JP2001323892A - Turbo type vacuum instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hybrid system turbo type vacuum instrument of which an axial length is shortened. SOLUTION: The turbo type vacuum instrument is provided with a turbo molecule pump TMP disposed at a transition flow area from a suction port 1K to a circumferential flow pump SP and formed between a rotor 2 and a housing 1; and a screw groove pump NP disposed at a transition flow area between the turbo molecule pump TMP and the circumferential flow pump SP and formed between the rotor 2 and the housing 1. A gas from the suction port 1K is discharged from a discharge port 1H provided on the housing 1. An outer periphery wall and an inner periphery wall have cylindrical parts 2P, 2L corresponding to a surface of the housing 1 and a circular disc part 2V connecting the cylindrical parts 2P, 2L to a rotation shaft 3. The turbo molecule pump TMP is formed between an outer periphery wall of this cylindrical part 2P and the housing 1 and the screw groove pump NP is formed between an inner periphery wall of the cylindrical part 2L and the housing 1. Accordingly, a shaft length as a vacuum instrument can be shortened and is advantageous for a small size.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotating shaft which is rotatably supported in a housing via a bearing, rotates the rotating shaft at a high speed, and drives a rotating body fixed to the rotating shaft to rotate the rotating body. The present invention relates to a turbo vacuum device that performs an exhaust function by a body turbo mechanism.

[0002]

2. Description of the Related Art As such a turbo vacuum device, single-purpose devices include a turbo dry pump and a turbo molecular pump. Further, as a turbo type composite device, that is, a hybrid type turbo type device, a combination type of a turbo type dry pump and a turbo molecular pump, or a combination of a turbo type dry pump and a turbo molecular pump and a thread groove pump further can be exemplified. Such a hybrid-type turbo vacuum device has been widely practiced conventionally. For example, as a general example, Japanese Patent Application Laid-Open No. 63-852 / 1988
No. 87, “Vacuum pump”, may be mentioned. It has an inlet above the housing and an outlet below. Then, a turbo molecular pump, a screw groove pump and a circumferential flow pump, that is, a turbo type dry pump are arranged in the housing from the intake port side.
The specific configuration is as shown in FIG.

FIG. 5 mainly shows a turbo type dry pump.
FIG. 3 is a longitudinal sectional view showing a configuration of a hybrid vacuum pump in which a turbo-molecular pump and a screw groove pump are installed on the intake port side, and schematically shows the configuration of a conventional vacuum pump. First, a turbo dry pump will be described.

[0004] This type of turbo-type dry pump DP
Is composed of a cylindrical housing 1 and this housing 1.
And a rotating body (hereinafter referred to as a rotor) 2 rotatably mounted on a bearing by a bearing. Specifically, the housing 1 has a bottomed shape as shown in the figure, and an opening at one axial end (upper side) is an intake port 1K, and an exhaust port at the other axial end (lower side) is in the middle. 1H is installed. The circumferential flow pump SP is constituted by a combination of the circumferential portion 2B of the rotor 2 and the stator 1T formed on the inner periphery of the housing 1. The circumferential flow pump SP is provided in a plurality of stages, that is, in a multistage shape in the axial direction of the rotor 2. A groove 1G is formed at an inner peripheral end of the stator portion 1T, and a groove 2G is also formed at an outer peripheral end of the rotor circumferential portion 2B. An air flow is generated by the relative displacement between the two grooves 1G and 2G, and the pump function is activated. This pump function is sequentially connected to the subsequent stage via the flow path 1N, and the gas is compressed as a whole. Although the two are not in contact with each other, a circumferential flow pump SP is formed by a combination thereof. By the operation of the multi-stage circumferential flow pump SP, the gas pressure-fed by the thread groove pump mechanism NP is further compressed, fed downward, and exhausted to the exhaust port 1H via the exhaust path 1R. That is, the circumferential flow pump SP of each stage compresses the gas on its circumference, and sends out the gas to the next stage circumferential flow pump SP via the flow path 1N at the end, and this is sequentially performed for each stage and exhausted. .

