JP7428101B2 - turbo molecular pump - Google Patents

Description

The present invention relates to turbomolecular pumps.

In turbomolecular pumps, the rotor is made of aluminum. The permissible temperature for the strength and durability of aluminum is relatively low compared to other metals. Generally, when a turbomolecular pump is in a high-speed rotation state in which it performs an evacuation action, the rotor is in a state of high tensile stress due to the action of high centrifugal force. When the rotor temperature exceeds the permissible temperature in a tensile stress state, permanent strain increases rapidly, causing a problem of reduced rotor life due to creep deformation. In the invention described in Patent Document 1, a black nickel plating layer with high thermal emissivity is formed on the surface of the rotor, and heat is efficiently radiated from the rotor to surrounding members such as stator blades and spacers, thereby suppressing a rise in rotor temperature. ing.

Japanese Patent Application Publication No. 2010-112202

However, there is a problem in that if the temperature of the stator blades and spacers that receive heat radiation from the rotor is high, the increase in rotor temperature cannot be effectively suppressed. That is, if the heat of the stator blades and spacers is not sufficiently transferred to the base, there is a problem in that a sufficient effect of heat transfer from the rotor to the stator blades and spacers by thermal radiation cannot be obtained.

A turbo-molecular pump according to an aspect of the present invention includes a plurality of stages of rotor blades, a plurality of stator blades provided alternately in the pump axial direction with respect to the plurality of stages of rotor blades, and a plurality of stages of the stator blades in the pump axial direction. a plurality of spacer rings that are alternately stacked with stator blades and constitute a stacked body together with the plurality of stages of stator blades, and a pump casing in which the plurality of stages of rotor blades and the stacked body are accommodated, the pump casing A first high emissivity layer having an emissivity higher than the emissivity of the base material of the pump casing is formed on the inner circumferential surface of the pump casing, and/or a first high emissivity layer is formed on the inner circumferential surface of the laminated body. A second high emissivity layer having an emissivity higher than the emissivity of the base material of the laminate is formed in the region.

According to the present invention, an increase in rotor temperature can be more effectively reduced.

FIG. 1 is a cross-sectional view of a turbomolecular pump. FIG. 2 is a diagram illustrating a method for cooling a pump rotor. FIG. 3 is a schematic diagram showing the structure of the black nickel plating layer. FIG. 4 is a diagram showing a comparative example. FIG. 5 is a diagram showing a modification.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view schematically showing a schematic configuration of a turbo-molecular pump 1. As shown in FIG. The turbo molecular pump 1 has a turbo pump stage composed of a plurality of stages of stator blades 30 and a plurality of stages of rotor vanes 40, and a thread groove pump stage composed of a stator 31 and a rotor cylindrical part 41. There is. In this embodiment, a magnetic bearing type turbo-molecular pump will be described as an example, but the present invention is also applicable to other bearing type turbo-molecular pumps such as ball bearings. Further, the present invention is also applicable to a turbomolecular pump having only a turbo pump stage without a thread groove pump stage.

The rotor blades 40 and the rotor cylindrical portion 41 are formed on the pump rotor 4a. The pump rotor 4a is fastened to a shaft 4b, which is a rotor shaft, by bolts (not shown). The shaft 4b is supported by magnetic levitation by magnetic bearings 34, 35, and 36 provided on the base 3. Although detailed illustrations are omitted, each of the magnetic bearings 34 to 36 includes an electromagnet and a displacement sensor. The floating position of the shaft 4b is detected by the displacement sensor.

The stator blades 30 in multiple stages are arranged alternately with respect to the rotor blades 40 in multiple stages provided in the axial direction of the pump rotor 4a. Each stator blade 30 is stacked and positioned in the pump axial direction via a spacer ring 33. When the fixing flange 20b of the casing 20 is fixed to the base 3 with bolts, the stacked body of the stator blades 30 and the spacer ring 33 is sandwiched between the base 3 and the casing 20. The stator 31 is attached to the base 3 by fixing a flange-shaped fixing portion 311 formed near the upper end of the figure to the base 3 with bolts 21 . In this embodiment, a thread groove is formed on the inner peripheral surface of the stator 31, but generally, a thread groove is formed on either the stator 31 or the rotor cylindrical portion 41. The base 3 is provided with a cooling water pipe 39 (hereinafter also referred to as a cooling water pipe).

