201105864 六、發明說明： 【發明所屬之技術領域】 本發明係有關於一種真空泵，尤其是一種渦輪分子真 空泵。 【先前技術】 設於一泵殼體內之真空泵包括一泵啷元件，其在渦輪 分子真空泵之情形中係以一泵轉子之形式呈現。此泵唧元 件被一軸所承載。此軸係藉由兩個軸承總成而被支撐在泵 殼體內。此支撐通常借一懸浮軸承與一固定軸承之助而被 實現。經由此可尤其被具體化爲一被動磁性軸承之懸浮軸 承，將產生一對於固定軸承之軸向偏壓，而此固定軸承係 一磁性軸承或一滾珠軸承。由於承載諸軸承元件中之一者 的泵殻體與承載諸軸承元件中之另一者的軸之間不同的熱 膨脹，因而將導致軸向之移位。此具有下列之結果：例如 在一被形成一滾珠軸承之固定軸承與一被形成一磁性軸承 之懸浮軸承的情形中，將會造成此磁性軸承之兩軸承元件 的軸向移位。由於此磁性軸承之兩軸承元件的軸向移位， 使得此軸承之軸向力將歷經改變。此依次具有下列結果： 在固定軸承中之軸向偏壓將端賴操作範圍而變化。在此諸 狀況下，負面之操作狀態可能會發生，其中例如將不再有 任何軸向偏壓力會作用在此固定軸承上。 在渦輪分子泵中，熱可被增大至130°C。相當大之移 位可能發生在軸向方向上，此尤其端視軸與泵殼體間之溫 201105864 差以及所使用之材料而定。例如，一混合支撐式之渦輪分 子泵可能需要此磁性軸承具有300 N/mm大小之徑向勁 度》因此，一大約600 N/mm之徑向勁度會被產生。最初 所設定之軸向軸承力則已經由於0.2 mm之軸向移位而改 變了大約200N。 本發明之目的在於提供一種真空泵，其中固定軸承在 整個操作範圍中承受一軸向偏壓力，較加一大致上恆定之 軸向偏壓力。 根據本發明，上述之目的係藉由申請專利範圍第1項 中所界定之諸特徵而被達成。 【發明內容】 根據本發明，爲了對該軸向移位作至少部分之補償， 兩個軸承總成中用以承載該軸之第一軸承總成在被連接至 泵殼體上的軸承元件與被連接至軸上的軸承元件之間配備 有一補償元件。藉由提供此一補償元件，其至少部分地補 償此諸軸承元件相對於彼此因熱膨脹所致之移位，而補償 元件作用在固定軸承上之軸向偏壓可在整個操作範圍期間 盡可能最大程度地被保持恆定。尤其，藉由適當地選擇該 補償元件之材料，使得有可能大致達到對此軸向移位之完 全補償’如此以致作用在該固定軸承上之軸向偏壓力將大 體上在整個操作範圍期間維持恆定。 根據本發明，該補償元件較佳係以一可使其僅作用在 該兩軸承元件中之一者上的方式被配置。在此方面，可經 201105864 由測試而檢査出該兩軸承元件中之何者將接受較大之軸向 移位，以便使得此補償元件可在此軸承上施加一相反之軸 向力。在真空泵中，尤其是渦輪分子泵，用以承載一或複 數個轉子之軸的軸向膨脹通常係較大於泵殻體之相對應膨 脹。在本發明中，藉由提供一作用在此兩軸承元件中之一 者上之補償元件，軸與泵殻體之不同軸向膨脹可至少部分 地，較佳大致全部地被補償。在此方面，根據一第一實施 例，此補償元件被配置成使其可作用在與泵殼體相連接之 軸承元件上。因此，如果此軸之軸向膨脹大於泵殼體之軸 向膨脹，則被連接至泵殻體上之軸承元件將進行一種跟隨 移動。在此，被連接至泵殻體上之軸承元件因轉子之熱膨 脹所造成的移位，以及被連接至殼體上之軸承元件因補償 元件所造成之移位，將發生在相同之方向上。 另外，可將此補償元件配置成使其將作用在與該軸相 連接之軸承元件上。如果此軸之軸向膨脹再次地大於殼體 之軸向膨張，則此補償元件將對抗被連接至軸上之軸承元 件因該軸之熱膨脹所造成的移位。 隨意地，亦可提供兩個補償元件，使得此兩補償元件 中之一者作用在與軸相連接之軸承元件上，而另一個補償 元件則作用在與泵殼體相連接之軸承元件上。在此，此兩 補償元件之補償方向係彼此相反。此一配置所具有優點在 於：由個別補償元件所導致之個別軸承元件的軸向移位將 是較小的，此情形乃是因爲該兩軸承元件將在相反之方向 201105864 上位移之故’而這導致了此兩補償元件中之每一者將只需 實現一部分之軸向補償。 如同也用於軸承兀件之情形者，補償元件較佳地係以 一環狀方式被配置且較佳地被構形爲一環。尤其較佳地使 用一補償元件’其包括一大體上具有一特別高熱膨脹係數 之材料。在一種位於一所有側邊均被高勁度材料所限定之 體積內之配置情形中，亦即一補償元件被配置在一密封室 中之情形中，具有等方熱特性之補償材料將是有用的。聚 合物是特別適合作爲此一方面之材料。在補償元件並不被 配置在一密封室中而尤其是在徑向方向上並不被限定之情 形中，此補償材料較佳地包括非等方性材料，且其更佳地 係由非等方性材料所構成。此材料被包含並配置成可分別 在軸之縱長方向與軸向方向上具有一高熱膨脹係數，且同 時在徑向方向上具有一高勁度，而此外在徑向方向上之熱 膨脹則是小的。作爲一種此類型之補償元件，例如一被纏 繞於圓周方向上之CFK (碳纖維複合材料）護罩將是適合 的。此補償材料可包括適當的糊狀或流體材料。 較佳地，此補償元件.被提供爲一較佳由彈性材料所製 成之環，或爲一由多個被沿著一圓形線條配置且形成該補 償元件之個別構件所組成之總成。 尤其較佳地，此補償元件之材料係取決於在給定操作 狀態下所發生之軸向移位而被選定’其目的在於：由於此 補償元件之材料的熱膨脹係數，使得作用至固定軸承上所 201105864 需之偏壓力將在整個操作範圍中大致被維持》較佳地，此 補償元件之材料的選擇在此態樣下係以一種適當之方式被 進行，此材料因此具有一適當之熱膨脹係數。在從o°c至 120°C之溫度範圍中，此補償材料之熱膨脹係數將大於軸 材料之熱膨脹係數。此補償材料之熱膨脹係數及軸向膨脹 較佳地被訂定成使得軸向力之容許變更不會被超過。此軸 向力之容許變更可被界定成例如是在20°C處之初始値的 5 0%。 爲了防止此補償元件之徑向膨脹或至少將此膨脹保持 在一小範圍，較佳地提供一用於限制此徑向膨脹之限制元 件。在一環狀補償元件或多個被沿一圓形線條配置並形成 該補償元件之個別構件的情形中，此限制元件較佳也是成 環狀的。如果此補償元件正例如作用在與泵殼體相連接之 軸承元件上，則此補償元件較佳地沿著徑向被配置於一殼 體壁與一位於此補償元件內的環狀限制元件之間。對應 地，如果此補償元件正作用在與軸相連接之軸承元件上， 則此補償元件被配置在該軸的一外側面與一圍繞此補償元 件並較佳係爲環狀的限制元件之間。 根據一較佳實施例，第一軸承元件被構形爲一磁性軸 承，較佳地爲一永久磁性軸承。根據本發明，當作一固定 軸承之第二軸承元件被構形爲一滾針軸承，較佳地爲一滾 珠軸承。 爲了經由磁性軸承而施加一軸向力至固定軸承上，此 201105864 磁性軸承之兩軸承元件的諸個別磁性元件相對於彼此係成 軸向移位地被配置。根據本發明，補償元件之設置將使得 此微小之軸向移位在整個操作範圍中可大體上被維持。 其上被補償元件所作用之第一軸承總成（亦即，尤其 是磁性軸承）的軸承元件較佳係可軸向移位的。端視該補 償元件正作用在與泵殻體相連接之軸承元件上或是作用在 與軸相連接之軸承元件上而定的，此軸承元件在軸向之方 向上且以可移位方式被對應地連接至該泵殼體或至該軸。 較佳地，一重置元件被設置成使得相對應軸承元件之重置 在諸組件冷卻期間且因此在補償元件冷卻期間可被確保。 此例如被形成一彈簧型式之重置元件較佳地被配置在該於 軸向之方向上與補償元件成相對置之對應軸承元件的那一 側上。然而，亦可將此重置元件倂合至補償元件內。隨意 地，一個別之重置元件可被省略，如果此補償裝置在軸向 之方向上被緊固地連接至相對應之軸承元件，以致使得此 補償元件由於溫度變化所導致之收縮將造成此相對應軸承 元件被一起拉動。 【實施方式】 —位於一泵殼體10內之渦輪分子泵包括一被配置在 一軸12上之轉子14。此轉子14包括複數個徑向延伸之轉 子葉16。多個定子盤18則被配置在此諸轉子葉16之間， 且其亦朝徑向地延伸並被固定於殻體1〇內。藉相對於此諸 定子盤18而轉動轉子元件14，一介質將經由一設置在殼 201105864 體10中之入口 22而被朝向一出口 20方向輸送》 在此經說明之實施例中，軸12係由一作爲一懸浮 之第一軸承元件24以及一作爲一固定軸承之第二軸 件26所支撐。在此經說明之實施例中，第二軸承元f 被形成一滾珠軸承。第一軸承元件24係一磁性軸承。 根據本發明之第一較佳實施例（第1及2圖），該 軸承包括三個永久磁鐵，其可用作爲一與殻體10相連 軸承元件28。第二個軸承元件被配置在軸12上，並 地藉由三個永久磁鐵30而被具體化。