JP7435874B2 - Vacuum pump - Google Patents

Description

The present invention relates to a vacuum pump whose rotor is supported by rolling bearings.

2. Description of the Related Art Conventionally, vacuum pumps are known in which a rotating shaft of a rotor is supported by a grease-lubricated rolling bearing. Such vacuum pumps have a problem in that vibrations occur due to whirling caused by the unbalance of the rotor, and the vibrations are transmitted to the outside of the pump. For example, in a turbo molecular pump described in Patent Document 1, a rolling bearing is elastically supported by an elastic member to damp vibrations.

The turbo molecular pump described in Patent Document 1 includes a rolling bearing that supports a rotor, a holding part that elastically holds an outer ring of the rolling bearing, and a grease filling part between the outer ring and the holding part that is filled with grease. We are prepared.

Japanese Patent Application Publication No. 2016-56750

In the turbomolecular pump described in Patent Document 1, if the grease is not filled appropriately, the temperature control of the rotating body becomes insufficient, and the generated vibrations cannot be appropriately suppressed. Adjusting the amount of grease to be filled is a complicated manufacturing process.

A vacuum pump according to a preferred embodiment of the present invention includes a rolling bearing that supports a rotating body, and an elastic holding device that elastically supports an outer ring of the rolling bearing with an elastic member. The elastic holding device is provided on the outer peripheral side of the outer ring and includes a lubricant filling portion filled with lubricant and a cavity communicating with the lubricant filling portion.

According to the present invention, desired cooling function and vibration suppressing function can be achieved without going through complicated manufacturing processes.

FIG. 1 is a sectional view showing a schematic configuration of an embodiment in which the present invention is applied to a turbo-molecular pump. FIG. 2 is an enlarged view showing in detail the configuration of an embodiment of the elastic holding device. FIG. 3 is an enlarged view showing in detail the configuration of Modified Example 1 of the elastic holding device. FIG. 4 is an enlarged view showing in detail the configuration of Modification 2 of the elastic holding device. FIG. 5 is an enlarged view showing in detail the configuration of Modified Example 3 of the elastic holding device. FIG. 6 is an enlarged view showing in detail the configuration of Modified Example 4 of the elastic holding device.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
(Overall configuration of turbo molecular pump)
FIG. 1 is a diagram showing one embodiment of a vacuum pump according to the present invention, and is a sectional view of a turbo-molecular pump 100. The turbomolecular pump 100 houses a rotating body such as a rotor 3 in a casing made up of a base 2 and a casing 10. An intake port 10a is provided at the upper end of the casing 10, and an exhaust port 2a is provided at the base 2.
The rotor 3 is fastened to a shaft 1, and the shaft 1 is rotationally driven by a motor 4. The upper part of the shaft 1 to which the rotor 3 is fastened is rotatably supported by a permanent magnet bearing device PB, and the lower part by a rolling bearing device BB. The rotor 3 is provided with a rotary blade 30 and a cylindrical portion 31 as an exhaust function section. A fixed blade 20 as a fixed side exhaust function section is provided corresponding to the rotary blade 30. The rotary blade 30 and the fixed blade 20 constitute a turbo pump section. Corresponding to the cylindrical portion 31, a fixed cylinder 21 is provided as a fixed side exhaust function section. This cylindrical portion 31 and the fixed cylinder 21 constitute a Holweck pump portion (thread groove pump portion).
In such a turbo-molecular pump 100, the inside of the vacuum chamber is evacuated by evacuating the gas in the vacuum chamber (not shown) sucked in from the intake port 10a to the exhaust port 2a by the rotation of the rotating body.

