S2.

[0031] The thrust air bearing S1 is a hydrostatic air film formed by the supply of compressed air between the upper surface 21a of the stator 21 and the lower surface 11b of the thrust plate 11. This hydrostatic air film functions as a horizontal air bearing.

[0032] The air bearing of the rotary table S100 is formed as an air film of several micrometers to more than 10 micrometers (microns) between the rotor assembly 10, which is the rotating side, and the stator assembly 20, which is the stationary side. Due to the rigidity of this air film, the rotor assembly 10 is supported by the stator assembly 20 without contact.

[0033] The radial air bearing S2 is a vertical air bearing formed as a hydrostatic air film between the inner circumferential surface 21b of the stator 21 (Figure 2) and the outer circumferential surface of the rotor 12. The radial air bearing S2 has the function of restricting the radial runout of the rotor assembly 10.

[0034] By supplying compressed air from the air supply source 52, the rotary drive mechanism 51 rotates the rotor assembly 10 in a predetermined direction, causing the rotor assembly 10 to rotate without contact with the stator assembly 20.

[0035] (Structure of the sealing part) Next, the seal portion 15 and its surrounding structure will be described with reference to Figure 3. Figure 3 is an enlarged view of a portion of Figure 2. The seal portion 15 and its surrounding structure are formed by the thrust plate 11 and the stator assembly 20 and are located radially outward of the thrust air bearing S1.

[0036] The seal portion 15 is an air seal portion formed between the lower surface 11b of the thrust plate 11 and the upper surface of the sleeve 25. As shown in Figure 3, the seal portion 15 includes an inclined flow path 16 and a connecting portion 17. A cavity 18 is formed radially inward from the seal portion 15.

[0037] The inclined channel 16 has an inclined channel to prevent oil and other substances from entering from the outside. Specifically, the inclined channel 16 is formed such that the height of the channel increases as it moves radially inward from the outer surface 11c of the thrust plate 11. In this embodiment, the inclined channel 16 has a straight channel shape, but the inclined channel 16 may have a curved channel shape or a stepped channel shape.

[0038] In this embodiment, for example, the upper end surface of the sleeve 25 is located above the thrust air bearing S1, so that the end of the inclined flow channel 16 opposite to the inlet side is located above the thrust air bearing S1. The connecting portion 17 is a flow channel that connects the inclined flow channel 16 and the cavity 18. The connecting portion 17 extends radially from the end of the inclined flow channel 16 opposite to the inlet side, for example.

[0039] The cavity 18 is located between the thrust air bearing S1 and the seal portion 15. The cavity 18 is formed, for example, by a thrust plate 11, a stator 21, and a sleeve 25. The cavity 18 is a space for trapping dust and foreign matter. For example, the lower surface 18p of the cavity 18 is formed lower than the upper surface 21a of the stator 21 of the stator assembly 20. With this configuration, even if a certain amount of dust and foreign matter enters the cavity 18, the dust and foreign matter will not enter the interior of the thrust air bearing S1 until the amount of dust and foreign matter reaches the upper surface 21a.

[0040] As can be seen from Figure 3, the cavity 18 communicates with both the thrust air bearing S1 and the seal portion 15. When the rotary table S100 is in operation, compressed air discharged from the outer circumference of the thrust air bearing S1 passes through the cavity 18 and flows into the seal portion 15.

[0041] To maintain positive pressure inside the cavity 18 and considering the difficulty of machining, the seal gap h1 when compressed air is supplied is formed to be, for example, about 0.1 mm to 0.5 mm. The seal gap h1 is longer than the height of the bearing clearance of the thrust air bearing S1.

[0042] Although not shown in the diagram, in this embodiment, as an example, a water-repellent coating layer is formed on at least a portion of the surface of the rotor assembly 10 and the stator assembly 20 in the area facing the seal portion 15. The water-repellent coating layer is formed by a surface treatment that impregnates, for example, PTFE (polytetrafluoroethylene). The portion provided with such a water-repellent coating layer is less likely to wet with liquid, and as an example, the contact angle of the liquid exceeds 90°. When the contact angle of a liquid on a solid surface exceeds 90°, capillary action is less likely to occur, and thus the penetration of liquids such as water and oil is prevented.

