JPS6355396A - Turbo vacuum pump - Google Patents

Abstract

PURPOSE:To permit exhaust in a wide vacuum range, by using an axial flow blade as a first exhaust element, a mixed flow blade as a second exhaust element of a suction stage and a swirl flow blade as a third exhaust element on an exhaust side. CONSTITUTION:A rotor impeller 4 of an axial flow blade is provided on an outside surface of an upper stage of a rotor 1 and rotor impellers of mixing flow blades comprising a plurality of dynamic blade grooves disposed in a circumferential direction are provided with its exhaust side. A swirl flow blade 9 is provided on an outside circumference of a second rotor 2. With the arrangement, performance of exhaust elements such as an axial flow blade, a mixing flow blade or the like disposed on an outside circumference of a bell-shaped rotor can be effected sufficiently, whereby a single pump can exhaust gas in a range covering an atmospheric pressure to an ultra high vacuum pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a turbo vacuum pump, and more particularly to a turbo vacuum pump capable of evacuation from atmospheric pressure to ultra-high vacuum with a single pump.

[Conventional technology]

Conventional turbo vacuum pumps that can achieve ultra-high vacuum, that is, turbo molecular pumps, are those that use axial flow blades for the exhaust element, or those that use axial flow blades for the exhaust element as described in Japanese Patent Publication No. 47-33446. A structure that uses a thread groove molecular pump in combination, and a structure that combines an axial flow vane, a thread groove molecular pump, and a centrifugal element as an exhaust element have been proposed, as described in Japanese Patent Application Laid-Open No. 60-125795.

[Problem that the invention seeks to solve]

Conventional turbomolecular pumps use axial flow vanes for their exhaust elements, so their performance drops rapidly when the intake pressure reaches around 10-2 to 1o-3 Torr, so it is necessary to use an oil rotary pump for auxiliary exhaust. there were.

In addition, in the case of Japanese Patent Publication No. 47-33446, by using an axial flow vane and a threaded groove molecular pump in combination, the inlet pressure can be controlled by IT.
It is possible to increase the pressure to o r r, but even in this case, an auxiliary pump was required although it was small.

Furthermore, in the case of JP-A No. 60-125795, although an auxiliary pump is not required and the exhaust can be exhausted from atmospheric pressure, the centrifugal element constituting the exhaust element has an inlet port pressure in the pressure range from ITorr to 760Torr. So,
Since a sufficiently large compression ratio cannot be obtained, it is necessary to increase the number of blade rows of the centrifugal element, which not only makes it difficult to design a high-speed rotating body, but also causes large disc friction losses in the centrifugal element. However, there were drawbacks such as the need to significantly increase the capacity of the motor.

An object of the present invention is to provide a turbo vacuum pump that is capable of evacuation from atmospheric pressure to ultra-high vacuum with a single pump.

[Means for solving problems]

The present invention provides an axial flow blade as a means for solving the above problems.

By combining optimal exhaust elements such as mixed flow blades and swirl blades, ultra-vacuum can be obtained through high-speed rotation. That is, a fishing mirror-shaped first rotor and a second rotor disposed inside the fishing mirror-shaped first rotor are coaxially provided in the casing, and axial flow blades or A first exhaust element consisting of a mixed flow vane and a second exhaust element using a mixed flow vane or a screw groove molecular pump are arranged in upper and lower stages, and the second exhaust element is arranged inside a fishing mirror rotor.
A third exhaust element of a swirl vane is arranged on the outer circumference of the rotor,
The third exhaust element is arranged inside the first and second exhaust elements.

[Effect]

In the above configuration, if an axial flow blade is used for the first exhaust element on the intake side, a mixed flow blade is used for the second exhaust element, and a swirl blade is used for the third exhaust element on the exhaust side, gas molecules from the intake port is compressed at a pressure of 10''''3 Torr or less in the axial flow blade section, and 1
At A, it is compressed at a pressure of 10-3 to I Torr in the mixed flow wing section, further compressed at a pressure of I Tor or more in the swirl wing section, and exhausted from the exhaust port. In this manner, each evacuation element effectively operates at a predetermined pressure to obtain a high vacuum, and a single pump can evacuate from atmospheric pressure to ultra-high vacuum.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

FIG. 1 is a longitudinal sectional view showing the configuration of the present invention.

