JP2002070790A - Pressure producer and turbo-molecular pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure producer equipped with balanced radial roller bearing having superb rigidity and stability and a turbo-molecular pump. SOLUTION: This pressure producer generates negative or positive pressure in such a way that it discharges the working fluid to the one direction by the rotating of blades 5, 19. This pressure producer is equipped with an air bearing to control the movement of radial direction of a rotating shaft 14. The air bearing is equipped with plural rows of strip-like dynamic pressure producing area 41a, 41b forming V type dynamic pressure grooves along the direction of outer circumferential surface of cylinder 25. The region crook 43a of dynamic pressure groove 43 in the dynamic pressure producing area 41a located at the most outside is in place deviating the line from the center C1 of dynamic pressure producing area 41a to the roller bearing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure generator and a turbo molecular pump for generating a negative pressure or a positive pressure by sending a working fluid in one direction by rotation of a blade.

[0002]

2. Description of the Related Art Generally, it is necessary to obtain an ultra-high vacuum state in semiconductor-related devices such as a sputtering device, a CVD device, and an etching device, an electron microscope, a surface analysis device, and an environmental test device. As a device for obtaining such an ultra-high vacuum state, a turbo molecular pump is conventionally known. The turbo molecular pump is configured to generate a molecular flow by rotating a motor rotation shaft having a moving blade, thereby discharging a gas to generate an ultra-high vacuum.

In order to obtain an ultra-high vacuum, it is necessary to rotate the rotating shaft at a high speed, and to smoothly rotate at a high speed, it is necessary to employ a non-contact bearing suitable for the high-speed rotation.
Therefore, in recent turbo molecular pumps, an air bearing is employed as a bearing for supporting a load in a radial direction of a rotating shaft of a motor. Such an air bearing is formed on the outer peripheral surface of a cylindrical body that can rotate integrally with the rotating shaft. More specifically, two rows of dynamic pressure generating regions are formed on the outer peripheral surface of the tubular body, and a gas seal region is formed adjacent thereto. In the dynamic pressure generating region, for example, a herringbone-shaped dynamic pressure groove is formed. On the other hand, in the gas seal portion area, for example, a spiral seal groove is formed. The tubular body is housed in a surrounding member that is also tubular. Therefore, when the cylindrical body rotates together with the rotating shaft, a pressure gas film is formed in the clearance between the surrounding member and the air bearing portion by the action of the dynamic pressure groove.

[0004] A gas seal portion region formed at both ends of two rows of dynamic pressure generating portion regions is called a double gas seal type, and a gas seal portion region is provided only at one end of the two rows of dynamic pressure generating portion regions. Is called a single gas seal type. Also, in either type,
The width and the like of each dynamic pressure generating region are set to be equal.

[0005]

However, it has not always been said that the above-mentioned prior art air bearings have sufficient rigidity and stability for all types.

In particular, in the case of a single gas seal type air bearing, air in the dynamic pressure generating section located on the gas seal section is drawn to the gas seal section by the vacuuming action of the gas seal section. It was easy. Therefore, there is a problem that a sufficiently high dynamic pressure cannot be generated in the dynamic pressure generating section located on the gas seal section area side. Moreover, in the dynamic pressure generating region located on the gas seal portion region side, there is a problem that the pressure peak point due to the dynamic pressure is substantially shifted to the other dynamic pressure generating region region side. These have been major factors that hinder improvement in rigidity and stability of the radial bearing.

[0007] The present invention has been made in view of the above problems, and an object of the present invention is to provide a pressure generating device provided with a radial bearing having excellent rigidity and stability.