[0005] The basic principle and operation of the turbo-type dry pump have been described above. The rotor 2 has an H-shaped cross section as shown in the drawing, and a central portion thereof is connected to a rotary drive mechanism. Axle-mounted. Below this, an electric motor (motor) 4 for driving the rotating shaft 3 is integrally installed. The electric motor 4 is constituted by a combination of an armature winding 4M provided on the inner periphery of the housing 1 corresponding to the armature and a rotor winding 3M provided on the rotating shaft 3 corresponding to the rotor. The rotation shaft 3 is rotated at a high speed by the supply of the electric energy 9. In the drawing, 3S is a threaded portion at the upper end of the rotating shaft 3 and cooperates with the nut 3N.
The rotor 2 is fixed to the rotating shaft 3. The dry pump shown in FIG. 5 is a so-called hybrid dry pump in which the thread groove pump NP and the turbo molecular pump TMP are installed above the circumferential flow pump SP as described above.

In the following, this structure will be described in detail. Immediately above the circumferential flow pump SP, a thread groove 1M is firstly cut in the upper part of the inner periphery of the housing 1, and the rotor 2 is moved closer to the thread groove 1M. The upper cylindrical portion 2P faces each other. A combination of the thread groove 1M and the cylindrical portion 2P of the rotor 2 constitutes a so-called thread groove pump mechanism NP. With this configuration, the rotation of the rotor 2 compresses the molecules in the transition region of the gas and sends them downward.

[0007] Further, a turbo molecular pump TMP is installed on the side of the housing 1 closest to the intake port 1K. This turbo-molecular pump is composed of a combination of a plurality of stages of rotary blades RB extended on the outer periphery of a cylindrical portion 2P and fixed blades FB provided on the inner periphery of the housing 1 side, and the relative high speed rotation between the two. Generates a molecular flow and discharges the molecules downward.

[0008]

A basic problem in such a vacuum system using the hybrid system, that is, in a vacuum system in which two or more pump functions are combined, is that the vacuum system becomes large. By stacking various pumps in the axial direction, the overall length in the axial direction increases, and the natural frequency of the exhaust system decreases. As a result, there is a problem that resonance occurs at a rotational speed near the natural vibration frequency and high-speed rotation is not possible. In addition to increasing the size of the pump itself, it has a back pump (turbo dry pump, screw groove pump, etc.) as a turbo molecular pump, so the vacuum can be reduced to a sufficiently low pressure with the back pump. If the turbo-molecular pump is operated in a state where it is not pulled, the load is excessive, and therefore, there is a problem that a large-capacity type, that is, a large-sized electric motor (motor) for rotating this pump must be used. As described above, the enlargement of the pump itself also causes an increase in the size of the entire vacuum exhaust line.

[0009] The characteristics of the hybrid system make it possible to achieve a pressure environment from near atmospheric pressure to a high vacuum. In particular, in a turbo-molecular pump requiring a clean environment, oil-free and long life are required. Therefore, a magnetic bearing is employed as a rotor bearing. In this case, in a configuration in which the back pump is provided coaxially to bring the pressure of the exhaust port during operation closer to the atmosphere, the pressure difference from the intake port side becomes large, and the load in the axial direction (thrust) becomes excessive. For this reason, the axial magnetic bearing mechanism becomes large in size and its control becomes difficult.

Further, when a dynamic pressure gas bearing (for example, a foil bearing) is used instead of the magnetic bearing, it is necessary to supply cooling to the inside of the pump, that is, to the bearing, in order to prevent the bearing from becoming hot. In supplying the cooling gas, a sealing portion for preventing leakage is provided because it is necessary to prevent the cooling gas from leaking into the vacuum exhaust system. However, although the sealing portion is provided, the leakage of the cooling gas is inevitable, and the supply of the cooling gas needs to be limited to a predetermined amount. An object of the present invention is to provide a turbo vacuum device which solves such a problem.

