JPS6229797A - Turbo molecule pump - Google Patents

Abstract

PURPOSE:To make it possible to exhaust at high speed even under low vacuum by arranging a wedge-shaped vortex flow groove on both the outer periphery of a rotor and the inner periphery of a stator respectwely, and communicating one partition of the vortex flow groove to a suction side stage and its other partition to an exhaust side stage. CONSTITUTION:In a rotor 1, a moving blade groove 4 and a wedge-shaped vortex flow groove 5 are dug on a suction side and an exhaust side respectively. On a stator 3 opposite to the rotor 1, a stationary blade 6 and the wedge-shaped vortex flow groove 7 are dug on the suction side and the exhaust side respectively. The moving blade groove and stationary blade groove can perform both functions as an axial flow blade and a screw groove type molecule pump to produce practicable high compression ratio and high speedy exhaust function. Consequently, since the exhaust function can be effectively carried out up to about 10 Torr, a higher exhaust speed can be taken even under low vacuum state.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a turbo-molecular pump, and particularly to a turbo-molecular pump having a wide operating range on the low vacuum side.

[Background of the invention]

Conventional turbomolecular pumps generally use axial flow blades that have excellent pumping performance in the molecular flow region. but,
This type of turbomolecular pump is 10” to 10-”To
There was a drawback that when the pressure reached rr or more, the pumping speed suddenly decreased. For this reason, 10-"~10-' To
When used as an exhaust pump in a semiconductor manufacturing process such as dry etching, which repeats a high vacuum of RR and a low vacuum of 10 to 10-'' Torr in a short period of time, the exhaust speed at low vacuum is low, so The evacuation time was long, which hindered the improvement of throughput.In order to solve the above drawbacks, we combined the other flow molecular pump and the screw groove molecular pump as disclosed in Japanese Patent Publication No. 47-33446. A composite type turbomolecular pump has been proposed, and the range where the pumping speed decreases less is 10-' to 10-''T.
It has expanded to the low vacuum area of orr. However, even with this composite type pump, a sufficiently large pumping speed cannot be obtained in the viscous flow region of 10-1 Torr or more, and the
A turbomolecular pump having a pumping speed as high as rr is desired.

[Purpose of the invention]

An object of the present invention is to provide a turbomolecular pump that has a sufficiently high pumping speed even in a low vacuum of about 1'0 Torr and has a wide operating range on the low vacuum side.

[Summary of the invention]

The present invention provides a turbo-molecular pump that performs an exhaust action using a multi-stage group of blades disposed on a cylindrical rotor extending in the axial direction within a casing and a stator located on the opposite surface of the rotor. A plurality of wedge-shaped swirl grooves are arranged in the circumferential direction on the internal circumferential surface of the stator and the inner circumferential surface of the stator facing the stator, and a cylindrical surface is formed that separates the adjacent swirl grooves in a part of the circumferential direction of the stator and is separated from the rotor by a small gap. The present invention is characterized in that a partition portion is provided, and one of the swirl grooves on both sides of the partition portion is configured to communicate with the intake side stage, and the other vortex groove communicates with the exhaust side stage.

It is known that the vortex element shown in FIG. 1 can obtain a large compression ratio of around 10 in a single stage in a viscous flow region.A is a rotor, and b is a stator. However, when stacking these vortex elements in multiple stages to obtain high compression, the stator must be split in half, and the axial gap between the rotor and stator must be kept small to avoid deteriorating performance. Due to problems such as the number of steps required, it was not generally used in multiple stages. FIG. 2 shows the basic configuration of the present invention, in which a plurality of wedge-shaped swirl grooves CFd are provided in the outer circumferential surface of the rotor a and the inner circumferential surface of the stator b, respectively, in the local direction. When a vortex is generated as shown in the figure, it performs an exhaust effect. That is, by converting the speed head given to the fluid by the wedge-shaped vortex groove C provided in the rotor a into a static pressure head by the wedge-shaped vortex groove d provided in the stator b, the vortex is increased while increasing the pressure. Exhaust action occurs in the process of progressing in the direction of rotation. FIG. 3 shows a cross section of the swirl groove d communicating with the exhaust side stage, and FIG. 4 shows a cross section of the swirl grooves c and d facing each other other than the partition portion. When the above configuration is provided in multiple stages on the exhaust side of a turbo-molecular pump, the exhaust action is maintained even in a low vacuum in a viscous flow region of about 10 TOrr, and a sufficiently high pumping speed can be obtained even in a viscous flow region of about 10 TOrr. In addition, with the above configuration, there is no need to make the stator half a hole, multi-stage swirl grooves can be fabricated in one piece, and there are no manufacturing problems because there is no need to reduce the axial gap. do not have.