[0008]

According to a first aspect of the present invention, there is provided a motor having a rotating shaft whose movement in the radial and thrust directions is restricted by a non-contact bearing. A wing attached to the rotating shaft, wherein the rotation of the wing sends out a working fluid in one direction to generate a negative pressure or a positive pressure, and regulates a movement of the rotating shaft in a radial direction. The non-contact type bearing is an air bearing including a plurality of rows of belt-shaped dynamic pressure generating regions formed by forming a plurality of substantially V-shaped dynamic pressure grooves along a circumferential direction of an outer peripheral surface of a cylindrical body. The bent portion of the dynamic pressure groove in at least one of the dynamic pressure generating region located outside is arranged in a state shifted outward from the center of the dynamic pressure generating region along the bearing center line. It is characterized by being The pressure generator that the gist thereof.

According to a second aspect of the present invention, in the first aspect, the air bearing includes a gas seal portion region formed adjacent to one end of the plurality of rows of dynamic pressure generating portion regions, The bent portion of the dynamic pressure groove in the pressure generating portion region that is located closest to the gas seal portion region is located in the direction of the gas seal portion region along a bearing center line from the center of the dynamic pressure generating portion region. It is assumed that they are arranged in a shifted state.

According to a third aspect of the present invention, in the second aspect, the part of the dynamic pressure generating part located closest to the gas seal part area is formed wider than other parts. did.

According to a fourth aspect of the present invention, in the second or third aspect, the bending portion of the dynamic pressure groove in the dynamic pressure generating region adjacent to the dynamic pressure generating region located closest to the gas seal portion region. Are arranged so as to be displaced from the center of the dynamic pressure generating region along the bearing center line in a direction opposite to the direction of the gas seal region.

[0012] The invention according to claim 5 provides the invention according to claims 1 to 4.
In any one of the above, in the dynamic pressure generating portion region in which the bent portion of the dynamic pressure groove is arranged in a state shifted in a predetermined direction, a distance from one end of the dynamic pressure generating portion region to the bent portion ( L1) and the ratio (L1: L2) of the distance (L2) from the other end of the same dynamic pressure generation region to the bent portion.
Was 3/15 to 8/10.

[0013] The invention according to claim 6 is the invention according to claims 1 to 5.
The gist of the present invention is a turbo-molecular pump provided with the pressure generator according to any one of the above. Hereinafter, the “action” of the present invention will be described.

According to the first to fifth aspects of the present invention, by arranging the bent portion of the dynamic pressure groove in a state shifted in a predetermined direction, the pressure peak point due to the dynamic pressure generated by the dynamic pressure groove is in the same direction. shift. For this reason, the distance between the pressure peak points in the air bearing, in other words, the distance between the support points is increased, and as a result, the rigidity and stability of the bearing are improved.

According to the third aspect of the present invention, the portion of the dynamic pressure generating portion located closest to the gas seal portion is formed wide, so that the dynamic pressure generating portion has an air collecting capacity. Is higher than the others. Therefore, even if air is evacuated to the gas seal portion region side by the action of vacuum evacuation, it can be compensated for and the sufficient dynamic pressure can be generated.

According to the fourth aspect of the present invention, the distance between the pressure peak points in the air bearing is further increased, so that the rigidity and stability of the bearing are further improved. According to the fifth aspect of the present invention, since the distance ratio L1: L2 is set to a value within the above-described preferred range, the rigidity and stability of the bearing can be reliably improved. This ratio is 3 /
If it is smaller than 15, there is a risk that sufficient dynamic pressure may not be generated. Conversely, this ratio is 8/1
If it is larger than 0, the shift amount of the pressure peak point due to the dynamic pressure generated by the dynamic pressure groove becomes small, and it becomes impossible to increase the distance between the pressure peak points in the air bearing.

According to the sixth aspect of the present invention, since the radial bearing having excellent rigidity and stability is provided as described above, the rotating shaft can withstand a relatively large load and rotate at high speed. . Therefore, it is possible to provide a high-performance turbo-molecular pump capable of reliably obtaining an ultra-high vacuum state.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a turbo molecular pump according to an embodiment of the present invention will be described in detail with reference to FIGS.

