JPH03150041A - Enclosed actuator - Google Patents

Abstract

PURPOSE:To prevent impure gas from being discharged into an high vacuum environment by arranging a nonmagnetic metal barrier in a gap between the stator and the rotor of a motor thereby isolating the inner space of the stator from the rotor side space. CONSTITUTION:A nonmagnetic metal barrier 33 is arranged in a gap 19 between the stator 11 and the rotor 12 of a motor and the upper end of the barrier 33 is welded to the outer circumferential face 23A of a barrier 23 partitioning the upper space of the stator 11 whereas the lower end of the barrier 33 is welded to the outer circumferential face 24A of a flange 24 partitioning the lower space of the stator 11. Furthermore, the base section 23B of the barrier 23 is welded to the outer circumferential face of the stator 11 thus sealing the space airtightly. Consequently, the space accommodating a rotary drive coil 14, a stator 28 and the like is isolated perfectly from the outside of the rotor 12. By such arrangement, gas or moisture occluded by the rotary drive coil of the stator or the insulator thereof is prevented from being discharged as impure gas into a high vacuum environment.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is applicable to the magnetic poles of a motor in an atmosphere where even trace amounts of contaminants or impurity gas are not tolerated, such as in an ultra-high vacuum atmosphere, or in a corrosive gas atmosphere. The present invention relates to a closed type actuator suitable for use in an environment where the coils and coils are corroded.

[Conventional technology]

For example, in semiconductor manufacturing equipment, workpieces are processed in an ultra-high vacuum atmosphere in order to eliminate impurities as much as possible. The actuator used in that case is
For example, in the drive motor of a workpiece positioning device,
Since lubricants containing volatile components such as general grease cannot be used for drive shaft bearings, soft metals such as gold and silver are plated on the inner and outer rings of the bearings.

In addition, stable materials with excellent heat resistance and little emitted gas are selected for the drive motor's coil insulating material, wiring covering material, and adhesive for the laminated magnetic poles.

On the other hand, various actuators such as a bellows drive system, a magnetic coupling drive system, and a magnetic fluid seal drive system are conventionally known as means for introducing rotational output into an ultra-high vacuum chamber from the outside. Both have a structure in which the output end of a rotary shaft supported by a vacuum bearing is projected into a vacuum atmosphere, and a rotational force is applied to the input end by a drive device placed in the atmosphere. In other words, in the bellows type drive system, as shown in Fig. 3, the output end IA side of the rotating shaft l is supported by the vacuum bearing 2 and protrudes into the vacuum side V, and the other end side IB is a swash plate type oscillating shaft. A mechanism 3 is attached and sealed with a bellows 4. When this swash plate-type swinging mechanism 3 is rotated by a rotating device 5 placed in the atmosphere, the rotating shaft 1 rotates while the bellows 4 repeats expansion and contraction movements.

On the other hand, in the magnetic coupling type drive system, a rotor made of a magnetic material is fixed to the input end side of a rotating shaft, and the outer periphery of this rotor is surrounded and sealed with a housing. A magnet surrounding the rotor is disposed on the atmosphere side across the housing, and by rotationally driving the magnet, the rotating shaft l is rotated.

In addition, in the case of the magnetic fluid seal drive system, a housing made of a non-magnetic material is installed through the partition wall between the atmosphere side and the vacuum side, and a circular pole with a permanent magnet sandwiched between bearings arranged inside the housing is installed. In addition to providing the pole piece, a gap between the outer circumferential surface of the rotary shaft passing through the housing and the inner circumferential surface of the pole piece opposing thereto is sealed with a magnetic fluid.

[Problem to be solved by the invention]

Recently, the degree of integration of semiconductors has increased, and at the same time
Higher densification is progressing by reducing the pattern width of C. In order to manufacture wafers that can accommodate this miniaturization,
A high degree of uniformity in wafer quality is required. In order to meet this demand, it is important to further reduce the impurity gas concentration in the wafer low-pressure gas processing chamber.

Furthermore, in order to perform microfabrication as requested, an extremely high precision positioning device is required.

