JP4175834B2 - Turbo molecular pump seal structure - Google Patents

Turbo molecular pump seal structure Download PDF

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Publication number
JP4175834B2
JP4175834B2 JP2002168081A JP2002168081A JP4175834B2 JP 4175834 B2 JP4175834 B2 JP 4175834B2 JP 2002168081 A JP2002168081 A JP 2002168081A JP 2002168081 A JP2002168081 A JP 2002168081A JP 4175834 B2 JP4175834 B2 JP 4175834B2
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Prior art keywords
groove
herringbone
molecular pump
journal shaft
seal structure
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JP2004011567A (en
Inventor
哲郎 大林
昌司 井口
孝浩 上原
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Osaka Vacuum Ltd
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Osaka Vacuum Ltd
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C17/00—Sliding-contact bearings for exclusively rotary movement
    • F16C17/02—Sliding-contact bearings for exclusively rotary movement for radial load only
    • F16C17/026—Sliding-contact bearings for exclusively rotary movement for radial load only with helical grooves in the bearing surface to generate hydrodynamic pressure, e.g. herringbone grooves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C33/00—Parts of bearings; Special methods for making bearings or parts thereof
    • F16C33/02—Parts of sliding-contact bearings
    • F16C33/04—Brasses; Bushes; Linings
    • F16C33/06—Sliding surface mainly made of metal
    • F16C33/10—Construction relative to lubrication
    • F16C33/1025—Construction relative to lubrication with liquid, e.g. oil, as lubricant
    • F16C33/106—Details of distribution or circulation inside the bearings, e.g. details of the bearing surfaces to affect flow or pressure of the liquid
    • F16C33/107—Grooves for generating pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C2360/00—Engines or pumps
    • F16C2360/44—Centrifugal pumps
    • F16C2360/45—Turbo-molecular pumps

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Structures Of Non-Positive Displacement Pumps (AREA)
  • Non-Positive Displacement Air Blowers (AREA)
  • Sliding-Contact Bearings (AREA)

Description

【０００１】
【発明の属する技術分野】
本発明は、腐食性を有するガスや凝縮し易いガス等を含んだプロセスガスの排気に好適なターボ分子ポンプのシール構造に関する。
【０００２】
【従来の技術】
