vacuum pump

Abstract

To correct deviation of a gravity center position of a rotor from a rotation center.SOLUTION: A vacuum pump 1 includes a housing 2 and a rotor 4. The rotor 4 is arranged on an inner peripheral side of the housing 2 and is rotary driven and has a first cylindrical part 22, a wall part 23, and an opening 25. The first cylindrical part 22 extends in the direction of a rotation axis A1 of the rotor 4. The wall part 23 closes an end on an intake port 13 side of the first cylindrical part 22. The opening 25 is formed in the wall part 23 and communicates the intake port 13 side of the wall part 23 and an inner peripheral side of the first cylindrical part 22 with each other. A virtual gravity center position of the rotor when assuming that no opening 25 is formed is at a position deviated from the rotation center of the rotor 4. The opening 25 is formed so that the gravity center position of the rotor 4 moves from the virtual gravity center position in the direction of the rotation center.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] Some vacuum pumps include a rotor that is driven to rotate and a stator that cooperates with the rotor to exhaust gas. Some of these vacuum pumps are capable of exhausting gas guided into the space between the outer circumferential surface of the rotor and the inner circumferential surface of the stator, and also guide and exhaust gas into the space on the inner circumferential side of the rotor (see, for example, Patent Documents 1 and 2). Because these vacuum pumps can exhaust gas from both the outer circumferential side and the inner circumferential side of the rotor, they can exhaust gas at large flow rates. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5738869 [Patent Document 2] Patent No. 5763660 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above vacuum pump, a wall portion that closes the end of the rotor that is closest to the intake port of the vacuum pump has multiple pairs of openings. Gas drawn into the intake port of the vacuum pump passes through these openings and is guided into the space on the inner periphery of the rotor.

[0005] In conventional vacuum pumps capable of evacuating gas from the outer and inner sides of the rotor, a pair of openings is arranged in point symmetry with respect to the center of rotation of the rotor so that the center of gravity of the rotor does not shift when the openings are provided. However, depending on the rotor shape, components provided on the rotor, etc., the center of gravity of the rotor before the openings are provided may be located at a position offset from the center of rotation of the rotor. In this case, if the pair of openings are arranged in point symmetry with respect to the center of rotation of the rotor, the center of gravity of the rotor after the openings are provided will remain offset from the center of rotation, causing vibration and / or noise during operation of the vacuum pump. [Means for solving the problem]

[0006] A vacuum pump according to one aspect of the present invention draws in a gas to be pumped through an intake port and discharges it to the outside. The vacuum pump includes a housing and a rotor. The rotor is disposed on the inner periphery of the housing and driven to rotate, and has a first cylindrical portion, a wall portion, and an opening. The first cylindrical portion extends in the direction of the rotor's rotation axis. The wall portion closes the end of the first cylindrical portion on the intake port side. The opening is formed in the wall portion and connects the intake port side of the wall portion with the inner periphery of the first cylindrical portion. If the opening were not formed, the virtual center of gravity of the rotor would be located at a position offset from the center of rotation of the rotor. The opening is formed so that the center of gravity of the rotor moves from the virtual center of gravity toward the center of rotation. [Effects of the Invention]

[0007] In the vacuum pump according to one aspect of the present invention, the openings are formed so as to shift the virtual center of gravity of the rotor toward the center of rotation of the rotor. As a result, even if the center of gravity (virtual center of gravity) of the rotor is shifted from the center of rotation of the rotor when the openings are not formed, the center of gravity of the rotor is shifted to the center of rotation of the rotor by forming the openings. As a result, it is possible to reduce vibration and / or noise caused by the center of gravity of the rotor being shifted from the center of rotation of the rotor. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view of a vacuum pump according to an embodiment. [Figure 2] 10 is a diagram showing an example of conventional opening formation. [Figure 3] 10A and 10B are diagrams illustrating an example in which the center of gravity of the rotor is shifted to the center of rotation by making the sizes of a pair of circular openings different from each other. [Figure 4] 10A and 10B are diagrams illustrating an example in which the center of gravity of the rotor is shifted to the center of rotation by making the sizes of a pair of rectangular openings different. [Figure 5] 10A and 10B are diagrams illustrating an example of a case in which the center of gravity of a rotor is shifted to the center of rotation by making different sizes of a pair of slot-shaped openings. [Figure 6] 10 is a diagram showing an example of a case in which the center of gravity of the rotor is moved to the center of rotation by making the distance between one opening and the center of rotation different from the distance between the other opening and the center of rotation. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] A vacuum pump according to an embodiment will be described below with reference to the drawings. Fig. 1 is a cross-sectional view of the vacuum pump according to the embodiment. As shown in Fig. 1, the vacuum pump 1 includes a housing 2, a base 3, a rotor 4, and a stator.

