JPH102294A - Fitting structure of stator to base in turbo-molecular pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To securely fix the core of a stator to a base by making a ring-shaped spacer to be tightly fitted to the circumferential surface thereof within the elastic region with a material whose linear expansion coefficient is nearly equal to that of the base, so that the amount of tight fit is nearly constant in any temperature region. SOLUTION: Ring-shaped first and second stators 2, 4 are provided to the ring-shaped base 5 made of aluminum in a turbo-molecular pump. The respective stators 2, 4 are made up by winding coils 10, 11 to ring-shaped iron cores 7, 8 respectively, and both the stators 2, 4 are arranged at a prescribed interval with regard to the rotor 1. Further, a ring-shaped spacer 6 is tightly fitted to the inner circumferential surface 5A of the ring-shaped base 5 within the elastic region by means of shrinage fit or the like, and the spacer 6 is also made of aluminum so that the linear expansion coefficient thereof is made equal to that of the base 5. The respective cores 7, 8 of the stators 2, 4 are fixed to the spacer 6, and the rotor 1 is turned around its axis by producing the rotational magnetic fields to the respective coils 10, 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mounting structure of a stator to a base in a turbo-molecular pump for evacuating a vacuum chamber or the like.

[0002]

2. Description of the Related Art Conventionally, as a structure for mounting a stator to a base in a turbo-molecular pump, there is one shown in FIG. In this turbo molecular pump, gas and moisture are suctioned from a vacuum chamber (not shown) connected to the suction port 112 and discharged from the discharge port 113 by the stator blade 110 and the rotor blade 106 which rotate relatively.

[0003] The rotor blades 106 and the cylinder 105 are made of the same material, and are fixed to the shaft 103 using fastening members. Also, the stator blade 110 is
Is fixed to the base 107 made of aluminum. An annular iron core 115 of the stator 102 is shrink-fitted and fixed to the inner peripheral surface of the base 107.

[0004] The linear expansion coefficient of aluminum is larger than that of iron. For this reason, as shown in the characteristic curve of FIG. 2, if the core 115 is prevented from coming off the base 107 even at the upper limit of the pump operating temperature range R,
In the normal temperature region (X), the base 107 reaches the plastic deformation region beyond the elastic deformation region. Then, there is a problem that the creep or the like is likely to occur and the contact between the stator 102 and the shaft 103 or the damage of the bearing is apt to occur, thus lowering the reliability.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a base stator capable of securely fixing the stator core to the base over the entire pump operating temperature range without causing plastic deformation of the base. An object of the present invention is to provide a mounting structure.

[0006]

In order to achieve the above object, the structure for mounting the stator to the base in the turbo-molecular pump according to the first aspect of the present invention comprises an annular base and a material having a coefficient of linear expansion substantially equal to that of the base. It is characterized by comprising an annular spacer manufactured and fitted around an annular base in an elastic region, and a stator having a core fixed to an axial end face of the spacer by fastening means.

According to the first aspect of the present invention, the annular spacer tightly fitted within the elastic region on the peripheral surface of the annular base is made of a material having a linear expansion coefficient substantially equal to that of the base. As shown by the characteristic curve in FIG. 2, the amount of tightening is substantially constant and in the elastic range in any temperature range. The stator core is fixed to the end face of the spacer by fastening means. Therefore, according to the present invention, it is possible to securely fix the core of the stator to the base without causing creep or the like without causing plastic deformation of the base over the entire pump operation region. Therefore, reliability and safety can be improved. Further, since the tightening amount can be made substantially constant as described above, the tightening amount due to shrink fit can be minimized, and the shrink fitting temperature can be reduced to improve work safety.

According to a second aspect of the present invention, in the turbo molecular pump according to the first aspect, the stator has a core made of a material having a smaller linear expansion coefficient than the base and the spacer. It is characterized by having.

According to the second aspect of the present invention, the linear expansion coefficient of the core of the stator is smaller than the linear expansion coefficient of the base and the spacer. Therefore, even when the stator and the spacer are arranged on the inner peripheral surface of the base and the core of the stator is fitted to the base in the elastic region, the temperature rises. Sometimes the core does not plastically deform the base. Further, in this case, the radial positional accuracy of the stator can be ensured by fitting the core to the base in the elastic region. Therefore, it is not necessary to machine the inner peripheral surface of the stator core in order to secure the radial positional accuracy of the stator after assembly.

