A turbo-molecular pump comprises: a rotor having a plurality of stages of rotor blades and a cylindrical section; a plurality of stages of stationary blades alternately arranged with respect to the rotor blades; a stator arranged with a gap from the cylindrical section, the stator together with the cylindrical section constituting a screw groove pump section; a plurality of spacers stacked on a base, the spacers including at least one cooling spacer having a cooling section; a heater heating the stator; a temperature regulation section controlling the heater to regulate the temperature of the stator so as to be a reaction product accumulation prevention temperature; and an auxiliary ring for reaction product accumulation prevention at least a part of which is located in a space between the spacer facing a bottom step rotor blade, and the bottom step rotor blade.

TECHNICAL FIELD

The present invention relates to a turbo-molecular pump that is provided with a cooling passage for cooling a rotor having rotor blades and a temperature regulator.

BACKGROUND ART

Conventionally, in the process of dry etching, CVD, or the like in semiconductor manufacturing processes, processing is performed while supplying a large amount of gas in order to perform the process at high speed. Generally, a turbo-molecular pump that is provided with a turbine blade section and a screw groove pump section housed inside a pump case is used in the evacuation of a process chamber in the process of dry etching, CVD, or the like. When discharging a large amount of gas by the turbo-molecular pump, frictional heat generated in moving blades (rotor blades) is transmitted from the moving blades to stator blades (stationary blades), spacers, and a base in this order, and then released into cooling water in a cooling pipe provided in the base.

However, when discharging a larger amount of gas, the temperature of a rotor that includes the moving blades may disadvantageously exceed an allowable temperature. When the temperature of the rotor exceeds the allowable temperature, the speed of expansion by creep becomes higher. As a result, in any place in the turbine blade section and the screw groove pump section, disadvantageously, the moving blades and the stator blades may make contact with each other or the rotor and a screw stator may make contact with each other within a shorter period than a designed life.

Further, in this kind of semiconductor manufacturing apparatus, a reaction product is generated in etching or CVD, and the reaction product is likely to be accumulated on the screw stator of the screw groove pump section. A gap between the screw stator and the rotor is extremely small. Therefore, when a reaction product is accumulated on the screw stator, the screw stator and the rotor may be stuck to each other. As a result, the rotor may not be able to start rotating.

Therefore, the invention described in Patent Literature 1 (JP 3930297 B1) is provided with a first cooling water passage which cools rotor blades by cooling a pump case and a device for regulating the temperature of a screw stator (a heater and a second cooling water passage). The first cooling water passage is provided on the outer peripheral surface of the pump case, and cools the pump case to thereby cool stationary blades housed inside the pump case. In this manner, by providing the first cooling water passage and the temperature regulator, the temperature of the rotor is reduced and the accumulation of a reaction product on the screw stator is suppressed.

However, along with an increase in the size of a wafer to be processed, the flow amount of gas that should be discharged by the turbo-molecular pump increases, and the amount of heat generated due to the discharge of gas also increases. Therefore, a method in which the pump case is cooled as described in Patent Literature 1 does not have enough cooling capacity to cool the stationary blades. Further, the temperature of the base to which the pump case is fixed becomes high by temperature regulation. Therefore, heat flowing to the pump case from the base is a factor that inhibits cooling of the stationary blades. Therefore, a turbo-molecular pump that has sufficient cooling capacity to cool stationary blades and can regulate the temperature so that the temperature of the screw stator is a reaction product accumulation prevention temperature is required. On the other hand, when a turbo-molecular pump has sufficient cooling capacity to cool the stationary blades and the sublimation temperature of a reaction product is higher than the cooling temperature, the reaction product may be accumulated on the inner side of a spacer that corresponds to the bottom step moving blade, and the bottom step moving blade may disadvantageously make contact with the reaction product.

SUMMARY OF THE INVENTION

A turbo-molecular pump comprises: a rotor having a plurality of stages of rotor blades and a cylindrical section; a plurality of stages of stationary blades alternately arranged with respect to the rotor blades; a stator arranged with a gap from the cylindrical section, the stator together with the cylindrical section constituting a screw groove pump section; a plurality of spacers stacked on a base, the spacers including at least one cooling spacer having a cooling section; a heater heating the stator; a temperature regulation section controlling the heater to regulate the temperature of the stator so as to be a reaction product accumulation prevention temperature; and an auxiliary ring for reaction product accumulation prevention at least a part of which is located in a space between the spacer facing a bottom step rotor blade, and the bottom step rotor blade.

The auxiliary ring is formed separately from the base and in contact with the base so that heat of the base is transferred thereto, or the auxiliary ring is integrally formed with the base or the stator.

The auxiliary ring is arranged separated from the spacer.

The auxiliary ring has a layer which is formed on a surface facing the rotor blade and increases the heat absorption.

The turbo-molecular pump further comprises: a heat source heating the auxiliary ring; a heat insulation member thermally insulating the auxiliary ring from the base; and a controller controlling the heat source independently of the heater.

The turbo-molecular pump further comprises: a spacer cooling passage provided in the cooing section of the at least one cooling spacer; and a base cooling passage cooling the base. A coolant is supplied to the spacer cooling passage, and the coolant flows into the base cooling passage through the spacer cooling passage.

A turbo-molecular pump comprises: a rotor having a plurality of stages of rotor blades and a cylindrical section; a plurality of stages of stationary blades alternately arranged with respect to the rotor blades; a stator arranged with a gap from the cylindrical section, the stator together with the cylindrical section constituting a screw groove pump section; and a plurality of spacers stacked on a base, the spacers including a bottom step cooling spacer having a cooling section. On at least one of a contact surface of the bottom step stationary blade supported by the cooling spacer, the contact surface making contact with the cooling spacer, and a contact surface of the cooling spacer, the contact surface making contact with the bottom step stationary blade, a heat resistant section suppressing heat transfer from the bottom step stationary blade to the cooling spacer is provided.

