JP3045418B2 - Turbo vacuum pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a turbo vacuum pump having an exhaust port at atmospheric pressure, and more particularly to a turbo vacuum pump suitable for producing a compact and clean vacuum.

[0002]

2. Description of the Related Art As conventional turbo vacuum pumps having an exhaust port at atmospheric pressure, those described in, for example, JP-A-62-258186 and JP-A-2-91499 are known.

A turbo vacuum pump described in Japanese Patent Application Laid-Open No. 62-258186 is provided with a centrifugal compression pump stage and a circumferential flow compression pump stage in a housing having an intake port and an exhaust port. The centrifugal compression pump stage is configured by alternately combining a stator fixed to an inner wall of a housing and an impeller fixedly supported on a rotating shaft. The circumferential compression pump stage is configured by alternately combining a fixed plate fixed to an inner wall of a housing and an impeller fixedly supported on a rotating shaft.

As shown in FIG. 6, a turbo vacuum pump described in Japanese Patent Application Laid-Open No. 2-91499 has a circumferential flow compression pump stage comprising a circumferential flow impeller 30, a stator 31, and a lid 32. , A rotating shaft 35 rotatably supported by a housing 33 via a bearing 34, and the rotating shaft 3
And a driving unit including the high frequency motor 36 on the drive unit 5. The circumferential flow impeller 30 is formed in a cylindrical step shape in one direction, and a plurality of blades 37 are formed at each convex step angle of the cylindrical step shape.
Is installed. The stator 31 is opposed to the circumferential flow impeller 30 with a small gap kept therebetween, and a ventilation passage 38 is formed at an inner stepped concave corner.

[0005]

Problems to be Solved by the Invention
The turbo vacuum pump described in Japanese Patent No. 258186 discloses a centrifugal compression pump stage having a diffuser fixing plate and an impeller,
Also, since the fixing plate and the impeller of the circumferential flow compression pump stage are alternately combined, the fixed side must have a half-split structure, which makes it difficult to maintain the processing accuracy and increases the number of parts. In addition, the assemblability is not good.

Further, the turbo vacuum pump described in Japanese Patent Application Laid-Open No. 2-91499 has a stable pump because the stator can be integrally formed, so that the assemblability is good and the processing accuracy can be improved. Performance can be obtained. However, the ratio of the increment of the outer diameter of the impeller of each stage formed in a cylindrical step shape is not specified, and in order to obtain a desired performance, if the ratio of the increment is set to be large and constant, the impeller of each stage is Since the outer diameter of the cylinder increases, the compression function of each stage increases, and the number of stages can be reduced, but the disk friction loss of each stage increases, and as a result, the shaft power of the pump increases,
Motor capacity must be increased. Also, if the increment ratio is reduced, the outer diameter of the impeller can be reduced, so that the shaft power of the pump can be reduced and the motor capacity can be reduced, but the number of stages must be increased to obtain the desired performance. In addition, the dimension in the axial direction becomes long, and the compactness is not good.

A main object of the present invention is to provide a turbo vacuum pump which has good manufacturability and assemblability, can obtain desired performance with a small number of stages, and can be made more compact.

Another object of the present invention is to increase the ultimate pressure of a pump to a high vacuum without increasing the axial power of the pump even in a pressure range of an intermediate flow or a molecular flow, which is reduced in a circumferential flow compression pump stage. And a turbo vacuum pump capable of increasing the pumping speed.

[0009]

The main object is to provide a housing, a multi-stage circumferential impeller, and a stator, wherein the housing supports a rotating shaft and a motor of the circumferential impeller, The circumferential flow impeller is provided with a convex step angle having a cylindrical step shape, and a plurality of blades fixed on the circumference of the convex angle, and the stator has an intake port and an exhaust port, and an inner surface stepped. A concave angle and a ventilation path for compressed air formed at the concave angle are provided, and in the turbo vacuum pump in which a circumferential flow compression pump stage is formed by the circumferential flow impeller and the stator, from the exhaust port side, This is achieved by increasing the ratio of the increment of the outer diameter of the impeller to the intake port side, which is small on the exhaust port side and large on the intake port side.

