Vacuum pump

Abstract

To prevent solid matter from being bounced out of a vacuum pump while preventing the solid matter from being deposited in a recess of a rotor.SOLUTION: A vacuum pump 1 comprises: a housing 2 having a suction port 13; a rotor 4 housed in the housing 2, and rotationally driven to suction and exhaust gas from the suction port 13; and a lid member 43 that covers a recess 41 of the rotor 4. The lid member 43 has a conical shape with a vertex T on the side closer to the suction port 13 and a bottom surface B on the side closer to the rotor 4. A bus bar of the conical shape includes a first curved part 43A having such a curve that an angle between a tangent to the bus bar and a gas flow direction D1 increases from near the vertex to near the bottom surface.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a vacuum pump. [Background technology]

[0002] Some vacuum pumps rotate a rotor with rotor blades to suck the inside of an apparatus to be evacuated and discharge the sucked gas to the outside. The rotor of this vacuum pump may have a recess on the intake side for sucking gas. Some of the above-mentioned apparatus to be evacuated generate certain solid matter (for example, products generated in the apparatus to be evacuated), and these solid matter may flow into the vacuum pump and accumulate in the recess of the rotor. To prevent solid matter from accumulating in the recess of the rotor, a cover member is provided to cover the recess (see, for example, Patent Document 1 and Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 9,512,853 [Patent Document 2] International Publication No. 2022 / 181464 Summary of the Invention [Problem to be solved by the invention]

[0004] Some conventional lid members have a flat or approximately hemispherical shape. Lid members with such shapes have a large surface perpendicular to the direction of gas flow generated by the vacuum pump. A large surface perpendicular to the gas flow direction causes many of the solids that flow into the vacuum pump to bounce back in the opposite direction to the gas flow. In other words, lid members with a flat or approximately hemispherical shape cause many of the solids that flow into the vacuum pump to bounce back toward the device to be evacuated. Some conventional lid members have a linearly inclined surface, but because the inclination of the inclined surface is insufficient, such lid members also cause many of the solids that flow into the vacuum pump to bounce back toward the device to be evacuated.

[0005] Therefore, an object of the present invention is to prevent solid matter from accumulating in recesses in the rotor while preventing the solid matter from being splashed out of the vacuum pump. [Means for solving the problem]

[0006] A vacuum pump according to one aspect of the present invention includes a housing, a rotor, and a cover member. The housing has an intake port. The rotor is housed in the housing and is driven to rotate to suck and exhaust gas through the intake port. The rotor also has a recess facing the intake port. The cover member covers the recess in the rotor. In the vacuum pump described above, the cover member has a cone shape with an apex closer to the intake port and a base closer to the rotor. A generatrix of this cone shape includes a first curved portion having a curve in which the angle between a tangent to the generatrix and the gas flow direction increases from near the apex to near the base. [Effects of the Invention]

[0007] A lid member for a vacuum pump according to one aspect of the present invention has a conical shape with an apex closer to the intake port and a base closer to the rotor. The generatrix of this conical shape includes a first curved portion, in which the angle between a tangent to the generatrix and the gas flow direction increases from near the apex to near the base. A lid member having such a shape has a surface closer to the intake port at an angle close to the gas flow direction. Therefore, solids on the surface of the lid member closer to the intake port are not repelled toward the intake port and do not exit the vacuum pump. Meanwhile, the surface of the lid member closer to the bottom is angled closer to perpendicular to the gas flow direction but is positioned away from the center of the lid member. Therefore, a large centrifugal force acts on the surface of the lid member closer to the bottom due to the rotation of the rotor. This centrifugal force causes solids on the surface of the lid member closer to the bottom to fly in a direction nearly perpendicular to the gas flow. Therefore, even on the surface of the lid member closer to the bottom, solids are not repelled toward the intake port and do not exit the vacuum pump. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view of a vacuum pump. [Figure 2] 4A and 4B are diagrams showing the detailed configuration of the cover member. [Figure 3] FIG. 10 is a diagram schematically illustrating that a first curved line portion is expressed as a monotonically increasing function of the distance from the vertex. DETAILED DESCRIPTION OF THE INVENTION

[0009] The rotor blades used in vacuum pumps and a method for manufacturing the rotor blades will be described below. First, a vacuum pump equipped with the rotor blades will be described with reference to FIG. 1. FIG. 1 is a cross-sectional view of a vacuum pump 1. The 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. The first end 11 is provided with an intake port 13. The intake port 13 is connected to the interior of the exhaust target device (not shown) so that gas can flow therethrough. The first internal space S1 is in communication with the intake port 13. The second end 12 is located opposite the first end 11 in the axial direction of the rotor 4 (hereinafter simply referred to as the "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, a member made of aluminum.