The bottom step stationary blade is formed of an aluminum alloy, and alumite treatment is applied onto a surface of the bottom step stationary blade, the surface including at least the contact surface, to form the heat resistant section, and/or the cooling spacer is formed of an aluminum alloy, and alumite treatment is applied onto a surface of the cooling spacer, the surface including at least the contact surface, to form the heat resistant section.

The heat resistant section provided on the contact surface of the bottom step stationary blade or the contact surface of the cooling spacer is formed of a resin material.

The turbo-molecular pump further comprises: a heater heating the stator; a temperature regulation section controlling the heater to regulate the temperature of the stator so as to be a reaction product accumulation prevention temperature; a spacer cooling passage provided in the cooling section of the cooling spacer; and a base cooling passage cooling the base. A coolant is supplied to the base cooling passage, and the coolant flows into the spacer cooling passage through the base cooling passage.

The present invention makes it possible to provide the turbo-molecular pump that prevents the rotor blades from colliding with a reaction product while efficiently cooling the spacers and regulating the temperature of the stator in the screw groove pump section to improve the exhaust flow amount.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

First Embodiment

Hereinbelow, an embodiment of a turbo-molecular pump of the present invention will be described with reference to the drawings. The turbo-molecular pump is provided with a turbine blade section and a screw groove pump section housed inside a pump case.FIG. 1is a diagram illustrating the schematic configuration of the turbo-molecular pump according to the present invention. The turbo-molecular pump includes a pump main body1and a control unit (not illustrated, and described below) which controls the drive of the pump main body1. The control unit is provided with a main controller which controls the entire pump main body1, a motor controller which drives a motor36, a bearing controller which controls magnetic bearings provided in the pump main body1, a temperature regulation controller511(described below, seeFIG. 4), and the like.

In the following description, an active magnetic bearing type turbo-molecular pump will be described as an example. However, the present invention can also be applied to a turbo-molecular pump provided with a passive magnetic bearing using a permanent magnet and a turbo-molecular pump using a mechanical bearing.

In a rotor30, a plurality of stages of rotor blades30aand a cylindrical section30bwhich is provided on an exhaust downstream side with respect to the rotor blades30a. The rotor30is fastened to a shaft31as a rotor shaft. The rotor30and the shaft31constitute a pump rotor body. The shaft31is supported in a contactless manner by magnetic bearings37,38, and39which are provided in a base20. Electromagnets of the axial magnetic bearing39are arranged so as to sandwich a rotor disc35provided on the lower end of the shaft31in the axial direction.

The pump rotor body (the rotor30and the shaft31) which is magnetically levitated in a freely rotatable manner by the magnetic bearings37to39is driven to rotate at high speed by the motor36. For example, a three-phase brushless motor is used as the motor36. A motor stator36aof the motor36is provided in the base20, and a motor rotor36bwhich is provided with a permanent magnet is coupled to the shaft31. Emergency mechanical bearings26aand26bsupport the shaft31when the magnetic bearings are not operating.

A plurality of stages of stationary blades22are arranged between the respective stages of rotor blades30awhich are vertically adjacent to each other. The stationary blades22are sandwiched by a plurality of spacers23a, and positioned on the base20by a cooling spacer23b. In the turbo-molecular pump of the first embodiment, a plurality of spacers which positions the stationary blades22on the base20includes the cylindrical spacers23aand the cylindrical cooling spacer23bwhich bears the spacers23aand has a flange. As illustrated inFIG. 5(described later), the cooling spacer23band the lowest spacer23awhich is arranged above the cooling spacer23bmay be integrated with each other to from a cooling spacer23c.

When the case21is fixed to the base20with bolts40, a stacked body of the stationary blades22, the spacers23a, and the cooling spacer23bis fixed to the base20so as to be sandwiched between an upper end locking section21bof the case21and the base20. As a result, the stationary blades22are positioned in the axial direction (vertical direction in the drawing).

The turbo-molecular pump illustrated inFIG. 1is provided with a turbine blade section TP which includes the rotor blades30aand the stationary blades22and a screw groove pump section SP which includes the cylindrical section30band a screw stator24. Here, the structure in which a screw groove is formed on the screw stator24is described as an example. However, the screw groove may be formed on the cylindrical section30b. An exhaust port25is provided in an exhaust opening20aof the base20. A back pump (not illustrated) is connected to the exhaust port25. By driving the rotor30to rotate at high speed by the motor36while magnetically levitating the rotor30, gas molecules in a suction port21aare discharged toward the exhaust port25.

In the base20, a base cooling pipe46, a heater42, and a temperature sensor43for controlling the temperature of the screw stator24are provided. A coolant such as cooling water flows inside the base cooling pipe46, and abase cooling passage is thereby formed. The temperature of the screw stator24is regulated so as to prevent the accumulation of a reaction product. The temperature regulation will be described below. The heater42which includes a band heater is wound around the side face of the base20. Instead of this structure, a sheathed heater may be embedded in the base20, or provided in the screw stator24. As the temperature sensor43, for example, a thermistor or a thermocouple is used.

A spacer cooling pipe45is provided in a flange section232of the cooling spacer23b. In the turbo-molecular pump of the present embodiment, a heat transfer ring60is arranged on the upper surface of the base20on the inner side of the cooling spacer23b. The tip of the heat transfer ring60extends up to a position between the bottom step spacer23aand the bottom step rotor blade30a1. The heat transfer ring60will be described in detail with reference toFIGS. 2 and 3.

FIG. 2is an enlarged view of an area in which the cooling spacer23band the heat transfer ring60are arranged inFIG. 1.FIG. 3is a diagram of the cooling spacer23band the vicinity thereof viewed from the direction of III ofFIG. 2. As described above, the stacked body formed by alternately stacking the stationary blades22and the spacers23aon each other is mounted on the cooling spacer23b. The cooling spacer23bis provided with the flange section232in which the spacer cooling pipe45is provided and a ring-like spacer section231which bears the bottom step spacer23a.

