JPS60243392A - Turbo molecular pump - Google Patents

Abstract

PURPOSE:To increase a compression ratio by a method wherein the length of robot blade is shortened gradually toward the side of exhaust port while the thickness of the rotor blade is thickened gradually toward the side of the same port, in a turbo molecular pump. CONSTITUTION:In a turbo molecular pump, in which a rotor 2 is fixed to a driving shaft 1, the basic sections 21 of respective rotor 2 are formed with larger diameters in substantially lower half (2g-2i) located at the side of an exhaust port B and the length (l) of the blade is shortened sequentialy as the position thereof approaches to the side of exhaust port B while the thickness of the rotor blade is thickened sequentially in the same manner. Accordingly, a compression ratio gradually increasing section L may be formed in a part of axial direction and whereby the compression ratio of main body of the pump may be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application J] The present invention relates to a turbomolecular pump that can exhibit excellent pumping speed performance even in a low vacuum region.

[Prior art] As is well known, a turbomolecular pump is
ftIL+ Ik mu-l-roof 柟髫j GI 1 いまぎ 11
For this purpose, the pump body rotates at high speed and has a certain inclination.
And a light pointing in the opposite direction! Stator type (stator blade) with
Exchange with! ! - a group of impellers usually arranged in multiple stages.

By the way, this kind of pump is the month at Onaka J'F.

Since the contraction ratio is low, the dynamic f1 year'j +1 is low f!
There is an inconvenience that the exhaust performance drops dramatically in the empty region. Therefore, in order to alleviate this drawback, the rotor rhombus and stake size are multi-staged in the 4d+ direction of the rhombus group, and 1. In this case, the small I becomes unwieldy, making it difficult to rotate at high speed, and is disadvantageous in terms of cost. Specifically, in the conventional turbo molecular pop, l O
-' The exhaust speed deteriorates rapidly from Shingin/Tsume of about -10-' Torr, and becomes almost equal to nothing at about 0.1 Torr.

Therefore, when operating a turbomolecular pump in a low vacuum region, (turbomolecular pump) + (mechanical two).

It is common practice to connect an appropriate auxiliary vacuum pump, such as a auxiliary vacuum pump (rebooster pump) + (rotary pump), to cover its antagonism capacity (A system).

The present invention was made based on the technical foreground as described above, and by improving and devising the configuration of the blade wheel group. The purpose is to provide a turbo molecular pump that has a large compression ratio increasing function, thereby extending the pump's exhaust MT fb region to the lower vacuum side.

f-stage to solve the L problem] In order to achieve such an object, the present invention rotates the rotor material of a blade wheel group in which the rotor material and the stator blades are arranged intersectingly at high speed. In a turbomolecular pump that exhausts air,
In the small part of the blade group (both in the axial direction), the length of the rotor as long as the size of the rotor is gradually shortened toward the exhaust side, and the thickness of the rotor as long as the size of the rotor as described with the exhaust is reduced. The present invention is characterized in that a compression ratio gradually increasing portion R section is provided, which is formed to have a gradually larger size toward the side.7 [Example J Hereinafter, an example of undeveloped Theory 111.

11Δ and FIG. 2 show examples of the configuration of the main parts of the turbomolecular pump according to the present invention, where zJ<L. Namely.

A rotor body 2H with a predetermined inclination angle is provided radially from the outer periphery of the base part 2, as shown in No. 21Δ, on a drive shaft l located at the center and rotationally driven by a prime mover (not shown). The rotor 2 (2a, 2b...2i) is connected to the drive shaft 1
The rotors 2a, 2b+1, . . .
The stators 3a, 3b---3h are positioned and fixed by being sandwiched between annular spacers 4.4, respectively, and the stator blades 3■ having an inclination angle opposite to that of the rotor body 21 are attached to the rotor blades 211, 211. The rotor elements 2 and the stator 1311 arranged alternately constitute a necessary blade wheel group. When the rotor blade 2■ rotates at high speed together with the drive shaft l, the blade wheel group that bends collides with gas molecules and becomes axially interlocked with the gas molecules, resulting in cooperative operation with the stator blade 3■. The function is to forcefully generate a flow from the intake port A at one end to the exhaust port B at the other end, and exhaust the air.