(Permanent magnet bearing device PB)
The permanent magnet bearing device PB is a magnetic bearing using permanent magnets 6 and 7, and the cylindrical permanent magnet 6 is fixed to the rotor 3. On the other hand, the permanent magnet 7 on the fixed side is held by a magnet holder 11 and is arranged to face the inner circumferential side of the permanent magnet 6. A bearing holder 13 that holds the rolling bearing 9 is fixed to the center of the magnet holder 11 . The rolling bearing 9 is provided to limit the runout of the upper side of the shaft 1 in the radial direction, and a gap is formed between the inner ring of the rolling bearing 9 and the shaft 1. The size of this gap is set smaller than the size of the gap between the permanent magnets 6 and 7. This prevents the permanent magnets 6 and 7 from coming into contact with each other when the whirling of the rotor 3 becomes large.

(Rolling bearing device BB)
FIG. 2 is an enlarged view showing the configuration of the rolling bearing device BB in detail.
The rolling bearing device BB includes a rolling bearing 40 and an elastic holding device 50 that elastically holds the outer ring 42 of the rolling bearing 40.
The rolling bearing 40 has an inner ring 41 and an outer ring 42 provided on the outer periphery of the inner ring 41 via balls. The inner ring 41 is fixed to the shaft 1 with a nut 61. The outer ring 42 is elastically supported by the base 2 by an elastic holding device 50, as shown in FIG.

(Elastic holding device 50)
The elastic holding device 50 includes a bearing housing 51 fixed to the base 2, and a plurality of elastic members 52a, 52b, 52c (hereinafter also represented by the representative symbol 52) that elastically holds the outer ring 42 of the rolling bearing 40 with the bearing housing 51. A cup-shaped collar 53 that accommodates the lower outer peripheral edge of the outer ring 42, a grease filling part 56, a grease escape part 57, and at least grease GR filled in the grease filling part 56.

The bearing housing 51 has a lower cylindrical portion 51L and an upper cylindrical portion 51U. The lower cylindrical portion 51L is fixed to a lid 2b provided on the bottom surface of the base 2, as shown in FIG. Inside the upper cylindrical portion 51U and the lower cylindrical portion 51L, an elastic member 52 that elastically holds the outer ring 42, grease GR, and the like are held.

A ring-shaped elastic member 52a is provided between the upper surface 42a of the outer ring 42 and the inner peripheral surface 51ina of the bearing housing 51. A ring-shaped elastic member 52b is provided between a lower surface 53a of a cup-shaped collar 53 that accommodates the lower peripheral edge of the outer ring 42 and an upper surface 54a of a housing nut 54, which will be described later. A ring-shaped elastic member 52c is provided between the outer peripheral surface 42out of the outer ring 42 and the inner peripheral surface 51inc of the bearing housing 51. These three elastic members 52 elastically support the outer ring 42 on the bearing housing 51 in the radial direction and the thrust direction. That is, the shaft 1 is elastically supported in both the radial direction and the thrust direction by the elastic holding device 50.

A female thread 51S is provided on the inner peripheral surface of the lower cylindrical portion 51L of the bearing housing 51, and a ring-shaped housing nut 54 having a male thread 54S on the outer peripheral surface is screwed into the female thread 51S of the bearing housing 51. The elastic member 52 and the collar 53 are fixed within the bearing housing 51 by a housing nut 54. An O-ring 55 is provided between the upper peripheral edge of the housing nut 54 and the inner peripheral surface of the bearing housing 51 to prevent leakage of the grease GR.
The elastic members 52a and 52b and the O-ring 55 are compressed and deformed by being pressed by the tightening force of the housing nut 54.

The elastic members 52a and 52b mainly support the outer ring 42 in the axial direction (thrust support), and have very low rigidity against displacement of the outer ring 42 in the radial direction. Further, the elastic member 52c is an elastic member provided for radial support of the outer ring 42.

The elastic member 52c is compressed and deformed by the radial displacement of the shaft 1. Therefore, for example, when the shaft 1 is at the center position (ideal position where the radial displacement is zero), the gap between the outer circumferential surface of the elastic member 52c and the inner circumferential surface 51inc of the bearing housing 51 is almost zero or there is a slight gap. (<G1, G2), the radial support rigidity by the elastic member 52c can be made very small.