[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 first end 11 is attached to an apparatus to be evacuated (not shown). The apparatus to be evacuated is, for example, a process chamber of a semiconductor manufacturing apparatus. 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 direction of the rotation axis A1 of the rotor 4. 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.

[0011] The rotor 4 includes a shaft 21. The shaft 21 extends in the extension direction of the rotation axis A1. The shaft 21 is rotatably housed in the base 3. The rotor 4 includes a first cylindrical portion 22, a wall portion 23, and a second cylindrical portion 24.

[0012] The first cylindrical portion 22 extends in the extension direction of the rotation axis A1. Of the ends of the first cylindrical portion 22, the end closer to the intake port 13 is closed by a wall portion 23. An opening 25 is provided in this wall portion 23. The opening 25 is formed to connect the intake port 13 side of the wall portion 23 with the inner peripheral side of the first cylindrical portion 22. In other words, the opening 25 connects the second internal space S2 on the outside of the first cylindrical portion 22 with the third internal space S3 on the inner peripheral side of the first cylindrical portion 22. The opening 25 can have any shape. For example, the opening 25 can be circular, rectangular, and / or elongated.

[0013] A first pump member 26 is provided on the inner peripheral side of the first cylindrical portion 22. The first pump member 26 (first stator cylindrical portion) is formed in a cylindrical shape and is fixed to the base 3 so as to face the inner peripheral surface of the first cylindrical portion 22 with a small gap between them. A spiral groove 26a is provided on the outer peripheral surface of the first pump member 26 facing the inner peripheral surface of the first cylindrical portion 22.

[0014] The second cylindrical portion 24 has a diameter smaller than the diameter of the first cylindrical portion 22. The second cylindrical portion 24 is connected to the wall portion 23 on the side opposite to the intake port 13. Multiple stages of rotor blades 27 are provided on the second cylindrical portion 24. The multiple stages of rotor blades 27 are each connected to the outer periphery of the second cylindrical portion 24. The multiple rotor blades 27 are arranged at intervals from one another in the extension direction of the rotation axis A1. Although not shown in the drawings, the multiple stages of rotor blades 27 each extend radially from the shaft 21 as the center. Note that in the drawings, only one of the multiple stages of rotor blades 27 is given a reference numeral, and the reference numerals of the other rotor blades 27 are omitted.

[0015] It is preferable that openings 25 are disposed between the lowest rotor blades 27 closest to wall portion 23. In other words, openings 25 are preferably disposed so that openings 25 can be seen when the lowest rotor blades 27 are viewed from the intake port 13 side. This prevents the lowest rotor blades 27 from obstructing the flow of the exhaust target gas into openings 25, allowing the exhaust target gas to flow into openings 25 efficiently.

[0016] The stator includes multiple stages of stator vanes 31, a spacer 5, the first pump member 26, and a second pump member 32. The multiple stages of stator vanes 31 are sandwiched between upper and lower spacers 5 and arranged on the inner surface of the housing 2. The multiple stages of stator vanes 31 are arranged at intervals in the extension direction of the rotation axis A1. The multiple stages of stator vanes 31 are respectively arranged between the multiple stages of rotor vanes 27. Although not shown, the multiple stages of stator vanes 31 each extend radially from the shaft 21 as a center. Note that in the drawings, only one of the multiple stages of stator vanes 31 is labeled with a reference numeral, and the reference numerals of the other stator vanes 31 are omitted. The second pump member 32 (second stator cylindrical portion) is formed in a cylindrical shape and is fixed to the base 3 so as to face the outer circumferential surface of the first cylindrical portion 22 with a small gap therebetween. The inner circumferential surface of the second pump member 32, which faces the outer circumferential surface of the first cylindrical portion 22, is provided with a spiral groove 32a.