Now, in conventional turbo molecular pumps, the configuration of this impeller group is such that the length of the rotor is constant in the axial direction, or the length is formed between adjacent rotor blades at one point in the axial direction. It is customary to vary the blade length stepwise. Also, backsliding is when the rotor quality is uniformly formed in the axial direction. On the other hand, in the device according to the present invention, as shown in FIGS. 1 and 2, the exhaust
Approximately half a part located on the 2IB side (2g to 2i in the illustrated example)
Then, while the base portion 2I of each rotor 2 is made to have a large diameter, the blade length l of the rotor Q 2 II is set relatively to the exhaust r
−+ The stator r placed at the intersection with the rotor material 2
Of course, the blade length of B 311 will also be gradually shortened). Same 11! In addition, as is clear from FIG. 1, in this case, the lower half portions (2g to 2i) are made larger. Thus, the length l of the rotor quality 2 II
The compression ratio gradually increasing portion of this turbo-molecular pump is provided in the axial length portion of the impeller group where the thickness t and the thickness t are sequentially changed toward the exhaust port B side. (In addition, the rotors 2 located between the axial lengths need to shorten their likely lengths in sequence as described above, but for each rotor 2, it is necessary to change the blade length in the axial direction. ) In this way, if the large length 1 of each rotor 2 is formed to become shorter in turn toward the exhaust port B side, the depth of the passage that guides the gas molecules will be equal to the compression ratio. Since the ratio-increasing part is formed to be gradually narrower, the compression ratio of the exhaust gas sent through the rotor R211 and the stator ring 31 in the alternating direction is increased in each row 71 stage in that part. Also, each night is 2
If the blade thickness t of the rotor 2 is formed so that it becomes gradually thicker toward the exhaust side The compression ratio is gradually improved at each stage. Therefore, add these 1 to the same soup 1. Since the compression ratio of the exhaust gas is adjusted to the IJ effect due to the gradual increase in the exhaust gas, this turbo-molecular pump has the ability to exhaust air even in the low vacuum region.

As shown in 1- below, the present invention has a rotor length 1 and a blade thickness t)
It also has a means for forming a second female and provides a compression ratio gradual increase part in the blade wheel group, and the rotor on the +A side (28 to 2f in the illustrated example) has a blade length of While the blades with the same height and blade thickness are arranged, the exhaust 1-I
The 2.3-stage rotor on the B side (2g to 21 in the illustrated example) is
By making a sudden change from that on the intake port A side,
As shown in Fig. 2, the blade length 1 and the blade thickness t are later formed into III-order short ``'' and U'm-sized ``l-'' with the blade length 1 and blade thickness t facing the air hole B side. A compression ratio gradually increasing section is provided in the longer part.

Hereinafter, in the turbomolecular pump of the present invention listed in the Examples, its blades,'! , fj group, which effectively increases the compression ratio of the exhaust gas, the pumping speed curve can be extended toward the low vacuum side with a high ratio. In other words, it becomes +11 qi+) up to a lower position. Specifically, in the case of the illustrated example, even with a vacuum degree of I F'-10-'' Torr, a vacuum degree of less than 10-1 Torr and an evacuation speed of 0.1 Torr can be ensured. A certain amount of effective pumping speed can still be maintained even near ITorr l. Therefore, when using this pump, there is no need to worry about connecting auxiliary pumps in multiple stages for vacuum assistance as in the past, for example ( Even a simple exhaust system such as a turbo molecular pump) + (rotary pump) can be used.
From this point of view, the exhaust system can be simplified and costs can be reduced6.In addition, in the above embodiment, the case where the compression ratio gradually increasing part is provided at the end on the exhaust port B side is explained, but this gradually increasing part is at least What is necessary is just to provide it in a part of the axial direction. However, it is desirable to arrange blades with a constant length on the intake nA side in order to provide exhaust speed. Also,
In the illustrated example, the thickness of the stator is shown to be constant, or the thickness of the blades of the stakes may be increased to match the thickness of the blades of the rotor.

[Effect of the invention] Here it is! As mentioned above, the present invention improves the blade length and thickness of the rotor in the Z lj group [and also provides a compression ratio gradually increasing part in the bottom direction, so there is no need to The compression ratio increasing effect is exhibited in the pump body itself without adding a compression ratio increasing function, thereby providing a turbomolecular pump that can achieve an excellent pumping speed even in a low vacuum region.

[Brief explanation of the drawing]

Is Figure 1 a 1'X embodiment of the present invention? This is a longitudinal section 11 of the turbomolecular pump main body (11111!"I) shown in FIG.
They are a front view and a side view. l...Drive shaft 2.2a~2klllφ・To rotor 3a・3 @-[phase] Stator 2■...Rotor crack, 3■...Stator blade A conflict...Absorption % II, B conflict・Fist exhaust port L... Compression ratio gradual increase department representative Patent attorney Fu Akazawa

Claims (1)

[Claims] In a turbo-molecular pump that rotates at high speed the rotor joint of a group of impellers in which a rotor-type and a stator-type are arranged at an intersection of 11 and exhausts air, at least a part of the rotor group in the axial direction has a length of the rotor blades. A compression ratio gradually increasing portion is provided in which the thickness of the rotor blade is gradually increased toward the exhaust port side, and the thickness of the rotor blade is gradually increased toward the bleed port side. Turbomolecular pump.