When the above-mentioned conventional actuator is examined from this viewpoint, various problems are pointed out as follows.

In other words, in the case of drive motors used in ultra-high vacuum equipment, ■ Even if a stable material with excellent heat resistance and low emission gas is selected for the drive motor's coil insulation material and wiring coating material, organic As long as it is an insulating material, it is microscopically porous and has countless holes on its surface. Once exposed to the atmosphere, gas and water molecules are taken in and occluded in the pores on its surface, and it takes a long time to remove the occluded impurity molecules by vacuum evacuation.
A decline in production efficiency is inevitable.

Furthermore, since there is no heat dissipation due to air convection in a vacuum, if the coil temperature rises locally, the resistance in that area increases, accelerating heat generation, and causing burnout of the coil insulation coating. Easy to invite.

0 On the other hand, it is possible to reduce adsorbed impurity molecules by using an inorganic material for the coil insulating material and using a stainless steel tube sheathed wire for the wiring. However, in this case, not only the cost becomes very high, but also the proportion of the conductor such as steel in the coil winding space decreases, and the electrical resistance increases, resulting in a decrease in the capacity of the motor.

To address the problems described above when installing an actuator inside an ultra-high vacuum device, the actuator drive unit is installed outside the vacuum device, such as a bellows drive system, a magnetic coupling drive system, a magnetic fluid seal drive system, etc. When looking at the case where a bellows type drive system is installed, there is a large amount of backludge, and a magnetic coupling type drive system that transmits rotational force using magnetic attraction force has low rigidity, and both methods have problems in that high positioning accuracy cannot be achieved. There is.

In addition, in the magnetic fluid seal drive system, the heat resistance temperature of the magnetic fluid is as low as about 70°C, so the bakeout process of the ultra-high vacuum chamber (the process of releasing gas molecules and water molecules stored on the inner wall of the vacuum chamber, etc.)
There are problems in that it cannot withstand the heating temperature at which it is heated, and because it contains some volatile components, it releases gas.

Therefore, the present invention was made by focusing on these conventional problems, and its purpose is to eliminate the release of impurity gases in an ultra-high vacuum atmosphere and to enable highly accurate positioning. The object of the present invention is to solve the above-mentioned conventional problems by providing a sealed actuator.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a motor stator in which a rotary drive magnetic pole excited by a rotary drive coil is formed, and a motor stator that is arranged face to face with a slight gap between the magnetic pole face of the motor stator. a motor rotor rotatably supported via a rolling bearing; a non-magnetic metal partition is disposed in a gap between the motor stator and the motor rotor; A resolver detector may be provided as a displacement detection means for detecting relative displacement between the motor stator and the motor rotor, which is characterized by airtightly covering the space and being isolated from the motor rotor side space.

The inside of the actuator in which the motor stator was installed was hermetically covered with a non-magnetic metal partition wall to isolate it from the motor rotor side. Therefore, gas and moisture occluded in the rotary drive coil, insulating material, and the like of the motor stator are not released as impurities that contaminate the atmosphere. On the other hand, the rotary drive coil, insulating material, etc. of the motor stator are not eroded by the etching reactive gas used in semiconductor manufacturing.

Furthermore, the partition wall that separates the motor stator from an atmosphere that requires a high degree of cleanliness, such as in a vacuum chamber, is a non-magnetic metal partition inserted in the small gap between the motor stator and motor rotor. It does not interfere with the formation of a magnetic circuit formed by energizing the motor stator coil. Therefore, it is possible to control the rotation of the motor rotor with high accuracy by controlling the energization to the coil of the motor stator in an oven loop or a closed loop, and it is possible to perform highly accurate positioning.

In addition, since the non-magnetic metal partition wall does not affect the magnetic circuit formed through it, it is possible to provide a resolver as a rotational displacement detection means and output a rotation detection value for high positioning accuracy. .

〔Example〕

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

The sealed actuator 10 shown in FIG. 1 is a so-called outer rotor type direct drive motor in which a cup-shaped motor rotor 12 rotates outside a motor stator 11.

