JPS6388299A - Turbo molecular pump - Google Patents

Abstract

PURPOSE:To maintain the operating efficiency of a pump by forming each rotor vane from metal sheet plastically deformed, nipping the vane with ring spacers, and pressing the root of the blade part of the rotor vane with a detent boss of the ring spacer. CONSTITUTION:A rotor vane 4 is nipped by ring spacers 3, and a stator vane 10 is arranged between them. A detent boss 31 is furnished at the periphery of each ring spacer 3, and its end face 32 is formed in an angle corresponding to the slope at the root of the blade part of rotor vane. Thereby the centrifugal force applied to the rotor vane 4 can be retained even by the ring spacer, which ensures maintaining high speed rotation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a turbomolecular pump, which is effectively used to obtain an ultra-high vacuum.

[Prior art and its problems]

Conventionally, it has been known that a rotor rotating within a casing is formed from a plurality of ring spacers as a turbomolecular pump for obtaining high vacuum.

It was also known to sandwich rotor blades formed by plastic deformation from a metal plate member between these ring spacers (
For example, Japanese Patent Application Laid-open No. 101299/1983).

Forming the rotor blade by plastic deformation from a metal plate member in this way can reduce the manufacturing cost and is practically desirable. however,
In a turbomolecular pump, the rotor blades must rotate within the casing at extremely high rotational speeds in order to obtain a high vacuum.

Therefore, during operation, a large centrifugal force acts on the rotor blade, and there is a fear that the twist angle of the blade portion of the rotor blade may be changed due to this centrifugal force.

If the twist angle is deformed in this way, the operating efficiency as a turbo-molecular pump will be reduced, and a predetermined compression ratio etc. will not be obtained.

[Problem that the invention seeks to solve]

The present invention has been devised in view of the above points, and an object of the present invention is to form the rotor blades of a turbo-molecular pump by plastic deformation from a metal plate member, thereby making it possible to manufacture the turbo-molecular pump at low cost. Furthermore, the compressor of the present invention prevents deformation of the rotor blades during pump operation in the pump configured as described above,
The purpose is to enable the pump to always maintain good operating efficiency.

[Configuration and operation]

In order to achieve the above object, in the turbo molecular pump of the present invention, the rotor blades are formed by plastic deformation from a metal plate member,
In addition, a configuration is adopted in which the rotor blades are sandwiched between ring spacers. Furthermore, a locking protrusion having an angle corresponding to the inclination angle of the blade portion of the rotor blade is formed on the ring spacer. This locking protrusion is configured to press down the root of the blade portion of the rotor blade.

Since the root portion of the blade portion is pressed down by the locking protrusion in this manner, even if the rotor blade rotates at high speed, the inclination angle of the rotor blade will not be deformed due to centrifugal force.

〔Example〕

An embodiment of the pump of the present invention will be described below based on the drawings.

Reference numeral 1 in FIG. 1 denotes a casing, which is made of a material that is resistant to high vacuum, such as stainless steel. A cylindrical working chamber space 101 is formed inside this casing 1 . An inflow hole 18 is open on the upper side of the actuating chamber 101 in the drawing, and the lower side of the working chamber in the drawing communicates with the outflow hole 11. Note that the lower part of the casing 1 is fixed to a housing 16, and the outflow hole 11 is formed in this housing 16. Further, an outflow vibrator 17 is press-fitted into the outflow hole 11 portion of the housing 16. A three-layer AC motor 8 is fixed within the housing 16 .

This motor 8 rotates the shaft at high speed.

In other words, the motor is 20000rpm+ to 5000or
It rotates at a high speed of about pm. The shaft 6 is rotatably supported by bearings 14 and 15 that support high-speed rotation. These bearings 14 and 15 are grease-lubricated high-speed rotation bearings to withstand high vacuum (dry bearings are used as protective bearings when magnetic bearings are used).

Note that a magnetic bearing may be used instead of the dry bearings 14 and 15. In that case, shaft 6
is not in contact with either the housing 1G or the holding plate 13, and high-speed rotation can be performed even more smoothly.

An end spacer 21 is fixed to the shaft by a nut 7. Further, a large number of ring spacers 3 are stacked below the end spacer 21, and these many ring spacers 3 are attached to the end spacer 2 by through bolts 5.
1 is integrally fixed. The end of the through port 5 is fixed by a screw hole formed in the lower ring spacer 3 as shown in the figure.

A moving blade 4 is sandwiched between each ring spacer 30.

The rotor blade 4 is made of a metal that has sufficient strength to withstand centrifugal force during high-speed rotation and is relatively easily plastically worked, such as an aluminum alloy or a titanium alloy. Furthermore, since the rotor blades 4 are sandwiched between the ring spacers 4 described above, the distance between adjacent rotor blades 4 is always maintained at a constant value by the ring spacers 3.