[0043] (Effect of the sealing portion 15) During the operation of the rotary table S100, compressed air supplied to the thrust air bearing S1 is discharged from the outer circumference of the thrust air bearing S1 and supplied to the cavity 18 and the seal portion 15. In this way, the supply of compressed air to the seal portion 15 causes the seal portion 15 to function as an air seal.

[0044] In the rotary table S100, it is assumed that, for example, oil flows down from the upper surface of the thrust plate 11 along the outer circumferential surface 11c. Figure 4 is a cross-sectional view showing a rotary table of a comparative example. The rotary table 200 in Figure 4 is similar in configuration to that of the embodiment in that a rotor assembly 210 having a thrust plate 211 and a rotor 212 is rotatably supported by a stator assembly 220. However, a "seal portion" like that in this embodiment is not formed between the thrust plate 211 and the stator 221. In this configuration, there is a risk that oil from the upper surface of the thrust plate 211 may enter the thrust air bearing S1.

[0045] In contrast, in the rotary table S100 of this embodiment, as shown in Figure 3, the seal portion 15 includes an inclined passage 16, and this inclined passage 16 is formed so that the passage is inclined. Therefore, even if oil reaches the entrance of the inclined passage 16, it is difficult for the oil to flow into the interior of the inclined passage 16. Furthermore, not only is the passage inclined, but compressed air is supplied to the inclined passage 16, and the inclined passage 16 is under positive pressure, so the entry of oil into the passage is prevented more effectively. As a result, it is prevented from entering the cavity 18 and the thrust air bearing S1.

[0046] In the above explanation, oil was used as an example of entry, but other dust and foreign matter are also prevented from entering the thrust air bearing S1.

[0047] Although one embodiment of the present invention has been described above with reference to the drawings, the present invention is not limited to the specific structure described above. For example, the stator assembly 20 may not have a sleeve 25, and the seal portion 15 may be formed by the stator 21 and the thrust plate 11. Also, although a cavity 18 was provided in the above embodiment, a rotary table in one embodiment of the present invention may not have a configuration equivalent to a cavity 18.

[0048] (Effects of the rotary table S100 in the first embodiment) In the rotary table S100 of this embodiment as described above, a seal portion 15 is formed radially outward from the thrust air bearing S1. The seal portion 15 includes an inclined flow path 16 and is configured to allow compressed air to flow through it. Therefore, dust and foreign matter from the outside are less likely to enter the seal portion 15, and as a result, dust and foreign matter are also prevented from entering the thrust air bearing S1. Thus, the rotational performance of the rotary table S100 can be maintained over a long period of time.

[0049] In the rotary table S100, when the supply of compressed air is stopped and the machine is idle, the upper surface 21a of the stator 21 and the lower surface 11b of the thrust plate 11 are in solid contact, and the apparent bearing clearance becomes zero. If dust or foreign matter is present between the thrust plate 11 and the stator 21 in this state, this dust or foreign matter may cause the thrust plate 11 and the stator 21 to stick together. However, in the rotary table S100 of this embodiment, dust and foreign matter are prevented from entering the thrust air bearing S1, so the occurrence of such problems is suppressed.

[0050] In this embodiment, compressed air is also supplied to the cavity 18 and the seal portion 15, creating a positive pressure. As a result, the pressure-receiving area of ​​the thrust plate 11 that is subjected to the pressure of the compressed air increases, and the load capacity that can be loaded onto the surface of the thrust plate 11 can be increased.

[0051] In the configuration of this embodiment, a cavity 18 is also formed between the seal portion 15 and the thrust air bearing S1, and the lower surface 18p of the cavity 18 is lower than the upper surface 21a of the stator 21 that forms the thrust air bearing S1. Therefore, even if dust or foreign matter enters the cavity 18, this dust and foreign matter is trapped within the cavity 18 and is less likely to enter the thrust air bearing S1.

[0052] In this embodiment, the outer circumferential surface 11c of the thrust plate 11 is located radially outward from the inclined flow channel 16. Therefore, even if oil flows down along the outer circumferential surface 11c, for example, it is difficult for the oil to enter the inclined flow channel 16.

