Vacuum pump

Abstract

The objective of this invention is to prevent solids from accumulating in the recess of the rotor while preventing solids from bouncing back out of the vacuum pump. The vacuum pump (1) includes: a housing (2) having an inlet (13); a rotor (4) housed in the housing (2) and driven by rotation to draw gas from the inlet (13) and discharge it; and a cover member (43) covering the recess (41) of the rotor (4). The cover member (43) has a conical shape with a apex (T) on the side near the inlet (13) and a base (B) on the side near the rotor (4). The generatrix of the conical shape includes a first curved portion (43A) having a curve in which the angle between the tangent of the generatrix and the direction of gas flow (D1) increases from near the apex to near the base.

Description

Technical Field

[0001] This invention relates to a vacuum pump. Prior Technology

[0002] Regarding vacuum pumps, there exist devices that rotate a rotor with rotor blades to draw gas from the interior of an exhaust-target device and discharge the drawn-in gas to the outside. Regarding the rotor of such a vacuum pump, there are rotors with a recessed portion on the inlet side for drawing in gas. Regarding the exhaust-target device, there are devices that produce a predetermined solid substance (e.g., a product generated by the exhaust-target device), which flows into the vacuum pump and sometimes accumulates in the recessed portion of the rotor. To prevent the solid substance from accumulating in the recessed portion of the rotor, a cover member is provided to cover the recessed portion (e.g., see Patent Document 1 and Patent Document 2). [Existing Technical Documents] [Patent Literature]

[0003] [Patent Document 1] US Patent No. 9,512,853 [Patent Document 2] International Publication No. 2022 / 181464 Summary of the Invention

[0004] [The problem the invention aims to solve] Regarding existing cover members, there are members with a planar shape and a roughly hemispherical shape. Cover members of this shape have a large surface perpendicular to the flow direction of the gas based on the vacuum pump. This large surface perpendicular to the gas flow direction causes most of the solid material flowing into the vacuum pump to bounce back in the opposite direction to the gas flow. That is, cover members with a planar shape and a roughly hemispherical shape cause most of the solid material flowing into the vacuum pump to bounce back to the exhaust device, etc. Additionally, regarding existing cover members, there are also members with a straight inclined surface, but because the inclination of the inclined surface is insufficient, this type of cover member also causes most of the solid material flowing into the vacuum pump to bounce back to the exhaust device.

[0005] Therefore, the object of the present invention is to prevent solids from accumulating in the recess of the rotor while preventing the solids from bouncing back out of the vacuum pump.

[0006] [Technical means to solve the problem] One embodiment of the vacuum pump of the present invention includes a housing, a rotor, and a cover member. The housing has an air inlet. The rotor is housed in the housing and is driven by rotation to draw gas from the air inlet and discharge it. Additionally, the rotor has a recess on the portion facing the air inlet. The cover member covers the recess of the rotor. In the vacuum pump, the cover member has a conical shape with a apex on the side near the air inlet and a base on the side near the rotor. The generatrix of the conical shape includes a first curved portion, the first curved portion having an angle that increases from near the apex to near the base when the tangent of the generatrix is ​​perpendicular to the direction of gas flow.

[0007] [The effects of the invention] One aspect of the vacuum pump of the present invention has a cover member with a conical shape having a apex on the side near the air inlet and a bottom surface on the side near the rotor. Furthermore, the generatrix of the conical shape includes a first curved portion, the first curved portion having an angle that increases from near the apex to near the bottom surface when the tangent of the generatrix is ​​perpendicular to the gas flow direction. This type of cover member has a surface on the side near the air inlet with an angle close to the gas flow direction. Therefore, solids on the surface of the cover member near the air inlet are not ejected from the vacuum pump by bouncing back towards the air inlet. On the other hand, the surface of the cover member near the bottom surface is at an angle close to the gas flow direction, but is positioned away from the center of the cover member. Therefore, a large centrifugal force acts on the surface of the cover member near the bottom surface due to the rotation of the rotor. Due to this centrifugal force, solids on the surface of the cover member near the bottom surface splash in a direction close to perpendicular to the gas flow. Therefore, even on the surface of the cover member near the bottom surface, solids are not ejected from the vacuum pump by bouncing back towards the air inlet. Simple Explanation of the Diagram

[0008] Figure 1 is a cross-sectional view of the vacuum pump. Figure 2 is a diagram showing the detailed structure of the cover component. Figure 3 is a schematic representation of the first curved portion as a monotonically increasing function of distance from the vertex. Implementation

[0009] The rotor blades used in the vacuum pump and the manufacturing method of the rotor blades will be described below. First, a vacuum pump including rotor blades will be described using FIG1. ​​FIG1 is a cross-sectional view of vacuum pump 1. Vacuum pump 1 includes a housing 2, a base 3, a rotor 4, and a stator 5.