Another object is to provide at least one of a thread groove compression pump stage, a centrifugal compression pump stage and an axial flow compression pump stage on the low pressure side of the circumferential flow compression pump stage. Is achieved.

[0011]

According to the present invention, since the circumferential impeller, which is the rotor, is formed in the shape of a cylindrical step, there is no need to form the stator in a half-split structure. In addition, since the circumferential impeller can be inserted into and removed from the stator in the axial direction, the assemblability is good.

Further, in the present invention, the ratio of the increase in the outer diameter of the impeller on the exhaust side with a high pressure is reduced, and the ratio of the increase in the outer diameter of the impeller on the intake side with a low pressure is increased. Since the outer diameter of the impeller is reduced, the disc friction loss is reduced and the shaft power of the pump is reduced. If the ratio of the increment of the impeller outer diameter remains small, the compression ratio of each stage is small and the desired performance cannot be obtained because the outer diameter of the impeller is small. When the vehicle is compressed to a pressure of several tens Torr to several hundred Torr, the increase in the outer diameter of the impeller is increased. it can. Even if the impeller outer diameter becomes large, the pressure range is several hundred Torr or less, and the shaft power of the pump does not increase much. Therefore, the desired performance can be obtained with a small number of stages, and the shaft power of the pump can be reduced. Therefore, a motor having a small motor capacity can be used, and the pump can be downsized.

In the present invention, a thread groove compression pump stage, a centrifugal compression pump stage,
At least one of the axial-flow compression pump stages is installed, and in the pressure range of the intermediate flow and the molecular flow, which decreases in the circumferential-flow compression pump stage, the screw groove compression pump stage, the centrifugal compression pump stage, and the axial flow By the action of the compression pump stage, it is possible to increase the ultimate pressure of the pump to a high vacuum and increase the exhaust speed without increasing the axial power of the pump.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a longitudinal sectional view showing an embodiment of the turbo vacuum pump of the present invention, FIG. 2 is an enlarged longitudinal sectional view showing the vicinity of a blade of the embodiment shown in FIG. 1, and FIG. FIG.

The turbo vacuum pump of the embodiment shown in FIG. 1 has a pump mechanism comprising a circumferential impeller 30, a stator 31 and a lid 32, and a rotating shaft rotatably supported by a bearing 34 in a housing 33. 35 and a drive unit including a high-frequency motor 36 on the rotating shaft 35. The lid 32 is provided with an intake port 32A, and the stator 31
Is provided with an exhaust port 32B.

The circumferential flow impeller 30 is formed in the shape of a cylindrical step in one direction. The ratio of the increase in the outer diameter of the impeller on the exhaust side is small, and the ratio of the increase in the outer diameter of the intake side is large. ing. A plurality of blades 37 are arranged and fixed to each cylindrical stepped convex corner. The stator 31
As shown in FIG. 2 and FIG. 3, the circumferential direction impeller 30 is arranged so as to face the circumferential flow impeller 30 with a small gap, and surrounds the blade 37 of the circumferential flow impeller 30 in the circumferential direction 1 of the ventilation passage 38. Partition portions 39 are provided at various places. A suction port 38A is provided at the front of the partition portion 39 in the rotation direction of the circumferential flow impeller 30, and a discharge port 38B is provided at the rear in the rotation direction. The positions of the inlet 38A and the outlet 38B of each stage are shifted for each stage, and the inlet 38A is connected in series with the outlet 38B of the preceding stage.

As described above, since the circumferential impeller 30 and the stator 31 are opposed to each other on the circumference of the cylindrical stepped shape in one direction, the circumferential impeller 30 and the stator 31 are opposed to each other.
Can be formed by integral molding.

A plurality of blades 3 are provided at the cylindrical stepped convex corners.
7 and the circumferential impeller 3
A circumferential compression pump stage is formed by the stator 31 having the air passage 38 having a stepped inner surface and opposed to each other while maintaining a small gap between the inner surface and the inner space.

