JP2002221178A - Shaft sealing structure in vacuum pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure favourable sealing performance in a vacuum pump using fluorine contained oil. SOLUTION: Rubber made lip rings 50, 51 are arranged on peripheral surfaces 192, 202 of rotating shaft 19, 20 between radial bearings 37, 38 and rotors 27, 32. Leakage preventive projected lines 52, 53 are provided on sliding parts 501, 502 of the rubber made lip rings 50, 51. The leakage preventive projected lines 52, 53 energize the fluorine contained oil between the peripheral surfaces 192, 202 of the rotating shaft 19, 20 and the sliding parts 501, 511 to the side of a gear storage chamber 331 from the side of a pump chamber 43 in accordance with the rotation of the rotating shaft 19, 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shaft sealing structure in a vacuum pump which moves a gas transfer member in a pump chamber based on rotation of a rotary shaft and transfers gas by the operation of the gas transfer member to provide a suction effect. Things.

[0002]

2. Description of the Related Art A rotary shaft seal disclosed in Japanese Patent Application Laid-Open Nos. 7-317912 and 7-317913 includes a main seal element and a sub-seal element. The main seal element is arranged on the fluid storage chamber side, and the sub seal element is arranged on the air side. The main seal element prevents fluid leakage from the fluid storage chamber at a predetermined pressure to the air side. The sub-sealing element works so that fluctuations in air-side pressure that vary from below atmospheric pressure to above atmospheric pressure do not affect the main sealing element.

[0003] The main sealing element is made of synthetic resin,
The secondary sealing element is made of synthetic resin or rubber. As a synthetic resin to be used as a material of the seal element, a fluorine-based resin (for example, polytetrafluoroethylene) having a small sliding resistance, which is advantageous for preventing abrasion, is exclusively used.

The rotating shaft seal disclosed in Japanese Patent Application Laid-Open No. Hei 6-300142 comprises a first seal element made of rubber and a second seal element made of a fluororesin. First
The seal element is arranged on the fluid storage chamber side, and the second seal element is arranged on the air side. A spiral cut groove is formed in the second seal element. The spiral cut groove sends back the fluid that is about to leak from the fluid storage chamber side to the low pressure side to the fluid storage chamber side.

A vacuum pump which moves a gas transfer body in a pump chamber based on the rotation of a rotating shaft and transfers a gas by the operation of the gas transfer body to provide a suction action is disclosed in, for example, JP-A-2-157490 and JP-A-Hei. No. 6,101,674. In the case of such a vacuum pump,
The air side and the low pressure side are a pump chamber, and the fluid storage chamber is a housing that houses a gear mechanism for rotating a plurality of rotating shafts in synchronization.

[0006]

The sealing element is
Oil for lubricating the parts of the vacuum pump that require lubrication, such as the gear mechanism, bearings that rotatably support the rotary shaft, etc. (generally resistant to process gas and high energy radiation, non-flammable, non-contaminated) Fluorine oil having excellent properties, etc.) is prevented from leaking to the pump chamber side. However, the inventor of the present application has found that when the oil used for the vacuum pump is a fluorine oil, the sealing performance of the seal element having a cut groove made of a fluorine-based resin is significantly reduced. . That is, it has been found that the use of the second seal element made of a fluorine-based resin having a cut groove is not very useful.

[0007] It is an object of the present invention to provide a shaft seal structure capable of ensuring good sealing performance in a vacuum pump using fluorine oil.

[0008]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a vacuum pump which moves a gas transfer body in a pump chamber based on rotation of a rotating shaft and transfers gas by the operation of the gas transfer body to provide a suction action. According to the invention of claim 1, an oil-existing area for containing a fluorine oil for lubricating a required portion of the interior of the vacuum pump body for lubricating, and the rotating shaft between the oil-existing area and the pump chamber are provided. A rubber lip ring for shaft sealing disposed so as to be in sliding contact with the peripheral surface of the shaft, and pumping means provided in a sliding contact portion of the rubber lip ring in sliding contact with the peripheral surface of the rotating shaft. A pumping means, wherein the pumping means causes the fluorine oil between the peripheral surface of the rotary shaft and the sliding portion to be present from the pump chamber side with the rotation of the rotary shaft. Energize to the area side Was Unishi.