In the figure, a fishing mirror-shaped first rotor 1 is provided in a casing 2, and a second rotor 3 is provided inside this rotor 1.
is located. The rotors 1 and 3 are fastened to a coaxial motor shaft 14 with a nut 15, and as the motor shaft 14 rotates, the rotors 1 and 3 rotate together. Further, the motor shaft 14 is
A bearing 17 supported by the lower casing 16 and a base 18
It is supported via a bearing 19 supported by.

Rotor blades 4 of axial flow blades are provided on the intake side of the fishing mirror-shaped first rotor, that is, on the upper outer peripheral surface of the rotor 1,
Also, opposite to the rotor blades 4, stator blades 6, which are axial flow blades supported by a stator ring 5, are provided.

Furthermore, the exhaust side of the rotor 1, that is, the lower outer peripheral surface of the rotor 1 has a specific angle with respect to the axis of the rotor 1,
A mixed-flow blade 7 is provided with a plurality of rotor blade grooves arranged in the circumferential direction, and the stator surface facing the rotor blade 7 is provided with the A stator blade 8 is provided as a mixed flow blade formed of stator blade grooves arranged at an angle opposite to the rotor blade grooves.

A second rotor disposed inside the fishing mirror-shaped first rotor 1.
A swirl blade 9 is provided on the outer periphery of the rotor 3, and a ventilation passage 10 is provided on the stator surface facing the swirl blade 9. As shown in FIG. 2, a partition portion 11 is provided at one location in the circumferential direction of the ventilation path 1o to partition the ventilation path 1o with a small gap from the swirl blades 9. A suction port 121 is provided on both sides of the vortex mold 9 at the front in the rotation direction, and a discharge port 13 is provided at the rear in the rotation direction.

Further, a water jacket 22 is provided in the lower casing 16 to cool the heat generated by the compression of the swirl vanes and to cool the motor rotor 20 and motor stator 21 provided at the lower end of the motor shaft 14. Note that 24 is an exhaust port, and 25 is a flange.

Next, the operation of the present invention having the above configuration will be explained.

Due to the high-speed drive of the motor rotor 20, the rotors 1 and 3 rotate together through the common motor shaft 14, and gas molecules from the intake port 23 are compressed by the rotor blades 4 and stator blades 6 rotating in the axial flow blade section. It is further compressed by rotor blades 7 formed from rotor blade grooves rotating in the mixed flow blade part and stator blades 8 formed from stator blade grooves, and then compressed by the vortex type 9 in the swirl blade part and the ventilation passage on the stator surface. 10 and is exhausted from the exhaust port 24 via the discharge port 13. In this way, the vacuum chamber connected to the flange 25 can be evacuated from atmospheric pressure to ultra-high vacuum.

That is, when the rotors 1 and 3 are rotated, the suction side pressure of the vacuum chamber upstream of the vortex type, the axial flow blade portion, and the mixed flow blade portion can be made to be approximately ITorr due to the effect of the vortex type 9.

Furthermore, when the mixed flow blade becomes I Torr, the exhaust action of the mixed flow type can reduce the intake side pressure of the vacuum chamber upstream of the mixed flow type and the axial flow blade to about 10-4 to 10'''' Torr. In addition, the intake side pressure of the axial flow blade section is 10-4 ~
When the pressure reaches 10-' Torr, the inside of the vacuum chamber can be brought down to about 10-' Torr by the action of the axial flow blade.Furthermore, if the vacuum chamber is further subjected to baking treatment,
It is possible to obtain an ultra-high vacuum of approximately "" Torr or less.

The exhaust characteristics of each exhaust element described above are shown in FIG.

