EP3674551B1

EP3674551B1 - Vacuum pump apparatus

Info

Publication number: EP3674551B1
Application number: EP19217767.3A
Authority: EP
Inventors: Masami Nagayama
Original assignee: Ebara Corp
Current assignee: Ebara Corp
Priority date: 2018-12-28
Filing date: 2019-12-18
Publication date: 2024-01-24
Anticipated expiration: 2039-12-18
Also published as: JP2022128522A; CN111502954B; JP7141332B2; JP2020106005A; EP3674551A1; KR20200083239A; CN111502954A; TW202032014A; TWI826620B

Description

BACKGROUND OF THE INVENTION

Field of the Invention:

The present invention relates to a vacuum pump apparatus.

Description of the Related Art:

A vacuum pump (for example, a vacuum pump for exhausting a process gas, a high pumping speed vacuum pump, or the like) used for manufacturing a semiconductor and/or a flat panel such as an organic EL, liquid crystal is known.
In recent years, in the semiconductor manufacturing and/or the flat panel manufacturing, a flow rate of a process gas introduced into a process chamber has been increased due to performance enhancement of a semiconductor and/or enlargement of a panel. Under such circumstances, it is necessary to maintain the pressure in the process chamber at a certain pressure.
From the above-described necessity, a vacuum pump having a high pumping speed is required as a vacuum pump for exhausting the process gas, and a size of the vacuum pump is also increasing. However, as the size of the vacuum pump increases, an installation space of the vacuum pump apparatus in a semiconductor manufacturing plant and/or a flat panel manufacturing plant increases, and there is a problem in securing the installation space.

