JPH05272488A - Turbo-molecular pump - Google Patents

Abstract

PURPOSE:To provide a turbo-molecular pump constituted in such a way as to secure the original maximum exhaust speed without lowering the rotational stability of a rotor even if regulating the exhaust speed and also to avoid the whole exhaust system becoming large-sized. CONSTITUTION:A turbo-molecular pump is provided with such a movable stator blade 1a that a lower blade piece 12 is changed in phase in relation to an upper blade piece 11. This lower blade piece 12 is driven by blade drive mechanism 4 so as to prevent gas molecules from reaching a rotor blade 2a in the following stage from the stator blade 1a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a turbo molecular pump suitable for use in vacuum application equipment such as a semiconductor manufacturing apparatus in which the exhaust speed needs to be adjusted.

[0002]

2. Description of the Related Art A turbo molecular pump includes an impeller having rotor blades and stator blades arranged alternately in a plurality of stages in the axial direction. With this impeller, gas molecules sucked from the intake port can be struck in the axial direction and forcedly exhausted toward the exhaust port. By the way, when this turbo molecular pump is used for exhausting a chamber of a CVD apparatus, for example, the exhaust speed of the turbo molecular pump is adjusted in order to keep the pressure of the gas injected into the chamber constant. At that time, conventionally, it is customary to reduce the rotational speed of the rotor or provide a conductance valve between the turbo-molecular pump and the chamber.

[0003]

However, when the number of revolutions of the rotor is changed, the resonance frequency changes, or the rotation frequency and its harmonics match the resonance frequency, and the rotation of the rotor becomes unstable. And the bearing may be overloaded. Therefore, there is an inconvenience that the rotation speed cannot be arbitrarily set. On the other hand, if a conductance valve is used, the above problems are solved, but the maximum pumping speed also decreases, leading to a decrease in pump capacity,
In addition, there is a drawback that the entire exhaust system becomes large.

The present invention has been made by paying attention to such a problem. Even if the exhaust speed is adjusted, the stability of the rotor rotation is not deteriorated, and the original maximum exhaust speed is secured. Moreover, it is an object of the present invention to provide a turbo-molecular pump capable of avoiding an increase in the size of the entire exhaust system.

[0005]

In order to achieve such an object, the turbo-molecular pump of the present invention comprises an impeller in which rotor blades and stator blades are alternately arranged in a plurality of stages in the axial direction. Some of the impeller wings are movable,
A blade drive mechanism is connected to the movable blade, and when the movable blade is driven by the blade drive mechanism, it is possible to prevent the gas molecules from reaching the blade at the next stage from the movable blade. ..

As a concrete embodiment of the movable blade, the blade is divided into upper and lower halves, one of which is fixed and the other is supported rotatably in the circumferential direction. As the blade drive mechanism in that case, it is conceivable to drive the other blade piece in the circumferential direction so as to change the relative position to the one blade piece.

As another embodiment of the movable blade,
An example is a structure in which the blade is rotatably supported around the longitudinal axis, and in that case, the blade drive mechanism is one that can drive the blade and change the angle of the blade. Be done.

[0008]

With such a structure, when the movable blade is driven through the blade drive mechanism, the gas molecules are prevented from reaching the blade at the next stage from the blade, and as a result, even if the rotational speed of the rotor is constant, the turbo molecule is The pumping speed of the pump as a whole will be reduced. Therefore, when the exhaust speed is adjusted, the rotor rotation is not destabilized, and the maximum exhaust speed can be easily recovered by returning the blade to the original mounting state through the blade drive mechanism.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

In this turbo-molecular pump, as shown in FIG. 1, a rotor 2 supported by a shaft (not shown) is rotatably arranged in an outer cylinder 1, and rotor blades 2a projecting from the outer periphery of the rotor 2 are provided. And the stator blade 1 protruding from the inner circumference of the outer cylinder 1.
The impeller A is formed by alternately arranging a and a in multiple stages in the direction of the axis m. With this impeller A, gas molecules sucked from an intake port not shown in the upper part of FIG. 1 are struck in the direction of arrow x along the axis m, and even to an exhaust port not shown in the lower part of the same figure. It can be forced to exhaust.