As shown in FIG. 1, the turbo molecular pump 1 according to the present embodiment includes an upper housing 3 and a lower housing 4. The upper housing 3 is cylindrical and has an intake port 3a serving as a suction port for air exhausted from a vacuum chamber (not shown). A plurality of stationary blades 5 are attached to the inner peripheral surface of the upper housing 3 via a support member 6. These stationary blades 5 are in a state of extending radially inward of the upper housing 3.

A substantially annular support member 7 is fitted into the lower end opening of the upper housing 3. An annular recess 7 a is formed on the upper surface of the support member 7. Recess 7a
In one place on the bottom surface of the
b is formed. The exhaust pipe 8 is connected to the through hole 7b. In this state, the exhaust pipe 8 is fixed by bolts 9 screwed to the upper housing 3 via the support member 7. In addition, the support member 7 has a plurality of bolts 10 in a portion other than the exhaust pipe 8 (however, only one bolt is shown in the drawing).
Is fixed to the upper housing 3. The lower housing 4 is fixed to the support member 7 by a plurality of bolts 11. A distal end portion of the exhaust pipe 8 is drawn out of an opening 4 a formed in a side portion of the lower housing 4. The distal end of the exhaust pipe 8 is formed in a flange shape having an exhaust port 8a.

A brushless motor (hereinafter, referred to as a motor)
The motor 12 is supported in a state where the outer peripheral surface of the casing 13 is in contact with the inner peripheral surface of the support member 7. In this support state, the rotating shaft 14 is
It protrudes to the side. A seal member 15 is interposed between the support member 7 and the upper housing 3. Seal members 16 are interposed between the support member 7 and the motor 12, respectively. The space between the upper surface of the support member 7 and the air inlet 3a is an air intake chamber R. The air intake chamber R is
It is hermetically sealed by the seal members 15 and 16.

A rotor 17 is attached to the tip of the rotating shaft 14 by fastening a nut 18. Rotor 1
7 has a substantially cylindrical shape with a bottom. A plurality of moving blades 19 extending radially are provided on the outer peripheral surface of the rotor 17. These moving blades 19 are arranged so as to enter the gaps formed by the stationary blades 5. When the motor 12 is driven and the rotor 17 rotates, the air on the intake port 3 a side is drawn between the moving blade 19 and the stationary blade 5. As a result, a suction force for discharging air to the exhaust port 8a side is generated.

As shown in FIG. 1 and FIG.
A projection 13a is formed on the front end side (the right end side in FIG. 2) of the inner peripheral surface of the casing 13 constituting the above. The protrusion 13a projects annularly over the entire circumferential direction toward the motor axis. At the front end side of the inner peripheral surface of the casing 13, a step portion 13b is formed. A substantially annular closing member 20 is fitted into the step portion 13b, and in this state, the closing member 20 is fixed using a bolt (not shown). The closing member 20 has an insertion hole 20 passing through its axis.
a is formed.

Further, at the position corresponding to the base end of the rotating shaft 14 at the rear end side of the inner peripheral surface of the casing 13, the closing member 2 is provided.
1 is fitted. An insertion hole 21a is formed in the closing member 21 so as to pass through the axis thereof. Casing 13
In the region between the two closing members 20 and 21,
A motor chamber 22 is formed. The motor chamber 22 is communicated with the atmospheric pressure region through the insertion hole 21a.

The rotation shaft 14 is rotatably accommodated in the motor chamber 22. The base end side of the rotating shaft 14 is loosely inserted into the insertion hole 21 a of the closing member 21. The tip end of the rotating shaft 14 is loosely fitted into the insertion hole 20a of the closing member 20 and protrudes outward. Two bushes 23 are fixed to the rotating shaft 14 in a state of being fitted outside. A field magnet 24 as a rotor is held between the bushes 23. The field magnet 24 is constituted by four permanent magnet pieces provided around the rotation shaft 14. These permanent magnet pieces are alternately and annularly arranged so that adjacent magnetic poles have different polarities. Double bush 2
At the outer edge of the inner end face of each of the inner and outer faces 3, 23, there is formed a stepped portion 23a which is annularly cut along the circumferential direction. A cylindrical cover 25 as a cylindrical body formed of a ceramic sintered material is fitted between the step portions 23a. The cylindrical cover 25 surrounds the outer peripheral surface of the field magnet 24. The bush 23 has a balance adjustment function.