[0011]

In order to solve the above-mentioned problems, a turbo-type vacuum apparatus provided by the present invention supports a rotary shaft in a housing via a bearing, rotates the rotary shaft at high speed, and rotates the rotary shaft at a high speed. Between the circumferential portion of the rotating body attached to the rotating shaft and the stator formed on the inner circumferential surface of the housing,
A circumferential flow pump for compressing gas from the suction port of the housing, and a gas flow region disposed between the suction port and the circumferential flow pump, which is disposed between the rotating body and the housing. And a thread groove pump arranged between the rotating body and the housing, the turbo molecular pump being disposed so as to act on a transition flow region of gas between the turbo molecular pump and the circumferential flow pump. A turbo-type vacuum device that drives a rotating shaft to rotate a rotating body, and exhausts gas from the intake port through an exhaust port provided in a housing opposite to the intake port with respect to the circumferential flow pump. Wherein the rotating body has a cylindrical portion having an outer peripheral wall and an inner peripheral wall corresponding to the surface of the housing, and a disk portion connecting the cylindrical portion to a rotating shaft. At the Configure the turbomolecular pump, and is obtained by forming the screw groove pump at between the inner peripheral wall and the housing of the cylindrical portion. Therefore, the axial length of the vacuum device can be shortened, which is advantageous for miniaturization.

Further, the present invention provides four kinds of vacuum pumps each having a spiral groove formed in a disk portion between a thread groove pump and a circumferential flow pump, and a spiral groove pump having a housing surface corresponding to the spiral groove. It is a combination of pumps. Therefore, the exhaust characteristics can be improved by the four types of pumps, and the size of the pump device can be reduced. Still further, the present invention provides a bearing comprising a dynamic pressure gas bearing, a supply mechanism for externally supplying a cooling gas for cooling the dynamic pressure gas bearing, and a discharge mechanism for discharging the cooling gas from the atmosphere. A sealing mechanism provided and for suppressing the cooling gas from entering the exhaust system by each pump is constituted by a very small gap between the rotating circumferential portion of the circumferential flow pump and the housing.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The contents of the present invention will be described below with reference to the embodiments shown in the drawings. First, FIG. 1 is a longitudinal sectional view showing the configuration of a turbo type vacuum apparatus firstly provided by the present invention. In the embodiment shown in the drawing, a turbo type dry pump, a turbo molecular pump and a screw groove pump are organically similar to FIG. 1 shows an example of a vacuum pump of a hybrid type which is combined with each other.

In FIG. 1, the components and components denoted by the same reference numerals as those in FIG. 5 are the same as those in FIG. 5, and their functions are basically the same, and detailed description is omitted. In FIG.
The difference from FIG. 5 lies in the configuration of the cylindrical portion 2P constituting the turbo-molecular pump and the configuration of the thread groove pump, which is a feature of the present invention. That is, in the present invention, as shown in FIG.
And extends in the vertical axis direction around the disk portion 2V fixed to the center. A pump cylindrical portion 1P on the housing 1 side is formed on an inner peripheral surface of the lower thread groove pump cylindrical portion 2L so as to face the pump cylindrical portion 1L on the housing 1 side.
A thread groove NM is engraved on P.

When the cylindrical portion 2L rotates, the thread groove pump NP functions in cooperation with the thread groove NM.
As described above, the screw groove pump NP is characterized by being installed inside the cylindrical portion of the rotor 2, but with such a configuration, the axial length of the entire pump can be reduced. This makes it possible to increase the natural frequency of the entire pump, and enables high-speed rotation as the pump. The thread groove pump NP exhausts gas in the transition region between the turbo molecular pump TMP and the turbo type dry pump DP (circumferential flow pump SP), and is capable of high-speed rotation and has excellent exhaust characteristics. It works effectively as an auxiliary pump.

