JP4703279B2 - Thermal insulation structure of composite molecular pump - Google Patents

Description

  The present invention relates to a heat insulating structure of a complex molecular pump that is particularly suitable for evacuating a gas that is easily condensed.

  The compound molecular pump is composed of a turbo molecular pump unit in which moving blade stages and stationary blade stages are alternately arranged in multiple stages, and a thread groove vacuum pump unit connected to the subsequent stage of the turbo molecular pump. This is an evacuation device that exhausts gas in the flow region.

  However, when exhausting gas that is particularly likely to be adhered by the composite molecular pump, a heater is used to prevent the exhaust gas from adhering inside the composite molecular pump. Etc. are heated.

In the molecular pump having a thread groove vacuum pump portion having a structure in which a stator is disposed inside a cylindrical rotor, the applicant previously has a bearing housing that supports the rotating shaft of the rotor inside the thread groove vacuum pump portion. A heat shielding plate is provided with a small gap between the outer peripheral portion and the outer periphery of the bearing housing portion so as to cover the outer peripheral portion of the bearing housing portion, and the gap between the heat shielding plate and the thread groove vacuum pump portion is An application was filed for a heat insulating structure of a molecular pump formed in an exhaust gas passage from a thread groove vacuum pump (see Patent Document 1).
JP 2004-270692 A

  This is to prevent the exhaust gas heated in the stator of the thread groove vacuum pump portion from being cooled in the bearing housing portion standing on the lower casing.

  However, only the heat insulating structure of the above application has an upper casing or bearing housing portion having a turbo molecular pump portion adjacent to the heat of the heated thread groove vacuum pump portion (particularly the stator) through an intermediate casing of the molecular pump. Since it is also transmitted to the lower casing, there is a problem that energy for heating the exhaust gas is wasteful.

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems and prevent heat from being transmitted from a stator of a thread groove vacuum pump section to an upper casing and a lower casing and to save energy for heating the stator.

  In order to achieve the above object, the present invention provides a composite molecular pump having a turbo molecular pump section and a thread groove vacuum pump section connected to a subsequent stage of the turbo molecular pump section, wherein the composite molecular pump is the turbo molecular pump. A three-stage structure comprising an upper casing that covers the outer periphery of the section, an intermediate casing that includes the stator of the thread groove vacuum pump section and that is connected to the upper casing, and a lower casing that is connected to the intermediate casing A concentric fitting portion is provided in each of the connection portion between the upper casing and the intermediate casing and the connection portion between the intermediate casing and the lower casing, and one side is the outside and the other is the inside. The concentric fitting portions are connected so that the intermediate casing side is outside the concentric fitting at each concentric fitting portion.

  According to the present invention, heat can be prevented from being transmitted from the stator of the thread groove vacuum pump part to the turbo molecular pump part and the base part in the composite molecular pump, and energy saving for heating the stator can be achieved.

  Examples of the best mode of the composite molecular pump having the heat insulating structure of the present invention are shown below.

  A first embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a longitudinal sectional view of a complex molecular pump 1 of this embodiment.

  The composite molecular pump 1 includes a turbo molecular pump unit 2 in which moving blade stages 2 a and stationary blade stages 2 b are alternately arranged in multiple stages, and a thread groove vacuum pump unit 3 connected to the turbo molecular pump unit 2. .

  The upper casing 4 that covers the outer peripheral portion of the turbo molecular pump portion 2 is generally made of stainless steel or aluminum alloy, is formed in a cylindrical shape, and has a suction port 4a in the upper portion.

  A plurality of annular distance pieces 5 are continuously inserted into the inner peripheral portion of the upper casing 4, and the outer peripheral portion of the stationary blade stage 2 b is sandwiched between the adjacent distance pieces 5. It is fixed.

  A rotor 6 includes the rotor blade stage 2a in an upper part in multiple stages.

  The thread groove vacuum pump part 3 includes a cylindrical rotor part 6a below the rotor 6, an intermediate casing 7 covering the outer peripheral part of the cylindrical rotor part 6a, and an outer peripheral part and an inner peripheral part of the cylindrical rotor part 6a. The outer stator 3a and the inner stator 3b are provided in close proximity to each other.