An annular permanent magnet 26 is fixed to the outer end surface of the front bush 23 in a state of being fitted around the rotary shaft 14. On the inner surface of the closing member 20, a permanent magnet 26
An annular permanent magnet 27 is buried in a state where the rotating shaft 14 is loosely inserted so as to be opposed to. Further, an annular permanent magnet 28 is fixed to the outer end surface of the rear bush 23 in a state of being externally fitted to the rotating shaft 14. Closing member 21
An annular permanent magnet 29 is buried on the inner side surface of the first member so as to face the permanent magnet 28 in a state where the rotary shaft 14 is loosely inserted. The two opposing permanent magnets 28, 29 have a smaller diameter than the permanent magnets 26, 27. Permanent magnets 26-29
Are made of the same magnetic material, and in this embodiment, the material is a neodymium magnet. As the material of the permanent magnets 26 to 29, a samarium-based magnet or the like may be used.

The pair of permanent magnets 26 and 27 constitute a first thrust magnetic bearing 30, and the pair of permanent magnets 28 and 29 constitute a second thrust magnetic bearing 31. Therefore,
The rotation of the rotating shaft 14 in the thrust direction is restricted by the magnetic bearings 30 and 31.

The bush 23, the field magnet 24, the cylindrical cover 25, the permanent magnet 26,
28 are integrally fixed. As a result, the rotating body 32 is formed. Around the rotating body 32, a surrounding member 33 formed of a ceramic sintered material (insulating material) in a cylindrical shape is arranged. The surrounding member 33 is fixed between the protrusion 13a and the closing member 21 on the rear side.
A predetermined clearance is provided between the inner peripheral surface of the surrounding member 33 and the outer peripheral surface of the cylindrical cover 25. In the present embodiment, the clearance is set to 10 μm or less. In addition, as a material of the cylindrical cover 25 and the surrounding member 33, for example, a sintered material such as boron nitride, alumina, zirconia, aluminum nitride, silicon nitride, and boron nitride can be used.

As shown in FIGS. 2 and 3, a plurality of air supply holes 33a are formed in the surrounding member 33. In this embodiment, the air supply holes 33a are formed in two rows at equal intervals in the circumferential direction of the surrounding member 33, and a total of six air supply holes 33a are provided.

An air supply pipe 36 is fitted into the closing member 21. The air supply pipe 36 penetrating the closing member 21 connects the region on the outer peripheral surface side of the surrounding member 33 with the atmospheric pressure region. Therefore, when the brushless motor 12 is driven, air is introduced into a region on the outer peripheral surface side of the surrounding member 33 via the air supply pipe 36. Further, the introduced air is further introduced into the clearance between the inner peripheral surface of the surrounding member 33 and the outer peripheral surface of the cylindrical cover 25 via each air supply hole 33a.

A cylindrical yoke 38 is provided on the inner peripheral surface of the casing 13. On the outer peripheral surface of the surrounding member 33, three armature coils 39 as armatures are provided at equal intervals in the circumferential direction. The mechanical angle of each armature coil 39 in the circumferential direction is set to be 90 ° to 120 °.

Three magnetic sensors (Hall elements) 40 are provided on the outer peripheral surface of the surrounding member 33 immediately proximal to each armature coil 39. These magnetic sensors 40 detect the magnetic poles of the permanent magnet pieces constituting the field magnet 24. The rotation speed detection signal obtained by the detection is fed back to control means (not shown). As a result, the current flowing through each armature coil 39 is feedback-controlled, and the rotating shaft 14 rotates at a constant speed.

