JP6940862B2 - Exhaust system and electron beam laminated modeling equipment equipped with it - Google Patents

Description

The present invention relates to an exhaust system for creating a vacuum state, and also relates to an electron beam laminated modeling apparatus including the exhaust system.

In a device provided with a chamber as a vacuum vessel, an exhaust system equipped with various vacuum pumps is generally connected to the chamber in order to create a vacuum state in the chamber. As an apparatus provided with such an exhaust system, for example, there is an electron beam laminated modeling apparatus.

The electron beam laminated molding apparatus is for laminating and molding a metal model having a desired shape by irradiating a metal powder bed with an electron beam which is a high energy beam, and has attracted particular attention in recent years.

In the electron beam laminated molding apparatus, a metal powder bed is formed by spreading metal powder on the stage, and the metal powder bed is partially irradiated with the electron beam by scanning the electron beam. The metal powder of the portion melts and then solidifies, and the layers thus formed are repeatedly stacked to form a three-dimensional metal model.

Here, in the electron beam laminated molding apparatus, it is known that the metal powder contained in the metal powder bed is charged with the irradiation of the electron beam, and a so-called smoke phenomenon occurs in which the metal powder is scattered in the chamber. When the smoke phenomenon occurs, the scattered metal powder blocks the irradiation of the electron beam on the metal powder bed, which causes a decrease in the modeling speed and a decrease in the modeling accuracy.

As a method of suppressing the occurrence of this smoke phenomenon, Japanese Patent Application Laid-Open No. 2010-526694 (Patent Document 1) describes a method of introducing helium gas as an auxiliary gas into the chamber while maintaining a vacuum state in the chamber. Proposed.

More specifically, in Patent Document 1, the inside of the chamber is ^{exhausted to a high vacuum state of about 10 -3} [Pa] or less, the metal powder is preheated, and then helium gas is introduced into the chamber. It is described that the occurrence of the smoke phenomenon can be suppressed by performing the laminated molding by irradiating the electron beam while maintaining the pressure in the chamber at ^{about 10 -1 [Pa].}

The method described in Patent Document 1 utilizes the advantage that the electron beam is not easily disturbed by the helium gas because the collision cross-sectional area of the helium gas is small, and the low electrical resistance or the negative electron affinity of the helium gas. Etc. are intended for use.

_{In this way, in some devices, for example, oxygen gas (O 2} ) while keeping the partial pressure of a light gas (gas having a molecular weight of 4 or less) such as helium gas (He) relatively high in the chamber. , Nitrogen gas (N ₂ ), water vapor (H ₂ O), argon gas (Ar), etc., and the partial pressure of non-light gas (gas with molecular weight greater than 4), which is heavier than light gas, is relatively low. May be required to keep.

As a device that is required to keep the partial pressure of the non-light gas relatively low while keeping the partial pressure of the light gas relatively high in the chamber, the light gas (particularly helium gas) as described above is used. Devices that take advantage of the low electrical resistance or negative electron affinity of helium, and the small collision cross-sectional area of light gas that makes it difficult for particle beams to be disturbed by light gas molecules, and devices that take advantage of the high thermal conductivity of light gas. There are various devices such as a device that utilizes the fact that the gas has a helium leak, and in addition to the above-mentioned electron beam laminated modeling device, for example, a helium leak inspection that utilizes the characteristic of helium gas that it has a small molecular diameter and easily penetrates into minute gaps. Devices, etc. fall under this category.

Special Table 2010-526964A

Normally, an exhaust system applied to a device using a particle beam such as the above-mentioned electron beam laminated molding device is in a medium vacuum state (about 10 ^-1 [Pa] to 10 ² [Pa]) from an atmospheric pressure environment. An auxiliary vacuum pump such as an oil rotary vacuum pump for creating, and a composite molecular pump (downstream of the turbo molecular pump) for creating a ^{high vacuum state (about 10 -5} [Pa] to 10 ^{-1 [Pa]) from a medium vacuum state to a high vacuum state.} It is composed of a momentum transfer type mechanical pump system combined with a combined pump (composite pump provided with a thread groove vacuum pump on the side). Here, the auxiliary vacuum pump is installed on the exhaust path on the downstream side of the composite molecular pump.

When an attempt is made to realize the method described in Patent Document 1 by using this type of exhaust system, a new problem of consuming a large amount of helium gas arises.

Specifically, in a high vacuum state, the number of gas molecules naturally becomes very small because the gas molecules existing in the chamber under the atmospheric pressure environment or the low vacuum state are exhausted to the outside. On the other hand, the release of gas (desorption of gas molecules) from the inner wall surface of the chamber and the surface of various members (including the metal powder contained in the metal powder bed) installed in the chamber cannot be ignored, and in this state. When the exhaust is stopped, the pressure in the chamber gradually rises. At that time, since the released gas is mainly a non-light gas such as water vapor, the partial pressure of the non-light gas in the chamber also rises sharply accordingly.

Therefore, it was decided to temporarily create a high vacuum state using the above exhaust system, then introduce helium gas into the chamber and close various on-off valves to seal the chamber (that is, stop the exhaust). In this case, the electron beam is attenuated and scattered as the partial pressure of the non-light gas having a large collision cross section increases, which may lead to a decrease in the modeling speed and a decrease in the modeling accuracy.

In order to prevent the partial pressure increase of the non-light gas, it is necessary to operate the exhaust system constantly or intermittently while constantly or intermittently introducing the helium gas into the chamber.

However, in the electron beam laminated modeling apparatus, the time required for laminating and modeling a metal model of a desired shape is several hours to a dozen or so per piece even when modeling a relatively small metal model. It takes time, and it takes several tens of hours or more when forming a large metal model. Therefore, if helium gas is constantly or intermittently introduced into the chamber during this period, a large amount of helium gas is consumed as described above. The result will be.

If helium gas is constantly or intermittently introduced into the chamber and the amount of helium gas introduced is reduced, the consumption of helium gas can be suppressed to some extent, but the amount of helium gas in the chamber is reduced. Since the pressure drops, the smoke phenomenon cannot be sufficiently suppressed. Further, if the amount of helium gas introduced is reduced and the exhaust speed of the composite molecular pump is reduced, the release of non-light gas cannot be suppressed as described above. Therefore, not only the partial pressure of helium gas but also the amount of non-light gas The pressure also rises, and as a result, the electron beam is attenuated and scattered, resulting in a decrease in the modeling speed and a decrease in the modeling accuracy.

On the other hand, as a kind of vacuum pump that creates a vacuum state, a cryopump that exhausts gas by condensing gas molecules on the cryogenic surface using a cryogenic surface is known. A cryopump that has a cryogenic surface of about liquid hydrogen temperature (20 [K]) and does not have an adsorbent built-in is a vacuum pump that can exhaust non-light gas but does not exhaust light gas such as helium gas. By applying this, it becomes possible to suppress an increase in the partial pressure of the non-light gas without lowering the partial pressure of the light gas.

However, since the cryopump is a so-called storage type vacuum pump, after a certain amount of gas molecules are condensed and stored, further exhaust cannot be performed. Therefore, the cryopump returns the temperature of the cryogenic surface to room temperature, re-emits the condensed gas molecules, and exhausts the released gas using an auxiliary pump (non-reservoir pump) to regenerate it. Reproduction processing to be performed is required, and it cannot be used continuously.

Therefore, when the cryopump is applied to the electron beam laminated modeling apparatus, it becomes necessary to stop the laminated modeling process each time in order to perform the above-mentioned regeneration process, and as a result, the time required for the laminated modeling becomes longer. It leads to the problem of time consuming.

In this way, conventionally known exhaust systems and vacuum pumps maintain a vacuum state for a long period of time so as to keep the partial pressure of non-light gas relatively low while keeping the partial pressure of light gas relatively high. Had a problem that was unsuitable for.

On the other hand, in order to create such a vacuum state in the chamber at an early stage from an atmospheric pressure environment, light gas and non-light gas are once exhausted from the chamber at the same time as described above, and then the light gas is discharged into the chamber. It will be necessary to introduce it within. Therefore, it is not just a matter of selectively and mainly exhausting non-light gas.

Therefore, the present invention has been made to solve the above-mentioned problems, and is an exhaust system capable of simultaneously exhausting light gas and non-light gas, while selectively and mainly exhausting non-light gas. It is an object of the present invention to provide an electron beam laminated molding apparatus capable of suppressing the consumption of auxiliary gas while being excellent in molding speed and molding accuracy.

The exhaust system based on the present invention includes a turbo molecular pump having a first intake port and a first exhaust port, a thread groove vacuum pump having a second intake port and a second exhaust port, and a third intake port and a third exhaust port. It is provided with an auxiliary vacuum pump having a first port, a second port, and a three-way valve having a third port. The first exhaust port is connected to the second intake port, and is an exhaust path of a portion from the first intake port to the second exhaust port via the first exhaust port and the second intake port. An intermediate exhaust port is provided in the middle of the position. The first port is connected to the second exhaust port, the second port is connected to the intermediate exhaust port, and the third port is connected to the third intake port. The three-way valve can be selectively switched between a first exhaust state connecting the first port and the third port and a second exhaust state connecting the second port and the third port. .. In the exhaust system based on the present invention, in the first exhaust state, the gas taken in from the first intake port is the first exhaust port, the second intake port, the second exhaust port, and the third. The gas is exhausted from the third exhaust port via the intake port in this order, and in the second exhaust state, the gas taken in from the first intake port does not pass through the second exhaust port. The air is exhausted from the third exhaust port via the intermediate exhaust port and the third intake port in this order. Here, the auxiliary exhaust speed for a light gas having a molecular weight of 4 or less at the first exhaust port in the second exhaust state is a light having a molecular weight of 4 or less at the first exhaust port in the first exhaust state. It is smaller than the auxiliary exhaust speed for gas.