[0017] As shown in Fig. 1, a fourth internal space S4 is formed further downstream of the exhaust downstream ends of the first cylindrical portion 22, the first pump member 26, and the second pump member 32. The fourth internal space S4 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 fourth internal space S4 in the extension direction of the rotation axis A1. The exhaust downstream direction refers to the direction toward the fourth internal space S4.

[0018] The vacuum pump 1 includes a plurality of bearings 41A to 41E and a motor 42. The plurality of bearings 41A to 41E are attached to the base 3 at positions where the shaft 21 is housed. The plurality of bearings 41A to 41E rotatably support the rotor 4. The bearings 41A and 41E are, for example, ball bearings. Meanwhile, the other bearings 41B to 41D are, for example, magnetic bearings. However, the plurality of bearings 41B to 41D may be other types of bearings, such as ball bearings. The vacuum pump 1 also includes displacement sensors 43A and 43B. The displacement sensors 43A and 43B measure the radial displacement of the shaft 21.

[0019] The motor 42 drives the rotor 4 to rotate. The motor 42 includes a motor rotor 42A and a motor stator 42B. The motor rotor 42A is attached to the shaft 21. The motor stator 42B is attached to the base 3. The motor stator 42B is disposed opposite the motor rotor 42A.

[0020] In the vacuum pump 1, the multiple stages of rotor vanes 27 and the multiple stages of stator vanes 31 provided on the second cylindrical portion 24 constitute a turbomolecular pump section. The inner circumferential surface of the first cylindrical portion 22 and the first pump member 26, and the outer circumferential surface of the first cylindrical portion 22 and the second pump member 32 constitute a thread groove pump section. In the vacuum pump 1, the motor 42 rotates the rotor 4, causing the gas to be pumped to flow from the intake port 13 into the first internal space S1. The gas to be pumped in the first internal space S1 is guided by the turbomolecular pump section to the second internal space S2. The gas to be pumped guided to the second internal space S2 is then guided to the fourth internal space S4 by the thread groove pump section formed by the outer circumferential surface of the first cylindrical portion 22 and the second pump member 32.

[0021] In addition, the gas to be exhausted that has been introduced into the second internal space S2 passes through the opening 25 and is introduced into the third internal space S3 on the inner periphery side of the first cylindrical portion 22. The gas to be exhausted that has been introduced into the third internal space S3 is introduced into the fourth internal space S4 by a thread groove pump section formed by the inner circumferential surface of the first cylindrical portion 22 and the first pump member 26. That is, the gas to be exhausted that has been introduced into the second internal space S2 is introduced into the fourth internal space S4 by a thread groove pump section formed by the outer circumferential surface of the first cylindrical portion 22 and the second pump member 32, and a thread groove pump section formed by the inner circumferential surface of the first cylindrical portion 22 and the first pump member 26. The gas to be exhausted in the fourth internal space S4 is exhausted from the exhaust port 15. As a result, the inside of the device to be exhausted that is attached to the intake port 13 is brought into a high vacuum state.

[0022] As described above, in the vacuum pump 1, the gas to be pumped is guided from the intake port 13 to the second internal space S2 by the turbomolecular pump unit, is guided to the fourth internal space S4 by the two thread groove pump units, and is exhausted to the outside from the exhaust port 15. In this way, the gas to be pumped can be exhausted by the two thread groove pump units, so the vacuum pump 1 can exhaust a large flow rate of the gas to be pumped.

[0023] In the vacuum pump 1 having the above configuration, an opening 25 is provided in the wall portion 23 of the rotor 4 to guide the gas to be exhausted toward the inner periphery of the first cylindrical portion 22. In a conventional vacuum pump, as shown in FIG. 2, the opening 25 is configured as a pair of openings 25a', 25b', and multiple openings 25 (i.e., multiple pairs of openings 25a', 25b') are arranged at equal intervals along the circumferential direction of the first cylindrical portion 22. As shown in FIG. 2, the pair of openings 25a', 25b' are arranged symmetrically with respect to the center of rotation (rotation axis A1) of the rotor 4, and have the same shape and size. In this way, when a pair of openings of the same shape and size are arranged symmetrically with respect to the center of rotation of the rotor 4, the center of gravity of the rotor does not change before and after the formation of the opening 25. FIG. 2 shows an example of the formation of conventional openings.

