JP3518343B2 - Turbo vacuum pump - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is typified by a dry vacuum pump, a turbo-molecular pump, etc., and is a turbo-type vacuum exhaust device having a screw pump at least in part. About. 2. Description of the Related Art As a turbo-type vacuum evacuation apparatus, a gas flowing from a vacuum suction port is evacuated while being compressed along an outer periphery thereof by rotating a rotating body having a cylindrical or cylindrical shape. Some have a structure. In this type, a centrifugal compression pump stage capable of pumping in the molecular flow region is provided in a portion of the rotating body near the vacuum suction port,
A circumferential flow compression pump stage for further compressing the gas compressed to the viscous flow region by the centrifugal compression pump stage and exhausting the gas to the vacuum exhaust port is provided continuously with the centrifugal compression pump stage. Conventionally, the centrifugal compression pump stage has
The thing which adopted the screw type pump is known. In this screw type pump, a thread groove is provided on one of an outer peripheral surface of a rotating body and an inner peripheral surface of a housing for accommodating the rotating body, and gas is sucked and compressed along the thread groove by rotation of the rotating body. It is something that goes. [0004] Incidentally, in order to obtain a higher pumping speed with such a screw type pump, it was necessary to increase the diameter of the rotating body. However, in this case, not only the size of the device itself increases, but also the strength of the rotating body and the strength of a bearing for supporting the rotating body need to be improved due to an increase in centrifugal stress accompanying the size increase. This has limitations, and it has been difficult to increase the pumping speed beyond that limit. In view of the foregoing, an object of the present invention is to provide a turbo-type vacuum exhaust system capable of greatly improving the exhaust speed without increasing the size of the device or increasing the strength of members. And [0006] That is, a turbo-type vacuum evacuation apparatus according to the present invention is a turbo-type vacuum evacuation apparatus having at least a part thereof having a screw-type pump section. A rotating body having a shape, a housing accommodating the rotating body and rotatably supporting the rotating body; a columnar insertion body disposed in the housing while being inserted into an inner periphery of the rotating body; and the rotating body. Of the outer surface and the inner surface of the housing, or the inner surface of the housing and the outer surface of the insert, or the outer surface of the rotor and the outer surface of the insert, or the inner surface of the housing and the inner surface of the rotor Either a thread groove formed in any one of them, and a communication path for merging the compressed gas flowing along the outer peripheral surface and the inner peripheral surface of the rotating body, and a disk partitioning between the rotating bodies. Support A plate is integrally formed, a support shaft is attached to the support plate, and the support shaft is supported via a dynamic pressure gas bearing disposed in a bearing holding chamber formed in the housing. Between the outer peripheral surface of the lower rotating body and the housing, a circumferential pump portion is formed, through which the gas passing through the communication path is sent, and drives the dynamic pressure gas bearing and the support shaft to rotate. The motor and the motor are arranged at positions displaced from the screw groove along the direction from the vacuum suction port to the vacuum exhaust port so that these bearings and the motor are not exposed to the compressed gas. [0007] According to such a configuration, since the gas exhaust action is performed on both the outer peripheral surface and the inner peripheral surface of the rotating body, the apparatus is not enlarged and the strength of the rotating body and the like is not increased.
At the same rotational speed as the conventional one, it is possible to approximately double the gas exhaust speed in the screw pump section. However, in order to smooth the gas flow in the screw-type pump portion and improve the exhaust efficiency, a communication passage is opened near the terminal end of the screw-type pump portion in the rotating body and on the inner peripheral surface and the outer peripheral surface thereof. It is preferable to provide a plurality of gas outlet holes over the entire circumference. An embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 1, a dry vacuum pump, which is a turbo-type vacuum exhaust device according to this embodiment, has a housing 5
And a rotor 1 as a rotating body housed in the housing 5 and a support shaft 2 integrally attached to the rotor 1.
