JP4560933B2 - Turbo molecular pump - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention provides a turbo mechanism comprising a combination of a rotating blade attached to a rotating body integral with a rotating shaft by a motor and driven to rotate, and a fixed blade fixedly installed on a casing facing the rotating blade. The present invention relates to a turbo molecular pump that performs exhaust from the intake port side to the exhaust port side of the casing by operation of the turbo mechanism.
[0002]
[Prior art]
The turbo molecular pump performs exhaust by the operation of a turbo mechanism composed of a combination of rotor blades and fixed blades, and the configuration thereof is as shown in FIG. This turbo molecular pump is rotatably supported via a bearing SB on a fixed side mainly composed of, for example, an aluminum alloy fixed part 1F and a casing 1, and a holding frame 1M above the center of the fixed part 1F. The rotating shaft 5 is composed of a rotating shaft 5 that is rotationally driven by a motor M and a rotating body 2 that is integrally coupled to the rotating shaft 5. And the rotary blade 2B is attached to the outer periphery of this rotary body 2 in the form which protruded.
On the other hand, on the inner periphery of the casing 1, a ring-shaped spacer 1 </ b> S is installed in a laminated form, and a fixed wing 1 </ b> B is provided with a proximal end held between the spacers 1 </ b> S and protruding inward. . A turbo mechanism T is configured by a combination of the rotary blade 2B and the fixed blade 1B. Then, by the operation of the turbo mechanism T, that is, the high speed rotation on the rotary blade 2B side, the gas molecules sucked from the intake port 3 are beaten by the turbo mechanism T and compressed and exhausted toward the exhaust port 4.
[0003]
Further, a rotating cylindrical portion 2D is extended at the end of the rotating body 2 on the exhaust port 4 side, and the inner peripheral surface of the fixed cylindrical portion 1D in which the rotating cylindrical portion 2D is fixed to the casing 1. Close proximity support. Further, as shown by a two-dot chain line, a spiral groove 1N is formed on the inner peripheral surface of the fixed cylindrical portion 1D. A molecular drag pump that performs an exhaust function by a viscous flow is configured by cooperation of the spiral groove 1N and the rotating cylindrical portion 2D. Thus, a turbo molecular pump in which a turbo mechanism and a molecular drag pump are combined is called a hybrid turbo molecular pump. B is a vent for connecting the exhaust port 4 to an exhaust pipe (not shown).
[0004]
The rotating body 2 is also made of a metal material such as an aluminum alloy in order to withstand high-speed rotation. In the illustrated example, the rotating shaft 5 integrated with the rotating body 2 is supported with respect to the holding frame 1M by radial and thrust bearings SB arranged in a pair.
[0005]
Incidentally, the motor M is a high-frequency motor formed between the rotating shaft 5 and the holding frame 1M. Specifically, as shown in FIG. 6, the rotating shaft 5 is provided with a rotor winding, An armature winding is installed on the inner peripheral surface on the holding frame 1M side, and is configured by a combination of both. By this high-frequency motor M, the rotating body 2 is rotationally driven at 20000 to 100,000 rotations per minute.
[0006]
[Problems to be solved by the invention]
In such a turbo molecular pump, the material constituting the rotating body 2 has a defect, or the material of the rotating body 2 is gradually corroded by exhaust of corrosive gas or the like, and the strength decreases as the use continues. In some cases, the rotating body 2 may be damaged by centrifugal force due to high-speed rotation. When the breakage occurs, the rotating body 2 is unbalanced. Even if the unbalance is small, rotational energy such as vibration is transmitted to the casing 1 through the bearing SB because of high-speed rotation, and further the entire turbo molecular pump. Torque is generated. Then, it is dangerous to give a big impact to the exhaust device by breaking a fixing tool such as a bolt fixing the turbo molecular pump.
[0007]
Further, the main part and parts of the rotating body 2 that have been ruptured due to breakage collide with the fixed wing 1 </ b> B and give impact to the casing 1. This impact is large because of high-speed rotation. Therefore, in order to reduce the destruction of the entire turbo molecular pump due to this impact, it is necessary to strengthen the casing 1 and the like, and there is a problem that the size and weight must be increased.
The present invention is intended to provide a turbo molecular pump that solves such problems.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, a turbo molecular pump provided by the present invention has a plurality of stages of turbo mechanisms composed of a combination of fixed blades and rotor blades installed on the inner periphery of a casing, and the rotor blades are attached thereto. The rotating shaft integral with the rotating body is rotatably supported via a bearing with respect to the fixed portion integral with the casing, and is rotated by a motor so that molecules from the intake port of the casing are exhausted to the exhaust port. in the turbo molecular pump, the stator blade in each stage of said plurality of stages, a fixing member which is curved in the circumferential direction of the rotary shaft, a plurality of blades that Shin設in the radial direction of the rotary shaft from the stationary member And at least one stage of the fixed wing includes a rib extending from a fixing member provided in the stage in a radial direction of the rotating shaft to enhance a mechanical strength in a radial direction of the fixed wing of the stage , The It is obtained as provided by replacing a portion of the plurality of vanes provided in the. Therefore, the fixed blades in the turbo molecular pump are reinforced, and the strength of the turbo mechanism is improved.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described according to embodiments shown in the drawings.
