Vacuum pump and linked-type thread groove spacer

A vacuum pump which can prevent lowering of an exhaust performance of the vacuum pump, even if a linked-type thread groove spacer is fastened by a fixing bolt, is provided.The linked-type thread groove spacer according to an embodiment of the present invention includes a structure for linking a Siegbahn pump portion and a thread-groove pump portion. When this linked-type thread groove spacer is to be fastened, a countersunk hole is provided in advance in an exhaust channel portion, and the linked-type thread groove spacer is fastened to a base by a fixing bolt. As a result, a head part of the fixing bolt does not protrude to the exhaust channel, and the head part of the fixing bolt does not make resistance against an exhaust gas. Thus, lowering of the exhaust performance of the vacuum pump can be suppressed.

CROSS-REFERENCE OF RELATED APPLICATION

This application is a Section 371 National Stage Application of International Application No. PCT/JP2020/020400, filed May 22, 2020, which is incorporated by reference in its entirety and published as WO 2020/241521A1 on Dec. 3, 2020 and which claims priority of Japanese Application No. 2019-102755, filed May 31, 2019.

BACKGROUND

The present invention relates to a vacuum pump and a linked-type thread groove spacer. In more detail, in a vacuum pump having a thread-groove pump portion (cylindrical thread portion) and a Siegbahn pump portion, the present invention relates to a vacuum pump which suppresses lowering of an exhaust performance by a fixing bolt when the linked-type thread groove spacer is fastened, and a linked-type thread groove spacer.

A Siegbahn type molecular pump having a Siegbahn type configuration which has been conventionally used includes a rotor disc (rotor disc) and a stator disc installed with a clearance from the rotor disc in an axial direction, and a spiral groove (also called a spiral groove or a swirl groove) channel is engraved in at least either one of clearance opposed surfaces of the rotor disc and the stator disc. And it is a vacuum pump for exhaust by giving a dominant directionality from an inlet port to an outlet port by the spiral groove by imparting a momentum in a rotor-disc tangent direction (that is, a tangent direction of a rotating direction of the rotor disc) by the rotor disc to a gas molecule entering the spiral groove channel in a dispersed manner.

For industrial utilization of the Siegbahn-type molecular pump as above or a vacuum pump having the Siegbahn-type molecular pump portion, if the numbers of stages of the rotor disc and the stator disc are single, a compression ratio is insufficient and thus, the stages are provided in multiple. If the number of stages is increased in order to satisfy a desired compression performance, the size of the pump itself is increased.

Moreover, in the case of multiple stages, the rotor disc needs to have a half-split shape. Then, an outer cylinder (casing) of the pump needs to be prolonged to such a length that covers a Siegbahn portion (Siegbahn pump portion), and the size of the pump itself is increased in this case, too.

Moreover, a thread-groove type molecular pump having a thread-groove type pump type configuration has been manufactured by prolonging a length (thread length) of the thread groove portion or by constituting it with a parallel pass type in which two or more plural channels are provided in order to improve the compression performance in the thread portion (thread groove portion) particularly in a vacuum pump with a temperature raised specification and the like.

However, by prolonging the thread length, a portion in a peripheral structure (the casing and the like) of an exhaust structure became larger, or the number of complicated components increased by the parallel pass constitution, which raised a manufacturing cost.

FIG.8is a figure for explaining a conventional 1-Pass thread type vacuum pump.

In a conventional vacuum pump1001including a 1-Pass thread groove spacer2001having one channel, for example, when the compression performance is to be improved, a length of the thread groove portion in the axial direction needed to be prolonged. If the length of the thread groove portion in the axial direction is prolonged as above, a base3needs to be made larger by that portion, which raised the manufacturing cost.

Japanese Patent Application Publication No. 2017-106365 discloses a linked-type thread groove spacer for realizing size reduction while the exhaust performance of a thread-groove pump portion is maintained, and a vacuum pump in which the linked-type thread groove spacer is disposed. That is, the described linked-type thread groove spacer includes a structure for linking a Siegbahn pump portion and the thread-groove pump portion, a structure of the thread-groove pump portion, which is an exhaust element portion, is made a structure in which a Siegbahn type structure is mounted on a cylindrical thread so that each component is linked in the mounting portion. That is, a boundary in a channel between the Siegbahn portion and the cylindrical thread (thread-groove pump portion) is connected so as to be substantially at a right angle when seen from an axis direction of the vacuum pump, and channels of the Siegbahn portion and the thread-groove pump portion are connected. By means of this constitution, a compression channel length of the thread-groove pump portion is extended in a radial direction by the linked Siegbahn portion.