With such an exhaust system, in the first exhaust state, light gas and non-light gas heavier than the light gas are simultaneously taken in from the first intake port and exhausted from the third exhaust port through the second exhaust port. In addition, in the second exhaust state, the non-light gas is mainly taken in from the first intake port and exhausted from the third exhaust port through the intermediate exhaust port, so that the light gas and the non-light gas are simultaneously used. While it can be exhausted, it can be an exhaust system that can selectively and mainly exhaust non-light gas.

In the exhaust system based on the present invention, the total number of stages of the stationary blade stage and the moving blade stage of the turbo molecular pump, which are alternately installed between the first intake port and the intermediate exhaust port, is 10 stages. It is preferably 12 steps or more.

In the exhaust system based on the present invention, the gradient of the thread groove depth of the thread groove vacuum pump between the second intake port and the second exhaust port is greater than 0 and 0.04 or less. It is preferable to have.

In the exhaust system based on the present invention, the intermediate exhaust port may be provided in the exhaust path of the portion connecting the first exhaust port and the second intake port. In that case, the exhaust speed of the auxiliary vacuum pump at the third intake port in the second exhaust state is higher than the exhaust speed of the thread groove vacuum pump at the second intake port in the first exhaust state. Small is preferable.

In the exhaust system based on the present invention, an orifice may be provided in the exhaust passage of the portion connecting the intermediate exhaust port and the second port.

In the exhaust system based on the present invention, a booster vacuum pump may be installed in the exhaust passage of the portion connecting the second exhaust port and the first port.

In the exhaust system based on the present invention, it is preferable that the turbo molecular pump and the thread groove vacuum pump are composed of a composite molecular pump in which each rotor is integrated, in which case. It is preferable that the first exhaust port and the second intake port are connected inside the composite molecular pump. Further, in that case, the composite molecular pump has an intake port as the first intake port, a first exhaust port as the second exhaust port, and a second exhaust port as the intermediate exhaust port. It is preferable to do.

The electron beam laminated modeling apparatus based on the present invention includes a vacuum vessel, an electron beam generation source installed inside the vacuum vessel, and an electron beam generated inside the vacuum vessel and generated by the electron beam generation source. A laminated molding part that obtains a metal shaped object by irradiating the metal powder with a metal powder, a light gas supply source that introduces a light gas into the inside of the vacuum vessel, and an exhaust system based on the present invention connected to the vacuum vessel. And have.

By using such an electron beam laminated molding apparatus, it is possible to simultaneously exhaust light gas and non-light gas from the vacuum vessel, but it is also possible to selectively and mainly exhaust non-light gas. It is possible to obtain an electron beam laminated molding apparatus capable of suppressing the consumption of light gas as an auxiliary gas while being excellent in speed and molding accuracy.

According to the present invention, it is possible to realize an exhaust system capable of exhausting light gas and non-light gas at the same time, while selectively and mainly exhausting non-light gas. It is possible to realize an electron beam laminated molding apparatus that can suppress the consumption of auxiliary gas while being excellent in accuracy.

It is the schematic of the electron beam laminated modeling apparatus in Embodiment 1. FIG. It is a figure which showed schematic the structure of the exhaust system in Embodiment 1. FIG. It is a schematic cross-sectional view of the composite molecular pump shown in FIG. It is a figure which showed the 1st exhaust state in the exhaust system shown in FIG. It is a figure which showed the 2nd exhaust state in the exhaust system shown in FIG. It is a graph which showed the exhaust characteristic of the turbo molecular pump which concerns on Examples A and B. It is a schematic cross-sectional view which showed the shape of the thread groove of the thread groove vacuum pump which concerns on Examples a, b, c. It is a table which showed the gradient of the depth of the thread groove of the thread groove vacuum pump which concerns on Example a, b, c, d. It is a graph which showed the exhaust characteristic of the thread groove vacuum pump which concerns on Examples a, b, c. It is a table summarizing the exhaust characteristics when the thread groove vacuum pump according to Example a, b, c and the turbo molecular pump according to Example B are combined. It is a graph which showed the exhaust characteristic of the thread groove vacuum pump which concerns on Examples c, d. It is a table summarizing the exhaust characteristics when the thread groove vacuum pump according to Example c, d and the turbo molecular pump according to Example B are combined. It is a figure which showed roughly the structure of the exhaust system which concerns on the 1st modification. It is a figure which showed roughly the structure of the exhaust system which concerns on the 2nd modification. It is a figure which showed schematic the structure of the exhaust system in Embodiment 2. FIG. It is a schematic cross-sectional view of the composite molecular pump shown in FIG. It is a figure which showed schematic the structure of the exhaust system in Embodiment 3. FIG. It is a schematic cross-sectional view of the composite molecular pump shown in FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The embodiments shown below exemplify a case where the present invention is applied to an electron beam laminated modeling apparatus and an exhaust system provided therein. In the embodiments shown below, the same or common parts are designated by the same reference numerals in the drawings, and the description thereof will not be repeated.

(Embodiment 1)
FIG. 1 is a schematic view of an electron beam laminated modeling apparatus according to the first embodiment. First, with reference to FIG. 1, the configuration of the electron beam laminated modeling apparatus 100 according to the present embodiment will be described.

As shown in FIG. 1, the electron beam laminated modeling apparatus 100 includes a chamber 110 as a vacuum container, an electron gun 120 as an electron beam generation source, and a laminated modeling unit 130 which is a portion for laminating and modeling a metal model 400. The helium gas supply source 200 as a light gas supply source and the exhaust system 1A in the present embodiment described later are mainly provided.

The chamber 110 defines a first chamber portion 111 that defines a space in which an electron gun 120, a beam alignment 121, a focusing lens 122, an objective lens 123, and a polarizing device 124 are arranged, and a space in which a laminated molding portion 130 is provided. It has a second chamber portion 112. The space inside the first chamber portion 111 is maintained in an ultra-high vacuum state by an electron gun chamber exhaust system (not shown). On the other hand, in the space inside the second chamber portion 112, the partial pressure of helium gas as a light gas as an auxiliary gas is kept relatively high by the exhaust system 1A at the time of laminated molding, but the non-light gas is used. The partial pressure is maintained in a relatively low vacuum state.

The electron gun 120 includes a cathode and an anode, and a predetermined high voltage can be applied between them. The cathode is configured so that it can be heated to a high temperature state by a heating mechanism (not shown).

The electron beam EB is placed in an environment where thermions are generated by heating the cathode by a heating mechanism, and the thermoelectrons generated at the cathode are generated by applying a high voltage between the anode and the cathode. Is pulled out by the anode.

The beam alignment 121 is for aligning the optical axis of the electron beam EB emitted from the electron gun 120 with the optical axis of the focusing lens 122 by acting electromagnetically on the electron beam EB.

The focusing lens 122 and the objective lens 123 are for electromagnetically acting on the electron beam EB to concentrate the electron beam EB on a narrow area of the metal powder bed described later.

The polarizing device 124 is for bending the electron beam EB by electromagnetically acting on the electron beam EB so that the electron beam EB can be scanned on the metal powder bed. The polarizing device 124 can freely bend the electron beam EB emitted from the electron gun 120 in a direction intersecting the traveling direction thereof. In the drawing, the state is schematically indicated by an arrow DR1. Is shown.

The laminated molding unit 130 mainly includes a stage 131, a hopper 132, a rake 133, and a stage drive mechanism (not shown) that drives the stage 131 so as to be able to move up and down.

The stage 131 is arranged inside the second chamber portion 112 at a position where the electron beam EB can be irradiated. The stage 131 is a member that supports the metal powder bed formed by spreading the metal powder 300 on the main surface thereof, and can be raised and lowered in the direction of arrow DR2 shown in the drawing by the stage drive mechanism described above. Is supported by.

The hopper 132 and the rake 133 are arranged inside the second chamber portion 112 and are for handling the metal powder 300. The hopper 132 stores the metal powder 300 inside, and supplies the metal powder 300 toward the stage 131 in a required amount at a required timing. The rake 133 reciprocates in the direction of arrow DR3 shown in the drawing to spread the metal powder 300 supplied from the hopper 132 onto the stage 131 on the stage 131 so as to have a uniform thickness.

The helium gas supply source 200 is connected to the second chamber portion 112 via an on-off valve 201. The helium gas supply source 200 is for introducing helium gas into the second chamber portion 112, and by opening and closing the on-off valve 201, helium gas is required in the second chamber portion 112 at the required timing. Is supplied in large quantities.

The exhaust system 1A is connected to the second chamber portion 112 via a regulating valve 202. The exhaust system 1A is for creating a vacuum state in the second chamber portion 112 by exhausting gas molecules existing in the second chamber portion 112 to the outside.

In the electron beam laminated modeling apparatus 100 according to the present embodiment, the helium gas supply source 200 and the exhaust system 1A are properly operated so that the partial pressure of the light gas and the non-light gas can be divided in the pre-stage of the laminated modeling. A vacuum state in which both the partial pressure and the partial pressure are kept low is created at an early stage, and the partial pressure of the non-light gas is kept relatively low while the partial pressure of the helium gas is kept relatively high during the laminated molding. The vacuum state is maintained.

A vacuum gauge 210 is installed in the second chamber portion 112, and the degree of vacuum in the second chamber portion 112 is constantly measured by the vacuum gauge 210. Based on the degree of vacuum measured by the vacuum gauge 210, the above-mentioned vacuum state is realized by appropriately operating the helium gas supply source 200 and the exhaust system 1A.

At the time of laminated molding, first, the metal powder 300 composed of metal particles having a diameter of several [μm] to several tens [μm] supplied from the hopper 132 onto the stage 131 is thinly spread on the stage 131 by the rake 133. A metal powder bed is formed in. The thickness of the metal powder bed is, for example, about 10 [μm] to 100 [μm].

Next, the electron beam EB irradiates the metal powder bed formed on the stage 131. The electron beam EB emitted from the electron gun 120 is partially irradiated to a narrow area of the metal powder bed, and at this time, the electron beam EB is scanned by the polarizing device 124, so that the metal powder bed is covered with the electron beam EB. The electron beam EB is irradiated only at a position corresponding to the shape of the metal model 400 to be laminated.