爲了在固定軸》 上產生軸向偏壓力，第一個軸承元件28相對於第二個 元件3 0係成軸向移位地被配置。 在傳統之渦輪分子泵中，軸12與殼體10之不同 脹具有下列效果：在渦輪分子泵之操作過程中，第1 之諸內側軸承元件30將朝箭頭31之方向被更向左地 移位。根據本發明，爲了補償此移位，將設置一補償 32。在已說明之實施例中，此補償元件32係呈環狀且 地係由一種材料所製成，而此材料較佳地具有一軸向 脹係數，以致於儘管軸12與殼體10具有不同熱膨脹 側軸承元件2 8仍不會相對於內側軸承元件3 0而在軸 方向上移位。 如第2圖中可見，補償元件32之體積將因爲操作 所導致之加熱而被擴大。在已說明之實施例中，爲了 補償元件3 2完全沒有膨脹或僅只微小地徑向膨脹’將 軸承 承元 Ψ 26 磁性 接之 再度 Ρ： 26 軸承 熱膨 圖中 軸向 元件 較佳 熱膨 ，外 向之 期間 確保 提供 201105864 一環狀之限制元件3 4。 因此，補償元件32被配置在殼體10之內側36與環狀 限制元件3 4之間。經由一被可移位地托住並同樣呈環狀之 傳遞元件38，由補償元件32之軸向熱膨脹所導致之移位 將被傳遞至外側軸承元件28處。此傳遞元件38被構形爲 在所有之操作狀態下均可於軸向之方向上部分地覆蓋限制 元件34。藉此可確保的是此補償元件32始終被配置在一 密閉空件內，因而可制止補償元件3 2之徑向膨脹。 在沿著軸向之方向被配置成與補償元件32相對立之 外側軸承元件28之側面上設置了一重置元件40，其被具 體化成例如一彈簧。當操作溫度被降低時’此重置元件40 將再度地壓縮補償元件32，藉此而同樣地可在已被降低之 操作溫度下維持內側軸承元件30與外側軸承元件28間之 軸向移位。爲了獲致此效果，亦可經由補償元件32與傳遞 元件38而作用一拉力。 在第1及2圖所示之實施例中，補償元件3 2之補償將 因此在與軸12之熱膨脹相同之方向31上是有效的。 下文所述之諸另外實施例（第3至5圖）在某種程度 上係相同的，且類似之組件被標示以相同之元件符號。 在第二實施例（第3圖）中，軸12在軸承總成24之 區域中被構形爲一中空軸。被連接至軸12上之軸承元件 28被配置在此中空軸之內側。與軸承元件28相對置的， 軸承元件30被配置在殼體10之一伸入該中空軸內的圓柱 -10- 201105864 形突出部42上，而此軸承元件30被構形爲與第1及2圖 所述之軸承元件相當者。類似於第1圖所示者，一補償元 件32被提供以作用至軸承元件30上，以便補償因熱膨脹 所導致之軸向移位。 在第4圖所示之第三實施例中，軸12同樣被構形爲一 與第1圖所示之實施例相當的中空軸。除了在第1圖所示 之實施例中，補償元件32被提供以作用在與軸12相連接 之軸承元件30上。因此，補償元件32將以與軸12之熱膨 脹方向31相反的方向（箭頭44)作用。 在第四實施例（第5圖）中，軸12同樣被構形爲與第 3圖所示者相當之中空軸。在第4圖所示實施例中，補償 元件32同樣以一導致其作用在與軸12相連接之軸承元件 30上的方式被配置。因此，補償之方向將同樣地朝向與軸 12之熱膨脹方向31相反的方向。 雖然本發明已參照其多個特定實施例而被說明與圖 示，但此並非意欲將本發明限定於這些經圖式說明之實施 例。熟習本藝之人士將承認許多變化與修改可在不脫離被 界定於後附申請專利範圍中之本發明的真實範圍下被達 成。因此，本發明將涵蓋所有這些落在所附申請專利範圍 及其均等物之範圍內的變化與修改。 【圖式簡單說明】 本發明之包括其最佳模式及使熟習本藝之人士可據以 實施之完整且可行的揭示內容已配合參照附圖而被詳細地 -11- 201105864 提出於上文中，在此諸附圖中： 第1圖係一具有一非主動補償元件之渦輪分子泵之第 —較佳實施例的示意剖面圖，而此非主動補償元件上則被 一與殼體相連接之軸承元件所作用， 第2圖係第1圖所示之渦輪分子泵的剖面圖，其中此 補償元件係處於主動狀態下， 第3圖係一具有一非主動補償元件之渦輪分子泵之第 二較佳實施例的示意剖面圖，而此非主動補償元件上則被 一與殼體相連接之軸承元件所作用， 第4圖係一具有一非主動補償元件之渦輪分子泵之第 三較佳實施例的示意剖面圖，而此非主動補償元件上則被 一與軸相連接之軸承元件所作用，及 第5圖係一具有一非主動補償元件之渦輪分子泵之第 四較佳實施例的示意剖面圖，而此非主動補償元件上則被 一與軸相連接之軸承元件所作用。 【主要元件符號說明】 10 泵殼體 12 軸 14 轉子 16 轉子葉 18 定子盤 22 入口 20 出口 -12- 201105864 24 第 —* 軸 承 元 件 /第 一軸 承 總 成 26 第 二 軸 承 元 件 /第 二軸 承 總 成 28 軸 承 元 件 3 0 軸 承 元 件 3 1 箭 頭 32 補 償 元 件 34 限 制 元 件 3 6 殻 體 內 側 3 8 傳 遞 元 件 40 重 置 元 件 42 突 出 部 44 箭 頭 -13-201105864 VI. Description of the Invention: [Technical Field] The present invention relates to a vacuum pump, and more particularly to a turbomolecular vacuum pump. [Prior Art] A vacuum pump provided in a pump casing includes a pumping element which is presented in the form of a pump rotor in the case of a turbomolecular vacuum pump. This pumping element is carried by a shaft. This shaft is supported in the pump housing by two bearing assemblies. This support is usually achieved with the aid of a suspension bearing and a fixed bearing. Thus, the suspension bearing, which can be embodied in particular as a passive magnetic bearing, will produce an axial bias to the fixed bearing, which is a magnetic bearing or a ball bearing. The axial displacement will result from a different thermal expansion between the pump housing carrying one of the bearing elements and the shaft carrying the other of the bearing elements. This has the following results: for example, in the case of a fixed bearing formed with a ball bearing and a suspension bearing formed with a magnetic bearing, axial displacement of the two bearing members of the magnetic bearing will be caused. Due to the axial displacement of the two bearing elements of the magnetic bearing, the axial force of the bearing will be altered. This in turn has the following results: The axial bias in the fixed bearing will vary depending on the operating range. Under these conditions, a negative operating state may occur in