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

When the circumferential flow impeller 30 is driven at a high speed by the high frequency motor 36, the gas sucked in from the intake port 32A enters the ventilation passage 38 through the suction port 38A, and the blade 37 of the circumferential flow impeller 30 is moved. When the gas flows into the air, the gas attains a circumferential velocity by the blades 37 rotating at a high speed, and is discharged radially from between the blades 37 by centrifugal force. Draw and Feather 3 again
Enter between 7. The gas flowing in from the suction port 38A repeats the above-described operation several times while passing through the ventilation path 38 from the suction port 38A to the discharge port 38B, flows in a spiral screw shape in the ventilation path 38, and flows out from the circumferential flow impeller 30. Sufficient energy can be obtained, and the air is exhausted to the atmosphere from the exhaust port 32B directly connected to the final-stage exhaust port 38B.

FIG. 4A shows a case where the increment of the impeller outer diameter is small on the high pressure side and large on the low pressure side (embodiment of the present invention).
4B shows the predicted value of the shaft power, and FIG. 4B shows the predicted value of the shaft power when the increment of the outer diameter of the impeller is increased.
(C) shows a predicted value of the shaft power when the increment of the impeller outer diameter is reduced. The horizontal axis represents the number of stages, the vertical axis represents the impeller radius and the shaft power of each stage, the solid line 42 indicates the radius of the impeller, and the broken line 43 indicates the predicted value of the shaft power.
However, since the shaft power is predicted so that the outer diameter of the impeller on the discharge side and the suction pressure are the same, the number of stages is different.

In this embodiment of the present invention, as shown in FIG. 4A, the ratio of increment of the outer diameter of the impeller on the exhaust side with a high pressure is reduced, and the outer diameter of the impeller on the intake side with a low pressure is reduced. Since the ratio of the increment is increased, the outer diameter of the impeller is reduced on the high pressure side, so that the disc friction loss is small and the shaft power of the pump can be reduced. Since the outer diameter is small on the high pressure side, the compression ratio of each stage is small, but when the pressure is reduced from several tens Torr to several hundred Torr by impellers of several stages (four stages in the figure) with small increment ratios, Since the increment of the impeller outer diameter is increased, the compression ratio can be increased and the desired performance can be obtained by increasing the impeller outer diameter. Even if the impeller outer diameter becomes large, the pressure range is several hundred Torr or less, and the shaft power of the pump does not increase much. Therefore, desired performance can be obtained with a small number of stages, and the shaft power of the pump can be reduced, so that a motor having a small motor capacity can be used. In FIG. 4 (b), the number of stages can be reduced because the ratio of the increment of the outer diameter of the impeller is increased, but the disc friction loss is large and the shaft power of the pump is large. In FIG. 4C, the number of stages is large because the number of stages is large because the ratio of increments of the outer diameter of the impeller is small.

FIG. 5 is a longitudinal sectional view showing another embodiment of the turbo vacuum pump of the present invention.

In the embodiment shown in FIG. 5, a thread groove compression pump stage 41 is provided in addition to a circumferential flow compression pump stage 40 comprising a circumferential impeller 30 and a stator 31. In the embodiment shown in FIG. 1, as described above,
A high compression ratio can be obtained by the action of the circumferential pump stage imparting velocity energy to the gas and converting it into pressure. Therefore, good performance can be exhibited in the viscous flow pressure range, but the effect is reduced in the intermediate flow or molecular flow pressure range. Therefore, the ultimate pressure of the vacuum pump is limited to a low vacuum region.

Therefore, in the embodiment shown in FIG. 5, in order to obtain a pressure reaching the molecular flow pressure range and further increase the pumping speed, the intermediate flow and the molecular flow are applied to the low pressure side of the circumferential flow compression pump stage 40. An effectively acting thread groove compression pump stage 41 is provided. In the intermediate flow region and the molecular flow region, there is almost no disc friction loss, and the shaft power of the pump does not increase. Therefore, in the embodiment shown in FIG. 5, the ultimate pressure of the pump is made high vacuum without increasing the axial power of the pump, and the pumping speed is reduced by the thread groove compression pump stage 41 and the circumferential flow compression pump stage 40. Can be bigger.