  The outer stator 3a is provided with a thread groove on the inner periphery.

  The intermediate casing 7 is made of an aluminum alloy, is formed in a cylindrical shape, and is connected to the lower stage of the upper casing 4.

  The inner stator 3b is also made of an aluminum alloy and has a thread groove formed on the outer periphery thereof. The inner stator 3b has a flange 3b1 at one end thereof in close contact with the lower portion of the intermediate casing 7, It is fixed to the intermediate casing 7.

  Reference numeral 8 denotes a lower casing, which is connected to the lower stage of the intermediate casing 7.

  The lower casing 8 has a bearing housing portion 8a that supports the rotating shaft 6b of the rotor 6, and a cooling water pipe 8b for cooling the bearing housing portion 8a.

  Note that 9 is an exhaust pipe, and 10a and 10b are heaters for heating.

  The heater 10a is attached to the outer peripheral portion of the intermediate casing 7, and the heater 10b is attached to the outer peripheral portion of the exhaust pipe 9, and serves to prevent the exhausted gas from causing adhesion inside. have.

  The connection portion A between the upper casing 4 and the intermediate casing 7 includes a bolt 11a and a heat insulating member that fasten the upper casing side flange 4c and the intermediate casing side flange 7a.

  Details of the connection portion A are shown in FIG.

  That is, a heat insulating washer 11b is interposed between the upper casing side flange 4c and the intermediate casing side flange 7a, and the bolt 11a is inserted through the heat insulating washer 11b to fasten the flanges 4c and 7a. ing.

  Further, a washer 11c made of heat insulating material is interposed between the head of the bolt 11a and the seat of the intermediate casing side flange 7a.

  Further, a concentric fitting portion C is provided at a connection portion between the upper casing side flange 4c and the intermediate casing side flange 7a, and the outer peripheral portion of the intermediate casing side flange 7a is connected to the upper casing side at the concentric fitting portion C. It is formed so as to project toward the flange 4c side and to perform concentric fitting (static fit) with the upper casing side.

  Furthermore, the upper protrusion 7b of the intermediate casing 7 is loosely fitted and inserted into the inner peripheral portion of the upper casing 4, and an O-ring is interposed between the upper protrusion 7b and the inner peripheral portion of the upper casing 4. 7c is interposed to prevent the gas from leaking through the gap 7d between the outer peripheral portion of the upper protruding portion 7b and the inner peripheral portion of the upper casing 4.

  Here, the gap 7d (radial gap in the outer peripheral portion of the upper protruding portion 7b) is a radial direction associated with a temperature change of the upper casing 4 and the intermediate casing 7 when the intermediate casing 7 is heated by the heater 10a. In consideration of the thermal expansion of the heater 10a, the gap 7d is set appropriately so as to never become zero even when the heater 10a is heated.

  Reference numeral 12 denotes a columnar heat insulating member made of a heat-insulating material, and the columnar heat insulating member 12 is formed in a two-stage columnar structure including a thick columnar portion at the root and a thin columnar portion at the top.

  The columnar heat insulating member 12 is coated with a material having corrosion resistance on the surface to increase durability.

  Reference numeral 13 denotes a ridge, and the ridge 13 includes a plurality of disc springs, and a thin cylindrical portion of the columnar heat insulating member 12 is slidably inserted through the ridge 13.

  The columnar heat insulating member 12 is interposed between the upper surface portion of the intermediate casing 7 and the lower portion of the distance piece 5 together with the ridge 13, and the distance piece 5 is moved to the upper portion by the elastic force of the ridge 13. The pressure is applied toward the inlet 4 a of the casing 4.

  A plurality of combinations of the columnar heat insulating members 12 and the ridges 13 are arranged at equal pitch on the same circumference of the upper surface of the intermediate casing 7 as shown in FIG.

  In FIG. 1, the connecting portion B between the intermediate casing 7 and the lower casing 8 includes a bolt 14a for fastening the intermediate casing side second flange 7e and the lower casing side flange 8c, a heat insulating member, and the like.