According to a fourth aspect of the present invention, in the second aspect of the invention, the stator and the spacer are arranged on the inner peripheral surface of the base, and the core of the stator is loosely fitted to the base. In this case, after the clearance fit, the stator may be finished with a cylindrical grinder or the like. Therefore, it is not necessary to increase the dimensional accuracy of the stator core as a single component before assembly.

According to a fifth aspect of the present invention, in the second aspect, the stator and the spacer are arranged on the outer peripheral surface of the base, and the core of the stator is loosely fitted to the base. In this case, since the stator is on the outer peripheral surface of the base, finishing of the stator is facilitated.

According to a sixth aspect of the present invention, there is provided a turbo molecular pump according to the first aspect, wherein the stator has a core made of a material having a linear expansion coefficient substantially equal to that of the base and the spacer. It is characterized by having.

According to the present invention, the linear expansion coefficient of the stator core is substantially equal to the linear expansion coefficient of the base and the spacer. Therefore, even when the stator and the spacer are arranged on the inner peripheral surface of the base and the core of the stator is tightly fitted to the base in the elastic region as described in claim 7, the base of the base at the time of temperature rise can be formed. Does not cause plastic deformation. Further, in this case, the radial position accuracy of the stator can be ensured by tight fitting of the core to the base in the elastic region. Therefore, it is not necessary to machine the inner peripheral surface of the stator core in order to secure the radial positional accuracy of the stator after assembly.

According to an eighth aspect of the present invention, in the sixth aspect, the stator and the spacer are arranged on the inner peripheral surface of the base, and the core of the stator is loosely fitted to the base.
In this case, after the clearance fit, the stator may be finished with a cylindrical grinder or the like. Therefore, it is not necessary to increase the dimensional accuracy of the stator core as a single component before assembly.

According to a ninth aspect of the present invention, in the sixth aspect of the present invention, the stator and the spacer are disposed on the outer peripheral surface of the base, and the core of the stator is tightly fitted to the base in an elastic region. In this case, the radial position accuracy of the stator can be ensured by tight fitting of the core to the base in the elastic region.

According to a tenth aspect of the present invention, in the sixth aspect, the stator and the spacer are arranged on the outer peripheral surface of the base, and the core of the stator is loosely fitted in the base. In this case, since the stator is on the outer peripheral surface of the base, finishing of the stator is facilitated.

According to an eleventh aspect of the present invention, in the turbo molecular pump according to the first aspect, the stator has a core made of a material having a larger linear expansion coefficient than the base and the stator. It is characterized by having.

According to the eleventh aspect, the coefficient of linear expansion of the core of the stator is larger than the coefficient of linear expansion of the base and the spacer. Therefore, when the stator and the spacer are arranged on the inner peripheral surface of the base as described in claim 12, if the core of the stator is loosely fitted to the base, the core is not slid when the temperature rises. Is not plastically deformed.

According to a twelfth aspect of the present invention, in the eleventh aspect, the stator and the spacer are arranged on the inner peripheral surface of the base, and the core of the stator is loosely fitted to the base.
In this case, after the clearance fit, the stator may be finished with a cylindrical grinder or the like. Therefore, it is not necessary to increase the dimensional accuracy of the stator core as a single component before assembly.

According to the invention of claim 13, the stator and the spacer are arranged on the outer peripheral surface of the base, and the core of the stator is tightly fitted to the base in the elastic region. In this case,
By tightly fitting the stator to the base in the elastic range, the radial positional accuracy of the stator can be ensured. Therefore, there is no need to machine the peripheral surface of the stator core in order to ensure the radial positional accuracy of the stator after assembly.

Further, in the invention of claim 14, the stator and the spacer are arranged on the outer peripheral surface of the base, and the core of the stator is loosely fitted on the base. In this case, after the clearance fit, the stator may be finished with a cylindrical grinder or the like. Since the stator is on the outer peripheral surface of the base, the finishing of the stator is facilitated.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

FIG. 1 shows an embodiment of a structure for mounting a stator to a base in a turbo-molecular pump according to the present invention. This turbo molecular pump has the same structure as the conventional turbo molecular pump shown in FIG. 5 except for the portion shown in FIG. This embodiment includes an annular base 5 made of aluminum and annular first and second stators 2 and 4. The first stator 2 has an annular iron core 7 and a coil 10. The second stator 4 has an annular iron core 8 and a coil 11. The first stator 2 and the second stator 4 are separated from the rotor 1 by a predetermined gap.