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

[0012] A recess 41 is provided on the side of the rotor 4 facing the intake port 13 (i.e., the upper end surface of the rotor 4). A balance disk 42 is attached to the bottom surface of this recess 41. The balance disk 42 is a member for balancing the rotor 4. A cover member 43 is attached to the upper end of the balance disk 42. The cover member 43 is positioned so that the central axis of the cover member 43 coincides with or is close to the rotation axis of the rotor 4. The cover member 43 is fixed onto the balance disk 42 with screws or the like.

[0013] The lid member 43 is a member that covers the recess 41 of the rotor 4. The lid member 43 prevents solid matter that has flowed from the exhaust target device through the intake port 13 into the housing 2 from entering the recess 41. By providing the lid member 43, it is possible to prevent solid matter from accumulating in the recess of the rotor 4.

[0014] The rotor 4 includes multiple stages of rotor blades 22 and a rotor cylindrical portion 23. The multiple stages of rotor blades 22 are connected to the shaft 21 at an angle with respect to the axial direction A1. The multiple rotor blades 22 are arranged at intervals from one another in the axial direction A1. Although not shown, the multiple stages of rotor blades 22 each extend radially from the shaft 21 as a center. Note that in the drawings, only one of the multiple stages of rotor blades 22 is labeled with a reference numeral, and the reference numerals of the other rotor blades 22 are omitted. The rotor cylindrical portion 23 is arranged below the multiple stages of rotor blades 22. The rotor cylindrical portion 23 extends in the axial direction A1.

[0015] The stator 5 is disposed on the outer periphery of the rotor 4. The stator 5 includes multiple stages of stator blades 31 and a stator cylindrical portion 32. The multiple stages of stator blades 31 are connected to the inner surface of the housing 2, inclined in the opposite direction 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 determined appropriately depending on the rotation direction of the rotor 4, etc.

[0016] The multiple stages of stator blades 31 are arranged at intervals from one another in the axial direction A1. The multiple stages of stator blades 31 are respectively arranged between the multiple stages of rotor blades 22. The multiple stages of stator blades 31 each extend radially from the shaft 21. Note that in the drawings, only two of the multiple stages of stator blades 31 are labeled with reference numerals, and the reference numerals of 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 peripheral surface of the rotor cylindrical portion 23 with a small gap in the radial direction of the rotor cylindrical portion 23. A spiral groove is provided on the inner peripheral surface of the stator cylindrical portion 32 facing the rotor cylindrical portion 23.

[0017] As shown in FIG. 1, an exhaust space S2 is formed downstream of the exhaust downstream ends of the rotor cylindrical portion 23 and the stator cylindrical portion 32. The exhaust target gas exhausted from the exhaust target device is guided into the exhaust space S2. The exhaust space S2 is in communication with the exhaust port 15. The exhaust port 15 is provided in the base 3. Another vacuum pump (not shown) is connected to the exhaust port 15. The exhaust downstream side refers to the side closer to the exhaust space S2 in the axial direction A1. The exhaust downstream direction refers to the direction toward the exhaust space S2. This exhaust downstream direction is also 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. The bearings 44A and 44E are attached to the base 3 at positions where the shaft 21 is housed. The bearings 44A and 44E rotatably support the shaft 21. The bearings 44A and 44E are ball bearings. The magnetic bearings 44B to 44D are bearings that support the shaft 21 by magnetic force. Of these, the magnetic bearings 44B and 44C are radial magnetic bearings that support the shaft 21 in the radial direction. The magnetic bearing 44D is a thrust magnetic bearing that supports the shaft 21 in the axial direction.

[0019] The motor 45 drives the rotor 4 to rotate. The motor 45 includes a motor rotor 45A and a motor stator 45B. The motor rotor 45A is attached to the shaft 21. The motor stator 45B is attached to the base 3. The motor stator 45B is disposed opposite the motor rotor 45A.