which, for example, no axial biasing force will act on the fixed bearing. In a turbomolecular pump, heat can be increased to 130 °C. A considerable displacement may occur in the axial direction, which is particularly the difference between the end view axis and the pump housing temperature 201105864 and the materials used. For example, a hybrid-supported turbomolecular pump may require this magnetic bearing to have a radial stiffness of 300 N/mm. Therefore, a radial stiffness of about 600 N/mm will be produced. The axial bearing force initially set has been changed by approximately 200 N due to the axial displacement of 0.2 mm. SUMMARY OF THE INVENTION It is an object of the present invention to provide a vacuum pump wherein the fixed bearing is subjected to an axial biasing force over the entire operating range, plus a substantially constant axial biasing force. According to the present invention, the above object is achieved by the features defined in claim 1 of the patent application. SUMMARY OF THE INVENTION According to the present invention, in order to at least partially compensate for the axial displacement, the first bearing assembly of the two bearing assemblies for carrying the shaft is coupled to a bearing member on the pump housing. A compensating element is provided between the bearing elements that are connected to the shaft. By providing such a compensating element, which at least partially compensates for the displacement of the bearing elements relative to each other due to thermal expansion, the axial bias of the compensating element acting on the fixed bearing can be maximized throughout the operating range The degree is kept constant. In particular, by appropriately selecting the material of the compensating element, it is possible to substantially achieve full compensation for this axial displacement so that the axial biasing force acting on the fixed bearing will generally be maintained throughout the operating range. Constant. According to the invention, the compensating element is preferably configured in such a way that it acts only on one of the two bearing elements. In this regard, it can be checked by the test 201105864 which of the two bearing elements will undergo a larger axial displacement so that the compensating element can exert an opposing axial force on the bearing. In vacuum pumps, particularly turbomolecular pumps, the axial expansion of the shaft used to carry one or more of the rotors is typically greater than the corresponding expansion of the pump casing. In the present invention, by providing a compensating element acting on one of the two bearing elements, the different axial expansion of the shaft and the pump housing can be at least partially, preferably substantially fully compensated. In this regard, according to a first embodiment, the compensating element is configured to act on a bearing member that is coupled to the pump housing. Therefore, if the axial expansion of the shaft is greater than the axial expansion of the pump housing, the bearing element that is coupled to the pump housing will perform a follow-up movement. Here, the displacement of the bearing element connected to the pump housing due to the thermal expansion of the rotor, and the displacement of the bearing element connected to the housing by the compensating element, will occur in the same direction. Alternatively, the compensating element can be configured such that it will act on the bearing element that is coupled to the shaft. If the axial expansion of the shaft is again greater than the axial expansion of the housing, the compensating element will counteract the displacement of the bearing element attached to the shaft due to thermal expansion of the shaft. Optionally, two compensating elements can also be provided such that one of the two compensating elements acts on a bearing element that is coupled to the shaft and the other compensating element acts on the bearing element that is coupled to the pump housing. Here, the compensation directions of the two compensating elements are opposite to each other. This configuration has the advantage that the axial displacement of the individual bearing elements caused by the individual compensating elements will be small, in that case the two bearing elements will be displaced in the opposite direction 201105864. This results in each of the two compensating elements having to achieve only a portion of the axial compensation. As is also the case for bearing elements, the compensating element is preferably configured in an annular manner and is preferably configured as a ring. It is especially preferred to use a compensating element 'which comprises a material having a particularly high coefficient of thermal expansion. In the case of an arrangement in which all of the sides are within the volume defined by the high-stiffness material, that is, in the case where a compensating element is disposed in a sealed chamber, a compensating material having an equipotential thermal characteristic would be useful. of. Polymers are particularly suitable as materials for this aspect. In the case where the compensating element is not disposed in a sealed chamber and is not particularly limited in the radial direction, the compensating material preferably comprises an unequal material and it is more preferably non-equal Square material. The material is included and arranged to have a high coefficient of thermal expansion in the longitudinal direction and the axial direction of the shaft, respectively, and at the same time has a high stiffness in the radial direction, and in addition, the thermal expansion in the radial direction is small. As a compensating element of this type, for example, a CFK (carbon fiber composite) shroud wound around the circumferential direction would be suitable. This compensation material may comprise a suitable paste or fluid material. Preferably, the compensating element is provided as a ring preferably made of an elastic material or as an assembly of a plurality of individual members arranged along a circular line and forming the compensating element. . Particularly preferably, the material of the compensating element is selected depending on the axial displacement occurring in a given operating state. The purpose is to act on the fixed bearing due to the coefficient of thermal expansion of the material of the compensating element. The required partial pressure of 201105864 will be substantially maintained throughout the operating range. Preferably, the choice of material for the compensating element is performed in a suitable manner in this manner, and the material thus has a suitable coefficient of thermal expansion. . In the temperature range from o°c to 120 °C, the thermal expansion coefficient of this compensation material will be greater than the thermal expansion coefficient of the shaft material. The coefficient of thermal expansion and axial expansion of the compensating material are preferably set such that the permissible change in axial force is not exceeded. This allowable change in axial force can be defined, for example, as 50% of the initial enthalpy at 20 °C. In order to prevent radial expansion of the compensating element or at least maintain this expansion in a small range, a limiting element for limiting this radial expansion is preferably provided. In the case of an annular compensating element or a plurality of individual members arranged along a circular line and forming the compensating element, the limiting element is preferably also annular. If the compensating element is acting, for example, on a bearing element that is connected to the pump housing, the compensating element is preferably arranged radially along a housing wall and a ring-shaped limiting element in the compensating element. between. Correspondingly, if the compensating element is acting on a bearing element that is coupled to the shaft, the compensating element is disposed between an outer side of the shaft and a limiting element surrounding the compensating element and preferably annular . According to a preferred embodiment, the first bearing element is configured as a magnetic bearing, preferably a permanent magnetic bearing. According to the present invention, the second bearing member as a fixed bearing is configured as a needle bearing, preferably a ball bearing. In order to apply an axial force to the fixed bearing via the magnetic bearing, the individual magnetic elements of the two bearing elements of the 201105864 magnetic bearing are arranged axially displaced relative to each other. According to the invention, the arrangement of the compensating elements will cause this slight axial displacement to be substantially maintained throughout the operating range. The bearing elements of the first bearing assembly (i.e., especially the magnetic bearings) on which the compensating element acts are preferably axially displaceable. Depending on whether the compensating element is acting on a bearing element that is connected to the pump housing or on a bearing element that is connected to the shaft, the bearing element is displaced in the axial direction and in a displaceable manner. Correspondingly connected to the pump housing or to the shaft. Preferably, a reset element is arranged such that resetting of the corresponding bearing element can be ensured during cooling of the components and thus during cooling of the compensating element. Thus, for example, a reset element formed in a spring type is preferably disposed on the side of the corresponding bearing member that is opposite the compensating element in the axial direction. However, this reset element can also be incorporated into the compensation element. Optionally, a further resetting element can be omitted if the compensating device is securely connected in the axial direction to the corresponding bearing element such that the compensating element shrinks due to temperature changes will cause this The corresponding bearing elements are pulled together. [Embodiment] A turbomolecular pump located in a pump housing 10 includes a rotor 14 disposed on a shaft 12. This rotor 14 includes a plurality of radially extending rotor blades 16. A plurality of stator discs 18 are then disposed between the rotor blades 16 and which also extend radially and are secured within the housing 1 bore. By rotating the rotor member 14 relative to the stator discs 18, a medium will be transported toward an outlet 20 via an inlet 22 disposed in the body 10 of the housing 201105864. In the illustrated embodiment, the shaft 12 is It is supported by a first bearing element 24 as a suspension and a second shaft member 26 as a fixed bearing. In the illustrated embodiment, the second bearing element f is formed as a ball bearing. The first bearing element 24 is a magnetic bearing. In accordance with a first preferred embodiment of the invention (Figs. 1 and 2), the bearing includes three permanent magnets that can be used as a bearing member 28 coupled to the housing 10. The second bearing element is disposed on the shaft 12 and is embodied by three permanent magnets 30. In order to create an axial biasing force on the fixed shaft, the first bearing element 28 is arranged axially displaced relative to the second element 30. In a conventional turbomolecular pump, the different expansion of the shaft 12 from the housing 10 has the effect that during operation of the turbomolecular pump, the first inner bearing member 30 will be moved further to the left in the direction of arrow 31. Bit. In accordance with the present invention, a compensation 32 will be provided to compensate for this shift. In the illustrated embodiment, the compensating element 32 is annular and the ground is made of a material, and the material preferably has an axial expansion coefficient such that although the shaft 12 is different from the housing 10. The thermally expandable side bearing element 28 is still not displaced in the axial direction relative to the inner bearing element 30. As can be seen in Figure 2, the volume of the compensating element 32 will be enlarged due to the heating caused by the operation. In the illustrated embodiment, in order to compensate for the fact that the element 3 2 is completely inflated or only slightly radially expanded, the bearing element Ψ 26 is magnetically reconnected: 26 the axial element of the bearing is preferably thermally expanded, During the outward direction, it is ensured that a ring-shaped limiting element 34 is provided. Therefore, the compensating element 32 is disposed between the inner side 36 of the housing 10 and the annular restricting member 34. The displacement caused by the axial thermal expansion of the compensating element 32 is transmitted to the outer bearing element 28 via a displaceably supported and likewise annular transfer element 38. The transfer element 38 is configured to partially cover the restraining element 34 in the axial direction in all operational states. This ensures that the compensating element 32 is always arranged in a closed hollow, so that the radial expansion of the compensating element 32 can be prevented. A reset element 40 is provided on the side of the outer bearing member 28 which is arranged in the axial direction opposite the compensating element 32, which is embodied, for example, as a spring. When the operating temperature is lowered, the reset element 40 will again compress the compensating element 32, whereby the axial displacement between the inner bearing element 30 and the outer bearing element 28 can likewise be maintained at the reduced operating temperature. . In order to achieve this effect, a pulling force can also be applied via the compensating element 32 and the transmitting element 38. In the embodiment shown in Figures 1 and 2, the compensation of the compensating element 32 will therefore be effective in the same direction 31 as the thermal expansion of the shaft 12. The other embodiments (Figs. 3 to 5) described below are to some extent identical, and like components are labeled with the same element symbols. In the second embodiment (Fig. 3), the shaft 12 is configured as a hollow shaft in the region of the bearing assembly 24. A bearing member 28 that is coupled to the shaft 12 is disposed inside the hollow shaft. Opposite the bearing element 28, the bearing element 30 is disposed on a cylinder -10- 201105864 shaped projection 42 that extends into one of the hollow shafts, and the bearing element 30 is configured to be the first and The bearing components described in Figure 2 are equivalent. Similar to that shown in Fig. 1, a compensating element 32 is provided to act on the bearing member 30 to compensate for axial displacement due to thermal expansion. In the third embodiment shown in Fig. 4, the shaft 12 is also configured as a hollow shaft which is comparable to the embodiment shown in Fig. 1. In addition to the embodiment shown in Figure 1, a compensating element 32 is provided to act on the bearing element 30 that is coupled to the shaft 12. Therefore, the compensating element 32 will act in a direction opposite the thermal expansion direction 31 of the shaft 12 (arrow 44). In the fourth embodiment (Fig. 5), the shaft 12 is also configured as a hollow shaft corresponding to that shown in Fig. 3. In the embodiment shown in Fig. 4, the compensating element 32 is also configured in a manner that causes it to act on the bearing element 30 that is coupled to the shaft 12. Therefore, the direction of compensation will likewise be in the opposite direction to the direction of thermal expansion 31 of the shaft 12. While the invention has been illustrated and described with reference to the particular embodiments embodiments Those skilled in the art will recognize that many variations and modifications can be made without departing from the true scope of the invention as defined by the appended claims. Therefore, the present invention is intended to cover all such modifications and alternatives BRIEF DESCRIPTION OF THE DRAWINGS The complete and practicable disclosure of the present invention, including its best mode, and which can be implemented by those skilled in the art, has been set forth above in detail -11-201105864 with reference to the accompanying drawings. In the drawings: Figure 1 is a schematic cross-sectional view of a first preferred embodiment of a turbomolecular pump having a non-active compensating element, and the non-active compensating element is coupled to the housing. Figure 2 is a cross-sectional view of the turbomolecular pump shown in Fig. 1, wherein the compensating element is in an active state, and Fig. 3 is a second turbomolecular pump having a non-active compensating element. A schematic cross-sectional view of a preferred embodiment, wherein the non-active compensating element is acted upon by a bearing element coupled to the housing, and FIG. 4 is a third preferred embodiment of a turbomolecular pump having a non-active compensating element. A schematic cross-sectional view of an embodiment, wherein the non-active compensating element is acted upon by a bearing element coupled to the shaft, and FIG. 5 is a fourth preferred embodiment of a turbomolecular pump having an inactive compensating element A schematic cross-sectional view of the non-active compensating element is applied by a bearing element that is coupled to the shaft. [Main component symbol description] 10 Pump housing 12 Shaft 14 Rotor 16 Rotor blade 18 Stator disk 22 Inlet 20 Exit -12- 201105864 24 No.** Bearing component/first bearing assembly 26 Second bearing component/second bearing total 28 Bearing element 3 0 Bearing element 3 1 Arrow 32 Compensating element 34 Restricting element 3 6 Housing inside 3 8 Transfer element 40 Reset element 42 Projection 44 Arrow-13-