And dynamic pressure gas bearings 31 and 32 as non-contact type gas bearings for rotatably supporting the support shaft 2, and an electric motor 4 for rotating the support shaft 2. It is used standing up. The housing 5 has a rotor holding chamber 51 for accommodating the rotor 1 and a bearing holding chamber 52 provided continuously below the rotor holding chamber 51 and for accommodating the support shaft 2. The rotor holding chamber 51 includes a vacuum suction port 53 opened above the rotor 1 and a vacuum exhaust port 54 opened to the side of the rotor 1. In the bearing holding chamber 52, a motor disposition portion 55 for disposing a motor 4 described below at a lower end thereof, and a thrust bearing for disposing a thrust bearing 32 described below above the motor disposition portion 55. An arrangement unit 56 is provided. Further, an external connection path P extends from the lower end, and communicates with an external port PO opened on the outer surface of the housing 5. The rotor 1 has a cylindrical shape, and a disk-shaped support plate 12 for partitioning it like a bamboo node is integrally formed in the middle of the rotor 1. The upper end 2a is attached. The support shaft 2 has a columnar shape, and its intermediate portion is rotatably supported by dynamic pressure gas bearings 31 and 32, and is configured to rotate integrally with the rotor 1. Reference numeral 23 denotes a thrust bearing 32.
This is a disk body provided integrally to support the disk. The dynamic pressure gas bearings 31 and 32 include a journal bearing 31 for supporting the support shaft 2 against a load acting in the journal direction and a thrust bearing 32 for supporting the support shaft 2 against a load acting in the thrust direction. It is composed of The journal bearings 31 are provided at two places from above and below the support shaft 2. For example, the journal bearings 31 are formed by rolling a rectangular thin plate, and one end thereof is supported on the inner wall surface of the bearing holding chamber 52. And a plurality of leaf spring members which are provided around the outer periphery of the journal support plate 33 and elastically urge the journal support plate 33 inward to press against the support shaft 2. 34. The thrust bearing 32 is, for example, a ring-shaped thrust support plate 36 disposed above and below the disk body 23, respectively.
And a ring-shaped leaf spring member 37 disposed above and below the thrust support plate 36 to elastically urge the thrust support plate 36 to press and contact the disk body 23 . And
When the support shaft 2 is stationary or at a certain number of rotations or less, the journal support plate 33 and the thrust support plate 36 are brought into close proximity or close contact with the support shaft 2 by the elastic biasing force of the leaf spring members 34, 37. When the rotation speed of the support shaft 2 becomes equal to or more than a certain value, a dynamic pressure is generated around the support shaft 2 and on the upper and lower surfaces of the disk body 23 by using the gas entrained by the rotation of the support shaft 2. Board 3
3 and the thrust support plate 36 are retracted to form a gas film, and have a function of supporting the support shaft 2 through the gas film in a non-contact manner. In addition, this dynamic pressure gas bearing 31,
An inert gas such as nitrogen to be supplied to 32 is supplied from the external port PO. The motor 4 includes a rotor 41 incorporated below the lower end 2 b of the support shaft 2, specifically, below the disk 23 so as not to protrude from the outer peripheral surface 2 c thereof,
For example, it is of a DC brushless type having a stator 42 disposed on a motor disposing portion 55 set around 1 and directly drives the support shaft 2. In the present embodiment, an inverter (not shown) is used as a drive source of the motor 4.