The structure of a turbo molecular pump provided by the present invention is shown in FIG. FIG. 1 is a longitudinal sectional view of the entire turbomolecular pump, as in FIG. 6. The components and components indicated by the same reference numerals as in FIG. 6 are the same as those in FIG.
[0010]
The present invention is characterized in that at least one rib 1L is provided in the radial direction in the fixed blade 1B in at least one stage of the turbo mechanism T. The configuration of the rib 1L is as shown in FIG. The rib has a constant thickness, and the mechanical strength of the entire fixed wing 1B is increased. FIG. 2 shows a part (half) of one stage of the fixed wing 1B, but two ribs 1L are installed at intervals of 180 degrees. Therefore, the mechanical strength in the radial direction of the fixed wing 1B is increased, and even if the rotating body 2 is damaged and its parts collide, the rib 1L receives it or the entire fixed wing 1B. The effect on the casing 1 and the like is reduced.
[0011]
The turbo molecular pump provided by the present invention secondly is configured such that the fixed cylinder side, in particular, the fixed cylinder side of the thread groove pump mechanism in the hybrid turbo molecular pump is multi-partitioned, and the impact when the rotating body 2 is broken is applied to the fixed side. It is intended to absorb in the multi-part form.
Specifically, the fixed cylindrical portion 1D is configured as a divided fixed cylindrical portion 7 obtained by dividing the fixed cylindrical portion 1D into a plurality of divided bodies, and FIG. FIG. 3 is a view of the fixed cylindrical portion 7 as viewed from above. In the figure, the fixed cylindrical portion 7 is divided into two upper and lower semicircular members 7U and 7D with a horizontal line as a ridge, and 6 joins and fixes both of them. It is a bolt. Therefore, when the rotating body 2 is damaged and its fragments collide with the fixed cylindrical portion 7, both members 7U and 7D of the fixed cylindrical portion 7 try to expand with the energy.
At this time, a sudden tensile force acts on the bolt 6 and the bolt 6 is broken. Energy due to breakage of the rotating body 2 is consumed due to the breakage of the bolt 6, and the impact on the casing 1 and the like can be kept small.
As a method of dividing the fixed cylindrical portion 7, it is possible to use a shape that divides into three in the radial direction or a shape that divides into four. However, considering the ease and reality of processing and assembly, there are two or three divided shapes. desirable. Although two or three fixing bolts 6 are arranged in the axial direction, the material and size (diameter, etc.) of the fixing bolt 6 are set to absorb the impact.
[0012]
Further, in the turbo molecular pump provided by the present invention, the fixed cylindrical portion is formed in a double ring structure, and an impact when the rotating body 2 is damaged is absorbed by a combination of the double ring structure. There are three methods for combining the double ring structures. In the first method, the double ring is joined at the conical surface, the second method is to minimize the contact area of the double ring, and the third method is the double ring. A cushioning material is interposed between them.
[0013]
Hereinafter, these methods will be described.
First, the example which comprises the mutual connection surface of a double ring structure by a conical surface is shown by FIG. 4, FIG. That is, in both figures, 1U is an inner fixed cylindrical portion, and 1R is an outer fixed cylindrical portion. The joint surfaces of the two fixed cylindrical portions 1U and 1R are formed by a conical surface CF. . According to the joining of the two fixed cylindrical portions 1U and 1R by the conical surface CF, when the rotating body 2 is damaged and the broken piece collides with the inner fixed cylindrical portion 1U, the impact force is at the conical surface CF. The force is divided and transmitted to the outer fixed cylindrical portion 1R. Although this component force depends on the inclination angle of the conical surface CF, it is reduced as long as it is a component force.
[0014]
Next, the second system is a configuration in which the contact area between each other is minimized. As shown in FIG. 4, a plurality of recesses 1K are formed in the inner fixed cylindrical portion 1U. The recess 1K is formed on the outer circumferential conical surface, and is formed as an annular recess 1K. A plurality of the concave portions 1K are connected to each other, so that the convex portion 1S of the fixed cylindrical portion 1U therebetween is joined to the outer fixed cylindrical portion 1R. Therefore, when an impact due to the breakage of the rotating body 2 occurs, the impact is relieved by the collapse (collapse) of the convex portion 1S, that is, the portion where the contact surface is reduced by the impact force.