That is, the motor stator 11 is provided as a cylindrical shaft fixed to the shaft center and having an axial hole H in the center. A thousand-star stator magnetic pole 15 as a rotational drive magnetic pole excited by the rotational drive coil 14 is formed on its outer peripheral surface. The rotation drive coil 14 is wound around the motor stator magnetic pole 15 with an insulating material 13 in between.

A plurality of teeth having a constant pitch are provided at the tip of the motor stator magnetic pole 15 in parallel with the rotation axis.

On the other hand, the cup-shaped motor rotor 12 is rotatably attached to the outer surface of the motor stator 11 via vacuum rolling bearings 17 and 18 disposed coaxially with the motor stator 11 above and below the motor stator magnetic poles 15. A motor rotor magnetic pole 16 made of magnetic metal is provided on the inner circumferential surface of the motor rotor 12 so as to face the motor stator magnetic pole 15 of the motor stator 11 . The inner peripheral surface of the motor rotor magnetic pole 16 has the motor stator magnetic pole 1
A row of teeth is provided parallel to the teeth on the outer peripheral surface of No.5. The pitch of the tooth row is the same as that of the motor stator magnetic pole 15, but the teeth of the motor stator magnetic pole 15 and the tooth row of the motor rotor magnetic pole 16 are arranged so as to be relatively shifted in phase. Thus, by sequentially exciting the teeth of the motor stator magnetic pole 15 in the circumferential direction while controlling the supply of current to the rotation drive coil 14, the tooth row of the motor rotor magnetic pole 16 is sequentially attracted, and the motor rotor 12 is connected to the motor stator 1.
It is designed to rotate around 1.

The vacuum rolling bearings 17 and 18 are all plated with soft metal such as gold or silver on the inner and outer rings to provide metal lubrication without gas release. An outer ring 17a of the upper bearing 17 is fitted into the inner surface of the upper end of the motor rotor 12.

The inner ring 17b is fitted into the outer surface of the upper end of the motor stator 11, and is fixed by an annular bearing retainer 21 fixed to the upper end surface of the motor stator 11.

An outer ring 18a of the lower bearing 18 is fitted into the inner surface of the lower end of the motor rotor 12. The inner ring 18b is fitted into the outer surface of the lower end of the motor stator 11, and is fixed by an annular bearing retainer 22 attached to the lower extension 11A of the motor stator 11.

Upper end surface 12 of motor rotor 12 supported as described above
A to be rotated and driven is fixed to A with a bolt.

Further, a circular partition plate 23 is fitted and welded to the outer circumferential surface of the motor stator 11 directly below the upper bearing 17, and a circular partition plate 23 is fitted and welded to the outer circumferential surface of the motor stator 11 immediately below the lower bearing 18. A shaped collar 24 is provided to protrude, thereby dividing the space in which the motor rotor 12 is housed into the upper and lower parts.

The space S partitioned by the partition wall plate 23 and located above the motor rotor 12 is equipped with a high-resolution sensor as a displacement detection means for detecting the relative displacement between the motor stator 11 and the motor rotor 12 in order to position the motor with high precision. A resolver 26, which is a rotation detector, is built-in. A stator 28 of the resolver 26 having a coil 27 is fixed to the outer peripheral surface of the motor stator 11. On the other hand, the rotor 29 of the resolver 26 is fixed to the stepped portion of the motor rotor 12 so as to face the stator 28 .

On the outer peripheral surface of the magnetic pole of the stator 28 of this resolver 26,
Similar to the motor stator magnetic pole 15, a plurality of teeth having a constant pitch are provided parallel to the rotation axis, and the coil 27
is wound around each magnetic pole.

On the other hand, the rotor 29 of the resolver 26, like the motor rotor magnetic poles 16, has tooth rows with the same pitch but shifted in phase.