[0010] The housing 2 includes a first end 11, a second end 12, and a first internal space S1. An air inlet 13 is provided at the first end 11. The air inlet 13 is connected to the interior of an exhaust device (not shown) in a manner that allows gas to flow through. The first internal space S1 communicates with the air inlet 13. The second end 12 is located opposite to the first end 11 in the axial direction of the rotor 4 (hereinafter referred to as "axial direction A1"). The second end 12 is connected to a base 3. The base 3 includes a base end 14. The base end 14 is connected to the second end 12 of the housing 2. The base 3 is, for example, an aluminum component.

[0011] The rotor 4 is housed within the interior space of the housing 2. The rotor 4 includes a shaft 21. The shaft 21 extends along the axial direction A1. The shaft 21 is rotatably housed in the base 3. A thrust disk 21A is provided at the lower part of the shaft 21. Furthermore, a target 21B is screwed onto the lower end of the shaft 21.

[0012] A recess 41 is provided on the side of the rotor 4 facing the air inlet 13 (i.e., the upper end face of the rotor 4). A balance disc 42 is mounted on the bottom surface of the recess 41. The balance disc 42 is a component used to achieve balance of the rotor 4. A cover member 43 is mounted on the upper end of the balance disc 42. The cover member 43 is configured such that its central axis is aligned with or close to the rotation axis of the rotor 4. The cover member 43 is fixed to the balance disc 42 by screws or the like.

[0013] The cover member 43 is a member that covers the recess 41 of the rotor 4. The cover member 43 prevents solids from passing through the air inlet 13 and flowing into the housing 2 from entering the recess 41. By providing the cover member 43, it is possible to prevent solids from accumulating in the recess 41 of the rotor 4.

[0014] The rotor 4 includes multi-stage rotor blades 22 and a rotor cylindrical portion 23. The multi-stage rotor blades 22 are each connected to the shaft 21 at an angle relative to the axial direction A1. The multi-stage rotor blades 22 are arranged at intervals along the axial direction A1. Although not shown in the figure, the multi-stage rotor blades 22 extend radially about the shaft 21. Furthermore, in the figures, only one symbol for a multi-stage rotor blade 22 is used, while the symbols for the other rotor blades 22 are omitted. The rotor cylindrical portion 23 is disposed below the multi-stage rotor blades 22. The rotor cylindrical portion 23 extends along the axial direction A1.

[0015] The stator 5 is disposed on the outer periphery of the rotor 4. The stator 5 includes multi-stage stator blades 31 and a stator cylindrical portion 32. The multi-stage stator blades 31 are respectively inclined to the inner surface of the housing 2 in a direction opposite to the inclination of the rotor blades 22. For example, when the rotor blades 22 are inclined from the intake side to the exhaust side, the stator blades 31 are inclined from the exhaust side to the intake side. On the other hand, when the rotor blades 22 are inclined from the exhaust side to the intake side, the stator blades 31 are inclined from the intake side to the exhaust side. The inclination direction of the rotor blades 22 and the stator blades 31 can be appropriately determined according to the rotation direction of the rotor 4, etc.

[0016] Multi-stage stator blades 31 are arranged at intervals along the axial direction A1. The multi-stage stator blades 31 are respectively arranged between the multi-stage rotor blades 22. The multi-stage stator blades 31 extend radially about the shaft 21. Furthermore, in the accompanying drawings, only two reference numerals for the multi-stage stator blades 31 are shown, while the reference numerals for the other stator blades 31 are omitted. The stator cylindrical portion 32 is fixed in contact with the base 3. The stator cylindrical portion 32 is arranged facing the outer circumferential surface of the rotor cylindrical portion 23 with a slight gap in its radial direction. A helical groove is provided on the inner circumferential surface of the stator cylindrical portion 32 facing the rotor cylindrical portion 23.

