JPH04231699A - High speed rotary type vacuum pump - Google Patents

Abstract

PURPOSE:To reduce the shaft vibration and provide an excellent maintainability, by supporting the rotor on both sides thereof from an inside shaft center portion with a fixed shaft-supporting portion projectingly installed on a casing. CONSTITUTION:A fixed shaft-supporting portion 3 projected from a casing 1 is inserted into an inside shaft center portion 2a of a bottomed cylindrical rotor 2. Dynamic pressure gas bearings 4, 5 for supporting the rotor 2 at near both ends thereof in a floating manner without a contact condition. Since, with this structure, the rotor 2 is supported on both sides thereof by the dynamic gas bearings without contact resistance, shaft vibration is lessened whereby the rotation is stabilized. Further, oil change or the like becomes unnecessary, the maintainability becomes excellent, and the pump becomes compact in size.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-speed rotating vacuum pump used as a dry pump.

0002

2. Description of the Related Art FIG. 3 shows an example of a conventional high-speed rotation type vacuum pump. In this vacuum pump, a rotor 103 is fixed to an axial end of a shaft 104 between a casing 101 and a pump mechanism 102.
The pump mechanism 102 compresses gas sucked in through an intake port 105 that is disposed inside the casing 101 and opens above the casing 101, and exhausts the gas from an exhaust port 106 that opens to the side of the casing 101. It looks like this. The shaft 104 is supported on the casing 101 side below the rotor 103 via a pair of upper and lower rolling bearings 107 and 108.
8 is an oil tank 1 provided at the lower end of the casing 101.
From 2009 onwards, lubricating oil has been forcibly supplied.

FIG. 4 shows another example of a conventional high-speed rotation type vacuum pump. The exhaust system of this vacuum pump is shown in Figure 3.
A rotor 203 is disposed within the casing 201 with a rotor 203 fixed to the end of a shaft 204 to form a pump mechanism 202 between the casing 201 and the casing 201. Inlet port 20 opening above casing 201
The gas sucked in from the casing 201 is compressed by the pump mechanism 202 and can be exhausted from an exhaust port 206 opened on the side of the casing 201. The bearings of this pump are different from those shown in FIG. 3, and the shaft 204 is supported on the casing 201 side by a pair of upper and lower radial dynamic pressure gas bearings 207, 208 and a thrust dynamic pressure gas bearing 209.

0004

[Problems to be Solved by the Invention] However, in all of these rotor support structures, the rotor protrudes in a cantilevered manner to the outside of both bearings, so it is difficult to balance the rotor support state. The disadvantage is that it has poor performance and tends to cause vibration and noise. Also, since the rotor is fixed to the end of the shaft,
The installation space for the bearing and the installation space for the rotor must be secured separately in the axial direction, which results in the inconvenience that the entire structure becomes long in the axial direction, making it difficult to design compactly. . Furthermore, since the exhaust port opens at a position perpendicular to the rotor's axial flow direction and the flow path is bent within the casing, the exhaust resistance increases accordingly, opening the exhaust port to the atmosphere. It also becomes difficult to configure serial exhaust by connecting vacuum pumps in series. Furthermore, since the bearing shown in Figure 1 uses oil bearings, frequent replacement work is likely to occur as the viscosity of the oil decreases or the bearings deteriorate, and there is a risk of oil contamination with the process gas. On the other hand,
The one in Figure 2 is oil-free because it uses a hydrodynamic gas bearing.
However, in order for this bearing to function effectively, it is necessary to provide a wide gap for gas introduction, which is formed by a spiral groove, etc., which further increases the length in the axial direction. There is a strong tendency to

The present invention aims to effectively solve these problems.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the present invention takes the following measures.

That is, the high-speed rotation type vacuum pump of the present invention has a fixed shaft support protruding from the casing at the inner shaft center of the cylindrical rotor to form a pump mechanism between the rotor and the casing. A non-contact bearing capable of floating and supporting the vicinity of both ends of the rotor is disposed between the fixed shaft support and the rotor, and a non-contact bearing is disposed between the fixed shaft support and the rotor, and a non-contact bearing is disposed between the fixed shaft support and the rotor. - It is characterized by having an intake port and an exhaust port opened in the thing.