When the motor rotor 12 rotates, the rotor 29 of the resolver 26 also rotates, so the lactance between it and the teeth of the stator 28 changes. The rotational position of the motor rotor 12 is detected by digitizing the change by a resolver control circuit of a drive unit (not shown) and using it as a position signal. A magnetic shield plate 31 is interposed between the motor stator magnetic pole 15 and the resolver 26 and is fixed to the motor stator 11 . Further, 32 is a wiring hole passing through the inside and outside of the motor stator 11.

The gap 19 between the opposing surfaces of the motor stator 11 and the motor rotor 12 is filled with, for example, non-magnetic stainless steel SU33.
A thin cylindrical partition wall 33 made of a non-magnetic metal such as 04 is disposed to separate the two parts 11 and 12. The upper end of this partition J33 is welded to the outer circumferential surface 23A of the partition plate 23 that partitions the upper space of the motor stator 11.

Further, the lower end portion of the partition wall 33 is welded to the outer circumferential surface 24A of the collar 24 that partitions the lower space of the motor stator 11.

Welding of the upper and lower parts of the partition wall 33 and the base 23 of the partition plate 23
The welding point between B and the outer peripheral surface of the motor stator 11 is airtightly sealed. For this reason, motor stator 1
1, a rotational drive coil 14. Motor stator magnetic pole 15 and resolver 26 coil 27. The space in which the stator 28 and the like are housed is completely isolated from the outside on the motor rotor 12 side.

Note that the above welding is performed on the rotary drive coil 14 and its insulating material 1.
3. Because the process is carried out in a state where components made of materials with relatively low heat resistance, such as the coil 27 of the resolver 26, are built-in,
Electron beam welding and laser beam welding, which can limit temperature rise to localized areas, are used.

At the terminal of the lower extension portion 11A of the motor stator 11,
A vacuum flange 34 is seal welded.

Next, the action will be explained.

FIG. 2 shows a state in which the sealed actuator 10 is attached to a vacuum chamber, and the attachment provided in the chamber wall 35 is through the hole 3.
The main body of the sealed actuator IO is inserted into the vacuum tank interior V from 6, and the vacuum flange 34 is fixed to the tank wall 35 with bolts 36.

The space sealed by the partition wall 33 in the sealed actuator 10 is connected to the wiring hole 32 provided in the motor stator 11. Although it communicates with the atmosphere side A through the hole H, it is completely isolated from the inside V of the vacuum chamber. Therefore, the rotational drive coil 14 of the motor stator 11 and the resolver 26
Gas and moisture occluded in the coil 27 and their insulating material 13 are prevented from diffusing into the vacuum chamber (2) and contaminating the vacuum atmosphere.

Therefore, the inside V of the vacuum chamber can be easily evacuated, and a predetermined ultra-high vacuum can be reached in a short time even during beta-out, resulting in high production efficiency. Further, there is no need to take the trouble to use expensive inorganic materials for the coil insulation material. Furthermore, in the case of semiconductor manufacturing,
The partition wall 33 made of stainless steel also protects against the etching reactive gas introduced into the vacuum chamber interior V after evacuation.
Since the coil and the insulating material are protected by etching, there is no risk that the coil, insulating material, etc. will be etched.

Furthermore, since the rotation drive coil 14 communicates with the atmosphere, even if it generates heat due to energization, it can be dissipated by convection, and burnout of the coil due to local heat accumulation can be prevented. Note that since the rotation drive coil 14 is located on the atmosphere side, it is easy to forcefully cool the motor stator 11 by passing air or water into the interior of the motor stator 11 if necessary.

Furthermore, feedback control ensures extremely high precision in positioning the rotation of the motor rotor 12. That is, when a predetermined rotation drive coil 14 of the motor stator 11 is energized, a magnetomotive force is generated, and the teeth of the motor stator magnetic poles 15 are excited. Partition wall 3 made of non-magnetic metal
3 is sufficiently thin, the magnetic flux reaches the motor rotor 12 through the partition wall 33. A magnetic circuit is formed between the energized motor stator magnetic pole 15 and the opposing motor rotor magnetic pole 16, and the opposing teeth of the two magnetic poles strongly attract each other.