[0020] In the vacuum pump 1, the multiple stages of rotor blades 22 and the multiple stages of stator blades 31 form a turbomolecular pump section. The rotor cylindrical section 23 and the stator cylindrical section 32 form a thread groove pump section. In the vacuum pump 1, as the rotor 4 is rotated by the motor 45, the gas to be pumped flows from the inside of the device to be pumped into the first internal space S1 through the intake port 13. The gas to be pumped in the first internal space S1 passes through the turbomolecular pump section and the thread groove pump section and is guided to the exhaust space S2. The gas to be pumped in the exhaust space S2 is exhausted from the exhaust port 15. As a result, the inside of the device to be pumped attached to the intake port 13 is brought into a high vacuum state.

[0021] As described above, the vacuum pump 1 is provided with the cover member 43 that covers the recess 41 of the rotor 4. Providing the cover member 43 makes it possible to prevent solid matter that flows in from the device to be evacuated through the intake port 13 from accumulating in the recess 41. Furthermore, in this embodiment, the shape of the surface of the cover member 43 is determined so that solid matter that bounces off the surface of the cover member 43 does not bounce back in the opposite direction to the flow direction D1 of the gas to be evacuated and exit the vacuum pump 1 through the intake port 13.

[0022] The details of the cover member 43 will be described below with reference to Figures 1 and 2. Figure 2 is a diagram showing the detailed configuration of the cover member 43. As shown in Figure 1, the cover member 43 has a cone shape with a vertex T on the side closer to the intake port 13 and a base B on the side closer to the rotor 4. Specifically, the cover member 43 has a cone shape with a smaller convex shape on the side of the vertex T.

[0023] More specifically, the cover member 43 has a conical shape that widens from the side closer to the apex T to the side closer to the bottom surface B. In other words, the generatrix of the cover member 43 is configured as a curve such that the angle between a tangent to the generatrix and the flow direction D1 of the exhaust target gas increases from the vicinity of the apex T to the vicinity of the bottom surface B. For example, as shown in FIG. 2, the angle a between a tangent P1 to the generatrix of the cover member 43 at a point closer to the apex T and the flow direction D1 of the exhaust target gas is smaller than the angle b between a tangent P2 to the generatrix of the cover member 43 at a point closer to the bottom surface B and the flow direction D1 of the exhaust target gas. Here, the "generatrix of the cover member 43" refers to a line that forms the side surface of the cover member 43, and corresponds to the side surface portion when the cover member 43 is cut along the flow direction D1.

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

[0025] Among these, the first curved portion 43A has a curve in which the angle between the tangent of the generatrix and the flow direction D1 of the gas to be exhausted increases from the vicinity of the apex T to the vicinity of the bottom surface B. As shown in FIG. 3, in an XY coordinate system in which the apex T is the origin O, the axis parallel to the flow direction D1 is the X axis, and the axis perpendicular to the flow direction D1 is the Y axis, the first curved portion 43A can be expressed as a monotonically increasing function of the X axis value. Specifically, for an arbitrary value x on the X axis, the shape of the first curved portion 43A can be expressed as a monotonically increasing function f(x). The monotonically increasing function f(x) can be expressed, for example, as a monotonically increasing polynomial of quadratic or higher with respect to x (for example, a1x 2 +a2x 3 +···+a n x n (a1, a2, a n : constant) or an exponential function (e.g., M Nx (M, N: numbers greater than 1)) Fig. 3 is a diagram schematically showing that the first curve portion 43A is expressed by a monotonically increasing function of the distance from the vertex T.

[0026] In the above XY coordinate system, the value (x) on the X-axis corresponds to the distance from the vertex T in the flow direction D1. Since the first curved portion 43A is expressed as a monotonically increasing function f(x) of x, in other words, the first curved portion 43A can be expressed as a monotonically increasing function of the distance from the vertex T. Furthermore, the value (f(x)) on the Y-axis corresponds to the distance between the first curved portion 43A and the central axis (i.e., the X-axis) of the lid member 43. Since the first curved portion 43A is expressed as a monotonically increasing function f(x) of the distance from the vertex T, the first curved portion 43A is positioned farther from the central axis of the lid member 43 as it approaches the bottom surface B (as the x value increases).

[0027] In this way, it becomes easier to design and manufacture the first curved portion 43A by expressing it as a monotonically increasing function of the distance x from the vertex T. Note that the second curved portion 43B and the third curved portion 43C may also have shapes expressed as a function of the distance x from the vertex T.