[0009] Fluorine oil diffuses easily on the surface of the fluororesin, but on the surface of rubber, the fluorine oil does not diffuse as much as on the surface of the fluororesin. Fluorine oil that does not have a high diffusivity on the rubber surface is smoothly sent from the pump chamber side to the oil existing area side by pumping means provided on the sliding portion of the rubber lip ring.

According to the invention of claim 2, in claim 1,
The pumping means is configured to rotate the rotation shaft so as to urge the fluorine oil between the peripheral surface of the rotation shaft and the sliding portion from the pump chamber side to the oil existing region side with the rotation of the rotation shaft. Leak-preventing ridges slidably contacting the peripheral surface of the shaft.

According to the third aspect of the present invention, in the second aspect,
The leakage preventing ridge is non-annular, and the leakage preventing ridge moves from the pump chamber side to the oil existing area side as the rotation shaft moves in the rotation direction.

According to the second and third aspects of the present invention, the leakage preventing ridge sweeps the peripheral surface of the rotating shaft as the rotating shaft rotates. Fluorine oil in the sweep area of the leakage prevention ridge is swept from the pump chamber side to the oil existing area side.

According to a fourth aspect of the present invention, in any one of the second and third aspects, the leakage preventing ridge does not go around the axis of the rotating shaft but a plurality of the ridges around the axis. Arranged in line.

Without making a round around the axis of the rotating shaft,
The configuration in which a plurality of leakage prevention ridges are provided around the axis,
It is not necessary to increase the width of the sliding contact portion. According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the oil presence area is an area for accommodating a bearing for rotatably supporting the rotating shaft.

The oil for lubricating the bearing lubricates the rubber lip ring. According to a sixth aspect of the present invention, in any one of the first to fifth aspects, the vacuum pump arranges a plurality of the rotating shafts in parallel and arranges a rotor on each of the rotating shafts. The rotors on the rotating shaft that match each other are meshed with each other, and a roots pump having a plurality of pump chambers accommodating a plurality of rotors meshing with each other as a set or a single pump chamber is provided.

Such a vacuum pump is suitable as an object to which the present invention is applied. According to a seventh aspect of the present invention, in the sixth aspect, the plurality of rotation shafts are synchronously rotated by using a gear mechanism, and the oil presence area is an area for accommodating the gear mechanism.

The oil for lubricating the gear mechanism lubricates the rubber lip ring.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment in which the present invention is applied to a roots pump will be described below with reference to FIGS.

As shown in FIG. 1A, a front housing 13 is joined to a front end of a rotor housing 12 of the multi-stage roots pump 11, and a front housing 13 is provided.
The sealing body 36 is joined to the. Rotor housing 1
A rear housing 14 is joined to the rear end of the second housing 2. The rotor housing 12 includes a cylinder block 15 and a plurality of chamber forming walls 16. As shown in FIG. 2B, the cylinder block 15 includes a pair of block pieces 17 and 18, and the chamber forming wall 16 includes a pair of wall pieces 161 and 162. As shown in FIG.
The space between the chamber forming wall 3 and the space between the adjacent chamber forming walls 16 and the space between the rear housing 14 and the room forming wall 16 are pump chambers 39, 40, 41, and 4, respectively.
2,43.

A pair of rotating shafts 19 and 20 are rotatably supported by the front housing 13 and the rear housing 14 via radial bearings 21, 37, 22 and 38. Both rotating shafts 19 and 20 are arranged parallel to each other. The rotation shafts 19 and 20 are passed through the chamber forming wall 16.

A plurality of rotors 23, 24,
25, 26, 27 are integrally formed, and the same number of rotors 28, 29, 30, 31, 32 are integrally formed on the rotating shaft 20. The rotors 23 to 32 are
Are seen to be in the directions of the axes 191 and 201 of FIG. The thicknesses of the rotors 23, 24, 25, 26, and 27 are made smaller in this order.
The thicknesses of 8, 29, 30, 31, 32 become smaller in this order. The rotors 23 and 28 are housed in the pump chamber 39 in a state of being meshed with each other.
The pumps 4 and 29 are housed in the pump chamber 40 in a state of being engaged with each other. The rotors 25 and 30 are housed in the pump chamber 41 in a state of meshing with each other, and the rotors 26 and 31 are housed in the pump chamber 42 in a state of meshing with each other. The rotors 27 and 32 are housed in the pump chamber 43 in a state of being engaged with each other.