この種の従来のターボ分子ポンプのシール構造として、出願人は先に図４の如くころがり軸受ａを介して回転軸ｂを支承しているターボ分子ポンプｃにおいて、該ターボ分子ポンプｃのハウジングの静止部材ｄに径方向の揺動可能に嵌入された円筒状のブッシュｅと、該ブッシュｅの内周部に僅少の間隙を有して回動自在に該内周部を挿通した前記回転軸ｂの一部のジャーナル軸部ｆとからなり、該ジャーナル軸部ｆの外周部にヘリングボーン形溝ｇを回転方向に向かってへの字状に開いた形状に多数等間隔に凹設し、更に前記ジャーナル軸部ｆの外周部に前記へリングボーン形溝ｇに隣接してヘリカル溝ｈを多数等間隔に凹設したシール構造を提案した。（特願２０００−３４００８６）
【０００３】
これは、ころがり軸受ａのある大気圧側とポンプロータｋのある真空側との間を前記シール構造によって軸封しようとするものである。
【０００４】
先ず、へリングボーン形溝ｇの作用について説明する。
【０００５】
回転軸ｂが高速回転すると、前記へリングボーン形溝ｇが、あたかもコンプレッサーの羽根の如く作用し、ジャーナル軸部ｆの外周面近傍の気体を駆動して動圧を発生する。この圧力は、大気圧の２乃至３倍に相当する値となる。
【０００６】
然して、へリングボーン形溝ｇのあるジャーナル軸部ｆとブッシュｅとの隙間に偏心があると、この動圧は狭い隙間の方に強く作用して該隙間を広げるように働き、前記ブッシュｅの内周部と前記ジャーナル軸部ｆの外周部との間隙を所定の範囲に保つように作用する。
【０００７】
次にヘリカル溝ｈの作用について説明する。
【０００８】
ヘリカル溝ｈは前記へリングボーン形溝ｇの低圧側（ポンプロータｋ側）に隣接して配置されている。
【０００９】
そして、前記ブッシュｅと前記ジャーナル軸部ｆとの隙間の気体がポンプロータｋ側へ漏洩するのを防止するねじシール部として作用する。
【００１０】
このため、前記ヘリカル溝ｈは、回転軸ｂが回転したとき、真空側（ポンプロータｋ側）から気体を吸入するようなヘリカル溝ｈの傾斜に形成されている。
【００１１】
【発明が解決しようとする課題】
前記のシール構造において、ブッシュｅの内周部とジャーナル軸部ｆの外周部との隙間が少許偏心した場合、ヘリカル溝ｈのあるねじシール部の該拡大した隙間部にパージガス又は大気が多流に逆流し、この圧力が前記隙間を押し広げるように作用する。
【００１２】
この作用は前記へリングボーン形溝ｇの軸受作用とは逆の作用であり、へリングボーン形溝ｇによるブッシュｅの動圧浮上効果を阻害する。そして、このためブッシュｅとジャーナル軸部ｆとが固体接触の危険を生ずるという問題点があった。
【００１３】
本発明は前記の問題点を解消し、ブッシュｅとジャーナル軸部ｆとが固体接触を起こすことのないようなターボ分子ポンプのシール構造を提供することを目的とする。
【００１４】
【課題を解決するための手段】
本発明は上記の目的を達成すべく、ころがり軸受を介して回転軸を支承しているターボ分子ポンプにおいて、該ターボ分子ポンプのハウジングの静止部材に径方向の揺動可能に嵌入された円筒状のブッシュと、該ブッシュの内周部に僅少の間隙を有して回動自在に該内周部を挿通したジャーナル軸部とからなり、該ジャーナル軸部の外周部にヘリングボーン形溝を回転方向に向かってへの字状に開いた形状に凹設して動圧発生部を形成すると共に、該へリングボーン形溝に隣設した前記ジャーナル軸部の外周部にヘリカル溝を凹設してねじシール部を形成し、更に該ヘリカル溝の溝幅比、即ち溝幅と山幅との合計長さに対する溝幅の割合を前記へリングボーン形溝の溝幅比よりも大となるように形成したことを特徴とする。
【００１５】
【発明の実施の形態】
本発明の一実施の形態を図１乃至図３により説明する。
【００１６】
図１は本発明のターボ分子ポンプのシール構造部１の一部を断面で示しており、２はターボ分子ポンプの回転軸の一部のジャーナル軸部、３は円筒状のブッシュである。
【００１７】
前記ジャーナル軸部２は前述の従来例の如く回転軸の一部であって前記ブッシュ３の内周部に僅少の間隙Ｓを有して回動自在に挿通しており、又、該ブッシュ３は、前述の従来例の如くハウジングの静止部材に、径方向の揺動可能に嵌入されている。尚、矢印Ｘはジャーナル軸部２の回転方向を示す。
【００１８】
又、図１において、ジャーナル軸部２の上方が前述の従来例の如くポンプロータのある真空側であり、又、ジャーナル軸部２の下方が前述の従来例の如くころがり軸受のある大気圧側である。
【００１９】
ジャーナル軸部２の外周に凹設されているヘリカル溝２ａ即ちねじシール部及びヘリングボーン形溝２ｂ即ち動圧発生部の展開図を図２に示した。
【００２０】
図２において、２ａａ及び２ａｂはそれぞれヘリカル溝２ａの溝部及び山部を示し、これらヘリカル溝２ａの斜め方形の溝部２ａａと斜め方形の山部２ａｂは前記ジャーナル軸部２の外周面に該外周部を１周するように交互に等間隔に多数設けられている。
【００２１】
又、２ｂａ及び２ｂｂはそれぞれへリングボーン形溝２ｂの溝部及び山部を示し、これらへリングボーン形溝２ｂのヘの字状の溝部２ｂａとヘの字状の山部２ｂｂも前記ジャーナル軸部２の外周面に該外周部を一周するように交互に等間隔に多数設けられている。
【００２２】
そして前記ヘリカル溝２ａは、前記へリングボーン形溝２ｂの低圧側に隣り合って配設されている。
【００２３】