As with the spacers23a, the spacer section231is a ring-like component. A groove234which has an annular shape in a plan view is formed on the flange section232which extends toward the atmospheric side from the spacer section231as illustrated inFIG. 3. The groove234has an arc-like bottom face, and the spacer cooling pipe45is attached in contact with the bottom face. A coolant such as cooling water flows inside the spacer cooling pipe45, and a spacer cooling passage is thereby formed. A plurality of through holes230for bolt fastening are formed along the circumferential direction on the outer peripheral side of the groove234. A gap between the spacer cooling pipe45and the groove234is filled with thermal conductive grease, high thermal conductive resin, solder, or the like. The thermal conductivity of grease and resin is approximately 1 W/mK. On the other hand, the thermal conductivity of solder is 50 W/mK. Therefore, heat can be efficiently transferred.

Both ends of the spacer cooling pipe45are bent, so that a coolant supply section45aand a coolant discharge section45bare extracted to the side of the cooling spacer23b. A piping joint50is attached to each of the coolant supply section45aand the coolant discharge section45b. A coolant flows into the spacer cooling pipe45from the coolant supply section45a, then circularly flows along the spacer cooling pipe45, and is then discharged from the coolant discharge section45b.

The case21is attached so that a flange21cfaces the flange section232of the cooling spacer23b, and fixed to the base20with the bolts40. Heat insulation washers44each of which functions as a heat insulation member are provided in the respective bolts40. The heat insulation washers44are arranged between the base20and the cooling spacer23bto thermally insulate the base20and the cooling spacer23bfrom each other. As the material used in the heat insulation washers44, a material having a thermal conductivity that is lower than the thermal conductivity of the material used in the spacers23aand the cooling spacer23b(an aluminum alloy, for example) is used. For example, a stainless alloy or the like is desirably used among metal, and a resin having a heat resistant temperature of 120° or higher (an epoxy resin, for example) is desirably used among nonmetal.

A vacuum seal48is provided between the flange section232of the cooling spacer23band the base20. Also, a vacuum seal47is provided between the flange section232and the flange21c. The screw stator24is fixed to the base20with bolts49. The base20is heated by the heater42, and cooled by the base cooling pipe46in which a coolant flows. The temperature sensor43is arranged on the base20at a position near a part to which the screw stator24is fixed.

The heat transfer ring60described above is arranged on the upper surface of the base20on the vacuum inner face side of the cooling spacer23bso as to be concentric with a rotor axial center. The heat transfer ring60includes a ring main body61and a flange-like attachment section62which is formed on the bottom of the ring main body61in a bent manner, and has a generally L-shaped cross section. The heat transfer ring60is fixed to the upper surface of the base20with bolts66at a plurality of positions in the circumferential direction. The attachment section62of the heat transfer ring60abuts on the upper surface of the base20, so that heat of the base20is transferred to the heat transfer ring60. The ring main body61of the heat transfer ring60faces the inner surface of the bottom step spacer23aand the inner surface of the cooling spacer23bso as to cover these surfaces. Further, the ring main body61is separated from the inner surface of the bottom step spacer23aand the inner surface of the cooling spacer23b.

The tip of the ring main body61of the heat transfer ring60extends up to a position above a vacuum side tip of the cooling spacer23b. More specifically, the length of the bottom step rotor blade30a1is shorter than the length of the other rotor blades30a. Further, the tip of the ring main body61of the heat transfer ring60extends beyond a space in which the tip of the bottom step rotor blade30a1and the bottom step spacer23aface each other.

When the coolant for cooling the cooling spacer23bis water, the temperature of the vacuum side surface of the cooling spacer23bis 20° C. to 30° C. When the sublimation temperature of a reaction product is higher than the temperature of the vacuum side surface of the cooling spacer23b, the reaction product may be accumulated on the inner side of the cooling spacer23b. Similarly, when the bottom step spacer23ais cooled until the temperature of the vacuum side surface thereof becomes lower than the sublimation temperature of a reaction product, the reaction product may be accumulated on the inner side of the spacer23a. Therefore, the bottom step rotor blade30a1may disadvantageously make contact with the reaction product accumulated on the vacuum side surface of the spacer23aor the cooling spacer23bwhich faces the bottom step blade30a1.

Therefore, in the present invention, the heat transfer ring60is interposed between the bottom step rotor blade30a1and the spacer23aor the cooling spacer23b. The heat transfer ring60is heated to a temperature equal to or higher than the sublimation temperature of a reaction produce by heat transferred from the base20. As a result, the accumulation of the reaction product on the inner peripheral surface of the heat transfer ring60is prevented. Since the inner peripheral surface of the bottom step spacer23aand the inner peripheral surface of the cooling spacer23bare heated by the heat transfer ring60, a reaction production is less likely to be accumulated on these inner peripheral surfaces. Even when the bottom step spacer23ais not sufficiently heated up to the sublimation temperature and a reaction product is therefore accumulated on the inner peripheral surface thereof, since the inner peripheral surface of the bottom step spacer23adoes not directly face the bottom step rotor blade30a1by virtue of the heat transfer ring60, the rotor blade30a1does not collide with the accumulated reaction product. In this manner, the heat transfer ring60is auxiliarily placed for the purpose of preventing the accumulation of a reaction product, and can also be referred to as an auxiliary ring for reaction product accumulation prevention.

The heat transfer ring60can be formed of an aluminum alloy or SUS (stainless alloy). Further, the heat transfer ring60can be heated using radiant heat from the rotor blades30ain addition to heat transferred from the base20. In order to achieve this, a layer having high heat absorption such as an alumite layer and a black nickel plating layer may be formed on a surface of the ring main body61of the heat transfer ring60, the surface facing the rotor blade30a1.

The cooling spacer23bis used for cooling the stationary blades22. The cooling spacer23bis cooled by a coolant flowing inside the spacer cooling pipe45. Therefore, heat of the stationary blades22is transferred to the spacers23aand then to the cooling spacer23bas indicated by broken line arrows and released into the coolant inside the spacer cooling pipe45. On the other hand, when discharging gas producing a reaction product that is likely to be accumulated, heating performed by the heater42and cooling performed by the base cooling pipe46are controlled to make the temperature of the screw stator24equal to or higher than a temperature that does not cause the accumulation of the reaction product. As the temperature that does not cause the accumulation of a reaction product, a temperature equal to or higher than the sublimation temperature of the reaction product is employed.