Next, a radial air bearing for restricting the movement of the rotating shaft 14 in the radial direction will be described. FIG.
As shown in (b), the radial air bearing according to the present embodiment includes a surrounding member 33 whose inner peripheral surface is polished, and a cylindrical cover 25 surrounded by the surrounding member 33. I have. On the outer peripheral surface of the cylindrical cover 25, a plurality of rows (here, two rows) of dynamic pressure generating regions 41a and 41b are provided.
Is provided. The first dynamic pressure generating region 41a is located on the base end side of the rotary shaft 14, and the second dynamic pressure generating region 41b is located on the distal end side of the rotary shaft 14. A buffer region 44 having a predetermined width and having no groove structure is interposed between these dynamic pressure generating regions 41a and 41b. The dynamic pressure generating regions 41a and 41b are both formed so as to extend in a belt shape over the entire circumference of the cylindrical cover 25. A plurality of herringbone-shaped dynamic pressure grooves 43 are formed at equal intervals in the circumferential direction in the dynamic pressure generating regions 41a and 41b. In addition, these dynamic pressure grooves 43 collect the surrounding air toward its own bent portion 43a that is substantially V-shaped,
It serves to generate dynamic pressure.

In the present embodiment, both dynamic pressure generating section regions 4
The width of each of the dynamic pressure grooves 43 in 1a and 41b is set to 5 μm, and the depth thereof is set to 25 μm. The angles of the bent portions 43a of the dynamic pressure groove 43 are equal, and are both set to about 30 ° to 60 °.

A gas seal area 42 is provided immediately downstream of the first dynamic pressure generation area 41a via a buffer area 44 having a predetermined width. A spiral seal groove 42a is formed in the gas seal area 42.

As shown in FIG. 3B, the width (ie, the length along the bearing center line direction) W1 of the first dynamic pressure generating region 41a is equal to that of the second dynamic pressure generating region 41b. It is wider than the width W2. That is, one of the two dynamic pressure generating regions 41a and 41b located on the gas seal region 42 side is formed wider than the other. In the present embodiment, W1 is set to a value 1.5 to 2.0 times W2, specifically, W1 = 17 mm and W2 = 10 mm. In addition, the width of the two buffer regions 44 is set to 1.
It is set to 5 mm.

As shown in FIG. 3 (b), in the present embodiment, the bending portion 43a of the dynamic pressure generating groove 43 of both the dynamic pressure generating portion regions 41a is located at the central portion C1 of the dynamic pressure generating portion region 41a. Has not been placed. That is, the dynamic pressure groove pattern is formed not asymmetrically but asymmetrically with respect to the central portion C1.

More specifically, the bent portion 43a of the first dynamic pressure generating region 41a is
3 (a), it is displaced from the central portion C1 in the outward direction (toward the gas seal portion region 42, leftward in FIG. 3B) along the bearing center line.

Bending portion 4 of second dynamic pressure generating region 41b
3a is arranged in a state shifted from the central portion C1 of the dynamic pressure generating region 41b in a direction opposite to the gas seal portion region 42 direction (rightward in FIG. 3B) along the bearing center line.

Here, the dynamic pressure generating region 41a (or 4)
The distance from one end of 1b) to the bent portion 43a is defined as L1, and the distance from the other end of the same dynamic pressure generation region 41a (or 41b) to the bent portion 43a is defined as L2.

In this case, the ratio L1: L2 of the two distances is 3 /
It may be set to 15 to 8/10. If the ratio is smaller than 3/15, sufficient dynamic pressure may not be generated. Conversely, this ratio is 8
If the ratio is larger than / 10, the shift amount of the pressure peak points P1 and P2 due to the dynamic pressure generated by the dynamic pressure groove 43 decreases, and it becomes impossible to increase the distance between the pressure peak points P1 and P2 in the air bearing. is there. In the present embodiment, L in the first dynamic pressure generation region 41a
The value of 1: L2 is set to 6/12, and the value of L1: L2 in the second dynamic pressure generation region 41b is set to 6/12.