βＳはヘリカル溝２ａの溝角度、βＢはヘリングボーン形溝２ｂの溝角度を示す。
【００２４】
本実施の形態においては、ヘリカル溝２ａの溝角度βＳを２５°に、又、へリングボーン形溝２ｂの溝角度βＢを１５°に設定した。尚、従来のこの種のシール構造では、一般にβＳもβＢも同じ角度（２０°程度）に設定されている。
【００２５】
図３は前記ジャーナル軸部２のヘリカル溝２ａ又はヘリングボーン形溝２ｂにおける横断面図を示す。
【００２６】
即ち、２ａｃ及び２ａｄは、それぞれヘリカル溝２ａにおける円周方向の溝幅及び山幅を示し、又、２ｂｃ及び２ｂｄは、それぞれへリングボーン形溝２ｂにおける円周方向の溝幅及び山幅を示す。
【００２７】
ヘリカル溝２ａの溝幅比〔２ａｃ／（２ａｃ＋２ａｄ）〕をαＳとし、へリングボーン形溝２ｂの溝幅比〔２ｂｃ／（２ｂｃ＋２ｂｄ）〕をαＢとすると、本実施の形態では、ヘリカル溝２ａの溝幅比αＳを０．６に設定し、又、へリングボーン形溝２ｂの溝幅比αＢを０．４に設定した。尚、従来のこの種のシール構造では、一般にαＳもαＢも同じ溝幅比の０．５程度に設定されていた。
【００２８】
次に、本発明の作用及び効果について説明する。
【００２９】
従来の溝幅比（αＳ＝αＢ＝０．５）に設定したシール構造において、ジャーナル軸部２とブッシュ３との間隙部で振動を生じ不安定となることがあった。
【００３０】
これらの溝幅比をαＳ＝０．６、αＢ＝０．４となるように改造したところ、前記振動は収まり、安定となった。
【００３１】
即ち、同じ溝ピッチならば、ヘリカル溝２ａの溝幅をヘリングボーン形溝２ｂの溝幅よりも広げた方が、前記間隙部を安定に保つことができる。
【００３２】
これは、ヘリカル溝２ａ即ちねじシール部では溝幅比αＳを大きくして山部２ａｂの占める面積割合を小さくすることによりねじシール部の逆の軸受作用を減らし、又、へリングボーン形溝２ｂ即ち動圧発生部では溝幅比αＢを小さくして山部２ｂｂの占める面積割合を大きくすることにより動圧軸受部の軸受作用を増加させるためと考えられる。
【００３３】
尚、ヘリカル溝２ａとへリングボーン形溝２ｂとの溝幅比の割合は、αＳ／αＢを１．２乃至１．７の範囲とするのが好ましく、特にαＳ／αＢが１．５の値において最も好ましい結果が得られた。
【００３４】
又、従来の溝角度（βＳ＝βＢ＝２０°）に設定したシール構造において、ジャーナル軸部２とブッシュ３との間隙部に生ずる固有振動数の減衰比が０．０１６程度であったが、これをβＳ＝２５°、βＢ＝１５°に改造したところ、前記固有振動数の減衰比は０．０１８に改善された。
【００３５】
即ち、へリングボーン形溝２ｂの溝角度βＢよりもヘリカル溝２ａの溝角度βＳを大きくすることにより、前記間隙部に生ずる振動を早く減衰させて、安定方向に移行させることができる。
【００３６】
これは、ヘリカル溝２ａ即ちねじシール部では溝角度βＳを大きくしてポンプ作用を弱めることにより該ねじシール部の逆の軸受作用を減らし、又、へリングボーン形溝２ｂ即ち動圧発生部では溝角度βＢを小さくしてポンプ作用を強めることにより該動圧発生部の軸受作用を増加させるためと考えられる。
【００３７】
尚、これらの溝角度βＢ、βＳは、βＳがβＢよりも５°乃至１５°大きな角度とするのが好ましく、特にβＳがβＢよりも１０°大きな値において減衰比増大の効果が最も大きかった。
【００３８】
本実施の形態では、シール構造部１におけるヘリカル溝２ａとへリングボーン形溝２ｂにおいて、各溝幅比αＳ及びαＢをそれぞれ０．６及び０．４に設定すると共に各溝角度βＳ及びβＢををそれぞれ２５°及び１５°に設定したので、ヘリカル溝２ａのブッシュ３に対する逆軸受作用は減少し、ジャーナル軸部２とブッシュ３とが所定の間隙Ｓを保って安定に軸封を行なうように改善することができた。
【００３９】
尚、ヘリカル溝部の溝幅比αＳをヘリングボーン形溝部の溝幅比αＢよりも大とすること、又は、ヘリカル溝部の溝角度βＳをヘリングボーン形溝部の溝角度βＢよりも大きくすることは、これらの内の一方のみを採用するようにしてもよい。
【００４０】
【発明の効果】
このように本発明によれば、ターボ分子ポンプのシール構造において、ヘリカル溝及びヘリングボーン形溝を有するジャーナル軸部とブッシュとの間隙を安定に保つことができるので、該シール構造部において固体接触や焼き付きや磨耗を生じなくなる効果を有する。
【図面の簡単な説明】
【図１】本発明のターボ分子ポンプシール構造部の一部縦断面図である。
【図２】前記シール構造部のヘリカル溝及びヘリングボーン形溝の展開図である。
【図３】前記シール構造部のジャーナル軸部の横断面図である。
【図４】従来のターボ分子ポンプのシール構造の縦断面図である。
【符号の説明】
１ ターボ分子ポンプのシール構造部
２ ジャーナル軸部
２ａ ヘリカル溝
２ｂ へリングボーン形溝
３ ブッシュ
βＢ、βＳ 溝の傾斜角度（溝角度）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a seal structure of a turbo molecular pump suitable for exhausting a process gas containing a corrosive gas or a gas that easily condenses.