The shaft 4b to which the pump rotor 4a is connected is rotationally driven by the motor 10. When the magnetic bearing is not operating, the shaft 4b is supported by emergency mechanical bearings 37a, 37b. When the shaft 4b to which the pump rotor 4a is fastened is rotated at high speed by the motor 10, the gas on the intake port 20a side of the casing 20 is exhausted by the turbo pump stage (rotor blades 40, stator blades 30), and then the gas is exhausted by the turbo pump stage (rotor blades 40, stator blades 30). The gas is further exhausted by a threaded groove pump stage (rotor cylindrical portion 41, stator 31), and then exhausted from the exhaust port 38. An auxiliary pump is connected to the exhaust port 38.

When the flow rate of the gas to be exhausted increases, the temperature of the pump rotor 4a increases due to the heat generated by the exhaust. In particular, in the case of a magnetic bearing type turbomolecular pump, the pump rotor 4a and shaft 4b are magnetically levitated, making it difficult for heat to escape and increasing the temperature. In the case of the turbomolecular pump 1 shown in FIG. 1, as described later, thermal energy transmitted from the rotor blades 40 to the stator blades 30 by thermal radiation or gas molecules is radiated to the base 3 by heat transfer via the spacer ring 33. At the same time, heat is radiated from the spacer ring 33 to the casing 20 using thermal radiation, thereby suppressing the temperature rise of the pump rotor 4a.

FIG. 2 is a diagram illustrating a method of cooling the pump rotor 4a, and is a diagram showing a part of the turbo-molecular pump 1 shown in FIG. 1. Inside the casing 20, a pump rotor 4a in which multiple stages of rotor blades 40 are formed, multiple stages of stator blades 30, and a plurality of spacer rings 33 are housed. The stator blades 30 in multiple stages are stacked such that each stator blade 30 is sandwiched between a pair of upper and lower spacer rings 33 . A stack of stator blades 30 in multiple stages and spacer rings 33 in multiple stages is placed on the base 3.

As shown by the broken line arrow 51 in FIG. 2, thermal energy on the pump rotor side is transferred from the rotor blades 40 to the opposing stator blades 30 to the stator side using heat transfer and thermal radiation by gas molecules, and the pump rotor 4a to cool down. Thermal energy transferred from the rotor blades 40 to the stator blades 30 is transferred to the laminated portion of the stator blades 30 and the spacer ring 33 as shown by the broken line arrow 52, and further transferred to the laminated portion downstream as shown by the broken line arrow 52. (lower side in the illustration). Then, the thermal energy that has moved to the downstream side of the laminated portion is exhausted to the cooling water flowing through the base 3 and inside the cooling water pipe 39.
In addition, in order to prevent deposits from accumulating on the thread groove pump stage (rotor cylindrical portion 41, stator 31), a heater is placed on the base 3 to control the temperature of the thread groove pump stage together with the cooling water flowing through the cooling water pipe 39. You may.

In this embodiment, in order to make the heat transfer from the rotor blades 40 to the stator blades 30 by thermal radiation more effective, the rotor blades 40 and the stator blades 30 are subjected to surface treatment to increase the emissivity, for example, as shown in FIG. This is done in the area shown by the hatching in 2. In addition, in FIG. 2, high emissivity layers are formed on the outer circumferential surfaces 330 of all stages of the stacked spacer rings 33 and on the surface of the inner circumferential surface 200 of the casing 20 that faces the outer circumferential surfaces 330 of all stages. , a high emissivity layer may be formed on the outer circumferential surface 330 of some steps and the inner circumferential surface 200 opposing them.

