JPH03115797A - Vacuum pump - Google Patents

Abstract

PURPOSE:To obtain a large pumping speed under the transition condition in the initial time of the operation and perform the sufficient compression work against the molecular flow under the steady state by providing an open type impeller having retreating vanes and a fixed round plate to be located opposite to the front surface of the open type impeller in a centrifugal compression pump stage of pump stages. CONSTITUTION:A centrifugal compression pump stage 13 works as a centrifugal compressor under the transition condition in the initial time of the pump operation, and as a result, a large pumping speed can be obtained, and since it works as a siegbahn molecular pump against the molecular flow under the steady state, the sufficient compression work against the molecular flow can be obtained. Namely, against the viscous flow in the initial time of the pump operation, the viscous flow is centrifugally compressed by an open type impeller 13A having multiple retreating vanes, and under the steady state to be the high vacuum condition, the molecular flow can be compressed to the constant direction with the work of the retreating vanes of the open type impeller 13A and the fixed round plate 13B located opposite to the front surface of the open type impeller 13A.

Description

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

[Conventional technology]

As a conventional vacuum pump, one described in Japanese Unexamined Patent Publication No. 51-38113 is known. The structure of this vacuum pump will be explained with reference to FIG. In the figure: Since it is symmetrical, I will explain about the instrumental side.

1 is a housing having an intake port IA and an exhaust port IB;
Reference numeral 2 denotes a rotating shaft rotatably supported in the housing 1 via a bearing 7, and the housing 1 includes an axial flow turbomolecular pump stage 3, an additional molecular pump stage 4, a centrifugal compression pump stage 5, and a vortex compression pump stage. Pump stages 6 are sequentially arranged from the intake port IA side to the exhaust port IB side.

The axial turbomolecular pump stage 3 is constructed by alternately combining fixed plates 3B attached to the inner wall of the housing 1 and rotating disks 3A attached to the rotating shaft 2.

The additional molecular pump stage 4 includes a fixed plate 4B attached to the inner wall of the housing 1 and a disc-shaped impeller 4A attached to the rotating shaft 2.
It is composed of an alternating combination of The centrifugal compression pump stage 5 is constructed by alternately combining differential user fixing plates 5B attached to the inner wall of the housing 1 and impellers 5A attached to the rotating shaft 2. The vortex compression pump stage 6 is constructed by alternately combining fixed plates 6B attached to the inner wall of the housing 1 and rotating disks 6A attached to the rotating shaft 2.

On the other hand, the rotating shaft 2 is driven via a drive turbine 8, and the drive turbine 8 is connected to an air outlet 9A and an air outlet 9B provided on the side wall of the housing 1.

[Problem to be solved by the invention]

In the vacuum pump configured as described above, when a steady state is reached, each pump stage performs a sufficient compression action, and the pressure at the suction port, that is, the ultimate vacuum pressure, can reach a sufficiently low pressure. However, in a so-called transient state at the beginning of pump operation, a large pumping speed cannot be obtained. This is because in such a transient state, the pressure inside the pump is high, so the axial turbo-molecular pump stage 3 and the additional molecular pump stage 4, which are normally effective when the gas flow is a molecular flow or an intermediate flow, have almost no compression effect. This is because, in particular, the additional molecular pump stage has a narrow flow path cross-sectional area, and therefore has a large fluid resistance, resulting in a pressure loss for a large flow rate.

An object of the present invention is to obtain a vacuum pump that can obtain a large pumping speed in a transient state at the beginning of pump operation, and that also has a sufficient compression effect on molecular flow in a steady state.

[Means to solve the problem]

In order to achieve the above object, the present invention has an intake port, an exhaust port, and a pump stage that performs a pumping action, and in a steady state, dilute gas in a molecular flow pressure region is sucked and compressed from the intake port, and is then released from the exhaust port. In the vacuum pump, the pump stage has at least a centrifugal compression pump stage, and the centrifugal compression pump stage includes an open impeller mounted on a rotating shaft and having a plurality of retracting blades; It is characterized by comprising a fixed disc disposed to face the front surface.