Next, the operation of the turbo molecular pump 1 configured as described above will be described. When the motor 12 is driven, the action of the dynamic pressure groove 43 causes the air to flow through
a and is supplied to the clearance between the surrounding member 33 and the cylindrical cover 25. Therefore, the rotating body 32 rotates while floating from the inner peripheral surface of the surrounding member 33. When the rotating body 32 starts to rotate, the introduction of air is further promoted by the dynamic pressure groove 43, and a pressure gas film is formed at the clearance. The rotating shaft 14 is supported in a non-contact state via the pressure gas film.

Here, the graph of FIG. 4A shows the pressure distribution in the conventional air bearing, and the graph of FIG. 4B shows the pressure distribution in the air bearing of the embodiment. Note that, in both graphs, the black portions conceptually represent negative pressure, and the white portions conceptually represent positive pressure.

Referring to the graph of FIG. 4A, the gas seal area 42 has a negative pressure due to the action of evacuation, and the buffer area 44 has an atmospheric pressure. On the other hand, the first dynamic pressure generating region 41a has a positive pressure as a whole, but as a result, part of the air is taken to the gas seal portion region 42 side. You can see that it is. Therefore, the area of the white portion of the first dynamic pressure generating region 41a is smaller than the area of the white portion of the second dynamic pressure generating region 41b. That is, the dynamic pressure generated in the first dynamic pressure generating region 41a is smaller than the dynamic pressure generated in the second dynamic pressure generating region 41b, and the radial bearing has poor balance as a whole. I will.

On the other hand, when looking at the graph of FIG. 4B, in the case of the first dynamic pressure generating region 41a which is formed to be wide, the central portion is more centrally located than the second dynamic pressure generating region 41b. The ability to collect air into is increased. Therefore, even if a part of the air is taken to the gas seal part area 42 side by the action of the evacuation, the decrease in the first dynamic pressure generation part area 41a can be compensated in advance. In other words, the area of the white portion in the first dynamic pressure generating region 41a can be made substantially equal to the area of the white portion of the second dynamic pressure generating region 41b. Therefore, the dynamic pressure generated in the first dynamic pressure generating section area 41a,
The dynamic pressure generated in the second dynamic pressure generating region 41b is substantially equal, and the radial bearing is well balanced as a whole.

Further, as shown by the double-headed arrows in both graphs, the distance between the pressure peak points P1 and P2 due to the dynamic pressure generated by the dynamic pressure groove 43 is certainly longer in the embodiment than in the conventional example. You can see that it is.

Therefore, according to the present embodiment, the following effects can be obtained. (1) According to the present embodiment having the above configuration, the bent portions 43a of both the dynamic pressure generating region regions 41a, 41b are arranged so as to be away from each other. Therefore, the distance between the two pressure peak points P1 and P2 in the air bearing, in other words, the distance between the support points in the air bearing can be reliably increased as compared with the conventional example. As a result, a radial air bearing excellent in rigidity and stability can be realized.

(2) In the present embodiment, the dynamic pressure generating region 4
1a, 41b, the one located closest to the gas seal area 42 (ie, 41a) is the other one (ie, 41a).
It is formed wider than in b). For this reason, in the first dynamic pressure generating region 41a, the air collecting ability is higher than in the second dynamic pressure generating region 41b. Therefore, even if air is evacuated to the gas seal portion area 42 by the action of vacuum evacuation, the air can be compensated for, and sufficient dynamic pressure can be generated. This contributes to the improvement in the rigidity and stability of the bearing. In addition, by adopting this configuration, a balanced radial air bearing can be obtained.

(3) In this embodiment, the distance ratio L
1: L2 is set to a value within the above preferred range. For this reason, the rigidity and stability of the radial air bearing can be reliably improved.