By arranging the elastic members 52a, 52b, and 52c in this manner, the radial support rigidity caused by the elastic members 52a, 52b, and 52c can be made extremely small, and the rotor whirling in the radial direction is The resulting pump vibration can be suppressed.

(Grease filling part 56)
The elastic holding device 50 has a space 56 surrounded by the inner circumferential surface 51ind of the bearing housing 51, the outer circumferential surface 53out of the collar 53, the upper surface 54a of the housing nut 54, the elastic members 52b, 52C, and the O-ring 55. It is filled with grease (lubricant) GR. This space is called a grease filling section 56. While the grease GR has a function of cooling the rolling bearing 40 (cooling function), it also has a property of transmitting vibrations of the outer ring 42 to the bearing housing 51 (vibration transmittance). Vibration transmissibility is expressed in terms of vibration transmissibility, and when the vibration transmissibility is high, even a slight unbalance of the rotating body increases the vibration of the pump.

The radial clearance dimension G1 between the inner circumferential surface 51inb of the upper cylindrical portion 51U of the bearing housing 51 and the outer circumferential surface 42out of the outer ring 42 is such that even when the shaft 1 swings around, the outer circumferential surface 42out of the outer ring 42 and the bearing housing The dimensions are set such that the outer ring 42 does not come into contact with the inner circumferential surface 51inb of the outer ring 51, that is, the outer ring 42 is elastically supported by the elastic member 52c. Similarly, the radial clearance dimension G2 between the outer circumferential surface 53 out of the collar 53 and the inner circumferential surface 51 inc of the bearing housing 51 is such that even when the shaft 1 swings, The dimensions are set such that the outer ring 42 does not come into contact with the peripheral surface 51 inc, that is, the outer ring 42 is elastically supported by the elastic member 52c. The radial gap dimensions G1 and G2 are set, for example, to about 0.1 mm to 0.3 mm. Since the gap between the outer circumferential surface 53out of the collar 53 and the inner circumferential surface 51ind of the bearing housing 51 is filled with grease GR, G2>G1 in the embodiment.
Note that the gap size G1 is the gap size above the elastic member 52c, and the gap size G2 is the gap size below the elastic member 52c.

(Grease escape part 57)
Although the grease filling portion 56 is filled with a certain amount of grease GR, the cooling function may be low or the vibration transmission rate may be high. This is because if the volume of the grease filling part 56 varies due to dimensional tolerances of pump components and assembly tolerances such as screw tightening force during assembly, even if a certain amount of grease is filled into the grease filling part 56. It can be assumed that this is because the grease filling rate varies. The grease filling rate is a value obtained by dividing the volume of grease filled into the grease filling portion 56 by the volume of the grease filling portion 56.
Therefore, in the embodiment, a grease relief part 57 that communicates with the grease filling part 56 is provided in the bearing housing 51. Specifically, the grease escape portion 57 is a groove extending radially outward from the inner circumferential surfaces 51 inb, 51 inc of the bearing housing 51 and having a ring shape in plan view and having a predetermined thickness. The function of the grease escape portion 57 will be described later.

The volume of the grease filling portion 56 has a ± tolerance due to dimensional tolerances of parts, assembly tolerances, and the like. When the grease filling amount is set to an amount equivalent to the ideal volume (intermediate value) of the grease filling section 56 calculated as a design value, if the actual volume of the grease filling section 56 is larger than the intermediate value, the grease filling amount is A space is created within the portion 56 that is not filled with grease. Further, if the actual volume of the grease filling portion 56 is smaller than the ideal value, in the conventional structure without the grease escape portion 57, the grease filling portion 56 is filled with grease in a compressed state, making it easy to vibrate. If a space is not filled with grease in the grease filling portion 56, or if it is filled with an excessive amount of grease, the cooling function and vibration transmission properties cannot be satisfied.
This can be explained by the following influence coefficient.