[0017] As shown in Figure 1, an exhaust space S2 is formed further downstream of the exhaust downstream end of the rotor cylindrical portion 23 and the stator cylindrical portion 32. The exhaust target gas discharged from the exhaust target device is guided into the exhaust space S2. The exhaust space S2 is connected to the exhaust port 15. The exhaust port 15 is provided on the base 3. The exhaust port 15 is connected to other vacuum pumps (not shown). Furthermore, the term "exhaust downstream side" refers to the side closer to the exhaust space S2 in the axial direction A1. Additionally, the term "exhaust downstream direction" refers to the direction toward the exhaust space S2. Furthermore, the exhaust downstream direction is referred to as the flow direction D1 of the exhaust target gas.

[0018] The vacuum pump 1 includes bearings 44A and 44E, magnetic bearings 44B to 44D, and a motor 45. Bearings 44A and 44E are mounted on the base 3 at the location where the rotating shaft 21 is housed. Bearings 44A and 44E support the rotating shaft 21, enabling it to rotate. Bearings 44A and 44E are ball bearings. Magnetic bearings 44B to 44D are bearings that support the rotating shaft 21 using magnetic force. Specifically, magnetic bearings 44B and 44C are radial magnetic bearings that support the rotating shaft 21 radially. Magnetic bearing 44D is a thrust magnetic bearing that supports the rotating shaft 21 axially.

[0019] Motor 45 drives rotor 4 to rotate. Motor 45 includes motor rotor 45A and motor stator 45B. Motor rotor 45A is mounted on rotating shaft 21. Motor stator 45B is mounted on base 3. Motor stator 45B is arranged facing motor rotor 45A.

[0020] In vacuum pump 1, multi-stage rotor blades 22 and multi-stage stator blades 31 constitute a turbomolecular pump section. Additionally, rotor cylindrical section 23 and stator cylindrical section 32 constitute a grooved pump section. In vacuum pump 1, the rotor 4 is rotated by motor 45, causing the exhaust gas to flow from the interior of the exhaust device into the first internal space S1 via inlet 13. The exhaust gas in the first internal space S1 passes through the turbomolecular pump section and the grooved pump section and is guided to the exhaust space S2. The exhaust gas in the exhaust space S2 is discharged from exhaust port 15. As a result, the interior of the exhaust device installed at inlet 13 becomes a high vacuum state.

[0021] As described above, a cover member 43 is provided in the vacuum pump 1, which covers the recess 41 of the rotor 4. By providing the cover member 43, it is possible to prevent solids flowing in from the exhaust target device through the air inlet 13 from accumulating in the recess 41. In this embodiment, the shape of the surface of the cover member 43 is further determined so that solids that bounce back on the surface of the cover member 43 are not ejected from the air inlet 13 into the vacuum pump 1 in the opposite direction to the flow direction D1 of the exhaust target gas.

[0022] The following description uses Figures 1 and 2 to illustrate the details of the cover member 43. Figure 2 is a diagram showing the detailed structure of the cover member 43. As shown in Figure 1, the cover member 43 has a conical shape with a vertex T on the side near the air inlet 13 and a base B on the side near the rotor 4. Specifically, the cover member 43 has a conical shape with a small convex shape on the side near the vertex T.

[0023] More specifically, the cover member 43 has a conical shape that gradually widens from the side near the vertex T towards the side near the bottom surface B. In other words, the generatrix of the cover member 43 is formed by a curve in which the angle between the tangent of the generatrix and the flow direction D1 of the exhaust gas increases from near the vertex T to near the bottom surface B. For example, as shown in FIG2, the angle α between the tangent P1 at the point near the vertex T of the generatrix of the cover member 43 and the flow direction D1 of the exhaust gas is smaller than the angle b between the tangent P2 at the point near the bottom surface B of the generatrix of the cover member 43 and the flow direction D1 of the exhaust gas. Here, the term "generatrix of the cover member 43" refers to the line forming the side surface of the cover member 43, corresponding to the side surface portion when the cover member 43 is cut along the flow direction D1.