[0024] On the other hand, depending on the shape of the rotor 4, the components provided on the rotor 4, and the like, the center of gravity of the rotor 4 (hereinafter referred to as the virtual center of gravity) that would occur if the opening 25 were not formed may be located at a position offset from the center of rotation of the rotor 4. For example, in order to achieve sufficient pumping performance in the turbomolecular pump section, the rotor blades 27 do not necessarily have a point-symmetric shape. Furthermore, it is not always possible to arrange multiple rotor blades 27 point-symmetrically with respect to the center of rotation of the rotor 4. Thus, for example, when the shape or arrangement of the rotor blades 27 cannot be point-symmetric, the virtual center of gravity is usually located at a position slightly offset in the radial direction of the rotor 4 from the center of rotation of the rotor 4. If the virtual center of gravity is located at a position offset from the center of rotation of the rotor 4, the vacuum pump 1 generates vibrations and / or noise during operation.

[0025] Therefore, in the vacuum pump 1 according to this embodiment, when the virtual center of gravity is located at a position displaced from the center of rotation of the rotor 4, the opening 25 is formed so that the center of gravity of the rotor 4 moves from the virtual center of gravity toward the center of rotation of the rotor 4. A specific method for moving the center of gravity of the rotor 4 toward the center of rotation of the rotor 4 will be described below. The method for moving the center of gravity of the rotor will be described below by taking as an example a case where the opening 25 is formed by a pair of openings 25a, 25b that are arranged on either side of the center of rotation of the rotor 4 on a straight line L (FIGS. 3 to 5) that passes through the center of rotation of the rotor 4.

[0026] The center of gravity of the rotor 4 can be shifted by differentiating the sizes of a pair of openings 25a, 25b included in any of the openings 25. For example, as shown in FIGS. 3 to 5, the size of the opening 25a, 25b that is closer to the virtual center of gravity can be made larger than the size of the opening 25a, 25b that is farther from the virtual center of gravity. This shifts the center of gravity of the rotor 4 toward the center of rotation of the rotor 4. FIG. 3 illustrates an example of shifting the center of gravity of the rotor toward the center of rotation by differentiating the sizes of a pair of circular openings. FIG. 4 illustrates an example of shifting the center of gravity of the rotor toward the center of rotation by differentiating the sizes of a pair of rectangular openings. FIG. 5 illustrates an example of shifting the center of gravity of the rotor toward the center of rotation by differentiating the sizes of a pair of elongated openings.

[0027] By enlarging the opening on the side closer to the virtual center of gravity, the weight reduction of the rotor 4 on the side closer to the virtual center of gravity becomes greater than the weight reduction of the rotor 4 on the side farther from the virtual center of gravity. As a result, the center of gravity of the rotor 4 can be moved from the virtual center of gravity toward the center of rotation of the rotor 4.

[0028] When the pair of openings 25a, 25b are circular, for example, as shown in FIG. 3, the radius R1 of the opening of the pair of openings 25a, 25b closer to the virtual center of gravity position (opening 25a in FIG. 3) is made larger than the radius R2 of the opening farther from the virtual center of gravity position (opening 25b in FIG. 3).

[0029] When the pair of openings 25a, 25b is rectangular, for example, as shown in FIG. 4, the length a1 of one side of the opening (opening 25a in FIG. 4) closer to the virtual center of gravity and the length b1 of the side perpendicular to the side a1 are set larger than the lengths a2, b2 of the corresponding side of the opening (opening 25b in FIG. 4) farther from the virtual center of gravity. Note that when openings 25a, 25b are rectangular, the size of the pair of openings 25a, 25b can also be made different from each other by making the length of one side of the opening closer to the virtual center of gravity longer than the length of the corresponding side of the opening farther from the virtual center of gravity. In other words, the pair of openings 25a, 25b do not need to be similar to each other.