(Influence coefficient)
The influence coefficient can be expressed as cv=av/bv, which is the vibration acceleration av of the pump divided by the unbalance bv of the rotating body. Here, av, bv, and cv are vector quantities.
The grease filling rate of the grease filling portion 56 influences the influence coefficient cv. As the grease filling rate increases, the density of the grease increases, the temperature transfer rate from the rolling bearing 40 to the bearing housing 51 increases, and the temperature of a rotating body such as the rotor 3 tends to decrease. On the other hand, the vibration transmission rate from the rotating body to the bearing housing 51, that is, the base 2, also increases, and the pump becomes more likely to vibrate in response to the unbalanced amount of the rotating body constituted by the rotor 3 and the like. Therefore, the amount of grease filled (injected) into the bearing housing 51 needs to be controlled in a fixed amount using a syringe or the like.

The space volume of the grease filling portion 56 changes depending on the dimensional tolerance of each component such as the bearing housing 51, the elastic member 52, or the O-ring, assembly errors, and the degree of crushing of the elastic member 52 or the O-ring 55. It is difficult to maintain a constant grease filling rate for each turbomolecular pump by managing these dimensions and adjusting the amount of grease filling. Further, since the grease filling rate varies from turbo-molecular pump to turbo-molecular pump, the influence coefficient changes from turbo-molecular pump to turbo-molecular pump. If the influence coefficient differs for each turbomolecular pump, it is necessary to calibrate each turbomolecular pump when correcting the balance. However, if the influence coefficients of different turbomolecular pumps are the same, there is no need to calibrate each turbomolecular pump every time. Calibration refers to calculating the influence coefficient from changes in vibration by placing a test weight on the correction surface of a rotating body. The balance is corrected by finding the amount of correction from the influence coefficient obtained during calibration and the vibration vector before correction.

As shown in FIG. 2, a relief portion 57 communicating with the grease filling portion 56 is provided, and the grease filling portion 56 is filled with an amount of grease equivalent to the designed maximum volume Qmax of the grease filling portion 56, for example. When the actual volume Qact of the grease filling part 56 is smaller than the designed maximum volume Qmin, excess grease corresponding to Qmax-Qact flows from the grease filling part 56 to the escape part 57, but the grease filling part 56 is not filled with grease. It will be done. Furthermore, even when the actual volume Qact of the grease filling portion 56 is the designed maximum volume Qmax, the grease filling portion 56 is filled with grease. Thereby, even if the actual volume of the grease filling portion 56 is the designed minimum volume or the maximum volume, the grease filling rate that influences the influence coefficient can be kept constant.

Note that the grease used should have a sufficiently hard consistency. This does not flow due to vibrations during pump operation, the influence of the posture, or the influence of temperature rise within the pump specification range, and when the elastic member 52 of the elastic retainer 50 is tightened with the housing nut during assembly, the grease is compressed before it is compressed. This is to ensure that the surplus is pushed out to the relief portion 57.

The turbo molecular pump 100 of the embodiment described above has the following effects.
(1) The grease filling rate can be kept constant regardless of manufacturing tolerances and assembly tolerances of pump components (regardless of individual differences in pumps). Thereby, the vibration suppression function and cooling function by the grease can be guaranteed in any turbo molecular pump 100 without affecting the influence coefficient.
Additionally, calibration work for each vacuum pump is no longer necessary, reducing man-hours.
(2) Since the grease escape portion 57 is provided within the bearing housing 51, which is the largest component among the components of the elastic holding device 50, processing of the grease escape portion 57 is easy.

(3) The grease escape portion 57 is provided to extend in the radial direction within the bearing housing 51. The pump rotates at a high speed of tens of thousands of revolutions, and a large proportion of the pump vibration is generated in the radial direction from the bearing outer ring 42 to the grease. Therefore, the grease on the radially outer side of the bearing outer ring 42 has a large influence on vibration transmission, and by providing the grease escape portion 57 nearby, the vibration transmission rate can be stabilized and the influence coefficient can be kept constant.