SUMMARY OF THE INVENTION

In order to reduce the installation space, it is conceivable to employ a vertically arranged vacuum pump apparatus. However, when a fixed-side bearing is disposed below a pump rotor as in JP H6 053 793 U , solid matter generated by condensation of an exhaust gas adheres and deposits in a gap between the pump rotor and a pump casing. Further, when the pump is stopped, the temperature of the vacuum pump apparatus is decreased, so that the pump rotor excessively compresses the solid matter. As a result, the rotation of the pump rotor is disturbed, and the vacuum pump apparatus cannot be restarted. Attention is also drawn to GB 809 443 A , which relates to a root pump provided with a specific two-walled casing having an inner and an outer shell. The root pump may be used in a vertical arrangement, in which a pair of shafts supporting pump rotors are extending vertically. In this vertical arrangement, the inner shell defines a pump chamber housing the pump rotors fixed to the shafts, the shafts extending through end walls of the inner shell and being supported by bearings in the respective end walls of the inner shell. The outer shell houses the inner shell, as well as the respective ends of the shafts extending through the end walls of the inner shell. Adjacent the upper end wall, of the inner shell, a chamber for receiving electric motors coupled to the respective ends of the shafts is formed by the outer shell. Adjacent the lower end wall of the inner shell a chamber for receiving the respective ends of the shafts and a gear train connecting the shafts is provided. Furthermore, WO 2010/061939 A1 discloses a dry vacuum pump unit having a pair of pump rotors, a casing having an air intake port and an exhaust port and motor section for rotationally driving the pair of pump rotors, the motor section including a pair of magnet rotors rotating in synchronism with each other in the opposite directions without using timing gears. Finally, EP 2 642 127 Al discloses a vacuum pump with pump rotor bearings on a single side, the vacuum pump having a pumping speed below 50 m³/h, and a screw pump assembly with two helical rotors which are in mutual engagement in a suction chamber of a screw pump stator and a two-shaft synchronous drive with two cylinders.
It is therefore an object of the present invention to provide a vacuum pump apparatus capable of reducing an installation space of the vacuum pump apparatus and reliably restarting the vacuum pump apparatus.
In accordance with the present invention, a vacuum pump apparatus as set forth in claim 1 is provided. Further embodiments are inter alia disclosed in the dependent claims. The vacuum pump apparatus inter alia comprises: a pair of pump rotors arranged opposite to each other, the pair of pump rotors being a roots rotor or a claw rotor; a pair of shafts fixed to the pair of pump rotors, the pair of shafts extending in a vertical direction; a motor configured to rotate the pair of pump rotors; a pair of timing gears fixed to the pair of shafts, the pair of timing gears meshing with each other; a pump casing configured to house the pair of pump rotors; a fixed-side bearing arranged above the pair of pump rotors, the fixed-side bearing being restricted in movement in an axial direction of the pair of shafts; and a free-side bearing configured to support the shaft together with the fixed-side bearing, the free-side bearing being movable in the axial direction.
In an embodiment, the motor is arranged above the pair of pump rotors.
In an embodiment, the vacuum pump apparatus further comprises an operation controller electrically connected to the motor, the operation controller being configured to perform a rotation and a stop operation of the pump rotor by repeating driving and stopping the motor before completely stopping the operation of the vacuum pump apparatus.
In an embodiment, the operation controller repeats the driving and stopping of the motor at predetermined time intervals.
In an embodiment, the vacuum pump apparatus further comprises: a temperature sensor attached to an outer surface of the pump casing, wherein the operation controller repeats the driving and stopping of the motor based on a temperature change of the pump casing measured by the temperature sensor.
When the operation of the vertically arranged vacuum pump device is stopped, the shaft contracts upward with respect to the fixed-side bearing disposed above the pump rotor due to a temperature decrease of the shaft. Therefore, the lateral gap between the lower surface of the pump rotor and the pump casing is increased, and the pump rotor does not crush solid matter. As a result, restarting of the vacuum pump apparatus is not disturbed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing an embodiment of a vacuum pump apparatus;
FIG. 2 is a sectional view showing one embodiment of the bearing apparatus;
FIG. 3 is a view showing lubricating oil circulating inside the bearing apparatus;
FIG. 4 is a perspective view showing a rotating cylinder;
FIG. 5 is an enlarged view of the rotating cylinder;
FIG. 6 is an enlarged view of a tray;
FIG. 7A is a view showing a contact seal;
FIG. 7B is a view showing a contact seal;
FIG. 8 is a view showing another embodiment of the vacuum pump apparatus;
FIG. 9A is a view for explaining a problem that may occur in a vacuum pump apparatus arranged vertically;
FIG. 9B is a view for explaining a problem that may occur in the vacuum pump apparatus arranged vertically;
FIG. 10A is a view for explaining an effect of the vacuum pump apparatus in the embodiment shown in FIG. 8; and
FIG. 10B is a view for explaining an effect of the vacuum pump apparatus in the embodiment shown in FIG. 8.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention will be described below with reference to the drawings. In the drawings described below, identical or corresponding components will be denoted by identical reference numerals, and repetitive descriptions thereof are omitted.
FIG. 1 is a sectional view showing an embodiment of a vacuum pump apparatus 1. As shown in FIG. 1, the vacuum pump apparatus 1 is a vertical vacuum pump apparatus arranged in an upright posture. In the embodiment shown in FIG. 1, the vacuum pump apparatus 1 is mounted on a floor FL. The vacuum pump apparatus 1 is a pump apparatus that rotates at a high speed. The vacuum pump apparatus 1 is arranged vertically to reduce an installation space of the vacuum pump apparatus 1.
The vacuum pump apparatus 1 includes a pair of pump rotors (roots rotors in this embodiment) 6a, 6b, 6c, and 6d arranged opposite to each other, a pair of shafts (drive shaft) 8 to which these pump rotors 6a to 6d are fixed, a pump casing 5 housing the pump rotors 6a to 6d, and a motor 10 for rotating the pump rotors 6a to 6d via the shaft 8.
In the embodiment shown in FIG. 1, the structures of the pump rotors 6a to 6d are not limited to the roots rotor. The pump rotors 6a to 6d may be claw rotors or screw rotors.
The vacuum pump apparatus 1 includes a suction port 2 for sucking a gas and an exhaust port 4 for discharging the gas. The gas is sucked into the vacuum pump apparatus 1 through the suction port 2 and discharged from the exhaust port 4 by an operation of the vacuum pump apparatus 1 (see the arrow in FIG. 1). The suction port 2 and the exhaust port 4 are provided in the pump casing 5.
The pump casing 5 has a gas passage 35 formed in the pump casing 5. The gas compressed by the pump rotors 6a to 6d is discharged from the exhaust port 4 through the gas passage 35.
In FIG. 1, only one of the pair of pump rotors 6a to 6d is illustrated, and an illustration of the opposite pump rotor is omitted. Only one of the pair of shafts 8 is illustrated, and an illustration of the opposite shaft is omitted. In FIG. 1, the number of stages of the pump rotor is four. The number of stages of the pump rotor is not limited to this embodiment. The number of stages of the pump rotor can be appropriately selected according to a required degree of vacuum, a flow rate of an exhaust gas, and the like. In one embodiment, a single stage pump rotor may be provided.