Now, a drive unit (not shown) is discarded and a controlled motor current is sequentially applied to the plurality of rotation drive coils 14 arranged in order along the circumferential direction according to the arrangement. Then, the excitation of each tooth of the motor stator magnetic pole 15 is sequentially moved according to the order of energization, and the motor rotor 12 rotates. When the motor rotor 12 rotates, the rotor 29 of the resolver 26 also rotates. As a result, the lactance between the teeth with the stator 28 changes. By digitizing this change by a resolver control circuit of a drive unit (not shown) and using it as a position signal, precise feedback control of the rotation angle of the rotor 29 and, in turn, the rotation angle of the motor rotor 12 is performed, allowing highly accurate positioning.

Note that in the above embodiment, the rotation detector (for example, the resolver 2
6) and feedback control of the rotor position to achieve high-precision positioning. Highly accurate positioning may be performed using a loop control method.

Regarding the installation of the sealed actuator 10,
It is attached to the wall of the vacuum chamber with a flange, and the wiring is connected to the wiring hole 32 of the motor stator 11. Although the case where the operation is performed on the atmosphere side through the hole H is shown, the entire sealed actuator 10 is installed inside the vacuum chamber, and the wiring is connected to the sealed actuator 10.
This may be done through a metal pipe provided between the connector and the connector provided on the wall of the vacuum chamber.

In addition, although a configuration has been shown in which the motor stator 11 is located inside and the motor rotor 12 is located outside, in contrast to this, the motor stator 11 is located outside and the motor rotor 12 is located inside, and the rotor side is placed in a vacuum atmosphere. It is also possible to use

Furthermore, it is applicable not only to motors in which the motor stator 11 and motor rotor 12 are cylindrical and face each other on their circumferential surfaces, but also to motors in which both are disc-shaped and face each other in a plane. A partition wall is formed by a disk made of non-magnetic metal interposed in the gap between the stator side and the stator side by seal welding, and the rotor is supported by a vacuum bearing.

〔Effect of the invention〕

As explained above, according to the present invention, there is provided a motor stator in which a rotational drive magnetic pole excited by a rotational drive coil is formed, and a motor stator that is arranged face-to-face with a slight gap in between the magnetic pole face of the motor stator. A non-magnetic metal partition is airtightly disposed in the gap between the motor stator and the motor rotor, and a non-magnetic metal partition is airtightly disposed in the gap between the motor stator and the motor rotor. The space is isolated from the motor rotor side space. Therefore, even when the actuator is used in a high vacuum atmosphere in semiconductor manufacturing equipment or a reactive gas atmosphere, impurity gases are released into the high vacuum atmosphere from the coil and organic insulating material, which contain the most occluded gas among the actuator components. The coils, organic insulation, etc. will not be eroded.

Furthermore, the formation of a magnetic circuit between the motor stator and the motor rotor is not hindered by the non-magnetic metal partition wall, and it is possible to control the energization of the motor stator coil to realize rotation of the motor rotor and, in turn, highly accurate positioning of the driven object. .

[Brief explanation of the drawing]

FIG. 1 is a side view showing a half-section of an embodiment of the present invention, FIG. 2 is a view showing its installation, and FIG. 3 is a schematic sectional view showing an example of a conventional closed-type actuator. In the figure, 11 is a motor stator, 12 is a motor rotor, 1
4 is a rotary drive coil, 15 is a motor stator magnetic pole, 1
9 is a gap, 26 is a resolver, and 33 is a partition.

Claims (2)

[Claims] (1) A motor stator in which a rotational drive magnetic pole is excited by a rotational drive coil, and a motor stator that is disposed face-to-face with a slight gap from the magnetic pole face of the motor stator and is connected via a rolling bearing. a motor rotor rotatably supported by the motor stator, and a non-magnetic metal partition is disposed in a gap between the motor stator and the motor rotor to airtightly cover an internal space in which the motor stator is disposed, and a motor rotor side A closed actuator that is characterized by being isolated from space. (2) The sealed actuator according to claim 1, further comprising a resolver detector as a displacement detection means for detecting relative displacement between the motor stator and the motor rotor.