Vacuum Pump Equipment

Abstract

To provide a vacuum pump device that can reduce the installation space of a vacuum pump and can be reliably restarted. [Solution] The vacuum pump device 1 comprises a fixed-side bearing arranged above a pair of pump rotors, which is restricted in its axial movement of the shaft 8, and a free-side bearing which supports the shaft 8 together with the fixed-side bearing and is movable in the axial direction of the shaft 8. A lateral gap is formed between the pump casing 5 and the pair of pump rotors housed in the pump casing 5, in a direction perpendicular to the axial direction of the shaft 8, and the fixed-side bearing is in contact with circulating lubricating oil.

Description

[Technical field]

[0001] The present invention relates to a vacuum pump apparatus. [Background technology]

[0002] 2. Description of the Related Art Vacuum pumps (e.g., vacuum pumps for exhausting process gases, high exhaust speed vacuum pumps, etc.) used in the manufacture of semiconductors and / or flat panels such as organic electroluminescence (EL) and liquid crystal displays are known. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Utility Model Application Publication No. 6-53793 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, in semiconductor manufacturing and / or flat panel manufacturing, the flow rate of process gas introduced into the process chamber has been increasing due to the high performance of semiconductors and / or the large size of panels. However, even in this situation, it is necessary to maintain the pressure in the process chamber at a certain level.

[0005] Due to the above-mentioned needs, vacuum pumps with high exhaust speeds are required as vacuum pumps for exhausting process gases, and the size of vacuum pumps is also increasing. However, as the vacuum pumps become larger, the installation space required for vacuum pump devices increases in semiconductor manufacturing factories and / or flat panel manufacturing factories, and securing the installation space becomes a problem.

[0006] In order to reduce the installation space, it is conceivable to adopt a vertically-mounted vacuum pump device. However, when the fixed bearing is disposed below the pump rotor as in Patent Document 1, solid matter generated by condensation of the exhaust gas adheres and accumulates in the gap between the pump rotor and the pump casing, and further, when the pump is stopped, the temperature of the vacuum pump device drops, causing the pump rotor to excessively compress the solid matter, which results in the rotation of the pump rotor being hindered, and there is a risk that the vacuum pump device cannot be restarted.

[0007] Therefore, it is an object of the present invention to provide a vacuum pump device that can reduce the installation space for the vacuum pump device and can be reliably restarted. [Means for solving the problem]

[0008] In one aspect, a vacuum pump device for exhausting gas that may become solid by condensation is provided, the vacuum pump device comprising: a pair of pump rotors arranged opposite to each other and being either root rotors or claw rotors, a pump casing in which the pair of pump rotors are housed, a pair of shafts extending in a vertical direction to which the pair of pump rotors are fixed, a motor for rotating the pair of pump rotors, a pair of timing gears fixed to the pair of shafts and meshing with each other, a fixed-side bearing arranged above the pair of pump rotors and restricting movement in the axial direction of the shaft, and a free-side bearing supporting the shaft together with the fixed-side bearing and movable in the axial direction of the shaft, the pump casing forming a lateral gap in a direction perpendicular to the axial direction of the shaft between the pair of pump rotors housed in the pump casing, and the fixed-side bearing being in contact with circulating lubricating oil.

[0009] In one aspect, the motor is disposed above the pair of pump rotors. In one aspect, the vacuum pump apparatus includes an operation control device electrically connected to the motor, the operation control device repeatedly starting and stopping the motor to rotate and stop the pump rotor before completely stopping operation of the vacuum pump apparatus.

[0010] In one embodiment, the operation control device repeatedly starts and stops the motor at predetermined time intervals. In one aspect, the vacuum pump device is equipped with a temperature sensor attached to the outer surface of the pump casing, and the operation control device repeatedly starts and stops the motor based on temperature changes in the pump casing measured by the temperature sensor. Effect of the Invention

[0011] When the operation of the vertically-mounted vacuum pump device is stopped, the shaft contracts upwards with respect to the fixed bearing arranged above the pump rotor due to a drop in temperature. Therefore, the lateral gap between the lower surface of the pump rotor and the pump casing becomes large, and the pump rotor does not crush solid objects. As a result, restarting the vacuum pump device is not hindered. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a cross-sectional view illustrating an embodiment of a vacuum pump apparatus. [Diagram 2] FIG. 1 is a cross-sectional view showing an embodiment of a bearing device. [Diagram 3] FIG. 2 is a diagram showing lubricating oil circulating inside the bearing device. [Figure 4] FIG. [Diagram 5] FIG. [Figure 6] FIG. [Figure 7] 7(a) and 7(b) are diagrams showing contact seals. [Figure 8] FIG. 13 illustrates another embodiment of the vacuum pump device. [Figure 9] 9(a) and 9(b) are diagrams for explaining problems that may occur in a vertically-mounted vacuum pump apparatus. [Figure 10] 10(a) and 10(b) are diagrams for explaining the effects of the vacuum pump apparatus in the embodiment shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings described below, the same or corresponding components are designated by the same reference numerals and redundant description will be omitted.

[0014] FIG. 1 is a cross-sectional view showing one 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 position. In the embodiment shown in FIG. 1, the vacuum pump apparatus 1 is placed on a floor FL. The vacuum pump apparatus 1 is a pump apparatus that rotates at high speed. The vacuum pump apparatus 1 is arranged vertically in order to reduce the installation space thereof.