[0030] When the pair of openings 25a, 25b are shaped like elongated holes, for example, as shown in FIG. 5, the radius r1 of the semicircle at the end of the opening (opening 25a in FIG. 5) closer to the virtual center of gravity of the pair of openings 25a, 25b and the length c1 of the side connecting the two semicircles are set larger than the radius r2 of the semicircle at the end of the opening (opening 25b in FIG. 5) farther from the virtual center of gravity and the length c2 of the side connecting the two semicircles, respectively. Note that when openings 25a, 25b are shaped like elongated holes, only the radius r1 of the semicircle at the end of the opening closer to the virtual center of gravity may be set larger than the radius r2 of the semicircle at the end of the opening farther from the virtual center of gravity, or only the length c1 of the side connecting the two semicircles of the opening closer to the virtual center of gravity may be set larger than the length c2 of the side connecting the two semicircles of the opening farther from the virtual center of gravity. In other words, the pair of openings 25a, 25b do not need to be similar to each other.

[0031] The position of the center of gravity of the rotor 4 can be moved by making the distance between one opening included in any of the openings 25 and the center of rotation of the rotor 4 different from the distance between the other opening and the center of rotation of the rotor 4. For example, as shown in Fig. 6, of a pair of openings 25a, 25b of the same size, a distance D1 between the opening (opening 25a in Fig. 6) located closer to the virtual center of gravity and the center of rotation of the rotor 4 is made larger than a distance D2 between the opening (opening 25b in Fig. 6) located farther from the virtual center of gravity and the center of rotation of the rotor 4. Fig. 6 is a diagram showing an example of a case where the center of gravity of the rotor is moved to the center of rotation by making the distance between one opening and the center of rotation different from the distance between the other opening and the center of rotation.

[0032] By shifting the formation positions of the pair of openings 25a, 25b as described above, the position of the center of gravity of the rotor 4 can be moved in the direction of the center of rotation of the rotor 4 from the virtual center of gravity position.

[0033] Although FIG. 6 shows an example in which the pair of openings 25a, 25b are circular, even if the pair of openings 25a, 25b are rectangular or slot-shaped, the center of gravity of rotor 4 can be moved in the same manner as described above by making the distance between one opening and the center of rotation different from the distance between the other opening and the center of rotation.

[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] In the above embodiment, four pairs of openings 25a, 25b are provided in the wall portion 23 of the rotor 4. However, this is not limited to this, and any number of openings 25a, 25b can be formed. For example, only one pair of openings 25a, 25b arranged on a line L passing through the center of rotation of the rotor 4 may be provided, or two or three pairs of openings 25a, 25b may be provided. Furthermore, four or more pairs of openings 25a, 25b may be provided.

[0036] Alternatively, the opening 25 may be configured as an odd number of openings. For example, the opening 25 may be configured as a single opening, or 2n-1 (n: an integer of 2 or more) openings may be arranged at the vertices of a (2n-1)-sided polygon defined on the wall 23 to form the opening 25.

[0037] When the opening 25 is a pair of openings 25a, 25b, it is possible to combine the sizes of the pair of openings 25a, 25b with the distance between one opening and the center of rotation of the rotor 4 and the distance between the other opening and the center of rotation of the rotor 4.

[0038] In the above embodiment, the two pairs of openings 25a, 25b are different in size and / or have different distances to the center of rotation of the rotor 4. However, this is not limiting, and the number of pairs of openings 25a, 25b that are different in size and / or have different distances to the center of rotation of the rotor 4 can be any number determined depending on the position of the virtual center of gravity on the wall portion 23, etc.

[0039] When the opening 25 is a pair of openings 25a, 25b, the openings 25a, 25b may have different shapes and different sizes.

[0040] The vacuum pump 1 according to the above embodiment is a pump in which a turbomolecular pump section formed by multiple stages of rotor blades 27 and multiple stages of stator blades 31 provided on the second cylindrical portion 24 is integrated with a thread groove pump section formed by the first cylindrical portion 22, the first pump member 26, and the second pump member 32. However, this is not limiting, and the turbomolecular pump section may be omitted. In other words, the vacuum pump 1 may be a thread groove pump.

[0041] In the above embodiment, the first pump member 26 is provided with the spiral groove 26a, and the second pump member 32 is provided with the spiral groove 32a, but this is not limited to this. Spiral grooves may be formed on the outer and inner peripheral sides of the first cylindrical portion 22. Furthermore, the first pump member 26 and the second pump member 32 do not necessarily have to be provided with spiral grooves.

