JP2696370B2 - Circumferential groove vacuum pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Industrial application field The present invention relates to industrial vacuum equipment such as particle accelerators, experimental research equipment such as plasma physics, electron microscopes, surface analyzers, and semiconductor manufacturing vacuum equipment. The present invention relates to a circumferential groove vacuum pump useful in a range from molecular flow to viscous flow, that is, in a pressure range from high vacuum to medium vacuum.

(2) Prior Art As a vacuum pump having a useful evacuation performance in a range from a molecular flow to a viscous flow, the applicant has previously proposed a circumferential groove vacuum pump shown in FIGS. 63-1741
No. 48). That is, the first embodiment of this vacuum pump supports a rotating shaft having a rotating disk (c) in a housing having an inlet (a) and an outlet (b) as shown in FIGS. ,
A stator (d) having a concave portion in which the rotating disk (c) is interposed is fixed in the housing, and a notch step (e) or a cutting step (e) is provided on the periphery of both surfaces of the rotating disk (c). An annular groove is formed in a concave portion at a position opposed to the peripheral portion, and these cut step portions (e) are formed.
Alternatively, an annular groove is formed in the ventilation path (f), and a partition wall (g) is protruded from the stator (d) in the ventilation path (f),
The starting end of the ventilation path (f) on one side of the partition (g) is the intake port (a), and the end of the ventilation path (f) on the other side of the partition (g) is the exhaust port (b). ) And the second
The pump according to the embodiment has an intake port (a) as shown in FIGS.
And two outlets (b) are provided at intervals of 180 degrees, and two partitions (g) are provided in accordance with the two outlets. Thus, the ventilation at the two locations separated by the partitions (g) and (g) is provided. Since the gas molecules are compressed and evacuated in the passages (f) and (f), the evacuating speed is approximately doubled. Further, the pump of the third embodiment has three rotating disks as shown in FIGS. 18 and 19. (C) ... (c) is integrally formed in the boss portion (h), and the opposing surfaces of the rotating disk (c) and the stator (d) in the ventilation path (f) of the rotating disk (c). The distance between the air passages (f) and (f) is formed so that the distance between the air inlets (a) and the air outlets (b) becomes smaller gradually. The communication path (i) communicating between the roads (f) (f) and (f) (f) is connected to the intake port (a).
The positions are sequentially shifted from the side to the exhaust port (b) side, so that the gas molecules from the intake port (a) are sent through the communication path (i) while being passed through each ventilation path (f) ( f)
Are sequentially compressed so that a considerably high compression ratio can be obtained.

(3) Problems to be Solved by the Invention According to the first embodiment of the vacuum pump proposed by the applicant earlier, the intake port (a) can be made large, so that even if this is increased, the exhaust speed can be increased. The exhaust speed is limited by the cross-sectional area of the ventilation path (f), and according to the pump of the second embodiment, the effective length of the circumferential groove for performing the compression action, that is, the ventilation path (f) is shortened and the compression ratio is reduced. Further, according to the pump of the third embodiment, between the opposed surfaces of the rotating disk (c) side and the stator (d) side in the ventilation path (f) of each rotating disk (c). Since the distance is reduced from the side of the intake port (a) to the side of the exhaust port (b), there is a problem that the production is difficult and the production cost is increased.

An object of the present invention is to provide a circumferential groove vacuum pump that solves these problems, increases the compression ratio, increases the pumping speed, and reduces the manufacturing cost.

(4) Means for Solving the Problems In order to solve the above-mentioned problems, the present invention uses a peripheral portion of a high-speed rotating multi-stage rotating disk in a stator in a housing having an intake port and an exhaust port. In a circumferential groove vacuum pump of a type in which gas in an opposed circumferential groove-shaped ventilation path is sequentially compressed and exhausted, the Knudsen number (Kn) at the intake port represented by the following equation is set to 4 × 10 ^-3 or more, The intake port is connected to the air passages of two or more rotating disks on the intake port side.

Kn = λ / b (1) where λ is the mean free path of gas molecules at the operating pressure, b
Is the distance between the opposing surfaces of the ventilation path.

(5) Action The gas in the ventilation path is transported by the molecular drag effect due to the molecular friction of the gas due to the peripheral portions of the multi-stage rotating disk rotating at high speed, and transported, but the Knudsen number (Kn) is 4 ×. Since it is 10 ^-3 or more, a large compression ratio can be obtained, and a large exhaust speed can be obtained because the intake ports are both connected to the ventilation passages of the two or more rotating disks on the intake port side.

(6) Embodiment A first embodiment of the present invention will be described with reference to FIGS.