The gear housing 3 is mounted on the rear housing 14.
3 are assembled. The rotating shafts 19 and 20 penetrate through the rear housing 14 and protrude into the gear housing 33.
35 are fastened in a state where they are engaged with each other. An electric motor M is mounted on the gear housing 33. The driving force of the electric motor M is transmitted to the rotating shaft 1 via the shaft joint 44.
9, the rotating shaft 19 is rotated by the electric motor M in the direction of the arrow R1 in FIGS. 2 (a), 2 (b) and 3 (a). The rotation of the rotating shaft 19 is transmitted to the rotating shaft 20 via gears 34 and 35, and the rotating shaft 20 is
(B) and the rotation shaft 1 as shown by the arrow R2 in FIG.
9 rotates in the opposite direction. That is, the rotating shafts 19 and 20 are
It is rotated synchronously using the gears 34 and 35.

As shown in FIG. 2B, a passage 163 is formed in the chamber forming wall 16. An inlet 164 and an outlet 165 of the passage 163 are formed in the chamber forming wall 16. The adjacent pump chambers 39, 40, 41, 42, 43
It communicates via a passage 163.

As shown in FIG. 2A, the block piece 18
Is formed so that an inlet 181 communicates with the pump chamber 39. As shown in FIG.
Is formed so that a discharge port 171 communicates with the pump chamber 43. The gas introduced into the pump chamber 39 from the inlet 181 is rotated by the rotation of the rotors 23 and 28 to form the chamber forming wall 1.
6 from the inlet 164 via the passage 163 to the adjacent pump chamber 40 from the outlet 165. Hereinafter, similarly, the gas is transferred in the order of decreasing volume of the pump chamber, that is, in the order of the pump chambers 40, 41, 42, and 43. The gas transferred to the pump chamber 43 is discharged from the discharge port 171 to the outside. The rotors 23 to 32 are gas transfer bodies that transfer gas.

As shown in FIG. 1A, a seal housing 47 is formed around the rotary shaft 19 between the radial bearing 37 and the rotor 27, and a lip seal 45 is formed in the seal housing 47. Is housed. Rotational shaft 20 between radial bearing 38 and rotor 32
A seal accommodating chamber 48 is formed around the periphery of the lip seal 46. The seal housing chamber 47 communicates with the gear housing chamber 331 via a ring gap 371 of the radial bearing 37. The seal housing chamber 48 communicates with the gear housing chamber 331 via a ring gap 381 of the radial bearing 38.

As shown in FIGS. 1 (c) and 4 (b),
The lip seal 45 includes a ring-shaped holding fitting 49 and a rubber lip ring 51 held by the holding fitting 49. A circumferential sliding contact portion 511 is formed on the inner peripheral side of the rubber lip ring 51, and the sliding contact portion 511 is formed with a plurality of leakage prevention ridges 53. The leakage preventing ridge 53 comes into sliding contact with the peripheral surface 192 of the rotating shaft 19 as the rotating shaft 19 rotates. As shown in FIGS. 5 (b) and 4 (b), the plurality of leakage prevention ridges 53 are formed without rotating around the axis of the rubber lip ring 51, that is, the axis 191 of the rotary shaft 19. It is arranged around 191. The leakage prevention ridge 53 moves from the pump chamber 43 side to the gear housing chamber 331 side as it follows the rotation direction R1 of the rotating shaft 19.

As shown in FIGS. 1B and 4A,
The lip seal 46 includes a ring-shaped holding fitting 50 and a rubber lip ring 52 held by the holding fitting 50. A circumferential sliding contact portion 521 is formed on the inner peripheral side of the rubber lip ring 52, and the sliding contact portion 521 is formed with a plurality of leakage prevention protrusions 54. The leakage preventing ridge 54 slides on the peripheral surface 202 of the rotating shaft 20 as the rotating shaft 20 rotates. As shown in FIGS. 5 (a) and 4 (a), the plurality of leakage prevention ridges 54 are formed around the axis of the rubber lip ring 52, that is, without rotating around the axis 201 of the rotary shaft 20. It is arranged around 201. The leakage prevention ridge 54 moves from the pump chamber 43 side to the gear housing chamber 331 side as it follows the rotation direction R2 of the rotating shaft 20.