It is configured to rotate at an arbitrary rotation speed. Thus, in the dry vacuum pump of the present embodiment, a circumferential pump section 6 comprising a plurality of stages of circumferential pumps 61 is provided between the lower half 1a of the rotor 1 and the corresponding housing 5. In addition, a screw pump 7 is formed between the upper half 1b of the rotor 1 and the housing 5. Each circumferential pump 61 includes a disk-shaped wing body 62 provided on the outer periphery of the rotor 1 and a circumferential groove 63 provided around the inner circumferential surface 5a of the housing to house the wing body 62. The wing body 62 has a plurality of notches intermittently and radially provided on the upper surface of the outer peripheral portion thereof, so that a plurality of blades 62a are formed between the notch grooves and the adjacent notch grooves. It was done. Then, the gas is spirally moved along the circumferential groove 63 by the rotation of the rotor 1, specifically, the inverted U-shaped groove 64 provided in the circumferential groove 63. The U-shaped groove 64 does not go around and is not provided in a part. The gas moved along the rotation direction of the circumferential pump 61 and compressed is passed through a through hole 65 provided at the end of the circumferential groove 63 on the rotation direction side, and the next (lower) circumferential groove 63 is formed. Flows into. Then, the compressed gas is again compressed by the respective circumferential pumps 61 and sent to the lower circumferential pump 61 one after another, and is discharged from the final circumferential pump 61 to the outside of the housing 5 through the vacuum exhaust port 54. However, this operation is mainly performed in the viscous flow region, and the circumferential pump section 6 including the plurality of circumferential pumps 61 functions as a circumferential flow compression pump. As shown in FIGS. 1 and 2, the screw-type pump portion 7, which is a characteristic portion of the present embodiment, has an upper half 1b of the rotor 1 and an upper end supported by the housing 5, and A columnar insert 71 fitted in the half inner periphery 13 from above, a housing 5 surrounding the outer periphery of the rotor 1, an inner peripheral surface 5a of the housing 5, and an insert 7
Screw grooves 72, 73 formed on the outer peripheral surface 71a
It is composed of More specifically, the upper end of the insert 71 is supported by a disk support 8 fixed to the housing inner peripheral surface 5a near the vacuum suction port 53. Then vacuum suction port 5
A plurality of gas inflow holes 81 penetrate through the disk support 8 so as not to hinder the gas flow from 3. On the other hand, a gas outlet hole 14, which is a communication passage opening to the inner peripheral surface 1c and the outer peripheral surface 1d, is formed at the end portion of the screw type pump portion 7 of the rotor 1, that is, at the lower end portion of the upper rotor portion 1b. Are provided intermittently. The thread grooves 72 and 73 are formed in such a direction that gas flows downward as the rotor 1 rotates. Therefore, it goes without saying that the screw groove 72 formed on the inner peripheral surface 5a of the housing 5 and the screw groove 73 formed on the outer peripheral surface 71a of the insert 71 are oriented in the same direction. The gas exhausting operation of the screw pump 7 will be described below. The gas flowing from the vacuum suction port 53 is supplied to the screw type pump unit 7 by the rotation of the rotor 1, and the screw groove 72,
It is sent down along 73. Specifically, the gas inlet 8
The gas flowing in from 1 branches off as shown by the arrow A in the figure, goes to the inner peripheral surface 1c and the outer peripheral surface 1d of the rotor 1, and is sent downward by the screw grooves 72 and 73, respectively. Rotor 1
The gas flowing along the outer peripheral surface 1d of the rotor is directly sent to the next-stage circumferential pump section 6, and the gas flowing along the inner peripheral surface 1c of the rotor passes through the gas outlet hole 14 and flows along the outer peripheral surface 1d. And is sent to the circumferential pump unit 6. The above-described operation is performed in the molecular flow region, and the screw type pump unit 7 operates as a centrifugal compression pump. Thereafter, the gas is further compressed by the circumferential pump unit 6 and exhausted from the vacuum exhaust port 54 as described above. The rotor 1
Bearings 31 and 32 for supporting the support shaft 2 attached to the
In addition, the motor 4 that rotationally drives the support shaft 2 has a thread groove 7 along the direction from the vacuum suction port 53 to the vacuum exhaust port 54.