(1) shows a housing of the vacuum pump, (2) shows a rotating shaft supported in the housing (1), and the rotating shaft (2) has a motor connected at a lower end thereof and an upper end thereof. The rotating disk (3) is fixed together at a boss (3a) at the center thereof. Then, the rotating disk (3) was formed with notch steps (4) and (4) by cutting out the peripheral portions on both sides. Reference numeral (5) denotes a stator fixed to the inner surface of the housing (1). The stator (5) has an annular shape in which the rotating disk (3) is interposed at a position corresponding to the rotating disk (3). The recesses (6) are formed, and the recesses (6) and the notch steps (4) (4) form ventilation passages (7)... (7) on both sides of the peripheral portion of the rotating disk (3). ) Formed. In the recess (6), a partition (8) obtained by cutting off a portion through which the peripheral portion of the rotating disk (3) passes is protruded from the stator (5), and a two-stage partition is formed by the partition (8). The ventilation passages (7)... (7) of the rotating disks (3) and (3) are separated, and the ventilation passages of these two-stage rotating disks (3) and (3) on the side of the partition wall (8), that is, on the upstream side. (7) These two-stage rotating disks (3) (3) ventilation passages (7) communicating both the starting ends of (7) with the intake port (9) and the other side of the partition (8), that is, the downstream side. ... The end of (7) is connected to the exhaust port (10), and the mean free path of the gas molecules at the operating pressure is λ, and the annular surface facing the ventilation passage of the rotating disk and the Kn = λ / b (Kn Knudsen number) is set to 4 × 10 ⁻³ or more, where b is the distance between the opposed stator surfaces.

Thus, the rotating disk (3) is driven by the motor so that its peripheral speed is 0.1 to 1.0 times the probability average speed of gas molecules.
When rotated in the direction of arrow A in the figure, the ventilation paths (7) and (7) are formed around the rotating disks (3) and (3).
The gas molecules in these ventilation paths (7)... (7) hit both surfaces of the cutting steps (4). The transport effect is produced by the molecular drag effect due to the friction of the gas molecules, so that the gas molecules pass through the ventilation passages (7)... (7) from the intake port (9) as shown by the arrow B in FIGS. And is compressed and evacuated from the exhaust port (10) as shown by the arrow D in FIGS. 1 and 4, and has an evacuating action in a pressure range from the molecular flow to the viscous flow. According to the experiment by the inventor, the compression characteristics of the circumferential groove vacuum pump having the above configuration are as shown in FIG.

That is, the curve (A) shows the compression characteristics of the circumferential groove vacuum pump when the dimension of (b) is 5 mm. The horizontal axis is the exhaust pressure (P ₂ ), and the vertical axis is the intake pressure (P ₁ ). On the straight line R, the intake pressure (P ₁ ) and the exhaust pressure (P ₂ ) are equal and the compression ratio is 1. Note that the solid line portions on the horizontal axis and the vertical axis also show the value of Kn when b = 5 mm. And P ₁ ≦ 10 ⁻¹ Torr as shown in the curve (A).
, A compression ratio of about 14 times is obtained, and at P ₁ = 1 Torr, a compression ratio of 3 times is obtained.
The compression performance sharply decreases in the region where the value of Kn is 4 × 10 ⁻³ to 10 ⁻³ , and when Kn is smaller than this region, the compression performance further decreases and the compression ratio approaches 1.

Curve (B) shows the compression performance of the circumferential groove vacuum pump when the size of (b) is 20 mm, and the value indicated by the chain line and [] shows the value of Kn in this case. In the case of the curve (B), the pumping speed is about four times that in the case of (A). Then, in the region where the operating pressure rises and Kn becomes 4 × 10 ⁻³ to 10 ⁻³ , the compression performance drops sharply, and if Kn is smaller than this region, the curve (A)
As in the case of, the compression performance further decreases, and the compression ratio approaches 1.

From the above, Kn is 4 × 10 in the region from molecular flow to viscous flow.
^-3 or more and two-stage rotating disk (3) ventilation path (7) ...
By connecting (7) to the common intake port (9) and exhaust port (10), a high compression ratio can be obtained and the exhaust speed can be increased.

5 to 10 show a second embodiment of the present invention. In this embodiment, a three-stage rotating disk (3) (3 ') is used.
(3 ″) are fixed to the boss (3a), and the air inlet (9)
Ventilation path (7) of two-stage rotating disk (3) (3 ') on the side
(7 ') is connected to the intake port (9).
Rotating disk (3)
A communication path (11) connects between the ventilation path (7) (7 ') of (3') and the ventilation path (7 ") (7") of the rotating disk (3 ") on the side of the exhaust port (10). The exhaust port (10) communicates with the ventilation path (7 ") (7") of the rotating disk (3 ") on the exhaust port (10) side at a position shifted from the communication path (11) while communicating with the communication path (11). Thus, the gas molecules sucked from the intake port (9) are sequentially compressed in each of the ventilation paths (7), (7 '), (7 ") while being sent through the communication path, so that high compression is achieved. The ratio is obtained.