Aluminum is generally used as the material for the pump rotor 4a and the stator blades 30. Therefore, surface treatments for increasing the emissivity of the surfaces of the pump rotor 4a and stator blades 30 include, for example, black nickel plating (emissivity of about 0.7), black alumite treatment (emissivity of about 0.9), black Examples include, but are not limited to, painting treatment (emissivity of approximately 0.9). In addition, when aluminum material is used without surface treatment, the emissivity is about 0.1 to 0.2 on the oxidized surface, and the emissivity is about 0.1 to 0.2 on the oxidized surface. The emissivity is about 0.2.

FIG. 3 is a schematic diagram showing the structure of the black nickel plating layer. A Ni-P (nickel-phosphorous) layer 401 is formed on the surface of an aluminum base material M by electroless plating. Next, using the Ni--P layer 401 as a base, a Ni--P layer 402 is formed by electroless plating. Finally, the surface of the Ni--P layer 402 is etched to form a layer of black oxide film 403. Note that the Ni--P layer 402 in FIG. 3 may be omitted and the black oxide film 403 may be formed on the Ni--P layer 401.

Furthermore, in this embodiment, as shown by arrow 54 in FIG. 2, heat is radiated from spacer ring 33 to casing 20 by thermal radiation. Thereby, the cooling effect on the pump rotor 4a can be improved, and the effect of suppressing the rise in rotor temperature can be further enhanced. Specifically, as in the case of the pump rotor 4a and the stator blades 30, a surface that increases the emissivity is provided on the inner circumferential surface 200 of the casing 20 and the outer circumferential surface 330 of the spacer ring 33 opposite to the inner circumferential surface 200. Processed. Generally, the spacer ring 33 is made of aluminum, and the casing 20 is made of steel such as stainless steel. Then, by forming a black nickel plating layer, a black alumite layer, and a black paint layer in the hatched areas of each base material made of aluminum or stainless steel, the inner peripheral surface 200 of the casing 20 and the spacer ring 33 are formed. The outer circumferential surface 330 of is made of a high emissivity layer having a higher emissivity.

For example, if high emissivity surface treatment is not applied to the inner circumferential surface 200 and the outer circumferential surface 330, the thermal energy of the stacked body of the stator blades 30 and the spacer ring 33 is radiated almost only through the heat transfer path shown by the broken line arrow 53. I will do it. In such a case, as a method to further enhance the heat dissipation effect of the thermal energy of the laminate, there is a method of increasing the cross-sectional area of the heat transfer path indicated by the broken line arrow 53, as in the region indicated by the symbol A in FIG. However, since it is necessary to shorten the blade lengths of the stator blades 30 and the rotor blades 40 and increase the radial thickness of the spacer ring 33A, a new problem of deterioration in exhaust performance arises.

On the other hand, in this embodiment, thermal radiation from the spacer ring 33 to the casing 20 is used for heat radiation, so there is no need to increase the cross-sectional area of the heat transfer path indicated by the broken line arrow 54. Therefore, it is possible to improve heat dissipation performance without deteriorating exhaust performance. For example, when black body paint is applied to the outer circumferential surface of the spacer, the temperature of the casing 20 changes from 36.1°C to 37°C under conditions of a hydrogen gas flow rate of 28 mbarL/s and a back pressure of 38 Pa in a pump with a pumping speed of 3000 L/s. The temperature rose by 1°C to 1°C. This corresponds to a decrease in spacer temperature of about 3° C., assuming that the amount of heat for the temperature increase in the casing 20 is entirely due to the effect of applying the black body paint.

In addition, in the stacked body shown in FIG. 4, among the multiple stages of spacers 30, the contact area between the multiple stages of spacers on the downstream side and the stator blades is set to be larger than the contact area between the multiple stages of spacers on the upstream side and the stator blades. It's wide. The present invention may be applied to a vacuum pump having a laminate having this configuration. In this case, as described above, although the exhaust performance deteriorates, the temperature of the rotor blades is further reduced. That is, if a design that places emphasis on reducing the rotor blade temperature is required, the laminated body structure shown in FIG. 4 may be adopted.
In other words, the present invention does not positively exclude the laminate structure shown in FIG.