[0015] The vacuum pump device 1 includes a pair of pump rotors (Roots rotors in this embodiment) 6a, 6b, 6c, 6d arranged opposite each other, a pair of shafts (drive shafts) 8 to which the pump rotors 6a to 6d are fixed, a pump casing 5 in which the pump rotors 6a to 6d are housed, and a motor 10 that rotates the pump rotors 6a to 6d via the shaft 8.

[0016] 1, the structure of the pump rotors 6a to 6d is not limited to the Roots rotors, and the pump rotors 6a to 6d may be claw rotors or screw rotors.

[0017] The vacuum pump device 1 has an intake port 2 for drawing in gas and an exhaust port 4 for discharging the gas. When the vacuum pump device 1 is operated, gas is sucked into the inside of the vacuum pump device 1 through the intake port 2 and discharged from the exhaust port 4 (see the arrows in FIG. 1). The intake port 2 and the exhaust port 4 are provided in a pump casing 5.

[0018] The pump casing 5 has a gas flow passage 35 formed therein. The gas compressed by the pump rotors 6a to 6d passes through the gas flow passage 35 and is discharged from the exhaust port 4.

[0019] In FIG. 1, only one of a pair of pump rotors 6a to 6d is illustrated, and the pump rotor on the opposite side is omitted. Only one of a pair of shafts 8 is illustrated, and the shaft on the opposite side is omitted. In FIG. 1, the number of pump rotor stages is four, but the number of pump rotor stages is not limited to this embodiment. The number of pump rotor stages can be appropriately selected depending on the required degree of vacuum, exhaust gas flow rate, etc. In one embodiment, a single pump rotor stage may be provided.

[0020] The vacuum pump device 1 includes an operation control device 12 that controls the operation of the vacuum pump device 1. The operation control device 12 is electrically connected to the motor 10. The operation control device 12 is configured to control the rotation and stopping operations of the pump rotors 6a to 6d by driving and stopping the motor 10.

[0021] The shaft 8 extends vertically and is rotatably supported by a bearing 13 and a bearing device 15 (more specifically, bearings 20, 21 provided in the bearing device 15). The bearing 13 is disposed at one end portion (i.e., the lower end portion) of the shaft 8, and the bearing device 15 (more specifically, bearings 20, 21) is disposed at the other end portion (i.e., the upper end portion) of the shaft 8.

[0022] Timing gears 25 that mesh with each other are provided at one end of the shaft 8, and these timing gears 25 are housed in a gear cover 26 together with bearings 13. Note that only one of the pair of timing gears 25 is illustrated in FIG. 1. In the embodiment shown in FIG. 1, the timing gear 25 is disposed below the pump rotors 6a to 6d. In one embodiment, the timing gear 25 may be disposed above the pump rotors 6a to 6d.

[0023] The motor 10 includes a motor rotor 30 fixed to at least one of the two shafts 8, a motor stator 31 having a stator core around which a coil is wound, and a motor frame 32 that houses the motor rotor 30 and the motor stator 31. The motor stator 31 is disposed so as to surround the motor rotor 30, and is fixed to the inner circumferential surface of the motor frame 32.

[0024] When the motor 10 is driven, the pair of pump rotors 6a to 6d rotate in opposite directions via the timing gear 25, and gas is sucked into the pump casing 5 through the intake port 2. The sucked gas is transported downstream by the pump rotors 6a to 6d and discharged from the exhaust port 4.

[0025] The vacuum pump device 1 is a pump device that rotates at high speed and is arranged vertically. Therefore, the bearing device provided in the vacuum pump device 1 must also be arranged vertically. However, if a bearing device having a general structure is directly adopted in the vacuum pump device 1 capable of high-speed operation, there is a risk that the lubricating oil for lubricating and cooling the bearings 20, 21 may not be sufficiently supplied to the bearings 20, 21. In this case, each of the bearings 20, 21 cannot fully perform its function. Therefore, in this embodiment, the vacuum pump device 1 includes a bearing device 15 having a structure that allows the bearings 20, 21 to fully perform their functions. Hereinafter, the structure of the bearing device 15 will be described with reference to the drawings.

[0026] Fig. 2 is a cross-sectional view showing one embodiment of the bearing device 15. The bearing device 15 is an oil circulation type bearing device in which lubricating oil circulates inside the bearing device 15. Fig. 3 is a diagram showing the lubricating oil circulating inside the bearing device 15. In Fig. 3, reference symbols are omitted to make the drawing easier to understand. In Fig. 3, the flow of the lubricating oil is indicated by arrows.

[0027] As shown in FIG. 2, the bearing device 15 includes bearings 20, 21 supporting a shaft 8 extending vertically, a bearing housing 40 accommodating the bearings 20, 21, a rotating cylinder 45 that can be fixed to the shaft 8, and a bearing casing 46 that accommodates the bearings 20, 21, the bearing housing 40, and the rotating cylinder 45.

[0028] The bearings 20, 21 are arranged in series in the vertical direction. The bearings 20, 21 are bearings that receive the thrust load and radial load of the shaft 8. The bearing housing 40 accommodates the bearings 20, 21 and is arranged concentrically with the shaft 8 and the bearings 20, 21. In this embodiment, two bearings 20, 21 are provided, but the number of bearings is not limited to this embodiment. In one embodiment, a single bearing may be provided.