SUMMARY

However, the above-described Japanese Patent Application Publication No. 2017-106365 does not describe how to fix the linked-type thread groove spacer to a base, for example. That is, a method for fastening the linked-type thread groove spacer was not clear.

When a vacuum pump is to be assembled, the assembling work is easier by gradually stacking and assembling from a lower side (outlet port side). That is, when the linked-type thread groove spacer is to be fastened to the base, for example, if it can be fastened by a fixing bolt in an exhaust channel portion of the linked-type thread groove spacer, the work can be performed from an upper side of the vacuum pump, and there is no need to reverse the vacuum pump during the work, whereby work efficiency is improved.

On the other hand, if the fixing bolt is provided in the exhaust channel portion of the linked-type thread groove spacer, a head part of the fixing bolt makes resistance against an exhaust gas, and there was a concern that a performance of the vacuum pump is affected.

Thus, the present invention has an object to provide a vacuum pump whose exhaust performance is not lowered by providing a countersunk hole in the exhaust channel portion of the linked-type thread groove spacer and by fastening with the fixing bolt, and the linked-type thread groove spacer.

The present invention according to claim1provides a vacuum pump including a casing in which an inlet port or an outlet port is formed, a stator component enclosed in the casing, a Siegbahn pump portion, and a thread-groove pump portion, wherein a linked-type thread groove spacer having a structure for linking the Siegbahn pump portion and the thread-groove pump portion is provided; and a countersunk hole is provided in an exhaust channel surface of the linked-type thread groove spacer, and the linked-type thread groove spacer and the casing or the stator component are fastened by a fixing bolt disposed in the countersunk hole.

The present invention according to claim2provides the vacuum pump according to claim1, wherein a heating means for heating the thread-groove pump portion is provided on the casing or the stator component, and the fixing bolt is disposed in contact with a high-temperature portion of the casing or the stator component heated by the heating means.

The present invention according to claim3provides the vacuum pump according to claim2, wherein the fixing bolt has a material with greater heat conductivity than that of an iron bolt.

The present invention according to claim4provides a linked-type thread groove spacer which is used in a vacuum pump having a casing in which an inlet port or an outlet port is formed, a stator component enclosed in the casing, a Siegbahn pump portion, and a thread-groove pump portion, wherein the linked-type thread groove spacer has a structure for linking the Siegbahn pump portion and the thread-groove pump portion, and the linked-type thread groove spacer has a countersunk hole for a fixing bolt provided in an exhaust channel surface, and is fastened to the casing or the stator component by the fixing bolt.

According to the present invention, even if the linked-type thread groove spacer is fastened by the fixing bolt, lowering of the exhaust performance of the vacuum pump can be prevented.

DETAILED DESCRIPTION

(i) Outline of Embodiment

A linked-type thread groove spacer according to an embodiment of the present invention includes a structure for linking a Siegbahn pump portion and a thread-groove pump portion. By providing a countersunk hole in advance in the exhaust channel portion (exhaust channel surface) of this linked-type thread groove spacer and by fastening it to a base, for example, by a fixing bolt, protrusion of a head part of the fixing bolt, which makes resistance and lowers an exhaust performance of the vacuum pump, can be suppressed.

Moreover, since the countersunk hole is provided in the exhaust channel portion of the linked-type thread groove spacer and fastened by the fixing bolt, a mounting work can be performed from above (inlet port side) of the vacuum pump by gradually stacking in an assembling work of the vacuum pump and thus, working efficiency can be improved.

