JP2005036665A - Molecular drag pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a molecular drag pump reducing surface temperature of an upper end surface part of a rotor of a turbo molecular pump part as compared with a conventional one with meeting a demand of a device on which vacuum exhaust is performed for avoiding high temperature radiation heat from a molecular drag pump side and suppressing increase of manufacturing cost and running cost. <P>SOLUTION: In this molecular drag pump, the rotor of the turbo molecular pump part 2 is formed to enable to be separated into two of an upper part rotor 6a and the lower part rotor 6b, and packing 7a, 7b of heat insulating material is put therebetween to prevent heat transfer therebetween. Also in this molecular drag pump, a casing covering a stationary blade stage of the turbo molecular pump part 2 is formed to enable to be separated into two of an upper casing rotor 10a and the lower part casing 10b, and packing 11a, 11b of heat insulating material is put therebetween to prevent heat transfer therebetween. The upper part casing 10a and the lower part casing 10b are cooled by a cooling means using cooling water pipe. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a molecular pump that generates a high vacuum, and more particularly to a molecular pump in which a turbo molecular pump unit is arranged in the first stage.
[0002]
[Prior art]
An example of a conventional complex molecular pump is shown in FIG.
[0003]
The composite molecular pump includes a turbo molecular pump part a and a thread groove vacuum pump part n, and is formed in a bowl shape.
[0004]
The turbo molecular pump part a is arranged above the composite molecular pump (on the intake port f side), and the moving blade stages a1, a2, a3,... Are formed by projecting the moving blades radially on the outer periphery of the rotor c. Are arranged in multiple stages, and stationary blade stages b1, b2, b3,... Formed by arranging stationary blades radially between these rotor blade stages are provided in multiple stages.
[0005]
The thread groove vacuum pump part n includes a primary side thread groove vacuum pump part n1 formed by having an outer stator outside a cylindrical rotor part e provided continuously to a lower part of the rotor c, and the cylindrical rotor. It comprises a secondary-side thread groove vacuum pump part n2 formed with an inner stator inside the part e.
[0006]
Reference symbol h denotes a rotating shaft connected to the rotor c, and the rotating shaft h is pivotally supported by the bearing housing j.
[0007]
K is a cooling water pipe provided in the base portion m for cooling the bearing housing j and the like.
[0008]
The operation of the composite molecular pump is to suck exhaust gas from the intake port f, and from the exhaust port g through the turbo molecular pump part a, the primary-side thread groove vacuum pump part n1, and then the secondary-side thread groove vacuum pump part n2. Exhaust the exhaust.
[0009]
[Problems to be solved by the invention]
Some devices that are evacuated do not like the thermal effect from the side of the vacuum pump that evacuates.
[0010]
The surface temperature of the rotor of a conventional molecular pump is about 40 ° C. to 80 ° C. However, radiant heat from such a temperature is not preferable, and the surface temperature of the rotor is required to be room temperature or about 27 ° C. There was a case.
[0011]
In such a case, there is a conventional example in which a baffle plate is provided at the inlet of the molecular pump to prevent radiant heat from the rotor of the molecular pump.
[0012]
However, when the baffle plate is provided at the intake port as described above, the intake resistance increases, so that a vacuum pump with a high exhaust speed is required, resulting in a high cost.
[0013]
There is an example in which low temperature cooling water is circulated around the outer periphery of the molecular pump to lower the temperature of the entire molecular pump.
[0014]
However, in order to supply such low-temperature cooling water, a device for cooling the cooling water is further required, which is uneconomical.
[0015]
An object of the present invention is to provide a molecular pump that solves the above-described problems and does not have the influence of radiant heat from the vacuum pump side without using a baffle plate and using cooling water having a water temperature of a conventional level. And
[0016]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the present invention has a plurality of blade stages formed by projecting a plurality of blades radially on the outer periphery of the rotor, and a plurality of blades are arranged radially between these blade stages. In a turbomolecular pump having a plurality of stationary vane stages and / or a composite molecular pump having a thread groove vacuum pump connected to the turbomolecular pump, the rotor is an upper part having an upper rotor stage. A rotor and a lower rotor having a lower rotor blade stage are formed so as to be divided into two parts, and a heat insulating member is interposed between the upper rotor and the lower rotor so as to prevent heat conduction between them, A cooling means for cooling part or all of the stationary blade stage is provided in a casing covering the stationary blade stage, and the temperature of the upper rotor is cooled by the cooled stationary blade stage.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to FIG.