The other structure and operation of the embodiment shown in FIG. 5 are the same as those of the embodiment shown in FIG.

In the embodiment shown in FIG. 5, the screw groove compression pump stage 41 is used in the intermediate flow and molecular flow regions. However, the present invention is not limited to this. For example, a centrifugal compression pump stage and an axial flow compression pump stage are used. May be used alone or in combination.

[0029]

According to the first aspect of the present invention described above, since the shape of the circumferential flow impeller, which is the rotor, is formed in a cylindrical stepped shape, the stator is formed in a half-split structure. This eliminates the need for an integral structure, has the effect of improving manufacturability, and also has the effect of improving the ease of assembly because the circumferential flow impeller can be inserted into and removed from the stator in the axial direction. Further, according to the first aspect of the present invention,
By increasing the ratio of the increase in the outer diameter of the impeller from the exhaust port side to the intake port side at the exhaust port side and increasing it at the intake port side, the desired performance can be obtained with a small number of stages. Can reduce the outer diameter dimension of the impeller, thereby reducing the disc friction loss and using a motor having a small motor capacity. As a result, the pump can be downsized.

According to the second aspect of the present invention, at least one of a thread groove compression pump stage, a centrifugal compression pump stage, and an axial flow compression pump stage is provided on the low pressure side of the circumferential compression pump stage. In the pressure range of intermediate flow or molecular flow, which decreases in the circumferential flow compression pump stage, the shaft groove is operated by the action of the thread groove compression pump stage, centrifugal compression pump stage and axial flow compression pump stage. This has the effect of increasing the power.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing one embodiment of a turbo vacuum pump of the present invention.

FIG. 2 is an enlarged vertical sectional view near a blade in the embodiment shown in FIG.

FIG. 3 is an enlarged plan view as viewed from an arrow A in FIG. 2;

FIGS. 4A, 4B, and 4C are predicted values of shaft power of a turbo vacuum pump, respectively.

FIG. 5 is a longitudinal sectional view showing another embodiment of the turbo vacuum pump of the present invention.

FIG. 6 is a longitudinal sectional view showing a conventional turbo vacuum pump.

[Explanation of symbols]

Reference numeral 30: circumferential flow impeller, 31: stator, 32: lid, 32
A: intake port, 32B: exhaust port, 33: housing, 34
... bearing, 35 ... rotating shaft, 36 ... high frequency motor, 37 ... blades, 38 ... ventilation path, 38A ... suction port, 38B ... discharge port,
39: partition part, 40: circumferential compression pump stage, 41: screw groove compression pump stage, 42: impeller radius dimension, 43: predicted value of pump shaft power.

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Masahiro Mase 603, Kandamachi, Tsuchiura-shi, Ibaraki Hitachi, Ltd. Tsuchiura Plant (58) Fields investigated (Int. Cl. ⁷ , DB name) F04D 19/04 F04D 23/00 F04D 25/16

Claims (2)

(57) [Claims] 1. A housing, a multi-stage circumferential impeller,
A stator, and the housing supports a rotating shaft and a motor of a circumferential flow impeller, and the circumferential flow impeller has a cylindrical stepped convex portion angle, and is fixed on the circumference of the convex portion angle. A plurality of blades, and the stator is provided with an intake port and an exhaust port, an inner stepped concave angle, and a ventilation path for compressed air formed at the concave angle. In a turbo vacuum pump in which a circumferential flow compression pump stage is formed by a car and a stator, a ratio of an increment of an outer diameter of an impeller between the exhaust port side and the intake port side is small on an exhaust port side,
A turbo vacuum pump characterized in that it is enlarged on the intake side. 2. The method according to claim 1, wherein at least one of a thread groove compression pump stage, a centrifugal compression pump stage and an axial flow compression pump stage is provided on the low pressure side of the circumferential flow compression pump stage. The described turbo vacuum pump.