Next, a turbo vacuum device provided secondly by the present invention is characterized in that a spiral pump is organically coupled by cooperation of a housing and a disk of a rotary body in a thread groove pump. FIG. 2 is a diagram showing the configuration. FIG. 2 is not a longitudinal sectional view of the entire vacuum equipment, but is an enlarged longitudinal sectional view showing only a main part. Components indicated by the same reference numerals as those in FIG. 1 are the same as those in FIG. The operation is performed, and the detailed description is omitted. In the embodiment shown in FIG. 2, the thread groove pump NP provided on the inner cylinder side of the cylindrical portion 2L of the rotor 2 is installed below the disk portion 2V. Although this installation position is different from the embodiment of FIG. 1, the arrangement order of the turbo molecular pump → the screw groove pump → the turbo type dry pump is basically not different.

In the present invention shown in FIG. 2, a spiral groove 2E is formed in the lower surface of the disk portion 2V of the rotor 2. The upper end surface of the pump cylindrical portion 1P of the housing 1 faces the spiral groove 2E. A spiral pump EP is formed by cooperation of the cylindrical portion 2L and the spiral groove 2E. This spiral pump E
With the addition of P, the four pumps are organically coupled to one another, further improving the evacuation characteristics. Moreover, regardless of the thread groove pump NP or the spiral pump EP, it is installed in the region of the cylindrical portion 2L of the rotor 2, and the axial length is not increased, and the natural frequency is maintained high and high-speed rotation is possible. Becomes Therefore, the function of the turbo molecular pump TMP is sufficiently exhibited.

Further, in the turbo-type vacuum apparatus provided thirdly by the present invention, the spiral pump EP is arranged on the disk portion 2V of the rotor 2 while the arrangement of the thread groove pump NP is the same as that of the prior art. Things. FIG. 3 shows the configuration. That is, FIG. 3 is the same as the configuration shown in FIG. 5 except for the above-mentioned spiral pump EP.
The parts denoted by the same reference numerals as those in FIG. 5 are the same as those in FIG. 5 and perform the same functions, and detailed description thereof will be omitted. And the corresponding uppermost stator part SP
It is constituted by and. In the illustrated example, the thread groove pump NP is provided in parallel with the turbo molecular pump TMP in the axial direction, and the axial length is not reduced at this point. However, the combination of the spiral pump EP makes four types of pumps as a whole. The shaft length is shortened and the exhaust characteristics are improved.

The turbo type vacuum apparatus provided by the present invention in a fourth aspect is a hybrid type vacuum apparatus comprising three kinds of pumps (turbo molecular pump + screw groove pump + turbo type dry pump). This is an improved bearing mechanism. That is, the bearing employs a dynamic pressure gas bearing system. Specifically, a foil bearing is used to support the rotor 2 in a non-contact manner. At the same time, the gas supply system for cooling the bearing is devised, and is specifically as shown in FIG.

FIG. 4 shows a conventional configuration (FIG. 5) in which only the bearing mechanism is a foil bearing and a gas cooling supply mechanism is added. Hereinafter, this point will be described in detail. In FIG. 4, a rotary shaft 3 is formed with a flange portion 3F at a middle stage, and a foil bearing 5 for thrust is provided between upper and lower surfaces of the flange portion 3F and the housing 1. It is interposed. A radial foil bearing 6 is provided above and below the rotary shaft 3 between the cylindrical portion 1E of the housing 1 and the upper and lower portions in two stages. The foil bearings 5 and 6 generate gas dynamic pressure in a wedge-shaped space formed between the upper foil and the peripheral surface of the rotary shaft, and support the rotary shaft 3 in a non-contact state by the dynamic pressure. The foil bearing is usually provided with an under foil for elastically supporting the upper foil.