[0028] First curved portion 43A has a surface angled close to flow direction D1 on the side closer to intake port 13. Therefore, on the surface of first curved portion 43A closer to intake port 13, solid matter is not bounced back in the direction of intake port 13 and does not escape to the outside of vacuum pump 1.

[0029] On the other hand, the surface of the first curved portion 43A closer to the bottom surface B approaches an angle perpendicular to the flow direction D1, but is positioned away from the central axis of the cover member 43. Therefore, a large centrifugal force acts on the surface of the first curved portion 43A closer to the bottom surface B due to the rotation of the rotor 4. Due to this centrifugal force, solid matter that reaches the side of the first curved portion 43A closer to the bottom surface B is thrown in a direction nearly perpendicular to the flow direction D1. Therefore, even on the surface of the first curved portion 43A closer to the bottom surface B, solid matter is not bounced back toward the intake port 13 and does not leave the vacuum pump 1.

[0030] Second curved portion 43B is a curve connecting vertex T of cover member 43 and the upper end of first curved portion 43A. The portion of second curved portion 43B corresponding to vertex T has a small hemispherical shape. By making the portion corresponding to vertex T hemispherical shape, solid matter flowing in from air intake 13 can be prevented from bouncing back toward air intake 13, compared to when vertex T is pointed. The angle between the tangent to the portion of second curved portion 43B other than vertex T and flow direction D1 is small. Therefore, even in this portion of second curved portion 43B, solid matter is not bouncing back toward air intake 13 and does not exit vacuum pump 1.

[0031] As shown in FIG. 1, the portion of second curved portion 43B corresponding to vertex T protrudes from the upper end surface of rotor 4 facing intake port 13. This makes it possible to suppress turbulence in the flow of the gas to be exhausted at vertex T of cover member 43. That is, it becomes easier to generate a flow along the curved side surface of cover member 43, and solid matter can be moved along this flow. As a result, it is possible to suppress solid matter from being splashed in the direction of intake port 13 and exiting vacuum pump 1.

[0032] The third curved portion 43C is a curve that connects the lower end of the first curved portion 43A and the bottom surface B of the cover member 43. The tangent of the third curved portion 43C is at an angle nearly perpendicular to the flow direction D1, but is located away from the central axis of the cover member 43. Therefore, a large centrifugal force acts on the third curved portion 43C due to the rotation of the rotor 4. Due to this centrifugal force, solids that reach the third curved portion 43C are thrown in a direction nearly perpendicular to the flow direction D1. Therefore, even at the third curved portion 43C, solids are not bounced back toward the intake port 13 and do not exit the vacuum pump 1.

[0033] 1 and 2, bottom surface B of cover member 43 has a side parallel to flow direction D1. Therefore, the angle formed by the tangent to third curved portion 43C on the side closer to bottom surface B and flow direction D1 is smaller than the angle formed by the tangent to third curved portion 43C on the side closer to first curved portion 43A and flow direction D1.

[0034] Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the gist of the invention.

[0035] The vacuum pump 1 according to the above embodiment is a pump that integrates a turbomolecular pump composed of multiple stages of rotor blades 22 and multiple stages of stator blades 31, and a thread pump composed of a rotor cylindrical portion 23 and a stator cylindrical portion 32. However, the thread pump may be omitted. Alternatively, the rotor blades 22 and the stator blades 31 may be omitted, and the vacuum pump 1 may be composed only of a thread pump. In other words, the above-described cover member 43 can be applied to a vacuum pump composed only of a turbomolecular pump or a vacuum pump composed only of a thread pump.

[0036] In the above embodiment, the cover member 43 is attached onto the balance disc 42. However, this is not limiting, and the cover member 43 may be fixed directly to the recess 41 of the rotor 4 with screws or the like.

[0037] It will be appreciated by those skilled in the art that the exemplary embodiments described above are examples of the following aspects.

[0038] (First Aspect) A vacuum pump (e.g., vacuum pump 1) according to the first aspect 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 intake port (e.g., intake port 13). The rotor is housed in the housing and is driven to rotate, thereby drawing in and exhausting gas through the intake port. The rotor also has a recess (e.g., recess 41) facing the intake port. The cover member covers the recess in the rotor. In the above vacuum pump, the cover member has a cone shape with an apex (e.g., apex T) on the side closer to the intake port and a base (e.g., base B) on the side closer to the rotor. The generatrix of this cone shape includes a first curved portion (e.g., first curved portion 43A) having a curve in which the angle between a tangent to the generatrix and the gas flow direction increases from near the apex to near the base.