Therefore, the heat insulation washers44are arranged between the cooling spacer23band the base20so as to prevent heat from flowing to the stationary blades22from the base20in a high temperature state. Further, as can be seen fromFIG. 2, a gap is formed between the cooling spacer23band the flange21c. Therefore, heat does not flow from the case21to the cooling spacer23b.

FIG. 4is a diagram explaining a cooling piping system and a temperature regulation operation. The coolant discharge section45bof the spacer cooling pipe45, a coolant supply section46aof the base cooling pipe46, and a bypass pipe53are connected to a three-way valve52. An end of the bypass pipe53, the end not being connected to the three-way valve52, is connected to a coolant discharge section46bof the base cooling pipe46. The switching of the three-way valve52is controlled by the temperature regulation controller511of a control unit51which controls the drive of the pump main body1. The temperature regulation controller511controls the switching of the three-way valve52and ON/OFF of the heater42on the basis of a temperature detected by the temperature sensor43.

When a temperature detected by the temperature sensor43is less than a predetermined temperature, the temperature regulation controller511switches the outflow side of the three-way valve52to the bypass pipe53to bypass a coolant from the three-way valve52to the coolant discharge section46b. Further, the heater42is turned ON. As a result, the base20is heated by the heater42, and the temperature of the base20and the temperature of the screw stator24thereby increase. As the temperature of the base20increases, the temperature of the heat transfer ring60to which heat from the base20is transferred also increases and is maintained at the same temperature as the base20.

The predetermined temperature is equal to or higher than the sublimation temperature of the reaction product, and previously stored in a storage section (not illustrated) in the temperature regulation controller511. In the example illustrated inFIG. 2, the temperature sensor43is provided in the base20. Therefore, the predetermined temperature is set by taking a difference in temperature between apart in which the temperature sensor43is provided and the screw stator24into consideration.

When a temperature detected by the temperature sensor43is equal to or higher than the predetermined temperature, the temperature regulation controller511turns OFF the heater42and switches the outflow side of the three-way valve52to the coolant supply section46aof the base cooling pipe46to thereby supply the coolant to the base cooling pipe46. By performing such temperature regulation control by the temperature regulation controller511, the screw stator24is maintained at a temperature equal to or higher than the sublimation temperature of the reaction product, thereby making it possible to prevent the accumulation of the reaction product.

On the other hand, since the coolant is constantly supplied to the spacer cooling pipe45, the stationary blades22are maintained at a low temperature by the cooling spacer23b. As a result, the heat release from the rotor blades30ato the stationary blades22by radiation is accelerated, which makes it possible to maintain the rotor30at a lower temperature than a conventional one. As a result, it is possible to increase the exhaust flow amount.

In the present embodiment, giving a priority to a reduction in the rotor temperature, a coolant supply source is connected to the coolant supply section45aof the spacer coolant pipe45, and the base cooling pipe46is connected to the coolant discharge section45bof the spacer cooling pipe45. For example, when the spacer cooling pipe45is arranged on the downstream side of the base cooling pipe46, a coolant heated by the base cooling is supplied to the spacer cooling pipe45. When cooling the rotor30by cooling the stationary blades22by the spacer cooling pipe45, a lower temperature is more preferred as the temperature of a coolant flowing in the spacer cooling pipe45. Therefore, in order to improve the effect of the rotor temperature reduction, it is preferred to provide the base cooling pipe46on the downstream side of the spacer cooling pipe45. By improving the effect of the rotor temperature reduction, it is possible to cope with a larger gas flow amount.

As described above, the turbo-molecular pump of the present embodiment can achieve the following effects.

(1) The spacer cooling pipe45is provided in one of the spacers for positioning the stationary blades22, that is, in the cooling spacer23b, and the cooling spacer23bis cooled by a coolant flowing inside the spacer cooling pipe45. Further, the heat insulation washers44are arranged between the cooling spacer23barranged on the base20and the base20to thereby prevent heat from flowing to the cooling spacer23bfrom the base20which is in a high temperature state by the temperature regulation. Therefore, it is possible to effectively perform the cooling of the stationary blades22and the heating of the screw stator24by the temperature regulation. As a result, it is possible to increase the exhaust flow amount and prevent the accumulation of the reaction product on the screw stator24.

(2) The heat transfer ring60is placed on the base20to be temperature-regulated. The heat transfer ring60is arranged so that the outer peripheral surface of the ring60faces the vacuum side inner surface of the bottom step spacer23aand the vacuum side inner surface of the cooling spacer23bwith a predetermined gap therebetween. Heat is transferred to the heat transfer ring60from the base20, and the inner peripheral surface of the heat transfer ring60is heated to a temperature equal to or higher than the sublimation temperature of the reaction product. Therefore, the reaction product is not accumulated on the inner peripheral surface of the heat transfer ring60. Further, it is possible to prevent the reaction product from being accumulated on the vacuum side inner surface of the bottom step spacer23aand the vacuum side inner surface of the cooling spacer23b.

(3) The heat transfer ring60is fixed to the upper side of the base20with the bolts66, so that heat of the base20is transferred to the heat transfer ring60. Therefore, a heat source for heating the heat transfer ring60is not required, and the cost can be reduced.

(4) The tip of the heat transfer ring60extends to a gap between the tip of the bottom step rotor blade30a1and the bottom step spacer23a, the gap being located higher than the tip of the cooling spacer23b. That is, the heat transfer ring60covers the entire area of the vacuum side inner surface of the bottom step spacer23aand the entire area of the vacuum side inner surface of the cooling spacer23b. The heat transfer ring60is heated by heat transferred from the base20, and a reaction product is not accumulated on the surface thereof. Therefore, even when the bottom step spacer23aand the cooling spacer23bare cooled to a temperature lower than the sublimation temperature of the reaction product, the tip of the bottom step rotor blade30a1is prevented from colliding with the reaction product accumulated on the spacer23aor the cooling spacer23bas in a conventional one.