Stator blades IO are arranged so as to fill the gap between the rotor blades 4. The stationary blade 10 is also made of a metal that can be relatively easily plastically worked, such as an aluminum alloy or a titanium alloy. Also, in order to increase the compression ratio, static R
The distance between the IO and the rotor blade 4 is maintained at a minute gap.

Further, the static R10 is also held between the static spacers 9, and the static spacers 9 are fixed to the working chamber portion of the casing 1.

The shape of the above-described rotor blade will be explained based on FIGS. 2 and 3. The rotor blade 4 is formed by cutting out a disc-shaped plate member having a predetermined thickness t, with its upper surface serving as a reference surface. The inclination angle α of the rotor blade 4 is substantially constant over the entire length of the blade portion 41 thereof. However, this inclination angle α differs within each rotor blade 4. That is, the inclination angle α of the rotor blade 4 on the side closer to the inflow hole 18
is large, and the inclination angle α of the rotor blade 4 on the side closer to the outflow hole 11 is small. Therefore, the inclination angle α of the rotor blade 4 gradually decreases from the inlet hole 18 side toward the outlet hole 11 side. Alternatively, the inclination angle α may be set to 2 to 3 types, and the inflow hole 1
A large constant inclination angle α is set at several steps near the outlet hole 11, and a small constant inclination angle α is set at every several steps as it approaches the outflow hole 11.
to have.

Here, when the rotor blade 4 rotates at high speed, the rotor blade root 4
The centrifugal force F calculated as F ω 2 is added to ω 2.

In addition, m...the mass of one rotor blade part 41, r...
・Effective radius of rotor blade 4, ω...Rotational angular velocity, therefore, exhaust speed approximately 30017. To obtain a turbomolecular pump of , , the rotor blade tip diameter r+=125 and the rotor blade root diameter rg
=85m■, rotor blade plate thickness T+" 0.8mm
, the rotor blade blade width W1 = 4 fins, the twist angle β by plastic working = 30', the number of blades is 36, and when this turbo molecular pump is rotated at 50,000 rpm, the root portion 42 of the rotor blade 4 has F. ” A centrifugal force of 45 kg will be applied.

As shown in FIG. 4, if this centrifugal force F is applied to the root portion 42, m = 44 kir at the bending point 43 of the root portion 42.
・A bending moment of 1 m will be generated. Further, due to this bending moment m, a bending stress of Σ-59 kg/c++I is applied to the blade root portion 42. The above calculations were roughly performed assuming that the centrifugal force F acts on the center point of the plastically worked portion, as shown in FIGS. 5 to 8.

Here, when the moving blade 4 is formed of an aluminum alloy, the allowable stress of the aluminum alloy is approximately 22 kg/an
! Therefore, if the rotor blade 4 rotates at high speed up to 50,000 rotations, the centrifugal force F becomes larger than the allowable stress. In other words, the limit to which the rotor blade can rotate while maintaining a constant inclination angle α is about 30,000 r□.

Therefore, in this example, a locking protrusion 31 is formed protruding from the outer peripheral portion of the ring spacer 3 as shown in FIG. 9.10. The end surface 32 of the locking protrusion 31 is formed at an angle corresponding to the inclination angle α of the root portion 42 of the rotor blade portion 41. Therefore, the state in which the ring spacer 3 is combined with the rotor blade 4 is as shown in FIGS. 11 and 12. That is, the tip 32 of the locking projection 31 comes into close contact with the blade root 42, and the front surface of the locking projection 31 holds the plate root 32.

Note that the locking protrusion 31 of this ring spacer has a locking protrusion 3.
The cross-sectional shape is such that the sum of the bending stress due to the centrifugal force of the blade 1 itself and the bending stress due to the centrifugal force of the moving blade 4 is within the yield strength of the material. Regarding this example, in the dimensions shown in FIGS. 9 and 10, the width Wz of the locking portion 312 is 6.5.
tm, wall thickness tz=2mm.

Projection height H=lam and inclination angle α of the locking protrusion 31
= 15', the bending moment Mm due to the centrifugal force of the locking protrusion 31 itself = 7.58 kg/ *
In addition, the bending moment M due to the centrifugal force of the rotor blade 4
d=85.7 kg/am. Therefore, the bending stress Σb applied to the root of the locking protrusion 31 is 25 kg/d.
becomes. When an aluminum alloy is used as the ring spacer 3, this value is the allowable stress Σ of the aluminum alloy.
= 22 kg/ctA, and has sufficient durability. The centrifugal force applied to the ring spacer 3 is indicated by arrow F in FIG.

As described above, since the rotor blade 4 of this example is held by the locking protrusion 31 formed on the ring spacer, even if it rotates at a high speed of about 500 rotations, neither the tilt angle α nor the twist angle β will change due to centrifugal force. will not change. As a result of rotating the rotor blades 4 at high speed in this way, the inflow hole 1
Molecules flying into the casing 1 from 8 can be caught on the lower surface of the rotor blade 4. The molecules captured on the lower surface of the dynamic H4 fly out toward the outflow hole 11 side. Since the inclination angle α is configured to gradually decrease from the inflow hole 8 side to the outflow hole 11 side, the molecules are compressed and flow toward the outflow hole 11 side. As a result, the space in which the inflow hole 18 opens can be made into an ultra-high vacuum.