[0018]
FIG. 1 is a longitudinal sectional view of a composite molecular pump 1 employing the present invention. The composite molecular pump 1 is formed by connecting a turbo molecular pump portion 2 and a thread groove vacuum pump portion 3 in a bowl shape. The upper end portion has an intake port 4 and the lower portion has an exhaust port 5.
[0019]
The turbo molecular pump section 2 has a rotor assembly 6 formed so as to be divided into two vertically, and a multistage upper rotor blade stage 6a1 in which a plurality of rotor blades project radially from the outer periphery of the upper rotor 6a. , 6a2, ..., and a plurality of lower rotor blade stages 6b1, 6b2, ... in which a plurality of rotor blades project radially from the outer periphery of the lower rotor 6b connected to the upper rotor 6a. In this way, the packing 7a, 7b made of a heat insulating material is interposed between the upper rotor 6a and the lower rotor 6b so as to prevent heat conduction between them, and the rotor assembly 6 is formed as an integral part of both.
[0020]
A ceramic coating having an emissivity of about 0.9 is applied to part or all of the surfaces of the rotors 6a and 6b, that is, the rotor assembly 6 and the stationary blades, to increase the emissivity of the surface of the rotor and the like. The ceramic coating is to deposit an oxide film on the surface by electrolysis at a high voltage with an aluminum alloy rotor assembly or the like as an anode.
[0021]
There are upper stator blade stages 8a1, 8a2,... Formed by radially arranging a plurality of stator blades between the upper rotor blade stages 6a1, 6a2,. Each of the steps 8a1, 8a2,... Is held in an upper casing 10a that covers the outer periphery of the outer periphery of the step 8a1, 8a2,.
[0022]
Further, there are lower stator blade stages 8b1, 8b2,... Formed by radially arranging a plurality of stator blades between the lower rotor blade stages 6b1, 6b2,. Each of the blade stages 8b1, 8b2,... Is held in a lower casing 10b that covers an outer peripheral portion of the blade stage 8b1, 8b2,.
[0023]
The upper casing 10a and the lower casing 10b are integrally combined to form a casing assembly 10. Between the upper casing 10a and the lower casing 10b, packings 11a and 11b made of heat insulating material are interposed, The heat conduction between the two is prevented.
[0024]
The upper casing 10a and the lower casing 10b are each provided with a cooling water pipe 12a or 12b for cooling the upper casing 10a and the lower casing 10b so as to surround the casing 10a or the lower casing 10b, respectively.
[0025]
The thread groove vacuum pump portion 3 has the same structure as the conventional one, and is formed by having an outer stator 3a1 outside the cylindrical rotor portion 6c connected to the lower portion of the lower rotor 6b. It consists of a groove vacuum pump portion 3a and a secondary screw groove pump portion 3b formed with an inner stator 3b1 inside the cylindrical rotor portion 6c.
[0026]
The rotating shaft 13 is inserted into the cylindrical rotor portion 6c and connected to the lower surface of the lower rotor 6b. The rotating shaft 13 is rotatably supported by the bearing housing 14. The bearing housing 14 is erected at the center portion of the base portion 17 fixed to the lower end portion of the housing 3c of the thread groove vacuum pump portion 3.
[0027]
In addition, 15 is a motor for driving a rotating shaft, and 16 is a cooling water pipe disposed on the base portion 17.
[0028]
Next, the operation and effects of the complex molecular pump 1 of the present embodiment will be described.
[0029]
The intake port 4 of the complex molecular pump 1 is attached to a device that is evacuated, and the rotor assembly 6 is rotated at high speed to evacuate the device.
[0030]
Even if the heat generated by the exhaust action, the heat generated from the drive motor 15 and the heat generated from the bearing portion increase the temperature of the rotary shaft 13 and the rotor portion, and the temperature of the rotary shaft 13 and the rotor portion reaches about 40 ° C. to 80 ° C. The temperature of the upper rotor 6a of the rotor assembly 6 can be maintained at the radiant heat temperature allowed by the device, for example, 27 ° C.