(5) When a layer having high heat absorption such as an alumite layer and a black nickel plating layer is formed on the surface of the ring main body61of the heat transfer ring60, the surface facing the rotor blade30a1, the heat transfer ring60can be heated using radiant heat from the rotor blades30a1in addition to heat transferred from the base20. As a result, it is possible to more effectively increase the temperature of the heat transfer ring60.

The second to fifth embodiments will be described with reference toFIGS. 5 to 8. In the second to fifth embodiments, an embedded type cooling pipe45of a cooling spacer is shown.

Second Embodiment

FIG. 5is an enlarged view of an area in which a cooling spacer and an auxiliary ring are arranged as the second embodiment of the present invention.

The second embodiment illustrated inFIG. 5differs from the first embodiment in the following structure.

(a1) A cooling spacer23chas a structure obtained by integrating the cooling spacer23billustrated inFIG. 2and the bottom step spacer23aarranged above the cooling spacer23bwith each other. In other words, the bottom step spacer23aserves as the cooling spacer23c.

In a turbo-molecular pump of the second embodiment, a plurality of spacers for positioning stationary blades22on a base20includes a plurality of spacers23aand the cooling spacer23cwhich bears the spacers23awhile supporting the bottom step stationary blade22.

(a2) A heat transfer ring60A is integrally formed with the base20. Therefore, in this structure, it is not necessary to manufacture a heat transfer ring as a separate member. Both of the heat transfer ring60A and the base20may be formed of the same material such as SUS, or may also be formed of a clad material of different kinds of metal including an aluminum alloy for the heat transfer ring60A and SUS for the base20. Further, although not illustrated, a ring-like projection is integrally formed with the upper end of the base20which is made of metal such as SUS on the inner side of a heat transfer ring60A to be formed, and a heat transfer ring60A which is made of an aluminum alloy or the like as a separate member is integrated with the projection by shrinkage fitting.

As with the first embodiment, a layer having high heat absorption such as an alumite layer and a black nickel plating layer may be formed on a surface of the heat transfer ring60A, the surface facing the rotor blade30a1. The other configurations in the second embodiment are the same as those of the first embodiment. Therefore, the corresponding members will be denoted by the same reference sign, and description thereof will be omitted.

Also in the second embodiment, the same effects as in the first embodiment can be achieved. In the second embodiment, the tip of the heat transfer ring60A is lower than the vacuum side tip of the cooling spacer23c. However, the tip of the rotor blade30a1faces the inner peripheral surface of the heat transfer ring60A and the heat transfer ring60A is heated to a temperature equal to or higher than the sublimation temperature of generated gas. Therefore, a reaction product is not accumulated on the inner peripheral surface of the heat transfer ring60, and there is no possibility of the rotor blade30a1colliding with the accumulated reaction product. Further, since the cooling spacer23cis integrated with the bottom step spacer23a, cost reduction achieved by a reduction in the number of components can be expected.

Third Embodiment

FIG. 6is an enlarged view of an area in which a cooling spacer and an auxiliary ring are arranged as the third embodiment of the present invention. The third embodiment illustrated inFIG. 6differs from the second embodiment in the following structure.

(b1) A heat transfer ring60B is integrally formed with a screw stator24.

An attachment section of the screw stator24, the attachment section being attached to a base20, extends toward the outer peripheral side, and is bent upward on an end part thereof to form the heat transfer ring60B. As with the first embodiment, the screw stator24is fixed to the base20with bolts49. Accordingly, heat of the base20is transferred to the heat transfer ring60B.

In a turbo-molecular pump of the third embodiment, a plurality of spacers for positioning stationary blades22on the base20includes a plurality of spacers23aand a cooling spacer23cwhich bears the spacers23awhile supporting the bottom step stationary blade22.

As with the first embodiment, a layer having high heat absorption such as an alumite layer and a black nickel plating layer may be formed on a surface of the heat transfer ring60B, the surface facing the rotor blade30a1. The other configurations in the third embodiment are the same as those of the second embodiment. Therefore, the corresponding members will be denoted by the same reference sign, and description thereof will be omitted.

Fourth Embodiment

FIG. 7is an enlarged view of an area in which a cooling spacer and an auxiliary ring are arranged as the fourth embodiment of the present invention. The fourth embodiment illustrated inFIG. 7differs from the first embodiment in the following structure.

(c1) The second spacer from a base20is used as a cooling spacer23d. The cooling spacer23dincludes a spacer section231which functions as a spacer, a flange section232in which a spacer cooling pipe45is provided, and a cylindrical coupling section233which couples the spacer section231and the flange section232to each other.

In a turbo-molecular pump of the fourth embodiment, a plurality of spacers for positioning stationary blades22on the base20includes a plurality of spacers23aand the cooling spacer23dwhich bears the spacers23aexcepting the bottom step spacer23awhile supporting the bottom step stationary blade22and the second stationary blade22from the bottom.

The plurality of stages of stationary blades22are positioned by the spacers23aand the spacer section231. Therefore, a ring-like heat insulation member44cis arranged between the first spacer23afrom the base20and the base20. Further, a gap is formed between the flange section232and the base20without providing a heat insulation member therebetween. That is, a heat insulation layer of air is formed between the flange section232and the base20. Heat of the stationary blades22and the spacers23ais transferred to the spacer section231of the cooling spacer23das indicated by broken line arrows, and released into a coolant inside the spacer cooling pipe45through the coupling section233and the flange section232. In the fourth embodiment, the inner peripheral surface of the cooling spacer23ddoes not directly face the rotor blade30a1.

(c2) A heat transfer ring60B is integrally formed with a screw stator24.

An attachment section of the screw stator24, the attachment section being attached to the base20, extends toward the outer peripheral side, and is bent upward on an end part thereof to form the heat transfer ring60B. As with the first embodiment, the screw stator24is fixed to the base20with bolts49. Accordingly, heat of the base20is transferred to the heat transfer ring60B.