[0053] In this embodiment, compressed air discharged from the thrust air bearing S1 is also provided to flow into the seal portion 15. As mentioned above, the supply of compressed air to the seal portion 15 makes it difficult for dust and foreign matter to enter the seal portion 15. However, with this embodiment, in which compressed air discharged from the thrust air bearing S1 is sent to the seal portion 15, it is not necessary to form a dedicated supply channel for supplying compressed air to the cavity 18 or the seal portion 15, for example.

[0054] Although it is not essential in this invention that the seal portion 15 be formed between the sleeve 25 and the thrust plate 11, the configuration in which the seal portion 15 is formed by a part of the sleeve 25, which is a separate component from the stator 21, as in the above embodiment, has the following advantages. Specifically, since the shape of the seal portion 15 can be defined by processing a part of the sleeve 25, which can be manufactured as a smaller component than the stator 21, the processing work is easier compared to processing a part of the stator 21.

[0055] In this embodiment, a water-repellent coating layer is also formed on at least a portion of the area of ​​the thrust plate 11 or stator assembly 20 that faces the seal portion 15. The water-repellent effect of this coating layer prevents oil or the like from entering the seal portion 15.

[0056] [Second Embodiment] The cross-sectional shape of the sealing portion constituting the dustproof sealing structure of the present invention can be changed in various ways other than the shape shown in the above embodiment. Figure 5 is a cross-sectional view showing the configuration of the second embodiment.

[0057] The rotary table S110 in Figure 5 has a seal portion 15A with a different shape from the seal portion 15 of the first embodiment. The other configurations are the same as in the first embodiment. The rotary table S110 comprises a rotor assembly 10 and a stator assembly 20. The rotor assembly 10 has a thrust plate 11A and a rotor 12. The stator assembly 20 has a stator 21 and a sleeve 25A.

[0058] As shown in Figure 5, the sealing portion 15A includes a flow channel portion formed in a mountain shape in a vertical cross-sectional view. Specifically, the sealing portion 15A includes an inclined flow channel 16 and a connecting portion 17A.

[0059] Similar to the first embodiment, the inclined channel 16 is a channel in which the height of the channel increases as it moves radially inward from the outer circumferential surface 11c of the thrust plate 11A. The connecting portion 17A is a channel that connects the inclined channel 16 and the cavity 18, and is a channel in which the height of the channel decreases from the inclined channel 16 toward the cavity 18. In this embodiment, the inclined channel 16 and the connecting portion 17A form a channel portion with a mountain-shaped (inverted V-shaped) cross-sectional shape as shown in Figure 5.

[0060] Specifically, the mountain-shaped flow channel is formed between a convex portion 25a formed on the upper end of the sleeve 25 and a concave portion 11d formed on the lower surface 11b of the thrust plate 11. Although the overall shape is not shown, both the convex portion 25a and the concave portion 11d have an annular shape centered on the rotation axis C (Figure 1). As an example, the concave portion 11d is formed in a shape complementary to the convex portion 25a.

[0061] In this embodiment, since the seal portion 15A is a curved flow path that includes a mountain-shaped flow path portion, the seal portion 15A can be made longer compared to the configuration in the first embodiment. Therefore, even if dust or foreign matter enters the seal portion 15A, it will need to travel a longer distance to reach the cavity 18, making it more difficult for dust or foreign matter to enter the cavity 18.

[0062] [Third Embodiment] Figure 6 is a cross-sectional view showing the configuration of the third embodiment. The rotary table S120 in Figure 6 has a seal portion 15B with a different shape from the seal portion 15A of the second embodiment. The other configurations are the same as those of the second embodiment.

[0063] As shown in Figure 6, the seal portion 15B may include multiple mountain-shaped flow channels. Specifically, the seal portion 15B includes two mountain-shaped flow channels. More specifically, the seal portion 15B is formed by multiple protrusions 25a on the upper surface of the sleeve 25 and multiple recesses 11d on the lower surface 11b of the thrust plate 11B. The multiple protrusions 25a are concentrically formed annular protrusions, and the multiple recesses 11d are concentrically formed annular recesses.

[0064] In this embodiment, since the sealing portion 15B is a curved channel containing multiple mountain-shaped channels, the sealing portion 15B can be made longer compared to the second embodiment, and therefore, the entry of dust and foreign matter can be prevented more effectively.