The annular spacer 6 is fitted in the elastic area on the inner peripheral surface 5A of the annular base 5 by snap fit. This annular spacer 6 is made of aluminum similarly to the base 5. Therefore, the linear expansion coefficient of the base 5 and the linear expansion coefficient of the spacer 6 are equal.

The core 7 of the first stator 2 is
The spacer 6 is fastened to the spacer 6 by a bolt 14 which is inserted into a through hole 7A drilled in the core 7 and screwed into a screw hole 12 of the spacer 6 in a state of being in close contact with one axial end face 6A of the spacer 6. ing. Further, the core 7 is tightly fitted to the peripheral surface 5A of the base 5 in an elastic range. More specifically, as shown in the characteristic curve of FIG. 2, the core 7 is tightly fitted in the elastic region with respect to the base 5 in the normal temperature region.

On the other hand, the core 8 of the second stator 4 is inserted into a through hole 8A formed in the core 8 in a state in which the core 8 is in close contact with the other axial end face 6B of the spacer 6, and It is fastened to the spacer 6 by a bolt 15 screwed into the hole 13. The core 8 is loosely fitted to the peripheral surface 5A of the base 5. More specifically, as shown in the characteristic curve of FIG. 2, the core 8 has a loose fit with respect to the base 5 in a normal temperature range.

According to the structure for mounting the stator to the base in the turbo-molecular pump having the above configuration, the stator 2,
The coils 10 and 11 wound around the cores 7 and 8 of 4 generate a rotating magnetic field, thereby rotating the rotor 1 around its axis, and relatively rotating a rotor blade and a stator blade (not shown) to perform vacuum evacuation. .

Here, in this mounting structure, the annular spacer 6 fitted in the inner peripheral surface 5A of the annular base 5 in the elastic range is made of the same material as the base 5 and has a linear expansion coefficient. Since they are equal, the amount of tightening is constant in any temperature range and within the elastic range as shown by the characteristic curve in FIG. The first stator 2 and the second stator 4 are fixed to the end faces 6A and 6B of the spacer 6 with bolts 14 and 15. Therefore, according to this mounting structure, the cores 7 and 8 of the stator 2 are interposed via the spacers 6 without causing plastic deformation of the base 5 over the entire pump operation region R as shown in FIG. It can be securely fixed without causing creep or the like. Therefore, reliability and safety can be improved. Also,
Since the tightening amount can be made constant as described above, the tightening amount due to shrink fit can be minimized, and the shrink fit temperature can be reduced to improve work safety.

In this mounting structure, the core 7 of the first stator 2 is fitted on the peripheral surface 5A of the base 5 in an elastic region. By the tight fit of the core 7 to the base 5, the positional accuracy of the first stator 2 in the radial direction can be ensured. Therefore, it is not necessary to machine the inner peripheral surface 7B of the core 7 of the first stator 2 in order to secure the radial positional accuracy of the first stator 2 after assembly.

In this mounting structure, the core 8 of the second stator 4 is loosely fitted on the inner peripheral surface 5A of the base 5. Therefore, according to this mounting structure, after the core 8 of the second stator 4 is loosely fitted to the base 5 and assembled, the inner peripheral surface 8B of the core 8 may be finished with a cylindrical grinder or the like. Therefore, it is not necessary to increase the dimensional accuracy of the core 8 as a single component before assembly.

In this embodiment, the base 5 and the spacer 6 are made of the same aluminum. However, the base 5 and the spacer 6 need not always be made of the same material, and materials having substantially equal linear expansion coefficients are used. With base 5 and spacer 6
It is only necessary that these are manufactured.

In the above embodiment, as shown in FIG. 1, the base 5 and the stators 2 and 4 are provided around the rotor 1.
And the inner peripheral surface 5 of the base 5
A, the spacer 6 and the stators 2 and 4 are arranged.
As shown in the figure, the base 65, the spacer 6, the stators 2, 4
Outer rotor type in which the rotor 61 is disposed around the periphery. In FIG. 4, reference numerals 41 and 42 denote cores 7 and 8.
Target.