The type of rubber of the lip ring 51 in the present embodiment is fluorine rubber. Gear housing 33
Fluorine oil Y (shown in FIG. 3 (b)) is stored in a gear housing chamber 331 inside, and the fluorine oil Y is
Lubricate 5. The gear housing chamber 331 of the gear housing 33 that houses the gears 34 and 35 constituting the gear mechanism and the radial bearings 37 and 38 as bearings is an oil existing area. The oil stored in the gear storage chamber 331 is
5 is swept up. Gears 34, 35
The fluorine oil Y scraped up by the rotation of the lubrication lubricates the radial bearings 37 and 38. The fluorine oil Y that has entered the seal accommodating chambers 47 and 48 from the ring gaps 371 and 381 of the radial bearings 37 and 38 lubricates the sliding portions 511 and 521 of the rubber lip rings 51 and 52.

The leakage preventing ridge 53 provided on the rubber lip ring 51 is rotated by the rotation
9 urges the fluorine oil between the peripheral surface 192 and the sliding portion 511 from the pump chamber 43 side to the gear housing chamber 331 side which is the oil existing area. The leakage preventing ridge 54 provided on the rubber lip ring 52 causes the fluorine oil between the peripheral surface 202 of the rotating shaft 20 and the sliding contact portion 521 to move to the pump chamber 43 side as the rotating shaft 20 rotates. From the gear housing chamber 331 side.

In the first embodiment, the following effects can be obtained. (1-1) FIG. 6 shows three types of lubricating oils [fluoro oil Y, ND8
It is the graph which investigated the relationship between surface tension of (refrigeration machine oil) and engine oil Eg) and temperature. The horizontal axis in the graph represents temperature, and the vertical axis represents tension (unit: kPa). Curve F1 relates to fluorine oil Y, curve N relates to ND8, and curve E1 relates to engine oil. From the graph of FIG. 6, it can be seen that the surface tension of the fluoro oil Y is lower than that of ND8 and engine oil Eg.

FIG. 7A shows three kinds of lubricating oils (fluorine oils Y and ND) on a plate 59 made of polytetrafluoroethylene.
8 and the engine oil Eg) were placed in predetermined amounts, respectively, and the contact angle θ was measured. The contact angle θ of the fluoro oil Y is 10 ° or less, the contact angle θ of the ND 8 is about 64 °, and the contact angle θ of the engine oil Eg is about 51 °. FIG. 7 (b) shows three types of lubricating oils (fluoro oil Y, ND8 and engine oil E) on a plate 60 made of fluoro rubber.
g) shows the contents of an experiment in which the contact angle θ was measured with a predetermined amount of each. The contact angle θ of the fluorine oil Y is about 32 °, the contact angle θ of the ND8 is about 48 °, and the engine oil E
g has a contact angle θ of about 57 °. FIGS. 7A and 7B
From the graph, it can be seen that the fluorinated oil Y is easily diffused on the surface of the fluorinated resin, but the fluorinated oil Y is not diffused on the surface of the rubber as much as on the surface of the fluorinated resin.

FIG. 8 shows two kinds of lubricating oils (fluorine oil Y and engine oil Eg) using a lip ring made of polytetrafluoroethylene provided with a spiral groove disclosed in Japanese Patent Application Laid-Open No. 6-300142. 6 is a graph in which a relationship between a pumping amount of a rotating shaft and a rotation speed of a rotating shaft (19 or 20) is examined. The spiral groove carries the lubricating oil in the axial direction of the rotating shaft. The horizontal axis represents the number of rotations of the rotating shaft, and the vertical axis represents the pumping amount [unit: g / h, where g represents gram weight and h represents one hour]. Curve F2 relates to fluoro oil Y and curve E2
Refers to engine oil. According to the graph of FIG.
In a lip ring made of polytetrafluoroethylene having a spiral groove, the pumping amount of engine oil increases as the rotational speed increases. However, the pumping amount of the fluorinated oil Y becomes maximum when the rotation speed is around 2000 rpm, and this maximum amount is also small. Therefore, with a lip ring made of polytetrafluoroethylene provided with a spiral groove, a sufficient pumping amount for preventing oil leakage cannot be obtained. The reason that the pumping amount by the polytetrafluoroethylene sealing element having the spiral groove is not sufficient is that the surface tension is low and the fluorine oil Y which easily diffuses on the surface of the polytetrafluoroethylene cannot be taken into the spiral groove. is there. That is, even if a polytetrafluoroethylene seal element provided with a spiral groove is used, it is not very useful in terms of sealing performance with respect to the fluorine oil Y.