(4) The grease filling amount is set to be smaller than (designed maximum volume Qmax of grease filling part 56 + designed volume Qabs of relief part 57) and greater than (designed maximum volume Qmax of grease filling part 56). Therefore, the grease filling rate can be maintained constant regardless of various tolerances. Therefore, it is only necessary to control the amount of grease filled during manufacturing or maintenance, and manufacturing management is easy.

The grease escape portion 57 can be provided as in the following Modifications 1 to 4.
(Modifications 1 and 2)
As shown in FIGS. 3 and 4, grease relief portions 57a and 57b may be provided within the housing nut 54 so as to extend in the direction of the rotation axis. In the example shown in FIG. 3, the grease escape portion 57a is a cylindrical groove provided at the outermost peripheral portion of the grease filling portion 56, that is, at a location in contact with the O-ring 55. In FIG. 4, a grease relief part 57b is provided at a position of the same radius as the grease filling part 56 between the collar 53 and the bearing housing 51 among the grease filling part 56 formed on the upper surface of the housing nut 54. This relief portion 57b is also a cylindrical groove.
Modifications 1 and 2 can provide the same effects as the embodiment.
In this modification, the filled grease easily escapes into the cylindrical grooves 57a, 57b, and by keeping the grease filling rate at a small value, the heat dissipation effect is reduced, but the vibration reduction effect can be aimed at.

(Modifications 3 and 4)
As shown in FIGS. 5 and 6, grease relief portions 57c and 57d may be provided within the collar 53. In FIG. 5, a grease relief portion 57c is communicated with a grease filling portion 56 formed on the upper surface of the housing nut 54 and extends in the direction of the rotation axis. The grease escape portion 57c in FIG. 5 is a cylindrical groove extending in the direction of the rotation axis. In FIG. 6, a grease relief portion 57d is communicated with a grease filling portion 56 formed between the collar 53 and the bearing housing 51 and extends in the radial direction. The grease escape portion 57d in FIG. 6 is an annular ring groove that is annular in plan view and has a predetermined thickness. In the example of FIG. 6, the grease vibration transmissibility can be stabilized and the influence coefficient can be kept constant as in the embodiment.

(Modification 5)
In the turbo molecular pumps of the embodiment and modifications 1 to 4, the grease filling portion 56 is provided at least between the outer circumferential surface 53out of the collar 53 that accommodates the outer ring 42 and the inner circumferential surface 51ind of the bearing housing 51. There is. The grease filling portion 56 may be provided between the outer circumferential surface 42 out of the outer ring 42 and the inner circumferential surface 51 inb of the bearing housing 51 . For example, the gap having the dimension G1 explained in FIG. 2 may be used as the grease filling portion.

(Modification 6)
In the turbomolecular pumps of the embodiment and modifications 1 to 4, one grease escape part 57 is provided, but two or more grease filling parts 57 may be provided in the same member or in different members.

(Modification 7)
In the turbo molecular pumps of the embodiment and modifications 1 to 4, the elastic members 52a and 52b are provided on the upper and lower end surfaces of the outer ring 42, but only one of them may be provided.

(Other embodiments)
In the embodiments and modifications 1 to 4, the present invention is applied to a turbo-molecular pump, but the present invention is not limited to a turbo-molecular pump having a turbo pump section and a Holweck pump section in the exhaust function section; It can also be applied to vacuum pumps equipped with drag pumps, vacuum pumps equipped only with drag pumps such as Siegbahn pumps and Holweck pumps, or vacuum pumps that combine them.

Note that each of the embodiments described above may be used alone or in combination. This is because the effects of each embodiment can be achieved independently or in combination. Further, the present invention is not limited to the above embodiments in any way as long as the characteristics of the present invention are not impaired.