[0024] As shown in Figures 1 and 2, the generatrix of the cover member 43 has two points where the curvature changes (called inflection points). The generatrix of the cover member 43 can be divided into three regions by these two inflection points, each region having a different curve. Specifically, as shown in Figure 2, the generatrix of the cover member 43 can be divided into three regions by a first dividing line SE1 corresponding to the inflection point closer to the vertex T and a second dividing line SE2 corresponding to the inflection point closer to the bottom surface B. The middle region is called the first region AR1, the region on the vertex T side is called the second region AR2, and the region on the bottom surface B side is called the third region AR3. Furthermore, the generatrix of the first region AR1 is called the first curve portion 43A, the generatrix of the second region AR2 is called the second curve portion 43B, and the generatrix of the third region AR3 is called the third curve portion 43C. That is, the generatrix of the cover member 43 is composed of three different curves: the first curve portion 43A, the second curve portion 43B, and the third curve portion 43C.

[0025] The first curve portion 43A is characterized by the angle between the tangent to the generatrix and the flow direction D1 of the exhaust gas increasing from near the vertex T to near the bottom B. As shown in Figure 3, in an XY coordinate system with vertex T as the origin O, an axis parallel to the flow direction D1 as the X-axis, and an axis perpendicular to the flow direction D1 as the Y-axis, the first curve portion 43A can be represented as a monotonically increasing function of the X-axis value. Specifically, the shape of the first curve portion 43A relative to any value x of the X-axis can be represented as a monotonically increasing function f(x). The monotonically increasing function f(x) can be, for example, a monotonically increasing polynomial of degree two or higher with respect to x (e.g., a₁x₂ + a₂x₃ + ... + anxₙ (a₁, a₂, ..., an: constants)) or an exponential function (e.g., Mₙxₙ (M, N: numbers greater than 1)). Figure 3 is a schematic representation of the first curved portion 43A as a monotonically increasing function of distance from vertex T.

[0026] In the XY coordinate system, the value of the X-axis (x) corresponds to the distance from the vertex T in the flow direction D1. Since the first curved portion 43A is represented by a monotonically increasing function f(x) with respect to x, it can be said that the first curved portion 43A is represented by a monotonically increasing function with respect to the distance from the vertex T. Furthermore, the value of the Y-axis (f(x)) corresponds to the distance between the first curved portion 43A and the central axis (i.e., the X-axis) of the cover member 43. Since the first curved portion 43A is represented by a monotonically increasing function f(x) with respect to the distance from the vertex T, the first curved portion 43A is positioned away from the central axis of the cover member 43 as it approaches the bottom surface B (as the value of x increases).

[0027] Thus, the first curve portion 43A is easily designed and manufactured by representing it as a monotonically increasing function of the distance x from the vertex T. Furthermore, the second curve portion 43B and the third curve portion 43C can also be represented as functions of the distance x from the vertex T.

[0028] The first curved portion 43A has a surface on the side near the air inlet 13 that is at an angle close to the flow direction D1. Therefore, on the surface of the first curved portion 43A on the side near the air inlet 13, solids will not bounce back towards the air inlet 13 and be discharged outside the vacuum pump 1.

[0029] On the other hand, the surface of the first curved section 43A near the bottom surface B is at an angle nearly perpendicular to the flow direction D1, but it is positioned away from the central axis of the cover member 43. Therefore, a large centrifugal force from the rotation of the rotor 4 acts on the surface of the first curved section 43A near the bottom surface B. Due to this centrifugal force, solids reaching the surface of the first curved section 43A near the bottom surface B are splashed in a direction nearly perpendicular to the flow direction D1. Therefore, even on the surface of the first curved section 43A near the bottom surface B, solids are not ejected from the vacuum pump 1 towards the inlet 13.