  The details of the connection part B in FIG. 1 are shown in FIG.

  That is, a heat-insulating washer 14b is interposed between the intermediate casing-side second flange 7e and the lower casing-side flange 8c, and the bolt 14a is inserted through the heat-insulating washer 14b to connect the flanges 7e and 8c. It is concluded.

  Further, a heat insulating washer 14c is also interposed between the head of the bolt 14a and the seat of the intermediate casing side second flange 7e.

  Further, a concentric fitting portion D is provided at a connection portion between the intermediate casing side second flange 7e and the lower casing side flange 8c, and the outer peripheral portion of the intermediate casing side second flange 7e is provided at the concentric fitting portion D. The lower casing side flange 8c is projected so as to be concentrically fitted (statically fitted) with the lower casing side.

  Furthermore, the lower protrusion 7f of the intermediate casing 7 is loosely inserted into the inner peripheral portion of the lower casing 8 and is inserted between the lower protrusion 7f and the inner peripheral portion of the lower casing 8. 7 g is interposed to prevent gas from leaking through a gap 7 h between the outer peripheral portion of the lower protruding portion 7 f and the inner peripheral portion of the lower casing 8.

  Here, the gap 7h (the radial gap on the outer peripheral portion of the lower protrusion 7f) is the radial direction associated with the temperature change of the intermediate casing 7 and the lower casing 8 when the intermediate casing 7 is heated by the heater 10a. In consideration of the thermal expansion of the heater 10a, the gap 7h is appropriately set so as to never become zero even when the heater 10a is heated.

  Next, the operation and effect of the complex molecular pump 1 of the present embodiment will be described.

  The complex molecular pump 1 rotates the rotor 6 at high speed, and exhausts the exhaust gas sucked from the intake port 4 a side through the exhaust pipe 9.

  When the exhaust gas is a gas that easily condenses, the heater 10a is operated to warm the intermediate casing 7, and in particular, the gas is prevented from adhering to the thread groove of the thread groove vacuum pump section 3. ing.

  In order to prevent the heat of the heated intermediate casing 7 from being transmitted to the upper casing 4 and / or the lower casing 8, the connecting portions A and B above and below the intermediate casing 7 are connected between the phase coupling flanges. The heat-insulating washer 11b or 14b is intermittently interposed to reduce direct heat conduction, and the heat-insulating washer 11c or 14c is interposed in the head seat of each fastening bolt 11a or 14a, respectively. Heat conduction through 11a and 14a is also reduced.

  Further, a columnar heat insulating member 12 provided with a ridge 13 is interposed between the intermediate casing 7 and the distance piece 5, and the distance piece 5 is inserted into the inlet of the upper casing 4 by the elastic force of the ridge 13. While pressing to the 4a side, the heat of the intermediate casing 7 is prevented from being conducted to the distance piece 5 and the upper casing 4.

  The ridges 13 are supplemented when the upper casing 4 and the distance piece 5 fitted in the upper casing 4 have a difference in length in the axial direction due to a difference in thermal expansion. It plays a role to absorb.

  In addition, the ridge 13 is composed of a plurality of disc springs, but it may be composed of one coil spring instead of the plurality of disc springs.

  As described above, in the connection portion A or B of each casing, the heat insulating washer 11b or 14b is intermittently interposed, and the space portion is provided between the heat insulating washer 11b or 14b. Compared to the case where a continuous ring-shaped heat insulating member is interposed between the casing and the heat insulating member, the contact area between the casing and the heat insulating member is greatly reduced. The amount could be greatly reduced.

  In addition, since the columnar heat insulating member 12 is intermittently interposed between the distance piece 5 and the intermediate casing 7 and the space portion is provided between the columnar heat insulating members 12, a continuous ring that is continuous in the circumferential direction. Compared with the case where a heat insulating member is interposed, both the contact area between the intermediate casing 7 and the heat insulating member and the contact area between the upper casing 4 and the heat insulating member are greatly reduced. As a result, these heat insulating members The amount of heat transfer through the air can be greatly reduced.

