JPH0868389A - Molecular pump - Google Patents

Abstract

PURPOSE: To improve exhaust capacity and to reduce the size of a device by increasing intake conductance of an exhaust amount control part. CONSTITUTION: A pump rotary shaft and a plurality of intake control plates 7 movable forward and backward in a direction extending vertically to a pump rotary shaft are installed in the vicinity of the rotor vane (a moving vane) 2a of a molecular pump intake port and an exhaust gas amount is controlled by means of the intake control plates 7. When intake is effected without controlling an exhaust gas amount, a plurality of the intake control plates 7 are moved aside to a rotor rotation central part where intake air is not shielded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molecular pump for high vacuum evacuation and gas flow rate control, which is used in an apparatus for forming a thin film while exhausting gas such as a dry etching apparatus and a sputtering apparatus.

[0002]

2. Description of the Related Art An example of a conventional turbo molecular pump is shown in FIG. In the figure, T is a cross-sectional view of a conventionally known turbo molecular pump, and 20 is a magnetic bearing, which is composed of a permanent magnet 21 on the holder side and a permanent magnet 22 on the rotor side. 23 is a stator blade, 24 is a rotor blade, 25 is a rotor, 26 is a casing, 27 is a touch bearing, 28 is a rotating shaft, 29 is a motor, 30 is an angular contact ball bearing, 31 is a base A, 32
Is a base B, and 33 is an exhaust port. The operation of this turbo-molecular pump is the same as that conventionally known, and therefore its explanation is omitted. The butterfly valve 12 is rotatably arranged in a cylindrical casing 11 and holds a valve packing 13 on its outer peripheral portion. The butterfly valve 12
The shaft is fixed to the rotary shaft 14 whose axial direction is perpendicular to the intake direction, and one end of the rotary shaft 14 penetrates the casing 11 and is coupled to a rotary drive unit (not shown) installed outside the casing 11. It is rotated by the rotation drive unit via the rotary shaft 14 to perform the valve opening / closing operation. When the butterfly valve 12 is set to be perpendicular to the pump rotation axis direction, the valve packing 13 held on the outer peripheral portion of the butterfly valve 12 is inscribed inside the casing 11 to make an airtight seal, and the butterfly valve 12 is fully closed. If it is set parallel to the pump rotation axis direction, it will be in the fully open state and the displacement will be maximum. The displacement can be variably controlled by setting the butterfly valve 12 at an arbitrary position between fully closed and fully opened by the rotary drive unit. Reference numeral 11a is a pipe.

In the above-mentioned structure, in order to prevent the butterfly valve 12 from coming into contact with the turbo molecular pump and the like connected to the front and rear of the casing 11 when fully opened, a considerably wide space is required along the pump rotation axis direction. . Therefore, the length L of the casing in the pump rotation axis direction increases, and the exhaust conductance decreases. Further, since the exhaust conductance in high vacuum is proportional to the cube of the diameter D and inversely proportional to the length L in the exhaust direction, it is necessary to increase the diameter. However, in this configuration, since the length L in the exhaust direction needs to be larger than the diameter D, the user's demand for miniaturization of the vacuum evacuation device becomes an obstacle to the miniaturization of the device. .

[0004]

SUMMARY OF THE INVENTION The present invention solves the above problems and increases the exhaust conductance by reducing the length of the exhaust amount control unit in the pump rotation axis direction. The present invention provides a molecular pump that can be miniaturized.

[0005]

In order to achieve such an object, the present invention provides a plurality of intake control units that can move forward and backward in the direction perpendicular to the pump rotation axis in the vicinity of rotor blades (moving blades) on the intake side of a molecular pump. A plate is installed, and the conductance of the pump intake passage is variably controlled by this control plate.

[0006]

By moving a plurality of intake control plates in a plane perpendicular to the pump rotation axis, the conductance near the rotor blades (moving blades) is changed to control the exhaust amount. That is, a plurality of intake control plates are placed near the rotor blades (moving blades) (in the peripheral portion).
When it is moved, the displacement is minimized, and when it is moved toward the center, the displacement is increased.

[0007]

Embodiments of the present invention will be described below with reference to FIGS. The rotor 2 is arranged in the casing 1 of the turbo molecular pump so as to be rotatable at high speed, and the rotor 2
Rotor blades (moving blades) 2a projecting from the outer periphery of the rotor 1 and stator blades (static vanes) 4 projecting from between the laminated stator spacers 3 inscribed in the inner periphery of the casing 1 alternately face and face each other. They are arranged, and both perform an evacuation operation. This exhaust action increases as the peripheral speed of the rotor blade 2a increases, and there is an exhaust action in the ring-shaped exhaust space S near the blade at the pump intake port 5, but an exhaust action does not occur in the space inside the root of the rotor blade 2a. Absent. Four intake control plates 7 are installed at a position 10 to 20 mm from the uppermost part of the rotor blade 2a as shown in FIG. 2, and one end is attached to the motor shaft 8a of the stepping motor 8 installed inside the control part casing 6. Is held at the opposite end of the fixed arm 9. When controlling the exhaust amount, the intake control plate 7 is moved to the position of the ring-shaped exhaust space S near the rotor blade by the rotation of the stepping motor 8 at a predetermined angle, and the intake air is taken in accordance with the required exhaust characteristics (flow rate, pressure, etc.). The control plate 7 changes the conductance of the intake passage. In the case of maximizing the displacement, the intake control plate 7 is moved to a space inside the root of the rotor blade 2a as shown in FIG. 2 (b) to completely eliminate the shielding of the ring-shaped exhaust space S. During this operation, the four intake control plates 7 have different height positions so that they do not collide with each other due to movement but overlap with each other, and the intake control plates 7 are rotated by a predetermined angle by the rotation of the stepping motor 8.
Since the conductance of the intake passage can be gradually changed, it is possible to finely change the exhaust amount and control the flow rate precisely.

The shape of the intake control plate is effectively a string-shaped baffle plate piece along the inscribed circle of the casing as shown in the embodiment, but it is like a diaphragm piece of a camera. Various shapes such as ones can be used.

Further, the advancing / retreating of the intake control plate 7 may be performed by a linear motion with respect to the pump rotation center direction other than the above example. In addition to this turbo molecular pump, this system can also be applied to a molecular drag pump having a thread groove in at least one of a rotating cylinder and a fixed cylinder.

[0010]

As described above, according to the present invention, even if the diameter of the exhaust amount control section is increased, the length in the pump rotation axis direction can be reduced, so that the conductance of the intake air can be increased and the exhaust capacity of the device can be improved. Further, it can contribute to downsizing of the device.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a turbo molecular pump according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG. 1 showing the embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a conventional turbo molecular pump.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Casing 2 ... Rotor 2a ... Rotor blade 3 ... Stator spacer 4 ... Stator blade 6 ... Control part casing 7 ... Intake control plate 8 ... Stepping motor 12 ... Butterfly valve 13 ... Valve packing 14 ... Rotation shaft 20 ... Magnetic bearing S ... Exhaust space T ... Turbo molecular pump

Claims (1)

[Claims] 1. A molecular pump in which a rotor blade rotates at high speed to perform vacuum exhaust, in the vicinity of the rotor blade of a pump intake port,
A molecular pump characterized in that a plurality of intake control plates capable of advancing and retracting in a direction perpendicular to a pump rotation axis are installed, and the conductance of a pump intake passage is variably controlled by the intake control plates.