JP2805317B2 - Turbo molecular pump - Google Patents

Description

The present invention relates to a turbo-molecular pump, and more particularly to a bearing mechanism for a rotor.

<< Prior Art >> Conventionally, a turbo molecular pump (hereinafter, referred to as a "pump") has been used as a vacuum device for an electron microscope, an analytical instrument, or the like, or as a vacuum device for a semiconductor manufacturing device. In this pump, a plurality of stator blades are arranged in the axial direction of the cylinder on an inner wall surface of a substantially cylindrical casing, and a plurality of rotor blades are mounted on an outer wall surface of a rotor disposed inside the casing. And a motor mechanism whose rotor acts as a rotor of the motor.

When the rotor is rotated by the motor mechanism and the molecular flow region is formed between the stator blades and the rotor blades, the gas on the intake side is discharged to the exhaust side, and a high vacuum is formed on the intake side. .

Incidentally, since the rotor is rotated at a so-called ultra-high speed, a magnetic bearing has recently been used instead of a conventional bearing mechanism using a ball bearing.
That is, the rotor is levitated and held by the magnetic bearing mechanism and is rotated in a non-contact manner, so that the bearing life can be greatly extended. This magnetic bearing mechanism is provided with radial and axial electromagnets for holding the radial direction and the axial direction of the rotor shaft, and a position sensor for detecting the positions in both directions is provided. The exciting current of the electromagnet is controlled to be at the position.

<< Problems to be Solved by the Invention >> However, magnetic bearings are disclosed in Japanese Patent Application Laid-Open No. 57-1932.
No. 21, JP-B-62-20407, etc., in a pump using the above-mentioned conventional magnetic bearing, the rotor is supported by being floated and held by a radial electromagnet and an axial electromagnet. It was necessary to control so-called 3-axis control, 4-axis control or 5-axis control with electromagnets. That is, control of the X and Y axes in the radial direction by the radial electromagnet and control of the Z axis in the axial direction by the axial electromagnet are required.

Therefore, there is a disadvantage that the control means is complicated and the cost is increased. In addition, since all three, four or five axes are levitated and held by electromagnets, there is a disadvantage that the bearing mechanism is complicated.

<< Means for Solving the Problems >> The present invention has been made in view of the above problems, and an object of the present invention is to provide a simple pump for controlling a magnetic bearing. The stator blades attached to the inner wall surface of the casing and the rotor blades attached to the outer wall surface of the rotor arranged inside the casing are alternately arranged in the axial direction of the rotor, and the rotor is rotated. A turbo-molecular pump having a motor mechanism for rotating the rotor and sucking the air from one direction of the rotor shaft and exhausting the air in the other direction, wherein the rotor is provided at an upper end side of the rotor shaft, A substantially conical permanent magnet that regulates the axial position and the axial position, and is provided at the lower end of the rotor shaft to regulate the axial position of the rotor shaft. That a permanent magnet, as well as adjusting the axial position of the rotor shaft, is characterized in that the pivotally supported by a substantially conical electromagnet to regulate the radial position of the rotor shaft.

<< Operation >> In the bearing mechanism of the pump according to the present invention, the rotor is floated and held by the permanent magnet, and the axial position is controlled by adjusting the exciting current of the electromagnet.

<< Embodiment >> In the turbo-molecular pump shown in FIG. 1, a plurality of stator blades 2 are arranged on the inner wall surface of a casing 1 formed in a substantially cylindrical shape in the axial direction of the cylinder, and are arranged inside the same. A plurality of rotor blades 4 are alternately arranged on the outer wall surface of the rotor 3 and the stator blades 2 in the axial direction.

A cylindrical concave portion 5 is formed in the upper center of the rotor 3, a permanent magnet 6 is provided on a side surface thereof, and a permanent magnet 7 is provided at a position facing the permanent magnet 6 at a predetermined interval. A column-shaped upper support portion 8 is fixed to a side wall of the intake port a by an arm 9.