[Embodiments of the invention]

One embodiment of the present invention will now be described with reference to FIG. 5. In FIG. 5, a ronita 1 is disposed within a casing 2 and extends in the direction of its axis, forming a cylindrical shape. A stator 3 is arranged on the opposite surface of the rotor 1 and attached to the casing 2. The rotor 1 has a rotor blade groove 4 on the suction side;
A wedge-shaped vortex groove 5 is dug on the exhaust side, a stator blade groove 6 is dug on the opposite surface of the stator 3 on the intake side, and a wedge-shaped vortex groove 7 is formed on the exhaust side. The rotor blade groove and stationary blade groove will be explained in detail later. In addition, the rotor 1 has a rotating shaft 8
It is concluded with Natsuto 9. The rotating shaft has bearing holder 1
0, lower casing 1 via spring 11 and spring retainer 12
3 and a bearing 16 supported by the housing 15. The bearing is lubricated by grease lubrication.

Grease is supplied through grease inlets 18 and 19 provided in the lower casing and cover 17, respectively.

The rotor is driven by motor rotor 20. Motor stator 2
This is done using a high frequency motor. Power is supplied to the motor via a power supply connector 22.

As shown in detail in FIG. 6, the rotor blade groove 4 is dug on the outer circumferential surface of the rotor 1 at an angle θ with respect to the rotor axis z-z', and the starting edge 4a1 and the trailing edge 4b in the axial direction are They are formed aligned in the circumferential direction. Therefore, θ.

is an acute angle, and θ2 is an obtuse angle. The stator blade groove 6 is formed in the opposite direction to the rotor blade groove 4 at an angle θ' with respect to the rotor axis zz', and is formed so that a portion thereof overlaps with the rotor blade groove 4 in the axial direction. Arranged in Further, the blade grooves of the rotor blade groove 4 and the stator blade groove 6 are connected by a smooth curved surface R from the starting end 4a+6a or the rear end 4b, 6b to the groove bottom surfaces 4c, 6c. Since the rotor blade groove and stator blade groove configured in this manner can be used for both axial flow blades and screw groove molecular pumps, high compression ratios and high pumping speeds can be expected. With the configuration described above, when the rotor 1 is driven at high speed in the N direction, gas molecules are exhausted from the suction port 23 to the exhaust port 24, and the vacuum chamber connected via the connection flange 25 is made to have a high vacuum. be able to. Furthermore, even when the inside of a chamber is repeatedly cycled between low vacuum and high vacuum, such as in a semiconductor process, the wedge-shaped vortex grooves 5 and 7 have an evacuation effect up to about 10 Torr, so it is possible to maintain a low vacuum. However, the pumping speed is sufficiently high that pumping from low vacuum to high vacuum can be achieved in a short time. In addition to the above-mentioned characteristics of exhaust performance, in the turbomolecular pump of the example, the stator is placed outside the outer peripheral surface of the rotor, so even in the case of a multi-stage configuration, the stator does not need to have a half/split structure, and manufacturing is easy. It is.

〔Effect of the invention〕

According to the present invention, 10To
The pumping speed can be sufficiently high even in the viscous flow region up to about rr, and has the effect of shortening the pumping time from low vacuum to high vacuum.

[Brief explanation of drawings]

Fig. 1 is a side sectional view of the vortex pump, Fig. 2 is an axial arrow view of the wedge-shaped vortex groove, Fig. 3 and 4 are side sectional views of the wedge-shaped rotor blade groove and stationary blade groove. 5 is a cross-sectional view of an embodiment of the present invention, and FIG. 6 is a cylindrical development view of the moving blade groove and the stator blade groove.

Claims (1)

[Claims] 1. In a turbo-molecular pump that performs an exhaust action using a multi-stage group of blades respectively arranged on a cylindrical rotor extending in the axial direction within a casing and a stator located on the opposite surface of the rotor. , a plurality of wedge-shaped swirl grooves are arranged in the circumferential direction on the outer circumferential surface of the rotor and the inner circumferential surface of the stator opposite thereto, and adjacent swirl grooves are defined in a part of the circumferential direction of the stator, and the swirl grooves are separated from the rotor slightly. 1. A turbo-molecular pump characterized in that a partition is provided with a cylindrical surface separated by a gap, and one of the swirl grooves on both sides of the partition is configured to communicate with an intake side stage and the other with an exhaust side stage. 2. According to claim 1, the pump is configured by arranging a blade group consisting of rotor blade grooves and stator blade grooves on the intake side of a pump configured by providing swirl grooves in the rotor and stator, The rotor blade grooves are arranged on the outer peripheral surface of the rotor at a specific angle with respect to the rotor axis, and the stator blade grooves are arranged on the stator surface at an opposite direction angle with respect to the rotor axis. A turbo-molecular pump characterized in that the rotor blade grooves and the stationary blade grooves are arranged so that a portion of the rotor blade grooves overlap in the axial direction.