[0030] The second curved section 43B is the curve connecting the vertex T of the cover member 43 to the upper end of the first curved section 43A. The portion of the second curved section 43B corresponding to the vertex T has a small hemispherical shape. By making the portion corresponding to the vertex T hemispherical, compared to the case where the vertex T is pointed, it is possible to suppress the solid material flowing in from the air inlet 13 from bouncing back towards the air inlet 13. Regarding the portion of the second curved section 43B other than the vertex T, the angle between the tangent of this portion and the flow direction D1 is smaller. Specifically, the angle between the tangent of the portion of the second curved section 43B other than the vertex T and the flow direction D1 is smaller than the angle between the tangent of the first curved section 43A and the flow direction D1. Therefore, in this portion of the second curved section 43B, solid material will not bouncing back towards the air inlet 13 and being discharged outside the vacuum pump 1.

[0031] As shown in Figure 1, the portion of the second curved section 43B corresponding to the vertex T protrudes from the upper end face of the rotor 4 facing the air inlet 13. This suppresses turbulence in the flow of the exhaust gas at the vertex T of the cover member 43. Specifically, it facilitates the generation of flow along the curved side of the cover member 43, allowing solids to move along this flow. Consequently, it prevents solids from bouncing back towards the air inlet 13 and being discharged outside the vacuum pump 1.

[0032] The third curved section 43C is a curve connecting the lower end of the first curved section 43A to the bottom surface B of the cover member 43. The third curved section 43C has a tangent that is nearly perpendicular to the flow direction D1, but it is positioned away from the central axis of the cover member 43. Therefore, a large centrifugal force is applied to the third curved section 43C by the rotation of the rotor 4. This centrifugal force causes the solid material reaching the third curved section 43C to splash in a direction nearly perpendicular to the flow direction D1. Therefore, in the third curved section 43C, the solid material will not bounce back towards the air inlet 13 and be discharged outside the vacuum pump 1.

[0033] As shown in Figures 1 and 2, the bottom surface B of the cover member 43 has an edge parallel to the flow direction D1. Therefore, the angle between the tangent of the third curved portion 43C on the side near the bottom surface B and the flow direction D1 is smaller than the angle between the tangent of the third curved portion 43C on the side near the first curved portion 43A and the flow direction D1.

[0034] The above describes one embodiment of the present invention, but the present invention is not limited to the described embodiment and various modifications can be made without departing from the spirit of the invention.

[0035] The vacuum pump 1 in the described embodiment is an integrated pump consisting of a turbomolecular pump composed of multi-stage rotor blades 22 and multi-stage stator blades 31, and a grooved pump composed of a rotor cylindrical portion 23 and a stator cylindrical portion 32. However, the grooved pump may be omitted. Alternatively, the rotor blades 22 and stator blades 31 may be omitted, and the vacuum pump 1 may be composed solely of the grooved pump. That is, the cover member 43 may also be applicable to a vacuum pump composed solely of a turbomolecular pump or a vacuum pump composed solely of a grooved pump.

[0036] In the embodiment described, the cover member 43 is mounted on the balance disc 42. However, it is not limited to this; the cover member 43 may also be directly fixed to the recess 41 of the rotor 4 by screws or the like.

[0037] Those skilled in the art will understand that the above-described exemplary embodiments are specific examples of the following forms.

[0038] (First Embodiment) A vacuum pump of the first embodiment (e.g., vacuum pump 1) includes a housing (e.g., housing 2), a rotor (e.g., rotor 4), and a cover member (e.g., cover member 43). The housing has an inlet (e.g., inlet 13). The rotor is housed in the housing and is driven by rotation to draw gas from the inlet and discharge it. Additionally, the rotor has a recess (e.g., recess 41) on the portion facing the inlet. The cover member covers the recess of the rotor. In the vacuum pump, the cover member has a conical shape with a apex (e.g., apex T) on the side near the inlet and a base (e.g., base B) on the side near the rotor. The generatrix of the conical shape includes a first curved portion (e.g., first curved portion 43A), the first curved portion having a curve in which the angle between the tangent of the generatrix and the direction of gas flow increases from near the apex to near the base.