It is arranged at a position displaced from 2, 73 so as not to be exposed to the compressed gas. Therefore, according to the present embodiment configured as described above, since the pump action is performed on both the outer peripheral surface 1d and the inner peripheral surface 1c of the rotor 1, the apparatus becomes larger and the strength of the rotor 1 and the like is reduced. Without increasing the screw-type pump part 7
Gas exhaust speed at the same rotation can be increased about twice as much as the conventional one. Further, since a plurality of gas outlet holes 81 are provided intermittently over the entire circumference of the rotor 1, the gas flowing out from the lower end of the thread groove 73 provided on the insert 71 is reliably prevented from obstructing the rotor outer peripheral surface. 1
d, and the pressure loss in this portion can be made as small as possible. As an effect peculiar to the present embodiment, since the support shaft 2 is mounted in the rotor 1, the center of gravity of the rotor 1 and the positions of the dynamic pressure gas bearings 31 and 32 supporting the support shaft 2 become closer. This means that the rotation stability of the rotor 1 can be improved without difficulty. Further, since the rotor 41 of the motor 4 is embedded in the support shaft 2 so that the motor rotor 41 does not protrude from the outer peripheral surface 2c of the support shaft 2, the size can be reduced. Moreover, this allows the thrust support plate 36 and the leaf spring material 3
The inner diameter of 7 can be made substantially equal to the outer diameter of the support shaft 2, and these sizes can be made as small as possible. Further, the thrust support plate 3 constituting the dynamic pressure gas bearing 32
6 and the sliding speed of the leaf spring material 37 with the disk body 23 can be reduced as much as possible, and wear and friction loss can be reduced, thereby contributing to longer life and improved exhaust efficiency. The present invention is not limited to the embodiment described above. For example, the same operation and effect can be obtained by providing a thread groove on the outer peripheral surface and the inner peripheral surface of the rotor. In this case, in order to make the gas flow smoothly, it is desirable to open the gas outlet holes at the lower ends of the grooves provided on the inner peripheral surface of the rotor. Further, the gas bearing is not limited to the dynamic pressure gas bearing as in the embodiment, but may be a contact type bearing such as a rolling bearing. The arrangement of the bearings and the motor is not limited to the embodiment. further,
The present invention can be applied not only to a dry vacuum pump but also to a turbo molecular pump and the like. In addition, the present invention is not limited to the illustrated example described above, and various modifications can be made without departing from the spirit of the present invention. According to the present invention, as described in detail above, since the pump action is performed on both the outer peripheral surface and the inner peripheral surface of the rotating body, the cross-sectional area of the gas flow path increases, and Without increasing the size or increasing the strength of the rotating body or the like, it is possible to approximately double the gas exhaust speed at the screw pump section even at the same rotational speed as the conventional one.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall schematic sectional view of a dry vacuum pump according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of a main part, particularly showing the screw-type pump section of the embodiment. DESCRIPTION OF SYMBOLS 1 ... Rotor 1c ... Rotor inner peripheral surface 1d ... Rotor outer peripheral surface 13 ... Inner peripheral 14 ... Communication passage (gas outflow hole) 5 ... Housing 5a ... Housing inner peripheral surface 7 ... Screw type pump part 71 ... Insertion Body 71a: Insert outer peripheral surface 72, 73: Screw groove

Claims (1)

(57) [Claim 1] In a turbo-type vacuum evacuation apparatus having a screw pump at least in part, the screw pump includes a cylindrical rotating body and a rotating body. A housing for accommodating and rotatably supporting, a cylindrical insert inserted into the inner periphery of the rotator, and an outer peripheral surface and an inner peripheral surface of the rotator, or a housing A thread groove formed on any one of the inner peripheral surface of the insert and the outer peripheral surface of the insert, the outer peripheral surface of the rotary body and the outer peripheral surface of the insert, or the inner peripheral surface of the housing and the inner peripheral surface of the rotary body; A communication path for merging the compressed gas flowing along the outer peripheral surface and the inner peripheral surface of the body is provided, and a disk-shaped support plate that partitions between the rotating bodies is integrally formed, The support shaft is attached to this support plate The support shaft is supported via a dynamic pressure gas bearing provided in a bearing holding chamber formed in the housing, and the link is provided between the support shaft and the outer peripheral surface housing of the rotating body below the support plate. A gas passing through the passage is sent, a circumferential pump portion is formed, and the dynamic pressure gas bearing and the motor that rotationally drives the support shaft are moved along a direction from a vacuum suction port to a vacuum exhaust port. A turbo-type vacuum evacuation apparatus, wherein the bearing and the motor are arranged at positions displaced from a screw groove so as not to be exposed to a compressed gas.