The polarities of the two permanent magnets 6 and 7 are arranged to repel each other, so that a repulsive force acts between the rotor 3 and the upper support 8.

A ring-shaped recess 10 is provided on the lower end surface of the rotor 3 and a rotor of the motor mechanism is provided from the center thereof.
A conical protrusion 13 having a permanent magnet 12 is provided on a lower end surface of the lower end 11.

A flange 14 having an exhaust port b is provided at a lower portion of the casing 1.
Is provided, and a lower support portion 15 is provided at the center of the flange, whereby the flange 14 is sealed.

The lower support portion 15 is provided with a protruding cylinder 16 whose tip projects into the ring-shaped concave portion 10. The stator 17 of the motor mechanism is kept inside the side wall of the cylinder 16 at a predetermined distance from the rotor 11.
Are provided facing each other, and an electromagnet 18 is provided facing the conical surface of the projection 13 at a predetermined interval. A permanent magnet 19 is provided on the bottom surface of the cylinder 16 at a predetermined distance from the permanent magnet 12.
The 2,19 properties are arranged to attract each other.

In the drawings, the upper and lower support portions 8 and 15 and the rotor 3 are shown as one-piece for simplicity of the drawing, but they may be divided as necessary for assembling and production. Of course.

In the bearing mechanism having the above configuration, the upper part of the rotor 3 is held in the radial direction by the repulsive force of the permanent magnets 6 and 7, and the lower part is in the axial direction by the permanent magnets 12 and 19 (the rotor 3 moves downward in the drawing). Direction) is adjusted by the magnetic force by which the electromagnet 18 attracts the protruding portion 13 and is held floating. At this time, since the side surface of the convex portion 13 is formed on a cone, the attractive force of the electromagnet 18 is generated as a component force in the radial direction, and also acts as a radial bearing below the rotor 3.

The magnetic force of the electromagnet 18 is adjusted by detecting the axial position of the rotor 3 with a position sensor (not shown), and processing this detection signal by exciting current control means (not shown) to keep the rotor 3 floating at a predetermined target position. As electromagnet 18
This is performed by controlling the exciting current of.

In the drawings, reference numerals 20 and 21 denote dry bearings provided on the upper support portion 8 and the lower support portion 15, and are configured to be able to support the rotor 3 when the rotor 3 is touched down.

The rotor 3 which is levitated and held and supported as described above,
When a current is supplied from a driver (not shown) to the coil of the stator 17, a rotating magnetic field is generated, and the rotor 11, that is, the rotor 3 is rotated. Due to the rotation of the rotor 3, an exhaust action occurs in the molecular flow region between the stator blades 2 and the rotor blades 4, whereby air is taken in from the intake port a side and exhaust is made from the exhaust port b side.
A high vacuum is obtained on the inlet a side.

The turbo molecular pump shown in FIG. 1 has permanent magnets 6, 7, 12, and 19 disposed above and below the rotor 3, and an electromagnet 18 is disposed on the lower conical wall surface of the rotor 3 as desired. , So that the permanent magnets 6 and 7 on the upper part of the rotor 3 support the radial direction, and the permanent magnets 12 and 19 on the lower part of the rotor 3.
In addition, the electromagnet 18 supports the lower part of the rotor 3 in the radial direction and the axial direction of the rotor 3, and can easily float and hold at a predetermined target position only by adjusting the exciting current of the electromagnet 18. .

The turbo molecular pump shown in FIG. 2 differs from the turbo molecular pump shown in FIG. 1 in the upper bearing mechanism of the rotor 3.

That is, the permanent magnet 6 is provided on the side wall surface of the recess 15 of the rotor 3.
Are arranged in a substantially conical shape, and a permanent magnet 7 is arranged in the upper support portion 8 in a substantially conical shape with a predetermined distance from the permanent magnet 6. The polarity arrangement of these two permanent magnets 6 and 7 is provided in the direction of repulsion similarly to the turbo molecular pump shown in FIG. Accordingly, in the turbo-molecular pump shown in FIG. 2, the axial support at the upper part of the rotor 3 can be carried out not only in the radial direction but also in the axial direction by the component force generated by the side surfaces of the two permanent magnets 6 and 7. Therefore, in the turbo-molecular pump shown in FIG. 2, radial and axial bearings can be supported above and below the rotor 3, and a more stable bearing can be achieved.