A first aspect of the vacuum pump includes a rolling bearing that supports a rotating body, and an elastic holding device that elastically supports an outer ring of the rolling bearing with an elastic member, wherein the elastic holding device is provided on the outer peripheral side of the outer ring. It has a lubricant filling part filled with lubricant and a cavity communicating with the lubricant filling part.
Even if the volume of the grease filling portion varies due to component tolerances, assembly tolerances, etc., the grease filling rate can be kept at a constant value.
The vacuum pump of the second aspect is the vacuum pump of the first aspect, in which the cavity is formed to extend in the radial direction of the component of the elastic holding device.
Since the space is provided in a relatively large member of the elastic holding device, it is easy to make the space, and the volume can be set relatively large.
In the vacuum pump of the third aspect, in the vacuum pump of the first aspect or the second aspect, the elastic holding device includes a cylindrical bearing housing disposed on the outer circumferential side of the outer ring, and an elastic member placed inside the bearing housing. The hollow space is formed as a radially extending annular groove in the bearing housing near the lubricant filling portion on the radially outer side of the bearing outer ring.
Since the space is provided in a relatively large member of the elastic holding device, it is easy to make the space, and the volume can be set relatively large. Further, since the relief portion is provided in the vicinity of the lubricant filling portion within the bearing housing, the density of the lubricant is stabilized, the vibration transmission rate is stabilized, and the influence coefficient can be kept constant.
In the vacuum pump of the fourth aspect, in the vacuum pump of the first aspect or the second aspect, the elastic holding device includes a cylindrical bearing housing disposed on the outer circumferential side of the outer ring and an elastic member inside the bearing housing. The housing has a housing fixing member that is fixed by the housing fixing member, and the cavity is formed as a cylindrical groove extending in the direction of the rotation axis within the housing fixing member.
In the vacuum pump of the fifth aspect, in the vacuum pump of any one of the first to fourth aspects, the filling amount of the lubricant is smaller than the sum of the volume of the lubricant filling part and the volume of the cavity, The amount is greater than the volume of the lubricant filling section. By setting the filling amount in this manner, the grease filling portion can be reliably filled with grease.

DESCRIPTION OF SYMBOLS 1... Shaft, 2... Base, 3... Rotor, 6, 7... Permanent magnet, 8, 9... Rolling bearing, 40... Rolling bearing, 41... Inner ring, 42... Outer ring, 43... Collar, 50... Elastic holding device, 51 ...Bearing housing, 52a, 52b, 52c...Elastic member, 53...Collar, 54...Housing nut, 55...O ring, 56...Grease filling part, 57...Grease escape part (vacancy), 100...Turbo molecular pump, PB ...Permanent magnet bearing device, BB...Rolling bearing device

Claims (2)

A rolling bearing that supports a rotating body,
an elastic holding device that elastically supports the outer ring of the rolling bearing with an elastic member,
The elastic holding device includes:
a cylindrical bearing housing disposed on the outer peripheral side of the outer ring;
a lubricant filling part provided on the outer peripheral side of the outer ring and filled with lubricant;
a lubricant escape part communicating with the lubricant filling part,
The lubricant escape part is formed as a radially extending annular groove having a predetermined thickness in the vicinity of the lubricant filling part on the radially outer side of the bearing outer ring in the bearing housing. pump. A rolling bearing that supports a rotating body,
an elastic holding device that elastically supports the outer ring of the rolling bearing with an elastic member,
The elastic holding device includes:
a cylindrical bearing housing disposed on the outer peripheral side of the outer ring;
a lubricant filling part provided on the outer peripheral side of the outer ring and filled with lubricant;
a lubricant escape part communicating with the lubricant filling part;
a housing fixing member that fixes the elastic member within the bearing housing;
The lubricant filling part is formed on the upper surface of the housing fixing member,
In the vacuum pump, the lubricant escape part is formed as a cylindrical groove extending downward from the lubricant filling part in the rotation axis direction within the housing fixing member.

Images