JPH0275796A - Composite vacuum pump - Google Patents

Abstract

PURPOSE:To provide a composite molecular pump, having a high exhaust speed, at a low cost by a method wherein a turbo molecular pump part, a circumferential groove vacuum pump part, and a vortex pump part are disposed, in order named, from the suction port side in a casing having a suction port and an exhaust port. CONSTITUTION:In a casing 1, a turbo molecular pump part 2 is situated at an upper part, 8 circumferential groove pump part 3 is located therebelow, and a vortex pump part 4 is further provided below the circumferential groove pump part. The turbo molecular pump part 2 is formed with a number of moving vanes 2a protruded from the outer peripheral surface of a rotor 5 and a number of stationary blades 2b protruded from the inner peripheral surface of the casing 1, and the circumferential groove pump part 3 is provided with three rotary discs 3a protruded from the outer peripheral surface of the rotor 5. The vortex pump part 4 is formed with a number of radial blades 4a protruded from the outer peripheral surface of the rotor 5 and a stator 4c having a suction flow passage 4b positioned facing the radial blades.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Industrial Field of Application The present invention is applicable to particle accelerators, nuclear fusion experiments, experimental research equipment such as isotope separation, analytical measurement equipment such as electron microscopes and surface analyzers,
and industrial vacuum equipment such as semiconductor manufacturing vacuum equipment,
The present invention relates to a useful composite molecular pump that can reliably generate a clean vacuum in a suction pressure range from atmospheric pressure to high vacuum and ultra-high vacuum.

(2) Prior Art Conventionally, as shown in FIG. 20, a composite molecular pump of this type has a casing (C) having an intake port (a) and an exhaust port (b).
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. Note that (h) is the rotation axis of the rotor (g) of the turbomolecular pump section (d), thread groove pump section (e), and vortex pump section (f), and (i) is the rotation axis (h).
) is shown.

(3) Problems to be Solved by the Invention According to this conventional composite molecular pump, in order to provide sufficiently stable compression performance and increase pumping speed, the vortex pump section (f) is arranged in eight or more stages. Furthermore, the outer diameter of the rotor of the threaded groove pump section (e) in the preceding stage of the vortex pump section (f) is equal to or larger than the outer diameter of the vortex pump section (f).

In addition, in order to ensure sufficient pumping performance of the turbo molecular pump section (d) especially for hydrogen (H3) with a small molecular weight, the pumping speed of the threaded groove pump section (e) must be made sufficiently high. In order to widen the width of the thread groove of the pump part (e) and further increase the compression ratio sufficiently, it is necessary to increase the overall length of the thread groove.
) has a configuration that extends in the axial direction, and the overall length of the combined rotor (g) is relatively long and the outer diameter is also large.

Thus, in the conventional composite molecular pump, the rotor is integrally shaped and the shaft end is loaded, so that a bending moment acts on the rotating shaft (h) as the rotor (g) rotates at high speed, inducing vibration. Moreover, the thread groove pump part (e) has a thick outer cylinder part and is also heavy, and the total rotor (g
) becomes longer, so the moment of inertia around the axis of one revolution)
As Iz increases, the moments of inertia rx and ry around the X-axis and y-axis, which are perpendicular to the axis center line, become extremely large. In order for a rotating body that rotates at high speed to be able to operate stably at high speed with less 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 are larger than Iz, and there is a problem in that it is difficult to maintain dynamic balance to enable stable high-speed operation with little vibration.

An object of the present invention is to solve these problems and to provide a composite molecular pump at low cost that has a high pumping speed in a pressure range from atmospheric pressure to ultra-high vacuum.

(4) Means for Solving the Problem In order to achieve this problem, the present invention provides a housing having an intake port and an exhaust port, and includes a turbo molecular pump section, a circumferential groove vacuum pump section, and a circumferential groove vacuum pump section from the intake port side. It is characterized by sequential arrangement of vortex pump parts.

(5) In the initial state of operation, the gas that has flowed into the intake port becomes a turbulent flow mainly in the vortex pump section and is compressed and exhausted, and the inflowing gas then flows into the turbo molecular pump section in a molecular flow state, and the gas flows into the turbo molecular pump section in a molecular flow state. This portion is transferred and compressed by the rotating blades and stationary blades of the molecular pump section, which rotate at high speed. In the continuous circumferential groove pump section, this compressed and moved gas is transported by the molecular drag effect caused by the gas friction caused by the high-speed rotation of the rotating disk, especially around its periphery, resulting in a large pumping speed and sufficient compression. Under the action, the molecular flow becomes a viscous flow, flows into the inlet of the primary vortex pump section, is further compressed in the vortex pump section, is compressed to C atmospheric pressure, and is discharged into the atmosphere from the exhaust port.

