JP2687562B2 - Turbo molecular pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a turbo molecular pump (hereinafter abbreviated as TMP) that is widely used in various manufacturing and measurement fields that require high vacuum. is there.

[Prior Art] In TMP, turbines are constructed by alternately arranging rotor blades protruding from the outer circumference of the rotor and stator blades protruding from the inner circumference of the stator to knock out the molecules sucked from the intake port and force them to the exhaust port. Exhaust. This pump can exhibit excellent exhaust characteristics in the molecular flow region and is driven to rotate at a high speed of tens of thousands rpm. Therefore, in the past, three-phase induction motors (INDUCTION MO
TOR) or a DC brushless motor with a control power supply is configured around the shaft.

[Problems to be Solved by the Invention] However, in a three-phase induction motor, there is a problem that vibration occurs in the rotor due to torque ripple (cocking) generated from the inverter. Particularly in recent years, as the purpose of using TMP, the number of those who dislike vibration such as electron microscopes is increasing, and although such a motor is simple, it is likely to be restricted in application in this respect. On the other hand, the DC brushless motor has excellent controllability and enables low vibration, but this motor generates an eddy current in the core of the stator winding (projected inward from the yoke) by the rotation of the rotor, and the eddy current is generated. There is a drawback that drive torque is halved due to current loss. Therefore, when TMP rises,
It becomes difficult to speed up during steady operation and braking. Further, if the efficiency is low, a large-capacity control power source is required, which is very inconvenient in terms of cost and space.

The present invention has been made in view of such problems, and an object thereof is to suitably solve these problems with a simple structure.

[Means for Solving the Problems] The present invention employs the following means to achieve the above object.

That is, the TMP of the present invention includes a shaft to which a rotor having an opening is detachably attached, a magnet that is mounted on the shaft, and a magnet that is press-fitted into the opening of the rotor so as to be disposed at a position facing the magnet. And a yoke that is magnetically coupled to the magnet at that position, and a fixed coil that is interposed in a facing gap between the magnet and the yoke to apply a rotational force to the rotor. .

[Operation] With such a structure, the magnet, the yoke, and the coil constitute a so-called coreless / brushless motor, the original high controllability of the DC motor is obtained, and there is no torque ripple unlike the inverter, so the rotor Rotation can be made low vibration. Moreover, since the coil is provided without the core, eddy current is not generated even when the rotor rotates, and the driving torque can be output with high efficiency. Therefore, high-speed operation is possible, and the control power supply can be downsized and simplified.

In addition to these points, the outer diameter of the motor is reduced by that amount if there is no core. Therefore, the rotor opening can be made as small as possible to enhance the strength and toughness of the rotor, which makes it possible to reduce centrifugal force. The durability is increased, and it becomes possible to drive in a higher rotation range. Also in the yoke, since it is pressed into the rotor opening, it is reinforced against centrifugal force.
Further, since the rotor is detachably attached to the shaft, and the yoke is also provided separately from the magnet and press-fitted into the rotor, it is easy to disassemble the rotor and the shaft, and the fields of the rotor and the yoke are easily maintained. Is also excellent.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a TMP according to this embodiment, which has an opening 1
A shaft 2 to which a rotor 1 having a is detachably attached, a magnet 3 that is externally mounted on the shaft 2, and a magnet 3 that is press-fitted into an opening 1a of the rotor 1 and is disposed at a position facing the magnet 3. It is provided with a yoke 4 magnetically coupled to the magnet 3 at a position, and a fixed coil 5 inserted in a facing gap between the magnet 3 and the yoke 4 in order to apply a rotational force to the rotor 1.

More specifically, the outer shape of the TMP is the base 6 and the outer cylinder 7.
And the intake flange 8 and the shaft 2
A lower bearing 9 provided in the base 6 and an upper bearing 11 supported by the intake flange 8 via a shaft fixing portion 10 are rotatably supported. The shaft 2 is provided with a small diameter in a stepwise manner from the central portion to the tip portion. The cylindrical magnet 3 is fixed to the central portion by bonding or press fitting, and a screw groove is formed on the upper end portion to form the bolt portion 2a. Is formed. The magnet 3 is magnetized so as to generate a magnetic flux in the radial direction.

On the other hand, a bottom plate portion 1c having a through hole 1b projecting in the center is provided inside the rotor 1, and the shaft 2 is inserted through the through hole 1b and fixed. That is, the bottom plate portion 1c is loaded on the end face 2b of the central portion of the shaft 2, and the lock nut 1d is screwed and fastened to the tip bolt portion 2a.

A cup-shaped yoke (yoke) 4 is press-fitted into the opening 1a of the rotor 1, and the top plate 4a of the yoke 4 is inserted.
Is in contact with the upper end surface of the magnet 3 and is magnetically coupled to the magnet 3, and the vertical portion 4b is arranged to face the magnetic pole surface 3a of the magnet 3 with a certain gap. The fixed coil 5 for driving is inserted between the gaps.

