JPS6385290A - Vacuum pump - Google Patents

Abstract

PURPOSE:To effectively operate a vacuum pump in a wide pressure range by installing a siegbahn pump stage as the pump stage in the molecular flow or intermediate flow range and arranging a centrifugal compression pump stage and a circumferential flow compression pump stage, onto the slip stream side of the Siegbahn pump stage. CONSTITUTION:A rotary shaft 1 is rotatably supported by a bearing 7 in a housing 2 having a suction port 2A And an exhaust port 2B. In this case, in the housing 2, the following pump stages are arranged in succession from the suction port 2A side. In other words, an axial flow turbomolecular pump stage 3 in which axial flow vane wheels 3A And fixed vanes 3B are arranged alternately, siegbahn pump stage in which rotary discs 9A and fixed discs 9B are arranged alternately, centrifugal compression pump stage 5 in which centrifugal vane wheels 5A and fixed discs 5B are arranged alternately, and a circumferential flow compression pump stage 10 in which circumferential flow vane wheels 10A and fixed discs 10B are arranged alternately are arranged in connection. Therefore, the deterioration of the faculty of the vacuum pump due to the increase of the pressure at the suction port 2A can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a vacuum pump whose exhaust port is set to atmospheric pressure, and relates to a vacuum pump suitable for creating a clean vacuum in, for example, semiconductor manufacturing equipment.

[Conventional technology]

The structure of a conventional vacuum pump is shown in FIG. 6. A rotor 1 rotatably supported by a bearing 7 is housed in a casing 2 having an intake port 2A and an exhaust port 28tt. The whole consists of three axial flow turbomolecular pump stages. Additional molecular pump 4. Centrifugal compression pump stage5. The vortex compression pump stages 6 are successively arranged from the intake port side to the exhaust port side.

When the vacuum pump configured as described above is operated with the pressure at the exhaust port 2B at atmospheric pressure and the pressure at the intake port 2A has dropped sufficiently, the flow of gas inside the vacuum pump is as follows.
From the intake side to the exhaust side, the flow changes to molecular flow, intermediate flow, and viscous flow. On the other hand, the air pressure range in which each pump stage is most effective for evacuation is different, with the axial flow turbomolecular pump stage 3 and the additional molecular pump stage 4 in the molecular region, and the centrifugal pressure Kusunoki pump stage 5 in the molecular flow to intermediate region. The vortex compression pump stage 6 has a characteristic of good performance in the intermediate flow to viscous region.

Incidentally, related vacuum pumps of this type include, for example, Japanese Patent Application Laid-Open No. 51-38113.

[Problem that the invention seeks to solve]

In the vacuum pump according to the above-mentioned prior art, in a state where the pressure at the intake port 2A is not sufficiently reduced, such as in a transient operating state, ! If: There was a problem that the air speed decreased drastically. This is because the pressure at the intake 02 is high and the axial flow turbomolecular pump stage 3. When the gas flow in the additional molecular pump stage 4 becomes an intermediate flow or a viscous flow, the axial flow turbo molecular pump stage 3. This is because the pumping speed in the additional molecular pump stage 4 is significantly reduced, and in this state, the centrifugal compression pump stage 5 and the vortex compression pump stage 6 take on most of the pumping action. At this time, the back pressure of the centrifugal compression pump stage 5 depends on the performance of the vortex compression pump stage 6.

The vortex compression pump stage 6 used in this conventional example has a relatively narrow effective operating pressure range, and its performance deteriorates sharply in the pressure range near atmospheric pressure, making it impossible to obtain a sufficient compression ratio. The back pressure of the centrifugal compression pump stage 5 increases and the performance of the centrifugal compression pump stage 5 decreases.

Pumping speed tends to decrease. As described above, the above-mentioned conventional technology has a problem in that the flow in the axial turbo-molecular pump stage 3 becomes an intermediate flow and the pumping speed is drastically reduced when the pressure in the vortex compression pump stage 6 increases to near atmospheric pressure. However, there was a problem that the effective operating pressure range of the vacuum pump was narrow.

An object of the present invention is to provide a vacuum pump that operates effectively over a wide pressure range.

[Means for solving problems]

The above object is to provide a Siegbahn pump stage, which effectively performs evacuation in a higher pressure range than a trickle turbo-molecular pump stage, as a pump stage in the molecular flow and intermediate region, on the downstream side of the axial-flow turbo-molecular pump stage; Furthermore, this is achieved by providing a centrifugal compression pump stage 1 and a circumferential flow compression pump stage downstream of the Siegbahn pump stage.