(6) Embodiment An embodiment of the composite vacuum pump of the present invention will be described with reference to FIGS. 1 to 8.

(1) indicates a housing, and inside the housing (1) there is a turbo molecular pump part (2) at the top and a circumferential groove pump part (3) below it.
Further, a vortex pump section (4) is provided below the vortex pump section (4), and the turbo molecular pump section (2) has a large number of moving parts 1 (2L) protruding from the outer peripheral surface of the rotor (5) and the housing (1). ), and the circumferential groove pump part (3) has three rotary discs (3a) on the outer peripheral surface of the rotor (5). The rotating discs (3a) have thicknesses gradually increasing from the top to the bottom, and the peripheral parts of both sides are cut out to form notch steps (3b). The cutting depths of the cutting step portions (3b), (3b), and (7) of each of these rotary disks (3a) were made from large to small from the top to the bottom in the same manner as described above. Further, (3C) indicates a stator fixed to the inner surface of the housing (1), and the stator (3C) is attached to the rotating disk (3).
An annular recess (3d) into which the rotating disk (3a) is inserted is formed at a position corresponding to a), and the recess (3d)
3d) and the cut step portions (3b) l-b) provide ventilation passages (3e) (3e
) was formed.

Here, the distance between the facing surfaces of the rotating disk (3a) side and the stator (3c) side in the ventilation passages (3e) (3e) of each rotating disk (3a) is the notch step portion (3b) as described above. (3b
) from large to small from top to bottom depending on the depth of cut. In each of the recesses (3d), a partition wall (
, 3f) are provided to protrude from the stator (3c), and the partition wall (
The ventilation passages (3e) (3e) are separated by the ventilation passages (3e) (3e) of the adjacent rotating discs (3a) (3a).
e) and (3e) In (3e), the partition wall (3f) of the ventilation passage (3e) of the rotating disk (3a) on the upstream side (3e)
) and the starting end of the first side of the partition wall (3f) of the ventilation passage (36) (3e) of the rotating disk (3a) on the downstream side through a communication path (3g), Furthermore, these bulkheads (
3f) and the communication passage (3g) are formed by sequentially shifting the position 2 from the upstream side to the downstream side as shown in Figs. (3g) and is sequentially compressed in the ventilation passages (3e) (3e) of each rotating disk (3a), resulting in a considerably high compression ratio. and 1 of the partition wall (3f) of the ventilation passage (3B) (3e) of the rotating disk (3a) on the most upstream side.
The starting end of the side is connected to the first intermediate intake port (6) from the turbomolecular pump section (2) as shown in Fig. 1, and the ventilation path (3e) (3e) ( 7) Bulkhead (3f)
(7) Connect the other end of the vortex pump section (4) in FIG.
) was communicated with the second intermediate intake port (7).

The vortex pump section (4) has a large number of radial blades (4a) projecting from the outer circumferential surface of the rotor (5) and having radial recesses (4d), and suction passages (4) facing each of the radial blades (4a).
b) and a stator (4C) having a flow path (4C).
The terminal end of b) was communicated with the exhaust port (13) as shown in FIG.

In addition, the rotor (5) of each of the pump parts (2), (3), (4)
) is connected to an upper bearing (8a) provided in an upper part of an inner cylinder (lb) that projects upward from a motor housing (la) in a lower part of the housing (1) and the motor housing. It is supported by a lower bearing (8b) provided on the bottom plate (lc) of (1a), and the motor housing (la
) Induction motor, hysteresis motor,
- The rotor (9a) of a high frequency motor (9) consisting of a rotor, etc. is fixed, and the lower end of the shaft (5a) is lubricating oil in a lubricating oil tank (lO) provided below the bottom plate (IC). The centrifugal force caused by the high-speed rotation of the shaft (5a) driven by the high-frequency motor (9) causes lubricating oil to flow into the center hole (11) of the shaft (5a) and its branch holes (ll).
a) (lla) and is supplied to the upper bearing (8a). Further, the lower bearing (8b) is supplied with lubricating oil from a groove provided on the inner circumference of the motor housing (1a).