In such a structure, the illustrated stator blade 1a is divided into two parts, that is, a portion that originally corresponds to one blade, into an upper blade piece 11 and a lower blade piece 12, as shown in FIGS. The upper blade piece 11 is held by the outer peripheral side stator ring 11a and the inner peripheral side stator ring 11b, and the lower blade piece 12 is held by the outer peripheral side stator ring 12a and the inner peripheral side stator ring 12b. Has been done. The outer peripheral stator ring 11a of the upper blade piece 11 is fixed to the inner peripheral surface of the outer cylinder 1, and the outer peripheral stator ring 12a of the lower blade piece 12 is fixed to the outer cylinder 1 via a bearing 3 arranged between the outer peripheral stator ring 12a and the outer cylinder 1. It is rotatably supported around m.
Then, the blade drive mechanism 4 of the present invention is assembled to the lower blade 12. This wing drive mechanism 4 includes the lower wing piece 1
2 teeth 4 formed on the outer peripheral surface of the outer peripheral stator ring 12a
1, a wheel 43 having at least a part of a tooth 42 meshing with the tooth 41, and a motor 44 axially mounting the wheel 43 (step motor or motor with reduction gear)
When the motor 44 makes a minute rotation, the outer peripheral side stator ring 12a can be rotated by a desired angle. The wheel 43 and the motor 44 are housed in a bulging portion 1 a formed in a part of the outer cylinder 1.

Next, the operation of this embodiment will be described. As shown in FIGS. 1 to 3, the motor moves the lower blade 12 to the upper blade 11
When the pump is operated while it is stationary at the position where it is flush with the rotor, the rotor blades 2a move at high speed in the direction of the arrow in FIG. It is struck by the wings 2a obliquely downwards and is blown away. As a result, the gas molecules p next collide with the movable stator blade 1a, and thereafter move to the rotor blade 2a at the next stage. In this case, the smaller the adjoining gap between the upper blade piece 11 and the lower blade piece 12 constituting the movable stator blade 1a is as small as possible, the maximum exhaust speed at that time is the conventional stator shown in FIG. It approaches the pumping speed of a pump equipped with vanes 1a. Next, the motor 44 is driven to drive the outer circumferential stator ring 12a.
By a predetermined angle, as a result, the lower blade 12 and the inner peripheral stator ring 12b rotate integrally, and the lower blade 12 is positioned relative to the upper blade 11 as shown in FIG. When moving to, some of the gas molecules p blown off by the rotor blade 2a collide with the upper blade 11 and then further collide with the lower blade 12. Generally, the angle of the stator blade 1a is designed so that the gas molecule p can be repelled to the rotor blade 2a of the next stage most efficiently.
When it collides with the stator blades 1a, the velocity component of the gas molecule p in the direction of the axis m is significantly reduced, and even if the rotation speed of the rotor 2 is constant, the exhaust velocity of the entire pump is reduced. The rate of the decrease varies depending on the relative position of the lower blade 12 with respect to the upper blade 11, and in the present embodiment, the rate can be continuously changed by selecting the drive position of the motor 44. .. On the other hand, from this position again, the motor 44
When the lower blade 12 is returned to the position shown in FIG. 3 by driving, the flow of the gas molecules p returns to the original state, and the exhaust speed returns to the initial maximum exhaust speed.

However, in the case of the turbo molecular pump having such a structure, the rotor 2 is used when adjusting the exhaust speed.
Since it is not necessary to change the rotation speed of the rotor, there is no need to worry about instability of the rotor rotation, and the exhaust speed can be set freely. Therefore, it is convenient when it is desired to change the exhaust speed variously while continuously operating the CVD apparatus,
Further, the degree of freedom of application to various devices requiring different evacuation speeds is also improved. Further, in the present embodiment, the mounting state of the stator blade 1a itself is changed to realize the change of the exhaust speed, and it is difficult to restore the maximum exhaust speed because the exhaust system does not include another exhaust resistance. It never becomes. Therefore, it becomes extremely useful when applied to an apparatus or the like that requires ultra-high vacuum exhaust after gas treatment.