As a result, the metal powder located at the portion irradiated with the electron beam EB is heated and melted, and then the heating is released to solidify the metal powder. Of the metal powder bed, the metal powder located in the range not irradiated with the electron beam EB will maintain its powder state.

Next, the stage 131 is moved downward by a stage drive mechanism (not shown). The amount of movement at that time is the same as the thickness of the metal powder bed described above.

By repeatedly performing the above-mentioned steps, the metal model 400 is gradually laminated and modeled on the stage 131, and when the laminated modeling of the metal model 400 is completed, the above-mentioned steps are repeated. Implementation will be suspended.

In the above-mentioned irradiation step of the electron beam EB, in the process of melting and solidifying the metal particles by irradiating the electron beam EB, the surface of the metal model 400 already formed in the lower layer is also melted. As a result, the metal solidified bodies formed in each layer are integrated to form a laminated metal model.

FIG. 2 is a diagram schematically showing a configuration of an exhaust system according to the present embodiment. Next, the configuration of the exhaust system 1A according to the present embodiment will be described with reference to FIG. 2.

As shown in FIG. 2, the exhaust system 1A mainly includes a composite molecular pump 10A, an auxiliary vacuum pump 20, and a three-way valve 30 which are connected to each other by an exhaust pipe or the like, if necessary. Of these, the composite molecular pump 10A is configured as a composite pump including a turbo molecular pump 10a and a thread groove vacuum pump 10b, and the auxiliary vacuum pump 20 is configured by, for example, an oil rotary vacuum pump.

The composite molecular pump 10A is installed at a position on the upstream side of the exhaust passage provided in the exhaust system 1A, and the auxiliary vacuum pump 20 is installed at a position on the downstream side of the exhaust passage provided in the exhaust system 1A. There is. The three-way valve 30 is installed at a predetermined position in the exhaust path of the portion connecting the composite molecular pump 10A and the auxiliary vacuum pump 20.

The turbo molecular pump 10a included in the composite molecular pump 10A constitutes an upstream portion of an exhaust passage formed in the composite molecular pump 10A, and the thread groove vacuum pump 10b included in the composite molecular pump 10A is a composite. It constitutes a portion on the downstream side of the exhaust passage formed in the molecular pump 10A.

Here, as shown in FIG. 2, the turbo molecular pump 10a has a first intake port IL1 and a first exhaust port OL1, and the thread groove vacuum pump 10b has a second intake port IL2 and a second exhaust port. It has OL2. On the other hand, the auxiliary vacuum pump 20 has a third intake port IL3 and a third exhaust port OL3, and the three-way valve 30 has a first port P1, a second port P2, and a third port P3.

The first intake port IL1 of the turbo molecular pump 10a constitutes the intake port IP of the composite molecular pump 10A, and is connected to the second chamber portion 112 via the above-described regulating valve 202. The first exhaust port OL1 of the turbo molecular pump 10a is connected to the second intake port IL2 of the thread groove vacuum pump 10b.

The second intake port IL2 of the thread groove vacuum pump 10b is connected to the first exhaust port OL1 of the turbo molecular pump 10a as described above. The second exhaust port OL2 of the thread groove vacuum pump 10b constitutes the first exhaust port OP1 of the composite molecular pump 10A, and is connected to the first port P1 of the three-way valve 30.

Of the composite molecular pump 10A, the threaded groove vacuum pump 10b is connected from the first intake port IL1 of the turbo molecular pump 10a to the first exhaust port OL1 of the turbo molecular pump 10a and the second intake port IL2 of the threaded groove vacuum pump 10b. An intermediate exhaust port OL5 is provided at a position in the middle of the exhaust path of the portion leading to the second exhaust port OL2.

The intermediate exhaust port OL5 constitutes the second exhaust port OP2 of the composite molecular pump 10A, and is connected to the second port P2 of the three-way valve 30. In the present embodiment, the intermediate exhaust port OL5 is provided in the exhaust path of the portion connecting the first exhaust port OL1 of the turbo molecular pump 10a and the second intake port IL2 of the threaded groove vacuum pump 10b.

The third intake port IL3 of the auxiliary vacuum pump 20 is connected to the third port P3 of the three-way valve 30. The third exhaust port OL3 of the auxiliary vacuum pump 20 is open to the atmosphere.

Here, in the exhaust system 1A of the present embodiment, the three-way valve 30 connects the first exhaust state that connects the first port P1 and the third port P3, and the second port P2 and the third port P3. It is configured so that it can be selectively switched to the second exhaust state.

With this configuration, in the first exhaust state, the light gas and the non-light gas are simultaneously taken in from the intake port IP of the composite molecular pump 10A and exhausted from the third exhaust port OL3 of the auxiliary vacuum pump 20. In the second exhaust state, the non-light gas is mainly taken in from the intake port IP of the composite molecular pump 10A and exhausted from the third exhaust port OL3 of the auxiliary vacuum pump 20, the details of which will be described later. I will do it.

FIG. 3 is a schematic cross-sectional view of the composite molecular pump shown in FIG. Next, with reference to FIG. 3, the configuration of the composite molecular pump 10A provided in the exhaust system 1A in the present embodiment will be described. As described above, the composite molecular pump 10A is configured as a composite pump including the turbo molecular pump 10a and the thread groove vacuum pump 10b. Specifically, the rotor and the thread groove vacuum of the turbo molecular pump 10a The rotor of the pump 10b is integrated.

As shown in FIG. 3, the composite molecular pump 10A mainly includes a base 11, a stator 12, a casing 13, a rotor 14, and a rotor drive mechanism 15. The outer shell of the composite molecular pump 10A is composed of a base 11, a stator 12 and a casing 13, and a rotor 14 and a rotor remain inside the outer shell composed of the base 11, the stator 12 and the casing. The drive mechanism 15 is housed.

The base 11 is for supporting the stator 12 and the rotor drive mechanism 15, and is made of a metal member having a substantially disk-shaped shape. A first exhaust pipe 18 constituting the first exhaust port OP1 of the composite molecular pump 10A is attached to a predetermined position of the base 11.

The rotor drive mechanism 15 is for rotating the rotor 14 at a high speed, and is installed on a substantially central portion of the base 11. The rotor drive mechanism 15 includes a motor and a magnetic bearing, and further includes a housing 15a in which the motor and the magnetic bearing are housed, and a rotary shaft 15b as an output shaft.

The lower end side portion of the rotating shaft 15b is located inside the housing 15a, and the upper end side portion thereof is exposed to the outside of the housing 15a. The rotor 14 is fixed to the exposed portion of the rotating shaft 15b.

The motor housed inside the housing 15a rotates and drives the rotary shaft 15b to which the rotor 14 is fixed, and the magnetic bearing housed inside the housing 15a rotatably supports the rotary shaft 15b. Is. By driving these motors and magnetic bearings, the rotating shaft 15b rotates at high speed, which causes the rotor 14 to rotate at high speed inside the composite molecular pump 10A.

The rotor 14 is made of a metal member, and has a substantially cylindrical upper rotor portion 14a fixed to the rotating shaft 15b of the rotor drive mechanism 15 and a substantially cylindrical lower rotor portion 14b. doing. A plurality of moving blades 16 are provided on the outer peripheral portion of the upper rotor portion 14a at intervals along the axial direction, and the plurality of moving blades 16 are positioned so as to project outward in the radial direction. ing. On the other hand, the lower rotor portion 14b extends downward from the lower end of the upper rotor portion 14a so as to surround the housing 15a of the rotor drive mechanism 15 described above.

The stator 12 is made of a metal member having a substantially cylindrical shape, and is installed on the peripheral edge of the base 11. The stator 12 is located so as to surround the lower rotor portion 14b of the rotor 14 so as to face the outer peripheral surface of the lower rotor portion 14b. A second exhaust pipe 19 constituting the second exhaust port OP2 of the composite molecular pump 10A is attached to a predetermined position of the stator 12.

A female thread-shaped thread groove 12a is provided on the inner peripheral surface of the stator 12. The thread groove 12a is located at a predetermined distance on the outer peripheral surface of the lower rotor portion 14b.

As a result, the thread groove vacuum pump 10b is formed by the stator 12 and the lower rotor portion 14b of the portion facing the stator 12. The thread groove vacuum pump 10b exerts an exhaust function by rotating the rotor 14 at a high speed when the composite molecular pump 10A is operated.

The casing 13 is made of a metal member having a substantially cylindrical shape, and is installed on the stator 12. The casing 13 is located so as to surround the upper rotor portion 14a of the rotor 14. The opening provided in the upper part of the casing 13 constitutes the intake port IP of the composite molecular pump 10A.

A plurality of spacers and support members 13a are provided on the inner peripheral surface of the casing 13, and the plurality of stationary blades 17 are supported by the plurality of spacers and support members 13a. The plurality of stationary blades 17 are provided at intervals along the axial direction, and are positioned so as to project inward in the radial direction.

The plurality of moving blades 16 and the plurality of stationary blades 17 described above each have turbine blades that incline in different directions. Further, the plurality of moving blades 16 and the plurality of stationary blades 17 described above are arranged so that they are alternately located along the axial direction.

As a result, the turbo molecular pump 10a is composed of the plurality of moving blades 16 and the plurality of stationary blades 17. The turbo molecular pump 10a exerts an exhaust function by rotating the rotor 14 at a high speed when the composite molecular pump 10A is operating.

In the composite molecular pump 10A having the above-described configuration, the first intake port IL1 of the turbo molecular pump 10a is configured at the upper surface position of the blade arranged at the uppermost stage of the plurality of moving blades 16 and the plurality of stationary blades 17. Therefore, the first exhaust port OL1 of the turbo molecular pump 10a is configured at the lower surface position of the blade arranged at the lowermost stage among the plurality of moving blades 16 and the plurality of stationary blades 17.