[0039] The cover member of the first type of vacuum pump has a conical shape with a apex on the side near the air inlet and a bottom surface on the side near the rotor. Furthermore, the generatrix of the conical shape includes a first curved portion, where the angle between the tangent to the generatrix and the gas flow direction increases from near the apex to near the bottom. This type of cover member has a surface on the side near the air inlet with an angle close to the gas flow direction. Therefore, solids on the surface of the cover member near the air inlet are not ejected from the vacuum pump by bouncing back towards the air inlet. On the other hand, the surface of the cover member near the bottom surface is at an angle close to the gas flow direction, but is positioned away from the center of the cover member. Therefore, a large centrifugal force acts on the surface of the cover member near the bottom surface due to the rotation of the rotor. This centrifugal force causes solids on the surface of the cover member near the bottom surface to splash in a direction close to the gas flow. Therefore, even on the surface of the cover member near the bottom surface, solids are not ejected from the vacuum pump by bouncing back towards the air inlet.

[0040] (Second Embodiment) According to the vacuum pump of the first embodiment, the generatrix of the cone shape of the cover member can be formed by a first curved portion and a second curved portion (e.g., second curved portion 43B) on the side closer to the apex than the first curved portion. In the vacuum pump of the second embodiment, the apex of the cover member and the first curved portion can be connected continuously and smoothly.

[0041] (Third form) According to the vacuum pump of the second form, the portion of the second curved section corresponding to the vertex of the cover member may have a hemispherical shape. In the vacuum pump of the third form, compared with the case where the vertex of the cover member is pointed, it is possible to suppress the solid material flowing in from the air inlet from bouncing back towards the air inlet.

[0042] (Fourth Form) In a vacuum pump based on any of the first to third forms, the first curved portion can be represented by a monotonically increasing polynomial or exponential function with respect to the distance from the vertex of the cover member. In the fourth form of the vacuum pump, since the first curved portion can be represented by a mathematical expression, the cover member is easy to design and manufacture.

[0043] (Fifth Embodiment) In a vacuum pump according to any of the first to fourth embodiments, the apex of the cover member can protrude from the rotor's surface facing the air inlet. In the fifth embodiment of the vacuum pump, turbulence in the gas flow at the apex of the cover member can be suppressed. That is, flow along the curved side of the cover member is easily generated, allowing solids to move along said flow. As a result, the ejection of solids towards the air inlet and out of the vacuum pump can be prevented.

[0044] (Sixth Embodiment) According to the vacuum pump of the second embodiment, the generatrix of the cone shape may also include a third curved portion (e.g., the third curved portion 43C) on the side closer to the bottom surface than the first curved portion. In the vacuum pump of the sixth embodiment, the cover member can be formed into an optimal shape that prevents the solid from bouncing back towards the air inlet.

[0045] (Seventh Form) In the vacuum pump of the sixth form, the angle between the tangent of the third curved portion near the bottom surface and the gas flow direction can be smaller than the angle between the tangent of the third curved portion near the first curved portion and the gas flow direction. In the vacuum pump of the seventh form, the connection between the bottom surface of the cover member and the other sides can be smooth.

[0046] (Eighth Embodiment) According to the vacuum pump of the second embodiment, the angle between the tangent of the second curved portion (excluding the vertex) and the gas flow direction can be smaller than the angle between the tangent of the first curved portion and the gas flow direction. In the vacuum pump of the eighth embodiment, even in the portion of the second curved portion (excluding the vertex), the rebound of solids towards the inlet can be suppressed.

[0047] (Ninth Embodiment) In a vacuum pump according to any one of the first to eighth embodiments, the cover member may have a conical shape that gradually widens from the side near the apex toward the side near the bottom. In the vacuum pump of the ninth embodiment, on the surface of the cover member near the air inlet, solids are not allowed to bounce back toward the air inlet and be discharged out of the vacuum pump. On the surface of the cover member near the bottom, a large centrifugal force is applied by the rotation of the rotor, thus preventing solids from bouncing back toward the air inlet and being discharged out of the vacuum pump.

[0048] (Tenth Embodiment) In a vacuum pump according to any of the first to ninth embodiments, the first curved portion near the inlet can be configured such that it passes through a surface having an angle close to the gas flow direction, preventing solids from bouncing back towards the inlet. Furthermore, on the side of the cover member near the bottom surface, it can be configured such that it is positioned at an angle close to the gas flow direction but away from the center of the cover member, causing solids to splash in a direction nearly perpendicular to the gas flow direction via centrifugal force, preventing them from bouncing back towards the inlet. In the tenth embodiment of the vacuum pump, solids are discharged outside the vacuum pump without bouncing back towards the inlet.