Another feature of the present invention is that it has an inlet port, an exhaust port, and a pump stage that performs a pumping action, and in a steady state, dilute gas in a molecular flow pressure region is sucked in from the inlet port, compressed, and discharged from the exhaust port. In the vacuum pump, the pump stage has at least a centrifugal compression pump stage, and the centrifugal compression pump stage includes an open impeller mounted on a rotating shaft and having a plurality of retracting blades, and a front surface of the impeller. The present invention includes a fixed disk disposed to face the impeller, and blades provided on the back side of the impeller on the fixed disk facing inward in the rotational direction of the impeller.

[Effect]

The centrifugal compression pump stage works as a centrifugal compressor in a transient state at the beginning of pump operation, resulting in a large pumping speed, and works as a Siegbahn molecular pump for molecular flow in a steady state. Sufficient compressive action can also be obtained against the flow. In other words, the viscous flow at the beginning of the pump movement is centrifugally compressed by the open impeller having a plurality of retreating vanes, and in a steady state of high vacuum, the retreating vanes of the open impeller and this The molecular flow can be compressed in a fixed direction by the action of a fixed disk placed opposite the front surface of the impeller.

In addition, a fixed disk facing the back side of the open type impeller,
It goes without saying that the above-mentioned effect can be obtained by providing the fixed disk with blades provided on the back side of the impeller facing inward in the direction of rotation of the impeller.

Since the back side of the impeller can also function as a Siegbahn pump in a steady state, the compression action in a steady state can be further improved.2 [Embodiment] Hereinafter, an embodiment of the present invention will be described with reference to FIGS. This will be explained based on FIG. FIG. 1 shows the overall structure of a vacuum pump according to the present invention. In FIG.
Housing 1 having an intake port 11A and an exhaust port 11B
1, a rotating shaft 12 rotatably supported within the housing 11 via a bearing 21, and centrifugal compression pump stages sequentially arranged within the housing 11 from the intake port 11A side to the exhaust port 11B side. 13 and circumferential flow compression pump stage 14
It is equipped with The rotating shaft 12 is connected to the motor 1.
5.

As shown in FIGS. 2 and 3, the centrifugal compression pump stage 13 has a plurality of blades 16 facing inward with respect to the rotational direction on its back surface, and an open impeller 13A attached to the rotating shaft 12. , as shown in FIGS. 2 and 4, the housing 1
Fixed discs 13B are attached to the inner wall of the impeller 13A and have a plurality of blades 17 facing inward with respect to the rotation direction on a surface opposite to the back surface of the impeller 13A (the surface on which the blades 16 are not provided). It is arranged and configured. The diameter of the rotating body of this centrifugal compression pump stage 13 is the diameter of the rotating body of the centrifugal compression pump stage 1, which will be described later.
The diameter of the rotating body 4 is larger than that of the rotating body 4.

As shown in FIGS. 5 and 6, the circumferential flow compression pump stage 14 includes an impeller 14A attached to the rotating shaft 12 and having a plurality of blades 18 radially provided on the outer circumferential surface, and a fifth impeller 14A, as shown in FIGS. figure,
As shown in FIG. 7, a fixed disk 1 is attached to the inner wall of the housing 11 and has a U-shaped groove 19 on the surface facing the surface of the impeller 14A (the surface on which the blades 18 are provided).
4B are arranged alternately in parallel, and the 5th
As shown in FIG.
A ventilation passage 20 is formed by drilling the hole. The diameter on the outlet side of the rotating body of the circumferential flow compression pump stage 14 is smaller than the diameter on the inlet side. Thereby, the rotational power of this portion can be reduced.

Next, the operation of this embodiment will be explained.

In a transient state at the beginning of pump operation, the entire inside of the pump is under a high pressure close to atmospheric pressure, and the gas flow becomes a viscous flow, so that the centrifugal compression pump stage 13 acts as a centrifugal compressor. That is, the centrifugal compression pump stage impeller 13A
acts as a compressor impeller, and the impeller 13A and fixed disk 1
The flow path formed between the blades 17 between the blades 3B acts as a return channel that guides the flow from the outer diameter side to the inner diameter ml, and since the impeller 13A acts as a compressor,
The centrifugal compression pump stage 13 can act as a compressor to provide a large flow rate rather than as a pressure loss section.