As with the first embodiment, a layer having high heat absorption such as an alumite layer and a black nickel plating layer may be formed on a surface of the heat transfer ring60B, the surface facing the rotor blade30a1. The other configurations in the fourth embodiment are the same as those of the first embodiment. Therefore, the corresponding members will be denoted by the same reference sign, and description thereof will be omitted.

Also in the fourth embodiment, the same effects as in the first embodiment can be achieved. In the fourth embodiment, each of the bolts49is used to fix both of the screw stator24and the heat transfer ring60B to the base20. Therefore, assembling man hours can be reduced.

Fifth Embodiment

FIG. 8is an enlarged view of an area in which a cooling spacer and a heat transfer ring are arranged as the fifth embodiment of the present embodiment. In the first to fourth embodiments, heat of the base20is transferred to the heat transfer rings60,60A, and60B. On the other hand, in the fifth embodiment, a heating ring (auxiliary ring)60C which is heated by a heat source such as a sheathed heater is used. In a turbo-molecular pump of the fifth embodiment, as with the second embodiment, a plurality of spacers for positioning stationary blades22on a base20includes a plurality of spacers23aand a cooling spacer23cwhich bears the spacers23awhile supporting the bottom step stationary blade22. The heating ring60C is arranged on the upper surface of the base20with a heat insulation member72interposed therebetween. An annular heater, for example, a sheathed heater73is provided on the inner side of the heating ring60C. The heat insulation member72is formed of a material having low thermal conductivity such as a resin.

The temperature of the sheathed heater73is controlled by a control unit51separately from a heater42which controls the temperature of a screw stator24. Although not illustrated, it is preferred to provide a temperature sensor which detects the temperature of the auxiliary ring60C to control the temperature of the sheathed heater73. Alternatively, a constant current may be constantly supplied to the sheathed heater73when heating the base without providing a temperature sensor to thereby maintain the sheathed heater73at a predetermined temperature. Further, in this case, a value of the constant current supplied to the sheathed heater73may be changed corresponding to a temperature detected by a temperature sensor43which detects the temperature of the screw stator24.

The other configurations in the fifth embodiment are the same as those of the second embodiment. Therefore, the corresponding members will be denoted by the same reference sign, and description thereof will be omitted. The turbo-molecular pump of the fifth embodiment is further provided with the sheathed heater73which is a heat source for heating the heating ring60C, the insulation member72which thermally insulates the heating ring60C from the base20, and the controller which controls the sheathed heater73independently of the heater42provided in the base20. Therefore, the fifth embodiment can achieve the same effects as achieved in the first embodiment. Further, it is possible to independently control each of the temperature of the heating ring60C and the temperature of the screw stator24. Therefore, the flexibility of temperature control for preventing the accumulation of a reaction product can be increased.

Further, in the first to fifth embodiments, the cooling piping system in which the three-way valve52is used to connect the spacer cooling pipe45and the base cooling pipe46to each other has been described as an example. However, the spacer cooling pipe45and the base cooling pipe46may be connected to each other by an on-off valve. The on-off valve is inserted between the coolant supply section45aof the spacer cooling pipe45and an inlet port of the base cooling pipe46, and the temperature regulation controller511controls opening/closing of the on-off valve. Further, the coolant discharge section45bof the spacer cooling pipe45is bypass-connected to an outlet port of the base cooling pipe46.

When a temperature detected by the temperature sensor43is less than a predetermined temperature, the temperature regulation controller511closes the on-off valve and turns ON the heater42. A coolant flows thorough the spacer cooling pipe45to cool the rotor blades30a. However, the coolant does not flow to the base cooling pipe46, and is bypassed to the outlet port of the base cooling pipe46. Therefore, the base cooling pipe46is heated by the heater42, and the temperature of the screw stator24increases.

When a temperature detected by the temperature sensor43is equal to or higher than the predetermined temperature, the temperature regulation controller511turns OFF the heater42, and opens the on-off valve. The coolant is supplied to the spacer cooling pipe45and the base cooling pipe46. Therefore, the rotor blades30aand the screw stator24are cooled.

In the above embodiments, the structure in which a spacer that is closest to the base20, that is, the bottom step spacer23aor the second spacer23afrom the base20is used as the cooling spacer23b,23c, or23dhas been described as an example. However, any of the plurality of stages of spacers can be used as the cooling spacer23b,23c, or23d. However, it is necessary to cool the bottom step rotor blade30a1on which a reaction product is likely to be accumulated by the cooling spacer23b,23c, or23d. As the spacer section of the cooling spacer23b,23c, or23dis separated from the base20, the capacity of cooling the vicinity of bottom step rotor blade30a1decreases. Therefore, the position of the cooling spacer23b,23c, or23dis preferably closer to the base20. Further, it is recommended that the cooling spacer23b,23c, or23dbe located on the lower side with respect to half the stages of the spacers23a. For example, in a turbo-molecular pump having ten stages of spacers23a, it is preferred to use a spacer23athat is located lower than the fifth spacer23afrom the base20as the cooling spacer. Further, in a turbo-molecular pump having nine stages of spacers23a, it is preferred to use a spacer23athat is located lower than the fourth spacer23afrom the base20as the cooling spacer.

In the configuration illustrated inFIG. 2, since the bottom step stationary blade22is closest to the cooling spacer23bamong all of the stationary blades22on a heat path, the temperature of the bottom step stationary blade22is most likely to decrease and a reaction product is most likely to be accumulated on the bottom step stationary blade22. A chlorine-based or fluorine sulfide-based reaction product has a higher sublimation temperature and becomes more likely to be accumulated, as the degree of vacuum decreases (that is, the pressure increases). As an example of the vapor pressure curve of a reaction product,FIG. 9illustrates a vapor pressure curve L1in the case of aluminum chloride.