(ii) Details of Embodiment

The vacuum pump in the embodiment of the present invention has a thread-groove pump portion, which is a gas transfer mechanism including a Siegbahn pump portion in which a spiral groove having a ridge portion and a root portion is engraved (disposed) in at least either one of a stator disc disposed or a rotor disc disposed and moreover, a thread groove spacer in which the spiral groove is formed in an opposed surface with respect to a rotating cylinder and opposed to an outer peripheral surface of the rotating cylinder with a predetermined clearance therebetween, in which a gas is sent out to the outlet port side while being guided by the thread groove (spiral groove) accompanying rotation of the rotating cylinder by a high-speed rotation of the rotating cylinder.

And the Siegbahn pump portion and the thread-groove pump portion are linked by the linked-type thread groove spacer. When this linked-type thread groove spacer is to be fastened to a base, for example, a countersunk hole is provided in advance so that a head part of a fixing bolt is prevented from protruding to an exhaust channel and to obstruct exhaust after fastening with a fixing bolt.

Hereinafter, a preferred embodiment of the present invention will be described in detail by referring toFIG.1toFIG.7.

(ii-1) Configuration of Vacuum Pump

FIG.1is a diagram illustrating a schematic configuration example of a vacuum pump1according to a first embodiment of the present invention and illustrates a sectional view of the vacuum pump1in an axis direction.

It is to be noted that, in the embodiment of the present invention, explanation will be made with a diameter direction of a rotor blade referred to as a “radial (diameter/radius) direction” and a direction perpendicular to the diameter direction of the rotor blade as an “axis direction (or an axial direction)” for convenience.

A casing (outer cylinder)2forming a housing of the vacuum pump1has a substantially cylindrical shape and constitutes an enclosure of the vacuum pump1together with a base3provided on a lower part (outlet port6side) of the casing2. And inside this enclosure, a gas transfer mechanism, which is a structural body for having the vacuum pump1to exert an exhaust function is accommodated.

In this embodiment, this gas transfer mechanism is roughly constituted by a rotating portion (rotor portion/Siegbahn portion) rotatably supported and a stator portion (thread-groove pump portion) fixed to the enclosure.

Moreover, though not shown, a control device for controlling an operation of the vacuum pump1is connected to an outside of the housing of the vacuum pump1via an exclusive line.

On an end portion of the casing2, an inlet port4for introducing the gas into the vacuum pump1is formed. Moreover, on an end surface on the inlet port4side of the casing2, a flange portion5extending to an outer peripheral side is formed.

Furthermore, on the base3, an outlet port6for exhausting the gas from the vacuum pump1is formed.

A rotating portion includes a shaft7which is a rotating shaft, a rotor8disposed on this shaft7, a plurality of rotor blades9provided on the rotor8, and a rotor cylinder portion10provided on the outlet port6side (thread-groove pump portion). It is to be noted that the shaft7and the rotor8constitute a rotor portion.

Each of the rotor blades9is constituted by a disc-shaped disc member extending radially at a right angle to an axis of the shaft7. It is to be noted that, in this embodiment, a lowermost stage of the rotor blade9(on the outlet port6side) is constituted as a disc and to perform compression of a Siegbahn portion.

Moreover, the rotor cylinder portion10is constituted by a cylindrical member having a cylindrical shape concentric to a rotating axis of the rotor8.

Approximately in a middle of the shaft7in the axis direction, a motor portion for rotating the shaft7at a high speed is provided and is enclosed by a stator column80.

Moreover, in the stator column80, a radial magnetic bearing device for supporting the shaft7in a radial direction (radial direction) in a non-contact manner is provided on the inlet port4side and the outlet port6side with respect to the motor portion of the shaft7. Furthermore, on a lower end of the shaft7, an axial magnetic bearing device for supporting the shaft7in the axis direction (axial direction) in the non-contact manner is provided.

On an inner peripheral side of the enclosure (casing2), a stator portion (stator component) is formed. This stator portion is constituted by a stator blade50and the like and is constituted by a blade extending from an inner peripheral surface of the casing2toward the shaft7with inclination only by a predetermined angle from a plane perpendicular to the axis of the shaft7. And the stator blades50are separated from each other by a spacer (stator component) having a cylindrical shape and fixed.

It is to be noted that the rotor blades9and the stator blades50are disposed alternately and are formed in plural stages in the axis direction, and in order to satisfy an exhaust performance required for the vacuum pump, arbitrary numbers of rotor components and stator components can be provided as necessary.