In the above embodiment, the stator 2
Since the core of No. 4 was the iron cores 7 and 8, the linear expansion coefficient of the core was smaller than the linear expansion coefficients of the base 5 and the spacer 6. In this case, in the outer rotor type shown in FIG. 4, the cores 7, 8 are loosely fitted on the outer peripheral surface 65B of the base 65 to prevent plastic deformation of the cores 7, 8 due to expansion of the base 65 and the spacer 6.

Further, the linear expansion coefficients of the cores 7, 8 of the stators 2, 4 may be larger than the linear expansion coefficients of the base 5 and the spacer 6. In this case, in the inner rotor type as shown in FIG. 3, both the cores 7 and 8 are loosely fitted to the inner peripheral surface 55A of the base 55 to prevent plastic deformation of the base 55 due to expansion of the cores 7 and 8. To prevent. In FIG. 3, reference numerals 31 and 32 denote targets facing the cores 7 and 8, respectively. In the outer rotor type as shown in FIG. 4, even when the linear expansion coefficients of the cores 7 and 8 are larger than the linear expansion coefficients of the base 55 and the spacer 6, the cores 7 and 8 are fixed to the outer peripheral surface 65B of the base 65. May be fitted in the elastic region.

The linear expansion coefficients of the cores 7, 8 of the stators 2, 4 may be made equal to the linear expansion coefficients of the base 5 and the spacer 6. In this case, in both the inner rotor type and the outer rotor type, the cores 7 and 8 are connected to the base 5.
May be tightly fitted or tightly fitted.

In this embodiment, the bolts 14 and 15 are used as fastening means, but pins or caulking, welding, brazing, or bonding may be used as fastening means. In the above-described embodiment, the core 7 for the magnetic bearing and the core 8 for the motor are fastened to both ends of the spacer 6. However, when a plurality of radial magnetic bearings are provided in the axial direction, these cores are used. It may be configured to be fastened to both ends of the spacer 6.

[0037]

As is clear from the above, the mounting structure of the stator to the base in the turbo-molecular pump according to the first aspect of the present invention is made of an annular base and a material having a linear expansion coefficient substantially equal to that of the base. An annular spacer fitted around the annular base in an elastic region, and a stator having a core fixed to an axial end surface of the spacer by fastening means.

According to the first aspect of the present invention, the annular spacer fitted on the peripheral surface of the annular base within the elastic region is made of a material having a linear expansion coefficient substantially equal to that of the base. As shown by the characteristic curve in FIG. 2, the tightening amount is substantially constant and in the elastic range in any temperature range. The stator core is fixed to the end face of the spacer by fastening means. Therefore, according to the present invention, it is possible to securely fix the core of the stator to the base without causing creep or the like without causing plastic deformation of the base over the entire pump operation region. Therefore, reliability and safety can be improved. In addition, since the tightening amount can be made substantially constant as described above, the tightening amount due to shrink fit can be minimized, and the shrink fit temperature can be reduced to improve work safety.

According to a second aspect of the present invention, in the turbo molecular pump according to the first aspect, the stator has a core made of a material having a smaller linear expansion coefficient than the base and the spacer. Have.

According to the second aspect of the present invention, the linear expansion coefficient of the core of the stator is smaller than the linear expansion coefficients of the base and the spacer. Therefore, even when the stator and the spacer are arranged on the inner peripheral surface of the base and the core of the stator is fitted to the base in the elastic region, the temperature rises. Sometimes the core does not plastically deform the base. Further, in this case, the radial positional accuracy of the stator can be ensured by fitting the core to the base in the elastic region. Therefore, it is not necessary to machine the inner peripheral surface of the stator core in order to secure the radial positional accuracy of the stator after assembly.

According to a fourth aspect of the present invention, in the second aspect of the present invention, the stator and the spacer are arranged on the inner peripheral surface of the base, and the stator core is loosely fitted to the base. In this case, after the clearance fit, the stator may be finished with a cylindrical grinder or the like. Therefore, it is not necessary to increase the dimensional accuracy of the stator core as a single component before assembly.