The vacuum pump apparatus 1 includes an operation controller 12 for controlling the operation of the vacuum pump apparatus 1. The operation controller 12 is electrically connected to the motor 10. The operation controller 12 is configured to control a rotation and a stop operation of the pump rotors 6a to 6d by driving and stopping the motor 10.
The shaft 8 extends in a vertical direction, and is rotatably supported by a bearing 13 and a bearing apparatus 15 (more specifically, bearings 20 and 21 provided on the bearing apparatus 15). The bearing 13 is disposed at one end portion (i.e., a lower end portion) of the shaft 8. The bearing apparatus 15 (more specifically, the bearings 20 and 21) is disposed at the other end portion (i.e., an upper end portion) of the shaft 8.
Timing gears 25 meshing with each other are provided at one end of the shafts 8. These timing gears 25 are housed in a gear cover 26 together with the bearing 13. In FIG. 1, only one of the pair of timing gears 25 is illustrated. In the embodiment shown in FIG. 1, the timing gears 25 are disposed below the pump rotors 6a to 6d. In one embodiment, the timing gears 25 may be disposed above the pump rotors 6a to 6d.
The motor 10 includes a motor rotor 30 fixed to at least one of two shafts 8, a motor stator 31 having a stator core on which a coil is wound, and a motor frame 32 for housing the motor rotor 30 and the motor stator 31. The motor stator 31 is arranged so as to surround the motor rotor 30, and is fixed to an inner circumferential surface of the motor frame 32.
When the motor 10 is driven, the pair of pump rotors 6a to 6d is rotated in opposite directions via the timing gear 25, and a gas is sucked into the pump casing 5 through the suction port 2. The sucked gas is transferred a downstream by the pump rotors 6a to 6d and discharged from the exhaust port 4.
The vacuum pump apparatus 1 is a pump apparatus for rotating at a high speed and is arranged vertically. Therefore, the bearing apparatus provided in the vacuum pump apparatus 1 also needs to be arranged vertically. However, if a bearing apparatus having a general structure is employed as it is in the vacuum pump apparatus 1 capable of a high-speed operation, lubricating oil for lubricating and cooling each of the bearings 20 and 21 may be not sufficiently supplied to the bearings 20 and 21. In this case, each of the bearings 20 and 21 cannot exhibit its function sufficiently. Therefore, in this embodiment, the vacuum pump apparatus 1 includes the bearing apparatus 15 having a structure capable of sufficiently exhibiting the functions of the bearings 20 and 21. Hereinafter, the structure of the bearing apparatus 15 will be described with reference to the drawings.
FIG. 2 is a sectional view showing one embodiment of the bearing apparatus 15. The bearing apparatus 15 is an oil circulation type bearing apparatus in which lubricating oil circulates inside the bearing apparatus 15. FIG. 3 is a view showing the lubricating oil circulating inside the bearing apparatus 15. In FIG. 3, reference numerals are omitted for the purpose of making it easier to view the drawing. In FIG. 3, a flow of the lubricating oil is represented by arrows.
As shown in FIG. 2, the bearing apparatus 15 includes the bearings 20 and 21 for supporting the shaft 8 which extends in the vertical direction, a bearing housing 40 for housing the bearings 20 and 21, a rotating cylinder 45 which can be fixed to the shaft 8, and a bearing casing 46 for housing the bearings 20 and 21, the bearing housing 40, and the rotating cylinder 45.
The bearings 20, 21 are arranged in series in the vertical direction. The bearings 20 and 21 are bearings that receive a thrust load and a radial load on the shaft 8. The bearing housing 40 houses the bearings 20 and 21, and is arranged concentrically with the shaft 8 and the bearings 20 and 21. In this embodiment, two bearings 20, 21 are provided, however the number of bearings is not limited to this embodiment. In one embodiment, a single bearing may be provided. Further, in one embodiment, a free-side bearing that receives only the radial load may be provided.
A spacer 41 mounted on the shaft 8 and a fixture (for example, a shaft nut) 42 fixed to the shaft 8 via the spacer 41 are arranged above the bearing 20. The spacer 41 and the fixture 42 receive the thrust load (a load in an axial direction CL of the shaft 8) acting on the bearings 20 and 21. More specifically, the spacer 41 is in close contact with an inner race of the bearing 20, and the fixture 42 restricts a movement of the bearing 20 in the axial direction CL via the spacer 41.
The rotating cylinder 45 is disposed below the bearing 21 (in other words, the bearing housing 40). The rotating cylinder 45 is in close contact with an inner race of the bearing 21 and restricts a movement of the bearing 21 in the axial direction CL.
A seal member 43 fixed to the shaft 8 is arranged above the fixture 42. The seal member 43 is a member for preventing the lubricating oil disposed in the bearing casing 46 from leaking to the outside. The lubricating oil is a liquid for lubricating and cooling the bearings 20, 21.
The bearing casing 46 includes a side cover 50 which is connected to the pump casing 5 and stores the lubricating oil, a case member 51 which is disposed above the side cover 50 and constitutes an upper end portion of the bearing apparatus 15, and a bearing-support member 52 disposed between the side cover 50 and the case member 51. The bearing-support member 52 is sandwiched between the side cover 50 and the case member 51.
The side cover 50 has a through hole 50a at a center of the side cover 50 through which the shaft 8 penetrates, and two piston rings 55 are arranged between an outer circumferential surface of the shaft 8 and the through hole 50a. Each of the piston rings 55 is mounted on the shaft 8, and is arranged in series in the vertical direction to prevent leakage of lubricating oil to the outside.
The side cover 50 includes an annular inner circumferential wall 56 disposed adjacent to the shaft 8, an annular outer circumferential wall 57 disposed radially outwardly the inner circumferential wall 56, and a bottom wall 58 arranged between the inner circumferential wall 56 and the outer circumferential wall 57. The lubricating oil is held by the inner circumferential wall 56, the outer circumferential wall 57, and the bottom wall 58.
A water cooling jacket 90 is attached to an outer circumferential surface of the bearing casing 46, more specifically, to the outer circumferential wall 57 of the side cover 50 (see FIGS. 1 and 2). The water cooling jacket 90 has a structure in which cooling water circulates, and cools the lubricating oil held in the side cover 50 through the side cover 50.
The bottom wall 58 has a communication hole 59 that communicates with a space between the upper piston ring 55 and the lower piston ring 55. The communication hole 59 is a hole for supplying a shaft sealing gas (for example, an inert gas such as N₂ gas) to the space between the upper piston ring 55 and the lower piston ring 55.
The inner circumferential wall 56 is connected to the through hole 50a, and an upper end of the inner circumferential wall 56 is disposed at a position higher than the liquid level of the lubricating oil held by the side cover 50. With such an arrangement, the leakage of the lubricating oil to the outside due to an overflow of the inner circumferential wall 56 is suppressed.
When the shaft 8 is rotated, the rotating cylinder 45 fixed to the shaft 8 also is rotated together with the shaft 8, and the lubricating oil held by the side cover 50 is scooped above the side cover 50 by the rotating cylinder 45 (see FIG. 3). Hereinafter, a structure of the rotating cylinder 45 will be described with reference to the drawings.