(Modified example)
In the embodiment described above, as shown in FIG. 2, in the laminated portion of the stator blades 30 and the spacer ring 33, only the outer circumferential surface 330 of the spacer ring 33 faces the inner circumferential surface of the casing 20. Therefore, the outer peripheral surface 330 of the spacer ring 33 was subjected to a high emissivity surface treatment. However, if the laminated portion of the stator blades 30 and the spacer ring 33 has a configuration like the spacer ring 33B shown in the modified example of FIG. There is. In such a configuration, it is preferable to apply high emissivity surface treatment to the outer circumferential surface 300 of the stator blades 30 in order to improve heat dissipation performance by heat radiation.

In the embodiment described above, as shown in FIGS. 2 and 5, the inner circumferential surface 200 of the casing 20 and the surface of the member facing the inner circumferential surface, that is, the laminated body of the stator blades 30 and the spacer ring 33. Although the high emissivity surface treatment is applied to both the outer circumferential surface and the outer peripheral surface, it may be applied to either one of them. In either case, the heat dissipation performance to the casing 20 by thermal radiation is improved compared to the case where high emissivity surface treatment is not performed.

In the embodiment described above, as shown in FIG. 2, the mutually opposing surfaces of the rotor blades 40 and stator blades 30 of all stages are subjected to high emissivity surface treatment, but some stages are treated with high emissivity. The surface treatment may be performed. Moreover, even in the case of a configuration in which the surfaces of the rotor blades 40 and stator blades 30 are not subjected to high emissivity surface treatment and the surfaces of the base materials are exposed, the inner peripheral surface 200 of the casing 20 and the outer peripheral surface of the stator ring 33 By subjecting 330 to a high-emissivity surface treatment, it is possible to improve heat radiation from the laminated portion of stator blades 30 and spacer ring 33 due to thermal radiation. For example, in the structure shown in FIG. 5, even if the rotor blades 40 and stator blades 30 of all stages are not subjected to high emissivity surface treatment, only the outer circumferential surface 300 of the stator blades 30 is coated with high emissivity. By applying the treatment, the heat dissipation effect due to thermal radiation of the laminated portion can be made higher than when no surface treatment is applied.

By the way, when the pump rotor 4a rotating at high speed is broken, the broken pump rotor 4a collides with the stacked body of the spacer ring 33 and the stator blades 30, and further, the stacked body is rotated by the rotational energy of the pump rotor 4a. It collides with the casing 20 and comes to a sudden stop. Therefore, an excessive sudden stopping torque is applied to the casing 20. However, as described above, if a black nickel plating layer or a black alumite layer is formed on the inner circumferential surface 200 of the casing 20 and the outer circumferential surface 330 of the spacer ring 33, the surface hardness of the casing 20 and the spacer ring 33 will be increased, causing rotor damage. Occasionally, the spacer ring 33 slips with respect to the casing 20, which extends the sudden stop time and reduces the sudden stop torque.

It will be appreciated by those skilled in the art that the exemplary embodiments and variations described above are specific examples of the following aspects.

[1] A turbo-molecular pump according to one embodiment includes a plurality of stages of rotor blades, a plurality of stator blades provided alternately in the pump axial direction with respect to the plurality of stages of rotor blades, and a plurality of stator blades provided in the pump axial direction with respect to the plurality of stages of rotor blades. a plurality of spacer rings which are alternately stacked with the stator blades of the stages and constitute a laminate together with the stator blades of the plurality of stages; and a pump casing in which the rotor blades of the plurality of stages and the laminate are housed; A first high emissivity layer having an emissivity higher than that of the base material of the pump casing is formed on the inner circumferential surface of the pump casing, and/or a first high emissivity layer having an emissivity higher than that of the base material of the pump casing is formed, and/or A second high emissivity layer having an emissivity higher than that of the base material of the laminate is formed in a region facing the laminate.

For example, as shown in FIG. 2, the inner circumferential surface 200 of the casing 20 and the outer circumferential surface 330 of the spacer ring 33 have a high emissivity that is higher than the emissivity of those base materials (stainless steel material or aluminum material). By forming the layer, heat radiation from the spacer ring 33 to the casing 20 by thermal radiation can be improved.