[0065] [Variation] Figure 7 is a cross-sectional view showing the configuration of a modified rotary table. In the configuration of Figure 7, similar to the above embodiment, an inclined channel 16C is formed between the thrust plate 11 and the sleeve 25. In this inclined channel 16C, the channel width d1 on the side closer to the outer circumferential surface 11c of the thrust plate 11 is formed to be narrower than the channel width on the inside of the inclined channel 16C. With this configuration, in which the channel width d1 near the inlet is narrow and the channel width gradually increases, compared to a configuration where the channel width d1 is the same throughout, for example, liquid entry due to capillary force is less likely to occur, and thus the entry of dust and foreign matter can be prevented more effectively.

[0066] Although the present invention has been described above using embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments, and various modifications and changes are possible within the scope of its gist. For example, all or part of the apparatus can be configured by functionally or physically distributing and integrating in any unit. Furthermore, new embodiments resulting from any combination of multiple embodiments are also included in the embodiments of the present invention. The effects of the new embodiments resulting from the combinations are combined with the effects of the original embodiments. [Explanation of Symbols]

[0067] 10 Rotor Assembly 11 Thrust Plate 11a Top surface 11A Thrust Plate 11b Bottom side 11B Thrust Plate 11c Outer surface 11d recess 12 rotors 15. Seal part 15A Seal section 15B Seal section 16 Inclined channel 16C Inclined channel 17 Connection part 17A Connection 18 Cavity 18p bottom 20 Stator Assembly 20h recess 21 stata 21a Top side 21b Inner surface 21c Outer surface 22a Air intake restriction 22b Air intake throttle 25 sleeves 25a Convex part 25A sleeve 28 O-rings 30 Air passage 31 1st aisle 32 2nd aisle 32a Outer air supply groove 33 3rd aisle 34 4th aisle 50 bases 51 Rotary drive mechanism 52 Air supply source 53 Control device C Rotation axis d1 channel width h1 Gap in the seal area S1 Thrust Air Bearing S2 Radial Air Bearing S100 Rotating Table S110 Rotating Table S120 Rotating Table

Claims

1. A rotor assembly having a disc-shaped thrust plate and a cylindrical rotor provided on the lower surface of the thrust plate, A stator assembly that rotatably supports the rotor assembly, wherein compressed air is supplied between the lower surface of the thrust plate and the upper surface of the stator assembly to form a horizontal thrust air bearing between the lower surface of the thrust plate and the upper surface of the stator assembly, Equipped with, The thrust plate and the stator assembly have a seal portion through which compressed air flows, located radially outward from the thrust air bearing. The sealing portion includes an inclined channel in which the height of the channel increases as it moves radially inward from the outer circumferential surface of the thrust plate. Dustproof sealing structure.

2. The thrust plate and the stator assembly have a cavity formed between the thrust air bearing and the seal portion that communicates with the seal portion. The lower surface of the cavity is lower than the upper surface of the stator assembly that forms the thrust air bearing. The dustproof sealing structure according to claim 1.

3. The outer circumferential surface of the thrust plate is located radially outward from the inclined flow channel. The dustproof sealing structure according to claim 1 or 2.

4. The thrust plate and the stator assembly are arranged so that the compressed air discharged from the thrust air bearing flows into the seal portion. The dustproof sealing structure according to claim 1 or 2.

5. The stator assembly is A stator that forms a recess for receiving the rotor, A sleeve positioned on the outside of the stator, It has, The sealing portion is formed between the upper surface of the sleeve and the lower surface of the thrust plate. The dustproof sealing structure according to claim 1 or 2.

6. The sealing portion has a curved channel in a vertical cross-sectional view that includes at least one mountain-shaped section of the flow path. The inclined channel is formed in a part of the curved channel. The dustproof sealing structure according to claim 5.

7. Multiple protrusions are formed on the upper surface of the sleeve, Multiple recesses having a cross-sectional shape complementary to the convex portion are formed on the lower surface of the thrust plate. The plurality of protrusions and the plurality of recesses form multiple mountain-shaped portions in the flow path. The dustproof sealing structure according to claim 6.

8. A water-repellent coating layer is formed on at least a portion of the region of the thrust plate facing the seal portion, or on at least a portion of the region of the stator assembly facing the seal portion. The dustproof sealing structure according to claim 1 or 2.

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