[0029] A spacer 41 attached to the shaft 8 and a fixture (e.g., a shaft nut) 42 fixed to the shaft 8 via the spacer 41 are disposed above the bearing 20. The spacer 41 and fixture 42 receive the thrust load (load in the axial direction CL of the shaft 8) acting on the bearings 20, 21. More specifically, the spacer 41 is in close contact with the inner ring of the bearing 20, and the fixture 42, via the spacer 41, limits the movement of the bearing 20 in the axial direction CL.

[0030] 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 the inner ring of the bearing 21, and limits the movement of the bearing 21 in the axial direction CL.

[0031] A seal member 43 fixed to the shaft 8 is disposed above the fixture 42. The seal member 43 is a member that prevents leakage of the lubricating oil disposed inside the bearing casing 46 to the outside. The lubricating oil is a liquid that lubricates and cools the bearings 20, 21.

[0032] The bearing casing 46 includes a side cover 50 that is connected to the pump casing 5 and that stores lubricating oil, a case member 51 that is disposed above the side cover 50 and that constitutes the upper end portion of the bearing device 15, and a bearing support member 52 that is 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.

[0033] The side cover 50 has a through hole 50a in its center through which the shaft 8 passes, and two piston rings 55 are arranged between the outer circumferential surface of the shaft 8 and the through hole 50a. Each of the piston rings 55 is attached to the shaft 8 and arranged in series in the vertical direction to prevent leakage of lubricating oil to the outside.

[0034] 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 outward of the inner circumferential wall 56, and a bottom wall 58 disposed between the inner circumferential wall 56 and the outer circumferential wall 57. Lubricating oil is retained by the inner circumferential wall 56, the outer circumferential wall 57, and the bottom wall 58.

[0035] A water-cooled jacket 90 is attached to the 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-cooled 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.

[0036] The bottom wall 58 has a communication hole 59 that communicates with the 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.

[0037] The inner circumferential wall 56 is connected to the through hole 50a, and the 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 this arrangement, overflow of the inner circumferential wall 56 is suppressed, and the lubricating oil is prevented from leaking to the outside.

[0038] When the shaft 8 rotates, the rotating cylinder 45 fixed to the shaft 8 also rotates together with the shaft 8, and the lubricating oil held in the side cover 50 is scooped up above the side cover 50 by the rotating rotating cylinder 45 (see FIG. 3). The structure of the rotating cylinder 45 will be described below with reference to the drawings.

[0039] Fig. 4 is a perspective view showing the rotating cylinder 45. Fig. 5 is an enlarged view of the rotating cylinder 45. Note that the water-cooling jacket 90 is omitted in Fig. 5. As shown in Figs. 4 and 5, the rotating cylinder 45 has two slopes 70 formed on its outer circumferential surface 45a. Only one of the slopes 70 is depicted in Fig. 4.

[0040] The two slopes 70 are disposed at equal intervals along the circumferential direction of the rotating cylinder 45. The slopes 70 are disposed in a gap between the outer peripheral surface 45a of the rotating cylinder 45 and the inner surface of the outer peripheral wall 57. In this embodiment, two slopes 70 are provided, but 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 multiple slopes 70 are disposed at equal intervals along the circumferential direction of the rotating cylinder 45.

[0041] The rotating cylinder 45 includes an inner cylindrical portion 71 that can be fixed to the shaft 8, an outer cylindrical portion 72 that is disposed on the outside of the inner cylindrical portion 71, and an annular ring portion 73 that connects the inner cylindrical portion 71 and the outer cylindrical portion 72. The inner cylindrical portion 71 and the outer cylindrical portion 72 are disposed concentrically with the shaft 8.

[0042] The inner cylindrical portion 71 is disposed below the bearing 21, and the outer cylindrical portion 72 is disposed radially outside the bearing 21. The height of the outer cylindrical portion 72 is greater than the 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 molded members.

[0043] The outer peripheral surface 45a of the rotating cylinder 45 corresponds to the outer peripheral surface of the outer cylindrical portion 72. Therefore, it may be expressed that the slope 70 is provided on the outer peripheral surface of the outer cylindrical portion 72.

[0044] In this embodiment, the upper end 70a of the slope 70 is connected to the upper end 45b of the rotating cylinder 45, and the lower end 70b of the slope 70 is connected to the lower end 45c of the rotating cylinder 45. A scooping surface 70c is formed between the upper end 70a and the lower end 70b of the slope 70. The slope 70 has a curved shape that extends obliquely downward from the upper end 70a (i.e., the upper end 45b) to the lower end 70b (i.e., the lower end 45c) in the rotation direction of the rotating cylinder 45. In other words, the slope 70 is inclined with respect to the axial direction CL.

[0045] When the rotating cylinder 45 rotates together with the shaft 8, the slope 70 rotates around the center of the shaft 8. When the slope 70 rotates, 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 up lubricating oil moves obliquely upward through the annular gap between the outer circumferential surface 45a of the rotating cylinder 45 and the outer circumferential wall 57.

[0046] 2, an upper end of an outer peripheral wall 57 of the side cover 50 is disposed at a position higher than the rotating cylinder 45 fixed to the shaft 8. The bearing support member 52 extends horizontally and is connected to the upper end of the outer peripheral wall 57. The bearing support member 52 supports the bearing housing 40, and receives, via the bearing housing 40, radial loads (loads in a direction perpendicular to the axial direction CL of the shaft 8) and thrust loads (loads in a direction horizontal to the axial direction CL of the shaft 8) acting on the bearings 20, 21.