[2] In the turbomolecular pump according to [1] above, at least some of the rotor blades of the plurality of stages have a rotor blade having an emissivity higher than the emissivity of the base material of the rotor blade. A fourth high-emissivity layer having a higher emissivity than the base material of the stator blade is provided on the stator blade facing the rotor blade on which the high-emissivity layer is formed. A layer is formed.

In the example shown in FIG. 2, the high emissivity layer is formed on all of the multiple stages of rotor blades 40 and the multiple stages of stator blades 30, but some of the stages of rotor blades 40 and the opposing stator blades 30 have high emissivity layers. A high emissivity layer may be formed on the surface. Even in such a case, by forming a high emissivity layer on the inner circumferential surface 200 of the casing 20 and the outer circumferential surface 330 of the spacer ring 33, heat radiation from the spacer ring 33 to the casing 20 can be improved. can be achieved.

[3] The turbo-molecular pump according to [1] or [2] above includes a base on which the laminate is placed and a cooling water pipe for cooling the laminate. As shown in FIG. 2, the heat of the stacked body of the stator blades 30 and the spacer ring 33 is radiated from the outer circumferential surface 300 of the stacked body to the inner circumferential surface 200 of the casing 20 by thermal radiation indicated by the arrow 54, and As shown by an arrow 53, heat is radiated by heat transfer to the base 3 where the cooling water pipe line 39 is disposed.

[4] In the turbomolecular pump according to any one of [1] to [3] above, the high emissivity layer is a black nickel plating layer or a black alumite layer. By using a black nickel plating layer or a black alumite layer as the high emissivity layer formed on the inner peripheral surface 200 of the casing 20 and the outer peripheral surface 330 of the spacer ring 33, the surface hardness of the casing 20 and the spacer ring 33 can be increased. When the rotor breaks, the spacer ring 33 slides against the casing 20, thereby extending the sudden stop time and reducing the sudden stop torque.

Although various embodiments and modifications have been described above, the present invention is not limited to these. Other embodiments considered within the technical spirit of the present invention are also included within the scope of the present invention.

DESCRIPTION OF SYMBOLS 1... Turbo molecular pump, 3... Base, 4a... Pump rotor, 20... Casing, 30... Stator blade, 40... Rotor blade, 33, 33A, 33B... Spacer ring, 200... Inner peripheral surface, 300, 330... Outer peripheral surface

Claims (4)

multiple stages of rotor blades,
multiple stages of stator blades provided alternately in the pump axial direction with respect to the multiple stages of rotor blades;
a plurality of spacer rings that are alternately stacked with the plurality of stages of stator blades in the pump axial direction and constitute a stacked body together with the plurality of stages of stator blades;
a pump casing in which the plurality of stages of rotor blades and the laminate are housed,
A gap is formed between the inner circumferential surface of the pump casing and a region of the laminate that faces the inner circumferential surface,
A first high emissivity layer having an emissivity higher than that of the base material of the pump casing is formed on the inner circumferential surface of the pump casing, and/or a first high emissivity layer having an emissivity higher than that of the base material of the pump casing is formed, and/or A second high emissivity layer having an emissivity higher than the emissivity of the base material of the laminate is formed in the region facing the peripheral surface , so that the pump is removed from the spacer ring by thermal radiation. A turbo molecular pump that radiates heat to the casing . The turbomolecular pump according to claim 1,
A third high emissivity layer having an emissivity higher than the emissivity of a base material of the rotor blade is formed on at least some of the rotor blades of the plurality of stages of rotor blades,
A fourth high emissivity layer having an emissivity higher than the emissivity of a base material of the stator blade is formed on a stator blade facing the rotor blade on which the high emissivity layer is formed. pump. The turbomolecular pump according to claim 1 or 2,
A turbo-molecular pump comprising a base on which the laminate is placed and a cooling water pipe for cooling the laminate. The turbomolecular pump according to any one of claims 1 to 3,
The high emissivity layer is a black nickel plating layer or a black alumite layer, the turbo molecular pump.

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