Here, a thickness L [m], a cross-sectional area S [m ² ], and a thermal conductivity λ [W / (K · m)] are set between parallel flat plates having a temperature difference ΔT [K] between two planes. Considering the case where the heat insulating member having the heat flow is interposed, the heat flow rate Q [W] flowing from the high-temperature surface side to the low-temperature surface side of the two planes can be expressed by Expression (1).
Q = λ · S · ΔT / L (1)

  From this equation, the following can be understood. That is, when λ (the material of the heat insulating member), ΔT (temperature difference between the two surfaces of the heat insulating member) and L (the axial dimension of the heat insulating member) are constant, S (intermittently interposed in the circumferential direction). The heat flow rate (Q) flowing between the two surfaces with the heat insulating member interposed can be reduced to 1/5 by simply reducing the total cross-sectional area of the heat insulating member to 1/5, for example, and as a result, the heat is supplied to the heater 10a. It becomes possible to reduce electric power.

  If Q, λ, and L may be constant, the temperature difference (ΔT) between the two surfaces of the heat insulating member is increased by 5 times only by setting S to 1/5, for example, and the intermediate casing 7 is maintained at a high temperature. As a result, the outer stator 3a and the inner stator 3b of the thread groove vacuum pump portion are also maintained at a high temperature, and it is possible to further prevent the exhaust gas from adhering.

  Further, when Q, λ, and ΔT may be constant, the axial dimension (L) of the heat insulating member can also be reduced to 1/5 by simply setting S to 1/5, and as a result, the heat insulating member. The installation space in the axial direction can be reduced to 1/5, and the total volume (L × S) of the heat insulating member is 1/25, so that the cost of the heat insulating member can be simultaneously reduced.

  Furthermore, when Q, ΔT, and L may be constant, the selection range can be expanded to a material whose thermal conductivity (λ) is five times as a material of the heat insulating member by simply setting S to 1/5, for example. As a result, it is possible to select a comprehensive heat insulating member in consideration of compressive strength, workability, cost, availability, and the like.

  As described above, by applying the present invention, it is possible to realize an optimal heat insulating structure design corresponding to various purposes and conditions.

  The heat conductivity of the heat insulating member employed in the present invention is approximately less than 2 [W / (K · m)]. In selecting the material, as described above, the mechanical properties (hardness, compressive strength, etc.), workability, cost, etc. as the structural material were taken into consideration. As a result, the present invention employs a heat insulating material that contains an inorganic substance such as glass or ceramics as a main component and that slightly contains an organic substance as a binder.

  This type of material can be used as it is after processing for the heat insulating members 11b, 11c, 14b, and 14c disposed outside the complex molecular pump 1 (in the atmosphere).

  On the other hand, for the columnar heat insulating members 12 and 16 disposed inside the complex molecular pump 1 (in a vacuum), it is inappropriate to use it as it is after processing. That is, when a certain kind of gas (for example, a fluorine compound) is activated and flows into the composite molecular pump 1, the organic substance as a binder may be decomposed and corrosion may gradually progress. It is. Therefore, the columnar heat insulating members 12 and 16 made of the material are subjected to a corrosion-resistant surface treatment. As the type of surface treatment, for example, nickel-based surface treatment that has been proven in construction on the aluminum alloy rotor 6 of the composite molecular pump 1 is appropriate, but corrosion resistance to an active fluorine compound or the like is suitable. Any surface treatment can be used.

  Further, in the concentric fitting parts of the connecting parts A and B of the casings, the intermediate casing 7 made of aluminum alloy is formed so as to be outside the concentric fittings. In consideration of the temperature rise of the concentric fitting portion, the concentric fitting portion is prevented from being fixed, and the heating by the heater 10a causes each concentric fitting portion to be free from radial clearance as the temperature of the intermediate casing 7 rises. Thus, heat conduction due to radial contact from the intermediate casing 7 to another casing is suppressed. Due to such a radial heat insulating structure, the intermediate casing 7 can be maintained at a high temperature. As a result, the outer stator 3a and the inner stator 3b of the thread groove vacuum pump section 3 are also maintained at a high temperature, and the exhaust gas is condensed. It became possible to further prevent wearing.

