JPH064391U - Turbo molecular pump - Google Patents

Abstract

(57) [Summary] [Objective] To provide a turbo molecular pump suitable for use in higher speed rotation and in lower vacuum. [Configuration] Angular contact ball bearings are used for the rolling bearings. By mounting this angular ball bearing so that the axial load in the direction of the intake port due to the lift generated on the rotor blade becomes the load in the positive direction of the angular ball bearing, it is possible to withstand a large axial load in the direction of the intake port. . The permanent magnet of the magnetic bearing always generates an axial load in the direction of the intake port, and by applying this load as a preload to the angular contact ball bearing, the load in the direction opposite to the intake port can be easily applied even if there is shaft vibration or disturbance. Try not to join.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a turbo molecular pump and a molecular drag pump.

[0002]

[Prior art]

 A turbo molecular pump that rotates a rotor consisting of a rotor and a shaft at high speed and exhausts it in an axial flow is one that uses a combination of a rolling bearing and a magnetic bearing to support the rotor.

FIG. 5 is a sectional view of a conventional turbo-molecular pump using this combination. This pump includes a container composed of a casing C and bases B1 and B2, a rotor R provided with rotor blades RW, a stator blade SW provided on the inner circumference of the casing C, and a shaft S for rotating the rotor R. It is mainly composed of a motor M that rotationally drives the shaft S.

On the lower end side of the shaft S, a deep groove ball bearing 10 is used as a rolling bearing for supporting the shaft S. A permanent magnet 2 is attached to the rotor R connected to the upper side of the shaft S, and the permanent magnet 2 and the permanent magnet 1 provided on the side surface of the holder 5 facing the permanent magnet 2 magnetically support the magnetic bearing. Make up three.

The magnetic bearing 3 is adjusted so as not to generate a load in the axial direction. That is, by vertically moving the holder 5 connected to the support member 4 with the adjusting screw 6, the relative position between the permanent magnet 1 and the permanent magnet 2 is finely adjusted so that the axial load is not generated. There is.

[0006]

[Problems to be solved by the device]

 In the conventional turbo molecular pump, a deep groove ball bearing is used as the rolling bearing. This is because, in addition to radial load, the deep groove ball bearing can load both axial load in the inlet direction and anti-intake port direction if the value is small, so in either direction due to shaft vibration or disturbance. This is because even if an axial load is generated, it is possible to withstand such a small axial load. That is, in the state where the axial load is eliminated by adjusting the position of the permanent magnet of the magnetic bearing as described above, the value is small even if the axial load is generated by the load, so even with deep groove ball bearings it is sufficient. It was able to absorb the load.

However, recently, turbo molecular pumps have been required to have a higher rotation speed in order to improve the exhaust performance. It is also required to extend the usable area of the turbo molecular pump to a lower vacuum area. In turbo molecular pumps used in such applications, more lift is generated on the rotor blades, resulting in a larger axial load in the axial direction in the intake direction. In this case, the conventional deep-groove ball bearings could not withstand a large axial load and could damage the bearings.

An object of the present invention is to solve the above problems and to provide a turbo-molecular pump that can withstand use at higher speeds and use at lower vacuum.

[0009]

[Means for Solving the Problems]

 The present invention, which has been made to solve the above-mentioned problems, provides a turbo molecular pump in which one end of a rotor consisting of a rotor and a shaft is supported by a magnetic bearing, and the other end is supported by a rolling bearing. It is provided to support the applied radial load and adjust the position of the permanent magnet to generate an axial load in the direction of the intake port.The rolling bearing supports the radial load of the rotating body and is generated by the magnetic bearing. The angular ball bearing that can support the axial load in the direction of the intake port and the axial load due to the load is used, and a stopper is provided to restrict the displacement of the rotating body in the direction opposite to the intake port. To collect.

[0010]

[Action]

 In the turbo molecular pump of the present invention, an angular contact ball bearing is used as the rolling bearing instead of the conventional deep groove ball bearing. Angular contact ball bearings are directional with respect to axial loads, and can load a larger amount of load in the positive direction than deep groove ball bearings, but cannot load in the opposite direction.

Therefore, by mounting the angular ball bearing so that the axial load in the intake port direction becomes the positive load of the angular ball bearing, it is possible to withstand a large axial load in the intake port direction. become. In addition, the permanent magnet of the magnetic bearing constantly generates an axial load in the direction of the intake port, and by applying this load as a preload to the angular ball bearing, it is easy to counter-intake air even if there is shaft vibration or disturbance. It is possible to prevent the load from being applied in the mouth direction.

Further, by providing a stopper for preventing the rotating body from displacing on the side opposite to the intake port for a certain distance or more, even if the rotating body is about to be displaced toward the side opposite to the intake port due to large vibration or disturbance, However, since it comes into contact with this stopper, it is not displaced further to the side opposite to the intake port, and the generation of a large axial load in the direction opposite to the intake port can be eliminated.

[0013]

【Example】

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

FIG. 1 is a sectional view of a turbo molecular pump showing an embodiment according to the present invention. This pump comprises a container composed of a casing C and bases B1 and B2, a rotor R provided with rotor blades RW, a stator blade SW provided on the inner circumference of the casing C, and a shaft S for rotating the rotor R. , And a motor M that rotationally drives the shaft S.