[0047] The bearing support member 52 has two circulation holes 52a through which the lubricating oil scooped up by the slope 70 can pass. The two circulation holes 52a are disposed at equal intervals in the circumferential direction of the bearing support member 52. In this embodiment, two circulation holes 52a are provided, but the number of circulation holes 52a is not limited to this embodiment.

[0048] The case member 51 is connected to a bearing support member 52. The lubricating oil scooped up by the rotating cylinder 45 reaches the case member 51 through a flow hole 52a of the bearing support member 52. The lubricating oil that reaches the case member 51 collides with an upper end wall 51a of the case member 51, and the direction of the lubricating oil is changed and the lubricating oil is guided to the bearings 20, 21.

[0049] The upper end wall 51a of the case member 51 is disposed above the rotating cylinder 45 and the bearings 20, 21, and has a tapered shape that smoothly guides lubricating oil to the bearings 20, 21. More specifically, the upper end wall 51a has a curved portion 60 formed on its inner surface, and a tapered portion 61 connected to the curved portion 60. The tapered portion 61 is a projection that extends from the upper end wall 51a toward the bearing housing 40, and is disposed adjacent to the seal member 43.

[0050] Tapered portion 61 has a tapered shape in which the cross-sectional area of ​​tapered portion 61 gradually decreases from curved portion 60 toward bearing housing 40, and the lowest end of tapered portion 61 is disposed above bearing housing 40. Upper end wall 51a smoothly changes the direction of lubricating oil that collides with upper end wall 51a, and can guide the lubricating oil to bearings 20, 21 (see FIG. 3).

[0051] The bearing housing 40 includes a housing body 64 and a tray 65 disposed at the upper end of the housing body 64. Fig. 6 is an enlarged view of the tray 65. The tray 65 receives the lubricating oil that has been deflected by collision with the upper end wall 51a, and guides the lubricating oil to the bearings 20, 21. The tray 65 has a through hole 65a formed in the center thereof, an inner annular protrusion 66 connected to the through hole 65a, an outer annular protrusion 67 disposed on the outside of the inner annular protrusion 66, and a connection portion 68 that connects the inner annular protrusion 66 and the outer annular protrusion 67.

[0052] The inner annular projection 66 and the outer annular projection 67 are arranged concentrically with the axis 8. The inner annular projection 66 extends downward from the connection portion 68, i.e., toward the bearing 20, and the outer annular projection 67 extends upward from the connection portion 68, i.e., toward the upper end wall 51 a.

[0053] The inner annular projection 66 is in close contact with the outer ring of the bearing 20, limiting movement of the bearing 20 in the axial direction CL. The housing body 64 of the bearing housing 40 is in close contact with the outer ring of the bearing 21, limiting movement of the bearing 21 in the axial direction CL (see FIG. 2).

[0054] In this way, the bearings 20, 21 are fixed-side bearings in which movement of the bearings 20, 21 in the axial direction CL is limited by the fixing device 42, the bearing housing 40, and the rotating cylinder 45. The bearing 13, which is disposed on the opposite side of the bearings 20, 21 across the pump rotors 6a-6d, is a free-side bearing that is movable in the axial direction CL. The bearings 20, 21, which are fixed-side bearings, are disposed above the pump rotors 6a-6d, and the bearing 13, which is a free-side bearing, is disposed below the pump rotors 6a-6d.

[0055] The outer annular projection 67 is disposed at a position farther away from the shaft 8 than the tapered portion 61 of the upper end wall 51a (see FIG. 2). Therefore, the outer annular projection 67 can prevent the lubricating oil that has dropped from the tapered portion 61 onto the tray 65 from flowing outside the tray 65. The lubricating oil that has dropped onto the tray 65 passes through the gap between the through hole 65a and the spacer 41 and comes into contact with the bearings 20, 21, thereby lubricating and cooling the bearings 20, 21.

[0056] The lubricating oil that comes into contact with the bearings 20, 21 passes through the bearings 20, 21 and falls onto 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.

[0057] Centrifugal force due to the rotation of the rotating cylinder 45 acts on the lubricating oil held in the rotating cylinder 45. The lubricating oil passes through the gap between the housing body 64 and the outer cylindrical portion 72, and flows into the annular gap between the outer circumferential surface 45a of the rotating cylinder 45 and the outer circumferential wall 57. The lubricating oil is then scooped up by the slope 70 again.

[0058] In this way, a circulating flow of lubricating oil (i.e., an upward flow and a downward flow of lubricating oil) can be formed inside the bearing device 15. The circulating lubricating oil can come into contact with the bearings 20, 21 to lubricate and cool the bearings 20, 21. As a result, each of the bearings 20, 21 can fully perform its functions.

[0059] As shown in Fig. 2 and Fig. 5, the rotating cylinder 45 is disposed so as to surround a part of the bearing 21. The upper end of the outer cylindrical portion 72 is disposed at a position higher than the lower end of the rolling element 21a of the bearing 21. Preferably, the upper end of the outer cylindrical portion 72 is disposed at the same position as the center of the rolling element 21a. With this structure, when the operation of the vacuum pump device 1 is stopped, the rolling element 21a of the bearing 21 is always in contact with the lubricating oil held in the rotating cylinder 45. Therefore, the vacuum pump device 1 can resume the operation of the vacuum pump device 1 without putting the bearing 21 into an unlubricated state.