In the turbo-molecular pump shown in FIG. 3, the radial bearings above and below the rotor 3 have the same configuration as that of the turbo-molecular pump shown in FIG. 1, but the axial bearing is composed only of electromagnets. ing.

That is, the bearing at the lower part of the rotor 3 is provided at the lower part of the rotor 3 in place of the projection 13 shown in FIGS.
And a permanent magnet 23 is provided on the inner wall of the cylinder 22. On the other hand, from the bottom surface of the lower support
A protrusion 25 is provided so as to protrude into the space, and a permanent magnet 24 is provided around the side wall of the protrusion 25 at a predetermined distance from the permanent magnet 23. The polarities of these permanent magnets 23 and 24 are arranged so as to be repelled similarly to the upper permanent magnets 6 and 7. Therefore, the lower radial direction is supported by these two permanent magnets 23 and 24.

The axial bearing of the rotor 3 in this turbo molecular pump is performed by attracting the upper end of the cylinder 22 by the magnetic force of the electromagnet 18 provided inside the cylinder 16.

The rotation of the rotor 3 in this turbo-molecular pump is different from that of the inner rotor shown in the turbo-molecular pump of FIGS. For this reason, the stator 12 is arranged on the outer periphery of the cylinder 16, and the rotor 11 is provided on the outer wall of the ring-shaped recess.

The bearing mechanism in this turbo-molecular pump can be the same type of bearing on both the upper and lower sides of the rotor 3, and there is an advantage that the configuration can be further simplified.

<< Effect >> The present invention is provided on the upper end side of the rotor shaft as described above, and a substantially conical permanent magnet that regulates the radial position and the axial position of the rotor shaft, and is provided on the lower end side of the rotor shaft, A permanent magnet that regulates the axial position of the rotor shaft and a substantially conical electromagnet that regulates the axial position of the rotor shaft while regulating the axial position of the rotor shaft are arranged to support the rotor. With this configuration, the floating position of the rotor can be adjusted only by controlling the exciting current of one electromagnet, and can be performed by so-called one-axis control, so that the control means can be greatly simplified.

In addition, since the permanent magnets are arranged on the upper and lower ends, the assembling work is facilitated and the bearing span (distance) can be maximized, so that the stability during rotation can be improved.

Further, since the number of electromagnets can be reduced, the structure can be simplified, and effects such as a reduction in pump cost can be obtained.

[Brief description of the drawings]

1 to 3 are partially cutaway front views of a turbo-molecular pump. DESCRIPTION OF SYMBOLS 1 ... Casing 2 ... Stator blade 3 ... Rotor 4 ... Rotor blade 8 ... Upper support part 6, 7, 12, 19, 23, 24 ... Permanent magnet 11 ... Rotor 12 ... Stator 15 ...... Lower support part 18 ... electromagnet a ... intake port b ... exhaust port

Claims (1)

(57) [Claims] A stator blade attached to an inner wall surface of a casing and a rotor blade attached to an outer wall surface of a rotor disposed inside the casing are alternately arranged in the axial direction of the rotor. A turbo-molecular pump having a motor mechanism for rotating the rotor, and for rotating the rotor to take in air from one direction of the rotor shaft and exhaust it in the other direction, wherein the rotor is provided at an upper end side of the rotor shaft; A substantially conical permanent magnet that regulates a radial position and an axial position of the rotor shaft; a permanent magnet that is provided at a lower end side of the rotor shaft and regulates an axial position of the rotor shaft; The rotor shaft is supported by a substantially conical electromagnet which regulates the radial position and regulates the radial position of the rotor shaft. Turbo molecular pump.