FIG. 4 is a perspective view showing the rotating cylinder 45. FIG. 5 is an enlarged view of the rotating cylinder 45. In FIG. 5, an illustration of the water cooling jacket 90 is omitted. As shown in FIGS. 4 and 5, the rotating cylinder 45 includes two slopes 70 formed on an outer circumferential surface 45a of the rotating cylinder 45. In FIG. 4, only one slope 70 is illustrated.
Two slopes 70 are arranged at equal intervals along a circumferential direction of the rotating cylinder 45. Each of the slopes 70 is disposed in a gap between the outer circumferential surface 45a of the rotating cylinder 45 and an inner surface of the outer circumferential wall 57. In this embodiment, two slopes 70 are provided, however the number of slopes 70 is not limited to this embodiment. In one embodiment, three or more slopes 70 may be provided. Even in this case, the slopes 70 are arranged at equal intervals along the circumferential direction of the rotating cylinder 45.
The rotating cylinder 45 includes an inner cylindrical portion 71 that can be fixed to the shaft 8, an outer cylindrical portion 72 disposed outside the inner cylindrical portion 71, and an annular ring portion 73 that couples the inner cylindrical portion 71 and the outer cylindrical portion 72. The inner cylindrical portion 71 and the outer cylindrical portion 72 are arranged concentrically with the shaft 8.
The inner cylindrical portion 71 is disposed below the bearing 21, and the outer cylindrical portion 72 is disposed radially outwardly the bearing 21. A height of the outer cylindrical portion 72 is higher than a height of the inner cylindrical portion 71. In this embodiment, the inner cylindrical portion 71, the outer cylindrical portion 72, and the annular ring portion 73 are integrally formed members.
The outer circumferential surface 45a of the rotating cylinder 45 corresponds to an outer circumferential surface of the outer cylindrical portion 72. Therefore, the slope 70 may be represented as being provided on the outer circumferential surface of the outer cylindrical portion 72.
In this embodiment, an upper end portion 70a of the slope 70 is connected to an upper end 45b of the rotating cylinder 45, and a lower end portion 70b of the slope 70 is connected to a lower end 45c of the rotating cylinder 45. A scooping surface 70c is formed between the upper end portion 70a and the lower end portion 70b of the slope 70. The slope 70 has a curved shape that extends obliquely downward from the upper end portion 70a (i.e., the upper end 45b) toward the lower end portion 70b (i.e., the lower end 45c) in a rotation direction of the rotating cylinder 45. In other words, the slope 70 is inclined with respect to the axial direction CL.
When the rotating cylinder 45 is rotated with the shaft 8, the slope 70 is rotated around a center of the shaft 8. When the slope 70 is rotated, the scooping surface 70c advances in the rotation direction of the rotating cylinder 45, and scoops up the lubricating oil stored in the side cover 50. The scooped lubricating oil moves obliquely upward in an annular gap between the outer circumferential surface 45a of the rotating cylinder 45 and the outer circumferential wall 57.
As shown in FIG. 2, an upper end of the outer circumferential wall 57 of the side cover 50 is arranged at a position higher than the rotating cylinder 45 fixed to the shaft 8. The bearing-support member 52 extends in a horizontal direction, and is connected to the upper end of the outer circumferential wall 57. The bearing-support member 52 supports the bearing housing 40, and receives a radial load (a load in a direction perpendicular to the axial direction CL of the shaft 8) and a thrust load (a load in a direction parallel to the axial direction CL of the shaft 8) acting on the bearings 20 and 21 via the bearing housing 40.
The bearing-support member 52 has two flow holes 52a through which the lubricating oil scooped up by the slope 70 can pass. Two flow holes 52a are arranged at equal intervals in a circumferential direction of the bearing-support member 52. In this embodiment, two flow holes 52a are provided, however the number of flow holes 52a is not limited to this embodiment.
The case member 51 is connected to the bearing-support member 52. The lubricating oil scooped up by the rotating cylinder 45 reaches the case member 51 through the flow holes 52a of the bearing-support member 52. The lubricating oil that has reached the case member 51 collides with the upper end wall 51a of the case member 51, and a direction of the lubricating oil is changed, and is guided to the bearings 20 and 21.
The upper end wall 51a of the case member 51 is disposed above the rotating cylinder 45 and the bearings 20 and 21, and has a tapered shape for smoothly guiding the lubricating oil to the bearings 20 and 21. More specifically, the upper end wall 51a has a curved portion 60 formed on the inner surface of the upper end wall 51a, and a tapered portion 61 connected to the curved portion 60. The tapered portion 61 is a protrusion extending from the upper end wall 51a toward the bearing housing 40, and is disposed adjacent to the seal member 43.
The tapered portion 61 has a tapered shape in which a sectional area of the tapered portion 61 is gradually decreased from the curved portion 60 toward the bearing housing 40, and a lowermost end of the tapered portion 61 is arranged above the bearing housing 40. The upper end wall 51a can smoothly change the direction of the lubricating oil colliding with the upper end wall 51a and guide the lubricating oil to the bearings 20 and 21 (see FIG. 3).
The bearing housing 40 includes a housing main body 64 and a tray 65 disposed at an upper end of the housing main body 64. FIG. 6 is an enlarged view of the tray 65. The tray 65 guides the lubricating oil to the bearings 20 and 21 while receiving the lubricating oil whose direction has been changed by colliding with the upper end wall 51a. The tray 65 has a through hole 65a formed at a center of the tray 65, an inner annular protrusion 66 connected to the through hole 65a, an outer annular protrusion 67 disposed outside the inner annular protrusion 66, and a connection portion 68 for connecting the inner annular protrusion 66 and the outer annular protrusion 67.
The inner annular protrusion66 and the outer annular protrusion67 are arranged concentrically with the shaft 8. The inner annular protrusion 66 extends downward from the connection portion 68, i.e., toward the bearing 20, and the outer annular protrusion 67 extends upward from the connection portion 68, i.e., toward the upper end wall 51a.
The inner annular protrusion 66 is in close contact with an outer race of the bearing 20, and restricts a movement of the bearing 20 in the axial direction CL. The housing main body 64 of the bearing housing 40 is in close contact with an outer race of the bearing 21, and restricts a movement of the bearing 21 in the axial direction CL (see FIG. 2).
As described above, the bearings 20 and 21 are fixed-side bearings in which the movement of the bearings 20 and 21 in the axial direction CL is restricted by the fixture 42, the bearing housing 40, and the rotating cylinder 45. The bearing 13 disposed on the opposite side of the bearings 20 and 21 across the pump rotors 6a to 6d is a free-side bearing that can move in the axial direction CL. The bearings 20 and 21 as the fixed-side bearings are arranged above the pump rotors 6a to 6d, and the bearing 13 as a free-side bearing is arranged below the pump rotors 6a to 6d.
The outer annular protrusion 67 is disposed at a position further away from the shaft 8 than the tapered portion 61 of the upper end wall 51a (see FIG. 2). Therefore, the outer annular protrusion 67 can prevent the lubricating oil dropped from the tapered portion 61 onto the tray 65 from flowing outside the tray 65. The lubricating oil dropped onto the tray 65 contacts the bearings 20, 21 through the gap between the through hole 65a and the spacer 41, and as a result, lubricates and cools the bearings 20, 21.