Furthermore, in this embodiment, a thread-groove pump portion having a linked-type thread groove spacer20is disposed closer to the outlet port6side than the above-described Siegbahn pump portion.

In the linked-type thread groove spacer20, a thread groove (spiral groove) is formed in an opposed surface to the rotor cylinder portion10similarly to the conventional thread groove spacer.

An opposed surface side to the rotor cylinder portion10in the linked-type thread groove spacer20(that is, an inner peripheral surface in parallel with the axis of the vacuum pump1) is opposed to the outer peripheral surface of the rotor cylinder portion10with a predetermined clearance therebetween, and when the rotor cylinder portion10is rotated at a high speed, a gas compressed by the vacuum pump1is sent out to the outlet port6side while being guided by the thread groove accompanying rotation of the rotor cylinder portion10. That is, the thread groove is a channel for transferring the gas.

As described above, since the opposed surface to the rotor cylinder portion10in the linked-type thread groove spacer20and the rotor cylinder portion10are opposed to each other with the predetermined clearance therebetween, a gas transfer mechanism for transferring the gas in the thread groove formed in the inner peripheral surface on the axis direction side of the linked-type thread groove spacer20is constituted.

It is to be noted that, in order to reduce a force by which the gas backflows to the inlet port4side, the smaller this clearance is, the more it is desirable.

Moreover, a direction of the spiral groove formed in the linked-type thread groove spacer20is a direction toward the outlet port6, when the gas is transferred in the rotating direction of the rotor8in the spiral groove.

Furthermore, a depth of the spiral groove gets smaller as it goes closer to the outlet port6so that the gas transferred through the spiral groove is compressed as it goes closer to the outlet port6.

By means of the above-described configuration, in the vacuum pump1, the gas sucked through the inlet port4is compressed in the Siegbahn portion and then, further compressed in the thread-groove type pump portion and exhausted from the outlet port6and thus, the vacuum pump1can execute vacuum exhaust treatment in a vacuum chamber (not shown) disposed in the vacuum pump1.

This linked-type thread groove spacer20has a countersunk hole800for a fixing bolt700provided in advance in an exhaust channel for the gas and is fastened to the base3by the fixing bolt700. The countersunk hole800is provided in advance in order to prevent a head part710of the fixing bolt700from protruding and making exhaust resistance against the gas in the exhaust channel.

It is to be noted that the linked-type thread groove spacer20may be fixed to the casing2or another component inside the base3other than the base3.

On the base3, a cartridge-type heater900for heating the inside is disposed by being fixed by a bolt910. Deposition of an exhaust gas in the vacuum pump1is prevented by heating the inside of the vacuum pump1. This cartridge-type heater900may be disposed singularly or may be disposed in plural in a predetermined phase. Moreover, a band-shaped band heater may be used instead of this cartridge-type heater900.

(ii-2) Configuration of Linked-type Thread Groove Spacer

The above-described linked-type thread groove spacer20will be described in detail.

FIG.2is a diagram for explaining the linked-type thread groove spacer20according to the embodiment of the present invention.

As illustrated inFIG.2, the linked-type thread groove spacer20according to this embodiment has a thread-groove spacer axis perpendicular portion201and a thread-groove spacer axis parallel portion202.

The thread-groove spacer axis perpendicular portion201is constituted substantially perpendicularly (horizontally) to the axis direction of the vacuum pump1. And a surface on the inlet port4side of the thread-groove spacer axis perpendicular portion201is opposed (faced) to the rotor blade9of the Siegbahn portion with a predetermined clearance therebetween, and a spiral groove having a ridge portion and a root portion is engraved. On the other hand, a surface on the side opposite to the inlet port4side of the thread-groove spacer axis perpendicular portion201is disposed on the base3side.

The thread-groove spacer axis parallel portion202is constituted substantially in parallel with the axis direction of the vacuum pump1. And in the thread-groove spacer axis parallel portion202, a thread groove is formed in an inner peripheral surface, which is a surface opposed to the rotor cylinder portion10with a predetermined clearance therebetween.

(ii-3) Basic Structure of Linked Portion

FIG.3is a view for explaining the linked-type thread groove spacer20according to this embodiment.