Further, in the composite molecular pump 10A having the above-described configuration, the second intake port IL2 of the thread groove vacuum pump 10b is configured at the upper end position of the gap provided between the stator 12 and the lower rotor portion 14b of the rotor 14. Therefore, the second exhaust port OL2 of the threaded groove vacuum pump 10b is configured at the lower end position of the gap provided between the stator 12 and the lower rotor portion 14b of the rotor 14.

Further, in the composite molecular pump 10A having the above-described configuration, the intermediate exhaust port OL5 is configured at the upper end position of the ventilation path provided in the stator 12.

Here, the first intake port IL1 of the turbo molecular pump 10a communicates with the intake port IP of the composite molecular pump 10A provided in the upper part of the casing 13 via the space inside the casing 13. On the other hand, the first exhaust port OL1 of the turbo molecular pump 10a communicates with the second intake port IL2 of the threaded groove vacuum pump 10b via the space inside the casing 13, and also passes through the space inside the casing 13. Then, it communicates with the intermediate exhaust port OL5, and further communicates with the second exhaust port OP2 of the composite molecular pump 10A configured by the second exhaust pipe 19 connected to the stator 12 via the ventilation path provided in the stator 12. doing.

Further, the second intake port IL2 of the thread groove vacuum pump 10b communicates with the first exhaust port OL1 of the turbo molecular pump 10a via the space inside the casing 13, and also passes through the space inside the casing 13. Then, it communicates with the intermediate exhaust port OL5, and further communicates with the second exhaust port OP2 of the composite molecular pump 10A configured by the second exhaust pipe 19 connected to the stator 12 via the ventilation path provided in the stator 12. doing. On the other hand, the second exhaust port OL2 of the thread groove vacuum pump 10b is a composite composed of a first exhaust pipe 18 connected to the base 11 via a space inside the stator 12 and a ventilation path provided in the base 11. It communicates with the first exhaust port OP1 of the molecular pump 10A.

As a result, as described above, the turbo molecular pump 10a constitutes the upstream portion of the exhaust passage formed in the composite molecular pump 10A, and the thread groove vacuum pump 10b is placed in the composite molecular pump 10A. It constitutes a portion on the downstream side of the formed exhaust passage.

In other words, in the composite molecular pump 10A, the intake port IP is connected to the first exhaust port OP1 via the turbo molecular pump 10a and the thread groove vacuum pump 10b, while the intake port IP is the turbo molecular. It is also connected to the second exhaust port OP2 via only the pump 10a.

It should be noted that there are O-rings between the base 11 and the stator 12, between the stator 12 and the casing 13, between the base 11 and the first exhaust pipe 18, between the stator 12 and the second exhaust pipe 19, and the like. Etc. are interposed. As a result, the airtightness of the exhaust passage of the portion located between the intake port IP and the first exhaust port OP1 and the second exhaust port OP2 is ensured, and the occurrence of air leakage from the exhaust passage is prevented. can.

4 and 5 are diagrams showing the above-mentioned first exhaust state and the second exhaust state in the exhaust system according to the present embodiment, respectively. Next, with reference to these FIGS. 4 and 5, the above-mentioned first exhaust state and second exhaust state will be described in detail.

As shown in FIG. 4, in the first exhaust state, the three-way valve 30 is switched so that the first port P1 and the third port P3 of the three-way valve 30 are connected. In the first exhaust state, the first exhaust port OP1 of the composite molecular pump 10A and the third intake port IL3 of the auxiliary vacuum pump 20 are connected via the three-way valve 30.

As a result, in the exhaust system 1A, the turbo molecular pump 10a, the thread groove vacuum pump 10b, and the auxiliary vacuum pump 20 are connected in this order from the upstream side, whereby the first exhaust path EP1 shown in the figure is formed. Will be done. More specifically, in the first exhaust state, the gas taken in from the first intake port IL1 configured as the intake port IP is configured as the first exhaust port OL1, the second intake port IL2, and the first exhaust port OP1. The gas is exhausted from the third exhaust port OL3 via the second exhaust port OL2 and the third intake port IL3 in this order.

As shown in FIG. 5, in the second exhaust state, the three-way valve 30 is switched so that the second port P2 and the third port P3 of the three-way valve 30 are connected. In the second exhaust state, the second exhaust port OP2 of the composite molecular pump 10A and the third intake port IL3 of the auxiliary vacuum pump 20 are connected via the three-way valve 30.

As a result, in the exhaust system 1A, the turbo molecular pump 10a and the auxiliary vacuum pump 20 are connected in this order from the upstream side, whereby the second exhaust path EP2 shown in the figure is formed. More specifically, in the second exhaust state, the gas taken in from the first intake port IL1 configured as the intake port IP is the intermediate exhaust port OL5 configured as the first exhaust port OL1 and the second exhaust port OP2. And, it will be exhausted from the third exhaust port OL3 via the third intake port IL3 in this order. That is, the gas taken in from the first intake port IL1 configured as the intake port IP is different from the first exhaust state described above, and is different from the first exhaust state, and the second exhaust port OL2 configured as the second intake port IL2 and the first exhaust port OP1. Never go through.

Here, in general, in a turbo molecular pump, when the exhaust speed on the intake port side depends to a considerable extent on the auxiliary exhaust speed on the exhaust port side and the auxiliary exhaust speed on the exhaust port side is large, the intake port side The exhaust speed tends to increase, and when the auxiliary exhaust speed on the exhaust port side is small, the exhaust speed on the intake port side also tends to decrease. Further, the degree of dependence varies greatly depending on the type of gas to be exhausted, and the degree of dependence on light gas is greater than the degree of dependence on non-light gas. The auxiliary exhaust speed referred to here is set to the downstream side of the turbo molecular pump when the conductance of the exhaust path between the exhaust port of the turbo molecular pump and the vacuum pump arranged on the downstream side thereof is sufficiently large. It is basically equivalent to the exhaust speed on the intake side of the placed vacuum pump. That is, the auxiliary exhaust speed is equivalent to the exhaust speed on the second intake port IL2 side of the thread groove vacuum pump 10b in the above-mentioned first exhaust state, and the auxiliary vacuum pump in the above-mentioned second exhaust state. It is equivalent to the exhaust speed on the third intake port IL3 side of 20.

Further, normally, the exhaust speed of the auxiliary vacuum pump 20 composed of the oil rotary vacuum pump on the third intake port IL3 side is an order of magnitude higher than the exhaust speed of the thread groove vacuum pump 10b on the second intake port IL2 side. small.

Therefore, by switching the three-way valve 30, the auxiliary exhaust speed at the first exhaust port OL1 of the turbo molecular pump 10a in the second exhaust state is set at the first exhaust port OL1 of the turbo molecular pump 10a in the first exhaust state. It is orders of magnitude smaller than the auxiliary exhaust speed. As a result, the exhaust speed of the turbo molecular pump 10a in the second exhaust state at the first intake port IL1 is comparable to the exhaust speed in the first exhaust state for non-light gas, whereas it is light. For gas, it is significantly smaller than the exhaust speed in the first exhaust state.

Therefore, in the first exhaust state, the light gas and the non-light gas are simultaneously taken in from the intake port IP of the composite molecular pump 10A and are taken from the third exhaust port OL3 of the auxiliary vacuum pump 20 via the first exhaust path EP1. In the second exhaust state, the non-light gas is mainly taken in from the intake port IP of the composite molecular pump 10A and passed through the second exhaust path EP2 to the third exhaust port of the auxiliary vacuum pump 20. It will be exhausted from OL3. That is, in the second exhaust state, the displacement of helium gas as light gas is significantly smaller than that in the first exhaust state, while the displacement of non-light gas is maintained substantially the same as in the first exhaust state.

As a result, in the electron beam laminated molding apparatus 100 shown in FIG. 1 described above, the exhaust system 1A is stopped while the introduction of helium gas into the second chamber portion 112 by the helium gas supply source 200 is stopped in the stage prior to the laminated molding. By exhausting the inside of the second chamber portion 112 in the first exhaust state using the above, a high vacuum state can be created in a short time, and then, at the time of laminated molding, the helium gas supply source 200 is used. By introducing the helium gas into the second chamber portion 112 and exhausting the helium gas into the second chamber portion 112 in the second exhaust state using the exhaust system 1A, the partial pressure of the helium gas is relative. It is possible to maintain a vacuum state in which the partial pressure of the non-light gas is kept relatively low while being kept high.

Here, in the second exhaust state, since the displacement of helium gas as a light gas exhausted by the exhaust system 1A is small, the helium gas to be introduced into the second chamber portion 112 by the helium gas supply source 200. The amount of gas can be significantly reduced. Therefore, the partial pressure of the helium gas in the second chamber portion 112 can be kept relatively high while significantly suppressing the consumption of the helium gas.

Therefore, by applying the exhaust system 1A according to the present embodiment described above, it is possible to exhaust the light gas and the non-light gas at the same time, and at the same time, the non-light gas can be selectively and mainly exhausted. It is possible to realize this, and by using the electron beam laminated modeling apparatus 100 equipped with the exhaust system 1A, it is possible to suppress the consumption of helium gas as an auxiliary gas while being excellent in modeling speed and modeling accuracy. It becomes possible to realize an electron beam laminated modeling device.

Here, the total number of stages of the moving blades 16 and the stationary blades 17 constituting the turbo molecular pump 10a described above is preferably 10 or more and 12 or less. In the present embodiment, this is composed of a total of 11 stages of a 6-stage moving blade 16 and a 5-stage stationary blade 17. With this configuration, it is possible to increase the degree to which the exhaust speed for helium gas on the first intake port IL1 side depends on the auxiliary exhaust speed on the exhaust port side (that is, helium in the second exhaust state). The amount of gas exhaust can be further suppressed), and the selective exhaust of non-light gas can be promoted.

Since the total number of moving blades and stationary blades of a normal turbo molecular pump is 15 or more, when the total number of these stages is 10 or more and 12 or less as described above, it is a non-light gas. Not only can selective exhaust be promoted, but the turbo molecular pump 10a can also be significantly miniaturized.