[0060] The effect of the bearing device 15 having a structure that creates a circulating flow of lubricating oil will be described. It is possible to operate the vacuum pump device with the bearing constantly immersed in the lubricating oil. However, in the case of such a configuration, since the bearing rotates in the lubricating oil during operation of the vacuum pump device, the temperature rise of the bearing due to the heat of agitation of the lubricating oil is large, and there is a risk of the bearing being damaged. Therefore, when rotating at high speed (for example, 4000 min -1 It is not desirable to use this in a vacuum pump device 1 that requires a

[0061] According to this embodiment, the bearing device 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 heat of the lubricating oil due to agitation. As a result, each of the bearings 20 and 21 can fully perform its function.

[0062] According to this embodiment, the vacuum pump device 1 includes the bearing device 15 that ensures that the lubricating oil comes into contact with the bearings 20, 21, allowing the bearings 20, 21 to fully function. Therefore, the vacuum pump device 1 that is vertically disposed can be operated without any problems. As a result, the installation space of the vacuum pump device 1 can be reduced, and the vacuum pump device 1 can be operated at a high pumping speed.

[0063] Since the vacuum pump device 1 is disposed vertically, gravity acts on the lubricating oil in the bearing device 15. Furthermore, when the vacuum pump device 1 is in operation, if the flow rate of gas flowing in from the process chamber side changes or stops, the pump chamber pressure also changes, causing a pressure difference with the bearing chamber pressure, and gas moves between the higher pressure side and the lower pressure side. In particular, when a large flow rate of gas is exhausted and the pump chamber pressure and the bearing chamber pressure are high, if the gas flow from the process chamber side suddenly stops, the pump chamber pressure suddenly drops and a large pressure difference occurs with the bearing chamber side, so that a large flow rate 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 be carried by this flow and leak to the outside (pump chamber side).

[0064] If the lubricating oil leaks, the amount of lubricating oil in the bearing device 15 will decrease, which will reduce the amount of lubricating oil supplied to the bearings 20 and 21, possibly leading to bearing damage, and the leaked lubricating oil may flow back through the pump chamber into the process chamber, potentially contaminating the wafers. Therefore, the bearing device 15 has a structure that can reliably prevent the leakage of lubricating oil.

[0065] 5, the rotating cylinder 45 has a plurality of downward ribs 75, 76, 77 extending from its lower surface to the bottom wall 58 (i.e., downward) of the side cover 50. Each of these downward ribs 75, 76, 77 has a cylindrical shape and is disposed concentrically with the axis 8. Hereinafter, in this specification, the downward rib 75 may be referred to as the inner downward rib 75, the downward rib 76 may be referred to as the middle downward rib 76, and the downward rib 77 may be referred to as the outer downward rib 77.

[0066] The inner downward rib 75 and the intermediate downward rib 76 extend downwardly from the lower surface of the annular ring portion 73 , and the outer downward rib 77 extends downwardly from the lower surface of the outer cylindrical portion 72 .

[0067] The side cover 50 has a plurality of upward ribs 80, 81 extending from its bottom wall 58 toward the lower surface (i.e., upward) of the rotating cylinder 45. Each of the upward ribs 80, 81 has a cylindrical shape and is disposed 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.

[0068] The inner upward rib 80 has a passage portion (i.e., an oil passing portion) 80a that allows the passage of the lubricating oil. In this embodiment, two passage portions 80a are provided, but the number of the passage portions 80a is not limited to this embodiment. In addition, the outer upward rib 81 also has a passage portion (i.e., an oil passing portion) 81a that allows the passage of the lubricating oil. In this embodiment, two passage portions 81a are provided, but the number of the 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 portions 80a are holes for making the liquid level of the lubricating oil present between the inner circumferential wall 56 and the inner upward rib 80 equal to the liquid level of the lubricating oil present between the inner upward rib 80 and the outer upward rib 81. In addition, the passage portion 81a is a hole for making the liquid level of the lubricating oil between the inner upward rib 80 and the outer upward rib 81 the same as the liquid level of the lubricating oil between the outer upward rib 81 and the outer downward rib 77 of the rotating cylinder 45.

[0069] The passage 80a is a return flow passage that returns the lubricating oil that has passed through the gap between the inner upward rib 80 and the inner downward rib 75 to the space between the inner upward rib 80 and the outer upward rib 81. In one embodiment, the passage 80a may be a hole formed in the lower part of the inner upward rib 80. In another embodiment, the passage 80a may be a notch formed in the lower end of the inner upward rib 80. The passage 81a is a return flow passage that returns the lubricating oil that has passed through the pressure adjustment hole 74 described later and the lubricating oil that has returned from the passage 80a to the space between the outer peripheral surface 45a of the rotating cylinder 45 and the inner surface of the bearing casing 46 to lubricate the bearings 20 and 21. In one embodiment, the passage 81a may be a hole formed in the lower part of the outer upward rib 81. In another embodiment, the passage 81a may be a notch formed in the lower end of the outer upward rib 81.