As described above, the spiral groove having a perpendicular-portion ridge portion300and a perpendicular-portion root portion400is engraved in the thread-groove spacer axis perpendicular portion201, while a thread groove having a parallel-portion ridge portion500and a parallel-portion root portion600is formed in the thread-groove spacer axis parallel portion202.

Here, the linked-type thread groove spacer20of this embodiment is a linked-type thread groove spacer20in which the thread-groove spacer axis perpendicular portion201and the thread-groove spacer axis parallel portion202are formed integrally by manufacture using casting, for example, as illustrated inFIG.3.

As described above, by configuring the thread-groove spacer axis perpendicular portion201and the thread-groove spacer axis parallel portion202as an integrated type, a labor required for fastening and a manufacturing cost can be reduced as compared with a configuration by fastening of separate components.

As described above, in the vacuum pump1according to this embodiment, the gas is compressed in a channel perpendicular to the axial direction by the thread-groove spacer axis perpendicular portion201and the rotor blade9(Siegbahn portion) by disposing the linked-type thread groove spacer20. Subsequently, the gas is further compressed in a channel in parallel with the axial direction by the thread-groove spacer axis parallel portion202and the rotor cylinder portion10(thread-groove pump portion).

As described above, in the vacuum pump1according to this embodiment, the linked-type thread groove spacer20plays a role of connecting the gas channel from the perpendicular direction to the parallel direction with respect to the axial direction and thus, the channel for compressing the gas can be prolonged without prolonging a length (n) in the axis direction of the casing2(seeFIG.2) and a length (m) in the axis direction of the base3(seeFIG.2) (that is, while suppressing an increase in an entire height of the vacuum pump1). It is to be noted that the channel connected from the perpendicular direction to the parallel direction becomes a channel having an inverted “L” shape in the alphabet when seen on a section in the axis direction.

It is to be noted that, in this embodiment, the thread-groove spacer axis perpendicular portion201and the thread-groove spacer axis parallel portion202of the linked-type thread groove spacer20are configured as the integrated type, but this is not limiting. For example, even if the thread-groove spacer axis perpendicular portion201and the thread-groove spacer axis parallel portion202are configured by separate components, there is no problem in performances as long as they are configured in the inverted L-shape from the perpendicular direction to the parallel direction with respect to the axis direction as described above.

(ii-4) Fastening Method of Linked-type Thread Groove Spacer according to This Embodiment

FIG.4is a view illustrating a state where the fixing bolt700according to this embodiment is disposed in the exhaust channel portion of the linked-type thread groove spacer20.FIG.5is a perspective view illustrating a state where the fixing bolt700according to this embodiment is disposed in the exhaust channel portion of the linked-type thread groove spacer20.

As illustrated in these figures, the fixing bolts700are disposed in a predetermined number (plural) at equal intervals in the exhaust channel portion in the linked-type thread groove spacer20.

In the exhaust channel portion in the linked-type thread groove spacer20, the countersunk hole800for accommodating the fixing bolt700is opened in advance so that the head part710of the fixing bolt700does not protrude to the exhaust channel portion after the fixing bolt700is fastened.

This fixing bolt700is disposed in vicinity of the cartridge-type heater900and receives heat from this cartridge-type heater900so that a temperature does not become lower than a periphery.

When an assembling work of the vacuum pump1is to be performed, the work is performed more easily by assembling gradually upward (the inlet port4side) from the base3. Thus, this fixing bolt700is disposed in the exhaust channel portion of the linked-type thread groove spacer20. That is, by disposing the fixing bolt700in the exhaust channel portion of the linked-type thread groove spacer20, the assembling work can be easily performed from above.

It is to be noted that a flange, for example, can be provided for fastening at a spot irrelevant to the exhaust channel portion of the linked-type thread groove spacer20for fixing the linked-type thread groove spacer20, but it increases the number of components or a size of the vacuum pump1itself and thus, it is not employed in this embodiment.

FIG.6is a diagram illustrating a state in which, when the fixing bolt700is disposed in the exhaust channel portion of the linked-type thread groove spacer20, the countersunk hole800corresponding to a size of the fixing bolt700is provided in the exhaust channel portion of the linked-type thread groove spacer20in advance so that the head part710of the fixing bolt700does not protrude to the exhaust channel portion in this embodiment.