In the above embodiment, the latter is made wider than the former, assuming that the gas molecules collide with the upper blade 11 more than the lower blade 12, but the latter is wider than the former. Alternatively, the relationship may be reversed. Further, the movable stator blade 1a of the above embodiment may be applied to all the stator blades, or may be applied to only some of the stator blades. further,
The wing division is not limited to two divisions. Further, the configuration of the blade drive mechanism is not limited to the above embodiment, and a modified example as shown in FIG. 6 may be considered. In this blade drive mechanism 5, a magnetized portion 51 is provided in a part of the outer peripheral side stator ring 12a, and the arrangement position is adjusted by a spring 52 and a screw 53 on the outer wall of the outer cylinder 1 corresponding to the magnetized portion 51. A permanent magnet 54 is provided, and the N pole and the S pole are magnetically attracted between the permanent magnet 54 and the magnetized portion 51 to change the outer circumferential stator ring 12a to a phase position adjusted by the screw 53. It's something I got to get. If such a configuration is adopted, there are advantages that the same effects as those of the above-described embodiment can be obtained and that the blade drive mechanism 5 can be configured more simply than in the above-described embodiment. Further, in the blade drive mechanism 6 shown in FIG. 7, a magnetizing portion 61 similar to that in FIG. 6 is provided in a part of the outer peripheral side stator ring 12a, and then the stator ring 12a and the outer cylinder 1 are provided.
Are connected by a spring 62, and an electromagnet 63 is arranged on the outer wall of the outer cylinder 1 corresponding to the magnetized portion 61.
The magnetizing portion 61 is moved to a position where the attraction force by the spring and the elastic force of the spring 62 are balanced, and as a result, the stator ring 1
The phase of 2a can be changed. This is effective in automatically adjusting the exhaust speed with a simple configuration, and it is also possible to finely adjust the position of the stator ring 12a by the magnitude of the current i passing through the electromagnet 63.
Further, instead of dividing the stator blades to form the movable blades as in each of the above embodiments, the stator blades may be supported rotatably around the longitudinal axis to form the movable blades. As a blade drive mechanism in that case, a blade drive mechanism that can drive the blade to change the angle of the blade can be considered, and the exhaust speed can also be continuously adjusted by this. Furthermore, in each of the above examples, the movable blade is formed by using the stator blade, but the movable blade can also be formed by using the rotor blade in accordance with them. Other configurations can be variously modified without departing from the spirit of the present invention.

[0015]

Since the turbo molecular pump of the present invention has the structure described above, when it is applied to a CVD apparatus or the like, it is possible to continuously adjust the exhaust speed without lowering the stability of rotor rotation. Therefore, there is an effect that the original maximum pumping speed is not reduced and the size of the entire exhaust system can be easily avoided.

[Brief description of drawings]

FIG. 1 is a partial vertical sectional view schematically showing the relationship between a movable stator blade and a blade drive mechanism according to an embodiment of the present invention.

FIG. 2 is a partially cutaway plan view of FIG.

FIG. 3 is a developed view of rotor blades and movable stator blades in the direction of arrow III in FIG.

FIG. 4 is a diagram corresponding to FIG. 3 when the exhaust speed is reduced.

FIG. 5 is a diagram corresponding to FIG. 3 showing a conventional example.

FIG. 6 is a view corresponding to FIG. 2 showing another embodiment of the present invention.

FIG. 7 is a view corresponding to FIG. 2 showing still another embodiment of the present invention.

[Explanation of symbols]

 1a ... Stator blade (movable blade) 2a ... Rotor blade 4, 5, 6 ... Blade drive mechanism A ... Impeller m ... Shaft p ... Gas molecule

Claims (1)

[Claims] 1. A turbo molecular pump comprising an impeller in which rotor blades and stator blades are alternately arranged in a plurality of stages in an axial direction, wherein a part of the impeller blades is a movable blade, and the movable blade is driven by the blade. A turbo-molecular pump characterized by connecting the mechanisms so that when the movable blade is driven by the blade drive mechanism, it is possible to prevent the gas molecules from reaching the blade at the next stage from the movable blade.