[0039] The cover member of the vacuum pump according to the first aspect has a conical shape with an apex closer to the intake port and a base closer to the rotor. The generatrix of this conical shape includes a first curved portion, in which the angle between the tangent of the generatrix and the gas flow direction increases from near the apex to near the base. A cover member with this shape has a surface closer to the intake port at an angle close to the gas flow direction. Therefore, solids on the surface closer to the intake port of the cover member do not bounce back toward the intake port and do not exit the vacuum pump. Meanwhile, the surface closer to the bottom of the cover member is angled closer to perpendicular 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 closer to the bottom of the cover member due to the rotation of the rotor. This centrifugal force causes solids on the side closer to the bottom of the cover member to fly in a direction nearly perpendicular to the gas flow. Therefore, even on the surface closer to the bottom of the cover member, solids do not bounce back toward the intake port and do not exit the vacuum pump.

[0040] (Second Aspect) In the vacuum pump according to the first aspect, the generatrix of the cone shape of the cover member may be configured with a first curved portion and a second curved portion (for example, second curved portion 43B) that is closer to the apex than the first curved portion. In the vacuum pump according to the second aspect, the apex of the cover member and the first curved portion can be continuously and smoothly connected.

[0041] (Third Aspect) In the vacuum pump according to the second aspect, the portion of the second curved portion corresponding to the apex of the cover member may have a hemispherical shape. In the vacuum pump according to the third aspect, solid matter flowing in through the intake port can be prevented from bouncing back toward the intake port, compared to when the apex of the cover member is sharp.

[0042] (Fourth Aspect) In the vacuum pump according to any one of the first to third aspects, the first curved portion may be expressed by a polynomial or exponential function that monotonically increases at least quadratically with respect to the distance from the apex of the lid member. In the vacuum pump according to the fourth aspect, the first curved portion can be expressed by a mathematical formula, which makes it easier to design and manufacture the lid member.

[0043] (Fifth Aspect) In the vacuum pump according to any one of the first to fourth aspects, the apex of the cover member may protrude from the surface of the rotor facing the intake port. In the vacuum pump according to the fifth aspect, turbulence of the gas flow at the apex of the cover member can be suppressed. That is, a flow along the curved side surface of the cover member is easily generated, and solid matter can be moved along this flow. As a result, solid matter can be prevented from being splashed toward the intake port and exiting the vacuum pump. [Explanation of symbols]

[0044] 1: Vacuum pump 2: Housing 3: Bass 4: Rotor 5: Stator 11: First end 12:Second end 13: Air intake 14: Base end 15: Exhaust port 21: Shaft 21A: Thrust disc 21B: Target 22: Rotor blade 23: Rotor cylindrical part 31: Stator blade 32: Stator cylindrical part 41: Dent 42: Balance disc 43: Lid member 43A: 1st curve part 43B: 2nd curve part 43C: 3rd curve part 44A, 44E: Bearings 44B~44D: Magnetic bearings 45: Motor 45A: Motor rotor 45B: Motor stator S1: 1st internal space S2: Exhaust space

Claims

1. a housing having an air intake; a rotor that is housed in the housing and that is rotationally driven to suck and exhaust gas through the intake port, the rotor having a recess in a portion facing the intake port; a cover member that covers the recess of the rotor; Equipped with the cover member has a cone shape with a vertex on a side closer to the intake port and a bottom on a side closer to the rotor, a generatrix of the cone shape including a first curved portion having a curve in which an angle formed between a tangent to the generatrix and the gas flow direction increases from near the apex to near the bottom surface.

2. 2. The vacuum pump according to claim 1, wherein the generatrix of the cone shape is formed by the first curved portion and a second curved portion that is closer to the apex than the first curved portion.

3. 3. The vacuum pump according to claim 2, wherein the portion of the second curved portion corresponding to the apex has a hemispherical shape.

4. 2. The vacuum pump according to claim 1, wherein the first curve portion is expressed by a polynomial or exponential function that monotonically increases at least two times with respect to the distance from the vertex.

5. 2. The vacuum pump according to claim 1, wherein the apex protrudes from a surface of the rotor facing the intake port.

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