According to a fifth aspect of the present invention, in the second aspect of the present invention, when the stator and the spacer are arranged on the outer peripheral surface of the base and the core of the stator is loosely fitted on the base, the stator is formed. Since it is on the outer peripheral surface of the base, the finishing of the stator is facilitated.

According to a sixth aspect of the present invention, in the turbo molecular pump according to the first aspect, in the mounting structure of the stator to the base, the stator has a core made of a material having a linear expansion coefficient substantially equal to that of the base and the spacer. It is characterized by having.

According to the sixth aspect of the invention, the coefficient of linear expansion of the core of the stator is substantially equal to the coefficient of linear expansion of the base and the spacer. Therefore, even when the stator and the spacer are arranged on the inner peripheral surface of the base and the core of the stator is tightly fitted in the elastic region as described in claim 7, the base at the time of temperature rise can be improved. Does not lead to plastic deformation. Further, in this case, the radial positional accuracy of the stator can be ensured by fitting the core to the base in the elastic region. Therefore, it is not necessary to machine the inner peripheral surface of the stator core in order to secure the radial positional accuracy of the stator after assembly.

According to an eighth aspect of the present invention, in the sixth aspect of the present invention, the stator and the spacer are arranged on the inner peripheral surface of the base, and the core of the stator is loosely fitted to the base.
In this case, after the clearance fit, the stator may be finished with a cylindrical grinder or the like. Therefore, it is not necessary to increase the dimensional accuracy of the stator core as a single component before assembly.

According to a ninth aspect of the present invention, in the sixth aspect of the present invention, when the stator and the spacer are arranged on the outer peripheral surface of the base, and the core of the stator is fitted in the base in an elastic region, By fitting the core to the base in the elastic region, the radial positional accuracy of the stator can be ensured.

According to a tenth aspect of the present invention, in the sixth aspect, the stator and the spacer are arranged on the outer peripheral surface of the base, and the core of the stator is loosely fitted to the base. In this case, since the stator is on the outer peripheral surface of the base, finishing of the stator is facilitated.

According to an eleventh aspect of the present invention, there is provided the turbo-molecular pump according to the first aspect, wherein the stator has a core made of a material having a larger linear expansion coefficient than the base and the stator. It is characterized by having.

According to the eleventh aspect, the linear expansion coefficient of the stator core is larger than the linear expansion coefficients of the base and the spacer. Therefore, when the stator and the spacer are arranged on the inner peripheral surface of the base as described in claim 12, if the core of the stator is loosely fitted to the base, the core is not slid when the temperature rises. Is not plastically deformed.

According to a twelfth aspect of the present invention, in the eleventh aspect, the stator and the spacer are arranged on the inner peripheral surface of the base, and the core of the stator is loosely fitted to the base.
In this case, after the clearance fit, the stator may be finished with a cylindrical grinder or the like. Therefore, it is not necessary to increase the dimensional accuracy of the stator core as a single component before assembly.

Further, according to the invention of claim 13, when the stator and the spacer are arranged on the outer peripheral surface of the base and the core of the stator is fitted in the elastic region on the base, the stator is attached to the base. The radial position accuracy of the stator can be ensured by the interference fit in the elastic region. Therefore, there is no need to machine the peripheral surface of the stator core in order to ensure the radial positional accuracy of the stator after assembly.

In the invention of claim 14, the stator and the spacer are arranged on the outer peripheral surface of the base, and the stator core is loosely fitted on the base. In this case, after the clearance fit, the stator may be finished with a cylindrical grinder or the like. Since the stator is on the outer peripheral surface of the base, the finishing of the stator is facilitated.

[Brief description of the drawings]

FIG. 1 is a partial sectional view showing an embodiment of a mounting structure of a stator to a base in a turbo-molecular pump of the present invention.

FIG. 2 is a characteristic diagram showing a temperature change of a snap fit in the above embodiment and a conventional example.

FIG. 3 is a sectional view of a main part of a modification of the inner rotor type of the embodiment.

FIG. 4 is a sectional view of a main part of a modified example of the outer rotor type of the embodiment.