In the present embodiment, the leakage preventing ridge 53 provided on the rubber lip ring 51 sweeps the peripheral surface 192 of the rotating shaft 19 as the rotating shaft 19 rotates.
Fluorine oil Y in the sweep area of the leakage prevention ridge 53 is swept from the pump chamber 43 side to the gear housing chamber 331 side.
Further, the leakage preventing ridge 54 provided on the rubber lip ring 52 sweeps the peripheral surface 202 of the rotating shaft 20 as the rotating shaft 20 rotates. The fluorine oil Y in the sweeping region of the leakage prevention ridge 54 is supplied from the pump chamber 43 side to the gear housing chamber 33.
Swept to one side. Fluorine oil which does not have high diffusivity on the surface of the rubber is smoothly sent from the pump chamber 43 side to the gear housing chamber 331 side by the leakage prevention ridges 53, 54 of the rubber lip rings 51, 52. That is, the rubber lip rings 51 and 52 provided with the leakage prevention ridges 53 and 54 as the pumping means exhibit a high sealing property with respect to the fluorine oil Y.

(1-2) A single leak preventing ridge is attached to the axis 19
To make a full circle around 1,201, the axis 19
Rubber lip rings 51 in the directions of 1,201,
52, the width W of the sliding contact portions 511 and 521 [FIG.
(Illustrated in (b)). Sliding part 51
If the width W of 1,521 is increased, the sliding contact resistance is increased, which is not preferable. The configuration in which the leakage preventing ridges 53 and 54 are provided in a plurality of rows around the axes 191 and 201 without making a round around the axes 191 and 201 is the sliding contact portions 511 and 52.
It is not necessary to increase the width W of 1.

(1-3) Dry pump type roots pump 1
In 1, the use of the fluorine oil Y in the pump chambers 39 to 43 is not performed. The roots pump 11 that does not want the fluorine oil Y to exist in the pump chambers 39 to 43 is suitable as an application target of the present invention.

In the present invention, as shown in FIGS. 9 (a) and 9 (b),
Embodiment is also possible. 10 (a) and 10 (b)
As shown in the figure, when viewed in the radial direction of the rotating shafts 19 and 20, the inclined portion 57 that is inclined with respect to the axes 191 and 201.
1,581 and the starting end 5 orthogonal to the axes 191,201
The third embodiment in which the leakage preventing ridges 57 and 58 are formed from the ridges 72 and 582 is also possible. Inclined parts 571, 581
Bent portion 57 connecting the first and second end portions 572 and 582 at an obtuse angle
3, 583, the starting end 5 of the adjacent leakage prevention ridges 57, 58
72 and 582 are connected.

In the present invention, the following embodiments are also possible. (1) A spiral groove is used as a pumping means. (2) A fluorinated resin lip ring is arranged so as to be in contact with the peripheral surface of the rotary shaft between the rubber lip ring and the pump chamber. The fluorine resin lip ring works so that the fluctuation of the pressure on the pump chamber side which varies in a range from below atmospheric pressure to above atmospheric pressure does not affect the rubber lip ring. (3) Silicone rubber is used as the material of the rubber lip ring. (4) The present invention is applied to a vacuum pump other than a roots pump.

[0038]

As described above in detail, according to the present invention, the sliding contact of the rubber lip ring for the shaft seal disposed so as to be in sliding contact with the peripheral surface of the rotating shaft between the oil existing area and the pump chamber. A pumping means provided in the portion, and the pumping means attaches the fluorine oil between the peripheral surface of the rotating shaft and the sliding contact portion from the pump chamber side to the oil existing region side with the rotation of the rotating shaft. Therefore, an excellent effect that good sealing performance can be ensured in a vacuum pump using fluorine oil is obtained.

[Brief description of the drawings]

FIG. 1 shows a first embodiment, in which (a) is a plan sectional view of the whole multi-stage roots pump 11; (B) is an enlarged plan sectional view of a main part on the rotating shaft 20 side. (C) is an enlarged plan sectional view of a main part on the rotating shaft 19 side.

FIG. 2A is a sectional view taken along line AA of FIG. (B) is FIG.
BB sectional drawing of FIG.

FIG. 3A is a sectional view taken along line CC of FIG. 1; (B) is FIG.
FIG.

FIG. 4A is a plan cross-sectional view of a main part on the lip seal 46 side.
(B) is a plane sectional view of a main part of the lip seal 45 side.