Although such a foil bearing is of a non-contact support type, it is heated to a high temperature during operation. Then, cooling gas (inert gas such as nitrogen) is supplied to the foil bearing 5,
6 and the surrounding area. In the figure, 1R is a cooling gas supply port. The supplied cooling gas passes through the passage of the electric motor 4 through the passage, reaches the foil bearings 5 and 6, and cools the two foil bearings 5 and 6. After cooling, the cooling gas flows upward inside the cylindrical portion 1E of the housing 1, flows downward outside, and is discharged to the outside through the discharge port 1D.

In this case, the rotating part of the pump mechanism and the housing are not in contact with each other due to the foil bearing system. Therefore, the cooling gas enters the vacuum exhaust system and is exhausted from the exhaust port 1H. It is necessary to increase the size of the exhaust gas treatment equipment disposed after the turbo type vacuum equipment. To prevent this, it is necessary to suppress the intrusion of the evacuation system. Therefore, in the present invention, in the cooling gas flow path system, a seal portion LS for minimizing the intrusion is provided between the rotating portion and the housing 1 side. The seal portion LS is configured such that the lowest circumferential portion 2B on the rotor 2 side of the circumferential flow pump SP, that is, the circumferential portion closest to the exhaust port and the step portion 1Z on the housing 1 are brought as close as possible. ing. The present invention is characterized in that the seal portion LS is provided in such a portion. In the turbo vacuum device provided in the fourth embodiment, the arrangement and arrangement of the pumps are not limited to the illustrated example. For example, as shown in FIG. 1, the present invention can be applied to an embodiment in which a thread groove pump NP is disposed inside a cylindrical portion to reduce the axial length.

Although the features of the present invention have been described in detail above, the present invention is not limited to the embodiments shown in the above and illustrated examples, but includes many other modifications utilizing the above features. For example, in the case of a screw groove pump NP or a spiral pump EP, it is a matter of choice whether to provide the screw groove or the spiral groove on the rotor side or on the housing side. Include. Further, a thread groove pump may be provided on both sides of the circular outer cylinder of the cylindrical portion. Further, in the illustrated example, the turbo molecular pump TM
Although P and the circumferential flow pump NP are shown as an embodiment in which three or four stages are provided, this is a matter for drawing to facilitate understanding of the features of the invention, and actually has seven to ten stages. Therefore, the present invention is not limited to these numbers of stages. The screw groove and the spiral groove can be double grooves. Regarding the foil bearing system, in the illustrated example, an example of a system having an upper foil and an under foil is shown, but there is also a system in which one foil serves as both foils. May be used. The present invention is not limited to the illustrated example in these points as well.

[0024]

The turbo vacuum device provided by the present invention is as described in detail above, and is a hybrid vacuum device in which a turbo dry pump, a turbo molecular pump and a screw groove pump are organically combined. Also, there is an advantage that the axial length can be shortened and the natural frequency is high, so that high-speed rotation, which is a condition of a turbo-type vacuum device, can be realized without any support and a high vacuum can be obtained. Moreover, it provides compact, lightweight and economical vacuum equipment. Even if a dynamic pressure gas bearing system is adopted for the bearing, there is an advantage that the cooling can be performed smoothly, and a turbo-type vacuum device that meets the needs without adversely affecting the exhaust system can be provided.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a configuration of a turbo vacuum device according to the present invention.

FIG. 2 is a diagram showing a main part of a turbo vacuum device according to the present invention.

FIG. 3 is a diagram showing a main part of a turbo vacuum device according to the present invention.

FIG. 4 is a diagram showing a main part of a turbo vacuum device according to the present invention.