  Furthermore, the gap 7d between the outer peripheral part of the intermediate casing 7 and the inner peripheral part of the upper casing 4 (radial gaps on both the upper and lower sides of the O-ring 7c, see FIG. 2), and the outer peripheral part of the intermediate casing 7 The clearance 7h (both the upper and lower radial clearances of the O-ring 7g, see FIG. 3) in the inner periphery of the lower casing 8 never becomes zero even when the temperature of the intermediate casing 7 rises due to heating by the heater 10a. However, the heat conduction by the radial contact from the intermediate casing 7 to other casings is also suppressed. The intermediate casing 7 can be maintained at a high temperature by such a second radial heat insulating structure. As a result, the outer stator 3a and the inner stator 3b of the thread groove vacuum pump unit 3 are also maintained at a high temperature, and the exhaust gas is exhausted. It has become possible to further prevent gas adhesion.

  In this way, heat conduction due to radial contact and / or axial contact from the heated intermediate casing 7 to the upper casing 4 and / or the lower casing 8 or the distance piece 5 is prevented, so that the intermediate casing 7 maintained at a high temperature is maintained. Therefore, the outer stator 3a and the inner stator 3b of the thread groove vacuum pump part 3 are also maintained at a high temperature, and it is possible to prevent the exhaust gas from adhering, and less energy is required for heating the heater 10a. Further, the cooling water passing through the cooling water pipe 8b of the lower casing 8 is also saved, which is economical.

  A second embodiment of the present invention will be described with reference to FIGS.

  FIG. 5 is a longitudinal sectional view of the complex molecular pump 15 of this embodiment.

  The complex molecular pump 15 of the present embodiment has the same structure as the complex molecular pump 1 of the first embodiment. In the complex molecular pump 1 of the first embodiment, the upper surface portion of the intermediate casing 7, the distance piece 5, In contrast to the columnar heat insulating member 12 having the ridges 13 interposed therebetween, in Example 2, the columnar heat insulating member 16 having no ridges is connected to the upper surface portion of the intermediate casing 7 and the distance piece 5. This embodiment differs from the first embodiment in that a rib 17 having the same diameter as that of the distance piece 5 is interposed between the distance piece 5 and the suction port 4a of the upper casing 4.

  The details of the connection E between the upper casing 4 and the intermediate casing 7 in FIG. 5 are shown in FIG.

  That is, the columnar heat insulating member 16 interposed between the intermediate casing 7 and the distance piece 5 is made of a material having heat insulating properties similarly to the columnar heat insulating member 12 in the first embodiment, and has a large-diameter columnar portion at the root. And a plurality of columnar heat insulating members 16 are intermittently arranged at an equal pitch on the same circumference of the upper surface of the intermediate casing 7.

  As shown in FIG. 6, the heat of the intermediate casing 7 can be prevented from being conducted to the distance piece 5 and the upper casing 4 by interposing the columnar heat insulating member 16 and the heat insulating washer 11 b.

  Further, the strip 17 (FIG. 5) pushes the distance piece 5 toward the intermediate casing 7 and shafts due to a difference in thermal expansion between the distance piece 5 and the upper casing 4 in which the distance piece 5 is fitted. It plays the role of complementing or absorbing the difference in direction length.

  Further, when the ridge 17 is composed of a single disc spring, the spring rigidity thereof is very high. Therefore, the columnar heat insulating member 16 provided between the distance piece 5 and the intermediate casing 7 and the seat on the intermediate casing 7 side The height of the columnar heat insulating member 16 is adjusted by interposing a ring-shaped washer 16a therebetween.

  In the present embodiment, the shape of the heat insulating member is a two-stage cylindrical structure, but this is because the small diameter portion is inserted into a cylindrical recess provided in the distance piece 5 for positioning. The shape of the heat insulating member may be a simple cylinder or a rectangular plate as long as the arrangement and positioning are possible.

  The operation and effect of the complex molecular pump 15 of the second embodiment are substantially the same as those of the complex molecular pump 1 of the first embodiment.

  The molecular pump having the heat insulating structure of the present invention is used for evacuating a gas that is particularly easily condensed.