Further, the gradient of the depth of the thread groove 12a provided in the stator 12 constituting the thread groove vacuum pump 10b described above is preferably larger than 0 and 0.04 or less. With this configuration, the auxiliary exhaust speed for helium gas at the first exhaust port OL1 in the first exhaust state can be further increased, so that the displacement of helium gas in the first exhaust state can be increased. Can be done.

In the following, by applying the exhaust system 1A of the present embodiment, it is possible to exhaust light gas and non-light gas at the same time, while it is also possible to selectively and mainly exhaust non-light gas. Will be described in more detail.

_{Generally, in a high vacuum state, water vapor (H 2} O) is the most abundant gas molecules desorbed from the inner wall surface of the chamber and the like. Therefore, it is assumed here that the only released gas is water vapor.

Assuming that the auxiliary gas is helium gas and the released gas (impurity) is water vapor, the impurity ratio α in the chamber is PHe, which is the partial pressure of helium gas in the chamber, and PH is the partial pressure of water vapor in the chamber. _{Assuming 2} O, it is defined by the following equation (1).

Here, the flow rate of helium gas supplied into the chamber is QHe, the amount of water vapor released from the inner wall surface of the chamber is QH ₂ O, and the exhaust rate of helium gas at the intake port of the turbo molecular pump is SH. Assuming that the exhaust rate of water vapor at the intake port of the turbo molecular pump is SH ₂ O, the above equation (1) can be rewritten as the following equation (2).

Therefore, according to the above equation (2), in order to reduce the impurity ratio α, the helium gas is exhausted at the intake port of the turbo molecular pump with respect to _{the exhaust rate SH 2 O of water vapor at the intake port of the turbo molecular pump.} The speed She should be reduced.

Generally, in the free molecular region, the exhaust speed S at the intake port for a gas of the turbo molecular pump is the maximum exhaust speed Smax for the gas, the maximum compression ratio Kmax for the gas, and the exhaust port of the turbo molecular pump. It is expressed by the following equation (3) using the exhaust speed (auxiliary exhaust speed) Sfore for the gas.

Here, when the gas is a non-light gas, the condition of Kmax >> 1 is satisfied. Therefore, the above formula (3) uses the following formula (4) using ε1 represented by the following formula (4-1). -2) can be rewritten.

On the other hand, when the gas is a light gas and the Sfore is sufficiently large, the conditions of Kmax> 1 and Smax> Sfore are satisfied. Therefore, the above formula (3) is changed to the following formula (5-1). It can be rewritten to the following equation (5-2) using the shown ε2.

On the other hand, when the gas is a light gas and the Sfore is sufficiently small, the conditions of Kmax> 1 and Smax >> Sfore are satisfied. Therefore, the above equation (3) is expressed by the following equation (6-1). It can be rewritten to the following equation (6-2) using ε3 shown in.

Smax and Kmax are values determined by the design of the turbo molecular pump for each gas type, and Sfore is the capacity of the vacuum pump arranged on the downstream side of the turbo molecular pump as described above, and the turbo molecular pump and the vacuum pump. It depends on the conductance of the exhaust passage connecting with. Further, in principle, the Kmax of a light gas (here, helium gas) is orders of magnitude smaller than the Kmax of a non-light gas (here, water vapor).

In consideration of the above, by constructing an exhaust system so as to satisfy the following conditions, an exhaust system capable of simultaneously exhausting helium gas and water vapor, while selectively exhausting only water vapor can be achieved. It will be possible.

The first condition is to increase both _{SH and SH 2} O described above in order to exhaust more helium gas and water vapor at the same time. In _{order to increase SH 2} O, S may be brought closer to Smax according to the above equation (4-2), and as a result, ε1 may be sufficiently reduced. In order to increase She, S may be brought closer to Smax according to the above equation (5-2), and as a result, ε2 may be sufficiently reduced.

The second condition is to increase _{SH 2} O while reducing the above-mentioned SH in order to selectively and mainly exhaust only water vapor. In _{order to increase SH 2} O, S may be brought closer to Smax according to the above equation (4-2) as described above, and as a result, ε1 may be sufficiently reduced. In order to reduce She, S may be brought close to Sfore × Kmax according to the above equation (6-2), and as a result, ε3 may be sufficiently reduced.

Of these, reducing ε1 can be realized by designing a turbo molecular pump, and the design is relatively easy. On the other hand, ε2 and ε3 depend on the capacity of the vacuum pump installed on the downstream side of the turbo molecular pump and the conductance of the exhaust path connecting the turbo molecular pump and the vacuum pump, and these in a single vacuum pump. Since neither ε2 nor ε3 can be made small, this can be realized by forming a branch path on the downstream side of the turbo molecular pump and arranging vacuum pumps having different capacities in each of them. In order to reduce ε2, a vacuum pump having a large exhaust rate with respect to helium gas may be used, and to reduce ε3, a vacuum pump having a small exhaust rate with respect to helium gas may be used.

As described above, as in the exhaust system 1A in the present embodiment described above, as the first exhaust state, the thread groove vacuum pump 10b having a large exhaust speed with respect to helium gas is connected to the downstream side of the turbo molecular pump 10a, and the second exhaust. In the state, the auxiliary vacuum pump 20 composed of an oil rotary vacuum pump having a small exhaust speed with respect to helium gas is connected to the downstream side of the turbo molecular pump 10a, and the first exhaust state and the second exhaust state are set in three directions. By configuring the valve 30 to be selectively switchable, it is possible to realize an exhaust system in which light gas and non-light gas can be exhausted at the same time, while non-light gas can be selectively and mainly exhausted. Become.

FIG. 6 is a graph showing the exhaust characteristics of the turbo molecular pumps according to Examples A and B. Hereinafter, with reference to FIG. 6, the exhaust characteristics of the turbo molecular pump 10a to be provided in the exhaust system 1A in the present embodiment will be described.

As described above, in the turbo molecular pump, the exhaust speed on the intake port side depends to a considerable extent on the auxiliary exhaust speed on the exhaust port side. The graph shown in FIG. 6 is a graph showing the degree of this dependence. For each of the turbo molecular pumps according to Examples A and B, the exhaust speed on the intake port side with respect to helium gas and nitrogen gas and the exhaust port side. It shows the relationship with the auxiliary exhaust speed in. In the graph, the vertical axis represents the exhaust speed S [L / s] on the intake port side with respect to helium gas and nitrogen gas, and the horizontal axis represents the auxiliary exhaust speed Sfore [L / s] on the exhaust port side.

Example A is a standard turbo molecular pump having an exhaust speed of about 3000 [L / s] at the intake port, and has a total of 17 stages of stationary blade stages and moving blade stages. On the other hand, in Example B, the total number of stages of the stationary blade stage and the moving blade stage is reduced to 11 stages in the standard turbo molecular pump.

With reference to FIG. 6, in all of the turbo molecular pumps according to Examples A and B, for nitrogen gas, which is a non-light gas, the intake port side with respect to the change in the auxiliary exhaust speed on the exhaust port side. It can be understood that there is no significant change in the auxiliary exhaust speed, and the exhaust speed on the intake port side is maintained at 3100 [L / s].

On the other hand, in all of the turbo molecular pumps according to Examples A and B, for helium gas, which is a light gas, the auxiliary exhaust speed on the intake port side is large with respect to the change in the auxiliary exhaust speed on the exhaust port side. It can be understood that there is a change and the exhaust speed on the intake port side tends to decrease as the auxiliary exhaust speed on the exhaust port side decreases.

In this way, regardless of which of the turbo molecular pumps according to Examples A and B is used, by changing the auxiliary exhaust speed on the exhaust port side, the intake port side with respect to the non-light gas nitrogen gas is used. It is possible to increase or decrease the exhaust speed on the intake port side with respect to helium gas, which is a light gas, while maintaining the exhaust speed at the same level. Therefore, any turbo molecular pump can be provided in the exhaust system 1A according to the present embodiment as long as it has such exhaust characteristics.

Here, in the turbo molecular pump according to the A embodiment, when the auxiliary exhaust speed on the exhaust port side is about 60 to 400 [L / s], the exhaust speed with respect to the helium gas on the intake port side is about 2800 to. While it is maintained at about 3000, when the auxiliary exhaust speed on the exhaust port side falls below about 60 [L / s], the exhaust speed for helium gas on the intake port side suddenly decreases and exhausts. When the auxiliary exhaust speed on the mouth side is about 10 [L / s], the exhaust speed for helium gas on the intake port side is reduced to about 1800 [L / s].

On the other hand, in the turbo molecular pump according to the B embodiment, in the range where the auxiliary exhaust speed on the exhaust port side is smaller than 400 [L / s], the intake becomes smoother as the auxiliary exhaust speed on the exhaust port side decreases. When the exhaust speed for helium gas on the mouth side decreases and the auxiliary exhaust speed on the exhaust port side is about 10 [L / s], the exhaust speed for helium gas on the intake port side is about 300 [L / s]. ] Has decreased to the extent.

Therefore, in the turbo molecular pump according to the A embodiment, the exhaust speed with respect to the helium gas on the intake port side changes sensitively according to the change in the auxiliary exhaust speed on the exhaust port side, which is stable. Control may be difficult, and the exhaust speed itself for helium gas on the intake port side may not be extremely small.

On the other hand, in the turbo molecular pump according to the B embodiment, the exhaust speed for helium gas on the intake port side gradually changes according to the change in the auxiliary exhaust speed on the exhaust port side, which is more stable. Not only can the control be performed, but also the exhaust speed itself for helium gas on the intake port side can be sufficiently reduced.

Therefore, as described above, as the turbo molecular pump 10a provided in the exhaust system 1A in the present embodiment, it is more preferable that the total number of stages of the moving blades 16 and the stationary blades 17 is 10 or more and 12 or less. It can be said that.