The lubricating oil that has contacted the bearings 20 and 21 passes through the bearings 20 and 21 and falls on the rotating cylinder 45 (see FIG. 3). More specifically, the lubricating oil is held by the inner cylindrical portion 71, the outer cylindrical portion 72, and the annular ring portion 73.
Centrifugal force due to the rotation of the rotating cylinder 45 acts on the lubricating oil held by the rotating cylinder 45. The lubricating oil passes through a gap between the housing main body 64 and the outer cylindrical portion 72 to flow into the annular gap between the outer circumferential surface 45a of the rotating cylinder 45 and the outer circumferential wall 57. Thereafter, the lubricating oil is again scooped up by the slope 70.
In this manner, the bearing apparatus 15 can form a circulating flow of the lubricating oil (i.e., an upward flow and a downward flow of the lubricating oil) inside the bearing apparatus 15. The circulating lubricating oil can contact the bearings 20 and 21 to lubricate and cool the bearings 20 and 21. As a result, each of the bearings 20 and 21 can sufficiently exhibit its function.
As shown in FIGS. 2 and 5, the rotating cylinder 45 is arranged so as to surround a part of the bearing 21. The upper end of the outer cylindrical portion 72 is arranged at a position higher than a lower end of a roller 21a of the bearing 21. The upper end of the outer cylindrical portion 72 is preferably arranged at the same position as the center of the roller 21a. With such a structure, when the operation of the vacuum pump apparatus 1 is stopped, the rollers 21a of the bearing 21 always contact the lubricating oil held by the rotating cylinder 45. Therefore, the vacuum pump apparatus 1 can restart the operation of the vacuum pump apparatus 1 without bringing the bearing 21 into an unlubricated state.
The effect of the bearing apparatus 15 having the structure for forming the circulating flow of the lubricating oil will be described. A configuration is conceivable in which a vacuum pump apparatus is operated while a bearing is always immersed in lubricating oil. However, in such a configuration, during operation of the vacuum pump apparatus, the bearing is rotated in the lubricating oil, so that a temperature increase of the bearing due to a stirring heat of the lubricating oil is large, and the bearing may be damaged. Therefore, it is not desirable to employ the vacuum pump apparatus 1 which is rotated at a high speed (for example, 4000 min^-1).
According to this embodiment, the bearing apparatus 15 is configured to circulate the lubricating oil by the slope 70. Therefore, the bearings 20 and 21 are lubricated and cooled by the lubricating oil without being affected by the stirring heat of the lubricating oil. As a result, each of the bearings 20 and 21 can sufficiently exhibit its function.
According to this embodiment, the vacuum pump apparatus 1 includes the bearing apparatus 15 which can bring the lubricating oil into reliable contact with the bearings 20, 21 and sufficiently exhibit the functions of the bearings 20, 21. Therefore, the vacuum pump apparatus 1 arranged vertically can be operated without any problem. As a result, an installation space of the vacuum pump apparatus 1 can be reduced, and the vacuum pump apparatus 1 can be operated at a high pumping speed.
Since the vacuum pump apparatus 1 is arranged vertically, gravity acts on the lubricating oil in the bearing apparatus 15. Further, when a gas flow rate flowing from a process chamber side changes or stops during operation of the vacuum pump apparatus 1, a pressure in a pump chamber also changes, so that a pressure difference is generated between the pressure in the pump chamber and a pressure in a bearing chamber. Therefore, the gas moves from a high pressure side to a low pressure side between two pressures. In particular, when a gas inflow from the process chamber side stops at once in a state in which a large flow rate of the gas is exhausted and the pressure in the pump chamber and the pressure in the bearing chamber are high, the pressure of the pump chamber drops at once, and a large pressure difference between the pump chamber side and the bearing chamber side. Therefore, a large amount of gas flows from the bearing chamber side to the pump chamber side, and the lubricating oil (mist lubricating oil and liquid lubricating oil) may leak outside (pump chamber side) along with this flow.
When the lubricating oil leaks, the amount of lubricating oil in the bearing apparatus 15 is decreased, and the amount of lubricating oil supplied to the bearings 20 and 21 is decreased. Not only may the bearing be damaged, but also the leaked lubricating oil may flow back to the process chamber side via the pump chamber, causing wafer contamination. Therefore, the bearing apparatus 15 has a structure capable of reliably preventing the leakage of the lubricating oil.
As shown in FIG. 5, the rotating cylinder 45 includes a plurality of downward ribs 75, 76, 77 extending from the lower surface of the rotating cylinder 45 to the bottom wall 58 (i.e., below) of the side cover 50. Each of these downward ribs 75, 76, 77 has a cylindrical shape and is arranged concentrically with the shaft 8. Hereinafter, in this specification, the downward rib 75 may be referred to as an inner downward rib 75, the downward rib 76 may be referred to as an intermediate downward rib 76, and the downward rib 77 may be referred to as an outer downward rib 77.
The inner downward rib 75 and the intermediate downward rib 76 extend downward from a lower surface of the annular ring portion 73, and the outer downward rib 77 extends downward from a lower surface of the outer cylindrical portion 72.
The side cover 50 includes a plurality of upward ribs 80 and 81 extending from the bottom wall 58 of the side cover 50 toward the lower surface (i.e., above) of the rotating cylinder 45. Each of the upward ribs 80 and 81 has a cylindrical shape, and is arranged concentrically with the shaft 8. Hereinafter, in this specification, the upward rib 80 may be referred to as an inner upward rib 80, and the upward rib 81 may be referred to as an outer upward rib 81.
The inner upward rib 80 has passage portions (i.e., oil passage portions) 80a that allow the passage of the lubricating oil. In this embodiment, two passage portions 80a are provided, however the number of passage portions 80a is not limited to this embodiment. The outer upward rib 81 also has passage portions (i.e., oil passage portions) 81a that allow the passage of the lubricating oil. In this embodiment, two passage portions 81a are provided, however the number of passage portions 81a is not limited to this embodiment. The lubricating oil can pass through the passage portions 80a and the passage portions 81a. The passage portion 80a is a hole for making a liquid level of the lubricating oil existing between the inner circumferential wall 56 and the inner upward rib 80 equal to a liquid level of the lubricating oil existing between the inner upward rib 80 and the outer upward rib 81. The passage portion 81a is a hole for making a liquid level of the lubricating oil existing between the inner upward rib 80 and the outer upward rib 81 equal to a liquid level of the lubricating oil existing between the outer upward rib 81 and the outer downward rib 77 of the rotating cylinder 45.
The passage portion 80a is a return flow path for returning the lubricating oil that has passed through a gap between the inner upward rib 80 and the inner downward rib 75 to a space between the inner upward rib 80 and the outer upward rib 81. In one embodiment, the passage portion 80a may be a hole formed at a lower portion of the inner upward rib 80. In another embodiment, the passage portion 80a may be a cutout formed at a lower end of the inward upward rib 80. The passage portion 81a a return flow path for returning the lubricating oil to a space between the outer circumferential surface 45a of the rotating cylinder 45 and an inner surface of the bearing casing 46 in order to lubricate the bearings 20 and 21 with the lubricating oil that has passed through a pressure adjustment hole 74 described later and the lubricating oil that has returned from the passage portion 80a. In one embodiment, the passage portion 81a may be a hole formed below the outer upward rib 81. In another embodiment, the passage portion 81a may be a cutout formed at a lower end of the outer upward rib 81.