(4) The turbo-molecular pump 1 of this embodiment is provided with a radial air bearing having excellent rigidity and stability as described above. Therefore, the rotating shaft 14 can withstand a relatively large load and rotate at high speed. Therefore, it is possible to provide a high-performance turbo-molecular pump 1 that can reliably obtain an ultra-high vacuum state.

The embodiment of the present invention may be modified as follows. -In another example shown in Fig. 5A, the widths of both dynamic pressure generating section regions 41a and 41b are equal. As described above, it is also possible to adopt a structure in which the first dynamic pressure generating region 41a is not widened.

The dynamic pressure generating region 41a, 41b is not limited to two rows, but may be larger (ie, three rows, four rows,
5 rows ...). For example, in another example shown in FIG. 5B, three rows are formed because the third dynamic pressure generating section area 41c is added. Then, with respect to the added third dynamic pressure generation region 41c, the bent portion 43a of the dynamic pressure groove 43 is moved from the central portion C1 of the dynamic pressure generation region 41c to the gas seal portion region 42 along the bearing center line. It is arranged in a state shifted in the direction opposite to the direction. The bent portion 43a of the second dynamic pressure generation region 41b is not particularly displaced, but is disposed at the center C1 of the dynamic pressure generation region 41b.

In the embodiment or another example of FIG. 5 (a), only the first dynamic pressure generating region 41a is shifted from the central portion C1, and the second dynamic pressure generating region 41b is not shifted. It may be arranged in the central part C1 as it is.

The magnet constituting the thrust bearing is not limited to a permanent magnet, but may be an electromagnet. For example, if the fixed magnet is an electromagnet and the rotating shaft 14 is a permanent magnet, the structure of the motor 12 can be simplified and reduced in size.

The pressure generating device of the present invention may be embodied not only as a single gas seal type as in the embodiment and the like, but also as a double gas seal type.

The pressure generating device of the present invention may be embodied not only as having the brushless motor 12 as in the above embodiment, but also as having, for example, a motor with a brush. .

The pressure generating device of the present invention can be embodied not only as a turbo molecular pump but also as a compressor, for example. Next, in addition to the technical ideas described in the claims, technical ideas grasped by the above-described embodiments will be listed below.

(1) A motor provided with a rotating shaft whose movement in the radial and thrust directions is restricted by a non-contact bearing, and a wing attached to the rotating shaft, and a working fluid is supplied by rotation of the wing. In a pressure generating device that generates a negative pressure or a positive pressure by sending in one direction, a non-contact type bearing that regulates the radial movement of the rotating shaft includes a plurality of non-contact bearings along a circumferential direction of an outer peripheral surface of the cylindrical body. An air bearing including a plurality of rows of band-shaped dynamic pressure generating regions formed by forming a herringbone-shaped dynamic pressure groove, wherein the dynamic pressure grooves in at least one of the outermost dynamic pressure generating regions are arranged. The pressure generating device, wherein the bent portion is arranged so as to be offset from a central portion of the dynamic pressure generating portion region in an outward direction along a bearing center line.

(2) A motor having a rotating shaft whose movement in the radial and thrust directions is restricted by a non-contact type bearing, and a wing attached to the rotating shaft, and a working fluid is supplied by rotation of the wing. In a pressure generating device that generates a negative pressure or a positive pressure by sending in one direction, a non-contact type bearing that regulates the radial movement of the rotating shaft includes a plurality of non-contact bearings along a circumferential direction of an outer peripheral surface of the cylindrical body. An air bearing including a plurality of rows of belt-shaped dynamic pressure generating regions formed by forming a substantially V-shaped dynamic pressure groove, wherein the dynamic pressure grooves in the both dynamic pressure generating regions are located at the center of the dynamic pressure generating region. A pressure generating device characterized by being formed so as to be left-right asymmetric with respect to a part.

[0060]

As described above in detail, according to the first to fifth aspects of the present invention, it is an object to provide a pressure generating device including a radial bearing having excellent rigidity and stability.