InFIG. 9, the vertical axis shows the sublimation temperature (° C.) and the horizontal axis shows the pressure (Pa). Aluminum chloride is in a gaseous state above the curve L1, but in a solid state below the curve L1. As can be seen fromFIG. 9, since the sublimation temperature increases as the pressure increases, the reaction product is more likely to be accumulated on the more downstream side of the pump. In the above embodiments, the temperature regulation control using the heating by the heater42and the cooling by the cooling water inside the base cooling pipe46is performed to thereby prevent a reaction product from being accumulated on the screw stator24.

Generally, the rotor30is formed of an aluminum alloy. A temperature at which the creep phenomenon occurs in Aluminum is lower than that in the other kinds of metal. Therefore, in a turbo-molecular pump in which the rotor30rotates at high speed, it is necessary to suppress the temperature of the rotor so as to be lower than the creep temperature range. Accordingly, the flow amount of gas that can be discharged by the turbo-molecular pump is restricted by the temperature of the rotor. As a result, in the temperature condition illustrated inFIG. 9, it is not possible to further increase the flow amount of gas.

In view of the above, the cooling spacer23bis provide to cool the spacers23aand the stationary blades22to improve the heat releasing performance from the rotor blades30ato the stationary blades22, thereby reducing the temperature of the rotor blades30a. As a result, a margin of the temperature of the rotor blades with respect to heat generation during discharging gas becomes larger, and it is possible to increase the flow amount of gas that can be discharged.

FIG. 10illustrates the temperature of the stationary blades22when the cooling spacer23bis not provided (line L2) and the temperature of the stationary blades22when the cooling spacer23bis provided (line L3). Further, the curve L1(the vapor pressure curve of aluminum chloride) illustrated inFIG. 9is also illustrated inFIG. 10. The pressure in each of the screw stator24and the stationary blades22is one during discharging gas. The line L2is a line connecting points A, B, C2, D2, and E2to each other. On the other hand, the line L3is a line connecting points A, B, C3, D3, and E3to each other.

The point A indicates data (the pressure and the temperature) at a screw stator outlet, and the point B indicates data at a screw stator inlet. The screw stator24is maintained at a predetermined temperature by the temperature regulation control. Therefore, the temperature at the screw stator outlet and the temperature at the screw stator inlet when the cooling spacer23bis provided are the same as the temperature at the screw stator outlet and the temperature at the screw stator inlet when the cooling spacer23bis not provided, respectively. Further, the temperature at the screw stator outlet (A) is slightly higher than the temperature at the screw stator inlet (B) due to heat generated by discharging gas.

On the other hand, the points C2and C3indicate data of the bottom step stationary blade22, the points D2and D3indicate data of an intermediate stationary blade22, and the points E2and E3indicate data of the highest stationary blade22. In both of the cases of the lines L2and L3, heat flows from the rotor blades toward the screw stator. Therefore, the stationary blade temperature becomes higher as being separated from the screw stator24, that is, the temperature becomes lower in the order of the highest stage (E2, E3), the intermediate stage (D2, D3), and the lowest stage (C2, C3).

When the cooling spacer23bis provided (line L3), the temperature of the stationary blades22totally decreases compared to the case where the cooling spacer23bis not provided. In the example illustrated inFIG. 10, when a comparison is made regarding the temperature of the highest stationary blade22, the temperature is 110° C. in the line L2, but decreases to 60° C. in the line L3in which the cooling spacer23bis provided. As a result, the temperature of the bottom step stationary blade22(C3) becomes lower than the vapor pressure temperature (L1) at the same pressure. As a result, as described above, a reaction product is accumulated not only on the bottom step spacer23a, but also on the bottom step stationary blade22.

Therefore, in the sixth embodiment, a heat resistant section is provided in a contact region R between the bottom step stationary blade22and a cooling spacer23eofFIG. 11A. The heat resistant section suppresses heat from flowing to the cooling spacer23efrom the bottom step stationary blade22.FIG. 11Ais an enlarged view of apart in which the cooling spacer23eis provided. Also in the present embodiment, a heat transfer ring60A is provided on the inner peripheral side of the cooling spacer23e. The heat transfer ring60A constitutes a part of the base20. However, the present invention is not limited thereto, and the heat transfer ring60A may not be provided. In the configuration illustrated inFIGS. 11A to 11C, the bottom step stationary blade22is sandwiched between the bottom step spacer23aand the cooling spacer23e. In the configuration illustrated inFIG. 2, the stationary blade22is not sandwiched between the bottom step spacer23aand the cooling spacer23b. However, the cooling spacer23ecorresponds to one formed by integrating the cooling spacer23band the bottom step spacer23aofFIG. 2to each other.

FIG. 11Bis a diagram illustrating a case where a heat resistant section220is provided in the stationary blade. The heat resistant section220is provided in a contact region in the bottom step stationary blade22, specifically, the lower surface (a surface making contact with the cooling spacer23e) of an outer rib section22awhich is sandwiched between the cooling spacer23eand the bottom step spacer23a. Alternatively, instead of the heat resistant section220on the stationary blade22, a heat resistant section230may be provided in the cooling spacer23eas illustrated inFIG. 11C. The heat resistant section230is arranged on a surface of the cooling spacer23e, the surface making contact with the outer rib section22aof the stationary blade22. Further, both of the heat resistant sections220and230may be provided.

Examples of the heat resistant sections220and230are as follows. For example, when the material of the stationary blades22and the cooling spacer23eis an aluminum alloy, alumite treatment is applied onto the surface of the material, and the formed alumite layer is used as the heat resistant sections220and230. An alumite layer has a lower thermal conductivity than an aluminum alloy, and therefore functions as a heat resistant section. Further, instead of the alumite treatment, a resin such as an epoxy resin may be applied onto the contact surface, and the formed resin layer may be used as the heat resistant sections220and230.