[0008]

[Operation] By supporting the rotor from the inner shaft center on both sides using a fixed shaft support, shaft vibration during rotation can be suppressed more effectively than when it is supported in a cantilevered manner. As a result, it becomes possible to reliably reduce shaft vibration and improve the stability of rotor rotation. Furthermore, the space for arranging the rotor and the space for arranging the bearings can be overlapped at the same axial position, eliminating the need to secure them separately along the axial direction. It is possible to shorten the length in the axial direction. Furthermore, since the inlet and exhaust ports are provided in the axial flow direction of the rotor, the exhaust resistance is reduced, and it is also effective to connect vacuum pumps in series to construct a serial exhaust system.

[0009]

Embodiment An embodiment of the present invention will be described below with reference to FIG.

In this embodiment, a fixed shaft support projecting from the casing 1 is provided at the inner shaft center 2a of the bottomed cylindrical rotor 2 to form a pump mechanism 6 between the rotor 2 and the casing 1. 3 is inserted between the fixed shaft support 3 and the rotor 2.
a hydrodynamic gas bearing 4 that floats and supports the vicinity of both ends of the
5 are installed.

To be more specific, the rotor 2 has an inner shaft center portion 2a whose diameter is set slightly larger than the fixed shaft support 3, and a turbine rotor blade 2b on the upper part of the outer periphery. However, special rotor blades 2c are provided protruding from the lower part. On the other hand,
The thing 1 has an outer cylinder part 1a and a fixed shaft support 3 connected to a base part 1d.
The upper end 3a of the fixed shaft support 3 is extended to near the upper edge opening of the outer cylinder part 1a, and the upper end part 3a of the fixed shaft support 3 is connected to the upper end of the inner circumference of the outer cylinder part 1. -Bin stator blade 1
b, and special stator blades 1c are provided protruding from the lower inner periphery. The inner shaft center portion 2a of the rotor 2 is attached to this fixed shaft support 3.
When inserted deeply, the turbine section 6a consisting of blades 1b and 2b and the compressor section 6b consisting of blades 1c and 2c.
A pump mechanism 6 is formed in which the pump and the pump are connected in series.

Further, in order to configure the hydrodynamic gas bearings 4 and 5, a spiral groove (not shown) is provided on the outer periphery of the fixed shaft support 3. A midway portion thereof is communicated with the atmosphere through a hollow portion 3b provided in the fixed shaft support 3. That is, as the rotor 2 rotates, the suction effect generated in the gap between the spiral groove and the rotor 2 causes gas in the atmosphere to be drawn into the gap in a high-speed airflow state, thereby causing the rotor 2 to A dynamic pressure is generated between the rotor 2 and the fixed shaft support 3, and the rotor 2 can be floated and supported in the radial direction by the dynamic pressure. Further, spiral grooves (not shown) are provided on the upper and lower surfaces of the upper end enlarged portion 3a of the fixed shaft support 3 to constitute thrust dynamic pressure gas bearings 13 and 14. The fixed shaft support portion 3 is also communicated with the atmosphere through the hollow portion 3b of the fixed shaft support 3. That is, as the rotor 2 rotates, the suction effect generated in the gap between the spiral groove and the rotor 2 causes gas in the atmosphere to be drawn into the gap in a high-speed airflow state, thereby causing the rotor 2 to Dynamic pressure is generated between the rotor 2 and the fixed shaft support 3, and the rotor 2 can be floated and supported in the thrust direction by the dynamic pressure.

Furthermore, the upper edge opening of the casing 1 is set as an intake port 7, and a base portion that abuts from the intake port 7 along the axial flow direction (arrow direction) of the pump mechanism 6. An exhaust port 8 is opened at 1d.

In this vacuum pump, silicon steel plates 9c, each having a permanent magnet 9a and a coil 9b wound thereon, are buried at opposing positions on the inner periphery of the rotor 2 and the outer periphery of the fixed shaft support 3, respectively. , these are the DC brushless motor 9
It consists of Furthermore, the casing 1 is integrally equipped with a control circuit 9d connected to the motor 9 and a water cooling circuit 10 for absorbing heat generated by the compressor section 6b in the pump mechanism 6 and cooling the control circuit 9d at the same time. It is provided. 11
is a heat dissipation fin. In addition, 12 is a screw pump that also serves as a non-contact seal.
When the tank 9 does not naturally radiate heat, the gas flow generated in the screw pump 12 air-cools them.