[0070] In this embodiment, the outer downward rib 77 extends downward further than the inner downward rib 75 and the intermediate downward rib 76. The lower end 75a of the inner downward rib 75 and the lower end 76a of the intermediate downward rib 76 are disposed 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 disposed above the lubricating oil held in the side cover 50, and the lower end 77a of the outer downward rib 77 is immersed in the lubricating oil held in the side cover 50. The lower end 45c of the rotating cylinder 45 corresponds to the lower end 77a of the outer downward rib 77.

[0071] The rotating cylinder 45 has a pressure adjustment hole 74 extending in the vertical direction formed in its outer cylindrical portion 72. In this embodiment, two pressure adjustment holes 74 are provided, but the number of pressure adjustment holes 74 is not limited to this embodiment. In one embodiment, one pressure adjustment hole 74 may be provided.

[0072] As described above, the lower end 77a of the outer downward rib 77 is immersed in the lubricating oil. Therefore, if the pressure adjustment hole 74 is not provided, the passage of gas between the space above the rotating cylinder 45 (first space SP1) and the space below the rotating cylinder 45, in other words, the space surrounded by the outer downward rib 77 (second space SP2), is blocked by the lubricating oil. For example, while the vacuum pump device 1 is stopped, the first space SP1 and the second space SP2 are both at atmospheric pressure, but when the vacuum pump device 1 is started, the pressure on the pump chamber side decreases, so the pressure in the second space SP2 decreases, but the pressure in the first space SP1 remains at atmospheric pressure, so a pressure difference occurs between the two. As a result, the gas in the first space SP1 expands and pushes 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, causing the liquid level of the lubricating oil in the second space SP2 to rise, which may cause the lubricating oil to overflow the inner circumferential wall 56. In this embodiment, the pressure adjustment hole 74 is provided to allow the first space SP1 and the second space SP2 to communicate with each other, so that the pressure in the first space SP1 and the pressure in the second space SP2 are always the same. Therefore, the liquid level of the lubricating oil inside the outer downward rib 77 is prevented from rising.

[0073] The inner downward rib 75 is disposed radially outward of the inner circumferential wall 56. The inner upward rib 80 is disposed radially outward of the inner downward rib 75. The intermediate downward rib 76 is disposed radially outward of the inner upward rib 80. The outer upward rib 81 is disposed radially outward of the intermediate downward rib 76. The outer downward rib 77 is disposed radially outward of the outer upward rib 81.

[0074] In this way, the downward ribs 75, 76, 77 and the upward ribs 80, 81 are arranged alternately to form 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 in this order from the inner circumferential wall 56 to the outer circumferential wall 57.

[0075] When a pressure difference occurs between the space in the bearing casing 46 and the space in the pump casing 5 (the spatial pressure in the bearing casing 46 is higher than the spatial pressure in the pump casing 5), such as immediately after the vacuum pump device 1 discharges the process gas, the gas in the space in the bearing casing 46 moves in a zigzag manner through the labyrinth structure portion toward the pump casing 5, but the lubricating oil (mist lubricating oil and liquid lubricating oil) riding on the gas flow is shaken off from the gas flow due to its own weight by the zigzag path formed between the downward ribs 75, 76, 77 and the upward ribs 80, 81, and is blocked from proceeding to the pump casing 5. Therefore, the bearing device 15 can reliably prevent the lubricating oil from leaking into the pump casing 5.

[0076] 7(a) and 7(b) are diagrams showing contact seals. As shown in FIG. 7(a), in order to more reliably prevent leakage of lubricating oil, a contact seal (first contact seal) 85 may be disposed between the inner downward rib 75 of the rotating cylinder 45 and the inner peripheral wall 56 of the side cover 50. As shown in FIG. 7(b), a contact seal (second contact seal) 86 may be disposed between the shaft 8 and the inner peripheral wall 56 of the side cover 50. Although not shown, the bearing device 15 may include both the contact seals 85 and 86. Known contact seals may be adopted as the contact seals 85 and 86.

[0077] 8 is a diagram showing another embodiment of the vacuum pump device 1. The configuration of this embodiment that is not particularly described is the same as the above-described embodiment, so duplicated description will be omitted.

[0078] As shown in Fig. 8, the bearings 20, 21 are supported by a bearing support member 100 that supports the bearings 20, 21. In the embodiment shown in Fig. 8, the bearing support member 100 supports the bearings 20, 21 so as to restrict the movement of the bearings 20, 21 in the axial direction CL. Therefore, in the embodiment shown in Fig. 8, the bearings 20, 21 are fixed-side bearings. The bearing 13 disposed on the opposite side of the bearings 20, 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.

[0079] In the embodiment shown in FIG. 8, the bearings 20 and 21, which are fixed-side bearings, are disposed above the pump rotors 6a-6d (more specifically, the uppermost pump rotor 6a among the pump rotors 6a-6d). In the embodiment shown in FIG. 8, the bearing 13, which is a free-side bearing, is disposed below the bearings 20 and 21, which are fixed-side bearings, more specifically, below the pump rotors 6a-6d. In one embodiment, the bearing 13 may be disposed above the pump rotors 6a-6d. The bearing 13 may be disposed inside the bearing device 15. In one embodiment, the timing gear 25 may be disposed above the pump rotors 6a-6d.

[0080] The timing gear 25, the bearing 13, the pump rotors 6a to 6d, the bearing device 15, and the motor 10 are arranged in series in the vertical direction along the axial direction CL of the shaft 8. In the embodiment shown in FIG. 8, the pump rotors 6a to 6d are Roots rotors or claw rotors. Therefore, the vacuum pump device 1 is a Roots type pump device whose exhaust method is a Roots type or a Claw type pump device whose exhaust method is a Claw type. In a further embodiment, the pump device may be a compound type pump device in which at least one stage of the pump rotor is a Roots rotor or a Claw rotor. Although not shown, a heater for increasing the temperature of the pump casing 5 may be attached to the pump casing 5.

[0081] 8, the motor 10 is disposed above the bearing device 15 (more specifically, bearings 20, 21). This arrangement makes it possible to lower the center of gravity of the pump rotors 6a-6d and the pump casing 5, which are heavy components of the vacuum pump device 1. This improves the installation stability of the vacuum pump device 1 when it is moved and operated, and prevents the vacuum pump device 1 from tipping over.

[0082] When a Roots type or Claw type is adopted as the exhaust system, the gap between the pump casing 5 and each of the pump rotors 6a-6d in the direction perpendicular to the axial direction CL of the shaft 8 is extremely small. By forming such a minute gap, backflow of the exhausted process gas is suppressed, and the exhaust performance of the vacuum pump device 1 can be maintained. Hereinafter, this gap may be referred to as a lateral gap.

[0083] 9(a) and 9(b) are diagrams for explaining problems that may occur in a vertically-mounted vacuum pump apparatus. In FIG. 9(a) and FIG. 9(b), a pump rotor 6 and a pump casing 5 are depicted, and the lateral gap between the pump rotor 6 and the pump casing 5 is depicted in an exaggerated manner. In addition, the free-side bearing B1 is disposed above the pump rotor 6, and the fixed-side bearing B2 is disposed below the pump rotor 6. Note that the vacuum pump apparatus in FIG. 9(a) and FIG. 9(b) is an apparatus for explaining the above-mentioned problems, and has a different configuration from the vacuum pump apparatus 1 according to this embodiment.

[0084] During operation of this vacuum pump apparatus, the shaft 8 expands upwards relative to the fixed bearing B2 due to a rise in temperature, but because the temperature of the pump rotor 6 becomes higher than the temperature of the pump casing 5, the lower gap in the lateral gap between the pump rotor 6 fixed to the shaft 8 and the pump casing 5 becomes wider and the upper gap becomes narrower. When process gas is exhausted in this state, some of the exhausted gas solidifies due to its sublimation, and this solid matter (see the black circles in Figures 9(a) and 9(b)) adheres to and accumulates in the lateral gaps as well. However, due to the weight of the solid matter, more of it accumulates in the lateral gap between the underside of the pump rotor 6 and the pump casing 5.

[0085] 9(b), when the operation of the vacuum pump apparatus is stopped for maintenance of the vacuum pump apparatus or for maintenance of the exhaust gas treatment apparatus downstream of the vacuum pump apparatus, the shaft 8 contracts downward with respect to the fixed-side bearing B2 due to a drop in temperature. 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 becomes smaller. Therefore, the pump rotor 6 compresses the large amount of solid matter accumulated in the lateral gap between the lower surface of the pump rotor 6 and the pump casing 5.

[0086] In this way, the solid matter crushed by the pump rotor 6 hinders the rotation of the pump rotor 6, increases the load resistance of the motor, and in the worst case, the vacuum pump apparatus may not be able to be restarted.

[0087] 10(a) and 10(b) are diagrams for explaining the effect of the vacuum pump device 1 in the embodiment shown in FIG. 8. By disposing the bearings 20, 21 above the pump rotor 6a, when the operation of the vacuum pump device 1 is stopped, the shaft 8 contracts upward based on the bearings 20, 21, which are fixed bearings, due to a drop in temperature (see FIG. 10(b)). As a result, the lateral gap between the lower surface of each of the pump rotors 6a-6d fixed to the shaft 8 and the pump casing 5 becomes large. Therefore, the compression of solid matter accumulated in the lateral gap between the lower surface of each of the pump rotors 6a-6d and the pump casing 5 by each of the pump rotors 6a-6d is prevented. As a result, the restart of the vacuum pump device 1 is not hindered.

[0088] When the shaft 8 contracts upward, the lateral gap between the upper surface of each of the pump rotors 6a-6d fixed to the shaft 8 and the pump casing 5 becomes smaller. However, since the amount of solid matter accumulated in this lateral gap is small, the increase in the load resistance of the motor is extremely small. Therefore, restarting of the vacuum pump device 1 is hardly hindered. In the embodiment shown in FIG. 1 as well, the bearings 20, 21, which are fixed side bearings, are disposed above the pump rotors 6a-6d. The vacuum pump device 1 according to the embodiment shown in FIG. 1 can achieve the same effects as those described above.

[0089] In order to reliably prevent an increase in the load resistance of the motor, the operation control device 12 may perform repeated operations of rotating and stopping the pump rotors 6a to 6d by repeatedly driving and stopping the motor 10 before completely stopping the operation of the vacuum pump device 1.

[0090] The operation control device 12 incorporates a function for controlling the operation and stopping of the vacuum pump device 1, and stores an operation and stopping control pattern (i.e., a timing pattern for controlling the stopping of the vacuum pump device 1) that repeats starting and stopping the operation of the vacuum pump device 1 over time. Therefore, when the operation and stopping operation of the vacuum pump device 1 is started by operating the operation and stopping control function, the operation and stopping control pattern is executed. More specifically, the motor 10 is repeatedly started and stopped at a predetermined time interval.

