JP2627437B2 - Compound vacuum pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Industrial application field The present invention relates to an experimental research device such as a particle accelerator, a nuclear fusion experiment, an isotope separation, an analytical measuring device such as an electron microscope and a surface analyzer, and a semiconductor manufacturing vacuum. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a useful composite molecular pump capable of reliably generating a clean vacuum in an industrial vacuum device such as a device in a suction pressure range from atmospheric pressure to high vacuum and ultrahigh vacuum.

(2) Prior Art Conventionally, as a composite molecular pump of this type, a casing (c) having an intake port (a) and an exhaust port (b) as shown in FIG.
It is known that a turbo molecular pump section (d), a thread groove pump section (e) and a vortex pump section (f) are sequentially arranged from the intake port (a) side. (H) is a rotation axis of the rotor (g) of the turbo molecular pump section (d), the thread groove pump (e) and the vortex pump section (f), and (i) is a motor for rotating the rotation axis (h). Is shown.

(3) Problems to be Solved by the Invention According to the conventional composite molecular pump, in order to obtain a sufficiently stable compression performance and elongate the pumping speed,
The vortex pump section (f) is formed in eight or more stages, and the outer diameter of the rotor of the thread groove pump section (e) at the preceding stage of the vortex pump section (f) is equal to or greater than the outer diameter of the vortex pump section (f). It has a configuration.

In addition, in order to make the exhaust performance of the turbo molecular pump section (d) sufficient especially for hydrogen (H ₂ ) having a small molecular weight, the exhaust speed of the thread groove pump section (e) must be made sufficiently high. It is necessary to increase the width of the thread groove of the groove pump part (e) and further increase the total length of the screw groove in order to sufficiently increase the compression ratio. As a result, the rotor of the thread groove pump part (e) is axially moved. In contrast, the configuration is extended
The overall rotor (g) has a relatively long overall length and a large outer diameter.

Thus, in the conventional compound molecular pump, the rotor (g)
A bending moment acts on the rotation axis (h) with the high-speed rotation of, causing vibration. Moreover, the thread groove pump section (e) has a large outer cylinder portion and is heavy, and the overall length of the rotor (g) is long. Therefore, the moment of inertia Iz around the rotation axis becomes large, The moments of inertia Ix and Iy about the x-axis and the y-axis, which are orthogonal to the axis center line, become very large. In order for the rotating body that rotates at high speed to perform stable high-speed operation with little vibration, it is necessary that Ix and Iy be equal to or smaller than Iz. In the conventional composite molecular pump shown in FIG. 20, Ix and Iy were larger than Iz, and there was a problem that it was difficult to achieve dynamic balance so that stable high-speed operation with less vibration could be achieved.

An object of the present invention is to solve these problems and to provide an inexpensive composite molecular pump having a large pumping speed in a pressure range from atmospheric pressure to ultrahigh vacuum.

(4) Means for Solving the Problems In order to achieve this problem, the present invention provides a turbo molecular pump section, a circumferential groove vacuum pump section, and a vortex flow in a housing having an intake port and an exhaust port from the intake port side. A pump portion is sequentially arranged, the circumferential groove pump portion has a notch step formed by cutting out a peripheral portion of a plurality of rotating disks, and an annular concave portion formed in a stator in which the rotating disks are interposed. And a ventilation path formed in a peripheral portion of each rotating disk and a communication path communicating between adjacent ventilation paths.

(5) Operation In the initial state of the operation, the gas that has flowed into the intake port becomes a turbulent state mainly in the vortex pump section and is compressed and exhausted.
Thereafter, the inflowing gas flows into the turbo molecular pump section in a molecular flow state, and is transferred and compressed by the high-speed rotating blades and stationary vanes of the turbo molecular pump section. In the continuous circumferential groove pump section, the compressed and moved gas produces a transport effect due to the molecular drag effect due to gas friction of the rotating disk rotating at a high speed, particularly the peripheral portion thereof, so that a large pumping speed and sufficient compression are obtained. Under the action, the molecular flow becomes a viscous flow, flows into the suction port of the next vortex pump section, is further compressed in the vortex pump section, is compressed to approximately atmospheric pressure, and is discharged from the exhaust port to the atmosphere.

(6) Embodiment FIGS. 1 to 8 show one embodiment of the composite vacuum pump of the present invention.
Description will be made with reference to the drawings.