In a steady state in which the compression ratio of the circumferential flow compression pump stage 14 is increased and the pressure at the inlet of the circumferential flow compression pump stage is sufficiently low, that is, in a steady state in which this pressure is several Torr or less, centrifugal The gas flow near the inlet of the compression pump stage 13, ie, the vacuum pump inlet 11A, is an intermediate flow or molecular flow, and the centrifugal compression pump stage 13 acts as a Siegbahn molecular pump. That is, feather 1
The impeller 13A having 6 acts as a rotating disk with a spiral groove processed, and in combination with the back surface of the fixed disk 13B (the surface where the blades 17 are not provided), compresses from the inner diameter side to the outer diameter side. It acts as a fixed disk, and in combination with the back surface of the impeller 13A (the surface on which the blades 16 are not provided), it functions as a Siegbahn molecular pump that compresses from the outer diameter side toward the inner diameter side.

Similarly, in a steady state, the gas flowing into the circumferential compression pump stage 14 is sufficiently compressed in the centrifugal compression pump stage 13, so that the volumetric flow rate is almost zero. In other words, the circumferential flow compression pump stage 14 is operated in a state close to the closed state, but since the first circumferential flow compression pump stage has the characteristic of obtaining a high compression ratio in the closed state, it is possible to operate with a small number of stages. A sufficiently low ultimate pressure can be reached.

The number of stages of the centrifugal compression pump stage 13 and the circumferential flow compression pump stage 14 and the pump rotation speed are determined at the point where the pressure at the boundary between the two stages switches between the viscous flow and the intermediate flow in a steady operating state, that is, the number of holes T.
Set it to be orr. Usually, by combining 1 to 3 stages of centrifugal compression pump stages and 6 to 10 stages of circumferential flow compression pump stages, the pressure at the pump intake port 11A is 10-"~
10-'T o r r can be reached.

〔Effect of the invention〕

According to the present invention, the centrifugal compression pump stage operates as a centrifugal compressor in a transient state at the beginning of pump operation, and a large pumping speed can be obtained. In addition, it works as a Siegbahn molecular pump for molecular flow in a steady state, and has the effect of being able to obtain a sufficient compression effect.

[Brief explanation of drawings]

1 is a vertical sectional view showing the overall structure of the vacuum pump according to the present invention, FIG. 2 is a sectional view showing details of the centrifugal compression pump stage of the vacuum pump shown in FIG. 1, and FIG. -■ arrow view, Figure 4 is a view from IV-■ arrow in Figure 2, Figure 5 is a sectional view showing details of the circumferential flow compression pump stage of the vacuum pump shown in Figure 1, and Figure 6 is FIG. 5 is a view taken along the VI-VI arrow in FIG. 5, FIG. 7 is a view taken along the ■-■ arrow in FIG. 5, and FIG. 8 is a longitudinal sectional view of a conventional vacuum pump. 11...Housing, IIA...Intake port, IIB・
...Exhaust port, 12... Rotating shaft, 13... Centrifugal compression pump stage. 13A...Open type impeller, 13B...Fixed disc, 14...Circumferential flow compression pump stage, 14A...Impeller, 14B...Fixed disc, 16.17.18...・Feathers.

Claims (1)

[Claims] 1. It has an intake port, an exhaust port, and a pump stage that performs a pumping action, and in a steady state, dilute gas in the molecular flow pressure region is sucked in from the intake port, compressed, and discharged from the exhaust port. In a vacuum pump, the pump stage has at least a centrifugal compression pump stage, and the centrifugal compression pump stage includes an open impeller mounted on a rotating shaft and having a plurality of retreating vanes, and a front surface of the impeller. A vacuum pump comprising fixed discs arranged to face each other. 2. A vacuum pump having an intake port, an exhaust port, and a pump stage that performs a pumping action, and in a steady state, a dilute gas in a molecular flow pressure region is sucked in from the intake port, compressed, and discharged from the exhaust port. , the pump stage comprises at least a centrifugal compression pump stage, the centrifugal compression pump stage comprising:
an open-type impeller attached to a rotating shaft and having a plurality of retreating blades; a fixed disk disposed to face the front surface of the impeller; and a fixed disk disposed to face the back surface of the open-type impeller. 1. A vacuum pump comprising: a fixed disk; and blades provided on the back side of the impeller of the fixed disk facing inward in the rotational direction of the impeller. 3. The vacuum pump according to claim 2, characterized in that a plurality of blades are attached to a fixed disc facing the back side of the open type impeller. 4. A vacuum pump according to claim 2 or 3, characterized in that the centrifugal compression pump stages are provided in multiple stages.