[0002]
[Prior art]
As a seal structure of a conventional turbo molecular pump of this type, the applicant previously described in the turbo molecular pump c that supports the rotating shaft b via the rolling bearing a as shown in FIG. A cylindrical bush e fitted into the stationary member d so as to be capable of swinging in the radial direction, and the rotating shaft having a slight gap in the inner peripheral portion of the bush e and rotatably inserted through the inner peripheral portion. a journal shaft portion f of a part b, and herringbone-shaped grooves g are formed in the outer peripheral portion of the journal shaft portion f so as to be recessed at regular intervals in a shape opened in a letter shape toward the rotation direction, Furthermore, a seal structure was proposed in which a number of helical grooves h were recessed at equal intervals adjacent to the herringbone groove g on the outer periphery of the journal shaft part f. (Japanese Patent Application 2000-340086)
[0003]
This is to seal the shaft between the atmospheric pressure side with the rolling bearing a and the vacuum side with the pump rotor k by the seal structure.
[0004]
First, the operation of the herringbone groove g will be described.
[0005]
When the rotary shaft b rotates at high speed, the herringbone groove g acts as if it is a compressor blade, and drives the gas near the outer peripheral surface of the journal shaft portion f to generate dynamic pressure. This pressure is a value corresponding to 2 to 3 times the atmospheric pressure.
[0006]
However, if there is an eccentricity in the gap between the journal shaft portion f having the herringbone groove g and the bush e, the dynamic pressure acts strongly on the narrow gap to widen the gap, and the bush e Acts to keep the gap between the inner peripheral portion of the journal shaft and the outer peripheral portion of the journal shaft portion f within a predetermined range.
[0007]
Next, the operation of the helical groove h will be described.
[0008]
The helical groove h is arranged adjacent to the low pressure side (pump rotor k side) of the herringbone groove g.
[0009]
And it acts as a screw seal part which prevents the gas in the gap between the bush e and the journal shaft part f from leaking to the pump rotor k side.
[0010]
For this reason, the helical groove h is formed with an inclination of the helical groove h so that gas is sucked from the vacuum side (pump rotor k side) when the rotating shaft b rotates.
[0011]
[Problems to be solved by the invention]
In the above seal structure, when the clearance between the inner peripheral portion of the bush e and the outer peripheral portion of the journal shaft portion f is slightly decentered, a large amount of purge gas or air flows in the enlarged clearance portion of the screw seal portion having the helical groove h. This pressure acts to push the gap apart.
[0012]
This action is the opposite of the bearing action of the herringbone groove g and inhibits the dynamic pressure floating effect of the bush e by the herringbone groove g. For this reason, there is a problem that the bush e and the journal shaft portion f cause a risk of solid contact.
[0013]
An object of the present invention is to solve the above-mentioned problems and to provide a turbo molecular pump seal structure in which the bush e and the journal shaft portion f do not cause solid contact.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a turbo molecular pump that supports a rotating shaft via a rolling bearing, and is a cylindrical shape that is fitted in a stationary member of the turbo molecular pump housing so as to be able to swing in the radial direction. And a journal shaft portion that has a small gap in the inner peripheral portion of the bush and is rotatably inserted into the inner peripheral portion. A herringbone groove is rotated on the outer peripheral portion of the journal shaft portion. A dynamic pressure generating portion is formed by recessing in a shape that is open in a shape toward the direction, and a helical groove is recessed in the outer peripheral portion of the journal shaft adjacent to the herringbone groove. The screw seal portion is formed, and the groove width ratio of the helical groove, that is, the ratio of the groove width to the total length of the groove width and the crest width is larger than the groove width ratio of the herringbone groove. It is characterized by being formed.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to FIGS.