[0015]
In the third method, a buffer material is interposed between the two fixed cylindrical portions 1U and 1R. As shown in FIG. 5, the two fixed cylindrical portions 1U and 1R are formed so that their corresponding surfaces are conical surfaces. However, the two members are combined so as to have a constant interval therebetween, and a flexible member G such as a rubber material or a spring material is interposed (press-fitted) therebetween. The impact force received by the inner fixed cylindrical portion 1U by the intervention of the flexible member G is alleviated.
Since the turbo molecular pump provided by the present invention is as described above, the impact energy due to the breakage of the rotating body is absorbed by the rib 1L and the fixed cylindrical portion 1D of the fixed wing 1B, and the impact on the casing 1 and the like is greatly reduced. Will be.
[0016]
The turbo molecular pump provided by the present invention is as described in detail above, but is not limited to the above and illustrated examples, and includes various modified embodiments.
First, regarding the invention in which the rib 1L is installed on the fixed blade 1B of the turbo mechanism T in at least one stage in the multi-stage turbo mechanism T, there are at least one rib 1L provided in the radial direction, two in the illustrated example. However, it is conceivable to increase the strength by using three for every 120 angles or four for every 90 angles. Further, such ribs can be two or three stages.
[0017]
In addition, various modifications can be made in the case of a method of receiving an impact due to the breakage of the rotating body 2 at the fixed cylindrical portion 1D. This fixed cylindrical portion 1D is effective in the case of a hybrid type turbo molecular pump as shown in the figure, but can also be applied to a turbo molecular pump including a fixed cylindrical portion 1D that does not constitute a thread groove pump mechanism. . In this case, the fixed cylindrical portion 1D is provided only for receiving an impact due to the damage of the rotating body 2. Furthermore, a modified example can be given also about the shape of the fixed wing | blade which comprises a turbo mechanism. That is, in the illustrated example, the fixed wing is an example in which a ring is attached to the inner end side of the wing, as shown in FIG. 2, but the inner end of the wing is open and the fixed ring is attached to the outer end side. The present invention can also be applied to a turbo-molecular pump of the type that is attached and holds the fixing ring between the spacers. In this case, the rib extends inward from the outer fixing ring.
[0018]
As described above, the turbo molecular pump can be applied to turbo molecular pumps of various types and configurations regardless of the gist of the present invention. Therefore, for example, the illustrated example is a hybrid type turbo molecular pump, but it can also be applied to a turbo molecular pump having only a turbo function. The present invention can also be applied to a turbo molecular pump that supports the rotating body 2 with a magnetic bearing.
The present invention includes all these modified embodiments.
【The invention's effect】
Since the turbo molecular pump provided by the present invention is as described above in detail, the impact when the rotor blade is broken is moderated and transmitted to the pump casing, and the mounting structure of the pump can be simplified and simplified. It is not necessary to have a special structure for blocking the breaking member of the rotating body, that is, the metal block, and the pump can be downsized.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing a configuration of a turbo molecular pump according to the present invention.
FIG. 2 is a perspective view of a fixed blade in a turbo molecular pump according to the present invention.
FIG. 3 is a view showing a configuration of a fixing member of a turbo molecular pump according to the present invention.
FIG. 4 is a diagram showing a configuration of a fixed cylindrical portion in a turbo molecular pump according to the present invention.
FIG. 5 is a diagram showing another configuration of the fixed cylindrical portion in the turbo molecular pump according to the present invention.
FIG. 6 is a diagram showing a bearing configuration of a conventional turbo molecular pump.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Casing 1B ... Fixed wing | blade 1D ... Fixed cylindrical part 1U ... Inner fixed cylindrical part 1R ... Outer fixed cylindrical part 1K ... Recess 1L ... Rib 1S ... Convex part CF ... Conical surface 2 ... Rotating body 2B ... Rotation Blade 2D ... Rotating cylindrical portion 3 ... Intake port 4 ... Exhaust port 5 ... Rotating shaft 7 ... Divided fixed cylindrical portion T ... Turbo mechanism

Claims (1)

A turbo mechanism comprising a combination of fixed blades and rotary blades installed on the inner periphery of the casing has a plurality of stages, and a rotary shaft integrated with a rotary body provided with the rotary blades has a fixed shaft integrated with the casing. In a turbo molecular pump that is rotatably supported through a bearing and is driven to rotate by a motor to exhaust molecules from the intake port of the casing to the exhaust port,
The fixed wing includes a fixing member that is curved in the circumferential direction of the rotating shaft at each of the plurality of stages, and a plurality of wings that extend from the fixing member in the radial direction of the rotating shaft,
Furthermore, at least one stage of fixed blades, the rib to enhance the mechanical strength in the radial direction of the fixed blade from the fixed member stepped in Shin設in the radial direction of said rotary shaft provided in the stepped, stepped A turbo molecular pump characterized in that it is provided by replacing a part of the plurality of blades provided in the above.

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