[0031]
FIG. 2 is an example of a graph showing the relationship between the temperature of the cooling water passing through the cooling water pipes 12a and 12b provided in the upper casing 10a and the lower casing 10b and the surface temperature of the upper rotor 6a.
[0032]
That is, in FIG. 2, the X axis indicates the surface temperature of the upper rotor 6a, and the vertical axis Y indicates the temperature of the cooling water supplied to the cooling water pipes 12a and 12b.
[0033]
From this graph, it can be seen that the temperature of the supplied cooling water should be 26 ° C. in order to set the surface temperature of the upper rotor 6 a to 27 ° C.
[0034]
In this way, the upper casing 10a is cooled with cooling water to cool the upper stationary blade stages 8a1, 8a2,... And the annular distance piece 9 around the upper rotor 6a, thereby forming the upper portion of the rotor assembly 6. The temperature of the upper rotor 6a can be lowered to the required temperature from the apparatus side where the exhaust is performed.
[0035]
The upper rotor 6a radiates heat radiation corresponding to the surface temperature toward the intake port 4 and does not adversely affect the device.
[0036]
Further, the portions that are thermally cut off from the upper rotor 6a such as the lower rotor 6b and the rotating shaft 13 may remain at a high temperature of 40 ° C. to 80 ° C. in order to cool the upper rotor 6a. Only a slight increase in the amount of cooling water can meet the requirements on the apparatus side.
[0037]
The cooling water pipe 12b may be omitted.
[0038]
【The invention's effect】
As described above, according to the present invention, it is not necessary to provide a baffle plate at the intake port of the molecular pump in response to a request for evacuation of the apparatus that evacuates, and to avoid the influence of radiant heat from the molecular pump. There is no need for cooling water at a water temperature, and there is an effect that it is possible to provide a molecular pump having a low surface temperature at the upper end surface portion of the rotor by using cooling water at a normal temperature used in a conventional molecular pump.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a complex molecular pump employing the present invention.
FIG. 2 is an example of a graph showing the relationship between the cooling water temperature and the surface temperature of the upper rotor of the complex molecular pump.
FIG. 3 is a longitudinal sectional view of an example of a conventional complex molecular pump.
[Explanation of symbols]
1 Molecular pump (complex molecular pump)
2 Turbo molecular pump part 3 Thread groove vacuum pump part 6a Upper rotor 6b Lower rotor 7a, 7b, 11a, 11b Thermal insulation member (packing)
10a Upper casing 10b Lower casing 12a, 12b Cooling means (cooling water pipe)

Claims (4)

A turbo turbine having a plurality of rotor blade stages each having a plurality of rotor blades radially projecting from the outer periphery of the rotor, and a plurality of stator blade stages each having a plurality of stator blades radially disposed between the rotor blade stages. In a molecular pump and / or a composite molecular pump having a thread groove vacuum pump connected to the turbo molecular pump, the rotor includes an upper rotor having an upper blade stage and a lower rotor having a lower blade stage. In addition, a heat insulating member is interposed between the upper rotor and the lower rotor so as to prevent heat conduction therebetween, and the stator blades are formed on a casing covering the stator blade stage. A molecular pump provided with cooling means for cooling a part or all of the stage so as to cool the temperature of the upper rotor by the cooled stationary blade stage. A casing covering the stationary blade stage, an upper casing engaging the upper stationary blade stage disposed between the upper moving blade stages, and a lower part engaging the lower stationary blade stage disposed between the lower moving blade stages. The molecular pump according to claim 1, wherein the molecular pump is formed so as to be divided into two parts in the casing, and a heat insulating member is interposed between the upper casing and the lower casing to prevent heat conduction therebetween. The cooling means comprising cooling water pipes is installed in the upper casing and the lower casing or the upper casing, and the cooling means is formed so as to maintain the temperature of the upper rotor at room temperature or a specified temperature. Or the molecular pump of Claim 2. The molecular pump according to any one of claims 1 to 3, wherein a ceramic coating is formed on part or all of the surfaces of the rotor and the stationary blade including the moving blade.

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