In this embodiment, the outer downward rib 77 extends below the inner downward rib 75 and the intermediate downward rib 76. A lower end 75a of the inner downward rib 75 and a lower end 76a of the intermediate downward rib 76 are arranged at the same height. The lower end 75a of the inner downward rib 75 and the lower end 76a of the intermediate downward rib 76 are arranged above the lubricating oil held by the side cover 50, and a lower end 77a of the outer downward rib 77 is immersed in the lubrication oil held by the side cover 50. A lower end 45c of the rotating cylinder 45 corresponds to the lower end 77a of the outer downward rib 77.
The rotating cylinder 45 has the pressure adjustment hole 74 formed in the outer cylindrical portion 72. The pressure adjustment hole 74 extends in the vertical direction. In this embodiment, two pressure adjustment holes 74 are provided, however the number of pressure adjustment holes 74 is not limited to this embodiment. In one embodiment, one pressure adjustment hole 74 may be provided.
As described above, the lower end 77a of the outer downward rib 77 is immersed in the lubricating oil. Therefore, in a case where the pressure adjustment hole 74 is not provided, the passage of the gas is shut off by the lubricating oil between a space (first space SP1) above the rotating cylinder 45 and a space below the rotating cylinder 45, in other words, a space (second space SP2) surrounded by the outer downward rib 77. Therefore, for example, when the vacuum pump apparatus 1 is stopped, the first space SP1 and the second space SP2 are at the atmospheric pressure. However, when the vacuum pump apparatus 1 is started, the pressure in the pump chamber side is decreased, and the pressure in the second space SP2 is decreased. While the pressure in the first space SP1 remains at the atmospheric pressure, so that a pressure difference is generated between two spaces. As a result, the gas in the first space SP1 expands and presses the liquid level of the lubricating oil between the outer circumferential surface 45a of the rotating cylinder 45 and the inner surface of the bearing casing 46 to increase the liquid level of the lubricating oil in the second space SP2. Therefore, the lubricating oil may flow over the inner circumferential wall 56. In this embodiment, the pressure adjustment hole 74 can communicate the first space SP1 and the second space SP2. The pressure in the first space SP1 and the pressure in the second space SP2 are always the same. Therefore, an increase of the liquid level of the lubricating oil inside the outer downward rib 77 is prevented.
The inner downward rib 75 is disposed radially outwardly the inner circumferential wall 56. The inner upward rib 80 is disposed radially outwardly the inner downward rib 75. The intermediate downward rib 76 is disposed radially outwardly the inner upward rib 80. The outer upward rib 81 is disposed radially outwardly the intermediate downward rib 76. The outer downward rib 77 is disposed radially outwardly the outer upward rib 81.
In this manner, the downward ribs 75, 76, 77 and the upward ribs 80, 81 are alternately arranged and have a labyrinth structure. More specifically, the inner downward rib 75, the inner upward rib 80, the intermediate downward rib 76, the outer upward rib 81, and the outer downward rib 77 are arranged from the inner circumferential wall 56 to the outer circumferential wall 57 in this order.
When the pressure difference (the space pressure in the bearing casing 46 is higher than the space pressure in the pump casing 5) is generated between the space in the bearing casing 46 and the space in the pump casing 5 immediately after the vacuum pump apparatus 1 discharges a process gas, the gas in the space inside the bearing casing 46 zigzags through the labyrinth structure toward the pump casing 5. The lubricating oil (mist lubricating oil and liquid lubricating oil) moving along with the gas flow is shaken off of the gas flow due to its own weight by a zigzag path formed between the downward ribs 75, 76, 77 and the upward ribs 80, 81. As a result, the progress of the lubricating oil to the pump casing 5 is blocked. Therefore, the bearing apparatus 15 can reliably prevent the lubricating oil from leaking to the pump casing 5.
FIGS. 7A and 7B are views showing a contact seal. As shown in FIG. 7A, in order to more reliably prevent the leakage of the lubricating oil, a contact seal (first contact seal) 85 may be arranged between the inner downward rib 75 of the rotating cylinder 45 and the inner circumferential wall 56 of the side cover 50. As shown in FIG. 7B, a contact seal (second contact seal) 86 may be arranged between the shaft 8 and the inner circumferential wall 56 of the side cover 50. Although not shown in the drawing, the bearing apparatus 15 may include both the contact seals 85 and 86. Known contact seals can be employed as the contact seals 85 and 86.
FIG. 8 is a view showing another embodiment of the vacuum pump apparatus 1. Structures, which will not be described particularly in this embodiment, are identical to those of the above-described embodiment, and repetitive descriptions thereof are omitted.
As shown in FIG. 8, the bearings 20 and 21 are supported by a bearing-support member 100 for supporting the bearings 20 and 21. In the embodiment shown in FIG. 8, the bearing-support member 100 supports the bearings 20, 21 so as to limit the movement of the bearings 20, 21 in the axial direction CL. Therefore, also in the embodiment shown in FIG. 8, the bearings 20 and 21 are fixed-side bearings. The bearing 13 disposed on the opposite side of the bearings 20 and 21 across the pump rotors 6a to 6d is a free-side bearing. The vacuum pump apparatus 1 according to the embodiment shown in FIG. 8 may include a bearing apparatus 15 having the configuration shown in FIGS. 1 to 7.
In the embodiment shown in FIG. 8, the bearings 20 and 21, which are the fixed-side bearings, are provided above the pump rotors 6a to 6d (more specifically, the uppermost pump rotor 6a of the pump rotors 6a to 6d). In the embodiment shown in FIG. 8, the bearing 13 which is the free-side bearing is arranged below the bearings 20 and 21 which are the fixed-side bearings, more specifically, below the pump rotors 6a to 6d. In one embodiment, the bearing 13 may be arranged above the pump rotors 6a to 6d. The bearing 13 may be arranged inside the bearing apparatus 15. In one embodiment, the timing gear 25 may be arranged above the pump rotors 6a to 6d.
The timing gear 25, the bearing 13, the pump rotors 6a to 6d, the bearing apparatus 15, and the motor 10 are arranged vertically in series along the axial direction CL of the shaft 8. In the embodiment shown in FIG. 8, the pump rotors 6a to 6d are the roots rotors or the claw rotors. Therefore, the vacuum pump apparatus 1 is a roots-type pump apparatus having a roots-type exhaust system or a claw-type pump apparatus having a claw-type exhaust system. Further, in one embodiment, a combined pump apparatus in which at least one stage of the pump rotor is a roots rotor or a claw rotor may be used. Although not shown in the drawing, a heater for increasing the temperature of the pump casing 5 may be attached to the pump casing 5.
In the embodiment shown in FIG. 8, the motor 10 is arranged above the bearing apparatus 15 (more specifically, the bearings 20, 21). With such an arrangement, a position of the center of gravity of the pump rotors 6a to 6d and the pump casing 5, which are heavy components of the components of the vacuum pump apparatus 1, can be lowered. Therefore, an installation stability of the vacuum pump apparatus 1 during moving and operating of the vacuum pump apparatus 1 can be improved, and the vacuum pump apparatus 1 can be prevented from falling.