On the lower end side of the shaft S, an angular ball bearing 7 is used as a rolling bearing for supporting the shaft S. The upper surface of the base B2 faces below the shaft S at a narrow interval, and a stopper 8 is inserted on this surface so as not to come into contact with the lower surface of the shaft 7 in the normal state. A permanent magnet 2 is attached to a rotor R connected to the upper side of the shaft S, and a magnetic bearing 3 is constituted by the permanent magnet 1 provided on the side surface of the holder 5 so as to face the permanent magnet 2. There is.

Next, the operation of this configuration will be described.

The magnetic bearing 3 exerts a repulsive force between the permanent magnets so as to be stable in the radial direction, and is adjusted so that an axial load is always generated in the intake port direction. That is, the relative position between the permanent magnet 1 and the permanent magnet 2 is finely adjusted by moving the holder 5 connected to the support member 4 up and down with the adjusting screw 6 so that the load in the intake port direction is generated. For example, as shown in FIGS. 2 and 3, by displacing the permanent magnet 2 on the rotor R side to the intake port side (upper side) by a slight distance Z with respect to the permanent magnet 1 on the holder 5 side, Axial load in the inlet direction (positive) depending on Z can be generated.

The angular ball bearing 7 on the lower end side of the shaft S receives, as a preload, the axial load in the intake port direction (positive) generated by the magnetic bearing 3 in addition to the normal radial load. Due to this preload, even if a small axial load in the direction opposite to the intake port (negative) due to shaft vibration or disturbance is applied, a positive axial load can be held as the total load, and normal operation can be maintained as a bearing. Is.

Further, below the shaft S, the upper surface of the base B2 faces a narrow space, and a stopper 8 is inserted on this surface so as not to come into contact with the lower surface of the shaft 7 under normal conditions. . Even if a large vibration or disturbance is applied, the shaft S only contacts the stopper 8 and cannot be displaced further in the direction opposite to the intake port. Therefore, as shown in Fig. 2, by always setting the stopper position within the range where the positive axial load is received, it is possible to completely eliminate the negative axial load from being applied to the angular contact ball bearing.

Further, as a matter of course, the displacement of the shaft S in the direction of the intake port is regulated by the angular ball bearing itself, so that the rotary body including the shaft S and the rotor R is eventually controlled by the angular ball bearing itself. It is displaced between the regulating position and the regulating position of the stopper 8.

In order to prevent the rotor 8 from seizing even if the rotor R comes into contact with the stopper 8 during rotation, a lubricant such as grease or MoS 2 is used, or a material such as PTFE is used for the stopper 8.

A touchdown bearing 9 is provided on the upper side of the rotating body, and is normally kept out of contact with the shaft S so that when the shaft S shakes laterally due to a large vibration or disturbance, this shake can be regulated. If this is done, it will be safe against fluctuations in the radial direction.

FIG. 4 shows another embodiment of the present invention using the touchdown bearing 9. In this embodiment, the touch down bearing 9 is used as a stopper for the displacement of the rotating body in the direction opposite to the intake port. That is, the projection 11 is provided on the shaft portion near the upper portion of the touchdown bearing 9, and the projection S contacts the touchdown bearing 9 so that the shaft S cannot be displaced further in the direction opposite to the intake port. Although the present invention has been described with reference to a turbo molecular pump, the present invention can be similarly applied to a molecular drag pump such as a screw pump.

[0024]

[Effect of device]

 As described in detail above, according to the present invention, by using the angular ball bearing and providing the stopper, it becomes possible to bear a larger axial load than before, and the rotation is performed in order to improve the exhaust performance. It can now be used without problems even in an environment with a large axial load, such as when increasing the speed or when using in a lower vacuum range. Also, when the air was mistakenly introduced from the intake port or the exhaust port during operation of the turbo molecular pump, lift force acted and a large axial load was applied, causing a malfunction. We were able to create a structure that is unlikely to occur.

[Brief description of drawings]

FIG. 1 is a sectional view of a turbo molecular pump according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a displacement of a magnet of a magnetic bearing and an axial load.

FIG. 3 is a diagram showing a position of a magnet of a magnetic bearing when an axial load is generated.

FIG. 4 is a sectional view of a turbo molecular pump according to another embodiment of the present invention.

FIG. 5 is a sectional view of a conventional turbo molecular pump.

[Explanation of symbols]

 C: Casing R: Rotor B1, B2: Base S: Shaft 1: Permanent magnet (holder side) 2: Permanent magnet (rotor side) 3: Magnetic bearing 5: Holder 7: Angular ball bearing 8: Stopper

Claims (1)

[Scope of utility model registration request] 1. A turbo molecular pump in which one end of a rotor consisting of a rotor and a shaft is supported by a magnetic bearing and the other end is supported by a rolling bearing, wherein an angular contact ball bearing is used as the rolling bearing, and at the magnetic bearing side. By installing the mutual permanent magnets at different positions and generating an axial force in the direction of the intake port in the magnetic bearing part itself, while constantly applying an axial load in the direction of the intake port as a preload to the angular contact ball bearing, A turbo-molecular pump having a stopper for restricting displacement of the rotating body in the direction opposite to the intake port.