Thus, the dynamic El of each of the pump parts (2), (3), and (4)
l (2a), the rotating disk (3a), and the radial blades (4a) are integrated with the rotor (5), so there is little vibration even during high-speed rotation, and almost no noise is generated. , (13) indicates an exhaust port.

Next, the operation of the compound vacuum pump of the above embodiment will be explained.

When the rotor (5) starts to rotate due to the drive of the high-frequency motor (9), the gas flowing into the intake port (12) in its initial state changes from a turbulent flow to an intermediate flow state, causing the turbo molecular pump section (2) to rotate. It collides with the moving blade 1 (2a), and the moving blade (
2a) and the stationary blades (2b) protruding from the housing (1), momentum is given in the circumferential direction in which the drive 51 (2a) moves and in a downward direction parallel to the axis, and the stacking is performed. The rotor blade (2a) and the rotor blade (2b) are rotated to compress and move downward. It should be noted that during acceleration at the time of startup, the single molecule pump section (2) suffers from windage damage due to the presence of high density gas in the pump, and the acceleration torque relative to the moment of inertia of the rotating body becomes large. ) The rotation speed is controlled so that the input current does not become excessive.

Next, the gas compressed and moved by the molecular pump section (2) passes through the first intermediate intake port (6) and passes through the rotating disk ( 3a)
(3b) (3)
When it hits both sides of b), a transport effect occurs due to the drag effect caused by the friction of gas molecules, and the communication path (3g
) of each rotating disk (3a) through the ventilation passage (3e) (
3e) are sequentially transported as shown by the arrows in Fig. 2, and an exhaust effect occurs in the pressure range from molecular flow to viscous flow, achieving a large compression ratio as a whole, and the air is transferred to the rotor via the second intermediate intake port (7). (5) The vortex pump part (
It is compressed by the rotation of the radial blade (4a) in step 4). The compression ratio is 1.45 to 2.0, and by stacking the radial blades (4a) in multiple stages (about 10 stages), a compression ratio of about 70 is obtained. It can be compressed from suction pressures up to atmospheric pressure, ranging from less than 700 Pa (5.2 Torr) to atmospheric pressure. Therefore, according to the compound vacuum pump of this embodiment, gas can be pumped out at a high pumping speed from atmospheric pressure to ultra-high vacuum.

According to the experiments of one inventor, the turbomolecular pump section (
2), the rotor blade (2a) has an outer diameter of 200 mm, the circumferential groove pump section (3) has three stages, and the vortex pump section (4) has a rotor outer diameter of 130 mm, and the inlet pressure - When the pumping speed curve was determined, the graph shown in Fig. 9 was obtained, and the curve in this graph is a substantially concave curve when an auxiliary vacuum pump is connected to a conventional compound vacuum pump. It can be seen that an auxiliary vacuum pump is not required and a single vacuum pump can evacuate from atmospheric pressure to ultra-high vacuum. Moreover, FIGS. 10 to 12 show a second embodiment of the circumferential groove pump section (3), and in this embodiment, the rotation circles in the ventilation passages (3e) (3e) of each of the rotary disks (3a) are The distance sb between the facing surfaces of the plate (3a) side and the stator (3C) side is formed so as to gradually become smaller from the starting end to the ending end, thereby improving compression performance.

FIG. 13 shows a third embodiment of the circumferential groove pump section, and in this embodiment, the wall thickness of the cut step portions (3b) (3b) on the periphery of each rotary disk (3a) is are formed to become gradually thinner toward the outside, and these cut step portions (3
b) (3b) and the recesses (3, d) facing them;
The concave portion (3d) is formed so that the distance between the concave portion (3d) and the inner surface of the concave portion is the same at any position in the radial direction, and the distance becomes narrower as it goes outward.

FIG. 14 to FIG. 17 show a fourth embodiment of the circumferential groove pump section (3), in which two locations are provided at symmetrical positions with respect to the inlet and outlet ports of each rotating disk (3a), The exhaust speed is doubled by compressing the exhaust air in parallel.

FIG. 18 shows a second embodiment of the vortex pump section (4), in which the suction channel (4d) is provided in parallel on both sides of the radial blade (4a), and the cross section of the ventilation channel of the next stage is set in the parallel section. 70%
The structure is shown below.