[0091] When the vacuum pump device 1 is stopped, the temperature drops, and the shaft 8 also contracts upward, gradually compressing the solid matter accumulated in the horizontal gap between the upper surface of each of the pump rotors 6a-6d and the pump casing 5, but before the compressive force becomes large (to the extent that the motor 10 cannot be driven), the operation stop control function drives the motor 10 to rotate each of the pump rotors 6a-6d, so that the solid matter in contact with each of the pump rotors 6a-6d is flicked outward by the centrifugal force caused by the rotation, and is thus removed from the horizontal gap between each of the pump rotors 6a-6d and the pump casing 5. Furthermore, when the temperature of the vacuum pump device 1 rises during operation, the vacuum pump device 1 is stopped before the shaft 8 expands downward, and operation is started again when the shaft 8 contracts again and the upper surface of each of the pump rotors 6a-6d begins to compress the solid matter...by repeatedly performing such start-stop operations, it is possible to reliably prevent an increase in the load resistance of the motor 10.

[0092] As described above, the compression of solids by each of the pump rotors 6a-6d accompanying the contraction of the shaft 8 depends on the temperature drop of the vacuum pump apparatus 1. Therefore, in one embodiment, the vacuum pump apparatus 1 may include a temperature sensor (not shown) attached to the outer surface of the pump casing 5. This temperature sensor is electrically connected to the operation control device 12. The operation control device 12 repeatedly starts and stops the motor 10 based on the temperature change of the pump casing 5 measured by the temperature sensor. With this configuration as well, the vacuum pump apparatus 1 can prevent an increase in the load resistance of the motor 10 accompanying the contraction of the shaft 8.

[0093] In the above-described embodiment, a multi-stage vacuum pump apparatus having a multi-stage pump rotor has been described, but the present invention is not limited to this example, and a single-stage vacuum pump apparatus having a single-stage pump rotor may also be adopted.

[0094] Although an embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible within the scope of the claims and the technical ideas described in the specification and drawings. [Explanation of symbols]

[0095] 1 Vacuum pump equipment 2 Intake port 4 Exhaust port 5 Pump casing 6a, 6b, 6c, 6d Pump rotors 8-axis 10 Motor 12 Operation control device 13 Bearing (free side bearing) 15 Bearing device 20, 21 Bearing (fixed side bearing) 25 Timing gear 26 Gear cover 30 Motor rotor 31 Motor stator 32 Motor Frame 35 Gas flow path 40 Bearing housing 41 Spacer 42 Fixtures 43 Sealing material 45 Rotating Cylinder 45a Outer surface 45b top end 45c bottom end 46 Bearing casing 50 Side cover 50a through hole 51 Case material 51a Top end wall 52 Bearing support member 52a Distribution hole 55 Piston ring 56 Inner wall 57 Outer wall 58 Bottom wall 59 Through hole 60 Curved section 61 Tapered section 64 Housing body 65 Saucer 65a through hole 66 Inner annular protrusion 67 Outer annular process 68 Connection Site 70 Slope 70a Upper end 70b Bottom end 70c scooping surface 71 Inner cylindrical part 72 Outer cylindrical part 73 Annular ring section 74 Pressure adjustment hole 75 Inner downward rib 75a bottom end 76 Middle downward rib 76a bottom end 77 Outer downward rib 77a bottom end 80 Inner upward rib 80a Passage section 81 Outer upward rib 81a Passage section 85,86 Contact seal 90 Water-cooling jacket 100 Bearing support member

Claims

1. 1. A vacuum pump apparatus for exhausting gas that may become a solid by condensation, comprising: A pair of pump rotors arranged opposite each other and being root rotors or claw rotors; a pump casing in which the pair of pump rotors are housed; a pair of shafts extending vertically to which the pair of pump rotors are fixed; A motor that rotates the pair of pump rotors; a pair of timing gears fixed to the pair of shafts and meshing with each other; a fixed-side bearing arranged above the pair of pump rotors and restricting movement of the shaft in an axial direction; a free-side bearing that supports the shaft together with the fixed-side bearing and is movable in an axial direction of the shaft; a heater attached to the pump casing and configured to increase a temperature of the pump casing; The pump casing defines a lateral gap between the pair of pump rotors housed in the pump casing and the pair of pump rotors in a direction perpendicular to an axial direction of the shaft, A vacuum pump device, wherein the fixed-side bearing is in contact with lubricating oil circulating inside a bearing casing in which the fixed-side bearing is housed.

2. 2. The vacuum pump apparatus of claim 1, wherein the motor is disposed above the pair of pump rotors.

3. The vacuum pump apparatus includes an operation control device electrically connected to the motor; 3. The vacuum pump apparatus according to claim 1, wherein the operation control device executes rotation and stopping operations of the pump rotor by repeatedly starting and stopping the motor before completely stopping operation of the vacuum pump apparatus.

4. 4. The vacuum pump apparatus according to claim 3, wherein the operation control device repeatedly starts and stops the motor at predetermined time intervals.

5. the vacuum pump apparatus includes a temperature sensor attached to an outer surface of the pump casing; 4. The vacuum pump apparatus according to claim 3, wherein the operation control device repeatedly starts and stops the motor based on a change in temperature of the pump casing measured by the temperature sensor.

Images