According to the invention described in claim 6, it is possible to provide a high-performance turbo-molecular pump capable of reliably obtaining an ultra-high vacuum state.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a turbo-molecular pump according to an embodiment of the invention.

FIG. 2 is a sectional view of the brushless motor according to the embodiment;

FIG. 3A is a side view showing an outer peripheral surface of a cylindrical cover constituting a conventional air bearing, and FIG. 3B is a side view showing an outer peripheral surface of a cylindrical cover constituting an air bearing of the embodiment.

FIG. 4A is a schematic diagram showing a pressure distribution in a conventional air bearing, and FIG. 4B is a schematic diagram showing a pressure distribution in an air bearing of the embodiment.

FIGS. 5A and 5B are side views showing the outer peripheral surface of a cylindrical cover constituting an air bearing of another example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Turbo molecular pump, 5 ... Static blade as a blade, 12 ... Brushless motor as a motor, 14 ... Rotating shaft, 19 ...
Moving blades as wings, 25 ... a cylindrical cover as a cylindrical body, 4
1a, 41b: dynamic pressure generating region, 42: gas seal region, 43: dynamic pressure groove, 43a: bent portion, C1: central portion,
L1, L2 ... distance.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) H02K 5/16 H02K 5/16 Z 7/08 7/08 A F-term (reference) 3H022 AA03 BA06 CA13 CA15 CA32 CA53 CA58 DA08 DA15 3H031 DA02 FA14 FA32 FA34 3J011 BA02 CA02 KA02 MA02 5H605 BB05 CC04 CC05 EB06 EB38 5H607 BB01 BB14 CC01 DD03 DD16 FF30 GG09 GG12 GG14

Claims (6)

[Claims] 1. A motor having a rotating shaft whose movement in a radial direction and a thrust direction is restricted by a non-contact type bearing, and a wing attached to the rotating shaft. In the pressure generating device that generates a negative pressure or a positive pressure by sending in a direction, a non-contact type bearing that regulates the movement of the rotating shaft in a radial direction includes a plurality of substantially non-contact bearings along a circumferential direction of an outer peripheral surface of the cylindrical body. An air bearing having a plurality of rows of belt-shaped dynamic pressure generating sections formed by forming a V-shaped dynamic pressure groove, wherein the dynamic pressure generating section includes at least one of the outermost dynamic pressure generating sections. The pressure generating device, wherein the bent portion is arranged so as to be shifted outward from a central portion of the dynamic pressure generating region along a bearing center line. 2. The air bearing includes a gas seal section formed adjacent to one end of the plurality of rows of dynamic pressure generating sections, and the gas seal section of the dynamic pressure generating section is the most of the dynamic pressure generating sections. The bent part of the dynamic pressure groove in the one located on the side is arranged so as to be shifted from the center part of the dynamic pressure generating part area toward the gas seal part area along the bearing center line. The pressure generating device according to claim 1. 3. The pressure generating device according to claim 2, wherein one of the dynamic pressure generating regions located closest to the gas seal region is formed wider than the others. apparatus. 4. The bent portion of the dynamic pressure generating groove in the dynamic pressure generating region adjacent to the dynamic pressure generating region located closest to the gas seal portion region is located between the center of the dynamic pressure generating region and the center of the bearing. The pressure generating device according to claim 2, wherein the pressure generating device is arranged so as to be displaced along a line in a direction opposite to a direction of the gas seal portion region. 5. In the dynamic pressure generating section region in which a bending portion of the dynamic pressure groove is arranged in a state shifted in a predetermined direction,
The ratio (L1: L2) of the distance (L1) from one end of the dynamic pressure generating region to the bent portion to the distance (L2) from the other end of the dynamic pressure generating region to the bent portion is 3 / 15
The pressure generating device according to any one of claims 1 to 4, wherein the pressure generating device has a pressure of ８ to 8/10. 6. A turbo-molecular pump provided with the pressure generating device according to claim 1.