FIG. 7 is a schematic cross-sectional view showing the shape of the thread groove of the thread groove vacuum pump according to Examples a, b, c, and FIG. 8 is a schematic cross-sectional view showing the thread groove vacuum pump according to Examples a, b, c, d. It is a table which shows the gradient of the depth of the thread groove of. FIG. 9 is a graph showing the exhaust characteristics of the thread groove vacuum pump according to Examples a, b, and c, and FIG. 10 shows the thread groove vacuum pump according to Examples a, b, and C and Example B. It is a table summarizing the exhaust characteristics when combined with a turbo molecular pump. Further, FIG. 11 is a graph showing the exhaust characteristics of the thread groove vacuum pump according to Examples c and d, and FIG. 12 shows the thread groove vacuum pump according to Examples c and d and the turbo molecule according to Example B. It is a table summarizing the exhaust characteristics when combined with a pump. Hereinafter, with reference to these FIGS. 7 to 12, the exhaust characteristics of the thread groove vacuum pump 10b to be provided in the exhaust system 1A in the present embodiment will be described.

As described above, in the exhaust system 1A of the present embodiment, it is required to secure a large displacement of not only the non-light gas but also the light gas helium gas in the first exhaust state. Therefore, in the thread groove vacuum pump 10b, it is necessary to increase the exhaust speed with respect to helium gas as much as possible.

The exhaust characteristics of a threaded vacuum pump are greatly affected by the gradient of the threaded depth. Here, assuming four types of models in total of Examples a, b, c, and d having different thread groove depth gradients and shaft lengths, the exhaust speed with respect to helium gas in each model is examined.

As shown in FIGS. 7 and 8, in the thread groove vacuum pump according to Examples a, b, and c, the axial length of the stator 12 at the portion where the thread groove 12a is formed is set to 128.0 [mm]. , The depth at the upstream end of the thread groove 12a is 11.0 [mm], and the depth at the downstream end of the thread 12a is 1.5 [mm], 3.0 [mm], respectively. It was set to 6.0 [mm]. The depth gradients of the thread grooves 12a of the thread groove vacuum pump according to Examples a, b, and c are 0.074 [−], 0.063 [−], and 0.039 [−], respectively.

On the other hand, as shown in FIG. 8, in the thread groove vacuum pump according to the d of the embodiment, the axial length of the stator 12 of the portion where the thread groove 12a is formed is 168.0 [mm], and the upstream side of the thread groove 12a is set. The depth at the end was 12.56 [mm], and the depth at the downstream end of the thread groove 12a was 6.0 [mm], respectively. The gradient of the depth of the thread groove 12a of the thread groove vacuum pump according to the d of the embodiment is 0.039 [−].

In the thread groove vacuum pump according to the embodiment d, in the thread groove vacuum pump according to the embodiment c, the upstream end portion of the thread groove 12a is 40.0 [ It is extended to the upstream side by [mm]. This configuration assumes that in a standard composite molecular pump, the thread groove vacuum pump will be extended to the space obtained when the total number of rotor blades and stationary blades of the turbo molecular pump is reduced. ..

The graph shown in FIG. 9 shows how the exhaust characteristics of the thread groove vacuum pump change with respect to helium gas as a light gas and nitrogen gas as a non-light gas when the gradient of the depth of the thread groove is changed. Is shown. The graph shows the case where a certain amount of helium gas or nitrogen gas is flowing in the thread groove (18.1 [Pa · L / s] in terms of 10 [sccm] (20 [° C.]) (second chamber portion). The relationship between the pressure at the upstream end of the thread groove and the pressure at the downstream end of the thread groove (so-called back pressure) when the partial pressure is about 6.0 × 10 ^{-3 [Pa] in 112)} In the graph, the vertical axis represents the pressure Ps [Pa] at the upstream end of the thread groove, and the horizontal axis represents the pressure Pb [Pa] at the downstream end of the thread groove.

In the thread groove vacuum pump according to Example a, the gradient of the thread groove depth is larger than that of other thread groove vacuum pumps, and the back pressure resistance performance is improved, but the exhaust speed with respect to helium gas when Pb is low. Is small (that is, Ps is high).

On the other hand, in the thread groove vacuum pump according to the b embodiment, the gradient of the thread groove depth is smaller than that of the thread groove vacuum pump according to the a, and the back pressure resistance performance is slightly inferior, but the Pb is low. It can be seen that the exhaust rate with respect to helium gas is high (that is, Ps is low).

Further, in the thread groove vacuum pump according to Example c, the gradient of the thread groove depth is further smaller than that of the thread groove vacuum pump according to Example b, and the back pressure resistance performance is inferior. It can be seen that the exhaust rate for helium gas when Pb is low is very high (that is, Ps is very low).

Here, FIG. 10 assumes that the turbo molecular pump installed on the upstream side of the threaded groove vacuum pump is that of the above-described Example B, and the exhaust speed of the auxiliary vacuum pump installed on the downstream side of the threaded groove vacuum pump is 100. It is set to [L / s] and shows the exhaust characteristics of Examples a, b, and c when the helium gas is flowing in the thread groove by 10 [sccm]. Here, the pressure Ps [Pa] of the helium gas at the upstream end of the thread groove can be read from the graph shown in FIG. 9, and based on this, the auxiliary exhaust speed Sfore [L / S] at the first exhaust port of the turbo molecular pump ] Is calculated, and based on this, the exhaust rate She [L / s] with respect to the helium gas at the first intake port of the turbo molecular pump can be read from the graph shown in FIG.

As shown in FIG. 10, in Examples a, b, and c, the exhaust speeds She for helium gas at the first intake port of the turbo molecular pump are 2060 [L / s], 2150 [L / s], and 2230, respectively. It can be seen that it becomes [L / s]. By making the gradient of the thread groove depth of the thread groove vacuum pump smaller in this way, it is possible to secure a larger displacement amount of helium gas, which is a light gas, in the first exhaust state.

The graph shown in FIG. 11 shows how the exhaust characteristics of the thread groove vacuum pump change with respect to helium gas as a light gas and nitrogen gas as a non-light gas when the shaft length of the thread groove is changed. It is a thing. The graph shows the case where a certain amount (10 [sccm]) of helium gas or nitrogen gas is flowing in the thread groove (when the partial pressure is about 6.0 × 10 ^-3 [Pa] in the exhaust process). , The relationship between the pressure at the upstream end of the thread groove and the pressure at the downstream end of the thread groove (so-called back pressure) is shown. In the graph, the vertical axis represents the pressure Ps [Pa] at the upstream end of the thread groove, and the horizontal axis represents the pressure Pb [Pa] at the downstream end of the thread groove.

In the threaded groove vacuum pump according to the d of the embodiment, the axial length of the threaded groove is longer and the exhaust rate with respect to the helium gas is larger (that is, the Ps is lower) when the shaft length of the threaded groove is longer and the Pb is lower than that of the threaded groove vacuum pump according to the c. ) Is understood.

Here, FIG. 12 assumes that the turbo molecular pump installed on the upstream side of the threaded groove vacuum pump is that of the above-described Example B, and the exhaust speed of the auxiliary vacuum pump installed on the downstream side of the threaded groove vacuum pump is 100. It is set to [L / s] and shows the exhaust characteristics of Examples c and d when the helium gas is flowing in the thread groove by 10 [sccm]. Here, the pressure Ps [Pa] of the helium gas at the upstream end of the thread groove can be read from the graph shown in FIG. 11, and based on this, the auxiliary exhaust speed Sfore [L / S] at the first exhaust port of the turbo molecular pump ] Is calculated, and based on this, the exhaust rate She [L / s] with respect to the helium gas at the first intake port of the turbo molecular pump can be read from the graph shown in FIG.

As shown in FIG. 12, in Examples c and d, the exhaust speeds She for helium gas at the first intake port of the turbo molecular pump are 2230 [L / s] and 2300 [L / s], respectively. I understand. By lengthening the shaft length of the screw groove of the screw groove vacuum pump in this way, it is possible to secure a larger displacement amount of helium gas, which is a light gas, in the first exhaust state.

Therefore, as described above, as the thread groove vacuum pump 10b provided in the exhaust system 1A in the present embodiment, a thread groove depth gradient of more than 0 and 0.04 or less is more preferable. However, it can be said that a screw groove having a longer axial length is more preferable.

On the other hand, when any of the thread groove vacuum pumps according to Examples a, b, c, and d is used, the exhaust rate with respect to helium gas can be increased to a considerable extent, so that this is downstream of the turbo molecular pump. By connecting to the side, the auxiliary exhaust speed on the exhaust port side of the turbo molecular pump can be made higher than when the auxiliary vacuum pump that creates a low vacuum state is connected to the downstream side of the turbo molecular pump. Therefore, any thread groove vacuum pump can be provided in the exhaust system 1A according to the present embodiment as long as it has such an exhaust characteristic.

(First modification)
FIG. 13 is a diagram schematically showing the configuration of the exhaust system according to the first modification. Hereinafter, the exhaust system 1B according to the first modification based on the present embodiment will be described with reference to FIG. 13.

The exhaust system 1B shown in FIG. 13 is provided in the electron beam laminated modeling apparatus 100 according to the present embodiment in place of the exhaust system 1A described above. The exhaust system 1B differs in its configuration only in that it further has an orifice 40 when compared to the exhaust system 1A described above.

As shown in FIG. 13, the orifice 40 is provided in the exhaust path of the portion connecting the second exhaust port OP2 of the composite molecular pump 10A and the second port P2 of the three-way valve 30. The orifice 40 is for optimizing the auxiliary exhaust speed for helium gas at the first exhaust port OL1 of the turbo molecular pump 10a in the second exhaust state.

By providing the orifice 40, in the second exhaust state, the gas taken in from the first intake port IL1 configured as the intake port IP is configured as the first exhaust port OL1 and the second exhaust port OP2. The gas is exhausted from the third exhaust port OL3 via the intermediate exhaust port OL5, the orifice 40, and the third intake port IL3 in this order.

Hereinafter, the reason why the auxiliary exhaust speed with respect to the helium gas at the first exhaust port OL1 of the turbo molecular pump 10a is optimized in the second exhaust state by providing the orifice 40 will be described.