1 is a longitudinal sectional view of a complex molecular pump of Example 1. FIG. FIG. 2 is a detailed view of a part A in FIG. 1. 2 is a partial explanatory diagram of Example 1. FIG. FIG. 2 is a detailed view of a portion B in FIG. 1. 3 is a longitudinal sectional view of a complex molecular pump of Example 2. FIG. FIG. 6 is a detailed view of a portion E in FIG. 5.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,15 Compound molecular pump 2 Turbo molecular pump part 3 Screw groove vacuum pump part 4 Upper casing 5 Distance piece 7 Intermediate casing 8 Lower casing 11a, 14a Fastening bolt 11b, 11c, 14b, 14c Thermal insulation member (thermal insulation washer)
12, 16 Column-shaped heat insulating member 13, 17 Stroke A, B, E Connection part

Claims (9)

In the composite molecular pump having a turbo molecular pump part and a thread groove vacuum pump part connected to the subsequent stage of the turbo molecular pump part, the composite molecular pump includes an upper casing covering an outer periphery of the turbo molecular pump part, A three-stage casing comprising an intermediate casing connected to the upper casing with a stator of a thread groove vacuum pump section; and a lower casing connected to the intermediate casing; A concentric fitting portion is provided at each of the connecting portion between the casing and the intermediate casing and the connecting portion between the intermediate casing and the lower casing, and one of them is connected outside in a concentric manner with the other as an inner side, said intermediate casing in each concentric fitting portion of the composite molecular pump, characterized in that formed such that the outer of identity centered fitting Thermal structure. A vacuum seal portion for sealingly connecting the casing is disposed inside each concentric fitting portion of the casing, and the vacuum seal includes an outer peripheral surface of the upper protruding portion and an outer periphery of the lower protruding portion of the intermediate casing. Contact seal structure formed by each bottom surface of an O-ring groove engraved on the surface, each O-ring disposed in the O-ring groove, and an inner peripheral surface of the upper casing and an inner peripheral surface of the lower casing And an outer peripheral surface of the upper projecting portion of the intermediate casing and an inner peripheral surface of the upper casing, and a radial direction between the outer peripheral surface of the lower projecting portion of the intermediate casing and the inner peripheral surface of the lower casing. 2. The heat insulating structure for a complex molecular pump according to claim 1, wherein a gap is provided so that the outer peripheral surface and the inner peripheral surface do not always come into contact with each other . A plurality of heat insulating members are intermittently arranged / interposed in the circumferential direction at the connecting portion between the upper casing and the intermediate casing or the connecting portion between the intermediate casing and the lower casing, thereby providing a space between the heat insulating members. The heat insulating structure of the composite molecular pump according to claim 1 , wherein a portion is provided . The heat insulating member, wherein wherein said a upper casing and the intermediate casing or the intermediate casing and sandwiched adiabatic material washer made between the connecting part is inserted into a fastening bolt for fastening the lower casing Item 4. The heat insulating structure of the composite molecular pump according to Item 3 . The heat insulating structure for a composite molecular pump according to claim 4, wherein the heat insulating washer is interposed also on a fastening seating surface of a head of the fastening bolt . An annular distance piece for locking the stationary blade stage of the turbo molecular pump is installed on the inner peripheral portion of the upper casing, and a plurality of heat insulating members are disposed in the circumferential direction between the distance piece and the intermediate casing. heat insulating structure of the complex molecular pump according to any one of claims 1 to 5, characterized in that a space between each other intermittently is arranged and interposed heat insulating member. The heat insulating structure of the composite molecular pump according to claim 6 , wherein the surface of the heat insulating member is coated with nickel plating or a material having corrosion resistance . The composite molecule according to claim 6 or 7 , wherein a ridge formed by a disc spring having substantially the same diameter as that of the distance piece is interposed between the distance piece and the suction port portion of the upper casing. Pump insulation structure. Between the distance piece and said intermediate casing, according to claim 6 or claim 7, characterized in that the power spring of a coil spring or a plurality of disc springs in a circumferential direction of the plurality of locations intermittently is arranged and interposed The heat insulating structure of the composite molecular pump described in 1.

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