[0042] It will be appreciated by those skilled in the art that the exemplary embodiments described above are examples of the following aspects.

[0043] (First aspect) A vacuum pump sucks gas to be evacuated through an intake port and discharges it to the outside. The vacuum pump includes a housing and a rotor. The rotor is disposed on the inner periphery of the housing and is driven to rotate, and has a first cylindrical portion, a wall portion, and an opening. The first cylindrical portion extends in the direction of the rotor's rotation axis. The wall portion closes the end of the first cylindrical portion on the intake port side. The opening is formed in the wall portion and connects the intake port side of the wall portion with the inner periphery of the first cylindrical portion. If the opening were not formed, the virtual center of gravity of the rotor would be located at a position offset from the center of rotation of the rotor. The opening is formed so that the center of gravity of the rotor moves from the virtual center of gravity toward the center of rotation.

[0044] In the vacuum pump according to the first aspect, the openings are formed so as to shift the virtual center of gravity of the rotor toward the center of rotation of the rotor. As a result, even if the center of gravity (virtual center of gravity) of the rotor is located at a position displaced from the center of rotation of the rotor when the openings are not formed, by forming the openings, the center of gravity of the rotor is positioned at the center of rotation of the rotor. As a result, it is possible to reduce vibration and / or noise caused by the center of gravity of the rotor being displaced from the center of rotation of the rotor.

[0045] (Second Aspect) In the vacuum pump according to the first aspect, the opening may include a pair of openings arranged on a line passing through the center of rotation of the rotor, sandwiching the center of rotation of the rotor. In this case, the size of the opening closer to the virtual center of gravity may be larger than the size of the other opening. In the vacuum pump according to the second aspect, by enlarging the opening closer to the virtual center of gravity, the weight loss of the rotor closer to the virtual center of gravity is greater than the weight loss of the rotor farther from the virtual center of gravity. As a result, the center of gravity of the rotor can be moved from the virtual center of gravity toward the center of rotation of the rotor.

[0046] (Third Aspect) In the vacuum pump according to the first or second aspect, the opening may include a pair of openings arranged on a line passing through the center of rotation of the rotor, with the center of rotation of the rotor being sandwiched between them. In this case, the distance between the opening located closer to the virtual center of gravity and the center of rotation of the rotor may be greater than the distance between the other opening and the center of rotation of the rotor. In the vacuum pump according to the third aspect, by shifting the positions of the pair of openings, the center of gravity of the rotor can be moved from the virtual center of gravity toward the center of rotation of the rotor.

[0047] (Fourth Aspect) In the vacuum pump according to any one of the first to third aspects, the opening may be circular. In the vacuum pump according to the fourth aspect, the opening can be formed by a simple process.

[0048] (Fifth Aspect) In the vacuum pump according to any one of the first to third aspects, the opening may be rectangular. In the vacuum pump according to the fifth aspect, the opening can be formed by easy processing.

[0049] (Sixth Aspect) In the vacuum pump according to any one of the first to third aspects, the opening may be in the shape of an elongated hole. In the vacuum pump according to the sixth aspect, the opening can be formed by easy processing.

[0050] (Seventh Aspect) The vacuum pump according to any one of the first to sixth aspects may further include a first pump member. The first pump member is disposed opposite the inner circumferential surface of the first cylindrical portion, and as the first cylindrical portion rotates, the gas to be exhausted that has been guided to the inner circumferential side of the first cylindrical portion is discharged to the outside. In the vacuum pump according to the seventh aspect, the gas to be exhausted that has been guided to the inner circumferential side of the first cylindrical portion by the opening can be exhausted to the outside by the pump section constituted by the inner circumferential surface of the first cylindrical portion and the first pump member.

[0051] (Eighth Aspect) The vacuum pump according to any one of the first to seventh aspects may further include a second pump member. The second pump member is disposed opposite the outer circumferential surface of the first cylindrical portion, and as the first cylindrical portion rotates, the gas to be exhausted that has been guided to the outer circumferential side of the first cylindrical portion is exhausted to the outside. In the vacuum pump according to the eighth aspect, the gas to be exhausted that has been guided to the outer circumferential side of the first cylindrical portion can be exhausted to the outside by a pump section constituted by the outer circumferential surface of the first cylindrical portion and the second pump member.