[0049] 1: Vacuum pump 2: Shell 3: Base 4: Rotor 5: Stator 11: First end 12: Second end 13: Air Inlet 14: Base end 15: Exhaust port 21: Shaft 21A: Thrust plate 21B: Target 22: Rotor blades 23: Rotor cylindrical section 31: Stator blades 32: Stator cylindrical section 41: Depression 42: Balance disc 43: Cover component 43A: First Curve Section 43B: Second Curve Section 43C: Third Curve Section 44A, 44E: Bearings 44B, 44C, 44D: Magnetic bearings 45: Motor 45A: Motor rotor 45B: Motor stator a, b: Angles A1: Axis direction AR1: Area 1 AR2: Second Area AR3: Third Area B: Bottom surface D1: Flow direction of the exhaust gas / Flow direction / Gas flow direction f(x): Value of the y-axis / Monotonically increasing function / Monotonically increasing function with respect to x / Monotonically increasing function with respect to the distance from vertex T O: origin P1, P2: Tangents S1: First Internal Space S2: Exhaust space SE1: First dividing line SE2: Second dividing line T: Vertex x: any value on the X-axis X, Y: Axis

Claims

1. A vacuum pump, comprising: The casing has an air inlet; The rotor is a component housed in the housing and driven by rotation to draw gas from and discharge it from the air inlet, and has a recess in the portion facing the air inlet. And a cover member covering the recess of the rotor, the cover member having a conical shape having a apex on the side near the air inlet and a bottom surface on the side near the rotor, the generatrix of the conical shape including a first curved portion, the first curved portion having a curve in which the angle between the tangent of the generatrix and the flow direction of the gas increases from near the apex to near the bottom surface, the generatrix of the conical shape being formed by the first curved portion and a second curved portion on the side closer to the apex than the first curved portion, the portion of the second curved portion corresponding to the apex having a hemispherical shape, the generatrix of the conical shape also including a third curved portion on the side closer to the bottom surface than the first curved portion.

2. The vacuum pump according to claim 1, wherein, The first curve portion is represented by a monotonically increasing polynomial or exponential function with respect to the distance from the vertex, which is quadratic or higher.

3. The vacuum pump according to claim 1, wherein, The vertex protrudes from the surface of the rotor facing the air inlet.

4. The vacuum pump according to claim 1, wherein, The angle between the tangent of the third curved portion near the bottom surface and the direction of gas flow is smaller than the angle between the tangent of the third curved portion near the first curved portion and the direction of gas flow.

5. The vacuum pump according to claim 1, wherein, Regarding the portion of the second curve other than the vertex, the angle between the tangent of that portion and the direction of gas flow is smaller than the angle between the tangent of the first curve portion and the direction of gas flow.

6. The vacuum pump according to claim 1, wherein, The cover member has a conical shape that gradually widens from the side near the apex toward the side near the bottom.

7. The vacuum pump according to claim 1, wherein, The first curved portion is configured on the side near the air inlet such that it has a surface with an angle close to the direction of gas flow, so that the solid material will not bounce back towards the air inlet. On the side near the bottom surface of the cover member, it is configured such that it has an angle close to the direction of gas flow, but is positioned away from the center of the cover member, so that the solid material will splash in a direction close to the direction of gas flow by centrifugal force without bouncing back towards the air inlet.

8. A vacuum pump, comprising: The casing has an air inlet; The rotor is a component housed in the housing and driven by rotation to draw gas from and discharge it from the air inlet, and has a recess in the portion facing the air inlet. And a cover member covering the recess of the rotor, the cover member having a conical shape with a apex on the side near the air inlet and a bottom surface on the side near the rotor, the generatrix of the conical shape including a first curved portion, the first curved portion having a curve in which the angle between the tangent of the generatrix and the flow direction of the gas increases from near the apex to near the bottom surface, the generatrix of the conical shape being formed by the first curved portion and a second curved portion on the side closer to the apex than the first curved portion, the generatrix of the conical shape further including a third curved portion on the side closer to the bottom surface than the first curved portion, the angle between the tangent of the third curved portion on the side near the bottom surface and the flow direction of the gas being smaller than the angle between the tangent of the third curved portion on the side near the first curved portion and the flow direction of the gas.

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