[0016]
FIG. 1 is a cross-sectional view of a part of a seal structure part 1 of a turbo molecular pump according to the present invention, 2 is a journal shaft part of a part of a rotating shaft of the turbo molecular pump, and 3 is a cylindrical bush.
[0017]
The journal shaft portion 2 is a part of the rotating shaft as in the above-described conventional example, and is inserted through the inner peripheral portion of the bush 3 with a small gap S so as to be rotatable. Is inserted into the stationary member of the housing so as to be swingable in the radial direction as in the above-described conventional example. An arrow X indicates the direction of rotation of the journal shaft 2.
[0018]
In FIG. 1, the upper side of the journal shaft 2 is the vacuum side with the pump rotor as in the above-described conventional example, and the lower side of the journal shaft 2 is the atmospheric pressure side with the rolling bearing as in the above-described conventional example. It is.
[0019]
FIG. 2 shows a development view of the helical groove 2a, that is, the screw seal portion and the herringbone-shaped groove 2b, that is, the dynamic pressure generating portion, which are recessed in the outer periphery of the journal shaft portion 2.
[0020]
In FIG. 2, 2aa and 2ab indicate the groove portion and the crest portion of the helical groove 2a, respectively, and the slant square groove portion 2aa and the slant square crest portion 2ab of the helical groove 2a are formed on the outer peripheral surface of the journal shaft portion 2. Are provided alternately at equal intervals so as to make one round.
[0021]
Reference numerals 2ba and 2bb denote a groove portion and a crest portion of the herringbone groove 2b, respectively. The groove-shaped groove portion 2ba and the crest-shaped crest portion 2bb of the herringbone groove 2b are also the journal shaft portion. A large number of two outer peripheral surfaces are alternately provided at equal intervals so as to go around the outer peripheral portion.
[0022]
The helical groove 2a is arranged adjacent to the low pressure side of the herringbone groove 2b.
[0023]
β S represents the groove angle of the helical groove 2a, and β B represents the groove angle of the herringbone groove 2b.
[0024]
In the present embodiment, the groove angle beta S of the helical grooves 2a to 25 °, also was set groove angle beta B of the herringbone-shaped groove 2b to 15 ° to. In this type of conventional seal structure, generally β S and β B are set to the same angle (about 20 °).
[0025]
FIG. 3 shows a cross-sectional view of the helical groove 2a or herringbone groove 2b of the journal shaft portion 2. As shown in FIG.
[0026]
That is, 2ac and 2ad indicate the circumferential groove width and peak width in the helical groove 2a, respectively, and 2bc and 2bd indicate the circumferential groove width and peak width in the herringbone groove 2b, respectively. .
[0027]
When the groove width ratio [2ac / (2ac + 2ad)] of the helical groove 2a is α S and the groove width ratio [2bc / (2bc + 2bd)] of the herringbone groove 2b is α B , in this embodiment, the helical groove The groove width ratio α S of 2a was set to 0.6, and the groove width ratio α B of the herringbone groove 2b was set to 0.4. In this type of conventional seal structure, α S and α B are generally set to about 0.5 with the same groove width ratio.
[0028]
Next, the operation and effect of the present invention will be described.
[0029]
In the conventional seal structure set to the groove width ratio (α S = α B = 0.5), vibration may occur in the gap portion between the journal shaft portion 2 and the bush 3 and may become unstable.
[0030]
When these groove width ratios were modified so that α S = 0.6 and α B = 0.4, the vibrations were reduced and stabilized.
[0031]
That is, if the groove pitch is the same, the gap portion can be kept more stable by increasing the groove width of the helical groove 2a than that of the herringbone groove 2b.
[0032]
This reduces the bearing action of the reverse threaded seal portion by reducing the area ratio of the peak portions 2ab by increasing the groove width ratio alpha S is a helical groove 2a That thread seal portion, also, herringbone-shaped grooves in 2b i.e. dynamic pressure generating portion is believed to increase the bearing effect of the dynamic pressure bearing portion by enlarging the area ratio of peak portions 2bb by reducing the groove width ratio alpha B.
[0033]
The ratio of the groove width ratio of the herringbone-shaped groove 2b to the helical groove 2a is preferably set to α S / α B 1.2 to 1.7 range, in particular α S / α B 1 The most favorable result was obtained at a value of .5.
[0034]
Further, in the conventional groove angle (β S = β B = 20 °) is set in the seal structure, the natural frequency of the damping ratio caused the gap between the journal shaft part 2 and the bushing 3 was about 0.016 However, when this was modified to β S = 25 ° and β B = 15 °, the damping ratio of the natural frequency was improved to 0.018.