FIG. 5 is a diagram showing a configuration of a conventional turbo vacuum device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Housing 1T ... Stator 1K ... Intake port 1H ... Exhaust port 1P ... Cylindrical part for pumps 1E ... Cylindrical part 1N ... Flow path 1G ... Groove 1Z ... Step part 2 ... Rotor 2V ... ... Disc 2G ... Groove 2B ... Circumference 3 ... Rotating shaft 4 ... Electric motor 5,6 ... Foil bearing 9 ... Electric energy

Claims (4)

[Claims] 1. A rotating shaft is supported in a housing via a bearing, and the rotating shaft is rotated at a high speed. The rotating shaft is formed on a circumferential portion of a rotating body attached to the rotating shaft and an inner circumferential surface of the housing. Between the stator, a circumferential flow pump for compressing the gas from the suction port of the housing, and arranged to act on the molecular flow region of the gas from the suction port to the circumferential flow pump,
A turbo-molecular pump configured between the rotating body and the housing, and a turbo-molecular pump disposed between the turbo-molecular pump and the circumferential flow pump so as to act on a transition flow region of gas; And a thread groove pump configured between them, and drives the rotating shaft to rotate the rotating body,
In a turbo vacuum device for exhausting gas from the intake port through an exhaust port provided in a housing opposite to the intake port with respect to the circumferential flow pump, the rotating body has an outer peripheral wall and an inner peripheral wall of the housing. A cylindrical portion corresponding to the surface, a disk portion connecting the cylindrical portion to the rotating shaft, and the turbo molecular pump is formed between the outer peripheral wall of the cylindrical portion and the housing; A turbo-type vacuum device comprising the screw groove pump between a peripheral wall and a housing. 2. A spiral groove pump, wherein a spiral groove is formed in a disk portion between the screw groove pump and the circumferential flow pump, and the spiral groove pump has a housing surface corresponding to the spiral groove. 2. The turbo vacuum device according to claim 1. 3. A rotating shaft is rotatably supported in a housing via a bearing, and the rotating shaft is rotated at a high speed. The rotating shaft is formed on a circumferential portion of a rotating body attached to the rotating shaft and an inner circumferential surface of the housing. Between the stator, a circumferential flow pump for compressing the gas from the suction port of the housing, and arranged to act on the molecular flow region of the gas from the suction port to the circumferential flow pump,
A turbo-molecular pump configured between the rotating body and the housing, and a turbo-molecular pump disposed between the turbo-molecular pump and the circumferential flow pump so as to act on a transition flow region of gas; And a thread groove pump configured between them, and drives the rotating shaft to rotate the rotating body,
In a turbo-type vacuum device for exhausting gas from the intake port through an exhaust port provided in a housing opposite to the intake port with respect to the circumferential flow pump, an outer peripheral wall of the rotating body corresponds to a surface of the housing. It has a cylindrical portion and a disk portion that connects the cylindrical portion to the rotating shaft, a spiral groove is formed in the cylindrical portion, and a spiral groove pump is configured with a housing surface corresponding to the spiral groove. Turbo type vacuum equipment. 4. A rotating shaft is rotatably supported in a housing via a bearing, and the rotating shaft is rotated at a high speed. The rotating shaft is formed on a circumferential portion of a rotating body attached to the rotating shaft and on an inner circumferential surface of the housing. Between the stator, a circumferential flow pump for compressing the gas from the suction port of the housing, and arranged to act on the molecular flow region of the gas from the suction port to the circumferential flow pump,
Comprising a turbo-molecular pump configured between the rotating body and the housing, driving the rotating shaft to rotate the rotating body,
In a turbo type vacuum apparatus for exhausting gas from the intake port through an exhaust port provided in a housing opposite to the intake port with respect to the circumferential flow pump, a bearing is constituted by a dynamic pressure gas bearing, A supply mechanism that supplies a cooling gas from the outside to cool the gas bearings, a discharge mechanism that discharges the cooling gas from the atmosphere, and a seal mechanism that suppresses the entry of the cooling gas into the exhaust system by each pump are provided. A turbo-type vacuum device comprising a minimal gap between a rotating circumference of the circumferential flow pump and a housing.