For example, it is assumed that a turbo molecular pump as in Example B described above is used as the turbo molecular pump 10a, and an auxiliary vacuum pump 20 having an exhaust speed of 100 [L / s] is used. In that case, if the orifice 40 is not provided, the exhaust speed with respect to the helium gas on the intake port side of the turbo molecular pump is about 1750 [L / s] with reference to FIG. 6, and the helium gas in the second exhaust state. The displacement of is relatively large.

In this case, for example, in order to set the exhaust speed for helium gas on the intake port side of the turbo molecular pump to 687 [L / s], the conductance CH for helium gas is 29.4 [L / s] as the orifice 40. ] Can be used. As a result, the auxiliary exhaust speed for helium gas on the exhaust port side of the turbo molecular pump is reduced to 22.7 [L / s], so that the exhaust speed for helium gas on the intake port side of the turbo molecular pump is 687 [L]. / S] can be set.

Therefore, by providing the orifice 40 as described above, it is possible to optimize the auxiliary exhaust speed for helium gas at the first exhaust port OL1 of the turbo molecular pump 10a in the second exhaust state.

In this case, since the conductance CN ₂ of the orifice 40 with respect to nitrogen gas is 11.1 [L / s], the auxiliary exhaust speed with respect to nitrogen gas on the exhaust port side of the turbo molecular pump is 10.0 [L]. / S], and the exhaust rate for nitrogen gas on the intake port side of the turbo molecular pump is 3058 [L / s]. Therefore, in the second exhaust state, the exhaust of helium gas can be suppressed and the nitrogen gas can be selectively and mainly exhausted.

Instead of providing the orifice 40, the exhaust path of the portion connecting the second exhaust port OP2 of the composite molecular pump 10A and the second port P2 of the three-way valve 30 is narrow and has the same conductance as the orifice 40. It may be configured by piping.

(Second modification)
FIG. 14 is a diagram schematically showing the configuration of the exhaust system according to the second modification. Hereinafter, the exhaust system 1C according to the second modification based on the present embodiment will be described with reference to FIG. 14.

The exhaust system 1C shown in FIG. 14 is provided in the electron beam laminated modeling apparatus 100 according to the present embodiment in place of the exhaust system 1A described above. The exhaust system 1C is different in its configuration only in that it further has a booster vacuum pump 50 when compared with the exhaust system 1A described above.

As shown in FIG. 14, the booster vacuum pump 50 is provided in the exhaust path of the portion connecting the first exhaust port OP1 of the composite molecular pump 10A and the first port P1 of the three-way valve 30. More specifically, the booster vacuum pump 50 has a fourth intake port IL4 and a fourth exhaust port OL4, and the fourth intake port IL4 is a screw configured as the first exhaust port OP1 of the composite molecular pump 10A. It is connected to the second exhaust port OL2 of the groove vacuum pump 10b, and the fourth exhaust port OL4 is connected to the first port P1 of the three-way valve.

The booster vacuum pump 50 is for optimizing the auxiliary exhaust speed at the first exhaust port OL1 of the turbo molecular pump 10a in the first exhaust state. As the booster vacuum pump, a roots type vacuum pump or the like is appropriate.

By providing the booster vacuum pump 50, in the first exhaust state, the gas taken in from the first intake port IL1 configured as the intake port IP is the first exhaust port OL1, the second intake port IL2, and the second. 1 It is decided that the gas is exhausted from the third exhaust port OL3 via the second exhaust port OL2, the fourth intake port IL4, the fourth exhaust port OL4, and the third intake port IL3 configured as the exhaust port OP1 in this order. Become.

Hereinafter, the reason why the auxiliary exhaust speed at the first exhaust port OL1 of the turbo molecular pump 10a is optimized in the first exhaust state by providing the booster vacuum pump 50 will be described.

For example, a turbo molecular pump as in Example B described above is used as the turbo molecular pump 10a, a thread groove vacuum pump as described in Example c described above is used as the thread groove vacuum pump 10b, and the exhaust speed thereof is increased as an auxiliary vacuum pump. It is assumed that a 22.7 [L / s] pump is used. In that case, if the booster vacuum pump 50 is not provided, the auxiliary exhaust speed with respect to the helium gas on the exhaust port side of the thread groove vacuum pump in the first exhaust state is 22.7 [L / s], and the flow rate of the helium gas. For example, when 10 [sccm] (18.1 [Pa · L / s] in terms of 20 [° C.]), the pressure on the exhaust port side of the thread groove vacuum pump is 0.80 [Pa], so the screw. It can be seen from FIG. 11 that the pressure on the intake port side of the groove vacuum pump is 0.12 [Pa], and the auxiliary exhaust speed for helium at the exhaust port of the turbo molecular pump is 151 [L / s]. .. Therefore, based on FIG. 6, the exhaust speed at the intake port of the turbo molecular pump at this time is 2000 [L / s], and the displacement in the first exhaust state is smaller than that in the case of FIG. ..

Therefore, in this case, for example, in order to set the auxiliary exhaust speed on the exhaust port side of the thread groove vacuum pump to 100 [L / s], a booster vacuum pump 50 having an exhaust speed of 100 [L / s] is installed. You just have to do it.

Therefore, by providing the booster vacuum pump 50 as described above, the auxiliary exhaust speed at the first exhaust port OL1 of the turbo molecular pump 10a can be optimized in the first exhaust state.

In the second exhaust state, the booster vacuum pump 50 may be stopped or may be operated as it is.

(Embodiment 2)
FIG. 15 is a diagram schematically showing the configuration of the exhaust system according to the second embodiment, and FIG. 16 is a schematic cross-sectional view of the composite molecular pump shown in FIG. Hereinafter, the configurations of the exhaust system 1D and the composite molecular pump 10B provided therein will be described with reference to FIGS. 15 and 16.

The exhaust system 1D shown in FIG. 15 is provided in the electron beam laminated modeling apparatus 100 in the above-described embodiment instead of the exhaust system 1A in the above-described first embodiment. The exhaust system 1D is mainly different in its configuration in that the position where the intermediate exhaust port OL5 is formed is different when compared with the exhaust system 1A described above.

As shown in FIG. 15, in the exhaust system 1D, an intermediate exhaust port OL5 constituting the second exhaust port OP2 of the composite molecular pump 10B is provided at an intermediate position of the turbo molecular pump 10a. More specifically, the intermediate exhaust port OL5 is provided in the exhaust passage of the portion connecting the first intake port IL1 and the first exhaust port OL1 of the turbo molecular pump 10a.

Specifically, as shown in FIG. 16, the composite molecular pump 10B mainly includes the base 11, the stator 12, the casing 13, the rotor 14, and the rotor drive mechanism 15 as in the composite molecular pump 10A in the above-described embodiment. However, unlike the composite molecular pump 10A, the second exhaust pipe 19 is not attached to the stator 12, and the second exhaust pipe 19 is attached to the casing 13 instead.

Along with this, an opening for communicating the space inside the casing 13 and the second exhaust pipe 19 is provided in the portion of the casing 13 to which the second exhaust pipe 19 is attached. As a result, the intermediate exhaust port OL5 is formed in the opening provided in the casing 13. In this case, the total number of rotor blade stages and stationary blade stages included between the first intake port IL1 and the intermediate exhaust port OL5 is preferably 10 or more and 12 or less.

In the exhaust system 1D configured in this way, in the first exhaust state, the gas taken in from the first intake port IL1 configured as the intake port IP is the first exhaust port OL1, the second intake port IL2, and the first. It is exhausted from the third exhaust port OL3 via the second exhaust port OL2 and the third intake port IL3 configured as one exhaust port OP1 in this order, and in the second exhaust state, the intake port IP The gas taken in from the first intake port IL1 configured as is exhausted from the third exhaust port OL3 via the intermediate exhaust port OL5 and the third intake port IL3 configured as the second exhaust port OP2 in this order. Will be done.

Therefore, in the first exhaust state, helium gas as a light gas and non-light gas heavier than the helium gas are simultaneously sucked from the intake port IP of the composite molecular pump 10B and from the third exhaust port OL3 of the auxiliary vacuum pump 20. In the second exhaust state, the non-light gas is mainly taken in from the intake port IP of the composite molecular pump 10B and exhausted from the third exhaust port OL3 of the auxiliary vacuum pump 20. That is, in the second exhaust state, the displacement of helium gas as light gas is significantly smaller than that in the first exhaust state, while the displacement of non-light gas is maintained substantially the same as in the first exhaust state.

Therefore, even when the exhaust system 1D in the present embodiment is used, an effect similar to the effect described in the above-described first embodiment can be obtained, and light gas and non-light gas can be exhausted at the same time. On the other hand, it is possible to make an exhaust system that can selectively and mainly exhaust non-light gas, and by using an electron beam laminated molding device equipped with the exhaust system 1D, the molding speed and molding accuracy are excellent. However, it can be an electron beam laminated molding apparatus capable of suppressing the consumption of helium gas as an auxiliary gas.

(Embodiment 3)
FIG. 17 is a diagram schematically showing the configuration of the exhaust system according to the third embodiment, and FIG. 18 is a schematic cross-sectional view of the composite molecular pump shown in FIG. Hereinafter, the configurations of the exhaust system 1E and the composite molecular pump 10C provided therein will be described with reference to FIGS. 17 and 18.

The exhaust system 1E shown in FIG. 17 is provided in the electron beam laminated modeling apparatus 100 in the above-described embodiment instead of the exhaust system 1A in the above-described first embodiment. The exhaust system 1E is mainly different in its configuration in that the position where the intermediate exhaust port OL5 is formed is different when compared with the exhaust system 1A described above.

As shown in FIG. 17, in the exhaust system 1E, an intermediate exhaust port OL5 constituting the second exhaust port OP2 of the composite molecular pump 10C is provided at an intermediate position of the thread groove vacuum pump 10b. More specifically, the intermediate exhaust port OL5 is provided in the exhaust path of the portion connecting the second intake port IL2 and the second exhaust port OL2 of the thread groove vacuum pump 10b.