[Effect]

As mentioned above, the vacuum pump is installed from the suction side into the axial flow turbomolecular pump stage, the Siegbahn pump stage, and the centrifugal compression pump stage 1.
If configured by connecting circumferential flow compression pump stages,
Even if the inlet pressure rises and the flow becomes intermediate flow in the axial turbomolecular pump stage and the pumping speed decreases rapidly, the Siegbahn pump stage operates effectively within the same pressure range, so the pumping speed as a whole of the vacuum pump decreases. Since the reduction in 1-circumferential-flow compression pump stage is small, and the compression performance of the 1-circumferential-flow compression pump stage is better than that of the vortex-flow compression pump stage under high pressure conditions, the back pressure of the centrifugal compression pump stage can be maintained low, and the centrifugal compression pump stage performance can be prevented from deteriorating. As a result, the vacuum pump can be effectively operated in a wide pressure range from the molecular region to the viscous region.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. 1st
The figure is a diagram showing the overall structure of a vacuum pump according to an embodiment of the present invention.

In FIG. 1, a rotating shaft 1 is rotatably supported by a bearing 7 within a housing 2 having two intake ports and an exhaust port 2B, and a motor 10 attached to the rotating shaft 1
Driven by. Inside the housing 2, in order from the intake port side, there are an axial flow impeller 3A (Fig. 2(b)) attached to the one-rotation shaft 1 and a fixed impeller 3B fixed inside the housing 2 (see Fig. 2(b)).
A trickle turbomolecular pump stage configured by alternately arranging the pumps (Fig. 2(C)) and the rotating disk 9A (Fig. 3(a))
and a Siegbahn pump stage 9 constructed by alternately arranging fixed discs 9B (FIG. 3(b)).

Centrifugal impeller 5A (fourth
Figure (b)) and the fixed disk 5B fixed in the housing 2
(Fig. 4(C)) and a centrifugal compression pump stage 5 configured by alternately arranging the pumps (Fig. 4(C)) and a circumferential flow impeller 10A (Fig. 5(b)
)) and fixed disks 10B (FIG. 5(C)) are arranged in series with circumferential flow compression pump stages 10.

When the above vacuum pump is operated with the air pressure at the exhaust port 2B at atmospheric pressure, and the pressure at the intake port 2A is sufficiently reduced and the gas flow becomes a molecular flow, each pump stage has its own characteristics. Operating in the best pressure range. On the other hand, intake port 2
When the human pressure increases, the gas flow in the axial turbomolecular pump stage 3 becomes an intermediate flow, and the performance decreases.
The Siegbahn pump stage 9 operates effectively in a wide pressure range from molecular flow to intermediate flow, and the compression action in the circumferential flow compression pump stage 10 maintains the pressure state at which the centrifugal compression pump stage 5 operates effectively. Therefore, performance degradation due to pressure increase at the intake port 2A is small, and as a result, the vacuum pump can operate effectively over a wide pressure range.

Similar effects can be obtained by using a screw compression pump stage in place of the Siegbahn pump stage in the above embodiments.

〔Effect of the invention〕

According to the present invention, a decrease in the performance of the vacuum pump due to an increase in intake port pressure can be reduced, so that a vacuum pump that operates effectively over a wide pressure range can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view showing the overall structure of the vacuum pump of the present invention, FIGS. 2(a) to 2(c) are detailed views of the axial flow turbomolecular pump stage in FIG. 1, and FIG. a) and (b) are the first
4(a) to 4(c) are detailed views of the centrifugal compression pump stage of FIG.
5(a) to 5(c) are detailed views of the circumferential flow compression pump stage of FIG. 1, and FIG. 6 is a sectional view of a conventional vacuum pump. 2A... Intake 0.2B... Exhaust port, 3... Axial turbo molecular pump stage, 5... Centrifugal compression pump stage, 9...
・Jigue + Mil! :5 Agent Patent attorney Katsuo Ogawa 8th l eye 2nd mouth (su(su 30th (α) <b) 98...KrL Enkei (,,) 4th prisoner <b) 10F3... Camellia on a stretched tree 5 l (Su10B...fixed tomoe

Claims (1)

[Claims] 1. Consists of a housing having an intake port and an exhaust port, a starter provided within the housing, and a rotor rotatably supported within the housing, and as the rotor rotates, air is sucked in from the intake port. In an integrated vacuum pump that exhausts gas directly to the atmosphere from the exhaust port, an axial flow impeller provided on the rotor adjacent to the intake port and a fixed plate fixed in the housing are alternately arranged side by side. an axial-flow turbomolecular pump stage formed by the axial-flow turbomolecular pump stage, and a screw on one or both of a rotating disk provided on the rotor and a fixed disk fixed in the housing on the downstream side of the axial-flow turbomolecular pump stage. A Siegbahn pump stage is formed by providing a shaped groove, and a centrifugal impeller provided on the rotor and a fixed plate fixed in the housing are alternately juxtaposed on the downstream side of the Siegbahn pump stage. a centrifugal compression pump stage; a circumferential flow formed by alternately juxtaposing a circumferential flow impeller provided on the rotor and a fixed plate fixed in the housing on the downstream side of the centrifugal pressure pump stage; A vacuum pump characterized by being configured by connecting compression pump stages.