Further, a stainless alloy may be used as the material of the bottom step stationary blade22or the cooling spacer23eto thereby suppress heat from flowing to the cooling spacer23efrom the stationary blade22. The other stationary blades22than the bottom step one are formed of a metal material of an aluminum alloy. However, by forming the bottom step stationary blade22using a stainless alloy having a lower thermal conductivity, it is possible to suppress heat from flowing to the cooling spacer23efrom the bottom step stationary blade22. The same is true when the cooling spacer23eis formed of a stainless alloy. Further, the bottom step stationary blade22or the cooling spacer23emay be formed of a stainless alloy, and a resin such as an epoxy resin may be further applied onto the contact surface thereof.

As illustrated inFIGS. 11A to 11C, by providing the heat resistant section220or the heat resistant section230in the contact region R, heat is suppressed from flowing to the cooling spacer23efrom the bottom step stationary blade22, and the stationary blade temperature increases as indicated by a line L4ofFIG. 12. The temperature of the screw stator24is the same as that in the case of the lines L1and L2due to the temperature regulation control. However, since the heat resistant section220or230is provided, the amount of heat flowing from the stationary blades22to the cooling spacer23edecreases. Therefore, the temperature of each of the stationary blades22increases compared to the case where the heat resistant section is not provided (line L3), and the temperature of the bottom step stationary blade22(C4) becomes higher than the temperature of the vapor pressure curve L1at the same pressure. As a result, it is possible to suppress the accumulation of a reaction product on the bottom step stationary blade22.

In the example described above, the alumite treatment is applied only onto the lower surface of the outer rib22aof the stationary blade22. However, the alumite treatment may be applied to the entire surface of the stationary blade22. Also in this case, the same effect as achieved in the case where the alumite treatment is applied only onto the lower surface can be achieved. Further, when the alumite treatment is applied onto the entire surface of the stationary blade22, the emissivity on the stationary blade surface increases. Therefore, heat transfer by radiation from the rotor blades30ato the stationary blades22is improved, and the rotor blade temperature (that is, the rotor temperature) can be reduced. On the contrary, the temperature of the bottom step stationary blade22becomes higher than that in the case illustrated inFIG. 12.

Further, by employing the configuration of a cooling system as illustrated inFIG. 13, it is possible to further increase the temperature of each of the stationary blades22compared to the case ofFIG. 12(when the cooling system ofFIG. 4is employed).FIG. 13is a block diagram illustrating another example of the temperature regulation system and the cooling system illustrated inFIG. 4. In comparison with the configuration ofFIG. 4, the arrangement of the three-way valve52and the connection of the cooling system differ from those ofFIG. 4. In the example illustrated inFIG. 4, the spacer cooling pipe45is arranged on the upstream side of the flow of the coolant, the three-way valve52is arranged between the spacer cooling pipe45and the base cooling pipe46, and the bypass pipe53for the base cooling pipe46is provided.

On the other hand, in the example illustrated inFIG. 13, the base cooling pipe46is arranged on the upstream side of the flow of a coolant, the three-way valve52is arranged on the upstream side of the base cooling pipe46, and the bypass pipe53is provided to bypass the base cooling pipe46and the spacer cooling pipe45. That is, the bypass pipe53is connected in parallel to the spacer cooling pipe45and the base cooling pipe46which are connected in series.

By switching the three-way valve52, the coolant is supplied to either one of a path of the spacer cooling pipe45and the base cooling pie46connected in series, or the bypass pipe53. Control for the three-way valve52during temperature regulation is the same as that in the case ofFIG. 4. In the configuration illustrated inFIG. 13, a coolant heated by the base cooling pipe46is supplied to the spacer cooling pipe45. Therefore, the temperature of the coolant supplied to the cooling spacer23eis higher than that in the configuration illustrated inFIG. 4. As a result, as indicated by a line L5illustrated inFIG. 14, the temperature of each of the stationary blades22further increases. When the temperature of each of the stationary blades22is maintained further higher relative to the line L1in this manner, although the flow amount of gas that can be supplied decreases, it is possible to further suppress the accumulation of a reaction product on the stationary blades22(especially, on the bottom step stationary blade22). As a result, the maintenance interval can be made longer.

In the above embodiments, when the flow of a coolant in the base cooling pipe46and the spacer cooling pipe45is stopped during the temperature regulation control, the coolant is diverted to the bypass pipe53using the three-way valve52. Therefore, it is possible to prevent the coolant from stopping flowing in the cooling system of the entire apparatus. Generally, in a vacuum apparatus provided with a cooling system using a coolant, an alarm is generated when the flow of the coolant stops. However, when using the turbo-molecular pump of the present embodiment, an alarm is not generated during the temperature regulation. Of course, a two-way valve may be used instead of the three-way valve to allow a coolant to flow and stop. Further, in the above embodiment, the cooling spacer23eand the heat resistant section are provided in the turbo-molecular pump which performs the temperature regulation control using the heating by the heater42and the cooling by the coolant in the base cooling pipe46. However, the cooling spacer23eand the heat resistant section may be provided in a turbo-molecular pump having no temperature regulation system.

Further, a turbo-molecular pump obtained by appropriately combining the above embodiments may be employed.

In the above embodiments, the heat transfer ring is interposed between the bottom step rotor blade and the cooling spacer or the spacer. However, the heat transfer ring may be omitted, and a reaction product accumulation prevention layer may be provided on the vacuum side surface of the cooling spacer or the spacer in the following manner. Referring toFIG. 5of the second embodiment, a heat insulation layer which is made of a resin or the like and a metal layer which covers the heat insulation layer are formed on the vacuum side surface of the heat transfer ring60A. Metal used in the metal layer is preferably one having a smaller thermal conductivity than an aluminum alloy which is the material of the spacers such as SUS. The main body section of the heat transfer ring60A is cooled by a coolant flowing in the cooling pipe45. The vacuum side surface is maintained at a temperature higher than the temperature of the spacer main body section, that is, equal to or higher than the sublimation temperature of reactive gas by virtue of the heat insulation layer. Therefore, the material and the thickness of each of the heat insulation layer and the metal layer are set so as to maintain the temperature of the vacuum side surface equal to or higher than the sublimation temperature of the reactive gas.