In addition, the circumferential groove vacuum pump according to the present invention is not only a vacuum pump having only the pump element according to this operating principle, but also coaxially integrated and connected to a high vacuum pump element and a low vacuum pump element according to other operating principles, It can be configured as a composite vacuum pump, for example, as disclosed in Japanese Patent Application No.
By applying the present invention to the circumferential groove vacuum pump section of the combined vacuum pump section of the turbo molecular pump section and the circumferential groove vacuum pump section of No. 63-186632, the exhaust speed of this section can be increased. In the case of a large-sized machine, the overall performance can be further improved, and the applicant has previously proposed Japanese Patent Application No. 63-2041.
By applying the present invention to the circumferential groove vacuum pump section of the composite vacuum pump comprising the circumferential groove vacuum pump section and the vortex vacuum pump section of No. 28, the overall performance can be improved as described above,
Further, the present invention is applied to the circumferential groove vacuum pump section of a composite vacuum pump comprising a turbo molecular pump section, a circumferential groove vacuum pump section, and a vortex vacuum pump section of Japanese Patent Application No. 63-226533 previously proposed by the applicant. By applying this, the overall performance can be improved in the same manner as described above.

In each of the embodiments described above, the intake port is connected to the ventilation passage of the two-stage rotating disk on the intake port side. However, if necessary, the intake port is connected to the intake port side to obtain a large exhaust speed. 3
You may make it communicate with the ventilation path of the rotating plate more than steps.

(7) Effects of the Invention As described above, according to the present invention, the Knudsen number (Kn) is 4
X10 ^-3 or more, a large compression ratio can be obtained,
A large exhaust speed is obtained because the intake port is connected to the ventilation path of the two or more rotating disks on the intake port side, and furthermore, a rotating circle from the intake port side to the exhaust port side is obtained. Since the distance between the rotating disk and the stator in the plate ventilation path can be equalized, component processing can be standardized, the casting mold can be shared in the stator, etc., and the manufacturing cost of a multi-stage vacuum pump can be greatly reduced. And the like.

[Brief description of the drawings]

1 is a plan view of a main part of a first embodiment of the present invention, FIG. 2 is a sectional view taken along the line I-II of FIG. 1, and FIG. 3 is a line 0-III of FIG.
FIG. 4 is a sectional view taken along the line 0-IV of FIG. 1, and FIG.
FIG. 6 is a plan view of a main part of the second embodiment, and FIG.
FIG. 7 is a sectional view taken along line 0-III of FIG. 5,
8 is a sectional view taken along line 0-IV of FIG. 5, FIG. 9 is a sectional view taken along line 0-V of FIG. 5, FIG. 10 is a sectional view taken along line 0-VI of FIG. FIG. 12 is a graph showing compression characteristics, FIG. 12 is a plan view of a main part of the first embodiment of the conventional vacuum pump, FIG. 13 is a sectional view taken along the line I-II of FIG. 12, and FIG. FIG. 15 is a sectional view taken along line 0-III of FIG. 15, FIG. 15 is a plan view of a main part of a second embodiment of the conventional vacuum pump, FIG. 16 is a sectional view taken along line I-II of FIG. FIG. 15 is a sectional view taken along the line III-IV of FIG. 15, FIG. 18 is a plan view of a main part of a third embodiment of the conventional vacuum pump, and FIG.
FIG. 2 is a sectional view taken along the line II. (1) ... Housing (3) ... Rotating disk (5) ... Stator (7) ... Ventilation path (9) ... Intake port (10) ... Exhaust port

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Shoji Iguchi 1221 Kuginodacho, Hachioji-shi, Tokyo Inside the Osaka Vacuum Equipment Co., Ltd. Hachioji Plant (56) References JP-A-57-59098 (JP, A) JP-A Sho 63-85297 (JP, A) JP-A-63-192987 (JP, A)

Claims (1)

(57) [Claims] In a stator in a housing having an intake port and an exhaust port, gas in an opposed circumferential groove-shaped ventilation path is sequentially compressed and exhausted by a peripheral portion of a plurality of rotating disks rotating at high speed. In the circumferential groove vacuum pump of the formula, the Knudsen number (Kn) at the suction port represented by the following formula is set to 4 × 10 ⁻³ or more, and the suction port is connected to two or more rotary disks on the suction port side. A circumferential groove vacuum pump characterized in that it is connected to both ventilation passages. Kn = λ / b (1) where λ is the mean free path of the gas molecules at the operating pressure, and b is the distance between the facing surfaces of the ventilation path.