FIG. 5 is a cross-sectional view showing the whole of a conventional turbo-molecular pump.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... rotor, 2 ... 1st stator, 3 ... shaft part, 4 ... 2nd stator, 5 ... base, 5A ... peripheral surface, 6 ... spacer, 7 ...
Core, 7A: through hole, 7B: peripheral surface, 8: core, 8A: through hole, 8B: peripheral surface, 10, 11: coil, 12, 13: screw hole, 14, 15: bolt.

Claims (14)

[Claims] An annular base (5) is made of a material having a coefficient of linear expansion substantially equal to that of the base (5).
An annular spacer (6) tightly fitted in the elastic region around (5) and a core (7) fixed to the axial end surfaces (6A, 6B) of the spacer (6) by fastening means (14, 15). And a stator having a stator (2, 4) having a stator (8, 8). 2. The turbo-molecular pump according to claim 1, wherein the stator is attached to the base. The core is made of a material having a smaller linear expansion coefficient than the base and the spacer. Stator (2, 4) having
A structure for mounting a stator to a base in a turbo-molecular pump, comprising: 3. The turbo-molecular pump according to claim 2, wherein the stator (2, 4) and the spacer (6) are arranged on an inner peripheral surface of the base (5), and the stator ( 2) A structure for mounting a stator to a base in a turbo-molecular pump, wherein the core (7) is tightly fitted in the base (5) in an elastic range. 4. The turbo-molecular pump according to claim 2, wherein the stator (2, 4) and the spacer (6) are arranged on an inner peripheral surface of the base (5), and the stator ( (4) The mounting structure of the stator to the base in the turbo-molecular pump, wherein the core (8) is loosely fitted in the base (5). 5. The mounting structure of a turbo molecular pump according to claim 2, wherein the stator (2, 4) and the spacer (6) are arranged on an outer peripheral surface of the base (65). , 4) wherein the cores (7, 8) are loosely fitted in the base (5). 6. The turbo-molecular pump according to claim 1, wherein the core is formed of a material having a linear expansion coefficient substantially equal to that of the base (5) and the spacer (6). (2, 4)
A structure for mounting a stator to a base in a turbo-molecular pump, comprising: 7. The mounting structure of a turbo molecular pump according to claim 6, wherein the stator (2, 4) and the spacer (6) are arranged on the inner peripheral surface of the base (5), and the stator ( 2) A structure for mounting a stator to a base in a turbo-molecular pump, wherein the core (7) is tightly fitted in the base (5) in an elastic range. 8. The mounting structure of a turbo molecular pump according to claim 6, wherein the stator (2, 4) and the spacer (6) are connected to the base (5, 5).
The core (7,8) of the stator (2,4)
Is a mounting structure of the stator to the base in the turbo-molecular pump, which is loosely fitted in the base (5, 55). 9. The turbo-molecular pump according to claim 6, wherein the stator (2, 4) and the spacer (6) are arranged on an outer peripheral surface of the base (65). , 4) The mounting structure of the stator to the base in the turbo-molecular pump, wherein the cores (7, 8) are tightly fitted in the base in an elastic range. 10. The turbo-molecular pump according to claim 6, wherein the stator (2, 4) and the spacer (6) are arranged on the outer peripheral surface of the base (65). , 4) wherein the cores (7, 8) are loosely fitted in the base (65). 11. The structure for mounting a stator to a base in a turbo-molecular pump according to claim 1, wherein the cores (7, 8) made of a material having a linear expansion coefficient larger than that of the base (5) and the stator (6). Stator (2, 4) having
A structure for mounting a stator to a base in a turbo-molecular pump, comprising: 12. The turbo-molecular pump according to claim 11, wherein the stator (2, 4) and the spacer (6) are connected to the base (5, 5).
The core (7,8) of the stator (2,4)
Is a mounting structure of the stator to the base in the turbo-molecular pump, which is loosely fitted in the base (5, 55). 13. The turbo-molecular pump according to claim 11, wherein the stator (2, 4) and the spacer (6) are arranged on the outer peripheral surface of the base (65). , 4) wherein the cores (7, 8) are fitted in the base (65) in an elastic region. 14. The turbo-molecular pump according to claim 11, wherein the stator (2, 4) and the spacer (6) are arranged on an outer peripheral surface of the base (65). , 4) wherein the cores (7, 8) are loosely fitted in the base (65).