(1) shows a housing. In the housing (1), a turbo-molecular pump portion (2) is provided at an upper portion, a circumferential groove pump portion (3) is provided below the turbo-molecular pump portion (3), and a vortex pump portion (4) is provided thereunder. And the turbo molecular pump section (2) is provided with a rotor (5).
Blades (2a) protruding from the outer peripheral surface of the housing and the housing (1)
And a plurality of stationary blades (2b) protruding from the inner peripheral surface of the rotor, and the circumferential groove pump section (3) has three rotating disks (3a) projecting from the outer peripheral surface of the rotor (5). These rotating disks (3a) are formed in the notch steps (3b) (3b) by gradually reducing the thickness from the top to the bottom and cutting out the peripheral portions on both sides. The cutting depth of the cutting steps (3b) and (3b) of each of the rotating disks (3a) was changed from large to small in the same manner as described above from the top to the bottom. Reference numeral (3c) denotes a stator fixed to the inner surface of the housing (1), and the stator (3c) has an annular shape in which the rotating disk (3a) is interposed at a position corresponding to the rotating disk (3a). Recesses (3d) are formed, and the recesses (3d) and the cut notches (3b) (3b) form ventilation passages (3d) on both surfaces of the peripheral portion of each of the rotating disks (3a).
e) Formed (3e).

Here, the distance b between the opposed surfaces of the rotating disk (3a) side and the stator (3c) side in the ventilation path (3e) (3e) of each rotating disk (3a) is, as described above, the notch step (3b) According to the cutting depth of (3b), the size decreases from large to small as going from top to bottom. In each of the recesses (3d), a partition wall (3f) obtained by cutting off a portion through which the peripheral portion of the rotating disk (3a) passes is provided so as to protrude from the stator (3c), and a ventilation path is formed by the partition wall (3f). (3e)
(3e), the ventilation paths (3e) and (3e) of the adjacent rotating disks (3a) and (3a) and the ventilation paths (3e) and (3e) of the upstream rotating disk (3a) in (3e) and (3e) 3e) Ventilation path (3e) (3e) of the other end of partition wall (3f) and downstream rotating disk (3a)
A communication path (3g) communicates with the first end of the partition wall (3f) through the communication path (3g), and further connects the partition wall (3f) and the communication path (3g) from the upstream side to the downstream side as shown in FIGS. The gas molecules from the intake port (12) are sent through the communication path (3g) while passing through the air passages (3e) (3e) of the respective rotating disks (3a). Compression is performed sequentially in 3e), and a considerably high compression ratio is obtained. And one of the partition walls (3f) of the ventilation passages (3e) and (3e) of the most upstream rotating disk (3a).
As shown in FIG. 1, the starting end of the side is connected to the first intermediate intake port (6) from the turbo molecular pump section (2), and the ventilation paths (3e) and (3e) of the most downstream rotating disk (3a). The other end of the partition wall (3f) was connected to the second intermediate intake port (7) of the vortex pump section (4) in FIG.

The vortex pump section (4) is provided on the outer peripheral surface of the rotor (5) with a plurality of radial blades (4a) having radial recesses (4d) and suction passages (4b) respectively facing the blades.
The end of the flow path (4b) communicates with the exhaust port (13) as shown in FIG.

The shaft (5a) of the rotor (5) of each of the pump sections (2), (3) and (4) is a cylinder projecting upward from the motor housing (1a) below the housing (1). The upper bearing (8a) provided on the upper part of (1b) and the bottom plate (1) of the motor housing (1a)
c) is supported by a lower bearing (8b) provided at the lower part of the shaft (5a), and a high-frequency motor (9) comprising an induction motor, a hysteresis motor, etc. provided in the motor housing (1a). The rotor (9a) is fixed, and the lower end of the shaft (5a) is immersed in lubricating oil in a lubricating oil tank (10) provided below the bottom plate (1c). Due to the centrifugal force generated by the high-speed rotation of the shaft (5a) by the drive of 9), the lubricating oil flows into the upper bearing (8a) through the center hole (11) of the shaft (5a) and its branch holes (11a) (11a). Supplied. The lower bearing (8b) is supplied with lubricating oil from a groove provided on the inner periphery of the motor housing (1a).

Thus, since the rotor blade (2a), the rotating disk (3a) and the radial blade (4a) of each of the pump sections (2), (3) and (4) are integrally formed with the rotor (5), high speed operation is achieved. Vibration is small due to rotation, and almost no noise is generated. (12) indicates an intake port, and (13) indicates an exhaust port.

 Next, the operation of the composite vacuum pump of the above embodiment will be described.

When the rotor (5) starts rotating by driving the high-frequency motor (9), the gas that has flowed into the intake port (12) in the initial state changes from a turbulent flow to an intermediate flow state, and the turbo molecular pump section (2) rotates. The blade (2a) collides with the blade (2a).
a) and a stationary blade (2b) protruding from the housing (1) gives momentum in the circumferential direction in which the moving blade (2a) moves and in the downward direction parallel to the axis. The moving blade (2
Compression movement is caused by the rotation of a) and the stationary blade (2b).
During acceleration at the time of starting, the molecular pump section (2) increases windage loss due to the presence of high-density gas in the pump and acceleration torque with respect to the moment of inertia of the rotating body.
The number of rotations is controlled so that the input current of the high frequency motor (9) does not become excessive.

Next, the gas compressed and moved by the molecular pump section (2) passes through a first intermediate intake port (6) and is rotated by a rotating disk (3) of a circumferential groove pump section (3) formed integrally with the rotor (5). 3a)
Notch step (3b) (3b) of the peripheral part that rotates at the highest speed
The transport effect occurs due to the molecular drag effect due to gas molecule friction at this time on both surfaces of the rotating disk (3a) and the ventilation paths (3e) and (3e) of each rotating disk (3a) through the communication path (3g) in FIG. And in the pressure region in which the flow is from molecular flow to viscous flow, an exhaust action is produced to realize a large compression ratio as a whole, and is formed integrally with the rotor (5) through the second intermediate intake port (7). It is compressed by the rotation of the radial blade (4a) of the swirling pump section (4). The compression ratio is 1.45 to 2.0, and the radial blade (4a)
Approximately 70 compression ratios can be obtained by stacking around 10 stages in a vortex pump section.
It can be compressed from suction pressures below a (5.2 torr) to atmospheric pressure to atmospheric pressure. Therefore, according to the composite vacuum pump of the present embodiment, gas can be exhausted at a large exhaust speed from the atmospheric pressure to the ultrahigh vacuum.

Here, according to the experiment of the inventor, the outer diameter of the rotor blade (2a) of the turbo molecular pump section (2) is 200 mm, the circumferential groove pump section (3) is three stages, and the rotor of the vortex pump section (4) is provided. 13 outer diameter
A sample having a diameter of 0 mm was prepared, and an inlet pressure-evacuation speed curve was obtained. The graph of FIG. 9 was obtained, and the curve of this graph was almost the same as that obtained when an auxiliary vacuum pump was connected to a conventional composite vacuum pump. This is a curve, which indicates that the vacuum pump of the embodiment does not require an auxiliary vacuum pump and can be evacuated from atmospheric pressure to ultra-high vacuum by one vacuum pump. 10 to 12 show the second embodiment of the circumferential groove pump section (3).
An embodiment will be described. In this embodiment, each of the rotating disks (3
The distance b between the rotating disk (3a) side and the opposing surface on the stator (3c) side in the ventilation path (3e) (3e) of (a) is formed so as to gradually become smaller from the start end to the end. , With improved compression performance.

FIG. 13 shows a third embodiment of the circumferential groove pump portion, in which the thickness of the notch steps (3b) and (3b) at the periphery of each of the rotating disks (3a) is shown. Are formed gradually thinner toward the outside, and the distance b between the cut step portions (3b) and (3b) and the inner surface of the concave portion (3d) opposed thereto is reduced.
Is formed such that the interval becomes narrower as the concave portion (3d) is directed outward so that it becomes equal at any position in the radial direction.

FIGS. 14 to 17 show a fourth embodiment of the circumferential groove pump portion (3), provided at two locations symmetrical with respect to the center of the intake port and the discharge port of each rotary disk (3a). The exhaust speed is doubled by performing exhaust compression in parallel.

FIG. 18 shows a second embodiment of the vortex pump section (4), in which suction passages (4d) are provided in parallel on both sides of a radial blade (4a). The structure is set to 70%.

FIG. 19 shows a third embodiment of the vortex pump part (4), in which concave parts (4b) are provided on both surfaces of one radial blade (4a) to constitute a four-stage pump element. .

Even if a small number of stages such as a combination of the embodiment of FIG. 18 and one or two of the embodiment of FIG. 19 is used, it substantially corresponds to a vortex pump of a multi-stage radial blade.