The fixed coil 5 is attached and held to the inner periphery of a thin-walled cylindrical resin mold 5a (or itself is provided in a net shape) as shown in an enlarged view in FIG. It is set so that a magnetic biasing force in the rotating direction can be applied. Further, the resin mold 5a is covered with a substrate portion 12 on the outer periphery of the lower end thereof, and further, these are mounted on the base 6
It is carried on top. The board portion 12 is, for example, integrally molded with the resin mold 5a, and has a hall element 13 for detecting the relative position of the magnet 3 and the coil 5, and a position detection signal from the hall element 13 to obtain a position detection signal to the coil 5. It is equipped with a drive circuit (not shown) that controls the power supply state without any contact. Then, a control line 15 drawn from a control power supply (not shown) via an airtight introduction terminal 14 is connected to the drive circuit.

However, with a TMP with such a coreless / brushless motor installed internally, torque ripple unlike the inverter does not appear during rotational driving, so it is possible to stabilize the rotation of TMP during start-up and steady operation and reduce vibration. Therefore, it can be suitably applied to the intended use of an electron microscope or the like. Also, in recent TMP, active magnetic bearings are often used as non-contact bearings in order to increase the rotation speed of the rotor. Stabilization is desired. Therefore,
The illustrated TMP is also convenient for such a bearing. Moreover, as shown in FIGS. 4 and 5, the conventional DC brushless motor has the shaft 101 and the shaft 1
A magnet 102 mounted on 01, and a core 103 arranged on the outer periphery of the magnet 102 (protruding integrally from the yoke 105 inward)
And a coil 104 arranged to face the magnet 102 by being wound around the core 103.
The eddy current loss occurred in the core 103 when the rotor rotated, but in the present embodiment, the eddy current loss does not occur even when the rotor 1 rotates because the core is not present. Therefore, each operation of TMP acceleration, steady operation, and deceleration can be speeded up, and the control power supply can be covered with a small and simple one. Further, if no eddy current is generated, it is not necessary to form the yoke 105 into a thin plate and stack the yoke 105, which facilitates processing and assembly.

Further, the conventional motor had to increase the motor outer diameter because of the core 103, but in the present invention, the motor outer diameter can be reduced by the absence of the core (in the illustrated example, the coil wall thickness d ₁ : 0.6 to 1.0 mm, coil-to-yoke gap d ₂ : 0.3
To 0.5 mm, between the magnets-coil gap d _3: 0.3~0.5mm). As a result, the opening 1a recessed in the rotor 1 can be made as small as possible to enhance the strength and toughness of the rotor 1,
The durability against centrifugal force is increased, and higher-speed rotation drive is possible. Also in the yoke 4, the rotor opening 1a
Since it is pressed into, it is reinforced against centrifugal force. further,
The rotor 1 is detachably attached to the shaft 2,
Since the yoke 4 is also provided separately from the magnet 3 and press-fitted into the rotor 1, the rotor 1 and the shaft 2 and the rotor 1 and the yoke 4 can be easily disassembled, and maintenance is also excellent.

Furthermore, as another effect, since the motor is incorporated in the rotor opening 1a, the center of gravity can be located near the center of the shaft, and the distance between the shafts can be shortened, so that the stability as a rotating body is further improved. Become.

Although one embodiment of the present invention has been described above, the configuration of each part is not limited to the illustrated embodiment, and various modifications can be made without departing from the spirit of the present invention.

EFFECTS OF THE INVENTION Since the present invention has the coreless / brushless structure as described above, the high controllability inherent in a DC motor can be obtained, and the torque ripple as in an inverter is eliminated to stabilize the rotation and reduce the vibration. Is fulfilled. In addition, the eddy current loss, which has been a problem with conventional coreless brushless motors, is eliminated, efficiency is improved, the speed of TMP rise, steady operation, and braking is increased, and the control power supply is also compact and simple. it can. Further, since there is no core, the motor structure becomes compact, the thickness defect of the rotor is reduced, the strength is secured, and the yoke is reinforced against the centrifugal force by being press-fitted into the inner circumference of the rotor. Furthermore, since the rotor can be attached to and detached from the shaft, and the yoke is provided separately from the magnet and press-fitted into the rotor, the rotor and the shaft can be easily disassembled, and the rotor and the yoke can be easily disassembled for maintenance. It will be excellent.

[Brief description of the drawings]

1 to 3 show an embodiment of the present invention, and FIG.
FIG. 2 is a vertical cross-sectional view of P, FIG. 2 is a partially enlarged cross-sectional view showing details of essential parts, and FIG. 3 is a cross-sectional view taken along line III-III in FIG.
Further, FIGS. 4 and 5 show a conventional example, FIG. 4 is a sectional view corresponding to FIG. 2, and FIG. 5 is a sectional view taken along the line VV in FIG. 1 ... Rotor, 1a ... Opening 2 ... Shaft, 3 ... Magnet 4 ... Yoke, 5 ... Fixed coil

Claims (1)

(57) [Claims] 1. A shaft to which a rotor having an opening is detachably attached, a magnet which is mounted on the shaft, and a magnet which is press-fitted into the opening of the rotor so as to be disposed at a position opposite to the magnet. And a fixed coil inserted in a gap between the magnet and the yoke so as to apply a rotational force to the rotor. .