5A is a perspective view of a lip seal 46. FIG. (B) is a perspective view of the lip seal 45.

FIG. 6 is a graph showing the relationship between the surface tension of lubricating oil and temperature.

FIG. 7A is a simplified cross-sectional view showing a test content of a diffusibility of a lubricating oil on a polytetrafluoroethylene plate. (B) is a simplified cross-sectional view showing the test contents of the diffusivity of lubricating oil on a rubber plate.

FIG. 8 is a graph showing a relationship between a pumping amount and a rotation speed.

FIG. 9 shows the second embodiment, in which (a) is a plan sectional view of a rubber lip ring 51. (B) is a plan sectional view of the rubber lip ring 52.

10A and 10B show a third embodiment, and FIG. 10A is a plan sectional view of a rubber lip ring 51. FIG. (B) is a plan sectional view of the rubber lip ring 52.

[Explanation of symbols]

11 Multi-stage roots pump which is a vacuum pump. 19, 20
…Axis of rotation. 191, 201... Axis. 192, 202 ... peripheral surface. 23, 24, 25, 26, 27, 28, 29, 3
0, 31, 32: rotors serving as gas transfer bodies. Reference numeral 331 denotes a gear storage chamber serving as an oil existing area. 34, 35 ... gears constituting a gear mechanism. 37, 38: Radial bearings that serve as bearings. 43 ... Pump room. 51, 52 ... rubber lip rings. 511, 521: sliding contact portion. 53,54,55,5
6, 57, 58: Leakage prevention ridges serving as pumping means.
Y: Fluorine oil.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) F04C 29/02 311 F04C 29/02 311K (72) Inventor Satoru Kuramoto 2-1-1 Toyota-cho, Kariya City, Aichi Prefecture F term in Toyota Industries Corporation (reference) 3H029 AA06 AA09 AA18 AB06 BB01 BB16 BB44 CC08 CC16 CC17 CC20 CC26 CC32 CC34 CC35

Claims (7)

[Claims] 1. A vacuum pump for moving a gas transfer member in a pump chamber based on rotation of a rotary shaft and transferring a gas by the operation of the gas transfer member to provide a suction effect, wherein lubrication inside a body of the vacuum pump is required. An oil-existing region for containing a fluorine oil for lubricating a portion, and a rubber lip for a shaft seal disposed so as to be in sliding contact with a peripheral surface of the rotating shaft between the oil-existing region and the pump chamber. A ring; and a pumping means provided on a sliding portion of the rubber lip ring that slides on a peripheral surface of the rotating shaft, wherein the pumping means rotates the rotating shaft with rotation of the rotating shaft. A shaft sealing structure in a vacuum pump configured to urge the fluorine oil between the peripheral surface of the oil pump and the sliding contact portion from the pump chamber side to the oil existing area side. 2. The pumping means according to claim 1, wherein said pumping means urges said fluorine oil between said peripheral surface and said sliding contact portion from said pump chamber side to said oil existing area side with rotation of said rotary shaft. The shaft sealing structure in a vacuum pump according to claim 1, wherein the shaft is a leakage preventing ridge slidably in contact with a peripheral surface of the rotating shaft. 3. The leak preventing ridge is non-annular, and the leak preventing ridge shifts from the pump chamber side to the oil existing area side as it follows the rotation direction of the rotating shaft. A shaft sealing structure in the vacuum pump according to 1. 4. The leakage prevention ridge according to claim 2, wherein the plurality of leakage prevention ridges are provided in a plurality of rows around the axis without rotating around the axis of the rotation shaft. Shaft sealing device in a vacuum pump. 5. The oil-existing area is an area for accommodating a bearing for rotatably supporting the rotating shaft.
A shaft sealing structure in the vacuum pump according to claim 4. 6. The vacuum pump according to claim 1, wherein a plurality of said rotating shafts are arranged in parallel, a rotor is arranged on each of said rotating shafts, rotors on adjacent rotating shafts are meshed with each other, and said vacuum pump is in a state of being meshed with each other. The shaft sealing structure in a vacuum pump according to any one of claims 1 to 5, wherein the root pump is a plurality of pump chambers accommodating a plurality of rotors as one set, or a roots pump including a single pump chamber. 7. The shaft sealing structure in a vacuum pump according to claim 6, wherein the plurality of rotating shafts are rotated synchronously by using a gear mechanism, and the oil existing area is an area for accommodating the gear mechanism. .