(7) Advantageous Effects of the Invention According to the present invention, as described above, a turbo molecular pump portion, a circumferential groove pump portion, and a vacuum pump oil in which no vacuum pump oil is present in an exhaust compression operation portion are provided in a housing having an intake port and an exhaust port. The vortex pump section is sequentially arranged from the suction port side, and the gas from the suction port is compressed and transferred once in the turbo-molecular pump section, and then, in the circumferential groove pump section, particularly by the peripheral portion of the rotating disk that rotates at high speed. The gas produces an efficient transport effect by molecular drag due to gas molecule friction, and a radially larger intake port to the ventilation passage of the first rotating disk that determines the exhaust speed of the circumferential groove pump portion. Dimensions can be obtained, and thus a large pumping speed can be obtained.In addition, a high compression ratio can be obtained by a large number of radial blades provided in the vortex pump section, and the pressure can be increased from atmospheric pressure to ultra-high vacuum. Sufficient pumping speed can be obtained regardless of the molecular weight and chemical properties of the gas in the suction range, and the rotating body from the suction port side to the exhaust port side has the large pumping performance of the circumferential groove pump section. The effect of (1) is that the length in the axial direction can be significantly shortened compared to the past, the rotor of each pump can be integrated compactly, and it can be configured as a single rotor type connected to the end of the rotating shaft, thus suppressing the generation of vibration. It is possible to obtain a vacuum pump which can generate a clean vacuum which is compact, lightweight and oil-free without requiring high-precision machining for a small and lightweight rotor. Further, the composite vacuum pump according to the present invention has a corrosion resistance against harmful corrosive gas by coating the rotor and the stator integrated with an aluminum alloy with corrosion resistance, does not contaminate the lubricating oil, and constitutes the pump. All the parts provide centrifugal flow velocity to the gas, and the discharge ports of each stage are provided on the radially outer peripheral part, and the pump sucks the powder and granules together with the process gas or compresses Even if powder particles are generated by the chemical reaction,
Since it has an effect of sequentially discharging powder particles to an exhaust port, it is extremely useful and has a large economic effect in a semiconductor manufacturing vacuum apparatus or the like.

[Brief description of the drawings]

1 is an overall sectional view of a first embodiment of a composite vacuum pump according to the present invention, FIG. 2 is a sectional view taken along line II of FIG. 1, and FIG. 3 is a sectional view taken along line II-II of FIG. Fig. 4 is III-III in Fig. 2.
5 is a sectional view taken along the line IV-IV in FIG. 2, and FIG.
The drawing is a sectional view taken along the line VV of FIG. 2, and FIG.
FIG. 8 is a sectional view taken along line VII-VII of FIG. 2,
FIG. 9 is a graph showing the relationship between the inlet pressure and the exhaust speed,
10 to 12 are partial cross-sectional views of a second embodiment of the circumferential groove pump section, FIG. 13 is a partial cross-sectional view of the third embodiment of the circumferential groove pump section, and FIG. 14 is a circumferential groove pump. Second Example of the Fourth Embodiment
FIG. 15 is a sectional view taken along line II of FIG. 14, FIG. 16 is a sectional view taken along line II-II of FIG. 14, and FIG.
FIG. 18 is a vertical sectional view of a portion of a rotor showing a second embodiment of the vortex pump section, and FIG. 19 is a longitudinal section of a rotor section showing a third embodiment of the vortex pump section. Aerial view, 20th
The figure is a cross-sectional view of a conventional composite molecular pump. (1) Housing (2) Turbo molecular pump section (3) Circular groove pump section (4) Swirl pump section (12) Suction port (13) Exhaust port

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Shoji Iguchi 1221 Kuginodacho, Hachioji-shi, Tokyo Osaka Vacuum Equipment Co., Ltd. Hachioji factory (56) References JP-A-57-59098 (JP, A) JP-A Sho 63-85290 (JP, A)

Claims (1)

(57) [Claims] 1. A turbo molecular pump section, a circumferential groove pump section, and a vortex pump section are sequentially disposed in a housing having an intake port and an exhaust port from the intake port side. A notch step formed by cutting out the peripheral portion of the rotating disk and an annular recess formed in the stator in which the rotating disk is interposed, a ventilation path formed in the peripheral portion of each rotating disk, A composite vacuum pump comprising: a communication path that communicates between adjacent ventilation paths.