FIG. 19 shows a third embodiment of the vortex pump section (4), -
This figure shows a four-stage pump element constructed by providing recesses (4b) on both sides of a single radial grade (4a).

Even if there is a small number of stacked stages, such as by combining one or two of the embodiment shown in FIG. 18 and one or two of the embodiment shown in FIG. 19, it substantially corresponds to a vortex pump section with multiple stages of radial blades.

(7) Effects of the Invention As described above, according to the present invention, the turbo molecular pump section, the circumferential groove pump section, and the The vortex pump section is arranged sequentially from the intake port side, and the gas from the intake port is once compressed and transferred in the turbo molecular pump section, and then in the circumferential groove pump section, by the peripheral part of the rotating disk that rotates at a particularly high speed. The gas produces an efficient transport effect by molecular drag due to gas molecule friction, and 1
It becomes possible to take a large dimension in the radial direction of the intake port to the ventilation passage of the first stage rotary disk which determines the pumping speed of the circumferential groove pump section, and thus a large pumping speed can be obtained. Furthermore, a high compression ratio is achieved by the large number of radial blades installed in the vortex pump section, and the pumping speed is sufficient for each pressure field in the suction range from atmospheric pressure to ultra-high vacuum, regardless of the molecular weight and chemical properties of the gas. Due to the large pumping performance of the circumferentially grooved pump section, the rotating body extending from the intake port side to the exhaust port side can be significantly shortened in axial length compared to conventional systems, and the rotor of each pump section can be made smaller. It can be integrated into a single rotor type connected to the end of the rotating shaft, which can suppress the generation of vibration, and does not require high-precision machining for a small and lightweight rotor, making it compact, lightweight, and oil-free. A vacuum pump that can generate free, clean vacuum has the effect of being inexpensive. Furthermore, the composite vacuum pump according to the present invention has corrosion resistance against harmful and corrosive gases by coating the rotor and stator integrated with aluminum and miniram alloy with corrosion resistance, and the lubricating oil is not contaminated. All of the pump parts give a centrifugal flow velocity to the gas, and the discharge ports of each stage are provided on the outer periphery in the radial direction, so that the pump sucks powder and granules together with the process gas, or Even if granules are generated due to a chemical reaction during compression, the compressor operates without any trouble and has the effect of sequentially discharging the granules to the exhaust port, so it is extremely useful and economically effective in semiconductor manufacturing vacuum equipment and the like.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the entire first embodiment of the compound vacuum pump of the present invention, FIG. 2 is a cross-sectional view taken along the line II in FIG. 1, and FIG. 3 is a cross-sectional view taken along the line ■-II in FIG. The cross-sectional diagram is shown in Figure 2.
Figure 5 is a cross-sectional view taken along line 17-IV in Figure 2. Figure 6 is a cross-sectional view taken along line v-V in Figure 2. Figure 7 is a cross-sectional view taken along line VT-Vll in Figure 2. 8 is a sectional view taken along the line ■-■ in FIG. 2; FIG. 9 is a graph showing the relationship between intake port pressure and pumping speed; and FIGS. 13 is a partial sectional view of the third embodiment of the circumferential groove pump section, and FIG. 14 is a cross section corresponding to FIG. 2 showing the fourth embodiment of the circumferential groove pump section. Figure 15 is the 14th
16 is a cross-sectional view taken along line I-I in the figure, and FIG. 16 is II-I in FIG.
17 is a sectional view taken along line II in FIG. 14, FIG. 18 is a vertical sectional view of the rotor showing the second embodiment of the vortex pump section, and FIG. 19 is a sectional view taken along line II of FIG. 14. FIG. 20 is a longitudinal sectional view of a rotor portion showing a third embodiment of the present invention, and FIG. 20 is a sectional view of a conventional composite molecular pump. (1)...Housing (2)...Turbo molecular pump section (3)...Circumferential groove pump section (4)...Vortex pump section (12)...Intake port (13) ...Exhaust port applicant Osaka Vacuum Equipment Manufacturing Co., Ltd. Figure 19 Figure 20 Buttocks 1 port. Figure 1 Figure 2 Figure 5 Figure 6 Figure 7 Figure M8 d

Claims (1)

[Claims] A composite vacuum pump characterized in that a turbo molecular pump section, a circumferential groove pump section, and a vortex pump section are sequentially arranged from the intake port side in a housing having an intake port and an exhaust port.