[0035]
That is, to by increasing the groove angle beta S of the helical groove 2a than the groove angle beta B of the herringbone-shaped groove 2b, and quickly dampen vibrations generated in the gap, it is possible to shift to a stable direction.
[0036]
This reduces the bearing action in a reverse of the threaded seal part by weakening the pumping action by increasing the groove angle beta S in helical grooves 2a That thread seal portion, also, herringbone-shaped groove 2b i.e. dynamic pressure generating portion in believed to increase the bearing action of the animal pressure generating unit by enhancing the pumping action to reduce the groove angle beta B.
[0037]
Incidentally, these grooves angles beta B, beta S is, beta S is beta preferably in the 5 ° to 15 ° angle greater than B, especially beta S is the damping ratio increases at 10 ° greater than beta B The effect was the greatest.
[0038]
In the present embodiment, in the helical groove 2a and the herringbone groove 2b in the seal structure 1, the groove width ratios α S and α B are set to 0.6 and 0.4, respectively, and the groove angles β S are set. and so was set to beta B to 25 ° and 15 °, respectively, opposite the bearing action against the bush 3 of the helical groove 2a is reduced and stable shaft sealing and a journal shaft portion 2 and the bushing 3 with a predetermined gap S It was possible to improve to do.
[0039]
It is to be noted that the groove width ratio α S of the helical groove is made larger than the groove width ratio α B of the herringbone groove, or the groove angle β S of the helical groove is made larger than the groove angle β B of the herringbone groove. Only one of these may be adopted.
[0040]
【The invention's effect】
As described above, according to the present invention, in the seal structure of the turbo molecular pump, the gap between the journal shaft portion having the helical groove and the herringbone-shaped groove and the bush can be stably maintained. And has the effect of preventing seizure and wear.
[Brief description of the drawings]
FIG. 1 is a partial longitudinal sectional view of a turbo molecular pump seal structure according to the present invention.
FIG. 2 is a development view of a helical groove and a herringbone groove of the seal structure.
FIG. 3 is a transverse sectional view of a journal shaft portion of the seal structure portion.
FIG. 4 is a longitudinal sectional view of a seal structure of a conventional turbo molecular pump.
[Explanation of symbols]
1 turbomolecular pump of the sealing structure 2 journal shaft portion 2a helical groove 2b herring bone-shaped grooves 3 bush beta B, beta S grooves inclination angle (groove angle)

Claims (1)

ころがり軸受を介して回転軸を支承しているターボ分子ポンプにおいて、該ターボ分子ポンプのハウジングの静止部材に径方向の揺動可能に嵌入された円筒状のブッシュと、該ブッシュの内周部に僅少の間隙を有して回動自在に該内周部を挿通したジャーナル軸部とからなり、該ジャーナル軸部の外周部にヘリングボーン形溝を回転方向に向かってへの字状に開いた形状に凹設して動圧発生部を形成すると共に、該へリングボーン形溝に隣接した前記ジャーナル軸部の外周部にヘリカル溝を凹設してねじシール部を形成し、更に該ヘリカル溝の溝幅比、即ち溝幅と山幅との合計長さに対する溝幅の割合を前記へリングボーン形溝の溝幅比よりも大となるように形成した分子ポンプのシール構造。  In a turbo molecular pump that supports a rotating shaft via a rolling bearing, a cylindrical bush fitted into a stationary member of a housing of the turbo molecular pump so as to be swingable in a radial direction, and an inner peripheral portion of the bush It consists of a journal shaft part that is inserted through the inner peripheral part so as to be rotatable with a slight gap, and a herringbone-shaped groove is opened in a shape toward the rotation direction on the outer peripheral part of the journal shaft part. Concave in the shape to form a dynamic pressure generating part, and a helical groove is recessed in the outer peripheral part of the journal shaft part adjacent to the herringbone groove to form a screw seal part. The molecular pump seal structure is formed such that the ratio of the groove width to the total length of the groove width and the crest width is larger than the groove width ratio of the herringbone groove.
JP2002168081A 2002-06-10 2002-06-10 Turbo molecular pump seal structure Expired - Lifetime JP4175834B2 (en)

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WO2018159680A1 (en) * 2017-02-28 2018-09-07 株式会社 荏原製作所 Pump device and maintenance method for pump device
JP6859832B2 (en) * 2017-04-27 2021-04-14 日本電産株式会社 Fluid bearing equipment, motors and disk drives

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