That is, axial airfoils operate effectively at pressures below 10-3 Torr. Also, the mixed flow type has a 10
Operates effectively at pressures from -3 to ITorr. Furthermore, it can be seen that the vortex type operates more effectively than the axial flow blade and the mixed flow type at pressures higher than ITorr. In addition, in the same figure, it can be seen that the centrifugal element described in the prior art has almost the same characteristics as the mixed flow type, but the centrifugal element has a larger disc friction loss than the mixed flow type, so the centrifugal element was used instead of the mixed flow type. It is not recommended to use it.

After the exhaust process described above, a steady state is reached, but in a steady state, the number of blade rows of each exhaust element at the time of design differs slightly, but axial flow blades are under pressures of 1o-A11 to 1O-3T o r r. , the mixed flow type is under a pressure of 10-3 to ITorr,
The vortex type operates under pressures from 1 to 760 Torr.

In the above embodiment, an axial flow blade and a mixed flow type were used for the exhaust element disposed on the outer periphery of the rotor 1, but both of them may be of a mixed flow type. It is also possible to arrange an axial flow blade and a screw groove molecular pump below it, and by combining these exhaust elements with a swirl type exhaust element arranged around the outer periphery of the rotor 3, the same effect as in the embodiment can be obtained. be able to.

〔Effect of the invention〕

As described above, according to the present invention, since each element and the optimum exhaust element are combined in a structure, the total number of blade row stages can be reduced, thereby facilitating the design as a high-speed rotating body.

In addition, since the rotor with a vortex type is placed inside the fishing armor type rotor, the axial length of the rotor is significantly shortened, and the diameter and circumferential speed of the tip of the blade of the vortex type are small. Disk friction loss occurring in the wing section is significantly reduced. These make it easy to rotate at high speeds, making it possible to fully demonstrate the performance of exhaust elements such as axial flow blades and mixed flow types arranged around the outer periphery of the fishing-armor type rotor, allowing for applications ranging from atmospheric pressure to ultra-high vacuum. It becomes possible to exhaust the air with one pump.

In addition, since the motor shaft bearing is placed under atmospheric pressure, the lubricating oil from the bearing will not diffuse back to the intake side, eliminating the risk of contaminating the vacuum chamber with oil and maintaining the cleanliness of the pump. be able to.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view showing the configuration of an embodiment of the present invention, and FIG.
The figure is an explanatory view showing the state of the swirl vane section in Fig. 1 viewed from the axial direction, and Fig. 3 is a view showing the exhaust characteristics of each exhaust element. 1... Rotor, 2... Casing, 3
... Rotor, 4... Axial flow blade rotor blade,
5...Statoring. 6... Axial flow blade stator blade, 7... Mixed flow blade rotor blade. 8...Mixed flow blade stator blade. 9... Vortex blade, 10... Ventilation path, 11.
- Partition part, 12... Suction port, 13... Discharge port, 14... Motor shaft. 16...Lower casing, 2o...Motor rotor, 22...Water jacket, 23...Intake port. Figure 1

Claims (4)

[Claims] (1) A bell-shaped first rotor disposed in a casing, a second rotor provided inside the first rotor and capable of rotating coaxially with the first rotor, and the first rotor The first and second exhaust elements each include a group of blades arranged in upper and lower stages on the outer periphery of the second rotor, and the third exhaust element is a swirl blade formed on the outer periphery of the second rotor. Second
A turbo vacuum pump characterized in that a third exhaust element is disposed inside the exhaust element. (2) The turbo vacuum pump according to claim 1, wherein the first exhaust element is provided with an axial flow blade, and the second exhaust element is provided with a mixed flow blade. (3) The turbo vacuum pump according to claim 1, wherein mixed flow blades are arranged on the first and second exhaust elements. (4) The turbo vacuum pump according to claim 1, wherein an axial flow blade is arranged in the first exhaust element and a thread groove molecular pump is arranged in the second exhaust element.