In a case where the roots type or the claw type is adopted as the exhaust method, a gap between the pump casing 5 and each of the pump rotors 6a to 6d in a direction perpendicular to the axial direction CL of the shaft 8 is extremely small. By forming such a small gap, a backflow of the process gas to be discharged is suppressed, and an exhaust performance of the vacuum pump apparatus 1 can be maintained. Hereinafter, this gap may be referred to as a lateral gap.
FIGS. 9A and 9B are views for explaining a problem that may occur in a vacuum pump apparatus arranged vertically. In FIGS. 9A and 9B, the pump rotor 6 and the pump casing 5 are illustrated, and the lateral gap between the pump rotor 6 and the pump casing 5 is exaggerated. Further, the free-side bearing B1 is arranged above the pump rotor 6, and the fixed-side bearing B2 is arranged below the pump rotor 6. The vacuum pump apparatus in FIGS. 9A and 9B is an apparatus for explaining the above problem, and has a different configuration from the vacuum pump apparatus 1 according to this embodiment.
During operation of the vacuum pump apparatus, the shaft 8 expands upward with respect to the fixed-side bearing B2 due to a temperature increase of the shaft 8. However, since the temperature of the pump rotor 6 becomes higher than the temperature of the pump casing 5, regarding the lateral gap between the pump rotor 6 fixed to the shaft 8 and the pump casing 5, a lower gap is widened and an upper gap is narrowed. When the process gas is exhausted in this state, the exhaust gas is solidified due to its sublimability depending on the exhaust gas, so that solid matters (see black circles in FIGS. 9A and 9B) adhere and deposit in the lateral gap. More solid matters deposit in the lateral gap between the lower surface of the pump rotor 6 and the pump casing 5 due to its own weight.
In a state in which the solid matters are deposited, as shown in FIG. 9B, when the operation of the vacuum pump apparatus is stopped for maintenance of the vacuum pump apparatus or maintenance of an exhaust gas treatment apparatus on a downstream side of the vacuum pump apparatus, the shaft 8 contracts downward with respect to the fixed-side bearing B2 due to a temperature decrease of the shaft 8. As a result, the lateral gap between the lower surface of the pump rotor 6 fixed to the shaft 8 and the pump casing 5 is small. Therefore, the pump rotor 6 compresses a large amount of solid matters deposited in the lateral gap between the lower surface of the pump rotor 6 and the pump casing 5.
In this manner, the solid matters crushed by the pump rotor 6 disturb the rotation of the pump rotor 6, increase a load resistance of the motor, and in the worst case, the vacuum pump apparatus may not be able to restart.
FIGS. 10A and 10B are views for explaining an effect of the vacuum pump apparatus 1 in the embodiment shown in FIG. 8. By disposing the bearings 20 and 21 above the pump rotor 6a, when the operation of the vacuum pump apparatus 1 is stopped, the shaft 8 contracts upward with respect to the bearings 20 and 21 which are the fixed-side bearings due to the temperature decrease of the shaft 8 (see FIG. 10B). As a result, the lateral gap between the lower surface of each of the pump rotors 6a to 6d fixed to the shaft 8 and the pump casing 5 is increased. Therefore, the compression of the solid matters deposited in the lateral gap between the lower surface of each of the pump rotors 6a to 6d and the pump casing 5 by each of the pump rotors 6a to 6d is prevented. As a result, the restart of the vacuum pump apparatus 1 is not disturbed.
When the shaft 8 contracts upward, the lateral gap between the upper surface of each of the pump rotors 6a to 6d fixed to the shaft 8 and the pump casing 5 is decreased. However, since the amount of solid matters deposited in the lateral gap is small, the increase in the load resistance of the motor is very small. Therefore, the restart of the vacuum pump apparatus 1 is hardly disturbed. In the embodiment shown in FIG. 1 as well, the bearings 20, 21 as fixed-side bearings are arranged above the pump rotors 6a to 6d. The vacuum pump apparatus 1 according to the embodiment shown in FIG. 1 can achieve the same effects as the above effects.
In order to reliably prevent the increase in the load resistance of the motor, the operation controller 12 may perform a repeat operation of the rotation and the stop of the pump rotors 6a to 6d by repeatedly driving and stopping of the motor 10 before completely stopping the operation of the vacuum pump apparatus 1.
The operation controller 12 has a built-in operation stop control function of the vacuum pump apparatus 1, and stores an operation stop control pattern (i.e., a timing pattern for controlling the operation and the stop of the vacuum pump apparatus 1) for repeating an operation start and an operation stop of the vacuum pump apparatus 1 over time. Therefore, when an operation stop motion of the vacuum pump apparatus 1 is started by operating of the operation stop control function, the operation stop control pattern is performed. More specifically, the start and stop of the motor 10 are repeated at predetermined time intervals.
When the vacuum pump apparatus 1 is stopped, the temperature of the vacuum pump apparatus 1 is decreased. The shaft 8 also contracts upward, and the solid matters deposited in the lateral gap between the upper surface of each of the pump rotors 6a to 6d and the pump casing 5 are gradually compressed. However, the motor 10 is driven by the operation stop control function before a compression force is increased (so that the motor 10 cannot be driven), and each of the pump rotors 6a to 6d is rotated. Therefore, the solid matters that have been in contact with each of the pump rotors 6a to 6d are repelled outward by the centrifugal force of the rotation the each of the pump rotors 6a to 6d, and thus the solid matters are removed from the lateral gap between each of the pump rotors 6a to 6d and the pump casing 5. Further, the increase in the load resistance of the motor 10 can be reliably prevented by repeatedly performing a starting and stopping operation. This operation is as follows: the vacuum pump apparatus 1 is stopped before the temperature of the vacuum pump apparatus 1 is increased by the operation and the shaft 8 extends downward, and the operation starts again when the upper surface of each of the pump rotors 6a to 6d begins to compress the solid matters by contracting again the shaft 8.
As described above, the compression of the solid matters by each of the pump rotors 6a to 6d due to the contraction of the shaft 8 depends on the temperature decrease of the vacuum pump apparatus 1. Therefore, in one embodiment, the vacuum pump apparatus 1 may include a temperature sensor (not shown) attached to an outer surface of the pump casing 5. This temperature sensor is electrically connected to the operation controller 12. The operation controller 12 repeats starting and stopping of the motor 10 based on a temperature change of the pump casing 5 measured by the temperature sensor. Even with such a configuration, the vacuum pump apparatus 1 can prevent the load resistance of the motor 10 from increasing due to the contraction of the shaft 8.
In the above-described embodiment, a multi-stage vacuum pump apparatus including a multi-stage pump rotor has been described. However, the present invention is not limited to this example, and a single-stage vacuum pump apparatus including a single-stage pump rotor may be employed.
Although certain preferred embodiments of the present invention have been shown and described in detail, it should be understood that various changes and modifications may be made therein without departing from the scope of the appended claims.