An installation surface X of the head part710of the fixing bolt700and the exhaust channel portion of the linked-type thread groove spacer20is set to be a flat surface as much as possible. That is, the installation surface X cannot be a perfect flat surface since the exhaust channel portion of the linked-type thread groove spacer20has a structure inclined to an inner diameter side. Thus, a depth of counter sinking of the countersunk hole800is adjusted as appropriate so that the installation surface X becomes close to a flat surface, and the head part710of the fixing bolt700and a groove generated by the counter sinking do not make exhaust resistance.

As a result, such a state in which the head part710of the fixing bolt700makes exhaust resistance and affects the exhaust performance of the vacuum pump can be prevented.

In this embodiment, it is desirable that a disposed position of the fixing bolt700is a spot which does not affect the exhaust performance of the vacuum pump1as much as possible.

An exhaust gas passing through the exhaust channel portion of the linked-type thread groove spacer20has a nature that flows by following a wall surface of an inner side (inner diameter side). Thus, it is desirable that the disposed position of the fixing bolt700is close to the wall surface on an outer side, that is, on an outer side in the radial direction (direction away from a rotation center).

By disposing the fixing bolt700at the position as above, the influence on the exhaust performance of the vacuum pump1can be further prevented.

The fixing bolt700is disposed adjacent to a high-temperature member (the cartridge-type heater900or a member heated by the cartridge-type heater900)(seeFIG.4). If the disposed fixing bolt700(head part710) has a low temperature in the exhaust channel portion of the linked-type thread groove spacer20, the exhaust gas is solidified on that spot and deposited. In order to prevent this, it is desirable that a temperature of the fixing bolt700itself is raised.

Thus, the fixing bolt700is disposed at a spot subjected to a heat from a heat source (the cartridge-type heater900).

Moreover, since the fixing bolt700is not in contact on a full surface with the linked-type thread groove spacer20, there is a concern that it has a temperature lower than those on the other spots. Thus, it is desirable that a material has greater heat conductivity as much as possible.

Specific materials include stainless steel (SUS) and aluminum. The material of the fixing bolt700is not limited to those sold in an actual market but may be selected from metals with greater heat conductivity. Specifically, metal with greater heat conductivity than that of an iron bolt such as an aluminum bolt, for example, is preferable.

Considering workability from an upper part, the fixing bolt700is preferably a bolt with a hexagonal hole. A diameter of the head part710is preferably smaller such as 7.0 mm rather than 8.5 mm, for example. By having a bolt with the head part710with a small diameter, a hole diameter of the counter sinking can be made smaller, and movement resistance of a gas molecule in an exhaust gas in this countersunk portion can be reduced.

Moreover, by having the diameter of the countersunk hole800smaller than a specified diameter with respect to the fixing bolt700, a gap from the diameter of the head part710of the fixing bolt700is reduced. In this way, too, the movement resistance of the gas molecule in the exhaust gas in the countersunk portion can be reduced.

(ii-5) Variation of Fastening Method of Linked-type Thread Groove Spacer according to This Embodiment

Subsequently, a variation of this embodiment will be described by referring toFIG.7.

FIG.7is a diagram illustrating a variation of this embodiment in which an upper part of the installed fixing bolt700is covered with a cap550.

As described above, when a bolt with a hexagonal hole is used for the fixing bolt700, the hexagonal hole remains exposed to the exhaust channel portion of the linked-type thread groove spacer20. And the gas molecule of the exhaust gas can remain in the hexagonal hole or make resistance to the exhaust.

Thus, the head part710of the fixing bolt700is covered with the cap550. In order to dispose this cap550, the countersunk hole800is made slightly larger in advance.

This cap550preferably has a material of metal with greater heat conductivity in order to prevent a temperature to become lower than that of a periphery.

By means of this cap550, the gas molecule of the exhaust gas can be prevented from remaining at a disposed position of the fixing bolt700. Moreover, since smoothness of the exhaust channel portion of the linked-type thread groove spacer20can be ensured, the fixing bolt700is prevented from making resistance against the exhaust.

It is to be noted that the embodiment and each embodiment of the present invention may be configured by being combined as necessary.