[0052] (Ninth Aspect) In the vacuum pump according to any one of the first to eighth aspects, the rotor may have a second cylindrical portion. The second cylindrical portion is connected to the wall portion and has a diameter smaller than that of the first cylindrical portion. In this case, the vacuum pump may further include rotor blades and stator blades. The rotor blades are arranged on the outer periphery of the second cylindrical portion. The stator blades are arranged in positions facing the rotor blades. In the vacuum pump according to the ninth aspect, the turbomolecular pump portion constituted by the rotor blades and stator blades arranged on the second cylindrical portion can guide the gas to be exhausted toward the first cylindrical portion.

[0053] (Tenth Aspect) In the vacuum pump according to the ninth aspect, the openings may be disposed between rotor blades disposed closest to the wall. In the vacuum pump according to the tenth aspect, the rotor blades disposed closest to the wall do not obstruct the flow of the gas to be exhausted into the openings, so that the gas to be exhausted can be efficiently flowed into the openings. [Explanation of symbols]

[0054] 1. Vacuum pump 2. Housing 3. Bass 4 rotors 5 spacers 11 First end 12 Second end 13 Air intake 14 Base end 15 exhaust port 21 Shaft 22 First cylindrical section 23 Wall 24 Second cylindrical section 25 Opening 25a, 25a', 25b, 25b' opening 26 First pump member 26a Spiral groove 27 rotor blades 31 Stator blade 32 second pump member 32a Spiral groove 41A~41E bearings 42 Motor 42A motor rotor 42B Motor Stator 43A, 43B Displacement Sensor A1 rotation axis S1 1st internal space S2 2nd internal space S3 3rd internal space S4 4th internal space

Claims

1. A vacuum pump that sucks in a gas to be exhausted through an intake port and exhausts it to the outside, Housing and a rotor disposed on the inner circumferential side of the housing and driven to rotate; Equipped with The rotor is a first cylindrical portion extending in a direction of a rotation axis of the rotor; a wall portion that closes the end of the first cylindrical portion on the intake port side; an opening formed in the wall portion, the opening communicating an intake port side of the wall portion with an inner peripheral side of the first cylindrical portion; and a virtual center of gravity of the rotor when the opening is not formed is located at a position shifted from a center of rotation of the rotor; the opening is formed so that the center of gravity of the rotor moves from the virtual center of gravity toward the center of rotation. Vacuum pump.

2. the opening portion includes a pair of openings arranged on a line passing through the rotation center so as to sandwich the rotation center, 2. The vacuum pump according to claim 1, wherein the size of the opening located closer to the virtual center of gravity is made larger than the size of the other opening.

3. the opening portion includes a pair of openings arranged on a line passing through the rotation center so as to sandwich the rotation center, 2. The vacuum pump according to claim 1, wherein the distance between the opening located closer to the virtual center of gravity and the center of rotation is set larger than the distance between the other opening and the center of rotation.

4. 4. The vacuum pump according to claim 1, wherein the opening is circular.

5. 4. The vacuum pump according to claim 1, wherein the opening is rectangular.

6. 4. The vacuum pump according to claim 1, wherein the opening is an elongated hole.

7. 7. The vacuum pump according to claim 1, further comprising a first pump member disposed opposite an inner peripheral surface of the first cylindrical portion, the first pump member discharging the gas to be exhausted, which has been guided to the inner peripheral side of the first cylindrical portion, to the outside as the first cylindrical portion rotates.

8. 8. The vacuum pump according to claim 1, further comprising a second pump member disposed opposite an outer peripheral surface of the first cylindrical portion, and configured to discharge the gas to be exhausted, which has been guided to the outer peripheral side of the first cylindrical portion, to the outside as the first cylindrical portion rotates.

9. the rotor has a second cylindrical portion connected to the wall portion and having a diameter smaller than the diameter of the first cylindrical portion; The vacuum pump is rotor blades arranged on an outer periphery of the second cylindrical portion; a stator blade disposed opposite the rotor blade; The vacuum pump according to any one of claims 1 to 8, further comprising:

10. 10. The vacuum pump of claim 9, wherein the opening is located between rotor blades located closest to the wall portion.

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