In the above example, as shown in FIG. 13, the locking protrusion 31 was formed to protrude from the spacer ring 3 at a right angle, but it goes without saying that the locking protrusion 31 may have another shape. FIG. 14 shows another shape of the locking projection 31. In this example, the locking protrusion has a triangular cross section, and has a shape that corresponds not only to the inclination angle α of the rotor blade 4 but also to the twist angle β. That is, in the example shown in FIG. 14, the tip end 32 of the locking protrusion 31 has a shape that makes surface contact with the twisted part 44 of the rotor blade. With such a configuration, it is also possible to reduce the stress applied to the rotor blades 4. As a result, it is also possible to rotate the rotor blades 4 at an even higher speed.

Further, in the above example, the locking protrusion 31 is formed integrally with the ring spacer 3, but the locking protrusion 31 may be formed separately from the ring spacer 3. FIG. 15 shows an example in which only the locking protrusion 31 is formed separately from the ring spacer 3. Here, the locking protrusion 31 is made of a material that is relatively lightweight and has high bendability, such as stainless steel. This locking projection 31 is press-fitted into the lower surface of the ring spacer 3, and the twist corner portion 44 of the rotor blade 4 is supported by this locking projection 31. In FIG. 15, the locking protrusion 31 may be fixed to the ring spacer 3 by adhesive or the like, or may be simply inserted between the rotor blade 4 and the ring spacer 3. In the latter case, it will be pressed and held by the through bolt 5.

Furthermore, in the above example, a plurality of ring spacers 3 are connected by through bolts 5, but as shown in FIG. 16, a threaded portion is formed on the inner surface of each ring spacer 3,
This threaded portion may be coupled to a threaded portion on the outer periphery of the rotor. According to the example shown in FIG. 16, it is possible to reduce the weight of the rotor 2 portion.

Further, in the above example, the rotor blade 4 was bent at a predetermined inclination angle α using its upper surface as a reference plane as shown in FIG.
As shown in FIG. 7, the plate portion 41 may be bent with respect to the center plane of the rotor blade portion 4. Furthermore,
As shown in FIG. 18, the blade portion 41 may be formed by bending the lower surface of the rotor blade 4 as a reference plane.

〔Effect of the invention〕

As explained above, in the pump of the present invention, since the blade part of the dynamic M4 is supported by the ring spacer,
The centrifugal force applied to the rotor blades 4 can also be held by the ring spacer. As a result, the rotor blade 4 can be rotated at high speed, which is an excellent effect.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the pump of the present invention, FIG. 2 is a plan view of the rotor blade 4 shown in FIG. 1, FIG. 3 is a side view of the rotor blade 4 shown in FIG. 2, and FIG. Figure 1 is an explanatory diagram illustrating the centrifugal force applied to the rotor blade shown in the figure, Figures 5 to 8 are explanatory diagrams each illustrating the centrifugal force applied to the rotor blade, and Figure 9 is a plan view showing the ring spacer illustrated in Figure 1. , FIG. 10 is a side view of the ring spacer shown in FIG. 9, FIG. 11 is a plan view showing the ring spacer and moving blade shown in FIG. 1, and FIG. 12 is a side sectional view of the ring spacer and moving blade shown in FIG. 1. , FIG. 13 is a sectional view showing a combined state of the ring spacer and moving blade shown in FIG.
FIG. 4 is a cross-sectional view showing a combined state of a ring spacer and moving blade according to another example of the present invention, FIG. 15 is a cross-sectional view showing a combined state of a ring spacer and moving blade according to still another example of the present invention, FIG. 16 is a sectional view showing another example of the pump of the present invention, and FIGS. 17 and 18 are side views showing rotor blades of other examples of the present invention. DESCRIPTION OF SYMBOLS 1... Casing, 2... Rotor, 3... Ring spacer, 4... Moving blade, 6... Shaft, 8...
Motor, 9... Stationary spacer, 10... Stationary blade, 41
...Blade part. 42... Root part, α... Slope angle. Representative patent attorney Takashi Okabe. Figure 1 Figure 2. Fig. 3 Fig. 4 Fig. 5

Claims (1)

[Claims] a casing having a cylindrical working chamber space inside, an inflow hole communicating with the working chamber space, and an outflow hole communicating with the working chamber space; A shaft, a motor for rotating the shaft at high speed, a large number of ring spacers fixed to the shaft and rotating integrally with the shaft, and a large number of rotor blades sandwiched between the ring spacers and rotating integrally with the ring spacer, The rotor blade is formed by plastic deformation from a metal plate material, and the ring spacer is provided with a locking protrusion corresponding to the twist angle of the blade of the rotor blade, and this locking protrusion is attached to the root of the blade of the rotor blade. A turbo-molecular pump characterized by having a structure that is in close contact with the