Claims

A vacuum pump apparatus (1) comprising:
a pair of pump rotors (6a to 6d) arranged opposite to each other, the pair of pump rotors (6a to 6d) being a roots rotor or a claw rotor;

a pair of shafts (8) fixed to the pair of pump rotors (6a to 6d), the pair of shafts (8) extending in a vertical direction;

a motor (10) configured to rotate the pair of pump rotors (6a to 6d);

a pair of timing gears (25) fixed to the pair of shafts (8), the pair of timing gears (25) meshing with each other;
characterised by:
a fixed-side bearing (20, 21) arranged above the pair of pump rotors (6a to 6d), the fixed-side bearing (20, 21) being restricted in movement in an axial direction (CL) of the pair of shafts (8); and

a free-side bearing (13) configured to support the shaft (8) together with the fixed-side bearing (20, 21), the free-side bearing (13) being movable in the axial direction (CL).
The vacuum pump apparatus (1) according to claim 1, wherein the motor (10) is arranged above the pair of pump rotors (6a to 6d).
The vacuum pump apparatus (1) according to claims 1 or 2, further comprising an operation controller (12) electrically connected to the motor (10), the operation controller (12) being configured to perform a rotation and a stop operation of the pump rotor (6a to 6d) by repeating driving and stopping the motor (10) before completely stopping the operation of the vacuum pump apparatus (1).
The vacuum pump apparatus (1) according to claim 3, wherein the operation controller (12) is configured to repeat the driving and stopping of the motor (10) at predetermined time intervals.
The vacuum pump apparatus (1) according to claim 3, further comprising:
a pump casing (5) configured to house the pair of pump rotors (6a to 6d); and

a temperature sensor attached to an outer surface of the pump casing (5),
wherein the operation controller (12) is configured to repeat the driving and stopping of the motor (10) based on a temperature change of the pump casing (5) measured by the temperature sensor.
The vacuum pump apparatus (1) according to claim 1, further comprising: a bearing-support member (52; 100) configured to support the fixed-side bearing (20, 21), the bearing-support member (52; 100) limiting a movement of the fixed-side bearing (20, 21) in the axial direction. (6a to 6d) (1)