Specifically, as shown in FIG. 18, the composite molecular pump 10C mainly includes the base 11, the stator 12, the casing 13, the rotor 14, and the rotor drive mechanism 15 as in the composite molecular pump 10A in the above-described embodiment. However, unlike the composite molecular pump 10A, the stator 12 is divided into an outer stator portion 12A and an inner stator portion 12B, and a second exhaust pipe 19 is attached to the outer stator portion 12A. Has been done.

The outer stator portion 12A is made of a metal member having a substantially cylindrical shape, and is installed on the peripheral edge portion of the base 11. The inner stator portion 12B is made of a metal member having a substantially cylindrical shape, and is installed inside the outer stator portion 12A. The inner stator portion 12B is fixed to the outer stator portion 12A.

The outer stator portion 12A is located so as to surround the lower rotor portion 14b of the rotor 14 so as to face the outer peripheral surface of the lower rotor portion 14b. The lower rotor portion 14b of the rotor 14 is located so as to surround the inner stator portion 12B, whereby the inner stator portion 12B faces the inner peripheral surface of the lower rotor portion 14b of the rotor 14.

The inner peripheral surface of the outer stator portion 12A is provided with a female-thread-shaped primary thread groove portion 12a1 forming an upstream portion of the thread groove 12a, and the outer peripheral surface of the inner stator portion 12B is downstream of the thread groove 12a. A male thread-shaped secondary side thread groove portion 12a2 that constitutes a side portion is provided. The primary screw groove portion 12a1 is located on the outer peripheral surface of the lower rotor portion 14b at a predetermined distance, and the secondary thread groove portion 12a2 is located on the inner peripheral surface of the lower rotor portion 14b at a predetermined distance. There is.

The inner stator portion 12B is located so as to cover the lower end of the lower rotor portion 14b, whereby the exhaust passage formed between the primary side thread groove portion 12a1 and the lower rotor portion 14b and the secondary side screw The exhaust passage formed between the groove portion 12a2 and the lower rotor portion 14b is connected so as to communicate with each other.

As described above, the thread groove vacuum pump 10b is formed by the outer stator portion 12A, the inner stator portion 12B, and the rotor 14 in the portion facing the inner stator portion 12B.

As described above, the second exhaust pipe 19 is attached to the outer stator portion 12A, and the portion of the outer stator portion 12A to which the second exhaust pipe 19 is attached is an exhaust composed of a thread groove vacuum pump 10b. A ventilation path is provided so as to communicate with the middle position of the road. As a result, the intermediate exhaust port OL5 is formed at the inner end of the ventilation path provided in the outer stator portion 12A.

In the exhaust system 1E configured in this way, in the first exhaust state, the gas taken in from the first intake port IL1 configured as the intake port IP is the first exhaust port OL1, the second intake port IL2, and the first. It is exhausted from the third exhaust port OL3 via the second exhaust port OL2 and the third intake port IL3 configured as one exhaust port OP1 in this order, and in the second exhaust state, the intake port IP The gas taken in from the first intake port IL1 configured as is the first exhaust port OL1, the second intake port IL2, the intermediate exhaust port OL5 configured as the second exhaust port OP2, and the third intake port IL3 in this order. It will be exhausted from the third exhaust port OL3 via.

Therefore, in the first exhaust state, helium gas as a light gas and non-light gas heavier than the helium gas are simultaneously sucked from the intake port IP of the composite molecular pump 10C and from the third exhaust port OL3 of the auxiliary vacuum pump 20. In the second exhaust state, the non-light gas is mainly taken in from the intake port IP of the composite molecular pump 10C and exhausted from the third exhaust port OL3 of the auxiliary vacuum pump 20. That is, in the second exhaust state, the displacement of helium gas as light gas is significantly smaller than that in the first exhaust state, while the displacement of non-light gas is maintained substantially the same as in the first exhaust state.

Therefore, even when the exhaust system 1E in the present embodiment is used, an effect similar to the effect described in the above-described first embodiment can be obtained, and light gas and non-light gas can be exhausted at the same time. On the other hand, it is possible to make an exhaust system that can selectively and mainly exhaust non-light gas, and by using an electron beam laminated molding device equipped with the exhaust system 1E, the molding speed and the molding accuracy are excellent. However, it can be an electron beam laminated molding apparatus capable of suppressing the consumption of helium gas as an auxiliary gas.

In the above-described first to third embodiments and modifications thereof, a case where an exhaust system is configured by using a so-called composite molecular pump in which a turbo molecular pump and a thread groove vacuum pump are integrated has been described as an example. However, they do not necessarily have to be integrated, and they may be configured and connected as separate vacuum pumps.

In addition, the characteristic configurations shown in the above-described first to third embodiments and modifications thereof can be naturally combined within an allowable range in light of the gist of the present invention.

Further, in the above-described first to third embodiments and modifications thereof, the case where the exhaust system according to the present invention is applied to the electron beam laminated modeling apparatus has been described as an example, but other than the electron beam laminated modeling apparatus. Of course, it is also possible to apply it to an apparatus (for example, a helium leak inspection apparatus).

As described above, the above-described embodiment disclosed this time is an example in all respects and is not restrictive. The technical scope of the present invention is defined by the scope of claims and includes all modifications within the meaning and scope equivalent to the description of the scope of claims.

1A to 1E exhaust system, 10A to 10C composite molecular pump, 10a turbo molecular pump, 10b thread groove vacuum pump, 11 base, 12 stator, 12A outer stator part, 12B inner stator part, 12a thread groove, 12a1 primary side thread groove part, 12a2 Secondary screw groove, 13 casing, 13a spacer and support member, 14 rotor, 14a upper rotor, 14b lower rotor, 15 rotor drive mechanism, 15a housing, 15b rotary shaft, 16 moving blade, 17 stationary blade , 18 1st exhaust pipe, 19 2nd exhaust pipe, 20 auxiliary vacuum pump, 30 three-way valve, 40 orifice, 50 booster vacuum pump, 100 electron beam laminated molding device, 110 chamber, 111 first chamber part, 112 second chamber Unit, 120 Electronic Gun, 121 Beam Alignment, 122 Focusing Lens, 123 Objective Lens, 124 Polarizer, 130 Laminated Modeling Unit, 131 Stage, 132 Hopper, 133 Lake, 200 Helium Gas Supply Source, 201 On / Off Valve, 202 Adjusting Valve, 210 Vacuum gauge, 300 Metal powder, 400 Metal model, IP intake port, OP1 1st exhaust port, OP2 2nd exhaust port, IL1 1st intake port, OL1 1st exhaust port, IL2 2nd intake port, OL2 2nd Exhaust port, IL3 3rd intake port, OL3 3rd exhaust port, IL4 4th intake port, OL4 4th exhaust port, OL5 intermediate exhaust port, P1 1st port, P2 2nd port, P3 3rd port, EP1 1st Exhaust path, EP2 second exhaust path, EB electron beam.

Claims (9)

A turbo molecular pump having a first intake port and a first exhaust port,
A threaded vacuum pump with a second intake and a second exhaust,
An auxiliary vacuum pump having a third intake port and a third exhaust port,
With a three-way valve having a first port, a second port and a third port,
The first exhaust port is connected to the second intake port,
An intermediate exhaust port is provided at an intermediate position in the exhaust passage of the portion from the first intake port to the second exhaust port via the first intake port and the second intake port.
The first port is connected to the second exhaust port,
The second port is connected to the intermediate exhaust port,
The third port is connected to the third intake port, and the third port is connected to the third intake port.
The three-way valve can be selectively switched between a first exhaust state connecting the first port and the third port and a second exhaust state connecting the second port and the third port. ,
In the first exhaust state, the gas taken in from the first intake port passes through the first exhaust port, the second intake port, the second exhaust port, and the third intake port in this order. Exhausted from the third exhaust port
In the second exhaust state, the gas taken in from the first intake port passes through the intermediate exhaust port and the third intake port in this order without passing through the second exhaust port, and the third is exhausted from the exhaust port,
The auxiliary exhaust speed for light gas having a molecular weight of 4 or less at the first exhaust port in the second exhaust state is auxiliary for light gas having a molecular weight of 4 or less at the first exhaust port in the first exhaust state. An exhaust system that is less than the exhaust speed. The first aspect of claim 1, wherein the total number of stages of the stationary blade stage and the moving blade stage of the turbo molecular pump alternately installed between the first intake port and the intermediate exhaust port is 10 or more and 12 or less. Exhaust system. The exhaust system according to claim 1 or 2, wherein the gradient of the thread groove depth of the thread groove vacuum pump between the second intake port and the second exhaust port is greater than 0 and 0.04 or less. .. The exhaust system according to any one of claims 1 to 3, wherein the intermediate exhaust port is provided in an exhaust path of a portion connecting the first exhaust port and the second intake port. 4. The exhaust speed of the auxiliary vacuum pump at the third intake port in the second exhaust state is smaller than the exhaust speed of the thread groove vacuum pump at the second intake port in the first exhaust state. Exhaust system described in. The exhaust system according to any one of claims 1 to 5 , wherein an orifice is provided in an exhaust passage at a portion connecting the intermediate exhaust port and the second port. The exhaust system according to any one of claims 1 to 5 , wherein a booster vacuum pump is installed in an exhaust passage at a portion connecting the second exhaust port and the first port. The turbo molecular pump and the thread groove vacuum pump are composed of a composite molecular pump in which each rotor is integrated.
The first exhaust port and the second intake port are connected inside the composite molecular pump, and the first exhaust port and the second intake port are connected to each other.
The composite molecular pump has an intake port as the first intake port, a first exhaust port as the second exhaust port, and a second exhaust port as the intermediate exhaust port. The exhaust system according to any one of 7. With a vacuum container
An electron beam source installed inside the vacuum vessel and
A laminated molding unit provided inside the vacuum vessel and obtaining a metal model by irradiating the metal powder with an electron beam generated by the electron beam generation source.
A light gas supply source that introduces light gas inside the vacuum vessel,
An electron beam laminated modeling apparatus comprising the exhaust system according to any one of claims 1 to 8 connected to the vacuum vessel.

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