With the above configuration, the rotor 2 of the illustrated pump has dynamic pressure gas bearings 4, 5, 1 without contact resistance.
3 and 14, high-speed rotation can be easily achieved. For example, with the exhaust port 8 side open to the atmosphere, the intake port 7
It becomes possible to easily exhaust the side pressure to about 10-3 Torr. Of course, since this pump is a dry pump, it has a long life and can be used without fear of oil contamination. In addition, an intake port 7 and an exhaust port 8 are provided in the axial flow direction of the rotor 2, and this structure also contributes to improving compression performance from the viewpoint of not bending the exhaust flow path within the casing. This allows the exhaust port 8 to be easily opened to the atmosphere. Moreover, with such a configuration, the rotor 2 rotates while being supported from the inner shaft center 2a side between the bearings 4 and 5 disposed near both ends. Therefore, compared to the conventional cantilever support state, it is possible to effectively suppress shaft vibration during rotation of the rotor 2, and as a result, shaft vibration is reduced and the stability of rotor rotation is improved. It is possible to reliably improve the performance and achieve low-vibration and low-noise operation. Also,
Since the bearings 4 and 5 are installed inside the rotor 2, there is no need to separate the bearings 4 and 5 from the rotor 2 in the axial direction, and there is no need to separate the bearings 4 and 5 from the rotor 2. It has also been made more compact. In terms of compactness, the control circuit 9d
It is also effective to integrate the water cooling circuit 10 into the casing 1 and share the water cooling circuit 10 with the pump mechanism 6 and the control circuit 9d. Furthermore, by using the intake port 7 as a flange, other vacuum pumps with the same configuration can be connected in series.
This is an effective structure for easily configuring a serial exhaust system. Furthermore, the use of the DC brushless motor 9 as the motor also contributes to the miniaturization of the motor section and, by extension, the overall size of the pump.

Note that the present invention is not limited to the above embodiments. For example, in the above embodiment, the lower end opening of the fixed shaft support 3 is opened to the atmosphere to introduce air into the bearings 3, 4, 13, and 14, but this part is not connected to the exhaust port 8.
Depending on the installation location and the content of the exhaust air, there is a possibility that dirty air will drift around. In such a case, as shown in FIG. 2, a transverse groove 1e may be provided in the casing 1 to introduce the atmosphere from the side of the casing 1. In this case, it is more effective to attach a filter 14 or the like to the open end of the lateral groove 1e. Of course, a separate pressure source may be provided to supply the bearing gas without using the atmosphere. Further, the bearing may be a static pressure gas bearing or a magnetic bearing as long as it is non-contact, and the motor control circuit may be provided independently from the casing. Furthermore, the motor is not limited to a DC brushless motor, but may be an induction motor or the like. In addition, various modifications can be made without departing from the spirit of the present invention.

[0017]

[Effects of the Invention] Since the high-speed rotating vacuum pump of the present invention employs non-contact bearings, there is no need for frequent oil changes or bearing replacements, resulting in long life and excellent maintenance effects. In addition, by adopting a so-called outer rotor structure, the parts near both ends of the rotor are supported on both sides by bearings, so rotation is stable and low-vibration and low-noise operation is possible even up to high speed rotation. becomes possible. Furthermore, since the rotor and the bearing can be provided overlappingly at the same axial position, the effect of making the rotor compact in the axial direction can be obtained. Furthermore, since the intake port and exhaust port are provided along the axial flow direction of the pump mechanism, exhaust resistance is reduced and the exhaust port can be easily opened to the atmosphere when used as a back pump. If used as a flange, other vacuum pumps having the same configuration can be serially connected to the inlet port of the vacuum pump, thereby making it possible to easily form a series exhaust line.

[Brief explanation of the drawing]

FIG. 1 is an overall vertical cross-sectional view of a vacuum pump showing one embodiment of the present invention.

FIG. 2 is a partial vertical sectional view of a vacuum pump showing another embodiment of the present invention.

FIG. 3 is an overall vertical sectional view of a vacuum pump, showing a conventional example.

FIG. 4 is a partially cutaway perspective view of a vacuum pump, showing a conventional example.

[Explanation of symbols]

1...Casing 2...Rotor 2a...Inner shaft center part 3...Fixed shaft support 4, 5...Non-contact bearing (radial) 6...Pump mechanism 7...Intake port 8...Exhaust port

Claims (1)

[Claims] Claim 1: In order to configure a pump mechanism between the rotor and the casing, a fixed shaft support protruding from the casing is inserted into the inner shaft center of the cylindrical rotor, and the fixed shaft support and the A non-contact bearing capable of floating and supporting the vicinity of both ends of the rotor is provided between the rotor and an intake port and an exhaust port are opened in the casing along the axial flow direction of the pump mechanism. A high-speed rotating vacuum pump that is characterized by: